Redox regulation in human endothelial cells: a critical role for the glycocalyx in mechanotransduction of fluid shear stress

Abstract

Redox status in endothelial cells (EC) is focally regulated by fluid shear stress (FSS) forces acting on the vessel lumen. Notably, endogenous antioxidant genes targeted by the redox sensitive transcription factor nuclear factor E2-related factor 2 (Nrf2) are upregulated by unidirectional (US) FSS. The glycocalyx (GCX), a meshwork of glycosaminoglycans, is prominent in atheroprotected EC but scarce in atherosusceptible EC regions, and a prerequisite for FSS induced nitric oxide and reactive oxygen species generation. In this study, we investigate the role of the GCX as a modulator of redox signaling in human EC (HUVEC) subjected to either US (15 dynes/cm2) or oscillatory (±5 dynes/cm2, 1 Hz) shear for 48 h in microfluidic slides (Ibidi GmbH). The sialic acid (SA) component of the GCX and expression of heme oxygenase-1 (HO-1) were differentially regulated by US and OS compared to static cultures. Removal of SA with neuraminidase (2U/ml, 30 min) prior to US exposure abrogated HO-1 induction and enhanced mitochondrial superoxide in response to FSS. These findings demonstrate that FSS-sensitive Nrf2 signaling is dependent on mechanotransduction through the GCX, and restoration of the GCX may normalise redox homeostasis in atheroprone vascular regions.