In this grant application, we are focusing on the physiologic condition of sepsis, which is a term used to describe a severe illness arising from serious infection. The mortality rate of sepsis is >215,000 patients a year, and sepsis is the tenth leading cause of death in the US. The estimated yearly cost for treating the 650,000 new cases of sepsis per year is ~17 billion dollars making this disease a very costly medical condition. Numerous clinical trials for the treatment of this disease have been undertaken, but unfortunately, these trials have shown limited success. As such, there is a major need for new therapeutics to treat the disease. The studies proposed in this grant application are directly related to sepsis as we are examining the biosynthetic pathways of 3-PUFA-derived lipid mediators and eicosanoids. The temporal and spatial production of these specialized chemical mediators actively controls the hyperactive inflammatory response as a result of sepsis. The synthesis of eicosanoids and the 3-PUFA-derived lipid mediators, eicosapentaenoic acid (EPA)-derived lipid mediators, begins with the initial rate-limiting step, the formation of arachidonic aid (AA) for eicosanoids or EPA for the EPA derived lipid mediators, via group IVA cytosolic phospholipase A2 (cPLA2?). Ceramide-1-phosphate (C1P) is a bioactive sphingolipid and a direct activator of cPLA2? both in vitro and in cells. Furthermore, published findings from the Chalfant lab demonstrated that mutagenesis of critical amino acids for the C1P interaction in cPLA2? inhibited the ability of enzyme to translocate in response to several inflammatory agonists. Hence, C1P is required for the activation of cPLA2?, and is a major regulator of eicosanoid synthesis in cells. To further our understanding of the physiological relevance of this lipid:protein interaction in vivo, our laboratory created a knockin mouse with the C1P interaction site of cPLA2? ablated. Our preliminary data has demonstrated some intriguing findings for this new genetic model of cPLA2?. For example, some phenotypes reported for the cPLA2? knockout mouse were not apparent in the cPLA2? knockin mouse (e.g. spontaneous abortion) (29), while other phenotypes were dramatically accentuated in the cPLA2? knockin mouse such as complete resistance to LPS and fecal-induced septic shock. Interestingly, the cPLA2? knockin mouse demonstrated higher levels of anti-inflammatory eicosanoids as well as increased induction of the anti-inflammatory E-resolvins in response to fecal injection as compared to the cPLA2? knockout and wild-type mice. Based on these data, we hypothesize that the cPLA2? knockin mouse is resistant to sepsis due to the sustained production of anti-inflammatory lipid mediators caused by a novel "lipid-class switch" in cPLA2? substrate utilization. Our proposed experiments will explore this hypothesis in depth both ex vivo and in vivo.
We are focusing on the physiologic condition of sepsis, which is a term used to describe a severe illness arising from serious infection. The mortality rate of sepsis is >215,000 patients a year, and unfortunately, clinical trials for treating sepsis have shown limited success. As such, there is a major need for new therapeutics, and our studies explore the cellular mechanisms and bioactive lipids involved in ameliorating the condition of sepsis.
|Stiles, Megan; Qi, Hui; Sun, Eleanor et al. (2016) Sphingolipid profile alters in retinal dystrophic P23H-1 rats and systemic FTY720 can delay retinal degeneration. J Lipid Res 57:818-31|
|Katz, SebastiÃ¡n; Ernst, Orna; Avni, Dorit et al. (2016) Exogenous ceramide-1-phosphate (C1P) and phospho-ceramide analogue-1 (PCERA-1) regulate key macrophage activities via distinct receptors. Immunol Lett 169:73-81|
|Wijesinghe, Dayanjan S; Brentnall, Matthew; Mietla, Jennifer A et al. (2014) Ceramide kinase is required for a normal eicosanoid response and the subsequent orderly migration of fibroblasts. J Lipid Res 55:1298-309|