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/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 ... -  《-》

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 ... -  《-》

MicroRNA-124 regulates the expression of p62/p38 and promotes autophagy in the inflammatory pathogenesis of Parkinson's disease.

Yao L ，Zhu Z ，Wu J ，Zhang Y ，Zhang H ，Sun X ，Qian C ，Wang B ，Xie L ，Zhang S ，Lu G ... -  《-》

Loss of collapsin response mediator protein 4 suppresses dopaminergic neuron death in an 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced mouse model of Parkinson's disease.

Parkinson's disease (PD) is a progressive neurodegenerative disorder that is characterized by the selective loss of dopaminergic neurons in the substantia nigra pars compacta (SNc). Several lines of evidence suggest that neurodegeneration in PD is accelerated by a vicious cycle in which apoptosis in dopaminergic neurons triggers the activation of microglia and harmful inflammatory processes that further amplify neuronal death. Recently, we demonstrated that the deletion of collapsin response mediator protein 4 (CRMP4) suppresses inflammatory responses and cell death in a mouse model of spinal cord injury, leading to improved functional recovery. We thus hypothesized that Crmp4-/- mice may have limited inflammatory responses and a decrease in the loss of SNc dopaminergic neurons in an 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model. We observed CRMP4 expression in neurons, astrocytes, and microglia/macrophages following the injection of 25 mg/kg MPTP. We compared the number of dopaminergic neurons and the inflammatory response in SNc between Crmp4+/+ and Crmp4-/- mice after MPTP injection. Limited loss of SNc dopaminergic neurons and decreased activations of microglia and astrocytes were observed in Crmp4-/- mice. These results suggest that CRMP4 is a novel therapeutic target in the treatment of PD patients. We demonstrated that genetic CRMP4 deletion delays a vicious cycle of inflammation and neurodegeneration in a Parkinson's disease mouse model. MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) injection to wild-type mice induces collapsin response mediator protein 4 (CRMP4) up-regulation in neurons, astrocytes, and microglia. CRMP4-deficient mice show reduced inflammation and suppressed dopaminergic neuronal death after MPTP injection. These findings suggest that CRMP4 deletion may be a new therapeutic strategy against Parkinson's diseases.

Tonouchi A ，Nagai J ，Togashi K ，Goshima Y ，Ohshima T ... -  《-》