Peptide Bbeta(15-42) preserves endothelial barrier function in shock

Endothelial activation, dysfunction and permeability during severe infections

PURPOSE OF REVIEW

Over the last few years, there have been major advances in our understanding of the role of the microvascular endothelium in the pathogenesis of severe, systemic infections.

RECENT FINDINGS

Endothelial activation and dysfunction contribute directly to the morbidity and mortality of sepsis and other, severe systemic infections. The end-result of diffuse endothelial activation and dysfunction may be the loss of microvascular barrier integrity, leading to tissue edema, shock and multiple organ failure. Endothelial activation also leads to an increase in angiopoietin-2, which is known to destabilize barrier function and promote inflammation.

SUMMARY

The ratio of the secreted endothelial growth factors, angiopoietin-2 and angiopoietin-1 appears to be a useful prognostic tool during severe infections. Finally, agents that enhance endothelial barrier integrity may prove useful as therapies for sepsis.

Cyptoporus polysaccharide prevents lipopolysaccharide-induced acute lung injury associated with down-regulating Toll-like receptor 2 expression

AIM OF THE STUDY

To evaluate the effects and the possible mechanism of Cryptoporus polysaccharides (CP) extracted from fruiting body of Cryptoporus volvatus in lipopolysaccharide (LPS)-induced acute lung injury (ALI) in rats and mice.

MATERIALS AND METHODS

Acute lung injury was induced by intratracheally instillation of LPS into lung in either rats or mice, assessing leukocyte numbers and myeloperoxidase activity in bronchoalveolar lavage fluid, as well as evaluating cytokines mRNA and protein expressions, and Toll-like receptor 2 (TLR(2)) and nuclear factor (NF)-κB mRNA levels in the lung tissues of mice. Vascular permeability and edema of lung in mice, and arterial blood gas in rats were also performed.

RESULTS

In ALI, CP-treated mice and rats exhibited significantly reduced leukocyte invasion, myeloperoxidase activity, vascular permeability, edema of lung, as well as tumor necrosis factor-α and Interleukin-1β mRNA and protein expressions in the lung tissues compared with vehicle-treated mice. TLR(2) and NF-κB mRNA levels of the lung tissues were decreased in CP-treated mice in response to LPS. And decline in arterial blood gas was recovered in CP-treated rats.

CONCLUSIONS

Our results supported a protective role of CP in ALI and suggested that the reduction of the activation of TLR(2) and NF-κB signal pathway in lung injury may be relavant to the pretreatment of CP.

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.

Inhibition of Rac activity alleviates lipopolysaccharide-induced acute pulmonary injury in mice

BACKGROUND

Rac small GTPases play important roles in cytoskeleton and many cell functions including cell cycle, cell growth, cell adhesion and gene transcription. Here, we investigated the roles of Rac including Rac1 and Rac2 in lipopolysaccharide (LPS)-induced pulmonary injury.

METHODS

After LPS was intratracheally instilled to lungs in mice, Rac, CDC42 and RhoA activation assay by pull-down and West blot, inflammatory cell infiltration assay by counting cell numbers and lung histological examination, pro-inflammatory mediator mRNA expression assay by quantitative RT-PCR, measurement of myeloperoxidase (MPO) activity, Evans Blue and albumin accumulation by spectrophotometry were performed to evaluate the roles of Rac in pulmonary injury by using its specific inhibitor, NSC23766.

RESULTS

LPS challenge led to increases of both Rac1 and Rac2, but not CDC42 or RhoA activities in lungs, and intraperitoneal administration with NSC23766 inhibited both Rac1 and Rac2, but not CDC42 or RhoA activities. Treatment with NSC23766 at 1 or 3mg/kg not only reduced the inflammatory cells infiltration and MPO activities, but also inhibited pro-inflammatory mediators, tumor necrosis factor-α and interleukin-1β, mRNA expression. Moreover, in vitro neutrophil migration assay and in vivo microvascular permeability assay indicated that NSC23766 not only inhibited neutrophil transwell migration toward a chemoattractant, fMLP, but also reduced Evans Blue and albumin accumulation in LPS-challenged lungs. LPS activated both Rac1 and Rac2, but not CDC42 or RhoA activities in lungs, and specific inhibition of Rac activities by NSC23766 effectively alleviated LPS-induced injury.

