Role of the SDF-1/CXCR4 system in myocardial infarction

CXCR4/CXCL12 axis: "old" pathway as "novel" target for anti-inflammatory drug discovery

Inflammation is the body's defense response to exogenous or endogenous stimuli, involving complex regulatory mechanisms. Discovering anti-inflammatory drugs with both effectiveness and long-term use safety is still the direction of researchers' efforts. The inflammatory pathway was initially identified to be involved in tumor metastasis and HIV infection. However, research in recent years has proved that the CXC chemokine receptor type 4 (CXCR4)/CXC motif chemokine ligand 12 (CXCL12) axis plays a critical role in the upstream of the inflammatory pathway due to its chemotaxis to inflammatory cells. Blocking the chemotaxis of inflammatory cells by CXCL12 at the inflammatory site may block and alleviate the inflammatory response. Therefore, developing CXCR4 antagonists has become a novel strategy for anti-inflammatory therapy. This review aimed to systematically summarize and analyze the mechanisms of action of the CXCR4/CXCL12 axis in more than 20 inflammatory diseases, highlighting its crucial role in inflammation. Additionally, the anti-inflammatory activities of CXCR4 antagonists were discussed. The findings might help generate new perspectives for developing anti-inflammatory drugs targeting the CXCR4/CXCL12 axis.

Bioactive Compounds (BACs): A Novel Approach to Treat and Prevent Cardiovascular Diseases

Cardiovascular diseases (CVDs) are one of the leading disorders of serious death and cause huge economic loss to patients and society. It is estimated that about 18 million people have a high death ratio due to the incidence of CVDs such as (stroke, coronary heart disease, and non-ischemic heart failure). Bioactive compounds (BACs) are healthy nutritional ingredients providing beneficial effects and nutritional value to the human body. Epidemiological studies strongly shed light on several bioactive compounds that are favorable candidates for CVDs treatment. Globally, the high risk of CVDs and related results on human body parts made them a serious scenario in all communities. In this present review, we intend to collect previously published data concerned over the years concerning green-colored foods and their BACs that aim to work in the prevention, diagnosis, and/or systematic treating CVDs. We also comprehensively discussed the oral delivery of several bioactive compounds derived from fruits and vegetables and their bioavailability and physiological effects on human health. Moreover, their important characteristics, such as anti-inflammatory, lowering blood pressure, anti-obesity, antioxidant, anti-diabetics, lipid-lowering responses, improving atherosclerosis, and cardioprotective properties, will be elaborated further. More precisely, medicinal plants' advantages and multifaceted applications have been reported in this literature to treat CVDs. To the best of our knowledge, this is our first attempt that will open a new window in the area of CVDs with the opportunity to achieve a better prognosis and effective treatment for CVDs.

Efficacy Evaluation of SDF-1α-Based Polypeptides in an Acute Myocardial Infarction Model Using Structure-Based Drug Design

Stromal cell-derived factor-1 alpha (SDF-1α, CXCL12) mediates the migration of circulating cells to desired sites for tissue development, homeostasis, and regeneration and can be used to promote cardiac regeneration by recruiting stem cells. However, the use of SDF-1α in the injured heart necessitates not only higher binding affinity to its receptor, CXCR4+, but also better robustness against enzymatic degradation than other SDF-1 isoforms. Here, we conduct a screening of SDF-1α analog peptides that were designed by structure-based drug design (SBDD), a type of computer-aided drug design (CADD). We have developed in vitro and in vivo methods that enable us to estimate the effect of peptides on the migration of human mesenchymal stem cells (hMSCs) and cardiac regeneration in acute myocardial infarction (AMI)-induced animals, respectively. We demonstrate that one type of SDF-1α analog peptide, SDP-4, among the four analog peptides preselected by SBDD, is more potent than native SDF-1α for cardiac regeneration in myocardial infarction. It is interesting to note that the migratory effects of SDP-4 determined by a wound healing assay, a Transwell assay, and a 2D migration assay are comparable to those of SDF-1α. These results suggest that in vivo, as well as in vitro, screening of peptides developed by SBDD is a quintessential process to the development of a novel therapeutic compound for cardiac regeneration. Our finding also has an implication that the SDP-4 peptide is an excellent candidate for use in the regeneration of an AMI heart.

Inflammatory markers in acute myocardial infarction and the correlation with the severity of coronary heart disease

INTRODUCTION

The inflammatory hypothesis of atherosclerosis is appealing in acute coronary syndromes, but the dynamics and precise role are not established.

OBJECTIVES

The study investigates the levels of C reactive protein (CRP), interleukin 1β (IL-1β) and stromal-derived factor 1α (SDF-1α) at the time of acute myocardial infarction (AMI) and at 1 and 6 months afterwards, compared with a control group.

RESULTS

In the acute phase of AMI, CRP and SDF-1α were significantly higher, while IL-1β showed lower levels compared with controls. CRP positively correlated with coronary stenosis severity (rho = 0.3, p=.05) and negatively related with left ventricle ejection fraction (LVEF) at 1 month (rho= -0.43, p=.05). IL-1β weakly correlated with the severity of coronary lesions (rho =0.29, p=.02) and strongly with LVEF (rho= -0.8, p=.05). SDF-1α, slightly correlated with LVEF at 1 month (rho = 0.22, p=.01) and with the severity of coronary atherosclerosis (rho= -0.41, p=.003).

CONCLUSIONS

CRP, IL-1β and SDF-1α have important dynamic in the first 6 months after AMI and CRP and SDF-1α levels correlated with the severity of coronary lesions and LVEF at 1 month after the acute ischaemic event.

Up-regulation of chemokine receptor type 4 expression in the ischemic reperfused heart by alcoholic extract of Cichorium intybus rescue the heart from ischemia injury in male rat

OBJECTIVES

Cichorium intybus is used in traditional medicine for various diseases including heart disease. This study aimed at evaluating the chemokine receptor type 4 up-regulation and cardioprotective effects of hydroalcoholic extract of C. intybus in a rat model of ischemic reperfusion.

METHODS

Animals in four groups of eight rats each received vehicle or one of three doses of C. intybus (50, 100 or 200 mg/kg/d) for 14 days. Then they were subjected to 30 min of ischemia followed by 7 days of reperfusion. At the end of the experiment, blood specimens were prepared for serum assays. The level of myocardium chemokine receptor type 4 was also measured using RT-PCR.

KEY FINDINGS

Cichorium intybus (CI-50) improved infarct size, episodes of the ventricular ectopic beat, ventricular tachycardia, and duration of ventricular tachycardia, QTc shortening. It also stabilized the ST segment changes and increased heart rate during ischemia. The blood pressure decreased in CI-50 group in comparison to the control and CI-200 group. C. intybus increased serum superoxide dismutase and reduced lactate dehydrogenase activity, Cardiac Troponin I and malondialdehyde levels. C. intybus led to an increase in the expression of chemokine receptor type 4.

CONCLUSIONS

These findings suggest that C. intybus administration before ischemia is able to induce cardioprotective effect against ischemic reperfusion injury, probably through chemokine receptor type 4 over-expression and antioxidant activity.

Cell Death and Exosomes Regulation After Myocardial Infarction and Ischemia-Reperfusion

Cardiovascular disease (CVD) is the leading cause of death in the global population, accounting for about one-third of all deaths each year. Notably, with CVDs, myocardial damages result from myocardial infarction (MI) or cardiac arrhythmias caused by interrupted blood flow. Significantly, in the process of MI or myocardial ischemic-reperfusion (I/R) injury, both regulated and non-regulated cell death methods are involved. The critical factor for patients’ prognosis is the infarct area’s size, which determines the myocardial cells’ survival. Cell therapy for MI has been a research hotspot in recent years; however, exosomes secreted by cells have attracted much attention following shortcomings concerning immunogens. Exosomes are extracellular vesicles containing several biologically active substances such as lipids, nucleic acids, and proteins. New evidence suggests that exosomes play a crucial role in regulating cell death after MI as exosomes of various stem cells can participate in the cell damage process after MI. Hence, in the review herein, we focused on introducing various cell-derived exosomes to reduce cell death after MI by regulating the cell death pathway to understand myocardial repair mechanisms better and provide a reference for clinical treatment.

