HIF-1α Activation Research Articles

Ref-1 redox activity regulates retinal neovascularization by modulating transcriptional activation of HIF-1α.

Retinal neovascularization impairs visual function and is a hallmark of several neovascular eye diseases, including retinopathy of prematurity (ROP) and proliferative diabetic retinopathy (PDR). Current treatments include intravitreal injections of anti-vascular endothelial growth factor (VEGF) biologics, but these therapeutics are often accompanied by high treatment burden and resistance to therapy. Prior studies indicate that APE1/Ref-1, a multifunctional protein with both endonuclease (APE1) and redox-mediated transcriptional regulatory activity (Ref-1), activates multiple pro-angiogenic and pro-inflammatory signaling pathways by chemically reducing key cysteine residues in transcription factors, thereby activating them. Here, we investigated the previously unexplored role of Ref-1 in retinal neovascularization. We demonstrate that Ref-1 is highly expressed in endothelial cells in human PDR and in the oxygen-induced retinopathy (OIR) mouse model of retinal neovascularization. Ref-1 is also highly expressed in microglia and astrocytes in OIR. A small molecule Ref-1 redox inhibitor, APX2009, decreased retinal neovascularization in OIR after systemic delivery. Invitro, hypoxic endothelial cells did not exhibit upregulation of Ref-1 but rather increased Ref-1 nuclear localization. APX2009 decreased hypoxic endothelial cell proliferation and HIF-1α transcriptional activation. Thus, Ref-1 redox activity may be a novel therapeutic target for the treatment of retinal neovascularization, making APX2009 a promising systemic therapeutic approach for the treatment of vascular retinopathies such as ROP and PDR.

Golgi condensation causes intestinal lipid accumulation through HIF-1α-mediated GM130 ubiquitination by NEDD4.

The breakdown of Golgi proteins disrupts lipid trafficking, leading to lipid accumulation in the small intestine. However, the causal mechanism of the effects of Golgi protein degradation on the Golgi structure related to lipid trafficking in the small intestine remains unknown. Here we find that Golgi protein degradation occurs under hypoxic conditions in high-fat-diet-fed mice. Hypoxia-induced degradation promotes structural changes in the Golgi apparatus, termed 'Golgi condensation'. In addition, hypoxia-inducible factor 1α (HIF-1α) activation enhances Golgi condensation through the ubiquitination and degradation of Golgi matrix protein 130 (GM130), which is facilitated by neural precursor cell expressed developmentally downregulated protein 4 (NEDD4). Golgi condensation upon exposure to hypoxia promotes lipid accumulation, apolipoprotein A1 retention and decreased chylomicron secretion in the intestinal epithelium. Golgi condensation and lipid accumulation induced by GM130 depletion are reversed by exogenous GM130 induction in the intestinal epithelium. Inhibition of either HIF-1α or NEDD4 protects against GM130 degradation and, thereby, rescues cells from Golgi condensation, which further increases apolipoprotein A1 secretion and lipid accumulation both in vivo and in vitro. Furthermore, the HIF-1α inhibitor PX-478 prevents Golgi condensation, which decreases lipid accumulation and promotes high-density lipoprotein secretion in high-fat-diet-fed mice. Overall, our results suggest that Golgi condensation plays a key role in lipid trafficking in the small intestine through the HIF-1α- and NEDD4-mediated degradation of GM130, and these findings highlight the possibility that the prevention of structural modifications in the Golgi apparatus can ameliorate intestinal lipid accumulation in obese individuals.

SHP2 regulates the HIF-1 signaling pathway in the decidual human endometrial stromal cells.

The decidual endometrial stromal cells play a critical role in the establishment of uterine receptivity and pregnancy in human. Our previous studies demonstrate that protein tyrosine phosphatase 2 SHP2 is highly expressed in decidualized cells and governs the decidualization progress. However, the role and mechanism of SHP2 in the function of decidual cells remain unclear. Here, we screened proteins interacting with SHP2 in decidual hTERT-immortalized human endometrial stromal cells (T-HESCs) and identified Hypoxia-inducible factor-1 (HIF-1) signaling pathway as a potential SHP2-mediated signaling pathway through proximity-dependent biotinylation (BioID) analysis. Immunoprecipitation (Co-IP) revealed an interaction between SHP2 and HIF-1α, which colocalized to the nucleus in decidual cells. Furthermore, the SHP2 expression correlated with the transcriptional activation of HIF-1α and its downstream genes Beta-enolase (Eno3), Pyruvate kinase 2 (Pkm2), Aldolase C (Aldoc), and Facilitative glucose transporter 1 (Glut1). Knockdown or inhibition of SHP2 significantly reduced the mRNA and protein levels of HIF-1α and its downstream genes, as well as lactate production in decidual cells. We also established a hypoxia model of T-HESCs and 293T cells and found that hypoxic treatment induced the expression of SHP2 and HIF-1α, which colocalized in the nucleus. SHP2 forced-expression rescued the inhibitory effects of SHP2 deficiency on HIF-1α expression and lactate production. Finally, SHP2 binds to the promoter regions of HIF-1α and its target genes (Eno3, Pkm2, Aldoc, and Glut1). Collectively, our results suggest that SHP2 influences the function of decidual cells by HIF-1α signaling and provide a novel function mechanism of decidual stromal cells.

