Cardiolipin Remodeling by ALCAT1 Links Oxidative Stress and Mitochondrial Dysfunction to Cellular Senescence

Abstract

IntroductionCardiolipin is a major mitochondrial phospholipid that is required for ATP production, autophagy/mitophagy, and mitochondrial biogenesis. ALCAT1 promotes cardiolipin peroxidation by catalyzing pathological remodeling of cardiolipin with aberrant fatty acyl chains commonly found in aging, rendering cardiolipin highly sensitive to lipid oxidation by reactive oxygen species (ROS). Oxidized cardiolipin not only causes mitochondrial dysfunction, but also becomes a major source of ROS as lipid peroxides, further exacerbating oxidative stress. Recent development in the field has demonstrated a causative role of cellular senescence in aging and aging related diseases. However, the molecular mechanisms that promote cellular senescence in aging and aging‐related diseases remains elusive.ObjectiveTo determine whether oxidative stress and mitochondrial dysfunction induced by ALCAT1 link aberrant cardiolipin remodeling to cellular senescenceMethodsAdult C57BL/6 wild‐type and ALCAT1 Knockout (KO) mice were used for the studies. Primary vascular smooth muscle cells (VSMC) were isolated and cultured using standard protocols. Young cells were at passage 3 (P3) and old cells were at passage 11 (P11). Senescence associated beta galactosidase (SAβ‐Gal) and aconitase activity were used as biomarkers for cellular senescence and oxidative stress respectively. Cellular bioenergetics were assessed using a seahorse XF24 following treatment with or without xanthine/xanthine oxidase, a combination that generates superoxide. Advanced confocal live cell imaging was used to determine and monitor changes in mitochondrial dynamics, mitophagy, mtDNA, and mitochondrial membrane potential following treatment with hydrogen peroxide. TMRM, mitoTracker Green FM and mitoTracker Red, LysoTracker Green, Hoechst, and PicoGreen were used to label mitochondrial membrane potential, mitochondria, lysosome, nucleus, and mtDNA respectively. Lipid peroxidation products were quantified calorimetrically with a malondialdehyde (MDA) assay kit.ResultsWild‐type VSMC at P11 demonstrated a pronounced SAβ‐Gal staining, significant loss of aconitase activity and mitophagy function, decreased mtDNA, impaired mitochondrial function, and a significant increase in lipid peroxidation products.ConclusionALCAT1 KO protected against onset of cellular senescence by reducing sensitivity to lipid oxidation, which preserved mitochondrial function, mitophagy, and mtDNA. Taken together, our work puts forward a possible potential role of ALCAT1 in promoting cellular senescence.Support or Funding InformationNIH (2R01DK076685‐06A1), American Diabetes Association (1‐14‐BS‐185), the Barth Syndrome Foundation, and support from a NIH T32 training grant through the Barshop Institute's Biology of Aging T32 AG021890 (which has been supporting K.S.M since joining the Shi Lab in May 2016).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.