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Toll-like receptor 4 is essential to preserving cardiac function and survival in low-grade polymicrobial sepsis.

ABSTRACT: Toll-like receptor 4 (TLR4), the receptor for endotoxin, mediates hyperinflammatory response and contributes to high mortality during both endotoxin shock and severe sepsis. However, little is known about the role of TLR4 in the pathogenesis of low-grade polymicrobial sepsis, which is often associated with immunosuppression.Low-grade polymicrobial sepsis was generated by cecum ligation and puncture. Mortality was monitored in wild- type (C57BL/10ScSn) and TLR4def (C57BL/10ScCr) mice. Ex vivo heart and individual cardiomyocyte function were assessed in Langendorff (Hugo Sachs Elektronik; Harvard Apparatus, Holliston, MA) and IonOptix systems (IonOptix, Milton, MA), respectively. Serum chemistry was tested for liver and kidney injury. Cytokines were examined using a multiplex immunoassay. Neutrophil migratory and phagocytic functions were assessed using flow cytometry. Reactive oxygen species were measured using redox-sensitive dichlorodihydrofluorescein dye.Following cecum ligation and puncture, wild-type mice developed bacterial peritonitis with mild cardiac dysfunction (n=3 in sham and n=8 in cecum ligation and puncture) and a mortality of 23% within 14 days (n=22). In comparison, septic TLR4def mice had deleterious cardiac dysfunction (n=6 in sham and n=10 in cecum ligation and puncture), kidney and liver injury (n=7), and much higher mortality at 81% (n=21). The deleterious effects observed in septic TLR4def mice were associated with increased local and systemic cytokine response, reduced neutrophil migratory and phagocytic function, increased reactive oxygen species generation in leukocytes, and impaired bacterial clearance.TLR4 plays an essential role in host defense against low-grade polymicrobial sepsis by mediating neutrophil migratory/phagocytic functions, attenuating inflammation, reducing reactive oxygen species generation, and enhanced bacterial clearance.

SUBMITTER: Zhang M

PROVIDER: S-EPMC4237617 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Toll-like receptor 4 is essential to preserving cardiac function and survival in low-grade polymicrobial sepsis.

Zhang Ming M Zou Lin L Feng Yan Y Chen Yu-Jung YJ Zhou Qichang Q Ichinose Fumito F Chao Wei W

Anesthesiology 20141201 6

<h4>Background</h4>Toll-like receptor 4 (TLR4), the receptor for endotoxin, mediates hyperinflammatory response and contributes to high mortality during both endotoxin shock and severe sepsis. However, little is known about the role of TLR4 in the pathogenesis of low-grade polymicrobial sepsis, which is often associated with immunosuppression.<h4>Methods</h4>Low-grade polymicrobial sepsis was generated by cecum ligation and puncture. Mortality was monitored in wild- type (C57BL/10ScSn) and TLR4d ...[more]

