Association of TLR4 gene polymorphisms with sporadic Parkinson's disease in a Han Chinese population

Autophagic dysfunction and gut microbiota dysbiosis cause chronic immune activation in a Drosophila model of Gaucher disease

Mutations in the GBA1 gene cause the lysosomal storage disorder Gaucher disease (GD) and are the greatest known genetic risk factors for Parkinson's disease (PD). Communication between the gut and brain and immune dysregulation are increasingly being implicated in neurodegenerative disorders such as PD. Here, we show that flies lacking the Gba1b gene, the main fly orthologue of GBA1, display widespread NF-kB signalling activation, including gut inflammation, and brain glial activation. We also demonstrate intestinal autophagic defects, gut dysfunction, and microbiome dysbiosis. Remarkably, modulating the microbiome of Gba1b knockout flies, by raising them under germ-free conditions, partially ameliorates lifespan, locomotor and immune phenotypes. Moreover, we show that modulation of the immune deficiency (IMD) pathway is detrimental to the survival of Gba1 deficient flies. We also reveal that direct stimulation of autophagy by rapamycin treatment achieves similar benefits to germ-free conditions independent of gut bacterial load. Consistent with this, we show that pharmacologically blocking autophagosomal-lysosomal fusion, mimicking the autophagy defects of Gba1 depleted cells, is sufficient to stimulate intestinal immune activation. Overall, our data elucidate a mechanism whereby an altered microbiome, coupled with defects in autophagy, drive chronic activation of NF-kB signaling in a Gba1 loss-of-function model. It also highlights that elimination of the microbiota or stimulation of autophagy to remove immune mediators, rather than prolonged immunosuppression, may represent effective therapeutic avenues for GBA1-associated disorders.

Microbial sensing in the intestine

The gut microbiota plays a key role in host health and disease, particularly through their interactions with the immune system. Intestinal homeostasis is dependent on the symbiotic relationships between the host and the diverse gut microbiota, which is influenced by the highly co-evolved immune-microbiota interactions. The first step of the interaction between the host and the gut microbiota is the sensing of the gut microbes by the host immune system. In this review, we describe the cells of the host immune system and the proteins that sense the components and metabolites of the gut microbes. We further highlight the essential roles of pattern recognition receptors (PRRs), the G protein-coupled receptors (GPCRs), aryl hydrocarbon receptor (AHR) and the nuclear receptors expressed in the intestinal epithelial cells (IECs) and the intestine-resident immune cells. We also discuss the mechanisms by which the disruption of microbial sensing because of genetic or environmental factors causes human diseases such as the inflammatory bowel disease (IBD).

Sex differences in alpha-synucleinopathies: a systematic review

Background

Past research indicates a higher prevalence, incidence, and severe clinical manifestations of alpha-synucleinopathies in men, leading to a suggestion of neuroprotective properties of female sex hormones (especially estrogen). The potential pathomechanisms of any such effect on alpha-synucleinopathies, however, are far from understood. With that aim, we undertook to systematically review, and to critically assess, contemporary evidence on sex and gender differences in alpha-synucleinopathies using a bench-to-bedside approach.

Methods

In this systematic review, studies investigating sex and gender differences in alpha-synucleinopathies (Rapid Eye Movement (REM) Behavior Disorder (RBD), Parkinson's Disease (PD), Dementia with Lewy Bodies (DLB), Multiple System Atrophy (MSA)) from 2012 to 2022 were identified using electronic database searches of PubMed, Embase and Ovid.

Results

One hundred sixty-two studies were included; 5 RBD, 6 MSA, 20 DLB and 131 PD studies. Overall, there is conclusive evidence to suggest sex-and gender-specific manifestation in demographics, biomarkers, genetics, clinical features, interventions, and quality of life in alpha-synucleinopathies. Only limited data exists on the effects of distinct sex hormones, with majority of studies concentrating on estrogen and its speculated neuroprotective effects.

Conclusion

Future studies disentangling the underlying sex-specific mechanisms of alpha-synucleinopathies are urgently needed in order to enable novel sex-specific therapeutics.

