Role of MIF in myocardial ischaemia and infarction: insight from recent clinical and experimental findings

Impact of the MIF -173G/C variant on cardiovascular disease risk: a meta-analysis of 9,047 participants

Introduction

Many factors contribute to the risk of cardiovascular disease (CVD), an umbrella term for several different heart diseases, including inflammation. Macrophage migration inhibitory factor (MIF) is an important immune modulator that has been shown to be involved in the pathogenesis of different heart diseases, so understanding pathogenic variants of the MIF gene is important for risk stratification. We therefore conducted a meta-analysis to investigate whether the MIF -173G/C (rs755622) polymorphism is associated with CVD.

Methods

The PubMed, Science Direct, and Embase databases were searched from inception to June 2023 for case-control studies of the MIF -173G/C polymorphism and its relationship to any type of CVD. Correlations between the MIF -173G/C polymorphism and CVD were estimated by pooling the odds ratios (ORs) with 95% confidence intervals in allelic, dominant, and recessive models using random-effects meta-analysis.

Results

A total of 9,047 participants (4141 CVD cases and 4906 healthy controls) from 11 relevant studies were included. In the total population, there was no significant association between the MIF -173G/C (rs755622) polymorphism and the risk of developing CVD in the three different models. In a stratified analysis by ethnicity, the allelic model (C vs G) was significantly associated with CVD in the Arab and Asian populations (OR = 0.56, CI 0.42 -0.75 and OR = 1.28, CI 1.12 -1.46, respectively); the dominant model (CC+CG vs GG) was significantly associated with CVD in the Arab population (OR = 0.42, CI 0.30 -0.61); while the recessive model (GG+GC vs CC) was associated with CVD susceptibility in the Arab population (OR = 3.84, CI 1.57 -9.41). There were no significant associations between the MIF -173 G/C polymorphism and CVD risk in the European population. Conclusion, the MIF -173G/C polymorphism is associated with CVD in some populations.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, PROSPERO (CRD42023441139).

The relevance of serum macrophage migratory inhibitory factor and cognitive dysfunction in patients with cerebral small vascular disease

Cerebral small vascular disease (CSVD) is a common type of cerebrovascular disease, and an important cause of vascular cognitive impairment (VCI) and stroke. The disease burden is expected to increase further as a result of population aging, an ongoing high prevalence of risk factors (e.g., hypertension), and inadequate management. Due to the poor understanding of pathophysiology in CSVD, there is no effective preventive or therapeutic approach for CSVD. Macrophage migration inhibitory factor (MIF) is a multifunctional cytokine that is related to the occurrence and development of vascular dysfunction diseases. Therefore, MIF may contribute to the pathogenesis of CSVD and VCI. Here, reviewed MIF participation in chronic cerebral ischemia-hypoperfusion and neurodegeneration pathology, including new evidence for CSVD, and its potential role in protection against VCI.

Elevated plasma macrophage migration inhibitor factor is associated with hypertension and hypertensive left ventricular hypertrophy

Previous studies have found that the macrophage migration inhibitor factor is associated with endothelial dysfunction and ventricular remodelling. The aim of this study was to explore the potential relationship between plasma macrophage migration inhibitor factor levels and hypertension and hypertensive left ventricular hypertrophy. A total of 308 participants (including 187 uncomplicated hypertensive patients and 121 healthy controls) were enroled from 2017 to 2019. The association between macrophage migration inhibitor factors and hypertension and hypertensive left ventricular hypertrophy was estimated with univariate and multivariate logistic regression models. Elevated macrophage migration inhibitor factor was associated with the development of hypertension (second tertile: adjusted OR, 2.27, 95% CI, 1.24-4.16, P = 0.008; third tertile: adjusted OR, 5.43, 95% CI, 2.75-10.71, P < 0.001; compared with the first tertile). In addition, we assessed the association between macrophage migration inhibitor factor and left ventricular hypertrophy in hypertensive patients (n = 187). Plasma macrophage migration inhibitor factor was significantly correlated with hypertensive left ventricular mass index (r = 0.580, P < 0.001). In patients with hypertension, an elevated macrophage migration inhibitor factor was significantly associated with hypertensive left ventricular hypertrophy (second tertile: adjusted OR, 3.20, 95% CI, 1.17-8.78, P = 0.024; third tertile: adjusted OR, 24.95, 95% CI, 8.72-71.41, P < 0.001; compared with the first tertile). Receiver operating characteristic analysis indicated that macrophage migration inhibitor factor had reasonable predictive accuracy for the development of hypertensive left ventricular hypertrophy (area under curve 0.84, 95% CI 0.78-0.90, P < 0.001). Our data indicated that elevated macrophage migration inhibitor factor is associated with hypertension and hypertensive left ventricular hypertrophy.

D-dopachrome tautomerase in cardiovascular and inflammatory diseases-A new kid on the block or just another MIF?

Macrophage migration inhibitory factor (MIF) as well as its more recently described structural homolog D-dopachrome tautomerase (D-DT), now also termed MIF-2, are atypical cytokines and chemokines with key roles in host immunity. They also have an important pathogenic role in acute and chronic inflammatory conditions, cardiovascular diseases, lung diseases, adipose tissue inflammation, and cancer. Although our mechanistic understanding of MIF-2 is relatively limited compared to the extensive body of evidence available for MIF, emerging data suggests that MIF-2 is not only a functional phenocopy of MIF, but may have differential or even oppositional activities, depending on the disease and context. In this review, we summarize and discuss the similarities and differences between MIF and MIF-2, with a focus on their structures, receptors, signaling pathways, and their roles in diseases. While mainly covering the roles of the MIF homologs in cardiovascular, inflammatory, autoimmune, and metabolic diseases, we also discuss their involvement in cancer, sepsis, and chronic obstructive lung disease (COPD). A particular emphasis is laid upon potential mechanistic explanations for synergistic or cooperative activities of the MIF homologs in cancer, myocardial diseases, and COPD as opposed to emerging disparate or antagonistic activities in adipose tissue inflammation, metabolic diseases, and atherosclerosis. Lastly, we discuss potential future opportunities of jointly targeting MIF and MIF-2 in certain diseases, whereas precision targeting of only one homolog might be preferable in other conditions. Together, this article provides an update of the mechanisms and future therapeutic avenues of human MIF proteins with a focus on their emerging, surprisingly disparate activities, suggesting that MIF-2 displays a variety of activities that are distinct from those of MIF.

