Mechanistic comparison between MPTP and rotenone neurotoxicity in mice

ROS Regulate Rotenone-induced SH-SY5Y Dopamine Neuron Death Through Ferroptosis-mediated Autophagy and Apoptosis

Rotenone, a plant-derived natural insecticide, is widely used to induce Parkinson's disease (PD) models. However, the mechanisms of rotenone-induced cell death remain unclear. Here, we found that rotenone (0.01, 0.1, or 1 μmol/L) suppressed SH-SY5Y dopamine neuron viability and led to PD-like pathological changes, such as reduced tyrosine hydroxylase (TH) but increased α-synuclein. Rotenone increased the levels of intracellular reactive oxygen species (ROS) and mitochondrial ROS, as well as the levels of the antioxidants nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), ultimately resulting in oxidative stress. Moreover, rotenone significantly downregulated the expression of GPX4 and xCT but upregulated the expression of COX2 and NCOA4, which are markers of ferroptosis. Furthermore, rotenone decreased phosphorylated mTOR level but increased Beclin-1, ATG5, LC3 and p62 expression, suggesting that rotenone enhances autophagy and reduces autophagy flux. Additionally, rotenone reduced Bcl-2 levels and the mitochondrial membrane potential (MMP) while promoting BAX and Caspase-3 expression, thus initiating cell apoptosis. N-acetylcysteine (NAC), a ROS scavenger, and ferrostatin-1 (Fer-1) and deferoxamine (DFO), two ferroptosis inhibitors, significantly eliminated rotenone-induced autophagy and apoptosis. Moreover, ML385, a specific inhibitor of Nrf2, suppressed rotenone-induced ferroptosis. Our results demonstrated that ROS might mediate rotenone-induced PD-like pathological changes by regulating iron death, autophagy, and apoptosis. Inhibiting ferroptosis blocked the rotenone-induced increase in autophagy and apoptosis. Thus, the ability of ROS to regulate rotenone-induced death through autophagy and apoptosis is dependent on ferroptosis. The findings require validation in multiple neuronal cell lines and in vivo.

Lactoferrin Protects Against Rotenone-Induced Toxicity in Dopaminergic SH-SY5Y Cells through the Modulation of Apoptotic-Associated Pathways

Parkinson's disease (PD) is a common motor neurodegenerative disease that still lacks effective therapeutic options. Previous studies have reported that lactoferrin exhibited neuroprotective effects in cellular and animal models of PD, typically induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or 1-methyl-4-phenylpyridinium (MPP+) synthetic toxin. However, the neuroprotective capacity of lactoferrin in the rotenone-induced cellular model of PD remains relatively less established. Unlike MPTP/MPP+, rotenone is a naturally occurring environmental toxin known to induce chronic toxicity and increase the risk of PD in humans. In this study, we constructed a cellular model of PD by differentiating SH-SY5Y neuroblastoma cells with retinoic acid into mature dopaminergic neurons with increased β-tubulin III and tyrosine hydroxylase expression, followed by 24 h of rotenone exposure. Using this cellular model of PD, we showed that lactoferrin (1-10 µg/ml) pre-treatment for 48 h decreased loss of cell viability, mitochondrial membrane potential impairment, reactive oxygen species generation and pro-apoptotic activities (pan-caspase activation and nuclear condensation) in cells exposed to rotenone (1 and 5 µM) using biochemical assays, Hoechst 33342 staining and immunocytochemical techniques. We further demonstrated that 48 h of lactoferrin (10 µg/ml) pre-treatment decreased Bax:Bcl2 ratio and p42/44 mitogen-activated protein kinase expression but increased pAkt expression in 5 µM rotenone-exposed cells. Our study demonstrates that lactoferrin neuroprotective capacity is present in the rotenone-induced cellular model of PD, further supporting lactoferrin as a potential PD therapeutic that warrants further studies.

Targeting Mitochondrial Complex I Deficiency in MPP+/MPTP-induced Parkinson's Disease Cell Culture and Mouse Models by Transducing Yeast NDI1 Gene

BACKGROUND

MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), original found in synthetic heroin, causes Parkinson's disease (PD) in human through its metabolite MPP+ by inhibiting complex I of mitochondrial respiratory chain in dopaminergic neurons. This study explored whether yeast internal NADH-quinone oxidoreductase (NDI1) has therapeutic effects in MPTP- induced PD models by functionally compensating for the impaired complex I. MPP+-treated SH-SY5Y cells and MPTP-treated mice were used as the PD cell culture and mouse models respectively. The recombinant NDI1 lentivirus was transduced into SH-SY5Y cells, or the recombinant NDI1 adeno-associated virus (rAAV5-NDI1) was injected into substantia nigra pars compacta (SNpc) of mice.

