T_reg Cells Attenuate Pulmonary Venous Remodeling in PH-LHD via NLRC3 Signaling.

Abstract

Pulmonary venous remodeling is a key pathological feature of pulmonary hypertension associated with left heart disease (PH-LHD). This study aims to investigate the role of regulatory T (T_reg) cells in this process. We used mouse models with transverse aortic constriction and cell depletion of <i>Foxp3-DTR/tdTomato</i> mice to examine T_reg cells' function around pulmonary veins in PH-LHD in vivo. To confirm the effect of <i>Nlrc3</i>^<i>-/-</i> T_reg cells on PH-LHD, we utilized 3 mouse models: <i>Nlrc3</i> knockout mice, athymic mice, and endothelial cell lineage tracing <i>Cdh5CreERT2</i>^<i>+/</i>^<i>-</i><i>-mT/mG</i>^<i>+/</i>^<i>-</i> mice. The interaction proteins and signaling pathways of T_reg cells during endothelial-to-mesenchymal transition were elucidated by protein docking prediction, coimmunoprecipitation and cocultivation of T_reg cells with venous endothelial cells. T_reg cells were abundant around pulmonary veins of transverse aortic constriction-induced PH-LHD and were essential for promoting inflammation resolution and inhibiting pulmonary venous remodeling. <i>Nlrc3</i> expression was reduced in mice and patients with PH-LHD. NLRC3 (nucleotide-oligomerization domain-like receptor family CARD domain containing 3) deficiency inhibited T_reg cell proliferation and impaired their immunosuppressive and endothelial-to-mesenchymal transition-protective effects. Mechanistically, NLRC3 interacted with TRAM (TRIF-related adaptor molecule) and regulated interferon regulatory factor 3 (IRF3)/NF-κB (nuclear factor-κB) p65 signaling in cluster differentiation 4⁺ (CD4⁺) T cells. NLRC3-deficient T_reg cells promoted interleukin (IL)-18 expression through IRF3/NF-κB p65 signaling, and thus IL-18 secretion activated endothelial receptor tyrosine kinase (RTK) signaling, favoring endothelial-to-mesenchymal transition progression in pulmonary veins and PH-LHD progress. This process was reversible with IL-18 binding protein in vivo. NLRC3 is crucial for T_reg cells to prevent pulmonary venous remodeling in PH-LHD, primarily by modulating IL-18 secretion, which inhibits endothelial-to-mesenchymal transition and thereby improves disease progression and prognosis.