Lack of alpha2-antiplasmin promotes pulmonary heart failure via overrelease of VEGF after acute myocardial infarction

Alpha2-Antiplasmin: The Devil You Don't Know in Cerebrovascular and Cardiovascular Disease

Alpha2-antiplasmin (α2AP), the fast-reacting, serine protease inhibitor (serpin) of plasmin, was originally thought to play a key role in protection against uncontrolled, plasmin-mediated proteolysis of coagulation factors and other molecules. However, studies of humans and mice with genetic deficiency of α2AP have expanded our understanding of this serpin, particularly in disease states. Epidemiology studies have shown an association between high α2AP levels and increased risk or poor outcome in cardiovascular diseases. Mechanistic studies in disease models indicate that α2AP stops the body's own fibrinolytic system from dissolving pathologic thrombi that cause venous thrombosis, pulmonary embolism, arterial thrombosis, and ischemic stroke. In addition, α2AP fosters the development of microvascular thrombosis and enhances matrix metalloproteinase-9 expression. Through these mechanisms and others, α2AP contributes to brain injury, hemorrhage and swelling in experimental ischemic stroke. Recent studies also show that α2AP is required for the development of stasis thrombosis by inhibiting the early activation of effective fibrinolysis. In this review, we will discuss the key role played by α2AP in controlling thrombosis and fibrinolysis and, we will consider its potential value as a therapeutic target in cardiovascular diseases and ischemic stroke.

Microneedle-mediated gene delivery for the treatment of ischemic myocardial disease

Cardiovascular disorders are still the primary cause of mortality worldwide. Although intramyocardial injection can effectively deliver agents to the myocardium, this approach is limited because of its restriction to needle-mediated injection and the minor retention of agents in the myocardium. Here, we engineered phase-transition microneedles (MNs) coated with adeno-associated virus (AAV) and achieved homogeneous distribution of AAV delivery. Bioluminescence imaging revealed the successful delivery and transfection of AAV-luciferase. AAV-green fluorescent protein-transfected cardiomyocytes were homogeneously distributed on postoperative day 28. AAV-vascular endothelial growth factor (VEGF)-loaded MNs improved heart function by enhancing VEGF expression, promoting functional angiogenesis, and activating the Akt signaling pathway. The results indicated the superiority of MNs over direct muscle injection. Consequently, MNs might emerge as a promising tool with great versatility for delivering various agents to treat ischemic myocardial disease.

Collagen-binding VEGF targeting the cardiac extracellular matrix promotes recovery in porcine chronic myocardial infarction

An effective therapy for chronic myocardial infarction (MI) has yet to be developed. Vascular endothelial growth factor (VEGF) promotes angiogenesis and improves cardiac function after MI. However, non-targeted delivery of VEGF decreases its therapeutic efficacy. In this study, for targeting the cardiac extracellular matrix, a collagen-binding domain (CBD) VEGF was used to bind specifically to the collagen-rich cardiac extracellular matrix. When intramyocardially injected into the peri-infarct region of a chronically infarcted porcine heart, CBD-VEGF attenuated the remodeling of the left ventricle with a decreased infarct size and promoted cardiomyocyte survival and angiogenesis 3 months after injection. In the 12-month trial, mature vessel networks and myocardium-like tissues were observed in the infarct region after CBD-VEGF injection. Also these beneficial effects might derive from CBD-VEGF significantly protecting cardiomyocytes from apoptosis and recruiting cardiac progenitor cells to the infarcted region. These results demonstrated that CBD-VEGF could be a promising therapeutic strategy for chronic MI.

Design and Use of Chimeric Proteins Containing a Collagen-Binding Domain for Wound Healing and Bone Regeneration

Collagen-based biomaterials are widely used in the field of tissue engineering; they can be loaded with biomolecules such as growth factors (GFs) to modulate the biological response of the host and thus improve its potential for regeneration. Recombinant chimeric GFs fused to a collagen-binding domain (CBD) have been reported to improve their bioavailability and the host response, especially when combined with an appropriate collagen-based biomaterial. This review first provides an extensive description of the various CBDs that have been fused to proteins, with a focus on the need for accurate characterization of their interaction with collagen. The second part of the review highlights the benefits of various CBD/GF fusion proteins that have been designed for wound healing and bone regeneration.

