Assessment of The Association of OCT3/4 With GLUT1 And CD105 In Oral Squamous Cell Carcinoma Using Dual Immunohistochemistry

Background: Oral squamous cell carcinoma (OSCC) is the most common cancer type affecting the oral and maxillofacial region. This study aimed to investigate the role of cancer stem cells (CSCs) in angiogenesis and hypoxic response in OSCC.Methods: This retrospective observational study evaluated 56 cases of OSCC using dual immunohistochemistry. Octamer-binding transcription factor 3/4 (OCT3/4) marker was used for evaluation of CSC activity. Glucose transporter 1 (GLUT1) marker was used to evaluate the hypoxic response and angiogenesis, while endoglin (CD105) was used to evaluate the late stage of angiogenesis and blood vessel formation.Results: Overexpression of both OCT3/4 and GLUT1 was noted in early stage of hypoxic response and angiogenesis in OSCC, indicating the important role of CSCs in this phase. However, despite higher expression of CD105, the expression of CSC markers was not significant in the late stage of tumor progression and angiogenesis.Conclusions: CSCs could play important roles in initial stages of tumor progression and angiogenesis. Further studies are required to discover other biomarkers, their roles, and associated pathways of CSCs in OSCC.

Hypoxic Regulation of the Large-Conductance, Calcium and Voltage-Activated Potassium Channel, BK

Hypoxia is a condition characterized by a reduction of cellular oxygen levels derived from alterations in oxygen balance. Hypoxic events trigger changes in cell-signaling cascades, oxidative stress, activation of pro-inflammatory molecules, and growth factors, influencing the activity of various ion channel families and leading to diverse cardiovascular diseases such as myocardial infarction, ischemic stroke, and hypertension. The large-conductance, calcium and voltage-activated potassium channel (BK) has a central role in the mechanism of oxygen (O2) sensing and its activity has been related to the hypoxic response. BK channels are ubiquitously expressed, and they are composed by the pore-forming α subunit and the regulatory subunits β (β1–β4), γ (γ1–γ4), and LINGO1. The modification of biophysical properties of BK channels by β subunits underly a myriad of physiological function of these proteins. Hypoxia induces tissue-specific modifications of BK channel α and β subunits expression. Moreover, hypoxia modifies channel activation kinetics and voltage and/or calcium dependence. The reported effects on the BK channel properties are associated with events such as the increase of reactive oxygen species (ROS) production, increases of intracellular Calcium ([Ca2+]i), the regulation by Hypoxia-inducible factor 1α (HIF-1α), and the interaction with hemeproteins. Bronchial asthma, chronic obstructive pulmonary diseases (COPD), and obstructive sleep apnea (OSA), among others, can provoke hypoxia. Untreated OSA patients showed a decrease in BK-β1 subunit mRNA levels and high arterial tension. Treatment with continuous positive airway pressure (CPAP) upregulated β1 subunit mRNA level, decreased arterial pressures, and improved endothelial function coupled with a reduction in morbidity and mortality associated with OSA. These reports suggest that the BK channel has a role in the response involved in hypoxia-associated hypertension derived from OSA. Thus, this review aims to describe the mechanisms involved in the BK channel activation after a hypoxic stimulus and their relationship with disorders like OSA. A deep understanding of the molecular mechanism involved in hypoxic response may help in the therapeutic approaches to treat the pathological processes associated with diseases involving cellular hypoxia.

Understanding p300-transcription factor interactions using sequence variation and hybridization

The hypoxic response is central to cell function and plays a significant role in the growth and survival of solid tumours. HIF-1 regulates the hypoxic response by activating over 100 genes responsible for adaptation to hypoxia, making it a potential target for anticancer drug discovery. Although there is significant structural and mechanistic understanding of the interaction between HIF-1α and p300 alongside negative regulators of HIF-1α such as CITED2, there remains a need to further understand the sequence determinants of binding. In this work we use a combination of protein expression, chemical synthesis, fluorescence anisotropy and isothermal titration calorimetry for HIF-1α sequence variants and a HIF-1α- CITED hybrid sequence which we term CITIF. We show the HIF-1α sequence is highly tolerant to sequence variation through reduced enthalpic and less unfavourable entropic contributions, These data imply backbone as opposed to side chain interactions and ligand folding control the binding interaction and that sequence variations are tolerated as a result of adopting a more disordered bound interaction or fuzzy complex.

