Bronchoalveolar Lavage Fluid Protein Expression in Acute Respiratory Distress Syndrome Provides Insights into Pathways Activated in Subjects with Different Outcomes

Abstract

Acute respiratory distress syndrome (ARDS) is associated with high mortality. We sought to identify biological pathways in ARDS that differentiate survivors from non-survivors. We studied bronchoalveolar lavage fluid (BALF) from 36 patients with ARDS (20 survivors, 16 non-survivors). Each sample, obtained within seven days of ARDS onset, was depleted of high abundance proteins and labeled for iTRAQ LC-MS/MS separately. Protein identification and relative quantification was performed employing a target-decoy strategy. A variance weighted t-test was used to identify differential expression. Ingenuity Pathway Analysis was used to determine the canonical pathways that differentiated survivors from non-survivors. We identified 1115 high confidence proteins in the BALF out of which 142 were differentially expressed between survivors and non-survivors. These proteins mapped to multiple pathways distinguishing survivors from non-survivors, including several implicated in lung injury and repair such as coagulation/thrombosis, acute phase response signaling and complement activation. We also identified proteins assigned to fibrosis and ones involved in detoxification of lipid peroxide-mediated oxidative stress to be different in survivors and non-survivors. These results support our previous findings demonstrating early differences in the BALF protein expression in ARDS survivors vs. non-survivors, including proteins that counter oxidative stress and canonical pathways associated with fibrosis.

Figure 1

Canonical Pathways represented by proteins differentially expressed between ARDS survivors and non-survivors. Ingenuity Pathway Analysis (IPA) canonical pathways most significantly changed in ARDS survivors compared to non-survivors. The stacked bar chart displays the percentage of proteins in the canonical pathway that are more (light gray), less (dark gray) abundant in survivors or absent (white) our dataset. The secondary x-axis shows the −log of Benajmni-Hochberg corrected p-value indicating the statistical significance of each over-represented pathway (cutoff >1.3) and the line with solid diamonds is the −log of corrected p-value for that pathway. The numerical value on right side of each stacked bar is the number of genes in that canonical pathway in the IPA knowledgebase.