RESULTS

The study in vitro showed NDI1 prevented MPP+-induced change in cell morphology and decreased cell viability, mitochondrial coupling efficiency, complex I-dependent oxygen consumption, and mitochondria-derived ATP. The study in vivo revealed that rAAV-NDI1 injection significantly improved the motor ability and exploration behavior of MPTP-induced PD mice. Accordingly, NDI1 notably improved dopaminergic neuron survival, reduced the inflammatory response, and significantly increased the dopamine content in striatum and complex I activity in substantia nigra.

CONCLUSIONS

NDI1 compensates for the defective complex I in MPP+/MPTP-induced models, and vastly alleviates MPTP-induced toxic effect on dopaminergic neurons. Our study may provide a basis for gene therapy of sporadic PD with defective complex I caused by MPTP-like substance.

New insights in animal models of neurotoxicity-induced neurodegeneration

The high prevalence of neurodegenerative diseases is an unintended consequence of the high longevity of the population, together with the lack of effective preventive and therapeutic options. There is great pressure on preclinical research, and both old and new models of neurodegenerative diseases are required to increase the pipeline of new drugs for clinical testing. We review here the main models of neurotoxicity-based animal models leading to central neurodegeneration. Our main focus was on studying how changes in neurotransmission and neuroinflammation, mainly in rodent models, contribute to harmful processes linked to neurodegeneration. The majority of the models currently in use mimic Parkinson's disease (PD) and Alzheimer's disease (AD), which are the most common neurodegenerative conditions in older adults. AD is the most common age-related dementia, whereas PD is the most common movement disorder with also cases of dementia. Several natural toxins and xenobiotic agents induce dopaminergic neurodegeneration and can reproduce neuropathological traits of PD. The literature analysis of MPTP, 6-OH-dopamine, and rotenone models suggested the latter as a useful model when specific doses of rotenone were administrated systemically to C57BL/6 mice. Cholinergic neurodegeneration is mainly modelled with the toxin scopolamine, which is a useful rodent model for the screening of protective drugs against cognitive decline and AD. Several agents have been used to model neuroinflammation-based neurodegeneration and dementia in AD, including lipopolysaccharide (LPS), streptozotocin, and monomeric C-reactive protein. The bacterial agent LPS makes a useful rodent model for testing anti-inflammatory therapies to halt the development and severity of AD. However, neurotoxin models might be more useful than genetic models for drug discovery in PD but that is not the case in AD where they cannot beat the new developments in transgenic mouse models. Overall, we should work using all available models, either in vivo, in vitro, or in silico, considering the seriousness of the moment and urgency of developing effective drugs.

Mitochondrial dysfunction and oxidative stress: Role in chronic kidney disease

Chronic kidney disease (CKD) is associated with a variety of distinct disease processes that permanently change the function and structure of the kidney across months or years. CKD is characterized as a glomerular filtration defect or proteinuria that lasts longer than three months. In most instances, CKD leads to end-stage kidney disease (ESKD), necessitating kidney transplantation. Mitochondrial dysfunction is a typical response to damage in CKD patients. Despite the abundance of mitochondria in the kidneys, variations in mitochondrial morphological and functional characteristics have been associated with kidney inflammatory responses and injury during CKD. Despite these variations, CKD is frequently used to define some classic signs of mitochondrial dysfunction, including altered mitochondrial shape and remodeling, increased mitochondrial oxidative stress, and a marked decline in mitochondrial biogenesis and ATP generation. With a focus on the most significant developments and novel understandings of the involvement of mitochondrial remodeling in the course of CKD, this article offers a summary of the most recent advances in the sources of procured mitochondrial dysfunction in the advancement of CKD. Understanding mitochondrial biology and function is crucial for developing viable treatment options for CKD.

