Genotoxic and anti-genotoxic effects of esculin and its oligomer fractions against mitomycin C-induced DNA damages in mice

Esculin Alleviates Osteoarthritis Progression Through the Sirt1/NF-κB Pathway

Osteoarthritis (OA), a joint disease associated with inflammatory processes, contributes to joint destruction. Esculin (ESC) extracted from the stem bark of Fraxinus rhynchophylla Hance has been shown to possess anti-inflammatory properties. In this study, we investigated the effect of ESC on chondrocytes treated with IL-1β and its molecular mechanism. The importance and potential mechanism of ESC in the progression of OA were evaluated. The viability of chondrocytes after exposure to ESC was examined through the CCK-8 assays. The cells were then subjected to quantitative polymerase chain reaction (qPCR), western blot, and enzyme-linked immunosorbent assay (ELISA) techniques to analyze the degradation of the extracellular matrix (ECM) and occurrence of inflammation. The NF-κB mechanism was evaluated by western blot analysis, immunofluorescence (IF), and luciferase reporter assay. Molecular docking was performed to allow for predictions on proteins that interact with ESC. Moreover, the significance of Sirt1 was explored through a knockdown experiment based on siRNA. Micro-computed tomography (CT), H&E, Safranin O-Fast Green (S-O), and immunohistochemical analyses were carried out to assess the treatment efficacy of ESC on OA in destabilization of medial meniscus (DMM) models. ESC treatment effectively inhibited ECM degradation, modulated the levels of pro-inflammatory factors, and regulated the NF-κB signaling in chondrocytes exposed to IL-1β. Mechanistically, we found that ESCs bound to Sirt1 to inhibit the activity of the NF-κB mechanism. Furthermore, ESC treatment suppressed OA progression in the DMM models. Our findings reveal that ESC ameliorates OA progression via modulating the Sirt1/NF-κB axis. This demonstrates that ESC has the potential to be applied in the treatment of OA.

Integrating Concentration-Dependent Toxicity Data and Toxicokinetics To Inform Hepatotoxicity Response Pathways

Failure of animal models to predict hepatotoxicity in humans has created a push to develop biological pathway-based alternatives, such as those that use in vitro assays. Public screening programs (e.g., ToxCast/Tox21 programs) have tested thousands of chemicals using in vitro high-throughput screening (HTS) assays. Developing pathway-based models for simple biological pathways, such as endocrine disruption, has proven successful, but development remains a challenge for complex toxicities like hepatotoxicity, due to the many biological events involved. To this goal, we aimed to develop a computational strategy for developing pathway-based models for complex toxicities. Using a database of 2171 chemicals with human hepatotoxicity classifications, we identified 157 out of 1600+ ToxCast/Tox21 HTS assays to be associated with human hepatotoxicity. Then, a computational framework was used to group these assays by biological target or mechanisms into 52 key event (KE) models of hepatotoxicity. KE model output is a KE score summarizing chemical potency against a hepatotoxicity-relevant biological target or mechanism. Grouping hepatotoxic chemicals based on the chemical structure revealed chemical classes with high KE scores plausibly informing their hepatotoxicity mechanisms. Using KE scores and supervised learning to predict in vivo hepatotoxicity, including toxicokinetic information, improved the predictive performance. This new approach can be a universal computational toxicology strategy for various chemical toxicity evaluations.

Esculin protects human blood cells from bioallethrin-induced toxicity: An ex vivo study

Bioallethrin, a household insecticide, is a member of the pyrethroid family and is known for its adverse effects on human health. Human exposure to pyrethroids is unavoidable due to their widespread use in controlling several fatal vector-borne diseases, mostly in developing nations. Bioallethrin is known to induce oxidative stress in target cells, including erythrocytes. Here we have studied the protective effect of dietary antioxidant esculin on bioallethrin-induced damage in isolated human erythrocytes. The cells were incubated with 200 μM bioallethrin, without or with different concentrations of esculin (200, 400 and 600 μM), and the results compared to the untreated control samples. Bioallethrin-treated erythrocytes showed a significant increase in oxidative stress markers, like protein and lipid oxidation, accompanied by decrease in free amino groups and ratio of reduced to oxidized glutathione. There was enhanced generation of reactive oxygen and nitrogen species with changes in plasma membrane integrity. Bioallethrin oxidized hemoglobin to methemoglobin, which cannot transport oxygen. It altered the activities of antioxidant enzymes and lowered the electron donating and free radical quenching ability of erythrocytes. The cell morphology and redox system of erythrocyte membrane were also altered by bioallethrin. Treatment with esculin, prior to incubation with bioallethrin, led to significant restoration in all these parameters in an esculin concentration-dependent manner. Thus esculin attenuated the biolletherin-induced oxidative damage to erythrocytes. Esculin can, therefore, be an effective chemoprotectant against xenobiotic-induced toxicity in human erythrocytes.

