Effects of Cyanobacterial Harmful Algal Bloom Toxin Microcystin-LR on Gonadotropin-Dependent Ovarian Follicle Maturation and Ovulation in Mice

Toxins produced by cyanobacteria, an aquatic bacterium also known as blue-green algae, may harm women’s reproductive health, according to NIEHS-funded researchers. Cyanobacteria can produce toxins called microcystins (MCs) that people may encounter in contaminated food or water, or during water sports. A type of MC called MC-LR has been linked to a range of adverse health outcomes, but much remains unknown about how it may affect women’s reproductive health.

To address this gap, researchers examined how MC-LR affects follicles, which are small sacs within the ovaries, and ovulation. During the menstrual cycle, hormones prompt follicles to mature and release an egg in a process called ovulation.

The researchers exposed mice, a cell-based 3D model of a follicle, and hormone-producing human ovarian cells to MC-LR at a range of doses. They then assessed changes in gene and protein expression to determine the effects of MC-LR on follicle maturation, hormone secretion, and ovulation.

Compared with controls, mice exposed to long-term, low-dose MC-LR had 50% fewer corpora lutea — hormone-secreting structures that form after ovulation — suggesting that the algal toxin disrupted the ovulation process. When stimulated to produce more than one egg within a cycle, exposed mice had significantly fewer ovulated eggs compared with unexposed mice. Exposed mice accumulated MC-LR in the ovaries and had significantly lower expression of genes important in follicle maturation. Findings from the 3D model and human cell experiments showed that MC-LR reduced activity of a protein required for follicle maturation.

The study demonstrates how MC-LR disrupts follicle maturation and ovulation, and it suggests that exposure to the toxin, particularly during cyanobacterial bloom seasons, may heighten women’s risk of ovarian disorders, according to the authors. (MA)

Citation: Wang Y, Pattarawat P, Zhang J, Kim E, Zhang D, Fang M, Jannaman EA, Yuan Y, Chatterjee S, Kim JJ, Scott GI, Zhang Q, Xiao S. 2023. Effects of cyanobacterial harmful algal bloom toxin microcystin-LR on gonadotropin-dependent ovarian follicle maturation and ovulation in mice. Environ Health Perspect 131(6):67010.

Source: Environmental Factor (September 2023)