Proinflammatory cytokines and myocardial viability in patients after acute myocardial infarction

Microbiota, a New Playground for the Omega-3 Polyunsaturated Fatty Acids in Cardiovascular Diseases

Several cardioprotective mechanisms attributed to Omega-3 polyunsaturated fatty acids (PUFAs) have been studied and widely documented. However, in recent years, studies have supported the concept that the intestinal microbiota can play a much larger role than we had anticipated. Microbiota could contribute to several pathologies, including cardiovascular diseases. Indeed, an imbalance in the microbiota has often been reported in patients with cardiovascular disease and produces low-level inflammation. This inflammation contributes to, more or less, long-term development of cardiovascular diseases. It can also worsen the symptoms and the consequences of these pathologies. According to some studies, omega-3 PUFAs in the diet could restore this imbalance and mitigate its harmful effects on cardiovascular diseases. Many mechanisms are involved and included: (1) a reduction of bacteria producing trimethylamine (TMA); (2) an increase in bacteria producing butyrate, which has anti-inflammatory properties; and (3) a decrease in the production of pro-inflammatory cytokines. Additionally, omega-3 PUFAs would help maintain better integrity in the intestinal barrier, thereby preventing the translocation of intestinal contents into circulation. This review will summarize the effects of omega-3 PUFAs on gut micro-biota and the potential impact on cardiac health.

Protective Effect Of Vasicine Against Myocardial Infarction In Rats Via Modulation Of Oxidative Stress, Inflammation, And The PI3K/Akt Pathway

Background

Myocardial infarction is the leading cause of damage to the heart and is classified as a major cause of death related to cardiovascular disease. In the present study, we intended to investigate the protective effect of vasicine (VAS) against myocardial infarction in rats, and its mechanism.

Methods

Myocardial infarction was induced by isoproterenol (ISO, 100 mg/kg) at an interval of 24 h for 2 days. Different doses of VAS (2.5, 5, and 10 mg/kg body weight) were administered to the rats. The effect of VAS on oxidative stress markers such as, myocardial necrosis, myocardial ability and infarct volume, inflammatory cytokines, membrane-bound myocardial enzymes, and histopathological changes was investigated. Western blot analysis was also conducted to analyze the effect of VAS on autophagy (PI3K/Akt) and apoptosis (Bcl-2, Bax, and caspase-3). The number of apoptotic cells in the different groups was also identified using TUNEL.

Results

Results suggested that VAS causes reduction in myocardial necrosis by reduction of elevated LDH, CK-MB, and TnT levels. It also causes augmentation of left ventricular systolic pressure (LVSP) and myocardial contractility as determined in terms of +dp/dt_max and –dp/dt_max. Furthermore, VAS causes reduction of TNF-α and IL-6 levels. VAS also improved cardiac function via enhancing posterior wall thickness of the LV with concurrent increase in the mass of LV. In the present study, VAS caused activation of phosphorylated PI3K (p-PI3K) and phosphorylated Akt (p-Akt) in a dose-dependent manner. Furthermore, VAS suppressed apoptosis when tested on animals suffering from ISO-induced MI, by decreasing the expression of cleaved Caspase-3 and Bax while increasing the expression of Bcl-2.

Conclusion

In conclusion, vasicine has a protective effect against MI in vivo, through inhibiting oxidative stress, inflammation and excessive autophagy, to suppress apoptosis via activation of the PI3K/Akt/mTOR signaling pathway.