Urokinase-type Plasminogen Activator (uPA) Promotes Angiogenesis by Attenuating Proline-rich Homeodomain Protein (PRH) Transcription Factor Activity and De-repressing Vascular Endothelial Growth Factor (VEGF) Receptor Expression

Urokinase-type plasminogen activator (uPA) regulates angiogenesis and vascular permeability through proteolytic degradation of extracellular matrix and intracellular signaling initiated upon its binding to uPAR/CD87 and other cell surface receptors. Here, we describe an additional mechanism by which uPA regulates angiogenesis. Ex vivo VEGF-induced vascular sprouting from Matrigel-embedded aortic rings isolated from uPA knock-out (uPA(-/-)) mice was impaired compared with vessels emanating from wild-type mice. Endothelial cells isolated from uPA(-/-) mice show less proliferation and migration in response to VEGF than their wild type counterparts or uPA(-/-) endothelial cells in which expression of wild type uPA had been restored. We reported previously that uPA is transported from cell surface receptors to nuclei through a mechanism that requires its kringle domain. Intranuclear uPA modulates gene transcription by binding to a subset of transcription factors. Here we report that wild type single-chain uPA, but not uPA variants incapable of nuclear transport, increases the expression of cell surface VEGF receptor 1 (VEGFR1) and VEGF receptor 2 (VEGFR2) by translocating to the nuclei of ECs. Intranuclear single-chain uPA binds directly to and interferes with the function of the transcription factor hematopoietically expressed homeodomain protein or proline-rich homeodomain protein (HHEX/PRH), which thereby lose their physiologic capacity to repress the activity of vehgr1 and vegfr2 gene promoters. These studies identify uPA-dependent de-repression of vegfr1 and vegfr2 gene transcription through binding to HHEX/PRH as a novel mechanism by which uPA mediates the pro-angiogenic effects of VEGF and identifies a potential new target for control of pathologic angiogenesis.

Extracellular Vesicle Proteins Associated with Systemic Vascular Events Correlate with Heart Failure: An Observational Study in a Dyspnoea Cohort

Background

SerpinF2, SerpinG1, CystatinC and CD14 are involved in inflammatory processes and plasma extracellular vesicle (EV) -levels of these proteins have been reported to be associated with systemic vascular events. Evidence is accumulating that inflammatory processes may play a pivotal role both in systemic vascular events and in heart failure. Therefore, we studied the association between plasma extracellular vesicle SerpinF2-, SerpinG1-, CystatinC and CD14-levels and the occurrence of acute heart failure in patients.

Methods and Result

Extracellular vesicle protein levels of SerpinG1, SerpinF2, CystatinC and CD14 were measured in an observational study of 404 subjects presenting with dysponea at the emergency department (4B-cohort). Plasma extracellular vesicles were precipitated in a total extracellular vesicles (TEX)-fraction and in separate LDL- and HDL-subfractions. Extracellular vesicle protein levels were measured with a quantitative immune assay in all 3 precipitates. Out of 404 subjects, 141 (35%) were diagnosed with acutely decompensated heart failure. After correction for confounders (including comorbidities and medications), levels of CD14 in the HDL-fraction (OR 1.53, p = 0.01), SerpinF2 in the TEX-and LDL-fraction (ORs respectively 0.71 and 0.65, p<0.05) and SerpinG1 in the TEX-fraction (OR 1.55, p = 0.004) were statistically significantly related to heart failure. Furthermore, extracellular vesicle CD14- and SerpinF2-levels were significantly higher in heart failure patients with preserved ejection fraction than in those with reduced ejection fraction.

Conclusion

Extracellular vesicle levels of CD14, SerpinG1 and SerpinF2 are associated with the occurrence of heart failure in subjects suspected for acute heart failure, suggesting common underlying pathophysiological mechanisms for heart failure and vascular events.

