A Small-Molecule Inhibitor of Factor Inhibiting HIF Binding to a Tyrosine-Flip Pocket for the Treatment of Obesity.

In animals, limiting oxygen upregulates the hypoxia-inducible factor (HIF) and promotes a metabolic shift towards glycolysis. Factor inhibiting HIF (FIH) is an asparaginyl hydroxylase that regulates HIF function by reducing its interaction with histone acetyl transferases. HIF levels are negatively regulated by the HIF prolyl hydroxylases (PHDs) which, like FIH, are 2-oxoglutarate (2OG) oxygenases. Genetic loss of FIH promotes both glycolysis and aerobic metabolism. FIH has multiple non-HIF substrates making it challenging to connect its biochemistry with physiology. A structure-mechanism guided approach identified a highly potent in vivo active FIH inhibitor, ZG-2291, the binding of which promotes a conformational flip of a catalytically important tyrosine, enabling the selective inhibition of FIH over other Jumonji C subfamily 2OG oxygenases. Consistent with genetic studies, ZG-2291 promotes thermogenesis and ameliorates symptoms of obesity and metabolic dysfunction in ob/ob mice. The results reveal ZG-2291 as a useful probe for the physiological functions of FIH and identify FIH inhibition as a promising strategy for obesity treatment.

Effects of Environmental Hypoxia on Serum Hematological and Biochemical Parameters, Hypoxia-Inducible Factor (hif) Gene Expression and HIF Pathway in Hybrid Sturgeon (Acipenser schrenckii ♂ × Acipenser baerii ♀).

Hypoxia is a globally pressing environmental problem in aquatic ecosystems. In the present study, a comprehensive analysis was performed to evaluate the effects of hypoxia on physiological responses (hematology, cortisol, biochemistry, hif gene expression and the HIF pathway) of hybrid sturgeons (Acipenser schrenckii ♂ × Acipenser baerii ♀). A total of 180 hybrid sturgeon adults were exposed to dissolved oxygen (DO) levels of 7.00 ± 0.2 mg/L (control, N), 3.5 ± 0.2 mg/L (moderate hypoxia, MH) or 1.00 ± 0.1 mg/L (severe hypoxia, SH) and were sampled at 1 h, 6 h and 24 h after hypoxia. The results showed that the red blood cell (RBC) counts and the hemoglobin (HGB) concentration were significantly increased 6 h and 24 h after hypoxia in the SH group. The serum cortisol concentrations gradually increased with the decrease in the DO levels. Moreover, several serum biochemical parameters (AST, AKP, HBDB, LDH, GLU, TP and T-Bil) were significantly altered at 24 h in the SH group. The HIFs are transcription activators that function as master regulators in hypoxia. In this study, a complete set of six hif genes were identified and characterized in hybrid sturgeon for the first time. After hypoxia, five out of six sturgeon hif genes were significantly differentially expressed in gills, especially hif-1α and hif-3α, with more than 20-fold changes, suggesting their important roles in adaptation to hypoxia in hybrid sturgeon. A meta-analysis indicated that the HIF pathway, a major pathway for adaptation to hypoxic environments, was activated in the liver of the hybrid sturgeon 24 h after the hypoxia challenge. Our study demonstrated that hypoxia, particularly severe hypoxia (1.00 ± 0.1 mg/L), could cause considerable stress for the hybrid sturgeon. These results shed light on their adaptive mechanisms and potential biomarkers for hypoxia tolerance, aiding in aquaculture and conservation efforts.

Molecular mechanism of infectious spleen and kidney necrosis virus in manipulating the hypoxia-inducible factor pathway to augment virus replication.

