Zhongxiang Zhao

Activation of the farnesoid X receptor attenuates triptolide-induced liver toxicity.

BACKGROUND Triptolide, an active ingredient extracted from the Chinese herb Tripterygium wilfordii Hook f., has multiple pharmacological properties, including anti-inflammatory, immune-modulatory, and anti-proliferative activities. However, the hepatotoxicity of triptolide always limits its clinical applications. HYPOTHESIS/PURPOSE Farnesoid X receptor (FXR) is a ligand-activated transcription factor that plays a key role in hepatoprotection through the maintenance of liver metabolism homeostasis. This study explored the role of FXR in triptolide-induced cytotoxicity and investigated whether activation of FXR can protect against triptolide-induced liver injury. STUDY DESIGN The role of FXR in triptolide-induced cytotoxicity was investigated in HepG2 cells. In addition, the protective effect of the selective FXR agonist GW4064 on triptolide-induced hepatotoxicity was explored in BALB/c mice. METHODS HepG2 cells were transient transfected with FXR expression plasmid or FXR-siRNA. The cytotoxicity was compared using the MTT assay. The extent of liver injury was assessed by histopathology and serum aminotransferases. The expression of FXR and its target genes were detected by Western blot and qRT-PCR. RESULTS The transient overexpression of FXR protected against triptolide-induced cell death, whereas FXR knockdown with a specific small interfering RNA resulted in increased cytotoxicity. In BALB/c mice, treatment with the FXR agonist GW4064 attenuated triptolide-induced liver dysfunction, structural damage, glutathione depletion and lipid peroxidation. Moreover, the livers of GW4064-treated mice showed increased expression of FXR and several related target genes involved in phase II and phase III xenobiotic metabolism. CONCLUSION Taken together, these results indicate that activation of FXR attenuates triptolide-induced hepatotoxicity and provide direct implications for the development of novel therapeutic strategies against triptolide-induced hepatotoxicity.

New triterpene saponins from the root of Ilex pubescens.

Two new triterpene glycosides named ilexpublesnin A (1) and ilexpublesnin B (2) were isolated from the root of Ilex pubescens. Their structures were determined as 3-O-(β-D-xylopyranosyl)-28-O-(β-D-glucopyranosyl)-3β, 19α-dihydroxyurs-23-oxo-12-en-28-oic acid (1) and 28-O-(β-D-xylopyranosyl-(2→1)-β-D-glucopyranosyl)-3β, 19α-dihydroxyurs-23-oxo-12-en-28-oic acid (2) on the basis of chemical and spectroscopic methods.

Tanshinone IIA protects against acetaminophen-induced hepatotoxicity via activating the Nrf2 pathway

BACKGROUND Tanshinone IIA (Tan), the main active component of Salvia miltiorrhiza, has been demonstrated to have antioxidant activity. Acetaminophen (APAP), a widely used antipyretic and analgesic, can cause severe hepatotoxicity and liver failure when taken overdose. Oxidative stress has been reported to be involved in APAP-induced liver failure. PURPOSE This study aimed to investigate the effect of Tan on APAP-induced hepatotoxicity and the underlying mechanisms involved. STUDY DESIGN C57BL/6J mice were divided into six groups: (1) control, (2) APAP group, (3) APAP+Tan (30mg/kg) group, (4) Tan (30mg/kg) group, (5) APAP+Tan (10mg/kg) group, (6) Tan (10mg/kg) group. Mice in group 3 and 5 were pre-treated with specified dose of Tan by gavage and subsequently injected with an overdose of APAP intraperitoneally (i.p., 300mg/kg). The effect of Tan on Nrf2 pathway was investigated in HepG2 cells and mice. METHODS Plasma aspartate transaminase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH), liver glutathione (GSH), glutathione transferase (GST), glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) levels were determined after mice were sacrificed. Lipid peroxidation and histological examination were performed. The effect of Tan on the Nrf2 pathway was detected by western blotting and qRT-PCR. RESULTS Tan pretreatment reduced APAP-induced liver injury. Tan was able to activate Nrf2 and increase the expression levels of Nrf2 target genes, including glutamate-cysteine ligase catalytic subunit (GCLC), NAD(P)H:quinine oxidoreductase 1 (NQO1) and hemeoxygenase-1 (HO-1), in a dose-dependent manner in HepG2 cells. Consistent with our observations in HepG2 cells, Tan increased nuclear Nrf2 accumulation and upregulated mRNA and protein levels of the Nrf2 target genes GCLC, NQO1 and HO-1 in C57BL/6J mice compared with mice treated with APAP alone. CONCLUSIONS Our results demonstrate that Tan pretreatment could protect the liver from APAP-induced hepatic injury by activating the Nrf2 pathway. Tan may provide a new strategy for the protection against APAP-induced liver injury.

