Synthesis and catabolism of Camp are dysregulated in a knock-in mouse model of DYT1 dystonia

Synthesis and catabolism of cAMP are dysregulated in a knock-in mouse model of DYT1 dystonia V. Saviozzi1, S. Cardarelli1, V. D’Angelo2, I. Saverioni1, P. Bonsi3, A. Pisani2,3, S. Biagioni1, G. Sancesario2, M. Giorgi1. 1Department of Biology and Biotechnology, Sapienza University of Rome; 2Department of Systems Medicine, University of Rome Tor Vergata ; 3Santa Lucia Foundation, Rome. Objectives - DYT1 Dystonia is a movement disorder caused by a 3-bp deletion (Δgag) in TorsinA gene. In our previous work we demonstrated the opposite changes of a catabolic cAMP enzyme, PDE10A, level and activity in the basal ganglia direct and indirect pathways of a DYT1 overexpression model. This imbalance between basal ganglia pathways could be responsible for improperly focusing of movements in DYT1 dystonia. The widespread expression and utilization of cAMP as second messenger suggest the involvement of striatopallidal and striatonigral neuronal subtypes in the pathophysiology of dystonia. The aim of the present work is to characterize in a DYT1 knock-in model reproducing the human mutation (Tor1a+/Δgag) any changes both in the catabolic action of PDE10A and in the expression of A2a receptor as mediator of cAMP synthesis. Materials and Methods - Sections of basal ganglia (Striatum, Globus pallidus, Entopeduncular nucleus, Substantia nigra) were incubated with monoclonal anti PDE10A antibody (Pfizer) and polyclonal anti-A2a antibody (Enzo Life Sciences). The same antibodies were used to evaluate PDE10A and A2a receptor expression by western blot analysis. In each brain regions cAMP level was measured using EIA and PDE10A activity was assayed by tritiated substrate in the presence or absence of the specific inhibitor papaverine. Results – The results obtained in the DYT1 knock-in mouse displayed the same PDE10A variations observed in the previously published transgenic model. Moreover, in DYT1 knock-in mice, the expression of A2a receptor showed opposite changes in striatopallidal and striatoentipeduncular/nigral circuits, similar to PDE10A alterations. Discussion - Even if the role of TorsinA in the different accumulation of PDE10A and A2A receptor in the basal ganglia pathways requires a more in-depth analysis, it is important to note that the resulting global effect is the alteration of the intensity and duration of the signals that arrive to the final outputs. The inverse changes of PDE10A in striatal direct and indirect pathways can affect the rate of catabolism of second messengers, differentially modulating the functions of basal ganglia circuits, both in the striatum and in its projections areas. The activation of adenylate cyclase via the up regulation of A2A receptor could be a compensatory mechanism. Conclusions - Our data suggests that an alteration of cAMP pathway in striatal direct and indirect circuitry can be a general mechanism in the pathophysiology of DYT1 dystonia and that both PDE10A and A2A receptor dysregulations are involved in this pathology.