Middle age enhances expression of innate immunity genes in a female mouse model of pulmonary fibrosis.

The lungs are highly sensitive to tissue fibrosis, with a clear age-related component. Among the possible triggers of pulmonary fibrosis are repeated inhalations of fine organic particles. How age affects this response, is still far from being fully understood. We examined the impact of middle-age on gene expression in pulmonary fibrosis, using the novel "inhalation challenge set" mouse model. Our results demonstrate that the response of female mice to exposure of Pantoea agglomerans extract primarily involves various immune-related pathways and cell-cell/cell-extracellular matrix interactions. We found that middle-age had a strong effect on the response to the P. agglomerans-induced lung fibrosis, featured by a more rapid response and increased magnitude of expression changes. Genes belonging to innate immunity pathways (such as the TLR signaling and the NK-cell mediated cytotoxicity) were particularly up-regulated in middle-aged animals, suggesting that they may be potential targets for the treatment of pulmonary fibrosis caused by inhalations of organic particles. Our analysis also highlights the relevance of the "inhalation challenge set" mouse model to lung aging and related pathology.