The effects of the fibrin-derived peptide Bbeta(15-42) in acute and chronic rodent models of myocardial ischemia-reperfusion

Myocardial ischemia-reperfusion injury released cellular fibronectin containing domain A (CFN-EDA): A destructive positive loop amplifying arterial thrombosis formation and exacerbating myocardial reperfusion injury

Previous research has identified intravascular platelet thrombi in regions affected by myocardial ischemia-reperfusion (MI/R) injury and neighbouring areas. However, the occurrence of arterial thrombosis in the context of MI/R injury remains unexplored. This study utilizes intravital microscopy to investigate carotid artery thrombosis during MI/R injury in rats, establishing a connection with the presence of prothrombotic cellular fibronectin containing extra domain A (CFN-EDA) protein. Additionally, the study examines samples from patients with coronary artery disease (CAD) both before and after coronary artery bypass grafting (CABG). Levels of CFN-EDA significantly increase following MI with further elevation observed following reperfusion of the ischemic myocardium. Thrombotic events, such as thrombus formation and growth, show a significant increase, while the time to complete cessation of blood flow in the carotid artery significantly decreases following MI/R injury induced by ferric chloride. The acute infusion of purified CFN-EDA protein accelerates in-vivo thrombotic events in healthy rats and significantly enhances in-vitro adenosine diphosphate and collagen-induced platelet aggregation. Treatment with anti-CFN-EDA antibodies protected the rat against MI/R injury and significantly improved cardiac function as evidenced by increased end-systolic pressure-volume relationship slope and preload recruitable stroke work compared to control. Similarly, in a human study, plasma CFN-EDA levels were notably elevated in CAD patients undergoing CABG. Post-surgery, these levels continued to rise over time, alongside cardiac injury biomarkers such as cardiac troponin and B-type natriuretic peptide. The study highlights that increased CFN-EDA due to CAD or MI initiates a destructive positive feedback loop by amplifying arterial thrombus formation, potentially exacerbating MI/R injury.

Microvascular Leakage as Therapeutic Target for Ischemia and Reperfusion Injury

Reperfusion injury is a very common complication of various indicated therapies such as the re-opening of vessels in the myocardium or brain as well as reflow in hemodynamic shutdown (cardiac arrest, severe trauma, aortic cross-clamping). The treatment and prevention of reperfusion injury has therefore been a topic of immense interest in terms of mechanistic understanding, the exploration of interventions in animal models and in the clinical setting in major prospective studies. While a wealth of encouraging results has been obtained in the lab, the translation into clinical success has met with mixed outcomes at best. Considering the still very high medical need, progress continues to be urgently needed. Multi-target approaches rationally linking interference with pathophysiological pathways as well as a renewed focus on aspects of microvascular dysfunction, especially on the role of microvascular leakage, are likely to provide new insights.

Current View on the Molecular Mechanisms Underlying Fibrin(ogen)-Dependent Inflammation

Numerous studies have revealed the involvement of fibrinogen in the inflammatory response. To explain the molecular mechanisms underlying fibrinogen-dependent inflammation, two bridging mechanisms have been proposed in which fibrin(ogen) bridges leukocytes to endothelial cells. The first mechanism suggests that bridging occurs via the interaction of fibrinogen with the leukocyte receptor Mac-1 and the endothelial receptor ICAM-1 (intercellular adhesion molecule-1), which promotes leukocyte transmigration and enhances inflammation. The second mechanism includes bridging of leukocytes to the endothelium by fibrin degradation product E1 fragment through its interaction with leukocyte receptor CD11c and endothelial VE-cadherin to promote leukocyte transmigration. The role of E1 in promoting inflammation is inhibited by the fibrin-derived β15-42 fragment, and this has been suggested to result from its ability to compete for the E1-VE-cadherin interaction and to trigger signaling pathways through the src kinase Fyn. Our recent study revealed that the β15-42 fragment is ineffective in inhibiting the E1- or fibrin-VE-cadherin interaction, leaving the proposed signaling mechanism as the only viable explanation for the inhibitory function of β15-42. We have discovered that fibrin interacts with the very-low-density lipoprotein (VLDL) receptor, and this interaction triggers a signaling pathway that promotes leukocyte transmigration through inhibition of the src kinase Fyn. This pathway is inhibited by another pathway induced by the interaction of β15-42 with a putative endothelial receptor. In this review, we briefly describe the previously proposed molecular mechanisms underlying fibrin-dependent inflammation and their advantages/disadvantages and summarize our recent studies of the novel VLDL receptor-dependent pathway of leukocyte transmigration which plays an important role in fibrin-dependent inflammation.

Systemic low-grade inflammation and depressive symptomology at chronic phase of ischemic stroke: The chain mediating role of fibrinogen and neutrophil counts

BACKGROUND

Post-stroke depression (PSD) is the most common psychological consequence of stroke. Increased inflammatory markers resulting from ischemic stroke may played an important role in the pathogenesis of depressive symptomology. The present study was conducted to further elucidate the relationship between stroke severity, systemic low-grade inflammation and chronic phase post-stroke depressive symptomology (CP-PSDS).