Molecular interactions of esculin with bovine serum albumin and recognition of binding sites with spectroscopy and molecular docking

Esculin is structurally a hydroxycoumarin found in various medicinal plants. This study investigates the binding mode of esculin with bovine serum albumin by employing numerous spectroscopic studies and molecular docking approaches. Ultraviolet absorption spectroscopy revealed ground state complex formation between esculin and bovine serum albumin. At the same time, steady-state fluorescence studies showed quenching in the fluorescence emission spectra of BSA in the presence of esculin. To get insight into the location of the binding pocket of esculin on BSA, warfarin and ibuprofen site markers were used. Competitive site marker displacement assay revealed that esculin binds to Sudlow's site I (subdomain IIA) in bovine serum albumin. Thermodynamic parameters suggested that hydrogen bonding and van der Waals interaction stabilizes the esculin-BSA complex. Förster's non-radiation energy transfer analysis described the high propensity of energy transfer between bovine serum albumin and esculin. The molecular docking approach facilitated locating the binding pocket, amino acid residues involved, types of interacting forces, and binding energy (ΔG) between esculin and BSA. Circular dichroism revealed the effect of the binding of esculin on the secondary structure and helped understand the thermal unfolding profile of BSA in the presence of esculin.Communicated by Ramaswamy H. Sarm.

Esculin protects against methionine choline-deficient diet-induced non-alcoholic steatohepatitis by regulating the Sirt1/NF-κB p65 pathway

CONTEXT

Esculin, an active coumarin compound, has been demonstrated to exert anti-inflammatory effects. However, its potential role in non-alcoholic steatohepatitis (NASH) remains unclear.

OBJECTIVE

This study explored the hepatoprotective effect and the molecular mechanism of esculin in methionine choline-deficient (MCD) diet-induced NASH.

MATERIALS AND METHODS

Fifty C57BL/6J mice were divided into five groups: control, model, low dosage esculin (oral, 20 mg/kg), high dosage esculin (oral, 40 mg/kg), and silybin (oral, 105 mg/kg). All animals were fed a MCD diet, except those in the control group (control diet), for 6 weeks.

RESULTS

Esculin (20 and 40 mg/kg) inhibited MCD diet-induced hepatic lipid content (triglyceride: 16.95 ± 0.67 and 14.85 ± 0.78 vs. 21.21 ± 1.13 mg/g; total cholesterol: 5.10 ± 0.34 and 4.08 ± 0.47 vs. 7.31 ± 0.58 mg/g), fibrosis, and inflammation (ALT: 379.61 ± 40.30 and 312.72 ± 21.45 vs. 559.51 ± 37.01 U/L; AST: 428.22 ± 34.29 and 328.23 ± 23.21 vs. 579.36 ± 31.93 U/L). In vitro, esculin reduced tumour necrosis factor-α, interleukin-6, fibronectin, and collagen 4A1 levels, but had no effect on lipid levels in HepG2 cells induced by free fatty acid. Esculin increased Sirt1 expression levels and decreased NF-κB acetylation levels in vivo and in vitro. Interfering with Sirt1 expression attenuated the beneficial effect of esculin on inflammatory and fibrotic factor production in HepG2 cells.

CONCLUSIONS

These findings demonstrate that esculin ameliorates MCD diet-induced NASH by regulating the Sirt1/ac-NF-κB signalling pathway. Esculin could thus be employed as a therapy for NASH.

