Ischemic preconditioning-mediated cardioprotection is disrupted in heterozygous Flt-1 (VEGFR-1) knockout mice

Causal association between placental growth factor and coronary heart disease: a Mendelian randomization study

OBJECTIVE

Placental growth factor (PlGF), an important polypeptide hormone, plays an important regulatory role in various physiological processes. Observational studies have shown that PlGF is associated with the risk of coronary heart disease (CHD). However, the causal association between PlGF and CHD is unclear at present. This study aimed to investigate the causal association between genetically predicted PlGF levels and CHD.

METHODS

Single nucleotide polymorphisms (SNPs) associated with PlGF were selected as instrumental variables (IVs) to evaluate the causal association between genetically predicted circulating PlGF levels and CHD risk by two-sample Mendelian randomization (MR).

RESULTS

Inverse variance weighted (IVW) analysis showed that there was a suggestive causal association between genetically predicted PlGF level and the risk of CHD (OR = 0.79, 95% CI: 0.66-0.95, P = 0.011) overall. In addition, PlGF levels had a significant negative causal association with the risk of myocardial infarction (OR = 0.83, 95% CI: 0.72-0.95, P = 0.007). A negative correlation trend was found between PlGF level and the risk of angina pectoris (OR = 0.89, 95% CI: 0.79-1.01, P = 0.067). In addition, PlGF levels had a significant negative association with the risk of unstable angina pectoris (OR = 0.78, 95% CI: 0.64-0.94, P = 0.008). PlGF levels were negatively correlated with CHD events with suggestive significance (OR = 0.89, 95% CI: 0.80-0.99, P = 0.046).

CONCLUSION

Genetically predicted circulating PlGF levels are causally associated with the risk of CHD, especially acute coronary syndrome, and PlGF is a potential therapeutic target for CHD.

Placental growth factor exerts a dual function for cardiomyogenesis and vasculogenesis during heart development

Cardiogenic growth factors play important roles in heart development. Placental growth factor (PLGF) has previously been reported to have angiogenic effects; however, its potential role in cardiogenesis has not yet been determined. We analyze single-cell RNA-sequencing data derived from human and primate embryonic hearts and find PLGF shows a biphasic expression pattern, as it is expressed specifically on ISL1+ second heart field progenitors at an earlier stage and on vascular smooth muscle cells (SMCs) and endothelial cells (ECs) at later stages. Using chemically modified mRNAs (modRNAs), we generate a panel of cardiogenic growth factors and test their effects on enhancing cardiomyocyte (CM) and EC induction during different stages of human embryonic stem cell (hESC) differentiations. We discover that only the application of PLGF modRNA at early time points of hESC-CM differentiation can increase both CM and EC production. Conversely, genetic deletion of PLGF reduces generation of CMs, SMCs and ECs in vitro. We also confirm in vivo beneficial effects of PLGF modRNA for development of human heart progenitor-derived cardiac muscle grafts on murine kidney capsules. Further, we identify the previously unrecognized PLGF-related transcriptional networks driven by EOMES and SOX17. These results shed light on the dual cardiomyogenic and vasculogenic effects of PLGF during heart development.

Pharmacological Cardioprotection against Ischemia Reperfusion Injury-The Search for a Clinical Effective Therapy

Pharmacological conditioning aims to protect the heart from myocardial ischemia-reperfusion injury (IRI). Despite extensive research in this area, today, a significant gap remains between experimental findings and clinical practice. This review provides an update on recent developments in pharmacological conditioning in the experimental setting and summarizes the clinical evidence of these cardioprotective strategies in the perioperative setting. We start describing the crucial cellular processes during ischemia and reperfusion that drive acute IRI through changes in critical compounds (∆G_ATP, Na⁺, Ca²⁺, pH, glycogen, succinate, glucose-6-phosphate, mitoHKII, acylcarnitines, BH₄, and NAD⁺). These compounds all precipitate common end-effector mechanisms of IRI, such as reactive oxygen species (ROS) generation, Ca²⁺ overload, and mitochondrial permeability transition pore opening (mPTP). We further discuss novel promising interventions targeting these processes, with emphasis on cardiomyocytes and the endothelium. The limited translatability from basic research to clinical practice is likely due to the lack of comorbidities, comedications, and peri-operative treatments in preclinical animal models, employing only monotherapy/monointervention, and the use of no-flow (always in preclinical models) versus low-flow ischemia (often in humans). Future research should focus on improved matching between preclinical models and clinical reality, and on aligning multitarget therapy with optimized dosing and timing towards the human condition.