Infectious spleen and kidney necrosis virus (ISKNV), a member of the genus Megalocytivirus in the family Iridoviridae, can infect over 50 fish species and cause significant economic losses in Asia. Our previous study showed that hypoxia triggers the hypoxia-inducible factor pathway (HIF-pathway), leading to increased replication of ISKNV through promoting the upregulation of viral hypoxic response genes like orf077r. This study delved into the molecular mechanism of how ISKNV manipulates the HIF-pathway to enhance its replication. In vitro and in vivo experiments confirmed that ISKNV infection activated the HIF-pathway, which in turn promoted ISKNV replication. These findings suggest that ISKNV actively manipulates the HIF-pathway. Co-immunoprecipitation experiments revealed that the ISKNV-encoded protein VP077R interacts with the Von Hippel-Lindau (VHL) protein at the HIF-binding region, competitively inhibiting the interaction of HIF-1α with VHL. This prevents HIF degradation and activates the HIF-pathway. Furthermore, VP077R interacts with factor-inhibiting HIF (FIH), recruiting FIH and S-phase kinase-associated protein 1 (Skp1) to form an FIH - VP077R - Skp1 complex. This complex promotes FIH protein degradation via ubiquitination, further activating the HIF-pathway. These findings indicated that ISKNV takes over the HIF-pathway by releasing two "brakes" on this pathway (VHL and FIH) via VP077R, facilitating virus replication. We speculate that hypoxia initiates a positive feedback loop between ISKNV VP077R and the HIF pathway, leading to the outbreak of ISKNV disease. This work offers valuable insights into the complex interactions between the environment, host, and virus.

HIV coinfection exacerbates HBV-induced liver fibrogenesis through a HIF-1α- and TGF-ß1-dependent pathway.

BACKGROUND & AIMS: Persons with chronic HBV infection coinfected with HIV experience accelerated progression of liver fibrosis compared to those with HBV monoinfection. We aimed to determine whether HIV and its proteins promote HBV-induced liver fibrosis in HIV/HBV-coinfected cell culture models through HIF-1α and TGF-ß1 signaling. METHODS: The HBV-positive supernatant, purified HBV viral particles, HIV-positive supernatant, or HIV viral particles were directly incubated with cell lines or primary hepatocytes, hepatic stellate cells, and macrophages in mono or 3D spheroid coculture models. Cells were incubated with recombinant cytokines and HIV proteins including gp120. HBV sub-genomic constructs were transfected into NTCP-HepG2 cells. We also evaluated the effects of inhibitor of HIF-1α and HIV gp120 in a HBV carrier mouse model that was generated via hydrodynamic injection of the pAAV/HBV1.2 plasmid into the tail vein of wild-type C57BL/6 mice. RESULTS: We found that HIV and HIV gp120, through engagement with CCR5 and CXCR4 coreceptors, activate AKT and ERK signaling and subsequently upregulate hypoxia-inducible factor-1α (HIF-1α) to increase HBV-induced transforming growth factor-ß1 (TGF-ß1) and profibrogenic gene expression in hepatocytes and hepatic stellate cells. HIV gp120 exacerbates HBV X protein-mediated HIF-1α expression and liver fibrogenesis, which can be alleviated by inhibiting HIF-1α. Conversely, TGF-ß1 upregulates HIF-1α expression and HBV-induced liver fibrogenesis through the SMAD signaling pathway. HIF-1α small-interfering RNA transfection or the HIF-1α inhibitor (acriflavine) blocked HIV-, HBV-, and TGF-ß1-induced fibrogenesis. CONCLUSIONS: Our findings suggest that HIV coinfection exacerbates HBV-induced liver fibrogenesis through enhancement of the positive feedback between HIF-1α and TGF-ß1 via CCR5/CXCR4. HIF-1α represents a novel target for antifibrotic therapeutic development in HBV/HIV coinfection. IMPACT AND IMPLICATIONS: HIV coinfection accelerates the progression of liver fibrosis compared to HBV monoinfection, even among patients with successful suppression of viral load, and there is no sufficient treatment for this disease process. In this study, we found that HIV viral particles and specifically HIV gp120 promote HBV-induced hepatic fibrogenesis via enhancement of the positive feedback between HIF-1α and TGF-ß1, which can be ameliorated by inhibition of HIF-1α. These findings suggest that targeting the HIF-1α pathway can reduce liver fibrogenesis in patients with HIV and HBV coinfection.

Intermittent hypoxia induces myofibroblast differentiation and extracellular matrix production of MRC5s via HIF-1α-TGF-ß/Smad pathway.