Prediction of one-year adverse clinical outcomes by macrophage migration inhibitory factor in stemi patients

Biomarkers have taken one of the first places as diagnostic and prognostic tools in ST-segment elevation myocardial infarction (STEMI) and are consequently widely used as predictors of short-term and long-term prognosis. One of the promising biomarkers for early cardiovascular outcomes prediction is the pro-inflammatory cytokine macrophage migration inhibitory factor (MIF). The aim of the study was to elucidate a plausible predictive value of the MIF levels for one-year clinical outcomes in STEMI patients who underwent primary percutaneous coronary intervention (PCI). Materials and methods. 134 STEMI patients were enrolled in the study after receiving voluntary informed consent. All patients underwent conventional investigations, and additionally, the MIF levels were determined at baseline, directly before and after PCI. During 1-year follow-up, 37 % of patients reached the endpoint, which was composite and included all-cause mortality, non-fatal myocardial infarction, non-fatal stroke, hospitalization for unstable angina, heart failure decompensation, and urgent revascularization. Results. We have found that pre-PCI MIF levels > 3934 pg/mL (AUC=0.7; 95 % CI 0.578 to 0.753; Youden index=0.31; p=0.008) might be an independent predictor of composite endpoints with sensitivity 54 % and specificity 82 %. A positive correlation between MIF and inflammatory biomarkers was revealed (WBC count r=0.33, p=0.0001; CRP r=0.19, p=0.032). Adverse outcomes associated with higher pre- and post-PCI MIF levels (OR 1.0, 95 % CI 1.0001–1.0008; p=0.013 and OR 1.0, 95 % CI 1.0001–1.0009; p=0.019) and CRP that determined during the first week after the event (OR 1.0, 95 % CI 1.005–1.2, p=0.03). Kaplan-Meier analysis has shown a substantially lower long-term survival rate in patients with a MIF level > 3493 pg/ml compared to a MIF level ≤ 3493 pg/ml (Log rank=0.00025). Conclusions. The MIF levels exceeding 3934 ng/ml were associated with a higher risk of one-year adverse clinical outcomes in STEMI patients who underwent primary PCI.

Obstructive Sleep Apnea Syndrome In Vitro Model: Controlled Intermittent Hypoxia Stimulation of Human Stem Cells-Derived Cardiomyocytes

Cardiovascular morbidity is the leading cause of death of obstructive sleep apnea (OSA) syndrome patients. Nocturnal airway obstruction is associated with intermittent hypoxia (IH). In our previous work with cell lines, incubation with sera from OSA patients induced changes in cell morphology, NF-κB activation and decreased viability. A decrease in beating rate, contraction amplitude and a reduction in intracellular calcium signaling was also observed in human cardiomyocytes differentiated from human embryonic stem cells (hESC-CMs). We expanded these observations using a new controlled IH in vitro system on beating hESC-CMs. The Oxy-Cycler system was programed to generate IH cycles. Following IH, we detected the activation of Hif-1α as an indicator of hypoxia and nuclear NF-κB p65 and p50 subunits, representing pro-inflammatory activity. We also detected the secretion of inflammatory cytokines, such as MIF, PAI-1, MCP-1 and CXCL1, and demonstrated a decrease in beating rate of hESC-CMs following IH. IH induces the co-activation of inflammatory features together with cardiomyocyte alterations which are consistent with myocardial damage in OSA. This study provides an innovative approach for in vitro studies of OSA cardiovascular morbidity and supports the search for new pharmacological agents and molecular targets to improve diagnosis and treatment of patients.

Long-term prognostic value of macrophage migration inhibitory factor in ST-segment elevation myocardial infarction patients with metabolic syndrome after percutaneous coronary intervention

Metabolic syndrome (MetS) is a major risk factor for cardiovascular disease and negatively affecting the prognosis of patients with ST elevation myocardial infarction (STEMI). Macrophage migration inhibitory factor (MIF) is a multipotent cytokine involved in various cardiovascular and inflammatory diseases. In this prospective study, we investigate the value of MIF in the long-term prognosis of STEMI combined with MetS after emergency PCI. Circulating MIF levels were measured at admission, and major adverse cardiovascular and cerebrovascular events (MACCE) were monitored during the follow-up period of 4.9 (3.9–5.8) years. MACCE occurred in 92 patients (22.9%), which was significantly higher in MetS (69/255, 27.1%) than in the non-MS subgroup (23/146, 15.8%, P < 0.05). Patients with MetS developed MACCE had the highest admission MIF level. Kaplan-Meier survival analysis using the cutoff value of admission MIF (143 ng/ml) showed that patients with a higher MIF level had a greater incidence of MACCE than those with lower MIF levels in both the MetS (P < 0.0001) and non-MetS groups (P = 0.016). After adjustment for clinical variables, the value of MIF ≥ 143 ng/ml still had the predictive power for the MetS group [HR 9.56, 95% CI (5.397–16.944),P < 0.001]; nevertheless, it was not the case in the non-MetS group. Our findings indicated that MetS is a critical risk factor for adverse clinical outcomes in patients with STEMI, and a high admission MIF level has predictive power for the long-term MACCE, which is superior in STEMI patients with MetS and better than other traditional predictors.

Short-Term Blockade of Pro-Inflammatory Alarmin S100A9 Favorably Modulates Left Ventricle Proteome and Related Signaling Pathways Involved in Post-Myocardial Infarction Recovery

Prognosis after myocardial infarction (MI) varies greatly depending on the extent of damaged area and the management of biological processes during recovery. Reportedly, the inhibition of the pro-inflammatory S100A9 reduces myocardial damage after MI. We hypothesize that a S100A9 blockade induces changes of major signaling pathways implicated in post-MI healing. Mass spectrometry-based proteomics and gene analyses of infarcted mice left ventricle were performed. The S100A9 blocker (ABR-23890) was given for 3 days after coronary ligation. At 3 and 7 days post-MI, ventricle samples were analyzed versus control and Sham-operated mice. Blockade of S100A9 modulated the expressed proteins involved in five biological processes: leukocyte cell–cell adhesion, regulation of the muscle cell apoptotic process, regulation of the intrinsic apoptotic signaling pathway, sarcomere organization and cardiac muscle hypertrophy. The blocker induced regulation of 36 proteins interacting with or targeted by the cellular tumor antigen p53, prevented myocardial compensatory hypertrophy, and reduced cardiac markers of post-ischemic stress. The blockade effect was prominent at day 7 post-MI when the quantitative features of the ventricle proteome were closer to controls. Blockade of S100A9 restores key biological processes altered post-MI. These processes could be valuable new pharmacological targets for the treatment of ischemic heart. Mass spectrometry data are available via ProteomeXchange with identifier PXD033683.

Expression profile of macrophage migration inhibitory factor in periodontitis

OBJECTIVE

Macrophage migration inhibitory factor (MIF) is a pivotal mediator of host innate immunity and influences the development of several inflammatory diseases. The role of MIF in periodontitis is unclear.

METHODS

Eighteen periodontally healthy volunteers and 18 patients with stage III or IV periodontitis were enrolled. Blood samples and gingival tissues were collected from all individuals. The serum concentrations of MIF and MCP-1 were measured by ELISA. The protein and mRNA levels of MIF and MCP-1 in gingival tissue were evaluated by immunohistochemical staining and quantitative PCR. The levels of secreted MIF and MCP-1, as well as their mRNA levels, were determined by ELISA and quantitative PCR in oral epithelial cells infected with Porphyromonas gingivalis.

RESULTS

After adjusting for age, the level of MCP-1 was significantly higher in the serum and gingival tissue of periodontitis patients, as well as in infected epithelial cells. The serum concentration of MIF was increased in periodontitis patients (15.25 ± 2.16 ng/mL, P < 0.05) compared to healthy controls (10.43 ± 1.02 ng/mL). Increased MIF immunoreactivity was found in gingival epithelial tissue but not in the gingival connective tissue of periodontitis patients. The secretion of MIF was 3.82-fold higher in the supernatant of infected cells than in the supernatant of control (P < 0.01). No increase in the MIF mRNA level was found in either gingival tissue or epithelial cells.