Role of cytokines and inflammation in heart function during health and disease

By virtue of their actions on NF-κB, an inflammatory nuclear transcription factor, various cytokines have been documented to play important regulatory roles in determining cardiac function under both physiological and pathophysiological conditions. Several cytokines including TNF-α, TGF-β, and different interleukins such as IL-1 IL-4, IL-6, IL-8, and IL-18 are involved in the development of various inflammatory cardiac pathologies, namely ischemic heart disease, myocardial infarction, heart failure, and cardiomyopathies. In ischemia-related pathologies, most of the cytokines are released into the circulation and serve as biological markers of inflammation. Furthermore, there is an evidence of their direct role in the pathogenesis of ischemic injury, suggesting cytokines as potential targets for the development of some anti-ischemic therapies. On the other hand, certain cytokines such as IL-2, IL-4, IL-6, IL-8, and IL-10 are involved in the post-ischemic tissue repair and thus are considered to exert beneficial effects on cardiac function. Conflicting reports regarding the role of some cytokines in inducing cardiac dysfunction in heart failure and different types of cardiomyopathies seem to be due to differences in the nature, duration, and degree of heart disease as well as the concentrations of some cytokines in the circulation. In spite of extensive research work in this field of investigation, no satisfactory anti-cytokine therapy for improving cardiac function in any type of heart disease is available in the literature.

Potential contribution of the hepcidin-macrophage axis to plaque vulnerability in acute myocardial infarction in human

OBJECTIVES

Hepcidin-25 serves as a key peptide in the regulation of iron homeostasis and inflammation. It remains unknown whether hepcidin-25 plays an adverse role in atherosclerotic diseases. The aim of this study was to investigate whether hepcidin-25 is involved in the pathophysiology of coronary plaque vulnerability.

METHODS AND RESULTS

Serum hepcidin-25 levels were quantitatively determined by the LC-MS/MS assay system. Peripheral blood was collected from patients with acute myocardial infarction (MI, n=33) and patients with stable angina pectoris (sCAD, n=19). The levels of hepcidin-25, IL-6, and CRP were significantly higher in the patients with acute MI than in the patients with sCAD. Coronary blood was aspirated from the culprit arteries via a thrombectomy catheter in 16 of the MI patients. Serum from the aspirates contained higher levels of hepcidin-25 and IL-6 compared with the peripheral blood. In immunohistochemical staining, the macrophages of the plaques in the solid component of the aspirates were immunoreactive for hepcidin-25. To confirm the clinical observation, an in vitro study was performed using human macrophages and coronary endothelial cells. The hepcidin gene and protein were detected in the cultured macrophages but not in the endothelial cells. Hepcidin-25 exposure induced ferroportin degradation and reduced the survival rate of endothelial cells.

CONCLUSIONS

The results of the present study demonstrated that circulating hepcidin-25 and IL-6 were both elevated in the acute phase of MI and that hepcidin-25 released from plaque macrophages and other cell sources contributed to the plaque instability by inducing endothelial cell death.

Linoleic acid attenuates cardioprotection induced by resolvin D1

We previously observed that resolvin D1 (RvD1), a metabolite of the omega-3 polyunsaturated fatty acid (PUFA) docosahexaenoic acid, reduces infarct size by a mechanism involving the PI3-K/Akt pathway. In parallel, the beneficial effect of a high omega-3 PUFA diet on infarct size can be attenuated by increased omega-6 PUFA consumption. The present study was designed to determine if augmented linoleic acid (LA), an omega-6 PUFA administered at the same time, attenuates the cardioprotective action of RvD1. Male Sprague-Dawley rats received 0.1μg RvD1 alone or with one of three LA doses (1, 5 or 10μg) directly into the left ventricle chamber 5min before ischemia. The animals underwent 40min of ischemia by occlusion of the left descending coronary artery followed by 30min or 24h of reperfusion. Infarct size and neutrophil accumulation were evaluated after 24h of reperfusion, while caspase-3, -8 and -9 and Akt activities were assessed at 30min of reperfusion. LA attenuated cardioprotection afforded by RvD1, resulting in significantly increased infarct size. Neutrophil accumulation and Akt activity were similar between groups. Caspase activities, especially caspase-9, which could be activated by ischemia, were stimulated in the presence of LA, suggesting that this omega-6 PUFA accentuates ischemia intensity. The present results indicate that LA significantly attenuates the beneficial effect of RvD1 on infarct size. Therefore, reduction of omega-6 intake should be considered to maintain the protection afforded by RvD1.

