[Rotective Effects of Quercetin Against the Triptolide Induced Liver Injury and Relevant Mechanism Study].

OBJECTIVE: To explore the protective effects of quercetin (QE) on triptolide (TP) induced liver injury and the relevant mechanism. METHODS: Forty C57BL/6 mice were equally divided into 4 groups, control group, TP model group, 20 mg/kg QE treatment group and 80 mg/kg QE treatment group randomly. The 20 mg/kg and 80 mg/kg QE groups were gastrointestinal administration with QE at the dose of 0.2 mL/10 g for 10 d, twice daily, while other groups were administrated with equivalent normal saline. Four hours post the last dose, animals were gastrointestinal administered with TP at a dose of 500 µg/kg per mouse, except for NS control. All the mice were sacrificed 22 h later, blood and liver tissue samples were collected. The pathologic change of liver tissue was detected by HE staining. The level of aminotransferase (AST) and aspartate alanine aminotransferase (ALT) in serum, and the level of glutathione (GSH), malondialdehyde (MDA) and superoxide dismutase (SOD) in liver tissue homogenates were detected using the commercial kits. The level of interleukin (IL)-17, IL-10 and IL-6 in liver tissue homogenates was measured by ELISA. Hepatic expression of Toll-like receptor 4 (TLR4) was detected by Western blot. RESULTS: Compared with the control group, in the TP model group, hepatic lobule structure atrophied and even disappeared, hepatic cell necrosis and inflammatory cell infiltration are obvious. Additionally, in TP model group, serum ALT, AST and MDA levels were significantly increased, SOD and GSH levels were decreased, IL-6 and IL-17 levels were increased, IL-10 levels were decreased, and TLR4 protein levels were increased (P < 0.05). Compared with the TP model group, liver tissue injury and inflammatory cell infiltration were reduced in the QE group, and serum levels of ALT, AST, MDA, IL-6 and IL-17 were all decreased. TLR4 expression was down-regulated (P < 0.05) in both QE groups, and the decease levle was more significant in the high-dose QE group (P < 0.05, compared with the low-dose QE group). CONCLUSION: Quercetin can reduce TP-induced liver injury by reducing oxidative damage, promoting antioxidant and regulating cytokine secretion.

Quercetin protects mouse liver against triptolide-induced hepatic injury by restoring Th17/Treg balance through Tim-3 and TLR4-MyD88-NF-κB pathway.

Triptolide (TP) is a diterpene triepoxide with various biological activities, but its clinical applications have been limited by potential hepatotoxicity, which can be attributed to T helper 17 (Th17)/T regulatory (Treg) cell imbalance. Quercetin (QE), a natural flavonoid, has been reported to have many benefits and medicinal properties, including hepatoprotective activity against TP-induced liver injury. However, the hepatoprotection mechanisms have not been clarified. The present study was designed to explore the protective effect and the mechanism of QE against TP-induced liver injury. Treatment with QE (20, 50 and 80mg/kg) prior to TP administration restored TP-induced alterations in a certain dose range indicating that QE was able to inhibit TP-induced liver injury. One mechanism underlying this effect was the shifting balance in Th17 and Treg cells from Th17 dominance to Treg dominance. Furthermore, QE markedly decreased the expression level of the Th17-related pro-inflammatory cytokines interleukin (IL)-17 and IL-6, as well as the Th17 transcription factor retinoid-related orphan receptor-γt (ROR-γt). TP induced downregulation in the expression of anti-inflammatory cytokine IL-10, but the expression of Treg transcription factor forkhead/winged-helix family transcriptional repressor p3 (FoxP3) was restored by QE. In the process of exploring the possible hepatoprotective mechanisms of QE, we found that QE significantly reduced both protein and mRNA expression of Toll-like receptor 4 (TLR4), which in turn not only inactivated myeloid differentiation primary response gene 88 (MYD88), nuclear factor kappa B (NF-κB) and related inflammatory cytokines IL-6 and IL-17, but also simultaneously increased the levels of T-cell immunoglobulin and mucin domain-containing protein 3 (Tim-3). Furthermore, blocking of TLR4 enhanced the effect of QE in regulating the Th17/Treg imbalance. In summary, this report has demonstrated for the first time that the protection afforded by QE against TP-induced liver injury was associated with a shift in the balance of Th17 and Treg cells to Treg dominance, which was regulated by Tim-3 and TLR4-MyD88-NF-κB signaling pathway.

Epigallocatechin-3-gallate Prevents Triptolide-Induced Hepatic Injury by Restoring the Th17/Treg Balance in Mice.

Drug-induced liver injury (DILI) is the most common cause of acute liver failure. Disruption of the Th17/Treg balance can lead to hepatic inflammation, which causes the main symptoms of DILI. Here we investigate the protective mechanisms of (-)-Epigallocatechin-3-gallate (EGCG) on triptolide (TP)-induced DILI that shows the Th17/Treg imbalance. Pretreatment with EGCG (5[Formula: see text]mg/kg) for 10 days before TP (0.5[Formula: see text]mg/kg) administration in mice significantly reduced the increased alanine aminotransferase (ALT) level ([Formula: see text]) induced by TP treatment. The hepatic histology analysis further proved that EGCG protected mice from TP-induced liver injury. The imbalance of Th17/Treg was induced by TP treatment, as shown by the upregulation of TLR4 and downregulation of Tim3 expression. EGCG pretreatment can maintain the expression of TLR4 and Tim3 at normal levels to restore the Th17/Treg imbalance. In addition, EGCG can block the TP-induced expression of the downstream targets of TLR4, including MyD88, NF[Formula: see text]B, and retinoid related orphan receptor (ROR-[Formula: see text]t), while EGCG can restore the TP inhibition of forkhead/winged-helix family transcriptional repressor p3 (FoxP3) that is the downstream target of Tim3. Consequently, EGCG pretreatment can effectively inhibit the Th17-related pro-inflammatory cytokine (e.g. IL-17 and IL-6) upregulation induced by TP treatment. However, TP inhibition of Treg-related anti-inflammatory cytokine IL-10 production was restored by EGCG pretreatment. Taken together, these results suggest that EGCG possesses significant protective properties against TP-induced hepatic inflammatory injury, and that these properties are carried out via the restoration of the Th17/Treg imbalance by the inhibition of the TLR4 signaling pathway and the enhanced activation of the Tim3 signaling pathway.