CONCLUSIONS

Based on our limited evidence, we showed the level of MIF was related to periodontal conditions. P. gingivalis may contribute to the development and progression of periodontitis through MIF.

Functional variants in the promoter region of macrophage migration inhibitory factor rs755622 gene (MIF G173C) among patients with heart failure: Association with echocardiographic indices and disease severity

BACKGROUND

Heart failure (HF) is a serious public health concern resulting in death. An individual predisposition to HF is determined by relationship between genetic and environmental variables. The macrophage migration inhibitory factor (MIF) is a significant mediator that involved in a variety of inflammatory and cardiovascular diseases. To reveal contribution of MIF rs755622 G173C gene variants in the promoter region towards HF pathogenesis and investigate association between recognized genotype and clinical characteristics.

PATIENTS AND METHODS

We recruited 90 patients with HF, 63 with preserved ejection fraction (HFpEF) and 27 with reduced ejection fraction (HFrEF), and 60 age- and sex- matched controls. MIF rs755622 (G>C) single-nucleotide polymorphism was genotyped by PCR-RFLP method.

RESULTS

The GG genotype of MIF rs755622 gene polymorphism was more frequent in HF patients than in controls which increased the risk of HF by about 4.25 times (p<0.05). The distribution of the GG, GC and CC genotypes of MIF were 42%, 21% and 0.0% among HFrEF, and 33.3%, 55.6% and 11.1% among HFpEF respectively. Higher frequency of MIF rs755622 G allele among HFrEF (100%) compared to HFpEF (88.9%) (p = 0.007). MIF-GG genotype variant had significantly lower LVEF. In multivariate analysis, MIF-GG genotype was independent risk predictor among HF (OR 4.6).

CONCLUSION

MIF rs755622 (GG) could be considered as a probable genotypic risk factor for HF, especially in those with HFrEF which increases the possibility that MIF contribute to HF progression. MIF genotype assay may serve as early predictor and help to recognize those at great risk of developing HF.

Macrophage migration inhibitory factor increases atrial arrhythmogenesis through CD74 signaling

Macrophage migration inhibitory factor (MIF), a pleiotropic inflammatory cytokine, is highly expressed in patients with atrial fibrillation (AF). CD74 (major histocompatibility complex, class II invariant chain) is the main receptor for MIF. However, the role of the MIF/CD74 axis in atrial arrhythmogenesis is unclear. In this study, we investigated the effects of MIF/CD74 signaling on atrial electrophysiological characteristics and determined its underlying mechanisms. Confocal fluorescence microscopy, patch clamp, and western blot analysis were used to study calcium homeostasis, ionic currents, and calcium-related signaling in MIF-treated HL-1 atrial cardiomyocytes with or without anti-CD74 neutralized antibodies treatment. Furthermore, electrocardiographic telemetry recording and echocardiography were obtained from mice treated with MIF. Compared with controls, MIF-treated HL-1 myocytes had increased calcium transients, sarcoplasmic reticulum (SR) calcium content, Na⁺/Ca²⁺ exchanger (NCX) efflux rate, calcium leak, transient outward potassium current, and ultra-rapid delayed rectifier potassium current. Furthermore, MIF could induce expression of SR Ca²⁺ATPase, NCX, phosphorylation of ryanodine receptor 2 (RyR2), and activation of calcium/calmodulin kinase II (CaMKII) when compared with control cells. MIF-mediated electrical dysregulation and CaMKII-RyR2 signaling activation were attenuated through blocking of CD74. Moreover, MIF-injected mice had lesser left atrium fractional shortening, greater atrial fibrosis, and atrial ectopic beats than control (nonspecific immunoglobulin treated) or MIF combined with anti-CD74 neutralized antibody-treated mice. Consequently, our study on MIF/CD74 signaling has pointed out a new potential therapeutic intervention of AF patients with MIF elevation.

MIF gene rs755622 polymorphism positively associated with acute coronary syndrome in Chinese Han population: case-control study

Macrophage migration inhibitory factor (MIF) has been recognized as a major player in the pathogenesis of atherosclerosis. This study determined the association between polymorphisms of MIF gene and acute coronary syndrome (ACS). The polymorphism of MIF gene (rs755622, rs1007888 and rs2096525) was analyzed in 1153 healthy controls and 699 ACS cases in Chinese Han population. Plasma MIF level was also measured in part of ACS patients (139/19.9%) and healthy controls (129/11.2%) randomly. Most participants including healthy controls and ACS patients carried rs755622 GG (63.1% vs. 56.7%) and CG genotypes (33.1% vs. 38.9%) and G allele of rs755622 (79.6% vs. 76.1%, respectively), while CC genotype (3.8% vs. 4.4%) and C allele (20.4% vs. 23.9%) carriers were the lowest. Multivariate logistic regression analysis showed that carriers with rs755622 C allele had a higher risk of ACS compared to other genotypes (AOR = 1.278, 95% CI: 1.042-1.567). In addition, CC genotype carriers had the highest plasma levels of MIF than other genotype carriers. The MIF level in ACS patients with CC genotype was significantly higher than ACS patients carrying GG genotype and healthy controls carrying 3 different genotypes of MIF gene rs755622. Our findings indicate that MIF gene rs755622 variant C allele is associated with increased risk of ACS. Identification of this MIF gene polymorphism may help for predicting the risk of ACS.

Impaired Myocardial MIF/AMPK Activation Aggravates Myocardial Ischemia Reperfusion Injury in High-Fat Diet-Induced Obesity

Background:

Obese patients are more sensitive to myocardial ischemia, which has been linked with high mortality rates. The following study investigates the effects of impaired macrophage Migration Inhibitory Factor (MIF)/AMP-Activated Protein Kinase (AMPK) activation on increased susceptibility to myocardial ischemia/reperfusion (I/R) in high-fat diet-induced obesity.

Methods:

Male C57BL/6J mice were fed with a normal diet (10% kcal as fat, lean group) or a high-fat diet (60kcal as fat, obese group) for 12 consecutive weeks. To detect the MIF expression and AMPK activation in response to I/R in isolated hearts from lean and obese mice, myocardial samples were collected from left ventricular areas at different time points. To determine whether MIF supplementation is protective against I/R injury, recombined MIF (10 ng/mL) was applied before ischemia. Myocardial infarct size was estimated by triphenyltetrazolium staining. Western blot was used to detect myocardial MIF expression, AMPK activation and membrane glucose transporter 4 (Glut4) expression.

Results:

The expression of MIF was remarkably higher in obese group compared to lean group. Ischemia increased myocardial MIF expression and phosphorylation of AMPK in lean mice, whereas it had no significant effect on obese mice. Furthermore, administration of recombinant MIF increased ischemic AMPK activation and membrane Glut4 expression in both lean and obese mice, while it reduced the infarct size in lean mice only.

Conclusion:

An impaired MIF/AMPK activation response and consequent reduced membrane Glut4 expression may play an important role in increasing myocardial susceptibility to I/R in obesity.

