Glycyrrhetinic Acid Protects α-Naphthylisothiocyanate- Induced Cholestasis Through Regulating Transporters, Inflammation and Apoptosis

Abstract

Glycyrrhetinic acid (GA), the active metabolic product of Glycyrrhizin (GL) that is the main ingredient of licorice, was reported to protect against α-naphthylisothiocyanate (ANIT)- induced cholestasis. However, its protective mechanism remains unclear. In our work, the cholestatic liver injury in mice was caused by ANIT and GA was used for the treatment. We assessed cholestatic liver injury specific indexes, histopathological changes, bile acid transporters, inflammation and apoptosis. The results of liver biochemical index and histopathological examination showed that GA markedly attenuated ANIT-induced liver injury. Mechanism research suggested that GA could activate the expression of farnesoid x receptor (FXR) and its downstream bile acids transporters Na+/taurocholate co-transporting polypeptide (NTCP), bile salt export pump (BSEP) and multidrug resistance-associated protein 2 (MRP2), as well as the nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream proteins MRP3, MRP4. These transporters play a vital role in mediating bile acid homeostasis in hepatocytes. Moreover, GA could significantly inhibit the ANIT-induced activation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) inflammatory pathway and the increase of tumor necrosis factor-α (TNF-α) concentration in serum. Also, GA protected against ANIT-induced mitochondrial apoptosis by regulating the expression of Bcl-2, Bax, cleaved caspase 3 and cleaved caspase 9. In conclusion, GA alleviates the hepatotoxicity caused by ANIT by regulating bile acids transporters, inflammation and apoptosis, which suggests that GA may be a potential therapeutic agent for cholestasis.

Hepatoprotective Effects of Glycyrrhetinic Acid on Lithocholic Acid-Induced Cholestatic Liver Injury Through Choleretic and Anti-Inflammatory Mechanisms

“…We found that treatment with GA and PCN decreased the amounts of hepatic hydrophobic BAs (LCA, DCA, and CDCA) and increased that of hydrophilic BA (UDCA), indicating their potential to reduce hepatocyte inflammatory responses and liver injury. Our data agree with previous results that GA may protect against ANIT-induced cholestatic liver injury by activating FXR and downstream transporters ( Yan et al, 2021 ). Meanwhile, we found that GA exerted little effect on PXR activation, further supporting that FXR is the critical factor contributing to the choleretic effects of GA.…”

“…These findings suggested that the hepatoprotective effects of GA on LCA-induced cholestatic liver injury might be mediated through inhibition of the TLR/NF-κB pathway. Similar findings have been reported by Yan et al (2021) , and our findings further indicate that TLRs may be the intervention target of GA. Nevertheless, our current work is limited in its investigation of the dose-dependent effect of GA in LCA mice, and further research is necessary to establish a clearer relationship between the dose and hepatoprotective effects of GA. Intriguingly, in addition to the induction of drug-metabolizing enzymes through PXR activation, PCN could also interact with NF-κB to downregulate the expression of chemokines, including CCL2 and CXCL2 ( Okamura et al, 2020 ).…”

“…The GA dose used here (50 mg/kg) was chosen based on the literature ( Sun et al, 2017 ; Wang et al, 2017 ; Wu et al, 2021 ) and our previous studies. Furthermore, GA at a dose of 50 mg/kg effectively protected against cholestatic liver injury ( Wang et al, 2017 ; Yan et al, 2021 ). The GA and PCN were dissolved in DMSO and further diluted in corn oil with 2% DMSO in the final solution.…”

Liquorice Extract and 18β-Glycyrrhetinic Acid Protect Against Experimental Pyrrolizidine Alkaloid-Induced Hepatotoxicity in Rats Through Inhibiting Cytochrome P450-Mediated Metabolic Activation

“…According to the intake of the Compound Glycyrrhizin Tablets (containing 25 mg GL/per tablet), the suggested daily intake of GL is 225 mg/day for humans, which is approximately 20 mg/kg/day GA for rats. In our experiments, we used 50 mg/kg/day GA and 500 mg/kg/day EX (suggested daily intake of 5–20 g of liquorice root) for 5 consecutive days, which is close to the normal dose and has also been reported in many publications ( Lin et al, 1999 ; Zhang et al, 2019 ; Yan et al, 2021 ).…”

Screening of Biomarkers and Toxicity Mechanisms of Rifampicin-Induced Liver Injury Based on Targeted Bile Acid Metabolomics

“…Consistent with these results, Kim et al (Kim et al, 2017) reported that RIF-induced hepatotoxicity did not significantly increase ALP level, indicating a type of mixed liver injury via cholestasis and hepatocellular injury. In our study, RIF-induced liver injury was evaluated by measuring ALT, AST, bilirubin changes and H&E staining according to relevant studies (Lin et al, 2019;Fan et al, 2019;Yang et al, 2020c;Yan et al, 2021). We did not measure or quantify CK19 + bile duct mass or ALP levels to analyze hepatotoxicity caused by biliary duct dilatation, which is a limitation in the present study.…”