Willeke M. C. Jong

Deletion of the innate immune NLRP3 receptor abolishes cardiac ischemic preconditioning and is associated with decreased Il-6/STAT3 signaling

Objective Recent studies indicate that the innate immune system is not only triggered by exogenous pathogens and pollutants, but also by endogenous danger signals released during ischemia and necrosis. As triggers for the innate immune NLRP3 inflammasome protein complex appear to overlap with those for cardiac ischemia-reperfusion (I/R) and ischemic preconditioning (IPC), we explored the possibility that the NLRP3 inflammasome is involved in IPC and acute I/R injury of the heart. Principal Findings Baseline cardiac performance and acute I/R injury were investigated in isolated, Langendorff-perfused hearts from wild-type (WT), ASC−/− and NLRP3−/− mice. Deletion of NLRP3 inflammasome components ASC−/− or NLRP3−/− did not affect baseline performance. The deletions exacerbated I/R-induced mechanical dysfunction, but were without effect on I/R-induced cell death. When subjected to IPC, WT and ASC−/− hearts were protected against I/R injury (improved function and less cell death). However, IPC did not protect NLRP3−/− hearts against I/R injury. NLRP3−/− hearts had significantly decreased cardiac IL-6 levels with a trend towards lower IL-1β levels at end reperfusion, suggesting abrogation of IPC through diminished IL-6 and/or IL-1β signaling. Subsequent experiments showed that neutralising IL-6 using an antibody against IL-6 abrogated IPC in WT hearts. However, inhibition of the IL-1r receptor with the IL-1 receptor inhibitor Anakinra (100 mg/L) did not abrogate IPC in WT hearts. Analysis of survival kinases after IPC demonstrated decreased STAT3 expression in NLRP3−/− hearts when compared to WT hearts. Conclusions The data suggest that the innate immune NLRP3 protein, in an NLRP3-inflammasome-independent fashion, is an integral component of IPC in the isolated heart, possibly through an IL-6/STAT3 dependent mechanism.

The acute effects of acetate-balanced colloid and crystalloid resuscitation on renal oxygenation in a rat model of hemorrhagic shock

INTRODUCTION Fluid resuscitation therapy is the initial step of treatment for hemorrhagic shock. In the present study we aimed to investigate the acute effects of acetate-balanced colloid and crystalloid resuscitation on renal oxygenation in a rat model of hemorrhagic shock. We hypothesized that acetate-balanced solutions would be superior in correcting impaired renal perfusion and oxygenation after severe hemorrhage compared to unbalanced solutions. METHODS In anesthetized, mechanically ventilated rats, hemorrhagic shock was induced by withdrawing blood from the femoral artery until mean arterial pressure (MAP) was reduced to 30 mmHg. One hour later, animals were resuscitated with either hydroxyethyl starch (HES, 130/0.42 kDa) dissolved in saline (HES-NaCl; n=6) or a acetate-balanced Ringers solution (HES-RA; n=6), as well as with acetated Ringers solution (RA; n=6) or 0.9% NaCl alone (NaCl; n=6) until a target MAP of 80 mmHg was reached. Oxygen tension in the renal cortex (CμPO2), outer medulla (MμPO2), and renal vein were measured using phosphorimetry. RESULTS Hemorrhagic shock (MAP=30 mmHg) significantly decreased renal oxygenation and oxygen consumption. Restoring the MAP to 80 mmHg required 24.8±1.7 ml of NaCl, 21.7±1.4 ml of RA, 5.9±0.5 ml of HES-NaCl (p<0.05 vs. NaCl and RA), and 6.0±0.4 ml of HES-RA (p<0.05 vs. NaCl and RA). NaCl, RA, and HES-NaCl resuscitation led to hyperchloremic acidosis, while HES-RA resuscitation did not. Only HES-RA resuscitation could restore renal blood flow back to ∼85% of baseline level (from 1.9±0.1 ml/min during shock to 5.1 ml±0.2 ml/min 60 min after HES-RA resuscitation) which was associated with an improved renal oxygenation (CμPO2 increased from 24±2 mmHg during shock to 50±2 mmHg 60 min after HES-RA resuscitation) albeit not to baseline level. At the end of the protocol, creatinine clearance was decreased in all groups with no differences between the different resuscitation groups. CONCLUSION While resuscitation with the NaCl and RA (crystalloid solutions) and the HES-NaCl (unbalanced colloid solution) led to hyperchloremic acidosis, resuscitation with the HES-RA (acetate-balanced colloid solution) did not. The HES-RA was furthermore the only fluid restoring renal blood flow back to ∼85% of baseline level and most prominently improved renal microvascular oxygenation.

Nlrp3 plays no role in acute cardiac infarction due to low cardiac expression

a Laboratory of Experimental Intensive Care and Anesthesiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands b Department of Anesthesiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands c Department of Intensive Care, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands d Department of Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands

A transgenic mouse model for the simultaneous monitoring of ANF and BNP gene activity during heart development and disease

AIM The expression of Nppa (ANF) and Nppb (BNP) marks the chamber myocardium in the embryo, and both genes serve as early and accurate markers for hypertrophy and heart failure. Non-invasive visualization of Nppa-Nppb expression in living mice would enable to evaluate the disease state during the course of time in heart disease models. We sought to develop a method to assess the pattern and level of Nppa and Nppb expression within living mice. METHODS AND RESULTS A modified bacterial artificial chromosome containing a genomic segment spanning the Nppa-Nppb locus was randomly integrated into the mouse genome. Firefly Luciferase was inserted into Nppa and the red fluorescent protein gene Katushka into Nppb. Both reporters precisely recapitulated the spatio-temporal patterns of Nppa and Nppb, respectively. In a hypertrophy model (transverse aortic constriction) and myocardial infarction model (left anterior descending coronary artery occlusion), the non-invasively measured bioluminescent signal from Luciferase correlated with Nppa expression, and the intensity of red fluorescence with levels of the expression of Katushka and Nppb. After myocardial infarction, the border zone of the infarct area was readily identified by an increased intensity of Katushka fluorescence. CONCLUSIONS A genomic region sufficient to regulate the developmental pattern and stress response of Nppa and Nppb has been defined. The double reporter mice can be used for the functional imaging and investigation of cardiac hypertrophy and myocardial infarction in vivo.

A role for NLRP3 inflammasome in acute myocardial ischaemia-reperfusion injury?

With much interest we have read the recently published article by Sandanger et al .,1 where NLRP3 mRNA expression was shown to be increased 3–7 days following permanent occlusion of the left anterior descending artery. The increased expression was observed mainly in fibroblasts. The authors also compared hearts from wild-type (WT) C57Bl/6, NLRP3−/−, and ASC−/− mice, using an isolated Langendorff-perfused heart model of acute ischaemia-reperfusion injury. It was reported that deletion of NLRP3 improved cardiac function and reduced infarct size in the isolated heart model. The authors summarized the data and combined the results from the in …

Myocardial ischemia and reperfusion injury: Studies using transgenic and knockout mice

Transgenic and knockout mice are created and used for a large variety of research objectives. This overview describes the (genetically modified) mouse models that have been used to study the development of myocardial ischemia and reperfusion injury. The role of cytokines, chemokines, leukocytes, reactive oxygen species, anti-oxidants, NO, complement system, coagulation system, heat shock proteins, apoptosis and necrosis, and acute phase reactants are presented