Local delivery of human tissue kallikrein gene accelerates spontaneous angiogenesis in mouse model of hindlimb ischemia

Tissue kallikrein in cardiovascular, cerebrovascular and renal diseases and skin wound healing

Tissue kallikrein (KLK1) processes low-molecular weight kininogen to produce vasoactive kinins, which exert biological functions via kinin receptor signaling. Using various delivery approaches, we have demonstrated that tissue kallikrein through kinin B2 receptor signaling exhibits a wide spectrum of beneficial effects by reducing cardiac and renal injuries, restenosis and ischemic stroke, and by promoting angiogenesis and skin wound healing, independent of blood pressure reduction. Protection by tissue kallikrein in oxidative organ damage is attributed to the inhibition of apoptosis, inflammation, hypertrophy and fibrosis. Tissue kallikrein also enhances neovascularization in ischemic heart and limb. Moreover, tissue kallikrein/kinin infusion not only prevents but also reverses kidney injury, inflammation and fibrosis in salt-induced hypertensive rats. Furthermore, there is a wide time window for kallikrein administration in protection against ischemic brain infarction, as delayed kallikrein infusion for 24 h after cerebral ischemia in rats is effective in reducing neurological deficits, infarct size, apoptosis and inflammation. Importantly, in the clinical setting, human tissue kallikrein has been proven to be effective in the treatment of patients with acute brain infarction when injected within 48 h after stroke onset. Finally, kallikrein promotes skin wound healing and keratinocyte migration by direct activation of protease-activated receptor 1.

Human adult vena saphena contains perivascular progenitor cells endowed with clonogenic and proangiogenic potential

BACKGROUND

Clinical trials in ischemic patients showed the safety and benefit of autologous bone marrow progenitor cell transplantation. Non-bone marrow progenitor cells with proangiogenic capacities have been described, yet they remain clinically unexploited owing to their scarcity, difficulty of access, and low ex vivo expansibility. We investigated the presence, antigenic profile, expansion capacity, and proangiogenic potential of progenitor cells from the saphenous vein of patients undergoing coronary artery bypass surgery.

METHODS AND RESULTS

CD34-positive cells, negative for the endothelial marker von Willebrand factor, were localized around adventitial vasa vasorum. After dissection of the vein from surrounding tissues and enzymatic digestion, CD34-positive/CD31-negative cells were isolated by selective culture, immunomagnetic beads, or fluorescence-assisted cell sorting. In the presence of serum, CD34-positive/CD31-negative cells gave rise to a highly proliferative population that expressed pericyte/mesenchymal antigens together with the stem cell marker Sox2 and showed clonogenic and multilineage differentiation capacities. We called this population "saphenous vein-derived progenitor cells" (SVPs). In culture, SVPs integrated into networks formed by endothelial cells and supported angiogenesis through paracrine mechanisms. Reciprocally, endothelial cell-released factors facilitated SVP migration. These interactive responses were inhibited by Tie-2 or platelet-derived growth factor-BB blockade. Intramuscular injection of SVPs in ischemic limbs of immunodeficient mice improved neovascularization and blood flow recovery. At 14 days after transplantation, proliferating SVPs were still detectable in the recipient muscles, where they established N-cadherin-mediated physical contact with the capillary endothelium.

CONCLUSIONS

SVPs generated from human vein CD34-positive/CD31-negative progenitor cells might represent a new therapeutic tool for angiogenic therapy in ischemic patients.

Kinins in cardiac inflammation and regeneration: insights from ischemic and diabetic cardiomyopathy

The kallikrein-kinin system (KKS) is a system of vasoactive peptides, the kinins, involved in different aspects of remodeling, inflammation and angiogenesis. Kinins mediate their actions through two receptors, B1R and B2R. It is increasingly recognized that the KKS is involved in the inflammatory processes of the heart. Evidence shows that the B2R is beneficial in myocardial diseases, protecting from inflammation, fibrosis and apoptosis, while B1R shows a proinflammatory character contributing to the disease progression by increasing the production of cytokines and stimulating the migration of immune cells. Furthermore, novel important actions of the KKS and its receptors contribute to neovascularization and recruitment of endothelial progenitor cells in ischemic areas and endothelial dysfunction. The kinin receptors could therefore constitute potential therapeutic targets in the treatment of myocardial ischemia and diabetic cardiomyopathy.

Mechanisms in the loss of capillaries in systemic sclerosis: angiogenesis versus vasculogenesis

Systemic sclerosis (SSc, scleroderma) is a chronic, multisystem connective tissue disorder affecting the skin and various internal organs. Although the disease is characterized by a triad of widespread microangiopathy, fibrosis and autoimmunity, increasing evidence indicates that vascular damage is a primary event in the pathogenesis of SSc. The progressive vascular injury includes persistent endothelial cell activation/damage and apoptosis, intimal thickening, delamination, vessel narrowing and obliteration. These profound vascular changes lead to vascular tone dysfunction and reduced capillary blood flow, with consequent tissue ischemia and severe clinical manifestations, such as digital ulceration or amputation, pulmonary arterial hypertension and scleroderma renal crisis. The resulting tissue hypoxia induces complex cellular and molecular mechanisms in the attempt to recover endothelial cell function and tissue perfusion. Nevertheless, in SSc patients there is no evidence of significant angiogenesis and the disease evolves towards chronic tissue ischemia, with progressive and irreversible structural changes in multiple vascular beds culminating in the loss of capillaries. A severe imbalance between pro-angiogenic and angiostatic factors may also lead to impaired angiogenic response during SSc. Besides insufficient angiogenesis, defective vasculogenesis with altered numbers and functional defects of bone marrow-derived endothelial progenitor cells may contribute to the vascular pathogenesis of SSc. The purpose of this article is to review the contribution of recent studies to the understanding of the complex mechanisms of impaired vascular repair in SSc. Indeed, understanding the pathophysiology of SSc-associated vascular disease may be the key in dissecting the disease pathogenesis and developing novel therapies. Either angiogenic or vasculogenic mechanisms may potentially become in the future the target of therapeutic strategies to promote capillary regeneration in SSc.

Peptide hormone regulation of angiogenesis

It is now apparent that regulation of blood vessel growth contributes to the classical actions of hormones on development, growth, and reproduction. Endothelial cells are ideally positioned to respond to hormones, which act in concert with locally produced chemical mediators to regulate their growth, motility, function, and survival. Hormones affect angiogenesis either directly through actions on endothelial cells or indirectly by regulating proangiogenic factors like vascular endothelial growth factor. Importantly, the local microenvironment of endothelial cells can determine the outcome of hormone action on angiogenesis. Members of the growth hormone/prolactin/placental lactogen, the renin-angiotensin, and the kallikrein-kinin systems that exert stimulatory effects on angiogenesis can acquire antiangiogenic properties after undergoing proteolytic cleavage. In view of the opposing effects of hormonal fragments and precursor molecules, the regulation of the proteases responsible for specific protein cleavage represents an efficient mechanism for balancing angiogenesis. This review presents an overview of the actions on angiogenesis of the above-mentioned peptide hormonal families and addresses how specific proteolysis alters the final outcome of these actions in the context of health and disease.

The Tissue Kallikrein Family of Serine Proteases: Functional Roles in Human Disease and Potential as Clinical Biomarkers

Prostate specific antigen (PSA) or human kallikrein 3 (hK3) has long been an effective biomarker for prostate cancer. Now, other members of the tissue kallikrein (KLK) gene family are fast becoming of clinical interest due to their potential as prognostic biomarkers. particularly for hormone dependent cancers. The tissue kallikreins are serine proteases that are encoded by highly conserved multi-gene family clusters in rodents and humans. The rat and mouse loci contain 10 and 25 functional genes, respectively, while the human locus at 19q 13.4 contains 15 genes. The structural organization and size of these genes are similar across species; all genes have 5 coding exons that encode a prepro-enzyme. Although the physiological activators of these zymogens have not been described, in vitro biochemical studies show that some kallikreins can auto-activate and others can activate each other, suggesting that the kallikreins may participate in an enzymatic cascade similar to that of the coagulation cascade. These genes are expressed, to varying degrees, in a wide range of tissues suggesting a functional involvement in a diverse range of physiological and pathophysiological processes. These include roles in normal skin desquamation and psoriatic lesions, tooth development, neural plasticity, and Alzheimer's disease (AD). Of particular interest is the expression of many kallikreins in prostate, ovarian, and breast cancers where they are emerging as useful prognostic indicators of disease progression.

