Deletion of the EphA2 receptor exacerbates myocardial injury and the progression of ischemic cardiomyopathy

Recent advances of the Ephrin and Eph family in cardiovascular development and pathologies

Erythropoietin-producing hepatoma (Eph) receptors, comprising the largest family of receptor tyrosine kinases (RTKs), exert profound influence on diverse biological processes and pathological conditions such as cancer. Interacting with their corresponding ligands, erythropoietin-producing hepatoma receptor interacting proteins (Ephrins), Eph receptors regulate crucial events like embryonic development, tissue boundary formation, and tumor cell survival. In addition to their well-established roles in embryonic development and cancers, emerging evidence highlights the pivotal contribution of the Ephrin/Eph family to cardiovascular physiology and pathology. Studies have elucidated their involvement in cardiovascular development, atherosclerosis, postnatal angiogenesis, and, more recently, cardiac fibrosis and calcification, suggesting a promising avenue for therapeutic interventions in cardiovascular diseases. There remains a need for a comprehensive synthesis of their collective impact in the cardiovascular context. By exploring the intricate interactions between Eph receptors, ephrins, and cardiovascular system, this review aims to provide a holistic understanding of their roles and therapeutic potential in cardiovascular health and diseases.

EphA2 signaling within integrin adhesions regulates fibrillar adhesion elongation and fibronectin deposition

The multifunctional glycoprotein fibronectin influences several crucial cellular processes and contributes to multiple pathologies. While a link exists between fibronectin-associated pathologies and the receptor tyrosine kinase EphA2, the mechanism by which EphA2 promotes fibronectin matrix remodeling remains unknown. We previously demonstrated that EphA2 deletion reduces smooth muscle fibronectin deposition and blunts fibronectin deposition in atherosclerosis without influencing fibronectin expression. We now show that EphA2 expression is required for contractility-dependent elongation of tensin- and α5β1 integrin-rich fibrillar adhesions that drive fibronectin fibrillogenesis. Mechanistically, EphA2 localizes to integrin adhesions where focal adhesion kinase mediates ligand-independent Y772 phosphorylation, and mutation of this site significantly blunts fibrillar adhesion length. EphA2 deficiency decreases smooth muscle cell contractility by enhancing p190RhoGAP activation and reducing RhoA activity, whereas stimulating RhoA signaling in EphA2 deficient cells rescues fibrillar adhesion elongation. Together, these data identify EphA2 as a novel regulator of fibrillar adhesion elongation and provide the first data identifying a role for EphA2 signaling in integrin adhesions.

Diagnostic Value of Circulating Progranulin and Its Receptor EphA2 in Predicting the Atheroma Burden in Patients with Coronary Artery Disease

Background

Progranulin (PGRN) and its potential receptor Eph-receptor tyrosine kinase-type A2 (EphA2) are inflammation-related molecules that present on the atherosclerotic plaques. However, the roles of circulating PGRN and EphA2 in coronary artery disease (CAD) remain unclear.

Objective

To study the clinical significance of circulating PGRN and EphA2 levels in Chinese patients undergoing coronary angiography.

Methods

Levels of circulating EphA2 fragments and PGRN were examined in 201 consecutive individuals who underwent coronary angiography for suspected CAD in our center from Jan 2020 to Oct 2020. Demographic characteristics, results of biochemical and auxiliary examinations, and other relevant information were collected. The coronary atheroma burden was quantified by the Gensini score and the existence of chronic total occlusion (CTO). Univariate analysis and multivariate logistic regression analysis were used to analyze the risk factors for acute coronary syndrome (ACS). In patients with ACS and SAP, a receiver operating characteristic (ROC) curve was generated to detect the accuracy and discriminative ability of levels of EphA2 and PGRN, the Gensini score, and cardiac injury biomarkers as surrogate endpoints for CTO.

Results

Circulating EphA2 levels were significantly higher in patients with ACS than in subjects with stable angina pectoris (SAP) or control subjects (p < 0.001). A positive linear correlation was verified between EphA2 levels and the Gensini score (r = 0.306, p < 0.001), and negative correlation was detected with the left ventricular ejection fraction (LVEF) (r = −0.405, p < 0.001). Both PGRN and EphA2 were positively associated with cardiac injury biomarkers (i.e., NT-proBNP, cTnT, and hs-CRP) (p < 0.05). The area under the ROC curve of PGRN and EphA2 was 0.604 and 0.686, respectively (p < 0.01).

Conclusions

Higher circulating EphA2 and PGRN levels were detected in patients with ACS than in patients with SAP. Circulating EphA2 and PGRN levels might be diagnostic factors for predicting the atheroma burden in patients with CAD.

