Temsirolimus induces surfactant lipid accumulation and lung inflammation in mice

Interstitial lung disease (ILD) is a well-known adverse effect of mammalian target of rapamycin (mTOR) inhibitors. However, it remains unknown how lung toxicities are induced by mTOR inhibitors. Here, we constructed a mouse model of mTOR inhibitor-induced ILD using temsirolimus and examined the pathogenesis of the disease. Male ICR mice were treated with an intraperitoneal injection of different doses of temsirolimus (3 or 30 mg·kg−1·wk−1) or vehicle. Temsirolimus treatment increased capillary-alveolar permeability and induced neutrophil infiltration and fibrinous exudate into the alveolar space, indicating alveolar epithelial and/or endothelial injury. It also induced macrophage depletion and the accumulation of excessive surfactant phospholipids and cholesterols. Alveolar macrophage depletion is thought to cause surfactant lipid accumulation. To further examine whether temsirolimus has cytotoxic and/or cytostatic effects on alveolar macrophages and alveolar epithelial cells, we performed in vitro experi...