Autophagy plays an important role in triptolide-induced apoptosis in cardiomyocytes

Biochemical biomarkers for the toxicity induced by Traditional Chinese Medicine: A review update

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine (TCM) is widely used in China for disease treatment and has become a valuable resource for drug development due to its high efficacy and low risk of side-effects. However, growing toxicity reports has garnered significant global attention. A major challenge in addressing TCM-induced toxicity is lack of specific and sensitive biomarkers for diagnosing and predicting its toxicity. Identifying toxicological biomarkers reflecting TCM-induced toxicity is crucial for timely detection and intervention, and provides significant clues for elucidating the underlying toxic mechanism and key target.

AIM OF THE STUDY

This article aims to summarize and classify some potential toxicological biomarkers for side-effects induced by TCM and its contained phytochemical ingredients.

METHODS

The keywords "biomarkers", "traditional Chinese medicine", "Chinese herb", "phytochemical ingredient", "natural product", "toxicity", "hepatotoxicity", "nephrotoxicity", "cardiotoxicity" were used to collect relevant information from literature databases (including PubMed, Web of Science) up to October 2024.

RESULTS

Research has indicated that more sensitive and specific biomarkers are needed for reflecting TCM's side-effects. PA-protein adducts and AA-DNA adducts could be served as diagnostic biomarkers for hepatotoxicity and nephrotoxicity induced by TCM containing PA and AA, respectively. Multiple miRNAs like miRNA-122-3p, miRNA-5099, and miRNA-21-3p, as well as some endogenous metabolites such as hypoxanthine, choline, and L-valine could be potential biomarkers associated with TCM-induced hepatotoxicity, nephrotoxicity, and cardiotoxicity.

CONCLUSION

In this review, different research demonstrates that DNA/protein-adducts, noncoding RNAs, endogenous metabolites and so on show the potential to be new early-warning biomarkers for TCM-induced toxicity with high specificity and sensitivity.

Mechanisms of cancer cell death induction by triptolide: A comprehensive overview

The need for naturally occurring constituents is driven by the rise in the cancer prevalence and the unpleasant side effects associated with chemotherapeutics. Triptolide, the primary active component of "Tripterygium Wilfordii", has exploited for biological mechanisms and therapeutic potential against various tumors. Based on the recent pre-clinical investigations, triptolide is linked to the induction of death of cancerous cells by triggering cellular apoptosis via inhibiting heat shock protein expression (HSP70), and cyclin dependent kinase (CDKs) by up regulating expression of P21. MKP1, histone methyl transferases and RNA polymerases have all recently identified as potential targets of triptolide in cells. Autophagy, AKT signaling pathway and various pathways involving targeted proteins such as A-disintegrin & metalloprotease-10 (ADAM10), Polycystin-2 (PC-2), dCTP pyro-phosphatase 1 (DCTP1), peroxiredoxin-I (Prx-I), TAK1 binding protein (TAB1), kinase subunit (DNA-PKcs) and the xeroderma-pigmentosum B (XPB or ERCC3) have been exploited. Besides that, triptolide is responsible for enhancing the effectiveness of various chemotherapeutics. In addition, several triptolide moieties, including minnelide and LLDT8, have progressed in investigations on humans for the treatment of cancer. Targeted strategies, such as triptolide conjugation with ligands or triptolide loaded nano-carriers, are efficient techniques to confront toxicities associated with triptolide. We expect and anticipate that advances in near future, regarding combination therapies of triptolide, might be beneficial against cancerous cells.

Protective role of autophagy in triptolide-induced apoptosis of TM3 Leydig cells

Background and Objectives

Triptolide (TP) is known to impair testicular development and spermatogenesis in mammals, but the mechanism of the side effects still needs to be investigated. The aim of the research is to confirm whether TP can cause autophagy in TM3 Leydig cells and the potential molecular pathway in vitro.

Methods

TM3 Leydig cells are used to investigate the molecular pathway through Western blot, detection of apoptosis, transmission electron microscopy for autophagosomes and so on.

Results

The data show that TP treatment resulted in the decreasing of the viability of TM3 cells due to the increased apoptosis. Treated with TP, the formation of autophagosomes, the decrease in P62, and the increase in the conversion of LC3-I to LC3-II suggested the induction of autophagy. The induction of autophagy has accompanied the activation of the mTOR/P70S6K signal pathway. The viability of the TM3 cells was further inhibited when they were co-treated with autophagy inhibitor, chloroquine (CQ).

Conclusion

All these data suggest that autophagy plays a very important role in antagonizing TM3 cell apoptosis during the TP exposure.

Friend or foe? The dual role of triptolide in the liver, kidney, and heart

Triptolide, a controversial natural compound due to its significant pharmacological activities and multiorgan toxicity, has gained much attention since it was isolated from the traditional Chinese herb Tripterygium wilfordii Hook F. However, in addition to its severe toxicity, triptolide also presents powerful therapeutic potency in the same organs, such as the liver, kidney, and heart, which corresponds to the Chinese medicine theory of You Gu Wu Yun (anti-fire with fire) and deeply interested us. To determine the possible mechanisms involved in the dual role of triptolide, we reviewed related articles about the application of triptolide in both physiological and pathological conditions. Inflammation and oxidative stress are the two main ways triptolide exerts different roles, and the cross-talk between NF-κB and Nrf2 may be one of the mechanisms responsible for the dual role of triptolide and may represent the scientific connotation of You Gu Wu Yun. For the first time, we present a review of the dual role of triptolide in the same organ and propose the possible scientific connotation of the Chinese medicine theory of You Gu Wu Yun, hoping to promote the safe and efficient use of triptolide and other controversial medicines.

