Hypoxia-dependent regulation of inflammatory pathways in immune cells

Expression of HIF1α in intestinal epithelium restricts arthritis inflammation by inhibiting RIPK3-induced cell death machinery

OBJECTIVES

To investigate the mechanism by which intestinal epithelial cell (IEC) death induces arthritis.

METHODS

IEC death was assessed by staining for necroptosis and apoptosis markers and fluorescence in situ hybridisation at different time points during collagen-induced arthritis (CIA). During the development of CIA, messenger RNA (mRNA) sequencing was performed, followed by Gene Ontology enrichment analysis of differentially expressed genes. Mice deficient for hypoxia-inducible factor 1α (Hif1a) in IECs (Hif1a ∆IEC) were generated and induced for arthritis. mRNA sequencing, chromatin immunoprecipitated (ChIP) DNA sequencing and ChIP-qualitative PCR were performed on IECs from Hif1a ∆IEC mice and littermate controls. Effects of HIF1α stabilisation by inhibition of prolyl hydroxylase domain-containing enzymes and treatment with the inhibitor of receptor-interacting protein kinase-3 (RIPK3) were tested in intestinal organoids and in CIA.

RESULTS

IEC underwent apoptotic and necroptotic cell death at the onset of arthritis, leading to impaired gut barrier function. HIF1α was identified as one of the most upregulated genes in IECs during the onset of arthritis. Deletion of Hif1a in IEC enhanced IEC necroptosis, triggered intestinal inflammation and exacerbated arthritis. HIF1α was found to be a key transcriptional repressor for the necroptosis-inducing factor RIPK3. Enhanced RIPK3 expression, indicating necroptosis, was also found in the intestinal epithelium of patients with new-onset rheumatoid arthritis. Therapeutic stabilisation of HIF1α as well as small-molecule-based RIPK3 inhibition rescued intestinal necroptosis in vitro and in vivo and suppressed the development of arthritis.

CONCLUSION

Our results identify IEC necroptosis as a critical link between the gut and the development of arthritis.

Oxygen Therapy to Enhance Wound Healing After Revascularization

Oxygen is one of the important factors for wound healing and infection control. The revascularization procedure is amended to correct the tissue hypoxia problem by increasing the blood flow to obtain an adequate amount of oxygen. Hypoxic wounds are still the issue in the cases of unsuccessful or incomplete revascularization. The issue needs to be clarified and confirmed by proper methods for management to achieve wound healing and prevent limb loss. Oxygen therapy may benefit in the case of remaining hypoxia or wound infection in postrevascularization.

Transcriptomic analysis of the hypoxia-inducible factor 1α impact on the gene expression profile of chicken fibroblasts under hypoxia

Hypoxia-inducible factor 1 (HIF-1) is a transcriptional regulator that mediates cellular adaptive responses to hypoxia. Hypoxia-inducible factor 1α (HIF-1α) is involved in the development of ascites syndrome (AS) in broiler chickens. Therefore, studying the effect of HIF-1α on the cellular transcriptome under hypoxic conditions will help to better understand the mechanism of HIF-1α in the development of AS in broilers. In this study, we analyzed the gene expression profile of the chicken fibroblast cell line (DF-1) under hypoxic conditions by RNA-seq. Additionally, we constructed the HIF-1α knockdown DF-1 cell line by using the RNAi method and analyzed the gene expression profile under hypoxic conditions. The results showed that exposure to hypoxia for 48 h had a significant impact on the expression of genes in the DF-1 cell line, which related to cell proliferation, stress response, and apoptosis. In addition, after HIF-1α knockdown more differential expression genes appeared than in wild-type cells, and the expression of most hypoxia-related genes was either down-regulated or remained unchanged. Pathway analysis results showed that differentially expressed genes were mainly enriched in pathways related to cell proliferation, apoptosis, and oxidative phosphorylation. Our study obtained transcriptomic data from chicken fibroblasts at different hypoxic times and identified the potential regulatory network associated with HIF-1α. This data provides valuable support for understanding the transcriptional regulatory mechanism of HIF-1α in the development of AS in broilers.

The hypoxia response pathway in the Antarctic fish Notothenia coriiceps is functional despite a poly Q/E insertion mutation in HIF-1α

Antarctic notothenioid fishes, inhabiting the oxygen-rich Southern Ocean, possess a polyglutamine and glutamic acid (poly Q/E) insertion mutation in the master transcriptional regulator of oxygen homeostasis, hypoxia- inducible factor-1α (HIF-1α). To determine if this mutation impairs the ability of HIF-1 to regulate gene expression in response to hypoxia, we exposed Notothenia coriiceps, with a poly Q/E insertion mutation in HIF-1α that is 9 amino acids long, to hypoxia (2.3 mg L-1 O2) or normoxia (10 mg L -1 O2) for 12 h. Heart ventricles, brain, liver, and gill tissue were harvested and changes in gene expression quantified using RNA sequencing. Levels of glycogen and lactate were also quantified to determine if anaerobic metabolism increases in response to hypoxia. Exposure to hypoxia resulted in 818 unique differentially expressed genes (DEGs) in liver tissue of N. coriiceps. Many hypoxic genes were induced, including ones involved in the MAP kinase and FoxO pathways, glycolytic metabolism, and vascular remodeling. In contrast, there were fewer than 104 unique DEGs in each of the other tissues sampled. Lactate levels significantly increased in liver in response to hypoxia, indicating that anaerobic metabolism increases in response to hypoxia in this tissue. Overall, our results indicate that the hypoxia response pathway is functional in N. coriiceps despite a poly Q/E mutation in HIF-1α, and confirm that Antarctic fishes are capable of altering gene expression in response to hypoxia.

The Metabolic Syndrome, a Human Disease

This review focuses on the question of metabolic syndrome (MS) being a complex, but essentially monophyletic, galaxy of associated diseases/disorders, or just a syndrome of related but rather independent pathologies. The human nature of MS (its exceptionality in Nature and its close interdependence with human action and evolution) is presented and discussed. The text also describes the close interdependence of its components, with special emphasis on the description of their interrelations (including their syndromic development and recruitment), as well as their consequences upon energy handling and partition. The main theories on MS's origin and development are presented in relation to hepatic steatosis, type 2 diabetes, and obesity, but encompass most of the MS components described so far. The differential effects of sex and its biological consequences are considered under the light of human social needs and evolution, which are also directly related to MS epidemiology, severity, and relations with senescence. The triggering and maintenance factors of MS are discussed, with especial emphasis on inflammation, a complex process affecting different levels of organization and which is a critical element for MS development. Inflammation is also related to the operation of connective tissue (including the adipose organ) and the widely studied and acknowledged influence of diet. The role of diet composition, including the transcendence of the anaplerotic maintenance of the Krebs cycle from dietary amino acid supply (and its timing), is developed in the context of testosterone and β-estradiol control of the insulin-glycaemia hepatic core system of carbohydrate-triacylglycerol energy handling. The high probability of MS acting as a unique complex biological control system (essentially monophyletic) is presented, together with additional perspectives/considerations on the treatment of this 'very' human disease.

Downregulation of Hypoxia Inducible Factor-1α in Primary Human Natural Killer Cells Using Small Interfering RNA Delivery with ExPERT ATx by MaxCyte

Natural killer (NK) cells are innate cytokine-producing and cytolytic effector lymphocytes. Their function is responsive to environmental factors, e.g., hypoxia, a frequent feature of inflamed tissues. Such responses require that the NK cells up-regulate HIF-1α (hypoxia inducible factor-1α), the major mediator of cellular responses to hypoxia that affects cell survival as well as immune responses. Thus, a major approach to the study of NK cell effector function under hypoxic conditions involves the ability to regulate HIF-1α levels in primary human NK cells. One difficulty with this approach, however, is that NK cells are difficult-to-transfect cells and common transfection methods, including electroporation or lipofection, suffer from variable transfection efficiency and cell viability. Moreover, the detection of HIF-1α is technically challenging because of the rapid degradation of the protein under normoxic conditions. Here, using the commercially available ExPERT ATx by MaxCyte, we report a workflow for the reliable delivery of small interfering RNA (siRNA) for targeting HIF-1α expression in primary human NK cells. We further provide a protocol for the detection of HIF-1α by immunoblot analysis demonstrating its efficient downregulation by siRNA. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Isolation of natural killer cells from human peripheral blood mononuclear cells Basic Protocol 2: Delivery of non-coding small interfering RNA and HIF-1α targeting siRNA into natural killer cells using ExPERT ATx Basic Protocol 3: Assessing the downregulation of HIF-1α protein using immunoblot analysis Support Protocol 1: Exemplary assessment of transfection efficiency using fluorescently labeled non-targeting siRNA Support Protocol 2: Exemplary assessment of NK cell viability 20 hr post-transfection Support Protocol 3: Exemplary assessment of HIF-1α knockdown using immunoblot analysis.

NF-κB: Governing Macrophages in Cancer

Tumor-associated macrophages (TAMs) are the major component of the tumor microenvironment (TME), where they sustain tumor progression and or-tumor immunity. Due to their plasticity, macrophages can exhibit anti- or pro-tumor functions through the expression of different gene sets leading to distinct macrophage phenotypes: M1-like or pro-inflammatory and M2-like or anti-inflammatory. NF-κB transcription factors are central regulators of TAMs in cancers, where they often drive macrophage polarization toward an M2-like phenotype. Therefore, the NF-κB pathway is an attractive therapeutic target for cancer immunotherapy in a wide range of human tumors. Hence, targeting NF-κB pathway in the myeloid compartment is a potential clinical strategy to overcome microenvironment-induced immunosuppression and increase anti-tumor immunity. In this review, we discuss the role of NF-κB as a key driver of macrophage functions in tumors as well as the principal strategies to overcome tumor immunosuppression by targeting the NF-κB pathway.

Hypoxia-adenosine axis as therapeutic targets for acute respiratory distress syndrome

The human respiratory and circulatory systems collaborate intricately to ensure oxygen delivery to all cells, which is vital for ATP production and maintaining physiological functions and structures. During limited oxygen availability, hypoxia-inducible factors (HIFs) are stabilized and play a fundamental role in maintaining cellular processes for hypoxia adaptation. First discovered during investigations of erythropoietin production regulation, HIFs influence physiological and pathological processes, including development, inflammation, wound healing, and cancer. HIFs promote extracellular adenosine signaling by enhancing adenosine generation and receptor signaling, representing an endogenous feedback mechanism that curbs excessive inflammation, supports injury resolution, and enhances hypoxia tolerance. This is especially important for conditions that involve tissue hypoxia, such as acute respiratory distress syndrome (ARDS), which globally poses significant health challenges without specific treatment options. Consequently, pharmacological strategies to amplify HIF-mediated adenosine production and receptor signaling are of great importance.

COVID-19 pathogenesis

The pathogenesis of COVID-19 involves a complex interplay between host factors and the SARS-CoV-2 virus, leading to a multitude of clinical manifestations beyond the respiratory system. This chapter provides an overview of the risk factors, genetic predisposition, and multisystem manifestations of COVID-19, shedding light on the underlying mechanisms that contribute to extrapulmonary manifestations. The chapter discusses the direct invasion of SARS-CoV-2 into various organs as well as the indirect mechanisms such as dysregulation of the renin-angiotensin-aldosterone system (RAAS), immune response dysfunctions within the innate and adaptive immune systems, endothelial damage, and immunothrombosis. Furthermore, the multisystem manifestations of COVID-19 across different organ systems, including the cardiovascular, renal, gastrointestinal, hepatobiliary, nervous, endocrine and metabolic, ophthalmic, ear-nose-throat, reproductive, hematopoietic, and immune systems are discussed in detail. Each system exhibits unique manifestations that contribute to the complexity of the disease.

HIF-1α is positively associated with endometrial receptivity by regulating PKM2

PURPOSE

Numerous advancements have been introduced into the field of assisted reproductive technology (ART) in the past four decades. Nonetheless, implantation failure is still a key limiting step for a successful pregnancy. Building of endometrial receptivity (ER) is essential for successful implantation. However, the fundamental biological processes and mechanisms of ER remain elusive. Our study investigates the function of hypoxia inducible factor-1α (HIF-1α) during ER establishment and shed lights on the novel molecular mechanism by which HIF-1α regulates ER-related gene expression network.

METHODS

Levels of HIF-1α, homeobox A10 (HOXA10), insulin-like growth factor-binding protein 1 (IGFBP1), pyruvate kinase M2 (PKM2), and lactate dehydrogenase A (LDHA) in endometrial tissues were measured via real-time PCR, immunoblotting and immunohistochemistry. The correlation between HIF-1α and HOXA10, IGFBP1, PKM2, LDHA were analyzed separately. Ishikawa cells were treated with vector HIF-1α, HIF-1α-siRNA, and PKM2-siRNA. After transfection, the levels of HOXA10, IGFBP1, LDHA, and PKM2 were measured via real-time PCR and immunoblotting, and the lactate concentrations and cell migration of Ishikawa cells were measured.

RESULTS

Levels of HIF-1α, IGFBP1, HOXA10, LDHA, and PKM2 were significantly decreased in recurrent implantation failure (RIF) patients and levels of HOXA10, IGFBP1, PKM2, and LDHA were correlated with HIF-1α in endometrium. Then in a cellular model established by HIF-1α vector and HIF-1α-siRNA, the expression of HOXA10, IGFBP1, LDHA, PKM2, and lactate concentrations were dramatically upregulated and downregulated. And the expression of HOXA10, and IGFBP1 were dramatically decreased by PKM2-siRNA.

CONCLUSIONS

HIF-1α plays a crucial role in the building of ER through regulating glycolysis.

SUMOylation indirectly suppresses activity of the HIF-1α pathway in intestinal epithelial cells

The hypoxia-inducible factor (HIF) is a master regulator of the cellular transcriptional response to hypoxia. While the oxygen-sensitive regulation of HIF-1α subunit stability via the ubiquitin-proteasome pathway has been well described, less is known about how other oxygen-independent post-translational modifications impact the HIF pathway. SUMOylation, the attachment of SUMO (small ubiquitin-like modifier) proteins to a target protein, regulates the HIF pathway, although the impact of SUMO on HIF activity remains controversial. Here, we examined the effects of SUMOylation on the expression pattern of HIF-1α in response to pan-hydroxylase inhibitor dimethyloxalylglycine (DMOG) in intestinal epithelial cells. We evaluated the effects of SUMO-1, SUMO-2, and SUMO-3 overexpression and inhibition of SUMOylation using a novel selective inhibitor of the SUMO pathway, TAK-981, on the sensitivity of HIF-1α in Caco-2 intestinal epithelial cells. Our findings demonstrate that treatment with TAK-981 decreases global SUMO-1 and SUMO-2/3 modification and enhances HIF-1α protein levels, whereas SUMO-1 and SUMO-2/3 overexpression results in decreased HIF-1α protein levels in response to DMOG. Reporter assay analysis demonstrates reduced HIF-1α transcriptional activity in cells overexpressing SUMO-1 and SUMO-2/3, whereas pretreatment with TAK-981 increased HIF-1α transcriptional activity in response to DMOG. In addition, HIF-1α nuclear accumulation was decreased in cells overexpressing SUMO-1. Importantly, we showed that HIF-1α is not directly SUMOylated, but that SUMOylation affects HIF-1α stability and activity indirectly. Taken together, our results indicate that SUMOylation indirectly suppresses HIF-1α protein stability, transcriptional activity, and nuclear accumulation in intestinal epithelial cells.

Depletion of slow-cycling PDGFRα+ADAM12+ mesenchymal cells promotes antitumor immunity by restricting macrophage efferocytosis

The capacity to survive and thrive in conditions of limited resources and high inflammation is a major driver of tumor malignancy. Here we identified slow-cycling ADAM12+PDGFRα+ mesenchymal stromal cells (MSCs) induced at the tumor margins in mouse models of melanoma, pancreatic cancer and prostate cancer. Using inducible lineage tracing and transcriptomics, we demonstrated that metabolically altered ADAM12+ MSCs induced pathological angiogenesis and immunosuppression by promoting macrophage efferocytosis and polarization through overexpression of genes such as Gas6, Lgals3 and Csf1. Genetic depletion of ADAM12+ cells restored a functional tumor vasculature, reduced hypoxia and acidosis and normalized CAFs, inducing infiltration of effector T cells and growth inhibition of melanomas and pancreatic neuroendocrine cancer, in a process dependent on TGF-β. In human cancer, ADAM12 stratifies patients with high levels of hypoxia and innate resistance mechanisms, as well as factors associated with a poor prognosis and drug resistance such as AXL. Altogether, our data show that depletion of tumor-induced slow-cycling PDGFRα+ MSCs through ADAM12 restores antitumor immunity.

