Research ArticleGallic Acid Reverses Neurochemical Changes Induced by Prolonged Ethanol Exposure in the Zebrafish Brain
Introduction
Plants contain complex mixtures of secondary metabolites that have been investigated in recent decades as a nutritional source and play important roles in protecting human health. Among these metabolites, the most studied compounds are the polyphenols, which have been associated with reduced risks for some diseases such diabetes (Guasch-Ferré et al., 2017), cardiovascular diseases (Rasines-Perea and Teissedre, 2017), and neurodegenerative pathologies (Spagnuolo et al., 2016). Gallic acid (3,4,5-trihydroxybenzoic acid; GA) is a low-molecular weight triphenolic compound and is considered to be an intermediate derived from secondary metabolism in the shikimic acid pathway (Daglia et al., 2014). GA is present in several plants, especially green tea, grapes, mangoes and nuts, and is considered to be the primary polyphenol in the diet (Ramirez-Lopez et al., 2014).
Studies have attributed several properties to GA, including hepatoprotective (Perazzoli et al., 2017), antimicrobial (Zhao et al., 2018), anti-inflammatory (BenSaad et al., 2017), and anti-cancer (Russo et al., 2017) activity. These features are due to the fact that GA acts in the biochemistry of inflammation and in oxidative pathways. It has been suggested that this antioxidant effect has a close correlation with the elimination of free radicals, metal chelating effects, and the potential ability to interact with signal transduction pathways mediated by different enzymes (Daglia et al., 2014). Improvement in oxidative balance has been observed in studies related to neuroinflammation (Siddiqui et al. 2019), Parkinson’s disease (Chandrasekhar et al., 2018), and depression (Nagpal et al., 2012).
Ethanol is a psychoactive substance that alters neurotransmitter balance. Studies have broadly demonstrated that oxidative stress caused by ethanol consumption contributes to neurochemical and behavioral impairment in rodents (Amodeo et al., 2018, Mattalloni et al., 2019) and humans (Spear, 2018, Tapia-Rojas et al., 2017). Similar neurochemical changes have been observed using zebrafish as an alternative model for translational research investigating the effects of alcohol (Alexandre et al., 2019, Bernardo et al., 2019, Agostini et al., 2020).
The zebrafish is widely used for models to study the alcohol exposure and has revealed changes in behavior (Dewari et al., 2016, Müller et al., 2017) and in neurotransmission systems such as the dopaminergic (Paiva et al., 2020), purinergic (Rico et al., 2011), and cholinergic (Agostini et al., 2018) pathways. In addition, the zebrafish has antioxidant defenses, similar to that of mammals, suggesting that fish and mammals exhibit similar cellular responses to oxidative stress (Mohanty et al., 2017). Zebrafish can be used in studies investigating the effects of GA because enzymes related to GA metabolism have been identified, coded, and characterized in this animal model (Mohammed et al., 2012). Techer et al. (2015) evaluated the acute toxicity of GA in adult zebrafish using lethal concentrations (LC) and demonstrated that this molecule is practically non-toxic in this species [96 h, LC for 50% of the animals tested (i.e., LC50) > 100 mg/L].
Thus, considering the properties of GA and its potential neuroprotective effects, approaches to investigating neurotoxicity in zebrafish are promising and relevant. However, the literature still lacks evidence supporting the role of candidate molecules in toxicity models induced by alcohol treatment/abuse. Accordingly, the present study aimed to evaluate the effects of this triphenolic compound on the zebrafish brain, as well as to analyze its possible ability to modulate the negative effects of ethanol.
Section snippets
Reagents
Gallic acid ((HO)3C6H2CO2H, CAS number 149-91-7) was purchased from Sigma-Aldrich (St. Louis, MO, USA). All chemical was of analytical grade.
Animals
The experiments were performed using 360 wild-type phenotypes adult zebrafish (Danio rerio; 4–6 months old), of both sexes (50:50), obtained from a local commercial supplier (Recife Aquarios). All fishes were acclimated in your laboratory for at least 2 weeks in 50-L tanks (50 × 35 × 30 cm, length × width × height) with 28 cm high at a maximum density of
Effects of GA on the zebrafish brain
To the authors’ knowledge, there is no neurochemical evidence reflecting the effects of GA in the adult zebrafish brain. Thus, the strategy was to initially evaluate the effect of GA in isolation at concentrations of 5, 10, and 20 mg/L for varying lengths of time. Initially, the level of sulfhydryl groups, a marker of oxidative damage to proteins, was evaluated and demonstrated that the different concentrations of GA have a significant effect on this parameter (F3,30 = 11.32, p < 0.0001,
Discussion
In the present study, GA demonstrated a protective effect against the toxicity of prolonged exposure to ethanol through its cholinergic neurotransmission and antioxidant proprieties in the adult zebrafish brain. Initially, we evaluated the isolated effect of GA at 5, 10, and 20 mg/L on oxidative stress parameters in the zebrafish brain for 24 h and 48 h. Our results revealed an increase in TBA-RS levels at 20 mg/L for both exposure periods, suggesting lipoperoxidation. It has been reported that
Authors’ contributions
Wanderley had full access to all study data and takes responsibility for the data integrity and analysis accuracy.
Concept and design: Agostini, Rico and Wanderley.
Data acquisition: Agostini, Dal Santo, Baldin, Bernardo and Farias.
Data analysis and interpretation: Agostini, Dal Santo, Baldin, Bernardo, Rico and Wanderley.
Manuscript drafting: Agostini, Rico and Wanderley.
Manuscript critical revisions for important intellectual content: Agostini, Rico and Wanderley.
Administrative, technical, or
Conflict of interest
The authors declare that there is no conflict of interest regarding the publication of this article.
Ethics statement
The Ethics Committee of Federal University of Pernambuco (UFPE) has approved the present study.
Acknowledgements
This work was supported by DECIT/SCTIEMS through Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado de Santa Catarina (FAPESC), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES AUXPE PROEX N. 23038.027251/2016-85). E.P.R. were recipients of fellowships from CNPq research Grant (Universal 429302/2018-5).
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