1-Methyl-4-phenyl-1,2,3,6-tetrahydropyride neurotoxicity is attenuated in mice overexpressing Bcl-2

Abstract

The proto-oncogene Bcl-2 rescues cells from a wide variety of insults. Recent evidence suggests that Bcl-2 protects against free radicals and that it increases mitochondrial calcium-buffering capacity. The neurotoxicity of 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyride (MPTP) is thought to involve both mitochondrial dysfunction and free radical generation. We therefore investigated MPTP neurotoxicity in both Bcl-2 overexpressing mice and littermate controls. MPTP-induced depletion of dopamine and loss of [3H]mazindol binding were significantly attenuated in Bcl-2 overexpressing mice. Protection was more profound with an acute dosing regimen than with daily MPTP administration over 5 d. 1-Methyl-4-phenylpyridinium (MPP+) levels after MPTP administration were similar in Bcl-2 overexpressing mice and littermates. Bcl-2 blocked MPP+-induced activation of caspases. MPTP-induced increases in free 3-nitrotyrosine levels were blocked in Bcl-2 overexpressing mice. These results indicate that Bcl-2 overexpression protects against MPTP neurotoxicity by mechanisms that may involve both antioxidant activity and inhibition of apoptotic pathways.

Fig. 1.

Effects of MPTP administered at 15 mg/kg intraperitoneally every 2 hr for 4 doses on dopamine, DOPAC, and HVA in wild-type and Bcl-2 overexpressing mice. **p < 0.01; ***p < 0.001 compared with MPTP in controls.

Fig. 2.

Effects of MPTP administered at 15 mg/kg intraperitoneally every 2 hr for 4 doses on [³H]mazindol binding in the striatum in wild-type and Bcl-2 overexpressing mice. ***p < 0.001 compared with MPTP in controls.

Fig. 3.

Representative autoradiographs of total [³H]mazindol binding in the striatum in wild-type and Bcl-2 overexpressing mice after acute administration of MPTP.Left, Untreated wild-type mouse. Midleft, MPTP-treated wild-type mouse. Midright, Untreated Bcl-2 transgenic mouse. Right, MPTP-treated Bcl-2 transgenic mouse.

Fig. 4.

Effects of MPTP administered at 20 mg/kg intraperitoneally daily for 5 days on dopamine, DOPAC, and HVA in wild-type and Bcl-2 overexpressing mice. **p < 0.01 compared with MPTP in controls.

Fig. 5.

Effects of MPTP administered at 20 mg/kg intraperitoneally daily for 5 days on [³H]mazindol binding in the striatum in wild-type and Bcl-2 overexpressing mice. ***p < 0.001 compared with MPTP in controls.

Fig. 6.

Representative autoradiographs of total [³H]mazindol binding in the striatum in wild-type and Bcl-2 overexpressing mice after chronic administration of MPTP.Left, Untreated wild-type mouse. Midleft, MPTP-treated wild-type mouse. Midright, Untreated Bcl-2 transgenic mouse. Right, MPTP-treated Bcl-2 transgenic mouse.

Fig. 7.

Effects of MPTP administration on 3-nitrotyrosine concentrations in wild-type and Bcl-2 overexpressing mice. MPTP induced a significant increase in 3-nitrotyrosine at 3 hr after the last dose compared with saline treated controls, which was significantly attenuated in Bcl-2 overexpressing mice. *p < 0.05 compared with saline; #p < 0.05 compared with MPTP-treated wild type.

Fig. 8.

Striatal MPP⁺ injections induce Bcl-2-sensitive activation of caspase-2. MPP⁺ or vehicle (saline) were injected into the striatum of wild-type or Bcl-2 transgenic animals, and immunoblot analysis of striatal lysates was performed at 12 and 24 hr after injection. The 51 kDa band corresponds to caspase-2 (Nedd2/ICH-1_L), and the 24 kDa band represents a cleaved product of caspase-2.