Impact of neoadjuvant therapy on gut microbiome in patients with resectable/borderline resectable pancreatic ductal adenocarcinoma.

BACKGROUND: /Objectives: Effects of chemotherapy on gut microbiota have been reported in various carcinomas. The current study aimed to evaluate the changes in the gut microbiota before and after neoadjuvant chemotherapy (NAC) in patients with resectable (R) and borderline resectable (BR) pancreatic ductal adenocarcinoma (PDAC) and understand their clinical implications. METHODS: Twenty patients diagnosed with R/BR-PDAC were included in this study. Stool samples were collected at two points, before and after NAC, for microbiota analysis using 16S ribosomal RNA (16S rRNA) gene sequences. RESULTS: Of the 20 patients, 18 (90%) were treated with gemcitabine plus S-1 as NAC, and the remaining patients received gemcitabine plus nab-paclitaxel and a fluorouracil, leucovorin, irinotecan, and oxaliplatin combination. No significant differences were observed in the α- and ß-diversity before and after NAC. Bacterial diversity was not associated with Evans classification (histological grade of tumor destruction by NAC) or postoperative complications. The relative abundance of Actinobacteria phylum after NAC was significantly lower than that before NAC (P = 0.02). At the genus level, the relative abundance of Bifidobacterium before NAC in patients with Evans grade 2 disease was significantly higher than that in patients with Evans grade 1 disease (P = 0.03). Patients with Evans grade 2 lost significantly more Bifidobacterium than patients with Evans grade 1 (P = 0.01). CONCLUSIONS: The diversity of gut microbiota was neither decreased by NAC for R/BR-PDAC nor associated with postoperative complications. Lower incidence of Bifidobacterium genus before NAC may be associated with a lower pathological response to NAC.

Clinical impact of physician staffing transition in intensive care units: a retrospective observational study.

BACKGROUND: Intensivists play an essential role in improving the outcomes of critically ill patients in intensive care units (ICUs). The transition of ICU physician staffing from low-intensity ICUs (elective intensivist or no intensivist consultation) to high-intensity ICUs (mandatory intensivist consultation or a closed ICU) improves clinical outcomes. However, whether a transition from high-intensity to low-intensity ICU staffing affects ICU outcomes and quality of care remains unknown. METHODS: A retrospective observational study was conducted to examine the impact of high- versus low-intensity staffing models on all-cause mortality in a suburban secondary community hospital with 400 general beds and 8 ICU beds. The ICU was switched from a high-intensity staffing model (high-former period) to low-intensity staffing in July 2019 (low-mid period) and then back to high-intensity staffing in March 2020 (high-latter period). Patients admitted from the emergency department, general ward, or operating room after emergency surgery were enrolled in these three periods and compared, balancing the predicted mortality and covariates of the patients. The primary outcome was all-cause mortality analyzed using hazard ratios (HRs) from Cox proportional hazards regression. An interrupted time-series analysis (ITSA) was also conducted to evaluate the effects of events (level change) and time. RESULTS: There were 962 eligible admissions, of which 251, 213, and 498 occurred in the high-former, low-mid, and high-latter periods, respectively. In the matched group (n = 600), the all-cause mortality rate comparing the high-former period with the low-mid period showed an HR of 0.88 [95% confidence interval (CI), 0.56, 1.39; p = 0.58] and that comparing the high-latter period with the low-mid period showed an HR of 0.84 [95% CI, 0.54, 1.30; p = 0.43]. The result for comparison between the three periods was p = 0.80. ITSA showed level changes of 4.05% [95% CI, -13.1, 21.2; p = 0.63] when ICU staffing changed from the high-former to the low-mid period and 1.35% [95% CI, -13.8, 16.5; p = 0.86] when ICU staffing changed from the low-mid to the high-latter period. CONCLUSION: There was no statistically significant difference in all-cause mortality among the three ICU staffing periods. This study suggests that low-intensity ICU staffing might not worsen clinical outcomes in the ICU in a medium-sized community hospital. Multiple factors, including the presence of an intensivist, other medical staff, and practical guidelines, influence the prognosis of critically ill patients.

Sevoflurane Does Not Promote the Colony-Forming Ability of Human Mesenchymal Glioblastoma Stem Cells In Vitro.

