Characterizing the adult zebrafish model of Parkinson's disease: a systematic review of dynamic changes in behavior and physiology post-MPTP administration.

Introduction: Adult zebrafish are increasingly used in Parkinson's disease (PD) research due to their well-characterized dopaminergic system. Among the toxin-based models, the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is widely utilized to induce parkinsonism in adult zebrafish. Therefore, this review presents an overview of the procedures and the dynamic changes in behavior and physiology observed in the adult zebrafish PD model following a single intraperitoneal injection of MPTP. Methods: A systematic literature search in the PubMed and Google Scholar databases was conducted to identify relevant articles. Of the 165 articles identified, 9 were included in this review. These chosen articles are original works published before March 2024, all of which utilized adult zebrafish induced with MPTP as the model for PD. Other articles were excluded based on factors such as limited relevance, utilization of zebrafish embryos or larvae instead of adults, and variations in MPTP deliveries. Results: Studies indicated that the ideal model entails the utilization of mixed gender zebrafish aged between 4 and 6 months from the wild-type strain. The acceptable MPTP doses ranges between 20 µg/g (lowest) and 225 µg/g (highest) and doses above 292 µg/g are lethal. Furthermore, noticeable parkinsonian symptoms appear 1 day after administration and persist for more than 1 week. Discussion: Mitochondrial dysfunction precedes dopaminergic neurodegeneration within this experimental regime. A single administration of MPTP effectively induces PD in adult zebrafish. This study aids in crafting the adult zebrafish PD model, outlining the progressive behavioral and physiological changes ensuing from MPTP administration.

Liver X receptor α contribution to neuroinflammation and glial cells activation induced by MPTP: Implications for Parkinson's disease.

Parkinson's disease (PD) is the second most common neurodegenerative disorder whose etiology remains unknown. The immune system has been implicated in hallmarks of PD including aggregation of α-synuclein and death of dopaminergic neurons in the substantia nigra. As a core regulator of immune response and inflammation, liver X receptors (LXRs) have been shown to have protective effects in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD. With two isoforms of LXRs (LXRα and LXRß) expressed in the brain, their roles and distributions in this tissue remain largely unexplored. Here, we used MPTP to mimic symptoms and biomedical changes seen in PD in LXRα-/- and wild-type mice to investigate the role of LXRα in the etiology and progression of PD. We found that MPTP is unable to induce motor deficits, anxiety-like behavior in LXRα-/- mice, which has been seen in WT mice. Gene ontology analysis of RNA sequencing revealed that knockout of LXRα led to enrichment of the process, including immune response and inflammation in the midbrain. In addition, MPTP did not lead to dopaminergic neuron death in the striatum and substantia nigra in LXRα-/- mice, the basal GFAP protein level, and pro-inflammatory cytokines were elevated in LXRα-/- mice. Lastly, the microglia activation and astrogliosis caused by MPTP intoxication we found in WT mice were abolished in LXRα-/- mice. To sum up, we conclude that LXRα is a critical regulator in MPTP intoxication and may play a unique role in astrogliosis seen in the neuroinflammation of PD.

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated adult zebrafish as a model for Parkinson's Disease.

Dopamine (DA) is a catecholamine neurotransmitter that works to regulate cognitive functions. Patients affected by Parkinson's Disease (PD) experience a loss of dopaminergic neurons and downregulated neural DA production. This leads to cognitive and physical decline that is the hallmark of PD for which no cure currently exists. Danio rerio, or zebrafish, have become an increasingly popular disease model used in PD pharmaceutical development. This model still requires extensive development to better characterize which PD features are adequately represented. Furthermore, the great majority of PD zebrafish models have been performed in embryos, which may not be relevant towards age-related human PD. As an improvement, mature D. rerio were treated with neurotoxic prodrug 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) through intraperitoneal injection to induce parkinsonism. Behavioral analysis confirmed disparities in movement between saline-injected control and the MPTP-injected experimental group, with swim distance and speed significantly lowered seven days after MPTP injection. Simultaneously, cognitive decline was apparent in MPTP-injected zebrafish, demonstrated by decreased alternation in a y-maze. RT-qPCR confirmed trends consistent with downregulation in Parkinsonian genetic markers, specifically DA transporter (DAT), MAO-B, PINK1. In summary, mature zebrafish injected with MPTP present with similar movement and cognitive decline as compared to human disease. Despite its benefits, this model does not appear to recapitulate pathophysiology of the disease with the full profile of expected gene downregulation. Because of this, it is important that researchers looking for pharmacological interventions for PD only use this zebrafish model when targeting the human-relevant PD symptoms and causes that are represented.

