Therapeutic action against chronic cholestatic liver injury by low-dose fenofibrate involves anti-chemotaxis via JNK–AP1–CCL2/CXCL2 signaling

Inhibition of PCSK9 prevents and alleviates cholesterol gallstones through PPARα-mediated CYP7A1 activation

BACKGROUND & AIMS

Dysregulated cholesterol metabolism is the major factor responsible for cholesterol gallstones (CGS). Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a critical role in cholesterol homeostasis and its inhibitors secure approval for treating various cholesterol metabolic disorders such as hypercholesterolemia and cardiovascular diseases, but its role in CGS remains unclear. Our study aims to clarify mechanisms by which PCSK9 promotes CGS formation and explore the application of the PCSK9 inhibitor, alirocumab, in preventing and treating CGS.

APPROACH & RESULTS

The expressions of PCSK9 were notably increased in CGS patients' serum, bile, and liver tissues compared to those without gallstones. Moreover, among CGS patients, hepatic PCSK9 was positively correlated with hepatic cholesterol and negatively correlated with hepatic bile acids (BAs), suggesting PCSK9 was involved in disrupted hepatic cholesterol metabolism related to CGS. Mechanistically, in vitro experiments demonstrated that inhibition of PCSK9 enhanced nuclear expression of PPARα by diminishing its lysosomal degradation and subsequently activated CYP7A1 transcription. Finally, inhibition of PCSK9 prevented CGS formation and dissolved the existing stones in CGS mice by elevating the conversion of cholesterol into BAs through PPARα-mediated CYP7A1 activation. Additionally, serum PCSK9 level may function as a prognostic signature to evaluate the therapeutic efficacy of PCSK9 inhibitors.

CONCLUSIONS

Inhibition of PCSK9 exerts preventive and therapeutic effects on CGS by activating PPARα-mediated CYP7A1 expression and facilitating the conversion of cholesterol into BAs, which highlights the potential of PCSK9 inhibition as a promising candidate for preventing and treating CGS in clinical applications.

IMPACT AND IMPLICATIONS

PCSK9 plays a pivotal role in cholesterol metabolism and its inhibitors are approved for clinical use in cardiovascular diseases. Our study observes inhibition of PCSK9 prevents and dissolves CGS by activating PPARα-mediated CYP7A1 expression and facilitating the conversion of cholesterol into BAs. Mechanistically, PCSK9 inhibition enhanced the nuclear expression of PPARα by diminishing its lysosomal degradation and subsequently activated CYP7A1 transcription. Our study sheds light on the new function and mechanism of PCSK9 in CGS, providing a novel preventive and therapeutic target with potential clinical applications.

Hypericum perforatum L. and the Underlying Molecular Mechanisms for Its Choleretic, Cholagogue, and Regenerative Properties

Any defects in bile formation, secretion, or flow may give rise to cholestasis, liver fibrosis, cirrhosis, and hepatocellular carcinoma. As the pathogenesis of hepatic disorders is multifactorial, targeting parallel pathways potentially increases the outcome of therapy. Hypericum perforatum has been famed for its anti-depressive effects. However, according to traditional Persian medicine, it helps with jaundice and acts as a choleretic medication. Here, we will discuss the underlying molecular mechanisms of Hypericum for its use in hepatobiliary disorders. Differentially expressed genes retrieved from microarray data analysis upon treatment with safe doses of Hypericum extract and intersection with the genes involved in cholestasis are identified. Target genes are located mainly at the endomembrane system with integrin-binding ability. Activation of α5β1 integrins, as osmo-sensors in the liver, activates a non-receptor tyrosine kinase, c-SRC, which leads to the insertion of bile acid transporters into the canalicular membrane to trigger choleresis. Hypericum upregulates CDK6 that controls cell proliferation, compensating for the bile acid damage to hepatocytes. It induces ICAM1 to stimulate liver regeneration and regulates nischarin, a hepatoprotective receptor. The extract targets the expression of conserved oligomeric Golgi (COG) and facilitates the movement of bile acids toward the canalicular membrane via Golgi-derived vesicles. In addition, Hypericum induces SCP2, an intracellular cholesterol transporter, to maintain cholesterol homeostasis. We have also provided a comprehensive view of the target genes affected by Hypericum's main metabolites, such as hypericin, hyperforin, quercitrin, isoquercitrin, quercetin, kaempferol, rutin, and p-coumaric acid to enlighten a new scope in the management of chronic liver disorders. Altogether, standard trials using Hypericum as a neo-adjuvant or second-line therapy in ursodeoxycholic-acid-non-responder patients define the future trajectories of cholestasis treatment with this product.

