Plasmin-induced expression of cytokines and tissue factor in human monocytes involves AP-1 and IKKbeta-mediated NF-kappaB activation

Conserved Amblyomma americanum tick Serpin19, an inhibitor of blood clotting factors Xa and XIa, trypsin and plasmin, has anti-haemostatic functions

Tick saliva serine protease inhibitors (serpins) facilitate tick blood meal feeding through inhibition of protease mediators of host defense pathways. We previously identified a highly conserved Amblyomma americanum serpin 19 that is characterised by its reactive center loop being 100% conserved in ixodid ticks. In this study, biochemical characterisation reveals that the ubiquitously transcribed A. americanum serpin 19 is an anti-coagulant protein, inhibiting the activity of five of the eight serine protease blood clotting factors. Pichia pastoris-expressed recombinant (r) A. americanum serpin 19 inhibits the enzyme activity of trypsin, plasmin and blood clotting factors (f) Xa and XIa, with stoichiometry of inhibition estimated at 5.1, 9.4, 23.8 and 28, respectively. Similar to typical inhibitory serpins, recombinant A. americanum serpin 19 forms irreversible complexes with trypsin, fXa and fXIa. At a higher molar excess of recombinant A. americanum serpin 19, fXIIa is inhibited by 82.5%, and thrombin (fIIa), fIXa, chymotrypsin and tryptase are inhibited moderately by 14-29%. In anti-hemostatic functional assays, recombinant A. americanum serpin 19 inhibits thrombin but not ADP and cathepsin G activated platelet aggregation, delays clotting in recalcification and thrombin time assays by up to 250s, and up to 40s in the activated partial thromboplastin time assay. Given A. americanum serpin 19 high cross-tick species conservation, and specific reactivity of recombinant A. americanum serpin 19 with antibodies to A. americanum tick saliva proteins, we conclude that recombinant A. americanum serpin 19 is a potential candidate for development of a universal tick vaccine.

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.

Evaluation of recombinant Mycoplasma hyopneumoniae P97/P102 paralogs formulated with selected adjuvants as vaccines against mycoplasmal pneumonia in pigs

Pig responses to recombinant subunit vaccines containing fragments of eight multifunctional adhesins of the Mycoplasma hyopneumoniae (Mhp) P97/P102 paralog family formulated with Alhydrogel(®) or Montanide™ Gel01 were compared with a commercial bacterin following experimental challenge. Pigs, vaccinated intramuscularly at 9, 12 and 15 weeks of age with either of the recombinant formulations (n=10 per group) or Suvaxyn(®) M. hyo (n=12), were challenged with Mhp strain Hillcrest at 17 weeks of age. Unvaccinated, challenged pigs (n=12) served as a control group. Coughing was assessed daily. Antigen-specific antibody responses were monitored by ELISA in serum and tracheobronchial lavage fluid (TBLF), while TBLF was also assayed for cytokine responses (ELISA) and bacterial load (qPCR). At slaughter, gross and histopathology of lungs were quantified and damage to epithelial cilia in the porcine trachea was evaluated by scanning electron microscopy. Suvaxyn(®) M. hyo administration induced significant serological responses against Mhp strain 232 whole cell lysates (wcl) and recombinant antigen F3P216, but not against the remaining vaccine subunit antigens. Alhydrogel(®) and Montanide™ Gel01-adjuvanted antigen induced significant antigen-specific IgG responses, with the latter adjuvant eliciting comparable Mhp strain 232 wcl specific IgG responses to Suvaxyn(®) M. hyo. No significant post-vaccination antigen-specific mucosal responses were detected with the recombinant vaccinates. Suvaxyn(®) M. hyo was superior in reducing clinical signs, lung lesion severity and bacterial load but the recombinant formulations offered comparable protection against cilial damage. Lower IL-1β, TNF-α and IL-6 responses after challenge were associated with reduced lung lesion severity in Suvaxyn(®) M. hyo vaccinates, while elevated pathology scores in recombinant vaccinates corresponded to cytokine levels that were similarly elevated as in unvaccinated pigs. This study highlights the need for continued research into protective antigens and vaccination strategies that will prevent Mhp colonisation and establishment of infection.

Inhibition of plasmin attenuates murine acute graft-versus-host disease mortality by suppressing the matrix metalloproteinase-9-dependent inflammatory cytokine storm and effector cell trafficking

The systemic inflammatory response observed during acute graft-versus-host disease (aGVHD) is driven by proinflammatory cytokines, a 'cytokine storm'. The function of plasmin in regulating the inflammatory response is not fully understood, and its role in the development of aGVHD remains unresolved. Here we show that plasmin is activated during the early phase of aGVHD in mice, and its activation correlated with aGVHD severity in humans. Pharmacological plasmin inhibition protected against aGVHD-associated lethality in mice. Mechanistically, plasmin inhibition impaired the infiltration of inflammatory cells, the release of membrane-associated proinflammatory cytokines including tumor necrosis factor-α (TNF-α) and Fas-ligand directly, or indirectly via matrix metalloproteinases (MMPs) and alters monocyte chemoattractant protein-1 (MCP-1) signaling. We propose that plasmin and potentially MMP-9 inhibition offers a novel therapeutic strategy to control the deadly cytokine storm in patients with aGVHD, thereby preventing tissue destruction.

Plasmin deficiency leads to fibrin accumulation and a compromised inflammatory response in the mouse brain

BACKGROUND

Excess fibrin in blood vessels is cleared by plasmin, the key proteolytic enzyme in fibrinolysis. Neurological disorders and head trauma can result in the disruption of the neurovasculature and the entry of fibrin and other blood components into the brain, which may contribute to further neurological dysfunction.

OBJECTIVES

While chronic fibrin deposition is often implicated in neurological disorders, the pathological contributions attributable specifically to fibrin have been difficult to ascertain. An animal model that spontaneously acquires fibrin deposits could allow researchers to better understand the impact of fibrin in neurological disorders.

METHODS

Brains of plasminogen (plg)- and tissue plasminogen activator (tPA)-deficient mice were examined and characterized with regard to fibrin accumulation, vascular and neuronal health, and inflammation. Furthermore, the inflammatory response following intrahippocampal lipopolysaccharide (LPS) injection was compared between plg(-/-) and wild type (WT) mice.

RESULTS AND CONCLUSIONS

Both plg(-/-) and tPA(-/-) mice exhibited brain parenchymal fibrin deposits that appear to result from reduced neurovascular integrity. Markers of neuronal health and inflammation were not significantly affected by proximity to the vascular lesions. A compromised neuroinflammatory response was also observed in plg(-/-) compared to WT mice following intrahippocampal LPS injection. These results demonstrate that fibrin does not affect neuronal health in the absence of inflammation and suggest that plasmin may be necessary for a normal neuroinflammatory response in the mouse CNS.

Evaluation of gingival crevicular fluid levels of tissue plasminogen activator, plasminogen activator inhibitor 2, matrix metalloproteinase-3 and interleukin 1-β in patients with different periodontal diseases

OBJECTIVES

The purpose of this study was to evaluate the gingival crevicular fluid levels of interleukin-1beta (IL-1β), matrix metalloproteinases-3 (MMP-3), tissue type plasminogen activator (t-PA) and plasminogen activator inhibitor 2 (PAI-2) in patients with chronic periodontitis, aggressive periodontitis (AgP) and healthy individuals (controls).

MATERIAL AND METHODS

Systemically healthy (21 chronic periodontitis, 23 AgP and 20 controls) subjects were included in this study. Plaque index, gingival index, probing pocket depth and clinical attachment level were recorded and gingival crevicular fluid samples were collected. Assays for IL-1β, MMP-3, t-PA and PAI-2 levels in gingival crevicular fluid were carried out by an enzyme-linked immunosorbent assay. The one-sample Kolmogorov-Smirnov test, Mann-Whitney U test and Spearman correlation coefficient were used for data analyses.

