PR39, a peptide regulator of angiogenesis

Cathelicidins in inflammation and tissue repair: Potential therapeutic applications for gastrointestinal disorders

Cathelicidins, a family of host defense peptides, are highly expressed during infection, inflammation and wound healing. These peptides not only have broad-spectrum antimicrobial activities, but also modulate inflammation by altering cytokine response and chemoattraction of inflammatory cells in diseased tissues. In this connection, a mouse cathelicidin has been demonstrated to prevent inflammation in the colon through enhancing mucus production and reducing production of pro-inflammatory cytokines. In addition, cathelicidins promote wound healing through stimulation of re-epithelialization and angiogenesis at injured tissues. In an animal model of gastric ulceration, the rat cathelicidin promotes ulcer healing by inducing proliferation of gastric epithelial cells both in vitro and in vivo. In conclusion, cathelicidins represent an important group of effector molecules in the innate immune system that operates a complex integration of inflammation and tissue repair in the gastrointestinal mucosa and other organs.

The cytotoxic effects of the anti-bacterial peptides on leukocytes

Antimicrobial peptides are small molecular weight proteins with a large antibacterial spectrum. They can reach high local concentrations in tissues with active inflammation, being largely produced by immunocompetent cells. However, their effect on eukaryotic cells is still unclear. We have, therefore, studied three structurally different antimicrobial peptides (cecropin P1, PR-39 and NK-lysin) for their cytotoxic effects on blood mononuclear cells. None of the antimicrobial peptides tested exhibited significant cytotoxic effect on resting lymphocytes isolated either from peripheral blood or from the spleen with the exception of high concentrations (ten times higher than IC100 for Escherichia coli) of NK-lysin. Activated lymphocytes were, however, more sensitive to the cytotoxic effect of the antimicrobial peptides. Both activated T-cells and B-cells were dose dependent sensitive to NK-lysin while only activated B-cells but not activated T-cells were sensitive to PR-39. Cecropin did not exhibit any cytotoxic effect on activated lymphocytes either. By using several cell lines (3B6, K562, U932 and EL-4) we were able to show that NK-lysin has a broad necrotic effect while PR-39 has a cell specific apoptotic effect dependent on the specifically cellular uptake. In conclusion we show here that antimicrobial peptides are not cytotoxic for the resting eukaryotic cells but can be cytotoxic on activated immune cells through distinct mechanisms of cell death.

Therapeutic potential of HDPs as immunomodulatory agents

One of the most significant advances in medical history is the discovery and development of antibiotics, which in the middle of last century was flourishing and appeared to be the ultimate solution to the treatment of life-threatening human bacterial diseases. However, lately there has been a huge decline in the rate of discovery of new antimicrobial intervention strategies in parallel with an increasing incidence of multidrug-resistant pathogens; if these circumstances do not change we will continue to approach the end of the antibiotic era. Facing this dark future, scientists are considering new strategies for intervention tailored around the appropriate (selective) stimulation of the host's immune system, and particularly rapid acting innate immunity, as an alternative to direct targeting of microbial pathogens. One recent player in such an immunomodulatory strategy is the naturally occurring host defence peptides (HDP) and their synthetic innate defence regulator (IDR) analogues. In this chapter, we will discuss the potential therapeutic use of HDPs and IDRs as immunomodulatory agents.

The vasa vasorum in diseased and nondiseased arteries

The vasa vasorum form a network of microvasculature that originate primarily in the adventitial layer of large arteries. These vessels supply oxygen and nutrients to the outer layers of the arterial wall. The expansion of the vasa vasorum to the second order is associated with neovascularization related to progression of atherosclerosis. Immunohistological analysis of human plaques from autopsied aortas have defined plaque progression and show a significant correlation with vasa vasorum neovascularization. Recent technological advances in microcomputed tomography have enabled investigation of vasa vasorum structure and function in nondiseased large arteries from pigs and dogs. Smaller mammals, particularly mice with genetic modifications that enable disease development, have been used extensively to study the vasa vasorum in diseased vessels. Despite the fact that most mouse models that are used to study atherosclerosis are unable to develop plaque to the extent found in humans, studies in both humans and mice underscore the importance of angiogenic vasa vasorum in progression of atherosclerosis. Those who have examined the vasa vasorum in occluded vessels of nondiseased pigs and dogs find that inhibition of the vasa vasorum makes the animals atheroprone. Atherosclerosis is a multifactorial disease. There is increasing evidence that factors, produced in response to changes in the arterial wall, collaborate with the vasa vasorum to enhance the disease process.

Imaging myocardial angiogenesis

Imaging myocardial angiogenesis presents a major technical challenge because the ideal spatial resolution required is substantially higher than that available with standard X-ray angiography and nuclear medicine imaging. Moreover, these clinical imaging methods are currently inadequate (because of insufficient resolution) for clinical trials of angiogenic agents for the treatment of ischemic heart disease. Specialized techniques in MRI, ultrasonography, echocardiography and CT that are under development might provide improved means of imaging myocardial angiogenesis. Molecular imaging technologies are also being developed to improve resolution and to provide a better mechanistic insight into angiogenic therapies for ischemic heart diseases. This Review examines advanced methods for imaging angiogenesis. These technologies might soon permit data to be obtained directly from scientific studies and clinical trials.

Proteasome inhibitors and cardiac cell growth

Activation of the ubiquitin-proteasome system has been described in different models of cardiac hypertrophy. Cardiac cell growth in response to pressure or volume overload, as well as physiological adaptive hypertrophy, is accompanied by an increase in protein ubiquitination, proteasome subunit expression, and proteasome activity. Importantly, an inhibition of proteasome activity prevents and reverses cardiac hypertrophy and remodelling in vivo. The focus of this review is to provide an update about the mechanisms by which proteasome inhibitors affect cardiac cell growth in adaptive and maladaptive models of cardiac hypertrophy. In the first part, we summarize how the proteasome affects both proteolysis and protein synthesis in a context of cardiac cell growth. In the second part, we show how proteasome inhibition can prevent and reverse cardiac hypertrophy and remodelling in response to different conditions of overload.

