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

Fibrinogen Fragment X Mediates Endothelial Barrier Disruption via Suppression of VE-Cadherin

INTRODUCTION

Major traumatic injury is associated with early hemorrhage-related and late-stage deaths due to multiple organ failure (MOF). While improvements to hemostatic resuscitation have significantly reduced hemorrhage-related deaths, the incidence of MOF among trauma patients remains high. Dysregulation of vascular endothelial cell (EC) barrier function is a central mechanism in the development of MOF; however, the mechanistic triggers remain unknown. Accelerated fibrinolysis occurs in a majority of trauma patients, resulting in high circulating levels of fibrin(ogen) degradation products, such as fragment X. To date, the relationship between fragment X and EC dysregulation and barrier disruption is unknown. The goal of this study was to determine the effects of fragment X on EC barrier integrity and expression of paracellular junctional proteins that regulate barrier function.

METHODS

Human lung microvascular endothelial cells (HLMVECs) were treated with increasing concentrations of fragment X (1, 10, and 100 μg/mL), and barrier function was monitored using the xCELLigence live-cell monitoring system. Quantitative PCR (qPCR) was performed to measure changes in EC expression of 84 genes. Immunofluorescent (IF) cytostaining was performed to validate qPCR findings.

RESULTS

Fragment X treatment significantly increased endothelial permeability over time (P < 0.05). There was also a significant reduction in VE-cadherin mRNA expression in fragment X-treated HLMVECs compared to control (P = 0.01), which was confirmed by IF staining.

CONCLUSIONS

Fragment X may induce EC hyperpermeability by reducing VE-cadherin expression. This suggests that a targeted approach to disrupting EC-fragment X interactions could mitigate EC barrier disruption, organ edema, and MOF associated with major trauma.

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.

Protective Effect of Shenfu Injection () on Vascular Endothelial Damage in a Porcine Model of Hemorrhagic Shock

OBJECTIVE

To investigate the effects of Shenfu Injection (, SFI) on endothelial damage in a porcine model of hemorrhagic shock (HS).

METHODS

After being bled to a mean arterial pressure of 40±3 mm Hg and held for 60 min, 32 pigs were treated with a venous injection of either shed blood (transfusion group), shed blood and saline (saline group), shed blood and SFI (SFI group) or without resuscitation (sham group). Venous blood samples were collected and analyzed at baseline and 0, 1, 2, 4, and 6 h after HS. Tumor necrosis factor-α (TNF-α), serum interleuking (IL)-6, and IL-10 levels were measured by enzyme-linked immunosorbent assay (ELISA); expressions of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule 1 (ICAM -1), von Willebrand factor (vWF), plasminogen activator inhibitor-1 (PAI-1) and Bcl-2, Bax, and caspase-3 proteins were determined by Western blot.

RESULTS

The serum level of TNF-α in the SFI group was significantly lower than in the other groups at 0, 1, and 2 h after HS, while the level of IL-6 was lower at 4 and 6 h compared with the saline group (P<0.01 or P<0.05). The concentration of serum IL-10 was significantly higher in the SFI group than in the other groups at 0, 1, 4, and 6 h after HS (P<0.01). Western blot and immunohistochemistry of vascular tissue showed that the expression of caspase-3 was downregulated, and that of Bcl-2 and Bax was upregulated in the SFI group compared to other groups (P<0.05).

CONCLUSION

SFI attenuated endothelial injury in the porcine model of HS by inhibiting cell apoptosis, suppressing the formation of proinflammatory cytokines, and reducing endothelial activation.

Shenfu injection improves cerebral microcirculation and reduces brain injury in a porcine model of hemorrhagic shock

BACKGROUND

Shenfu injection (SFI) is a traditional Chinese herbal medicine which has been clinically used for treatment of septic shock and cardiac shock. The aim of this study was to clarify effects of SFI on cerebral microcirculation and brain injury after hemorrhagic shock (HS).

