Tumor necrosis factor alpha induces a metalloprotease-disintegrin, ADAM8 (CD 156): implications for neuron-glia interactions during neurodegeneration

A jack of all trades - ADAM8 as a signaling hub in inflammation and cancer

As a member of the family of A Disintegrin And Metalloproteinases (ADAM) ADAM8 is preferentially expressed in lymphatic organs, immune cells, and tumor cells. The substrate spectrum for ADAM8 proteolytic activity is not exclusive but is related to effectors of inflammation and signaling in the tumor microenvironment. In addition, complexes of ADAM8 with extracellular binding partners such as integrin β-1 cause an extensive intracellular signaling in tumor cells, thereby activating kinase pathways with STAT3, ERK1/2, and Akt signaling, which causes increased cell survival and enhanced motility. The cytoplasmic domain of ADAM8 harbors five SRC homology-3 (SH3) domains that can potentially interact with several proteins involved in actin dynamics and cell motility, including Myosin 1F (MYO1F), which is essential for neutrophil motility. The concept of ADAM8 thus involves immune cell recruitment, in most cases leading to an enhancement of inflammatory (asthma, COPD) and tumor (including pancreatic and breast cancers) pathologies. In this review, we report on available studies that qualify ADAM8 as a therapeutic target in different pathologies. As a signaling hub, ADAM8 controls extracellular, intracellular, and intercellular communication, the latter one mainly mediated by the release of extracellular vesicles with ADAM8 as cargo. Here, we will dissect the contribution of different domains to these distinct ways of communication in several pathologies. We conclude that therapeutic targeting attempts for ADAM8 should consider blocking more than a single domain and that this requires a thorough evaluation of potent molecules targeting ADAM8 in an in vivo setting.

A Disintegrin and Metalloproteinase-8 Protects Against Erastin-Induced Neuronal Ferroptosis via Activating Nrf2/HO-1/FTH1 Signaling Pathway

Ferroptosis is a type of iron-dependent programmed cell death caused by the imbalance between oxidants and antioxidants. A disintegrin and metalloproteinase-8 (ADAM8) is a metalloproteinase that mediates cell adhesion, cell migration, and proteolytic activity. However, the molecular mechanism of ADAM8 regulating ferroptosis after neural disorder is unclear, especially in the neuron. In the present study, we identified the protective role of ADAM8 in Erastin-induced ferroptosis in vitro of the HT22 cells. It was found that overexpression of ADAM8 resulted in upregulated expression of GPX4 and FTH1 along with the decreased reactive oxygen species (ROS) production and reduced neuronal death; however, knockdown of ADAM8 resulted in an opposite. Mechanically, using the Nrf2 activator NK-252 and inhibitor nrf2-IN-1, we dmonstrated that ADAM8 regulates Erastin-mediated neuronal ferroptosis via activating the Nrf2/HO-1/FTH1 signaling pathway. In conclusion, the current study suggested that ADAM8 inhibited Erastin-induced neuronal ferroptosis through activating the Nrf2/HO-1/FTH1 signaling pathway, playing a protective role in vitro of the HT22 cell line. ADAM8 may be a promising and feasible target for neuronal survival in diseases of neural disorder.

Advancements in Single-Cell RNA Sequencing Research for Neurological Diseases

Neurological diseases are a major cause of the global burden of disease. Although the mechanisms of the occurrence and development of neurological diseases are not fully clear, most of them are associated with cells mediating neuroinflammation. Yet medications and other therapeutic options to improve treatment are still very limited. Single-cell RNA sequencing (scRNA-seq), as a delightfully potent breakthrough technology, not only identifies various cell types and response states but also uncovers cell-specific gene expression changes, gene regulatory networks, intercellular communication, and cellular movement trajectories, among others, in different cell types. In this review, we describe the technology of scRNA-seq in detail and discuss and summarize the application of scRNA-seq in exploring neurological diseases, elaborating the corresponding specific mechanisms of the diseases as well as providing a reliable basis for new therapeutic approaches. Finally, we affirm that scRNA-seq promotes the development of the neuroscience field and enables us to have a deeper cellular understanding of neurological diseases in the future, which provides strong support for the treatment of neurological diseases and the improvement of patients' prognosis.

Identification of a novel macrophage-related prognostic signature in colorectal cancer

Colorectal cancer (CRC) is one of the most prevalent and deadliest illnesses all around the world. Growing proofs demonstrate that tumor-associated macrophages (TAMs) are of critical importance in CRC pathogenesis, but their mechanisms remain yet unknown. The current research was designed to recognize underlying biomarkers associated with TAMs in CRC. We screened macrophage-related gene modules through WGCNA, selected hub genes utilizing the LASSO algorithm and COX regression, and established a model. External validation was performed by expression analysis using datasets GSE14333, GSE74602, and GSE87211. After validating the bioinformatics results using real-time quantitative reverse transcription PCR, we identified SPP1, C5AR1, MMP3, TIMP1, ADAM8 as potential biomarkers associated with macrophages in CRC.

Transcriptomic Analysis of lncRNAs and their mRNA Networks in Cerebral Ischemia in Young and Aged Mice

BACKGROUND

Ischemic stroke comprises 75% of all strokes and it is associated with a great frailty and casualty rate. Certain data suggest multiple long non-coding Ribonucleic Acids (lncRNAs) assist the transcriptional, post-transcriptional, and epigenetic regulation of genes expressed in the CNS (Central Nervous System). However, these studies generally focus on differences in the expression patterns of lncRNAs and Messenger Ribonucleic Acids (mRNAs) in tissue samples before and after cerebral ischemic injury, ignoring the effects of age.

METHODS

In this study, differentially expressed lncRNA analysis was performed based on RNAseq data from the transcriptomic analysis of murine brain microglia related to cerebral ischemia injury in mice at different ages (10 weeks and 18 months).

RESULTS

The results showed that the number of downregulate differentially expressed genes (DEGs) in aged mice was 37 less than in young mice. Among them, lncRNA Gm-15987, RP24- 80F7.5, XLOC_379730, XLOC_379726 were significantly down-regulated. Then, Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that these specific lncRNAs were mainly related to inflammation. Based on the lncRNA/mRNA coexpression network, the mRNA co-expressed with lncRNA was mainly enriched in pathways, such as immune system progression, immune response, cell adhesion, B cell activation, and T cell differentiation. Our results indicate that the downregulation of lncRNA, such as Gm-15987, RP24- 80F7.5, XLOC_379730, and XLOC_379726 in aged mice may attenuate microglial-induced inflammation via the progress of immune system progression immune response, cell adhesion, B cell activation, and T cell differentiation.

CONCLUSION

The reported lncRNAs and their target mRNA during this pathology have potentially key regulatory functions in the cerebral ischemia in aged mice while being important for diagnosing and treating cerebral ischemia in the elderly.

Bruton's tyrosine kinase-bearing B cells and microglia in neuromyelitis optica spectrum disorder

BACKGROUND

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory autoimmune disease of the central nervous system that involves B-cell receptor signaling as well as astrocyte-microglia interaction, which both contribute to evolution of NMOSD lesions.

MAIN BODY

Through transcriptomic and flow cytometry analyses, we found that Bruton's tyrosine kinase (BTK), a crucial protein of B-cell receptor was upregulated both in the blood and cerebrospinal fluid of NMOSD patients. Blockade of BTK with zanubrutinib, a highly specific BTK inhibitor, mitigated the activation and maturation of B cells and reduced production of causal aquaporin-4 (AQP4) autoantibodies. In a mouse model of NMO, we found that both BTK and pBTK expression were significantly increased in microglia. Transmission electron microscope scan demonstrated that BTK inhibitor ameliorated demyelination, edema, and axonal injury in NMO mice. In the same mice colocalization of GFAP and Iba-1 immunofluorescence indicated a noticeable increase of astrocytes-microglia interaction, which was alleviated by zanubrutinib. The smart-seq analysis demonstrated that treatment with BTK inhibitor instigated microglial transcriptome changes including downregulation of chemokine-related genes and genes involved in the top 5 biological processes related to cell adhesion and migration, which are likely responsible for the reduced crosstalk of microglia and astrocytes.