Near-Infrared Light-Activatable Dual-Action Nanoparticle Combats the Established Biofilms of Methicillin-Resistant Staphylococcus aureus and Its Accompanying Inflammation

Clinically, inhibition of both bacterial infection and excessive inflammation is a crucial step for improved wound treatments. Herein, the fabrication of near-infrared-light (NIR)-activatable deoxyribonuclease (DNase)-carbon monoxide (CO)@mesoporous polydopamine nanoparticles (MPDA NPs) is demonstrated for efficient elimination of methicillin-resistant Staphylococcus aureus (MRSA) biofilms and the following anti-inflammatory activity. Specifically, thermosensitive CO-gas-releasing donors (CO releasing molecules, FeCO) are first encapsulated into MPDA NPs, followed by covalently immobilizing deoxyribonuclease I (DNase I) on the surfaces of MPDA NPs. DNase I can degrade the extracellular DNA in biofilms, which site specifically destroys the compactness of the biofilms. With NIR irradiation, DNase-CO@MPDA NPs display great photothermal ability, and further trigger on-demand delivery of bactericidal CO gas that can adequately permeate the impaired biofilms. Eventually, they achieve effective MRSA biofilm elimination in virtue of the synergistic effects of both DNase I participation and CO-gas-potentiated photothermal therapy. Importantly, the inflammatory responses of DNase-CO@MPDA NPs and NIR-treated wounds are simultaneously alleviated owing to the anti-inflammatory features of released CO. Finally, NIR-activatable DNase-CO@MPDA NPs accelerate the healing process of MRSA-biofilm-infected cutaneous wounds. Taken together, this phototherapeutic strategy displays great therapeutic potential in treating the formidable clinical problems caused by MRSA biofilms and the accompanying inflammation.

Analyzing Impetus of Regenerative Cellular Therapeutics in Myocardial Infarction

Both vasculature and myocardium in the heart are excessively damaged following myocardial infarction (MI), hence therapeutic strategies for treating MI hearts should concurrently aim for true cardiac repair by introducing new cardiomyocytes to replace lost or injured ones. Of them, mesenchymal stem cells (MSCs) have long been considered a promising candidate for cell-based therapy due to their unspecialized, proliferative differentiation potential to specific cell lineage and, most importantly, their capacity of secreting beneficial paracrine factors which further promote neovascularization, angiogenesis, and cell survival. As a consequence, the differentiated MSCs could multiply and replace the damaged tissues to and turn into tissue- or organ-specific cells with specialized functions. These cells are also known to release potent anti-fibrotic factors including matrix metalloproteinases, which inhibit the proliferation of cardiac fibroblasts, thereby attenuating fibrosis. To achieve the highest possible therapeutic efficacy of stem cells, the other interventions, including hydrogels, electrical stimulations, or platelet-derived biomaterials, have been supplemented, which have resulted in a narrow to broad range of outcomes. Therefore, this article comprehensively analyzed the progress made in stem cells and combinatorial therapies to rescue infarcted myocardium.

The Effect of DPP-4i on Endothelial Function and Arterial Stiffness in Patients with Type 2 Diabetes: A Systematic Review of Randomized Placebo-controlled Trials

We systematically reviewed the literature regarding the impact of dipeptidyl peptidase-4 inhibitors (DPP-4i) on vascular function, including endothelial function and arterial stiffness, as predictors of atherosclerosis progression and cardiovascular disease in patients with type 2 diabetes mellitus (T2DM). We searched PubMed in order to identify clinical trials that investigated the effect of DPP-4i on vascular function in patients with T2DM when compared with placebo. Although 168 articles were initially found, only 6 studies (total 324 patients) investigated the effect of DPP-4i in comparison with placebo, specifically linagliptin and sitagliptin, and satisfied the inclusion criteria. There are scarce data to indicate that linagliptin may enhance endothelial function and exert a slight beneficial effect on arterial wall properties. Sitagliptin seems to have a neutral effect on these variables. Further trials are needed to elucidate the topic. The standards of reporting were in accordance with the PRISMA guidelines.

Circulating angiogenic cells in glioblastoma: toward defining crucial functional differences in CAC-induced neoplastic versus reactive neovascularization

Background

In order to identify suitable therapeutic targets for glioma anti-angiogenic therapy, the process of neovascularization mediated by circulating angiogenic cells (CACs) needs to be scrutinized.

Methods

In the present study, we compared the expression of neovascularization-related genes by 3 circulating CAC subsets (hematopoietic progenitor cells [HPCs], CD34⁺, and KDR⁺ cells; internal controls: peripheral blood mononuclear cells and circulating endothelial cells) of treatment-naïve patients with glioblastoma (GBM) to those of patients undergoing reactive neovascularization (myocardial infarction (MI). CACs from umbilical cord (representing developmental neovascularization) and healthy subjects served as controls. Fluorescent-activated cell sorting was used to isolate CACs, RT-PCR to determine the expression levels of a panel of 48 neovascularization-related genes, and Luminex assays to measure plasma levels of 21 CAC-related circulating molecules.

Results

We found essential differences in gene expression between GBM and MI CACs. GBM CACs had a higher expression of proangiogenic factors (especially, KITL, CXCL12, and JAG1), growth factor and chemotactic receptors (IGF1R, TGFBR2, CXCR4, and CCR2), adhesion receptor monomers (ITGA5 and ITGA6), and matricellular factor POSTN. In addition, we found major differences in the levels of neovascularization-related plasma factors. A strong positive correlation between plasma MMP9 levels and expression of CXCR4 in the CAC subset of HPCs was found in GBM patients.

Conclusions

Our findings indicate that CAC-mediated neovascularization in GBM is characterized by more efficient CAC homing to target tissue and a more potent proangiogenic response than in physiologic tissue repair in MI. Our findings can aid in selecting targets for therapeutic strategies acting against GBM-specific CACs.

TRAF5 protects against myocardial ischemia reperfusion injury via AKT signaling

During the processes of myocardial ischemia reperfusion (I/R) injury, inflammation and apoptosis play an important role. I/R and its induced acute myocardial infarction (AMI) with high morbidity and mortality, and there is no effective treatment for it so far. TRAF5 has been shown to regulate inflammation and apoptosis in atherosclerosis, steatosis and melanoma cells, but its function in myocardial I/R injury is still unclear. This study demonstrates that the expression of TRAF5 is significant up-regulation in heart tissues of I/R injury mice and hypoxia/reoxygenation (H/R)-stimulated cardiomyocytes. TRAF5 knockout mice exhibites heavier heart damage, inflammatory response and cell death after myocardial I/R injury. Further, TRAF5 overexpression inhibites inflammation and apoptosis of H/R-stimulated cardiomyocytes. Mechanistically, we prove that TRAF5 promotes the activation of AKT. Overall, our study indicates that TRAF5 can regulate the processes of myocardial I/R injury. TRAF5 can be a new therapy target for myocardial I/R injury.

Stromal Cell-derived Factor-1 and CXC Chemokine Receptor Type-4 are Associated with Cardiovascular Disease in Patients under Hemodialysis

Background

Cardiovascular disease (CVD) is the most common cause of death among patients with end-stage renal disease especially whom under hemodialysis (HD). Stromal cell-derived factor-1 (SDF-1) and its receptor CXC chemokine receptor type-4 (CXCR4) could contribute to CVD. The main aim of this study was to evaluate the association between SDF-1 and CXCR4 with CVD and its related risk factors in patients under HD.

Methods

Sixty patients under HD and 29 healthy subjects were recruited in the study. The serum levels and relative messenger RNA (mRNA) expressions of SDF-1 and CXCR4 were measured using enzyme-linked immunosorbent assay and real-time polymerase chain reaction in patients and controls, respectively. CVD history of the patients was obtained.

Results

Twenty patients (33.3%) had a history of CVD. The mean levels of serum and relative mRNA expressions of SDF-1 and CXCR4 were higher in patients than controls and also in patients with a history of CVD than patients without it. The serum levels and relative expressions of SDF-1 and CXCR4 were positively correlated with blood urea nitrogen, parathyroid hormone, and high-sensitivity C-reactive protein and inversely correlated with hemoglobin. The history of CVD was the independent predictor of serum levels of SDF-1 and CXCR4 and also relative mRNA expression of CXCR4.

