Stromal cell derived factor-1 (SDF-1) targeting reperfusion reduces myocardial infarction in isolated rat hearts

Development of a Sustained Release Nano-In-Gel Delivery System for the Chemotactic and Angiogenic Growth Factor Stromal-Derived Factor 1α

Stromal-Derived Factor 1α (SDF) is an angiogenic, chemotactic protein with significant potential for applications in a range of clinical areas, including wound healing, myocardial infarction and orthopaedic regenerative approaches. The 26-min in vivo half-life of SDF, however, has limited its clinical translation to date. In this study, we investigate the use of star-shaped or linear poly(glutamic acid) (PGA) polypeptides to produce PGA-SDF nanoparticles, which can be incorporated into a tyramine-modified hyaluronic acid hydrogel (HA-TA) to facilitate sustained localised delivery of SDF. The physicochemical properties and biocompatibility of the PGA-SDF nanoparticle formulations were extensively characterised prior to incorporation into a HA-TA hydrogel. The biological activity of the SDF released from the nano-in-gel system was determined on Matrigel®, scratch and Transwell® migration assays. Both star-shaped and linear PGA facilitated SDF nanoparticle formation with particle sizes from 255-305 nm and almost complete SDF complexation. Star-PGA-SDF demonstrated superior biocompatibility and was incorporated into a HA-TA gel, which facilitated sustained SDF release for up to 35 days in vitro. Released SDF significantly improved gap closure on a scratch assay, produced a 2.8-fold increase in HUVEC Transwell® migration and a 1.5-fold increase in total tubule length on a Matrigel® assay at 12 h compared to untreated cells. Overall, we present a novel platform system for the sustained delivery of bioactive SDF from a nano-in-gel system which could be adapted for a range of biomedical applications.

The lncRNA ROR/miR-124-3p/TRAF6 axis regulated the ischaemia reperfusion injury-induced inflammatory response in human cardiac myocytes

Myocardial ischaemia reperfusion injury (MIRI) is considered the primary cause of death in patients with cardiovascular diseases. Recently, long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) have been found to be involved in the pathogenesis of MIRI. However, whether lncRNA ROR and miR-124-3p play roles in MIRI and the underlying mechanism remain undetermined. HCMs were exposed to hypoxic conditions for 2 h followed by re-oxygenation (H/R) treatment. Expression of miR-124-3p and lncRNA ROR in HCMs was measured by qRT-PCR. TRAF6 expression was evaluated by qRT-PCR and western blotting. ELISA and qRT-PCR were conducted to assess the production of TNF-α, IL-6, and IL-1β. The interaction between miR-124-3p and TRAF6, as well as between miR-124-3p and lncRNA ROR, was verified by dual-luciferase reporter assay. Cell apoptosis was detected by flow cytometry analysis. Our data revealed that miR-124-3p was significantly downregulated, while TRAF6 and lncRNA ROR were upregulated in both MIRI rat model and H/R treated HCMs. Overexpression of miR-124-3p reversed the H/R-induced cell apoptosis and upregulation of TNF-α, IL-6, and IL-1β. Mechanistically, miR-124-3p bound and negatively regulated TRAF6 expression in HCMs. Moreover, TRAF6 overexpression significantly blocked the effects of miR-124-3p mimics on cell apoptosis and inflammatory response of HCMs, which involved the NF-κB pathway. Further analysis showed that lncRNA ROR sponged and negatively regulated miR-124-3p in HCMs. Overexpression of IL-1β was demonstrated to promote H/R induced cell apoptosis in HCMs. In addition, overexpression of ROR further enhanced the H/R-induced inflammation and cell apoptosis through its action on miR-124-3p. The lncRNA ROR/miR-124-3p/TRAF6 axis regulated the H/R-induced cell apoptosis and inflammatory response of HCMs.

Therapeutic strategies utilizing SDF-1α in ischaemic cardiomyopathy

Heart failure is rapidly increasing in prevalence and will redraw the global landscape for cardiovascular health. Alleviating and repairing cardiac injury associated with myocardial infarction (MI) is key to improving this burden. Homing signals mobilize and recruit stem cells to the ischaemic myocardium where they exert beneficial paracrine effects. The chemoattractant cytokine SDF-1α and its associated receptor CXCR4 are upregulated after MI and appear to be important in this context. Activation of CXCR4 promotes both cardiomyocyte survival and stem cell migration towards the infarcted myocardium. These effects have beneficial effects on infarct size, and left ventricular remodelling and function. However, the timing of endogenous SDF-1α release and CXCR4 upregulation may not be optimal. Furthermore, current ELISA-based assays cannot distinguish between active SDF-1α, and SDF-1α inactivated by dipeptidyl peptidase 4 (DPP4). Current therapeutic approaches aim to recruit the SDF-1α-CXCR4 pathway or prolong SDF-1α life-time by preventing its cleavage by DPP4. This review assesses the evidence supporting these approaches and proposes SDF-1α as an important confounder in recent studies of DPP4 inhibitors.

Activation of the mammalian target of rapamycin signaling pathway underlies a novel inhibitory role of ring finger protein 182 in ventricular remodeling after myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury (MIRI) is a major cause of cardiovascular disease, leading to mortality and disability associated with coronary occlusion worldwide. A correlation of mammalian target of rapamycin (mTOR)/nuclear factor-kappa B (NF-κB) signaling pathway has been observed with brain damage resulting from myocardial ischemia. Therefore, by establishing MIRI rat model, this study aimed to explore whether ring finger protein 182 (RNF182) regulates the mTOR signaling pathway affecting MIRI. Initially, MIRI rat model was successfully established, followed by either treatment of shRNF182 or phosphoesterase (PITE) (inhibitor of the mTOR signaling pathway). Then, the serum levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA), left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS), left ventricular systolic pressure (LVSP), and left ventricular end-diastolic pressure (LVEDP) were determined, followed by detection of myocardial infarct sizes and myocardial cell apoptosis. Moreover, the levels of related genes/proteins were determined to further determine the mechanisms of RNF182 in MIRI. First, RNF182 was upregulated in MIRI. Another key observation of this study was that rats with shRNF182 presented with downregulated SOD, GSH-Px, and MDA in serum, accompanied by decreased levels of LVEF, LVFS, LVSP, and LVEDP. In addition, both reduced myocardial infarct sizes and apoptosis of myocardial cells were observed after silencing RNF182. Furthermore, silencing of the RNF182 was observed to downregulate Bcl 2-associated X and cysteine proteinase 3 but upregulate mTOR, ribosome protein subunit 6 kinase 1, eukaryotic elongation factor 2, and B-cell lymphoma-2. Importantly, the effects of RNF182 silencing were reversed after PITE treatment. In conclusion, our study demonstrates that RNF182 silencing can prevent ventricular remodeling in rats after MIRI by activating the mTOR signaling pathway.

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.

The Dipeptidyl Peptidase 4 Substrate CXCL12 Has Opposing Cardiac Effects in Young Mice and Aged Diabetic Mice Mediated by Ca2+ Flux and Phosphoinositide 3-Kinase γ

Blood glucose-lowering therapies can positively or negatively affect heart function in type 2 diabetes, or they can have neutral effects. Dipeptidyl peptidase 4 (DPP-4) inhibitors lower blood glucose by preventing the proteolytic inactivation of glucagon-like peptide 1 (GLP-1). However, GLP-1 is not the only peptide substrate of DPP-4. Here, we investigated the GLP-1-independent cardiac effects of DPP-4 substrates. Pointing to GLP-1 receptor (GLP-1R)-independent actions, DPP-4 inhibition prevented systolic dysfunction equally in pressure-overloaded wild-type and GLP-1R knockout mice. Likewise, DPP-4 inhibition or the DPP-4 substrates substance P or C-X-C motif chemokine ligand 12 (CXCL12) improved contractile recovery after no-flow ischemia in the hearts of otherwise healthy young adult mice. Either DPP-4 inhibition or CXCL12 increased phosphorylation of the Ca²⁺ regulatory protein phospholamban (PLN), and CXCL12 directly enhanced cardiomyocyte Ca²⁺ flux. In contrast, hearts of aged obese diabetic mice (which may better mimic the comorbid patient population) had diminished levels of PLN phosphorylation. In this setting, CXCL12 paradoxically impaired cardiac contractility in a phosphoinositide 3-kinase γ-dependent manner. These findings indicate that the cardiac effects of DPP-4 inhibition primarily occur through GLP-1R-independent processes and that ostensibly beneficial DPP-4 substrates can paradoxically worsen heart function in the presence of comorbid diabetes.

