Infliximab reduces peripheral inflammation, neuroinflammation, and extracellular GABA in the cerebellum and improves learning and motor coordination in rats with hepatic encephalopathy

Suppression by central adenosine A3 receptors of the cholinergic defense against cardiovascular aberrations of sepsis: role of PI3K/MAPKs/NFκB signaling

Introduction: Despite the established role of peripheral adenosine receptors in sepsis-induced organ dysfunction, little or no data is available on the interaction of central adenosine receptors with sepsis. The current study tested the hypothesis that central adenosine A3 receptors (A3ARs) modulate the cardiovascular aberrations and neuroinflammation triggered by sepsis and their counteraction by the cholinergic antiinflammatory pathway. Methods: Sepsis was induced by cecal ligation and puncture (CLP) in rats pre-instrumented with femoral and intracisternal (i.c.) catheters for hemodynamic monitoring and central drug administration, respectively. Results: The CLP-induced hypotension, reduction in overall heart rate variability (HRV) and sympathovagal imbalance towards parasympathetic predominance were abolished by i.v. nicotine (100 μg/kg) or i.c. VUF5574 (A3AR antagonist, 2 µg/rat). In addition, the selective A3AR agonist, 3-iodobenzyl-5'-N-methylcarboxamidoadenosine IB-MECA, 4 µg/rat, i.c.) exaggerated the hypotension and cardiac autonomic dysfunction induced by sepsis and opposed the favorable nicotine actions against these septic manifestations. Immunohistochemically, IB-MECA abolished the nicotine-mediated downregulation of NFκB and NOX2 expression in rostral ventrolateral medullary areas (RVLM) of brainstem of septic rats. The inhibitory actions of IB-MECA on nicotine responses disappeared after i.c. administration of PD98059 (MAPK-ERK inhibitor), SP600125 (MAPK-JNK inhibitor) or wortmannin (PI3K inhibitor). Moreover, infliximab (TNFα inhibitor) eliminated the IB-MECA-induced rises in RVLM-NFκB expression and falls in HRV, but not blood pressure. Conclusion: Central PI3K/MAPKs pathway mediates the A3AR counteraction of cholinergic defenses against cardiovascular and neuroinflammatory aberrations in sepsis.

Allopregnanolone and its antagonist modulate neuroinflammation and neurological impairment

Neuroinflammation accompanies several brain disorders, either as a secondary consequence or as a primary cause and may contribute importantly to disease pathogenesis. Neurosteroids which act as Positive Steroid Allosteric GABA-A receptor Modulators (Steroid-PAM) appear to modulate neuroinflammation and their levels in the brain may vary because of increased or decreased local production or import from the systemic circulation. The increased synthesis of steroid-PAMs is possibly due to increased expression of the mitochondrial cholesterol transporting protein (TSPO) in neuroinflammatory tissue, and reduced production may be due to changes in the enzymatic activity. Microglia and astrocytes play an important role in neuroinflammation, and their production of inflammatory mediators can be both activated and inhibited by steroid-PAMs and GABA. What is surprising is the finding that both allopregnanolone, a steroid-PAM, and golexanolone, a novel GABA-A receptor modulating steroid antagonist (GAMSA), can inhibit microglia and astrocyte activation and normalize their function. This review focuses on the role of steroid-PAMs in neuroinflammation and their importance in new therapeutic approaches to CNS and liver disease.

Increased levels and activation of the IL-17 receptor in microglia contribute to enhanced neuroinflammation in cerebellum of hyperammonemic rats

BACKGROUND

Patients with liver cirrhosis may show minimal hepatic encephalopathy (MHE) with mild cognitive impairment and motor incoordination. Rats with chronic hyperammonemia reproduce these alterations. Motor incoordination in hyperammonemic rats is due to increased GABAergic neurotransmission in cerebellum, induced by neuroinflammation, which enhances TNFα-TNFR1-S1PR2-CCL2-BDNF-TrkB pathway activation. The initial events by which hyperammonemia triggers activation of this pathway remain unclear. MHE in cirrhotic patients is triggered by a shift in inflammation with increased IL-17. The aims of this work were: (1) assess if hyperammonemia increases IL-17 content and membrane expression of its receptor in cerebellum of hyperammonemic rats; (2) identify the cell types in which IL-17 receptor is expressed and IL-17 increases in hyperammonemia; (3) assess if blocking IL-17 signaling with anti-IL-17 ex-vivo reverses activation of glia and of the TNFα-TNFR1-S1PR2-CCL2-BDNF-TrkB pathway.

RESULTS

IL-17 levels and membrane expression of the IL-17 receptor are increased in cerebellum of rats with hyperammonemia and MHE, leading to increased activation of IL-17 receptor in microglia, which triggers activation of STAT3 and NF-kB, increasing IL-17 and TNFα levels, respectively. TNFα released from microglia activates TNFR1 in Purkinje neurons, leading to activation of NF-kB and increased IL-17 and TNFα also in these cells. Enhanced TNFR1 activation also enhances activation of the TNFR1-S1PR2-CCL2-BDNF-TrkB pathway which mediates microglia and astrocytes activation.

CONCLUSIONS

All these steps are triggered by enhanced activation of IL-17 receptor in microglia and are prevented by ex-vivo treatment with anti-IL-17. IL-17 and IL-17 receptor in microglia would be therapeutic targets to treat neurological impairment in patients with MHE.

Two-Month Voluntary Ethanol Consumption Promotes Mild Neuroinflammation in the Cerebellum but Not in the Prefrontal Cortex, Hippocampus, or Striatum of Mice

Chronic ethanol exposure often triggers neuroinflammation in the brain's reward system, potentially promoting the drive for ethanol consumption. A main marker of neuroinflammation is the microglia-derived monocyte chemoattractant protein 1 (MCP1) in animal models of alcohol use disorder in which ethanol is forcefully given. However, there are conflicting findings on whether MCP1 is elevated when ethanol is taken voluntarily, which challenges its key role in promoting motivation for ethanol consumption. Here, we studied MCP1 mRNA levels in areas implicated in consumption motivation-specifically, the prefrontal cortex, hippocampus, and striatum-as well as in the cerebellum, a brain area highly sensitive to ethanol, of C57BL/6 mice subjected to intermittent and voluntary ethanol consumption for two months. We found a significant increase in MCP1 mRNA levels in the cerebellum of mice that consumed ethanol compared to controls, whereas no significant changes were observed in the prefrontal cortex, hippocampus, or striatum or in microglia isolated from the hippocampus and striatum. To further characterize cerebellar neuroinflammation, we measured the expression changes in other proinflammatory markers and chemokines, revealing a significant increase in the proinflammatory microRNA miR-155. Notably, other classical proinflammatory markers, such as TNFα, IL6, and IL-1β, remained unaltered, suggesting mild neuroinflammation. These results suggest that the onset of neuroinflammation in motivation-related areas is not required for high voluntary consumption in C57BL/6 mice. In addition, cerebellar susceptibility to neuroinflammation may be a trigger to the cerebellar degeneration that occurs after chronic ethanol consumption in humans.

Protective effects of Tinospora cordifolia miers extract against hepatic and neurobehavioral deficits in thioacetamide-induced hepatic encephalopathy in rats via modulating hyperammonemia and glial cell activation

ETHNOPHARMACOLOGICAL RELEVANCE

Tinospora cordifolia (TC) a potential medicinal herb, has been ethnobotanically used as an eco-friendly supplement to manage various diseases, including cerebral fever. Earlier studies have shown that TC exhibits diverse beneficial effects, including hepatoprotective and neuroprotective effects. However, the effects of TC remain unexplored in animal models of encephalopathy including hepatic encephalopathy (HE).

AIM OF THE STUDY

To evaluate the effects of TC stem extract against thioacetamide (TAA)-induced behavioural and molecular alterations in HE rats.

METHODS AND MATERIALS

The extract was preliminarily screened through phytochemical and HR-LC/MS analysis. Animals were pre-treated with TC extract at doses 30 and 100 mg/kg, orally. Following 7 days of TC pre-treatment, HE was induced by administering TAA (300 mg/kg, i. p. thrice). Behavioural assessments were performed after 56 h of TAA first dose. The animals were then sacrificed to assess biochemical parameters in serum, liver and brain. Liver tissue was used for immunoblotting and histological studies to evaluate inflammatory and fibrotic signalling. Moreover, brain tissue was used to evaluate brain edema, activation of glial cells (GFAP, IBA-1) and NF-κB/NLRP3 downstream signalling via immunoblotting and immunohistochemical analysis in cortex and hippocampus.

RESULTS

The pre-treatment with TC extract effective mitigated TAA-induced behavioural alterations, lowered serum LFT (AST, ALT, ALP, bilirubin) and oxidative stress markers in liver and brain. TC treatment significantly modulated hyperammonemia, cerebral edema and preserved the integrity of BBB proteins in HE animals. TC treatment attenuated TAA-induced histological changes, tissue inflammation (pNF-κB (p65), TNF-α, NLRP3) and fibrosis (collagen, α-SMA) in liver. In addition, immunoblotting analysis revealed TC pre-treatment inhibited fibrotic proteins such as vimentin, TGF-β1 and pSmad2/3 in the liver. Our study further showed that TC treatment downregulated the expression of MAPK/NF-κB inflammatory signalling, as well as GFAP and IBA-1 (glial cell markers) in cortex and hippocampus of TAA-intoxicated rats. Additionally, TC-treated animals exhibited reduced expression of caspase3/9 and BAX induced by TAA.

CONCLUSION

This study revealed promising insights on the protective effects of TC against HE. The findings clearly demonstrated that the significant inhibition of MAPK/NF-κB signalling and glial cell activation could be responsible for the observed beneficial effects of TC in TAA-induced HE rats.

