Sepsis is one of the leading causes of death in intensive care units affecting more than 18 million people worldwide. In the last decade more than 60 clinical trials failed in the field of septic shock. Moreover, clinical studies show that effective therapies in similar diseases have only moderate effect at the case of sepsis. The reason is not fully understood, however, the application of new synthetic and natural molecules and identification of new therapeutic targets give the opportunity to promote the treatment of the disease. Endotoxin, or lipopolysaccharide (LPS), is a component of Gram-negative bacteria and is an extremely potent toxin. Lipid A has been recognized to be the main toxic moiety of LPS and is responsible for many of the pathophysiological responses leading to multiple organ failure in Gram negative sepsis. Exposure to specific mediators of the sepsis syndrome, particularly bacterial endotoxins, yields endocrine, metabolic, and procoagulant changes commonly found in patients with severe sepsis, causes well documented hemodynamic effects similar to those observed during sepsis, and results in acute systemic organ injury and associated metabolic abnormalities, including altered metabolism of oxygen and other energy substrates, typical of the septic condition. Although precise mechanisms by which sepsis leads to multiple organ dysfunction are unknown, growing evidence suggests that blocking the main inflammatory signaling pathways might be a strategy to control the pathophysiology of sepsis. Nuclear factor-κB (NF-κB) as one of the most important inflammatory transcription factors plays a crucial role in regulation of uncontrollable inflammatory processes leading to sepsis. A number of enzymes and adaptor proteins play important role in signaling pathway between the cell surface TLR4 receptor and the NF-κB transcription factor, localized in the nucleus. On the basis of our recent results TRAF6, a ubiquitination –activated adaptor protein, is in the focus of our study which activates NF-κB through the IKK complex.
We want to examine the role of TRAF6 – a key adaptor protein in the NF-κB pathway – in LPS-induced septic shock model. Our aim is twofold: in one hand we want to determine the effect of inhibition of TRAF6 during the early and late phase of sepsis using in vitro (RAW 264.7 cell line, RAW-Blue™ cell line, primary intraperitoneal macrophages) and in vivo (mouse septic shock model) systems. Upon LPS stimulation, beside the well characterized early activation of NF-κB there is a late phase activation, as well. In our study we focus our attention on this clinically more relevant late response. On the other hand, we want to establish a model system in which we can determine and analyze the effect of different potential inhibitory compounds in inflammatory processes.
Members of the team: Csenge Antus, Nikoletta Kálmán, Fruzsina Fónai, Balázs Radnai, Péter Jakus, Balázs Veres; TDK students: Hisatomi Kensuke, Gergő Berke, Péter Dombóvári