The role of autophagy in Parkinson's disease: rotenone-based modeling

Antiplatelet therapy as a novel approach in Parkinson's disease: Repositioning Ticagrelor to alleviate rotenone-induced parkinsonism via modulation of ER stress, apoptosis, and autophagy

Cardiovascular diseases, such as myocardial infarction, ischemic stroke, and coronary heart ailments have been closely associated with Parkinson's disease (PD). Despite this established link, the potential neuroprotective impact of the potent antiplatelet agent ticagrelor (Tica) remains unexplored against PD. Thus, we hypothesized that Tica could be repurposed as a therapeutic agent against PD. Rotenone experimental model was adopted in Wistar male rats by administering rotenone subcutaneously on alternate days during a 21-day experimental period and treating a subset of rats with Tica orally for the last 11 consecutive days. The administration of Tica improved motor function (open field test, hanging wire test) and restored striatal histological features. Additionally, Tica opposed the rotenone effect and markedly obliterated the striatal α-synuclein content but enhanced the protein expression of tyrosine hydroxylase and dopamine content. On the molecular level, Tica inhibited striatal endoplasmic reticulum stress (ERS) as evidenced by the downregulation of the ER-resident transmembrane sensor inositol-requiring enzyme 1 alpha and its downstream molecular targets, TNF receptor-associated factor 2 and c-Jun N-terminal kinase, along with a reduction in caspase-3 activity. On the other hand, Tica augmented the autophagy machinery by upregulating the autophagosome markers Beclin-1 and light chain 3-II, while inhibiting the content of cathepsin D. Therefore, the current study is the first to accentuate the neuroprotective potential of Tica in a rat model of PD via modulating the crosstalk between ERS, apoptosis, and autophagy to represent a potential novel therapeutic candidate for managing PD, particularly in patients with or prone to cardiovascular diseases.

The neurotoxicity of pesticides: Implications for Parkinson's disease

Parkinson's disease (PD) is the fastest-growing neurodegenerative disorder worldwide, and no effective cure is currently available. Neuropathologically, PD is characterized by the selective degeneration of dopaminergic neurons in the substantia nigra and by the accumulation of alpha-synuclein (aSyn)-rich proteinaceous inclusions within surviving neurons. As a multifactorial disorder, approximately 85 % of PD cases are sporadic with unknown etiology. Among the many risk factors implicated in PD, exposure to neurotoxic pesticides stands out as a significant contributor. While the effects of many are still uncharacterized, it has already been shown that rotenone, paraquat, maneb, and dieldrin affect critical cellular pathways, including mitochondrial and proteasomal dysfunction, aSyn aggregation, autophagy dysregulation, and disruption of dopamine metabolism. With the constant rise in pesticide usage to meet the demands of a growing human population, the risk of environmental contamination and subsequent PD development is also increasing. This review explores the molecular mechanisms by which pesticide exposure influences PD development, shedding light on their role in the pathogenesis of PD and highlighting the need for preventative measures and regulatory oversight to mitigate these risks.

Neuroprotective capacity of Celastrus paniculatus on rotenone-induced parkinsonism in zebrafish model

INTRODUCTION

Parkinson's disease, a neurodegenerative disorder, affects millions globally, with age, genetics, and environmental conditions increasing risk. Global burden could reach 12 million by 2050. To observe the effect of Celastrus paniculatus in rotenone-induced Parkinsonism in zebrafish model.

METHOD

The fishes were divided into four groups and the experiment was carried out for 21days. Group I- Control; Group II- Rotenone induced (5 µg/L) dissolved in 0.1% DMSO; Group III - Aqueous extract of Celastrus paniculatus (CP) (20 µg/L) and Group IV - Rot + CP. After 21 days zebrafish was sacrificed and the brain was isolated for further analysis. The neurobehavioral studies were done using open field test, novel tank test and light and dark test, and the cognitive behavior using T-maze and customized fish maze. The antioxidant, neurotransmitter, mitochondrial assay and mRNA expressions were seen.

RESULT

The rotenone has shown an increased freezing bout, decreased exploration of the tank and average speed has demonstrated motor impairment and also memory impairment was exhibited. There was elevated cortisol and LPO and reduced antioxidant status. The neurotransmitters changes and mitochondrial dysfunction were also observed. The study showed increased in α-synuclein and decreased in DJ1 and LRRK2 expressions. In the present study, the aqueous extract of CP has cognitive dysfunctions and improves memory. CP has also shown amelioration against the production of ROS, mitochondrial dysfunctions and DNA damages caused by rotenone.

CONCLUSION

CP is known for its medicinal and pharmacological properties. CP has also shown to improve the cognitive dysfunction caused by rotenone and have showed an improvement in effect.

Methylmercury induces inflammatory response and autophagy in microglia through the activation of NLRP3 inflammasome

Methylmercury (MeHg) is a global environmental pollutant with neurotoxicity, which can easily crosses the blood-brain barrier and cause irreversible damage to the human central nervous system (CNS). CNS inflammation and autophagy are known to be involved in the pathology of neurodegenerative diseases. Meanwhile, MeHg has the potential to induce microglia-mediated neuroinflammation as well as autophagy. This study aims to further explore the exact molecular mechanism of MeHg neurotoxicity. We conducted in vitro studies using BV2 microglial cell from the central nervous system of mice. The role of inflammation and autophagy in the damage of BV2 cells induced by MeHg was determined by detecting cell viability, cell morphology and structure, reactive oxygen species (ROS), antioxidant function, inflammatory factors, autophagosomes, inflammation and autophagy-related proteins. We further investigated the relationship between the inflammatory response and autophagy induced by MeHg by inhibiting them separately. The results indicated that MeHg could invade cells, change cell structure, activate NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome and autophagosome, release a large amount of inflammatory factors and trigger the inflammatory response and autophagy. It was also found that MeHg could disrupt the antioxidant function of cells. In addition, the inhibition of NLRP3 inflammasome alleviated both cellular inflammation and autophagy, while inhibition of autophagy increased cellular inflammation. Our current research suggests that MeHg might induce BV2 cytotoxicity through inflammatory response and autophagy, which may be mediated by the NLRP3 inflammasome activated by oxidative stress.

MCC950 reduces autophagy and improves cognitive function by inhibiting NLRP3-dependent neuroinflammation in a rat model of Alzheimer's disease

Alzheimer's disease (AD) is the seventh most common cause of mortality and one of the major causes of disability and vulnerability in the elderly. AD is characterized by gradual cognitive deterioration, the buildup of misfolded amyloid beta (Aβ) peptide, and the generation of neurofibrillary tangles. Despite enormous scientific progress, there is no effective cure for AD. Thus, exploring new treatment options to stop AD or at least slow down its progress is important. In this study, we investigated the potential therapeutic effects of MCC950 on NLRP3-mediated inflammasome-driven inflammation and autophagy in AD. Rats treated with streptozotocin (STZ) exhibited simultaneous activation of the NLRP3 inflammasome and autophagy, as confirmed by Western blot, immunofluorescence, and co-immunoprecipitation analyses. MCC950, a specific NLRP3 inhibitor, was intraperitoneally administered (50 mg/kg body weight) to rats with AD-like symptoms induced by intracerebroventricular STZ injections (3 mg/kg body weight). MCC950 effectively suppressed STZ-induced cognitive impairment and anxiety by inhibiting NLRP3-dependent neuroinflammation. Moreover, our findings indicate that MCC950 exerts neuroprotective effects by attenuating autophagy in neuronal cells. The inhibiting effects of MCC950 on inflammasome activation and autophagy were reproduced in vitro, provding further mechansistic insights into MCC950 therapeutic action. Our findings suggest that MCC950 impedes the progression of AD and may also improve cognitive function through the mitigation of autophagy and NLRP3 inflammasome inhibition.