Neuroinflammation alters GABAergic neurotransmission in hyperammonemia and hepatic encephalopathy, leading to motor incoordination. Mechanisms and therapeutic implications

Enhanced GABAergic neurotransmission contributes to impairment of motor coordination and gait and of cognitive function in different pathologies, including hyperammonemia and hepatic encephalopathy. Neuroinflammation is a main contributor to enhancement of GABAergic neurotransmission through increased activation of different pathways. For example, enhanced activation of the TNFα-TNFR1-NF-κB-glutaminase-GAT3 pathway and the TNFα-TNFR1-S1PR2-CCL2-BDNF-TrkB pathway in cerebellum of hyperammonemic rats enhances GABAergic neurotransmission. This is mediated by mechanisms affecting GABA synthesizing enzymes GAD67 and GAD65, total and extracellular GABA levels, membrane expression of GABAA receptor subunits, of GABA transporters GAT1 and GAT three and of chloride co-transporters. Reducing neuroinflammation reverses these changes, normalizes GABAergic neurotransmission and restores motor coordination. There is an interplay between GABAergic neurotransmission and neuroinflammation, which modulate each other and altogether modulate motor coordination and cognitive function. In this way, neuroinflammation may be also reduced by reducing GABAergic neurotransmission, which may also improve cognitive and motor function in pathologies associated to neuroinflammation and enhanced GABAergic neurotransmission such as hyperammonemia, hepatic encephalopathy or Parkinson's disease. This provides therapeutic targets that may be modulated to improve cognitive and motor function and other alterations such as fatigue in a wide range of pathologies. As a proof of concept it has been shown that antagonists of GABAA receptors such as bicuculline reduces neuroinflammation and improves cognitive and motor function impairment in rat models of hyperammonemia and hepatic encephalopathy. Antagonists of GABAA receptors are not ideal therapeutic tools because they can induce secondary effects. As a more effective treatment to reduce GABAergic neurotransmission new compounds modulating it by other mechanisms are being developed. Golexanolone reduces GABAergic neurotransmission by reducing the potentiation of GABAA receptor activation by neurosteroids such as allopregnanolone. Golexanolone reduces neuroinflammation and GABAergic neurotransmission in animal models of hyperammonemia, hepatic encephalopathy and cholestasis and this is associated with improvement of fatigue, cognitive impairment and motor incoordination. This type of compounds may be useful therapeutic tools to improve cognitive and motor function in different pathologies associated with neuroinflammation and increased GABAergic neurotransmission.

Infliximab alleviates memory impairment in rats with chronic pain by suppressing neuroinflammation and restoring hippocampal neurogenesis

Patients with chronic pain commonly report impaired memory. Increasing evidence has demonstrated that inhibition of neurogenesis by neuroinflammation plays a crucial role in chronic pain-associated memory impairments. There is currently a lack of treatment strategies for this condition. An increasing number of clinical trials have reported the therapeutic potential of anti-inflammatory therapies targeting tumour necrosis factor-α (TNF-α) for inflammatory diseases. The present study investigated whether infliximab alleviates chronic pain-associated memory impairments in rats with chronic constriction injury (CCI). We demonstrated that infliximab alleviated spatial memory impairment and hyperalgesia induced by CCI. Furthermore, infliximab inhibited the activation of hippocampal astrocytes and microglia and decreased the release of proinflammatory cytokines in CCI rats. Furthermore, infliximab reversed the decrease in the numbers of newborn neurons and mature neurons in the dentate gyrus (DG) caused by chronic pain. Our data provide evidence that infliximab alleviates chronic pain-associated memory impairments, suppresses neuroinflammation and restores hippocampal neurogenesis in a CCI model. These facts indicate that infliximab may be a potential therapeutic agent for the treatment of chronic pain and associated memory impairments.

A neural mass model for disturbance of alpha rhythm in the minimal hepatic encephalopathy

One of the early markers of minimal hepatic encephalopathy (MHE) is the disruption of alpha rhythm observed in electroencephalogram (EEG) signals. However, the underlying mechanisms responsible for this occurrence remain poorly understood. To address this gap, we develop a novel biophysical model MHE-AWD-NCM, encompassing the communication dynamics between a cortical neuron population (CNP) and an astrocyte population (AP), aimed at investigating the relationship between alpha wave disturbance (AWD) and mechanistical principles, specifically concerning astrocyte-neuronal communication in the context of MHE. In addition, we introduce the concepts of peak power density and peak frequency within the alpha band as quantitative measures of AWD. Our model faithfully reproduces the characteristic EEG phenomenology during MHE and shows how impairments of communication between CNP and AP could promote AWD. The results suggest that the disruptions in feedback neurotransmission from AP to CNP, along with the inhibition of GABA uptake by AP from the extracellular space, contribute to the observed AWD. Moreover, we found that the variation of external excitatory stimuli on CNP may play a key role in AWD in MHE. Finally, the sensitivity analysis is also performed to assess the relative significance of above factors in influencing AWD. Our findings align with the physiological observations and provide a more comprehensive understanding of the complex interplay of astrocyte-neuronal communication that underlies the AWD observed in MHE, which potentially may help to explore the targeted therapeutic interventions for the early stage of hepatic encephalopathy.

Morphine aggravates inflammatory, behavioral, and hippocampal structural deficits in septic rats

Although pain and sepsis are comorbidities of intensive care units, reported data on whether pain control by opioid analgesics could alter inflammatory and end-organ damage caused by sepsis remain inconclusive. Here, we tested the hypothesis that morphine, the gold standard narcotic analgesic, modifies behavioral and hippocampal structural defects induced by sepsis in male rats. Sepsis was induced with cecal ligation and puncture (CLP) and behavioral studies were undertaken 24 h later in septic and/or morphine-treated animals. The induction of sepsis or exposure to morphine (7 mg/kg) elicited similar: (i) falls in systolic blood pressure, (ii) alterations in spatial memory and learning tested by the Morris water maze, and (iii) depression of exploratory behavior measured by the new object recognition test. These hemodynamic and cognitive defects were significantly exaggerated in septic rats treated with morphine compared with individual interventions. Similar patterns of amplified inflammatory (IL-1β) and histopathological signs of hippocampal damage were noted in morphine-treated septic rats. Additionally, the presence of intact opioid receptors is mandatory for the induction of behavioral and hemodynamic effects of morphine because no such effects were observed when the receptors were blocked by naloxone. That said, our findings suggest that morphine provokes sepsis manifestations of inflammation and interrelated hemodynamic, behavioral, and hippocampal deficits.

TNF-α blockage by etanercept restores spatial learning and reduces cellular degeneration in the hippocampus during liver cirrhosis

Hepatic encephalopathy (HE) is one of the most debilitating cerebral complications of liver cirrhosis. The one-year survival of patients with liver cirrhosis and severe encephalopathy is less than 50%. Recent studies have indicated that neuroinflammation is a new player in the pathogenesis of HE, which seems to be involved in the development of cognitive impairment. In this study, we demonstrated neurobehavioral and neuropathological consequences of liver cirrhosis and tested the therapeutic potential of the tumor necrosis factor-α (TNF-α) inhibitor, etanercept. Sixty male adult Wistar albino rats (120-190 g) were allocated into four groups, where groups I and IV served as controls. Thioacetamide (TAA; 300 mg/kg) was intraperitoneally injected twice a week for five months to induce liver cirrhosis in group II (n = 20). Both TAA and etanercept (2 mg/kg) were administered to group III (n = 20). At the end of the experiment, spatial learning was assessed using Morris water maze. TNF-α was detected in both serum and hippocampus. The excised brains were also immunohistochemically stained with glial fibrillary acidic protein (GFAP) to estimate both the number and integrity of hippocampal astrocytes. Ultrastructural changes in the hippocampus were characterized by transmission electron microscopy. The results showed that blocking TNF-α by etanercept was accompanied by a lower TNF-α expression and a higher number of GFAP-positive astrocytes in the hippocampus. Etanercept intervention alleviated the neuronal and glial degenerative changes and impeded the deterioration of spatial learning ability. In conclusion, TNF-α is strongly involved in the development of liver cirrhosis and the associated encephalopathy. TNF-α blockers may be a promising approach for management of hepatic cirrhosis and its cerebral complications.

Effectiveness of Adjunctive High-Dose Infliximab Therapy to Improve Disability-Free Survival Among Patients With Severe Central Nervous System Tuberculosis: A Matched Retrospective Cohort Study

BACKGROUND

Few treatment options exist for patients with severe central nervous system (CNS) tuberculosis (TB) worsening due to inflammatory lesions, despite optimal antitubercular therapy (ATT) and steroids. Data regarding the efficacy and safety of infliximab in these patients are sparse.

METHODS

We performed a matched retrospective cohort study based on Medical Research Council (MRC) grading system and modified Rankin Scale (mRS) scores comparing 2 groups of adults with CNS TB. Cohort A received at least 1 dose of infliximab after optimal ATT and steroids between March 2019 and July 2022. Cohort B received only ATT and steroids. Disability-free survival (mRS score ≤2) at 6 months was the primary outcome.

RESULTS

Baseline MRC grades and mRS scores were similar between the cohorts. Median duration before initiation of infliximab therapy from start of ATT and steroids was 6 (IQR: 3.7-13) months and for neurological deficits was 4 (IQR: 2-6.2) months. Indications for infliximab were symptomatic tuberculomas (20/30; 66.7%), spinal cord involvement with paraparesis (8/30; 26.7%), and optochiasmatic arachnoiditis (3/30; 10%), worsening despite adequate ATT and steroids. Severe disability (5/30 [16.7%] and 21/60 [35%]) and all-cause mortality (2/30 [6.7%] and 13/60 [21.7%]) at 6 months were lower in cohort A versus cohort B, respectively. In the combined study population, only exposure to infliximab was positively associated (aRR: 6.2; 95% CI: 2.18-17.83; P = .001) with disability-free survival at 6 months. There were no clear infliximab-related side effects noted.

CONCLUSIONS

Infliximab may be an effective and safe adjunctive strategy among severely disabled patients with CNS TB not improving despite optimal ATT and steroids. Adequately powered phase 3 clinical trials are required to confirm these early findings.