RESULTS

Gingival crevicular fluid levels of t-PA and IL-1β were significantly higher in chronic periodontitis and AgP groups than in the control group (p < 0.001). MMP-3 levels in gingival crevicular fluid were detected as significantly higher in the chronic periodontitis and AgP groups compared with the control group (p < 0.05). The t-PA/PAI-2 rate of patients with chronic periodontitis and AgP were significantly higher than the control group (p < 0.05). The positive correlations were found among the PAI-2, t-PA, IL-1β and MMP-3 levels in gingival crevicular fluid. The volume of the gingival crevicular fluid correlated with all of the clinical parameters (p < 0.001). There were positive correlations between the gingival crevicular fluid levels of PAI-2 and the probing pocket depth and between gingival crevicular fluid levels of PAI-2 and the clinical attachment level (p < 0.01). Similarly, significant correlations were found between t-PA levels and probing pocket depth and between t-PA levels and clinical attachment level measurements (p < 0.001).

CONCLUSION

The present data showed that gingival crevicular fluid levels of IL-1 β, MMP-3 and t-PA increased in periodontal disease regardless of the periodontitis type and played a part in tissue destruction.

New insights into the role of Plg-RKT in macrophage recruitment

Plasminogen (PLG) is the zymogen of plasmin, the major enzyme that degrades fibrin clots. In addition to its binding and activation on fibrin clots, PLG also specifically interacts with cell surfaces where it is more efficiently activated by PLG activators, compared with the reaction in solution. This results in association of the broad-spectrum proteolytic activity of plasmin with cell surfaces that functions to promote cell migration. Here, we review emerging data establishing a role for PLG, plasminogen receptors and the newly discovered plasminogen receptor, Plg-RKT, in macrophage recruitment in the inflammatory response, and we address mechanisms by which the interplay between PLG and its receptors regulates inflammation.

Amino-functionalized nanoparticles as inhibitors of mTOR and inducers of cell cycle arrest in leukemia cells

Activation of the mammalian target of rapamycin (mTOR) has been implicated in anticancer drug resistance, type 2 diabetes, and aging. Here, we show that surface functionalization of polystyrene nanoparticles with amino groups (PS-NH2), but not with carboxyl groups (PS-COOH), induces G2 cell-cycle arrest and inhibition of proliferation in three leukemia cell lines. Besides, PS-NH2 inhibit angiogenesis and proliferation of leukemia cells xenografted onto the chick chorioallantoic membrane. At the molecular level, PS-NH2 inhibit, whereas PS-COOH activate mTOR signaling in leukemia cells. Consistently, PS-NH2 block activation of the mTOR downstream targets, Akt and p70 ribosomal S6 kinase 1, and induce overexpression of the cell-cycle regulator p21(Cip1/Waf1) and degradation of cyclin B1. After addition, both types of particles rapidly induce autophagy in leukemia cells. Yet, only in PS-NH2-treated cells, acidic vesicular organelles show elevated pH and impaired processing of procathepsin B. Moreover, solely in PS-NH2-treated cells, autophagy is followed by permeabilization of acidic vesicular organelles and induction of apoptosis. By contrast, primary macrophages, which do not exhibit activated mTOR signaling, proved relatively resistant to PS-NH2-induced toxicity. These data indicate that functionalized nanoparticles can be used to control activation of mTOR signaling pathways, and to influence proliferation and viability of malignant cells.

Ursolic acid inhibits tumor angiogenesis and induces apoptosis through mitochondrial-dependent pathway in Ehrlich ascites carcinoma tumor

Ursolic acid (UA) is a pentacyclic triterpene naturally occurring in many plant foods. In the present study, we investigated anti-cancer activity of UA in vivo in Ehrlich ascites carcinoma (EAC) tumor. 15 × 10(6) EAC cells were implanted intraperitoneally (i.p., ascitic tumor) and subcutaneous (s.c., solid tumor) in Swiss albino mice. Mice with established tumors received UA i.p. at 25, 50 and 100mg/kg bw for 14 d in ascitic and 100mg/kg bw in solid tumor for 30 d. On day 15, blood samples were collected for hematological assessment of hemoglobin (Hb%), RBCs, WBCs and PCV. Tumor volume, cell viability, angiogenic, anti-angiogenic, anti-inflammatory factors and antioxidant parameters were determined. Immunohistochemistry analysis for VEGF, iNOS, CD31, caspase-3 and Bax were also performed. UA significantly inhibited tumor growth, cell viability, in both ascites and solid tumor model in vivo (p<0.001). The anti-angiogenic effects were accompanied with decreased VEGF, iNOS, TNF-α and increased IL-12 levels. UA at 100mg/kg bw dose significantly increased SOD and CAT activity (p<0.01). GSH and TBARS were increased as compared to control group (p<0.001). Furthermore, UA increased total RBCs, WBCs as well as Hb% significantly (p<0.05) compared to cyclophosphamide (CP). Histopathological examination of tumor cells in the treated group demonstrated signs of apoptosis with chromatin condensation and cell shrinkage. Decreased peritoneal angiogenesis showed the anti-angiogenic potential. UA downregulated VEGF & iNOS expression whereas bax and caspase-3 expressions were upregulated suggesting drug induced tumor cell apoptosis through activating the pro-apoptotic bcl-2 family and caspase-3 and downregulation of VEGF. The present study sheds light on the potent antitumor property of the UA and can be extended further to develop therapeutic protocols for treatment of cancer.

Binding of pro-migratory serum factors to electrospun PLLA nano-fibers

Architecture of the poly(l-lactic acid) (PLLA) scaffolds is known to affect protein affinity and binding strength. Here, we demonstrate that nanofibrous electrospun PLLA scaffolds reversibly absorb the pro-migratory serum factors that stimulate migration of vascular smooth muscle via an NFkB-dependent mechanism. Further, we demonstrate that mesenchymal stem cells seeded on the PLLA scaffolds do not enhance muscle migration but may maintain the ability of induced cells to migrate in an NFkB-independent manner. These findings further support the promising application of PLLA scaffolds for therapeutic angiogenesis and vascular graft engineering.

Transforming growth factor-Beta and urokinase-type plasminogen activator: dangerous partners in tumorigenesis-implications in skin cancer

Transforming growth factor-beta (TGF-β) is a pleiotropic factor, with several different roles in health and disease. TGF-β has been postulated as a dual factor in tumor progression, since it represses epithelial tumor development in early stages, whereas it stimulates tumor progression in advanced stages. During tumorigenesis, cancer cells acquire the capacity to migrate and invade surrounding tissues and to metastasize different organs. The urokinase-type plasminogen activator (uPA) system, comprising uPA, the uPA cell surface receptor, and plasminogen-plasmin, is involved in the proteolytic degradation of the extracellular matrix and regulates key cellular events by activating intracellular signal pathways, which together allow cancer cells to survive, thus, enhancing cell malignance during tumor progression. Due to their importance, uPA and its receptor are tightly transcriptionally regulated in normal development, but are deregulated in cancer, when their activity and expression are related to further development of cancer. TGF-β regulates uPA expression in cancer cells, while uPA, by plasminogen activation, may activate the secreted latent TGF-β, thus, producing a pernicious cycle which contributes to the enhancement of tumor progression. Here we review the specific roles and the interplay between TGF-β and uPA system in cancer cells and their implication in skin cancer.