METHODS

A total of 897 stroke patients were consecutively recruited in this multicenter prospective cohort study and followed up for 1 year. The analytical sample consisted of 436 patients with ischemic stroke (23.4% female, median age = 57 years) from this cohort. Serum concentrations of inflammatory markers were measured in all 436 patients with ischemic stroke, from fasting morning venous blood samples on admission. Stroke severity was evaluated using the National Institutes of Health Stroke Scale (NIHSS) on admission and post-stroke depressive symptomology (PSDS) was evaluated by 17-item Hamilton Rating Scale for Depression (HRSD).

RESULTS

In the fully adjusted models, we observed that 1) NIHSS (Model 2: β = 0.200, 95%CI, 0.057 ∼ 0.332), fibrinogen (Model 2: β = 0.828, 95%CI, 0.269 ∼ 1.435), white blood cell counts (WBC, model 2: β = 0.354, 95%CI, 0.122 ∼ 0.577) and neutrophil counts (Model 2: β = 0.401, 95%CI, 0.126 ∼ 0.655) can independently predict the CP-PSDS after ischemic stroke onset; 2) fibrinogen (Indirect effect = 0.027, 95%CI, 0.007 ∼ 0.063, 13.4% mediated), WBC (Indirect effect = 0.024, 95%CI, 0.005 ∼ 0.058, 11.8% mediated) and neutrophil counts (Indirect effect = 0.030, 95%CI, 0.006 ∼ 0.069, 14.8% mediated) could partially mediate the association between stroke severity and CP-PSDS, and 3) stroke severity might cause CP-PSDS partly through the chain-mediating role of both fibrinogen and neutrophil counts (chain mediated effect = 0.003, 95%CI, 0.000 ∼ 0.011, p = 0.025, 1.6% mediated).

CONCLUSIONS

Findings revealed that fibrinogen, WBC and neutrophil counts may be independent predictors of CP-PSDS and partial mediators of the relationship between stroke severity and CP-PSDS among patients with ischemic stroke. In addition, the chain mediating effect of fibrinogen and neutrophil counts might play an important role in the occurrence of CP-PSDS. However, no inflammatory markers were associated with CP-PSDS in females.

Synthetic Fibrin-Derived Bβ15-42 Peptide Delays Thrombus Resolution in a Mouse Model

[Figure: see text].

Binding to carboxypeptidase M mediates protective effects of fibrinopeptide Bβ15-42

During fibrinolysis a 28-amino-acid peptide is generated besides other degradation products of fibrin. This peptide, called Bβ_15-42, which is cleaved by plasmin from the end of the fibrin Bβ-chain, is protective in myocardial and renal ischemia/reperfusion injury and improves the outcome in experimental sepsis. Bβ_15-42 has been shown to mediate different beneficial effects in endothelial cells through binding to vascular endothelial-cadherin. Here, we provide in vitro and in vivo evidence that Bβ_15-42 has additional cell protective activity in tubular cells, which is caused by a distinct mechanism. As vascular endothelial-cadherin is not expressed by tubular cells we used ligand-receptor capture technology LRC-TriCEPS to search for tubular cell surface receptors and identified carboxypeptidase M (CBPM) as a novel binding partner of Bβ_15-42. Silencing CBPM with siRNA reduced the protective potential of Bβ_15-42 against tubular cell stress. Bβ_15-42 inhibited the enzymatic activity of CBPM and modified the impact of CBPM on bradykinin signaling. We conclude that beneficial properties of Bβ_15-42 are not restricted to endothelial cells but are also active in epithelial cells where cytoprotection depends on CBPM binding.

Fibrin-VLDL Receptor-Dependent Pathway Promotes Leukocyte Transmigration by Inhibiting Src Kinase Fyn and is a Target for Fibrin β15-42 Peptide

According to the current view, binding of fibrin degradation product E₁ fragment to endothelial VE-cadherin promotes transendothelial migration of leukocytes and thereby inflammation, and fibrin-derived β15-42 peptide reduces leukocyte transmigration by competing with E₁ for binding to VE-cadherin and, in addition, by signaling through Src kinase Fyn. However, the very low affinity of β15-42 to VE-cadherin raised a question about its ability to inhibit E₁-VE-cadherin interaction. Further, our previous study revealed that fibrin promotes leukocyte transmigration through the very-low-density lipoprotein (VLDL) receptor (VLDLR)-dependent pathway and suggested a possible link between the inhibitory properties of β15-42 and this pathway. To test such a link and the proposed inhibitory mechanisms for β15-42, we performed in vitro experiments using surface plasmon resonance, enzyme-linked immunosorbent assay, and leukocyte transendothelial migration assay, and in vivo studies with wild-type and VLDLR-deficient mice using mouse model of peritonitis. The experiments revealed that β15-42 cannot inhibit E₁-VE-cadherin interaction at the concentrations used in the previous in vivo studies leaving the proposed Fyn-dependent signaling mechanism as a viable explanation for the inhibitory effect of β15-42. While testing this mechanism, we confirmed that Fyn plays a critical role in controlling fibrin-induced transendothelial migration of leukocytes and found that signaling through the VLDLR-dependent pathway results in inhibition of Fyn, thereby increasing leukocyte transmigration. Furthermore, our in vivo experiments revealed that β15-42 inhibits this pathway, thereby preventing inhibition of Fyn and reducing leukocyte transmigration. Thus, this study clarifies the molecular mechanism underlying the VLDLR-dependent pathway of leukocyte transmigration and reveals that this pathway is a target for β15-42.