Background and Objectives: Clinically used concentrations of sevoflurane, an inhaled anesthetic, have been reported to significantly inhibit tumor growth. We investigated the effects of sevoflurane on sphere formation and the proliferation of human glioblastoma stem cells (GSCs) to determine whether sevoflurane exerts short- and long-term effects on human tumor cells. Materials and Methods: High-grade patient-derived GSCs (MD13 and Me83) were exposed to 2% sevoflurane. To evaluate the effect of sevoflurane on viability, proliferation, and stemness, we performed a caspase-3/7 essay, cell proliferation assay, and limiting dilution sphere formation assays. The expression of CD44, a cell surface marker of cancer stem-like cells in epithelial tumors, was evaluated using quantitative reverse transcription PCR. Differences between groups were evaluated with a one-way analysis of variance (ANOVA). Results: Sevoflurane exposure for 4 days did not significantly promote caspase 3/7 activity in MD13 and Me83, and cell proliferation was not observed after 5 days of exposure. Furthermore, prolonged exposure to sevoflurane for 6 days did not promote the sphere-forming and proliferative potential of MD13 and Me83 cells. These results suggest that sevoflurane does not promote either apoptosis, proliferative capacity, or the colony-forming ability of human mesenchymal glioblastoma stem cells in vitro. Conclusions: Sevoflurane at clinically used concentrations does not promote the colony-forming ability of human mesenchymal glioblastoma stem cells in vitro. It is very important for neurosurgeons and anesthesiologists to know that sevoflurane, a volatile anesthetic used in surgical anesthesia, would not exacerbate the disease course of GSCs.

AGE/RAGE axis regulates reversible transition to quiescent states of ALK-rearranged NSCLC and pancreatic cancer cells in monolayer cultures.

Cancer recurrence due to tumor cell quiescence after therapy and long-term remission is associated with cancer-related death. Previous studies have used cell models that are unable to return to a proliferative state; thus, the transition between quiescent and proliferative states is not well understood. Here, we report monolayer cancer cell models wherein the human non-small cell lung carcinoma cell line H2228 and pancreatic cancer cell line AsPC-1 can be reversibly induced to a quiescent state under hypoxic and serum-starved (HSS) conditions. Transcriptome and metabolome dual-omics profiles of these cells were compared with those of the human lung adenocarcinoma cell line A549, which was unable to enter a quiescent state under HSS conditions. The quiescence-inducible cells had substantially lower intracellular pyruvate and ATP levels in the quiescent state than in the proliferative state, and their response to sudden demand for energy was dramatically reduced. Furthermore, in quiescence-inducible cells, the transition between quiescent and proliferative states of these cells was regulated by the balance between the proliferation-promoting Ras and Rap1 signaling and the suppressive AGE/RAGE signaling. These cell models elucidate the transition between quiescent and proliferative states, allowing the development of drug-screening systems for quiescent tumor cells.

Successful identification of Granulicatella adiacens in postoperative acute infectious endophthalmitis using a bacterial 16S ribosomal RNA gene-sequencing platform with MinION™: A case report.

Purpose: To evaluate the efficacy of identifying the bacteria by aqueous sampling and vitreous sampling in postoperative infectious endophthalmitis using 16S ribosomal RNA (rRNA) gene analysis with a nanopore sequencer (MinION™). Observation: A 55-year-old woman who underwent cataract surgery at an ophthalmology clinic 18 days ago was referred to our hospital for suspected endophthalmitis. She had light perception visual acuity in her right eye; however, the eye was severely inflamed, with a hypopyon and a fibrinous membrane in the anterior chamber. The fundus was not visible because of vitreous opacity on a B-scan image. Based on the diagnosis of postoperative acute infectious endophthalmitis, we performed a vitrectomy, intraocular lens extraction, and silicone oil tamponade. On postoperative day 14, the inflammation resolved. An aqueous sample was collected before surgical treatment, and the vitreous sample was collected during the operation. Both samples underwent 16S rRNA gene analysis with a nanopore sequencer MinION™ to identify the causative organism. Conclusions and Importance: In the aqueous humor, Granulicatella adiacens and Cutibacterium acnes were identified before the operation, while only Granulicatella adiacens was detected in the vitreous sample after the operation. Although the aqueous humor sample might contain commensal bacteria, it could provide a predictable result before the operation. It can also provide a substitute for a vitreous sample to allow earlier identification of the causative organism.

Efficacy of active hexose correlated compound on survival of patients with resectable/borderline resectable pancreatic cancer: a study protocol for a double-blind randomized phase II study.

