Rosiglitazone decreases peroxisome proliferator receptor-gamma levels in microglia and inhibits TNF-alpha production: new evidences on neuroprotection in a progressive Parkinson's disease model

Function and Mechanism of Abscisic Acid on Microglia-Induced Neuroinflammation in Parkinson's Disease

Parkinson's disease (PD), as a neurologically implemented disease with complex etiological factors, has a complex and variable pathogenesis. Accompanying further research, neuroinflammation has been found to be one of the possible factors in its pathogenesis. Microglia, as intrinsic immune cells in the brain, play an important role in maintaining microenvironmental homeostasis in the brain. However, over-activation of neurotoxic microglia in PD promotes neuroinflammation, which further increases dopaminergic (DA) neuronal damage and exacerbates the disease process. Therefore, targeting and regulating the functional state of microglia is expected to be a potential avenue for PD treatment. In addition, plant extracts have shown great potential in the treatment of neurodegenerative disorders due to their abundant resources, mild effects, and the presence of multiple active ingredients. However, it is worth noting that some natural products have certain toxic side effects, so it is necessary to pay attention to distinguish medicinal ingredients and usage and dosage when using to avoid aggravating the progression of diseases. In this review, the roles of microglia with different functional states in PD and the related pathways inducing microglia to transform into neuroprotective states are described. At the same time, it is discussed that abscisic acid (ABA) may regulate the polarization of microglia by targeting them, promote their transformation into neuroprotective state, reduce the neuroinflammatory response in PD, and provide a new idea for the treatment of PD and the selection of drugs.

The Contribution of Type 2 Diabetes to Parkinson's Disease Aetiology

Type 2 diabetes (T2D) and Parkinson's disease (PD) are chronic disorders that have a significant health impact on a global scale. Epidemiological, preclinical, and clinical research underpins the assumption that insulin resistance and chronic inflammation contribute to the overlapping aetiologies of T2D and PD. This narrative review summarises the recent evidence on the contribution of T2D to the initiation and progression of PD brain pathology. It also briefly discusses the rationale and potential of alternative pharmacological interventions for PD treatment.

Disease mechanisms as subtypes: Immune dysfunction in Parkinson's disease

In recent years, the contraposition between inflammatory and neurodegenerative processes has been increasingly challenged. Inflammation has been emphasized as a key player in the onset and progression of Parkinson disease (PD) and other neurodegenerative disorders. The strongest indicators of the involvement of the immune system derived from evidence of microglial activation, profound imbalance in phenotype and composition of peripheral immune cells, and impaired humoral immune responses. Moreover, peripheral inflammatory mechanisms (e.g., involving the gut-brain axis) and immunogenetic factors are likely to be implicated. Even though several lines of preclinical and clinical studies are supporting and defining the complex relationship between the immune system and PD, the exact mechanisms are currently unknown. Similarly, the temporal and causal connections between innate and adaptive immune responses and neurodegeneration are unsettled, challenging our ambition to define an integrated and holistic model of the disease. Despite these difficulties, current evidence is providing the unique opportunity to develop immune-targeted approaches for PD, thus enriching our therapeutic armamentarium. This chapter aims to provide an extensive overview of past and present studies that explored the implication of the immune system in neurodegeneration, thus paving the road for the concept of disease modification in PD.

Design and Development of Novel Glitazones for Activation of PGC-1α Signaling Via PPAR-γ Agonism: A Promising Therapeutic Approach against Parkinson's Disease

Herein, we rationally designed and developed two novel glitazones (G1 and G2) to target peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α) signaling through peroxisome proliferator-activated receptors (PPAR)-γ agonism as a therapeutic for Parkinson's disease (PD). The synthesized molecules were analyzed by mass spectrometry and NMR spectroscopy. The neuroprotective functionality of the synthesized molecules was assessed by a cell viability assay in lipopolysaccharide-intoxicated SHSY5Y neuroblastoma cell lines. The ability of these new glitazones to scavenge free radicals was further ascertained via a lipid peroxide assay, and pharmacokinetic properties were verified using in silico absorption, distribution, metabolism, excretion, and toxicity analyses. The molecular docking reports recognized the mode of interaction of the glitazones with PPAR-γ. The G1 and G2 exhibited a noticeable neuroprotective effect in lipopolysaccharide-intoxicated SHSY5Y neuroblastoma cells with the half-maximal inhibitory concentration value of 2.247 and 4.509 μM, respectively. Both test compounds prevented 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced motor impairment in mice, as demonstrated by the beam walk test. Further, treating the diseased mice with G1 and G2 resulted in significant restoration of antioxidant enzymes glutathione and superoxide and reduced the intensity of lipid peroxidation inside the brain tissues. Histopathological analysis of the glitazones-treated mice brain revealed a reduced apoptotic region and a rise in the number of viable pyramidal neurons and oligodendrocytes. The study concluded that G1 and G2 showed promising results in treating PD by activating PGC-1α signaling in brain via PPAR-γ agonism. However, more extensive research is necessary for a better understanding of functional targets and signaling pathways.

PPARs and Their Neuroprotective Effects in Parkinson's Disease: A Novel Therapeutic Approach in α-Synucleinopathy?

Parkinson's disease (PD) is the most common α-synucleinopathy worldwide. The pathognomonic hallmark of PD is the misfolding and propagation of the α-synuclein (α-syn) protein, observed in post-mortem histopathology. It has been hypothesized that α-synucleinopathy triggers oxidative stress, mitochondrial dysfunction, neuroinflammation, and synaptic dysfunction, leading to neurodegeneration. To this date, there are no disease-modifying drugs that generate neuroprotection against these neuropathological events and especially against α-synucleinopathy. Growing evidence suggests that peroxisome proliferator-activated receptor (PPAR) agonists confer neuroprotective effects in PD, however, whether they also confer an anti-α-synucleinopathy effect is unknown. Here we analyze the reported therapeutic effects of PPARs, specifically the gamma isoform (PPARγ), in preclinical PD animal models and clinical trials for PD, and we suggest possible anti-α-synucleinopathy mechanisms acting downstream from these receptors. Elucidating the neuroprotective mechanisms of PPARs through preclinical models that mimic PD as closely as possible will facilitate the execution of better clinical trials for disease-modifying drugs in PD.

Neuroprotective Effect of Swertiamarin in a Rotenone Model of Parkinson's Disease: Role of Neuroinflammation and Alpha-Synuclein Accumulation

Parkinson's disease (PD) is a progressive neurodegenerative disease with no permanent cure affecting around 1% of the population over 65. There is an urgency to search for a disease-modifying agent with fewer untoward effects. PD pathology involves the accumulation of toxic alpha-synuclein (α-syn) and neuronal inflammation leading to the degeneration of dopaminergic (DAergic) neurons. Swertiamarin (SWE), a well-studied natural product, possesses a strong anti-inflammatory effect. It is a secoiridoid glycoside isolated from Enicostemma littorale Blume. SWE showed a reversal effect on the α-syn accumulation in the 6-hydroxydopamine (6-OHDA)-induced Caenorhabditis elegans model of PD. However, there are no reports in the literature citing the effect of SWE as a neuroprotective agent in rodents. The present study aimed to evaluate the anti-inflammatory activity of SWE against lipopolysaccharide (LPS)-induced C6 glial cell activation and its neuroprotective effect in the intrastriatal rotenone mouse PD model. SWE treatment showed a significant reduction in interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) levels in LPS-induced C6 glial cell activation. Further, our studies demonstrated the suppression of microglial and astroglial activation in substantia nigra (SN) after administration of SWE (100 mg/kg, intraperitoneally) in a rotenone mouse model. Moreover, SWE alleviated the rotenone-induced α-syn overexpression in the striatum and SN. SWE ameliorated the motor impairment against rotenone-induced neurotoxicity and mitigated the loss of DAergic neurons in the nigrostriatal pathway. Therefore, SWE has the potential to develop as an adjunct therapy for PD, but it warrants further mechanistic studies.

