Abstract 327: Gclm-dependent Gsh Synthesis Regulates Efferocytosis During Atherosclerosis

Abstract

Atherosclerosis, a chronic inflammatory disease characterized by the accumulation of lipids, apoptotic cells, and fibrous elements within the arterial wall, can lead to plaque rupture, one of the most common causes of death in cardiovascular disease (CVD). Rupture prone plaques, characterized by large necrotic cores and thin fibrous caps, lead to acute luminal thrombosis resulting in myocardial infarctions (MI) and strokes. Apoptotic cell (AC) accumulation coupled with deficiency in their clearance, results in necrotic core formation. Macrophages are responsible for clearing ACs through efferocytosis; however, as atherosclerosis progresses efferocytosis is impaired. AC accumulation contributes to the chronic inflammatory response in CVD. Within this response, reactive oxygen species production increases disrupting cellular redox balance. Glutathione (GSH), the main antioxidant in the body, maintains redox balance; however, it fails to do so in atherosclerosis. Reports have shown that a single nucleotide polymorphism (SNP) in the promoter region of the modifier subunit of GCL (GCLM), a rate limiting enzyme responsible for de novo synthesis of GSH, limits its transcription under oxidative stress and is associated with increased risk of MI. Moreover, deletion of GCLM shows an increase in atherosclerotic plaque area and necrotic core, however it remains unknown how GCLM contributes to necrotic core formation and increased CVD incidence. Methods: Bone marrow derived macrophages from WT, Het, and KO GCLM mutant mice and peripheral blood mononuclear cells (PBMCs) from blood donors were isolated and used for efferocytosis and protein assays. PBMCs and atherosclerosis plaque sections were used for SNP genotyping and in situ efferocytosis assays. Results: Efferocytosis impairment correlated with decreased GCLM expression in mice. The presence of a SNP in GCLM significantly decreases efferocytosis in vitro as well as in situ in stage 5 human plaques. Conclusion: These results suggest that loss of GCLM in macrophages impairs primary and secondary efferocytosis in mice. This is corroborated with the inhibition of GSH synthesis. We also observed an impairment in efferocytosis in human macrophages with and without the presence of the risk allele in GCLM.