eNAMPT/TLR4 signaling drives PAH cellular phenotypic switching and lung vascular remodeling

Background: The attenuation of cellular phenotypic switchingdriving PAH vascular remodeling remains an unmet therapeutic need. As eNAMPT (nicotinamide phosphoribosyltransferase)/TLR4 signaling significantly contributes to PH pathobiology, an eNAMPT-neutralizing ALT-100 mAb was utilized to rescue monocrotaline (MCT) and hypoxia/Sugen (Hy/Su) preclinical PH rat models and to evaluate eNAMPT/TLR4 involvement in endothelial cell (EC), smooth muscle cell (SMC) and monocyte/macrophage phenotypic switching. Methods: MCT-PH or Hy/Su-PH rats received IgG or ALT-100 mAb (subQ, beginning week 4) with measurements of PH severity and lung tissue scRNAseq at day 42. Results: PH severity indices (hemodynamic, histologic, vascular remodeling) were significantly attenuated in MCT-PH and Hy/Su-PH rats receiving ALT-100 mAb. scRNAseq studies revealed Hy/Su exposure increased populations of ECs undergoing EC-to-mesenchymal cell transition (EndMT), proliferating SMCs, and monocytes undergoing macrophage differentiation. Cellular phenotypic switching was ameliorated in Hy/Su-mAb rats. Conclusions: Autocrine/paracrine eNAMPT/TLR4 signaling contributes to accelerated cellular phenotypic switching, a druggable strategy to reverse vascular remodeling.