Therapeutic angiogenesis in the management of critical limb ischemia: current concepts and review

Critical limb ischemia (CLI) represents the most severe form of peripheral arterial disease. Manifestations of CLI include rest pain, ischemic ulcers, and/or gangrene. The presence of CLI frequently leads to amputation, and furthermore, patients with CLI are at an increased risk of cardiovascular events including death. Treatment options for CLI when revascularization is not possible are extremely limited. Therapeutic angiogenesis is a promising new tool in the management of CLI. There is a growing body of evidence demonstrating the safety and efficacy of therapeutic angiogenesis with gene and cell therapy. Many factors must be considered in formulating clinically efficacious gene and/or cell therapies. The dosing regimen, route of delivery, and choice of growth factor or cell population must be decided. Although the optimal regimen of therapeutic angiogenesis has yet to be identified, building on the knowledge gained from the early pioneering studies may help to identify the best combination.

In vivo properties of the proangiogenic peptide QK

The main regulator of neovascularization is Vascular Endothelial Growth Factor (VEGF). We recently demonstrated that QK, a de novo engineered VEGF mimicking peptide, shares in vitro the same biological properties of VEGF, inducing capillary formation and organization. On these grounds, the aim of this study is to evaluate in vivo the effects of this small peptide. Therefore, on Wistar Kyoto rats, we evaluated vasomotor responses to VEGF and QK in common carotid rings. Also, we assessed the effects of QK in three different models of angiogenesis: ischemic hindlimb, wound healing and Matrigel plugs. QK and VEGF present similar endothelium-dependent vasodilatation. Moreover, the ability of QK to induce neovascularization was confirmed us by digital angiographies, dyed beads dilution and histological analysis in the ischemic hindlimb as well as by histology in wounds and Matrigel plugs. Our findings show the proangiogenic properties of QK, suggesting that also in vivo this peptide resembles the full VEGF protein. These data open to new fields of investigation on the mechanisms of activation of VEGF receptors, offering clinical implications for treatment of pathophysiological conditions such as chronic ischemia.

Macrophage-specific overexpression of antimicrobial peptide PR-39 inhibits intracellular growth of Salmonella enterica serovar Typhimurium in macrophage cells

Although purified and synthesised PR-39 shows potent antibacterial effects in vitro, its ability to kill intracellular bacteria in macrophages, which are a major cause of refractory intracellular infection, has not yet been demonstrated. Both to enhance its antimicrobial potential and to reduce systemic side effects, it would be desirable to deliver PR-39 into macrophage cells and to limit its activation to the site of infection. To address this issue, PR-39 DNA was inserted into the eukaryotic expression plasmid pIRES2-EGFP and the adenoviral vector Ad-MSP, from which PR-39 can be specifically expressed in macrophage cells from the macrophage-specific promoter. pIRES2-EGFP/PR39 and Ad-MSP/PR-39 were either transduced or infected into macrophage RAW264.7 cells for stable or transient expression of PR-39. PR-39 expression in macrophage cells was subsequently confirmed by reverse transcription polymerase chain reaction (RT-PCR) and immunocytochemistry. Furthermore, its antimicrobial activity in macrophage cells was evaluated by colony enumeration assay. Results showed that the macrophage-specific promoter could initiate targeted expression of PR-39 only in macrophage RAW264.7 cells. Moreover, either stable or transient expression of PR-39 in macrophage cells conferred enhanced antimicrobial activity against Salmonella enterica serovar Typhimurium. Our results have demonstrated that macrophage-specific expression of antimicrobial peptide PR-39 in macrophages could inhibit the growth of intracellular S. Typhimurium and indicated it to be a novel and promising approach for the control of refractory intracellular infection.

Regulation of angiogenesis by oxygen sensing mechanisms

The choices for blood vessels to undergo angiogenesis or stay quiescent are mostly determined by the status of tissue oxygenation. A major link between tissue hypoxia and active angiogenesis is the accumulation of hypoxia-inducible factor (HIF)-alpha subunits which play a major role in the transcriptional activation of genes encoding angiogenic factors. HIF-alpha abundance is negatively regulated by a subfamily of dioxygenases referred to as prolyl hydroxylase domain-containing proteins (PHDs) which use O(2) as a substrate to hydroxylate HIF-alpha subunits and hence tag them for rapid degradation. Under hypoxic conditions, HIF-alpha subunits accumulate due to reduced hydroxylation efficiency and form transcriptionally active heterodimers with HIF-1ss to activate the expression of angiogenic factors and other proteins important for cellular adaptation to hypoxia. Angiogenesis is regulated by a combination of at least two different mechanisms. The paracrine mechanism is mediated by non-endothelial expression of angiogenic factors such as vascular endothelial growth factor (VEGF)-A, which in turn interact with endothelial cell surface receptors to initiate angiogenic activities. In the autocrine mechanism, endothelial cell themselves are induced to express VEGF-A, which collaborate with the paracrine mechanism to support angiogenesis and protect vascular integrity. Because of critical roles of PHDs and HIFs in regulating angiogenic activities, studies are underway to assess their candidacy as targets for angiogenesis therapies.

Porcine host defense peptides: expanding repertoire and functions

Host defense peptides (HDPs) are a large group of innate immune effectors that are also termed antimicrobial peptides. Because of the rapid progress that has been made in completing several animal genomes, many HDPs have been systemically defined using bioinformatic analysis and partially characterized using reverse genomic approaches. In pigs, about 30 HDPs have been identified and partially characterized relative to structure and function. Antimicrobial activity of porcine HDPs has been extensively evaluated against a broad spectrum of microorganisms in vitro and evaluated for their protective role in vivo. Increasing evidence indicates that HDPs are functionally differentiated during posttranslational and postsecretory processing, and that the structural units for antimicrobial and immunoregulatory functions are separate. These findings suggest promising new avenues for therapeutic drug design based on HDPs, including porcine HDPs. This review summarizes and discusses advances in porcine HDPs research during the last decade with an emphasis on the rapidly expanding profiles and biological functions.

Shared circuitry: developmental signaling cascades regulate both embryonic and adult coronary vasculature

Ischemic heart disease is the most common cause of heart failure and is among the leading causes of mortality worldwide. Therapies used for the treatment of this disease aim to restore blood flow to severely narrowed or occluded coronary arteries by either catheter-based or surgical means. Although these strategies prove efficacious for many patients, a substantial number of individuals fail to improve following these procedures. Recently, a noninvasive strategy has been proposed, focusing on the use of endogenous growth factors that trigger the growth of new coronary arteries. Using the developing heart as a model, several groups have identified some of the key pathways that not only govern the development of the coronary vascular system but also promote the growth of the adult coronary vasculature. Here, we review the major morphological events and signaling cascades that mediate the formation of the coronary vasculature in the embryo. We further describe the mechanism by which many of these same pathways also regulate the adult coronary vasculature and their potential use in the treatment of ischemic heart disease.

