RESUMO
Hypoxia signaling plays a major role in non-malignant and malignant hyperproliferative diseases. Pulmonary hypertension (PH), a hypoxia-driven vascular disease, is characterized by a glycolytic switch similar to the Warburg effect in cancer. Ras association domain family 1A (RASSF1A) is a scaffold protein that acts as a tumour suppressor. Here we show that hypoxia promotes stabilization of RASSF1A through NOX-1- and protein kinase C- dependent phosphorylation. In parallel, hypoxia inducible factor-1 α (HIF-1α) activates RASSF1A transcription via HIF-binding sites in the RASSF1A promoter region. Vice versa, RASSF1A binds to HIF-1α, blocks its prolyl-hydroxylation and proteasomal degradation, and thus enhances the activation of the glycolytic switch. We find that this mechanism operates in experimental hypoxia-induced PH, which is blocked in RASSF1A knockout mice, in human primary PH vascular cells, and in a subset of human lung cancer cells. We conclude that RASSF1A-HIF-1α forms a feedforward loop driving hypoxia signaling in PH and cancer.
Assuntos
Hipóxia Celular , Hipertensão Pulmonar/patologia , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Neoplasias Pulmonares/patologia , Proteínas Supressoras de Tumor/metabolismo , Animais , Modelos Animais de Doenças , Glicólise , Células HEK293 , Células HeLa , Humanos , Hipertensão Pulmonar/cirurgia , Pulmão/irrigação sanguínea , Pulmão/patologia , Pulmão/cirurgia , Masculino , Camundongos , Camundongos Knockout , Miócitos de Músculo Liso , NADPH Oxidase 1/metabolismo , Cultura Primária de Células , Regiões Promotoras Genéticas/genética , Ligação Proteica , Proteína Quinase C/metabolismo , Proteólise , Artéria Pulmonar/citologia , Transdução de Sinais , Proteínas Supressoras de Tumor/genéticaRESUMO
Pulmonary hypertension (PH) is characterized by increased proliferation and apoptosis resistance of pulmonary artery smooth muscle cells (PASMCs). Forkhead box O (FoxO) transcription factors are key regulators of cellular proliferation. Here we show that in pulmonary vessels and PASMCs of human and experimental PH lungs, FoxO1 expression is downregulated and FoxO1 is inactivated via phosphorylation and nuclear exclusion. These findings could be reproduced using ex vivo exposure of PASMCs to growth factors and inflammatory cytokines. Pharmacological inhibition and genetic ablation of FoxO1 in smooth muscle cells reproduced PH features in vitro and in vivo. Either pharmacological reconstitution of FoxO1 activity using intravenous or inhaled paclitaxel, or reconstitution of the transcriptional activity of FoxO1 by gene therapy, restored the physiologically quiescent PASMC phenotype in vitro, linked to changes in cell cycle control and bone morphogenic protein receptor type 2 (BMPR2) signaling, and reversed vascular remodeling and right-heart hypertrophy in vivo. Thus, PASMC FoxO1 is a critical integrator of multiple signaling pathways driving PH, and reconstitution of FoxO1 activity offers a potential therapeutic option for PH.