Neuroprotective and anti-inflammatory effects of a therapy combining agonists of nicotinic α7 and σ1 receptors in a rat model of Parkinson’s disease

To date there is no treatment able to stop or slow down the loss of dopaminergic neurons that characterizes Parkinson’s disease.It was recently observed in a rodent model of Alzheimer’s disease that the interaction between the α7 subtype of nicotinic acetylcholine receptor(α7-nAChR)and sigma-1 receptor(σ1-R)could exert neuroprotective effects through the modulation of neuroinflammation which is one of the key components of the pathophysiology of Parkinson’s disease.In this context,the aim of the present study was to assess the effects of the concomitant administration of N-(3R)-1-azabicyclo[2.2.2]oct-3-yl-furo[2,3-c]pyridine-5-carboxamide(PHA)543613 as an α7-nAChR agonist and 2-(4-morpholinethyl)1-phenylcyclohexanecarboxylate(PRE)-084 as aσ1-R agonist in a well-characterized 6-hydroxydopamine rat model of Parkinson’s disease.The animals received either vehicle separately or the dual therapy PHA/PRE once a day until day 14 postlesion.Although no effect was noticed in the amphetamine-induced rotation test,our data has shown that the PHA/PRE treatment induced partial protection of the dopaminergic neurons(15-20%),assessed by the dopamine transporter density in the striatum and immunoreactive tyrosine hydroxylase in the substantia nigra.Furthermore,this dual therapy reduced the degree of glial activation consecutive to the 6-hydroxydopamine lesion,i.e,the 18 kDa translocation protein density and glial fibrillary acidic protein staining in the striatum,and the CD11b and glial fibrillary acidic protein staining in the substantia nigra.Hence,this study reports for the first time that concomitant activation of α7-nAChR andσ1-R can provide a partial recovery of the nigro-striatal dopaminergic neurons through the modulation of microglial activation.The study was approved by the Regional Ethics Committee(CEEA Val de Loire n°19)validated this protocol(Authorization N°00434.02)on May 15,2014.

Alpha-7 nicotinic acetylcholine receptor agonist treatment in a rat model of Huntington's disease and involvement of heme oxygenase-1

Neuroinflammation is a common element involved in the pathophysiology of neurodegenerative diseases.We recently reported that repeated alpha-7 nicotinic acetylcholine receptor（α7 n ACh R） activations by a potent agonist such as PHA 543613 in quinolinic acid-injured rats exhibited protective effects on neurons.To further investigate the underlying mechanism,we established rat models of early-stage Huntington＇s disease by injection of quinolinic acid into the right striatum and then intraperitoneally injected 12 mg/kg PHA 543613 or sterile water,twice a day during 4 days.Western blot assay results showed that the expression of heme oxygenase-1（HO-1）,the key component of the cholinergic anti-inflammatory pathway,in the right striatum of rat models of Huntington＇s disease subjected to intraperitoneal injection of PHA 543613 for 4 days was significantly increased compared to the control rats receiving intraperitoneal injection of sterile water,and that the increase in HO-1 expression was independent of change in α7 n ACh R expression.These findings suggest that HO-1 expression is unrelated to α7 n ACh R density and the increase in HO-1 expression likely contributes to α7 n ACh R activation-related neuroprotective effect in early-stage Huntington＇s disease.