DNA methyltransferases expressions in mice tongue exposed to waterpipe smoke.

objectiveWaterpipe smoking has gained widespread use nowadays, especially among young adults. As this type of smoke has been described to contain toxins and carcinogens, this study evaluated DNA methyltransferase (DNMT) 1 and 3b expression, and inflammation, on the dorsal surface, ventral surface and lateral border of Swiss mice's tongues exposed to waterpipe smoke. METHODOLOGY: Animals were divided into 6 groups (n=60): control, 7, 15, 30, 60, and 90 days of consecutive exposure to waterpipe smoke in a whole-body exposure system. After each period, tongues were analyzed using hematoxylin/eosin staining for inflammation status and immunohistochemistry for DNMT1 and DNMT3b.

resultsDNMT3b showed lower immunoexpression from 7 to 60 days; at 90 days, expression was similar to that of control or there was upregulation on the ventral surface compared with control. DNMT1 exhibited lower expression at all exposure times, with the ventral surface showing similar expression to that of control at 90 days. Waterpipe smoke was not able to induce acute or chronic inflammation in mice tongue.

conclusionWaterpipe smoke may result in a DNA hypomethylation pattern in initial exposure periods, contributing to activate proto-oncogenes and/or genomic instability. Over long periods, it may lead to a methylation pattern similar to that of control or even to hypermethylation, silencing tumor suppressor genes. These alterations in the genome due to hypo/hypermethylation contribute largely for the development of diseases such as oral cancer.