Conclusions

The higher levels of serum and relative mRNA expressions of SDF-1 and CXCR4 were associated with CVD in patients under HD. Furthermore, SDF-1 and CXCR4 were associated with several traditional and uremia-related CVD risk factors in such patients.

[Comparative study with the effect of stromal cell derived factor-1 on osteogenic differentiation of human healthy and inflammatory periodontal ligament stem cells]

OBJECTIVE

This study aims to compare the osteogenic differentiation capability of stem cells derived from human inflammatory periodontal ligament tissues (iPDLSCs) with those of stem cells derived from healthy periodontal ligament tissues (hPDLSCs). Both types of tissues were induced by stromal cell derived factor (SDF-1) in vitro.

METHODS

iPDLSCs and hPDLSCs were primarily cultured by tissue digestion method and purified by limited dilution cloning. The cells were passaged and identified by stem cell surface marker expression through flow cytometry. Then, we used thiazolyl blue tetrazolium bromide to detect and compare the proliferation capabilities of the iPDLSCs and hPDLSCs. Express of bone volumes were detected by alizarin red staining after SDF-1 was added to the cells. Using alkaline phosphatase, we evaluated the osteogenic differentiation capability of the cells induced by SDF-1. The expression levels of the osteogenesis-related genes of the cells induced by SDF-1 were determined by reverse transcription-polymerase chain reaction.

RESULTS

After purification, both iPDLSCs and hPDLSCs expressed stem cell markers. hPDLCSs had a higher proliferation capability than iPDLSCs. Osteogenesis-related genes had higher expression levels in the cells induced by SDF-1 than in those without induction (P<0.05). SDF-1 at 50 and 200 ng·mL⁻¹ concentration greatly affected the differen-tiation capabilities of iPDLSCs and hPDLSCs respectively.

CONCLUSIONS

iPDLSCs and hPDLSCs had osteogenic differentia-tion capability. The level of osteogenic differentiation in normal and inflamed periodontal ligament stem cells increases after SDF-1 induction.

Stromal cell-derived factor-1α signals via the endothelium to protect the heart against ischaemia-reperfusion injury

AIMS

The chemokine stromal derived factor-1α (SDF-1α) is known to protect the heart acutely from ischaemia-reperfusion injury via its cognate receptor, CXCR4. However, the timing and cellular location of this effect, remains controversial.

METHODS AND RESULTS

Wild type male and female mice were subjected to 40 min LAD territory ischaemia in vivo and injected with either saline (control) or SDF-1α prior to 2 h reperfusion. Infarct size as a proportion of area at risk was assessed histologically using Evans blue and triphenyltetrazolium chloride. Our results confirm the cardioprotective effect of exogenous SDF-1α in mouse ischaemia-reperfusion injury and, for the first time, show protection when SDF-1α is delivered just prior to reperfusion, which has important therapeutic implications. The role of cell type was examined using the same in vivo ischaemia-reperfusion protocol in cardiomyocyte- and endothelial-specific CXCR4-null mice, and by Western blot analysis of endothelial cells treated in vitro. These experiments demonstrated that the acute infarct-sparing effect is mediated by endothelial cells, possibly via the signalling kinases Erk1/2 and PI3K/Akt. Unexpectedly, cardiomyocyte-specific deletion of CXCR4 was found to be cardioprotective per se. RNAseq analysis indicated altered expression of the mitochondrial protein co-enzyme Q10b in these mice.

CONCLUSIONS

Administration of SDF-1α is cardioprotective when administered prior to reperfusion and may, therefore, have clinical utility. SDF-1α-CXCR4-mediated cardioprotection from ischaemia-reperfusion injury is contingent on the cellular location of CXCR4 activation. Specifically, cardioprotection is mediated by endothelial signalling, while cardiomyocyte-specific deletion of CXCR4 has an infarct-sparing effect per se.

Role of pyroptosis in cardiovascular diseases

Pyroptosis is a form of programmed necrosis, and is morphologically and mechanistically unique form of programmed cell death compared to others, such as apoptosis and autophagic cell death. More specifically, pyroptosis features gasdermin family-mediated membrane pore formation and subsequent cell lysis, as well as release of pro-inflammatory intracellular contents including IL-1β, IL-18 and HMGB1. Mechanistically, pyroptosis is driven by two main signaling pathways - one mediated by caspase-1 and the other by caspase-4/5/11. Recent studies show that pyroptosis is implicated in several cardiovascular diseases. In this review, we summarize recent scientific discoveries of pyroptosis's involvement in atherosclerosis, myocardial infarction, diabetic cardiomyopathy, reperfusion injury and myocarditis. We also organized new and emerging evidence suggesting that pyroptosis signaling pathways may be potential therapeutic targets in cardiovascular diseases.

Loss of miR-144 signaling interrupts extracellular matrix remodeling after myocardial infarction leading to worsened cardiac function

We have previously shown that MicroRNA (miR) -144 is a key modulator of the acute cardioprotection associated with remote ischemic preconditioning and post myocardial infarction (MI) remodeling. In this study we examine the biology of the remodeling response after permanent ligation of the left anterior descending coronary artery in male miR-144 KO mice, and wild-type littermates (WT). Collagen content and cross linking were determined by hydroxyproline and pyridinoline assays, MI size and scar thickness were measured post PicoSirius Red staining, and cardiac function was evaluated by echocardiography. miR-144 KO mice developed normally with normal cardiac function, however after MI, infarction size was greater and scar thickness was reduced in miR-144 KO mice compared with WT littermates. miR-144 KO mice had a lower incidence of acute cardiac rupture compared with WT littermates early after MI but there was impaired late remodeling, reflected by increased total cardiac collagen content and collagen cross-linkage associated with changes in Zeb1/LOX1 axis, and decreased left ventricular ejection fraction. We conclude that miR-144 is involved in extracellular matrix remodeling post MI and its loss leads to increased myocardial fibrosis and impaired functional recovery.

Supramolecular poly(acrylic acid)/F127 hydrogel with hydration-controlled nitric oxide release for enhancing wound healing

Topical nitric oxide (NO) delivery has been shown to accelerate wound healing. However, delivering NO to wounds at appropriate rates and doses requires new biomaterial-based strategies. Here, we describe the development of supramolecular interpolymer complex hydrogels comprising PEO-PPO-PEO (F127) micelles embedded in a poly(acrylic acid) (PAA) matrix, with S-nitrosoglutathione (GSNO) molecules dissolved in the hydrophilic domain. We show that PAA:F127/GSNO hydrogels start releasing NO upon hydration at rates controlled by their rates of water absorption. SAXS measurements indicate that the supramolecular structure of the hydrogels retains long-range order domains of F127 micelles. The PAA/F1227 hydrogels displayed dense morphologies and reduced rates of hydration. The NO release rates remain constant over the first 200 min, are directly correlated with the hydration rates of the PAA:F127/GSNO hydrogels, and can be modulated in the range of 40 nmol/g h to 1.5 μmol/g h by changing the PAA:F127 mass ratio. Long-term NO-release profiles over 5 days are governed by the first-order exponential decay of GSNO, with half-lives in the range of 0.5-3.4 days. A preliminary in vivo study on full-thickness excisional wounds in mice showed that topical NO release from the PAA:F127/GSNO hydrogels is triggered by exudate absorption and leads to increased angiogenesis and collagen fiber organization, as well as TGF-β, IGF-1, SDF-1, and IL-10 gene expressions in the cicatricial tissue. In summary, these results suggest that hydration-controlled NO release from topical PAA:F127/GSNO hydrogels is a potential strategy for enhancing wound healing.

STATEMENT OF SIGNIFICANCE

The topical delivery of nitric oxide (NO) to wounds may provide significant beneficial results and represent a promising strategy to treat chronic wounds. However, wound dressings capable of releasing NO after application and allowing the modulation of NO release rates, demand new platforms. Here, we describe a novel strategy to overcome these challenges, based on the use of supramolecular poly(acrylic acid) (PAA):F127 hydrogels charged with the NO donor S-nitrosoglutathione (GSNO) from whereby the NO release can be triggered by exudate absorption and delivered to the wound at rates controlled by the PAA:F127 mass ratio. Preliminary in vivo results offer a proof of concept for this strategy by demonstrating increased angiogenesis; collagen fibers organization; and TGF-β, IGF-1, SDF-1, and IL-10 gene expressions in the cicatricial tissue after topical treatment with a PAA:F127/GSNO hydrogel.

