Induction of Matrix Metalloproteinase-3 (MMP-3) Expression in the Microglia by Lipopolysaccharide (LPS) via Upregulation of Glycoprotein Nonmetastatic Melanoma B (GPNMB) Expression

Oxidative stress and dysregulated long noncoding RNAs in the pathogenesis of Parkinson's disease

Parkinson's disease (PD) is a progressive age-related neurodegenerative disease whose annual incidence is increasing as populations continue to age. Although its pathogenesis has not been fully elucidated, oxidative stress has been shown to play an important role in promoting the occurrence and development of the disease. Long noncoding RNAs (lncRNAs), which are more than 200 nucleotides in length, are also involved in the pathogenesis of PD at the transcriptional level via epigenetic regulation, or at the post-transcriptional level by participating in physiological processes, including aggregation of the α-synuclein, mitochondrial dysfunction, oxidative stress, calcium stabilization, and neuroinflammation. LncRNAs and oxidative stress are correlated during neurodegenerative processes: oxidative stress affects the expression of multiple lncRNAs, while lncRNAs regulate many genes involved in oxidative stress responses. Oxidative stress and lncRNAs also affect other processes associated with neurodegeneration, including mitochondrial dysfunction and increased neuroinflammation that lead to neuronal death. Therefore, modulating the levels of specific lncRNAs may alleviate pathological oxidative damage and have neuroprotective effects. This review discusses the general mechanisms of oxidative stress, pathological mechanism underlying the role of oxidative stress in the pathogenesis of PD, and teases out the mechanisms through which lncRNAs regulate oxidative stress during PD pathogenesis, as well as identifies the possible neuroprotective mechanisms of lncRNAs. Reviewing published studies will help us further understand the mechanisms underlying the role of lncRNAs in the oxidative stress process in PD and to identify potential therapeutic strategies for PD.

Human VCP mutant ALS/FTD microglia display immune and lysosomal phenotypes independently of GPNMB

BACKGROUND

Microglia play crucial roles in maintaining neuronal homeostasis but have been implicated in contributing to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). However, the role of microglia in ALS/FTD remains incompletely understood.

METHODS

Here, we generated highly enriched cultures of VCP mutant microglia derived from human induced pluripotent stem cells (hiPSCs) to investigate their cell autonomous and non-cell autonomous roles in ALS pathogenesis. We used RNA-sequencing, proteomics and functional assays to study hiPSC derived VCP mutant microglia and their effects on hiPSC derived motor neurons and astrocytes.

RESULTS

Transcriptomic, proteomic and functional analyses revealed immune and lysosomal dysfunction in VCP mutant microglia. Stimulating healthy microglia with the inflammatory inducer lipopolysaccharide (LPS) showed partial overlap with VCP mutant microglia in their reactive transformation. LPS-stimulated VCP mutant microglia displayed differential activation of inflammatory pathways compared with LPS-stimulated healthy microglia. Conserved gene expression changes were identified between VCP mutant microglia, SOD1 mutant mice microglia, and postmortem ALS spinal cord microglial signatures, including increased expression of the transmembrane glycoprotein GPNMB. While knockdown of GPNMB affected inflammatory and phagocytosis processes in microglia, this was not sufficient to ameliorate cell autonomous phenotypes in VCP mutant microglia. Secreted factors from VCP mutant microglia were sufficient to activate the JAK-STAT pathway in hiPSC derived motor neurons and astrocytes.

CONCLUSIONS

VCP mutant microglia undergo cell autonomous reactive transformation involving immune and lysosomal dysfunction that partially recapitulate key phenotypes of microglia from other ALS models and post mortem tissue. These phenotypes occur independently of GPNMB. Additionally, VCP mutant microglia elicit non cell autonomous responses in motor neurons and astrocytes involving the JAK-STAT pathway.

Glycoprotein non-metastatic melanoma protein B (GPNMB): An attractive target in atherosclerosis

Atherosclerosis (AS), the leading cause of cardiovascular diseases, is heavily influenced by inflammation, lipid accumulation, autophagy, and aging. The expression of glycoprotein non-metastatic melanoma B (GPNMB) has been observed to correlate with lipid content, inflammation, and aging, progressively increasing as atherosclerosis advances through its various stages, from baseline to early and advanced phases. However, the interaction between GPNMB and AS is controversial. Knockout of GPNMB has been shown to increase atherosclerotic plaque burden in mice. Conversely, targeted elimination of GPNMB-positive cells reduced atherosclerotic burden. These seemingly contradictory findings underscore the complexity of the issue and highlight the need for further research to reconcile these discrepancies and to elucidate the precise role of GPNMB in the pathogenesis of AS.