Autophagy mediates the secretion of macrophage migration inhibitory factor from cardiomyocytes upon serum-starvation

Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine. It is elevated early in the blood of acute myocardial infarction patients. However, it is unclear whether and how MIF is released. This study investigated the cellular source and mechanism of MIF release from hearts. An ischemia-mimic treatment induced the secretion of MIF from neonatal rat cardiomyocytes but not from fibroblasts. The treatment did not cause significant leakage of lactate dehydrogenase, suggesting that ischemia induced the MIF secretion without causing severe cell damage. Plasma samples from patients with acute chest pain at the emergency department were collected for the detection of MIF. MIF levels in patients with acute coronary syndrome (ACS) increased early, when cardiac injury markers were not yet elevated, suggesting that ischemia can induce MIF secretion before the occurrence of severe myocardial damage. Serum-starvation caused MIF secretion from rat cardiomyocytes and Langendorff-perfused rat hearts. The secretion was suppressed by the inhibition of autophagy by inhibitors or by silencing of Atg5. In conclusion, serum-starvation induces the secretion of MIF from cardiomyocytes via autophagy dependent pathway. Clarifying the mechanism of MIF secretion will be helpful for its application in the early diagnosis and treatment of ACS.

Circulating MIF Levels Predict Clinical Outcomes in Patients With ST-Elevation Myocardial Infarction After Percutaneous Coronary Intervention

BACKGROUND

The purpose of the study was to assess the value of admission macrophage migration inhibitory factor (MIF) levels in predicting clinical outcomes in ST-elevation myocardial infarction (STEMI) patients.

METHODS

For this study we recruited 498 STEMI patients after they received percutaneous coronary intervention (PCI), 40 with stable angina pectoris and 137 healthy participants. Plasma MIF levels were measured at admission and after PCI. The primary end points were in-hospital mortality and major adverse cardio-and/or cerebrovascular events (MACCE) during hospitalization and 3.2-year follow-up period.

RESULTS

Admission MIF levels were elevated in 88.4% of STEMI patients over the upper reference limit of healthy controls and it was 3- to 7-fold higher than that in stable angina pectoris and control groups (122 ± 61 vs 39 ± 19 vs 17 ± 8 ng/mL; P < 0.001). Admission MIF levels were significantly higher in patients who died after myocardial infarction vs survivors. For predicting in-hospital mortality using the optimal cutoff value (127.8 ng/mL) of MIF, the area under the receiver operating characteristic curve for MIF was 0.820, similar area under the receiver operating characteristic curve values for predicting short-term outcomes were observed for high-sensitivity troponin T, CK-MB, N-terminal probrain natriuretic peptide, and Global Registry of Acute Coronary Events (GRACE) score. Although peak high-sensitivity troponin T and N-terminal probrain natriuretic peptide also predicted MACCE during the follow-up period, only higher admission MIF levels predicted in-hospital mortality and MACCE during the 3.2-year follow-up. Multivariate regression analysis showed the independent predictive value of a higher admission MIF level (≥ 127.8 ng/mL) on in-hospital mortality (odds ratio, 9.1; 95% confidence interval, 1.7-47.2) and 3.2-year MACCE (hazard ratio, 2.8; 95% confidence interval, 1.5-5.6).

CONCLUSIONS

A higher admission MIF level is an independent predictor for in-hospital mortality and long-term MACCE in STEMI patients who underwent PCI.

Protective cardiac conditioning by an atypical cytokine

Ischemic heart disease (IHD) represents the leading cause of morbidity and mortality worldwide. Therapy options generally aim at restoring the blood flow to the heart muscle and relieve the ischemic insult. Paradoxically, coronary artery reperfusion itself, both during emergency intervention in ST segment elevation myocardial infarction (STEMI) patients or in the setting of elective cardiac surgery, damages the heart muscle, a phenomenon known as myocardial ischemia-reperfusion (I/R) injury (IRI). Ischemic preconditioning (IPC) is defined by episodes of ‘sub-lethal’ ischemia and reperfusion prior to prolonged coronary artery occlusion. It has been extensively studied as a promising approach to attenuate IRI, but two recent multicenter clinical trials of remote IPC (RIPC) on clinical outcomes have been disappointing. Macrophage migration-inhibitory factor (MIF) is a structurally unique chemokine-like inflammatory cytokine. MIF is pro-atherogenic, but has a complex function in the ischemic heart with a surprising potential as a local cardioprotective factor in early myocardial ischemia. A recent paper published in Clinical Science by Ruze et al. [9], now suggests that MIF could be a key player mediating IPC in the ischemic heart. Employing a Mif gene knockout mouse model, the study indicates a role for endogenous MIF in IPC-mediated protection from myocardial IRI. It could assist in understanding how this atypical cytokine controls ischemic heart pathologies and may set the stage for novel MIF-based therapeutic strategies in IHD.

Extracellular Vesicles Released by Allogeneic Human Cardiac Stem/Progenitor Cells as Part of Their Therapeutic Benefit

The positive effects of therapeutic human allogeneic cardiac stem/progenitor cells (hCPC) in terms of cardiac repair/regeneration are very likely mediated by paracrine effects. Our previous studies revealed the advantageous immune interactions of allogeneic hCPC and proposed them as part of the positive paracrine effects occurring upon their application postmyocardial infarction (MI). Currently, extracellular vesicles/exosomes (EV/Exs) released by stem/progenitor cells are also proposed as major mediators of paracrine effects of therapeutic cells. Along this line, we evaluated contribution of EV/Exs released by therapeutic hCPC to the benefit of their successful allogeneic clinical application. Through tailored allogeneic in vitro human assay models mimicking the clinical setting, we demonstrate that hCPC‐released EV/Exs were rapidly and efficiently up‐taken by chief cellular actors of cardiac repair/regeneration. This promoted MAPK/Erk1/2 activation, migration, and proliferation of human leukocyte antigens (HLA)‐mismatched hCPC, mimicking endogenous progenitor cells and cardiomyocytes, and enhanced endothelial cell migration, growth, and organization into tube‐like structures through activation of several signaling pathways. EV/Exs also acted as pro‐survival stimuli for HLA‐mismatched monocytes tuning their phenotype toward an intermediate anti‐inflammatory pro‐angiogenic phenotype. Thus, while positively impacting the intrinsic regenerative and angiogenic programs, EV/Exs released by therapeutic allogeneic hCPC can also actively contribute to shaping MI‐inflammatory environment, which could strengthen the benefits of hCPC allogeneic interactions. Collectively, our data might forecast the application of allogeneic hCPC followed by their cell‐free EV/Exs as a strategy that will not only elicit the cell‐contact mediated reparative/regenerative immune response but also have the desired long‐lasting effects through the EV/Exs. stem cells translational medicine2019;8:911&924

Correlation between Plasma Macrophage Migration Inhibitory Factor Levels and Long-Term Prognosis in Patients with Acute Myocardial Infarction Complicated with Diabetes