Rapamycin Increases the Development Competence of Yak (Bos grunniens) Oocytes by Promoting Autophagy via Upregulating 17β-Estradiol and HIF-1α During In Vitro Maturation

High-quality oocyte production strategies play an important role in animal-assisted reproductive biotechnologies, and rapamycin (Rap) has been commonly used to increase the development potential of mammalian oocytes. The purpose of this study is to evaluate the effects and possible molecular mechanisms of rap on the maturation of yak oocytes. Different concentrations of Rap were supplemented during in vitro maturation (IVM) of yak oocytes. The maturation rates of oocytes and development rates of parthenogenetically activated embryos were assessed. The levels of 17β-estradiol (E2) were detected via ELISA, and the expression of autophagy-related factors, steroidogenic enzymes, and HIF-1α was detected via qRT-PCR, western blotting, and fluorescence microscopy, respectively. In addition, the impacts of E2 and HIF-1α on Rap-mediated oocyte autophagy were investigated by investigating the activities of E2 and HIF-1α. Our results showed that 0.1 nM Rap substantially enhanced the developmental ability of yak oocytes. In this group, the levels of E2, CYP19A1, CYP17A1, and autophagy-related factors were also significantly increased, and the expression of ATG5 and BECN1 in subsequent embryos was also increased. Further analysis revealed that Rap tends to enhance the development competence of yak oocytes and that the levels of autophagy-related factors are reduced when the activity of E2 or HIF-1α is inhibited. Furthermore, the levels of E2, CYP19A1, and CYP17A1 were downregulated when the activity of HIF-1α was inhibited, and the levels of HIF-1α were also significantly reduced by the estrogen receptor antagonist G15. Nevertheless, the levels of CYP11A1 mRNA in mature yak COCs were not significantly different among these groups, a phenomenon which implies that the levels of E2 were not correlated with the CYP11A1 content in yak COCs. There was an increasing tendency for the development competence of yak oocytes at the optimum concentration of Rap during IVM. The potential underlying mechanism is that Rap can activate autophagy and upregulate the levels of E2 and HIF-1α in mature oocytes. Additionally, the levels of both E2 and HIF-1α are regulated by each other and involve Rap-regulated autophagy in oocytes.

Bacopa monnieri Extract Diminish Hypoxia-Induced Anxiety by Regulating HIF-1α Signaling and Enhancing the Antioxidant Defense System in Hippocampus.

Hypoxia is a significant stressor, and stabilized hypoxia-inducible factor-1α (HIF-1α) regulates the expression of numerous genes, leading to various biochemical, molecular, physiological and genomic changes. The body's oxygen-sensing system activates gene expression to protect brain tissues from hypoxia. Gamma-aminobutyric acid, an inhibitory neurotransmitter, regulates brain excitability during hypoxia through the activation of HIF-1 α. Herbal medicines have been widely used for managing various toxicological effects and disorders including hypoxia; however, the data on safety, efficacy and the molecular mechanisms that increase vulnerability or lethality against hypoxia are still lacking and urgently need to be investigated. The Current study aims to investigate how Bacopa monnieri extract (BME), specially CDRI-08 affects the hippocampus of mice subjected to conditions that simulate hypoxia. The pre and co-treatment of mice involved administrating BME (200mg/kg BW) for 14days, followed by exposure to CoCl2 (40mg/kg BW). BME decreased the levels of reactive oxygen species (ROS) and lipid peroxidation, while it increased the Gamma-aminobutyric acid receptor subunit-ɑ1 (GABAAR-ɑ1) level as well as the activity of antioxidant enzymes superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx). Furthermore BME reduced the levels of HIF-1α and its downstream targets glucose transporter-1 (GLUT-1) and erythropoietin (EPO) in the DG, CA1, and CA3 regions of hippocampus. Additionally, results obtained from the open field, elevated zero maze and plus maze tests indicate that BME restores anxiety caused by hypoxia. Together, these findings suggested that BME mitigates the harmful effects of oxidative stress and altered hypoxia related signaling in hippocampus; and may provide a basis for its therapeutic use in the recovery from hypoxia-led anxiety.

Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitor Roxadustat Accelerates Wound Healing in a Mouse Hind limb Lymphedema Model.

Objective: Drugs regulating hypoxia-inducible factor (HIF)-1α have not been investigated for wound healing in lymphedema. Therefore, we examined the effects of drug modulation of HIF-1α activity for wound healing in our previously developed mouse model of nonirradiated hind limb lymphedema. Approach: Mouse hind limb lymphedema models (n = 17) and a sham group (n = 6) were created using 8- to 10-week-old male C57BL/6N mice. Mice with hind limb lymphedema were randomized into experimental groups receiving roxadustat, 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1), or dimethyl sulfoxide and were given intraperitoneal injections every 2 days for up to 2 weeks. Four days after the surgery, an 8-mm diameter full-thickness skin wound was created in the hind limb. The number of days required for wound closure and the percentage of wounds closed were measured. Skin samples taken at wound creation were evaluated by histological and molecular analysis. Results: Administration of roxadustat accelerated wound healing, whereas YC-1 delayed it, with a significant decrease and increase in skin thickness, respectively. The relative mRNA expression of Hif1α, matrix metalloproteinase-3, and interleukin-6 was significantly higher in the roxadustat group and that of metalloproteinase-9 was significantly lower in the roxadustat group compared with the control group. Innovation: This study is the first to demonstrate delayed wound healing in a mouse model of hind limb lymphedema and the first to demonstrate the promotion of significant wound healing through the use of roxadustat. Conclusion: Roxadustat exerts wound-healing effects and may promote the regulation of extracellular matrix remodeling via gene expression in hind limb lymphedema wound models.

Hypoxia-inducible factor 2α promotes protective Th2 cell responses during intestinal helminth infection.

Th2 cells must sense and adapt to the tissue milieu in order to provide protective host immunity and tissue repair. Here, we examined the mechanisms promoting Th2 cell differentiation and function within the small intestinal lamina propria. Single cell RNA-seq analyses of CD4 + T cells from the small intestinal lamina propria of helminth infected mice revealed high expression of the gene Epas1 , encoding the transcription factor hypoxia-inducible factor 2a (HIF2α). In vitro , exposure to hypoxia or genetic HIF2α activation promoted Th2 cell differentiation, even under non-polarizing conditions. In mice, HIF2α activation in CD4 + T cells promoted intestinal Th2 cell accumulation in the absence of infection, and HIF2α-deficiency impaired CD4 + T cell-mediated host immunity to intestinal helminth infection. Our findings identified hypoxia, and the oxygen-regulated transcription factor Hypoxia-Inducible Factor 2α (HIF2α), as key regulators of Th2 cell differentiation and function within the small intestine.

Aryl Hydrocarbon Receptor Establishes a Delicate Balance between the Level of the Trace Amine Tryptamine and Monoamine Oxidase Activity in the Brain and Periphery in Health and Conditions such as Neurodegenerative, Neurodevelopmental, and Psychiatric Disorders.

The purpose of this review was to analyse the literature regarding the correlation between the level of tryptamine, aryl hydrocarbon receptor (AHR) signalling pathway activation, and monoamine oxidase (MAO)-A and MAO-B activity in health and conditions such as neurodegenerative, neurodevelopmental, and psychiatric disorders. Tryptamine is generated through the decarboxylation of tryptophan by aromatic amino acid decarboxylase (AADC) in the central nervous system (CNS), peripheral nervous system (PNS), endocrine system, and gut bacteria. Organ-specific metabolism of tryptamine, which is mediated by different MAO isoforms, causes this trace amine to have different pharmacokinetics between the brain and periphery. Reactive oxygen species (ROS) generated by MAO can influence miRNA-CYP enzyme regulatory network and affect mitochondrial function. Tryptamine regulates AHR function by acting as an endogenous ligand for AHR, initiating AHR activation and inhibiting the expression of the CYP1A1 and CYP1A2 genes. The dysregulation of AHR signalling, triggered by endogenous tryptamine binding, can disrupt the regulation of prolactin levels. Depending on the tryptamine concentration and context, tryptamine can be beneficial or harmful. By acting as an agonist of inhibitory serotonin receptors and trace-amine associated receptor 1 (TAAR1) and an antagonist of excitatory serotonin receptors, it can engage in diverse physiological interactions with serotonin. Increased tryptamine production is observed under hypoxic conditions and is associated with hypoxia-inducible factor 1α (HIF-1α) activation, leading to AHR activation. Dysregulation of the association between tryptamine levels, AHR signalling pathway activation, and MAO activity are observed in Alzheimer's disease (AD), Parkinson's Disease (PD), Autism Spectrum Disorder (ASD) and schizophrenia.

