{
  "abstract": "Introduction and Objectives Acute exposure of pulmonary vascular endothelial cells to pathological hypoxia initiates the secretion of pro-inflammatory mediators and increases the expression of leukocyte adhesion molecules that promotes the recruitment of myeloid-lineage cells into the lung. The infiltration of activated neutrophils into hypoxic regions of the lung has been reported in a multitude of pulmonary diseases, including Pulmonary Hypertension, resulting in the release cytotoxic proteins and proteases that cause local tissue damage and vascular remodelling. However, a complete understanding of the hypoxic signalling pathway that initiates the migration of myeloid-lineage cells into the lung remains unclear.Methods and Results A time-course (1–14 days) of wild-type mice exposed to acute hypoxia (10% oxygen) confirmed the migration of myeloid cells into pulmonary tissues. Lung single cell multi-colour FACs analysis identified a significant increase in both neutrophil and monocyte derived cell populations following 3-days hypoxia, with a significant increase in the neutrophil sub-population CXCR4 +/VEGFR1+ (pro-angiogenic). Blood neutrophil counts fluctuated with a trend towards decreasing CXCR4 expression following hypoxia exposure, suggesting an increase in neutrophil mobilisation from the bone marrow. Here, we show the normal increase in myeloid lineage cells following hypoxia exposure was absent in mice with pulmonary endothelial Hypoxia Inducible Factor (HIF)2a deletion; the total cell count for lung neutrophils and monocytes was not significantly different from wild-type animals breathing room air. This is a HIF2a specific event because loss of pulmonary endothelial HIF1a did not affect hypoxia-induced cell migration. RNA-seq analysis of human pulmonary artery endothelial cells (hPAEC) exposed to hypoxia identified a significant increase in target genes associated with leukocyte adhesion, and trans-endothelial migration. The co-culture of PT2385 (HIF2a inhibitor) with hPAEC exposed to hypoxia significantly reduced the expression of leukocyte adhesion molecules and chemokines.Conclusion Our data support pre-clinical studies in pulmonary hypertension which identified that drug intervention with a HIF2a specific inhibitor significantly reduced the migration of both monocytes and neutrophils into the lung. Further investigations are required to fully elucidate the role of HIF2a in leukocyte/endothelial transmigration and understand the potential beneficial effect of inhibiting HIF2a signalling in other neutrophil-driven pulmonary diseases.",
  "authors": [
    {
      "affiliations": [
        "Imperial College London, London, UK"
      ],
      "name": "KM Lodge"
    },
    {
      "affiliations": [
        "Imperial College London, London, UK"
      ],
      "name": "S Nakanishi"
    },
    {
      "affiliations": [
        "CICbioGUNE, Bilbao, Spain"
      ],
      "name": "A Palazon"
    },
    {
      "affiliations": [
        "Imperial College London, London, UK"
      ],
      "name": "N Pisacano"
    },
    {
      "affiliations": [
        "Karolinska Institutet, Stockholm, Sweden"
      ],
      "name": "RS Johnson"
    },
    {
      "affiliations": [
        "Imperial College London, London, UK"
      ],
      "name": "A Cowburn"
    }
  ],
  "title": "P239 Endothelial HIF2a signalling modulates hypoxia driven myeloid cell migration into the lung",
  "uid": "c0974b07-827f-56d4-963c-b3fbc1dc878b"
}