Role of kinin B2 receptor signaling in the recruitment of circulating progenitor cells with neovascularization potential

Reduced migratory function of circulating angiogenic progenitor cells (CPCs) has been associated with impaired neovascularization in patients with cardiovascular disease (CVD). Previous findings underline the role of the kallikrein-kinin system in angiogenesis. We now demonstrate the involvement of the kinin B2 receptor (B(2)R) in the recruitment of CPCs to sites of ischemia and in their proangiogenic action. In healthy subjects, B(2)R was abundantly present on CD133(+) and CD34(+) CPCs as well as cultured endothelial progenitor cells (EPCs) derived from blood mononuclear cells (MNCs), whereas kinin B1 receptor expression was barely detectable. In transwell migration assays, bradykinin (BK) exerts a potent chemoattractant activity on CD133(+) and CD34(+) CPCs and EPCs via a B(2)R/phosphoinositide 3-kinase/eNOS-mediated mechanism. Migration toward BK was able to attract an MNC subpopulation enriched in CPCs with in vitro proangiogenic activity, as assessed by Matrigel assay. CPCs from cardiovascular disease patients showed low B(2)R levels and decreased migratory capacity toward BK. When injected systemically into wild-type mice with unilateral limb ischemia, bone marrow MNCs from syngenic B(2)R-deficient mice resulted in reduced homing of sca-1(+) and cKit(+)flk1(+) progenitors to ischemic muscles, impaired reparative neovascularization, and delayed perfusion recovery as compared with wild-type MNCs. Similarly, blockade of the B(2)R by systemic administration of icatibant prevented the beneficial effect of bone marrow MNC transplantation. BK-induced migration represents a novel mechanism mediating homing of circulating angiogenic progenitors. Reduction of BK sensitivity in progenitor cells from cardiovascular disease patients might contribute to impaired neovascularization after ischemic complications.

Tissue kallikrein promotes neovascularization and improves cardiac function by the Akt-glycogen synthase kinase-3beta pathway

AIMS

We investigated the role of the Akt-glycogen synthase kinase (GSK)-3beta signalling pathway in mediating the protective effects of tissue kallikrein on myocardial injury by promoting angiogenesis and blood flow in rats after myocardial infarction (MI).

METHODS AND RESULTS

Human tissue kallikrein gene in an adenoviral vector, with or without co-administration of dominant-negative Akt (Ad.DN-Akt) or constitutively active GSK-3beta (Ad.GSK-3betaS9A), was injected into rat myocardium after MI. The expression of recombinant human kallikrein in rat heart significantly improved cardiac function and reduced infarct size 10 days after gene delivery. Kallikrein administration significantly increased myocardial blood flow as well as capillary and arteriole densities in the infarcted myocardium. Kallikrein increased cardiac Akt and GSK-3beta phosphorylation in conjunction with decreased GSK-3beta activity and the upregulation of vascular endothelial growth factor (VEGF) and VEGF receptor-2 (VEGFR-2). All of kallikrein's effects on the myocardium were abrogated by Ad.DN-Akt and Ad.GSK-3betaS9A. Moreover, in cultured human aortic endothelial cells, tissue kallikrein stimulated capillary tube formation and promoted cell migration; however, these effects were blocked by Ad.DN-Akt, Ad.GSK-3betaS9A, icatibant (a kinin B2 receptor antagonist), Tki (a VEGF receptor tyrosine kinase inhibitor), and a neutralizing VEGF antibody. In addition, tissue kallikrein decreased GSK-3beta activity via the phosphatidylinositol 3-kinase-Akt pathway and enhanced VEGF and VEGFR-2 expression in endothelial cells.

CONCLUSION

These data provide the first direct evidence that tissue kallikrein protects against acute-phase MI by promoting neovascularization, restoring regional blood flow and improving cardiac function through the kinin B2 receptor-Akt-GSK-3beta and VEGF signalling pathways.

Influence of the kallikrein-kinin system on prostate and breast tumour angiogenesis

BACKGROUND/AIMS

Angiogenesis is important for the growth and progression of cancer cells. There is some evidence that the kallikrein-kinin system (KKS) is involved in cancer and angiogenesis. The present study investigated the effect of increasing concentrations of prostate and breast tumour cell metabolites on the proliferation of cultured endothelial cells, their tissue kallikrein (TK) secretion and KKS expression.

METHODS

Expression of TK and kinin receptors was investigated by immunochemistry, and secretion of TK by ELISA. Cell proliferation was measured by a chromogenic assay. KKS proteins were also immunolocalised in an endothelial tumour co-culture model.

RESULTS

KKS proteins were found in projections of all cell types as well as at points of heterogeneous contact. Tumour metabolites increased the secretion of TK from endothelial cells, with corresponding decreases in intracellular amounts, while also increasing proliferation of the endothelial cells.

CONCLUSIONS

These findings indicate that the KKS may be one of the more important players in angiogenesis associated with prostate and breast tumours.

B2-kinin receptor plays a key role in B1-, angiotensin converting enzyme inhibitor-, and vascular endothelial growth factor-stimulated in vitro angiogenesis in the hypoxic mouse heart

AIMS

Angiotensin converting enzyme (ACE) inhibition reduces heart disease and vascular stiffness in hypertension and leads to kinin accumulation. In this study, we analysed the role and importance of two kinin receptor subtypes in angiogenesis during ACE inhibition in an in vitro model of angiogenesis of the mouse heart.

METHODS AND RESULTS

First, we analysed the angiogenic properties of bradykinin and enalapril on wild-type C57Bl/6 and B2 receptor(-/-) mouse heart under normoxia (21% O(2)) and hypoxia (1% O(2)) in vitro and the contribution of B1 and B2 kinin receptors to this effect. Bradykinin induced dose-dependent endothelial sprout formation in vitro in adult mouse heart only under hypoxia (1.7 fold, n = 6, P < 0.05). The B2 receptor mediated sprouting that was induced by bradykinin and vascular endothelial growth factor (VEGF(164); n = 6, P < 0.05), but did not mediate sprouting that was induced by growth factors bFGF or PDGF-BB. Enalapril induced sprouting through both the B1 and B2 kinin receptors, but it required the presence of the B2 receptor in both scenarios and was dependent on BK synthesis. B1-receptor agonists induced sprout formation via the B1 receptor (2.5 fold, n = 6, P < 0.05), but it required the presence of the B2 receptor for them to do so. Both B2-receptor and B1-receptor agonist-induced angiogenesis required nitric oxide biosynthesis.

CONCLUSION

The kinin B2 receptor plays a crucial role in angiogenesis that is induced by different vasoactive molecules, namely bradykinin, ACE inhibitors, B1-stimulating kinin metabolites, and VEGF164 in an in vitro model of angiogenesis of mouse heart under hypoxia. Therapeutic treatment of hypertensive patients by using ACE inhibitors may potentially benefit the ischaemic heart through inducing B2-dependent heart neovascularization.

Tissue kallikrein and kinin infusion promotes neovascularization in limb ischemia

Adenovirus-mediated kallikrein delivery has been shown to promote blood vessel growth in the limb under both ischemic and normoperfused conditions. Here we investigated whether a continuous supply of kallikrein and kinin peptide can induce neovascularization in a rat model of hindlimb ischemia. Rats underwent femoral artery ligation and localized injection of tissue kallikrein, bradykinin or B1 receptor agonist, followed by infusion of proteins by osmotic minipump. Regional blood flow was monitored weekly by laser Doppler perfusion imaging. Three weeks after surgery, rats receiving kallikrein and kinins showed a significant increase in the perfusion ratio of ischemic vs. normoperfused limb compared to control rats. Similarly, a microsphere assay showed that kallikrein and kinins significantly increased regional blood flow without altering blood pressure. Moreover, kallikrein and kinins significantly augmented capillary and arteriole densities, as quantified by immunostaining with CD-31 and smooth muscle α-actin. Both tissue kallikrein and bradykinin increased hemoglobin content in Matrigel implants in mice, providing further evidence of the angiogenic properties. Kinins, when delivered subcutaneously via Matrigel in rats, also increased regional perfusion. This is the first demonstration that local application of tissue kallikrein protein or kinin peptide has therapeutic value in the treatment of ischemic disease by promoting neovascularization.