Mitochondrial Calcium Transport During Autophagy Initiation

While it has been shown that Ca2+ dynamics at the ER membrane is essential for the initiation of certain types of autophagy such as starvation-induced autophagy, how mitochondrial Ca2+ transport changes during the first stage of autophagy is not systemically characterized. An investigation of mitochondrial Ca2+ dynamics during autophagy initiation may help us determine the relationship between autophagy and mitochondrial Ca2+ fluxes. Here we examine acute mitochondrial and ER calcium responses to a panel of autophagy inducers in different cell types. Mitochondrial Ca2+ transport and Ca2+ transients at the ER membrane are triggered by different autophagy inducers. The mitophagy-inducer-initiated mitochondrial Ca2+ uptake relies on mitochondrial calcium uniporter and may decelerate the following mitophagy. In neurons derived from a Parkinson's patient, mitophagy-inducer-triggered mitochondrial Ca2+ influx is faster, which may slow the ensuing mitophagy.

Sodium-dependent glucose co-transporter-2 inhibitor empagliflozin exerts neuroprotective effects in rotenone-induced Parkinson's disease model in zebrafish; mechanism involving ketogenesis and autophagy

Sodium-dependent glucose co-transporter-2 (SGLT2) inhibitor empagliflozin (EMP), is the new class of oral hypoglycemic agent approved as a treatment for Type 2 diabetes. SGLT2 inhibitors may induce ketogenesis through inhibiting the renal reabsorption of glucose. In recent years, positive effects of ketogenic diets on neurodegenerative diseases such as Parkinson's disease (PD) have been reported by improving autophagy. We aimed to evaluate the effects of EMP treatment as a SGLT2 inhibitor that can mimic the effects of ketogenic diet, in rotenone induced PD model in zebrafish focusing on ketogenesis, autophagy, and molecular pathways related with PD progression including oxidative stress and inflammation. Adult zebrafish were exposed to rotenone and EMP for 30 days. Y-Maze task and locomotor analysis were performed. Neurotransmitter levels were determined by liquid chromatography tandem- mass spectrometry (LC-MS/MS). Lipid peroxidation (LPO), nitric oxide (No), alkaline phosphatase, superoxide dismutase, glutathione, glutathione S-transferase (GST), sialic acid, acetylcholinesterase, and the expressions of autophagy, ketogenesis and PD-related genes were determined. Immunohistochemical staining was performed for the microglial marker L-plastin (Lcp1) and tyrosine hydroxylase (Th). EMP treatment improved DOPAC/DA ratio, Y-Maze task, locomotor activity, expressions of Th and Lcp-1, autophagy and inflammation related (mTor, atg5, tnfα, sirt1, il6, tnfα); PD-related (lrrk2, park2, park7, pink1), and ketone metabolism-related genes (slc16a1b, pparag, and pparab), and oxidant-damage in brain in the rotenone group as evidenced by decreased LPO, No, and improved antioxidant molecules. Our results showed benefical effects of EMP as a SGLT2 inhibitor in neurotoxin-induced PD model in zebrafish. We believe our study, will shed light on the mechanism of the effects of SGLT2 inhibitors, ketogenesis and autopahgy in PD.

High Yield of Functional Dopamine-like Neurons Obtained in NeuroForsk 2.0 Medium to Study Acute and Chronic Rotenone Effects on Oxidative Stress, Autophagy, and Apoptosis

Several efforts to develop new protocols to differentiate in in vitro human mesenchymal stromal cells (hMSCs) into dopamine (DA) neurons have been reported. We have formulated NeuroForsk 2.0 medium containing fibroblast growth factor type beta (FGFb), brain-derived neurotrophic factor (BDNF), melatonin, purmorphamine, and forskolin. We report for the first time that menstrual stromal cells (MenSCs) cultured in NeuroForsk 2.0 medium for 7 days transdifferentiated into DA-like neurons (DALNs) expressing specific DA lineage markers tyrosine hydroxylase-positive cells (TH+) and DA transporter-positive (DAT+) cells and were responsive to DA-induced transient Ca2+ influx. To test the usefulness of this medium, DALNs were exposed to rotenone (ROT), a naturally occurring organic neurotoxin used extensively to chemically induce an in vitro model of Parkinson's disease (PD), which is a movement disorder characterized by the specific loss of DA neurons. We wanted to determine whether ROT induces apoptotic cell death and autophagy pathway under acute or chronic conditions in DALNs. Here, we report that acute ROT exposure induced several molecular changes in DALNS. ROT induced a loss of mitochondrial membrane potential (ΔΨm), high expression of parkin (PRKN), and high colocalization of dynamin-related protein 1 (DRP1) with the mitochondrial translocase of the outer membrane of mitochondria 20 (TOMM20) protein. Acute ROT also induced the appearance of DJ-1Cys106-SO3, as evidenced by the generation of H2O2 and oxidative stress (OS) damage. Remarkably, ROT triggered the phosphorylation of leucine-rich repeat kinase 2 (LRRK2) at residue Ser935 and phosphorylation of α-Syn at residue Ser129, a pathological indicator. ROT induced the accumulation of lipidated microtubule-associated protein 1B-light chain 3 (LC3B), a highly specific marker of autophagosomes. Finally, ROT induced cleaved caspase 3 (CC3), a marker of activated caspase 3 (CASP3) in apoptotic DALNs compared to untreated DANLs. However, the chronic condition was better at inducing the accumulation of lysosomes than the acute condition. Importantly, the inhibitor of the LRRK2 kinase PF-06447475 (PF-475) almost completely blunted ROT-induced apoptosis and reduced ROT-induced accumulation of lysosomes in both acute and chronic conditions in DALNs. Our data suggest that LRRK2 kinase regulated both apoptotic cell death and autophagy in DALNs under OS. Given that defects in mitochondrial complex I activity are commonly observed in PD, ROT works well as a chemical model of PD in both acute and chronic conditions. Therefore, prevention and treatment therapy should be guided to relieve DALNs from mitochondrial damage and OS, two of the most important triggers in the apoptotic cell death of DALNs.

Transcriptomics and Proteomics Approach for the Identification of Altered Blood microRNAs and Plasma Proteins in Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disorder caused by the selective destruction of dopaminergic neurons (DA-nergic). Clinically, PD is diagnosed based on developing signs and symptoms. A neurological and physical examination and sometimes medical and family history also help in the diagnosis of PD. However, most of these features are visible when more than 80% of the dopaminergic neurons have degenerated. An understanding of the selective degeneration process at the cellular and molecular level and the development of new biomarkers are required for effective PD management. Several studies have been carried out using a selected set of miRNAs/ mRNAs and proteins to develop biomarkers of PD; however, an unbiased and combined miRNA-protein profiling study was required to identify the markers of progressive and selected degeneration of dopaminergic neurons in PD patients. In the present study, we have carried out global protein profiling through LC-MS/MS and miRNA profiling by using a "brain-specific" miRNA array panel of 112 miRNAs in PD patients and healthy controls to find the unprejudiced group of proteins and miRNAs that are deregulating in PD. In the whole blood samples of PD patients compared to healthy controls, the expression of 23 miRNAs and 289 proteins was significantly increased, whereas the expression of 4 miRNAs and 132 proteins was considerably downregulated. Network analysis, functional enrichment, annotation, and analysis of miRNA-protein interactions were also performed as part of the bioinformatics investigation of the discovered miRNAs and proteins revealing several pathways that lead to PD development and pathogenesis. Based on the analysis of miRNA and protein profiling, we have identified four miRNAs (hsa-miR-186-5p, miR-29b, miR-139 & has-miR-150-5p) and four proteins (YWHAZ, PSMA4, HYOU1, & SERPINA1), which can be targeted for the development of new biomarkers of PD. In vitro studies have identified the role of miR-186-5p in regulating the levels of the YWHAZ/YWHAB & CALM2 gene, which has shown maximum downregulation in PD patients and is known for its role in neuroprotection from apoptotic cell death & calcium regulation. In conclusion, our research has identified a group of miRNA-proteins that can be developed as PD biomarkers; however, future studies on the release of these miRNAs and proteins in extracellular vesicles circulating in the blood of PD patients can further validate these as specific biomarkers of PD.

