Fentanyl activates hypoxia-inducible factor 1 in neuronal SH-SY5Y cells and mice under non-hypoxic conditions in a µ-opioid receptor-dependent manner.

Hypoxia-inducible factor 1 (HIF-1) is the main transcription factor responsible for hypoxia-induced gene expression. Perioperative drugs including anesthetics have been reported to affect HIF-1 activity. However, the effect of fentanyl on HIF-1 activity is not well documented. In this study, we investigated the effect of fentanyl and other opioids on HIF-1 activity in human SH-SY5Y neuroblastoma cells, hepatoma Hep3B cells, lung adenocarcinoma A549 cells and mice. Cells were exposed to fentanyl, and HIF-1 protein expression was examined by Western blot analysis using anti-HIF-1α and ß antibodies. HIF-1-dependent gene expression was investigated by semi-quantitative real-time reverse transcriptase (RT)-PCR (qRT-PCR) and luciferase assay. Furthermore, fentanyl was administered intraperitoneally and HIF-1-dependent gene expression was investigated by qRT-PCR in the brains and kidneys of mice. A 10-µM concentration of fentanyl and other opioids, including 1 µM morphine and 4 µM remifentanil, induced HIF-1α protein expression and HIF-1 target gene expression in an opioid receptor-dependent manner in SH-SY5Y cells with activity peaking at 24h. Fentanyl did not augment HIF-1α expression during hypoxia-induced induction. HIF-1α stabilization assays and experiments with cycloheximide revealed that fentanyl increased translation from HIF-1α mRNA but did not stabilize the HIF-1α protein. Furthermore, fentanyl induced HIF-1 target gene expression in the brains of mice but not in their kidneys in a naloxone-sensitive manner. In this report, we describe for the first time that fentanyl, both in vitro and in vivo, induces HIF-1 activation under non-hypoxic conditions, leading to increases in expression of genes associated with adaptation to hypoxia.

Persisting mild hypothermia suppresses hypoxia-inducible factor-1alpha protein synthesis and hypoxia-inducible factor-1-mediated gene expression.

The transcription factor hypoxia-inducible factor-1 (HIF-1) plays an essential role in regulating gene expression in response to hypoxia-ischemia. Ischemia causes the tissue not only to be hypoxic but also to be hypothermic because of the hypoperfusion under certain circumstances. On the other hand, the induced hypothermia is one of the most common therapeutic modalities to extend tolerance to hypoxia. Although hypoxia elicits a variety of cellular and systemic responses at different organizational levels in the body, little is known about how hypoxia-induced responses are affected by low temperature. We examined the influence of mild hypothermic conditions (28-32 degrees C) on HIF-1 in both in vitro and in vivo settings. In vitro experiments adopting cultured cells elucidated that hypoxia-induced HIF-1 activation was resistant to 4-h exposure to the low temperature. In contrast, exposure to the low temperature as long as 24 h suppressed HIF-1 activation and the subsequent upregulation of HIF-1 target genes such as VEGF or GLUT-1. HIF-1alpha protein stability in the cell was not affected by hypothermic treatment. Furthermore, intracellular ATP content was reduced under 1% O(2) conditions but was not largely affected by hypothermic treatment. The evidence indicates that reduction of oxygen consumption is not largely involved in suppression of HIF-1. In addition, we demonstrated that HIF-1 DNA-binding activity and HIF-1-dependent gene expressions induced under 10% O(2) atmosphere in mouse brain were not influenced by treatment under 3-h hypothermic temperature but were inhibited under 5-h treatment. On the other hand, we indicated that warming ischemic legs of mice for 24 h preserved HIF-1 activity. In this report we describe for the first time that persisting low temperature significantly reduced HIF-1alpha neosynthesis under hypoxic conditions, leading to a decrease in gene expression for adaptation to hypoxia in both in vitro and in vivo settings.