CONCLUSIONS

Our results show that BTK activity is enhanced both in B cells and microglia and BTK inhibition contributes to the amelioration of NMOSD pathology. These data collectively reveal the mechanism of action of BTK inhibition and corroborate BTK as a viable therapeutic target.

Decoding DNA sequence-driven evolution of the human brain epigenome at cellular resolution

DNA-based evolutionary comparisons of regulatory genomic elements enable insight into functional changes, overcoming tissue inaccessibility. Here, we harnessed adult and fetal cortex single-cell ATAC-seq datasets to uncover DNA substitutions specific to the human and human-ancestral lineages within apes. We found that fetal microglia identity is evolutionarily divergent in all lineages, whereas other cell types are conserved. Using multiomic datasets, we further identified genes linked to multiple lineage-divergent gene regulatory elements and implicated biological pathways associated with these divergent features. We also uncovered patterns of transcription factor binding site evolution across lineages and identified expansion of bHLH-PAS factor targets in human-hominin lineages, and MEF2 factor targets in the ape lineage. Finally, conserved features were more enriched in brain disease variants, whereas there was no distinct enrichment on the human lineage compared to its ancestral lineages. Our study identifies major evolutionary patterns in the human brain epigenome at cellular resolution.

Changes of gene expression in peripheral blood mononuclear cells of lung cancer patients with or without anorexia

BACKGROUND & AIMS

Anorexia is a disabling symptom in cancer and we aimed at investigating the role of changes in gene expression in lung cancer patients presenting with anorexia.

METHODS

Genome-wide transcriptomic profiling was assessed in PBMCs RNA from newly diagnosed lung cancer patients and in a control group. RT-qPCR was used for selected genes.

RESULTS

RNA-Seq analysis revealed among groups a large number of differentially expressed genes mainly implicated in immune system regulation, oxidative stress and cytokine-mediated inflammation signaling pathways. In particular, we identified a total of 983 DEGs (843 up-regulated; 140 down-regulated) in anorexic cancer compared to controls. A selected number of DEGs including ADAM8, SMAD4, CCR4 and CLU were differentially expressed within cancer group according to the presence/absence of anorexia. In terms of RT-qPCR, ADAM8 was less expressed in cancer patients than controls (p < 0.001), and in anorexic patients vs controls (p = 0.001). The expression of SMAD4 was lower in cancer vs controls (p = 0.005), and in anorexic patients vs controls (p = 0.009). We observed lower CCR4 expression in both anorexic and non-anorexic vs control (p = 0.004, p = 0.011, respectively) and a similar trend was present for CLU.

CONCLUSIONS

Our data shed new light on the role of specific genes and their associated molecular pathways as potential key mechanisms for the development of anorexia and may represent a novel landmark for understanding the complex pathophysiology of impaired appetite in cancer.

The versatile roles of ADAM8 in cancer cell migration, mechanics, and extracellular matrix remodeling

The posttranslational proteolytic cleavage is a unique and irreversible process that governs the function and half-life of numerous proteins. Thereby the role of the family of A disintegrin and metalloproteases (ADAMs) plays a leading part. A member of this family, ADAM8, has gained attention in regulating disorders, such as neurogenerative diseases, immune function and cancer, by attenuating the function of proteins nearby the extracellular membrane leaflet. This process of "ectodomain shedding" can alter the turnover rate of a number of transmembrane proteins that function in cell adhesion and receptor signal transduction. In the past, the major focus of research about ADAMs have been on neurogenerative diseases, such as Alzheimer, however, there seems to be evidence for a connection between ADAM8 and cancer. The role of ADAMs in the field of cancer research has gained recent attention, but it has been not yet been extensively addressed. Thus, this review article highlights the various roles of ADAM8 with particular emphasis on pathological conditions, such as cancer and malignant cancer progression. Here, the shedding function, direct and indirect matrix degradation, effects on cancer cell mobility and transmigration, and the interplay of ADAM8 with matrix-embedded neighboring cells are presented and discussed. Moreover, the most probable mechanical impact of ADAM8 on cancer cells and their matrix environment is addressed and debated. In summary, this review presents recent advances in substrates/ligands and functions of ADAM8 in its new role in cancer and its potential link to cell mechanical properties and discusses matrix mechanics modifying properties. A deeper comprehension of the regulatory mechanisms governing the expression, subcellular localization, and activity of ADAM8 is expected to reveal appropriate drug targets that will permit a more tailored and fine-tuned modification of its proteolytic activity in cancer development and metastasis.

Heterogeneity analysis of astrocytes following spinal cord injury at single-cell resolution

Astrocytes play many important functions in response to spinal cord injury (SCI) in an activated manner, including clearance of necrotic tissue, formation of protective barrier, maintenance of microenvironment balance, interaction with immune cells, and formation of the glial scar. More and more studies have shown that the astrocytes are heterogeneous, such as inflammatory astrocyte 1 (A1) and neuroprotective astrocyte 2 (A2) types. However, the subtypes of astrocyte resulting from SCI have not been clearly defined. In this study, using single-cell RNA sequencing, we constructed the transcriptomic profile of astrocytes from uninjured spinal cord tissue and injured tissue nearby the lesion epicenter at 0.5, 1, 3, 7, 14, 60, and 90 days after mouse hemisection spinal cord surgery. Our analysis uncovered six transcriptionally distinct astrocyte states, including Atp1b2⁺ , S100a4⁺ , Gpr84⁺ , C3⁺ /G0s2⁺ , GFAP⁺ /Tm4sf1⁺ , and Gss⁺ /Cryab⁺ astrocytes. We used these new signatures combined with canonical astrocyte markers to determine the distribution of morphologically and physiologically distinct astrocyte population at injured sites by immunofluorescence staining. Then we identified the dynamic evolution process of each astrocyte subtype following SCI. Finally, we also revealed the evolution of highly expressed genes in these astrocyte subtypes at different phases of SCI. Together, we provided six astrocyte subtypes at single-cell resolution following SCI. These data not only contribute to understand the heterogeneity of astrocytes during SCI but also help to find new astrocyte subtypes as a target for SCI repair.

The potential role of DNA methylation as preventive treatment target of epileptogenesis

Pharmacological therapy of epilepsy has so far been limited to symptomatic treatment aimed at neuronal targets, with the result of an unchanged high proportion of patients lacking seizure control. The dissection of the intricate pathological mechanisms that transform normal brain matter to a focus for epileptic seizures—the process of epileptogenesis—could yield targets for novel treatment strategies preventing the development or progression of epilepsy. While many pathological features of epileptogenesis have been identified, obvious shortcomings in drug development are now believed to be based on the lack of knowledge of molecular upstream mechanisms, such as DNA methylation (DNAm), and as well as a failure to recognize glial cell involvement in epileptogenesis. This article highlights the potential role of DNAm and related gene expression (GE) as a treatment target in epileptogenesis.

ADAM8 signaling drives neutrophil migration and ARDS severity

Acute respiratory distress syndrome (ARDS) results in catastrophic lung failure and has an urgent, unmet need for improved early recognition and therapeutic development. Neutrophil influx is a hallmark of ARDS and is associated with the release of tissue-destructive immune effectors, such as matrix metalloproteinases (MMPs) and membrane-anchored metalloproteinase disintegrins (ADAMs). Here, we observed using intravital microscopy that Adam8-/- mice had impaired neutrophil transmigration. In mouse pneumonia models, both genetic deletion and pharmacologic inhibition of ADAM8 attenuated neutrophil infiltration and lung injury while improving bacterial containment. Unexpectedly, the alterations of neutrophil function were not attributable to impaired proteolysis but resulted from reduced intracellular interactions of ADAM8 with the actin-based motor molecule Myosin1f that suppressed neutrophil motility. In 2 ARDS cohorts, we analyzed lung fluid proteolytic signatures and identified that ADAM8 activity was positively correlated with disease severity. We propose that in acute inflammatory lung diseases such as pneumonia and ARDS, ADAM8 inhibition might allow fine-tuning of neutrophil responses for therapeutic gain.

