The Pyrazole Derivative BTP2 Attenuates IgG Immune Complex-induced Inflammation.

Store-operated calcium entry (SOCE) is the most common mode of calcium influx in non-excitable cells, including immune cells. The two STIM isoforms mediate SOCE as well as Fc receptor (FcR)-downstream activation of macrophages and mast cells-which appears to be relevant in vivo, in models of antibody-dependent tissue injury and allergy. Hence, the pathway of SOCE may be a therapeutic target for treatment of immune complex (IC)-mediated autoimmunity and allergic asthma. The pyrazole derivative, BTP2 is an efficient inhibitor of SOCE, which has already been shown to attenuate allergic inflammation. However, its effect on Fc gamma receptor (FcγR) signaling and IC-induced tissue injury had not yet been studied. Here, we show that BTP2 is a potent inhibitor of SOCE in primary macrophages, blocking FcγR-mediated responses. To investigate the effect of inhibition of SOCE in IC-mediated tissue injury, we induced reverse passive Arthus reaction to IgG immune complexes in the skin and lungs of BTP2- or control-treated mice. Treatment with BTP2 resulted in markedly attenuated inflammation in both the skin and the lungs. Our findings indicate the involvement of SOCE in FcγR-mediated responses in vitro and in vivo and suggest that BTP2-mediated inhibition of SOCE may have a therapeutic potential on IC-mediated autoimmunity.