Pravastatin inhibits fibrinogen- and FDP-induced inflammatory response via reducing the production of IL-6, TNF-α and iNOS in vascular smooth muscle cells

Atherosclerosis is a chronic inflammatory response of the arterial wall to pro‑atherosclerotic factors. As an inflammatory marker, fibrinogen directly participates in the pathogenesis of atherosclerosis. Our previous study demonstrated that fibrinogen and fibrin degradation products (FDP) produce a pro‑inflammatory effect on vascular smooth muscle cells (VSMCs) through inducing the production of interleukin‑6 (IL‑6), tumor necrosis factor‑α (TNF‑α) and inducible nitric oxide synthase (iNOS). In the present study, the effects of pravastatin on fibrinogen‑ and FDP‑induced expression of IL‑6, TNF‑α and iNOS were observed in VSMCs. The results showed that pravastatin dose‑dependently inhibited fibrinogen‑ and FDP‑stimulated expression of IL‑6, TNF‑α and iNOS in VSMCs at the mRNA and protein level. The maximal inhibition of protein expression of IL‑6, TNF‑α and iNOS was 46.9, 42.7 and 49.2% in fibrinogen‑stimulated VSMCs, and 50.2, 49.8 and 53.6% in FDP‑stimulated VSMCs, respectively. This suggests that pravastatin has the ability to relieve vascular inflammation via inhibiting the generation of IL‑6, TNF‑α and iNOS. The results of the present study may aid in further explaining the beneficial effects of pravastatin on atherosclerosis and related cardiovascular diseases. In addition, they suggest that application of pravastatin may be beneficial for prevention of atherosclerosis formation in hyperfibrinogenemia.

Myocardial healing requires Reg3β-dependent accumulation of macrophages in the ischemic heart

Cardiac healing after myocardial ischemia depends on the recruitment and local expansion of myeloid cells, particularly macrophages. Here we identify Reg3β as an essential regulator of macrophage trafficking to the damaged heart. Using mass spectrometry-based secretome analysis, we found that dedifferentiating cardiomyocytes release Reg3β in response to the cytokine OSM, which signals through Jak1 and Stat3. Loss of Reg3β led to a large decrease in the number of macrophages in the ischemic heart, accompanied by increased ventricular dilatation and insufficient removal of neutrophils. This defect in neutrophil removal in turn caused enhanced matrix degradation, delayed collagen deposition and increased susceptibility to cardiac rupture. Our data indicate that OSM, acting through distinct intracellular pathways, regulates both cardiomyocyte dedifferentiation and cardiomyocyte-dependent regulation of macrophage trafficking. Release of OSM from infiltrating neutrophils and macrophages initiates a positive feedback loop in which OSM-induced production of Reg3β in cardiomyocytes attracts additional OSM-secreting macrophages. The activity of the feedback loop controls the degree of macrophage accumulation in the heart, which is instrumental in myocardial healing.

Cardiac biomarkers in acute myocardial infarction

Each year, a large number of patients are seen in the Emergency Department with presentations necessitating investigation for possible acute myocardial infarction. Patients can be stratified by symptoms, risk factors and electrocardiogram results but cardiac biomarkers also have a prime role both diagnostically and prognostically. This review summarizes both the history of cardiac biomarkers as well as currently available (established and novel) assays. Cardiac troponin, our current "gold standard" biomarker criterion for the diagnosis of myocardial infarction has high sensitivity and specificity for this diagnosis and therapies instituted in patients with elevated troponin have been shown to influence outcomes. Other markers of myocardial necrosis, inflammation and neurohormonal activity have also been shown to have either diagnostic or prognostic utility, but none have been shown to be superior to troponin. The measurement of multiple biomarkers and the use of point of care markers may accelerate current diagnostic protocols for the assessment of such patients.

