GSNOR deficiency attenuates MPTP-induced neurotoxicity and autophagy by facilitating CDK5 S-nitrosation in a mouse model of Parkinson's disease.

The S-nitrosoglutathione reductase (GSNOR) is a key denitrosating enzyme that regulates protein S-nitrosation, a process which has been found to be involved in the pathogenesis of Parkinson's disease (PD). However, the physiological function of GSNOR in PD remains unknown. In a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model, we found that GSNOR expression was significantly increased and accompanied by autophagy mediated by MPTP-induced cyclin dependent kinase 5 (CDK5), behavioral dyskinesias and dopaminergic neuron loss. Whereas, knockout of GSNOR, or treatment with the GSNOR inhibitor N6022, alleviated MPTP-induced PD-like pathology and neurotoxicity. Mechanistically, deficiency of GSNOR inhibited MPTP-induced CDK5 kinase activity and CDK5-mediated autophagy by increasing S-nitrosation of CDK5 at Cys83. Our study indicated that GSNOR is a key regulator of CDK5 S-nitrosation and is actively involved in CDK5-mediated autophagy induced by MPTP.

Jiao L ，Su LY ，Liu Q ，Luo R ，Qiao X ，Xie T ，Yang LX ，Chen C ，Yao YG ... -  《-》

Melatonin attenuates MPTP-induced neurotoxicity via preventing CDK5-mediated autophagy and SNCA/α-synuclein aggregation.

Su LY ，Li H ，Lv L ，Feng YM ，Li GD ，Luo R ，Zhou HJ ，Lei XG ，Ma L ，Li JL ，Xu L ，Hu XT ，Yao YG ... -  《-》

Downregulation of miR-124 in MPTP-treated mouse model of Parkinson's disease and MPP iodide-treated MN9D cells modulates the expression of the calpain/cdk5 pathway proteins.

Parkinson's disease (PD) is a debilitating neurodegenerative disorder causing severe motor disabilities resulting from the loss of dopaminergic neurons in the substantia nigra pars compacta (SNc) region of the midbrain. MicroRNAs (miRNAs) are small, non-coding RNAs which play a major role in several cellular processes in health and disease by regulating gene expression post-transcriptionally. Aberrant miRNA expression has been detected in post-mortem human PD brain samples, in vitro and in vivo PD models. However, none of the studies have focused on the role of the brain-abundant miR-124 in PD. In this study, we have evaluated the expression changes of miR-124 in the SN of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model. MiRNA expression analysis by qPCR revealed a decrease in the expression of brain-enriched miR-124 in the SN of MPTP-treated mice as compared to controls. Further, in vitro study revealed a decrease in the expression of miR-124 in MN9D dopaminergic neurons treated with methyl phenyl pyridinium (MPP) iodide. The expression of calpains 1 and 2 which is modulated by miR-124 was increased in the SNc of MPTP-treated mice as observed at different time points after treatment and in the MN9D dopaminergic neurons treated with MPP iodide leading to increased expression of the p35 cleavage product, p25 and cyclin-dependent kinase 5 (cdk5). Calpain-p25-mediated increase in cdk5 expression leading to dopaminergic neuronal death has been demonstrated in human PD and MPTP-PD models. Increased expression of calpain 1/cdk5 pathway proteins was observed in anti-miR-124-transfected MN9D cells in our studies. Knockdown of miR-124 led to increased production of reactive oxygen species (ROS) and hydrogen peroxide (H2O2) both known to increase oxidative stress. Further, experiments with miR-124 target protector sequences specific to calpain 1 revealed an interaction of miR-124 with calpain 1. Overexpression of miR-124 after MPP iodide treatment on MN9D cells was found to attenuate the expression of the calpain 1/p25/cdk5 proteins while improving cell survival. These results suggest that miR-124 acts to modulate the expression of calpain/cdk5 pathway proteins in the dopaminergic neurons. A better understanding of the mechanisms controlling the expression of miR-124 will aid in targeting miR-124 for better treatment strategies for PD.

