Direct and intergenerational effects in reproductive parameters of adult male Wistar rats and their offspring after subchronic exposure to polystyrene nanoplastics

Abstract

Polystyrene is among the most prevalent types of plastic debris. Polystyrene nanoplastics (PS-NP) cause several alterations in young rodent reproductive tissue and fertility. Here, we investigated if the exposure to PS-NP (500 nm) in adult (90 days-old) male Wistar rats affects reproductive parameters and causes intergenerational effects on the offspring. Study 1: animals (n = 10/group) were exposed by gavage to either distilled water (vehicle; Control group), 0.15 mg/d of PS-NP (Low Dose) or 1.50 mg/d of PS-NP (High Dose) for 60 days. Sperm quality and testosterone serum levels were measured. Study 2: the exposure protocol was repeated using only Control (n = 10) and High Dose (n = 9) groups, then blood leukocytes, histopathology of the testis and the epididymis, and fertility parameters were evaluated. At the end of treatment males (F0) were mated with untreated females (70 - 90 days-old) to produce the first generation (F1) evaluated on Study 3 (Control: n = 7; High Dose: n = 8). Study 3: intergenerational damage was assessed in the male and female offspring (F1). The presence of sperm cytoplasmic droplets and the relative number of sperm in the cauda epididymis increased in the High Dose group (Study 1), as well as the relative number of monocytes in the blood stream (Study 2). Intergenerational effects were observed such as the dysregulation of the estrous cycle of F1-females (Study 3). Given that rats exhibit significantly higher fertility rates than humans, these results could imply that long-term environmental exposure to different types of plastics might have potential consequences for human reproductive health.