Disturbed mitochondrial redox state and tissue energy charge in cholestasis

Molecular insights into experimental models and therapeutics for cholestasis

Cholestatic liver disease (CLD) is a range of conditions caused by the accumulation of bile acids (BAs) or disruptions in bile flow, which can harm the liver and bile ducts. To investigate its pathogenesis and treatment, it is essential to establish and assess experimental models of cholestasis, which have significant clinical value. However, owing to the complex pathogenesis of cholestasis, a single modelling method can merely reflect one or a few pathological mechanisms, and each method has its adaptability and limitations. We summarize the existing experimental models of cholestasis, including animal models, gene-knockout models, cell models, and organoid models. We also describe the main types of cholestatic disease simulated clinically. This review provides an overview of targeted therapy used for treating cholestasis based on the current research status of cholestasis models. In addition, we discuss the respective advantages and disadvantages of different models of cholestasis to help establish experimental models that resemble clinical disease conditions. In sum, this review not only outlines the current research with cholestasis models but also projects prospects for clinical treatment, thereby bridging basic research and practical therapeutic applications.

The protective effect of forsythiaside A on 3,5-diethoxycarbonyl-1,4-dihydrocollidine-induced cholestatic liver injury in mice: Based on targeted metabolomics and molecular biology technology

Cholestasis is a disorder of bile secretion and excretion caused by a variety of etiologies. At present, there is a lack of functional foods or drugs that can be used for intervention. Forsythiaside A (FTA) is a natural phytochemical component isolated from the medicinal plant Forsythia suspensa (Thunb.) Vahl, which has a significant hepatoprotective effect. In this study, we investigated whether FTA could alleviate liver injury induced by cholestasis. In vitro, FTA reversed the decrease in viability of human intrahepatic bile duct epithelial cells, the decrease in antioxidant enzymes (SOD1, CAT and GSH-Px), and cell apoptosis induced by lithocholic acid. In vivo, FTA protected mice from 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-induced liver injury, abnormal serum biochemical indexes, abnormal bile duct hyperplasia, and inflammatory infiltration. Furthermore, FTA treatment alleviated liver fibrosis by inhibiting collagen deposition and HSC activation. The metabonomic results showed that DDC-induced bile acid disorders in the liver and serum were reversed after FTA treatment, which may benefit from the activation of the FXR/BSEP axis. In addition, FTA treatment increased the levels of antioxidant enzymes in the serum and liver. Meanwhile, FTA treatment inhibited ROS and MDA levels and cleaved caspase 3 protein expression, thereby reducing DDC-induced hepatic oxidative stress and apoptosis. Further studies showed that the antioxidant effects of FTA were dependent on the activation of the BRG1/NRF2/HO-1 axis. In a word, FTA has a significant hepatoprotective effect on cholestatic liver injury, and can be further developed as a functional food or drug to prevent and treat cholestatic liver injury.

PGC1α deficiency reverses cholestasis-induced liver injury via attenuating hepatic inflammation and promoting bile duct remodeling

OBJECTIVES

Cholestatic liver diseases are characterized by hepatocellular damage, cholangiocyte proliferation, and progressive fibrosis. Bile duct ligation (BDL) is widely used to resemble liver injuries induced by cholestasis. Peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α) was reported to play a critical role in multiple biological responses. Nevertheless, whether PGC1α is involved in bile acid metabolism and biliary disorders remains unclear. This study aimed to investigate the effect of PGC1α on hepatic responses after cholestatic injury.

MATERIALS AND METHODS

Wild-type mice were subjected to BDL or sham surgery for 14 days and human liver specimens from patients with primary biliary cholangitis (PBC) were collected to detect the expression of PGC1α. Hepatic-specific PGC1α knockout mice (HKO) were constructed and subjected to BDL, in which the effects of PGC1α on cholestatic liver injury were demonstrated by biochemical and histopathological assessments, immunoblotting, and metabolomics.

