Rapamycin Regulates Bleomycin-Induced Lung Damage in SP-C-Deficient Mice

Abstract

Injury to the distal respiratory epithelium has been implicated as an underlying cause of idiopathic lung diseases. Mutations that result in SP-C deficiencies are linked to a small subset of spontaneous and familial cases of interstitial lung disease (ILD) and interstitial pulmonary fibrosis (IPF). Gene-targeted mice that lack SP-C (𝑆𝑓𝑡𝑝𝑐−/−) develop an irregular ILD-like disease with age and are a model of the human SP-C related disease. In the current study, we investigated whether rapamycin could ameliorate bleomycin-induced fibrosis in the lungs of 𝑆𝑓𝑡𝑝𝑐−/− mice. 𝑆𝑓𝑡𝑝𝑐+/+ and −/− mice were exposed to bleomycin with either preventative administration of rapamycin or therapeutic administration beginning eight days after the bleomycin injury. Rapamycin-treatment increased weight loss and decreased survival of bleomycin-treated 𝑆𝑓𝑡𝑝𝑐+/+ and 𝑆𝑓𝑡𝑝𝑐−/− mice. Rapamycin did not reduce the fibrotic disease in the prophylactic or rescue experiments of either genotype of mice. Further, rapamycin treatment augmented airway resistance and reduced lung compliance of bleomycin-treated 𝑆𝑓𝑡𝑝𝑐−/− mice. Rapamycin treatment was associated with an increased expression of profibrotic Th2 cytokines and reduced expression of INF-γ. These findings indicate that novel therapeutics will be required to treat individuals with SP-C deficient ILD/IPF.