Characterization of STAT, IRF and NF-kappaB signalling pathways involved in sepsis

Sepsis is characterized by mysregulation of the immune system in response to invasion of microorganisms. Microbes or microbial components initiate a complex signalling cascade that elicits an overwhelming pro-inflammatory response resulting in systemic dysfunction, vasculatory collapse, multiple organ failure and death. The key signalling pathways mediating sepsis are known to be regulated by transcription factor family members Nuclear Factor-kappaB (NF-kappaB), Signal Transducers and Activators of Transcription (STAT) and Interferon Regulatory Factor (IRF). These transcription factors mediate pathways that modulate the expression of hundreds of genes involved in the inflammatory response including cytokines, chemokines, cell-adhesion molecules and inducible nitric oxide synthase (iNOS). Consequently, modulation of these pathways may be a novel therapeutic strategy to reduce the severity and mortality in patients with sepsis and septic shock. Although, NF-kappaB, STAT and IRF transcription factor families broadly regulate activation of genes involved in the inflammatory response, sub-family members have distinct regulatory gene targets within this response. The aim of this research was firstly, to design and optimize a set of reporter constructs whose activity is driven by NFkappaB, STAT and IRF sub-family members. Secondly, to use these constructs to elucidate transcription factors utilized in signalling pathways elicited by human cardiac myocytes responding to a tissue culture model of bacterial sepsis. Results show the NF-kappaB driven reporter construct is activated by treatment with either Escherichia coli or Staphylococcus aureus while the reporter construct known to bind IRF 3,7 and 8 is activated by Escherichia coli but not Staphylococcus aureus . In addition to successfully developing a set of NF-kappaB, STAT and IRF specific reporter constructs, these data suggest that transcription factor activation may be regulated in a stimulus dependent manner.