Background. The Nod‐Like‐Receptor‐Protein‐3 (NLRP3) inflammasome and the Interleukin‐6 (IL‐6) pathways are central mechanisms of the inflammatory response in myocardial reperfusion injury. Expanding our knowledge about the inflammasome signaling axis is important to improve treatment options. In a cross‐sectional study, we aimed to study presence, localization, and genetic expression of inflammasome‐ and IL‐6‐ signaling‐related proteins in coronary thrombi and circulating leukocytes from ST‐elevation myocardial infarction (STEMI) patients, with relation to myocardial injury and time from symptoms to PCI. Methods. Intracoronary thrombi were aspirated from 33 STEMI patients. Blood samples were drawn. mRNA of Toll‐Like‐Receptor‐4 (TLR4), NLRP3, caspase 1, Interleukin‐1β (IL1‐β), Interleukin‐18 (IL‐18), IL‐6, IL‐6‐receptor (IL‐6R), and glycoprotein 130 (gp130) were isolated from thrombi and circulating leukocytes and relatively quantified by RT‐PCR. A part of each thrombus was embedded in paraffin for histology and immunohistochemistry analyses. Results. Genes encoding the 8 markers were present in 76‐100% of thrombi. Expression of TLR4 in thrombi significantly correlated to troponin T (r = 0.455, p = 0.013), as did NLRP3 (r = 0.468, p = 0.024). Troponin T correlated with expression in circulating leukocytes of TLR4 (r = 0.438, p = 0.011), NLRP3 (r = 0.420, p = 0.0149), and IL‐1β (r = 0.394, p = 0.023). IL‐6R expression in thrombi correlated significantly to troponin T (r = 0.434, p = 0.019), whereas gp130 was inversely correlated (r = −0.398, p = 0.050). IL‐6 in circulating leukocytes correlated inversely to troponin T (r = −0.421, p = 0.015). There were no significant correlations between genes expressed in thrombi and time from symptom to PCI. Conclusions. The inflammasome signaling pathway was actively regulated in coronary thrombi and in circulating leukocytes from patients with STEMI, in association with myocardial damage measured by troponin T. This supports the strategy of medically targeting this pathway in treating myocardial infarction and contributes to sort out optimal timing and targets for anti‐inflammatory treatment. The study is registered at clinicaltrials.gov with identification number NCT02746822.

Background: Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) are considered important both in atherosclerosis and remodeling after acute myocardial infarction (AMI). We aimed to study genetic expression and presence of MMP-2, MMP-9, TIMP-1, TIMP-2 and the extracellular MMP-inducer (EMMPRIN) in coronary thrombi. Circulating levels and genetic expression in circulating leukocytes were also assessed, and relations to degree of myocardial injury measured by troponin T and time from symptom to PCI were explored. Expression of cell markers were also analyzed, indicating relations to cell types. Methods: Intracoronary thrombi were aspirated from 33 patients with ST-elevation myocardial infarction (STEMI). Blood samples with Pax-gene tubes were drawn at end of PCI and the next day. RNA was isolated from thrombi and leukocytes, and genes were relatively quantified by RT-PCR. Each thrombus was preserved for histology and immunohistochemistry analyzes. Results: Genes coding for the five markers were present in 84–100% of thrombi and immunohistochemically stained in 96–100%. Expression of TIMP-1 in thrombi and in leukocytes correlated significantly to peak troponin T (r = 0.393 P = 0.026, r = 0.469 P = 0.006, respectively). No significant correlations between genes expressed in thrombi and time from symptom to PCI were observed. TIMP-1 was connected mainly to monocytes/macrophages in the thrombi. Conclusion: MMP-2, MMP-9, TIMP-1, TIMP-2 and EMMPRIN were highly expressed in human coronary thrombi. The correlation between troponin T and the expression of TIMP-1 both in thrombi and in leukocytes at time of PCI indicates that TIMP-1 plays a role in myocardial damage early post-MI.

Inflammation contributes to myocardial injury in ST-elevation myocardial infarction (STEMI). Interleukin-6 receptor (IL-6R) inhibition has been shown to mitigate myocardial injury and reduce levels of the prothrombotic and inflammatory mediator, neutrophil extracellular traps (NETs). The enzyme peptidylarginine deiminase 4 (PAD4) is central in NET formation. We hypothesized that PAD4 links IL-6R activation and NET formation. Methods: We conducted thrombus aspiration and peripheral blood sampling in 33 STEMI patients. In thrombi and leukocytes, we quantified the mRNA of IL-6, IL-6R, and PAD4. In peripheral blood, the protein levels of IL-6, IL-6R, PAD4, dsDNA, H3Cit, MPO-DNA, and troponin T were quantified. Results: In thrombi and circulating leukocytes, PAD4 mRNA was associated with IL-6R mRNA (thrombi: β = 0.34, 95% CI [0.16–0.53], p = 0.001, circulating leukocytes: β = 0.92, 95% CI [0.07–1.77], p = 0.036). There were no correlations between PAD4 and IL-6 in thrombi and leukocytes. The protein levels of IL-6R were associated with the NET marker H3Cit (r_s = 0.40, p = 0.02). In thrombi, PAD4 mRNA was associated with high levels of troponin T (β = 1.15 95% CI [0.27–2.04], p = 0.013). Conclusion: We demonstrate an association between PAD4, IL-6R, and troponin release in STEMI patients. Our findings indicate a PAD4-mediated connection between IL-6R and NET formation and highlight PAD4 as a potential treatment target for mitigating inflammation and myocardial injury in STEMI.