The signaling pathway of hypoxia inducible factor in regulating gut homeostasis

Hypoxia represent a condition in which an adequate amount of oxygen supply is missing in the body, and it could be caused by a variety of diseases, including gastrointestinal disorders. This review is focused on the role of hypoxia in the maintenance of the gut homeostasis and related treatment of gastrointestinal disorders. The effects of hypoxia on the gut microbiome and its role on the intestinal barrier functionality are also covered, together with the potential role of hypoxia in the development of gastrointestinal disorders, including inflammatory bowel disease and irritable bowel syndrome. Finally, we discussed the potential of hypoxia-targeted interventions as a novel therapeutic approach for gastrointestinal disorders. In this review, we highlighted the importance of hypoxia in the maintenance of the gut homeostasis and the potential implications for the treatment of gastrointestinal disorders.

Novel anemia therapies in chronic kidney disease: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

Anemia is common in patients with chronic kidney disease and is associated with a high burden of morbidity and adverse clinical outcomes. In 2012, Kidney Disease: Improving Global Outcomes (KDIGO) published a guideline for the diagnosis and management of anemia in chronic kidney disease. Since then, new data from studies assessing established and emerging therapies for the treatment of anemia and iron deficiency have become available. Beginning in 2019, KDIGO planned 2 Controversies Conferences to review the new evidence and its potential impact on the management of anemia in clinical practice. Here, we report on the second of these conferences held virtually in December 2021, which focused on a new class of agents-the hypoxia-inducible factor-prolyl hydroxylase inhibitors (HIF-PHIs). This report provides a review of the consensus points and controversies from this second conference and highlights areas that warrant prioritization for future research.

Tumor Abnormality-Oriented Nanomedicine Design

Anticancer nanomedicines have been proven effective in mitigating the side effects of chemotherapeutic drugs. However, challenges remain in augmenting their therapeutic efficacy. Nanomedicines responsive to the pathological abnormalities in the tumor microenvironment (TME) are expected to overcome the biological limitations of conventional nanomedicines, enhance the therapeutic efficacies, and further reduce the side effects. This Review aims to quantitate the various pathological abnormalities in the TME, which may serve as unique endogenous stimuli for the design of stimuli-responsive nanomedicines, and to provide a broad and objective perspective on the current understanding of stimuli-responsive nanomedicines for cancer treatment. We dissect the typical transport process and barriers of cancer drug delivery, highlight the key design principles of stimuli-responsive nanomedicines designed to tackle the series of barriers in the typical drug delivery process, and discuss the "all-into-one" and "one-for-all" strategies for integrating the needed properties for nanomedicines. Ultimately, we provide insight into the challenges and future perspectives toward the clinical translation of stimuli-responsive nanomedicines.

Hypoxic State of Cells and Immunosenescence: A Focus on the Role of the HIF Signaling Pathway

Hypoxia activates hypoxia-related signaling pathways controlled by hypoxia-inducible factors (HIFs). HIFs represent a quick and effective detection system involved in the cellular response to insufficient oxygen concentration. Activation of HIF signaling pathways is involved in improving the oxygen supply, promoting cell survival through anaerobic ATP generation, and adapting energy metabolism to meet cell demands. Hypoxia can also contribute to the development of the aging process, leading to aging-related degenerative diseases; among these, the aging of the immune system under hypoxic conditions can play a role in many different immune-mediated diseases. Thus, in this review we aim to discuss the role of HIF signaling pathways following cellular hypoxia and their effects on the mechanisms driving immune system senescence.

Comparative effectiveness and acceptability of HIF prolyl-hydroxylase inhibitors versus for anemia patients with chronic kidney disease undergoing dialysis: a systematic review and network meta-analysis

Background: The comparative benefits and acceptability of HIF-PHIs for treating anemia have not been well researched to date. We sought to compare the effectiveness of 6 HIF-PHIs and 3 ESAs for the treatment of renal anemia patients undergoing dialysis. Data sources: Cochrane Central Register of Controlled Trials, PubMed, Embase, Cochrane Library, MEDLINE, Web of Science, and clinicaltrials.gov databases. Results: Twenty-five RCTs (involving 17,204 participants) were included, all of which were designed to achieve target Hb levels by adjusting thee dose of HIF-PHIs. Regarding the efficacy in achieving target Hb levels, no significant differences were found between HIF-PHIs and ESAs in Hb response at the dose-adjusted designed RCTs selected for comparison. Intervention with roxadustat showed a significantly lower risk of RBC transfusion than rhEPO, with an OR and 95% CI of 0.76 (0.56-0.93). Roxadustat and vadadustat had higher risks of increasing the discontinuation rate than ESAs; the former had ORs and 95% CIs of 1.58 (95% CI: 1.21-2.06) for rhEPO, 1.66 (1.16-2.38) for DPO (darbepoetin alfa), and 1.76 (1.70-4.49) for MPG-EPO, and the latter had ORs and 95% CIs of 1.71 (1.09-2.67) for rhEPO, 1.79 (1.29-2.49) for DPO, and 2.97 (1.62-5.46) for MPG-EPO. No differences were observed in the AEs and SAEs among patients who received the studied drugs. Results of a meta-analysis of gastrointestinal disorders among AEs revealed that vadadustat was less effect on causing diarrea than DPO, with an OR of 0.97 (95% CI, 0.9-0.99). Included HIF-PHIs, were proven to be more effective than ESAs in reducing hepcidin levels and increasing TIBC and serum iron level with OR of -0.17 (95% CI, -0.21 to -0.12), OR of 0.79 (95% CI, 0.63-0.95), and OR of 0.39 (95% CI, 0.33-0.45), respectively. Conclusion: HIF-PHIs and ESAs have their characteristics and advantages in treating anemia undergoing dialysis. With the selected dose-adjusted mode, some HIF-PHIs appeared to be a potential treatment for DD-CKD patients when ompared with rhEPO, due to its effectiveness in decreasing the risk of RBC transfusion rate or regulating iron or lipid metabolism while achieving target Hb levels. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=306511; Identifier: CRD42022306511.

Proteomic analysis to identification of hypoxia related markers in spinal tuberculosis: a study based on weighted gene co-expression network analysis and machine learning

OBJECTIVE

This article aims at exploring the role of hypoxia-related genes and immune cells in spinal tuberculosis and tuberculosis involving other organs.

METHODS

In this study, label-free quantitative proteomics analysis was performed on the intervertebral discs (fibrous cartilaginous tissues) obtained from five spinal tuberculosis (TB) patients. Key proteins associated with hypoxia were identified using molecular complex detection (MCODE), weighted gene co-expression network analysis(WGCNA), least absolute shrinkage and selection operator (LASSO), and support vector machine recursive feature Elimination (SVM-REF) methods, and their diagnostic and predictive values were assessed. Immune cell correlation analysis was then performed using the Single Sample Gene Set Enrichment Analysis (ssGSEA) method. In addition, a pharmaco-transcriptomic analysis was also performed to identify targets for treatment.

RESULTS

The three genes, namely proteasome 20 S subunit beta 9 (PSMB9), signal transducer and activator of transcription 1 (STAT1), and transporter 1 (TAP1), were identified in the present study. The expression of these genes was found to be particularly high in patients with spinal TB and other extrapulmonary TB, as well as in TB and multidrug-resistant TB (p-value < 0.05). They revealed high diagnostic and predictive values and were closely related to the expression of multiple immune cells (p-value < 0.05). It was inferred that the expression of PSMB9, STAT 1, and TAP1 could be regulated by different medicinal chemicals.

CONCLUSION

PSMB9, STAT1, and TAP1, might play a key role in the pathogenesis of TB, including spinal TB, and the protein product of the genes can be served as diagnostic markers and potential therapeutic target for TB.

Pathophysiological mechanisms and therapeutic approaches in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a common breathing disorder in sleep in which the airways narrow or collapse during sleep, causing obstructive sleep apnea. The prevalence of OSAS continues to rise worldwide, particularly in middle-aged and elderly individuals. The mechanism of upper airway collapse is incompletely understood but is associated with several factors, including obesity, craniofacial changes, altered muscle function in the upper airway, pharyngeal neuropathy, and fluid shifts to the neck. The main characteristics of OSAS are recurrent pauses in respiration, which lead to intermittent hypoxia (IH) and hypercapnia, accompanied by blood oxygen desaturation and arousal during sleep, which sharply increases the risk of several diseases. This paper first briefly describes the epidemiology, incidence, and pathophysiological mechanisms of OSAS. Next, the alterations in relevant signaling pathways induced by IH are systematically reviewed and discussed. For example, IH can induce gut microbiota (GM) dysbiosis, impair the intestinal barrier, and alter intestinal metabolites. These mechanisms ultimately lead to secondary oxidative stress, systemic inflammation, and sympathetic activation. We then summarize the effects of IH on disease pathogenesis, including cardiocerebrovascular disorders, neurological disorders, metabolic diseases, cancer, reproductive disorders, and COVID-19. Finally, different therapeutic strategies for OSAS caused by different causes are proposed. Multidisciplinary approaches and shared decision-making are necessary for the successful treatment of OSAS in the future, but more randomized controlled trials are needed for further evaluation to define what treatments are best for specific OSAS patients.

