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Limón ID, Angulo-Cruz I, Sánchez-Abdon L, Patricio-Martínez A. Disturbance of the Glutamate-Glutamine Cycle, Secondary to Hepatic Damage, Compromises Memory Function. Front Neurosci 2021; 15:578922. [PMID: 33584185 PMCID: PMC7873464 DOI: 10.3389/fnins.2021.578922] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 01/06/2021] [Indexed: 12/13/2022] Open
Abstract
Glutamate fulfils many vital functions both at a peripheral level and in the central nervous system (CNS). However, hyperammonemia and hepatic failure induce alterations in glutamatergic neurotransmission, which may be the main cause of hepatic encephalopathy (HE), an imbalance which may explain damage to both learning and memory. Cognitive and motor alterations in hyperammonemia may be caused by a deregulation of the glutamate-glutamine cycle, particularly in astrocytes, due to the blocking of the glutamate excitatory amino-acid transporters 1 and 2 (EAAT1, EAAT2). Excess extracellular glutamate triggers mechanisms involving astrocyte-mediated inflammation, including the release of Ca2+-dependent glutamate from astrocytes, the appearance of excitotoxicity, the formation of reactive oxygen species (ROS), and cell damage. Glutamate re-uptake not only prevents excitotoxicity, but also acts as a vital component in synaptic plasticity and function. The present review outlines the evidence of the relationship between hepatic damage, such as that occurring in HE and hyperammonemia, and changes in glutamine synthetase function, which increase glutamate concentrations in the CNS. These conditions produce dysfunction in neuronal communication. The present review also includes data indicating that hyperammonemia is related to the release of a high level of pro-inflammatory factors, such as interleukin-6, by astrocytes. This neuroinflammatory condition alters the function of the membrane receptors, such as N-methyl-D-aspartate (NMDA), (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) AMPA, and γ-aminobutyric acid (GABA), thus affecting learning and spatial memory. Data indicates that learning and spatial memory, as well as discriminatory or other information acquisition processes in the CNS, are damaged by the appearance of hyperammonemia and, moreover, are associated with a reduction in the production of cyclic guanosine monophosphate (cGMP). Therefore, increased levels of pharmacologically controlled cGMP may be used as a therapeutic tool for improving learning and memory in patients with HE, hyperammonemia, cerebral oedema, or reduced intellectual capacity.
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Affiliation(s)
| | - Isael Angulo-Cruz
- Laboratorio de Neurofarmacología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | - Lesli Sánchez-Abdon
- Laboratorio de Neurofarmacología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | - Aleidy Patricio-Martínez
- Laboratorio de Neurofarmacología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
- Facultad de Ciencias Biológicas, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
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Kreisel W, Schaffner D, Lazaro A, Trebicka J, Merfort I, Schmitt-Graeff A, Deibert P. Phosphodiesterases in the Liver as Potential Therapeutic Targets of Cirrhotic Portal Hypertension. Int J Mol Sci 2020; 21:E6223. [PMID: 32872119 PMCID: PMC7503357 DOI: 10.3390/ijms21176223] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 08/23/2020] [Accepted: 08/25/2020] [Indexed: 02/06/2023] Open
Abstract
Liver cirrhosis is a frequent condition with high impact on patients' life expectancy and health care systems. Cirrhotic portal hypertension (PH) gradually develops with deteriorating liver function and can lead to life-threatening complications. Other than an increase in intrahepatic flow resistance due to morphological remodeling of the organ, a functional dysregulation of the sinusoids, the smallest functional units of liver vasculature, plays a pivotal role. Vascular tone is primarily regulated by the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway, wherein soluble guanylate cyclase (sGC) and phosphodiesterase-5 (PDE-5) are key enzymes. Recent data showed characteristic alterations in the expression of these regulatory enzymes or metabolite levels in liver cirrhosis. Additionally, a disturbed zonation of the components of this pathway along the sinusoids was detected. This review describes current knowledge of the pathophysiology of PH with focus on the enzymes regulating cGMP availability, i.e., sGC and PDE-5. The results have primarily been obtained in animal models of liver cirrhosis. However, clinical and histochemical data suggest that the new biochemical model we propose can be applied to human liver cirrhosis. The role of PDE-5 as potential target for medical therapy of PH is discussed.
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Affiliation(s)
- Wolfgang Kreisel
- Department of Medicine II, Gastroenterology, Hepatology, Endocrinology, and Infectious Diseases, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany
| | - Denise Schaffner
- Institute for Exercise and Occupational Medicine, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany; (D.S.); (A.L.); (P.D.)
