Early expression of angiogenesis factors in acute myocardial ischemia and infarction

Experimental study of the effects of marrow mesenchymal stem cells transfected with hypoxia-inducible factor-1alpha gene

Objective. To construct the eukaryotic expression vector hypoxia-inducible factor 1α-pcDNA_3.1 and to investigate its transfective efficiency into mesenchymal stem cells (MSCs) in vitro and the expression of HIF-1α gene in MSCs. Methods. mRNA of Wistar Rats' myocardial cells was extracted, and cDNA was synthesized with Reverse Transcription Kit, HIF-1α was amplified by polymerase chain reaction (PCR), and constructed into pcDNA_3.1. Transfected HIF-1α-pcDNA_3.1 into MSCs by liposome mediated method. The expression of HIF-1α in the cells was detected by Western Blot Analysis and ELISA. Results. Eukaryotic expression vector HIF-1α-pcDNA_3.1 was constructed successfully. Analyzed by flow cytometer, The MSCs' surfaces mark were CD44+, SH3(CD73)+, CD34−, CD45− and the CD44+ cells and SH3(CD73)+ cells were 94.7% and 97.3%, respectively, showing the high purity of the cultured MSCs. After inducing, the cultured MSCs can differentiate into osteoblasts and adipocytes successfully. In HIF-1α gene transfected MSCs, the expression of HIF-1α mRNA and HIF-1α protein were both increased obviously. Conclusion. HIF-1α was cloned successfully. HIF-1α-pcDNA_3.1 can be transfected into MSCs by liposome-mediated method effectively and which resulting stable expression of HIF-1α in transfected MSCs.

eNOS activation by physical forces: from short-term regulation of contraction to chronic remodeling of cardiovascular tissues

Nitric oxide production in response to flow-dependent shear forces applied on the surface of endothelial cells is a fundamental mechanism of regulation of vascular tone, peripheral resistance, and tissue perfusion. This implicates the concerted action of multiple upstream "mechanosensing" molecules reversibly assembled in signalosomes recruiting endothelial nitric oxide synthase (eNOS) in specific subcellular locales, e.g., plasmalemmal caveolae. Subsequent short- and long-term increases in activity and expression of eNOS translate this mechanical stimulus into enhanced NO production and bioactivity through a complex transcriptional and posttranslational regulation of the enzyme, including by shear-stress responsive transcription factors, oxidant stress-dependent regulation of transcript stability, eNOS regulatory phosphorylations, and protein-protein interactions. Notably, eNOS expressed in cardiac myocytes is amenable to a similar regulation in response to stretching of cardiac muscle cells and in part mediates the length-dependent increase in cardiac contraction force. In addition to short-term regulation of contractile tone, eNOS mediates key aspects of cardiac and vascular remodeling, e.g., by orchestrating the mobilization, recruitment, migration, and differentiation of cardiac and vascular progenitor cells, in part by regulating the stabilization and transcriptional activity of hypoxia inducible factor in normoxia and hypoxia. The continuum of the influence of eNOS in cardiovascular biology explains its growing implication in mechanosensitive aspects of integrated physiology, such as the control of blood pressure variability or the modulation of cardiac remodeling in situations of hemodynamic overload.

New molecular imaging targets to characterize myocardial biology

Molecular imaging represents a targeted approach to noninvasively assess biologic (both physiologic and pathologic) processes in vivo. Ideally the goal of molecular imaging is not just to provide diagnostic and prognostic information based on identification of the molecular events associated with a pathologic process but rather to guide individually tailored pharmacologic, cell-based, or genetic therapeutic regimens. This article reviews the recent advances in myocardial molecular imaging in the context of the cardiovascular processes of angiogenesis, apoptosis, inflammation, and ventricular remodeling. The focus is on radiotracer-based single photon emission computed tomography and positron emission tomography molecular imaging approaches.

Targeting proteins for destruction by the ubiquitin system: implications for human pathobiology

Cellular proteins are in a dynamic state maintained by synthesis and degradation. The ubiquitin proteolytic pathway is responsible for the degradation of the bulk of cellular proteins including short-lived, regulatory, and misfolded/denatured proteins. Ubiquitin-mediated proteolysis involves covalent attachment of multiple ubiquitin molecules to the protein substrate and degradation of the targeted protein by the 26S proteasome. Recent understanding of the molecular mechanisms involved provides a framework to understand a wide variety of human pathophysiological states as well as therapeutic interventions. This review focuses on the response to hypoxia, inflammatory diseases, neurodegenerative diseases, and muscle-wasting disorders, as well as human papillomaviruses, cervical cancer and other malignancies.

Physiological replacement of T3 improves left ventricular function in an animal model of myocardial infarction-induced congestive heart failure

BACKGROUND

Patients with congestive heart failure (CHF) often have low serum triiodothyronine (T(3)) concentrations. In a rodent model of myocardial infarction-induced CHF and low serum T(3), we hypothesized that replacing T(3) to euthyroid levels would improve left ventricular function without producing untoward signs of thyrotoxicosis.

METHODS AND RESULTS

Adult male Sprague-Dawley rats were subjected to left anterior descending coronary artery ligation (myocardial infarction). One week post-myocardial infarction, left ventricular fractional shortening was significantly reduced to 22+/-1% in CHF animals versus 38+/-1% for sham-operated controls (P<0.001). Serum T(3) concentration was also significantly reduced (80+/-3 versus 103+/-6 ng/dL; P<0.001), in CHF animals versus Shams. At 9 weeks post-myocardial infarction, systolic function (+dP/dt max) was significantly attenuated in CHF animals (4773+/-259 versus 6310+/-267 mmHg/s; P<0.001) as well as diastolic function measured by half time to relaxation (15.9+/-1.2 versus 11.1+/-0.3 ms; P<0.001). alpha-myosin heavy chain expression was also significantly reduced by 77% (P<0.001), and beta-myosin heavy chain expression was increased by 21%. Continuous T(3) replacement was initiated 1 week post-myocardial infarction with osmotic mini-pumps (6 microg/kg/d), which returned serum T(3) concentrations to levels similar to Sham controls while resting conscious heart rate, arterial blood pressure and the incidence of arrhythmias were not different. At 9 weeks, systolic function was significantly improved by T(3) replacement (6279+/-347 mmHg/s; P<0.05) and a trend toward improved diastolic function (12.3+/-0.6 ms) was noted. T(3) replacement in CHF animals also significantly increased alpha- and reduced beta-MHC expression, (P<0.05).

CONCLUSIONS

These data indicate that T(3) replacement to euthyroid levels improves systolic function and tends to improve diastolic function, potentially through changes in myocardial gene expression.

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.