Thiazolidinedione use and risk of Parkinson's disease in patients with type 2 diabetes mellitus

The health burden of Parkinson's disease (PD) and diabetes increases rapidly in China. However, no population-based study of the association between glucose lowering agents and PD incidence has been conducted in mainland Chinese population. Preclinical studies indicate that thiazolidinediones (TZDs) have neuroprotective effects against PD through stimulating peroxisome proliferator-activated receptor gamma. Nevertheless, debate remains in human studies. We assembled a retrospective cohort of type 2 diabetes mellitus (T2DM) patients who were new users of TZDs or alpha glucosidase inhibitors (AGIs) using the Yinzhou Regional Health Care Database. A Cox model with inverse probability of treatment weighting (IPTW) was applied to estimate the hazard ratio (HR) of PD incidence associated with the use of TZDs compared with AGIs. The final cohort included 12,704 new users of TZDs and 49,696 new users of AGIs. The incidence of PD was 135 per 100,000 person-years in TZD users and 203 per 100,000 person-years in the AGI group. An inverse association between use of TZDs and incidence of PD, with a HR of 0.74 (95% confidence interval, 0.59-0.92), was observed after adjusting for potential confounding using IPTW. The results of various subgroup analyses and sensitivity analyses were consistent with the findings of the primary analysis. Our results indicated that the use of TZD is associated with a decreased risk of PD incidence in a mainland Chinese population with T2DM. Given the heavy disease burden of PD and diabetes in China, these findings could provide some evidence for developing effective prevention and control measures to reduce the future incidence of PD in China.

An Update on the Current and Emerging Use of Thiazolidinediones for Type 2 Diabetes

Guidelines have increasingly stressed the concept that adequate glycemic control is required to prevent or decrease the macro- and microvascular complications of type 2 diabetes mellitus (T2DM). PPAR-gamma agonists (“glitazones”) are no longer prioritized due to their effects on heart failure. However, the association between these drugs and innovative therapies could be a valuable tool to attenuate the risk factors of the metabolic syndrome. Glitazones are used for the treatment of diabetes and associated comorbidities. There is substantial scientific evidence demonstrating the effect of glitazones at a cardiometabolic level, as well as on hematological and neurological pathologies that point to their usefulness. The use of glitazones has always been controversial both for the type of patients who must take these drugs and for the side effects associated with them. Unfortunately, the recent guidelines do not include them among the preferred drugs for the treatment of hyperglycemia and rosiglitazone is out of the market in many countries due to an adverse cardiovascular risk profile. Even though real-life studies have proven otherwise, and their pleiotropic effects have been highlighted, they have been unable to achieve primacy in the choice of antihyperglycemic drugs. It would be appropriate to demonstrate the usefulness of pioglitazone and its therapeutic benefit with further cardiovascular safety studies.

Neuroinflammation in Parkinson"s Disease and its Treatment Opportunities

Parkinson’s disease (PD) is a complex, chronic, and progressive neurodegenerative disease that is characterized by irreversible dopaminergic neuronal loss in the substantia nigra. Alpha-synuclein is normally a synaptic protein that plays a key role in PD due to pathological accumulation as oligomers or fibrils. Clustered alpha-synuclein binds to the Toll-like receptors and activates the microglia, which initiates a process that continues with pro-inflammatory cytokine production and secretion. Pro-inflammatory cytokine overproduction and secretion induce cell death and accelerate PD progression. Microglia are found in a resting state in physiological conditions. Microglia became activated by stimulating Toll-like receptors on it under pathological conditions, such as alpha-synuclein aggregation, environmental toxins, or oxidative stress. The interaction between Toll-like receptors and its downstream pathway triggers an activation series, leads to nuclear factor-kappa B activation, initiates the inflammasome formation, and increases cytokine levels. This consecutive inflammatory process leads to dopaminergic cell damage and cell death. Microglia become overactive in response to chronic inflammation, which is observed in PD and causes excessive cytotoxic factor production, such as reactive oxidase, nitric oxide, and tumor necrosis factor-alpha. This inflammatory process contributes to the exacerbation of pathology by triggering neuronal damage or death. Current treatments, such as dopaminergic agonists, anticholinergics, or monoamine oxidase inhibitors alleviate PD symptoms, but they can not stop the disease progression. Finding a radical treatment option or stopping the progression is essential when considering that PD is the second most reported neurodegenerative disorder. Many cytokines are released during inflammation, and they can start the phagocytic process, which caused the degradation of infected cells along with healthy ones. Therefore, targeting the pathological mechanisms, such as microglial activation, mitochondrial dysfunction, and oxidative stress, that should be involved in the treatment program is important. Neuroinflammation is one of the key factors involved in PD pathogenesis as well as alpha-synuclein accumulation, synaptic dysfunction, or dopaminergic neuronal loss, especially in the substantia nigra. Therefore, evaluating the therapeutic efficiency of the mechanisms is important, such as microglial activation and nuclear factor-kappa B pathway or inflammasome formation inhibition, and cytokine release interruption against neuroinflammation may create new treatment possibilities for PD. This study examined the pathological relation between PD and neuroinflammation, and targeting neuroinflammation as an opportunity for PD treatments, such as Toll-like receptor antagonists, NOD-like receptor family pyrin domain containing-3 inflammasome inhibitors, cytokine inhibitors, peroxisome proliferator-activated receptor-γ agonists, reactive oxygen species inhibitors, and nonsteroidal anti-inflammatory drugs.

Parkinson's Disease and Sugar Intake-Reasons for and Consequences of a Still Unclear Craving

Lately, studies have shown that patients with Parkinson’s disease (PD) report a strong craving for sweets and consume significantly more fast-acting carbohydrates than healthy controls. Consuming food with a high-sugar content is assumed to lead to an increase in insulin concentration, which could positively influence dopamine concentration in the brain and unconsciously be used by patients as kind of “self-medication” to compensate for a lack of dopamine in PD. On the other hand, high-sugar intake could also lead to insulin resistance and diabetes, which is discussed as a causative factor for progressive neurodegeneration in PD. In this critical appraisal, we discuss the role of sugar intake and insulin on dopamine metabolism in patients with PD and how this could influence the potential neurodegeneration mediated by insulin resistance.

Advances in Potential Cerebrospinal Fluid Biomarkers for Autoimmune Encephalitis: A Review

Autoimmune encephalitis (AE) is a severe inflammatory disease of the brain. Patients with AE demonstrate amnesia, seizures, and psychosis. Recent studies have identified numerous associated autoantibodies (e.g., against NMDA receptors (NMDARs), LGI1, etc.) involved in the pathogenesis of AE, and the levels of diagnosis and treatment are thus improved dramatically. However, there are drawbacks of clinical diagnosis and treatment based solely on antibody levels, and thus the application of additional biomarkers is urgently needed. Considering the important role of immune mechanisms in AE development, we summarize the relevant research progress in identifying cerebrospinal fluid (CSF) biomarkers with a focus on cytokines/chemokines, demyelination, and nerve damage.

Microglia Phenotypes in Aging and Neurodegenerative Diseases

Neuroinflammation is a hallmark of many neurodegenerative diseases (NDs) and plays a fundamental role in mediating the onset and progression of disease. Microglia, which function as first-line immune guardians of the central nervous system (CNS), are the central drivers of neuroinflammation. Numerous human postmortem studies and in vivo imaging analyses have shown chronically activated microglia in patients with various acute and chronic neuropathological diseases. While microglial activation is a common feature of many NDs, the exact role of microglia in various pathological states is complex and often contradictory. However, there is a consensus that microglia play a biphasic role in pathological conditions, with detrimental and protective phenotypes, and the overall response of microglia and the activation of different phenotypes depends on the nature and duration of the inflammatory insult, as well as the stage of disease development. This review provides a comprehensive overview of current research on the various microglia phenotypes and inflammatory responses in health, aging, and NDs, with a special emphasis on the heterogeneous phenotypic response of microglia in acute and chronic diseases such as hemorrhagic stroke (HS), Alzheimer’s disease (AD), and Parkinson’s disease (PD). The primary focus is translational research in preclinical animal models and bulk/single-cell transcriptome studies in human postmortem samples. Additionally, this review covers key microglial receptors and signaling pathways that are potential therapeutic targets to regulate microglial inflammatory responses during aging and in NDs. Additionally, age-, sex-, and species-specific microglial differences will be briefly reviewed.

