HGF secretion by FBs is enhanced by prostaglandin E2 (PGE2) secreted by influenza virus-infected AECs, which is inhibited by indomethacin. A: lung FBs were stimulated by conditioned medium from AECs with or without PR8 (MOI = 0.5) and with or without 10 μM indomethacin and with or without 10 μg/ml IL-1Ra, and culture medium was harvested at 48 h after stimulation. The HGF concentration of this culture medium was measured by ELISA (n = 3). B: arachidonic acid metabolites secreted by influenza virus-infected AECs were analyzed by mass spectrometry. The range of maximal stimulation: PGE2, 17.1–22.5 ng/sample; range of thromboxane B2 (TXB2), 0.26–2.16 ng/sample; range of 5-hydroxyeicosatetraenoic acid (5-HETE), 0.16–0.35 ng/sample; 15-HETE, 3.51–6.06 ng/sample; n = 3. C: lung FBs were stimulated by 10−9 M PGE2, 10−7 M TXB2, 10−6 M TXB2, or 10−5 M TXB2, and culture medium was harvested at 48 h after stimulation. The HGF concentration of this culture medium was measured by ELISA (n = 3). Ethanol was a vehicle control for PGE2 and TXB2.