Neuronal guidance proteins in cardiovascular inflammation

Cardiovascular pathologies are often induced by inflammation. The associated changes in the inflammatory response influence vascular endothelial biology; they complicate the extent of ischaemia and reperfusion injury, direct the migration of immune competent cells and activate platelets. The initiation and progression of inflammation is regulated by the classical paradigm through the system of cytokines and chemokines. Therapeutic approaches have previously used this knowledge to control the extent of cardiovascular changes with varying degrees of success. Neuronal guidance proteins (NGPs) have emerged in recent years and have been shown to be significantly involved in the control of tissue inflammation and the mechanisms of immune cell activation. Therefore, proteins of this class might be used in the future as targets to control the extent of inflammation in the cardiovascular system. In this review, we describe the role of NGPs during cardiovascular inflammation and highlight potential therapeutic options that could be explored in the future.

EphrinA1-Fc Attenuates Ventricular Remodeling and Dysfunction in Chronically Nonreperfused WT but not EphA2-R-M mice

Background: EphrinA1-Fc abolishes acute I/R injury and attenuates nonreperfused cardiac injury 4 days after permanent occlusion in mice. The goal of this study was to assess the capacity of a single intramyocardial administration of ephrinA1-Fc at the time of coronary artery ligation, to determine the degree to which early salvage effects translate to reduced adverse remodeling after 4 weeks of nonreperfused myocardial infarction (MI) in wild-type B6 and EphA2-R-M (EphA2 receptor null) mice. Methods: At 4 weeks post-MI, echocardiography, histologic and immunohistochemical analyses of B6 mouse hearts were performed. Primary mouse cardiac fibroblasts (FBs) isolated from B6 mice cultured in the presence of low and high dose ephrinA1-Fc, both with and without pro-fibrotic TGF-β stimulation and Western blots, were probed for relative expression of remodeling proteins MMP-2, MMP-9 and TIMP-1, in addition to DDR2 and (p)SMAD2/3/totalSMAD2/3. Results: EphrinA1-Fc preserved a significant degree of contractile function, decreased adverse left ventricular remodeling, attenuated excessive compensatory hypertrophy, and decreased interstitial fibrosis in wild-type (WT) B6 mouse hearts. In contrast, most of these parameters were poorer in ephrinA1-Fc-treated EphA2-R-M mice. Of note, fibrosis was proportionately decreased, implying that other EphA receptor(s) are more important in regulating the pro-fibrotic response. Primary FBs showed disparate alteration of MMP-2, MMP-9 and TIMP-1, as well as DDR2 and p-SMAD2/3/totalSMAD2/3, which indicates that matrix remodeling and cardiac fibrosis in the injured heart are influenced by ephrinA1-Fc. Conclusion: This study demonstrates the capacity of a single administration of ephrinA1-Fc at the onset of injury to attenuate long-term nonreperfused post-MI ventricular remodeling that results in progressive heart failure, and the important role of EphA2 in mitigating the deleterious effects.

Harnessing the Power of Eph/ephrin Biosemiotics for Theranostic Applications

Comprehensive basic biological knowledge of the Eph/ephrin system in the physiologic setting is needed to facilitate an understanding of its role and the effects of pathological processes on its activity, thereby paving the way for development of prospective therapeutic targets. To this end, this review briefly addresses what is currently known and being investigated in order to highlight the gaps and possible avenues for further investigation to capitalize on their diverse potential.

Tyrosine kinase Eph receptor A6 sensitizes glioma-initiating cells towards bone morphogenetic protein-induced apoptosis

Bone morphogenetic protein (BMP) signaling plays important roles in glioblastoma multiforme (GBM), a lethal form of brain tumor. BMP reduces GBM tumorigenicity through its differentiation‐ and apoptosis‐inducing effects on glioma‐initiating cells (GIC). However, some GIC do not respond to the tumor suppressive effects of BMP. Using a phosphoreceptor tyrosine kinase array, we found that EPHA6 (erythropoietin‐producing hepatocellular carcinoma receptor A6) phosphorylation was regulated by BMP‐2 signaling in some GIC. Analysis of The Cancer Genome Atlas showed that EPHA6 expression was lower in patients with GBM than in the normal brain, and that high EPHA6 expression was correlated with better prognosis. EPHA6 receptor increased the susceptibility of both sensitive and resistant GIC to BMP‐2‐induced apoptosis. The cooperative effect on apoptosis induction depended on the kinase activity of BMP type I receptor but was independent of EPHA6 kinase function. Overexpression of the EPHA6 receptor in GIC resulted in the formation of a protein complex of EPHA6 receptor and the BMP type I receptor ALK‐2, which was associated with BMP‐induced apoptosis in GIC. Intracranial injection of GIC into nude mice showed that gain‐of‐function of EPHA6 together with BMP‐2 pretreatment slowed GBM tumor progression in the mouse brain and promoted mouse survival. In summary, EPHA6 together with BMP‐2 signaling led to apoptotic cell death in GIC, and thus is a putative tumor suppressor in GBM.