Pathomorphological Manifestations and the Course of the Cervical Cancer Disease Determined by Variations in the TLR4 Gene

Cervical cancer (CC) is often associated with human papillomavirus (HPV). Chronic inflammation has been described as one of the triggers of cancer. The immune system fights diseases, including cancer. The genetic polymorphism of pathogen recognition receptors potentially influences the infectious process, development, and disease progression. Many candidate genes SNPs have been contradictory demonstrated to be associated with cervical cancer by association studies, GWAS. TLR4 gene activation can promote antitumor immunity. It can also result in immunosuppression and tumor growth. Our study aimed to investigate eight selected polymorphisms of the TLR4 gene (rs10759932, rs1927906, rs11536898, rs11536865, rs10983755, rs4986790, rs4986791, rs11536897) and to determine the impact of polymorphisms in genotypes and alleles on the pathomorphological characteristics and progression in a group of 172 cervical cancer subjects with stage I-IV. Genotyping was performed by RT-PCR assay. We detected that the CA genotype and A allele of rs11536898 were significantly more frequent in patients with metastases (p = 0.026; p = 0.008). The multivariate logistic regression analysis confirmed this link to be significant. The effect of rs10759932 and rs11536898 on progression-free survival (PFS) and overall survival (OS) has been identified as important. In univariate and multivariate Cox analyses, AA genotype of rs11536898 was a negative prognostic factor for PFS (p = 0.024; p = 0.057, respectively) and OS (p = 0.008; p = 0.042, respectively). Rs11536898 C allele predisposed for longer PFS (univariate and multivariate: p = 0.025; p = 0.048, respectively) and for better OS (univariate and multivariate: p = 0.010; p = 0.043). The worse prognostic factor of rs10759932 in a univariate and multivariate Cox analysis for survival was CC genotype: shorter PFS (p = 0.032) and increased risk of death (p = 0.048; p = 0.015, respectively). The T allele of rs10759932 increased longer PFS (univariate and multivariate: p = 0.048; p = 0.019, respectively) and longer OS (univariate and multivariate: p = 0.037; p = 0.009, respectively). Our study suggests that SNPs rs10759932 and rs11536898 may have the potential to be markers contributing to the assessment of the cervical cancer prognosis. Further studies, preferably with larger groups of different ethnic backgrounds, are needed to confirm the results of the current study.

Toll-Like Receptor 4 Gene Polymorphisms and Susceptibility to Schizophrenia: A Case-Control Study

Schizophrenia is a common psychiatric disorder that exhibits a variety of symptoms. The exact etiology and pathogenesis are still doubtful. However, genetic and environmental factors seem to have a role. Years ago, the role of the immune system was focused on auto-antibodies, cytokines, different types of immune cells and immune genes. The Toll-like receptors (TLR) are a cornerstone of the innate immune system, particularly TLR4. TLR4 primarily recognises gram-negative lipopolysaccharides bacteria. This case-control study, for the first time to our knowledge, examined the role of TLR4 gene polymorphisms in 142 Egyptian schizophrenic patients and 175 healthy controls. Using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), four single nucleotide polymorphisms (SNPs) were investigated in the TLR4 gene rs11536889, rs10759931, rs1927911, and rs1927914. The Positive and Negative Syndrome Scale (PANSS) was used in diagnosis and assessment. A statistically significant association was observed between rs11536889, rs1927911 and rs1927914, but no association was found between rs10759931. There was no association between the different SNP genotypes and PANSS, except between rs1927914 and general psychopathologic symptoms. This study shows a strong association between TLR4 rs11356889 and rs1927911 minor alleles and schizophrenia. These findings could be additional evidence for the immune system's role in schizophrenia development. However, more studies with a more significant sample number, TLR4 protein assessment, and a larger number of SNPs are recommended.

The role of Toll-like receptors and neuroinflammation in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder, characterized by motor and non-motor symptoms, significantly affecting patients' life. Pathologically, PD is associated with the extensive degeneration of dopaminergic neurons in various regions of the central nervous system (CNS), specifically the substantia nigra. This neuronal loss is accompanied by the aggregation of misfolded protein, named α-synuclein.

