Oxygen sensing and adaptability won the 2019 Nobel Prize in Physiology or medicine

Enantio- and Diastereoselective Total Synthesis of Belzutifan Enabled by Rh-Catalyzed Hydrogenation

Herein, we report a nine-step synthesis of belzutifan enabled by a novel Rh-catalyzed asymmetric hydrogenation to install the contiguous fluorinated stereocenters with high enantioselectivity. Moreover, the final ketone reduction in the synthesis proceeds with high diastereoselectivity, leading to the expedient assembly of the stereotriad. In contrast to the original 16-step synthesis, this route avoids a lengthy bromination-oxidation sequence and introduces the sulfone functionality via nucleophilic aromatic substitution, obviating the need for transition metal catalysis.

Von Hippel-Lindau protein signalling in clear cell renal cell carcinoma

The distinct pathological and molecular features of kidney cancer in adaptation to oxygen homeostasis render this malignancy an attractive model for investigating hypoxia signalling and potentially developing potent targeted therapies. Hypoxia signalling has a pivotal role in kidney cancer, particularly within the most prevalent subtype, known as renal cell carcinoma (RCC). Hypoxia promotes various crucial pathological processes, such as hypoxia-inducible factor (HIF) activation, angiogenesis, proliferation, metabolic reprogramming and drug resistance, all of which contribute to kidney cancer development, growth or metastasis formation. A substantial portion of kidney cancers, in particular clear cell RCC (ccRCC), are characterized by a loss of function of Von Hippel-Lindau tumour suppressor (VHL), leading to the accumulation of HIF proteins, especially HIF2α, a crucial driver of ccRCC. Thus, therapeutic strategies targeting pVHL-HIF signalling have been explored in ccRCC, culminating in the successful development of HIF2α-specific antagonists such as belzutifan (PT2977), an FDA-approved drug to treat VHL-associated diseases including advanced-stage ccRCC. An increased understanding of hypoxia signalling in kidney cancer came from the discovery of novel VHL protein (pVHL) targets, and mechanisms of synthetic lethality with VHL mutations. These breakthroughs can pave the way for the development of innovative and potent combination therapies in kidney cancer.

The immunoreactivity of GLI1 and VEGFA is a potential prognostic factor in kidney renal clear cell carcinoma

Kidney renal clear cell carcinoma (KIRC) is the most common type of kidney cancer and its pathogenesis is strongly associated with VHL-HIF-VEGF signaling. SHH ligand is the upstream SHH pathway regulator, while GLI1 is its major effector that stimulates as a transcription factor, i.a. expression of VEGFA gene. The aim of present study was to assess the prognostic significance of SHH, GLI1 and VEGFA immunoreactivity in KIRC tissues. The analysis included paired tumor and normal samples from 34 patients with KIRC. The immunoreactivity of SHH, GLI1 and VEGFA proteins was determined by immunohistochemical (IHC) renal tissues staining. The IHC staining results were assessed using the immunoreactive score (IRS) method which takes into account the number of cells showing a positive reaction and the intensity of the reaction. Increased GLI1 protein immunoreactivity was observed in KIRC tissues, especially in early-stage tumors, according to the TNM classification. Elevated expression of the VEGFA protein was noted primarily in high-grade KIRC samples according to the Fuhrman/WHO/ISUP scale. Moreover, a directly proportional correlation was observed between SHH and VEGFA immunoreactivity in TNM 3 + 4 and Fuhrman/ISUP/WHO 3 + 4 tumor tissues as well as in samples of patients with shorter survival. We also observed an association between shorter patient survival as well as increased and decreased immunoreactivity, of the VEGFA and GLI1, respectively. The aforementioned findings suggest that the expression pattern of SHH, GLI1 and VEGFA demonstrates prognostic potential in KIRC.

Mitochondrial complex I ROS production and redox signaling in hypoxia

Mitochondria are a main source of cellular energy. Oxidative phosphorylation (OXPHOS) is the major process of aerobic respiration. Enzyme complexes of the electron transport chain (ETC) pump protons to generate a protonmotive force (Δp) that drives OXPHOS. Complex I is an electron entry point into the ETC. Complex I oxidizes nicotinamide adenine dinucleotide (NADH) and transfers electrons to ubiquinone in a reaction coupled with proton pumping. Complex I also produces reactive oxygen species (ROS) under various conditions. The enzymatic activities of complex I can be regulated by metabolic conditions and serves as a regulatory node of the ETC. Complex I ROS plays diverse roles in cell metabolism ranging from physiologic to pathologic conditions. Progress in our understanding indicates that ROS release from complex I serves important signaling functions. Increasing evidence suggests that complex I ROS is important in signaling a mismatch in energy production and demand. In this article, we review the role of ROS from complex I in sensing acute hypoxia.

