Hif-1 alpha Knockdown Reduces Glycolytic Metabolism and Induces Cell Death of Human Synovial Fibroblasts Under Normoxic Conditions

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Increased glycolysis and HIF-1 alpha activity are characteristics of cells under hypoxic or inflammatory conditions. Besides, in normal O-2 environments, elevated rates of glycolysis support critical cellular mechanisms such as cell survival. The purpose of this study was to analyze the contribution of HIF-1 alpha to the energy metabolism and survival of human synovial fibroblasts (SF) under normoxic conditions. HIF-1 alpha was silenced using lentiviral vectors or small-interfering RNA (siRNA) duplexes. Expression analysis by qRT-PCR and western blot of known HIF-1 alpha target genes in hypoxia demonstrated the presence of functional HIF-1 alpha in normoxic SF and confirmed the glycolytic enzyme glyceraldehyde3-phosphate dehydrogenase (GAPDH) as a HIF-1 alpha target even in normoxia. HIF-1 alpha silencing induced apoptotic cell death in cultured SF and, similarly, treatment with glycolytic, but not with OXPHOS inhibitors, induced SF death. Finally, in vivo HIF-1 alpha targeting by siRNA showed a significant reduction in the viability of human SF engrafted into a murine air pouch. Our results demonstrate that SF are highly dependent on glycolytic metabolism and that HIF-1 alpha plays a regulatory role in glycolysis even under aerobic conditions. Local targeting of HIF-1 alpha provides a feasible strategy to reduce SF hyperplasia in chronic arthritic diseases.
© NATURE PUBLISHING GROUP 2017 Artículo firmado por más de 10 autores. We are grateful to Vanessa Miranda for technical assistance, and to Ines Garcia-Consuegra and Sara Asensio (Servicio de Proteomica, Instituto de Investigacion Sanitaria Hospital 12 de Octubre) for assisting with western blot experiments. This work was supported by the Fondo de Investigacion Sanitaria, Instituto de Salud Carlos III (FIS 12/439, RETICS RD12/009 RIER, and Miguel Servet program CP13/00014 to GC) cofinanced by European Regional Development Fund (FEDER), and by the Comunidad de Madrid (RAPHYME-CM S2010/BMD2350).
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