Neuroinflammation and oxidative stress: Co-conspirators in the pathology of Parkinson’s disease

Cannabinoids: Role in Neurological Diseases and Psychiatric Disorders

An impact of legalization and decriminalization of marijuana is the gradual increase in the use of cannabis for recreational purposes, which poses a potential threat to society and healthcare systems worldwide. However, the discovery of receptor subtypes, endogenous endocannabinoids, and enzymes involved in synthesis and degradation, as well as pharmacological characterization of receptors, has led to exploration of the use of cannabis in multiple peripheral and central pathological conditions. The role of cannabis in the modulation of crucial events involving perturbed physiological functions and disease progression, including apoptosis, inflammation, oxidative stress, perturbed mitochondrial function, and the impaired immune system, indicates medicinal values. These events are involved in most neurological diseases and prompt the gradual progression of the disease. At present, several synthetic agonists and antagonists, in addition to more than 70 phytocannabinoids, are available with distinct efficacy as a therapeutic alternative in different pathological conditions. The present review aims to describe the use of cannabis in neurological diseases and psychiatric disorders.

Biomarkers of Parkinson's Disease

Background

Parkinson's disease (PD) is a degenerative brain disease characterised by motor and non-motor symptoms. Motor disabilities, including dystonia and dyskinesia, cause speech and movement difficulties and limit many aspects of life. Factors affecting PD refer to the various internal and external conditions that contribute to the onset, severity and progression of the disease. These factors can be broadly categorised into genetic, environmental and lifestyle-related factors.

Summary

The primary objective of this prospective cohort study is to investigate the association between environmental exposures and genetic predisposition and the risk of developing PD. Secondary objectives include examining the relationships between these factors and clinical outcomes in PD, such as disease severity and progression. We have utilised the data from other research studies, which primarily involve recruiting a cohort of individuals at high risk for PD based on their family history and/or environmental exposure history. These research studies also include participants who will undergo clinical evaluations, including neurological examinations and cognitive assessments, and provide biospecimens for genetic analysis. Environmental exposure histories will be obtained through questionnaires and medical records fetched by the authors of these research studies. In all these studies, participants were followed up regularly over several years to monitor the development of PD and to assess disease progression.

Key message

This study provided valuable insights into the role of environmental exposures and genetic predisposition in the development and progression of PD. The results of this study may inform strategies for preventing or delaying the onset of PD in high-risk individuals, as well as guide the development of targeted interventions for those already diagnosed with the disease.

Canagliflozin attenuates neurodegeneration and ameliorates dyskinesia through targeting the NLRP3/Nurr1/GSK-3β/SIRT3 pathway and autophagy modulation in rotenone-lesioned rats

Despite a deep understanding of Parkinson's disease (PD) and levodopa-induced dyskinesia (LID) pathogenesis, current therapies are insufficient to effectively manage the progressive nature of PD or halt LID. Growing hypotheses suggested the NOD-like receptor 3 (NLRP3) inflammasome and orphan nuclear receptor-related 1 (Nurr1)/glycogen synthase kinase-3β (GSK-3β) and peroxisome proliferator-activated receptor γ (PPARγ) coactivator-1α (PGC-1α)/sirtuin 3 (SIRT3) pathways as potential avenues for halting neuroinflammation and oxidative stress in PD.

AIMS

This study investigated for the first time the neuroprotective effect of canagliflozin against PD and LID in rotenone-intoxicated rats, emphasizing the crosstalk among the NLRP3/caspase-1 cascade, PGC-1α/SIRT3 pathway, mammalian target of rapamycin (mTOR)/beclin-1, and Nurr1/β-catenin/GSK-3β pathways as possible treatment strategies in PD and LID. Also, correlating NLRP3 expression with all evaluated parameters.

MAIN METHODS

The PD rat model was induced via eleven rotenone (1.5 mg/kg) subcutaneous injections day after day. Canagliflozin (20 mg/kg) and/or L-dopa/carbidopa (100/25 mg/kg) were orally administered daily from the beginning until the end of the experiment.

KEY FINDINGS

Canagliflozin significantly improved neurobehavioral and histological assessments, whereas dyskinesia scores declined. The improvement was confirmed through tyrosine hydroxylase and β-catenin upregulation in contrast to NLRP3 and caspase-1 in substantia nigra pars compacta, as revealed immunohistochemically. In addition, canagliflozin induced a prominent elevation in dopamine, Nurr1, PGC-1α, SIRT3, and beclin-1, whereas mTOR and GSK-3β expressions were downregulated.

SIGNIFICANCE

Our results revealed the aspiring canagliflozin neuroprotective properties against PD and LID in rotenone-lesioned rats via the assumed anti-inflammatory activity and implication of NLRP3/caspase-1, Nurr1/GSK-3β/β-catenin, PGC-1α/SIRT3, and beclin-1/mTOR pathways.

The effect of a nicotine-rich diet with/without redistribution of dietary protein on motor indices in patients with Parkinson's disease: A randomized clinical trial

BACKGROUND

The aim of designing this clinical trial is to investigate the impact of a nicotine-rich diet with/without protein redistribution on the motor indices of patients with Parkinson's disease (PD).

METHODS

We randomly divided 45 patients (age > 50) with PD into three groups including: nicotine-rich diet (20 µg per day) group (group N; n = 15), nicotine-rich diet with protein redistribution group (group N + P; n = 15), and control group (group C; n = 15). In all group, the diet was isocaloric, and participants received six meals and snacks. After 12 weeks, the Unified Parkinson's Disease Rating Scale part III (UPDRS), serum alpha-synuclein levels, serum apolipoprotein A1, serum cotinine, and anthropometric parameters were measured in the three groups before and 12 weeks after the beginning of the study.

RESULTS

All of the enrolled patients completed the study. The UPDRS score was improved by 1.47 and 1.95 units in the N and N + P groups compared to the placebo (P < 0.001). On the other hand, effect size of N and N + P diets for α-synuclein were -52.82 and -175.85, respectively. The differences were significant compared to the control group (P < 0.05). Also, the effect of the both diets on serum cotinine compared to the control group was significant (P < 0.05). Although the effect size for UPDRS, α-synuclein, and cotinine in N + P diet were higher than N group, the differences were not statistically significant (P > 0.05). Also, the obtained results showed that there were no significant effects on anthropometric variables and serum levels of Apolipoprotein A1 in diet-receiving groups (P > 0.05).

CONCLUSIONS

The results of our study indicated that nicotine consumption in an isocaloric diet, while preventing a decrease in anthropometric indices, leads to improvements in motor indices and a reduction in alpha-synuclein levels. Additional and larger controlled trials are required to validate these findings.

A comprehensive review of natural compounds and their structure-activity relationship in Parkinson's disease: exploring potential mechanisms

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive loss of dopamine-producing cells in the Substantia nigra region of the brain. Complementary and alternative medicine approaches have been utilized as adjuncts to conventional therapies for managing the symptoms and progression of PD. Natural compounds have gained attention for their potential neuroprotective effects and ability to target various pathways involved in the pathogenesis of PD. This comprehensive review aims to provide an in-depth analysis of the molecular targets and mechanisms of natural compounds in various experimental models of PD. This review will also explore the structure-activity relationship (SAR) of these compounds and assess the clinical studies investigating the impact of these natural compounds on individuals with PD. The insights shared in this review have the potential to pave the way for the development of innovative therapeutic strategies and interventions for PD.

Supplementation with Bifidobacterium animalis subsp. lactis MH-022 for remission of motor impairments in a 6-OHDA-induced Parkinson's disease rat model by reducing inflammation, reshaping the gut microbiome, and fostering specific microbial taxa

Inflammation significantly influences the degeneration of dopaminergic neurons in Parkinson's disease (PD), which is potentially intensified by associated gut dysbiosis. The therapeutic potential of probiotics, due to their antioxidant, anti-inflammatory, and gut microbiota modulatory properties, is explored herein as a means to improve gut health and influence the gut-brain-microbiota axis in the context of PD. In this study, we investigated the role and possible mechanism of Bifidobacterium animalis subsp. lactis MH-022 (B. lactis MH-022) supplementation in a 6-hydroxydopamine (6-OHDA)-induced rat model of PD. Findings demonstrated that B. lactis MH-022 supplementation markedly ameliorated motor deficits, preserved dopaminergic neurons, enhanced the antioxidant capacity, and mitigated inflammation through restoring mitochondrial function. Furthermore, B. lactis MH-022 supplementation significantly altered the gut microbiota composition, augmenting the production of short-chain fatty acids and promoting the proliferation of beneficial bacterial taxa, thereby reinforcing their anti-inflammatory properties. Correlation analyses established strong associations between specific bacterial taxa and improvements in motor function, antioxidant levels, and reductions in inflammation markers. These insights emphasize the therapeutic potential of B. lactis MH-022 in modulating diverse aspects of PD, particularly highlighting its role in reducing inflammation, restoring mitochondrial function, enhancing antioxidant capacity, and reshaping the gut microbiota. This multifaceted approach underscores the probiotic's potential in reducing neuroinflammation and protecting dopaminergic neurons, thus offering a promising avenue for PD treatment.