Adipose-Derived Stem Cells Improve Angiogenesis and Lymphangiogenesis in a Hypoxic Dermal Regeneration Model In Vitro

Background and Objectives: Impaired wound healing represents an unsolved medical issue with a high impact on patients’ quality of life and global health care. Even though hypoxia is a significant limiting factor for wound healing, it reveals stimulating effects in gene and protein expression at cellular levels. In particular, hypoxically treated human adipose tissue-derived stem cells (ASCs) have previously been used to stimulate tissue regeneration. Therefore, we hypothesized that they could promote lymphangiogenesis or angiogenesis. Materials and Methods: Dermal regeneration matrices were seeded with human umbilical vein endothelial cells (HUVECs) or human dermal lymphatic endothelial cells (LECs) that were merged with ASCs. Cultures were maintained for 24 h and 7 days under normoxic or hypoxic conditions. Finally, gene and protein expression were measured regarding subtypes of VEGF, corresponding receptors, and intracellular signaling pathways, especially hypoxia-inducible factor-mediated pathways using multiplex-RT-qPCR and ELISA assays. Results: All cell types reacted to hypoxia with an alteration of gene expression. In particular, vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor B (VEGFB), vascular endothelial growth factor C (VEGFC), vascular endothelial growth factor receptor 1 (VEGFR1/FLT1), vascular endothelial growth factor receptor 2 (VEGFR2/KDR), vascular endothelial growth factor receptor 3 (VEGFR3/FLT4), and prospero homeobox 1 (PROX1) were overexpressed significantly depending on upregulation of hypoxia-inducible factor 1 alpha (HIF-1a). Moreover, co-cultures with ASCs showed a more intense change in gene and protein expression profiles and gained enhanced angiogenic and lymphangiogenic potential. In particular, long-term hypoxia led to continuous stimulation of HUVECs by ASCs. Conclusions: Our findings demonstrated the benefit of hypoxic conditioned ASCs in dermal regeneration concerning angiogenesis and lymphangiogenesis. Even a short hypoxic treatment of 24 h led to the stimulation of LECs and HUVECs in an ASC-co-culture. Long-term hypoxia showed a continuous influence on gene expressions. Therefore, this work emphasizes the supporting effects of hypoxia-conditioned-ASC-loaded collagen scaffolds on wound healing in dermal regeneration.

Butadiyne-linked porphyrin nanoring as a highly selective O2 gas sensor: A fast response hybrid sensor

The butadiyne-linked six-metalloporphyrin nanoring (Mg₆-P₆) and it's complex with a hexapyridyl template, Mg₆-P₆·T₆ have a great potential for employment in future nanoelectronic applications such as a nanosensor for small gas molecules. The goal of this study is to scrutinize and improvement of the CO, N_2, and O₂ gas sensing capacity of Mg₆-P₆ and Mg₆-P₆·T₆ using DFT calculations at CAM-B3LYP/6-31G (d,p) level of theory. The geometrical structures, binding energies, band gaps, the density of states (DOS), adsorption energies, HOMO and LUMO energies, Fermi level energies (E_FL), NBO, FMO and TD-DFT spectrum were calculated to predict gas adsorption properties of Mg₆-P₆ and Mg₆-P₆·T₆ systems. Based on the calculated adsorption energies and remarkable decrease in the Eg, it is expected that the Mg₆-P₆ and Mg₆-P₆·T₆ are sensitive to O₂ molecule. Surprisingly, the Mg₆-P₆-O₂ and specially the Mg₆-P₆.T₆-O₂ record promising values of recovery times for different attempt frequencies. Therefore, the results open a way for the development of a new and selective O₂ nanosensor in the presence of CO and N₂ gas molecules.

The Impact of Exercise on Immunity, Metabolism, and Atherosclerosis

Physical exercise represents an effective preventive and therapeutic strategy beneficially modifying the course of multiple diseases. The protective mechanisms of exercise are manifold; primarily, they are elicited by alterations in metabolic and inflammatory pathways. Exercise intensity and duration strongly influence the provoked response. This narrative review aims to provide comprehensive up-to-date insights into the beneficial effects of physical exercise by illustrating the impact of moderate and vigorous exercise on innate and adaptive immunity. Specifically, we describe qualitative and quantitative changes in different leukocyte subsets while distinguishing between acute and chronic exercise effects. Further, we elaborate on how exercise modifies the progression of atherosclerosis, the leading cause of death worldwide, representing a prime example of a disease triggered by metabolic and inflammatory pathways. Here, we describe how exercise counteracts causal contributors and thereby improves outcomes. In addition, we identify gaps that still need to be addressed in the future.

Effectiveness of Intermittent Hypoxia-Hyperoxia Therapy in Different Pathologies with Possible Metabolic Implications

Intermittent oxygen therapy (IHT), initially used in the hypoxic administration variant, has been shown to be effective in various pathologies studied, from cardiopulmonary to vascular and metabolic pathologies and more. IHT used to prevent and treat various diseases has thus gained more and more attention as the years have passed. The mechanisms underlying the beneficial effects have been investigated at multiple biological levels, from systemic physiological reactions to genomic regulation. In the last decade, a new method of intermittent oxygen therapy has been developed that combines hypoxic and hyperoxic periods. They can be applied both at rest and during physical exercise, hence the specific indications in sports medicine. It has been hypothesized that replacing normoxia with moderate hyperoxia may increase the adaptive response to the intermittent hypoxic stimulus by upregulating reactive oxygen species and hypoxia-inducible genes. This systematic literature review is based on the "Preferred Reporting Items for Systematic Reviews and Meta-Analysis"-"PRISMA"-methodology, the widely internationally accepted method.

