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

Hypoxia and extracellular vesicles: A review on methods, vesicular cargo and functions

Hypoxia is an essential hallmark of several serious diseases such as cardiovascular and metabolic disorders and cancer. A decline in the tissue oxygen level induces hypoxic responses in cells which strive to adapt to the changed conditions. A failure to adapt to prolonged or severe hypoxia can trigger cell death. While some cell types, such as neurons, are highly vulnerable to hypoxia, cancer cells take advantage of a hypoxic environment to undergo tumour growth, angiogenesis and metastasis. Hypoxia-induced processes trigger complex intercellular communication and there are now indications that extracellular vesicles (EVs) play a fundamental role in these processes. Recent developments in EV isolation and characterization methodology have increased the awareness of the importance of EV purity in functional and cargo studies. Cell death, a hallmark of severe hypoxia, is a known source of intracellular contaminants in isolated EVs. In this review, methodological aspects of studies investigating hypoxia-induced EVs are critically evaluated. Key concerns and gaps in the current knowledge are highlighted and future directions for studies are set. To accelerate and advance research, an in-depth analysis of the functions and cargo of hypoxic EVs, compared to normoxic EVs, is provided with the focus on the altered microRNA contents of the EVs.

Hypoxia-inducible factor 2 alpha impairs human cytotrophoblast syncytialization: New insights into placental dysfunction and fetal growth restriction

Insufficient remodeling of uterine arteries causes pregnancy-related diseases, including fetal growth restriction and preeclampsia. In these situations, reduced maternal blood flow in the placenta is thought to be responsible for the persistence of a low oxygen environment throughout pregnancy. We hypothesized that chronic activation of transcription factors hypoxia-inducible factors (HIFs) actively participates in placental underdevelopment, which impairs fetal growth. The computer-assisted analysis in pathological placentas revealed an increased number of HIF-2α-positive nuclei in the syncytium compared to normal human placentas, while HIF-1α stabilization was unchanged. Specific involvement of HIF-2α was confirmed in primary human cytotrophoblasts rendered deficient for HIF1A or HIF2A. Silencing HIF2A increased the expression of main syncytialization markers as well as differentiation and syncytium formation. It also improved placental growth factor bioavailability. None of these changes was seen when silencing HIF1A. Conversely, the experimental induction of HIF-2α expression repressed forskolin-induced differentiation in BeWo choriocarcinoma cells. Our mechanistic insights evidence that transcription factor HIF-2α impairs placental function, thus suggesting its participation in fetal growth restriction and preeclampsia when placentas become chronically hypoxic. Furthermore, it suggests the possibility to develop novel molecular targeting therapies for placental dysfunction.

Correcting Smad1/5/8, mTOR, and VEGFR2 treats pathology in hereditary hemorrhagic telangiectasia models

Hereditary hemorrhagic telangiectasia (HHT), a genetic bleeding disorder leading to systemic arteriovenous malformations (AVMs), is caused by loss-of-function mutations in the ALK1/ENG/Smad1/5/8 pathway. Evidence suggests that HHT pathogenesis strongly relies on overactivated PI3K/Akt/mTOR and VEGFR2 pathways in endothelial cells (ECs). In the BMP9/10-immunoblocked (BMP9/10ib) neonatal mouse model of HHT, we report here that the mTOR inhibitor, sirolimus, and the receptor tyrosine kinase inhibitor, nintedanib, could synergistically fully block, but also reversed, retinal AVMs to avert retinal bleeding and anemia. Sirolimus plus nintedanib prevented vascular pathology in the oral mucosa, lungs, and liver of the BMP9/10ib mice, as well as significantly reduced gastrointestinal bleeding and anemia in inducible ALK1-deficient adult mice. Mechanistically, in vivo in BMP9/10ib mouse ECs, sirolimus and nintedanib blocked the overactivation of mTOR and VEGFR2, respectively. Furthermore, we found that sirolimus activated ALK2-mediated Smad1/5/8 signaling in primary ECs - including in HHT patient blood outgrowth ECs - and partially rescued Smad1/5/8 activity in vivo in BMP9/10ib mouse ECs. These data demonstrate that the combined correction of endothelial Smad1/5/8, mTOR, and VEGFR2 pathways opposes HHT pathogenesis. Repurposing of sirolimus plus nintedanib might provide therapeutic benefit in patients with HHT.

Plasma expression of HIF-1α as novel biomarker for the diagnosis of obstructive sleep apnea-hypopnea syndrome

Background

Obstructive sleep apnea‐hypopnea syndrome (OSAHS) is a common breathing disorder during sleep with potential lethality and multi‐complications. Polysomnography (PSG) is now the golden standard for the diagnosis obstructive sleep apnea‐hypopnea syndrome. However, PSG is expensive and time‐consuming. Therefore, it is important to find inexpensive and convenient biomarkers for the diagnosis of OSAHS.

Objective

The present study aimed to explore the potential diagnostic value of HIF‐1α for OSAHS and its clinical significance.

Methods

This study consisted of 368 patients admitted to the sleep laboratory. The patients were classified according to their apnea‐hypopnea index (AHI) scores as OSA negative (AHI < 5), mild‐moderate (AHI:5‐30), and severe OSA (AHI > 30), and severe OSA treated with continuous positive airway pressure (CPAP). qRT‐PCR was used to detect mRNA levels in the plasma; Pearson's correlation analysis was performed to analyze the correlation of HIF‐1α mRNA level and the clinicopathological factors of OSAHS; ROC curve was constructed to evaluate the diagnostic value of HIF‐1α mRNA.

Results

HIF‐1α mRNA was significantly up‐regulated in the plasma of OSAHS patients, especially patients with severe OSAHS. HIF‐1α mRNA was positively correlated with the AHI and ODI but negatively correlated with the mean oxygen saturation in patients with OSAHS. Results of ROC curve showed that HIF‐1α is a sensitive biomarker for the diagnosis of OSAHS, especially severe OSAHS.

Conclusions

HIF‐1α mRNA might be used as s a convenient and inexpensive method for triaging OSAHS patients PSG assessment in the hospital and evaluate the curative effect.

Topical bendazol inhibits experimental myopia progression and decreases the ocular accumulation of HIF-1α protein in young rabbits

PURPOSE

To investigate the inhibitory effect of bendazol on form-deprivation myopia (FDM) in rabbits as well as the underlying biochemical processes.

METHODS

Forty-eight 3-week-old New Zealand white rabbits were randomly assigned to three groups: a control group, a form-deprivation (FD) group and an FD + bendazol group (treated with 1% bendazol in the FD eyes). Refraction, corneal curvature, vitreous chamber depth (VCD) and axial length (AL) were assessed using streak retinoscopy, keratometry, and A-scan ultrasonography, respectively. Eyeballs were enucleated for histological analysis, and ocular tissues were homogenized to determine the mRNA and protein expression of hypoxia-inducible factor-1α (HIF-1α) and muscarinic acetylcholine receptors (mAChRs).

RESULTS

Bendazol inhibited the progression of FDM and suppressed the upregulation of HIF-1α. At week 6, in the control, FD and FD + bendazol groups, the refraction values were 1.38 ± 0.43, 0.03 ± 0.47 and 1.25 ± 0.35 D, respectively (p < 0.001); the ALs were 13.91 ± 0.11, 14.15 ± 0.06 and 13.97 ± 0.10 mm, respectively (p < 0.001) and the VCDs were 6.56 ± 0.06, 6.69 ± 0.07 and 6.61 ± 0.06 mm, respectively (p < 0.001). HIF-1α was upregulated in FD eyes but downregulated in FD + bendazol eyes, while the mAChRs were the opposite.

CONCLUSIONS

In the FD rabbit model, bendazol significantly inhibits the development of myopia and downregulates HIF-1α expression, which may provide a novel therapeutic approach for myopia control.

Host-Directed Therapy in Tuberculosis: Targeting Host Metabolism

Mycobacterium tuberculosis (Mtb) has complex and intricate interactions with host immune cells. Mtb can survive, persist, and grow within macrophages and thereby circumvent detection by the innate immune system. Recently, the field of immunometabolism, which focuses on the link between metabolism and immune function, has provided us with an improved understanding of the role of metabolism in modulating immune function. For example, host immune cells can switch from oxidative phosphorylation to glycolysis in response to infection, a phenomenon known as the Warburg effect. In this state, immune cells are capable of amplifying production of both antimicrobial pro-inflammatory mediators that are critical for the elimination of bacteria. Also, cells undergoing the Warburg effect upregulate production of nitric oxide augment the synthesis of bioactive lipids. In this review, we describe our current understanding of the Warburg effect and discuss its role in promoting host immune responses to Mtb. In most settings, immune cells utilize the Warburg effect to promote inflammation and thereby eliminate invading bacteria; interestingly, Mtb exploits this effect to promote its own survival. A better understanding of the dynamics of metabolism within immune cells together with the specific features that contribute to the pathogenesis of tuberculosis (TB) may suggest potential host-directed therapeutic targets for promoting clearance of Mtb and limiting its survival in vivo.

