Self-protection against triptolide-induced toxicity in human hepatic cells via Nrf2-ARE-NQO1 pathway

Cytoprotective Effect of Bambusae caulis in Liquamen by Blocking Oxidative Stress in Hepatocytes

Bambusae caulis in Liquamen (BCL), which is extracted from heat-treated fresh bamboo stems, is a traditional herbal medicine widely used in Eastern countries. Recently, it has been reported to have anti-inflammatory and whitening effects. However, the protective effect of BCL on hepatocytes has not yet been elucidated. The present study aimed to determine whether BCL prevents oxidative stress induced by tert-butyl hydroperoxide (t-BHP) and exerts cytoprotective effects on hepatocytes. High-performance liquid chromatography and liquid chromatography with tandem mass spectroscopy were performed to analyze the type of polyphenols present in BCL. The activities of antioxidant enzymes and hepatocyte viability were assessed. The benzoic acid content was the highest among polyphenols present in BCL. Benzoic acid acts as a scavenger of free radicals, including reactive oxygen species. BCL increased the expression of antioxidant enzymes (glutamate-cysteine ligase and NADPH quinone dehydrogenase (1)) by activating nuclear factor erythroid 2-related factor 2 and reduced tBHP-induced cell death by inhibiting oxidative stress. BCL inhibited tBHP-induced phosphorylation of p38 and c-Jun N-terminal kinase but not that of extracellular signal-regulated kinase. In conclusion, BCL is a promising therapeutic candidate for treating oxidative-stress-induced hepatocyte damage.

Variable p53/Nrf2 crosstalk contributes to triptolide-induced hepatotoxic process

This study was to investigate the potential mechanism of triptolide-induced hepatotoxicity. We found a novel and variable role of p53/Nrf2 crosstalk in triptolide-induced hepatotoxic process. Low doses of triptolide led to adaptive stress response without obvious toxicity, while high levels of triptolide caused severe adversity. Correspondingly, at the lower levels of triptolide treatment, nuclear translocation of Nrf2 as well as its downstream efflux transporters multidrug resistance proteins and bile salt export pump expressions were significantly enhanced, so did p53 pathways that also increased; at a toxic concentration, total and nuclear accumulations of Nrf2 decreased, while p53 showed an obvious nuclear translocation. Further studies showed the cross-regulation between p53 and Nrf2 after different concentrations of triptolide treatment. Under mild stress conditions, Nrf2 induced p53 highly expression to maintain the pro-survival outcome, while p53 showed no obvious effect on Nrf2 expression and transcriptional activity. Under high stress conditions, the remaining Nrf2 as well as the largely induced p53 mutually inhibited each other, leading to a hepatotoxic result. Nrf2 and p53 could physically and dynamically interact. Low levels of triptolide enhanced the interaction between Nrf2 and p53. Reversely, p53/Nrf2 complex dissociated at high levels of triptolide treatment. Altogether, variable p53/Nrf2 crosstalk contributes to triptolide-induced self-protection and hepatotoxicity, by modulating which may be a potential strategy for triptolide-induced hepatotoxicity intervention.

The molecular pathogenesis of triptolide-induced hepatotoxicity

Triptolide (TP) is the major pharmacologically active ingredient and toxic component of Tripterygium wilfordii Hook. f. However, its clinical potential is limited by a narrow therapeutic window and multiple organ toxicity, especially hepatotoxicity. Furthermore, TP-induced hepatotoxicity shows significant inter-individual variability. Over the past few decades, research has been devoted to the study of TP-induced hepatotoxicity and its mechanism. In this review, we summarized the mechanism of TP-induced hepatotoxicity. Studies have demonstrated that TP-induced hepatotoxicity is associated with CYP450s, P-glycoprotein (P-gp), oxidative stress, excessive autophagy, apoptosis, metabolic disorders, immunity, and the gut microbiota. These new findings provide a comprehensive understanding of TP-induced hepatotoxicity and detoxification.

Qingluotongbi formula regulates the LXRα-ERS-SREBP-1c pathway in hepatocytes to alleviate the liver injury caused by Tripterygium wilfordii Hook. f

ETHNOPHARMACOLOGICAL RELEVANCE

Tripterygium wilfordii Hook. f. (TW) is widely used to treat autoimmune and inflammatory diseases; however, its development and application is limited by its significant association with liver injury. The compound formula Qingluotongbi (QLT) employs TW as its main component and is used to treat rheumatoid arthritis with no adverse reactions, suggesting that QLT may reduce the liver toxicity of TW.

AIM OF THE STUDY

We examined whether TW interferes with lipid metabolism to induce liver injury, and evaluated the protective effect of QLT in in vivo and in vitro experiments.