GENERAL SIGNIFICANCE

Rac could be a potential target for therapeutic intervention of pulmonary inflammation.

Fibrinogen β-derived Bβ(15-42) peptide protects against kidney ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury in the kidney is a major cause of acute kidney injury (AKI) in humans and is associated with significantly high mortality. To identify genes that modulate kidney injury and repair, we conducted genome-wide expression analysis in the rat kidneys after I/R and found that the mRNA levels of fibrinogen (Fg)α, Fgβ, and Fgγ chains significantly increase in the kidney and remain elevated throughout the regeneration process. Cellular characterization of Fgα and Fgγ chain immunoreactive proteins shows a predominant expression in renal tubular cells and the localization of immunoreactive Fgβ chain protein is primarily in the renal interstitium in healthy and regenerating kidney. We also show that urinary excretion of Fg is massively increased after kidney damage and is capable of distinguishing human patients with acute or chronic kidney injury (n = 25) from healthy volunteers (n = 25) with high sensitivity and specificity (area under the receiver operating characteristic of 0.98). Furthermore, we demonstrate that Fgβ-derived Bβ(15-42) peptide administration protects mice from I/R-induced kidney injury by aiding in epithelial cell proliferation and tissue repair. Given that kidney regeneration is a major determinant of outcome for patients with kidney damage, these results provide new opportunities for the use of Fg in diagnosis, prevention, and therapeutic interventions in kidney disease.

Potential Agents against Plasma Leakage

Shock due to severe plasma leakage may happen in infectious diseases such as severe dengue and sepsis due to various bacterial infections, which may be deleterious and may lead to death. Various substances and proteins are known to modulate the effects of proleakage mediators and counteract the deleterious effect of plasma leakage. Some of the various substances and proteins such as focal adhesion kinase (FAK), the Rho GTPases, protein kinase A, and caveolin-1 have dual actions; therefore they are not suitable for therapy. However, sphingosine 1phosphate and its receptor agonists, Angiopoetin-1, Slit, and Bbeta15-42 may be promising.

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.

p190RhoGAP mediates protective effects of oxidized phospholipids in the models of ventilator-induced lung injury

Products resulting from oxidation of cell membrane phospholipid 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (OxPAPC) exhibit potent protective effects against lung endothelial cell (EC) barrier dysfunction caused by pathologically relevant mechanical forces and inflammatory agents. These effects were linked to enhancement of peripheral cytoskeleton and cell adhesion interactions mediated by small GTPase Rac and inhibition of Rho-mediated barrier-disruptive signaling. However, the mechanism of OxPAPC-induced, Rac-dependent Rho downregulation critical for vascular barrier protection remains unclear. This study tested the hypothesis that Rho negative regulator p190RhoGAP is essential for OxPAPC-induced lung barrier protection against ventilator-induced lung injury (VILI), and investigated potential mechanism of p190RhoGAP targeting to adherens junctions (AJ) via p120-catenin. OxPAPC induced peripheral translocation of p190RhoGAP, which was abolished by knockdown of Rac-specific guanine nucleotide exchange factors Tiam1 and Vav2. OxPAPC also induced Rac-dependent tyrosine phosphorylation and association of p190RhoGAP with AJ protein p120-catenin. siRNA-induced knockdown of p190RhoGAP attenuated protective effects of OxPAPC against EC barrier compromise induced by thrombin and pathologically relevant cyclic stretch (18% CS). In vivo, p190RhoGAP knockdown significantly attenuated protective effects of OxPAPC against ventilator-induced lung vascular leak, as detected by increased cell count and protein content in the bronchoalveolar lavage fluid, and tissue neutrophil accumulation in the lung. These results demonstrate for the first time a key role of p190RhoGAP for the vascular endothelial barrier protection in VILI.

