Abstract Rationale Pulmonary arterial hypertension (PAH) is a disease with high morbidity and mortality characterized by arterial remodeling due to vascular cell hyperproliferation and proinflammatory immune response. With few treatment options available, elucidating the underlying dysregulated innate immune response could identify future novel therapeutic targets. Chitinase 3-like-1 (Chi3l1) is a secreted glycoprotein shown to impact cellular injury and repair through inhibiting apoptosis, mediating fibrosis and modulating inflammation. High Chi3l1 levels are associated with worse hemodynamics in PAH. Our lab has previously shown that Chi3L1 is expressed in macrophages and contributes to vascular remodeling in a hypoxia-induced PAH mouse model. In addition, Chi3l1 knock out (Chi3l1-/-) and Chi3l1 overexpressed transgenic mice exposed to hypoxia have distinct metabolomic profiles. We hypothesize that Chi3l1 influences macrophage metabolic pathways promoting vascular remodeling in PAH. Methods Bone-marrow derived macrophages (BMDM) isolated from wild-type (WT) and Chi3l1-/- mice were analyzed with Seahorse assay to evaluate ATP production, and RT-PCR to evaluate glycolic and tricarboxylic acid (TCA) cycle activities. Next, fresh human peripheral blood mononuclear cells (PBMCs) from PAH patients were characterized with flow cytometry to evaluate immune cell composition; gated CD14+ CD45+ double positive monocytes were then evaluated for the expression of IL13RA2, Gal-3, and CRTH2, receptors of Chi3l1. Subsequently, human PBMCs were evaluated for the expression of CD14, Chi3l1, and pyruvate carboxylase (Pcx) with immunofluorescence. Results Our findings show increased ATP production and glycolytic activity in BMDMs derived from Chi3l1-/- mice as compared to WT mice. Chi3l1-/- macrophages have reduced expression of Pcx and increased expression of pyruvate dehydrogenase (Pdh), along with increased glycolytic and TCA cycle intermediates. Human monocytes from PAH express Chi3l1 receptors. These cells also express both Chi3L1 and pyruvate carboxylase. Conclusion Our data indicates that Chi3l1 plays a role in glycolytic activity and mitochondrial respiration in the murine macrophages. Human monocytes from PBMCs of PAH patients co-express Chi3l1 and its receptors as well as pyruvate carboxylase. These findings highlight Chi3l1 impact on macrophage metabolism as an area of future research to elucidate dysregulated pathways in PAH that may be future targets for therapies. This abstract is funded by: None
Dunlop et al. (Fri,) studied this question.