Neuroprotective approaches to halt Parkinson's disease progression

One of the most significant threats in Parkinson's disease (PD) is neurodegeneration. Neurodegeneration at both nigral as well as non-nigral regions of the brain is considered responsible for disease progression in PD. The key factors that initiate neurodegeneration are oxidative stress, neuroinflammation, mitochondrial complex-1 inhibition, and abnormal α-synuclein (SNCA) protein aggregations. Nigral neurodegeneration results in motor symptoms (tremor, bradykinesia, rigidity, shuffling gait, and postural instability) whereas; non-nigral neurodegeneration is responsible for non-motor symptoms (depression, cognitive dysfunctions, sleep disorders, hallucination, and psychosis). The available therapies for PD aim at increasing dopamine levels. The medications such as Monoamine oxidase B (MAO-B) inhibitors, catechol o-methyltransferase (COMT) inhibitors, Dopamine precursor (Levodopa), dopamine agonists, and dopamine reuptake inhibitors drastically improve the motor symptoms and quality of life only in the early stages of the disease. However, dopa resistant motor symptoms (abnormality in posture, speech impediment, gait, and balance problems), dopa resistant non-motor signs (sleep problems, autonomic dysfunction, mood, and cognitive impairment, pain), and drug-related side effects (motor fluctuations, psychosis, and dyskinesias) are considered responsible for the failure of these therapies. Further, none of the treatments, alone or in combination, are capable of halting the disease progression in the long run. Therefore, there is a need to develop safe and efficient neuroprotective agents, which can slow or stop the disease progression for the better management of PD. In this review, an effort has been made to discuss the various mechanisms responsible for progressive neurodegeneration (disease progression) in PD and also multiple strategies available for halting disease progression.

Reducing neuroinflammation via therapeutic compounds and lifestyle to prevent or delay progression of Parkinson's disease

Parkinson's disease (PD) is the second most common age-associated neurodegenerative disorder and is characterised by progressive loss of dopamine neurons in the substantia nigra. Peripheral immune cell infiltration and activation of microglia and astrocytes are observed in PD, a process called neuroinflammation. Neuroinflammation is a fundamental response to protect the brain but, when chronic, it triggers neuronal damage. In the last decade, central and peripheral inflammation were suggested to occur at the prodromal stage of PD, sustained throughout disease progression, and may play a significant role in the pathology. Understanding the pathological mechanisms of PD has been a high priority in research, primarily to find effective treatments once symptoms are present. Evidence indicates that early life exposure to neuroinflammation as a consequence of life events, environmental or behaviour factors such as exposure to infections, pollution or a high fat diet increase the risk of developing PD. Many studies show healthy habits and products that decrease neuroinflammation also reduce the risk of PD. Here, we aim to stimulate discussion about the role of neuroinflammation in PD onset and progression. We highlight that reducing neuroinflammation throughout the lifespan is critical for preventing idiopathic PD, and present epidemiological studies that detail risk and protective factors. It is possible that introducing lifestyle changes that reduce neuroinflammation at the time of PD diagnosis may slow symptom progression. Finally, we discuss compounds and therapeutics to treat the neuroinflammation associated with PD.

Addressing Peroxisome Proliferator-Activated Receptor-gamma in 3-Nitropropionic Acid-Induced Striatal Neurotoxicity in Rats

Telmisartan (TEL) is an angiotensin II type 1 receptor blocker and a partial activator of peroxisome proliferator-activated receptor-gamma (PPARγ), which regulates inflammatory and apoptotic pathways. Increasing evidence has demonstrated the PPARγ agonistic property of TEL in several brain disorders. This study aims to explore the neuroprotective impact of TEL in 3-nitropropionic acid (3-NP)-induced neurotoxicity in rats. The PPARγ effect of TEL was affirmed by using the PPARγ agonist pioglitazone (PIO), and the antagonist GW9662. 3-NP led to a significant reduction in body weight alongside motor and cognitive functioning. The striata of the 3-NP-treated rats showed energy-deficit, microglia-mediated inflammatory reactions, apoptotic damage as well as histopathological lesions. PIO and TEL improved motor and cognitive perturbations induced by 3-NP, as confirmed by striatal histopathological examination, energy restoration, and neuronal preservation. Both drugs improved mitochondrial biogenesis evidenced by elevated mRNA expression of PPARγ, PGC-1α, and TFAM, alongside increased striatal ATP and SDH. The mitochondrial effect of TEL was beyond PPARγ activation. As well, their anti-inflammatory effect was attributed to suppression of microglial activation, and protein expression of pS536 p65 NF-κB with marked attenuation of striatal inflammatory mediator's release. Anti-inflammatory cytokine IL-10 expression was concurrently increased. TEL effectively participated in neuronal survival as it promoted phosphorylation of Akt/GSK-3β, further increased Bcl-2 expression, and inhibited cleavage of caspase-3. Interestingly, co-treatment with GW9662 partially revoked the beneficial effects of TEL. These findings recommend that TEL improves motor and cognitive performance, while reducing neuronal inflammation and apoptosis in 3-NP-induced neurotoxicity via a PPARγ-dependent mechanism.

Role of JAK-STAT and PPAR-Gamma Signalling Modulators in the Prevention of Autism and Neurological Dysfunctions

The Janus-kinase (JAK) and signal transducer activator of transcription (STAT) signalling pathways regulate gene expression and control various factors involved in normal physiological functions such as cell proliferation, neuronal development, and cell survival. JAK activation phosphorylates STAT3 in astrocytes and microglia, and this phosphorylation has been linked to mitochondrial damage, apoptosis, neuroinflammation, reactive astrogliosis, and genetic mutations. As a regulator, peroxisome proliferator-activated receptor gamma (PPAR-gamma), in relation to JAK-STAT signalling, prevents this phosphorylation and aids in the treatment of the above-mentioned neurocomplications. Changes in cellular signalling may also contribute to the onset and progression of autism. Thus, PPAR-gamma agonist upregulation may be associated with JAK-STAT signal transduction downregulation. It may also be responsible for attenuating neuropathological changes by stimulating SOCS3 or involving RXR or SMRT, thereby reducing transcription of the various cytokine proteins and genes involved in neuronal damage. Along with JAK-STAT inhibitors, PPAR-gamma agonists could be used as target therapeutic interventions for autism. This research-based review explores the potential involvement and mutual regulation of JAK-STAT and PPAR-gamma signalling in controlling multiple pathological factors associated with autism.

Pharmacologic Recruitment of Endogenous Neural Stem/Progenitor Cells for the Treatment of Spinal Cord Injury

STUDY DESIGN

Laboratory study using a rat T9 contusion model of spinal cord injury.

OBJECTIVE

This study aims to examine whether a combinatory treatment of Pioglitazone (PGZ) and granulocyte colony-stimulating factor (GCSF) can support neural stem/progenitor cells (NSPCs) directly and provide a sustainable microenvironment through immunomodulatory mechanisms.

SUMMARY OF BACKGROUND DATA

Neuroinflammation plays a crucial role in the progression of spinal cord injury (SCI) and hinders NSPC-mediated repair and regeneration. Broad acting drugs that mitigate inflammation and support NSPC proliferation have not been tested together in SCI research models.

METHODS

Isolated NSPCs were treated with vehicle control, PGZ, GCSF, or both PGZ and GSCF for 24 hours and stained with proliferation marker Ki67. Adult female Sprague-Dawley rats sustained moderate-to-severe contusion-based SCI at T9 and were administered either vehicle control, PGZ, GCSF, or both PGZ and GCSF treatments.

RESULTS

Immunocytochemistry revealed that cultured NSPCs treated with both drugs produced higher numbers of actively proliferating cells and total cell numbers. ELISA on spinal cord tissue lysates at 1, 3, and 7 days post-injury (DPI) demonstrated that animals treated with PGZ, GCSF, or combination therapy showed significantly higher doublecortin levels at 7 DPI compared to control animals (P < 0.05). Immunohistochemistry of injured tissue at 3, 7, and 14 DPI revealed no difference of ependymal NSPC proliferation between groups, but showed a significant decrease in lesion size with combination therapy compared to controls. Functional recovery was assessed by the Basso, Beattie, Bresnahan locomotor rating scale. Animals treated with both drugs had significantly higher levels of function at 1 (P < 0.001), 3 (P < 0.001), 7 (P < 0.05), and 14 (P < 0.05) DPI compared to controls.

CONCLUSION

These results indicate that PGZ and GCSF treatment synergistically enhance NSPCs numbers and improve functional recovery after SCI. Our findings support an immunomodulatory strategy to recruit native NSPCs as a potential acute care intervention for SCI.Level of Evidence: N/A.