Plasmin activity in the porcine airways is enhanced during experimental infection with Mycoplasma hyopneumoniae, is positively correlated with proinflammatory cytokine levels and is ameliorated by vaccination

In Mycoplasma hyopneumoniae (Mhp) infection of swine, the host immune response is considered a major driver of lung pathology; however the underlying inflammatory mechanisms are not well understood. The serine protease plasmin is being increasingly recognised as a significant player in inflammatory processes. Here we compare plasmin activity in tracheobronchial lavage fluid (TBLF) from pigs experimentally challenged with Mhp that were either unvaccinated (n=10), or vaccinated with the commercial vaccine Suvaxyn(®) M.hyo (n=10). TBLF collected immediately prior to challenge and at 21 d and 35 d post-challenge was also assayed for levels of proinflammatory cytokines (TNF-α, IL-1β and IL-6), and for bacterial load (by qPCR). Clinical signs, pathology, cytokine analyses and qPCR all indicated that vaccinated pigs had significantly reduced disease relative to unvaccinated animals. Plasmin activity increased significantly in TBLF collected at 21 d post-challenge compared to pre-challenge TBLF in unvaccinated (P<0.01), but not vaccinated animals (P>0.05). A significant correlation was observed between bacterial load and plasmin activity in the 21 d (r=0.66; P<0.01) and the 35 d post-challenge samples, (r=0.62; P<0.01). Plasmin activity was also significantly correlated with levels of TNF-α, IL-1β and IL-6 at 21 d (r=0.78, P<0.0001; r=0.77, P<0.0001; r=0.64, P<0.005) and with TNF-α and IL-1β at 35 d post-challenge (r=0.77, P<0.0001; r=0.74, P<0.0005). Our results indicate that plasminogen is activated to plasmin in the respiratory tract of pigs as part of the host inflammatory response to Mhp infection and that this effect is ameliorated by vaccination.

Plasmin induces intercellular adhesion molecule 1 expression in human endothelial cells via nuclear factor-κB/mitogen-activated protein kinases-dependent pathways

Activation of endothelial cells (ECs) by proinflammatory stimuli triggers expression of cellular adhesion molecules including intercellular adhesion molecule 1 (ICAM-1) on the cell surface. Such molecules mediate the transendothelial migration of inflammatory cells, which is an early key step of atherogenesis. We have previously demonstrated that plasmin activates human inflammatory cells via the annexin A2 heterotetramer (A2t). Here we show that human umbilical vein endothelial cells (HUVECs) and human microvascular endothelial cells express high amounts of A2t, as shown by Western blotting, fluorescence microscopy and flow cytometry. Activation of HUVEC by plasmin led to cleavage of the annexin A2 subunit of the receptor complex, followed by the activation of Akt/nuclear factor (NF)-kB signaling, and phosphorylation of MAP kinases p38 and ERK1/2. Further, plasmin stimulates the NF-kB/p38-dependent expression of ICAM-1 by HUVEC. The plasmin-induced activation of cells was abolished when annexin A2 was down-regulated by small-interfering RNA. In vivo, we show co-localization of the ECs marker CD31 with the plasmin receptor A2t and ICAM-1 in human atherosclerotic plaques of human femoral arteries, which also exhibit activated NF-κB signaling as revealed by immunofluorescence staining for phosphorylated Iκbα. In addition, plasma of patients with advanced atherosclerosis exhibited enhanced plasmin activity and up-regulated levels of plasmin-α2-antiplasmin. These data point to a previously unrecognized functional role of plasmin in EC biology, which could be of particular relevance in the development of atherosclerosis.

Requirement of plasminogen binding to its cell-surface receptor α-enolase for efficient regeneration of normal and dystrophic skeletal muscle

Adult regenerative myogenesis is central for restoring normal tissue structure and function after muscle damage. In muscle repair after injury, as in severe myopathies, damaged and necrotic fibers are removed by infiltrating inflammatory cells and then replaced by muscle stem cells or satellite cells, which will fuse to form new myofibers. Extracellular proteolysis mediated by uPA-generated plasmin plays a critical role in controlling inflammation and satellite-cell-dependent myogenesis. α-enolase has been described as plasminogen receptor in several cell types, where it acts concentrating plasmin proteolytic activity on the cell surface. In this study, we investigated whether α-enolase plasminogen receptor plays a regulatory role during the muscular repair process. Inhibitors of α-enolase/plasminogen binding: MAb11G1 (a monoclonal antibody against α-enolase) and ε-aminocaproic acid, EACA (a lysine analogue) inhibited the myogenic abilities of satellite cells-derived myoblasts. Furthermore, knockdown of α-enolase decreased myogenic fusion of myoblasts. Injured wild-type mice and dystrophic mdx mice were also treated with MAb11G1 and EACA. These treatments had negative impacts on muscle repair impairing satellite cell functions in vitro in agreement with blunted growth of new myofibers in vivo. Furthermore, both MAb11G1 and EACA treatments impaired adequate inflammatory cell infiltration and promoted extracellular matrix deposition in vivo, which resulted in persistent degeneration. These results demonstrate the novel requirement of α-enolase for restoring homeostasis of injured muscle tissue, by controlling the pericellular localization of plasmin activity.

α-Enolase, a multifunctional protein: its role on pathophysiological situations

α-Enolase is a key glycolytic enzyme in the cytoplasm of prokaryotic and eukaryotic cells and is considered a multifunctional protein. α-enolase is expressed on the surface of several cell types, where it acts as a plasminogen receptor, concentrating proteolytic plasmin activity on the cell surface. In addition to glycolytic enzyme and plasminogen receptor functions, α-Enolase appears to have other cellular functions and subcellular localizations that are distinct from its well-established function in glycolysis. Furthermore, differential expression of α-enolase has been related to several pathologies, such as cancer, Alzheimer's disease, and rheumatoid arthritis, among others. We have identified α-enolase as a plasminogen receptor in several cell types. In particular, we have analyzed its role in myogenesis, as an example of extracellular remodelling process. We have shown that α-enolase is expressed on the cell surface of differentiating myocytes, and that inhibitors of α-enolase/plasminogen binding block myogenic fusion in vitro and skeletal muscle regeneration in mice. α-Enolase could be considered as a marker of pathological stress in a high number of diseases, performing several of its multiple functions, mainly as plasminogen receptor. This paper is focused on the multiple roles of the α-enolase/plasminogen axis, related to several pathologies.

The serine protease plasmin triggers expression of the CC-chemokine ligand 20 in dendritic cells via Akt/NF-κB-dependent pathways

The number of dendritic cells is increased in advanced atherosclerotic lesions. In addition, plasmin, which might stimulate dendritic cells, is generated in atherosclerotic lesions. Here, we investigated cytokine and chemokine induction by plasmin in human dendritic cells. In human atherosclerotic vessel sections, plasmin colocalized with dendritic cells and the CC-chemokine ligand 20 (CCL20, MIP-3α), which is important for homing of lymphocytes and dendritic cells to sites of inflammation. Stimulation of human dendritic cells with plasmin, but not with catalytically inactivated plasmin, induced transcriptional regulation of CCL20. By contrast, proinflammatory cytokines such as TNF-α, IL-1α, and IL-1β were not induced. The plasmin-mediated CCL20 expression was preceded by activation of Akt and MAP kinases followed by activation of the transcription factor NF-κB as shown by phosphorylation of its inhibitor IκBα, by nuclear localization of p65, its phosphorylation, and binding to NF-κB consensus sequences. The plasmin-induced CCL20 expression was dependent on Akt- and ERK1/2-mediated phosphorylation of IκBα on Ser32/36 and of p65 on Ser276, whereas p38 MAPK appeared to be dispensable. Thus, plasmin triggers release of the chemokine CCL20 from dendritic cells, which might facilitate accumulation of CCR6⁺ immune cells in areas of plasmin generation such as inflamed tissues including atherosclerotic lesions.

Amino-functionalized polystyrene nanoparticles activate the NLRP3 inflammasome in human macrophages

Specifically designed and functionalized nanoparticles hold great promise for biomedical applications. Yet, the applicability of nanoparticles is critically predetermined by their surface functionalization. Here we demonstrate that amino-functionalized polystyrene nanoparticles (PS-NH(2)) of ∼100 nm in diameter, but not carboxyl- or nonfunctionalized particles, trigger NLRP3 inflammasome activation and subsequent release of proinflammatory interleukin 1β (IL-1β) by human macrophages. PS-NH(2) induced time-dependent proton accumulation in lysosomes associated with lysosomal destabilization, release of cathepsin B, and damage of the mitochondrial membrane. Accumulation of mitochondrial reactive oxygen species was accompanied by oxidation of thioredoxin, a protein playing a central role in maintaining the cellular redox balance. Upon oxidation, thioredoxin dissociated from the thioredoxin-interacting protein (TXNIP). Liberated TXNIP, in turn, interacted with the NLRP3 protein, resulting in a conformational change of the pyrin domain of the NLRP3 protein, as was predicted by molecular modeling. Consequently, this prompted assembly of the NLRP3 inflammasome complex with recruitment and activation of caspase-1, inducing IL-1β release by cleavage of pro-IL-1β. The central role of the NLRP3 inflammasome for cytokine production was confirmed by in vitro knockdown of NLRP3 and of the adaptor protein ASC, confirming that other inflammasomes were not activated by PS-NH(2). The PS-NH(2)-mediated proinflammatory macrophage activation could be antagonized by the radical scavenger N-acetyl-L-cysteine, which prevented mitochondrial damage, caspase-1 activation, and the subsequent release of IL-1β. Our study reveals the molecular mechanism of NLRP3 inflammasome activation by amino-functionalized nanoparticles and suggests a strategy as to how such adverse effects could be antagonized.