Hypoxia-inducible factors and essential hypertension: narrative review of experimental and clinical data

Hypoxia-inducible factor (HIFs) is a new class of drug developed for the management of anemia in chronic kidney disease (CKD) patients. HIFs increase the production of erythropoietin in the kidney and liver, enhance the absorption and utilization of iron, and stimulate the maturation and proliferation of erythroid progenitor cells. Besides, HIFs regulate many physiologic processes by orchestrating the transcription of hundreds of genes. Essential hypertension (HT) is an epidemic worldwide. HIFs play a role in many biological processes involved in the regulation of blood pressure (BP). In the current review, we summarize pre-clinical and clinical studies investigating the relationship between HIFs and BP regulation in patients with CKD, conflicting issues, and discuss future potential strategies.

Physiological and pathophysiological mechanisms of the molecular and cellular biology of angiogenesis and inflammation in moyamoya angiopathy and related vascular diseases

Rationale

The etiology and pathophysiological mechanisms of moyamoya angiopathy (MMA) remain largely unknown. MMA is a progressive, occlusive cerebrovascular disorder characterized by recurrent ischemic and hemorrhagic strokes; with compensatory formation of an abnormal network of perforating blood vessels that creates a collateral circulation; and by aberrant angiogenesis at the base of the brain. Imbalance of angiogenic and vasculogenic mechanisms has been proposed as a potential cause of MMA. Moyamoya vessels suggest that aberrant angiogenic, arteriogenic, and vasculogenic processes may be involved in the pathophysiology of MMA. Circulating endothelial progenitor cells have been hypothesized to contribute to vascular remodeling in MMA. MMA is associated with increased expression of angiogenic factors and proinflammatory molecules. Systemic inflammation may be related to MMA pathogenesis.

Objective

This literature review describes the molecular mechanisms associated with cerebrovascular dysfunction, aberrant angiogenesis, and inflammation in MMA and related cerebrovascular diseases along with treatment strategies and future research perspectives.

Methods and results

References were identified through a systematic computerized search of the medical literature from January 1, 1983, through July 29, 2022, using the PubMed, EMBASE, BIOSIS Previews, CNKI, ISI web of science, and Medline databases and various combinations of the keywords "moyamoya," "angiogenesis," "anastomotic network," "molecular mechanism," "physiology," "pathophysiology," "pathogenesis," "biomarker," "genetics," "signaling pathway," "blood-brain barrier," "endothelial progenitor cells," "endothelial function," "inflammation," "intracranial hemorrhage," and "stroke." Relevant articles and supplemental basic science articles almost exclusively published in English were included. Review of the reference lists of relevant publications for additional sources resulted in 350 publications which met the study inclusion criteria. Detection of growth factors, chemokines, and cytokines in MMA patients suggests the hypothesis of aberrant angiogenesis being involved in MMA pathogenesis. It remains to be ascertained whether these findings are consequences of MMA or are etiological factors of MMA.

Conclusions

MMA is a heterogeneous disorder, comprising various genotypes and phenotypes, with a complex pathophysiology. Additional research may advance our understanding of the pathophysiology involved in aberrant angiogenesis, arterial stenosis, and the formation of moyamoya collaterals and anastomotic networks. Future research will benefit from researching molecular pathophysiologic mechanisms and the correlation of clinical and basic research results.

Hypoxia Drives Material-Induced Heterotopic Bone Formation by Enhancing Osteoclastogenesis via M2/Lipid-Loaded Macrophage Axis

Heterotopic ossification (HO) is a double-edged sword. Pathological HO presents as an undesired clinical complication, whereas controlled heterotopic bone formation by synthetic osteoinductive materials shows promising therapeutic potentials for bone regeneration. However, the mechanism of material-induced heterotopic bone formation remains largely unknown. Early acquired HO being usually accompanied by severe tissue hypoxia prompts the hypothesis that hypoxia caused by the implantation coordinates serial cellular events and ultimately induces heterotopic bone formation in osteoinductive materials. The data presented herein shows a link between hypoxia, macrophage polarization to M2, osteoclastogenesis, and material-induced bone formation. Hypoxia inducible factor-1α (HIF-1α), a crucial mediator of cellular responses to hypoxia, is highly expressed in an osteoinductive calcium phosphate ceramic (CaP) during the early phase of implantation, while pharmacological inhibition of HIF-1α significantly inhibits M2 macrophage, subsequent osteoclast, and material-induced bone formation. Similarly, in vitro, hypoxia enhances M2 macrophage and osteoclast formation. Osteoclast-conditioned medium enhances osteogenic differentiation of mesenchymal stem cells, such enhancement disappears with the presence of HIF-1α inhibitor. Furthermore, metabolomics analysis reveals that hypoxia enhances osteoclastogenesis via the axis of M2/lipid-loaded macrophages. The current findings shed new light on the mechanism of HO and favor the design of more potent osteoinductive materials for bone regeneration.

Endotyping COPD: hypoxia-inducible factor-2 as a molecular "switch" between the vascular and airway phenotypes?

COPD is a heterogeneous disease with multiple clinical phenotypes. COPD endotypes can be determined by different expressions of hypoxia-inducible factors (HIFs), which, in combination with individual susceptibility and environmental factors, may cause predominant airway or vascular changes in the lung. The pulmonary vascular phenotype is relatively rare among COPD patients and characterised by out-of-proportion pulmonary hypertension (PH) and low diffusing capacity of the lung for carbon monoxide, but only mild-to-moderate airway obstruction. Its histologic feature, severe remodelling of the small pulmonary arteries, can be mediated by HIF-2 overexpression in experimental PH models. HIF-2 is not only involved in the vascular remodelling but also in the parenchyma destruction. Endothelial cells from human emphysema lungs express reduced HIF-2α levels, and the deletion of pulmonary endothelial Hif-2α leads to emphysema in mice. This means that both upregulation and downregulation of HIF-2 have adverse effects and that HIF-2 may represent a molecular "switch" between the development of the vascular and airway phenotypes in COPD. The mechanisms of HIF-2 dysregulation in the lung are only partly understood. HIF-2 levels may be controlled by NAD(P)H oxidases via iron- and redox-dependent mechanisms. A better understanding of these mechanisms may lead to the development of new therapeutic targets.

Roxadustat protect mice from DSS-induced colitis in vivo by up-regulation of TLR4

BACKGROUND

The incidence of inflammatory bowel disease (IBD) is growing in the population. At present, the etiology of inflammatory bowel disease remains unclear, and there is no effective and low-toxic therapeutic drug. The role of the PHD-HIF pathway in relieving DSS-induced colitis is gradually being explored.

METHODS

Wild-type C57BL/6 mice were used as a model of DSS-induced colitis to explore the important role of Roxadustat in alleviating DSS-induced colitis. High-throughput RNA-Seq and qRT-PCR methods were used to screen and verify the key differential genes in the colon of mice between normal saline (NS) and Roxadustat groups.

RESULTS

Roxadustat could alleviate DSS-induced colitis. Compared with the mice in the NS group, TLR4 were significantly up-regulated in the Roxadustat group. TLR4 KO mice were used to verify the role of TLR4 in the alleviation of DSS-induced colitis by Roxadustat.

CONCLUSION

Roxadustat has a repairing effect on DSS-induced colitis, and may alleviate DSS-induced colitis by targeting the TLR4 pathway and promote intestinal stem cell proliferation.

Immunometabolism and microbial metabolites at the gut barrier: Lessons for therapeutic intervention in inflammatory bowel disease

The concept of immunometabolism has emerged recently whereby the repolarizing of inflammatory immune cells toward anti-inflammatory profiles by manipulating cellular metabolism represents a new potential therapeutic approach to controlling inflammation. Metabolic pathways in immune cells are tightly regulated to maintain immune homeostasis and appropriate functional specificity. Because effector and regulatory immune cell populations have different metabolic requirements, this allows for cellular selectivity when regulating immune responses based on metabolic pathways. Gut microbes have a major role in modulating immune cell metabolic profiles and functional responses through extensive interactions involving metabolic products and crosstalk between gut microbes, intestinal epithelial cells, and mucosal immune cells. Developing strategies to target metabolic pathways in mucosal immune cells through the modulation of gut microbial metabolism has the potential for new therapeutic approaches for human autoimmune and inflammatory diseases, such as inflammatory bowel disease. This review will give an overview of the relationship between metabolic reprogramming and immune responses, how microbial metabolites influence these interactions, and how these pathways could be harnessed in the treatment of inflammatory bowel disease.