The intravenous anesthetic propofol inhibits lipopolysaccharide-induced hypoxia-inducible factor 1 activation and suppresses the glucose metabolism in macrophages.

PURPOSE: Hypoxia-inducible factor 1 (HIF-1) is a master transcription factor of hypoxia-induced gene expression. Anesthetics and perioperative drugs have been reported to affect HIF-1 activity. However, the effect of propofol on HIF-1 activity is not well documented. In this study, we investigated the effect of propofol on HIF-1 activation using macrophage-differentiated THP-1 cells. METHODS: Cells were exposed to lipopolysaccharide (LPS) under 20 or 1% O(2) conditions with or without propofol treatment. The cell lysate was subjected to Western blot analysis using anti-HIF-1alpha and HIF-1beta antibodies. HIF-1-dependent gene expression was investigated by quantitative real-time reverse-transcriptase PCR analysis and luciferase assay. The amount of cellular lactate and ATP was assayed. RESULTS: Propofol suppressed HIF-1alpha protein accumulation induced by LPS, but not by hypoxia in the THP-1 cells in a dose-dependent manner by inhibiting the neo-synthesis of HIF-1alpha protein. Induction of the HIF-1 downstream gene expression including glucose transporter 1, enolase 1, lactate dehydrogenase A, pyruvate dehydrogenase kinase-1 and vascular endothelial growth factor was inhibited by propofol. Propofol suppressed LPS-induced lactate accumulation and ATP content in THP-1 cells. CONCLUSION: Our experimental results indicate that propofol inhibits HIF-1 activation and downstream gene expression induced by LPS and suppressed HIF-1-dependent glucose metabolic reprogramming. HIF-1 suppression by propofol in macrophages may explain molecular mechanisms behind the inhibitory effect of propofol on cellular inflammatory responses.

The intravenous anesthetics barbiturates inhibit hypoxia-inducible factor 1 activation.

Hypoxia-inducible factor 1 (HIF-1) is a master transcription factor of hypoxia-induced gene expression. Anesthetics and perioperative drugs have been reported to affect HIF-1 activity. However, the effect of barbiturates on HIF-1 activity has not been reported. In this study, we investigated the effect of thiopental and thiamylal on HIF-1 activity using the neuronal SH-SY5Y cells, the non-neuronal HEK293 cells, and the macrophage-differentiated THP-1 cells. Cells were exposed to 20% or 1% O(2) conditions with or without thiopental or thiamylal treatment. The cell lysate were subjected to Western blot analysis using anti-HIF-1alpha and -HIF-1beta antibodies. HIF-1-dependent gene expression was investigated by semi-quantitative real-time RT-PCR and luciferase assay. Hydroxylation of HIF-1alpha protein was evaluated by in vitro pulldown assay using recombinant protein. Both thiopental and thiamylal reversibly suppressed hypoxia-induced HIF-1 activation in the neuronal and the non-neuronal cells in a dose-dependent manner. Moreover, the barbiturates inhibited lipopolysaccharide-induced HIF-1alpha expression in THP-1 cells. The HIF-1-downstream gene expression was also inhibited by the barbiturates. HIFalpha-hydroxylases activity and HIF-1alpha stability were not affected but the HIF-1alpha protein neosynthesis was inhibited by the barbiturates. Our experimental results indicate that barbiturates inhibit induced HIF-1 activation and downstream genes expression.

The calcium channel blocker cilnidipine selectively suppresses hypoxia-inducible factor 1 activity in vascular cells.