PURPOSE: To investigate whether or not intermittent hypoxia (IH), the main characteristic of obstructive sleep apnea (OSA) may affect the myofibroblast differentiation and extracellular matrix (ECM) production of lung fibroblast through the HIF-1α-TGF-ß/Smad pathway and assess the interventional role of a HIF-1α inhibitor, 2-methoxyestradiol (2-ME2). METHOD: The human lung fibroblast MRC5 cells were exposed to normoxia or IH conditions, and the expression of myofibroblast differentiation marker α-smooth muscle actin (α-SMA) and ECM protein collagen I were evaluated. To clarify the underlying mechanism, the expression level of HIF-1α, TGF-ß, and p-Smads/Smads were measured and the effects of inhibiting HIF-1α with 2-ME2 on the α-SMA expression level and ECM production through the TGF-ß/Smad pathway were assessed. Si HIF-1α was applied to genetically inhibit HIF-1α in MRC5 cells, and the related proteins were assessed. RESULTS: IH increased the protein and mRNA expression of Collagen I and α-SMA of MRC5 cells in a time-dependent manner. IH activated the protein and mRNA level of HIF-1α and TGF-ß and increased the phosphorylation of Smad2/Smad3 of MRC5 cells in a time-dependent manner. 2-ME2 inhibited the activation of HIF-1α induced by IH and decreased overexpression of TGF-ß, p-Smad2/Smad2, and p-Smad3/Smad3, which in turn partially reversed the upregulation of α-SMA and Collagen I induced by IH in MRC5 cells. When HIF-1α was successfully silenced by si-HIF-1α, upregulation of TGF-ß induced by intermittent hypoxia was partially decreased. CONCLUSIONS: This study showed that IH contributes to myofibroblast differentiation and excessive ECM production of MRC5 cells through activation of the HIF-1α-TGF-ß/Smad pathway. 2-ME2 partially attenuated myofibroblast differentiation induced by IH by inhibiting the HIF-1α-TGF-ß/Smad pathway.

Sex differences in antioxidant ability and energy metabolism level resulting in the difference of hypoxia tolerance in red swamp crayfish (Procambarus clarkii).

Sexual dimorphism widely exists in crustaceans. However, sex differences in the hypoxia tolerance of crayfish have rarely been reported. In this study, the differences in hypoxia tolerance between the two sexes of crayfish were assessed according to mortality, pathological features of hepatopancreas, antioxidant enzyme activity and differentially expressed genes (DEGs) analysis using transcriptome. The results showed that male crayfish displayed significantly higher mortality than the female under hypoxia stress (p < 0.05). Furthermore, female crayfish demonstrated higher levels of antioxidant enzyme activity. Hematoxylin-eosin staining analysis revealed that the damage of hepatopancreas was more severe in the male crayfish compared to the female crayfish. Additionally, there was higher expression level of the DEGs in hypoxia-inducible factor (HIF) pathway and higher energy metabolism level in the female compared to the male. Together, these findings suggest that the female crayfish with higher antioxidant ability and energy metabolism level exhibits stronger hypoxia tolerance than the male crayfish, providing the theoretical support for investigating sex differences in hypoxia tolerance among crustaceans.

Piezoeletric cold atmospheric plasma induces apoptosis and autophagy in human hepatocellular carcinoma cells through blocking glycolysis and AKT/mTOR/HIF-1α pathway.