- Department of Pharmaceutical Biology and Biotechnology, University of Freiburg, 79104 Freiburg, Germany;
- Department of Radiology–Medical Physics, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany
| | - Adhara Lazaro
- Institute for Exercise and Occupational Medicine, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany; (D.S.); (A.L.); (P.D.)
| | - Jonel Trebicka
- Translational Hepatology, Department of Internal Medicine I, Goethe University Clinic Frankfurt, 60590 Frankfurt, Germany;
| | - Irmgard Merfort
- Department of Pharmaceutical Biology and Biotechnology, University of Freiburg, 79104 Freiburg, Germany;
| | | | - Peter Deibert
- Institute for Exercise and Occupational Medicine, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany; (D.S.); (A.L.); (P.D.)
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Melatonin prevented spatial deficits and increases in brain asymmetric dimethylarginine in young bile duct ligation rats. Neuroreport 2019; 29:541-546. [PMID: 29384993 PMCID: PMC6023590 DOI: 10.1097/wnr.0000000000000972] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Bile duct ligation (BDL) in young rats can cause impaired liver function and cognition deficits. Nitric oxide is implicated in hepatic encephalopathy and is also involved in cognition. In this study, we examined the role of brain asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, in young BDL rats with spatial deficits. Young male Sprague-Dawley rats aged 17 days were assigned to four groups: laparotomy (SHAM), laparotomy plus 5 mg melatonin delivered through a pellet (SHAMM) for 4 weeks, BDL for 4 weeks, and BDL plus 5 mg melatonin delivered through a pellet (BDLM) for 4 weeks. Their spatial memory was assessed using a Morris water-maze task. Plasma and brains were collected for biochemical and ADMA analyses. We found that the BDL group had significantly elevated levels of ADMA in the plasma, the prefrontal cortex, and the dorsal hippocampus, and worse spatial performance than that of the control groups. Melatonin administration prevented an increase in the ADMA levels in the plasma, prefrontal cortex, and dorsal hippocampus, and prevented spatial deficits in BDL rats. In addition, melatonin maintained brain-derived neurotrophic factor in the dorsal hippocampus at a level comparable with controls. We concluded that melatonin is effective in preventing spatial deficits and decreasing ADMA levels in the plasma, prefrontal cortex, and dorsal hippocampus in young BDL rats. Brain ADMA levels might play a role in BDL-induced spatial deficits.
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Sheen JM, Chen YC, Hsu MH, Tain YL, Yu HR, Huang LT. Combined Intraperitoneal and Intrathecal Etanercept Reduce Increased Brain Tumor Necrosis Factor-Alpha and Asymmetric Dimethylarginine Levels and Rescues Spatial Deficits in Young Rats after Bile Duct Ligation. Front Cell Neurosci 2016; 10:167. [PMID: 27445694 PMCID: PMC4917524 DOI: 10.3389/fncel.2016.00167] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 06/09/2016] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Rats subjected to bile duct ligation (BDL) exhibit increased systemic oxidative stress and brain dysfunction characteristic of hepatic encephalopathy (HE), including fatigue, neurotransmitter alterations, cognitive and motor impairment, and brain inflammation. The levels of tumor necrosis factor-alpha (TNF-α) and asymmetric dimethylarginine (ADMA) are both increased in plasma and brain in encephalopathy induced by chronic liver failure. This study first determined the temporal profiles of TNF-α and ADMA in the plasma, brain cortex, and hippocampus in young BDL rats. Next, we examined whether etanercept was beneficial in preventing brain damage. METHODS Young rats underwent sham ligation or BDL at day 17 ± 1 for 4 weeks. Treatment group rats were administered etanercept (10 mg/kg) intraperitoneally (IP) three times per week with or without etanercept (100 μg) intrathecally (IT) three times in total. RESULTS We found increased plasma TNF-α, soluble tumor necrosis factor receptor 1 (sTNFR1), soluble tumor necrosis factor receptor 2 (sTNFR2), and ADMA levels, increased cortical TNF-α mRNA and protein and ADMA, and hippocampal TNF-α mRNA and protein, and spatial defects in young BDL rats. The increase in cortex TNF-α mRNA and ADMA were reduced by IP etanercept or combined IP and IT etanercept. Dually IP/IT etanercept administration reduced the increased cortical and hippocampal TNF-α mRNA and protein level as well as spatial deficits. CONCLUSIONS We conclude that combined intraperitoneal and intrathecal etanercept reduce increased brain TNF-α and ADMA levels and rescues spatial deficits in young rats after BDL.