When It Comes to an End: Oxidative Stress Crosstalk with Protein Aggregation and Neuroinflammation Induce Neurodegeneration

Neurodegenerative diseases are characterized by a progressive loss of neurons in the brain or spinal cord that leads to a loss of function of the affected areas. The lack of effective treatments and the ever-increasing life expectancy is raising the number of individuals affected, having a tremendous social and economic impact. The brain is particularly vulnerable to oxidative damage given the high energy demand, low levels of antioxidant defenses, and high levels of metal ions. Driven by age-related changes, neurodegeneration is characterized by increased oxidative stress leading to irreversible neuronal damage, followed by cell death. Nevertheless, neurodegenerative diseases are known as complex pathologies where several mechanisms drive neuronal death. Herein we discuss the interplay among oxidative stress, proteinopathy, and neuroinflammation at the early stages of neurodegenerative diseases. Finally, we discuss the use of the Nrf2-ARE pathway as a potential therapeutic strategy based on these molecular mechanisms to develop transformative medicines.

Tumor Microenvironment in Ovarian Cancer: Function and Therapeutic Strategy

Ovarian cancer is one of the leading causes of death in patients with gynecological malignancy. Despite optimal cytoreductive surgery and platinum-based chemotherapy, ovarian cancer disseminates and relapses frequently, with poor prognosis. Hence, it is urgent to find new targeted therapies for ovarian cancer. Recently, the tumor microenvironment has been reported to play a vital role in the tumorigenesis of ovarian cancer, especially with discoveries from genome-, transcriptome- and proteome-wide studies; thus tumor microenvironment may present potential therapeutic target for ovarian cancer. Here, we review the interactions between the tumor microenvironment and ovarian cancer and various therapies targeting the tumor environment.

Antianemia Drug Roxadustat (FG-4592) Protects Against Doxorubicin-Induced Cardiotoxicity by Targeting Antiapoptotic and Antioxidative Pathways

Doxorubicin (DOX) is broadly used in treating various malignant tumors. However, its cardiotoxicity limits its clinical use. Roxadustat (FG-4592) is a new hypoxia-inducible factor prolyl hydroxylase (HIF-PHD) inhibitor and has been approved for treating anemia in chronic kidney diseases (CKD) patients. However, the role of FG-4592 in DOX-induced cardiotoxicity remains unknown. In this study, mouse cardiac function was evaluated by echocardiography, plasma LDH/CK-MB, and heart HE staining. Cell viability, apoptosis, oxidative stress, inflammation, and HIF-target genes were evaluated in mouse cardiac tissue and cardiac cells exposed to DOX with FG-4592 pretreatment. DOX-sensitive HepG2 and MCF-7 cell lines were used to evaluate FG-4592 effect on the anticancer activity of DOX. We found that FG-4592 alleviated DOX-induced cardiotoxicity shown by the protection against cardiac dysfunction, cardiac apoptosis, and oxidative stress without the effect on inflammatory response. FG-4592 alone did not change the cardiac function, cardiomyocyte morphology, oxidative stress, and inflammation in vivo. FG-4592 could protect cardiomyocytes against DOX-induced apoptosis and ROS production in line with the upregulation of HIF-1α and its target genes of Bcl-2 and SOD2. Importantly, FG-4592 displayed anticancer property in cancer cells treated with or without DOX. These findings highlighted the protective effect of FG-4592 on DOX-induced cardiotoxicity possibly through upregulating HIF-1α and its target genes antagonizing apoptosis and oxidative stress.

Dysregulation of hypoxia-inducible factor-1α (Hif1α) expression in the Hmox1-deficient placenta

Introduction

Severe hypoxia exists in placentas during early pregnancy, with reoxygenation during mid-gestation. Hypoxia-inducible factor-1α (Hif1α), an oxygen sensor, initiates placental vascular development. We have shown that the placental vasculature in Hmox1-deficient (Hmox1^+/−, Het) pregnancies is impaired, with morphological defects similar to Hif1α-deficient placentas.

Materials and methods

Whole wild-type (WT) and Het mouse placentas were collected at E8.5 (1%–3% O₂) and E9.5–15.5 (8%–10% O₂). mRNA levels were determined using real-time RT-PCR or PCR arrays and protein levels using Western blot. Bone marrow-derived macrophages (BMDMs) from WT, Het, and Hmox1 knockout (KO) mice, representing different Hmox1 cellular levels, were generated to study the role of Hmox1 on Hif1α ′s response to hypoxia-reoxygenation and gestational age-specific placental lysates.

Results

Hif1α was expressed in WT and Het placentas throughout gestation, with protein levels peaking at E8.5 and mRNA levels significantly upregulated from E9.5–E13.5, but significantly lower in Het placentas. Genes associated with angiogenesis (Vegfa, Vegfr1, Mmp2, Cxcl12, Angpt1, Nos3), antioxidants (Sod1, Gpx1), and transcription factors (Ap2, Bach1, Nrf2) were significantly different in Het placentas. In response to in vitro hypoxia-reoxygenation and to WT or Het placental lysates, Hif1α transcription was lower in Het and Hmox1 KO BMDMs compared with WT BMDMs.

Discussion

These findings suggest that deficiencies in Hmox1 underlie the insufficient placental Hif1α response to hypoxia-reoxygenation during gestation and subsequently impair downstream placental vascular formation. Therefore, a dysregulation of Hif1α expression caused by any genetic defect or environmental influence in early pregnancy could be the root cause of pregnancy disorders.

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Expression of Hif1α in wild-type (WT) placentas is gestational age-dependent.

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Hif1α expression is reduced in Hmox1-deficient placentas.

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Expression of angiogenic genes is altered in Hmox1-deficient placentas.

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Hypoxia-reoxygenation induces a differential expression of Hif1α in cells.

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Adding placental lysates dysregulates expression of Hif1α in Hmox1-deficient cells.

Retinal Physiology and Circulation: Effect of Diabetes

In this article, we present a discussion of diabetes and its complications, including the macrovascular and microvascular effects, with the latter of consequence to the retina. We will discuss the anatomy and physiology of the retina, including aspects of metabolism and mechanisms of oxygenation, with the latter accomplished via a combination of the retinal and choroidal blood circulations. Both of these vasculatures are altered in diabetes, with the retinal circulation intimately involved in the pathology of diabetic retinopathy. The later stages of diabetic retinopathy involve poorly controlled angiogenesis that is of great concern, but in our discussion, we will focus more on several alterations in the retinal circulation occurring earlier in the progression of disease, including reductions in blood flow and a possible redistribution of perfusion that may leave some areas of the retina ischemic and hypoxic. Finally, we include in this article a more recent area of investigation regarding the diabetic retinal vasculature, that is, the alterations to the endothelial surface layer that normally plays a vital role in maintaining physiological functions. © 2020 American Physiological Society. Compr Physiol 10:933-974, 2020.

Physiology of the Endometrium and Regulation of Menstruation

The physiological functions of the uterine endometrium (uterine lining) are preparation for implantation, maintenance of pregnancy if implantation occurs, and menstruation in the absence of pregnancy. The endometrium thus plays a pivotal role in reproduction and continuation of our species. Menstruation is a steroid-regulated event, and there are alternatives for a progesterone-primed endometrium, i.e., pregnancy or menstruation. Progesterone withdrawal is the trigger for menstruation. The menstruating endometrium is a physiological example of an injured or “wounded” surface that is required to rapidly repair each month. The physiological events of menstruation and endometrial repair provide an accessible in vivo human model of inflammation and tissue repair. Progress in our understanding of endometrial pathophysiology has been facilitated by modern cellular and molecular discovery tools, along with animal models of simulated menses. Abnormal uterine bleeding (AUB), including heavy menstrual bleeding (HMB), imposes a massive burden on society, affecting one in four women of reproductive age. Understanding structural and nonstructural causes underpinning AUB is essential to optimize and provide precision in patient management. This is facilitated by careful classification of causes of bleeding. We highlight the crucial need for understanding mechanisms underpinning menstruation and its aberrations. The endometrium is a prime target tissue for selective progesterone receptor modulators (SPRMs). This class of compounds has therapeutic potential for the clinical unmet need of HMB. SPRMs reduce menstrual bleeding by mechanisms still largely unknown. Human menstruation remains a taboo topic, and many questions concerning endometrial physiology that pertain to menstrual bleeding are yet to be answered.

