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Needham E, Webb G. Hepatic encephalopathy: a neurologist's perspective. Pract Neurol 2024; 24:200-206. [PMID: 38453473 DOI: 10.1136/pn-2023-003802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/18/2024] [Indexed: 03/09/2024]
Abstract
Liver disease is increasingly common, estimated to affect over 25% of the world's population. Failure of the liver to maintain a normal metabolic milieu leads to impaired brain function (hepatic encephalopathy), and conditions that cause liver disease can themselves predispose to neurological disease. As neurologists' involvement with the acute take increases, it is important that we are familiar with the neurological complications of liver disease, their investigation and management, and to know which other neurological diseases occur in this patient population. In this article, we review the causes, presentation and treatment of hepatic encephalopathy, and discuss important differential diagnoses in patients with liver disease who present with neurological disturbance.
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Affiliation(s)
- Edward Needham
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
- Department of Neurology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Gwilym Webb
- Department of Hepatology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
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2
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Heybe MA, Mehta KJ. Role of albumin infusion in cirrhosis-associated complications. Clin Exp Med 2024; 24:58. [PMID: 38551716 PMCID: PMC10980629 DOI: 10.1007/s10238-024-01315-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Accepted: 02/29/2024] [Indexed: 04/01/2024]
Abstract
Cirrhosis is an advanced-stage liver disease that occurs due to persistent physiological insults such as excessive alcohol consumption, infections, or toxicity. It is characterised by scar tissue formation, portal hypertension, and ascites (accumulation of fluid in the abdominal cavity) in decompensated cirrhosis. This review evaluates how albumin infusion ameliorates cirrhosis-associated complications. Since albumin is an oncotic plasma protein, albumin infusion allows movement of water into the intravascular space, aids with fluid resuscitation, and thereby contributes to resolving cirrhosis-induced hypovolemia (loss of extracellular fluid) seen in ascites. Thus, albumin infusion helps prevent paracentesis-induced circulatory dysfunction, a complication that occurs when treating ascites. When cirrhosis advances, other complications such as spontaneous bacterial peritonitis and hepatorenal syndrome can manifest. Infused albumin helps mitigate these by exhibiting plasma expansion, antioxidant, and anti-inflammatory functions. In hepatic encephalopathy, albumin infusion is thought to improve cognitive function by reducing ammonia concentration in blood and thereby tackle cirrhosis-induced hepatocyte malfunction in ammonia clearance. Infused albumin can also exhibit protective effects by binding to the cirrhosis-induced proinflammatory cytokines TNFα and IL6. While albumin administration has shown to prolong overall survival of cirrhotic patients with ascites in the ANSWER trial, the ATTIRE and MACHT trials have shown either no effect or limitations such as development of pulmonary oedema and multiorgan failure. Thus, albumin infusion is not a generic treatment option for all cirrhosis patients. Interestingly, cirrhosis-induced structural alterations in native albumin (which lead to formation of different albumin isoforms) can be used as prognostic biomarkers because specific albumin isoforms indicate certain complications of decompensated cirrhosis.
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Affiliation(s)
- Mohamed A Heybe
- GKT School of Medical Education, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - Kosha J Mehta
- Centre for Education, Faculty of Life Sciences and Medicine, King's College London, London, UK.
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3
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Verkhratsky A, Butt A, Li B, Illes P, Zorec R, Semyanov A, Tang Y, Sofroniew MV. Astrocytes in human central nervous system diseases: a frontier for new therapies. Signal Transduct Target Ther 2023; 8:396. [PMID: 37828019 PMCID: PMC10570367 DOI: 10.1038/s41392-023-01628-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Revised: 08/15/2023] [Accepted: 08/22/2023] [Indexed: 10/14/2023] Open
Abstract
Astroglia are a broad class of neural parenchymal cells primarily dedicated to homoeostasis and defence of the central nervous system (CNS). Astroglia contribute to the pathophysiology of all neurological and neuropsychiatric disorders in ways that can be either beneficial or detrimental to disorder outcome. Pathophysiological changes in astroglia can be primary or secondary and can result in gain or loss of functions. Astroglia respond to external, non-cell autonomous signals associated with any form of CNS pathology by undergoing complex and variable changes in their structure, molecular expression, and function. In addition, internally driven, cell autonomous changes of astroglial innate properties can lead to CNS pathologies. Astroglial pathophysiology is complex, with different pathophysiological cell states and cell phenotypes that are context-specific and vary with disorder, disorder-stage, comorbidities, age, and sex. Here, we classify astroglial pathophysiology into (i) reactive astrogliosis, (ii) astroglial atrophy with loss of function, (iii) astroglial degeneration and death, and (iv) astrocytopathies characterised by aberrant forms that drive disease. We review astroglial pathophysiology across the spectrum of human CNS diseases and disorders, including neurotrauma, stroke, neuroinfection, autoimmune attack and epilepsy, as well as neurodevelopmental, neurodegenerative, metabolic and neuropsychiatric disorders. Characterising cellular and molecular mechanisms of astroglial pathophysiology represents a new frontier to identify novel therapeutic strategies.
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Affiliation(s)
- Alexei Verkhratsky
- International Joint Research Centre on Purinergic Signalling/School of Health and Rehabilitation, Chengdu University of Traditional Chinese Medicine, Chengdu, China.
- Department of Forensic Analytical Toxicology, School of Forensic Medicine, China Medical University, Shenyang, China.
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.
- Achucarro Centre for Neuroscience, IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.
- Department of Stem Cell Biology, State Research Institute Centre for Innovative Medicine, LT-01102, Vilnius, Lithuania.
| | - Arthur Butt
- Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK
| | - Baoman Li
- Department of Forensic Analytical Toxicology, School of Forensic Medicine, China Medical University, Shenyang, China
| | - Peter Illes
- International Joint Research Centre on Purinergic Signalling/School of Health and Rehabilitation, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- Rudolf Boehm Institute for Pharmacology and Toxicology, University of Leipzig, 04109, Leipzig, Germany
| | - Robert Zorec
- Celica Biomedical, Lab Cell Engineering, Technology Park, 1000, Ljubljana, Slovenia
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia
| | - Alexey Semyanov
- Department of Physiology, Jiaxing University College of Medicine, 314033, Jiaxing, China
| | - Yong Tang
- International Joint Research Centre on Purinergic Signalling/School of Health and Rehabilitation, Chengdu University of Traditional Chinese Medicine, Chengdu, China.
- Key Laboratory of Acupuncture for Senile Disease (Chengdu University of TCM), Ministry of Education/Acupuncture and Chronobiology Key Laboratory of Sichuan Province, Chengdu, China.
| | - Michael V Sofroniew
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
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Jo D, Lim YH, Jung YS, Kim YK, Song J. Circular RNA Tmcc1 improves astrocytic glutamate metabolism and spatial memory via NF-κB and CREB signaling in a bile duct ligation mouse model: transcriptional and cellular analyses. J Neuroinflammation 2023; 20:121. [PMID: 37217942 DOI: 10.1186/s12974-023-02806-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 05/16/2023] [Indexed: 05/24/2023] Open
Abstract
BACKGROUND Hepatic encephalopathy-induced hyperammonemia alters astrocytic glutamate metabolism in the brain, which is involved in cognitive decline. To identify specific therapeutic strategies for the treatment of hepatic encephalopathy, various molecular signaling studies, such as non-coding RNA functional study, have been conducted. However, despite several reports of circular RNAs (circRNAs) in the brain, few studies of circRNAs in hepatic encephalopathy-induced neuropathophysiological diseases have been conducted. METHODS In this study, we performed RNA sequencing to identify whether the candidate circRNA cirTmcc1 is specifically expressed in the brain cortex in a bile duct ligation (BDL) mouse model of hepatic encephalopathy. RESULTS Based on transcriptional and cellular analysis, we investigated the circTmcc1-dysregulation-induced changes in the expression of several genes that are associated with intracellular metabolism and astrocyte function. We found that the circTmcc1 binds with the NF-κB p65-CREB transcriptional complex and regulates the expression of the astrocyte transporter EAAT2. Furthermore, circTmcc1 contributed to the secretion of proinflammatory mediators and glutamate metabolism in astrocytes and subsequently modulated an improvement in spatial memory by mediating neuronal synaptic plasticity. CONCLUSIONS Thus, circTmcc1 may be a promising circRNA candidate for targeted interventions to prevent and treat the neuropathophysiological complications that occur due to hepatic encephalopathy.
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Affiliation(s)
- Danbi Jo
- Department of Anatomy, Chonnam National University Medical School, Seoyangro 264, Jeollanam-Do, Hwasun, 58128, Republic of Korea
- Chonnam National University, Seoyangro 264, Hwasun, 58128, Republic of Korea
| | - Yeong-Hwan Lim
- Department of Biochemistry, Chonnam National University Medical School, Seoyangro 264, Hwasun, 58128, Republic of Korea
| | - Yoon Seok Jung
- Department of Anatomy, Chonnam National University Medical School, Seoyangro 264, Jeollanam-Do, Hwasun, 58128, Republic of Korea
| | - Young-Kook Kim
- Department of Biochemistry, Chonnam National University Medical School, Seoyangro 264, Hwasun, 58128, Republic of Korea
| | - Juhyun Song
- Department of Anatomy, Chonnam National University Medical School, Seoyangro 264, Jeollanam-Do, Hwasun, 58128, Republic of Korea.
- Chonnam National University, Seoyangro 264, Hwasun, 58128, Republic of Korea.
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5
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Shahbazi A, Sepehrinezhad A, Vahdani E, Jamali R, Ghasempour M, Massoudian S, Sahab Negah S, Larsen FS. Gut Dysbiosis and Blood-Brain Barrier Alteration in Hepatic Encephalopathy: From Gut to Brain. Biomedicines 2023; 11:1272. [PMID: 37238943 PMCID: PMC10215854 DOI: 10.3390/biomedicines11051272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Revised: 03/20/2023] [Accepted: 03/28/2023] [Indexed: 05/28/2023] Open
Abstract
A common neuropsychiatric complication of advanced liver disease, hepatic encephalopathy (HE), impacts the quality of life and length of hospital stays. There is new evidence that gut microbiota plays a significant role in brain development and cerebral homeostasis. Microbiota metabolites are providing a new avenue of therapeutic options for several neurological-related disorders. For instance, the gut microbiota composition and blood-brain barrier (BBB) integrity are altered in HE in a variety of clinical and experimental studies. Furthermore, probiotics, prebiotics, antibiotics, and fecal microbiota transplantation have been shown to positively affect BBB integrity in disease models that are potentially extendable to HE by targeting gut microbiota. However, the mechanisms that underlie microbiota dysbiosis and its effects on the BBB are still unclear in HE. To this end, the aim of this review was to summarize the clinical and experimental evidence of gut dysbiosis and BBB disruption in HE and a possible mechanism.
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Affiliation(s)
- Ali Shahbazi
- Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran 1449614535, Iran; (A.S.); (S.M.)
- Department of Neuroscience, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences, Tehran 1449614535, Iran;
| | - Ali Sepehrinezhad
- Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran 1449614535, Iran; (A.S.); (S.M.)
- Department of Neuroscience, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences, Tehran 1449614535, Iran;
- Neuroscience Research Center, Mashhad University of Medical Sciences, Mashhad 9919191778, Iran
| | - Edris Vahdani
- Department of Microbiology, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari 4815733971, Iran;
| | - Raika Jamali
- Research Development Center, Sina Hospital, Tehran University of Medical Sciences, Tehran 1417653761, Iran
- Digestive Disease Research Institute, Tehran University of Medical Sciences, Tehran 1417653761, Iran
| | - Monireh Ghasempour
- Department of Neuroscience, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences, Tehran 1449614535, Iran;
| | - Shirin Massoudian
- Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran 1449614535, Iran; (A.S.); (S.M.)
| | - Sajad Sahab Negah
- Neuroscience Research Center, Mashhad University of Medical Sciences, Mashhad 9919191778, Iran
- Department of Neuroscience, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad 9919191778, Iran
- Shefa Neuroscience Research Center, Khatam Alanbia Hospital, Tehran 9815733169, Iran
| | - Fin Stolze Larsen
- Department of Intestinal Failure and Liver Diseases, Rigshospitalet, Inge Lehmanns Vej 5, 2100 Copenhagen, Denmark
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Gu L, Yin X, Cheng Y, Wang X, Zhang M, Zou X, Wang L, Zhuge Y, Zhang F. Overweight/Obesity Increases the Risk of Overt Hepatic Encephalopathy after Transjugular Intrahepatic Portosystemic Shunt in Cirrhotic Patients. J Pers Med 2023; 13:jpm13040682. [PMID: 37109068 PMCID: PMC10141800 DOI: 10.3390/jpm13040682] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 04/12/2023] [Accepted: 04/17/2023] [Indexed: 04/29/2023] Open
Abstract
The purpose of this study was to investigate the effect of body mass index (BMI) on the prevalence of overt hepatic encephalopathy (OHE) after the transjugular intrahepatic portosystemic shunt (TIPS) procedure in decompensated cirrhotic patients. A retrospective observational cohort study of 145 cirrhotic patients receiving TIPS was carried out in our department from 2017 to 2020. The relationships between BMI and clinical outcomes including OHE, as well as risk factors of developing post-TIPS OHE, were analyzed. BMI was categorized as normal weight (18.5 ≤ BMI < 23.0 kg/m2), underweight (BMI < 18.5 kg/m2), and overweight/obese (BMI ≥ 23.0 kg/m2). Among the 145 patients, 52 (35.9%) were overweight/obese and 50 (34%) had post-TIPS OHE. Overweight/obese patients more frequently had OHE compared with normal weight patients (OR: 2.754, 95% CI: 1.236-6.140; p = 0.013). Overweight/obesity (p = 0.013) and older age (p = 0.030) were independent risk factors for post-TIPS OHE according to the logistic regression analysis. Kaplan-Meier curve analysis suggested that overweight/obese patients had the highest cumulative incidence of OHE (log-rank p = 0.0118). In conclusion, overweight/obesity and older age may raise the risk of post-TIPS OHE in cirrhotic patients.