New clerodane diterpenoids from Croton crassifolius.

Two new clerodane diterpenoids (1-2), one new clerodane diterpenoid alkaloid (3), as well as thirteen known compounds were isolated from Croton crassifolius. The structures of new compounds were established by a combination of spectroscopic methods, including HRMS, (1)H NMR, (13)C NMR, (1)H (1)H COSY, HSQC, HMBC, NOESY and X-ray crystallographic analysis. Compound 3 is firstly reported as the clerodane-type diterpenoid alkaloid in natural products. All of the compounds were evaluated for in vitro cytotoxic activities against CT26.WT cell using the MTT method.

Protective effect of Wuzhi tablet (Schisandra sphenanthera extract) against cisplatin-induced nephrotoxicity via Nrf2-mediated defense response.

UNLABELLED Cisplatin is a potent anti-cancer agent for various types of tumors. However, the clinical use of cisplatin is often limited by its nephrotoxicity. This study reports that WZ tablet (WZ, a preparation of an ethanol extract of Schisandra sphenanthera) mitigates cisplatin-induced toxicity in renal epithelial HK-2 cells and in mice. Pretreatment of HK-2 cells with WZ ameliorated cisplatin-induced cytotoxicity caused by oxidative stress, as was demonstrated by reductions in the levels of reactive oxygen species (ROS) and increased levels of glutathione (GSH). WZ facilitated the nuclear accumulation of the transcription factor NF-E2-related factor 2 (Nrf2) and the subsequent expression of its target genes such as NAD(P)H quinine oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1) and glutamate cysteine ligase (GCL). Protective effects of WZ on cisplatin-induced nephrotoxicity were also observed in mice. WZ attenuated cisplatin-induced renal dysfunction, structural damage and oxidative stress. The nuclear accumulation of Nrf2 and its target genes were increased by WZ treatment. Taken together, these findings demonstrated WZ have a protective effect against cisplatin-induced nephrotoxicity by activation of the Nrf2 mediated defense response, which is of significant importance for therapeutic intervention in cisplatin induced renal injury.

Role of Nrf2 activation and NF-κB inhibition in valproic acid induced hepatotoxicity and in diammonium glycyrrhizinate induced protection in mice

Diammonium glycyrrhizinate (DG), an active compound extracted and purified from liquorices root, has been reported to exhibit antioxidant and anti-inflammatory properties. The aim of this study was to investigate the effect and underlying mechanisms of DG on the hepatotoxicity induced by valproic acid (VPA). DG at the dose of 60mg/kg was orally administered with VPA (100mg/kg) to mice once daily for 14 consecutive days. DG treatment attenuated VPA-induced liver dysfunction, structural damage, glutathione depletion and decrease in antioxidant enzymes in BALB/C mice. DG prevented VPA-induced depletion of cytosolic nuclear factor E2-related factor 2 (Nrf2) and suppression of nuclear translocation of Nrf2, which, in turn, up-regulated phase II/antioxidant enzyme activities. The effects of VPA and DG on Nrf2 expression in HepG2 cells were in consistent with that of mice. Furthermore, an increase in the nuclear levels of nuclear factor-kappaB (NF-κB) was observed in the livers of VPA-treated mice that coincided with induction of inflammatory cytokines. In contrast, DG inhibited NF-κB translocation and that subsequently decreased inflammatory cytokines. Taken together, these results demonstrate that DG attenuates VPA-induced liver injury through increasing the expression of Nrf2 mediated phase II/antioxidant enzymes and simultaneously decreasing the expression of inflammatory mediators.

3',4',5',5,7-pentamethoxyflavone sensitizes Cisplatin-resistant A549 cells to Cisplatin by inhibition of Nrf2 pathway.

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important redox-sensitive transcription factor that regulates the expression of several cytoprotective genes. More recently, genetic analyses of human tumors have indicated that Nrf2 may cause resistance to chemotherapy. In this study, we found that the expression levels of Nrf2 and its target genes GCLC, HO-1, NQO1 were significantly higher in cisplatin-resistant A549 (A549/CDDP) cells than those in A549 cells, and this resistance was partially reversed by Nrf2 siRNA. 3′,4′,5′,5,7-Pentamethoxyflavone (PMF), a natural flavonoid extracted from Rutaceae plants, sensitized A549/CDDP to CDDP and substantially induced apoptosis compared with that of CDDP alone treated group, and this reversal effect decreased when Nrf2 was downregulated by siRNA. Mechanistically, PMF reduced Nrf2 expression leading to a reduction of Nrf2 downstream genes, and in contrast, this effect was decreased by blocking Nrf2 with siRNA. Taken together, these results demonstrated that PMF could be used as an effective adjuvant sensitizer to increase the efficacy of chemotherapeutic drugs by downregulating Nrf2 signaling pathway.

