TNFR2‐mediated Survival via Orai1‐3‐dependent Calcium Influx in Compensated Cardiac Hypertrophy

Abstract

Compensated cardiac hypertrophy (CH) is associated with the emergence of Orai1-3 voltage- and store-independent Ca2+ entry activated by Arachidonic Acid (AA). Our objectives were to determine Orai1-3 activating pathways and to evaluate the protective potential of Orai1-3 to limit transition to heart failure (HF). We considered tumor necrosis factor α (TNFα) as a stimulatory candidate since it is a known enhancer of cytosolic phospholipase A2 (cPLA2) activity and a major component of the inflammatory response that develops with CH. We performed Ca2+ imaging studies and measure Orai1-3-dependent Ca2+ influx on adult rat cardiomyocytes (CM) which developed hypertrophy in response to either in-vitro or in-vivo chronic treatment with isoproterenol. Orai1-3 were modulated using pharmacological inhibitor in-vitro or intra-cardiac delivery of Orai1 or 3 silencing RNA in-vivo. We show that TNFα enhances Orai-dependent Ca2+ influx in hypertrophic CM via the TNFR2 pathway as attested by inhibition with neutralizing anti-TNFR2 antibodies but insensitivity to anti-TNFR1 antibodies. TNFα activation of Orai-dependent Ca2+ influx is impaired upon incubation with a cPLA2 inhibitor or a lipoxygenase inhibitor, highlighting the role of AA synthesis and further lipoxygenase-dependent metabolism. Finally, TNFR2-induced activation of Orai1-3-dependent Ca2+ influx increases survival of hypertrophic CM to oxidative stress. Our study highlights a close interplay between early inflammation and adaptative Orai1-3-dependent Ca2+ influx. These data further recommend identification of pharmacological interventions targeting Orai1-3 to limit transition to HF.