Prevention of L-Dopa-Induced Dyskinesias by MPEP Blockade of Metabotropic Glutamate Receptor 5 Is Associated with Reduced Inflammation in the Brain of Parkinsonian Monkeys

Proinflammatory markers were found in brains of Parkinson’s disease (PD) patients. After years of L-Dopa symptomatic treatment, most PD patients develop dyskinesias. The relationship between inflammation and L-Dopa-induced dyskinesias (LID) is still unclear. We previously reported that MPEP (a metabotropic glutamate receptor 5 antagonist) reduced the development of LID in de novo MPTP-lesioned monkeys. We thus investigated if MPEP reduced the brain inflammatory response in these MPTP-lesioned monkeys and the relationship to LID. The panmacrophage/microglia marker Iba1, the phagocytosis-related receptor CD68, and the astroglial protein GFAP were measured by Western blots. The L-Dopa-treated dyskinetic MPTP monkeys had increased Iba1 content in the putamen, substantia nigra, and globus pallidus, which was prevented by MPEP cotreatment; similar findings were observed for CD68 contents in the putamen and globus pallidus. There was a strong positive correlation between dyskinesia scores and microglial markers in these regions. GFAP contents were elevated in MPTP + L-Dopa-treated monkeys among these brain regions and prevented by MPEP in the putamen and subthalamic nucleus. In conclusion, these results showed increased inflammatory markers in the basal ganglia associated with LID and revealed that MPEP inhibition of glutamate activity reduced LID and levels of inflammatory markers.

The Effects of Rosiglitazone on Task Specific Anxiety-Like Behavior and Novelty Seeking in a Model of Chronic Adolescent Unpredictable Stress

Adolescence is characterized as a period of increased social behavior, risk taking, and novelty seeking, partly due to ongoing maturation in critical brain areas and the hypothalamic-pituitary-adrenal (HPA) negative-feedback system. During this period there is heightened vulnerability to stress that can drive neuro-immune-endocrine remodeling, resulting in the emergence of maladaptive behaviors that increase susceptibility to alcohol and substance abuse. Here we used a rat model to investigate the impact of chronic adolescent unpredictable stress on a battery of behavioral measures to assess anxiety, novelty seeking, risk taking, depression, and voluntary ethanol consumption while determining whether the PPARγ agonist rosiglitazone can attenuate these effects. Adolescent female rats that experienced stress showed increased risk taking behavior and novelty seeking behavior with no change in ethanol consumption. The administration of rosiglitazone during stress induction attenuated stress-induced cortisol elevation, normalized risk taking behavior in a model anxiety, and attenuated novelty seeking in a task-specific manner. Depressive-like behavior was not impacted by adolescent unpredictable stress or the administration of rosiglitazone. The results from this study demonstrate that exposure to unpredictable stress during adolescence increases the prevalence of maladaptive behaviors that are known to increase susceptibility to alcohol and substance abuse, and that rosiglitazone may be an effective therapeutic to attenuate the emergence of select risk taking and novelty seeking behaviors in females.

Repurposing old molecules for new indications: Defining pillars of success from lessons in the past

Drug repurposing or studying existing drugs for potential therapeutic utility in newer indications has been identified as an attractive option for treating a number of diseases. Various strategies of drug repurposing include serendipitous observation of drug's unexpected effects, directing the failed investigational drugs to new indications and currently adopted systematic approach to identify, screen and develop existing drug molecules for new off-label indications. Drug repurposing is able to constructively overcome the bottleneck restraints encountered during traditional de novo drug development process in grounds of timelines, cost and resources. However, success rates of drug repurposing programs are not very impressive. Through a meticulous examination of some failed repurposing attempts we aimed to identify key factors leading to high attrition rate in such studies. Based on the fundamental elements of knowledge and evaluation, we have defined four pillars toward improving success rate in drug repurposing programs viz. sound knowledge of the repurposed drug's pharmacological characteristics (pillar 1: drug pharmacology); drug formulation considerations in new indication (pillar 2: drug formulation); evaluation in representative biological assays with translational potential (pillar 3: evaluation in biological assays); and robust clinical trial methodologies including biomarker driven approach to provide conclusive evidence of repurposed drug's efficacy in new indication (pillar 4: clinical evaluation). In addition to the pharmacological challenges, certain regulatory concerns, including lack of clear guidelines for evaluation and market exclusivity pose hurdles in the application of drug repurposing, which may however be overcome to a great extent by adopting some strategies as discussed in this review.

Two Birds One Stone: The Neuroprotective Effect of Antidiabetic Agents on Parkinson Disease-Focus on Sodium-Glucose Cotransporter 2 (SGLT2) Inhibitors

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease affecting more than 1% of the population over 65 years old. The etiology of the disease is unknown and there are only symptomatic managements available with no known disease-modifying treatment. Aging, genes, and environmental factors contribute to PD development and key players involved in the pathophysiology of the disease include oxidative stress, mitochondrial dysfunction, autophagic-lysosomal imbalance, and neuroinflammation. Recent epidemiology studies have shown that type-2 diabetes (T2DM) not only increased the risk for PD, but also is associated with PD clinical severity. A higher rate of insulin resistance has been reported in PD patients and is suggested to be a pathologic driver in this disease. Oral diabetic drugs including sodium-glucose cotransporter 2 (SGLT2) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, and dipeptidyl peptidase-4 (DPP-4) inhibitors have been shown to provide neuroprotective effects in both PD patients and experimental models; additionally, antidiabetic drugs have been demonstrated to lower incidence rates of PD in DM patients. Among these, the most recently developed drugs, SGLT2 inhibitors may provide neuroprotective effects through improving mitochondrial function and antioxidative effects. In this article, we will discuss the involvement of mitochondrial-related oxidative stress in the development of PD and potential benefits provided by antidiabetic agents especially focusing on sglt2 inhibitors.

Nuclear receptors of NR1 and NR4 subfamilies in the regulation of microglial functions and pathology

This review provides an overview of researches on the NR1 and NR4 nuclear receptors involved in the regulation of microglial functions. Nuclear receptors are attractive candidates for drug targets in the therapies of the central nervous system disorders, because the activation of these receptors is expected to regulate the functions and the phenotypes of microglia, by controlling the expression of specific gene subsets and also by regulating the cellular signaling mechanisms in a nongenomic manner. Several members of NR1 nuclear receptor subfamily have been examined for their ability to regulate microglial functions. For example, stimulation of vitamin D receptor inhibits the production of pro-inflammatory factors and increases the production of anti-inflammatory cytokines. Similar regulatory actions of nuclear receptor ligands on inflammation-related genes have also been reported for other NR1 members such as retinoic acid receptors, peroxisome proliferator-activated receptors (PPARs), and liver X receptors (LXRs). In addition, stimulation of PPARγ and LXRs may also result in increased phagocytic activities of microglia. Consistent with these actions, the agonists at nuclear receptors of NR1 subfamily are shown to produce therapeutic effects on animal models of various neurological disorders such as experimental allergic encephalomyelitis, Alzheimer's disease, Parkinson's disease, and ischemic/hemorrhagic stroke. On the other hand, increasing lines of evidence suggest that the stimulation of NR4 subfamily members of nuclear receptors such as Nur77 and Nurr1 also regulates microglial functions and alleviates neuropathological events in several disease models. Further advancement of these research fields may prove novel therapeutic opportunities.

Elucidating the Neuroprotective Role of PPARs in Parkinson's Disease: A Neoteric and Prospective Target

One of the utmost frequently emerging neurodegenerative diseases, Parkinson's disease (PD) must be comprehended through the forfeit of dopamine (DA)-generating nerve cells in the substantia nigra pars compacta (SN-PC). The etiology and pathogenesis underlying the emergence of PD is still obscure. However, expanding corroboration encourages the involvement of genetic and environmental factors in the etiology of PD. The destruction of numerous cellular components, namely oxidative stress, ubiquitin-proteasome system (UPS) dysfunction, autophagy-lysosome system dysfunction, neuroinflammation and programmed cell death, and mitochondrial dysfunction partake in the pathogenesis of PD. Present-day pharmacotherapy can alleviate the manifestations, but no therapy has been demonstrated to cease disease progression. Peroxisome proliferator-activated receptors (PPARs) are ligand-directed transcription factors pertaining to the class of nuclear hormone receptors (NHR), and are implicated in the modulation of mitochondrial operation, inflammation, wound healing, redox equilibrium, and metabolism of blood sugar and lipids. Numerous PPAR agonists have been recognized to safeguard nerve cells from oxidative destruction, inflammation, and programmed cell death in PD and other neurodegenerative diseases. Additionally, various investigations suggest that regular administration of PPAR-activating non-steroidal anti-inflammatory drugs (NSAIDs) (ibuprofen, indomethacin), and leukotriene receptor antagonists (montelukast) were related to the de-escalated evolution of neurodegenerative diseases. The present review elucidates the emerging evidence enlightening the neuroprotective outcomes of PPAR agonists in in vivo and in vitro models experiencing PD. Existing articles up to the present were procured through PubMed, MEDLINE, etc., utilizing specific keywords spotlighted in this review. Furthermore, the authors aim to provide insight into the neuroprotective actions of PPAR agonists by outlining the pharmacological mechanism. As a conclusion, PPAR agonists exhibit neuroprotection through modulating the expression of a group of genes implicated in cellular survival pathways, and may be a propitious target in the therapy of incapacitating neurodegenerative diseases like PD.

