C26-07 Metabolite-Sensitive AHR-ARNT Axis Drives Endothelial Plasticity and Vascular Remodeling in Pulmonary Hypertension

Abstract Rationale Pulmonary arterial hypertension (PAH) is characterized by maladaptive vascular remodeling driven by endothelial cell (EC) proliferation, metabolic reprogramming, and phenotypic transformation. Our recent single-cell lung endothelial atlas revealed a small population of mitotically active general capillary ECs (Flot1+ gCaps) that expand 10-fold under hypoxia and seed proliferative and transitional states. However, the molecular mechanism coupling EC metabolism to transcriptional reprogramming remains unknown. We hypothesized that anaplerotic flux activates metabolite-sensitive the aryl hydrocarbon receptor AHR-ARNT transcriptional axis, reprogramming Flot1+ ECs into proliferative and mesenchymal states that drive PAH. Methods Su/Hx rats were treated with dual anaplerotic inhibitors (R162+PAA) targeting GLUD1 and PC. Right ventricular systolic pressure (RVSP) and Fulton index were measured. Lungs were analyzed by histology, immunoblotting, and high-resolution single-cell RNA sequencing (Parse, 140k cells/run). AHR-ARNT pathway activity was quantified using AHRR response. Mechanistic validation was performed in human lung microvascular ECs (HLMVECs) and isolated Flot1+ ECs exposed to Su/hypoxia or anaplerotic metabolites (OAA+a-KG). Results Dual anaplerosis inhibition reversed PAH even in established disease, normalizing RVSP and vascular remodeling. This was accompanied by decreased proliferative signaling and restored mitochondrial PDH. scRNA-seq revealed that AHRR, an AHR-axis reporter, was upregulated in Flot1+ gCaps and transitional EC clusters in Su/Hx lungs but absent in controls. We delineated proliferative, EndMT, and EHT-prone lineages of lung endothelial cells. In vitro, OAA+a-KG induced AHR-ARNT nuclear translocation and accumulation in ECs. In the cell-culture, Su/Hx model activates EndMT/EHT markers (a-SMA, F13A1). Pharmacologic inhibition of ARNT with acriflavine (5 mg/kg, i.p.) fully normalized RVSP and right-ventricular hypertrophy in Su/Hx rats, confirming the AHR-ARNT axis as a required driver of disease initiation and progression. Conclusions Anaplerotic reprogramming links endothelial metabolism to transcription by activating a metabolite-sensitive AHR-ARNT pathway, which promotes EC proliferation and their transformation into mesenchymal and pro-thrombotic cells. This connection between mitochondrial metabolism and endothelial plasticity provides a potential therapeutic target for remodeling in PAH. This abstract is funded by: NIH