Role of p38 Mapk in development of acute hepatic injury in Long-Evans Cinnamon (LEC) rats, an animal model of human Wilson's disease

Inhibition of ASIC1a-Mediated ERS Improves the Activation of HSCs and Copper Transport Under Copper Load

Hepatolenticular degeneration (HLD) is an autosomal recessive genetic disease caused by the toxic accumulation of copper in the liver. Excessive copper will disrupt the redox balance in cells and tissues, causing ischemia, hypoxia, and inflammation. Acid-sensitive ion channel 1a is a cationic channel activated by extracellular acid and allowing Ca²⁺ and Na⁺ to flow into cells. Its expression appears in inflammation, arthritis, fibrotic tissue, and damaged environment, but its role in hepatolenticular degeneration has not been studied. This study established a Wistar rat model of high copper accumulation and used CuSO₄ to induce the activation of HSC-T6 in an in vitro experiment. In vivo, Wistar rats were examined to determine the serum copper concentration, serum ALT and AST activities, and liver copper accumulation, and liver tissue HE staining and immunohistochemical analyses were conducted. The expression of ASIC1a, α-SMA, Collagen-Ι, GRP78, XBP1, ATP7B, and CCS were detected. Besides, immunofluorescence technology can detect the expression of the phosphorylated protein in vitro. It is suggested that ASIC1a is involved in the quality control of the endoplasmic reticulum, which degrades mutant ATP7B and increases the accumulation of copper. After blocking or silencing the expression of ASIC1a, ELISA can detect the level of inflammatory factors, the expression of endoplasmic reticulum stress-related factors, and ATP7B was improved in a higher copper environment reduction of copper deposition was observed in liver Timm’s staining. Collectively, we conclude that ASIC1a is involved in the HSC activation induced by copper accumulation and promotes the occurrence of hepatolenticular fibrosis.

Drug Discovery in Liver Disease Using Kinome Profiling

The liver is one of the most important organs, playing critical roles in maintaining biochemical homeostasis. Accordingly, disease of the liver is often debilitating and responsible for untold human misery. As biochemical nexus, with kinases being master regulators of cellular biochemistry, targeting kinase enzymes is an obvious avenue for treating liver disease. Development of such therapy, however, is hampered by the technical difficulty of obtaining comprehensive insight into hepatic kinase activity, a problem further compounded by the often unique aspects of hepatic kinase activities, which makes extrapolations from other systems difficult. This consideration prompted us to review the current state of the art with respect to kinome profiling approaches towards the hepatic kinome. We observe that currently four different approaches are available, all showing significant promise. Hence we postulate that insight into the hepatic kinome will quickly increase, leading to rational kinase-targeted therapy for different liver diseases.

Role of endoplasmic reticulum stress and protein misfolding in disorders of the liver and pancreas

The endoplasmic reticulum (ER) is the site of synthesis and folding of membrane and secretory proteins. The fraction of protein passing through the ER represents a large proportion of the total protein in the cell. Protein folding, glycosylation, sorting and transport are essential tasks of the ER and a compromised ER folding network has been recognized to be a key component in the disease pathogenicity of common neurodegenerative, metabolic and malignant diseases. On the other hand, the ER protein folding machinery also holds significant potential for therapeutic interventions. Many causes can lead to ER stress. A disturbed calcium homeostasis, the generation of reactive oxygen species (ROS) and a persistent overload of misfolded proteins within the ER can drive the course of adisease. In this review the role of ER-stress in diseases of the liver and pancreas will be examined using pancreatitis and Wilson´s disease as examples. Potential therapeutic targets in ER-stress pathways will also be discussed.

Age and Sex but Not ATP7B Genotype Effectively Influence the Clinical Phenotype of Wilson Disease

