The serine protease plasmin triggers expression of MCP-1 and CD40 in human primary monocytes via activation of p38 MAPK and janus kinase (JAK)/STAT signaling pathways

The hemostatic and anti-inflammatory effects of intravenous single-dose of tranexamic acid in double-segment posterior lumbar interbody fusion: a case control study

This study aims to observe the hemostatic and anti-inflammatory effects of intravenous administration of tranexamic acid (TXA) in dual segment posterior lumbar interbody fusion (PLIF). The data of 53 patients with lumbar disease treated with double-segment PLIF were included in this study. The observation group was received a single-dose intravenous of TXA (1 g/100 mL) 15 min before skin incision after general anesthesia. The control group was not received TXA. The observation indicators included postoperative activated partial prothrombin time (APTT), thrombin time (PT), thrombin time (TT), fibrinogen (FIB), platelets (PLT), and postoperative deep vein thrombosis in the lower limbs, surgical time, intraoperative bleeding volume, postoperative drainage volume, transfusion rate, postoperative hospital stay, red blood cell (RBC), hemoglobin (HB), hematocrit (HCT), C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) on the 1st, 4th, 7th, and last tested day after surgery. All patients successfully completed the operation, and there was no deep vein thrombosis after operation. There was no statistically significant difference in postoperative APTT, PT, TT, FIB, PLT, surgical time, and postoperative hospital stay between the two groups (p > 0.05). The intraoperative bleeding volume, postoperative drainage volume, and transfusion rate in the observation group were lower than those in the control group, and the differences were statistically significant (p < 0.05). There was no statistically significant difference in RBC, HB, HCT, CRP, and ESR between the two groups on the 1st, 4th, 7th, and last tested day after surgery (p > 0.05). Intravenous administration of TXA in dual segment PLIF does not affect coagulation function and can reduce bleeding volume, postoperative drainage volume, and transfusion rate. Moreover, it does not affect the postoperative inflammatory response.

Apoptosis in post-streptococcal glomerulonephritis and mechanisms for failed of inflammation resolution

Post-streptococcal glomerulonephritis is a condition resulting from infection by group A beta-hemolytic streptococcus. The main mechanism involves the formation of immune complexes formed in the circulation or in situ on the glomerular basement membrane, which activates complement and causes various inflammatory processes. Cellular mechanisms have been reported in the induction of kidney damage represented by the infiltration of innate cells (neutrophils and monocyte/macrophages) and adaptive cells (CD4 + lymphocytes and CD8 + lymphocytes) of the immune system. These cells induce kidney damage through various mechanisms. It has been reported that nephritogenic antigens are capable of inducing inflammatory processes early, even before the formation of immune complexes. Usually, this disease progresses towards clinical and renal normalization; however, in a smaller number of patients, it evolves into chronicity and persistent kidney damage. Hypotheses have been proposed regarding the mechanisms underlying this progression to chronicity including failure to induce apoptosis and failure to phagocytose apoptotic cells, allowing these cells to undergo membrane permeabilization and release pro-inflammatory molecules into the environment, thereby perpetuating renal inflammation. Other mechanisms involved include persistent infection, genetic background of the host's complement system, tubulointerstitial changes, and pre-existing kidney damage due to old age and comorbidities.

Angiotensin II and post-streptococcal glomerulonephritis

BACKGROUND

Post-streptococcal glomerulonephritis (PSGN) is a consequence of the infection by group A beta-hemolytic streptococcus. During this infection, various immunological processes generated by streptococcal antigens are triggered, such as the induction of antibodies and immune complexes. This activation of the immune system involves both innate and acquired immunity. The immunological events that occur at the renal level lead to kidney damage with chronic renal failure as well as resolution of the pathological process (in most cases). Angiotensin II (Ang II) is a molecule with vasopressor and pro-inflammatory capacities, being an important factor in various inflammatory processes. During PSGN some events are defined that make Ang II conceivable as a molecule involved in the inflammatory processes during the disease.

CONCLUSION

This review is focused on defining which reported events would be related to the presence of this hormone in PSGN.

Monoclonal enolase-1 blocking antibody ameliorates pulmonary inflammation and fibrosis

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronic fatal disease with limited therapeutic options. The infiltration of monocytes and fibroblasts into the injured lungs is implicated in IPF. Enolase-1 (ENO1) is a cytosolic glycolytic enzyme which could translocate onto the cell surface and act as a plasminogen receptor to facilitate cell migration via plasmin activation. Our proprietary ENO1 antibody, HL217, was screened for its specific binding to ENO1 and significant inhibition of cell migration and plasmin activation (patent: US9382331B2).

METHODS

In this study, effects of HL217 were evaluated in vivo and in vitro for treating lung fibrosis.

RESULTS

Elevated ENO1 expression was found in fibrotic lungs in human and in bleomycin-treated mice. In the mouse model, HL217 reduced bleomycin-induced lung fibrosis, inflammation, body weight loss, lung weight gain, TGF-β upregulation in bronchial alveolar lavage fluid (BALF), and collagen deposition in lung. Moreover, HL217 reduced the migration of peripheral blood mononuclear cells (PBMC) and the recruitment of myeloid cells into the lungs. In vitro, HL217 significantly reduced cell-associated plasmin activation and cytokines secretion from primary human PBMC and endothelial cells. In primary human lung fibroblasts, HL217 also reduced cell migration and collagen secretion.

CONCLUSIONS

These findings suggest multi-faceted roles of cell surface ENO1 and a potential therapeutic approach for pulmonary fibrosis.

Serum PAI-1/BDNF Ratio Is Increased in Alzheimer's Disease and Correlates with Disease Severity

We previously demonstrated that serum levels of plasminogen activator inhibitor-1 (PAI-1), which inhibits both the tissue plasminogen activator (tPA) and plasmin activity, are increased in patients with Alzheimer's disease. tPA/plasmin not only prevents the accumulation of β-amyloid in the brain but also is involved in the synthesis of the brain-derived neurotrophic factor (BDNF), a neurotrophin whose levels are reduced in Alzheimer. In the present study, we compared BDNF serum levels in Alzheimer patients with dementia to those in Alzheimer patients with amnestic mild cognitive impairment and to cognitively healthy controls. Moreover, we examined whether the PAI-1/BDNF ratio correlates with disease severity, as measured by Mini-Mental State Examination. Our results showed that BDNF serum levels are lower (13.7% less) and PAI-1 levels are higher in Alzheimer patients with dementia than in Alzheimer patients with amnestic mild cognitive impairment patients (23% more) or controls (36% more). Furthermore, the PAI-1/BDNF ratio was significantly increased in Alzheimer patients as compared to amnestic mild cognitive impairment (36.4% more) and controls (40% more). Lastly, the PAI-1/BDNF ratio negatively correlated with the Mini-Mental score. Our results suggest that increased PAI-1 levels in Alzheimer, by impairing the production of the BDNF, are implicated in disease progression. They also indicate that the PAI-1/BDNF ratio could be used as a marker of Alzheimer. In support of this hypothesis, a strong negative correlation between the PAI-1/BDNF ratio and the Mini-Mental score was observed.

Crosstalk between the plasminogen/plasmin system and inflammation resolution

The plasminogen/plasmin (Plg/Pla) system, best known for its classical role in thrombolysis, has been recently highlighted as a regulator of other biological processes in mammals, including key steps involved in the resolution of inflammation. Inflammation resolution is a complex process coordinated by different cellular effectors, notably leukocytes, and active mediators, and is initiated shortly after the inflammatory response begins. Once the inflammatory insult is eliminated, an effective and timely engagement of proresolution programs prevents persistent inflammation, thereby avoiding excessive tissue damage, fibrosis, and the development of autoimmunity. Interestingly, recent studies demonstrate that Plg/Pla and their receptor, plasminogen receptor KT (Plg-RKT), regulate key steps in inflammation resolution. The number of studies investigating the involvement of the Plg/Pla system in these and other aspects of inflammation, including degradation of extracellular matrices, immune cell migration, wound healing, and skeletal growth and maintenance, highlights key roles of the Plg/Pla system during physiological and pathologic conditions. Here, we discuss robust evidence in the literature for the emerging roles of the Plg/Pla system in key steps of inflammation resolution. These findings suggest that dysregulation in Plg production and its activation plays a role in the pathogenesis of inflammatory diseases. Elucidating central mechanisms underlying the role of Plg/Pla in key steps of inflammation resolution either in preclinical models of inflammation or in human inflammatory conditions, can provide a rationale for the development of new pharmacologic interventions to promote resolution of inflammation, and open new pathways for the treatment of thromboinflammatory conditions.

