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Microcystin-LR acute exposure increases AChE activity via transcriptional ache activation in zebrafish (Danio rerio)
Luiza Wilges Kist1, Denis Broock Rosemberg, Talita Carneiro Brandão Pereira
1Laboratório de Biologia Genômica e Molecular, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul, Avenida Ipiranga, 6681, 90619-900 Porto Alegre, RS, Brazil.
Abstract:
Microcystins (MCs) constitute a family of cyanobacterial toxins, with more than 80 variants. These toxins are able to induce hepatotoxicity in several organisms mainly through the inhibition of protein phosphatases PP1 and PP2A and oxidative stress generation. Since recent evidence shows that MCs can either accumulate in brain or alter behavior patterns of fish species, in this study we tested the in vitro and in vivo effects of MC-LR at different concentrations on acetylcholinesterase (AChE) activity in zebrafish brain. In vivo studies showed that 100 μg/L MC-LR led to a significant increase in the AChE activity (27%) when zebrafish were exposed to the toxin dissolved in water, but did not cause any significant changes when injected intraperitoneally. In addition, semiquantitative RT-PCR analysis demonstrated that 100 μg/L MC-LR exposure also increased ache mRNA levels in zebrafish brain. The in vitro assays did not reveal any significant changes in AChE activity. These findings provide the first evidence that brain AChE is another potential target for MCs and suggest that the observed increases in AChE enzymatic activity and in ache transcript levels after MC-LR exposure depend, at least partially, on branchial uptake or ingestion.
Insights
Microcystins (MCs) can increase acetylcholinesterase (AChE) activity and gene expression in zebrafish brains, particularly when absorbed through gills or ingested. This suggests brain AChE is a potential target for these cyanotoxins.
Area of Science:
- Environmental toxicology
- Neuroscience
- Biochemistry
Background:
- Microcystins (MCs) are cyanobacterial toxins with over 80 variants.
- MCs primarily cause hepatotoxicity by inhibiting protein phosphatases and inducing oxidative stress.
- Emerging evidence suggests MCs may affect fish brain function and behavior.
Purpose of the Study:
- To investigate the in vitro and in vivo effects of MC-LR on acetylcholinesterase (AChE) activity in zebrafish brains.
- To determine if MC-LR impacts AChE enzymatic activity or gene expression.
Main Methods:
- Exposure of zebrafish to MC-LR via water and intraperitoneal injection.
- Measurement of AChE activity in zebrafish brain tissue.
- Analysis of ache mRNA levels using semiquantitative RT-PCR.
- In vitro assays to assess direct effects on AChE activity.
Main Results:
- In vivo exposure to 100 μg/L MC-LR in water significantly increased zebrafish brain AChE activity by 27%.
- Intraperitoneal injection of MC-LR did not significantly alter AChE activity.
- MC-LR exposure elevated ache mRNA levels in zebrafish brains.
- In vitro assays showed no significant changes in AChE activity.
Conclusions:
- Zebrafish brain AChE is a potential target for microcystins.
- Increased AChE activity and ache transcript levels are likely mediated by MC-LR uptake via branchial absorption or ingestion.
- These findings highlight a novel neurotoxic mechanism of MCs in aquatic organisms.
