Abstract 1159: Critical Role of Caveolin-3 in Adiponectin Transmembrane Signaling and Cardioprotection
Impaired adiponectin (APN) production/signaling plays a causative role in type 2 diabetic cardiac injury. However, how hyperglycemia/hyperlipidemia (HG/HL) adversely impacts APN signaling is unclear. We recently demonstrated that APN receptor 1 (ADPR1) colocalizes and directly interacts with caveolin-3 (CAV3). However, the biological/pathological role of this novel bi-protein interaction remains completely unknown. Neonatal rat cardiomyocytes were cultured in normal control (NC) or HG/HL culture medium for 24 or 72h. Cav3/APNR1 expression and interaction, sensitivity to simulated ischemia/reperfusion (SI/R, 5h/6h), and efficacy of APN protection against SI/R injury were determined. HG/HL had no significant effect on APNR1 expression. Short-time HG/HL (24h) modestly increased (+1.45-fold vs. NC, P<0.05) whereas long-time HG/HL (72h) significantly reduced Cav3 expression (61±3.4% of NC, P<0.01) and Cav3/APNR1 interaction. Interestingly, short-time HG/HL enhanced protective efficacy of APN in SI/R cells (P<0.05 vs. NC) whereas long-time HG/HL significantly blunted protective efficacy of APN (caspase-3 activity: 32±2.5% reduction vs. 51±3.4% reduction in NC; LDH release: 27±2.6% reduction vs. 59±3.0% reduction in NC, P<0.01). To determine the biologic significance of Cav3/APNR1 interaction in APN transmembrane signaling, and to obtain direct evidence supporting a cause-effect relationship in reduced Cav3/APNR1 interaction and blunted APN cardioprotection, the effect of APN on AMPK activation, SI/R-induced oxidative/nitrative stress and cell death were compared in adult cardiomyocytes isolated from wild type littermates (WT) and Cav3−/− mice. In cells from WT mice, APN caused 3.1-fold increase in AMPK phosphorylation and 61±4.1% and 58±4.1% reduction in SI/R-induced peroxynitrite formation and LDH release (P<0.01). However, in cells from Cav3−/− mice, APN failed to activate AMPK. Moreover, the anti-oxidant/anti-nitrative and cardioprotective effects of APN in SI/R cells were virtually abolished in Cav3−/− cardiomyocytes (P>0.05 vs. vehicle). These results provided the first evidence that Cav3/APNR1 interaction plays a critical role in APN transmembrane signaling and anti-ischemic/cardiac protection.
This research has received full or partial funding support from the American Heart Association, Great Rivers Affiliate (Delaware, Kentucky, Ohio, Pennsylvania & West Virginia).