METHODS

Twenty-one domestic male Beijing Landrace pigs were randomly divided into three groups: SFI group (SFI, n = 8), saline group (SA, n = 8) or sham operation group (SO, n = 5). In the SFI group, animals were induced to HS by rapid bleeding to a mean arterial pressure of 40 mmHg within 10 minutes and maintained at 40±3 mmHg for 60 minutes. Volume resuscitation (shed blood and crystalloid) and SFI were given after 1 hour of HS. In the SA group, animals received the same dose of saline instead of SFI. In the SO group, the same surgical procedure was performed but without inducing HS and volume resuscitation. The cerebral microvascular flow index (MFI), nitric oxide synthase (NOS) expression, aquaporin-4 expression, interleukin-6, tumor necrosis factor-α (TNF-α) and ultrastructural of microvascular endothelia were measured.

RESULTS

Compared with the SA group, SFI significantly improved cerebral MFI after HS. SFI up regulated cerebral endothelial NOS expression, but down regulated interleukin-6, TNF-α, inducible NOS and aquaporin-4 expression compared with the SA group. The cerebral microvascular endothelial injury and interstitial edema in the SFI group were lighter than those in the SA group.

CONCLUSIONS

Combined application of SFI with volume resuscitation after HS can improve cerebral microcirculation and reduce brain injury.

Protective effect of Shenfu on gut epithelium in a porcine model of hemorrhagic shock

This study aimed to explore the protective effect of Shenfu on the hemodynamics and gut integrity in a porcine model of hemorrhagic shock. Hemorrhagic shock was induced in 32 domestic pigs with a rapid bleeding via the arterial sheath to a mean arterial pressure of 40 mm Hg within 10 min. Animals with hemorrhagic shock were then randomly assigned into the negative control group (n=8), receiving neither blood transfusion nor drug treatment; the blood transfusion group, in which animals were given blood transfusion alone; the saline group, in which animals were blood transfused and resuscitated with saline (3 mL/kg); and the Shenfu group, in which animals received blood transfusion and resuscitation with Shenfu (3 mL/kg). Blood tumor necrosis factor-alpha (TNF-ɑ) and interleukin-6 were measured using ELISAs. Tissue levels of superoxide dismutase (SOD), malondialdehyde (MDA), Na⁺/K⁺-ATPase, Ca++ATPase, myeloperoxidase (MPO), and fatty acid binding protein 2 (FABP2) were determined using respective quantitation kits. Fluid resuscitation with Shenfu significantly improved HR, CI, and MAP of pig with hemorrhagic shock, which was accompanied with mitigation of tissue damages in intestinal epithelium. Blood TNF-ɑ was reduced in the Shenfu group. Bcl-2 and cleaved caspase-3 expression in intestinal tissues were elevated and decreased, respectively, in pigs treated with Shenfu. Notably, treatment with Shenfu suppressed oxidative stress markers MDA, MPO, and FABP2 in the intestine. Oppositely, SOD, Na⁺/K⁺-ATPase and Ca++ATPase levels in intestinal tissues were promoted by Shenfu treatment. Shenfu demonstrates significant protective effect on the hemodynamics and gut epithelium of pigs with hemorrhagic shock.

Shen-fu injection alleviates acute renal injury by reducing cytokine levels and modulating apoptosis in a porcine hemorrhagic shock model

PURPOSE

Shen-fu injection (SFI) was used to intervene in the resuscitation of porcine hemorrhagic shock (HS) model to study its protective effects on acute kidney injury.

METHODS

After 60 min of HS, 28 animals were randomly assigned into four groups. The groups were as follows: hemorrhagic shock group (HS); HS resuscitation with shed-blood group (HSR); HS resuscitation with shed-blood and SFI (1 mL·kg-1) group (HSR-SFI); and the sham operation group (Sham). The bloods were analyzed for serum creatinine (sCr), cystatin C (CysC) and neutrophil gelatinase-associated lipocalin (NGAL). BAX, Bcl-2, and caspase-3 protein expressions by Western blot analysis and immunohistochemical staining. The renal tissues were removed and pathologic changes were observed.

RESULTS

Mean aortic pressure (MAP) in HSR-SFI groups were higher than that in HSR groups after shock. At the 6th hour after shock, the urine volume per hour in the HSR-SFI groups was more than that in the HSR groups. The sCr, NGAL, CysC and cytokine levels of HSR-SFI groups were lower. The Bcl-2 expression was increased in the HSR-SFI groups. The BAX and caspase-3 expressions were reduced. The histopathologic score in the HSR-SFI was lower.

