Efficient pulmonary fibrosis therapy via regulating macrophage polarization using respirable cryptotanshinone-loaded liposomal microparticles

Lung inflammation and fibrogenesis are the two main characteristics during the development of pulmonary fibrosis (PF), which are particularly associated with pulmonary macrophages. In this context, whether cryptotanshinone (CTS) could alleviate PF through regulating macrophage polarization were preliminarily demonstrated in vitro. Then the time course of PF and its relationship with macrophage polarization was determined in BLM-induced mice based on cytokine levels in bronchoalveolar lavage fluid (BALF), lung histopathology, flow cytometric analysis, mRNA and protein expression. CTS was loaded into macrophage-targeted and responsively released mannose-modified liposomes (Man-lipo), and the liposomes were then embedded into mannitol microparticles (M-MPs) using spray drying to achieve efficient pulmonary delivery. Afterwards, how CTS regulates macrophage polarization in vivo during different time courses of PF was probed. Furthermore, the molecular mechanisms of CTS against PF by regulating macrophage polarization were elucidated in vivo and in vitro. The full-course therapy group could achieve comparable therapeutic effects compared with the positive control drug PFD group. CTS can alleviate PF through regulating macrophage polarization, mainly by inhibiting NLRP3/TGF-β1 pathway during the inflammation course and modulating MMP-9/TIMP-1 balance during the fibrosis development course, providing new insights into chronic PF treatment.