BACKGROUND: The prognosis of pancreatic ductal adenocarcinoma remains very poor. One possible reason for the short survival of patients with this disease is malnutrition, which can be present at the initial diagnosis, and continue after pancreatectomy. Then, it is important to improve nutritional status and to decrease adverse events during neoadjuvant and adjuvant chemotherapy. Active hexose correlated compound (AHCC) is a standardized extract of cultured Lentinula edodes mycelia, and is considered a potent biological response modifier in the treatment of cancer. To evaluate the survival impact of AHCC on the patients with pancreatic ductal adenocarcinoma, we plan to perform this trial. METHODS: This is a prospective multicenter phase II trial in patients with resectable/borderline resectable pancreatic ductal adenocarcinoma to investigate the efficacy of AHCC regarding survival. Patients will begin taking AHCC or placebo on the first day of neoadjuvant therapy. AHCC or placebo will be continued until 2 years after surgery. The primary endpoint will be 2-year disease-free survival. The secondary endpoints are the completion rate, dose intensity, and adverse event profile of preoperative chemotherapy; response rate to preoperative chemotherapy; rate of decrease in tumor marker (carbohydrate antigen 19-9, carcinoembryonic antigen) concentrations during preoperative chemotherapy; entry rate, completion rate, dose intensity, and adverse event profile of adjuvant chemotherapy; safety of the protocol therapy (adverse effect of AHCC); 2-year overall survival rate; and nutrition score before and after preoperative chemotherapy, and before and after adjuvant chemotherapy. We will enroll 230 patients, and the study involves eight leading Japanese institutions that are all high-volume centers in pancreatic surgery. DISCUSSION: AHCC is expected to function as a supportive food in patients with pancreatic ductal adenocarcinoma, to reduce the proportion of severe adverse events related to neoadjuvant chemotherapy, and to increase the completion proportion of multimodal treatments, resulting in improved survival. TRIAL REGISTRATION: The trial protocol has been registered in the protocol registration system at the Japan Registry of Clinical Trials (Trial ID: jRCTs051200029 ). At the time of the submission of this paper (October 2020), the protocol version is 2.0. The completion date is estimated to be November 2024.

A chemoproteoinformatics approach demonstrates that aspirin increases sensitivity to MEK inhibition by directly binding to RPS5.

MEK inhibitors are among the most successful molecularly targeted agents used as cancer therapeutics. However, to treat cancer more efficiently, resistance to MEK inhibitor-induced cell death must be overcome. Although previous genetic approaches based on comprehensive gene expression analysis or RNAi libraries led to the discovery of factors involved in intrinsic resistance to MEK inhibitors, a feasible combined treatment with the MEK inhibitor has not yet been developed. Here, we show that a chemoproteoinformatics approach identifies ligands overcoming the resistance to cell death induced by MEK inhibition as well as the target molecule conferring this resistance. First, we used natural products, perillyl alcohol and sesaminol, which induced cell death in combination with the MEK inhibitor trametinib, as chemical probes, and identified ribosomal protein S5 (RPS5) as their common target protein. Consistently, trametinib induced cell death in RPS5-depleted cancer cells via upregulation of the apoptotic proteins BIM and PUMA. Using molecular docking and molecular dynamics (MD) simulations, we then screened FDA- and EMA-approved drugs for RPS5-binding ligands and found that acetylsalicylic acid (ASA, also known as aspirin) directly bound to RPS5, resulting in upregulation of BIM and PUMA and induction of cell death in combination with trametinib. Our chemoproteoinformatics approach demonstrates that RPS5 confers resistance to MEK inhibitor-induced cell death, and that aspirin could be repurposed to sensitize cells to MEK inhibition by binding to RPS5.

Inhibiting SARS-CoV-2 infection in vitro by suppressing its receptor, angiotensin-converting enzyme 2, via aryl-hydrocarbon receptor signal.

