Objectives: Myocardial failure, leading to inotrope-unresponsive shock, is the predominant cause of death in meningococcal and other forms of septic shock. Proinflammatory cytokines released in septic shock are known to have myocardial depressant effects. We previously showed that interleukin 6 is a major myocardial depressant factor in children with meningococcal septicemia. In the current study, we aimed to investigate the mechanisms by which interleukin 6 induces myocardial failure in meningococcal sepsis and to identify potential novel therapeutic targets.
Design: Laboratory-based study.
Setting: University hospital and laboratories.
Patients: Children with a clinical diagnosis of meningococcal septic shock.
Methods: We studied interleukin 6-induced signaling events, both in vitro using isolated rat ventricular cardiac myocytes as a model of myocardial contractility and in whole blood from children with meningococcal sepsis.
Measurements and Main Results: We demonstrated involvement of Janus kinase 2, phosphatidylinositol 3-kinase, Akt, and p38 mitogen-activated protein kinase in interleukin 6-induced negative inotropy in isolated cardiac myocytes. Inhibition of p38 mitogen-activated protein kinase not only reversed interleukin 6-induced myocardial depression in both rat and human myocytes, but restored inotrope responsiveness. Cardiomyocytes transduced with dominant-negative p38 mitogen-activated protein kinase showed no interleukin 6-induced myocardial depression. To investigate p38 mitogen-activated protein kinase in vivo, we profiled global RNA expression patterns in peripheral blood of children with meningococcal septicemia. Transcripts for genes mapping to the p38 mitogen-activated protein kinase pathway showed significantly altered levels of abundance with a high proportion of genes of this pathway affected.
Conclusions: Our findings demonstrate an integral role of the p38 mitogen-activated protein kinase pathway in interleukin 6-mediated cardiac contractile dysfunction and inotrope insensitivity. Dysregulation of the p38 mitogen-activated protein kinase pathway in meningococcal septicemia suggests that this pathway may be an important target for novel therapies to reverse myocardial dysfunction in patients with meningococcal septic shock who are not responsive to inotropic support.
From the Departments of Paediatrics (NP, HE, VJW, CAH, ML) and Cardiac Medicine (NP, JLF, SEH), Imperial College London, London UK; Stanford University School of Medicine (MG, DAR), Stanford, CA, and VA Palo Alto Health Care System, Palo Alto, CA; Brighton and Sussex Medical School (SJW), University of Sussex, Sussex, UK; and St George's Medical Biomics Centre (JLD), St George's, University of London, London, UK.
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This work was funded by research grant funding from The Meningitis Research Foundation, Meningitis UK and a Wellcome Trust/Burroughs–Wellcome Infectious Diseases Initiative Award. Dr. Pathan is a HEFCE clinical senior lecturer. The study was supported by the National Institute for Health Research Comprehensive Biomedical Research Centre at St Mary's Hospital and the BHF Centre of Excellence at Imperial College London.
Mr. Pathan and Dr. Franklin contributed equally to this article. Mr. Eleftherohorinou and Dr. Wright contributed equally to this article. Drs. Harding and Levin contributed equally to this article.
Mr. Pathan received funding from the Meningitis Research Foundation. Dr. Griffiths received funding from Wellcome Trust. Dr. Harding received funding from a Heart U.K. grant. The remaining authors have not disclosed any potential conflicts of interest.
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