Stromal cell-derived factor-1α-encapsulated albumin/heparin nanoparticles for induced stem cell migration and intervertebral disc regeneration in vivo

Intervertebral disc (IVD) degeneration may cause many diseases and pain. Stem cell migration toward the site of IVD degeneration is a key factor for IVD regeneration. In the current study, we prepared albumin/heparin nanoparticles (BHNPs) as injectable carriers of stromal cell-derived factor-1α (SDF-1α, also known as C-X-C motif chemokine 12), a powerful chemoattractant for the homing of bone marrow resident mesenchymal stem cells (MSCs), for protection of the molecule against degradation for a sustained release. The NPs have relatively uniform small size, with a diameter of about 110 nm. The NPs possess a high loading capacity of SDF-1α with a sustained release profile. The bioactivity of the obtained BHNPs/SDF was then studied in vitro and in vivo. The BHNPs/SDF can induce migration of MSCs in a dose-dependent manner in vitro. After injected into the damaged disc, BHNPs/SDF induce much better regeneration of annulus fibrosus and nucleus pulposus, compared to SDF-1α and BHNPs alone, evidenced with better histological grade scores and higher expression of SOX9, Aggrecan, and Collagen type II at the level of both mRNA and protein. This study provides a simple nanoplatform to load SDF-1α and protect it against degradation, with potential application in inductive tissue regeneration in vivo.

STATEMENT OF SIGNIFICANCE

Stem cell migration toward the site of IVD degeneration is a key event to promote IVD regeneration. In the current study, we prepared albumin/heparin nanoparticles (BHNPs) as injectable carriers to protect SDF-1α against degradation and for the sustained release of the molecule. After injected into the damaged disc, BHNPs/SDF induced much better regeneration of IVD, compared to SDF-1α and BHNPs alone. This study provides a simple nanoplatform to load SDF-1α and protect it from degradation, with potential application in inductive tissue regeneration in vivo.

Role of NLRP3 inflammasome in the pathogenesis of cardiovascular diseases

NLRP3 inflammasome is a key multiprotein signaling platform that tightly controls inflammatory responses and coordinates antimicrobial host defenses by activating caspase-1 for the subsequent maturation of pro-inflammatory cytokines, IL-1β and IL-18, and induces pyroptosis. The assembly and activation of NLRP3 inflammasome are linked to the pathogenesis of several cardiovascular disease risk factors, such as hypertension and diabetes, and their major consequences-myocardial remodeling. The study of the NLRP3 inflammasome in these cardiovascular disease states may uncover important triggers and endogenous modulators of the disease, and lead to new treatment strategies. This review outlines current insights into NLRP3 inflammasome research associated with cardiovascular diseases and discusses the questions that remain in this field.

Pro-angiogenic effect of RANTES-loaded polysaccharide-based microparticles for a mouse ischemia therapy

Peripheral arterial disease results from the chronic obstruction of arteries leading to critical hindlimb ischemia. The aim was to develop a new therapeutic strategy of revascularization by using biodegradable and biocompatible polysaccharides-based microparticles (MP) to treat the mouse hindlimb ischemia. For this purpose, we deliver the pro-angiogenic chemokine Regulated upon Activation, Normal T-cell Expressed and Secreted (RANTES)/CCL5 in the mouse ischemic hindlimb, in solution or incorporated into polysaccharide-based microparticles. We demonstrate that RANTES-loaded microparticles improve the clinical score, induce the revascularization and the muscle regeneration in injured mice limb. To decipher the mechanisms underlying RANTES effects in vivo, we demonstrate that RANTES increases the spreading, the migration of human endothelial progenitor cells (EPC) and the formation of vascular network. The main receptors of RANTES i.e. CCR5, syndecan-4 and CD44 expressed at endothelial progenitor cell surface are involved in RANTES-induced in vitro biological effects on EPC. By using two RANTES mutants, [E66A]-RANTES with impaired ability to oligomerize, and [⁴⁴AANA⁴⁷]-RANTES mutated in the main RANTES-glycosaminoglycan binding site, we demonstrate that both chemokine oligomerization and binding site to glycosaminoglycans are essential for RANTES-induced angiogenesis in vitro. Herein we improved the muscle regeneration and revascularization after RANTES-loaded MP local injection in mice hindlimb ischemia.

Danshensu accelerates angiogenesis after myocardial infarction in rats and promotes the functions of endothelial progenitor cells through SDF-1α/CXCR4 axis

The present study was performed to investigate the potential role of Danshensu in therapeutic angiogenesis in ischemic myocardium and endothelial progenitor cells (EPCs) function. The rat model of myocardial infarction (MI) injury was induced by left anterior descending coronary artery ligation for 14 days. Danshensu significantly alleviated myocardial ischemia injury by ameliorating left ventricular function and reducing infarct size. Furthermore, Danshensu potentiated post-ischemia neovascularization as evidenced by increased microvessel density in infarction boundary zone, as well as the expression of marker proteins vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). Moreover, Danshensu notably promoted stromal cell-derived factor-1α (SDF-1α) level in plasma and C-X-C chemokine receptor type 4 (CXCR4) expression in peri-infarction myocardium, and AMD3100 (CXCR4 antagonist) could reverse the angiogenic and cardioprotective effects of Danshensu. For in vitro study, EPCs were isolated from bone marrow of rats. On the one hand, Danshensu provided significant cytoprotection against hypoxia insult by boosting EPCs viability and inhibiting apoptosis, and upregulated Akt phosphorylation. On the other hand, Danshensu enhanced proangiogenic functions of EPCs on cell migration and tube formation, and increased SDF-1α and CXCR4 expression. Likewise, the cytoprotection and proangiogenic functions of Danshensu on EPCs were partly negated by LY294002 (PI3K antagonist) and CXCR4 siRNA, respectively. Taken together, our results suggested that the cardioprotection of Danshensu in MI rats may be related to promoting myocardial neovascularization. The possible mechanisms may involve improving EPCs survival in hypoxia condition through Akt phosphorylation, and accelerating EPCs proangiogenic functions through SDF-1α/CXCR4 axis.

Resveratrol activates endogenous cardiac stem cells and improves myocardial regeneration following acute myocardial infarction