Glitazones Activate PGC-1α Signaling via PPAR-γ: A Promising Strategy for Antiparkinsonism Therapeutics

Understanding various aspects of Parkinson's disease (PD) by researchers could lead to a better understanding of the disease and provide treatment alternatives that could significantly improve the quality of life of patients suffering from neurodegenerative disorders. Significant progress has been made in recent years toward this goal, but there is yet no available treatment with confirmed neuroprotective effects. Recent studies have shown the potential of PPARγ agonists, which are the ligand activated transcriptional factor of the nuclear hormone superfamily, as therapeutic targets for various neurodegenerative disorders. The activation of central PGC-1α mediates the potential role against neurogenerative diseases like PD, Huntington's disease, Alzheimer's disease, and amyotrophic lateral sclerosis. Further understanding the mechanism of neurodegeneration and the role of glitazones in the activation of PGC-1α signaling could lead to a novel therapeutic interventions against PD. Keeping this aspect in focus, the present review highlights the pathogenic mechanism of PD and the role of glitazones in the activation of PGC-1α via PPARγ for the treatment of neurodegenerative disorders.

The CD200R1 microglial inhibitory receptor as a therapeutic target in the MPTP model of Parkinson's disease

Background

It is suggested that neuroinflammation, in which activated microglial cells play a relevant role, contributes to the development of Parkinson’s disease (PD). Consequently, the modulation of microglial activation is a potential therapeutic target to be taken into account to act against the dopaminergic neurodegeneration occurring in this neurological disorder. Several soluble and membrane-associated inhibitory mechanisms contribute to maintaining microglial cells in a quiescent/surveillant phenotype in physiological conditions. However, the presence of activated microglial cells in the brain in PD patients suggests that these mechanisms have been somehow overloaded. We focused our interest on one of the membrane-associated mechanisms, the CD200-CD200R1 ligand-receptor pair.

Methods

The acute MPTP experimental mouse model of PD was used to study the temporal pattern of mRNA expression of CD200 and CD200R1 in the context of MPTP-induced dopaminergic neurodegeneration and neuroinflammation. Dopaminergic damage was assessed by tyrosine hydroxylase (TH) immunoreactivity, and neuroinflammation was evaluated by the mRNA expression of inflammatory markers and IBA1 and GFAP immunohistochemistry. The effect of the modulation of the CD200-CD200R1 system on MPTP-induced damage was determined by using a CD200R1 agonist or CD200 KO mice.

Results

MPTP administration resulted in a progressive decrease in TH-positive fibres in the striatum and TH-positive neurons in the substantia nigra pars compacta, which were accompanied by transient astrogliosis, microgliosis and expression of pro- and anti-inflammatory markers. CD200 mRNA levels rapidly decreased in the ventral midbrain after MPTP treatment, while a transient decrease of CD200R1 mRNA expression was repeatedly observed in this brain area at earlier and later phases. By contrast, a transient increase in CD200R1 expression was observed in striatum. The administration of a CD200R1 agonist resulted in the inhibition of MPTP-induced dopaminergic neurodegeneration, while microglial cells showed signs of earlier activation in CD200-deficient mice.

Conclusions

Collectively, these findings provide evidence for a correlation between CD200-CD200R1 alterations, glial activation and neuronal loss. CD200R1 stimulation reduces MPTP-induced loss of dopaminergic neurons, and CD200 deficiency results in earlier microglial activation, suggesting that the potentiation of CD200R1 signalling is a possible approach to controlling neuroinflammation and neuronal death in PD.

PPARγ/PGC1α signaling as a potential therapeutic target for mitochondrial biogenesis in neurodegenerative disorders

Neurodegenerative diseases represent some of the most devastating neurological disorders, characterized by progressive loss of the structure and function of neurons. Current therapy for neurodegenerative disorders is limited to symptomatic treatment rather than disease modifying interventions, emphasizing the desperate need for improved approaches. Abundant evidence indicates that impaired mitochondrial function plays a crucial role in pathogenesis of many neurodegenerative diseases and so biochemical factors in mitochondria are considered promising targets for pharmacological-based therapies. Peroxisome proliferator-activated receptors-γ (PPARγ) are ligand-inducible transcription factors involved in regulating various genes including peroxisome proliferator-activated receptor gamma co-activator-1 alpha (PGC1α). This review summarizes the evidence supporting the ability of PPARγ-PGC1α to coordinately up-regulate the expression of genes required for mitochondrial biogenesis in neurons and provide directions for future work to explore the potential benefit of targeting mitochondrial biogenesis in neurodegenerative disorders. We have highlighted key roles of NRF2, uncoupling protein-2 (UCP2), and paraoxonase-2 (PON2) signaling in mediating PGC1α-induced mitochondrial biogenesis. In addition, the status of PPARγ modulators being used in clinical trials for Parkinson's disease (PD), Alzheimer's disease (AD) and Huntington's disease (HD) has been compiled. The overall purpose of this review is to update and critique our understanding of the role of PPARγ-PGC1α-NRF2 in the induction of mitochondrial biogenesis together with suggestions for strategies to target PPARγ-PGC1α-NRF2 signaling in order to combat mitochondrial dysfunction in neurodegenerative disorders.

Parkinson's Disease: Can Targeting Inflammation Be an Effective Neuroprotective Strategy?

The reason why dopamine neurons die in Parkinson’s disease remains largely unknown. Emerging evidence points to a role for brain inflammation in neurodegeneration. Essential questions are whether brain inflammation happens sufficiently early so that interfering with this process can be expected to slow down neuronal death and whether the contribution from inflammation is large enough so that anti-inflammatory agents can be expected to work. Here I discuss data from human PD studies indicating that brain inflammation is an early event in PD. I also discuss the role of T-lymphocytes and peripheral inflammation for neurodegeneration. I critically discuss the failure of clinical trials targeting inflammation in PD.

PPARγ activation suppresses the expression of MMP9 by downregulating NF-κB post intracerebral hemorrhage

Peroxisome proliferator-activated receptor-gamma (PPARγ) is critical in protecting against inflammatory and oxidative stresses post brain injury. We have previously reported that rosiglitazone, an agonist of PPARγ, was effective to prevent microglia from apoptosis and ameliorate neuronal injuries post intracerebral hemorrhage (ICH) with suppression of matrix metalloproteinase-9 (MMP9) expression. However, molecular mechanisms linking how PPARγ decreases MMP9 remain unknown. Here, we hypothesize that PPARγ downregulates MMP9 expression post hemorrhage by inhibiting nuclear factor kappa B (NF-κB), an upstream regulator of MMPs gene and also key transcription factor involved in the control of immune and neuroinflammatory responses. We found both in vivo and in vitro that PPARγ was significantly downregulated post ICH with prominent increases of NF-κB and MMP9. Activation of PPARγ using rosiglitazone decreased the expression of both NF-κB and MMP9, while reversed effects were observed when administrating the PPARγ antagonist GW9662. Besides, inhibiting NF-κB by JSH-23 also suppressed the expression of MMP9, with only limited effect on PPARγ. Further studies revealed prominent colocalizations of NF-κB with PPARγ and MMP9, respectively. Finally, direct interactions of NF-κB with PPARγ and MMP9 gene were also confirmed, respectively, by protein and chromatin immunoprecipitations. These results suggested a role of NF-κB in mediating the reduction of MMP9 by PPARγ, potentially providing a new therapeutic target for brain hemorrhage.