Cardioprotective Effect of the SDF-1α/CXCR4 Axis in Ischemic Postconditioning in Isolated Rat Hearts

BACKGROUND AND OBJECTIVES

Information about the role of the stromal cell-derived factor-1α (SDF-1α)/chemokine receptor type 4 (CXCR4) axis in ischemic postconditioning (IPOC) is currently limited. We hypothesized that the SDF-1α/CXCR4 signaling pathway is directly involved in the cardioprotective effect of IPOC.

METHODS

Isolated rat hearts were divided into four groups. The control group was subjected to 30-min of regional ischemia and 2-hour of reperfusion (n=12). The IPOC group was induced with 6 cycles of 10-second reperfusion and 10-second global ischemia (n=8) in each cycle. The CXCR4 antagonist, AMD3100, was applied before reperfusion in the IPOC group (AMD+IPOC group, n=11) and control group (AMD group, n=9). Hemodynamic changes with electrocardiography were monitored and infarct size was measured. The SDF-1α, lactate dehydrogenase (LDH) and creatine kinase (CK) concentrations in perfusate were measured. We also analyzed extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt phosphorylation state expression.

RESULTS

IPOC significantly reduced infarct size, but AMD3100 attenuated the infarct reducing effect of IPOC. IPOC significantly decreased LDH and CK, but these effects were reversed by AMD3100. ERK1/2 and Akt phosphorylation increased with IPOC and these effects were blocked by AMD3100.

CONCLUSION

Based on the results of this study, SDF-1α/CXCR4 signaling may be involved in IPOC cardioprotection and this signaling pathway couples to the ERK1/2 and Akt pathways.

Mitochondrial ATP-Sensitive Potassium Channels Play a Role in Reducing Both Myocardial Infarction and Reperfusion Arrhythmia in Remote Ischemic Preconditioned Hearts

Background

Mitochondrial ATP-sensitive potassium (mKATP) channels play a role in reperfusion arrhythmias (RAs) in ischemia-reperfusion (I/R) injury. Evidence suggests that remote ischemic preconditioning (RIPC) reduces RAs, however not much is known on the mechanistic role of mKATP in RIPC. We evaluated whether mKATP channels are associated with reducing arrhythmia and infarct size in RIPC.

Methods

Isolated rat hearts received 30 minutes of regional ischemia followed by 2 hours of reperfusion through the Langendorff perfusion system. RIPC was induced by 3 cycles of 5 minutes occlusion and 5 minutes release of the bilateral femoral artery. The animals were randomly divided into 4 groups as follows: 1) CON, I/R injury but not RIPC, 2) RIPC, 3) HD+RIPC, pretreatment of the selective mKATP channel blocker, 5-hydroxydecanoate (5-HD), in RIPC, and 4) HD, pretreatment of 5-HD in CON. Cardiodynamics and infarct size were determined. The severity of arrhythmia was quantitated via the Curtis and Walker scoring system as well as the Lepran scoring system.

Results

RIPC significantly reduced the infarct size over AR (25.7 ± 2.6%) compared to CON (37.0 ± 2.6%, P < 0.05). The selective mKATP channel blocker 5-HD significantly inhibited the infarct-reducing effect of RIPC (39.3 ± 3.0%, P < 0.05 vs. RIPC). Additionally, RIPC significantly reduced the arrhythmia score compared to CON (14.6 ± 1.9 to 8.7 ± 0.4, P = 0.023, by Curtis and Walker’s system, 16.1 ± 2.1 to 9.1 ± 0.5, P = 0.006, by Lepran’s system). The anti-arrhythmic effect of RIPC was blocked by 5-HD (15.5 ± 1.6 and 16.0 ± 1.2, by Curtis and Walker’s and Lepran’s system, respectively).

