Inflammatory process as a determinant factor for the degeneration of substantia nigra dopaminergic neurons

Histamine and receptors in neuroinflammation: Their roles on neurodegenerative diseases

Histamine, an auto-reactive substance and mediator of inflammation, is synthesized from histidine through the action of histidine decarboxylase (HDC). It primarily acts on histamine receptors in the central nervous system (CNS). Increasing evidence suggests that histamine and its receptors play a crucial role in neuroinflammation, thereby modulating the pathology of neurodegenerative diseases. Recent studies have demonstrated that histamine regulates the phenotypic switching of microglia and astrocytes, inhibits the production of pro-inflammatory cytokines, and alleviates inflammatory responses. In the CNS, our research group has also found that histamine and its receptors are involved in regulating inflammatory responses and play a central role in ameliorating chronic neuroinflammation in neurodegenerative diseases. In this review, we will discuss the role of histamine and its receptors in neuroinflammation associated with neurodegenerative diseases, potentially providing a novel therapeutic target for the treatment of chronic neuroinflammation-related neurodegenerative diseases in clinical settings.

Blood-brain barrier biomarkers

The blood-brain barrier (BBB) is a dynamic interface that regulates the exchange of molecules and cells between the brain parenchyma and the peripheral blood. The BBB is mainly composed of endothelial cells, astrocytes and pericytes. The integrity of this structure is essential for maintaining brain and spinal cord homeostasis and protection from injury or disease. However, in various neurological disorders, such as traumatic brain injury, Alzheimer's disease, and multiple sclerosis, the BBB can become compromised thus allowing passage of molecules and cells in and out of the central nervous system parenchyma. These agents, however, can serve as biomarkers of BBB permeability and neuronal damage, and provide valuable information for diagnosis, prognosis and treatment. Herein, we provide an overview of the BBB and changes due to aging, and summarize current knowledge on biomarkers of BBB disruption and neurodegeneration, including permeability, cellular, molecular and imaging biomarkers. We also discuss the challenges and opportunities for developing a biomarker toolkit that can reliably assess the BBB in physiologic and pathophysiologic states.

Periodontitis and Neuropathic Diseases: A Literature Review

Aim

This narrative review aimed at identifying the existing scientific literature investigating periodontitis and neuropathic diseases.

Materials and Methods

A search of the literature published between 2000 and 2022 was carried out in the electronic databases of Scopus and PubMed. Studies in which the eligible articles were mainly published in English were included. Descriptive correlational studies, case-control studies, comparative studies, and cohort studies were also included. The following main keywords were used: "Neuropathic diseases," "Periodontitis," "Alzheimer's disease," and "Porphyromonas gingivalis."

Results

This narrative review found that cognitively impaired persons with severe periodontitis had a higher prevalence and incidence of periodontal diseases than the rest of the population. A significant positive correlation of salivary interleukin (IL)-1beta and immediate recall scores involved in cognition was also evident. It indicates that the most investigated parameter was whether there is any common link between periodontal disease and neurodegeneration. No randomized controlled clinical studies were found in the current literature review.

Conclusions

Based on the literature reviewed, there is currently no strong scientific evidence to support or discourage the cause-effect relationship of periodontal diseases and neurodegenerative diseases.

Association of chronic periodontitis with multiple sclerosis: A systematic review and meta-analysis

BACKGROUND

Chronic periodontitis (CP) is a multifactorial, chronic inflammatory disease of microbial etiology that manifests as a result of the dysfunction of the immune mechanism, culminating in the destruction of the alveolar bone of the jaws. Multiple sclerosis (MS) is an autoimmune disorder that affects the central nervous system (CNS), leads to demyelination and degeneration of nerve axons and often causes severe physical and/or cognitive impairment. As CP and MS involve inflammatory mechanisms and immune dysfunction, researchers have attempted to study the association between them.

AIM

To systematically review the literature on the epidemiological association between CP and MS in adults.

METHODS

PRISMA 2020 statement was used in the study protocol. The design was done according to the Cochrane methodology. A comprehensive literature search was performed in PubMed, Scopus and Cochrane databases; a manual search and evaluation of the gray literature was also performed. The meta-analysis was performed by Review Manager (RevMan) 5.4. Odds ratio (OR) with 95% confidence interval (CI) was defined as the effect size of the outcome. Heterogeneity was assessed by Chi-square and I2. The articles evaluated were written in English, without a time limit, concern observational studies (patient-controls) and report the diagnostic criteria of the diseases. Duplicate entries were excluded. To evaluate the reliability of the results of each study, Newcastle-Ottawa Scale (NOS) and GRADE tools were used. Two independent reviewers did all evaluations with a resolution of discrepancies by a third.

RESULTS

Meta-analysis included three observation studies examined 3376 people. MS patients are significantly more likely to be diagnosed with CP than healthy controls (OR 1.93, 95% CI 1.54-2.42, p<0.0001).

CONCLUSION

A high prevalence of CP was found among MS patients compared with healthy controls. Healthcare professionals should be aware of the association between these pathological entities to provide patients with high-quality care through an effective and holistic diagnostic and therapeutic approach.

Peridontitis as a Risk Factor for Attention Deficit Hyperactivity Disorder: Possible Neuro-inflammatory Mechanisms

Periodontitis is a condition caused mostly by the creation of a biofilm by the bacterium P. gingivalis, which releases toxins and damages the tooth structure. Recent research studies have reported association between dental health and neuropsychiatric illnesses. Neuroinflammation triggered by the first systemic inflammation caused by the bacterium present in the oral cavities is a plausible explanation for such a relationship. Substantial amount of evidence supports the role of neuroinflammation and dysfunction of the dopaminergic system in the pathology of ADHD (Attention deficit hyperactivity disorders). Recent epidemiological, microbiological and inflammatory findings strengthen that, periodontal bacteria, which cause systemic inflammation can contribute to neuroinflammation and finally ADHD. Although both diseases are characterized by inflammation, the specific pathways and crosslink's between periodontitis and ADHD remain unknown. Here, the authors describe the inflammatory elements of periodontitis, how this dental illness causes systemic inflammation, and how this systemic inflammation contributes to deteriorating neuroinflammation in the evolution of ADHD. Therefore, the aim of this review is to present possible links and mechanisms that could confirm the evidence of this association.

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.

