Abstract 109: Adiponectin Inhibits TNF-a-Induced Vascular Inflammatory Response via Caveolin-Mediated Ceramidase Recruitment and Activation

Anti-inflammatory and vascular protective actions of adiponectin (APN) are well-recognized. However, many fundamental questions remain unanswered. The current study attempted to identify the APN receptor subtype responsible for APN’s vascular protective action, and investigate the role of ceramidase activation in APN anti-inflammatory signaling. Wild type (WT) or gene manipulated HUVEC were treated with TNFα in the presence and absence of APN. The effect of APN on TNFα-induced inflammatory and oxidative/nitrative stress was determined. In WT HUVEC, APN significantly reduced TNFα-induced ICAM-1 expression and attenuated TNFα-induced superoxide and peroxynitrite formation (P<0.01). These anti-inflammatory actions were virtually abolished by AdipoR1-, but not AdipoR2-, knockdown (KD). Treatment with APN significantly increased neutral ceramidase (nCDase) activity (3.7-fold, P<0.01). AdipoR1-KD markedly (P0.05), reduced APN-induced nCDase activation. More importantly, siRNA mediated nCDase-KD markedly blocked the effect of APN upon TNFα-induced ICAM-1 expression (P0.05), and modestly inhibited APN anti-inflammatory effect (P87% of APN-induced nCDase activation was lost. Whereas APN treatment failed to inhibit TNFα-induced ICAM-1 expression, treatment with S1P or SEW (S1P receptor agonist) remained effective in Cav1-KD cells in reducing TNFα-induced ICAM-1 expression (P<0.01). AdipoR1 and Cav1 co-localized and co-precipitated in HUVECs. APN treatment did not affect this interaction. Moreover, re-expression of WT Cav1 in Cav1-KD cells restored nCDase activation in response to APN (P<0.01 vs. vehicle), whereas re-expression of a mutated Cav1 blocking AdipoR1/Cav1 interaction failed to restore APN-mediated nCDase activation. Finally, there is weak basal Cav1/nCDase interaction, which significantly increased following APN treatment. These results demonstrate for the first time that APN inhibits TNFα-induced inflammatory response via Cav1-mediated ceramidase recruitment and activation in an AdipoR1- dependent fashion.