Tgfβ signaling stimulates glycolysis to promote the genesis of synovial joint interzone in developing mouse embryonic limbs.

The initial interzone cells for synovial joints originate from chondrocytes, but such critical transition is minimally understood. With single-cell RNA sequencing (scRNA-seq) of murine embryonic knee joint primordia, we discovered that heightened expression of glycolysis genes characterized developing interzone cells when compared to flanking chondrocytes. Conditional deletion of the glucose transporters Glut1 and/or Glut3, in either the incipient pre-skeletal mesenchyme with Prx1Cre or in chondrocytes with Col2Cre, disrupted interzone formation dose-dependently. In contrast, deletion of Glut1/3 in established interzone cells with Gdf5Cre did not have similar severe disruption of joint development. scRNA-seq revealed that Glut1/3 deletion by Prx1Cre impeded Tgfβ signaling in the developing interzone cells. Direct elimination of Tgfβ signaling with Prx1Cre partially phenocopied the deletion of Glut1/3 in impairing interzone formation. Tgfβ stimulated glycolysis in chondrocytes via activation of mTOR and Hif1α in vitro. The data support that the essential conversion of chondrocytes to interzone cells requires a transient elevation of glycolysis partly dependent on Tgfβ signaling.

Hypoxia-inducible factor 2 regulates alveolar regeneration after repetitive injury in three-dimensional cellular and in vivo models.

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease in which repetitive epithelial injury and incomplete alveolar repair result in accumulation of profibrotic intermediate/transitional "aberrant" epithelial cell states. The mechanisms leading to the emergence and persistence of aberrant epithelial populations in the distal lung remain incompletely understood. By interrogating single-cell RNA sequencing (scRNA-seq) data from patients with IPF and a mouse model of repeated lung epithelial injury, we identified persistent activation of hypoxia-inducible factor (HIF) signaling in these aberrant epithelial cells. Using mouse genetic lineage-tracing strategies together with scRNA-seq, we found that these disease-emergent aberrant epithelial cells predominantly arose from airway-derived (Scgb1a1-CreER-traced) progenitors and exhibited transcriptional programs of Hif2a activation. In mice treated with repetitive intratracheal bleomycin, deletion of Epas1 (Hif2a) but not Hif1a, from airway-derived progenitors, or administration of the small-molecule HIF2 inhibitor PT-2385, using both prevention and rescue approaches, attenuated experimental lung fibrosis, reduced the appearance of aberrant epithelial cells, and promoted alveolar repair. In mouse alveolar organoids, genetic or pharmacologic inhibition of Hif2 promoted alveolar differentiation of airway-derived epithelial progenitors. In addition, treatment of human distal lung organoids with PT-2385 increased colony-forming efficiency, enhanced protein and transcriptional markers of alveolar type 2 epithelial cell maturation, and prevented the emergence of aberrant epithelial cells. Together, these studies showed that HIF2 activation drives the emergence of aberrant epithelial populations after repetitive injury and that targeted HIF2 inhibition may represent an effective therapeutic strategy to promote functional alveolar repair in IPF and other interstitial lung diseases.

Sustained hypoxia but not intermittent hypoxia induces HIF-1α transcriptional response in human aortic endothelial cells.

