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Capsaicin prevents degeneration of dopamine neurons by inhibiting glial activation and oxidative stress in the MPTP model of Parkinson's disease

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ABSTRACT

The effects of capsaicin (CAP), a transient receptor potential vanilloid subtype 1 (TRPV1) agonist, were determined on nigrostriatal dopamine (DA) neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease (PD). The results showed that TRPV1 activation by CAP rescued nigrostriatal DA neurons, enhanced striatal DA functions and improved behavioral recovery in MPTP-treated mice. CAP neuroprotection was associated with reduced expression of proinflammatory cytokines (tumor necrosis factor-α and interleukin-1β) and reactive oxygen species/reactive nitrogen species from activated microglia-derived NADPH oxidase, inducible nitric oxide synthase or reactive astrocyte-derived myeloidperoxidase. These beneficial effects of CAP were reversed by treatment with the TRPV1 antagonists capsazepine and iodo-resiniferatoxin, indicating TRPV1 involvement. This study demonstrates that TRPV1 activation by CAP protects nigrostriatal DA neurons via inhibition of glial activation-mediated oxidative stress and neuroinflammation in the MPTP mouse model of PD. These results suggest that CAP and its analogs may be beneficial therapeutic agents for the treatment of PD and other neurodegenerative disorders that are associated with neuroinflammation and glial activation-derived oxidative damage.

No MeSH data available.


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Capsaicin (CAP) reduces 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced oxidant production and activation of NADPH oxidase in the substantia nigra (SN) in vivo. (a–f) Animals receiving phosphate-buffered saline (PBS) as a control (a), CAP (0.5 mg kg−1) alone (b), MPTP (c), MPTP+CAP (d), MPTP+CAP+CZP (e) or MPTP+CAP+I-RTX (f) were killed 3 days after the last MPTP injection. SN tissues were prepared for hydroethidine histochemistry to detect oxidant production. Five to seven animals were used for each experimental group. Dotted lines indicate the SNpc. (g) Western blot analyses showed the phosphorylation of cytosolic subunits p47phox and p47phox–gp9phox binding 3 days after MPTP injection, indicating activation of NADPH oxidase in the SN. The animals were killed 3 days after the last MPTP administration, and the SN tissues were isolated. Tissue lysates were immunoprecipitated with an anti-p47phox antibody and analyzed by immunoblotting with antibodies against p47phox, gp91phox and phospho-serine. The total p47phox level indicates protein-loading control. (h) The graph represents phospho-serine and gp91phox levels expressed relative to the total p47phox. Means±s.e.m. of four samples. *P<0.01, **P<0.001, compared with PBS; #P<0.01, ##P<0.001, compared with MPTP only; &P<0.01, &&P<0.001, compared with MPTP and CAP. (i–n) The SN tissues obtained from the same animals used in a–f were prepared for 8-OHdG immunostaining to detect oxidative damage in the SN. Control (i), CAP (0.5 mg kg−1) alone (j), MPTP (k), MPTP+CAP (l), MPTP+CAP+CZP (m) or MPTP+CAP+I-RTX (n). (o) Immunoreactivity of 8-OhdG in the SN was measured using Image J. n=5–7. Note that CAP prevented MPTP-induced DNA damage in the SN, which was reversed by the TRPV1 antagonists (CZP or I-RTX). C, Control; CAP, capsaicin; M, MPTP; MC, MPTP+CAP; MCC, MPTP+CAP+CZP. ***P<0.001, significantly different from controls; ###P<0.001, significantly different from MPTP only, &&&P<0.001, significantly different from MC (analysis of variance and Student–Newman–Keuls analysis).
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fig4: Capsaicin (CAP) reduces 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced oxidant production and activation of NADPH oxidase in the substantia nigra (SN) in vivo. (a–f) Animals receiving phosphate-buffered saline (PBS) as a control (a), CAP (0.5 mg kg−1) alone (b), MPTP (c), MPTP+CAP (d), MPTP+CAP+CZP (e) or MPTP+CAP+I-RTX (f) were killed 3 days after the last MPTP injection. SN tissues were prepared for hydroethidine histochemistry to detect oxidant production. Five to seven animals were used for each experimental group. Dotted lines indicate the SNpc. (g) Western blot analyses showed the phosphorylation of cytosolic subunits p47phox and p47phox–gp9phox binding 3 days after MPTP injection, indicating activation of NADPH oxidase in the SN. The animals were killed 3 days after the last MPTP administration, and the SN tissues were isolated. Tissue lysates were immunoprecipitated with an anti-p47phox antibody and analyzed by immunoblotting with antibodies against p47phox, gp91phox and phospho-serine. The total p47phox level indicates protein-loading control. (h) The graph represents phospho-serine and gp91phox levels expressed relative to the total p47phox. Means±s.e.m. of four samples. *P<0.01, **P<0.001, compared with PBS; #P<0.01, ##P<0.001, compared with MPTP only; &P<0.01, &&P<0.001, compared with MPTP and CAP. (i–n) The SN tissues obtained from the same animals used in a–f were prepared for 8-OHdG immunostaining to detect oxidative damage in the SN. Control (i), CAP (0.5 mg kg−1) alone (j), MPTP (k), MPTP+CAP (l), MPTP+CAP+CZP (m) or MPTP+CAP+I-RTX (n). (o) Immunoreactivity of 8-OhdG in the SN was measured using Image J. n=5–7. Note that CAP prevented MPTP-induced DNA damage in the SN, which was reversed by the TRPV1 antagonists (CZP or I-RTX). C, Control; CAP, capsaicin; M, MPTP; MC, MPTP+CAP; MCC, MPTP+CAP+CZP. ***P<0.001, significantly different from controls; ###P<0.001, significantly different from MPTP only, &&&P<0.001, significantly different from MC (analysis of variance and Student–Newman–Keuls analysis).