Since understanding molecular mechanisms of SARS-CoV-2 infection is extremely important for developing effective therapies against COVID-19, we focused on the internalization mechanism of SARS-CoV-2 via ACE2. Although cigarette smoke is generally believed to be harmful to the pathogenesis of COVID-19, cigarette smoke extract (CSE) treatments were surprisingly found to suppress the expression of ACE2 in HepG2 cells. We thus tried to clarify the mechanism of CSE effects on expression of ACE2 in mammalian cells. Because RNA-seq analysis suggested that suppressive effects on ACE2 might be inversely correlated with induction of the genes regulated by aryl hydrocarbon receptor (AHR), the AHR agonists 6-formylindolo(3,2-b)carbazole (FICZ) and omeprazole (OMP) were tested to assess whether those treatments affected ACE2 expression. Both FICZ and OMP clearly suppressed ACE2 expression in a dose-dependent manner along with inducing CYP1A1. Knock-down experiments indicated a reduction of ACE2 by FICZ treatment in an AHR-dependent manner. Finally, treatments of AHR agonists inhibited SARS-CoV-2 infection into Vero E6 cells as determined with immunoblotting analyses detecting SARS-CoV-2 specific nucleocapsid protein. We here demonstrate that treatment with AHR agonists, including FICZ, and OMP, decreases expression of ACE2 via AHR activation, resulting in suppression of SARS-CoV-2 infection in mammalian cells.

Polysulfide inhibits hypoxia-elicited hypoxia-inducible factor activation in a mitochondria-dependent manner.

In cellular signaling, the diverse physiological actions of biological gases, including O2, CO, NO, and H2S, have attracted much interest. Hypoxia-inducible factors (HIFs), including HIF-1 and HIF-2, are transcription factors that respond to reduced intracellular O2 availability. Polysulfides are substances containing varying numbers of sulfur atoms (H2Sn) that are generated endogenously from H2S by 3-mercaptopyruvate sulfurtransferase in the presence of O2, and regulate ion channels, specific tumor suppressors, and protein kinases. However, the effect of polysulfides on HIF activation in hypoxic mammalian cells is largely unknown. Here, we have investigated the effect of polysulfide on cells in vitro. In established cell lines, polysulfide donors reversibly reduced cellular O2 consumption and inhibited hypoxia-induced HIF-1α protein accumulation and the expression of genes downstream of HIFs; however, these effects were not observed in anoxia. In Von Hippel-Lindau tumor suppressor (VHL)- and mitochondria-deficient cells, polysulfides did not affect HIF-1α protein synthesis but destabilized it in a VHL- and mitochondria-dependent manner. For the first time, we show that polysulfides modulate intracellular O2 homeostasis and regulate HIF activation and subsequent hypoxia-induced gene expression in a VHL- and mitochondria-dependent manner.

Development of antitumor biguanides targeting energy metabolism and stress responses in the tumor microenvironment.

To develop antitumor drugs capable of targeting energy metabolism in the tumor microenvironment, we produced a series of potent new biguanide derivatives via structural modification of the arylbiguanide scaffold. We then conducted biological screening using hypoxia inducible factor (HIF)-1- and unfolded protein response (UPR)-dependent reporter assays and selective cytotoxicity assay under low glucose conditions. Homologation studies of aryl-(CH2)n-biguanides (n = 0-6) yielded highly potent derivatives with an appropriate alkylene linker length (n = 5, 6). The o-chlorophenyl derivative 7l (n = 5) indicated the most potent inhibitory effects on HIF-1- and UPR-mediated transcriptional activation (IC50; 1.0 ± 0.1 µM, 7.5 ± 0.1 µM, respectively) and exhibited selective cytotoxicity toward HT29 cells under low glucose condition (IC50; 1.9 ± 0.1 µM). Additionally, the protein expression of HIF-1α induced by hypoxia and of GRP78 and GRP94 induced by glucose starvation was markedly suppressed by the biguanides, thereby inhibiting angiogenesis. Metabolic flux and fluorescence-activated cell sorting analyses of tumor cells revealed that the biguanides strongly inhibited oxidative phosphorylation and activated compensative glycolysis in the presence of glucose, whereas both were strongly suppressed in the absence of glucose, resulting in cellular energy depletion and apoptosis. These findings suggest that the pleiotropic effects of these biguanides may contribute to more selective and effective killing of cancer cells due to the suppression of various stress adaptation systems in the tumor microenvironment.

Cigarette Smoke Extract Activates Hypoxia-Inducible Factors in a Reactive Oxygen Species-Dependent Manner in Stroma Cells from Human Endometrium.