Obstructive sleep apnea (OSA) is characterized by intermittent hypoxic environments at the cellular level and is an independent risk factor for the development of cardiovascular disease. Endothelial cell (EC) dysfunction precedes the development of cardiovascular disease; however, the mechanisms by which ECs respond to these intermittent hypoxic events are poorly understood. To better understand EC responses to hypoxia, we examined the effects of sustained hypoxia (SH) and intermittent hypoxia (IH) on the activation of HIF-1α in ECs. While SH stabilized HIF-1α and led to its nuclear localization, IH did not activate HIF-1α and the expression of its target genes. Using RNA-sequencing, we evaluated transcriptional responses of ECs to hypoxia. SH induced the expression of HIF-1α and hypoxia response genes, while IH affected cell-cycle regulation genes. A cytoscape protein-protein interaction network for EC response to hypoxia was created with differentially expressed genes. The network comprises cell-cycle regulation, inflammatory signaling via NF-κB and response to VEGF stimulus subnetworks on which SH and IH had distinct activities. As OSA is associated with elevated catecholamines, we investigated the effect of epinephrine on the EC response to SH and IH. Transcriptomic responses under IH and epinephrine revealed protein-protein interaction networks emphasizing distinct subnetworks, including cytokine-mediated TNFα signaling via NF-κB, Wnt/LRP/DKK signaling and cell cycle regulation. This study reveals differential transcriptomic responses under SH and IH characterised by HIF-1α transcriptional response induced only by SH, but not by IH. The study also features the potential molecular events that may occur at the vascular level in OSA.

Yu-Xue-Bi capsule ameliorates aggressive synovitis and joint damage in rheumatoid arthritis via modulating the SUCNR1/HIF-1α/TRPV1 axis.

Specific treatment for rheumatoid arthritis (RA) is still an unmet need. Yu-Xue-Bi (YXB) capsule effectively treats RA with blood stasis syndrome (BS). However, its mechanism remains unclear. Exploring and elucidating the therapeutic effect and pharmacological mechanism of YXB capsule in treating RA. This study identified differentially expressed genes (DEGs) in patients with RA and BS compared to healthy controls using clinical transcriptomics data. Clinical symptoms of RA and BS, and the related genes were collected from the SoFDA and HPO databases. Candidate bioactive constituents in YXB were identified via UPLC-QTOF/MS and evaluated using ADMET rules. Putative targets were predicted, and a network linking disease-related DEGs and drug targets was constructed. Key targets were screened utilizing random walk-with-restart (RWR) algorithms and verified through experiments using rat models of collagen-induced arthritis with BS (CIA-BS model) in vivo. We found 1220 DEGs along with 976 clinical symptom-related genes, as RA with BS-related genes. Chemical profiling identified 193 YXB constituents, with 98 meeting optimal ADMET criteria. We predicted 459 putative targets for these constituents. Network calculations screened 209 key targets, 129 RA with BS-related genes and 92 YXB targets involved in immune inflammation, blood stagnation, and hyperalgesia imbalance. Notably, the SUCNR1/HIF-1α/TRPV1 axis was enriched by YXB targets against RA with BS. Experimentally, YXB inhibited inflamed joint deterioration, including synovial inflammation, cartilage damage and bone erosion, relieving mechanical and cold allodynia hyperglasia. It reversed hemorrheology and vascular function in CIA-BS rats, restoring SDHB and eNOS expression, preventing SDHA, SUCNR1 and HIF-1α activation, reducing SUCN, TNF-α and IL-1β production, and TRPV1 and TRPA1 expression. Our data support YXB's therapeutic effects on aggressive RA-BS by modulating the SUCNR1/HIF-1α/TRPV1 axis.

TIPE drives a cancer stem-like phenotype by promoting glycolysis via PKM2/HIF-1α axis in melanoma.

TIPE (TNFAIP8) has been identified as an oncogene and participates in tumor biology. However, how its role in the metabolism of tumor cells during melanoma development remains unclear. Here, we demonstrated that TIPE promoted glycolysis by interacting with pyruvate kinase M2 (PKM2) in melanoma. We found that TIPE-induced PKM2 dimerization, thereby facilitating its translocation from the cytoplasm to the nucleus. TIPE-mediated PKM2 dimerization consequently promoted HIF-1α activation and glycolysis, which contributed to melanoma progression and increased its stemness features. Notably, TIPE specifically phosphorylated PKM2 at Ser 37 in an extracellular signal-regulated kinase (ERK)-dependent manner. Consistently, the expression of TIPE was positively correlated with the levels of PKM2 Ser37 phosphorylation and cancer stem cell (CSC) markers in melanoma tissues from clinical samples and tumor bearing mice. In summary, our findings indicate that the TIPE/PKM2/HIF-1α signaling pathway plays a pivotal role in promoting CSC properties by facilitating the glycolysis, which would provide a promising therapeutic target for melanoma intervention.