Oxygen - Mitochondrial fuel as a missing link in depressive pathophysiology

Major depressive disorder (MDD) causes enormous individual suffering and socioeconomic costs. Biochemical mechanisms leading to MDD are poorly understood and therapy success is not satisfactory. At present, there is evidence of low-grade inflammation, oxidative stress, and most interestingly, a disturbed energy metabolism in MDD and other mental health diseases. Mitochondria play a central part in energy production and stress signaling. Mitochondrial electron transport chain uses molecular oxygen (O2) as final electron acceptor during adenosine triphosphate production attributing a crucial role to an intact O2 supply. Adaptation to altered O2 availability by the highly conserved hypoxic response is essential for maintaining allostasis. Previous research confirmed the role of O2 metabolism in the pathophysiology of MDD. In this perspective article, we compile the evidence linking O2 transport, O2 homeostasis, and mitochondrial energy metabolism to MDD. Furthermore, we hypothesize that inflammation and oxidative stress-related alterations in O2 transport might lead to a hypoxic response, which explains changes in O2 homeostasis and energy metabolism in MDD. Our forthcoming studies will investigate the interplay between energy metabolism and O2 homeostasis in MDD that aim to improve the overall understanding of the pathophysiology of MDD and to guide medical and psychological diagnostics towards a holistic strategy.

The evolutionary and physiological significance of the Hif pathway in teleost fishes

ABSTRACT The hypoxia-inducible factor (HIF) pathway is a key regulator of cellular O2 homeostasis and an important orchestrator of the physiological responses to hypoxia (low O2) in vertebrates. Fish can be exposed to significant and frequent changes in environmental O2, and increases in Hif-α (the hypoxia-sensitive subunit of the transcription factor Hif) have been documented in a number of species as a result of a decrease in O2. Here, we discuss the impact of the Hif pathway on the hypoxic response and the contribution to hypoxia tolerance, particularly in fishes of the cyprinid lineage, which includes the zebrafish (Danio rerio). The cyprinids are of specific interest because, unlike in most other fishes, duplicated paralogs of the Hif-α isoforms arising from a teleost-specific genome duplication event have been retained. Positive selection has acted on the duplicated paralogs of the Hif-α isoforms in some cyprinid sub-families, pointing to adaptive evolutionary change in the paralogs. Thus, cyprinids are valuable models for exploring the evolutionary significance and physiological impact of the Hif pathway on the hypoxic response. Knockout in zebrafish of either paralog of Hif-1α greatly reduces hypoxia tolerance, indicating the importance of both paralogs to the hypoxic response. Here, with an emphasis on the cardiorespiratory system, we focus on the role of Hif-1α in the hypoxic ventilatory response and the regulation of cardiac function. We explore the effects of the duration of the hypoxic exposure (acute, sustained or intermittent) on the impact of Hif-1α on cardiorespiratory function and compare relevant data with those from mammalian systems.

Activation of HIF1α Rescues the Hypoxic Response and Reverses Metabolic Dysfunction in the Diabetic Heart

Type 2 diabetes (T2D) impairs Hypoxia-Inducible Factor (HIF)1α activation, a master transcription factor that drives cellular adaptation to hypoxia. Reduced activation of HIF1α contributes to the impaired post-ischaemic remodelling observed following myocardial infarction in T2D. Molidustat is a HIF stabiliser currently undergoing clinical trials for the treatment of renal anaemia associated with chronic kidney disease, however, it may provide a route to pharmacologically activate HIF1α in the T2D heart. <br><p>In human cardiomyocytes, molidustat stabilised HIF1α and downstream HIF target genes, promoting anaerobic glucose metabolism. In hypoxia, insulin resistance blunted HIF1α activation and downstream signalling, but this was reversed by molidustat. In T2D rats, oral treatment with molidustat rescued the cardiac metabolic dysfunction caused by T2D, promoting glucose metabolism and mitochondrial function, whilst suppressing fatty acid oxidation and lipid accumulation. This resulted in beneficial effects on post-ischemic cardiac function, with the impaired contractile recovery in T2D heart reversed by molidustat treatment. <br>In conclusion, pharmacological HIF1α stabilisation can overcome the blunted hypoxic response induced by insulin resistance. In vivo this corrected the abnormal metabolic phenotype and impaired post-ischaemic recovery of the diabetic heart. Therefore, molidustat may be an effective compound to further explore the clinical translatability of HIF1α activation in the diabetic heart. </p> <p></p>

Activation of HIF1α Rescues the Hypoxic Response and Reverses Metabolic Dysfunction in the Diabetic Heart