Potential Targets for the Protective Effect of Astaxanthin on Ethanolinduced Damage in Rat Liver Mitochondria.

BACKGROUND: Alcohol intoxication leads to multiple degenerative disorders in the structure and function of mitochondria. The mechanisms underlying these disorders, as well as ways to prevent them, are an urgent task in biomedicine. We investigate the mechanism of the positive effect of AX on rat liver mitochondria after chronic alcohol administration and suggest the targets of its effects. In this work, we continued our studies of astaxanthin (AX) as a possible protector of mitochondria from the toxic effects of ethanol. METHOD: In our experiments, we used the Lieber-DeCarly model of chronic alcohol intoxication, which allows high-dose alcohol intake. Four groups of animals were used in the experiments: group 1 (control), group 2 (treated with AX), group 3 (treated with ethanol), and group 4 (treated with ethanol and AX together). Rat liver mitochondria (RLM) were isolated by the standard method modified in our laboratory. A multifunctional chamber with built-in electrodes was used to determine mitochondrial functions. Electrophoresis followed by Western blot analysis was used to detect mitochondrial proteins. Statistical significance was calculated using t-test Student-Newman- Keuls test. RESULT: AX has been shown to have a positive effect on the functioning of the mitochondrial permeability transition pore (mPTP), the regulation of signaling pathways, as well as mitochondrial dynamics. It was found that AX is able to suppress the degenerative effect of alcohol on liver mitochondria. Targets for the protective action of AX in rat liver mitochondria (RLM) have been proposed. CONCLUSION: The discovered protective effect of AX on liver mitochondria during alcohol damage may contribute to the development of new strategies for the treatment of alcohol- induced damage.

Polygala fallax Hemsl. ameliorated high glucose-induced podocyte injury by modulating mitochondrial mPTP opening through the SIRT1/PGC-1α pathway.

This study aimed to investigate the effects and molecular mechanism of PF on high glucose (HG)-induced podocyte injury. Results found that PF increased proliferation activity, decreased apoptosis, LDH, and caspase-3 levels, and increased nephrin and podocin expression in HG-induced cells. Similarly, PF improved HG-induced mitochondrial damage, decreased Ca2+ and ROS content, alleviated oxidative stress, inhibited mPTP opening, increased mitochondrial membrane potential, and decreased the expressions of Drp1, Bak, Bax, and Cytc in cytoplasm, increased the expressions of SIRT1, PGC-1α, HSP70, HK2, and Cytc in mitochondria of podocytes. The use of mPTP agonist/blocker and SIRT1 inhibitor confirmed that PF alleviates HG-induced podocyte injury by regulating mitochondrial mPTP opening through SIRT1/PGC-1α. In addition, PF affected HK2-VDAC1 protein binding to regulate mPTP opening via the SIRT1/PGC-1α pathway. In conclusion, PF-regulated HK2-VDAC1 protein binding affected mitochondrial mPTP opening and improved HG-induced podocyte injury through the SIRT1/PGC-1α pathway.

l-theanine, the unique constituent of tea, improves neuronal survivability by curtailing inflammatory responses in MPTP model of Parkinson's disease.