Overview on the Polyphenol Avenanthramide in Oats (Avena sativa Linn.) as Regulators of PI3K Signaling in the Management of Neurodegenerative Diseases

Avenanthramides (Avns) and their derivatives, a group of polyphenolic compounds found abundantly in oats (Avena sativa Linn.), have emerged as promising candidates for neuroprotection due to their immense antioxidant, anti-inflammatory, and anti-apoptotic properties. Neurodegenerative diseases (NDDs), characterized by the progressive degeneration of neurons, present a significant global health burden with limited therapeutic options. The phosphoinositide 3-kinase (PI3K) signaling pathway plays a crucial role in cell survival, growth, and metabolism, making it an attractive target for therapeutic intervention. The dysregulation of PI3K signaling has been implicated in the pathogenesis of various NDDs including Alzheimer's and Parkinson's disease. Avns have been shown to modulate PI3K/AKT signaling, leading to increased neuronal survival, reduced oxidative stress, and improved cognitive function. This review explores the potential of Avn polyphenols as modulators of the PI3K signaling pathway, focusing on their beneficial effects against NDDs. Further, we outline the need for clinical exploration to elucidate the specific mechanisms of Avn action on the PI3K/AKT pathway and its potential interactions with other signaling cascades involved in neurodegeneration. Based on the available literature, using relevant keywords from Google Scholar, PubMed, Scopus, Science Direct, and Web of Science, our review emphasizes the potential of using Avns as a therapeutic strategy for NDDs and warrants further investigation and clinical exploration.

Animal models of Parkinson's disease: bridging the gap between disease hallmarks and research questions

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by motor and non-motor symptoms. More than 200 years after its first clinical description, PD remains a serious affliction that affects a growing proportion of the population. Prevailing treatments only alleviate symptoms; there is still neither a cure that targets the neurodegenerative processes nor therapies that modify the course of the disease. Over the past decades, several animal models have been developed to study PD. Although no model precisely recapitulates the pathology, they still provide valuable information that contributes to our understanding of the disease and the limitations of our treatment options. This review comprehensively summarizes the different animal models available for Parkinson's research, with a focus on those induced by drugs, neurotoxins, pesticides, genetic alterations, α-synuclein inoculation, and viral vector injections. We highlight their characteristics and ability to reproduce PD-like phenotypes. It is essential to realize that the strengths and weaknesses of each model and the induction technique at our disposal are determined by the research question being asked. Our review, therefore, seeks to better aid researchers by ensuring a concrete discernment of classical and novel animal models in PD research.

Ursolic acid enhances autophagic clearance and ameliorates motor and non-motor symptoms in Parkinson's disease mice model

Protein aggregation and the abnormal accumulation of aggregates are considered as common mechanisms of neurodegeneration such as Parkinson's disease (PD). Ursolic acid (UA), a natural pentacyclic triterpenoid compound, has shown a protective activity in several experimental models of brain dysfunction through inhibiting oxidative stress and inflammatory responses and suppressing apoptotic signaling in the brain. In this study, we investigated whether UA promoted autophagic clearance of protein aggregates and attenuated the pathology and characteristic symptoms in PD mouse model. Mice were injected with rotenone (1 mg · kg-1 · d-1, i.p.) five times per week for 1 or 2 weeks. We showed that rotenone injection induced significant motor deficit and prodromal non-motor symptoms accompanied by a significant dopaminergic neuronal loss and the deposition of aggregated proteins such as p62 and ubiquitin in the substantia nigra and striatum. Co-injection of UA (10 mg · kg-1 · d-1, i.p.) ameliorated all the rotenone-induced pathological alterations. In differentiated human neuroblastoma SH-SY5Y cells, two-step treatment with a proteasome inhibitor MG132 (0.25, 2.5 μM) induced marked accumulation of ubiquitin and p62 with clear and larger aggresome formation, while UA (5 μM) significantly attenuated the MG132-induced protein accumulation. Furthermore, we demonstrated that UA (5 μM) significantly increased autophagic clearance by promoting autophagic flux in primary neuronal cells and SH-SY5Y cells; UA affected autophagy regulation by increasing the phosphorylation of JNK, which triggered the dissociation of Bcl-2 from Beclin 1. These results suggest that UA could be a promising therapeutic candidate for reducing PD progression from the prodromal stage by regulating abnormal protein accumulation in the brain.

Curcumin Modulates p62-Keap1-Nrf2-Mediated Autophagy in Rotenone-Induced Parkinson's Disease Mouse Models

Autophagy mediates self-digestion of abnormally aggregated proteins and organelles present in the cytoplasm. This mechanism may prove to be neuroprotective against Parkinson's disease (PD) by clearing misfolded α-synuclein (α-syn) aggregates from dopaminergic neurons. p62, an adaptor protein acts as a selective substrate for autophagy and regulates the formation as well as the degradation of protein aggregates. p62 sequesters keap1 freeing Nrf2 and consequently activating the transcription of its target genes. In the present study, we aimed to investigate the anti-parkinsonian activity of curcumin targeting primarily activation of autophagy via the Nrf2-Keap1 pathway. The mice were subcutaneously injected with rotenone (2.5 mg/kg bodyweight) and co-treated with oral administration of curcumin (80 mg/kg bodyweight) for 35 days. Following completion of dosing, motor activities, anti-oxidative potential, mitochondrial dysfunction, and various protein expressions, including Nrf2, Keap1, p62, LC3, Bcl2, Bax, and caspase 3, were assessed. The results revealed that curcumin restored the motor coordination and anti-oxidative activity while improving the mitochondrial functioning in PD mice. Autophagy was evaluated by the change in the expression of autophagic markers, p62 and LC3-II. Reduced p62 and LC3-II expressions in the rotenone mouse model of PD confirmed the compromised autophagy pathway, consequently increasing the aggregation of misfolded protein α-syn. Whereas, curcumin treatment-enhanced autophagy-mediated clearance of misfolded α-syn proteins by increasing the LC3-II expression and blocked apoptotic cascade. Curcumin administration upregulated the Nrf2 expression and normalized the Nrf2-Keap1 pathway, which justifies the improved anti-oxidative activity. Therefore, the findings reveal that curcumin is a Nrf2-inducer and is endowed with neuroprotective potential, which may prove to be a potential candidate for the anti-Parkinson's disease treatment therapy.

Neuroprotective Effect of Phloretin in Rotenone-Induced Mice Model of Parkinson's Disease: Modulating mTOR-NRF2-p62 Mediated Autophagy-Oxidative Stress Crosstalk

BACKGROUND

Parkinson's disease (PD) is an age-related progressive multifactorial, neurodegenerative disease. The autophagy and Keap1-Nrf2 axis system are both implicated in the oxidative-stress response, metabolic stress, and innate immunity, and their dysregulation is associated with pathogenic processes in PD. Phloretin (PLT) is a phenolic compound reported possessing anti-inflammatory and antioxidant activities.

OBJECTIVE

To evaluate the neuroprotective potential of PLT in PD via modulating the autophagy-antioxidant axisMethods:The neuroprotective effect of PLT was evaluated in vitro using rotenone (ROT) exposed SH-SY5Y cell line and in vivo using ROT administered C57BL/6 mice. Mice were administered with PLT (50 and 100 mg/kg, p.o.) concomitantly with ROT (1 mg/kg, i.p) for 3 weeks. Locomotive activity and anxiety behaviors were assessed using rotarod and open field tests respectively. Further apoptosis (Cytochrome-C, Bax), α-Synuclein (α-SYN), tyrosine hydroxylase (TH), antioxidant proteins (nuclear factor erythroid 2-related factor 2 (NRF2), heme oxygenase-1 (HO-1) and autophagic (mTOR, Atg5,7, p62, Beclin,LC3B-I/II) protein activity were evaluated both in in vitro and in vivo.

RESULTS

PLT improved locomotive activity and anxiety-like behavior in mice. Further PLT diminished apoptotic cell death, α-SYN expression and improved the expression of TH, antioxidant, and autophagic regulating protein.