Cigarette smoking (CS) is a major contributing factor in the development of a large number of fatal and debilitating disorders, including degenerative diseases and cancers. Smoking and passive smoking also affect the establishment and maintenance of pregnancy. However, to the best of our knowledge, the effects of smoking on the human endometrium remain poorly understood. In this study, we investigated the regulatory mechanism underlying CS-induced hypoxia-inducible factor (HIF)-1α activation using primary human endometrial stromal cells and an immortalized cell line (KC02-44D). We found that the CS extract (CSE) increased reactive oxygen species levels and stimulated HIF-1α protein stabilization in endometrial stromal cells, and that CS-induced HIF-1α-dependent gene expression under non-hypoxic conditions in a concentration- and time-dependent manner. Additionally, we revealed the upregulated expression of a hypoxia-induced gene set following the CSE treatment, even under normoxic conditions. These results indicated that HIF-1α might play an important role in CS-exposure-induced cellular stress, inflammation, and endometrial remodeling.

Pulmonary vein thrombosis and cerebral infarction after video-assisted thoracic surgery of the left upper lobe: a case series.

BACKGROUND: Pulmonary vein thrombosis (PVT) and cerebral infarction are rare but critical complications after video-assisted thoracic surgery (VATS). CASE PRESENTATION: We experienced two cases of massive middle cerebral artery infarction after VATS for the left upper lobe. Although the precise source of their embolus was never identified, both cases were clinically suspected PVT. Unfortunately, case 2 died because of progressive cerebral herniation. We decided to perform contrast-enhanced computed tomography routinely after VATS for the left upper lobectomy (VATS-LUL) after these cases. Case 3, a 79-year-old female patient, underwent VATS-LUL for lung cancer. She developed PVT in the stump of the left upper pulmonary vein on postoperative day 4. Anti-coagulation therapy was begun immediately and continued for 3 months. She was free of complications 7 months after the operation. CONCLUSION: PVT and cerebral infarction may occur after VATS-LUL. Appropriate postoperative management is required to recognize PVT and to prevent life-threatening stroke.

Deactivation of Glutaminolysis Sensitizes PIK3CA-Mutated Colorectal Cancer Cells to Aspirin-Induced Growth Inhibition.

Aspirin is one of the most promising over-the-counter drugs to repurpose for cancer treatment. In particular, aspirin has been reported to be effective against PIK3CA-mutated colorectal cancer (CRC); however, little information is available on how the PIK3CA gene status affects its efficacy. We found that the growth inhibitory effects of aspirin were impaired upon glutamine deprivation in PIK3CA-mutated CRC cells. Notably, glutamine dependency of aspirin-mediated growth inhibition was observed in PIK3CA-mutated cells but not PIK3CA wild type cells. Mechanistically, aspirin induced G1 arrest in PIK3CA-mutated CRC cells and inhibited the mTOR pathway, inducing the same phenotypes as glutamine deprivation. Moreover, our study including bioinformatic approaches revealed that aspirin increased the expression levels of glutaminolysis-related genes with upregulation of activating transcription factor 4 (ATF4) in PIK3CA-mutated CRC cells. Lastly, the agents targeting glutaminolysis demonstrated significant combined effects with aspirin on PIK3CA-mutated CRC cells. Thus, these findings not only suggest the correlation among aspirin efficacy, PIK3CA mutation and glutamine metabolism, but also the rational combinatorial treatments of aspirin with glutaminolysis-targeting agents against PIK3CA-mutated CRC.

Thyroid Hormone Facilitates in vitro Decidualization of Human Endometrial Stromal Cells via Thyroid Hormone Receptors.

Endometrial stromal cells differentiate into decidual cells through the process of decidualization. This differentiation is critical for embryo implantation and the successful establishment of pregnancy. Recent epidemiological studies have suggested that thyroid hormone is important in the endometrium during implantation, and it is commonly believed that thyroid hormone is essential for proper development, differentiation, growth, and metabolism. This study aimed to investigate the impact of thyroid hormone on decidualization in human endometrial stromal cells (hESCs) and define its physiological roles in vitro by gene targeting. To identify the expression patterns of thyroid hormone, we performed gene expression profiling of hESCs during decidualization after treating them with the thyroid hormone levothyroxine (LT4). A major increase in decidual response was observed after combined treatment with ovarian steroid hormones and thyroid hormone. Moreover, LT4 treatment also affected the regulation of many transcription factors important for decidualization. We found that type 3 deiodinase, which is particularly important in fetal and placental tissues, was upregulated during decidualization in the presence of thyroid hormone. Further, it was observed that progesterone receptor, an ovarian steroid hormone receptor, was involved in thyroid hormone-induced decidualization. In the absence of thyroid hormone receptor (TR), due to the simultaneous silencing of TRα and TRß, thyroid hormone expression was unchanged during decidualization. In summary, we demonstrated that thyroid hormone is essential for decidualization in the endometrium. This is the first in vitro study to find impaired decidualization as a possible cause of infertility in subclinical hypothyroidism (SCH) patients.