Cell Heterogeneity Uncovered by Single-Cell RNA Sequencing Offers Potential Therapeutic Targets for Ischemic Stroke

Ischemic stroke is a detrimental neurological disease characterized by an irreversible infarct core surrounded by an ischemic penumbra, a salvageable region of brain tissue. Unique roles of distinct brain cell subpopulations within the neurovascular unit and peripheral immune cells during ischemic stroke remain elusive due to the heterogeneity of cells in the brain. Single-cell RNA sequencing (scRNA-seq) allows for an unbiased determination of cellular heterogeneity at high-resolution and identification of cell markers, thereby unveiling the principal brain clusters within the cell-type-specific gene expression patterns as well as cell-specific subclusters and their functions in different pathways underlying ischemic stroke. In this review, we have summarized the changes in differentiation trajectories of distinct cell types and highlighted the specific pathways and genes in brain cells that are impacted by stroke. This review is expected to inspire new research and provide directions for investigating the potential pathological mechanisms and novel treatment strategies for ischemic stroke at the level of a single cell.

Leukocyte Membrane Enzymes Play the Cell Adhesion Game

For a long time, proteins with enzymatic activity have not been usually considered to carry out other functions different from catalyzing chemical reactions within or outside the cell. Nevertheless, in the last few years several reports have uncovered the participation of numerous enzymes in other processes, placing them in the category of moonlighting proteins. Some moonlighting enzymes have been shown to participate in complex processes such as cell adhesion. Cell adhesion plays a physiological role in multiple processes: it enables cells to establish close contact with one another, allowing communication; it is a key step during cell migration; it is also involved in tightly binding neighboring cells in tissues, etc. Importantly, cell adhesion is also of great importance in pathophysiological scenarios like migration and metastasis establishment of cancer cells. Cell adhesion is strictly regulated through numerous switches: proteins, glycoproteins and other components of the cell membrane. Recently, several cell membrane enzymes have been reported to participate in distinct steps of the cell adhesion process. Here, we review a variety of examples of membrane bound enzymes participating in adhesion of immune cells.

Propofol mediates pancreatic cancer cell activity through the repression of ADAM8 via SP1

Propofol is a commonly used anesthetic with controversial effects on cancer cells. A growing number of studies have demonstrated that low concentrations of propofol are associated with tumor suppression and when used as an intravenous anesthesia improved recurrence‑free survival rates for many cancers, but deeper insights into its underlying mechanism are needed. The study detailed herein focused upon the effect of propofol on pancreatic cancer cells and the mechanism by which propofol reduces A disintegrin and metalloproteinase 8 (ADAM8) expression. The ability of propofol to impact the proliferation, migration and cell cycle of pancreatic cancer cell lines was assessed in vitro. This was mechanistically explored following the identification of SP1 binding sites within ADAM8, which enabled the regulatory effects of specificity protein 1 (SP1) on ADAM8 following propofol treatment to be further explored. Ultimately, this study was able to show that propofol significantly inhibited the proliferation, migration and invasion of pancreatic cancer cells and decreased the percentage of cells in S‑phase. Propofol treatment was also shown to repress ADAM8 and SP1 expression, but was unable to affect ADAM8 expression following knockdown of SP1. Moreover, a direct physical interaction between SP1 and ADAM8 was verified using co‑immunoprecipitation and dual‑luciferase reporter assays. Cumulatively, these results suggest that propofol represses pathological biological behaviors associated with pancreatic cancer cells through the suppression of SP1, which in turn results in lower ADAM8 mRNA expression and protein levels.

Adulthood systemic inflammation accelerates the trajectory of age-related cognitive decline

In order to understand the long-term effects of systemic inflammation, it is important to distinguish inflammation-induced changes in baseline cognitive function from changes that interact with aging to influence the trajectory of cognitive decline. Lipopolysaccharide (LPS; 1 mg/kg) or vehicle was administered to young adult (6 months) male rats via intraperitoneal injections, once a week for 7 weeks. Longitudinal effects on cognitive decline were examined 6 and 12 months after the initial injections. Repeated LPS treatment, in adults, resulted in a long-term impairment in memory, examined in aged animals (age 18 months), but not in middle-age (age 12 months). At 12 months following injections, LPS treatment was associated with a decrease in N-methyl-D-aspartate receptor-mediated component of synaptic transmission and altered expression of genes linked to the synapse and to regulation of the response to inflammatory signals. The results of the current study suggest that the history of systemic inflammation is one component of environmental factors that contribute to the resilience or susceptibility to age-related brain changes and associated trajectory of cognitive decline.

A Disintegrin and Metalloproteinase (ADAM) Family: Their Significance in Malignant Tumors of the Central Nervous System (CNS)

Despite the considerable advances in diagnostic methods in medicine, central nervous system (CNS) tumors, particularly the most common ones-gliomas-remain incurable, with similar incidence rates and mortality. A growing body of literature has revealed that degradation of the extracellular matrix by matrix metalloproteinases (MMPs) might be involved in the pathogenesis of CNS tumors. However, the subfamily of MMPs, known as disintegrin and metalloproteinase (ADAM) proteins are unique due to both adhesive and proteolytic activities. The objective of our review is to present the role of ADAMs in CNS tumors, particularly their involvement in the development of malignant gliomas. Moreover, we focus on the diagnostic and prognostic significance of selected ADAMs in patients with these neoplasms. It has been proven that ADAM12, ADAMTS4 and 5 are implicated in the proliferation and invasion of glioma cells. In addition, ADAM8 and ADAM19 are correlated with the invasive activity of glioma cells and unfavorable survival, while ADAM9, -10 and -17 are associated with tumor grade and histological type of gliomas and can be used as prognostic factors. In conclusion, several ADAMs might serve as potential diagnostic and prognostic biomarkers as well as therapeutic targets for malignant CNS tumors. However, future research on ADAMs biology should be performed to elucidate new strategies for tumor diagnosis and treatment of patients with these malignancies.

Alcohol Dependence in Rats Is Associated with Global Changes in Gene Expression in the Central Amygdala

Alcohol dependence is associated with adverse consequences of alcohol (ethanol) use and is evident in most severe cases of alcohol use disorder (AUD). The central nucleus of the amygdala (CeA) plays a critical role in the development of alcohol dependence and escalation of alcohol consumption in dependent subjects. Molecular mechanisms underlying the CeA-driven behavioral changes are not well understood. Here, we examined the effects of alcohol on global gene expression in the CeA using a chronic intermittent ethanol (CIE) vapor model in rats and RNA sequencing (RNA-Seq). The CIE procedure resulted in robust changes in CeA gene expression during intoxication, as the number of differentially expressed genes (DEGs) was significantly greater than those expected by chance. Over-representation analysis of cell types, functional groups and molecular pathways revealed biological categories potentially important for the development of alcohol dependence in our model. Genes specific for astrocytes, myelinating oligodendrocytes, and endothelial cells were over-represented in the DEG category, suggesting that these cell types were particularly affected by the CIE procedure. The majority of the over-represented functional groups and molecular pathways were directly related to the functions of glial and endothelial cells, including extracellular matrix (ECM) organization, myelination, and the regulation of innate immune response. A coordinated regulation of several ECM metalloproteinases (e.g., Mmp2; Mmp14), their substrates (e.g., multiple collagen genes and myelin basic protein; Mbp), and a metalloproteinase inhibitor, Reck, suggests a specific mechanism for ECM re-organization in response to chronic alcohol, which may modulate neuronal activity and result in behavioral changes, such as an escalation of alcohol drinking. Our results highlight the importance of glial and endothelial cells in the effects of chronic alcohol exposure on the CeA, and demonstrate further insight into the molecular mechanisms of alcohol dependence in rats. These molecular targets may be used in future studies to develop therapeutics to treat AUD.

Peptide-Based Inhibitors of ADAM and ADAMTS Metalloproteinases

ADAM and ADAMTS are two large metalloproteinase families involved in numerous physiological processes, such as shedding of cell-surface protein ectodomains and extra-cellular matrix remodelling. Aberrant expression or dysregulation of ADAMs and ADAMTSs activity has been linked to several pathologies including cancer, inflammatory, neurodegenerative and cardiovascular diseases. Inhibition of ADAM and ADAMTS metalloproteinases have been attempted using various small molecules and protein-based therapeutics, each with their advantages and disadvantages. While most of these molecular formats have already been described in detail elsewhere, this mini review focuses solely on peptide-based inhibitors, an emerging class of therapeutic molecules recently applied against some ADAM and ADAMTS members. We describe both linear and cyclic peptide-based inhibitors which have been developed using different approaches ranging from traditional medicinal chemistry and rational design strategies to novel combinatorial peptide-display technologies.