Myocardial Protection and Current Cancer Therapy: Two Opposite Targets with Inevitable Cost

Myocardial protection against ischemia/reperfusion injury (IRI) is mediated by various ligands, activating different cellular signaling cascades. These include classical cytosolic mediators such as cyclic-GMP (c-GMP), various kinases such as Phosphatydilinositol-3- (PI3K), Protein Kinase B (Akt), Mitogen-Activated-Protein- (MAPK) and AMP-activated (AMPK) kinases, transcription factors such as signal transducer and activator of transcription 3 (STAT3) and bioactive molecules such as vascular endothelial growth factor (VEGF). Most of the aforementioned signaling molecules constitute targets of anticancer therapy; as they are also involved in carcinogenesis, most of the current anti-neoplastic drugs lead to concomitant weakening or even complete abrogation of myocardial cell tolerance to ischemic or oxidative stress. Furthermore, many anti-neoplastic drugs may directly induce cardiotoxicity via their pharmacological effects, or indirectly via their cardiovascular side effects. The combination of direct drug cardiotoxicity, indirect cardiovascular side effects and neutralization of the cardioprotective defense mechanisms of the heart by prolonged cancer treatment may induce long-term ventricular dysfunction, or even clinically manifested heart failure. We present a narrative review of three therapeutic interventions, namely VEGF, proteasome and Immune Checkpoint inhibitors, having opposing effects on the same intracellular signal cascades thereby affecting the heart. Moreover, we herein comment on the current guidelines for managing cardiotoxicity in the clinical setting and on the role of cardiovascular confounders in cardiotoxicity.

Snake venom vascular endothelial growth factors (svVEGFs): Unravelling their molecular structure, functions, and research potential

Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis, a physiological process characterized by the formation of new vessels from a preexisting endothelium. VEGF has also been implicated in pathologic states, such as neoplasias, intraocular neovascular disorders, among other conditions. VEGFs are distributed in seven different families: VEGF-A, B, C, D, and PIGF (placental growth factor), which are identified in mammals; VEGF-E, which are encountered in viruses; and VEGF-F or svVEGF (snake venom VEGF) described in snake venoms. This is the pioneer review of svVEGF family, exploring its distribution among the snake venoms, molecular structure, main functions, and potential applications.

Identification of Post-myocardial Infarction Blood Expression Signatures Using Multiple Feature Selection Strategies

Myocardial infarction (MI) is a type of serious heart attack in which the blood flow to the heart is suddenly interrupted, resulting in injury to the heart muscles due to a lack of oxygen supply. Although clinical diagnosis methods can be used to identify the occurrence of MI, using the changes of molecular markers or characteristic molecules in blood to characterize the early phase and later trend of MI will help us choose a more reasonable treatment plan. Previously, comparative transcriptome studies focused on finding differentially expressed genes between MI patients and healthy people. However, signature molecules altered in different phases of MI have not been well excavated. We developed a set of computational approaches integrating multiple machine learning algorithms, including Monte Carlo feature selection (MCFS), incremental feature selection (IFS), and support vector machine (SVM), to identify gene expression characteristics on different phases of MI. 134 genes were determined to serve as features for building optimal SVM classifiers to distinguish acute MI and post-MI. Subsequently, functional enrichment analyses followed by protein-protein interaction analysis on 134 genes identified several hub genes (IL1R1, TLR2, and TLR4) associated with progression of MI, which can be used as new diagnostic molecules for MI.

Treatment with placental growth factor attenuates myocardial ischemia/reperfusion injury

Studies have established that oxidative stress plays an important role in the pathology of myocardial ischemia/reperfusion injury (MIRI). Vascular endothelial growth factor receptor 1 (VEGFR1) activation was reported to reduce oxidative stress and apoptosis. In the present study, we tested the hypothesis that the activation of VEGFR1 by placental growth factor (PlGF) could reduce MIRI by regulating oxidative stress. Mouse hearts and neonatal mouse cardiomyocytes were subjected to ischemia/reperfusion (I/R) and oxygen glucose deprivation (OGD), respectively. PlGF pretreatment markedly ameliorated I/R injury, as demonstrated by reduced infarct size and improved cardiac function. The protection was associated with a reduction of cardiomyocyte apoptosis. Similarly, our in vitro study showed that PlGF treatment improved cell viability and reduced cardiomyocyte apoptosis. Also, activation of VEGFR1 by PlGF suppressed intracellular and mitochondrial reactive oxygen species (ROS) generation. However, VEGFR1 neutralizing monoclonal antibody, which preventing PlGF binding, totally blocked this protective effect. In conclusion, activation of VEGFR1 could protect heart from I/R injury by suppression of oxidative stress and apoptosis.