Vascular growth in ischemic limbs: a review of mechanisms and possible therapeutic stimulation

Stimulation of vascular growth to treat limb ischemia is promising, and early results obtained from uncontrolled clinical trials using angiogenic agents, e.g., vascular endothelial growth factor, led to high expectations. However, negative results from recent placebo-controlled trials warrant further research. Here, current insights into mechanisms of vascular growth in the adult, in particular the role of angiogenic factors, the immune system, and bone marrow, were reviewed, together with modes of its therapeutic stimulation and results from recent clinical trials. Three concepts of vascular growth have been described to date-angiogenesis, vasculogenesis, and arteriogenesis (collateral artery growth)-which represent different aspects of an integrated process. Stimulation of arteriogenesis seems clinically most relevant and has most recently been attempted using autologous bone marrow transplantation with some beneficial results, although the mechanism of action is not completely understood. Better understanding of the highly complex molecular and cellular mechanisms of vascular growth may yet lead to meaningful clinical applications.

Phosphoinositide 3-kinase gamma gene knockout impairs postischemic neovascularization and endothelial progenitor cell functions

OBJECTIVE

We evaluated whether phosphatidylinositol 3-kinase gamma (PI3Kgamma) plays a role in reparative neovascularization and endothelial progenitor cell (EPC) function.

METHODS AND RESULTS

Unilateral limb ischemia was induced in mice lacking the PI3Kgamma gene (PI3Kgamma-/-) or expressing a catalytically inactive mutant (PI3Kgamma(KD/KD)) and wild-type controls (WT). Capillarization and arteriogenesis were reduced in PI3Kgamma-/- ischemic muscles resulting in delayed reperfusion compared with WT, whereas reparative neovascularization was preserved in PI3Kgamma(KD/KD). In PI3Kgamma-/- muscles, endothelial cell proliferation was reduced, apoptosis was increased, and interstitial space was infiltrated with leukocytes but lacked cKit+ progenitor cells that in WT muscles typically surrounded arterioles. PI3Kgamma is constitutively expressed by WT EPCs, with expression levels being upregulated by hypoxia. PI3Kgamma-/- EPCs showed a defect in proliferation, survival, integration into endothelial networks, and migration toward SDF-1. The dysfunctional phenotype was associated with nuclear constraining of FOXO1, reduced Akt and eNOS phosphorylation, and decreased nitric oxide (NO) production. Pretreatment with an NO donor corrected the migratory defect of PI3Kgamma-/- EPCs. PI3Kgamma(KD/KD) EPCs showed reduced Akt phosphorylation, but constitutive activation of eNOS and preserved proliferation, survival, and migration.

CONCLUSIONS

We newly demonstrated that PI3Kgamma modulates angiogenesis, arteriogenesis, and vasculogenesis by mechanisms independent from its kinase activity.

New insights into the functional mechanisms and clinical applications of the kallikrein-related peptidase family

The Kallikrein-related peptidase (KLK) family consists of fifteen conserved serine proteases that form the largest contiguous cluster of proteases in the human genome. While primarily recognized for their clinical utilities as potential disease biomarkers, new compelling evidence suggests that this family plays a significant role in various physiological processes, including skin desquamation, semen liquefaction, neural plasticity, and body fluid homeostasis. KLK activation is believed to be mediated through highly organized proteolytic cascades, regulated through a series of feedback loops, inhibitors, auto-degradation and internal cleavages. Gene expression is mainly hormone-dependent, even though transcriptional epigenetic regulation has also been reported. These regulatory mechanisms are integrated with various signaling pathways to mediate multiple functions. Dysregulation of these pathways has been implicated in a large number of neoplastic and non-neoplastic pathological conditions. This review highlights our current knowledge of structural/phylogenetic features, functional role and regulatory/signaling mechanisms of this important family of enzymes.

Aberrant human tissue kallikrein levels in the stratum corneum and serum of patients with psoriasis: dependence on phenotype, severity and therapy

BACKGROUND

Human tissue kallikreins (KLKs) are a family of 15 trypsin-like or chymotrypsin-like secreted serine proteases (KLK1-KLK15). Multiple KLKs have been quantitatively identified in normal stratum corneum (SC) and sweat as candidate desquamation-related proteases.

OBJECTIVES

To quantify KLK5, KLK6, KLK7, KLK8, KLK10, KLK11, KLK13 and KLK14 in the SC and serum of patients with psoriasis, and their variation between lesional and nonlesional areas and with phenotype, therapy and severity. The overall SC serine protease activities were also measured.

METHODS

Enzyme-linked immunosorbent assays and enzymatic assays were used.

RESULTS

The lesional SC of psoriasis generally contained significantly higher levels of all KLKs. KLK6, KLK10 and KLK13 levels were significantly elevated even in the nonlesional SC. The overall trypsin-like, plasmin-like and furin-like activities were significantly elevated in the lesional SC. Plasmin-like activity was significantly elevated also in the nonlesional SC. The SC chymotrypsin-like activity was only slightly elevated in psoriasis. KLK7 serum levels did not differ between normal volunteers and patients with psoriasis. Serum KLK6, KLK8, KLK10 and KLK13 levels in patients with untreated psoriasis significantly correlated with Psoriasis Area and Severity Index score. Serum KLK5 and KLK11 levels decreased in patients with psoriasis after therapy, especially with etretinate. Patients with erythrodermic psoriasis exhibited significantly higher serum KLK levels than normal subjects or patients with psoriasis vulgaris or arthropathic psoriasis.

CONCLUSIONS

We found aberrant KLK levels in the SC and serum of patients with psoriasis and suggest that KLKs might be involved in the pathogenesis of this disease.

Spatio-temporal expression of MMP-2, MMP-9 and tissue kallikrein in uteroplacental units of the pregnant guinea-pig (Cavia porcellus)

BACKGROUND

In humans trophoblast invasion and vascular remodeling are critical to determine the fate of pregnancy. Since guinea-pigs share with women an extensive migration of the trophoblasts through the decidua and uterine arteries, and a haemomonochorial placenta, this species was used to evaluate the spatio-temporal expression of three enzymes that have been associated to trophoblast invasion, MMP-2, MMP-9 and tissue kallikrein (K1).

METHODS

Uteroplacental units were collected from early to term pregnancy. MMP-2, MMP-9 and K1 were analysed by immunohistochemistry and Western blot. The activities of MMP-2 and MMP-9 were assessed by gelatin zymography.

RESULTS

Immunoreactive MMP-2, MMP-9 and K1 were detected in the subplacenta, interlobar and labyrinthine placenta, syncytial sprouts and syncytial streamers throughout pregnancy. In late pregnancy, perivascular or intramural trophoblasts expressed the three enzymes. The intensity of the signal in syncytial streamers was increased in mid and late pregnancy for MMP-2, decreased in late pregnancy for MMP-9, and remained stable for K1. Western blots of placental homogenates at days 20, 40 and 60 of pregnancy identified bands with the molecular weights of MMP-2, MMP-9 and K1. MMP-2 expression remained constant throughout gestation. In contrast, MMP-9 and K1 attained their highest expression during midgestation. Placental homogenates of 20, 40 and 60 days yielded bands of gelatinase activity that were compatible with MMP-2 and MMP-9 activities. ProMMP-2 and MMP-9 activities did not vary along pregnancy, while MMP-2 and MMP-9 increased at 40 and 40-60 days respectively.

CONCLUSION

The spatio-temporal expression of MMPs and K1 supports a relevant role of these proteins in trophoblast invasion, vascular remodeling and placental angiogenesis, and suggests a functional association between K1 and MMP-9 activation.

Regional and global protective effects of tissue kallikrein gene delivery to the peri-infarct myocardium

BACKGROUND

The kallikrein-kinin system participates in the maintenance of the cardiovascular phenotype. We previously demonstrated that human tissue kallikrein gene (hTK) transfer promotes the healing of ischemic limbs. The present investigation aimed to test the original hypothesis that hTK delivery to the peri-infarct myocardium would prevent post-ischemic heart failure.

