PINK1 Silencing Modifies Dendritic Spine Dynamics of Mouse Hippocampal Neurons

miR-101a-3p/ROCK2 axis regulates neuronal injury in Parkinson's disease models

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disease characterized by the loss of dopaminergic neurons in substantia nigra pars compacta (SNpc). This study focuses on deciphering the role of microRNA (miR)-101a-3p in the neuronal injury of PD and its regulatory mechanism.

METHODS

We constructed a mouse model of PD by intraperitoneal injection of 1-methyl 4-phenyl 1, 2, 3, 6-tetrahydropyridine hydrochloride (MPTP), and used 1-methyl-4-phenylpyridinium (MPP+) to treat Neuro-2a cells to construct an in-vitro PD model. Neurological dysfunction in mice was evaluated by swimming test and traction test. qRT-PCR was utilized to examine miR-101a-3p expression and ROCK2 expression in mouse brain tissues and Neuro-2a cells. Western blot was conducted to detect the expression of α-synuclein protein and ROCK2 in mouse brain tissues and Neuro-2a cells. The targeting relationship between miR-101a-3p and ROCK2 was determined by dual-luciferase reporter gene assay. The apoptosis of neuro-2a cells was assessed by flow cytometry.

RESULTS

Low miR-101a-3p expression and high ROCK2 expression were found in the brain tissues of PD mice and MPP+-treated Neuro-2a cells; PD mice showed decreased neurological disorders, and apoptosis of Neuro-2a cells was increased after MPP+ treatment, both of which were accompanied by increased accumulation of α-synuclein protein. After miR-101a-3p was overexpressed, the neurological function of PD mice was improved, and the apoptosis of Neuro-2a cells induced by MPP+ was alleviated, and the accumulation of α-synuclein protein was reduced; ROCK2 overexpression counteracted the protective effect of miR-101a-3p. Additionally, ROCK2 was identified as the direct target of miR-101a-3p.

CONCLUSION

MiR-101a-3p can reduce neuronal apoptosis and neurological deficit in PD mice by inhibiting ROCK2 expression, suggesting that miR-101a-3p is a promising therapeutic target for PD.

A proteogenomic view of Parkinson's disease causality and heterogeneity

The pathogenesis and clinical heterogeneity of Parkinson's disease (PD) have been evaluated from molecular, pathophysiological, and clinical perspectives. High-throughput proteomic analysis of cerebrospinal fluid (CSF) opened new opportunities for scrutinizing this heterogeneity. To date, this is the most comprehensive CSF-based proteomics profiling study in PD with 569 patients (350 idiopathic patients, 65 GBA + mutation carriers and 154 LRRK2 + mutation carriers), 534 controls, and 4135 proteins analyzed. Combining CSF aptamer-based proteomics with genetics we determined protein quantitative trait loci (pQTLs). Analyses of pQTLs together with summary statistics from the largest PD genome wide association study (GWAS) identified 68 potential causal proteins by Mendelian randomization. The top causal protein, GPNMB, was previously reported to be upregulated in the substantia nigra of PD patients. We also compared the CSF proteomes of patients and controls. Proteome differences between GBA + patients and unaffected GBA + controls suggest degeneration of dopaminergic neurons, altered dopamine metabolism and increased brain inflammation. In the LRRK2 + subcohort we found dysregulated lysosomal degradation, altered alpha-synuclein processing, and neurotransmission. Proteome differences between idiopathic patients and controls suggest increased neuroinflammation, mitochondrial dysfunction/oxidative stress, altered iron metabolism and potential neuroprotection mediated by vasoactive substances. Finally, we used proteomic data to stratify idiopathic patients into "endotypes". The identified endotypes show differences in cognitive and motor disease progression based on previously reported protein-based risk scores.Our findings not only contribute to the identification of new therapeutic targets but also to shape personalized medicine in CNS neurodegeneration.