Systemic Rotenone Administration Causes Extra-Nigral Alterations in C57BL/6 Mice

Systemic administration of rotenone replicates several pathogenic and behavioural features of Parkinson's disease (PD), some of which cannot be explained by deficits of the nigrostriatal pathway. In this study, we provide a comprehensive analysis of several neurochemical alterations triggered by systemic rotenone administration in the CNS of C57BL/6 mice. Mice injected with either 1, 3 or 10 mg/kg rotenone daily via intraperitoneal route for 21 days were assessed weekly for changes in locomotor and exploratory behaviour. Rotenone treatment caused significant locomotor and exploratory impairment at dosages of 3 or 10 mg/kg. Molecular analyses showed reductions of both TH and DAT expression in the midbrain, striatum and spinal cord, accompanied by altered expression of dopamine receptors and brain-derived neurotrophic factor (BDNF). Rotenone also triggered midbrain-restricted inflammatory responses with heightened expression of glial markers, which was not seen in extra-nigral regions. However, widespread alterations of mitochondrial function and increased signatures of oxidative stress were identified in both nigral and extra-nigral regions, along with disruptions of neuroprotective peptides, such as pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal peptide (VIP) and activity-dependent neuroprotective protein (ADNP). Altogether, this study shows that systemic rotenone intoxication, similarly to PD, causes a series of neurochemical alterations that extend at multiple CNS levels, reinforcing the suitability of this pre-clinical model for the study extra-nigral defects of PD.

New models of Parkinson's like neuroinflammation in human microglia clone 3: Activation profiles induced by INF-γ plus high glucose and mitochondrial inhibitors

Microglia activation and neuroinflammation have been extensively studied in murine models of neurodegenerative diseases; however, to overcome the genetic differences between species, a human cell model of microglia able to recapitulate the activation profiles described in patients is needed. Here we developed human models of Parkinson's like neuroinflammation by using the human microglia clone 3 (HMC3) cells, whose activation profile in response to classic inflammatory stimuli has been controversial and reported only at mRNA levels so far. In fact, we showed the increased expression of the pro-inflammatory markers iNOS, Caspase 1, IL-1β, in response to IFN-γ plus high glucose, a non-specific disease stimulus that emphasized the dynamic polarization and heterogenicity of the microglial population. More specifically, we demonstrated the polarization of HMC3 cells through the upregulation of iNOS expression and nitrite production in response to the Parkinson's like stimuli, 6-hydroxidopamine (6-OHDA) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), the latter depending on the NF-κB pathway. Furthermore, we identified inflammatory mediators that promote the pro-inflammatory activation of human microglia as function of different pathways that can simulate the phenotypic transition according to the stage of the pathology. In conclusion, we established and characterized different systems of HMC3 cells activation as in vitro models of Parkinson's like neuroinflammation.

Açai Berry Mitigates Parkinson's Disease Progression Showing Dopaminergic Neuroprotection via Nrf2-HO1 Pathways

The current pharmacological treatment for Parkinson's disease (PD) is focused on symptom alleviation rather than disease prevention. In this study, we look at a new strategy to neuroprotection that focuses on nutrition, by a supplementation with Açai berry in an experimental models of PD. Daily orally supplementation with Açai berry dissolved in saline at the dose of 500 mg/kg considerably reduced motor and non-motor symptom and neuronal cell death of the dopaminergic tract induced by 4 injections of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Furthermore, Açai berry administration reduced α-synuclein aggregation in neurons, enhanced tyrosine hydroxylase and dopamine transporter activities, and avoided dopamine depletion. Moreover, Açai berry administration was able to reduce astrogliosis and microgliosis as well as neuronal death. Its beneficial effects could be due to its bioactive phytochemical components that are able to stimulate nuclear factor erythroid 2-related factor 2 (Nrf2) by counteracting the oxidative stress and neuroinflammation that are the basis of this neurodegenerative disease.

CREB Inactivation by HDAC1/PP1γ Contributes to Dopaminergic Neurodegeneration in Parkinson's Disease

