Proline-induced changes in acetylcholinesterase activity and gene expression in zebrafish brain: reversal by antipsychotic drugs

Abstract

Hyperprolinemia is an inherited disorder of proline metabolism and hyperprolinemic patients can present neurological manifestations, such as seizures, cognitive dysfunctions, and schizoaffective disorders. However, the mechanisms related to these symptoms are still unclear. In the present study, we evaluated the in vivo and in vitro effects of proline on acetylcholinesterase (AChE) activity and gene expression in the zebrafish brain. For the in vivo studies, animals were exposed at two proline concentrations (1.5 and 3.0mM) during 1h or 7 days (short- or long-term treatments, respectively). For the in vitro assays, different proline concentrations (ranging from 3.0 to 1000 μM) were tested. Long-term proline exposures significantly increased AChE activity for both treated groups when compared to the control (34% and 39%). Moreover, the proline-induced increase on AChE activity was completely reverted by acute administration of antipsychotic drugs (haloperidol and sulpiride), as well as the changes induced in ache expression. When assessed in vitro, proline did not promote significant changes in AChE activity. Altogether, these data indicate that the enzyme responsible for the control of acetylcholine levels might be altered after proline exposure in the adult zebrafish. These findings contribute for better understanding of the pathophysiology of hyperprolinemia and might reinforce the use of the zebrafish as a complementary vertebrate model for studying inborn errors of amino acid metabolism.

Keywords: 5,5′-dithiobis-2-nitrobenzoic acid; AChE; ANOVA; BuChE; DA; DTNB; EDTA; EGTA; HPI; HPII; Hyperprolinemia type I; RT-qPCR; S.E.M.; SCh; acetylcholinesterase; analysis of variance; butyrylcholinesterase; diethylene-dinitrilo-tetraacetic acid; dopamine; ethylene glycol bis(betaaminoethyl ether)-N,N,N′,N′-tetraacetic acid; haloperidol; hyperprolinemia; hyperprolinemia type II; inherited diseases; proline; quantitative real-time reverse transcription polymerase chain reaction; standard error of mean; supiride; thiocholine; zebrafish.