Vascular endothelial growth factors in cardiovascular medicine

The discovery of vascular endothelial growth factors (VEGFs) and their receptors has considerably improved the understanding of the development and function of endothelial cells. Each member of the VEGF family appears to have a specific function: VEGF-A induces angiogenesis (i.e. growth of new blood vessels from preexisting ones), placental growth factor mediates both angiogenesis and arteriogenesis (i.e. the formation of collateral arteries from preexisting arterioles), VEGF-C and VEGF-D act mainly as lymphangiogenic factors. The study of the biology of these endothelial growth factors has allowed a major progress in the comprehension of the genesis of the vascular system and its abnormalities observed in various pathologic conditions (atherosclerosis and coronary artery disease). The role of VEGF in the atherogenic process is still unclear, but actual evidence suggests both detrimental (development of a neoangiogenetic process within the atherosclerotic plaque) and beneficial (promotion of collateral vessel formation) effects. VEGF and other angiogenic growth factors (fibroblast growth factor), although initially promising in experimental studies and in initial phase I/II clinical trials in patients with ischemic heart disease or peripheral arterial occlusive disease, have subsequently failed to show significant therapeutic improvements in controlled clinical studies. Challenges still remain about the type or the combination of angiogenic factors to be administered, the form (protein vs. gene), the route, and the duration of administration.

Mesenchymal stem cells can participate in ischemic neovascularization

BACKGROUND

Cells from the bone marrow contribute to ischemic neovascularization, but the identity of these cells remains unclear. The authors identify mesenchymal stem cells as a bone marrow-derived progenitor population that is able to engraft into peripheral tissue in response to ischemia.

METHODS

A murine model of skin ischemia was used. Bone marrow, blood, and skin were harvested at different time points and subjected to flow cytometric analysis for mesenchymal and hematopoietic markers (n = 3 to 7 per time point). Using a parabiotic model pairing donor green fluorescent protein (GFP)-positive with recipient wild-type mice, progenitor cell engraftment was examined in ischemic tissue by fluorescence microscopy, and engrafted cells were analyzed by flow cytometry for endothelial and mesenchymal markers. In vitro, the ability of both bone marrow- and adipose-derived mesenchymal stem cells to adopt endothelial characteristics was examined by analyzing (1) the ability of mesenchymal stem cells to take up DiI-acetylated low-density lipoprotein and Alexa Fluor lectin, and (2) phenotypic changes of mesenchymal stem cells co-cultured with GFP-labeled endothelial cells or under hypoxic/vascular endothelial growth factor stimulation.

RESULTS

In vivo, the bone marrow mesenchymal stem cell population decreased significantly immediately after surgery, with subsequent engraftment of these cells in ischemic tissue. Engrafted cells lacked the panhematopoietic antigen CD45, consistent with a mesenchymal origin. In vitro, bone marrow- and adipose-derived mesenchymal stem cells took up DiI-acetylated low-density lipoprotein and Alexa Fluor lectin, and expressed endothelial markers under hypoxic conditions.

CONCLUSIONS

The authors' data suggest that mesenchymal precursor cells can give rise to endothelial progenitors. Consequently, cell-based therapies augmenting the mesenchymal stem cell population could represent powerful alternatives to current therapies for ischemic vascular disease.

Non-invasive Monitoring of Angiogenesis in Cardiology

Angiogenesis plays an important role in the pathophysiology of atherosclerosis and after myocardial infarction. Furthermore, angiogenesis has been the focus of many therapeutic strategies. In view of that, a direct and clear understanding of the role of these pathways in the living subject is needed. Molecular Imaging has emerged as a powerful tool to study biological processes non-invasively. In this review, evidence will be presented and discussed on the feasibility of different molecular imaging strategies to study the involvement of angiogenic pathways in the assessment of the atherosclerotic disease and as a tool to assess angiogenic therapy. Focus will be placed on those imaging modalities with the potential to be translated to clinical use.

mAKAP compartmentalizes oxygen-dependent control of HIF-1alpha

The activity of the transcription factor hypoxia-inducible factor 1alpha (HIF-1alpha) is increased in response to reduced intracellular oxygen. Enzymes of the protein ubiquitin machinery that signal the destruction or stabilization of HIF-1alpha tightly control this transcriptional response. Here, we show that muscle A kinase-anchoring protein (mAKAP) organized ubiquitin E3 ligases that managed the stability of HIF-1alpha and optimally positioned it close to its site of action inside the nucleus. Functional experiments in cardiomyocytes showed that depletion of mAKAP or disruption of its targeting to the perinuclear region altered the stability of HIF-1alpha and transcriptional activation of genes associated with hypoxia. Thus, we propose that compartmentalization of oxygen-sensitive signaling components may influence the fidelity and magnitude of the hypoxic response.

Isoprostanes Inhibit Vascular Endothelial Growth Factor–Induced Endothelial Cell Migration, Tube Formation, and Cardiac Vessel Sprouting In Vitro, As Well As Angiogenesis In Vivo via Activation of the Thromboxane A 2 Receptor

Isoprostanes are endogenously formed end products of lipid peroxidation. Furthermore, they are markers of oxidative stress and independent risk markers of coronary heart disease. In patients experiencing coronary heart disease, impaired angiogenesis may exacerbate insufficient blood supply of ischemic myocardium. We therefore hypothesized that isoprostanes may exert detrimental cardiovascular effects by inhibiting angiogenesis. We studied the effect of isoprostanes on vascular endothelial growth factor (VEGF)-induced migration and tube formation of human endothelial cells (ECs), and cardiac angiogenesis in vitro as well as on VEGF-induced angiogenesis in the chorioallantoic membrane assay in vivo. The isoprostanes 8-iso-PGF 2α , 8-iso-PGE 2 , and 8-iso-PGA 2 inhibited VEGF-induced migration, tube formation of ECs, and cardiac angiogenesis in vitro, as well as VEGF-induced angiogenesis in vivo via activation of the thromboxane A 2 receptor (TBXA2R): the specific TBXA2R antagonists SQ-29548, BM 567, and ICI 192,605 but not the thromboxane A 2 synthase inhibitor ozagrel blocked the effect of isoprostanes. The isoprostane 8-iso-PGA 2 degraded into 2 biologically active derivatives in vitro, which also inhibited EC tube formation via the TBXA2R. Moreover, short hairpin RNA–mediated knockdown of the TBXA2R antagonized isoprostane-induced effects. In addition, Rho kinase inhibitor Y-27632 reversed the inhibitory effect of isoprostanes and the thromboxane A 2 mimetic U-46619 on EC migration and tube formation. Finally, the various isoprostanes exerted a synergistic inhibitory effect on EC tube formation. We demonstrate for the first time that isoprostanes inhibit angiogenesis via activation of the TBXA2R. By this mechanism, isoprostanes may contribute directly to exacerbation of coronary heart disease and to capillary rarefaction in disease states of increased oxidative stress.

