Lonneke Smeding

STRUCTURAL CHANGES OF THE HEART DURING SEVERE SEPSIS OR SEPTIC SHOCK

ABSTRACT Cardiovascular dysfunction is common in severe sepsis or septic shock. Although functional alterations are often described, the elevated serum levels of cardiac proteins and autopsy findings of myocardial immune cell infiltration, edema, and damaged mitochondria suggest that structural changes to the heart during severe sepsis and septic shock may occur and may contribute to cardiac dysfunction. We explored the available literature on structural (versus functional) cardiac alterations during experimental and human endotoxemia and/or sepsis. Limited data suggest that the structural changes could be prevented, and myocardial function improved by (pre-)treatment with platelet-activating factor, cyclosporin A, glutamine, caffeine, simvastatin, or caspase inhibitors.

Sepsis-induced myocardial depression is associated with transcriptional changes in energy metabolism and contractile related genes: A physiological and gene expression-based approach

Background:Increased nitric oxide production and altered mitochondrial function have been implicated in sepsis-induced cardiac dysfunction. The molecular mechanisms underlying myocardial depression in sepsis and the contribution of nitric oxide in this process however, are incompletely understood. Objectives:To assess the transcriptional profile associated with sepsis-induced myocardial depression in a clinically relevant mouse model, and specifically test the hypothesis that critical transcriptional changes are inducible nitric oxide synthase-dependent. Design:Laboratory investigation. Setting:University affiliated research laboratory. Subjects:C57/BL6 wild type and congenic B6 129P2-Nos2tm1Lau/J (iNOS−/−) mice. Interventions:Assessment of myocardial function after 48 hrs of induction of polymicrobial sepsis by caecal ligation and perforation. Measurements and Results:We compared the myocardial transcriptional profile in C57/BL6 wild type mice and congenic B6 129P2-Nos2tm1Lau/J litter mates after 48 hrs of polymicrobial sepsis induced by caecal ligation and perforation. Profiling of 22,690 expressed sequence tags by gene set enrichment analysis demonstrated that inducible nitric oxide synthase −/− failed to down regulate critical bioenergy and metabolism related genes including the gene for peroxisome proliferator-activated receptor gamma coactivator 1. Bioinformatics analysis identified a striking concordance in down regulation of transcriptional activity of proliferator-activated receptor gamma coactivator 1-related transcription factors resulting in sepsis associated myocardial remodeling as shown by isoform switching in the expression of contractile protein myosin heavy chain. In inducible nitric oxide synthase −/− deficient mice, contractile depression was minimal, and the transcriptional switch was absent. Conclusions:Metabolic and myosin isoform gene expression switch in sepsis-induced myocardial depression is inducible nitric oxide synthase-dependent. Furthermore, we suggest that the molecular switch favoring the expression of fetal isoforms of contraction related proteins is associated with regulation of proliferator-activated receptor gamma coactivator 1 and related transcription factors in an inducible nitric oxide synthase-dependent manner.

Salutary effect of resveratrol on sepsis-induced myocardial depression

Objectives:We hypothesized that resveratrol administration would reverse sepsis-dependent downregulation of peroxisome proliferator activated receptor-&ggr; coactivator 1&agr;, preserve mitochondrial integrity, and rescue animals from sepsis-induced myocardial failure. Setting:Teaching hospital research laboratory. Interventions:Cecal ligation and puncture in mice was performed to induce sepsis. Mice that underwent cecal ligation and puncture were randomly assigned to receive resveratrol (30 mg/kg or 60 mg/kg) or vehicle 1 mL sodium chloride 0.9% subcutaneously in the scruff of the neck directly after surgery and at 16, 24, and 40 hrs, respectively. Measurements and Results:Forty-eight hrs after cecal ligation and puncture, cardiac performance was established using echocardiography. Mitochondrial integrity was evaluated with electron microscopy, and changes in gene expression were evaluated with microarray analysis. Survival at 48 hrs was just under 50% and comparable between groups. Myocardial contractile function significantly improved after resveratrol treatment. Resveratrol-treated mice developed focal areas of edema, whereas vehicle-treated mice developed significant, diffuse myocardial edema. Electron microscopy revealed widespread swollen mitochondria with ruptured outer membranes, autophagosomes, and vacuolation of the internal compartment, which were significantly attenuated in resveratrol-treated animals. Resveratrol treatment significantly increased cardiac expression of peroxisome proliferator–activated receptor-&ggr; coactivator 1a. Microarray analysis revealed that resveratrol treatment resulted in upregulation of the peroxisome proliferator–activated receptor-&ggr; coactivator gene set containing genes known to be regulated by this transcriptional coactivator. Our data strongly suggest that administration of resveratrol modulates bioenergy metabolism, substrate utilization, oxidative stress, and detoxification pathways associated with both mitochondrial and cardiac pathological conditions, but does not alter mortality from sepsis. Conclusions:The salutary effects of resveratrol on cecal ligation and puncture-induced myocardial dysfunction are associated with increased peroxisome proliferator–activated receptor-&ggr; coactivator 1a abundance and function. Preservation of myocardial energy production capacity, prevention of secondary injury, mitigation of inflammation, and reversal of sepsis-induced myocardial remodeling are likely to underlie its beneficial effects. This however, does not result in improved survival.