CONCLUSION

Taken together, present data deciphers that the PLT effectively improves motor and non-motor symptoms via modulating the mTOR/NRF2/p62 pathway-mediated feedback loop. Hence, PLT could emerge as a prospective disease-modifying drug for PD management.

Rotenone causes mitochondrial dysfunction and prevents maturation in porcine oocytes

Rotenone is a commonly used insecticidal chemical in agriculture and it is an inhibitor of mitochondrial complex Ⅰ. Previous studies have found that rotenone induces the production of reactive oxygen species (ROS) by inhibiting electron transport in the mitochondria of somatic and germ cells. However, there is little precise information on the effects of rotenone exposure in porcine oocytes during in vitro maturation, and the mechanisms underlying these effects have not been determined. The Cumulus-oocyte complexes were supplemented with different concentrations of rotenone to elucidate the effects of rotenone exposure on the meiotic maturation of porcine oocytes during in vitro maturation for about 48 hours. First, we found that the maturation rate and expansion of cumulus cells were significantly reduced in the 3 and 5 μM rotenone-treated groups. Subsequently, the concentration of rotenone was determined to be 3 μM. Also, immunofluorescence, western blotting, and image quantification analyses were performed to test the rotenone exposure on the meiotic maturation, total and mitochondrial ROS, mitochondrial function and biogenesis, mitophagy and apoptosis in porcine oocytes. Further experiments showed that rotenone treatment induced mitochondrial dysfunction and failure of mitochondrial biogenesis by repressing the level of SIRT1 during in vitro maturation of porcine oocytes. In addition, rotenone treatment reduced the ratio of active mitochondria to total mitochondria, increased ROS production, and decreased ATP production. The levels of LC3 and active-caspase 3 were significantly increased by rotenone treatment, indicating that mitochondrial dysfunction induced by rotenone increased mitophagy but eventually led to apoptosis. Collectively, these results suggest that rotenone interferes with porcine oocyte maturation by inhibiting mitochondrial function.

Delivery of the reduced form of vitamin K2(20) to NIH/3T3 cells partially protects against rotenone induced cell death

Mitochondria generate energy through the action of the electron transport chain (ETC) and ATP synthase. Mitochondrial malfunction can lead to various disorders, including neurodegenerative diseases. Several reports have shown that menaquinone-4 (MK-4, vitamin K₂₍₂₀₎), a safe drug for osteoporosis, may improve mitochondrial function. Here, we hypothesized that the efficient delivery of menahydroquinone-4 (MKH), an active form of MK-4, could exert a supporting effect. We verified the effects of MKH delivery on mitochondrial dysfunction by using MK-4 and MKH ester derivatives in NIH/3T3 mouse fibroblast cells treated with mitochondrial inhibitors. MK-4 and MKH derivatives suppressed cell death, the decline in mitochondrial membrane potential (MMP), excessive reactive oxygen species (ROS) production, and a decrease in intrinsic coenzyme Q₉ (CoQ₉) induced by rotenone (ROT, complex I inhibitor). MK-4 and MKH derivatives delivered MKH to NIH/3T3 cells, acting as an effective MKH prodrug, proving that the delivered MKH may reflect the mitigation effects on ROT-induced mitochondrial dysfunction. MKH prodrugs are also effective against 3-nitropropionic acid (3-NP, complex II inhibitor) and carbonyl cyanide-m-chlorophenylhydrazone (CCCP, uncoupler)-induced cell death. In conclusion, MKH delivery may mitigate mitochondrial dysfunction by maintaining MMP, ROS, and CoQ₉, indicating that MKH prodrugs may be good candidates for treating mitochondrial disorders.

Impact of Environmental Risk Factors on Mitochondrial Dysfunction, Neuroinflammation, Protein Misfolding, and Oxidative Stress in the Etiopathogenesis of Parkinson's Disease

As a prevalent progressive neurodegenerative disorder, Parkinson's disease (PD) is characterized by the neuropathological hallmark of the loss of nigrostriatal dopaminergic (DAergic) innervation and the appearance of Lewy bodies with aggregated α-synuclein. Although several familial forms of PD have been reported to be associated with several gene variants, most cases in nature are sporadic, triggered by a complex interplay of genetic and environmental risk factors. Numerous epidemiological studies during the past two decades have shown positive associations between PD and several environmental factors, including exposure to neurotoxic pesticides/herbicides and heavy metals as well as traumatic brain injury. Other environmental factors that have been implicated as potential risk factors for PD include industrial chemicals, wood pulp mills, farming, well-water consumption, and rural residence. In this review, we summarize the environmental toxicology of PD with the focus on the elaboration of chemical toxicity and the underlying pathogenic mechanisms associated with exposure to several neurotoxic chemicals, specifically 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), rotenone, paraquat (PQ), dichloro-diphenyl-trichloroethane (DDT), dieldrin, manganese (Mn), and vanadium (V). Our overview of the current findings from cellular, animal, and human studies of PD provides information for possible intervention strategies aimed at halting the initiation and exacerbation of environmentally linked PD.

Neuroprotective and therapeutic effects of calcitriol in rotenone-induced Parkinson’s disease rat model

Parkinson’s disease (PD) is the second most common neurodegenerative disease. Treatment of PD is challenging, as current treatment strategies are only symptomatic and do not stop disease development. Recent studies reported neuroprotective effects of calcitriol in PD through its antioxidant and anti-inflammatory properties. The exact pathomechanisms of PD are not yet fully understood. So, investigation of different molecular pathways is challenging. Sirtuin-1 (Sirt1) modulates multiple physiological processes, including programmed cell death, DNA repair, and inflammation. Furthermore, defective autophagy is considered a key pathomechanism in PD as it eliminates protein aggregation and dysfunctional cell organelles. The present study investigated the involvement of autophagy and Sirt1/NF-κB molecular pathway in rotenone-induced PD and explored the protective and restorative effects of calcitriol through these mechanisms. Therefore, behavioral tests were used to test the effect of calcitriol on motor disability and equilibrium. Furthermore, the histological and neuronal architecture was assessed. The expression of genes encoding neuroinflammation and autophagy markers was determined by qPCR while their protein levels were determined by Western blot analysis and immune-histochemical staining. Our results indicate that behavioral impairments and dopaminergic neuron depletion in the rotenone-induced PD model were improved by calcitriol administration. Furthermore, calcitriol attenuated rotenone-induced neuroinflammation and autophagy dysfunction in PD rats through up-regulation of Sirt1 and LC3 and down-regulation of P62 and NF-κB expression levels. Thus, calcitriol could induce a neuro-protective and restorative effect in the rotenone-induced PD model by modulating autophagy and Sirt1/NF-κB pathway.

MALAT1 lncRNA and Parkinson's Disease: The role in the Pathophysiology and Significance for Diagnostic and Therapeutic Approaches

Parkinson's disease (PD) is the second most common age-related neurodegenerative disorder. PD is characterized by progressive loss of dopamine-producing neurons in the substantia nigra (SN) region of brain tissue followed by the α-synuclein-based Lewy bodies' formation. These conditions are manifested by various motor and non-motor symptoms such as resting tremor, limb rigidity, bradykinesia and posture instability, cognitive impairment, sleep disorders, and emotional and memory dysfunctions. Long non-coding RNAs (lncRNAs) are closely related to protein-coding genes and are involved in various biological processes. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) lncRNA is involved in different pathways, including alternative splicing, transcriptional regulation, and post-transcriptional regulation, and also interacts with RNAs as a miRNA sponge. MALAT1 is highly expressed in brain tissues and several lines of evidence suggested it is probably involved in synapse generation and other neurophysiological pathways. This narrative review discussed all aspects of MALAT1-associated mechanisms involved in the PD pathogenesis, i.e., perturbed α-synuclein homeostasis, apoptosis and autophagy, and neuro-inflammation. Lastly, the possible applications of MALAT1 as a diagnostic biomarker and its importance to developing therapeutic strategies were highlighted. The literature search was conducted using neurodegeneration, neurodegenerative disorders, Parkinson's disease, lncRNA, and MALAT1 as search items in Google Scholar, Web of Knowledge, PubMed, and Scopus up to December 2021.