TIPE drives a cancer stem-like phenotype by promoting glycolysis via PKM2/HIF-1α axis in melanoma

TIPE (TNFAIP8) has been identified as an oncogene and participates in tumor biology. However, how its role in the metabolism of tumor cells during melanoma development remains unclear. Here, we demonstrated that TIPE promoted glycolysis by interacting with pyruvate kinase M2 (PKM2) in melanoma. We found that TIPE-induced PKM2 dimerization, thereby facilitating its translocation from the cytoplasm to the nucleus. TIPE-mediated PKM2 dimerization consequently promoted HIF-1α activation and glycolysis, which contributed to melanoma progression and increased its stemness features. Notably, TIPE specifically phosphorylated PKM2 at Ser 37 in an extracellular signal-regulated kinase (ERK)-dependent manner. Consistently, the expression of TIPE was positively correlated with the levels of PKM2 Ser37 phosphorylation and cancer stem cell (CSC) markers in melanoma tissues from clinical samples and tumor bearing mice. In summary, our findings indicate that the TIPE/PKM2/HIF-1α signaling pathway plays a pivotal role in promoting CSC properties by facilitating the glycolysis, which would provide a promising therapeutic target for melanoma intervention.

Lactate Promotes Hypoxic Granulosa Cells' Autophagy by Activating the HIF-1α/BNIP3/Beclin-1 Signaling Axis.

The avascular nature of the follicle creates a hypoxic microenvironment, establishing a niche where granulosa cells (GCs) rely on glycolysis to produce energy in the form of lactate (L-lactate). Autophagy, an evolutionarily conserved stress-response process, involves the formation of autophagosomes to encapsulate intracellular components, delivering them to lysosomes for degradation. This process plays a critical role in maintaining optimal follicular development. However, whether hypoxia regulates autophagy in GCs via lactate remains unclear. In this study, we investigated lactate-induced autophagy under hypoxia by utilizing glycolysis inhibitors or silencing related genes. We observed a significant increase in autophagy in ovarian GCs under hypoxic conditions, indicated by elevated LC3II levels and reduced P62 levels. Suppressing lactate production through glycolytic inhibitors (2-DG and oxamate) or silencing lactate dehydrogenase (LDHA/LDHB) effectively reduced hypoxia-induced autophagy. Further investigation revealed that the HIF1-α/BNIP3/Beclin-1 axis is essential for lactate-induced autophagy under hypoxic conditions. Inhibiting HIF-1α activity using siRNAs or PX-478 downregulated BNIP3 expression and subsequently suppressed autophagy. Similarly, BNIP3 silencing with siRNAs repressed lactate-induced autophagy in hypoxic conditions. Mechanistically, immunoprecipitation experiments showed that BNIP3 disrupted pre-existing Bcl-2/Beclin-1 complexes by competing with Bcl-2 to form Bcl-2/BNIP3 complexes. This interaction released Beclin-1, which subsequently triggered lactate-induced autophagy under hypoxic conditions. These findings unveil a novel mechanism by which hypoxia regulates GC autophagy through lactate production, highlighting its potential role in sustaining follicular development under hypoxic conditions.

Proteoglycan 4 (Lubricin) and regulation of xanthine oxidase in synovial macrophage as a mechanism of controlling synovitis

BackgroundSynovial macrophages (SMs) are important effectors of joint health and disease. A novel Cx3CR1 + TREM2 + SM population expressing the tight junction protein claudin-5, was recently discovered in synovial lining. Ablation of these SMs was associated with onset of arthritis. Proteoglycan 4 (PRG4) is a mucinous glycoprotein that fulfills lubricating and homeostatic roles in the joint. The aim of this work is to study the role of PRG4 in modulating synovitis in the context of SM homeostasis and assess the contribution of xanthine oxidase (XO)-hypoxia inducible factor alpha (HIF-1a) axis to this regulation.MethodsWe used Prg4FrtloxP/FrtloxP;R26FlpoER/+, a novel transgenic mouse, where the Prg4Frt allele normally expresses the PRG4 protein and was designed to flank the first two exons of Prg4 with a flippase recognition target and “LOXP” sites. Inducing flippase activity with tamoxifen (TAM) inactivates the Frt allele and thus creates a conditional knockout state. We studied anti-inflammatory SMs and XO by quantitative immunohistochemistry, isolated RNA and studied immune pathway activations by multiplexed assays and isolated SMs and studied PRG4 signaling dysfunction in relation to glycolytic switching due to pro-inflammatory activation. Prg4 inactivated mice were treated with oral febuxostat, a specific XO inhibitor, and quantification of Cx3CR1 + TREM2 + SMs, XO immunostaining and synovitis assessment were conducted.ResultsPrg4 inactivation induced Cx3CR1 + TREM2 + SM loss (p < 0.001) and upregulated glycolysis and innate immune pathways in the synovium. In isolated SMs, Xdh (p < 0.01) and Hif1a (p < 0.05) were upregulated. Pro-inflammatory activation of SMs was evident by enhanced glycolytic flux and XO-generated reactive oxygen species (ROS). Febuxostat reduced glycolytic flux (p < 0.001) and HIF-1a levels (p < 0.0001) in SMs. Febuxostat also reduced systemic inflammation (p < 0.001), synovial hyperplasia (p < 0.001) and preserved Cx3CR1 + TREM2 + SMs (p < 0.0001) in synovia of Prg4 inactivated mice.ConclusionsPRG4 is a biologically significant modulator of synovial homeostasis via inhibition of XO expression and downstream HIF-1a activation. PRG4 signaling is anti-inflammatory and promotes synovial homeostasis in chronic synovitis, where direct XO inhibition is potentially therapeutic in chronic synovitis.