Diterpenoid alkaloids and flavonoids from Delphinium trichophorum.

Five hetisane-type C20-diterpenoid alkaloids, trichodelphinines A-E, one delnudine-type C20-diterpenoid alkaloid, trichodelphinine F and three known flavonoids, quercetin, quercetin 3-O-β-D-glucopyranoside, and quercetin 3-O-β-D-glucopyranoside-7-O-α-L-arabinopyranoside, were isolated from whole plants of Delphinium trichophorum Franch. Their structures were elucidated on the basis of extensive spectroscopic analysis, including HSQC, HMBC, (1)H-(1)H COSY, NOESY and X-ray crystallographic analysis, and from chemical evidence. The cytotoxic activities of the diterpenoid alkaloids were evaluated using the MTT method, and the IC50 values of their cytotoxicity against A549 cancer cells ranged from 12.03 to 52.79 μM.

Antiplatelet aggregation triterpene saponins from the barks of Ilex rotunda

Four new triterpene saponins, rotundinosides A-D (1-4) and seven known triterpene saponins (5-11) were isolated from a methanol extract of the barks of Ilex rotunda Thunb. The new saponins were characterized as 3-O-β-d-glucopyranosy1-(1→2)-β-d-xylopyranosyl siaresinolic acid 28-O-β-d-glucopyranoside (1), 3-O-[β-d-glucopyranosy1-(1→2)-β-d-xylopyranosyl]-3β,19α-dihydroxyurs-12-en-28-oic-O-β-d-glucopranosy1ester (2), 3-O-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosy1-(1→2)-α-l-arabinopyranosyl]-3β,19α-dihydroxyurs-12-en-28-oic-O-β-d-glucopyranosy1 ester (3), and 3-O-α-l-rhamanopyranosyl-(1→2)-β-d-glucopyranosy1-(1→2)-α-l-arabinopyranosyl ilexgenin B 28-O-β-d-glucopyranosy1 ester (4), respectively. Their structures were established by extensive spectroscopic analysis, including HSQC, HMBC, (1)H-(1)H COSY, NOESY and acid hydrolysis, and also by the comparison of their spectroscopic data with those of related compounds. The known compounds 5-11 were all obtained from this species for the first time. The biological activity of compounds 1-11 against ADP induced platelet aggregation in rabbit plasma was determined. Among the tested compounds 1, 3, 5 and 10 exhibited strong inhibition of platelet aggregation in vitro, with IC50 values of 11.4±2.2, 10.4±1.3, 13.2±2.4, and 15.1±3.4μM, respectively.

Valproate induced hepatic steatosis by enhanced fatty acid uptake and triglyceride synthesis

ABSTRACT Steatosis is the characteristic type of VPA‐induced hepatotoxicity and may result in life‐threatening hepatic lesion. Approximately 61% of patients treated with VPA have been diagnosed with hepatic steatosis through ultrasound examination. However, the mechanisms underlying VPA‐induced intracellular fat accumulation are not yet fully understood. Here we demonstrated the involvement of fatty acid uptake and lipogenesis in VPA‐induced hepatic steatosis in vitro and in vivo by using quantitative real‐time PCR (qRT‐PCR) analysis, western blotting analysis, fatty acid uptake assays, Nile Red staining assays, and Oil Red O staining assays. Specifically, we found that the expression of cluster of differentiation 36 (CD36), an important fatty acid transport, and diacylglycerol acyltransferase 2 (DGAT2) were significantly up‐regulated in HepG2 cells and livers of C57B/6J mice after treatment with VPA. Furthermore, VPA treatment remarkably enhanced the efficiency of fatty acid uptake mediated by CD36, while this effect was abolished by the interference with CD36‐specific siRNA. Also, VPA treatment significantly increased DGAT2 expression as a result of the inhibition of mitogen‐activated protein kinase kinase (MEK) – extracellular regulated kinase (ERK) pathway; however, DGAT2 knockdown significantly alleviated VPA‐induced intracellular lipid accumulation. Additionally, we also found that sterol regulatory element binding protein‐1c (SREBP‐1c)‐mediated fatty acid synthesis may be not involved in VPA‐induced hepatic steatosis. Overall, VPA‐triggered over‐regulation of CD36 and DGAT2 could be helpful for a better understanding of the mechanisms underlying VPA‐induced hepatic steatosis and may offer novel therapeutic strategies to combat VPA‐induced hepatotoxicity. HIGHLIGHTSVPA induced hepatic steatosis and modulated genes associated with lipid metabolism.CD36‐mediated fatty acid uptake contributed to VPA‐induced lipid accumulation.VPA increased the hepatic level of DGAT2 through inhibiting MEK‐ERK pathway and enhanced triglyceride synthesis.SREBP‐1c‐mediated fatty acid synthesis was not involved in VPA‐induced hepatic steatosis.