NGF Modulates Cholesterol Metabolism and Stimulates ApoE Secretion in Glial Cells Conferring Neuroprotection against Oxidative Stress

Cholesterol plays a crucial role in the brain, where its metabolism is particularly regulated by astrocytic activity. Indeed, adult neurons suppress their own cholesterol biosynthesis and import this sterol through ApoE-rich particles secreted from astrocytes. Recent evidence suggests that nerve growth factor (NGF) may exert neurotrophic activity by influencing cell metabolism. Nevertheless, the effect of NGF on glial cholesterol homeostasis has still not been elucidated. Thus, the aim of this project is to assess whether NGF could influence cholesterol metabolism in glial cells. To reach this objective, the U373 astrocyte-derived cell line was used as an experimental model. Immunoblot and ELISA analysis showed that proteins and enzymes belonging to the cholesterol metabolism network were increased upon NGF treatment in glial cells. Furthermore, NGF significantly increased ApoE secretion and the amount of extracellular cholesterol in the culture medium. Co-culture and U373-conditioned medium experiments demonstrated that NGF treatment efficiently counteracted rotenone-mediated cytotoxicity in N1E-115 neuronal cells. Conversely, neuroprotection mediated by NGF treatment was suppressed when N1E-115 were co-cultured with ApoE-silenced U373 cells. Taken together, these data suggest that NGF controls cholesterol homeostasis in glial cells. More importantly, NGF exerts neuroprotection against oxidative stress, which is likely associated with the induction of glial ApoE secretion.

Metabolomics analysis highlights Yashtimadhu (Glycyrrhiza glabra L.)-mediated neuroprotection in a rotenone-induced cellular model of Parkinson's disease by restoring the mTORC1-AMPK1 axis in autophagic regulation

Parkinson's disease (PD) is an age-associated progressive neurodegenerative movement disorder, and its management strategies are known to cause complications with prolonged usage. We aimed to explore the neuroprotective mechanism of the Indian traditional medicine Yashtimadhu, prepared from the dried roots of Glycyrrhiza glabra L. (licorice) in the rotenone-induced cellular model of PD. Retinoic acid-differentiated IMR-32 cells were treated with rotenone (PD model) and Yashtimadhu extract. Mass spectrometry-based untargeted and targeted metabolomic profiling was carried out to discover altered metabolites. The untargeted metabolomics analysis highlighted the rotenone-induced dysregulation and Yashtimadhu-mediated restoration of metabolites involved in the metabolism of nucleic acids, amino acids, lipids, and citric acid cycle. Targeted validation of citric acid cycle metabolites showed decreased α-ketoglutarate and succinate with rotenone treatment and rescued by Yashtimadhu co-treatment. The dysregulation of the citric acid cycle by rotenone-induced energetic stress via dysregulation of the mTORC1-AMPK1 axis was prevented by Yashtimadhu. Yashtimadhu co-treatment restored rotenone-induced ATG7-dependent autophagy and eventually caspases-mediated cell death. Our analysis links the metabolic alterations modulating energy stress and autophagy, which underlies the Yashtimadhu-mediated neuroprotection in the rotenone-induced cellular model of PD.

Application of neurotoxin- and pesticide-induced animal models of Parkinson's disease in the evaluation of new drug delivery systems

Parkinson's disease (PD) is the second most prevalent neuro-degenerative disease after Alzheimer´s disease. It is characterized by motor symptoms such as akinesia, bradykinesia, tremor, rigidity, and postural abnormalities, due to the loss of nigral dopaminergic neurons and a decrease in the dopa-mine contents of the caudate-putamen structures. To this date, there is no cure for the disease and available treatments are aimed at controlling the symptoms. Therefore, there is an unmet need for new treatments for PD. In the past decades, animal models of PD have been proven to be valuable tools in elucidating the nature of the pathogenic processes involved in the disease, and in designing new pharmacological approaches. Here, we review the use of neurotoxin-induced and pesticide-induced animal models of PD, specifically those induced by rotenone, paraquat, maneb, MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and 6-OHDA (6-hydroxydopamine), and their application in the development of new drug delivery systems for PD.

HEXA-018, a Novel Inducer of Autophagy, Rescues TDP-43 Toxicity in Neuronal Cells

The autophagy-lysosomal pathway is an essential cellular mechanism that degrades aggregated proteins and damaged cellular components to maintain cellular homeostasis. Here, we identified HEXA-018, a novel compound containing a catechol derivative structure, as a novel inducer of autophagy. HEXA-018 increased the LC3-I/II ratio, which indicates activation of autophagy. Consistent with this result, HEXA-018 effectively increased the numbers of autophagosomes and autolysosomes in neuronal cells. We also found that the activation of autophagy by HEXA-018 is mediated by the AMPK-ULK1 pathway in an mTOR-independent manner. We further showed that ubiquitin proteasome system impairment- or oxidative stress-induced neurotoxicity was significantly reduced by HEXA-018 treatment. Moreover, oxidative stress-induced mitochondrial dysfunction was strongly ameliorated by HEXA-018 treatment. In addition, we investigated the efficacy of HEXA-018 in models of TDP-43 proteinopathy. HEXA-018 treatment mitigated TDP-43 toxicity in cultured neuronal cell lines and Drosophila. Our data indicate that HEXA-018 could be a new drug candidate for TDP-43-associated neurodegenerative diseases.

Animal models of Parkinson's disease: a guide to selecting the optimal model for your research

Parkinson's disease (PD) is a complex, multisystem disorder characterised by α-synuclein (SNCA) pathology, degeneration of nigrostriatal dopaminergic neurons, multifactorial pathogenetic mechanisms and expression of a plethora of motor and non-motor symptoms. Animal models of PD have already been instructive in helping us unravel some of these aspects. However, much remains to be discovered, requiring continued interrogation by the research community. In contrast with the situation for many neurological disorders, PD benefits from of a wide range of available animal models (pharmacological, toxin, genetic and α-synuclein) but this makes selection of the optimal one for a given study difficult. This is especially so when a study demands a model that displays a specific combination of features. While many excellent reviews of animal models already exist, this review takes a different approach with the intention of more readily informing this decision-making process. We have considered each feature of PD in turn - aetiology, pathology, pathogenesis, motor dysfunctions and non-motor symptoms (NMS) - highlighting those animal models that replicate each. By compiling easily accessible tables and a summary figure, we aim to provide the reader with a simple, go-to resource for selecting the optimal animal model of PD to suit their research needs.

Ferruginol prevents degeneration of dopaminergic neurons by enhancing clearance of α-synuclein in neuronal cells

Lewy bodies are characteristic spherical inclusions in Parkinson's disease (PD) that are formed by α-synuclein fibrils. Ferruginol (Fer) is an amonomeric compound isolated from a traditional Chinese herb. Here, we show that Fer exerted potent neuroprotective effects in both in vitro and in vivo PD models. Neuronal cells transfected with A53T mutant (A53T) α-synuclein plasmids and treated with Fer exhibited attenuated the cytotoxicity induced by pathogenic A53T α-synuclein overexpression. Further, when we transfected neuronal cells with siRNA-SNCA (alpha-synuclein) plasmids and incubated them with Fer, the protective role of Fer decreased. We also found that Fer was a potent α-synuclein inhibitor in neuronal cells, which promotes the clearance of αsynuclein in dopaminergic neurons exposed to 1-Methyl-4-phenylpyridinium (MPP +). Fer could inhibit abnormal α-synuclein aggregation and dopaminergic neuron depletion in A53T-Tg mice, suggesting that a role for Fer in α-synuclein accumulation and nigrostriatal pathway injury. Our study revealed that Fer strongly alleviated neurodegeneration by promoting α-synuclein clearance, indicating a neuroprotective role against α-synuclein oligomer-induced neurodegeneration, which makes it a promising candidate for the treatment of PD and other neurodegenerative diseases.

