Effect of NF-kappa B (NF-kB) p50 (Nfkb1) deletion on ozone-induced pulmonary transcriptome changes in mice

Background: Ozone (O3) is the predominant oxidant air pollutant associated with respiratory inflammation, lung dysfunction, and worsening preexisting airway diseases. We previously determined that lack of NF-kB signlaing pathway suppressed lung injury and inflammation caused by O3 in mice. The current study was to determine transcriptome mechanisms orchestrated by NF-kB during the development of pulmonary O3 injury. Methods: To investigate the role of NF-kB1 pathway in lung gene expression changes, Nfkb1-deficient (Nfkb1-/-) and wild-type (Nfkb1+/+) mice were exposed to air or 0.3-ppm O3. Total RNAs were isolated from lung homogenates and cDNA microarray analyses were performed to elucidate NF-kB1-directed transcriptomics in basal lungs (air-exposed) as well as in the lung exposed to O3 (48 hr). Results: In air-exposed Nfkb1-/- lungs, leukocyte extravasation/adhesion and antigen presentation genes were overexpressed while immunity genes were suppressed, supporting the dual role of Nf-kB1 homodimer as a transcriptional repressor as well as transcriptional activator and the phenotype of Nfkb1-/- mice (defective response to infection and specific antibody production). After O3 exposure. Nfkb1-/- mice showed suppressed expression of lung cell cycle genes and enhanced expression of DNA damage checkpoint regulation pathway genes, compared to Nfkb1+/+ mice. Conclusion: Overall, deficiency of NF-kB1 in mouse lungs altered transcriptomes to protect lungs from O3-induced inflammation, cell proliferation, and DNA damages. PARALLEL study design with 12 samples comparing 4 groups of gene and exposure: (2 groups Nfkb1+/+ wild type; air-48 hr O3 exposure) (2 groups Nfkb1-/- knockout; air-48 hr O3 exposure). Biological replicates: 3 per group.