PMID: 24937074

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Project description:BackgroundSex differences in sepsis are underexplored and incompletely understood. Cardiac function in early sepsis is pivotal in determining survival; hyperdynamic left ventricular ejection fraction is associated with higher mortality. Female sex may be cardioprotective, but variable experimental findings have not controlled for hypovolaemia. Sex-specific local cardiac versus peripheral inflammation in causing cardiovascular dysfunction also remain unclear. We therefore examined whether there are sex-specific differences in cardiac function in early sepsis, controlling for volaemic status and sex-specific differences in the peripheral inflammatory response initiated by tumour necrosis factor (TNFα).MethodsWe used an experimental polymicrobial sepsis (faecal slurry) model titrated to minimise hypovolaemia as a confounding factor. We quantified cardiac function (transthoracic cardiac echocardiography) 1 week before, and 18 h after, sepsis. Cardiac injury (troponin I), inflammation and immune cell infiltration (flow cytometry) were quantified in naïve and septic female and male mice 18 h after sepsis. To evaluate the sex-specific influence of TNFα derived from peripheral leukocytes, we repeated the experiments in iRHOM2-/- mice that are unable to shed TNFα exclusively from circulating leucocytes.ResultsSerum troponin I increased to 1.39 ± 0.38 ng mL-1 (from undetectable levels in controls) 18 h after onset of normovolaemic sepsis to a similar extent in both sexes. Stroke volume in male mice increased by 8 µL [(3-13); p = 0.004], compared to individualised pre-sepsis values. By contrast, stroke volume remained at baseline levels in females [mean difference: 4 µL (- 1 to 9)]. Messenger RNA levels of markers for cardiac injury/inflammation after sepsis (real-time polymerase-chain reaction) were elevated in male wild-type mice compared to female wild types (n = 10/sex), with higher cardiac mRNA levels of atrial natriuretic peptide, inflammation (TNFα) and oxidative stress (superoxide dismutase-1), although serum troponin I values were similarly elevated. Flow cytometry analysis of cardiac tissue showed doubling of CD4 + leukocyte infiltration in male mice. Sex-specific cardiac physiologic differences were similar in iRHOM2-/- mice that are unable to shed TNFα exclusively from leucocytes.ConclusionsIn early normovolaemic polymicrobial sepsis, a relative hyperdynamic response develops in male mice. Myocardial stress/injury after early sepsis is limited in females, with less cardiac infiltration of CD4 + leukocytes but independent of shedding of TNFα from peripheral circulating leukocytes.

Project description:Peroxisome proliferator-activated receptor-? is significantly down-regulated in circulating leukocytes from children with sepsis. Peroxisome proliferator-activated receptor-? null (Ppara) mice have greater mortality than wild-type mice when subjected to sepsis by cecal ligation and puncture. We sought to characterize the role of peroxisome proliferator-activated receptor-? in sepsis and to identify the mechanism whereby peroxisome proliferator-activated receptor-? confers a survival advantage.Prospective randomized preclinical study.Laboratory investigation.Male C57Bl/6J and Ppara mice (B6.129S4-Ppara/J), aged 12-16 weeks.Bone marrow chimeric mice were generated and subjected to cecal ligation and puncture. Survival was measured for 7 days. Separate groups of nontransplanted mice underwent cecal ligation and puncture and were euthanized 24 hours later for plasma and tissue analyses.Ppara mice had dramatically reduced survival compared with wild-type mice irrespective of the peroxisome proliferator-activated receptor-? status of the bone marrow they received (3% vs 63%; p < 0.0001). No difference in survival was observed between Ppara mice that received wild-type versus Ppara marrow or in wild-type mice receiving wild-type versus Ppara marrow. In septic, nontransplanted mice at 24 hours, Ppara mice had elevated cardiac troponin levels compared with wild-type mice. Cardiac histologic injury scores were greater in Ppara versus wild-type mice. Expression of transcription factors and enzymes related to fatty acid oxidation in the heart were profoundly down-regulated in both wild-type and Ppara mice, but more so in the Ppara mice.Peroxisome proliferator-activated receptor-? expression in nonhematopoietic tissues plays a critical role in determining clinical outcome in experimental polymicrobial sepsis and is more important to survival in sepsis than hematopoietic peroxisome proliferator-activated receptor-? expression. Cardiac injury due to inadequate energy production from fatty acid substrate is a probable mechanism of decreased survival in Ppara mice. These results suggest that altered peroxisome proliferator-activated receptor-?-mediated cellular metabolism may play an important role in sepsis-related end-organ injury and dysfunction, especially in the heart.

