Activated macrophages have been implicated in
lung injury and
fibrosis induced by the cytotoxic
alkylating agent,
nitrogen mustard (NM). Herein, we determined if macrophage activation is associated with histone modifications and altered
miRNA expression. Treatment of rats with NM (0.125 mg/kg, i.t.) resulted in increases in phosphorylation of H2A.X in lung macrophages at 1 d and 3 d post-exposure. This DNA damage response was accompanied by methylation of
histone (H) 3
lysine (
K) 4 and acetylation of H3K9, marks of transcriptional activation, and methylation of H3K36 and H3K9, marks associated with transcriptional repression. Increases in
histone acetyl
transferase and
histone deacetylase were also observed in macrophages 1 d and 28 d post-NM exposure. PCR array analysis of
miRNAs (miR)s involved in
inflammation and
fibrosis revealed unique and overlapping expression profiles in macrophages isolated 1, 3, 7, and 28 d post-NM. An IPA Core Analysis of predicted
mRNA targets of differentially expressed
miRNAs identified significant enrichment of Diseases and Functions related to cell cycle arrest, apoptosis, cell movement, cell adhesion, lipid metabolism, and
inflammation 1 d and 28 d post NM.
miRNA-
mRNA interaction network analysis revealed highly connected
miRNAs representing key upstream regulators of mRNAs involved in significantly enriched pathways including miR-34c-5p and miR-27a-3p at 1 d post NM and miR-125b-5p, miR-16-5p, miR-30c-5p, miR-19b-3p and miR-148b-3p at 28 d post NM. Collectively, these data show that NM promotes
histone remodeling and alterations in
miRNA expression linked to lung macrophage responses during inflammatory injury and
fibrosis.