8-Methoxypsoralen disrupts MDR3-mediated phospholipids efflux and bile acid homeostasis and its relevance to hepatotoxicity

Cnidii Fructus: A traditional Chinese medicine herb and source of antiosteoporotic drugs

BACKGROUND

Osteoporosis (OP) is a prevalent chronic metabolic bone disease for which limited countermeasures are available. Cnidii Fructus (CF), primarily derived from Cnidium monnieri (L.) Cusson., has been tested in clinical trials of traditional Chinese medicine for the management of OP. Accumulating preclinical studies indicate that CF may be used against OP.

MATERIALS AND METHODS

Comprehensive documentation and analysis were conducted to retrieve CF studies related to its main phytochemical components as well as its pharmacokinetics, safety and pharmacological properties. We also retrieved information on the mode of action of CF and, in particular, preclinical and clinical studies related to bone remodeling. This search was performed from the inception of databases up to the end of 2022 and included PubMed, China National Knowledge Infrastructure, the National Science and Technology Library, the China Science and Technology Journal Database, Weipu, Wanfang, the Web of Science and the China National Patent Database.

RESULTS

CF contains a wide range of natural active compounds, including osthole, bergapten, imperatorin and xanthotoxin, which may underlie its beneficial effects on improving bone metabolism and quality. CF action appears to be mediated via multiple processes, including the osteoprotegerin (OPG)/receptor activator of nuclear factor-κB ligand (RANKL)/receptor activator of nuclear factor-κB (RANK), Wnt/β-catenin and bone morphogenetic protein (BMP)/Smad signaling pathways.

CONCLUSION

CF and its ingredients may provide novel compounds for developing anti-OP drugs.

8-methoxypsoralen protects against acetaminophen-induced liver injury by antagonising Cyp2e1 in mice

This study aimed to investigate the effect and mechanism of 8-methoxypsoralen (8-MOP) on acetaminophen (APAP)-induced hepatotoxicity in mice. The study found that one hour after intraperitoneal injection of 300 mg/kg APAP, treatment with 40 mg/kg,80 mg/kg and 120 mg/kg 8-MOP could reduce serum transaminase level and histopathological liver necrosis area. Elevated mRNA expression of liver inflammatory mediators caused by excessive APAP was also reversed. 8-MOP significantly reduced APAP-induced hepatotoxicity dose-dependently, and the highest therapeutic dose of 8-MOP (120 mg/kg) had no harmful effects on the liver. Cocktail probe assay revealed that 8-MOP can inhibit Cyp2e1 enzymatic activities of mice, thereby reducing the production of acetaminophen-cysteine (APAP-CYS), a toxic metabolite of APAP. 8-MOP had no significant effect on the protein and gene expression of Cyp2e1. The three-dimensional structures of mouse Cyp2e1 were constructed by homologous modeling. Molecular docking showed that 8-MOP had a good binding effect on the enzyme activity site of Cyp2e1. In summary, 8-MOP dose-dependently attenuated APAP-induced hepatotoxicity by binding to Cyp2e1 and occupying the active center of the enzyme, thus competitively inhibiting the oxidative metabolism of APAP, and reducing the generation of toxic product APAP-CYS.

Psoralea corylifolia L.: a comprehensive review of its botany, traditional uses, phytochemistry, pharmacology, toxicology, quality control and pharmacokinetics

Psoralea corylifolia L. (PCL), referred to as "Bu-gu-zhi" in Chinese, has great medicinal values since ancient times. PCL is the dried ripe fruit of Psoralea corylifolia L., which has been widely used in traditional Chinese medicine (TCM) for the treatment of kidney-yang deficiency, enuresis and urinary frequency, chills and pain of the waist and knees, dawn diarrhea and vitiligo. In this paper, a systematic of the botany, traditional uses, phytochemistry, pharmacology, toxicology, quality control and pharmacokinetics of PCL was presented, along with future research directions. According to the results, PCL contains approximately 163 chemical components, including coumarins, flavonoids, monoterpene phenols, benzofurans, glycosides, lipids, fatty acids, and volatile oils. PCL and its active ingredients have a variety of pharmacological activities, such as anti-inflammatory, antibacterial, antiviral, antioxidant, antitumor, antiosteoporosis, cardioprotective, neuroprotective, and immunomodulatory. Further study of quality control standards and potential mechanisms of PCL is also needed. In addition, more toxicological studies will also contribute to the progress of clinical trials.

Xanthotoxin (8-methoxypsoralen): A review of its chemistry, pharmacology, pharmacokinetics, and toxicity

Xanthotoxin (XAT) is a natural furanocoumarins, a bioactive psoralen isolated from the fruit of the Rutaceae plant Pepper, which has received increasing attention in recent years due to its wide source and low cost. By collecting and compiling literature on XAT, the results show that XAT exhibits significant activity in the treatment of various diseases, including neuroprotection, skin repair, osteoprotection, organ protection, anticancer, antiinflammatory, antioxidative stress and antibacterial. In this paper, we review the pharmacological activity and potential molecular mechanisms of XAT for the treatment of related diseases. The data suggest that XAT can mechanistically induce ROS production and promote apoptosis through mitochondrial or endoplasmic reticulum pathways, regulate NF-κB, MAPK, JAK/STAT, Nrf2/HO-1, MAPK, AKT/mTOR, and ERK1/2 signaling pathways to exert pharmacological effects. In addition, the pharmacokinetics properties and toxicity of XAT are discussed in this paper, further elucidating the relationship between structure and efficacy. It is worth noting that data from clinical studies of XAT are still scarce, limiting the use of XAT in the clinic, and in the future, more in-depth studies are needed to determine the clinical efficacy of XAT.

Transcriptomics and metabolomics analyses provide insights into the difference in toxicity of benzo[a]pyrene and 6-chlorobenzo[a]pyrene to human hepatic cells

The toxicological information of chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs), as derivatives of PAHs, is still relatively lacking. In this study, a combination of transcriptomics and metabolomics approach was adopted to explore the changes in toxicity to human L02 hepatocytes after chlorination of benzo[a]pyrene (B[a]P) at 6 position. In general, 6-Cl-B[a]P produced a stronger toxicity to human hepatic cells than did parent B[a]P. When exposure concentrations were 5 and 50 nM, 6-Cl-B[a]P caused a weaker transcriptomic perturbation relative to B[a]P, whereas a stronger metabolomic perturbation, a stronger oxidative stress and a stronger inhibition effect on cell viability were caused by 6-Cl-B[a]P than did parent B[a]P. Pathway enrichment analysis indicated that 6-Cl-B[a]P produced a more widely perturbation to metabolic pathways than did B[a]P. Although they both significantly impaired the function of mitochondrial electron transport chain (ETC), the exact mechanism is different. B[a]P suppressed the expression of 20 genes regulating mitochondrial ETC mainly via AhR activation. However, 6-Cl-B[a]P produced a stronger inhibition on the activities of complexes I and V than did B[a]P. Meanwhile, 6-Cl-B[a]P also exhibited a stronger inhibition effect on mitochondrial β oxidation of fatty acid. Furthermore, 6-Cl-B[a]P and B[a]P both significantly disturbed the nucleotide metabolism, glycerophospholipid metabolism and amino acid metabolism in L02 cells.

Bergapten: A review of its pharmacology, pharmacokinetics, and toxicity

Bergapten is a natural furocoumarin, also known as 5-methoxypsoralen, and its medicinal value has been paid more and more attention. By sorting out the pharmacological literature of bergapten, we found that bergapten has a wide range of pharmacological effects, including neuroprotection, organ protection, anticancer, antiinflammatory, antimicrobial, and antidiabetes effects. However，bergapten has complex impacts on the hepatic metabolic enzyme. Moreover, pharmacokinetic studies showed that bergapten has higher absolute bioavailability and can cross the blood-brain barrier and has a great potential for treating brain disease, but the mechanism needs further clarification to make greater use of its ability to treat brain diseases. Furthermore, the phototoxicity of bergapten combined with ultraviolet light has always been mentioned. In view of its wide range of pharmacological activities, bergapten is expected to be a potential drug candidate for the treatment of diabetes and diabetes-induced osteoporosis, epilepsy, Alzheimer's disease, depression, and cancer. However, further studies are needed to elucidate its molecular mechanisms and targets. The phototoxicity of bergapten as a side effect should be further avoided. On the other hand, the photoactivation of bergapten in the anticancer aspect can be better utilized.