Wilson disease (WD) is an inherited disorder of hepatic copper metabolism with considerable variation in clinical presentations, the most common ones being liver disease and neuropsychiatric disturbances. This study investigated the clinical presentation in relation to mutations in a large cohort of patients with WD. A total of 1,357 patients (702 children, 655 adults; 1,172 index patients, 185 siblings, all with a Leipzig score ≥4, male/female: 679/678) were studied. The age and the symptoms at presentation were used as key phenotypic markers. Index patients were clinically classified as having either hepatic (n = 711) or neurologic disease (n = 461). Seven hundred fifteen (52.7%) patients had a liver biopsy at diagnosis. DNA was sequenced by the Genetic Analyzers ABI Prism 310 (Perkin Elmer) or 3500 (Applied Biosystems). Three hundred ninety-four different mutation combinations were detected. The most frequent mutation was H1069Q (c.3207C>A; allele frequency: 46.9%), followed by P767P-fs (c.2304dupC; 2.85%), P1134P-fs (c.3402delC; 2.8%), and R969Q (c.2755C>T; 2.18%). There was no correlation between mutations and individual clinical manifestation. There was a gender effect in index patients: Hepatic presentation was more common in females (male/female: 328/383) and neurologic presentation in males (259/202; P < 0.001). At diagnosis, 39.5% of children/adolescents (≤18 years) and 58% of adults already had cirrhosis. The presence of cirrhosis did not correlate with the genotype. Conclusion: These findings refine and extend our understanding of the natural history and individual spectrum/manifestations of WD. Initially, there is asymptomatic hepatic involvement, which may progress and become symptomatic. Neurologic symptoms present many years later.

A20 rescues hepatocytes from apoptosis through the NF-κB signaling pathway in rats with acute liver failure

Background: Acute liver failure (ALF) is a disease of acute derangements in the hepatic synthetic function with defects involving innate immune responses, which was reported to be negatively regulated by tumor necrosis factor α-induced protein 3 (A20). Herein, the present study was conducted to investigate the effects the A20 protein on the proliferation and apoptosis of hepatocytes through the nuclear factor (NF)-κB signaling pathway in the rat models simulating ALF.Methods: Male Wistar rats were used to simulate ALF in the model rats. Next, the positive expression of A20 and Caspase-3 proteins was measured in liver tissues. Rat hepatocytes were separated and subjected to pyrrolidine dithiocarbamate (PDTC, inhibitor of NF-κB pathway) or A20 siRNA. Additionally, both mRNA and protein levels of A20, NF-κB, tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6), and receptor-interacting protein 1 (RIP1) were determined. Finally, we detected the hepatocyte proliferation, cell cycle entry, and apoptosis.Results: ALF rats displayed a lower positive expression of A20 protein and a higher expression of Caspase-3 protein. Furthermore, A20 was down-regulated, while NF-κB, TRAF6, and RIP1 were all up-regulated in ALF rats. Notably, A20 inhibited activation of NF-κB signaling pathway. The blockade of NF-κB signaling pathway enhanced proliferation and cell cycle progression of hepatocytes, whereas inhibited apoptosis of hepatocytes. On the contrary, A20 siRNA reversed the above situation.Conclusion: A20 inhibits apoptosis of hepatocytes and promotes the proliferation through the NF-κB signaling pathway in ALF rats, potentially providing new insight into the treatment of ALF.

A systems biology approach reveals new endoplasmic reticulum-associated targets for the correction of the ATP7B mutant causing Wilson disease

Copper (Cu) is an important trace element required for the activity of essential enzymes. However, excess Cu compromises the redox balance in cells and tissues causing serious toxicity. The process of disposal of excess Cu from organisms relies on the activity of Cu-transporting ATPase ATP7B. ATP7B is mainly expressed in liver hepatocytes where it sequesters the potentially toxic metal and mediates its excretion into the bile. Mutations in the ATP7B gene cause Wilson disease (WD), which is characterized by the accumulation of toxic Cu in the liver due to the scarce expression of ATP7B as well as the failure of ATP7B mutants to pump Cu and/or traffic to the Cu-excretion sites. The most frequent ATP7B mutant, H1069Q, still presents a significant Cu-transporting activity, but undergoes retention within the endoplasmic reticulum (ER) where the mutant is rapidly degraded. Expression of this ATP7B mutant has been recently reported to activate the p38 and JNK stress kinase pathways, which, in turn, trigger quality control mechanisms leading to the arrest of ATP7B-H1069Q in the ER and to the acceleration of its degradation. However, the main molecular players operating in these p38/JNK-dependent ER quality control pathways remain to be discovered. By using a combination of RNAseq, bioinformatics and RNAi approaches, we found a cluster of ER quality control genes whose expression is controlled by p38 and JNK and is required for the efficient retention of the ATP7B-H1069Q mutant in the ER. Silencing these genes reduced the accumulation of the ATP7B mutant in the ER and facilitated the mutant sorting and export to the Golgi and post-Golgi copper excretion sites. In sum, our findings reveal the ER-associated genes that could be utilized for the correction of ATP7B mutants and, hence, for the normalization of Cu homeostasis in Wilson disease.