Hypoxia inducible factor-1α knockout does not impair acute thermal tolerance or heat hardening in zebrafish

The rapid increase in critical thermal maximum (CTmax) in fish (or other animals) previously exposed to critically high temperature is termed 'heat hardening', which likely represents a key strategy to cope with increasingly extreme environments. The physiological mechanisms that determine acute thermal tolerance, and the underlying pathways facilitating heat hardening, remain debated. It has been posited, however, that exposure to high temperature is associated with tissue hypoxia and may be associated with the increased expression of hypoxia-inducible factor-1 (Hif-1). We studied acute thermal tolerance in zebrafish (Danio rerio) lacking functional Hif-1α paralogs (Hif-1aa and Hif-1ab double knockout; Hif-1α-/-), which are known to exhibit markedly reduced hypoxia tolerance. We hypothesized that Hif-1α-/- zebrafish would suffer reduced acute thermal tolerance relative to wild type and that the heat hardening ability would be lost. However, on the contrary, we observed that Hif-1α-/- and wild-type fish did not differ in CTmax, and both genotypes exhibited heat hardening of a similar degree when CTmax was re-tested 48 h later. Despite exhibiting impaired hypoxia tolerance, Hif-1α-/- zebrafish display unaltered thermal tolerance, suggesting that these traits are not necessarily functionally associated. Hif-1α is accordingly not required for short-term acclimation in the form of heat hardening.

The Characteristics of Human iPS Cells and siRNA Transfection Under Hypoxia

The characteristics of pluripotent cells have great potential for basic and clinical research and application. We describe the effect of normoxia or hypoxia regarding the proliferation and pluripotency of human iPS cells using colony number counting and real-time polymerase chain reaction (PCR). In addition, the function of hypoxia-inducible factors (HIFs) in human iPS cells under hypoxic conditions is evaluated in relation to the expression of pluripotency markers by siRNA and real-time PCR. Furthermore, we introduce the change of HIF-2α expression when signal transducer and activator of transcription 3 (STAT3) is suppressed by its inhibitor, Stattic or S31 201, using RT-PCR.

Troxerutin attenuates oxygen‑glucose deprivation and reoxygenation‑induced oxidative stress and inflammation by enhancing the PI3K/AKT/HIF‑1α signaling pathway in H9C2 cardiomyocytes

Myocardial ischemia-reperfusion (MI/R) injury is a complex pathological process that occurs when tissues are reperfused following a prolonged period of ischemia. Troxerutin has been reported to have cardioprotective functions. However, the underlying mechanism by which troxerutin protects against MI/R injury has not been fully elucidated. The aim of the present study was to explore whether troxerutin-mediated protection against oxygen-glucose deprivation/reoxygenation (OGD/R)-induced H9C2 cell injury was associated with the inhibition of oxidative stress and the inflammatory response by regulating the PI3K/AKT/hypoxia-inducible factor-1α (HIF-1α) signaling pathway. The results of the present study suggested that troxerutin pretreatment prevented the OGD/R-induced reduction in cell viability, and the increase in lactate dehydrogenase activity and apoptosis. Troxerutin reversed OGD/R-induced the inhibition of the PI3K/AKT/HIF-1α signaling pathway as demonstrated by the increased expression of PI3K and HIF-1α, and the increased ratio of phosphorylated AKT/AKT. LY294002, a selective PI3K inhibitor, inhibited the PI3K/AKT/HIF-1α signaling pathway and further attenuated the protective effect of troxerutin against OGD/R-induced H9C2 cell damage. Furthermore, small interfering (si)RNA-mediated knockdown of HIF-1α reduced troxerutin-induced protection against OGD/R injury. Troxerutin pretreatment alleviated OGD/R-induced oxidative stress, as demonstrated by the reduced generation of reactive oxygen species and malonaldehyde content, and the increased activities of superoxide dismutase and glutathione peroxidase, which were reduced by HIF-1α-siRNA. Troxerutin-induced decreases in the levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor-α in OGD/R conditions were also reduced by HIF-1α-siRNA. The results from the present study indicated that troxerutin aggravated OGD/R-induced H9C2 cell injury by inhibiting oxidative stress and the inflammatory response. The primary underlying protective mechanism of troxerutin was mediated by the activation of the PI3K/AKT/HIF-1α signaling pathway.

An extracellular oxygen carrier during prolonged pulmonary preservation improves post-transplant lung function

BACKGROUND

The use of a novel extracellular oxygen carrier (EOC) preservation additive known as HEMO2Life has recently been shown to lead to a superior preservation of different types of solid organs. Our study aimed to investigate the effect of this EOC on extending lung preservation time and its mechanism of action.

METHODS

Donor pigs were randomly allocated to either of the following 2 groups (n = 6 per group): (1) 36 hours cold preservation or (2) 36 hours cold preservation with 1 g/liter of EOC. The lungs were evaluated through 12 hours of normothermic ex vivo lung perfusion (EVLP) followed by a left-single lung transplant into a recipient pig. Grafts were reperfused for 4 hours, followed by right pulmonary artery clamping to assess graft oxygenation function.

RESULTS

During EVLP assessment, EOC-treated lungs showed improvements in physiologic parameters, whereas the control lungs deteriorated. After a total of 48 hours of preservation (36 hours cold + 12 hours normothermic EVLP), transplanted grafts in the treatment group displayed significantly better oxygenation than in the controls (PaO2/FiO2: 437 ± 36 mm Hg vs 343 ± 27 mm Hg, p = 0.041). In addition, the use of EOC led to significantly less edema formation (wet-to-dry ratio: 4.95 ± 0.29 vs 6.05 ± 0.33, p = 0.026), less apoptotic cell death (p = 0.041), improved tight junction preservation (p = 0.002), and lower levels of circulating IL-6 within recipient plasma (p = 0.004) compared with non-use of EOC in the control group after transplantation.

CONCLUSION

The use of an EOC during an extended pulmonary preservation period led to significantly superior early post-transplant lung function.

Loss of hypoxia-inducible factor 1α affects hypoxia tolerance in larval and adult zebrafish (Danio rerio)

The coordination of the hypoxic response is attributed, in part, to hypoxia-inducible factor 1α (Hif-1α), a regulator of hypoxia-induced transcription. After the teleost-specific genome duplication, most teleost fishes lost the duplicate copy of Hif-1α, except species in the cyprinid lineage that retained both paralogues of Hif-1α (Hif1aa and Hif1ab). Little is known about the contribution of Hif-1α, and specifically of each paralogue, to hypoxia tolerance. Here, we examined hypoxia tolerance in wild-type (Hif1aa^+/+ab^+/+) and Hif-1α knockout lines (Hif1aa^-/-; Hif1ab^-/-; Hif1aa^-/-ab^-/-) of zebrafish (Danio rerio). Critical O₂ tension (P_crit; the partial pressure of oxygen (PO₂) at which O₂ consumption can no longer be maintained) and time to loss of equilibrium (LOE), two indices of hypoxia tolerance, were assessed in larvae and adults. Knockout of both paralogues significantly increased P_crit (decreased hypoxia tolerance) in larval fish. Prior exposure of larvae to hypoxia decreased P_crit in wild-type fish, an effect mediated by the Hif1aa paralogue. In adults, individuals with a knockout of either paralogue exhibited significantly decreased time to LOE but no difference in P_crit. Together, these results demonstrate that in zebrafish, tolerance to hypoxia and improved hypoxia tolerance after pre-exposure to hypoxia (pre-conditioning) are mediated, at least in part, by Hif-1α.

Targeting Mitochondria during Cold Storage to Maintain Proteasome Function and Improve Renal Outcome after Transplantation

Kidney transplantation is the preferred treatment for end-stage kidney disease (ESKD). Compared to maintenance dialysis, kidney transplantation results in improved patient survival and quality of life. Kidneys from living donors perform best; however, many patients with ESKD depend on kidneys from deceased donors. After procurement, donor kidneys are placed in a cold-storage solution until a suitable recipient is located. Sadly, prolonged cold storage times are associated with inferior transplant outcomes; therefore, in most situations when considering donor kidneys, long cold-storage times are avoided. The identification of novel mechanisms of cold-storage-related renal damage will lead to the development of new therapeutic strategies for preserving donor kidneys; to date, these mechanisms remain poorly understood. In this review, we discuss the importance of mitochondrial and proteasome function, protein homeostasis, and renal recovery during stress from cold storage plus transplantation. Additionally, we discuss novel targets for therapeutic intervention to improve renal outcomes.

Pathophysiological implications of hypoxia in human diseases

Oxygen is essentially required by most eukaryotic organisms as a scavenger to remove harmful electron and hydrogen ions or as a critical substrate to ensure the proper execution of enzymatic reactions. All nucleated cells can sense oxygen concentration and respond to reduced oxygen availability (hypoxia). When oxygen delivery is disrupted or reduced, the organisms will develop numerous adaptive mechanisms to facilitate cells survived in the hypoxic condition. Normally, such hypoxic response will cease when oxygen level is restored. However, the situation becomes complicated if hypoxic stress persists (chronic hypoxia) or cyclic normoxia-hypoxia phenomenon occurs (intermittent hypoxia). A series of chain reaction-like gene expression cascade, termed hypoxia-mediated gene regulatory network, will be initiated under such prolonged or intermittent hypoxic conditions and subsequently leads to alteration of cellular function and/or behaviors. As a result, irreversible processes occur that may cause physiological disorder or even pathological consequences. A growing body of evidence implicates that hypoxia plays critical roles in the pathogenesis of major causes of mortality including cancer, myocardial ischemia, metabolic diseases, and chronic heart and kidney diseases, and in reproductive diseases such as preeclampsia and endometriosis. This review article will summarize current understandings regarding the molecular mechanism of hypoxia in these common and important diseases.

Role of the lysyl oxidase family in organ development (Review)

Lysyl oxidase proteins (LOXs) are amine oxidases, which are mainly located in smooth muscle cells and fibroblasts and serve an important role in the formation of the extracellular matrix (ECM) in a copper-dependent manner. Owing to the ability of LOX proteins to modulate crosslinking between collagens and to promote the deposition of other fibers, they serve crucially in organogenesis and the subsequent organ development, as well as disease initiation and progression. In addition, ECM formation significantly influences organ morphological formation in both cancer- and non-tumor-related diseases, in addition to cellular epigenetic transformation and migration, under the influence of LOXs. A number of different signaling pathways regulate the LOXs expression and their enzymatic activation. The tissue remodeling and transformation process shares some resemblance between oncogenesis and embryogenesis. Additionally the roles that LOXs serve appeared to be stressed during oncogenesis and tumor metastasis. It has also been indicated LOXs have a noteworthy role in non-tumor diseases. Nonetheless, the role of LOXs in systemic or local organ development and disease control remains unknown. In the present study, the essential roles that LOXs play in embryogenesis were unveiled partially, whereas the role of LOXs in organ or systematic development requires further investigations. The present review aimed to discuss the roles of members of the LOX family in the context of the remodeling of organogenesis and organ development. In addition, the consequences of the malfunction of these proteins related to the development of abnormalities and resulting diseases is discussed.

A Simple and Effective Sample Preparation Strategy for MALDI-MS Imaging of Neuropeptide Changes in the Crustacean Brain Due to Hypoxia and Hypercapnia Stress

Matrix-assisted laser desorption/ionization (MALDI)-MS imaging has been utilized to image a variety of biomolecules, including neuropeptides. Washing a tissue section is an effective way to eliminate interfering background and improve detection of low concentration target analyte molecules; however, many previous methods have not been tested for neuropeptide analysis via MALDI-MS imaging. Using crustaceans as a neurological model organism, we developed a new, simple washing procedure and applied this method to characterize neuropeptide changes due to hypoxia stress. With a 10 s 50:50 EtOH:H₂O wash, neuropeptide coverage was improved by 1.15-fold, while normalized signal intensities were increased by 5.28-fold. Specifically, hypoxia and hypercapnia stress conditions were investigated due to their environmental relevance to marine invertebrates. Many neuropeptides, including RFamides, pyrokinin, and cardioactive peptides, showed distinct up- and down-regulation for specific neuropeptide isoforms. Since crustacean neuropeptides are homologous to those found in humans, results from these studies can be applied to understand potential roles of neuropeptides involved in medical hypoxia and hypercapnia.

Contemporary Periodization of Altitude Training for Elite Endurance Athletes: A Narrative Review

Since the 1960s there has been an escalation in the purposeful utilization of altitude to enhance endurance athletic performance. This has been mirrored by a parallel intensification in research pursuits to elucidate hypoxia-induced adaptive mechanisms and substantiate optimal altitude protocols (e.g., hypoxic dose, duration, timing, and confounding factors such as training load periodization, health status, individual response, and nutritional considerations). The majority of the research and the field-based rationale for altitude has focused on hematological outcomes, where hypoxia causes an increased erythropoietic response resulting in augmented hemoglobin mass. Hypoxia-induced non-hematological adaptations, such as mitochondrial gene expression and enhanced muscle buffering capacity may also impact athletic performance, but research in elite endurance athletes is limited. However, despite significant scientific progress in our understanding of hypobaric hypoxia (natural altitude) and normobaric hypoxia (simulated altitude), elite endurance athletes and coaches still tend to be trailblazers at the coal face of cutting-edge altitude application to optimize individual performance, and they already implement novel altitude training interventions and progressive periodization and monitoring approaches. Published and field-based data strongly suggest that altitude training in elite endurance athletes should follow a long- and short-term periodized approach, integrating exercise training and recovery manipulation, performance peaking, adaptation monitoring, nutritional approaches, and the use of normobaric hypoxia in conjunction with terrestrial altitude. Future research should focus on the long-term effects of accumulated altitude training through repeated exposures, the interactions between altitude and other components of a periodized approach to elite athletic preparation, and the time course of non-hematological hypoxic adaptation and de-adaptation, and the potential differences in exercise-induced altitude adaptations between different modes of exercise.

Expression of HIF-1α and VEGF in feline mammary gland carcinomas: association with pathological characteristics and clinical outcomes

Background

The microenvironment within solid malignant tumors, including feline mammary gland carcinomas (FMGCs), is commonly hypoxic, possibly due to the lack of functional blood vessels in rapidly proliferating neoplastic tissue. Malignant cells can undergo genetic and adaptive changes that prevent them from dying due to oxygen deprivation through expressions of hypoxia-inducible factor 1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF). Therefore, HIF-1α and VEGF are ideal biomarkers for cancer therapy and prognostic evaluation. The aims of this study were to evaluate the expression of HIF-1α and VEGF in feline mammary carcinomas and analyze their correlations with clinical and pathological factors, such as clinical stage, histologic grading, regional metastasis, and overall survival rate.

Results

Paraffin-embedded tissue samples collected from 72 cats with FMGCs were retrospectively studied. Histologic pattern and histologic grading (Elston and Ellis grading system) of these FMGCs were determined. Our data indicated that grade II tubulopapillary carcinomas (43/72, 59.7%) prevailed in this study, and most FMCGs showed apparent necrosis, squamous metaplasia, and intratumoral stromal response. According to the results of immunohistochemical (IHC) stainings performed in tissue microarrays (TMAs), HIF-1α and VEGF overexpressions were respectively noted in 69.4% (50/72) and 77.8% (56/72) of FMGC cases. Chi-square test showed no correlation of HIF-1α overexpression with clinical and pathological factors. VEGF overexpression was significantly correlated with histologic pattern (p = 0.021), stromal response (p = 0.048), squamous metaplasia (p = 0.001), and lymphovascular invasion (p = 0.007). However, neither HIF-1α nor VEGF overexpression was correlated with histologic grading and metastasis. Of 38 cats with 1-year follow-up, IHC stainings of HIF-1α and VEGF were performed on whole tissue sections. The results showed that overexpression of HIF-1α was significantly correlated with the overall survival rate (p < 0.05) (log-rank test), whereas there was no significant correlation between VEGF overexpression and overall survival rate.

Conclusions

This study suggests that the overexpression of HIF-1α may indicate poor prognosis/overall survival rate in cats with FMGCs. Developing compounds that inhibit HIF-1α may be a potential approach to FMGC treatment.

Cracking the Cell Death Code

Cell death is an invariant feature throughout our life span, starting with extensive scheduled cell death during morphogenesis and continuing with death under homeostasis in adult tissues. Additionally, cells become victims of accidental, unscheduled death following injury and infection. Cell death in each of these occasions triggers specific and specialized responses in the living cells that surround them or are attracted to the dying/dead cells. These responses sculpt tissues during morphogenesis, replenish lost cells in homeostasis to maintain tissue/system function, and repair damaged tissues after injury. Wherein lies the information that sets in motion the cascade of effector responses culminating in remodeling, renewal, or repair? Here, we attempt to provide a framework for thinking about cell death in terms of the specific effector responses that accompanies various modalities of cell death. We also propose an integrated threefold "cell death code" consisting of information intrinsic to the dying/dead cell, the surroundings of the dying cell, and the identity of the responder.

Cardiolipin remodeling in Barth syndrome and other hereditary cardiomyopathies

Mitochondria play a prominent role in cardiac energy metabolism, and their function is critically dependent on the integrity of mitochondrial membranes. Disorders characterized by mitochondrial dysfunction are commonly associated with cardiac disease. The mitochondrial phospholipid cardiolipin directly interacts with a number of essential protein complexes in the mitochondrial membranes including the respiratory chain, mitochondrial metabolite carriers, and proteins critical for mitochondrial morphology. Barth syndrome is an X-linked disorder caused by an inherited defect in the biogenesis of the mitochondrial phospholipid cardiolipin. How cardiolipin deficiency impacts on mitochondrial function and how mitochondrial dysfunction causes cardiomyopathy has been intensively studied in cellular and animal models of Barth syndrome. These findings may also have implications for the molecular mechanisms underlying other inherited disorders associated with defects in cardiolipin, such as Sengers syndrome and dilated cardiomyopathy with ataxia (DCMA).

Tumor Hypoxia: Impact on Radiation Therapy and Molecular Pathways

Tumor hypoxia is a common feature of the microenvironment in solid tumors, primarily due to an inadequate, and heterogeneous vascular network. It is associated with resistance to radiotherapy and results in a poorer clinical outcome. The presence of hypoxia in tumors can be identified by various invasive and non-invasive techniques, and there are a number of approaches by which hypoxia can be modified to improve outcome. However, despite these factors and the ongoing extensive pre-clinical studies, the clinical focus on hypoxia is still to a large extent lacking. Hypoxia is a major cellular stress factor and affects a wide range of molecular pathways, and further understanding of the molecular processes involved may lead to greater clinical applicability of hypoxic modifiers. This review is a discussion of the characteristics of tumor hypoxia, hypoxia-related molecular pathways, and the role of hypoxia in treatment resistance. Understanding the molecular aspects of hypoxia will improve our ability to clinically monitor hypoxia and to predict and modify the therapeutic response.

Cytotoxic necrotizing factor 1 promotes bladder cancer angiogenesis through activating RhoC

Uropathogenic Escherichia coli (UPEC), a leading cause of urinary tract infections, is associated with prostate and bladder cancers. Cytotoxic necrotizing factor 1 (CNF1) is a key UPEC toxin; however, its role in bladder cancer is unknown. In the present study, we found CNF1 induced bladder cancer cells to secrete vascular endothelial growth factor (VEGF) through activating Ras homolog family member C (RhoC), leading to subsequent angiogenesis in the bladder cancer microenvironment. We then investigated that CNF1-mediated RhoC activation modulated the stabilization of hypoxia-inducible factor 1α (HIF1α) to upregulate the VEGF. We demonstrated in vitro that active RhoC increased heat shock factor 1 (HSF1) phosphorylation, which induced the heat shock protein 90α (HSP90α) expression, leading to stabilization of HIF1α. Active RhoC elevated HSP90α, HIF1α, VEGF expression, and angiogenesis in the human bladder cancer xenografts. In addition, HSP90α, HIF1α, and VEGF expression were also found positively correlated with the human bladder cancer development. These results provide a potential mechanism through which UPEC contributes to bladder cancer progression, and may provide potential therapeutic targets for bladder cancer.

The Influence of Bcl-3 Expression on Cell Migration and Chemosensitivity of Gastric Cancer Cells via Regulating Hypoxia-Induced Protective Autophagy

Purpose

Gastric cancer is a highly metastatic malignant tumor, often characterized by chemoresistance and high mortality. In the present study, we aimed to investigate the role of B-cell lymphoma 3 (Bcl-3) protein on cell migration and chemosensitivity of gastric cancer.

Materials and Methods

The gastric cancer cell lines, AGS and NCI-N87, were used for the in vitro studies and the in vivo studies were performed using BALB/c nude mice. Western blotting, wound healing assay, Cell Counting Kit-8 assay, immunohistochemistry, and terminal deoxynucleotidyl transferase dUTP nick end labeling assay were used to evaluate the role of Bcl-3 in gastric cancer.

Results

We found that the protein expression of hypoxia (HYP)-inducible factor-1α and Bcl-3 were markedly upregulated under hypoxic conditions in both AGS and NCI-N87 cells in a time-dependent manner. Interestingly, small interfering RNA-mediated knockdown of Bcl-3 expression affected the migration and chemosensitivity of the gastric cancer cells. AGS and NCI-N87 cells transfected with si-RNA-Bcl-3 (si-Bcl-3) showed significantly reduced migratory ability and increased chemosensitivity to oxaliplatin, 5-fluorouracil, and irinotecan. In addition, si-Bcl-3 restored the autophagy induced by HYP. Further, the protective role of si-Bcl-3 on the gastric cancer cells could be reversed by the autophagy inducer, rapamycin. Importantly, the in vivo xenograft tumor experiments showed similar results.

Conclusions

Our present study reveals that Bcl-3 knockdown inhibits cell migration and chemoresistance of gastric cancer cells through restoring HYP-induced autophagy.

Various forms of HIF-1α protein characterize the clear cell renal cell carcinoma cell lines

Renal cell carcinoma (RCC) represents around 2-3% of all malignancies diagnosed in adult patients. Most frequent (around 70-80% cases) and the most aggressive subtype is clear cell RCC (ccRCC). Mutations in VHL (von Hippel Lindau) gene, characteristic for this cancer type, lead to altered activity of the trimeric VBC (pVHL-elongin B-C) complex and consequently to HIF-1α stabilization. In this study, we present results of exhaustive investigation of HIF-1α alternative transcript variants abundance in A498, CAKI-1, and 786-O ccRCC cell lines. We proved the existence of truncated HIF-1α protein form (HIF1A∆-6) in A498 and HIF1A gene rearrangements in 786-O cell lines. Subsequently, we found that HIF1A∆2-6 was more stable than the full-length HIF-1α. Moreover, the shorter HIF-1α was insensitive for hypoxia and was overaccumulated after proteasome inhibitor treatment indicative of potential diversified roles of full-length and truncated HIF-1α forms in the cell. We also showed that A498, CAKI-1, and 786-O exhibit differential expression of various regulatory genes involved in the control of metabolic processes, that is, glucose and lipid metabolism, and encoding subunits of such machineries like SWI/SNF chromatin remodeling complex. Furthermore, these cell lines exhibited differential responses to axitinib, everolimus, and sunitinib-anticancer drugs-in normoxia and hypoxia as well as various alterations in metabolism-related regulatory processes. Finally, we have shown that overexpression of truncated HIF1A∆2-6 form may affect the protein level of endogenous full-length HIF-1α protein. Thus, our study proves an important role of HIF-1α in the ccRCC development.

Improvement of human pancreatic islet quality after co-culture with human adipose-derived stem cells

The aim of this study was to investigate whether co-culture of human islets with adipose-derived stem cells (ASCs) can improve islet quality and to evaluate which factors play a role in the protective effect of ASCs against islet dysfunction. Islets and ASCs were cultured in three experimental groups for 24 h, 48 h, and 72 h: 1) indirect co-culture of islets with ASC monolayer (Islets/ASCs); 2) islets alone; and 3) ASCs alone. Co-culture with ASCs improved islet viability and function in all culture time-points analyzed. VEGFA, HGF, IL6, IL8, IL10, CCL2, IL1B, and TNF protein levels were increased in supernatants of islet/ASC group compared to islets alone, mainly after 24 h. Moreover, VEGFA, IL6, CCL2, HIF1A, XIAP, CHOP, and NFKBIA genes were differentially expressed in islets from the co-culture condition compared to islets alone. In conclusion, co-culture of islets with ASCs promotes improvements in islet quality.

The Treatment of Impaired Wound Healing in Diabetes: Looking among Old Drugs

Chronic wounds often occur in patients with diabetes mellitus due to the impairment of wound healing. This has negative consequences for both the patient and the medical system and considering the growing prevalence of diabetes, it will be a significant medical, social, and economic burden in the near future. Hence, the need for therapeutic alternatives to the current available treatments that, although various, do not guarantee a rapid and definite reparative process, appears necessary. We here analyzed current treatments for wound healing, but mainly focused the attention on few classes of drugs that are already in the market with different indications, but that have shown in preclinical and few clinical trials the potentiality to be used in the treatment of impaired wound healing. In particular, repurposing of the antiglycemic agents dipeptidylpeptidase 4 (DPP4) inhibitors and metformin, but also, statins and phenyotin have been analyzed. All show encouraging results in the treatment of chronic wounds, but additional, well designed studies are needed to allow these drugs access to the clinics in the therapy of impaired wound healing.

An Updated Panorama of "Living Low-Training High" Altitude/Hypoxic Methods

With minimal costs and travel constraints for athletes, the “living low-training high” (LLTH) approach is becoming an important intervention for modern sport. The popularity of the LLTH model of altitude training is also associated with the fact that it only causes a slight disturbance to athletes' usual daily routine, allowing them to maintain their regular lifestyle in their home environment. In this perspective article, we discuss the evolving boundaries of the LLTH paradigm and its practical applications for athletes. Passive modalities include intermittent hypoxic exposure at rest (IHE) and Ischemic preconditioning (IPC). Active modalities use either local [blood flow restricted (BFR) exercise] and/or systemic hypoxia [continuous low-intensity training in hypoxia (CHT), interval hypoxic training (IHT), repeated-sprint training in hypoxia (RSH), sprint interval training in hypoxia (SIH) and resistance training in hypoxia (RTH)]. A combination of hypoxic methods targeting different attributes also represents an attractive solution. In conclusion, a growing number of LLTH altitude training methods exists that include the application of systemic and local hypoxia stimuli, or a combination of both, for performance enhancement in many disciplines.

DEAD Box Protein Family Member DDX28 Is a Negative Regulator of Hypoxia-Inducible Factor 2α- and Eukaryotic Initiation Factor 4E2-Directed Hypoxic Translation

Hypoxia is a deficiency in oxygen delivery to tissues and is connected to physiological and pathophysiological processes such as embryonic development and cancer. The master regulators of oxygen homeostasis in mammalian cells are the heterodimeric hypoxia-inducible transcription factors 1 and 2 (HIF-1 and HIF-2, respectively). The oxygen-labile HIF-2α subunit has been implicated not only in transcription but also as a regulator of eukaryotic initiation factor 4E2 (eIF4E2)-directed hypoxic translation. Here, we have identified the DEAD box protein family member DDX28 as an interactor and negative regulator of HIF-2α that suppresses HIF-2α's ability to activate eIF4E2-directed translation. Stable silencing of DDX28 via short hairpin RNA (shRNA) in hypoxic human U87MG glioblastoma cells caused an increase of eIF4E2 binding to the m⁷GTP cap structure and the translation of eIF4E2 target mRNAs (including the HIF-2α mRNA itself). DDX28 depletion elevated nuclear and cytoplasmic HIF-2α protein, but HIF-2α transcriptional activity did not increase, possibly due to its already high nuclear abundance in hypoxic control cells. Depletion of DDX28 conferred a proliferative advantage to hypoxic, but not normoxic, cells. DDX28 protein levels are reduced in several cancers, including gliomas, relative to levels in normal tissue. Therefore, we uncover a regulatory mechanism for this potential tumor suppressor in the repression of HIF-2α- and eIF4E2-mediated translation activation of oncogenic mRNAs.

Circadian-Hypoxia Link and its Potential for Treatment of Cardiovascular Disease

Throughout the evolutionary time, all organisms and species on Earth evolved with an adaptation to consistent oscillations of sunlight and darkness, now recognized as 'circadian rhythm.' Single-cellular to multisystem organisms use circadian biology to synchronize to the external environment and provide predictive adaptation to changes in cellular homeostasis. Dysregulation of circadian biology has been implicated in numerous prevalent human diseases, and subsequently targeting the circadian machinery may provide innovative preventative or treatment strategies. Discovery of 'peripheral circadian clocks' unleashed widespread investigations into the potential roles of clock biology in cellular, tissue, and organ function in healthy and diseased states. Particularly, oxygen-sensing pathways (e.g. hypoxia inducible factor, HIF1), are critical for adaptation to changes in oxygen availability in diseases such as myocardial ischemia. Recent investigations have identified a connection between the circadian rhythm protein Period 2 (PER2) and HIF1A that may elucidate an evolutionarily conserved cellular network that can be targeted to manipulate metabolic function in stressed conditions like hypoxia or ischemia. Understanding the link between circadian and hypoxia pathways may provide insights and subsequent innovative therapeutic strategies for patients with myocardial ischemia. This review addresses our current understanding of the connection between light-sensing pathways (PER2), and oxygen-sensing pathways (HIF1A), in the context of myocardial ischemia and lays the groundwork for future studies to take advantage of these two evolutionarily conserved pathways in the treatment of myocardial ischemia.

Population Structure, and Selection Signatures Underlying High-Altitude Adaptation Inferred From Genome-Wide Copy Number Variations in Chinese Indigenous Cattle

Copy number variations (CNVs) have been demonstrated as crucial substrates for evolution, adaptation and breed formation. Chinese indigenous cattle breeds exhibit a broad geographical distribution and diverse environmental adaptability. Here, we analyzed the population structure and adaptation to high altitude of Chinese indigenous cattle based on genome-wide CNVs derived from the high-density BovineHD SNP array. We successfully detected the genome-wide CNVs of 318 individuals from 24 Chinese indigenous cattle breeds and 37 yaks as outgroups. A total of 5,818 autosomal CNV regions (683 bp-4,477,860 bp in size), covering ~14.34% of the bovine genome (UMD3.1), were identified, showing abundant CNV resources. Neighbor-joining clustering, principal component analysis (PCA), and population admixture analysis based on these CNVs support that most Chinese cattle breeds are hybrids of Bos taurus taurus (hereinafter to be referred as Bos taurus) and Bos taurus indicus (Bos indicus). The distribution patterns of the CNVs could to some extent be related to the geographical backgrounds of the habitat of the breeds, and admixture among cattle breeds from different districts. We analyzed the selective signatures of CNVs positively involved in high-altitude adaptation using pairwise Fst analysis within breeds with a strong Bos taurus background (taurine-type breeds) and within Bos taurus×Bos indicus hybrids, respectively. CNV-overlapping genes with strong selection signatures (at top 0.5% of Fst value), including LETM1 (Fst = 0.490), TXNRD2 (Fst = 0.440), and STUB1 (Fst = 0.420) within taurine-type breeds, and NOXA1 (Fst = 0.233), RUVBL1 (Fst = 0.222), and SLC4A3 (Fst=0.154) within hybrids, were potentially involved in the adaptation to hypoxia. Thus, we provide a new profile of population structure from the CNV aspects of Chinese indigenous cattle and new insights into high-altitude adaptation in cattle.

Dietary GABA enhances hypoxia tolerance of a bottom-dwelling carp, Cirrhinus mrigala by modulating HIF-1α, thyroid hormones and metabolic responses

The Indian major carp, mrigal (Cirrhinus mrigala), is a bottom-dwelling fish that can survive hypoxic episodes in its natural environment. We hypothesise that it can better survive hypoxic conditions by altering metabolic responses through GABA (Gamma-aminobutyric acid) supplementation. In the first experiment, the hypoxia tolerance time of the fishes was evaluated under extreme anoxic conditions after feeding with GABA, which showed that GABA had improved survival time under hypoxia. To study the response of dietary GABA in hypoxia-exposed fish, the branchial HIF-1α expression levels, serum thyroid hormone levels and hepatic metabolic responses were assessed in the subsequent experiment. The treatment groups were fed for 60 days with experimental diets containing 4 levels of GABA (0.00% G, 0.50% G, 0.75% G and 1.0%G) and were subjected to 72-h hypoxia exposure (0.5 ± 0.02 mg L^-1 dissolved oxygen (DO)) whereas a control group was maintained under normoxic conditions (6.0 ± 0.21 mg L^-1 DO). The five treatment groups with three replicates were C0 (0% G + normoxia), H0 (0% G + hypoxia), H0.5 (0.50% G + hypoxia), H0.75 (0.75% G + hypoxia) and H1.0 (1.00% G + hypoxia). The results indicated that GABA supplementation triggered downregulation of HIF 1 alpha expression. When compared with the control group, decreased thyroxine (T4) and triiodothyronine (T3) levels were observed in the GABA-fed hypoxic groups. However, TSH (thyroid stimulating hormone) level remained unchanged in all the treatments. The LDH (lactate dehydrogenase) level in hypoxia-exposed groups was decreased by GABA supplementation. Our study demonstrated that GABA supplementation restores acute hypoxia-induced HIF-1α expression, thyroid hormone levels and LDH activities. On the other hand, it enhanced the citrate synthase (CS) activities at 0.5-1.00%, which showed a sharp decline in hypoxia. Hypoxia caused increase in the serum metabolites such as glucose, lactate, cholesterol and triglycerides. However, GABA supplementation was partially effective in reducing glucose and lactate level while triglycerides and cholesterol values remained unchanged. Overall, our results suggested a potential role of GABA in suppressing metabolism during hypoxia exposure, which can increase the chances of survival of the species Cirrhinus mrigala during hypoxia.

