Jeffrey B. Travers, M.D., Ph.D. (Advisor); Michael Kemp, Ph.D. (Committee Member); Ravi Sahu, Ph.D. (Committee Member)
Master of Science (MS)
Ethanol (EtOH), in combination with thermal burn injury, is a clinically significant problem resulting in an increase in morbidity and mortality due to acute multi-organ toxicity from excess systemic cytokine release. This intoxicated thermal burn affects close to 50% of the total numbers of hospital-admitted burn patients and currently has no standard treatment. However, using in vitro cellular and in vivo murine models, our group has provided data implicating the augmented production of the lipid mediator Platelet-activating factor (PAF) in keratinocytes in response to intoxicated thermal burn injury in the subsequent pathology. Of importance, our group has demonstrated that activation of the keratinocyte PAF-receptor (PAFR) results in the generation of subcellular microvesicle particles (MVP) which carry, and thus, serve to protect this labile lipid mediator PAF. The goal of the current studies is to define the exact mechanisms by which EtOH + burn injury generates augmented PAF production, and the role of MVP in this process. Using the human keratinocyte derived cell line HaCaT, we demonstrate that EtOH alone can generate MVP at EtOH dosages of 1% or more over 4 hours and synergizes with thermal burn injury. Use of PAFR-positive and PAFR-negative epithelial cell lines as well as siRNA knock-down approaches of the PAFR in HaCaT cells in conjunction with EtOH + burn studies, all indicate that burn injury-induced MVP release is PAFR-dependent. Moreover, studies using wild-type and PAFR-KO mice demonstrate increased numbers of MVP in the skin and in plasma following intoxicated burn injury in a PAFR-dependent manner. Studies with HaCaT cells revealed that the MVP contain large amounts of PAFR agonistic activity. Our final study in HaCaT cells revealed that the cytosolic phospholipase A2 (cPLA2) inhibitor pyrrophenone, which blocks enzymatic PAF synthesis, also attenuates the exaggerated MVP formation in response to EtOH + thermal burn injury. These studies fit with a novel model whereby EtOH + thermal burn injury generates increased PAF via cPLA2 activation through the lipid mediated Platelet-activating factor pathway, which then generates high levels of PAF-laden MVP which are in part responsible for the subsequent pathology of intoxicated thermal burn injury.
Department or Program
Department of Pharmacology and Toxicology
Year Degree Awarded
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