METHODS AND RESULTS

Myocardial infarction (MI) was induced in anesthetized mice by permanently occluding the left coronary descendant. hTK was delivered to the peri-infarct myocardium via an adenoviral vector (Ad.hTK). Controls received Ad.Null or saline. Survival rate was similar among groups. Ad.hTK increased the number of circulating endothelial progenitor cells and promoted the growth of capillaries and arterioles in the peri-infarct myocardium. In addition, Ad.hTK increased the abundance of cardiac progenitor cells (CPCs) in the peri-infarct and suppressed the apoptotic death of peri-infarct cardiomyocytes in vivo and ex vivo. As a consequence of these beneficial effects, at 5 weeks from MI, hTK-transduced hearts were protected from post-MI ventricular dilatation and showed better systolic and diastolic functions.

CONCLUSIONS

Ad.hTK benefits the neovascularization and viability of peri-infarct myocardium and increases CPC abundance, thereby decreasing ventricular dysfunction. Our study significantly adds to the knowledge of the protective effects of TK gene transfer on ischemic diseases and opens new avenues for the treatment of post-MI cardiac failure.

Mechanisms of Disease: the tissue kallikrein–kinin system in hypertension and vascular remodeling

The pathogenesis of arterial hypertension often involves a rise in systemic vascular resistance (vasoconstriction and vascular remodeling) and impairment of salt excretion in the kidney (inappropriate salt retention despite elevated blood pressure). Experimental and clinical evidence implicate an imbalance between endogenous vasoconstrictor and vasodilator systems in the development and maintenance of hypertension. Kinins (bradykinin and lys-bradykinin) are endogenous vasodilators and natriuretic peptides known best for their ability to antagonize angiotensin-induced vasoconstriction and sodium retention. In humans, angiotensin-converting enzyme inhibitors, a potent class of antihypertensive agents, lower blood pressure at least partially by favoring enhanced kinin accumulation in plasma and target tissues. The beneficial actions of kinins in renal and cardiovascular disease are largely mediated by nitric oxide and prostaglandins, and extend beyond their recognized role in lowering blood pressure to include cardioprotection and nephroprotection. This article is a review of exciting, recently generated genetic, biochemical and clinical data from studies that have examined the importance of the tissue kallikrein-kinin system in protection from hypertension, vascular remodeling and renal fibrosis. Development of novel therapeutic approaches to bolster kinin activity in the vascular wall and in specific compartments in the kidney might be a highly effective strategy for the treatment of hypertension and its complications, including cardiac hypertrophy and renal failure.

New vectors and strategies for cardiovascular gene therapy

Cardiovascular diseases are the major cause of morbidity and mortality in both men and women in industrially developed countries. These disorders may result from impaired angiogenesis, particularly in response to hypoxia. Despite many limitations, gene therapy is still emerging as a potential alternative for patients who are not candidates for traditional revascularization procedures, like angioplasty or vein grafts. This review focuses on recent approaches in the development of new gene delivery vectors, with great respect to newly discovered AAV serotypes and their modified forms. Moreover, some new cardiovascular gene therapy strategies have been highlighted, such as combination of different angiogenic growth factors or simultaneous application of genes and progenitor cells in order to obtain stable and functional blood vessels in ischemic tissue.

Nitropravastatin stimulates reparative neovascularisation and improves recovery from limb Ischaemia in type-1 diabetic mice

BACKGROUND AND PURPOSE

Mature endothelial cells and their progenitors are dysfunctional in diabetes, resulting in deficient neovascularisation following arterial occlusion. This study aimed to evaluate the therapeutic activity of a nitric oxide (NO) releasing statin in the setting of experimental diabetes and peripheral ischaemia.

EXPERIMENTAL APPROACH

The effects of NCX 6550, an NO-releasing pravastatin derivative, on angiogenesis in ischaemic limbs was studied in normoglycaemic mice or mice made diabetic by treatment with streptozotocin (STZ). Control mice received an equimolar dosage of the parent statin compound, pravastatin. The therapeutic action of NCX 6550 was also tested in mice lacking the gene for endothelial nitric oxide synthase (eNOS).

KEY RESULTS

In normoglycaemic or STZ-diabetic CD1 mice, only NCX 6550 stimulated skeletal muscle revascularisation. In addition, NCX 6550 induced greater improvement in limb reperfusion and salvage, than pravastatin. The number of circulating endothelial progenitor cells was decreased in STZ-diabetic mice, this defect being prevented by NCX 6550 and, to a lesser extent by pravastatin. In vitro, high glucose concentrations reduced the migratory capacity of endothelial progenitor EPCs, which was partly reversed by preincubation with pravastatin and completely reversed by NCX 6550. The postischaemic recovery of eNOS knockout mice was severely impaired as a consequence of depressed angiogenesis and this recovery was improved by treatment with NCX 6550, but not with pravastatin.

CONCLUSIONS AND IMPLICATIONS

These findings indicate that incorporation of a bioactive NO moiety improves the therapeutic profile of statins for the treatment of peripheral vascular disease.

Angiotensin II receptor blocker provides pancreatic beta-cell protection independent of blood pressure lowering in diabetic db/db mice

AIM

Several epidemiological studies have suggested that treatment with angiotensin II type 1 receptor blocker provided a risk reduction of developing type 2 diabetes. The aim of this study was to investigate whether and how chronic candesartan treatment can attenuate the deleterious influence of the hyperactive local intra-islet renin-angiotensin system in the diabetes state.

METHODS

Eight-week-old db/db mice were randomized to candesartan 1 mg/kg, candesartan 10 mg/kg, manidipine 10 mg/kg, or placebo via gavage for 6 weeks. Their age-matched nondiabetic littermates db/m mice were treated with placebo and acted as nondiabetic controls. After 6 weeks' treatment, an intraperitoneal glucose tolerance test, immunohistochemical staining of oxidative stress markers, insulin, CD31, azan staining and an electron microscopy observation were performed.

RESULTS

Chronic candesartan treatment provided an improvement of glucose tolerance, and greatly rescued islet beta-cell mass. Candesartan treatment also notably decreased staining intensity of oxidative stress markers, as well as attenuating intra-islet fibrosis and improving blood supply in the islet. In the electron microscopy observation, candesartan-treated animals exhibited improved granulation and less remarkable endoplasmic reticulum and Golgi bodies; furthermore, candesartan treatment greatly relieved the swelling of mitochondria to nearly normal. Both the benefits of reducing oxidative stress and ultrastructure protection were in a dose-dependent and blood pressure-independent manner.

CONCLUSION

After diabetes was initiated, candesartan treatment could not reverse the state of diabetes, but it effectively improved glucose tolerance and protected beta-cell function by attenuating oxidative stress, islet fibrosis, sparsity of blood supply and ultrastructure disruption in a dose-dependent and blood pressure-independent manner.

Therapeutic angiogenesis: Translating experimental concepts to medically relevant goals

Angiogenesis is central to many physiological and pathological phenomena. In physiological angiogenesis, new vessels are well shaped and their growth is finely tuned to match the metabolic needs of tributary tissues. Accordingly, neovascularization is activated by physical exercise and destabilized by non-use. In contrast, pathological blood vessels that are observed in retinal neovascularization, cancer or in ischemic tissues are leaky, irregularly shaped, and tend to form arterial-venous fistulae. A great deal of attention is focused on new approaches for medical manipulation of vascular growth. These methods are aimed at facilitating the reperfusion of ischemic tissues or eradicating pathological vasculature. In this position paper, we challenge the rationale of therapeutic angiogenesis for the cure of myocardial and peripheral ischemia. Therapeutic angiogenesis aims at combating the insufficiency of, or insensitivity to angiogenic factors in the setting of atherosclerotic-induced arterial occlusion. However, clinical evidence indicates that such a defect is not common among patients with ischemic disease, as a whole. Genetic and environmental factors could account for the great heterogeneity in the expression of the master angiogenic factors. Future improvements in the strategy would require the introduction of in vitro assays and in vivo imaging systems for assessing human angiogenesis. Finally, the promise is to find individualized angiogenesis-based therapies for a genuine cure of ischemia and prevention of organ failure.