Impact of the Pla protease substrate α2-antiplasmin on the progression of primary pneumonic plague

Many pathogens usurp the host hemostatic system during infection to promote pathogenesis. Yersinia pestis, the causative agent of plague, expresses the plasminogen activator protease Pla, which has been shown in vitro to target and cleave multiple proteins within the fibrinolytic pathway, including the plasmin inhibitor α2-antiplasmin (A2AP). It is not known, however, if Pla inactivates A2AP in vivo; the role of A2AP during respiratory Y. pestis infection is not known either. Here, we show that Y. pestis does not appreciably cleave A2AP in a Pla-dependent manner in the lungs during experimental pneumonic plague. Furthermore, following intranasal infection with Y. pestis, A2AP-deficient mice exhibit no difference in survival time, bacterial burden in the lungs, or dissemination from wild-type mice. Instead, we found that in the absence of Pla, A2AP contributes to the control of the pulmonary inflammatory response during infection by reducing neutrophil recruitment and cytokine production, resulting in altered immunopathology of the lungs compared to A2AP-deficient mice. Thus, our data demonstrate that A2AP is not significantly affected by the Pla protease during pneumonic plague, and although A2AP participates in immune modulation in the lungs, it has limited impact on the course or ultimate outcome of the infection.

Modified VEGF targets the ischemic myocardium and promotes functional recovery after myocardial infarction

Vascular endothelial growth factor (VEGF) promotes angiogenesis and improves cardiac function after myocardial infarction (MI). However, the non-targeted delivery of VEGF decreases its therapeutic efficacy due to an insufficient local concentration in the ischemic myocardium. In this study, we used a specific peptide to modify VEGF and determined that this modified VEGF (IMT-VEGF) localized to the ischemic myocardium through intravenous injection by interacting with cardiac troponin I (cTnI). When IMT-VEGF was used to mediate cardiac repair in a rat model of ischemia-reperfusion (I-R) injury, we observed a decreased scar size, enhanced angiogenesis and improved cardiac function. Moreover, an alternative treatment using the repeated administration of a low-dose IMT-VEGF also promoted angiogenesis and functional recovery. The therapeutic effects of IMT-VEGF were further confirmed in a pig model of MI as the result of the conserved properties of its interacting protein, cTnI. These results suggest a promising therapeutic strategy for MI based on the targeted delivery of IMT-VEGF.

Endogenous α2-antiplasmin is protective during severe gram-negative sepsis (melioidosis)

RATIONALE

α2-Antiplasmin (A2AP) is a major inhibitor of fibrinolysis by virtue of its capacity to inhibit plasmin. Although the fibrinolytic system is strongly affected by infection, the functional role of A2AP in the host response to sepsis is unknown.

OBJECTIVES

To study the role of A2AP in melioidosis, a common form of community-acquired sepsis in Southeast Asia and Northern Australia caused by the gram-negative bacterium Burkholderia pseudomallei.

METHODS

In a single-center observational study A2AP was measured in patients with culture-proven septic melioidosis. Wild-type and A2AP-deficient (A2AP(-/-)) mice were intranasally infected with B. pseudomallei to induce severe pneumosepsis (melioidosis). Parameters of inflammation and coagulation were measured, and survival studies were performed.

MEASUREMENTS AND MAIN RESULTS

Patients with melioidosis showed elevated A2AP plasma levels. Likewise, A2AP levels in plasma and lung homogenates were elevated in mice infected with B. pseudomallei. A2AP-deficient (A2AP(-/-)) mice had a strongly disturbed host response during experimental melioidosis as reflected by enhanced bacterial growth at the primary site of infection accompanied by increased dissemination to distant organs. In addition, A2AP(-/-) mice showed more severe lung pathology and injury together with an increased accumulation of neutrophils and higher cytokine levels in lung tissue. A2AP deficiency further was associated with exaggerated systemic inflammation and coagulation, increased distant organ injury, and enhanced lethality.

CONCLUSIONS

This study is the first to identify A2AP as a protective mediator during gram-negative (pneumo)sepsis by limiting bacterial growth, inflammation, tissue injury, and coagulation.

Vascular endothelial growth factor and uPA/suPAR system in early and advanced chronic kidney disease patients: a new link between angiogenesis and hyperfibrinolysis?