Identification and Quantitation of the Bioactive Components in Wasted Aralia elata Leaves Extract with Endothelial Protective Activity

Aralia elata, a renowned medicinal plant with a rich history in traditional medicine, has gained attention for its potential therapeutic applications. However, the leaves of this plant have been largely overlooked and discarded due to limited knowledge of their biological activity and chemical composition. To bridge this gap, a comprehensive study was conducted to explore the therapeutic potential of the 70% ethanol extract derived from Aralia elata leaves (LAE) for the treatment of cardiovascular disease (CVD). Initially, the cytotoxic effects of LAE on human umbilical vein endothelial cells (HUVECs) were assessed, revealing no toxicity within concentrations up to 5 μg/mL. This suggests that LAE could serve as a safe raw material for the development of health supplements and drugs aimed at promoting cardiovascular well-being. Furthermore, the study found that LAE extract demonstrated anti-inflammatory properties in HUVECs by modulating the PI3K/Akt and MAPK signaling pathways. These findings are particularly significant as inflammation plays a crucial role in the progression of CVD. Moreover, LAE extract exhibited the ability to suppress the expression of adhesion molecules VCAM-1 and ICAM-1, which are pivotal in leukocyte migration to inflamed blood vessels observed in various pathological conditions. In conjunction with the investigation on therapeutic potential, the study also established an optimal HPLC-PDA-ESI-MS/MS method to identify and confirm the chemical constituents present in 24 samples collected from distinct regions in South Korea. Tentative identification revealed the presence of 14 saponins and nine phenolic compounds, while further analysis using PCA and PLS-DA allowed for the differentiation of samples based on their geographical origins. Notably, specific compounds such as chlorogenic acid, isochlorogenic acid A, and quercitrin emerged as marker compounds responsible for distinguishing samples from different regions. Overall, by unraveling its endothelial protective activity and identifying key chemical constituents, this research not only offers valuable insights for the development of novel treatments but also underscores the importance of utilizing and preserving natural resources efficiently.

A prognostic gene signature for gastric cancer and the immune infiltration-associated mechanism underlying the signature gene, PLG

BACKGROUND

Globally, gastric cancer (GC) is a common and lethal solid malignant tumor. Identifying the molecular signature and its functions can provide mechanistic insights into GC development and new methods for targeted therapy.

METHODS

Differentially expressed genes (DEGs) and prognostic genes (from univariate Cox regression analysis) were overlapped to obtain prognostic DEGs. Subsequently, molecular modules and the functions of these prognostic DEGs were identified by Metascape and Gene Ontology (GO)/Kyoto Encyclopedia of Genes and Genomes (KEGG)/Gene Set Enrichment Analysis (GSEA) enrichment analyses, respectively. Protein-protein interaction (PPI) networks of up- and down-regulated prognostic DEGs in GC were analyzed using the MCC algorithm of the Cytohubba plug-in in Cytoscape. The prognostic gene signature was defined on hub genes of the PPI networks by least absolute shrinkage and selection operator (LASSO)-Cox regression analysis. Furthermore, the expressional level of PLG in our clinical GC samples was validated by quantitative PCR (qPCR), western blotting, and immunohistochemistry (IHC). Subsequently, the PLG expression-correlation analysis was performed to assess the role of PLG in GC progression. Immune infiltration analysis was performed by single-sample gene set enrichment analysis (ssGSEA) to assess the inhibitory effect of PLG on immune infiltration.

RESULTS

Firstly, Up- and down-regulated prognostic DEGs and hub genes in protein-protein interaction (PPI) networks in GC were identified. A prognostic five-gene signature (i.e., PLG, SPARC, FGB, SERPINE1, and KLHL41) was identified. Among the five genes, the relationship between plasminogen (PLG) and GC remains largely unclear. Moreover, the functions of PLG-correlated genes in GC, like 'fibrinolysis', 'hemostasis', 'ion channel complex', and 'transporter complex' were identified. In addition, PLG expression correlated negatively with the infiltration of almost all immune cell types. Interestingly, the expression of PLG was significantly and highly correlated with that of CD160, an immune checkpoint inhibitor.

CONCLUSION

Our findings defined a new five-gene signature for predicting GC prognosis, but more validation is required to assess the effects and mechanism of the five genes, especially PLG, for the development of new GC therapies.

Tranexamic Acid and Plasminogen/Plasmin Glaring Paradox in COVID-19

Coronavirus disease 2019 (COVID-19) is caused by a severe acute respiratory syndrome, coronavirus type 2 (SARS-CoV-2), leading to acute tissue injury and an overstated immune response. In COVID-19, there are noteworthy changes in the fibrinolytic system with the development of coagulopathy. Therefore, modulation of the fibrinolytic system may affect the course of COVID-19. Tranexamic acid (TXA) is an anti-fibrinolytic drug that reduces the conversion of plasminogen to plasmin, which is necessary for SARS-CoV-2 infectivity. In addition, TXA has anti-inflammatory, anti-platelet, and anti-thrombotic effects, which may attenuate the COVID-19 severity. Thus, in this narrative review, we try to find the beneficial and harmful effects of TXA in COVID-19.

JAK/STAT pathway: Extracellular signals, diseases, immunity, and therapeutic regimens

Janus kinase/signal transduction and transcription activation (JAK/STAT) pathways were originally thought to be intracellular signaling pathways that mediate cytokine signals in mammals. Existing studies show that the JAK/STAT pathway regulates the downstream signaling of numerous membrane proteins such as such as G-protein-associated receptors, integrins and so on. Mounting evidence shows that the JAK/STAT pathways play an important role in human disease pathology and pharmacological mechanism. The JAK/STAT pathways are related to aspects of all aspects of the immune system function, such as fighting infection, maintaining immune tolerance, strengthening barrier function, and cancer prevention, which are all important factors involved in immune response. In addition, the JAK/STAT pathways play an important role in extracellular mechanistic signaling and might be an important mediator of mechanistic signals that influence disease progression, immune environment. Therefore, it is important to understand the mechanism of the JAK/STAT pathways, which provides ideas for us to design more drugs targeting diseases based on the JAK/STAT pathway. In this review, we discuss the role of the JAK/STAT pathway in mechanistic signaling, disease progression, immune environment, and therapeutic targets.

The Role of MRE11 in the IL-6/STAT3 Pathway of Lung Cancer Cells

MRE11 is a pivotal protein for ATM activation during double-strand DNA break. ATM kinase activations may act as lung cancer biomarkers. The IL-6/STAT3 pathway plays an important role in tumor metastasis, including lung cancer. However, the mechanism between MRE11 and the IL-6/STAT3 pathway is still unclear. In this study, we discovered that MRE11 can interact with STAT3 under IL-6 treatment and regulate STAT3 Tyr705 phosphorylation. After the knockdown of MRE11 in lung cancer cells, we discovered that IL-6 or the conditional medium of THP-1 cells can induce the mRNA expression of STAT3 downstream genes, including CCL2, in the control cells, but not in MRE11-knockdown lung cancer cells. Moreover, CCL2 secretion was lower in MRE11-knockdown lung cancer cells than in control cells after treatment with the conditional medium of RAW264.7 cells. In addition, MRE11 deficiency in lung cancer cells decreases their ability to recruit RAW 264.7 cells. Furthermore, MRE11 is a potential target for lung cancer therapy.

Fibrinolysis in COVID-19: Impact on Clot Lysis and Modulation of Inflammation

COVID-19 is a multisystem disease caused by SARS-CoV-2 and is associated with an imbalance between the coagulation and fibrinolytic systems. Overall, hypercoagulation, hypofibrinolysis and fibrin-clot resistance to fibrinolysis predispose patients to thrombotic and thromboembolic events. In the lungs, the virus triggers alveolar and interstitial fibrin deposition, endothelial dysfunction, and pulmonary intravascular coagulation, all events intrinsically associated with the activation of inflammation and organ injury. Adding to the pathogenesis of COVID-19, there is a positive feedback loop by which local fibrin deposition in the lungs can fuel inflammation and consequently dysregulates coagulation, a process known as immunothrombosis. Therefore, fibrinolysis plays a central role in maintaining hemostasis and tissue homeostasis during COVID-19 by cleaning fibrin clots and controlling feed-forward products of coagulation. In addition, components of the fibrinolytic system have important immunomodulatory roles, as evidenced by studies showing the contribution of Plasminogen/Plasmin (Plg/Pla) to the resolution of inflammation. Herein, we review clinical evidence for the dysregulation of the fibrinolytic system and discuss its contribution to thrombosis risk and exacerbated inflammation in severe COVID-19. We also discuss the current concept of an interplay between fibrinolysis and inflammation resolution, mirroring the well-known crosstalk between inflammation and coagulation. Finally, we consider the central role of the Plg/Pla system in resolving thromboinflammation, drawing attention to the overlooked consequences of COVID-19-associated fibrinolytic abnormalities to local and systemic inflammation.