Inhibition of human and rabbit arterial smooth muscle cell migration mediated by the kinin B1 receptor: role of receptor density and released mediators

Bradykinin (BK)-related peptides are suspected to negatively influence diverse functions in vascular smooth muscle cells (SMCs), notably via stimulation of the inducible B1 receptor (B1R), and have been shown to inhibit the migration of rat SMCs. The present study had several objectives: (i) to test whether B1R mediates the inhibition of migration of arterial SMCs from additional species (the human and the rabbit); (ii) whether B1R density influences this action and whether autocrine NO or prostanoid release modulate it; and (iii) the possible signaling interaction between the B1R and phosphatidylinositol-3 kinase (PI-3K) has been addressed. The peptidase resistant B1R agonist Sar-[D-Phe8]des-Arg9-BK (10 nmol/L – 1 μmol/L) was an inhibitor of migration in human or rabbit arterial SMCs in a wound closure assay, more effectively if the medium composition allowed a high B1R expression (20% fetal bovine serum (FBS) + interleukin-1β (IL-1β) in human SMCs, 10% FBS in rabbit cells). The effect of the B1R agonist on motility was abrogated by a B1R antagonist, B-9858, but not by the B2R antagonist Hoe 140; a peptidase-resistant B2R agonist, [Phe8Ψ(CH2-NH)-Arg9]BK, had a marginal or no effect on migration. Sar-[D-Phe8]des-Arg9-BK (1 μmol/L) did not significantly influence SMC proliferation. The B1R-mediated inhibition of SMC migration was not affected by pharmacological inhibition of the nitric oxide synthases or cyclooxygenases-1 or -2, but was correlated to an inhibition of PI-3K in both types of SMCs. The inhibition of SMC migration mediated by the kinin B1R is likely independent from NO or prostanoid release, applicable to several species, and correlated to receptor density and the inhibition of PI-3K.

Murine models of myocardial and limb ischemia: Diagnostic end-points and relevance to clinical problems

Ischemic disease represents the new epidemic worldwide. Animal models of ischemic disease are useful because they can help us to understand the underlying pathogenetic mechanisms and develop new therapies. The present review article summarizes the results of a consensus conference on the status and future development of experimentation in the field of cardiovascular medicine using murine models of peripheral and myocardial ischemia. The starting point was to recognize the limits of the approach, which mainly derive from species- and disease-related differences in cardiovascular physiology. For instance, the mouse heart beats at a rate 10 times faster than the human heart. Furthermore, healing processes are more rapid in animals, as they rely on mechanisms that may have lost relevance in man. The main objective of the authors was to propose general guidelines, diagnostic end points and relevance to clinical problems.

Tissue kallikrein and kinin receptor expression in an angiogenic co-culture neuroblastoma model

The sprouting of new blood vessels from pre-existing vasculature (angiogenesis) is essential for tumour survival, influenced by tumour cell-endothelial cell interactions and is tightly regulated by biochemical cues including the kallikrein-kinin system (KKS). We examined the structural interaction between neuroblastomas and endothelial cells (HUVECs) in 2-D and 3-D (matrigel) in vitro, co-culture models by light microscopy, and performed in situ mono- and co-labelling of various KKS proteins. Neuroblastomas formed footplate-like multiple contacts on angiogenic HUVECs without disrupting differentiation of HUVECs into cord-like structures. Tissue kallikrein and the kinin B1R and B2R receptors were demonstrated on interacting neuroblastomas and HUVECs to varying degrees, as well as at actual heterogeneous contact zones in both 2-D and 3-D models. This KKS immuno-reactivity was generally confined to peri-nuclear regions on HUVECs but concentrated on cell extensions on neuroblastomas. The KKS, known to enhance DNA synthesis and process pro-angiogenic precursors of both tumour cells and the extra-cellular matrix, may, by its multi-functional activities at sites of tumour-blood vessel interactions, regulate aspects of both angiogenesis and tumourigenesis.

The role of bradykinin B1 receptor on cardiac remodeling in stroke-prone spontaneously hypertensive rats (SHR-SP)

An angiotensin-converting enzyme inhibitor (ACE-I) reduces cardiac remodeling and a bradykinin B2 receptor (B2R) antagonist partially abolishes this ACE-I effect. However, bradykinin has two different types of receptor, the B1 receptor (B1R) and B2R. Although B1R is induced under several pathological conditions, including hypertension, the role of cardiac B1R in hypertension is not clear. We therefore investigated the role of cardiac B1R in stroke-prone spontaneously hypertensive rats (SHR-SP) and Wistar-Kyoto (WKY) rats. The B1R mRNA expression level in the heart was significantly higher in SHR-SP than in WKY rats. Chronic infusion of a B1R antagonist for 4 weeks significantly elevated blood pressure and left-ventricular weight of SHR-SP. Morphological analysis indicated that cardiomyocyte size and cardiac fibrosis significantly increased after administration of the B1R antagonist. The phosphorylation of mitogen-activated protein (MAP) kinases, including ERK, p38, and JNK, was significantly increased in the hearts of SHR-SP rats receiving the B1R antagonist. The TGF-β1 expression level was significantly increased in SHR-SP rats treated with the B1R antagonist compared to that in WKY rats. The B1R antagonist significantly increased phosphorylation of Thr495 in endothelial nitric oxide synthase (eNOS), which is an inhibitory site of eNOS. These results suggest that the role of B1R in the heart may be attenuation of cardiac remodeling via inhibition of the expression of MAP kinases and TGF-β1 through an increase in eNOS activity in a hypertensive condition.

Benfotiamine accelerates the healing of ischaemic diabetic limbs in mice through protein kinase B/Akt-mediated potentiation of angiogenesis and inhibition of apoptosis

AIMS/HYPOTHESIS

Benfotiamine, a vitamin B1 analogue, reportedly prevents diabetic microangiopathy. The aim of this study was to evaluate whether benfotiamine is of benefit in reparative neovascularisation using a type I diabetes model of hindlimb ischaemia. We also investigated the involvement of protein kinase B (PKB)/Akt in the therapeutic effects of benfotiamine.

METHODS

Streptozotocin-induced diabetic mice, given oral benfotiamine or vehicle, were subjected to unilateral limb ischaemia. Reparative neovascularisation was analysed by histology. The expression of Nos3 and Casp3 was evaluated by real-time PCR, and the activation state of PKB/Akt was assessed by western blot analysis and immunohistochemistry. The functional importance of PKB/Akt in benfotiamine-induced effects was investigated using a dominant-negative construct.

RESULTS

Diabetic muscles showed reduced transketolase activity, which was corrected by benfotiamine. Importantly, benfotiamine prevented ischaemia-induced toe necrosis, improved hindlimb perfusion and oxygenation, and restored endothelium-dependent vasodilation. Histological studies revealed the improvement of reparative neovascularisation and the inhibition of endothelial and skeletal muscle cell apoptosis. In addition, benfotiamine prevented the vascular accumulation of advanced glycation end products and the induction of pro-apoptotic caspase-3, while restoring proper expression of Nos3 and Akt in ischaemic muscles. The benefits of benfotiamine were nullified by dominant-negative PKB/Akt. In vitro, benfotiamine stimulated the proliferation of human EPCs, while inhibiting apoptosis induced by high glucose. In diabetic mice, the number of circulating EPCs was reduced, with the deficit being corrected by benfotiamine.

CONCLUSIONS/INTERPRETATION

We have demonstrated, for the first time, that benfotiamine aids the post-ischaemic healing of diabetic animals via PKB/Akt-mediated potentiation of angiogenesis and inhibition of apoptosis. In addition, benfotiamine combats the diabetes-induced deficit in endothelial progenitor cells.

The tissue kallikrein-kinin system protects against cardiovascular and renal diseases and ischemic stroke independently of blood pressure reduction

Tissue kallikrein (hK1) cleaves low-molecular-weight kininogen to produce kinin peptide, which binds to kinin receptors and triggers a wide spectrum of biological effects. Tissue kallikrein levels are reduced in humans and in animal models with hypertension, cardiovascular and renal diseases. Transgenic mice or rats over-expressing human tissue kallikrein or kinin B2 receptor are permanently hypotensive, and somatic kallikrein gene delivery reduces blood pressure in several hypertensive rat models. Moreover, kallikrein gene delivery or kallikrein protein infusion can directly improve cardiac, renal and neurological function without blood pressure reduction. Kallikrein has pleiotropic effects in inhibiting apoptosis, inflammation, proliferation, hypertrophy and fibrosis, and promoting angiogenesis and neurogenesis in different experimental animal models. Kallikrein's effects can be blocked by kinin B2 receptor antagonists. Mechanistically, tissue kallikrein/kinin leads to increased nitric oxide levels and Akt activation, and reduced reactive oxygen species formation, TGF-beta1 expression, MAPK and nuclear factor-kappaB activation. Our studies indicate that tissue kallikrein, through the kinin B2 receptor and nitric oxide formation, can protect against oxidative damage in cardiovascular and renal diseases and ischemic stroke. These novel findings suggest that kallikrein/kinin may serve as new drug targets for the prevention and treatment of heart failure, renal disease and stroke in humans.

