Sepsis, a maladaptive response to infection, is a common and lethal syndrome. Many studies have examined the activities of leukocytes and endothelial cells in sepsis or in surrogate models, but the role of platelets in the disease process has received far less attention. This paucity of insight is both surprising and potentially limiting, because there is abundant evidence that platelets are activated and contribute to the vascular and inflammatory manifestations in most, if not all, septic patients. We have identified novel platelet responses that may contribute to sepsis. In this regard, we found that megakaryocytes transfer a functional spliceosome to human platelets and that activated platelets splice constitutively expressed pre-mRNAs into mature transcripts. In preliminary data, we show that platelets isolated from septic patients express spliced mRNA for tissue factor and, as a result, have increased procoagulant activity. Here, we build on these preliminary findings by initiating a set of pre-clinical screens to determine if key agonists present in the septic milieu activate the spliceosome of human platelets and whether inhibitory reagents block pre-mRNA splicing and reduce sepsis associated inflammation. In order to complete our studies within two years, we narrow the scope of specific aim 1 and accelerate studies in aim 2. Specifically, revised aim 1 will characterize pre-mRNA splicing events and activation of the spliceosome in platelets isolated from septic patients with blood culture positive bacteremia. Plasma and bacteria from these sepsis patients will be used to perform studies in the second aim, which defines the mechanisms that control pre-mRNA splicing events in human platelets exposed to septic situations.
Aim 2 also examines the inhibitory properties of reagents that block pre-mRNA splicing in purified platelet preparations and whole blood model systems of sepsis. Together, these studies will generate new insights into the molecular pathobiology of sepsis and may provide new targets for therapeutic intervention.
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