Carboxyl Functionalization of N-MWCNTs with Stone-Wales Defects and Possibility of HIF-1α Wave-Diffusive Delivery

Nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) are widely used for drug delivery. One of the main challenges is to clarify their interaction with hypoxia-inducible factor 1 alpha (HIF-1α), the lack of which leads to oncological and cardiovascular diseases. In the presented study, N-MWCNTs were synthesized by catalytic chemical vapor deposition and irradiated with argon ions. Their chemical state, local structure, interfaces, Stone-Wales defects, and doping with nitrogen were analyzed by high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Using experimental data, supercells of functionalized N-MWCNTs with an oxygen content of 2.7, 4 and 6 at. % in carboxyl groups were built by quantum chemical methods. Our analysis by the self-consistent charge density functional tight-binding (SCC DFTB) method shows that a key role in the functionalization of CNTs with carboxyl groups belongs to Stone-Wales defects. The results of research in the decoration of CNTs with HIF-1α demonstrate the possibility of wave-diffusion drug delivery. The nature of hybridization and relaxation determines the mechanism of oxygen regulation with HIF-1α molecules, namely, by OH-(OH-C) and OH-(O=C) chemical bonds. The concentration dependence of drug release in the diffusion mode suggests that the best pattern for drug delivery is provided by the tube with a carboxylic oxygen content of 6 at. %.

Tumor hypoxia: From basic knowledge to therapeutic implications

Diminished oxygen availability, termed hypoxia, within solid tumors is one of the most common characteristics of cancer. Hypoxia shapes the landscape of the tumor microenvironment (TME) into a pro-tumorigenic and pro-metastatic niche through arrays of pathological alterations such as abnormal vasculature, altered metabolism, immune-suppressive phenotype, etc. In addition, emerging evidence suggests that limited efficacy or the development of resistance towards antitumor therapy may be largely due to the hypoxic TME. This review will focus on summarizing the knowledge about the molecular machinery that mediates the hypoxic cellular responses and adaptations, as well as highlighting the effects and consequences of hypoxia, especially for angiogenesis regulation, cellular metabolism alteration, and immunosuppressive response within the TME. We also outline the current advances in novel therapeutic implications through targeting hypoxia in TME. A deep understanding of the basics and the role of hypoxia in the tumor will help develop better therapeutic avenues in cancer treatment.

Pulmonary Oxygen Exchange in a Rhythmically Expanding–Contracting Alveolus–Capillary Model

Pulmonary gas exchanges are vital to human health, and disruptions to this process have been associated with many respiratory diseases. Previous gas exchange studies have predominately relied on whole-body testing and theoretical analysis with 1D or static models. However, pulmonary gas exchanges are inherently a dynamic process in 3D spaces with instantaneous interactions between air, blood, and tissue. This study aimed to develop a computational model for oxygen exchange that considered all factors mentioned above. Therefore, an integrated alveolus–membrane–capillary geometry was developed with prescribed rhythmic expansion/contraction. Airflow ventilation, blood perfusion, and oxygen diffusion were simulated using COMSOL. The temporal and spatial distribution of blood flow and oxygen within the capillaries were simulated under varying breathing depths and cardiac outputs. The results showed highly nonuniform blood flow distributions in the capillary network, while the rhythmic oscillation further increased this nonuniformity, leading to stagnant blood flow in the distal vessels. A static alveolus–capillary geometry underestimated perfusion by 11% for normal respirations, and the deviation grew with breathing depth. The rhythmic motion caused a phase lag in the blood flow. The blood PO2 reached equilibrium with the alveolar air after traveling 1/5–1/3 of the capillary network. The time to reach this equilibrium was significantly influenced by the air–blood barrier diffusivity, while it was only slightly affected by the perfusion rate. The computational platform in this study could be instrumental in obtaining refined knowledge of pulmonary O2 exchanges.

Lighting up Nobel Prize-winning studies with protein intrinsic disorder

Intrinsically disordered proteins and regions (IDPs and IDRs) and their importance in biology are becoming increasingly recognized in biology, biochemistry, molecular biology and chemistry textbooks, as well as in current protein science and structural biology curricula. We argue that the sequence → dynamic conformational ensemble → function principle is of equal importance as the classical sequence → structure → function paradigm. To highlight this point, we describe the IDPs and/or IDRs behind the discoveries associated with 17 Nobel Prizes, 11 in Physiology or Medicine and 6 in Chemistry. The Nobel Laureates themselves did not always mention that the proteins underlying the phenomena investigated in their award-winning studies are in fact IDPs or contain IDRs. In several cases, IDP- or IDR-based molecular functions have been elucidated, while in other instances, it is recognized that the respective protein(s) contain IDRs, but the specific IDR-based molecular functions have yet to be determined. To highlight the importance of IDPs and IDRs as general principle in biology, we present here illustrative examples of IDPs/IDRs in Nobel Prize-winning mechanisms and processes.