Role of cystatins in tumor neovascularization

Cystatins form a large superfamily of proteins with diverse biologic activities. All members of the cystatin superfamily share the presence of one, two or three cystatin domains. Cystatins were initially believed to act mainly as inhibitors of lysosomal cysteine proteases. In recent years, however, there has been increased awareness of additional or alternate biologic functions for these proteins. In this review, the authors will discuss the most recent findings and hypotheses that suggest that some members of the cystatin superfamily may play important roles during tumor progression. Special emphasis is given to their potential role as novel anti-angiogenic agents.

Ovarian cancer, the coagulation pathway, and inflammation

Epithelial ovarian cancer (EOC) represents the most frequent cause of death in the United States from a cancer involving the female genital tract. Contributing to the overall poor outcome in EOC patients, are the metastases to the peritoneum and stroma that are common in this cancer. In one study, cDNA microarray analysis was performed on fresh tissue to profile gene expression in patients with EOC. This study showed a number of genes with significantly altered expression in the pelvic peritoneum and stroma, and in the vicinity of EOC implants. These genes included those encoding coagulation factors and regulatory proteins in the coagulation cascade and genes encoding proteins associated with inflammatory responses. In addition to promoting the formation of blood clots, coagulation factors exhibit many other biologic functions as well as tumorigenic functions, the later including tumor cell proliferation, angiogenesis, invasion, and metastasis. Coagulation pathway proteins involved in tumorigenesis consist of factor II (thrombin), thrombin receptor (protease-activated receptors), factor III (tissue factor), factor VII, factor X and factor I (fibrinogen), and fibrin and factor XIII. In a recent study we conducted, we found that factor XII, factor XI, and several coagulation regulatory proteins, including heparin cofactor-II and epithelial protein C receptor (EPCR), were also upregulated in the peritoneum of EOC. In this review, we summarize evidence in support of a role for these factors in promoting tumor cell progression and the formation of ascites. We also discuss the different roles of coagulation factor pathways in the tumor and peritumoral microenvironments as they relate to angiogenesis, proliferation, invasion, and metastasis. Since inflammatory responses are another characteristic of the peritoneum in EOC, we also discuss the linkage between the coagulation cascade and the cytokines/chemokines involved in inflammation. Interleukin-8, which is considered an important chemokine associated with tumor progression, appears to be a linkage point for coagulation and inflammation in malignancy. Lastly, we review findings regarding the inflammatory process yielded by certain clinical trials of agents that target members of the coagulation cascade in the treatment of cancer. Current data suggest that disrupting certain elements of the coagulation and inflammation processes in the tumor microenvironment could be a new biologic approach to cancer therapeutics.

Putative roles of kinin receptors in the therapeutic effects of angiotensin 1-converting enzyme inhibitors in diabetes mellitus

The role of endogenous kinins and their receptors in diabetes mellitus is being confirmed with the recent developments of molecular and genetic animal models. Compelling evidence suggests that the kinin B(2) receptor is organ-protective and partakes to the therapeutic effects of angiotensin 1-converting enzyme inhibitors (ACEI) and angiotensin AT(1) receptor antagonists. Benefits derive primarily from vasodilatory, antihypertensive, antiproliferative, antihypertrophic, antifibrotic, antithrombotic and antioxidant properties of kinin B(2) receptor activation. Mechanisms include the formation of nitric oxide and prostacyclin and the inhibition of NAD(P)H oxidase activity involving classical and novel signalling pathways. Kinin B(2) receptor also ameliorates insulin resistance by increasing glucose uptake and supply, and by inducing glucose transporter-4 translocation either directly or through phosphorylation of insulin receptor. The kinin B(1) receptor, which is induced by the cytokine network, growth factors and hyperglycaemia, mediates hyperalgesia, vascular hyperpermeability and leukocytes infiltration in diabetic animals. However, emerging data highlight reno- and cardio-protective effects mediated by kinin B(1) receptor under chronic ACEI therapy in diabetes mellitus. Thus, the Janus-faced of kinin receptors needs to be taken into account in future drug development. For instance, locally acting kinin B(1)/B(2) receptor agonists if used in a safe therapeutic window may represent a more rationale strategy in the prevention and management of diabetic complications. Because kinin B(2) receptor antagonists may further increase insulin resistance, the persisting dogma that restricts the development of kinin receptor analogues to antagonists (that is still relevant to abrogate pain and inflammation) needs to be revisited.

International union of pharmacology. XLV. Classification of the kinin receptor family: from molecular mechanisms to pathophysiological consequences

Kinins are proinflammatory peptides that mediate numerous vascular and pain responses to tissue injury. Two pharmacologically distinct kinin receptor subtypes have been identified and characterized for these peptides, which are named B1 and B2 and belong to the rhodopsin family of G protein-coupled receptors. The B2 receptor mediates the action of bradykinin (BK) and lysyl-bradykinin (Lys-BK), the first set of bioactive kinins formed in response to injury from kininogen precursors through the actions of plasma and tissue kallikreins, whereas the B(1) receptor mediates the action of des-Arg9-BK and Lys-des-Arg9-BK, the second set of bioactive kinins formed through the actions of carboxypeptidases on BK and Lys-BK, respectively. The B2 receptor is ubiquitous and constitutively expressed, whereas the B1 receptor is expressed at a very low level in healthy tissues but induced following injury by various proinflammatory cytokines such as interleukin-1beta. Both receptors act through G alpha(q) to stimulate phospholipase C beta followed by phosphoinositide hydrolysis and intracellular free Ca2+ mobilization and through G alpha(i) to inhibit adenylate cyclase and stimulate the mitogen-activated protein kinase pathways. The use of mice lacking each receptor gene and various specific peptidic and nonpeptidic antagonists have implicated both B1 and B2 receptors as potential therapeutic targets in several pathophysiological events related to inflammation such as pain, sepsis, allergic asthma, rhinitis, and edema, as well as diabetes and cancer. This review is a comprehensive presentation of our current understanding of these receptors in terms of molecular and cell biology, physiology, pharmacology, and involvement in human disease and drug development.

Therapeutic angiogenesis and vasculogenesis for tissue regeneration

Therapeutic angiogenesis/vasculogenesis holds promise for the cure of ischaemic disease. The approach postulates the manipulation of spontaneous healing response by supplementation of growth factors or transplantation of vascular progenitor cells. These supplements are intended to foster the formation of arterial collaterals and promote the regeneration of damaged tissues. Angiogenic factors are generally delivered in the form of recombinant proteins or by gene transfer using viral vectors. In addition, new non-viral methods are gaining importance for their safer profile. The association of growth factors with different biological activity might offer distinct advantages in terms of efficacy, yet combined approaches require further optimization. Alternatively, substances with pleiotropic activity might be considered, by virtue of their ability to target multiple mechanisms. For instance, some angiogenic factors not only stimulate the growth of arterioles and capillaries, but also inhibit vascular destabilization triggered by metabolic and oxidative stress. Transplantation of endothelial progenitor cells was recently proposed for the treatment of peripheral and myocardial ischaemia. Progenitor cells can be transplanted either without any preliminary conditioning or after ex vivo genetic manipulation. Delivery of genetically modified progenitor cells eliminates the drawback of immune response against viral vectors and makes feasible repeating the therapeutic procedure in case of injury recurrence. It is envisioned that these new approaches of regenerative medicine will open unprecedented opportunities for the care of life-threatening diseases.

