Shubhankar Das

Mangiferin attenuates methylmercury induced cytotoxicity against IMR-32, human neuroblastoma cells by the inhibition of oxidative stress and free radical scavenging potential

Mangiferin (MGN), a C-glucosylxanthone was investigated for its ability to protect against methylmercury (MeHg) induced neurotoxicity by employing IMR-32 (human neuroblastoma) cell line. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] and clonogenic cell survival assays confirmed the efficacy of MGN supplementation in attenuating MeHg-induced cytotoxicity. Pre-treatment with MGN significantly (p<0.01) inhibited MeHg-induced DNA damage (micronuclei, olive tail moment and % tail DNA) thereby demonstrating MGNs antigenotoxic potential. Also, pre-treatment with MGN significantly reduced MeHg-induced oxidative stress, intra-cellular Ca(2+) influx and inhibited depolarization of mitochondrial membrane. MGN pre-treated cells demonstrated a significant (p<0.05) increase in the GSH and GST levels followed by a significant (p<0.05) decrease in malondialdehyde (MDA) formation. In addition, inhibition of MeHg induced apoptotic cell death by MGN was demonstrated by microscopic, Annexin-V FITC and DNA fragmentation assays and further confirmed by western blot analysis. The present findings indicated the protective effect of MGN against MeHg induced toxicity, which may be attributed to its anti-genotoxic, anti-apoptotic and anti-lipid peroxidative potential plausibly because of its free radical scavenging ability, which reduced the oxidative stress and in turn facilitated the down-regulation of mitochondrial apoptotic signalling pathways.

Some new indole–coumarin hybrids; Synthesis, anticancer and Bcl-2 docking studies

Hybrid molecules have attracted attention for their improved biological activity, selectivity and lesser side effects profile, distinct from their individual components. In the quest for novel anticancer drug entities, three series of indole-coumarin hybrids - 3-(1-benzyl-1H-indol-2-yl)-2H-chromen-2-ones, 2-(2-oxo-2H-chromen-3-yl)-1H-indole-3-carbaldehydes and 2-(2-oxo-2H-chromen-3-yl)-1H-indole-3-carboxylic acids were synthesized. All the synthesized compounds were characterized by spectral techniques like IR, (1)H NMR, (13)C NMR, mass spectrometry and elemental analysis. In silico docking studies of synthesized molecules with apoptosis related gene Bcl-2 that is recognized to play an important role in tumerogenesis were carried out. Dose-dependent cytotoxic effect of the compounds in human breast adenocarcinoma (MCF-7) and normal cell lines were assessed using MTT assay and compared with that of the standard marketed drug, Vincristine. Compound 4c had a highly lipophilic bromine substituent capable of forming halogen bond and was identified as a potent molecule both in docking as well as cytotoxicity studies. Flow cytometric cell cycle analysis of 4c exhibited apoptotic mode of cell death due to cell cycle arrest in G2/M phase. Structure activity relationship of these hybrid molecules was also studied to determine the effect of steric and electronic properties of the substituents on cell viability.

Thymol, a monoterpene phenolic derivative of cymene, abrogates mercury-induced oxidative stress resultant cytotoxicity and genotoxicity in hepatocarcinoma cells

Thymol (TOH) was investigated for its ability to protect against mercuric chloride (HgCl2)‐induced cytotoxicity and genotoxicity using human hepatocarcinoma (HepG2) cell line. 3‐(4,5‐Dimethylthiazol‐2‐yl)−2,5‐diphenyl tetrazolium bromide assay confirmed the efficacy of TOH pretreatment in attenuating HgCl2‐induced cytotoxicity. Pretreatment with TOH inhibited HgCl2‐induced genotoxicity, depolarization of mitochondrial membrane, oxidative stress, and mitochondrial superoxide levels. Interestingly, TOH (100 µM) alone elevated the intracellular basal glutathione S‐transferase (GST) levels and TOH pretreatment abrogated the decrease in glutathione, GST, superoxide dismutase, and catalase levels even after HgCl2 intoxication. Furthermore, TOH was also capable of inhibiting HgCl2‐induced apoptotic as well as necrotic cell death analyzed by flowcytometric analysis of cells dual stained with Annexin‐FITC/propidium iodide. The present findings clearly indicate the cytoprotective potential of TOH against HgCl2‐induced toxicity, which may be attributed to its free radical scavenging ability which facilitated in reducing oxidative stress and mitochondrial damage thereby inhibiting cell death.

