Xiaojiaoyang Li

Triptolide: Progress on research in pharmacodynamics and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE Tripterygium wilfordii Hook. f. (Tripterygium wilfordii), also known as Huangteng and gelsemium elegan, is a traditional Chinese medicine that has been marketed in China as Tripterygium wilfordii glycoside tablets. Triptolide (TP), an active component in Tripterygium wilfordii extracts, has been used to treat various diseases, including lupus, cancer, rheumatoid arthritis and nephritic syndrome. This review summarizes recent developments in the research on the pharmacodynamics, pharmacokinetics, pharmacy and toxicology of TP, with a focus on its novel mechanism of reducing toxicity. This review provides insight for future studies on traditional Chinese medicine, a field that is both historically and currently important. MATERIALS AND METHODS We included studies published primarily within the last five years that were available in online academic databases (e.g., PubMed, Google Scholar, CNKI, SciFinder and Web of Science). RESULTS TP has a long history of use in China because it displays multiple pharmacological activities, including anti-rheumatism, anti-inflammatory, anti-tumor and neuroprotective properties. It has been widely used for the treatment of various diseases, such as rheumatoid arthritis, nephritic syndrome, lupus, Behcet׳s disease and central nervous system diseases. Recently, numerous breakthroughs have been made in our understanding of the pharmacological efficacy of TP. Although TP has been marketed as a traditional Chinese medicine, its multi-organ toxicity prevents it from being widely used in clinical practice. CONCLUSIONS Triptolide, a biologically active natural product extracted from the root of Tripterygium wilfordii, has shown promising pharmacological effects, particularly as an anti-tumor agent. Currently, in anti-cancer research, more effort should be devoted to investigating effective anti-tumor targets and confirming the anti-tumor spectrum and clinical indications of novel anti-tumor pro-drugs. To apply TP appropriately, with high efficacy and low toxicity, the safety and non-toxic dose range for specific target organs and diseases should be determined, the altered pathways and mechanisms of exposure need to be clarified, and an early warning system for toxicity needs to be established. With further in-depth study of the efficacy and toxicity of TP, we believe that TP will become a promising multi-use drug with improved clinical efficacy and safety in the future.

Taurocholate Induces Cyclooxygenase-2 Expression via the Sphingosine 1-phosphate Receptor 2 in a Human Cholangiocarcinoma Cell Line

Background: Cyclooxygenase-2 (COX-2) and sphingosine 1-phosphate receptor 2 (S1PR2) are highly expressed in human cholangiocarcinoma (CCA) and taurocholate (TCA) promotes CCA cell growth via S1PR2. Results: TCA-mediated activation of S1PR2 contributed to COX-2 expression and CCA cell growth. Conclusion: S1PR2 plays a critical role in TCA-induced COX-2 expression and CCA growth. Significance: S1PR2 represents a novel therapeutic target for CCA. Cholangiocarcinoma (CCA) is a rare, but highly malignant primary hepatobiliary cancer with a very poor prognosis and limited treatment options. Our recent studies reported that conjugated bile acids (CBAs) promote the invasive growth of CCA via activation of sphingosine 1-phosphate receptor 2 (S1PR2). Cyclooxygenase-2 (COX-2)-derived prostaglandin E2 (PGE2) is the most abundant prostaglandin in various human malignancies including CCA. Previous studies have indicated that COX-2 was highly expressed in CCA tissues, and the survival rate of CCA patients was negatively associated with high COX-2 expression levels. It has also been reported that CBAs induce COX-2 expression, whereas free bile acids inhibit COX-2 expression in CCA mouse models. However, the underlying cellular mechanisms and connection between S1PR2 and COX-2 expression in CCA cells have still not been fully elucidated. In the current study, we examined the role of S1PR2 in conjugated bile acid (taurocholate, (TCA))-induced COX-2 expression in a human HuCCT1 CCA cell line and further identified the potential underlying cellular mechanisms. The results indicated that TCA-induced invasive growth of human CCA cells was correlated with S1PR2-medated up-regulation of COX-2 expression and PGE2 production. Inhibition of S1PR2 activation with chemical antagonist (JTE-013) or down-regulation of S1PR2 expression with gene-specific shRNA not only reduced COX-2 expression, but also inhibited TCA-induced activation of EGFR and the ERK1/2/Akt-NF-κB signaling cascade. In conclusion, S1PR2 plays a critical role in TCA-induced COX-2 expression and CCA growth and may represent a novel therapeutic target for CCA.