MATERIALS AND METHODS

After administration of QLT and its ingredients, HepaRG cells and SD rats were tested for biochemical indicators, hepatocytes lipid changes, and rat liver pathological changes, and then we analyzed for the gene expression of liver X receptor α (LXRα), endoplasmic reticulum stress (ERS) key proteins, sterol regulatory element binding protein-1c (SREBP-1c), and lipid-synthesizing enzymes. In HepaRG cells, the protein expression of glucose-regulated protein 78 kDa (GRP78) and LXRα was detected after addition of an LXRα inhibitor, LXRα agonist, and ERS inhibitor.

RESULTS

TW caused significant elevation of biochemical indicators and lipid droplet deposition in hepatocytes, as well as upregulated the gene expression of LXRα, ERS key proteins, SREBP-1c, and lipid-synthesizing enzymes in both in vitro and in vivo settings, and caused liver injury in rats. QLT can alleviate the lipotoxic liver injury caused by TW. LXRα agonist further activated ERS induced by TW, whereas LXRα inhibitor significantly reduced ERS and lipotoxic injury induced by TW in HepaRG cells.

CONCLUSIONS

TW upregulated LXRα to activate ERS and increased the gene expression of SREBP-1c and lipid-synthesizing enzymes, leading to increased lipid synthesis in hepatocytes to result in liver injury. QLT inhibited the LXRα-ERS-SREBP-1c pathway and reduced abnormal lipid synthesis in hepatocytes and the hepatotoxicity of TW.

Ginsenoside Rb1 Attenuates Triptolide-Induced Cytotoxicity in HL-7702 Cells via the Activation of Keap1/Nrf2/ARE Pathway

Triptolide (TP) is the major bioactive compound extracted from Tripterygium wilfordii Hook F. It exerts anti-inflammatory, antirheumatic, antineoplastic, and neuroprotective effects. However, the severe hepatotoxicity induced by TP limits its clinical application. Ginsenoside Rb1 has been reported to possess potential hepatoprotective effects, but its mechanism has not been fully investigated. This study was aimed at investigating the effect of ginsenoside Rb1 against TP-induced cytotoxicity in HL-7702 cells, as well as the underlying mechanism. The results revealed that ginsenoside Rb1 effectively reversed TP-induced cytotoxicity in HL-7702 cells. Apoptosis induced by TP was suppressed by ginsenoside Rb1 via inhibition of death receptor-mediated apoptotic pathway and mitochondrial-dependent apoptotic pathway. Pretreatment with ginsenoside Rb1 significantly reduced Bax/Bcl-2 ratio and down-regulated the expression of Fas, cleaved poly ADP-ribose polymerase (PARP), cleaved caspase-3, and -9. Furthermore, ginsenoside Rb1 reversed TP-induced cell cycle arrest in HL-7702 cells at S and G2/M phase, via upregulation of the expressions of cyclin-dependent kinase 2 (CDK2), cyclin E, cyclin A, and downregulation of the expressions of p53, p21, and p-p53. Ginsenoside Rb1 increased glutathione (GSH) and superoxide dismutase (SOD) levels, but decreased the reactive oxygen species (ROS) and malondialdehyde (MDA) levels. Pretreatment with ginsenoside Rb1 enhanced the expression levels of nuclear factor-erythroid 2-related factor 2 (Nrf2), total Nrf2, NAD(P)H: quinone oxidoreductases-1 (NQO-1), heme oxygenase-1 (HO-1), and Kelch-like ECH-associated protein 1 (Keap1)/Nrf2 complex. Therefore, ginsenoside Rb1 effectively alleviates TP-induced cytotoxicity in HL-7702 cells through activation of the Keap1/Nrf2/ARE antioxidant pathway.

The anti-UV properties of Saussurea involucrate Matsum. & Koidz. Via regulating PI3K/Akt pathway in B16F10 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Ultra Violet (UV) radiation is the major reason for reactive oxygen species (ROS) forming, skin cell damage, melanin production, and could horribly cause skin cancer. Saussureae Involucratae Herba (SIH) is the aerial part of Saussurea involucrata Matsum. & Koidz. This Material Medica is popular with both in Uyghur and Chinese medicines filed. SIH is one of the famous species of the Asteraceae family and which prescribed for skin protection from UV-induced damage according to China Pharmacopeia (2020). However, the detailed working mechanism involved is still not elucidated.

AIM OF THE STUDY

We would like to probe the potential transduction pathway of SIH against UV-induced skin cell damages in cultured B16F10 cells.

METHODS

Western blot, luciferase assay, laser confocal, RT-PCR and flow cytometer were employed here to verify the protective pharmaceutical value of SIH in cultured B16F10 cells after UV pre-treatment.