Regulation of Transactivation at C-TAD Domain of HIF-1α by Factor-Inhibiting HIF-1α (FIH-1): A Potential Target for Therapeutic Intervention in Cancer

Hypoxia-inducible factor-1alpha (HIF-1α) is a major transcription factor that adapts to low oxygen homeostasis and regulates the expression of several hypoxic genes, which aid in cancer survival and development. It has recently piqued the interest of translational researchers in the disciplines of cancer sciences. Hypoxia triggers an ample adaptive mechanism mediated via the HIF-1α transcriptional domain. Anaerobic glycolysis, angiogenesis, metastasis, and mitophagy are adaptive mechanisms that support tumor survival by promoting oxygen supply and regulating oxygen demand in hypoxic tumor cells. Throughout this pathway, the factor-inhibiting HIF-1α is a negative regulator of HIF-1α leading to its hydroxylation at the C-TAD domain of HIF-1α under normoxia. Thus, hydroxylated HIF-1α is unable to proceed with the transcriptional events due to interference in binding of C-TAD and CBP/p300. From this review, we can hypothesize that remodeling of FIH-1 activity is a unique mechanism that decreases the transcriptional activity of HIF-1α and, as a result, all of its hypoxic consequences. Hence, this review manuscript details the depth of knowledge of FIH-1 on hypoxia-associated cellular and molecular events, a potential strategy for targeting hypoxia-induced malignancies.

Hypoxia as a Modulator of Inflammation and Immune Response in Cancer

A clear association between hypoxia and cancer has heretofore been established; however, it has not been completely developed. In this sense, the understanding of the tumoral microenvironment is critical to dissect the complexity of cancer, including the reduction in oxygen distribution inside the tumoral mass, defined as tumoral hypoxia. Moreover, hypoxia not only influences the tumoral cells but also the surrounding cells, including those related to the inflammatory processes. In this review, we analyze the participation of HIF, NF-κB, and STAT signaling pathways as the main components that interconnect hypoxia and immune response and how they modulate tumoral growth. In addition, we closely examine the participation of the immune cells and how they are affected by hypoxia, the effects of the progression of cancer, and some innovative applications that take advantage of this knowledge, to suggest potential therapies. Therefore, we contribute to the understanding of the complexity of cancer to propose innovative therapeutic strategies in the future.

Molecular dynamics and 3D-QSAR studies on indazole derivatives as HIF-1α inhibitors

Hypoxia-inducible factor (HIF) is a transcriptional factor which plays a crucial role in tumour metastasis thereby responsible for development of various forms of cancers. Indazole derivatives have been reported in the literature as potent HIF-1α inhibitor via interaction with key residues of the HIF-1α active site. Taking into consideration the role HIF-1α in cancer and potency of indazole derivative against HIF-1α; it was considered of interest to correlate structural features of known indazole derivatives with specified HIF-1α inhibitory activity to map pharmacophoric features through Three-dimensional quantitative structural activity relationship (3D-QSAR) and pharmacophore mapping. Field and Gaussian based 3D-QSAR studies were performed to realize the variables influencing the inhibitory potency of HIF-1α inhibitors. Field and Gaussian- based 3D-QSAR models were validated through various statistical measures generated by partial least square (PLS). The steric and electrostatic maps generated for both 3D-QSAR provide a structural framework for designing new inhibitors. Further; 3D-maps were also helpful in understanding variability in the activity of the compounds. Pharmacophore mapping also generates a common five-point pharmacophore hypothesis (A₁D₂R₃R₄R₅_4) which can be employed in combination with 3D-contour maps to design potent HIF-1α inhibitors. Molecular docking and molecular dynamics (MD) simulation of the most potent compound 39 showed good binding efficiency and was found to be quite stable in the active site of the HIF-1α protein. The developed 3D-QSAR models; pharmacophore modelling; molecular docking studies along with the MD simulation analysis may be employed to design lead molecule as selective HIF-1α inhibitors for the treatment of Cancer.

Bioenergetic and Metabolic Adaptation in Tumor Progression and Metastasis

The ability of cancer cells to adjust their metabolism in response to environmental changes is a well-recognized hallmark of cancer. Diverse cancer and non-cancer cells within tumors compete for metabolic resources. Metabolic demands change frequently during tumor initiation, progression and metastasis, challenging our quest to better understand tumor biology and develop novel therapeutics. Vascularization, physical constraints, immune responses and genetic instability promote tumor evolution resulting in immune evasion, opportunities to breach basement membrane barriers and spread through the circulation and lymphatics. In addition, the unfolded protein response linked to the ubiquitin proteasome system is a key player in addressing stoichiometric imbalances between nuclear and mitochondrially-encoded protein subunits of respiratory complexes, and nuclear-encoded mitochondrial ribosomal protein subunits. While progressive genetic changes, some of which affect metabolic adaptability, contribute to tumorigenesis and metastasis through clonal expansion, epigenetic changes are also important and more dynamic in nature. Understanding the role of stromal and immune cells in the tumor microenvironment in remodeling cancer cell energy metabolism has become an increasingly important area of research. In this perspective, we discuss the adaptations made by cancer cells to balance mitochondrial and glycolytic energy metabolism. We discuss how hypoxia and nutrient limitations affect reductive and oxidative stress through changes in mitochondrial electron transport activity. We propose that integrated responses to cellular stress in cancer cells are central to metabolic flexibility in general and bioenergetic adaptability in particular and are paramount in tumor progression and metastasis.

Long-Term Cardiac Damage Associated With Abdominal Irradiation in Mice

Aims: Irradiation is an effective treatment for tumors but has been associated with cardiac dysfunction. However, the precise mechanisms remain incompletely elucidated. This study investigated the long-term cardiac damage associated with abdominal irradiation and explored possible mechanisms.

