Rice bran proteins inhibit effects of angiotensin and oxidative stress in murine macrophage cells.

Rice bran contains a number of compounds which have shown to present beneficial effects on cardiovascular system. The rennin-angiotensin system is suggested to play roles in insulin resistance and cardiovascular diseases. Rice bran products have been reported to ameliorate type 2 diabetes. The protein fraction from rice bran is a rich source of valuable nutrition, however, there is only few reports on its effects on angiotensin system. Rice protein hydrolysates (RBP) were prepared from defatted Hom-Mali rice cultivated in the North-East region of Thailand with controlled enzymatic hydrolysis. Murine macrophage RAW 264.7 cells were cultured in DMEM media supplemented with 10% fetal bovine serum. Exposure of RAW 264.7 cells to angiotensin-I (ANG-I) and ANG-II resulted in stimulation of superoxide formation, as detected by lucigenin enhanced chemiluminescent assay. RBP (20-400ug/mL) concentration-dependently suppressed the oxidant formation. The suppression effect may be in part due to the inhibition of angiotensin converting enzyme (ACE) activity, as shown by an in vitro assay using rabbit ACE and specific substrate. Thus, RBP possesses ACE inhibiting activity and Since ANG may participate in inflammatory processes in diabetes and metabolic syndrome, nitric oxide formation was measured as a marker of induction of iNOS. Rice bran protein hydrolysates (100-800 ug/mL) showed to suppress ANG-I and ANG-II-induced nitric oxide generation. This study suggests that rice bran protein hydrolysates could suppress angiotensin-mediated oxidative stress and may provide beneficial effect as food supplement in diseases with oxidative stress conditions. [ABSTRACT FROM AUTHOR]