title: MPP(+)-induced cytotoxicity in neuroblastoma cells: Antagonism and reversal by guanosine.
abstract: Guanosine exerts neuroprotective effects in the central nervous system. Apoptosis, a morphological form of programmed cell death, is implicated in the pathophysiology of Parkinson's disease (PD). MPP(+), a dopaminergic neurotoxin, produces in vivo and in vitro cellular changes characteristic of PD, such as cytotoxicity, resulting in apoptosis. Undifferentiated human SH-SY5Y neuroblastoma cells had been used as an in vitro model of Parkinson's disease. We investigated if extracellular guanosine affected MPP(+)-induced cytotoxicity and examined the molecular mechanisms mediating its effects. Exposure of neuroblastoma cells to MPP(+) (10 muM-5 mM for 24-72 h) induced DNA fragmentation in a time-dependent manner (p < 0.05). Administration of guanosine (100 muM) before, concomitantly with or, importantly, after the addition of MPP(+) abolished MPP(+)-induced DNA fragmentation. Addition of MPP(+) (500 muM) to cells increased caspase-3 activity over 72 h (p < 0.05), and this was abolished by pre- or co-treatment with guanosine. Exposure of cells to pertussis toxin prior to MPP(+) eliminated the anti-apoptotic effect of guanosine, indicating that this effect is dependent on a Gi protein-coupled receptor, most likely the putative guanosine receptor. The protection by guanosine was also abolished by the selective inhibitor of the enzyme PI-3-K/Akt/PKB (LY294002), confirming that this pathway plays a decisive role in this effect of guanosine. Neither MPP(+) nor guanosine had any significant effect on alpha-synuclein expression. Thus, guanosine antagonizes and reverses MPP(+)-induced cytotoxicity of neuroblastoma cells via activation of the cell survival pathway, PI-3-K/Akt/PKB. Our results suggest that guanosine may be an effective pharmacological intervention in PD.
authors.affiliation: Departments of Medicine, McMaster University, Hamilton, ON, Canada.
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Pettifer
authors.forename: Shucui
authors.initials: S
authors.lastname: Jiang
authors.forename: Christian
authors.initials: C
authors.lastname: Bau
authors.forename: Patrizia
authors.initials: P
authors.lastname: Ballerini
authors.forename: Iolanda
authors.initials: I
authors.lastname: D'Alimonte
authors.forename: Eva S
authors.initials: ES
authors.lastname: Werstiuk
authors.forename: Michel P
authors.initials: MP
authors.lastname: Rathbone