Hepatocellular carcinoma (HCC) is the sixth most prevalent cancer and the fourth leading cause of cancer-related death worldwide. Advanced or metastatic HCC is currently managed using systemic drug therapy with unsatisfactory patient survival. Cold atmospheric plasma has emerged as a promising, physicochemical, and broad-spectrum oncotherapy. In this preclinical study, we investigated the anti-neoplastic functions and mechanism of piezoelectric direct discharge technology-based CAP, Piezo-CAP, on HCC in vitro and in vivo. Various HCC cells lines, such as SMMC7721, HepG2 and LM3, were used as in vitro cancer model for the phenotypic and mechanistic studies. Specifically, the cell counting Kit-8 and colony formation assay, flow cytometry, Transwell assay, Western blot, reactive oxygen species (ROS) assay, and glutathione to oxidized glutathione ratio (GSH/GSSG) assay were used to demonstrate plasma-induced changes in HCC cell proliferation, cell cycle progression, migration and invasion, epithelial-to-mesenchymal transition, intracellular ROS, and antioxidant capacity, respectively. In addition, the Acridine orange and ethidium bromide (AO/EB) staining and transmission electron microscopy were performed for cellular and subcellular assessment of HCC cell apoptosis. The Ad-mCherry-RFP-LC3B fluorescent double-labeled lentiviral system was used to detect autophagic flux. On the other hand, RNA-sequencing, quantitative real-time PCR, and Western blot were used to demonstrate plasma-induced metabolic and molecular disruption of tumor glycolysis and oncogenic proliferation, respectively. In vivo experiments using a human cell-line-derived xenograft model and immunohistochemistry (IHC) were utilized to investigate the mechanism. Piezo-CAP exerted anti-neoplastic functions through inhibiting cell proliferation, migration and invasion, and promote cell apoptosis and autophagy. Treatment of Piezo-CAP could suppress proliferation and induce autophagy of HCC cells through simultaneously disrupts cancer survival pathways of redox deregulation, glycolytic pathway, and PI3K/AKT/mTOR/HIF1α pathway signaling. Moreover, upon translation of these in vitro results into the tissue level, Piezo-CAP significantly suppressed in situ tumor growth. These findings collectively suggest that Piezo-CAP-induced apoptosis and autophagy of HCC cells though a multitargeted blockade of major cancer survival pathways of deregulated redox balance, glycolysis, and PI3K/AKT/mTOR/HIF-1α signaling.

Targeting Endothelial HIF2α/ARNT Expression for Ischemic Heart Disease Therapy.

Ischemic heart disease (IHD) is a major cause of mortality and morbidity worldwide, with novel therapeutic strategies urgently needed. Endothelial dysfunction is a hallmark of IHD, contributing to its development and progression. Hypoxia-inducible factors (HIFs) are transcription factors activated in response to low oxygen levels, playing crucial roles in various pathophysiological processes related to cardiovascular diseases. Among the HIF isoforms, HIF2α is predominantly expressed in cardiac vascular endothelial cells and has a key role in cardiovascular diseases. HIFß, also known as ARNT, is the obligate binding partner of HIFα subunits and is necessary for HIFα's transcriptional activity. ARNT itself plays an essential role in the development of the cardiovascular system, regulating angiogenesis, limiting inflammatory cytokine production, and protecting against cardiomyopathy. This review provides an overview of the current understanding of HIF2α and ARNT signaling in endothelial cell function and dysfunction and their involvement in IHD pathogenesis. We highlight their roles in inflammation and maintaining the integrity of the endothelial barrier, as well as their potential as therapeutic targets for IHD.

Myxozoans (Cnidaria) do not Retain Key Oxygen-Sensing and Homeostasis Toolkit Genes.

For aerobic organisms, both the hypoxia-inducible factor pathway and the mitochondrial genomes are key players in regulating oxygen homeostasis. Recent work has suggested that these mechanisms are not as highly conserved as previously thought, prompting more surveys across animal taxonomic levels, which would permit testing of hypotheses about the ecological conditions facilitating evolutionary loss of such genes. The Phylum Cnidaria is known to harbor wide variation in mitochondrial chromosome morphology, including an extreme example, in the Myxozoa, of mitochondrial genome loss. Because myxozoans are obligate endoparasites, frequently encountering hypoxic environments, we hypothesize that variation in environmental oxygen availability could be a key determinant in the evolution of metabolic gene networks associated with oxygen-sensing, hypoxia-response, and energy production. Here, we surveyed genomes and transcriptomes across 46 cnidarian species for the presence of HIF pathway members, as well as for an assortment of hypoxia, mitochondrial, and stress-response toolkit genes. We find that presence of the HIF pathway, as well as number of genes associated with mitochondria, hypoxia, and stress response, do not vary in parallel to mitochondrial genome morphology. More interestingly, we uncover evidence that myxozoans have lost the canonical HIF pathway repression machinery, potentially altering HIF pathway functionality to work under the specific conditions of their parasitic lifestyles. In addition, relative to other cnidarians, myxozoans show loss of large proportions of genes associated with the mitochondrion and involved in response to hypoxia and general stress. Our results provide additional evidence that the HIF regulatory machinery is evolutionarily labile and that variations in the canonical system have evolved in many animal groups.