CONCLUSIONS

SFI may reduce the risk of acute kidney injury (AKI) following hemorrhagic shock by attenuating systemic inflammatory responses, and regulating the expression of apoptosis-related proteins.

Cadherins, Selectins, and Integrins in CAM-DR in Leukemia

The interaction between leukemia cells and the bone microenvironment is known to provide drug resistance in leukemia cells. This phenomenon, called cell adhesion-mediated drug resistance (CAM-DR), has been demonstrated in many subsets of leukemia including B- and T-acute lymphoblastic leukemia (B- and T-ALL) and acute myeloid leukemia (AML). Cell adhesion molecules (CAMs) are surface molecules that allow cell-cell or cell-extracellular matrix (ECM) adhesion. CAMs not only recognize ligands for binding but also initiate the intracellular signaling pathways that are associated with cell proliferation, survival, and drug resistance upon binding to their ligands. Cadherins, selectins, and integrins are well-known cell adhesion molecules that allow binding to neighboring cells, ECM proteins, and soluble factors. The expression of cadherin, selectin, and integrin correlates with the increased drug resistance of leukemia cells. This paper will review the role of cadherins, selectins, and integrins in CAM-DR and the results of clinical trials targeting these molecules.

Ebola Hemorrhagic Shock Syndrome-on-a-Chip

Ebola virus, for which we lack effective countermeasures, causes hemorrhagic fever in humans, with significant case fatality rates. Lack of experimental human models for Ebola hemorrhagic fever is a major obstacle that hinders the development of treatment strategies. Here, we model the Ebola hemorrhagic syndrome in a microvessel-on-a-chip system and demonstrate its applicability to drug studies. Luminal infusion of Ebola virus-like particles leads to albumin leakage from the engineered vessels. The process is mediated by the Rho/ROCK pathway and is associated with cytoskeleton remodeling. Infusion of Ebola glycoprotein (GP_1,2) generates a similar phenotype, indicating the key role of GP_1,2 in this process. Finally, we measured the potency of a recently developed experimental drug FX06 and a novel drug candidate, melatonin, in phenotypic rescue. Our study confirms the effects of FX06 and identifies melatonin as an effective, safe, inexpensive therapeutic option that is worth investigating in animal models and human trials.

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 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.

Fibrinogen (FI)

Das Hauptsubstrat der Gerinnung ist Fibrinogen (FI). Bei akuter Blutung ist es zumeist der erste Gerinnungsfaktor, der kritische Grenzwerte erreicht (150–200 mg/dl). FI kann hervorragend mittels point-of-care-tauglicher viskoelastischer Methoden (Thrombelstographie oder Thrombelastometrie) monitiert werden. Die Substitution kann mittels Frischplasma, Cryopräzipitat oder Fibrinogenkonzentrat erfolgen. Frischplasma ist nicht besonders effektiv, mit einer erhöhten Morbidität, insbesondere bei kritisch Kranken, sowie mit Volumenbelastung assoziiert. Cryopräzipitat wird in einigen europäischen Ländern nicht angeboten. Die Gabe von Fibrinogenkonzentrat wird in verschiedenen Leitlinien empfohlen. Als Akut-Phase-Protein kann FI physiologischerweise bei Entzündungsprozessen, schweren Verletzungen sowie nach großen Operationen in kurzer Zeit auf über 1000 mg/dl ansteigen; wobei hier Fibrinogenspaltprodukte anti-inflammatorische und sogar antibakterielle Eigenschaften haben.

