WIN 64338 hydrochloride Ethanol can affect biological system
Ethanol can affect biological systems directly, or also through the interactions between these systems, which become important in the actions promoted by alcohol consumption. Its metabolites acetaldehyde and acetate play a key role in the WIN 64338 hydrochloride mediating some effects of ethanol (Israel et al., 1994, Deitrich, 2004). Furthermore, it is well established that acetaldehyde mediates the toxic effects of ethanol, and studies were aimed at unraveling its effects in pathological conditions (Quertemont et al., 2005). According to this knowledge, we may not discard the involvement of these metabolites in promoting alterations on ADA activity after chronic ethanol exposure. Ethanol stimulates cAMP signaling through at least two mechanisms: (i) accumulation of extracellular adenosine due inhibition of the type I equilibrative nucleoside transporter (ENT 1) (Choi et al., 2004). (ii) The catabolic pathway of ethanol by liver generating acetate, which is converted to Acetyl-CoA, a process that requires ATP and yields AMP (Carmichael et al., 1991). This AMP is converted to adenosine by the 5′-nucleotidase (Bianchi and Spychala, 2003), leading to an increase of adenosine levels. In this study we demonstrated an inhibition on ADA activity from membrane fractions after 28days of ethanol exposure. Since it has been demonstrated the presence of ADA activity in the brain membranes suggesting the existence of an ecto-ADA in zebrafish, ADA activity could be another important pathway to study the control of extracellular adenosine levels. Adenosine A2A receptors has been stimulated by ethanol through inhibition of (ENT1) in culture dNG108-15 cells (Nagy et al., 1990). Since A2A receptors are coupled to G protein coupled receptors (GS-coupled), this increases levels of intracellular cAMP and stimulates protein kinase A (PKA) (Mailliard and Diamond, 2004). This activation of PKA permits to phosphorylate substrates. Therefore, we suggest that the inhibition observed adenosine deamination after 28days of ethanol exposure from membrane fractions could be related, at least in part, to the modulation of this intracellular pathway. Precisely, genetics is a promising way to benefit from many advances to understanding of the neurobiology of addictions and associated behaviors. Techniques related to this area led to the identification of brain mechanisms in which a genetic variation may influence individual vulnerability towards alcohol dependence. In addition, the interaction between genetic and environmental factors are crucial to influencing the increase in cases of alcoholism (Pinto and Ansseau, 2009). Studies have previously demonstrated that chronic ethanol exposure promoted changes in the expression of a number of genes belonging to diverse functional groups (Liu et al., 2004, Mayfield et al., 2002). In order to verify whether chronic ethanol exposure could affect ADA-related genes of zebrafish at transcriptional level, we performed RT-PCR analysis. We observed that each gene displays a specific profile of response according to the time of ethanol exposure. Interestingly, an inhibition of ADA activity in membrane fractions after 28days of ethanol exposure was observed concomitantly with increasing expression pattern for dal ADA2-1, ADA2-2 and ADAL genes. Similarly, the distinct effect promoted by ethanol was observed in cholinergic system in zebrafish brain (Rico et al., 2007). Ethanol increase of ACh hydrolysis and decrease of AChE mRNA levels. One explanation for this mechanism is the negative feedback loop, in which is a transcription machinery can be controlled by proteins and/or products of enzymatic reactions (Krishna et al., 2006). Thus, there could be a regulatory interface between ADA activity and ADA-releated genes in zebrafish brain. Another explanation is that each gene could be modulated by independent mechanisms. Therefore, the effects observed in all ADA-related genes, could represent the scenario of expression of members of the ADA family for each period of exposure. However, the mechanisms involved in this modulatory effect of ethanol on ADA transcripts from zebrafish brain still require further investigations.