New therapeutic strategies for prevention of multiple organ dysfunction associated with shock of various aetiologies
Zusammenfassung der Projektergebnisse
Sepsis is the systemic response to infection with a wide range of clinical symptoms often leading to multiple organ dysfunction. To date, therapies for sepsis are mostly supportive in nature and there is still an unmet need for new specific therapeutic strategies to improve the outcome of septic patients. This project was aimed to investigate novel therapeutic approaches to ameliorate multiple organ dysfunction in experimental sepsis. Clinical trials have demonstrated the tissue-protective role of erythropoietin (EPO) in various conditions, but the positive effects were accompanied by significant adverse side effects that are attributable to the well-described haematopoietic effects of EPO. There is limited evidence that the tissue-protective effects of EPO are mediated by a heterocomplex of the erythropoietin receptor and the beta-common receptor (βcR), which is pharmacologically distinct from the erythropoietin receptor homodimer that is responsible for erythropoiesis. However, the role of EPO in sepsis-induced cardiac dysfunction is unknown and the role of EPO in sepsis-induced acute renal dysfunction/injury (AKI) is still controversial. The impact of the βcR for potential beneficial effects afforded by EPO in sepsis-associated multiple organ dysfunction has not been investigated yet. This study had the objective to investigate the effects (and ultimately the therapeutic potential) of EPO in sepsis-associated cardiac dysfunction and AKI and to elucidate the underlying signalling mechanism(s). Cardiac function [in vivo (echocardiography) and ex vivo (Langendorff-perfused heart)] and kidney function/injury (serum analysis, histology, immunohistochemistry) was assessed in wild-type and βcR knockout mice, that were subjected to endotoxaemia [lipopolysaccharide (LPS); young mice] for 16-18 hours or polymicrobial sepsis (caecal ligation and puncture (CLP); aged mice] for 24 hours. Mice received EPO (1000 IU/kg body weight) 1 hour after LPS or CLP. Most notably, the results of this study demonstrate for the first time that the βcR is essential for the improvements in the impaired systolic contractility and the attenuation of AKI afforded by EPO in experimental sepsis. Furthermore, semi-quantitative immunoblot analysis of mouse hearts and kidneys revealed that these beneficial effects of EPO are associated with the activation of pro-survival pathways [Akt and endothelial nitric oxide synthase (eNOS)] and the inhibition of pro-inflammatory signalling pathways [glycogen synthase kinase (GSK)-3β and nuclear factor (NF)-κB] in a βcR dependent manner. Therefore, targeting the βcR with exclusive agonists may represent a novel therapeutic approach for the improvement of sepsis-associated multiple organ dysfunction avoiding the haematopoietic side effects of EPO. The NF-κB protein complex is of great importance for the regulation of inflammation and is activated by IκB-Kinase (IKK). There is now good evidence that a large number of interventions, like EPO, that inhibit the activation of the transcription factor NF-κB also reduce multiple organ dysfunction in sepsis. Furthermore, clinical studies suggest a correlation between enhanced NF-κB activation in sepsis and poor outcome. Inhibitors of κB (IκBs) mask the nuclear localization signals of NF-κB proteins and sequester NF-κB as an inactive complex in the cytoplasm. IκB kinase (IKK) specifically phosphorylates IκBs, which results subsequently in the ubiquitination and degradation of IκBs. Thus, the NF-κB complex is liberated to enter the nucleus and to control DNA transcription. This raises the important, but hitherto unaddressed question as to whether one can improve the multiple organ dysfunction caused by sepsis by specifically inhibiting IKK. I was able to demonstrate for the first time that the delayed (1 h after induction of disease) selective inhibition of IKK via the specific IKK inhibitor IKK 16 (1 mg/kg body weight) reduces the multiple organ dysfunction induced by LPS/Peptidoglycan (young mice) or polymicrobial sepsis (CLP; aged mice) in the mouse at 24 hours. Results of semi-quantitative immunoblot analysis of mouse hearts and livers suggest that the organ protective properties of IKK 16 in experimental sepsis are (at least in part) attributable to inhibition of NF-κB-mediated pro-inflammatory activity, decreased inducible nitric oxide synthase (iNOS) expression and, interestingly, the activation of the wellknown Akt/eNOS survival pathway. Therefore selective inhibition of IKK may be a novel therapeutic approach to improve the organ dysfunction/injury caused by sepsis and other conditions associated with systemic inflammation.
Projektbezogene Publikationen (Auswahl)
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(2012). Erythropoietin reduces the acute kidney injury in experimental sepsis via activation of the β-common receptor. 7th Congress of the International Federation of Shock Societies, 35th Annual Conference on Shock. June 9 – 13, Miami Beach, Florida, USA. Abstract published in: Supplement to Shock, Vol. 37, Supplement 1, P 67, June 2012
Coldewey, S. M., Khan, A., Rogazzo, M., Collino, M., Kapoor, A., Patel, N. S., Thiemermann, C.
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(2013). Die Inhibition der IκB-Kinase verbessert die Sepsis-assoziierte myokardiale Dysfunktion in der Maus. 27. Wissenschaftliche Arbeitstage der DGAI in Würzburg, February 22 – 23, Würzburg, Germany. Anästh Intensivmedizin, 54:334-379, July 2013
Coldewey, S. M., Collino, M., Rogazzo, M., Patel, N. S., Thiemermann, C.
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(2013). Erythropoietin attenuates acute kidney dysfunction in murine experimental sepsis by activation of the beta-common receptor. Kidney Int, [Epub ahead of print]
Coldewey, S. M., Khan, A. I., Kapoor, A., Collino, M., Rogazzo, M., Brines, M., Cerami, A., Hall, P., Sheaff, M., Kieswich, J. E., Yakoob, M. M., Patel, N. S.,Thiemermann, C.
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(2013). Erythropoietin attenuates cardiac dysfunction in experimental sepsis via activation of the beta-common receptor. Dis Model Mech 6, 1021-30
Khan, A. I., Coldewey, S. M., Patel, N. S., Rogazzo, M., Collino, M., Yaqoob, M. M., Radermacher, P., Kapoor, A., Thiemermann, C.
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(2013). Inhibition of IκB kinase reduces the multiple organ dysfunction caused by sepsis in the mouse. Dis Model Mech 6, 1031-42
Coldewey, S. M., Rogazzo, M., Collino, M., Patel, N. S., Thiemermann, C.
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2013). Novel therapeutic strategies to reduce multiple organ dysfunction in experimental sepsis. PhD thesis. Queen Mary University of London
Coldewey S. M.