The multifaceted role of fibrinogen in tissue injury and inflammation

The canonical role of the hemostatic and fibrinolytic systems is to maintain vascular integrity. Perturbations in either system can prompt primary pathological end points of hemorrhage or thrombosis with vessel occlusion. However, fibrin(ogen) and proteases controlling its deposition and clearance, including (pro)thrombin and plasmin(ogen), have powerful roles in driving acute and reparative inflammatory pathways that affect the spectrum of tissue injury, remodeling, and repair. Indeed, fibrin(ogen) deposits are a near-universal feature of tissue injury, regardless of the nature of the inciting event, including injuries driven by mechanical insult, infection, or immunological derangements. Fibrin can modify multiple aspects of inflammatory cell function by engaging leukocytes through a variety of cellular receptors and mechanisms. Studies on the role of coagulation system activation and fibrin(ogen) deposition in models of inflammatory disease and tissue injury have revealed points of commonality, as well as context-dependent contributions of coagulation and fibrinolytic factors. However, there remains a critical need to define the precise temporal and spatial mechanisms by which fibrinogen-directed inflammatory events may dictate the severity of tissue injury and coordinate the remodeling and repair events essential to restore normal organ function. Current research trends suggest that future studies will give way to the identification of novel hemostatic factor-targeted therapies for a range of tissue injuries and disease.

Sanhuang Xiexin decoction promotes good functional outcome in acute ischemic stroke

OBJECTIVES

To explore the efficiency and safety of Sanhuang Xiexin decoction in the treatment of acute ischemic stroke (AIS) patients after endovascular intervention examination.

METHODS

In this prospective observational study, 121 AIS patients admitted in our hospital were enrolled from January 2012 to December 2015. They were randomly divided into two groups, 61 patients received Sanhuang Xiexin decoction + basic treatment (SX group) and 60 patients received basic treatment (control group). The prescription of Sanhuang Xiexin decoction was taken in the SX group, with one dose (100 ml), twice a day for 7 days orally. For all patients, blood samples were drawn on the first morning and sixth morning after endovascular intervention examination under fasting state for Fib (fibrinogen), PAgT (platelet aggregation test), CRP (C-reactive protein), and TMAO (trimethylamine oxide) tested. Estimate the changes in plasma Fib, PAgT, CRP, and TMAO levels and the syndrome of fire-heat scores.

RESULTS

The plasma Fib, PAgT, CRP, and TMAO levels in the SX group were significantly lower than those in the control group (P_Fib  < 0.01, P_PAgT  < 0.01, P_CRP  = 0.02, P_TMAO  < 0.01). The syndrome of fire-heat scores in the SX group was significantly lower than that in the control group (p < 0.01). The incidences of ischemic cerebrovascular events within 3 and 6 months after endovascular intervention treatment in the SX group were lower than those in the control group (P_3 month  = 0.04, P_6month  = 0.03).

CONCLUSIONS

The prescription of Sanhuang Xiexin is efficient and safe in the treatment of AIS patients after endovascular intervention examination through reducing the inflammatory factors.

Cellular and molecular approaches to enhance myocardial recovery after myocardial infarction

Reperfusion therapy has resulted in significant improvement in post-myocardial infarction morbidity and mortality in over the last 4 decades. Nonetheless, it is well recognized that simply restoring patency of the epicardial artery may not stop or reverse damage at microvascular level, and myocardial salvage is often suboptimal. Numerous efforts have been undertaken to elucidate the mechanisms underlying extensive myonecrosis to facilitate the discovery of therapies to provide additional and incremental benefits over current therapeutic pathways. To date, conclusively effective strategies to promote myocardial recovery have not yet been established. Novel approaches are investigating the foundational cellular and molecular bases of myocardial ischemia and irreversible injury. Herein, we review the emerging concepts and proposed therapies that may improve myocardial protection and reduce infarct size. We examine the preclinical and clinical evidence for reduced infarct size with these strategies, including anti-inflammatory agents, intracellular ion channel modulators, agents affecting the reperfusion injury salvage kinase (RISK) and nitric oxide signaling pathways, modulators of mitochondrial function, anti-apoptotic agents, and stem cell and gene therapy. We review the potential reasons of failures to date and the potential for new strategies to further promote myocardial recovery and improve prognosis.

