The Role of Phospholipid Methylation in 1-Methyl-4-Phenyl-Pyridinium Ion (MPP+)-Induced Neurotoxicity in PC12 Cells

Serum-Based Lipid Panels for Diagnosis of Idiopathic Parkinson's Disease

Parkinson's disease (PD) is a highly prevalent neurodegenerative movement disorder with an unclear etiology and a lack of definite diagnostic tests and effective treatments. About 95% of PD cases are idiopathic, in which none of the well-known genes underlying familial parkinsonism are mutated. We used untargeted liquid chromatography-mass spectrometry (LC-MS/MS) to profile the serum lipidome of 50 patients with different stages of idiopathic PD (early, mid, or advanced) and 45 age-matched controls. When comparing the PD patients to the control subjects, 169 lipids were significantly altered in both a univariate analysis and a multivariate partial least-squares discriminant analysis (PLS-DA). Compared to the controls, the patients with PD had higher levels of unsaturated triacylglycerides (e.g., TG O-56:9 and TG 52:3), saturated lysophosphatidylcholines (LPC 17:0, 16:0, and 15:0), and hydroxyeicosatetraenoic acid (12-HETE), while lower levels of phosphatidylserines (e.g., PS 40:4 and PS 16:0_22:4), sphingomyelins (SM 42:1), and ceramides (e.g., Cer 40:0 and 42:0) were found between the PD patients and the controls. A panel of 10 significantly altered lipids (PS 40:0, Cer 40:0, Cer 42:0, LPC 17:0, LPC 15:0, PC 37:7, PE O-40:8, PC O-42:4, FA 23:0, and SM 42:1) resulted in a strong receiver operating characteristic curve with an AUC = 0.974. This panel may, therefore, be useful for diagnosing PD. In addition, lipid panels may prove useful for distinguishing among the progression stages of PD. Using one-way ANOVA, 155 lipid species were significantly altered among the PD stages. Parkinson's disease progressed from the early to advanced stages with decreasing levels of PC 31:1, PC 38:4, and LPE 22:5. Conversely, LPC-O 20:0, PC O-42:3, FA 19:0, and FA 22:2 showed an increase in their levels with disease progression. Overall, this study shows an intriguing number of robust changes in specific serum lipids that may become useful for diagnosing PD and its progression, once panels have been validated in larger clinical trials and prospective studies.

The Metabolomic Approach Reveals the Alteration in Human Serum and Cerebrospinal Fluid Composition in Parkinson's Disease Patients

Parkinson’s disease (PD) is a major public health problem. Since currently there are no reliable diagnostic tools to reveal the early steps of PD, new methods should be developed, including those searching the variations in human metabolome. Alterations in human metabolites could help to establish an earlier and more accurate diagnosis. The presented research shows a targeted metabolomics study of both of the serum and CSF from PD patients, atypical parkinsonian disorders (APDs) patients, and the control. The use of the LC-MS/MS system enabled to quantitate 144 analytes in the serum and 51 in the CSF. This information about the concentration enabled for selection of the metabolites useful for differentiation between the studied group of patients, which should be further evaluated as candidates for markers of screening and differential diagnosis of PD and APDs. Among them, the four compounds observed to be altered in both the serum and CSF seem to be the most important: tyrosine, putrescine, trans-4-hydroxyproline, and total dimethylarginine. Furthermore, we indicated the metabolic pathways potentially related to neurodegeneration processes. Our studies present evidence that the proline metabolism might be related to neurodegeneration processes underlying PD and APDs. Further studies on the proposed metabolites and founded metabolic pathways may significantly contribute to understanding the molecular background of PD and improving the diagnostics and treatment in the future.