Discrete components of tea possess multitude of health advantages. Escalating evidence advocate a consequential association between habitual tea consumption and a subsided risk of Parkinson's disease (PD). l-theanine is a non-protein amino acid inherent in tea plants, which exhibits structural resemblance with glutamate, the copious excitatory neurotransmitter in brain. Neuromodulatory effects of l-theanine are evident from its competency in traversing the blood brain barrier, promoting a sense of calmness beyond enervation, and enhancing cognition and attention. Despite the multifarious reports on antioxidant properties of l-theanine and its potential to regulate brain neurotransmitter levels, it is obligatory to understand its exact contribution in ameliorating the pathophysiology of PD. In this study, MPTP-induced mouse model was established and PD-like symptoms were developed in test animals where an increasing dosage of l-theanine (5, 25, 50, 100 and 250 mg/kg) was intraperitoneally administered for 23 days. 50 and 100 mg/kg dosage of l-theanine alleviated motor impairment and specific non-motor symptoms in Parkinsonian mice. The dosage of 100 mg/kg of l-theanine also improved striatal dopamine and serotonin level and tyrosine-hydroxylase positive cell count in the substantia nigra. Most crucial finding of the study is the proficiency of l-theanine to diminish astroglial injury as well as nitric oxide synthesis, which suggests its possible credential to prevent neurodegeneration by virtue of its anti-inflammatory attribute.

A review of MPTP-induced parkinsonism in adult zebrafish to explore pharmacological interventions for human Parkinson's disease.

Novel work in adult zebrafish, Danio rerio, to recapitulate human neurodegenerative disease has proven useful in both pharmaceutical development and research on genetic disease. Due to high genetic homology to humans, affordable husbandry, relatively quick life cycle breeding times, and robust embryo production, zebrafish offer a promising model to test pharmaceutical performance in a high throughput, in vivo setting. Currently, most research in zebrafish models of Parkinson's disease induces the disease in larval or embryonic stage organisms due to ease of administration, with advancement through developmental stages taking only a matter of days. The use of early-stage organisms limits the usability of zebrafish as models for adult disease and specifically age-related neurodegenerative conditions. Recently, researchers have sought to extend the usability of zebrafish into models for Parkinson's disease. Specifically, 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has emerged as a prodrug that upon injection well-encompasses the biochemical mechanisms and symptomology associated with Parkinson's disease. By utilizing MPTP in an adult zebrafish model, advancements in Parkinson's disease research may be achieved. This paper highlights the recent research on this model, comparing it to the human form of Parkinson's disease.

Pathological Role of High Sugar in Mitochondrial Respiratory Chain Defect-Augmented Mitochondrial Stress.

According to many research groups, high glucose induces the overproduction of superoxide anions, with reactive oxygen species (ROS) generally being considered the link between high glucose levels and the toxicity seen at cellular levels. Respiratory complex anomalies can lead to the production of ROS. Calcium [Ca2+] at physiological levels serves as a second messenger in many physiological functions. Accordingly, mitochondrial calcium [Ca2+]m overload leads to ROS production, which can be lethal to the mitochondria through various mechanisms. F1F0-ATPase (ATP synthase or complex V) is the enzyme responsible for catalyzing the final step of oxidative phosphorylation. This is achieved by F1F0-ATPase coupling the translocation of protons in the mitochondrial intermembrane space and shuttling them to the mitochondrial matrix for ATP synthesis to take place. Mitochondrial complex V T8993G mutation specifically blocks the translocation of protons across the intermembrane space, thereby blocking ATP synthesis and, in turn, leading to Neuropathy, Ataxia, and Retinitis Pigmentosa (NARP) syndrome. This study seeks to explore the possibility of [Ca2+]m overload mediating the pathological roles of high glucose in defective respiratory chain-mediated mitochondrial stress. NARP cybrids are the in vitro experimental models of cells with F1FO-ATPase defects, with these cells harboring 98% of mtDNA T8993G mutations. Their counterparts, 143B osteosarcoma cell lines, are the parental cell lines used for comparison. We observed that NARP cells mediated and enhanced the death of cells (apoptosis) when incubated with hydrogen peroxide (H2O2) and high glucose, as depicted using the MTT assay of cell viability. Furthermore, using fluorescence probe-coupled laser scanning confocal imaging microscopy, NARP cells were found to significantly enable mitochondrial reactive oxygen species (mROS) formation and enhance the depolarization of the mitochondrial membrane potential (ΔΨm). Elucidating the mechanisms of sugar-enhanced toxicity on the mitochondria may, in the future, help to alleviate the symptoms of patients with NARP syndromes and other neurodegenerative diseases.