Upregulation of vascular endothelial growth factor receptor-1 contributes to sevoflurane preconditioning-mediated cardioprotection

Purpose

Sevoflurane preconditioning (SPC) can provide myocardial protective effects similar to ischemic preconditioning. However, the exact mechanism of SPC remains unclear. Previous studies indicate that vascular endothelial growth factor receptor 1 (VEGFR-1) is involved in ischemic preconditioning-mediated cardioprotection. This study was designed to determine the significance of VEGFR-1 signaling in SPC-mediated cardioprotection.

Materials and methods

Myocardial ischemia–reperfusion (I/R) rat model was established using the Langendorff isolated heart perfusion apparatus. Additionally, after 15 min of baseline equilibration, the isolated hearts were pretreated with 2.5% sevoflurane, 2.5% sevoflurane+MF1 10 μmol/L, or 2.5% sevoflurane+placental growth factor 10 μmol/L, and then subjected to 30 min of global ischemia and 120 min of reperfusion. The changes in hemodynamic parameters, myocardial infarct size, and the levels of creatine kinase-MB, lactate dehydrogenase, cardiac troponin-I, tumor necrosis factor-α, and interleukin 6 in the myocardium were evaluated.

Results

Compared to the I/R group, pretreatment with 2.5% sevoflurane significantly improved the cardiac function, limited myocardial infarct size, reduced cardiac enzyme release, upregulated VEGFR-1 expression, and decreased inflammation. In addition, the selective VEGFR-1 agonist, placental growth factor, did not enhance the cardioprotection and anti-inflammation effects of sevoflurane, while the specific VEGFR-1 inhibitor, MF1, completely reversed these effects.

Conclusion

Our data have demonstrated that 2.5% sevoflurane preconditioning alleviates heart I/R injury, which is probably mediated by the anti-inflammatory property and upregulation of VEGFR-1.

Improving Cell Engraftment in Cardiac Stem Cell Therapy

Myocardial infarction (MI) affects millions of people worldwide. MI causes massive cardiac cell death and heart function decrease. However, heart tissue cannot effectively regenerate by itself. While stem cell therapy has been considered an effective approach for regeneration, the efficacy of cardiac stem cell therapy remains low due to inferior cell engraftment in the infarcted region. This is mainly a result of low cell retention in the tissue and poor cell survival under ischemic, immune rejection and inflammatory conditions. Various approaches have been explored to improve cell engraftment: increase of cell retention using biomaterials as cell carriers; augmentation of cell survival under ischemic conditions by preconditioning cells, genetic modification of cells, and controlled release of growth factors and oxygen; and enhancement of cell survival by protecting cells from excessive inflammation and immune surveillance. In this paper, we review current progress, advantages, disadvantages, and potential solutions of these approaches.

In vivo and in vitro effect of hepatocarcinoma lymph node metastasis by upregulation of Annexin A7 and relevant mechanisms

We unveiled the association of Annexin A7 with vascular endothelial growth factor-C (VEGF-C) and the effect of upregulation of Annexin A7 in Hca-F and Hca-P cells on inhibiting hepatocarcinoma (HCC) lymph node metastasis (LNM) in vitro and in vivo. A total of 200 inbred 615 mice were randomly divided into four equal groups inoculated with Hca-F, Hca-P, FAnxa7-upregulated, and PAnxa7-upregulated cells, respectively. The primary tumor, popliteal, inguinal, and iliac lymph nodes were prepared for immunohistochemical (IHC) staining, real-time quantitative polymerase chain reaction (qRT-PCR) analysis, Western blot, and hematoxylin-eosin (H&E) staining. There was over 50 % increase both in the number of FAnxa7-upregulated and PAnxa7-upregulated cells migrated through the filter compared to their controls (FAnxa7-control, Hca-F and PAnxa7-control, Hca-P). However, no significant differences were noted in invasion ability between them (all P > 0.05). Tumor lymph vessels were significantly reduced in FAnxa7-upregulated and PAnxa7-upregulated tumors when compared with Hca-F and Hca-P tumors (all P < 0.05). Blood vessel density did not differ significantly between FAnxa7-upregulated and PAnxa7-upregulated tumors and Hca-F and Hca-P tumors. Enzyme-linked immunosorbent assay (ELISA) for VEGF-C showed that upregulating Annexin A7 decreased VEGF-C secretion in FAnxa7-upregulated and PAnxa7-upregulated cells (P < 0.05). The IHC staining result showed that the level of serum Annexin A7 was found to be statistically higher in all experimental groups than that in the control group (P < 0.05). The present results indicated that alterations in serum Annexin A7 expression may be of prognostic relevance in HCC lymphatic metastasis.