Yeast two-hybrid screening of proteins interacting with plasmin receptor subunit: C-terminal fragment of annexin A2

AIM

To identify proteins that interact with the C-terminal fragment of annexin A2 (A2IC), generated by plasmin cleavage of the plasmin receptor, a heterotetramer (AA2t) containing annexin A2.

METHODS

The gene that encodes the A2IC fragment was obtained from PCR-amplified cDNA isolated from human monocytes, and was ligated into the pBTM116 vector using a DNA ligation kit. The resultant plasmid (pBTM116-A2IC) was sequenced with an ABI PRISM 310 Genetic Analyzer. The expression of an A2IC bait protein fused with a LexA-DNA binding domain (BD) was determined using Western blot analysis. The identification of proteins that interact with A2IC and are encoded in a human monocyte cDNA library was performed using yeast two-hybrid screening. The DNA sequences of the relevant cDNAs were determined using an ABI PRISM BigDye terminator cycle sequencing ready reaction kit. Nucleotide sequence databases were searched for homologous sequences using BLAST search analysis (http://www.ncbi.nlm.nih.gov). Confirmation of the interaction between the protein LexA-A2IC and each of cathepsin S and SNX17 was conducted using a small-scale yeast transformation and X-gal assay.

RESULTS

The yeast transformed with plasmids encoding the bait proteins were screened with a human monocyte cDNA library by reconstituting full-length transcription factors containing the GAL4-active domain (GAL4-AD) as the prey in a yeast two-hybrid approach. After screening 1×10(7) clones, 23 independent β-Gal-positive clones were identified. Sequence analysis and a database search revealed that 15 of these positive clones matched eight different proteins (SNX17, ProCathepsin S, RPS2, ZBTB4, OGDH, CCDC32, PAPD4, and actin which was already known to interact with annexin A2).

CONCLUSION

A2IC A2IC interacts with various proteins to form protein complexes, which may contribute to the molecular mechanism of monocyte activation induced by plasmin. The yeast two-hybrid system is an efficient approach for investigating protein interactions.

Safety and effectiveness of two treatment regimes with tranexamic acid to minimize inflammatory response in elective cardiopulmonary bypass patients: a randomized double-blind, dose-dependent, phase IV clinical trial

BACKGROUND

In cardiopulmonary bypass (CPB) patients, fibrinolysis may enhance postoperative inflammatory response. We aimed to determine whether an additional postoperative dose of antifibrinolytic tranexamic acid (TA) reduced CPB-mediated inflammatory response (IR).

METHODS

We performed a randomized, double-blind, dose-dependent, parallel-groups study of elective CPB patients receiving TA. Patients were randomly assigned to either the single-dose group (40 mg/Kg TA before CPB and placebo after CPB) or the double-dose group (40 mg/Kg TA before and after CPB).

RESULTS

160 patients were included, 80 in each group. The incident rate of IR was significantly lower in the double-dose-group TA2 (7.5% vs. 18.8% in the single-dose group TA1; P = 0.030). After adjusting for hypertension, total protamine dose and temperature after CPB, TA2 showed a lower risk of IR compared with TA1 [OR: 0.29 (95% CI: 0.10-0.83), (P = 0.013)]. Relative risk for IR was 2.5 for TA1 (95% CI: 1.02 to 6.12). The double-dose group had significantly lower chest tube bleeding at 24 hours [671 (95% CI 549-793 vs. 826 (95% CI 704-949) mL; P = 0.01 corrected-P significant] and lower D-dimer levels at 24 hours [489 (95% CI 437-540) vs. 621(95% CI: 563-679) ng/mL; P = 0.01 corrected-P significant]. TA2 required lower levels of norepinephrine at 24 h [0.06 (95% CI: 0.03-0.09) vs. 0.20(95 CI: 0.05-0.35) after adjusting for dobutamine [F = 6.6; P = 0.014 corrected-P significant]. We found a significant direct relationship between IL-6 and temperature (rho = 0.26; P < 0.01), D-dimer (rho = 0.24; P < 0.01), norepinephrine (rho = 0.33; P < 0.01), troponin I (rho = 0.37; P < 0.01), Creatine-Kinase (rho = 0.37; P < 0.01), Creatine Kinase-MB (rho = 0.33; P < 0.01) and lactic acid (rho = 0.46; P < 0.01) at ICU arrival. Two patients (1.3%) had seizure, 3 patients (1.9%) had stroke, 14 (8.8%) had acute kidney failure, 7 (4.4%) needed dialysis, 3 (1.9%) suffered myocardial infarction and 9 (5.6%) patients died. We found no significant differences between groups regarding these events.

CONCLUSIONS

Prolonged inhibition of fibrinolysis, using an additional postoperative dose of tranexamic acid reduces inflammatory response and postoperative bleeding (but not transfusion requirements) in CPB patients. A question which remains unanswered is whether the dose used was ideal in terms of safety, but not in terms of effectiveness.

Beneficial and detrimental effects of plasmin(ogen) during infection and sepsis in mice

Plasmin has been proposed to be an important mediator during inflammation/infection. In this study, by using mice lacking genes for plasminogen, tissue-type plasminogen activator (tPA), and urokinase-type PA (uPA), we have investigated the functional roles of active plasmin in infection and sepsis. Two models were used: an infection model by intravenous injection of 1×10⁷ CFU of S. aureus, and a sepsis model by intravenous injection of 1.6×10⁸ CFU of S. aureus. We found that in the infection model, wild-type (WT) mice showed significantly higher survival rates than plasminogen-deficient (plg^-/-) mice. However, in the sepsis model, plg^-/- or tPA^-/-/uPA^-/- mice showed the highest survival rate whereas WT and tPA^+/-/uPA^+/- mice showed the lowest survival rate, and plg^+/-, tPA^-/-, and uPA^-/- mice had an intermediate survival rate. These results indicate that the levels of active plasmin are critical in determining the survival rate in the sepsis, partly through high levels of inflammatory cytokines and enhanced STAT3 activation. We conclude that plasmin is beneficial in infection but promotes the production of inflammatory cytokines in sepsis that may cause tissue destruction, diminished neutrophil function, and an impaired capacity to kill bacteria which eventually causes death of these mice.

(8R)-3β,8-dihydroxypolypoda-13E,17E,21-triene induces cell cycle arrest and apoptosis in treatment-resistant prostate cancer cells

Mastic, a resinous exudate from Pistacia lentiscus, has been reported to exhibit selective cytotoxicity against different cancer cell lines. There are, however, no data published correlating distinct mastic-derived compounds with the postulated cytotoxic activity. A polypodane-type bicyclic triterpenoid, (8R)-3β,8-dihydroxypolypoda-13E,17E,21-triene (1), was isolated from P. lentiscus oleogum resin. In androgen-independent PC-3 prostate cancer cells, 1 potently inhibited the expression of cyclins D1 and E, but had no effect on the expression of the cyclin kinase inhibitor p21(Waf1/Cip1). Inhibition of the expression of cell cycle-regulating cyclins resulted in cell cycle arrest in the G₀/G₁ phase, reduction in the number of cells in the S phase, and the triggering of apoptosis, as detected by increased expression of phosphatidylserine on the cell surface and by formation of DNA laddering. In addition, 1 suppressed the formation of prostate cancer colonies in soft agar and inhibited proliferation, angiogenesis, and the growth of prostate tumors xenografted onto chick chorioallantoic membranes without overt systemic toxicity. Taken together, these data show that 1 triggers apoptosis in chemoresistant, androgen-independent human prostate cancer cells in vitro and in vivo. Thus, 1 may serve as a lead compound for targeting so far incurable androgen-insensitive prostate cancers.

