The Influence of L-arginine on Cell Proliferation, iNOS Expression and Cell Cycle in the Human Colon Carcinoma Cell Line LS174

The relationship between the L-Arg-NO pathway and tumor growth has not yet been clearly elucidated. The aim of this study was to explore the effects of L-arginine (L-Arg) on cell proliferation, inducible nitric oxide synthase (iNOS) expression and the cell cycle in the human colon carcinoma cell line LS174. LS174 cells were cultured with L-Arg at different concentrations for different times. The MTT method was employed to evaluate the level of cell proliferation. The production of nitric oxide (NO) in the culture supernatants was detected by the enzymatic reduction of nitrate. The distribution of the cell cycle was detected using flow cytometry (FCM). The expression levels of iNOS were determined by western blot and immunohistochemical staining. The growth of LS174 cells was promoted by L-Arg at low concentrations (0.125 mmol/L) and inhibited at high concentrations (0.5, 2, 8, or 32 mmol/L). The levels of NO increased with increasing concentrations of L-Arg. Compared with the control group, the ratio of cells in S phase was increased after 48 hour’ treatments with high concentrations of L-Arg (0.5, 2, 8 or 32 mmol/L) (P<0.05,P<0.01); but there was no obvious difference after treatments with a low concentration (0.125 mmol/L) (P>0.05). With the increase in L-Arg concentrations, the expression of iNOS increased. L-Arg can induce the expression of iNOS resulting in an increase the production of NO. Low concentrations of L-Arg can promote growth, whereas high concentrations can inhibit the growth and proliferation of LS174 cells. High concentrations of L-Arg can induce S phase arrest. [Yan-feng Gao, Xiao-Ying Ding, Wei Yuan, Xiao-Gang Liu, Xiong-wei Huo. The Influence of L-arginine on Cell Proliferation, iNOS Expression and Cell Cycle in the Human Colon Carcinoma Cell Line LS174. Life Sci J 2014;11(7):317-323]. (ISSN:1097-8135). http://www.lifesciencesite.com. 37