PGC-1α/NRF1-dependent cardiac mitochondrial biogenesis: A druggable pathway of calycosin against triptolide cardiotoxicity

Mitochondrion-related cardiotoxicity due to cardiotoxin stimuli is closely linked to abnormal activities of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), followed by co-inactivation of nuclear respiratory factor-1(NRF1). Pharmacological interventions targeting mitochondria may be effective for developing agents against cardiotoxicity. Herein, in triptolide-treated H9C2 cardiomyocytes, we observed defective mitochondrial biogenesis and respiration, characterized by depletion of mitochondrial mass and mitochondrial DNA copy number, downregulation of mitochondrial respiratory chain complexes subunits, and disorders of mitochondrial membrane potential and mitochondrial oxidative phosphorylation. Dysregulation of mitochondria led to cardiac pathological features, such as myocardial fiber fracture, intercellular space enlargement, and elevation of serum aspartate aminotransferase, creatine kinase isoenzyme, lactate dehydrogenase, and cardiac troponin I. However, following calycosin treatment, an active compound from Astragali Radix, the mitochondrion-related disorders at both cell and tissue levels were significantly ameliorated, which was facilitated by the activation of PGC-1α via deacetylation, followed by NRF1 co-activation. Calycosin-enhanced PGC-1α deacetylation is impelled by increasing sirtuin-1 expression and NAD⁺/NADH ratio. PGC-1α/NRF1 signaling in calycosin-mediated mitochondrial biogenesis protection was further confirmed by NRF1 knockdown and PGC-1α inhibition with SR18292. We conclude that calycosin ameliorated triptolide-induced cardiotoxicity by protecting PGC-1α/NRF1-dependent cardiac mitochondrial biogenesis and respiration, which is the druggable pathway for cardiotoxicity mitigation.

SLC7A11/GPX4 Inactivation-Mediated Ferroptosis Contributes to the Pathogenesis of Triptolide-Induced Cardiotoxicity

Triptolide exhibits promising efficacy in various cancers and immune diseases while its clinical application has been strongly restricted by its severe side effects, especially cardiotoxicity. However, the underlying mechanism of triptolide-induced cardiotoxicity (TIC) remains unclear. The RNA-seq analysis of triptolide-injured AC16 human cardiomyocyte cell line hinted that ferroptosis is involved in TIC. Further experimental validations proved that triptolide triggered ferroptosis, as evidenced by significant accumulation of lipid peroxidation (4-HNE and MDA levels) and ferrous iron, as well as depletion of intracellular GSH. Furthermore, triptolide-induced iron overload involved the upregulation of TF/TRFC/DMT1 signal axis and the degradation of ferritin, which contribute to ROS generation via Fenton reaction. In addition, inhibition of the antioxidant Nrf2/HO-1 pathway was observed in TIC, which may also lead to the overproduction of lethal lipid peroxides. Mechanistically, using streptavidin-biotin affinity pull-down assay and computational molecular docking, we unveiled that triptolide directly binds to SLC7A11 to inactivate SLC7A11/GPX4 signal axis. More importantly, employment of a ferroptosis inhibitor Ferrostatin-1 alleviated TIC by partially reversing the inhibitory effects of triptolide on SLC7A11/GPX4 signal. Altogether, our study demonstrated that SLC7A11/GPX4 inactivation-mediated ferroptosis contributed to the pathogenesis of TIC. Combating ferroptosis may be a promising therapeutic avenue to prevent TIC.

Protective Effect of XinJiaCongRongTuSiZiWan on the Reproductive Toxicity of Female Rats Induced by Triptolide

Background

Although triptolide (TP) has been widely used for the treatment of inflammatory, autoimmune diseases, and various kinds of tumors, the long experimental and clinical applications have exhibited severe reproductive system toxicity in TP-treated animals and patients. More importantly, the underlying molecular mechanism involved in TP-induced reproductive system toxicity still needs more research.

Methods

Adult female Sprague Dawley rats and human ovarian granulosa cell lines were treated with TP and then treated with XinJiaCongRongTuSiZiWan (XJCRTSZW). Histological analysis and follicle count were executed using H&E staining. Hormone (E2, AMH, FSH, LH, and INH B) concentrations, inflammation indicators (IL-1β, IL-6, and TNF-α), oxidative stress indicators (SOD, GSH-Px, and MDA), apoptosis rate, protein distribution and expression (SIRT1, AMPK, and 8-OhdG), cell viability, relative protein levels (beclin-1, LC3-II/LC3-I, p62, procaspase-3, cleaved caspase-3, p-SIRT1, SIRT1, p-AMPKα-1, AMPKα-1, Akt, and p-Akt), autophagosome were detected by ELISA, commercial biochemical detection kits, flow cytometry, immunohistochemistry, CCK-8, western blotting, and transmission electron microscope, respectively.