Expression levels of the metalloproteinase ADAM8 critically regulate proliferation, migration and malignant signalling events in hepatoma cells

Hepatocellular carcinoma (HCC) is one of the most common metastatic tumours. Tumour growth and metastasis depend on the induction of cell proliferation and migration by various mediators. Here, we report that the A Disintegrin and Metalloproteinase (ADAM) 8 is highly expressed in murine HCC tissues as well as in murine and human hepatoma cell lines Hepa1-6 and HepG2, respectively. To establish a dose-dependent role of different ADAM8 expression levels for HCC progression, ADAM8 expression was either reduced via shRNA- or siRNA-mediated knockdown or increased by using a retroviral overexpression vector. These two complementary approaches revealed that ADAM8 expression levels correlated positively with proliferation, clonogenicity, migration and matrix invasion and negatively with apoptosis of hepatoma cells. Furthermore, the analysis of pro-migratory and proliferative signalling pathways revealed that ADAM8 expression level was positively associated with expression of β1 integrin as well as with the activation of focal adhesion kinase (FAK), mitogen-activated protein kinase (MAPK), Src kinase and Rho A GTPase. Finally, up-regulation of promigatory signalling and cell migration was also seen with a proteolytically inactive ADAM8 mutant. These findings reveal that ADAM8 is critically up-regulated in hepatoma cells contributes to cell proliferation and survival and furthermore induces pro-migratory signalling pathways independently of its proteolytic activity. By this, ADAM8 can promote cell functions most relevant for HCC growth and metastasis.

Genome-wide transcriptomic analysis of microglia reveals impaired responses in aged mice after cerebral ischemia

Senescence-associated alterations in microglia may have profound impact on cerebral homeostasis and stroke outcomes. However, the lack of a transcriptome-wide comparison between young and aged microglia in the context of ischemia limits our understanding of aging-related mechanisms. Herein, we performed RNA sequencing analysis of microglia purified from cerebral hemispheres of young adult (10-week-old) and aged (18-month-old) mice five days after distal middle cerebral artery occlusion or after sham operation. Considerable transcriptional differences were observed between young and aged microglia in healthy brains, indicating heightened chronic inflammation in aged microglia. Following stroke, the overall transcriptional activation was more robust (>13-fold in the number of genes upregulated) in young microglia than in aged microglia. Gene clusters with functional implications in immune inflammatory responses, immune cell chemotaxis, tissue remodeling, and cell-cell interactions were markedly activated in microglia of young but not aged stroke mice. Consistent with the genomic profiling predictions, post-stroke cerebral infiltration of peripheral immune cells was markedly decreased in aged mice compared to young mice. Moreover, post-ischemic aged microglia demonstrated reduced interaction with neighboring neurons and diminished polarity toward the infarct lesion. These alterations in microglial gene response and behavior may contribute to aging-driven vulnerability and poorer recovery after ischemic stroke.

Transcriptomic and functional studies reveal undermined chemotactic and angiostimulatory properties of aged microglia during stroke recovery

Age-dependent alterations in microglia behavior have been implicated in neurodegeneration and CNS injuries. Here, we compared the transcriptional profiles of young versus aged microglia during stroke recovery. CD45intermediateCD11b+ microglia were FACS-isolated from the brains of young (10-week-old) and aged (18-month-old) male mice with sham operation or 14 days after distal middle cerebral artery occlusion and subjected to RNA-sequencing analysis. Functional groups enriched in young microglia are indicative of upregulation in cell movement, cell interactions, inflammatory responses and angiogenesis, while aged microglia exhibited a reduction or no change in these features. We confirmed reduced chemoattractive capacities of aged microglia toward ischemic brain tissue in organotypic slide co-cultures, and delayed accumulation of aged microglia around dead neurons injected into the striatum in vivo. In addition, aging is associated with an overall failure to increase the expression of microglial genes involved in cell-cell interactions, such as CXCL10. Finally, impaired upregulation of pro-angiogenic genes in aged microglia was associated with a decline in neovascularization in aged mice compared to young mice after distal middle cerebral artery occlusion. This study provides a new resource to understand the mechanisms underlying microglial alterations in the aged brain milieu and sheds light on new strategies to improve microglial functions in aged stroke victims.

Comparative Transcriptome Analysis of the Regenerating Zebrafish Telencephalon Unravels a Resource With Key Pathways During Two Early Stages and Activation of Wnt/β-Catenin Signaling at the Early Wound Healing Stage

Owing to its pronounced regenerative capacity in many tissues and organs, the zebrafish brain represents an ideal platform to understand the endogenous regeneration mechanisms that restore tissue integrity and function upon injury or disease. Although radial glial and neuronal cell populations have been characterized with respect to specific marker genes, comprehensive transcriptomic profiling of the regenerating telencephalon has not been conducted so far. Here, by processing the lesioned and unlesioned hemispheres of the telencephalon separately, we reveal the differentially expressed genes (DEGs) at the early wound healing and early proliferative stages of regeneration, i.e., 20 h post-lesion (hpl) and 3 days post-lesion (dpl), respectively. At 20 hpl, we detect a far higher number of DEGs in the lesioned hemisphere than in the unlesioned half and only 7% of all DEGs in both halves. However, this difference disappears at 3 dpl, where the lesioned and unlesioned hemispheres share 40% of all DEGs. By performing an extensive comparison of the gene expression profiles in these stages, we unravel that the lesioned hemispheres at 20 hpl and 3 dpl exhibit distinct transcriptional profiles. We further unveil a prominent activation of Wnt/β-catenin signaling at 20 hpl, returning to control level in the lesioned site at 3 dpl. Wnt/β-catenin signaling indeed appears to control a large number of genes associated primarily with the p53, apoptosis, forkhead box O (FoxO), mitogen-activated protein kinase (MAPK), and mammalian target of rapamycin (mTOR) signaling pathways specifically at 20 hpl. Based on these results, we propose that the lesioned and unlesioned hemispheres react to injury dynamically during telencephalon regeneration and that the activation of Wnt/β-catenin signaling at the early wound healing stage plays a key role in the regulation of cellular and molecular events.

Mice defective in interferon signaling help distinguish between primary and secondary pathological pathways in a mouse model of neuronal forms of Gaucher disease

BACKGROUND

The type 1 interferon (IFN) response is part of the innate immune response and best known for its role in viral and bacterial infection. However, this pathway is also induced in sterile inflammation such as that which occurs in a number of neurodegenerative diseases, including neuronopathic Gaucher disease (nGD), a lysosomal storage disorder (LSD) caused by mutations in GBA.

METHODS

Mice were injected with conduritol B-epoxide, an irreversible inhibitor of acid beta-glucosidase, the enzyme defective in nGD. MyTrMaSt null mice, where four adaptors of pathogen recognition receptors (PRRs) are deficient, were used to determine the role of the IFN pathway in nGD pathology. Activation of inflammatory and other pathways was analyzed by a variety of methods including RNAseq.

RESULTS

Elevation in the expression of PRRs associated with the IFN response was observed in CBE-injected mice. Ablation of upstream pathways leading to IFN production had no therapeutic benefit on the lifespan of nGD mice but attenuated neuroinflammation. Primary and secondary pathological pathways (i.e., those associated or not with mouse survival) were distinguished, and a set of ~210 genes including those related to sphingolipid, cholesterol, and lipoprotein metabolism, along with a number of inflammatory pathways related to chemokines, TNF, TGF, complement, IL6, and damage-associated microglia were classified as primary pathological pathways, along with some lysosomal and neuronal genes.

CONCLUSIONS

Although IFN signaling is the top elevated pathway in nGD, we demonstrate that this pathway is not related to mouse viability and is consequently defined as a secondary pathology pathway. By elimination, we defined a number of critical pathways that are directly related to brain pathology in nGD, which in addition to its usefulness in understanding pathophysiological mechanisms, may also pave the way for the development of novel therapeutic paradigms by targeting such pathways.

