Aims N ucleotide-binding oligomerization domain- L ike R eceptor with a P yrin domain 3 (NLRP3) is considered necessary for initiating a profound sterile inflammatory response. NLRP3 forms multi-protein complexes with A poptosis-associated S peck-like protein containing a C aspase recruitment domain (ASC) and Caspase-1, which activate pro-interleukin-1β (IL-1β) and pro-IL-18. The role of NLRP3 in cardiac cells is not known. Thus, we investigated the expression and function of NLRP3 during myocardial ischaemia. Methods and results Myocardial infarction (MI) was induced in adult C57BL/6 mice and Wistar rats by ligation of the coronary artery. A marked increase in NLRP3, IL-1β, and IL-18 mRNA expression was found in the left ventricle after MI, primarily located to myocardial fibroblasts. In vitro studies in cells from adult mice showed that myocardial fibroblasts released IL-1β and IL-18 when primed with lipopolysaccharide and subsequently exposed to the danger signal adenosine triphosphate, a molecule released after tissue damage during MI. When hearts were isolated from NLRP3-deficient mice, perfused and subjected to global ischaemia and reperfusion, a marked improvement of cardiac function and reduction of hypoxic damage was found compared with wild-type hearts. This was not observed in ASC-deficient hearts, potentially reflecting a protective role of other ASC-dependent inflammasomes or inflammasome-independent effects of NLRP3. Conclusion This study shows that the NLRP3 inflammasome is up-regulated in myocardial fibroblasts post-MI, and may be a significant contributor to infarct size development during ischaemia–reperfusion.

Immune responses are initiated when molecules of microbial origin are sensed by the Toll‐like receptors (TLRs). We now report the identification of essential molecular components for the trafficking of the lipopolysaccharide (LPS) receptor complex. LPS was endocytosed by a receptor‐mediated mechanism dependent on dynamin and clathrin and colocalized with TLR4 on early/sorting endosomes. TLR4 was ubiquitinated and associated with the ubiquitin‐binding endosomal sorting protein hepatocyte growth factor‐regulated tyrosine kinase substrate, Hrs. Inhibition of endocytosis and endosomal sorting increased LPS signaling. Finally, the LPS receptor complex was sorted to late endosomes/lysosomes for degradation and loading of associated antigens onto HLA class II molecules for presentation to CD4+ T cells. Our results show that endosomal trafficking of the LPS receptor complex is essential for signal termination and LPS‐associated antigen presentation, thus controlling both innate and adaptive immunity through TLR4.

Abstract.  Ørn S, Ueland T, Manhenke C, Sandanger Ø, Godang K, Yndestad A, Mollnes TE, Dickstein K, Aukrust P (Stavanger University Hospital, Stavanger; Oslo University Hospital Rikshospitalet; University of Bergen, Bergen; University of Oslo; Oslo; Norway). Increased interleukin‐1β levels are associated with left ventricular hypertrophy and remodelling following acute ST segment elevation myocardial infarction treated by primary percutaneous coronary intervention. J Intern Med 2012; 272: 267–276.Objectives.  To assess the relationship between interleukin (IL)‐1‐related molecules, infarct size and left ventricular (LV) remodelling following acute myocardial infarction (MI).Methods.  Forty‐two patients with first‐time diagnosis of ST segment elevation MI (STEMI), with a single occluded vessel successfully revascularized by primary percutaneous coronary intervention (PCI), were recruited to this observational study conducted at a university teaching hospital and followed for 1 year.Main outcome measures.  Plasma levels of IL‐1β, IL‐1 receptor antagonist (IL‐1Ra), IL‐18 and caspase‐1 were analysed before and 2 days, 1 week and 2 months after PCI. Serial cardiac magnetic resonance imaging (CMR) was used for the assessment of infarct size and LV remodelling. CMR findings at 1 year was the primary outcome variable.Results.  Univariate analysis showed that IL‐1‐related mediators were strongly (IL‐1 β), moderately (caspase‐1) and weakly (IL‐1Ra) associated with impaired myocardial function and noninfarct mass, but not infarct size, 1 year after reperfused STEMI. In multivariate analyses, troponin T predicted LV ejection fraction (LVEF), infarct size and LV end‐diastolic (LVEDVi) and end‐systolic volume index (LVESVi). However, significant additional variance was explained by IL‐1β, IL‐18 and caspase‐1. IL‐1β levels at 2 months, IL‐18 at 2 days and pre‐PCI caspase‐1 were predictors of LVEF. Caspase‐1 and in particular IL‐1β at 2 days were the only predictors of noninfarct mass. IL‐1β and IL‐18 at 2 days were predictors of LVEDVi, whilst pre‐PCI levels of IL‐1β contributed to prediction of LVESVi. By contrast, pro‐B‐type natriuretic peptide, C‐reactive protein, IL‐6 and transforming growth factor‐β1 (TGF‐β1) had no or only a weak (TGF‐β1) association with these CMR parameters in multivariate analyses.Conclusions.  IL‐1β levels after STEMI were strongly associated with impaired myocardial function and noninfarct LV mass after 1 year, suggesting a potential role for IL‐1β as a predictor of maladaptive myocardial remodelling following reperfused MI.

Sepsis and septic shock, caused by an excessive systemic host-inflammatory response, are associated with high morbidity and mortality. The complement system and TLRs provide important pattern recognition receptors initiating the cytokine storm by extensive cross-talk. We hypothesized that double blockade of complement C5 and the TLR coreceptor CD14 could improve survival of experimental polymicrobial sepsis. Mice undergoing cecal ligation and puncture (CLP)–induced sepsis were treated with neutralizing anti-CD14 Ab biG 53, complement C5 inhibitor coversin (Ornithodoros moubata C inhibitor), or a combination thereof. The inflammatory study (24-h observation) revealed statistically significant increases in 22 of 24 measured plasma biomarkers in the untreated CLP group, comprising 14 pro- and anti-inflammatory cytokines and 8 chemokines, growth factors, and granulocyte activation markers. Single CD14 or C5 blockade significantly inhibited 20 and 19 of the 22 biomarkers, respectively. Combined CD14 and C5 inhibition significantly reduced all 22 biomarkers (mean reduction 85%; range 54–95%) compared with the untreated CLP group. Double blockade was more potent than single treatment and was required to significantly inhibit IL-6 and CXCL1. Combined inhibition significantly reduced morbidity (motility and eyelid movement) and mortality measured over 10 d. In the positive control CLP group, median survival was 36 h (range 24–48 h). Combined treatment increased median survival to 96 h (range 24–240 h) (p = 0.001), whereas survival in the single-treatment groups was not significantly increased (median and range for anti-CD14 and anti-C5 treatment were 36 h [24–48 h] and 48 h [24–96 h]). Combined with standard intervention therapy, specific blockade of CD14 and C5 might represent a promising new therapeutic strategy for treatment of polymicrobial sepsis.