Effects of Simvastatin on Cartilage Homeostasis in Steroid-Induced Osteonecrosis of Femoral Head by Inhibiting Glucocorticoid Receptor.

Steroid-induced osteonecrosis of femoral head (SONFH) is one of the most common bone disorders in humans. Statin treatment is beneficial in preventing the development of SONFH through anti-inflammation effects and inhibition of the glucocorticoid receptor (GR). However, potential mechanisms of statin action remain to be determined. In this study, pulse methylprednisolone (MP) treatment was used to induce SONFH in broilers, and then MP-treated birds were administrated with simvastatin simultaneously to investigate the changes in cartilage homeostasis. Meanwhile, chondrocytes were isolated, cultured, and treated with MP, simvastatin, or GR inhibitor in vitro. The changes in serum homeostasis factors, cell viability, and expression of GR were analyzed. The results showed that the morbidity of SONFH in the MP-treated group increased significantly compared with the simvastatin-treated and control group. Furthermore, MP treatment induced apoptosis and high-level catabolism and low-level anabolism in vitro and vivo, while simvastatin significantly decreased catabolism and slightly recovered anabolism via inhibiting GR and the hypoxia-inducible factor (HIF) pathway. The GR inhibitor or its siRNA mainly affected the catabolism of cartilage homeostasis in vitro. In conclusion, the occurrence of SONFH in broilers was related to the activation of GR and HIF pathway, and imbalance of cartilage homeostasis. Simvastatin and GR inhibitor maintained cartilage homeostasis via GR and the HIF pathway.

Oxidative stress-mediated synergistic deleterious effects of nano- and microplastics in the hypoxia-conditioned marine rotifer Brachionus plicatilis.

While pollution due to nano- and micro-sized plastics (NMPs) and hypoxic conditions both occur in coastal areas, the deleterious potential of co-exposure to hypoxia and NMPs (hypoxia and micro-sized plastics, HMPs; hypoxia and nano-sized plastics, HNPs) is largely unclear. Here, we provide evidence for multigenerational effects of HMP and HNP in the marine rotifer Brachionus plicatilis by investigating changes in its life traits, antioxidant system, and hypoxia-inducible factor (HIF) pathway using an orthogonal experimental design, with nanoscale and microscale particles measuring 0.05 µm and 6.0 µm in diameter, respectively, and hypoxic conditions of 0.5 mg/L for six generations. Combined exposure to NMPs and hypoxia caused a significant decrease in fecundity and overproduction of reactive oxygen species (ROS). The HIF pathway and circadian clock genes were also significantly upregulated in response to HMP and HNP exposure. In particular, synergistic deleterious effects of HNP were evident, suggesting that size-dependent toxicity can be a major driver of the effects of hypoxia and NMP co-exposure. After several generations of exposure, ROS levels returned to basal levels and transcriptomic resilience was observed, although rotifer reproduction remained suppressed. These findings help eluciating the underlying molecular mechanisms involved in responses to plastic pollution in hypoxic conditions.

Hypoxia triggers the outbreak of infectious spleen and kidney necrosis virus disease through viral hypoxia response elements.