Differential uptake of functionalized polystyrene nanoparticles by human macrophages and a monocytic cell line

Tumor cell lines are often used as models for the study of nanoparticle-cell interactions. Here we demonstrate that carboxy (PS-COOH) and amino functionalized (PS-NH2) polystyrene nanoparticles of ∼100 nm in diameter are internalized by human macrophages, by undifferentiated and by PMA-differentiated monocytic THP-1 cells via diverse mechanisms. The uptake mechanisms also differed for all cell types and particles when analyzed either in buffer or in medium containing human serum. Macrophages internalized ∼4 times more PS-COOH than THP-1 cells, when analyzed in serum-containing medium. By contrast, in either medium, THP-1 cells internalized PS-NH2 more rapidly than macrophages. Using pharmacological and antisense in vitro knockdown approaches, we showed that, in the presence of serum, the specific interaction between the CD64 receptor and the particles determines the macrophage uptake of particles by phagocytosis, whereas particle internalization in THP-1 cells occurred via dynamin II-dependent endocytosis. PMA-differentiated THP-1 cells differed in their uptake mechanism from macrophages and undifferentiated THP-1 cells by internalizing the particles via macropinocytosis. In line with our in vitro data, more intravenously applied PS-COOH particles accumulated in the liver, where macrophages of the reticuloendothelial system reside. By contrast, PS-NH2 particles were preferentially targeted to tumor xenografts grown on the chorioallantoic membrane of fertilized chicken eggs. Our data show that the amount of internalized nanoparticles, the uptake kinetics, and its mechanism may differ considerably between primary cells and a related tumor cell line, whether differentiated or not, and that particle uptake by these cells is critically dependent on particle opsonization by serum proteins.

Plasmin inhibitors prevent leukocyte accumulation and remodeling events in the postischemic microvasculature

Clinical trials revealed beneficial effects of the broad-spectrum serine protease inhibitor aprotinin on the prevention of ischemia-reperfusion (I/R) injury. The underlying mechanisms remained largely unclear. Using in vivo microscopy on the cremaster muscle of male C57BL/6 mice, aprotinin as well as inhibitors of the serine protease plasmin including tranexamic acid and ε-aminocaproic acid were found to significantly diminish I/R-elicited intravascular firm adherence and (subsequent) transmigration of neutrophils. Remodeling of collagen IV within the postischemic perivenular basement membrane was almost completely abrogated in animals treated with plasmin inhibitors or aprotinin. In separate experiments, incubation with plasmin did not directly activate neutrophils. Extravascular, but not intravascular administration of plasmin caused a dose-dependent increase in numbers of firmly adherent and transmigrated neutrophils. Blockade of mast cell activation as well as inhibition of leukotriene synthesis or antagonism of the platelet-activating-factor receptor significantly reduced plasmin-dependent neutrophil responses. In conclusion, our data suggest that extravasated plasmin(ogen) mediates neutrophil recruitment in vivo via activation of perivascular mast cells and secondary generation of lipid mediators. Aprotinin as well as the plasmin inhibitors tranexamic acid and ε-aminocaproic acid interfere with this inflammatory cascade and effectively prevent postischemic neutrophil responses as well as remodeling events within the vessel wall.

Feedback regulation of endothelial cell surface plasmin generation by PKC-dependent phosphorylation of annexin A2

In response to blood vessel injury, hemostasis is initiated by platelet activation, advanced by thrombin generation, and tempered by fibrinolysis. The primary fibrinolytic protease, plasmin, can be activated either on a fibrin-containing thrombus or on cells. Annexin A2 (A2) heterotetramer (A2·p11)(2) is a key profibrinolytic complex that assembles plasminogen and tissue plasminogen activator and promotes plasmin generation. We now report that, in endothelial cells, plasmin specifically induces activation of conventional PKC, which phosphorylates serine 11 and serine 25 of A2, triggering dissociation of the (A2·p11)(2) tetramer. The resulting free p11 undergoes ubiquitin-mediated proteasomal degradation, thus preventing further translocation of A2 to the cell surface. In vivo, pretreatment of A2(+/+) but not A2(-/-) mice with a conventional PKC inhibitor significantly reduced thrombosis in a carotid artery injury model. These results indicate that augmentation of fibrinolytic vascular surveillance by blockade of serine phosphorylation is A2-dependent. We also demonstrate that plasmin-induced phosphorylation of A2 requires both cleavage of A2 and activation of Toll-like receptor 4 on the cell surface. We propose that plasmin can limit its own generation by triggering a finely tuned "feedback" mechanism whereby A2 becomes serine-phosphorylated, dissociates from p11, and fails to translocate to the cell surface.

Lysosomal degradation of the carboxydextran shell of coated superparamagnetic iron oxide nanoparticles and the fate of professional phagocytes

Contrast agents based on dextran-coated superparamagnetic iron oxide nanoparticles (SPIO) are internalized by professional phagocytes such as hepatic Kupffer cells, yet their role in phagocyte biology remains largely unknown. Here we investigated the effects of the SPIO ferucarbotran on murine Kupffer cells and human macrophages. Intravenous injection of ferucarbotran into mice led to rapid accumulation of the particles in phagocytes and to long-lasting increased iron deposition in liver and kidneys. Macrophages incorporate ferucarbotran in lysosomal vesicles containing α-glucosidase, which is capable of degrading the carboxydextran shell of the ferucarbotran particles. Intravenous injection of ferucarbotran into mice followed by incorporation of the nanoparticles into Kupffer cells triggered apoptosis and the subsequent depletion of Kupffer cells. In macrophages, the proinflammatory cytokine TNF-α increased the apoptosis rate, the reactive oxygen species production and the activation of c-Jun N-terminal kinase elicited by ferucarbotran, which might be mediated by the induction of cytoplasmic phospholipase A2 by TNF-α. Notably, the nanoparticle-induced apoptosis of murine Kupffer cells could be prevented by treatment of the mice with the radical scavenger edaravone. Thus, nanosized carboxydextran-coated SPIO-based contrast agents are retained for extended time periods by liver macrophages, where they elicit delayed cell death, which can be antagonized by a therapeutic radical scavenger.

Plasmin Triggers Chemotaxis of Monocyte-Derived Dendritic Cells Through an Akt2-Dependent Pathway and Promotes a T-Helper Type-1 Response

Objective— Dendritic cells (DC) accumulate in atherosclerotic arteries where they can modulate atherogenesis. We investigated whether plasmin might alter the function of human DC.

Methods and Results— Stimulation of monocyte-derived DC with plasmin elicited a time-dependent actin polymerization and chemotaxis comparable to that triggered by the standard chemoattractant formyl-methionyl-leucyl-phenylalanine. Plasmin triggered rapid activation of Akt and mitogen-activated protein kinases, followed by phosphorylation of the regulatory myosin light chain and chemotaxis. For the chemotactic DC migration, the activation of Akt and p38 and extracellular signal-regulated kinase 1/2 mitogen-activated protein kinases were indispensable, as shown by pharmacological inhibitors. DC express Akt1 and Akt2, but not Akt3. However, in DC, plasmin activates exclusively Akt2 via a p38 mitogen-activated protein kinase-dependent pathway. Accordingly, knockdown of Akt2 with short-hairpin RNA, but not of Akt1, blocked the plasmin-induced extracellular signal-regulated kinase 1/2 activation and the chemotactic response. Moreover, plasmin-stimulated DC induced polarization of CD4 + T cells toward the interferon-γ–producing, proinflammatory Th1 phenotype. Consistent with a role for DC and adaptive immune response in atherogenesis, we demonstrate DC in human atherosclerotic vessels and show that plasmin is abundant in human atherosclerotic lesions, where it colocalizes with DC.