Macrophage migration inhibitory factor (MIF), a widely expressed pleiotropic cytokine, is reportedly involved in several cardiovascular diseases, in addition to inflammatory diseases. Plasma MIF levels are elevated in the early phase of acute cardiac infarction. This study is aimed at investigating the correlation between plasma MIF levels and cardiac function and prognosis in patients with acute ST-segment elevation myocardial infarction (STEMI) with or without diabetes mellitus. Overall, 204 patients with STEMI who underwent emergency percutaneous coronary intervention were enrolled: 57 and 147 patients in the diabetes and nondiabetes STEMI groups, respectively. Sixty-five healthy people were selected as controls. Plasma MIF levels were measured at the time of diagnosis. Basic clinical data and echocardiographic findings within 72 h of admission were collected. Patients were followed up, and echocardiograms were reviewed at the 12-month follow-up. Plasma MIF levels were significantly higher in the diabetes and nondiabetes STEMI groups than in the control group and in patients with Killip grade ≥ II STEMI than in those with Killip grade I. Plasma MIF levels were negatively correlated with the left ventricular ejection fraction (LVEF) of myocardial infarction in patients with or without diabetes in the acute phase of infarction, whereas the left ventricular diastolic dysfunction (LVDD) was positively correlated. MIF levels in the nondiabetes STEMI group were positively correlated with N-terminal pro-b-type natriuretic peptide levels and were associated with LVEF and LVDD at the 12-month follow-up. The risk of adverse cardiovascular and cerebrovascular events was significantly higher in the MIF high-level group (≥52.7 ng/mL) than in the nondiabetes STEMI group 36 months after presentation. Thus, MIF levels in STEMI patients with or without diabetes can reflect acute cardiac function. In STEMI patients without diabetes, MIF levels can also indicate cardiac function and long-term prognosis at the 12-month follow-up.

Admission macrophage migration inhibitory factor predicts long-term prognosis in patients with ST-elevation myocardial infarction

Aims

We previously showed in patients with ST-segment elevated myocardial infarction (STEMI) that admission levels of macrophage migration inhibitory factor (MIF) predict infarct size. We studied whether admission MIF alone or in combination with other biomarkers is useful for risk assessment of acute and chronic clinical outcomes in STEMI patients.

Methods and results

A total of 658 STEMI patients treated with primary percutaneous coronary intervention (PCI) were consecutively recruited. MIF level was determined at admission and echocardiography performed on day-3 and then 12 months post-MI. Patients were followed for a median period of 64 months. Major endpoints included ST-segment resolution, all-cause mortality, and major adverse cardiovascular events (MACE). High MIF level was associated with larger enzymatic infarct size, incomplete resolution of ST-segment elevation post-PCI, impaired left ventricular ejection fraction (LVEF), and poorer improvement of LVEF (all P < 0.001). After adjustment for classical risk factors standard biomarkers and day-3 LVEF, admission MIF remained independently prognostic for all-cause mortality [hazard ratio (HR) 2.27, 95% confidence interval (CI) 1.43-3.22], and MACE (HR 1.39, 95% CI 1.12-1.71, both P < 0.05). MIF was a significant additive predictor of all-cause mortality with a net reclassification improvement of 0.34 (P = 0.02). Furthermore, patients in high tertile of both admission MIF and day-3 Nt-proBNP had the highest mortality risk relative to other tertile groups (HR 11.28, 95% CI 4.82-26.94; P < 0.001).

Conclusion

STEMI patients with high admission MIF level experienced a poorer recovery of cardiac function and worse long-term adverse outcomes. Combination of Nt-proBNP with MIF further improves prognostic capability.

Macrophage Migration Inhibitory Factor (MIF) Expression Increases during Myocardial Infarction and Supports Pro-Inflammatory Signaling in Cardiac Fibroblasts

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine known to play a major role in inflammatory diseases such as myocardial infarction (MI), where its expression increases. Cardio-protective functions of MIF during ischemia have been reported. Recently, the structurally related MIF-2 was identified and similar effects are assumed. We wanted to further investigate the role of MIF and MIF-2 on inflammatory processes during MI. Therefore, we subjected mice to experimentally induced MI by coronary occlusion for one and five days. During the acute phase of MI, the gene expression of Mif was upregulated in the infarct zone, whereas Mif-2 was downregulated, suggesting a minor role of MIF-2. Simulating ischemic conditions or mechanical stress in vitro, we demonstrated that Mif expression was induced in resident cardiac cells. To investigate possible auto-/paracrine effects, cardiomyocytes and cardiac fibroblasts were individually treated with recombinant murine MIF, which in turn induced Mif expression and the expression of pro-inflammatory genes in cardiac fibroblasts. Cardiomyocytes did not respond to recombinant MIF with pro-inflammatory gene expression. While MIF stimulation alone did not change the expression of pro-fibrotic genes in cardiac fibroblasts, ischemia reduced their expression. Mimicking the increased MIF levels during MI, we exposed cardiac fibroblasts to simulated ischemia in the presence of MIF, which led to further reduced expression of pro-fibrotic genes. The presented data show that MIF was expressed by resident cardiac cells during MI. In vitro, Mif expression was induced by different external stimuli in cardiomyocytes and cardiac fibroblasts. Addition of recombinant MIF protein increased the expression of pro-inflammatory genes in cardiac fibroblasts including Mif expression itself. Thereby, cardiac fibroblasts may amplify Mif expression during ischemia promoting cardiomyocyte survival.

The Multitasking Potential of Alarmins and Atypical Chemokines

When the human genome was sequenced, it came as a surprise that it contains “only” 21,306 protein-coding genes. However, complexity and diversity are multiplied by alternative splicing, non-protein-coding transcripts, or post-translational modifications (PTMs) on proteome level. Here, we discuss how the multi-tasking potential of proteins can substantially enhance the complexity of the proteome further, while at the same time offering mechanisms for the fine-regulation of cell responses. Discoveries over the past two decades have led to the identification of “surprising” and previously unrecognized functionalities of long known cytokines, inflammatory mediators, and intracellular proteins that have established novel molecular networks in physiology, inflammation, and cardiovascular disease. In this mini-review, we focus on alarmins and atypical chemokines such as high-mobility group box protein-1 (HMGB-1) and macrophage migration-inhibitory factor (MIF)-type proteins that are prototypical examples of these classes, featuring a remarkable multitasking potential that allows for an elaborate fine-tuning of molecular networks in the extra- and intracellular space that may eventually give rise to novel “task”-based precision medicine intervention strategies.

Atrial Fibrillation and Acute Myocardial Infarction – An Inflammation-Mediated Association

Atrial fibrillation (AF) is an increasingly widespread healthcare problem. AF can frequently present as a complication in acute coronary syndromes (ACS), especially in ST-elevation acute myocardial infarction (AMI), in which case it is the most frequent supraventricular rhythm disturbance with an estimated incidence of 6.8-21%. The presence of AF in ACS heralds worse outcomes in comparison to subjects in sinus rhythm, and several studies have shown that in AMI patients, both new-onset and pre-existing AF are associated with a higher risk of major adverse cardiovascular and cerebrovascular events during hospitalization. The cause of newonset AF in AMI is multifactorial. Although still incompletely understood, the mechanisms involved in the development of AF in acute myocardial ischemic events include the neurohormonal activation of the sympathetic nervous system that accompanies the AMI, ischemic involvement of the atrial myocytes, ventricular dysfunction, and atrial overload. The identification of patients at risk for AF is of great significance as it may lead to prompt therapeutic interventions and closer follow-up, thus improving prognosis and decreasing cardiovascular and cerebrovascular events. The present manuscript aims to summarize the current research findings related to new-onset AF in AMI patients, as well as the predictors and prognostic impact of this comorbid association.

