Single microcystin exposure impairs the hypothalamic-pituitary-gonadal axis at different levels in female rats

Microcystin (MC) is most common cyanobacterial toxin. Few studies have evaluated the MC effects on the hypothalamic-pituitary-gonadal (HPG) axis and metabolic function. In this study, we assessed whether MC exposure results in HPG axis and metabolic changes. Female rats were exposed to a single dose of MC at environmentally relevant levels (5, 20 and 40 μg/kg). After 24 h, we evaluated reproductive and metabolic parameters for 15 days. MC reduced the hypothalamic GnRH protein expression, increased the pituitary protein expression of GnRHr and IL-6. MC reduced LH levels and increased FSH levels. MC reduced the primary follicles, increased the corpora lutea, elevated levels of anti-Müllerian hormone (AMH) and progesterone, and decreased estrogen levels. MC increased ovarian VEGFr, LHr, AMH, ED1, IL-6 and Gp91-phox protein expression. MC increased uterine area and reduced endometrial gland number. A blunted estrogen-negative feedback was observed in MC rats after ovariectomy, with no changes in LH levels compared to intact MC rats. Therefore, these data suggest that a MC leads to abnormal HPG axis function in female rats.

Effects of microcystin-LR on mammalian ovaries

The ovaries play critical roles in regulating oocyte maturation and sex steroid hormone production and thus are critical for female reproduction. Ovarian function relies on hormone receptors and signaling pathways, making the ovaries potential targets for environmental factors, such as microcystins (MCs). MCs are a diverse group of cyanobacterial toxins generally found in eutrophic water or algal blooms. Here, we review relevant research on the associations between MC exposure and ovarian dysfunction, including their effects on ovarian morphology, folliculogenesis, steroid production, oxidative stress, endoplasmic reticulum stress, apoptosis, autophagy, and fertility. This review covers the most recent in vitro and in vivo studies in mammals. We also discuss important gaps in the literature. Overall, current evidence indicates that MC exposure causes impairments in ovarian function, but further studies are needed to elucidate the mechanisms through which MCs affect ovarian function and other female endocrine functions.