Hydroxytyrosol, a dietary phenolic compound forestalls the toxic effects of methylmercury-induced toxicity in IMR-32 human neuroblastoma cells.

This study demonstrates the protective potential of hydroxytyrosol (HT), an olive oil phenol, against methylmercury (MeHg)‐induced neurotoxicity using IMR‐32 human neuroblastoma cell line. HT inhibited MeHg‐induced cytotoxicity and genotoxicity as confirmed by MTT, micronucleus, and comet assays. Cells preconditioned with HT showed reduction of MeHg‐induced cellular oxidative stress along with the maintenance of glutathione, superoxide dismutase, glutathione‐S‐tranferase, and catalase. Fluorescence microscopy and DNA ladder assays indicated the inhibitory effect of HT against MeHg‐induced apoptosis, which was further established by Western blotting. An effective concentration of 5 µM HT caused downregulation of p53, bax, cytochrome c, and caspase 3 and upregulation of prosurvival proteins including nuclear factor erythroid 2‐related factor 2 (Nrf2) and metallothionein. This work indicates the cytoprotective potential of HT against MeHg‐induced toxicity primarily by the lowering of oxidative stress, which may be endorsed to its antigenotoxic and antiapoptotic potential, in addition to its free radical scavenging ability.

Naringin abates adverse effects of cadmium-mediated hepatotoxicity: An experimental study using HepG2 cells: RATHI ET AL.

This study investigated the protective potential of Naringin (NIN) against cadmium chloride (CdCl2) mediated hepatotoxicity using human hepatocellular carcinoma (HepG2) cells. An optimal concentration of NIN (5 μM) was potent enough to confer cytoprotection against CdCl2 (50 μM) as was observed by MTT assay. Preconditioning with NIN maintained redox homeostasis, mitochondrial membrane potential, and reduced apoptosis as marked by decrease in the percentage sub‐G0/G1 and Annexin V‐FITC/propidium iodide positive cells (apoptotic). NIN pretreatment maintained the levels of protein thiol along with endogenous activities of Superoxide dismutase, Glutathione S‐transferase, and Catalase and lowered lipid peroxidation. Decreased Bax/Bcl2 ratio along with reduced Caspase 3 cleavage and Cytochrome c release indicated that NIN conditioning blocked mitochondrial‐mediated apoptosis. Increased Nrf2 and metallothionein (MT) acted as adaptive response in the presence of cadmium. Thus, the protective mechanism of NIN is attributed to its antioxidant potential which aids in redox homeostasis and prevents CdCl2 mediated cytotoxicity.

Harmonization of Mangiferin on methylmercury engendered mitochondrial dysfunction.

Mangiferin (MGN), a C‐glucosylxanthone abundantly found in mango plants, was studied for its potential to ameliorate methylmercury (MeHg) induced mitochondrial damage in HepG2 (human hepatocarcinoma) cell line. Cell viability experiments performed using 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐ diphenyltetrazolium bromide (MTT) showed protective property of MGN in annulling MeHg‐induced cytotoxicity. Conditioning the cells with optimal dose of MGN (50 µM) lowered MeHg‐induced oxidative stress, calcium influx/efflux, depletion of mitochondrial trans‐membrane potential and prevented mitochondrial fission as observed by decrease in Mitotracker red fluorescence, expression of pDRP1 (serine 616), and DRP1 levels. MGN pre‐treated cells demonstrated elevation in the activities of glutathione (GSH), Glutathione‐S‐transferase (GST), Glutathione peroxidase (GPx), Glutathione reductase (GR), reduced levels of Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) and mitochondrial electron transport chain (ETC) enzyme complexes. In addition, the anti‐apoptotic effect of MGN was clearly indicated by the reduction in MeHg‐induced apoptotic cells analyzed by flowcytometric analysis after Annexin V‐FITC/propidium iodide staining. In conclusion, the present work demonstrates the ability of a dietary polyphenol, MGN to ameliorate MeHg‐mediated mitochondrial dysfunction in human hepatic cells in vitro. This hepatoprotective potential may be attributed predominantly to the free radical scavenging/antioxidant property of MGN, by facilitating the balancing of cellular Ca2+ ions, maintenance of redox homeostasis and intracellular antioxidant activities, ultimately preserving the mitochondrial function and cell viability after MeHg intoxication. As MeHg intoxication occurs over a period of time, continuous consumption of such dietary compounds may prove to be very useful in promoting human health.