VEGFR1 treatment activated the hypoxic response after left PNX.

Regulation of hypoxia-induced factor (HIF) is demonstrated (A). In a normoxic condition, HIF is hydroxylated by prolyl hydroxylase (PH), ubiquitinated by von-Hippel Lindau (VHL), and destined for degradation. In a hypoxic condition, HIF is stabilized, which leads to dimerization with HIF1β and activation of multiple signaling pathways. VEGFR1 treatment increased the expression of HIF2α in the lung (B). On immunohistochemistry (IHC), both VEGF and HIF2α colocalized with SP-C (C), indicating that they were produced in alveolar epithelial cell (AEC) type II. Furthermore, VEGF did not colocalize with Aquaporin-5, a marker for AEC type I, or Vimentin, a marker for fibroblasts (D). On qPCR, VEGFR1-treated lung also displayed increased expression of many HIF-regulated factors, including platelet-derived growth factor α (PDGFα), pyruvate dehydrogenase kinase (PDK), hexose kinase (HK), and CXC chemokine receptor 4 (CXCR4), as well as factors involved in HIF degradation, including VHL and PH (E). Data are expressed as mean ± standard error (SE).