Neurodegenerative diseases and catechins: (-)-epigallocatechin-3-gallate is a modulator of chronic neuroinflammation and oxidative stress

Catechins, a class of phytochemicals found in various fruits and tea leaves, have garnered attention for their diverse health-promoting properties, including their potential in combating neurodegenerative diseases. Among these catechins, (-)-epigallocatechin-3-gallate (EGCG), the most abundant polyphenol in green tea, has emerged as a promising therapeutic agent due to its potent antioxidant and anti-inflammatory effects. Chronic neuroinflammation and oxidative stress are key pathological mechanisms in neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). EGCG has neuroprotective efficacy due to scavenging free radicals, reducing oxidative stress and attenuating neuroinflammatory processes. This review discusses the molecular mechanisms of EGCG's anti-oxidative stress and chronic neuroinflammation, emphasizing its effects on autoimmune responses, neuroimmune system interactions, and focusing on the related effects on AD and PD. By elucidating EGCG's mechanisms of action and its impact on neurodegenerative processes, this review underscores the potential of EGCG as a therapeutic intervention for AD, PD, and possibly other neurodegenerative diseases. Overall, EGCG emerges as a promising natural compound for combating chronic neuroinflammation and oxidative stress, offering novel avenues for neuroprotective strategies in the treatment of neurodegenerative disorders.

Brain delivery of fibronectin through bioactive phosphorous dendrimers for Parkinson's disease treatment via cooperative modulation of microglia

Effective treatment of Parkinson's disease (PD), a prevalent central neurodegenerative disorder particularly affecting the elderly population, still remains a huge challenge. We present here a novel nanomedicine formulation based on bioactive hydroxyl-terminated phosphorous dendrimers (termed as AK123) complexed with fibronectin (FN) with anti-inflammatory and antioxidative activities. The created optimized AK123/FN nanocomplexes (NCs) with a size of 223 nm display good colloidal stability in aqueous solution and can be specifically taken up by microglia through FN-mediated targeting. We show that the AK123/FN NCs are able to consume excessive reactive oxygen species, promote microglia M2 polarization and inhibit the nuclear factor-kappa B signaling pathway to downregulate inflammatory factors. With the abundant dendrimer surface hydroxyl terminal groups, the developed NCs are able to cross blood-brain barrier (BBB) to exert targeted therapy of a PD mouse model through the AK123-mediated anti-inflammation for M2 polarization of microglia and FN-mediated antioxidant and anti-inflammatory effects, thus reducing the aggregation of α-synuclein and restoring the contents of dopamine and tyrosine hydroxylase to normal levels in vivo. The developed dendrimer/FN NCs combine the advantages of BBB-crossing hydroxyl-terminated bioactive per se phosphorus dendrimers and FN, which is expected to be extended for the treatment of different neurodegenerative diseases.

A neurotherapeutic approach with Lacticaseibacillus rhamnosus E9 on gut microbiota and intestinal barrier in MPTP-induced mouse model of Parkinson's disease

The gut microbiota plays a crucial role in neural development and progression of neural disorders like Parkinson's disease (PD). Probiotics have been suggested to impact neurodegenerative diseases via gut-brain axis. This study aims to investigate the therapeutic potential of Lacticaseibacillus rhamnosus E9, a high exopolysaccharide producer, on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)-induced mouse model of PD. C57BL/6 mice subjected to MPTP were fed L. rhamnosus E9 for fifteen days and sacrificed after the last administration. Motor functions were determined by open-field, catalepsy, and wire-hanging tests. The ileum and the brain tissues were collected for ELISA, qPCR, and immunohistochemistry analyses. The cecum content was obtained for microbiota analysis. E9 supplementation alleviated MPTP-induced motor dysfunctions accompanied by decreased levels of striatal TH and dopamine. E9 also reduced the level of ROS in the striatum and decreased the DAT expression while increasing the DR1. Furthermore, E9 improved intestinal integrity by enhancing ZO-1 and Occludin levels and reversed the dysbiosis of the gut microbiota induced by MPTP. In conclusion, E9 supplementation improved the MPTP-induced motor deficits and neural damage as well as intestinal barrier by modulating the gut microbiota in PD mice. These findings suggest that E9 supplementation holds therapeutic potential in managing PD through the gut-brain axis.

Selenium Nanoparticles as Neuroprotective Agents: Insights into Molecular Mechanisms for Parkinson's Disease Treatment

Oxidative stress and the accumulation of misfolded proteins in the brain are the main causes of Parkinson's disease (PD). Several nanoparticles have been used as therapeutics for PD. Despite their therapeutic potential, these nanoparticles induce multiple stresses upon entry. Selenium (Se), an essential nutrient in the human body, helps in DNA formation, stress control, and cell protection from damage and infections. It can also regulate thyroid hormone metabolism, reduce brain damage, boost immunity, and promote reproductive health. Selenium nanoparticles (Se-NPs), a bioactive substance, have been employed as treatments in several disciplines, particularly as antioxidants. Se-NP, whether functionalized or not, can protect mitochondria by enhancing levels of reactive oxygen species (ROS) scavenging enzymes in the brain. They can also promote dopamine synthesis. By inhibiting the aggregation of tau, α-synuclein, and/or Aβ, they can reduce the cellular toxicities. The ability of the blood-brain barrier to absorb Se-NPs which maintain a healthy microenvironment is essential for brain homeostasis. This review focuses on stress-induced neurodegeneration and its critical control using Se-NP. Due to its ability to inhibit cellular stress and the pathophysiologies of PD, Se-NP is a promising neuroprotector with its anti-inflammatory, non-toxic, and antimicrobial properties.

Therapeutic potential of thymoquinone and its nanoformulations in neuropsychological disorders: a comprehensive review on molecular mechanisms in preclinical studies

Thymoquinone (THQ) and its nanoformulation (NFs) have emerged as promising candidates for the treatment of neurological diseases due to their diverse pharmacological properties, which include anti-inflammatory, antioxidant, and neuroprotective effects. In this study, we conducted an extensive search across reputable scientific websites such as PubMed, ScienceDirect, Scopus, and Google Scholar to gather relevant information. The antioxidant and anti-inflammatory properties of THQ have been observed to enhance the survival of neurons in affected areas of the brain, leading to significant improvements in behavioral and motor dysfunctions. Moreover, THQ and its NFs have demonstrated the capacity to restore antioxidant enzymes and mitigate oxidative stress. The primary mechanism underlying THQ's antioxidant effects involves the regulation of the Nrf2/HO-1 signaling pathway. Furthermore, THQ has been found to modulate key components of inflammatory signaling pathways, including toll-like receptors (TLRs), nuclear factor-κB (NF-κB), interleukin 6 (IL-6), IL-1β, and tumor necrosis factor alpha (TNFα), thereby exerting anti-inflammatory effects. This comprehensive review explores the various beneficial effects of THQ and its NFs on neurological disorders and provides insights into the underlying mechanisms involved.

Protective effect of increased O-GlcNAc cycling against 6-OHDA induced Parkinson's disease pathology

This study aimed to elucidate the role of O-GlcNAc cycling in 6-hydroxydopamine (6-OHDA)-induced Parkinson's disease (PD)-like neurodegeneration and the underlying mechanisms. We observed dose-dependent downregulation of O-GlcNAcylation, accompanied by an increase in O-GlcNAcase following 6-OHDA treatment in both mouse brain and Neuro2a cells. Interestingly, elevating O-GlcNAcylation through glucosamine (GlcN) injection provided protection against PD pathogenesis induced by 6-OHDA. At the behavioral level, GlcN mitigated motor deficits induced by 6-OHDA, as determined using the pole, cylinder, and apomorphine rotation tests. Furthermore, GlcN attenuated 6-OHDA-induced neuroinflammation and mitochondrial dysfunction. Notably, augmented O-GlcNAcylation, achieved through O-GlcNAc transferase (OGT) overexpression in mouse brain, conferred protection against 6-OHDA-induced PD pathology, encompassing neuronal cell death, motor deficits, neuroinflammation, and mitochondrial dysfunction. These collective findings suggest that O-GlcNAcylation plays a crucial role in the normal functioning of dopamine neurons. Moreover, enhancing O-GlcNAcylation through genetic and pharmacological means could effectively ameliorate neurodegeneration and motor impairment in an animal model of PD. These results propose a potential strategy for safeguarding against the deterioration of dopamine neurons implicated in PD pathogenesis.

Neuroinflammation in Neurodegenerative Disorders: Current Knowledge and Therapeutic Implications

Neurodegenerative disorders (NDs) have become increasingly common during the past three decades. Approximately 15% of the total population of the world is affected by some form of NDs, resulting in physical and cognitive disability. The most common NDs include Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease. Although NDs are caused by a complex interaction of genetic, environmental, and lifestyle variables, neuroinflammation is known to be associated with all NDs, often leading to permanent damage to neurons of the central nervous system. Furthermore, numerous emerging pieces of evidence have demonstrated that inflammation not only supports the progression of NDs but can also serve as an initiator. Hence, various medicines capable of preventing or reducing neuroinflammation have been investigated as ND treatments. While anti-inflammatory medicine has shown promising benefits in several preclinical models, clinical outcomes are often questionable. In this review, we discuss various NDs with their current treatment strategies, the role of neuroinflammation in the pathophysiology of NDs, and the use of anti-inflammatory agents as a potential therapeutic option.