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Affiliation(s)
- Lihong Gu
- Department of Gastroenterology, Affiliated Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210008, China
| | - Xiaochun Yin
- Department of Gastroenterology, Affiliated Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210008, China
| | - Yang Cheng
- Department of Gastroenterology, Affiliated Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210008, China
| | - Xixuan Wang
- Department of Gastroenterology, Affiliated Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210008, China
| | - Ming Zhang
- Department of Gastroenterology, Affiliated Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210008, China
| | - Xiaoping Zou
- Department of Gastroenterology, Affiliated Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210008, China
| | - Lei Wang
- Department of Gastroenterology, Affiliated Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210008, China
| | - Yuzheng Zhuge
- Department of Gastroenterology, Affiliated Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210008, China
| | - Feng Zhang
- Department of Gastroenterology, Affiliated Drum Tower Hospital, Medical School, Nanjing University, Nanjing 210008, China
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Sepehrinezhad A, Stolze Larsen F, Ashayeri Ahmadabad R, Shahbazi A, Sahab Negah S. The Glymphatic System May Play a Vital Role in the Pathogenesis of Hepatic Encephalopathy: A Narrative Review. Cells 2023; 12:cells12070979. [PMID: 37048052 PMCID: PMC10093707 DOI: 10.3390/cells12070979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 02/20/2023] [Accepted: 03/21/2023] [Indexed: 04/14/2023] Open
Abstract
Hepatic encephalopathy (HE) is a neurological complication of liver disease resulting in cognitive, psychiatric, and motor symptoms. Although hyperammonemia is a key factor in the pathogenesis of HE, several other factors have recently been discovered. Among these, the impairment of a highly organized perivascular network known as the glymphatic pathway seems to be involved in the progression of some neurological complications due to the accumulation of misfolded proteins and waste substances in the brain interstitial fluids (ISF). The glymphatic system plays an important role in the clearance of brain metabolic derivatives and prevents aggregation of neurotoxic agents in the brain ISF. Impairment of it will result in aggravated accumulation of neurotoxic agents in the brain ISF. This could also be the case in patients with liver failure complicated by HE. Indeed, accumulation of some metabolic by-products and agents such as ammonia, glutamine, glutamate, and aromatic amino acids has been reported in the human brain ISF using microdialysis technique is attributed to worsening of HE and correlates with brain edema. Furthermore, it has been reported that the glymphatic system is impaired in the olfactory bulb, prefrontal cortex, and hippocampus in an experimental model of HE. In this review, we discuss different factors that may affect the function of the glymphatic pathways and how these changes may be involved in HE.
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Affiliation(s)
- Ali Sepehrinezhad
- Department of Neuroscience, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences, Tehran 1449614535, Iran
- Neuroscience Research Center, Mashhad University of Medical Sciences, Mashhad 9919191778, Iran
| | - Fin Stolze Larsen
- Department of Gastroenterology and Hepatology, Rigshospitalet, Copenhagen University Hospital, 999017 Copenhagen, Denmark
| | | | - Ali Shahbazi
- Department of Neuroscience, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences, Tehran 1449614535, Iran
- Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran 1449614535, Iran
| | - Sajad Sahab Negah
- Neuroscience Research Center, Mashhad University of Medical Sciences, Mashhad 9919191778, Iran
- Shefa Neuroscience Research Center, Khatam Alanbia Hospital, Tehran 1449614535, Iran
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Häussinger D, Dhiman RK, Felipo V, Görg B, Jalan R, Kircheis G, Merli M, Montagnese S, Romero-Gomez M, Schnitzler A, Taylor-Robinson SD, Vilstrup H. Hepatic encephalopathy. Nat Rev Dis Primers 2022; 8:43. [PMID: 35739133 DOI: 10.1038/s41572-022-00366-6] [Citation(s) in RCA: 55] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/12/2022] [Indexed: 01/18/2023]
Abstract
Hepatic encephalopathy (HE) is a prognostically relevant neuropsychiatric syndrome that occurs in the course of acute or chronic liver disease. Besides ascites and variceal bleeding, it is the most serious complication of decompensated liver cirrhosis. Ammonia and inflammation are major triggers for the appearance of HE, which in patients with liver cirrhosis involves pathophysiologically low-grade cerebral oedema with oxidative/nitrosative stress, inflammation and disturbances of oscillatory networks in the brain. Severity classification and diagnostic approaches regarding mild forms of HE are still a matter of debate. Current medical treatment predominantly involves lactulose and rifaximin following rigorous treatment of so-called known HE precipitating factors. New treatments based on an improved pathophysiological understanding are emerging.
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Affiliation(s)
- Dieter Häussinger
- Department of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
| | - Radha K Dhiman
- Department of Hepatology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, (Uttar Pradesh), India
| | - Vicente Felipo
- Laboratory of Neurobiology, Centro de Investigación Principe Felipe, Valencia, Spain
| | - Boris Görg
- Department of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Rajiv Jalan
- Liver Failure Group ILDH, Division of Medicine, UCL Medical School, Royal Free Campus, London, UK.,European Foundation for the Study of Chronic Liver Failure, Barcelona, Spain
| | - Gerald Kircheis
- Department of Gastroenterology, Diabetology and Hepatology, University Hospital Brandenburg an der Havel, Brandenburg Medical School, Brandenburg an der Havel, Germany
| | - Manuela Merli
- Department of Translational and Precision Medicine, Universita' degli Studi di Roma - Sapienza, Roma, Italy
| | | | - Manuel Romero-Gomez
- UCM Digestive Diseases, Virgen del Rocío University Hospital, Institute of Biomedicine of Seville (HUVR/CSIC/US), University of Seville, Seville, Spain
| | - Alfons Schnitzler
- Institute of Clinical Neuroscience and Medical Psychology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Simon D Taylor-Robinson
- Department of Surgery and Cancer, St. Mary's Hospital Campus, Imperial College London, London, UK
| | - Hendrik Vilstrup
- Department of Hepatology and Gastroenterology, Aarhus University Hospital, Aarhus, Denmark
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Zielińska M, Albrecht J, Popek M. Dysregulation of Astrocytic Glutamine Transport in Acute Hyperammonemic Brain Edema. Front Neurosci 2022; 16:874750. [PMID: 35733937 PMCID: PMC9207324 DOI: 10.3389/fnins.2022.874750] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 05/17/2022] [Indexed: 11/13/2022] Open
Abstract
Acute liver failure (ALF) impairs ammonia clearance from blood, which gives rise to acute hyperammonemia and increased ammonia accumulation in the brain. Since in brain glutamine synthesis is the only route of ammonia detoxification, hyperammonemia is as a rule associated with increased brain glutamine content (glutaminosis) which correlates with and contributes along with ammonia itself to hyperammonemic brain edema-associated with ALF. This review focuses on the effects of hyperammonemia on the two glutamine carriers located in the astrocytic membrane: Slc38a3 (SN1, SNAT3) and Slc7a6 (y + LAT2). We emphasize the contribution of the dysfunction of either of the two carriers to glutaminosis- related aspects of brain edema: retention of osmotically obligated water (Slc38a3) and induction of oxidative/nitrosative stress (Slc7a6). The changes in glutamine transport link glutaminosis- evoked mitochondrial dysfunction to oxidative-nitrosative stress as formulated in the “Trojan Horse” hypothesis.
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Arjunan A, Sah DK, Jung YD, Song J. Hepatic Encephalopathy and Melatonin. Antioxidants (Basel) 2022; 11:antiox11050837. [PMID: 35624703 PMCID: PMC9137547 DOI: 10.3390/antiox11050837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Revised: 04/06/2022] [Accepted: 04/24/2022] [Indexed: 11/25/2022] Open
Abstract
Hepatic encephalopathy (HE) is a severe metabolic syndrome linked with acute/chronic hepatic disorders. HE is also a pernicious neuropsychiatric complication associated with cognitive decline, coma, and death. Limited therapies are available to treat HE, which is formidable to oversee in the clinic. Thus, determining a novel therapeutic approach is essential. The pathogenesis of HE has not been well established. According to various scientific reports, neuropathological symptoms arise due to excessive accumulation of ammonia, which is transported to the brain via the blood–brain barrier (BBB), triggering oxidative stress and inflammation, and disturbing neuronal-glial functions. The treatment of HE involves eliminating hyperammonemia by enhancing the ammonia scavenging mechanism in systemic blood circulation. Melatonin is the sole endogenous hormone linked with HE. Melatonin as a neurohormone is a potent antioxidant that is primarily synthesized and released by the brain’s pineal gland. Several HE and liver cirrhosis clinical studies have demonstrated impaired synthesis, secretion of melatonin, and circadian patterns. Melatonin can cross the BBB and is involved in various neuroprotective actions on the HE brain. Hence, we aim to elucidate how HE impairs brain functions, and elucidate the precise molecular mechanism of melatonin that reverses the HE effects on the central nervous system.
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Affiliation(s)
- Archana Arjunan
- Department of Anatomy, Chonnam National University Medical School, Hwasun 58128, Korea;
| | - Dhiraj Kumar Sah
- Department of Biochemistry, Chonnam National University Medical School, Hwasun 58128, Korea;
| | - Young Do Jung
- Department of Biochemistry, Chonnam National University Medical School, Hwasun 58128, Korea;
- Correspondence: (Y.D.J.); (J.S.); Tel.: +82-61-379-2706 (J.S.)
| | - Juhyun Song
- Department of Anatomy, Chonnam National University Medical School, Hwasun 58128, Korea;
- BioMedical Sciences Graduate Program (BMSGP), Chonnam National University, 264 Seoyangro, Hwasun 58128, Korea
- Correspondence: (Y.D.J.); (J.S.); Tel.: +82-61-379-2706 (J.S.)
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11
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Serum Ammonia in Cirrhosis: Clinical Impact of Hyperammonemia, Utility of Testing, and National Testing Trends. Clin Ther 2022; 44:e45-e57. [DOI: 10.1016/j.clinthera.2022.01.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/10/2022] [Accepted: 01/10/2022] [Indexed: 02/07/2023]
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Kolos EA, Korzhevskii DE. Glutamine Synthetase in the Cells of the Developing Rat Spinal Cord. Russ J Dev Biol 2021. [DOI: 10.1134/s1062360421050040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Egerton A, Dunn JT, Singh N, Yu Z, O'Doherty J, Koychev I, Webb J, Claridge S, Turkheimer FE, Marsden PK, Hammers A, Gee A. Evaluation of [ 13N]ammonia positron emission tomography as a potential method for quantifying glutamine synthetase activity in the human brain. EJNMMI Res 2020; 10:146. [PMID: 33270177 PMCID: PMC7714883 DOI: 10.1186/s13550-020-00731-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 11/21/2020] [Indexed: 11/22/2022] Open
Abstract
PURPOSE The conversion of synaptic glutamate to glutamine in astrocytes by glutamine synthetase (GS) is critical to maintaining healthy brain activity and may be disrupted in several brain disorders. As the GS catalysed conversion of glutamate to glutamine requires ammonia, we evaluated whether [13N]ammonia positron emission tomography (PET) could reliability quantify GS activity in humans. METHODS In this test-retest study, eight healthy volunteers each received two dynamic [13N]ammonia PET scans on the morning and afternoon of the same day. Each [13N]ammonia scan was preceded by a [15O]water PET scan to account for effects of cerebral blood flow (CBF). RESULTS Concentrations of radioactive metabolites in arterial blood were available for both sessions in five of the eight subjects. Our results demonstrated that kinetic modelling was unable to reliably distinguish estimates of the kinetic rate constant k3 (related to GS activity) from K1 (related to [13N]ammonia brain uptake), and indicated a non-negligible back-flux of [13N] to blood (k2). Model selection favoured a reversible one-tissue compartmental model, and [13N]ammonia K1 correlated reliably (r2 = 0.72-0.92) with [15O]water CBF. CONCLUSION The [13N]ammonia PET method was unable to reliably estimate GS activity in the human brain but may provide an alternative index of CBF.
