Meprin and ADAM proteases as triggers of systemic inflammation in sepsis

The Role of Fc Receptors in the Innate Immune System of Flounders Purported to Be Homologs of FcγRII and FcγRIII

FcγR is a significant opsonin receptor located on the surface of immune cells, playing a crucial role in Ab-dependent cell-mediated immunity. Our previous work revealed opposite expression trends of FcγRII and FcγRIII in flounder mIgM+ B lymphocytes after phagocytosis of antiserum-opsonized Edwardsiella tarda. This observation suggests that FcγRII and FcγRIII might serve distinct functions in Ig-opsonized immune responses. In this study, we prepared rFcγRIII as well as its corresponding Abs to investigate the potential roles of FcγRII and FcγRIII in the Ab-dependent immune response of IgM+ B cells. Our findings indicate that, unlike FcγRII, FcγRIII does not participate in Ab-dependent cellular phagocytosis. Instead, it is involved in cytokine production and bacterial killing in mIgM+ B lymphocytes. Additionally, we identified platelet-derived ADAM17 as a key factor in regulating FcγRIII shedding and cytokine release in mIgM+ B lymphocytes. These results elucidate the functions of FcγRII and FcγRIII in the innate immunology of mIgM+ B lymphocytes and contribute to an improved understanding of the regulatory roles of FcγRs in the phagocytosis of teleost B lymphocytes.

Discovery of dual-target natural inhibitors of meprins α and β metalloproteases for inflammation regulation: pharmacophore modelling, molecular docking, ADME prediction, and molecular dynamics studies

Meprins, zinc-dependent metalloproteinases belonging to the metzincin family, have been associated with various inflammatory diseases due to their abnormal expression and activity. In this study, we utilized pharmacophore modelling to identify crucial features for discovering potential dual inhibitors targeting meprins α and β. We screened four pharmacophoric features against a library of 270,540 natural compounds from the Zinc database, resulting in 84,092 matching compounds. Molecular docking was then performed on these compounds, targeting the active sites of meprins α and β. Docking results revealed six compounds capable of interacting with both isoforms, with binding affinities ranging from -10.0 to -10.5 kcal/mol and -6.9 to -9.9 kcal/mol for meprin α and β, respectively. Among these compounds, ZINC000008790788 and ZINC000095099469 displayed superior docking scores and MM-GBSA binding free energy compared to reference ligands. Furthermore, these two compounds exhibited acceptable predicted pharmacokinetic properties and stable interactions with meprins α and β during molecular dynamics simulations. This study presents a comprehensive approach for identifying potential dual inhibitors of meprin α and β, offering insights into the development of therapeutic interventions for inflammatory diseases associated with meprin dysregulation.

Targeting IL-6 trans-signalling: past, present and future prospects

Interleukin-6 (IL-6) is a key immunomodulatory cytokine that affects the pathogenesis of diverse diseases, including autoimmune diseases, chronic inflammatory conditions and cancer. Classical IL-6 signalling involves the binding of IL-6 to the membrane-bound IL-6 receptor α-subunit (hereafter termed 'mIL-6R') and glycoprotein 130 (gp130) signal-transducing subunit. By contrast, in IL-6 trans-signalling, complexes of IL-6 and the soluble form of IL-6 receptor (sIL-6R) signal via membrane-bound gp130. A third mode of IL-6 signalling - known as cluster signalling - involves preformed complexes of membrane-bound IL-6-mIL-6R on one cell activating gp130 subunits on target cells. Antibodies and small molecules have been developed that block all three forms of IL-6 signalling, but in the past decade, IL-6 trans-signalling has emerged as the predominant pathway by which IL-6 promotes disease pathogenesis. The first selective inhibitor of IL-6 trans-signalling, sgp130, has shown therapeutic potential in various preclinical models of disease and olamkicept, a sgp130Fc variant, had promising results in phase II clinical studies for inflammatory bowel disease. Technological developments have already led to next-generation sgp130 variants with increased affinity and selectivity towards IL-6 trans-signalling, along with indirect strategies to block IL-6 trans-signalling. Here, we summarize our current understanding of the biological outcomes of IL-6-mediated signalling and the potential for targeting this pathway in the clinic.