Autophagy promotes membrane trafficking of NR2B to alleviate depression by inhibiting AQP4 expression in mice

Depression is a high-incidence mental illness that seriously affects human health. AQP4 has been reported to be closely associated with depression, while the underlying mechanism is still unclear. This work aimed to investigate the functional role of AQP4 in depression. Depression mouse model was constructed by administration of chronic social defeat stress (CSDS). We found that AQP4 was highly expressed in the hippocampal tissues of CSDS mice. AQP4 knockdown alleviated depression and enhanced the expression of NR2B and PSD95 in CSDS mice. Moreover, primary hippocampal neurons were treated with N-methyl-d-aspartate (NMDA) to induce neuron injury. AQP4 overexpression repressed cell viability and promoted apoptosis of NMDA-treated primary hippocampal neurons. AQP4 up-regulation repressed the expression of NR2B (surface), and enhanced the expression of NR2B (intracellular), P-NR2B, CaMK II and CK2 in the NMDA-treated primary hippocampal neurons. The influence conferred by AQP4 up-regulation was abolished by KN-93 (CaMK II inhibitor) or TBB (CK2 inhibitor) treatment. Rapamycin treatment enhanced the expression of NR2B (surface), and repressed the expression of AQP4, NR2B (intracellular) and P-NR2B in the primary hippocampal neurons by activating autophagy. The activated autophagy alleviated depression in CSDS mice by repressing AQP4 expression. In conclusion, our data demonstrated that autophagy ameliorated depression by repressing AQP4 expression in mice, and AQP4 knockdown promoted membrane trafficking of NR2B and inhibited phosphorylation of NR2B via CaMK II/CK2 pathway. Thus, our work suggests that AQP4 may be a promising molecular target for the development of antidepressant drugs.

Oxidative stress and synaptic dysfunction in rodent models of Parkinson's disease

Parkinson's disease (PD) is a multifactorial disorder involving a complex interplay between a variety of genetic and environmental factors. In this scenario, mitochondrial impairment and oxidative stress are widely accepted as crucial neuropathogenic mechanisms, as also evidenced by the identification of PD-associated genes that are directly involved in mitochondrial function. The concept of mitochondrial dysfunction is closely linked to that of synaptic dysfunction. Indeed, compelling evidence supports the role of mitochondria in synaptic transmission and plasticity, although many aspects have not yet been fully elucidated. Here, we will provide a brief overview of the most relevant evidence obtained in different neurotoxin-based and genetic rodent models of PD, focusing on mitochondrial impairment and synaptopathy, an early central event preceding overt nigrostriatal neurodegeneration. The identification of early deficits occurring in PD pathogenesis is crucial in view of the development of potential disease-modifying therapeutic strategies.

PINK1-mediated Drp1S616 phosphorylation modulates synaptic development and plasticity via promoting mitochondrial fission

Dynamic change of mitochondrial morphology and distribution along neuronal branches are essential for neural circuitry formation and synaptic efficacy. However, the underlying mechanism remains elusive. We show here that Pink1 knockout (KO) mice display defective dendritic spine maturation, reduced axonal synaptic vesicles, abnormal synaptic connection, and attenuated long-term synaptic potentiation (LTP). Drp1 activation via S616 phosphorylation rescues deficits of spine maturation in Pink1 KO neurons. Notably, mice harboring a knockin (KI) phosphor-null Drp1^S616A recapitulate spine immaturity and synaptic abnormality identified in Pink1 KO mice. Chemical LTP (cLTP) induces Drp1^S616 phosphorylation in a PINK1-dependent manner. Moreover, phosphor-mimetic Drp1^S616D restores reduced dendritic spine localization of mitochondria in Pink1 KO neurons. Together, this study provides the first in vivo evidence of functional regulation of Drp1 by phosphorylation and suggests that PINK1-Drp1^S616 phosphorylation coupling is essential for convergence between mitochondrial dynamics and neural circuitry formation and refinement.