The inflammatory actions of coagulant and fibrinolytic proteases in disease

Aside from their role in hemostasis, coagulant and fibrinolytic proteases are important mediators of inflammation in diseases such as asthma, atherosclerosis, rheumatoid arthritis, and cancer. The blood circulating zymogens of these proteases enter damaged tissue as a consequence of vascular leak or rupture to become activated and contribute to extravascular coagulation or fibrinolysis. The coagulants, factor Xa (FXa), factor VIIa (FVIIa), tissue factor, and thrombin, also evoke cell-mediated actions on structural cells (e.g., fibroblasts and smooth muscle cells) or inflammatory cells (e.g., macrophages) via the proteolytic activation of protease-activated receptors (PARs). Plasmin, the principle enzymatic mediator of fibrinolysis, also forms toll-like receptor-4 (TLR-4) activating fibrin degradation products (FDPs) and can release latent-matrix bound growth factors such as transforming growth factor-β (TGF-β). Furthermore, the proteases that convert plasminogen into plasmin (e.g., urokinase plasminogen activator) evoke plasmin-independent proinflammatory actions involving coreceptor activation. Selectively targeting the receptor-mediated actions of hemostatic proteases is a strategy that may be used to treat inflammatory disease without the bleeding complications of conventional anticoagulant therapies. The mechanisms by which proteases of the coagulant and fibrinolytic systems contribute to extravascular inflammation in disease will be considered in this review.

Endothelial barrier dysfunction in septic shock

The endothelium provides an essential and selective membrane barrier that regulates the movement of water, solutes, gases, macromolecules and the cellular elements of the blood from the tissue compartment in health and disease. Its structure and continuous function is essential for life for all vertebrate organisms. Recent evidence indicates that the endothelial surface does not have a passive role in systemic inflammatory states such as septic shock. In fact, endothelial cells are in dynamic equilibrium with a myriad of inflammatory mediators and elements of the innate immune and coagulation systems to orchestrate the host response in sepsis. The barrier function of the endothelial surface is almost uniformly impaired in septic shock, and it is likely that this contributes to adverse outcomes. In this review, we will highlight recent advances in the understanding of the signalling events that regulate endothelial function and molecular events that induce endothelial dysfunction in sepsis. Endothelial barrier repair strategies as a treatment for sepsis include modulation of C5a, high-mobility group box 1 and VEGF receptor 2; stimulation of angiopoietin-1, sphingosine 1 phosphate receptor 1 and Slit; and a number of other innovative approaches.

Fibrinolysis and the control of blood coagulation

Fibrin plays an essential role in hemostasis as both the primary product of the coagulation cascade and the ultimate substrate for fibrinolysis. Fibrinolysis efficiency is greatly influenced by clot structure, fibrinogen isoforms and polymorphisms, the rate of thrombin generation, the reactivity of thrombus-associated cells such as platelets, and the overall biochemical environment. Regulation of the fibrinolytic system, like that of the coagulation cascade, is accomplished by a wide array of cofactors, receptors, and inhibitors. Fibrinolytic activity can be generated either on the surface of a fibrin-containing thrombus, or on cells that express profibrinolytic receptors. In a widening spectrum of clinical disorders, acquired and congenital defects in fibrinolysis contribute to disease morbidity, and new assays of global fibrinolysis now have potential predictive value in multiple clinical settings. Here, we summarize the basic elements of the fibrinolytic system, points of interaction with the coagulation pathway, and some recent clinical advances.

Pulmonary function after hemorrhagic shock and resuscitation in a porcine model

BACKGROUND

Hemorrhagic shock may trigger an inflammatory response and acute lung injury. The combination adenosine, lidocaine (AL) plus Mg(2+) (ALM) has organ-protective and anti-inflammatory properties with potential benefits in resuscitation.The aims of this study were to investigate: (1) pulmonary function and inflammation after hemorrhagic shock; (2) the effects of ALM/AL on pulmonary function and inflammation.

METHODS

Pigs (38 kg) were randomized to: sham + saline (n = 5); sham + ALM/AL (n = 5); hemorrhage control (n = 11); and hemorrhage + ALM/AL (n = 9). Hemorrhage animals bled to a mean arterial pressure (MAP) of 35 mmHg for 90 min, received resuscitation with Ringer's acetate and 20 ml of 7.5% NaCl with ALM to a minimum MAP of 50 mmHg, after 30 min shed blood and 0.9% NaCl with AL were infused. Hemorrhage controls did not receive ALM/AL. Primary endpoints were pulmonary wet/dry ratio, PaO2 /FiO2 ratio (partial pressure of arterial oxygen to the fraction of inspired oxygen), cytokine and protein measurements in bronchoalveolar lavage fluid (BALF) and lung tissue, neutrophil invasion and blood flow in lung tissue.