Methods and Results: Wild-type C57BL6/J mice were divided into two groups: untreated controls (Con) and treatment group receiving 15 Gy of abdominal gamma irradiation (AIR). Both groups received normal feeding for 12 months. The AIR group showed reductions in left ventricular ejection fraction (LVEF), fractional shortening (FS), left ventricular end-diastolic internal diameter (LVID; d), left ventricular end-diastolic volume (LV Vol. diastolic volume (LV Vol; d) and mitral transtricuspid flow late diastolic filling velocity (MV A). It also showed increased fibrosis, reduced conduction velocity and increased conduction heterogeneity. Non-targeted metabolomics showed the differential metabolites were mainly from amino acid metabolism. Further KEGG pathway annotation and enrichment analysis revealed that abnormalities in arginine and proline metabolism, lysine degradation, d-arginine and d-ornithine metabolism, alanine, aspartate and glutamate metabolism, and arginine biosynthesis.

Conclusion: Abdominal irradiation causes long-term damage to the non-irradiated heart, as reflected by electrical and structural remodeling and mechanical dysfunction associated with abnormal amino acid biosynthesis and metabolism.

Key promoters of tumor hallmarks

Evolution of tumor hallmarks is a result of accommodation of tumor cells with their nearby milieu called tumor microenvironment (TME). Accommodation or adaptive responses is highly important for a cell to survive, without which no cell is allowed to take any further steps in tumorigenesis. Metabolism of cancer cells is largely depended on stroma. Composition and plasticity of cells within the stroma is highly affected from inflammatory setting of TME. Hypoxia which is a common event in many solid cancers, is known as one of the key hallmarks of chronic inflammation and the master regulator of metastasis. Transforming growth factor (TGF)-β is produced in the chronic inflammatory and chronic hypoxic settings, and it is considered as a cardinal factor for induction of all tumor hallmarks. Aging, obesity and smoking are the main predisposing factors of cancer, acting mainly through modulation of TME.

Engineering strategies to capture the biological and biophysical tumor microenvironment in vitro

Despite decades of research and advancements in diagnostic and treatment modalities, cancer remains a major global healthcare challenge. This is due in part to a lack of model systems that allow investigating the mechanisms underlying tumor development, progression, and therapy resistance under relevant conditions in vitro. Tumor cell interactions with their surroundings influence all stages of tumorigenesis and are shaped by both biological and biophysical cues including cell-cell and cell-extracellular matrix (ECM) interactions, tissue architecture and mechanics, and mass transport. Engineered tumor models provide promising platforms to elucidate the individual and combined contributions of these cues to tumor malignancy under controlled and physiologically relevant conditions. This review will summarize current knowledge of the biological and biophysical microenvironmental cues that influence tumor development and progression, present examples of in vitro model systems that are presently used to study these interactions and highlight advancements in tumor engineering approaches to further improve these technologies.

Effects of moderate-intensity intermittent hypoxic training on health outcomes of patients recovered from COVID-19: the AEROBICOVID study protocol for a randomized controlled trial

Background

Recent studies point to a lower number and reduced severity of cases in higher altitude cities with decreased oxygen concentration. Specific literature has shown several benefits of physical training, so, in this sense, physical training with hypoxic stimulus appears as an alternative that supports the conventional treatments of the COVID-19 patient’s recovery. Thus, this study’s primary aim is to analyze the effects of moderate-intensity intermittent hypoxic training on health outcomes in COVID-19 recovered patients.

Methods

A clinical trial controlled double-blind study was designed. Participants (30–69 years old) will be recruited among those with moderate to severe COVID-19 symptoms, approximately 30 days after recovery. They will be included in groups according to the training (T) and recovery (R) association with hypoxia (H) or normoxia (N): (a) T_H:R_H, (b) T_N:R_H, (c) T_N:R_N, and last (d) the control group. The 8-week exercise bike intervention will be carried out with a gradual load increase according to the established periods, three times a week in sets of 5 min, 90 to 100% of the anaerobic threshold (AT), and a 2.5-min break. Blood will be collected for genotyping. First, after 4 weeks (partial), after 8 weeks, and later, 4 weeks after the end of the physical training intervention, participants will perform assessments. The primary outcome is the maximum oxygen consumption (VO₂peak). The secondary outcomes include lung function, inflammatory mediators, hematological, autonomic parameters, AT, body composition analysis, quality of life, mental health, anthropometric measurements, and physical fitness. The statistical analysis will be executed using the linear regression model with mixed effects at a 5% significance level.

Discussion

This study is designed to provide evidence to support the clinical benefits of moderate-intensity intermittent hypoxic training as a part of the treatment of patients recovered from COVID-19. It may also provide evidence on the efficacy and safety of intermittent hypoxic training in different health conditions. Lastly, this study presents an innovative strategy enabling up to 16 participants in the same training session.

Trial registration

ClinicalTrials.gov RBR-5d7hkv. Registered after the start of inclusion on 3 November 2020 with the Brazilian Clinical Trials Registry

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05414-2.

From oxygen sensing to angiogenesis: Targeting the hypoxia signaling pathway in metastatic kidney cancer

PURPOSE

This article summarizes examples of current and emerging therapies that target the hypoxia and angiogenesis signaling pathways in the clear cell type of renal cell cancer (RCC), with an emphasis on the hypoxia signaling pathway.

