Short-term Treatment of RAW264.7 Macrophages with Adiponectin Increases Tumor Necrosis Factor-α (TNF-α) Expression via ERK1/2 Activation and Egr-1 Expression

Abstract

Adiponectin is an adipokine with potent anti-inflammatory properties. However, the mechanisms by which adiponectin suppresses macrophage function are not well understood. Treatment of RAW264.7 macrophages with adiponectin for 18 h decreased lipopolysaccharide (LPS)-stimulated tumor necrosis factor-␣ (TNF-␣) production. Here we demonstrate that globular adiponectin (gAcrp) initially increased TNF-␣ expression in RAW264.7 macrophages; this TNF-␣ then contributed to increased expression of interleukin-10, which in turn was required for the development of tolerance to subsequent LPS exposure. gAcrp-mediated increases in TNF-␣ mRNA accumulation were associated with increased TNF-␣ promoter activity. gAcrp increased the DNA binding activity of both Egr-1 and NFB; mutation of either the Egr-1 or NFB binding sites in the TNF-␣ promoter decreased gAcrp-stimulated promoter activity. Further, co-transfection with either dominant negative Egr-1 or the IB super-repressor prevented gAcrp-stimulated TNF-␣ promoter activity. gAcrp also increased Egr-1 promoter activity, mRNA accumulation, and DNA binding activity. Inhibition of ERK1/2 with U0126 potently suppressed gAcrp-stimulated Egr-1 promoter activity, as well as TNF-␣ promoter activity. In summary, these data demonstrate that adiponectin initially increases TNF-␣ production by macrophages via ERK1/ 23 Egr-1 and NFB-dependent mechanisms; these increases in TNF-␣ in turn lead to increased expression of interleukin-10 and an eventual dampening of LPS-mediated cytokine production in macrophages.

Suppression of Lipopolysaccharide-stimulated Tumor Necrosis Factor-α Production by Adiponectin Is Mediated by Transcriptional and Post-transcriptional Mechanisms

“…Truncations of the promoter to Ϫ161, deleting two B sites as well as the Egr-1 site, decreased TNF-␣ promoter/Luc activity by 70% over the 4-h treatment with gAcrp. This is consistent with previous data demonstrating a key role for Egr-1 and NFB in mediating increased TNF-␣ expression after 1-4-h exposure to gAcrp (12). However, after 24 h, TNF-␣ promoter/Luc activity was not affected by removal of these promoter elements (Fig.…”

“…Phosphorylation of ERK1/2 and p38 MAPK and the quantity of IB were measured by Western blot analysis as described previously (12). Immunoreactive TTP was also measured by Western blot and normalized to Hsc70 as a loading control.…”

“…Interestingly several recent reports demonstrate that short term treatment of macrophages with adiponectin first increases the expression of inflammatory cytokines, such as TNF-␣ and interleukin (IL)-6 (12, 13). Continued exposure to adiponectin then promotes the expression of anti-inflammatory mediators, such as IL- 10 (12, 14), and the eventual development of tolerance to proinflammatory signals, including resistance to subsequent challenge with the tolllike receptor 4 ligand, LPS, and the toll-like receptor 3 ligand, poly(I⅐C) (12,13).…”

Interleukin-10 attenuates vascular responses to endothelin-1 via effects on ERK1/2-dependent pathway

“…IL-10 also suppresses cyclooxgenase-2 expression by downregulation of p38 MAPK and ERK2 (31). Moreover, several reports have shown that IL-10 inhibits ERK1/2 activity and that this is important, for example, for the downregulation of polymorphonuclear neutrophil functions and CD40-mediated induction of IL-1␤ and TNF-␣ synthesis by monocytes (6,33,39).…”

Trovafloxacin Potentiation of Lipopolysaccharide-Induced Tumor Necrosis Factor Release from RAW 264.7 Cells Requires Extracellular Signal-Regulated Kinase and c-Jun N-Terminal Kinase

“…For example, long-term ethanol treatment increases LPS-induced TNF mRNA expression and TNF protein release by macrophages in an ERK-dependent manner (Kishore et al, 2002;Pritchard and Nagy, 2005). In addition, both pro-and anti-inflammatory effects of adiponectin on LPS-induced TNF release in RAW cells are mediated through ERK-dependent signaling (Park et al, 2007;Huang et al, 2008). ERK signaling plays a significant role in experimental models of inflammatory liver injury from alcohol or bile acid exposure (Mandrekar and Szabo, 2009;Allen et al, 2010).…”