Results

XJCRTSZW administration notably improved the TP-treated pathological symptoms, including few mature follicles in the ovary and less granular cell layer, and disordered the arrangement of the follicle, lymphocytes and plasma cells infiltration, and necrosis, shedding, and follicular cystic dilatation of the granular layer follicle cells in the ovarian stroma. Furthermore, XJCRTSZW treatment observably enhanced the TP-induced reduction of primary follicles and secondary follicles numbers and decreased the TP-induced elevation of atretic follicle numbers and the expression of AMPK, SIRT1, and 8-OhdG in GCs in vivo. Moreover, XJCRTSZW application significantly increased the TP-induced diminishment of E2, AMH, and LNH-B concentrations, apoptosis rate, SOD and GSH-Px concentrations, and p62 protein level; however, it declined the TP-induced augmentation of MDA level, the levels of IL-1β, IL-6, and TNF-α, autophagosome, beclin-1, LC3-II/LC3-I, cleaved-caspase-3, p-AMPKα-1, and p-SIRT1 protein levels both in vivo and in vitro. Besides, XJCRTSZW treatment prominently enhanced the TP-induced decrease of cell viability in vitro.

Conclusion

XJCRTSZW can alleviate TP-induced reproductive toxicity via apoptosis, inflammation, and oxidative stress both in vivo and in vitro. Moreover, XJCRTSZW ameliorates TP-induced reproductive toxicity through AMPK/SIRT and Akt signaling axis mediated autophagy both in vivo and in vitro.

Therapeutic potential of triptolide in autoimmune diseases and strategies to reduce its toxicity

With the increasing epidemiology of autoimmune disease worldwide, there is an urgent need for effective drugs with low cost in clinical treatment. Triptolide, the most potent bioactive compound from traditional Chinese herb Tripterygium Wilfordii Hook F, possesses immunosuppression and anti-inflammatory activity. It is a potential drug for the treatment of various autoimmune diseases, but its clinical application is still restricted due to severe toxicity. In this review, the pharmacodynamic effects and pharmacological mechanisms of triptolide in autoimmune diseases are summarized. Triptolide exerts therapeutic effect by regulating the function of immune cells and the expression of cytokines through inflammatory signaling pathways, as well as maintaining redox balance and gut microbiota homeostasis. Meanwhile, the research progress on toxicity of triptolide to liver, kidney, reproductive system, heart, spleen, lung and gastrointestinal tract has been systematically reviewed. In vivo experiments on different animals and clinical trials demonstrate the dose- and time- dependent toxicity of triptolide through different administration routes. Furthermore, we focus on the strategies to reduce toxicity of triptolide, including chemical structural modification, novel drug delivery systems, and combination pharmacotherapy. This review aims to reveal the potential therapeutic prospect and limitations of triptolide in treating autoimmune diseases, thus providing guiding suggestions for further study and promoting its clinical translation.

Risk Compounds, Preclinical Toxicity Evaluation, and Potential Mechanisms of Chinese Materia Medica-Induced Cardiotoxicity

Chinese materia medica (CMM) has been applied for the prevention and treatment of diseases for thousands of years. However, arrhythmia, myocardial ischemia, heart failure, and other cardiac adverse reactions during CMM application were gradually reported. CMM-induced cardiotoxicity has aroused widespread attention. Our review aimed to summarize the risk compounds, preclinical toxicity evaluation, and potential mechanisms of CMM-induced cardiotoxicity. All relevant articles published on the PubMed, Embase, and China National Knowledge Infrastructure (CNKI) databases for the latest twenty years were searched and manually extracted. The risk substances of CMM-induced cardiotoxicity are relatively complex. A single CMM usually contains various risk compounds, and the same risk substance may exist in various CMM. The active and risk substances in CMM may be transformed into each other under different conditions, such as drug dosage, medication methods, and body status. Generally, the risk compounds of CMM-induced cardiotoxicity can be classified into alkaloids, terpenoids, steroids, heavy metals, organic acids, toxic proteins, and peptides. Traditional evaluation methods of chemical drug-induced cardiotoxicity primarily include cardiac function monitoring, endomyocardial biopsy, myocardial zymogram, and biomarker determination. In the preclinical stage, CMM-induced cardiotoxicity should be systematically evaluated at the overall, tissue, cellular, and molecular levels, including cardiac function, histopathology, cytology, myocardial zymogram, and biomarkers. Thanks to the development of systematic biology, the higher specificity and sensitivity of biomarkers, such as genes, proteins, and metabolic small molecules, are gradually applied for evaluating CMM-induced cardiotoxicity. Previous studies on the mechanisms of CMM-induced cardiotoxicity focused on a single drug, monomer or components of CMM. The interaction among ion homeostasis (sodium, potassium, and calcium ions), oxidative damage, mitochondrial injury, apoptosis and autophagy, and metabolic disturbance is involved in CMM-induced cardiotoxicity. Clarification on the risk compounds, preclinical toxicity evaluation, and potential mechanisms of CMM-induced cardiotoxicity must be beneficial to guide new CMM development and post-marketed CMM reevaluation.