Neuroprotective properties of the Lilium brownii extracts in the experimental model of Parkinson's disease.

Lilium brownii (L. brownii) is a plant that can be used for both medicine and food. Its bulbs are commonly used to treat neurological disorders like depression, insomnia, and Parkinson's disease (PD). However, the mechanism by which it treats PD is not yet fully understood. This study aims to investigate the possible mechanism of L. brownii extract in treating PD and to compare the efficacy of ethanol and aqueous extracts of L. brownii. In this study, mice with PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP) were given L. brownii extracts for 30 days, and the effects of both extracts were then evaluated. Our study demonstrated that both extracts of L. brownii effectively improved motor dysfunction in PD mice induced by MPTP. Additionally, they increased the number of neurons in the substantia nigra region of the mice. Moreover, both extracts reduced levels of malondialdehyde (MDA) and ferrous ion (Fe2+), while increasing levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in serum. They also influenced the expression of proteins associated with the p62-Keap1-Nrf2 pathway. Interestingly, while both extracts had similar behavioral effects, the ethanol extract appeared to have a more significant impact on individual proteins in the p62-Keap1-Nrf2 pathway compared to the aqueous extract, possibly due to its higher phenolic acid glyceride content. In conclusion, L. brownii shows promise as an effective and safe treatment for PD.

Nynrin preserves hematopoietic stem cell function by inhibiting the mitochondrial permeability transition pore opening.

Mitochondria are key regulators of hematopoietic stem cell (HSC) homeostasis. Our research identifies the transcription factor Nynrin as a crucial regulator of HSC maintenance by modulating mitochondrial function. Nynrin is highly expressed in HSCs under both steady-state and stress conditions. The knockout Nynrin diminishes HSC frequency, dormancy, and self-renewal, with increased mitochondrial dysfunction indicated by abnormal mPTP opening, mitochondrial swelling, and elevated ROS levels. These changes reduce HSC radiation tolerance and promote necrosis-like phenotypes. By contrast, Nynrin overexpression in HSCs diminishes irradiation (IR)-induced lethality. The deletion of Nynrin activates Ppif, leading to overexpression of cyclophilin D (CypD) and further mitochondrial dysfunction. Strategies such as Ppif haploinsufficiency or pharmacological inhibition of CypD significantly mitigate these effects, restoring HSC function in Nynrin-deficient mice. This study identifies Nynrin as a critical regulator of mitochondrial function in HSCs, highlighting potential therapeutic targets for preserving stem cell viability during cancer treatment.

Itga5-PTEN signaling regulates striatal synaptic strength and motor coordination in Parkinson's disease.

Background: Parkinson's disease (PD) is marked by the loss of dopaminergic neurons in the substantia nigra pars compacta, leading to motor and cognitive dysfunctions. The molecular mechanisms underlying synaptic alterations in PD remain elusive, with a focus on the role of Itga5 in synaptic integrity and motor coordination and TAT-Itga5 was designed to suppress PTEN activity in this investigation. Methods: This study utilized MPTP-induced PD animal models to investigate the expression and role of Itga5 in the striatum. Techniques included quantitative PCR, Western blotting, immunostaining, CRISPR-CasRx-mediated knockdown, electrophysiological assays, behavioral tests, and mass spectrometry. Results: Itga5 expression was significantly reduced in MPTP-induced PD models. In these models, a marked decrease in dendritic spine density and a shift towards thinner spines in striatal GABA neurons were observed, suggesting impaired synaptic integration. Knockdown of Itga5 resulted in reduced dendritic branching, decreased mushroom spines, and increased thin spines, altering synaptic architecture. Electrophysiological analyses revealed changes in action potential and spontaneous excitatory postsynaptic currents, indicating altered synaptic transmission. Motor behavior assessments showed that Itga5 deficiency led to impairments in fine motor control and coordination. Furthermore, Itga5 was found to interact with PTEN, affecting AKT signaling crucial for synaptic development and motor coordination. Conclusion: The study demonstrates that Itga5 plays a critical role in maintaining synaptic integrity and motor coordination in PD. The Itga5-PTEN-AKT pathway represents a potential therapeutic target for addressing synaptic and motor dysfunctions in PD.