The role of sphingosine 1-phosphate receptor 2 in bile-acid–induced cholangiocyte proliferation and cholestasis-induced liver injury in mice

Bile duct obstruction is a potent stimulus for cholangiocyte proliferation, especially for large cholangiocytes. Our previous studies reported that conjugated bile acids (CBAs) activate the protein kinase B (AKT) and extracellular signal‐regulated kinase 1 and 2 (ERK1/2) signaling pathways through sphingosine 1‐phosphate receptor (S1PR) 2 in hepatocytes and cholangiocarcinoma cells. It also has been reported that taurocholate (TCA) promotes large cholangiocyte proliferation and protects cholangiocytes from bile duct ligation (BDL)‐induced apoptosis. However, the role of S1PR2 in bile‐acid–mediated cholangiocyte proliferation and cholestatic liver injury has not been elucidated. Here, we report that S1PR2 is the predominant S1PR expressed in cholangiocytes. Both TCA‐ and sphingosine‐1‐phosphate (S1P)‐induced activation of ERK1/2 and AKT were inhibited by JTE‐013, a specific antagonist of S1PR2, in cholangiocytes. In addition, TCA‐ and S1P‐induced cell proliferation and migration were inhibited by JTE‐013 and a specific short hairpin RNA of S1PR2, as well as chemical inhibitors of ERK1/2 and AKT in mouse cholangiocytes. In BDL mice, expression of S1PR2 was up‐regulated in whole liver and cholangiocytes. S1PR2 deficiency significantly reduced BDL‐induced cholangiocyte proliferation and cholestatic injury, as indicated by significant reductions in inflammation and liver fibrosis in S1PR2 knockout mice. Treatment of BDL mice with JTE‐013 significantly reduced total bile acid levels in serum and cholestatic liver injury. Conclusion: This study suggests that CBA‐induced activation of S1PR2‐mediated signaling pathways plays a critical role in obstructive cholestasis and may represent a novel therapeutic target for cholestatic liver diseases. (Hepatology 2017;65:2005‐2018).

The role of long noncoding RNA H19 in gender disparity of cholestatic liver injury in multidrug resistance 2 gene knockout mice

The multidrug resistance 2 knockout (Mdr2–/–) mouse is a well‐established model of cholestatic cholangiopathies. Female Mdr2–/– mice develop more severe hepatobiliary damage than male Mdr2–/– mice, which is correlated with a higher proportion of taurocholate in the bile. Although estrogen has been identified as an important player in intrahepatic cholestasis, the underlying molecular mechanisms of gender‐based disparity of cholestatic injury remain unclear. The long noncoding RNA H19 is an imprinted, maternally expressed, and estrogen‐targeted gene, which is significantly induced in human fibrotic/cirrhotic liver and bile duct–ligated mouse liver. However, whether aberrant expression of H19 accounts for gender‐based disparity of cholestatic injury in Mdr2–/– mice remains unknown. The current study demonstrated that H19 was markedly induced (∼200‐fold) in the livers of female Mdr2–/– mice at advanced stages of cholestasis (100 days old) but not in age‐matched male Mdr2–/– mice. During the early stages of cholestasis, H19 expression was minimal. We further determined that hepatic H19 was mainly expressed in cholangiocytes, not hepatocytes. Both taurocholate and estrogen significantly activated the extracellular signal–regulated kinase 1/2 signaling pathway and induced H19 expression in cholangiocytes. Knocking down H19 not only significantly reduced taurocholate/estrogen‐induced expression of fibrotic genes and sphingosine 1‐phosphate receptor 2 in cholangiocytes but also markedly reduced cholestatic injury in female Mdr2–/– mice. Furthermore, expression of small heterodimer partner was substantially inhibited at advanced stages of liver fibrosis, which was reversed by H19 short hairpin RNA in female Mdr2–/– mice. Similar findings were obtained in human primary sclerosing cholangitis liver samples. Conclusion: H19 plays a critical role in the disease progression of cholestasis and represents a key factor that causes the gender disparity of cholestatic liver injury in Mdr2–/– mice. (Hepatology 2017;66:869–884).