Hypoxia frequently occurs in aquatic environments, especially in aquaculture areas. However, research on the relationship between hypoxic aquatic environments with viral diseases outbreak is limited, and its underlying mechanisms remain elusive. Herein, we demonstrated that hypoxia directly triggers the outbreak of infectious spleen and kidney necrosis virus (ISKNV) disease. Hypoxia or activated hypoxia-inducible factor (HIF) pathway could remarkably increase the levels of viral genomic DNA, titers, and gene expression, indicating that ISKNV can response to hypoxia and HIF pathway. To reveal the mechanism of ISKNV respond to HIF pathway, we identified the viral hypoxia response elements (HREs) in ISKNV genome. Fifteen viral HREs were identified, and four related viral genes responded to the HIF pathway, in which the hre-orf077r promoter remarkably responded to the HIF pathway. The level of orf077r mRNA dramatically increased after the infected cells were treated with dimethyloxalylglycine (DMOG) or the infected cells/fish subjected to hypoxic conditions, and overexpressed orf077r could remarkably increase the ISKNV replication. These finding shows that hypoxic aquatic environments induce the expression of viral genes through the viral HREs to promote ISKNV replication, indicating that viral HREs might be important biomarkers for the evaluation of the sensitivity of aquatic animal viral response to hypoxia stress. Furthermore, the frequencies of viral HREs in 43 species aquatic viral genomes from 16 families were predicted and the results indicate that some aquatic animal viruses, such as Picornavirdea, Dicistronviridae, and Herpesviridae, may have a high risk to outbreak when the aquatic environment encounters hypoxic stress.

SFRP1 modulates astrocyte-to-microglia crosstalk in acute and chronic neuroinflammation.

Neuroinflammation is a common feature of many neurodegenerative diseases. It fosters a dysfunctional neuron-microglia-astrocyte crosstalk that, in turn, maintains microglial cells in a perniciously reactive state that often enhances neuronal damage. The molecular components that mediate this critical communication are not fully explored. Here, we show that secreted frizzled-related protein 1 (SFRP1), a multifunctional regulator of cell-to-cell communication, is part of the cellular crosstalk underlying neuroinflammation. In mouse models of acute and chronic neuroinflammation, SFRP1, largely astrocyte-derived, promotes and sustains microglial activation, and thus a chronic inflammatory state. SFRP1 promotes the upregulation of components of the hypoxia-induced factor-dependent inflammatory pathway and, to a lower extent, of those downstream of the nuclear factor-kappa B. We thus propose that SFRP1 acts as an astrocyte-to-microglia amplifier of neuroinflammation, representing a potential valuable therapeutic target for counteracting the harmful effect of chronic inflammation in several neurodegenerative diseases.

Genome-Wide DNA Methylation Changes Associated With High-Altitude Acclimatization During an Everest Base Camp Trek.

The individual physiological response to high-altitude hypoxia involves both genetic and non-genetic factors, including epigenetic modifications. Epigenetic changes in hypoxia factor pathway (HIF) genes are associated with high-altitude acclimatization. However, genome-wide epigenetic changes that are associated with short-term hypoxia exposure remain largely unknown. We collected a series of DNA samples from 15 participants of European ancestry trekking to Everest Base Camp to identify DNA methylation changes associated with incremental altitude ascent. We determined genome-wide DNA methylation levels using the Illumina MethylationEPIC chip comparing two altitudes: baseline 1,400 m (day 0) and elevation 4,240 m (day 7). The results of our epigenome-wide association study revealed 2,873 significant differentially methylated positions (DMPs) and 361 significant differentially methylated regions (DMRs), including significant positions and regions in hypoxia inducible factor (HIF) and the renin-angiotensin system (RAS) pathways. Our pathway enrichment analysis identified 95 significant pathways including regulation of glycolytic process (GO:0006110), regulation of hematopoietic stem cell differentiation (GO:1902036), and regulation of angiogenesis (GO:0045765). Lastly, we identified an association between the ACE gene insertion/deletion (I/D) polymorphism and oxygen saturation, as well as average ACE methylation. These findings shed light on the genes and pathways experiencing the most epigenetic change associated with short-term exposure to hypoxia.

Bioactive glasses and electrospun composites that release cobalt to stimulate the HIF pathway for wound healing applications.