Patients who died with steatohepatitis or liver cirrhosis show neuroinflammation and neuronal loss in hippocampus

BACKGROUND

Neuroinflammation in the cerebral cortex of patients who died with liver cirrhosis and neuroinflammation, and neuronal death in the cerebellum of patients who died with steatohepatitis or cirrhosis, were reported. Hippocampal neuroinflammation could contribute to cognitive decline in patients with liver disease, but this has yet to be studied. The study aims were to assess if hippocampus from patients who died with steatohepatitis or cirrhosis showed: (i) glial activation, (ii) altered cytokine content, (iii) immune cell infiltration, (iv) neuronal apoptosis and (v) neuronal loss.

METHODS

Post-mortem hippocampus was obtained from 6 controls, 19 patients with steatohepatitis (SH) and 4 patients with liver cirrhosis. SH patients were divided into SH1 (n = 9), SH2 (n = 6) and SH3 (n = 4) groups depending on disease severity. Glial activation, IL-1β and TNFα content, CD4 lymphocyte and monocyte infiltration, neuronal apoptosis and neuronal loss were analyzed by immunohistochemistry.

RESULTS

Patients who died in SH1 showed astrocyte activation, whereas those who died in SH2 also showed microglial activation, CD4 lymphocyte and monocyte infiltration, neuronal apoptosis and neuronal loss. These changes remained in patients in SH3, who also showed increased IL-1β and TNFα. Patients who died of liver cirrhosis did not show CD4 lymphocyte infiltration, neuronal apoptosis or increase in TNFα, but still showed glial activation, increased IL-1β and neuronal loss.

CONCLUSIONS

Patients with steatohepatitis showed glial activation, immune cell infiltration, apoptosis and neuronal loss. Glial activation and neuronal loss remained in cirrhotic patients. This may explain the irreversibility of some cognitive alterations in hepatic encephalopathy. Cognitive reserve may contribute to different grades of cognitive impairment despite similar neuronal loss.

Anti-inflammatory strategies for hepatic encephalopathy: preclinical studies

Hepatic encephalopathy (HE) is a potentially reversible neuropsychiatric syndrome. Often, HE causes cognitive and motor dysfunctions due to an acute or chronic insufficiency of the liver or a shunting between the hepatic portal vein and systemic vasculature. Liver damage induces peripheral changes, such as in the metabolism and peripheral inflammatory responses that trigger exacerbated neuroinflammation. In experimental models, anti-inflammatory strategies have demonstrated neuroprotective effects, leading to a reduction in HE-related cognitive and motor impairments. In this scenario, a growing body of evidence has shown that peripheral and central nervous system inflammation are promising preclinical targets. In this review, we performed an overview of FDA-approved drugs and natural compounds which are used in the treatment of other neurological and nonneurological diseases that have played a neuroprotective role in experimental HE, at least in part, through anti-inflammatory mechanisms. Despite the exciting results from animal models, the available data should be critically interpreted, highlighting the importance of translating the findings for clinical essays.

Effects of oxidative stress on hepatic encephalopathy pathogenesis in mice

Oxidative stress plays a crucial role in the pathogenesis of hepatic encephalopathy (HE), but the mechanism remains unclear. GABAergic neurons in substantia nigra pars reticulata (SNr) contribute to the motor deficit of HE. The present study aims to investigate the effects of oxidative stress on HE in male mice. The results validate the existence of oxidative stress in both liver and SNr across two murine models of HE induced by thioacetamide (TAA) and bile duct ligation (BDL). Systemic mitochondria-targeted antioxidative drug mitoquinone (Mito-Q) rescues mitochondrial dysfunction and oxidative injury in SNr, so as to restore the locomotor impairment in TAA and BDL mice. Furthermore, the GAD2-expressing SNr population (SNr^GAD2) is activated by HE. Both overexpression of mitochondrial uncoupling protein 2 (UCP2) targeted to SNr^GAD2 and SNr^GAD2-targeted chemogenetic inhibition targeted to SNr^GAD2 rescue mitochondrial dysfunction in TAA-induced HE. These results define the key role of oxidative stress in the pathogenesis of HE.

Hepatic encephalopathy: investigational drugs in preclinical and early phase development

INTRODUCTION

Hepatic encephalopathy (HE) is a neuropsychiatric syndrome, in patients with liver disease, which affects life quality and span. Current treatments are lactulose or rifaximin, acting on gut microbiota. Treatments aiming ammonia levels reduction have been tested with little success.

AREAS COVERED

Pre-clinical research shows that the process inducing HE involves sequentially: liver failure, altered microbiome, hyperammonemia, peripheral inflammation, changes in immunophenotype and extracellular vesicles and neuroinflammation, which alters neurotransmission impairing cognitive and motor function. HE may be reversed using drugs acting at any step: modulating microbiota with probiotics or fecal transplantation; reducing peripheral inflammation with anti-TNFα, autotaxin inhibitors or silymarin; reducing neuroinflammation with sulforaphane, p38 MAP kinase or phosphodiesteras 5 inhibitors, antagonists of sphingosine-1-phosphate receptor 2, enhancing meningeal lymphatic drainage or with extracellular vesicles from mesenchymal stem cells; reducing GABAergic neurotransmission with indomethacin or golexanolone.

EXPERT OPINION

A factor limiting the progress of HE treatment is the lack of translation of research advances into clinical trials. Only drugs acting on microbiota or ammonia reduction have been tested in patients. It is urgent to change the mentality on how to approach HE treatment to develop clinical trials to assess drugs acting on the immune system/peripheral inflammation, neuroinflammation or neurotransmission to improve HE.

Active Clinical Trials in Hepatic Encephalopathy: Something Old, Something New and Something Borrowed

Hepatic encephalopathy (HE) is a potentially reversible neurocognitive syndrome that occurs in patients with acute or chronic liver disease. Currently, most of the therapies for HE aim to reduce ammonia production or increase its elimination. To date, only two agents have been approved as treatments for HE: lactulose and rifaximin. Many other drugs have also been used, but data to support their use are limited, preliminary or lacking. The aim of this review is to provide an overview and discussion of the current development of treatments for HE. Data from ongoing clinical trials in HE were obtained from the ClinicalTrials.gov website, and a breakdown analysis of studies that were active on August 19th, 2022, was performed. Seventeen registered and ongoing clinical trials for therapeutics targeting HE were identified. More than 75% of these agents are in phase II (41.2%) or in phase III (34.7%). Among them, there are many old acquaintances in the field, such as lactulose and rifaximin, some new entries such as fecal microbiota transplantation and equine anti-thymocyte globulin, an immunosuppressive agent, but also some therapies borrowed from other conditions, such as rifamycin SV MMX and nitazoxanide, two antimicrobial agents FDA approved for the treatment of some types of diarrheas or VE303 and RBX7455, two microbiome restoration therapies, currently used as treatment of high-risk Clostridioides difficile infections. If working, some of these drugs could soon be used as valid alternatives to current therapies when ineffective or be approved as novel therapeutic approaches to improve the quality of life of HE patients.

Effect of Huangdisan grain on improving cognitive impairment in VD rats and its mechanism in immune inflammatory response

BACKGROUND

Vascular dementia (VD) is the second most common type of dementia after Alzheimer's disease (AD). Although the incidence rate is very high, there is no definitive treatment for VD. And it has serious impact on the quality of life of VD patients. In recent years, more and more studies about the clinical efficacy and pharmacological effects of traditional Chinese medicine (TCM) in the treatment of VD have been conducted. And Huangdisan grain has been used to treat VD patients with a good curative effect in clinic.

OBJECTIVE

This study was designed to investigate the effect of Huangdisan grain on the inflammatory response and cognitive function of VD rats modeled by bilateral common carotid artery occlusion (BCCAO), that aimed to improve the treatment methods for VD.

METHODS

8-week-old healthy SPF male Wistar rats (280 ± 20 g) were randomly divided into the normal group (Gn, n = 10), sham operated group (Gs, n = 10), and operated group (Go, n = 35). The VD rat models in Go group were established by BCCAO. 8 weeks after surgery, the operated rats were screened by the hidden platform trail of Morris Water Maze (MWM), and the rats with cognitive dysfunction were further randomly divided into the impaired group (Gi, n = 10) and TCM group (Gm, n = 10). The VD rats in Gm group were given the intragastric administration of Huangdisan grain decoction once a day for 8 weeks, and the other groups were given intragastric administration of normal saline. Then the cognitive ability of rats in each group was detected by the MWM Test. The lymphocyte subsets in peripheral blood and hippocampus of rats were measured by flow cytometry. The levels of cytokines (IL-1β, IL-2, IL-4, IL-10, TNF-α, INF-γ, MIP-2, COX-2, iNOS) in peripheral blood and hippocampus were measured by ELISA (enzyme linked immunosorbent assay). The number of Iba-1⁺ CD68⁺ co-positive cells in the CA1 region of hippocampus was measured by immunofluorescence.

