Fig. 6

Metformin ameliorates PD-like pathology in MPTP-induced PD model via delay of cGAS-mediated astrocytes senescence. A Mesencephalic primary neurons were treated with astrocytic conditioned medium (ACM) from astrocytes transfected with Mfn2 plasmid and then stimulated with metformin (0.2 mM) and MPP⁺. Representative pictures of MAP2 (green) immunostaining. DAPI stains nucleus (blue). B, C Quantification of relative the number of neurons (B) and mean total neuritis length (C, Three independent experiments). D Mesencephalic primary neurons were treated with astrocytic conditioned medium (ACM) from astrocytes transfected with cGAS siRNA (si-cGAS) and then stimulated with metformin (0.2 mM) and MPP⁺. Representative pictures of MAP2 (green) immunostaining. DAPI stains nucleus (blue). E, F Quantification of relative the number of neurons (E) and mean total neuritis length (F, four independent experiments). G, H the time taken to turn around (Time-turn) and descend a pole (Time-total) was recorded in pole test (n = 9–12 animals for each group). I Time on the rod was measured by the rotarod test (n = 10–13 animals for each group). J, K Movement distance within 5 min was recorded by open field test (n = 10–13 animals for each group). L, M Representative immunoblots (L) and quantification of relative expression of TH (M) in the SNpc (n = 5 animals for each group). N Microphotographs of TH-positive neurons in the SNpc. O Stereological counts of TH-positive neurons in the SNpc (n = 6 animals for each group). P Proposed model depicting metformin inhibits astrocyte senescence via Mfn2-mtDNA-cGAS-STUNG signal in PD. The data shown are the mean ± SEM. Two-way ANOVA with Tukey’s post-hoc tests were used. **p < 0.01, ***p < 0.001, NS: no significant