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Affiliation(s)
- Jiunn-Ming Sheen
- Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of MedicineKaohsiung, Taiwan; Graduate Institute of Clinical Medical Sciences, Chang Gung University College of MedicineKaohsiung, Taiwan
| | - Yu-Chieh Chen
- Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine Kaohsiung, Taiwan
| | - Mei-Hsin Hsu
- Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine Kaohsiung, Taiwan
| | - You-Lin Tain
- Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine Kaohsiung, Taiwan
| | - Hong-Ren Yu
- Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine Kaohsiung, Taiwan
| | - Li-Tung Huang
- Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine Kaohsiung, Taiwan
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Belghiti M, Agusti A, Hernandez-Rabaza V, Cabrera-Pastor A, Llansola M, Felipo V. Sildenafil Treatment Eliminates Pruritogenesis and Thermal Hyperalgesia in Rats with Portacaval Shunts. Neurochem Res 2016; 42:788-794. [PMID: 27321307 DOI: 10.1007/s11064-016-1980-3] [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: 04/19/2016] [Revised: 06/11/2016] [Accepted: 06/13/2016] [Indexed: 11/24/2022]
Abstract
Pruritus is a common symptom in chronic liver diseases, which may also alter thermal sensitivity. The underlying mechanisms remain unclear and treatments are not satisfactory. Portal-systemic shunting has been proposed to alter thermal sensitivity in cirrhotics. Inflammation-induced enhanced activity of the Transient Receptor Potential Vanilloid 1 (TRPV1) may contribute to pruritus and thermal hyperalgesia. Sildenafil reduces neuroinflammation in portacaval shunt (PCS) rats. The aims were to assess whether: (1) PCS rats show enhanced scratching or thermal sensitivity; (2) TRPV1 activity is enhanced in PCS rats; (3) treatment with sildenafil reduces TRPV1 activation, scratching and thermal hyperalgesia. Rats were treated with sildenafil beginning 3 weeks after surgery. The number of scratches performed were counted. Thermal hyperalgesia was analyzed using the Hargreaves' Plantar Test. TRPV1 activation by measuring the increase in Ca2+ induced by capsaicin in dorsal root ganglia neurons. PCS rats show enhanced scratching behavior, reaching 66 ± 5 scratches/h (p < 0.01) at 21 days after surgery, while controls show 37 ± 2 scratches/h. PCS rats show thermal hyperalgesia. Paw withdrawal latency was reduced (p < 0.05) to 10 ± 1 s compared to controls (21 ± 2 s). Capsaicin-induced calcium increase was higher in dorsal root ganglia cultures from PCS rats, indicating TRPV1functional increase. PCS rats show enhanced scratching behavior and thermal sensitivity and are a good model to study these alterations in chronic liver diseases. Enhanced sensitivity and activity of TRPV1 channel underlies these alterations. Treatment with sildenafil reduces TRPV1 channel sensitivity and activity and normalizes scratching behavior and thermal sensitivity.
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Affiliation(s)
- Majedeline Belghiti
- Laboratory of Neurobiology, Centro de Investigación Príncipe Felipe, Eduardo Primo Yufera, 3, 46012, Valencia, Spain
| | - Ana Agusti
- Instituto de Investigación Sanitaria INCLIVA, Valencia, Spain
| | - Vicente Hernandez-Rabaza
- Laboratory of Neurobiology, Centro de Investigación Príncipe Felipe, Eduardo Primo Yufera, 3, 46012, Valencia, Spain
| | - Andrea Cabrera-Pastor
- Laboratory of Neurobiology, Centro de Investigación Príncipe Felipe, Eduardo Primo Yufera, 3, 46012, Valencia, Spain
| | - Marta Llansola
- Laboratory of Neurobiology, Centro de Investigación Príncipe Felipe, Eduardo Primo Yufera, 3, 46012, Valencia, Spain
| | - Vicente Felipo
- Laboratory of Neurobiology, Centro de Investigación Príncipe Felipe, Eduardo Primo Yufera, 3, 46012, Valencia, Spain.