Quercetin attenuates lipopolysaccharide-induced hepatic inflammation by modulating autophagy and necroptosis

Lipopolysaccharide (LPS) from Gram-negative bacteria initially induces liver inflammation with proinflammatory cytokines expressions. However, the underlying hepatoprotective mechanism of quercetin on LPS-induced hepatic inflammation remains unclear. Specific pathogen-free chicken embryos (n = 120) were allocated control vehicle, PBS with or without ethanol vehicle, LPS (125 ng/egg) with or without quercetin treatment (10, 20, or 40 nmol/egg, respectively), quercetin groups (10, 20, or 40 nmol/egg). Fifteen-day-old embryonated eggs were inoculated abovementioned solutions via the allantoic cavity. At embryonic d 19, the livers of the embryos were collected for histopathological examination, RNA extraction, real-time polymerase chain reaction, and immunohistochemistry investigation. We found that the liver presented inflammatory response (heterophils infiltration) after LPS induction. The LPS-induced mRNA expressions of inflammation-related factors (TLR4, TNFα, IL-1β, IL-10, IL-6, MYD88, NF-κB1, p38, and MMP3) were upregulated after LPS induction when compared with the PBS group, while quercetin could downregulate these expressions as compared with the LPS group. Quercetin significantly decreased the immunopositivity to TLR4 and MMP3 in the treatment group when compared with the LPS group. Quercetin could significantly downregulate the mRNA expressions of autophagy-related genes (ATG5, ATG7, Beclin-1, LC3A, and LC3B) and necroptosis-related genes (Fas, Bcl-2, Drp1, and RIPK1) after LPS induction. Quercetin significantly decreased the immunopositivity to LC3 in the treatment group when compared with the LPS group; meanwhile, quercetin significantly decreased the protein expressions of LC3-I, LC3-II, and the rate of LC3-II/LC3-I. In conclusions, quercetin can alleviate hepatic inflammation induced by LPS through modulating autophagy and necroptosis.

Tumor associated microglia/macrophages utilize GPNMB to promote tumor growth and alter immune cell infiltration in glioma

Tumor-associated microglia and blood-derived macrophages (TAMs) play a central role in modulating the immune suppressive microenvironment in glioma. Here, we show that GPNMB is predominantly expressed by TAMs in human glioblastoma multiforme and the murine RCAS-PDGFb high grade glioma model. Loss of GPNMB in the in vivo tumor microenvironment results in significantly smaller tumor volumes and generates a pro-inflammatory innate and adaptive immune cell microenvironment. The impact of host-derived GPNMB on tumor growth was confirmed in two distinct murine glioma cell lines in organotypic brain slices from GPNMB-KO and control mice. Using published data bases of human glioma, the elevated levels in TAMs could be confirmed and the GPNMB expression correlated with a poorer survival.

Progranulin and GPNMB: interactions in endo-lysosome function and inflammation in neurodegenerative disease

BACKGROUND

Alterations in progranulin (PGRN) expression are associated with multiple neurodegenerative diseases (NDs), including frontotemporal dementia (FTD), Alzheimer's disease (AD), Parkinson's disease (PD), and lysosomal storage disorders (LSDs). Recently, the loss of PGRN was shown to result in endo-lysosomal system dysfunction and an age-dependent increase in the expression of another protein associated with NDs, glycoprotein non-metastatic B (GPNMB).

MAIN BODY

It is unclear what role GPNMB plays in the context of PGRN insufficiency and how they interact and contribute to the development or progression of NDs. This review focuses on the interplay between these two critical proteins within the context of endo-lysosomal health, immune function, and inflammation in their contribution to NDs.

SHORT CONCLUSION

PGRN and GPNMB are interrelated proteins that regulate disease-relevant processes and may have value as therapeutic targets to delay disease progression or extend therapeutic windows.