Mechanism of Action of Topical Tranexamic Acid in the Treatment of Melasma and Sun-Induced Skin Hyperpigmentation

Tranexamic acid (TXA) has anti-plasmin activity and has been shown when administered orally to be effective against melasma, for which it is considered first-line pharmacotherapy. Several studies have shown that topically applied TXA is also effective against melasma and skin hyperpigmentation caused by sunburn and inflammation. The TXA concentration in the epidermis and dermis/vasculature has been estimated from its distribution in the skin after closed application, and topically applied TXA has thus been shown to act on neutrophils and mast cells in the dermis and on the vascular system. It is unlikely that topically applied TXA acts on dermal neutrophils or mast cells or on the vascular system to form thrombi. As discussed in the present review, studies on the effects of topical TXA on the hyperpigmentation process indicate that the resulting skin-lightening mechanism involves the suppression of cytokine/chemical mediator production, which stimulates melanin production via the keratinocyte-derived urokinase-type plasminogen activator and plasminogen derived from dermal vascular in the basal layer of the epidermis, thereby suppressing the production of excessive melanin to prevent hyperpigmentation.

Nephritis-Associated Plasmin Receptor (NAPlr): An Essential Inducer of C3-Dominant Glomerular Injury and a Potential Key Diagnostic Biomarker of Infection-Related Glomerulonephritis (IRGN)

Nephritis-associated plasmin receptor (NAPlr) was originally isolated from the cytoplasmic fraction of group A Streptococci, and was found to be the same molecule as streptococcal glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and plasmin receptor (Plr) on the basis of nucleotide and amino acid sequence homology. Its main functions include GAPDH activity, plasmin-binding capacity, and direct activation of the complement alternative pathway (A-P). Plasmin trapped by deposited NAPlr triggers the degradation of extracellular matrix proteins, such as glomerular basement membranes and mesangial matrix, and the accumulation of macrophages and neutrophils, leading to the induction of plasmin-related endocapillary glomerular inflammation. Deposited NAPlr at glomerular endocapillary site directly activates the complement A-P, and the endocapillary release of complement-related anaphylatoxins, C3a and C5a, amplify the in situ endocapillary glomerular inflammation. Subsequently, circulating and in situ-formed immune complexes participate in the glomerular injury resulting in NAPlr-mediated glomerulonephritis. The disease framework of infection-related glomerulonephritis (IRGN) has been further expanded. GAPDH of various bacteria other than Streptococci have been found to react with anti-NAPlr antibodies and to possess plasmin-binding activities, allowing glomerular NAPlr and plasmin activity to be utilized as key biomarkers of IRGN.

Annexin A2: The Diversity of Pathological Effects in Tumorigenesis and Immune Response

Annexin A2 (ANXA2) is widely used as a marker in a variety of tumors. By regulating multiple signal pathways, ANXA2 promotes the epithelial-mesenchymal transition, which can cause tumorigenesis and accelerate thymus degeneration. The elevated ANXA2 heterotetramer facilitates the production of plasmin, which participates in pathophysiologic processes such as tumor cell invasion and metastasis, bleeding diseases, angiogenesis, inducing the expression of inflammatory factors. In addition, the ANXA2 on the cell membrane mediates immune response via its interaction with surface proteins of pathogens, C1q, toll-like receptor 2, anti-dsDNA antibodies and immunoglobulins. Nuclear ANXA2 plays a role as part of a primer recognition protein complex that enhances DNA synthesis and cells proliferation by acting on the G1-S phase of the cell. ANXA2 reduction leads to the inhibition of invasion and metastasis in multiple tumor cells, bleeding complications in acute promyelocytic leukemia, retinal angiogenesis, autoimmunity response and tumor drug resistance. In this review, we provide an update on the pathological effects of ANXA2 in both tumorigenesis and the immune response. We highlight ANXA2 as a critical protein in numerous malignancies and the immune host response.

An inhibitor of leukotriene-A4 hydrolase from bat salivary glands facilitates virus infection

SignificanceAn immunosuppressant protein (MTX), which facilitates virus infection by inhibiting leukotriene A₄ hydrolase (LTA₄H) to produce the lipid chemoattractant leukotriene B₄ (LTB₄), was identified and characterized from the submandibular salivary glands of the bat Myotis pilosus. To the best of our knowledge, this is a report of an endogenous LTA₄H inhibitor in animals. MTX was highly concentrated in the bat salivary glands, suggesting a mechanism for the generation of immunological privilege and immune tolerance and providing evidence of viral shedding through oral secretions. Moreover, given that the immunosuppressant MTX selectively inhibited the proinflammatory activity of LTA₄H, without affecting its antiinflammatory activity, MTX might be a potential candidate for the development of antiinflammatory drugs by targeting the LTA₄-LTA₄H-LTB₄ inflammatory axis.

Histone 2B Facilitates Plasminogen-Enhanced Endothelial Migration through Protease-Activated Receptor 1 (PAR1) and Protease-Activated Receptor 2 (PAR2)

Plasminogen and its multiple receptors have been implicated in the responses of many different cell types. Among these receptors, histone 2B (H2B) has been shown to play a prominent role in macrophage responses. The contribution of H2B to plasminogen-induced endothelial migration, an event relevant to wound healing and angiogenesis, is unknown. Plasminogen enhanced the migration of endothelial cells, which was inhibited by both Protease-Activated Receptor-1 (PAR1) and 2 (PAR2) antagonists. H2B was detected on viable endothelial cells of venous and arterial origin, and an antibody to H2B that blocks plasminogen binding also inhibited the plasminogen-dependent migration by these cells. The antibody blockade was as effective as PAR1 or PAR2 antagonists in inhibiting endothelial cell migration. In pull-down experiments, H2B formed a complex with both PAR1 and PAR2 but not β3 integrin, another receptor implicated in endothelial migration in the presence of plasminogen. H2B was found to be associated with clathrin adapator protein, AP2µ (clathrin AP2µ) and β-arrestin2, which are central to the internationalization/signaling machinery of the PARs. These associations with PAR1-clathrin adaptor AP2µ- and PAR2-β-arrestin2-dependent internalization/signaling pathways provide a mechanism to link plasminogen to responses such as wound healing and angiogenesis.

Roles of the tissue-type plasminogen activator in immune response

The COVID-19 pandemic has once again brought to the forefront the existence of a tight link between the coagulation/fibrinolytic system and the immunologic processes. Tissue-type plasminogen activator (tPA) is a serine protease with a key role in fibrinolysis by converting plasminogen into plasmin that can finally degrade fibrin clots. tPA is released in the blood by endothelial cells and hepatocytes but is also produced by various types of immune cells including T cells and monocytes. Beyond its role on hemostasis, tPA is also a potent modulator of inflammation and is involved in the regulation of several inflammatory diseases. Here, after a brief description of tPA structure, we review its new functions in adaptive immunity focusing on T cells and antigen presenting cells. We intend to synthesize the recent knowledge on proteolysis- and receptor-mediated effects of tPA on immune response in physiological and pathological context.

A novel β-glucan-oligonucleotide complex selectively delivers siRNA to APCs via Dectin-1

Delivering therapeutic nucleic acids to targeted cells and organs has been a challenge for decades. A novel technology to deliver oligonucleotide therapeutics to immune cells is here described. In this approach, a macromolecular complex of oligonucleotides and the β-1,3-glucan schizophyllan (SPG) is selectively delivered to cells expressing a lectin receptor, Dectin-1, via SPG-Dectin-1 interaction. Detailed investigation of Dectin-1-expressing cells revealed that Dectin-1 is expressed in all subsets of monocytes as well as dendritic cell (DC) populations, including conventional DCs (cDCs) and plasmacytoid DCs (pDCs), in humans. The expression patterns in mice and humans are comparable, except for the expression in pDCs. The results indicate that Dectin-1 is expressed on cells capable of professional antigen presentation, except for B cells. We chose CD40 as a target gene for small interfering RNA (siRNA) as CD40 expression in antigen-presenting cells (APCs), particularly in DCs, plays critical roles in regulating immune responses. Dose-dependent cellular uptake of siCD40-SPG complexes was confirmed in cells expressing Dectin-1. Gene silencing activity was confirmed in vitro by the reduction of CD40 mRNA and by the site-specific cleavage of CD40 mRNA as determined by the 5' RNA ligase-mediated rapid amplification of cDNA ends (5'RLM-RACE) technique. In vivo activity of siCD40-SPG complexes was demonstrated as the reduced CD40 protein expression in monocytes and DCs in mice. Furthermore, the in vivo activity of siCD40-SPG targeting human CD40 was confirmed in cynomolgus monkeys by the 5'RLM-RACE technique. In conclusion, we have demonstrated the receptor-ligand binding-mediated delivery of siRNA targeting immune-regulating monocytes and DCs via the interaction of SPG and its receptor, Dectin-1. As monocytes and DCs play central roles in inducing and controlling immune responses, Dectin-1-targeted delivery of nucleic acids should provide a useful tool for developing drugs to treat a wide range of diseases, including autoimmune diseases, allergy, and cancer, as well as transplantation.