Calcium ion is one of the most important second messengers of cellular signal transduction including hypoxia-elicited signals. In this study, we investigated the effects of the L-type calcium channel blockers such as nifedipine, efonidipine cilnidipine, diltiazem, and verapamil, on the activity of hypoxia-inducible factor-1 (HIF-1), a key transcription factor in control of hypoxia-induced gene expression. Using the lung carcinoma cell line A549 cells, human aortic smooth muscle cells, and human umbilical vein endothelial cells, we demonstrated that cilnidipine exclusively suppressed HIF-1 activity and the expressions of downstream genes in a cell-type specific manner. We also demonstrated that cilnidipine blocked the synthesis of the HIF-1alpha protein not by affecting activity of the intracellular hypoxia-sensing element prolyl hydroxylases but inhibiting activity of Akt and mitogen-activated protein kinase and that the inhibition is not dependent on the effect on calcium homeostasis.

Macrophage migration inhibitory factor activates hypoxia-inducible factor in a p53-dependent manner.

BACKGROUND: Macrophage migration inhibitory factor (MIF) is not only a cytokine which has a critical role in several inflammatory conditions but also has endocrine and enzymatic functions. MIF is identified as an intracellular signaling molecule and is implicated in the process of tumor progression, and also strongly enhances neovascularization. Overexpression of MIF has been observed in tumors from various organs. MIF is one of the genes induced by hypoxia in an hypoxia-inducible factor 1 (HIF-1)-dependent manner. METHODS/PRINCIPAL FINDINGS: The effect of MIF on HIF-1 activity was investigated in human breast cancer MCF-7 and MDA-MB-231 cells, and osteosarcoma Saos-2 cells. We demonstrate that intracellular overexpression or extracellular administration of MIF enhances activation of HIF-1 under hypoxic conditions in MCF-7 cells. Mutagenesis analysis of MIF and knockdown of 53 demonstrates that the activation is not dependent on redox activity of MIF but on wild-type p53. We also indicate that the MIF receptor CD74 is involved in HIF-1 activation by MIF at least when MIF is administrated extracellularly. CONCLUSION/SIGNIFICANCE: MIF regulates HIF-1 activity in a p53-dependent manner. In addition to MIF's potent effects on the immune system, MIF is linked to fundamental processes conferring cell proliferation, cell survival, angiogenesis, and tumor invasiveness. This functional interdependence between MIF and HIF-1alpha protein stabilization and transactivation activity provide a molecular mechanism for promotion of tumorigenesis by MIF.

[Awareness during anesthesia with sevoflurane: a case report].

We report a case of a patient who experienced awareness during general anesthesia with sevoflurane. A 71-year-old man, weighing 57 kg, was operated on for a malignant tumor of the parotid gland. He was given 2 mg diazepam orally as a premedication. General anesthesia was induced by thiamylal 200 mg, fentanyl 50 microg, and up to 5% of sevoflurane. Muscle relaxation was obtained with vecuronium 6 mg, and the patient was intubated. After induction, fentanyl 150 microg was added, but no other intravenous anesthetics or muscle relaxants were used. The end-expiratory concentration of sevoflurane was maintained at 0.8% to 1.7% before the start of surgery, and 1.5% to 2.9% during surgery. The operation lasted for 10.4 hours. His left eye was guarded by ointment but kept open for observation by the surgeon of facial movement following muscle stimulation. The surgical course, emergence, and the postoperative course were uneventful. On the fifth postoperative day, the patient started to describe his visual memory during the operation, although he did not remember any pain or discomfort. We believe that visual input through his open eyes, the effect of cranial bone oscillation by the surgery, and the idiosyncrasy of the patient contributed to his intraoperative recall.

[Anesthetic management of morbidly obese patients using inhalation induction with high concentrations of sevoflurane].

We describe successful anesthetic management of three morbidly obese patients, using inhalation induction with high concentrations of sevoflurane. In morbidly obese patients, reduced airway space of the pharynx can cause upper airway obstruction after the induction of general anesthesia and may explain difficult mask ventilation. For these patients, careful airway management is essential during the anesthetic induction. In inhalation induction with sevoflurane, the incidence of transient apnea is lower and the control over depth of anesthesia is easier as compared with intravenous induction. Therefore, sevoflurane may be an excellent induction agent in morbidly obese patients with a potentially difficult airway.