Macrophage mitochondrial damage from StAR transport of 7-hydroperoxycholesterol: implications for oxidative stress-impaired reverse cholesterol transport

Abstract

StAR family proteins in vascular macrophages participate in reverse cholesterol transport (RCT). We hypothesize that under pathophysiological oxidative stress, StARs will transport not only cholesterol to macrophage mitochondria, but also pro-oxidant cholesterol hydroperoxides (7-OOHs), thereby impairing early-stage RCT. Upon stimulation with dibutyryl-cAMP, RAW264.7 macrophages exhibited a strong time-dependent induction of mitochondrial StarD1 and plasma membrane ABCA1, which exports cholesterol. 7α-OOH uptake by stimulated RAW cell mitochondria (like cholesterol uptake) was strongly reduced by StarD1 knockdown, consistent with StarD1 involvement. Upon uptake by mitochondria, 7α-OOH (but not redox-inactive 7α-OH) triggered lipid peroxidation and membrane depolarization while reducing ABCA1 upregulation. These findings provide strong initial support for our hypothesis.

Keywords: 1-palmitoyl-2-sn-glycero-3-phosphocholine; 3-(4,5-dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium bromide; 3β-hydroxycholest-5-ene-7α-hydroperoxide; 4,4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-diaza-s-inda-cene-3-undecanoic acid; 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethyl-benzimidazolylcarbocyanine iodide; 7α-OH; 7α-OOH; ABCA1; ATP binding cassette transporter A1; C11-BODIPY; ChOOH(s); Cholesterol hydroperoxide; JC-1; MTT; Macrophage; Oxidative stress; PBS; POPC; Reverse cholesterol transport; SUV(s); StAR protein; StarD1; StarD4; cholest-5-ene-3β,7α-diol; cholesterol hydroperoxide(s); db-cAMP; dibutyryl-cAMP; phosphate-buffered saline; small unilamellar vesicle(s); type-1 steroidogenic acute regulatory domain protein; type-4 steroidogenic acute regulatory domain protein.