Cytosolic Glutathione S-Transferase Change after Deoxycholate Exposure in Colon Cancer Cell Lines

Park, Dong Kook; Shin, Ji Hyun; Park, Seok Gun; Cheung, Sun Young

Abstract

PURPOSE: Bile acids (especially deoxycholate) was known to be toxic and mutagenic on colon epithelium. They proposed at least four mechanisms for the bile acid toxicity. It is the one of these mechanisms that bile acid inhibits the xenobiotic metabolizing enzyme activity (esp glutathione S-transferase, GST). So we measured the cytosolic GST level of colon carcinoma cell lines after deoxycholate exposure whether or not the deoxycholate lowered the cytosolic GST activity.
METHODS
Three colon cancer cell lines (LoVo, SW480, HT29) were used for this study. We calculated the cellular toxicity by MTS method. And cytosolic GST activity was measured according to the method as Habig described. For total GST activity, 2.5 mM 1-chloro-2,4-dinitrobenzene was used for substrate, and measured as absorbance in 340 nm.
RESULTS
Basal cytosolic GST level for LoVo, SW480, HT29 cell line was 514.59+/-27.01, 291.63+/-38.44 and 344.58+/-47.92 nmol/min/mg cytosol protein. GST level did not changed significantly after 5 days culture without DCA. But GST level was decreased significantly to 128.63+/-21.35, 134.33+/-41.76 and 163.10+/-22.73 nmol/min/mg cytosol protein each cell line after 5 days deoxycholate exposure (p<0.005).
CONCLUSION
Cytosolic GST level was lowered significantly after deoxycholate exposure for 5 days. One of the mechanisms of bile acid toxicity for colon cancer cell is proposed to inhibit cytosolic GST activity.