Adiponectin Inhibits Tumor Necrosis Factor-α–Induced Vascular Inflammatory Response via Caveolin-Mediated Ceramidase Recruitment and ActivationNovelty and Significance

Rationale: Anti-inflammatory and vascular protective actions of adiponectin are well recognized. However, many fundamental questions remain unanswered. Objective: The current study attempted to identify the adiponectin receptor subtype responsible for adiponectin’s vascular protective action and investigate the role of ceramidase activation in adiponectin anti-inflammatory signaling. Methods and Results: Adiponectin significantly reduced tumor necrosis factor (TNF)α–induced intercellular adhesion molecule-1 expression and attenuated TNFα-induced oxidative/nitrative stress in human umbilical vein endothelial cells. These anti-inflammatory actions were virtually abolished by adiponectin receptor 1 (AdipoR1-), but not AdipoR2-, knockdown (KD). Treatment with adiponectin significantly increased neutral ceramidase (nCDase) activity (3.7-fold; P 87% of adiponectin-induced nCDase activation was lost. Whereas adiponectin treatment failed to inhibit TNFα-induced intercellular adhesion molecule-1 expression, treatment with sphingosine-1-phosphate or SEW (sphingosine-1-phosphate receptor agonist) remained effective in Cav1-KD cells. AdipoR1 and Cav1 colocalized and coprecipitated in human umbilical vein endothelial cells. Adiponectin treatment did not affect this interaction. There is weak basal Cav1/nCDase interaction, which significantly increased after adiponectin treatment. Knockout of AdipoR1 or Cav1 abolished the inhibitory effect of adiponectin on leukocyte rolling and adhesion in vivo. Conclusions: These results demonstrate for the first time that adiponectin inhibits TNFα-induced inflammatory response via Cav1-mediated ceramidase recruitment and activation in an AdipoR1-dependent fashion.