Pro-inflammatory effect of fibrinogen and FDP on vascular smooth muscle cells by IL-6, TNF-α and iNOS

AIMS

Atherosclerosis is a chronic inflammatory response of the arterial wall to multiple endothelial injuries. As one of the inflammatory markers, fibrinogen has been implicated in pathogenesis of atherosclerosis. But, it is not completely understood whether atherogenesis of fibrinogen is related to its pro-inflammatory effect on vascular smooth muscle cells (VSMCs). The purpose of the present study was to observe effects of fibrinogen and fibrin degradation products (FDP) on interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), and inducible nitric oxide synthase (iNOS) generation in rat VSMCs.

MAIN METHODS

Rat VSMCs were cultured, and fibrinogen and FDP were used as stimulants for IL-6, TNF-α, and iNOS. IL-6 and TNF-α level in the supernatant were measured by ELISA, mRNA expression of IL-6, TNF-α, and iNOS were assayed with RT-PCR, and protein expression of iNOS was detected with western blot and immunocytochemistry.

KEY FINDINGS

Fibrinogen and FDP both significantly stimulated mRNA and protein expressions of IL-6, TNF-α and iNOS in VSMCs in time- and concentration-dependent ways. The pro-inflammatory potency of FDP is higher than fibrinogen, which seems to mean that smaller fragments of the protein have greater pro-inflammatory activity. Fibrinogen and FDP promote more protein expressions of IL-6 and TNF-α compared to iNOS, suggesting that fibrinogen and FDP produce a pro-inflammatory effect on VSMCs mainly by IL-6 and TNF-α.

SIGNIFICANCE

These findings are helpful to better understand pro-inflammatory effect of fibrinogen on VSMCs involved in atherogenesis, and imply a therapeutic strategy targeting hyperfibrinogenemia in atherosclerosis.

Elevation of matrix metalloproteinases and interleukin-6 in the culprit coronary artery of myocardial infarction

BACKGROUND

Interleukin-6 (IL-6) and metalloproteinases (MMPs) are involved in the instability of vulnerable plaque associated with the induction of acute myocardial infarction (AMI). We examined the regional changes of cytokines, MMPs and adhesion molecules in patients with AMI to elucidate how these factors are involved in the onset of AMI.

MATERIALS AND METHODS

One hundred and twenty-two patients with AMI were included. Blood was aspirated from the culprit coronary artery with a thrombectomy catheter, and was also sampled from peripheral veins during the coronary intervention. Control samples were obtained from the peripheral blood of age-matched patients.

RESULTS

The serum levels of IL-6 (P < 0.05), tumour necrosis factor-alpha (P < 0.005), MMP-1 (P < 0.001), MMP-13 (P < 0.001), soluble intercellular adhesion molecule-1 (P < 0.005), and soluble vascular cellular adhesion molecule-1 (P < 0.05) in peripheral blood were significantly higher in the AMI group than in the controls. Aspirated serum contained significantly higher levels of IL-6 (P < 0.001), MMP-1 (P < 0.001), and MMP-13 (P < 0.05) compared to the peripheral blood of AMI. Serum IL-6 levels were significantly higher in the aspirated than in the peripheral blood in the patients hospitalized within 6 h and 6-12 h, but were similar in the aspirated and peripheral blood of the patients hospitalized 12-24 h after the onset of AMI. There were no differences between the aspirated serum and peripheral blood in the levels of interleukin-1beta and MMP-2.

CONCLUSIONS

The levels of MMP-1, MMP-13 and IL-6 were higher in the culprit coronary artery than in the peripheral blood. These factors appear to be involved in the early stage of AMI.

No association of interleukin-6 gene polymorphism (-174 G/C) with premature coronary artery disease in a Turkish cohort

OBJECTIVES

Interleukin-6 (IL-6) may contribute to the inflammatory response by activating endothelial cells and stimulating the synthesis of fibrinogen. It might thus be important in the pathogenesis of inflammation associated with coronary artery disease (CAD). Several studies suggested that the -174 C allele was associated with an increased prevalence of coronary heart disease. The aim of this study was to investigate further the association of the IL-6 -174 G/C allele status with premature CAD.