Expression pattern and prognostic impact of glycoprotein non-metastatic B (GPNMB) in triple-negative breast cancer

Glycoprotein non-metastatic B (GPNMB) is a transmembrane protein overexpressed in numerous cancers including triple-negative breast cancers (TNBC). It has been linked to promote cancer aggressiveness and implicated as a novel target for GPNMB-expressing cancers. In current study, we aimed to explore the clinical significance of GPNMB in TNBC. Among 759 specimens, immunohistochemistry (IHC) exhibited GPNMB expressions were variable in different subtypes and significantly higher in TNBC. Kaplan-Meier analysis revealed GPNMB overexpression in TNBC was associated with worse prognosis especially distant metastasis (P = 0.020, HR = 2.515, CI 1.154-5.480). Multivariate analysis showed GPNMB expression was an independent prognostic factor in terms of recurrence and distant metastasis (P = 0.008, HR = 3.22, CI 1.36-7.61; P = 0.017, HR = 3.08, CI 1.22-7.74). In silico analysis showed high mRNA expression of GPNMB was associated with distant metastasis and GPNMB was overexpressed in TNBC. Furthermore, GPNMB positively correlated with epithelial-mesenchymal transition (EMT) regulators, mesenchymal marker vimentin, MMP and integrins. The protein levels of Twist and MMP2 were upregulated by GPNMB overexpression in TNBC cells. GPNMB-enhanced cell invasion was attenuated by broad spectrum MMP inhibitor (GM 6001) and the selective inhibitor of MMP-2 (ARP100). In summary, GPNMB expression is prevalent in TNBC and may be implicated as a prognostic biomarker in patients with TNBC.

Functional Domains and Evolutionary History of the PMEL and GPNMB Family Proteins

The ancient paralogs premelanosome protein (PMEL) and glycoprotein nonmetastatic melanoma protein B (GPNMB) have independently emerged as intriguing disease loci in recent years. Both proteins possess common functional domains and variants that cause a shared spectrum of overlapping phenotypes and disease associations: melanin-based pigmentation, cancer, neurodegenerative disease and glaucoma. Surprisingly, these proteins have yet to be shown to physically or genetically interact within the same cellular pathway. This juxtaposition inspired us to compare and contrast this family across a breadth of species to better understand the divergent evolutionary trajectories of two related, but distinct, genes. In this study, we investigated the evolutionary history of PMEL and GPNMB in clade-representative species and identified TMEM130 as the most ancient paralog of the family. By curating the functional domains in each paralog, we identified many commonalities dating back to the emergence of the gene family in basal metazoans. PMEL and GPNMB have gained functional domains since their divergence from TMEM130, including the core amyloid fragment (CAF) that is critical for the amyloid potential of PMEL. Additionally, the PMEL gene has acquired the enigmatic repeat domain (RPT), composed of a variable number of imperfect tandem repeats; this domain acts in an accessory role to control amyloid formation. Our analyses revealed the vast variability in sequence, length and repeat number in homologous RPT domains between craniates, even within the same taxonomic class. We hope that these analyses inspire further investigation into a gene family that is remarkable from the evolutionary, pathological and cell biology perspectives.

The Role of GPNMB in Inflammation

Inflammation is a response to a lesion in the tissue or infection. This process occurs in a specific manner in the central nervous system and is called neuroinflammation, which is involved in neurodegenerative diseases. GPNMB, an endogenous glycoprotein, has been recently related to inflammation and neuroinflammation. GPNMB is highly expressed in macrophages and microglia, which are cells involved with innate immune response in the periphery and the brain, respectively. Some studies have shown increased levels of GPNMB in pro-inflammatory conditions, such as LPS treatment, and in pathological conditions, such as neurodegenerative diseases and cancer. However, the role of GPNMB in inflammation is still not clear. Even though most studies suggest that GPNMB might have an anti-inflammatory role by promoting inflammation resolution, there is evidence that GPNMB could be pro-inflammatory. In this review, we gather and discuss the published evidence regarding this interaction.