UDCA and CDCA alleviate 17α-ethinylestradiol-induced cholestasis through PKA-AMPK pathways in rats.

Estrogen-induced cholestasis, known as intrahepatic cholestasis of pregnancy (ICP), is an estrogen-related liver disease that is widely recognized as female or pregnancy-specific. Our previous findings showed that the synthetic estrogen, 17α-ethinylestradiol (EE), induced cholestatic injury through ERK1/2-LKB1-AMP-activated protein kinase (AMPK) signaling pathway and its mediated suppression of farnesoid X receptor (FXR). To investigate the role played by bile acids in EE-induced cholestasis, we evaluated the effects of chenodeoxycholic acid (CDCA), ursodeoxycholic acid (UDCA) and deoxycholic acid (DCA) on sandwich cultured rat primary hepatocytes (SCRHs) and an in vivo rat model. Our results showed that, both CDCA and UDCA significantly induced time- and concentration-dependent reduction in AMPK phosphorylation in SCRHs. Despite having different effects on FXR activation, CDCA and UDCA both inhibited EE-induced AMPK activation, accompanied with the up-regulation of FXR and its downstream bile acid transporters. However, although DCA activates FXR and induces SHP, it was unable to alleviate EE-induced FXR suppression and further aggravated EE-induced cholestasis. We further demonstrated that both CDCA and UDCA, but not DCA, activated cyclic AMP dependent protein kinase (PKA) in SCRHs and the livers of male rats (8weeks old) liver. Furthermore, PKA antagonist, H89, blocked the AMPK inhibition by CDCA and UDCA, and pharmacological and genetic activation of PKA suppressed EE-induced AMPK activation and its downstream effects. Collectively, these results suggest that CDCA and UDCA protect against estrogen-induced cholestatic injury via PKA signaling pathway and up-regulation of EE-suppressed FXR, which suggests a potential therapeutic target for ICP.

Alpha-naphthylisothiocyanate impairs bile acid homeostasis through AMPK-FXR pathways in rat primary hepatocytes

Alpha-naphthylisothiocyanate (ANIT) is widely used to induce cholestasis in basic researches. Although direct damage induced by ANIT to bile duct epithelial cells has been documented in previous studies, few works investigated ANIT-induced effects on hepatocytes. Our previous study indicated that activated AMP-activated protein kinase (AMPK) inhibited farnesoid X receptor (FXR) expression and further participated in the pathogenesis of estrogen-induced cholestasis. However, whether ANIT has effects on bile acid homeostasis in hepatocytes, and the role of AMPK-FXR pathway played in these effects remain unclear. In this study, our results showed that ANIT induced intracellular bile acid accumulation without obvious cellular toxicity in sandwich cultured rat primary hepatocytes (SCRHs), accompanied with significant decreased expression of FXR and bile acid transporters. AMPK activation via ERK1/2-LKB1 pathway was critical for ANIT-induced effects on hepatocytes. Compound C, specific AMPK inhibitor, blocked ANIT-regulated gene expression, decreased bile acid accumulation and recovered bile canalicular structure both in vitro and in vivo. Furthermore, the expression of A1 adenosine receptor (A1AR), a potential cholestatic target, was relatively low in hepatocytes compared with expression in rat whole livers. Consistent with these findings, DPCPX, a classic antagonist of A1AR, had no effect on ANIT-induced hepatocytes injury. In summary, our results indicate that AMPK-FXR signaling is critical for ANIT-induced toxic effects on hepatocytes, provide new insights into the pathogenesis of ANIT-induced cholestasis, and suggest AMPK-FXR pathway as a potential therapeutic target for cholestasis.

