Microcystis aeruginosa decreased fish appetite via inducing intestinal inflammation

Abstract

Microcystis aeruginosa is a dominant and widely distributed cyanobacterium that plays a major role in the formation and recurrence of harmful algal blooms in lakes. While it is known to cause intestinal inflammation and appetite dysregulation in fish, the relationship between these effects and their underlying molecular mechanisms remains poorly understood. This study explored the impact of M. aeruginosa-induced intestinal inflammation on fish appetite, with a focus on the underlying molecular pathways, using Pseudorasbora parva exposed to M. aeruginosa for 96 h. We found a significant increase in inflammatory cells in the intestinal tract, accompanied by notable changes in glycerophospholipid and tryptophan metabolism, pathways associated with inflammation and appetite regulation. Key inflammatory markers interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-1 beta (IL-1β), Nuclear factor-kappaB (NF-κB), and tumor necrosis factor-alpha (TNF-α) were significantly elevated, while orexigenic factors orexins, ghrelin, acetylcholine (Ach), and dopamine (DA) were markedly reduced. In contrast, anorexigenic factors 5-Hydroxytryptamine (5-HT), gamma-aminobutyric acid (GABA), proopiomelanocortin (POMC), and glucagon-like peptide-1 (GLP-1) showed significant increases. Correlation analysis revealed that inflammatory markers were negatively correlated with orexigenic factors and positively correlated with anorexigenic factors. These findings indicate that M. aeruginosa-induced intestinal inflammation is a potential mechanism underlying reduced appetite in fish. This study provides novel insights into the toxic effects of M. aeruginosa on fish and offers a new perspective on the mechanisms by which it suppresses fish appetite, contributing to the broader understanding of the ecological and physiological impacts of cyanobacterial blooms.