The Potential of Hydrogen Sulfide Donors in Treating Cardiovascular Diseases

Hydrogen sulfide (H2S) has long been considered as a toxic gas, but as research progressed, the idea has been updated and it has now been shown to have potent protective effects at reasonable concentrations. H2S is an endogenous gas signaling molecule in mammals and is produced by specific enzymes in different cell types. An increasing number of studies indicate that H2S plays an important role in cardiovascular homeostasis, and in most cases, H2S has been reported to be downregulated in cardiovascular diseases (CVDs). Similarly, in preclinical studies, H2S has been shown to prevent CVDs and improve heart function after heart failure. Recently, many H2S donors have been synthesized and tested in cellular and animal models. Moreover, numerous molecular mechanisms have been proposed to demonstrate the effects of these donors. In this review, we will provide an update on the role of H2S in cardiovascular activities and its involvement in pathological states, with a special focus on the roles of exogenous H2S in cardiac protection.

Hexavalent chromium induces renal apoptosis and autophagy via disordering the balance of mitochondrial dynamics in rats

The use of hexavalent chromium (Cr(VI)) in many industrial processes has resulted in serious environmental pollution problems. Cr(VI) causes organ toxicity in animals after ingestion or inhalation. However, the exact mechanism by which Cr(VI) produces kidney damage remains elusive. Herein, we investigated whether Cr(VI)-induced kidney damage is related to the disorder of mitochondrial dynamics. In this study, 28 male rats were divided into four groups and intraperitoneally injected with 0, 2, 4, and 6 mg/kg body weight potassium dichromate for 5 weeks. Experiment included analysis of renal histopathology and ultrastructure, determination of biochemical indicators, and measurement of related protein content. The results showed that Cr(VI) induced kidney injury through promotion of oxidative stress, apoptosis, and disorder of mitochondrial dynamics in a dose-dependent manner. The protein levels of the silent information regulator two ortholog 1 (Sirt1), peroxisome proliferation-activated receptor-g coactivator-1a (PGC-1a), and autophagy-related proteins were significantly decreased after Cr(VI) exposure. These findings suggest that Cr(VI) leads to the disorder of mitochondrial dynamics by inhibiting the Sirt1/PGC-1a pathway, which leads to renal apoptosis and autophagy in rats.

Morroniside Inhibits H2O2-Induced Podocyte Apoptosis by Down-Regulating NOX4 Expression Controlled by Autophagy In Vitro

Podocyte apoptosis is the common pathological basis for the progression of various kidney diseases. The overexpression of NOX4, a key enzyme involved in oxidative stress, has been proved to participate in the occurrence of podocyte apoptosis. Autophagy is a kind of adaptive response of cells under stress. However, as a “double-edged sword”, the effect of autophagy on apoptosis in different cells and conditions is complex and variable, which has not been fully explained yet. Morroniside, extracted from the traditional medicinal plant Cornus officinalis, has remarkable antioxidant and anti-apoptosis effects, and has been proven to inhibit the overexpression of NOX4 in kidney tissue. Therefore, H₂O₂ was used in this study to explore the effects of autophagy on podocyte NOX4 overexpression and apoptosis induced by oxidative stress, as well as the protection mechanism of morroniside in podocytes. The results showed that the autophagy activator rapamycin, as well as the autophagy inhibitor chloroquine, could induce podocyte apoptosis cultured in normal condition, and chloroquine could also significantly increase the NOX4 expression. The NOX4 expression and apoptosis rate of podocytes increased after H₂O₂ treatment, the expression of LC3-II decreased, and the expressions of p62, mTOR, and p-mTOR increased. The intervention of morroniside and rapamycin improved autophagy activity and inhibited NOX4 overexpression and apoptosis induced by H₂O₂. And chloroquine reversed the inhibitory effect of morroniside on NOX4 overexpression and podocyte apoptosis. Taken together, our results suggest that the expression level of NOX4 in podocytes is regulated by autophagy activity. Morroniside can reduce oxidative stress induced podocyte apoptosis by restoring the damaged autophagy flux and inhibit the overexpression of NOX4.

Role of Mitochondria in Cancer Stem Cell Resistance

Cancer stem cells (CSC) are associated with the mechanisms of chemoresistance to different cytotoxic drugs or radiotherapy, as well as with tumor relapse and a poor prognosis. Various studies have shown that mitochondria play a central role in these processes because of the ability of this organelle to modify cell metabolism, allowing survival and avoiding apoptosis clearance of cancer cells. Thus, the whole mitochondrial cycle, from its biogenesis to its death, either by mitophagy or by apoptosis, can be targeted by different drugs to reduce mitochondrial fitness, allowing for a restored or increased sensitivity to chemotherapeutic drugs. Once mitochondrial misbalance is induced by a specific drug in any of the processes of mitochondrial metabolism, two elements are commonly boosted: an increment in reactive nitrogen/oxygen species and, subsequently, activation of the intrinsic apoptotic pathway.