Plasmin and Plasminogen System in the Tumor Microenvironment: Implications for Cancer Diagnosis, Prognosis, and Therapy

Simple Summary

In this review, we present a detailed discussion of how the plasminogen-activation system is utilized by tumor cells in their unrelenting attack on the tissues surrounding them. Plasmin is an enzyme which is responsible for digesting several proteins that hold the tissues surrounding solid tumors together. In this process tumor cells utilize the activity of plasmin to digest tissue barriers in order to leave the tumour site and spread to other parts of the body. We specifically focus on the role of plasminogen receptor—p11 which is an important regulatory protein that facilitates the conversion of plasminogen to plasmin and by this means promotes the attack by the tumour cells on their surrounding tissues.

Abstract

The tumor microenvironment (TME) is now being widely accepted as the key contributor to a range of processes involved in cancer progression from tumor growth to metastasis and chemoresistance. The extracellular matrix (ECM) and the proteases that mediate the remodeling of the ECM form an integral part of the TME. Plasmin is a broad-spectrum, highly potent, serine protease whose activation from its precursor plasminogen is tightly regulated by the activators (uPA, uPAR, and tPA), the inhibitors (PAI-1, PAI-2), and plasminogen receptors. Collectively, this system is called the plasminogen activation system. The expression of the components of the plasminogen activation system by malignant cells and the surrounding stromal cells modulates the TME resulting in sustained cancer progression signals. In this review, we provide a detailed discussion of the roles of plasminogen activation system in tumor growth, invasion, metastasis, and chemoresistance with specific emphasis on their role in the TME. We particularly review the recent highlights of the plasminogen receptor S100A10 (p11), which is a pivotal component of the plasminogen activation system.

The molecular structure and role of CCL2 (MCP-1) and C-C chemokine receptor CCR2 in skeletal biology and diseases

Monocyte chemoattractant protein-1, also called chemokine (C-C motif) ligand 2 (CCL2) or small inducible cytokine A2, is an inflammatory mediator capable of recruiting monocytes, memory T cells, and dendritic cells. CCL2 is a member of the CC chemokine superfamily, which binds to its receptor, C-C motif chemokine receptor-2 (CCR2), for the induction of chemotactic activity and an increase of calcium influx. It exerts multiple effects on a variety of cells, including monocytes, macrophages, osteoclasts, basophils, and endothelial cells, and is involved in a diverse range of diseases. This review discusses the molecular structure and role of CCL2 and CCR2 in skeletal biology and disease. Molecular structure analyses reveal that CCL2 shares a conserved C-C motif; however, it has only limited sequence homology with other CCL family members. Likewise, CCR2, as a member of the G-protein-coupled seven-transmembrane receptor superfamily, shares conserved cysteine residues, but exhibits very limited sequence homology with other CCR family members. In the skeletal system, the expression of CCL2 is regulated by a variety of factors, such as parathyroid hormone/parathyroid hormone-related peptide, interleukin 1b, tumor necrosis factor-α and transforming growth factor-beta, RANKL, and mechanical forces. The interaction of CCL2 and CCR2 activates several signaling cascades, including PI3K/Akt/ERK/NF-κB, PI3K/MAPKs, and JAK/STAT-1/STAT-3. Understanding the role of CCL2 and CCR2 will facilitate the development of novel therapies for skeletal disorders, including rheumatoid arthritis, osteolysis and other inflammatory diseases related to abnormal chemotaxis.

Fibrinolysis: A Primordial System Linked to the Immune Response

The fibrinolytic system provides an essential means to remove fibrin deposits and blood clots. The actual protease responsible for this is plasmin, formed from its precursor, plasminogen. Fibrin is heralded as it most renowned substrate but for many years plasmin has been known to cleave many other substrates, and to also activate other proteolytic systems. Recent clinical studies have shown that the promotion of plasmin can lead to an immunosuppressed phenotype, in part via its ability to modulate cytokine expression. Almost all immune cells harbor at least one of a dozen plasminogen receptors that allows plasmin formation on the cell surface that in turn modulates immune cell behavior. Similarly, a multitude of pathogens can also express their own plasminogen activators, or contain surface proteins that provide binding sites host plasminogen. Plasmin formed under these circumstances also empowers these pathogens to modulate host immune defense mechanisms. Phylogenetic studies have revealed that the plasminogen activating system predates the appearance of fibrin, indicating that plasmin did not evolve as a fibrinolytic protease but perhaps has its roots as an immune modifying protease. While its fibrin removing capacity became apparent in lower vertebrates these primitive under-appreciated immune modifying functions still remain and are now becoming more recognised.

Crosstalk between alveolar macrophages and alveolar epithelial cells/fibroblasts contributes to the pulmonary toxicity of gefitinib

Gefitinib is an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor indicated for the first-line treatment of patients with metastatic or advanced non-small cell lung cancer (NSCLC) whose tumors have specific EGFR mutations. Pulmonary toxicity is one of the fatal adverse effects of gefitinib and the underlying mechanism remains unclear. Here we demonstrated that alveolar macrophages contributed to gefitinib-induced pulmonary toxicity through promoting alveolar epithelial cells to undergo epithelial to mesenchymal transition (EMT) and inducing activation and antiapoptotic effect in fibroblasts. Further, we found that alveolar macrophage-secreted MCP-1 worked as a key factor in the pathologic changes of these two cell types. Gefitinib increased Mcp-1 transcription level via the nuclear import of the transcription factor STAT3. In conclusion, our data uncovered the underlying mechanisms of macrophage-promoted pulmonary toxicity in the presence of gefitinib. MCP-1 antibody or inhibition of STAT3 activation may represent novel therapeutic strategies for preventing gefitinib-induced pulmonary toxicity.

Acute post-streptococcal glomerulonephritis: analysis of the pathogenesis

Increasing evidence supports a central role of the immune system in acute post streptococcal glomerulonephritis (APSGN), but the current view of how streptococcal biology affects immunity, and vice versa, remains to be clarified. Renal glomerular immune complex deposition is critical in the initiation of APSGN; however, mechanisms previous to immune complex formation could modulate the initiation and the progression of the disease. Initial and late renal events involved in the nephritis can also be related to host factors and streptococcal factors. In this review we describe the mechanisms reported for the APSGN pathogenesis, the interactions of streptococcal products with renal cells and leukocytes, the possible effects of different nephritogenic antigens in the renal environment and the possibility that APSGN is not just due to a single streptococcal antigen and its antibody; instead, kidney damage may be the result of different factors acting at the same time related to both streptococcus and host factors. Addressing these points should help us to better understand APSGN physiopathology.

The Immunologic Effect of Early Intravenous Two and Four Gram Bolus Dosing of Tranexamic Acid Compared to Placebo in Patients With Severe Traumatic Bleeding (TAMPITI): A Randomized, Double-Blind, Placebo-Controlled, Single-Center Trial

Background

The hemostatic properties of tranexamic acid (TXA) are well described, but the immunological effects of TXA administration after traumatic injury have not been thoroughly examined. We hypothesized TXA would reduce monocyte activation in bleeding trauma patients with severe injury.

Methods

This was a single center, double-blinded, randomized controlled trial (RCT) comparing placebo to a 2 g or 4 g intravenous TXA bolus dose in trauma patients with severe injury. Fifty patients were randomized into each study group. The primary outcome was a reduction in monocyte activation as measured by human leukocyte antigen-DR isotype (HLA-DR) expression on monocytes 72 h after TXA administration. Secondary outcomes included kinetic assessment of immune and hemostatic phenotypes within the 72 h window post-TXA administration.

Results

The trial occurred between March 2016 and September 2017, when data collection ended. 149 patients were analyzed (placebo, n = 50; 2 g TXA, n = 49; 4 g TXA, n = 50). The fold change in HLA-DR expression on monocytes [reported as median (Q1–Q3)] from pre-TXA to 72 h post-TXA was similar between placebo [0.61 (0.51–0.82)], 2 g TXA [0.57 (0.47–0.75)], and 4 g TXA [0.57 (0.44–0.89)] study groups (p = 0.82). Neutrophil CD62L expression was reduced in the 4 g TXA group [fold change: 0.73 (0.63–0.97)] compared to the placebo group [0.97 (0.78–1.10)] at 24 h post-TXA (p = 0.034). The fold decrease in plasma IL-6 was significantly less in the 4 g TXA group [1.36 (0.87–2.42)] compared to the placebo group [0.46 (0.19–1.69)] at 72 h post-TXA (p = 0.028). There were no differences in frequencies of myeloid or lymphoid populations or in classical complement activation at any of the study time points.

