eNAMPT Is a Novel Damage-associated Molecular Pattern Protein That Contributes to the Severity of Radiation-induced Lung Fibrosis

• Published in: American journal of respiratory cell and molecular biology Vol. 66; no. 5; pp. 497 - 509
• Main Authors: Garcia, Alexander N, Casanova, Nancy G, Kempf, Carrie L, Bermudez, Tadeo, Valera, Daniel G, Song, Jin H, Sun, Xiaoguang, Cai, Hua, Moreno-Vinasco, Liliana, Gregory, Taylor, Oita, Radu C, Hernon, Vivian Reyes, Camp, Sara M, Rogers, Claude, Kyubwa, Espoir M, Menon, Naresh, Axtelle, James, Rappaport, Jay, Bime, Christian, Sammani, Saad, Cress, Anne E, Garcia, Joe G N
• Format: Journal Article
• Language: English
• Published: United States American Thoracic Society 01.05.2022
• Subjects: Alarmins - metabolism; Animals; Antibodies, Monoclonal; Cytokines - metabolism; Fibrosis; Inflammation; Ionizing radiation; Lung - pathology; Lung Injury - pathology; Medical research; Medical treatment; Mice; Mice, Inbred C57BL; Nicotinamide phosphoribosyltransferase; Nicotinamide Phosphoribosyltransferase - genetics; Original Research; Phosphoribosyltransferase; Pulmonary fibrosis; Pulmonary Fibrosis - genetics; Pulmonary Fibrosis - metabolism; Radiation; Thorax; TLR4 protein; Toll-Like Receptor 4 - metabolism; Toll-like receptors; nicotinamide phosphoribosyltransferase; eNAMPT; whole-lung thoracic irradiation; TLR4; DAMP
• ISSN: 1044-1549; 1535-4989
• DOI: 10.1165/rcmb.2021-0357OC

The paucity of therapeutic strategies to reduce the severity of radiation-induced lung fibrosis (RILF), a life-threatening complication of intended or accidental ionizing radiation exposure, is a serious unmet need. We evaluated the contribution of eNAMPT (extracellular nicotinamide phosphoribosyltransferase), a damage-associated molecular pattern (DAMP) protein and TLR4 (Toll-like receptor 4) ligand, to the severity of whole-thorax lung irradiation (WTLI)-induced RILF. Wild-type (WT) and heterozygous C57BL6 mice and nonhuman primates (NHPs, ) were exposed to a single WTLI dose (9.8 or 10.7 Gy for NHPs, 20 Gy for mice). WT mice received IgG (control) or an eNAMPT-neutralizing polyclonal or monoclonal antibody (mAb) intraperitoneally 4 hours after WTLI and weekly thereafter. At 8-12 weeks after WTLI, NAMPT expression was assessed by immunohistochemistry, biochemistry, and plasma biomarker studies. RILF severity was determined by BAL protein/cells, hematoxylin and eosin, and trichrome blue staining and soluble collagen assays. RNA sequencing and bioinformatic analyses identified differentially expressed lung tissue genes/pathways. NAMPT lung tissue expression was increased in both WTLI-exposed WT mice and NHPs. mice and eNAMPT polyclonal antibody/mAb-treated mice exhibited significantly attenuated WTLI-mediated lung fibrosis with reduced: ) NAMPT and trichrome blue staining; ) dysregulated lung tissue expression of smooth muscle actin, p-SMAD2/p-SMAD1/5/9, TGF-β, TSP1 (thrombospondin-1), NOX4, IL-1β, and NRF2; ) plasma eNAMPT and IL-1β concentrations; and ) soluble collagen. Multiple WTLI-induced dysregulated differentially expressed lung tissue genes/pathways with known tissue fibrosis involvement were each rectified in mice receiving eNAMPT mAbs.The eNAMPT/TLR4 inflammatory network is essentially involved in radiation pathobiology, with eNAMPT neutralization an effective therapeutic strategy to reduce RILF severity.