Peripheral administration of the Class-IIa HDAC inhibitor MC1568 partially protects against nigrostriatal neurodegeneration in the striatal 6-OHDA rat model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterised by nigrostriatal dopaminergic (DA) neurodegeneration. There is a critical need for neuroprotective therapies, particularly those that do not require direct intracranial administration. Small molecule inhibitors of histone deacetylases (HDIs) are neuroprotective in in vitro and in vivo models of PD, however it is unknown whether Class IIa-specific HDIs are neuroprotective when administered peripherally. Here we show that 6-hydroxydopamine (6-OHDA) treatment induces protein kinase C (PKC)-dependent nuclear accumulation of the Class IIa histone deacetylase (HDAC)5 in SH-SY5Y cells and cultured DA neurons in vitro. Treatment of these cultures with the Class IIa-specific HDI, MC1568, partially protected against 6-OHDA-induced cell death. In the intrastriatal 6-OHDA lesion in vivo rat model of PD, MC1568 treatment (0.5 mg/kg i.p.) for 7 days reduced forelimb akinesia and partially protected DA neurons in the substantia nigra and their striatal terminals from 6-OHDA-induced neurodegeneration. MC1568 treatment prevented 6-OHDA-induced increases in microglial activation in the striatum and substantia nigra. Furthermore, MC1568 treatment decreased 6-OHDA-induced increases in nuclear HDAC5 in nigral DA neurons. These data suggest that peripheral administration of Class IIa-specific HDIs may be a potential therapy for neuroprotective in PD.

Rifampicin ameliorates lipopolysaccharide-induced cognitive and motor impairments via inhibition of the TLR4/MyD88/NF-κB signaling pathway in mice

OBJECTIVES

Aberrant microglial responses promote neuroinflammation in neurodegenerative diseases. However, rifampicin's effect on cognitive and motor sequelae of inflammation remains unknown. Therefore, we investigated whether rifampicin exerts neuroprotection against lipopolysaccharide (LPS)-induced cognitive and motor impairments.

METHODS

A mouse model of LPS-induced cognitive and motor impairment was established. Adult C57BL/6 mice were injected intraperitoneally with 25 mg/kg rifampicin 30 min before intraperitoneal microinjection of LPS (750 μg/kg) daily until study end. Treatments and behavioral experiments were performed once daily for 7 days. Behavioral tests and pathological/biochemical assays were performed to evaluate LPS-induced damage to the hippocampus and substantia nigra (SN).

RESULTS

Rifampicin attenuated LPS-induced cognitive and motor impairments, based on performance in the behavioral tests. Rifampicin suppressed the release of pro-inflammatory mediators, including tumor necrosis factor-α, interleukin-1β, and prostaglandin E₂ in the serum and nitric oxide (NO) in brain tissue, and cyclooxygenase-2 and inducible nitric oxide synthase levels. Immunofluorescence revealed that rifampicin inhibited LPS-induced microglial activation in the hippocampus and SN, thus protecting the neurons. Rifampicin inhibited the activation of the toll-like receptor 4 (TLR4)/myeloid differentiation primary response 88 (MyD88)/nuclear factor kappa B (NF-κB) signaling pathway. Rifampicin downregulated TLR4 and MyD88 protein levels and inhibited NF-κB inhibitor alpha and NF-κB inhibitor kinase beta phosphorylation, thus reducing p65 nuclear transfer by inhibiting NF-κB signaling activation in LPS-treated mice.

CONCLUSION

Rifampicin protects against LPS-induced neuroinflammation and attenuates cognitive and motor impairments by inhibiting the TLR4/MyD88/NF-κB signaling pathway. Our findings might aid the development of novel therapies to treat progressive neurodegenerative diseases.

Potential Role of Natural Polyphenols against Protein Aggregation Toxicity: In Vitro, In Vivo, and Clinical Studies

One of the main features of neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease is the amyloidogenic behavior of disease-specific proteins including amyloid β, tau, α-synuclein, and mutant Huntingtin which participate in the formation, accumulation, and deposition of toxic misfolded aggregates. Consequently, these proteins not only associated with the progress of their respective neurodegenerative pathologies but also qualify as disease-specific biomarkers. The aim of using natural polyphenols is to target amyloid-dependent proteopathies by decreasing free radical damage and inhibiting and dissolving amyloid fibrils. We explore the effectiveness of the polyphenols epigallocatechin-3-gallate, oleuropein aglycone, and quercetin on their ability to inhibit aggregation of amyloid β, tau, and α-synuclein and mitigate other pathological features for Alzheimer's disease and Parkinson's disease. The analysis was carried from in vitro and cell line studies to animal models and clinical trials. This Review describes the use of phytochemical compounds as prophylactic agents for Alzheimer's disease, Parkinson's disease, and other proteopathies.

Association of Tooth Loss with New-Onset Parkinson's Disease: A Nationwide Population-Based Cohort Study

Introduction

Tooth loss is associated with poor oral hygiene. During insufficient oral sanitation, focal infection and inflammation can occur and these reactions may induce systemic inflammation. Systemic inflammatory reaction may be related to the degeneration of dopamine neurons in the substantia nigra. We hypothesized that tooth loss is related to increased risk of new-onset Parkinson's disease.

Methods

Between 2003 and 2006, we included 153,165 participants from the national health insurance system-health screening cohort in Korea. The incidence of new-onset Parkinson's disease was defined as International Classification of Diseases-10 code “G20,” accompanying the prescription records for any anti-Parkinson's disease medication.

Results

Approximately 19.9% of the included participants had periodontal disease. After a median duration of 10.4 years, 1,227 (0.8%) cases of new-onset Parkinson's disease were noted. The number of tooth loss was positively related to an increased risk of new-onset Parkinson's disease. Contrastingly, the frequency of tooth brushings and dental clinic visits for any causes as well as competent dental care were negatively related to the development of new-onset Parkinson's disease. In multivariable analysis, the number of tooth loss (≥15) was positively related to new-onset Parkinson's disease development (hazard ratio: 1.38, 95% confidence interval (1.03–1.85), p=0.029, p for trend = 0.043) after adjusting variables.

Conclusion

Our study demonstrated that the number of tooth loss was positively correlated with a higher risk of new-onset Parkinson's disease development in a longitudinal study setting. Increased number of tooth loss may be an important risk indicator of new-onset Parkinson's disease.