Understanding the pathogenesis of nigral dopaminergic neurodegeneration is critical for developing mechanism-based treatments for Parkinson's disease (PD). In the nigral dopaminergic neurons of postmortem human PD brains, we found that CREB, a well-recognized pro-survival transcription factor in neurons, was inactivated by dephosphorylation at Ser133. CREB dephosphorylation correlated with decreased expression of NURR1, one of its target genes crucial for dopaminergic neuron survival, confirming that CREB function was impaired in nigral dopaminergic neurons in PD. An MPTP mouse model was used to further elucidate the mechanism underlying CREB dephosphorylation. Protein phosphatase 1γ (PP1γ), which dephosphorylates CREB, was constitutively associated with histone deacetylase 1 (HDAC1). HDAC1 promotes CREB Ser133 dephosphorylation via a stable interaction with PP1γ. We found that CREB interacted with the HDAC1/PP1γ complex during dopaminergic neurodegeneration. Importantly, increased CREB/HDAC1 interaction occurred in the nigral dopaminergic neurons of PD patients as demonstrated using a proximity ligation assay. Disrupting CREB/HDAC1 interaction via either overexpression of GAL4 M1, a CREB mutant, or administration of trichostatin A, a pan-HDAC inhibitor, restored the expression levels of phospho-CREB (Ser133) and NURR1, and protected nigral dopaminergic neurons in the MPTP-treated mouse brain. Collectively, our results demonstrated that HDAC1/PP1γ-mediated CREB inactivation contributed to dopaminergic neuronal degeneration. Disruption of CREB/HDAC1 interaction has the potential to be a new approach for PD therapy.SIGNIFICANCE STATEMENT Parkinson's disease (PD) is the most common movement disorder attributed to the progressive loss of dopaminergic neurons in the substantia nigra. Understanding the pathogenesis of nigral dopaminergic neurodegeneration is critical for developing mechanism-based treatments for PD. We found in nigral dopaminergic neurons of postmortem human PD brains that CREB, a well-recognized pro-survival transcription factor in neurons, was inactivated by dephosphorylation at Ser133. HDAC1, constitutively associated with PP1γ, interacted with CREB to mediate its dephosphorylation during dopaminergic neurodegeneration. Disrupting CREB/HDAC1 interaction restored CREB activity and protected nigral dopaminergic neurons in the MPTP mouse brains. This work suggests that disruption of the CREB/HDAC1 interaction to restore CREB activity may be a potential therapeutic approach in PD.

Comparison of the effect of rotenone and 1‑methyl‑4‑phenyl‑1,2,3,6‑tetrahydropyridine on inducing chronic Parkinson's disease in mouse models

Animal models for Parkinson's disease (PD) are very useful in understanding the pathogenesis of PD and screening for new therapeutic approaches. The present study compared two commonly used neurotoxin‑induced mouse models of chronic PD to guide model selection, explore the pathogenesis and mechanisms underlying PD and develop effective treatments. The chronic PD mouse models were established via treatment with rotenone or 1‑methyl‑4‑phenyl‑1,2,3,6-tetrahydropyridine (MPTP) for 6 weeks. The effects of rotenone and MPTP in the mice were compared by assessing neurobehavior, neuropathology and mitochondrial function through the use of the pole, rotarod and open field tests, immunohistochemistry for tyrosine hydroxylase (TH), glial fibrillary acidic protein (GFAP), ionized calcium‑binding adapter molecule 1 (Iba‑1), neuronal nuclear antigen (NeuN) and (p)S129 α‑synuclein, immunofluorescence for GFAP, Iba‑1 and NeuN, western blotting for TH, oxygen consumption, complex I enzyme activity. The locomotor activity, motor coordination and exploratory behavior in both rotenone and MPTP groups were significantly lower compared with the control group. However, behavioral tests were no significant differences between the two groups. In the MPTP group, the loss of dopaminergic (DA) neurons in the substantia nigra (SN) pars compacta, the reduction of the tyrosine hydroxylase content in the SN and striatum and the astrocyte proliferation and microglial activation in the SN were more significant compared with the rotenone group. Notably, mitochondrial‑dependent oxygen consumption and complex I enzyme activity in the SN were significantly reduced in the rotenone group compared with the MPTP group. In addition, Lewy bodies were present only in SN neurons in the rotenone group. Although no significant differences in neurobehavior were observed between the two mouse models, the MPTP model reproduced the pathological features of PD more precisely in terms of the loss of DA neurons, decreased dopamine levels and neuroinflammation in the SN. On the other hand, the rotenone model was more suitable for studying the role of mitochondrial dysfunction (deficient complex I activity) and Lewy body formation in the SN, which is a characteristic pathological feature of PD. The results indicated that MPTP and rotenone PD models have advantages and disadvantages, therefore one or both should be selected based on the purpose of the study.

