Kim Jin-Ju, Yang Eun-Jeong, Molina David Judith, Cho Sunjoo, Ficarella Maria, Pape Nils, Schiffer Josephin Elizabeth, Njeim Rachel, Kim Stephanie S, Lo Re Claudia, Fontanella Antonio, Kaber Maria, Sloan Alexis, Merscher Sandra, Fornoni Alessia
Katz Family Division of Nephrology and Hypertension, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
Peggy and Harold Katz Family Drug Discovery Center, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
Int J Mol Sci. 2024 Dec 6;25(23):13134. doi: 10.3390/ijms252313134.
Mitochondrial dysfunction is a critical factor in the pathogenesis of Alport syndrome (AS), contributing to podocyte injury and disease progression. Ezetimibe, a lipid-lowering drug, is known to inhibit cholesterol and fatty acid uptake and to reduce triglyceride content in the kidney cortex of mice with AS. However, its effects on lipid droplet (LD) utilization by mitochondria have not been explored. Transmission electron microscopy (TEM) and mitochondrial functional assays (ATP production, mitochondrial membrane potential, and citrate synthase activity) were used to investigate the impact of ezetimibe on LD-mitochondria contact formation and mitochondrial function in KO (AS) and wildtype (WT) podocytes. TEM analysis revealed significant mitochondrial abnormalities in AS podocytes, including swollen mitochondria and reduced cristae density, while mitochondrial function assays showed decreased ATP production and lowered mitochondrial membrane potential. AS podocytes also demonstrated a higher content of LD but with reduced LD-mitochondria contact sites. Ezetimibe treatment significantly increased the number of LD-mitochondria contact sites, enhanced fatty acid transfer efficiency, and reduced intracellular lipid accumulation. These changes were associated with a marked reduction in the markers of lipotoxicity, such as apoptosis and oxidative stress. Mitochondrial function was significantly improved, evidenced by increased basal respiration, ATP production, maximal respiration capacity, and the restoration of mitochondrial membrane potential. Additionally, mitochondrial swelling was significantly reduced in ezetimibe-treated AS podocytes. Our findings reveal a novel role for ezetimibe in enhancing LD-mitochondria contact formation, leading to more efficient fatty acid transfer, reduced lipotoxicity, and improved mitochondrial function in AS podocytes. These results suggest that ezetimibe could be a promising therapeutic agent for treating mitochondrial dysfunction and lipid metabolism abnormalities in AS.
线粒体功能障碍是Alport综合征（AS）发病机制中的一个关键因素，导致足细胞损伤和疾病进展。依折麦布是一种降脂药物，已知它能抑制胆固醇和脂肪酸摄取，并降低AS小鼠肾皮质中的甘油三酯含量。然而，其对线粒体利用脂滴（LD）的影响尚未得到研究。采用透射电子显微镜（TEM）和线粒体功能测定（ATP生成、线粒体膜电位和柠檬酸合酶活性）来研究依折麦布对KO（AS）和野生型（WT）足细胞中LD-线粒体接触形成和线粒体功能的影响。TEM分析显示AS足细胞中线粒体存在明显异常，包括线粒体肿胀和嵴密度降低，而线粒体功能测定显示ATP生成减少和线粒体膜电位降低。AS足细胞中LD含量也较高，但LD-线粒体接触位点减少。依折麦布治疗显著增加了LD-线粒体接触位点的数量，提高了脂肪酸转运效率，并减少了细胞内脂质积累。这些变化与脂毒性标志物（如细胞凋亡和氧化应激）的显著降低有关。线粒体功能得到显著改善，表现为基础呼吸、ATP生成、最大呼吸能力增加以及线粒体膜电位恢复。此外，依折麦布处理的AS足细胞中线粒体肿胀明显减轻。我们的研究结果揭示了依折麦布在增强LD-线粒体接触形成方面的新作用，从而导致更有效的脂肪酸转运、降低脂毒性并改善AS足细胞的线粒体功能。这些结果表明，依折麦布可能是治疗AS中线粒体功能障碍和脂质代谢异常的一种有前景的治疗药物。