Receptor tyrosine kinase profiling of ischemic heart identifies ROR1 as a potential therapeutic target

BACKGROUND

Receptor tyrosine kinases (RTK) are potential targets for the treatment of ischemic heart disease. The human RTK family consists of 55 members, most of which have not yet been characterized for expression or activity in the ischemic heart.

METHODS

RTK gene expression was analyzed from human heart samples representing healthy tissue, acute myocardial infarction or ischemic cardiomyopathy. As an experimental model, pig heart with ischemia-reperfusion injury, caused by cardiopulmonary bypass, was used, from which phosphorylation status of RTKs was assessed with a phospho-RTK array. Expression and function of one RTK, ROR1, was further validated in pig tissue samples, and in HL-1 cardiomyocytes and H9c2 cardiomyoblasts, exposed to hypoxia and reoxygenation. ROR1 protein level was analyzed by Western blotting. Cell viability after ROR1 siRNA knockdown or activation with Wnt-5a ligand was assessed by MTT assays.

RESULTS

In addition to previously characterized RTKs, a group of novel active and regulated RTKs was detected in the ischemic heart. ROR1 was the most significantly upregulated RTK in human ischemic cardiomyopathy. However, ROR1 phosphorylation was suppressed in the pig model of ischemia-reperfusion and ROR1 phosphorylation and expression were down-regulated in HL-1 cardiomyocytes subjected to short-term hypoxia in vitro. ROR1 expression in the pig heart was confirmed on protein and mRNA level. Functionally, ROR1 activity was associated with reduced viability of HL-1 cardiomyocytes in both normoxia and during hypoxia-reoxygenation.

CONCLUSIONS

Several novel RTKs were found to be regulated in expression or activity in ischemic heart. ROR1 was one of the most significantly regulated RTKs. The in vitro findings suggest a role for ROR1 as a potential target for the treatment of ischemic heart injury.

Anatomical-Molecular Distribution of EphrinA1 in Infarcted Mouse Heart Using MALDI Mass Spectrometry Imaging

EphrinA1 is a tyrosine kinase receptor localized in the cellular membrane of healthy cardiomyocytes, the expression of which is lost upon myocardial infarction (MI). Intra-cardiac injection of the recombinant form of ephrinA1 (ephrinA1-Fc) at the time of ligation in mice has shown beneficial effects by reducing infarct size and myocardial necrosis post-MI. To date, immunohistochemistry and Western blotting comprise the only experimental approaches utilized to localize and quantify relative changes of ephrinA1 in sections and homogenates of whole left ventricle, respectively. Herein, we used matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) coupled with a time-of-flight mass spectrometer (MALDI/TOF MS) to identify intact as well as tryptic fragments of ephrinA1 in healthy controls and acutely infarcted murine hearts. The purpose of the present study was 3-fold: (1) to spatially resolve the molecular distribution of endogenous ephrinA1, (2) to determine the anatomical expression profile of endogenous ephrinA1 after acute MI, and (3) to identify molecular targets of ephrinA1-Fc action post-MI. The tryptic fragments detected were identified as the ephrinA1-isoform with 38% and 34% sequence coverage and Mascot scores of 25 for the control and MI hearts, respectively. By using MALDI-MSI, we have been able to simultaneously measure the distribution and spatial localization of ephrinA1, as well as additional cardiac proteins, thus offering valuable information for the elucidation of molecular partners, mediators, and targets of ephrinA1 action in cardiac muscle. Graphical Abstract ᅟ.