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Sheen JM, Chen YC, Tain YL, Huang LT. Increased circulatory asymmetric dimethylarginine and multiple organ failure: bile duct ligation in rat as a model. Int J Mol Sci 2014; 15:3989-4006. [PMID: 24603538 PMCID: PMC3975379 DOI: 10.3390/ijms15033989] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 02/04/2014] [Accepted: 02/26/2014] [Indexed: 02/06/2023] Open
Abstract
Bile duct ligation (BDL)-treated rats exhibit cholestasis, increased systemic oxidative stress, and liver fibrosis, which ultimately lead to liver cirrhosis. Asymmetric dimethylarginine (ADMA) is a competitive inhibitor of nitric oxide synthase that can decrease the synthesis of nitric oxide. BDL rats have higher plasma and hepatic ADMA levels, which may be due to increased hepatic protein arginine methyltransferase-1 and decreased dimethylarginine dimethylaminohydrolase expression. BDL rats also exhibit renal and brain damage characterized by increased tissue ADMA concentrations. The increased plasma ADMA levels and multiple organ damages seen here are also observed following multiple organ failures associated with critical illness. This review discusses the dysregulation of ADMA in major organs in BDL rats and the role of increased ADMA in multiple organ damages.
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Affiliation(s)
- Jiunn-Ming Sheen
- Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung 833, Taiwan.
| | - Yu-Chieh Chen
- Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung 833, Taiwan.
| | - You-Lin Tain
- Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung 833, Taiwan.
| | - Li-Tung Huang
- Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung 833, Taiwan.
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Balasubramaniyan V, Wright G, Sharma V, Davies NA, Sharifi Y, Habtesion A, Mookerjee RP, Jalan R. Ammonia reduction with ornithine phenylacetate restores brain eNOS activity via the DDAH-ADMA pathway in bile duct-ligated cirrhotic rats. Am J Physiol Gastrointest Liver Physiol 2012; 302:G145-52. [PMID: 21903766 DOI: 10.1152/ajpgi.00097.2011] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Ammonia is central in the pathogenesis of hepatic encephalopathy, which is associated with dysfunction of the nitric oxide (NO) signaling pathway. Ornithine phenylacetate (OP) reduces hyperammonemia and brain water in cirrhotic animals. This study aimed to determine whether endothelial NO synthase activity is altered in the brain of cirrhotic animals, whether this is associated with changes in the endogenous inhibitor, asymmetric-dimethylarginine (ADMA) and its regulating enzyme, dimethylarginine-dimethylaminohydrolase (DDAH-1), and whether these abnormalities are restored by ammonia reduction using OP. Sprague-Dawley rats were studied 4-wk after bile duct ligation (BDL) (n = 16) or sham operation (n = 8) and treated with placebo or OP (0.6 g/kg). Arterial ammonia, brain water, TNF-α, plasma, and brain ADMA were measured using standard techniques. NOS activity was measured radiometrically, and protein expression for NOS enzymes, ADMA, DDAH-1, 4-hydroxynonenol ((4)HNE), and NADPH oxidase (NOX)-1 were measured by Western blotting. BDL significantly increased arterial ammonia (P < 0.0001), brain water (P < 0.05), and brain TNF-α (P < 0.01). These were reduced significantly by OP treatment. The estimated eNOS component of constitutive NOS activity was significantly lower (P < 0.05) in BDL rat, and this was significantly attenuated in OP-treated animals. Brain ADMA levels were significantly higher and brain DDAH-1 significantly lower in BDL compared with sham (P < 0.01) and restored toward normal following treatment with OP. Brain (4)HNE and NOX-1 protein expression were significantly increased in BDL rat brain, which were significantly decreased following OP administration. We show a marked abnormality of NO regulation in cirrhotic rat brains, which can be restored by reduction in ammonia concentration using OP.
