Role of 3beta-hydroxysteroid-delta 24 reductase in mediating antiinflammatory effects of high-density lipoproteins in endothelial cells.

OBJECTIVE: The purpose of this study was to investigate the ability of high-density lipoproteins (HDLs) to upregulate genes with the potential to protect against inflammation in endothelial cells. METHODS AND
RESULTS: Human coronary artery endothelial cells (HCAECs) were exposed to reconstituted HDLs (rHDLs) for 16 hours before being activated with tumor necrosis factor-alpha (TNF-alpha) for 5 hours. rHDLs decreased vascular cell adhesion molecule-1 (VCAM-1) promoter activity by 75% (P<0.05), via the nuclear factor-kappa B (NF-kappaB) binding site. rHDLs suppressed the canonical NF-kappaB pathway and decreased many NF-kappaB target genes. Suppression of NF-kappaB and VCAM-1 expression by rHDLs or native HDLs was dependent on an increase in 3beta-hydroxysteroid-Delta 24 reductase (DHCR24) levels (P<0.05). The effect of HDLs on DHCR24 is dependent on SR-BI but not ABCAI or ABCGI. Silencing DHCR24 expression increased NF-kappaB (1.2-fold, P<0.05), VCAM-1 (30-fold, P<0.05), and NF-kappaB p50 (4-fold, P<0.05) and p65 subunits (150-fold, P<0.05). TNF-alpha activation of siDHCR24-treated cells increased expression of VCAM-1 (550-fold, P<0.001) and NF-kappaB (9-fold, P<0.001) that could no longer be suppressed by rHDLs.
CONCLUSIONS: Results suggest that antiinflammatory effects of rHDLs are mediated partly through an upregulation of DHCR24. These findings raise the possibility of considering DHCR24 as a target for therapeutic modulation.