Hypoxia and Intestinal Inflammation: Common Molecular Mechanisms and Signaling Pathways

The gastrointestinal tract (GI) has a unique oxygenation profile. It should be noted that the state of hypoxia can be characteristic of both normal and pathological conditions. Hypoxia-inducible factors (HIF) play a key role in mediating the response to hypoxia, and they are tightly regulated by a group of enzymes called HIF prolyl hydroxylases (PHD). In this review, we discuss the involvement of inflammation hypoxia and signaling pathways in the pathogenesis of inflammatory bowel disease (IBD) and elaborate in detail on the role of HIF in multiple immune reactions during intestinal inflammation. We emphasize the critical influence of tissue microenvironment and highlight the existence of overlapping functions and immune responses mediated by the same molecular mechanisms. Finally, we also provide an update on the development of corresponding therapeutic approaches that would be useful for treatment or prophylaxis of inflammatory bowel disease.

Hypoxia and TNF-α Synergistically Induce Expression of IL-6 and IL-8 in Human Fibroblast-like Synoviocytes via Enhancing TAK1/NF-κB/HIF-1α Signaling

Hypoxia and increased levels of inflammatory cytokines in the joints are characteristics of rheumatoid arthritis (RA). However, the effects of hypoxia and tumor necrosis factor-α (TNF-α) on interleukin (IL)-6 and IL-8 production on fibroblast-like synoviocytes (FLSs) remain to be clarified. This study aimed to explore how hypoxia and TNF-α affect the expression of IL-6 and IL-8 in human FLSs isolated from RA patients. Hypoxia or TNF-α treatment alone significantly increased the expression and promoter activity of IL-6, IL-8, and hypoxia-inducible factor-1α (HIF-1α). Treatment of hypoxic FLSs with TNF-α further significantly elevated the expression of these cytokines and enhanced promoter activity of HIF-1α, which was abrogated by treatment with the HIF-1α inhibitor YC-1. Similarly, TNF-α alone elevated the phosphorylation and promoter activity of nuclear factor-κBp65 (NF-κBp65) in the FLSs. These effects were further enhanced by the combined treatment of hypoxia and TNFα but were attenuated by the NF-κB inhibitor BAY11-7082. NF-κB-p65 inhibition decreased the effect of TNF-α on HIF-1α upregulation in the FLSs in response to hypoxia. The combination of hypoxia and TNF-α also significantly upregulated transforming growth factor-β-activated kinase 1 (TAK1) expression, and silencing TAK1 dramatically decreased NF-κB-p65, HIF-1α, IL-6, and IL-8 expression under the same conditions. Our results indicate that hypoxia and TNF-α synergistically increase IL-6 and IL-8 expression in human FLSs via enhancing TAK1/NF-κB/HIF-1α signaling.

Hypoxia Attenuates Colonic Innate Immune Response and Inhibits TLR4/NF-κB Signaling Pathway in Lipopolysaccharide-Induced Colonic Epithelial Injury Mice

High altitude hypoxia can lead to a spectrum of gastrointestinal problems. As the first line of host immune defense, innate immune response in the intestinal mucosa plays a pivotal role in maintaining intestinal homeostasis and protecting against intestinal injury at high altitude. This study aimed to investigate the effect of hypoxia on the colonic mucosal barrier and toll-like receptor 4 (TLR4)-mediated innate immune responses in the colon. The mice were exposed to a hypobaric chamber to simulate a 5,000 m plateau environment for 7 days, and the colonic mucosa changes were recorded. At the same time, the inflammation model was established by lipopolysaccharide (LPS) to explore the effects of hypoxia on the TLR4/nuclear factor kappa B (NF-κB) signaling pathway and its downstream inflammatory factors [tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and interferon (IFN)-γ] in the colon. We found that hypoxic exposure caused weight loss and structural disturbance of the colonic mucosa in mice. Compared with the control group, the protein levels of TLR4 [fold change (FC) = 0.75 versus FC = 0.23], MyD88 (FC = 0.80 versus FC = 0.30), TIR-domain-containing adaptor protein inducing interferon-β (TRIF: FC = 0.89 versus FC = 0.38), and NF-κB p65 (FC = 0.75 versus FC = 0.24) in the colon of mice in the hypobaric hypoxia group were significantly decreased. LPS-induced upregulation of the TLR4/NF-κB signaling and its downstream inflammatory factors was inhibited by hypoxia. Specifically, compared with the LPS group, the protein levels of TLR4 (FC = 1.18, FC = 0.86), MyD88 (FC = 1.20, FC = 0.80), TRIF (FC = 1.20, FC = 0.86), and NF-κB p65 (FC = 1.29, FC = 0.62) and the mRNA levels of IL-1β (FC = 7.38, FC = 5.06), IL-6 (FC = 16.06, FC = 9.22), and IFN-γ (FC = 2.01, FC = 1.16) were reduced in the hypobaric hypoxia plus LPS group. Our findings imply that hypoxia could lead to marked damage of the colonic mucosa and a reduction of TLR4-mediated colonic innate immune responses, potentially reducing host defense responses to colonic pathogens.

HIF-1α promotes paraquat induced acute lung injury and implicates a role NF-κB and Rac2 activity

Paraquat (PQ) is a bipyridine herbicide and oral exposure is the main way of PQ exposure with a very high mortality. At present, it is believed that large number of oxygen free radicals are generated and cause lipid peroxidation of tissue and organ cell membranes after PQ is absorbed. PQ exposure could cause multiple organ dysfunction, among which acute lung injury is the most common and most serious. However, its specific mechanism is still unclear. In this study, the C57BL/6J mouse (alveolar epithelial cell-specific knockout HIF-1α) model of acute lung injury (40 mg/kg PQ) at several time pointes and a model of acute type II alveolar epithelial cell (A549, 800 μM PQ) injury constructed. The oxidative stress (ROS, MDA) and inflammatory response (IL-1β, IL-6, TNF-α) were significantly inhibited in the alveolar epithelial cell-specific knockout of HIF-1α mice and siRNA technology to inhibit HIF-1α in alveolar epithelial cells. Further proteomic analysis showed that the expression of Rac2 protein, which is closely related to oxidative stress, was significantly increased after PQ exposure. And the inhibition of Rac2 expression in vitro significantly alleviated PQ-induced oxidative stress and inflammatory response. The expression of Rac2 protein was regulated by HIF-1α. The above suggests that HIF-1α may promote oxidative stress and inflammatory response in alveolar epithelial cells by regulating the expression of Rac2, and then participate in the promotion of PQ exposure-induced acute lung injury.

Transcriptomic responses of Galápagos finches to avian poxvirus infection

Emerging pathogens can have devastating effects on naïve hosts, but disease outcomes often vary among host species. Comparing the cellular response of different hosts to infection can provide insight into mechanisms of host defence. Here, we used RNA-seq to characterize the transcriptomic response of Darwin's finches to avian poxvirus, a disease of concern in the Galápagos Islands. We tested whether gene expression differs between infected and uninfected birds, and whether transcriptomic differences were related either to known antiviral mechanisms and/or the co-option of the host cellular environment by the virus. We compared two species, the medium ground finch (Geospiza fortis) and the vegetarian finch (Platyspiza crassirostris), to determine whether endemic Galápagos species differ in their response to pox. We found that medium ground finches had a strong transcriptomic response to infection, upregulating genes involved in the innate immune response including interferon production, inflammation, and other immune signalling pathways. In contrast, vegetarian finches had a more limited response, and some changes in this species were consistent with viral manipulation of the host's cellular function and metabolism. Many of the transcriptomic changes mirrored responses documented in model and in vitro studies of poxviruses. Our results thus indicate that many pathways of host defence against poxviruses are conserved among vertebrates and present even in hosts without a long evolutionary history with the virus. At the same time, the differences we observed between closely related species suggests that some endemic species of Galápagos finch could be more susceptible to avian pox than others.

