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

Abstract

Increased glycolysis and HIF-1α activity are characteristics of cells under hypoxic or inflammatory conditions. Besides, in normal O2 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-1α to the energy metabolism and survival of human synovial fibroblasts (SF) under normoxic conditions. HIF-1α was silenced using lentiviral vectors or small-interfering RNA (siRNA) duplexes. Expression analysis by qRT-PCR and western blot of known HIF-1α target genes in hypoxia demonstrated the presence of functional HIF-1α in normoxic SF and confirmed the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a HIF-1α target even in normoxia. HIF-1α 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-1α 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-1α plays a regulatory role in glycolysis even under aerobic conditions. Local targeting of HIF-1α provides a feasible strategy to reduce SF hyperplasia in chronic arthritic diseases.

H2O2-preconditioned human adipose-derived stem cells (HC016) increase their resistance to oxidative stress by overexpressing Nrf2 and bioenergetic adaptation

“…At least three different experiments were performed and data were expressed as mean ± SD. *p < 0.05 [54], which provides strong evidence that HIF-1α plays an important role in cell proliferation and survival processes. Moreover, some studies have pointed to the importance of aerobic glycolysis in normal proliferating cells as a mechanism for minimizing oxidative stress [55], considering that pyruvate, generated by glycolytic metabolism, may be an efficient scavenger of ROS and therefore protect cells from oxidative stress [56].…”

Hypoxia exposure induced cisplatin resistance partially via activating p53 and hypoxia inducible facor‑1α in non‑small cell lung cancer A549 cells

“…HIF-1α is the focus of the majority of studies due to its expression in all cells of all metazoan species and it transcriptionally regulates multiple genes that mediate glycolysis ( 24 ). HIF-1α activity is mainly regulated post-transcriptionally in response to hypoxia; consequently, HIF-1α serves a critical role in regulating glycolysis through its downstream target gene GAPDH under hypoxic conditions ( 25 ). In the present study, hypoxia was demonstrated to upregulate the expression of HIF-1α, and therefore partially promote glycolysis in A549 cells.…”

Modulating Iron for Metabolic Support of TB Host Defense

“…This allows heterodimerization of HIF1α with its β-subunit, and translocation into the nucleus where HIF1α binds to hypoxia-response elements linked with a variety of genes involved in various cellular processes, including inducing pfkfb3 and IL1 β transcription ( 168 , 169 ). Moreover, GLUT1, as well as a number of other glycolytic enzymes such as phosphofructokinase, are upregulated to promote anaerobic glycolysis, to compensate for the lack of OXPHOS ( 170 – 172 ). Iron chelator-induced inhibition of PHD proteins and the resulting HIF1α stabilization encompasses the potential to trigger this molecular cascade during Mtb infection under aerobic conditions, thus, boosting the pro-inflammatory response of the infected host macrophage and promoting clearance of the infection.…”