SUMMARY

Mammalian cells transduce signals of decreased oxygen to hypoxia inducible factor (HIF), an intracellular heterodimer that mediates the adaptation of normal and tumor cells to oxygen deprivation. HIF is frequently overexpressed in cancer cells and is involved in the transcriptional activation of many genes essential for cell invasion, migration, survival, and angiogenesis (including vascular endothelial growth factor [VEGF]). Moreover, HIF confers resistance to cytotoxic chemotherapy and radiation therapy and is associated with poor prognosis in patients with cancer. Blocking the activity of HIF inhibits the expression of VEGF and oncogenic pathways, resulting in the inhibition of tumor growth. Interestingly, activation of oncogenes and/or inactivation of tumor suppressor genes (eg, the gene encoding von Hippel-Lindau [VHL] tumor suppressor protein) can activate tumorigenesis even with normal levels of oxygen, providing support for the notion that the HIF-VHL-VEGF axis is amenable to targeted therapies for the treatment of RCC. This article highlights the current understanding of the hypoxia signaling pathway and its relevance to RCC development. Pharmacologic agents targeting the hypoxia and angiogenesis signaling pathways are discussed.

CONCLUSION

Development of novel therapeutic agents that target the hypoxia and angiogenesis signaling pathways holds promise in the management of metastatic clear cell RCC.

Von Hippel-Lindau tumor suppressor pathways & corresponding therapeutics in kidney cancer

The identification and application of the Von Hippel-Lindau (VHL) gene is a seminal breakthrough in kidney cancer research. VHL and its protein pVHL are the root cause of most kidney cancers, and the cascading pathway below them is crucial for understanding hypoxia, in addition to the aforementioned tumorigenesis routes and treatments. We reviewed the history and functions of VHL/pVHL and Hypoxia-inducible factor (HIF), their well-known activities under low-oxygen environments as an E3 ubiquitin ligase and as a transcription factor, respectively, as well as their non-canonical functions revealed recently. Additionally, we discussed how their dysregulation promotes tumorigenesis: beginning with chromosome 3 p-arm (3p) loss/epigenetic methylation, followed by two-allele knockout, before the loss of complimentary tumor suppressor genes leads cells down predictable oncological paths. These different pathways can ultimately determine the grade, outcome, and severity of the deadliest genitourinary cancer. We finished by investigating current and proposed schemes to therapeutically treat clear cell renal cell carcinoma (ccRCC) by manipulating the hypoxic pathway utilizing Vascular Endothelial Growth Factor (VEGF) inhibitors, mammalian target of rapamycin complex 1 (mTORC1) inhibitors, small molecule HIF inhibitors, immune checkpoint blockade therapy, and synthetic lethality.

Hypoxia-Driven Effects in Cancer: Characterization, Mechanisms, and Therapeutic Implications

Hypoxia, a common feature of solid tumors, greatly hinders the efficacy of conventional cancer treatments such as chemo-, radio-, and immunotherapy. The depletion of oxygen in proliferating and advanced tumors causes an array of genetic, transcriptional, and metabolic adaptations that promote survival, metastasis, and a clinically malignant phenotype. At the nexus of these interconnected pathways are hypoxia-inducible factors (HIFs) which orchestrate transcriptional responses under hypoxia. The following review summarizes current literature regarding effects of hypoxia on DNA repair, metastasis, epithelial-to-mesenchymal transition, the cancer stem cell phenotype, and therapy resistance. We also discuss mechanisms and pathways, such as HIF signaling, mitochondrial dynamics, exosomes, and the unfolded protein response, that contribute to hypoxia-induced phenotypic changes. Finally, novel therapeutics that target the hypoxic tumor microenvironment or interfere with hypoxia-induced pathways are reviewed.

Roxadustat for Treating Anemia in Patients with CKD Not on Dialysis: Results from a Randomized Phase 3 Study

BACKGROUND

Current anemia therapies for patients with non-dialysis-dependent CKD may require injection and medical visits. Roxadustat, an oral hypoxia-inducible factor prolyl hydroxylase inhibitor, stimulates erythropoiesis and improves iron homeostasis.

METHODS

In this double-blind phase 3 study, we randomized patients with non-dialysis-dependent CKD stages 3-5 and hemoglobin <10.0 g/dl (1:1) to thrice-weekly 70-mg oral roxadustat or placebo. Doses were titrated throughout the study based on hemoglobin levels. The primary efficacy end point was mean change from baseline in hemoglobin averaged over weeks 28-52 versus placebo, irrespective of rescue therapy use. We assessed patients for adverse events.

RESULTS

The study included 2781 patients, 1393 who received roxadustat and 1388 who received placebo. Mean baseline hemoglobin was 9.1 g/dl for both groups. The mean change in hemoglobin from baseline was 1.75 g/dl (95% confidence interval [95% CI], 1.68 to 1.81) with roxadustat versus 0.40 g/dl (95% CI, 0.33 to 0.47) with placebo, (P<0.001). Among 411 patients with baseline elevated high-sensitivity C-reactive protein, mean change in hemoglobin from baseline was 1.75 g/dl (95% CI, 1.58 to 1.92) with roxadustat versus 0.62 g/dl (95% CI, 0.44 to 0.80) with placebo, (P<0.001). Roxadustat reduced the risk of red blood cell transfusion by 63% (hazard ratio, 0.37; 95% CI, 0.30 to 0.44). The most common adverse events with roxadustat and placebo, respectively, were ESKD (21.0% versus 20.5%), urinary tract infection (12.8% versus 8.0%), pneumonia (11.9% versus 9.4%), and hypertension (11.5% versus 9.1%).