Genetic and environmental determinants of variation in the plasma lipidome of older Australian twins

The critical role of blood lipids in a broad range of health and disease states is well recognised but less explored is the interplay of genetics and environment within the broader blood lipidome. We examined heritability of the plasma lipidome among healthy older-aged twins (75 monozygotic/55 dizygotic pairs) enrolled in the Older Australian Twins Study (OATS) and explored corresponding gene expression and DNA methylation associations. 27/209 lipids (13.3%) detected by liquid chromatography-coupled mass spectrometry (LC-MS) were significantly heritable under the classical ACE twin model (h2 = 0.28-0.59), which included ceramides (Cer) and triglycerides (TG). Relative to non-significantly heritable TGs, heritable TGs had a greater number of associations with gene transcripts, not directly associated with lipid metabolism, but with immune function, signalling and transcriptional regulation. Genome-wide average DNA methylation (GWAM) levels accounted for variability in some non-heritable lipids. We reveal a complex interplay of genetic and environmental influences on the ageing plasma lipidome.

Functions of 'A disintegrin and metalloproteases (ADAMs)' in the mammalian nervous system

'A disintegrin and metalloproteases' (ADAMs) are a family of transmembrane proteins with diverse functions in multicellular organisms. About half of the ADAMs are active metalloproteases and cleave numerous cell surface proteins, including growth factors, receptors, cytokines and cell adhesion proteins. The other ADAMs have no catalytic activity and function as adhesion proteins or receptors. Some ADAMs are ubiquitously expressed, others are expressed tissue specifically. This review highlights functions of ADAMs in the mammalian nervous system, including their links to diseases. The non-proteolytic ADAM11, ADAM22 and ADAM23 have key functions in neural development, myelination and synaptic transmission and are linked to epilepsy. Among the proteolytic ADAMs, ADAM10 is the best characterized one due to its substrates Notch and amyloid precursor protein, where cleavage is required for nervous system development or linked to Alzheimer's disease (AD), respectively. Recent work demonstrates that ADAM10 has additional substrates and functions in the nervous system and its substrate selectivity may be regulated by tetraspanins. New roles for other proteolytic ADAMs in the nervous system are also emerging. For example, ADAM8 and ADAM17 are involved in neuroinflammation. ADAM17 additionally regulates neurite outgrowth and myelination and its activity is controlled by iRhoms. ADAM19 and ADAM21 function in regenerative processes upon neuronal injury. Several ADAMs, including ADAM9, ADAM10, ADAM15 and ADAM30, are potential drug targets for AD. Taken together, this review summarizes recent progress concerning substrates and functions of ADAMs in the nervous system and their use as drug targets for neurological and psychiatric diseases.

ADAM8 in invasive cancers: links to tumor progression, metastasis, and chemoresistance

Ectodomain shedding of extracellular and membrane proteins is of fundamental importance for cell-cell communication in neoplasias. A Disintegrin And Metalloproteinase (ADAM) proteases constitute a family of multifunctional, membrane-bound proteins with traditional sheddase functions. Their protumorigenic potential has been attributed to both, essential (ADAM10 and ADAM17) and 'dispensable' ADAM proteases (ADAM8, 9, 12, 15, and 19). Of specific interest in this review is the ADAM proteinase ADAM8 that has been identified as a significant player in aggressive malignancies including breast, pancreatic, and brain cancer. High expression levels of ADAM8 are associated with invasiveness and predict a poor patient outcome, indicating a prognostic and diagnostic potential of ADAM8. Current knowledge of substrates and interaction partners gave rise to the hypothesis that ADAM8 dysregulation affects diverse processes in tumor biology, attributable to different functional cores of the multidomain enzyme. Proteolytic degradation of extracellular matrix (ECM) components, cleavage of cell surface proteins, and subsequent release of soluble ectodomains promote cancer progression via induction of angiogenesis and metastasis. Moreover, there is increasing evidence for significance of a non-proteolytic function of ADAM8. With the disintegrin (DIS) domain ADAM8 binds integrins such as β1 integrin, thereby activating integrin signaling pathways. The cytoplasmic domain is critical for that activation and involves focal adhesion kinase (FAK), extracellular regulated kinase (ERK1/2), and protein kinase B (AKT/PKB) signaling, further contributing to cancer progression and mediating chemoresistance against first-line therapies. This review highlights the remarkable effects of ADAM8 in tumor biology, concluding that pharmacological inhibition of ADAM8 represents a promising therapeutic approach not only for monotherapy, but also for combinatorial therapies.

Significantly altered peripheral blood cell DNA methylation profile as a result of immediate effect of metformin use in healthy individuals

BACKGROUND

Metformin is a widely prescribed antihyperglycemic agent that has been also associated with multiple therapeutic effects in various diseases, including several types of malignancies. There is growing evidence regarding the contribution of the epigenetic mechanisms in reaching metformin's therapeutic goals; however, the effect of metformin on human cells in vivo is not comprehensively studied. The aim of our study was to examine metformin-induced alterations of DNA methylation profiles in white blood cells of healthy volunteers, employing a longitudinal study design.

RESULTS

Twelve healthy metformin-naïve individuals where enrolled in the study. Genome-wide DNA methylation pattern was estimated at baseline, 10 h and 7 days after the start of metformin administration. The whole-genome DNA methylation analysis in total revealed 125 differentially methylated CpGs, of which 11 CpGs and their associated genes with the most consistent changes in the DNA methylation profile were selected: POFUT2, CAMKK1, EML3, KIAA1614, UPF1, MUC4, LOC727982, SIX3, ADAM8, SNORD12B, VPS8, and several differentially methylated regions as novel potential epigenetic targets of metformin. The main functions of the majority of top-ranked differentially methylated loci and their representative cell signaling pathways were linked to the well-known metformin therapy targets: regulatory processes of energy homeostasis, inflammatory responses, tumorigenesis, and neurodegenerative diseases.

CONCLUSIONS

Here we demonstrate for the first time the immediate effect of short-term metformin administration at therapeutic doses on epigenetic regulation in human white blood cells. These findings suggest the DNA methylation process as one of the mechanisms involved in the action of metformin, thereby revealing novel targets and directions of the molecular mechanisms underlying the various beneficial effects of metformin.

TRIAL REGISTRATION

EU Clinical Trials Register, 2016-001092-74. Registered 23 March 2017, https://www.clinicaltrialsregister.eu/ctr-search/trial/2016-001092-74/LV .

Reduced ADAM8 levels upon non-surgical periodontal therapy in patients with chronic periodontitis

OBJECTIVE

To determine effect of non-surgical periodontal treatment on a disintegrin and metalloproteinase 8 (ADAM8) levels in gingival crevicular fluid (GCF) of patients with chronic periodontitis (CP) in comparison with those of patients with gingivitis and to find correlations between ADAM8 levels and clinical parameters.

DESIGN

Twenty-two and eleven patients with CP and gingivitis, respectively, were examined for four clinical parameters, probing depth, clinical attachment level, gingival and plaque indices. GCF from the selected gingivitis or periodontitis sites with distinct severities was sampled by Periopaper strips. The non-surgical treatments, including scaling and/or root planing and oral hygiene instruction, were provided for all patients. Clinical measurements and GCF sampling were repeated at three months after the treatments. ADAM8 concentrations were analyzed by ELISA and normalized by GCF volumes or total protein amounts.

RESULTS

All patients exhibited significant improvement of almost every clinical parameter after treatment, whereas the median ADAM8 concentrations were significantly decreased at the moderate and severe periodontitis sites of patients with CP (p < 0.05). Moreover, the significantly positive correlations between ADAM8 concentrations and four clinical parameters were found in both moderate and severe groups (p < 0.05).

CONCLUSION

ADAM8 concentrations were decreased by non-surgical periodontal therapy in patients with chronic periodontitis at the moderate and severe sites and were correlated with four clinical parameters, implying that GCF ADAM8 levels reflect inflammatory and bone-resorbing activities in the periodontal pocket.