Annexin A7 suppresses lymph node metastasis of hepatocarcinoma cells in a mouse model

Background

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death in China. This study investigated the effects of Annexin A7 (ANXA7) on the inhibition of HCC lymph node metastasis in a mouse model.

Methods

The stable knockup and knockdown of Annexin A7-expressing HCC cells using Annexin A7 cDNA and shRNA vectors, respectively, were injected into a mouse footpad to establish primary and metastatic tumors in mice. On the 14th, 21st, and 28th days after HCC cells inoculation, the mice were sacrificed for inspection of primary and secondary tumors and immunohistochemistry of Annexin A7 expression.

Results

The lymph node metastasis rate of the F_{ANXA7-control} group was 77%, and the lymph node metastasis rate of the F_ANXA7-down group was 100% (p < 0.05). In contrast, the lymph node metastasis rate of the P_ANXA7-up group was 0% and that of the P_{ANXA7-control} group was 36% (p < 0.05). Furthermore, immunohistochemistry experiments revealed that the subcellular localization of Annexin A7 protein in both primary and lymph node-metastasized tumors was mainly in the cytosol. In addition, the expression of the 47 kDa and 51 kDa isoforms of Annexin A7 protein changed during tumor progression.

Conclusion

This study indicated that Annexin A7 expression was able to inhibit HCC lymph node metastasis, whereas knockdown of Annexin A7 expression significantly induced HCC metastasis to local lymph nodes.

Ischemic postconditioning attenuates liver warm ischemia-reperfusion injury through Akt-eNOS-NO-HIF pathway

BACKGROUND

Ischemic postconditioning (IPO) has been demonstrated to attenuate ischemia/reperfusion (I/R) injury in the heart and brain, its roles to liver remain to be defined. The study was undertaken to determine if IPO would attenuate liver warm I/R injury and its protective mechanism.

METHODS

Mice were divided into sham, I/R, IPO+I/R (occlusing the porta hepatis for 60 min, then treated for three cycles of 10 sec brief reperfusion consecutively, followed by a persistent reperfusion); L-NAME+ sham (L-NAME, 16 mg/kg, i.v., 5 min before repefusion); L-NAME+I/R; and L-NAME+ IPO. Blood flow of caudate and left lobe of the liver was blocked. Functional and morphologic changes of livers were evaluated. Contents of nitric oxide, eNOS and iNOS in serum were assayed. Concentration of eNOS, iNOS, malondialdehyde (MDA) and activity of superoxide dismutase (SOD) in hepatic tissue were also measured. Expressions of Akt, p-Akt and HIF-1α protein were determined by western blot. Expressions of TNF-α and ICAM-1 were measured by immunohistochemistry and RT-PCR.

RESULTS

IPO attenuated the dramatically functional and morphological injuries. The levels of ALT was significantly reduced in IPO+I/R group (p < 0.05). Contents of nitric oxide and eNOS in serum were increased in the IPO+I/R group (p < 0.05). IPO also up-regulated the concentration of eNOS, activity of SOD in hepatic tissue (p < 0.05), while reduced the concentration of MDA (p < 0.05). Moreover, protein expressions of HIF-1α and p-Akt were markedly enhanced in IPO+I/R group. Protein and mRNA expression of TNF-α and ICAM-1 were markedly suppressed by IPO (p < 0.05). These protective effects of IPO could be abolished by L-NAME.

CONCLUSIONS

We found that IPO increased the content of NO and attenuated the overproduction of ROS and I/R-induced inflammation. Increased NO contents may contribute to increasing HIF-1α level, and HIF-1α and NO would simultaneously protect liver from I/R injury. These findings suggested IPO may have the therapeutic potential through Akt-eNOS-NO-HIF pathway for the better management of liver I/R injury.

Rb1 postconditioning attenuates liver warm ischemia-reperfusion injury through ROS-NO-HIF pathway

AIMS

Ginsenoside Rb1 could prevent ischemic neuronal death and focal cerebral ischemia, but its roles to liver warm I/R injury remain to be defined. We determined if Rb1 would attenuate warm I/R injury in mice.