Conclusion

In trauma patients with severe injury, 4 g intravenous bolus dosing of TXA has minimal immunomodulatory effects with respect to leukocyte phenotypes and circulating cytokine levels.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT02535949.

Enolase 1 differentially contributes to cell transformation in lung cancer but not in esophageal cancer

Enolase transforms 2-phospho-D-glycerate into phosphoenolpyruvate during glycolysis. The human enolase (ENO) family comprises three members named ENO3, which is restricted to muscle tissues, ENO2, which is neuron- and neuroendocrine tissue-specific, and ENO1, which is expressed in almost all tissues. ENO1 is involved in various types of human cancer, including retinoblastoma, hepatocellular carcinoma, pancreatic cancer, renal cell carcinoma, cholangiocarcinoma and gastric cancer. Furthermore, ENO1 enhances cell transformation in numerous cancer cell lines. It has been reported that ENO1 is involved in various activities that are detrimental to cell transformation, including apoptosis and differentiation. However, a few studies demonstrated that ENO1 can be down- or upregulated in various types of lung cancer, which suggests that ENO1 has an ambiguous role in the development of lung cancer. The present study aimed to investigate the differential influences of ENO1 on various types of cancer, and to clarify the role of ENO1 in lung cancer in particular. Western blotting was performed to assess ENO1 protein expression levels in lung cancer and esophageal cancer tissues. Furthermore, exogenous ENO1 was overexpressed in cell lines derived from various tissues and single cell proliferation, flowcytometric analysis, and western blotting were performed to determine the cell proliferation rate, cell transformation status, cell cycle progression and the expression of cell cycle regulators, such as cyclins and cyclin-dependent kinases, and survival factors, such as MAPK and AKT. The results demonstrated that ENO1 was upregulated in collected panels of lung cancer tissues, but not in esophageal cancer tissues. In addition, overexpression of ectopic ENO1 promoted cell proliferation and survival in lung cancer cell lines, which was not the case in other cells, including an esophageal cell line. Furthermore, mechanistic analyses revealed that ENO1 enhanced cell proliferation by accelerating G₁ progression and upregulating G₁ phase cyclin-dependent kinase 6 (CDK6), and improved cell survival by upregulating p38 in the MAPK cascade and increasing p-AKT in the AKT cascade, in particular in lung cancer cell lines. Overall, the results from the present study demonstrated that ENO1 may contribute to the development of lung cancers, but not esophageal cancers.

Plasminogen and the Plasminogen Receptor, Plg-RKT, Regulate Macrophage Phenotypic, and Functional Changes

Inflammation resolution is an active process that functions to restore tissue homeostasis. Clearance of apoptotic leukocytes by efferocytosis at inflammatory sites plays an important role in inflammation resolution and induces remarkable macrophage phenotypic and functional changes. Here, we investigated the effects of deletion of either plasminogen (Plg) or the Plg receptor, Plg-R_KT, on the resolution of inflammation. In a murine model of pleurisy, the numbers of total mononuclear cells recruited to the pleural cavity were significantly decreased in both Plg^−/− and Plg-R_KT^−/− mice, a response associated with decreased levels of the chemokine CCL2 in pleural exudates. Increased percentages of M1-like macrophages were determined in pleural lavages of Plg^−/− and Plg-R_KT^−/− mice without significant changes in M2-like macrophage percentages. In vitro, Plg and plasmin (Pla) increased CD206/Arginase-1 expression and the levels of IL-10/TGF-β (M2 markers) while decreasing IFN/LPS-induced M1 markers in murine bone-marrow-derived macrophages (BMDMs) and human macrophages. Furthermore, IL4-induced M2-like polarization was defective in BMDMs from both Plg^−/− and Plg-R_KT^−/− mice. Mechanistically, Plg and Pla induced transient STAT3 phosphorylation, which was decreased in Plg^−/− and Plg-R_KT^−/− BMDMs after IL-4 or IL-10 stimulation. The extents of expression of CD206 and Annexin A1 (important for clearance of apoptotic cells) were reduced in Plg^−/− and Plg-R_KT^−/− macrophage populations, which exhibited decreased phagocytosis of apoptotic neutrophils (efferocytosis) in vivo and in vitro. Taken together, these results suggest that Plg and its receptor, Plg-R_KT, regulate macrophage polarization and efferocytosis, as key contributors to the resolution of inflammation.

Tissue-type plasminogen activator neutralizes LPS but not protease-activated receptor-mediated inflammatory responses to plasmin

Tissue-type plasminogen activator (tPA) activates fibrinolysis and also suppresses innate immune system responses to LPS in bone marrow-derived macrophages (BMDMs) and in vivo in mice. The objective of this study was to assess the activity of tPA as a regulator of macrophage physiology in the presence of plasmin. Enzymatically active and enzymatically inactive (EI) tPA appeared to comprehensively block the response to LPS in BMDMs, including expression of proinflammatory cytokines such as TNF-α and IL-1β and anti-inflammatory cytokines such as IL-10 and IL-1 receptor antagonist. The activity of EI-tPA as an LPS response modifier was conserved in the presence of plasminogen. By contrast, in BMDMs treated with tPA and plasminogen or preactivated plasmin, in the presence or absence of LPS, increased proinflammatory cytokine expression was observed and tPA failed to reverse the response. Plasmin independently activated NF-κB, ERK1/2, c-Jun N-terminal kinase, and p38 mitogen-activated protein kinase in BMDMs, which is characteristic of proinflammatory stimuli. Plasmin-induced cytokine expression was blocked by ε-aminocaproic acid, aprotinin, and inhibitors of the known plasmin substrate, Protease-activated receptor-1 (PAR-1), but not by N-methyl-d-aspartate receptor inhibitor, which blocks the effects of tPA on macrophages. Cytokine expression by BMDMs treated with the PAR-1 agonist, TFLLR, was not inhibited by EI-tPA, possibly explaining why EI-tPA does not inhibit macrophage responses to plasmin and providing evidence for specificity in the ability of tPA to oppose proinflammatory stimuli. Regulation of innate immunity by the fibrinolysis system may reflect the nature of the stimulus and a balance between the potentially opposing activities of tPA and plasmin.

Antifibrinolytic Therapy and Perioperative Considerations

Fibrinolysis is a physiologic component of hemostasis that functions to limit clot formation. However, after trauma or surgery, excessive fibrinolysis may contribute to coagulopathy, bleeding, and inflammatory responses. Antifibrinolytic agents are increasingly used to reduce bleeding, allogeneic blood administration, and adverse clinical outcomes. Tranexamic acid is the agent most extensively studied and used in most countries. This review will explore the role of fibrinolysis as a pathologic mechanism, review the different pharmacologic agents used to inhibit fibrinolysis, and focus on the role of tranexamic acid as a therapeutic agent to reduce bleeding in patients after surgery and trauma.

Exploring the interaction between Mycobacterium tuberculosis enolase and human plasminogen using computational methods and experimental techniques

Surface localized microbial enolases' binding with human plasminogen has been increasingly proven to have an important role in initial infection cycle of several human pathogens. Likewise, surface localized Mycobacterium tuberculosis (Mtb) enolase also binds to human plasminogen, and this interaction may entail crucial consequences for granuloma stability. The current study is the first attempt to explore the plasminogen interacting residues of enolase from Mtb. Beginning with the structural modeling of Mtb enolase, the binding pose of Mtb enolase and human plasminogen was predicted using protein-protein docking simulations. The binding pose revealed the interface region with interacting residues and molecular interactions. Next, the interacting residues were refined and ranked by using various criteria. Finally, the selected interacting residues were tested experimentally for their involvement in plasminogen binding. The two consecutive lysine residues, Lys-193 and Lys-194, turned out to be active residues for plasminogen binding. These residues when substituted for alanine along with the most active residue Lys-429, that is, the triple mutant (K193A + K194A + K429A) Mtb enolase, exhibited 40% reduction in plasminogen binding. It is worth noting that Mtb enolase lost nearly half of the plasminogen binding activity with only three simultaneous substitutions, without any significant secondary structure perturbation. Further, the sequence comparison between Mtb and human enolase isoforms suggests the possibility of selective targeting of Mtb enolase to obstruct binding of human plasminogen.

