Fig. 4.

Replenishment of miRNA let-7b-3p decreases the RWPE^NOX-induced expression of Th2 cytokines and histological changes. A: let-7b-3p mimic decreases mRNA levels of Il4, Il5, and Il13. The let-7b-3p mimic or its inhibitor were instilled 1 h before and 35 h after RWPE^NOX challenge. Mice were euthanized 1 h after miRNA addition, and total RNAs were isolated. One microgram of reverse-transcribed RNA from individual lungs was subjected to qRT-PCR analysis (see materials and methods) for the expression of Il4 (A), Il5 (B), and Il13 (C). D and E: let-7b-3p mimic decreased the mucus levels induced by RWPE^NOX challenge. The let-7b-3p inhibitor increased, while its mimic decreased, the density of magenta-colored lung epithelial cells (D). Changes in periodic acid-Schiff staining are consistent with MUC5A levels in BALF (E). F and G: let-7b-3p mimic decreased the density of collagen deposition induced by RWPE^NOX in OGG1^P mice (F). Lungs were subjected to acid hydrolysis, and the resulting hydroxyproline contents (G) were determined as described in materials and methods. A–C, E, and G: data are presented as means ± SE of five mice. *P < 0.05, **P < 0.01, ***P < 0.001. D and F: histological images show representative staining of six sections per mouse for each treatment.