Associations of High Attenuation Area-Related Proteomic Biomarkers with Fibrotic or Subpleural Interstitial Lung Abnormalities

Abstract

Rationale: High-attenuation area (HAA) is a computed tomography (CT) tool that correlates with lung inflammation and fibrosis. Systemic molecular correlates of HAA (e.g., plasma proteins) may inform biological processes involved in interstitial lung disease. Objectives: To identify plasma proteins that associate with HAA and correlate with a higher probability of developing new-onset fibrotic or subpleural interstitial lung abnormalities (ILAs). Methods: Plasma protein levels were measured using a semiquantitative aptamer-based platform in MESA (the Multi-Ethnic Study of Atherosclerosis; N = 5,486) and SPIROMICS (Subpopulations and Intermediate Outcome Measures in COPD Study; N = 1,781). Linear regression models identified HAA-associated proteins after adjustment for demographic and socioeconomic factors, CT scanner parameters, study center, and batch. Associations of HAA-related proteins with new-onset fibrotic or subpleural ILAs were examined in MESA participants with ILA assessments on full-lung CT 10 years later. Immunohistochemical staining of select proteins was performed in lung tissue from pulmonary fibrosis cases. Measurements and Main Results: There were 75 proteins detected that were significantly associated with HAA in MESA and SPIROMICS. Gene Ontology analysis of these proteins identified processes involved in immune cell chemotaxis and cellular growth and apoptosis. Seven proteins were associated with a higher probability of new-onset fibrotic or subpleural ILAs in MESA, and two of these, junctional adhesion molecule-like protein and GTP cyclohydrolase 1 feedback regulatory protein, stained in areas of fibrosis in lung tissue from patients with interstitial lung disease. Conclusions: Plasma proteins associated with more HAA are involved in immune and cellular processes and associate with new-onset fibrotic-subpleural ILA.

Keywords: interstitial lung disease; proteomics; radiomics.

Figure 1.

Workflow of analysis

Figure 2.

(A) Volcano plot of proteins associated with high attenuation areas in replication cohort, SPIROMICS. Linear regression model adjusted for age, sex, smoking history, cigarette pack-years, height, weight, waist circumference, education attainment, income, principal components of genetic ancestry, lung volume imaged, percent emphysema, and scanner parameters (scanner manufacturer and radiation dose). Bonferroni-corrected p-value cutoff <0.00011574 used to test for statistical significance. Repeat protein names on volcano plot indicate multiple aptamers. (B) Gene ontology enrichment analysis of validated proteins that associate with high attenuation areas.

Figure 3.

Plots of changes in plasma proteomic biomarkers between Exam 1 (2000–2002) and Exam 5 (2010–2012) and probability of Exam 5 fibrotic or subpleural interstitial lung abnormalities in MESA. Generalized additive models used to plot associations with adjustment for baseline age, sex, smoking history, cigarette pack-years, height, weight, waist circumference, glomerular filtration rate, education attainment, income, study site, principal components of genetic ancestry, and batch, and Exam 1 protein level. X-axis is the difference in log₂-transformed protein levels between Exam 1 (2000–2002) and Exam 5 (2010–2012). One participant was removed from analysis due to outlier measurements in all six proteins.

Figure 4.

Immunohistochemistry (IHC) staining of JAML in IPF lung tissue at (A) 12x, (B) 40x, and (C) 400x magnification. GCHFR immunostaining of IPF lung tissue at (D) 12x, (E) 40x, and (F) 400x magnification.