Whole body and hematopoietic ADAM8 deficiency does not influence advanced atherosclerotic lesion development, despite its association with human plaque progression

Although A Disintegrin And Metalloproteinase 8 (ADAM8) is not crucial for tissue development and homeostasis, it has been implicated in various inflammatory diseases by regulating processes like immune cell recruitment and activation. ADAM8 expression has been associated with human atherosclerosis development and myocardial infarction, however a causal role of ADAM8 in atherosclerosis has not been investigated thus far. In this study, we examined the expression of ADAM8 in early and progressed human atherosclerotic lesions, in which ADAM8 was significantly upregulated in vulnerable lesions. In addition, ADAM8 expression was most prominent in the shoulder region of human atherosclerotic lesions, characterized by the abundance of foam cells. In mice, Adam8 was highly expressed in circulating neutrophils and in macrophages. Moreover, ADAM8 deficient mouse macrophages displayed reduced secretion of inflammatory mediators. Remarkably, however, neither hematopoietic nor whole-body ADAM8 deficiency in mice affected atherosclerotic lesion size. Additionally, except for an increase in granulocyte content in plaques of ADAM8 deficient mice, lesion morphology was unaffected. Taken together, whole body and hematopoietic ADAM8 does not contribute to advanced atherosclerotic plaque development, at least in female mice, although its expression might still be valuable as a diagnostic/prognostic biomarker to distinguish between stable and unstable lesions.

The metalloproteinase ADAM8 promotes leukocyte recruitment in vitro and in acute lung inflammation

Alveolar leukocyte recruitment is a hallmark of acute lung inflammation and involves transmigration of leukocytes through endothelial and epithelial layers. The disintegrin and metalloproteinase (ADAM) 8 is expressed on human isolated leukocytic cells and can be further upregulated on cultured endothelial and epithelial cells by proinflammatory cytokines. By shRNA-mediated knockdown we show that leukocytic ADAM8 is required on monocytic THP-1 cells for chemokine-induced chemotaxis as well as transendothelial and transepithelial migration. Furthermore, ADAM8 promotes α_L-integrin upregulation and THP-1 cell adhesion to endothelial cells. On endothelial cells ADAM8 enhances transendothelial migration and increases cytokine-induced permeability. On epithelial cells the protease facilitates migration in a wound closure assay but does not affect transepithelial leukocyte migration. Blood leukocytes and bone marrow-derived macrophages (BMDM) from ADAM8-deficient mice show suppressed chemotactic response. Intranasal application of LPS to mice is accompanied with ADAM8 upregulation in the lung. In this model of acute lung inflammation ADAM8-deficient mice are protected against leukocyte infiltration. Finally, transfer experiments of BMDM in mice indicate that ADAM8 exerts a promigratory function predominantly on leukocytes. Our study provides in vitro and in vivo evidence that ADAM8 on leukocytes holds a proinflammatory function in acute lung inflammation by promoting alveolar leukocyte recruitment.

Synthesis and biological evaluation of analogues of the potent ADAM8 inhibitor cyclo(RLsKDK) for the treatment of inflammatory diseases and cancer metastasis

The metalloproteinase ADAM8 serves as a pivotal catalyst in the development of inflammatory diseases and cancer metastasis. The cyclic peptide cyclo(RLsKDK) has been shown to inhibit the enzymatic activity of ADAM8 with high specificity and potency. Herein we report a structure-activity relationship (SAR) study of cyclo(RLsKDK) that involves the synthesis and biological evaluation of the lead compound and structural analogues thereof. This study provides insight into the ligand-receptor interactions that govern the binding of cyclo(RLsKDK) to the ADAM8 disintegrin domain and represents a stepping stone for the development of new treatments for inflammatory diseases and cancer metastasis.

ADAM8 as a drug target in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) has a grim prognosis with less than 5% survivors after 5 years. High expression levels of ADAM8, a metalloprotease-disintegrin, are correlated with poor clinical outcome. We show that ADAM8 expression is associated with increased migration and invasiveness of PDAC cells caused by activation of ERK 1/2 and higher MMP activities. For biological function, ADAM8 requires multimerisation and associates with β1-integrin on the cell surface. A peptidomimetic ADAM8 inhibitor, BK-1361, designed by structural modelling of the disintegrin domain, prevents ADAM8 multimerisation. In PDAC cells, BK-1361 affects ADAM8 function leading to reduced invasiveness, and less ERK 1/2 and MMP activation. BK-1361 application in mice decreased tumour burden and metastasis of implanted pancreatic tumour cells and provides improved metrics of clinical symptoms and survival in a Kras^G12D-driven mouse model of PDAC. Thus, our data integrate ADAM8 in pancreatic cancer signalling and validate ADAM8 as a target for PDAC therapy.

The selective glucocorticoid receptor modulator CORT108297 restores faulty hippocampal parameters in Wobbler and corticosterone-treated mice

Mutant Wobbler mice are models for human amyotrophic lateral sclerosis (ALS). In addition to spinal cord degeneration, Wobbler mice show high levels of blood corticosterone, hyperactivity of the hypothalamic-pituitary-adrenal axis and abnormalities of the hippocampus. Hypersecretion of glucocorticoids increase hippocampus vulnerability, a process linked to an enriched content of glucocorticoid receptors (GR). Hence, we studied if a selective GR antagonist (CORT108297) with null affinity for other steroid receptors restored faulty hippocampus parameters of Wobbler mice. Three months old genotyped Wobbler mice received s.c. vehicle or CORT108297 during 4 days. We compared the response of doublecortin (DCX)+ neuroblasts in the subgranular layer of the dentate gyrus (DG), NeuN+ cells in the hilus of the DG, glial fibrillary acidic protein (GFAP)+ astrocytes and the phenotype of Iba1+ microglia in CORT108297-treated and vehicle-treated Wobblers. The number of DCX+ cells in Wobblers was lower than in control mice, whereas CORT108297 restored this parameter. After CORT108297 treatment, Wobblers showed diminished astrogliosis, and changed the phenotype of Iba1+ microglia from an activated to a quiescent form. These changes occurred without alterations in the hypercorticosteronemia or the number of NeuN+ cells of the Wobblers. In a separate experiment employing control NFR/NFR mice, treatment with corticosterone for 5 days reduced DCX+ neuroblasts and induced astrocyte hypertrophy, whereas treatment with CORT108297 antagonized these effects. Normalization of neuronal progenitors, astrogliosis and microglial phenotype by CORT108297 indicates the usefulness of this antagonist to normalize hippocampus parameters of Wobbler mice. Thus, CORT108297 opens new therapeutic options for the brain abnormalities of ALS patients and hyperadrenocorticisms.

Expression of A disintegrin and metalloprotease 8 is associated with cell growth and poor survival in colorectal cancer

Background

A disintegrin and metalloprotease 8 (ADAM8) has been reported to be associated with various malignancies. However, no studies have examined ADAM8 association in colorectal cancer (CRC). The aim of this study was to investigate the expression and function of ADAM8 in CRC.

Methods

Expression level of ADAM8 in CRC was evaluated by quantitative RT-PCR, western blot and immunohistochemical staining analysis. The role of ADAM8 in colorectal carcinogenesis was evaluated by in vitro assays. The correlations between ADAM8 status and clinicopathological features including survival were analyzed.

Results

ADAM8 was highly expressed in CRC tissues compared with adjacent normal tissues. Knockdown of ADAM8 in two CRC cell lines resulted in reduced cellular growth and proliferation, and increased apoptosis. Immunohistochemistry analysis showed no significant correlations of ADAM8 protein expression with clinicopathologic features. Survival analysis indicated that patients with ADAM8-positive tumors had worse 5-year overall survival (OS, p = 0.037) and 5-year disease free survival (DFS, p = 0.014) compared with those with ADAM8-negative tumors. Multivariate analysis indicated ADAM8 expression was an independent prognostic factor for both OS and DFS (both p< 0.001). Subgroup analysis showed that 5-year OS of colon cancer, T3-T4 stage and N0 stage was worse for patients with ADAM8-positive tumors than those with ADAM8-negative tumors (p< 0.05). The 5-year DFS in colon cancer, T3-T4 stage, N0 stage, TNM stage II, adenocarcinoma, moderate differentiation and male patient subgroups was also worse for patients with ADAM8-positive tumors than those with ADAM8-negative tumors (p < 0.05).

Conclusions

Our results show that ADAM8 is overexpressed in CRC, promotes cell growth and correlates with worse OS and DFS, and thus could serve as a biomarker for individual CRC patient therapy.

