Article Figures & Data
Figures
- Fig. 1.
Effect of minocycline on MPTP-induced SNpc dopaminergic neuronal death. In saline-injected control mice treated without (A) or with (B; 45 mg/kg twice daily) minocycline, there are numerous SNpc TH-positive neurons (brown; A, B). MPTP (18 mg/kg for 4 injections) reduces the number of SNpc TH-positive neurons (C) 7 d after the last injection. In mice treated with both MPTP and minocycline, there is a noticeable attenuation of SNpc TH-positive neuronal loss (D). At a lower MPTP dosage (16 mg/kg for 4 injections), loss of TH-positive structures is less (E) and minocycline protection is more obvious (F). Scale bar, 50 μm. Bar graph shows SNpc TH-positive neuronal counts (G) assessed under the various experimental conditions. Minocycline 1,6, 11, 22,45, Mice injected with minocycline at 1.4, 6.1, 11.3, 22.5, and 45.0 mg/kg twice daily. *p < 0.05, fewer than saline-injected or minocycline-injected control mice. #p > 0.05, same as MPTP-injected mice. **p < 0.05, fewer than control mice but more than MPTP-injected mice. ##p < 0.05, more than MPTP-injected mice and not different from control mice. Values are means ± SEM (n = 6–8 per group).
- Fig. 2.
Effect of minocycline on MPTP-induced striatal dopaminergic fiber loss. In saline-injected control mice treated without (A) or with (B; 45 mg/kg twice daily) minocycline, there are a high density of striatal TH-positive fibers. MPTP (18 mg/kg for 4 injections) reduces the density of striatal TH-positive fibers (C) 7 d after the last injection. In mice treated with both MPTP and minocycline, there is also a noticeable striatal TH-positive fiber loss (D). At a lower MPTP dosage (16 mg/kg for 4 injections), loss of TH-positive structures is less (E) and minocycline protection is obvious (F). Scale bar, 1 mm. Bar graph shows striatal TH-positive optical density (G) assessed under the various experimental conditions (F(5,33) = 41.475;p < 0.001). *p < 0.05, fewer than saline-injected or minocycline-injected control mice. #p > 0.05, same as MPTP-injected mice. **p < 0.05, more than MPTP-injected mice but fewer than control mice. Values are means ± SEM (n= 6–8 per group).
- Fig. 3.
Minocycline prevents MPTP-induced MAC-1 transcription. A, B, Ventral midbrain MAC-1 mRNA levels but not GFAP mRNA levels are increased by 24 hr after MPTP injection compared with those of saline- or minocycline-injected mice. Minocycline prevents MPTP-induced MAC-1 mRNA increases. MAC-1 and GFAP mRNA values are normalized with GAPDH. Values are mean ± SEM ratios (n = 5–7 mice per group).Saline, Saline-treated; Mc, minocycline-treated;MPTP, MPTP-treated; M + Mc, MPTP plus minocycline-treated. *p < 0.05, higher than both saline- and minocycline-injected control groups. **p < 0.05, lower than MPTP-injected group and not different from both control groups.
- Fig. 4.
Minocycline prevents MPTP-induced microglia reaction. Microglia cells (brown) and TH-positive neurons (gray blue) are seen in both SNpc and striatum of all mice. One day after the last MPTP injection, numerous activated microglia (larger cell body, poorly ramified short and thick processes) are seen in SNpc (A, B) and striatum (C, D). Mice injected with both MPTP and minocycline show minimal microglial activation in SNpc (E) and striatum (G); here, microglial cell bodies are small and processes are thin and ramified (F, H). Scale bar:A, C, E, G, 1 mm; B, D, F,H, 100 μm.
- Fig. 5.
Minocycline does not affect MPTP-induced astrocytic reaction. One day after the last injection of MPTP, there is a mild astrocytic response (A, B), but 7 d after the last injection of MPTP, it becomes conspicuous (C, D). Minocycline does not affect the astrocytic response (E, F) 7 d after MPTP administration. Scale bar: A,C, E, 1 mm; B,D, F, 100 μm.
- Fig. 6.
Effects of MPTP and minocycline on microglial-derived deleterious factors IL-1β (A), iNOS (B), and NADPH–oxidase (C, D). MPTP (18 mg/kg for 4 injections) increases ventral midbrain mature IL-1β formation, iNOS catalytic activity, and NADPH–oxidase activation, as evidenced by the translocation of its subunit p67phox from the cytosol to the plasma membrane, 1 d after the last injection of MPTP. Minocycline (45 mg/kg twice daily) attenuates MPTP-related effects on mature IL-1β, iNOS, and NADPH–oxidase.Saline, Saline-treated; Mc, minocycline-treated; M, MPTP-treated;M+Mc, MPTP plus minocycline-treated. *p < 0.05, more than saline-injected or minocycline-injected control mice. **p < 0.05, less than MPTP-injected mice but not different from both control groups. Values are means ± SEM (n = 5–8 mice per group).
- Fig. 7.
Minocycline attenuates MPTP-induced striatal damage by inhibiting microglia but not just by inhibiting iNOS. The optical density of striatal TH-positive fibers varied significantly among the various groups (F(7,47) = 83.576;p < 0.001). Minocycline, Mice injected with minocycline 45 mg/kg twice daily. MPTP, Mice injected with MPTP (4 injections of 16 mg/kg). *p < 0.05, fewer than saline-injected or minocycline-injected control mice. #p < 0.05, fewer than control mice but no different than wild-type mice injected with MPTP. **p < 0.05, fewer than control but more than MPTP-injected mice. # #p < 0.05, more than MPTP-injected mice but no different from wild-type mice injected with both MPTP and minocycline.
Tables
Saline Minocycline MPTP MPTP–minocycline Ventral midbrain 16.2 ± 1.3 18.5 ± 1.7 32.2 ± 6.0* 21.8 ± 1.81-160 Cerebellum 13.1 ± 0.8 14.0 ± 2.1 13.4 ± 1.0 11.7 ± 1.1 Nitrotyrosine levels are significantly different among groups in the ventral midbrain (F(3,23) = 4.56;p < 0.05) but not in cerebellum (F(3,23) = 0.618; p > 0.05).
↵* p < 0.05, more than saline-injected and minocycline-injected control mice.
↵F1-160 p < 0.05, less than MPTP-injected mice but not different from both control groups. Saline, Mice injected with saline; Minocycline, mice injected with minocycline only (45 mg/kg twice daily); MPTP, mice injected with MPTP only (18 mg/kg MPTP for 4 injections in one day); MPTP–minocycline, mice injected with both MPTP and minocycline. Values are means ± SEM (n = 6–8 per group).
MPP+ level Treatment MPTP only MPTP–minocycline pretreatment MPTP–minocycline post-treatment μg/gm tissue 6.42 ± 0.92 5.21 ± 0.66 6.52 ± 0.59 [3H]MPP+ uptake Minocycline (μm) 0 10 100 333 % of control 100 98 ± 3 96 ± 3 82 ± 1 MPP+-induced lactate Minocycline (μm) 0 10 100 333 μm/100 mg protein 74 ± 4 71 ± 6 70 ± 6 67 ± 6 For MPP+ levels, minocycline (45 mg/kg) was given either 30 min before or after MPTP administration. Values are means ± SEM of either six mice per group (MPP+levels) or three independent experiments each performed in duplicate ([3H]MPP+ uptake and lactate levels). None of the presented values differ significantly (p > 0.05) from MPTP only (MPP+ levels) or from 0 μmminocycline ([3H]MPP+ uptake and lactate levels).