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Affiliation(s)
- Alice Egerton
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, 16 De Crespigny Park, London, SE5 8AF, UK.
| | - Joel T Dunn
- School of Biomedical Engineering and Imaging Sciences, St Thomas' Hospital, King's College London, London, SE1 7EH, UK
- King's College London & Guy's and St. Thomas' PET Centre, London, SE1 7EH, UK
| | - Nisha Singh
- School of Biomedical Engineering and Imaging Sciences, St Thomas' Hospital, King's College London, London, SE1 7EH, UK
- King's College London & Guy's and St. Thomas' PET Centre, London, SE1 7EH, UK
- Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, SE5 7AF, UK
- Department of Psychiatry, Warneford Hospital, University of Oxford, Oxford, OX3 7JX, UK
| | - Zilin Yu
- School of Biomedical Engineering and Imaging Sciences, St Thomas' Hospital, King's College London, London, SE1 7EH, UK
| | - Jim O'Doherty
- School of Biomedical Engineering and Imaging Sciences, St Thomas' Hospital, King's College London, London, SE1 7EH, UK
- King's College London & Guy's and St. Thomas' PET Centre, London, SE1 7EH, UK
- Clinical Imaging Research Centre, National University of Singapore, Singapore, 117599, Singapore
| | - Ivan Koychev
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, 16 De Crespigny Park, London, SE5 8AF, UK
- Department of Psychiatry, Warneford Hospital, University of Oxford, Oxford, OX3 7JX, UK
| | - Jessica Webb
- School of Biomedical Engineering and Imaging Sciences, St Thomas' Hospital, King's College London, London, SE1 7EH, UK
| | - Simon Claridge
- School of Biomedical Engineering and Imaging Sciences, St Thomas' Hospital, King's College London, London, SE1 7EH, UK
| | - Federico E Turkheimer
- Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, SE5 7AF, UK
| | - Paul K Marsden
- School of Biomedical Engineering and Imaging Sciences, St Thomas' Hospital, King's College London, London, SE1 7EH, UK
- King's College London & Guy's and St. Thomas' PET Centre, London, SE1 7EH, UK
| | - Alexander Hammers
- School of Biomedical Engineering and Imaging Sciences, St Thomas' Hospital, King's College London, London, SE1 7EH, UK
- King's College London & Guy's and St. Thomas' PET Centre, London, SE1 7EH, UK
| | - Antony Gee
- School of Biomedical Engineering and Imaging Sciences, St Thomas' Hospital, King's College London, London, SE1 7EH, UK
- King's College London & Guy's and St. Thomas' PET Centre, London, SE1 7EH, UK
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Ding L, Zhang F, He Q, Li Z, Shi X, Li R, Zhang X. Differentiation of suprasellar meningiomas from non-functioning pituitary macroadenomas by 18F-FDG and 13N-Ammonia PET/CT. BMC Cancer 2020; 20:564. [PMID: 32552842 PMCID: PMC7301455 DOI: 10.1186/s12885-020-06852-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 04/12/2020] [Indexed: 12/30/2022] Open
Abstract
Background Differentiation of suprasellar meningiomas (SSMs) from non-functioning pituitary macroadenomas (NFPMAs) is useful for clinical management. We investigated the utility of 13N-ammonia combined with 18F-FDG positron emission tomography (PET)/computed tomography (CT) in distinguishing SSMs from NFPMAs retrospectively. Methods Fourteen NFPMA patients and eleven SSM patients with histopathologic diagnosis were included in this study. Every patient underwent both 18F-FDG and 13N-ammonia PET/CT scans. The tumor to gray matter (T/G) ratios were calculated for the evaluation of tumor uptake. Results The uptake of 18F-FDG was higher in NFPMAs than SSMs, whereas the uptake of 13N-ammonia was obviously lower in NFPMAs than SSMs. The differences of 18F-FDG and 13N-ammonia uptake between the two groups were significant respectively (0.92[0.46] vs 0.59[0.29], P < 0.05, 18F-FDG; 1.58 ± 0.56 vs 2.80 ± 1.45, P < 0.05, 13N-ammonia). Tumor classification demonstrated a high overall accuracy of 96.0% for differential diagnosis. When the two traces were combined, only 1 SSM was misclassified into the NFPMA group. Conclusion SSMs and NFPMAs have different metabolic characteristics on 18F-FDG and 13N-ammonia PET images. The combination of these two tracers can effectively distinguish SSMs from NFPMAs.
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Affiliation(s)
- Lei Ding
- Department of the Medical Imaging, The First Affiliated Hospital, Sun Yat-sen University, 58# Zhongshan Er Road, Guangzhou, Guangdong Province, 510080, People's Republic of China
| | - Fangling Zhang
- Department of the Medical Imaging, The First Affiliated Hospital, Sun Yat-sen University, 58# Zhongshan Er Road, Guangzhou, Guangdong Province, 510080, People's Republic of China.,Department of Radiology, Hospital of Stomatology, Guanghua School of Stomatology, Sun Yat-sen University; Guangdong Provincial Key Laboratory of Stomatology, 56#, Cemetery west Road, Guangzhou, Guangdong Province, 510055, People's Republic of China
| | - Qiao He
- Department of the Medical Imaging, The First Affiliated Hospital, Sun Yat-sen University, 58# Zhongshan Er Road, Guangzhou, Guangdong Province, 510080, People's Republic of China
| | - Zhoulei Li
- Department of the Medical Imaging, The First Affiliated Hospital, Sun Yat-sen University, 58# Zhongshan Er Road, Guangzhou, Guangdong Province, 510080, People's Republic of China
| | - Xinchong Shi
- Department of the Medical Imaging, The First Affiliated Hospital, Sun Yat-sen University, 58# Zhongshan Er Road, Guangzhou, Guangdong Province, 510080, People's Republic of China
| | - Ruocheng Li
- Department of the Medical Imaging, The First Affiliated Hospital, Sun Yat-sen University, 58# Zhongshan Er Road, Guangzhou, Guangdong Province, 510080, People's Republic of China
| | - Xiangsong Zhang
- Department of the Medical Imaging, The First Affiliated Hospital, Sun Yat-sen University, 58# Zhongshan Er Road, Guangzhou, Guangdong Province, 510080, People's Republic of China.
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Dam G, Aamann L, Vistrup H, Gluud LL. The role of Branched Chain Amino Acids in the treatment of hepatic Encephalopathy. J Clin Exp Hepatol 2018; 8:448-451. [PMID: 30568347 PMCID: PMC6286665 DOI: 10.1016/j.jceh.2018.06.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Accepted: 06/11/2018] [Indexed: 12/12/2022] Open
Abstract
The relationship between intake of nutrients and Hepatic Encephalopathy (HE) dates back to the historical roots of experimental hepatology. Branched-Chain Amino Acids (BCAA; Isoleucine, leucine and valine) have attracted particular interest and in 1956 Müting described the amino acid pattern in patients with cirrhosis. The abnormal plasma pattern has been characterized by the ratio between BCAA and aromatic amino acids in plasma, the so called 'Fischer´s ratio'. This ratio has been associated with the grade of HE. Under normal conditions, ammonia detoxification predominantly takes place in the liver. When the liver fails, the homeostasis is altered and muscle tissue becomes the main alternative organ for at least temporary detoxification of ammonia. BCAA are believed to support this muscle ammonia detoxification and the ammonia lowering effect of BCAA has been intensely investigated. In this review the effect of BCAA on muscle ammonia metabolism and the protein sparing and anabolic effects of BCAA are discussed. A Cochrane metaanalysis showed that BCAA had beneficial effects on HE with a number needed to treat of 5 patients (RR 0.73, 95% CI 0.61 to 0.88). The combined evidence suggests that although the pathophysiology is poorly understood, there is evidence to support clinical benefits of BCAA. BCAAs enhance muscle mass and exert anabolic effects via stimulation of protein synthesis. The beneficial long-term effects of BCAA on HE could be related to these effects and not only related to Branched-Chain Amino Acid increased ammonia metabolism.
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Affiliation(s)
- Gitte Dam
- Department of Medicine V (Hepatology and Gastroenterology), Aarhus University Hospital, Aarhus, Denmark
- Address for correspondence: Gitte Dam, Department of Medicine V (Hepatology and Gastroenterology), Aarhus University Hospital, Aarhus, Denmark.
| | - Luise Aamann
- Department of Medicine V (Hepatology and Gastroenterology), Aarhus University Hospital, Aarhus, Denmark
| | - Hendrik Vistrup
- Department of Medicine V (Hepatology and Gastroenterology), Aarhus University Hospital, Aarhus, Denmark
| | - Lise Lotte Gluud
- Department of Gastroenterology, Hvidovre Hospital, Copenhagen University, Hvidovre, Denmark
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Abstract
Delirium Tremens (DT) falls in the most severe spectrum of alcohol withdrawal, which could potentially result in death, unless managed promptly and adequately. The prevalence of DT in general population is <1% and nearly 2% in patients with alcohol dependence. DT presents with a combination of severe alcohol withdrawal symptoms and symptoms of delirium with agitation and sometimes hallucination. Clinical and laboratory parameters which predict DT have been discussed. Assessment of DT includes assessment of severity of alcohol withdrawal, evaluation of delirium, and screening for underlying medical co-morbidities. Liver disease as a co-morbidity is very common in patients with DT and that could complicate the clinical presentation, determine the treatment choice, and influence the outcome. Benzodiazepines are the mainstay of treatment for DT. Diazepam and lorazepam are preferred benzodiazepine, depending upon the treatment regime and clinical context. In benzodiazepine refractory cases, Phenobarbital, propofol, and dexmedetomidine could be used.
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17
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Wang W, Lu H, Lu X, Wang D, Wang Z, Dai W, Wang J, Liu P. Effect of tumor necrosis factor-α on the expression of the ammonia transporter Rhcg in the brain in mice with acute liver failure. J Neuroinflammation 2018; 15:234. [PMID: 30134917 PMCID: PMC6106833 DOI: 10.1186/s12974-018-1264-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 07/31/2018] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Ammonia and tumor necrosis factor-alpha (TNF-α) play important roles in the mechanisms of hepatic encephalopathy (HE). Rhesus glycoprotein C (Rhcg) is important for ammonia transport especially in the kidney. The aim of the present study was to investigate the role of Rhcg in the brain in acute liver failure (ALF) and the effect of TNF-α on Rhcg expression. METHODS ALF mouse models were generated by treatment with D-galactosamine (D-GalN) and lipopolysaccharide (LPS), or D-GalN and TNF-α. ALF induction was blocked by pretreatment with anti-TNF-α IgG. The levels of serum TNF-α were determined by ELISA. Blood ammonia and brain ammonia concentrations were detected using an ammonia assay kit. The expression and distribution of Rhcg in the brain tissues of ALF mice were examined by western blotting, real-time PCR, immunohistochemical, and immunofluorescence analyses. RESULTS Serum TNF-α levels were increased in the LPS/D-GalN group. Blood and brain ammonia were increased in the LPS/D-GalN- and TNF-α/D-GalN-induced ALF groups. Rhcg mRNA and protein levels were elevated in both ALF groups, consistent with the increase in blood and brain ammonia. Rhcg was mainly expressed in vascular endothelial cells and astrocytes. Pretreatment with anti-TNF-α IgG antibody downregulated Rhcg in brain tissues in the LPS/D-GalN group, prevented the occurrence of ALF, and reduced blood and brain ammonia levels in the LPS/D-GalN group. CONCLUSION TNF-α promoted the transport of ammonia from the blood to brain tissues and exacerbated the toxic effects of ammonia by upregulating Rhcg.
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Affiliation(s)
- Wen Wang
- Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Hui Lu
- Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Xu Lu
- Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Donglei Wang
- Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Zhaohan Wang
- Gastroenterology and Hepatology Department, Jiangxi Provincial People's Hospital, Nanchang City, Jiangxi Province, People's Republic of China
| | - Wenying Dai
- Department of Intervention, the Sixth People's Hospital of Shenyang, Shenyang City, Liaoning Province, People's Republic of China
| | - Jinyong Wang
- Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Pei Liu
- Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang, 110001, Liaoning Province, People's Republic of China. .,The Institute of Liver Diseases of China Medical University, Shenyang, Liaoning Province, China.