NIR-II light therapy improves cognitive performance in MPTP induced Parkinson's disease rat models: A preliminary experimental study.

Cognitive impairment is an important component of non motor symptoms in Parkinson's disease (PD), and if not addressed in a timely manner, it can easily progress to dementia. However, no effective method currently exists to completely prevent or reverse cognitive impairment associated with PD. We therefore aimed to investigate the therapeutic effect of near-infrared region II light (NIR-II) region illumination on cognitive impairment in PD through behavioral experiments (water maze and rotary rod) and multiple fluorescence immunohistochemistry techniques. The 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced group was compared with the MPTP- untreated rat group, showing a significant reduction in escape latency and significant increase in the fall latency in the MPTP-treated group. The horizontal analysis results indicated that NIR-II phototherapy improved the learning and cognitive abilities as well as coordination and balance abilities of rats. Post-treatment, the MPTP rats showed significantly shortened, escape latency, prolonged target quadrant residence time, and prolonged fall latency compared with pre-treatment. The longitudinal analysis results reaffirmed that NIR-II phototherapy improved the learning and cognitive abilities as well as coordination and balance abilities of rats. The multiple fluorescence immunohistochemistry analysis trend plot showed that the activated microglia and astrocytes in the hippocampus were highest in MPTP-induced PD untreated group, moderate in MPTP-induced PD treatment group, and lowest in the control group. Our data indicates that NIR-II illumination improves learning and cognitive impairment as well as coordination and balance abilities in PD rats by downregulating the activation of microglia and astrocytes in the hippocampus.

The neuroprotective potential of magnesium in Parkinson's disease.

Pathogenic mechanisms implicated in the development of Parkinson disease (PD) are multifaceted and include alpha synuclein aggregation, oxidative stress due to generation of reactive oxygen species (ROS), mitochondrial dysfunction, apoptosis, imbalance of trace elements as well as endoplasmic reticulum stress, and inflammation. Alteration in the homeostasis of bivalent cations, such as iron, magnesium and calcium, has been implicated in the pathogenesis of PD. Low levels of magnesium have been associated with accelerated dopaminergic cell loss in animal PD models, and magnesium has been shown to have a neuroprotective effect in PD models. Evidence of a low magnesium level in the brain of PD individuals, with a low magnesium level in the diet, increasing the risk of PD, further strengthens the role of magnesium deficiency in the pathogenesis of PD. The presence of low-level magnesium in brain tissue and high level in CSF and serum support the possibility of dysfunctional magnesium transporters in PD. Indeed, variants in magnesium transport channels, such as TRPM7 and SLC41A1, have been recently detected in PD individuals. Magnesium, being an NMDA antagonist, could also have a therapeutic role in levodopa-induced dyskinesia. There are no clinical studies indicating a neuroprotective role of magnesium in PD, however, the Mediterranean diet and variants of the diet have been associated with a lower risk of PD, which may be due to the magnesium-rich constituents of the diet. Further clinical trials encompassing therapeutic models to optimize channel function, coupled with a high magnesium diet, may pave the way for promising neuroprotective intervention for PD.

Effects of Age and MPTP-Induced Parkinson's Disease on the Expression of Genes Associated with the Regulation of the Sleep-Wake Cycle in Mice.