MAIN TEXT

Recent studies detected several clues of neuroinflammation in PD samples using postmortem human PD brains and various PD animal models. Some evidence of neuroinflammation in PD patients included higher levels of proinflammatory cytokines in serum and cerebrospinal fluid (CSF), presence of activated microglia in various brain regions such as substantia nigra, infiltration of peripheral inflammatory cells in affected brain regions, and altered function of cellular immunity like monocytes phagocytosis defects. On the other side, Toll-like receptors (TLRs) are innate immune receptors primarily located on microglia, as well as other immune and non-immune cells, expressing pivotal roles in recognizing exogenous and endogenous stimuli and triggering inflammatory responses. Most studies indicated an increased expression of TLRs in the brain and peripheral blood cells of PD samples. Besides, this upregulation was associated with excessive neuroinflammation followed by neurodegeneration in affected regions. Therefore, evidence proposed that TLR-mediated neuroinflammation might lead to a dopaminergic neural loss in PD patients. In this regard, TLR2, TLR4, and TLR9 have the most prominent roles.

CONCLUSION

Although the presence of inflammation in acute phases of PD might have protective effects concerning the clearance of α-synuclein and delaying the disease advancement, the chronic activation of TLRs and neuroinflammation might lead to neurodegeneration, resulting in the disease progression. Therefore, this study aimed to review additional evidence of the contribution of TLRs and neuroinflammation to PD pathogenesis, with the hope that TLRs could serve as novel disease-modifying therapeutic targets in PD patients in the future.

Neuroinflammation Upregulated Neuronal Toll-Like Receptors 2 and 4 to Drive Synucleinopathy in Neurodegeneration

Background: Parkinson’s disease (PD) is characterized by intraneuronal α-synuclein aggregation called Lewy bodies and progressive dopaminergic neurodegeneration. Toll-like receptor (TLR) signaling is a major pathway mediating inflammation. The molecular link on how neuroinflammation upregulates neuronal TLRs and induces accumulation of α-synuclein aggregates to drive synucleinopathy remains to be determined.

Objective: Despite conditioned medium from microglia and TLR agonists were utilized to study their effects on neuronal cells, a Transwell coculture system, comprising lipopolysaccharide-activated microglia on top and retinoic acid-differentiated SH-SY5Y cells at the bottom more mimicking in vivo neuroinflammation, was employed to elucidate the mechanism of activated microglia on neuronal cells.

Methods: Genetic variants of TLRs in PD patients were genotyped and the multiplex cytokines, sRAGE, and HMGB1were assessed. A coculture system was employed to measure α-synuclein aggregates and neurite shortening by confocal microscope. The expression of TLR2/4 and autophagy flux was detected by western blot and immunofluorescence.

Results: PD patients showed higher plasma levels of proinflammatory cytokines and genetic TLR4 variant, c.896 A > G (p. D299G). Elevated proinflammatory cytokines in coculture medium was also seen. Phosphorylation and aggregation of α-synuclein, shortening of neurite, upregulation of TLR2/4 expression, activation of downstream p38 and JNK, and dampening of autophagic flux were seen in SH-SY5Y cells cocultured with activated microglia. Those were prevented by inhibiting TLR2/4 and p38/JNK signaling.

Conclusion: Activated microglia-derived neuroinflammation induced neuronal TLR2/4-p38/JNK activation to perturb autophagy, causing accumulation of α-synuclein aggregates and neurite shortening. Targeting neuronal TLR2/4 pathway might be a mechanistic-based therapy for neurodegenerative disease, such as PD.

Intestinal Inflammation and Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease which significantly influences the life quality of patients. The protein α-synuclein plays an important driving role in PD occurrence and development. Braak's hypothesis suggests that α-synuclein is produced in intestine, and then spreads into the central nervous system through the vagus nerve. The abnormal expression of α-synuclein has been found in inflammatory bowel disease (IBD). Intestinal inflammation and intestinal dysbiosis have been involved in the occurrence and development of PD. The present review aimed to summarize recent advancements in studies focusing on intestinal inflammation and PD, especially the mechanisms through which link intestinal inflammation and PD. The intestinal dysfunctions such as constipation have been introduced as non-motor manifestations of PD. The possible linkages between IBD and PD, including genetic overlaps, inflammatory responses, intestinal permeability, and intestinal dysbiosis, are mainly discussed. Although it is not confirmed whether PD starts from intestine, intestinal dysfunction may affect intestinal microenvironment to influence central nervous system, including the α-synuclein pathologies and systematic inflammation. It is expected to develop some new strategies in the diagnosis and treatment of PD from the aspect of intestine. It may also become an exciting direction to find better ways to regulate the composition of gut microorganism to treat PD.