Mentions: We recently demonstrated that MPTP induced microglia-derived production of ROS, such as hydrogen peroxide and superoxide, through NADPH oxidase activation, resulting in degeneration of DA neurons in the SN.20, 21, 28 Accordingly, we examined the effect of CAP on MPTP-induced oxidant production in the SN. Hydroethidine histochemical staining revealed significant increases in ethidium (that is, fluorescent product of oxidized hydroethidine) in the MPTP-lesioned SN (Figure 4c) compared with PBS-treated control mice (Figure 4a). In the CAP-treated MPTP-lesioned SN, the in vivo production of oxidants was significantly reduced (Figure 4d), which was reversed by the TRPV1 antagonists CZP (Figure 4e) and I-RTX (Figure 4f), indicating TRPV1 involvement. As controls, CAP alone had no effect on the production of oxidants (Figure 4b).


Capsaicin prevents degeneration of dopamine neurons by inhibiting glial activation and oxidative stress in the MPTP model of Parkinson's disease
Capsaicin (CAP) reduces 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced oxidant production and activation of NADPH oxidase in the substantia nigra (SN) in vivo. (a–f) Animals receiving phosphate-buffered saline (PBS) as a control (a), CAP (0.5 mg kg−1) alone (b), MPTP (c), MPTP+CAP (d), MPTP+CAP+CZP (e) or MPTP+CAP+I-RTX (f) were killed 3 days after the last MPTP injection. SN tissues were prepared for hydroethidine histochemistry to detect oxidant production. Five to seven animals were used for each experimental group. Dotted lines indicate the SNpc. (g) Western blot analyses showed the phosphorylation of cytosolic subunits p47phox and p47phox–gp9phox binding 3 days after MPTP injection, indicating activation of NADPH oxidase in the SN. The animals were killed 3 days after the last MPTP administration, and the SN tissues were isolated. Tissue lysates were immunoprecipitated with an anti-p47phox antibody and analyzed by immunoblotting with antibodies against p47phox, gp91phox and phospho-serine. The total p47phox level indicates protein-loading control. (h) The graph represents phospho-serine and gp91phox levels expressed relative to the total p47phox. Means±s.e.m. of four samples. *P<0.01, **P<0.001, compared with PBS; #P<0.01, ##P<0.001, compared with MPTP only; &P<0.01, &&P<0.001, compared with MPTP and CAP. (i–n) The SN tissues obtained from the same animals used in a–f were prepared for 8-OHdG immunostaining to detect oxidative damage in the SN. Control (i), CAP (0.5 mg kg−1) alone (j), MPTP (k), MPTP+CAP (l), MPTP+CAP+CZP (m) or MPTP+CAP+I-RTX (n). (o) Immunoreactivity of 8-OhdG in the SN was measured using Image J. n=5–7. Note that CAP prevented MPTP-induced DNA damage in the SN, which was reversed by the TRPV1 antagonists (CZP or I-RTX). C, Control; CAP, capsaicin; M, MPTP; MC, MPTP+CAP; MCC, MPTP+CAP+CZP. ***P<0.001, significantly different from controls; ###P<0.001, significantly different from MPTP only, &&&P<0.001, significantly different from MC (analysis of variance and Student–Newman–Keuls analysis).
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fig4: Capsaicin (CAP) reduces 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced oxidant production and activation of NADPH oxidase in the substantia nigra (SN) in vivo. (a–f) Animals receiving phosphate-buffered saline (PBS) as a control (a), CAP (0.5 mg kg−1) alone (b), MPTP (c), MPTP+CAP (d), MPTP+CAP+CZP (e) or MPTP+CAP+I-RTX (f) were killed 3 days after the last MPTP injection. SN tissues were prepared for hydroethidine histochemistry to detect oxidant production. Five to seven animals were used for each experimental group. Dotted lines indicate the SNpc. (g) Western blot analyses