Prognostic significance and dynamic change of plasma macrophage migration inhibitory factor in patients with acute ST-elevation myocardial infarction

Macrophage migration inhibitory factor (MIF) has been reported as an inflammatory cytokine in many inflammatory diseases, including rheumatoid arthritis and ischemic diseases. However, dynamic changes of MIF within the first 24 hours on admission and potential prognostic significance following ST-elevation myocardial infarction (STEMI) have been little known. In this study, we examined the dynamic change of MIF level and its potential diagnostic and prognostic value after the onset of STEMI. Plasma MIF levels were evaluated in symptomatic subjects who received coronary angiogram with a median 27 months follow-up for the development of major adverse cardiovascular events (MACEs).Of all 993 subjects, patients with STEMI showed a significantly higher MIF levels than in patients with non-ST elevation acute coronary syndrome, stable angina, and normal coronary artery, respectively (P < .01). Plasma MIF levels elevated as early as 12 hours post-onset of STEMI and peaked rapidly within 24 hours, and remained elevated from about day 5 till day 9 during hospitalization. In multivariate analysis, MIF was associated with a decreased risk of MACEs occurrence in STEMI patients after adjustment for traditional cardiovascular risk factors [hazard ratio 0.81, (0.72-0.90), P < .001]. The ROC curve for MACEs was 0.72 (95% CI 0.62-0.80, P < .001) and 0.85 (95% CI 0.80-0.90, P < .001) using Framingham risk factors only and combined with MIF, individually.Measurement of MIF adds potential information for the early diagnosis of acute STEMI and significantly improves risk prediction of MACEs when added to a prognostic model with traditional Framingham risk factors.

Soluble CD74 Reroutes MIF/CXCR4/AKT-Mediated Survival of Cardiac Myofibroblasts to Necroptosis

Background Although macrophage migration inhibitory factor ( MIF ) has been demonstrated to mediate cardioprotection in ischemia/reperfusion injury and antagonize fibrotic effects through its receptor, CD 74, the function of the soluble CD 74 receptor ectodomain ( sCD 74) and its interaction with circulating MIF have not been explored in cardiac disease. Methods and Results Cardiac fibroblasts were isolated from hearts of neonatal mice and differentiated into myofibroblasts. Co-treatment with recombinant MIF and sCD 74 induced cell death ( P<0.001), which was mediated by receptor-interacting serine/threonine-protein kinase ( RIP) 1/ RIP 3-dependent necroptosis ( P=0.0376). This effect was specific for cardiac fibroblasts and did not affect cardiomyocytes. Gene expression analyses using microarray and RT - qPCR technology revealed a 4-fold upregulation of several interferon-induced genes upon co-treatment of myofibroblasts with sCD 74 and MIF (Ifi44: P=0.011; Irg1: P=0.022; Clec4e: P=0.011). Furthermore, Western blot analysis confirmed the role of sCD 74 as a modulator of MIF signaling by diminishing MIF -mediated protein kinase B ( AKT) activation ( P=0.0197) and triggering p38 activation ( P=0.0641). We obtained evidence that sCD 74 inhibits MIF -mediated survival pathway through the C-X-C chemokine receptor 4/ AKT axis, enabling the induction of CD 74-dependent necroptotic processes in cardiac myofibroblasts. Preliminary clinical data revealed a lowered sCD 74/ MIF ratio in heart failure patients (17.47±10.09 versus 1.413±0.6244). Conclusions These findings suggest that treatment of cardiac myofibroblasts with sCD 74 and MIF induces necroptosis, offering new insights into the mechanism of myofibroblast depletion during scar maturation. Preliminary clinical data provided first evidence about a clinical relevance of the sCD 74/ MIF axis in heart failure, suggesting that these proteins may be a promising target to modulate cardiac remodeling and disease progression in heart failure.

MIF mRNA Expression and Soluble Levels in Acute Coronary Syndrome

Acute coronary syndrome (ACS) describes any condition characterized by myocardial ischaemia and reduction in blood flow. The physiopathological process of ACS is the atherosclerosis where MIF operates as a major regulator of inflammation. The aim of this study was to assess the mRNA expression of MIF gene and its serum levels in the clinical manifestations of ACS and unrelated individuals age- and sex-matched with patients as the control group (CG). All samples were run using the conditions indicated in TaqMan Gene Expression Assay protocol. Determination of MIF serum levels were performed by enzyme-linked immunosorbent assay and MIF ELISA Kit. ST-segment elevation myocardial infraction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI) showed 0.8 and 0.88, respectively, less expression of MIF mRNA with regard to CG. UA and STEMI presented more expression than NSTEMI 5.23 and 0.68, respectively. Otherwise, ACS patients showed significant higher MIF serum levels (p=0.02) compared with CG. Furthermore, the highest soluble levels of MIF were presented by STEMI (11.21 ng/dL), followed by UA (10.34 ng/dL) and finally NSTEMI patients (8.75 ng/dL); however, the differences were not significant. These novel observations further establish the process of MIF release after cardiovascular events and could support the idea of MIF as a new cardiac biomarker in ACS.

Circulating macrophage migration inhibitory factor (MIF) in patients with heart failure

BACKGROUND

Heart failure (HF) is characterized by impaired systolic ejection capacity and/or diastolic filling of the heart, leading to a multisystem disorder. Remote organ failure, systemic inflammation or pulmonary hypertension (PH) are hallmarks of the pathophysiological changes in HF. The Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine that is involved in a variety of cardiovascular and inflammatory diseases. Circulating MIF levels and their potential role as a disease marker in the different subgroups of HF have not been investigated yet. We here aimed to unravel a potential role of MIF in HF.

METHODS AND RESULTS

MIF plasma levels were assessed in 249 consecutive patients with HF. MIF was detectable in all investigated subjects and showed no difference with regard to the nature of HF (preserved or reduced ejection fraction). Spearman correlation revealed an association with inflammatory biomarkers (white blood cell count r = 0.18, p = 0.005; c-reactive protein r = 0.20, p = 0.003). MIF was associated with higher pulmonary artery systolic pressure (PASP) as assessed by echocardiography (r = 0.23, p < 0.001). Log-transformed PASP was also independently associated with MIF in a multivariable linear regression model (p = 0.02). Follow-up (FU) data after 180 days revealed that patients with increased MIF values (in ng/ml) were more likely to reach the endpoint all-cause mortality (HR 1.01, 95% CI 1.004-1.02, p = 0.005, per unit change).

CONCLUSION

MIF is detectable in the circulation of patients with HF and might be associated with clinical endpoints in HF, markers of inflammation and PH. These promising results should stimulate further research to elucidate the role of MIF in the multisystem disorder of HF.

The Role of Cardiokines in Heart Diseases: Beneficial or Detrimental?

Cardiovascular disease remains the leading cause of morbidity and mortality, imposing a major disease burden worldwide. Therefore, there is an urgent need to identify new therapeutic targets. Recently, the concept that the heart acts as a secretory organ has attracted increasing attention. Proteins secreted by the heart are called cardiokines, and they play a critical physiological role in maintaining heart homeostasis or responding to myocardial damage and thereby influence the development of heart diseases. Given the critical role of cardiokines in heart disease, they might represent a promising therapeutic target. This review will focus on several cardiokines and discuss their roles in the pathogenesis of heart diseases and as potential therapeutics.