The Adverse Outcome Pathway Framework Applied to Neurological Symptoms of COVID-19

Several reports have shown that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has the potential to also be neurotropic. However, the mechanisms by which SARS-CoV-2 induces neurologic injury, including neurological and/or psychological symptoms, remain unclear. In this review, the available knowledge on the neurobiological mechanisms underlying COVID-19 was organized using the AOP framework. Four AOPs leading to neurological adverse outcomes (AO), anosmia, encephalitis, stroke, and seizure, were developed. Biological key events (KEs) identified to induce these AOs included binding to ACE2, blood–brain barrier (BBB) disruption, hypoxia, neuroinflammation, and oxidative stress. The modularity of AOPs allows the construction of AOP networks to visualize core pathways and recognize neuroinflammation and BBB disruption as shared mechanisms. Furthermore, the impact on the neurological AOPs of COVID-19 by modulating and multiscale factors such as age, psychological stress, nutrition, poverty, and food insecurity was discussed. Organizing the existing knowledge along an AOP framework can represent a valuable tool to understand disease mechanisms and identify data gaps and potentially contribute to treatment, and prevention. This AOP-aligned approach also facilitates synergy between experts from different backgrounds, while the fast-evolving and disruptive nature of COVID-19 emphasizes the need for interdisciplinarity and cross-community research.

Metabolic response provides insights into the mechanism of adaption to hypoxia in largemouth bass (Micropterus salmoides) under intermittent hypoxic conditions

In metabolism, molecular oxygen is a necessary substrate. Oxygen imbalances are linked to a variety of circumstances in the organism's homeostasis. Recently, the positive effects of hypoxia treatment in improving exercise ability and hypoxia tolerance have become a research focus. We explored the effects of intermittent hypoxia exposure (IHE, for one hour or three hours per day) on the hypoxia tolerance of largemouth bass in this study. The results showed that (1) IHE significantly reduced the LOEcrit (the critical O₂ tension for loss of equilibrium) value of largemouth bass, indicating that its hypoxia tolerance was enhanced. (2) The level of oxidative stress in the liver decreased in the HH3 group (exposed to a hypoxic condition for 3 h per day) compared to HH1 group (exposed to a hypoxic condition for 1 h per day). (3) IHE reduced the content of lactic acid and enhanced the process of gluconeogenesis in the liver. (4) Importantly, lipid mobilization and fatty acid oxidation in the liver of largemouth bass were significantly enhanced during IHE. In short, the results of this study indicate that IHE can improve hypoxia tolerance by regulating the energy metabolism of largemouth bass.

A Novel Hypoxia Related Marker in Blood Link to Aid Diagnosis and Therapy in Osteoarthritis

Osteoarthritis (OA) is a common chronic degenerative arthritis. Its treatment options are very limited. At present, hypoxia is a prominent factor in OA. This study aimed to re-explore the mechanism between hypoxia and OA, which provides new insights into the diagnosis and therapy of OA. We acquired the OA-related expression profiles of GSE48556, GSE55235, and GSE55457 for our analysis. Using gene set variation analysis (GSVA), we found significant differences in hypoxia. These differences result from multiple pathways, such as the p53 signaling pathway, cell senescence, the NF-kappa B signaling pathway, Ubiquitin-mediated proteolysis, and apoptosis. Meanwhile, the single-sample gene set enrichment analysis (ssGSEA) showed that hypoxia was significantly associated with the level of immune cell infiltration in the immune microenvironment. Thus, we believe that hypoxia is useful for the diagnosis and treatment of OA. We successfully constructed a novel hypoxia-related index (HRI) based on seven hypoxia-related genes (ADM, CDKN3, ENO1, NDRG1, PGAM1, SLC2A1, VEGFA) by least absolute shrinkage and binary logistic regression of the generalized linear regression. HRI showed potential for improving OA diagnosis through receiver operation characteristic (ROC) analysis (AUC training cohort = 0.919, AUC testing cohort = 0.985). Moreover, we found that celastrol, droxinostat, torin-2, and narciclasine may be potential therapeutic compounds for OA based on the Connectivity Map (CMap). In conclusion, hypoxia is involved in the development and progression of OA. HRI can improve diagnosis and show great potential in clinical application. Celastrol, droxinostat, torin-2, and narciclasine may be potential compounds for the treatment of OA patients.

Hypoxia: molecular pathophysiological mechanisms in human diseases

Hypoxia, a low O2 tension, is a fundamental feature that occurs in physiological events as well as pathophysiological conditions, especially mentioned for its role in the mechanism of angiogenesis, glucose metabolism, and cell proliferation/survival. The hypoxic state through the activation of specific mechanisms is an aggravating circumstance commonly noticed in multiple sclerosis, cancer, heart disease, kidney disease, liver disease, lung disease, and in inflammatory bowel disease. On the other hand, hypoxia could play a key role in tissue regeneration and repair of damaged tissues, especially by acting on specific tissue stem cells, but their features may result as a disadvantage when it is concerned for neoplastic stem cells. Furthermore, hypoxia could also have a potential role in tissue engineering and regenerative medicine due to its capacity to improve the performance of biomaterials. The current review aims to highlight the hypoxic molecular mechanisms reported in different pathological conditions to provide an overview of hypoxia as a therapeutic agent in regenerative and molecular therapy.

Graphical abstract

Inhibition of hypoxia-inducible factor-prolyl hydroxylation protects from cyclophosphamide-induced bladder injury and urinary dysfunction

Disruption of the blood-urine barrier can result in acute or chronic inflammatory bladder injury. Activation of the oxygen-regulated hypoxia-inducible factor (HIF) pathway has been shown to protect mucosal membranes by increasing the expression of cytoprotective genes and by suppressing inflammation. The activity of HIF is controlled by prolyl hydroxylase domain (PHD) dioxygenases, which have been exploited as therapeutic targets for the treatment of anemia of chronic kidney disease. Here, we established a mouse model of acute cyclophosphamide (CYP)-induced blood-urine barrier disruption associated with inflammation and severe urinary dysfunction to investigate the HIF-PHD axis in inflammatory bladder injury. We found that systemic administration of dimethyloxalylglycine or molidustat, two small-molecule inhibitors of HIF-prolyl hydroxylases, profoundly mitigated CYP-induced bladder injury and inflammation as assessed by morphological analysis of transmural edema and urothelial integrity and by measuring tissue cytokine expression. Void spot analysis to examine bladder function quantitatively demonstrated that HIF-prolyl hydroxylase inhibitor administration normalized micturition patterns and protected against CYP-induced alteration of urinary frequency and micturition patterns. Our study highlights the therapeutic potential of HIF-activating small-molecule compounds for the prevention or therapy of bladder injury and urinary dysfunction due to blood-urine barrier disruption.NEW & NOTEWORTHY Disruption of the blood-urine barrier can result in acute or chronic inflammatory bladder injury. Here, we demonstrate that pharmacological inhibition of hypoxia-inducible factor (HIF)-prolyl hydroxylation prevented bladder injury and protected from urinary dysfunction in a mouse model of cyclophosphamide-induced disruption of the blood-urine barrier. Our study highlights a potential role for HIF-activating small-molecule compounds in the prevention or therapy of bladder injury and urinary dysfunction and provides a rationale for future clinical studies.

The Molecular Role of HIF1α Is Elucidated in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is potentially fatal blood cancer, but there is an unmet need to discover novel molecular biomarkers. The hypothesis of this study aimed to elucidate the relationship of HIF1α with the redox system, Krebs cycles, notch1, and other regulatory proteins to better understand the pathophysiology and clinical relevance in chronic myeloid leukemia (CML) patients, as the molecular mechanism of this axis is still not clear. This study included CML patient samples (n = 60; 60: blood; 10: bone marrow tissues) and compared them with healthy controls (n = 20; blood). Clinical diagnosis confirmed on bone marrow aspiration, marrow trephine biopsy, and BCR/ABL1 translocation. Cases were subclassified into chronic, accelerated, and blast crises as per WHO guidelines. Molecular experiments included redox parameters, DNA fragmentation, Krebs cycle metabolites, and gene expression by RT-PCR/Western blot/LC-MS, PPI (STRING), Pearson correlation, and ROC curve analysis. Here, our findings show that p210/p190BCR/ABL1 translocation is common in all blast crisis phases of CML. Redox factor/Krebs oncometabolite concentrations were high, leading to upregulation and stabilization of HIF1α. HIF1α leads to the pathogenesis in CML cells by upregulating their downstream genes (Notch 2/4/Ikaros/SIRT1/Foxo-3a/p53, etc.). Whereas, downregulated ubiquitin proteasomal and apoptotic factors in CML pateints, can trigger degradation of HIF1α through proline hydroxylation. However, HIF1α showed a negative corelation with the notch1 pathway. Notch1 plays a tumor-suppressive role in CML and might have the potential to be used as a diagnostic marker along with other factors in CML patients. The outcome also revealed that oxidant treatment could not be effective in augmentation with conventional therapy because CML cells can enhance the levels of antioxidants for their survival. HIF1α might be a novel therapeutic target other than BCR/ABL1 translocation.