Therapeutic effect of fenofibrate for non-alcoholic steatohepatitis in mouse models is dependent on regime design

Background: Non-alcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver diseases. In most cases, NAFLD progresses from benign steatosis to steatohepatitis (NASH), and then to cirrhosis. No treatment is currently approved for NAFLD/NASH in the clinic. Fenofibrate (FENO) has been clinically used to treat dyslipidemia for more than a half century, but its effects on NASH are not established. FENO's half-life is quite different between rodent and human. The aim of this study was to investigate the potential of pharmacokinetic-based FENO regime for NASH treatment and the underlying mechanisms. Methods: Two typical mouse NASH models, methionine-choline deficient (MCD) diet-fed mice and choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD)-fed mice, were used. MCD model was designed as therapeutic evaluation in experiment 1 and CDAHFD model was designed as preventive in experiment 2. Three doses of FENO (5, 25, 125 mg/kg), two times a day (BID), were administered to the above models. Serum markers of liver injury, cholestasis, and the histology of liver tissues were investigated. Normal mice were used as a model in experiment 3 for toxicity evaluation, Quantitative-PCR and Western Blot assays were used to investigate the inflammatory responses, bile acid synthesis as well as lipid catabolism. Results: Mice on the MCD and CDAHFD diets developed steatohepatitis as expected. Treatment with FENO (25 mg/kg·BID) significantly decreased hepatic steatosis, inflammation and fibrosis in both therapeutic and preventive models. In the MCD model, the therapeutic action of FENO (25 mg/kg·BID) and 125 mg/kg·BID on histopathology and the expression of inflammatory cytokines were comparable. In reducing macrophage infiltration and bile acid load, FENO (25 mg/kg·BID) was superior to 125 mg/kg·BID. In all the aspects mentioned above, FENO (25 mg/kg·BID) was the best among the 3 doses in the CDAHFD model. In a third experiment, the effects of FENO (25 mg/kg·BID) and 125 mg/kg·BID on lipid catabolism were comparable, but 125 mg/kg·BID increased the expression of inflammatory factors and bile acid load. In both models, FENO (5 mg/kg·BID) showed little effect in hepatic steatosis and inflammation, neither the adverse effects. FENO (125 mg/kg·BID) aggravated liver inflammation, increased bile acid synthesis, and promoted the potential of liver proliferation. In toxicity risk assay, FENO (25 mg/kg·BID) treatment showed low potential to trigger bile acid synthesis, inflammation and hepatocyte proliferation. Conclusion: A new regime, FENO (25 mg/kg·BID) is potentially a therapeutic strategy for the NASH treatment. Translational medicine is warranted to prove its effectiveness in the clinic.

Hepatocytic AP-1 and STAT3 contribute to chemotaxis in alphanaphthylisothiocyanate-induced cholestatic liver injury

The development of cholestatic liver injury (CLI) involves inflammation, but the dominant pathway mediating the chemotaxis is not yet established. This work explored key signaling pathway mediating chemotaxis in CLI and the role of Kupffer cells in the inflammatory liver injury. Probe inhibitors T-5224 (100 mg/kg) for AP-1 and C188-9 (100 mg/kg) for STAT3 were used to validate key inflammatory pathways in alpha-naphthylisothiocyanate (ANIT, 100 mg/kg)-induced CLI. Two doses of GdCl₃ (10 mg/kg and 40 mg/kg) were used to delete Kupffer cells and explore their role in CLI. Serum and liver samples were collected for biochemical and mechanism analysis. The liver injury in ANIT-treated mice were significantly increased supported by biochemical and histopathological changes, and neutrophils gathering around the necrotic loci. Inhibitor treatments down-regulated liver injury biomarkers except the level of total bile acid. The chemokine Ccl2 increased by 170-fold and to a less degree Cxcl2 by 45-fold after the ANIT treatment. p-c-Jun and p-STAT3 were activated in the group A but inhibited by the inhibitors in western blot analysis. The immunofluorescence results showed AP-1 not STAT3 responded to inhibitors in ANIT-induced CLI. With or without GdCl₃, there was no significant difference in liver injury among the CLI groups. In necrotic loci in CLI, CXCL2 colocalized with hepatocyte biomarker Albumin, not with the F4/80 in Kupffer cells. Conclusively, AP-1 played a more critical role in the inflammation cascade than STAT3 in ANIT-induced CLI. Hepatocytes, not the Kupffer cells released chemotactic factors mediating the chemotaxis in CLI.

Unveiling the anti-senescence effects and senescence-associated secretory phenotype (SASP) inhibitory mechanisms of Scutellaria baicalensis Georgi in low glucose-induced astrocytes based on boolean network

BACKGROUND

Astrocytes senescence has been demonstrated in the aging brain and Alzheimer's disease (AD). Moreover, lower glucose metabolism has been confirmed in the early stage of AD. However, whether low glucose could induce astrocytes senescence remain ambiguous. Studies have shown that the ethanol extracts of Scutellaria baicalensis Georgi (SGE) exert neuroprotective and anti-aging effects, while whether SGE could delay astrocytes senescence was unclear.