ADAM10-a "multitasker" in sepsis: focus on its posttranslational target

BACKGROUND

Sepsis has a complex pathogenesis in which the uncontrolled systemic inflammatory response triggered by infection leads to vascular barrier disruption, microcirculation dysfunction and multiple organ dysfunction syndrome. Numerous recent studies reveal that a disintegrin and metalloproteinase 10 (ADAM10) acts as a "molecular scissor" playing a pivotal role in the inflammatory response during sepsis by regulating proteolysis by cleaving various membrane protein substrates, including proinflammatory cytokines, cadherins and Notch, which are involved in intercellular communication. ADAM10 can also act as the cellular receptor for Staphylococcus aureus α-toxin, leading to lethal sepsis. However, its substrate-specific modulation and precise targets in sepsis have not yet to be elucidated.

METHODS

We performed a computer-based online search using PubMed and Google Scholar for published articles concerning ADAM10 and sepsis.

CONCLUSIONS

In this review, we focus on the functions of ADAM10 in sepsis-related complex endothelium-immune cell interactions and microcirculation dysfunction through the diversity of its substrates and its enzymatic activity. In addition, we highlight the posttranslational mechanisms of ADAM10 at specific subcellular sites, or in multimolecular complexes, which will provide the insight to intervene in the pathophysiological process of sepsis caused by ADAM10 dysregulation.

Dysregulation of metalloproteinases in spinal ligament degeneration

PURPOSE

Degenerative changes in the spinal ligaments, such as hypertrophy or ossification, are important pathophysiological mechanisms of secondary spinal stenosis and neurological compression. Extracellular matrix (ECM) remodeling is one of the major pathological changes in ligament degeneration, and in this remodeling, ECM proteinase-mediated degradation of elastin and collagen plays a vital role. Zinc-dependent endopeptidases, including matrix metalloproteinases (MMPs), a disintegrin and metalloproteinases (ADAMs), and ADAMs with thrombospondin-1 motifs (ADAMTSs) are key factors in ECM remodeling. This review aims to elucidate the underlying mechanisms of these metalloproteinases in the initiation and progression of spinal ligament degeneration.

METHODS

We clarify current literature on the dysregulation of MMPs/ADAMs/ADAMTS and their endogenous inhibitors in degenerative spinal ligament diseases. In addition, some instructive information was excavated from the raw data of the relevant high-throughput analysis.

RESULTS AND CONCLUSIONS

The dysregulation of metalloproteinases and their endogenous inhibitors may affect ligament degeneration by involving several interrelated processes, represented by ECM degradation, fibroblast proliferation, and osteogenic differentiation. Antagonists of the key targets of the processes may in turn ease ligament degeneration.

IL-6 signaling in acute exercise and chronic training: Potential consequences for health and athletic performance

The cytokine interleukin-6 (IL-6) is involved in a diverse set of physiological processes. Traditionally, IL-6 has been thought of in terms of its inflammatory actions during the acute phase response and in chronic conditions such as rheumatoid arthritis and obesity. However, IL-6 is also an important signaling molecule during exercise, being acutely released from working muscle fibers with increased exercise duration, intensity, and muscle glycogen depletion. In this context, IL-6 enables muscle-organ crosstalk, facilitating a coordinated response to help maintain muscle energy homeostasis, while also having anti-inflammatory actions. The range of actions of IL-6 can be explained by its dichotomous signaling pathways. Classical signaling involves IL-6 binding to a cell-surface receptor (mbIL-6R; present on only a small number of cell types) and is the predominant signaling mechanism during exercise. Trans-signaling involves IL-6 binding to a soluble version of its receptor (sIL-6R), with the resulting complex having a much greater half-life and the ability to signal in all cell types. Trans-signaling drives the inflammatory actions of IL-6 and is the predominant pathway in disease. A single nucleotide polymorphism (rs2228145) on the IL-6R gene can modify the classical/trans-signaling balance through increasing the levels of sIL-6R. This SNP has clinical significance, having been linked to inflammatory conditions such as rheumatoid arthritis and type 1 diabetes, as well as to the severity of symptoms experienced with COVID-19. This review will describe how acute exercise, chronic training and the rs2228145 SNP can modify the IL-6 signaling pathway and the consequent implications for health and athletic performance.