Disturbances in hemostasis and abnormal angiogenesis are components in the plaque growth and destabilization. The role of the vascular endothelial growth factor (VEGF) in the perturbation of hemostasis in chronic kidney disease (CKD) is still unknown. In this preliminary study, we investigate the relation between VEGF and the parameters of coagulation: tissue factor (TF), its inhibitor (TFPI), and fibrinolytic system: urokinase-type plasminogen activator (uPA), its soluble receptor (suPAR), tissue-type plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1), plasmin/antiplasmin complexes (PAP) in the patients with mild-to-moderate, and severe CKD and healthy controls. All indices (except TFPI) were raised in CKD patients, particularly in those with severe CKD, compared with controls. The strong positive correlations were between VEGF and some parameters, both coagulation (TF, TFPI, TF/TFPI ratio) and fibrinolytic system (uPA, suPAR, PAP). The relationships were also between the individual hemostatic parameters. In multiple regression analysis, VEGF and kidney dysfunction markers (urea and creatinine levels) were independently associated with uPA, and VEGF was independently associated with suPAR levels. Moreover, PAP was independently associated with age and suPAR. This study represents the first to investigate the relation between VEGF and the activation both coagulation and fibrinolysis in CKD patients. VEGF and the parameters of hemostatic system activation were higher in the CKD group than in the controls with a significant correlation between them. VEGF was independently associated with uPA/suPAR system, whereas suPAR was independently related to PAP levels, suggesting a new link between abnormal angiogenesis and hyperfibrinolysis in this population.

Alpha II Antiplasmin Deficiency Complicating Pregnancy: A Case Report

Background. Alpha II antiplasmin is a protein involved in the inhibition of fibrinolysis. A deficiency in this protein leads to increased hemorrhage. It is inherited in an autosomal recessive fashion. Case. 30-year-old Gravida 1, Para 0, presented for prenatal care with her first and subsequently her second pregnancy. Her medical history was significant for a known deficiency in alpha II antiplasmin. Her first and second pregnancies were complicated by nonobstetrical hemorrhage requiring transfusions and severe preeclampsia requiring preterm deliveries. Conclusion. Alpha II antiplasmin deficiency resulted in multiple episodes of nonobstetrical hemorrhages requiring transfusion and ultimately preterm deliveries due to severe preeclampsia. Both infants and mother had a good outcome. The presence of this disorder may require a multidisciplinary team approach involving obstetricians, pediatricians, and hematologists. Precis. Alpha II antiplasmin deficiency is a rare autosomal recessive disorder leading to increased fibrinolysis and hemorrhage. We present a case report of a pregnancy complicated by this disorder.

Coexpression of VEGF and angiopoietin-1 promotes angiogenesis and cardiomyocyte proliferation reduces apoptosis in porcine myocardial infarction (MI) heart

VEGF and angiopoietin-1 (Ang1) are two major angiogenic factors being investigated for the treatment of myocardial infarction (MI). Targeting VEGF and Ang1 expression in the ischemic myocardium can increase their local therapeutic effects and reduce possible adverse effects. Adeno-associated viral vectors (AAVs) expressing cardiac-specific and hypoxia-inducible VEGF [AAV-myosin light chain-2v (MLC)VEGF] and Ang1 (AAV-MLCAng1) were coinjected (VEGF/Ang1 group) into six different sites of the porcine myocardium at the peri-infarct zone immediately after ligating the left descending coronary artery. An identical dose of AAV-Cytomegalovirus (CMV)LacZ or saline was injected into control animals. AAV genomes were detected in the liver in addition to the heart. RT-PCR, Western blotting, and ELISA analyses showed that VEGF and Ang1 were predominantly expressed in the myocardium in the infarct core and border of the infarct heart. Gated single-photon emission computed tomography analyses showed that the VEGF/Ang1 group had better cardiac function and myocardial perfusion at 8 wk than at 2 wk after vector injection. Compared with the saline and LacZ controls, the VEGF/Ang1 group expressed higher phosphorylated Akt and Bcl-xL, less Caspase-3 and Bad, and had higher vascular density, more proliferating cardiomyocytes, and less apoptotic cells in the infarct and peri-infarct zones. Thus, cardiac-specific and hypoxia-induced coexpression of VEGF and Ang1 improves the perfusion and function of porcine MI heart through the induction of angiogenesis and cardiomyocyte proliferation, activation of prosurvival pathways, and reduction of cell apoptosis.