RESULTS

In the hemorrhage groups, wet/dry ratio increased significantly compared with the sham groups. PaO2 /FiO2 ratio decreased during shock but normalized after resuscitation. BALF did not indicate significant pulmonary inflammation, oxidative stress or increased permeability. Intervention with ALM caused a temporary increase in pulmonary vascular resistance and reduced urea diffusion across the alveolar epithelia, but had no effect on wet/dry ratio.

CONCLUSION

Hemorrhagic shock and resuscitation did not cause acute lung injury or pulmonary inflammation. The question whether ALM/AL has the potential to attenuate acute lung injury is unanswered.

The small fibrinopeptide Bβ15-42 as renoprotective agent preserving the endothelial and vascular integrity in early ischemia reperfusion injury in the mouse kidney

Disruption of the renal endothelial integrity is pivotal for the development of a vascular leak, tissue edema and consequently acute kidney injury. Kidney ischemia amplifies endothelial activation and up-regulation of pro-inflammatory mechanisms. After restoring a sufficient blood flow, the kidney is damaged through complex pathomechanisms that are classically referred to as ischemia and reperfusion injury, where the disruption of the inter-endothelial connections seems to be a crucial step in this pathomechanism. Focusing on the molecular cell-cell interaction, the fibrinopeptide Bβ_15–42 prevents vascular leakage by stabilizing these inter-endothelial junctions. The peptide associates with vascular endothelial-cadherin, thus preventing early kidney dysfunction by preserving blood perfusion efficacy, edema formation and thus organ dysfunction. We intended to demonstrate the early therapeutic benefit of intravenously administered Bβ_15–42 in a mouse model of renal ischemia and reperfusion. After 30 minutes of ischemia, the fibrinopeptide Bβ_15–42 was administered intravenously before reperfusion was commenced for 1 and 3 hours. We show that Bβ_15–42 alleviates early functional and morphological kidney damage as soon as 1 h and 3 h after ischemia and reperfusion. Mice treated with Bβ_15–42 displayed a significantly reduced loss of VE-cadherin, indicating a conserved endothelial barrier leading to less neutrophil infiltration which in turn resulted in significantly reduced structural renal damage. The significant reduction in tissue and serum neutrophil gelatinase-associated lipocalin levels reinforced our findings. Moreover, renal perfusion analysis by color duplex sonography revealed that Bβ_15–42 treatment preserved resistive indices and even improved blood velocity. Our data demonstrate the efficacy of early therapeutic intervention using the fibrinopeptide Bβ_15–42 in the treatment of acute kidney injury resulting from ischemia and reperfusion. In this context Bβ_15–42 may act as a potent renoprotective agent by preserving the endothelial and vascular integrity.

Resuscitation after hemorrhagic shock: the effect on the liver--a review of experimental data

The liver is currently considered to be one of the first organs to be subjected to the hypoxic insult inflicted by hemorrhagic shock. The oxidative injury caused by resuscitation also targets the liver and can lead to malfunction and the eventual failure of this organ. Each of the various fluids, vasoactive drugs, and pharmacologic substances used for resuscitation has its own distinct effect(s) on the liver, and the anesthetic agents used during surgical resuscitation also have an impact on hepatocytes. The aim of our study was to identify the specific effect of these substances on the liver. To this end, we conducted a literature search of MEDLINE for all types of articles published in English, with a focus on articles published in the last 12 years. Our search terms were "hemorrhagic shock," "liver," "resuscitation," "vasopressors," and "anesthesia." Experimental studies form the majority of articles found in bibliographic databases. The effect of a specific resuscitation agent on the liver is assessed mainly by measuring apoptotic pathway regulators and inflammation-induced indicators. Apart from a wide range of pharmacological substances, modifications of Ringer's Lactate, colloids, and pyruvate provide protection to the liver after hemorrhage and resuscitation. In this setting, it is of paramount importance that the treating physician recognize those agents that may attenuate liver injury and avoid using those which inflict additional damage.

Linking inflammation and coagulation: novel drug targets to treat organ ischemia

PURPOSE OF REVIEW

Activation of the coagulation system during ischemia/reperfusion injury is an unavoidable event and even further augmented during cardiovascular surgery. Clotting not only leads to disturbance of blood rheology but also enhances the inflammatory response. We aim to highlight the inflammatory properties of the coagulation system and novel potential therapeutic approaches targeting both features.