The Fibrin Cleavage Product Bβ15-42 Channels Endothelial and Tubular Regeneration in the Post-acute Course During Murine Renal Ischemia Reperfusion Injury

Early and adequate restoration of endothelial and tubular renal function is a substantial step during regeneration after ischemia reperfusion (IR) injury, occurring, e.g., in kidney transplantation, renal surgery, and sepsis. While tubular epithelial cell injury has long been of central importance, recent perception includes the renal vascular endothelium. In this regard, the fibrin cleavage product fibrinopeptide Bβ_15-42 mitigate IR injury by stabilizing interendothelial junctions through its affinity to VE-cadherin. Therefore, this study focused on the effect of Bβ_15-42 on post-acute physiological renal regeneration. For this, adult male C57BL/6 mice were exposed to a 30 min bilateral renal ischemia and reperfusion for 24 h or 48 h. Animals were randomized in a non-operative control group, two operative groups each treated with i.v. administration of either saline or Bβ_15-42 (2.4 mg/kg) immediately prior to reperfusion. Endothelial activation and inflammatory response was attenuated in renal tissue homogenates by single application of Bβ_15-42. Meanwhile, Bβ_15-42 did not affect acute kidney injury markers. Regarding the angiogenetic players VEGF-A, Angiopoietin-1, Angiopoietin-2, however, we observed significant higher expressions at mRNA and trend to higher protein level in Bβ_15-42 treated mice, compared to saline treated mice after 48 h of IR, thus pointing toward an increased angiogenetic activity. Similar dynamics were observed for the intermediate filament vimentin, the cytoprotective protein klotho, stathmin and the proliferation cellular nuclear antigen, which were significantly up-regulated at the same points in time. These results suggest a beneficial effect of anatomical contiguously located endothelial cells on tubular regeneration through stabilization of endothelial integrity. Therefore, it seems that Bβ_15-42 represents a novel pharmacological approach in the targeted therapy of acute renal failure in everyday clinical practice.

The Fibrin-Derived Peptide Bβ15-42 (FX06) Ameliorates Vascular Leakage and Improves Survival and Neurocognitive Recovery: Implications From Two Animal Models of Cardiopulmonary Resuscitation

OBJECTIVES

The fibrin-derived peptide Bβ15-42 (FX06) has been proven to attenuate ischemia/reperfusion injury. We tested the hypothesis that Bβ15-42 improves survival rate and neurocognitive recovery after cardiopulmonary resuscitation.

DESIGN

Pig and mouse model of cardiopulmonary resuscitation.

SETTING

Two university hospitals.

SUBJECTS

Pigs and mice.

INTERVENTIONS

Pigs (n = 16) were subjected to 8-minute cardiac arrest. Successful resuscitated pigs (n = 12) were randomized either to 3 mg/kg Bβ15-42 followed by a continuous infusion of 1 mg/kg/hr for 5 hours (pFX06; n = 6) or the control group (pCONTROL; n = 6). Cardiac damage, function, and hemodynamics were recorded up to 8 hours. Mice (n = 52) were subjected to 4-minute cardiac arrest followed by cardiopulmonary resuscitation, and randomized either to two boli of 2.4 mg/kg Bβ15-42 (mFX06; n = 26) or the control group (mCONTROL; n = 26). Fourteen-day survival rate, neurocognitive function, and endothelial integrity (additional experiment with n = 26 mice) were evaluated.

MEASUREMENTS AND MAIN RESULTS

Bβ15-42 reduced cumulative fluid intake (3,500 [2,600-4,200] vs 6,800 [5,700-7,400] mL; p = 0.004) within 8 hours in pigs. In mice, Bβ15-42 improved 14-day survival rate (mFX06 vs mCONTROL; 11/26 vs 6/26; p < 0.05) and fastened neurocognitive recovery in the Water-Maze test (15/26 vs 9/26 mice with competence to perform test; p < 0.05). Bβ15-42-treated mice showed a significant higher length of intact pulmonary endothelium and reduced pulmonary leukocyte infiltration.

CONCLUSIONS

This study confirms the new concept of an important role of fibrin derivatives in global ischemia/reperfusion injury, which can be attenuated by the fibrin-derived peptide Bβ15-42.

Proteomics in paediatric cardiac surgery: is a personalised approach feasible?

The incidence of congenital cardiac abnormalities remains high. Paediatric patients with congenital cardiac defects often require surgery at a young age. The surgeries are often long and complex, rendering this population particularly vulnerable to the deleterious effects of cardiopulmonary bypass and cardiac surgery. The search for cardioprotective strategies is ongoing in an attempt to reduce the morbidity in this population. In the post-genomic era, it is apparent that simply determining the genomic sequences holds little diagnostic potential and means to determine progression of disease and response to treatment. The field of proteomics is expanding and application of proteomic techniques in the clinical setting holds great potential to advance our understanding of the proteomic changes involved in specific disease stages. This review will assess the application of proteomic techniques in the setting of paediatric cardiac surgery and highlight the need to obtain a clear understanding of the role of various proteins in children with cardiac conditions. The success and challenges of the available proteomic technology will be discussed as well as the future potential of proteomic methods for advancing our understanding of protein changes in children requiring cardiac surgery.