Gardenin A treatment attenuates inflammatory markers, synuclein pathology and deficits in tyrosine hydroxylase expression and improves cognitive and motor function in A53T-α-syn mice

Oxidative stress and neuroinflammation are widespread in the Parkinson's disease (PD) brain and contribute to the synaptic degradation and dopaminergic cell loss that result in cognitive impairment and motor dysfunction. The polymethoxyflavone Gardenin A (GA) has been shown to activate the NRF2-regulated antioxidant pathway and inhibit the NFkB-dependent pro-inflammatory pathway in a Drosophila model of PD. Here, we evaluate the effects of GA on A53T alpha-synuclein overexpressing (A53TSyn) mice. A53TSyn mice were treated orally for 4 weeks with 0, 25, or 100 mg/kg GA. In the fourth week, mice underwent behavioral testing and tissue was harvested for immunohistochemical analysis of tyrosine hydroxylase (TH) and phosphorylated alpha synuclein (pSyn) expression, and quantification of synaptic, antioxidant and inflammatory gene expression. Results were compared to vehicle-treated C57BL6J mice. Treatment with 100 mg/kg GA improved associative memory and decreased abnormalities in mobility and gait in A53TSyn mice. GA treatment also reduced pSyn levels in both the cortex and hippocampus and attenuated the reduction in TH expression in the striatum seen in A53Tsyn mice. Additionally, GA increased cortical expression of NRF2-regulated antioxidant genes and decreased expression of NFkB-dependent pro-inflammatory genes. GA was readily detectable in the brains of treated mice and modulated the lipid profile in the deep gray brain tissue of those animals. While the beneficial effects of GA on cognitive deficits, motor dysfunction and PD pathology are promising, future studies are needed to further fully elucidate the mechanism of action of GA, optimizing dosing and confirm these effects in other PD models.

Imperatorin inhibits oxidative stress injury and neuroinflammation via the PI3K/AKT signaling pathway in the MPTP-induced Parkinson's disease mouse

Parkinson's disease (PD) is a disorder of neurodegeneration. Imperatorin is an active natural furocoumarin characterized by antioxidant, anti-inflammatory, and potent vasodilatory properties. Therefore, we aimed to investigate the biological functions of imperatorin and its mechanisms against PD progression. C57BL/6 mice were intraperitoneally injected with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 30 mg/kg) daily for 5 consecutive days to mimic PD conditions in vivo. The MPTP-induced PD model mice were intraperitoneally injected with imperatorin (5 mg/kg) for 25 consecutive days after MPTP administration. The motor and cognitive functions of mice were examined by rotarod test, hanging test, narrow beam test and Morris water maze test. After analysis of MWM test, the expression levels of tyrosine hydroxylase and Iba-1 in the substantia nigra pars compacta were measured by immunohistochemistry staining, immunofluorescence staining and western blotting. The expression levels of striatal dopamine and its metabolite 3,4-dihydroxyphenylacetic acid were also measured. The protein levels of inducible nitric-oxide synthase, cyclooxygenase-2, phosphorylated phosphatidylinositol 3-kinase (PI3K) and phosphorylated protein kinase B (Akt) in the mouse striatum were estimated by western blotting. The expression levels of proinflammatory cytokines including tumor necrosis factor, interleukin (IL)-1β and IL-6 in the mouse striatum were measured by ELISA kits. The expression levels of superoxide dismutase, malondialdehyde and glutathione in the mouse midbrains were measured with commercially available kits. TUNEL staining was performed to identify the apoptosis of midbrain cells. Histopathologic changes in the mouse striata were assessed by hematoxylin-eosin staining. Imperatorin treatment markedly improved spatial learning and memory abilities of MPTP-induced PD mice. The MPTP-induced dopaminergic neuron loss in the mouse striata was inhibited by imperatorin. Imperatorin also suppressed neuroinflammation and neuronal oxidative stress in the midbrains of MPTP-induced PD mice. Mechanistically, imperatorin treatment inhibited the MPTP-induced reduction in the PI3K/Akt pathway. Imperatorin treatment can prevent dopaminergic neuron degeneration and improve cognitive functions via its potent antioxidant and anti-inflammatory properties in an MPTP-induced PD model in mice by regulating the PI3K/Akt pathway.

Therapeutic potential of Coumarin-polyphenolic acid hybrids in PD: Inhibition of α-Syn aggregation and disaggregation of preformed fibrils, leading to reduced neuronal inclusion formation

This study focuses on the discovery of new potential drugs for treating PD by targeting the aggregation of α-Syn. A series of hybrids combining Coumarin and phenolic acid were designed and synthesized. Four particularly promising compounds were identified, showing strong inhibitory effects with IC50 values ranging from low micromolar to submicromolar concentrations, as low as 0.63 μM. These compounds exhibited a higher binding affinity to α-Syn residues and effectively hindered the entire aggregation process, maintaining the proteostasis conformation of α-Syn and preventing the formation of β-sheet aggregates. This approach holds significant promise for PD prevention. Additionally, these candidate compounds demonstrated the ability to break down preformed α-Syn oligomers and fibrils, resulting in the formation of smaller aggregates and monomers. Moreover, the candidate compounds showed impressive effectiveness in inhibiting α-Syn aggregation within nerve cells, thereby reducing the likelihood of α-Syn inclusion formation resembling Lewy bodies, which highlights their potential for treating PD.

Unravelling the Parkinson's puzzle, from medications and surgery to stem cells and genes: a comprehensive review of current and future management strategies

Parkinson's disease (PD) is a neurodegenerative disorder, prevalent in the elderly population. Neuropathological hallmarks of PD include loss of dopaminergic cells in the nigro-striatal pathway and deposition of alpha-synuclein protein in the neurons and synaptic terminals, which lead to a complex presentation of motor and non-motor symptoms. This review focuses on various aspects of PD, from clinical diagnosis to currently accepted treatment options, such as pharmacological management through dopamine replacement and surgical techniques such as deep brain stimulation (DBS). The review discusses in detail the potential of emerging stem cell-based therapies and gene therapies to be adopted as a cure, in contrast to the present symptomatic treatment in PD. The potential sources of stem cells for autologous and allogeneic stem cell therapy have been discussed, along with the progress evaluation of pre-clinical and clinical trials. Even though recent techniques hold great potential to improve the lives of PD patients, we present the importance of addressing the safety, efficacy, ethical, cost, and regulatory concerns before scaling them to clinical use.

Formoterol attenuated mitochondrial dysfunction in rotenone-induced Parkinson's disease in a rat model: Role of PINK-1/PARKIN and PI3K/Akt/CREB/BDNF/TrKB axis

β2-adrenoreceptors (β2AR have been identified recently as regulators of the α-synuclein gene (SNCA), one of the key milieus endorsed in injury of dopamine neurons in Parkinson's disease (PD). Accumulation of α-synuclein leads to mitochondrial dysfunction via downregulation of mitophagy proteins (PINK-1 and PARKIN) and inhibition of mitochondria biogenesis (PGC-1α) along with an increase in the master inflammatory regulator NF-κB p65 production that provokes neurodegeneration and diminishes neuroprotective signaling pathway (PI3k/Akt/CREB/BDNF). Recently, formoterol exhibited a promising neuroprotective effect against neurodegenerative conditions associated with brain inflammation. Therefore, the present investigation aims to unveil the possible neuroprotective activity of formoterol, β2AR agonist, against rotenone-induced PD in rats. Rats received rotenone (1.5 mg/kg; s.c.) every other day for 3 weeks and cured with formoterol (25 μg/kg/day; i.p.) 1 hr. after rotenone administration, starting from day 11. Formoterol treatment succeeded in upregulating β2-adrenoreceptor expression in PD rats and preserving the function and integrity of dopaminergic neurons as witnessed by enhancement of muscular performance in tests, open field, grip strength-meter, and Rotarod, besides the increment in substantia nigra and striatal tyrosine hydroxylase immunoexpression. In parallel, formoterol boosted mitophagy by activation of PINK1 and PARKIN and preserved mitochondrial membrane potential. Additionally, formoterol stimulated the neuro-survival signaling axis via stimulation of PI3k/pS473-Akt/pS133-CREB/BDNF cascade to attenuate neuronal loss. Noteworthy formoterol reduces neuro-inflammatory status by decreasing NFκBp65 immunoexpression and TNF-α content. Finally, formoterol's potential as a stimulant therapy of mitophagy via the PINK1/PARKIN axis and regulation of mitochondrial biogenesis by increasing PGC-1α to maintain mitochondrial homeostasis along with stimulation of PI3k/Akt/CREB/BDNF axis.