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Ekse S, Clapp LH, Revhaug A, Ytrebø LM. Endothelium-derived hyperpolarization factor (EDHF) is up-regulated in a pig model of acute liver failure. Scand J Gastroenterol 2007; 42:356-65. [PMID: 17354116 DOI: 10.1080/00365520600930636] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Acute liver failure (ALF) is hemodynamically characterized by hyperdynamic circulation, but the pathophysiologic mechanisms underlying these disturbances are not known. The purposes of the present experiments were: to study systemic and peripheral hemodynamics in vivo, to measure changes in vascular reactivity in vitro, and to determine the role of endothelium-dependent vasodilator pathways in a well-validated porcine model of ALF. METHODS Landrace pigs (24-29 kg) were allocated to sham operation (n=8) or ALF induced by hepatic devascularization (n=9). Systemic and regional hemodynamics were monitored. Femoral artery rings were prepared for isometric tension recordings 8 h after ALF induction. Contractile responses to phenylephrine were assessed in ring segments of endothelium-intact femoral arteries in the absence or presence of inhibitors of endothelium-derived hyperpolarizing factor, nitric oxide synthase, cyclooxygenase and heme oxygenase pathways. RESULTS Pigs with ALF developed a hyperdynamic circulation. Cardiac index increased (PGT<0.001), while mean arterial pressure (PGT=0.012) and systemic vascular resistance decreased (PGT<0.001) in this group. Femoral artery blood flow decreased in controls, while it remained unchanged in ALF (PGT=0.010). Accordingly, vascular resistance across the hind leg was significantly decreased (PGT<0.001) in ALF. The combination of Ca2+-activated potassium channel inhibitors charybdotoxin and apamin, which block the release of endothelium-derived hyperpolarizing factor, increased the contraction force (ANOVA, PGT=0.05) and Emax (P=0.01) to phenylephrine in ALF. In contrast, inhibitors of nitric oxide synthase, cyclooxygenase and heme oxygenase pathways did not increase isometric contraction force. CONCLUSIONS Endothelium dependent hyperpolarization of vascular smooth muscle contributes to the development of hyperdynamic circulation in ALF.
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MESH Headings
- Analysis of Variance
- Animals
- Apamin/pharmacology
- Biological Factors/metabolism
- Blood Pressure/drug effects
- Cardiac Output/drug effects
- Charybdotoxin/pharmacology
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Endothelium, Vascular/physiopathology
- Enzyme Inhibitors/pharmacology
- Female
- Femoral Artery/drug effects
- Femoral Artery/metabolism
- Femoral Artery/physiopathology
- Heme Oxygenase (Decyclizing)/drug effects
- Heme Oxygenase (Decyclizing)/metabolism
- Isometric Contraction/drug effects
- Liver Circulation/drug effects
- Liver Failure, Acute/metabolism
- Liver Failure, Acute/physiopathology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/physiopathology
- Nitric Oxide Synthase/drug effects
- Nitric Oxide Synthase/metabolism
- Phenylephrine/pharmacology
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Calcium-Activated/drug effects
- Potassium Channels, Calcium-Activated/metabolism
- Prostaglandin-Endoperoxide Synthases/drug effects
- Prostaglandin-Endoperoxide Synthases/metabolism
- Swine
- Up-Regulation/drug effects
- Vascular Resistance/drug effects
- Vasoconstriction/drug effects
- Vasoconstrictor Agents/pharmacology
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Affiliation(s)
- Sveinung Ekse
- Department of Anesthesiology and Intensive Care, University of Tromsø, University Hospital Northern Norway, Tromsø, Norway
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Jover R, Rodrigo R, Felipo V, Insausti R, Sáez-Valero J, García-Ayllón MS, Suárez I, Candela A, Compañ A, Esteban A, Cauli O, Ausó E, Rodríguez E, Gutiérrez A, Girona E, Erceg S, Berbel P, Pérez-Mateo M. Brain edema and inflammatory activation in bile duct ligated rats with diet-induced hyperammonemia: A model of hepatic encephalopathy in cirrhosis. Hepatology 2006; 43:1257-66. [PMID: 16729306 DOI: 10.1002/hep.21180] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Studies of the pathogenesis of hepatic encephalopathy are hampered by the lack of a satisfactory animal model. We examined the neurological features of rats after bile duct ligation fed a hyperammonemic diet (BDL+HD). Six groups were studied: sham, sham pair-fed, hyperammonemic, bile duct ligation (BDL), BDL pair fed, and BDL+HD. The BDL+HD rats were made hyperammonemic via an ammonia-containing diet that began 2 weeks after operation. One week later, the animals were sacrificed. BDL+HD rats displayed an increased level of cerebral ammonia and neuroanatomical characteristics of hepatic encephalopathy (HE), including the presence of type II Alzheimer astrocytes. Both BDL and BDL+HD rats showed activation of the inflammatory system. BDL+HD rats showed an increased amount of brain glutamine, a decreased amount of brain myo-inositol, and a significant increase in the level of brain water. In coordination tests, BDL+HD rats showed severe impairment of motor activity and performance as opposed to BDL rats, whose results seemed only mildly affected. In conclusion, the BDL+HD rats displayed similar neuroanatomical and neurochemical characteristics to human HE in liver cirrhosis. Brain edema and inflammatory activation can be detected under these circumstances.
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Affiliation(s)
- Rodrigo Jover
- Gastroenterology Department, Hospital General Universitario de Alicante, Alicante, Spain.