Collagen-targeting vascular endothelial growth factor improves cardiac performance after myocardial infarction

BACKGROUND

Vascular endothelial growth factor (VEGF) is an important active protein for the induction of angiogenesis and improvement in cardiac function after myocardial ischemia; however, the lack of a delivery system targeted to the injured myocardium reduces the local therapeutic efficacy of VEGF and increases its possible adverse effects.

METHODS AND RESULTS

We produced a fusion protein (CBD-VEGF) consisting of VEGF and a collagen-binding domain (CBD). The fusion protein specifically bound to type I collagen in vitro. In addition, CBD-VEGF promoted human umbilical vein endothelial cell proliferation after binding to collagen, which indicates that it retained both growth factor activity and collagen-binding ability. When implanted subcutaneously in rats, collagen membranes loaded with CBD-VEGF were significantly vascularized. After it was injected into rats with acute myocardial infarction, CBD-VEGF was largely retained in the cardiac extracellular matrix, in which collagen I was rich. Four weeks after VEGF or CBD-VEGF was injected into the infarct border zone, cardiac function detected by echocardiography and hemodynamics was preserved in the CBD-VEGF group. Administration of CBD-VEGF also induced reduction of scar size, whereas native VEGF did not have these effects. In addition, a significant increase in the number of capillary vessels in infarcted hearts was found in the CBD-VEGF group.

CONCLUSIONS

The injection of CBD-VEGF improved cardiac function in rats with induced acute myocardial infarction. This could potentially provide a new treatment option for myocardial infarction.

Vascular endothelial growth factors in pulmonary edema: an update

Pulmonary edema is a life-threatening complication of critical illness. Identification of the underlying mechanisms of pulmonary edema is a prerequisite for the development of adequate treatment. The initial description of fluid transportation across capillaries (Starling's law) while of critical importance, did not provide full insight into the underlying pathophysiology of vascular leakage. Pulmonary edema can be differentiated into two distinct categories based on the Starling theory; the high-permeability type is attributed to inflammatory changes occurring in conditions such as the adult respiratory distress syndrome (ARDS) and the cardiogenic type is characterized by an imbalance in the Starling hydrostatic forces and occurs in acute or decompensated heart failure. However, it has long been recognized that there is significant overlap between the various types of pulmonary edema, raising important questions regarding the role of novel mechanisms that may contribute to the development of interstitial and alveolar leakage. Recently, several studies on VEGF, an angiogenic growth factor which affects endothelial permeability, have identified this molecule as a potential regulator of vascular leakage and repair in pulmonary edema. We review here the underlying the mechanisms by which VEGF may do this and will discuss the still unanswered questions regarding vascular pharmacology in the setting of pulmonary edema.

Lack of alpha2-antiplasmin improves cutaneous wound healing via over-released vascular endothelial growth factor-induced angiogenesis in wound lesions

BACKGROUND

The fibrinolytic system is supposed to play an important role in the degradation of extracellular matrices for physiological and pathological tissue remodeling; however, the detailed mechanism regarding how this system affects cutaneous wound healing remains to be clarified.

METHODS AND RESULTS

We performed experimental cutaneous wounding in mice with a deficiency of alpha(2)-antiplasmin (alpha(2)AP), which is a potent and specific plasmin inhibitor. We found that an accelerated wound closure was observed in alpha(2)AP-deficient (alpha(2)AP-/-) mice in comparison with wild type (WT) mice. Moreover, we observed that a greater increase of angiogenesis occurred in the process of wound healing in alpha(2)AP-/- mice than in the WT mice. Intriguingly, mRNA expression of vascular endothelial growth factor (VEGF), which is the best characterized positive regulator of angiogenesis, in wound lesions was found to show a greater increase in the early phase of the healing process in alpha(2)AP-/- mice than in WT mice. In addition, the amount of released-VEGF from the explanted fibroblasts of alpha(2)AP-/- mice increased dramatically more than in the WT mice. Finally, the intra-jugular administration of anti-VEGF antibody clearly suppressed the increased angiogenesis and accelerated wound closure in the wound lesion of alpha(2)AP-/- mice.