RESULTS

Our result revealed that SIH attenuates ROS formation after UV-induced damage in B16F10 cells in a dose-dependent manner. Moreover, the transcriptional and translational anti-oxidative encoding genes were up-regulated under the presence of SIH. Further studies showed that SIH activated transcriptional activity of anti-oxidant response element (ARE). Moreover, we found that SIH dramatically stimulates PI3K/Akt phosphorylation in cultured B16F10 cells, this result was further verified by its specific inhibitors, LY294002 and Tocris.

CONCLUSION

Our findings concluded that SIH protect melanoma cells from UV damages via activating PI3K/Akt signaling and which could provide scientific evidence for anti-UV pharmaceutical values of this herbal extract.

Nephrotoxicity of Herbal Medicine and Its Prevention

Herbal medicine (HM) has been widely used to treat diseases for thousands of years and has greatly contributed to the health of human beings. Many new drugs have been developed from HM, such as artemisinin. However, artemisinin has adverse effects, such as renal toxicity. In 1993, a study conducted in Belgium reported for the first time that the root extracts of Aristolochia obliqua S. M. Hwang led to progressive interstitial renal fibrosis. The nephrotoxicity of HM has attracted worldwide attention. More than 100 kinds of HM induce renal toxicity, including some herbs, animal HMs, and minerals. This paper aimed to summarize the HM compounds that cause nephrotoxicity, the mechanisms underlying the toxicity of these compounds, biomarkers of renal injury, and prevention strategies. These findings provide a basis for follow-up studies on the prevention and treatment of HM nephrotoxicity.

Protective Effect of Vitamin C on Triptolide-induced Acute Hepatotoxicity in Mice through mitigation of oxidative stress

Triptolide, a purified diterpenoid from the herb Tripterygium wilfordii Hook.f., was widely used to treat many diseases. However, the hepatotoxicity of triptolide limited its clinical use. Research showed oxidative stress played an important role in triptolide-induced liver injury. To investigate the effect of vitamin C, which was one of the most effective antioxidants, on triptolide-induced hepatotoxicity and its potential mechanism in mice. In the present study, acute liver injury was induced by intraperitoneal injection of triptolide and vitamin C was orally administered. The results showed treatment with vitamin C prevented the triptolide-induced liver injury by reducing the levels of aspartate transaminase from 286.86 to 192.48 U/mL and alanine aminotransferase from 746.75 to 203.36 U/mL. Histopathological changes of liver corresponded to the same trend. Furthermore, vitamin C also protected the liver against triptolide-induced oxidative stress by inhibiting the generation of malondialdehyde (2.22 to 1.49 nmol/mgprot) and hydrogen peroxide (14.74 to 7.19 mmol/gprot) and restoring the level of total superoxide dismutase (24.32 to 42.55 U/mgprot) and glutathione (7.69 to 13.03 μg/mgprot). These results indicated that vitamin C could protect against triptolide-induced liver injury via reducing oxidative stress, and vitamin C may pose a significant health protection in the clinical use of triptolide.

Mechanisms of Triptolide-Induced Hepatotoxicity and Protective Effect of Combined Use of Isoliquiritigenin: Possible Roles of Nrf2 and Hepatic Transporters

Triptolide (TP), the main bioactive component of Tripterygium wilfordii Hook F, can cause severe hepatotoxicity. Isoliquiritigenin (ISL) has been reported to be able to protect against TP-induced liver injury, but the mechanisms are not fully elucidated. This study aims to explore the role of nuclear transcription factor E2-related factor 2 (Nrf2) and hepatic transporters in TP-induced hepatotoxicity and the reversal protective effect of ISL. TP treatment caused both cytotoxicity in L02 hepatocytes and acute liver injury in mice. Particularly, TP led to the disorder of bile acid (BA) profiles in mice livers. Combined treatment of TP with ISL effectively alleviated TP-induced hepatotoxicity. Furthermore, ISL pretreatment enhanced Nrf2 expressions and nuclear accumulations and its downstream NAD(P)H: quinine oxidoreductase 1 (NQO1) expression. Expressions of hepatic P-gp, MRP2, MRP4, bile salt export pump, and OATP2 were also induced. In addition, in vitro transport assays identified that neither was TP exported by MRP2, OATP1B1, or OATP1B3, nor did TP influence the transport activities of P-gp or MRP2. All these results indicate that ISL may reduce the hepatic oxidative stress and hepatic accumulations of both endogenous BAs and exogenous TP as well as its metabolites by enhancing the expressions of Nrf2, NQO1, and hepatic influx and efflux transporters. Effects of TP on hepatic transporters are mainly at the transcriptional levels, and changes of hepatic BA profiles are very important in the mechanisms of TP-induced hepatotoxicity.