Abstract 12494: Role of Ceramide in Estrogen-Induced Oxidative Stress in Endothelial Cells From Individuals Assigned Male at Birth

Abstract

Compared to cis-males and females, risk for cardiovascular disease (CVD) is elevated in trans-females undergoing estrogen-containing gender affirming therapy. We have previously shown that continuous estrogen treatment of arterioles from healthy adults assigned male at birth promotes microvascular endothelial dysfunction, however the mechanism through which estrogen contributes to endothelial damage remains unknown. Estrogen increases expression of neutral sphingomyelinase (NSmase), an enzyme responsible for the production of ceramides. Ceramides are bioactive sphingolipids that can increase cellular levels of hydrogen peroxide (H 2 O 2 ). Together, we hypothesize that estrogen increases endothelial levels of oxidative stress through NSmase-mediated ceramide formation. Primary male human umbilical vein endothelial cells (HUVECs; pooled from n=3) were seeded in 8-well microscopy plates prior to treatments. Peroxy yellow 1 (PY1) was used to measure changes in endothelial H 2 O 2 . Wells were imaged at 20x and analyzed using ImageJ. Difference between %change in fluorescence ±standard error (SE) is reported, and significance is determined using One-Way ANOVA. Treatment with 17β-estradiol (E2; 100nM, 48hrs) increased endothelial H 2 O 2 production (control, n=6 vs E2, n=7; 13.9±6.3, p=0.038), an effect diminished in the presence of the NSmase inhibitor GW4869 (GW4869, 4μM, 48hrs; control, n=6 vs E2+GW4869, n=7; 1.7±6.3, p=0.78). Signal specificity for H 2 O 2 was confirmed with PEG-catalase treatment (500U/ml, 48hrs; control, n=6 vs E2+catalase, n=3; 2.3±7.9, p=0.77). Together, these results suggest that estrogen increases oxidative stress in endothelial cells isolated from individuals assigned male at birth which can be prevented through inhibition of the ceramide-forming enzyme NSmase. This work offers mechanistic insight into how estrogen containing gender affirming therapy may potentially contribute to endothelial damage and increase CVD risk in trans-females.