New insights in vascular development: vasculogenesis and endothelial progenitor cells

In the course of new blood vessel formation, two different processes--vasculogenesis and angiogenesis--have to be distinguished. The term vasculogenesis describes the de novo emergence of a vascular network by endothelial progenitors, whereas angiogenesis corresponds to the generation of vessels by sprouting from pre-existing capillaries. Until recently, it was thought that vasculogenesis is restricted to the prenatal period. During the last decade, one of the most fascinating innovations in the field of vascular biology was the discovery of endothelial progenitor cells and vasculogenesis in the adult. This review aims at introducing the concept of adult vasculogenesis and discusses the efforts to identify and characterize adult endothelial progenitors. The different sources of adult endothelial progenitors like haematopoietic stem cells, myeloid cells, multipotent progenitors of the bone marrow, side population cells and tissue-residing pluripotent stem cells are considered. Moreover, a survey of cellular and molecular control mechanisms of vasculogenesis is presented. Recent advances in research on endothelial progenitors exert a strong impact on many different disciplines and provide the knowledge for functional concepts in basic fields like anatomy, histology as well as embryology.

Regulation of hypoxic response elements on the expression of vascular endothelial growth factor gene transfected to rat skeletal myoblasts under hypoxic environment

The regulation of hypoxic response elements on the expression of vascular endothelial growth factor (VEGF) gene transfected to primary cultured rat skeletal myoblasts under hypoxic environment was investigated. pEGFP-C3-9HRE-CMV-VEGF vector was constructed with molecular biology technique and transfected to primary cultured rat skeletal myoblasts by lipofectamine in vitro. Gene expression of transfected myoblasts was detected by RT-PCR, Western blot and fluorescence microscope under different oxygen concentrations and different hypoxia time. The results showed that in hypoxia group, the VEGF gene bands were seen and with the decrease of oxygen concentrations and prolongation of hypoxia time, the expression of VEGF mRNA was obviously increased. Under hypoxic environment, the expression of VEGF protein in the transfected myoblasts was significantly increased. EGFP was expressed only under hypoxic environment but not under normoxic environment. It was concluded that hypoxia promoter could be constructed with HRE and regulate the expression of VEGF gene under hypoxic and normoxic environment, which could enhance the reliability of gene therapy.

Identification of serum endoglin as a novel prognostic marker after acute myocardial infarction

Endoglin is a proliferation-associated and hypoxia-inducible protein expressed in endothelial cells. The levels of soluble circulating endoglin and their prognostic significance in patients with acute myocardial infarction (AMI) are not known. In this observational prospective study serum endoglin levels were measured by ELISA in 183 AMI patients upon admission to hospital and 48 hrs later and in 72 healthy controls. Endoglin levels in AMI patients on admission were significantly lower than in healthy controls (4.25 ± 0.99 ng/ml versus 4.59 ± 0.87 ng/ml; P= 0.013), and decreased further in the first 48 hours (3.65 ± 0.76 ng/ml, P < 0.001). Upon follow-up (median 319 days), patients who died had a significantly greater decrease in serum endoglin level over the first 48 hrs than those who survived (1.03 ± 0.91 versus 0.54 ± 0.55 ng/ml; P= 0.025). Endoglin decrease was an independent predictor of short-term (30 days) (hazard ratio 2.33;95% CI = 1.27–4.23; P= 0.006) cardiovascular mortality, and also predicts overall cardiovascular mortality during the follow-up (median 319 days) in AMI patients (hazard ratio 2.13;95% CI = 1.20–3.78; P= 0.01). In conclusion, early changes in serum endoglin may predict mortality after AMI.

Permanent coronary artery occlusion: cardiovascular MR imaging is platform for percutaneous transendocardial delivery and assessment of gene therapy in canine model

PURPOSE

To provide evidence that vascular endothelial growth factor (VEGF) genes delivered transendocardially with magnetic resonance (MR) imaging guidance may neovascularize or improve vascular recruitment in occlusive infarction.

MATERIALS AND METHODS

All experimental procedures received approval from the institutional committee on animal research. Dogs with permanent coronary artery occlusion were imaged twice (3 days after occlusion for assessment of acute infarction; a mean of 50 days after occlusion +/- 3 [standard error of the mean] for assessment of chronic infarction). A mixture of plasmid VEGF and plasmid LacZ (n = 6, treated animals) or plasmid LacZ and sprodiamide (n = 6, placebo control animals) was delivered to four sites. MR fluoroscopy was used to target and monitor delivery of genes. The effectiveness of this delivery approach was determined by using MR imaging methods to assess perfusion, left ventricular (LV) function, myocardial viability, and infarct resorption. Histologic evaluation of neovascularization was then performed.

RESULTS

MR fluoroscopic guidance of injectates was successful in both groups. Treated animals with chronic, but not those with acute, infarction showed the following differences compared with control animals: (a) steeper mean maximum upslope perfusion (200 sec(-1) +/- 32 vs 117 sec(-1) +/- 15, P = .02), (b) higher peak signal intensity (1667 arbitrary units +/- 100 vs 1132 arbitrary units +/- 80, P = .002), (c) increased ejection fraction (from 27.9% +/- 1.2 to 35.3% +/- 1.6, P = .001), (d) smaller infarction size (as a percentage of LV mass) at MR imaging (8.5% +/- 0.9 vs 11.3% +/- 0.9, P = .048) and triphenyltetrazolium chloride staining (9.4% +/- 1.5 vs 12.7% +/- 0.4, P = .05), and (e) higher vascular density (as number of vessels per square millimeter) at the border (430 +/- 117 vs 286 +/- 19, P = .0001) and core (307 +/- 112 vs 108 +/- 17, P = .0001).

CONCLUSION

The validity of plasmid VEGF gene delivered with MR fluoroscopic guidance into occlusive infarction was confirmed by neovascularization associated with improved perfusion, LV function, and infarct resorption.

Activation of negative regulators of the hypoxia-inducible factor (HIF) pathway in human end-stage heart failure

The hypoxia-inducible transcription factor HIF is induced early in acute myocardial ischemia in humans, but it is unknown whether this activation of HIF persists during chronic heart failure. The HIF system was characterized in left ventricular myocardia from 18 explanted failing hearts and 11 non-failing donor hearts by quantitative RT-PCR and Western analysis. HIF-1alpha mRNA levels were significantly decreased while its natural antisense transcript aHIF was nearly twofold higher (p<0.01) in failing myocardia than in control hearts. Moreover, compared to donor hearts a significantly increased expression of HIF-3alpha, which may act as a competitive inhibitor of HIF-1/2alpha activity, and PHD3, which upon hydroxylation of prolyl residues directs HIF-alpha subunits towards proteasomal degradation, was observed in the failing myocardium. Although negative regulators of HIF were induced, the HIF pathway obviously remains activated in chronic human heart failure, because prototype HIF target genes, such as ABCG2, VEGF, and BNIP3, were significantly induced.