Sericin alleviates motor dysfunction by modulating inflammation and TrkB/BDNF signaling pathway in the rotenone-induced Parkinson's disease model

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the degeneration of nigrostriatal dopaminergic neurons and movement impairment. Based on theories, neuroinflammatory processes may be vital in the etiology of PD and other neurodegenerative diseases. Reports show that rotenone has neurotoxic, inflammatory, and motor impairment effects in PD. Sericin is a natural polymer with effective properties, such as neuroprotective and anti-inflammatory. Therefore, this study aimed to examine the effects of sericin administration on motor dysfunction by modulating inflammation and tyrosine kinase B/brain-derived neurotrophic factor (TrkB/BDNF) pathway in the rotenone-induced PD model.

METHODS

Wistar male rats (3-months-old) were treated with rotenone (2 mg/kg every 48 h for 30 days) to induce a rotenone-induced PD model. Also, sericin was administered orally at dose of 200 mg/kg every 48 h for 30 days. Rotarod and bar tests were performed for motor dysfunction. The protein levels of BDNF, c-fos, TrkB, tumor necrosis factor- α (TNF-α), interleukin-6 (IL-6) and catalase activity were evaluated in the striatum area.

RESULTS

Results showed that sericin increased latent time in the rotarod test and decreased the time staying on the pole in the bar test compared to the PD group (P < 0.001 for both tests). Moreover, sericin treatments decreased TNF-α (P < 0.001) and IL-6 (P < 0.001) concentration levels and enhanced the levels of BDNF (P < 0.001), c-fos (P < 0.001), TrkB (P < 0.001) proteins and catalase activity (P < 0.05) in the striatum area compared to the PD group.

CONCLUSION

These results support a protective benefit of sericin therapy in a rotenone-induced PD paradigm by reducing motor impairment, inflammatory response, and disruption of the TrkB/BDNF signaling pathway.

Gardenin A improves cognitive and motor function in A53T-α-syn mice

Oxidative stress and neuroinflammation are widespread in the Parkinson's disease (PD) brain and contribute to the synaptic degradation and dopaminergic cell loss that result in cognitive impairment and motor dysfunction. The polymethoxyflavone Gardenin A (GA) has been shown to activate the NRF2-regulated antioxidant pathway and inhibit the NFkB-dependent pro-inflammatory pathway in a Drosophila model of PD. Here, we evaluate the effects of GA on A53T alpha-synuclein overexpressing (A53TSyn) mice. A53TSyn mice were treated orally for 4 weeks with 0, 25, or 100 mg/kg GA. In the fourth week, mice underwent behavioral testing and tissue was harvested for immunohistochemical analysis of tyrosine hydroxylase (TH) and phosphorylated alpha synuclein (pSyn) expression, and quantification of synaptic, antioxidant and inflammatory gene expression. Results were compared to vehicle-treated C57BL6 mice. Treatment with 100 mg/kg GA improved associative memory and decreased abnormalities in mobility and gait in A53TSyn mice. GA treatment also reduced cortical and hippocampal levels of pSyn and attenuated the reduction in TH expression in the striatum. Additionally, GA increased cortical expression of NRF2-regulated antioxidant genes and decreased expression of NFkB-dependent pro-inflammatory genes. GA was readily detectable in the brains of treated mice and modulated the lipid profile in the deep gray brain tissue of those animals. While the beneficial effects of GA on cognitive deficits, motor dysfunction and PD pathology are promising, future studies are needed to further fully elucidate the mechanism of action of GA, optimizing dosing and confirm these effects in other PD models.

Significance Statement

The polymethoxyflavone Gardenin A can improve cognitive and motor function and attenuate both increases in phosphorylated alpha synuclein and reductions in tyrosine hydroxylase expression in A53T alpha synuclein overexpressing mice. These effects may be related to activation of the NRF2-regulated antioxidant response and downregulation of NFkB-dependent inflammatory response by Gardenin A in treated animals. The study also showed excellent brain bioavailability of Gardenin A and modifications of the lipid profile, possibly through interactions between Gardenin A with the lipid bilayer, following oral administration. The study confirms neuroprotective activity of Gardenin A previously reported in toxin induced Drosophila model of Parkinson's disease.

Significant potential of melatonin therapy in Parkinson's disease - a meta-analysis of randomized controlled trials

Objective

Since its discovery as an antioxidant, melatonin has been increasingly recognized for its therapeutic potential beyond sleep disturbances in neurodegenerative disorders. This study aims to evaluate efficacy of various melatonin doses, treatment durations, and formulations, in alleviating motor symptoms and sleep disturbances in Parkinson's disease, the second most common neurodegenerative disorder worldwide.

Methods

PubMed, Cochrane Library, ClinicalTrials.gov and other databases were systematically searched to retrieve randomized controlled trials (RCTs) administrating melatonin to Parkinson's disease patients until June 10th, 2023. Outcomes including Unified Parkinson Disease Rating Scale (UPDRS) scores and Pittsburgh Sleep Quality Index (PSQI) scores, were pooled and reported as mean differences (MD) with 95% confidence intervals (CIs). Meta-analysis was performed using an inverse variance random-effects model in Review Manager 5.4 software. Trial Sequential Analysis was performed to avoid false-positive results from random errors.

Results

Five RCTs with a total of 155 patients were included. Statistically significant reductions in UPDRS total scores were observed in groups receiving Melatonin ≥10 mg/day (MD = -11.35, 95% CI: -22.35 to -0.35, I2 = 0%, p = 0.04) and immediate release formulations (MD = -11.35, 95% CI: -22.35 to -0.35, I2 = 0%, p = 0.04). No significant effects on individual UPDRS II, III, and IV scores were observed, regardless of melatonin dosage and treatment duration. Moreover, significant improvements in PSQI scores were observed with only immediate-release melatonin formulations (MD = -2.86, 95% CI: -4.74 to -0.97, I2 = 0%, p = 0.003).

Conclusion

Melatonin ≥10 mg/day for a minimum duration of ≥12 weeks in immediate-release formulations consistently demonstrated significant therapeutic potential in improving motor symptom and sleep disturbances in Parkinson disease. However, further trials are warranted to investigate its impact when initiated early in the disease course to fully explore its true therapeutic potential.

Systematic review registration

Unique identifier: CRD42023427491 (PROSPERO).

Inhibition of abnormal C/EBPβ/α-Syn signaling pathway through activation of Nrf2 ameliorates Parkinson's disease-like pathology

Parkinson's disease (PD) is characterized by the formation of Lewy bodies (LBs) in the brain. These LBs are primarily composed of α-Synuclein (α-Syn), which has aggregated. A recent report proposes that CCAAT/enhancer-binding proteins β (C/EBPβ) may act as an age-dependent transcription factor for α-Syn, thereby initiating PD pathologies by regulating its transcription. Potential therapeutic approaches to address PD could involve targeting the regulation of α-Syn by C/EBPβ. This study has revealed that Nrf2, also known as nuclear factor (erythroid-derived 2)-like 2 (NFE2L2), suppresses the transcription of C/EBPβ in SH-SY5Y cells when treated with MPP+ . To activate Nrf2, sulforaphane, an Nrf2 activator, was administered. Additionally, C/EBPβ was silenced using C/EBPβ-DNA/RNA heteroduplex oligonucleotide (HDO). Both approaches successfully reduced abnormal α-Syn expression in primary neurons treated with MPP+ . Furthermore, sustained activation of Nrf2 via its activator or inhibition of C/EBPβ using C/EBPβ-HDO resulted in a reduction of aberrant α-Syn expression, thus leading to an improvement in the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc) in mouse models induced by 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) and those treated with preformed fibrils (PFFs). The data presented in this study illustrate that the activation of Nrf2 may provide a potential therapeutic strategy for PD by inhibiting the abnormal C/EBPβ/α-Syn signaling pathway.

Jobelyn® improves motor dysfunctions induced by haloperidol in mice via neuroprotective mechanisms relating to modulation of cAMP response-element binding protein and mitogen-activated protein kinase

The clinical efficacy of haloperidol in the treatment of psychosis has been limited by its tendency to cause parkinsonian-like motor disturbances such as bradykinesia, muscle rigidity and postural instability. Oxidative stress-evoked neuroinflammation has been implicated as the key neuropathological mechanism by which haloperidol induces loss of dopaminergic neurons and motor dysfunctions. This study was therefore designed to evaluate the effect of Jobelyn® (JB), an antioxidant supplement, on haloperidol-induced motor dysfunctions and underlying molecular mechanisms in male Swiss mice. The animals were distributed into 5 groups (n = 8), and treated orally with distilled water (control), haloperidol (1 mg/kg) alone or in combination with each dose of JB (10, 20 and 40 mg/kg), daily for 14 days. Thereafter, changes in motor functions were evaluated on day 14. Brain biomarkers of oxidative stress, proinflammatory cytokines (tumor necrosis factor-alpha and interleukin-6), cAMP response-element binding protein (CREB), mitogen-activated protein kinase (MAPK) and histomorphological changes were also investigated. Haloperidol induces postural instability, catalepsy and impaired locomotor activity, which were ameliorated by JB. Jobelyn® attenuated haloperidol-induced elevated brain levels of MDA, nitrite, proinflammatory cytokines and also boosted neuronal antioxidant profiles (GSH and catalase) of mice. It also restored the deregulated brain activities of CREB and MAPK, and reduced the histomorphological distortions as well as loss of viable neuronal cells in the striatum and prefrontal cortex of haloperidol-treated mice. These findings suggest possible benefits of JB as adjunctive remedy in mitigating parkinsonian-like adverse effects of haloperidol through modulation of CREB/MAPK activities and oxidative/inflammatory pathways.