Excitotoxicity, calcium and mitochondria: a triad in synaptic neurodegeneration

Glutamate is the most commonly engaged neurotransmitter in the mammalian central nervous system, acting to mediate excitatory neurotransmission. However, high levels of glutamatergic input elicit excitotoxicity, contributing to neuronal cell death following acute brain injuries such as stroke and trauma. While excitotoxic cell death has also been implicated in some neurodegenerative disease models, the role of acute apoptotic cell death remains controversial in the setting of chronic neurodegeneration. Nevertheless, it is clear that excitatory synaptic dysregulation contributes to neurodegeneration, as evidenced by protective effects of partial N-methyl-D-aspartate receptor antagonists. Here, we review evidence for sublethal excitatory injuries in relation to neurodegeneration associated with Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis and Huntington's disease. In contrast to classic excitotoxicity, emerging evidence implicates dysregulation of mitochondrial calcium handling in excitatory post-synaptic neurodegeneration. We discuss mechanisms that regulate mitochondrial calcium uptake and release, the impact of LRRK2, PINK1, Parkin, beta-amyloid and glucocerebrosidase on mitochondrial calcium transporters, and the role of autophagic mitochondrial loss in axodendritic shrinkage. Finally, we discuss strategies for normalizing the flux of calcium into and out of the mitochondrial matrix, thereby preventing mitochondrial calcium toxicity and excitotoxic dendritic loss. While the mechanisms that underlie increased uptake or decreased release of mitochondrial calcium vary in different model systems, a common set of strategies to normalize mitochondrial calcium flux can prevent excitatory mitochondrial toxicity and may be neuroprotective in multiple disease contexts.

Correlation of distinct behaviors to the modified expression of cerebral Shank1,3 and BDNF in two autistic animal models

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder featuring altered neuronal circuitry and consequently impaired social interactions, restrictive interests plus repetitive stereotypic activities. In the present study, differentiated behaviors of valproic (VPA) and propionic (PPA) acid-mediated autism rats were correlated to cerebral scaffolding proteins (Shank1,3) and BDNF expression variations. Sprague-Dawley offspring that received VPA during pregnancy displayed a notably diminished permanence (-78 %, p < 0.01) in the light chamber of light dark (LD) test, reduced exploratory tasks, i.e. grooming (-90 %) and rearing (-65 %). Moreover, they executed extremely greater climbing intervals (+300 %, p < 0.001) in novel cage (NC) test, plus exhibited an extremely reduced (-331 %) discrimination index in novel object recognition (NOR) test when compared to controls. PPA-treated postnatal days (PND) 12-16 rats also displayed anxiety-like behaviors, although in a less evident manner, as indicated by a moderate time (+55 %; p < 0.05) spent in dark chamber along with notable and moderate decreases in digging (-78 %) plus grooming (-52 %), respectively. Contextually, VPA- more than PPA supplied opposite Shank1,3 expression changes in cerebellum (CB; -62 %; +78 %), dorsomedial prefrontal cortex (DM-PFC; +95 % -76 %), respectively, while resulting extremely upregulated in hippocampus (HIP; +125 % - +155 %). Even BDNF resulted to be substantially and notably diminished in HIP (-85 %) and DM-PFC (-72 %), respectively, of VPA rats while it was only moderately reduced (-35 % to -45 %) in these same areas of PPA rats. The early altered brain-specific expression levels accounting for different behavioral performances may provide useful diagnostic indications and constitute valuable therapeutic strategies for autistic patients.

Regulation of Mitochondrial Dynamics in Parkinson's Disease-Is 2-Methoxyestradiol a Missing Piece?

Mitochondria, as "power house of the cell", are crucial players in cell pathophysiology. Beyond adenosine triphosphate (ATP) production, they take part in a generation of reactive oxygen species (ROS), regulation of cell signaling and cell death. Dysregulation of mitochondrial dynamics may lead to cancers and neurodegeneration; however, the fusion/fission cycle allows mitochondria to adapt to metabolic needs of the cell. There are multiple data suggesting that disturbed mitochondrial homeostasis can lead to Parkinson's disease (PD) development. 2-methoxyestradiol (2-ME), metabolite of 17β-estradiol (E2) and potential anticancer agent, was demonstrated to inhibit cell growth of hippocampal HT22 cells by means of nitric oxide synthase (NOS) production and oxidative stress at both pharmacologically and also physiologically relevant concentrations. Moreover, 2-ME was suggested to inhibit mitochondrial biogenesis and to be a dynamic regulator. This review is a comprehensive discussion, from both scientific and clinical point of view, about the influence of 2-ME on mitochondria and its plausible role as a modulator of neuron survival.