Conclusions

The selective mKATP channel blocker, 5-HD, inhibited the infarct-limitation and anti-arrhythmic effect of RIPC. The mKATP channels play a role in the reduction of both infarct size and RAs in RIPC.

Lack of an Association between the SDF-1 rs1801157 Polymorphism and Coronary Heart Disease: A Meta-Analysis

Recent studies have shown that the single-nucleotide polymorphism (SNP) rs1801157 in the stromal cell-derived factor (SDF)-1 gene is associated with susceptibility to coronary heart disease (CHD). However, published studies have shown inconsistent results. Therefore, a meta-analysis was carried out to evaluate the association between rs1801157 and CHD in the literature. A systematic literature search was performed using the PubMed, Web of Science, Cochrane Library, Chinese National Knowledge Infrastructure and Chinese Wan Fang databases. Heterogeneity and publication bias were also evaluated. Seven eligible studies that involved 4656 cases and 2654 controls were finally included in this meta-analysis. Overall, the results showed that the rs1801157 polymorphism was not statistically associated with the risk of CHD under all genetic models but that rs1801157 was associated with decreased susceptibility to myocardial infarction (MI) in subgroup analyses. Moreover, no association was found between rs1801157 and the susceptibility to CHD in either Caucasians or Asians. In conclusion, our meta-analysis demonstrated that the rs1801157 polymorphism is not associated with the susceptibility to CHD but may be associated with a decreased risk of MI. However, further large-scale, case-control studies with rigorous designs should be conducted to confirm these conclusions.

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.

Protein kinase G1 α overexpression increases stem cell survival and cardiac function after myocardial infarction

BACKGROUND

We hypothesized that overexpression of cGMP-dependent protein kinase type 1α (PKG1α) could mimic the effect of tadalafil on the survival of bone marrow derived mesenchymal stem cells (MSCs) contributing to regeneration of the ischemic heart.

METHODS AND RESULTS

MSCs from male rats were transduced with adenoviral vector encoding for PKG1α ((PKG1α)MSCs).Controls included native MSCs ((Nat)MSCs) and MSCs transduced with an empty vector ((Null)MSCs). PKG1α activity was increased approximately 20, 5 and 16 fold respectively in (PKG1α)MSCs. (PKG1α)MSCs showed improved survival under oxygen and glucose deprivation (OGD) which was evidenced by lower LDH release, caspase-3/7 activity and number of positive TUNEL cells. Anti-apoptotic proteins pAkt, pGSK3β, and Bcl-2 were significantly increased in (PKG1α)MSCs compared to (Nat)MSCs and (Null)MSCs. Higher release of multiple prosurvival and angiogenic factors such as HGF, bFGF, SDF-1 and Ang-1 was observed in (PKG1α)MSCs before and after OGD. In a female rat model of acute myocardial infarction, (PKG1α)MSCs group showed higher survival compared with (Null)MSCs group at 3 and 7 days after transplantation as determined by TUNEL staining and sry-gene quantitation by real-time PCR. Increased anti-apoptotic proteins and paracrine factors in vitro were also identified. Immunostaining for cardiac troponin I combined with GFP showed increased myogenic differentiation of (PKG1α)MSCs. At 4 weeks after transplantation, compared to DMEM group and (Null)MSCs group, (PKG1α)MSCs group showed increased blood vessel density in infarct and peri-infarct areas (62.5±7.7; 68.8±7.3 per microscopic view, p<0.05) and attenuated infarct size (27.2±2.5%, p<0.01). Heart function indices including ejection fraction (52.1±2.2%, p<0.01) and fractional shortening (24.8%±1.3%, p<0.01) were improved significantly in (PKG1α)MSCs group.

CONCLUSION

Overexpression of PKG1α transgene could be a powerful approach to improve MSCs survival and their angiomyogenic potential in the infarcted heart.