Abstract：
Mono-2-ethylhexyl phthalic acid (MEHP) is the most toxic metabolite of the plasticizer di-2-ethylhexyl phthalic acid (DEHP), and studies have shown that MEHP causes serious reproductive effects. However, its exact mechanisms of action remain elusive. In this study, we aimed to investigate the reproductive effects of MEHP and preliminarily explore its underlying molecular mechanisms. We found that TM3 cells gradually secreted less testosterone and intracellular free cholesterol with increasing MEHP exposure. MEHP exposure inhibited lipophagy and the Sirt1/Foxo1/Rab7 signaling pathway in TM3 cells, causing aberrant accumulation of intracellular lipid droplets. Addition of the Sirt1 agonist SRT1720 and Rab7 agonist ML-098 alleviated the inhibition of lipophagy and increased free cholesterol and testosterone contents in TM3 cells. SRT1720 alleviated the inhibitory effect of MEHP on the Sirt1/Foxo1/Rab7 signaling pathway, whereas ML-098 only alleviated the inhibition of Rab7 protein expression by MEHP and had no effect on Sirt1 and Foxo1 protein expression. This suggests that MEHP inhibits lipophagy in TM3 cells by suppressing the Sirt1/Foxo1/Rab7 signaling pathway, ultimately leading to a further decrease in cellular testosterone secretion. This study improves our current understanding of the toxicity and molecular mechanisms of action of MEHP and provides new insights into the reproductive effects of phthalic acid esters.
摘要：
单-2-乙基己基邻苯二甲酸（MEHP）是增塑剂二-2-乙基己基邻苯二甲酸（DEHP）的毒性最强的代谢产物，研究表明，MEHP会引起严重的生殖影响。然而,其确切的作用机制仍然难以捉摸。在这项研究中,我们旨在研究MEHP的生殖效应并初步探讨其潜在的分子机制。我们发现，随着MEHP暴露的增加，TM3细胞逐渐分泌更少的睾丸激素和细胞内游离胆固醇。MEHP暴露抑制TM3细胞的吸脂性和Sirt1/Foxo1/Rab7信号通路,导致细胞内脂滴的异常积累。添加Sirt1激动剂SRT1720和Rab7激动剂ML-098减轻了对脂质吞噬的抑制，并增加了TM3细胞中的游离胆固醇和睾丸激素含量。SRT1720减轻MEHP对Sirt1/Foxo1/Rab7信号通路的抑制作用,而ML-098仅减轻MEHP对Rab7蛋白表达的抑制作用，对Sirt1和Foxo1蛋白表达无影响。这表明MEHP通过抑制Sirt1/Foxo1/Rab7信号通路抑制TM3细胞的吸脂性,最终导致细胞睾酮分泌进一步减少。这项研究提高了我们目前对MEHP的毒性和分子作用机制的理解，并为邻苯二甲酸酯的生殖效应提供了新的见解。
