Direct coupling between arachidonic acid-induced Ca 2+ release and Ca 2+ entry in HEK293 cells

Abstract

Arachidonic acid (AA) modulates intracellular Ca 2+ signaling via Ca 2+ release or/and Ca 2+ entry. However, the mechanism underlies either process is unknown; nor is it clear as to whether the two processes are mechanistically linked. By using Fura2/AM, we found that AA induced mobilization of internal Ca 2+ store and an increment in Ca 2+, Mn 2+ and Ba 2+ influx in HEK293 cells. The AA-mediated Ca 2+ signaling was not due to AA metabolites, and insensitive to capacitative Ca 2+ entry inhibitors. Interestingly, isotetrandrine and Gd 3+ inhibited both AA-induced Ca 2+ release and Ca 2+ entry in a concentration-dependent manner without affecting Ca 2+ discharge caused by carbachol, caffeine, or thapsigargin. Additionally, similar pattern of inhibition was observed with tetracaine treatment. More importantly, the three compounds exhibited almost equal potent inhibition of AA-initiated Ca 2+ release as well as Ca 2+ influx. Therefore, this study, for the first time, provides evidence for a direct coupling between AA-mediated Ca 2+ release and Ca 2+ entry.