Cardioprotection: a review of current practice in global ischemia and future translational perspective

The idea of protecting the heart from ischemic insult during heart surgery to allow elective cardiac arrest is as old as the idea of cardiac surgery itself. The current gold standard in clinical routine is a high potassium regimen added either to crystalloid or blood cardioplegic solutions inducing depolarized arrest. Ongoing patient demographic changes with increasingly older, comorbidly ill patients and increasing case complexity with increasingly structurally abnormal hearts as morphological correlate paired with evolutions in pediatric cardiac surgery allowing more complex procedures than ever before redefine requirements for cardioprotection. Many, in part adversarial, regimens to protect the myocardium from ischemic insults have entered clinical routine; however, functional recovery of the heart is still often impaired due to perfusion injury. Myocardial reperfusion damage is a key determinant of postoperative organ functional recovery, morbidity, and mortality in adult and pediatric patients. There is a discrepancy between what current protective strategies are capable of and what they are expected to do in a rapidly changing cardiac surgery community. An increased understanding of the molecular players of ischemia reperfusion injury offers potential seeds for new cardioprotective regimens and may further displace boundaries of what is technically feasible.

Modifications in rat plasma proteome after remote ischemic preconditioning (RIPC) stimulus: identification by a SELDI-TOF-MS approach

Remote ischemic preconditioning’s (RIPC) ability to render the myocardium resistant to subsequent prolonged ischemia is now clearly established in different species, including humans. Strong evidence suggests that circulating humoral mediators play a key role in signal transduction, but their identities still need to be established. Our study sought to identify potential circulating RIPC mediators using a proteomic approach. Rats were exposed to 10-min limb ischemia followed by 5- (RIPC 5′) or 10-min (RIPC 10′) reperfusion prior to blood sampling. The control group only underwent blood sampling. Plasma samples were isolated for proteomic analysis using surface-enhanced laser desorption and ionization - time of flight - mass spectrometry (SELDI-TOF-MS). A total of seven proteins, including haptoglobin and transthyretin, were detected as up- or down-regulated in response to RIPC. These proteins had previously been identified as associated with organ protection, anti-inflammation, and various cellular and molecular responses to ischemia. In conclusion, this study indicates that RIPC results in significant modulations of plasma proteome.

Remote ischemic preconditioning (RIPC) modifies plasma proteome in humans

Remote Ischemic Preconditioning (RIPC) induced by brief episodes of ischemia of the limb protects against multi-organ damage by ischemia-reperfusion (IR). Although it has been demonstrated that RIPC affects gene expression, the proteomic response to RIPC has not been determined. This study aimed to examine RIPC induced changes in the plasma proteome. Five healthy adult volunteers had 4 cycles of 5 min ischemia alternating with 5 min reperfusion of the forearm. Blood samples were taken from the ipsilateral arm prior to first ischaemia, immediately after each episode of ischemia as well as, at 15 min and 24 h after the last episode of ischemia. Plasma samples from five individuals were analysed using two complementary techniques. Individual samples were analysed using 2Dimensional Difference in gel electrophoresis (2D DIGE) and mass spectrometry (MS). Pooled samples for each of the time-points underwent trypsin digestion and peptides generated were analysed in triplicate using Liquid Chromatography and MS (LC-MS). Six proteins changed in response to RIPC using 2D DIGE analysis, while 48 proteins were found to be differentially regulated using LC-MS. The proteins of interest were involved in acute phase response signalling, and physiological molecular and cellular functions. The RIPC stimulus modifies the plasma protein content in blood taken from the ischemic arm in a cumulative fashion and evokes a proteomic response in peripheral blood.

The heart-protective mechanism of nitronyl nitroxide radicals on murine viral myocarditis induced by CVB3

Our previous researches showed that nitronyl nitroxyl derivatives, NNP and NNVP were good anti-oxidants and provided radioprotective effects in C6 cells. The objective of the present study is to investigate the possible antiviral effects and underlying pharmacological of the two nitronyl nitroxide radicals against CVB3 in vitro and in vivo. The results showed that NNP and NNVP were some of the most potent compounds in terms of their antiviral effects by protecting myocardial cells against oxidative damage of free radicals. Treatment with NNP or NNVP could decrease the intracellular ROS level in vitro. They could lead to a significant decrease in activities of biochemical markers AST, CK and LDH in infected murine serum and could increase SOD and CAT activities and decreased MDA activities compared with infected control in vivo. NNP and NNVP could reduce NO production in infected mice by reacting with NO to produce the imino nitroxides which was confirmed by ESR spectrometry. In addition, NNP and NNVP could both decrease the mRNA expression of proinflammatory cytokines, TNF-α, IL-2 and IL-6. In conclusion, nitronyl nitroxide radicals NNP and NNVP were shown to have antiviral activities against CVB3 and they may represent potential therapeutic agents for viral myocarditis.