Parkinson's disease (PD) is characterized by a long prodromal period, during which patients often have sleep disturbances. The histaminergic system and circadian rhythms play an important role in the regulation of the sleep-wake cycle. Changes in the functioning of these systems may be involved in the pathogenesis of early stages of PD and may be age-dependent. Here, we have analyzed changes in the expression of genes associated with the regulation of the sleep-wake cycle (Hnmt, Hrh1, Hrh3, Per1, Per2, and Chrm3) in the substantia nigra (SN) and striatum of normal male mice of different ages, as well as in young and adult male mice with an MPTP-induced model of the early symptomatic stage (ESS) of PD. Age-dependent expression analysis in normal mouse brain tissue revealed changes in Hrh3, Per1, Per2, and Chrm3 genes in adult mice relative to young mice. When gene expression was examined in mice with the MPTP-induced model of the ESS of PD, changes in the expression of all studied genes were found only in the SN of adult mice with the ESS model of PD. These data suggest that age is a significant factor influencing changes in the expression of genes associated with sleep-wake cycle regulation in the development of PD.

Positive allosteric mGluR2 modulation with BINA alleviates dyskinesia and psychosis-like behaviours in the MPTP-lesioned marmoset.

There is mounting evidence that positive allosteric modulation of metabotropic glutamate type 2 receptors (mGluR2) is an efficacious approach to reduce the severity of L-3,4-dihydroxyphenylalanine (L-DOPA)-induced dyskinesia, psychosis-like behaviours (PLBs), while conferring additional anti-parkinsonian benefit. However, the mGluR2 positive allosteric modulators (PAMs) tested so far, LY-487,379 and CBiPES, share a similar chemical scaffold. Here, we sought to assess whether similar benefits would be conferred by a structurally-distinct mGluR2 PAM, biphenylindanone A (BINA). Six 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned marmosets exhibiting dyskinesia and PLBs were administered L-DOPA with either vehicle or BINA (0.1, 1, and 10 mg/kg) in a randomised within-subject design and recorded. Behaviour was analysed by a blinded rater who scored the severity of each of parkinsonism, dyskinesia and PLBs. When added to L-DOPA, BINA 0.1 mg/kg, 1 mg/kg, and 10 mg/kg all significantly reduced the severity of global dyskinesia, by 40%, 52% and 53%, (all P < 0.001) respectively. BINA similarly attenuated the severity of global PLBs by 35%, 48%, and 50%, (all P < 0.001) respectively. Meanwhile, BINA did not alter the effect of L-DOPA on parkinsonism exhibited by the marmosets. The results of this study provide incremental evidence of positive allosteric modulation of mGluR2 as an effective therapeutic strategy for alleviating dyskinesia and PLBs, without hindering the anti-parkinsonian action of L-DOPA. Furthermore, this therapeutic benefit does not appear to be confined to a particular chemical scaffold.

Mitochondrial DNA release via the mitochondrial permeability transition pore activates the cGAS-STING pathway, exacerbating inflammation in acute Kawasaki disease.

BACKGROUND: Kawasaki disease (KD) is an immune vasculitis of unknown origin, characterized by transient inflammation. The activation of the cGAS-STING pathway, triggered by mitochondrial DNA (mtDNA) release, has been implicated in the onset of KD. However, its specific role in the progression of inflammation during KD's acute phase remains unclear. METHODS: We measured mtDNA and 2'3'-cGAMP expression in KD patient serum using RT-qPCR and ELISA. A murine model of KD was induced by injecting Lactobacillus casei cell wall extract (LCWE), after which cGAS-STING pathway activation and inflammatory markers were assessed via immunohistochemistry, western blot, and RT-qPCR. Human umbilical vein endothelial cells (HUVECs) were treated with KD serum and modulators of the cGAS-STING pathway for comparative analysis. Mitochondrial function was evaluated using Mitosox staining, mPTP opening was quantified by fluorescence microscopy, and mitochondrial membrane potential (MMP) was determined with JC-1 staining. RESULTS: KD patient serum exhibited increased mtDNA and 2'3'-cGAMP expression, with elevated levels of pathway-related proteins and inflammatory markers observed in both in vivo and in vitro models. TEM confirmed mitochondrial damage, and further studies demonstrated that inhibition of mPTP opening reduced mtDNA release, abrogated cGAS-STING pathway activation, and mitigated inflammation. CONCLUSION: These findings indicate that mtDNA released through the mPTP is a critical activator of the cGAS-STING pathway, contributing significantly to KD-associated inflammation. Targeting mtDNA release or the cGAS-STING pathway may offer novel therapeutic approaches for KD management.

