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Polystyrene microplastics impair the functions of cultured mouse Leydig (TM3) and Sertoli (TM4) cells by inducing
Giulia Grillo1, Sara Falvo1, Debora Latino1
1Department of Environmental Biological and Pharmaceutical Sciences and Technologies, University of Campania Luigi Vanvitelli, Caserta, Italy.
Abstract:
Many laboratory studies demonstrated that the exposure to microplastics causes testosterone deficiency and spermatogenic impairment in mammals; however, the mechanism underlying this process remains still unclear. In this study, we investigated the effects of polystyrene microplastics (PS-MP) on the proliferation and functionality of cultured Leydig (TM3) and Sertoli (TM4) cells, focusing on the mitochondrial compartment and its association with the endoplasmic reticulum (ER). The in vitro exposure to PS-MP caused a substantial reduction in cellular viability in TM3 and TM4 cells. In TM3 cells PS-MP inhibited the protein levels of StAR and of steroidogenic enzymes 3β-HSD and 17β-HSD, and in TM4 cells PS-MP inhibited the protein levels of the androgen receptors other than the activity of lactate dehydrogenase (LDH). PS-MP inhibited the functions of TM3 and TM4, as evidenced by the decrease of the phosphorylation of ERK1/2 and Akt in both cell lines. The oxidative stress caused by PS-MP decreased antioxidant defense in TM3 and TM4 cells, promoting autophagic and apoptotic processes. Furthermore, we found mitochondrial dysfunction and activation of ER stress. It is known that mitochondria are closely associated with ER to form the Mitochondrial-Associated Endoplasmic Reticulum Membranes (MAM), the site of calcium ions transfer as well as of lipid biosynthesis-involved enzymes and cholesterol transport from ER to the mitochondria. For the first time, we studied this aspect in PS-MP-treated TM3 and TM4 cells and MAMs dysregulation was observed. This study is the first to elucidate the intracellular mechanism underlying the effects of PS-MPs in somatic testicular cells, corroborating that PS-MP might be one of the causes of an increase in male infertility through the impairment of steroidogenesis in Leydig cells and of the nurse function of Sertoli cells. Thus, our findings contributed with new information to the mechanism underlying the effects of PS-MP on the male reproductive system.
Insights
Polystyrene microplastics (PS-MP) harm male fertility by damaging testicular cells. This study reveals PS-MP disrupts Leydig and Sertoli cell function, impacting steroid production and sperm health.
Area of Science:
- Reproductive Biology
- Environmental Toxicology
- Cell Biology
Background:
- Microplastic exposure is linked to male reproductive issues, but underlying mechanisms are unclear.
- Polystyrene microplastics (PS-MP) are common environmental contaminants.
- Testicular somatic cells, Leydig (TM3) and Sertoli (TM4), are crucial for male reproductive function.
Purpose of the Study:
- To investigate the effects of PS-MP on TM3 and TM4 cell viability, function, and intracellular mechanisms.
- To elucidate the role of mitochondrial and endoplasmic reticulum (ER) stress in PS-MP-induced testicular toxicity.
- To examine PS-MP effects on Mitochondrial-Associated Endoplasmic Reticulum Membranes (MAMs) in testicular cells.
Main Methods:
- In vitro exposure of cultured TM3 and TM4 cells to PS-MP.
- Assessment of cellular viability, protein levels (StAR, 3β-HSD, 17β-HSD, androgen receptors), enzyme activity (LDH), and signaling pathways (p-ERK1/2, p-Akt).
- Analysis of oxidative stress markers, autophagy, apoptosis, mitochondrial function, ER stress, and MAMs integrity.
Main Results:
- PS-MP significantly reduced TM3 and TM4 cell viability.
- PS-MP inhibited steroidogenesis in TM3 cells and androgen receptor function in TM4 cells.
- PS-MP induced oxidative stress, autophagy, apoptosis, mitochondrial dysfunction, ER stress, and MAMs dysregulation in both cell types.
Conclusions:
- PS-MP impairs Leydig cell steroidogenesis and Sertoli cell function through intracellular mechanisms involving mitochondrial and ER stress.
- Dysregulation of MAMs is a novel finding in PS-MP-induced testicular toxicity.
- PS-MP exposure poses a significant risk to male reproductive health, potentially contributing to infertility.