Beyond Host Defense: Deregulation of Drosophila Immunity and Age-Dependent Neurodegeneration

Age-dependent neurodegenerative disorders are a set of diseases that affect millions of individuals worldwide. Apart from a small subset that are the result of well-defined inherited autosomal dominant gene mutations (e.g., those encoding the β-amyloid precursor protein and presenilins), our understanding of the genetic network that underscores their pathology, remains scarce. Genome-wide association studies (GWAS) especially in Alzheimer's disease patients and research in Parkinson's disease have implicated inflammation and the innate immune response as risk factors. However, even if GWAS etiology points toward innate immunity, untangling cause, and consequence is a challenging task. Specifically, it is not clear whether predisposition to de-regulated immunity causes an inadequate response to protein aggregation (such as amyloid or α-synuclein) or is the direct cause of this aggregation. Given the evolutionary conservation of the innate immune response in Drosophila and humans, unraveling whether hyperactive immune response in glia have a protective or pathological role in the brain could be a potential strategy in combating age-related neurological diseases.

Preoperative Sleep Disturbance Exaggerates Surgery-Induced Neuroinflammation and Neuronal Damage in Aged Mice

Postoperative cognitive dysfunction (POCD) is defined as new cognitive impairment (memory impairment and impaired performance) after surgery, especially in aged patients. Sleep disturbance is a common phenomenon before surgery that has been increasingly thought to affect patient recovery. However, little is known about the functional impact of preoperative sleep disturbance on POCD. Here, we showed that tibial fracture surgery induced cognitive deficit and production of proinflammatory cytokines interleukin-6 (IL-6) and IL-1β, along with microglia and astrocyte activation, neuronal damage, and blood-brain barrier (BBB) disruption. Preoperative sleep disturbance enhanced the surgery-induced neuroinflammation, neuronal damage, BBB disruption, and memory impairment 24 h after surgery. Taken together, these results demonstrated that preoperative sleep disturbance aggravated postoperative cognitive function in aged mice and the mechanism may be related to central nervous system (CNS) inflammation and neuronal damage.

Divergent Effects of Metformin on an Inflammatory Model of Parkinson's Disease

The oral antidiabetic drug metformin is known to exhibit anti-inflammatory properties through activation of AMP kinase, thus protecting various brain tissues as cortical neurons, for example. However, the effect of metformin on the substantia nigra (SN), the main structure affected in Parkinson’s disease (PD), has not yet been studied in depth. Inflammation is a key feature of PD and it may play a central role in the neurodegeneration that takes place in this disorder. The aim of this work was to determine the effect of metformin on the microglial activation of the SN of rats using the animal model of PD based on the injection of the pro-inflammogen lipopolysaccharide (LPS). In vivo and in vitro experiments were conducted to study the activation of microglia at both the cellular and molecular levels. Our results indicate that metformin overall inhibits microglia activation measured by OX-6 (MHCII marker), IKKβ (pro-inflammatory marker) and arginase (anti-inflammatory marker) immunoreactivity. In addition, qPCR experiments reveal that metformin treatment minimizes the expression levels of several pro- and anti-inflammatory cytokines. Mechanistically, the drug decreases the phosphorylated forms of mitogen-activated protein kinases (MAPKs) as well as ROS generation through the inhibition of the NADPH oxidase enzyme. However, metformin treatment fails to protect the dopaminergic neurons of SN in response to intranigral LPS. These findings suggest that metformin could have both beneficial and harmful pharmacological effects and raise the question about the potential use of metformin for the prevention and treatment of PD.

Urate inhibits microglia activation to protect neurons in an LPS-induced model of Parkinson's disease

Background

Multiple risk factors contribute to the progression of Parkinson’s disease, including oxidative stress and neuroinflammation. Epidemiological studies have revealed a link between higher urate level and a lower risk of developing PD. However, the mechanistic basis for this association remains unclear. Urate protects dopaminergic neurons from cell death induced by oxidative stress. Here, we investigated a novel role of urate in microglia activation in a lipopolysaccharide (LPS)-induced PD model.

Methods

We utilized Griess, ELISA, real-time PCR, Western blot, immunohistochemistry, and immunofluorescence to detect the neuroinflammation. For Griess, ELISA, Western blot, and immunofluorescence assay, cells were seeded in 6-well plates pre-coated with poly-l-lysine (PLL) and incubated for 24 h with the indicated drugs. For real-time PCR assay, cells were seeded in 6-well plates pre-coated with PLL and incubated for 6 h with the indicated drugs. For animal experiments, rats were injected with urate or its vehicle twice daily for five consecutive days before and after stereotaxic surgery. Rats were killed and brain tissues were harvested after 4 weeks of LPS injection.

Results

In cultured BV2 cells and rat primary microglia, urate suppressed proinflammatory cytokine production and inducible cyclooxygenase 2 and nitric oxide synthase expression to protect dopaminergic neurons from the toxic effects of activated microglia. The neuroprotective effects of urate may also be associated with the stimulation of anti-inflammatory factors interleukin 10 and transforming growth factor β1. Intracellular urate level was increased in a dose-dependent manner upon co-treatment with urate and LPS as compared with LPS alone, an effect that was abrogated by pretreatment with probenecid (PBN), an inhibitor of both glucose transporter 9 and urate transporter 1 (URAT1). PBN also abolished the anti-inflammatory effect of urate. Consistent with these in vitro observations, the number of tyrosine hydroxylase-positive neurons was decreased and the loss of motor coordination was reversed by urate administration in an LPS-induced rat model of PD. Additionally, increased plasma urate level abolished the reduction of URAT1 expression, the increase in the expression of interleukin-1β, and the number of ionized calcium-binding adaptor molecule 1-positive microglia along with changes in their morphology.

Conclusions

Urate protects neurons against cytotoxicity induced by microglia activation via modulating urate transporter-mediated intracellular urate level.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1175-8) contains supplementary material, which is available to authorized users.

2-Pentadecyl-2-Oxazoline Reduces Neuroinflammatory Environment in the MPTP Model of Parkinson Disease

Current pharmacological management of Parkinson disease (PD) does not provide for disease modification, but addresses only symptomatic features. Here, we explore a new approach to neuroprotection based on the use of 2-pentadecyl-2-oxazoline (PEA-OXA), the oxazoline derivative of the fatty acid amide signaling molecule palmitoylethanolamide (PEA), in an experimental model of PD. Daily oral treatment with PEA-OXA (10 mg/kg) significantly reduced behavioral impairments and neuronal cell degeneration of the dopaminergic tract induced by four intraperitoneal injections of the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on 8-week-old male C57 mice. Moreover, PEA-OXA treatment prevented dopamine depletion, increased tyrosine hydroxylase and dopamine transporter activities, and decreased α-synuclein aggregation in neurons. PEA-OXA treatment also diminished nuclear factor-κB traslocation, cyclooxygenase-2, and inducible nitric oxide synthase expression and through upregulation of the nuclear factor E2-related factor 2 pathway, induced activation of Mn-superoxide dismutase and heme oxygenase-1. Further, PEA-OXA modulated microglia and astrocyte activation and preserved microtubule-associated protein-2 alterations. In conclusion, pharmacological activation of nuclear factor E2-related factor 2 pathways with PEA-OXA may be effective in the future therapy of PD.