CONCLUSIONS

Roxadustat effectively increased hemoglobin in patients with non-dialysis-dependent CKD and reduced the need for red blood cell transfusion, with an adverse event profile comparable to that of placebo.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Safety and Efficacy Study of Roxadustat to Treat Anemia in Patients With CKD, Not on Dialysis, NCT02174627.

Tumor Hypoxia as a Barrier in Cancer Therapy: Why Levels Matter

Simple Summary

Hypoxia is a common feature of solid tumors and associated with poor outcome in most cancer types and treatment modalities, including radiotherapy, chemotherapy, surgery and, most likely, immunotherapy. Emerging strategies, such as proton therapy and combination therapies with radiation and hypoxia targeted drugs, provide new opportunities to overcome the hypoxia barrier and improve therapeutic outcome. Hypoxia is heterogeneously distributed both between and within tumors and shows large variations across patients not only in prevalence, but importantly, also in level. To best exploit the emerging strategies, a better understanding of how individual hypoxia levels from mild to severe affect tumor biology is vital. Here, we discuss our current knowledge on this topic and how we should proceed to gain more insight into the field.

Abstract

Hypoxia arises in tumor regions with insufficient oxygen supply and is a major barrier in cancer treatment. The distribution of hypoxia levels is highly heterogeneous, ranging from mild, almost non-hypoxic, to severe and anoxic levels. The individual hypoxia levels induce a variety of biological responses that impair the treatment effect. A stronger focus on hypoxia levels rather than the absence or presence of hypoxia in our investigations will help development of improved strategies to treat patients with hypoxic tumors. Current knowledge on how hypoxia levels are sensed by cancer cells and mediate cellular responses that promote treatment resistance is comprehensive. Recently, it has become evident that hypoxia also has an important, more unexplored role in the interaction between cancer cells, stroma and immune cells, influencing the composition and structure of the tumor microenvironment. Establishment of how such processes depend on the hypoxia level requires more advanced tumor models and methodology. In this review, we describe promising model systems and tools for investigations of hypoxia levels in tumors. We further present current knowledge and emerging research on cellular responses to individual levels, and discuss their impact in novel therapeutic approaches to overcome the hypoxia barrier.

Hypoxia and Oxygen-Sensing Signaling in Gene Regulation and Cancer Progression

Oxygen homeostasis regulation is the most fundamental cellular process for adjusting physiological oxygen variations, and its irregularity leads to various human diseases, including cancer. Hypoxia is closely associated with cancer development, and hypoxia/oxygen-sensing signaling plays critical roles in the modulation of cancer progression. The key molecules of the hypoxia/oxygen-sensing signaling include the transcriptional regulator hypoxia-inducible factor (HIF) which widely controls oxygen responsive genes, the central members of the 2-oxoglutarate (2-OG)-dependent dioxygenases, such as prolyl hydroxylase (PHD or EglN), and an E3 ubiquitin ligase component for HIF degeneration called von Hippel–Lindau (encoding protein pVHL). In this review, we summarize the current knowledge about the canonical hypoxia signaling, HIF transcription factors, and pVHL. In addition, the role of 2-OG-dependent enzymes, such as DNA/RNA-modifying enzymes, JmjC domain-containing enzymes, and prolyl hydroxylases, in gene regulation of cancer progression, is specifically reviewed. We also discuss the therapeutic advancement of targeting hypoxia and oxygen sensing pathways in cancer.

The combination of forskolin and VPA increases gene expression efficiency to the hypoxia/neuron-specific system

Background

Spinal cord injury (SCI) tends to damage neural tissue and generate a hypoxic environment. Studies have confirmed that single therapy with gene or stem cells is inefficient, but research into combining stem cells and gene therapy in treating tissue damage has been undertaken to overcome the related limitations, which include low gene delivery efficiency and therapeutic outcome. Thus, a combination of stem cells, gene therapy, and a hypoxia-specific system may be useful for the reconstruction of SCI.

Methods

To synergistically treat SCI, a combined platform using a hypoxia/neuron-inducible gene expression system (HNIS) and human induced-neural stem cells (hiNSCs) produced by direct reprogramming was designed. Sox2- or nestin-positive hiNSCs were differentiated to Tuj1-, MAP2-, or NeuN-positive neurons.

Results

HNIS showed consistent hypoxia/neuron-specific gene expression in hiNSCs cultured under hypoxia. In particular, the HNIS-hiNSC combined platform revealed a complex pattern with higher gene expression compared with a single platform. In addition, we found that an optimal combination of small molecules, such as CHIR99021, valproic acid (VPA), glycogen synthase kinase-3β (GSK3β), and histone deacetylase (HDAC) inhibitors, could significantly enhance gene expression with HNIS-hiNSCs in the hypoxic environment.

Conclusions

This experiment demonstrated that HNIS-hiNSCs combined with GSK3 and HDAC inhibitors may present another promising strategy in the treatment of SCI.