Rapid stabilization of vulnerable carotid plaque within 1 month of pitavastatin treatment in patients with acute coronary syndrome

We determined time course of stabilization of echolucent carotid plaques by statin therapy in patients with acute coronary syndrome (ACS). Treatment with 4 mg/d pitavastatin (n = 33) or placebo (n = 32) was initiated within 3 days after onset of ACS in 65 patients with echolucent carotid plaque. Vulnerable carotid plaques were assessed by measuring plaque echolucency using carotid ultrasound with integrated backscatter (IBS) analysis before and 1 month after treatment in all patients. The calibrated IBS value (intima-media IBS value minus adventia IBS) of vulnerable carotid plaques favorably changed at 1 month after treatment in both groups, but the echolucency at 1 month improved more in the pitavastatin than in the placebo group (pitavastatin group: -18.7 +/- 3.3 dB at pretreatment versus -12.7 +/- 2.3 dB at 1 month *P < 0.001; placebo: -19.0 +/- 3.5 dB versus -16.9 +/- 3.2 dB, P < 0.05, *P < 0.01 versus the value at 1 month in placebo group). Levels of CRP, VEGF, and TNFalpha at 1 month were significantly lower in pitavastatin than placebo group. In conclusion, pitavastatin improved carotid plaque echolucency within 1 month of therapy in patients with ACS, in association with decrease in the inflammatory biomarkers related to vulnerable plaques.

Hypoxia-inducible factor-1alpha induces the coronary collaterals for coronary artery disease

BACKGROUND

Marked variability exists in coronary artery collaterals in patients with ischemic heart disease. Multiple factors are thought to play a role in collateral development; however, the contribution of hypoxia inducible factor-1alpha (HIF-1alpha), which is a transcriptional activator that functions as a master regulator of oxygen homeostasis, is not completely clear. It could play an important role in modulating collateral development.

OBJECTIVE

The objective of this study is to investigate the changes and significance of expression of HIF-1alpha in patients with coronary artery collaterals.

METHODS

Collateral vessels were determined in 98 patients with >or=70% narrowing of at least one coronary artery without earlier revascularization, 42 patients with coronary artery collaterals and 56 patients with no coronary artery collaterals. Extent of collaterals was expressed as scores according to the Rentrop scoring system. Another 50 cases with normal coronary arteries were selected as control. The levels of HIF-1alpha protein expression in monocyte and lymphocyte in the participants were tested by immunohistochemistry (IHC) and western blot; mRNA levels were measured using reverse transcriptase PCR technique.

RESULTS

Compared with the control with normal coronary artery, the patients had higher expression of HIF-1alpha protein tested by IHC and western blot (52.6+/-10.2 vs. 13.7+/-6.2 by IHC, 50.8+/-4.5 vs. 6.5+/-1.8 by western blot); furthermore, significantly higher HIF-1alpha expression was observed in patients with collaterals compared with patients with no collaterals (81.5+/-11.8 vs. 20.7+/-9.4 by IHC; 87.2+/-6.5 vs. 9.5+/-1.4 by western blot). On the transcriptional levels of HIF-1alpha, the result was the same as the protein, there was significant difference of HIF-1alpha between the three groups. The patients with collaterals were the highest (127.3+/-23.9), followed by patients with no collaterals (35.7+/-12.3), and the control were the lowest (23.5+/-9.3). A highly positive correlation was observed between the expression/transcription of HIF-1alpha and collateral score (P<0.01, IHC: r1=0.78, reverse transcriptase PCR: r2=0.69, western blot: r3=0.84).

CONCLUSION

These data suggest that higher inductions of HIF-1alpha are associated with coronary collaterals, thus implying that HIF-1alpha may promote coronary collateral formation. Detection of HIF-1alpha expression might be helpful to predict prognosis of patients with coronary artery disease.

Therapeutic angiogenesis: a new treatment approach for ischemic heart disease--part I

Angiogenesis is the biologic process of forming new blood vessels and is being investigated as an innovative therapeutic approach to help manage ischemic heart disease and peripheral vascular disease. Research studies have identified various angiogenic growth factors and progenitor cells that can enhance new blood vessel formation. Preclinical investigations in animal models have explored the potential use of growth factors with and without progenitor cells to treat myocardial ischemia. The results of clinical trials with growth factor infusions and gene therapy techniques to enhance growth factor production have shown some promise, but therapeutic angiogenesis remains at an early stage of development.

The immune system and cardiac repair

Myocardial infarction is the most common cause of cardiac injury and results in acute loss of a large number of myocardial cells. Because the heart has negligible regenerative capacity, cardiomyocyte death triggers a reparative response that ultimately results in formation of a scar and is associated with dilative remodeling of the ventricle. Cardiac injury activates innate immune mechanisms initiating an inflammatory reaction. Toll-like receptor-mediated pathways, the complement cascade and reactive oxygen generation induce nuclear factor (NF)-kappaB activation and upregulate chemokine and cytokine synthesis in the infarcted heart. Chemokines stimulate the chemotactic recruitment of inflammatory leukocytes into the infarct, while cytokines promote adhesive interactions between leukocytes and endothelial cells, resulting in transmigration of inflammatory cells into the site of injury. Monocyte subsets play distinct roles in phagocytosis of dead cardiomyocytes and in granulation tissue formation through the release of growth factors. Clearance of dead cells and matrix debris may be essential for resolution of inflammation and transition into the reparative phase. Transforming growth factor (TGF)-beta plays a crucial role in cardiac repair by suppressing inflammation while promoting myofibroblast phenotypic modulation and extracellular matrix deposition. Myofibroblast proliferation and angiogenesis result in formation of highly vascularized granulation tissue. As the healing infarct matures, fibroblasts become apoptotic and a collagen-based matrix is formed, while many infarct neovessels acquire a muscular coat and uncoated vessels regress. Timely resolution of the inflammatory infiltrate and spatial containment of the inflammatory and reparative response into the infarcted area are essential for optimal infarct healing. Targeting inflammatory pathways following infarction may reduce cardiomyocyte injury and attenuate adverse remodeling. In addition, understanding the role of the immune system in cardiac repair is necessary in order to design optimal strategies for cardiac regeneration.