Monoamine Oxidase Inhibitors: From Classic to New Clinical Approaches

Monoamine oxidases (MAOs) are involved in the oxidative deamination of different amines and neurotransmitters. This pointed them as potential targets for several disorders and along the last 70 years a wide variety of MAO inhibitors have been developed as successful drugs for the treatment of complex diseases, being the first drugs approved for depression in the late 1950s. The discovery of two MAO isozymes (MAO-A and B) with different substrate selectivity and tissue expression patterns led to novel therapeutic approaches and to the development of new classes of inhibitors, such as selective irreversible and reversible MAO-B inhibitors and reversible MAO-A inhibitors. Significantly, MAO-B inhibitors constitute a widely studied group of compounds, some of them approved for the treatment of Parkinson's disease. Further applications are under development for the treatment of Alzheimer's disease, amyotrophic lateral sclerosis, and cardiovascular diseases, among others. This review summarizes the most important aspects regarding the development and clinical use of MAO inhibitors, going through mechanistic and structural details, new indications, and future perspectives. Monoamine oxidases (MAOs) catalyze the oxidative deamination of different amines and neurotransmitters. The two different isozymes, MAO-A and MAO-B, are located at the outer mitochondrial membrane in different tissues. The enzymatic reaction involves formation of the corresponding aldehyde and releasing hydrogen peroxide (H₂O₂) and ammonia or a substituted amine depending on the substrate. MAO's role in neurotransmitter metabolism made them targets for major depression and Parkinson's disease, among other neurodegenerative diseases. Currently, these compounds are being studied for other diseases such as cardiovascular ones.

Glial cells in Parkinson´s disease: protective or deleterious?

Glial cells have been identified more than 100 years ago, and are known to play a key role in the central nervous system (CNS) function. A recent piece of evidence is emerging showing that in addition to the capacity of CNS modulation and homeostasis, glial cells are also being looked like as a promising cell source not only to study CNS pathologies initiation and progression but also to the establishment and development of new therapeutic strategies. Thus, in the present review, we will discuss the current evidence regarding glial cells' contribution to neurodegenerative diseases as Parkinson's disease, providing cellular, molecular, functional, and behavioral data supporting its active role in disease initiation, progression, and treatment. As so, considering their functional relevance, glial cells may be important to the understanding of the underlying mechanisms regarding neuronal-glial networks in neurodegeneration/regeneration processes, which may open new research opportunities for their future use as a target or treatment in human clinical trials.

Antidiabetic drugs for Alzheimer's and Parkinson's diseases: Repurposing insulin, metformin, and thiazolidinediones

Medical and scientific communities have been striving to disentangle the complexity of neurodegenerative diseases, particularly Alzheimer's disease (AD) and Parkinson's disease (PD), in order to develop a cure or effective treatment for these diseases. Along this journey, it has become important to identify the early events occurring in the prodromal phases of these diseases and the disorders that increase the risk of neurodegeneration highlighting common pathological features. This strategy has led to a wealth of evidence identifying diabetes, mainly type 2 diabetes mellitus (T2DM) as a main risk factor for the onset and progression of AD and PD. Impaired glucose metabolism, insulin resistance, and mitochondrial dysfunction are features common to both type 2 diabetes mellitus (T2DM), and AD and PD, and they appear before clinical diagnosis of the two neurodegenerative diseases. These could represent the strategic nodes of therapeutic intervention. Following this line of thought, a conceivable approach is to repurpose antidiabetic drugs as valuable agents that may prevent or reduce the risk of cognitive decline and neurodegeneration. This review summarizes the past and current findings that link AD and PD with T2DM, emphasizing the common pathological mechanisms. The efficacy of antidiabetic drugs, namely intranasal insulin, metformin, and thiazolidinediones, in the prevention and/or treatment of AD and PD is also discussed.

Rojo A, Manda G, Boscá L, Cuadrado A. Inflammation in Parkinson's Disease: Mechanisms and Therapeutic Implications

Parkinson's disease (PD) is a common neurodegenerative disorder primarily characterized by the death of dopaminergic neurons that project from the substantia nigra pars compacta. Although the molecular bases for PD development are still little defined, extensive evidence from human samples and animal models support the involvement of inflammation in onset or progression. However, the exact trigger for this response remains unclear. Here, we provide a systematic review of the cellular mediators, i.e., microglia, astroglia and endothelial cells. We also discuss the genetic and transcriptional control of inflammation in PD and the immunomodulatory role of dopamine and reactive oxygen species. Finally, we summarize the preclinical and clinical approaches targeting neuroinflammation in PD.

Mitochondrial dysfunction plays a key role in the development of neurodegenerative diseases in diabetes

Mitochondria have an essential function in cell survival due to their role in bioenergetics, reactive oxygen species generation, calcium buffering, and other metabolic activities. Mitochondrial dysfunctions are commonly found in neurodegenerative diseases (NDs), and diabetes is a risk factor for NDs. However, the role of mitochondria in diabetic neurodegeneration is still unclear. In the present study, we review the latest evidence on the role of mitochondrial dysfunctions in the development of diabetes-related NDs and the underlying molecular mechanisms. Hypoglycemic agents, especially metformin, have been proven to have neuroprotective effects in the treatment of diabetes, in which mitochondria could act as one of the underlying mechanisms. Other hypoglycemic agents, including thiazolidinediones (TZDs), dipeptidyl peptidase 4 (DPP-4) inhibitors, and glucagon-like peptide 1 (GLP-1) receptor agonists, have gained more attention because of their beneficial effects on NDs, presumably by improving mitochondrial function. Our review highlights the notion that mitochondria could be a promising therapeutic target in the treatment of NDs in patients with diabetes.

The Novel Role of PPAR Alpha in the Brain: Promising Target in Therapy of Alzheimer's Disease and Other Neurodegenerative Disorders

Peroxisome proliferator activated receptor alpha (PPAR-α) belongs to the family of ligand-regulated nuclear receptors (PPARs). These receptors after heterodimerization with retinoid X receptor (RXR) bind in promotor of target genes to PPAR response elements (PPREs) and act as a potent transcription factors. PPAR-α and other receptors from this family, such as PPAR-β/δ and PPAR-γ are expressed in the brain and other organs and play a significant role in oxidative stress, energy homeostasis, mitochondrial fatty acids metabolism and inflammation. PPAR-α takes part in regulation of genes coding proteins that are involved in glutamate homeostasis and cholinergic/dopaminergic signaling in the brain. Moreover, PPAR-α regulates expression of genes coding enzymes engaged in amyloid precursor protein (APP) metabolism. It activates gene coding of α secretase, which is responsible for non-amyloidogenic pathway of APP degradation. It also down regulates β secretase (BACE-1), the main enzyme responsible for amyloid beta (Aβ) peptide release in Alzheimer Diseases (AD). In AD brain expression of genes of PPAR-α and PPAR-γ coactivator-1 alpha (PGC-1α) is significantly decreased. PPARs are altered not only in AD but in other neurodegenerative/neurodevelopmental and psychiatric disorder. PPAR-α downregulation may decrease anti-oxidative and anti-inflammatory processes and could be responsible for the alteration of fatty acid transport, lipid metabolism and disturbances of mitochondria function in the brain of AD patients. Specific activators of PPAR-α may be important for improvement of brain cells metabolism and cognitive function in neurodegenerative and neurodevelopmental disorders.

Cannabidiol and Cannabinoid Compounds as Potential Strategies for Treating Parkinson's Disease and L-DOPA-Induced Dyskinesia

Parkinson's disease (PD) and L-DOPA-induced dyskinesia (LID) are motor disorders with significant impact on the patient's quality of life. Unfortunately, pharmacological treatments that improve these disorders without causing severe side effects are not yet available. Delay in initiating L-DOPA is no longer recommended as LID development is a function of disease duration rather than cumulative L-DOPA exposure. Manipulation of the endocannabinoid system could be a promising therapy to control PD and LID symptoms. In this way, phytocannabinoids and synthetic cannabinoids, such as cannabidiol (CBD), the principal non-psychotomimetic constituent of the Cannabis sativa plant, have received considerable attention in the last decade. In this review, we present clinical and preclinical evidence suggesting CBD and other cannabinoids have therapeutic effects in PD and LID. Here, we discuss CBD pharmacology, as well as its neuroprotective effects and those of other cannabinoids. Finally, we discuss the modulation of several pro- or anti-inflammatory factors as possible mechanisms responsible for the therapeutic/neuroprotective potential of Cannabis-derived/cannabinoid synthetic compounds in motor disorders.

