Defective vascular smooth muscle cell tafazzin impairs mitochondrial function and promotes atherosclerosis in preclinical models.

Atherosclerotic lesions show significant mitochondrial dysfunction but the underlying mechanisms and consequences remain unknown. Cardiolipin is a phospholipid found exclusively in the mitochondrial inner membrane, the site of oxidative phosphorylation. Tafazzin is a trans-acylase that acylates immature monolysocardiolipin to mature cardiolipin. Tafazzin mutations can result in Barth's Syndrome, which is characterised by dilated cardiomyopathy, skeletal myopathy and impaired growth. However, a role for tafazzin in atherosclerosis development has not been previously identified. Here we show that tafazzin expression is decreased in atherosclerotic lesions and specifically in plaque vascular smooth muscle cells (VSMCs). MicroRNA 125a-5p expression is increased in plaques, downregulates tafazzin expression and is induced by oxidised low-density lipoprotein in a NFκB-dependent manner. Silencing tafazzin or overexpression of mutant tafazzin decreases VSMC cardiolipin content and mitochondrial respiration, and promotes apoptosis and atherosclerosis. In contrast tafazzin overexpression increases respiration, protects against apoptosis and increases features of plaque stability. Tafazzin therefore has important effects on VSMC mitochondrial function and atherosclerosis, and is a potential therapeutic target in atherosclerotic disease.