Inhibition of Noncanonical Ca2+ Oscillation/Calcineurin/GSK-3β Pathway Contributes to Anti-Inflammatory Effect of Sigma-1 Receptor Activation

Abstract

Further understanding the mechanism for microglia activation is necessary for developing novel anti-inflammatory strategies. Our previous study found that the activation of sigma-1 receptor can effectively inhibit the neuroinflammation, independent of the canonical mechanisms, such as NF-κB, JNK and ERK inflammatory pathways. Thus, it is reasonable that an un-identified, non-canonical pathway contributes to the activation of microglia. In the present study, we found that a sigma-1 receptor agonist of 2-morpholin-4-ylethyl 1-phenylcyclohexane-1-carboxylate (PRE-084) suppressed lipopolysaccharide (LPS) elevated nitric oxide (NO) content in BV-2 microglia culture supernatant and LPS-raised mRNA levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), inducible nitric oxide synthase (iNOS) in BV-2 microglia. Moreover, PRE-084 alleviated LPS-increased Ser 9 de-phosphorylation of glycogen synthase kinase-3 beta (GSK-3β), LPS-elevated catalytic activity of calcineurin, and LPS-raised percent and frequency of Ca²⁺ oscillatory BV-2 cells. We further found that the inhibitory effect of PRE-084 was reversed by a calcineurin activator of chlorogenic acid and a GSK-3β activator of pyrvinium. Moreover, an IP₃ receptor inhibitor of 2-aminoethoxydiphenyl borate mimicked the anti-inflammatory activity of PRE-084. Thus, we identified a noncanonical pro-neuroinflammary pathway of Ca²⁺ oscillation/Calcineurin/GSK-3β and the inhibition of this pathway is necessary for the anti-inflammatory activity of sigma-1 receptor activation.

Keywords: Ca2+ oscillation; Calcineurin; Glycogen synthase kinase-3 beta; Neuroinflammation; Sigma-1 receptor.