CONCLUSION

The lack of alpha(2)AP markedly causes an over-release of VEGF from the fibroblasts in cutaneous wound lesions, thereby inducing angiogenesis around the area, and thus resulting in an accelerated-wound closure.

CONCLUSIONS

This is the first report to describe the crucial role that alpha(2)AP plays following angiogenesis in the process of wound healing. Our results provide new insight into the role of alpha(2)AP on cutaneous wound healing.

The fibrinolysis inhibitor alpha2-antiplasmin in the human cornea

PURPOSE

To determine whether the cornea contains and expresses, at the gene level, the major plasmin inhibitor alpha2-antiplasmin.

METHODS

Corneal sections were immunostained for alpha2-antiplasmin. Extracts of human corneal stroma, epithelium, and endothelium were subjected to immunodot blot and Western blot analysis. Total RNA and alpha2-antiplasmin specific primers were used for RT-PCR. The cDNA was sequenced.

RESULTS

Alpha2-antiplasmin was observed in all three corneal layers by immunolocalization and Western blots. The major alpha2-antiplasmin form observed in most extracts was the 70-kDa form. Total alpha2-antiplasmin was present at 0.119 +/- 0.014 microg/epithelium (n = 10) and 1.45 +/- 0.47 microg/stroma (n = 10). Alpha2-antiplasmin mRNA was detected in epithelial and stromal extracts and cultured human corneal stromal cells. The sequences of the PCR products were identical to that for human alpha2-antiplasmin.

CONCLUSIONS

Alpha2-antiplasmin and its mRNA are present in the cornea and may serve to regulate corneal plasmin activity.

P2Y12 receptors play a significant role in the development of platelet microaggregation in patients with diabetes

Ninety-eight diabetic patients (type 2) were studied together with 24 healthy normotensive controls. Microaggregates (particle scale, <25 microm) of platelets were detected by a laser scattering system. Microaggregates in the control group showed a time-dependent reversible change; however, they existed continuously in 82 of 98 diabetic patients. When platelets of diabetics were stimulated by a shear stress alone without ADP, 74 also showed spontaneous and irreversible microaggregates even though they were not observed in all control subjects. In control subjects, microaggregates were inhibited by MRS2279 (a P2Y1 antagonist), but not AR-C69931MX (a P2Y12 antagonist). However, AR-C69931MX prevented irreversible microaggregates in diabetic patients. When either aspirin or ticlopidine was administered to diabetic patients with irreversible microaggregates, both drugs significantly decreased microaggregates induced by a low dose of ADP. Ticlopidine additionally reduced the microaggregates induced by shear stress alone. In conclusion, microaggregates of platelets via P2Y12 receptors could play a key role in the hypersensitivity of platelets in diabetic patients, and the measurement of microaggregation could be a useful marker to estimate of thrombogenesis. These findings present a possible new means for patients with diabetes to prevent ischemic events.

Simvastatin enhances the regeneration of endothelial cells via VEGF secretion in injured arteries

The search for a novel therapy for endothelial regenerating is an area of intensive investigation. Recent experimental and clinical evidence strongly suggests that 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors (statins) have several physiological effects independent of low-density lipoprotein cholesterol reduction. We here report that the carotid arterial blood flow after endothelial injury in hamsters treated with simvastatin was restored, in contrast to the situation in nontreated hamsters. Histologic observations showed a prompt recovery of endothelial cells with a much higher DNA synthesis index in repaired endothelium of hamsters treated with simvastatin. The amount of secreted vascular endothelial cell growth factor (VEGF) by cultured vascular smooth muscle cells from hamsters treated with simvastatin was significantly increased. Mevalonate reduced the amount of VEGF secretion by simvastatin in vitro. Finally, an injection of either an anti-VEGF antibody or an anti-VEGF receptor-1 (Flt-1) antibody, but not anti-VEGF receptor-2 (Flk-1), reduced the prompt endothelial healing. Simvastatin regulates endothelial regenerating by an over-release of VEGF and by this may result in prompt endothelial healing after vascular injury. Our results provide new insights into the role of statin and VEGF in the pathogenesis of vascular diseases.

