Figure 3.

Inhibition of BCL-2 and BCL-xL during the late fibrotic and resolution phase of the bleomycin mouse model activates the unfolded protein response (UPR) in the mesenchymal cells. (A) Schematic of bleomycin injury model and late treatment with navitoclax. Vehicle or navitoclax (50 mg/kg) was given by gavage to the mice 15 days after bleomycin injury and for 5 consecutive days. (B) Bcl-2 mRNA expression 15 days after bleomycin injury measured in flow-sorted epithelial and mesenchymal cells. n = 3 mice. (C) UMAP of mesenchymal cells isolated 21 days post–bleomycin injury and treated with vehicle or navitoclax. (D) Top enriched canonical pathways identified using ingenuity pathway analysis on the differentially expressed genes in the alveolar fibroblast cluster between vehicle- and navitoclax-treated samples. (E) Dot plot of differentially expressed genes in mesenchymal cells isolated from BV or BN samples selected for their relevance to UPR. The expression levels of genes were indicated by the color and size of the circle. (F) Validation in an independent cohort of navitoclax-treated bleomycin-injured mice of the reduced expression of Bcl-2 mRNA after treatment and activation of expression of genes encoding key players of UPR in flow-sorted mesenchymal cells. n = 6–9 mice per group. Data represent mean ± SD. *P < 0.05, **P < 0.01, and NS = not statistically significant, as determined by unpaired two-tailed t test. Each data point represents one mouse sample. Epi. = Epcam+cells; Mes. = mesenchymal cells; UMAP = uniform manifold approximation and projection.