MAIN METHODS

Mice were divided into sham, I/R, Rb1+I/R (Rb1 postconditioning, 20mg/kg, i.p. after ischemia), sham+L-NAME, I/R+L-NAME, and Rb1+I/R+L-NAME groups using 60min of the liver median and left lateral lobes ischemia. Serum levels of alanine aminotransferase (ALT) were measured and morphology changes of livers were evaluated. Contents of nitric oxide (NO) and nitric oxide synthase (NOS), malondialdehye (MDA) and activity of superoxide dismutase (SOD) were measured. Expressions of Akt, p-Akt, iNOS, HIF-1alpha, tumor necrosis factor-a (TNF-α) and intercellular adhesion molecule-1 (ICAM-1) were also determined by western blot or immunohistochemistry.

KEY FINDINGS

Rb1 postconditioning attenuated the dramatically functional and morphological injuries. The levels of ALT were significantly reduced in Rb1 group (p<0.05). Rb1 upregulated the concentrations of NO, iNOS in serum, iNOS, and activity of SOD in hepatic tissues (p<0.05), while it dramatically reduced the concentration of MDA (p<0.05). Protein expressions of p-Akt, iNOS and HIF-1alpha were markedly enhanced in Rb1 group. Protein and mRNA expressions of TNF-α and ICAM-1 were markedly suppressed by Rb1 (p<0.05).

SIGNIFICANCE

We found that Rb1 postconditioning could protect liver from I/R injury by upregulating the content of NO and NOS, and also HIF-1alpha protein expression. These protective effects could be abolished by L-NAME. These findings suggested Rb1 may have the therapeutic potential through ROS-NO-HIF pathway for management of liver warm I/R injury.

Toll-like receptor 2 mediates mesenchymal stem cell-associated myocardial recovery and VEGF production following acute ischemia-reperfusion injury

Toll-like receptor 2 (TLR2), a key component of the innate immune system, is linked to inflammation and myocardial dysfunction after ischemia-reperfusion injury (I/R). Treatment of the heart with mesenchymal stem cells (MSCs) is known to improve myocardial recovery after I/R in part by paracrine factors such as VEGF. However, it is unknown whether TLR2 activation on the MSCs affects MSC-mediated myocardial recovery and VEGF production. We hypothesized that the knockout of TLR2 on the MSCs (TLR2KO MSCs) would 1) improve MSC-mediated myocardial recovery and 2) increase myocardial and MSC VEGF release. With the isolated heart perfusion system, Sprague-Dawley rat hearts were subjected to I/R and received one of three intracoronary treatments: vehicle, male wild-type MSCs (MWT MSCs), or TL2KO MSCs. All treatments were performed immediately before ischemia, and heart function was measured continuously. Postreperfusion, heart homogenates were analyzed for myocardial VEGF production. Contrary to our hypothesis, only MWT MSC treatment significantly improved the recovery of left ventricular developed pressure and the maximal positive and negative values of the first derivative of pressure. In addition, VEGF production was greatest in hearts treated with MWT MSCs. To investigate MSC production of VEGF, MSCs were activated with TNF in vitro and the supernatants collected for ELISA. In vitro basal levels of MSC VEGF production were similar. However, with TNF activation, MWT MSCs produced significantly more VEGF, whereas activated TLR2KO MSC production of VEGF was unchanged. Finally, we observed that MWT MSCs proliferated more rapidly than TLR2KO MSCs. These data indicate that TLR2 may be essential to MSC-mediated myocardial recovery and VEGF production.

Preconditioning and stem cell survival

The harsh ischemic and cytokine-rich microenvironment in the infarcted myocardium, infiltrated by the inflammatory and immune cells, offers a significant challenge to the transplanted donor stem cells. Massive cell death occurs during transplantation as well as following engraftment which significantly lowers the effectiveness of the heart cell therapy. Various approaches have been adopted to overcome this problem nevertheless with multiple limitations with each of these current approaches. Cellular preconditioning and reprogramming by physical, chemical, genetic, and pharmacological manipulation of the cells has shown promise and "prime" the cells to the "state of readiness" to withstand the rigors of lethal ischemia in vitro as well as posttransplantation. This review summarizes the past and present novel approaches of ischemic preconditioning, pharmacological and genetic manipulation using preconditioning mimetics, recombinant growth factor protein treatment, and reprogramming of stem cells to overexpress survival signaling molecules, microRNAs, and trophic factors for intracrine, autocrine, and paracrine effects on cytoprotection.