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10
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Davies NA, Hodges SJ, Pitsillides AA, Mookerjee RP, Jalan R, Mehdizadeh S. Hepatic guanylate cyclase activity is decreased in a model of cirrhosis: a quantitative cytochemistry study. FEBS Lett 2006; 580:2123-8. [PMID: 16563392 DOI: 10.1016/j.febslet.2006.02.080] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2006] [Accepted: 02/23/2006] [Indexed: 12/29/2022]
Abstract
The production of nitric oxide (NO) in liver disease and its role in vascular control has been a subject of much interest in recent years. However, the activity of guanylate cyclase (GC), the enzyme activated by NO has received little attention with regard to liver disease. In this study we have utilised a quantitative cytochemical technique to examine the activity of GC on a per cell basis in a rat model of cirrhosis. Our results show a significant reduction in GC activity, indicating that vascular regulation is likely to be substantially affected irrespective of NO generation in this disease model.
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Affiliation(s)
- Nathan A Davies
- The UCL Institute of Hepatology, Division of Medicine, University College London, 69-75 Chenies Mews, London, UK
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Abstract
The biokinetics of guanosine 3',5'-cyclic monophosphate (cGMP) is characterized by three distinct processes: synthesis by guanylate cyclases (GCs), conversion of cGMP to GMP by cyclic nucleotide phosphodiesterases (PDEs) and the excretion of unchanged cGMP by transport proteins in the cell membrane. Efflux is observed in virtually all cell types including cells which originate from brain. Studies of intact cells, in which metabolic inhibitors and probenecid reduced extrusion of cGMP and wherein cGMP was extruded against concentration gradients, indicated the existence of ATP requiring organic anion transport system(s). Functional studies of inside-out vesicles have revealed cGMP transport systems wherein translocation is coupled to hydrolysis of ATP. The extrusion of cGMP is inhibited by a number of unrelated compounds and this indicates that cGMP is substrate for multispecific transporters. Recent transfection studies suggest that members of the MRP (multidrug resistance protein) family; MRP4, MRP5 and MRP8 translocate cGMP across the cell membrane. Many of the MRPs have been detected in brain. In addition tertiary active transport by the organic anion transporter family has also been identified. At least one member (OAT1) shows relative high affinity for cGMP and is also expressed in brain. The biological significance of cGMP transporters has to be clarified. Their role in cGMP biokinetics, being responsible for one of the cellular elimination pathways, is well established. However, there is growing evidence that extracellular cGMP has effects on cell physiology and pathophysiology by an auto- or paracrine mechanism.
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Affiliation(s)
- Georg Sager
- Department of Pharmacology, Faculty of Medicine, Institute of Medical Biology, University of Tromsø, NB 9037, Tromsø, Norway.
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Lombardi G, Miglio G, Dianzani C, Mesturini R, Varsaldi F, Chiocchetti A, Dianzani U, Fantozzi R. Glutamate modulation of human lymphocyte growth: in vitro studies. Biochem Biophys Res Commun 2004; 318:496-502. [PMID: 15120628 DOI: 10.1016/j.bbrc.2004.04.053] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2004] [Indexed: 11/23/2022]
Abstract
Peripheral blood mononuclear cell (PBMC) proliferation induced by phytohemagglutinin, or by anti-CD3 alone or plus anti-CD28 monoclonal antibodies (mAb) was inhibited by glutamate (Glu) in a concentration-dependent manner. This inhibition was not reproduced by selective ionotropic Glu receptor agonists, whereas it was potentiated by l-buthionine-(S,R)-sulfoximine, which depletes glutathione (GSH) stores, and counteracted by 2-mercaptoethanol, a preserver of cell thiols. The inhibitory effects of Glu were related to depletion of intracellular GSH stores, since it decreased GSH levels in a concentration-dependent manner. Furthermore, Glu modulated cytokine secretion by anti-CD3 mAb activated PBMC: it increased IFN-gamma (+44.3+/-8.2%) and IL-10 (+31.6+/-9.7%) secretion, whereas that of IL-2, IL-4, IL-5, and TNF-alpha was not affected. These data suggest that high levels of Glu, which can be reached in damaged tissues, modulate lymphocyte responses to activating stimuli by favouring polarization of the T helper effector response.
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Affiliation(s)
- Grazia Lombardi
- Interdisciplinary Research Center of Autoimmune Diseases, DISCAFF Department, Eastern Piedmont University, Via Bovio 6, 28100 Novara, Italy.
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