Mechanical ventilation with high tidal volumes attenuates myocardial dysfunction by decreasing cardiac edema in a rat model of LPS-induced peritonitis

BackgroundInjurious mechanical ventilation (MV) may augment organ injury remote from the lungs. During sepsis, myocardial dysfunction is common and increased endothelial activation and permeability can cause myocardial edema, which may, among other factors, hamper myocardial function. We investigated the effects of MV with injuriously high tidal volumes on the myocardium in an animal model of sepsis.MethodsNormal rats and intraperitoneal (i.p.) lipopolysaccharide (LPS)-treated rats were ventilated with low (6 ml/kg) and high (19 ml/kg) tidal volumes (Vt) under general anesthesia. Non-ventilated animals served as controls. Mean arterial pressure (MAP), central venous pressure (CVP), cardiac output (CO) and pulmonary plateau pressure (Pplat) were measured. Ex vivo myocardial function was measured in isolated Langendorff-perfused hearts. Cardiac expression of endothelial vascular cell adhesion molecule (VCAM)-1 and edema were measured to evaluate endothelial inflammation and leakage.ResultsMAP decreased after LPS-treatment and Vt-dependently, both independent of each other and with interaction. MV Vt-dependently increased CVP and Pplat and decreased CO. LPS-induced peritonitis decreased myocardial function ex vivo but MV attenuated systolic dysfunction Vt-dependently. Cardiac endothelial VCAM-1 expression was increased by LPS treatment independent of MV. Cardiac edema was lowered Vt-dependently by MV, particularly after LPS, and correlated inversely with systolic myocardial function parameters ex vivo.ConclusionMV attenuated LPS-induced systolic myocardial dysfunction in a Vt-dependent manner. This was associated with a reduction in cardiac edema following a lower transmural coronary venous outflow pressure during LPS-induced coronary inflammation.

Aggravation of myocardial dysfunction by injurious mechanical ventilation in LPS-induced pneumonia in rats

BackgroundMechanical ventilation (MV) may cause ventilator-induced lung injury (VILI) and may thereby contribute to fatal multiple organ failure. We tested the hypothesis that injurious MV of lipopolysaccharide (LPS) pre-injured lungs induces myocardial inflammation and further dysfunction ex vivo, through calcium (Ca2+)-dependent mechanism.Materials and methodsN = 35 male anesthetized and paralyzed male Wistar rats were randomized to intratracheal instillation of 2 mg/kg LPS or nothing and subsequent MV with lung-protective settings (low tidal volume (Vt) of 6 mL/kg and 5 cmH2O positive end-expiratory pressure (PEEP)) or injurious ventilation (high Vt of 19 mL/kg and 1 cmH2O PEEP) for 4 hours. Myocardial function ex vivo was evaluated in a Langendorff setup and Ca2+ exposure. Key mediators were determined in lung and heart at the mRNA level.ResultsInstillation of LPS and high Vt MV impaired gas exchange and, particularly when combined, increased pulmonary wet/dry ratio; heat shock protein (HSP)70 mRNA expression also increased by the interaction between LPS and high Vt MV. For the heart, C-X-C motif ligand (CXCL)1 and Toll-like receptor (TLR)2 mRNA expression increased, and ventricular (LV) systolic pressure, LV developed pressure, LV +dP/dtmax and contractile responses to increasing Ca2+ exposure ex vivo decreased by LPS. High Vt ventilation aggravated the effects of LPS on myocardial inflammation and dysfunction but not on Ca2+ responses.ConclusionsInjurious MV by high Vt aggravates the effects of intratracheal instillation of LPS on myocardial dysfunction, possibly through enhancing myocardial inflammation via pulmonary release of HSP70 stimulating cardiac TLR2, not involving Ca2+ handling and sensitivity.

