Differential involvement of Ras‐GRF1 and Ras‐GRF2 in L‐DOPA‐induced dyskinesia. Issue 6 (24th April 2015)

• Record Type: Journal Article
• Authors: Bido, Simone; Solari, Nicola; Indrigo, Marzia; D'Antoni, Angela; Brambilla, Riccardo; Morari, Michele; Fasano, Stefania
• Is Part Of: Annals of clinical and translational neurology. Volume 2:Issue 6(2015:Jun.)
• Page Start: 662
• Page End: 678
• Publication Date: 2015-04-24
• Subjects: Nervous system -- Diseases -- Periodicals; Neurology -- Periodicals; 616.8005
• DOI: 10.1002/acn3.202
• Languages: English
• ISSNs: 2328-9503

Abstract

<abstract abstract-type="main" id="acn3202-abs-0001"> <title>Abstract</title> <sec id="acn3202-sec-0001" sec-type="section"> <title>Objective</title> <p>Recent findings have shown that pharmacogenetic manipulations of the Ras‐ERK pathway provide a therapeutic means to tackle <sc>l</sc>‐3, 4‐dihydroxyphenylalanine (<sc>l</sc>‐DOPA)‐induced dyskinesia (LID). First, we investigated whether a prolonged <sc>l</sc>‐DOPA treatment differentially affected ERK signaling in medium spiny neurons of the direct pathway (dMSNs) and in cholinergic aspiny interneurons (ChIs) and assessed the role of Ras‐GRF1 in both subpopulations. Second, using viral‐assisted technology, we probed Ras‐GRF1 and Ras‐GRF2 as potential targets in this pathway. We investigated how selective blockade of striatal Ras‐GRF1 or Ras‐GRF2 expression impacted on LID (induction, maintenance, and reversion) and its neurochemical correlates.</p> </sec> <sec id="acn3202-sec-0002" sec-type="section"> <title>Methods</title> <p>We used both Ras‐GRF1 knockout mice and lentiviral vectors (LVs) delivering short‐hairpin RNA sequences (shRNAs) to obtain striatum‐specific gene knockdown of Ras‐GRF1 and Ras‐GRF2. The consequences of these genetic manipulations were evaluated in the 6‐hydroxydopamine mouse model of Parkinson's disease. Escalating doses of <sc>l</sc>‐DOPA were administered and then behavioral analysis with immunohistochemical assays and in vivo microdialysis were performed.</p> </sec> <sec id="acn3202-sec-0003" sec-type="section"> <title>Results</title> <p>Ras‐GRF1 was found essential in controlling ERK signaling in dMSNs, but its ablation did not prevent ERK activation in ChIs. Moreover, striatal injection of LV‐shRNA/Ras‐GRF1 attenuated dyskinesia development and ERK‐dependent signaling, whereas LV‐shRNA/Ras‐GRF2 was without effect, ruling out the involvement of Ras‐GRF2 in LID expression. Accordingly, Ras‐GRF1 but not Ras‐GRF2 striatal gene‐knockdown reduced <sc>l</sc>‐DOPA‐induced GABA and glutamate release in the substantia nigra pars reticulata, a neurochemical correlate of dyskinesia. Finally, inactivation of Ras‐GRF1 provided a prolonged anti‐dyskinetic effect for up to 7 weeks and significantly attenuated symptoms in animals with established LID.</p> </sec> <sec id="acn3202-sec-0004" sec-type="section"> <title>Interpretation</title> <p>Our results suggest that Ras‐GRF1 is a promising target for LID therapy based on Ras‐ERK signaling inhibition in the striatum.</p> </sec> </abstract>