GSK-3ß promotes PA-induced apoptosis through changing ß-arrestin 2 nucleus location in H9c2 cardiomyocytes.

ABSTRACT

Palmitic acid (PA), a type of saturated fatty acids, induces cardiovascular diseases by causing cardiomyocyte apoptosis with unclear mechanisms. Akt participates in PA-induced cardiomyocyte apoptosis. GSK-3ß is a substrate of Akt, we investigated its role in PA-induced apoptosis. We reveal that PA inhibits GSK-3ß phosphorylation accompanied by inactivation of Akt in H9c2 cardiomyocytes. We also reveal that inhibition the activity of GSK-3ß by its inhibitor LiCl or knockdown by siRNA significantly attenuates PA-induced cardiomyocyte apoptosis, this suggesting that GSK-3ß plays a pro-apoptotic role. To detect its downstream factors, we analyzed the roles of JNK, p38 MAPK and ß-arrestin 2 (ß-Arr2). Here, we report that GSK-3ß regulate PA-induced cardiomyocyte apoptosis by affecting the distribution of ß-Arr2. PA diminishes the protein level of ß-Arr2 and changes its distribution from nucleus to cytoplasm. Either inhibition of ß-Arr2 by its siRNA or overexpression of its protein level by transfection of ß-Arr2 full-length plasmid promotes PA-induced cardiomyocyte apoptosis, which remind us to focus on the changes of its location. ß-Arr2 siRNA decreased the background level of ß-Arr2 in nucleus in normal H9c2 cells. Overexpression of ß-Arr2 increased cytoplasm level of ß-Arr2 as PA did. While LiCl, the inhibitor of GSK-3ß decreased PA-induced apoptosis, accompany with increased nucleus level of ß-Arr2. Then we concluded that GSK-3ß is closely associated with cardiomyocyte apoptosis induced by PA, it performs its pro-apoptotic function by affecting the location of ß-Arr2. LiCl inhibits PA-induced cardiomyocyte apoptosis, which might provide novel therapeutic for cardiovascular diseases induced by metabolic syndrome.