ORIGINAL RESEARCH article
Front. Endocrinol.
Sec. Neuroendocrine Science
Volume 16 - 2025 | doi: 10.3389/fendo.2025.1568923
Short-Term Ingestion of Sublethal Microcystin Levels Disrupts Stress Response in Male Mice
Provisionally accepted- 1Kent State University, Kent, United States
- 2University of Adelaide, Adelaide, South Australia, Australia
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Cyanobacterial harmful algal blooms (cHABs) produce various cyanotoxins, primarily microcystin leucine arginine (MC-LR). Studies demonstrated that intraperitoneal delivery of high-dose MC-LR affects the rat stress response, which is regulated by the hypothalamus-pituitary-adrenal (HPA) axis. In general, during stress parvocellular neurons in the hypothalamic paraventricular nucleus (PVN) secrete corticotropinreleasing hormone (CRH), triggering adrenocorticotropic hormone (ACTH) release from the anterior pituitary, which leads to increased cortisol in humans and corticosterone in rats and mice. Here, we tested the hypothesis that short-term sublethal ingestion of MC-LR activates the peripheral and central components of the HPA axis. First, we found that young adult male mice gavaged with MC-LR (50 μg/kg bw, p.o.) every 2 days for 21 days had elevated plasma corticosterone levels when compared to H2O (vehicle) mice.Ingestion of contaminated fresh water is a likely natural route of MC-LR exposure for animals, including humans. Second, Crh and arginine vasopressin (Avp) mRNA expressions were elevated in the hypothalamus of MC-LR-dosed mice. Third, ΔFOSB (i.e., long-term cell activity marker) immunofluorescence in the PVN and hippocampal dentate gyrus (DG) of MC-LR mice was significantly elevated compared to vehicle mice, but not in cornu ammonis (CA) 1, 2 and 3. In contrast, MC-LR mice had reduced hypothalamic glucocorticoid receptor (Gr) mRNA expression. Fourth, no significant changes were found in the mRNA expression of the inflammatory markers: tumor necrosis factor α (Tnf-α) and interleukin-1β (IL-1β) in the hypothalamus, liver, and spleen and C-reactive protein (Crp) in the liver and spleen. These data indicate that short-term ingestion of sublethal levels of MC-LR resulted in increased peripheral and central HPA axis activity.
Keywords: Cyanobacterial harmful algal bloom, microcystin, Brain, stress response, Inflammation
Received: 30 Jan 2025; Accepted: 29 Apr 2025.
Copyright: © 2025 Ghaju, Pakuwal, Takeshita, Mou and Chung. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Salan Ghaju, Kent State University, Kent, United States
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