Autophagy in Triptolide-Mediated Cytotoxicity in Hepatic Cells

Triptolide is a major active ingredient isolated from the traditional Chinese herb Tripterygium wilfordii Hook F. However, its use in clinical practice is limited due to its severe hepatotoxicity. Autophagy, a highly conserved intracellular process, is essential for maintaining cytoplasmic homeostasis. Considering that abnormalities in autophagy are closely associated with drug-mediated hepatotoxicity, we applied human normal liver HL7702 cells to elucidate the roles of autophagy in triptolide-induced hepatotoxicity. Our study revealed that triptolide was cytotoxic to HL7702 cells. It markedly increased autophagosome formation and expression of autophagy-related proteins, namely Beclin1 and microtubule-associated protein 1 light chain 3II, and induced oxidative stress. These proautophagic effects were counteracted by pretreatment with N-acetylcysteine, a reactive oxygen species scavenger. Moreover, the pharmacological suppression of autophagy further exacerbated triptolide-elicited decrease in cell viability, increase in lactate dehydrogenase leakage, and activation of apoptosis proteases (caspase 3 and caspase 9). Our findings suggest that triptolide-induced oxidative stress consequently enhances autophagic activity, and autophagy is a cytoprotective mechanism against triptolide-induced cytotoxicity in HL7702 cells.

Triptolide induces toxicity in inner ear stem cells via promoting DNA damage

Emerging evidence and clinical case reports have observed a risk of cytotoxic effects of triptolide in patients. We aimed to investigate the triptolide-induced toxicity in mouse inner ear stem cells. The utricular sensory epithelium from adult BALB/C6 mice was used for the isolation of inner ear stem cells. Sphere formation assay was applied to examine the stemness of the cells. Cell count kit-8 and Bromodeoxyuridine assays were employed to detect the cell proliferation ability. Cell apoptosis was measured with Annexin V-FITC & propidium iodide Apoptosis kit. The relative expression levels of gamma H2A histone family member X (γH2AX), tumor suppressor p53-binding protein 1 (53BP1) and optic atrophy 1 (OPA-1) were measured by Western Blot. Mitochondrial function was analyzed by the MitoGreen green-fluorescent mitochondrial dye kit. Triptolide significantly inhibited the cell viability and proliferation and suppressed the capability of sphere formation. Furthermore, triptolide induced apoptosis as indicated by increased expression of DNA damage repair markers γH2AX and 53BP1. Moreover, triptolide influenced the function of mitochondria by inducing the cleavage of OPA-1. Our work clarifies the toxicity of triptolide in mouse inner ear stem cells, which provides clues of the toxicology mechanism for future studies and basis for clinical use.

Autophagy in Human Health and Disease: Novel Therapeutic Opportunities

SIGNIFICANCE

In eukaryotes, autophagy represents a highly evolutionary conserved process, through which macromolecules and cytoplasmic material are degraded into lysosomes and recycled for biosynthetic or energetic purposes. Dysfunction of the autophagic process has been associated with the onset and development of many human chronic pathologies, such as cardiovascular, metabolic, and neurodegenerative diseases as well as cancer. Recent Advances: Currently, comprehensive research is being carried out to discover new therapeutic agents that are able to modulate the autophagic process in vivo. Recent evidence has shown that a large number of natural bioactive compounds are involved in the regulation of autophagy by modulating several transcriptional factors and signaling pathways.

CRITICAL ISSUES

Critical issues that deserve particular attention are the inadequate understanding of the complex role of autophagy in disease pathogenesis, the limited availability of therapeutic drugs, and the lack of clinical trials. In this context, the effects that natural bioactive compounds exert on autophagic modulation should be clearly highlighted, since they depend on the type and stage of the pathological conditions of diseases.

FUTURE DIRECTIONS

Research efforts should now focus on understanding the survival-supporting and death-promoting roles of autophagy, how natural compounds interact exactly with the autophagic targets so as to induce or inhibit autophagy and on the evaluation of their pharmacological effects in a more in-depth and mechanistic way. In addition, clinical studies on autophagy-inducing natural products are strongly encouraged, also to highlight some fundamental aspects, such as the dose, the duration, and the possible synergistic action of these compounds with conventional therapy.

MicroRNA expression, targeting, release dynamics and early-warning biomarkers in acute cardiotoxicity induced by triptolide in rats

Tripterygium wilfordii Hook. F. is a plant used in traditional Chinese medicine to treat rheumatoid arthritis, lupus erythematosus, and psoriasis in China. However, its main active substance, triptolide, has toxic effects on the heart, liver, and kidneys, which limit its clinical application. Therefore, determining the mechanism of cardiotoxicity in triptolide and identifying effective early-warning biomarkers is beneficial for preventing irreversible myocardial injury. We observed changes in microRNAs and aryl hydrocarbon receptor (AhR) as potential biomarkers in triptolide-induced acute cardiotoxicity by using techniques such as polymerase chain reaction (PCR) assay. The results revealed that triptolide increased the heart/body ratio and caused myocardial fiber breakage, cardiomyocyte hypertrophy, increased cell gaps, and nuclear dissolution in treated male rats. Real-time PCR array detection revealed a more than 2-fold increase in the expression of 108 microRNA genes in the hearts of the male rats; this not only regulated the signaling pathways of ErbB, FOXO, AMPK, Hippo, HIF-1α, mTOR, and PI3K-Akt but also participated in biological processes such as cell adhesion, cell cycling, action potential, locomotory behavior, apoptosis, and DNA binding. Moreover, triptolide reduced the circulatory and cardiac levels of AhR protein as a target of these microRNAs and the messenger RNA expression of its downstream gene CYP1 A1. However, decreases in myocardial lactate dehydrogenase, creatine kinase MB, catalase, and glutathione peroxidase activity and an increase in circulating cardiac troponin I were observed only in male rats. Moreover, plasma microRNAs exhibited dynamic change. These results revealed that circulating microRNAs and AhR protein are potentially early-warning biomarkers for triptolide-induced cardiotoxicity.