PINK1/PARKIN signalling in neurodegeneration and neuroinflammation

Mutations in the PTEN-induced kinase 1 (PINK1) and Parkin RBR E3 ubiquitin-protein ligase (PARKIN) genes are associated with familial forms of Parkinson’s disease (PD). PINK1, a protein kinase, and PARKIN, an E3 ubiquitin ligase, control the specific elimination of dysfunctional or superfluous mitochondria, thus fine-tuning mitochondrial network and preserving energy metabolism. PINK1 regulates PARKIN translocation in impaired mitochondria and drives their removal via selective autophagy, a process known as mitophagy. As knowledge obtained using different PINK1 and PARKIN transgenic animal models is being gathered, growing evidence supports the contribution of mitophagy impairment to several human pathologies, including PD and Alzheimer’s diseases (AD). Therefore, therapeutic interventions aiming to modulate PINK1/PARKIN signalling might have the potential to treat these diseases. In this review, we will start by discussing how the interplay of PINK1 and PARKIN signalling helps mediate mitochondrial physiology. We will continue by debating the role of mitochondrial dysfunction in disorders such as amyotrophic lateral sclerosis, Alzheimer’s, Huntington’s and Parkinson’s diseases, as well as eye diseases such as age-related macular degeneration and glaucoma, and the causative factors leading to PINK1/PARKIN-mediated neurodegeneration and neuroinflammation. Finally, we will discuss PINK1/PARKIN gene augmentation possibilities with a particular focus on AD, PD and glaucoma.

The Links between Parkinson's Disease and Cancer

Epidemiologic studies indicate a decreased incidence of most cancer types in Parkinson’s disease (PD) patients. However, some neoplasms are associated with a higher risk of occurrence in PD patients. Both pathologies share some common biological pathways. Although the etiologies of PD and cancer are multifactorial, some factors associated with PD, such as α-synuclein aggregation; mutations of PINK1, PARKIN, and DJ-1; mitochondrial dysfunction; and oxidative stress can also be involved in cancer proliferation or cancer suppression. The main protein associated with PD, i.e., α-synuclein, can be involved in some types of neoplastic formations. On the other hand, however, its downregulation has been found in the other cancers. PINK1 can act as oncogenic or a tumor suppressor. PARKIN dysfunction may lead to some cancers’ growth, and its expression may be associated with some tumors’ suppression. DJ-1 mutation is involved in PD pathogenesis, but its increased expression was found in some neoplasms, such as melanoma or breast, lung, colorectal, uterine, hepatocellular, and nasopharyngeal cancers. Both mitochondrial dysfunction and oxidative stress are involved in PD and cancer development. The aim of this review is to summarize the possible associations between PD and carcinogenesis.

PINK1 alleviates thermal hypersensitivity in a paclitaxel-induced Drosophila model of peripheral neuropathy

Paclitaxel is a representative anticancer drug that induces chemotherapy-induced peripheral neuropathy (CIPN), a common side effect that limits many anticancer chemotherapies. Although PINK1, a key mediator of mitochondrial quality control, has been shown to protect neuronal cells from various toxic treatments, the role of PINK1 in CIPN has not been investigated. Here, we examined the effect of PINK1 expression on CIPN using a recently established paclitaxel-induced peripheral neuropathy model in Drosophila larvae. We found that the class IV dendritic arborization (C4da) sensory neuron-specific expression of PINK1 significantly ameliorated the paclitaxel-induced thermal hyperalgesia phenotype. In contrast, knockdown of PINK1 resulted in an increase in thermal hypersensitivity, suggesting a critical role for PINK1 in sensory neuron-mediated thermal nociceptive sensitivity. Interestingly, analysis of the C4da neuron morphology suggests that PINK1 expression alleviates paclitaxel-induced thermal hypersensitivity by means other than preventing alterations in sensory dendrites in C4da neurons. We found that paclitaxel induces mitochondrial dysfunction in C4da neurons and that PINK1 expression suppressed the paclitaxel-induced increase in mitophagy in C4da neurons. These results suggest that PINK1 mitigates paclitaxel-induced sensory dendrite alterations and restores mitochondrial homeostasis in C4da neurons and that improvement in mitochondrial quality control could be a promising strategy for the treatment of CIPN.