The effect and mechanism of interfering the nicotinamide mononucleotide adenylyltransferase 1 gene in Parkinson′s disease mouse models

Objective To investigate the effect and mechanism of interfering the nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1) gene in Parkinson′s disease (PD) mouse models. Methods Thirty mice were randomly assigned to three groups: the 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) group, the small interfering nicotinamide mononucleotide adenylyltransferase 1 (siNMNAT1)+ MPTP group, and the control group, with 10 mice in each group. After injecting siRNA-green fluorescent protein (GFP) lentivirals directly into substantia nigra (SN), mice received intraperitoneal injections of MPTP, which was the siNMNAT1+ MPTP group. While the MPTP group was only with injections of MPTP, and the control group was with neither siRNA nor MPTP. Then we assessed the motor coordination ability firstly. To observe the variation of nigrostriatal pathway, the counts of dopamanergic neurons in SN were measured by tyrosine hydroxylase (TH) immunofluorescence staining. And the expression of TH in striatum, which was used to estimate the dopaminergic neurons axonal variation, was analyzed by RT-PCR. Then the expression of TH, SOD1, Bcl2, Bax, Bcl2/Bax in SN was estimated through Western blotting. Results Compared with the control group, the siNMNAT1+ MPTP group and the MPTP group decreased significantly in motor coordination ability (creep down time: siNMNAT1+ MPTP group (62.8±15.7) s, MPTP group (77.9±13.5) s, control group (122.0±25.2) s), dopamanergic neuron counts (siNMNAT1+ MPTP group 45.0±6.7, MPTP group 68.0±11.3, control group 93.0±12.8) and the striatal TH expression (Creep down time: t=-6.291, P=0.000; t=-4.865, P=0.000. Dopamanergic neuron counts: t=-10.482, P=0.000; t=-4.624, P=0.000. TH expression: t=-9.117, P=0.000; t=-5.716, P=0.000). Although the siNMNAT1+ MPTP group showed lower coordination ability than the MPTP group, there was no statistically significant difference. Whereas the counts of dopamanergic neurons in SN (t=-5.487, P=0.000), the expression of TH in striatum (t=-5.146, P=0.003), SOD1 (t=-4.143, P=0.001) and Bcl2/Bax (t=-6.303, P=0.000) were obviously decreased in the siNMNAT1+ MPTP group, in which Bax increased significantly (t=3.550, P=0.002). Conclusions Interfering the expression of NMNAT1 aggravated the neurodegeneration in PD, and the mechanism might be related to oxidative stress and programmed cell death. Key words: Nicotinamide mononucleotide adenylyltransferase 1; Gene expression; Parkinson disease; 1-Methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine