HIF-1: mediator of physiological and pathophysiological responses to hypoxia

Precocious neuronal differentiation and disrupted oxygen responses in Kabuki syndrome

Chromatin modifiers act to coordinate gene expression changes critical to neuronal differentiation from neural stem/progenitor cells (NSPCs). Lysine-specific methyltransferase 2D (KMT2D) encodes a histone methyltransferase that promotes transcriptional activation and is frequently mutated in cancers and in the majority (>70%) of patients diagnosed with the congenital, multisystem intellectual disability disorder Kabuki syndrome 1 (KS1). Critical roles for KMT2D are established in various non-neural tissues, but the effects of KMT2D loss in brain cell development have not been described. We conducted parallel studies of proliferation, differentiation, transcription, and chromatin profiling in KMT2D-deficient human and mouse models to define KMT2D-regulated functions in neurodevelopmental contexts, including adult-born hippocampal NSPCs in vivo and in vitro. We report cell-autonomous defects in proliferation, cell cycle, and survival, accompanied by early NSPC maturation in several KMT2D-deficient model systems. Transcriptional suppression in KMT2D-deficient cells indicated strong perturbation of hypoxia-responsive metabolism pathways. Functional experiments confirmed abnormalities of cellular hypoxia responses in KMT2D-deficient neural cells and accelerated NSPC maturation in vivo. Together, our findings support a model in which loss of KMT2D function suppresses expression of oxygen-responsive gene programs important to neural progenitor maintenance, resulting in precocious neuronal differentiation in a mouse model of KS1.

Resilience to acute kidney injury in offspring of maternal protein restriction

Protein restriction (PR) during pregnancy induces morphofunctional alterations related to deficient nephrogenesis. We studied the renal functional and morphological significance of PR during pregnancy and/or lactation in adult male rat offspring and the repercussions on acute kidney injury (AKI) severity. Female rats were randomly assigned to the following groups: control diet during pregnancy and lactation (CC), control diet during pregnancy and PR diet during lactation (CR), PR during pregnancy and control diet during lactation (RC), and PR during pregnancy and lactation (RR). Three months after birth, at least 12 male offspring of each group randomly underwent either bilateral renal ischemia for 45 min [ischemia-reperfusion (IR)] or sham surgery. Thus, eight groups were studied 24 h after reperfusion: CC, CC + IR, CR, CR + IR, RC, RC + IR, RR, and RR + IR. Under basal conditions, the CR, RC, and RR groups exhibited a significant reduction in nephron number that was associated with a reduction in renal blood flow. Glomerular hyperfiltration was present as a compensatory mechanism to maintain normal renal function. mRNA levels of several vasoactive, antioxidant, and anti-inflammatory molecules were decreased. After IR, renal function was similarly reduced in all of the studied groups. Although all of the offspring from maternal PR exhibited renal injury, the magnitude was lower in the RC and RR groups, which were associated with faster renal blood flow recovery, differential vasoactive factors, and hypoxia-inducible factor-1α signaling. Our results show that the offspring from maternal PR are resilient to AKI induced by IR that was associated with reduced tubular injury and a differential hemodynamic response.

Immunometabolism of Phagocytes During Mycobacterium tuberculosis Infection

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) remains as a leading killer among infectious diseases worldwide. The nature of the host immune response dictates whether the initial Mtb infection is cleared or progresses toward active disease, and is ultimately determined by intricate host-pathogen interactions that are yet to be fully understood. The early immune response to infection is mediated by innate immune cells, including macrophages and neutrophils that can phagocytose Mtb and mount an antimicrobial response. However, Mtb can exploit these innate immune cells for its survival and dissemination. Recently, it has become clear that the immune response and metabolic remodeling are interconnected, which is highlighted by the rapid evolution of the interdisciplinary field of immunometabolism. It has been proposed that the net outcome to Mtb infection—clearance or chronic disease—is likely a result of combined immunologic and metabolic activities of the immune cells. Indeed, host cells activated by Mtb infection have strikingly different metabolic requirements than naïve/non-infected cells. Macrophages activated by Mtb-derived molecules or upon phagocytosis acquire a phenotype similar to M1 with elevated production of pro-inflammatory molecules and rely on glycolysis and pentose phosphate pathway to meet their bioenergetic and metabolic requirements. In these macrophages, oxidative phosphorylation and fatty acid oxidation are dampened. However, the non-infected/naive, M2-type macrophages are anti-inflammatory and derive their energy from oxidative phosphorylation and fatty acid oxidation. Similar metabolic adaptations also occur in other phagocytes, including dendritic cells, neutrophils upon Mtb infection. This metabolic reprogramming of innate immune cells during Mtb infection can differentially regulate their effector functions, such as the production of cytokines and chemokines, and antimicrobial response, all of which can ultimately determine the outcome of Mtb-host interactions within the granulomas. In this review, we describe key immune cells bolstering host innate response and discuss the metabolic reprogramming in these phagocytes during Mtb infection. We focused on the major phagocytes, including macrophages, dendritic cells and neutrophils and the key regulators involved in metabolic reprogramming, such as hypoxia-inducible factor-1, mammalian target of rapamycin, the cellular myelocytomatosis, peroxisome proliferator-activator receptors, sirtuins, arginases, inducible nitric acid synthase and sphingolipids.

Metabolic Maturation of Human Pluripotent Stem Cell-Derived Cardiomyocytes by Inhibition of HIF1α and LDHA

RATIONALE

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) are a readily available, robustly reproducible, and physiologically appropriate human cell source for cardiac disease modeling, drug discovery, and toxicity screenings in vitro. However, unlike adult myocardial cells in vivo, hPSC-CMs cultured in vitro maintain an immature metabolic phenotype, where majority of ATP is produced through aerobic glycolysis instead of oxidative phosphorylation in the mitochondria. Little is known about the underlying signaling pathways controlling hPSC-CMs' metabolic and functional maturation.

OBJECTIVE

To define the molecular pathways controlling cardiomyocytes' metabolic pathway selections and improve cardiomyocyte metabolic and functional maturation.

METHODS AND RESULTS

We cultured hPSC-CMs in different media compositions including glucose-containing media, glucose-containing media supplemented with fatty acids, and glucose-free media with fatty acids as the primary carbon source. We found that cardiomyocytes cultured in the presence of glucose used primarily aerobic glycolysis and aberrantly upregulated HIF1α (hypoxia-inducible factor 1α) and its downstream target lactate dehydrogenase A. Conversely, glucose deprivation promoted oxidative phosphorylation and repressed HIF1α. Small molecule inhibition of HIF1α or lactate dehydrogenase A resulted in a switch from aerobic glycolysis to oxidative phosphorylation. Likewise, siRNA inhibition of HIF1α stimulated oxidative phosphorylation while inhibiting aerobic glycolysis. This metabolic shift was accompanied by an increase in mitochondrial content and cellular ATP levels. Furthermore, functional gene expressions, sarcomere length, and contractility were improved by HIF1α/lactate dehydrogenase A inhibition.

CONCLUSIONS

We show that under standard culture conditions, the HIF1α-lactate dehydrogenase A axis is aberrantly upregulated in hPSC-CMs, preventing their metabolic maturation. Chemical or siRNA inhibition of this pathway results in an appropriate metabolic shift from aerobic glycolysis to oxidative phosphorylation. This in turn improves metabolic and functional maturation of hPSC-CMs. These findings provide key insight into molecular control of hPSC-CMs' metabolism and may be used to generate more physiologically mature cardiomyocytes for drug screening, disease modeling, and therapeutic purposes.

Non-coding RNA in endothelial-to-mesenchymal transition

Endothelial-to-mesenchymal transition (EndMT) is the process wherein endothelial cells lose their typical endothelial cell markers and functions and adopt a mesenchymal-like phenotype. EndMT is required for development of the cardiac valves, the pulmonary and dorsal aorta, and arterial maturation, but activation of the EndMT programme during adulthood is believed to contribute to several pathologies including organ fibrosis, cardiovascular disease, and cancer. Non-coding RNAs, including microRNAs, long non-coding RNAs, and circular RNAs, modulate EndMT during development and disease. Here, we review the mechanisms by which non-coding RNAs facilitate or inhibit EndMT during development and disease and provide a perspective on the therapeutic application of non-coding RNAs to treat fibroproliferative cardiovascular disease.

Hypoxia-Inducible Factor-1α (HIF-1α) Promotes Hypoxia-Induced Invasion and Metastasis in Ovarian Cancer by Targeting Matrix Metallopeptidase 13 (MMP13)

Background

Hypoxia promotes cancer progression. Hypoxia-inducible factor-1α (HIF-1α) has been reported to enhance tumor invasion and metastasis via activating downstream genes, such as matrix metalloproteinases (MMPs). The purpose of this study was to explore the probable roles of HIF-1α and MMP13 in the invasion and metastasis of ovarian cancer under hypoxic conditions.

Material/Methods

The expression of HIF-1α and MMP13 protein were detected with immunohistochemistry staining in ovarian cancer tissues, metastatic lesions, and normal fallopian tissues. Ovarian cancer A2780 cells were cultured under normoxic condition and hypoxic condition. mRNA and protein expression of HIF-1α and MMP13 were detected by RT-PCR and Western blot analysis. The effects of siRNA against HIF-1α on MMP13 expression were examined by RT-PCR and Western blot analysis. Transwell invasion assays were performed to test the invasive ability of A2780 cells.

Results

Immunohistochemistry staining showed significantly higher expression of HIF-1α and MMP13 protein in ovarian cancer tissues and metastatic lesions than in normal fallopian tissues. HIF-1α and MMP13 expression were closely related. After exposure to hypoxia, mRNA and protein levels of HIF-1α and MMP13 were upregulated. siRNA effectively inhibited HIF-1α expression and MMP13 expression. The number of invading A2780 cells decreased after HIF-1α was silenced.

Conclusions

This study suggests that HIF-1α promotes ovarian cancer cell invasion through a MMP13 mechanism. It might be an effective strategy targeting HIF-1α - MMP13 to inhibit invasion and metastasis of ovarian cancer.

Tumor Hypoxia As an Enhancer of Inflammation-Mediated Metastasis: Emerging Therapeutic Strategies

Metastasis is the leading cause of cancer-related deaths. Recent research has implicated tumor inflammation as a promoter of metastasis. Myeloid, lymphoid, and mesenchymal cells in the tumor microenvironment promote inflammatory signaling amongst each other and together with cancer cells to modulate sustained inflammation, which may enhance cancer invasiveness. Tumor hypoxia, a state of reduced available oxygen present in the majority of solid tumors, acts as a prognostic factor for a worse outcome and is known to have a role in tumor inflammation through the regulation of inflammatory mediator signals in both cancer and neighboring cells in the microenvironment. Multiple methods to target tumor hypoxia have been developed and tested in clinical trials, and still more are emerging as the impacts of hypoxia become better understood. These strategies include mechanistic inhibition of the hypoxia inducible factor signaling pathway and hypoxia activated pro-drugs, leading to both anti-tumor and anti-inflammatory effects. This prompts a need for further research on the prevention of hypoxia-mediated inflammation in cancer. Hypoxia-targeting strategies seem to have the most potential for therapeutic benefit when combined with traditional chemotherapy agents. This paper will serve to summarize the role of the inflammatory response in metastasis, to discuss how hypoxia can enable or enhance inflammatory signaling, and to review established and emerging strategies to target the hypoxia-inflammation-metastasis axis.

Effects of dietary supplementation of three strains of Lactococcus lactis on HIFs genes family expression of the common carp following Aeromonas hydrophila infection

HIFs (Hypoxia inducible factors) are the main regulators of the expression change of oxygen-dependent genes, in addition, they also play important roles in immune regulation. HIFs participate in infectious diseases and inflammatory responses, providing us a new therapeutic target for the treatment of diseases. In this study, 16 HIFs were identified in common carp genome database. Comparative genomics analysis showed large expansion of HIF gene family and approved the four round whole genome duplication (WGD) event in common carp. To further understand the function of HIFs, the domain architectures were predicted. All HIF proteins had the conserved HLH-PAS domain, which were essential for them to form dimer and bind to the downstream targets. The differences in domain of HIFα and HIFβ might result in their different functions. Phylogenetic analysis revealed that all HIFs were divided into two subfamilies and the HIFs in common carp were clustered with their teleost counterparts indicating they are highly conservative during evolution. In addition, the tissue distribution was examined by RT-PCR showed that most of HIF genes had a wide range of tissue distribution but exhibited tissue-specific expression patterns. The expression divergences were observed between the copy genes, for example, HIF1A-1, HIF2A-1, ARNT-2 had wide tissue distribution while their copies had limited tissue distribution, proving the function divergence of copies post the WGD event. In order to find an effective activation of HIFs and apply to treatment of aquatic diseases, we investigate the dietary supplementation effects of different strains of Lactococcus lactis on the expression of HIFα subfamily members in kidney of common carp infected with A. hydrophila. In addition, all of the HIF genes have a high expression in the early stages of infection, and decreased in the treatment time point of 48 h in common carp. This phenomenon confirms that as a switch, the main function of HIFs is to regulate the production of immune response factors in early infection. So activation of the switch may be an effective method for infectious disease treatment. As expected, the treatment groups improved the expression of HIFs compared with the control group, and the effects of the three strains are different. The strain1 of L. lactis had a stronger induction on HIF genes than strain2 and strain3, and it might be applied as a potential activation of HIF genes for disease treatment. So, adding befitting L. lactis maybe a well method to activate the HIF genes to protect them from mycobacterial infection.

Study on the effect of CaMKKβ-mediated AMPK activation on the glycolysis and the quality of different altitude postmortem bovines longissimus muscle

This study investigated the activity of adenosine monophosphate-activated protein kinase (AMPK), glycolysis, and meat quality index in three altitude bovines during postmortem aging process. Local cattle (altitude:1,500 m), Gannan yak (3,000 m), and Yushu yak (4,500 m) postmortem Longissimus Dorsi (LD) muscle were used. Results indicated that CaCl₂ significantly increased the AMPK activity by increasing the calcium-regulated protein kinase kinase (CaMKKβ) activity. Besides, AMPK activation enhanced the activity of lactate dehydrogenase (LDH) and Ca²⁺ -ATPase and accelerated the rate of muscle maturation during postmortem aging. Moreover, the expression of HIF-1, PRKAA2, and GLUT4 genes in high-altitude Yushu yak was higher than that of low-altitude bovines. CaCl₂ activates AMPK by activating CaMKKβ cascade and accelerates postmortem glycolysis affecting the intramuscular environment, color, and muscle protein degradation to accelerate postmortem muscle maturation, suggesting that AMPK has essential effects on postmortem muscle glycolysis and quality, and can regulate muscle quality by regulating postmortem muscle AMPK activity. PRACTICAL APPLICATIONS: Insufficient postmortem glycolysis usually leads to DFD (dark, firm, and dry) meat. Beef have relatively high incidences of DFD meat, which has an unattractive dark color and causes significant loss to the meat industry. Therefore, AMPK, which can regulate postmortem glycolysis to affect meat quality, is a valid research target.

Optimization of transdermal deferoxamine leads to enhanced efficacy in healing skin wounds

Chronic wounds remain a significant burden to both the healthcare system and individual patients, indicating an urgent need for new interventions. Deferoxamine (DFO), an iron-chelating agent clinically used to treat iron toxicity, has been shown to reduce oxidative stress and increase hypoxia-inducible factor-1 alpha (HIF-1α) activation, thereby promoting neovascularization and enhancing regeneration in chronic wounds. However due to its short half-life and adverse side effects associated with systemic absorption, there is a pressing need for targeted DFO delivery. We recently published a preclinical proof of concept drug delivery system (TDDS) which showed that transdermally applied DFO is effective in improving chronic wound healing. Here we present an enhanced TDDS (eTDDS) comprised exclusively of FDA-compliant constituents to optimize drug release and expedite clinical translation. We evaluate the eTDDS to the original TDDS and compare this with other commonly used delivery methods including DFO drip-on and polymer spray applications. The eTDDS displayed excellent physicochemical characteristics and markedly improved DFO delivery into human skin when compared to other topical application techniques. We demonstrate an accelerated wound healing response with the eTDDS treatment resulting in significantly increased wound vascularity, dermal thickness, collagen deposition and tensile strength. Together, these findings highlight the immediate clinical potential of DFO eTDDS to treating diabetic wounds. Further, the topical drug delivery platform has important implications for targeted pharmacologic therapy of a wide range of cutaneous diseases.

Stem Cell Mobilization Is Lifesaving in a Large Animal Preclinical Model of Acute Liver Failure

INTRODUCTION

Acute liver failure (ALF) affects 2000 Americans each year with no treatment options other than liver transplantation. We showed previously that mobilization of endogenous stem cells is protective against ALF in rodents. The objective of this study was to assess whether stem cell mobilizing drugs are lifesaving in a large animal preclinical model of ALF, to assess readiness for a clinical trial.

METHODS

Male Yorkshire pigs (14-18 kg) were divided into 2 groups, control (n = 6) and treatment (n = 6). All pigs received an intravenous bolus of the hepatotoxin D-galactosamine (0.5 g/kg) via central line and were followed up until death or day 28. Treated animals received simultaneous intramuscular injection of plerixafor (1 mg/kg) and G-CSF (2 μg/kg) at baseline, 24 and 48 hours after toxin infusion to mobilize endogenous stem cells, as previously described. Control animals received saline.

RESULTS

All control animals (6/6) succumbed to liver failure within 91 hours, confirmed by clinical, biochemical, and histopathological evidence of ALF. In the treatment group (5/6) animals survived indefinitely despite comparable biochemical changes during the first 48 hours (P = 0.003). White blood cell count increased by a mean of 4× in the treated group at the peak of mobilization (P = 0.0004).

CONCLUSIONS

Stem cell mobilizing drugs were lifesaving in a preclinical large animal model of ALF. Since no therapeutic options other than liver transplantation are currently available for critically ill patients with ALF, a multicenter clinical trial is warranted.

Hypoxia alters the release and size distribution of extracellular vesicles in pancreatic cancer cells to support their adaptive survival

Pancreatic tumors are highly desmoplastic and poorly-vascularized, and therefore must develop adaptive mechanisms to sustain their survival under hypoxic condition. Extracellular vesicles (EV) play vital roles in pancreatic tumor pathobiology by facilitating intercellular communication. Here we studied the effect of hypoxia on the release of EVs and examined their role in adaptive survival of pancreatic cancer (PC) cells. Hypoxia promoted the release of EV in PC cell lines, MiaPaCa and AsPC1, wherein former exhibited a far greater induction. Moreover, a time-dependent, measurable and significant increase was recorded for small EV (SEV) in both the cell lines with only minimal induction observed for medium (MEV) and large EVs (LEV). Similarly, noticeable changes in size distribution of SEV were also recorded with a shift toward smaller average size under extreme hypoxia. Thrombospondin (apoptotic bodies marker) was exclusively detected on LEVs, while Arf6 (microvesicles marker) was mostly present on MEV with some expression in LEV as well. However, CD9 and CD63 (exosome markers) were expressed in both SEV and MEVs with a decreased expression recorded under hypoxia. Among all subfractions, SEV was the most bioactive in promoting the survival of hypoxic PC cells and hypoxia-inducible factor-1α stabilization was involved in heightened EV release under hypoxia and for their potency to promote hypoxic cell survival. Altogether, our findings provide a novel mechanism for the adaptive hypoxic survival of PC cells and should serve as the basis for future investigations on broader functional implications of EV.

PIN1 transcript variant 2 acts as a long non-coding RNA that controls the HIF-1-driven hypoxic response

The transcription factor HIF-1 induces the expression of genes that are essential for cell survival and oxygen homeostasis in hypoxic conditions. The prolyl isomerase Pin1 plays a role in the regulation of HIF-1α. However, the mechanism by which Pin1 controls HIF-1α remains controversial. Surprisingly, we here show that a PIN1 transcript downregulates HIF-1α as a long non-coding RNA. Pin1-silencing siRNAs augmented the hypoxia-induced expression of HIF-1α, thereby upregulating the expression of HIF-1 target genes. However, the overexpression of Pin1 protein did not inhibit the hypoxic expression of HIF-1α. Pin1 restoration in Pin1-depleted cells also failed to reverse the induction of HIF-1α by Pin1 knockdown. Unexpectedly, HIF-1α was found to be induced by both siRNAs for PIN1 transcript variants 1/2 and that for PIN1 transcript variants 2/3, indicating that the PIN1 transcript variant 2 (PIN1-v2) is responsible for HIF-1α induction. Mechanistically, PIN1-v2, which is classified as a long non-coding RNA due to early termination of translation, was evaluated to inhibit the transcription of HIF1A gene. In conclusion, PIN1-v2 may function in balancing the HIF-1-driven gene expression under hypoxia.

Convulsive Stress Mimics Brain Hypoxia and Promotes the P-Glycoprotein (P-gp) and Erythropoietin Receptor Overexpression. Recombinant Human Erythropoietin Effect on P-gp Activity

Erythropoietin (EPO) is not only a hormone that promotes erythropoiesis but also has a neuroprotective effect on neurons attributed to its known anti-apoptotic action. Previously, our group has demonstrated that recombinant-human EPO (rHu-EPO) can protect neurons and recovery motor activity in a chemical focal brain hypoxia model (Merelli et al., 2011). We and others also have reported that repetitive seizures can mimic a hypoxic- like condition by HIF-1α nuclear translocation and high neuronal expression P-gp. Here, we report that a single 20-min status epilepticus (SE) induces P-gp and EPO-R expression in cortical pyramidal neurons and only P-gp expression in astrocytes. In vitro, excitotoxic stress (300 μM glutamate, 5 min), can also induce the expression of EPO-R and P-gp simultaneously with both HIF-1α and NFkB nuclear translocation in primary cortical neurons. Primary astrocytes exposed to chemical hypoxia with CoCl₂ (0.3 mM, 6 h) increased P-gp expression as well as an increased efflux of Rhodamine 123 (Rho123) that is a P-gp substrate. Tariquidar, a specific 3^er generation P-gp-blocker was used as an efflux inhibitor control. Astrocytes treated with rHu-EPO showed a significant recovery of the Rho123 retention in a similar way as seen by Tariquidar, demonstrating for first time that rHu-EPO can inhibit the P-gp-dependent efflux activity. Taking together, these data suggest that stimulation of EPO depending signaling system could not only play a central role in brain cell protection, but this system could be a new tool for reverse the pharmacoresistant phenotype in refractory epilepsy as well as in other pharmacoresistant hypoxic brain diseases expressing P-gp.

Exposure to parental smoking during pregnancy and handgrip strength in 7-10-year old children

BACKGROUND

Maternal smoking during pregnancy is a risk factor associated with intrauterine growth retardation and postnatal complications.

AIM

To assess the relationship between prenatal exposure to smoking on hand grip strength in children 7-10 years of age.

STUDY DESIGN

Generalized Linear Model (GLM) was used to assess the relationship between grip strength and smoking status of parents, controlling for social status, birth outcome and body size.

OUTCOME MEASURES

Height, weight and hand grip strength were measured by trained staff. Smoking status of both parents during pregnancy, mother's level of education and birth outcome were reported by questionnaire.

SUBJECTS

734 records (297 boys, 437 girls) of healthy children aged 7-10 years from a survey conducted in 2001-2003 in randomly selected primary schools of Łódź.

RESULTS/CONCLUSION

Boys exposed to both maternal and paternal smoking during prenatal life showed lower muscular strength at 7-10 years, but a similar relationship was not observed in girls. Intrauterine hypoxia due to maternal smoking during pregnancy and subsequent postnatal exposure to maternal and paternal smoking may have attenuated the formation and subsequent development of muscle fibres in boys.

Impact of the gene-gene interactions related to the HIF-1α signaling pathway with the knee osteoarthritis development

INTRODUCTION/OBJECTIVES

Articular cartilage is the target tissue of osteoarthritis (OA), and because it lacks capillary networks, the microenvironment is hypoxic. Hypoxia inducible factor-1 alpha (HIF-1α) regulates the homeostasis of this tissue. The aim of this study was to investigate whether genetic polymorphisms of the HIF-1α signaling pathway are involved in the development of knee OA.

METHOD

We performed a case-control association study and genotyped 134 knee OA patients and 267 healthy controls. All participants were genotyped in order to evaluate 42 SNPs from 22 genes involved in the HIF-1α signaling pathway using the OpenArray technology. Gene-gene interactions (epistasis) were analyzed using the multifactor dimensionality reduction (MDR) method.

RESULTS

The MDR analysis showed epistasis between AKT2 (rs8100018) and IGF1 (rs2288377), AKT2 (rs8100018) and IGF1 (rs35767), IGF1 (rs35767) and COL2A1 (rs1793953), and between GSK3B (rs6438552) and IGF1 (rs35767) polymorphisms, with information gain values of 21.24%, 8.37%, 9.93%, and 5.73%, respectively. Additionally, our model allowed us to identify high- and low-risk genotypes among COL2A1 rs1793953, GSK3B rs6438552, AKT2 rs8100018, and IGF1 rs35767 polymorphisms.

CONCLUSIONS

Knowing the interactions of these polymorphisms involved in HIF-1α signaling pathway could provide a new diagnostic support tool to identify individuals at high risk of developing knee OA.

Hypoxia and aging

Eukaryotic cells require sufficient oxygen (O₂) for biological activity and survival. When the oxygen demand exceeds its supply, the oxygen levels in local tissues or the whole body decrease (termed hypoxia), leading to a metabolic crisis, threatening physiological functions and viability. Therefore, eukaryotes have developed an efficient and rapid oxygen sensing system: hypoxia-inducible factors (HIFs). The hypoxic responses are controlled by HIFs, which induce the expression of several adaptive genes to increase the oxygen supply and support anaerobic ATP generation in eukaryotic cells. Hypoxia also contributes to a functional decline during the aging process. In this review, we focus on the molecular mechanisms regulating HIF-1α and aging-associated signaling proteins, such as sirtuins, AMP-activated protein kinase, mechanistic target of rapamycin complex 1, UNC-51-like kinase 1, and nuclear factor κB, and their roles in aging and aging-related diseases. In addition, the effects of prenatal hypoxia and obstructive sleep apnea (OSA)-induced intermittent hypoxia have been reviewed due to their involvement in the progression and severity of many diseases, including cancer and other aging-related diseases. The pathophysiological consequences and clinical manifestations of prenatal hypoxia and OSA-induced chronic intermittent hypoxia are discussed in detail.

Modulation of hypoxia-inducible factor-1α/cyclo-oxygenase-2 pathway associated with attenuation of intestinal mucosa inflammatory damage by Acanthopanax senticosus polysaccharides in lipopolysaccharide-challenged piglets

Intestinal barrier inflammatory damage is commonly accompanied by hypoxia. The hypothesis that dietary Acanthopanax senticosus polysaccharides (ASPS) might modulate the hypoxia-inducible factor-1α (HIF-1α) signalling pathway and contribute to attenuate intestinal injury was tested in lipopolysaccharide (LPS)-challenged piglets. Thirty-six weaned pigs were randomly allocated to one of the following three groups: (1) basal diet + saline challenge; (2) basal diet + LPS challenge; (3) basal diet with 800 mg/kg ASPS + LPS challenge. LPS was injected at 15, 18 and 21 d, and intestinal sections were sampled following blood collection at 21 d . The results showed ASPS reversed (P < 0·05) LPS-induced decrease in average daily feed intake and rise (P < 0·05) of diarrhoea incidence and index. Biochemical index reflecting gut barrier damage and function involving ileal pro-inflammatory cytokines (TNF-α and IL-1β) and enzyme activity (diamine oxidase and lactase), as well as circulatory d-xylose, was normalised (P < 0·05) in LPS-challenged piglets receiving ASPS. ASPS also ameliorated intestinal morphological deterioration of LPS-challenged piglets, proved by elevated ileal villus height (P < 0·05) and improved appearance of epithelial villus and tight junction ultrastructure. Moreover, ASPS prevented LPS-induced amplification of inflammatory mediators, achieved by depressed ileal mRNA abundance of TNF-α, inducible NO synthase and IL-1β concentration. Importantly, ileal protein expressions of HIF-1α, cyclo-oxygenase-2 (COX-2) and NFκB p65 were also suppressed with ASPS administration (P < 0·05). Collectively, these results suggest the improvement of mucosal inflammatory damage and diarrhoea in immune stress piglets is possibly associated with a novel finding where HIF-1α/COX-2 pathway down-regulation is involved in NFκB p65-inducible releasing of inflammatory cytokines by dietary ASPS.

Porcine Fetal-Derived Fibroblasts Alter Gene Expression and Mitochondria to Compensate for Hypoxic Stress During Culture

The Warburg effect is characterized by decreased mitochondrial oxidative phosphorylation and increased glycolytic flux in adequate oxygen. The preimplantation embryo has been described to have characteristics of the Warburg effect, including similar changes in gene expression and mitochondria, which are more rudimentary in appearance. We hypothesized hypoxia would facilitate anaerobic glycolysis in fibroblasts thereby promoting gene expression and media metabolite production reflecting the Warburg effect hallmarks in early embryos. Additionally, we speculated that hypoxia would induce a rudimentary small mitochondrial phenotype observed in several cell types evidenced to demonstrate the Warburg effect. While many have examined the role hypoxia plays in pathological conditions, few studies have investigated changes in primary cells which could be used in somatic cell nuclear transfer. We found that cells grown in 1.25% O₂ had normal cell viability and more, but smaller mitochondria. Several hypoxia-inducible genes were identified, including seven genes for glycolytic enzymes. In conditioned media from hypoxic cells, the quantities of gluconolactone, cytosine, and uric acid were decreased indicating higher consumption than control cells. These results indicate that fibroblasts alter gene expression and mitochondria to compensate for hypoxic stress and maintain viability. Furthermore, the metabolic changes observed, making them more similar to preimplantation embryos, could be facilitating nuclear reprogramming making these cells more amendable to future use in somatic cell nuclear transfer.

The influence of progesterone on bovine uterine fluid energy, nucleotide, vitamin, cofactor, peptide, and xenobiotic composition during the conceptus elongation-initiation window

Conceptus elongation coincides with one of the periods of greatest pregnancy loss in cattle and is characterized by rapid trophectoderm expansion, commencing ~ Day 13 of pregnancy, i.e. before maternal pregnancy recognition. The process has yet to be recapitulated in vitro and does not occur in the absence of uterine gland secretions in vivo. Moreover, conceptus elongation rates are positively correlated to systemic progesterone in maternal circulation. It is, therefore, a maternally-driven and progesterone-correlated developmental phenomenon. This study aimed to comprehensively characterize the biochemical composition of the uterine luminal fluid on Days 12-14 - the elongation-initiation window - in heifers with normal vs. high progesterone, to identify molecules potentially involved in conceptus elongation initiation. Specifically, nucleotide, vitamin, cofactor, xenobiotic, peptide, and energy metabolite profiles of uterine luminal fluid were examined. A total of 59 metabolites were identified, of which 6 and 3 displayed a respective progesterone and day effect, whereas 16 exhibited a day by progesterone interaction, of which 8 were nucleotide metabolites. Corresponding pathway enrichment analysis revealed that pyridoxal, ascorbate, tricarboxylic acid, purine, and pyrimidine metabolism are of likely importance to to conceptus elongation initiation. Moreover, progesterone reduced total metabolite abundance on Day 12 and may alter the uterine microbiome.

The SLC34A2-ROS-HIF-1-induced up-regulation of EZH2 expression promotes proliferation and chemo-resistance to apoptosis in colorectal cancer

Growing evidence has uncovered that SLC34A2 plays an evident role in the progression in several types of tumors. However, the biological function and underlying molecular mechanisms of SLC34A2 remain largely unknown. Here, we indicated that SLC34A2 expression was markedly increased in SW480 and HT29 cell line cells compared with that in normal colorectal epithelial cell line cells. Array analysis displayed that the expression of enhancer of zeste 2 (EZH2) decreased considerably when SLC34A2 was knocked down. We demonstrated that SLC34A2 induced EZH2 expression and activated its promoter activity. Serial 5′ deletion and site-directed mutagenesis revealed that the induction of EZH2 expression by SLC34A2 was dependent upon the hypoxia-inducible factor 1 (HIF-1)-2 binding site directly within EZH2 promoter. Moreover, HIF-1 activation was proved essential for SLC34A2-induced EZH2 expression. Reactive oxygen species (ROS) generation contributed to the stabilization of HIF-1α by leading to the binding of HIF-1α to the EZH2 promoter, which resulted in increased EZH2 expression. Additionally, we showed that the inhibition of both HIF-1α expression and ROS generation by YC-1 or BHA, respectively, decreased SLC34A2-induced EZH2 overexpression. Significantly, SLC34A2-induced EZH2 overexpression promoted the proliferation and chemo-resistance to apoptosis in colorectal cancer (CRC) cells in vitro and in vivo. Altogether, we conclude that the SLC34A2-ROS-HIF-1-induced overexpression of EZH2 promotes CRC cells proliferation and chemo-resistance to apoptosis. SLC34A2-ROS-HIF-1-EZH2 signaling pathway might serve as a novel therapeutic target against CRC.

Parabronchial remodeling in chicks in response to embryonic hypoxia

The embryonic development of parabronchi occurs mainly during the second half of incubation in precocious birds, which makes this phase sensitive to possible morphological modifications induced by O₂ supply limitation. Thus, we hypothesized that hypoxia during the embryonic phase of parabronchial development induces morphological changes that remain after hatching. To test this hypothesis, chicken embryos were incubated entirely (21 days) under normoxia or partially under hypoxia (15% O₂ during days 12 to 18). Lung structures, including air capillaries, blood capillaries, infundibula, atria, parabronchial lumen, bronchi, blood vessels larger than capillaries and interparabronchial tissue, in 1- and 10-day-old chicks were analyzed using light microscopy-assisted stereology. Tissue barrier and surface area of air capillaries were measured using electron microscopy-assisted stereology, allowing for calculation of the anatomical diffusion factor. Hypoxia increased the relative volumes of air and blood capillaries, structures directly involved in gas exchange, but decreased the relative volumes of atria in both groups of chicks, and the parabronchial lumen in older chicks. Accordingly, the surface area of the air capillaries and the anatomical diffusion factor were increased under hypoxic incubation. Treatment did not alter total lung volume, relative volumes of infundibula, bronchi, blood vessels larger than capillaries, interparabronchial tissue or the tissue barrier of any group. We conclude that hypoxia during the embryonic phase of parabronchial development leads to a morphological remodeling, characterized by increased volume density and respiratory surface area of structures involved in gas exchange at the expense of structures responsible for air conduction in chicks up to 10 days old.

MicroRNA-126 regulates Hypoxia-Inducible Factor-1α which inhibited migration, proliferation, and angiogenesis in replicative endothelial senescence

Whereas a healthy endothelium maintains physiological vascular functions, endothelial damage contributes to the development of cardiovascular diseases. Endothelial senescence is the main determinant of endothelial dysfunction and thus of age-related cardiovascular disease. The objective of this study is to test the involvement of microRNA-126 and HIF-1α in a model of replicative endothelial senescence and the interrelationship between both molecules in this in vitro model. We demonstrated that senescent endothelial cells experience impaired tube formation and delayed wound healing. Senescent endothelial cells failed to express HIF-1α, and the microvesicles released by these cells failed to carry HIF-1α. Of note, HIF-1α protein levels were restored in HIF-1α stabilizer-treated senescent endothelial cells. Finally, we show that microRNA-126 was downregulated in senescent endothelial cells and microvesicles. With regard to the interplay between microRNA-126 and HIF-1α, transfection with a microRNA-126 inhibitor downregulated HIF-1α expression in early passage endothelial cells. Moreover, while HIF-1α inhibition reduced tube formation and wound healing closure, microRNA-126 levels remained unchanged. These data indicate that HIF-1α is a target of miRNA-126 in protective and reparative functions, and suggest that their therapeutic modulation could benefit age-related vascular disease.

Impairment of HIF-1α-mediated metabolic adaption by NRF2-silencing in breast cancer cells

Hypoxia, a common element in the tumor environment, leads to Hypoxia-Inducible Factor-1α (HIF-1α) stabilization to modulate cellular metabolism as an adaptive response. In a previous study, we showed that inhibition of the nuclear factor erythroid 2-like-2 (NFE2L2; NRF2), a master regulator of many genes coping with electrophilic and oxidative stress, elevated the level of miR-181c and induced mitochondrial dysfunction in colon cancer cells. In this study, we demonstrate that NRF2-silencing hindered HIF-1α accumulation in hypoxic breast cancer cells and subsequently suppressed hypoxia-inducible expression of glycolysis-associated glucose transporter-1, hexokinase-2, pyruvate dehydrogenase kinase-1, and lactate dehydrogenase A. HIF-1α dysregulation in NRF2-silenced cancer cells was associated with miR-181c elevation. Overexpression of miR-181c in breast cancer cells blocked HIF-1α accumulation and diminished hypoxia-inducible levels of glycolysis enzymes, whereas the inhibition of miR-181c in NRF2-silenced cells restored HIF-1α accumulation. In a subsequent metabolomic analysis, hypoxic incubation increased the levels of metabolites involved in glycolysis and activated the pentose phosphate pathway (PPP) in control cells. However, these elevations were less pronounced in NRF2-silenced cells. In particular, hypoxic incubation increased the levels of amino acids, which implies a shift to catabolic metabolism, and the increased levels were higher in control cells than in NRF2-silenced cells. Concurrently, hypoxia activated BCL2 interacting protein 3 (BNIP3)-mediated autophagy in the control cells and miR-181c was found to be involved in this autophagy activation. Taken together, these results show that hypoxia-induced metabolic changes to glycolysis, the PPP, and autophagy are inhibited by NRF2-silencing through miR-181c-mediated HIF-1α dysregulation. Therefore, targeting NRF2/miR-181c could be an effective strategy to counteract HIF-1α-orchestrated metabolic adaptation of hypoxic cancer cells.

RNA-binding protein, human antigen R regulates hypoxia-induced autophagy by targeting ATG7/ATG16L1 expressions and autophagosome formation

Autophagy, a prosurvival mechanism offers a protective role during acute kidney injury. We show novel findings on the functional role of RNA binding protein, HuR during hypoxia-induced autophagy in renal proximal tubular cells-2 (HK-2). HK-2 cells showed upregulated expressions of HuR and autophagy-related proteins such as autophagy related 7 (ATG7), autophagy related 16 like 1 (ATG16L1), and LC3II under hypoxia. Increased autophagosome formation was visualized as LC3 puncta in hypoxic cells. Further, short hairpin-RNA-mediated loss of HuR function in HK-2 cells significantly decreased ATG7 and ATG16L1 protein expressions. Bioinformatics prediction revealed HuR motif binding on the coding region of ATG7 and AU-rich element at 3'UTR ATG16L1 messnger RNA (mRNA). The RNA immunoprecipitation study showed that HuR was predominantly associated with ATG7 and ATG16L1 mRNAs under hypoxia. In addition, HuR enhanced autophagosome formation by regulating LC3II expressions. These results show that HuR regulates ATG7 and ATG16L1 expressions and thereby mediate autophagy in HK-2 cells. Importantly, HuR knockdown cells underwent apoptosis during hypoxia as observed through the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Collectively, these findings show the crucial role of HuR under hypoxia by regulating autophagy and suppressing apoptosis in renal tubular cells.

Poor outcome in hypoxic endometrial carcinoma is related to vascular density

Background

Identification of endometrial carcinoma (EC) patients at high risk of recurrence is lacking. In this study, the prognostic role of hypoxia and angiogenesis was investigated in EC patients.

Methods

Tumour slides from EC patients were stained by immunofluorescence for carbonic anhydrase IX (CAIX) as hypoxic marker and CD34 for assessment of microvessel density (MVD). CAIX expression was determined in epithelial tumour cells, with a cut-off of 1%. MVD was assessed according to the Weidner method. Correlations with disease-specific survival (DSS), disease-free survival (DFS) and distant disease-free survival (DDFS) were calculated using Kaplan–Meier curves and Cox regression analysis.

Results

Sixty-three (16.4%) of 385 ECs showed positive CAIX expression with high vascular density. These ECs had a reduced DSS compared to tumours with either hypoxia or high vascular density (log-rank p = 0.002). Multivariable analysis showed that hypoxic tumours with high vascular density had a reduced DSS (hazard ratio [HR] 3.71, p = 0.002), DDFS (HR 2.68, p = 0.009) and a trend for reduced DFS (HR 1.87, p = 0.054).

Conclusions

This study has shown that adverse outcome in hypoxic ECs is seen in the presence of high vascular density, suggesting an important role of angiogenesis in the metastatic process of hypoxic EC. Differential adjuvant treatment might be indicated for these patients.

Expression of the oxygen-sensitive transcription factor subunit HIF-1α in patients suffering from secondary Raynaud syndrome

Anti-ischemic therapy remains a challenge due to the complexity of hypoxia response pathways. Hypoxia-inducible factor (HIF)-1 is a heterodimer transcription factor consisting of 2 subunits, HIF-1α and HIF-1β. Hypoxia-dependent activation of HIF-1α regulates cellular O₂ homeostasis. Raynaud syndrome (RS), as a comorbidity of the autoimmune disease systemic sclerosis (SS), is characterized by vasospasms that limit blood flow to the limbs, resulting in hypoxia. A single-center randomized study was conducted to compare prostaglandin E1 (PgE1) therapy with a treatment combining PgE1 and an endothelin-1 blocker, bosentan. A total of 30 patients suffering from SS with RS were enrolled. We examined the regulation of HIF-1α, its target heme oxygenase-1 (HMOX-1), and the serum levels of the HIF-1α protein in a subset of patients as well as in ten healthy individuals. The expression of HIF-1α and HMOX-1 in monocytes was measured using absolute plasmid-based quantitative real-time PCR, whereas serum HIF-1α levels were measured with ELISA. Samples were taken at the time of randomization and after 24 weeks. We found that HIF-1α and HMOX-1 mRNA expression in monocytes and serum HIF-1α protein levels were significantly higher in the SS/RS patients compared to the healthy control group. Single-drug therapy significantly increased HIF-1α and HMOX-1 mRNA expression in monocytes and serum HIF-1α protein levels in the SS/RS patients compared to those at the time of randomization, whereas combining PgE1 with an endothelin-1 blocker prevented the further increases in HIF-1α and HMOX-1 expression. We propose HIF-1α and HMOX-1 as novel markers for anti-ischemic therapy in RS.

Caffeic Acid Phenethyl Ester Rescues Pulmonary Arterial Hypertension through the Inhibition of AKT/ERK-Dependent PDGF/HIF-1α In Vitro and In Vivo

Pulmonary arterial hypertension (PAH) is characterized by pulmonary arterial proliferation and remodeling, resulting in a specific increase in right ventricle systolic pressure (RVSP) and, ultimately right ventricular failure. Recent studies have demonstrated that caffeic acid phenethyl ester (CAPE) exerts a protective role in NF-κB-mediated inflammatory diseases. However, the effect of CAPE on PAH remains to be elucidated. In this study, monocrotaline (MCT) was used to establish PAH in rats. Two weeks after the induction of PAH by MCT, CAPE was administrated by intraperitoneal injection once a day for two weeks. Pulmonary hemodynamic measurements and pulmonary artery morphological assessments were examined. Our results showed that administration of CAPE significantly suppressed MCT-induced vascular remodeling by decreasing the HIF-1α expression and PDGF-BB production, and improved in vivo RV systolic performance in rats. Furthermore, CAPE inhibits hypoxia- and PDGF-BB-induced HIF-1α expression by decreasing the activation of the AKT/ERK pathway, which results in the inhibition of human pulmonary artery smooth muscle cells (hPASMCs) proliferation and prevention of cells resistant to apoptosis. Overall, our data suggest that HIF-1α is regarded as an alternative target for CAPE in addition to NF-κB, and may represent a promising therapeutic agent for the treatment of PAH diseases.

Angiogenesis in Pancreatic Cancer: Pre-Clinical and Clinical Studies

Angiogenesis is a crucial event in tumor development and progression, occurring by different mechanisms and it is driven by pro- and anti-angiogenic molecules. Pancreatic cancer vascularization is characterized by a high microvascular density, impaired microvessel integrity and poor perfused vessels with heterogeneous distribution. In this review article, after a brief introduction on pancreatic cancer classification and on angiogenesis mechanisms involved in its progression, the pre-clinical and clinical trials conducted in pancreatic cancer treatment using anti-angiogenic inhibitors will be described. Finally, we will discuss the anti-angiogenic therapy paradox between the advantage to abolish vessel supply to block tumor growth and the disadvantage due to reduction of drug delivery at the same time. The purpose is to identify new anti-angiogenic molecules that may enhance treatment regimen.

Glycolysis Regulates Human Embryonic Stem Cell Self-Renewal under Hypoxia through HIF-2α and the Glycolytic Sensors CTBPs

Glycolysis and hypoxia are key regulators of human embryonic stem cell (hESC) self-renewal, but how changes in metabolism affect gene expression is poorly understood. C-terminal binding proteins (CTBPs) are glycolytic sensors that through NADH binding link the metabolic state of the cell to its gene expression, by acting as transcriptional corepressors, or coactivators. However, the role of CTBPs in hESCs has not previously been investigated. A direct interaction between hypoxia-inducible factor 2α (HIF-2α) and the CTBP proximal promoters in hESCs cultured only under hypoxia was demonstrated. Decreasing the rate of flux through glycolysis in hESCs maintained under hypoxia resulted in a reduction of CTBPs, OCT4, SOX2, and NANOG, but also in the expression of HIF-2α. Silencing CTBP expression resulted in the loss of pluripotency marker expression demonstrating that CTBPs are involved in hESC maintenance. These data suggest that under hypoxia, glycolysis regulates self-renewal through HIF-2α and the induction of the metabolic sensors CTBPs.

VEGF in Signaling and Disease: Beyond Discovery and Development

The discovery of vascular endothelial-derived growth factor (VEGF) has revolutionized our understanding of vasculogenesis and angiogenesis during development and physiological homeostasis. Over a short span of two decades, our understanding of the molecular mechanisms by which VEGF coordinates neurovascular homeostasis has become more sophisticated. The central role of VEGF in the pathogenesis of diverse cancers and blinding eye diseases has also become evident. Elucidation of the molecular regulation of VEGF and the transformative development of multiple therapeutic pathways targeting VEGF directly or indirectly is a powerful case study of how fundamental research can guide innovation and translation. It is also an elegant example of how agnostic discovery and can transform our understanding of human disease. This review will highlight critical nodal points in VEGF biology, including recent developments in immunotherapy for cancer and multitarget approaches in neovascular eye disease.

Effects of dietary supplementation of DL-2-hydroxy-4(methylthio) butanoic acid on antioxidant capacity and its related gene expression in lung and liver of broilers exposed to low temperature

DL-2-hydroxy-4(methylthio) butanoic acid (DL-HMTBA) exhibits a higher antioxidant capability in vitro as compared to DL-Met, but the mechanism is still not known. A total of 400 8-day-old broiler chicks were allotted to a 2 [low (12 to 14°C) vs. control temperature (thermoneutral, 24 to 26°C)] × 2 (0.17% or 0.51% of DL-HMTBA) factorial arrangement to investigate effects of DL-HMTBA on antioxidant capacity and its related gene expression in lung and liver of broilers exposed to low temperature. The hepatic glutathione (GSH), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activities were decreased, whereas protein carbonyl and malodndialdehyde contents in lung were increased in low temperature (P < 0.05). Dietary supplementation of 0.51% DL-HMTBA increased (P < 0.05) GSH and GSH-Px activity in liver and SOD activity in lung in spite of the temperature. The greater gene expression of GSH reductase and lower expression of GSH synthetase (P < 0.01) were observed in lung of broilers that were maintained at low temperature. Higher DL-HMTBA supplementation induced greater (P < 0.05) mRNA expression of glutathione-S transferase in lung, GSH synthetase in liver and lung, as well as lower expression of GSH reductase in lung, and this effect were more obvious for the chicks exposed to low temperature (interaction, P < 0.05). Chicks that were maintained under low temperature had the lower expression of cystathionine β-synthase (CβS), whereas those fed 0.51% DL-HMTBA increased the CβS expression in liver under low temperature (interaction, P ≤ 0.05). The γ-glutamylcysteine synthetase and Met adenosyltransferase 1 (MAT1) gene expression were downregulated (P < 0.05) by low temperature and the higher (P = 0.02) expression of MAT1 was observed in lung of chicks fed 0.51% DL-HMTBA. It indicated that under low temperature, DL-HMTBA supplementation at 0.51% upregulated gene expression of GSH synthesis and Met transsulfuration pathway in liver and lung to increase the antioxidant capacity, and then mitigate the negative effects of cold stress for broilers.

MicroRNAs, Hypoxia and the Stem-Like State as Contributors to Cancer Aggressiveness

MicroRNAs (miRNAs) are small non-coding RNA molecules that play key regulatory roles in cancer acting as both oncogenes and tumor suppressors. Due to their potential roles in improving cancer prognostic, predictive, diagnostic and therapeutic approaches, they have become an area of intense research focus in recent years. Several studies have demonstrated an altered expression of several miRNAs under hypoxic condition and even shown that the hypoxic microenvironment drives the selection of a more aggressive cancer cell population through cellular adaptations referred as the cancer stem-like cell. These minor fractions of cells are characterized by their self-renewal abilities and their ability to maintain the tumor mass, suggesting their crucial roles in cancer development. This review aims to highlight the interconnected role between miRNAs, hypoxia and the stem-like state in contributing to the cancer aggressiveness as opposed to their independent contributions, and it is based in four aggressive tumors, namely glioblastoma, cervical, prostate, and breast cancers.

A bioinformatics study on characteristics, metabolic pathways, and cellular functions of the identified S-nitrosylated proteins in postmortem pork muscle

This study aimed to determine the characteristics, metabolic pathways and cellular functions of S-nitrosylated proteins from pork postmortem muscle using bioinformatics analysis. The results showed that S-nitrosylated proteins had a broad range of molecular weight and pI value and were mainly located in the functional region of secondary structure. The motif revealed the lysine (K) positioned at -5, -7, +1 and +5 through the S-nitrosocysteine while "C-X-X-C" was identified as the motif for non-S-nitrosylation-modified cysteine. The proteins were widely localized in cell compartments and mostly belonged to enzymes participating in the metabolic process. Glycolysis was the most significant pathways of S-nitrosylated proteins in postmortem muscle. The cell death of muscle cells was predicted to be inhibited by S-nitrosylation with the potential influence on the apoptosis. Those identified pathways and cellular functions of S-nitrosylation are proposed to have a profound influence on meat quality and should be highly regarded.

Renal effects of exendin-4 in an animal model of brain death

Organ transplantation is the gold standard therapy for the majority of patients with terminal organ failure. However, it is still a limited treatment especially due to the low number of brain death (BD) donors in relation to the number of waiting list recipients. Strategies to increase the quantity and quality of donor organs have been studied, and the administration of exendin-4 (Ex-4) to the donor may be a promising approach. Male Wistar rats were randomized into 3 groups: (1) control, without central nervous system injury; (2) BD induced experimentally, and (3) BD induced experimentally + Ex-4 administered immediately after BD induction. After BD induction, animals were monitored for 6 h before blood collection and kidney biopsy. Kidney function was assessed by biochemical quantification of plasma kidney markers. Gene and protein expressions of inflammation- and stress-related genes were evaluated by RT-qPCR and immunoblot analysis. Animals treated with Ex-4 had lower creatinine and urea levels compared with controls. BD induced oxidative stress in kidney tissue through increased expression of Ucp2, Sod2 and Inos, and Ex-4 administration reduced the expression of these genes. Ex-4 also induced increased expression of the anti-apoptotic Bcl2 gene. Nlrp3 and Tnf expressions were up-regulated in the BD group compared with controls, but Ex-4 treatment had no effect on these genes. Our findings suggest that Ex-4 administration in BD rats reduces BD-induced kidney damage by decreasing the expression of oxidative stress genes and increasing the expression of Bcl2.

Oncogenic kinases and perturbations in protein synthesis machinery and energetics in neoplasia

Notwithstanding that metabolic perturbations and dysregulated protein synthesis are salient features of cancer, the mechanism underlying coordination of cellular energy balance with mRNA translation (which is the most energy consuming process in the cell) is poorly understood. In this review, we focus on recently emerging insights in the molecular underpinnings of the cross-talk between oncogenic kinases, translational apparatus and cellular energy metabolism. In particular, we focus on the central signaling nodes that regulate these processes (e.g. the mechanistic/mammalian target of rapamycin MTOR) and the potential implications of these findings on improving the anti-neoplastic efficacy of oncogenic kinase inhibitors.

Holo-Lactoferrin Modified Liposome for Relieving Tumor Hypoxia and Enhancing Radiochemotherapy of Cancer

Hypoxic microenvironments in the solid tumor play a negative role in radiotherapy. Holo-lactoferrin (holo-Lf) is a natural protein, which acts as a potential ligand of transferrin receptor (TfR). In this work, an anticancer drug, doxorubicin (Dox)-loaded liposome-holo-Lf nanocomposites, is developed for tumor targeting and imaging guided combined radiochemotherapy. Dox-loaded liposome-holo-Lf (Lf-Liposome-Dox) nanocomposites exhibit significant cellular uptake likely owing to the TfR receptor-mediated targeting accumulation of Lf-Liposome-Dox nanocomposites. Additionally, the nanocomposites exhibit high accumulation in the tumor site after intravenous injection as evidenced from in vivo fluorescence imaging. More importantly, it is found that the holo-Lf has the ability to catalyze the conversion of hydrogen peroxide (H₂ O₂ ) to oxygen for relieving the tumor hypoxic microenvironment. Photoacoustic imaging further confirms the abundant generation of oxygen in the presence of Lf-Liposome-Dox nanocomposites. Based on these findings, in vivo combined radiochemotherapy is performed using Lf-Liposome-Dox as therapeutic agent, achieving excellent cancer treatment effect. The study further promotes the potential biomedical application of holo-Lf in cancer treatment.

Targeting JUN, CEBPB, and HDAC3: A Novel Strategy to Overcome Drug Resistance in Hypoxic Glioblastoma

Hypoxia is a predominant feature in glioblastoma (GBM) and contributes greatly to its drug resistance. However, the molecular mechanisms which are responsible for the development of the resistant phenotype of GBM under hypoxic conditions remain unclear. To analyze the key pathways promoting therapy resistance in hypoxic GBM, we utilized the U87-MG cell line as a human GBM cell model and the human brain HEB cell line as a non-neoplastic brain cell model. These cell lines were cultured in the presence of 21, 5, and 1% O2 for 24 h. We detected the changes in transcriptional profiling and analyzed the biological processes and functional interactions for the genes with different expression levels under different hypoxia conditions. The results indicated that those alterations of U87-MG cells presented specific transcriptional signature in response to diverse hypoxia levels. Gene ontology analysis revealed that the genes related to the DNA replication and cell cycle were suppressed, while the genes involved in tissue and system development to promote cancer development were activated following hypoxia. Moreover, functional interaction analysis suggested that the epigenetic regulator HDAC3 and the transcriptional factors CEBPB and JUN played a central role in organ and system developmental process pathway. Previous studies reported the global alterations caused by activation of HDAC3, CEBPB, and JUN could form the molecular basis of the resistance to chemotherapy and radiation therapy of hypoxic GBM. In our study, the significant growth inhibitory effect of temozolomide on hypoxic GBM cells could be promoted under downregulation of these genes. The experiment suggested that HDAC3, CEBPB, and JUN were closely involved in the drug-resistance phenotype of hypoxic GBM. In summary, we profiled the hypoxia-dependent changes in the transcriptome of the U87-MG cell line and the human brain cell line HEB to identify the transcriptional signatures of U87-MG cells and elucidate the role of hypoxia in the drug-resistant phenotype of GBM. Furthermore, we identified three key genes and explored their important roles in the drug resistance of hypoxic GBM.

Molecular Characterization of Hypoxic Alveolar Epithelial Cells After Lung Contusion Indicates an Important Role for HIF-1α

OBJECTIVE

To understand the fate and regulation of hypoxic type II alveolar epithelial cells (AECs) after lung contusion (LC).

BACKGROUND

LC due to thoracic trauma is a major risk factor for the development of acute respiratory distress syndrome. AECs have recently been implicated as a primary driver of inflammation in LC. The main pathological consequence of LC is hypoxia, and a key mediator of adaptation to hypoxia is hypoxia-inducible factor (HIF)-1. We have recently published that HIF-1α is a major driver of acute inflammation after LC through type II AEC.

METHODS

LC was induced in wild-type mice (C57BL/6), luciferase-based hypoxia reporter mice (ODD-Luc), and HIF-1α conditional knockout mice. The degree of hypoxia was assessed using hypoxyprobe and in vivo imaging system. The fate of hypoxic AEC was evaluated by luciferase dual staining with caspases-3 and Ki-67, terminal deoxynucleotidyl transferase dUTP nick end labeling, and flow cytometry with ApoStat. NLRP-3 expression was determined by western blot. Laser capture microdissection was used to isolate AECs in vivo, and collected RNA was analyzed by Q-PCR for HIF-related pathways.

RESULTS

Global hypoxia was present after LC, but hypoxic foci were not uniform. Hypoxic AECs preferentially undergo apoptosis. There were significant reductions in NLRP-3 in HIF-1α conditional knockout mice. The expression of proteins involved in HIF-related pathways and inflammasome activation were significantly increased in hypoxic AECs.

CONCLUSIONS

These are the first in vivo data to identify, isolate, and characterize hypoxic AECs. HIF-1α regulation through hypoxic AECs is critical to the initiation of acute inflammation after LC.

Preparation and evaluation of trityl-loaded lipid nanocapsules as oxygen sensors for electron paramagnetic resonance oximetry

Oxygen is essential in physiology and pathophysiology. Electron paramagnetic resonance (EPR) oximetry, using oxygen sensitive paramagnetic materials, could be attractive for measuring oxygen in tissues. The aim of the present study was to assess the properties of lipid nanocapsules (LNCs) loaded with the nitroxide tempo-benzoate (TB) or tetrathiatriarylmethyl (TAM) radicals. LNCs loaded with the EPR probes were successfully prepared by the phase inversion process leading to nanocapsules of about 60 nm. LNCs protected the TB radical against reduction in vitro. The calibration of the EPR line width (LW) as a function of the pO2 showed a two-fold increase in sensitivity with TAM-LNC compared to hydrophilic trityl radical. The TAM-LNCs were evaluated in vivo. Contrarily to unencapsulated TAM, for which a rapid decrease in EPR signal was observed, the half-life of TAM-LNCs administered in muscles or in tumours exceeded an hour. Carbogen-challenges in mice demonstrated that the TAM-LNCs responded well to changes in oxygen environment. However, the apparent pO2 values acquired were higher than the expected physiological values. These results warrant further investigation in the formulation of stable nano-objects encapsulating EPR oxygen sensitive probes.

Hypoxia Mimetic Agents for Ischemic Stroke

Every year stroke claims more than 6 million lives worldwide. The majority of them are ischemic stroke. Small molecule-based therapeutics for ischemic stroke has attracted a lot of attention, but none has been shown to be clinically useful so far. Hypoxia-inducible factor-1 (HIF-1) plays a crucial role in the transcriptional adaptation of cells to hypoxia. Small molecule-based hypoxia-mimetic agents either stabilize HIF-1α via HIF-prolyl hydroxylases (PHDs) inhibition or through other mechanisms. In both the cases, these agents have been shown to confer ischemic neuroprotection in vitro and in vivo. The agents which act via PHD inhibition are mainly classified into iron chelators, iron competitors, and 2 oxoglutarate (2OG) analogs. This review discusses HIF structure and key players in the HIF-1 degradation pathway as well as the genes, proteins and chemical molecules that are connected to HIF-1 and how they affect cell survival following ischemic injury. Furthermore, this review gives a summary of studies that used PHD inhibitors and other HIF-1α stabilizers as hypoxia-mimetic agents for the treatment of ischemic injury.

Molecular switch model for cardiomyocyte proliferation

This review deals with the human adult cardiomyocyte proliferation as a potential source for heart repair after injury. The mechanism to regain the proliferative capacity of adult cardiomyocytes is a challenge. However, recent studies are promising in showing that the ‘locked’ cell cycle of adult cardiomyocytes could be released through modulation of cell cycle checkpoints. In support of this are the signaling pathways of Notch, Hippo, Wnt, Akt and Jak/Stat that facilitate or inhibit the transition at cell cycle checkpoints. Cyclins and cyclin dependant kinases (CDKs) facilitate this transition which in turn is regulated by inhibitory action of pocket protein e.g. p21, p27 and p57. Transcription factors e.g. E2F, GATA4, TBx20 up regulate Cyclin A, A2, D, E, and CDK4 as promoters of cell cycle and Meis-1 and HIF-1 alpha down regulate cyclin D and E to inhibit the cell cycle. Paracrine factors like Neuregulin-1, IGF-1 and Oncostatin M and Extracellular Matrix proteins like Agrin have been involved in cardiomyocyte proliferation and dedifferentiation processes.

A molecular switch model is proposed that transforms the post mitotic cell into an actively dividing cell. This model shows how the cell cycle is regulated through on- and off switch mechanisms through interaction of transcription factors and signaling pathways with proteins of the cell cycle checkpoints. Signals triggered by injury may activate the right combination of the various pathways that can ‘switch on’ the proliferation signals leading to myocardial regeneration.

Delayed Remote Ischemic Preconditioning ConfersRenoprotection against Septic Acute Kidney Injury via Exosomal miR-21

Sepsis is a common and life-threatening systemic disorder, often leading to acute injury of multiple organs. Here, we show that remote ischemic preconditioning (rIPC), elicited by brief episodes of ischemia and reperfusion in femoral arteries, provides protective effects against sepsis-induced acute kidney injury (AKI).

Methods: Limb rIPC was conducted on mice in vivo 24 h before the onset of cecal ligation and puncture (CLP), and serum exosomes derived from rIPC mice were infused into CLP-challenged recipients. In vitro, we extracted and identified exosomes from differentiated C2C12 cells (myotubes) subjected to hypoxia and reoxygenation (H/R) preconditioning, and the exosomes were administered to lipopolysaccharide (LPS)-treated mouse tubular epithelial cells (mTECs) or intravenously injected into CLP-challenged miR-21 knockout mice for rescue experiments.

Results: Limb rIPC protected polymicrobial septic mice from multiple organ dysfunction, systemic accumulation of inflammatory cytokines and accelerated parenchymal cell apoptosis through upregulation of miR-21 in a hypoxia-inducible factor 1α (HIF-1α)-dependent manner in the ischemic limbs of mice. However, in miR-21 knockout mice or mice that received HIF-1α siRNA injection into hind limb muscles, the organ protection conferred by limb rIPC was abolished. Mechanistically, we discovered that miR-21 was transported from preischemic limbs to remote organs via serum exosomes. In kidneys, the enhanced exosomal miR-21 derived from cultured myotubes with H/R or the serum of mice treated with rIPC integrated into renal tubular epithelial cells and then targeted the downstream PDCD4/NF-κB and PTEN/AKT pathways, exerting anti-inflammatory and anti-apoptotic effects and consequently attenuating sepsis-induced renal injury both in vivo and in vitro.

Conclusion: This study demonstrates a critical role for exosomal miR-21 in renoprotection conferred by limb rIPC against sepsis and suggests that rIPC and exosomes might serve as the possible therapeutic strategies for sepsis-induced kidney injury.

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.

Hypoxia-Activated, Small-Molecule-Induced Gene Expression

Hypoxia, a condition of reduced oxygen, occurs in a wide variety of biological contexts, including solid tumors and bacterial biofilms, which are relevant to human health. Consequently, the development of chemical tools to study hypoxia is vital. Here we report a hypoxia-activated, small-molecule-mediated gene expression system using a bioreductive prodrug of the inducer isopropyl 1-thio-β-d-galactopyranoside. As a proof-of-concept we have placed the production of a green fluorescent protein under the control of hypoxia. Our system has the potential to be extended to regulate the production of any given protein of choice.

Isoliquiritin Apioside Suppresses in vitro Invasiveness and Angiogenesis of Cancer Cells and Endothelial Cells

Several components isolated from Glycyrrhizae radix rhizome (GR), including glycyrrhizin, liquiritin, and liquiritigenin, have been shown to induce cancer cell death and inhibit cancer metastasis. Isoliquiritin apioside (ISLA), a component isolated from GR, has been effective for treating tetanic contraction and genotoxicity. However, the effects of ISLA on the metastasis and angiogenesis of malignant cancer cells and endothelial cells (ECs) have not been reported. In this study, we found that up to 100 μM ISLA did not affect cell proliferation but efficiently suppressed the metastatic ability of HT1080 cells, as assessed by scratch-wound migration, Transwell^® migration, scratch-wound invasion, Transwell^® invasion, and three-dimensional spheroid invasion. ISLA significantly decreased phorbol 12-myristate 13-acetate (PMA)-induced increases in matrix metalloproteinase (MMP) activities and suppressed PMA-induced activation of mitogen-activated protein kinase as well as NF-κB, which are involved in cancer metastasis. In addition, ILSA treatment reduced the production of pro-angiogenic factors in HT1080 cells, including MMP-9, placental growth factor, and vascular endothelial growth factor under normoxia as well as hypoxia conditions, by impairing the hypoxia-inducible factor-1α pathway. We also found that the abilities of human umbilical vein ECs to migrate across the Transwell^® and to form tube-like structures were significantly reduced by ISLA treatment. Moreover, using the chorioallantoic membrane assay, vessel formation with or without vascular endothelial growth factor was significantly suppressed by ISLA. These results suggested that ISLA possesses anti-metastatic and anti-angiogenic abilities in malignant cancer cells and ECs, with no cytotoxicity. ISLA may therefore be a safe and effective lead compound to develop anti-cancer drug for limiting the spread of primary tumors to distant organs to form secondary tumors.

Hypoxia-Inducible Factor 1 alpha (HIF-1α)/Vascular Endothelial Growth Factor (VEGF) Pathway Participates in Angiogenesis of Myocardial Infarction in Muscone-Treated Mice: Preliminary Study

BACKGROUND Angiogenesis plays a crucial role in myocardial infarction (MI) treatment by ameliorating myocardial remodeling, thus improving cardiac function and preventing heart failure. Muscone has been reported to have beneficial effects on cardiac remodeling in MI mice. However, the effects of muscone on angiogenesis in MI mice and its underlying mechanisms remain unknown. MATERIAL AND METHODS Mice were randomly divided into sham, MI, and MI+muscone groups. The MI mouse model was established by ligating the left anterior descending coronary artery. Mice in the sham group received the same procedure except for ligation. Mice were administered muscone or an equivalent volume of saline for 4 consecutive weeks. Cardiac function was evaluated by echocardiograph after MI for 2 and 4 weeks. Four weeks later, all mice were sacrificed and Masson's trichrome staining was used to assess myocardial fibrosis. Isolectin B4 staining was applied to evaluate the angiogenesis in mouse hearts. Immunohistochemistry, Western blot analysis, and quantitative real-time polymerase chain reaction (qPCR) were performed to analyze expression levels of HIF-1a and its downstream genes. RESULTS Compared with the MI group, muscone treatment significantly improved cardiac function and reduced myocardial fibrosis. Moreover, muscone enhanced angiogenesis in the peri-infarct region and p-VEGFR2 expression in the vascular endothelial cells. Western blot analysis and qPCR showed that muscone upregulated expression levels of HIF-1a and VEGFA. CONCLUSIONS Muscone improved cardiac function in MI mice through augmented angiogenesis. The potential mechanism of muscone treatment in regulating angiogenesis of MI mice was upregulating expression levels of HIF-1α and VEGFA.

Pan-cancer characterisation of microRNA across cancer hallmarks reveals microRNA-mediated downregulation of tumour suppressors

microRNAs are key regulators of the human transcriptome across a number of diverse biological processes, such as development, aging and cancer, where particular miRNAs have been identified as tumour suppressive and oncogenic. In this work, we elucidate, in a comprehensive manner, across 15 epithelial cancer types comprising 7316 clinical samples from the Cancer Genome Atlas, the association of miRNA expression and target regulation with the phenotypic hallmarks of cancer. Utilising penalised regression techniques to integrate transcriptomic, methylation and mutation data, we find evidence for a complex map of interactions underlying the relationship of miRNA regulation and the hallmarks of cancer. This highlighted high redundancy for the oncomiR-1 cluster of oncogenic miRNAs, in particular hsa-miR-17-5p. In addition, we reveal extensive miRNA regulation of tumour suppressor genes such as PTEN, FAT4 and CDK12, uncovering an alternative mechanism of repression in the absence of mutation, methylation or copy number changes.