Stem cell antigen-1-positive (Sca-1+) cardiac stem cells (CSCs) therapy for myocardial regeneration following acute myocardial infarction (AMI) is limited by insufficient cell viability and a high rate of apoptosis, due to the poor regional microenvironment. Resveratrol, which is a compound extracted from red wine, has been reported to protect myocardial tissue post‑AMI by increasing the expression of angiogenic and chemotactic factors. The present study aimed to investigate the effects of resveratrol on Sca‑1+ CSCs, and to optimize Sca‑1+ CSCs therapy for myocardial regeneration post‑AMI. C57/BL6 mice (age, 6 weeks) were divided into two groups, which received intragastric administration of PBS or 2.5 mg/kg.d resveratrol. The endogenous expression of Sca‑1+ CSCs in the heart was assessed on day 7. Furthermore, C57/BL6 mice underwent left anterior descending coronary artery ligation for the construction of an AMI model, and received an injection of 1x106 CSCs into the peri‑ischemic area (n=8/group). Mice received intragastric administration of PBS or resveratrol (2.5 mg/kg.d) for 4 weeks after cell transplantation. Echocardiography was used to evaluate cardiac function 4 weeks after cell transplantation. Capillary density and cardiomyocyte apoptosis in the peri‑ischemic myocardium were assessed by cluster of differentiation 31 immunofluorescent staining and terminal deoxynucleotidyl transferase‑mediated dUTP nick end labeling assay, respectively. Western blot analysis was conducted to detect the protein expression levels of vascular endothelial growth factor (VEGF) and stromal cell‑derived factor (SDF)‑1α in the myocardium. Treatment with resveratrol increased the number of endogenous Sca‑1+ CSCs in heart tissue after 7 days (PBS vs. Res, 1.85±0.41/field vs. 3.14±0.26/field, P<0.05). Furthermore, intragastric administration of resveratrol significantly increased left ventricle (LV) function 4 weeks after AMI, as determined by an increase in LV fractional shortening (CSCs vs. Res + CSCs, 28.82±1.58% vs. 31.18±2.02%, P<0.05), reduced LV end‑diastolic diameter (CSCs vs. Res + CSCs, 0.37±0.01 mm vs. 0.35±0.02 mm, P<0.05), and reduced LV end‑systolic diameter (CSCs vs. Res + CSCs, 0.26±0.01 mm vs. 0.23±0.02 mm, P<0.05). These protective effects were predominantly achieved via an increase in capillary density (CSCs vs. Res + CSCs, 281.02±24.08/field vs. 329.75±36.69/field, P<0.05) and a reduction in cardiomyocyte apoptosis (CSCs vs. Res + CSCs, 1.5±0.54/field vs. 0.83±0.40/field, P<0.05) in peri‑ischemic myocardium. Western blot analysis indicated that VEGF and SDF‑1α were upregulated in resveratrol‑treated myocardium after a 7 day treatment or 4 weeks after AMI (7 days VEGF PBS vs. Res, 0.89±0.07 vs. 1.21±0.02, P<0.05; SDF‑1α PBS vs. Res, 0.66±0.04 vs. 1.33±0.04, P<0.05; 4 weeks VEGF CSCs vs. Res + CSCs, 0.54±0.03 vs. 0.93±0.13, P<0.05; SDF‑1α CSCs vs. Res + CSCs, 0.53±0.03 vs. 0.93±0.03, P<0.05). Resveratrol activated endogenous CSCs, increased capillary density and decreased cardiomyocyte apoptosis in the peri‑ischemic myocardium, and augmented the effects of CSCs transplantation. These effects may be caused by the upregulation of VEGF and SDF‑1α.

Testosterone and Voluntary Exercise Promote Angiogenesis in Hearts of Rats with Diabetes by Enhancing Expression of VEGF-A and SDF-1a

OBJECTIVES

Impaired angiogenesis in cardiac tissue is a major complication of diabetes. This study was aimed to evaluate the effects of testosterone and voluntary exercise on vascular endothelial growth factor-A (VEGF-A), stromal cell-derived factor 1a (SDF-1a) and myocardial capillary density in heart of rats with diabetes.

METHODS

Type 1 diabetes was induced by intraperitoneal injection of 55 mg/kg of streptozotocin in 80 male Wistar rats. After 42 days of treatment with testosterone (2 mg/kg/day) or voluntary exercise alone or in combination, angiogenesis was determined in the hearts by immunostaining for PECAM-1/CD31. The expressions of VEGF-A and SDF-1a levels in heart were also determined by the ELISA method.

RESULTS

Our results showed that capillary density, VEGF-A and SDF-1a levels in the heart were significantly decreased in castrated rats with diabetes, whereas these effects were reversed by testosterone and exercise. Furthermore, simultaneous treatment of castrated rats with diabetes with testosterone and exercise had a synergistic effect on capillary density, VEGF-A and SDF-1a levels in the heart. In the group with diabetes, either testosterone or exercise increased capillary density, VEGF-A and SDF-1a protein levels in heart tissue. However, the effects of combination therapy in rats with diabetes with testosterone and exercise on capillary density, VEGF-A and SDF-1a levels in the heart was synergistic.

CONCLUSIONS

Our findings suggest that testosterone and exercise can promote neoangiogenesis in rats with diabetes and in castrated rats with diabetes. The proangiogenesis effect of testosterone and exercise is associated with the enhanced expression of VEGF-A and SDF-1a in heart tissue.

Controlled Release of Collagen-Binding SDF-1α Improves Cardiac Function after Myocardial Infarction by Recruiting Endogenous Stem Cells

Stromal cell-derived factor-1α (SDF-1α) is a well-characterized chemokine that mobilizes stem cells homing to the ischemic heart, which is beneficial for cardiac regeneration. However, clinically administered native SDF-1α diffuses quickly, thus decreasing its local concentration, and results in side effects. Thus, a controlled release system for SDF-1α is required to produce an effective local concentration in the ischemic heart. In this study, we developed a recombinant chemokine, consisting of SDF-1α and a collagen-binding domain, which retains both the SDF-1α and collagen-binding activity (CBD-SDF-1α). In an in vitro assay, CBD-SDF-1α could specifically bind to a collagen gel and achieve sustained release. An intramyocardial injection of CBD-SDF-1α after acute myocardial infarction demonstrated that the protein was largely tethered in the ischemic area and that controlled release had been achieved. Furthermore, CBD-SDF-1α enhanced the recruitment of c-kit positive (c-kit⁺) stem cells, increased capillary density and improved cardiac function, whereas NAT-SDF-1α had no such beneficial effects. Our findings demonstrate that CBD-SDF-1α can specifically bind to collagen and achieve controlled release both in vitro and in vivo. Local delivery of this protein could mobilize endogenous stem cells homing to the ischemic heart and improve cardiac function after myocardial infarction.

The contributions of dipeptidyl peptidase IV to inflammation in heart failure

Circulating dipeptidyl peptidase IV (DPPIV) activity correlates with cardiac dysfunction in humans and experimental heart failure (HF) models. Similarly, inflammatory markers are associated with poorer outcomes in HF patients. However, the contributions of DPPIV to inflammation in HF remain elusive. Therefore, this study aimed to investigate whether the cardioprotective effects of DPPIV inhibition after myocardial injury are accompanied by reduced cardiac inflammation, whether circulating DPPIV activity correlates with the levels of systemic inflammatory markers in HF patients, and whether leukocytes and/or splenocytes may be one of the sources of circulating DPPIV in HF. Experimental HF was induced in male Wistar rats by left ventricular myocardial injury after radiofrequency catheter ablation. The rats were divided into three groups: sham, HF, and HF + DPPIV inhibitor (sitagliptin). Six weeks after surgery, cardiac function, perfusion and inflammatory status were evaluated. Sitagliptin treatment improved cardiac function and perfusion, reduced macrophage infiltration, and diminished the levels of inflammatory biomarkers including TNF-α, IL-1β, and CCL2. In HF patients, serum DPPIV activity correlated with CCL2, suggesting that leukocytes may be the source of circulating DPPIV in HF. Unexpectedly, DPPIV release was higher in splenocytes from HF rats and similar in HF circulating mononuclear cells compared with those from sham, suggesting an organ-specific modulation of DPPIV in HF. Collectively, our data provide new evidence that the cardioprotective effects of DPPIV inhibition in HF may be due to suppression of inflammatory cytokines. Moreover, they suggest that a vicious circle between DPPIV and inflammation may contribute to HF development and progression.

Dipeptidyl peptidase-4 inhibition improves cardiac function in experimental myocardial infarction: Role of stromal cell-derived factor-1α

BACKGROUND

In addition to degrading glucagon-like peptide-1 (GLP-1), dipeptidyl peptidase-4 (DPP-4) inactivates several chemokines, including stromal cell-derived factor-1α (SDF-1α), a pro-angiogenic and cardiomyocyte protective protein. We hypothesized that DPP-4 inhibition may confer benefit following myocardial infarction (MI) in the diabetic setting as a consequence of enhanced SDF-1α availability rather than potentiating GLP-1. To test this we compared the effects of saxagliptin with those of liraglutide and used the SDF-1α receptor (CXCR4) antagonist plerixafor.

METHODS

Studies were conducted in streptozotocin-diabetic rats. Rats were randomized to receive saxagliptin (10 mg/kg per day), liraglutide (0.2 mg/kg, s.c., b.i.d.), plerixafor (1 mg/kg per day, s.c.), saxagliptin plus plerixafor or vehicle (1% phosphate-buffered saline). Two weeks later, rats underwent experimental MI, with cardiac function examined 4 weeks after MI.