Time Course of Neurobehavioral Disruptions and Regional Brain Metabolism Changes in the Rotenone Mice Model of Parkinson’s Disease

Parkinson’s disease (PD) is characterized by slow progression with a long prodromal stage and the gradual evolution of both neuropsychological symptoms and subtle motor changes, preceding motor dysfunction. Thus, in order for animal models of PD to be valid, they should reproduce these characteristics of the disease. One of such models, in which neuropathology is induced by chronic injections of low doses of mitochondrial toxin rotenone, is well established in rats. However, data on this model adapted to mice remain controversial. We have designed the study to describe the timecourse of motor and non-motor symptoms during chronic subcutaneous administration of rotenone (4 mg/kg daily for 35 days) in C57BL/6 mice. We characterize the underlying neuropathological processes (dopaminergic neuron degeneration, regional brain metabolism, monoamine neurotransmitter and lipid peroxidation changes) at different timepoints: 1 day, 2 weeks and 5 weeks of daily rotenone exposure. Based on the behavioral data, we can describe three stages of pathology: cognitive changes from week 2 of rotenone exposure, subtle motor changes in week 3–4 and motor dysfunction starting roughly from week 4. Neuropathological changes in this model include a general decrease in COX activity in different areas of the brain (acute effect of rotenone) and a more specific decrease in midbrain (chronic effect), followed by significant neurodegeneration in SNpc but not VTA by the 5th week of rotenone exposure. However, we were unable to find changes in the level of monoamine neurotransmitters neither in the striatum nor in the cortex, nor in the level of lipid peroxidation in the brainstem. Thus, the gradual progression of pathology in this model is linked with metabolic changes, rather than with oxidative stress or tonic neurotransmitter release levels. Overall, this study supports the idea that a low-dose rotenone mouse model can also reproduce different stages of PD as well as rats.

3-Pyridinylboronic Acid Ameliorates Rotenone-Induced Oxidative Stress Through Nrf2 Target Genes in Zebrafish Embryos

Parkinson's disease (PD) is one of the most common forms of neurodegenerative diseases and research on potential therapeutic agents for PD continues. Rotenone is a neurotoxin that can pass the blood-brain barrier and is used to generate PD models in experimental animals. Boron is a microelement necessary for neural activity in the brain. Antioxidant, non-cytotoxic, anti-genotoxic, anti-carcinogenic effects of boric acid, the salt compound of boron has been reported before. Boronic acids have been approved for treatment by FDA and are included in drug discovery studies and pyridine boronic acids are a subclass of heterocyclic boronic acids used in drug design and discovery as substituted pyridines based on crystal engineering principles. The aim of our study was to determine the effect of 3-pyridinylboronic acid in rotenone-exposed zebrafish embryos, focusing on oxidant-antioxidant parameters and gene expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) target genes gclm, gclc, hmox1a, nqo1, and PD related genes, brain-derived neurotrophic factor, dj1, and tnfα. Zebrafish embryos were exposed to Rotenone (10 μg/l); Low Dose 3-Pyridinylboronic acid (100 μM); High Dose 3-Pyridinylboronic acid (200 μM); Rotenone + Low Dose-3-Pyridinylboronic acid (10 μg/l + 100 μM); Rotenone + High Dose-3-Pyridinylboronic acid (10 μg/l + 200 μM) in well plates for 96 h post-fertilization (hpf). Our study showed for the first time that 3-pyridinylboronic acid, as a novel sub-class of the heterocyclic boronic acid compound, improved locomotor activities, ameliorated oxidant-antioxidant status by decreasing LPO and NO levels, and normalized the expressions of bdnf, dj1, tnf⍺ and Nrf2 target genes hmox1a and nqo1 in rotenone exposed zebrafish embryos. On the other hand, it caused the deterioration of the oxidant-antioxidant balance in the control group through increased lipid peroxidation, nitric oxide levels, and decreased antioxidant enzymes. We believe that these results should be interpreted in the context of the dose-toxicity and benefit-harm relationship of the effects of 3-pyridinylboronic.

The Positive Role and Mechanism of Herbal Medicine in Parkinson's Disease

Parkinson's disease (PD) is a complex neurodegenerative disease, manifested by the progressive functional impairment of the midbrain nigral dopaminergic neurons. Due to the unclear underlying pathogenesis, disease-modifying drugs for PD remain elusive. In Asia, such as in China and India, herbal medicines have been used in the treatment of neurodegenerative disease for thousands of years, which recently attracted considerable attention because of the development of curative drugs for PD. In this review, we first summarized the pathogenic factors of PD including protein aggregation, mitochondrial dysfunction, ion accumulation, neuroinflammation, and oxidative stress, and the related recent advances. Secondly, we summarized 32 Chinese herbal medicines (belonging to 24 genera, such as Acanthopanax, Alpinia, and Astragalus), 22 Chinese traditional herbal formulations, and 3 Indian herbal medicines, of which the ethanol/water extraction or main bioactive compounds have been extensively investigated on PD models both in vitro and in vivo. We elaborately provided pictures of the representative herbs and the structural formula of the bioactive components (such as leutheroside B and astragaloside IV) of the herbal medicines. Also, we specified the potential targets of the bioactive compounds or extractions of herbs in view of the signaling pathways such as PI3K, NF-κB, and AMPK which are implicated in oxidative and inflammatory stress in neurons. We consider that this knowledge of herbal medicines or their bioactive components can be favorable for the development of disease-modifying drugs for PD.