PU-91 drug rescues human age-related macular degeneration RPE cells; implications for AMD therapeutics

Since mitochondrial dysfunction is implicated in the pathogenesis of AMD, this study is based on the premise that repurposing of mitochondria-stabilizing FDA-approved drugs such as PU-91, might rescue AMD RPE cells from AMD mitochondria-induced damage. The PU-91 drug upregulates PGC-1α which is a critical regulator of mitochondrial biogenesis. Herein, we tested the therapeutic potential of PU-91 drug and examined the additive effects of treatment with PU-91 and esterase inhibitors i.e., EI-12 and EI-78, using the in vitro transmitochondrial AMD cell model. This model was created by fusing platelets obtained from AMD patients with Rho⁰ i.e., mitochondria-deficient, ARPE-19 cell lines. The resulting AMD RPE cell lines have identical nuclei but differ in their mitochondrial DNA content, which is derived from individual AMD patients. Briefly, we report significant improvement in cell survival, mitochondrial health, and antioxidant potential in PU-91-treated AMD RPE cells compared to their untreated counterparts. In conclusion, this study identifies PU 91 as a therapeutic candidate drug for AMD and repurposing of PU-91 will be a smoother transition from lab bench to clinic since the pharmacological profiles of PU-91 have been examined already.

Beneficial effects of curtailing immune susceptibility in an Alzheimer's disease model

BACKGROUND

Currently, there are no effective therapeutic options for Alzheimer's disease, the most common, multifactorial form of dementia, characterized by anomalous amyloid accumulation in the brain. Growing evidence points to neuroinflammation as a major promoter of AD. We have previously shown that the proinflammatory cytokine TNFSF10 fuels AD neuroinflammation, and that its immunoneutralization results in improved cognition in the 3xTg-AD mouse.

METHODS

Here, we hypothesize that inflammatory hallmarks of AD might parallel with central and peripheral immune response dysfunction. To verify such hypothesis, we used a triple transgenic mouse model of AD. 3xTg-AD mice were treated for 12 months with an anti-TNFSF10 antibody, and thereafter immune/inflammatory markers including COX2, iNOS, IL-1β and TNF-α, CD3, GITR, and FoxP3 (markers of regulatory T cells) were measured in the spleen as well as in the hippocampus.

RESULTS

Spleens displayed accumulation of amyloid-β1-42 (Aβ1-42), as well as high expression of Treg cell markers FoxP3 and GITR, in parallel with the increased levels of inflammatory markers COX2, iNOS, IL-1β and TNF-α, and blunted IL-10 expression. Moreover, CD3 expression was increased in the hippocampus, consistently with FoxP3 and GITR. After chronic treatment of 3xTg-AD mice with an anti-TNFSF10 antibody, splenic FoxP3, GITR, and the above-mentioned inflammatory markers expression was restored to basal levels, while expression of IL-10 was increased. A similar picture was observed in the hippocampus. Such improvement of peripheral and CNS inflammatory/immune response was associated with decreased microglial activity in terms of TNFα production, as well as decreased expression of both amyloid and phosphorylated tau protein in the hippocampus of treated 3xTg-AD mice. Interestingly, we also reported an increased expression of both CD3 and FoxP3, in sections from human AD brain.

CONCLUSIONS

We suggest that neuroinflammation in the brain of 3xTg-AD mice triggered by TNFSF10 might result in a more general overshooting of the immune response. Treatment with an anti-TNFSF10 antibody blunted inflammatory processes both in the spleen and hippocampus. These data confirm the detrimental role of TNFSF10 in neurodegeneration, and corroborate the hypothesis of the anti-TNFSF10 strategy as a potential treatment to improve outcomes in AD.

Immunomodulatory drugs alleviate l-dopa-induced dyskinesia in a rat model of Parkinson's disease

BACKGROUND

Thalidomide and closely related analogues are used clinically for their immunomodulatory and antiangiogenic properties mediated by the inhibition of the proinflammatory cytokine tumor necrosis factor α. Neuroinflammation and angiogenesis contribute to classical neuronal mechanisms underpinning the pathophysiology of l-dopa-induced dyskinesia, a motor complication associated with l-dopa therapy in Parkinson's disease. The efficacy of thalidomide and the more potent derivative 3,6'-dithiothalidomide on dyskinesia was tested in the 6-hydroxydopamine Parkinson's disease model.

METHODS

Three weeks after 6-hydroxydopamine infusion, rats received 10 days of treatment with l-dopa plus benserazide (6 mg/kg each) and thalidomide (70 mg/kg) or 3,6'-dithiothalidomide (56 mg/kg), and dyskinesia and contralateral turning were recorded daily. Rats were euthanized 1 hour after the last l-dopa injection, and levels of tumor necrosis factor-α, interleukin-10, OX-42, vimentin, and vascular endothelial growth factor immunoreactivity were measured in their striatum and substantia nigra reticulata to evaluate neuroinflammation and angiogenesis. Striatal levels of GLUR1 were measured as a l-dopa-induced postsynaptic change that is under tumor necrosis factor-α control.

RESULTS

Thalidomide and 3,6'-dithiothalidomide significantly attenuated the severity of l-dopa-induced dyskinesia while not affecting contralateral turning. Moreover, both compounds inhibited the l-dopa-induced microgliosis and excessive tumor necrosis factor-α in the striatum and substantia nigra reticulata, while restoring physiological levels of the anti-inflammatory cytokine interleukin-10. l-Dopa-induced angiogenesis was inhibited in both basal ganglia nuclei, and l-dopa-induced GLUR1 overexpression in the dorsolateral striatum was restored to normal levels.

CONCLUSIONS

These data suggest that decreasing tumor necrosis factor-α levels may be useful to reduce the appearance of dyskinesia, and thalidomide, and more potent derivatives may provide an effective therapeutic approach to dyskinesia. © 2019 International Parkinson and Movement Disorder Society.

Neuronal NMDAR Currents of the Hippocampus and Learning Performance in Autoimmune Anti-NMDAR Encephalitis and Involvement of TNF-α and IL-6

Among autoimmune encephalitis, patients with anti-N-methyl D- aspartate receptor (NMDAR) encephalitis typically present epileptic seizures, memory deficits and psychiatric symptoms. However, the signal mechanisms leading to the functional disorders of autoantibodies are largely unclear. In this study, anti-NMDAR antibody was administered into dentate gyri against the NR1 subunit of the NMDAR. The purpose of the study examined the effects of pro-inflammatory tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) on neuronal NMDAR currents of the hippocampus in rats with anti-NMDAR encephalitis and we further determined the role played by TNF-α and IL-6 in modulating learning performance. In results, we observed a decrease in amplitude of the NMDAR-mediated excitatory postsynaptic currents (NMDAR-EPSCs) in the hippocampal neurons of animals treated with anti-NMDAR. In those rats with anti-NMDAR, we also observed impaired learning performance in the Morris water maze and spatial working memory test. Of note, cerebral infusion of TNF-α and IL-6 worsened NMDAR-EPSCs and this was accompanied with exaggeration of impaired learning performance. In conclusion, our findings suggest that the role played by neuroinflammation in exacerbating the memory impairment found in animals treated with anti-NMDAR. Anti-inflammation is a potential target in improving the memory impairment induced by anti-NMDA encephalitis.

Immune system and new avenues in Parkinson’s disease research and treatment

Parkinson’s disease (PD) is a progressive neurological disorder characterized by degeneration of dopaminergic neurons in the substantia nigra. However, although 200 years have now passed since the primary clinical description of PD by James Parkinson, the etiology and mechanisms of neuronal loss in this disease are still not fully understood. In addition to genetic and environmental factors, activation of immunologic responses seems to have a crucial role in PD pathology. Intraneuronal accumulation of α-synuclein (α-Syn), as the main pathological hallmark of PD, potentially mediates initiation of the autoimmune and inflammatory events through, possibly, auto-reactive T cells. While current therapeutic regimens are mainly used to symptomatically suppress PD signs, application of the disease-modifying therapies including immunomodulatory strategies may slow down the progressive neurodegeneration process of PD. The aim of this review is to summarize knowledge regarding previous studies on the relationships between autoimmune reactions and PD pathology as well as to discuss current opportunities for immunomodulatory therapy.

