Neuro‐ and hepatic toxicological profile of (S)‐2,4‐diaminobutanoic acid in embryonic, adolescent and adult zebrafish

Abstract

(S)‐2,4‐Diaminobutanoic acid (DABA) is a noncanonical amino acid often co‐produced by cyanobacteria along with β‐N‐methylamino‐l‐alanine (BMAA) in algal blooms. Although BMAA is a well‐established neurotoxin, the toxicity of DABA remains unclear. As part of our development of biocompatible materials, we wish to make use of DABA as both a building block and as the end‐product of enzymatically induced depolymerization; however, if it is toxic at very low concentrations, this would not be possible. We examined the toxicity of DABA using both in vivo embryonic and adult zebrafish models. At higher sublethal concentrations (700 μm), the fish demonstrated early signs of cardiotoxicity. Adolescent zebrafish were able to tolerate a higher concentration. Post‐mortem histological analysis of juvenile zebrafish showed no liver or brain abnormalities associated with hepato‐ or neurotoxicity. Combined, these results show that DABA exhibits no overt toxicity at concentrations (100‐300 μm) within an order of magnitude of those envisioned for its application. This study further highlights the low cost and ease of using zebrafish as an early‐stage toxicological screening tool.

The Cyanotoxin 2,4-DAB Reduces Viability and Causes Behavioral and Molecular Dysfunctions Associated with Neurodegeneration in Larval Zebrafish

“…These results are supported by a previous dose response study using zebrafish larvae in which 300 μM was sufficient to produce signs of cardiotoxicity ( Ferraiuolo et al 2019 ). These results contrast with those from in vitro studies in which 2,4-DAB did not elicit an effect on viability at concentrations lower than 2000 μM or 1000 μM in human liver/brain cancer cells or mouse motoneuron-like cells, respectively ( Ferraiuolo et al 2019 ; Martin et al 2019 ). This distinction underscores the importance of studying toxin exposures in an in vivo context.…”

“…This distinction underscores the importance of studying toxin exposures in an in vivo context. Although exposure to BMAA or 2,4-DAB alone has previously been shown to cause morphological defects in larval zebrafish (Purdie et al 2009;Ferraiuolo et al 2019), we did not observe any significant morphological defects upon exposure to BMAA, AEG, or 2,4-DAB at 500 µM. This could be due to differences in zebrafish strain, embryo medium, exposure route, or observer analysis.…”

“…Some recent in vitro studies have found that AEG and 2,4-DAB are toxic to neurons in culture ( Main et al 2018 ; Martin et al 2019 ), but whether they exert neurotoxic effects in vivo has not been established. To the best of our knowledge, only one prior study has tested the toxic effects of 2,4-DAB in animals ( Ferraiuolo et al 2019 ), while none have evaluated the toxicity of AEG in an animal model or examined whether these cyanotoxins interact. Thus, we aimed to measure both the individual and the combined toxic effects of BMAA, AEG, and 2,4-DAB in vivo.…”

The cyanotoxin 2,4-DAB enhances mortality and causes behavioral and molecular dysfunctions associated with neurodegeneration in larval zebrafish

“…The effects of 2,4-DAB on viability are dose dependent, as the lowest observed effect level was 250µM (data not shown). These results are supported by a previous dose response study using zebrafish larvae in which 300μM was sufficient to produce signs of cardiotoxicity (Ferraiuolo et al 2019). These results contrast with those from in vitro studies in which 2,4-DAB did not elicit an effect on viability at concentrations lower than 2000µM or 1000µM in human liver/ brain cancer cells or mouse motoneuron-like cells, respectively (Ferraiuolo et al 2019;Martin et al 2019).…”

“…This distinction underscores the importance of studying toxin exposures in an in vivo context. Although exposure to BMAA or 2,4-DAB alone has previously been shown to cause morphological defects in larval zebrafish (Ferraiuolo et al 2019;Purdie et al 2009), we did not observe any significant morphological defects upon exposure to BMAA, AEG, or 2,4-DAB at 500µM. This could be due to differences in zebrafish strain, embryo medium, exposure route, or observer analysis.…”