Differences in xanthotoxin metabolites in seven mammalian liver microsomes

Xanthotoxin, abundantly occurring in fruits, vegetables, grapefruit juice and oils, is widely used in medicine for the treatment of psoriasis and vitiligo. Xanthotoxin possesses the ability to inhibit mechanism-based cytochrome P450 (CYP450)-mediated activities in rats and mice. Furthermore, it time-dependently obstructs a number of CYP450-mediated functions in humans. CYP450 enzymes are most abundant in the liver and induce metabolic activation of numerous xenobiotic compounds. The present study aimed to identify the similarities and differences in xanthotoxin metabolism in liver microsomes of 7 mammalian species, including human liver microsomes (HLM), Rhesus monkey liver microsomes (RMLM), Cynomolgus monkey liver microsomes (CMLM), Sprague Dawley rat liver microsomes (RLM), mouse liver microsomes (MLM), Dunkin Hartley guinea pig liver microsomes (PLM) and Beagle dog liver microsomes (DLM). Ultra-high performance liquid chromatography/quadrupole time-of-flight mass spectrometric analysis was used to determine the metabolites. A total of 3 metabolites were detected in RMLM, CMLM and RLM. Furthermore, two metabolites were observed in MLM, HLM, PLM and DLM. By analyzing the type and quantity of metabolites, the metabolism of xanthotoxin in MLM was indicated to be most similar to that in HLM. The metabolic transformations of xanthotoxin in the liver microsomes of the 7 species were analyzed in further detail. On the whole, the results of the present study provide a deeper understanding of the metabolic patterns of xanthotoxin in liver microsomes of different species, which may prove to be advantageous regarding the metabolic mechanisms of action of xanthotoxin. Further insight into drug metabolism with respect to different species will also aid in the selection of appropriate animal models for further research.

Sphingosine 1-phosphate receptor-1 specific agonist SEW2871 ameliorates ANIT-induced dysregulation of bile acid homeostasis in mice plasma and liver

Dysregulated bile acid (BA) homeostasis is an extremely significant pathological phenomenon of intrahepatic cholestasis, and the accumulated BA could further trigger hepatocyte injury. Here, we showed that the expression of sphingosine-1-phosphate receptor 1 (S1PR1) was down-regulated by α-naphthylisothiocyanate (ANIT) in vivo and in vitro. The up-regulated S1PR1 induced by SEW2871 (a specific agonist of S1PR1) could improve ANIT-induced deficiency of hepatocyte tight junctions (TJs), cholestatic liver injury and the disrupted BA homeostasis in mice. BA metabolic profiles showed that SEW2871 not only reversed the disruption of plasma BA homeostasis, but also alleviated BA accumulation in the liver of ANIT-treated mice. Further quantitative analysis of 19 BAs showed that ANIT increased almost all BAs in mice plasma and liver, all of which were restored by SEW2871. Our data demonstrated that the top performing BAs were taurine conjugated bile acids (T-), especially taurocholic acid (TCA). Molecular mechanism studies indicated that BA transporters, synthetase, and BAs nuclear receptors (NRs) might be the important factors that maintained BA homeostasis by SEW2871 in ANIT-induced cholestasis. In conclusion, these results demonstrated that S1PR1 selective agonists might be the novel and potential effective agents for the treatment of intrahepatic cholestasis by recovering dysregulated BA homeostasis.

