Association of monocyte myeloperoxidase with incident cardiovascular disease: The Atherosclerosis Risk in Communities Study

Myeloperoxidase as a Promising Therapeutic Target after Myocardial Infarction

Coronary artery disease (CAD) and myocardial infarction (MI) remain leading causes of death and disability worldwide. CAD begins with the formation of atherosclerotic plaques within the intimal layer of the coronary arteries, a process driven by persistent arterial inflammation and oxidation. Myeloperoxidase (MPO), a mammalian haem peroxidase enzyme primarily expressed within neutrophils and monocytes, has been increasingly recognised as a key pro-inflammatory and oxidative enzyme promoting the development of vulnerable coronary atherosclerotic plaques that are prone to rupture, and can precipitate a MI. Mounting evidence also implicates a pathogenic role for MPO in the inflammatory process that follows a MI, which is characterised by the rapid infiltration of activated neutrophils into the damaged myocardium and the release of MPO. Excessive and persistent cardiac inflammation impairs normal cardiac healing post-MI, resulting in adverse cardiac outcomes and poorer long-term cardiac function, and eventually heart failure. This review summarises the evidence for MPO as a significant oxidative enzyme contributing to the inappropriate inflammatory responses driving the progression of CAD and poor cardiac healing after a MI. It also details the proposed mechanisms underlying MPO's pathogenic actions and explores MPO as a novel therapeutic target for the treatment of unstable CAD and cardiac damage post-MI.

Myeloperoxidase induces monocyte migration and activation after acute myocardial infarction

Introduction

Myocardial infarction (MI) is a significant contributor to morbidity and mortality worldwide. Many individuals who survive the acute event continue to experience heart failure (HF), with inflammatory and healing processes post-MI playing a pivotal role. Polymorphonuclear neutrophils (PMN) and monocytes infiltrate the infarcted area, where PMN release high amounts of the heme enzyme myeloperoxidase (MPO). MPO has numerous inflammatory properties and MPO plasma levels are correlated with prognosis and severity of MI. While studies have focused on MPO inhibition and controlling PMN infiltration into the infarcted tissue, less is known on MPO's role in monocyte function.

Methods and results

Here, we combined human data with mouse and cell studies to examine the role of MPO on monocyte activation and migration. We revealed a correlation between plasma MPO levels and monocyte activation in a patient study. Using a mouse model of MI, we demonstrated that MPO deficiency led to an increase in splenic monocytes and a decrease in cardiac monocytes compared to wildtype mice (WT). In vitro studies further showed that MPO induces monocyte migration, with upregulation of the chemokine receptor CCR2 and upregulation of inflammatory pathways identified as underlying mechanisms.

Conclusion

Taken together, we identify MPO as a pro-inflammatory mediator of splenic monocyte recruitment and activation post-MI and provide mechanistic insight for novel therapeutic strategies after ischemic injury.

High-Dose Vitamin B6 (Pyridoxine) Displays Strong Anti-Inflammatory Properties in Lipopolysaccharide-Stimulated Monocytes

Vitamin B6 is shown to have anti-inflammatory properties, which makes it an interesting nutraceutical agent. Vitamin B6 deficiency is well established as a contributor to inflammatory-related conditions, whilst B6 supplementation can reverse these inflammatory effects. There is less information available regarding the effects of high-dose vitamin B6 supplementation as a therapeutic agent. This study set out to examine the effects of high-dose vitamin B6 on an LPS-stimulated monocyte/macrophage cell population via an analysis of protein and gene expression using an RT2 profiler PCR array for Human Innate and Adaptive Immune responses. It was identified that high-dose vitamin B6 has a global anti-inflammatory effect on lipopolysaccharide-induced inflammation in monocyte/macrophage cells by downregulating the key broad-spectrum inflammatory mediators CCL2, CCL5, CXCL2, CXCL8, CXCL10, CCR4, CCR5, CXCR3, IL-1β, IL-5, IL-6, IL-10, IL-18, IL-23-a, TNF-α, CSF2, DDX58, NLRP3, NOD1, NOD2, TLR-1 -2 -4 -5 -7 -8 -9, MYD88, C3, FOXP3, STAT1, STAT3, STAT6, LYZ, CASP-1, CD4, HLA-E, MAPK1, MAPK8 MPO, MX-1, NF-κβ, NF-κβ1A, CD14, CD40, CD40LG, CD86, Ly96, ICAM1, IRF3, ITGAM, and IFCAM2. The outcomes of this study show promise regarding vitamin B6 within the context of a potent broad-spectrum anti-inflammatory mediator and could prove useful as an adjunct treatment for inflammatory-related diseases.