If it's not one thing, HIF's another: immunoregulation by hypoxia inducible factors in disease

Hypoxia‐inducible factors (HIFs) have emerged in recent years as critical regulators of immunity. Localised, low oxygen tension is a hallmark of inflamed and infected tissues. Subsequent myeloid cell HIF stabilisation plays key roles in the innate immune response, alongside emerging oxygen‐independent roles. Manipulation of regulatory proteins of the HIF transcription factor family can profoundly influence inflammatory profiles, innate immune cell function and pathogen clearance and, as such, has been proposed as a therapeutic strategy against inflammatory diseases. The direction and mode of HIF manipulation as a therapy are dictated by the inflammatory properties of the disease in question, with innate immune cell HIF reduction being, in general, advantageous during chronic inflammatory conditions, while upregulation of HIF is beneficial during infections. The therapeutic potential of targeting myeloid HIFs, both genetically and pharmacologically, has been recently illuminated in vitro and in vivo, with an emerging range of inhibitory and activating strategies becoming available. This review focuses on cutting edge findings that uncover the roles of myeloid cell HIF signalling on immunoregulation in the contexts of inflammation and infection and explores future directions of potential therapeutic strategies.

Metabolic reprogramming and angiogenesis in primary cutaneous Merkel cell carcinoma: expression of hypoxia-inducible factor-1α and its central downstream factors

BACKGROUND

Metabolic reprogramming and altered gene expression mediated by hypoxia-inducible factors play crucial roles during tumour growth and progression. Nevertheless, studies analysing the expression of hypoxia-inducible factor-1α and its downstream targets in Merkel cell carcinoma (MCC) are lacking but are warranted to shed more light on MCC pathogenesis and to potentially provide new therapeutic options.

OBJECTIVES

To analyse the immunohistochemical expression of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor-A (referred to as VEGF throughout the manuscript), VEGF receptor-2 (VEGFR-2), VEGF receptor-3 (VEGFR-3), glucose transporter-1 (Glut-1), monocarboxylate transporter 4 (MCT4) and carbonic anhydrase IX (CAIX) in primary cutaneous MCC.

METHODS

The 16 paraffin-embedded primary cutaneous MCCs (Merkel cell polyomavirus (McPyV) positive/negative: 11/5) were analysed by immunohistochemistry, namely HIF-1α, VEGF, VEGFR-2 (KDR), VEGFR-3 (FLT4), Glut-1, MCT4 and CAIX. An established quantification score (QS) was applied to quantitate the protein expression by considering the percentage of positive tumour cells (0: 0%; 1: up to 1%; 2: 2-10%; 3: 11-50%; 4: >50%) in relation to the staining intensity (0: negative; 1: low; 2: medium; 3: strong).

RESULTS

HIF-1α was expressed in all MCCs and predominantly found at the invading edges of tumour margins. The HIF-1α downstream factors Glut-1, MCT4 and CAIX were expressed in 13 of 16 MCC (81%), 14 of 16 MCC (88%) and 16 of 16 MCC (100%), respectively. Interestingly, VEGF and VEGFR-2 were not expressed in tumour cells, whereas VEGFR-3 was expressed in all MCCs. HIF-1α was expressed significantly stronger in McPyV⁺ tumours (QS: 10.36 ± 2.41) than in McPyV^- tumours (QS: 5.40 ± 1.34; P = 0.002). Similarly, VEGFR-3 was also expressed significantly stronger in McPyV⁺ tumours (QS: 10.00 ± 2.52) than in McPyV^- tumours (QS: 5.40 ± 3.43, P = 0.019).

CONCLUSIONS

Our data provide first evidence for a role of HIF-1α in induced metabolic reprogramming contributing to MCC pathogenesis. The metabolic signatures of McPyV⁺ and McPyV^- tumours seem to show relevant differences.

HIF-hypoxia signaling in skeletal muscle physiology and fibrosis

Hypoxia refers to the decrease in oxygen tension in the tissues, and the central effector of the hypoxic response is the transcription factor Hypoxia-Inducible Factor α (HIF1-α). Transient hypoxia in acute events, such as exercising or regeneration after damage, play an important role in skeletal muscle physiology and homeostasis. However, sustained activation of hypoxic signaling is a feature of skeletal muscle injury and disease, which can be a consequence of chronic damage but can also increase the severity of the pathology and worsen its outcome. Here, we review evidence that supports the idea that hypoxia and HIF-1α can contribute to the establishment of fibrosis in skeletal muscle through its crosstalk with other profibrotic factors, such as Transforming growth factor β (TGF-β), the induction of profibrotic cytokines expression, as is the case of Connective Tissue Growth Factor (CTGF/CCN2), or being the target of the Renin-angiotensin system (RAS).

The von Hippel-Lindau Tumor Suppressor Gene: Implications and Therapeutic Opportunities

The discovery of the von Hippel-Lindau (VHL) gene marked a milestone in our understanding of clear cell renal cell carcinoma (ccRCC) pathogenesis. VHL inactivation is not only a defining feature of ccRCC, but also the initiating event. Herein, we discuss canonical and noncanonical pVHL functions, as well as breakthroughs shaping our understanding of ccRCC evolution and evolutionary subtypes. We conclude by presenting evolving strategies to therapeutically exploit effector mechanisms downstream of pVHL.