TLR2 and TLR4 in Parkinson's disease pathogenesis: the environment takes a toll on the gut

Parkinson's disease (PD) is an incurable, devastating disorder that is characterized by pathological protein aggregation and neurodegeneration in the substantia nigra. In recent years, growing evidence has implicated the gut environment and the gut-brain axis in the pathogenesis and progression of PD, especially in a subset of people who exhibit prodromal gastrointestinal dysfunction. Specifically, perturbations of gut homeostasis are hypothesized to contribute to α-synuclein aggregation in enteric neurons, which may spread to the brain over decades and eventually result in the characteristic central nervous system manifestations of PD, including neurodegeneration and motor impairments. However, the mechanisms linking gut disturbances and α-synuclein aggregation are still unclear. A plethora of research indicates that toll-like receptors (TLRs), especially TLR2 and TLR4, are critical mediators of gut homeostasis. Alongside their established role in innate immunity throughout the body, studies are increasingly demonstrating that TLR2 and TLR4 signalling shapes the development and function of the gut and the enteric nervous system. Notably, TLR2 and TLR4 are dysregulated in patients with PD, and may thus be central to early gut dysfunction in PD. To better understand the putative contribution of intestinal TLR2 and TLR4 dysfunction to early α-synuclein aggregation and PD, we critically discuss the role of TLR2 and TLR4 in normal gut function as well as evidence for altered TLR2 and TLR4 signalling in PD, by reviewing clinical, animal model and in vitro research. Growing evidence on the immunological aetiology of α-synuclein aggregation is also discussed, with a focus on the interactions of α-synuclein with TLR2 and TLR4. We propose a conceptual model of PD pathogenesis in which microbial dysbiosis alters the permeability of the intestinal barrier as well as TLR2 and TLR4 signalling, ultimately leading to a positive feedback loop of chronic gut dysfunction promoting α-synuclein aggregation in enteric and vagal neurons. In turn, α-synuclein aggregates may then migrate to the brain via peripheral nerves, such as the vagal nerve, to contribute to neuroinflammation and neurodegeneration typically associated with PD.

Toll-like receptor 4 deficiency facilitates α-synuclein propagation and neurodegeneration in a mouse model of prodromal Parkinson's disease

The evidence linking innate immunity mechanisms and neurodegenerative diseases is growing, but the specific mechanisms are incompletely understood. Experimental data suggest that microglial TLR4 mediates the uptake and clearance of α-synuclein also termed synucleinophagy. The accumulation of misfolded α-synuclein throughout the brain is central to Parkinson's disease (PD). The distribution and progression of the pathology is often attributed to the propagation of α-synuclein. Here, we apply a classical α-synuclein propagation model of prodromal PD in wild type and TLR4 deficient mice to study the role of TLR4 in the progression of the disease. Our data suggest that TLR4 deficiency facilitates the α-synuclein seed spreading associated with reduced lysosomal activity of microglia. Three months after seed inoculation, more pronounced proteinase K-resistant α-synuclein inclusion pathology is observed in mice with TLR4 deficiency. The facilitated propagation of α-synuclein is associated with early loss of dopamine transporter (DAT) signal in the striatum and loss of dopaminergic neurons in substantia nigra pars compacta of TLR4 deficient mice. These new results support TLR4 signaling as a putative target for disease modification to slow the progression of PD and related disorders.

Possible Link between SARS-CoV-2 Infection and Parkinson's Disease: The Role of Toll-Like Receptor 4

Parkinson's disease (PD) is the most common neurodegenerative motor disorder characterized by selective degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) of the midbrain, depletion of dopamine (DA), and impaired nigrostriatal pathway. The pathological hallmark of PD includes the aggregation and accumulation α-synuclein (α-SYN). Although the precise mechanisms underlying the pathogenesis of PD are still unknown, the activation of toll-like receptors (TLRs), mainly TLR4 and subsequent neuroinflammatory immune response, seem to play a significant role. Mounting evidence suggests that viral infection can concur with the precipitation of PD or parkinsonism. The recently identified coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of ongoing pandemic coronavirus disease 2019 (COVID-19), responsible for 160 million cases that led to the death of more than three million individuals worldwide. Studies have reported that many patients with COVID-19 display several neurological manifestations, including acute cerebrovascular diseases, conscious disturbance, and typical motor and non-motor symptoms accompanying PD. In this review, the neurotropic potential of SARS-CoV-2 and its possible involvement in the pathogenesis of PD are discussed. Specifically, the involvement of the TLR4 signaling pathway in mediating the virus entry, as well as the massive immune and inflammatory response in COVID-19 patients is explored. The binding of SARS-CoV-2 spike (S) protein to TLR4 and the possible interaction between SARS-CoV-2 and α-SYN as contributing factors to neuronal death are also considered.