Kallikrein–kinin in stroke, cardiovascular and renal disease

Tissue kallikrein, a serine proteinase, produces the potent vasodilator kinin peptide from kininogen substrate. The levels of tissue kallikrein are reduced in humans and animal models with hypertension, cardiovascular and renal disease. Using transgenic and somatic gene transfer approaches, we investigated the role of the tissue kallikrein-kinin system in cardiovascular, renal and central nervous systems. A single injection of the human tissue kallikrein gene in plasmid DNA or an adenoviral vector resulted in a prolonged reduction of blood pressure and attenuation of hypertrophy and fibrosis in the heart and kidney of several hypertensive animal models. Furthermore, enhanced kallikrein-kinin levels after gene transfer exerted beneficial effects, with protection against cardiac remodelling, renal injuries, restenosis, cerebral infarction and neurological deficits in normotensive animal models without haemodynamic effects, indicating direct actions of kallikrein independent of its ability to lower blood pressure. The effects of kallikrein were mediated by the kinin B2 receptor, as the specific B2 receptor antagonist icatibant abolished the actions of kallikrein. Moreover, kallikrein-kinin exhibited pleiotropic effects by inhibiting apoptosis, inflammation, hypertrophy and fibrosis, and promoting angiogenesis and neurogenesis in the heart, kidney, brain and blood vessel. Exogenous administration of kallikrein also led to increased nitric oxide (NO)/cGMP and cAMP levels, and reduced NAD(P)H oxidase activities, superoxide formation and pro-inflammatory cytokine levels. These results indicate a novel role of kallikrein-kinin through the kinin B2 receptor as an antioxidant and anti-inflammatory agent in protection against stroke, cardiovascular and renal disease, and may uncover new drug targets for the prevention and treatment of heart failure, vascular injury, end-stage renal disease and stroke in humans.

Changing the logic of therapeutic angiogenesis for ischemic disease

The worldwide epidemic of ischemic disease urgently requires innovative treatments. Recently, therapeutic angiogenesis has emerged as a noninvasive supply-side approach, aimed at promoting neovascularization in underperfused tissues through the local delivery of angiogenic growth factors. Successful preclinical studies paved the way for the first clinical trials, with single growth factors given as recombinant proteins or genes. However, clinical results have not matched the initial promises. Our opinion is that the logic of therapeutic angiogenesis needs profound revision. Here, we introduce the concept that pleiotropic agents can stimulate the healing of all the components of ischemic tissue. We also propose prophylactic interventions to delay vascular senescence. The optimization of therapeutic angiogenesis will open unprecedented opportunities for the care of life-threatening ischemic disease.

Increased circulating levels of tissue kallikrein in systemic sclerosis correlate with microvascular involvement

BACKGROUND

In systemic sclerosis (SSc) the lack of an angiogenic response to hypoxia may be due to inappropriate synthesis of angiogenic and angiostatic factors. Tissue kallikrein (t-kallikrein), regulating the kallikrein-kinin system and acting on the microcirculation, is a potent angiogenic agent, and kallistatin is its natural inhibitor.

OBJECTIVE

To evaluate, in patients with SSc, t-kallikrein and kallistatin levels and their correlation with clinical features and measures of microvascular involvement.

PATIENTS AND METHODS

Serum levels of t-kallikrein and kallistatin (ELISA) and t-kallikrein skin expression (immunohistochemistry) were studied in patients with SSc, and evaluated for subset (dSSc or lSSc), clinical and immunological features, and microvascular involvement (ulcers, telangiectasias, nailfold videocapillaroscopy).

RESULTS

Circulating levels of t-kallikrein were higher in SSc than in controls (p<0.001). T-kallikrein did not differ between lSSc and dSSc, although it was higher in lSSc than in controls (p<0.001).T-kallikrein levels were higher in patients with early and active capillaroscopic pattern than in those with late pattern (p = 0.019 and 0.023). Patients with giant capillaries and capillary microhaemorrhages had higher t-kallikrein concentrations than patients with architectural derangement (p = 0.04). No differences in kallistatin levels were detected between patients with SSc and controls, or between lSSc and dSSc. In early SSc skin, the presence of t-kallikrein was found in endothelial and in perivascular inflammatory cells, while no staining in skin of advanced SSc was detected.

CONCLUSION

T-kallikrein levels are increased in patients with SSc, particularly in lSSc, and are associated with early and active capillaroscopic patterns. T-kallikrein may play a part in SSc microvascular changes.

Role of the B1 kinin receptor in the regulation of cardiac function and remodeling after myocardial infarction

Kinins exert cardioprotective effects via 2 G-protein-coupled receptors, B1 and B2. Using B1 kinin receptor gene knockout mice (B1-/-), we tested the hypotheses that the B1 receptor plays an important role in preservation of cardiac function, whereas lack of B1 may accelerate cardiac remodeling and dysfunction after myocardial infarction, and that B2 receptors may compensate for lack of B1, whereas blockade of B2 receptors in B1-/- mice may cause further deterioration of cardiac function and remodeling. Female B1-/- mice and wild-type controls (C57BL/6J, B1+/+) underwent sham surgery or myocardial infarction and were treated with either vehicle or B2-antagonist (icatibant, 500 microg/kg per day, subcutaneous) for 8 weeks. We found that in sham myocardial infarction, B1-/- mice had a larger left ventricular diastolic chamber dimension both initially and at 4 to 8 weeks compared with B1+/+. Left ventricular mass and myocyte size were also larger in B1-/- with sham operation than in B1+/+, although cardiac function did not differ between strains. After myocardial infarction, cardiac remodeling and function were similar in both strains, although B1-/- mice tended to have lower blood pressure. Blockade of B2 receptors tended to worsen cardiac remodeling and dysfunction in B1-/- but not in B1+/+. These results may suggest that B2 receptors play an important role in compensating for lack of B1 receptors in mice with myocardial infarction. Dual blockade of both B1 and B2 eliminates this compensation, leading to further deterioration of cardiac dysfunction and remodeling after myocardial infarction.

The emerging roles of human tissue kallikreins in cancer

Human tissue kallikreins (hKs), which are encoded by the largest contiguous cluster of protease genes in the human genome, are secreted serine proteases with diverse expression patterns and physiological roles. Although primarily known for their clinical applicability as cancer biomarkers, recent evidence implicates hKs in many cancer-related processes, including cell-growth regulation, angiogenesis, invasion and metastasis. They have been shown to promote or inhibit neoplastic progression, acting individually and/or in cascades with other hKs and proteases, and might represent attractive targets for therapeutic intervention.

CCR2-/- knockout mice revascularize normally in response to severe hindlimb ischemia

OBJECTIVE

Monocyte chemoattractant protein-1 (MCP-1) is reported to stimulate ischemia-induced arteriogenesis (collateral artery development) by recruiting monocytes and macrophages into areas of active arteriogenesis. To determine whether the MCP-1-mediated response occurs through its receptor, CC-chemokine receptor 2 (CCR2), we induced hindlimb ischemia in mice lacking the receptor for MCP-1 (CCR2 -/- ) and measured limb blood flow recovery, collateral artery development, and monocyte and macrophage recruitment.

METHODS AND RESULTS

Hindlimb ischemia was induced by excising the left femoral artery in CCR2 -/- and wild-type mice. Hindlimb blood flow recovery, as measured using laser Doppler perfusion imaging, was equivalent in both groups ( P = .78 for foot and P = 0.38 for calf). Collateral artery development, as measured by angiography at postoperative day 14 and 31, likewise did not differ between the 2 groups ( P = .46 and P = .67). Counts of monocytes and macrophages in calf and thigh muscle sections of mice sacrificed on postoperative day 7 revealed that although CCR2 -/- mice recruited 44% fewer monocytes and macrophages to areas of ischemia in the calf, they recruited similar numbers of monocytes and macrophages to areas of active arteriogenesis in the thigh. Intercellular adhesion molecule-1 and MCP-1 mRNA levels were higher in the thigh muscle of CCR2 -/- mice than in wild-type mice (5.5-fold and 42.3-fold induction operated to unoperated vs 2.6-fold and 6.1-fold induction operated to unoperated, respectively).

CONCLUSIONS

Blood flow recovery, arteriogenesis, and monocyte and macrophage recruitment to the thigh was normal in CCR2 -/- mice. However, monocyte and macrophage recruitment to the ischemic calf was diminished in CCR2 -/- mice. Our results show that MCP-1 signaling through CCR2 is not required for physiologic arteriogenesis in response to severe hindlimb ischemia. ICAM-1 upregulation may substitute for MCP-1 signaling through CCR2 in order to allow normal arteriogenesis in CCR2 -/- mice.