METHODS

A total of 120 patients and 105 controls were included in the study. The IL-6 -174 G/C polymorphism was genotyped using PCR-restriction fragment length polymorphism.

RESULTS

The genotype distribution of the -174 G/C polymorphism was not different in premature CAD patients (GG: 53%; GC: 42.6%; CC: 4.3%) and controls (GG: 54.3%; GC: 39%; CC: 6.7%) (P=0.72). The prevalence of the C allele was 25.6% in patients and 26.1% in controls. By multiple regression analysis, family history, smoking, diabetes, and hypertension were independent risk factors of premature CAD, but not IL-6 genotype.

CONCLUSIONS

We conclude that the IL-6 -174 G/C polymorphism is not associated with the risk of premature CAD, and does not contribute to cardiovascular risk stratification.

Inflammation and sleep in healthy individuals

STUDY OBJECTIVES

Inflammation is relatively common in individuals with a sleep disorder and is associated with quality of sleep. The purpose of this study was to examine whether inflammation is associated with quality of sleep in healthy individuals.

DESIGN & SETTING

Observational study in a General Clinical Research Center.

PARTICIPANTS

This study characterized inflammation and polysomno-graphically verified sleep in 124 African American and Caucasian American women and men without a sleep disorder.

MEASUREMENTS AND RESULTS

Circulating levels of 3 markers and/or mediators of inflammation known to be elevated in sleep disorders and in cardiovascular disease were determined (interleukin-6 [IL-6] endothelin-1 [ET-1], soluble intercellular adhesion molecule-1 [sICAM-1]). Sleep was characterized by polysomnography. Multiple linear regression analyses showed that increasing age, male sex, and African American ethnicity were independently associated with poorer sleep. After controlling for these variables, higher levels of ET-1 were independently associated with greater sleep latency (P < or = 0.01), greater rapid eye movement (REM) latency (P < or = 0.01), more slow wave sleep (P < or = 0.05), and less stage 1 sleep (P < or = 0.01). Higher IL-6 levels were independently associated with greater REM latency (P < or = 0.05).

CONCLUSIONS

The findings suggest that, in individuals without a known sleep disorder, ET-1, a potent vasoconstrictor and mediator of inflammation, is associated with more deep sleep, whereas both ET-1 and IL-6 are associated with increased latency of sleep and of REM. The findings underscore the complex relationships between peripheral markers of inflammation and sleep.

Correlation between cardiac oxidative stress and myocardial pathology due to acute and chronic norepinephrine administration in rats

Background: To investigate the cardiotoxic role of reactive oxygen species (ROS) and of products derived from catecholamines auto-oxidation, we studied: (1) the response of antioxidant cardiac cellular defence systems to oxidative stress induced by norepinephrine (NE) administration, (2) the effect of NE administration on cardiac β₁-adrenergic receptors by means of receptor binding assay, (3) the cellular morphological alterations related to the biologically cross-talk between the NE administration and cytokines [tumor necrosis factor-alpha (TNF-α), monocyte chemotactic protein-1 (MCP-1), interleukins IL6, IL8, IL10]Methods and Results: A total of 195 male rats was used in the experiment. All animals underwent electrocardiogram (EKG) before being sacrificed. The results obtained show that NE administration influences the antioxidant cellular defence system significantly increasing glutathione peroxidase (GPx) activity, glutathione reductase (GR) and superoxide dismutase (SOD). The oxidized glutathione (GSH/GSSG) ratio significantly decreases and malondialdehyde (MDA) levels increase showing a state of lipoperoxidation of cardiac tissue. We describe a significant apoptotic process randomly sparse in the damaged myocardium and the effect of ROS on the NE-mediated TNF-α, MCP-1, and IL6, IL8, IL10 production. Conclusions: Our results support the hypothesis that catecholamines may induce oxidative damage through reactive intermediates resulting from their auto-oxidation, irrespective of their interaction with adrenergic receptors, thus representing an important factor in the pathogenesis of catecholamines-induced cardiotoxicity. The rise of the cardioinhibitory cytokines may be interpreted as the adaptive response of jeopardized myocardium with respect to the cardiac dysfunction resulting from NE injection.

