A64-01 Hypoxia Inducible Factor-1 In Cx3cr1-expressing Cells Is Dispensable to Schistosomiasis-induced and Hypoxic Pulmonary Hypertension

Abstract Rationale Hypoxia inducible factor-1 (HIF-1) has been shown to promote various forms of pulmonary hypertension (PH) in animals, but its role specifically in inflammatory cells remains under characterized. We previously demonstrated that in mice with schistosomiasis-induced PH (Sch-PH), transcription of Hif-1α and most of its glycolytic targets is upregulated in the lung IMs, and that HIF-1 deletion in lysozyme M (LysM)-positive myeloid cells was protective against Sch-PH. In hypoxia-PH, we showed the necessity of C-C motif chemokine ligand 2 (CCL2), produced by fractalkine receptor (CX3CR1)+ resident lung interstitial macrophages (IMs) in the recruitment of C-C chemokine receptor 2 (CCR2)+ lung IMs, leading to pulmonary vascular remodeling. We hypothesized that glycolysis by CX3CR1+ resident lung IMs are glucose-avid and that HIF-1α deletion specifically in CX3CR1+ cells protects mice from both Sch-PH and hypoxia-PH. Methods We measured glucose uptake in lung macrophages from wildtype mice by intraperitoneally injecting 2-NBDG (a fluorescent glucose analogue) 3 days after hypoxia exposure or intravenous Schistosoma mansoni egg challenge. As a proxy for HIF-1-induced glycolysis, we measured 2-NBDG uptake using multicolor flow cytometry. Hif-1αLoxP/LoxP mice were crossed with CX3CR1CreER mice to generate HIF-1αΔCX3CR1 mice. Prior to hypoxia or Schistosoma mansoni egg exposure, the HIF-1αΔCX3CR1 mice received either tamoxifen or corn oil (vehicle control), with tamoxifen-injected Hif-1αLoxP/LoxP mice serving as a second control group. Both male and female mice were used. Right ventricular systolic pressure (RVSP) was measured during right heart catheterization, and right ventricular hypertrophy was assessed. Results We observed significantly increased 2-NBDG uptake by both CX3CR1 + (resident) and CCR2 + (recruited) subsets of lung IMs, suggesting schistosomiasis and hypoxia-induced glycolysis upregulation in both populations. Tamoxifen-treated HIF-1αΔCX3CR1 mice were not protected from Sch-PH or hypoxia-PH, with both RVSP and right ventricular hypertrophy unchanged compared to the two control groups. CONCLUSIONS Hif-1α deletion in CX3CR1+ cells did not attenuate murine Sch-PH or hypoxia-PH, suggesting that CX3CR1-negative myeloid cells, such as the recruited CCR2+ lung IMs, may significantly contribute to the Hif-1α-associated glucose utilization, and hypoxia-PH and Sch-PH pathogenesis. This abstract is funded by: NHLBI