GLP-1 receptor agonists effect on cognitive function in patients with and without type 2 diabetes

Glucagon-like peptide 1 (GLP-1) is a hormone of the incretin family, secreted in response to nutrient ingestion, and plays a role in metabolic homeostasis. GLP-1 receptor agonist has a peripheral and a central action, including stimulation of glucose-dependent insulin secretion and insulin biosynthesis, inhibition of glucagon secretion and gastric emptying, and inhibition of food intake. Through their mechanism, their use in the treatment of type 2 diabetes has been extended to the management of obesity, and numerous trials are being conducted to assess their cardiovascular effect. Type 2 diabetes appears to share common pathophysiological mechanisms with the development of cognitive disorders, such as Alzheimer's and Parkinson's disease, related to insulin resistance. In this review, we aim to examine the pathological features between type 2 diabetes and dementia, GLP-1 central effects, and analyze the relevant literature about the effect of GLP-1 analogs on cognitive function of patients with type 2 diabetes but also without. Results tends to show an improvement in some brain markers (e.g. hippocampal connections, cerebral glucose metabolism, hippocampal activation on functional magnetic resonance imaging), but without being able to demonstrate a strong correlation to cognitive scores. Some epidemiological studies suggest that GLP-1 receptor agonists may offer a protective effect, by delaying progression to dementia when diabetic patients are treated with GLP-1 receptor agonists. Ongoing trials are in progress and may provide disease-modifying care for Alzheimer's disease and Parkinson's disease patients in the future.

Gut Microbial Alteration in MPTP Mouse Model of Parkinson Disease is Administration Regimen Dependent

Parkinson Disease (PD) is one of the most common neurodegenerative disorders characterized by loss of dopaminergic neurons involved in motor functions. Growing evidence indicates that gut microbiota communicates with the brain known as the gut-brain axis (GBA). Mitochondrial toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is commonly used in animal studies to investigate the GBA in PD. Various MPTP administration regimens are performed in PD mouse models involving one to multiple injections in 1 day or one injection per day for several days. The aim of this study is to investigate if the impact of MPTP on gut microbiota differs depending on the administration regimen. C57BL/6 mice were treated with acute or subchronic regimens of MPTP. Motor functions were assessed by open-field, catalepsy, and wire hanging tests. The cecum and the brain samples were obtained for microbiota and gene expression analyses, respectively. MPTP administration regimens differed in their ability to alter the gut microbiota. Firmicutes and Bacteroidota were both increased in subchronic mice while did not change and decreased, respectively, in acute mice. Verrucomicrobiota was elevated in acute MPTP mice but dropped in subchronic MPTP mice. Muribaculaceae was the predominant genus in all groups but acute mice. In acute mice, Akkermansia was increased and Colidextribacter was decreased; however, they showed an opposite trend in subchronic mice. These data suggest that MPTP mouse model cause a gut microbiota dysbiosis in an administration regimen dependent manner, and it is important to take consideration of mouse model to investigate the GBA in neurodegenerative diseases including PD.

The nonsynaptic plasticity in Parkinson's disease: Insights from an animal model

BACKGROUND

The 6-OHDA nigro-striatal lesion model has already been related to disorders in the excitability and synchronicity of neural networks and variation in the expression of transmembrane proteins that control intra and extracellular ionic concentrations, such as cation-chloride cotransporters (NKCC1 and KCC2) and Na+/K+-ATPase and, also, to the glial proliferation after injury. All these non-synaptic mechanisms have already been related to neuronal injury and hyper-synchronism processes.

OBJECTIVE

The main objective of this study is to verify whether mechanisms not directly related to synaptic neurotransmission could be involved in the modulation of nigrostriatal pathways.

METHODS

Male Wistar rats, 3 months old, were submitted to a unilateral injection of 24 µg of 6-OHDA, in the striatum (n = 8). The animals in the Control group (n = 8) were submitted to the same protocol, with the replacement of 6-OHDA by 0.9% saline. The analysis by optical densitometry was performed to quantify the immunoreactivity intensity of GFAP, NKCC1, KCC2, Na+/K+-ATPase, TH and Cx36.

RESULTS

The 6-OHDA induced lesions in the striatum, were not followed by changes in the expression cation-chloride cotransporters and Na+/K+-ATPase, but with astrocytic reactivity in the lesioned and adjacent regions of the nigrostriatal. Moreover, the dopaminergic degeneration caused by 6-OHDA is followed by changes in the expression of connexin-36.

CONCLUSIONS

The use of the GJ blockers directly along the nigrostriatal pathways to control PD motor symptoms is conjectured. Electrophysiology of the striatum and the substantia nigra, to verify changes in neuronal synchronism, comparing brain slices of control animals and experimental models of PD, is needed.

Dual Anta-Inhibitors Targeting Protein Kinase CK1δ and A2A Adenosine Receptor Useful in Neurodegenerative Disorders

Currently, the number of patients with neurodegenerative pathologies is estimated at over one million, with consequences also on the economic level. Several factors contribute to their development, including overexpression of A_2A adenosine receptors (A_2AAR) in microglial cells and up-regulation and post-translational alterations of some casein kinases (CK), among them, CK-1δ. The aim of the work was to study the activity of A_2AAR and CK1δ in neurodegeneration using in-house synthesized A_2A/CK1δ dual anta-inhibitors and to evaluate their intestinal absorption. Experiments were performed on N13 microglial cells, which were treated with a proinflammatory CK cocktail to simulate an inflammatory state typical of neurodegenerative diseases. Results showed that the dual anta-inhibitors have the ability to counteract the inflammatory state, even if compound 2 is more active than compound 1. In addition, compound 2 displayed an important antioxidant effect similar to the reference compound ZM241385. Since many known kinase inhibitors are very often unable to cross lipid bilayer membranes, the ability of A_2A/CK1δ double anta-inhibitors to cross the intestinal barrier was investigated by an everted gut sac assay. HPLC analysis revealed that both compounds are able to cross the intestinal barrier, making them promising candidates for oral therapy.

Neuromelanin: Its role in the pathogenesis of idiopathic Parkinson's disease and potential as a therapeutic target

Parkinson's disease is an increasingly prevalent condition that involves the marked loss of dopaminergic neurons in the substantia nigra pars compacta. These neurons pigmented with neuromelanin along with other regions of the brain are almost exclusively victims of neurodegeneration in the disease. The link between neuromelanin and Parkinson's disease has been widely studied for decades. While many studies have outlined the pigment's neuroprotective function as a potent free radical scavenger, antioxidant, and ion-chelator, it has also been observed to play a role in cell death due to mitochondrial dysfunction and oxidative stress, especially in the parkinsonian disease state. This is due to the damaging effects of neuromelanin precursors, neuromelanin-related ion dysregulation and intra- and extraneuronal neuromelanin accumulation. Current and emerging therapeutic endeavours guided by these pathological processes may include antioxidant therapy, proteostasis enhancement, ion chelation and neuromelanin-targeted immunotherapy to prevent the accumulation, formation and effects of neuromelanin and oxidative neuromelanin precursors. Some of these therapeutic strategies are already in nascent stages, while others have produced mixed results in clinical trials. This review aims to provide an update on how neuromelanin and neuromelanin-related substances may be linked to the pathogenesis of Parkinson's disease and how future therapeutic strategies may be able to hamper or prevent neuromelanin-related pathological processes and ultimately modify disease progression in Parkinson's.

Synergistic effects of lipopolysaccharide and rotenone on dopamine neuronal damage in rats

INTRODUCTION

The etiology of Parkinson's disease (PD) is still unknown. Until now, oxidative stress and neuroinflammation play a crucial role in the pathogenesis of PD. However, the specific synergistic role of oxidative stress and neuroinflammation in the occurrence and development of PD remains unclear.

METHODS

The changes in motor behavior, dopamine (DA) neurons quantification and their mitochondrial respiratory chain, glial cells activation and secreted cytokines, Nrf2 signaling pathway, and redox balance in the brain of rats were evaluated.

RESULTS

Lipopolysaccharide (LPS)-induced neuroinflammation and rotenone (ROT)-induced oxidative stress synergistically aggravated motor dysfunction, DA neuron damage, activation of glial cells, and release of related mediators, activation of Nrf2 signaling and destruction of oxidative balance. In addition, further studies indicated that after ROT-induced oxidative stress caused direct damage to DA neurons, LPS-induced inflammatory effects had stronger promoting neurotoxic effects on the above aspects.

CONCLUSIONS

Neuroinflammation and oxidative stress synergistically aggravated DA neuronal loss. Furtherly, oxidative stress followed by neuroinflammation caused more DA neuronal loss than neuroinflammation followed by oxidative stress.