Basic Biology of Hypoxic Responses Mediated by the Transcription Factor HIFs and its Implication for Medicine.

Oxygen (O2) is essential for human life. Molecular oxygen is vital for the production of adenosine triphosphate (ATP) in human cells. O2 deficiency leads to a reduction in the energy levels that are required to maintain biological functions. O2 acts as the final acceptor of electrons during oxidative phosphorylation, a series of ATP synthesis reactions that occur in conjunction with the electron transport system in mitochondria. Persistent O2 deficiency may cause death due to malfunctioning biological processes. The above account summarizes the classic view of oxygen. However, this classic view has been reviewed over the last two decades. Although O2 is essential for life, higher organisms such as mammals are unable to biosynthesize molecular O2 in the body. Because the multiple organs of higher organisms are constantly exposed to the risk of "O2 deficiency," living organisms have evolved elaborate strategies to respond to hypoxia. In this review, I will describe the system that governs oxygen homeostasis in the living body from the point-of-view of the transcription factor hypoxia-inducible factor (HIF).

Pharmacological polysulfide suppresses glucose-stimulated insulin secretion in an ATP-sensitive potassium channel-dependent manner.

Hydrogen sulfide (H2S) is an endogenous gaseous transmitter synthesized in various cell types. It is well established that H2S functions in many physiological processes, including the relaxation of vascular smooth muscle, mediation of neurotransmission, regulation of inflammation, and modulation of insulin signaling. In recent years, it has been revealed that polysulfides, substances with a varying number of sulfur atoms (H2Sn), are generated endogenously from H2S in the presence of oxygen. A series of studies describes that sulfane sulfur has the unique ability to bind reversibly to other sulfur atoms to form hydropersulfides and polysulfides, and that polysulfides activate ion channels and promote calcium influx. Furthermore, polysulfides regulate tumor suppressor activity, promote the activation of transcription factors targeting antioxidant genes and regulate blood pressure by vascular smooth muscle relaxation. Insulin secretion from pancreatic ß cells plays a critical role in response to increased blood glucose concentration. H2S has emerged as an important regulator of glycemic control and exhibits characteristic regulation of glucose homeostasis. However, the effects of polysulfides on glucose-stimulated insulin secretion (GSIS) are largely unknown. In this study, we demonstrated that pharmacological polysulfide salts including Na2S2, Na2S3, and Na2S4 considerably inhibit GSIS in mouse and rat pancreatic ß-cell-derived MIN6 and INS-1 cell lines, and that the effect is dependent on the activation of ATP-sensitive potassium channels. In addition, we demonstrated that a mixture of Na2S and diethylamine NONOate inhibits GSIS in a similar way to the pharmacological administration of polysulfide salts.

Cancerous phenotypes associated with hypoxia-inducible factors are not influenced by the volatile anesthetic isoflurane in renal cell carcinoma.

The possibility that anesthesia during cancer surgery may affect cancer recurrence, metastasis, and patient prognosis has become one of the most important topics of interest in cancer treatment. For example, the volatile anesthetic isoflurane was reported in several studies to induce hypoxia-inducible factors, and thereby enhance malignant phenotypes in vitro. Indeed, these transcription factors are considered critical regulators of cancer-related hallmarks, including "sustained proliferative signaling, evasion of growth suppressors, resistance to cell death, replicative immortality, angiogenesis, invasion, and metastasis." This study aimed to investigate the impact of isoflurane on the growth and migration of derivatives of the renal cell line RCC4. We indicated that isoflurane treatment did not positively influence cancer cell phenotypes, and that hypoxia-inducible factors (HIFs) maintain hallmark cancer cell phenotypes including gene expressions signature, metabolism, cell proliferation and cell motility. The present results indicate that HIF activity is not influenced by the volatile anesthetic isoflurane.

An intimate crosstalk between iron homeostasis and oxygen metabolism regulated by the hypoxia-inducible factors (HIFs).

