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

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.

[Steroidogenic acute regulatory protein-related lipid transfer 4 (StarD4) promotes breast cancer cell proliferation and its mechanism]

Oncogene StarD4 had the function of promoting proliferation and metastasis of triple-negative breast cancer (TNBC), but its clinical value and molecular mechanism are unknown. This paper found that StarD4 was highly expressed in cancer tissues of TNBC patients, and higher expression level of StarD4 in TNBC patient resulted in poorer prognosis. Based on transcriptomics of MDA-MB-231 cell model, the results of bioinformatics analysis showed that down-regulated expression level of StarD4 led to overall downregulation of cholesterol-relative genes and significant enrichment of cancer mechanism and pathway. Further analysis and investigation verified that StarD4 might cross-promote the protein stability of receptor ITGA5 through the cholesterol pathway to enhance TNBC progression, which provides guidance for clinical application of TNBC diagnosis and treatment.