Microcystin-LR acute exposure increases AChE activity via transcriptional ache activation in zebrafish (Danio rerio) brain

AbstractMicrocystins (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 100μg/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 100μg/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

Aumento na expressão gênica das nucleotidases cerebrais de ratos epilépticos tratados com drogas anticonvulsivantes

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AMACO is a component of the basement membrane-associated fraser complex

Fraser syndrome (FS) is a phenotypically variable, autosomal recessive disorder characterized by cryptophthalmus, cutaneous syndactyly, and other malformations resulting from mutations in FRAS1, FREM2, and GRIP1. Transient embryonic epidermal blistering causes the characteristic defects of the disorder. Fras1, Frem1, and Frem2 form the extracellular Fraser complex, which is believed to stabilize the basement membrane. However, several cases of FS could not be attributed to mutations in FRAS1, FREM2, or GRIP1, and FS displays high clinical variability, suggesting that there is an additional genetic, possibly modifying contribution to this disorder. An extracellular matrix protein containing VWA-like domains related to those in matrilins and collagens (AMACO), encoded by the VWA2 gene, has a very similar tissue distribution to the Fraser complex proteins in both mouse and zebrafish. Here, we show that AMACO deposition is lost in Fras1-deficient zebrafish and mice and that Fras1 and AMACO interact directly via their chondroitin sulfate proteoglycan (CSPG) and P2 domains. Knockdown of vwa2, which alone causes no phenotype, enhances the phenotype of hypomorphic Fras1 mutant zebrafish. Together, our data suggest that AMACO represents a member of the Fraser complex

Acetylcholinesterase activity and antioxidant capacity of zebrafish brain is altered by heavy metal exposure

Pollution is a world problem with immeasurable consequences. Heavy metal compounds are frequently found as components of anthropogenic pollution. Here we evaluated the effects of the treatment with cadmium acetate, lead acetate, mercury chloride, and zinc chloride in acetylcholinesterase activity and gene expression pattern, as well as the effects of these treatments in antioxidant competence in the brain of an aquatic and well-established organism for toxicological analysis, zebrafish (Danio rerio,Cyprinidae). Mercury chloride and lead acetate promoted a significant decrease in acetylcholinesterase activitywhereas they did not alter the gene expression pattern. In addition, the antioxidant competence was decreased after exposure to mercury chloride. The data presented here allowed us to hypothesize a signal transmission impairment, through alterations in cholinergic transmission, and also in the antioxidant competence of zebrafish brain tissue as some of the several effects elicited by these pollutants

Maternal caffeine intake affects acetylcholinesterase in hippocampus of neonate rats

Transcriptional factors and signalling molecules from intracellular metabolism modulate a complex set of events during brain development. Neurotransmitter and neuromodulator synthesis and their receptor expressions vary according to different stages of brain development. The dynamics of signalling systems is often accompanied by alterations in enzyme expression and activity. Adenosine is a neuromodulator that controls the release of several neurotransmitters, including acetylcholine, which is an important neurotransmitter during brain development. Caffeine is a non-specific antagonist of adenosine receptors and can reach the immature brain. We evaluated the effects of rat maternal caffeine intake (1 g/L) on acetylcholine degradation and acetylcholinesterase expression from hippocampus of 7-, 14- and 21-day-old neonates in caffeine-treated and control groups. Caffeine was not able to change the age-dependent increase of acetylcholinesterase activity or the age-dependent decrease of acetylcholinesterase expression. However, caffeine promoted an increase of acetylcholinesterase activity (42%) without modifications on the level of acetylcholinesterase mRNA transcripts in 21-day-old rats. Considering the high score of phosphorylatable residues on acetylcholinesterase, this profile can be associated with a possible regulation by specific phosphorylation sites. These results highlight the ability of maternal caffeine intake to interfere on cholinergic neurotransmission during brain development

<i>capn12</i> and <i>msxc</i> transgenes are co-expressed with a fin mesenchymal cell marker.

<p>(A, E) When <i>capn12</i>^mn0261Gt and <i>msxc</i>^mn0245Gt are crossed into an ET37 background, both Capn12^mn0261Gt-mRFP and MsxC^mn0245Gt-mRFP co-localize with ET37 EGFP-positive fin mesenchymal cells (FMCs) (arrowheads). ET37 also labels the cleft cells along the MFF edge (open arrowheads). Neither Capn12^mn0261Gt-mRFP nor MsxC^mn0245Gt-mRFP localizes to the cleft cells. (B-H) ET37 EGFP labels all FMCs within the fin (arrowheads), both proximal (upper arrowheads) and distal (lower arrowheads), and is present throughout FMC cell bodies and in the extended “arbors” of distal FMCs (lower arrowheads). Both Capn12^mn0261Gt-mRFP and MsxC^mn0245Gt-mRFP localization show similarities with and differences from ET37 EGFP. (B-D) Both ET37 EGFP and Capn12^mn0261Gt-mRFP are expressed in proximal and distal FMCs (arrowheads) but unlike ET37 EGFP, Capn12^mn0261Gt-mRFP localizes to the periphery of FMCs (arrowheads). (F-H) MsxC^mn0245Gt-mRFP co-localizes with ET37 EGFP, but differs from Capn12^mn0261Gt-mRFP. MsxC^mn0245Gt-mRFP is much weaker in proximal FMCs (upper arrowheads) than in distal FMCs (lower arrowheads). Unlike Capn12^mn0261Gt-mRFP, MsxC^mn0245Gt-mRFP subcellular localization is not noticeably distinct from that of ET37 EGFP.</p