PURPOSE

This study investigated the anti-senescence effect of SGE in low glucose-induced T98G cells and primary astrocytes, and explored the possible mechanisms based on boolean network.

METHODS

The neuroprotective effects of SGE in low glucose-induced T98G cells were evaluated by measurement of cell viability, LDH, ROS and ATP. The anti-senescence effects of SGE were investigated by detection of senescence-associated β-galactosidase (SA-β-Gal), senescence-associated secretory phenotype (SASP), cell cycle and senescence-related markers. The possible mechanisms of SGE in delaying astrocytes senescence were discovered through integrating transcriptomics with boolean network, and validation experiments were further performed.

RESULTS

Our results revealed that low glucose could induce astrocytes senescence, and SGE could delay astrocytes senescence by decreasing the staining rate of SA-β-gal, reducing secretions of SASP factors (IL-6, CXCL1, MMP-1), alleviating cell cycle arrest in G0/G1 phase, decreasing the formation of punctate DNA foci and down-regulating the expression of p16INK4A, p21 and γH2A.X. Transcriptomics and further verification results showed that SGE could markedly inhibit the mRNA expression levels of SASP factors (CXCL10, CXCL2, CCL2, IL-6, CXCR4, CCR7). Moreover, C-X-C motif chemokine 10 (CXCL10) was predicted to be the key SASP factor affecting the network stability by using boolean network. Further experiments validated that SGE could markedly reduce CXCL10 level, decrease the secretion of IL-6 and inhibit cell migration in CXCL10 induced primary astrocytes.

CONCLUSION

In summary, our research unmasks that the anti-senescence effects of SGE were highly correlated with the suppression of SASP secretions, and CXCL10 mediated the SASP inhibition effect of SGE in low glucose-induced astrocytes. Our study highlights that the delay of astrocytes senescence and the inhibition of SASP might be a new mechanism of SGE for alleviating neurodegenerative diseases such as AD.

Fenofibrate ameliorates olanzapine's side effects without altering its central effect: emphasis on FGF-21-adiponectin axis

The present work was designed to investigate whether fenofibrate could ameliorate olanzapine deleterious effect on insulin resistance via its effect on fibroblast growth factor-21 (FGF-21)-adiponectin axis without affecting olanzapine antipsychotic effect in postweaning socially isolated reared female rats. Treatment with olanzapine (6 mg/kg, intraperitoneally) or fenofibrate (100 mg/kg, orally) have been started 5 weeks after isolation, then behavioral tests, hippocampal content of neurotransmitters, and brain-derived neurotrophic factor (BDNF) were assessed. Moreover, insulin resistance, lipid profile, FGF-21, adiponectin, inflammatory, and oxidative stress markers of adipose tissue were assessed. Treatment of isolated-reared animals with olanzapine, or fenofibrate significantly ameliorated the behavioral and biochemical changes induced by postweaning social isolation. Co-treatment showed additive effects in improving hippocampal BDNF level. Besides, fenofibrate reduced the elevation in weight gain, adiposity index, insulin resistance, lipid profile, and FGF-21 level induced by olanzapine treatment. Also, fenofibrate increased adiponectin level which was reduced upon olanzapine treatment. Moreover, fenofibrate improved both adipose tissue oxidative stress and inflammatory markers elevation as a result of olanzapine treatment. Fenofibrate could ameliorate olanzapine-induced insulin resistance without affecting its central effect in isolated reared rats via its action on FGF-21-adiponectin axis.

FXR activation prevents liver injury induced by Tripterygium wilfordii preparations

Tripterygium glycosides tablets (TGT) and Tripterygium wilfordii tablets (TWT) are the preparations of Tripterygium wilfordii used to treat rheumatoid arthritis (RA) in the clinic, but the hepatotoxicity was reported frequently. This study aimed to determine the potential toxicity mechanism of liver injury induced by the preparations of Tripterygium wilfordii in mice.Here, we performed metabolomic analysis, pathological analysis and biochemical analysis of samples from mice with liver injury induced by TGT and TWT, which revealed that liver injury was associated with bile acid metabolism disorder. Quantitative real-time PCR (QPCR) and western blot indicated that the above changes were accompanied by inhibition of farnesoid X receptor (FXR) signalling.Liver injury from TWT could be alleviated by treatment of the FXR agonist obeticholic acid (OCA) via activation of the FXR to inhibit the c-Jun N-terminal kinase (JNK) pathway and improve bile acid metabolism disorder by activating bile salt export pump (BSEP) and organic solute-transporter-β (OSTB). The data demonstrate that FXR signalling pathway plays a key role in T. wilfordii-induced liver injury, which could be alleviated by activated FXR.These results indicate that FXR activation by OCA may offer a promising therapeutic opportunity against hepatotoxicity from the preparations of T. wilfordii.