The effect of HIF on metabolism and immunity

Cellular hypoxia occurs when the demand for sufficient molecular oxygen needed to produce the levels of ATP required to perform physiological functions exceeds the vascular supply, thereby leading to a state of oxygen depletion with the associated risk of bioenergetic crisis. To protect against the threat of hypoxia, eukaryotic cells have evolved the capacity to elicit oxygen-sensitive adaptive transcriptional responses driven primarily (although not exclusively) by the hypoxia-inducible factor (HIF) pathway. In addition to the canonical regulation of HIF by oxygen-dependent hydroxylases, multiple other input signals, including gasotransmitters, non-coding RNAs, histone modifiers and post-translational modifications, modulate the nature of the HIF response in discreet cell types and contexts. Activation of HIF induces various effector pathways that mitigate the effects of hypoxia, including metabolic reprogramming and the production of erythropoietin. Drugs that target the HIF pathway to induce erythropoietin production are now approved for the treatment of chronic kidney disease-related anaemia. However, HIF-dependent changes in cell metabolism also have profound implications for functional responses in innate and adaptive immune cells, and thereby heavily influence immunity and the inflammatory response. Preclinical studies indicate a potential use of HIF therapeutics to treat inflammatory diseases, such as inflammatory bowel disease. Understanding the links between HIF, cellular metabolism and immunity is key to unlocking the full therapeutic potential of drugs that target the HIF pathway.

Hypoxia-dependent changes in cellular metabolism have important implications for the effective functioning of multiple immune cell subtypes. This Review describes the inputs that shape the hypoxic response in individual cell types and contexts, and the implications of this response for cellular metabolism and associated alterations in immune cell function.

Hypoxia is a common feature of particular microenvironments and at sites of immunity and inflammation, resulting in increased activity of the hypoxia-inducible factor (HIF).

In addition to hypoxia, multiple inputs modulate the activity of the HIF pathway, allowing nuanced downstream responses in discreet cell types and contexts.

HIF-dependent changes in cellular metabolism mitigate the effects of hypoxia and ensure that energy needs are met under conditions in which oxidative phosphorylation is reduced.

HIF-dependent changes in metabolism also profoundly affect the phenotype and function of immune cells.

The immunometabolic effects of HIF have important implications for targeting the HIF pathway in inflammatory disease.

Small nucleolar RNAs and SNHGs in the intestinal mucosal barrier: Emerging insights and current roles

BACKGROUND

Previous studies have focused on the involvement of small nucleolar RNAs (snoRNAs) and SNHGs in tumor cell proliferation, apoptosis, invasion, and metastasis via multiple pathways, including phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT), Wnt/β catenin, and mitogen-activated protein kinase (MAPK). These molecular mechanisms affect the integrity of the intestinal mucosal barrier.

AIM OF REVIEW

Current evidence regarding snoRNAs and SNHGs in the context of the mucosal barrier and modulation of homeostasis is fragmented. In this review, we collate the established information on snoRNAs and SNHGs as well as discuss the major pathways affecting the mucosal barrier.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Intestinal mucosal immunity, microflora, and the physical barrier are altered in non-neoplastic diseases such as inflammatory bowel diseases. Dysregulated snoRNAs and SNHGs may impact the intestinal mucosal barrier to promote the pathogenesis and progression of multiple diseases. SnoRNAs or SNHGs has been shown to be associated with poor disease behaviors, indicating that they may be exploited as prognostic biomarkers. Additionally, clarifying the complicated interactions between snoRNAs or SNHGs and the mucosal barrier may provide novel insights for the therapeutic treatment targeting strengthen the intestinal mucosal barrier.

Neuroinflammation in Vascular Cognitive Impairment and Dementia: Current Evidence, Advances, and Prospects

Vascular cognitive impairment and dementia (VCID) is a major heterogeneous brain disease caused by multiple factors, and it is the second most common type of dementia in the world. It is caused by long-term chronic low perfusion in the whole brain or local brain area, and it eventually develops into severe cognitive dysfunction syndrome. Because of the disease’s ambiguous classification and diagnostic criteria, there is no clear treatment strategy for VCID, and the association between cerebrovascular pathology and cognitive impairment is controversial. Neuroinflammation is an immunological cascade reaction mediated by glial cells in the central nervous system where innate immunity resides. Inflammatory reactions could be triggered by various damaging events, including hypoxia, ischemia, and infection. Long-term chronic hypoperfusion-induced ischemia and hypoxia can overactivate neuroinflammation, causing apoptosis, blood–brain barrier damage and other pathological changes, triggering or aggravating the occurrence and development of VCID. In this review, we will explore the mechanisms of neuroinflammation induced by ischemia and hypoxia caused by chronic hypoperfusion and emphasize the important role of neuroinflammation in the development of VCID from the perspective of immune cells, immune mediators and immune signaling pathways, so as to provide valuable ideas for the prevention and treatment of the disease.

Hypotension as a marker or mediator of perioperative organ injury: a narrative review

Perioperative hypotension has been repeatedly associated with organ injury and worse outcome, yet many interventions to reduce morbidity by attempting to avoid or reverse hypotension have floundered. In part, this reflects uncertainty as to what threshold of hypotension is relevant in the perioperative setting. Shifting population-based definitions for hypertension, plus uncertainty regarding individualised norms before surgery, both present major challenges in constructing useful clinical guidelines that may help improve clinical outcomes. Aside from these major pragmatic challenges, a wealth of biological mechanisms that underpin the development of higher blood pressure, particularly with increasing age, suggest that hypotension (however defined) or lower blood pressure per se does not account solely for developing organ injury after major surgery. The mosaic theory of hypertension, first proposed more than 60 yr ago, incorporates multiple, complementary mechanistic pathways through which clinical (macrovascular) attempts to minimise perioperative organ injury may unintentionally subvert protective or adaptive pathways that are fundamental in shaping the integrative host response to injury and inflammation. Consideration of the mosaic framework is critical for a more complete understanding of the perioperative response to acute sterile and infectious inflammation. The largely arbitrary treatment of perioperative blood pressure remains rudimentary in the context of multiple complex adaptive hypertensive endotypes, defined by distinct functional or pathobiological mechanisms, including the regulation of reactive oxygen species, autonomic dysfunction, and inflammation. Developing coherent strategies for the management of perioperative hypotension requires smarter, mechanistically solid interventions delivered by RCTs where observer bias is minimised.

Targeting HIF-1α Function in Cancer through the Chaperone Action of NQO1: Implications of Genetic Diversity of NQO1

HIF-1α is a master regulator of oxygen homeostasis involved in different stages of cancer development. Thus, HIF-1α inhibition represents an interesting target for anti-cancer therapy. It was recently shown that the HIF-1α interaction with NQO1 inhibits proteasomal degradation of the former, thus suggesting that targeting the stability and/or function of NQO1 could lead to the destabilization of HIF-1α as a therapeutic approach. Since the molecular interactions of NQO1 with HIF-1α are beginning to be unraveled, in this review we discuss: (1) Structure–function relationships of HIF-1α; (2) our current knowledge on the intracellular functions and stability of NQO1; (3) the pharmacological modulation of NQO1 by small ligands regarding function and stability; (4) the potential effects of genetic variability of NQO1 in HIF-1α levels and function; (5) the molecular determinants of NQO1 as a chaperone of many different proteins including cancer-associated factors such as HIF-1α, p53 and p73α. This knowledge is then further discussed in the context of potentially targeting the intracellular stability of HIF-1α by acting on its chaperone, NQO1. This could result in novel anti-cancer therapies, always considering that the substantial genetic variability in NQO1 would likely result in different phenotypic responses among individuals.

Sensitive Activatable Nanoprobes for Real-Time Ratiometric Magnetic Resonance Imaging of Reactive Oxygen Species and Ameliorating Inflammation In Vivo

Imaging-guided real-time monitoring of the treatment process of inflammatory diseases is important for the timely adjustment of treatment planning to lower unnecessary side effects and improve treatment outcomes. However, it is difficult to reflect the dynamic changes of inflammation in vivo with enough tissue penetration depth. Here a novel nanotheranostic agent (denominated TMSN@PM) with platelet membrane (PM)-coated, tempol-grafted, manganese-doped, mesoporous silica nanoparticles is developed. The PM endows the TMSN@PM with the ability to target inflammation sites, which are verified by fluorescence imaging with Cyanine5 carboxylic acid (Cy5)-labeled TMSN@PM. Under the inflammatory environment (mild acidity and excess reactive oxygen species (ROS)), TMSN@PM can scavenge the excess ROS, thereby alleviating inflammation, degrade, and release manganese ions for enhanced magnetic resonance imaging (MRI). The relaxation changes (ΔR₁ ) are almost linearly correlated with the concentration of H₂ O₂ , which can reflect the degree of inflammation. This method offers a non-invasive imaging-based strategy for early prediction of the therapeutic outcomes in inflammatory therapy, which may contribute to precision medicine in terms of prognostic stratification and therapeutic planning in future.