The hypoglycemic mechanism of catalpol involves increased AMPK-mediated mitochondrial biogenesis

Mitochondria serve as sensors of energy regulation and glucose levels, which are impaired by diabetes progression. Catalpol is an iridoid glycoside that exerts a hypoglycemic effect by improving mitochondrial function, but the underlying mechanism has not been fully elucidated. In the current study we explored the effects of catalpol on mitochondrial function in db/db mice and C2C12 myotubes in vitro. After oral administration of catalpol (200 mg·kg⁻¹·d⁻¹) for 8 weeks, db/db mice exhibited a decreased fasting blood glucose level and restored mitochondrial function in skeletal muscle. Catalpol increased mitochondrial biogenesis, evidenced by significant elevations in the number of mitochondria, mitochondrial DNA levels, and the expression of three genes associated with mitochondrial biogenesis: peroxisome proliferator-activated receptor gammaco-activator 1 (PGC-1α), mitochondrial transcription factor A (TFAM) and nuclear respiratory factor 1 (NRF1). In C2C12 myotubes, catalpol significantly increased glucose uptake and ATP production. These effects depended on activation of AMP-activated protein kinase (AMPK)-mediated mitochondrial biogenesis. Thus, catalpol improves skeletal muscle mitochondrial function by activating AMPK-mediated mitochondrial biogenesis. These findings may guide the development of a new therapeutic approach for type 2 diabetes.

Current insights in the complexities underlying drug-induced cholestasis

Drug-induced cholestasis (DIC) poses a major challenge to the pharmaceutical industry and regulatory agencies. It causes both drug attrition and post-approval withdrawal of drugs. DIC represents itself as an impaired secretion and flow of bile, leading to the pathological hepatic and/or systemic accumulation of bile acids (BAs) and their conjugate bile salts. Due to the high number of mechanisms underlying DIC, predicting a compound's cholestatic potential during early stages of drug development remains elusive. A profound understanding of the different molecular mechanisms of DIC is, therefore, of utmost importance. Although many knowledge gaps and caveats still exist, it is generally accepted that alterations of certain hepatobiliary membrane transporters and changes in hepatocellular morphology may cause DIC. Consequently, liver models, which represent most of these mechanisms, are valuable tools to predict human DIC. Some of these models, such as membrane-based in vitro models, are exceptionally well-suited to investigate specific mechanisms (i.e. transporter inhibition) of DIC, while others, such as liver slices, encompass all relevant biological processes and, therefore, offer a better representation of the in vivo situation. In the current review, we highlight the principal molecular mechanisms associated with DIC and offer an overview and critical appraisal of the different liver models that are currently being used to predict the cholestatic potential of drugs.

Metabolomics of Aurantio-Obtusin-Induced Hepatotoxicity in Rats for Discovery of Potential Biomarkers

Aurantio-obtusin is an anthraquinone derived from Cassia obtusifolia (cassiae semen). It is also used as a tool and a detection index for the identification of cassiae semen, as stipulated by the Chinese Pharmacopoeia. Anthraquinones, the main components in cassiae semen, have been reported to show hepatotoxicity. This study investigates the hepatotoxicity of aurantio-obtusin in male Sprague–Dawley rats. We randomly divided the animals into a blank control group and treated three test groups with different doses of aurantio-obtusin: Low dose (4 mg/kg), medium dose (40 mg/kg), and high dose (200 mg/kg). Each group was treated with aurantio-obtusin for 28 days, whereas the control group was administered an equal volume of 0.5% carboxymethyl cellulose sodium salt (CMC-Na) aqueous solution. Subsequently, we conducted biochemical, hematological, and pathological investigations and determined the weight of different organs. We used serum metabolomics to identify possible biomarkers related to hepatotoxicity. The low-dose group showed no significant liver injury, whereas the medium- and high-dose groups manifested obvious liver injury. Compared with the control group, the test groups showed an increase in alanine transaminase, aspartate transaminase, and alkaline phosphatase levels. The liver organ coefficient also significantly increased. Additionally, we found significant changes in the hematological indices. Metabolomics analysis showed that aurantio-obtusin induced 28 endogenous markers related to liver injury. Our data indicate that aurantio-obtusin induces hepatotoxicity in rat liver in a dose-dependent manner and is mediated by pathways involving bile acids, fatty acids, amino acids, and energy metabolism. In particular, changes in bile acid content during treatment with therapeutic agents containing aurantio-obtusin deserve increased attention.