SRT1720 Alleviates ANIT-Induced Cholestasis in a Mouse Model

Intrahepatic cholestasis is a kind of clinical syndrome along with hepatotoxicity which caused by intrahepatic and systemic accumulations of bile acid. There are several crucial generating factors of the pathogenesis of cholestasis, such as inflammation, dysregulation of bile acid transporters and oxidative stress. SIRT1 is regarded as a class III histone deacetylase (HDAC). According to a set of researches, SIRT1 is one of the most important factors which can regulate the hepatic bile acid metabolism. SRT1720 is a kind of activator of SIRT1 which is 1000 times more potent than resveratrol, and this paper is aimed to study its protective influence on hepatotoxicity and cholestasis induced by alpha-naphthylisothiocyanate (ANIT) in mice. The findings revealed that SRT1720 treatment increased FXR and Nrf2 gene expressions to shield against hepatotoxicity and cholestasis induced by ANIT. The mRNA levels of hepatic bile acid transporters were also altered by SRT1720. Furthermore, SRT1720 enhanced the antioxidative system by increasing Nrf2, SOD, GCLc, GCLm, Nqo1, and HO-1 gene expressions. In conclusion, a protective influence could be provided by SRT1720 to cure ANIT-induced hepatotoxicity and cholestasis, which was partly through FXR and Nrf2 activations. These results indicated that SIRT1 could be regarded as a therapeutic target to cure the cholestasis.

Cholangiocyte‐derived exosomal long noncoding RNA H19 promotes cholestatic liver injury in mouse and humans

Cholestatic liver injury is an important clinical problem with limited understanding of disease pathologies. Exosomes are small extracellular vesicles released by a variety of cells, including cholangiocytes. Exosome‐mediated cell‐cell communication can modulate various cellular functions by transferring a variety of intracellular components to target cells. Our recent studies indicate that the long noncoding RNA (lncRNA), H19, is mainly expressed in cholangiocytes, and its aberrant expression is associated with significant down‐regulation of small heterodimer partner (SHP) in hepatocytes and cholestatic liver injury in multidrug resistance 2 knockout (Mdr2−/−) mice. However, how cholangiocyte‐derived H19 suppresses SHP in hepatocytes remains unknown. Here, we report that cholangiocyte‐derived exosomes mediate transfer of H19 into hepatocytes and promote cholestatic injury. Hepatic H19 level is correlated with severity of cholestatic injury in both fibrotic mouse models, including Mdr2−/− mice, a well‐characterized model of primary sclerosing cholangitis (PSC), or CCl4‐induced cholestatic liver injury mouse models, and human PSC patients. Moreover, serum exosomal‐H19 level is gradually up‐regulated during disease progression in Mdr2−/− mice and patients with cirrhosis. H19‐carrying exosomes from the primary cholangiocytes of wild‐type (WT) mice suppress SHP expression in hepatocytes, but not the exosomes from the cholangiocytes of H19−/− mice. Furthermore, overexpression of H19 significantly suppressed SHP expression at both transcriptional and posttranscriptional levels. Importantly, transplant of H19‐carrying serum exosomes of old fibrotic Mdr2−/− mice significantly promoted liver fibrosis (LF) in young Mdr2−/− mice. Conclusion: Cholangiocyte‐derived exosomal‐H19 plays a critical role in cholestatic liver injury. Serum exosomal H19 represents a noninvasive biomarker and potential therapeutic target for cholestatic diseases. (Hepatology 2018).