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Guo Q, Zhang QQ, Chen JQ, Zhang W, Qiu HC, Zhang ZJ, Liu BM, Xu FG. Liver metabolomics study reveals protective function of Phyllanthus urinaria against CCl 4-induced liver injury. Chin J Nat Med 2018; 15:525-533. [PMID: 28807226 DOI: 10.1016/s1875-5364(17)30078-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Indexed: 12/15/2022]
Abstract
Phyllanthus Urinaria L. (PUL) is a traditional Chinese medicine used to treat hepatic and renal disorders. However, the mechanism of its hepatoprotective action is not fully understood. In the present study, blood biochemical indexes and liver histopathological changes were used to estimate the extent of hepatic injury. GC/MS and LC/MS-based untargeted metabolomics were used in combination to characterize the potential biomarkers associated with the protective activity of PUL against CCl4-induced liver injury in rats. PUL treatment could reverse the increase in ALT, AST and ALP induced by CCl4 and attenuate the pathological changes in rat liver. Significant changes in liver metabolic profiling were observed in PUL-treated group compared with liver injury model group. Seventeen biomarkers related to the hepatoprotective effects of PUL against CCl4-induced liver injury were screened out using nonparametric test and Pearson's correlation analysis (OPLS-DA). The results suggested that the potential hepatoprotective effects of PUL in attenuating CCl4-induced hepatotoxicity could be partially attributed to regulating L-carnitine, taurocholic acid, and amino acids metabolism, which may become promising targets for treatment of liver toxicity. In conclusion, this study provides new insights into the mechanism of the hepatoprotection of Phyllanthus Urinaria.
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Affiliation(s)
- Qing Guo
- MOE Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Nanjing 210009, China; State key laboratory of natural medicine, China Pharmaceutical University, Nanjing 210009, China
| | - Qian-Qian Zhang
- MOE Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Nanjing 210009, China; State key laboratory of natural medicine, China Pharmaceutical University, Nanjing 210009, China
| | - Jia-Qing Chen
- MOE Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Nanjing 210009, China; State key laboratory of natural medicine, China Pharmaceutical University, Nanjing 210009, China
| | - Wei Zhang
- State Key Laboratory for Quality Research in Chinese Medicines, Macau University of Science & Technology, Avenida Wai Long, Taipa, Macau, China
| | - Hong-Cong Qiu
- Guangxi Key Laboratory of Traditional Chinese Medicine Quality Standards, Nanning 530022, China
| | - Zun-Jian Zhang
- MOE Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Nanjing 210009, China; State key laboratory of natural medicine, China Pharmaceutical University, Nanjing 210009, China
| | - Bu-Ming Liu
- Guangxi Key Laboratory of Traditional Chinese Medicine Quality Standards, Nanning 530022, China.
| | - Feng-Guo Xu
- MOE Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Nanjing 210009, China; State key laboratory of natural medicine, China Pharmaceutical University, Nanjing 210009, China.
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Modarres HP, Janmaleki M, Novin M, Saliba J, El-Hajj F, RezayatiCharan M, Seyfoori A, Sadabadi H, Vandal M, Nguyen MD, Hasan A, Sanati-Nezhad A. In vitro models and systems for evaluating the dynamics of drug delivery to the healthy and diseased brain. J Control Release 2018; 273:108-130. [PMID: 29378233 DOI: 10.1016/j.jconrel.2018.01.024] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Revised: 01/22/2018] [Accepted: 01/23/2018] [Indexed: 12/12/2022]
Abstract
The blood-brain barrier (BBB) plays a crucial role in maintaining brain homeostasis and transport of drugs to the brain. The conventional animal and Transwell BBB models along with emerging microfluidic-based BBB-on-chip systems have provided fundamental functionalities of the BBB and facilitated the testing of drug delivery to the brain tissue. However, developing biomimetic and predictive BBB models capable of reasonably mimicking essential characteristics of the BBB functions is still a challenge. In addition, detailed analysis of the dynamics of drug delivery to the healthy or diseased brain requires not only biomimetic BBB tissue models but also new systems capable of monitoring the BBB microenvironment and dynamics of barrier function and delivery mechanisms. This review provides a comprehensive overview of recent advances in microengineering of BBB models with different functional complexity and mimicking capability of healthy and diseased states. It also discusses new technologies that can make the next generation of biomimetic human BBBs containing integrated biosensors for real-time monitoring the tissue microenvironment and barrier function and correlating it with the dynamics of drug delivery. Such integrated system addresses important brain drug delivery questions related to the treatment of brain diseases. We further discuss how the combination of in vitro BBB systems, computational models and nanotechnology supports for characterization of the dynamics of drug delivery to the brain.
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Affiliation(s)
- Hassan Pezeshgi Modarres
- BioMEMS and Bioinspired Microfluidic Laboratory, Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Canada; Center for BioEngineering Research and Education, University of Calgary, Calgary, Canada
| | - Mohsen Janmaleki
- BioMEMS and Bioinspired Microfluidic Laboratory, Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Canada; Center for BioEngineering Research and Education, University of Calgary, Calgary, Canada
| | - Mana Novin
- BioMEMS and Bioinspired Microfluidic Laboratory, Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Canada; Center for BioEngineering Research and Education, University of Calgary, Calgary, Canada
| | - John Saliba
- Biomedical Engineering, Department of Mechanical Engineering, Faculty of Engineering and Architecture, American University of Beirut, Beirut 1107 2020, Lebanon
| | - Fatima El-Hajj
- Biomedical Engineering, Department of Mechanical Engineering, Faculty of Engineering and Architecture, American University of Beirut, Beirut 1107 2020, Lebanon
| | - Mahdi RezayatiCharan
- Breast Cancer Research Center (BCRC), ACECR, Tehran, Iran; School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran
| | - Amir Seyfoori
- Breast Cancer Research Center (BCRC), ACECR, Tehran, Iran; School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran, Iran
| | - Hamid Sadabadi
- BioMEMS and Bioinspired Microfluidic Laboratory, Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Canada; Center for BioEngineering Research and Education, University of Calgary, Calgary, Canada
| | - Milène Vandal
- Departments of Clinical Neurosciences, Cell Biology and Anatomy, Biochemistry and Molecular Biology, University of Calgary, Calgary, Canada
| | - Minh Dang Nguyen
- Departments of Clinical Neurosciences, Cell Biology and Anatomy, Biochemistry and Molecular Biology, University of Calgary, Calgary, Canada
| | - Anwarul Hasan
- Biomedical Engineering, Department of Mechanical Engineering, Faculty of Engineering and Architecture, American University of Beirut, Beirut 1107 2020, Lebanon; Department of Mechanical and Industrial Engineering, College of Engineering, Qatar University, Doha, 2713, Qatar
| | - Amir Sanati-Nezhad
- BioMEMS and Bioinspired Microfluidic Laboratory, Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Canada; Center for BioEngineering Research and Education, University of Calgary, Calgary, Canada.
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Soares AF, Lei H. Non-invasive diagnosis and metabolic consequences of congenital portosystemic shunts in C57BL/6 J mice. NMR IN BIOMEDICINE 2018; 31:e3873. [PMID: 29266459 DOI: 10.1002/nbm.3873] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 10/31/2017] [Accepted: 11/02/2017] [Indexed: 06/07/2023]
Abstract
This study demonstrates the suitability of magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) for the imaging of congenital portosystemic shunts (PSS) in mice, a vascular abnormality in which mesenteric blood bypasses the liver and is instead drained directly to the systemic circulation. The non-invasive diagnosis performed in tandem with other experimental assessments permits further characterization of liver, whole-body and brain metabolic defects associated with PSS. Magnetic resonance measurements were performed in a 26-cm, horizontal-bore, 14.1-T magnet. MRA was obtained with a three-dimensional gradient echo sequence (GRE; in-plane resolution, 234 × 250 × 234 μm3 ) using a birdcage coil. Two-dimensional GRE MRI with high spatial resolution (in-plane resolution, 100 × 130 μm2 ; slices, 30 × 0.3 mm) was performed using a surface coil. Brain- (dorsal hippocampus) and liver-localized 1 H magnetic resonance spectroscopy (MRS) was also performed with the surface coil. Whole-body metabolic status was evaluated with an oral glucose tolerance test (OGTT). Both MRA and anatomical MRI allowed the identification of hepatic vessels and the diagnosis of PSS in mice. The incidence of PSS was about 10%. Hepatic lipid content was higher in PSS than in control mice (5.1 ± 2.8% versus 1.8 ± 0.6%, p = 0.02). PSS mice had higher brain glutamine concentration than controls (7.3 ± 1.0 μmol/g versus 2.7 ± 0.6 μmol/g, p < 0.0001) and, conversely, lower myo-inositol (4.2 ± 0.6 μmol/g versus 6.0 ± 0.4 μmol/g, p < 0.0001), taurine (9.7 ± 1.2 μmol/g versus 11.0 ± 0.4 μmol/g, p < 0.01) and total choline (0.9 ± 0.1 μmol/g versus 1.2 ± 0.1 μmol/g, p < 0.001) concentrations. Fasting blood glucose and plasma insulin were lower in PSS than in control mice (4.7 ± 0.5mM versus 8.8 ± 0.6mM, p < 0.0001; and 0.04 ± 0.03 μg/L versus 0.3 ± 0.2 μg/L, p = 0.02, respectively). Glucose clearance during OGTT was delayed and less efficient in PSS mice than in controls. Thus, given the non-negligible incidence of PSS in inbred mice, the undiagnosed presence of PSS will, importantly, have an impact on experimental outcomes, notably in studies addressing brain, liver or whole-body metabolism.
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Affiliation(s)
- Ana Francisca Soares
- École Polytechnique Fédérale de Lausanne - Laboratory for Functional and Metabolic Imaging (LIFMET), Lausanne, Switzerland
| | - Hongxia Lei
- École Polytechnique Fédérale de Lausanne, Center for Biomedical Imaging (CIBM), Lausanne, Switzerland
- University of Geneva, Department of Radiology, Faculty of Medicine, Geneva, Switzerland
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Peter MS, Simi S. Hypoxia Stress Modifies Na +/K +-ATPase, H +/K +-ATPase, [Formula: see text], and nkaα1 Isoform Expression in the Brain of Immune-Challenged Air-Breathing Fish. J Exp Neurosci 2017; 11:1179069517733732. [PMID: 29238219 PMCID: PMC5721975 DOI: 10.1177/1179069517733732] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 08/18/2017] [Indexed: 12/23/2022] Open
Abstract
Fishes are equipped to sense stressful stimuli and are able to respond to environmental stressor such as hypoxia with varying pattern of stress response. The functional attributes of brain to hypoxia stress in relation to ion transport and its interaction during immune challenge have not yet delineated in fish. We, therefore, explored the pattern of ion transporter functions and messenger RNA (mRNA) expression of α1-subunit isoforms of Na+/K+-ATPase (NKA) in the brain segments, namely, prosencephalon (PC), mesencephalon (MC), and metencephalon (MeC) in an obligate air-breathing fish exposed either to hypoxia stress (30 minutes forced immersion in water) or challenged with zymosan treatment (25-200 ng g−1 for 24 hours) or both. Zymosan that produced nonspecific immune responses evoked differential regulation of NKA, H+/K+-ATPase (HKA), and Na+/NH4+-ATPase (NNA) in the varied brain segments. On the contrary, hypoxia stress that demanded activation of NKA in PC and MeC showed a reversed NKA activity pattern in MeC of immune-challenged fish. A compromised HKA and NNA regulation during hypoxia stress was found in immune-challenged fish, indicating the role of these brain ion transporters to hypoxia stress and immune challenges. The differential mRNA expression of α1-subunit isoforms of NKA, nkaα1a, nkaα1b, and nkaα1c, in hypoxia-stressed brain showed a shift in its expression pattern during hypoxia stress-immune interaction in PC and MC. Evidence is thus presented for the first time that ion transporters such as HKA and NNA along with NKA act as functional brain markers which respond differentially to both hypoxia stress and immune challenges. Taken together, the data further provide evidence for a differential Na+, K+, H+, and NH4+ ion signaling that exists in brain neuronal clusters during hypoxia stress-immune interaction as a result of modified regulations of NKA, HKA, and NNA transporter functions and nkaα1 isoform regulation.
