Abstract 8963: Role of Caveolin-Centered Adiponectin Signalsome and Neutral Ceramidase in Adiponectin's Anti-Inflammatory, Anti-Oxidative and Anti-Nitrative Signaling
Endothelial and vascular protective actions of adiponectin (APN) are well-recognized, but its underlying transmembrane and intracellular signaling remain largely unknown. Recently, we demonstrated that caveolin plays an essential role in the formation of a membrane-situated APN signalsome containing adiponectin receptor (AdipoR), APPL1, and adenylate cyclase (AC). However, the significance of this signalsome in APN vascular biology has not been investigated. Moreover, a very recent study suggested that AdipoR may function as a neutral ceramidase. However, the pathological importance of APN-activated ceramidase in APN’s vascular protective action remains completely unknown. Our current study investigated the relationship between caveolin-1 (Cav1) and ceramidase in APN’s anti-inflammatory, anti-oxidative, and anti-nitrative actions. Pre-treatment of HUVECs with APN (2 µg/ml) significantly increased ceramidase activity (3.7-fold, P<0.01), and decreased TNFα-induced ICAM-1 expression (P<0.05), iNOS/NADPH oxidase expression (P<0.01), and NO/superoxide/peroxynitrite overproduction (P<0.01). These indicators of APN biological function were either markedly reduced (P<0.001) or completely lost in Cav1 knockdown cells. Neutral ceramidase knockdown virtually abolished the effect of APN upon TNFα-induced ICAM-1 expression, but only modestly inhibited the effect of APN upon TNFα-induced iNOS/NADPH oxidase expression or NO/superoxide/peroxynitrite overproduction. In contrast to APPL1 and AC, no Cav1/ceramidase interaction was detected during basal conditions, indicating the absence of ceramidase from the APN signalsome. However, Cav1/ceramidase complex was clearly detected when HUVECs were stimulated with APN. Finally, knockdown of AdipoR1 or both AdipoR1/R2 respectively markedly and completely abolished APN activation of ceramidase. These results demonstrate for the first time that the Cav1-centered APN signalsome plays an essential role in mediating APN’s vascular biological actions. Moreover, these results support that APN-induced Cav1-dependent recruitment of ceramidase to the APN signalsome is responsible for APN’s anti-inflammatory effects.
- © 2011 by American Heart Association, Inc.