LL37/FPR2 regulates neutrophil mPTP promoting the development of neutrophil extracellular traps in diabetic retinopathy.

Diabetic retinopathy (DR) is characterized by chronic, low-grade inflammation. This state may be related to the heightened production of neutrophil extracellular traps (NETs) induced by high glucose (HG). Human cathelicidin antimicrobial peptide (LL37) is an endogenous ligand of G protein-coupled chemoattractant receptor formyl peptide receptor 2 (FPR2), expressed on neutrophils and facilitating the formation and stabilization of the structure of NETs. In this study, we detected neutrophils cultured under different conditions, the retinal tissue of diabetic mice, and fibrovascular epiretinal membranes (FVM) samples of patients with proliferative diabetic retinopathy (PDR) to explore the regulating effect of LL37/FPR2 on neutrophil in the development of NETs during the process of DR. Specifically, HG or NG with LL37 upregulates the expression of FPR2 in neutrophils, induces the opening of mitochondrial permeability transition pore (mPTP), promotes the increase of reactive oxygen species and mitochondrial ROS, and then leads to the rise of NET production, which is mainly manifested by the release of DNA reticular structure and the increased expression of NETs-related markers. The PI3K/AKT signaling pathway was activated in neutrophils, and the phosphorylation level was enhanced by FPR2 agonists in vitro. In vivo, increased expression of NETs markers was detected in the retina of diabetic mice and in FVM, vitreous fluid, and serum of PDR patients. Transgenic FPR2 deletion led to decreased NETs in the retina of diabetic mice. Furthermore, in vitro, inhibition of the LL37/FPR2/mPTP axis and PI3K/AKT signaling pathway decreased NET production induced by high glucose. These results suggested that FPR2 plays an essential role in regulating the production of NETs induced by HG, thus may be considered as one of the potential therapeutic targets.

Discovery of novel benzimidazole derivatives as selective and reversible monoamine oxidase B inhibitors for Parkinson's disease treatment.

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta. The development of novel scaffolds for human monoamine oxidase B (hMAO-B) inhibitors with reversible properties represents an important strategy to improve the efficacy and safety for PD treatment. In the current work, we have devised and assessed two innovative derivative series serving as hMAO-B inhibitors. These series have utilized benzimidazole as a scaffold and strategically incorporated a primary amide group, which is recognized as a pivotal pharmacophore in subsequent activity screening and reversible mode of action. Among these compounds, 16d has emerged as the most potent hMAO-B inhibitor with an IC50 value of 67.3 nM, comparable to safinamide (IC50 = 42.6 nM) in vitro. Besides, 16d demonstrated good selectivity towards hMAO-B isoenzyme with a selectivity index over 387. Importantly, in line with the design purpose, 16d inhibited hMAO-B in a competitive and reversible manner (Ki = 82.50 nM). Moreover, 16d exhibited a good safety profile in both cellular and acute toxicity assays in mice. It also displayed ideal pharmacokinetic properties and blood-brain barrier permeability in vivo, essential prerequisites for central nervous system medicines. In the MPTP-induced PD mouse model, 16d significantly alleviated the motor impairment, especially muscle relaxation and motor coordination. Therefore, 16d, serving as a lead compound, holds instructive significance for subsequent investigations regarding its application in the treatment of PD.

