Hypertensive stretch regulates endothelial cell inflammation and apoptosis through ceramide metabolism

Abstract

Hypertension and cardiovascular disease (CVD) are associated with elevated plasma levels of ceramides (Cer), a type of membrane sphingolipids (SPLs). Increased cellular Cer levels are known to cause vascular endothelial cell (EC) dysfunction. However, Cer metabolism changes due to EC exposure to high-magnitude “hy-pertensive” cyclic stretch (HCS) and their role in EC dysfunction are poorly defined. Cultured human ECs exposed to HCS (15% elon¬gation at 1 Hz, 24 h) exhibited increased oxidative stress, upreg¬ulation of genes for cytokines and leukocyte adhe¬sion molecules, increased inflammatory response to a low concentration of tumor necrosis factor-α, and increased apoptosis compared to ECs exposed to “normotensive” CS (NCS; 5% elongation at 1 Hz, 24 h). Lipidomics analysis of EC pellets at 4 or 24 h of CS detected no differ¬ence in Cer levels and significantly higher sphingomyelin (SM) levels at 24 h of HCS compared to NCS. Cer immunostaining showed significantly higher Cer levels at both the perinuclear and peripheral subcellular regions in HCS compared to the corresponding regions in NCS. HCS signifi¬cantly increased the concentrations of certain long-chain Cer in the extracellular media compared to NCS. Phar¬macological inhibition of key enzymes in Cer biosynthesis, i.e., de novo synthesis and SM hy¬drolysis pathways, significantly inhibited HCS-induced EC inflammation and apoptosis, sug¬gesting that Cer generated from SM, via the sphingomyelinase family of enzymes, and accumulated at specific sub¬cellular compartments may be respon¬sible for the HCS-induced EC dysfunction. In summary, Cer act as mechanotransducers that connect hypertensive stretch to EC inflamma-tion and apoptosis, and promote CVD.