RECENT FINDINGS

Heparin, a thrombin inhibitor, is still the drug of choice for preventing coagulation following, for example, cardiovascular surgery. On the contrary, much effort is done to evaluate the utilization of direct thrombin inhibitors to prevent ischemia/reperfusion injury. Furthermore, targeting the inflammatory potential of the coagulation system seems to be very promising. Fibrin(ogen) and its degradation products modulate the inflammatory response, especially by inducing leukocyte migration. Inhibiting these pro-inflammatory effects, for example, by administration of Bβ15-42 was recently shown to be beneficial under various inflammatory conditions.

SUMMARY

Ischemia and reperfusion are common activators of coagulation that is also accompanied by inflammation. Therefore, targeting this well orchestrated system might be of therapeutic benefit, as its mode of action is dual: clotting inhibition and anti-inflammation. This novel therapeutic approach might at least be of benefit in the treatment of systemic inflammatory syndromes following, that is, cardiovascular surgery.

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.

Novel aspects of fibrin(ogen) fragments during inflammation

Coagulation is fundamental for the confinement of infection and/or the inflammatory response to a limited area. Under pathological inflammatory conditions such as arthritis, multiple sclerosis or sepsis, an uncontrolled activation of the coagulation system contributes to inflammation, microvascular failure and organ dysfunction. Coagulation is initiated by the activation of thrombin, which, in turn, triggers fibrin formation by the release of fibrinopeptides. Fibrin is cleaved by plasmin, resulting in clot lysis and an accompanied generation of fibrin fragments such as D and E fragments. Various coagulation factors, including fibrinogen and/or fibrin [fibrin(ogen)] and also fibrin degradation products, modulate the inflammatory response by affecting leukocyte migration and cytokine production. Fibrin fragments are mostly proinflammatory, however, Bβ15-42 in particular possesses potential antiinflammatory effects. Bβ15-42 inhibits Rho-kinase activation by dissociating Fyn from Rho and, hence prevents stress-induced loss of endothelial barrier function and also leukocyte migration. This article summarizes the state-of-the-art in inflammatory modulation by fibrin(ogen) and fibrin fragments. However, further research is required to gain better understanding of the entire role fibrin fragments play during inflammation and, possibly, disease development.

Extracorporeal immune therapy with immobilized agonistic anti-Fas antibodies leads to transient reduction of circulating neutrophil numbers and limits tissue damage after hemorrhagic shock/resuscitation in a porcine model

Background

Hemorrhagic shock/resuscitation is associated with aberrant neutrophil activation and organ failure. This experimental porcine study was done to evaluate the effects of Fas-directed extracorporeal immune therapy with a leukocyte inhibition module (LIM) on hemodynamics, neutrophil tissue infiltration, and tissue damage after hemorrhagic shock/resuscitation.

Methods

In a prospective controlled double-armed animal trial 24 Munich Mini Pigs (30.3 ± 3.3 kg) were rapidly haemorrhaged to reach a mean arterial pressure (MAP) of 35 ± 5 mmHg, maintained hypotensive for 45 minutes, and then were resuscitated with Ringer' solution to baseline MAP. With beginning of resuscitation 12 pigs underwent extracorporeal immune therapy for 3 hours (LIM group) and 12 pigs were resuscitated according to standard medical care (SMC). Haemodynamics, haematologic, metabolic, and organ specific damage parameters were monitored. Neutrophil infiltration was analyzed histologically after 48 and 72 hours. Lipid peroxidation and apoptosis were specifically determined in lung, bowel, and liver.

Results

In the LIM group, neutrophil counts were reduced versus SMC during extracorporeal immune therapy. After 72 hours, the haemodynamic parameters MAP and cardiac output (CO) were significantly better in the LIM group. Histological analyses showed reduction of shock-related neutrophil tissue infiltration in the LIM group, especially in the lungs. Lower amounts of apoptotic cells and lipid peroxidation were found in organs after LIM treatment.

Conclusions

Transient Fas-directed extracorporeal immune therapy may protect from posthemorrhagic neutrophil tissue infiltration and tissue damage.

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).