Strategic targets to induce neovascularization by resveratrol in hypercholesterolemic rat myocardium: role of caveolin-1, endothelial nitric oxide synthase, hemeoxygenase-1, and vascular endothelial growth factor

Endothelial dysfunction and impaired angiogenesis constitute a hallmark of hypercholesterolemia. This study was designed to examine the effects of resveratrol, an antioxidant with lipid-lowering properties similar to those of statins, on neovascularization along with caveolar interaction with proangiogenic molecules in hypercholesterolemic rats. Animals were divided into: rats maintained on a normal diet (control group); rats maintained on a 5% high-cholesterol diet for 8 weeks (HC group); and rats maintained on a 5% high-cholesterol diet for 8 weeks and administered resveratrol (20 mg/kg) orally for 2 weeks (HCR group). Myocardial infarction was induced by ligating the left anterior descending artery. Herein we examined a novel method for stimulating myocardial angiogenesis by pharmacological preconditioning with resveratrol at both the capillary and arteriolar levels and the potential role of hemeoxygenase-1, endothelial nitric oxide synthase and caveolin-1 in mediating such a response. We also investigated the functional relevance of such treatment by assessing whether the induced neovascularization can help preserve left ventricle-contractile functional reserve in the setting of a chronic hypercholesterolemic condition. Four weeks after sham surgery and left anterior descending artery occlusion, rats underwent echocardiographic evaluation, which revealed improvement in ejection fraction and fractional shortening in the HCR group compared with the HC group. Left ventricular tissue sections displayed increased capillary and arteriolar density in the HCR group compared with the HC group. Western blot analysis revealed downregulation of vascular endothelial growth factor and hemeoxygenase-1 and increased association of caveolin-1 eNOS in the HC group, decreasing the availability of eNOS to the system; which was reversed with resveratrol treatment in the HCR group. This study was further validated in cardiac-specific hemeoxygenase-1-overexpressed mice assuming molecular cross-talk between the targets. Hence, our data identified potential regulators that primarily attenuate endothelial dysfunction by resveratrol therapy in hypercholesterolemic myocardium.

Strategies to promote donor cell survival: combining preconditioning approach with stem cell transplantation

Stem cell transplantation has emerged as a potential modality in cardiovascular therapeutics due to their inherent characteristics of self-renewal, unlimited capacity for proliferation and ability to cross lineage restrictions and adopt different phenotypes. Constrained by extensive death in the unfriendly milieu of ischemic myocardium, the results of heart cell therapy in experimental animal models as well as clinical studies have been less than optimal. Several factors which play a role in early cell death after engraftment in the ischemic myocardium include: absence of survival factors in the transplanted heart, disruption of cell-cell interaction coupled with loss of survival signals from matrix attachments, insufficient vascular supply and elaboration of inflammatory cytokines resulting from ischemia and/or cell death. This article reviews various signaling pathways involved in triggering highly complex forms of cell death and provides critical appreciation of different novel anti-death strategies developed from the knowledge gained from using an ischemic preconditioning approach. The use of pharmacological preconditioning for up-regulation of pro-survival proteins and cardiogenic markers in the transplanted stem cells will be discussed.

Heterozygous disruption of Flk-1 receptor leads to myocardial ischaemia reperfusion injury in mice: application of affymetrix gene chip analysis

This study addresses an important clinical issue by identifying potential candidates of vascular endothelial growth factor (VEGF) signalling through the Flk-1 receptor that trigger cardioprotective signals under ischaemic stress. Isolated working mouse hearts of both wild-type (WT) and Flk-1^+/− were subjected to global ischaemia (I) for 30 min. followed by 2 hrs of reperfusion (R). Flk-1^+/− myocardium displayed almost 50% reduction in Flk-1 mRNA as examined by quantitative real-time RT-PCR at the baseline level. Flk-1^+/− mouse hearts displayed reduction in left ventricular functional recovery throughout reperfusion (dp/dt 605 versus 884), after 2 hrs (P < 0.05). Coronary (1.9 versus 2.4 ml) and aortic flow (AF) (0.16 versus 1.2 ml) were reduced in Flk-1^+/− after 2 hrs of reperfusion. In addition, increased infarct size (38.4%versus 28.41%, P < 0.05) and apoptotic cardiomyocytes (495 versus 213) were observed in Flk-1^+/− knockout (KO) mice. We also examined whether ischaemic preconditioning (PC), a novel method to induce cardioprotection against ischaemia reperfusion injury, through stimulating the VEGF signalling pathway might function in Flk-1^+/− mice. We found that knocking down Flk-1 resulted in significant reduction in the cardioprotective effect by PC compared to WT. Affymetrix gene chip analysis demonstrated down-regulation of important genes after IR and preconditioning followed by ischaemia reperfusion in Flk-1^+/− mice compared to WT. To get insight into the underlying molecular pathways involved in ischaemic PC, we determined the distinct and overlapping biological processes using Ingenuity pathway analysis tool. Independent evidence at the mRNA level supporting the Affymetrix results were validated using real-time RT-PCR for selected down-regulated genes, which are thought to play important roles in cardioprotection after ischaemic insult. In summary, our data indicated for the first time that ischaemic PC modifies genomic responses in heterozygous VEGFR-2/Flk-1 KO mice and abolishes its cardioprotective effect on ischaemic myocardium.