Mitochondrial Oxidative Stress Promotes Cardiac Remodeling in Myocardial Infarction through the Activation of Endoplasmic Reticulum Stress

We have evaluated cardiac function and fibrosis in infarcted male Wistar rats treated with MitoQ (50 mg/kg/day) or vehicle for 4 weeks. A cohort of patients admitted with a first episode of acute MI were also analyzed with cardiac magnetic resonance and T1 mapping during admission and at a 12-month follow-up. Infarcted animals presented cardiac hypertrophy and a reduction in the left ventricular ejection fraction (LVEF) and E- and A-waves (E/A) ratio when compared to controls. Myocardial infarction (MI) rats also showed cardiac fibrosis and endoplasmic reticulum (ER) stress activation. Binding immunoglobulin protein (BiP) levels, a marker of ER stress, were correlated with collagen I levels. MitoQ reduced oxidative stress and prevented all these changes without affecting the infarct size. The LVEF and E/A ratio in patients with MI were 57.6 ± 7.9% and 0.96 ± 0.34, respectively. No major changes in cardiac function, extracellular volume fraction (ECV), or LV mass were observed at follow-up. Interestingly, the myeloperoxidase (MPO) levels were associated with the ECV in basal conditions. BiP staining and collagen content were also higher in cardiac samples from autopsies of patients who had suffered an MI than in those who had died from other causes. These results show the interactions between mitochondrial oxidative stress and ER stress, which can result in the development of diffuse fibrosis in the context of MI.

A Review of Novel Cardiac Biomarkers in Acute or Chronic Cardiovascular Diseases: The Role of Soluble ST2 (sST2), Lipoprotein-Associated Phospholipase A2 (Lp-PLA2), Myeloperoxidase (MPO), and Procalcitonin (PCT)

While the received traditional predictors are still the mainstay in the diagnosis and prognosis of CVD events, increasing studies have focused on exploring the ancillary effect of biomarkers for the aspiring of precision. Under which circumstances, soluble ST2 (sST2), lipoprotein-associated phospholipase A2 (Lp-PLA2), myeloperoxidase (MPO), and procalcitonin (PCT) have recently emerged as promising markers in the field of both acute and chronic cardiovascular diseases. Existent clinical studies have demonstrated the significant associations between these markers with various CVD outcomes, which further verified the potentiality of markers in helping risk stratification and diagnostic and therapeutic work-up of patients. The current review article is aimed at illuminating the applicability of these four novels and often neglected cardiac biomarkers in common clinical scenarios, including acute myocardial infarction, acute heart failure, and chronic heart failure, especially in the emergency department. By thorough classification, combination, and discussion of biomarkers with clinical and instrumental evaluation, we hope the current study can provide insights into biomarkers and draw more attention to their importance.

Associations of myeloperoxidase, interleukin-17A and heparin-binding EGF-like growth factor levels with in-stent restenosis after percutaneous coronary intervention: a single-centre case-control study in China

OBJECTIVES

To investigate the changes in serum myeloperoxidase (MPO), interleukin (IL)-17A and heparin-binding EGF-like growth factor (HB-EGF) levels before and after percutaneous coronary intervention (PCI), and to evaluate the associations of MPO, IL-17A and HB-EGF levels with the 1-year restenosis rate.

DESIGN

Case-control study.

SETTINGS

Xiangyang Central Hospital between January 2012 and December 2017.

PARTICIPANTS

Patients with coronary heart disease who underwent PCI.

INTERVENTIONS

Not applicable.