Fibrinogen as a key regulator of inflammation in disease

The interaction of coagulation factors with the perivascular environment affects the development of disease in ways that extend beyond their traditional roles in the acute hemostatic cascade. Key molecular players of the coagulation cascade like tissue factor, thrombin, and fibrinogen are epidemiologically and mechanistically linked with diseases with an inflammatory component. Moreover, the identification of novel molecular mechanisms linking coagulation and inflammation has highlighted factors of the coagulation cascade as new targets for therapeutic intervention in a wide range of inflammatory human diseases. In particular, a proinflammatory role for fibrinogen has been reported in vascular wall disease, stroke, spinal cord injury, brain trauma, multiple sclerosis, Alzheimer's disease, rheumatoid arthritis, bacterial infection, colitis, lung and kidney fibrosis, Duchenne muscular dystrophy, and several types of cancer. Genetic and pharmacologic studies have unraveled pivotal roles for fibrinogen in determining the extent of local or systemic inflammation. As cellular and molecular mechanisms for fibrinogen functions in tissues are identified, the role of fibrinogen is evolving from a marker of vascular rapture to a multi-faceted signaling molecule with a wide spectrum of functions that can tip the balance between hemostasis and thrombosis, coagulation and fibrosis, protection from infection and extensive inflammation, and eventually life and death. This review will discuss some of the main molecular links between coagulation and inflammation and will focus on the role of fibrinogen in inflammatory disease highlighting its unique structural properties, cellular targets, and signal transduction pathways that make it a potent proinflammatory mediator and a potential therapeutic target.

Interaction of fibrin with VE-cadherin and anti-inflammatory effect of fibrin-derived fragments

BACKGROUND

The interaction of the fibrin βN-domain with VE-cadherin on endothelial cells is implicated in transendothelial migration of leukocytes, and the β15-42 fragment representing part of this domain has been shown to inhibit this process. However, our previous study revealed that only a dimeric (β15-66)(2) fragment, corresponding to the full-length βN-domain and mimicking its dimeric arrangement in fibrin, bound to VE-cadherin.

OBJECTIVE

To test our hypothesis that dimerization of β15-42-containing fragments increases their affinity for VE-cadherin and ability to inhibit transendothelial migration of leukocytes.

METHODS

Interaction of β15-42-containing fragments with VE-cadherin was characterized by ELISA and surface plasmon resonance. The inhibitory effect of such fragments was tested in vitro with a leukocyte transendothelial migration assay and in vivo with mouse models of peritonitis and myocardial ischemia-reperfusion injury.

RESULTS

First, we prepared the monomeric β15-42 and β15-64 fragments and their dimeric forms, (β15-44)(2) and (β15-66)(2) , and studied their interaction with the fibrin-binding domain of VE-cadherin, VE-cad(3). The experiments revealed that both dimeric fragments bound to VE-cad(3) with high affinity, whereas the affinities of β15-42 and β15-64 were significantly lower. Next, we tested the ability of these fragments to inhibit leukocyte transmigration in vitro and infiltration into the inflamed peritoneum in vivo, and found that the inhibitory effects of the dimers on these processes were also superior. Furthermore, (β15-44)(2) significantly reduced myocardial injury induced by ischemia-reperfusion.

CONCLUSION

The results confirm our hypotheses and indicate that (β15-66)(2) and (β15-44)(2) , which exhibited much higher affinity for VE-cadherin, are highly effective in suppressing inflammation by inhibiting leukocyte transmigration.

Bβ(15-42) attenuates the effect of ischemia-reperfusion injury in renal transplantation

Renal ischemia-reperfusion contributes to reduced renal allograft survival. The peptide Bβ(15-42), a breakdown product of fibrin, attenuates inflammation induced by ischemia-reperfusion in the heart by competitively blocking the binding of leukocytes to endothelial VE-cadherin, but whether it could improve outcomes in renal transplantation is unknown. Here, we tested the ability of Bβ(15-42) to ameliorate the effects of renal ischemic injury during allogenic kidney transplantation in mice. In our renal transplantation model (C57BL/6 into BALB/c mice), treatment with Bβ(15-42) at the time of allograft reperfusion resulted in significantly improved survival of recipients during the 28-day follow-up (60% versus 10%). Bβ(15-42) treatment decreased leukocyte infiltration, expression of endothelial adhesion molecules, and proinflammatory cytokines. Treatment significantly attenuated allogenic T cell activation and reduced cellular rejection. Moreover, Bβ(15-42) significantly reduced tubular epithelial damage and apoptosis, which we reproduced in vitro. These data suggest that Bβ(15-42) may have therapeutic potential in transplant surgery by protecting grafts from ischemia-reperfusion injury.

The VE-cadherin binding domain of fibrinogen induces endothelial barrier permeability and enhances transendothelial migration of malignant breast epithelial cells