Glycoprotein nonmetastatic melanoma protein B: A key mediator and an emerging therapeutic target in autoimmune diseases

The glycoprotein nonmetastatic melanoma protein B (GPNMB, also known as osteoactivin) is highly expressed in many cell types and regulates the homeostasis in various tissues. In different physiological contexts, it functions as a melanosome-associated protein, membrane-bound surface receptor, soluble ligand, or adhesion molecule. Therefore, GPNMB is involved in cell differentiation, migration, inflammation, metabolism, and neuroprotection. Because of its various involvement in different physiological conditions, GPNMB has been implicated in many diseases, including cancer, neurological disorders, and more recently immune-mediated diseases. This review summarizes the regulation and function of GPNMB in normal physiology, and discusses the involvement of GPNMB in disease conditions with a particular focus on its potential role and therapeutic implications in autoimmunity.

Seasonal adaptations of the hypothalamo-neurohypophyseal system of the dromedary camel

The “ship” of the Arabian and North African deserts, the one-humped dromedary camel (Camelus dromedarius) has a remarkable capacity to survive in conditions of extreme heat without needing to drink water. One of the ways that this is achieved is through the actions of the antidiuretic hormone arginine vasopressin (AVP), which is made in a specialised part of the brain called the hypothalamo-neurohypophyseal system (HNS), but exerts its effects at the level of the kidney to provoke water conservation. Interestingly, our electron microscopy studies have shown that the ultrastructure of the dromedary HNS changes according to season, suggesting that in the arid conditions of summer the HNS is in an activated state, in preparation for the likely prospect of water deprivation. Based on our dromedary genome sequence, we have carried out an RNAseq analysis of the dromedary HNS in summer and winter. Amongst the 171 transcripts found to be significantly differentially regulated (>2 fold change, p value <0.05) there is a significant over-representation of neuropeptide encoding genes, including that encoding AVP, the expression of which appeared to increase in summer. Identification of neuropeptides in the HNS and analysis of neuropeptide profiles in extracts from individual camels using mass spectrometry indicates that overall AVP peptide levels decreased in the HNS during summer compared to winter, perhaps due to increased release during periods of dehydration in the dry season.

Microglia express GPNMB in the brains of Alzheimer's disease and Nasu-Hakola disease

Glycoprotein non-metastatic melanoma protein B (GPNMB) is a type I transmembrane glycoprotein first identified in low-metastatic human melanoma cell lines as a regulator of tumor growth. GPNMB is widely expressed in various tissues, where it is involved in cell differentiation, migration, inflammation/anti-inflammation, tissue regeneration, and neuroprotection. GPNMB is identified in microglia of adult rat brains, neurons and astrocytes of GPNMB transgenic (Tg) mouse brains, and motor neurons of amyotrophic lateral sclerosis (ALS) patients. Nasu-Hakola disease (NHD) is a rare autosomal recessive disorder, characterized by progressive presenile dementia and formation of multifocal bone cysts, caused by genetic mutations of either TYROBP (DAP12) or TREM2. TREM2 and DAP12 constitute a receptor/adaptor signaling complex expressed exclusively on osteoclasts, dendritic cells, macrophages, and microglia. Pathologically, the brains of NHD patients exhibit leukoencephalopathy, astrogliosis, accumulation of axonal spheroids, and remarkable activation of microglia predominantly in the white matter of frontal and temporal lobes and the basal ganglia. At present, molecular mechanisms responsible for development of leukoencephaolpathy in NHD brains remain totally unknown. Recent evidence indicates that disease-associated microglia (DAM) that cluster around amyloid plaques express high levels of GPNMB in Alzheimer's disease (AD) brains. Because microglia act as a key regulator of leukoencephalopathy in NHD brains, it is proposed that GPNMB expressed on microglia might play a protective role in progression of leukoencephalopathy possibly via active phagocytosis of myelin debris. In the present study using immunohistochemistry, we have attempted to clarify the expression of GPNMB in NHD brains, compared with AD brains. We found that microglia accumulating in the white matter express an intense GPNMB immunoreactivity in both NHD and AD brains, suggesting that the accumulation of GPNMB-immunoreactive microglia is a general phenomenon in neurodegenerative brains.