MIF family cytokines in cardiovascular diseases and prospects for precision-based therapeutics

INTRODUCTION

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine with chemokine-like functions that increasingly is being studied in different aspects of cardiovascular disease. MIF was first identified as a proinflammatory and pro-survival mediator within the immune system, and a second structurally related MIF family member, D-dopachrome tautomerase (a.k.a. MIF-2), was reported recently. Both MIF family members are released by myocardium and modulate the manifestations of cardiovascular disease, specifically in myocardial ischemia. Areas covered: A scientific overview is provided for the involvement of MIF family cytokines in the inflammatory pathogenesis of atherosclerosis, myocardial infarction, and ischemia-reperfusion injury. We summarize findings of experimental, human genetic and clinical studies, and suggest therapeutic opportunities for modulating the activity of MIF family proteins that potentially may be applied in a MIF allele specific manner. Expert opinion: Knowledge of MIF, MIF-2 and their receptor pathways are under active investigation in different types of cardiovascular diseases, and novel therapeutic opportunities are being identified. Clinical translation may be accelerated by accruing experience with MIF-directed therapies currently in human testing in cancer and autoimmunity.

Exogenous Administration of Recombinant MIF at Physiological Concentrations Failed to Attenuate Infarct Size in a Langendorff Perfused Isolated Mouse Heart Model

Purpose

Evidence suggests a two-pronged role of endogenous macrophage migration inhibitory factor (MIF) release in ischemia/reperfusion injury. We aimed to assess whether its exogenous administration confers cardioprotection.

Methods

Male C57/BL6 mice were randomly allocated to receive recombinant mouse MIF (rMIF) at physiological (ng/mL) concentrations in a dose–response fashion before or after a protocol of 35 min of ischemia and 2 h of reperfusion in an isolated Langendorff-perfused model with infarct size as endpoint. Isolated primary cardiomyocytes were also used for cell survival studies using rMIF at a supra-physiological concentration of 1 μg/mL. Pro-survival kinase activation was also studied using Western blot analyses.

Results

Exogenous MIF did not elicit a cardioprotective effect either when administered before the ischemic insult or when applied at reperfusion. rMIF did not confer protection when it was applied immediately before or after a hypoxia/reoxygenation insult in primary isolated cardiomyocytes. Consistently, hearts treated with MIF did not show a significant increase in phosphorylated Akt and ERK1/2.

Conclusion

The exogenous administration of rMIF in a physiological concentration range both before ischemia and at reperfusion did not show cardioprotective effects. Although these results do not address the role of endogenous MIF after an ischemic insult followed by reperfusion, they may limit the potential translational value of rMIF.

From basic mechanisms to clinical applications in heart protection, new players in cardiovascular diseases and cardiac theranostics: meeting report from the third international symposium on "New frontiers in cardiovascular research"

In this meeting report, particularly addressing the topic of protection of the cardiovascular system from ischemia/reperfusion injury, highlights are presented that relate to conditioning strategies of the heart with respect to molecular mechanisms and outcome in patients' cohorts, the influence of co-morbidities and medications, as well as the contribution of innate immune reactions in cardioprotection. Moreover, developmental or systems biology approaches bear great potential in systematically uncovering unexpected components involved in ischemia-reperfusion injury or heart regeneration. Based on the characterization of particular platelet integrins, mitochondrial redox-linked proteins, or lipid-diol compounds in cardiovascular diseases, their targeting by newly developed theranostics and technologies opens new avenues for diagnosis and therapy of myocardial infarction to improve the patients' outcome.

Elevated plasma migration inhibitory factor in hypertension-hyperlipidemia patients correlates with impaired endothelial function

Migration inhibitory factor (MIF) has been shown to be critical in the pathology of early artherosclerosis; this article aim to investigate the plasma levels of MIF in hypertension plus hyperlipidemia patients.A total of 39 hypertension plus hyperlipidemia patients without any previous treatment were enrolled (HTN-HLP). Twenty-five healthy subjects were enrolled as the healthy control group (HEALTHY). Plasma MIF was measured by ELISA; laboratory and clinical characteristics were analyzed. HUVECs were treated with pooled plasma from HTN-HLP and HEALTHY groups, and the protein levels of adhesion molecules VCAM-1 and ICAM-1 were determined by ELISA. We found that plasma MIF was significantly elevated in the HTN-HLP group. Serum NO and eNOS levels were significantly lower; serum ET-1 (endothelin) levels were significantly higher in the HTN-HLP group. Furthermore, blood pressure, baPWV (brachial-ankle pulse wave velocity), and serum ET-1 level were significantly positively; serum NO and eNOS levels were negatively correlated with plasma MIF levels. Plasma from HTN-HLP significantly stimulated VCAM-1 and ICAM-1 protein expression on the surface of HUVECs.Plasma MIF was elevated in HTN-HLP patients and correlates with impaired endothelial function.

Plasma Macrophage Migration Inhibitor Factor Is Elevated in Response to Myocardial Ischemia

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a key regulator of inflammatory responses, including in the heart. Plasma MIF is elevated early in the course of acute myocardial infarction. In this study, we hypothesized that plasma MIF may also be increased in acute myocardial ischemia.

METHODS AND RESULTS

Patients undergoing cardiac stress test (stress nuclear myocardial perfusion scan or stress echocardiography) were recruited. Twenty-two patients had a stress test indicative of myocardial ischemia and were compared with 62 patients who had a negative stress test. Plasma MIF was measured by ELISA before and after the stress test. MIF was also measured in patients with peripheral arterial occlusive disease before and after exercise causing claudication. Gene and protein expression of MIF was measured in mouse cardiac and skeletal muscle tissue by real-time polymerase chain reaction and western blot, respectively. Plasma MIF was elevated at 5 and 15 minutes after stress (relative to before stress) in patients with a positive test, compared with those with a negative test. In contrast, high-sensitivity troponin T and C-reactive protein were not altered after stress in either group. MIF was not altered after exercise in PAOD patients, despite the occurrence of claudication, suggesting that plasma MIF is not a marker for skeletal muscle ischemia. This may be explained by a lower gene and protein expression of MIF in skeletal muscle than the heart.

CONCLUSIONS

Our results suggest that plasma MIF is an early marker for acute myocardial ischemia.

Intermittent Hypoxia Causes Inflammation and Injury to Human Adult Cardiac Myocytes

BACKGROUND

Intermittent hypoxia may occur in a number of clinical scenarios, including interruption of myocardial blood flow or breathing disorders such as obstructive sleep apnea. Although intermittent hypoxia has been linked to cardiovascular and cerebrovascular disease, the effect of intermittent hypoxia on the human heart is not fully understood. Therefore, in the present study, we compared the cellular responses of cultured human adult cardiac myocytes (HACMs) exposed to intermittent hypoxia and different conditions of continuous hypoxia and normoxia.

METHODS

HACMs were exposed to intermittent hypoxia (0%-21% O2), constant mild hypoxia (10% O2), constant severe hypoxia (0% O2), or constant normoxia (21% O2), using a novel cell culture bioreactor with gas-permeable membranes. Cell proliferation, lactate dehydrogenase release, vascular endothelial growth factor release, and cytokine (interleukin [IL] and macrophage migration inhibitory factor) release were assessed at baseline and after 8, 24, and 72 hours of exposure. A signal transduction pathway finder array was performed to determine the changes in gene expression.

