Department of Cell Biology & Institute of Biomedicine, College of Life Science and Technology, Jinan University, Guangzhou 510632, China; Guangdong Provincial Key Laboratory of Bioengineering Medicine, Jinan University, Guangzhou 510632, China.
Department of Urology, The sixth affiliated hospital of Jinan University, Dongguan 523570, China.
Ecotoxicol Environ Saf. 2023 Nov 1;266:115610. doi: 10.1016/j.ecoenv.2023.115610. Epub 2023 Oct 21.
Cadmium (Cd) exposure damages the reproductive system. Lipid droplets (LDs) play an important role in steroid-producing cells to provide raw material for steroid hormone. We have found that the LDs of Leydig cells exposed to Cd are bigger than those of normal cells, but the effects on steroidogenesis and its underlying mechanism remains unclear. Using Isobaric tag for relative and absolute quantitation (iTARQ) proteomics, phosphodiesterase beta-2 (PLCβ2) was identified as the most significantly up-regulated protein in immature Leydig cells (ILCs) and adult Leydig cells (ALCs) derived from male rats exposed to maternal Cd. Consistent with high expression of PLCβ2, the size of LDs was increased in Leydig cells exposed to Cd, accompanied by reduction in cholesterol and progesterone (P4) levels. However, the high PLCβ2 did not result in high diacylglycerol (DAG) level, because Cd exposure up-regulated diacylglycerol kinases ε (DGKε) to promote the conversion from DAG to phosphatidic acid (PA). Exogenous PA, which was consistent with the intracellular PA concentration induced by Cd, facilitated the formation of large LDs in R2C cells, followed by reduced P4 level in the culture medium. When PLCβ2 expression was knocked down, the increased DGKε caused by Cd was reversed, and then the PA level was decreased to normal. As results, large LDs returned to normal size, and the level of total cholesterol was improved to restore steroidogenesis. The accumulation of PA regulated by PLCβ2-DAG-DGKε signal pathway is responsible for the formation of large LDs and insufficient steroid hormone synthesis in Leydig cells exposed to Cd. These data highlight that LD is an important target organelle for Cd-induced steroid hormone deficiency in males.
镉（Cd）暴露会损害生殖系统。脂滴（LDs）在类固醇生成细胞中发挥重要作用，为类固醇激素提供原料。我们发现，暴露于 Cd 的 Leydig 细胞中的 LDs 比正常细胞中的更大，但对类固醇生成及其潜在机制的影响仍不清楚。使用相对和绝对定量同位素标记（iTRAQ）蛋白质组学，发现磷酸二酯酶β-2（PLCβ2）是暴露于母源性 Cd 的雄性大鼠来源的未成熟 Leydig 细胞（ILCs）和成年 Leydig 细胞（ALCs）中表达上调最显著的蛋白质。与 PLCβ2 的高表达一致，暴露于 Cd 的 Leydig 细胞中的 LDs 增大，同时胆固醇和孕酮（P4）水平降低。然而，高 PLCβ2 并未导致高二酰基甘油（DAG）水平，因为 Cd 暴露上调二酰基甘油激酶 ε（DGKε）以促进 DAG 向磷酸脂酰基（PA）的转化。细胞内由 Cd 诱导的 PA 与外源性 PA 一致，促进 R2C 细胞中形成大的 LDs，随后培养基中 P4 水平降低。当 PLCβ2 表达被敲低时，Cd 引起的 DGKε 增加被逆转，随后 PA 水平降低至正常。结果，大的 LDs 恢复正常大小，总胆固醇水平得到改善，恢复类固醇生成。由 PLCβ2-DAG-DGKε 信号通路调节的 PA 积累是导致暴露于 Cd 的 Leydig 细胞中形成大的 LDs 和类固醇激素合成不足的原因。这些数据强调了 LD 是 Cd 诱导的男性类固醇激素缺乏的重要靶细胞器。
