title: Reduced striatal ecto-nucleotidase activity in schizophrenia patients supports the "adenosine hypothesis".
abstract: Schizophrenia (SZ) is a major chronic neuropsychiatric disorder characterized by a hyperdopaminergic state. The hypoadenosinergic hypothesis proposes that reduced extracellular adenosine levels contribute to dopamine D2 receptor hyperactivity. ATP, through the action of ecto-nucleotidases, constitutes a main source of extracellular adenosine. In the present study, we examined the activity of ecto-nucleotidases (NTPDases, ecto-5'-nucleotidase, and alkaline phosphatase) in the postmortem putamen of SZ patients (n = 13) compared with aged-matched controls (n = 10). We firstly demonstrated, by means of artificial postmortem delay experiments, that ecto-nucleotidase activity in human brains was stable up to 24 h, indicating the reliability of this tissue for these enzyme determinations. Remarkably, NTPDase-attributable activity (both ATPase and ADPase) was found to be reduced in SZ patients, while ecto-5'-nucleotidase and alkaline phosphatase activity remained unchanged. In the present study, we also describe the localization of these ecto-enzymes in human putamen control samples, showing differential expression in blood vessels, neurons, and glial cells. In conclusion, reduced striatal NTPDase activity may contribute to the pathophysiology of SZ, and it represents a potential mechanism of adenosine signalling impairment in this illness.
authors.affiliation: Bellvitge Biomedical Research Institute-IDIBELL, L'Hospitalet de Llobregat, Spain.
authors.forename: Elisabet
authors.initials: E
authors.lastname: Aliagas
authors.forename: Izaskun
authors.initials: I
authors.lastname: Villar-Menéndez
authors.forename: Jean
authors.initials: J
authors.lastname: Sévigny
authors.forename: Mercedes
authors.initials: M
authors.lastname: Roca
authors.forename: Miriam
authors.initials: M
authors.lastname: Romeu
authors.forename: Isidre
authors.initials: I
authors.lastname: Ferrer
authors.forename: Mireia
authors.initials: M
authors.lastname: Martín-Satué
authors.forename: Marta
authors.initials: M
authors.lastname: Barrachina
mesh_terms: D000241:Adenosine / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000368:Aged; D000369:Aged, 80 and over; D003342:Corpus Striatum / Q000201:enzymology*; D015536:Down-Regulation; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011699:Putamen / Q000201:enzymology*; D012559:Schizophrenia / Q000201:enzymology*; D014018:Tissue Distribution
chemical_list: D000251:Adenosine Triphosphatases; C027201:ectoATPase; D000241:Adenosine