Biological approaches to ischemic tissue repair: gene- and cell-based strategies

Gene therapy is a potential therapeutic strategy for treatment of ischemic vascular diseases; however, the clinical application of gene therapy has met some anticipated challenges. Recent randomized, controlled trials suggest that patients with cardiovascular disease may also benefit from cell-based therapies, and the optimal treatment regimen may combine both approaches to take advantage of potential synergy between the underlying therapeutic mechanisms. This review discusses recent research into both gene and cell therapy and considers the potential application of a combined treatment approach for cardiovascular and cerebrovascular ischemic diseases.

Telomere Gap Between Granulocytes and Lymphocytes Is a Determinant for Hematopoetic Progenitor Cell Impairment in Patients With Previous Myocardial Infarction

Objective— We have previously demonstrated that ischemic cardiomyopathy is associated with selective impairment of progenitor cell function in the bone marrow and in the peripheral blood, which may contribute to an unfavorable left ventricular remodeling process.

Methods and Results— With this study, we intended to identify the influence of telomere length on bone marrow functionality in 50 patients with coronary artery disease (CAD) and previous myocardial infarction. Mean telomere length (mTL) was measured simultaneously in peripheral blood leukocytes and mononuclear bone marrow cells (BMC), using the flow-FISH method. Telomere erosion already occurred at the bone marrow level, whereby age (39 bp/yr, P =0.025) and the number of affected vessels (434 bp/vessel, P =0.029) were the only independent predictors. Lymphocytes demonstrated significant TL shortening between BMCs and peripheral blood in CAD patients (−1011±897 bp) as opposed to an increase in a young control group (+235±459 bp, P <0.001). SDF- and VEGF-specific migration of BMCs correlated with mTL of lymphocytes ( r =0.42, P <0.001) and was significantly reduced in CAD patients. Finally, the telomere length difference between granulocytes and lymphocytes was the most determinant for telomere-associated bone marrow impairment ( P <0.001).

Conclusion— In patients with CAD, telomere shortening of BMCs is dependent on both age and the extent of CAD and correlates with bone marrow cell functionality.

Oxygenated perfluorochemicals improve cell survival during reoxygenation by pacifying mitochondrial activity

Perfluorochemicals (PFCs) are known to provide a unique tool for controlled uptake and delivery of oxygen. We have characterized the effects of incremental oxygen delivery on cell viability of human ischemic cardiomyocytes using chemically inert PFCs as oxygen carrier. We have found that cell viability after prolonged ischemia depends on the dose of oxygen supplementation by oxygenated (ox) PFCs during reoxygenation. Although reoxygenation with the transient addition of oxPFCs in high concentrations (2250 microMO2 in 0.4 muM PFCs) results in decreased cell viability compared with normoxic reoxygenation, cell survival increases by 30 +/- 4% after reoxygenation with moderate oxPFC concentrations (750 muM O2 in 0.1 microM PFCs). Immunoblot analysis revealed that oxPFC-supplemented reoxygenation causes marked (16-fold) deactivation of death-associated protein kinase (DAPK) signaling an increase in mitochondrial membrane potential and a decreased steady-state level of superoxide by 19 +/- 3%. Reoxygenation with oxPFCs is further responsible for a 2-fold activation of AMP-activated protein kinase (AMPK) signaling an inadequate ATP supply by oxidative phosphorylation during reoxygenation. Addition of oxPFCs stabilizes both hypoxia-inducible factor (HIF) 1-alpha and 2-alpha during reoxygenation. Overall, these results indicate that moderate doses of oxPFCs can improve cell survival during reoxygenation, causing deactivation of DAPK, up-regulation of AMPK, and HIF1-alpha and 2-alpha stabilization. These effects of oxPFCs are dose-dependent, and they lead to a stabilization of the mitochondrial membrane potential, decreased steady-state levels of superoxide, and pacification of mitochondrial activity.

Impact of myocardial infarct proteins and oscillating pressure on the differentiation of mesenchymal stem cells: effect of acute myocardial infarction on stem cell differentiation

Stem cell transplantation in acute myocardial infarction (AMI) has emerged as a promising therapeutic option. We evaluated the impact of AMI on mesenchymal stem cell (MSC) differentiation into cardiomyocyte lineage. Cord blood-derived human MSCs were exposed to in vitro conditions simulating in vivo environments of the beating heart with acute ischemia, as follows: (a) myocardial proteins or serum obtained from sham-operated rats, and (b) myocardial proteins or serum from AMI rats, with or without application of oscillating pressure. Expression of cardiac-specific markers on MSCs was greatly induced by the infarcted myocardial proteins, compared with the normal proteins. It was also induced by application of oscillating pressure to MSCs. Treatment of MSCs with infarcted myocardial proteins and oscillating pressure greatly augmented expression of cardiac-specific genes. Such expression was blocked by inhibitor of transforming growth factor beta(1) (TGF-beta(1)) or bone morphogenetic protein-2 (BMP-2). In vitro cellular and electrophysiologic experiments showed that these differentiated MSCs expressing cardiomyocyte-specific markers were able to make a coupling with cardiomyocytes but not to selfbeat. The pathophysiologic significance of in vitro results was confirmed using the rat AMI model. The protein amount of TGF-beta(1) and BMP-2 in myocardium of AMI was significantly higher than that in normal myocardium. When MSCs were transplanted to the heart and analyzed 8 weeks later, they expressed cardiomyocyte-specific markers, leading to improved cardiac function. These in vitro and in vivo results suggest that infarct-related biological and physical factors in AMI induce commitment of MSCs to cardiomyocyte-like cells through TGF-beta/BMP-2 pathways.

Imaging of VEGF receptor in a rat myocardial infarction model using PET

Myocardial infarction (MI) leads to left ventricular (LV) remodeling, which leads to the activation of growth factors such as vascular endothelial growth factor (VEGF). However, the kinetics of a growth factor's receptor expression, such as VEGF, in the living subject has not yet been described. We have developed a PET tracer (64Cu-DOTA-VEGF121 [DOTA is 1,4,7,10-tetraazadodecane-N,N',N'',N'''-tetraacetic acid]) to image VEGF receptor (VEGFR) expression after MI in the living subject.

METHODS

In Sprague-Dawley rats, MI was induced by ligation of the left coronary artery and confirmed by ultrasound (n = 8). To image and study the kinetics of VEGFRs, 64Cu-DOTA-VEGF121 PET scans were performed before MI induction (baseline) and on days 3, 10, 17, and 24 after MI. Sham-operated animals served as controls (n = 3).

RESULTS

Myocardial origin of the 64Cu-DOTA-VEGF121 signal was confirmed by CT coregistration and autoradiography. VEGFR specificity of the 64Cu-DOTA-VEGF121 probe was confirmed by in vivo use of a 64Cu-DOTA-VEGFmutant. Baseline myocardial uptake of 64Cu-DOTA-VEGF121 was minimal (0.30 +/- 0.07 %ID/g [percentage injected dose per gram of tissue]); it increased significantly after MI (day 3, 0.97 +/- 0.05 %ID/g; P < 0.05 vs. baseline) and remained elevated for 2 wk (up to day 17 after MI), after which time it returned to baseline levels.

