Protective effect of Salacia oblonga against tobacco smoke-induced DNA damage and cellular changes in pancreatic β-cells

Abstract

Context: Tobacco smoking generates a tremendous amount of free radicals that induce oxidative stress (OS) in diabetics (pancreatic islet cells are defective). Salacia oblonga Wall. (Celastraceae) is a proven antioxidant and antidiabetic plant whose mechanism of action is yet to be explored.Objective: The present study focuses on the protective ability of S. oblonga in tobacco smoke-induced oxidatively stressed pancreatic β-cell line.Materials and methods: The RINm5f cell line was exposed to tobacco smoke concentrate (TSC) (0.5–10%, 24 h), plant extract (1–75 µg/ml, 3 h), and their combinations. Cell viability was determined through MTT assay. Microscopic analysis was carried out in unstained and nonyl acridine orange-stained cells. The effect of toxic doses of TSC on DNA integrity was analyzed through DNA fragmentation assay. The TSC-induced nitric oxide generation was determined spectrophototmetrically. The expression of anti-apoptotic protein Bcl-X under the above treatment conditions was carried out through RT-PCR.Results: The LD50 dose for TSC was found to be 1% TSC. Salacia oblonga extracts (10 and 15 µg/ml) were found to be optimum safe doses that significantly increased cell viability and decreased the nitric oxide production in TSC-treated cells. Pre-treatment with plant extract suppressed apoptosis through probable increase in the expression of anti-apoptotic protein Bcl-X in TSC-treated cells. Thus, the overall efficiency of plant extract in recovering cellular damage was proven.Discussion and conclusion: The results suggest that TSC-induced cellular alterations are related to rise in nitric oxide and Bcl-X mRNA expression and propose that S. oblonga may confer significant cytoprotection against OS-mediated injury in β-cells.