JN403, an alpha-7-nicotine-acetylcholine-receptor agonist, reduces alpha-synuclein induced inflammatory parameters of in vitro microglia but fails to attenuate the reduction of TH positive nigral neurons in a focal alpha-synuclein overexpression mouse model of Parkinson's disease.
Alpha-7-nicotine-acetylcholine-receptor (7-nAChRs) agonists modulate the cholinergic antiinflammatory pathway to attenuate proinflammatory signals and reduce dopaminergic neuronal cell loss in toxin-induced experimental murine models of Parkinsons disease (PD). The protein -synuclein (Syn) is considered to represent the major pathogenic component in the etiology and progression of sporadic PD. However, no research has been performed to evaluate the effect of 7-nAChR agonists in human Syn mediated models of PD. We, therefore, investigated the effect of the compound JN403, an 7-nAChR specific agonist, in Syn treated in vitro microglia culture and in a human Syn overexpression in vivo mouse model. In primary mouse microglia cells, Syn fragment 61-140 treatment increased the release of nitric oxide (NO), tumor necrosis factor (TNF)- and interleukin (IL)-6, and decreased cell viability. In contrast, 100 nM or 1 M of JN403 co-incubation significantly reduced the level of NO and TNF- release in the microglial cells. For in-vivo testing of JN403, a recombinant adeno-associated viral vector (rAAV)-mediated unilateral intranigral overexpression of human wild-type-Syn (WT-Syn) or of the control protein luciferase (luc) was induced via stereotactic delivery in C57/BL6N mice. Targeted WT-Syn overexpression reduced 20% of the number of tyrosine hydroxylase (TH) positive (+) nigral neurons after 10 weeks. Subcutaneous daily treatment of 30 mg/kg JN403 over 9 weeks starting at postoperative week 1 did not alter the decrease of TH+ neuronal numbers, and microglial density in WT-Syn overexpression mouse model. The reduced density of TH+ striatal terminals in the WT-Syn groups was also not recovered by the JN403 treatment. In summary, JN403, an 7-nAChR specific agonist shows a beneficial effect on ameliorating proinflammatory signals in Syn exposed microglia cells. However, no significant in-vivo treatment effect was found in an intranigral WT-Syn overexpression mouse model of PD.