Triptolide impairs thioredoxin system by suppressing Notch1-mediated PTEN/Akt/Txnip signaling in hepatocytes

Triptolide (TP) is the main ingredient of Chinese herb Tripterygium wilfordii Hook f. (TWHF). Despite of its multifunction in pharmaceutics, accumulating evidences showed that TP caused obvious hepatotoxicity in clinic. The current study investigated the role of Notch1 signaling in TP-induced hepatotoxicity. Our data indicated that TP inhibited the protein expression of Notch1 and its active form Notch intracellular domain (NICD) leading to increased PTEN (phosphatase and tensin homolog deleted on chromosome ten) expression. Moreover, PTEN triggered Txnip (thioredoxin-interacting protein) activation by inhibiting Akt phosphorylation, which resulted in reduction of Trx (thioredoxin). In conclusion, TP caused liver injury through initiating oxidative stress in hepatocyte. This study indicated the potency of Notch1 to protect against TP-induced hepatotoxicity.

Ochratoxin A induces cytoprotective autophagy via blocking AKT/mTOR signaling pathway in PK-15 cells

Ochratoxin A (OTA) could cause a variety of toxicological effects especially nephrotoxicity in animals and humans. Autophagy is a highly conserved metabolic process that plays an important role in the maintenance of cellular homeostasis under stress. However, the role of autophagy in OTA-induced nephrotoxicity is unknown. In the present study, we demonstrated that OTA treatment at 2.0-8.0 μM could increase cytotoxicity of PK-15 cells by inducing apoptosis as shown by the increased Annexin V/PI staining, increased caspase-3 and PARP cleavage and increased apoptotic nuclei. Meantime, autophagy was triggered when OTA was administrated, as indicated by markedly increased expressions of LC3-II, ATG5 and Beclin-1, accumulation of GFP-LC3 dots and increased double- or single-membrane vesicles. OTA treatment decreased p-AKT and p-mTOR activities, and OTA-induced autophagy was inhibited when insulin was applied. Furthermore, OTA treatments with autophagy inhibitors (3-methyladenine or chloroquine) or knockdown of autophagy-related genes (ATG5 or Beclin-1) resulted in significantly reduced autophagy level and enhanced cytotoxicity. In conclusion, OTA induces cytoprotective autophagy against its cytotoxicity and inactivation of AKT/mTOR axis plays a critical role in autophagy induction.

Triptolide, A Potential Autophagy Modulator

As a major active component extracted from traditional Chinese herb Tripterygium wilfordii Hook F, triptolide exhibits multiple pharmacological effects. Autophagy is an evolutionary conserved intracellular catabolic process involved in cytoplasmic materials degradation. Autophagic dysfunction contributes to the pathologies of many human diseases, which makes it a promising therapeutic target. Recent studies have shown that triptolide exerts neuroprotection, anti-tumor activities, organ toxicity, and podocyte protection by modulating autophagy. This article highlights the current information on triptolide-modulated autophagy, analyzes the possible pathways involved, and describes the crosstalk between autophagy and apoptosis modulated by triptolide, in hope of providing implications for the roles of autophagy in pharmacological effects of triptolide and expanding its novel usage as an autophagy modulator.

Synthesis, Characterization, and Evaluation of Triptolide Cell-Penetrating Peptide Derivative for Transdermal Delivery of Triptolide

Triptolide (TP) has been used as one of the most common systemic treatments for various diseases since the 1960s. However, TP displays diverse side effects on various organs, which limits its clinical application. To overcome this issue, numerous C-14-hydroxyl group derivatives of TP have been synthesized. In this research, the C-14-hydroxyl group of TP is modified by a cell-penetrating peptide polyarginine (R₇). The derivative TP-disulfide-CR₇ (TP-S-S-CR₇) containing a disulfide linkage between TP and R₇ possesses less toxicity at various concentrations on the immortal human keratinocyte (HaCaT) cell line by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay compared with free TP. Treating HaCaT cells with TP (100 nM) could increase intracellular ROS (reactive oxygen species) and decrease the activity of SOD (superoxide dismutase). Meanwhile, treating HaCaT cells with equimolar concentration of TP-S-S-CR₇ did not cause both of the above TP-induced alterations. In addition, TP-S-S-CR₇ did not show significant dermal toxicity on guinea pigs and could efficiently overcome the barrier of corneum and then reach epidermis and dermis within 2 h of transdermal administration. In addition, there was a relatively lower concentration of TP in blood indicating less toxicity on organs. Such results suggest that topical therapy using polyarginine is possible by the transdermal delivery of TP.

