SIRT3 attenuates MPTP-induced nigrostriatal degeneration via enhancing mitochondrial antioxidant capacity.

Parkinson's disease (PD) is one of the most common neurodegenerative diseases, which is characterized by progressive degeneration of nigrostriatal dopaminergic neurons. There is a growing consensus that mitochondrial dysfunction and oxidative stress play a crucial role in PD pathogenesis. Sirtuin3 (SIRT3) is the major mitochondria NAD(+)-dependent deacetylase that acts as a regulator of mitochondrial protein function; it is essential for maintaining mitochondrial integrity. Although SIRT3 was reported to have anti-oxidative stress activity in an in vitro study, there is no explicit in vivo evidence for the involvement of SIRT3 in the etiology of PD. The present study shows that SIRT3 null mice do not exhibit motor and non-motor deficits compared with wild-type controls. However, SIRT3 deficiency dramatically exacerbated the degeneration of nigrostriatal dopaminergic neurons in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice. SIRT3 null mice exposed to MPTP also exhibited decreased superoxide dismutase 2, a specific mitochondrial antioxidant enzyme, and reduced glutathione peroxidase expression compared with wild-type controls. Taken together, these findings strongly support that SIRT3 has a possible role in MPTP-induced neurodegeneration via preserving free radical scavenging capacity in mitochondria.

Sirtuin 2 (SIRT2) enhances 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced nigrostriatal damage via deacetylating forkhead box O3a (Foxo3a) and activating Bim protein.

Sirtuins are NAD-dependent protein deacetylases that were shown to have beneficial effects against age-related diseases. SIRT2 is a strong deacetylase that is highly expressed in brain. It has been associated with neurodegenerative diseases. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a dopaminergic neurotoxin that replicates most of the clinical features of Parkinson disease (PD) and produces a reliable and reproducible lesion of the nigrostriatal dopaminergic pathway and neurodegeneration after its systemic administration. Chronic administration of MPTP induces lesion via apoptosis. We show here that SIRT2 deacetylates Foxo3a, increases RNA and protein levels of Bim, and as a result, enhances apoptosis in the MPTP model of PD. We also show that neurodegeneration induced by chronic MPTP regimen is prevented by genetic deletion of SIRT2 in mouse. Deletion of SIRT2 leads to the reduction of apoptosis due to an increase in acetylation of Foxo3a and a decrease in Bim levels. We demonstrate that SIRT2 deacetylates Foxo3a, activates Bim, and induces apoptosis only in 1-methyl-4-phenylpyridinium-treated cells. Therefore, designing SIRT2 inhibitors might be helpful to develop effective treatments for PD.

Protective role of SIRT5 against motor deficit and dopaminergic degeneration in MPTP-induced mice model of Parkinson's disease.

Parkinson's disease (PD) is characterized by progressive loss of nigrostriatal dopaminergic neurons that results in motor deficits including resting tremor, rigidity, bradykinesia, and postural instability. Despite decades of intensive study, the underlying molecular mechanisms are not fully understood. Multiple lines of evidence indicate that mitochondrial dysfunction and oxidative stress contribute to neuronal death, which is the key feature of neurodegeneration. Mitochondria are pivotal organelles that host essential functions in neuronal viability including energy production, oxidative phosphorylation, calcium buffering, redox homeostasis and apoptosis. SIRT5, which localizes in the mitochondrial matrix, is nicotinamide adenine dinucleotide (NAD(+))-dependent histone deacetylase. The physiological and pathophysiological functions of SIRT5 in vivo remain elusive although it is known to be an important energy sensor. Here, we investigated the role of SIRT5 in the pathogenesis of PD mice induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We present evidence that SIRT5 deficiency, by itself, does not affect motor and non-motor functions; however, lack of SIRT5 exacerbates MPTP-induced motor deficits. Consistently, MPTP-exposed SIRT5 knockout mice exhibited more severe nigrostriatal dopaminergic degeneration than that observed in wild-type controls. Furthermore, deletion of SIRT5 leads to a larger decrease, relative to control, in the expression level of manganese superoxide dismutase (SOD2), a mitochondria-specific antioxidant enzyme, after MPTP induction. These findings indicate that SIRT5 ameliorates MPTP-induced nigrostriatal dopaminergic degeneration via preserving mitochondrial antioxidant capacity.

SIRT2 enhances 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced nigrostriatal damage via apoptotic pathway.

Sirtuins are NAD-dependent protein deacetylases that were shown to have protective effects against different age-related diseases. SIRT2 is a strong deacetylase that is highly expressed in brain. It has been associated with neurodegenerative diseases. MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) is a dopaminergic neurotoxin that displays clinical features of Parkinson's Disease (PD). MPTP leads to the degeneration of nigrostriatal dopaminergic pathway after its systemic administration. Chronic administration of MPTP induces lesion via apoptosis. We show here that SIRT2 deacetylates Foxo3a, increases RNA and protein levels of Bim, and as a result enhances apoptosis in the MPTP model of PD. We also show that neurodegeneration induced by chronic MPTP regimen is prevented by genetic deletion of SIRT2 in mouse. Deletion of SIRT2 leads to the reduction of apoptosis due to an increase in acetylation of Foxo3a and a decrease in Bim levels. We demonstrate that SIRT2 deacetylates Foxo3a, activates Bim, and induces apoptosis only in MPP(+)-treated cells. Therefore, designing SIRT2 inhibitors might be helpful in developing effective treatments for PD.

Resveratrol attenuates L-DOPA-induced hydrogen peroxide toxicity in neuronal cells.

A variety of polyphenol antioxidant compounds derived from natural products have demonstrated neuroprotective activity against neuronal cell death. The objective of this study was to investigate the effect of resveratrol (RESV) and bioflavonoids in attenuating hydrogen peroxide (H(2)O(2))-induced oxidative stress in neuronal cells. H2O2 levels were increased by the addition of L-3,4-dihydroxyphenylalanine (L-DOPA) to cultured dopaminergic SKNSH cells. H(2)O(2) was monitored by peroxyfluor-1, a selective H(2)O(2) optical probe. To examine the neuroprotective effects of RESV and bioflavonoids against L-DOPA, we cotreated RESV, quercetin, or (-) epigallocatechin gallate with L-DOPA and monitored for H(2)O(2) levels. The combination of RESV and L-DOPA was 50% more effective at reducing H(2)O(2) levels than the combination of quercetin or epigallocatechin gallate with L-DOPA. However, the combination of each antioxidant with L-DOPA was effective at preserving cell viability.