Current research status of HLA in immune-related diseases

Human leukocyte antigen (HLA), also known as human major histocompatibility complex (MHC), is encoded by the HLA gene complex, and is currently known to have the highest gene density and the most polymorphisms among human chromosomal areas. HLA is divided into class I antigens, class II antigens, and class III antigens according to distribution and function. Classical HLA class I antigens include HLA-A, HLA-B, and HLA-C; HLA class II antigens include HLA-DP, HLA-DQ, and HLA-DR; nonclassical HLA class I and II molecules include HLA-F, E, H, X, DN, DO, and DM; and others, such as complement, are class III antigens. HLA is closely related to the body's immune response, regulation, and surveillance and is of great significance in the study of autoimmune diseases, tumor immunity, organ transplantation, and reproductive immunity. HLA is an important research topic that bridges immunology and clinical diseases. With the development of research methods and technologies, there will be more discoveries and broader prospects.

The Inhibition of miR-873 Provides Therapeutic Benefit in a Lipopolysaccharide-Induced Neuroinflammatory Model of Parkinson's Disease

Background and Purpose. Alterations in cholesterol homeostasis have been reported in cell and animal models of Parkinson's disease (PD), although there are inconsistent data about the association between serum cholesterol levels and risk of PD. Here, we investigated the effects of miR-873 on lysosomal cholesterol homeostasis and progressive dopaminergic neuron damage in a lipopolysaccharide-(LPS) induced model of PD. Experimental Approach. To evaluate the therapeutic benefit of the miR-873 sponge, rats were injected with a LV-miR-873 sponge or the control vector 3 days before the right-unilateral injection of LPS into the substantia nigra (SN) pars compacta, or 8 and 16 days after LPS injection. Normal SH-SY5Y cells or SH-SY5Y cells overexpressing α-synuclein were used to evaluate the distribution of α-synuclein and cholesterol in lysosomes and to assess the autophagic flux after miR-873 transfection or ABCA1 silencing. The inhibition of miR-873 significantly ameliorated the LPS-induced accumulation of α-synuclein and loss of dopaminergic neurons in the SN at the early stage. miR-873 mediated the inhibition of ABCA1 by LPS. miR-873 transfection or ABCA1 silencing increased the lysosomal cholesterol and α-synuclein levels, and decreased the autophagic flux. The knockdown of ABCA1 or A20, which are the downstream target genes of miR-873, exacerbated the damage to LPS-induced dopaminergic neurons. Conclusion and Implications. The results suggest that the inhibition of miR-873 may play a dual protective role by improving intracellular cholesterol homeostasis and neuroinflammation in PD. The therapeutic effects of the miR-873 sponge in PD may be due to the upregulation of ABCA1 and A20.

Peripheral innate immune and bacterial signals relate to clinical heterogeneity in Parkinson's disease

The innate immune system is implicated in Parkinson's disease (PD), but peripheral in-vivo clinical evidence of the components and driving mechanisms involved and their relationship with clinical heterogeneity and progression to dementia remain poorly explored. We examined changes in peripheral innate immune-related markers in PD cases (n = 41) stratified according to risk of developing early dementia. 'Higher Risk'(HR) (n = 23) and 'Lower Risk' (LR) (n = 18) groups were defined according to neuropsychological predictors and MAPT H1/H2 genotype, and compared to age, gender and genotype-matched controls. Monocyte subsets and expression of key surface markers were measured using flow cytometry. Serum markers including alpha-synuclein, inflammasome-related caspase-1 and bacterial translocation-related endotoxin were measured using quantitative immuno-based assays. Specific markers were further investigated using monocyte assays and validated in plasma samples from a larger incident PD cohort (n = 95). We found that classical monocyte frequency was elevated in PD cases compared to controls, driven predominantly by the HR group, in whom Toll-Like Receptor (TLR)4+ monocytes and monocyte Triggering Receptor Expressed on Myeloid cells-2 (TREM2) expression were also increased. Monocyte Human Leukocyte Antigen (HLA)-DR expression correlated with clinical variables, with lower levels associated with worse cognitive/motor performance. Notably, monocyte changes were accompanied by elevated serum bacterial endotoxin, again predominantly in the HR group. Serum alpha-synuclein and inflammasome-related caspase-1 were decreased in PD cases compared to controls regardless of group, with decreased monocyte alpha-synuclein secretion in HR cases. Further, alpha-synuclein and caspase-1 correlated positively in serum and monocyte lysates, and in plasma from the larger cohort, though no associations were seen with baseline or 36-month longitudinal clinical data. Principal Components Analysis of all monocyte and significant serum markers indicated 3 major components. Component 1 (alpha-synuclein, caspase-1, TLR2+ monocytes) differentiated PD cases and controls in both groups, while Component 2 (endotoxin, monocyte TREM2, alpha-synuclein) did so predominantly in the HR group. Component 3 (classical monocytes, alpha-synuclein) also differentiated cases and controls overall in both groups. These findings demonstrate that systemic innate immune changes are present in PD and are greatest in those at higher risk of rapid progression to dementia. Markers associated with PD per-se (alpha-synuclein, caspase-1), differ from those related to cognitive progression and clinical heterogeneity (endotoxin, TREM2, TLR4, classical monocytes, HLA-DR), with mechanistic and therapeutic implications. Alpha-synuclein and caspase-1 are associated, suggesting inflammasome involvement common to all PD, while bacterial translocation associated changes may contribute towards progression to Parkinson's dementia. Additionally, HLA-DR-associated variations in antigen presentation/clearance may modulate existing clinical disease.

Association Between Toll-Like Receptor 4 (TLR4) and Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) Genetic Variants and Clinical Progression of Huntington's Disease

BACKGROUND

Although Huntington's disease (HD) is caused by a single dominant gene, it is clear that there are genetic modifiers that may influence the age of onset and disease progression.

OBJECTIVES

We sought to investigate whether new inflammation-related genetic variants may contribute to the onset and progression of HD.

METHODS

We first used postmortem brain material from patients at different stages of HD to look at the protein expression of toll-like receptor 4 (TLR4) and triggering receptor expressed on myeloid cells 2 (TREM2). We then genotyped the TREM2 R47H gene variant and 3 TLR4 single nucleotide polymorphisms in a large cohort of HD patients from the European Huntington's Disease Network REGISTRY.

RESULTS

We found an increase in the number of cells expressing TREM2 and TLR4 in postmortem brain samples from patients dying with HD. We also found that the TREM2 R47H gene variant was associated with changes in cognitive decline in the large cohort of HD patients, whereas 2 of 3 TLR4 single nucleotide polymorphisms assessed were associated with changes in motor progression in this same group.

CONCLUSIONS

These findings identify TREM2 and TLR4 as potential genetic modifiers for HD and suggest that inflammation influences disease progression in this condition. © 2019 International Parkinson and Movement Disorder Society.

Toll-like receptors and their therapeutic potential in Parkinson's disease and α-synucleinopathies

Toll-like receptors (TLRs) are pattern recognition receptors which mediate an inflammatory response upon the detection of specific molecular patterns found on foreign organisms and on endogenous damage-related molecules. These receptors play a major role in the activation of microglia, the innate immune cells of the CNS, and are also expressed in peripheral tissues, including blood mononuclear cells and the gut. It is well established that immune activation, in both the brain and periphery, is a feature of Parkinson's disease as well as other α-synucleinopathies. Aggregated forms of α-synuclein can act as ligands for TLRs (particularly TLR2 and TLR4), and hence these receptors may play a critical role in mediating a detrimental immune response to this protein, as well as other inflammatory signals in Parkinson's and related α-synucleinopathies. In this review, the potential role of TLRs in contributing to the progression of these disorders is discussed. Existing evidence comes predominantly from studies in in vitro and in vivo models, as well as analyses of postmortem human brain tissue and pre-clinical studies of TLR inhibitors. This evidence is evaluated in detail, and the potential for therapeutic intervention in α-synucleinopathies through TLR inhibition is discussed.

