D29-06 Activation of NAMPT Restores Alveolar Progenitor Cell Function in Idiopathic Pulmonary Fibrosis

Abstract Rationale Idiopathic pulmonary fibrosis (IPF) is a fatal form of interstitial lung disease with limited treatment options. It is widely accepted that IPF pathogenesis is an epithelial driven process triggered by repeating injury and inadequate repairing of alveolar type II (AT2) cells that leads to exaggerated fibroblast activation and unremitting lung fibrosis. Hence, the therapeutics aimed at promoting AT2 progenitor regenerative capacity are urgent needed. We have reported recently that downregulation of NAD+ signaling contributed to the impaired progenitor function of IPF AT2s. In the current study, we found that a key NAD+ biosynthesis enzyme, nicotinamide phosphoribosyltransferase (NAMPT), was significantly downregulated in IPF AT2s. Methods We compared NAMPT expression levels in AT2s from healthy and IPF lungs. The role of NAMPT in AT2 renewal was assessed via an in vitro 3D-organoid model with specific activators, including NAT, and an in vivo AT2-specific Nampt deletion mouse model. Bleomycin induced lung fibrosis was evaluated in mice with AT2-specific Nampt deficiency or in mice treated with NAT. Results ScRNA-seq data analysis and qPCR revealed a significant decrease in NAMPT transcriptional levels in AT2 cells from IPF lungs compared to those from healthy donor lungs. Activation of NAMPT by specific activators, NAT enhanced colony formation efficiency (CFE) of AT2 cells isolated from both healthy and IPF lungs in vitro. Moreover, NAT treatment promoted AT2 cell regeneration and mitigated lung fibrosis in bleomycin injured C57BL/6 mice in vivo. AT2 cells with Nampt deletion exhibited reduced renewal capacities, and mice with Nampt deletion in AT2 cells demonstrated exacerbated pulmonary fibrosis following bleomycin injury. Bulk RNA-seq analysis suggested that NAT-induced NAMPT activation rescued the expression of SOD2 and other oxidative stress response genes which are downregulated in AT2 cells from IPF lungs. Several mitochondria related genes were also elevated by NAT treatment, indicating a direct role of NAMPT in regulating mitochondrial function in AT2 cells. Furthermore, knockdown NAMPT in healthy AT2s increased mitochondrial superoxide. Conclusion In summary, our findings indicate that NAMPT plays a significant role in regulating the renewal of AT2s by modulating oxidative stress and mitochondrial dysfunction. The activation of NAMPT, such as through NAT treatment, demonstrates a notable impact on promoting AT2 renewal in both human IPF and bleomycin-injured mouse lungs, while also aiding in the mitigation of pulmonary fibrosis in a mouse model. This study suggests that activating NAMPT in AT2s could present a promising therapeutic approach for treating IPF. This abstract is funded by: This research was funded by R35-HL150829 (P.W.N.) and R01-AG078655 (J. L. and P.W.N.) from National Institutes of Health.