Human antimicrobial protein hCAP18/LL-37 promotes a metastatic phenotype in breast cancer

Introduction

Human cathelicidin antimicrobial protein, hCAP18, and its C-terminal peptide LL-37 is a multifunctional protein. In addition to being important in antimicrobial defense, it induces chemotaxis, stimulates angiogenesis and promotes tissue repair. We previously showed that human breast cancer cells express high amounts of hCAP18, and hypothesised that hCAP18/LL-37 may be involved in tumour progression.

Methods

hCAP18 mRNA was quantified in 109 primary breast cancers and compared with clinical findings and ERBB2 mRNA expression. Effects of exogenous LL-37 and transgenic overexpression of hCAP18 on ErbB2 signalling were investigated by immunoblotting using extracts from breast cancer cell lines ZR75-1 and derivatives of MCF7. We further analysed the impact of hCAP18/LL-37 on the morphology of breast cancer cells grown in soft agar, on cell migration and on tumour development in severe combined immunodeficiency (SCID) mice.

Results

The expression of hCAP18 correlated closely with that of ERBB2 and with the presence of lymph node metastases in oestrogen receptor-positive tumours. hCAP18/LL-37 amplified Heregulin-induced mitogen-activated protein kinase (MAPK) signalling through ErbB2, identifying a functional association between hCAP18/LL-37 and ErbB2 in breast cancer. Treatment with LL-37 peptide significantly stimulated the migration of breast cancer cells and their colonies acquired a dispersed morphology indicative of increased metastatic potential. A truncated version of LL-37 competitively inhibited LL-37 induced MAPK phosphorylation and significantly reduced the number of altered cancer cell colonies induced by LL-37 as well as suppressed their migration. Transgenic overexpression of hCAP18 in a low malignant breast cancer cell line promoted the development of metastases in SCID mice, and analysis of hCAP18 transgenic tumours showed enhanced activation of MAPK signalling.

Conclusions

Our results provide evidence that hCAP18/LL-37 contributes to breast cancer metastasis.

Development of targeted angiogenic medicine

Strategies to alter angiogenesis have been successfully translated from the bench to bedside. With an estimated number of more than 500 million patients worldwide potentially benefiting from it, it is a prime example of targeted therapy that is increasingly changing the face of clinical medicine. Most efforts to stimulate or inhibit angiogenesis in the past were focused on the key angiogenic factor vascular endothelial growth factor (VEGF), resulting in the approval by the Food and Drug Administration of several drugs for the treatment of cancer and ocular disease. However, mounting clinical evidence reveals that inhibition of VEGF causes resistance and class-specific side effects, while therapeutic angiogenesis by delivering VEGF protein is more challenging than anticipated in human patients. Hence, alternatives are needed, and modulation of oxygen-sensitive enzymes (prolyl hydroxylase domain proteins) and of hypoxia induced transcription factors has recently emerged as a potential novel strategy to treat cancer and ischemic diseases. Furthermore, placental growth factor is a disease-specific angiogenic target, whose inhibition reduces cancer growth without causing major side effects, while its delivery induces revascularization of ischemic tissues. In this review, we summarize recent developments and discuss questions that arise in the exciting, rapidly developing field of angiogenic medicine, including a brief description of its possible implications in neurodegenerative diseases.

Midkine prevents ventricular remodeling and improves long-term survival after myocardial infarction

Cardiac remodeling is thought to be the major cause of chronic heart dysfunction after myocardial infarction (MI). However, molecules involved in this process have not been thoroughly elucidated. In this study we investigated the long-term effects of the growth factor midkine (MK) in cardiac remodeling after MI. MI was produced by ligation of the left coronary artery. MK expression was progressively increased after MI in wild-type mice, and MK-deficient mice showed a higher mortality. Exogenous MK improved survival and ameliorated left ventricular dysfunction and fibrosis not only of MK-deficient mice but also of wild-type mice. Angiogenesis in the peri-infarct zone was also enhanced. These in vivo changes induced by exogenous MK were associated with the activation of phosphatidylinositol 3-kinase (PI3K)/Akt and MAPKs (ERK, p38) and the expression of syndecans in the left ventricular tissue. In vitro experiments using human umbilical vein endothelial cells confirmed the potent angiogenic action of MK via the PI3K/Akt pathway. These results suggest that MK prevents the cardiac remodeling after MI and improves the survival most likely through an enhancement of angiogenesis. MK application could be a new therapeutic strategy for the treatment of ischemic heart failure.

Molecular basis for proline- and arginine-rich peptide inhibition of proteasome

PR39, a naturally occurring and cell-permeable proline- and arginine-rich peptide, blocks the degradation of inhibitor of nuclear factor kappaB (IkappaBalpha), thereby attenuating inflammation. It is a noncompetitive and reversible inhibitor of 20S proteasome. To identify its basis of action, we used solution NMR spectroscopy and mutational analyses of the active fragment, PR11, which identified amino acids required for human 20S proteasome inhibiting activity. We then examined PR11-mediated changes in the expression of nuclear factor kappaB-dependent genes in situ. The results provide prerequisites for proteasome inhibition by proline- and arginine-rich peptides, providing a powerful new tool to investigate inflammatory processes. These findings offer new leads in developing drugs to treat heart diseases or stroke.

LL-37 regulates the overexpression of vascular endothelial growth factor (VEGF) and c-IAP-2 in human keratinocytes

BACKGROUND

The antimicrobial peptide PR39 is a porcine cathelicidin with angiogenic and antiapoptotic activities, as it can regulate the expression of vascular endothelial growth factor (VEGF) and inhibitor apoptosis protein-2 (c-IAP-2) in endothelial cells. The human homolog LL-37 has been found to be highly expressed in human keratinocytes from psoriatic patients, but it is not known whether LL-37 can modulate the expression of VEGF and c-IAP-2 in keratinocytes, as both molecules are involved in the overgrowth of psoriatic skin. Therefore, in this work, we studied the possible role of CAP18/LL-37 in the modulation of VEGF and c-IAP-2 expression in human keratinocytes.