EphrinA1-Fc attenuates myocardial ischemia/reperfusion injury in mice

EphrinA1, a membrane-bound receptor tyrosine kinase ligand expressed in healthy cardiomyocytes, is lost in injured cells following myocardial infarction. Previously, we have reported that a single intramyocardial injection of chimeric ephrinA1-Fc at the time of ischemia reduced injury in the nonreperfused myocardium by 50% at 4 days post-MI by reducing apoptosis and inflammatory cell infiltration. In a clinically relevant model of acute ischemia (30min)/reperfusion (24hr or 4 days) injury, we now demonstrate that ephrinA1-Fc reduces infarct size by 46% and completely preserves cardiac function (ejection fraction, fractional shortening, and chamber dimensions) in the short-term (24hrs post-MI) as well as long-term (4 days). At 24 hours post-MI, diminished serum inflammatory cell chemoattractants in ephrinA1-Fc-treated mice reduces recruitment of neutrophils and leukocytes into the myocardium. Differences in relative expression levels of EphA-Rs are described in the context of their putative role in mediating cardioprotection. Validation by Western blotting of selected targets from mass spectrometry analyses of pooled samples of left ventricular tissue homogenates from mice that underwent 30min ischemia and 24hr of reperfusion (I/R) indicates that ephrinA1-Fc administration alters several regulators of signaling pathways that attenuate apoptosis, promote autophagy, and shift from FA metabolism in favor of increased glycolysis to optimize anaerobic ATP production. Taken together, reduced injury is due a combination of adaptive metabolic reprogramming, improved cell survival, and decreased inflammatory cell recruitment, suggesting that ephrinA1-Fc enhances the capacity of the heart to withstand an ischemic insult.

Current Understanding of the Pathways Involved in Adult Stem and Progenitor Cell Migration for Tissue Homeostasis and Repair

With the advancements in the field of adult stem and progenitor cells grows the recognition that the motility of primitive cells is a pivotal aspect of their functionality. There is accumulating evidence that the recruitment of tissue-resident and circulating cells is critical for organ homeostasis and effective injury responses, whereas the pathobiology of degenerative diseases, neoplasm and aging, might be rooted in the altered ability of immature cells to migrate. Furthermore, understanding the biological machinery determining the translocation patterns of tissue progenitors is of great relevance for the emerging methodologies for cell-based therapies and regenerative medicine. The present article provides an overview of studies addressing the physiological significance and diverse modes of stem and progenitor cell trafficking in adult mammalian organs, discusses the major microenvironmental cues regulating cell migration, and describes the implementation of live imaging approaches for the exploration of stem cell movement in tissues and the factors dictating the motility of endogenous and transplanted cells with regenerative potential.

EphA2-receptor deficiency exacerbates myocardial infarction and reduces survival in hyperglycemic mice

Background

We have previously shown that EphrinA1/EphA expression profile changes in response to myocardial infarction (MI), exogenous EphrinA1-Fc administration following MI positively influences wound healing, and that deletion of the EphA2 Receptor (EphA2-R) exacerbates injury and remodeling. To determine whether or not ephrinA1-Fc would be of therapeutic value in the hyperglycemic infarcted heart, it is critical to evaluate how ephrinA1/EphA signaling changes in the hyperglycemic myocardium in response to MI.

Methods

Streptozotocin (STZ)-induced hyperglycemia in wild type (WT) and EphA2-receptor mutant (EphA2-R-M) mice was initiated by an intraperitoneal injection of STZ (150 mg/kg) 10 days before surgery. MI was induced by permanent ligation of the left anterior descending coronary artery and analyses were performed at 4 days post-MI. ANOVAs with Student-Newman Keuls multiple comparison post-hoc analysis illustrated which groups were significantly different, with significance of at least p < 0.05.

Results

Both WT and EphA2-R-M mice responded adversely to STZ, but only hyperglycemic EphA2-R-M mice had lower ejection fraction (EF) and fractional shortening (FS). At 4 days post-MI, we observed greater post-MI mortality in EphA2-R-M mice compared with WT and this was greater still in the EphA2-R-M hyperglycemic mice. Although infarct size was greater in hyperglycemic WT mice vs normoglycemic mice, there was no difference between hyperglycemic EphA2-R-M mice and normoglycemic EphA2-R-M mice. The hypertrophic response that normally occurs in viable myocardium remote to the infarct was noticeably absent in epicardial cardiomyocytes and cardiac dysfunction worsened in hyperglycemic EphA2-R-M hearts post-MI. The characteristic interstitial fibrotic response in the compensating myocardium remote to the infarct also did not occur in hyperglycemic EphA2-R-M mouse hearts to the same extent as that observed in the hyperglycemic WT mouse hearts. Differences in neutrophil and pan-leukocyte infiltration and serum cytokines implicate EphA2-R in modulation of injury and the differences in ephrinA1 and EphA6-R expression in governing this are discussed.

Conclusions

We conclude that EphA2-mutant mice are more prone to hyperglycemia-induced increased injury, decreased survival, and worsened LV remodeling due to impaired wound healing.