PRIMARY AND SECONDARY OUTCOME MEASURES

Not applicable.

RESULTS

Finally, 407 and 132 patients were included in the control and in-stent restenosis (ISR) groups, respectively. The general clinical characteristics of the patients were not significantly different between the two groups. The MPO, IL-17A and HB-EGF levels were not significantly different between the two groups at baseline but significantly increased after PCI. The ISR group showed higher levels of MPO, IL-17A and HB-EGF compared with the control group at all postoperative time points. Multivariable analysis showed that MPO, IL-17A and HB-EGF were associated with increased ISR [MPO (OR=1.003; 95% CI: 1.001 to 1.005; p=0.002), IL-17A (OR=1.015; 95% CI: 1.009 to 1.020; p<0.0001) and HB-EGF (OR=2.256; 95% CI: 1.103 to 4.009; p=0.002)]. All three factors had sensitivity and specificity ≥68% for ISR.

CONCLUSIONS

HB-EGF could be used for the detection of ISR after PCI and could be of use for the prediction of ISR, but the value of MPO and IL-17A might be more limited. This will have to be validated in future studies.

Myeloperoxidase As a Multifaceted Target for Cardiovascular Protection

Significance: Myeloperoxidase (MPO) is a heme peroxidase that is primarily expressed by neutrophils. It has the capacity to generate several reactive species, essential for its inherent antimicrobial activity and innate host defense. Dysregulated MPO release, however, can lead to tissue damage, as seen in several diseases. Increased MPO levels in circulation are therefore widely associated with conditions of increased oxidative stress and inflammation. Recent Advances: Several studies have shown a strong correlation between MPO and cardiovascular disease (CVD), through which elevated levels of circulating MPO are linked to poor prognosis with increased risk of CVD-related mortality. Accordingly, circulating MPO is considered a "high-risk" biomarker for patients with acute coronary syndrome, atherosclerosis, heart failure, hypertension, and stroke, thereby implicating MPO as a multifaceted target for cardiovascular protection. Consistently, recent studies that target MPO in animal models of CVD have demonstrated favorable outcomes with regard to disease progression. Critical Issues: Although most of these studies have established a critical link between circulating MPO and worsening cardiac outcomes, the mechanisms by which MPO exerts its detrimental effects in CVD remain unclear. Future Directions: Elucidating the mechanisms by which elevated MPO leads to poor prognosis and, conversely, investigating the beneficial effects of therapeutic MPO inhibition on alleviating disease phenotype will facilitate future MPO-targeted clinical trials for improving CVD-related outcomes.

Myeloperoxidase and the Risk of CKD Progression, Cardiovascular Disease, and Death in the Chronic Renal Insufficiency Cohort (CRIC) Study

BACKGROUND

Myeloperoxidase (MPO) catalyzes the formation of reactive nitrogen species and levels are elevated in patients with chronic kidney disease (CKD). Although increased oxidative stress and inflammation are associated with progression of CKD and cardiovascular disease (CVD), relationships between MPO concentration, CKD progression, CVD, and death remain unclear.

STUDY DESIGN

Prospective cohort.

SETTING & PARTICIPANTS

3,872 participants from the Chronic Renal Insufficiency Cohort (CRIC) who had MPO measured at baseline.

EXPOSURE

Baseline MPO concentration.

OUTCOMES

CKD progression (kidney transplantation, dialysis initiation, or 50% decline in baseline estimated glomerular filtration rate [eGFR] and eGFR≤15mL/min/1.73m²), CVD (heart failure, myocardial infarction, or stroke), and death.

ANALYTICAL APPROACH

Cox proportional hazards models.

RESULTS

In adjusted analyses, higher MPO level (per 1-SD increase in log-transformed MPO) was associated with 10% higher risk for CKD progression (adjusted HR, 1.10; 95% CI, 1.01-1.19; P=0.03), 12% higher risk for CVD (adjusted HR, 1.12; 95% CI, 1.03-1.22; P<0.01), and 13% increased risk for death (adjusted HR, 1.13; 95% CI, 1.04-1.22; P<0.01). There was evidence for effect modification of the association of MPO level with CKD progression by baseline eGFR (P interaction=0.02), but not for CVD (P interaction=0.2) or death (P interaction=0.1). In stratified analyses, MPO level (per 1-SD increase in log-transformed MPO) was associated with greater risk for CKD progression among participants with eGFR>45mL/min/1.73m² (adjusted HR, 1.23; 95% CI, 1.03-1.46; P=0.02) compared with those with eGFR≤45mL/min/1.73m² (adjusted HR, 1.10; 95% CI, 1.02-1.20; P=0.02). The association of MPO level with CVD and death was no longer significant after adjustment for cardiac biomarkers.

LIMITATIONS

Potential residual confounding, lack of repeated measurements of MPO.

CONCLUSIONS

Higher MPO level was associated with increased risk for CKD progression, but not with CVD and death in patients with CKD from CRIC. Whether therapies aimed at reducing MPO activity can result in improved clinical outcomes is yet to be determined.

LncRNA MALAT1 Suppression Protects Endothelium against oxLDL-Induced Inflammation via Inhibiting Expression of MiR-181b Target Gene TOX

Rare studies have been conducted to investigate the exact interactions between lung adenocarcinoma transcript 1 (MALAT1), thymocyte selection-associated high mobility group box (TOX), and miRNAs in the pathogenesis of atherosclerosis (AS). We aim to investigate the crosstalk between MALAT1 and TOX and evaluate whether the regulatory mechanism was associated with the miRNA network. AS tissues were collected to determine the level of MALAT1 expression in AS patients, together with determination of miR-181b expression. Cultured endothelial cells were utilized to analyze the expressions of MALAT1, miR-181b, and TOX in the presence of oxLDL. Luciferase activity assay was conducted to evaluate the potential target sites of miR-181b on MALAT1 and TOX. In this study, we demonstrated that MALAT1 was upregulated in patients with AS. MALAT1 silencing significantly downregulated the expression of the miR-181b target gene TOX via reversing the effect of miR181b. Importantly, positive modulation of miR181b and inhibition of MALAT1 and TOX significantly attenuated oxLDL-induced endothelial inflammation and oxidative stress. Moreover, the MAPK signal pathways in endothelial cells were also inhibited through regulation of above endogenous RNAs. In summary, MALAT1 suppression protects the endothelium from oxLDL-induced inflammation and oxidative stress in endothelial cells by upregulation of miR-181b and downregulation of TOX.

Myeloperoxidase - A bridge linking inflammation and oxidative stress with cardiovascular disease

Myeloperoxidase (MPO) is a member of the superfamily of heme peroxidases that is mainly expressed in neutrophils and monocytes. MPO-derived reactive species play a key role in neutrophil antimicrobial activity and human defense against various pathogens primarily by participating in phagocytosis. Elevated MPO levels in circulation are associated with inflammation and increased oxidative stress. Multiple lines of evidence suggest an association between MPO and cardiovascular disease (CVD) including coronary artery disease, congestive heart failure, arterial hypertension, pulmonary arterial hypertension, peripheral arterial disease, myocardial ischemia/reperfusion-related injury, stroke, cardiac arrhythmia and venous thrombosis. Elevated MPO levels are associated with a poor prognosis including increased risk for overall and CVD-related mortality. Elevated MPO may signify an increased risk for CVD for at least 2 reasons. First, low-grade inflammation and increased oxidative stress coexist with many metabolic abnormalities and comorbidities and consequently an elevated MPO level may represent an increased cardiometabolic risk in general. Second, MPO produces a large number of highly reactive species which can attack, destroy or modify the function of every known cellular component. The most common MPO actions relevant to CVD are generation of dysfunctional lipoproteins with an increased atherogenicity potential, reduced NO availability, endothelial dysfunction, impaired vasoreactivity and atherosclerotic plaque instability. These actions strongly suggest that MPO is directly involved in the pathophysiology of CVD. In this regard MPO may be seen as a mediator or an instrument through which inflammation promotes CVD at molecular and cellular level. Clinical value of MPO therapeutic inhibition remains to be tested.