Glycoprotein Non-Metastatic Protein B: An Emerging Biomarker for Lysosomal Dysfunction in Macrophages

Several diseases are caused by inherited defects in lysosomes, the so-called lysosomal storage disorders (LSDs). In some of these LSDs, tissue macrophages transform into prominent storage cells, as is the case in Gaucher disease. Here, macrophages become the characteristic Gaucher cells filled with lysosomes laden with glucosylceramide, because of their impaired enzymatic degradation. Biomarkers of Gaucher cells were actively searched, particularly after the development of costly therapies based on enzyme supplementation and substrate reduction. Proteins selectively expressed by storage macrophages and secreted into the circulation were identified, among which glycoprotein non-metastatic protein B (GPNMB). This review focusses on the emerging potential of GPNMB as a biomarker of stressed macrophages in LSDs as well as in acquired pathologies accompanied by an excessive lysosomal substrate load in macrophages.

The glycoprotein GPNMB is selectively elevated in the substantia nigra of Parkinson's disease patients and increases after lysosomal stress

GPNMB is a glycoprotein observed upon tissue damage and inflammation and is associated with astrocytes, microglia, and macrophages. Gene variations in GPNMB are linked with Parkinson's disease (PD) risk, and changes in protein levels of GPNMB have been found in lysosomal storage disorders, including Gaucher's disease with glucocerebrosidase (GCase) deficiency. In the current study, GPNMB increases were seen in the substantia nigra (SN) of PD patients compared to age-matched controls. Such PD patients have a decrease in GCase activity and corresponding elevation of glycosphingolipids in the SN (Rocha et al., 2015a). Interestingly, transgenic mice modelling synucleinopathy did not show GPNMB elevations or altered GCase activity levels compared to wild-type mice. However, upon CBE-induced GCase lysosomal dysfunction with elevated glycosphingolipids in wild-type mice, there were similar changes in GPNMB levels in the brain as seen in PD patient brains. These results indicate that GPNMB levels do not depend on alpha-synuclein load per se but relate directly to the lipidopathy changes induced by CBE-mediated GCase inhibition. The experimental modelling of elevating glycolipids resulted in GPNMB elevations with glial activation in several brain regions in mice. This is the first demonstration of region-specific elevations of GPNMB protein in Parkinson's disease. The presence of GPNMB in PD patient substantia nigra, the induction of GPNMB after experimental glycosphingolipid increases, but not with pure alpha-synucleinopathy, point towards the potential for primary lipid-induced degeneration in PD.

Glycoprotein nonmetastatic melanoma protein B accelerates tumorigenesis of cervical cancer in vitro by regulating the Wnt/β-catenin pathway

Cervical cancer is one of the most common cancers among women around the world. However, the underlying mechanism involved in cervical cancer progression is incompletely known. In the present study, we determined the role of glycoprotein nonmetastatic melanoma protein B (GPNMB) in tumorigenesis of cervical cancer. According to the GEO database, we found that GPNMB expression was significantly higher in cervical cancer than in normal cervix epithelium. A similar pattern was observed in GPNMB expression in cultured cervical cancer cells and normal cervical epithelial cells. Compared with the control, GPNMB knockdown significantly decreased the proliferation and migration capacity, but enhanced the apoptosis capacity of SiHa and HeLa cells. Additionally, the activity of MMP-2 and MMP-9 were aberrantly increased in SiHa and HeLa cells compared with normal cervical epithelial cells, whereas their activities were strongly inhibited by GPNMB siRNA. Furthermore, Wnt/β-catenin signaling was activated by GPNMB in SiHa and HeLa cells. Increased MMP-2/MMP-9 expression was suppressed by Dkk-1, inhibitor of Wnt/β-catenin signaling, while it was enhanced by stimulator BIO. The proliferation, migration, and apoptosis capacity of HeLa cells were found to be affected by Dkk-1 and BIO to different extents. In conclusion, we demonstrated that GPNMB contributed to the tumorigenesis of cervical cancer, at least in part, by regulating MMP-2/MMP-9 activity in tumor cells via activation of canonical Wnt/β-catenin signaling. This might be a potential therapeutic target for treating human cervical cancer.