Increase of circulating endothelial progenitor cells in patients with coronary artery disease after exercise-induced ischemia

OBJECTIVE

The concept of neovascularization in response to tissue ischemia has been extended by the finding of postnatal vasculogenesis initiated by endothelial progenitor cells (EPCs). The aim of this study was to analyze whether a maximal stress test in patients with coronary artery disease (CAD) increases the number of circulating EPCs.

METHODS AND RESULTS

Blood concentration of EPCs was analyzed by FACS and cell culture assay in CAD patients with (n=16) or without (n=12) exercise-induced myocardial ischemia and in healthy subjects (n=11) for up to 144 hours after maximal stress test. Plasma concentrations of vascular endothelial growth factor (VEGF), basic fibroblast growth factor, tumor necrosis factor-alpha, and granulocyte macrophage-colony stimulating factor were determined by ELISA. EPCs increased significantly in ischemic patients, with a maximum after 24 to 48 hours (cell culture: 3.3+/-0.5-fold increase; FACS: 3.1+/-0.6-fold increase) and returned to baseline within 72 hour. In nonischemic patients and healthy subjects, no EPC increase was detectable. VEGF levels in ischemic patients increased significantly after 2 to 6 hours (maximum after 2 hours; 4.0+/-1.1-fold increase) and no change was observed in nonischemic patients and healthy subjects; DeltaVEGF and DeltaEPC correlated significantly (r=0.66).

CONCLUSIONS

Patients with symptomatic CAD respond to a single episode of exercise-induced myocardial ischemia with a time-dependent increase in circulating EPCs. This increase may be related to and preceded by an increase in plasma VEGF.

The regulation of liver regeneration by the plasmin/alpha 2-antiplasmin system

BACKGROUND/AIMS

The regeneration after liver injury is regulated by the release and activation of several growth factors. The role of the plasmin/alpha(2)-antiplasmin (alpha(2)-AP) system in liver regeneration was investigated.

METHODS

CCl(4) was injected intraperitoneally into the mice deficient (-/-) in fibrinolytic factors: alpha(2)-AP-/-, plasminogen (Plg) -/-, and Plg-/-.alpha(2)-AP-/-, and wild-type (WT) mice. The liver tissue was examined for its microscopic appearance, fibrinolytic activity, and fibronectin levels.

RESULTS

In the gene deficient and WT mice, the livers exhibited the same extent of necrosis 2 days after the CCl(4) injection. The livers of the WT mice normalized after 7 days, and the alpha(2)-AP-/- mice normalized after 5 days. In contrast, the livers of the Plg-/- and Plg-/-.alpha(2)-AP-/- mice remained in the damaged state until 14 days after the liver injury. The injection of anti-alpha(2)-AP antibody in the WT mice improved the regeneration after the liver injury, and the injection of tranexamic acid in the alpha(2)-AP-/- mice reduced.

CONCLUSIONS

These results suggest that the plasmin/alpha(2)-AP system played an important role in hepatic repair via clearance from the injury area.

Lack of alpha 2-antiplasmin promotes re-endothelialization via over-release of VEGF after vascular injury in mice

We here report that the arterial blood flow after endothelial injury in mice deficient in alpha 2-antiplasmin (alpha 2-AP-/- mice) was well maintained compared with that of wild-type mice. Moreover, the development of neointima 4 weeks after injury in alpha 2-AP-/- mice was significantly decreased. Histologic observations showed a prompt recovery of endothelial cells with a much higher proliferating index in repaired endothelium in alpha 2-AP-/- mice. The amount of secreted vascular endothelial growth factor (VEGF) by explanted vascular smooth muscle cells (SMCs) from alpha 2-AP-/- mice was significantly increased. In separate experiments using a human endothelial cell (EC) line, we could demonstrate that plasminogen binds to ECs and that this binding can be prevented by alpha 2-AP. Finally, an injection of either an anti-VEGF receptor-1 antibody or alpha 2-AP reduced the prompt endothelial healing. alpha 2-AP is the main inactivator of plasmin, which cleaves extracellular matrix-bound VEGF to release a diffusible proteolytic fragment. Lack of alpha 2-AP, therefore, could lead to a local over-release of VEGF by the continuously active plasmin in the injured area, which could result in a prompt re-endothelialization after vascular injury. Our results provide new insight into the role of alpha 2-AP and VEGF in the pathogenesis of re-endothelialization following vascular injury.

