Platelet activation in septic shock

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DESCRIPTION (provided by applicant): Michael Puskarich, MD, an Assistant Professor in the University of Mississippi Medical Center's Department of Emergency Medicine, will utilize this K-23 Award to transition into an independent patient-oriented researcher. Author of 18 publications in peer-reviewed journals, Dr. Puskarich will have completed Drexel University's Master's degree program in Clinical Research prior to receipt of his K-23 Award. His career goal is to be a leading clinician scientist with nationally recognized expertise in translational emergency medicine research. The Mentoring Plan developed for the candidate, Michael Puskarich, MD, is comprehensive in nature and designed to accommodate Dr. Puskarich's transition to an independent research investigator during this award's project period. His mentoring team includes a Primary Mentor, Alan E. Jones, MD; a Co-Mentor, George Dale, PhD; and a Mentee Advisory Committee, consisting of Jonathan Holser, PhD, Jeffrey Kline, MD, Merry Lindsey, PhD, and Richard Summers, MD. Together, they have the breadth of expertise and experience to provide the candidate with the tools he needs for his professional development. Together with his mentors, Dr. Puskarich has identified several objectives for his successful career development. These include (1) advancing his expertise and experience in clinical and translational sepsis research; (2) enhancing his translational research techniques; (3) advancing his knowledge of platelet, microcirculatory, and mitochondrial physiology; (4) gaining additional experience in scientific and grant writing; (5) enhancing his standing as an academic leader; and (6) becoming an effective mentor to others. Dr. Puskarich will accomplish these objectives through a rigorous career development plan that includes formal coursework, specialized training, attendance at workshops and seminars, active participation in professional societies and on university-wide committees, regular scheduled meetings with his mentors and members of his Mentee Advisory Committee, and completion of his research study. Milestones and estimated allocation of Dr. Puskarich's professional time for each of his career development activities have been identified. Dr. Puskarich's proposed research project is an ancillary study of an ongoing NIGMS-funded project (R01GM103799-01), for which Dr. Puskarich's primary mentor serves as PI. The ancillary study has been approved by the parent study's DSMB, and a letter of support is included in the Protection of Human Subjects section. The primary aim of the parent study, L-Carnitine Treatment for Vasopressor Dependent Septic Shock" (more commonly referred to as the Rapid Administration of Carnitine in sEpsis-or RACE Study) is to assess whether L-carnitine reduces cumulative organ failure and predicted probability of mortality in patients with septic shock. The study design is that of a randomized, double-blind, placebo-controlled, dose/efficacy-finding trial that utilizes a Bayesian adaptive approach and response-adaptive randomization. Within 24 hours of the diagnosis of septic shock, patients are randomized to a 12 hour infusion of one of three doses of L-carnitine (6, 12, or 18 grams) or placebo and followed to outcome. Up to 250 patients from 10 hospitals throughout the U.S. will be participating, and the study is currently in its first year of patient enrollment. Dr. Puskarichwill be able to take advantage of the infrastructure of the parent study and explore areas of inquiry not included in the parent study; specifically, the role of highly activated (HA) platelets in sepss; the significance of altered platelet mitochondrial function in the pathogenesis of sepsis; and the effects of L- carnitine on cellular respiration and HA platelet formation. The study is designed to achieve three specific aims: Aim #1: Determine if the percentage of HA platelets generated following DA stimulation in vitro is increased in patients with sepsis compared to matched controls, and determine if this percentage is associated with microcirculatory flow index (MFI) and Sequential Organ Failure Assessment (SOFA) score. The hypothesis is that sepsis increases the propensity for platelets to become highly activated following dual-agonist (DA) stimulation with thrombin and convulxin (a collagen mimetic) in vitro. This in vitro measurement reflects the in vivo environment in sepsis, which is characterized by high circulating thrombin and endothelial damage, with exposure of subendothelial collagen. As HA platelets are highly procoagulant, an increase in their formation will promote microcirculatory thrombosis and organ failure. Aim #2: : Determine if the percentage of HA platelets generated following SA stimulation in vitro is increased in patients with sepsis compared to matched controls, is associated with leak respiration, and is associated with MFI and SOFA score. The hypothesis is that a subset of platelets is primed for a HA transition following SA-stimulation with thrombin alone secondary to sepsis-induced reactive oxygen species (ROS) injury, evidenced by increased leak respiration. This subset of platelets, in turn, further contributes to microcirculatory thrombosis and organ failure. Aim #3: Test if L-carnitine treatment significantly decreases leak respiration and SA-stimulated HA platelet formation compared to placebo, with concomitant improvements in MFI and SOFA score. The hypothesis is that L-carnitine treatment will decrease SA-stimulated, but not DA-stimulated HA platelet formation, with concomitant decreases in thrombosis and organ failure. L-carnitine decreases sepsis-induced ROS damage, decreasing formation of SA-stimulated HA platelets. This decrease, in turns, mitigates microcirculatory thrombosis and organ failure.