??-ARRESTINS REGULATE LIPOPOLYSACCHARIDE (LPS)-INDUCED SIGNALING AND PROINFLAMMATORY GENE EXPRESSION

Abstract

Previous studies have implicated a role of heterotrimeric Gi proteins in signaling leading to inflammatory mediator production induced by LPS. β-arrestins 1 and 2 alter G protein-coupled receptors signaling. We have reported that in the β-arrestins 2 knockout mouse embryonic fibroblasts, LPS-induced IL-6 production was decreased. We hypothesized that β-arrestins 1 and/or 2 regulate LPS-induced signaling and pro-inflammatory mediator gene expression. siRNA depletion of β-arrestins 1/2 in HEK 293 cells permanently transfected with TLR4, CD14 and MD2 and β-arrestin 2 knockout (KO) mice were employed to investigate the role of β-arrestins in LPS signaling. Our data demonstrate that siRNA induced β-arrestin 2 depletion decreased LPS-induced ERK1/2 activation (37±12%), whereas, β-arrestin 1 depletion had no effect. However, depletion of both β-arrestin 1 and 2 in HEK cells reduced LPS-induced IL-8 expression (46±2% and 39±4% respectively, Figure). LPS-induced TNFα and IL-6 production was significantly decreased (37±11%, 45±10%) in splenocytes from β-arrestin 2 KO mice compared to wild type mice. These data implicate a novel role of β-arrestins in regulating LPS-induced pro-inflammatory gene expression. (Supported by NIH GM27673 and GM67202)FigureData represent means ± SE from three independent experiments. *, p<0.05 compared to basal level; #, p<0.05 compared to LPS-stimulated groups.