Kanagaraj N ，Beiping H ，Dheen ST ，Tay SS ... -  《-》

CDK5-USP30 signaling pathway regulates MAVS-mediated inflammation via suppressing mitophagy in MPTP/MPP(+) PD model.

The discovery of MPTP, an industrial chemical and contaminant of illicit narcotics, which causes parkinsonism in humans, non-human primates and rodents, has led to environmental pollutants exposure being convicted as key candidate in Parkinson's disease (PD) pathogenesis. Though MPTP-induced mitochondrial dysfunction and neuroinflammation are mainly responsible for the causative issue of MPTP neurotoxicity, the underlying mechanism involved remains unclear. Here, we reveal a novel signaling mechanism of CDK5-USP30-MAVS regulating MPTP/MPP+ induced PD. MPP+ (the toxic metabolite of MPTP) treatment not only led to the increased protein levels of USP30 but also to mitophagy inhibition, mitochondrial dysfunction, and MAVS-mediated inflammation in BV2 microglial cells. Both mitophagy stimulation (Urolithin A administration) and USP30 knockdown relieved MAVS-mediated inflammation via restoring mitophagy and mitochondrial function in MPP+-induced cell model. Notably, MPTP/MPP+-induced CDK5 activation regulated USP30 phosphorylation at serine 216 to stabilize USP30. Moreover, CDK5-USP30 pathway promoted MAVS-mediated inflammation in MPTP/MPP+-induced PD model. Inhibition of CDK5 not only had a protective effect on MPP+-induced cell model of PD via suppressing the upregulation of USP30 and the activation of MAVS inflammation pathway in vitro, but also prevented neurodegeneration in vivo and alleviated movement impairment in MPTP mouse model of PD. Overall, our study reveal that CDK5 blocks mitophagy through phosphorylating USP30 and activates MAVS inflammation pathway in MPTP/MPP+-induced PD model, which suggests that CDK5-USP30-MAVS signaling pathway represents a valuable treatment strategy for PD induced by environmental neurotoxic pollutants in relation to MPTP.

Ren Y ，Wu X ，Bai T ，Yang N ，Yuan Y ，Xu L ，Wen Y ，Wen Y ，Wang Z ，Zhou L ，Zou F ，Li W ... -  《-》

Cdk5/p25 specific inhibitory peptide TFP5 rescues the loss of dopaminergic neurons in a sub-acute MPTP induced PD mouse model.

Parkinson's disease (PD) is pathologically characterized by progressively loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and the formation of Lewy bodies. In 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) induced PD mice models, the calpain- cyclin-dependent kinase 5 (Cdk5)-myocyte enhancer factor 2 (MEF2) signaling has been proven in governing dopaminergic neuronal death. Under MPTP insult, p35 is cleaved by calpain into p25, which binds to Cdk5 and exhibits hyperactivity of Cdk5/p25. Cdk5/p25 inactivates MEF2, a survivor factor, which is critical for DA neuronal death. In this study, neuroprotective effect of the Cdk5/p25 specific peptide, TFP5, was evaluated in sub-acute MPTP induced PD mouse model by intraperitoneal (i.p.) injection of MPTP for five consecutive days. The results indicated that the levels of p35 and p25, and p25/p35 ratio increased in the sub-acute MPTP mice. TFP5 broadly reached cortex neuron, hippocampus and SNpc areas after i.p. injections. Pretreatment with 45mg/kg/day TFP5, as well as 10mgkg/day Cdk5 inhibitor roscovitine, for three days significantly rescued DA neuronal loss up to 9.8% or 9.7% respectively compared to the saline treated group. Treatment of TFP5 and roscovitine reduced the levels of inactive form of MEF2 and cleaved caspase 3, thus protected apoptosis of DA neurons against MPTP insult. Our results propose that TFP5 might be a potential therapeutic candidate for PD.

Zhang Q ，Xie H ，Ji Z ，He R ，Xu M ，He Y ，Huang J ，Pan S ，Hu Y ... -  《-》