Hypoxic environment may enhance migration/penetration of endocrine resistant MCF7- derived breast cancer cells through monolayers of other non-invasive cancer cells in vitro

The response of cancer cells to hypoxic conditions found within the interior of a tumor mass is mediated through the hypoxia inducible factor (HIF) cascade and is thought to promote metastasis. However, given their distant proximity from blood vessels as compared to normoxic cells at the vascularised tumor periphery, it is uncertain if these cells can migrate through the tumor mass to gain access. Hypoxia was simulated by exposure to cobalt chloride or deferoxamine in normal (MCF10A) and cancerous [estrogen receptor (ER)−ve (pII), and ER +ve (YS1.2/ EII)] cells. In this report, HIF1α expression and localization was measured using western blotting, ELISA, and immunofluorescence, cell proliferation by MTT assay, motility and invasion by wound healing, live cell imaging, matrigel and co-culture in chambered slides. We found that the expression and nuclear translocation of HIF1α was significantly elevated by hypoxia, which inhibited cell proliferation, but significantly increased motility of pII cells and their penetration into and through a dense layer of adjacent EII cells, as well as their selective emergence out of a co-culture. These data suggest that endocrine resistant pII cancer cells, having undergone epithelial to mesenchymal transition are able to penetrate through other cell layers, with possible enhancement in response to hypoxia.

Hypoxia-Inducible Factor-1α: The Master Regulator of Endothelial Cell Senescence in Vascular Aging

Aging is one of the hottest topics in biomedical research. Advances in research and medicine have helped to preserve human health, leading to an extension of life expectancy. However, the extension of life is an irreversible process that is accompanied by the development of aging-related conditions such as weakness, slower metabolism, and stiffness of vessels. It also debated that aging can be considered an actual disease with aging-derived comorbidities, including cancer or cardiovascular disease. Currently, cardiovascular disorders, including atherosclerosis, are considered as premature aging and represent the first causes of death in developed countries, accounting for 31% of annual deaths globally. Emerging evidence has identified hypoxia-inducible factor-1α as a critical transcription factor with an essential role in aging-related pathology, in particular, regulating cellular senescence associated with cardiovascular aging. In this review, we will focus on the regulation of senescence mediated by hypoxia-inducible factor-1α in age-related pathologies, with particular emphasis on the crosstalk between endothelial and vascular cells in age-associated atherosclerotic lesions. More specifically, we will focus on the characteristics and mechanisms by which cells within the vascular wall, including endothelial and vascular cells, achieve a senescent phenotype.

Iron and Sphingolipids as Common Players of (Mal)Adaptation to Hypoxia in Pulmonary Diseases

Hypoxia, or lack of oxygen, can occur in both physiological (high altitude) and pathological conditions (respiratory diseases). In this narrative review, we introduce high altitude pulmonary edema (HAPE), acute respiratory distress syndrome (ARDS), Chronic Obstructive Pulmonary Disease (COPD), and Cystic Fibrosis (CF) as examples of maladaptation to hypoxia, and highlight some of the potential mechanisms influencing the prognosis of the affected patients. Among the specific pathways modulated in response to hypoxia, iron metabolism has been widely explored in recent years. Recent evidence emphasizes hepcidin as highly involved in the compensatory response to hypoxia in healthy subjects. A less investigated field in the adaptation to hypoxia is the sphingolipid (SPL) metabolism, especially through Ceramide and sphingosine 1 phosphate. Both individually and in concert, iron and SPL are active players of the (mal)adaptation to physiological hypoxia, which can result in the pathological HAPE. Our aim is to identify some pathways and/or markers involved in the physiological adaptation to low atmospheric pressures (high altitudes) that could be involved in pathological adaptation to hypoxia as it occurs in pulmonary inflammatory diseases. Hepcidin, Cer, S1P, and their interplay in hypoxia are raising growing interest both as prognostic factors and therapeutical targets.

Non-circadian aspects of BHLHE40 cellular function in cancer

While many genes specifically act as oncogenes or tumor suppressors, others are tumor promoters or suppressors in a context-dependent manner. Here we will review the basic-helix-loop-helix (BHLH) protein BHLHE40, (also known as BHLHB2, STRA13, DEC1, or SHARP2) which is overexpressed in gastric, breast, and brain tumors; and downregulated in colorectal, esophageal, pancreatic and lung cancer. As a transcription factor, BHLHE40 is expressed in the nucleus, where it binds to target gene promoters containing the E-box hexanucleotide sequence, but can also be expressed in the cytoplasm, where it stabilizes cyclin E, preventing cyclin E-mediated DNA replication and cell cycle progression. In different organs BHLHE40 regulates different targets; hence may have different impacts on tumorigenesis. BHLHE40 promotes PI3K/Akt/mTOR activation in breast cancer, activating tumor progression, but suppresses STAT1 expression in clear cell carcinoma, triggering tumor suppression. Target specificity likely depends on cooperation with other transcription factors. BHLHE40 is activated in lung and esophageal carcinoma by the tumor suppressor p53 inducing senescence and suppressing tumor growth, but is also activated under hypoxic conditions by HIF-1α in gastric cancer and hepatocellular carcinomas, stimulating tumor progression. Thus, BHLHE40 is a multi-functional protein that mediates the promotion or suppression of cancer in a context dependent manner.

Down-regulation of microRNA-31 suppresses hepatic fibrosis induced by carbon tetrachloride

MicroRNA-31 (miR-31) is among the most frequently altered microRNAs in human diseases, and altered expression of miR-31 has been detected in a large variety of diseases types. miR-31 could also regulate a variety of cell functions including hepatic fibrosis. Hepatic stellate cells (HSCs) are regarded as the major cell type involved in hepatic fibrosis. Male BALB/c mice (five mice per group aged 6 weeks) received 200 μL of body weight of carbon tetrachloride (10% CCl4) mixed with olive oil intraperitoneally, and the first dose was doubled. To induce hepatic fibrosis, carbon tetrachloride was injected twice a week for 4, 6, 8, and 10 weeks. Control animals were injected with an equal volume of olive oil at the same time intervals. We found that miR-31 expression and fibrosis-related factors in four hepatic fibrosis stages. However, we noted that inhibition of miR-31 was down-regulated fibrosis-related factor expression in F1–F3 stages, but no F4 stage. Thus, we hypothesize that miR-31 may mediate hepatic fibrosis. In this research, we found that inhibition of miR-31 expression significantly inhibited HSC activation. The biological function of miR-31 during HSC activation might be through targeting hypoxia-inducible factor 1-alpha inhibitor (HIF1AN). Inhibition of miR-31 can reduce the transcription factor activity of hypoxia inducible factor 1 (HIF-1) by targeting the biological effects of HIF1AN with the condition of hypoxia. In later hepatic fibrosis could be rescue combining with inhibition of miR-31 and adding heparin-binding EGF-like growth factor (HBEGF).

Generation of a hypoxia-sensing mouse model

Oxygen (O₂ ) homeostasis is essential to the metazoan life. O₂ -sensing or hypoxia-regulated molecular pathways are intimately involved in a wide range of critical cellular functions and cell survival from embryogenesis to adulthood. In this report, we have designed an innovative hypoxia sensor (O₂ CreER) based on the O₂ -dependent degradation domain of the hypoxia-inducible factor-1α and Cre recombinase. We have further generated a hypoxia-sensing mouse model, R26-O₂ CreER, by targeted insertion of the O₂ CreER-coding cassette in the ROSA26 locus. Using the ROSA^mTmG mouse strain as a reporter, we have found that this novel hypoxia-sensing mouse model can specifically identify hypoxic cells under the pathological condition of hind-limb ischemia in adult mice. This model can also label embryonic cells including vibrissal follicle cells in E13.5-E15.5 embryos. This novel mouse model offers a valuable genetic tool for the study of hypoxia and O₂ sensing in mammalian systems under both physiological and pathological conditions.

