Endothelial FGF signaling is protective in hypoxia-induced pulmonary hypertension
Kel Vin Woo, Isabel Y. Shen, Carla J. Weinheimer, Attila Kovacs, Jessica Nigro, Chieh-Yu Lin, Murali Chakinala, Derek E. Byers, David M. Ornitz
Kel Vin Woo, Isabel Y. Shen, Carla J. Weinheimer, Attila Kovacs, Jessica Nigro, Chieh-Yu Lin, Murali Chakinala, Derek E. Byers, David M. Ornitz
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Research Article Cell biology Vascular biology

Endothelial FGF signaling is protective in hypoxia-induced pulmonary hypertension

Abstract

Hypoxia-induced pulmonary hypertension (PH) is one of the most common and deadliest forms of PH. Fibroblast growth factor receptors 1 and 2 (FGFR1/2) are elevated in patients with PH and in mice exposed to chronic hypoxia. Endothelial FGFR1/2 signaling is important for the adaptive response to several injury types and we hypothesized that endothelial FGFR1/2 signaling would protect against hypoxia-induced PH. Mice lacking endothelial FGFR1/2, mice with activated endothelial FGFR signaling, and human pulmonary artery endothelial cells (HPAECs) were challenged with hypoxia. We assessed the effect of FGFR activation and inhibition on right ventricular pressure, vascular remodeling, and endothelial-mesenchymal transition (EndMT), a known pathologic change seen in patients with PH. Hypoxia-exposed mice lacking endothelial FGFRs developed increased PH, while mice overexpressing a constitutively active FGFR in endothelial cells did not develop PH. Mechanistically, lack of endothelial FGFRs or inhibition of FGFRs in HPAECs led to increased TGF-β signaling and increased EndMT in response to hypoxia. These phenotypes were reversed in mice with activated endothelial FGFR signaling, suggesting that FGFR signaling inhibits TGF-β pathway–mediated EndMT during chronic hypoxia. Consistent with these observations, lung tissue from patients with PH showed activation of FGFR and TGF-β signaling. Collectively, these data suggest that activation of endothelial FGFR signaling could be therapeutic for hypoxia-induced PH.

Authors

Kel Vin Woo, Isabel Y. Shen, Carla J. Weinheimer, Attila Kovacs, Jessica Nigro, Chieh-Yu Lin, Murali Chakinala, Derek E. Byers, David M. Ornitz

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Figure 11

Effect of FGFR inhibition on endothelial-mesenchymal transition in human pulmonary artery endothelial cells (HPAECs).

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Effect of FGFR inhibition on endothelial-mesenchymal transition in human...
(A) Representative images of CDH5 (red) and αSMA (green) immunofluorescence in HPAECs treated with FGFR inhibitor BGJ398 under hypoxic conditions compared with controls in normoxia. Scale bar: 10 μm. (B) Quantification of the number of colonies of αSMA-positive cells per culture well in HPAECs treated with the FGFR inhibitor BGJ398 under hypoxic conditions compared with controls in normoxia, n = 4–10. Closed circles, HPAECs in normoxia treated with vehicle; open circle, HPAECs in hypoxia treated with vehicle; closed squares, HPAECs in normoxia treated with inhibitor; open squares, HPAECs in hypoxia treated with inhibitor. (C) Representative Western blots and quantification of p-Smad2/3 normalized to total Smad proteins, n = 5. (D) Representative Western blots and quantification of αSMA normalized to β-actin, n = 3. See complete unedited blots in the supplemental material. Statistical significance was determined by 2-way ANOVA with Holm-Šídák multiple comparison test. All data are shown as the mean ± SEM. *P < 0.05, **P < 0.01. (E) Proposed model showing FGF inhibition of hypoxia-stimulated TGF-β signaling in endothelial-mesenchymal transition.