WITHDRAWN: Toxicity of triptolide and the molecular mechanisms involved

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Tris (1, 3-dichloro-2-propyl) phosphate induces apoptosis and autophagy in SH-SY5Y cells: Involvement of ROS-mediated AMPK/mTOR/ULK1 pathways

Tris (1, 3-dichloro-2-propyl) phosphate (TDCIPP), an extensively used organophosphorus flame retardant, is frequently detected in the environment and biota. Recent studies have shown that TDCIPP has neurotoxic effects. We hypothesized that the neurotoxicity might occur via the induction of the apoptosis and autophagy pathways. In the present study, we investigated TDCIPP-induced apoptotic death and autophagy in SH-SY5Y cells. Treatment with TDCIPP induced increased reactive oxygen species (ROS) generation and cell apoptosis, as well as autophagy. The autophagy inhibitor 3-methyladenine (3-MA) markedly decreased the expression of the autophagy marker beclin-1, microtubule-associated protein light chain 3-II (LC3II), p62/sequestosome 1 (SQSTM1) degradation, and promoted apoptosis. Conversely, the autophagy inducer rapamycin (Rapa) alleviated TDCIPP-induced apoptosis and markedly increased the expression of the autophagy markers. Pretreatment with N-acetyl cysteine (NAC) eliminated the increased ROS generation, resulting in increased cell viability. For further examination of the signaling pathways involved in TDCIPP-induced autophagy, compound C, a pharmacological inhibitor of adenosine monophosphate activated protein kinase (AMPK) was used. Western blotting showed that compound C markedly reduced the expression of phospho-AMPK (p-AMPK) and phospho-Unc-51-like kinase 1 (p-ULK1), increased phospho-mammalian target of rapamycin (p-mTOR) expression, and decreased beclin-1 and LC3II expression. These results suggested that the AMPK/mTOR/ULK1 signaling pathway was involved in TDCIPP-induced autophagy. The antioxidant NAC antagonized TDCIPP-induced activation of AMPK and autophagy. Taken together, our findings provide the first evidence that TDCIPP promotes apoptosis and autophagy simultaneously and that this process involves the ROS-mediated AMPK/mTOR/ULK1 pathways. Lastly, the induction of autophagy is a protective mechanism against TDCIPP-induced apoptosis.

EFFECT OF TRIPTOLIDE ON PROLIFERATION AND APOPTOSIS OF ANGIOTENSIN II-INDUCED CARDIAC FIBROBLASTS IN VITRO: A PRELIMINARY STUDY

BACKGROUND

The effect of triptolide (TPL) on cardiac fibroblasts (CFbs) and cardiac fibrosis remain unknown till now. This study was conducted to explore the effects of TPL on proliferation and apoptosis of angiotensin II (Ang II)-induced CFbs.

MATERIALS AND METHODS

Ang II was used to promote proliferation of CFbs. Two dosages of TPL (10ng/ml and 100ng/ml) were chosen. MTT assay was used to detect cell survival rate in vitro. Flow cytometer was performed to analyze apoptosis of CFbs. Hydroxyproline concentration was detected with hydroxyproline assay kit. Quantitative real-time PCR was used to detect the expression of TGF-β1 and Smad3 mRNA.

RESULTS

Ang II promoted CFbs proliferation significantly. Compared to Ang II group, TPL markedly reduced the viability of CFbs and its Hydroxyproline concentration (P<0.05). Besides, TPL can significantly promote apoptosis of CFbs (P<0.05). Furthermore, TPL reduced the expressions of TGF-βΙ and Smad3 mRNA in Ang II-induced CFbs (P<0.05).

CONCLUSION

TPL can inhibit the proliferation of CFbs in rats by down-regulating TGF-β1/Smad3 signaling pathway. TPL might be a promising therapeutic drug for myocardial fibrosis.

Inhibition of glycogen synthase kinase 3beta ameliorates triptolide-induced acute cardiac injury by desensitizing mitochondrial permeability transition

Triptolide (TP), a diterpene triepoxide, is a major active component of Tripterygium wilfordii extracts, which are prepared as tablets and has been used clinically for the treatment of inflammation and autoimmune disorders. However, TP's therapeutic potential is limited by severe adverse effects. In a previous study, we reported that TP induced mitochondria dependent apoptosis in cardiomyocytes. Glycogen synthase kinase-3β (GSK-3β) is a multifunctional serine/threonine kinase that plays important roles in the necrosis and apoptosis of cardiomyocytes. Our study aimed to investigate the role of GSK-3β in TP-induced cardiotoxicity. Inhibition of GSK-3β activity by SB 216763, a potent and selective GSK-3 inhibitor, prominently ameliorated the detrimental effects in C57BL/6J mice with TP administration, which was associated with a correction of GSK-3β overactivity. Consistently, in TP-treated H9c2 cells, SB 216763 treatment counteracted GSK-3β overactivity, improved cell viability, and prevented apoptosis by modulating the expression of Bcl-2 family proteins. Mechanistically, GSK-3β interacted with and phosphorylated cyclophilin F (Cyp-F), a key regulator of mitochondrial permeability transition pore (mPTP). GSK-3β inhibition prevented the phosphorylation and activation of Cyp-F, and desensitized mPTP. Our findings suggest that pharmacological targeting of GSK-3β could represent a promising therapeutic strategy for protecting against cardiotoxicity induced by TP.