METHODS

The CAP18/LL-37 gene was cloned into a plasmid that contained green fluorescent protein (GFP). This plasmid was called pGFP-CAP18/LL-37. The expression of LL-37, VEGF, and c-IAP-2 was determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting in HaCaT cells transfected with pGFP-CAP18/LL-37. Specific DNAzymes were used to break the CAP18/LL-37 mRNA (DNAz-CAP18/LL-37).

RESULTS

HaCaT cells transfected with pGFP-CAP18/LL-37 showed the upregulation of VEGF and c-IAP-2 mRNAs. Hypoxia-inducible factor-1alpha (HIF-1alpha) mRNA expression did not change during the assays; however, its protein was increased, as well as the VEGF protein. HaCaT cells cotransfected with pGFP-CAP18/LL-37 and DNAz-CAP18/LL-37 showed depleted expression of LL-37, VEGF, and c-IAP-2 mRNAs.

CONCLUSIONS

These results suggest that LL-37 may modulate the expression of VEGF and c-IAP-2 via HIF-1alpha in human keratinocytes.

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.

(2R)-[(4-Biphenylylsulfonyl)amino]-N-hydroxy-3-phenylpropionamide (BiPS), a matrix metalloprotease inhibitor, is a novel and potent activator of hypoxia-inducible factors

Hypoxia-inducible factors (HIFs) are unstable heterodimeric transcription factors and decisive elements for the transcriptional regulation of genes important in the adaptation to low-oxygen conditions. Hypoxia is the ubiquitous inducer of HIFs, stabilizing the alpha-subunit and permitting the formation of a functional HIF complex. Here, we identify (2R)-[(4-biphenylylsulfonyl)amino]-N-hydroxy-3-phenylpropionamide (BiPS), a commercially available metalloprotease-2 and -9 inhibitor, as a rapid and potent inducer of HIFs. We show that in different cell lines, BiPS induces the HIF-alpha subunit by inhibiting its degradation through stabilization of its labile oxygen-dependent degradation domain. This is achieved through the inhibition of HIF-1alpha hydroxylation. The HIF-1 complex, formed after BiPS treatment, is capable of DNA binding and activation of HIF target genes, including the expression of vascular endothelial growth factor. Because novel HIF activators have generated considerable interest in the possible treatment of different ischemic diseases, we believe that BiPS and derivative molecules could have strong therapeutic potential.

Development of a novel antimicrobial peptide, AG-30, with angiogenic properties

The utility of various synthetic peptides has been investigated in clinical trials of the treatment of cancers, infectious diseases and endocrine diseases. In the process of functional gene screening with in silico analysis for molecules with angiogenic properties, we generated a small peptide, angiogenic peptide (AG)-30, that possesses both antimicrobial and pro-inflammatory activities. AG-30 has an α-helix structure with a number of hydrophobic or net positively charged amino acids and a propensity to fold into amphipathic structures. Indeed, AG-30 exhibited antimicrobial activity against various bacteria, induced vascular endothelial cell growth and tube formation in a dose-dependent manner and increased neovascularization in a Matrigel plug assay. As a result, AG-30 up-regulated expression of angiogenesis-related cytokines and growth factors for up to 72 hrs in human aortic endothelial cells. To further evaluate the angiogenic effect of AG-30 in vivo, we developed a slow-release AG-30 system utilizing biodegradable gelatin microspheres. In the ischaemic mouse hind limb, slow-release AG-30 treatment results in an increase in angiogenic score, an increase in blood flow (as demonstrated by laser Doppler imaging) and an increase in capillary density (as demonstrated by immunostaining with anti-CD31 antibody). These data suggest that the novel peptide, AG-30, may have therapeutic potential for ischaemic diseases.

Myocardial hypertrophy in the absence of external stimuli is induced by angiogenesis in mice

Although studies have suggested a role for angiogenesis in determining heart size during conditions demanding enhanced cardiac performance, the role of EC mass in determining the normal organ size is poorly understood. To explore the relationship between cardiac vasculature and normal heart size, we generated a transgenic mouse with a regulatable expression of the secreted angiogenic growth factor PR39 in cardiomyocytes. A significant change in adult mouse EC mass was apparent by 3 weeks following PR39 induction. Heart weight; cardiomyocyte size; vascular density normalization; upregulation of hypertrophy markers including atrial natriuretic factor, beta-MHC, and GATA4; and activation of the Akt and MAP kinase pathways were observed at 6 weeks post-induction. Treatment of PR39-induced mice with the eNOS inhibitor L-NAME in the last 3 weeks of a 6-week stimulation period resulted in a significant suppression of heart growth and a reduction in hypertrophic marker expression. Injection of PR39 or another angiogenic growth factor, VEGF-B, into murine hearts during myocardial infarction led to induction of myocardial hypertrophy and restoration of myocardial function. Thus stimulation of vascular growth in normal adult mouse hearts leads to an increase in cardiac mass.

Mechanisms of adaptive angiogenesis to tissue hypoxia

Angiogenesis is mostly an adaptive response to tissue hypoxia, which occurs under a wide variety of situations ranging from embryonic development to tumor growth. In general, angiogenesis is dependent on the accumulation of hypoxia inducible factors (HIFs), which are heterodimeric transcription factors of alpha and beta subunits. Under normoxia, HIF heterodimers are not abundantly present due to oxygen dependent hydroxylation, polyubiquitination, and proteasomal degradation of alpha subunits. Under hypoxia, however, alpha subunits are stabilized and form heterodimers with HIF-1beta which is not subject to oxygen dependent regulation. The accumulation of HIFs under hypoxia allows them to activate the expression of many angiogenic genes and therefore initiates the angiogenic process. In recent years, however, it has become clear that various other mechanisms also participate in fine tuning angiogenesis. In this review, I discuss the relationship between hypoxia and angiogenesis under five topics: (1) regulation of HIF-alpha abundance and activity by oxygen tension and other conditions including oxygen independent mechanisms; (2) hypoxia-regulated expression of angiogenic molecules by HIFs and other transcription factors; (3) responses of vascular cells to hypoxia; (4) angiogenic phenotypes due to altered HIF signaling in mice; and (5) role of the HIF pathway in pathological angiogenesis. Studies discussed under these topics clearly indicate that while mechanisms of oxygen-regulated HIF-alpha stability provide exciting opportunities for the development of angiogenesis or anti-angiogenesis therapies, it is also highly important to consider various other mechanisms for the optimization of these procedures.