Sex-Related Differences of Lipid Metabolism Induced by Triptolide: The Possible Role of the LXRα/SREBP-1 Signaling Pathway

Triptolide, a diterpenoid isolated from the plant Tripterygium wilfordii Hook. f., exerts a unique bioactive spectrum of anti-inflammatory and anticancer activities. However, triptolide’s clinical applications are limited due to its severe toxicities. Fatty liver toxicity occurs in response to triptolide, and this toxic response significantly differs between males and females. This report investigated the pathogenesis underlying the sex-related differences in the dyslipidosis induced by triptolide in rats. Wistar rats were administered 0, 150, 300, or 450 μg triptolide/kg/day by gavage for 28 days. Ultrastructural examination revealed that more lipid droplets were present in female triptolide-treated rats than in male triptolide-treated rats. Furthermore, liver triglyceride, total bile acid and free fatty acid levels were significantly increased in female rats in the 300 and 450 μg/kg dose groups. The expression of liver X receptor α (LXRα) and its target genes, cholesterol 7α-hydroxylase (CYP7A1) and Sterol regulatory element-binding transcription factor 1(SREBP-1), increased following triptolide treatment in both male and female rats; however, the female rats were more sensitive to triptolide than the male rats. In addition, the expression of acetyl-CoA carboxylase 1(ACC1), a target gene of SREBP-1, increased in the female rats treated with 450 μg triptolide/kg/day, and ACC1 expression contributed to the sex-related differences in the triptolide-induced dysfunction of lipid metabolism. Our results demonstrate that the sex-related differences in LXR/SREBP-1-mediated regulation of gene expression in rats are responsible for the sex-related differences in lipid metabolism induced by triptolide, which likely underlie the sex-related differences in triptolide hepatotoxicity. This study will be important for predicting sex-related effects on the pharmacokinetics and toxicity of triptolide and for improving its safety.

Protective effects of SRT1720 via the HNF1α/FXR signalling pathway and anti-inflammatory mechanisms in mice with estrogen-induced cholestatic liver injury.

Sirtuin 1 (SIRT1) is the most conserved mammalian NAD+-dependent protein deacetylase and is a member of the silent information regulator 2 (Sir2) families of proteins (also known as Sirtuins). In the liver, hepatic SIRT1 modulates bile acid metabolism through the regulation of farnesoid X receptor (FXR) expression. FXR is one of the most important nuclear receptors involved in the regulation of bile acid metabolism. SIRT1 modulates the FXR expression at multiple levels, including direct deacetylation of this transcription factor and transcriptional regulation through hepatocyte nuclear factor 1α (HNF1α). Therefore, hepatic SIRT1 is a vital regulator of the HNF1α/FXR signalling pathway and hepatic bile acid metabolism. However, whether SIRT1 is a suitable therapeutic target for the treatment of cholestasis is unknown. In the present study, we examined the protective effect of SRT1720, which is a specific activator of SIRT1, against 17α-ethinylestradiol (EE)-induced cholestasis in mice. Our data demonstrated that SRT1720 significantly prevented EE-induced changes in the serum levels of total bile acids (TBA), total bilirubin (TBIL), γ-glutamyltranspeptidase (γ-GGT) and alkaline phosphatase (ALP). SRT1720 also relieved EE-induced liver pathological injuries as indicated by haematoxylin and eosin (H&E) staining. SRT1720 treatment protected against EE-induced liver injury through the HNF1α/FXR signalling pathway, which up-regulated the expression of hepatic efflux transporter (Bsep and Mrp2) and hepatic uptake transporters (Ntcp and Oatp1b2). Moreover, SRT1720 significantly inhibited the TNF-α and IL-6 levels induced by EE. These findings indicate that SRT1720 exerts a dose-dependent protective effect on EE-induced cholestatic liver injury in mice and that the mechanism underlying this activity is related to the activation of the HNF1α/FXR signalling pathway and anti-inflammatory mechanisms.