Role of metalloproteases in the CD95 signaling pathways

CD95L (also known as FasL or CD178) is a member of the tumor necrosis family (TNF) superfamily. Although this transmembrane ligand has been mainly considered as a potent apoptotic inducer in CD95 (Fas)-expressing cells, more recent studies pointed out its role in the implementation of non-apoptotic signals. Accordingly, this ligand has been associated with the aggravation of inflammation in different auto-immune disorders and in the metastatic occurrence in different cancers. Although it remains to decipher all key factors involved in the ambivalent role of this ligand, accumulating clues suggest that while the membrane bound CD95L triggers apoptosis, its soluble counterpart generated by metalloprotease-driven cleavage is responsible for its non-apoptotic functions. Nonetheless, the metalloproteases (MMPs and ADAMs) involved in the CD95L shedding, the cleavage sites and the different stoichiometries and functions of the soluble CD95L remain to be elucidated. To better understand how soluble CD95L triggers signaling pathways from apoptosis to inflammation or cell migration, we propose herein to summarize the different metalloproteases that have been described to be able to shed CD95L, their cleavage sites and the biological functions associated with the released ligands. Based on these new findings, the development of CD95/CD95L-targeting therapeutics is also discussed.

Meprin β expression modulates the interleukin-6 mediated JAK2-STAT3 signaling pathway in ischemia/reperfusion-induced kidney injury

Meprin metalloproteinases have been implicated in the pathophysiology of ischemia/reperfusion (IR)-induced kidney injury. Previous in vitro data showed that meprin β proteolytically processes interleukin-6 (IL-6) resulting in its inactivation. Recently, meprin-β was also shown to cleave the IL-6 receptor. The goal of this study was to determine how meprin β expression impacts IL-6 and downstream modulators of the JAK2-STAT3-mediated signaling pathway in IR-induced kidney injury. IR was induced in 12-week-old male wild-type (WT) and meprin β knockout (βKO) mice and kidneys obtained at 24 h post-IR. Real-time PCR, western blot, and immunostaining/microscopy approaches were used to quantify mRNA and protein levels respectively, and immunofluorescence counterstaining with proximal tubule (PT) markers to determine protein localization. The mRNA levels for IL-6, CASP3 and BCL-2 increased significantly in both genotypes. Interestingly, western blot data showed increases in protein levels for IL-6, CASP3, and BCL-2 in the βKO but not in WT kidneys. However, immunohistochemical data showed increases in IL-6, CASP3, and BCL-2 proteins in select kidney tubules in both genotypes, shown to be PTs by immunofluorescence counterstaining. IR-induced increases in p-STAT-3 and p-JAK-2 in βKO at a global level but immunoflourescence counterstaining demonstrated p-JAK2 and p-STAT3 increases in select PT for both genotypes. BCL-2 increased only in the renal corpuscle of WT kidneys, suggesting a role for meprins expressed in leukocytes. Immunohistochemical analysis confirmed higher levels of leukocyte infiltration in WT kidneys when compared to βKO kidneys. The present data demonstrate that meprin β modulates IR-induced kidney injury in part via IL-6/JAK2/STAT3-mediated signaling.

Pseudomonas aeruginosa Triggered Exosomal Release of ADAM10 Mediates Proteolytic Cleavage in Trans

Pneumonia is a life-threatening disease often caused by infection with Streptococcus pneumoniae and Pseudomonas aeruginosa. Many of the mediators (e.g., TNF, IL-6R) and junction molecules (e.g., E-cadherin) orchestrating inflammatory cell recruitment and loss of barrier integrity are proteolytically cleaved through a disintegrin and metalloproteinases (ADAMs). We could show by Western blot, surface expression analysis and measurement of proteolytic activity in cell-based assays, that ADAM10 in epithelial cells is upregulated and activated upon infection with Pseudomonas aeruginosa and Exotoxin A (ExoA), but not upon infection with Streptococcus pneumoniae. Targeting ADAM10 by pharmacological inhibition or gene silencing, we demonstrated that this activation was critical for cleavage of E-cadherin and modulated permeability and epithelial integrity. Stimulation with heat-inactivated bacteria revealed that the activation was based on the toxin repertoire rather than the interaction with the bacterial particle itself. Furthermore, calcium imaging experiments showed that the ExoA action was based on the induction of calcium influx. Investigating the extracellular vesicles and their proteolytic activity, we could show that Pseudomonas aeruginosa triggered exosomal release of ADAM10 and proteolytic cleavage in trans. This newly described mechanism could constitute an essential mechanism causing systemic inflammation in patients suffering from Pseudomonas aeruginosa-induced pneumonia stimulating future translational studies.