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Cigarette smoke reversibly activates hypoxia-inducible factor 1 in a reactive oxygen species-dependent manner.

ABSTRACT: Cigarette smoke (CS) is a major contributor to the development of a large number of fatal and debilitating disorders. However, the precise molecular mechanisms underlying the effects of CS in lung disease are largely unknown. To elucidate these pathophysiological processes, we examined the in vitro and in vivo effects of CS extract (CSE) and CS on the transcription factor, hypoxia-inducible factor 1 (HIF-1). CSE induced concentration- and time-dependent accumulation of HIF-1? protein in human lung epithelial-like cells under non-hypoxic conditions. Genes upregulated by HIF-1, including vascular endothelial growth factor and regulated in development and DNA damage response 1, both of which are involved in smoking-induced emphysematous changes, were increased by CSE treatment under non-hypoxic conditions in vitro and in vivo. Further investigation revealed that reactive oxygen species were generated in cells exposed to CSE and were required for CSE-mediated induction of HIF-1? protein, as was activation of phosphoinositide 3-kinase and mitogen-activated protein kinase pathways. In conclusion, we demonstrated that CSE and CS induced HIF-1 activation in vitro and in vivo, respectively. The evidence warrants further investigation to indicate that HIF-1 plays an important role in CS-induced gene expression, which is deeply involved in pulmonary cellular stress and small airway remodelling.

SUBMITTER: Daijo H

PROVIDER: S-EPMC5041075 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Cigarette smoke reversibly activates hypoxia-inducible factor 1 in a reactive oxygen species-dependent manner.

Daijo Hiroki H Hoshino Yuma Y Kai Shinichi S Suzuki Kengo K Nishi Kenichiro K Matsuo Yoshiyuki Y Harada Hiroshi H Hirota Kiichi K

Scientific reports 20160929

Cigarette smoke (CS) is a major contributor to the development of a large number of fatal and debilitating disorders. However, the precise molecular mechanisms underlying the effects of CS in lung disease are largely unknown. To elucidate these pathophysiological processes, we examined the in vitro and in vivo effects of CS extract (CSE) and CS on the transcription factor, hypoxia-inducible factor 1 (HIF-1). CSE induced concentration- and time-dependent accumulation of HIF-1α protein in human lu ...[more]

PMID: 27680676

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Project description:BACKGROUND:Mitochondria are more than just the powerhouse of cells; they dictate if a cell dies or survives. Mitochondria are dynamic organelles that constantly undergo fusion and fission in response to environmental conditions. We showed previously that mitochondria of cells in a low oxygen environment (hypoxia) hyperfuse to form enlarged or highly interconnected networks with enhanced metabolic efficacy and resistance to apoptosis. Modifications to the appearance and metabolic capacity of mitochondria have been reported in cancer. However, the precise mechanisms regulating mitochondrial dynamics and metabolism in cancer are unknown. Since hypoxia plays a role in the generation of these abnormal mitochondria, we questioned if it modulates mitochondrial function. The mitochondrial outer-membrane voltage-dependent anion channel 1 (VDAC1) is at center stage in regulating metabolism and apoptosis. We demonstrated previously that VDAC1 was post-translationally C-terminal cleaved not only in various hypoxic cancer cells but also in tumor tissues of patients with lung adenocarcinomas. Cells with enlarged mitochondria and cleaved VDAC1 were also more resistant to chemotherapy-stimulated cell death than normoxic cancer cells. RESULTS:Transcriptome analysis of mouse embryonic fibroblasts (MEF) knocked out for Vdac1 highlighted alterations in not only cancer and inflammatory pathways but also in the activation of the hypoxia-inducible factor-1 (HIF-1) signaling pathway in normoxia. HIF-1α was stable in normoxia due to accumulation of reactive oxygen species (ROS), which decreased respiration and glycolysis and maintained basal apoptosis. However, in hypoxia, activation of extracellular signal-regulated kinase (ERK) in combination with maintenance of respiration and increased glycolysis counterbalanced the deleterious effects of enhanced ROS, thereby allowing Vdac1 (-/-) MEF to proliferate better than wild-type MEF in hypoxia. Allografts of RAS-transformed Vdac1 (-/-) MEF exhibited stabilization of both HIF-1α and HIF-2α, blood vessel destabilization, and a strong inflammatory response. Moreover, expression of Cdkn2a, a HIF-1-target and tumor suppressor gene, was markedly decreased. Consequently, RAS-transformed Vdac1 (-/-) MEF tumors grew faster than wild-type MEF tumors. CONCLUSIONS:Metabolic reprogramming in cancer cells may be regulated by VDAC1 through vascular destabilization and inflammation. These findings provide new perspectives into the understanding of VDAC1 in the function of mitochondria not only in cancer but also in inflammatory diseases.

Project description:Excessive production of mitochondrial reactive oxygen species (ROS) is a central mechanism for the development of diabetes complications. Recently, hypoxia has been identified to play an additional pathogenic role in diabetes. In this study, we hypothesized that ROS overproduction was secondary to the impaired responses to hypoxia due to the inhibition of hypoxia-inducible factor-1 (HIF-1) by hyperglycemia. The ROS levels were analyzed in the blood of healthy subjects and individuals with type 1 diabetes after exposure to hypoxia. The relation between HIF-1, glucose levels, ROS production and its functional consequences were analyzed in renal mIMCD-3 cells and in kidneys of mouse models of diabetes. Exposure to hypoxia increased circulating ROS in subjects with diabetes, but not in subjects without diabetes. High glucose concentrations repressed HIF-1 both in hypoxic cells and in kidneys of animals with diabetes, through a HIF prolyl-hydroxylase (PHD)-dependent mechanism. The impaired HIF-1 signaling contributed to excess production of mitochondrial ROS through increased mitochondrial respiration that was mediated by Pyruvate dehydrogenase kinase 1 (PDK1). The restoration of HIF-1 function attenuated ROS overproduction despite persistent hyperglycemia, and conferred protection against apoptosis and renal injury in diabetes. We conclude that the repression of HIF-1 plays a central role in mitochondrial ROS overproduction in diabetes and is a potential therapeutic target for diabetic complications. These findings are timely since the first PHD inhibitor that can activate HIF-1 has been newly approved for clinical use. This work was supported by grants from the Swedish Research Council, Stockholm County Research Council, Stockholm Regional Research Foundation, Bert von Kantzows Foundation, Swedish Society of Medicine, Kung Gustaf V:s och Drottning Victorias Frimurarestifelse, Karolinska Institute's Research Foundations, Strategic Research Programme in Diabetes, and Erling-Persson Family Foundation for S-B.C.; grants from the Swedish Research Council and Swedish Heart and Lung Foundation for T.A.S.; and ERC consolidator grant for M.M.

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Cigarette smoke reversibly activates hypoxia-inducible factor 1 in a reactive oxygen species-dependent manner.

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Cigarette smoke reversibly activates hypoxia-inducible factor 1 in a reactive oxygen species-dependent manner.

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