Fig. 4.

Effects of intravenous (I.V.) versus intratracheal (I.T.) delivery of PD-L1 siRNA on pulmonary protein leak in mice with indirect acute lung injury (iALI). Intravenous delivery (A) of PD-L1 siRNA significantly decreased the protein leak in iALI mice compared with PBS or control siRNA-treated hemorrhagic shock followed by cecal ligation and puncture (Hem-CLP) groups. In contrast, intratracheal delivery (B) of PD-L1 siRNA did not alter the protein leak in all iALI groups. Values are means ± SE; n = 6 mice per group; *P < 0.05 vs. sham; #P < 0.05 vs. PD-L1 siRNA-treated group, by one-way ANOVA and a Student–Newman–Keuls test. Intravenous delivery of siRNA attenuated Hem-CLP-induced lung injury (H&E staining). Representative images of H&E-stained lung tissue sections from intravenous siRNA-treated mice: PBS+sham (C); PBS+Hem-CLP (D); control siRNA⁺Hem-CLP (E); and PD-L1 siRNA⁺Hem-CLP (F) (original magnification: ×200; scale bar: 100 μm), as well as semiquantitive digital determination of these morphological changes (G) [% of open alveolar space in each image as determined image analysis (means ± SE; n = 3 per group; *P < 0.05 vs. sham; #P < 0.05 vs. PD-L1 siRNA-treated group, by Mann–Whitney U test)]. Alternatively, no such protection was seen with intratracheal delivery of PD-L1 siRNA to Hem-CLP mice (H–L).