RESULTS

Glycemic control and MI size were similar in all groups. Four weeks after MI, mortality was reduced in saxagliptin-treated rats compared with vehicle treatment (P < 0.05). Furthermore, rats receiving saxagliptin had improved cardiac function compared with vehicle-treated rats (P < 0.05). Antagonism of CXCR4 prevented the improvement in cardiac function in saxagliptin-treated rats and was associated with increased mortality (P < 0.05).

CONCLUSION

Saxagliptin-mediated DPP-4 inhibition, but not liraglutide-mediated GLP-1R agonism, improved cardiac function after MI independent of glucose lowering. These findings suggest that non-GLP-1 actions of DPP-4 inhibition, such as SDF-1α potentiation, mediate biological effects.

Crosstalk between SDF-1/CXCR4 and SDF-1/CXCR7 in cardiac stem cell migration

Stromal cell-derived factor 1 (SDF-1) is a chemokine that can be expressed in injured cardiomyocytes after myocardial infarction (MI). By combining with its receptor CXCR4, SDF-1 induced stem and progenitor cells migration. CXCR7, a novel receptor for SDF-1, has been identified recently. We aimed to explore the roles of SDF-1/CXCR4 and SDF-1/CXCR7 pathway and their crosstalk in CSCs migration. In the present study, CXCR4 and CXCR7 expression were identified in CSCs. Transwell assay showed that SDF-1 caused CSCs migration in a dose- and time-dependent manner, which could be significantly suppressed by CXCR4 or CXCR7 siRNA. Phospho-ERK, phospho-Akt and Raf-1 significantly elevated in CSCs with SDF-1 stimulation. Knockdown of CXCR4 or CXCR7 significantly decreased phospho-ERK or phospho-Akt, respectively, and eventually resulted in the inhibition of CSCs migration. Moreover, western blot showed that MK2206 (Akt inhibitor) increased the expression of phospho-ERK and Raf-1, whereas PD98059 (ERK inhibitor) had no effect on phospho-Akt and Raf-1. GW5074 (Raf-1 inhibitor) upregulated the expression of phospho-ERK, but had no effect on phospho-Akt. The present study indicated that SDF-1/CXCR7/Akt and SDF-1/CXCR4/ERK pathway played important roles in CSCs migration. Akt phosphorylation inhibited Raf-1 activity, which in turn dephosphorylated ERK and negatively regulated CSCs migration.

Caloric restriction and the adipokine leptin alter the SDF-1 signaling axis in bone marrow and in bone marrow derived mesenchymal stem cells

Growing evidence suggests that the chemokine stromal cell-derived factor-1 (SDF-1) is essential in regulating bone marrow (BM) derived mesenchymal stromal/stem cell (BMSC) survival, and differentiation to either a pro-osteogenic or pro-adipogenic fate. This study investigates the effects of caloric restriction (CR) and leptin on the SDF-1/CXCR4 axis in bone and BM tissues in the context of age-associated bone loss. For in vivo studies, we collected bone, BM cells and BM interstitial fluid from 12 and 20 month-old C57Bl6 mice fed ad-libitum (AL), and 20-month-old mice on long-term CR with, or without, intraperitoneal injection of leptin for 10 days (10 mg/kg). To mimic conditions of CR in vitro, 18 month murine BMSCs were treated with (1) control (Ctrl): normal proliferation medium, (2) nutrient restriction (NR): low glucose, low serum medium, or (3) NR + leptin: NR medium + 100 ng/ml leptin for 6-48 h. In BMSCs both protein and mRNA expression of SDF-1 and CXCR4 were increased by CR and CR + leptin. In contrast, the alternate SDF-1 receptor CXCR7 was decreased, suggesting a nutrient signaling mediated change in SDF-1 axis signaling in BMSCs. However, in bone SDF-1, CXCR4 and 7 gene expression increase with age and this is reversed with CR, while addition of leptin returns this to the "aged" level. Histologically bone formation was lower in the calorically restricted mice and BM adipogenesis increased, both effects were reversed with the 10 day leptin treatment. This suggests that in bone CR and leptin alter the nutrient signaling pathways in different ways to affect the local action of the osteogenic cytokine SDF-1. Studies focusing on the molecular interaction between nutrient signaling by CR, leptin and SDF-1 axis may help to address age-related musculoskeletal changes.

Impact of Either GLP-1 Agonists or DPP-4 Inhibitors on Pathophysiology of Heart Failure

Since diabetes mellitus (DM) is the most common cause of heart failure (HF), it is critically important to clarify whether incretin hormones including glucagon-like peptide-1 (GLP-1), which play an important role in blood glucose control, mediate cardioprotection. There are many lines of basic research evidence indicating that GLP-1 improves the pathophysiology of HF: In murine and canine HF models, either GLP-1 analogues or DPP-IV inhibitors improved cardiac functions. The first question that arises is how either GLP-1 analogues or DPP-IV inhibitors mediate cardioprotection. Cardiovascular diseases are tightly linked to impaired glucose tolerance (IGT): IGT is not only one of the causes of cardiovascular events but also the result of HF. Indeed, the treatment of IGT improved HF, showing that one of the mechanisms attributable to DPP-IV inhibitors is related to the improvement of IGT. Intriguingly, either DPP-IV inhibitors or GLP-1 analogues mediate cardioprotection even without IGT, suggesting two possible explanations: One is that GLP-1 analogues directly activate the prosurvival kinases, such as Akt and Erk1/2, and another is that DPP-IV inhibition increases cardioprotective peptides such as BNP and SDF-1α. The next question is whether cardioprotection is translated to clinical medicine. Small scale clinical trials proved their cardioprotective effects; however, several large scale clinical trials have not proved the beneficial effects of DPP-IV inhibitors. Taken together, GLP-1 analogues or DPP-IV inhibitors can mediate cardioprotection, however, what needs to be clarified is who mainly receives their benefits among the patients with cardiovascular diseases and/or DM.

Serum CXCL12 Levels as a Novel Predictor of Future Stroke Recurrence in Patients with Acute Ischemic Stroke

Previous studies had shown that CXC chemokine ligand-12 (CXCL12) plays a significant role in animal models of ischemic stroke, but its role in human stroke is unclear. The aim of this study was to test the relationship between elevated serum circulating CXCL12 levels and the 1-year stroke recurrence in Chinese patients with acute ischemic stroke (AIS). All consecutive patients with first-ever acute ischemic stroke from January 2011 to September 2013 were recruited to participate in the study. Serum levels of CXCL12 and National Institute of Health Stroke Scale (NIHSS) were measured at the time of admission. Logistic regression analysis was used to evaluate the stroke recurrence according to serum CXCL12 levels. Receiver operating characteristic (ROC) curve was used to evaluate the accuracy of serum CXCL12 in predicting stroke recurrence. Clinical follow-up was performed at 1 year. In our study, 248 patients finished the 1-year follow-up. At 1-year follow-up, 31 patients had a recurrence ischemic stroke. The median CXCL12 levels were significantly higher in those who sustained a recurrence ischemic stroke compared with those who did not [24.2 ng/mL (IQR 15.4-33.7) vs 6.5 ng/mL (IQR 3.4-10.2); Z = 8.258, P < 0.0001]. In multivariate analysis, there was an increased risk of stroke recurrence associated with serum CXCL12 levels ≥12.15 ng/mL (OR 9.122, 95 % CI 6.103-15.104) after adjusting for above possible confounders. The time to recurrence stroke distribution between patients with baseline CXCL12 levels ≥12.15 ng/mL and those with baseline CXCL12 levels <12.15 ng/mL were significantly different (P < 0.0001, log-rank test). Elevated circulating CXCL12 levels at admission are strongly associated with the future recurrence of ischemic stroke in Chinese patients with AIS. Further studies are warranted to confirm this association and define the role for CXCL12 as a novel predictor biomarker for stroke recurrence.

Risk of breast cancer with CXCR4-using HIV defined by V3 loop sequencing

OBJECTIVE

Evaluate the risk of female breast cancer associated with HIV-CXCR4 (X4) tropism as determined by various genotypic measures.