Estradiol Metabolism: Crossroads in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a debilitating and progressive disease that predominantly develops in women. Over the past 15 years, cumulating evidence has pointed toward dysregulated metabolism of sex hormones in animal models and patients with PAH. 17β-estradiol (E2) is metabolized at positions C2, C4, and C16, which leads to the formation of metabolites with different biological/estrogenic activity. Since the first report that 2-methoxyestradiol, a major non-estrogenic metabolite of E2, attenuates the development and progression of experimental pulmonary hypertension (PH), it has become increasingly clear that E2, E2 precursors, and E2 metabolites exhibit both protective and detrimental effects in PH. Furthermore, both experimental and clinical data suggest that E2 has divergent effects in the pulmonary vasculature versus right ventricle (estrogen paradox in PAH). The estrogen paradox is of significant clinical relevance for understanding the development, progression, and prognosis of PAH. This review updates experimental and clinical findings and provides insights into: (1) the potential impacts that pathways of estradiol metabolism (EMet) may have in PAH; (2) the beneficial and adverse effects of estrogens and their precursors/metabolites in experimental PH and human PAH; (3) the co-morbidities and pathological conditions that may alter EMet and influence the development/progression of PAH; (4) the relevance of the intracrinology of sex hormones to vascular remodeling in PAH; and (5) the advantages/disadvantages of different approaches to modulate EMet in PAH. Finally, we propose the three-tier-estrogen effects in PAH concept, which may offer reconciliation of the opposing effects of E2 in PAH and may provide a better understanding of the complex mechanisms by which EMet affects the pulmonary circulation–right ventricular interaction in PAH.

AT-533, a novel Hsp90 inhibitor, inhibits breast cancer growth and HIF-1α/VEGF/VEGFR-2-mediated angiogenesis in vitro and in vivo

The inhibition of angiogenesis is suggested to be an attractive strategy for cancer therapeutics. Heat shock protein 90 (Hsp90) is closely related to tumorigenesis as it regulates the stabilization and activated states of many client proteins that are essential for cell survival and tumor growth. Here, we investigated the mechanism whereby AT-533, a novel Hsp90 inhibitor, inhibits breast cancer growth and tumor angiogenesis. Based on our results, AT-533 suppressed the tube formation, cell migration, and invasion of human umbilical vein endothelial cells (HUVECs), and was more effective than the Hsp90 inhibitor, 17-AAG. Furthermore, AT-533 inhibited angiogenesis in the aortic ring, Matrigel plug, and chorioallantoic membrane (CAM) models. Mechanically, AT-533 inhibited the activation of VEGFR-2 and the downstream pathways, including Akt/mTOR/p70S6K, Erk1/2 and FAK, in HUVECs, and the viability of breast cancer cells and the HIF-1α/VEGF signaling pathway under hypoxia. In vivo, AT-533 also inhibited tumor growth and angiogenesis by inducing apoptosis and the HIF-1α/VEGF signaling pathway in breast cancer cells. Taken together, our findings indicate that the Hsp90 inhibitor, AT-533, suppresses breast cancer growth and angiogenesis by blocking the HIF-1α/VEGF/VEGFR-2 signaling pathway. AT-533 may thus be a potentially useful drug candidate for breast cancer therapy.

Molecular and Cellular Response of Co-cultured Cells toward Cobalt Chloride (CoCl2)-Induced Hypoxia

Cobalt chloride (CoCl₂) is a well-known hypoxia mimetic mediator that induces hypoxia-like responses. CoCl₂, a mediator confirmed to alleviate hypoxia-inducible factor-1 (HIF-1), has been associated with a variety of hypoxic responses. HIF-1 is the foremost transcriptionfactor that is particularly activated during hypoxia and regulates various genes. Therefore, this study aimed to investigate the cellular and molecular responses of the co-cultured cells under the influence of the CoCl₂-induced hypoxic condition. Mono- and co-cultured C2C12 and 3T3-L1 cells were exposed to CoCl₂, and a significant induction in HIF-1, reactive oxygen species and lipid peroxidase and a reduction in glutathione and catalase were observed. The expressions of proapoptotic genes like Bax, p53, caspase-9, and caspase-3 were notably increased, whereas the antiapoptotic gene, i.e., Bcl2, was downregulated during hypoxia in mono- as well as co-cultured C2C12 cells. However, the co-cultured C2C12 cells show significantly lower induction in oxidative stress and expression of apoptotic genes in comparison to monocultured C2C12 cells. Whereas, the co-cultured 3T3-L1 cells show comparatively higher oxidative stress and apoptotic event in comparison to monocultured 3T3-L1 cells. The reason may be the communication between the cells and some soluble factors that help in cell survival/death from hypoxia. Moreover, it may also be due to the fact that fat and muscle cells interact and communicate via proximity and mutual ability when growing together. Therefore, the co-culture system provides a unique approach to intercellular communication between the two different cell types.

Regulation of MicroRNA-155 and Its Related Genes Expression by Inositol Hexaphosphate in Colon Cancer Cells

Inositol hexaphosphate (IP6), a natural dietary component, has been found as an antitumor agent by stimulating apoptosis and inhibiting cancer cell proliferation, their migration, and metastasis in diverse cancers including colon cancer. However, molecular mechanisms of its action have not been well understood. In recent years, microRNAs (miRNAs) have been reported to play important roles in a broad range of biologic processes, such as cell growth, proliferation, apoptosis, or autophagy. These small noncoding molecules regulate post-transcriptional expression of targets genes via degradation of transcript or inhibition of protein synthesis. Aberrant expression and/or dysregulation of miRNAs have been characterized during tumor development and progression, thus, they are potential molecular targets for cancer prevention. The aim of this study was to investigate the effect of IP6 on the miRNAs expression profile in Caco-2 colon cancer cells. 84 miRNAs were analyzed in Caco-2 cells treated with 2.5 mM and 5 mM IP6 by the use of PCR (Polymerase Chain Reaction) array. The effect of 5 mM IP6 on selected potential miR-155 targets was determined by real-time (RT)-qPCR and ELISA (quantitative Polymerase Chain Reaction and Enzyme-Linked Immunosorbent Assay )method. The results indicated alteration in the specific 10 miRNA expression in human colon cancer cells following their treatment with 5 mM IP6. It down-regulated 8 miRNAs (miR-155, miR-210, miR-144, miR-194, miR-26b, miR-126, miR-302c, and miR-29a) and up-regulated 2 miRNAs (miR-223 and miR-196b). In silico analysis revealed that FOXO3a, HIF-1α, and ELK3 mRNAs are those of predicted targets of miR-155. IP6 at the concentration of 5 mM markedly induced FOXO3a and HIF-1a genes’ expression at both mRNA and protein level and decreased the amount of ELK3 mRNA as well as protein concentration in comparison to the control. In conclusion, the present study indicates that one of the mechanisms of antitumor potential of IP6 is down-regulation of the miR-155 expression in human colon cancer cells. Moreover, the expression of genes that are targeted by miRNA are also modulated by IP6.

Reperfusion Microvascular Ischemia After Prolonged Coronary Occlusion: Implications And Treatment With Local Supersaturated Oxygen Delivery

Following a prolonged coronary arterial occlusion, heterogeneously scattered, focal regions of low erythrocyte flow are commonly found throughout the reperfused myocardium. Experimental studies have also demonstrated the presence of widespread, focally patchy regions of microvascular ischemia during reperfusion (RMI). However, the potential contribution of RMI to tissue viability and function has received little attention in the absence of practical clinical methods for its detection. In this review, the anatomic/functional basis of RMI is summarized, along with the evidence for its presence in reperfused myocardium. Advances in microcirculation research related to obstructive responses of vascular endothelial cells and blood elements to the effects of hypoxia and low shear stress are discussed, and a potential cycle of intensification of RMI from such responses and progressive loss of functional capillary density is presented. In capillaries with impaired erythrocyte flow, compensatory increases in the delivery of oxygen, because of its low solubility in plasma, are effective only at high partial pressures. As discussed herein, attenuation of the cycle with oxygen at hyperbaric levels in plasma is, very likely, responsible for improved tissue level perfusion noted experimentally. Observed clinical benefits from intracoronary SuperSaturated oxygen (SSO₂) delivery, including infarct size reduction, can be attributed to attenuation of RMI with improvement in microvascular blood flow.

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.