Plasma Cytochrome c as Biomarker of Traumatic Injury and Predictor of Outcome

Overview

Cytochrome c is a mitochondrial protein that plays a key role in energy metabolism. When mitochondria are injured, cytochrome c may leave mitochondria and reach the bloodstream. The investigators plan to investigate whether circulating cytochrome c levels may serve as biomarker of traumatic injury correlating with (1) severity of traumatic injury, (2) development of organ dysfunction, and (3) clinical outcomes. The Trauma Services at ALGH will enroll over 8 months 100 consecutive trauma patients who require intubation for mechanical ventilation and survive to hospital admission. The Resuscitation Institute at RFUMS will measure cytochrome c levels in plasma taken upon hospital admission and subsequently at 24, 48, and 72 hours, with additional plasma stored for markers to be defined at a later time. Blood cytochrome c levels will be analyzed in relation to severity of traumatic injury, development of organ dysfunction, and clinical outcomes including survival and functional status (adjusted for covariates such as age, gender, type of trauma, time to stabilization, comorbidities, etc.) using information obtained as part of routine medical care. Successful completion of this project will support blood cytochrome c as biomarker of traumatic injury which could be used to identify severity, predict outcomes, and assess novel mitochondrial protective strategies.

The investigators propose to determine whether plasma cytochrome c could serve as clinical biomarker of traumatic injury by examining the relationship between plasma levels of cytochrome c and the severity of the initial injury upon arrival to the hospital, subsequent development of organ dysfunction, and clinical outcomes. Cytochrome c is a mitochondrial protein that plays a crucial role in energy metabolism enabling transfer of electrons from complex III (i.e., cytochrome c reductase) to complex IV (cytochrome c oxidase). Upon mitochondrial injury and contingent on severity, cytochrome c may be released to the cytosol and subsequently to the bloodstream. The rationale for this project stems from: (1) observations at the Resuscitation Institute in animal models of cardiac arrest and resuscitation in which plasma cytochrome c correlates directly with the severity of post-resuscitation left ventricular dysfunction and inversely with survival and (2) observations by others reporting a correlation between plasma cytochrome c and severity of organ injury. The investigators hypothesize that plasma cytochrome c measured upon arrival to the hospital reflects the severity of the initial traumatic injury resulting from the aggregate effects of direct injury to organs, ischemic injury consequent to blood loss, delays in stabilization, and preexistent comorbidity - all factors that can injure mitochondria. The investigators further hypothesize that the initial cytochrome c plasma level combined with the levels measured during the subsequent three days of hospitalization correlate with the development of organ dysfunction, and clinical outcomes. The current proposal is structured in three specific aims: Specific Aim 1 (collection of blood samples and clinical data): For this aim the investigator plans to enroll 100 consecutive trauma victims admitted to Advocate Lutheran General Hospital (ALGH) over a period of 8 months presenting with single or multisystem injuries and meeting specific entry and exclusion criteria developed to ensure a broad range of injury severity. Blood will be sampled within 15 minutes of hospital arrival (e.g., in the Emergency Department or Operating Room) and subsequently at 24, 48, and 72 hours. Plasma will be separated and stored at -80 °C for subsequent batch measurement of cytochrome c (and other markers of mitochondrial injury that may become available at the time of analysis) in the Resuscitation Institute at Rosalind Franklin Univer-sity of Medicine and Science (RFUMS). Clinical data will be extracted from tools used clinically - including the Illinois Trauma Registry Worksheet and the medical record - and used to: (i) record severity of initial traumatic injury by calculating the Trauma Score - Injury Severity Score (TRISS) along with a detailed assessment of individual organs injury; (ii) estimate the severity of blood loss based on base deficit and transfusion needs; (iii) determine subsequent development of organ dysfunction by calculating the Multiple Organ Dysfunction Score (MODS) and the Sequential Organ Failure Score; and (iv) assess outcomes by measuring length of stay in the Intensive Care Unit (ICU), length of stay in the hospital, survival upon hospital discharge, and functional status upon hospital discharge. Specific Aim 2 (analysis of plasma cytochrome c): Frozen samples of arterial plasma, stored at -80°C at ALGH, will be transferred to the Resuscitation Institute at RFU and cytochrome c measured using electrochemiluminescence. Specific Aim 3 (statistical analysis and modeling): A database devoid of patient identifiers will be created merging the clinical information with values of plasma cytochrome c levels and other markers as they become available. Considering the pilot nature of the project, statistical modeling and analysis will be primarily exploratory focused on identifying relationships between plasma cytochrome c levels upon hospital arrival and clinical elements contributing of the severity of primary traumatic injury. The analysis and modeling will also include examining the predictive value of the initial and subsequent plasma cytochrome c levels on development of organ dysfunction and clinical outcomes. The long-term goal of the project is to develop plasma cytochrome c as biomarker of traumatic injury and other clinical conditions associated with mitochondrial injury that could be used at the bedside - i.e., after developing point of care assays - for (1) assessing severity of illness, (2) prognostication of outcome, and (3) clinical re-search on novel therapeutic interventions aimed at reducing mitochondrial injury.