showed the phosphorylation of cytosolic subunits p47phox and p47phox–gp9phox binding 3 days after MPTP injection, indicating activation of NADPH oxidase in the SN. The animals were killed 3 days after the last MPTP administration, and the SN tissues were isolated. Tissue lysates were immunoprecipitated with an anti-p47phox antibody and analyzed by immunoblotting with antibodies against p47phox, gp91phox and phospho-serine. The total p47phox level indicates protein-loading control. (h) The graph represents phospho-serine and gp91phox levels expressed relative to the total p47phox. Means±s.e.m. of four samples. *P<0.01, **P<0.001, compared with PBS; #P<0.01, ##P<0.001, compared with MPTP only; &P<0.01, &&P<0.001, compared with MPTP and CAP. (i–n) The SN tissues obtained from the same animals used in a–f were prepared for 8-OHdG immunostaining to detect oxidative damage in the SN. Control (i), CAP (0.5 mg kg−1) alone (j), MPTP (k), MPTP+CAP (l), MPTP+CAP+CZP (m) or MPTP+CAP+I-RTX (n). (o) Immunoreactivity of 8-OhdG in the SN was measured using Image J. n=5–7. Note that CAP prevented MPTP-induced DNA damage in the SN, which was reversed by the TRPV1 antagonists (CZP or I-RTX). C, Control; CAP, capsaicin; M, MPTP; MC, MPTP+CAP; MCC, MPTP+CAP+CZP. ***P<0.001, significantly different from controls; ###P<0.001, significantly different from MPTP only, &&&P<0.001, significantly different from MC (analysis of variance and Student–Newman–Keuls analysis).
Mentions: We recently demonstrated that MPTP induced microglia-derived production of ROS, such as hydrogen peroxide and superoxide, through NADPH oxidase activation, resulting in degeneration of DA neurons in the SN.20, 21, 28 Accordingly, we examined the effect of CAP on MPTP-induced oxidant production in the SN. Hydroethidine histochemical staining revealed significant increases in ethidium (that is, fluorescent product of oxidized hydroethidine) in the MPTP-lesioned SN (Figure 4c) compared with PBS-treated control mice (Figure 4a). In the CAP-treated MPTP-lesioned SN, the in vivo production of oxidants was significantly reduced (Figure 4d), which was reversed by the TRPV1 antagonists CZP (Figure 4e) and I-RTX (Figure 4f), indicating TRPV1 involvement. As controls, CAP alone had no effect on the production of oxidants (Figure 4b).

View Article: PubMed Central - PubMed

ABSTRACT

The effects of capsaicin (CAP), a transient receptor potential vanilloid subtype 1 (TRPV1) agonist, were determined on nigrostriatal dopamine (DA) neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease (PD). The results showed that TRPV1 activation by CAP rescued nigrostriatal DA neurons, enhanced striatal DA functions and improved behavioral recovery in MPTP-treated mice. CAP neuroprotection was associated with reduced expression of proinflammatory cytokines (tumor necrosis factor-&alpha; and interleukin-1&beta;) and reactive oxygen species/reactive nitrogen species from activated microglia-derived NADPH oxidase, inducible nitric oxide synthase or reactive astrocyte-derived myeloidperoxidase. These beneficial effects of CAP were reversed by treatment with the TRPV1 antagonists capsazepine and iodo-resiniferatoxin, indicating TRPV1 involvement. This study demonstrates that TRPV1 activation by CAP protects nigrostriatal DA neurons via inhibition of glial activation-mediated oxidative stress and neuroinflammation in the MPTP mouse model of PD. These results suggest that CAP and its analogs may be beneficial therapeutic agents for the treatment of PD and other neurodegenerative disorders that are associated with neuroinflammation and glial activation-derived oxidative damage.

No MeSH data available.


Related in: MedlinePlus