Vagus nerve stimulation improves locomotion and neuronal populations in a model of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a progressive, neurodegenerative disorder with no disease-modifying therapies, and symptomatic treatments are often limited by debilitating side effects. In PD, locus coeruleus noradrenergic (LC-NE) neurons degenerate prior to substantia nigra dopaminergic (SN-DA) neurons. Vagus nerve stimulation (VNS) activates LC neurons, and decreases pro-inflammatory markers, allowing improvement of LC targets, making it a potential PD therapeutic.

OBJECTIVE

To assess therapeutic potential of VNS in a PD model.

METHODS

To mimic the progression of PD degeneration, rats received a systemic injection of noradrenergic neurotoxin DSP-4, followed one week later by bilateral intrastriatal injection of dopaminergic neurotoxin 6-hydroxydopamine. At this time, a subset of rats also had vagus cuffs implanted. After eleven days, rats received a precise VNS regimen twice a day for ten days, and locomotion was measured during each afternoon session. Immediately following final stimulation, rats were euthanized, and left dorsal striatum, bilateral SN and LC were sectioned for immunohistochemical detection of monoaminergic neurons (tyrosine hydroxylase, TH), α-synuclein, astrocytes (GFAP) and microglia (Iba-1).

RESULTS

VNS significantly increased locomotion of lesioned rats. VNS also resulted in increased expression of TH in striatum, SN, and LC; decreased SN α-synuclein expression; and decreased expression of glial markers in the SN and LC of lesioned rats. Additionally, saline-treated rats after VNS, had higher LC TH and lower SN Iba-1.

CONCLUSIONS

Our findings of increased locomotion, beneficial effects on LC-NE and SN-DA neurons, decreased α-synuclein density in SN TH-positive neurons, and neuroinflammation suggest VNS has potential as a novel PD therapeutic.

Anti-Inflammatory Modulation of Microglia via CD163-Targeted Glucocorticoids Protects Dopaminergic Neurons in the 6-OHDA Parkinson's Disease Model

Increasing evidence supports a decisive role for inflammation in the neurodegenerative process of Parkinson's disease (PD). The immune response in PD seems to involve, not only microglia, but also other immune cells infiltrated into the brain. Indeed, we observed here the infiltration of macrophages, specifically CD163+ macrophages, into the area of neurodegeneration in the 6-hydroxydopamine (6-OHDA) PD model. Therefore, we investigated the therapeutic potential of the infiltrated CD163+ macrophages to modulate local microglia in the brain to achieve neuroprotection. To do so, we designed liposomes targeted for the CD163 receptor to deliver dexamethasone (Dexa) into the CD163+ macrophages in the 6-OHDA PD model. Our data show that a fraction of the CD163-targeted liposomes were carried into the brain after peripheral intravenous injection. The 6-OHDA-lesioned rats that received repeated intravenous CD163-targeted liposomes with Dexa for 3 weeks exhibited better motor performance than the control groups and had minimal glucocorticoid-driven side effects. Furthermore, these animals showed better survival of dopaminergic neurons in substantia nigra and an increased number of microglia expressing major histocompatibility complex II. Therefore, rats receiving CD163-targeted liposomes with Dexa were partially protected against 6-OHDA-induced dopaminergic neurodegeneration, which correlated with a distinctive microglia response. Altogether, our data support the use of macrophages for the modulation of brain neurodegeneration and specifically highlight the potential of CD163-targeted liposomes as a therapeutic tool in PD.

SIGNIFICANCE STATEMENT

The immune response now evident in the progression of Parkinson's disease comprises both local microglia and other immune cells. We provide evidence that CD163+ macrophages can be a target to modulate brain immune response to achieve neuroprotection in the 6-hydroxydopamine model. To do so, we targeted the CD163+ population, which to a low but significant extent infiltrated in the neurodegenerating area of the brain. Specially designed liposomes targeted for the CD163 receptor were loaded with glucocorticoids and injected peripherally to modify the infiltrated CD163 cells toward an anti-inflammatory profile. This modification of the CD163 population resulted in a distinctive microglial response that correlated with decreased dopaminergic cell death and better motor performance.

Effect of LPS treatment on tyrosine hydroxylase expression and Parkinson-like behaviors

Puberty is a critical period of development during which the brain undergoes reorganizing and remodeling. Exposure to stress during this period is thought to interfere with normal brain development and increase susceptibility to mental illnesses. In female mice, pubertal exposure to lipopolysaccharide (LPS), a bacterial endotoxin, has been shown to alter sexual, anxiety-like, and depression-like behaviors and cognition in an enduring manner. However, the mechanisms underlying these effects remain unknown. The present study examined age and sex difference in tyrosine hydroxylase (TH) expression and dopamine-dependent and Parkinson-like behaviors following LPS treatment. The results show that LPS treatment during adulthood causes an enduring increase in TH expression in many of the brain regions examined. In contrast, there is no change in TH expression following LPS treatment during puberty. However, pubertal LPS treatment induces enduring behavioral deficits in tests of Parkinson-like behaviors, more so in male than in female mice. These results suggest that the low levels of TH following exposure to pubertal immune challenge may predispose mice to Parkinson-like behavior. These findings add to our understanding of stress and immune responses during puberty and their impact on mental health later in life.

Melatonin as a Therapeutic Resource for Inflammatory Visual Diseases

BACKGROUND

Uveitis and optic neuritis are prevalent ocular inflammatory diseases, and highly damaging ocular conditions. Both diseases are currently treated with corticosteroids, but they do not have adequate efficacy and are often associated with severe side effects. Thus, uveitis and optic neuritis remain a challenging field to ophthalmologists and a significant public health concern.

OBJECTIVE

This review summarizes findings showing the benefits of a treatment with melatonin in experimental models of these inflammatory ocular diseases.

