Acute and subchronic copper treatments alter extracellular nucleotide hydrolysis in zebrafish brain membranes.
Copper is a divalent cation with physiological importance since deficiency of copper homeostasis can cause serious neurological diseases. ATP is an important signalling molecule stored at nerve endings and its inactivation is promoted by ecto-nucleotidases. In this study, we verified the effect of acute and subchronic copper treatments on ecto-nucleotidase activities in zebrafish brain membranes. Treatment with copper sulfate (15 microg/L) during 24h inhibited ATP hydrolysis (16%), whereas ADP and AMP hydrolysis were not altered. Nevertheless, a 96-h exposure with the copper concentration mentioned above inhibited NTPDase (31% and 42% for ATP and ADP hydrolysis, respectively) and ecto-5'-nucleotidase (40%) activities. NTPDase1, NTPDase2_mg and NTPDase2_mv transcripts were decreased after copper exposures during 24 and 96 h. Subchronic copper treatment also reduced the NTPDase2_mq and ecto-5'-nucleotidase expression. In vitro assays demonstrated that NTPDase activities were reduced after copper exposure during 40 min. ATP hydrolysis was inhibited at 0.25, 0.5 and 1mM (13%, 31% and 48%, respectively) and ADP hydrolysis also had a significant decrease at these same copper concentrations (41%, 63% and 68%, respectively). In contrast to the subchronic exposure, no significant changes on ecto-5'-nucleotidase were observed after in vitro assays. Lineweaver-Burk plots suggested that both inhibitory effects on nucleotide hydrolysis may occur in a non-competitive manner. Altogether, these findings indicate that copper is able to promote distinct changes on ecto-nucleotidases after in vivo and in vitro treatments and, consequently, it could control the nucleotide and nucleoside levels, modulating the purinergic signalling.
Rosemberg
Denis Broock
DB
Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos 2600-Anexo, 90035-003 Porto Alegre, RS, Brazil.
Rico
Eduardo Pacheco
EP
Senger
Mario Roberto
MR
Arizi
Marcelo de Bem
Mde B
Dias
Renato Dutra
RD
Bogo
Maurício Reis
MR
Bonan
Carla Denise
CD
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000249:Adenosine Monophosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D003300:Copper / Q000633:toxicity*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006868:Hydrolysis; D008566:Membranes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015027:Zebrafish
D012333:RNA, Messenger; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D003300:Copper; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C027201:ectoATPase