Atorvastatin improves depression in MPTP-lesioned mice
The tail suspension experiment tested the depression status of the mice, and the immobility time of the limbs and body reflected depression in the mice. As shown in Fig. 1a, the immobility time was longer in the MPTP group than in the control group (F(1,7) = 158.26, p < 0.0001). After atorvastatin treatment, the immobility time was significantly reduced compared with that in the MPTP mice (F(1,7) = 15.32, p = 0.0185) but was significantly increased compared with that in the control group (F(1,7) = 49.36, p = 0.0007).
Atorvastatin improves anxiety in MPTP-lesioned mice
To verify the effect of atorvastatin on the anxiety of MPTP mice, we tested the anxiety of the mice with the elevated plus maze test. The anxiety level in the open-field test was determined based on the time the mice spent in a corner or on the dark side of the enclosure. The longer they stayed in the open arms, the lower their anxiety. As shown in Fig. 1b, the ratio of the time the MPTP mice spent in the center to the time spent in a corner or in darkness within 10 min was significantly greater than the same ratio for mice in the control group, as shown in Fig. 1b (F(1,7) = 28.00, p = 0.0047). This ratio was significantly reduced in the MPTP mice after atorvastatin treatment (F(1,7) = 9.16, p = 0.0236). However, some level of anxiety persisted after treatment with atorvastatin, as this ratio remained greater than that of the control group (F(1,7) = 11.26, p = 0.0106).
Atorvastatin improves muscle capacity in MPTP mice
The classic rotarod test is used to measure the movement capacity of mice. We noticed that atorvastatin significantly improved depression and anxiety in the MPTP mice, so we were interested in whether atorvastatin could improve muscle control. The results of the rotarod test are shown in Fig. 1c. The MPTP mice took significantly less time to fall off the rod than the control group (F(1,7) = 19.57, p = 0.0067). However, atorvastatin treatment in the MPTP mice significantly increased the length of time taken to fall relative to untreated MPTP mice (F(1,7) = 9.86, p = 0.0358). Therefore, it could be inferred that atorvastatin treatment improved muscle capacity in MPTP mice because no other significant differences were seen relative to the control group (F(1,7) = 3.72, p = 0.0712).
Atorvastatin increases the expression of tyrosine hydroxylase and decreases phosphorylated Ser129 in MPTP-lesioned mice
Tyrosine hydroxylase (TH) was significantly reduced in MPTP-treated mice, but after the administration of atorvastatin, TH significantly increased compared to the MPTP group, as shown in Fig. 2(a-d). Furthermore, we also measured the phosphorylation of α-Syn at Ser129, as shown in Fig. 2(e-h). After MPTP lesioning, phosphorylated Ser129 was increased in the substantia nigra, as shown in Fig. 2g. After atorvastatin treatment, the number and extent of phosphorylated Ser129 were significantly decreased compared to the MPTP group.
Atorvastatin promotes autophagic flux in MPTP-lesioned mCherry-eGFP tag mice
The fluorescence labeling of eGFP-mCherry-LC3 can reflect changes in the autophagic flux of dopaminergic neurons. We detected changes in autophagic flux in the substantia nigra by immunofluorescence, as shown in Fig. 3 a-i. Compared to the control group, after atorvastatin treatment, the fluorescence intensity of eGFP and mCherry in the substantia nigra did not significantly change. In MPTP-lesioned mCherry-eGFP-tagged mice, the fluorescence of eGFP and mCherry significantly increased and tended to aggregate from the dispersion state, similar to small particles, to form a group, as shown in Fig. 3g. Atorvastatin decreased the eGFP fluorescence intensity compared to MPTP, as shown in Fig. 3d. The yellow color after the merge tended to be approximately red in Fig. 3k.
Atorvastatin decreases the expression level of α-Syn Ser129 and increases the ratio of LC3II/LC3I in MPTP-lesioned mice
The immunofluorescence results of the expression of LC3 and α-Syn Ser129 are shown in Fig. 4a-h. Atorvastatin alone had no significant effect on LC3 expression compared with the control group, while MPTP treatment significantly decreased the level of LC3 aggregation. Atorvastatin reversed the decrease in LC3 caused by MPTP damage in MPTP-lesioned mice. We also found that atorvastatin alone had no significant effect on α-Syn Ser129, and MPTP significantly increased the expression level of α-Syn Ser129. The increased α-Syn Ser129 could be reversed by atorvastatin in MPTP-lesioned mice.