8-methoxysmyrindiol from Gerbera piloselloides (L.) Cass. and its vasodilation effects on isolated rat mesenteric arteries

Gerbera piloselloides (L.) Cass. (Compositae) possesses various biological effects. It is used as an oriental remedy for relieving cough and resolving phlegm. The present study is to investigate the vasodilation effects of Gerbera piloselloides on isolated rat mesenteric arteries (MAs) and the potential mechanism. Different organic extracts of Gerbera piloselloides were tested, and an HPLC-UV-FD-based analytical method was established to identify the active constituents. The principal components, namely, 8-MOP (8-methoxypsoralan) and 8-MSD (8-methoxysmyrindiol), were found to be predominant in the extracts of petroleum ether and dichloroform, which showed stronger vasodilation activities. 8-MSD was isolated from Gerbera piloselloides by silica gel column chromatography coupled with a Waters 2545 high throughput autopurification system, and its vasodilation effects were explored by an assay of tension on rat MA rings. The results suggest that 8-MSD induces vascular relaxation in rat MAs via an endothelium-dependent mechanism involving the Kir channel, which enables Ca²⁺ entry in the cell and activates production of NO. The present research indicates that 8-MSD may be therapeutically useful as an anti-hypertension agent and to potentially treat cardiovascular and gastrointestinal diseases.

Acute liver failure associated with Fructus Psoraleae: a case report and literature review

Background

Fructus Psoraleae is the seed of Psoralea corylifolia Linn. Fructus Psoraleae has been shown to be effective in treating some skin diseases, such as vitiligo. As a main ingredient in five types of herbs in the Qubaibabuqi tablet formula, Fructus Psoraleae plays an important role in the treatment of vitiligo. Fructus Psoraleae has potential hepatotoxicity, thus Qubaibabuqi tablets also have potential liver toxicity.

Case presentation

A 53-year-old woman who was diagnosed with vitiligo in September 2017 was treated with Qubaibabuqi tablets. After approximately 7 months of treatment, the patient developed a severe, diffuse yellow staining of the skin and sclera in March 2018. On admission, she was diagnosed with acute cholestatic hepatitis associated with Fructus Psoraleae. Despite receiving active treatment, her condition rapidly deteriorated and she died 5 days later due to acute liver failure and multiple organ dysfunction. To the best of our knowledge, there are only six reported cases of liver injury associated with Fructus Psoraleae described in the English language literature; however, cases of acute liver failure associated with the use of Fructus Psoraleae have not been described.

Conclusion

As a main ingredient in the Qubaibabuqi tablet formula, Fructus Psoraleae has potential hepatotoxicity. This potentially fatal adverse effect should be considered when physicians prescribe Qubaibabuqi tablets.

[mRNA expression of MDR3 gene in the blood of preterm infants with parenteral nutrition-associated cholestasis]

OBJECTIVE

To study the association between the expression of the MDR3 gene and the pathogenesis of parenteral nutrition-associated cholestasis (PNAC) in preterm infants.

METHODS

Among the preterm infants who were admitted to the hospital from June 2011 to November 2017 and received parenteral nutrition for more than 14 days, 80 who did not develop PNAC were enrolled as non-PNAC group, and 76 who developed PNAC were enrolled as PNAC group. On days 1, 14, 30, 60 and 90 after birth, serum hepatobiliary biochemical parameters [alanine aminotransferase (ALT), total bilirubin (TBil), direct bilirubin (DBil), total bile acid (TBA) and gamma-glutamyl transpeptidase (γ-GT)], fibrosis indices [hyaluronic acid, laminin, procollagen III N-terminal peptide and type IV collagen] and clinical manifestations were observed. Real-time quantitative PCR was used to measure the mRNA expression of MDR3 in both groups, and the correlation between the mRNA expression of MDR3 and serum hepatobiliary biochemical parameters was analyzed.