A Tau-Driven Adverse Outcome Pathway Blueprint Toward Memory Loss in Sporadic (Late-Onset) Alzheimer's Disease with Plausible Molecular Initiating Event Plug-Ins for Environmental Neurotoxicants

The worldwide prevalence of sporadic (late-onset) Alzheimer's disease (sAD) is dramatically increasing. Aging and genetics are important risk factors, but systemic and environmental factors contribute to this risk in a still poorly understood way. Within the frame of BioMed21, the Adverse Outcome Pathway (AOP) concept for toxicology was recommended as a tool for enhancing human disease research and accelerating translation of data into human applications. Its potential to capture biological knowledge and to increase mechanistic understanding about human diseases has been substantiated since. In pursuit of the tau-cascade hypothesis, a tau-driven AOP blueprint toward the adverse outcome of memory loss is proposed. Sequences of key events and plausible key event relationships, triggered by the bidirectional relationship between brain cholesterol and glucose dysmetabolism, and contributing to memory loss are captured. To portray how environmental factors may contribute to sAD progression, information on chemicals and drugs, that experimentally or epidemiologically associate with the risk of AD and mechanistically link to sAD progression, are mapped on this AOP. The evidence suggests that chemicals may accelerate disease progression by plugging into sAD relevant processes. The proposed AOP is a simplified framework of key events and plausible key event relationships representing one specific aspect of sAD pathology, and an attempt to portray chemical interference. Other sAD-related AOPs (e.g., Aβ-driven AOP) and a better understanding of the impact of aging and genetic polymorphism are needed to further expand our mechanistic understanding of early AD pathology and the potential impact of environmental and systemic risk factors.

β-Cells Different Vulnerability to the Parkinsonian Neurotoxins Rotenone, 1-Methyl-4-phenylpyridinium (MPP+) and 6-Hydroxydopamine (6-OHDA)

Neurotoxins such as rotenone, 1-methyl-4-phenylpyridinium (MPP⁺) and 6-hydroxydopamine (6-OHDA) are well known for their high toxicity on dopaminergic neurons and are associated with Parkinson's disease (PD) in murine models and humans. In addition, PD patients often have glucose intolerance and may develop type 2 diabetes (T2D), whereas T2D patients have higher risk of PD compared to general population. Based on these premises, we evaluated the toxicity of these three toxins on pancreatic β-cell lines (INS-1 832/13 and MIN6) and we showed that rotenone is the most potent for reducing β-cells viability and altering mitochondrial structure and bioenergetics in the low nanomolar range, similar to that found in dopaminergic cell lines. MPP⁺ and 6-OHDA show similar effects but at higher concentration. Importantly, rotenone-induced toxicity was counteracted by α-tocopherol and partially by metformin, which are endowed with strong antioxidative and cytoprotective properties. These data show similarities between dopaminergic neurons and β-cells in terms of vulnerability to toxins and pharmacological agents capable to protect both cell types.

Mitochondrial Ca2+ oscillation induces mitophagy initiation through the PINK1-Parkin pathway

Dysregulation of the PINK1/Parkin-mediated mitophagy is essential to Parkinson’s disease. Although important progress has been made in previous researches, the biochemical reagents that induce global and significant mitochondrial damage may still hinder deeper insights into the mechanisms of mitophagy. The origin of PINK1/Parkin pathway activation in mitophagy remains elusive. In this study, we develop an optical method, ultra-precise laser stimulation (UPLaS) that delivers a precise and noninvasive stimulation onto a submicron region in a single mitochondrial tubular structure. UPLaS excites localized mitochondrial Ca²⁺ (mitoCa²⁺) oscillations with tiny perturbation to mitochondrial membrane potential (MMP) or mitochondrial reactive oxygen species. The UPLaS-induced mitoCa²⁺ oscillations can directly induce PINK1 accumulation and Parkin recruitment on mitochondria. The Parkin recruitment by UPLaS requires PINK1. Our results provide a precise and noninvasive technology for research on mitophagy, which stimulates target mitochondria with little damage, and reveal mitoCa²⁺ oscillation directly initiates the PINK1-Parkin pathway for mitophagy without MMP depolarization.

Bisavenathramide Analogues as Nrf2 Inductors and Neuroprotectors in In Vitro Models of Oxidative Stress and Hyperphosphorylation

Oxidative stress is crucial to the outbreak and advancement of neurodegenerative diseases and is a common factor to many of them. We describe the synthesis of a library of derivatives of the 4-arylmethylen-2-pyrrolin-5-one framework by sequential application of a three-component reaction of primary amines, β-dicarbonyl compounds, and α-haloketones and a Knoevenagel condensation. These compounds can be viewed as cyclic amides of caffeic and ferulic acids, and are also structurally related to the bisavenanthramide family of natural antioxidants. Most members of the library showed low cytotoxicity and good activity as inductors of Nrf2, a transcription factor that acts as the master regulator of the antioxidant response associated with activation of the antioxidant response element (ARE). Nrf2-dependent protein expression was also proved by the significant increase in the levels of the HMOX1 and NQO1 proteins. Some compounds exerted neuroprotective properties in oxidative stress situations, such as rotenone/oligomycin-induced toxicity, and also against protein hyperphosphorylation induced by the phosphatase inhibitor okadaic acid. Compound 3i, which can be considered a good candidate for further hit-to-lead development against neurodegenerative diseases due to its well-balanced multitarget profile, was further characterized by proving its ability to reduce phosphorylated Tau levels.

The Cross-Links of Endoplasmic Reticulum Stress, Autophagy, and Neurodegeneration in Parkinson's Disease

Parkinson’s disease (PD) is the most common neurodegenerative movement disorder, and it is characterized by the selective loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc), as well as the presence of intracellular inclusions with α-synuclein as the main component in surviving DA neurons. Emerging evidence suggests that the imbalance of proteostasis is a key pathogenic factor for PD. Endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) and autophagy, two major pathways for maintaining proteostasis, play important roles in PD pathology and are considered as attractive therapeutic targets for PD treatment. However, although ER stress/UPR and autophagy appear to be independent cellular processes, they are closely related to each other. In this review, we focused on the roles and molecular cross-links between ER stress/UPR and autophagy in PD pathology. We systematically reviewed and summarized the most recent advances in regulation of ER stress/UPR and autophagy, and their cross-linking mechanisms. We also reviewed and discussed the mechanisms of the coexisting ER stress/UPR activation and dysregulated autophagy in the lesion regions of PD patients, and the underlying roles and molecular crosslinks between ER stress/UPR activation and the dysregulated autophagy in DA neurodegeneration induced by PD-associated genetic factors and PD-related neurotoxins. Finally, we indicate that the combined regulation of ER stress/UPR and autophagy would be a more effective treatment for PD rather than regulating one of these conditions alone.

Mitochondrial Reactive Oxygen Species Regulate Immune Responses of Macrophages to Aspergillus fumigatus

Reactive Oxygen Species (ROS) are highly reactive molecules that can induce oxidative stress. For instance, the oxidative burst of immune cells is well known for its ability to inhibit the growth of invading pathogens. However, ROS also mediate redox signalling, which is important for the regulation of antimicrobial immunity. Here, we report a crucial role of mitochondrial ROS (mitoROS) in antifungal responses of macrophages. We show that mitoROS production rises in murine macrophages exposed to swollen conidia of the fungal pathogen Aspergillus fumigatus compared to untreated macrophages, or those treated with resting conidia. Furthermore, the exposure of macrophages to swollen conidia increases the activity of complex II of the respiratory chain and raises mitochondrial membrane potential. These alterations in mitochondria of infected macrophages suggest that mitoROS are produced via reverse electron transport (RET). Significantly, preventing mitoROS generation via RET by treatment with rotenone, or a suppressor of site IQ electron leak, S1QEL1.1, lowers the production of pro-inflammatory cytokines TNF-α and IL-1β in macrophages exposed to swollen conidia of A. fumigatus. Rotenone and S1QEL1.1 also reduces the fungicidal activity of macrophages against swollen conidia. Moreover, we have established that elevated recruitment of NADPH oxidase 2 (NOX2, also called gp91phox) to the phagosomal membrane occurs prior to the increase in mitoROS generation. Using macrophages from gp91phox-/- mice, we have further demonstrated that NOX2 is required to regulate cytokine secretion by RET-associated mitoROS in response to infection with swollen conidia. Taken together, these observations demonstrate the importance of RET-mediated mitoROS production in macrophages infected with A. fumigatus.

