Influenza Infects Lung Microvascular Endothelium Leading to Microvascular Leak: Role of Apoptosis and Claudin-5
(A) Lung endothelium was infected with live or replication-deficient influenza (MOI 8) for 24 hours and then visualized by phase contrast microscopy. Cells exposed to replication-deficient influenza appear much healthier than cells infected with live virus and similar to infected cells. Images were captured as above and are representative of 3 experiments. (B–C) Endothelial apoptosis after exposure to replication-deficient influenza at the indicated MOI was assessed by binding of Annexin V 24 hours later. Histogram (B) is representative of 5 experiments. The percentage of Annexin V-positive cells (C) was similar in all groups. Results (mean, SE) are from 5 experiments. (D) The caspase-inhibitor ZVAD-FMK does not attenuate endothelial permeability induced by replication-deficient influenza. Cells were infected with UV flu (MOI 8) with or without 80 µM ZVAD-FMK for 24 hours. Permeability to dextran was measured. Results (mean, SD) are representative of 3 experiments, *p<0.05.