Abstract 16286: Absence of Fxyd1 is Associated With a Female-specific Pro-inflammatory and Hypercholesterolemic Environment: Implications for Atherosclerosis

Abstract

Introduction: Bioavailability of nitric oxide (NO) is often compromised in early atherosclerosis, driving disease onset. This is usually due to dysfunctional endothelial nitric oxide synthase (eNOS). We have found that the transmembrane protein, FXYD1, is highly concentrated in the caveolae sub-cellular region and is closely associated with eNOS. Our preliminary data suggest that FXYD1 protects eNOS from redox-dependent inactivation. So, we hypothesise that FXYD1 may protect against atherosclerosis. Hypothesis: We aimed to test the role of FXYD1 in a murine model of atherosclerosis Methods: We produced a novel mutant mouse line by cross-breeding FXYD1 heterozygote (FXYD1 +/- ) and apolipoprotein E knock out (ApoE -/- ) mice. FXYD1 -/- /ApoE -/- and FXYD1 +/+ /ApoE -/- littermates were fed a high fat/high cholesterol diet from 6-8 weeks of age for 16 weeks. At sacrifice, blood was taken, and plasma was separated for analysis of cholesterol and pro-inflammatory cytokines using ELISA. The thoracic aorta was isolated and formalin-fixed to assess atherosclerotic plaque development using oil red O stain. Immunoblotting for eNOS expression was performed in heart lysates. Results: Plasma total cholesterol was significantly increased in FXYD1-/-/ApoE-/- female mice (n = 14 compared to FXYD1+/+/ApoE-/- mice (n = 21; p<0.05)). Circulating IL-1β levels were also significantly increased in female FXYD1-/-/ApoE-/- vs. FXYD1+/+/ApoE-/- mice. Despite this, there was no effect on plaque size as determined by oil red O stain of fixed aortae. eNOS protein expression was decreased in heart tissue from FXYD1-/-/ApoE-/- vs. FXYD1+/+/ApoE-/- female mice which may lead to lower NO generation. All of the FXYD1-mediated changes were specific to female mice as we detected no differences in these parameters in littermate males. Conclusions: FXYD1-/- atherosclerotic female mice have higher circulating lipids and pro-inflammatory cytokines, but this does not appear to alter plaque development in the short term. Ongoing studies will determine the effect on plaque stability and role of FXYD1 in lipidomics. FXYD1 appears to have an anti-inflammatory role and may also be involved in cholesterol metabolism or handling. This could provide a novel therapeutic angle for females.