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Affiliation(s)
- Mc Subhash Peter
- Department of Zoology, University of Kerala, Thiruvananthapuram, India.,Inter-University Centre for Evolutionary and Integrative Biology, University of Kerala, Thiruvananthapuram, India
| | - Satheesan Simi
- Department of Zoology, University of Kerala, Thiruvananthapuram, India
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Or M, Devriendt N, Kitshoff AM, Peremans K, Vandermeulen E, Paepe D, Polis I, Martlé V, de Rooster H. Ammonia concentrations in arterial blood, venous blood, and cerebrospinal fluid of dogs with and without congenital extrahepatic portosystemic shunts. Am J Vet Res 2017; 78:1313-1318. [DOI: 10.2460/ajvr.78.11.1313] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Dhanda S, Sandhir R. Blood-Brain Barrier Permeability Is Exacerbated in Experimental Model of Hepatic Encephalopathy via MMP-9 Activation and Downregulation of Tight Junction Proteins. Mol Neurobiol 2017; 55:3642-3659. [PMID: 28523565 DOI: 10.1007/s12035-017-0521-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 04/06/2017] [Indexed: 12/27/2022]
Abstract
The present study was designed to investigate the mechanisms involved in blood-brain barrier (BBB) permeability in bile duct ligation (BDL) model of chronic hepatic encephalopathy (HE). Four weeks after BDL surgery, a significant increase was observed in serum bilirubin levels. Masson trichrome staining revealed severe hepatic fibrosis in the BDL rats. 99mTc-mebrofenin retention was increased in the liver of BDL rats suggesting impaired hepatobiliary transport. An increase in permeability to sodium fluorescein, Evans blue, and fluorescein isothiocyanate (FITC)-dextran along with increase in water and electrolyte content was observed in brain regions of BDL rats suggesting disrupted BBB. Increased brain water content can be attributed to increase in aquaporin-4 mRNA and protein expression in BDL rats. Matrix metalloproteinase-9 (MMP-9) mRNA and protein expression was increased in brain regions of BDL rats. Additionally, mRNA and protein expression of tissue inhibitor of matrix metalloproteinases (TIMPs) was also increased in different regions of brain. A significant decrease in mRNA expression and protein levels of tight junction proteins, viz., occludin, claudin-5, and zona occluden-1 (ZO-1) was observed in different brain regions of BDL rats. VCAM-1 mRNA and protein expression was also found to be significantly upregulated in different brain regions of BDL animals. The findings from the study suggest that increased BBB permeability in HE involves activation of MMP-9 and loss of tight junction proteins.
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Affiliation(s)
- Saurabh Dhanda
- Department of Biochemistry, Basic Medical Science Block-II, Sector-25, Panjab University, Chandigarh, 160014, India
| | - Rajat Sandhir
- Department of Biochemistry, Basic Medical Science Block-II, Sector-25, Panjab University, Chandigarh, 160014, India.
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Adlimoghaddam A, Sabbir MG, Albensi BC. Ammonia as a Potential Neurotoxic Factor in Alzheimer's Disease. Front Mol Neurosci 2016; 9:57. [PMID: 27551259 PMCID: PMC4976099 DOI: 10.3389/fnmol.2016.00057] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 07/06/2016] [Indexed: 11/13/2022] Open
Abstract
Ammonia is known to be a potent neurotoxin that causes severe negative effects on the central nervous system. Excessive ammonia levels have been detected in the brain of patients with neurological disorders such as Alzheimer disease (AD). Therefore, ammonia could be a factor contributing to the progression of AD. In this review, we provide an introduction to the toxicity of ammonia and putative ammonia transport proteins. We also hypothesize how ammonia may be linked to AD. Additionally, we discuss the evidence that support the hypothesis that ammonia is a key factor contributing to AD progression. Lastly, we summarize the old and new experimental evidence that focuses on energy metabolism, mitochondrial function, inflammatory responses, excitatory glutamatergic, and GABAergic neurotransmission, and memory in support of our ammonia-related hypotheses of AD.
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Affiliation(s)
- Aida Adlimoghaddam
- Division of Neurodegenerative Disorders, St. Boniface Hospital Research Winnipeg, MB, Canada
| | - Mohammad G Sabbir
- Division of Neurodegenerative Disorders, St. Boniface Hospital Research Winnipeg, MB, Canada
| | - Benedict C Albensi
- Division of Neurodegenerative Disorders, St. Boniface Hospital ResearchWinnipeg, MB, Canada; Department of Pharmacology & Therapeutics, University of ManitobaWinnipeg, MB, Canada
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Li Z, Ji X, Wang W, Liu J, Liang X, Wu H, Liu J, Eggert US, Liu Q, Zhang X. Ammonia Induces Autophagy through Dopamine Receptor D3 and MTOR. PLoS One 2016; 11:e0153526. [PMID: 27077655 PMCID: PMC4831814 DOI: 10.1371/journal.pone.0153526] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Accepted: 03/30/2016] [Indexed: 12/25/2022] Open
Abstract
Hyperammonemia is frequently seen in tumor microenvironments as well as in liver diseases where it can lead to severe brain damage or death. Ammonia induces autophagy, a mechanism that tumor cells may use to protect themselves from external stresses. However, how cells sense ammonia has been unclear. Here we show that culture medium alone containing Glutamine can generate milimolar of ammonia at 37 degrees in the absence of cells. In addition, we reveal that ammonia acts through the G protein-coupled receptor DRD3 (Dopamine receptor D3) to induce autophagy. At the same time, ammonia induces DRD3 degradation, which involves PIK3C3/VPS34-dependent pathways. Ammonia inhibits MTOR (mechanistic target of Rapamycin) activity and localization in cells, which is mediated by DRD3. Therefore, ammonia has dual roles in autophagy: one to induce autophagy through DRD3 and MTOR, the other to increase autophagosomal pH to inhibit autophagic flux. Our study not only adds a new sensing and output pathway for DRD3 that bridges ammonia sensing and autophagy induction, but also provides potential mechanisms for the clinical consequences of hyperammonemia in brain damage, neurodegenerative diseases and tumors.
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Affiliation(s)
- Zhiyuan Li
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, P. R. China
| | - Xinmiao Ji
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, P. R. China
| | - Wenchao Wang
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, P. R. China
| | - Juanjuan Liu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, P. R. China
- University of Science and Technology of China, Hefei, Anhui, P. R. China
| | - Xiaofei Liang
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, P. R. China
| | - Hong Wu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, P. R. China
- University of Science and Technology of China, Hefei, Anhui, P. R. China
| | - Jing Liu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, P. R. China
| | - Ulrike S Eggert
- Department of Chemistry and Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom
| | - Qingsong Liu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, P. R. China
- University of Science and Technology of China, Hefei, Anhui, P. R. China
| | - Xin Zhang
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, P. R. China
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Northrop NA, Halpin LE, Yamamoto BK. Peripheral ammonia and blood brain barrier structure and function after methamphetamine. Neuropharmacology 2016; 107:18-26. [PMID: 26972828 DOI: 10.1016/j.neuropharm.2016.03.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 03/07/2016] [Accepted: 03/09/2016] [Indexed: 01/28/2023]
Abstract
An effect of the widely abuse psychostimulant, methamphetamine (Meth), is blood-brain-barrier (BBB) disruption; however, the mechanism by which Meth causes BBB disruption remains unclear. Recently it has been shown that Meth produces liver damage and consequent increases in plasma ammonia. Ammonia can mediate oxidative stress and inflammation, both of which are known to cause BBB disruption. Therefore, the current studies examined the role of peripheral ammonia in Meth-induced disruption of BBB structure and function. A neurotoxic Meth regimen (10 mg/kg, ip, q 2 h, ×4) administered to rats increased plasma ammonia and active MMP-9 in the cortex 2 h after the last Meth injection, compared to saline treated rats. At 24 h after Meth treatment, decreased immunoreactivity of BBB structural proteins, occludin and claudin-5, and increased extravasation of 10,000 Da FITC-dextran were observed, as compared to saline controls. Pretreatment with lactulose (5.3 g/kg, po, q 12 h), a drug that remains in the lumen of the intestine and promotes ammonia excretion, prevented the Meth-induced increases in plasma ammonia. These results were paralleled by the prevention of decreases in BBB structural proteins, increases in extravasation of 10,000 Da FITC-dextran and increases in active MMP-9. The results indicate that Meth-induced increases in ammonia produce BBB disruption and suggest that MMP-9 activation mediates the BBB disruption. These findings identify a novel mechanism of Meth-induced BBB disruption that is mediated by plasma ammonia and are the first to identify a peripheral contribution to Meth-induced BBB disruption.
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Affiliation(s)
- Nicole A Northrop
- Department of Neurosciences, University of Toledo College of Medicine, 3000 Arlington Ave., Toledo, OH 43614, USA
| | - Laura E Halpin
- Department of Neurosciences, University of Toledo College of Medicine, 3000 Arlington Ave., Toledo, OH 43614, USA
| | - Bryan K Yamamoto
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202, USA.
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Montes S, Castro-Chávez A, Florian-Soto C, Heras-Romero Y, Ríos C, Rivera-Mancía S. Bumetanide increases manganese accumulation in the brain of rats with liver damage. Eur J Pharmacol 2016; 774:127-34. [DOI: 10.1016/j.ejphar.2016.02.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 01/26/2016] [Accepted: 02/03/2016] [Indexed: 11/30/2022]
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Patidar KR, Bajaj JS. Covert and Overt Hepatic Encephalopathy: Diagnosis and Management. Clin Gastroenterol Hepatol 2015; 13:2048-61. [PMID: 26164219 PMCID: PMC4618040 DOI: 10.1016/j.cgh.2015.06.039] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 06/30/2015] [Accepted: 06/30/2015] [Indexed: 02/06/2023]
Abstract
Hepatic encephalopathy (HE) is part of a spectrum of neurocognitive changes in cirrhosis. HE is divided into 2 broad categories based on severity: covert hepatic encephalopathy (CHE) and overt hepatic encephalopathy (OHE). CHE has a significant impact on a patient's quality of life, driving performance, and recently has been associated with increased hospitalizations and death. Likewise, OHE is associated with increased rates of hospitalizations and mortality, and poor quality of life. Given its significant burden on patients, care takers, and the health care system, early diagnosis and management are imperative. In addition, focus also should be directed on patient and family member education on the disease progression and adherence to medications. Treatment strategies include the use of nonabsorbable disaccharides, antibiotics (ie, rifaximin), and, potentially, probiotics. Other therapies currently under further investigation include L-ornithine-L-aspartate, ornithine phenylacetate, glycerol phenylbutyrate, molecular adsorbent recirculating system, and albumin infusion.
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Affiliation(s)
- Kavish R Patidar
- Division of Gastroenterology, Hepatology and Nutrition, Virginia Commonwealth University and McGuire VA Medical Center, Richmond, Virginia
| | - Jasmohan S Bajaj
- Division of Gastroenterology, Hepatology and Nutrition, Virginia Commonwealth University and McGuire VA Medical Center, Richmond, Virginia.
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Kimoloi S, Rashid K. Potential role of Plasmodium falciparum-derived ammonia in the pathogenesis of cerebral malaria. Front Neurosci 2015; 9:234. [PMID: 26190968 PMCID: PMC4490226 DOI: 10.3389/fnins.2015.00234] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 06/18/2015] [Indexed: 12/19/2022] Open
Abstract
Cerebral malaria (CM) is the most severe complication associated with Plasmodium falciparum infection. The exact pathogenic mechanisms leading to the development of CM remains poorly understood while the mortality rates remain high. Several potential mechanisms including mechanical obstruction of brain microvasculature, inflammation, oxidative stress, cerebral energy defects, and hemostatic dysfunction have been suggested to play a role in CM pathogenesis. However, these proposed mechanisms, even when considered together, do not fully explain the pathogenesis and clinicopathological features of human CM. This necessitates consideration of alternative pathogenic mechanisms. P. falciparum generates substantial amounts of ammonia as a catabolic by-product, but lacks detoxification mechanisms. Whether this parasite-derived ammonia plays a pathogenic role in CM is presently unknown, despite its potential to cause localized brain ammonia elevation and subsequent neurotoxic effects. This article therefore, explores and proposes a potential role of parasite-derived ammonia in the pathogenesis and neuropathology of CM. A consideration of parasite-derived ammonia as a factor in CM pathogenesis provides plausible explanations of the various features observed in CM patients including how a largely intravascular parasite can cause neuronal dysfunction. It also provides a framework for rational development and testing of novel drugs targeting the parasite's ammonia handling.