Long Non-coding RNAs in Parkinson's Disease

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder and is associated with a range of motor and non-motor clinical symptoms. The underlying molecular pathogenesis of PD involves a variety of pathways and mechanisms, including α-synuclein proteostasis, mitochondrial dysfunction, oxidative stress, autophagy and apoptosis, neuroinflammation, and epigenetic regulation. Long non-coding RNAs (lncRNAs) are involved in the regulation of multiple pathological processes of PD. In this review, we provide an overview of large-scale studies on lncRNA expression profiling in PD patients and models, as well as highlight the impacts of lncRNAs on the pathogenesis of PD, which could provide basic information regarding the putative lncRNA-based biomarkers and therapeutic targets for the early diagnosis and treatment strategies for PD.

Apelin-13 Protects Dopaminergic Neurons against Rotenone-Induced Neurotoxicity through the AMPK/mTOR/ULK-1 Mediated Autophagy Activation

Parkinson’s disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Several brain–gut peptides are able to exert neuroprotective effects on the nigrostriatal dopaminergic system. Apelin-13 is a neuropeptide, conveying potential neuroprotective activities. However, whether, and how, apelin-13 could antagonize rotenone-induced neurotoxicity has not yet been elucidated. In the present study, rotenone-treated SH-SY5Y cells and rats were used to clarify whether apelin-13 has protective effects on dopaminergic neurons, both in vivo and in vitro. The results showed that apelin-13 could protect SH-SY5Y cells from rotenone-induced injury and apoptosis. Apelin-13 was able to activate autophagy, and restore rotenone induced autophagy impairment in SH-SY5Y cells, which could be blocked by the autophagy inhibitor 3-Methyladenine. Apelin-13 activated AMPK/mTOR/ULK-1 signaling, AMPKα inhibitor compound C, as well as apelin receptor blockage via siRNA, which could block apelin-13-induced signaling activation, autophagy activation, and protective effects, in rotenone-treated SH-SY5Y cells. These results indicated that apelin-13 exerted neuroprotective properties against rotenone by stimulating AMPK/mTOR/ULK-1 signaling-mediated autophagy via the apelin receptor. We also observed that intracerebroventricular injection of apelin-13 could alleviate nigrostriatal dopaminergic neuron degeneration in rotenone-treated rats. Our findings provide new insights into the mechanism by which apelin-13 might attenuate neurotoxicity in PD.

The effect of low dose amphetamine in rotenone-induced toxicity in a mice model of Parkinson's disease

OBJECTIVES

The effects of low dose amphetamine on oxidative stress and rotenone-induced neurotoxicity and liver injury were examined in vivo in a mice model of Parkinson's disease.

MATERIALS AND METHODS

Male mice were treated with rotenone (1.5 mg/kg, every other day for two weeks, subcutaneously). Mice received either the vehicle or amphetamine intraperitoneally at doses of 0.5, 1.0, or 2.0 mg/kg. Oxidative stress was assessed by measurement of the lipid peroxidation product malondialdehyde (MDA), nitric oxide (NO), total anti-oxidant capacity (TAC), and paraoxonase-1 (PON-1) activity in the brain and liver. In addition, brain concentrations of nuclear factor kappa B (NF-κB) and tyrosine hydroxylase were determined and histopathology and Bax/Bcl-2 immunohistochemistry were performed.

RESULTS

The levels of lipid peroxidation and NO were increased and TAC and PON-1 were decreased significantly compared with vehicle-injected control mice. There were also significantly increased NF-κB and decreased tyrosine hydroxylase in the brain following rotenone administration. These changes were significantly attenuated by amphetamine. Rotenone caused neurodegenerative changes in the substantia nigra, cerebral cortex, and hippocampus. The liver showed degenerative changes in hepatocytes and infiltration of Kupffer cells. Bax/Bcl2 ratio was significantly increased in brain and liver tissues. Amphetamine prevented these histopathological changes and the increase in apoptosis evoked by rotenone.

CONCLUSION

These results suggest that low dose amphetamine exerts anti-oxidant and anti-apoptotic effects, protects against rotenone-induced neurodegeneration, and could prevent neuronal cell degeneration in Parkinson's disease.

Overexpression of MicroRNA-133a Inhibits Apoptosis and Autophagy in a Cell Model of Parkinson's Disease by Downregulating Ras-Related C3 Botulinum Toxin Substrate 1 (RAC1)

Background

Parkinson’s disease (PD) is a movement disorder. microRNA (miR)-133 expression is reduced in PD patients and in mice with a dopamine neuron deficiency. We aimed to identify the mechanism of miR-133a in apoptosis and autophagy in PD.

Material/Methods

The optimal concentration of MPP⁺ (1-methyl-4-phenylpyridinium ion) was initially determined to construct a PD cell model. Gain-of function experiments were carried out to evaluate the role of miR-133a in PD. The levels of miR-133a, RAC1 (Ras-related C3 botulinum toxin substrate 1), apoptosis-related factors, and autophagy-related factors were detected after detection of cell proliferation, cell cycle, and apoptosis. Transmission electron microscopy was applied to observe autophagosomes, and immunofluorescence staining was performed to detect LC3 and further analyze the effect of miR-133a on autophagy in a PD cell model.

Results

Low miR-133a expression was detected in a cell model of MPP⁺-induced PD. After overexpressing miR-133a, cell proliferation increased, and apoptosis (cleaved caspase-3 and Bax levels decreased, while Bcl2 levels increased) and autophagy was inhibited (LC3II/I and Beclin-1 levels decreased, while p62 levels increased). MiR-133a targeted RAC1. RACY upregulation attenuated the inhibitory effects of miR-133a on PC12 cell apoptosis and autophagy.

Conclusions

Our data highlighted that miR-133a overexpression prevented apoptosis and autophagy in a cell model of MPP⁺-induced PD by inhibiting RAC1 expression.

HOTAIR drives autophagy in midbrain dopaminergic neurons in the substantia nigra compacta in a mouse model of Parkinson's disease by elevating NPTX2 via miR-221-3p binding

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by progressive cell loss, largely confined to mesencephalic dopamine neurons of the substantia nigra. This study investigated the functional relevance of the HOX transcript antisense intergenic RNA (HOTAIR)/microRNA-221-3 (miR-221-3p)/neuronal pentraxin II (NPTX2) axis in the process of dopaminergic neuron autophagy using PD mouse models. The PD mouse models were established by intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine (MPTP), while PD cell model was constructed by pretreatment with 1-methyl-4-phenylpyridinium (MPP⁺). The expression of HOTAIR was then examined using RT-qPCR. In addition, the interactions between HOTAIR, miR-221-3p, and NPTX2 were detected through RIP and dual-luciferase reporter gene assays. CCK-8 assay was performed to measure cell viability, and the expression of autophagy-related genes was determined using Western blot analysis. HOTAIR was found to be significantly expressed in the substantia nigra compact tissues and MN9D cells following PD modeling. HOTAIR could bind to miR-221-3p and elevate the NPTX2 expression, which resulted in diminished cell viability and enhanced autophagy of dopaminergic neurons both in vitro and in vivo. In summary, down-regulation of HOTAIR could potentially inhibit the autophagy of dopaminergic neurons in the substantia nigra compacta in a mouse model of PD, thus saving the demise of dopaminergic neurons.