RESULTS

In the PNAC group, serum levels of hepatobiliary biochemical parameters and fibrosis indices increased on day 14 after birth and reached the peak on day 30 after birth, followed by a reduction on day 60 after birth. On days 14, 30, 60 and 90 after birth, the PNAC group had significantly higher serum levels of hepatobiliary biochemical parameters and fibrosis indices than the non-PNAC group (P<0.05). The PNAC group had higher relative mRNA expression of MDR3 in peripheral blood cells than the non-PNAC group (P<0.05). In the PNAC group, the relative mRNA expression of MDR3 in peripheral blood cells was negatively correlated with serum levels of hepatobiliary biochemical parameters (ALT, TBil, DBil, TBA and γ-GT) (P<0.001).

CONCLUSIONS

High mRNA expression of MDR3 in preterm infants may be associated with the development of PNAC, and further studies are needed to identify the mechanism.

Adaptive homeostasis of the vitamin D-vitamin D nuclear receptor axis in 8-methoxypsoralen-induced hepatotoxicity

8-methoxypsoralen (8-MOP) with ultraviolet A radiation therapy (PUVA) is the standard therapy for patients with psoriasis, despite the reported potential risks of 8-MOP-induced cholestatic liver injury in both humans and animals. Usually, patients with chronic cholestasis exhibit lower serum 25-hydroxy vitamin D (25(OH)D) levels. But those patients receiving PUVA for psoriasis showed an increase in serum 25(OH)D levels, probably highlighting that the vitamin D-vitamin D nuclear receptor (VD-VDR) axis play a protective role in 8-MOP-induced hepatotoxicity. The present study confirmed 8-MOP could increase serum 25(OH)D levels in conventional lighting and diet (CLD) and vitamin D deficient (VDD) Sprague-Dawley rats. Potential liver risks were also found in CLD and VDD rats after 8-MOP treatment. We proved that 8-MOP could be a potent ligand for VDR using molecular docking and luciferase report assay. Effect of 8-MOP on VDR subcellular distribution was determined using human liver cell line L02. We found 8-MOP could increase VDR protein expression in the nuclear and cytosol extracts and also total cell extracts in L02. siRNAs for VDR were used to determine the role of VDR in protecting 8-MOP-induced cholestasis and potential cellular mechanisms. The results showed 8-MOP could affect the CYP7A1, SHP and MRP3 expression via VDR, and such effects could be reversed by knockdown of VDR expression, suggesting a vital role of VDR involved in 8-MOP-regulated bile acid synthesis and transportation. In conclusion, these results revealed activation of VD-VDR axis may play a beneficial role in 8-MOP-mediated regulation of bile acid synthesis and transportation.

Mitochondrial dysfunction and inhibition of myoblast differentiation in mice with high-fat-diet-induced pre-diabetes

Pre-diabetes is characterized by impaired glucose tolerance (IGT) and/or impaired fasting glucose. Impairment of skeletal muscle function is closely associated with the progression of diabetes. However, the entire pathological characteristics and mechanisms of pre-diabetes in skeletal muscle remain fully unknown. Here, we established a mouse model of pre-diabetes, in which 6-week-old male C57BL6/J mice were fed either normal diet or high-fat diet (HFD) for 8 or 16 weeks. Both non-fasting and fasting glucose levels and the results of glucose and insulin tolerance tests showed that mice fed an 8-week HFD developed pre-diabetes with IGT; whereas mice fed a 16-week HFD presented with impaired fasting glucose and impaired glucose tolerance (IFG-IGT). Mice at both stages of pre-diabetes displayed decreased numbers of mitochondria in skeletal muscle. Moreover, IFG-IGT mice exhibited decreased mitochondrial membrane potential and ATP production in skeletal muscle and muscle degeneration characterized by a shift in muscle fibers from predominantly oxidative type I to glycolytic type II. Western blotting and histological analysis confirmed that myoblast differentiation was only inhibited in IFG-IGT mice. For primary skeletal muscle satellite cells, inhibition of differentiation was observed in palmitic acid-induced insulin resistance model. Moreover, enhanced myoblast differentiation increased glucose uptake and insulin sensitivity. These findings indicate that pre-diabetes result in mitochondrial dysfunction and inhibition of myoblast differentiation in skeletal muscle. Therefore, interventions that enhance myoblast differentiation may improve insulin resistance of diabetes at the earlier stage.