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Affiliation(s)
- Sammy Kimoloi
- Department of Medical Laboratory Sciences, Masinde Muliro University of Science and Technology Kakamega, Kenya
| | - Khalid Rashid
- Biochemistry and Molecular Biology Department, Egerton University Nakuru, Kenya
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Bobermin LD, Wartchow KM, Flores MP, Leite MC, Quincozes-Santos A, Gonçalves CA. Ammonia-induced oxidative damage in neurons is prevented by resveratrol and lipoic acid with participation of heme oxygenase 1. Neurotoxicology 2015; 49:28-35. [PMID: 26003724 DOI: 10.1016/j.neuro.2015.05.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 05/14/2015] [Accepted: 05/15/2015] [Indexed: 12/29/2022]
Abstract
Ammonia is a metabolite that, at high concentrations, is implicated in neurological disorders, such as hepatic encephalopathy (HE), which is associated with acute or chronic liver failure. Astrocytes are considered the primary target of ammonia toxicity in the central nervous system (CNS) because glutamine synthetase (GS), responsible for ammonia metabolism in CNS, is an astrocytic enzyme. Thus, neuronal dysfunction has been associated as secondary to astrocytic impairment. However, we demonstrated that ammonia can induce direct effects on neuronal cells. The cell viability was decreased by ammonia in SH-SY5Y cells and cerebellar granule neurons. In addition, ammonia induced increased reactive oxygen species (ROS) production and decreased GSH intracellular content, the main antioxidant in CNS. As ammonia neurotoxicity is strongly associated with oxidative stress, we also investigated the potential neuroprotective roles of the antioxidants, resveratrol (RSV) and lipoic acid (LA), against ammonia toxicity in cerebellar granule neurons. RSV and LA were able to prevent the oxidative damage induced by ammonia, maintaining the levels of ROS production and GSH close to basal values. Both antioxidants also decreased ROS production and increased GSH content under basal conditions (in the absence of ammonia). Moreover, we showed that heme oxygenase 1 (HO1), a protein associated with protection against stress conditions, is involved in the beneficial effects of RSV and LA in cerebellar granule neurons. Thus, this study reinforces the neuroprotective effects of RSV and LA. Although more studies in vivo are required, RSV and LA could represent interesting therapeutic strategies for the management of HE.
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Affiliation(s)
- Larissa Daniele Bobermin
- Department of Biochemistry, Institute of Basic Health Sciences, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.
| | - Krista Minéia Wartchow
- Department of Biochemistry, Institute of Basic Health Sciences, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Marianne Pires Flores
- Department of Biochemistry, Institute of Basic Health Sciences, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Marina Concli Leite
- Department of Biochemistry, Institute of Basic Health Sciences, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - André Quincozes-Santos
- Department of Biochemistry, Institute of Basic Health Sciences, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Carlos-Alberto Gonçalves
- Department of Biochemistry, Institute of Basic Health Sciences, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil
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Ott P, Vilstrup H. Cerebral effects of ammonia in liver disease: current hypotheses. Metab Brain Dis 2014; 29:901-11. [PMID: 24488230 DOI: 10.1007/s11011-014-9494-7] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2013] [Accepted: 01/21/2014] [Indexed: 12/15/2022]
Abstract
Hyperammonemia is necessary for development of the cerebral complications to liver disease including hepatic encephalopathy and cerebral edema but the mechanisms are unclear. Ammonia is taken up by the brain in proportion to its arterial concentration. The flux into the brain is most likely by both diffusion of NH3 and mediated transport of NH4 (+) . Astrocytic detoxification of ammonia involves formation of glutamine at concentrations high enough to produce cellular edema, but compensatory mechanisms reduce this effect. Glutamine can be taken up by astrocytic mitochondria and initiate the mitochondrial permeability transition but the clinical relevance is uncertain. Elevated astrocytic glutamine interferes with neurotransmission. Thus, animal studies show enhanced glutamatergic neurotransmission via the NMDA receptor which may be related to the acute cerebral complications to liver failure, while impairment of the NMDA activated glutamate-NO-cGMP pathway could relate to the behavioural changes seen in hepatic encephalopathy. Elevated glutamine also increases GABA-ergic tone, an effect which is aggravated by mitochondrial production of neurosteroids; this may relate to decreased neurotransmission and precipitation of encephalopathy by GABA targeting drugs. Hyperammonemia may compromise cerebral energy metabolism as elevated cerebral lactate is generally reported. Hypoxia is unlikely since cerebral oxygen:glucose utilisation and lactate:pyruvate ratio are both normal in clinical studies. Ammonia inhibits α-ketoglutaratedehydrogenase in isolated mitochondria, but the clinical relevance is dubious due to the observed normal cerebral oxygen:glucose utilization. Recent studies suggest that ammonia stimulates glycolysis in excess of TCA cycle activity, a hypothesis that may warrant further testing, in being in accordance with the limited clinical observations.
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Affiliation(s)
- Peter Ott
- Department of Hepatology and Gastroenterology, Aarhus University Hospital, 8000C, Aarhus, Denmark,
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Perfusion-metabolism coupling in recurrent gliomas: a prospective validation study with 13N-ammonia and 18F-fluorodeoxyglucose PET/CT. Neuroradiology 2014; 56:893-902. [PMID: 24989883 DOI: 10.1007/s00234-014-1389-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 06/03/2014] [Indexed: 10/25/2022]
Abstract
INTRODUCTION We assessed the validity of "perfusion-metabolism coupling" hypothesis in recurrent glioma with 13N-ammonia (13N-NH3) PET/CT and 18F-fluorodeoxyglucose (18F-FDG) PET/CT. METHODS Fifty-six consecutive patients (age, 38.8 ± 12.1 years; 62.5% males) with histologically proven and previously treated glioma presenting with clinical suspicion of recurrence were prospectively enrolled and evaluated with 13N-NH3 PET/CT and 18F-FDG PET/CT. PET/CT images were evaluated both qualitatively and semiquantitatively. Tumor to white matter uptake ratio (T/W) and tumor to gray matter uptake ratio (T/G) were calculated and analyzed for both the modalities. A combination of clinico-radiological follow-up, repeated imaging, and biopsy (when available) were considered as the reference standard. RESULTS Based on the reference standard, 27/56 patients had recurrence. 13N-NH3 PET/CT and 18F-FDG PET/CT were concordant in 55/56 patients. Overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 13N-NH3PET/CT were 77.8, 86.2, 84.0, 80.7, and 82.1%, respectively, and for 18F-FDG PET/CT were 77.8, 89.7, 87.5, 81.2, and 83.9%, respectively. There was excellent agreement between results of 13N-NH3 PET/CT and 18F-FDG PET/CT (ĸ = 0.964; P < 0.001). The performances of 13N-NH3 PET/CT and 18F-FDG PET/CT were not significantly different between high-grade and low-grade glioma (P = 1.000). A strong positive correlation was noted between the uptake ratios derived on the two modalities (ρ = 0.866, P < 0.001 for T/W; ρ = 0.918, P < 0.001 for T/G). CONCLUSION A combination of 13N-NH3 PET/CT and 18F-FDG PET/CT demonstrates that perfusion and metabolism are coupled in recurrent gliomas. These tracers target two different but interrelated aspects of the same pathologic process and can be used as surrogates for each other.
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Khangembam BC, Sharma P, Karunanithi S, Singhal A, Das CJ, Kumar P, Julka PK, Bandopadhyaya GP, Kumar R, Malhotra A, Bal C. 13N-Ammonia PET/CT for detection of recurrent glioma: a prospective comparison with contrast-enhanced MRI. Nucl Med Commun 2014; 34:1046-54. [PMID: 24025920 DOI: 10.1097/mnm.0b013e328365bb41] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE We assessed the value of N-ammonia PET-computed tomography (PET/CT) in recurrent glioma and compared the results with those of contrast-enhanced MRI (CE MRI). MATERIALS AND METHODS Fifty-two (mean age, 39.8±11.6 years; male, 33; female, 19) histopathologically proven and previously treated glioma patients with clinical suspicion of recurrence were evaluated with 13N-ammonia PET/CT and CE MRI. PET/CT images were evaluated qualitatively and quantitatively (maximum standardized uptake value). Tumour to white matter (T/W), tumour to grey matter (T/G) and tumour to pituitary (T/P) ratios were calculated and cutoff levels were derived with receiver operating characteristic curve analysis. Sensitivity, specificity and predictive values were compared. A combination of clinical follow-up, repeat imaging and biopsy (when available) was taken as the reference standard. RESULTS On the basis of the reference standard, 23 out of 52 patients were seen to have recurrence. Overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 13N-ammonia PET/CT were 82.6, 86.2, 82.6, 86.2 and 84.6%, respectively, whereas those of CE MRI were 96.7, 48.3, 59.5, 93.3 and 69.2%, respectively. Overall, 13N-ammonia PET/CT was statistically superior to CE MRI (P=0.001). In low-grade tumours, 13N-ammonia PET/CT performed better than MRI with an accuracy of 86.8 versus 68.4% (P=0.003). In high-grade tumours, both the modalities had comparable performances with accuracies of 78.6% for N-ammonia PET/CT and 71.4% for CE MRI (P=0.250). Among the ratios, T/P was the most useful, with the largest area under the curve (0.825; P=0.0001). CONCLUSION N-Ammonia PET/CT shows higher accuracy compared with contrast-enhanced MRI for detecting recurrent gliomas, particularly in low-grade tumours.
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Affiliation(s)
- Bangkim C Khangembam
- Departments of aNuclear Medicine bRadiodiagnosis cRadiation Oncology, All India Institute of Medical Sciences, New Delhi, India
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Abstract
OBJECTIVE Noninvasive evaluation of glioma is of great help for clinical practice. In this study, we investigated the utility of 13N-ammonia in the evaluation of untreated gliomas and compared the results with that of 18F-FDG. METHODS Forty-five consecutive patients with final diagnosis of glioma were included in this study. PET/CT imaging was performed for all of them with both 18F-FDG and 13N-ammonia as tracers. Imaging results were analyzed by tumor-to-gray matter (T/G) ratios. Receiver operating characteristic curve analysis was conducted to determine the optimal T/G cutoff values of each tracer between low-grade and high-grade gliomas. RESULTS Forty-eight separate lesions were identified in all (grade II, n = 16; grade III, n = 12; and grade IV, n = 20). Twenty-nine out of 32 high-grade lesions (91%) showed higher uptakes than normal gray matter with N-ammonia in comparison with the result of 21 lesions (66%) with 18F-FDG. The optimal T/G cutoff values for 18F-FDG and 13N-ammonia were 0.64 and 0.86 separately with the area under each curve 0.910 and 0.943. The sensitivity and specificity of predicting high-grade gliomas with optimal cutoff values were 83% and 93% for 18F-FDG and 94% and 94% for 13N-ammonia, respectively. CONCLUSION 13N-Ammonia is superior to 18F-FDG not only in separating low-grade gliomas from high-grade ones but also in the detection of high-grade gliomas for better tumor to normal gray matter contrast.
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Chen XL, Wee NLJE, Hiong KC, Ong JLY, Chng YR, Ching B, Wong WP, Chew SF, Ip YK. Properties and expression of Na+/K+-ATPase α-subunit isoforms in the brain of the swamp eel, Monopterus albus, which has unusually high brain ammonia tolerance. PLoS One 2013; 8:e84298. [PMID: 24391932 PMCID: PMC3877266 DOI: 10.1371/journal.pone.0084298] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 11/13/2013] [Indexed: 01/15/2023] Open
Abstract
The swamp eel, Monopterus albus, can survive in high concentrations of ammonia (>75 mmol l(-1)) and accumulate ammonia to high concentrations in its brain (4.5 µmol g(-1)). Na(+)/K(+)-ATPase (Nka) is an essential transporter in brain cells, and since NH4(+) can substitute for K(+) to activate Nka, we hypothesized that the brain of M. albus expressed multiple forms of Nka α-subunits, some of which might have high K(+) specificity. Thus, this study aimed to clone and sequence the nka α-subunits from the brain of M. albus, and to determine the effects of ammonia exposure on their mRNA expression and overall protein abundance. The effectiveness of NH4(+) to activate brain Nka from M. albus and Mus musculus was also examined by comparing their Na(+)/K(+)-ATPase and Na(+)/NH4(+)-ATPase activities over a range of K(+)/NH4(+) concentrations. The full length cDNA coding sequences of three nkaα (nkaα1, nkaα3a and nkaα3b) were identified in the brain of M. albus, but nkaα2 expression was undetectable. Exposure to 50 mmol l(-1) NH4Cl for 1 day or 6 days resulted in significant decreases in the mRNA expression of nkaα1, nkaα3a and nkaα3b. The overall Nka protein abundance also decreased significantly after 6 days of ammonia exposure. For M. albus, brain Na(+)/NH4(+)-ATPase activities were significantly lower than the Na(+)/K(+)-ATPase activities assayed at various NH4(+)/K(+) concentrations. Furthermore, the effectiveness of NH4(+) to activate Nka from the brain of M. albus was significantly lower than that from the brain of M. musculus, which is ammonia-sensitive. Hence, the (1) lack of nkaα2 expression, (2) high K(+) specificity of K(+) binding sites of Nkaα1, Nkaα3a and Nkaα3b, and (3) down-regulation of mRNA expression of all three nkaα isoforms and the overall Nka protein abundance in response to ammonia exposure might be some of the contributing factors to the high brain ammonia tolerance in M. albus.