RESULTS

Oxidative and nitrosative damage, tumor necrosis factor, and prostaglandin production have been involved in the pathogeny of uveitis and optic neuritis. Melatonin is an efficient antioxidant and antinitridergic, and has the ability to reduce prostaglandin and tumor necrosis factor levels both in the retina and optic nerve. Moreover, melatonin not only prevents functional and structural consequences of experimental uveitis and optic neuritis, but it is also capable of suppressing the actively ongoing ocular inflammatory response.

CONCLUSIONS

Since melatonin protects ocular tissues against inflammation, it could be a potentially useful anti-inflammatory therapy in ophthalmology.

Viscoelastic and ultrastructural characteristics of whole blood and plasma in Alzheimer-type dementia, and the possible role of bacterial lipopolysaccharides (LPS)

Alzheimer-type dementia (AD) is a neurodegenerative disorder and the most common form of dementia. Patients typically present with neuro- and systemic inflammation and iron dysregulation, associated with oxidative damage that reflects in hypercoagulability. Hypercoagulability is closely associated with increased fibrin(ogen) and in AD patients fibrin(ogen) has been implicated in the development of neuroinflammation and memory deficits. There is still no clear reason precisely why (a) this hypercoagulable state, (b) iron dysregulation and (c) increased fibrin(ogen) could together lead to the loss of neuronal structure and cognitive function. Here we suggest an alternative hypothesis based on previous ultrastructural evidence of the presence of a (dormant) blood microbiome in AD. Furthermore, we argue that bacterial cell wall components, such as the endotoxin lipopolysaccharide (LPS) of Gram-negative strains, might be the cause of the continuing and low-grade inflammation, characteristic of AD. Here, we follow an integrated approach, by studying the viscoelastic and ultrastructural properties of AD plasma and whole blood by using scanning electron microscopy, Thromboelastography (TEG^®) and the Global Thrombosis Test (GTT^®). Ultrastructural analysis confirmed the presence and close proximity of microbes to erythrocytes. TEG^® analysis showed a hypercoagulable state in AD. TEG^® results where LPS was added to naive blood showed the same trends as were found with the AD patients, while the GTT^® results (where only platelet activity is measured), were not affected by the added LPS, suggesting that LPS does not directly impact platelet function. Our findings reinforce the importance of further investigating the role of LPS in AD.

Aquaporin-4 deficiency diminishes the differential degeneration of midbrain dopaminergic neurons in experimental Parkinson's disease

Parkinson's disease (PD) is primarily due to the progressive, selective and irreversible loss of dopaminergic (DA) neurons in the substantia nigra (SN). Interestingly, DA neurons in the ventral and lateral SN are much more susceptible than adjacent dopamine neurons in the ventral tegmental area (VTA) not only in human PD but in many PD model systems. However, the molecular causes of regional vulnerability in PD remain unknown. In our previous studies, we established acute PD animal models by administration of MPTP (1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine), and found that AQP4 knockout mice were significantly more prone to MPTP-induced neurotoxicity. Here, we further observe that AQP4 deficiency resulted in the same susceptible to MPTP between SN DA neuron and VTA neurons both in acute and chronic PD model. Moreover, we show that AQP4 deficiency increased the numbers of reactive astrocytes and microglias not only in the SN and but also in the VTA under basal and MPTP-induced situations. Meanwhile, AQP4 deficiency disrupted the balance of the pro-inflammatory cytokine/neurotrophin in midbrain. Taken together, these results demonstrate that glial AQP4 is involved in the susceptibility differences of DA neurons between SN and VTA, although the precise mechanism of AQP4 remains to be explored. Moreover, these findings also suggest that these susceptibility differences are not only due to intrinsic neuronal factors, but also attribute to differences in astrocytes of these regions.

Coumarin: A Privileged Scaffold for the Design and Development of Antineurodegenerative Agents

Drug development for neurodegenerative diseases (NDs) is foremost task for the medicinal chemists in the 21st century. Coumarins are exemplary of an assorted and aptitudinally useful set of drugs. Coumarins play a momentous role in several pharmacological and medicinal aspects. Its analogues are anticipated to play a significant role in the development of new therapeutic leads for NDs. Their promising applications in the field of ND medication are exemplified by clinical candidates such as nodakenin that have been potent for demoting memory impairment. Apart from ND, clinically used anticoagulant warfarin, anticoagulant dicoumarol, and antibiotic coumermycin, novobiocin and chartesium grab the interest of researchers in coumarins. It would be worthwhile to look at the different biological processes that could cause neurodegeneration, thereby establishing a link with distinct coumarin derivatives to serve the purpose of medication. This review undertakes estimation of the wide spectrum of studies focusing coumarin to the domain of drug research for ND. Herein, we search for multitarget coumarin-based inhibitors and their scope for NDs. Future challenges in coumarin-based drug development have been discussed, and emphases have been laid on the future perspectives of coumarins as possible drugs in the future for the treatment of NDs.

Lymphocytes reduce nigrostriatal deficits in the 6-hydroxydopamine mouse model of Parkinson's disease

Neuroinflammation is a well-known neuropathological feature of Parkinson's disease (PD), but it remains controversial whether it is causal or consequential to neurodegeneration. While the role of microglia in the pathogenesis has been thoroughly investigated in human and different rodent models, data concerning the impact of the adaptive immune system on the pathogenesis of PD are still rare, although lymphocyte populations were found in brain tissue of PD patients and have been implicated in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-mediated neurodegeneration in mice. To test the hypothesis that the adaptive immune system contributes to the progression of PD in the murine 6-hydroxydopamine (6-OHDA) model, we performed unilateral 6-OHDA injection into the medial forebrain bundle and compared wild-type mice with recombination activating gene-1 deficient mice (RAG-1(-/-)), that lack mature lymphocytes. After 6-OHDA injection, immune-deficient mice moved significantly slower and less often than wild-type mice. Rotarod analysis displayed a shorter latency to fall in RAG-1(-/-) mice. Immunohistochemical analysis in wild-type mice demonstrated a higher CD8+ T cell density in the ipsilesional striatum compared to sham-operated animals. Cell counts of tyrosine hydroxylase positive dopaminergic neurons of the substantia nigra in immune compromised mice were significantly reduced compared to wild-type mice. Wild type bone marrow reconstitution into RAG-1(-/-) recipients rescued the clinical deterioration as well as the neurodegeneration in RAG-1(-/-) deficient recipients ameliorated clinical symptoms and neurodegeneration after 6-OHDA treatment. Our data indicate that lymphocytes reduce the clinical and neuropathological impact of 6-OHDA lesioning and thus may play a protective role in this toxic mouse model of PD.

