Anti-inflammatory effects of lipoic acid through inhibition of GSK-3β in lipopolysaccharide-induced BV-2 microglial cells

Abstract

Activated microglial cells play an important role in immune and inflammatory responses in CNS and play a role in neurodegenerative diseases. We examined the effects of lipoic acid (LA) on inflammatory responses of BV-2 microglial cells activated by lipopolysaccharide (LPS), and explored the underlying mechanisms of action of LA. BV-2 cells treated with LPS showed an up-regulation of mRNA of the pro-inflammatory molecules, inducible nitric oxide synthase (iNOS). LA suppressed the expression of iNOS and furthermore, LPS-induced production of nitrite. Moreover, LA suppressed the nuclear translocation of RelA, a component of nuclear factor-kappa B (NF-κB) that contains transcriptional activator domain for LPS. The mechanisms of LA-mediated anti-inflammatory effects on microglia remain unknown, and we suggested an involvement of Akt/glycogen synthase kinase-3β (GSK-3β) phosphorylation. The results showed that inhibitor of phosphatidylinositol 3-kinase prevented LA-mediated suppression of LPS induction of RelA and expression of iNOS. Furthermore, these inflammatory actions were prevented by GSK-3β inhibitors. These data demonstrate a role for LA as a chemical modulator of inflammatory responses by microglia, and thus may be a therapeutic strategy for treating neurodegenerative diseases with an inflammatory component.

Keywords: Akt; GSK-3β; IL-1β; Inflammation; LA; LPS; LY; LY294002; LiCl; Lipoic acid; Microglia; NF-κB; TNFα; glycogen synthase kinase-3β; iNOS; inducible nitric oxide synthase; interleukin-1β; lipoic acid; lipopolysaccharide; lithium chloride; nuclear factor-kappa B; tumor necrosis factor α.