Molecular Pathogenesis of Chewable Tobacco.

Abstract

In Pakistan, extensive use of several precarious chewable tobacco formulations has made oral cancer the second leading malignancy. Selection of literature was done by a survey of studies published from 1990 to 2017 mainly, from PUBMED and few from other search engines, on naswar, gutka, areca nut and betel quid, which included published reviews, original articles and other data sources on chewable tobacco, its epidemiology, pathological implications, and psychological effects. These studies have revealed that the chemicals in these formulations bind and mutate DNA of oral mucosa through down regulating cellular repair pathways and upregulating genetic networks associated with pathogenesis. Areca nut, having aercoline (the major alkaloid) causes carcinogenicity, mutagenicity, and genotoxicity of oral mucosa through increased production of growth factors and corticotrophin-releasing hormone, and genetic alteration in expression of CASP8, APAF-1, BAX, BAD, and upregulation of caspas-3. Gutka addiction leads to precancerous lesions resulting in characteristic facial abnormalities, following trismus. Naswar, in addition to oral cancer, causes adverse cardiovascular events by reducing glutathione per oxidase (GPx) and super-oxide dismutase (SOD), serum levels of HDL, whereas, increasing the ratio of cholesterol, LDL, triglycerides and LDL-C/HDL-C. Betel quid (Paan), causes psychoactivity affecting central and autonomic nervous systems leading to dependence with decreased cognition, euphoria, sweating, salivation, palpitation, heightened alertness and zest to work. Metabolically, cardio-acceleration, cortical desynchronisation of EEG, elevated plasma noradrenaline and adrenaline were found. This review highlights the corrosive effects of various most popular chewable tobacco formulations; and damage done by their cocktail of carcinogenic substances and added ingredients, leading to oropharangeal cancer.