Molecular Basis for Priming of the Neutrophil NADPH Oxidase in Trauma and Sepsis

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

DESCRIPTION (provided by applicant): The leading cause of morbidity in Surgical Intensive Care Units in the U.S. is acute lung injury and respiratory failure due to sepsis and trauma, leading to multi-organ system failure (MOSF) and death. A substantial component of the host fissure injury involved in the pathogenesis of ARDS and MOSF likely results from reactive oxygen species (ROS) produced by neutrophils. There currently exists a 2-hit model for the development of MOSF following sepsis and trauma. In this model, the initial injury "primes" neutrophils and other components of the immune system so that a secondary insult, which would otherwise be relatively innocuous, now results in an exaggerated inflammatory response. The excessive release of neutrophil-derived proteases and toxic ROS causes uncontrolled damage to adjacent tissues, leading to tissue dysfunction, organ failure, and death. Earlier work has suggested that there exists a direct correlation between the level of neutrophil activation in trauma patients and injury severity and prognosis. To date, however, it has not been possible to use this information in the clinical setting because there lacks a test that is capable of rapid bedside diagnosis of patients with primed neutrophils. The research objectives are to develop an ELISA assay that can rapidly diagnose neutrophil priming in critically ill patients, and to investigate whether the results of this assay could be used to guide therapy and improve the care of trauma and sepsis patients. In addition, it will be determined whether the products of DIC directly contribute to initiation or maintenance of the primed state. The neutrophil NADPH oxidase molecule is the respiratory burst enzyme that produces the toxic ROS during the inflammatory response. Activation of NADPH oxidase involves the formation of a p47phox:p67phox:p40phox heterodimer as well as phosphorylation of the p47phox subunit. The ELISA assays will be developed to detect the presence of the heterodimer as well as the phosphorylated p47phox subunit. The primed state, however, is transient and primed neutrophils do revert to their unprimed resting state over time. Previous work has shown that one or more factors present within whole blood from severely traumatized patients maintain neutrophils in their primed state. Plasma from ICU patients with documented DIC and prepared "DIC-like" plasma will be incubated with neutrophils isolated from healthy volunteers and assayed to detect presence of primed neutrophils. PUBLIC HEALTH RELEVANCE: This information may reveal new therapeutic approaches to limit the development of MOSF through targeted inhibition of coagulation factor-mediated neutrophil priming. In regards to public health, the overall goal of this research project is to reduce morbidity and mortality from MOSF in Surgical Intensive Care Units.