The PKM2/HIF-1α Axis is Involved in the Pathogenesis of Endometriosis via TGF-β1 under Endometrial Polyps.

Endometriosis patients exhibit a cancer-like glycolytic phenotype. The pyruvate kinase M2 (PKM2)/hypoxia-inducible factor-1 alpha (HIF-1α) axis plays important roles in glycolysis-related diseases, but its role in patients with endometrial polyps (EPs) combined with endometriosis has not been validated. EP samples were collected from patients with and without endometriosis. PKM2, HIF-1α, and transforming growth factor-beta 1 (TGF-β1) levels were detected by immunohistochemistry (IHC), quantitative polymerase chain reaction, western blotting, and/or immunofluorescence. Primary endometrial stromal cells (ESCs) and non-endometriotic patient-derived ESCs (NESCs) were isolated from patients with EP with or without endometriosis. PKM2 loss-of-function assays in ESCs and gain-of-function assays in NESCs were performed to assess the function of PKM2. The effects of PKM2 and TGF-β1 on the promoter activity of HIF-1α were determined by dual-luciferase reporter assay. PKM2 was overexpressed in ESCs compared to NESCs. Furthermore, PKM2 knockdown repressed viability, decreased migration and invasion, and restrained glycolysis of ESCs, accompanied by reduced HIF-1α levels and weakened promoter activity of HIF-1α. In addition, PKM2 overexpression had the opposite effect on these indicators in NESCs. Of note, an anti-TGF-β1 Ab reversed the PKM2-overexpression-mediated effects on cell viability, migration, and invasion, but not glycolysis or HIF-1α promoter activity, in NESCs. Additionally, PKM2, HIF-1α, and TGF-β1 levels were higher in EP samples with endometriosis than in EP samples without endometriosis, and there were positive correlations between PKM2, HIF-1α, and TGF-β1 IHC scores in all EP samples. PKM2/HIF-1α-axis-dependent glycolysis participates in the pathogenesis of EP combined with endometriosis by mediating TGF-β1 signaling.

A New Severe Congenital Neutropenia Syndrome Associated with Autosomal Recessive COPZ1 Mutations.

We have identified a new inherited bone marrow (BM) failure syndrome with severe congenital neutropenia (CN) caused by autosomal recessive mutations in the coatomer protein complex I (COPI) subunit zeta 1 (COPZ1) gene. A stop-codon COPZ1 mutation and a missense mutation were found in three patients from two unrelated families. While two affected siblings with a stop-codon COPZ1 mutation suffered from congenital neutropenia (CN) that involves other hematological lineages, and non-hematological tissues, the patient with a missense COPZ1 mutation had isolated neutropenia. Both COPZ1 mutations were localized to a highly evolutionarily conserved region. The resulting truncated COPZ1 protein was predicted to display diminished interaction with its COPI complex partner, COPG1. These findings were consistent with the observed block in retrograde protein transport from the Golgi to the ER in human fibroblasts carrying truncated COPZ1. Human CD34+ cells with truncated or missense COPZ1 had significantly impaired granulocytic differentiation and in zebrafish embryos, truncated Copz1 also resulted in defective myelopoiesis. Intracellularly, truncated COPZ1 downregulated JAK/STAT/CEBPE/G-CSFR signaling and hypoxia-responsive pathways while inducing STING, interferon-stimulated genes, stimulating oxidative phosphorylation activity, and increasing reactive oxygen species (ROS) levels in CD34+ cells. Missense COPZ1 deregulated interferon and JAK/STAT signaling but less than the truncated protein. Finally, treatment with the small molecule HIF1α activator IOX2 or transduction of cells with COPZ2 cDNA restored defective granulopoiesis in COPZ1-mutated CD34+ cells, offering potential therapeutic options.