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Affiliation(s)
- Xiu L. Chen
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Nicklaus L. J. E. Wee
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Kum C. Hiong
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Jasmine L. Y. Ong
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - You R. Chng
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Biyun Ching
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Wai P. Wong
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Shit F. Chew
- Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, Singapore, Republic of Singapore
| | - Yuen K. Ip
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
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Scott TR, Kronsten VT, Hughes RD, Shawcross DL. Pathophysiology of cerebral oedema in acute liver failure. World J Gastroenterol 2013; 19:9240-9255. [PMID: 24409052 PMCID: PMC3882398 DOI: 10.3748/wjg.v19.i48.9240] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 10/28/2013] [Accepted: 11/19/2013] [Indexed: 02/06/2023] Open
Abstract
Cerebral oedema is a devastating consequence of acute liver failure (ALF) and may be associated with the development of intracranial hypertension and death. In ALF, some patients may develop cerebral oedema and increased intracranial pressure but progression to life-threatening intracranial hypertension is less frequent than previously described, complicating less than one third of cases who have proceeded to coma since the advent of improved clinical care. The rapid onset of encephalopathy may be dramatic with the development of asterixis, delirium, seizures and coma. Cytotoxic and vasogenic oedema mechanisms have been implicated with a preponderance of experimental data favouring a cytotoxic mechanism. Astrocyte swelling is the most consistent neuropathological finding in humans with ALF and ammonia plays a definitive role in the development of cytotoxic brain oedema. The mechanism(s) by which ammonia induces astrocyte swelling remains unclear but glutamine accumulation within astrocytes has led to the osmolyte hypothesis. Current evidence also supports an alternate ‘Trojan horse’ hypothesis, with glutamine as a carrier of ammonia into mitochondria, where its accumulation results in oxidative stress, energy failure and ultimately astrocyte swelling. Although a complete breakdown of the blood-brain barrier is not evident in human ALF, increased permeation to water and other small molecules such as ammonia has been demonstrated resulting from subtle alterations in the protein composition of paracellular tight junctions. At present, there is no fully efficacious therapy for cerebral oedema other than liver transplantation and this reflects our incomplete knowledge of the precise mechanisms underlying this process which remain largely unknown.
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Ip YK, Hou Z, Chen XL, Ong JLY, Chng YR, Ching B, Hiong KC, Chew SF. High brain ammonia tolerance and down-regulation of Na+:K+:2Cl(-) Cotransporter 1b mRNA and protein expression in the brain of the Swamp Eel, Monopterus albus, exposed to environmental ammonia or terrestrial conditions. PLoS One 2013; 8:e69512. [PMID: 24069137 PMCID: PMC3777983 DOI: 10.1371/journal.pone.0069512] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 06/11/2013] [Indexed: 01/19/2023] Open
Abstract
Na(+):K(+):2Cl(-) cotransporter 1 (NKCC1) has been implicated in mediating ischemia-, trauma- or ammonia-induced astrocyte swelling/brain edema in mammals. This study aimed to determine the effects of ammonia or terrestrial exposure on ammonia concentrations in the plasma and brain, and the mRNA expression and protein abundance of nkcc/Nkcc in the brain, of the swamp eel Monopterusalbus. Ammonia exposure led to a greater increase in the ammonia concentration in the brain of M. albus than terrestrial exposure. The brain ammonia concentration of M. albus reached 4.5 µmol g(-1) and 2.7 µmol g(-1) after 6 days of exposure to 50 mmol l(-1) NH4Cl and terrestrial conditions, respectively. The full cDNA coding sequence of nkcc1b from M. albus brain comprised 3276 bp and coded for 1092 amino acids with an estimated molecular mass of 119.6 kDa. A molecular characterization indicated that it could be activated through phosphorylation and/or glycosylation by osmotic and/or oxidative stresses. Ammonia exposure for 1 day or 6 days led to significant decreases in the nkcc1b mRNA expression and Nkcc1b protein abundance in the brain of M. albus. In comparison, a significant decrease in nkcc1b mRNA expression was observed in the brain of M. albus only after 6 days of terrestrial exposure, but both 1 day and 6 days of terrestrial exposure resulted in significant decreases in the protein abundance of Nkcc1b. These results are novel because it has been established in mammals that ammonia up-regulates NKCC1 expression in astrocytes and NKCC1 plays an important role in ammonia-induced astrocyte swelling and brain edema. By contrast, our results indicate for the first time that M. albus is able to down-regulate the mRNA and protein expression of nkcc1b/Nkcc1b in the brain when confronted with ammonia toxicity, which could be one of the contributing factors to its extraordinarily high brain ammonia tolerance.
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Affiliation(s)
- Yuen K. Ip
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Zhisheng Hou
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Xiu L. Chen
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Jasmine L. Y. Ong
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - You R. Chng
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Biyun Ching
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Kum C. Hiong
- Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
| | - Shit F. Chew
- Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, Singapore, Republic of Singapore
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Martins YC, Daniel-Ribeiro CT. A new hypothesis on the manifestation of cerebral malaria: the secret is in the liver. Med Hypotheses 2013; 81:777-83. [PMID: 23978689 DOI: 10.1016/j.mehy.2013.08.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Accepted: 08/06/2013] [Indexed: 02/06/2023]
Abstract
Despite the abundance of information on cerebral malaria (CM), the pathogenesis of this disease is not completely understood. At present, two nonexclusive dominant hypotheses exist to explain how the neurological syndrome manifests: the sequestration (or mechanical) hypothesis and the inflammatory hypothesis. The sequestration hypothesis states that sequestration of Plasmodium falciparum-parasitized red blood cells (pRBCs) to brain capillary endothelia causes obstruction of capillary blood flow followed by brain tissue anoxia and coma. The inflammatory hypothesis postulates that P. falciparum infection releases toxic molecules in the circulation, inducing an imbalanced systemic inflammatory response that leads to coagulopathy, brain endothelial cell dysfunction, accumulation of leukocytes in the brain microcirculation, blood brain barrier (BBB) leakage, cerebral vasoconstriction, edema, and coma. However, both hypotheses, even when considered together, are not sufficient to fully explain the pathogenesis of CM. Here, we propose that the development of acute liver failure (ALF) together with BBB breakdown are the necessary and sufficient conditions for the genesis of CM. ALF is characterized by coagulopathy and hepatic encephalopathy (HE) in a patient without pre-existing liver disease. Signs of hepatic dysfunction have been shown to occur in 2.5-40% of CM patients. In addition, recent studies with murine models demonstrated that mice presenting experimental cerebral malaria (ECM) had hepatic damage and brain metabolic changes characteristic of HE. However, the occurrence of CM in patients with mild or without apparent hepatocellular liver damage and the presence of liver damage in non-CM murine models indicate that the development of ALF during malaria infection is not the single factor responsible for neuropathology. To solve this problem, we also propose that BBB breakdown contributes to the pathogenesis of CM and synergizes with hepatic failure to cause neurological signs and symptoms. BBB dysfunction would thus occur in CM by a mechanism similar to the one occurring in sepsis and is in agreement with the inflammatory hypothesis. Nevertheless, differently from in the inflammatory hypothesis, BBB leakage would facilitate the penetration of ammonia and other toxins into the brain parenchyma, but would not be sufficient to cause CM when occurring alone. We believe our hypothesis better explains the pathogenesis of CM, does not have problems to deal with the exception data not explained by the previous hypotheses, and reveals new targets for adjunctive therapy.
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Affiliation(s)
- Yuri Chaves Martins
- Laboratório de Pesquisas em Malária, Instituto Oswaldo Cruz and Centro de Pesquisa Diagnóstico e Treinamento em Malária, Fiocruz, Rio de Janeiro, RJ, Brazil; Department of Pathology, Albert Einstein College of Medicine, The Bronx, NY, USA.
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Abstract
Ammonia is believed to play a key role in the development of hepatic encephalopathy (HE) with increased formation of glutamine playing a central role. It has been debated whether blood ammonia enters the brain by passive diffusion and/or active transport by ion-transporters and that changes in blood pH could affect the blood-to-brain transfer of ammonia. It has also been proposed that the permeability-surface area product for ammonia across the blood-brain barrier (PSBBB) should be increased in cirrhosis and HE. In the present paper it is argued that changes in blood pH does not alter PSBBB for ammonia and the question of passive diffusion versus active transport of ammonia remains unresolved. Furthermore, recent studies do not find evidence for increased PSBBB for ammonia in cirrhosis. The main determent for cerebral uptake of blood ammonia (i.e. flux) is the arterial blood ammonia concentration. This means that the only way to protect the brain from hyperammonemia is by lowering blood ammonia, inhibit cerebral uptake of ammonia, or by manipulating cerebral ammonia metabolism so that less glutamine is produced.
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Affiliation(s)
- Michael Sørensen
- Department of Nuclear Medicine & PET Centre, Aarhus University Hospital, Noerrebrogade 44, DK-8000 Aarhus C, Denmark.
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Alterations of blood-brain barrier and associated factors in acute liver failure. Gastroenterol Res Pract 2013; 2013:841707. [PMID: 23762040 PMCID: PMC3677611 DOI: 10.1155/2013/841707] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 04/08/2013] [Accepted: 05/07/2013] [Indexed: 01/30/2023] Open
Abstract
Brain edema in acute liver failure (ALF) remains lethal. Cytotoxic mechanisms associated with brain edema have been well recognized, but the role of vasogenic mechanisms of brain edema has not been explored. Intact tight junctions (TJs) between brain capillary endothelial cells are critical for normal BBB function. Recent reports found significant alterations in the tight junction elements including occludin and claudin-5, suggesting a vasogenic injury in the blood-brain barrier (BBB) integrity. However, the role of TJ in ALF has not been completely understood. This paper reviews the role of the paracellular tight junction in the increased selective BBB permeability that leads to brain edema in ALF and furthermore explores the effect of systemic inflammatory cytokines on the tight junction dysfunction.
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Simultaneous double hemodialysis for the control of refractory hyperammonemia. Int J Artif Organs 2013; 36:135-8. [PMID: 23404638 DOI: 10.5301/ijao.5000177] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/10/2012] [Indexed: 01/09/2023]
Abstract
INTRODUCTION In adults, hyperammonemia is generally associated with hepatic dysfunction or as a complication of urinary diversions when infected or obstructed. Hyperammonemia has also rarely been reported in association with multiple myeloma. With modest elevations, hyperammonemia often leads to encephalopathy. However, when ammonia reaches extreme levels cerebral edema and herniation may occur leading to coma, seizures, or death. CASE We describe a 72-year-old Caucasian male with a history of end-stage renal disease (ESRD) and multiple myeloma who developed profound encephalopathy and eventual obtundation. He was found to have severe hyperammonemia that was not due to any identified hepatic impairment. His hyperammonemia proved to be refractory to medical therapy with cathartics and antibiotics, prolonged high-flux hemodialysis, and even continuous venovenous hemodialysis (CVVHD). This metabolic derangement as well as encephalopathy was eventually reversed with simultaneous CVVHD and extended daily hemodialysis (EDD). A more durable response was achieved after vincristine and dexamethasone were administered, which allowed the patient to resume his previous intermittent hemodialysis (IHD) schedule. The patient regained his full sensorium and was eventually discharged to home. CONCLUSIONS Simultaneous double hemodialysis may be used as an important adjunct in treating refractory hyperammonemia.
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Manganese and ammonia interactions in the brain of cirrhotic rats: effects on brain ammonia metabolism. Neurochem Res 2012; 37:1074-84. [PMID: 22290316 DOI: 10.1007/s11064-012-0710-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 01/13/2012] [Accepted: 01/18/2012] [Indexed: 01/18/2023]
Abstract
Hepatic encephalopathy is a major complication of cirrhosis. Ammonia and manganese have been associated with hepatic encephalopathy underlying mechanisms. Motor impairment and brain edema are common signs of hepatic encephalopathy. In the present study a model of liver damage in rats was combined with ammonia and manganese exposure to evaluate the role of these substances separately and their interactions on brain glutamine, water content and motor coordination. Additionally, we explored brain levels of each substance -Mn and ammonia- in the presence or absence of the other. Liver damage was induced by bile duct ligation. Rats were exposed to MnCl2 in drinking water (1 mg Mn/ml) and to ammonia in chow pellets containing 20% ammonium acetate (w/w). As expected, manganese and ammonia levels increased in the brain of cirrhotic rats exposed to these substances; in these animals, glutamine brain levels also increased and positively correlated with tissue water content in cortex. A three way-ANOVA showed that manganese favored ammonia and glutamine accumulation in brain, and possibly their subsequent deleterious effects, as evidenced by the fact that manganese and ammonia accumulation in the brain of cirrhotic rats severely affected motor function. These results suggest that even when controlling ammonia levels in cirrhotic patients, reduction of manganese intake is also a potential strategy to be considered in clinical practice.
