Figure 5

H5N1/483 but not H1N1/54-induced apoptosis is partially dependent on the up-regulation of TRAIL in AECs.

(A) The mRNA expression of influenza matrix gene and (B) immunofluorescent staining of influenza M and NP proteins (green) in AECs at 24 hpi were shown. (C) The mRNA expression of TRAIL in AECs was measured at 6 and 24 hpi. Data are means ± SEM of three biological replicates. ***p < 0.001, compared with corresponding mock calculated by two way ANOVA with Bonferroni’s post-test. ^###p < 0.001, compared between H1N1/54 and H5N1/483 calculated by two-tailed Student’s t-test. (D–F) AECs were transfected with control (ctr) or DR4 siRNAs. (D) The knock-down efficiencies were assessed by qPCR. Data are means ± SEM of three biological replicates, ***p < 0.001, compared between ctr and DR4 siRNA transfected cells calculated by two-tailed Student’s t-test. (E) 24 h after transfection, the cells were infected with mock, H1N1/54, or H5N1/483 at MOI 2 and subjected to TUNEL assay at 20, 24 and 30 hpi. Micrographs of apoptotic cells (in green) and nucleus (in blue) at 30 hpi are shown. (F) Percentages of apoptotic cells induced by the two viruses in siRNA transfected cells were shown. Data are means ± SEM of three biological replicates, *p < 0.05; **p < 0.01, compared between ctr and DR4 siRNA transfected cells infected with the same virus at indicated time points calculated by two-tailed Student’s t-test.