Activation of Sarco/Endoplasmic Reticulum Ca2+-ATPase by Natural Polyphenolic Compounds. Mechanism of Protection against Oxidative Stress

Many redox diseases, including diabetes, are associated with an imbalance of calcium homeostasis, regulated mainly by a Ca2+-ATPase pump (SERCA). Dysfunction of this enzyme may be prevented by natural polyphenolic compounds, representing a possible supporting treatment. Compounds that increase SERCA activity/expression may be useful for the treatment of diabetic complications. Stimulation of SERCA1 activity was analyzed experimentally and by molecular modeling. SERCA1 activity under methylglyoxal- and palmitate-induced oxidative stress was evaluated. The viability of INS-1E cells and insulin secretion were determined. [6]-Gingerol, resveratrol, and ellagic acid increased SERCA1 activity and exerted a protective effect under oxidative stress in the noncellular system. We found for the first time that the binding of polyphenols ([6]-gingerol, resveratrol, ellagic acid) to Glu439 in the SERCA1 P-domain may be critical for the stimulation of its activity. Moreover, this binding may also be important in the protective effects against oxidative stress. Direct stimulation of SERCA1 activity by ellagic acid was observed for the first time. In INS-1E cells, these compounds increased insulin secretion.