Protective Effect of Chrysin, a Dietary Flavone against Genotoxic and Oxidative Damage Induced by Mitomycin C in Balb/C Mice

Anticancer drugs, such as Mitomycin C (MMC), can interact with biological molecules and cause genetic damage in normal cells. In this respect, we investigated the potential of chrysin, a flavone known as a potent scavenger of free radicals generated by anticancer agents, to protect mice against MMC-induced genotoxicity. The amount of DNA damage in the liver, kidney and bone marrow cells, in Balb/C mice treated with MMC (6 mg/kg, i.p) and the frequency of chromosomal aberrations indicated the genotoxic effect of MMC. Besides, a significant increase in the activities of antioxidant enzymes (SOD, CAT, GPx, GST) and lipid peroxidation is revealed. On the other hand, we noticed a regression of the genotoxic effect when studying the same parameters in Balb/C mice treated with chrysin (40 mg/kg b. wt., i.p) 24 h prior to MMC (6 mg/kg, i.p) injection. This study concluded that the protective effect of chrysin against genotoxicity of MMC results partly from its antioxidant effect.

Identification of compounds that inhibit the binding of Keap1a/Keap1b Kelch DGR domain with Nrf2 ETGE/DLG motifs in zebrafish

The Keap1-Nrf2-ARE system serves as a premier defence mechanism to curb oxidative stress, which remains as one of the major causes of ageing and pathogenesis in various diseases. Nrf2 is the principal master regulator of the cellular defence system, and its activation remains the prospective therapeutic approach against chronic diseases. One of the recent strategies is to disrupt Keap1-Nrf2 protein-protein interaction (PPI) that alters the docking of Keap1 with Nrf2 by compounds occupying a position in the Keap1 blocking the interface with Nrf2. In this study, we made an attempt to identify the compounds with anticancer, antioxidant and anti-inflammatory properties to disrupt Keap1a/b-Nrf2 PPI through in silico molecular docking in zebrafish. The phylogenetic analysis of Keap1 proteins revealed the existence of orthologous Keap1-Nrf2-ARE system in lower vertebrates that includes zebrafish. The DGR domains of zebrafish Keap1a and Keap1b were modelled with Modeller 9.19 using Keap1 of Mus musculus (PDB ID:5CGJ) as template. Based on the docking calculations, top hit compounds were identified to disrupt both Keap1a and Keap1b interaction with Nrf2 which include quercetin 3,4'-diglucoside, flavin adenine dinucleotide disodium salt hydrate, salvianolic acid A, tunicamycin and esculin. The LC₅₀ of esculin in 3 dpf zebrafish larvae is 5 mmol/L, and the qRT-PCR results showed that esculin significantly increased the transcription of Nrf2 target genes-Gstpi, Nqo1, Hmox1a and Prdx1 in 3 dpf zebrafish larvae. These potential hits could serve as safer Nrf2 activators due to their non-covalent disruption of Keap1-Nrf2 PPI and be developed into efficacious preventive/therapeutic agents for various diseases.

Heated naringin mitigate the genotoxicity effect of Mitomycin C in BALB/c mice through enhancing the antioxidant status

A major problem with cancer chemotherapy is its severe toxic effects on non-target tissues. Assessment of natural products for their protective effect against anticancer drugs induced toxicity is gaining importance in cancer biology. The aim of the present study was to evaluate the effect of native and thermal treated naringin on the protective effect against mitomycin C (MMC) induced genotoxicity. The genotoxicity in liver kidney and brain cells isolated from Balb/C mice were evaluated by performing the comet assay. Antioxidant and lipid peroxidation assays were carried out to understand the protective effects of these compounds. The comet assay showed that heated and native naringin were not genotoxic at the tested dose (40 mg/kg b.w) on liver, kidney and brain cells. A significant decrease in DNA damages was observed, at the tested doses (20 mg/kg b.w and 40 mg/kg b.w) suggesting a protective role of these molecules against the genotoxicity induced by mitomycin C on liver, kidney and brain cells. Moreover, administration of MMC (6 mg/kg b.w.) altered the activities of glutathione peroxidase and superoxide dismutase accompanied by a significant increase of lipid peroxidation. Pretreatment of mouse with heated and native naringin before MMC administration significantly raised the glutathione peroxidase and superoxide dismutase activities followed by a reduced MMC-induced lipid peroxidation. Our study demonstrated that heat treatment of naringin preserve activities of native naringin. The genoprotective properties of heated and native naringin against MMC could be attributed to its antioxidant activities and its inhibitory effect on lipid peroxidation.