Chronic stress as a risk factor for Alzheimer's disease

This review aims to point out that chronic stress is able to accelerate the appearance of Alzheimer's disease (AD), proposing the former as a risk factor for the latter. Firstly, in the introduction we describe some human epidemiological studies pointing out the possibility that chronic stress could increase the incidence, or the rate of appearance of AD. Afterwards, we try to justify these epidemiological results with some experimental data. We have reviewed the experiments studying the effect of various stressors on different features in AD animal models. Moreover, we also point out the data obtained on the effect of chronic stress on some processes that are known to be involved in AD, such as inflammation and glucose metabolism. Later, we relate some of the processes known to be involved in aging and AD, such as accumulation of β-amyloid, TAU hyperphosphorylation, oxidative stress and impairement of mitochondrial function, emphasizing how they are affected by chronic stress/glucocorticoids and comparing with the description made for these processes in AD. All these data support the idea that chronic stress could be considered a risk factor for AD.

Lithium ameliorates lipopolysaccharide-induced microglial activation via inhibition of toll-like receptor 4 expression by activating the PI3K/Akt/FoxO1 pathway

Background

Lithium, an effective mood stabilizer for the treatment of bipolar disorders, has been recently suggested to have a role in neuroprotection during neurodegenerative diseases. The pathogenesis of neurological disorders often involves the activation of microglia and associated inflammatory processes. Thus, in this study, we aimed to understand the role of lithium in microglial activation and to elucidate the underlying mechanism(s).

Methods

Primary microglial cells were pretreated with lithium and stimulated with lipopolysaccharide (LPS). The cells were assessed regarding the responses of pro-inflammatory cytokines, and the associated signaling pathways were evaluated.

Results

Lithium significantly inhibited LPS-induced microglial activation and pro-inflammatory cytokine production. Further analysis showed that lithium could activate PI3K/Akt signaling. Analyses of the associated signaling pathways demonstrated that the lithium pretreatment led to the suppression of LPS-induced toll-like receptor 4 (TLR4) expressions via the PI3K/Akt/FoxO1 pathway.

Conclusions

This study demonstrates that lithium can inhibit LPS-induced TLR4 expression and microglial activation through the PI3K/Akt/FoxO1 signaling pathway. These results suggest that lithium plays an important role in microglial activation and neuroinflammation-related diseases, which may lead to a new therapeutic strategy for the treatment of neuroinflammation-related disorders.

Glucocorticoid receptors in the retina, Müller glia and the formation of Müller glia-derived progenitors

Identification of the signaling pathways that influence the reprogramming of Müller glia into neurogenic retinal progenitors is key to harnessing the potential of these cells to regenerate the retina. Glucocorticoid receptor (GCR) signaling is commonly associated with anti-inflammatory responses and GCR agonists are widely used to treat inflammatory diseases of the eye, even though the cellular targets and mechanisms of action in the retina are not well understood. We find that signaling through GCR has a significant impact upon the ability of Müller glia to become proliferating Müller glia-derived progenitor cells (MGPCs). The primary amino acid sequence and pattern of GCR expression in the retina is highly conserved across vertebrate species, including chickens, mice, guinea pigs, dogs and humans. In all of these species we find GCR expressed by the Müller glia. In the chick retina, we find that GCR is expressed by progenitors in the circumferential marginal zone (CMZ) and is upregulated by Müller glia in acutely damaged retinas. Activation of GCR signaling inhibits the formation of MGPCs and antagonizes FGF2/MAPK signaling in the Müller glia. By contrast, we find that inhibition of GCR signaling stimulates the formation of proliferating MGPCs in damaged retinas, and enhances the neuronal differentiation while diminishing glial differentiation. Given the conserved expression pattern of GCR in different vertebrate retinas, we propose that the functions and mechanisms of GCR signaling are highly conserved and are mediated through the Müller glia. We conclude that GCR signaling directly inhibits the formation of MGPCs, at least in part, by interfering with FGF2/MAPK signaling.

Peripheral leukocyte apoptosis in patients with Parkinsonism: correlation with clinical characteristics and neuroimaging findings

Apoptosis of both brain neurons and peripheral blood leukocyte is believed to be an important biomarker for evaluating the functional status of Parkinson's disease (PD). However, their correlation remains unknown. A better understanding of the pathophysiology of neurodegeneration is essential for the treatment and prevention of PD. The present study demonstrated that leukocyte apoptosis is significantly higher in PD patients and is associated with central dopamine neuron loss by using ^99mTc-TRODAT-1 SPECT. The leukocyte apoptosis and striatal dopamine transporter uptake ratios were further associated with increased severity and longer duration of disease. The interaction between brain and systemic inflammation may be responsible for the neurodegenerative disease progression.

Suppression of CXCL2 upregulation underlies the therapeutic effect of the retinoid Am80 on intracerebral hemorrhage in mice

We previously demonstrated that a synthetic retinoic acid receptor agonist, Am80, attenuated intracerebral hemorrhage (ICH)-induced neuropathological changes and neurological dysfunction. Because inflammatory events are among the prominent features of ICH pathology that are affected by Am80, this study investigated the potential involvement of proinflammatory cytokines/chemokines in the effect of Am80 on ICH. ICH induced by collagenase injection into mouse striatum caused prominent upregulation of mRNAs for interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6, CXCL1, CXCL2, and CCL3. We found that dexamethasone (DEX) and Am80 differently modulated the increase in expression of these cytokines/chemokines; TNF-α expression was attenuated only by DEX, whereas CXCL2 expression was attenuated only by Am80. Expression of IL-1β and IL-6 was inhibited both by DEX and Am80. Neurological assessments revealed that Am80, but not DEX, significantly alleviated motor dysfunction of mice after ICH. From these results, we suspected that CXCL2 might be critically involved in determining the extent of motor dysfunction. Indeed, magnetic resonance imaging-based classification of ICH in individual mice revealed that invasion of hematoma into the internal capsule, which has been shown to cause severe neurological disabilities, was associated with higher levels of CXCL2 expression than ICH without internal capsule invasion. Moreover, a CXCR1/2 antagonist reparixin ameliorated neurological deficits after ICH. Overall, suppression of CXCL2 expression may contribute to the beneficial effect of Am80 as a therapeutic agent for ICH, and interruption of CXCL2 signaling may provide a promising target for ICH therapy.