Adenoviral-delivered angiopoietin-1 reduces the infarction and attenuates the progression of cardiac dysfunction in the rat model of acute myocardial infarction

In acute myocardial infarction (AMI), prognosis and mortality rate are closely related to the infarct size and the progression of postinfarction cardiac failure. Angiogenic gene therapy has presented a new approach for the treatment of AMI. Angiopoietin-1 (Ang1) is a critical angiogenic factor for vascular maturation and enhances vascular endothelial growth factor (VEGF)-induced angiogenesis in a complementary manner. We hypothesized that gene therapy using Ang1 for AMI might promote angiogenesis cooperatively with intrinsic VEGF, since high concentrations of circulating VEGF have been reported in AMI. To evaluate our hypothesis, we employed a rat AMI model and adenoviral Ang1 (HGMW-approved gene symbol ANGPT1) gene transfer to the heart. A significant increase in capillary density and reduction in infarct sizes were noted in the infarcted hearts with adenoviral Ang1 gene treatment compared with control infarcted hearts treated with saline or adenoviral vector containing the beta-galactosidase gene. Furthermore, the Ang1 group showed significantly higher cardiac performance in echocardiography (55.0% of ejection fraction, P < 0.05 vs control) than the saline or adenoviral controls (36.0 or 40.5%, respectively) 4 weeks after myocardial infarction. The adenoviral delivery of Ang1 during the acute phase of myocardial infarction would be feasible to attenuate the progression of cardiac dysfunction in the rat model.

Alpha2-antiplasmin plays a significant role in acute pulmonary embolism

The importance of pulmonary embolism (PE) due to venous thrombosis is recognized in the treatment of vascular diseases. We have investigated the physiological effects of plasmin generation in experimental acute PE using mice deficient in plasminogen (Plg-/-) or alpha2-antiplasmin (alpha2-AP-/-). PE was induced by continuous induction of venous thrombus in the left jugular vein by endothelial injury due to photochemical reaction. The mortality of wild-type mice was 68.8% at 2 h after the initiation of venous thrombosis and it was significantly reduced in alpha2-AP-/- mice (41.7%). In contrast, Plg-/- mice did not survive. Histological evidence of thromboembolism in the lung was obtained in all mice. However, whereas a strict thromboembolism was observed in Plg-/- mice, only a few thrombi were detected in the lungs of alpha2-AP-/- mice. Plasma fibrinogen levels measured in mice were not different. When alpha2-AP was infused in alpha2-AP-/- mice, the mortality was indistinguishable from wild-type mice. Tissue-type plasminogen activator (tPA) did not reduce the mortality due to acute PE in wild-type mice. However, in alpha2-AP-/- mice, tPA (0.52 mg x kg-1) significantly decreased the mortality compared with that of alpha2-AP-/- mice without tPA. The bleeding time was not significantly prolonged in either type of mice treated with tPA. The lack of plasminogen increases the mortality due to acute PE while a lack of alpha2-AP decreases the mortality rate, which can be further reduced by tPA administration. Therefore, the combination of inhibition of alpha2-AP with thrombolytic therapy could be beneficial in the treatment of acute PE.

Old dogs and new tricks: proteases, inhibitors, and cell migration

A new model for the actions of plasminogen activator inhibitors (PAIs) on cell migration may resolve the conflicting research data on these proteins in metastasis and angiogenesis. Results from two groups reveal a role for PAI-1 in promoting cycles of attachment and detachment of the cell from the extracellular matrix that is independent of its role as an enzymatic inhibitor of urokinase-type plasminogen activator (uPA). Through the formation of a complex of integrins, uPA and its receptor, and the clearance receptors of the low-density lipoprotein family, PAI-1 may promote endocytosis and recycling of these adhesion-controlling proteins, allowing cycling of cellular attachment and detachment.