RESULTS

Compared with the Gn group, the escape latencies of the Gi group were prolonged (P < 0.01), the time spent in the former platform quadrant was shortened (P < 0.01), and the number of times of crossing over the former platform location was reduced (P < 0.05). But compared with the Gi group, the escape latencies of Gm group were shortened (P < 0.01), the time spent in the former platform quadrant was prolonged (P < 0.05), and the number of times of crossing over the former platform location was increased (P < 0.05). The number of Iba-1⁺ CD68⁺ co-positive cells in the CA1 region of hippocampus of VD rats in Gi group was increased (P < 0.01) compared with the Gn group. And the proportions of T Cells, CD4⁺ T Cells, CD8⁺ T Cells in the hippocampus were increased (P < 0.01). The level of pro-inflammatory cytokines in the hippocampus was increased significantly, such as IL-1β (P < 0.01), IL-2 (P < 0.01), TNF-α (P < 0.05), IFN-γ (P < 0.01), COX-2 (P < 0.01), MIP-2 (P < 0.01) and iNOS (P < 0.05). And the level of IL-10 (P < 0.01), a kind of anti-inflammatory cytokine, was decreased. The proportions of T Cells (P < 0.05), CD4⁺ T Cells (P < 0.01) and NK Cells (P < 0.05) in the peripheral blood of the VD rats in Gi group were decreased, and the level of IL-1β, IL-2, TNF-α, IFN-γ, COX-2, MIP-2 and iNOS was increased significantly (P < 0.01) compared with the Gn group. Meanwhile, the level of IL-4 and IL-10 was decreased (P < 0.01). Huangdisan grain could reduce the number of Iba-1⁺ CD68⁺ co-positive cells in the CA1 region of hippocampus (P < 0.01), decrease the proportions of T Cells, CD4⁺ T Cells, CD8⁺ T Cells and the level of IL-1β, MIP-2 in hippocampus (P < 0.01) of VD rats. Moreover, it could rise the proportion of NK Cells (P < 0.01) and the level of IL-4 (P < 0.05), IL-10 (P < 0.05), and decrease the level of IL-1β (P < 0.01), IL-2 (P < 0.05), TNF-α (P < 0.01), IFN-γ (P < 0.01), COX-2 (P < 0.01) and MIP-2 (P < 0.01) in peripheral blood of VD rats.

CONCLUSION

This study indicated that Huangdisan grain could decrease the activation of microglia/macrophages, regulate the proportions of lymphocyte subsets and the level of cytokines, which could adjust the immunologic abnormalities of VD rats, and ultimately improve cognitive function.

Extracellular vesicles from mesenchymal stem cells reduce neuroinflammation in hippocampus and restore cognitive function in hyperammonemic rats

Chronic hyperammonemia, a main contributor to hepatic encephalopathy (HE), leads to neuroinflammation which alters neurotransmission leading to cognitive impairment. There are no specific treatments for the neurological alterations in HE. Extracellular vesicles (EVs) from mesenchymal stem cells (MSCs) reduce neuroinflammation in some pathological conditions. The aims were to assess if treatment of hyperammonemic rats with EVs from MSCs restores cognitive function and analyze the underlying mechanisms. EVs injected in vivo reach the hippocampus and restore performance of hyperammonemic rats in object location, object recognition, short-term memory in the Y-maze and reference memory in the radial maze. Hyperammonemic rats show reduced TGFβ levels and membrane expression of TGFβ receptors in hippocampus. This leads to microglia activation and reduced Smad7-IkB pathway, which induces NF-κB nuclear translocation in neurons, increasing IL-1β which alters AMPA and NMDA receptors membrane expression, leading to cognitive impairment. These effects are reversed by TGFβ in the EVs from MSCs, which activates TGFβ receptors, reducing microglia activation and NF-κB nuclear translocation in neurons by normalizing the Smad7-IkB pathway. This normalizes IL-1β, AMPA and NMDA receptors membrane expression and, therefore, cognitive function. EVs from MSCs may be useful to improve cognitive function in patients with hyperammonemia and minimal HE.

The role of brain inflammation and abnormal brain oxygen homeostasis in the development of hepatic encephalopathy

Hepatic encephalopathy (HE) is a frequent complication of chronic liver disease (CLD) and has a complex pathogenesis. Several preclinical and clinical studies have reported the presence of both peripheral and brain inflammation in CLD and their potential impact in the development of HE. Altered brain vascular density and tone, as well as compromised cerebral and systemic blood flow contributing to the development of brain hypoxia, have also been reported in animal models of HE, while a decrease in cerebral metabolic rate of oxygen and cerebral blood flow has consistently been observed in patients with HE. Whilst significant strides in our understanding have been made over the years, evaluating all these mechanistic elements in vivo and showing causal association with development of HE, have been limited through the practical constraints of experimentation. Nonetheless, improvements in non-invasive assessments of different neurophysiological parameters, coupled with techniques to assess changes in inflammatory and metabolic pathways, will help provide more granular insights on these mechanisms. In this special issue we discuss some of the emerging evidence supporting the hypothesis that brain inflammation and abnormal oxygen homeostasis occur interdependently during CLD and comprise important contributors to the development of HE. This review aims at furnishing evidence for further research in brain inflammation and oxygen homeostasis as additional therapeutic targets and potentially diagnostic markers for HE.

Extracellular Vesicles From Hyperammonemic Rats Induce Neuroinflammation in Cerebellum of Normal Rats: Role of Increased TNFα Content

Hyperammonemia plays a main role in the neurological impairment in cirrhotic patients with hepatic encephalopathy. Rats with chronic hyperammonemia reproduce the motor incoordination of patients with minimal hepatic encephalopathy, which is due to enhanced GABAergic neurotransmission in cerebellum as a consequence of neuroinflammation. Extracellular vesicles (EVs) could play a key role in the transmission of peripheral alterations to the brain to induce neuroinflammation and neurological impairment in hyperammonemia and hepatic encephalopathy. EVs from plasma of hyperammonemic rats (HA-EVs) injected to normal rats induce neuroinflammation and motor incoordination, but the underlying mechanisms remain unclear. The aim of this work was to advance in the understanding of these mechanisms. To do this we used an ex vivo system. Cerebellar slices from normal rats were treated ex vivo with HA-EVs. The aims were: 1) assess if HA-EVs induce microglia and astrocytes activation and neuroinflammation in cerebellar slices of normal rats, 2) assess if this is associated with activation of the TNFR1-NF-kB-glutaminase-GAT3 pathway, 3) assess if the TNFR1-CCL2-BDNF-TrkB pathway is activated by HA-EVs and 4) assess if the increased TNFα levels in HA-EVs are responsible for the above effects and if they are prevented by blocking the action of TNFα. Our results show that ex vivo treatment of cerebellar slices from control rats with extracellular vesicles from hyperammonemic rats induce glial activation, neuroinflammation and enhance GABAergic neurotransmission, reproducing the effects induced by hyperammonemia in vivo. Moreover, we identify in detail key underlying mechanisms. HA-EVs induce the activation of both the TNFR1-CCL2-BDNF-TrkB-KCC2 pathway and the TNFR1-NF-kB-glutaminase-GAT3 pathway. Activation of these pathways enhances GABAergic neurotransmission in cerebellum, which is responsible for the induction of motor incoordination by HA-EVs. The data also show that the increased levels of TNFα in HA-EVs are responsible for the above effects and that the activation of both pathways is prevented by blocking the action of TNFα. This opens new therapeutic options to improve motor incoordination in hyperammonemia and also in cirrhotic patients with hepatic encephalopathy and likely in other pathologies in which altered cargo of extracellular vesicles contribute to the propagation of the pathology.

Pathogenesis of sepsis-associated encephalopathy: more than blood-brain barrier dysfunction

Sepsis-associated encephalopathy is a common neurological complication of sepsis and is responsible for higher mortality and poorer long-term outcomes in septic patients. Sepsis-associated encephalopathy symptoms can range from mild delirium to deep coma, which occurs in up to 70% of patients in intensive care units. The pathological changes in the brain associated with sepsis include cerebral ischaemia, cerebral haemorrhage, abscess and progressive multifocal necrotic leukoencephalopathy. Several mechanisms are involved in the pathogenesis of sepsis-associated encephalopathy, such as blood-brain barrier dysfunction, cerebral blood flow impairment, glial cell activation, leukocyte transmigration, and neurotransmitter disturbances. These events are interrelated and influence each other, therefore they do not act as independent factors. This review is focused on new evidence showing the pathological process of sepsis-associated encephalopathy.

Rifaximin Improves Spatial Learning and Memory Impairment in Rats with Liver Damage-Associated Neuroinflammation

Patients with non-alcoholic fatty liver disease (NAFLD) may show mild cognitive impairment. Neuroinflammation in the hippocampus mediates cognitive impairment in rat models of minimal hepatic encephalopathy (MHE). Treatment with rifaximin reverses cognitive impairment in a large proportion of cirrhotic patients with MHE. However, the underlying mechanisms remain unclear. The aims of this work were to assess if rats with mild liver damage, as a model of NAFLD, show neuroinflammation in the hippocampus and impaired cognitive function, if treatment with rifaximin reverses it, and to study the underlying mechanisms. Mild liver damage was induced with carbon-tetrachloride. Infiltration of immune cells, glial activation, and cytokine expression, as well as glutamate receptors expression in the hippocampus and cognitive function were assessed. We assessed the effects of daily treatment with rifaximin on the alterations showed by these rats. Rats with mild liver damage showed hippocampal neuroinflammation, reduced membrane expression of glutamate N-methyl-D-aspartate (NMDA) receptor subunits, and impaired spatial memory. Increased C-C Motif Chemokine Ligand 2 (CCL2), infiltration of monocytes, microglia activation, and increased tumor necrosis factor α (TNFα) were reversed by rifaximin, that normalized NMDA receptor expression and improved spatial memory. Thus, rifaximin reduces neuroinflammation and improves cognitive function in rats with mild liver damage, being a promising therapy for patients with NAFLD showing mild cognitive impairment.

Infliximab and/or MESNA alleviate doxorubicin-induced Alzheimer's disease-like pathology in rats: A new insight into TNF-α/Wnt/β-catenin signaling pathway

AIMS

The current study aimed to elucidate the neurotoxic potential of DOX to induce AD-like pathology paying attention to the role of wingless-integrated/β-catenin (Wnt/β-catenin) signaling pathway. A major aim was to evaluate the efficacy of infliximab (IFX) either individually or in combination with 2-mercaptoethane sulfonate sodium (MESNA) on the DOX-induced neurotoxicity in rats.

METHODOLOGY

AD-like pathology was induced in adult male Wistar rats by intraperitoneal (i.p.) administration of DOX at a dose of 3.5 mg/kg twice a week for 3 weeks. DOX-injected rats were then treated with either INF at a single dose of 5 mg/kg i.p. (IFX group), MESNA at a dose of 160 mg/kg/day i.p. for 4 weeks (MESNA group) or their combination at the same specified doses (INF + MESNA group). At the end of the study period, behavioral assessment was performed and the brain tissue samples were harvested at sacrifice.

KEY FINDINGS

DOX-treated rats significantly exhibited AD-like brain injury, increased amyloid burden, enhanced neuroinflammation and apoptosis, and multifocal histological injury in the cerebral cortex with widespread vacuolations. IFX and MESNA significantly reversed all the aforementioned detrimental effects in the DOX-treated rats.

SIGNIFICANCE

The study has provided sufficient evidence of the potential of IFX and/or MESNA to ameliorate the DOX-induced neurotoxicity, with the best improvement observed with their combined administration. A new insight has been introduced into the critical role of Wnt/β-catenin activation.

Hyperammonemia Enhances GABAergic Neurotransmission in Hippocampus: Underlying Mechanisms and Modulation by Extracellular cGMP

Rats with chronic hyperammonemia reproduce the cognitive and motor impairment present in patients with hepatic encephalopathy. It has been proposed that enhanced GABAergic neurotransmission in hippocampus may contribute to impaired learning and memory in hyperammonemic rats. However, there are no direct evidences of the effects of hyperammonemia on GABAergic neurotransmission in hippocampus or on the underlying mechanisms. The aims of this work were to assess if chronic hyperammonemia enhances the function of GABA_A receptors in hippocampus and to identify the underlying mechanisms. Activation of GABA_A receptors is enhanced in hippocampus of hyperammonemic rats, as analyzed in a multielectrode array system. Hyperammonemia reduces membrane expression of the GABA transporters GAT1 and GAT3, which is associated with increased extracellular GABA concentration. Hyperammonemia also increases gephyrin levels and phosphorylation of the β3 subunit of GABA_A receptor, which are associated with increased membrane expression of the GABA_A receptor subunits α1, α2, γ2, β3, and δ. Enhanced levels of extracellular GABA and increased membrane expression of GABA_A receptors would be responsible for the enhanced GABAergic neurotransmission in hippocampus of hyperammonemic rats. Increasing extracellular cGMP reverses the increase in GABA_A receptors activation by normalizing the membrane expression of GABA transporters and GABA_A receptors. The increased GABAergic neurotransmission in hippocampus would contribute to cognitive impairment in hyperammonemic rats. The results reported suggest that reducing GABAergic tone in hippocampus by increasing extracellular cGMP or by other means may be useful to improve cognitive function in hyperammonemia and in cirrhotic patients with minimal or clinical hepatic encephalopathy.

The neurogliovascular unit in hepatic encephalopathy

Hepatic encephalopathy (HE) is a neurological complication of hepatic dysfunction and portosystemic shunting. It is highly prevalent in patients with cirrhosis and is associated with poor outcomes. New insights into the role of peripheral origins in HE have led to the development of innovative treatment strategies like faecal microbiota transplantation. However, this broadening of view has not been applied fully to perturbations in the central nervous system. The old paradigm that HE is the clinical manifestation of ammonia-induced astrocyte dysfunction and its secondary neuronal consequences requires updating. In this review, we will use the holistic concept of the neurogliovascular unit to describe central nervous system disturbances in HE, an approach that has proven instrumental in other neurological disorders. We will describe HE as a global dysfunction of the neurogliovascular unit, where blood flow and nutrient supply to the brain, as well as the function of the blood-brain barrier, are impaired. This leads to an accumulation of neurotoxic substances, chief among them ammonia and inflammatory mediators, causing dysfunction of astrocytes and microglia. Finally, glymphatic dysfunction impairs the clearance of these neurotoxins, further aggravating their effect on the brain. Taking a broader view of central nervous system alterations in liver disease could serve as the basis for further research into the specific brain pathophysiology of HE, as well as the development of therapeutic strategies specifically aimed at counteracting the often irreversible central nervous system damage seen in these patients.

Neuroinflammation in neurological disorders: pharmacotherapeutic targets from bench to bedside

Neuroinflammation is one of the host defensive mechanisms through which the nervous system protects itself from pathogenic and or infectious insults. Moreover, neuroinflammation occurs as one of the most common pathological outcomes in various neurological disorders, makes it the promising target. The present review focuses on elaborating the recent advancement in understanding molecular mechanisms of neuroinflammation and its role in the etiopathogenesis of various neurological disorders, especially Alzheimer's disease (AD), Parkinson's disease (PD), and Epilepsy. Furthermore, the current status of anti-inflammatory agents in neurological diseases has been summarized in light of different preclinical and clinical studies. Finally, possible limitations and future directions for the effective use of anti-inflammatory agents in neurological disorders have been discussed.

Effects of long-term infliximab and tocilizumab treatment on anxiety-like behavior and cognitive function in naive rats

BACKGROUND

Circulating cytokines have been proposed to be implicated in the development of mood disorders and cognitive impairment. This study aims to examine the effect of chronic treatment with infliximab, a tumor necrosis factor-alpha (TNF-alpha) inhibitor, and tocilizumab, an antibody against interleukin-6 (IL-6) receptor on anxiety-like behavior and cognitive function.

METHODS

Twenty-eight male, Wistar rats were randomly allocated into negative control, vehicle, infliximab and tocilizumab groups. After 8 weeks of intraperitoneal drug administration, rats performed the elevated-plus maze, the elevated-zero maze, the olfactory social memory and the passive avoidance tests. Brain sections at the level of the hippocampus, the amygdala and the prefrontal cortex were histologically examined. Finally, hippocampal and amygdaloid brain-derived neurotrophic factor (BDNF) expression was determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR).

RESULTS

Infliximab group exhibited a significantly higher number of entries and time spent into the open arms of the mazes, showing a lower level of anxiety. In the olfactory social memory test, tocilizumab significantly increased the ratio of interaction. Both infliximab- and tocilizumab-treated animals had a significantly lower latency time in the passive avoidance test that suggests an improved memory. Histological examination revealed similar morphology and neuronal density between groups. BDNF expression levels were significantly increased in the groups receiving anti-cytokine treatment.

CONCLUSIONS

Our findings suggest that long-term peripheral TNF-alpha and IL-6 inhibition improves anxiety and cognitive function in rats and leads to an increased BDNF expression in the brain.

The NF-κB Nucleolar Stress Response Pathway

The nuclear organelle, the nucleolus, plays a critical role in stress response and the regulation of cellular homeostasis. P53 as a downstream effector of nucleolar stress is well defined. However, new data suggests that NF-κB also acts downstream of nucleolar stress to regulate cell growth and death. In this review, we will provide insight into the NF-κB nucleolar stress response pathway. We will discuss apoptosis mediated by nucleolar sequestration of RelA and new data demonstrating a role for p62 (sequestosome (SQSTM1)) in this process. We will also discuss activation of NF-κB signalling by degradation of the RNA polymerase I (PolI) complex component, transcription initiation factor-IA (TIF-IA (RRN3)), and contexts where TIF-IA-NF-κB signalling may be important. Finally, we will discuss how this pathway is targeted by aspirin to mediate apoptosis of colon cancer cells.

Rifaximin Prevents T-Lymphocytes and Macrophages Infiltration in Cerebellum and Restores Motor Incoordination in Rats with Mild Liver Damage

In patients with liver cirrhosis, minimal hepatic encephalopathy (MHE) is triggered by a shift in peripheral inflammation, promoting lymphocyte infiltration into the brain. Rifaximin improves neurological function in MHE by normalizing peripheral inflammation. Patients who died with steatohepatitis showed T-lymphocyte infiltration and neuroinflammation in the cerebellum, suggesting that MHE may already occur in these patients. The aims of this work were to assess, in a rat model of mild liver damage similar to steatohepatitis, whether: (1) the rats show impaired motor coordination in the early phases of liver damage; (2) this is associated with changes in the immune system and infiltration of immune cells into the brain; and (3) rifaximin improves motor incoordination, associated with improved peripheral inflammation, reduced infiltration of immune cells and neuroinflammation in the cerebellum, and restoration of the alterations in neurotransmission. Liver damage was induced by carbon tetrachloride (CCl₄) injection over four weeks. Peripheral inflammation, immune cell infiltration, neuroinflammation, and neurotransmission in the cerebellum and motor coordination were assessed. Mild liver damage induces neuroinflammation and altered neurotransmission in the cerebellum and motor incoordination. These alterations are associated with increased TNFa, CCL20, and CX3CL1 in plasma and cerebellum, IL-17 and IL-15 in plasma, and CCL2 in cerebellum. This promotes T-lymphocyte and macrophage infiltration in the cerebellum. Early treatment with rifaximin prevents the shift in peripheral inflammation, immune cell infiltration, neuroinflammation, and motor incoordination. This report provides new clues regarding the mechanisms of the beneficial effects of rifaximin, suggesting that early rifaximin treatment could prevent neurological impairment in patients with steatohepatitis.

The Dual Role of the GABAA Receptor in Peripheral Inflammation and Neuroinflammation: A Study in Hyperammonemic Rats

Cognitive and motor impairment in minimal hepatic encephalopathy (MHE) are mediated by neuroinflammation, which is induced by hyperammonemia and peripheral inflammation. GABAergic neurotransmission in the cerebellum is altered in rats with chronic hyperammonemia. The mechanisms by which hyperammonemia induces neuroinflammation remain unknown. We hypothesized that GABA_A receptors can modulate cerebellar neuroinflammation. The GABA_A antagonist bicuculline was administrated daily (i.p.) for four weeks in control and hyperammonemic rats. Its effects on peripheral inflammation and on neuroinflammation as well as glutamate and GABA neurotransmission in the cerebellum were assessed. In hyperammonemic rats, bicuculline decreases IL-6 and TNFα and increases IL-10 in the plasma, reduces astrocyte activation, induces the microglia M2 phenotype, and reduces IL-1β and TNFα in the cerebellum. However, in control rats, bicuculline increases IL-6 and decreases IL-10 plasma levels and induces microglial activation. Bicuculline restores the membrane expression of some glutamate and GABA transporters restoring the extracellular levels of GABA in hyperammonemic rats. Blocking GABA_A receptors improves peripheral inflammation and cerebellar neuroinflammation, restoring neurotransmission in hyperammonemic rats, whereas it induces inflammation and neuroinflammation in controls. This suggests a complex interaction between GABAergic and immune systems. The modulation of GABA_A receptors could be a suitable target for improving neuroinflammation in MHE.

Babao Dan improves neurocognitive function by inhibiting inflammation in clinical minimal hepatic encephalopathy

BACKGROUND AND PURPOSE

Inflammation has been considered a precipitating event that contributes to neurocognitive dysfunction in minimal hepatic encephalopathy (MHE). Inhibition TLR-4 related inflammation can effectively improve neurocognitive dysfunction of MHE. Our previous study showed that Babao Dan (BBD) effectively inhibited inflammation and ameliorated neurocognitive function in rats with acute hepatic encephalopathy (HE) and chronic HE. The mechanism may lie in the regulation of TLR4 signaling pathway. Therefore, this study aimed to evaluate the role of BBD in the treatment of MHE patients with cirrhosis and to elucidate the underlying mechanism by which BBD regulated TLR4 pathway to alleviate inflammation.

METHODS

A randomized controlled trial (n = 62) was conducted to evaluate the clinical efficacy between BBD plus lactulose (n = 31) and lactulose alone (n = 31) in MHE patients by testing neurocognitive function (NCT-A and DST), blood ammonia, liver function (ALT, AST and TBIL) and blood inflammation (IL-1β, IL-6 and TNF-α). Afterward, we detected NO, inflammatory cytokines (IL-1β, IL-6 and TNF-α) and the phosphorylation of P65, JNK, ERK as well as P38 in LPS-activated rat primary bone marrow-derived macrophages (BMDMs), peritoneal macrophages (PMs), and mouse primary BMDMs/PMs/microglia/astrocytes, to investigate the underlying mechanism of BBD inhibiting inflammation through TLR4 pathway. Also, the survival rate of mice, liver function (ALT, AST), blood inflammation (IL-1β, IL-6 and TNF-α), inflammatory cytokines (IL-1β, IL-6 and TNF-α) and histopathological changes in the liver, brain and lung were measured to assess the anti-inflammatory effect of BBD on neurocognitive function in endotoxin shock/endotoxemia mice.

RESULTS

BBD combined with lactulose significantly ameliorated neurocognitive function by decreasing NCT-A (p＜0.001) and increasing DST (p＜0.001); inhibited systemic inflammation by decreasing IL-1β (p＜0.001), IL-6(p＜0.001) and TNF-α (p＜0.001); reduced ammonia level (p = 0.005), and improved liver function by decreasing ALT(p = 0.043), AST(p = 0.003) and TBIL (p = 0.026) in MHE patients. Furthermore, BBD inhibited gene and protein expression of IL-1β, IL-6 and TNF-α as well as NO in rat primary BMDMs/PMs, and mouse primary BMDMs/PMs/microglia/astrocytes in a dose-dependent manner. BBD inhibited the activation of mouse primary BMDMs/PMs/microglia/astrocytes by regulating TLR4 pathway involving the phosphorylation of P65, JNK, ERK and P38. Also, BBD reduced the mortality of mice with endotoxin shock/endotoxemia; serum levels of ALT, AST, IL-1β, IL-6 and TNF-α; gene expression of IL-1β, IL-6 and TNF-α in the liver, brain and lung, and tissue damage in the liver and lung.

CONCLUSION

Our study provided for the first time clinical and experimental evidence supporting the use of BBD in MHE, and revealed that BBD could play a crucial role in targeting and regulating TLR4 inflammatory pathway to improve neurocognitive function in MHE patients.

Association of Peripheral Plasma Neurotransmitters with Cognitive Performance in Chronic High-altitude Exposure

Long-term living at high altitude causes significant impairment of cognitive function. Central neurotransmitters are potential mediators of cognitive performance. We aimed to determine whether there were significant associations between select peripheral plasma neurotransmitters and cognitive performance in humans with chronic high-altitude (HA) exposure and to determine the association between peripheral plasma neurotransmitters and brain neurotransmitters in rats after chronic hypobaric hypoxia (HH) exposure. We demonstrated that 3,4-dihydroxy-L-phenylalanine (DOPA), dopamine, serotonin, 5-hydroxyindole-3-acetic acid (5-HIAA) and GABA in the peripheral plasma were associated with cognitive performance in humans with HA exposure. Consistent with this result, peripheral plasma DOPA, dopamine, serotonin, 5-HIAA and glutamate were associated with brain neurotransmitter levels after chronic HH exposure in rats. These results provide experimental data indicating that neurotransmitter levels and cognitive performance are modified in chronic high-altitude exposure, with a possible causal effect.

Infliximab Can Improve Traumatic Brain Injury by Suppressing the Tumor Necrosis Factor Alpha Pathway

Traumatic brain injury (TBI) has both high morbidity and mortality rates and can negatively influence physical and mental health, while also causing extreme burden to both individual and society. Hitherto, there is no effective treatment for TBI because of the complexity of the brain anatomy and physiology. Currently, management strategies mainly focus on controlling inflammation after TBI. Tumor necrotizing factor alpha (TNF-α) plays a crucial role in neuroinflammation post-TBI. TNF-α acts as the initiator of downstream inflammatory signaling pathways, and its activation can trigger a series of inflammatory reactions. Infliximab is a monoclonal anti-TNF-α antibody that reduces inflammation. Herein, we review the latest findings pertaining to the role of TNF-α and infliximab in TBI. We seek to present a comprehensive clinical application prospect of infliximab in TBI and, thus, discuss potential strategies of infliximab in treating TBI.

Use of Infliximab to Treat Paradoxical Tuberculous Meningitis Reactions

We documented dramatic responses to infliximab in 4 tuberculous meningitis cases with severe paradoxical reactions after effective antibacterial treatment, despite high-dose steroids. In every instance, infliximab was used as a last resort after all other options were exhausted, resulting in delayed initiation that may have adversely affected patient outcomes.

Sexual function and depression in polycystic ovary syndrome: Is it associated with inflammation and neuromodulators?

Numerous studies have been carried out on depression and sexual dysfunction concomitant with polycystic ovary syndrome (PCOS). Increasing evidence has revealed the importance of inflammation in the etiology of PCOS. In addition, it has been known that some neuromodulators affect depression and sexual function. However, their effects on PCOS are not known. This study aimed to evaluate the relationship of depression and sexual function with cytokines and neuromodulators in PCOS patients. The present study included 20 fertile and 30 infertile patients diagnosed with PCOS and 30 healthy volunteers. Metabolic and endocrine parameters, interleukin (IL)-1β, IL-6, TNFα, γ-aminobutyric acid (GABA), Glutamate, Brain-derived neurotrophic factor (BDNF) serum levels, Beck Depression Index (BDI) and Female Sexual Function Index (FSFI) scores of the patients were compared between the groups. TNFα, IL-1β, IL-6, glutamate, GABA, and BDI scores were found to be significantly higher (p < 0.05) in the PCOS group (p < 0.05). Glutamate, TNFα, IL-1β, and IL-6 values were higher whereas GABA and BDNF values were lower in pateints with moderate and severe depression (p < 0.05). There were no statistically significant relationships between these parameters and the FSFI scores (p > 0.05). Multivariate logistic regression analysis was conducted with potential factors that may affect sexual dysfunction. The results indicated that high waist-to-hip ratio (WHR) (> 0.80) with an odds ratio of 1.81 in PCOS patients, and body mass index (BMI) with an odds ratio of 2.3 and high WHR (> 0.80) with an odds ratio of 1.97 in all patients were found to be independent risk factors affecting sexual dysfunction. The results of the present study suggested that chronic low-dose inflammation seen in PCOS may interact with some neuromodulators, leading to the development of depression. However, no relationship was found between these parameters and sexual function.

Possible involvement of D2/D3 receptor activation in ischemic preconditioning mediated protection of the brain

Ischemic stroke is a medical condition that arises because of poor blood supply to the brain. Reperfusion being salvage to the brain further causes, exacerbation of tissue injury, known as reperfusion injury. Ischemic preconditioning (IPC) has been known to provide benefits against ischemia reperfusion (I/R) injury. Dopamine D2/D3 receptor mediated several pathways are also reported as mediators in the IPC mediated neuroprotection. This study investigates the possible involvement of D2/D3 receptor activation in IPC mediated neuroprotection in the I/R brain. Global cerebral ischemia/reperfusion (GCI/R) injury in swiss albino mice was induced by occluding the common carotid arteries for 17 min, followed by 24 h reperfusion. IPC was provided by giving 3 episodes of I/R prior to Ischemia (17 min). Morris water maze (MWM) was used to assess the spatial learning, memory and Rota rod, lateral push test as well as inclined beam test were conducted to assess the motor functions in animals. Cerebral oxidative markers (thiobarbituric acid reactive species-TBARS, reduced glutathione-GSH, superoxide dismutase-SOD, and catalase-CAT), inflammatory markers (IL-6, IL-10, TNF-α, and myeloperoxidase-MPO), acetylcholinesterase activity-AChE, infarct size (% weight and % volume), and histopathological changes were also assessed. Haloperidol (0.05 mg/kg, i.p) was used to antagonize the effects of D2/D3 receptor activation. I/R animals showed reduction in memory, motor function, increase in cerebral oxidative stress, inflammation, AChE activity, infarct size and histopathological changes. Episodes of IPC prior to ischemia, attenuated the deleterious effects of I/R injury. Administration of haloperidol abolished the protective effects of IPC. Hence, it may be concluded that IPC mediated neuroprotection may involves dopamine D2/D3 receptor activation in mice.

Chronic hyperammonemia induces peripheral inflammation that leads to cognitive impairment in rats: Reversed by anti-TNF-α treatment

BACKGROUND & AIMS

Chronic hyperammonemia induces neuroinflammation which mediates cognitive impairment. How hyperammonemia induces neuroinflammation remains unclear. We aimed to assess whether: chronic hyperammonemia induces peripheral inflammation, and whether this then contributes to neuroinflammation, altered neurotransmission and impaired spatial learning - before assessing whether this neuroinflammation and impairment is reversible following hyperammonemia elimination or treatment of peripheral inflammation with anti-TNF-α.

METHODS

Chronic hyperammonemia was induced by feeding rats an ammonia-containing diet. Peripheral inflammation was analyzed by measuring PGE2, TNF-α, IL-6 and IL-10. We tested whether chronic anti-TNF-α treatment improves peripheral inflammation, neuroinflammation, membrane expression of glutamate receptors in the hippocampus and spatial learning.

RESULTS

Hyperammonemic rats show a rapid and reversible induction of peripheral inflammation, with increased pro-inflammatory PGE2, TNF-α and IL-6, followed at around 10 days by reduced anti-inflammatory IL-10. Peripheral anti-TNF-α treatment prevents peripheral inflammation induction and the increase in IL-1b and TNF-α and microglia activation in hippocampus of the rats, which remain hyperammonemic. This is associated with prevention of the altered membrane expression of glutamate receptors and of the impairment of spatial memory assessed in the radial and Morris water mazes.

CONCLUSIONS

This report unveils a new mechanism by which chronic hyperammonemia induces neurological alterations: induction of peripheral inflammation. This suggests that reducing peripheral inflammation by safe procedures would improve cognitive function in patients with minimal hepatic encephalopathy.

LAY SUMMARY

This article unveils a new mechanism by which chronic hyperammonemia induces cognitive impairment in rats: chronic hyperammonemia per se induces peripheral inflammation, which mediates many of its effects on the brain, including induction of neuroinflammation, which alters neurotransmission, leading to cognitive impairment. It is also shown that reducing peripheral inflammation by treating rats with anti-TNF-α, which does not cross the blood-brain barrier, prevents hyperammonemia-induced neuroinflammation, alterations in neurotransmission and cognitive impairment.

Abrogating doxorubicin-induced chemobrain by immunomodulators IFN-beta 1a or infliximab: Insights to neuroimmune mechanistic hallmarks

Chemobrain is a well-established clinical syndrome that impairs patient's daily function, in particular attentiveness, coordination and multi-tasking. Thus, it interferes with patient's quality of life. The putative pharmacological intervention against chemobrain relies on understanding the molecular mechanisms underlying it. This study aimed to examine the potential neuroprotective effects of two immunomodulators: Interferon-β-1a (IFN-β-1a), as well as Tumor necrosis function-alpha (TNF-α) inhibitor; Infliximab in doxorubicin (DOX)-induced chemobrain in rats. Besides, the current study targets investigating the possible molecular mechanisms in terms of neuromodulation and interference with different death routes controlling neural homeostasis. Herein, the two immunomodulators IFN-β-1a at a dose of 300,000 units; s.c.three times per week, or Infliximab at a dose of 5 mg/kg/week; i.p. once per week were examined against DOX (2 mg/kg/w, i.p.) once per week for 4 consecutive weeks in rats.The consequent behavioral tests and markers for cognitive impairment, oxidative stress, neuroinflammation, apoptosis and neurobiological abnormalities were further evaluated. Briefly, IFN-β-1a or Infliximab significantly protected against DOX-induced chemobrain. IFN-β-1a or Infliximab ameliorated DOX-induced hippocampal histopathological neurodegenerative changes, halted DOX-induced cognitive impairment, abrogated DOX-induced mitochondrial oxidative, inflammatory and apoptotic stress, mitigated DOX-induced autophagic dysfunction and finally upregulated the mitophagic machineries. In conclusion, these findings suggest that either IFN-β-1a or Infliximab offers neuroprotection against DOX-induced chemobrain which could be explained by their antioxidant, anti-inflammatory, pro-autophagic, pro-mitophagic and antiapoptotic effects. Future clinical studies are recommended to personalize either use of IFN-β-1a or infliximab to ameliorate DOX-induced chemobrain.

Extracellular Vesicle Biomarkers Reveal Inhibition of Neuroinflammation by Infliximab in Association with Antidepressant Response in Adults with Bipolar Depression

Accumulating evidence suggests that neuroinflammation is involved in bipolar disorder (BD) pathogenesis. The tumor necrosis factor-alpha (TNF-α) antagonist infliximab was recently reported to improve depressive symptoms in a subpopulation of individuals with BD and history of childhood maltreatment. To explore the mechanistic mediators of infliximab's effects, we investigated its engagement with biomarkers of cellular response to inflammation derived from plasma extracellular vesicles enriched for neuronal origin (NEVs). We hypothesized that infliximab, compared to placebo, would decrease TNF-α receptors (TNFRs) and nuclear factor-kappa B (NF-κB) pathway signaling biomarkers, and that history of childhood abuse would moderate infliximab's effects. We immunocaptured NEVs from plasma samples collected at baseline and at weeks 2, 6, and 12 (endpoint) from 55 participants of this clinical trial and measured NEV biomarkers using immunoassays. A subset of participants (n = 27) also underwent whole-brain magnetic resonance imaging at baseline and endpoint. Childhood physical abuse moderated treatment by time interactions for TNFR1 (χ² = 9.275, p = 0.026), NF-κB (χ² = 13.825, p = 0.003), and inhibitor of NF-κB (IκBα) (χ² = 7.990, p = 0.046), indicating that higher levels of physical abuse were associated with larger biomarker decreases over time. Moreover, the antidepressant response to infliximab was moderated by TNFR1 (χ² = 7.997, p = 0.046). In infliximab-treated participants, reductions in TNFR1 levels were associated with improvement of depressive symptoms, an effect not detected in the placebo group. Conversely, reductions in TNFR1 levels were associated with increased global cortical thickness in infliximab- (r = -0.581, p = 0.029), but not placebo-treated, patients (r = 0.196, p = 0.501). In conclusion, we report that NEVs revealed that infliximab engaged the TNFR/NF-κB neuro-inflammatory pathway in individuals with BD, in a childhood trauma-dependent manner, which was associated with clinical response and brain structural changes.

Extracellular Vesicles from Hyperammonemic Rats Induce Neuroinflammation and Motor Incoordination in Control Rats

Minimal hepatic encephalopathy is associated with changes in the peripheral immune system which are transferred to the brain, leading to neuroinflammation and thus to cognitive and motor impairment. Mechanisms by which changes in the immune system induce cerebral alterations remain unclear. Extracellular vesicles (EVs) seem to play a role in this process in certain pathologies. The aim of this work was to assess whether EVs play a role in the induction of neuroinflammation in cerebellum and motor incoordination by chronic hyperammonemia. We characterized the differences in protein cargo of EVs from plasma of hyperammonemic and control rats by proteomics and Western blot. We assessed whether injection of EVs from hyperammonemic to normal rats induces changes in neuroinflammation in cerebellum and motor incoordination similar to those exhibited by hyperammonemic rats. We found that hyperammonemia increases EVs amount and alters their protein cargo. Differentially expressed proteins are mainly associated with immune system processes. Injected EVs enter Purkinje neurons and microglia. Injection of EVs from hyperammonemic, but not from control rats, induces motor incoordination, which is mediated by neuroinflammation, microglia and astrocytes activation and increased IL-1β, TNFα, its receptor TNFR1, NF-κB in microglia, glutaminase I, and GAT3 in cerebellum. Plasma EVs from hyperammonemic rats carry molecules necessary and sufficient to trigger neuroinflammation in cerebellum and the mechanisms leading to motor incoordination.

Sustained hyperammonemia induces TNF-a IN Purkinje neurons by activating the TNFR1-NF-κB pathway

Background

Patients with liver cirrhosis may develop hepatic encephalopathy. Rats with chronic hyperammonemia exhibit neurological alterations mediated by peripheral inflammation and neuroinflammation. Motor incoordination is due to increased TNF-a levels and activation of its receptor TNFR1 in the cerebellum.

The aims were to assess (a) whether peripheral inflammation is responsible for TNF-a induction in hyperammonemic rats, (b) the cell type(s) in which TNF-a is increased, (c) whether this increase is associated with increased nuclear NF-κB and TNFR1 activation, (d) the time course of TNF-a induction, and (e) if TNF-a is induced in the Purkinje neurons of patients who die with liver cirrhosis.

Methods

We analyzed the level of TNF-a mRNA and NF-κB in microglia, astrocytes, and Purkinje neurons in the cerebellum after 1, 2, and 4 weeks of hyperammonemia. We assessed whether preventing peripheral inflammation by administering an anti-TNF-a antibody prevents TNF-a induction. We tested whether TNF-a induction is reversed by R7050, which inhibits the TNFR1-NF-κB pathway, in ex vivo cerebellar slices.

Results

Hyperammonemia induced microglial and astrocyte activation at 1 week. This was followed by TNF-a induction in both glial cell types at 2 weeks and in Purkinje neurons at 4 weeks. The level of TNF-a mRNA increased in parallel with the TNF-a protein level, indicating that TNF-a was synthesized in Purkinje cells. This increase was associated with increased NF-κB nuclear translocation. The nuclear translocation of NF-κB and the increase in TNF-a were reversed by R7050, indicating that they were mediated by the activation of TNFR1. Preventing peripheral inflammation with an anti-TNF-a antibody prevents TNF-a induction.

Conclusion

Sustained (4 weeks) but not short-term hyperammonemia induces TNF-a in Purkinje neurons in rats. This is mediated by peripheral inflammation. TNF-a is also increased in the Purkinje neurons of patients who die with liver cirrhosis. The results suggest that hyperammonemia induces TNF-a in glial cells and that TNF-a released by glial cells activates TNFR1 in Purkinje neurons, leading to NF-κB nuclear translocation and the induction of TNF-a expression, which may contribute to the neurological alterations observed in hyperammonemia and hepatic encephalopathy.