Project description:OBJECTIVES:The intestinal epithelium compartmentalizes the sterile bloodstream and the commensal bacteria in the gut. Accumulating evidence suggests that this barrier is impaired in sepsis, aggravating systemic inflammation. Previous studies reported that cathelicidin is differentially expressed in various tissues in sepsis. However, its role in sepsis-induced intestinal barrier dysfunction has not been investigated. DESIGN:To examine the role of cathelicidin in polymicrobial sepsis, cathelicidin wild-(Cnlp+/+) and knockout (Cnlp-/-) mice underwent cecal-ligation and puncture (CLP) followed by the assessment of septic mortality and morbidity as well as histological, biochemical, immunological, and transcriptomic analyses in the ileal tissues. We also evaluated the prophylactic and therapeutic efficacies of vitamin D3 (an inducer of endogenous cathelicidin) in the CLP-induced murine polymicrobial sepsis model. RESULTS:The ileal expression of cathelicidin was increased by three-fold after CLP, peaking at 4?h. Knockout of Cnlp significantly increased 7-day mortality and was associated with a higher murine sepsis score. Alcian-blue staining revealed a reduced number of mucin-positive goblet cells, accompanied by reduced mucin expression. Increased number of apoptotic cells and cleavage of caspase-3 were observed. Cnlp deletion increased intestinal permeability to 4kD fluorescein-labeled dextran and reduced the expression of tight junction proteins claudin-1 and occludin. Notably, circulating bacterial DNA load increased more than two-fold. Transcriptome analysis revealed upregulation of cytokine/inflammatory pathway. Depletion of Cnlp induced more M1 macrophages and neutrophils compared with the wild-type mice after CLP. Mice pre-treated with cholecalciferol (an inactive form of vitamin D3) or treated with 1alpha, 25-dihydroxyvitamin D3 (an active form of VD3) had decreased 7-day mortality and significantly less severe symptoms. Intriguingly, the administration of cholecalciferol after CLP led to worsened 7-day mortality and the associated symptoms. CONCLUSIONS:Endogenous cathelicidin promotes intestinal barrier integrity accompanied by modulating the infiltration of neutrophils and macrophages in polymicrobial sepsis. Our data suggested that 1alpha, 25-dihydroxyvitamin D3 but not cholecalciferol is a potential therapeutic agent for treating sepsis.

Project description:The development of cardiac dysfunction caused by microbial infection predicts high mortality in sepsis patients. Specialized pro-resolving mediators (SPMs) mediate resolution of inflammation in many inflammatory diseases, and are differentially expressed in plasma of sepsis patients. Here, we investigated whether the levels of SPMs are altered in the murine septic heart following polymicrobial sepsis-induced cardiac dysfunction. Ten weeks-old male C57BL/6 mice were subjected to polymicrobial sepsis induced by cecal ligation and puncture (CLP), which is a clinically relevant sepsis model receiving analgesics, antibiotics, and fluid resuscitation. CLP caused a significant systolic dysfunction assessed by echocardiography. The hearts were subjected to LC-MS/MS based lipid mediator profiling. Many SPMs were significantly reduced in septic hearts, among which RvE1 had a ~93-fold reduction. Treatment of CLP mice with synthetic RvE1 (1 μg/mouse i.v.) at 1 h after CLP increased peritoneal macrophages number, particularly MHC II- macrophages. RvE1 reduced pro-inflammatory gene expression (interleukin-1β, interleukin-6, and CCL2) in lipopolysaccharide-stimulated bone marrow-derived macrophages (BMDMs) in vitro. RvE1 attenuated cardiac dysfunction in septic mice and increased cardiac phosphorylated Akt; decreased cardiac phosphorylated IκB kinase α/β, nuclear translocation of the NF-κB subunit p65, extracellular signal-regulated kinase 1/2, and c-Jun amino-terminal kinases 1/2. Most notably, RvE1 treatment reduced peritoneal bacterial load and promoted phagocytosis activity of BMDMs. In conclusion, cardiac SPMs, particularly RvE1, are substantially reduced in mice with polymicrobial sepsis. Delayed therapeutic administration of RvE1 to mice with polymicrobial sepsis attenuates the cardiac dysfunction through modulating immuno-inflammatory responses. In addition to the above effects, the ability to enhance bacterial clearance makes RvE1 an ideal therapeutic to reduce the sequalae of polymicrobial sepsis.

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Toll-like receptor 4 is essential to preserving cardiac function and survival in low-grade polymicrobial sepsis.

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Toll-like receptor 4 is essential to preserving cardiac function and survival in low-grade polymicrobial sepsis.

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