Zinc Oxide Nanoparticles Induced Testicular Toxicity Through Inflammation and Reducing Testosterone and Cell Viability in Adult Male Rats

Zinc oxide nanoparticles (ZnO NPs) have wide applications in daily life. Therefore, there is growing interest in the potential harmful impacts of these particles on human health. The present study was conducted to investigate the potential toxic effects of ZnO NPs (40 and 70 nm) compared to ZnO on the testes of rats. ZnO NPs were synthesized and characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Adult male rats were randomly divided into four groups (n = 8): Group I (control), Group II (ZnO) received daily oral administration of ZnO (50 mg/kg), and Groups III and IV received daily oral administration of ZnO NPs of 40 nm or 70 nm at 50 mg/kg, respectively. All treatments continued for 50 consecutive days. ZnO and ZnO NPs reduced body and testis weights, sperm count and motility, serum luteinizing hormone (LH) and testosterone levels, testicular cytochrome p450 17A1 (CYP17A1) and cytochrome p450 1B1 (CYP1B1) concentrations, and the expression of p53 and cdk1. These treatments elevated testicular myeloperoxidase and serum acid phosphatase activities as well as sperm abnormalities. ZnO NPs reduced LH levels, which decreased CYP17A1 and CYP1B1, resulting in reduced synthesis of testosterone. ZnO NPs enhanced testicular inflammation and reduced cell viability. All these effects were manifested as reduced sperm motility and increased sperm deformities. Compared to macromolecules, nanoparticles exhibited significantly higher toxicity. The larger diameter ZnO NPs had more profound toxicity than the smaller-sized particles.