Structural and Energetic Affinity of Annocatacin B with ND1 Subunit of the Human Mitochondrial Respiratory Complex I as a Potential Inhibitor: An In Silico Comparison Study with the Known Inhibitor Rotenone

ND1 subunit possesses the majority of the inhibitor binding domain of the human mitochondrial respiratory complex I. This is an attractive target for the search for new inhibitors that seek mitochondrial dysfunction. It is known, from in vitro experiments, that some metabolites from Annona muricata called acetogenins have important biological activities, such as anticancer, antiparasitic, and insecticide. Previous studies propose an inhibitory activity of bovine mitochondrial respiratory complex I by bis-tetrahydrofurans acetogenins such as annocatacin B, however, there are few studies on its inhibitory effect on human mitochondrial respiratory complex I. In this work, we evaluate the in silico molecular and energetic affinity of the annocatacin B molecule with the human ND1 subunit in order to elucidate its potential capacity to be a good inhibitor of this subunit. For this purpose, quantum mechanical optimizations, molecular dynamics simulations and the molecular mechanics/Poisson-Boltzmann surface area (MM/PBSA) analysis were performed. As a control to compare our outcomes, the molecule rotenone, which is a known mitochondrial respiratory complex I inhibitor, was chosen. Our results show that annocatacin B has a greater affinity for the ND1 structure, its size and folding were probably the main characteristics that contributed to stabilize the molecular complex. Furthermore, the MM/PBSA calculations showed a 35% stronger binding free energy compared to the rotenone complex. Detailed analysis of the binding free energy shows that the aliphatic chains of annocatacin B play a key role in molecular coupling by distributing favorable interactions throughout the major part of the ND1 structure. These results are consistent with experimental studies that mention that acetogenins may be good inhibitors of the mitochondrial respiratory complex I.

Using Rotenone to Model Parkinson's Disease in Mice: A Review of the Role of Pharmacokinetics

Rotenone is a naturally occurring toxin that inhibits complex I of the mitochondrial electron transport chain. Several epidemiological studies have shown an increased risk of Parkinson's disease (PD) in individuals exposed chronically to rotenone, and it has received great attention for its ability to reproduce many critical features of PD in animal models. Laboratory studies of rotenone have repeatedly shown that it induces in vivo substantia nigra dopaminergic cell loss, a hallmark of PD neuropathology. Additionally, rotenone induces in vivo aggregation of α-synuclein, the major component of Lewy bodies and Lewy neurites found in the brain of PD patients and another hallmark of PD neuropathology. Some in vivo rotenone models also reproduce peripheral signs of PD, such as reduced intestinal motility and peripheral α-synuclein aggregation, both of which are thought to precede classical signs of PD in humans, such as cogwheel rigidity, bradykinesia, and resting tremor. Nevertheless, variability has been noted in cohorts of animals exposed to the same rotenone exposure regimen and also between cohorts exposed to similar doses of rotenone. Low doses, administered chronically, may reproduce PD symptoms and neuropathology more faithfully than excessively high doses, but overlap between toxicity and parkinsonian motor phenotypes makes it difficult to separate if behavior is examined in isolation. Rotenone degrades when exposed to light or water, and choice of vehicle may affect outcome. Rotenone is metabolized extensively in vivo, and choice of route of exposure influences greatly the dose used. However, male rodents may be capable of greater metabolism of rotenone, which could therefore reduce their total body exposure when compared with female rodents. The pharmacokinetics of rotenone has been studied extensively, over many decades. Here, we review these pharmacokinetics and models of PD using this important piscicide.