The role of cathelicidin and defensins in pulmonary inflammatory diseases

Antimicrobial peptides (AMPs) protect the epithelia of mucosal organs like the respiratory or the gastrointestinal tract from invading microorganisms. As an integral part of the innate immune system they display antimicrobial activity against gram- and gram-negative bacteria as well as against fungi and enveloped and non-enveloped viruses. Besides their microbicidal effects they have important functions in the regulation of repair and inflammation. AMPs are sometimes referred to as 'alarmins' due to their ability to recruit, modulate and activate components of the immune system. In contrast, some AMPs suppress activation of the immune system. AMPs are also involved in tissue repair, cancer biology and angiogenesis. Based on their antimicrobial and immunomodulatoy functions, AMPs are probably involved in the pathogenesis of infectious and inflammatory diseases of the lung. Inborn or acquired deficiencies contribute to susceptibility to infection and colonisation. The potential pro-inflammatory role of AMPs contributes to the disease processes in inflammatory disorders such as asthma, chronic obstructive pulmonary disease, sepsis or pulmonary fibrosis. This review summarises the knowledge about the functions of AMPs in the pulmonary innate host defence system and their role in respiratory disease.

Imaging of angiogenesis in cardiology

In the past decade, there have been major improvements in our understanding of angiogenesis at the genetic, molecular and cellular levels. Concentrated efforts in this area have led to new therapeutic approaches to ischaemic heart disease using angiogenic factors, gene therapy and progenitor cells. Despite very promising experimental results in animal studies, large clinical trials have failed to confirm the results in patients with coronary artery disease. Important questions such as selection of growth factors and donor cells, as well as the timing, dose and route of administration, have been raised and need to be answered. Molecular imaging approaches which may provide specific markers of the angiogenic process (e.g. integrin expression in endothelial cells) have been introduced and are expected to address some of these questions. Although few clinical imaging results are currently available, animal studies suggest the potential role of molecular imaging for characterisation of the angiogenetic process in vivo and for the monitoring of therapeutic effects.

The Antimicrobial Peptide PR-39 has a Protective Effect Against HeLa Cell Apoptosis

PR-39 is a cathelicidin with antimicrobial properties, which acts as a suppressor of inflammation and exerts a number of additional activities. We investigated for the first time the effect of PR-39 on human cells, by addressing the possible interference with HeLa cell metabolism. We observed that the continuous administration of PR-39 to HeLa cell cultures was not cytotoxic and did not interfere with DNA synthesis. When used in combination with a panel of drugs inducing apoptosis through different mechanisms of action, i.e. etoposide, bleomycin, tert-butylhydroperoxide and 2-deoxy-d-ribose, PR-39 attenuated the apoptotic response of HeLa cells.

Protection against myocardial ischemia-reperfusion injury by the angiogenic Masterswitch protein PR 39 gene therapy: the roles of HIF1alpha stabilization and FGFR1 signaling

PR-39, a proline-arginine-rich angiogenic response peptide, has been implicated in myocardial ischemic reperfusion injury. The present study examined the cardioprotective abilities of PR39 gene therapy. Male C57Bl/J6 mice were randomized to intramyocardial injecton of 10(9) p.f.u. adenovirus encoding PR39 (PR39), FGFR1 dominant negative signaling construct (FGFR1-dn), empty vector (EV), or PR39 adenovirus plus 4 microg of plasmid endcoding a HIF1alpha dominant negative construct (PR39 + HIF1alpha-dn). Seven days later, hearts were subjected to 20 min of ischemia (I) and 2 h. reperfusion (R) ex vivo and aortic and coronary flow, left ventricular developed pressure (LVDP), and LVdp/dt were measured. Myocardial infarct (MI) size and cardiomyocyte apoptosis were measured by TTC staining and TUNEL, respectively. PR39 expression was robust up to 14 days after gene transfer and was absent after EV and FGFR1-dn. Hemodynamics showed no differences at baseline, and heart rate remained unchanged in all groups throughout the experiment. After I-R, hemodynamics remained unchanged in PR39 hearts, but deteriorated significantly in the other groups, except for aortic flow, which remained significantly higher in FGFR1-dn than in EV and PR39 + HIF1alpha-dn (p < 0.05), although it was lower than in PR39 (p < 0.05). MI was 8.7 +/- 0.9 % in PR39, 23.8 +/- 1.1% in FGFR1-dn, 29.9 +/- 2.2% in EV, and 30.8 +/- 2.7 % in PR39 + HIF1alpha-dn (PR39 vs. other groups: p < 0.05; FGFR1-dn vs. EV and PR39 + HIF1alpha-dn: p < 0.05). In PR39, HIF-1alpha protein was higher than in FGFR1-dn and EV. Importantly, cotransfection of HIF1alpha-dn with PR39 completely abolished cardioprotection by PR39. Cardioprotection by PR39 is likely conveyed by protective metabolic and survival responses through HIF1-alpha stabilization and not by angiogenesis, because baseline coronary flow was the same in all groups. Abrogation of FGFR1 signaling conveyed an intermediate degree of cardioprotection.

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.

Under-expression of VHL and over-expression of HDAC-1, HIF-1?, LL-37, and IAP-2 in affected skin biopsies of patients with psoriasis

BACKGROUND

A feature of psoriasis is the rapid proliferation of keratinocytes, during which apoptosis is blocked and angiogenesis starts. It is known that tumor hypoxic cells produce histone deacetylase-1 (HDAC-1), which up-regulates hypoxia-inducible factor-1alpha (HIF-1alpha) and down-regulates von Hippel-Lindau (VHL) protein by up-regulating vascular endothelial growth factor (VEGF) expression. It has been reported recently that the porcine peptide PR39 (homologous to human LL-37) has angiogenic and antiapoptotic activity. Thus, LL-37, induced by insulin-like growth factor-1 (IGF-1), could help in the production of VEGF. PR39 also induces the expression of inhibitor of apoptosis protein-2 (IAP-2), which blocks apoptosis. The purpose of this work was to analyze whether these genes and their proteins are expressed in psoriatic biopsies.

METHODS

Using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) messenger RNA (mRNA) expression and immunohistochemical staining, we studied VHL, IAP-2, and related genes in skin biopsies from psoriatic patients and healthy subjects.

