Macrophage Activation in the Lung during the Progression of Nitrogen Mustard Induced Injury is Associated with Altered miRNA Expression

Abstract

Abstract Activated macrophages have been implicated in lung injury and fibrosis induced by the cytotoxic alkylating agent, nitrogen mustard (NM). Accumulating evidence suggests that phenotypic activation of macrophages during initiation, progression, and resolution of inflammatory responses is regulated by groups of miRNAs that act in concert to coordinate cellular activity. Herein, we determined if macrophage activation after NM injury was associated with altered miRNA expression. Male rats were exposed to NM (0.125 mg/kg, i.t.) and PCR array analysis of miRNAs involved in inflammation and fibrosis was performed in alveolar macrophages recovered from bronchoalveolar lavage. Results revealed unique and overlapping miRNA expression profiles in macrophages isolated 1, 3, 7, and 28 d post-NM. Seven miRNAs were upregulated in macrophages throughout the time-course, while three miRNAs were uniquely expressed 1 d post-NM, six at 3 d, six at 7 d, and nineteen at 28 d. Linkage with macrophage RNA-seq data showed differentially expressed miRNAs regulated mRNAs involved in STAT3, IL-6 and iNOS inflammatory signaling pathways at 1 d, and IL-4, PPAR and Sirtuin signaling at 28 d post-NM. Ingenuity Pathway Analysis predicted miR-21-5p, miR-29, miR-26a, miR-34a and let-7a as key regulators of macrophage mobilization, activation, and lipid homeostasis after NM. Collectively, these data show that NM promotes alterations in miRNA expression linked to lung macrophage responses during inflammatory injury and fibrosis. These findings provide clues on pathways regulating macrophage activation and may help identify novel therapeutic targets. This work was supported by NIH grants AR055073, ES004738, HL086621, ES005022, ES030984, and ES007148.