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Nguyen JH. Blood-brain barrier in acute liver failure. Neurochem Int 2011; 60:676-83. [PMID: 22100566 DOI: 10.1016/j.neuint.2011.10.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 10/20/2011] [Accepted: 10/26/2011] [Indexed: 12/16/2022]
Abstract
Brain edema remains a challenging obstacle in the management of acute liver failure (ALF). Cytotoxic mechanisms associated with brain edema have been well recognized, but evidence for vasogenic mechanisms in the pathogenesis of brain edema in ALF has been lacking. Recent reports have not only shown a role of matrix metalloproteinase-9 in the pathogenesis of brain edema in experimental ALF but have also found significant alterations in the tight junction elements including occludin and claudin-5, suggesting a vasogenic injury in the blood-brain barrier (BBB) integrity. This article reviews and explores the role of the paracellular tight junction proteins in the increased selective BBB permeability that leads to brain edema in ALF.
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Affiliation(s)
- Justin H Nguyen
- Division of Transplant Surgery, Department of Transplantation, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL 32224, United States.
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Skowrońska M, Albrecht J. Alterations of blood brain barrier function in hyperammonemia: an overview. Neurotox Res 2011; 21:236-44. [PMID: 21874372 PMCID: PMC3246587 DOI: 10.1007/s12640-011-9269-4] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 08/12/2011] [Accepted: 08/17/2011] [Indexed: 02/01/2023]
Abstract
Ammonia is a neurotoxin involved in the pathogenesis of neurological conditions associated with hyperammonemia, including hepatic encephalopathy, a condition associated with acute—(ALF) or chronic liver failure. This article reviews evidence that apart from directly affecting the metabolism and function of the central nervous system cells, ammonia influences the passage of different molecules across the blood brain barrier (BBB). A brief description is provided of the tight junctions, which couple adjacent cerebral capillary endothelial cells to each other to form the barrier. Ammonia modulates the transcellular passage of low-to medium-size molecules, by affecting their carriers located at the BBB. Ammonia induces interrelated aberrations of the transport of the large neutral amino acids and aromatic amino acids (AAA), whose influx is augmented by exchange with glutamine produced in the course of ammonia detoxification, and maybe also modulated by the extracellularly acting gamma-glutamyl moiety transferring enzyme, gamma-glutamyl-transpeptidase. Impaired AAA transport affects neurotransmission by altering intracerebral synthesis of catecholamines (serotonin and dopamine), and producing “false neurotransmitters” (octopamine and phenylethylamine). Ammonia also modulates BBB transport of the cationic amino acids: the nitric oxide precursor, arginine, and ornithine, which is an ammonia trap, and affects the transport of energy metabolites glucose and creatine. Moreover, ammonia acting either directly or in synergy with liver injury-derived inflammatory cytokines also evokes subtle increases of the transcellular passage of molecules of different size (BBB “leakage”), which appears to be responsible for the vasogenic component of cerebral edema associated with ALF.
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Affiliation(s)
- Marta Skowrońska
- Departament of Neurotoxicology, Mossakowski Medical Research Centre, Polish Academy of Sciences, 02-106 Warszawa, Pawińskiego 5, Poland
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Toris GT, Bikis CN, Tsourouflis GS, Theocharis SE. Hepatic encephalopathy: an updated approach from pathogenesis to treatment. Med Sci Monit 2011; 17:RA53-63. [PMID: 21278704 PMCID: PMC3524698 DOI: 10.12659/msm.881387] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
One of the most serious complications of chronic or fulminant liver failure is hepatic encephalopathy (HE), associated most commonly with cirrhosis. In the presence of chronic liver disease, HE is a sign of decompensation, while in fulminant liver failure its development represents a worrying sign and usually indicates that transplantation will be required. Despite the significance of HE in the course of liver disease, the progress in development of new therapeutic options has been unremarkable over the last 20 years. An up-to-date review regarding HE, including both research and review articles. HE is a serious and progressive, but potentially reversible, disorder with a wide spectrum of neuropsychiatric abnormalities and motor disturbances that ranges from mild alteration of cognitive and motor function to coma and death. Although a clear pathogenesis is yet to be determined, elevated ammonia in serum and the central nervous system is the mainstay for pathogenesis and treatment of HE. Management includes early diagnosis and prompt treatment of precipitating factors. Clinical trials and extensive clinical experience have established the efficacy of diverse substances in HE treatment. Novel therapies with clinical promise include: L-ornithine L-aspartate, sodium benzoate, phenylacetate, AST-120, and the molecular adsorbent recirculating system. Eventually, liver transplantation is often the most successful long-term therapy for HE.
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Affiliation(s)
- Giannakis T Toris
- Department of Forensic Medicine and Toxicology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
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Xiangsong Z, Weian C, Dianchao Y, Xiaoyan W, Zhifeng C, Xiongchong S. Usefulness of 13N-NH3 PET in the evaluation of brain lesions that are hypometabolic on 18F-FDG PET. J Neurooncol 2011; 105:103-7. [DOI: 10.1007/s11060-011-0570-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Accepted: 03/26/2011] [Indexed: 11/30/2022]
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Ip YK, Chew SF. Ammonia production, excretion, toxicity, and defense in fish: a review. Front Physiol 2010; 1:134. [PMID: 21423375 PMCID: PMC3059970 DOI: 10.3389/fphys.2010.00134] [Citation(s) in RCA: 173] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2010] [Accepted: 09/06/2010] [Indexed: 12/20/2022] Open
Abstract
Many fishes are ammonotelic but some species can detoxify ammonia to glutamine or urea. Certain fish species can accumulate high levels of ammonia in the brain or defense against ammonia toxicity by enhancing the effectiveness of ammonia excretion through active NH4+transport, manipulation of ambient pH, or reduction in ammonia permeability through the branchial and cutaneous epithelia. Recent reports on ammonia toxicity in mammalian brain reveal the importance of permeation of ammonia through the blood-brain barrier and passages of ammonia and water through transporters in the plasmalemma of brain cells. Additionally, brain ammonia toxicity could be related to the passage of glutamine through the mitochondrial membranes into the mitochondrial matrix. On the other hand, recent reports on ammonia excretion in fish confirm the involvement of Rhesus glycoproteins in the branchial and cutaneous epithelia. Therefore, this review focuses on both the earlier literature and the up-to-date information on the problems and mechanisms concerning the permeation of ammonia, as NH(3), NH4+ or proton-neutral nitrogenous compounds, across mitochondrial membranes, the blood-brain barrier, the plasmalemma of neurons, and the branchial and cutaneous epithelia of fish. It also addresses how certain fishes with high ammonia tolerance defend against ammonia toxicity through the regulation of the permeation of ammonia and related nitrogenous compounds through various types of membranes. It is hoped that this review would revive the interests in investigations on the passage of ammonia through the mitochondrial membranes and the blood-brain barrier of ammonotelic fishes and fishes with high brain ammonia tolerance, respectively.
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Affiliation(s)
- Yuen K Ip
- Department of Biological Sciences, National University of Singapore Singapore, Republic of Singapore.
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Berg RM, Taudorf S, Bailey DM, Lundby C, Larsen FS, Pedersen BK, Møller K. Cerebral net exchange of large neutral amino acids after lipopolysaccharide infusion in healthy humans. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2010; 14:R16. [PMID: 20149231 PMCID: PMC2875531 DOI: 10.1186/cc8873] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 12/16/2009] [Accepted: 02/11/2010] [Indexed: 01/25/2023]
Abstract
INTRODUCTION Alterations in circulating large neutral amino acids (LNAAs), leading to a decrease in the plasma ratio between branched-chain and aromatic amino acids (BCAA/AAA ratio), may be involved in sepsis-associated encephalopathy. We hypothesised that a decrease in the BCAA/AAA ratio occurs along with a net cerebral influx of the neurotoxic AAA phenylalanine in a human experimental model of systemic inflammation. METHODS The BCAA/AAA ratio, the cerebral delivery, and net exchange of LNAAs and ammonia were measured before and 1 hour after a 4-hour intravenous infusion of Escherichia coli lipopolysaccharide (LPS) in 12 healthy young men. RESULTS LPS induced systemic inflammation, reduced the BCAA/AAA ratio, increased the cerebral delivery and unidirectional influx of phenylalanine, and abolished the net cerebral influx of the BCAAs leucine and isoleucine. Furthermore, a net cerebral efflux of glutamine, which was independent of the cerebral net exchange of ammonia, was present after LPS infusion. CONCLUSIONS Systemic inflammation may affect brain function by reducing the BCAA/AAA ratio, thereby changing the cerebral net exchange of LNAAs.
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Affiliation(s)
- Ronan Mg Berg
- Centre of Inflammation and Metabolism, Department of Infectious Diseases, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark.
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Wilkinson DJ, Smeeton NJ, Watt PW. Ammonia metabolism, the brain and fatigue; revisiting the link. Prog Neurobiol 2010; 91:200-19. [PMID: 20138956 DOI: 10.1016/j.pneurobio.2010.01.012] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 01/27/2010] [Accepted: 01/29/2010] [Indexed: 12/15/2022]
Abstract
This review addresses the ammonia fatigue theory in light of new evidence from exercise and disease studies and aims to provide a view of the role of ammonia during exercise. Hyperammonemia is a condition common to pathological liver disorders and intense or exhausting exercise. In pathology, hyperammonemia is linked to impairment of normal brain function and the onset of the neurological condition, hepatic encephalopathy. Elevated blood ammonia concentrations arise due to a diminished capacity for removal via the liver and lead to increased exposure of organs, such as the brain, to the toxic effects of ammonia. High levels of brain ammonia can lead to deleterious alterations in astrocyte morphology, cerebral energy metabolism and neurotransmission, which may in turn impact on the functioning of important signalling pathways within the neuron. Such changes are believed to contribute to the disturbances in neuropsychological function, in particular the learning, memory, and motor control deficits observed in animal models of liver disease and also patients with cirrhosis. Hyperammonemia in exercise occurs as a result of an increased production by contracting muscle, through adenosine monophosphate (AMP) deamination (the purine nucleotide cycle) and branched chain amino acid (BCAA) deamination prior to oxidation. Plasma concentrations of ammonia during exercise often achieve or exceed those measured in liver disease patients, resulting in increased cerebral uptake. In this article we propose that exercise-induced hyperammonemia may lead to concomitant disturbances in brain function, potentially through similar mechanisms underpinning pathology, which may impact on performance as fatigue or reduced function, especially during extreme exercise.
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Affiliation(s)
- Daniel J Wilkinson
- Department of Sport and Exercise Science, Chelsea School, University of Brighton, 30 Carlisle Road, Eastbourne, UK.
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Kitzberger R, Funk GC, Holzinger U, Miehsler W, Kramer L, Kaider A, Ferenci P, Madl C. Severity of organ failure is an independent predictor of intracranial hypertension in acute liver failure. Clin Gastroenterol Hepatol 2009; 7:1000-6. [PMID: 19465152 DOI: 10.1016/j.cgh.2009.05.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2008] [Revised: 04/05/2009] [Accepted: 05/13/2009] [Indexed: 02/07/2023]
Abstract
BACKGROUND & AIMS Ionized ammonia (NH(3)) and partial pressure of the gaseous ammonia (pNH(3)) are associated with hepatic encephalopathy and intracranial hypertension in patients with acute liver failure; NH(3) is also believed to contribute to extrahepatic organ failure. We investigated whether the severity of organ failure was associated with intracranial hypertension and evaluated the correlation between NH(3) and pNH(3) and grade of hepatic encephalopathy. METHODS In 87 patients with acute liver failure admitted to the intensive care unit, we simultaneously evaluated arterial ammonia, pNH(3), clinical grade of hepatic encephalopathy, the sequential organ failure assessment score (SOFA score), and evidence of intracranial hypertension. RESULTS In comparing patients with intracranial hypertension (n = 37) with patients without intracranial hypertension (n = 50), the highest NH(3) and pNH(3) levels and SOFA scores before onset of intracranial hypertension were independent predictors of intracranial hypertension (P < .001). Among patients with NH(3) levels less than 146 mumol/L, those with intracranial hypertension had a higher SOFA score than those without intracranial hypertension (median, 10 vs 5.5; P = .004), despite the patients' similar levels of NH(3). NH(3) (r = 0.68, P < .0001) and pNH(3) (r = 0.78, P < .0001) both correlated with grade of hepatic encephalopathy. However, in multiple regression analysis, only pNH(3) (P < .0001) was shown to be a significant independent parameter for predicting grade of hepatic encephalopathy (P = .27). CONCLUSIONS SOFA score and ammonia levels are independent predictors of intracranial hypertension. In patients with acute liver failure admitted to the intensive care unit, pNH(3) level is a better predictor of clinical grade of hepatic encephalopathy than arterial NH(3) level.
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Affiliation(s)
- Reinhard Kitzberger
- Department of Gastroenterology, Hepatology and Medical Intensive Care Medicine, Medical University Hospital Vienna, Vienna, Austria.
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