Differential chemoattractant response in adipocytes and macrophages to the action of acylation stimulating protein

Obesity is characterized by chronic low-grade inflammation with increased adipose tissue pro-inflammatory cytokine production. Acylation stimulating protein (ASP) stimulates triglyceride synthesis and glucose transport via its receptor C5L2. Circulating ASP is increased in obesity, insulin resistance and metabolic syndrome. The present study examines the effects of normal (50 nM), high physiological (200 nM) and pathological (600 nM) levels of ASP on inflammatory changes in 3T3-L1 adipocytes and J774 macrophages and the underlying mechanisms involved. Treatment with ASP for 24 h increased monocyte chemoattractant protein-1 (MCP1, 800%, P < 0.001) and keratinocyte-derived chemokine (KC, >150%, P < 0.01) secretion in adipocytes in a dose-dependent manner, with no effect on IL-6 or adiponectin. In macrophages, ASP had no effect on these cytokines. C5a, a ligand for C5L2 and C5aR receptors, differed from ASP. Macrophage-adipocyte coculture increased MCP-1 and adiponectin secretion, and ASP further enhanced secretion (P < 0.001 and P < 0.05, respectively) at doses of 50 nM and 200 nM. ASP increased Ser468 and Ser536 phosphorylation of p65 NFκB in a time- and concentration-dependent manner (P < 0.05) as well as phosphorylation of Akt Ser473 (p = 0.02). ASP and insulin stimulations of Ser536 p65 NFκB phosphorylation were comparable (both p < 0.05) but not additive. Both inhibition of PI3kinase (with wortmannin) and NFκB (with BAY