Cytosolic phospholipase A2 mediates mechanical stretch‐induced apoptosis via caspase‐3 in human renal proximal tubular epithelial (HK‐2) cells

Abstract

Although several studies have been performed investigating the effects of cyclic strain on apoptosis in renal proximal tubular cells, its mechanism to induce apoptosis is not fully understood. Phospholipase A2 (PLA2) is a signaling molecule that regulates arachidonic acid production and participates in inflammatory responses. The aim of this study was to investigate whether cPLA2 could modulate cyclic stretch‐mediated cell death in human renal proximal tubular cells (HK‐2 cells) and to examine the mechanism(s) of any effects observed. Stretch‐induced apoptosis was detected by measuring histone associated DNA fragments using ELISA and caspase assays. The application of cyclic stretch significantly increased apoptosis and caspase‐3 activity in HK‐2 cells. Inhibition of cPLA2 by AACOCF3 and MAFP or by treatment of cPLA2 short interfering RNAs (siRNAs) attenuated both apoptosis and caspase‐3 activation by cyclic stretch, supporting the importance of cPLA2 as a mediator of stretch‐induced apoptosis in renal proximal tubular cells. In addition, inhibition of caspase‐3 prevented stretch‐induced apoptosis. Furthermore, arachidonic acid itself induced time‐ and dose‐dependent increases in capase‐3 activity and apoptosis in HK‐2 cells. These findings suggest that cPLA2‐mediated activation of caspase‐3 plays a key role in cyclic stretch‐induced renal cell apoptosis.