Proteomic Analysis of Endothelial Lipid Rafts Reveals a Novel Role of Statins in Antioxidation

As inhibitors of 3-hydroxy-3-methylglutaryl coenzyme
A reductase,
statins have pleiotropic vascular-protective effects, such as anti-inflammatory
and antioxidative effects. We investigated the short-term beneficial
effects of statins on modulating the translocation of lipid-raft-related
proteins in endothelial cells (ECs). Human umbilical vein ECs were
treated with atorvastatin for 30 min or 2 h; lipid-raft proteins were
isolated and examined by quantitative proteome assay. Functional classification
of identified proteins in lipid rafts revealed upregulated antioxidative
proteins; downregulated proteins were associated with inflammation
and cell adhesion. Among proteins verified by Western blot analysis,
endoplasmic reticulum protein 46 (ERp46) showed increased level in
lipid rafts with atorvastatin. Further, atorvastatin inhibited the
activation of membrane-bound NADPH oxidase in both untreated and angiotensin
II-treated ECs, as shown by reduced reactive oxygen species production.
Co-immunoprecipitation and immunofluorescence experiments revealed
that atorvastatin increased the association of ERp46 and Nox2, an
NADPH oxidase isoform, in lipid rafts, thereby inhibiting Nox2 assembly
with its regulatory subunits, such as p47phox and p67phox. Our results
reveal a novel antioxidative role of atorvastatin by promoting the
membrane translocation of ERp46 and its binding with Nox2 to inhibit
Nox2 activity in ECs, which may offer another insight into the pleiotropic
functions of statins.