Conclusion— Plasmin generation in the atherosclerotic vessel wall might contribute to accumulation of DC, activation of the adaptive immune response, and aggravation of atherosclerosis.

Tirucallic acids are novel pleckstrin homology domain-dependent Akt inhibitors inducing apoptosis in prostate cancer cells

Activation of the serine/threonine kinase Akt is associated with aggressive clinical behavior of prostate cancer. We found that the human prostate cancer cell lines LNCaP and PC-3 express predominantly Akt1 and Akt2. Selective down-regulation of Akt1, but not Akt2, by short-hairpin RNA reduced the viability of prostate cancer cells. In addition, structurally different Akt inhibitors were cytotoxic for the prostate cancer cells, confirming that the Akt pathway is indispensable for their viability. We have purified the tetracyclic triterpenoids 3-oxo-tirucallic acid, 3-alpha-acetoxy-tirucallic acid, and 3-beta-acetoxy-tirucallic acid from the oleogum resin of Boswellia carterii to chemical homogeneity. The acetoxy-derivatives in particular potently inhibited the activities of human recombinant Akt1 and Akt2 and of constitutively active Akt immunoprecipitated from PC-3 cells, whereas inhibitor of nuclear factor-kappaB kinases remained unaffected. Docking data indicated that these tetracyclic triterpenoids form hydrogen bonds within the phosphatidylinositol binding pocket of the Akt pleckstrin homology domain. Accordingly, 3-beta-acetoxy-tirucallic acid did not inhibit the activity of Akt1 lacking the pleckstrin homology domain. In the prostate cancer cell lines investigated, these compounds inhibited the phosphorylation of cellular Akt and the Akt signaling pathways, including glycogen synthase kinase-3beta and BAD phosphorylation, nuclear accumulation of p65, the androgen receptor, beta-catenin, and c-Myc. These events culminated in the induction of apoptosis in prostate cancer, but not in nontumorigenic cells. The tirucallic acid derivatives inhibited proliferation and induced apoptosis in tumors xenografted onto chick chorioallantoic membranes and decreased the growth of pre-established prostate tumors in nude mice without overt systemic toxicity. Thus, tirucallic acid derivatives represent a new class of Akt inhibitors with antitumor properties.

TNFα-mediated plasminogen activation on neutrophils is involved in the high plasmin activity in mammary secretion of drying-off cows

Interactions between inflammatory cytokines and plasminogen (Pg) activation system on immune cells are yet to be established. In previous studies we reported a somatic cell-associated elevation of proteolytic activity in mammary secretion of drying-off goats and cows. The purposes of the present study were to examine the role of TNF-α in polymorphonuclear neutrophil (PMN)-associated Pg activation, and the significance of this activation pathway for overall plasmin (Pm) activity in mammary secretion of drying-off cows. Results of experiments in vitro showed that the spontaneous Pg activation observed on fresh preparations of bovine blood PMN was completely blocked by anti bovine TNF-α antibody, and was further up-regulated by exogenous bovine TNF-α. Monitoring the parameters of mammary secretion of drying-off cows revealed that both somatic cell counts and differential PMN ratio was significantly elevated at weeks 1, 2 and 3 of milk stasis. Nevertheless, specific activity of soluble Pm in mammary secretion increased and the level of 17-kDa TNF-α decreased immediately following milk stasis. Iimmunoblotting revealed that although both 26-kDa pro-TNF-α and 17-kDa TNF-α were consistently present in somatic cells of mammary secretion collected at weeks 0, 1, 2 and 3 of milk stasis, only 26-kDa pro-TNF-α was present in somatic cells of milk during lactation. In-vitro assay indicated that cell-free mammary secretion of drying-off cows exerted no Pg activation bioactivity towards bovine blood PMN. Altogether, the current study suggests the existence of an active TNF-α-Pg-Pm autocrine/paracrine loop on the massively infiltrated PMN inside udders of drying-off cows, which involves extensive binding and internalization of 17-kDa TNF-α on PMN and consequently activation of Pg, resulting in high Pm activity and low 17-kDa TNF-α level in mammary secretion. These coordinated mechanisms may play a role in the defence of drying-off mammary gland.

A novel function of thrombin-activatable fibrinolysis inhibitor during rat liver regeneration and in growth-promoted hepatocytes in primary culture

Thrombin-activatable fibrinolysis inhibitor (TAFI) exhibits anti-fibrinolytic activity by removing C-terminal lysine residues from fibrin or plasminogen receptor proteins on the cellular surface, and plays an important role in the regulation of fibrinolysis. In this study, we examined the regulation of TAFI in hepatocytes during liver regeneration, and revealed its pivotal role in hepatocyte proliferation. In rat models, partial hepatectomy or carbon tetrachloride (CCl4)-induced acute liver injury suppressed the levels of plasma TAFI activity and hepatic TAFI mRNA, whereas this operation markedly increased both the hepatic plasmin activity and the level of proliferating cell nuclear antigen. In primary cultures of rat hepatocytes, the TAFI mRNA level was decreased under growth-promoting culture conditions. Treatment of the hepatocytes with TAFI siRNA increased the amount of plasmin on the hepatocytes and promoted hepatocyte proliferation. We concluded that TAFI regulates plasmin activity through its enzymatic activity whereby it reduces the plasminogen-binding capacity of the hepatocytes. The TAFI gene expression is down-regulated in hepatocyte proliferation for producing a fibrinolytic microenvironment suitable for cell growth. This is the first report on the role of TAFI in the pericellular fibrinolysis necessary for cellular proliferation.

Interaction analyses of human monocytes co-cultured with different forms of Aspergillus fumigatus

Monocytes play a major role in the cellular defence against Aspergillus fumigatus in immunocompromised patients. To obtain a better understanding of the mechanisms involved in this interaction, phagocytosis and gene expression profiling of human monocytes was carried out after incubation with A. fumigatus resting, swollen and germinating conidia and hyphae (for 3, 6 and 9 h). The majority of monocytes phagocytosed up to three conidia during the first 3 h of incubation. Microarray analysis showed an increased expression level of immune-relevant genes, which was dependent on the germination state of the fungus and the incubation period. Among these genes, those encoding interleukin-8, macrophage inflammatory protein 3-α (CCL20) and monocyte chemotactic protein-1 (CCL2) were found to be potential key regulators involved in the A. fumigatus-induced immune response. In addition, A. fumigatus was found to be an inducer of the genes encoding urokinase type plasminogen activator (uPA), urokinase type plasminogen activator receptor (uPAR),plasminogen activator inhibitor (PAI), pentraxin-3 (PTX3) and intercellular adhesion molecule-1 (ICAM-1), which, in combination, may contribute to thrombosis and local lung tissue injury.

Identification of fibronectin type I domains as amyloid-binding modules on tissue-type plasminogen activator and three homologs

The serine protease tissue-type plasminogen activator (tPA), a key enzyme in hemostasis, is activated by protein aggregates with amyloid-like properties. tPA is implicated in various pathologies, including amyloidoses. A major task is to further elucidate the mechanisms of amyloid pathology. We here show that the fibronectin type I domain of tPA mediates the interaction with amyloid protein aggregates. We found that in contrast to full-length tPA, a deletion-mutant of tPA, lacking the first three N-terminal domains (including the fibronectin type I domain), fails to activate in response to amyloid protein aggregates. Using recombinantly produced domains of tPA in direct binding assays, we subsequently mapped the amyloid-binding region to the fibronectin type I domain. This domain co-localized with congophilic plaques in brain sections from patients with Alzheimer's disease. Fibronectin type I domains from homologous proteases factor XII, hepatocyte growth factor activator and from the extracellular matrix protein fibronectin also bound to aggregated amyloidogenic peptides. Finally, we demonstrated that the isolated fibronectin type I domain inhibits amyloid-induced aggregation of blood platelets. The identification of the fibronectin type I domain as an amyloid-binding module provides new insights into the (patho-) physiological role of tPA and the homologous proteins which may offer new targets for intervention in amyloid pathology.