To further confirm our conclusions, we analyzed the protein expression of LC3 and α-Syn Ser129, as shown in Fig 4a-d. Atorvastatin alone had no significant effect on LC3 or α-Syn Ser129 compared with the control group. MPTP decreased the ratio of LC3II/LC3I (Fig. 5b) and increased the expression level of α-Syn Ser129 (Fig. 5c) compared to the control group. Atorvastatin decreased the expression level of α-Syn Ser129 and increased the ratio of LC3II/LC3I compared to the MPTP-lesioned group.
Effect of atorvastatin on the protein expression of NOX2, LC3 and α-Syn Ser129 in MPTP-lesioned mCherry-eGFP-tagged mice
To further study the protective mechanism of atorvastatin in PD mice, we used MPTP-injured mCherry-eGFP-tagged mice as an animal model of Parkinson's disease. Compared with the control group, the atorvastatin group had no significant effect on NOX2, LC3 or α-Syn Ser129. MPTP increased the protein expression of NOX2 (Fig. 6b) and α-Syn Ser129 (Fig. 6c) and decreased the ratio of LC3II/LC3I (Fig. 6d) compared to the control group. Compared to the MPTP group, atorvastatin decreased the protein expression of NOX2 and α-Syn Ser129 and increased the ratio of LC3II/LC3I.
Inhibition of NOX2 increases the protein level of LC3 and decreases α-Syn Ser129in MPTP-lesioned mCherry-eGFP-tagged mice
To further explore the relationship among NOX2, LC3 and α-Syn Ser129, we used gp91-phox shRNA (m) lentivirus to perform a brain localization injection in mCherry-eGFP tagged mice to inhibit the expression of NOX2. The protein expression of NOX2, LC3 and α-Syn Ser129 in the substantia nigra after inhibiting NOX2 is shown in Fig. 7a-d. Fig. 7b shows that the expression of NOX2 was significantly inhibited. The changes in α-Syn Ser129 and LC-3II/LC3-I were similar to those with atorvastatin treatment after NOX2 was inhibited. As shown in Fig. 7c, compared to the control group, MPTP significantly increased the protein expression of α-Syn Ser129, while inhibiting NOX2 reversed the increase in α-Syn Ser129 caused by MPTP. Compared to the MPTP group, after inhibiting NOX2, the increase in the ratio of LC3-II/LC3-I was inhibited.
Inhibition of NOX2 promotes autophagic flux in MPTP-lesioned mCherry-eGFP-tagged mice
To further explore the effect of NOX2 on autophagic flux, we used gp91-phox shRNA (m) lentivirus to perform a brain localization injection in mCherry-eGFP-tagged mice to inhibit the expression of NOX2. The changes in autophagic flux in the substantia nigra after inhibiting NOX2 are shown in Fig. 8a-l. The role of NOX2-shRNA was similar to that of atorvastatin. Compared to the control group, after atorvastatin treatment, the fluorescence intensity of eGFP and mCherry in the substantia nigra did not significantly change. In MPTP-lesioned mCherry-eGFP-tagged mice, the fluorescence of eGFP and mCherry significantly increased and tended to aggregate from the dispersion state. Inhibiting NOX2 decreased the eGFP fluorescence intensity compared to the MPTP group, and the yellow color after the merge tended to be approximately red.
Atorvastatin increases antioxidant stress by inhibiting NOX2
MPTP can induce oxidative stress by the Nrf2/Keap1/ARE pathway. Therefore, we explored the effect of atorvastatin on the antioxidant stress of Nrf2 and downstream HO-1 and NQO-1. As shown in Fig. 9a,b, Nrf2 expression was significantly reduced under MPTP induction, and the expression of single NOX2-shRNA or atorvastatin treatment on Nrf2 was not significant. Atorvastatin and NOX2 inhibition significantly increased Nrf2 expression in the MPTP-induced group compared with the single MPTP group. As shown in Figure 9a, c and d, the expression of HO-1 and NQO-1 was similar to that of Nrf2. MPTP significantly reduced the expression of HO-1 and NQO-1. The inhibition of atorvastatin and NOX2 could rescue the expression levels of HO-1 and NQO-1. It can be concluded that atorvastatin can increase the level of antioxidant stress by inhibiting NOX2, affecting Nrf2 and downstream HO-1 and NQO-1.