ANXA7 expression represents hormone-relevant tumor suppression in different cancers

Tumor suppressor function of ubiquitously expressed Annexin-A7, ANXA7 (10q21) that is involved in exocytosis and membrane fusion was based on cancer prone phenotype in Anxa7(+/-) mice as well as ANXA7 role in human prostate and breast cancers. To clarify ANXA7 biomarker and tumor suppressor function, we analyzed its expression pattern in comparison to the prostate-specific biomarker NKX3.1. Immunohistochemistry-based ANXA7 and NKX3.1 protein expression was analyzed on human tissue microarrays of 4,061 specimens from a wide spectrum of the histopathologically well-characterized tumors in different stages compared to corresponding normal tissues. Decreased ANXA7 expression was mostly associated with high invasive potential in multiple tumors. Although some metastases retained relatively high ANXA7 rates compared to primary cancer tissues, the lymph node metastases from different sites (including prostate and breast) had decreased ANXA7 expression in comparison to the intact lymphatic tissues. Major ANXA7 downregulation pattern was deviated in tumors of glandular (especially neuroendocrine) origin. ANXA7 and NKX3.1 proteins were synexpressed in the male urogenital system and adrenal gland. Gene expression profiling in prostate and breast cancers (SMD) revealed distinct hormone-related profiles for NKX3.1 and ANXA7, where ANXA7 expression correlated with steroid sulfatase which has a pivotal role in steroidogenesis. Abundant protein presence in adrenal gland and its loss in hormone-refractory prostate cancer indicated that ANXA7 can be relevant to steroidogenesis and androgen sensitivity in particular. With tumor suppressor pattern validated in different tumors, ANXA7 can be an attractive diagnostic and therapeutic target associated with the hormone and/or neurotransmitter-mediated modulation of tumorigenesis.

Expression and function of vascular endothelial growth factor receptors (Flt-1 and Flk-1) in vascular adventitial fibroblasts

Vascular endothelial growth factor receptors (VEGFRs) are previously considered to exist exclusively in endothelial cells. However, little is known if the receptors are expressed in other non-endothelial cells. In this study, we measured activation of two VEGFRs, Flk-1 and Flt-1, and their biological functions in cultured adventitial fibroblasts and injured rat carotid injury arteries induced by balloon angioplasty. Our results indicated that Flt-1, but not Flk-1, existed in adventitial fibroblasts. Angiotensin II increased Flt-1 protein expression in a time- and concentration-dependent manner. Adventitial fibroblast migration stimulated by vascular endothelial growth factor (VEGF) and placental growth factor (PIGF) required Flt-1 expression. The Flt-1-induced adventitial fibroblast migration was blocked by anti-Flt-1 neutralizing antibody and soluble VEGFR1 protein (sFlt-1). However, Flt-1 activation did not enhance cell proliferation. In addition, Flt-1 expression was significantly increased in the neointima and adventitia in injured rat carotid arteries. We concluded that functional expression of Flt-1 in adventitial fibroblasts might be an important mediator in the pathogenesis of vascular remodeling after arterial injury.

VEGFR1 (Flt-1+/-) gene knockout leads to the disruption of VEGF-mediated signaling through the nitric oxide/heme oxygenase pathway in ischemic preconditioned myocardium

This report demonstrates that mice deficient in Flt-1 failed to establish ischemic preconditioning (PC)-mediated cardioprotection in isolated working buffer-perfused ischemic/reperfused (I/R) hearts compared to wild type (WT) subjected to the same PC protocol. WT and Flt-1+/- mice were divided into four groups: (1) WT I/R, (2) WT + PC, (3) Flt-1+/- I/R, and (4) Flt-1+/- + PC. Group 1 and 3 mice were subjected to 30 min of ischemia followed by 2 h of reperfusion and group 2 and 4 mice were subjected to four episodes of 4-min global ischemia followed by 6 min of reperfusion before ischemia/reperfusion. For both wild-type and Flt-1+/- mice, the postischemic functional recovery for the hearts was lower than the baseline, but the recovery for the knockout mice was less compared to the WT mice even in preconditioning. The myocardial infarction and apoptosis were higher in Flt-1+/- compared to wild-type I/R. Flt-1+/- KO mice demonstrated pronounced inhibition of the expression of iNOS, p-AKT & p-eNOS. Significant inhibition of STAT3 & CREB were also observed along with the inhibition of HO-1 mRNA. Results demonstrate that Flt-1+/- mouse hearts are more susceptible to ischemia/reperfusion injury and also document that preconditioning is not as effective as found in WT and therefore suggest the importance of VEGF/Flt-1 signaling in ischemic/reperfused myocardium.