RESULTS

The expression of PGC1α was upregulated in the liver of PBC patients and murine models. Both in vivo and in vitro experiments supported the protective effects of PGC1α on cholestasis-induced hepatocyte injury. Infiltrated inflammatory cells after BDL were decreased in HKO mice. Inhibited Wnt/β-Catenin pathway and enhanced Notch signaling promoted transdifferentiation of hepatic progenitor cells (HPC)/ hepatocytes into cholangiocytes, leading to the greater ductular reaction observed in the HKO mice. But bile acids metabolism and mitochondrial function were not affected due to hepatic PGC1α deficiency in cholestasis.

CONCLUSIONS

Hepatic-specific deletion of PGC1α regulated liver regeneration by promoting ductular reactions, thereby exerting protective effects against BDL-induced liver injury, which could be a new potential therapeutic target.

Hepatic TNFRSF12A promotes bile acid-induced hepatocyte pyroptosis through NFκB/Caspase-1/GSDMD signaling in cholestasis

Tumor necrosis factor receptor superfamily member-12A (TNFRSF12A) plays a critical role in inflammation and cell death. It is expressed in multiple tissues yet extremely low in normal liver. To date, little is known about its role in cholestasis. Therefore, we sought to delineate the role of TNFRSF12A in cholestasis and its underlying mechanisms. Human liver tissues were collected from patients with obstructive cholestasis (OC) or primary biliary cholangitis (PBC). Tnfrsf12a knockout (KO) mice were generated. Cholestasis was induced by bile-duct ligation (BDL) or 0.1% 5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-feeding. Human hepatoma PLC/PRF/5-ASBT and THP1 cell lines or primary mouse hepatocytes were used for mechanistic studies. Hepatic TNFRSF12A expression was markedly increased in OC or PBC patients. Genetic ablation of Tnfrsf12a in BDL- and 0.1%DDC-induced cholestatic mice significantly attenuated cholestatic liver injury with remarkable reduction of hepatocyte pyroptosis but without changing scores of necroptosis and apoptosis. Morphological features of hepatocyte pyroptosis and increased levels of pyroptosis-related proteins, NLRP3, cleaved-Caspase-1, and cleaved-GSDMD in OC patients and BDL-mice confirmed this observation. Further mechanistic studies revealed that bile acids (BAs) induced TNFRSF12A expression by enhancing the transcription factor c-JUN binding to the TNFRSF12A promoter and subsequently initiated hepatocyte pyroptosis by the NFκB/Caspase-1/GSDMD signaling. Interestingly, TWEAK, a typical ligand of TNFRSF12A, secreted by infiltrated macrophages in cholestatic livers, enhanced TNFRSF12A-induced hepatocyte pyroptosis. Taken together, we report, for the first time, that hepatic TNFRSF12A is dramatically increased in human cholestasis. Deletion of TNFRSF12A inhibits BAs-induced hepatocyte pyroptosis through the NFκB/Caspase-1/GSDMD signaling and thereby ameliorates cholestatic liver injury. As such, targeting TNFRSF12A could be a promising approach to treating cholestasis.

Pulmonary inflammation, oxidative stress, and fibrosis in a mouse model of cholestasis: the potential protective properties of the dipeptide carnosine

Cholestasis is a clinical complication that primarily influences the liver. However, it is well known that many other organs could be affected by cholestasis. Lung tissue is a major organ influenced during cholestasis. Cholestasis-induced lung injury could induce severe complications such as respiratory distress, serious pulmonary infections, and tissue fibrosis. Unfortunately, there is no specific pharmacological intervention against this complication. Several studies revealed that oxidative stress and inflammatory response play a role in cholestasis-induced lung injury. Carnosine (CARN) is a dipeptide found at high concentrations in different tissues of humans. CARN's antioxidant and antiinflammatory properties are repeatedly mentioned in various experimental models. This study aimed to assess the role of CARN on cholestasis-induced lung injury. Rats underwent bile duct ligation (BDL) to induce cholestasis. Broncho-alveolar lavage fluid (BALF) levels of inflammatory cells, pro-inflammatory cytokines, and immunoglobulin were monitored at scheduled intervals (7, 14, and 28 days after BDL). Moreover, lung tissue histopathological alterations and biomarkers of oxidative stress were evaluated. A significant increase in BALF inflammatory cells, TNF-α, IL-1β, IL-6, and immunoglobulin-G (IgG) was detected in the BALF of BDL rats. Moreover, lung tissue histopathological changes, collagen deposition, increased TGF-β, and elevated levels of oxidative stress biomarkers were evident in cholestatic animals. It was found that CARN (100 and 500 mg/kg, i.p.) significantly alleviated lung oxidative stress biomarkers, inflammatory response, tissue fibrosis, and histopathological alterations. These data indicate the potential protective properties of CARN in the management of cholestasis-induced pulmonary damage. The effects of CARN on inflammatory response and oxidative stress biomarkers seems to play a crucial role in its protective properties in the lung of cholestatic animals.