RESULTS

An over-expression of the mRNA for HDAC-1, HIF-1alpha, LL-37, and IGF-1 in psoriatic skin, in comparison with skin from healthy subjects, was found. The antiangiogenic VHL mRNA and protein were under-expressed in psoriatic skin and highly expressed in healthy skin. The antiapoptotic IAP-2 was over-expressed in dermal endothelial cells from psoriatic skin. The pro-apoptotic Bax, Fas, and FasL mRNAs were expressed.

CONCLUSIONS

These findings suggest that there could be an association of HDAC-1, HIF-1alpha, LL-37, VHL, and IAP-2 with angiogenic and apoptotic mechanisms in psoriasis.

Antimicrobial peptides derived from growth factors

Growth factors, comprising diverse protein and peptide families, are involved in a multitude of developmental processes, including embryogenesis, angiogenesis, and wound healing. Here we show that peptides derived from HB-EGF, amphiregulin, hepatocyte growth factor, PDGF-A and PDGF-B, as well as various FGFs are antimicrobial, demonstrating a previously unknown activity of growth factor-derived peptides. The peptides killed the Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa, and the Gram-positive Bacillus subtilis, as well as the fungus Candida albicans. Several peptides were also active against the Gram-positive S. aureus. Electron microscopy analysis of peptide-treated bacteria, paired with analysis of peptide effects on liposomes, showed that the peptides exerted membrane-breaking effects similar to those seen after treatment with the "classical" human antimicrobial peptide LL-37. Furthermore, HB-EGF was antibacterial per se, and its epitope GKRKKKGKGLGKKRDPCLRKYK retained its activity in presence of physiological salt and plasma. No discernible hemolysis was noted for the growth factor-derived peptides. Besides providing novel templates for design of peptide-based antimicrobials, our findings demonstrate a previously undisclosed link between the family of growth factors and antimicrobial peptides, both of which are induced during tissue remodelling and repair.

Multifunctional antimicrobial peptides: therapeutic targets in several human diseases

Antimicrobial peptides have emerged as promising agents against antibiotic-resistant pathogens. They represent essential components of the innate immunity and permit humans to resist infection by microbes. These gene-encoded peptides are found mainly in phagocytes and epithelial cells, showing a direct activity against a wide range of microorganisms. Their role has now broadened from that of simply endogenous antibiotics to multifunctional mediators, and their antimicrobial activity is probably not the only primary function. Although antimicrobial peptide deficiency, dysregulation, or overproduction is not known to be a direct cause of any single human disease, numerous studies have now provided compelling evidence for their involvement in the complex network of immune responses and inflammatory diseases, thereby influencing diverse processes including cytokine release, chemotaxis, angiogenesis, wound repair, and adaptive immune induction. The purpose of this review is to highlight recent literature, showing that antimicrobial peptides are associated with several human conditions including infectious and inflammatory diseases, and to discuss current clinical development of peptide-based therapeutics for future use.

Regulation of angiogenesis by hypoxia and hypoxia-inducible factors

Maintenance of oxygen homeostasis is critical for the survival of multicellular organs. As a result, both invertebrates and vertebrates have developed highly specialized mechanisms to sense changes in oxygen levels and to mount adequate cellular and systemic responses to these changes. Hypoxia, or low oxygen tension, occurs in physiological situations such as during embryonic development, as well as in pathological conditions such as ischemia, wound healing, and cancer. A primary effector of the adaptive response to hypoxia in mammals is the hypoxia-inducible factor (HIF) family of transcription regulators. These proteins activate the expression of a broad range of genes that mediate many of the responses to decreased oxygen concentration, including enhanced glucose uptake, increased red blood cell production, and the formation of new blood vessels via angiogenesis. This latter process is dynamic and results in the establishment of a mature vascular system that is indispensable for proper delivery of oxygen and nutrients to all cells in both normal tissue and hypoxic regions. Angiogenesis is essential for normal development and neoplastic disease as tumors must develop mechanisms to stimulate vascularization to meet increasing metabolic demands. The link between hypoxia and the regulation of angiogenesis is an area of intense research and the molecular details of this connection are still being elaborated. This chapter will provide an overview of current knowledge and highlight new insights into the importance of HIF and hypoxia in angiogenesis in both physiological and pathophysiological conditions.

Expression of β-defensins pBD-1 and pBD-2 along the small intestinal tract of the pig: Lack of upregulation in vivo upon Salmonella typhimurium infection

Defensins are antimicrobial peptides that play an important role in the innate immune response in the intestine. Up to date, only one beta-defensin (pBD-1), has been described in pig, which was found to be expressed at low levels in the intestine. We set-up a quantitative PCR method to detect the gene expression of pBD-1 and a newly discovered porcine beta-defensin, pBD-2. Expression of pBD-1 mRNA increased from the proximal to the distal part of the intestine whereas pBD-2 expression decreased. The main gene expression sites for pBD-2 were kidney and liver, whereas pBD-1 was mainly expressed in tongue. The porcine small intestinal segment perfusion (SISP) technique was used to investigate effects of Salmonella typhimurium DT104 on intestinal morphology and pBD-1 and pBD-2 mRNA levels in vivo. The early responses were studied 2, 4 and 8 h post-infection in four separate jejunal and ileal segments. Immunohistochemistry showed invasion of the mucosa by Salmonella and changes in intestinal morphology. However, no concomitant changes in expression of either pBD-1 or pBD-2 were observed. We conclude that at least two defensins are differentially expressed in the intestine of pigs, and that expression of both defensins is not altered by S. typhimurium under these conditions.