Fibrin deposition and exudation of plasma fibrinogen (Fg) have long been recognized as hallmarks of inflammation, cardiovascular disease and neoplasia. The Fg-beta(15-42) domain binds to the endothelial cell adhesion molecule, VE-cadherin, promoting endothelial cell proliferation, angiogenesis and leukocyte diapedesis. Furthermore, spontaneous blood-borne and lymphatic metastasis of some types of tumor emboli requires plasma fibrin(ogen); however, the molecular mechanisms by which this occurs are poorly understood. We sought to determine whether Fg-beta(15-42) and VE-cadherin binding interactions promote endothelial barrier permeability and breast cancer cell transendothelial migration (TEM) using transwell insert culture systems. Synthetic peptides containing/missing residues beta(15-17) critical for Fg-beta(15-42) binding to VE-cadherin, and antibodies that bind to Fg-beta(15-21) (T2G1) and VE-cadherin (BV9) were used to induce or inhibit Fg-mediated permeability and TEM. Fg induced dose-dependent permeability of human umbilical vein and microvascular endothelial but not epithelial cell barriers. Maximal Fg-induced endothelial permeability required Fg-beta(15-42) and VE-cadherin-binding interactions involving Fg-beta(15-17). Fg-induced TEM of malignant MDA-MB-231 and MCF-7 breast cancer cells also required Fg-beta(15-42) and VE-cadherin binding; however, such TEM was independent of E-cadherin or estrogen receptor expression. In contrast, Fg did not induce TEM of nonmalignant MCF-10A breast epithelial cells. Fg-induced endothelial permeability was retained in the presence of MDA-MB-231 but inhibited in the presence of MCF-10A cells. It is intriguing to speculate that loss of Fg-beta(15-42) binding by premalignant breast epithelial cells serves as a molecular switch to induce a highly aggressive, metastatic breast cancer phenotype. Hence, Fg-beta(15-42) represents a potential molecular target for therapeutic intervention of breast cancer metastasis.

Bbeta15-42 (FX06) reduces pulmonary, myocardial, liver, and small intestine damage in a pig model of hemorrhagic shock and reperfusion

OBJECTIVE

The fibrin-derived peptide Bbeta15-42 (also called FX06) has been shown to reduce myocardial infarct size following ischemia/reperfusion. Hemorrhagic shock (HS) followed by volume resuscitation represents a similar scenario, whereby a whole organism is vulnerable to reperfusion injury.

DESIGN

We subjected male farm-bred landrace pigs ( approximately 30 kg) to HS by withdrawing blood to a mean arterial pressure of 40 mm Hg for 60 minutes. Pigs were then resuscitated with shed blood and crystalloids for 60 minutes, and at this time, FX06 (2.4 mg/kg, n = 8) or vehicle control (phosphate buffered saline; 2.4 mg/kg, n = 7) was injected as an intravenous bolus.

SETTING

University hospital laboratory.

SUBJECTS

Anesthetized male farm-bred landrace pigs.

MEASUREMENTS AND MAIN RESULTS

Data are presented as mean +/- sd. Five hours after resuscitation, controls presented acute lung injury (Pao2/Fio2-ratio <300 mm Hg; extra-vascular lung water index (marker for lung injury): 9.0 +/- 1.8 mL/kg) and myocardial dysfunction/damage (cardiac index: 4.3 +/- 0.25 L/min/m; stroke volume index: 30 +/- 6 mL/m; cardiac TnT levels: 0.58 +/- 0.25 ng/mL). In contrast, FX06-treated animals showed significantly improved pulmonary and circulatory function (Pao2/Fio2-ratio >*400 mm Hg; extra-vascular lung water index: *5.2 +/- 2.1 mL/kg, cardiac index: *6.3 +/- 1.4 L/min/m; stroke volume index: *51 +/- 11 mL/m; cardiac TnT levels: *0.11 +/- 0.09 ng/mL; *p < 0.05). Also, tissue oxygenation (tpO2; mm Hg) was significantly improved during reperfusion in FX06-treated pigs when compared with controls (liver 51 +/- 4 vs. *65 +/- 4; serosa 44 +/- 5 vs. *55 +/- 7; mucosa 14 +/- 4 vs. *26 +/- 4). Finally, FX06 reduced accumulation of myeloperoxidase-positive cells (mainly neutrophils) in myocardium, liver, and small intestine and reduced interleukin-6 plasma levels (*p < 0.05; compared with controls).

CONCLUSION

We conclude that in a pig model of HS and reperfusion, administration of FX06 during reperfusion protects shock- susceptible organs such as heart, lung, liver, and small intestine.

Effect of intravenous FX06 as an adjunct to primary percutaneous coronary intervention for acute ST-segment elevation myocardial infarction results of the F.I.R.E. (Efficacy of FX06 in the Prevention of Myocardial Reperfusion Injury) trial

OBJECTIVES

The purpose of this study was to investigate whether FX06 would limit infarct size when given as an adjunct to percutaneous coronary intervention.

BACKGROUND

FX06, a naturally occurring peptide derived from human fibrin, has been shown to reduce myocardial infarct size in animal models by mitigating reperfusion injury.

METHODS

In all, 234 patients presenting with acute ST-segment elevation myocardial infarction were randomized in 26 centers. FX06 or matching placebo was given as intravenous bolus at reperfusion. Infarct size was assessed 5 days after myocardial infarction by late gadolinium enhanced cardiac magnetic resonance imaging. Secondary outcomes included size of necrotic core zone and microvascular obstruction at 5 days, infarct size at 4 months, left ventricular function, troponin I levels, and safety.

RESULTS

There were no baseline differences between groups. On day 5, there was no significant difference in total late gadolinium enhanced zone in the FX06 group compared with placebo (reduction by 21%; p = 0.207). The necrotic core zone, however, was significantly reduced by 58% (median 1.77 g [interquartile range 0.0, 9.09 g] vs. 4.20 g [interquartile range 0.3, 9.93 g]; p < 0.025). There were no significant differences in troponin I levels (at 48 h, -17% in the FX06 group). After 4 months, there were no longer significant differences in scar size. There were numerically fewer serious cardiac events in the FX06-treated group, and no differences in adverse events.