Rare earth cerium oxide nanoparticles attenuated liver fibrosis in bile duct ligation mice model

Liver fibrosis is one of the major liver complications which eventually progresses to liver cirrhosis and liver failure. Cerium oxide nanoparticles, also known as nanoceria (NC) are nanoparticles with potential antioxidant and anti-inflammatory activities. Herein, we evaluated the hepatoprotective and anti-fibrotic effects of nanoceria (NC) against bile duct ligation (BDL) induced liver injury. NC were administered i.p. for 12 days (0.5 and 2 mg/kg) to C57BL/6J mice. The biochemical markers of liver injury, oxidative and nitrosative stress markers, inflammatory cytokines were evaluated. Fibrosis assessment and mechanistic studies were conducted to assess the hepatoprotective effects of NC. Administration of NC proved to significantly ameliorate liver injury as evident by reduction in SGOT, SGPT, ALP and bilirubin levels in the treated animals. NC treatment significantly reduced the hydroxyproline levels and expression of fibrotic markers. In summary, our findings establish the hepatoprotective and anti-fibrotic effects of NC against BDL induced liver injury and liver fibrosis. These protective effects were majorly ascribed to their potential ROS inhibition and antioxidant activities through catalase, superoxide dismutase (SOD)-mimetic properties and auto-regenerating capabilities.

Glycine protects the male reproductive system against lead toxicity via alleviating oxidative stress, preventing sperm mitochondrial impairment, improving kinematics of sperm, and blunting the downregulation of enzymes involved in the steroidogenesis

Lead (Pb) is a highly toxic heavy metal widely dispersed in the environment because of human industrial activities. Many studies revealed that Pb could adversely affect several organs, including the male reproductive system. Pb-induced reproductive toxicity could lead to infertility. Thus, finding safe and clinically applicable protective agents against this complication is important. It has been found that oxidative stress plays a fundamental role in the pathogenesis of Pb-induced reprotoxicity. Glycine is the simplest amino acid with a wide range of pharmacological activities. It has been found that glycine could attenuate oxidative stress and mitochondrial impairment in various experimental models. The current study was designed to evaluate the role of glycine in Pb-induced reproductive toxicity in male mice. Male BALB/c mice received Pb (20 mg/kg/day; gavage; 35 consecutive days) and treated with glycine (250 and 500 mg/kg/day; gavage; 35 consecutive days). Then, reproductive system weight indices, biomarkers of oxidative stress in the testis and isolated sperm, sperm kinetic, sperm mitochondrial indices, and testis histopathological alterations were monitored. A significant change in testis, epididymis, and Vas deferens weight was evident in Pb-treated animals. Markers of oxidative stress were also significantly increased in the testis and isolated sperm of the Pb-treated group. A significant disruption in sperm kinetic was also evident when mice received Pb. Moreover, Pb exposure caused significant deterioration in sperm mitochondrial indices. Tubular injury, tubular desquamation, and decreased spermatogenic index were histopathological alterations detected in Pb-treated mice. It was found that glycine significantly blunted oxidative stress markers in testis and sperm, improved sperm mitochondrial parameters, causing considerable higher velocity-related indices (VSL, VCL, and VAP) and percentages of progressively motile sperm, and decreased testis histopathological changes in Pb-exposed animals. These data suggest glycine as a potential protective agent against Pb-induced reproductive toxicity. The effects of glycine on oxidative stress markers and mitochondrial function play a key role in its protective mechanism.