Bindarit reduces the incidence of acute aortic dissection complicated lung injury via modulating NF-κB pathway

The pathogenesis of acute aortic dissection (AAD) complicated acute lung injury (ALI) is not currently well defined. At present, no effective animal model has been established for AAD complicated ALI, which hinders research and development of an appropriate treatment regimen for the concurrent conditions. The aim of the present study was to evaluate the therapeutic effects of bindarit (Bnd), an indazolic derivative, on the production of monocyte chemoattractant protein (MCP)-1 in angiotensin II (AngII)-induced complicated ALI in rats. An AAD complicated ALI rat model was established using aminopropionitrile (BAPN) and AngII. The pathological features of AAD complicated ALI were assessed via biochemical and histopathological evaluations. AngII-stimulated human pulmonary microvascular endothelial cells (hPMVECs) were used to assess the effects of Bnd on MCP-1 expression. Western blot analysis was performed to analyze the expression of proteins that may be associated with the process. AAD complicated ALI was established following BAPN and AngII interference, and a massive accumulation of macrophages was observed in the lung tissues of the study rats. Bnd was able to significantly attenuate the incidence of AAD complicated ALI (P<0.05), and significantly inhibit the accumulation of macrophages (P<0.05). The overexpression of MCP-1 induced by AngII in hPMVECs was significantly inhibited by Bnd (P<0.05), which may be associated with downregulation of the classical nuclear factor-κB pathway. Bnd was able to attenuate the incidence of AAD complicated ALI, and inhibit the accumulation of macrophages in vivo. These findings provide a basis for future applications of Bnd as part of a therapeutic treatment schedule for aortic dissection complicated lung injury.

Danshen improves survival of patients with advanced lung cancer and targeting the relationship between macrophages and lung cancer cells

In traditional Chinese medicine, Salvia miltiorrhiza Bunge (danshen) is widely used in the treatment of numerous cancers. However, its clinical effort and mechanism in the treatment of advanced lung cancer are unclear. In our study, the in vivo protective effort of danshen in patients with advanced lung cancer were validated using data from the National Health Insurance Research Database in Taiwan. We observed in vitro that dihydroisotanshinone I (DT), a bioactive compound in danshen, exerts anticancer effects through many pathways. First, 10 μM DT substantially inhibited the migration ability of lung cancer cells in both macrophage and macrophage/lung cancer direct mixed coculture media. Second, 10 μM DT repressed the phosphorylation of signal transducer and activator of transcription 3 (STAT3), the protein expression of S-phase kinase associated protein-2 (Skp2), and the mRNA levels of STAT3-related genes, including chemokine (C–C motif) ligand 2 (CCL2). In addition, 10 μM DT suppressed the macrophage recruitment ability of lung cancer cells by reducing CCL2 secretion from both macrophages and lung cancer cells. Third, 20 μM DT induced apoptosis in lung cancer cells. Furthermore, DT treatment significantly inhibited the final tumor volume in a xenograft nude mouse model. In conclusion, danshen exerts protective efforts in patients with advanced lung cancer. These effects can be attributed to DT-mediated interruption of the cross talk between lung cancer cells and macrophages and blocking of lung cancer cell proliferation.

Adiponectin inhibits oxidization-induced differentiation of T helper cells through inhibiting costimulatory CD40 and CD80

Adiponectin is a multifunctional adipokine that has several oligomeric forms in the blood stream, which broadly regulates innate and acquired immunity. Therefore, in this study, we aimed to observe the differentiation of T helper (Th) cells and expression of costimulatory signaling molecules affected by adiponectin. The mRNA and protein expression levels of adiponectin and its receptors in oxidized low density lipoprotein cholesterol-treated endothelial cells were assayed by real time PCR and immunofluorescence. The endothelial cells were then treated with adiponectin with or without adipoR1 or adipoR2 siRNA and co-cultured with T lymphocytes. The distribution of Th1, Th2 and Th17 subsets were assayed by flow cytometry. The effects of adiponectin on costimulatory signaling molecules HLA-DR, CD80, CD86 and CD 40 was also assayed by flow cytometry. The results showed that endothelial cells expressed adiponectin and its receptor adipoR1 and adipoR2, but not T-cadherin. Adiponectin suppressed Th1 and Th17 differentiation through adipoR1 receptor, contributed to the inhibition of CD80 and CD40, and inhibited differentiation of Th1 and Th17 by inhibiting antigen presenting action.

Chemically different non-thermal plasmas target distinct cell death pathways

A rigorous biochemical analysis of interactions between non-thermal plasmas (NTPs) and living cells has become an important research topic, due to recent developments in biomedical applications of non-thermal plasmas. Here, we decouple distinct cell death pathways targeted by chemically different NTPs. We show that helium NTP cells treatment, results in necrosome formation and necroptosis execution, whereas air NTP leads to mTOR activation and autophagy inhibition, that induces mTOR-related necrosis. On the contrary, ozone (abundant component of air NTP) treatment alone, exhibited the highest levels of reactive oxygen species production leading to CypD-related necrosis via the mitochondrial permeability transition. Our findings offer a novel insight into plasma-induced cellular responses, and reveal distinct cell death pathways triggered by NTPs.

Sodium azide suppresses LPS-induced expression MCP-1 through regulating IκBζ and STAT1 activities in macrophages

Sodium azide (NaN₃) is a chemical compound with multiple toxic effects on vascular and neuronal systems, causing hypotension and neurotoxicity, respectively. In order to test its effects on the immune system, human and mouse macrophage-like cell lines were treated with nontoxic doses of NaN₃ and the changes in LPS-induced inflammatory activation was measured. Interestingly, the LPS-induced expression of monocyte chemoattractant protein (MCP)-1 was suppressed by NaN₃ without affecting the expression of IL-8 and TNF-α. Further analysis of cellular signaling mediators involved in the expression of these cytokines revealed that NaN₃ suppressed the LPS-induced activation of signal transducers and activator of transcription (STAT)1 and inhibitor of κB (IκB) ς, which are involved in the LPS-induced expression of MCP-1, while the LPS-induced activation of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) was not affected. The LPS-induced expression of MCP-2 and CXCL10, which are also regulated by STAT1, was suppressed by NaN₃. Similarly, the LPS-induced expression of IL-6, which is regulated by IκBζ, was suppressed by NaN₃. These results demonstrate that NaN₃ selectively suppresses the LPS-induced expression of pro-inflammatory mediators through the suppression of STAT1 and IκBζ activation. These new findings about the activity of NaN₃ may contribute to the development of specific regulators of macrophage activity during acute and chronic inflammation.

Pharmacological targeting of plasmin prevents lethality in a murine model of macrophage activation syndrome

Macrophage activation syndrome (MAS) is a life-threatening disorder characterized by a cytokine storm and multiorgan dysfunction due to excessive immune activation. Although abnormalities of coagulation and fibrinolysis are major components of MAS, the role of the fibrinolytic system and its key player, plasmin, in the development of MAS remains to be solved. We established a murine model of fulminant MAS by repeated injections of Toll-like receptor-9 (TLR-9) agonist and d-galactosamine (DG) in immunocompetent mice. We found plasmin was excessively activated during the progression of fulminant MAS in mice. Genetic and pharmacological inhibition of plasmin counteracted MAS-associated lethality and other related symptoms. We show that plasmin regulates the influx of inflammatory cells and the production of inflammatory cytokines/chemokines. Collectively, our findings identify plasmin as a decisive checkpoint in the inflammatory response during MAS and a potential novel therapeutic target for MAS.

Recombinant tissue plasminogen activator enhances microparticle release from mouse brain-derived endothelial cells through plasmin

Thrombolysis with recombinant tissue plasminogen activator (rt-PA) is currently the only approved pharmacological strategy for acute ischemic stroke. However, rt-PA exhibits vascular toxicity mainly due to endothelial damage. To investigate the mechanisms underlying rt-PA-induced endothelial alterations, we assessed the role of rt-PA in the generation of endothelial microparticles (EMPs), emerging biological markers and effectors of endothelial dysfunction. The mouse brain-derived endothelial cell line bEnd.3 was used. Cells were treated with rt-PA at 20, 40 or 80μg/ml for 15 or 24h, and EMPs were quantified in the culture media using Annexin-V staining coupled with flow cytometry. Rt-PA enhanced EMP release from bEnd.3 cells with a maximal increase at the 40μg/ml dose for 24h (+78% compared to controls). Using tranexamic acid and aprotinin we demonstrated that plasmin is responsible for rt-PA-induced EMP release. The p38 MAPK inhibitor SB203580 and the poly(ADP-ribose)polymerase (PARP) inhibitor PJ34 also reduced rt-PA-induced EMP production, suggesting that p38 MAPK and PARP are downstream intracellular effectors of rt-PA/plasmin. Rt-PA also altered through plasmin the morphology and the confluence of bEnd.3 cells. By contrast, these changes did not implicate p38 MAPK and PARP. This study demonstrates that rt-PA induces the production of microparticles by cerebral endothelial cells, through plasmin, p38 MAPK and PARP pathways. Determining the phenotype of these EMPs to clarify their role on the endothelium in ischemic conditions could thus be of particular interest.