Control of endothelial barrier function by regulating vascular endothelial-cadherin

PURPOSE OF REVIEW

Proper control of endothelial cell contacts is the basis for maintenance of the vascular barrier function. Loss of this function leads to leak of fluid and protein from the vasculature and extensive leaks cause shock and death. The endothelial barrier also controls the entry of leukocytes into tissue and it is believed that leukocytes target endothelial cell contacts to reach sites of inflammation.

RECENT FINDINGS

Within the last 2 years several new molecular players and molecular interactions have been identified that either help in stabilizing the endothelial contacts or mediate their opening if triggered by the appropriate stimuli. Novel signaling mechanisms have been identified that regulate endothelial cell contacts. Whether, how and to what extent the complex of the endothelial specific adhesion molecule vascular endothelial-cadherin and its associated catenins is involved in these processes will be a major focus of this article.

SUMMARY

Endothelial cell contacts are regulated by a complex interplay between various receptors and signaling mediators that control the plasticity of the cytoskeleton and the function of junctional adhesion molecules. Knowing and understanding the essential players of this network will allow development of agents that could prevent breakdown of the vascular permeability barrier in shock or that could block leukocyte extravasation and thereby antagonize inflammation.

The fibrin-derived peptide Bbeta(15-42) significantly attenuates ischemia-reperfusion injury in a cardiac transplant model

BACKGROUND

The inflammatory response after prolonged ischemia and subsequent reperfusion leads to increased risk of primary organ dysfunction after cardiac transplantation. It has been demonstrated that the fibrin-derived peptide Bbeta(15-42) (also called FX06) reduces infarct size in coronary artery occlusion/reperfusion models by inhibition of leukocyte migration. Further, Bbeta(15-42) preserves endothelial barrier function. The purpose of this study was to investigate whether Bbeta(15-42) has a protective effect in cardiac allografts exposed to prolonged global ischemia and subsequent in vivo reperfusion.

METHODS

Hearts of male Lewis rats were flushed and stored in cold Bretschneider preservation solution for 4 or 8 hr. Bbeta(15-42) was administered before being transplanted into syngeneic recipients. Serum samples were collected for troponin-T measurements. Hemodynamic performance was evaluated after a reperfusion period of 24 hr. Morphologic quantification of myocardial necrosis was performed in hearts exposed to 24 hr or 10 days of reperfusion.

RESULTS

Allografts from Bbeta(15-42) treated animals showed less myocardial necrosis (2.5% +/- 2.5% vs. 18.4% +/- 9.2%, P=0.0019) and decreased values of cardiac troponin-T (1.1 +/- 0.6 ng/mL vs. 2.7+/-2.3 ng/mL, P=0.0045), reduced number of infiltrating leukocytes (7.2 +/- 13.6 vs. 49.2 +/- 34.9 per high powerfield, P=0.0045), and superior cardiac output (78.1 +/- 1.8 mL/min vs. 21.7 +/- 4 mL/min, P = 0.0034). Hearts exposed to 0 and 4 hr of ischemia showed no severe signs of myocardial damage.

CONCLUSION

Bbeta(15-42) ameliorates the ischemia-reperfusion injury in transplanted hearts during extended cold ischemia by reduction of infiltrating leukocytes. This experimental protocol provides evidence that Bbeta(15-42) may play a useful role in organ preservation, but clinical evaluation is warranted.

Matrix biology meets toxinology

Venoms are cocktails containing pharmacologically active compounds, which drastically affect essential functions of the neuromuscular and cardiovascular system, as well as of blood, kidney and other organs. As the extracellular matrix and its contacts with cells are responsible for maintaining the integrity and functionality of these organs and tissues, it is not surprising that several venom components target matrix molecules and their respective cellular receptors. Many venom components, such as matrix-degrading enzymes, disintegrins, and C-type lectin-like proteins, have been identified and have laid the foundation for the frontier research field of matrix toxinology. Interestingly, many toxins consist of domains which are structurally homologous to modules and domains of matrix proteins, their proteinases and cellular receptors. In addition to finding new agents and tools, which specifically interact with matrix molecules and their receptors, the characterization of known matrix-targeting toxins will provide insights into their molecular modes of action and thus may lead to potential new therapeutic strategies for treating matrix-related diseases, such as blood clotting and thrombocyte-mediated disorders, but also tumor malignancies.