Oleuropein confers neuroprotection against rotenone-induced model of Parkinson's disease via BDNF/CREB/Akt pathway

Major pathological features of Parkinson's disease (PD) include increase in oxidative stress leading to the aggregation of α-synuclein, mitochondrial dysfunction and apoptosis of dopaminergic neurons. In addition, downregulation of the expression of neurotrophic factors like-Brain Derived Neurotrophic Factor (BDNF) is also involved in PD progression. There has been a lot of interest in trophic factor-based neuroprotective medicines over the past few decades to treat PD symptoms. Rotenone, an insecticide, inhibits the mitochondrial complex I causing overproduction of ROS, oxidative stress, and aggregation of α-synuclein. It has been shown that BDNF and Tropomyosin receptor kinase B (TrkB) interaction initiates the regulation of neuronal cell development and differentiation by the serine/threonine protein kinases like Akt and GSK-3β. Additionally, Transcription factor CREB (cAMP Response Element-binding protein) also determines the gene expression of BDNF. The homeostasis of these signalling cascades is compromised with the progression of PD. Therefore, maintaining the equilibrium of these signalling cascades will delay the onset of PD. Oleuropein (OLE), a polyphenolic compound present in olive leaves has been documented to cross blood brain barrier and shows potent antioxidative property. In the present study, the dose of 8, 16 and 32 mg/kg body weight (bwt) OLE was taken for dose standardisation. The optimised doses of 16 and 32 mg/kg bwt was found to be neuroprotective in Rotenone induced PD mouse model. OLE improves motor impairment and upregulate CREB regulation along with phosphorylation of Akt and GSK-3β in PD mouse. In addition, OLE also reduces the mitochondrial dysfunction by activation of enzyme complexes and downregulates the proapoptotic markers in Rotenone intoxicated mouse model. Overall, our study suggests that OLE may be used as a therapeutic agent for treatment of PD by regulating BDNF/CREB/Akt signalling pathway.

Traversing through the cell signaling pathways of neuroprotection by betanin: therapeutic relevance to Alzheimer's Disease and Parkinson's Disease

Modulation of cell signaling pathways is the key area of research towards the treatment of neurodegenerative disorders. Altered Nrf2-Keap1-ARE (Nuclear factor erythroid-2-related factor 2-Kelch-like ECH-associated protein 1-Antioxidant responsive element) and SIRT1 (Sirtuin 1) cell signaling pathways are considered to play major role in the etiology and pathogenesis of Alzheimer's disease (AD) and Parkinson's disease (PD). Strikingly, betanin, a betanidin 5-O-β-D-glucoside compound is reported to show commendable anti-oxidative, anti-inflammatory and anti-apoptotic effects in several disease studies including AD and PD. The present review discusses the pre-clinical studies demonstrating the neuroprotective effects of betanin by virtue of its potential to ameliorate oxidative stress, neuroinflammation, abnormal protein aggregation and cell death. It highlights the direct linkage between the neuroprotective abilities of betanin and upregulation of the Nrf2-Keap1-ARE and SIRT1 signaling pathways. The review further hypothesizes the involvement of the betanin-Nrf2-ARE route in the inhibition of beta-amyloid aggregation through beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), one of the pivotal hallmarks of AD. The present review hereby for the first time elaborately discusses the reported neuroprotective abilities of betanin and decodes the Nrf2 and SIRT1 modulating potential of betanin as a primary mechanism of action behind, hence highlighting it as a novel drug candidate for the treatment of neurodegenerative diseases in the near future.

LncRNA SNHG15 mediates 1-methyl-4-phenylpyridinium (MPP+)-induced neuronal damage through targeting miR-29c-3p/SNCA axis

BACKGROUND

Parkinson's disease (PD) is the most prevalent neurodegenerative disease in the elderly people. Long non-coding ribose nucleic acids (LncRNAs) can serve as molecular sponges for micro RNA (miRNA) and regulate gene expression, which is implicated in the occurrence and progression of PD. In this work, we investigated the functional role of lncRNA SNHG15 in a neuronal damage cell model and its potential mechanism.

METHODS

SK-N-SH cells treated with 1-methyl-4-phenylpyridinium (MPP⁺) were employed as the in vitro cellular model to mimic neuronal degeneration. The expression levels of SNHG15, miR-29c-3p, and SNCA were determined by qRT-PCR. ELISA, CCK-8 proliferation assay, and flow cytometry were conducted to explore the effects of SNHG15 and miR-29c-3p on the production of inflammatory factors, cell proliferation, and apoptosis, respectively. Dual-luciferase reporter assay was utilized to validate the functional interactions among SNHG15, miR-29c-3p, and SNCA. SNCA protein levels were examined by Western blot.

RESULTS

SNHG15 was highly induced in the cell model of MPP⁺-induced neuronal damage. SNHG15 knockdown significantly mitigated MPP⁺-induced damages in SK-N-SH cells. SNHG15 served as a sponge to down-regulate miR-29c-3p, thereby releasing the inhibition of miR-29c-3p on SNCA expression, which promoted neuronal damages upon MPP⁺ challenge.

CONCLUSION

The upregulation of SNHG15 upon MPP⁺ challenge mediates neuronal damages in SK-N-SH cells by regulating miR-29c-3p/SNCA axis. Future work is required to validate these findings in PD patients and animal models, which could provide insights into the diagnosis and therapy of PD.

Neuroprotective potential of plant derived parenchymal stem cells extract on environmental and genetic models of Parkinson disease through attenuation of oxidative stress and neuroinflammation

Parkinson's disease (PD) is a neurodegenerative disorder characterized by both motor and non-motor features. The current treatment regimen for PD are dopamine enhancers which have been reported to worsen the disease prognosis after long term treatment, thus, the need for better treatment options. This study sought to investigate the protective action of Double Stem Cell® (DSC), a blend of stem cells extracts from Swiss apples (Malus Domestica) and Burgundy grapes (Vitis vinifera) on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinsonism in mice and genetic model of PD in Drosophila melanogaster. Male albino mice were pretreated with MPTP (4 × 20 mg/kg, i.p., two hourly in 8 h), twelve hours before administration of DSC (8, 40, or 200 mg/kg, p.o.). Thereafter, behavioural, biochemical and immunohistochemical assays were carried out. The impact of vehicle or DSC supplementation on α-synuclein aggregation was evaluated in Drosophila melanogaster using the UAS-Gal4 system, female DDC-Gal4 flies were crossed with male UAS-α-synuclein, the progenies were examined for fecundity, locomotion, memory, and lifespan. MPTP-induced motor deficits in open field test (OFT), working memory impairment (Y-maze test (YMT)) and muscle incoordination (rotarod test) were ameliorated by DSC (8, 40 or 200 mg/kg) through dose-dependent and significant improvements in motor, cognitive and motor coordination. Moreso, MPTP exposure caused significant increase in lipid peroxidation and decrease in antioxidant enzymes activities (glutathione, catalase and superoxide dismutase) in the midbrain which were attenuated by DSC. MPTP-induced expression of microglia (iba-1), astrocytes (glia fibrillary acidic protein; GFAP) as well as degeneration of dopamine neurons (tyrosine hydroxylase positive neurons) in the substantia nigra (SN) were reversed by DSC. Supplementation of flies feed with graded concentration of DSC (0.8, 4 or 20 mg/ml) did not affect fecundity but improved climbing activity and lifespan. Findings from this study showed that Double Stem Cell improved motor and cognitive functions in both mice and Drosophila through attenuation of neurotoxin-induced oxidative stress and neuroinflammation.

Association between C-reactive protein-albumin ratio and overall survival in Parkinson's disease using publicly available data: A retrospective cohort study

Background

At present, many studies have confirmed that inflammation plays a central role in Parkinson's disease (PD). The inflammatory index is related to the prognosis of the disease, but a single inflammatory index has some limitations. The C-reactive protein-albumin ratio (CAR) is a better marker of inflammation or nutritional status than C-reactive protein (CRP) or albumin (Alb), but there is limited study on the association between CAR and the overall survival (OS) of PD.

Object

To study the association between CAR and OS in PD patients.

Methods

All of these data were obtained from the Dryad Digital Repository, based on which we conducted a secondary analysis. The study was conducted by the Department of Neurology, the National Regional Center for Neurological Disorders, and the National Hospital of Utano study between March 2004 to November 2007. The final analytic sample included 235 PD patients with the outcome of survival or all-cause death from the study registration to the endpoint. In this study, univariate and multivariate COX regression analyses were used to calculate the adjusted hazard ratio (HR), with a 95% confidence interval (CI). In addition, the association between CAR and OS in PD patients was explored by Kaplan-Meier curve and subgroup analysis.

