Adenosine A1 and A2A receptors are involved on guanosine protective effects against oxidative burst and mitochondrial dysfunction induced by 6-OHDA in striatal slices

6-Hydroxydopamine (6-OHDA) is the most used toxin in experimental Parkinson's disease (PD) models. 6-OHDA shows high affinity for the dopamine transporter and once inside the neuron, it accumulates and undergoes non-enzymatic auto-oxidation, promoting reactive oxygen species (ROS) formation and selective damage of catecholaminergic neurons. In this way, our group has established a 6-OHDA in vitro protocol with rat striatal slices as a rapid and effective model for screening of new drugs with protective effects against PD. We have shown that co-incubation with guanosine (GUO, 100 mu M) prevented the 6-OHDA-induced damage in striatal slices. As the exact GUO mechanism of action remains unknown, the aim of this study was to investigate if adenosine A(1) (A(1)R) and/or A(2A) receptors (A(2A)R) are involved on GUO protective effects on striatal slices. Pre-incubation with DPCPX, an A(1)R antagonist prevented guanosine effects on 6-OHDA-induced ROS formation and mitochondrial membrane potential depolarization, while CCPA, an A(1)R agonist, did not alter GUO effects. Regarding A(2A)R, the antagonist SCH58261 had similar protective effect as GUO in ROS formation and mitochondrial membrane potential. Additionally, SCH58261 did not affect GUO protective effects. The A(2A)R agonist CGS21680, although, completely blocked GUO effects. Finally, the A(1)R antagonist DPCPX, and the A(2A)R agonist CGS21680 also abolished the preventive guanosine effect on 6-OHDA-induced ATP levels decrease. These results reinforce previous evidence for a putative interaction of GUO with A(1)R-A(2A)R heteromer as its molecular target and clearly indicate a dependence on adenosine receptors modulation to GUO protective effect.

Automated summary

The study demonstrated that the A(1) receptor antagonist DPCPX prevented the effects of guanosine on 6-OHDA-induced ROS formation and mitochondrial membrane potential depolarization, while the A(1) receptor agonist CCPA did not affect GUO effects. In terms of A(2A) receptors, the antagonist SCH58261 exhibited similar protective effects as guanosine in ROS formation and mitochondrial membrane potential. These results suggest a crucial role of adenosine receptor modulation in the protective effect of guanosine.