Mature dendritic cells express functional thrombin receptors triggering chemotaxis and CCL18/pulmonary and activation-regulated chemokine induction

Protease-activated receptors (PARs) are a family of G protein-coupled receptors that are activated by serine protease-mediated proteolytic cleavage of their extracellular domain. We have previously characterized the expression and function of PARs in human monocytes and macrophages, yet information about PARs in dendritic cells (DC) is scarce. Monocyte-derived immature DC do not express PARs. Upon maturation with LPS, but not with TNF-alpha or CD40 ligand, DC express PAR1 and PAR3, but not PAR2 or PAR4. Stimulation of DC with the serine protease thrombin or PAR1-activating peptide elicits actin polymerization and concentration-dependent chemotactic responses in LPS-, but not in TNF-alpha-matured DC. The thrombin-induced migration is a true chemotaxis with only negligible chemokinesis. Stimulation of PARs with thrombin or the respective receptor-activating peptides activates ERK1/2 and Rho kinase as well as subsequent phosphorylation of the regulatory myosin L chain 2. The ERK1/2- and Rho kinase 1-mediated phosphorylation of myosin L chain 2 was indispensable for the PAR-mediated chemotaxis as shown by pharmacological inhibitors. Additionally, thrombin stimulated the Rho-dependent release of the CC chemokine CCL18/pulmonary and activation-regulated chemokine, which induces chemotaxis of lymphocytes and immature DC as well as fibroblast proliferation. The colocalization of CD83(+) DC with CCL18 in human atherosclerotic plaques revealed by immunofluorescence microscopy combined with the presence of functionally active thrombin receptors on mature DC point to a previously unrecognized functional role of thrombin in DC biology. The thrombin-induced stimulation of mature DC may be of particular relevance in atherosclerotic lesions, which harbor all components of this novel mechanism.

IL-10 inhibits cysteinyl leukotriene-induced activation of human monocytes and monocyte-derived dendritic cells

The immunoregulatory cytokine IL-10 plays an essential role in down-modulating adaptive and innate immune responses leading to chronic inflammatory diseases. In contrast, cysteinyl leukotrienes (cysLTs), important proinflammatory mediators of cell trafficking and innate immune responses, are thought to enhance immune reactions in the pathogenesis of diseases, such as bronchial asthma, atherosclerosis, and pulmonary fibrosis. The aim of this study was to determine the IL-10 regulatory role in cysLT-induced activation of human monocytes and monocyte-derived dendritic cells. Herein we show that cysLT-induced activation and chemotaxis of human monocytes and monocyte-derived immature dendritic cells (iDC) are inhibited by IL-10 pretreatment. IL-10 down-regulated cysLT type 1 and 2 receptors' mRNA in a time- and concentration-dependent fashion. cysLT-induced activation of monocytes and iDCs measured by intracellular calcium flux and immediate-early gene expression (FBJ murine osteosarcoma viral oncogen homolog B and early growth response-2) was potently decreased by IL-10 and by the cysLT antagonist MK571. Chemotaxis of monocytes and iDCs to increasing concentrations of leukotriene D(4) (LTD(4)) was also inhibited by IL-10. LTD(4) enhanced iDC migration in response to CCL5. IL-10 selectively inhibited LTD(4)-induced chemotaxis without affecting migration to CCL5. These data indicate that cysLT-induced activation of human monocytes and dendritic cells may be specifically inhibited by IL-10, suggesting a direct link between the 5-lipoxygenase proinflammatory pathway and IL-10 regulatory mechanisms. Antileukotriene therapies may reproduce some regulatory mechanisms played by IL-10 in inflammatory processes.

Endometriosis and tissue factor

Tissue factor (TF), is a cellular receptor that binds the ligand factor VII/VIIa to initiate the blood coagulation cascade. In addition to its role as the initiator of the hemostatic cascade, TF is known to be involved in angiogenesis via an interaction with factor VIIa and protease-activated receptor-2 (PAR-2). In this article we review previous studies from our laboratory demonstrating that the pattern and level of TF expression is altered in multiple cell types derived from eutopic and ectopic endometrium from women with endometriosis compared with normal endometrium. We posit that the inflammatory environment that occurs in ectopic and eutopic endometrium from patients with disease results in high TF expression that in turn, signals via PAR-2 to further produce inflammatory cytokine or chemokine production and macrophage recruitment. Thus, our studies suggest that TF might be an ideal target for therapeutic intervention in endometriosis.

Tranexamic acid attenuates inflammatory response in cardiopulmonary bypass surgery through blockade of fibrinolysis: a case control study followed by a randomized double-blind controlled trial

Introduction

Extracorporeal circulation induces hemostatic alterations that lead to inflammatory response (IR) and postoperative bleeding. Tranexamic acid (TA) reduces fibrinolysis and blood loss after cardiopulmonary bypass (CPB). However, its effects on IR and vasoplegic shock (VS) are not well known and elucidating these effects was the main objective of this study.

Methods

A case control study was carried out to determine factors associated with IR after CPB. Patients undergoing elective CPB surgery were randomly assigned to receive 2 g of TA or placebo (0.9% saline) before and after intervention. We performed an intention-to-treat analysis, comparing the incidence of IR and VS. We also analyzed several biological parameters related to inflammation, coagulation, and fibrinolysis systems. We used SPSS version 12.2 for statistical purposes.

Results

In the case control study, 165 patients were studied, 20.6% fulfilled IR criteria, and the use of TA proved to be an independent protective variable (odds ratio 0.38, 95% confidence interval 0.18 to 0.81; P < 0.01). The clinical trial was interrupted. Fifty patients were randomly assigned to receive TA (24) or placebo (26). Incidence of IR was 17% in the TA group versus 42% in the placebo group (P = 0.047). In the TA group, we observed a significant reduction in the incidence of VS (P = 0.003), the use of norepinephrine (P = 0.029), and time on mechanical ventilation (P = 0.018). These patients showed significantly lower D-dimer, plasminogen activator inhibitor 1, and creatine-kinase levels and a trend toward lower levels of soluble tumor necrosis factor receptor and interleukin-6 within the first 24 hours after CPB.

Conclusion

The use of TA attenuates the development of IR and VS after CPB.

Trial registration number

ISRCTN05718824.

Antiinflammatory and Antiatherogenic Effects of the NF-κB Inhibitor Acetyl-11-Keto-β-Boswellic Acid in LPS-Challenged ApoE −/− Mice

Objective— In this article, we studied the effect of acetyl-11-keto-β-boswellic acid (AKβBA), a natural inhibitor of the proinflammatory transcription factor NF-κB on the development of atherosclerotic lesions in apolipoprotein E–deficient (apoE −/− ) mice.

Methods and Results— Atherosclerotic lesions were induced by weekly LPS injection in apoE −/− mice. LPS alone increased atherosclerotic lesion size by ≈100%, and treatment with AKβBA significantly reduced it by ≈50%. Moreover, the activity of NF-κB was also reduced in the atherosclerotic plaques of LPS-injected apoE −/− mice treated with AKβBA. As a consequence, AKβBA treatment led to a significant downregulation of several NF-κB–dependent genes such as MCP-1, MCP-3, IL-1α, MIP-2, VEGF, and TF. By contrast, AKβBA did not affect the plasma concentrations of triglycerides, total cholesterol, antioxidized LDL antibodies, and various subsets of lymphocyte-derived cytokines. Moreover, AKβBA potently inhibited the IκB kinase (IKK) activity immunoprecipitated from LPS-stimulated mouse macrophages and mononuclear cells leading to decreased phosphorylation of IκBα and inhibition of p65/NF-κB activation. Comparable AKβBA-mediated inhibition was also observed in LPS-stimulated human macrophages.