Background. Inflammation is central in development of cardiovascular disease (CVD). Aberrant function of the Nod-Like Receptor Protein 3 (NLRP3) inflammasome, a central mediator in the proinflammatory response, has been associated with atherosclerosis. The influence of genetic determinants on this inflammatory pathway and its downstream effects is less known. We aimed to investigate the frequency of a single NLRP3 gene variant according to clinical outcome in CVD and its influence on NLRP3-related markers. Methods. In this observational study, we included 1001 patients with chronic coronary syndrome. Blood samples were drawn at inclusion, including whole-blood and PAXgene tubes for DNA and RNA isolation, respectively. Allelic discrimination of the NLRP3 single nucleotide polymorphism rs10754555 was performed; and gene expression of NLRP3, Toll-Like Receptor 4, Interleukin- (IL-) 1β, and IL-18 was relatively quantified, both methods by RT-PCR. Circulating IL-6, high-sensitivity (hs) C-reactive protein, IL-18, and IL-12 were measured by enzyme-like immunosorbent assays. Clinical endpoints during 2 years ( ) were a composite of unstable angina pectoris, myocardial infarction, nonhemorrhagic stroke, and death. Results. Minor allele frequency of the NLRP3 variant was 0.36. In all, no association of the NLRP3 variant with clinical subgroups or outcome was found, neither any significant influence on the genes’ mRNA expression or circulating protein. However, in years (25 percentile), the variant G-allele is associated with significant lower risk of suffering a composite event ( (95% CI 0.19, 0.97), , adjusted). In the same age group, the NLRP3 gene was accordingly downregulated in G-allele carriers vs. noncarriers, and circulating IL12 was significantly reduced ( , both). In years, no significant effect of the variant was observed. Conclusion. The age-related reduced risk of composite endpoint in rs10754555 G-allele carriers accompanied by diminished NLRP3 mRNA expression is hypothesis generating and needs to be further explored. The study is registered at http://www.clinicaltrials.gov, with identification number NCT00222261.

The fibrinolytic system plays an important role in coronary artery atherothrombosis, and especially circulating plasminogen-activator inhibitor (PAI) type 1 (PAI-1) associates with increased mortality, infarct size and heart failure in patients with myocardial infarction (MI). In a cross-sectional study, we aimed to study whether genes encoding tissue plasminogen activator (tPA), urinary-type plasminogen activator (uPA), PAI-1 and PAI-2 are expressed in coronary thrombi from acute ST-elevation MI (STEMI) patients. Any relations to myocardial injury measured by peak troponin T, time from symptom onset to Percutaneous Coronary Intervention (PCI), and to different cell types present in the thrombi were also explored. Intracoronary thrombi were aspirated from 33 STEMI patients treated with primary PCI. The thrombi were snap-frozen for gene expression analyses, relatively quantified by RT PCR. Peripheral blood samples were drawn. Correlations were performed by Spearmans rho. The genes were present in 74–94% of the thrombi. Median peak troponin T was 3434 μ/L and median ischemic time 152 min. There were no significant correlations between the measured genes and troponin T, or ischemic time. Genes encoding tPA, u-PA, PAI-1 and PAI-2 all correlated significantly to the presence of monocytes/macrophages (CD68) in the thrombi (p = 0.028, p < 0.001, p = 0.003, p < 0.001). PAI-1 and PAI-2 also correlated to endothelial cells (CD31) (p = 0.002, p = 0.016). uPA associated with neutrophil granulocytes (CD 66b) (p = 0.019). Genes encoding tPA, uPA, PAI-1 and PAI-2 were highly expressed in human coronary thrombi from STEMI patients, indicating fibrinolytic regulators playing active roles in the thrombi, although not related to myocardial injury. All markers related to the presence of monocytes/macrophages, indicating connection to local inflammatory cells. The study is registered at clinicaltrials.gov with identification number NCT02746822.

Microvesicles (MVs) are actively secreted by cells. The NLRP3-inflammasome and the interleukin 6 (IL-6)-pathways are central in cardiovascular disease. Knowledge of how the inflammasome influences the MVs is limited. In a cross-sectional study, we assessed whether MVs in plasma associate with genes encoding inflammasome signalling in coronary thrombi. Moreover, any relationships between inflammasome activation and phosphatidylserine (PS) externalization, determined through Annexin V (AV⁺) labelling, and myocardial injury, assessed by cardiac troponin T (cTnT), were analysed. Intracoronary thrombi and blood samples from STEMI patients (n = 33) were investigated. mRNA of NLRP3, caspase-1, interleukin-1β (IL-1β), interleukin-18 (IL-18), IL-6, soluble IL-6-receptor (sIL-6R), and glycoprotein-130 (gp130) were isolated from the thrombi and relatively quantified by RT-PCR. MVs were analysed by flow cytometry. Total AV⁺ MVs, mainly reflecting hypercoagulability, correlated positively to NLRP3 gene expression (r = 0.545, p = 0.009). A similar pattern was seen for platelet, endothelial and leukocyte derived MVs, separately. The majority of the MVs were AV⁻ (96%). Total and AV⁻ MVs correlated inversely with IL-1β (r = −0.399 and −0.438, respectively, p < 0.05, both) and gp130 (r = −0.457 and −0.502, respectively, p < 0.05, both). No correlations between MVs and cTnT were observed. Our findings indicate an association between NLRP3-inflammasome in coronary thrombi and procoagulant AV⁺ MVs in STEMI patients. The inverse relationships between AV⁻ MVs and the gene expression of inflammasome activation may indicate an immuno-dampening role of this subpopulation.