Early Myocardial Dysfunction is Not Caused by Mitochondrial Abnormalities in a Rat Model of Peritonitis

BACKGROUND Patients with complicated intra-abdominal infections are prone to develop multiple organ failure, including myocardial dysfunction. We hypothesized that early dysfunction during sepsis is associated with inflammation, mitochondrial injury, impaired mitochondrial function, and activation of mitochondrial biogenesis. MATERIALS AND METHODS Rats received lipopolysaccharide (LPS, n = 11) intraperitoneally. Healthy rats (n = 6) served as controls. Myocardial function was measured ex vivo in an isolated Langendorff-perfused heart set-up. Myocardial vascular cell adhesion molecule-1 (VCAM-1) expression was determined by immunofluorescence microscopy. Cytochrome c release and cytochrome c oxidase (COX IV) activity were measured by immunohistochemistry and enzyme histochemistry, respectively. Protein expression of tumor necrosis factor-α (TNF-α), B-cell lymphoma (Bcl)-2, peroxisome proliferator activated receptor γ cofactor 1α (PGC-1α), and mitochondrial transcription factor A (TFAM) were analyzed by Western blot technique. Mitochondria were studied by electron microscopy. RESULTS Two hours after LPS injection, developed pressure had decreased and after 4 h myocardial contractility (+dP/dt) and relaxation (-dP/dt) also had decreased. TNF-α protein expression was increased after 2 h and returned to normal at 4 h, whereas after 4 h VCAM-1 expression was higher in LPS-treated animals. At 2 h a substrate-dependent increase in COXIV-activity was seen, but no mitochondrial damage occurred as cytochrome c release, COX IV activity and Bcl-2, PGC-1α or TFAM expression were not changed. Electron microscopy did not reveal differences in myocardial mitochondrial characteristics between LPS-treated and control rats. CONCLUSIONS Early myocardial dysfunction in sepsis is associated with myocardial inflammation but not with mitochondrial injury, impaired mitochondrial function, or activated mitochondrial biogenesis.

Pulse pressure variation does not reflect stroke volume variation in mechanically ventilated rats with lipopolysaccharide-induced pneumonia.

The present study examined the relationship between centrally measured stroke volume variation (SVV) and peripherally derived pulse pressure variation (PPV) in the setting of increased total arterial compliance (CArt). Ten male Wistar rats were anaesthetized, paralysed and mechanically ventilated before being randomized to receive intrapulmonary lipopolysaccharide (LPS) or no LPS. Pulse pressure (PP) was derived from the left carotid artery, whereas stroke volume (SV) was measured directly in the left ventricle. Values of SVV and PPV were calculated over three breaths. Balloon inflation of a catheter positioned in the inferior vena cava was used, for a maximum of 30 s, to decrease preload while the SVV and PPV measurements were repeated. Values of CArt were calculated as SV/PP. Intrapulmonary LPS increased CArt and SV. Values of SVV and PPV increased in both LPS‐treated and untreated rats during balloon inflation. There was a correlation between SVV and PPV in untreated rats before (r = 0.55; P = 0.005) and during (r = 0.69; P < 0.001) occlusion of the vena cava. There was no such correlation in LPS‐treated rats either before (r = −0.08; P = 0.70) or during (r = 0.36; P = 0.08) vena cava occlusion. In conclusion, under normovolaemic and hypovolaemic conditions, PPV does not reflect SVV during an increase in CArt following LPS‐induced pneumonia in mechanically ventilated rats. Our data caution against their interchangeability in human sepsis.

What is new in Shock, July 2009?: from bench to bedside.

This issue of Shock; incorporates new insights in the field of sepsis or I/R-induced inflammation and organ (e.g., lung, heart, and hepatosplanchnic) injury and dysfunction. Novel mechanisms and potential therapies are described in experimental and clinical settings, which may become relevant in the clinical arena in the future. We discuss the published articles in the context of some recent literature after grouping them into major domains.