Conclusion— The inhibition of NF-κB activity by plant resins from species of the Boswellia family might represent an alternative for classical medicine treatments for chronic inflammatory diseases such as atherosclerosis. (Arterioscler Thromb Vasc Biol. 2008;28:272-277)

Chronic plasminogen activator inhibitor-1 (PAI-1) overexpression dampens CD25+ lymphocyte recruitment after lipopolysaccharide endotoxemia in mouse lung

BACKGROUND

Plasma plasminogen activator inhibitor-1 (PAI-1) level rises during sepsis and confers a worse prognosis. PAI-1 participation to sepsis has been poorly documented and was mainly associated with fibrin deposits. Beside fibrin deposits, increased tissue PAI-1 expression may contribute to the poor outcome of endotoxemia through other mechanisms.

OBJECTIVE AND METHODS

During lipopolysaccharide (LPS) challenge, the role of PAI-1 in the early phase of inflammation was examined in the lungs of transgenic mice that either overexpress or lack the PAI-1 gene (PAI-1Tg or PAI-1(-/-)).

RESULTS

Analysis of leukocytes revealed that neutrophil and macrophage infiltrations did not differ for PAI-1Tg and wild-type (WT) mice. Remarkably, CD25+ lymphocyte infiltration was totally blunted in PAI-1Tg lungs and inversely correlated with fibrin depositions. In parallel, mRNA levels of the regulatory T cell (Treg) markers FoxP3, CTLA-4, and GITR were significantly lower in PAI-1Tg than in WT lungs after LPS challenge. These data are supported by opposite results in PAI-1(-/-) lungs. The systemic compartments (spleen and peripheral blood) showed no decrease in CD25+, CD4+ CD25+ lymphocytes, and Treg markers in PAI-1Tg mice after LPS injection compared with WT mice. In addition, plasma and lung concentrations of interleukin-6 (IL-6) and macrophage inflammatory protein-1alpha (MIP-1alpha) were significantly higher in PAI-1Tg mice than WT mice.

CONCLUSION

Our results suggest that chronic tissue PAI-1 overexpression influences the early phase of the inflammatory response during endotoxemia through the control of T lymphocyte traffic.

Plasmin Triggers Cytokine Induction in Human Monocyte-Derived Macrophages

OBJECTIVE

Fibrinolytic activity is upregulated in atherosclerotic lesions, yet little is known about the role of plasmin in macrophage function. We postulated a direct effect of plasmin on human monocyte-derived macrophages.

METHODS AND RESULTS

Plasmin activates macrophages via the annexin A2 heterotetramer composed of annexin A2 and S100A10 with subsequent stimulation of Janus kinase JAK1/TYK2 signaling. JAK1/TYK2 leads to STAT3 activation, Akt-dependent NF-kappaB activation, and phosphorylation of extracellular signal-regulated kinase 1/2 and mitogen-activated kinase p38. These signaling pathways trigger nuclear translocation of STAT3 and p65 transcription factors and the induction of the proinflammatory cytokines tumor necrosis factor-alpha and IL-6. Inhibitors of JAK, p38, and NF-kappaB revealed that these signaling pathways are indispensable for the plasmin-mediated tumor necrosis factor-alpha and IL-6 induction. By contrast, the extracellular signal-regulated kinase 1/2 activation is essential only for the IL-6 expression. The activation clearly depends on the proteolytic activity of plasmin, which cleaves the A2 subunit of the annexin A2 heterotetramer. Downregulation of each of the receptor subunits by antisense oligodeoxynucleotides abolished the plasmin-induced expression of proinflammatory cytokines stressing the crucial role the annexin A2 heterotetramer.

CONCLUSIONS

Plasmin generated at sites of inflammation such as atherosclerotic lesions will trigger cytokine expression in human macrophages.

Associations between peri-implant crevicular fluid volume, concentrations of crevicular inflammatory mediators, and composite IL-1A ?889 and IL-1B +3954 genotype: A cross-sectional study on implant recall patients with and without clinical signs of peri-implantitis

OBJECTIVES

To assess possible relationships between peri-implant crevicular fluid (PICF) volumes, biochemical markers of the peri-implant immune response, and periodontitis-associated genotype.

MATERIAL AND METHODS

PICF samples from 29 implant maintenance patients, 24 wearing overdentures, five having single crowns and bridgework (11 patients with peri-implantitis and 18 individuals with healthy peri-implant conditions), were analyzed for per site and per crevicular-fluid-volume concentrations of interleukin-1beta, plasminogen activator inhibitor type 2, and prostaglandin E2 by ELISA. Associations between the three substance concentrations and to crevicular fluid flow rate were analyzed by linear regression analysis. The possible differentiating influence of the composite interleukin-1A and -1B genotype on the patients' peri-implant health and biochemical inflammatory status was checked formally with t-test statistics and the Wilcoxon' test. One implant per patient was chosen for analysis.

RESULTS

In patients with healthy peri-implant conditions, genotype-positive individuals showed elevated crevicular fluid flow rates and at the same time reduced mediator concentrations. In patients with an implant affected from peri-implantitis, no statistically significant influence of the periodontitis-associated genotype around the fixture can be stated. There was no statistical difference between per site and per crevicular-fluid-volume concentration analyses. All three mediator concentrations were positively related to each other, while there was a strong negative correlation between crevicular fluid volume and plasminogen activator inhibitor 2 or prostaglandin E2.

CONCLUSIONS

The Interleukin-1 polymorphism investigated exerted only little influence on the peri-implant crevicular immune response, and this influence appeared to be of limited impact in sites with established peri-implantitis lesions.

Plasminogen activator inhibitor type-1-deficient mice have an enhanced IFN-gamma response to lipopolysaccharide and staphylococcal enterotoxin B

Plasminogen activator inhibitor type-1 (PAI-1) is a major inhibitor of fibrinolysis by virtue of its capacity to inhibit urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA). Systemic inflammation is invariably associated with elevated circulating levels of PAI-1, and during human sepsis plasma PAI-1 concentrations predict an unfavorable outcome. Knowledge about the functional role of PAI-1 in a systemic inflammatory response syndrome is highly limited. In this study, we determined the role of endogenous PAI-1 in cytokine release induced by administration of LPS or staphylococcal enterotoxin B (SEB). Both LPS and SEB elicited secretion of PAI-1 into the circulation of normal wild-type (Wt) mice. Relative to Wt mice, PAI-1 gene-deficient (PAI-1(-/-)) mice demonstrated strongly elevated plasma IFN-gamma concentrations after injection of either LPS or SEB. In addition, PAI-1(-/-) splenocytes released more IFN-gamma after incubation with LPS or SEB than Wt splenocytes. Both PAI-1(-/-) CD4+ and CD8+ T cells produced more IFN-gamma upon stimulation with SEB. LPS-induced IFN-gamma release in mice deficient for uPA, the uPA receptor, or tPA was not different from IFN-gamma release in LPS-treated Wt mice. These results identify a novel function of PAI-1 during systemic inflammation, where endogenous PAI-1 serves to inhibit IFN-gamma release by a mechanism that does not depend on its interaction with uPA/uPA receptor or tPA.

TagSNP evaluation for the association of 42 inflammation loci and vascular disease: evidence of IL6, FGB, ALOX5, NFKBIA, and IL4R loci effects

Inflammatory markers have consistently been associated with vascular disease. Evidence of genetic polymorphisms in inflammatory loci that predict severe carotid artery disease (CAAD) would suggest that this relationship is not secondary to other correlated factors, but related to inflammation itself. We examined the full common genetic variation in 42 inflammatory loci for prediction of severe CAAD versus ultrasound proven controls using a tagSNP approach. For selected loci, monocyte RNA levels were contrasted in subjects with and without CAAD. We confirm the association of IL6(-174), FGB (-455), and ALOX5 with CAAD and show that multiple ALOX5 SNPs independently predict CAAD. We provide evidence for previously unreported associations of SNPs in IL4R, NFKBIA, and PLG with CAAD, and weaker evidence for associations with CSF3, IL10RA, and VCAM1. The NFKBIA and IL10RA expression levels significantly differed between subjects with CAAD and controls. These results support a role for genetic variation related to inflammation in CAAD and a causal role for specific gene products.