Cancer therapy targeting the fibrinolytic system

The tumor microenvironment is recognized as a key factor in the multiple stages of cancer progression, mediating local resistance, immune-escape and metastasis. Cancer growth and progression require remodeling of the tumor stromal microenvironment, such as the development of tumor-associated blood vessels, recruitment of bone marrow-derived cells and cytokine processing. Extracellular matrix breakdown achieved by proteases like the fibrinolytic factor plasmin and matrix metalloproteases is necessary for cell migration crucial for cancer invasion and metastasis. Key components of the fibrinolytic system are expressed in cells of the tumor microenvironment. Plasmin can control growth factor bioavailability, or the regulation of other proteases leading to angiogenesis, and inflammation. In this review, we will focus on the role of the fibrinolytic system in the tumor microenvironment summarizing our current understanding of the role of the fibrinolytic factors for the modulation of the local chemokine/cytokine milieu, resulting in myeloid cell recruitment, which can promote neoangiogenesis.

The putative role of Rhipicephalus microplus salivary serpins in the tick-host relationship

Inflammation and hemostasis are part of the host's first line of defense to tick feeding. These systems are in part serine protease mediated and are tightly controlled by their endogenous inhibitors, in the serpin superfamily (serine protease inhibitors). From this perspective ticks are thought to use serpins to evade host defenses during feeding. The cattle tick Rhipicephalus microplus encodes at least 24 serpins, of which RmS-3, RmS-6, and RmS-17 were previously identified in saliva of this tick. In this study, we screened inhibitor functions of these three saliva serpins against a panel of 16 proteases across the mammalian defense pathway. Our data confirm that Pichia pastoris-expressed rRmS-3, rRmS-6, and rRmS-17 are likely inhibitors of pro-inflammatory and pro-coagulant proteases. We show that rRmS-3 inhibited chymotrypsin and cathepsin G with stoichiometry of inhibition (SI) indices of 1.8 and 2.0, and pancreatic elastase with SI higher than 10. Likewise, rRmS-6 inhibited trypsin with SI of 2.6, chymotrypsin, factor Xa, factor XIa, and plasmin with SI higher than 10, while rRmS-17 inhibited trypsin, cathepsin G, chymotrypsin, plasmin, and factor XIa with SI of 1.6, 2.6, 2.7, 3.4, and 9.0, respectively. Additionally, we observed the formation of irreversible complexes between rRmS-3 and chymotrypsin, rRmS-6/rRmS-17 and trypsin, and rRmS-3/rRmS-17 and cathepsin G, which is consistent with typical mechanism of inhibitory serpins. In blood clotting assays, rRmS-17 delayed plasma clotting by 60 s in recalcification time assay, while rRmS-3 and rRmS-6 did not have any effect. Consistent with inhibitor function profiling data, 2.0 μM rRmS-3 and rRmS-17 inhibited cathepsin G-activated platelet aggregation in a dose-responsive manner by up to 96% and 95% respectively. Of significant interest, polyclonal antibodies blocked inhibitory functions of the three serpins. Also notable, antibodies to Amblyomma americanum, Ixodes scapularis, and Rhipicephalus sanguineus tick saliva proteins cross-reacted with the three R. microplus saliva serpins, suggesting the potential of these proteins as candidates for universal anti-tick vaccines.

Cancer Cell-derived Exosomes Induce Mitogen-activated Protein Kinase-dependent Monocyte Survival by Transport of Functional Receptor Tyrosine Kinases

Tumor-associated macrophages (TAM) play pivotal roles in cancer initiation and progression. Monocytes, the precursors of TAMs, normally undergo spontaneous apoptosis within 2 days, but can subsist in the inflammatory tumor microenvironment for continuous survival and generation of sufficient TAMs. The mechanisms underlying tumor-driving monocyte survival remain obscure. Here we report that cancer cell-derived exosomes were crucial mediators for monocyte survival in the inflammatory niche. Analysis of the survival-promoting molecules in monocytes revealed that cancer cell-derived exosomes activated Ras and extracellular signal-regulated kinases in the mitogen-activated protein kinase (MAPK) pathway, resulting in the prevention of caspase cleavage. Phosphorylated receptor tyrosine kinases (RTKs), such as phosphorylated epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER-2), were abundantly expressed in cancer cell-derived exosomes. Knock-out of EGFR or/and HER-2, or alternatively, inhibitors against their phosphorylation significantly disturbed the exosome-mediated activation of the MAPK pathway, inhibition of caspase cleavage, and increase in survival rate in monocytes. Moreover, the deprived survival-stimulating activity of exosomes due to null expression of EGFR and HER-2 could be restored by activation of another RTK, insulin receptor. Overall, our study uncovered a mechanism of tumor-associated monocyte survival and demonstrated that cancer cell-derived exosomes can stimulate the MAPK pathway in monocytes through transport of functional RTKs, leading to inactivation of apoptosis-related caspases. This work provides insights into the long sought question on monocyte survival prior to formation of plentiful TAMs in the tumor microenvironment.

Differential Gene Expression in Coiled versus Flow-Diverter-Treated Aneurysms: RNA Sequencing Analysis in a Rabbit Aneurysm Model

BACKGROUND AND PURPOSE

The biologic mechanisms leading to aneurysm healing or rare complications such as delayed aneurysm ruptures after flow-diverter placement remain poorly understood. We used RNA sequencing following implantation of coils or flow diverters in elastase aneurysms in rabbits to identify genes and pathways of potential interest.

MATERIALS AND METHODS

Aneurysms were treated with coils (n = 5) or flow diverters (n = 4) or were left untreated for controls (n = 6). Messenger RNA was isolated from the aneurysms at 4 weeks following treatment. RNA samples were processed by using RNA-sequencing technology and were analyzed by using the Ingenuity Pathway Analysis tool.

RESULTS

With RNA sequencing for coiled versus untreated aneurysms, 464/9990 genes (4.6%) were differentially expressed (58 down-regulated, 406 up-regulated). When we compared flow-diverter versus untreated aneurysms, 177/10,041 (1.8%) genes were differentially expressed (8 down-regulated, 169 up-regulated). When we compared flow-diverter versus coiled aneurysms, 13/9982 (0.13%) genes were differentially expressed (8 down-regulated, 5 up-regulated). Keratin 8 was overexpressed in flow diverters versus coils. This molecule may potentially play a critical role in delayed ruptures due to plasmin production. We identified overregulation of apelin in flow diverters, supporting the preponderance of endothelialization, whereas we found overexpression of molecules implicated in wound healing (dectin 1 and hedgehog interacting protein) for coiled aneurysms. Furthermore, we identified metallopeptidases 1, 12, and 13 as overexpressed in coiled versus untreated aneurysms.

CONCLUSIONS

We observed different physiopathologic responses after endovascular treatment with various devices. Flow diverters promote endothelialization but express molecules that could potentially explain the rare delayed ruptures. Coils promote wound healing and express genes potentially implicated in the recurrence of coiled aneurysms.

Increased MCP-1 gene expression in monocytes of severe OSA patients and under intermittent hypoxia

PURPOSE

Obstructive sleep apnea (OSA) is known to be a risk factor of coronary artery disease. Monocyte chemoattractant protein-1 (MCP-1), as a critical factor for monocyte infiltration, is known to play a role in the development of atherosclerosis. This study aimed to investigate the effect of intermittent hypoxia, the hallmark of OSA, on the MCP-1 expression of monocytes.

METHODS

Peripheral blood was sampled from 61 adults enrolled for suspected OSA. RNA was prepared from the isolated monocytes for the analysis of MCP-1. The effect of in vitro intermittent hypoxia on the regulation and function of MCP-1 was investigated on THP-1 monocytic cells and human monocytes. The mRNA and secreted protein levels were investigated by RT/real-time PCR and enzyme-linked immunosorbent assay, respectively.

RESULTS

Monocytic MCP-1 gene expression was found to be increased significantly in severe OSA patients. In vitro intermittent hypoxia was demonstrated to increase the mRNA and protein expression levels of MCP-1 dose- and time-dependently in THP-1 monocytic cells. The MCP-1 mRNA expression in monocytes isolated from OSA patient was induced to a much higher level compared to that from normal control. Pre-treatment with inhibitor for p42/44 MAPK or p38 MAPK suppressed the activation of MCP-1 expression by intermittent hypoxia.