CONCLUSION

We demonstrate the feasibility of imaging VEGFRs in the myocardium. In summary, we imaged and described the kinetics of 64Cu-DOTA-VEGF121 uptake in a rat model of MI. Studies such as the one presented here will likely play a major role when studying pathophysiology and assessing therapies in different animal models of disease and, potentially, in patients.

Targeted imaging of hypoxia-induced integrin activation in myocardium early after infarction

The alphavbeta3-integrin is expressed in angiogenic vessels in response to hypoxia and represents a potential novel target for imaging myocardial angiogenesis. This study evaluated the feasibility of noninvasively tracking hypoxia-induced alphavbeta3-integrin activation within the myocardium as a marker of angiogenesis early after myocardial infarction. Acute myocardial infarction was produced by coronary artery occlusion in rodent and canine studies. A novel (111)In-labeled radiotracer targeted at the alphavbeta3-integrin ((111)In-RP748) was used to localize regions of hypoxia-induced angiogenesis early after infarction. In rodent studies, the specificity of (111)In-RP748 for alphavbeta3-integrin was confirmed with a negative control compound ((111)In-RP790), and regional uptake of these compounds correlated with (201)Tl perfusion and a (99m)Tc-labeled nitroimidazole (BRU59-21), which was used as a quantitative marker of myocardial hypoxia. The ex vivo analysis demonstrated that only (111)In-RP748 was selectively retained in infarcted regions with reduced (201)Tl perfusion and correlated with uptake of BRU59-21. In canine studies, myocardial uptake of (111)In-RP748 was assessed using in vivo single-photon-emission computed tomography (SPECT), ex vivo planar imaging, and gamma well counting of myocardial tissue and correlated with (99m)Tc-labeled 2-methoxy-2-methyl-propyl-isonitrile ((99m)Tc-sestamibi) perfusion. Dual-radiotracer in vivo SPECT imaging of (111)In-RP748 and (99m)Tc-sestamibi provided visualization of (111)In-RP748 uptake within the infarct region, which was confirmed by ex vivo planar imaging of excised myocardial slices. Myocardial (111)In-RP748 retention was associated with histological evidence of alphavbeta3-integrin expression/activation in the infarct region. (111)In-RP748 imaging provides a novel noninvasive approach for evaluation of hypoxia-induced alphavbeta3-integrin activation in myocardium early after infarction and may prove useful for directing and evaluating angiogenic therapies in patients with ischemic heart disease.

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.

Hypoxia-inducible factor-dependent degeneration, failure, and malignant transformation of the heart in the absence of the von Hippel-Lindau protein

Hypoxia-inducible transcription factor 1 (HIF-1) and HIF-2alpha regulate the expression of an expansive array of genes associated with cellular responses to hypoxia. Although HIF-regulated genes mediate crucial beneficial short-term biological adaptations, we hypothesized that chronic activation of the HIF pathway in cardiac muscle, as occurs in advanced ischemic heart disease, is detrimental. We generated mice with cardiac myocyte-specific deletion of the von Hippel-Lindau protein (VHL), an essential component of an E3 ubiquitin ligase responsible for suppressing HIF levels during normoxia. These mice were born at expected frequency and thrived until after 3 months postbirth, when they developed severe progressive heart failure and premature death. VHL-null hearts developed lipid accumulation, myofibril rarefaction, altered nuclear morphology, myocyte loss, and fibrosis, features seen for various forms of human heart failure. Further, nearly 50% of VHL(-/-) hearts developed malignant cardiac tumors with features of rhabdomyosarcoma and the capacity to metastasize. As compelling evidence for the mechanistic contribution of HIF-1alpha, the concomitant deletion of VHL and HIF-1alpha in the heart prevented this phenotype and restored normal longevity. These findings strongly suggest that chronic activation of the HIF pathway in ischemic hearts is maladaptive and contributes to cardiac degeneration and progression to heart failure.

Role of hypoxia-inducible factor in cell survival during myocardial ischemia-reperfusion

Hypoxia-inducible factor (HIF) is the principal transcription factor involved in the regulation of transcriptional responses to hypoxia. During hypoxia, HIF-alpha levels accumulate and trigger an increase in expression of genes involved in glycolysis, glucose metabolism, mitochondrial function, cell survival, apoptosis, and resistance to oxidative stress. In this regard, HIF activation plays an essential role in triggering cellular protection and metabolic alterations from the consequences of oxygen deprivation. This suggests that HIF activation should confer protection against ischemia-reperfusion (I/R) injury, although this protection might require HIF activation before the onset of lethal ischemia. Studies using enhanced expression of HIF-1alpha suggest that its upregulation may be a beneficial therapeutic modality in the treatment or prevention of ischemic injury. HIF-regulated gene expression may mediate the late phase of preconditioning, and constitutive HIF activity may influence the expression of genes that are required for the cell to be able to respond to acute preconditioning. This article reviews the current literature on the role of HIF in balancing protection and cell death in the face of ischemia and I/R injury.

Nuclear Ca2+ sparks and waves mediated by inositol 1,4,5-trisphosphate receptors in neonatal rat cardiomyocytes

Dynamic nuclear Ca(2+) signals play pivotal roles in diverse cellular functions including gene transcription, cell growth, differentiation, and apoptosis. Here we report a novel nuclear Ca(2+) regulatory mechanism mediated by inositol 1,4,5-trisphosphate receptors (IP(3)Rs) around the nucleus in developing cardiac myocytes. Activation of IP(3)Rs by alpha(1)-adrenergic receptor (alpha(1)AR) stimulation or by IP(3) application (in saponin-permeabilized cells) increases Ca(2+) spark frequency preferentially in the region around the nucleus in neonatal rat ventricular myocytes. A nuclear enrichment of IP(3)R distribution supports the higher responsiveness of Ca(2+) release in this particular region. Strikingly, we observed "nuclear Ca(2+)waves" that engulf the entire nucleus without spreading into the bulk cytosol. alpha(1)AR stimulation enhances the occurrence of nuclear Ca(2+) waves and confers them the ability to trigger cytosolic Ca(2+) waves via IP(3)R-dependent pathways. This finding accounts, at least partly, for a profound frequency-dependent modulation of global Ca(2+) oscillations during alpha(1)AR stimulation. Thus, IP(3)R-mediated Ca(2+) waves traveling in the nuclear region provide active, autonomous regulation of nuclear Ca(2+) signaling, which provides for not only the local signal transduction, but also a pacemaker to drive global Ca(2+) transient in the context of alpha(1)AR stimulation in developing cardiac myocytes.