Type 2 diabetes (T2D) impairs Hypoxia-Inducible Factor (HIF)1α activation, a master transcription factor that drives cellular adaptation to hypoxia. Reduced activation of HIF1α contributes to the impaired post-ischaemic remodelling observed following myocardial infarction in T2D. Molidustat is a HIF stabiliser currently undergoing clinical trials for the treatment of renal anaemia associated with chronic kidney disease, however, it may provide a route to pharmacologically activate HIF1α in the T2D heart. <br><p>In human cardiomyocytes, molidustat stabilised HIF1α and downstream HIF target genes, promoting anaerobic glucose metabolism. In hypoxia, insulin resistance blunted HIF1α activation and downstream signalling, but this was reversed by molidustat. In T2D rats, oral treatment with molidustat rescued the cardiac metabolic dysfunction caused by T2D, promoting glucose metabolism and mitochondrial function, whilst suppressing fatty acid oxidation and lipid accumulation. This resulted in beneficial effects on post-ischemic cardiac function, with the impaired contractile recovery in T2D heart reversed by molidustat treatment. <br>In conclusion, pharmacological HIF1α stabilisation can overcome the blunted hypoxic response induced by insulin resistance. In vivo this corrected the abnormal metabolic phenotype and impaired post-ischaemic recovery of the diabetic heart. Therefore, molidustat may be an effective compound to further explore the clinical translatability of HIF1α activation in the diabetic heart. </p> <p></p>

Reduced Endothelin-2 and Hypoxic Signaling Pathways in Granulosa-Lutein Cells of PCOS Women

Granulosa-lutein cells (GLCs) from PCOS women display reduced HIF-1α and EDN2 levels, suggesting their role in PCOS etiology. Here, we investigated the mechanisms involved in aberrant EDN2 expression in PCOS, and its association with HIF-1α. Various HIF-1α-dependent factors were studied in GLCs from PCOS and compared to normally ovulating women. MicroRNA-210 (miR-210), its target genes (SDHD and GPD1L), and HIF-1α-responsive genes (EDN2 and VEGFA) differed in GLCs from PCOS, compared with those of healthy women. Levels of miR-210—designated hypoxiamiR—and EDN2 were reduced in the PCOS GLCs; concomitantly, GPD1L and SDHD levels were elevated. Cultured GLCs retained low EDN2 expression and had low HIF-1α levels, providing evidence for a disrupted hypoxic response in the PCOS GLCs. However, VEGFA expression was elevated in these cells. Next, miR-210 levels were manipulated. miR-210-mimic stimulated EDN2 twice as much as the miR-NC-transfected cells, whereas miR-210-inhibitor diminished EDN2, emphasizing the importance of hypoxiamiR for EDN2 induction. Intriguingly, VEGFA transcripts were reduced by both miR-210-mimic and -inhibitor, demonstrating that EDN2 and VEGFA are distinctly regulated. Disrupted hypoxic response in the GLCs of periovulatory follicles in PCOS women may play a role in ovulation failure, and in the reduced fertility prevalent in this syndrome.

Oxygen-dependent changes in binding partners and post-translational modifications regulate the abundance and activity of HIF-1α/2α

Cellular adaptation to low-oxygen environments is mediated in part by the hypoxia-inducible factors (HIFs). Like other transcription factors, the stability and transcriptional activity of HIFs—and consequently, the hypoxic response—are regulated by post-translational modifications (PTMs) and changes in protein-protein interactions. Our current understanding of PTM-mediated regulation of HIFs is primarily based on in vitro protein fragment–based studies typically validated in fragment-expressing cells treated with hypoxia-mimicking compounds. Here, we used immunoprecipitation-based mass spectrometry to characterize the PTMs and binding partners for full-length HIF-1α and HIF-2α under normoxic (21% oxygen) and hypoxic (1% oxygen) conditions. Hypoxia substantially altered the complexity and composition of the HIFα protein interaction networks, particularly for HIF-2α, with the hypoxic networks of both isoforms being enriched for mitochondrial proteins. Moreover, both HIFα isoforms were heavily covalently modified. We identified ~40 PTM sites composed of 13 different types of modification on both HIFα isoforms, including multiple cysteine modifications and an unusual phosphocysteine. More than 80% of the PTMs identified were not previously known and about half exhibited oxygen dependency. We further characterized an evolutionarily conserved phosphorylation of Ser31 in HIF-1α as a regulator of its transcriptional function, and we propose functional roles for Thr406, Thr528, and Ser581 in HIF-2α. These data will help to delineate the different physiological roles of these closely related isoforms in fine-tuning the hypoxic response.