Associations of TLR4 gene polymorphisms with the risk of age-related macular degeneration in a Chinese Han population

The study was designed to reveal the relationship of toll-like receptor 4 (TLR4, rs1927914 and rs1927907) polymorphisms with risk of age-related macular degeneration (AMD), as well as the adjustment of this association by some environmental and lifestyle factors in Chinese Han population.TLR4 polymorphisms were genotyped by polymerase chain reaction-restricted fragment length polymorphisms and direct sequencing method in 138 AMD patients and 146 healthy controls. Genotype distribution in the control group was checked with Hardy-Weinberg equilibrium. Association of TLR4 polymorphisms and AMD risk was evaluated by χ test and adjusted by age and sex, smoking and drinking. Odds ratio (OR) with 95% confidence interval (95% CI) was used to represent the association strength. Logistic regressive analysis was used to calculate the adjusted OR values.CC genotype of rs1927914 had significantly lower frequency in AMD patients (P = .010), indicated a negative association with AMD risk (crude: OR = 0.358, 95% CI = 0.162-0.791; adjusted: OR = 0.355, 95% CI = 0.160-0.789). C allele of rs1927914 might decrease the susceptibility of AMD (crude: OR = 0.698, 95% CI = 0.497-0.982; adjusted: OR = 0.698, 95% CI = 0.495-0.984). No significant association has been discovered between TLR4 rs1927907 polymorphism and AMD susceptibility. Strong linkage disequilibrium existed between rs1927914 and rs1927907 polymorphisms. C-C haplotype was negatively associated with AMD risk (OR = 0.242, 95% CI = 0.121-0.485; OR = 0.242, 95% CI = 0.120-0.488).CC genotype and C allele of rs1927914 were significantly associated with the decreased AMD susceptibility.

Ceramides in Parkinson's Disease: From Recent Evidence to New Hypotheses

Ceramides (Cer) constitute a class of lipids present in the cell membranes where they act as structural components, but they can also work as signaling molecules. Increasing genetic and biochemical evidence supports a link between deregulation of ceramide metabolism in the brain and neurodegeneration. Here, we provide an overview of the genes and cellular pathways that link Cer with Parkinson’s disease and discuss how ceramide pathobiology is gaining increasing interest in the understanding of the pathological mechanisms that contribute to the disease and in the clinical and therapeutic side.

Vinpocetine regulates levels of circulating TLRs in Parkinson's disease patients

BACKGROUND

The pathogenesis of Parkinson's disease (PD) is complex; it includes mitochondrial dysfunction, oxidative stress, and neuroinflammation. Notably, Toll-like receptors (TLRs) may activate inflammatory or anti-inflammatory responses in Parkinson's disease. Vinpocetine has been tested as an anti-inflammatory in both animal and in vitro research. Thus, it is important to test whether the anti-inflammatory properties of vinpocetine may have a protective effect in PD patients.

METHODS

Eighty-nine Parkinson's disease patients and 42 healthy controls were recruited for this study. All patients were randomly assigned to either the traditional therapy group (T PD group, n = 46) or the vinpocetine group (V PD group, n = 43), in a blinded manner. Both treatments were administered for 14 days.

RESULTS

Administration of vinpocetine reduced mRNA levels of TLR2/4, as well as protein levels of the downstream signalling molecules, MyD88 and NF-κB; moreover, it lowered the expression levels of serum inflammatory cytokines, TNF-α and MCP-1. Notably, vinpocetine increased TLR3 mRNA levels, as well as protein levels of the downstream signalling molecules TRIF-β and IRF-3, and serum levels of the anti-inflammatory cytokines IL-10 and IL-8. Furthermore, vinpocetine produced a robust increase in the Mini Mental State Examination score, compared to that achieved by using levodopa therapy.

CONCLUSION

Vinpocetine treatment may exhibit anti-inflammatory activity and alleviate cognitive impairment.