BACKGROUND: Bioactive glasses are traditionally associated with bonding to bone through a hydroxycarbonate apatite (HCA) surface layer but the release of active ions is more important for bone regeneration. They are now being used to deliver ions for soft tissue applications, particularly wound healing. Cobalt is known to simulate hypoxia and provoke angiogenesis. The aim here was to develop new bioactive glass compositions designed to be scaffold materials to locally deliver pro-angiogenic cobalt ions, at a controlled rate, without forming an HCA layer, for wound healing applications. METHODS: New melt-derived bioactive glass compositions were designed that had the same network connectivity (mean number of bridging covalent bonds between silica tetrahedra), and therefore similar biodegradation rate, as the original 45S5 Bioglass. The amount of magnesium and cobalt in the glass was varied, with the aim of reducing or removing calcium and phosphate from the compositions. Electrospun poly(ε-caprolactone)/bioactive glass composites were also produced. Glasses were tested for ion release in dissolution studies and their influence on Hypoxia-Inducible Factor 1-alpha (HIF-1α) and expression of Vascular Endothelial Growth Factor (VEGF) from fibroblast cells was investigated. RESULTS: Dissolution tests showed the silica rich layer differed depending on the amount of MgO in the glass, which influenced the delivery of cobalt. The electrospun composites delivered a more sustained ion release relative to glass particles alone. Exposing fibroblasts to conditioned media from these composites did not cause a detrimental effect on metabolic activity but glasses containing cobalt did stabilise HIF-1α and provoked a significantly higher expression of VEGF (not seen in Co-free controls). CONCLUSIONS: The composite fibres containing new bioactive glass compositions delivered cobalt ions at a sustained rate, which could be mediated by the magnesium content of the glass. The dissolution products stabilised HIF-1α and provoked a significantly higher expression of VEGF, suggesting the composites activated the HIF pathway to stimulate angiogenesis.

Cross-Species Insights Into Genomic Adaptations to Hypoxia.

Over millions of years, vertebrate species populated vast environments spanning the globe. Among the most challenging habitats encountered were those with limited availability of oxygen, yet many animal and human populations inhabit and perform life cycle functions and/or daily activities in varying degrees of hypoxia today. Of particular interest are species that inhabit high-altitude niches, which experience chronic hypobaric hypoxia throughout their lives. Physiological and molecular aspects of adaptation to hypoxia have long been the focus of high-altitude populations and, within the past decade, genomic information has become increasingly accessible. These data provide an opportunity to search for common genetic signatures of selection across uniquely informative populations and thereby augment our understanding of the mechanisms underlying adaptations to hypoxia. In this review, we synthesize the available genomic findings across hypoxia-tolerant species to provide a comprehensive view of putatively hypoxia-adaptive genes and pathways. In many cases, adaptive signatures across species converge on the same genetic pathways or on genes themselves [i.e., the hypoxia inducible factor (HIF) pathway). However, specific variants thought to underlie function are distinct between species and populations, and, in most cases, the precise functional role of these genomic differences remains unknown. Efforts to standardize these findings and explore relationships between genotype and phenotype will provide important clues into the evolutionary and mechanistic bases of physiological adaptations to environmental hypoxia.

Dual-drug loaded micelle for combinatorial therapy targeting HIF and mTOR signaling pathways for ovarian cancer treatment.

Mutations in the tumor protein (TP53) and the mammalian target of rapamycin (mTOR) pathway have been elucidated as driver mutations in ovarian carcinomas that transform into an invasive phenotype under hypoxic conditions. Chetomin (CHE) targets the hypoxic pathway while Everolimus (EVR) acts on the mTOR pathway. Poor aqueous solubilities of both compounds limit their clinical applications. Diblock copolymer nanoplatforms of methoxy poly(ethylene glycol)2000-block-poly (lactic acid)1800 (mPEG2000-b-PLA1800) and (mPEG4000-b-PLA2200) were used to formulate individual and dual drug loaded micelles (DDM) using the solvent evaporation method. The CHE micelles (CHE-M) had a size of 21 nm with CHE loading of 0.5 mg/mL while the EVR micelles (EVR-M) and the DDM had a size around 35 and 39 nm, respectively, with EVR loading up to 2.3 mg/mL. The anti-proliferative effects of these micelles have been tested in vitro in three ovarian cell lines (ES2, OVCAR3 and TOV21G) with the DDM exhibiting a strong synergistic anti-proliferative effect in the ES2 and the TOV21G cells. The DDM were able to significantly induce tumor regression in ES2 ovarian xenograft mouse models by inhibiting angiogenesis and inducing apoptosis when compared to the individual micelles. The inhibition of hypoxia inducible factor (HIF) and the mTOR pathways has been elucidated using immunohistochemistry studies. In conclusion, we have developed a mPEG-b-PLA based micellar nanoplatform that could prevent drug resistance by delivering multiple drugs at therapeutically relevant concentrations for effectively treating ovarian carcinomas.