Intestine epithelial-specific hypoxia-inducible factor-1α overexpression ameliorates western diet-induced MASLD.

Intestine epithelial hypoxia-inducible factor-1α (HIF-1α) plays a critical role in maintaining gut barrier function. The aim of this study was to determine whether pharmacological or genetic activation of intestinal HIF-1α ameliorates western diet-induced metabolic dysfunction-associated steatotic liver disease. Metabolic effects of pharmacological activation of HIF-1α by dimethyloxalylglycine were evaluated in HIF-α luciferase reporter (ODD-luc) mice. Male and/or female intestinal epithelial-specific Hif1α overexpression mice (Hif1αLSL/LSL;VilERcre) and wild-type littermates (Hif1αLSL/LSL) were fed with regular chow diet, high fructose (HFr) or high-fat (60% Kcal) high-fructose diet (HFHFr) for 8 weeks. Metabolic phenotypes were profiled. Dimethyloxalylglycine treatment led to increased intestine HIF-α luciferase activity and decreased blood glucose levels in HFr diet-fed male ODD-luc mice. Male Hif1αLSL/LSL;VilERcre mice exhibited markedly improved glucose tolerance compared to Hif1αLSL/LSL mice in response to HFr diet. Eight weeks HFHFr feeding led to obesity in both Hif1αLSL/LSL;VilERcre and Hif1αLSL/LSL mice. However, male Hif1αLSL/LSL;VilERcre mice exhibited markedly attenuated hepatic steatosis along with reduced liver size and liver weight compared to male Hif1αLSL/LSL mice. Moreover, HFHFr-induced systemic inflammatory responses were mitigated in male Hif1αLSL/LSL;VilERcre mice compared to male Hif1αLSL/LSL mice, and those responses were not evident in female mice. Ileum RNA-seq analysis revealed that glycolysis/gluconeogenesis was up in male Hif1αLSL/LSL;VilERcre mice, accompanied by increased epithelial cell proliferation. Moreover, an in vitro study showed that HIF stabilization enhances glycolysis in intestine organoids. Our data provide evidence that pharmacological or genetic activation of intestinal HIF-1α markedly ameliorates western diet-induced metabolic dysfunction-associated steatotic liver disease in a sex-dependent manner. The underlying mechanism is likely attributed to HIF-1α activation-induced upregulation of glycolysis, which, in turn, leads to enhanced epithelial cell proliferation and augmented gut barrier function.

Roles of ferroptosis in the development of diabetic nephropathy

Diabetic nephropathy is a common microvascular complication of diabetes mellitus and one of the main causes of death in patients with diabetes mellitus. Ferroptosis is a newly discovered iron-dependent regulated cell death, which may contribute to the pathogenesis and development of diabetic nephropathy. Adenosine monophosphate-activated protein kinase (AMPK)-mediated ferroptosis-related signaling pathways can slow down the progression of diabetic nephropathy, but excessive activation of AMPK signaling pathway may induce cells to undergo autophagic death. Activation of the signaling pathway mediated by nuclear factor-erythroid 2-related factor (Nrf) 2 and heme oxygenase (HO)-1 can inhibit ferroptosis of cells and alleviate diabetic nephropathy. However, the regulatory effect of HO-1 on ferroptosis is bidirectional, and activation of HIF-1α/HO-1 pathway may lead to intracellular iron overload and ultimately promote ferroptosis. Transforming growth factor (TGF)-β1 mediated signaling pathways can accelerate lipid peroxidation by down-regulating the levels of SLC7A11/GSH/GPX4. The ferroptosis-related signaling pathways mediated by exosome lncRNAs/circRNAs/miRNAs are also involved in the pathogenesis and development of diabetic nephropathy. In addition, signaling pathways mediated by stimulator of interferon gene (STING) and the novel ferroptosis promoter acyl-CoA synthetase long-chain family (ACSL) 1 can induce ferroptosis to promote the progression of diabetic nephropathy. In this review, we focus on the roles of ferroptosis in diabetic nephropathy through the signaling pathways mediated by AMPK, Nrf2/HO-1, TGF-β and exosomes, to elaborate the pathogenesis and development of diabetic nephropathy, and the potential therapeutic target for diabetic nephropathy.