CONCLUSIONS

This is the first study to demonstrate the increase of MCP-1 gene expression in monocytes of severe OSA patients. In addition, monocytic MCP-1 gene expression can be induced under intermittent hypoxia.

Prerequisites for Functional Interleukin 31 Signaling and Its Feedback Regulation by Suppressor of Cytokine Signaling 3 (SOCS3)

Interleukin-31 (IL-31) is a T helper type 2 cell-derived cytokine tightly associated with inflammatory skin disorders. IL-31-induced signaling is mediated by a receptor complex composed of oncostatin M receptor β and the cytokine-specific receptor subunit IL-31Rα, of which there are several isoforms. The latter can be classified as long or short isoforms with respect to their intracellular domain. At present, the signaling capabilities of the different isoforms remain inchoately understood, and potential mechanisms involved in negative regulation of IL-31Rα signaling have so far not been studied in detail. Here, we show that both the long and short isoforms of IL-31Rα are capable of inducing STAT signaling. However, the presence of a functional JAK-binding box within IL-31Rα is an essential prerequisite for functional IL-31-mediated STAT3 signaling. Moreover, both the long and short isoforms require oncostatin M receptor β for their activity. We also show that IL-31 induces expression of four suppressor of cytokine signaling family members and provide evidence that SOCS3 acts as a potent feedback inhibitor of IL-31-induced signaling. Taken together, this study identifies crucial requirements for IL-31 signaling and shows its counter-regulation by SOCS3.

Role of tubulointerstitial plasmin in the progression of IgA nephropathy

BACKGROUND

Plasmin has recently been reported to be associated with renal fibrosis in experimental models, but its role in human renal diseases is unclear.

METHODS

Fifty-seven patients with IgA nephropathy (IgAN) were evaluated retrospectively. Plasmin in their renal biopsy tissues was assessed by in situ zymography using a plasmin-sensitive synthetic peptide, and the relationships between patients' histologic or clinical parameters and their renal plasmin activity [assessed semiquantitatively by calculating the positively stained percentage of the total tubulointerstitial (TI) area] were evaluated.

RESULTS

Plasmin activity was observed almost exclusively in the TI space (mainly in the interstitium and partly in the tubular epithelial cells) and was significantly stronger in patients with TI lesion (tubular atrophy/interstitial fibrosis and tubulointerstitial inflammation) than in those without TI lesion. It was significantly and positively correlated with the global glomerulosclerosis rate and significantly and negatively correlated with estimated glomerular filtration rate not only at the time of renal biopsy but also at the end of the follow-up period. Double stainings for plasmin activity and inflammatory cells, cytokeratin, or α-smooth muscle actin (α-SMA) in selected patients revealed TI infiltration of inflammatory cells, attenuated tubular epithelial expression of cytokeratin, and augmented interstitial expression of α-SMA close to upregulated plasmin activity in the TI space.

CONCLUSIONS

These data suggest that TI plasmin is associated with TI inflammation leading to renal fibrosis, and can cause the decline in renal function seen in patients with IgAN. Reducing plasmin in situ may therefore be a promising therapeutic approach slowing renal fibrogenesis and improving renal function.

Exploitation of plasmin(ogen) by bacterial pathogens of veterinary significance

The plasminogen (Plg) system plays an important homeostatic role in the degradation of fibrin clots, extracellular matrices and tissue barriers important for cellular migration, as well as the promotion of neurotransmitter release. Plg circulates in plasma at physiologically high concentrations (150-200μg ml(-1)) as an inactive proenzyme. Proteins enriched in lysine and other positively charged residues (histidine and arginine) as well as glycosaminoglycans and gangliosides bind Plg. The binding interaction initiates a structural adjustment to the bound Plg that facilitates cleavage by proteases (plasminogen activators tPA and uPA) that activate Plg to the active serine protease plasmin. Both pathogenic and commensal bacteria capture Plg onto their cell surface and promote its conversion to plasmin. Many microbial Plg-binding proteins have been described underpinning the importance this process plays in how bacteria interact with their hosts. Bacteria exploit the proteolytic capabilities of plasmin by (i) targeting the mammalian fibrinolytic system and degrading fibrin clots, (ii) remodeling the extracellular matrix and generating bioactive cleavage fragments of the ECM that influence signaling pathways, (iii) activating matrix metalloproteinases that assist in the destruction of tissue barriers and promote microbial metastasis and (iv) destroying immune effector molecules. There has been little focus on the exploitation of the fibrinolytic system by veterinary pathogens. Here we describe several pathogens of veterinary significance that possess adhesins that bind plasmin(ogen) onto their cell surface and promote its activation to plasmin. Cumulative data suggests that these attributes provide pathogenic and commensal bacteria with a means to colonize and persist within the host environment.

From plasminogen to plasmin: role of plasminogen receptors in human cancer

Cell surface-associated proteolysis mediated by plasmin (PLA) is an essential feature of wound healing, angiogenesis and cell invasion, processes that are dysregulated in cancer development, progression and systemic spread. The generation of PLA, initiated by the binding of its precursor plasminogen (PLG) to the cell surface, is regulated by an array of activators, inhibitors and receptors. In this review, we will highlight the importance of the best-characterized components of the PLG/PLA cascade in the pathogenesis of cancer focusing on the role of the cell surface-PLG receptors (PLG-R). PLG-R overexpression has been associated with poor prognosis of cancer patients and resistance to chemotherapy. We will also discuss recent findings on the molecular mechanisms regulating cell surface expression and distribution of PLG-R.

Plasmin induces in vivo monocyte recruitment through protease-activated receptor-1-, MEK/ERK-, and CCR2-mediated signaling

The plasminogen (Plg)/plasmin (Pla) system is associated with a variety of biological activities beyond the classical dissolution of fibrin clots, including cell migration, tissue repair, and inflammation. Although the capacity of Plg/Pla to induce cell migration is well defined, the mechanism underlying this process in vivo is elusive. In this study, we show that Pla induces in vitro migration of murine fibroblasts and macrophages (RAW 264.7) dependent on the MEK/ERK pathway and by requiring its proteolytic activity and lysine binding sites. Plasmin injection into the pleural cavity of BALB/c mice induced a time-dependent influx of mononuclear cells that was associated with augmented ERK1/2 and IκB-α phosphorylation and increased levels of CCL2 and IL-6 in pleural exudates. The inhibition of protease activity by using a serine protease inhibitor leupeptin or two structurally different protease-activated receptor-1 antagonists (SCH79797 and RWJ56110) abolished Pla-induced mononuclear recruitment and ERK1/2 and IκB-α phosphorylation. Interestingly, inhibition of the MEK/ERK pathway abolished Pla-induced CCL2 upregulation and mononuclear cell influx. In agreement with a requirement for the CCL2/CCR2 axis to Pla-induced cell migration, the use of a CCR2 antagonist (RS504393) prevented the Plg/Pla-induced recruitment of mononuclear cells to the pleural cavity and migration of macrophages at transwell plates. Therefore, Pla-induced mononuclear cell recruitment in vivo was dependent on protease-activated receptor-1 activation of the MEK/ERK/NF-κB pathway, which led to the release of CCL2 and activation of CCR2.

The interaction of enolase-1 with caveolae-associated proteins regulates its subcellular localization

Cell-surface-associated proteolysis plays a crucial role in embryonic development, monocyte/macrophage recruitment and tumour cell invasion. The glycolytic enzyme ENO-1 (enolase-1) is translocated from the cytoplasm to the cell surface, where it binds PLG (plasminogen) to enhance pericellular plasmin production and cell motility. In the present study, ENO-1 was found to localize to a specialized subset of lipid rafts called caveolae as demonstrated by fluorescence confocal microscopy and sucrose gradient ultracentrifugation. Co-immunoprecipitation studies revealed that ENO-1 interacts with Cav-1 (caveolin-1), but not with Cav-2, via the CSD (Cav-scaffolding domain). Moreover, an evolutionarily conserved CBM (Cav-binding motif) F296DQDDWGAW304 was identified within ENO-1. The point mutation W301A within the ENO-1 CBM was, however, not sufficient to disrupt ENO-1-Cav-1 interaction, whereas the mutations F296A and W304A markedly affected ENO-1 protein expression. Furthermore, ENO-1 was found associated with Annx2 (annexin 2), representing another caveolar protein, and this interaction was dependent on Cav-1 expression. Knockdown of Cav-1 and Annx2 markedly decreased cell surface expression of ENO-1. ENO-1 overexpression increased cell migration and invasion in a Cav-1-dependent manner. Thus the differential association of ENO-1 with caveolar proteins regulates ENO-1 subcellular localization and, consequently, ENO-1-dependent cell migration and invasion.