Results

This study included 235 PD patients with an average age of 62.25 years, including 135 females and 100 males, and 45 died during the follow-up period. CAR was associated with gender, modified Hoehn-Yahr stages (mH-Y), and Mini-Mental State Examination (MMSE) of PD patients. In the COX multivariate regression model, after adjusting the age, gender, PD duration, mH-Y, MMSE, and the non-steroidal anti-inflammatory drugs, CAR was found to be associated with the OS in PD (HR = 1.54, 95% CI = 1.01-2.34, p = 0.044). Subgroup analysis showed that the subgroup did not play an interactive role in the association between the prognosis of patients with CAR and PD (p for interaction >0.05), and the results remained stable.

Conclusions

The all-cause mortality of PD patients with a high level of CAR is higher, which indicates that the poor overall survival of PD patients is associated with the increase of CAR. The CAR may be a reliable prognostic biomarker for PD patients.

Feruloylated oligosaccharides ameliorate MPTP-induced neurotoxicity in mice by activating ERK/CREB/BDNF/TrkB signalling pathway

BACKGROUND

Feruloylated oligosaccharides (FOs) are natural esterification products of ferulic acid and oligosaccharides.

STUDY DESIGN

In this study, we examined whether FOs contribute to the ensured survival of nigrostriatal dopamine neurons and inhibition of neuroinflammation in Parkinson's disease (PD).

METHODS

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 30 mg/kg) was injected intraperitoneally into mice to establish a Parkinson's disease (PD) mouse model. FOs (15 and 30 mg/kg) were orally administered daily to the MPTP-treated mice. The rotarod test, balance beam test, immunofluorescence, enzyme-linked immunosorbent assay (ELISA), quantitative PCR (qPCR), and western blot analyses were performed to examine the neuroprotective effects of FOs on MPTP-treated mice.

RESULTS

Our study indicated that FOs increased the survival of dopamine neurons in the substantia nigra pars compacta (SNc) of the MPTP-treated mice. The neuroprotective effects of FOs were accompanied by inhibited glial activation and reduced inflammatory cytokine production. The mechanistic experiments revealed that the neuroprotective effects of FOs might be mediated through the activation of the ERK/CREB/BDNF/TrkB signalling pathway.

CONCLUSION

This study provides new insights into the mechanism underlying the anti-neuroinflammatory effect of phytochemicals and may facilitate the development of dietary supplements for PD patients. Our results indicate that FOs can be used as potential modulators for the prevention and treatment of PD.

Machine learning analysis of the UK Biobank reveals IGF-1 and inflammatory biomarkers predict Parkinson's disease risk

INTRODUCTION

Parkinson's disease (PD) is the most common movement disorder, and its prevalence is increasing rapidly worldwide with an ageing population. The UK Biobank is the world's largest and most comprehensive longitudinal study of ageing community volunteers. The cause of the common form of PD is multifactorial, but the degree of causal heterogeneity among patients or the relative importance of one risk factor over another is unclear. This is a major impediment to the discovery of disease-modifying therapies.

METHODS

We used an integrated machine learning algorithm (IDEARS) to explore the relative effects of 1,753 measured non-genetic variables in 334,062 eligible UK Biobank participants, including 2,719 who had developed PD since their recruitment into the study.

RESULTS

Male gender was the highest-ranked risk factor, followed by elevated serum insulin-like growth factor 1 (IGF-1), lymphocyte count, and neutrophil/lymphocyte ratio. A group of factors aligned with the symptoms of frailty also ranked highly. IGF-1 and neutrophil/lymphocyte ratio were also elevated in both sexes before PD diagnosis and at the point of diagnosis.

DISCUSSION

The use of machine learning with the UK Biobank provides the best opportunity to explore the multidimensional nature of PD. Our results suggest that novel risk biomarkers, including elevated IGF-1 and NLR, may play a role in, or are indicative of PD pathomechanisms. In particular, our results are consistent with PD being a central manifestation of a systemic inflammatory disease. These biomarkers may be used clinically to predict future PD risk, improve early diagnosis and provide new therapeutic avenues.

Does Drinking Coffee Reduce the Incidence of Parkinson's Disease?

Parkinson's disease (PD) is an increasing threat to first-world nations as their population ages, with around one in 100 suffering from it by age 60. Incurable, with treatments that do little to delay disease progression, PD induces severe disability and even death in those afflicted. The search for preventative measures has revealed the widely used psychoactive stimulant caffeine, which competitively inhibits adenosine receptors to induce a wide variety of effects. The inhibition of inflammation and microglial cell activation to reduce reactive oxygen species (ROS)-induced cellular damage and the resultant mitochondrial dysfunction of the dopaminergic neurons appears to be the main pathway, inducing neuronal loss via the activation of the intrinsic pathway to apoptosis. Mouse models and human data reinforce that caffeine delays the onset of PD in a dose-dependent manner. Evidence suggests it is more beneficial in men than women and is not beneficial at all in women undergoing hormone replacement therapy (HRT). Additionally, some studies suggest that although caffeinated drinks such as cola and tea are beneficial, there may be other products in coffee that prevent the effect, though this requires further research. Although there is strong evidence that caffeine is neuroprotective, there is less evidence that it delays the onset of PD. Given the association with cardiovascular disease, it may be disadvantageous overall to the majority of the population to supplement caffeine, though still a beneficial preventative technique for individuals with a genetic predisposition to PD that may otherwise suffer early onset.

Neuroprotective effect of secukinumab against rotenone induced Parkinson's disease in rat model: Involvement of IL-17, HMGB-1/TLR4 axis and BDNF/TrKB cascade

Neuroinflammatory status produced via activation of toll like receptor-4 (TLR-4) and interleukin-17 receptor (IL-17R) is one of the principal mechanisms involved in dopaminergic neuronal loss in Parkinson's disease (PD). Activation of TLR-4 and IL-17R stimulates reactive oxygen species (ROS) and proinflammatory cytokines (IL-17, IL-1β, TNFα, IL-6) production that augments neurodegeneration and reduces neuro-survival axis (TrKB/Akt/CREB/BDNF). So, reducing IL-17-driven neuroinflammation via secukinumab, monoclonal antibody against IL-17A, may be one of therapeutic approach for PD. Moreover, the aim was extended to delineate the possible neuroprotective mechanism involved against neuronal loss in rotenone induced PD in rats. Rats received 11 subcutaneous injection of rotenone (1.5 mg/kg) every other day for 21 consecutive days and treated with 2 subcutaneous injections of secukinumab (15 mg/kg) on day 9 and 15, one hour after rotenone administration. Treatment with secukinumab improved motor impairment and muscle incoordination induced by rotenone, as verified by open field and rotarod tests. Moreover, secukinumab attenuated neuronal loss and improve histopathological profile. Noteworthy, secukinumab reduces neuro-inflammatory status by hindering the interaction between IL and 17A and IL-17RA together with inhibiting the activation of TLR-4 and its downstream cascade including pS536-NFκB p65, IL-1β and HMGB-1. Additionally, secukinumab stimulated neuro-survival signalling cascade via activation pY515-TrKB receptor and triggered upsurge in its downstream targets (pS473-Akt/pS133-CREB/BDNF). Furthermore, secukinumab increased striatal tyrosine hydroxylase immunoexpression, the rate limiting step in dopamine biosynthesis, to guard against dopaminergic neuronal loss. In conclusion, secukinumab exerts a neuroprotective effect against rotenone induced neuronal loss via inhibition IL17A/IL17RA interaction and HMGB-1/TLR-4/NF-κBp65/IL1β signalling cascade, together with activation of TrKB/ Akt/CREB/BDNF axis.

Psychobiotics and Elderly Health

While aging with physiological dimensions refers to the changes seen with chronological age, on the other hand, aging with psychological dimensions refers to the change of humans’ capacity to adaptively. Such as learning, psychomotor, problem-solving and personality traits. With the improvement of life quality in recent years, the average life expectancy and therefore the incidence of neurodegenerative diseases among the elderly have also increased. Although the aging process is universal, progressive, gradual and unstoppable, human gut microbiota-targeted aging management is a new approach to health and anti-aging. Nutrition plays a big factor in the elderly population with providing adequate cognitive and physical functions and when taking the right nutrition it also reduces the risk of chronic diseases. When adding functional foods into the diet, it can play a significant role to reduce the risk of diet-related diseases. Such as probiotics and prebiotics. In recent years, a new subclass of probiotics called ‘psychobiotics’ has emerged. These psychobiotics are defined as probiotics that, when taken in appropriate amounts, it creates positive psychiatric effects in human psychopathology. Examination of this new class of probiotics provides a glimmer of hope for the effective management of neurodegenerative diseases and various psychiatric disorders, especially with increasing life expectancy. Also, recommending the use of probiotics in old age will contribute to the treatment of some health problems related to aging.

