Adiponectin suppresses macrophage activity via
a number of mechanisms. For example, adiponectin inhibits the proliferation of myelomonocytic progenitor cells, dampens the up-regulation of endothelial adhesion molecules in response to inflammatory signals, suppresses phagocytic activity, as well as reduces LPS-stimulated cytokine production in macrophages.6–8 Chronic ethanol exposure decreases adiponectin concentrations in rats and mice9, 10; treatment of mice with adiponectin during chronic ethanol exposure prevents the development of liver injury, decreasing both steatosis and TNF-α expression in the liver.10 Although the mechanisms for these therapeutic effects of adiponectin are not well understood, the decrease NVP-AUY922 mouse in steatosis is most likely related to the critical role of adiponectin in regulation of glucose and lipid homeostasis. Furthermore, we have previously reported that adiponectin treatment normalizes LPS-induced TNF-α production in primary cultures of Kupffer cells after chronic ethanol exposure,9 suggesting that adiponectin therapy may directly suppress the pro-inflammatory activity this website of
Kupffer cells after chronic ethanol feeding. Recent data suggest an important link between adiponectin and IL-10, two critical anti-inflammatory mediators that may contribute to ethanol-induced liver injury. For example, adiponectin induces the expression of IL-10 messenger RNA (mRNA) and protein in cultured macrophages.11, 12 Expression of IL-10 is required for the anti-inflammatory effects of adiponectin in RAW 264.7 macrophages because immunoneutralization of IL-10 prevents gAcrp-mediated desensitization to LPS.11 IL-10 mediates its anti-inflammatory functions via induction of IL-10–inducible genes, including heme oxygenase-1 (HO-1) and suppressor of cytokine signaling 上海皓元医药股份有限公司 3 (SOCS3).2 Induction of these genes involves the activation of STAT3
signaling pathways. Adiponectin and HO-1 pathways also interact. For example, increased adiponectin expression is associated with increased expression of HO-1 and enhanced cardiac protection in diabetic rats.13 Furthermore, induction of HO-1 increases adiponectin expression in Zucker rats, leading to decreased TNF-α expression and reduced adipogenesis.14 HO-1 has anti-apoptotic, anti-inflammatory, and anti-proliferative properties.15 There is a growing appreciation that HO-1, in particular, is an important downstream mediator of the anti-inflammatory effects of IL-10 in macrophages.15 HO-1, and its downstream mediator carbon monoxide, both inhibit LPS-induced expression of pro-inflammatory cytokines and increase LPS-induced expression of IL-10 in macrophages.15 Induction of HO-1 prevents ethanol-induced oxidative damage in cultured hepatocytes16 and also decreases complement-mediated injury in the endothelium.