Endothelial precursor cells

The discovery and subsequent characterization of endothelial precursor cells (EPCs) has stimulated interest in their potential use in older persons. Understanding the mechanisms that underlie EPC availability and function has important clinical implications for this age group. In this review, we discuss aspects of EPCs that are relevant to their role in angiogenesis and cardiovascular disease. We then review the limited data on features of EPCs that are known to be altered in aging and might better define their clinical utility in older persons.

In vivo hepatocyte growth factor gene transfer reduces myocardial ischemia-reperfusion injury through its multiple actions

BACKGROUND

Hepatocyte growth factor (HGF) is reported to protect the heart against ischemia-reperfusion injury. However, whether in vivo adenovirus-mediated HGF gene transfer before ischemia is protective against ischemia-reperfusion and its precise mechanisms are still unknown.

METHODS AND RESULTS

By using a rabbit model of ischemia-reperfusion injury, we demonstrate that HGF gene transfer is cardioprotective through its multiple beneficial actions, such as angiogenesis, Bcl-2 overexpression, and decreasing hydroxyl radicals, deoxyuride-5'-triphosphate biotin nick end labeling (TUNEL)-positive myocytes, and fibrotic area. After HGF gene transfer, the rabbits underwent 30 minutes of coronary occlusion and 30 minutes, 4 hours, 48 hours, and 14 days of reperfusion. The infarct size at 48 hours of reperfusion was significantly reduced in the HGF group (13.4% +/- 2.3%) compared with that in the LacZ group (36.5% +/- 2.0%) and saline group (40.3% +/- 3.2%). At 14 days of reperfusion, HGF gene transfer improved left ventricular ejection fraction and fractional shortening, reduced the fibrotic area, and increased the capillary density in the risk area. At 4 hours of reperfusion, Bcl-2 protein was overexpressed and the incidence of TUNEL-positive myocytes was significantly decreased in the risk area in the HGF group compared with the LacZ and saline groups. The myocardial interstitial 2,5-dihydroxybenzoic acid level, an indicator of hydroxyl radical, increased during 30 minutes of ischemia and 30 minutes of reperfusion in the LacZ and saline groups, and was significantly inhibited in the HGF group.

CONCLUSION

HGF gene therapy may be a novel therapeutic strategy against unstable angina pectoris or severe angina pectoris, which may progress to acute myocardial infarction.

Augmented healing process in female mice with acute myocardial infarction

BACKGROUND

It is well established that premenopausal women are protected from cardiovascular disease. This gender difference in favor of females is also demonstrated in animal studies. Our research group previously found that female mice had much lower incidence of cardiac rupture and mortality than did males during the acute phase of myocardial infarction (MI); however, the mechanisms responsible for such protection are not fully understood.

OBJECTIVE

The aim of this study was to determine whether the favorable cardiac effect observed in female mice with MI is due to an augmented healing process that includes less inflammation, reduced matrix degradation, and enhanced neovascularization.

METHODS

Twelve-week-old male and female C57BL/6J mice were subjected to MI by ligating the left anterior descending coronary artery and then euthanized at 1, 4, 7, or 14 days post-MI. Inflammatory cell infiltration and myofibroblast transformation, matrix metalloproteinase (MMP)-2 and MMP-9 activity, tissue inhibitor of metalloproteinase (TIMP)-I expression, and neovascularization were examined by immunohistochemistry, zymography, Western blot, and laser scanning confocal microscopy, respectively. Cardiac function was evaluated by echocardiography on day 14.

RESULTS

We found that: (1) neutrophil infiltration during the early phase of MI (1-4 days) was much lower in females than in males and was associated with lower MMP-9 activity and higher TIMP-1 protein expression, indicating less-exaggerated inflammation and extracellular matrix degradation in females; (2) myofibroblast transformation, as indicated by expression of alpha-smooth muscle actin, was significantly greater in females than in males at day 7 of MI (P<0.05), indicating facilitated collagen deposition and scar formation; and (3) neovascularization (vascular area in the infarct border) was markedly increased in females, and was associated with better preserved cardiac function and less left ventricular dilatation.

CONCLUSION

Our data suggest that less-exaggerated early inflammation and augmented reparative fibrotic response, indicated by enhanced myofibroblast transformation, may contribute greatly to low rupture rates in females during the acute and subacute phases of MI, whereas enhanced neovascularization may lead to better preserved cardiac function post-MI.

Adenoviral gene transfer of sphingosine kinase 1 protects heart against ischemia/reperfusion-induced injury and attenuates its postischemic failure

Sphingosine kinase 1 (SPK1) has been identified as a central mediator of ischemia preconditioning and plays a protective role in ischemia/reperfusion (I/R)-induced cardiomyocyte death. In the present study, we investigated the protective effect of adenovirus-mediated SPK1 gene (Ad-SPK1) transfer on I/R-induced cardiac injury, and evaluated its therapeutic action on postinfarction heart failure. Cardiac SPK1 activity was increased about 5-fold by injection of Ad-SPK1, compared with injection of adenovirus carrying the green fluorescent protein gene (Ad-GFP). A more potent performance and a lower incidence of arrhythmia were observed in Ad-SPK1-injected hearts during the reperfusion period, compared with Ad-GFP-injected hearts. An enzymatic activity assay showed that creatine kinase release was also less in Ad-SPK1-injected hearts. To investigate the therapeutic action of the SPK1 gene on postischemic heart failure, the left anterior descending branch of the coronary artery in Wistar rats was ligated after direct intramyocardial injection of Ad-SPK1 or Ad-GFP as a control. Ad-SPK1 injection significantly preserved cardiac systolic and diastolic function, as evidenced by left ventricular (LV) systolic pressure, LV end-diastolic pressure, and peak velocity of contraction (dP/dt). The LV morphometric parameters of Ad-SPK1-treated animals were also preserved. In addition, SPK1 gene delivery significantly enhanced angiogenesis and reduced fibrosis. These results demonstrate that adenovirus-mediated SPK1 gene transfer could efficiently prevent I/R-induced myocardial injury and attenuate postischemic heart failure. Thus, SPK1 gene delivery would be a novel strategy for the treatment of coronary heart disease.

The relationship between vascular endothelial growth factor (VEGF) and microalbuminuria in patients with essential hypertension

OBJECTIVE

The existence of microalbuminuria (MAU) in patients with essential hypertension is a strong indicator of microvascular damage. Although endothelial dysfunction and increased vascular permeability both have a role in the development of MAU, its ethiopathogenesis in hypertensive patients is not yet clearly understood. Vascular endothelial growth factor (VEGF) is the most important regulator of pathological or physiological angiogenesis and it additionally leads to increased vascular permeability. This study aims to assess the relationship of serum VEGF levels to MAU in non-complicated, newly-diagnosed essential hypertensive patients (EHs).