Novel Approaches for the Treatment of Alzheimer's and Parkinson's Disease

Neurodegenerative disorders affect around one billion people worldwide. They can arise from a combination of genomic, epigenomic, metabolic, and environmental factors. Aging is the leading risk factor for most chronic illnesses of old age, including Alzheimer’s and Parkinson’s diseases. A progressive neurodegenerative process and neuroinflammation occur, and no current therapies can prevent, slow, or halt disease progression. To date, no novel disease-modifying therapies have been shown to provide significant benefit for patients who suffer from these devastating disorders. Therefore, early diagnosis and the discovery of new targets and novel therapies are of upmost importance. Neurodegenerative diseases, like in other age-related disorders, the progression of pathology begins many years before the onset of symptoms. Many efforts in this field have led to the conclusion that exits some similar events among these diseases that can explain why the aging brain is so vulnerable to suffer neurodegenerative diseases. This article reviews the current knowledge about these diseases by summarizing the most common features of major neurodegenerative disorders, their causes and consequences, and the proposed novel therapeutic approaches.

Novel Targets for Parkinson's Disease: Addressing Different Therapeutic Paradigms and Conundrums

Parkinson's disease (PD) is a neurodegenerative disease that is pathologically characterized by degeneration of dopamine neurons in the substantia nigra pars compacta (SNpc). PD leads to clinical motor features that include rigidity, tremor, and bradykinesia. Despite multiple available therapies for PD, the clinical features continue to progress, and patients suffer progressive disability. Many advances have been made in PD therapy which directly target the cause of the disease rather than providing symptomatic relief. A neuroprotective or disease modifying strategy that can slow or cease clinical progression and worsening disability remains as a major unmet medical need for PD management. The present review discusses potential novel therapies for PD that include recent interventions in the form of immunomodulatory techniques and stem cell therapy. Further, an introspective approach to identify numerous other novel targets that can alleviate PD pathogenesis and enable physicians to practice multitargeted therapy and that may provide a ray of hope to PD patients in the future are discussed.

Pioglitazone Represents an Effective Therapeutic Target in Preventing Oxidative/Inflammatory Cochlear Damage Induced by Noise Exposure

Recent progress in hearing loss research has provided strong evidence for the imbalance of cellular redox status and inflammation as common predominant mechanisms of damage affecting the organ of Corti including noise induced hearing loss. The discovery of a protective molecule acting on both mechanisms is challenging. The thiazolidinediones, a class of antidiabetic drugs including pioglitazone and rosiglitazone, have demonstrated diverse pleiotrophic effects in many tissues where they exhibit anti-inflammatory, anti-proliferative, tissue protective effects and regulators of redox balance acting as agonist of peroxisome proliferator-activated receptors (PPARs). They are members of the family of ligand regulated nuclear hormone receptors that are also expressed in several cochlear cell types, including the outer hair cells. In this study, we investigated the protective capacity of pioglitazone in a model of noise-induced hearing loss in Wistar rats and the molecular mechanisms underlying this protective effects. Specifically, we employed a formulation of pioglitazone in a biocompatible thermogel providing rapid, uniform and sustained inner ear drug delivery via transtympanic injection. Following noise exposure (120 dB, 10 kHz, 1 h), different time schedules of treatment were employed: we explored the efficacy of pioglitazone given immediately (1 h) or at delayed time points (24 and 48 h) after noise exposure and the time course and extent of hearing recovery were assessed. We found that pioglitazone was able to protect auditory function at the mid-high frequencies and to limit cell death in the cochlear basal/middle turn, damaged by noise exposure. Immunofluorescence and western blot analysis provided evidence that pioglitazone mediates both anti-inflammatory and anti-oxidant effects by decreasing NF-κB and IL-1β expression in the cochlea and opposing the oxidative damage induced by noise insult. These results suggest that intratympanic pioglitazone can be considered a valid therapeutic strategy for attenuating noise-induced hearing loss and cochlear damage, reducing inflammatory signaling and restoring cochlear redox balance.

Boosting phagocytosis and anti-inflammatory phenotype in microglia mediates neuroprotection by PPARγ agonist MDG548 in Parkinson's disease models

BACKGROUND AND PURPOSE

Microglial phenotype and phagocytic activity are deregulated in Parkinson's disease (PD). PPARγ agonists are neuroprotective in experimental PD, but their role in regulating microglial phenotype and phagocytosis has been poorly investigated. We addressed it by using the PPARγ agonist MDG548.

EXPERIMENTAL APPROACH

Murine microglial cell line MMGT12 was stimulated with LPS and/or MDG548, and their effect on phagocytosis of fluorescent microspheres or necrotic neurons was investigated by flow cytometry. Cytokines and markers of microglia phenotype, such as mannose receptor C type 1; MRC1), Ym1 and CD68 were measured by elisa and fluorescent immunohistochemistry. Levels of Beclin-1, which plays a role in microglial phagocytosis, were measured by Western blotting. In the in vivo MPTP-probenecid (MPTPp) model of PD in mice, MDG548 was tested on motor impairment, nigral neurodegeneration, microglial activation and phenotype.

KEY RESULTS

In LPS-stimulated microglia, MDG548 increased phagocytosis of both latex beads and necrotic cells, up-regulated the expression of MRC1, CD68 and to a lesser extent IL-10, while blocking the LPS-induced increase of TNF-α and iNOS. MDG548 also induced Beclin-1. Chronic MPTPp treatment in mice down-regulated MRC1 and TGF-β and up-regulated TNF-α and IL-1β immunoreactivity in activated CD11b-positive microglia, causing the death of nigral dopaminergic neurons. MDG548 arrested MPTPp-induced cell death, enhanced MRC1 and restored cytokine levels.

CONCLUSIONS AND IMPLICATIONS

This study adds a novel mechanism for PPARγ-mediated neuroprotection in PD and suggests that increasing phagocytic activity and anti-inflammatory markers may represent an effective disease-modifying approach.

New Therapeutics to Modulate Mitochondrial Function in Neurodegenerative Disorders

BACKGROUND

Mitochondrial function and energy metabolism are impaired in neurodegenerative diseases. There is evidence for these functional declines both within the brain and systemically in Alzheimer's disease, Parkinson's disease, and Amyotrophic Lateral Sclerosis. Due to these observations, therapeutics targeted to alter mitochondrial function and energy pathways are increasingly studied in pre-clinical and clinical settings.

METHODS

The goal of this article was to review therapies with specific implications on mitochondrial energy metabolism published through May 2016 that have been tested for treatment of neurodegenerative diseases.

RESULTS

We discuss implications for mitochondrial dysfunction in neurodegenerative diseases and how this drives new therapeutic initiatives.

CONCLUSION

Thus far, treatments have achieved varying degrees of success. Further investigation into the mechanisms driving mitochondrial dysfunction and bioenergetic failure in neurodegenerative diseases is warranted.

Polarization of Microglia to the M2 Phenotype in a Peroxisome Proliferator-Activated Receptor Gamma-Dependent Manner Attenuates Axonal Injury Induced by Traumatic Brain Injury in Mice

Increasing evidence indicates that activated microglia play an important role in the inflammatory response following traumatic brain injury (TBI). Inhibiting M1 and stimulating M2 activated microglia have demonstrated protective effects in several animal models of central nervous system diseases. However, it is not clear whether the polarization of microglia to M2 attenuates axonal injury following TBI. In this study, we used a lateral fluid percussion injury device to induce axonal injury in mice. Mice were randomly assigned to the sham, TBI, TBI + rosiglitazone (peroxisome proliferator-activated receptor gamma [PPAR-γ] agonist), and TBI + GW9662 (PPAR-γ antagonist) groups. Axonal injury was assessed using immunohistochemical staining for beta amyloid precursor protein. The inflammatory response was assessed by enzyme-linked immunosorbent assay, microglia polarization was assessed using specific markers of M1 and M2 microglia, and neurological function was assessed using the neurological severity score. Following TBI, microglia of the M1 phenotype increased significantly, while those of the M2 phenotype decreased. Rosiglitazone-induced PPAR-γ activation promoted microglia polarization to the M2 phenotype, which reduced the inflammatory response, attenuated axonal injury in the cerebral cortex, and improved neurological function. Conversely, GW9662 inhibited the polarization of microglia to M2 and aggravated inflammation and axonal injury. Our in vitro findings in lipopolysaccharide-induced microglia were consistent with those of our in vivo experiments. In conclusion, the polarization of microglia to the M2 phenotype via PPAR-γ activation attenuated axonal injury following TBI in mice, which may be a potential therapeutic approach for TBI-induced axonal injury.