Amelioration of LPS-induced inflammation response in microglia by AMPK activation

Adenosine 5′-monophosphate-activated protein kinase (AMPK) is a key regulator of cellular energy homeostasis via modulating metabolism of glucose, lipid, and protein. In addition to energy modulation, AMPK has been demonstrated to associate with several important cellular events including inflammation. The results showed that ENERGI-F704 identified from bamboo shoot extract was nontoxic in concentrations up to 80 μM and dose-dependently induced phosphorylation of AMPK (Thr-172) in microglia BV2 cells. Our findings also showed that the treatment of BV2 with ENERGI-F704 ameliorated the LPS-induced elevation of IL-6 and TNF-α production. In addition, ENERGI-F704 reduced increased production of nitric oxide (NO) and prostaglandin E2 (PGE2) via downregulating the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2), respectively. Moreover, ENERGI-F704 decreased activated nuclear translocation and protein level of NF-κB. Inhibition of AMPK with compound C restored decreased NF-κB translocation by ENERGI-F704. In conclusion, ENERGI-F704 exerts inhibitory activity on LPS-induced inflammation through manipulating AMPK signaling and exhibits a potential therapeutic agent for neuroinflammatory disease.

ADAM8 in asthma. Friend or foe to airway inflammation?

Airway inflammation has been suggested as the pathological basis in asthma pathogenesis. Recruitment of leukocytes from the vasculature into airway sites is essential for induction of airway inflammation, a process thought to be mediated by a disintegrin and metalloprotease 8 (ADAM8). However, there is an apparent controversy about whether ADAM8 helps or hampers transmigration of leukocytes through endothelium in airway inflammation of asthma. This review outlines the current contradictory concepts concerning the role of ADAM8 in airway inflammation, particularly focusing on the recruitment of leukocytes during asthma, and attempts to bridge the existing experimental data on the basis of the functional analysis of different domains of ADAM8 and their endogenous processing in vivo. We suggest a possible hypothesis for the specific mechanism by which ADAM8 regulates the transmigration of leukocytes to explain the disparity existing in current studies, and we also raise some questions that require future investigations.

Src plays a key role in ADAM28 expression in v-src-transformed epithelial cells and human carcinoma cells

ADAM28, a disintegrin and metalloproteinase 28, is overexpressed by carcinoma cells with direct correlations with carcinoma cell proliferation and progression in human lung and breast carcinomas. However, the molecular mechanisms of ADAM28 gene expression in carcinoma cells remain elusive. Herein, we investigated the expression of ADAM28 in Madin-Darby canine kidney epithelial cells transformed by oncogenes, including v-src, LMP1, ErbB2, Ha-Ras, and c-Fos, and found that v-src transformants selectively induce ADAM28. Implantation of the v-src transformants showed a progressively growing tumor, which was significantly suppressed by local injections of anti-ADAM28 antibody. ADAM28 expression in v-src transformants was partially inhibited by treatment with inhibitors to Src kinase, mitogen-activated protein kinase kinase (MEK), phosphatidylinositol 3-kinase (PI3K), or mammalian target of rapamycin, and abrogated by v-Src kinase inhibitor, radicicol, or a mixture of MEK and PI3K inhibitors. Human carcinoma cell lines of the lung, breast, ovary, kidney, and colon showed ADAM28 expression, which was correlated with phosphorylation of c-Src and suppressed by the inhibitors in a similar way to v-src transformants. IHC of the human tumor tissues demonstrated co-expression of ADAM28 and phosphorylated Src in neoplastic cells of the breast, lung, and colon carcinomas and some adenomas of the colon, but not in nonneoplastic colon mucosa. Our data provide, to the best of our knowledge, the first evidence that Src is an inducer of ADAM28 gene expression through the MEK/extracellular signal-regulated kinase and PI3K/mammalian target of rapamycin pathways.

Adam8 limits the development of allergic airway inflammation in mice

To determine whether a disintegrin and metalloproteinase-8 (Adam8) regulates allergic airway inflammation (AAI) and airway hyperresponsiveness (AHR), we compared AAI and AHR in wild-type (WT) versus Adam8(-/-) mice in different genetic backgrounds sensitized and challenged with OVA or house dust mite protein extract. OVA- and house dust mite-treated Adam8(-/-) mice had higher lung leukocyte counts, more airway mucus metaplasia, greater lung levels of some Th2 cytokines, and higher methacholine-induced increases in central airway resistance than allergen-treated WT mice. Studies of OVA-treated Adam8 bone marrow chimeric mice confirmed that leukocyte-derived Adam8 predominantly mediated Adam8's anti-inflammatory activities in murine airways. Airway eosinophils and macrophages both expressed Adam8 in WT mice with AAI. Adam8 limited AAI and AHR in mice by reducing leukocyte survival because: 1) Adam8(-/-) mice with AAI had fewer apoptotic eosinophils and macrophages in their airways than WT mice with AAI; and 2) Adam8(-/-) macrophages and eosinophils had reduced rates of apoptosis compared with WT leukocytes when the intrinsic (but not the extrinsic) apoptosis pathway was triggered in the cells in vitro. ADAM8 was robustly expressed by airway granulocytes in lung sections from human asthma patients, but, surprisingly, airway macrophages had less ADAM8 staining than airway eosinophils. Thus, ADAM8 has anti-inflammatory activities during AAI in mice by activating the intrinsic apoptosis pathway in myeloid leukocytes. Strategies that increase ADAM8 levels in myeloid leukocytes may have therapeutic efficacy in asthma.

Neuroprotective effects of toll-like receptor 4 antagonism in spinal cord cultures and in a mouse model of motor neuron degeneration

Sustained inflammatory reactions are common pathological events associated with neuron loss in neurodegenerative diseases. Reported evidence suggests that Toll-like receptor 4 (TLR4) is a key player of neuroinflammation in several neurodegenerative diseases. However, the mechanisms by which TLR4 mediates neurotoxic signals remain poorly understood. We investigated the role of TLR4 in in vitro and in vivo settings of motor neuron degeneration. Using primary cultures from mouse spinal cords, we characterized both the proinflammatory and neurotoxic effects of TLR4 activation with lipopolysaccharide (activation of microglial cells, release of proinflammatory cytokines and motor neuron death) and the protective effects of a cyanobacteria-derived TLR4 antagonist (VB3323). With the use of TLR4-deficient cells, a critical role of the microglial component with functionally active TLR4 emerged in this setting. The in vivo experiments were carried out in a mouse model of spontaneous motor neuron degeneration, the wobbler mouse, where we preliminarily confirmed a protective effect of TLR4 antagonism. Compared with vehicle- and riluzole-treated mice, those chronically treated with VB3323 showed a decrease in microglial activation and morphological alterations of spinal cord neurons and a better performance in the paw abnormality and grip-strength tests. Taken together, our data add new understanding of the role of TLR4 in mediating neurotoxicity in the spinal cord and suggest that TLR4 antagonists could be considered in future studies as candidate protective agents for motor neurons in degenerative diseases.

The neural cell adhesion molecules L1 and CHL1 are cleaved by BACE1 protease in vivo

The β-site amyloid precursor protein-cleaving enzyme BACE1 is a prime drug target for Alzheimer disease. However, the function and the physiological substrates of BACE1 remain largely unknown. In this work, we took a quantitative proteomic approach to analyze the secretome of primary neurons after acute BACE1 inhibition, and we identified several novel substrate candidates for BACE1. Many of these molecules are involved in neuronal network formation in the developing nervous system. We selected the adhesion molecules L1 and CHL1, which are crucial for axonal guidance and maintenance of neural circuits, for further validation as BACE1 substrates. Using both genetic BACE1 knock-out and acute pharmacological BACE1 inhibition in mice and cell cultures, we show that L1 and CHL1 are cleaved by BACE1 under physiological conditions. The BACE1 cleavage sites at the membrane-proximal regions of L1 (between Tyr(1086) and Glu(1087)) and CHL1 (between Gln(1061) and Asp(1062)) were determined by mass spectrometry. This work provides molecular insights into the function and the pathways in which BACE1 is involved, and it will help to predict or interpret possible side effects of BACE1 inhibitor drugs in current clinical trials.

Elevated levels of a disintegrin and metalloproteinase 8 in gingival crevicular fluid of patients with periodontal diseases

BACKGROUND

A disintegrin and metalloproteinase 8 (ADAM8) is involved in inflammation and is essential for osteoclastogenesis. Elevated ADAM8 levels are detected in human serum and other body fluids in several inflammatory conditions. Therefore, we hypothesized that ADAM8 levels are also raised in gingival crevicular fluid (GCF) of patients with periodontal diseases.