Host stromal bradykinin B2 receptor signaling facilitates tumor-associated angiogenesis and tumor growth

We evaluated the significance of the host kallikrein-kinin system in tumor angiogenesis and tumor growth using two rodent models genetically deficient in a kallikrein-kinin system. Inoculation of Walker 256 carcinoma cells into the s.c. tissues of the back of normal Brown Norway Kitasato rats (BN-Ki rats) resulted in the rapid development of solid tumors with marked angiogenesis. By contrast, in kininogen-deficient Brown Norway Katholiek rats (BN-Ka rats), which cannot generate intrinsic bradykinin (BK), the weights of the tumors and the extent of angiogenesis were significantly less than those in BN-Ki rats. Daily administration of B(2) receptor antagonists significantly reduced angiogenesis and tumor weights in BN-Ki rats to levels similar to those in BN-Ka rats but did not do so in BN-Ka rats. Angiogenesis and tumor growth were significantly suppressed in B(2) receptor knockout mice bearing sarcoma 180 compared with their wild-type counterparts. Immunoreactive vascular endothelial growth factor (VEGF) was localized in Walker tumor stroma more extensively in BN-Ki rats than in BN-Ka rats, although immunoreactive B(2) receptor also was detected in the stroma to the same extent in both types of rats. Cultured stromal fibroblasts isolated from BN-Ki rats and BN-Ka rats produced VEGF in response to BK (10(-8)-10(-6) m), and this stimulatory effect of BK was abolished with a B(2) receptor antagonist, Hoe140 (10(-5) m). These results suggest that BK generated from kininogens supplied from the host may facilitate tumor-associated angiogenesis and tumor growth by stimulating stromal B(2) signaling to up-regulate VEGF production mainly in fibroblasts.

Transplantation of low dose CD34+KDR+ cells promotes vascular and muscular regeneration in ischemic limbs

Hematopoietic progenitor cell transplantation can contribute to revascularization of ischemic tissues. Yet, the optimal cell population to be transplanted has yet to be determined. We have compared the therapeutic potential of two subsets of human cord blood CD34+ progenitors, either expressing the VEGF-A receptor 2 (KDR) or not. In serum-free starvation culture, CD34+KDR+ cells reportedly showed greater resistance to apoptosis and ability to release VEGF-A, as compared with CD34+KDR- cells. When injected into the hind muscles in immunodeficient SCIDbg mice subjected to unilateral ischemia, a low number (10(3)) of CD34+KDR+ cells improved limb salvage and hemodynamic recovery better than a larger dosage (10(4)) of CD34+KDR- cells. The neovascularization induced by KDR+ cells was significantly superior to that promoted by KDR- cells. Similarly, endothelial cell apoptosis and interstitial fibrosis were significantly attenuated by KDR+ cells, which differentiated into mature human endothelial cells and also apparently skeletal muscle cells. This study demonstrates that a low number of CD34+KDR+ cells favors reparative neovascularization and possibly myogenesis in limb ischemia, suggesting the potential use of this cell population in regenerative medicine.

Prevention of cardiac fibrosis and left ventricular dysfunction in diabetic cardiomyopathy in rats by transgenic expression of the human tissue kallikrein gene

Diabetic cardiomyopathy includes fibrosis. Kallikrein (KLK) can inhibit collagen synthesis and promote collagen breakdown. We investigated cardiac fibrosis and left ventricular (LV) function in transgenic rats (TGR) expressing the human kallikrein 1 (hKLK1) gene in streptozotocin (STZ) -induced diabetic conditions. Six weeks after STZ injection, LV function was determined in male Sprague-Dawley (SD) rats and TGR(hKLK1) (n=10/group) by a Millar tip catheter. Total collagen content (Sirius Red staining) and expression of types I, III, and VI collagen were quantified by digital image analysis. SD-STZ hearts demonstrated significantly higher total collagen amounts than normoglycemic controls, reflected by the concomitant increment of collagen types I, III, and VI. This correlated with a significant reduction of LV function vs. normoglycemic controls. In contrast, surface-specific content of the extracellular matrix, including collagen types I, III, and VI expression, was significantly lower in TGR(hKLK1)-STZ, not exceeding the content of SD and TGR(hKLK1) controls. This was paralleled by a preserved LV function in TGR(hKLK1)-STZ animals. The kallikrein inhibitor aprotinin and the bradykinin (BK) B2 receptor antagonist icatibant reduced the beneficial effects on LV function and collagen content in TGR(hKLK1)-STZ animals. Transgenic expression of hKLK1 counteracts the progression of LV contractile dysfunction and extracellular matrix remodeling in STZ-induced diabetic cardiomyopathy via a BK B2 receptor-dependent pathway.

Genetically Engineered Stem Cell Therapy for Tissue Regeneration

Therapeutic angiogenesis/vasculogenesis represents a new approach to treat patients with ischemic disease not curable with conventional treatment. This review focuses on the rationale and preliminary results of combining stem cell and gene therapy for regenerative medicine. Under disease conditions, impaired neovascularization results from diminished vascular growth factor production and primary dysfunction of endothelial cells and their progenitors. Advances in our ability to genetically manipulate cells ex vivo has provided the technological platform to implement stem cell biology and circumvent the potential hazard of direct gene transfer. Ex vivo engineered endothelial progenitor cells have been used for the treatment of peripheral limb ischemia. The approach eliminates the drawback of immune response against viral vectors and makes feasible repeating the therapeutic procedure in case of injury recurrence. The strategy of using stem cells as vectors for curative agents proved to be of value for the treatment of pulmonary hypertension and thrombosis. Transplantation of neural stem cells genetically modified to secrete nerve growth factor was able to ameliorate the death of striatal projection neurons caused by transient focal ischemia in the adult rat. By a similar approach, engineered neural stem cells might be used for treating neurodegenerative disorders. Therefore, genetic manipulation of stem cells opens new avenues for regenerative medicine.

Prophylactic gene therapy with human tissue kallikrein ameliorates limb ischemia recovery in type 1 diabetic mice

Diabetes macro- and microvascular disease causes tissue hypoperfusion. This deficit, together with a failure to mount an adequate angiogenic response, might explain why vascular occlusion evolves more severely among diabetic patients. The present study investigated whether prophylactic gene therapy with human tissue kallikrein (hTK) may protect diabetic limbs from the consequences of supervening ischemia. Vehicle (saline) or an adenovirus carrying the gene for either hTK (Ad.hTK) or luciferase (Ad.Luc) was injected into left adductor muscles of streptozotocin-induced type 1 diabetic mice 2 weeks before operative occlusion of the ipsilateral femoral artery. Saline-injected nondiabetic mice served as controls. Hindlimb blood flow recovery was analyzed sequentially over the 2 weeks after ischemia induction. At necroscopy, microvessel density and endothelial cell proliferation and apoptosis were quantified in skeletal muscles. We found that limb perfusion recovery of saline-injected type 1 diabetic mice is delayed because of insufficient reparative neovascularization and excessive activation of endothelial cell apoptosis. By contrast, prophylactic Ad.hTK renewed the ability to mount an appropriate neovascularization response to ischemia, suppressed apoptosis, and upregulated endothelial nitric oxide synthase expression. Ultimately, correction of diabetic endotheliopathy by Ad.hTK allowed proper perfusion recovery as seen in nondiabetic mice. These discoveries disclose new therapeutic options for the treatment of diabetic complications.

Intramuscular electroporation with the pro-opiomelanocortin gene in rat adjuvant arthritis

Endogenous opioid peptides have an essential role in the intrinsic modulation and control of inflammatory pain, which could be therapeutically useful. In this study, we established a muscular electroporation method for the gene transfer of pro-opiomelanocortin (POMC) in vivo and investigated its effect on inflammatory pain in a rat model of rheumatoid arthritis. The gene encoding human POMC was inserted into a modified pCMV plasmid, and 0-200 microg of the plasmid-POMC DNA construct was transferred into the tibialis anterior muscle of rats treated with complete Freund's adjuvant (CFA) with or without POMC gene transfer by the electroporation method. The safety and efficiency of the gene transfer was assessed with the following parameters: thermal hyperalgesia, serum adrenocorticotropic hormone (ACTH) and endorphin levels, paw swelling and muscle endorphin levels at 1, 2 and 3 weeks after electroporation. Serum ACTH and endorphin levels of the group into which the gene encoding POMC had been transferred were increased to about 13-14-fold those of the normal control. These levels peaked 1 week after electroporation and significantly decreased 2 weeks after electroporation. Rats that had received the gene encoding POMC had less thermal hypersensitivity and paw swelling than the non-gene-transferred group at days 3, 5 and 7 after injection with CFA. Our promising results showed that transfer of the gene encoding POMC by electroporation is a new and effective method for its expression in vivo, and the analgesic effects of POMC cDNA with electroporation in a rat model of rheumatoid arthritis are reversed by naloxone.