Short-term effects of an endotoxin on substantia nigra dopamine neurons

Inflammation has been implicated in the pathology of several neurodegenerative diseases, including Parkinson׳s disease (PD). Studies using the endotoxin lipopolysaccharide (LPS), a potent inflammogen, show that systemic insults can trigger prolonged microglial activation and pro-inflammatory cytokine production leading to degeneration of substantia nigra (SN) dopamine (DA) neurons, mimicking idiopathic PD. Because rapid effects of LPS on SN neurons had not been investigated previously, the focus of this study is to assess time-dependent alterations in SN neuroinflammation, DAergic neurons, and neuronal signaling cascades following LPS administration. LPS (5mg/kg, i.p.) or saline (0.9% NaCl) was administered to 8-month-old male mice. At 3h, 5h, and 12h post-injection, the morphology of the SN was assessed using antibodies directed against tyrosine hydroxylase (TH, DAergic marker), Iba-1 (pan-microglial marker), phospho-ERK, and phospho-CREB (signaling). LPS administration significantly reduced TH-immunoreactivity (ir) at all time-points with the greatest reduction observed at 12h post-injection. Reduced TH-ir was accompanied by a significant increase in activated microglia at all time-points following LPS. By 12h post-injection, LPS-treated mice exhibited activated as well as reactive microglia, which can result in neuronal damage. These data demonstrate that the initial reduction in TH-ir observed after an LPS injection was not concomitant with morphological alterations in microglial cells, even though a significant increase in phospho-ERK was observed in glial cells as soon as 3h post-injection. It is possible that the initial alteration in DA phenotype (TH reduction) may perpetuate an inflammatory response that persists and leads to further DAergic damage.

Neuroprotective and symptomatic effects of targeting group III mGlu receptors in neurodegenerative disease

Neurodegenerative disorders possess common pathological mechanisms, such as protein aggregation, inflammation, oxidative stress (OS) and excitotoxicity, raising the possibility of shared therapeutic targets. As a result of the selective cellular and regional expression of group III metabotropic glutamate (mGlu) receptors, drugs targeting such receptors have demonstrated both neuroprotective properties and symptomatic improvements in several models of neurodegeneration. In recent years, the discovery and development of subtype-selective ligands for the group III mGlu receptors has gained pace, allowing further research into the functions of these receptors and revealing their roles in health and disease. Activation of this class of receptors results in neuroprotection, with a variety of underlying mechanisms implicated. Group III mGlu receptor stimulation prevents excitotoxicity by inhibiting glutamate release from neurons and microglia and increasing glutamate uptake by astrocytes. It also attenuates the neuroinflammatory response by reducing glial reactivity and encourages neurotrophic phenotypes. This article will review the current literature with regard to the neuroprotective and symptomatic effects of group III mGlu receptor activation and discuss their promise as therapeutic targets in neurodegenerative disease. We review the neuroprotective and symptomatic effects of targeting group III mGlu receptors in neurodegenerative disease: Excess extracellular glutamate causes overactivation of NMDA receptors resulting in excitotoxicity. Externalization of phosphatidylserine stimulates phagocytosis of neurons by activated microglia, which contribute to damage through glutamate and pro-inflammatory factor release. Reactive astrocytes produce cytotoxic factors enhancing neuronal cell death. Activation of group III mGlu receptors by glutamate and/or mGlu receptor ligands results in inhibition of glutamate release from presynaptic terminals and microglia, reducing excitotoxicity. Astrocytic glutamate uptake is increased and microglia produce neurotrophic factors.

Primary phagocytosis of neurons by inflamed microglia: potential roles in neurodegeneration

Microglial phagocytosis of dead or dying neurons can be beneficial by preventing the release of damaging and/or pro-inflammatory intracellular components. However, there is now evidence that under certain conditions, such as inflammation, microglia can also phagocytose viable neurons, thus executing their death. Such phagocytic cell death may result from exposure of phosphatidylserine (PS) or other eat-me signals on otherwise viable neurons as a result of physiological activation or sub-toxic insult, and neuronal phagocytosis by activated microglia. In this review, we discuss the mechanisms of phagocytic cell death and its potential roles in Alzheimer’s Disease, Parkinson’s Disease, and Frontotemporal Dementia.

Paraquat induces epigenetic changes by promoting histone acetylation in cell culture models of dopaminergic degeneration

Environmental neurotoxic exposure to agrochemicals has been implicated in the etiopathogenesis of Parkinson's disease (PD). The widely used herbicide paraquat is among the few environmental chemicals potentially linked with PD. Since epigenetic changes are beginning to emerge as key mechanisms in neurodegenerative diseases, herein we examined the effects of paraquat on histone acetylation, a major epigenetic change in chromatin that can regulate gene expression, chromatin remodeling, cell survival and cell death. Exposure of N27 dopaminergic cells to paraquat induced histone H3 acetylation in a time-dependent manner. However, paraquat did not alter acetylation of another core histone H4. Paraquat-induced histone acetylation was associated with decreased total histone deacetylase (HDAC) activity and HDAC4 and 7 protein expression levels. To determine if histone acetylation plays a role in paraquat-induced apoptosis, the novel HAT inhibitor anacardic acid was used. Anacardic acid treatment significantly attenuated paraquat-induced caspase-3 enzyme activity, suppressed proteolytic activation and kinase activity of protein kinase C delta (PKCδ) and also blocked paraquat-induced cytotoxicity. Together, these results demonstrate that the neurotoxic agent paraquat induced acetylation of core histones in cell culture models of PD and that the inhibition of HAT activity by anacardic acid protects against apoptotic cell death, indicating that histone acetylation may represent key epigenetic changes in dopaminergic neuronal cells during neurotoxic insults.

Peripheral inflammation increases the damage in animal models of nigrostriatal dopaminergic neurodegeneration: possible implication in Parkinson's disease incidence

Inflammatory processes described in Parkinson's disease (PD) and its animal models appear to be important in the progression of the pathogenesis, or even a triggering factor. Here we review that peripheral inflammation enhances the degeneration of the nigrostriatal dopaminergic system induced by different insults; different peripheral inflammations have been used, such as IL-1β and the ulcerative colitis model, as well as insults to the dopaminergic system such as 6-hydroxydopamine or lipopolysaccharide. In all cases, an increased loss of dopaminergic neurons was described; inflammation in the substantia nigra increased, displaying a great activation of microglia along with an increase in the production of cytokines such as IL-1β and TNF-α. Increased permeability or disruption of the BBB, with overexpression of the ICAM-1 adhesion molecule and infiltration of circulating monocytes into the substantia nigra, is also involved, since the depletion of circulating monocytes prevents the effects of peripheral inflammation. Data are reviewed in relation to epidemiological studies of PD.

