Hypoxic Conditions Research Articles

Inhibition of NLRP3 inflammasome by MCC950 under hypoxia alleviates photoreceptor apoptosis via inducing autophagy in Müller glia.

NLRP3 inflammasome activation has emerged as a critical initiator of inflammatory response in ischemic retinopathy. Here, we identified the effect of a potent, selective NLRP3 inhibitor, MCC950, on autophagy and apoptosis under hypoxia. Neonatal mice were exposed to hyperoxia for 5 days to establish oxygen-induced retinopathy (OIR) model. