Regulation of autophagy by ST3GAL2-mediated α2-3 sialylated glycosphingolipids in hepatic encephalopathy.

In neurological diseases, the regulation of autophagy plays a crucial role in their pathology, particularly the relationship between autophagy and hepatic encephalopathy (HE) which merits detailed investigation. Glycosphingolipids are abundant and broadly functional in the nervous system and are closely associated with autophagy. However, the specific link and mechanisms between glycosphingolipids and autophagy in HE remain unclear. This study aims to explore the impact of glycosphingolipid changes on the autophagy in HE and its potential mechanisms. Utilizing lectin microarrays, we observed elevated expression levels of α2-3 sialylated glycosphingolipid in the brain tissue of HBV transgenic mice and ammonia-induced astrocyte models, suggesting that the increase in α2-3 sialylated glycosphingolipid is related to HE. Further research revealed that the increased expression of α2-3 sialylated glycosphingolipid, mediated by ST3GAL2, affects autophagy by regulating the autophagy initiation complex Vps34-Beclin-1. In summary, our research not only comprehensively reveals the changes in brain glycosphingolipid during HBV-related HE but also elucidates the interactions and regulatory mechanisms between α2-3 sialylated glycosphingolipid and autophagy. This study provides a new perspective on understanding the pathogenesis of HE and offers novel theories and targets for future research and treatment strategies.

Intestinal Dysbacteriosis Contributes to Persistent Cognitive Impairment after Resolution of Acute Liver Failure.

Regulating the gut microbiota alleviates hepatic encephalopathy (HE). Whether it is imperative to withhold treatment for microbial imbalance after liver functional recovery remains unclear. The aim of this work was to elucidate the alterations in cognitive behavior, liver function, synaptic transmission, and brain metabolites in acute liver failure (ALF) mice before and after hepatic function recovery. Towards this end, thioacetamide was injected intraperitoneally to establish an ALF mouse model, which induced HE. Hierarchical clustering analysis indicated that while the liver functions normalized, cognitive dysfunction and intestinal dysbacteriosis occurred in the ALF mice 14 days after thioacetamide injection. In addition, fecal microbiota transplantation from the ALF mice with liver function recovery induced liver injury and cognitive impairment. Alterations in synaptic transmission were found in the ALF mice with liver function improvement, and the correlations between the gut bacteria and synaptic transmission in the cortex were significant. Finally, apparent alterations in the brain metabolic profiles of the ALF mice were detected after liver function improvement by performing 1H nuclear magnetic resonance spectroscopy, suggesting a risk of HE. These results showed that intestinal dysbacteriosis in ALF mice with liver function recovery is sufficient to induce liver injury and cognitive impairment. This indicates that continuous care may be necessary for monitoring microbial imbalance even in patients with ALF-induced HE whose liver function has recovered significantly.

Astrocyte-secreted lipocalin-2 elicits bioenergetic failure-induced neuronal death that is causally related to high fatality in a mouse model of hepatic encephalopathy.

Hepatic encephalopathy (HE) is a neurological complication arising from acute liver failure with poor prognosis and high mortality; the underlying cellular mechanisms are still wanting. We previously found that neuronal death caused by mitochondrial dysfunction in rostral ventrolateral medulla (RVLM), which leads to baroreflex dysregulation, is related to high fatality in an animal model of HE. Lipocalin-2 (Lcn2) is a secreted glycoprotein mainly released by astrocytes in the brain. We noted the presence of Lcn2 receptor (Lcn2R) in RVLM neurons and a parallel increase of Lcn2 gene in astrocytes purified from RVLM during experimental HE. Therefore, our guiding hypothesis is that Lcn2 secreted by reactive astrocytes in RVLM may underpin high fatality during HE by eliciting bioenergetic failure-induced neuronal death in this neural substrate. In this study, we first established the role of astrocyte-secreted Lcn2 in a liver toxin model of HE induced by azoxymethane (100 µg/g, ip) in C57BL/6 mice, followed by mechanistic studies in primary astrocyte and neuron cultures prepared from postnatal day 1 mouse pups. In animal study, immunoneutralization of Lcn2 reduced apoptotic cell death in RVLM, reversed defunct baroreflex-mediated vasomotor tone and prolonged survival during experimental HE. In our primary cell culture experiments, Lcn2 produced by cultured astrocytes and released into the astrocyte-conditioned medium significantly reduced cell viability of cultured neurons. Recombinant Lcn2 protein reduced cell viability, mitochondrial ATP (mitoATP) production, and pyruvate dehydrogenase (PDH) activity but enhanced the expression of pyruvate dehydrogenase kinase (PDK) 1, PDK3 and phospho-PDHA1 (inactive PDH) through MAPK/ERK pathway in cultured neurons, with all cellular actions reversed by Lcn2R knockdown. Our results suggest that astrocyte-secreted Lcn2 upregulates PDKs through MAPK/ERK pathway, which leads to reduced PDH activity and mitoATP production; the reinforced neuronal death in RVLM is causally related to baroreflex dysregulation that underlies high fatality associated with HE.

Deficiency of leucine-rich repeat kinase 2 aggravates thioacetamide-induced acute liver failure and hepatic encephalopathy in mice.

BACKGROUND: Hepatic encephalopathy (HE) is closely associated with inflammatory responses. However, as a crucial regulator of the immune and inflammatory responses, the role of leucine-rich repeat kinase 2 (LRRK2) in the pathogenesis of HE remains unraveled. Herein, we investigated this issue in thioacetamide (TAA)-induced HE following acute liver failure (ALF). METHODS: TAA-induced HE mouse models of LRRK2 wild type (WT), LRRK2 G2019S mutation (Lrrk2G2019S) and LRRK2 knockout (Lrrk2-/-) were established. A battery of neurobehavioral experiments was conducted. The biochemical indexes and pro-inflammatory cytokines were detected. The prefrontal cortex (PFC), striatum (STR), hippocampus (HIP), and liver were examined by pathology and electron microscopy. The changes of autophagy-lysosomal pathway and activity of critical Rab GTPases were analyzed. RESULTS: The Lrrk2-/--HE model reported a significantly lower survival rate than the other two models (24% vs. 48%, respectively, p < 0.05), with no difference found between the WT-HE and Lrrk2G2019S-HE groups. Compared with the other groups, after the TAA injection, the Lrrk2-/- group displayed a significant increase in ammonium and pro-inflammatory cytokines, aggravated hepatic inflammation/necrosis, decreased autophagy, and abnormal phosphorylation of lysosomal Rab10. All three models reported microglial activation, neuronal loss, disordered vesicle transmission, and damaged myelin structure. The Lrrk2-/--HE mice presented no severer neuronal injury than the other genotypes. CONCLUSIONS: LRRK2 deficiency may exacerbate TAA-induced ALF and HE in mice, in which inflammatory response is evident in the brain and aggravated in the liver. These novel findings indicate a need of sufficient clinical awareness of the adverse effects of LRRK2 inhibitors on the liver.

Excessive intragastric alcohol administration exacerbates hepatic encephalopathy and provokes neuronal cell death in male rats with chronic liver disease.

Hepatic encephalopathy (HE) is defined as decline in neurological function during chronic liver disease (CLD). Alcohol is a major etiological factor in the pathogenesis of fibrosis/cirrhosis and has also been documented to directly impact the brain. However, the role of alcohol in the development of HE in CLD remains unclear. Here, we investigated the impact of excessive alcohol administration on neurological deterioration in rats with CLD. Starting day 7 post-BDL surgery, rats were administered alcohol twice daily (51% v/v ethanol, 3 g/kg, via gavage) for 4 weeks. Motor coordination was assessed weekly using rotarod and anxiety-like behavior was evaluated with open field and elevated plus maze at 5 weeks. Upon sacrifice, brains were collected for western blot and immunohistochemical analyses to investigate neuronal integrity and oxidative stress status. Alcohol worsened motor coordination performance and increased anxiety-like behavior in BDL rats. Impairments were associated with decreased neuronal markers of NeuN and SMI311, increased apoptotic markers of cleaved/pro-caspase-3 and Bax/Bcl2, increased necroptosis markers of pRIP3 and pMLKL, decreased total antioxidant capacity (TAC), and increased 4-hydroxynonenal (4-HNE)modified proteins in the cerebellum of BDL-alcohol rats when compared to respective controls. Immunofluorescence confirmed the colocalization of cleaved caspase-3 and pMLKL in the granular neurons of the cerebellum of BDL-alcohol rats. Excessive alcohol consumption exacerbates HE which leads to associated apoptotic and necroptotic neuronal loss in the cerebellum of BDL-alcohol rats. Additionally, higher levels of 4-HNE and decreased TAC in the cerebellum of BDL-alcohol rats suggest oxidative stress is the triggering factor of apoptotic and necroptotic neuronal loss/injury.

Altered brain iron deposition in patients with minimal hepatic encephalopathy: an MRI quantitative susceptibility mapping study.

AIM: To explore the use of quantitative susceptibility mapping (QSM) in assessing changes in brain iron deposits and their association with cognitive function in patients with minimal hepatic encephalopathy (MHE). MATERIALS AND METHODS: The study cohort comprised 27 cases with hepatitis B-associated cirrhosis with MHE (MHE group), 25 with hepatitis B-associated cirrhosis without MHE (NMHE group), and 25 healthy controls (HC group). Iron deposits in the bilateral frontal white matter, caudate nucleus (CN), putamen, globus pallidus, thalamus, red nucleus, substantia nigra (SN), hippocampus, and dentate nucleus were measured by QSM. The associations between iron deposition with the time taken to complete number connection tests A (NCT-A) and the score on digital-symbol test (DST) were analysed. RESULTS: Susceptibility values differed significantly in the bilateral CN, left thalamus, right SN, and left hippocampus in the MHE group compared with the other groups and were positively associated with the times taken to complete the NCT-A in the bilateral CN, left thalamus, and right SN and negatively associated with DST scores in the bilateral CN, left TH, and left HP. CONCLUSION: Reduced cognitive function in MHE patients was significantly associated with abnormally increased iron deposition in certain brain areas. The quantification of brain iron deposition by QSM may thus be an objective and accurate means of evaluating MHE.

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.

Gallic acid and metformin co-administration reduce oxidative stress, apoptosis and inflammation via Fas/caspase-3 and NF-κB signaling pathways in thioacetamide-induced acute hepatic encephalopathy in rats.

BACKGROUND: Hepatic encephalopathy (HE) is a consequence of chronic or acute liver diseases. This study evaluates the combined effect of gallic acid (GA), and metformin (Met) on the liver and brain damage associated with HE. METHODS: Acute HE was induced by a single dose of thioacetamide (TAA) (300 mg/kg) as an I.P. injection. Treated groups received GA group (100 mg/kg/day, p.o), Met (200 mg/kg/day, p.o), or their combination for 25 consecutive days before TAA injection. RESULTS: The administration of TAA induced various biochemical and histopathological alterations. In contrast, treatment with GA either alone or combined with Met resulted in improved liver functions by the significant reduction in serum ALT, AST, and ALP activities, and ammonia levels. Inflammatory mediators; TNF-α, IL-6, and NFkß levels were decreased by these treatments as well as apoptotic cascade via down-regulation of FAS and caspase-3 (CASP-3) expression in hepatic tissues. Furthermore, GA and Met either alone or combined protected the liver and brain tissues from damage by increased glutathione concentration while decreasing malondialdehyde. In addition, it was accompanied by the improvement of the brain neurotransmitter profile via the restoration of norepinephrine, dopamine, and serotonin levels. Based on our data, this is the first study to report a novel combined hepatoprotective and cognitive enhancing effect of GA and Met against TAA-induced acute liver and brain injury. CONCLUSION: GA and Met combination resulted in a prominent improvement in HE complications, relative to monotherapy. Both agents potentiated the antioxidant, anti-inflammatory, and anti-apoptotic effects of each other.

Dynamic evolution of brain structural patterns in liver transplantation recipients: a longitudinal study based on 3D convolutional neuronal network model.

OBJECTIVES: To evaluate the dynamic evolution process of overall brain health in liver transplantation (LT) recipients, we employed a deep learning-based neuroanatomic biomarker to measure longitudinal changes of brain structural patterns before and 1, 3, and 6 months after surgery. METHODS: Because of the ability to capture patterns across all voxels from a brain scan, the brain age prediction method was adopted. We constructed a 3D-CNN model through T1-weighted MRI of 3609 healthy individuals from 8 public datasets and further applied it to a local dataset of 60 LT recipients and 134 controls. The predicted age difference (PAD) was calculated to estimate brain changes before and after LT, and the network occlusion sensitivity analysis was used to determine the importance of each network in age prediction. RESULTS: The PAD of patients with cirrhosis increased markedly at baseline (+ 5.74 years) and continued to increase within one month after LT (+ 9.18 years). After that, the brain age began to decrease gradually, but it was still higher than the chronological age. The PAD values of the OHE subgroup were higher than those of the no-OHE, and the discrepancy was more obvious at 1-month post-LT. High-level cognition-related networks were more important in predicting the brain age of patients with cirrhosis at baseline, while the importance of primary sensory networks increased temporarily within 6-month post-LT. CONCLUSIONS: The brain structural patterns of LT recipients showed inverted U-shaped dynamic change in the early stage after transplantation, and the change in primary sensory networks may be the main contributor. KEY POINTS: • The recipients' brain structural pattern showed an inverted U-shaped dynamic change after LT. • The patients' brain aging aggravated within 1 month after surgery, and the subset of patients with a history of OHE was particularly affected. • The change of primary sensory networks is the main contributor to the change in brain structural patterns.

Extracellular vesicles from hyperammonemic rats induce neuroinflammation in hippocampus and impair cognition in control rats.

Patients with liver cirrhosis show hyperammonemia and peripheral inflammation and may show hepatic encephalopathy with cognitive impairment, reproduced by rats with chronic hyperammonemia. Peripheral inflammation induces neuroinflammation in hippocampus of hyperammonemic rats, altering neurotransmission and leading to cognitive impairment. Extracellular vesicles (EVs) may transmit pathological effects from the periphery to the brain. We hypothesized that EVs from peripheral blood would contribute to cognitive alterations in hyperammonemic rats. The aims were to assess whether EVs from plasma of hyperammonemic rats (HA-EVs) induce cognitive impairment and to identify the underlying mechanisms. Injection of HA-EVs impaired learning and memory, induced microglia and astrocytes activation and increased TNFα and IL-1ß. Ex vivo incubation of hippocampal slices from control rats with HA-EVs reproduced these alterations. HA-EVs increased membrane expression of TNFR1, reduced membrane expression of TGFßR2 and Smad7 and IκBα levels and increased IκBα phosphorylation. This led to increased activation of NF-κB and IL-1ß production, altering membrane expression of NR2B, GluA1 and GluA2 subunits, which would be responsible for cognitive impairment. All these effects of HA-EVs were prevented by blocking TNFα, indicating that they were mediated by enhanced activation of TNFR1 by TNFα. We show that these mechanisms are very different from those leading to motor incoordination, which is due to altered GABAergic neurotransmission in cerebellum. This demonstrates that peripheral EVs play a key role in the transmission of peripheral alterations to the brain in hyperammonemia and hepatic encephalopathy, inducing neuroinflammation and altering neurotransmission in hippocampus, which in turn is responsible for the cognitive deficits.

Residual Amino Acid Imbalance in Rats during Recovery from Acute Thioacetamide-Induced Hepatic Encephalopathy Indicates Incomplete Healing.

The delayed consequences of the influence of hepatic encephalopathy (HE) on the metabolism of animals have not been studied enough. We have previously shown that the development of acute HE under the influence of the thioacetamide (TAA) toxin is accompanied by pathological changes in the liver, an imbalance in CoA and acetyl CoA, as well as a number of metabolites of the TCA cycle. This paper discusses the change in the balance of amino acids (AAs) and related metabolites, as well as the activity of glutamine transaminase (GTK) and ω-amidase enzymes in the vital organs of animals 6 days after a single exposure to TAA. The balance of the main AAs in blood plasma, liver, kidney, and brain samples of control (n = 3) and TAA-induced groups (n = 13) of rats that received the toxin at doses of 200, 400, and 600 mg/kg was considered. Despite the apparent physiological recovery of the rats at the time of sampling, a residual imbalance in AA and associated enzymes persisted. The data obtained give an idea of the metabolic trends in the body of rats after their physiological recovery from TAA exposure and may be useful for prognostic purposes when choosing the necessary therapeutic agents.

Clinical significance of measuring hepatic venous pressure gradient on transjugular liver biopsy for patients with pre-cirrhotic bridging fibrosis liver disease.

PURPOSE: To demonstrate that patients with pre-cirrhotic bridging fibrosis (Meta-analysis of Histological Data in Viral Hepatitis, METAVIR stage F3) and clinically significant portal hypertension (CSPH, Hepatic Venous Pressure Gradient ≥10 mmHg) experience a higher rate of clinical decompensation than patients without CSPH. MATERIALS AND METHODS: 128 consecutive patients with pathology proven bridging fibrosis without cirrhosis between 2012 and 2019 were reviewed. Inclusion criteria were patients with HVPG measurement obtained during the same outpatient transjugular liver biopsy and clinical follow up of at least two years. Primary endpoint included rate of overall complication related to portal hypertension including evidence of either ascites, presence of varices on imaging or endoscopy, or evidence of hepatic encephalopathy. RESULTS: Among 128 patients with bridging fibrosis (67 females and 61 males; average age 56 years), 42 (33%) and 86 (67%) were with and without CSPH (HVPG ≥10 mmHg). Median follow-up time was 4 years. Rate of overall complication (either ascites, varices or hepatic encephalopathy) in patients with and without CSPH was 36/42 (86%) and 39/86 (45%) (p < .001) respectively. Rate of developing ascites, varices and hepatic encephalopathy in patients with and without CSPH was 21/42 (50%) vs 26/86 (30%) (p = .034), 32/42 (76%) vs 26/86 (30%) (p ≤ .001) and 18/42 (43%) vs 12/86 (14%) (p = .001) respectively. CONCLUSION: Patients with pre-cirrhotic bridging fibrosis and CSPH were associated with higher rates of developing ascites, varices and hepatic encephalopathy. Measuring HVPG during transjugular liver biopsy provides additional prognostic value in anticipating clinical decompensation in patients with pre-cirrhotic bridging fibrosis.

Nodular Regenerative Hyperplasia Is Not a Rare Condition After Liver Transplantation: Incidence, Predictive Factors, and Impact on Survival.

BACKGROUND: The objectives of this study were to evaluate incidence and to identify the risk factors of occurrence and the predictive factors of symptomatic forms of nodular regenerative hyperplasia (NRH) after liver transplantation (LT). METHODS: To identify risk factors of NRH following LT, we included 1648 patients transplanted from 2004 to 2018 and compared the patients developing NRH after LT to those who did not. To identify predictive factors of symptomatic NRH, we selected 115 biopsies displaying NRH and compared symptomatic to asymptomatic forms. Symptomatic NRH was defined as the presence of ascites, esophageal varices, hepatic encephalopathy, portal thrombosis, retransplantation, or death related to NRH. RESULTS: The incidence of NRH following LT was 5.1%. In multivariate analysis, the independent factor of developing NRH after LT was the donor's age (odds ratio [OR] = 1.02; confidence interval, 1.01-1.03; P = 0.02). Symptomatic forms occurred in 29 (25.2%) patients: 19 (16.5%) patients presented with ascites, 13 (11.3%) with esophageal varices, 4 (3.5%) with hepatic encephalopathy, and 8 (7%) with portal thrombosis. The median period before the onset of symptoms was 8.4 (1.5-11.3) y after LT. The spleen size at diagnosis/before LT ratio (OR = 12.5; 114.17-1.37; P = 0.0252) and thrombectomy during transplantation (OR = 11.17; 1.48-84.11; P = 0.0192) were associated with symptomatic NRH in multivariate analysis. CONCLUSIONS: NRH following LT is frequent (5.1%) and leads to symptomatic portal hypertension in 25.2% of patients. Using older grafts increases the risk of developing NRH after LT. Clinicians should screen for signs of portal hypertension, particularly in measuring spleen size.

Minimal hepatic encephalopathy is associated to alterations in eye movements.

Minimal hepatic encephalopathy (MHE) is diagnosed using PHES battery, but other tests are more sensitive, and a simple tool for early MHE detection is required. Assessment of saccadic eye movements is useful for early detection of cognitive alterations in different pathologies. We characterized the alterations in saccadic eye movements in MHE patients, its relationship with cognitive alterations and its utility for MHE diagnosis. One-hundred and eighteen cirrhotic patients (86 without and 32 with MHE) and 35 controls performed PHES and Stroop test and an eye movements test battery by OSCANN system: visual saccades, antisaccades, memory-guided saccades, fixation test and smooth pursuit. We analyzed 177 parameters of eye movements, assessed their diagnostic capacity for MHE, and correlated with cognitive alterations. MHE patients showed alterations in 56 of the 177 variables of eye movements compared to NMHE patients. MHE patients showed longer latencies and worse performance in most eye movements tests, which correlated with mental processing speed and attention impairments. The best correlations found were for antisaccades and memory-guided saccades, and some parameters in these tests could be useful for discriminating MHE and NMHE patients. Eye movements analysis could be a new, rapid, reliable, objective, and reproducible tool for early diagnose MHE.

Inhibition of Autotaxin Ameliorates LPA-Mediated Neuroinflammation and Alleviates Neurological Dysfunction in Acute Hepatic Encephalopathy.

Growing evidence suggests an essential role of neuroinflammation in behavioral abnormalities associated with hepatic encephalopathy (HE). Here, we report the involvement of autotaxin-lysophosphatidic acid (LPA) signaling in HE's pathogenesis. We demonstrate that the autotaxin (ATX) inhibitor PF-8380 attenuates neuroinflammation and improves neurological dysfunction in the mouse model of HE. In the thioacetamide (TAA)-induced model of HE, we found a twofold increase in the levels of ammonia in the brain and in plasma along with a significant change in HE-related behavioral parameters. Mice with HE show an increased brain weight, increased levels of tumor necrosis factor-α (TNF-α), IL-1ß (interleukin-1ß), interleukin-6 (IL-6), and LPA 18:0 in the cerebral cortex and hippocampus, and increased levels of LPA 18:0 in plasma. Treatment with the autotaxin inhibitor (ATXi) did not affect liver injury, as we observed no change in liver function markers including aspartate aminotransferase (AST), alanine aminotransferase (ALT), and total bilirubin (TBIL) and no change in ammonia levels in the brain and plasma. However, ATXi treatment significantly ameliorated the neuroinflammation, reduced the levels of LPA 18:0 in the cerebral cortex and hippocampus in the brain and plasma, and reduced brain edema and the levels of IL1ß, IL-6, and TNF-α. The neurobehavioral symptoms for HE such as the cognitive and motor function deficit and overall clinical grading score were significantly improved in ATXi-treated mice. Mouse astrocytes and microglia stimulated with NH4CL with or without ATXi showed significant attenuation of oxidative stress and the neuroinflammatory effect of NH4CL in ATXi-treated cells.

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.

Decreased brain noradrenaline in minimal hepatic encephalopathy is associated with cognitive impairment in rats.

BACKGROUND AND AIMS: Minimal hepatic encephalopathy (MHE) is a common neuropsychiatric complication in patients with cirrhosis. Alterations in monoamine neurotransmitters have been associated with the pathogenesis of MHE. We investigated the levels of hippocampal noradrenergic neurotransmitter in a rat model of thioacetamide-induced chronic liver failure-related MHE, and their role in cognitive impairment. MATERIALS: 18 male Sprague-Dawley (SD) rats were equally divided in MHE and control groups. A rat model of MHE was established by intraperitoneal injection of thioacetamide (TAA) for 12 weeks. Cognitive function was assessed using the Morris water maze (MWM) test and locomotor activity and exploratory behavior assessed with open field test. The concentration of hippocampal noradrenaline (NE) was detected by ELISA, and the magnetic susceptibility value in the hippocampus was detected by quantitative susceptibility mapping. Hippocampal iron content was quantified by Prussian blue staining. RESULTS: MHE rats performed significantly poorer than their control counterparts in the MWM test, as seen by decreased number of platform crossings and time in the target quadrant, and increased path length to reach the target zone (P < 0.05 for all parameters). In the open field test, the MHE group exhibited lower locomotor activity and exploratory behavior than the control group (P < 0.05 for all parameters). We detected pronounced iron staining in the hippocampus of MHE rats, whereas no iron-stained particles were found in control rats. We observed an imbalance of inflammatory (increased pro- and decreased anti-) cytokines in the hippocampus of MHE rats. Further analysis of the data showed that the level of hippocampal noradrenaline in MHE rats was significantly lower than that of control rats (P < 0.05). We observed a correlation between the level of inflammatory cytokine and noradrenaline land susceptibility value in the rat hippocampus of the MHE group. CONCLUSION: Our results suggest that MHE associated with TAA-induced chronic liver failure is associated with alterations in noradrenergic neurotransmission. We propose that iron imbalance in the brain might lead to reduction in the levels of noradrenaline, and cognitive impairment.

Galium aparine L. protects against acetaminophen-induced hepatotoxicity in rats.

The toxicity of acetaminophen (N-acetyl-para-aminophenol (APAP)) is the most frequent cause of drug-induced liver damage. Galium aparine L. (GA) is traditionally used to treat jaundice. We aimed to investigate the hepatoprotective potential of GA in the APAP-induced hepatic encephalopathy (HE) rat model. Qualitative phytochemical characterization of GA was performed by LC/Q-TOF/MS analysis. Wistar rats were pretreated with GA (250 and 500 mg/kg b.wt. per oral) for five days. On the 6th day, the rats were exposed to APAP (1500 mg/kg b.wt. oral gavage) and behavioral tests (open field and passive avoidance tests) were applied on the 7th and 8th days. The animals were killed, and biochemical and histopathological parameters were assessed in blood and hepatic specimens. GA pretreated rats exhibited a significant reduction in APAP-induced liver damage, evidenced by the reduction in liver necrosis and alanine aminotransferase (ALT), aspartate aminotransferase (AST), and bilirubin (BIL). GA demonstrated an anxiolytic effect, as seen in the acquisition trial and grooming behavior. The short-term memory performances of animals were not changed in all groups, suggesting that APAP intoxication did not affect hippocampal function. These results show that GA extract markedly exerts hepatoprotective activity, while its effect on hepatic encephalopathy was limited.

Long Noncoding RNAs Regulate Hyperammonemia-Induced Neuronal Damage in Hepatic Encephalopathy.

Background: Hyperammonemia can result in various neuropathologies, including sleep disturbance, memory loss, and motor dysfunction in hepatic encephalopathy. Long noncoding RNA (lncRNA) as a group of noncoding RNA longer than 200 nucleotides is emerging as a promising therapeutic target to treat diverse diseases. Although lncRNAs have been linked to the pathogenesis of various diseases, their function in hepatic encephalopathy has not yet been elucidated. Research Design and Methods. To identify the roles of lncRNAs in hepatic encephalopathy brain, we used a bile duct ligation (BDL) mouse model and examined the alteration of neuronal cell death markers and neuronal structure-related proteins in BDL mouse cortex tissue. Furthermore, analysis of the transcriptome of BDL mouse brain cortex tissues revealed several lncRNAs critical to the apoptosis and neuronal structural changes associated with hepatic encephalopathy. Results: We confirmed the roles of the lncRNAs, ZFAS1, and GAS5 as strong candidate lncRNAs to regulate neuropathologies in hepatic encephalopathy. Our data revealed the roles of lncRNAs, ZFAS1, and GAS5, on neuronal cell death and neural structure in hyperammonemia in in vivo and in vitro conditions. Conclusion: Thus, we suggest that the modulation of these lncRNAs may be beneficial for the treatment of hepatic encephalopathy.

A critical review of bile acids and their receptors in hepatic encephalopathy.

Hepatic encephalopathy describes an array of neurological complications that arise due to liver insufficiency. The pathogenesis of hepatic encephalopathy shares a longstanding association with hyperammonemia and inflammation, and recently, aberrant bile acid signaling has been implicated in the development of key features of hepatic encephalopathy. These key features include neuronal dysfunction, neuroinflammation and blood-brain barrier permeability. This review summarizes the findings of recent studies demonstrating a role for bile acids in the pathogenesis of hepatic encephalopathy via one of three main bile acid receptors and speculates on the possible downstream consequences of aberrant bile acid signaling.