Glycoprotein Non-Metastatic Melanoma Protein B (GPNMB) and Cancer: A Novel Potential Therapeutic Target

Glycoprotein non-metastatic melanoma protein B (GPNMB) is a transmembrane protein enriched on the cell surface of cancer cells, including melanoma, glioblastoma, and triple-negative breast cancer. There is growing evidence identifying GPNMB as a tumor-promoter; however, despite its biological and clinical significance, the molecular mechanisms engaged by GPNMB to promote tumorigenesis are not well understood. GPNMB promotes aggressive behaviors such as tumor cell proliferation, migration, and invasion. The extracellular domain of GPNMB shed from the cell surface interacts with integrins to facilitate in the recruitment of immune-suppressive and pro-angiogenic cells to the tumor microenvironment, thereby enhancing tumor migration and invasion. GPNMB also modulates receptor tyrosine kinases and integrin signaling in a cell autonomous fashion, leading to downstream kinase signaling that in turn triggers the expression and secretion of tumorigenic factors such as matrix metalloproteinases (MMPs) and cytokines. Therefore, GPNMB exerts its pro-tumorigenic role both intracellularly and in a paracrine fashion through shedding its extracellular domain. This review highlights the importance of GPNMB in cancer progression and discusses molecular mediators of GPNMB-induced tumor growth and invasion.

Targeting GPNMB with glembatumumab vedotin: Current developments and future opportunities for the treatment of cancer

GPNMB has emerged as an immunomodulator and an important positive mediator of tumor progression and metastasis in numerous solid cancers. Tumor intrinsic GPNMB-mediated effects on cellular signaling, coupled with the ability of GPNMB to influence the primary tumor and metastatic microenvironments in a non-cell autonomous fashion, combine to augment malignant cancer phenotypes. In addition, GPNMB is often overexpressed in a variety of cancers, making it an attractive therapeutic target. In this regard, glembatumumab vedotin, an antibody-drug conjugate (ADC) that targets GPNMB, is currently in clinical trials as a single agent in multiple cancers. In this review, we will describe the physiological functions of GPNMB in normal tissues and summarize the processes through which GPNMB augments tumor growth and metastasis. We will review the pre-clinical and clinical development of glembatumumab vedotin, evaluate on-going clinical trials, explore emerging opportunities for this agent in new disease indications and discuss exciting possibilities for this ADC in the context of combination therapies.

MMP-3 Deficiency Alleviates Endotoxin-Induced Acute Inflammation in the Posterior Eye Segment

Matrix metalloproteinase-3 (MMP-3) is known to mediate neuroinflammatory processes by activating microglia, disrupting blood-central nervous system barriers and supporting neutrophil influx into the brain. In addition, the posterior part of the eye, more specifically the retina, the retinal pigment epithelium (RPE) and the blood-retinal barrier, is affected upon neuroinflammation, but a role for MMP-3 during ocular inflammation remains elusive. We investigated whether MMP-3 contributes to acute inflammation in the eye using the endotoxin-induced uveitis (EIU) model. Systemic administration of lipopolysaccharide induced an increase in MMP-3 mRNA and protein expression level in the posterior part of the eye. MMP-3 deficiency or knockdown suppressed retinal leukocyte adhesion and leukocyte infiltration into the vitreous cavity in mice subjected to EIU. Moreover, retinal and RPE mRNA levels of intercellular adhesion molecule 1 (Icam1), interleukin 6 (Il6), cytokine-inducible nitrogen oxide synthase (Nos2) and tumor necrosis factor α (Tnfα), which are key molecules involved in EIU, were clearly reduced in MMP-3 deficient mice. In addition, loss of MMP-3 repressed the upregulation of the chemokines monocyte chemoattractant protein (MCP)-1 and (C-X-C motif) ligand 1 (CXCL1). These findings suggest a contribution of MMP-3 during EIU, and its potential use as a therapeutic drug target in reducing ocular inflammation.

Glycoprotein non-metastaticmelanoma protein B promotes glioma motility and angiogenesis through the Wnt/β-catenin signaling pathway

Glioma is a common tumor with high mortality and poor overall survival. However, the regulatory mechanisms of glioma tumorigenesis and glioma cell motility are completely unknown. Here, we investigated the role of glycoprotein non-metastatic melanoma protein B in glioma. The expression of glycoprotein non-metastatic melanoma protein B is observed to be aberrantly regulated in glioma tissues and cells, and high levels of glycoprotein non-metastatic melanoma protein B present an inverse correlation with the survival of glioma patients. Compared with the control, glycoprotein non-metastatic melanoma protein B inhibition significantly retarded the proliferation and migration of human glioma cells. The tube formation ability of HBMECs induced by glioma cells was also remarkably reduced by glycoprotein non-metastatic melanoma protein B silencing. Increased levels of VEGF-C and TEM7 were down-regulated by the suppression of glycoprotein non-metastatic melanoma protein B in glioma cells. Additionally, the activity of MMP-2/3/9 was assessed in glioma cells using Western blotting and gelatin zymography assay; their activities were strongly decreased following the suppression of glycoprotein non-metastatic melanoma protein B. Further studies suggested that canonical Wnt/β-catenin pathway was activated, but was inactivated by glycoprotein non-metastatic melanoma protein B suppression in glioma cells. In conclusion, we demonstrate that glycoprotein non-metastatic melanoma protein B might be an inducer for glioma and could enhance matrix metalloproteinase activity through Wnt/β-catenin pathway to contribute to glioma tumorigenesis. This may represent a new understanding for malignant glioma.