Psoralen Induced Liver Injury by Attenuating Liver Regenerative Capability

Psoralen is a major component of the common traditional Chinese medicine Fructus Psoraleae (FP). In this study, we focused on psoralen to explore FP-induced hepatotoxicity and the underlying mechanisms. The acute oral median lethal dose of psoralen in ICR mice was determined to be 1,673 mg/kg. C57BL/6 mice were administered psoralen intragastrically at doses of 400 mg/kg or 800 mg/kg, and were sacrificed 24 h after treatment. Changes in various hepatotoxicity indicators demonstrated that psoralen can cause mild liver injury in mice. Psoralen inhibited the viability of normal human liver L02 cells in vitro by inducing S-phase arrest. In addition, psoralen in both the mouse livers and L02 cells upregulated cyclin E1 and p27 protein levels. The 2/3 partial hepatectomy mouse model was used to further explore the effects of psoralen on the liver regeneration and hepatocellular cycle arrest in vivo. The results showed that the decrease of liver regenerative and self-healing capabilities induced by hepatocellular cycle arrest may play an important role in the hepatotoxicity of psoralen. The further mechanism researches indicated that psoralen-induced hepatotoxicity was associated with inhibition of mTOR signalling pathway and mitochondrial injury; furthermore, MHY, an mTOR activator, partly alleviated the inhibition of mTOR and S-phase cycle arrest induced by psoralen in L02 cells. In conclusion, in this study we showed for the first time, that psoralen significantly induced liver injury in mice; the decrease of liver regenerative and compensatory capabilities induced by hepatocellular cycle arrest may play an important role in the progression of hepatotoxicity associated with the upregulation of cyclin E1 and p27, as well as the inhibition of mTOR signalling and mitochondrial injury. Our findings may contribute to the reduction of hepatotoxicity risk induced by Fructus Psoraleae.

A new hypoglycemic mechanism of catalpol revealed by enhancing MyoD/MyoG-mediated myogenesis

AIMS

Enhancing myogenesis has been identified as a possible target to improve insulin sensitivity and protect against metabolic diseases. Catalpol, an iridoid glycoside, has been shown to exert a hypoglycaemic effect by improvement of insulin sensitivity; however, the underlying mechanism remains unknown. In this study, we tested whether catalpol has the potential to improve insulin sensitivity by augmenting myogenesis.

MAIN METHODS

We examined the hypoglycaemic mechanism of catalpol in db/db mice and C2C12 cells. db/db mice were treated with catalpol (200 mg/kg) for 8 consecutive weeks. Serum analysis, skeletal muscle performance and histology, and gene and protein expression were performed. In vitro glucose uptake, gene and protein expression were determined, and small interfering RNA was used to identify the underlying hypoglycaemic mechanism of catalpol.

KEY FINDINGS

In this study, we tested whether catalpol has the potential to improve skeletal insulin sensitivity by augmenting myogenesis, in which we found that, catalpol treatment in db/db mice lowered blood glucose and improved insulin sensitivity via activation of phosphatidylinositol‑3‑Kinase (PI3K)/protein kinase B (AKT) pathway. Moreover, catalpol-treated mice exhibited enhanced myogenesis, as evidenced by increased myogenic differentiation (MyoD), myogenin (MyoG) and myosin heavy chain (MHC) expressions. The in vitro experimental results showed that both catalpol and metformin enhanced glucose uptake via activation of PI3K/AKT pathway. However, unlike metformin, the PI3K/AKT pathway activation by catalpol was dependent on enhanced MyoD/MyoG-mediated myogenesis.

SIGNIFICANCE

Improvement of insulin sensitivity by enhancing MyoD/MyoG-mediated myogenesis may constitute a new therapeutic approach for treating type 2 diabetes.