Smoking Impairs Hematoma Formation and Dysregulates Angiogenesis as the First Steps of Fracture Healing

Bone fracture healing is an overly complex process in which inflammation, osteogenesis, and angiogenesis are tightly coupled, and delayed fracture repair is a very common health risk. One of the major causes of delayed healing is the formation of insufficient vasculature. Precise regulation of blood vessels in bone and their interplay with especially osteogenic processes has become an emerging topic within the last years; nevertheless, regulation of angiogenesis in (early) diseased fracture repair is still widely unknown. Here, we aim to develop an in vitro model for the analysis of early fracture healing which also enables the analysis of angiogenesis as a main influencing factor. As smoking is one of the main risk factors for bone fractures and developing a delay in healing, we model smoking and non-smoking conditions in vitro to analyze diverging reactions. Human in vitro fracture hematomas mimicking smokers’ and non-smokers’ hematomas were produced and analyzed regarding cell viability, inflammation, osteogenic and chondrogenic differentiation, and angiogenic potential. We could show that smokers’ blood hematomas were viable and comparable to non-smokers. Smokers’ hematomas showed an increase in inflammation and a decrease in osteogenic and chondrogenic differentiation potential. When analyzing angiogenesis, we could show that the smokers’ hematomas secrete factors that drastically reduced HUVEC proliferation and tube formation. With an angiogenesis array and gene expression analysis, we could identify the main influencing factors: Anpgt1/2, Tie2, and VEGFR2/3. In conclusion, our model is suitable to mimic smoking conditions in vitro showing that smoking negatively impacts early vascularization of newly formed tissue.

Renal hypoxia-HIF-PHD-EPO signaling in transition metal nephrotoxicity: friend or foe?

The kidney is the main organ that senses changes in systemic oxygen tension, but it is also the key detoxification, transit and excretion site of transition metals (TMs). Pivotal to oxygen sensing are prolyl-hydroxylases (PHDs), which hydroxylate specific residues in hypoxia-inducible factors (HIFs), key transcription factors that orchestrate responses to hypoxia, such as induction of erythropoietin (EPO). The essential TM ion Fe is a key component and regulator of the hypoxia–PHD–HIF–EPO (HPHE) signaling axis, which governs erythropoiesis, angiogenesis, anaerobic metabolism, adaptation, survival and proliferation, and hence cell and body homeostasis. However, inadequate concentrations of essential TMs or entry of non-essential TMs in organisms cause toxicity and disrupt health. Non-essential TMs are toxic because they enter cells and displace essential TMs by ionic and molecular mimicry, e. g. in metalloproteins. Here, we review the molecular mechanisms of HPHE interactions with TMs (Fe, Co, Ni, Cd, Cr, and Pt) as well as their implications in renal physiology, pathophysiology and toxicology. Some TMs, such as Fe and Co, may activate renal HPHE signaling, which may be beneficial under some circumstances, for example, by mitigating renal injuries from other causes, but may also promote pathologies, such as renal cancer development and metastasis. Yet some other TMs appear to disrupt renal HPHE signaling, contributing to the complex picture of TM (nephro-)toxicity. Strikingly, despite a wealth of literature on the topic, current knowledge lacks a deeper molecular understanding of TM interaction with HPHE signaling, in particular in the kidney. This precludes rationale preventive and therapeutic approaches to TM nephrotoxicity, although recently activators of HPHE signaling have become available for therapy.

Under-Oil Autonomously Regulated Oxygen Microenvironments: A Goldilocks Principle-Based Approach for Microscale Cell Culture

Oxygen levels in vivo are autonomously regulated by a supply-demand balance, which can be altered in disease states. However, the oxygen levels of in vitro cell culture systems, particularly microscale cell culture, are typically dominated by either supply or demand. Further, the oxygen microenvironment in these systems is rarely monitored or reported. Here, a method to establish and dynamically monitor autonomously regulated oxygen microenvironments (AROM) using an oil overlay in an open microscale cell culture system is presented. Using this method, the oxygen microenvironment is dynamically regulated via the supply-demand balance of the system. Numerical simulation and experimental validation of oxygen transport within multi-liquid-phase, microscale culture systems involving a variety of cell types, including mammalian, fungal, and bacterial cells are presented. Finally, AROM is applied to establish a coculture between cells with disparate oxygen demands-primary intestinal epithelial cells (oxygen consuming) and Bacteroides uniformis (an anaerobic species prevalent in the human gut).

COVID-19, Oxidative Stress, and Neuroinflammation in the Depression Route

COVID-19 is associated with oxidative stress, peripheral hyper inflammation, and neuroinflammation, especially in individuals with a more severe form of the disease. Some studies provide evidence on the onset or exacerbation of major depressive disorder (MDD), among other psychiatric disorders due to COVID-19. Oxidative stress and neuroinflammation are associated conditions, especially in the more severe form of MDD and in refractoriness to available therapeutic strategies. Inflammatory cytokines in the COVID-19 hyper inflammation process can activate the hypothalamic–pituitary–adrenal (HPA) axis and the indoleamine-2,3-dioxygenase (IDO) enzyme. IDO activation can reduce tryptophan and increase toxic metabolites of the kynurenine pathway, which increases glial activation, neuroinflammation, toxicity, and neuronal death. This review surveyed a number of studies and analyzed the mechanisms of oxidative stress, inflammation, and neuroinflammation involved in COVID-19 and depression. Finally, the importance of more protocols that can help elucidate the interaction between these mechanisms underlying COVID-19 and MDD and the possible therapeutic strategies involved in the interaction of these mechanisms are highlighted.

Cancer-Associated Fibroblasts: Mechanisms of Tumor Progression and Novel Therapeutic Targets

Simple Summary

The tumor microenvironment plays an important role in determining the biological behavior of several of the more aggressive malignancies. Among the various cell types evident in the tumor “field”, cancer-associated fibroblasts (CAFs) are a heterogenous collection of activated fibroblasts secreting a wide repertoire of factors that regulate tumor development and progression, inflammation, drug resistance, metastasis and recurrence. Insensitivity to chemotherapeutics and metastatic spread are the major contributors to cancer patient mortality. This review discusses the complex interactions between CAFs and the various populations of normal and neoplastic cells that interact within the dynamic confines of the tumor microenvironment with a focus on the involved pathways and genes.

Abstract

Cancer-associated fibroblasts (CAFs) are a heterogenous population of stromal cells found in solid malignancies that coexist with the growing tumor mass and other immune/nonimmune cellular elements. In certain neoplasms (e.g., desmoplastic tumors), CAFs are the prominent mesenchymal cell type in the tumor microenvironment, where their presence and abundance signal a poor prognosis in multiple cancers. CAFs play a major role in the progression of various malignancies by remodeling the supporting stromal matrix into a dense, fibrotic structure while secreting factors that lead to the acquisition of cancer stem-like characteristics and promoting tumor cell survival, reduced sensitivity to chemotherapeutics, aggressive growth and metastasis. Tumors with high stromal fibrotic signatures are more likely to be associated with drug resistance and eventual relapse. Clarifying the molecular basis for such multidirectional crosstalk among the various normal and neoplastic cell types present in the tumor microenvironment may yield novel targets and new opportunities for therapeutic intervention. This review highlights the most recent concepts regarding the complexity of CAF biology including CAF heterogeneity, functionality in drug resistance, contribution to a progressively fibrotic tumor stroma, the involved signaling pathways and the participating genes.

The mechanism underlying extrapulmonary complications of the coronavirus disease 2019 and its therapeutic implication

The coronavirus disease 2019 (COVID-19) is a highly transmissible disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that poses a major threat to global public health. Although COVID-19 primarily affects the respiratory system, causing severe pneumonia and acute respiratory distress syndrome in severe cases, it can also result in multiple extrapulmonary complications. The pathogenesis of extrapulmonary damage in patients with COVID-19 is probably multifactorial, involving both the direct effects of SARS-CoV-2 and the indirect mechanisms associated with the host inflammatory response. Recognition of features and pathogenesis of extrapulmonary complications has clinical implications for identifying disease progression and designing therapeutic strategies. This review provides an overview of the extrapulmonary complications of COVID-19 from immunological and pathophysiologic perspectives and focuses on the pathogenesis and potential therapeutic targets for the management of COVID-19.