Oxygen and iron are among the most abundant elements and have significant roles in human biology. Iron is essential for oxygen transport and is a component of molecular O2-carrying proteins, such as hemoglobin and myoglobin. Iron is also a constituent of redox enzymes and can occupy multiple oxidation states. An elaborate system has evolved to stringently regulate the concentrations of both, free iron and oxygen, in various sites of the body. The final destination for iron and oxygen in the cells is the mitochondria. The mitochondria require substantial amounts of iron for heme synthesis and maturation of iron-sulfur clusters, and oxygen, as the electron acceptor in oxidative phosphorylation. Therefore, the balance between the control of iron availability and the physiology of hypoxic responses is critical for maintaining cell homeostasis. Several lines of study have clearly demonstrated that the transcription factors, hypoxia-inducible factors (HIFs), play a central role in cellular adaptation to critically low oxygen levels in both normal and compromised tissues. It has also been shown that several target genes of HIFs are involved in iron homeostasis, reflecting the molecular links between oxygen homeostasis and iron metabolism. Furthermore, HIF activation is modulated by intracellular iron, through regulation of hydroxylase activity, which requires iron as a cofactor. In addition, HIF-2α translation is controlled by iron regulatory protein (IRP) activity, providing another level of interdependence between iron and oxygen homeostasis.

Suppression of mitochondrial oxygen metabolism mediated by the transcription factor HIF-1 alleviates propofol-induced cell toxicity.

A line of studies strongly suggest that the intravenous anesthetic, propofol, suppresses mitochondrial oxygen metabolism. It is also indicated that propofol induces the cell death in a reactive oxygen species (ROS)-dependent manner. Because hypoxia-inducible factor 1 (HIF-1) is a transcription factor which is involved in cellular metabolic reprogramming by modulating gene expressions of enzymes including glycolysis pathway and oxygen utilization of mitochondria, we examined the functional role of HIF-1 activity in propofol-induced cell death. The role of HIF-1 activity on oxygen and energy metabolisms and propofol-induced cell death and caspase activity was examined in renal cell-derived RCC4 cells: RCC4-EV cells which lack von Hippel-Lindau protein (VHL) protein expression and RCC4-VHL cells, which express exogenous VHL, and in neuronal SH-SY5Y cells. It was demonstrated that HIF-1 is involved in suppressing oxygen consumption and facilitating glycolysis in cells and that the resistance to propofol-induced cell death was established in a HIF-1 activation-dependent manner. It was also demonstrated that HIF-1 activation by treatment with HIFα-hydroxylase inhibitors such as n-propyl gallate and dimethyloxaloylglycine, alleviated the toxic effects of propofol. Thus, the resistance to propofol toxicity was conferred by HIF-1 activation by not only genetic deletion of VHL but also exposure to HIFα-hydroxylase inhibitors.

Activation of hypoxia-inducible factor 1 attenuates periapical inflammation and bone loss.

Hypoxia (low oxygen level) is an important feature during infections and affects the host defence mechanisms. The host has evolved specific responses to address hypoxia, which are strongly dependent on the activation of hypoxia-inducible factor 1 (HIF-1). Hypoxia interferes degradation of HIF-1 alpha subunit (HIF-1α), leading to stabilisation of HIF-1α, heterodimerization with HIF-1 beta subunit (HIF-1ß) and subsequent activation of HIF-1 pathway. Apical periodontitis (periapical lesion) is a consequence of endodontic infection and ultimately results in destruction of tooth-supporting tissue, including alveolar bone. Thus far, the role of HIF-1 in periapical lesions has not been systematically examined. In the present study, we determined the role of HIF-1 in a well-characterised mouse periapical lesion model using two HIF-1α-activating strategies, dimethyloxalylglycine (DMOG) and adenovirus-induced constitutively active HIF-1α (CA-HIF1A). Both DMOG and CA-HIF1A attenuated periapical inflammation and tissue destruction. The attenuation in vivo was associated with downregulation of nuclear factor-κappa B (NF-κB) and osteoclastic gene expressions. These two agents also suppressed NF-κB activation and subsequent production of proinflammatory cytokines by macrophages. Furthermore, activation of HIF-1α by DMOG specifically suppressed lipopolysaccharide-stimulated macrophage differentiation into M1 cells, increasing the ratio of M2 macrophages against M1 cells. Taken together, our data indicated that activation of HIF-1 plays a protective role in the development of apical periodontitis via downregulation of NF-κB, proinflammatory cytokines, M1 macrophages and osteoclastogenesis.