Triptolide induces protective autophagy through activation of the CaMKKβ-AMPK signaling pathway in prostate cancer cells

Triptolide, an active compound extracted from the Chinese herb thunder god vine (Tripterygium wilfordii Hook F.), has potent anti-tumor activity. Recently, triptolide was found to induce autophagy in cancer cells. However, the effects of triptolide on autophagy in human prostate cancer (PCa) cells have not yet been clearly elucidated. In this study, we demonstrated that triptolide induces autophagy in three PCa cell lines, PC-3, LNCaP and C4-2. Furthermore, we found that triptolide mediates intracellular accumulation of free calcium by stimulating the endoplasmic reticulum (ER) stress response. This activates the CaMKKβ-AMPK signaling pathway, which in turn inhibits mTOR and activates both ULK1 and Beclin 1, finally resulting in autophagy. Moreover, we found that treatment with autophagy inhibitors 3-methyladenine (3-MA) and chloroquine (CQ) enhances triptolide-induced PCa cell death and growth inhibition. Using a PC-3-xenografted mouse model, we showed that blocking autophagy with CQ significantly promoted triptolide-induced tumor growth inhibition in vivo. Overall, our results show that triptolide induces protective autophagy through the CaMKKβ-AMPK pathway in PCa cells, implying that a combination of triptolide with autophagy inhibitors may potentially be an effective therapeutic strategy for PCa.

Bypassing Mechanisms of Mitochondria-Mediated Cancer Stem Cells Resistance to Chemo- and Radiotherapy

Cancer stem cells (CSCs) are highly resistant to conventional chemo- and radiotherapeutic regimes. Therefore, the multiple drug resistance (MDR) of cancer is most likely due to the resistance of CSCs. Such resistance can be attributed to some bypassing pathways including detoxification mechanisms of reactive oxygen and nitrogen species (RO/NS) formation or enhanced autophagy. Unlike in normal cells, where RO/NS concentration is maintained at certain threshold required for signal transduction or immune response mechanisms, CSCs may develop alternative pathways to diminish RO/NS levels leading to cancer survival. In this minireview, we will focus on elaborated mechanisms developed by CSCs to attenuate high RO/NS levels. Gaining a better insight into the mechanisms of stem cell resistance to chemo- or radiotherapy may lead to new therapeutic targets thus serving for better anticancer strategies.

Triptolide disrupts fatty acids and peroxisome proliferator-activated receptor (PPAR) levels in male mice testes followed by testicular injury: A GC-MS based metabolomics study

Triptolide is the major active ingredient of Tripterygium Glycosides (TG), a traditional Chinese medicine with very potent anti-inflammatory effects and has been used in China for the treatment of rheumatoid arthritis and many other inflammatory diseases. However, clinical application of triptolide is restricted due to its multiple side effects, especially male infertility. The mechanism of triptolide on reproduction toxicity remains unclear. In the present study, a GC-MS based metabolomic approach was employed to evaluate the mechanism of triptolide-induced reproductive toxicity as well as identify potential novel biomarkers for the early detection of spermatogenesis dysfunction. In brief, male mice were divided into two groups with or without triptolide intraperitoneal injection at 60 μg/kg/day for 2 weeks and toxic effect of triptolide on testicular tissues were examined by biochemical indicator analysis, testis histopathologic analysis, and sperm quantity analysis. Metabolomics technology was then performed to evaluate systematically the endogenous metabolites profiling. Our results demonstrated that triptolide suppressed the marker-enzymes of spermatogenesis and testosterone levels, decreased sperm counts, reduced the gonad index and destroyed the microstructure of testis. Multivariate data analysis revealed that mice with triptolide induced testicular toxicity could be distinctively differentiated from normal animals and 35 and 39 small molecule metabolites were changed significantly in testis and serum, respectively (Fold-changes >1.5, P<0.05), in triptolide-treated mice. Abnormal level of fatty acids, an important energy source of sertoli cells with critical role in maintaining normal function of the testis tissue, was observed in triptolide-treated mice. Additionally, the protein expressions of PPAR, a transcription factor known to play a pivotal role in lipid and energy metabolism was significantly decreased in the testis tissue of triptolide-treated mice. In summary, our study represents the first comprehensive GC-MS based metabolomics analysis of triptolide-induced testicular toxicity. We reported for the first time that exposure to triptolide led to marked changes of a panel of endogenous metabolites in both testis and serum. The impairment of spermatogenesis may be caused by abnormal lipid and energy metabolism in testis via the down-regulation of PPARs mediated by triptolide. The presence of research suggested that PPARs and its related fatty acids metabolism may serve as potential targets for intervention or treatment of male infertility induced by triptolide.