METHODS

A breast cancer case-control study, with pairwise comparisons of tropism determination methods, was conducted. From the Women's Interagency HIV Study repository, one stored plasma specimen was selected from 25 HIV-infected cases near the breast cancer diagnosis date and 75 HIV-infected control women matched for age and calendar date. HIV-gp120 V3 sequences were derived by Sanger population sequencing (PS) and 454-pyro deep sequencing (DS). Sequencing-based HIV-X4 tropism was defined using the geno2pheno algorithm, with both high-stringency DS [false-positive rate (3.5) and 2% X4 cutoff], and lower stringency DS (false-positive rate, 5.75 and 15% X4 cutoff). Concordance of tropism results by PS, DS, and previously performed phenotyping was assessed with kappa (κ) statistics. Case-control comparisons used exact P values and conditional logistic regression.

RESULTS

In 74 women (19 cases, 55 controls) with complete results, prevalence of HIV-X4 by PS was 5% in cases vs 29% in controls (P = 0.06; odds ratio, 0.14; confidence interval: 0.003 to 1.03). Smaller case-control prevalence differences were found with high-stringency DS (21% vs 36%, P = 0.32), lower stringency DS (16% vs 35%, P = 0.18), and phenotyping (11% vs 31%, P = 0.10). HIV-X4 tropism concordance was best between PS and lower stringency DS (93%, κ = 0.83). Other pairwise concordances were 82%-92% (κ = 0.56-0.81). Concordance was similar among cases and controls.

CONCLUSIONS

HIV-X4 defined by population sequencing (PS) had good agreement with lower stringency DS and was significantly associated with lower odds of breast cancer.

Potential role of dipeptidyl peptidase IV in the pathophysiology of heart failure

Dipeptidyl peptidase IV (DPPIV) is a widely expressed multifunctional serine peptidase that exists as a membrane-anchored cell surface protein or in a soluble form in the plasma and other body fluids. Numerous substrates are cleaved at the penultimate amino acid by DPPIV, including glucagon-like peptide-1 (GLP-1), brain natriuretic peptide (BNP) and stromal cell-derived factor-1 (SDF-α), all of which play important roles in the cardiovascular system. In this regard, recent reports have documented that circulating DPPIV activity correlates with poorer cardiovascular outcomes in human and experimental heart failure (HF). Moreover, emerging evidence indicates that DPPIV inhibitors exert cardioprotective and renoprotective actions in a variety of experimental models of cardiac dysfunction. On the other hand, conflicting results have been found when translating these promising findings from preclinical animal models to clinical therapy. In this review, we discuss how DPPIV might be involved in the cardio-renal axis in HF. In addition, the potential role for DPPIV inhibitors in ameliorating heart disease is revised, focusing on the effects of the main DPPIV substrates on cardiac remodeling and renal handling of salt and water.

What is Wrong With Cardiac Conditioning? We May be Shooting at Moving Targets

Early recanalization of the occluded culprit coronary artery clearly reduces infarct size in both animal models and patients and improves clinical outcomes. Unfortunately, reperfusion can seldom be accomplished before some myocardium infarcts. As a result there has been an intensive search for interventions that will make the heart resistant to infarction so that reperfusion could salvage more myocardium. A number of interventions have been identified in animal models, foremost being ischemic preconditioning. It protects by activating signaling pathways that prevent lethal permeability transition pores from forming in the heart’s mitochondria at reperfusion. Such conditioning can be accomplished in a clinically relevant manner either by staccato reperfusion (ischemic postconditioning) or by pharmacological activation of the conditioning signaling pathways prior to reperfusion. Unfortunately, clinical trials of ischemic postconditioning and pharmacologic conditioning have been largely disappointing. We suggest that this may be caused by inappropriate use as models intended to mimic the clinical scenario of young healthy animals that receive none of the many drugs currently given to our patients. Patients may be resistant to some forms of conditioning because of comorbidities, for example, diabetes, or they may already be conditioned by adjunct medications, for example, P2Y12 inhibitors or opioids. Incremental technological improvements in patient care may render some approaches to cardioprotection redundant, and thus the clinical target may be continually changing, while our animal models have not kept pace. In remote conditioning, a limb is subjected to ischemia/reperfusion prior to or during coronary reperfusion. Its mechanism is not as well understood as that of ischemic preconditioning, but the results have been very encouraging. In the present article, we will review ischemic, remote, and pharmacologic conditioning and possible confounders that could interfere with their efficacy in clinical trials in 2 settings of myocardial ischemia: (1) primary angioplasty in acute myocardial infarction and (2) elective angioplasty.

Remote ischemic conditioning

In remote ischemic conditioning (RIC), brief, reversible episodes of ischemia with reperfusion in one vascular bed, tissue, or organ confer a global protective phenotype and render remote tissues and organs resistant to ischemia/reperfusion injury. The peripheral stimulus can be chemical, mechanical, or electrical and involves activation of peripheral sensory nerves. The signal transfer to the heart or other organs is through neuronal and humoral communications. Protection can be transferred, even across species, with plasma-derived dialysate and involves nitric oxide, stromal derived factor-1α, microribonucleic acid-144, but also other, not yet identified factors. Intracardiac signal transduction involves: adenosine, bradykinin, cytokines, and chemokines, which activate specific receptors; intracellular kinases; and mitochondrial function. RIC by repeated brief inflation/deflation of a blood pressure cuff protects against endothelial dysfunction and myocardial injury in percutaneous coronary interventions, coronary artery bypass grafting, and reperfused acute myocardial infarction. RIC is safe and effective, noninvasive, easily feasible, and inexpensive.

Cardiovascular actions of incretin-based therapies

Glucagon-like peptide-1 receptor (GLP-1R) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors represent 2 distinct classes of incretin-based therapies used for the treatment of type 2 diabetes mellitus. Activation of GLP-1R signaling or inhibition of DPP-4 activity produces a broad range of overlapping and unique cardiovascular actions. Native GLP-1 regulates cardiovascular biology via activation of the classical GLP-1R, or through GLP-1(9-36), a cardioactive metabolite generated by DPP-4-mediated cleavage. In contrast, clinically approved GLP-1R agonists are not cleaved to GLP-1(9-36) and produce the majority of their actions through the classical GLP-1R. The cardiovascular mechanisms engaged by DPP-4 inhibition are more complex, encompassing increased levels of intact GLP-1, reduced levels of GLP-1(9-36), and changes in levels of numerous cardioactive peptides. Herein we review recent experimental and clinical advances that reveal how GLP-1R agonists and DPP-4 inhibitors affect the normal and diabetic heart and coronary vasculature, often independent of changes in blood glucose. Improved understanding of the complex science of incretin-based therapies is required to optimize the selection of these therapeutic agents for the treatment of diabetic patients with cardiovascular disease.

DPP-4 inhibition attenuates cardiac dysfunction and adverse remodeling following myocardial infarction in rats with experimental diabetes

AIMS

Following myocardial infarction (MI), individuals with diabetes have a two-fold increase in the risk of heart failure, due in part to excessive loss of cardiac microvasculature. Endothelial integrity and restitution are mediated in part by stromal cell-derived factor-1α (SDF-1α), a chemokine that is elaborated by ischemic tissue but rapidly degraded by dipeptidyl peptidase-4 (DPP-4). Accordingly, we hypothesized that inhibiting this enzyme may confer benefit following myocardial infarction in the diabetic setting beyond its effect on glycemia.

METHODS AND RESULTS

Fischer F344 rats with streptozotocin (STZ)-diabetes were randomized to receive vehicle or the DPP-4 inhibitor, sitagliptin (300 mg/kg/day). Two weeks later, animals underwent experimental MI, induced by ligation of the left anterior descending coronary artery. Cardiac function was assessed by conductance catheterization and echocardiography along with cardiac structure 4 weeks post-MI. Following MI, untreated diabetic rats developed both systolic and diastolic cardiac dysfunction, in association with endothelial cell loss, fibrosis, and myocyte hypertrophy. Without affecting plasma glucose, sitagliptin treatment led to an improvement in passive left ventricular compliance, increased endothelial cell density, reduced myocyte hypertrophy, and a reduction in the abundance of collagen 1 (all P < 0.05). Systolic function was unchanged.

CONCLUSIONS

This study shows that DPP-4 inhibition attenuates several, but not all, aspects of cardiac dysfunction and adverse remodeling in the post-MI setting.

