Ceramide Mediates Vascular Dysfunction in Diet-Induced Obesity by PP2A-Mediated Dephosphorylation of the eNOS-Akt Complex

Abstract

Vascular dysfunction that accompanies obesity and insulin resistance may be mediated by lipid metabolites. We sought to determine if vascular ceramide leads to arterial dysfunction and to elucidate the underlying mechanisms. Pharmacological inhibition of de novo ceramide synthesis, using the Ser palmitoyl transferase inhibitor myriocin, and heterozygous deletion of dihydroceramide desaturase prevented vascular dysfunction and hypertension in mice after high-fat feeding. These findings were recapitulated in isolated arteries in vitro, confirming that ceramide impairs endothelium-dependent vasorelaxation in a tissue-autonomous manner. Studies in endothelial cells reveal that de novo ceramide biosynthesis induced protein phosphatase 2A (PP2A) association directly with the endothelial nitric oxide synthase (eNOS)/Akt/Hsp90 complex that was concurrent with decreased basal and agonist-stimulated eNOS phosphorylation. PP2A attenuates eNOS phosphorylation by preventing phosphorylation of the pool of Akt that colocalizes with eNOS and by dephosphorylating eNOS. Ceramide decreased the association between PP2A and the predominantly cytosolic inhibitor 2 of PP2A. We conclude that ceramide mediates obesity-related vascular dysfunction by a mechanism that involves PP2A-mediated disruption of the eNOS/Akt/Hsp90 signaling complex. These results provide important insight into a pathway that represents a novel target for reversing obesity-related vascular dysfunction.

Molecular Biology of Atherosclerosis

“…Ceramide was found to relieve binding of phosphatase PPA2 from an inhibitory cytosolic binding protein and facilitate the direct association of PPA2 with the Akt/eNOS/HSP90 complex. As a result, there was a reduction in the phosphorylation status of eNOS S1177 and S617 and probably Akt as well, together with physical displacement of Akt from the complex (2080). Thus ceramide signaling appears to impair transmission of an insulin signal through Akt to eNOS not by blocking upstream Akt activation but by enhancing phosphatase activity directed at Akt and at least some of its targets.…”

Circulating ceramides are inversely associated with cardiorespiratory fitness in participants aged 54–96 years from the Baltimore Longitudinal Study of Aging

“…Treatments targeting ceramides may be potentially very effective for preventing or treating these conditions (Mielke et al ., 2015). For example, elevated plasma ceramides cause vascular endothelial dysfunction by promoting endothelial cell growth arrest, oxidative stress, senescence and death, disrupting insulin signaling and increasing inflammation (Zhang et al ., 2012; Symons & Abel, 2013). Perhaps through these same mechanisms, ceramides may contribute to the early stages of atherosclerosis (Ichi et al ., 2006; Bismuth et al ., 2008) and the accumulation of ceramide in the myocardium may cause cardiac dysfunction in obese and diabetic individuals, even in the absence of hypertension and myocardial ischemia (Park & Goldberg, 2012).…”

Examining the Role of Insulin in the Regulation of Cardiovascular Health

“…The association with caveolin-1 inhibits eNOS activity [28], whereas association with Hsp90 has been reported to promote eNOS activity [27]. Insulin has been reported to promote Hsp90-eNOS association in bovine endothelial cells, and the disruption of Hsp90-eNOS binding inhibited insulin-stimulated eNOS activation [7,29]. Furthermore, stimulation of human endothelial cells with insulin has been reported to increase transport of the eNOS substrate L-arginine in an Akt-dependent manner [26].…”