Association of TLR4 gene polymorphisms with childhood Henoch-Schönlein purpura in a Chinese population

Recent studies demonstrated that aberrant activation of Toll-like receptor (TLR) 4 was involved in the pathogenesis of Henoch-Schönlein purpura (HSP). In this study, we evaluated the association between TLR4 gene polymorphisms and the risk of childhood HSP in a Chinese population. A total of 175 HSP patients and 186 controls were recruited in this case-control study. Three single-nucleotide polymorphisms of the TLR4 gene (rs1927914, rs10759932 and rs1927907) were genotyped using the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and Sequenom MassARRAY system. Our results revealed that a significantly reduced risk for HSP was associated with the G allele (OR = 0.71; p = 0.023) and G/G genotype (OR = 0.49; p = 0.021) of rs1927914. We also showed that rs1927914 variant decreased the risk of HSP in recessive inheritance model (OR = 0.55; p = 0.035, G/G vs A/A + A/G). In addition, we observed that a significantly decreased frequency of the haplotype GTC (rs1927914-rs10759932-rs1927907) in HSP patients compared with controls (OR = 0.56; p = 0.028). Our data suggested that TLR 4 rs1927914 polymorphism was associated with the decreased susceptibility to HSP in the Chinese children.

Advances in understanding genomic markers and pharmacogenetics of Parkinson's disease

INTRODUCTION

The inheritance pattern of Parkinson's disease (PD) is likely multifactorial (owing to the interplay of genetic predisposition and environmental factors). Many pharmacogenetic studies have tried to establish a possible role of candidate genes in PD risk. Several studies have focused on the influence of genes in the response to antiparkinsonian drugs and in the risk of developing side-effects of these drugs.

AREAS COVERED

This review presents an overview of current knowledge, with particular emphasis on the most recent advances, both in case-control association studies on the role of candidate genes in the risk for PD as well as pharmacogenetic studies on the role of genes in the development of side effects of antiparkinsonian drugs. The most reliable results should be derived from meta-analyses of case-control association studies on candidate genes involving large series of PD patients and controls, and from genome-wide association studies (GWAS).

EXPERT OPINION

Prospective studies of large samples involving several genes with a detailed history of exposure to environmental factors in the same cohort of subjects, should be useful to clarify the role of genes in the risk for PD. The results of studies on the role of genes in the development of side-effects of antiparkinsonian drugs should, at this stage, only be considered preliminary.

Evidence for a role of adaptive immune response in the disease pathogenesis of the MPTP mouse model of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease and results from the loss of dopaminergic neurons of the nigrostriatal pathway. The pathogenesis of PD is poorly understood, but inflammatory processes have been implicated. Indeed increases in the number of major histocompatibility complex II (MHC II) reactive cells have long been recognised in the brains of PD patients at post-mortem. However whether cells expressing MHC II play an active role in PD pathogenesis has not been delineated. This was addressed utilising a transgenic mouse null for MHC II and the parkinsonian toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In wild-type mice MHC II levels in the ventral midbrain were upregulated 1-2 days after MPTP treatment and MHC II was localized in both astrocytes and microglia. MHC II null mice showed significant reductions in MPTP-induced dopaminergic neuron loss and a significantly reduced invasion of astrocytes and microglia in MHC II null mice receiving MPTP compared with controls. In addition, MHC II null mice failed to show increases in interferon-γ or tumour necrosis factor-α in the brain after MPTP treatment, as was found in wild-type mice. However, interleukin-1β was significantly increased in both wild-type and MHC II null mice. These data indicate that in addition to microglial cell/myeloid cell activation MHC Class II-mediated T cell activation is required for the full expression of pathology in this model of PD.

Pathways to Parkinsonism Redux: convergent pathobiological mechanisms in genetics of Parkinson's disease

In the past few years, there have been a large number of genes identified that contribute to the lifetime risk of Parkinson's disease (PD). Some genes follow a Mendelian inheritance pattern, but others are risk factors for apparently sporadic PD. Here, we will focus on those genes nominated by genome-wide association studies (GWAS) in sporadic PD, with a particular emphasis on genes that overlap between familial and sporadic disease such as those encoding a-synuclein (SNCA), tau (MAPT), and leucine-rich repeat kinase 2 (LRRK2). We will advance the view that there are likely relationships between these genes that map not only to neuronal processes, but also to neuroinflammation. We will particularly discuss evidence for a role of PD proteins in microglial activation and regulation of the autophagy-lysosome system that is dependent on microtubule transport in neurons. Thus, there are at least two non-mutually exclusive pathways that include both non-cell-autonomous and cell-autonomous mechanisms in the PD brain. Collectively, these data have highlighted the amount of progress made in understanding PD and suggest ways forward to further dissect this disorder.