Cadmium-induced disruption of exosomal secretion and cellular pathways in leydig cells

Cadmium is a toxic heavy metal, disrupts different cellular secretions and induce pathological changes in the male reproductive system. However, cadmium-induced disruption of exosomal secretion and cellular pathways in Leydig cells is largely unknown. In this study, 30 C57BL/6 male mice were divided into two groups: one receiving purified water and the other 50 mg/L CdCl2 for three months. This is a first report, both in vivo and in vitro analyses showed that the control group exhibited strong immunoreactivity and immunosignaling with high secretion of exosomal proteins CD63 and multivesicular bodies (MVBs) through immunohistochemistry, immunofluorescence, and transmission electron microscopy. Leydig cells in the control group maintained a normal steroidogenic pathway, supporting the production of healthy, motile spermatozoa. Conversely, the cadmium-treated group showed irregularly dispersed Leydig cells with condensed nuclei and vacuolated mitochondria. Cadmium exposure led to reduced immunoreactivity, immunosignaling, and expression of CD63 in Leydig cells, with a noticeable lack of MVBs secretion. Additionally, cadmium significantly down-regulated the Steroidogenesis regulatory proteins STAR, CYP11A1, CYP17A1, 3BHSD1, 17BHSD1 and AR of Leydig cells. It also disrupted autophagic flux evidenced by increased expression of ATG5, ATG7, LC3, P62, and LAMP2 proteins. Furthermore, cadmium up-regulated apoptotic proteins (Caspase-3, Caspase-8, and Bax) and down-regulated the anti-apoptotic protein Bcl-2. This study provides novel insights into the detrimental effects of cadmium on Leydig cells' secretory pathways, highlighting disruptions in exosomal-MVBs secretion, autophagy and apoptosis, thereby posing significant risks to male fertility.