Rhein alleviates MPTP-induced Parkinson's disease by suppressing neuroinflammation via MAPK/IκB pathway.

Background: Parkinson's disease (PD) is a common neurodegenerative disease with a rapid increase in incidence in recent years. Existing treatments cannot slow or stop the progression of PD. It was proposed that neuroinflammation leads to neuronal death, making targeting neuroinflammation a promising therapeutic strategy. Our previous studies have demonstrated that rhein protects neurons in vitro by inhibiting neuroinflammation, and it has been found to exhibit neuroprotective effects in Alzheimer's disease and epilepsy, but its neuroprotective mechanisms and effects on PD are still unclear. Methods: PD animal model was induced by 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine (MPTP). ELISA, RT-qPCR, western blot and Immunofluorescence were used to detect the levels of inflammatory cytokines and M1 polarization markers. The protein expression levels of signaling pathways were measured by western blot. Hematoxylin-eosin (HE) staining showed that rhein did not damage the liver and kidney. Two behavioral tests, pole test and rotarod test, were used to evaluate the improvement effect of rhein on movement disorders. The number of neurons in the substantia nigra was evaluated by Nissl staining. Immunohistochemistry and western blot were used to detect tyrosine hydroxylase (TH) and α-synuclein. Results: Rhein inhibited the activation of MAPK/IκB signaling pathway and reduced the levels of pro-inflammatory cytokines (IL-1ß, IL-6 and TNF-α) and M1 polarization markers of microglia in vivo. In a mouse model of PD, rhein ameliorated movement disorders, reduced dopaminergic neuron damage and α-synuclein deposition. Conclusion: Rhein inhibits neuroinflammation through MAPK/IκB signaling pathway, thereby reducing neurodegeneration, α-synuclein deposition, and improving movement disorders in Parkinson's disease.

Effect of the mGlu2 positive allosteric modulator biphenyl-indanone A as a monotherapy and as adjunct to a low dose of L-DOPA in the MPTP-lesioned marmoset.

Activation of metabotropic glutamate 2 (mGlu2) receptors is a potential novel therapeutic approach for the treatment of parkinsonism. Thus, when administered as monotherapy or as adjunct to a low dose of L-3,4-dihydroxyphenylalanine (L-DOPA), the mGlu2 positive allosteric modulator (PAM) LY-487,379 alleviated parkinsonism in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned primates. Here, we sought to investigate the effect of biphenyl-indanone A (BINA), a highly selective mGlu2 PAM whose chemical scaffold is unrelated to LY-487,379, to determine if a structurally different mGlu2 PAM would also confer anti-parkinsonian benefit. In monotherapy experiments, MPTP-lesioned marmosets were injected with either vehicle, L-DOPA/benserazide (15/3.75 mg/kg, positive control) or BINA (0.1, 1, 10 mg/kg). In adjunct to a low L-DOPA dose experiments, MPTP-lesioned marmosets were injected with L-DOPA/benserazide (7.5/1.875 mg/kg) in combination with vehicle or BINA (0.1, 1, 10 mg/kg). Parkinsonism, dyskinesia and psychosis-like behaviours (PLBs) were then quantified. When administered alone, BINA 1 and 10 mg/kg decreased parkinsonism severity by ~22% (p < 0.01) and ~47% (p < 0.001), when compared with vehicle, which was comparable with the global effect of a high L-DOPA dose. When administered in combination with a low L-DOPA dose, BINA 1 and 10 mg/kg decreased global parkinsonism by ~38% (p < 0.001) and ~53% (p < 0.001). BINA 10 mg/kg decreased global dyskinesia by ~94% (p < 0.01) and global PLBs by ~92% (p < 0.01). Our results provide additional evidence that mGlu2 positive allosteric modulation elicits anti-parkinsonian effects. That this benefit is not related to a particular chemical scaffold suggests that it may be a class effect rather than the effect of a specific molecule.