Abstract 127: The Lung-Associated Self-Antigen Type V Collagen is Regulated by Nuclear Factor of Activated T Cells Isoform c3 in Chronic Hypoxia

Abstract

Chronic hypoxia (CH)-induced pulmonary hypertension (PH) is a progressive and often fatal consequence of chronic lung diseases, chronic exposure to high altitude and sleep apnea. PH results from arterial remodeling, enhanced vasoreactivity, and Th17 cell-mediated perivascular inflammation. Naturally occurring “nTH17” cells, can be detected in fetal life and are in homeostatic equilibrium with natural T regulatory cells. nTH17 cells are specific for a limited range of self-antigens, including type V collagen (colV). ColV is normally hidden from the immune system within type I col in the extracellular matrix of the lungs. We have shown that type V collagen is a self-antigen uncovered by CH. On the other hand, we have shown that mice lacking nuclear factor of activated T cells isoform c3 (NFATc3) globally and specifically in smooth muscle (SMC-NFATc3 KO) are protected from CH-induced PH. No differences in cardiac function were detected between SMC-NFATc3 KO and control mice using a Vevo LAZR-X ultrasound system before CH. In silico analysis of Col5A1 promoter shows NFATc3 binding sites. Therefore, we hypothesized that smooth muscle NFATc3 upregulates Col5A1 expression contributing to the development of acute autoreactivity to collagen V in response to CH, representing an upstream mechanism in PH development. Col5A1 was one of the 1792 genes differentially affected by both CH and smooth muscle NFATc3 in isolated pulmonary arteries (RNA Illumina Sequencing). Col5A1 mRNA increased significantly after 5 days of CH in control mice (fold change from normoxia±SD=2.2±0.8, n=5) vs. SMC-NFATc3 KO (0.8±0.3, n=3, p<0.03). Cellular autoimmunity to colV was determined using a trans-vivo delayed-type hypersensitivity assay (TV-DTH). Splenocytes from 5 days CH-exposed control mice displayed a TV-DTH colV response significantly higher than that from CH-exposed SMC-NFATc3 KO mice (footpad swelling [10 -4 ”] ± SD of naïve recipient mice injected with cells from CH control mice 25.6±4.2, n=8 vs. CH SMC-NFATc3 KO mice 5.3±0.5, n=7; p<0.0001). Our results suggest that smooth muscle NFATc3 is important for CH-induced PH in adult mice, in part, by regulating the expression of the lung self-antigen ColV contributing to pulmonary vascular inflammation.