Effects of low-dose milrinone on weaning from cardiopulmonary bypass and after in patients with mitral stenosis and pulmonary hypertension

The phosphodiesterase inhibitor milrinone is usually preferred in patients with pulmonary hypertension and myocardial dysfunction after cardiopulmonary bypass. We investigated the effects of low-dose milrinone on pulmonary hypertension in the immediate pre- and postoperative period. Forty-seven patients were randomized to the control and milrinone groups. All patients had mean pulmonary artery pressure greater than 30 mmHg and pulmonary capillary wedge pressure greater than 20 mmHg and were candidates for mitral valve replacement for rheumatic mitral stenosis. Twenty-four patients received a loading dose of milrinone 25 microg/kg(-1) during weaning from cardiopulmonary bypass, followed by a maintenance dose of 0.25 microg/kg(-1)/min(-1) to the end of the surgery. Cardiac output and other hemodynamic variables were noted at induction, weaning from bypass, and postoperative 1 h. Pulmonary artery pressure, capillary wedge pressure, and central venous pressure were significantly lower in the milrinone group during weaning after cardiopulmonary bypass, while other variables were roughly similar. However, patients in the control group required higher doses of vasodilators, inotropes, and antiarrhythmic agents. Mean arterial pressure in the milrinone group was significantly lower at 1 h postoperatively than in the control group; however, the patients did not need many more vasopressors. Fluid restriction and diuretic agent use were more significant in the control group. Systemic arterial hypotension and vasopressor requirements with milrinone use at inotropic doses were not observed at the doses used for the study. A total of 21.7% of the patients in the control group required vasopressors in the perioperative period. Both groups demonstrated similar hematologic variables except that the hemoglobin level in the control group was significantly lower during postoperative days 1 and 7. Low-dose milrinone for a short-term during weaning from cardiopulmonary bypass may be used in patients with mitral stenosis and pulmonary hypertension for its effects on pulmonary artery pressures, less inotropic and vasopressor requirements, and fluid balance.

Interleukin-6 and the risk of future cardiovascular events in patients with angina pectoris and/or healed myocardial infarction

The aim of this study was to evaluate the prognostic value of interleukin-6 (IL-6) for myocardial infarction (MI) and mortality in a population with stable coronary artery disease (CAD) during a mean period of 6.3 years. IL-6 is a major proinflammatory cytokine of acute phase response; elevated levels are associated with worse prognosis in unstable angina and after acute MI. However, data regarding its long-term prognostic value in stable CAD are limited and controversial. A nested case-control study design was used. Of 3,090 patients with stable CAD, 129 with an adequate blood sample for IL-6 and who reached the end points (MI or sudden death) were randomly selected. Each case was 1:1 matched with 129 controls (alive at the end of the study and free of cardiovascular events) according to age, gender, and treatment. Of the 129 cases, 113 had a MI as the initial event, and for the other 16 the initial event was sudden death. There were 8 patients who first had a MI and later died suddenly. IL-6 was significantly higher in cases (2.34 pg/ml) than in controls (1.65 pg/ml) (p = 0.0004). IL-6 was significantly correlated with C-reactive protein (r = 0.2, p = 0.002); a borderline significance was also found for fibrinogen (r = 0.11, p = 0.07). Each increase of 1 pg/ml in IL-6 was associated with a 1.70 (range 1.23 to 2.45) increased relative odds of subsequent MI or sudden death. Events rate per 1,000 patients-years for the 5 quintiles of IL-6 were 72.26, 89.61, 79.76, 142.53, and 181.08, respectively (p <0.0001). A significantly higher risk in the upper quintile was found (odds ratio, 3.44; 95% confidence interval 1.57 to 8.13). In conclusion, elevated IL-6 levels are strongly associated with future cardiac events and mortality in a population with stable CAD during a long-term follow-up.