METHODS

Forty-five patients with periodontal diseases (n = 15 for each group: the group of patients with gingivitis, the group with aggressive periodontitis [AgP], and the group with chronic periodontitis [CP]) and 15 volunteers who exhibited healthy gingiva were recruited. Four periodontal parameters, gingival index, plaque index, probing depth, and clinical attachment level, were recorded before GCF collection. The presence of ADAM8 in GCF was shown by immunoblotting using anti-human ADAM8 polyclonal antibody against its prodomain, and the ADAM8 levels were measured by an enzyme-linked immunosorbent assay.

RESULTS

Four immunoreactive bands at 120, 70, 50, and <30 kDa were detected in the groups of patients with periodontitis, whose intensities were stronger than those in the group of patients with gingivitis, consistent with significantly greater ADAM8 levels in both groups of patients, with either CP or AgP, than those in the group of patients with gingivitis and in the group that was healthy (P <0.001). Moreover, the ADAM8 levels correlated significantly with the four periodontal parameters (P <0.001), indicating that ADAM8 levels are positively associated with the degree of periodontal tissue inflammation and destruction.

CONCLUSIONS

The ADAM8 levels are elevated in the GCF of patients with periodontal diseases, including gingivitis, CP, and AgP, in comparison to control participants who are healthy, and they correlate with four clinical parameters that reflect the degree of disease severity.

MT5-MMP, ADAM-10, and N-cadherin act in concert to facilitate synapse reorganization after traumatic brain injury

Matrix metalloproteinases (MMPs) influence synaptic recovery following traumatic brain injury (TBI). Membrane type 5-matrix metalloproteinase (MT5-MMP) and a distintegrin and metalloproteinase-10 (ADAM-10) are membrane-bound MMPs that cleave N-cadherin, a protein critical to synapse stabilization. This study examined protein and mRNA expression of MT5-MMP, ADAM-10, and N-cadherin after TBI, contrasting adaptive and maladaptive synaptogenesis. The effect of MMP inhibition on MT5-MMP, ADAM-10, and N-cadherin was assessed during maladaptive plasticity and correlated with synaptic function. Rats were subjected to adaptive unilateral entorhinal cortical lesion (UEC) or maladaptive fluid percussion TBI+bilateral entorhinal cortical lesion (TBI+BEC). Hippocampal MT5-MMP and ADAM-10 protein was significantly elevated 2 and 7 days post-injury. At 15 days after UEC, each MMP returned to control level, while TBI+BEC ADAM-10 remained elevated. At 2 and 7 days, N-cadherin protein was below control. By the 15-day synapse stabilization phase, UEC N-cadherin rose above control, a shift not seen for TBI+BEC. At 7 days, increased TBI+BEC ADAM-10 transcript correlated with protein elevation. UEC ADAM-10 mRNA did not change, and no differences in MT5-MMP or N-cadherin mRNA were detected. Confocal imaging showed MT5-MMP, ADAM-10, and N-cadherin localization within reactive astrocytes. MMP inhibition attenuated ADAM-10 protein 15 days after TBI+BEC and increased N-cadherin. This inhibition partially restored long-term potentiation induction, but did not affect paired-pulse facilitation. Our results confirm time- and injury-dependent expression of MT5-MMP, ADAM-10, and N-cadherin during reactive synaptogenesis. Persistent ADAM-10 expression was correlated with attenuated N-cadherin level and reduced functional recovery. MMP inhibition shifted ADAM-10 and N-cadherin toward adaptive expression and improved synaptic function.

Regulating inflammation: ADAM8--a new player in the game

Leukocyte recruitment to sites of inflammation proceeds in a cascade-like fashion. However, it is less clear how the complex interactions among the different adhesion molecules involved in this process are coordinately regulated. A report in this issue of the European Journal of Immunology [Eur. J. Immunol. 2011. 41: 3436-3442] shows that ADAM8 may participate in the control of the adhesion molecule P-selectin glycoprotein ligand 1. This finding suggests a new role for ADAM8 in the regulation of inflammatory processes.

Cellular prion protein regulates its own α-cleavage through ADAM8 in skeletal muscle

The ubiquitously expressed cellular prion protein (PrP(C)) is subjected to the physiological α-cleavage at a region critical for both PrP toxicity and the conversion of PrP(C) to its pathogenic prion form (PrP(Sc)), generating the C1 and N1 fragments. The C1 fragment can activate caspase 3 while the N1 fragment is neuroprotective. Recent articles indicate that ADAM10, ADAM17, and ADAM9 may not play a prominent role in the α-cleavage of PrP(C) as previously thought, raising questions on the identity of the responsible protease(s). Here we show that, ADAM8 can directly cleave PrP to generate C1 in vitro and PrP C1/full-length ratio is greatly decreased in the skeletal muscles of ADAM8 knock-out mice; in addition, the PrP C1/full-length ratio is linearly correlated with ADAM8 protein level in myoblast cell line C2C12 and in skeletal muscle tissues of transgenic mice. These results indicate that ADAM8 is the primary protease responsible for the α-cleavage of PrP(C) in muscle cells. Moreover, we found that overexpression of PrP(C) led to up-regulation of ADAM8, suggesting that PrP(C) may regulate its own α-cleavage through modulating ADAM8 activity.

ADAM-8, a metalloproteinase, drives acute allergen-induced airway inflammation

Asthma is a complex disease linked to various pathophysiological events including the activity of proteinases. The multifunctional A disintegrin and metalloproteinases (ADAMs) displaying the ability to cleave membrane-bound mediators or cytokines appear to be key mediators in various inflammatory processes. In the present study, we investigated ADAM-8 expression and production in a mouse model of allergen-induced airway inflammation. In allergen-exposed animals, increased expression of ADAM-8 was found in the lung parenchyma and in DC purified from the lungs. The potential role of ADAM-8 in the development of allergen-induced airway inflammation was further investigated by the use of an anti-ADAM-8 antibody and ADAM-8 knockout animals. We observed a decrease in allergen-induced acute inflammation both in BALF and the peribronchial area in anti-ADAM-8 antibody-treated mice and in ADAM-8-deficient mice (ADAM-8(-/-) ) after allergen exposure. ADAM-8 depletion led to a significant decrease of the CD11c(+) lung DC. We also report lower levels of CCL11 and CCL22 production in antibody-treated mice and ADAM-8- deficient mice that might be explained by decreased eosinophilic inflammation and lower numbers of DC, respectively. In conclusion, ADAM-8 appears to favour allergen-induced acute airway inflammation by promoting DC recruitment and CCL11 and CCL22 production.

The metalloprotease-disintegrin ADAM8 is essential for the development of experimental asthma

RATIONALE

Expression of the metalloprotease ADAM8 is increased in patients with asthma, but the functional significance of elevated ADAM8 expression in the context of asthma pathogenesis remains elusive.

OBJECTIVES

To study development of asthma in ADAM8-deficient mice.

METHODS

Ovalbumin-induced asthma was studied in wild-type, ADAM8-deficient, and ADAM8-chimeric mice. Lung inflammation was assessed by histology, analysis of bronchoalveolar lavage, and airway hyperresponsiveness.

MEASUREMENTS AND MAIN RESULTS

ADAM8-deficient mice are highly resistant to the development of ovalbumin-induced airway inflammation and hyperresponsiveness. ADAM8 expression was induced in both hematopoietic cells and the nonhematopoietic microenvironment after induction of asthma, and ADAM8 expression in both cell populations was required for the full manifestation of asthma. Interestingly, loss of ADAM8 on T cells alone was sufficient to significantly decrease the asthma response. The attenuated response was not due to an intrinsic defect in antigen presentation or cytokine production but reflected an impaired migration of T cells, eosinophils, CD11b(+) CD11c(-), and CD11c(+) cells from blood vessels to the lung and alveolar space, suggesting a general hematopoietic cell deficiency in the absence of ADAM8.

CONCLUSIONS

The results show that ADAM8 plays a proinflammatory role in airway inflammation. The milder disease outcome in the absence of ADAM8 suggests that this protein might be an interesting new target in treatment of this, and potentially other, inflammatory diseases in which recruitment of inflammatory cells is an essential part of pathogenesis.