Mitochondrial 3243A\u2009>\u2009G mutation confers pro-atherogenic and pro-inflammatory properties in MELAS iPS derived endothelial cells

Nicole Min Qian Pek,Jeremy Kah Sheng Pang,Beatrice Xuan Ho,Yong Fan,Boon-Seng Soh,Henry He Yang,Shi-Yan Ng,Jin-Hui Hor,Omer An,Yang Yu,Qian Hua Phua

doi:10.1038/s41419-019-2036-9

Abstract

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a mitochondrial disorder that is commonly caused by the m.3243A > G mutation in the MT-TL1 gene encoding for mitochondrial tRNA(Leu(UUR)). While clinical studies reported cerebral infarcts, atherosclerotic lesions, and altered vasculature and stroke-like episodes (SLE) in MELAS patients, it remains unclear how this mutation causes the onset and subsequent progression of the disease. Here, we report that in addition to endothelial dysfunction, diseased endothelial cells (ECs) were found to be pro-atherogenic and pro-inflammation due to high levels of ROS and Ox-LDLs, and high basal expressions of VCAM-1, in particular isoform b, respectively. Consistently, more monocytes were found to adhere to MELAS ECs as compared to the isogenic control, suggesting the presence of an atherosclerosis-like pathology in MELAS. Notably, these disease phenotypes in endothelial cells can be effectively reversed by anti-oxidant treatment suggesting that the lowering of ROS is critical for treating patients with MELAS syndrome.

Highlights

Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome is one of the most common maternally inherited mitochondrial disorders with 80% of MELAS patients carrying the m.3243A > G mutation in the MT-TL1 gene that encodes for tRNA (Leu-UUR)[1,2]
endothelial cells (ECs) differentiation from MELAS induced pluripotent stem cells (iPSCs) was less efficient, the ECs derived from all three human pluripotent stem cells (hPSCs) lines were shown to express specific endothelial markers such as CD31, endothelial nitric oxide synthase, vonWillebrand Factor, Ve-Cadherin (VeCAD) and vascular cell adhesion molecule-1 (VCAM-1), both at the transcript as well as at the protein levels (Fig. 1d, e)
As clinical manifestations of mitochondrial disorders are typically caused by dysregulations of energy production, we examined the expression levels of several genes encoding for various mitochondrial complexes in the electron transport chain (ETC) such as ATP synthase subunit beta (ATP5B), cytochrome c oxidase subunit 5B (COX5B), succinate dehydrogenase complex subunit A (SDHA), NADH:ubiquinone oxidoreductase subunit A1 (NDUFA1), NADH-ubiquinone oxidoreductase chain 1 and 5 (MT-ND1and MT-ND5)

Summary

Introduction

Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome is one of the most common maternally inherited mitochondrial disorders with 80% of MELAS patients carrying the m.3243A > G mutation in the MT-TL1 gene that encodes for tRNA (Leu-UUR)[1,2]. Transfer RNA (Leu-UUR) plays critical roles in the translation of proteins essential for the assembly and function of mitochondrial complexes in the electron transport chain. The translational defects caused by the m.3243A > G gene mutation disrupts the oxidative phosphorylation function of the electron transport chain. An end-product of glycolysis, eventually accumulates and leads to lactic acidosis that is observed in MELAS patients[4]. Resultant inefficient energy production to cope with energetic stress has been associated with oxidative stresses found in MELAS5

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Results

Conclusion