Figure 1.

Influenza A virus (IAV) and toll-like receptor 7 agonists induce alveolar macrophage matrix metalloproteinase-9 (MMP-9) production. (A) MH-S cells were stimulated with or without live or UV-inactivated WSN strain of IAV at different MOIs for indicated periods of time (n = 4, four independent experiments). (B) MH-S cells were stimulated with or without HKx31 virus at different MOIs for 48 h before harvest (n = 4, four independent experiments). (C) MH-S cells were stimulated with or without poly I:C (50 µg/ml), R848 (10 µM), imiquimod (Imiq, 1 µg/ml), or LPS (1 µg/ml) for indicated periods of time (n = 3, three independent experiments). (D) Primary alveolar macrophages of wild-type mice stimulated with or without Imiq (1 µg/ml) for indicated periods of time. (E) Thioglycollate-elicited peritoneal macrophages stimulated with or without HKx31 virus (MOI = 10) for 48 h. (F,G) Wild-type mice were infected with 5 × 10³ PFU of WSN virus intratracheally for 2 days. Alveolar macrophages (Siglec-F⁺F4/80⁺) in bronchoalveolar lavage were sorted and Mmp9 and viral nucleoprotein mRNA were quantified by qPCR and normalized against Actb. Primary neutrophils from bone marrow were stimulated with or without (H) Imiq (1 µg/ml) and (I) WSN virus (MOI = 1) for 24 h. (D–I) Each dot represents cells from one mouse. (A–E,H,I) MMP-9 in culture supernatants was quantified by ELISA. Data presented are the mean + SD. *p < 0.05, **p < 0.01, and ***p < 0.001 when compared to unstimulated cells. (A–D) was analyzed by one-way ANOVA, followed by (A) Turkey’s, (B) Sidak’s, (C,D) Dunnett’s post hoc tests, and (E–I) by Mann–Whitney U-test.