Detoxification of 6-hydroxydopamine-induced Parkinsonian neurodegeneration by G-CYPMPO, a novel radical trapper

Abstract

2-(5,5-Dimethyl-2-oxo-2-λ(5)-[1,3,2]dioxaphosphinan-2-yl)-2-methyl-3,4-dihydro-2H-pyrroline N-oxide {2-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphinan-2-yl)-3,4-dihydro-2-methyl-2H-pyrrole N-oxide, G-CYPMPO} as the stable crystals having gauche conformation was successfully synthesized as a novel 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO)-type spin trap agent. However, the function of G-CYPMPO in vivo is still unclear. Thus, the purpose of this study was to evaluate the effects of G-CYPMPO in an in vivo model of Parkinson's disease (PD). Rats were microinjected with 6-hydroxydopamine (6-OHDA, 32nmol) in the presence or absence of G-CYPMPO (0.4, 1.2, 4nmol). We investigated behavioral and histochemical parameters in this rat model of PD. In addition, to examine the effects of G-CYPMPO against oxidative stress, we used electron spin resonance (ESR) spectrometry. Intranigral injection of 6-OHDA alone induced a massive loss of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra pars compacta (SNpc). Co-microinjection of G-CYPMPO significantly prevented 6-OHDA-induced dopaminergic neurodegeneration and behavioral impairments. Immunoreactivities for glial markers, such as cluster of differentiation antigen-11b (CD11b) and glial fibrillary acidic protein (GFAP), were notably detected in the SNpc of rats injected with 6-OHDA alone. These immunoreactivities were markedly suppressed by the co-microinjection of G-CYPMPO, similar to the results in vehicle-treated rats. In addition, G-CYPMPO directly trapped hydroxyl radical (OH) generated from 6-OHDA and Fe(2+) in a concentration-dependent manner. These results suggest that G-CYPMPO attenuates 6-OHDA-induced dopaminergic neurodegeneration in a rat model of PD, and is a useful tool for biological research.