RESULTS

In comparison with constant normoxia and constant mild hypoxia, intermittent hypoxia induced earlier and greater inflammatory response and extent of cell injury as evidenced by lower cell numbers and higher lactate dehydrogenase, vascular endothelial growth factor, and proinflammatory cytokine (IL-1β, IL-6, IL-8, and macrophage migration inhibitory factor) release. Constant severe hypoxia showed more detrimental effects on HACMs at later time points. Pathway analysis demonstrated that intermittent hypoxia primarily altered gene expression in oxidative stress, Wnt, Notch, and hypoxia pathways.

CONCLUSIONS

Intermittent and constant severe hypoxia, but not constant mild hypoxia or normoxia, induced inflammation and cell injury in HACMs. Cell injury occurred earliest and was greatest after intermittent hypoxia exposure. Our in vitro findings suggest that intermittent hypoxia exposure may produce rapid and substantial damage to the human heart.

Macrophage migration inhibitory factor promotes cardiac stem cell proliferation and endothelial differentiation through the activation of the PI3K/Akt/mTOR and AMPK pathways

Macrophage migration inhibitory factor (MIF) has pleiotropic immune functions in a number of inflammatory diseases. Recent evidence from expression and functional studies has indicated that MIF is involved in various aspects of cardiovascular disease. In this study, we aimed to determine whether MIF supports in vitro c-kit⁺CD45⁻ cardiac stem cell (CSC) survival, proliferation and differentiation into endothelial cells, as well as the possible mechanisms involved. We observed MIF receptor (CD74) expression in mouse CSCs (mCSCs) using PCR and immunofluorescence staining, and MIF secretion by mCSCs using PCR and ELISA in vitro. Increasing amounts of exogenous MIF did not affect CD74 expression, but promoted mCSC survival, proliferation and endothelial differentiation. By contrast, treatment with an MIF inhibitor (ISO-1) or siRNA targeting CD74 (CD74-siRNA) suppressed the biological changes induced by MIF in the mCSCs. Increasing amounts of MIF increased the phosphorylation of Akt and mammalian target of rapamycin (mTOR), which are known to support cell survival, proliferation and differentiation. These effects of MIF on the mCSCs were abolished by LY294002 [a phosphoinositide 3-kinase (PI3K) inhibitor] and MK-2206 (an Akt inhibitor). Moreover, adenosine monophosphate-activated protein kinase (AMPK) phosphorylation increased following treatment with MIF. The AMPK inhibitor, compound C, partly blocked the pro-proliferative effects of MIF on the mCSCs. In conclusion, our results suggest that MIF promotes mCSC survival, proliferation and endothelial differentiation through the activation of the PI3K/Akt/mTOR and AMPK signaling pathways. Thus, MIF may prove to be a potential therapeutic factor in the treatment of heart failure and myocardial infarction by activating CSCs.

Impact of MIF Gene Promoter Variations on Risk of Rheumatic Heart Disease and Its Age of Onset in Saudi Arabian Patients

Although macrophage migration inhibitory factor (MIF) has consistently been shown to be an important immune modulator, data on the association between MIF promoter variations and the risk of developing rheumatic heart disease (RHD) remain inconclusive. RHD is an important complication of streptococcal infections in the Middle East, not least in Saudi Arabia, and identifying risk markers is an important priority. Therefore, we investigated the association between two functional MIF promoter variations and RHD susceptibility and severity in Saudi patients: the MIF-173G > C substitution (rs755622) and the MIF-794 CATT5-8 tetranucleotide repeat (rs5844572). Three hundred twenty-six individuals (124 RHD patients and 202 age-, sex-, and ethnically matched healthy controls) were genotyped using allelic discrimination and fragment analysis. Data were analyzed with respect to disease susceptibility, severity, sex, and age of onset. There was a significantly lower frequency of 173C allele carriage in RHD patients compared to controls [odds ratio (OR) = 0.47; 95% confidence intervals (CIs) = 0.28-0.77; p = 0.003]. Interestingly, the 173C allele was associated with late disease onset (p = 0.001). The 794 5-repeat allele was associated with decreased RHD risk (OR = 0.56; 95% CIs = 0.38-0.82; p = 0.003). In contrast, the 794 6-repeat allele was associated with increased risk of RHD (OR = 1.7; 95% CIs = 1.2-2.5; p = 0.002). MIF promoter variations appear to have a dual role in RHD, with 173C allele non-carriers at higher risk of developing RHD at a younger age. These results require further validation in larger multi-ethnic cohorts, and functional studies are necessary to understand the underlying molecular mechanisms driving the at-risk phenotype.

Systemic inflammatory response following acute myocardial infarction

Acute cardiomyocyte necrosis in the infarcted heart generates damage-associated molecular patterns, activating complement and toll-like receptor/interleukin-1 signaling, and triggering an intense inflammatory response. Inflammasomes also recognize danger signals and mediate sterile inflammatory response following acute myocardial infarction (AMI). Inflammatory response serves to repair the heart, but excessive inflammation leads to adverse left ventricular remodeling and heart failure. In addition to local inflammation, profound systemic inflammation response has been documented in patients with AMI, which includes elevation of circulating inflammatory cytokines, chemokines and cell adhesion molecules, and activation of peripheral leukocytes and platelets. The excessive inflammatory response could be caused by a deregulated immune system. AMI is also associated with bone marrow activation and spleen monocytopoiesis, which sustains a continuous supply of monocytes at the site of inflammation. Accumulating evidence has shown that systemic inflammation aggravates atherosclerosis and markers for systemic inflammation are predictors of adverse clinical outcomes (such as death, recurrent myocardial infarction, and heart failure) in patients with AMI.

Increased circulating macrophage migration inhibitory factor levels are associated with coronary artery disease

BACKGROUND

To evaluate the macrophage migration inhibitory factor and E-selectin levels in patients with acute coronary syndrome.

MATERIALS/METHODS

We examined the plasma migration inhibitory factor and E-selectin levels in 87 patients who presented with chest pain at our hospital. The patients were classified into two groups according to their cardiac status. Sixty-five patients had acute myocardial infarction, and 22 patients had non-cardiac chest pain (non-coronary disease). We designated the latter group of patients as the control group. The patients who presented with acute myocardial infarction were further divided into two subgroups: ST-elevated myocardial infarction (n = 30) and non-ST elevated myocardial infarction (n = 35).

RESULTS

We found higher plasma migration inhibitory factor levels in both acute myocardial infarction subgroups than in the control group. However, the E-selectin levels were similar between the acute myocardial infarction and control patients. In addition, we did not find a significant difference in the plasma migration inhibitory factor levels between the ST elevated myocardial infarction and NST-elevated myocardial infarction subgroups.

DISCUSSION

The circulating concentrations of migration inhibitory factor were significantly increased in acute myocardial infarction patients, whereas the soluble E-selectin levels were similar between acute myocardial infarction patients and control subjects. Our results suggest that migration inhibitory factor may play a role in the atherosclerotic process.