Targeting of cannabinoid receptor 1 for antagonism in profibrotic alveolar macrophages mitigates pulmonary fibrosis

Pulmonary fibrosis (PF) is a life-threatening disease that requires effective and well-tolerated therapeutic modalities. Previously, the distinct pathogenic roles of cannabinoid receptor 1 (CB1R) and inducible nitric oxide synthase (iNOS) in the lungs and their joint therapeutic targeting were highlighted in PF. However, the cell-specific role of CB1R in PF has not been explored. Here, we demonstrate that CB1R in alveolar macrophages (AMs) mediates the release of anandamide into the alveoli, which promotes PF by inducing profibrotic macrophages that are accessible to locally delivered antifibrotic therapy. A multitargeted therapy may improve therapeutic efficacy in PF. Pulmonary delivery of 0.5 mg/kg/day MRI-1867 (zevaquenabant), a peripherally acting hybrid CB1R/iNOS inhibitor, is as effective as systemic delivery of 10 mg/kg/day, and also matches the efficacy of nintedanib in mitigating bleomycin-induced PF. A systems pharmacology approach reveals that zevaquenabant and nintedanib treatments reverse pathologic changes in both distinct and shared PF-related pathways, which are conserved in human and mouse. Moreover, zevaquenabant treatment also attenuated fibrosis and profibrotic mediators in human precision-cut lung slices. These findings establish CB1R-expressing AMs as a therapeutic target and support local delivery of dual CB1R/iNOS inhibitor zevaquenabant by inhalation as an effective, well-tolerated, and safer strategy for PF. Overall design: We used 52-week-old C57BL/6J mice (aged mice) to generate bleomycin-induced pulmonary fibrosis model by treating mice with either saline or bleomycin (1 U/kg) by a single oropharyngeal administration. The saline group serves as a healthy control group. Bleomycin-administered mice were randomized to equilibrate their body weight reduction and to assign them to different treatment groups at day 10 post-bleomycin. Pharmacological treatments were performed between day 10 and day 28 post-bleomycin with vehicle, MRI-1867 (Dual-inhibitor of CB1R/iNOS, 0.5 mg/kg, oropharyngeal), rimonabant (CB1R antagonist, 10 mg/kg, intraperitoneally), 1400W (iNOS inhibitor, 10 mg/kg, intraperitoneally), and nintedanib (tyrosine kinase inhibitor, 60 mg/kg, orally). Lung tissues were collected on day 28 post-bleomycin for RNAseq analysis.