METHODS

This study included 30 newly-diagnosed EHs with MAU, 46 newly-diagnosed EHs without MAU and 46 healthy controls. None of the EHs had diabetes, renal impairment or atherosclerotic diseases. Serum VEGF levels were measured using the ELISA method.

RESULTS

Serum levels of VEGF were significantly higher in EHs with MAU when compared with patients without MAU (225.15+/-109.34 pg/mL versus 166.78+/-114.35 pg/mL, p: 0.04) or controls (225.15+/-109.34 pg/mL versus 144.91+/-96.60 pg/mL, p: 0.007). On the other hand, no significant difference was observed between the non-MAU and control groups. In the univariate analysis, serum levels of VEGF, were positively correlated with systolic blood pressure (R: 0.253 p: 0.001), diastolic blood pressure (R: 0.162 p: 0.04), mean arterial pressure (R: 0.239 p: 0.002), creatinine clearance (R: 0.172 p: 0.04) and MAU (R: 0.338 p: 0.002). In the multiple linear regression analysis, VEGF levels were independently related to MAU (beta: 0.248, p: 0.02).

CONCLUSION

VEGF levels are higher in EHs in the presence of MAU. These high values may be important in the early diagnosis of vascular damage in EHs. Additionally, VEGF may increase glomerular permeability and lead to MAU in EHs.

Effect of modified glucose-insulin-potassium on free fatty acids, matrix metalloproteinase, and myoglobin in ST-elevation myocardial infarction

Insulin has a free fatty acid (FFA)-suppressive effect, vascular endothelial growth factor (VEGF)- and matrix metalloproteinase (MMP)-lowering effect, and a potential myocardial-protective effect. Whether low-dose insulin exerts these effects in patients with acute myocardial infarction (MI) was investigated. Thirty-two patients administered thrombolytics and heparin were randomly assigned to a modified glucose-insulin-potassium (GIK) regimen (insulin 2.5 U/hour, dextrose and potassium titrated to prevent hyperglycemia) or normal saline solution and potassium (controls) for 48 hours. Plasma FFA, serum VEGF, pro-MMP-1, and myoglobin were measured at baseline and sequentially for 48 hours. FFA concentrations were increased at baseline; increased further in the first 4 hours in controls (p<or=0.008), but not in the GIK group, and were higher at 4 hours in controls compared with the GIK group (p=0.0009). VEGF decreased to 7% of baseline at 2 hours and remained suppressed in both groups (p=0.0008). Pro-MMP-1 decreased in both groups (p<0.005), but this decrease was seen earlier at 2 hours in the GIK group compared with 4 hours in controls. There was no significant increase in myoglobin at 2 hours in the GIK group, whereas there was a significant increase in controls. Mean blood glucose was 131 mg/dl in controls and 124 mg/dl in the GIK group (p=NS). In conclusion, this modified GIK regimen attenuated the increase in FFA, but did not suppress it to less than the threshold for myocardial FFA uptake. It suppressed pro-MMP-1 rapidly and decreased myoglobin, whereas heparin suppressed VEGF in patients with acute MI. This provided additional rationale for conducting a trial to assess the clinical benefits of this modified GIK regimen in patients with acute MI.

Polymorphisms in hypoxia inducible factor 1 and the initial clinical presentation of coronary disease

BACKGROUND

Only some patients with coronary artery disease (CAD) develop acute myocardial infarction (MI), and emerging evidence suggests vulnerability to MI varies systematically among patients and may have a genetic component. The goal of this study was to assess whether polymorphisms in genes encoding elements of pathways mediating the response to ischemia affect vulnerability to MI among patients with underlying CAD.

METHODS

We prospectively identified patients at the time of their initial clinical presentation of CAD who had either an acute MI or stable exertional angina. We collected clinical data and genotyped 34 polymorphisms in 6 genes (ANGPT1, HIF1A, THBS1, VEGFA, VEGFC, VEGFR2).

RESULTS

The 909 patients with acute MI were significantly more likely than the 466 patients with stable angina to be male, current smokers, and hypertensive, and less likely to be taking beta-blockers or statins. Three polymorphisms in HIF1A (Pro582Ser, rs11549465; rs1087314; and Thr418Ile, rs41508050) were significantly more common in patients who presented with stable exertional angina rather than acute MI, even after statistical adjustment for cardiac risk factors and medications. The HIF-mediated transcriptional activity was significantly lower when HIF1A null fibroblasts were transfected with variant HIF1A alleles than with wild-type HIF1A alleles.

CONCLUSIONS

Polymorphisms in HIF1A were associated with development of stable exertional angina rather than acute MI as the initial clinical presentation of CAD.

Keeping the engine primed: HIF factors as key regulators of cardiac metabolism and angiogenesis during ischemia

Myocardial ischemia, the most common cause of cardiac hypoxia in clinical medicine, occurs when oxygen delivery cannot meet myocardial metabolic requirements in the heart. This deficiency can result from either a reduced supply of oxygen (decreased coronary bloodflow) or an increased myocardial demand for oxygen (increased wall stress or afterload). Patients with stable coronary artery disease as well as patients experiencing acute myocardial infarction can experience episodes of severe ischemia. Although hypoxia is an obligatory component, it is not the sole environmental stress experienced by the ischemic heart. Reperfusion after ischemia is associated with increased oxidative stress as the heart reverts to aerobic respiration and thereby generates toxic levels of reactive oxygen species (ROS). During mild ischemia, mitochondrial function is partially compromised and substrate preferences adapt to sustain adequate ATP generation. With severe ischemia, mitochondrial function is markedly compromised and anaerobic metabolism must provide energy no matter what the cost in generation of toxic ROS adducts. Ischemia produces a variety of environmental stresses that impair cardiovascular function. As a result, multiple signaling pathways are activated in mammalian cells during ischemia/reperfusion injury in an attempt to minimize cellular injury and maintain cardiac output. Amongst the transcriptional regulators activated are members of the hypoxia inducible factor (HIF) transcription factor family. HIF factors regulate a variety of genes that affect a myriad of cellular processes including metabolism, angiogenesis, cell survival, and oxygen delivery, all of which are important in the heart. In this review, we will focus on the metabolic and angiogenic aspects of HIF biology as they relate to the heart during ischemia. We will review the metabolic requirements of the heart under normal as well as hypoxic conditions, the effects of preconditioning and its regulation as it pertains to HIF biology, the apparent roles of HIF-1 and HIF-2 in intermediary metabolism, and translational applications of HIF-1 and HIF-2 biology to cardiac angiogenesis. Increased understanding of the role of HIFs in cardiac ischemia will ultimately influence clinical cardiovascular practice.