Dipeptidyl peptidase-4 inhibitors are associated with improved left ventricular diastolic function after acute myocardial infarction in diabetic patients

Dipeptidyl peptidase-4 (DPP4) is an integral membrane glycoprotein that modulates the pathological state of diabetes mellitus (DM), and DPP4 inhibitors are a new class of anti-type-2 DM drugs. Recent preclinical studies have associated DPP4 inhibition with improved myocardial systolic and diastolic function. Based on preclinical findings, we investigated associations between the administration of DPP4 inhibitors and cardiac function after acute myocardial infarction (AMI) in a clinical setting. We enrolled 34 patients with diabetes who were treated for acute myocardial infarction at our hospital between January 2010 and December 2012. We retrospectively compared changes in cardiac parameters determined by trans-thoracic echocardiography between patients treated with (DPP4-I group; n = 13) or without (non-DPP4-I group; n = 21) a DPP4 inhibitor during follow-up. The values of E/e' and of e'/a' significantly decreased and increased, respectively, in the DPP4-I, compared with the non-DPP4-I group (-2.53 ± 5.53 vs. 2.58 ± 5.68, p = 0.038 and 0.08 ± 0.23 vs. -0.12 ± 0.21, p = 0.036, respectively). We concluded that DPP4 inhibitors could improve E/e' and e'/a' in patients with DM and AMI and thus might be effective for treating left ventricular diastolic failure.

Stromal derived factor 1α: a chemokine that delivers a two-pronged defence of the myocardium

Alleviating myocardial injury associated with ST elevation myocardial infarction is central to improving the global burden of coronary heart disease. The chemokine stromal cell-derived factor 1α (SDF-1α) has dual potential benefit in this regard. Firstly, SDF-1α is up-regulated in experimental and clinical studies of acute myocardial infarction (AMI) and regulates stem cell migration to sites of injury. SDF-1α delivery to the myocardium after AMI is associated with improved stem cell homing, angiogenesis, and left ventricular function in animal models, and improvements in heart failure and quality of life in humans. Secondly, SDF-1α may have a role in remote ischaemic conditioning (RIC), the phenomenon whereby non-lethal ischaemia–reperfusion applied to an organ or tissue remote from the heart protects the myocardium from lethal ischaemia–reperfusion injury (IRI). SDF-1α is increased in the serum of rats subjected to RIC and protects against myocardial IRI in ex vivo studies. Despite these potential pleiotropic effects, a limitation of SDF-1α is its short plasma half-life due to cleavage by dipeptidyl peptidase-4 (DPP-4). However, DPP-4 inhibitors increase the half-life of SDF-1α by preventing its degradation and are also protective against lethal IRI. In summary, SDF-1 potentially delivers a ‘two-pronged’ defence of the myocardium: acutely protecting it from IRI while simultaneously stimulating repair by recruiting stem cells to the site of injury. In this article we examine the evidence for acute and chronic cardioprotective roles of SDF-1α and discuss potential therapeutic manipulations of this mechanism with DPP-4 inhibitors to protect against lethal tissue injury in the clinical setting.

Plasminogen regulates cardiac repair after myocardial infarction through its noncanonical function in stem cell homing to the infarcted heart

OBJECTIVES

The purpose of this study was to investigate the role of plasminogen (Plg) in stem cell-mediated cardiac repair and regeneration after myocardial infarction (MI).

BACKGROUND

An MI induces irreversible tissue damage, eventually leading to heart failure. Bone marrow (BM)-derived stem cells promote tissue repair and regeneration after MI. Thrombolytic treatment with Plg activators significantly improves the clinical outcome in MI by restoring cardiac perfusion. However, the role of Plg in stem cell-mediated cardiac repair remains unclear.

METHODS

An MI was induced in Plg-deficient (Plg(-/-)) and wild-type (Plg(+/+)) mice by ligation of the left anterior descending coronary artery. Stem cells were visualized by in vivo tracking of green fluorescent protein (GFP)-expressing BM cells after BM transplantation. Cardiac function, stem cell homing, and signaling pathways downstream of Plg were examined.

RESULTS

Granulocyte colony-stimulating factor, a stem cell mobilizer, significantly promoted BM-derived stem cell (GFP(+)c-kit(+) cell) recruitment into the infarcted heart and stem cell-mediated cardiac repair in Plg(+/+) mice. However, Plg deficiency markedly inhibited stem cell homing and cardiac repair, suggesting that Plg is critical for stem cell-mediated cardiac repair. Moreover, Plg regulated C-X-C chemokine receptor type 4 (CXCR4) expression in stem cells in vivo and in vitro through matrix metalloproteinase-9. Lentiviral reconstitution of CXCR4 expression in BM cells successfully rescued stem cell homing to the infarcted heart in Plg-deficient mice, indicating that CXCR4 has a critical role in Plg-mediated stem cell homing after MI.

CONCLUSIONS

These findings have identified a novel role for Plg in stem cell-mediated cardiac repair after MI. Thus, targeting Plg may offer a new therapeutic strategy for stem cell-mediated cardiac repair after MI.

NLRP3 inflammasome as a novel player in myocardial infarction

Inflammasomes are multiple protein complexes that serve as molecular platforms to activate caspase-1 and regulate maturation of a potent proinflammatory cytokine, interleukin (IL)-1β, as well as proinflammatory cell death, pyroptosis. Although several types of inflammasomes have been reported so far, recent investigations indicate that the NLRP3 inflammasome recognizes non-microbial danger signals and leads to sterile inflammatory responses in various disease conditions. Sterile inflammatory responses are also implicated in the development of myocardial infarction (MI). In particular, IL-1β is an early and prominent mediator of inflammatory responses in MI, suggesting the pathophysiologic role of NLRP3 inflammasomes in MI. This review highlights the current state of knowledge regarding the role of NLRP3 inflammasomes in MI.

Emerging roles for platelets as immune and inflammatory cells

Despite their small size and anucleate status, platelets have diverse roles in vascular biology. Not only are platelets the cellular mediator of thrombosis, but platelets are also immune cells that initiate and accelerate many vascular inflammatory conditions. Platelets are linked to the pathogenesis of inflammatory diseases such as atherosclerosis, malaria infection, transplant rejection, and rheumatoid arthritis. In some contexts, platelet immune functions are protective, whereas in others platelets contribute to adverse inflammatory outcomes. In this review, we will discuss platelet and platelet-derived mediator interactions with the innate and acquired arms of the immune system and platelet-vessel wall interactions that drive inflammatory disease. There have been many recent publications indicating both important protective and adverse roles for platelets in infectious disease. Because of this new accumulating data, and the fact that infectious disease continues to be a leading cause of death globally, we will also focus on new and emerging concepts related to platelet immune and inflammatory functions in the context of infectious disease.

Remote ischaemic preconditioning involves signalling through the SDF-1α/CXCR4 signalling axis

Ischaemic preconditioning is one of the most potent experimental modalities known to decrease infarct size after ischaemia and reperfusion. Much interest has been stimulated by the phenomenon of remote ischaemic conditioning (RIC), in which the preconditioning stimulus is applied to a limb remote from the heart to stimulate cardioprotection via an unidentified humoral factor, believed to be a protein between 3.5 and 15 kDa. Stromal cell-derived factor-1 (SDF-1α or CXCL12) is a chemokine of 10 kDa that is induced by hypoxia and recruits stem cells, but also exerts direct, acute, cardioprotection via its receptor, CXCR4. The serum dipeptidase DPPIV cleaves and inactivates SDF-1α. We measured SDF-1α in rat plasma and found it was significantly increased by RIC. DPPIV activity was unchanged after RIC, suggesting that increased synthesis or release or SDF-1α caused the increase in plasma levels. AMD3100, a highly specific inhibitor of CXCR4, was used to investigate the hypothesis that SDF-1α is involved in RIC. RIC in rats, which decreased infarct size from 53 ± 3 % to 27 ± 3 % (n = 6, P < 0.05), was blocked in rats treated with AMD3100 (40 ± 4 %). RIC also improved functional recovery of cardiac papillary muscle, and this, too, was blocked by AMD3100. Direct application of SDF-1α was confirmed to be protective in this model and was blocked by AMD3100. RIC stimulates SDF-1α release, and this 10-kDa peptide appears to be required for the mechanism of RIC.