Upregulation of Hypoxia-Inducible Factor (HIF)-1α and HIF-2α in Leptomeningeal Vascular Malformations of Sturge-Weber Syndrome

Cutaneous and leptomeningeal vascular malformations are hallmarks of the Sturge-Weber Syndrome (SWS), resulting in chronic ischemic tissue damage. The mechanisms underlying the pathobiology of these progressive lesions are unknown. Aberrant expression of angiogenic factors has been implicated in the genesis and maintenance of vascular malformations. To assess the role of angiogenesis in SWS vascular lesions we determined the expression of key angiogenic factors by immunohistochemistry and in situ hybridization in 8 SWS patients (age: 8 months to 18 years). We observed increased expression of vascular endothelial growth factor (VEGF), its cognate receptors VEGFR-1, VEGFR-2, and neuropilin (NP)-1 as well as Tie2 in leptomeningeal SWS blood vessels. Intriguingly, these factors are known to be transcriptionally induced by hypoxia-inducible factor (HIF). The HIF system has emerged as the key regulatory system of responses to hypoxia. Immunohistochemical analysis demonstrated markedly elevated nuclear HIF-1alpha and HIF-2alpha protein levels in SWS vessels. Concomitantly, SWS vessels revealed signs of enhanced endothelial cell (EC) turnover as evidenced by increased EC proliferation and apoptosis. Thus, in terms of angiogenesis, vascular malformations in SWS are not static lesions but constitute dynamic structures. Our observation of a dysregulated HIF-alpha expression in SWS vessels are in agreement with recent findings that EC-specific HIF activation provides a setting which supports and sustains angiogenesis and could be of potential use for developing therapeutic strategies to treat these currently incurable lesions.

The future of therapeutic myocardial angiogenesis

Despite improvements in its medical and surgical management, ischemic coronary disease remains responsible for significant morbidity, mortality, and economic burden in developed nations. Therapeutic myocardial angiogenesis is an attractive treatment option for patients with end-stage coronary disease who have failed percutaneous and surgical methods of revascularization. Over the past decade, our understanding of the biology of new blood vessel formation has improved significantly, and consequently, the use of growth factors to induce myocardial angiogenesis has been attempted in preclinical and clinical trials. Although growth factor therapy had demonstrated tremendous success in animal models, clinical trials have shown limited benefit in patients with coronary disease. Vascular endothelial growth factors and fibroblast growth factors are perhaps the most potent inducers of angiogenesis that have been used in animal models, and the only ones that have been used in clinical trials. This review outlines the biology of new vessel formation and the effects of these growth factors in the context of myocardial angiogenesis with an emphasis on the effects on the endothelium. It also provides a brief overview of delivery strategies and summarizes the preclinical and clinical evidence relating to exogenous growth factor delivery for myocardial angiogenesis. Lastly, we discuss the limitations and future challenges of angiogenic therapy.

Tumor macrophage redox and effector mechanisms associated with hypoxia

Monocytes are recruited from the circulation into solid tumors where they differentiate into macrophages with unique phenotypes. While macrophages utilize oxygen in a broad range of immune effector functions, the generation of reactive oxygen and nitrogen oxide species is less clear in the setting of hypoxia, which can be a prominent feature of solid tumors. The relationships among innate immunity, redox systems, and the plasticity of phenotypic changes tumor-associated macrophages undergo in conjunction with tumor hypoxia will be examined.

Heparan sulfate proteoglycan-dependent neutrophil chemotaxis toward PR-39 cathelicidin

Cathelicidins are mammalian proteins containing a C-terminal cationic antimicrobial domain. Porcine PR-39 cathelicidin affects leukocyte biology. Mechanisms of action may involve alteration of heparan sulfate proteoglycan-dependent functions in inflammatory cells. It was tested whether PR-39 affects human neutrophil migration and if such effects involve heparan sulphate proteoglycans. Neutrophils were from forearm venous blood of healthy donors. Migration was tested in modified Boyden chamber assays. Involvement of heparan sulfate proteoglycans was tested by their chemical modification and by the use of specific antibodies. PR-39 induced migration in neutrophils in a concentration dependent manner. Modification of heparan sulfate proteoglycans with sodium chlorate inhibited migration whereas chemotaxis toward the chemoattractant formyl-Met-Leu-Phe was not affected. Removal of heparan sulfates or chondroitin sulfates from the surface of neutrophils by heparinase or chondroitinase inhibited migration toward PR-39. In conclusion, antimicrobial PR-39 stimulates human neutrophil chemotaxis in a heparan sulfate proteoglycan-dependent manner. Involvment of syndecans is likely as both heparinase and chondroitinase were abrogating. Data suggest active participation of heparan sulfate proteoglycans of neutrophils in cathelicidin peptide-mediated regulation of the antimicrobial host defense.

Lipopolysaccharide from Escherichia coli induces the expression of vascular endothelial growth factor via toll-like receptor 4 in human limbal fibroblasts

Corneal neovascularization can be induced by a severe ocular infection, injury or immunological diseases. The vascular endothelial growth factor (VEGF) is the main cytokine involved in this phenomenon, inducing angiogenesis from the vascularized ocular tissues. As the limbal tissue is located between conjunctival and corneal tissues, we suggest that the limbal cells are participating in the production of VEGF induced by bacterial components as LPS. In this work, RT-PCRs and immunoblots were used to investigate the expression of VEGF and other pro-angiogenic genes in primary cultures of human limbal fibroblasts (PCHLF) treated with lipopolysaccharide (LPS) from Escherichia coli. We found that the expression of VEGF was initiated at 6 h and reaches its highest expression at 72 h after stimulation with LPS. Up-regulation of toll-like receptor 4 (TLR4) after 3 h of treatment was also observed. LPS-induced the expression of VEGF in a dose-dependent manner, and the blocking of TLR4 with an anti-TLR4 antibody prevented VEGF expression. We also analyzed the molecules that modulate VEGF expression. LPS did not induce the up-regulation of LL-37 nor the hypoxia induced factor 1 alpha (HIF-1alpha) mRNA expression, however, an up-regulation of interleukin 13 receptor alpha 1 (IL-13Ralpha1) and interleukin 4 receptor alpha (IL-4Ralpha) were observed after 3 and 12 h of stimulation, respectively. The expression of interleukin 13 did not change throughout the treatment. These results suggest that TLR4, IL-13Ralpha1 and IL-4Ralpha induced by LPS in PCHLF could be playing an important role in the corneal neovascularization.