CONCLUSIONS

In this proof-of-concept trial, FX06 reduced the necrotic core zone as one measure of infarct size on magnetic resonance imaging, while total late enhancement was not significantly different between groups. The drug appears safe and well tolerated. (Efficacy of FX06 in the Prevention of Myocardial Reperfusion Injury [F.I.R.E.]; NCT00326976).

A double blind, single centre, sub-chronic reperfusion trial evaluating FX06 following haemorrhagic shock in pigs

OBJECTIVE

Haemorrhagic shock causes ischaemia and subsequent fluid resuscitation causes reperfusion injury, jointly resulting in high morbidity and mortality. We tested whether the anti-inflammatory fibrin-derived peptide, Bbeta(15-42), also called FX06, is tissue protective in a model of haemorrhagic shock.

METHODS

In a pig model, we standardised the severity of haemorrhagic shock by achieving a cumulative oxygen deficit of approximately 100ml/kg body weight by withdrawing blood over a period of 1h. This was followed by resuscitation with shed blood and full electrolyte solution, and pigs were monitored for 3 days. At reperfusion, 17 pigs were randomly assigned to FX06 or solvent treatment.

RESULTS

FX06-treated pigs demonstrated improved cardiac function (stroke volume index: 67ml/m(2) versus 33ml/m(2)), decreased troponin T release in the early reperfusion (0.24ng/ml versus 0.78ng/ml), decreased AST levels after 24h (106U/l versus 189U/l) and decreased creatinine levels after 24h (108micromol/l versus 159micromol/l). Furthermore, FX06-treated pigs demonstrated preservation of the gut/blood barrier, while controls demonstrated high endotoxin plasma levels indicating translocation of bacteria and/or its products (0.2EU/ml versus 24.3EU/ml) after 24h. This study also demonstrates a significantly improved neurological performance in the FX06 group as determined by S100beta serum levels (0.72microg/l versus 1.25microg/l) after 48h and neurological deficit scores (11 versus 70) after 24h.

CONCLUSION

FX06 - when administered as an adjunct to fluid resuscitation therapy - is organ protective in pigs. Further investigations are warranted to reveal the protective mechanism of FX06.

The fibrin-derived peptide Bbeta15-42 is cardioprotective in a pig model of myocardial ischemia-reperfusion injury

OBJECTIVE

The fibrin-derived peptide Bbeta15-42 has been shown to reduce infarct size in rodent models of ischemia-reperfusion injury. To increase its potential for translation into the clinic, we studied the effects of Bbeta15-42 in pigs, whose coronary anatomy is similar to that of humans. In addition, we evaluated the pharmacokinetics and safety of Bbeta15-42 in several species, including humans.

DESIGN

Animal study and phase I trial.

SETTING

University hospital and contract research laboratories.

SUBJECTS

Pigs/healthy volunteers.

INTERVENTIONS

Male farm-bred Landrace pigs were subjected to 1 hr of left anterior descending coronary artery occlusion followed by 3 hrs of reperfusion. At the time of reperfusion, Bbeta15-42 (2.4 mg/kg, n = 6) or random peptide (control; 2.4 mg/kg, n = 6) was administered as an intravenous bolus. As a positive control, pigs were subjected to ischemic preconditioning (n = 6). Cardiac damage and hemodynamics were recorded. Biodistribution and pharmacokinetics of Bbeta15-42 were determined in rats and dogs. In a phase I trial involving 30 male healthy volunteers, pharmacokinetics and safety were tested in a randomized, double-blinded, placebo-controlled, parallel-group, single ascending dose study.

MEASUREMENTS AND MAIN RESULTS

Bbeta15-42 and ischemic preconditioning significantly reduced myocardial infarct size and troponin I levels. Bbeta15-42 also reduces interleukin-6 levels, underlining its anti-inflammatory properties. Furthermore, in humans, the pharmacokinetics of the peptide Bbeta15-42 were comparable to those of animals, and no serious adverse effects were observed.

CONCLUSIONS

Bbeta15-42 elicits cardioprotection in pigs and is clinically safe in phase I testing of humans. This study confirms the new concept of a pathogenic role of fibrin derivatives in myocardial reperfusion injury, which can be inhibited by peptide Bbeta15-42.

[New reflections on inflammation and coagulation]

Inflammation is the host's defense mechanism to infection or injury, including surgical procedures. In the clinical setting non-infectious inflammation, activation of the coagulation cascade and deterioration of endothelial function play an important role in cardiology (e.g. percutaneous transluminal coronary angioplasty, PTCA), intensive care medicine (e.g. polytrauma), cardiac (e.g. extracorporal circulation) and vascular surgery (e.g. reperfusion injury). Imbalances in the inflammatory response are mainly responsible for the often fatal course in conditions such as myocardial infarction, sepsis, hemorrhagic fever (ebola, dengue), graft rejection and autoimmune diseases. Great efforts are being undertaken worldwide to understand the regulation of inflammation in order to develop new drugs which can modulate the pathologic inflammation reaction.