Review on Cross Talk between Neurotransmitters and Neuroinflammation in Striatum and Cerebellum in the Mediation of Motor Behaviour

Neurological diseases particularly Alzheimer's disease (AD), Parkinson's disease (PD), stroke, and epilepsy are on the rise all around the world causing morbidity and mortality globally with a common symptom of gradual loss or impairment of motor behaviour. Striatum, which is a component of the basal ganglia, is involved in facilitating voluntary movement while the cerebellum is involved in the maintenance of balance and coordination of voluntary movements. Dopamine, serotonin, gamma-aminobutyric acid (GABA), and glutamate, to name a few, interact in regulating the excitation and inhibition of motor neurons. In another hand, interestingly, the motor loss associated with neurological diseases is possibly resulted from neuroinflammation induced by the neuroimmune system. Toll-like receptors (TLRs) are present in the central nervous system (CNS), specifically and primarily expressed in microglia and are also found on neurons and astrocytes, functioning mainly in the regulation of proinflammatory cytokine production. TLRs are always found to be associated or involved in the induction of neuroinflammation in neurodegenerative diseases. Activation of toll-like receptor 4 (TLR4) through TLR4 agonist, lipopolysaccharide (LPS), stimulation initiate a signaling cascade whereby the TLR4-LPS interaction has been found to result in physiological and behavioural changes including retardation of motor activity in the mouse model. TLR4 inhibitor TAK-242 was reflected in the reduction of the spinal cord pathology along with the motor improvement in ALS mouse. There is cross talk with neuroinflammation and neurochemicals. For example, TLR4 activation by LPS is noted to release proinflammatory cytokines, IL-1β, from microglia that subsequently suppresses GABA receptor activities at the postsynaptic site and reduces GABA synthesis at the presynaptic site. Glial glutamate transporter activities are also found to be suppressed, showing the association between TLR4 activation and the related neurotransmitters and corresponding receptors and transporters in the event of neuroinflammation. This review is helpful to understand the connection between neurotransmitter and neuroinflammation in striatum- and cerebellum-mediated motor behaviour.

Microglial expression of GAT-1 in the cerebral cortex

Microglial cells are the immune cells of the brain that, by sensing the microenvironment, permit a correct brain development and function. They communicate with other glial cells and with neurons, releasing and responding to a number of molecules that exert effects on surrounding cells. Among these, neurotransmitters and, in particular, gamma-aminobutyric acid (GABA) has recently gained interest in this context. We demonstrated the expression of GABA transporter 1 (GAT-1) in microglial cells both in soma and cell processes. We show that microglial cell treatment with 1,2,5,6-tetrahydro-1-[2-[[(diphenylmethylene)amino]oxy]ethyl]-3-pyridinecarboxylic acid hydrochloride (NNC-711), a potent and selective GAT-1 inhibitor, significantly reduced Na⁺ -dependent GABA uptake. On the other hand, GABA uptake was significantly increased by cell treatment with (S)-1-[2-[tris(4-methoxyphenyl)methoxy]ethyl]-3-piperidinecarboxylic acid (SNAP-5114), a GAT-2/3 inhibitor, and this effect was completely blocked by the botulinum toxin BoNT/C1, that specifically cleaves and inactives syntaxin 1A (STX1A). Overall, these findings show that microglial cells express GAT-1 and indicate that STX1A plays an important role in the regulation of GAT-1-dependent GABA uptake in microglia.

Selective improvement by rifaximin of changes in the immunophenotype in patients who improve minimal hepatic encephalopathy

Background

Minimal hepatic encephalopathy (MHE) in cirrhotic patients is associated with specific changes in parameters of the immune system reflecting a more pro-inflammatory environment than in patients without MHE. The aims of this work were to assess the effects of rifaximin treatment of cirrhotic patients with MHE on: (1) MHE; (2) intermediate (CD14⁺⁺CD16⁺) pro-inflammatory monocytes; (3) expression of early activation marker CD69 in T lymphocytes; (4) autoreactive CD4⁺CD28⁻ T lymphocytes; (5) differentiation of CD4⁺ T lymphocytes to Th follicular and Th22; (6) serum IgG levels; and (7) levels of some pro-inflammatory cytokines.

Methods

These parameters were measured by immunophenotyping and cytokine profile analysis in 30 controls without liver disease, 30 cirrhotic patients without MHE and 22 patients with MHE. Patients with MHE were treated with rifaximin and the same parameters were measured at 3 and 6 months of treatment. We assessed if changes in these parameters are different in patients who improve MHE (responders) and those who remain in MHE (non-responders).

Results

Rifaximin improved MHE in 59% of patients with MHE. In these responder patients rifaximin normalized all alterations in the immune system measured while in non-responders it normalizes only IL-6, CCL20, and differentiation of T lymphocytes to Th22. Non-responder patients do not show increased expression of CD69 before treatment.

Conclusions

Rifaximin normalizes changes in the immune system in patients who improve MHE but not in non-responders. Some alterations before treatment are different in responders and non-responders. Understanding these differences may identify predictors of the response of MHE to rifaximin.

Microglia-derived TNF-α mediates endothelial necroptosis aggravating blood brain-barrier disruption after ischemic stroke

Endothelium (EC) is a key component of blood–brain barrier (BBB), and has an important position in the neurovascular unit. Its dysfunction and death after cerebral ischemic/reperfusion (I/R) injury not only promote evolution of neuroinflammation and brain edema, but also increase the risk of intracerebral hemorrhage of thrombolytic therapies. However, the mechanism and specific interventions of EC death after I/R injury are poorly understood. Here we showed that necroptosis was a mechanism underlying EC death, which promoted BBB breakdown after I/R injury. Treatment of rats with receptor interacting protein kinase 1 (RIPK1)-inhibitor, necrostatin-1 reduced endothelial necroptosis and BBB leakage. We furthermore showed that perivascular M1-like microglia-induced endothelial necroptosis leading to BBB disruption requires tumor necrosis factor-α (TNF-α) secreted by M1 type microglia and its receptor, TNF receptor 1 (TNFR1), on endothelium as the primary mediators of these effects. More importantly, anti-TNFα (infliximab, a potent clinically used drug) treatment significantly ameliorate endothelial necroptosis, BBB destruction and improve stroke outcomes. Our data identify a previously unexplored role for endothelial necroptosis in BBB disruption and suggest infliximab might serve as a potential drug for stroke therapy.

Peripheral inflammation induces neuroinflammation that alters neurotransmission and cognitive and motor function in hepatic encephalopathy: Underlying mechanisms and therapeutic implications

Several million patients with liver cirrhosis suffer minimal hepatic encephalopathy (MHE), with mild cognitive and coordination impairments that reduce their quality of life and life span. Hyperammonaemia and peripheral inflammation act synergistically to induce these neurological alterations. We propose that MHE appearance is because of the changes in peripheral immune system, which are transmitted to brain, leading to neuroinflammation that alters neurotransmission leading to cognitive and motor alterations. We summarize studies showing that MHE in cirrhotic patients is associated with alterations in the immune system and that patients died with HE show neuroinflammation in cerebellum, with microglial and astrocytic activation and Purkinje cell loss. We also summarize studies in animal models of MHE on the role of peripheral inflammation in neuroinflammation induction, how neuroinflammation alters neurotransmission and how this leads to cognitive and motor alterations. These studies identify therapeutic targets and treatments that improve cognitive and motor function. Rats with MHE show neuroinflammation in hippocampus and altered NMDA and AMPA receptor membrane expression, which impairs spatial learning and memory. Neuroinflammation in cerebellum is associated with altered GABA transporters and extracellular GABA, which impair motor coordination and learning in a Y maze. These alterations are reversed by treatments that reduce peripheral inflammation (anti-TNFα, ibuprofen), neuroinflammation (sulphoraphane, p38 inhibitors), GABAergic tone (bicuculline, pregnenolone sulphate) or increase extracellular cGMP (sildenafil or cGMP). The mechanisms identified would also occur in other chronic diseases associated with inflammation, aging and some mental and neurodegenerative diseases. Treatments that improve MHE may also be beneficial to treat these pathologies.

Bicuculline Reduces Neuroinflammation in Hippocampus and Improves Spatial Learning and Anxiety in Hyperammonemic Rats. Role of Glutamate Receptors

Patients with liver cirrhosis may develop minimal hepatic encephalopathy (MHE) with mild cognitive impairment. Hyperammonemia is a main contributor to cognitive impairment in MHE, which is mediated by neuroinflammation. GABAergic neurotransmission is altered in hyperammonemic rats. We hypothesized that, in hyperammonemic rats, (a) enhanced GABAergic tone would contribute to induce neuroinflammation, which would be improved by reducing GABAergic tone by chronic bicuculline treatment; (b) this would improve spatial learning and memory impairment; and (c) modulation of glutamatergic neurotransmission would mediate this cognitive improvement. The aim of this work was to assess the above hypotheses. Bicuculline was administrated intraperitoneally once a day for 4 weeks to control and hyperammonemic rats. The effects of bicuculline on microglia and astrocyte activation, IL-1β content, on membrane expression of AMPA and NMDA glutamate receptors subunits in the hippocampus and on spatial learning and memory as well as anxiety were assessed. Treatment with bicuculline reduces astrocyte activation and IL-1β but not microglia activation in the hippocampus of hyperammonemic rats. Bicuculline reverses the changes in membrane expression of AMPA receptor subunits GluA1 and GluA2 and of the NR2B (but not NR1 and NR2A) subunit of NMDA receptors. Bicuculline improves spatial learning and working memory and decreases anxiety in hyperammonemic rats. In hyperammonemia, enhanced activation of GABAA receptors in the hippocampus contributes to some but not all aspects of neuroinflammation, to altered glutamatergic neurotransmission and to impairment of spatial learning and memory as well as anxiety, all of which are reversed by reducing activation of GABAA receptors with bicuculline.