Differential regulation of porcine beta-defensins 1 and 2 upon Salmonella infection in the intestinal epithelial cell line IPI-2I

Intestinal epithelial cells represent the first line of defence against pathogenic bacteria in the lumen of the gut. Besides acting as a physical barrier, epithelial cells orchestrate the immune response through the production of several innate immune mediator molecules including beta-defensins. Here, we establish the porcine intestinal cell line IPI-2I as a new model system to test the regulation of porcine beta-defensins 1 and 2. Gene expression of both defensins was highly upregulated by foetal calf serum components in normal growth medium. In serum-free medium, baseline expression remained low, but pBD-2 gene expression was increased 10-fold upon infection with Salmonella Typhimurium. Arcobacter cryaerophilus and Salmonella Enteritidis, pathogenic bacteria with comparable adhesion and invasion characteristics, failed to increase pBD-2 mRNA levels. Heat killed or colistin-treated Salmonella Typhimurium had no effect, showing that the upregulation of pBD-2 was dependent on the viability of the Salmonella Typhimurium. Gene expression of pBD-1 was regulated differently since an increase in pBD-1 mRNA was observed by Salmonella Enteritidis infection. We conclude that the IPI-2I cells can serve as a new model to study porcine beta-defensin regulation and that pBD-1 and pBD-2 are differentially regulated in this cell line.

Natural product-derived small molecule activators of hypoxia-inducible factor-1 (HIF-1)

Hypoxia-inducible factor-1 (HIF-1) is a key mediator of oxygen homeostasis that was first identified as a transcription factor that is induced and activated by decreased oxygen tension. Upon activation, HIF-1 upregulates the transcription of genes that promote adaptation and survival under hypoxic conditions. HIF-1 is a heterodimer composed of an oxygen-regulated subunit known as HIF-1alpha and a constitutively expressed HIF-1beta subunit. In general, the availability and activity of the HIF-1alpha subunit determines the activity of HIF-1. Subsequent studies have revealed that HIF-1 is also activated by environmental and physiological stimuli that range from iron chelators to hormones. Preclinical studies suggest that HIF-1 activation may be a valuable therapeutic approach to treat tissue ischemia and other ischemia/hypoxia-related disorders. The focus of this review is natural product-derived small molecule HIF-1 activators. Natural products, relatively low molecular weight organic compounds produced by plants, animals, and microbes, have been and continue to be a major source of new drugs and molecular probes. The majority of known natural product-derived HIF-1 activators were discovered through the pharmacological evaluation of specifically selected individual compounds. On the other hand, the combination of natural products chemistry with appropriate high-throughput screening bioassays may yield novel natural product-derived HIF-1 activators. Potent natural product-derived HIF-1 activators that exhibit a low level of toxicity and side effects hold promise as new treatment options for diseases such as myocardial and peripheral ischemia, and as chemopreventative agents that could be used to reduce the level of ischemia/reperfusion injury following heart attack and stroke.

Hypoxia-inducible factor-1 (HIF-1)

Adaptation to low oxygen tension (hypoxia) in cells and tissues leads to the transcriptional induction of a series of genes that participate in angiogenesis, iron metabolism, glucose metabolism, and cell proliferation/survival. The primary factor mediating this response is the hypoxia-inducible factor-1 (HIF-1), an oxygen-sensitive transcriptional activator. HIF-1 consists of a constitutively expressed subunit HIF-1beta and an oxygen-regulated subunit HIF-1alpha (or its paralogs HIF-2alpha and HIF-3alpha). The stability and activity of the alpha subunit of HIF are regulated by its post-translational modifications such as hydroxylation, ubiquitination, acetylation, and phosphorylation. In normoxia, hydroxylation of two proline residues and acetylation of a lysine residue at the oxygen-dependent degradation domain (ODDD) of HIF-1alpha trigger its association with pVHL E3 ligase complex, leading to HIF-1alpha degradation via ubiquitin-proteasome pathway. In hypoxia, the HIF-1alpha subunit becomes stable and interacts with coactivators such as cAMP response element-binding protein binding protein/p300 and regulates the expression of target genes. Overexpression of HIF-1 has been found in various cancers, and targeting HIF-1 could represent a novel approach to cancer therapy.

Cationic antimicrobial peptides as novel cytotoxic agents for cancer treatment

Cancer treatment by conventional chemotherapy is hindered by toxic side effects and the frequent development of multi-drug resistance by cancer cells. Cationic antimicrobial peptides (CAPs) are a promising new class of natural-source drugs that may avoid the shortcomings of conventional chemotherapy because certain CAPs exhibit selective cytotoxicity against a broad spectrum of human cancer cells, including neoplastic cells that have acquired a multi-drug-resistant phenotype. Tumour cell killing by CAPs is usually by a cell membrane-lytic effect, although some CAPs can trigger apoptosis in cancer cells via mitochondrial membrane disruption. Furthermore, certain CAPs are potent inhibitors of blood vessel development (angiogenesis) that is associated with tumour progression. This article reviews the mechanisms by which CAPs exert anticancer activity and discusses the potential application of selected CAPs as therapeutic agents for the treatment of human cancers.

Lipopolysaccharide (Endotoxin)-host defense antibacterial peptides interactions: role in bacterial resistance and prevention of sepsis

Lipopolysaccharide (LPS) is the major molecular component of the outer membrane of Gram-negative bacteria and serves as a physical barrier providing the bacteria protection from its surroundings. LPS is also recognized by the immune system as a marker for the detection of bacterial pathogen invasion, responsible for the development of inflammatory response, and in extreme cases to endotoxic shock. Because of these functions, the interaction of LPS with LPS binding molecules attracts great attention. One example of such molecules are antimicrobial peptides (AMPs). These are large repertoire of gene-encoded peptides produced by living organisms of all types, which serve as part of the innate immunity protecting them from pathogen invasion. AMPs are known to interact with LPS with high affinities. The biophysical properties of AMPs and their mode of interaction with LPS determine their biological function, susceptibility of bacteria to them, as well as the ability of LPS to activate the immune system. This review will discuss recent studies on the molecular mechanisms underlying these interactions, their effects on the resistance of the bacteria to AMPs, as well as their potential to neutralize LPS-induced endotoxic shock.

Regulation of angiogenesis by hypoxia-inducible factor 1

Hypoxia is an imbalance between oxygen supply and demand that occurs in cancer and in ischemic cardiovascular disease. Hypoxia-inducible factor 1 (HIF-1) was originally identified as the transcription factor that mediates hypoxia-induced erythropoietin expression. More recently, the delineation of molecular mechanisms of angiogenesis has revealed a critical role for HIF-1 in the regulation of angiogenic growth factors. In this review, we discuss the role of HIF-1 in developmental, adaptive and pathological angiogenesis. In addition, potential therapeutic interventions involving modulation of HIF-1 activity in ischemic cardiovascular disease and cancer will be discussed.