Fig 1.
SA00025 entered the brain and modulated the transcription of dopaminergic target genes.
The chemical structure of SA00025: 2-{3-[2-(4-chlorophenyl)imidazo[1,2-a]-pyridin-6-yl]phenyl}propan-2-ol (A). The Nurr1 agonist compound was administered once daily for 7 consecutive days (30mg/kg/ day) in naive rats by oral gavage (B). The compound was observed in the brain at 1 hour after the last gavage and reached a maximum concentration at 4 hrs post-gavage treatment (C). High levels of the compound were still observed in the brains of rats at 24 hrs and returned to baseline at 48 hrs (C). SA00025 caused a transcriptional upregulation of Nurr1, TH and VMAT at 1-hour post daily gavage and a transcriptional downregulation of VMAT, DAT and c-RET at 4 hours post-gavage treatment (D). A normalization of Nurr1, TH and VMAT expression was observed at 4–48 hours post-gavage treatment (D). Transcription of all dopaminergic target genes was equivalent between compound and vehicle treated rats at 48 hours post-gavage treatment (D). TH protein levels were elevated at 4 hours post-gavage treatment (E). Significance is annotated as p<0.05* & p<0.001*** compared vehicle treatment (dashed lines), unpaired T-tests and ANOVA. N = 4–8/ group. Graphs are expressed as mean ± SEM.
Fig 2.
SA00025 caused neuroprotection in the 6-OHDA lesion model primed with dsRNA inflammatory stimulant (poly(I:C)).
Rats received an initial unilateral injection of poly(I:C) in the SN (Start—day 0) and a subsequent unilateral injection of 6-OHDA in the striatum (day 12) (A). Rats were also administered daily with the Nurr1 agonist (30mg/kg/ day) or vehicle treatment throughout the paradigm (day 1–32) and were sacrificed at day 33 (A). 24 hrs following the last gavage treatment levels of the compound were significantly elevated in brain homogenates and was absent in vehicle treated conditions (B). Representative photomicrographs indicate the Nurr1 agonist caused a protective affect on TH +ve (brown) and NeuN +ve (grey) neurons within the SNpc and TH +ve fibers in the striatum (C). Rats had a significant sparing of dopaminergic neurons in the SNpc after 32 days of treatment with the compound, compared to vehicle treatment (D). Dopamine neuron fibers in the rostral striatum were also significantly spared with Nurr1 agonist treatment compared to vehicle treatment (E). Significance is annotated as p<0.05*, unpaired T-tests. N = 6–8/ group. Graphs are expressed at mean ± SEM. Abbreviations: dorsal lateral striatum (DL Stri) & medial striatum (M Stri). Scale bars = 200μm. TH and NeuN +ve neurons are indicated by black arrow heads and NeuN +ve neurons are indicated by grey arrows.
Fig 3.
SA00025 induced anti-inflammatory activity in the 6-OHDA lesion model primed with dsRNA inflammatory stimulant (poly(I:C)).
There was a significant increase in the amount IBA-1 +ve microglia in the SNpc scored as rating 1 (ramified and resting) and a significant decrease in microglia scored at rating 3 (bushy and reactive) with 32 days of Nurr1 agonist treatment, compared to vehicle (A). Representative photomicrographs show that Nurr1 agonist treatment caused a reduction in IBA-1 +ve microglia that were bushy and reactive and an increase in IBA-1 +ve microglia that were ramified and resting in the SNpc (B). Representative photomicrographs show that Nurr1 agonist treatment also caused a reduction in the immunofluorescent intensity of IBA-1 +ve microglia (green) and GFAP +ve astrocytes (C). Optical density analysis indicated that Nurr1 agonist treatment caused a significant decrease in IBA-1 (D) and GFAP (E) staining in the SNpc, compared to vehicle conditions. Significance is annotated as p<0.05*, 2- way ANOVA. N = 6–8/ group. Graphs are expressed at mean ± SEM. Scale bars = 100μm.
Table 1.
Cytokine and Chemokine protein levels in the SNpc following Nurr1 agonist treatment.