Abstract
Connarus ruber Planchon, a dicotyledon of Connaraceae, is distributed throughout tropical regions; it grows in Maués in the Amazon. We have shown that its aqueous extract has a genotoxicity-suppressing effect against ultra violet C (UVC) in cultured human cells. Recently, we investigated whether it also shows a genotoxicity-suppressing effect against inhaled cigarette smoke in mice. The genotoxicity-suppressing effect against tobacco smoking has been showed clinically, suggesting that it could potentially reduce the risk of tobacco carcinogenesis. Apoptosis is an important factor to determine the fate of mutant cells to develop into cancer cells. In this study, aqueous extract of Connarus was examined to induce apotosis in cells exposed to oxidative stress.
Human lymphoblastoid TK6 P53+/+and WTK1 P53-/- cells were exposed to H₂O₂ at 25 μｇ/mL for 30 min, and then culture for 48 and 96 h in the presence of Connarus extract. The tear drop assay slides were prepared immediately after the exposure to H₂O₂, 48 h culture, and 96 h culture. In TK6 P53+/+cells exposed to H₂O₂ but not un-exposed to H₂O₂, the apoptotic cell frequency increased after 96 h culture with Connarus extract in, showing that Connarus extract can induce apoptosis in the cells exposed but not un-exposed to oxidative stress. On the other hand, in WTK1 P53-/-cells either exposed and un-exposed to H₂O₂, the apoptotic cell frequency did nit increased after 96 h culture with Connarus extract in, showing that Connarus extract can induce apoptosis in P53+/+cells exposed to oxidative stress. P53 protein plays an important role to induce apotosis to exclude saviorly damaged cells before the fixation of DNA damage, from which it could be considered that Connarus can inhibit initiation step by to exclusion of saviorly damaged cells. Therefore, it could be concluded that Connarus can be effectively used to reduce carcinogenic risk.
