Arecolin Induces Cell Cycle Dysregulation and Apoptosis in Gingiual Fibroblasts

Abstract

The habit of betel quid chewing, common in Taiwan, is causally associated with the pathogenesis of oral submucous fibrosis and an increased risk of oral cancer. The effect of arecoline, an alkaloid of betel quid ingredient, on the cytotoxic susceptibility of the gingival fibroblasts was investigated. Cells grown in near confluence, were exposed to various concentrations of arecoline (0.25 to 2.0 mM), and a dose-dependent decrease in the cell viability was observed. Phase contrast microscopy showed that arecoline (＞1.0 mM) caused the morphological alterations in those cells including cell shrinkage, detactment of the cell from its neighbors, cytoplasmic and chromatin condensation that were characteristics of apoptosis. Apoptotic DNA degradation was validated and quantitated using terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling method (TUNEL). Approximately 42% of the cells exposed to 2.0 mM of arecoline for 24-h were TUNEL-positive. Apoptosis was also shown to be coincided with an accumulation of cells in G2/M phase along with concomitant decreases in G0/ G1- and S- phases. Although the mechanisms by which arecoline initiates apoptosis in these cells were presently unknown, yet we found that exogenously added antioxidant enzymes such as catalase and superoxide dismutase, could partially protect the arecoline-induced cell death suggesting that reactive oxygen species were likely to be involved. Together, arecoline-induced cytotoxic effects of gingival fibroblasts my lead to the dysregulation of connective tissue metabolism and the significance of it should not be overlooked.