Neurotoxin-Induced Rodent Models of Parkinson's Disease: Benefits and Drawbacks

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by cardinal motor impairments, including akinesia and tremor, as well as by a host of non-motor symptoms, including both autonomic and cognitive dysfunction. PD is associated with a death of nigral dopaminergic neurons, as well as the pathological spread of Lewy bodies, consisting predominantly of the misfolded protein alpha-synuclein. To date, only symptomatic treatments, such as levodopa, are available, and trials aiming to cure the disease, or at least halt its progression, have not been successful. Wong et al. (2019) suggested that the lack of effective therapy against neurodegeneration in PD might be attributed to the fact that the molecular mechanisms standing behind the dopaminergic neuronal vulnerability are still a major scientific challenge. Understanding these molecular mechanisms is critical for developing effective therapy. Thirty-five years ago, Calne and William Langston (1983) raised the question of whether biological or environmental factors precipitate the development of PD. In spite of great advances in technology and medicine, this question still lacks a clear answer. Only 5-15% of PD cases are attributed to a genetic mutation, with the majority of cases classified as idiopathic, which could be linked to exposure to environmental contaminants. Rodent models play a crucial role in understanding the risk factors and pathogenesis of PD. Additionally, well-validated rodent models are critical for driving the preclinical development of clinically translatable treatment options. In this review, we discuss the mechanisms, similarities and differences, as well as advantages and limitations of different neurotoxin-induced rat models of PD. In the second part of this review, we will discuss the potential future of neurotoxin-induced models of PD. Finally, we will briefly demonstrate the crucial role of gene-environment interactions in PD and discuss fusion or dual PD models. We argue that these models have the potential to significantly further our understanding of PD.

Ellagic Acid Prevents Dopamine Neuron Degeneration from Oxidative Stress and Neuroinflammation in MPTP Model of Parkinson's Disease

Parkinson's disease (PD) is one of the most common neurodegenerative diseases and is characterized by progressive dopaminergic neurodegeneration in the substantia nigra pars compacta area. In the present study, treatment of EA for 1 week at a dose of 10 mg/kg body weight prior to MPTP (25 mg/kg body weight) was carried out. MPTP administration caused oxidative stress, as evidenced by decreased activities of superoxide dismutase and catalase, and the depletion of reduced glutathione with a concomitant rise in the lipid peroxidation product, malondialdehyde. It also significantly increased the pro-inflammatory cytokines and elevated the inflammatory mediators like cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in the striatum. Immunohistochemical analysis revealed a loss of dopamine neurons in the SNc area and a decrease in dopamine transporter in the striatum following MPTP administration. However, treatment with EA prior to MPTP injection significantly rescued the dopaminergic neurons and dopamine transporter. EA treatment further restored antioxidant enzymes, prevented the depletion of glutathione and inhibited lipid peroxidation, in addition to the attenuation of pro-inflammatory cytokines. EA also reduced the levels of COX-2 and iNOS. The findings of the present study demonstrate that EA protects against MPTP-induced PD and the observed neuroprotective effects can be attributed to its potent antioxidant and anti-inflammatory properties.

Mitochondrial dysfunction and the AKI-to-CKD transition

Acute kidney injury (AKI) has been widely recognized as an important risk factor for the occurrence and development of chronic kidney disease (CKD). Even milder AKI has adverse consequences and could progress to renal fibrosis, which is the ultimate common pathway for various terminal kidney diseases. Thus, it is urgent to develop a strategy to hinder the transition from AKI to CKD. Some mechanisms of the AKI-to-CKD transition have been revealed, such as nephron loss, cell cycle arrest, persistent inflammation, endothelial injury with vascular rarefaction, and epigenetic changes. Previous studies have elucidated the pivotal role of mitochondria in acute injuries and demonstrated that the fitness of this organelle is a major determinant in both the pathogenesis and recovery of organ function. Recent research has suggested that damage to mitochondrial function in early AKI is a crucial factor leading to tubular injury and persistent renal insufficiency. Dysregulation of mitochondrial homeostasis, alterations in bioenergetics, and organelle stress cross talk contribute to the AKI-to-CKD transition. In this review, we focus on the pathophysiology of mitochondria in renal recovery after AKI and progression to CKD, confirming that targeting mitochondria represents a potentially effective therapeutic strategy for the progression of AKI to CKD.

Multiple neuroprotective features of Scutellaria pinnatifida-derived small molecule

Parkinson's disease (PD) is one of the most prevalent neurodegenerative disorders with no precise etiology. Multiple lines of evidence support that environmental factors, either neurotoxins or neuroinflammation, can induce Parkinsonism. In this study, we purified an active compound, neobaicalein (Skullcapflavone II), from the roots of Scutellaria pinnatifida (S. pinnatifida). Neobaicalein not only had protective impacts on rotenone-induced neurotoxicity but in glial cultures, it dampened the inflammatory response when stimulated with lipopolysaccharide (LPS). Neobaicalein had high antioxidant activity without any obvious toxicity. In addition, it could raise the cell viability, decrease early apoptosis, reduce the generation of reactive oxygen species (ROS), and keep the neurite's length normal in the treated SH-SY5Y cells. Pathway enrichment analysis (PEA) and target prediction provided insights into the PD related genes, protein-protein interaction (PPI) network, and the key proteins enriched in the signaling pathways. Furthermore, docking simulation (DS) on the proteins of the PD-PPI network revealed that neobaicalein might interact with the key proteins involved in PD pathology, including MAPK14, MAPK8, and CASP3. It also blocks the destructive processes, such as cell death, inflammation, and oxidative stress pathways. Our results demonstrate that neobaicalein alleviates pathological effects of factors related to PD, and may provide new insight into PD therapy.

GSK-3β Contributes to Parkinsonian Dopaminergic Neuron Death: Evidence From Conditional Knockout Mice and Tideglusib

Glycogen synthase kinase-3 (GSK-3) dysregulation has been implicated in nigral dopaminergic neurodegeneration, one of the main pathological features of Parkinson’s disease (PD). The two isoforms, GSK-3α and GSK-3β, have both been suggested to play a detrimental role in neuronal death. To date, several studies have focused on the role of GSK-3β on PD pathogenesis, while the role of GSK-3α has been largely overlooked. Here, we report in situ observations that both GSK-3α and GSK-3β are dephosphorylated at a negatively acting regulatory serine, indicating kinase activation, selectively in nigral dopaminergic neurons following exposure of mice to 1-methyl-4-pheny-1,2,3,6-tetrahydropyridine (MPTP). To identify whether GSK-3α and GSK-3β display functional redundancy in regulating parkinsonian dopaminergic cell death, we analysed dopaminergic neuron-specific Gsk3a null (Gsk3a^ΔDat) and Gsk3b null (Gsk3b^ΔDat) mice, respectively. We found that Gsk3b^ΔDat, but not Gsk3a^ΔDat, showed significant resistance to MPTP insult, revealing non-redundancy of GSK-3α and GSK-3β in PD pathogenesis. In addition, we tested the neuroprotective effect of tideglusib, the most clinically advanced inhibitor of GSK-3, in the MPTP model of PD. Administration of higher doses (200 mg/kg and 500 mg/kg) of tideglusib exhibited significant neuroprotection, whereas 50 mg/kg tideglusib failed to prevent dopaminergic neurodegeneration from MPTP toxicity. Administration of 200 mg/kg tideglusib improved motor symptoms of MPTP-treated mice. Together, these data demonstrate GSK-3β and not GSK-3α is critical for parkinsonian neurodegeneration. Our data support the view that GSK-3β acts as a potential therapeutic target in PD and tideglusib would be a candidate drug for PD neuroprotective therapy.

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.

Comprehensive Analysis of Neurotoxin-Induced Ablation of Dopaminergic Neurons in Zebrafish Larvae

Neurotoxin exposure of zebrafish larvae has been used to mimic a Parkinson’s disease (PD) phenotype and to facilitate high-throughput drug screening. However, the vulnerability of zebrafish to various neurotoxins was shown to be variable. Here, we provide a direct comparison of ablative effectiveness in order to identify the optimal neurotoxin-mediated dopaminergic (DAnergic) neuronal death in larval zebrafish. Transgenic zebrafish, Tg(dat:eGFP), were exposed to different concentrations of the neurotoxins MPTP, MPP⁺, paraquat, 6-OHDA, and rotenone for four days, starting at three days post-fertilization. The LC₅₀ of each respective neurotoxin concentration was determined. Confocal live imaging on Tg(dat:eGFP) showed that MPTP, MPP⁺, and rotenone caused comparable DAnergic cell loss in the ventral diencephalon (vDC) region while, paraquat and 6-OHDA caused fewer losses of DAnergic cells. These results were further supported by respective gene expression analyses of dat, th, and p53. Importantly, the loss of DAnergic cells from exposure to MPTP, MPP⁺, and rotenone impacted larval locomotor function. MPTP induced the largest motor deficit, but this was accompanied by the most severe morphological impairment. We conclude that, of the tested neurotoxins, MPP⁺ recapitulates a substantial degree of DAnergic ablation and slight locomotor perturbations without systemic defects indicative of a Parkinsonian phenotype.