Working with Hypoxia.

A hypoxic environment can be defined as a region of the body or the whole body that is deprived of oxygen. Hypoxia is a feature of many diseases, such as cardiovascular disease, tissue trauma, stroke, and solid cancers. A loss of oxygen supply usually results in cell death; however, when cells gradually become hypoxic, they may survive and continue to thrive as described for conditions that promote metastatic growth. The role of hypoxia in these pathogenic pathways is therefore of great interest, and understanding the effect of hypoxia in regulating these mechanisms is fundamentally important. This chapter gives an extensive overview of these mechanisms. Moreover, given the challenges posed by tumor hypoxia we describe the current methods to simulate and detect hypoxic conditions followed by a discussion on current and experimental therapies that target hypoxic cells.

Evolutionary Genetics of Hypoxia and Cold Tolerance in Mammals.

Low oxygen and fluctuant ambient temperature pose serious challenges to mammalian survival. Physiological adaptations in mammals to hypoxia and low temperatures have been intensively investigated, yet their underlying molecular mechanisms need further exploration. Independent invasions of high-altitude plateaus, subterranean burrows and marine environments by different mammals provide opportunities to conduct such analyses. Here, we focused on six genes in the hypoxia inducible factor (HIF) pathway and two non-shivering thermogenesis (NST)-related genes [PPAR co-activator 1 (PGC-1) and uncoupling protein 1 (UCP1)] in representative species of pikas and other mammals to understand whether these loci were targeted by natural selection during independent invasions to conditions characterized by hypoxia and temperature fluctuations by high-altitude, subterranean and marine mammals. Our analyses revealed pervasive positive selection signals in the HIF pathway genes of mammals occupying high-altitude, subterranean and aquatic ecosystems; however, the mechanisms underlying their independent adaptations to hypoxic environments varied by taxa, since different genes were positively selected in each taxon and expression levels of individual genes varied among species. Additionally, parallel amino acid substitutions were also detected in hypoxia-tolerant mammals, indicating that convergent evolution may play a role in their independent adaptations to hypoxic environments. However, divergent evolutionary histories of NST-related genes were noted, since significant evidence of positive selection was observed in PGC-1 and UCP1 in high-altitude species and subterranean rodents; however, UCP1 may have already lost its function in diving cetaceans, which may be related to the thick blubber layer of adipose and connective tissue in these mammals.

Oxaloacetate induces apoptosis in HepG2 cells via inhibition of glycolysis.

Most cancer cells perform glycolysis despite having sufficient oxygen. The specific metabolic pathways of cancer cells have become the focus of cancer treatment. Recently, accumulating evidence indicates oxidative phosphorylation (OXPHOS) and glycolysis can be regulated with each other. Thus, we suggest that the glycolysis of cancer cells is inhibited by restoring or improving OXPHOS in cancer cells. In our study, we found that oxaloacetate (OA) induced apoptosis in HepG2 cells in vivo and in vitro. Meanwhile, we found that OA induced a decrease in the energy metabolism of HepG2 cells. Further results showed that the expression and activity of glycolytic enzymes were decreased with OA treatment. Conversely, the expression and activity of enzymes involved in the TCA cycle and OXPHOS were increased with OA treatment. The results indicate that OA can inhibit glycolysis through enhancement of OXPHOS. In addition, OA-mediated suppression of HIF1α, p-Akt, and c-myc led to a decrease in glycolysis level. Therefore, OA has the potential to be a novel anticancer drug.