A Scientometric Analysis and Visualization of Research on Parkinson's Disease Associated With Pesticide Exposure

The etiology and pathogenesis of Parkinson's disease (PD) have not yet been clearly described. Both genetic and environmental factors contribute to the onset and progression of PD. Some pesticides have been demonstrated to be associated with PD by many previous studies and experiments, and an increasing number of researchers have paid attention to this area in recent years. This paper aims to explore the knowledge structure, analyze the current research hot spots, and discuss the research trend through screening and summarizing the present literature. Based on 1767 articles from the Web of Science Core Collection and PubMed database, this study carried out the analysis from the keywords, cited references, countries, authors, and some other aspects by using Citespace. The hot topics, valuable articles, and productive authors in this research field could be found after that. To the best of our knowledge, this is the first study to specifically visualize the relationship between pesticide exposure and PD, and forecast research tendency in the future.

MiR-142-5p Protects Against 6-OHDA-Induced SH-SY5Y Cell Injury by Downregulating BECN1 and Autophagy

BACKGROUND

MiR-142-5p has been demonstrated to hold significant implications in neurological diseases. However, the impact and underlying regulatory mechanism of miR-142-5p in Parkinson's disease (PD) are still ominous.

METHODS

To simulate the PD, 6-hydroxydopamine (6-OHDA)-treated SH-SY5Y cell model was used in this study. Levels of messenger RNA and protein were tested by quantitative real-time polymerase chain reaction and Western blot analyses, respectively. The direct interaction between miR-142-5p and Beclin 1 (BECN1) was assessed by luciferase reporter assay. Furthermore, Cell Counting Kit-8 assay was performed to assess cytotoxicity of SH-SY5Y cell.

RESULTS

In consequence, a significant decrease of miR-142-5p was observed in 6-OHDA-induced SH-SY5Y cells. Over-/Low-expressed miR-142-5p resulted in a significant enhancement/inhibition on cell vitalities of 6-OHDA-treated SH-SY5Y cells, which might be modulated by repressing cellular autophagy through inhibiting level of BECN1 and LC3 II/LC3 I and elevating P62 level. Luciferase reporter assay showed that the BECN1 was the target gene of miR-142-5p. Additionally, the loss/gain of BECN1 rescued/blocked the effects of miR-142-5p on the viability of 6-OHDA-induced SH-SY5Y cells.

CONCLUSIONS

These results highlight that miR-142-5p functions as a neuroprotective regulator in 6-OHDA-induced neuronal SH-SY5Y cells simulating PD model in vitro via regulating autophagy-related protein BECN1 and autophagy to influence cell viability.

Involvement of Akt/mTOR in the Neurotoxicity of Rotenone-Induced Parkinson's Disease Models

Rotenone has recently been widely used to establish Parkinson’s disease (PD) models to replicate the features of PD. However, the mechanisms involved in rotenone neurotoxicity have not been elucidated. The aim of the present study was to identify the neurotoxicity of rotenone through intraperitoneal injection in mice and to investigate the global changes of phosphorylation proteomic profiles in rotenone-injured SH-SY5Y cells through a label-free proteomic analysis using a PTMScan with LC–MS/MS. ICR (Institute of Cancer Research) mice were intraperitoneally injected with different dosages of rotenone (1 mg/kg/d or 3 mg/kg/d) daily for 21 consecutive days. Rotenone caused a dose-dependent decrease in locomotor activities and a decrease in the number of Nissl-positive and tyrosine hydroxylase (TH)-immunoreactive neurons in the substantia nigra pars compacta (SNpc). Here, 194 phosphopeptides on 174 proteins were detected in SH-SY5Y cells, and 37 phosphosites on 33 proteins displayed statistically significant changes in expression after rotenone injury. The downregulation of phosphorylated Akt and mTOR was further confirmed by western blot analysis. A specific Akt activator, SC79, could protect cell viability and induce autophagy in rotenone-injured SH-SY5Y cells. This study indicates the involvement of the Akt/mTOR (mammalian target of rapamycin) signaling pathway in rotenone-injured SH-SY5Y cells and provides molecular information for the neurotoxicity of rotenone.

Function of Atg11 in non-selective autophagy and selective autophagy of Candida albicans

Candida albicans is an important opportunistic pathogenic fungus in the human body. It is a common microbe inhabiting on the mucosa surfaces of healthy individuals, but may cause infections when the host immune system is weak. Autophagy is a "self-eating" process in eukaryotes, which can recover and utilize damaged organelles and misfolded proteins. Here we investigated the role of the autophagy-related protein Atg11 in C. albicans. Deletion of ATG11 led to the defect in growth under the nitrogen starvation condition. Western blotting and GFP localization further revealed that the transport and degradation of Atg8 was blocked in the atg11Δ/Δ mutant under both the nitrogen starvation and hypha-inducing conditions. Moreover, degradation of both Lap41 (the indicator of the cytoplasm-to-vacuole pathway) and Csp37 (the indicator of mitophagy) was also thoroughly suppressed in this mutant under nitrogen starvation. These results indicated that Atg11 plays an essential role in both non-selective and selective autophagy in C. albicans.

Neuroprotective effect of anodal transcranial direct current stimulation on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity in mice through modulating mitochondrial dynamics

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the accumulation of protein inclusions and the loss of dopaminergic neurons. Abnormal mitochondrial homeostasis is thought to be important for the pathogenesis of PD. Transcranial direct current stimulation (tDCS), a noninvasive brain stimulation technique, constitutes a promising approach for promoting recovery of various neurological conditions. However, little is known about its mechanism of action. The present study elucidated the neuroprotective effects of tDCS on the mitochondrial quality control pathway in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model. We used the MPTP-induced neurotoxicity in vivo model. Mice were stimulated for 5 consecutive days with MPTP treatment. After observation of behavioral alteration using the rotarod test, mice were sacrificed for the measurement of the PD- and mitochondrial quality control-related protein levels in the substantia nigra. tDCS improved the behavioral alterations and changes in tyrosine hydroxylase levels in MPTP-treated mice. Furthermore, tDCS attenuated mitochondrial damage, as indicated by diminished mitochondrial swelling and mitochondrial glutamate dehydrogenase activity in the MPTP-induced PD mouse model. MPTP significantly increased mitophagy and decreased mitochondrial biogenesis-related proteins. These changes were attenuated by tDCS. Furthermore, MPTP significantly increased fission-related protein dynamin-related protein 1 with no effect on fusion-related protein mitofusin-2, and tDCS attenuated these changes. Our findings demonstrated the neuroprotective effect of anodal tDCS on the MPTP-induced neurotoxic mouse model through suppressing excessive mitophagy and balancing mitochondrial dynamics. The neuroprotective effect of anodal tDCS with modulation of mitochondrial dynamics provides a new therapeutic strategy for the treatment of PD.

Role of autophagy in environmental neurotoxicity

Human exposure to neurotoxic pollutants (e.g. metals, pesticides and other chemicals) is recognized as a key risk factor in the pathogenesis of neurodegenerative disorders. Emerging evidence indicates that an alteration in autophagic pathways may be correlated with the onset of the neurotoxicity resulting from chronic exposure to these pollutants. In fact, autophagy is a natural process that permits to preserving cell homeostasis, through the seizure and degradation of the cytosolic damaged elements. However, when an excessive level of intracellular damage is reached, the autophagic process may also induce cell death. A correct modulation of specific stages of autophagy is important to maintain the correct balance in the organism. In this review, we highlight the critical role that autophagy plays in neurotoxicity induced by the most common classes of environmental contaminants. The understanding of this mechanism may be helpful to discover a potential therapeutic strategy to reduce side effects induced by these compounds.

Discovery of the novel autophagy inhibitor aumitin that targets mitochondrial complex I

Macroautophagy is a conserved eukaryotic process for degradation of cellular components in response to lack of nutrients. It is involved in the development of diseases, notably cancer and neurological disorders including Parkinson's disease. Small molecule autophagy modulators have proven to be valuable tools to dissect and interrogate this crucial metabolic pathway and are in high demand. Phenotypic screening for autophagy inhibitors led to the discovery of the novel autophagy inhibitor aumitin. Target identification and confirmation revealed that aumitin inhibits mitochondrial respiration by targeting complex I. We show that inhibition of autophagy by impairment of mitochondrial respiration is general for several mitochondrial inhibitors that target different mitochondrial complexes. Our findings highlight the importance of mitochondrial respiration for autophagy regulation.