Exendin-4 Reversed the PC12 Cell Damage Induced by circRNA CDR1as/miR-671/GSK3β Signaling Pathway

The purpose of this paper is to study the effect of circRNA cerebellar degeneration-related protein 1 antisense RNA(CDR1as)/miR-671/GSK3β signaling pathway on PC12 cell injury and the mechanism of Exendin-4 (Ex-4) in PC12 cell injury protection. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) was used to detect the expression levels of circular RNA CDR1as and miR-671 in PC12 cells. By overexpressing or knocking out CDR1as, miR-671, and GSK3β, the role of CDR1as, miR-671, and GSK3β in PC12 cell injury was analyzed. The binding of CDR1as to miR-671 and GSK3β to miR-671 was verified by dual luciferase reporter assay. PC12 cells were treated with 1-methyl-4 phenyl-pyridine ion (MPP⁺) to construct a PC12 cell damage model. PC12 cell transfection experiments were used to confirm the role of CDR1as/miR-671/GSK3β signal axis in PC12 cell damage, and the role of Ex-4 in the association of circRNA CDR1as/miR-671/GSK3β signaling axis and PC12 cell damage. PC12 cell damage was detected by 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and cellular lactate dehydrogenase (LDH) release. Ex-4 reversed the phosphorylation levels of PI3K, AKT, and GSK-3β in MPP⁺-treated PC12 cells, and reduced MPP⁺-induced PC12 cell damage. CircRNA CDR1as upregulated the expression of GSK3β by sponge miR-671. Ex-4 downregulated CDR1as expression and upregulated miR-671 expression in MPP⁺-induced PC12 cell. Silencing of CDR1as reduced MPP⁺-induced PC12 cell damage. CDR1as transfection downregulated the expression of miR-671 in PC12 cells, promoted the expression and phosphorylated of GSK3β, and induced PC12 cell damage. GSK3β silencing reversed CDR1as-induced PC12 cell damage. CDR1as promoted the phosphorylation level of GSK3β in PC12 cells to cause cell damage; Ex-4 reversed the phosphorylation of GSK3β caused by CDR1as in PC12 cells and reduced the PC12 cell damage caused by CDR1as. Ex-4 reverses the damage of PC12 cells induced by CDR1as/miR-671/GSK3β signaling pathway.

Dual effects of S-adenosyl-methyonine on PC12 cells exposed to the dopaminergic neurotoxin MPP. J Pharm Pharmacol 2020;72:1427-1435. [PMID: 32602113 DOI: 10.1111/jphp.13323]

OBJECTIVES

To investigate S-adenosyl-methyonine (SAM) effects on PC12 cells viability and neuritogenesis treated with MPP+ (1-methyl-4-phenylpyridinium).

METHODS

PC12 cell viability test (MTT assay) in DMEM medium with SAM and/or MPP+; PC12 cell neuritogenesis test in F-12K medium with nerve growth factor (NGF); DNMT activity in PC12 cells (DNMT Activity Assay Kit) with SAM and/or MPP+.

KEY FINDINGS

(1) MPP+ decreased cell viability; (2) SAM did not affect cell viability per se, but it increased MPP+ neurotoxicity when co-incubated with the neurotoxin, an effect abolished by DNA methyltransferases (DNMT) inhibitors; (3) pretreatment with SAM for 30 min or 24 h before MPP+ addition had no effect on cell viability. Neuritogenesis: Treatment with SAM for 30 min or 24 h (1) increased cell differentiation per se, (2) increased NGF differentiating effects (additive effect) and (3) blocked the neuritogenesis impairment induced by MPP+. SAM with MPP+ increased the DNMT activity, whereas SAM alone or MPP+ alone did not.

CONCLUSIONS

(1) SAM might induce neurotoxic or neuroprotective effects on PC12 cells, depending on the exposure conditions; (2) DNMT inhibitors might attenuate the MPP+ exacerbation toxicity induced by SAM; (3) DNA methylation might be involved in the observed effects of SAM (needs further investigation).