Tempol and silymarin rescue from zinc-induced degeneration of dopaminergic neurons through modulation of oxidative stress and inflammation

Oxidative stress and inflammation are the key players in the toxic manifestation of sporadic Parkinson's disease and zinc (Zn)-induced dopaminergic neurodegeneration. A synthetic superoxide dismutase (SOD) mimetic, tempol, and a naturally occurring antioxidant, silymarin protect against oxidative stress-mediated damage. The study intended to explore the effects of tempol and silymarin against Zn-induced dopaminergic neurodegeneration. Exposure to Zn produced neurobehavioral deficits and striatal dopamine depletion. Zn reduced glutathione content and glutathione-S-transferase activity and increased lipid peroxidation, superoxide dismutase activity, and level of pro-inflammatory mediators [nuclear factor-kappa B (NF-κB), tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6)]. Zn also attenuated the expression of tyrosine hydoxylase (TH), vesicular monoamine transporter 2 (VMAT-2), mitochondrial B-cell lymphoma-2 (Bcl-2), and procaspase-3 and 9 proteins and number of TH-positive neurons. Conversely, Zn elevated the expression of dopamine transporter (DAT) and mitochondrial Bcl-2-associated X (Bax) protein along with mitochondrial cytochrome c release. Administration of tempol significantly alleviated Zn-induced motor impairments, dopamine depletion, reduction in TH expression, and loss of TH-positive neurons similar to silymarin. Silymarin mitigated Zn-induced oxidative stress and inflammation and restored the expression of dopamine transporters and levels of pro-apoptotic proteins akin to tempol. The results demonstrate that both tempol and silymarin protect against Zn-induced dopaminergic neuronal loss through the suppression of oxidative stress and inflammation.

Chronic Treatment with the Probiotics Lacticaseibacillus rhamnosus GG and Bifidobacterium lactis BB12 Attenuates Motor Impairment, Striatal Microglial Activation, and Dopaminergic Loss in Rats with 6-Hydroxydopamine-induced Hemiparkinsonism

Gut dysbiosis is considered a risk factor for Parkinson's disease (PD), and chronic treatment with probiotics could prevent it. Here we report the assessment of a probiotic mixture [Lacticaseibacillus rhamnosus GG (LGG), and Bifidobacterium animalis lactis BB-12 (BB-12)] administered to male rats 2 weeks before and 3 weeks after injecting 6-hydroxydopamine (6-OHDA) into the right striatum, a model that mimics the early stages of PD. Before and after lesion, animals were subjected to behavioral tests: narrow beam, cylinder test, and apomorphine (APO)-induced rotations. Dopaminergic (DA) denervation and microglia recruitment were assessed with tyrosine hydroxylase (TH⁺) and ionized calcium-binding protein-1 adapter (Iba1⁺) immunostaining, respectively. Post 6-OHDA injury, rats treated with sunflower oil (probiotics vehicle) developed significant decrease in crossing speed and increases in contralateral paw slips (narrow beam), forepaw use asymmetry (cylinder), and APO-induced rotations. In striatum, 6-OHDA eliminated ≈2/3 of TH⁺ area and caused significant increase of Iba1⁺ microglia population. Retrograde axonal degeneration suppressed ≈2/5 of TH⁺ neurons in the substantia nigra pars compacta (SNpc). In hemiparkinsonian rats, probiotics treatment significantly improved the crossing speed, and also reduced paw slips (postlesion days 14 and 21), the loss of TH⁺ neurons in SNpc, and the loss of TH⁺ area and of Iba1⁺ microglia count in striatum, without affecting the proportion of microglia morphological phenotypes. Probiotics treatment did not attenuate forepaw use asymmetry nor APO-induced rotations. These results indicate that the mixture of probiotics LGG and BB-12 protects nigrostriatal DA neurons against 6-OHDA-induced damage, supporting their potential as preventive treatment of PD.

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.

Suppression of abnormal α-synuclein expression by activation of BDNF transcription ameliorates Parkinson's disease-like pathology

Parkinson’s disease (PD) is characterized by the formation of Lewy bodies (LBs) in the brain. LBs are mainly composed of phosphorylated and aggregated α-synuclein (α-Syn). Thus, strategies to reduce the expression of α-Syn offer promising therapeutic avenues for PD. DNA/RNA heteroduplex oligonucleotides (HDOs) are a novel technology for gene silencing. Using an α-Syn-HDO that specifically targets α-Syn, we examined whether α-Syn-HDO attenuates pathological changes in the brain of mouse models of PD. Overexpression of α-Syn induced dopaminergic neuron degeneration through inhibition of cyclic AMP-responsive-element-binding protein (CREB) and activation of methyl CpG binding protein 2 (MeCP2), resulting in brain-derived neurotrophic factor (BDNF) downregulation. α-Syn-HDO exerted a more potent silencing effect on α-Syn than α-Syn-antisense oligonucleotides (ASOs). α-Syn-HDO attenuated abnormal α-Syn expression and ameliorated dopaminergic neuron degeneration via BDNF upregulation by activation of CREB and inhibition of MeCP2. These findings demonstrated that inhibition of α-Syn by α-Syn-HDO protected against dopaminergic neuron degeneration via activation of BDNF transcription. Therefore, α-Syn-HDO may serve as a new therapeutic agent for PD.

The Relationship between Stress, Inflammation, and Depression

A narrative review about the relationship between stress, inflammation, and depression is made as follows: Chronic stress leads to various stress-related diseases such as depression. Although most human diseases are related to stress exposure, the common pathways between stress and pathophysiological processes of different disorders are still debatable. Chronic inflammation is a crucial component of chronic diseases, including depression. Both experimental and clinical studies have demonstrated that an increase in the levels of pro-inflammatory cytokines and stress hormones, such as glucocorticoids, substantially contributes to the behavioral alterations associated with depression. Evidence suggests that inflammation plays a key role in the pathology of stress-related diseases; however, this link has not yet been completely explored. In this study, we aimed to determine the role of inflammation in stress-induced diseases and whether a common pathway for depression exists. Recent studies support pharmacological and non-pharmacological treatment approaches significantly associated with ameliorating depression-related inflammation. In addition, major depression can be associated with an activated immune system, whereas antidepressants can exert immunomodulatory effects. Moreover, non-pharmacological treatments for major depression (i.e., exercise) may be mediated by anti-inflammatory actions. This narrative review highlights the mechanisms underlying inflammation and provides new insights into the prevention and treatment of stress-related diseases, particularly depression.

Crosstalk between regulatory non-coding RNAs and oxidative stress in Parkinson’s disease

Parkinson’s disease is the second most common neurodegenerative disease after Alzheimer’s disease, which imposes an ever-increasing burden on society. Many studies have indicated that oxidative stress may play an important role in Parkinson’s disease through multiple processes related to dysfunction or loss of neurons. Besides, several subtypes of non-coding RNAs are found to be involved in this neurodegenerative disorder. However, the interplay between oxidative stress and regulatory non-coding RNAs in Parkinson’s disease remains to be clarified. In this article, we comprehensively survey and overview the role of regulatory ncRNAs in combination with oxidative stress in Parkinson’s disease. The interaction between them is also summarized. We aim to provide readers with a relatively novel insight into the pathogenesis of Parkinson’s disease, which would contribute to the development of pre-clinical diagnosis and treatment.

Neuronutraceuticals Combating Neuroinflammaging: Molecular Insights and Translational Challenges—A Systematic Review

Neuropathologies, such as neuroinflammaging, have arisen as a serious concern for preserving the quality of life due to the global increase in neurodegenerative illnesses. Nowadays, neuronutraceuticals have gained remarkable attention. It is necessary to investigate the bioavailability, off-target effects, and mechanism of action of neuronutraceuticals. To comprehend the comprehensive impact on brain health, well-designed randomized controlled trials testing combinations of neuronutraceuticals are also necessary. Although there is a translational gap between basic and clinical research, the present knowledge of the molecular perspectives of neuroinflammaging and neuronutraceuticals may be able to slow down brain aging and to enhance cognitive performance. The present review also highlights the key emergent issues, such as regulatory and scientific concerns of neuronutraceuticals, including bioavailability, formulation, blood–brain permeability, safety, and efficacy.

Effects of obesity on neuroinflammatory and neurochemical parameters in an animal model of reserpine-induced Parkinson's disease

Obesity is associated with low-grade chronic inflammation and oxidative stress, affecting the brain's reward system by decreasing dopaminergic neurotransmission. It is known that dopaminergic neurotransmission is also reduced in Parkinson's disease (PD), and high adiposity is considered a risk factor for the development of several neurodegenerative diseases, including PD. This study aimed to assess the effects of obesity on neuroinflammatory and neurochemical parameters in an animal model of reserpine-induced PD. The obese group showed increased inflammation and oxidative damage as well as inhibition of mitochondrial respiratory chain complexes I and II and DNA damage in the evaluated structures. The PD group did not show inflammation or mitochondrial dysfunction but exhibited oxidative damage in the hippocampus. The combination group (obesity + PD) showed reduced inflammation and oxidative stress and increased activity of complexes I and II of the mitochondrial respiratory chain in most of the analyzed structures. On the other hand, obesity + PD caused oxidative damage to proteins in the liver, prefrontal cortex, striatum, and cerebral cortex and oxidative stress in the hypothalamus, resulting in reduced catalase activity. Furthermore, the combination group showed DNA damage in blood, liver, and cerebral cortex. In conclusion, it was observed that the association of obesity and PD did not increase inflammation, oxidative stress, or mitochondrial dysfunction in most of the evaluated structures but increased oxidative damage and induced mechanisms that led to DNA damage in peripheral tissues and brain structures.