No association of GPNMB rs156429 polymorphism with Parkinson's disease, amyotrophic lateral sclerosis and multiple system atrophy in Chinese population

BACKGROUND

The rs156429 polymorphism in the glycoprotein nonmetastatic melanoma protein B (GPNMB) gene was found to be associated with the risk for Parkinson disease (PD) in Caucasian population by genome-wide association studies (GWAS). Recently, encoded protein, GPNMB, was identified as a novel neuro-protective factor in amyotrophic lateral sclerosis (ALS). The overlapping of clinical manifestations and pathologic characteristics among PD, ALS, and multiple system atrophy (MSA) are observed.

OBJECT

This study aimed at investigating the possible associations of the polymorphism and the three neurodegenerative diseases: PD, ALS and MSA in a Chinese population.

METHODS

All of the subjects, including PD (n=1096), sporadic ALS (SALS) (n=876) and MSA (n=356) patients, and 829 health controls (HCs) were included. All subjects were genotyped for this polymorphism using Sequenom iPLEX Assay technology.

RESULTS

No differences were found in the genotype distributions and minor allele frequency of GPNMB rs156429 between PD patients and HCs, between SALS patients and HCs, between MSA patients and HCs, and between subgroups of PD, ALS and MSA patients with regard to clinical features such as sex, age of onset, presence or absence of cognitive abnormality, depression and anxiety.

CONCLUSION

Lack of association identified in our study suggests that it may be premature to conclude associations between GPNMB rs156429 and SALS, PD and MSA. More studies on such an association involving a larger number of participants are needed to confirm the present findings.

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.

Convergent evidence for mGluR5 in synaptic and neuroinflammatory pathways implicated in ASD

The pathogenesis of Autism Spectrum Disorder (ASD), a serious neurodevelopmental disorder, is poorly understood. We review evidence for alterations in glutamatergic signalling in the aetiology of ASD, with a focus on the metabotropic glutamate receptor-5 (mGluR5). mGluR5 signalling is important for synapse formation, neuroplasticity and long term potentiation as well as neuroprotection and has been shown to have a regulatory role in neuroinflammation. Evidence for neuroinflammation in ASD is supported by increase in pro-inflammatory cytokines in the blood and cerebrospinal fluid (CSF) and increased number and activation of microglia in postmortem dorsolateral prefrontal cortex (DLPFC). mGlur5 signalling has also been shown to downregulate microglial activation. Therefore, we focus on mGluR5 as a potential unifying explanation for synapse alteration and neuroinflammation seen in ASD. Data from mGluR5 knockout mouse models, and syndromic and non syndromic forms of ASD are discussed in relation to how alterations in mGluR5 are associated with ASD symptoms. This review supports altered mGluR5 functioning as a convergent point in ASD pathogenesis and indicates more research is warranted into mGluR5 as a potential therapeutic target.

Inflammation is genetically implicated in Parkinson's disease

Inflammation has long been associated with the pathogenesis of Parkinson's disease (PD) but the extent to which it is a cause or consequence is sill debated. Over the past decade a number of genes have been implicated in PD. Relatively rare missense mutations in genes such as LRRK2, Parkin, SNCA and PINK1 are causative for familial PD whereas more common variation in genes, including LRRK2, SNCA and GBA, comprise risk factors for sporadic PD. Determining how the function of these genes and the proteins they encode are altered in PD has become a priority, as results will likely provide much needed insights into contributing causes. Accumulating evidence indicates that many of these genes function in pathways that regulate aspects of immunity, particularly inflammation, suggesting close associations between PD and immune homeostasis.