The Role of Lipids in Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disease characterized by a progressive loss of dopaminergic neurons from the nigrostriatal pathway, formation of Lewy bodies, and microgliosis. During the past decades multiple cellular pathways have been associated with PD pathology (i.e., oxidative stress, endosomal-lysosomal dysfunction, endoplasmic reticulum stress, and immune response), yet disease-modifying treatments are not available. We have recently used genetic data from familial and sporadic cases in an unbiased approach to build a molecular landscape for PD, revealing lipids as central players in this disease. Here we extensively review the current knowledge concerning the involvement of various subclasses of fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, and lipoproteins in PD pathogenesis. Our review corroborates a central role for most lipid classes, but the available information is fragmented, not always reproducible, and sometimes differs by sex, age or PD etiology of the patients. This hinders drawing firm conclusions about causal or associative effects of dietary lipids or defects in specific steps of lipid metabolism in PD. Future technological advances in lipidomics and additional systematic studies on lipid species from PD patient material may improve this situation and lead to a better appreciation of the significance of lipids for this devastating disease.

Elevated homocysteine by levodopa is detrimental to neurogenesis in parkinsonian model

BACKGROUND

Modulation of neurogenesis that acts as an endogenous repair mechanism would have a significant impact on future therapeutic strategies for Parkinson's disease (PD). Several studies demonstrated dopaminergic modulation of neurogenesis in the subventricular zone (SVZ) of the adult brain. Levodopa, the gold standard therapy for PD, causes an increase in homocysteine levels that induces neuronal death via N-methyl-D-aspartate (NMDA) receptor. The present study investigated whether elevated homocysteine by levodopa treatment in a parkinsonian model would modulate neurogenesis via NMDA receptor signal cascade and compared the effect of levodopa and pramipexol (PPX) on neurogenic activity.

METHODOLOGY/PRINCIPAL FINDINGS

Neurogenesis was assessed in vitro using neural progenitor cells (NPCs) isolated from the SVZ and in vivo with the BrdU-injected animal model of PD using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Modulation of homocysteine levels was evaluated using co-cultures of NPCs and astrocytes and PD animals. Immunochemical and Western blot analyses were used to measure neurogenesis and determine the cell death signaling. Levodopa treatment increased release of homocysteine on astrocytes culture media as well as in plasma and brain of PD animals. Increased homocysteine by levodopa led to increased apoptosis of NPCs through the NMDA receptor-dependent the extracellular signal-regulated kinase (ERK) signaling pathways. The administration of a NMDA antagonist significantly attenuated apoptotic cell death in levodopa-treated NPCs and markedly increased the number of BrdU-positive cells in the SVZ of levodopa-treated PD animals. Comparative analysis revealed that PPX treatment significantly increased the number of NPCs and BrdU-positive cells in the SVZ of PD animals compared to levodopa treatment. Our present study demonstrated that increased homocysteine by levodopa has a detrimental effect on neurogenesis through NMDA receptor-mediated ERK signaling pathway.

CONCLUSIONS/SIGNIFICANCE

Modulation of levodopa-induced elevated homocysteine by NMDA antagonist or dopamine agonist has a clinical relevance for PD treatment in terms of adult neurogenesis.

Phospholipid mediated plasticity in exocytosis observed in PC12 cells

Membrane composition serves to identify intracellular compartments, signal cell death, as well as to alter a cell's electrical and physical properties. Here we use amperometry to show that supplementation with the phospholipids phosphatidylcholine (PC), phosphatidylethanolamine (PE), sphingomyelin (SM), and phosphatidylserine (PS) can alter several aspects of exocytosis. Changes in the amperometric peak shape derived from individual exocytosing vesicles reveal that PC slows expulsion of neurotransmitter while PE accelerates expulsion of neurotransmitter. Amperometry data reveal a reduced amount of catecholamine released per event from PC-treated cells while electron micrographs indicate the vesicles in these cells are 50% larger than controls, thus providing evidence of pharmacological changes in vesicle concentration. Addition of SM appears to affect the rate of fusion pore expansion, indicated by slower peak rise times, but does not affect decay times or quantal size. Addition of PS results in a 1.7-fold increase in the number of events elicited by high-K(+) depolarization. Electron micrographs of PS-treated cells suggest that increased vesicle recruitment underlies enhanced secretion. We did not observe any effect of phosphatidylinositol (PI) treatment. Together these data suggest that differences in membrane composition affect exocytosis and might be involved in mechanisms of cell function controlling the dynamics of communication via exocytosis.