Ischemic Preconditioning And Myocardial Infarction: An Update and Perspective

Myocardial infarction is the leading cause of mortality in Western societies with annual expenditures of $431.8 billion spent on coronary artery disease in man. Therapeutics to combat infarction from myocardial injury, based on studies of ischemic preconditioning (IPC), are currently in progress. Hence, this review provides an update on IPC, including general and molecular mechanisms responsible for IPC and the effects of IPC in models of aging or disease. A summary of therapeutics shown to possess efficacy in preclinical and clinical trials and future directions of studies regarding cardiac IPC are also discussed.

Reactive oxygen species drives myocardial angiogenesis?

Neovascularization, the natural physiological process of formation of new blood vessels, is extremely important for ameliorating the function of the heart that undergoes ischemic stress. This process is potentially important for the treatment of ischemic heart and limb diseases, which includes formation of capillaries (angiogenesis) and collateral arteries. Ischemia or coronary artery occlusion induces vascular endothelial growth factor (VEGF) in the experimental rat myocardial infarction model, and this molecule encourages development of coronary collateral circulation and retention of the blood supply to the ischemic area. Restoration of the blood supply to the ischemic area prevents cardiomyocyte death and cardiac remodeling. Among the various triggers and enhancers of angiogenesis, hypoxic or ischemic preconditioning, as well as pharmacologic agents such as statin and resveratrol, have been identified as important stimuli for the induction of new vessel growth. It has already been demonstrated that the VEGF family and its receptor system is the fundamental regulator in the redox cell signaling of angiogenesis. This review article will focus on the role of reactive oxygen species in the process of myocardial angiogenesis.

Hypoxia inducible factor-1 activation by prolyl 4-hydroxylase-2 gene silencing attenuates myocardial ischemia reperfusion injury

Hypoxia inducible factor-1 (HIF-1) regulates changes in transcription of key genes such as inducible NO synthase (iNOS) in hypoxic/ischemic environments. In normoxia, HIF-1 activation is controlled by HIF-1alpha-prolyl 4-hydroxylases, which target HIF-1alpha for ubiquitination and proteasomal degradation. We hypothesized that normoxic HIF-1 preservation could attenuate cardiac ischemia/reperfusion injury via a preconditioning effect. HIF-1 preservation was achieved by using small interfering RNA (siRNA) to silence murine HIF-1alpha-prolyl-4 hydroxylase-2 (PHD2). PHD2 siRNA reduced PHD2 mRNA expression 89+/-1.5% (P<0.001) in a time- and concentration-dependent manner in normoxic murine microvascular endothelial cells (EC). PHD2 silencing in normoxic EC stabilized HIF-1alpha protein levels while significantly increasing HIF-1 transcriptional activity and iNOS mRNA expression. Wild-type mice infused with PHD2 siRNA (1.5 microg/g body weight) showed a 61+/-2.4% (P<0.05) reduction in cardiac PHD2 mRNA within 24 hours. In addition HIF-1alpha protein levels and HIF-1-dependent iNOS mRNA levels were increased. PHD2 siRNA-transfected hearts from wild-type mice (n=6) subjected to 30 minutes ischemia followed by 60 minutes reperfusion exhibited reduced infarct size when compared with saline-treated controls (9.7+/-1.9% versus 31.6+/-1.8%, respectively, P<0.0001, n=6) and to control mice transfected with a nontargeting siRNA control (28.4+/-3.0%, P<0.0001, n=6). Hearts from iNOS knockout mice receiving PHD2 siRNA by identical injection protocol (n=6) exhibited infarct size indistinguishable from saline controls (28.7+/-1.3%). These results show that in vitro and in vivo, PHD2 silencing using a siRNA strategy produces transcriptionally active HIF-1. Normoxic activation of HIF-1 in hearts following in vivo PHD2 siRNA administration attenuates reperfusion injury via an iNOS-dependent pathway.