Glial cell line-derived neurotrophic factor protects midbrain dopaminergic neurons against lipopolysaccharide neurotoxicity

Aberrant microglia activation causes dopaminergic neuronal loss and nitric oxide produced by microglia plays a critical role in dopaminergic neuronal degeneration. However, no study has determined if GDNF protects dopaminergic neurons via inhibiting nitric oxide generation in Parkinson's disease animal model. We report that GDNF not only reduces lipopolysaccharide-induced degeneration of dopaminergic neurons, suppresses microglia activation and nitric oxide generation, but also reverses the inhibition of phosphoinositide 3-kinase (PI3K) in dopaminergic neurons and microglia. It suggests that the neuroprotective effect of GDNF on dopaminergic neurons may be related to its suppression of microglia activation-mediated nitric oxide via releasing the inhibition of PI3K in both neurons and microglia.

Selective neuronal vulnerability to oxidative stress in the brain

Oxidative stress (OS), caused by the imbalance between the generation and detoxification of reactive oxygen and nitrogen species (ROS/RNS), plays an important role in brain aging, neurodegenerative diseases, and other related adverse conditions, such as ischemia. While ROS/RNS serve as signaling molecules at physiological levels, an excessive amount of these molecules leads to oxidative modification and, therefore, dysfunction of proteins, nucleic acids, and lipids. The response of neurons to this pervasive stress, however, is not uniform in the brain. While many brain neurons can cope with a rise in OS, there are select populations of neurons in the brain that are vulnerable. Because of their selective vulnerability, these neurons are usually the first to exhibit functional decline and cell death during normal aging, or in age-associated neurodegenerative diseases, such as Alzheimer's disease. Understanding the molecular and cellular mechanisms of selective neuronal vulnerability (SNV) to OS is important in the development of future intervention approaches to protect such vulnerable neurons from the stresses of the aging process and the pathological states that lead to neurodegeneration. In this review, the currently known molecular and cellular factors that contribute to SNV to OS are summarized. Included among the major underlying factors are high intrinsic OS, high demand for ROS/RNS-based signaling, low ATP production, mitochondrial dysfunction, and high inflammatory response in vulnerable neurons. The contribution to the selective vulnerability of neurons to OS by other intrinsic or extrinsic factors, such as deficient DNA damage repair, low calcium-buffering capacity, and glutamate excitotoxicity, are also discussed.

Microglial responses to dopamine in a cell culture model of Parkinson's disease

Activated microglia appear to selectively attack dopamine (DA) neurons in the Parkinson's disease (PD) substantia nigra. We investigated potential mechanisms using culture models. As targets, human SH-SY5Y cells were left undifferentiated (UNDIFF) or were differentiated with retinoic acid (RA) or RA plus brain-derived neurotrophic factor (RA/BDNF). RA/BDNF-treated cells were immunoreactive for tyrosine hydroxylase and the DA transporter, took up exogenous DA, and released DA after K(+) stimulation. Undifferentiated and RA-treated cells lacked these characteristics of a DA phenotype. Co-culture of target cells with human elderly microglia resulted in elevated toxicity in DA phenotype (RA/BDNF) cells. Lipopolysaccharide (LPS) plus K(+)-stimulated DA release enhanced toxicity by 500-fold. DA induced microglial chemotaxis in Boyden chambers. Spiperone inhibited this effect. Cultured human elderly microglia expressed mRNAs for D1-D4 but not D5 DA receptors. The microglia, as well as PD microglia in situ, were also immunoreactive for D1-D4 but not D5 DA receptors. These findings demonstrate that activated microglia express DA receptors, and suggest that this mechanism may play a role in the selective vulnerability of DA neurons in PD.

Mesenchymal stem cell transplantation attenuates blood brain barrier damage and neuroinflammation and protects dopaminergic neurons against MPTP toxicity in the substantia nigra in a model of Parkinson's disease

Immunomodulatory effects of transplanted mesenchymal stem cells (MSCs) in the treatment of Parkinson's disease were studied in the MPTP-induced mouse model. MPTP treatment induced a significant loss of dopaminergic neurons, decreased expressions of claudin 1, claudin 5 and occludin in the substantia nigra compacta (SNc), and functional damage of the blood brain barrier (BBB). Our study further discovered that infiltration of MBLs into the brain to bind with microglia was detected in the SNc of MPTP-treated mice, suggesting that the BBB compromise and MBL infiltration might be involved in the pathogenesis of MPTP-induced PD. In addition, MPTP treatment also increased the expression of mannose-binding lectins (MBLs) in the liver tissue. Intravenous transplantation of MSCs into MPTP-treated mice led to recovery of BBB integrity, suppression of MBL infiltration at SNc and MBL expression in the liver, suppression of microglial activation and prevention of dopaminergic neuron death. No transplanted MSCs were observed to differentiate into dopaminergic neurons, while the MSCs migrated into the SNc and released TGF-beta1 there. Therefore, intravenous transplantation of MSCs which protect dopaminergic neurons from MPTP toxicity may be engaged in anyone or a combination of these mechanisms: repair of the BBB, reduction of MBL in the brain, inhibition of microglial cytotoxicity, and direct protection of dopaminergic neurons.

The intranigral injection of tissue plasminogen activator induced blood-brain barrier disruption, inflammatory process and degeneration of the dopaminergic system of the rat

Tissue-type plasminogen activator (tPA) is the only drug approved for the treatment of thromboembolic stroke, but it might lead to some neurotoxic side effects. tPA is a highly specific serine proteinase, one of the two principal plasminogen activators and one of the three trypsin-like serine proteinases of the tissue kallikrein family. We have observed that tPA injection in the SN leads to the degeneration of the dopaminergic neurons in a dose-dependent manner, without affecting the GABAergic neurons. We also found that tPA injected in the substantia nigra of rats produced the disruption of the blood-brain barrier (BBB) integrity, the induction of microglial activation, the loss of astroglia and the expression of aquaporin 4 (AQP4), as well as an increase in the expression of NMDA receptors and the brain derived neurothrophic factor (BDNF). All these effects, along with the changes produced in the phosphorylated forms of several MAP kinases and the transcription factor CREB, and the increase in the expression of nNOS and iNOS observed under our experimental conditions, could be involved in the loss of dopaminergic neurons.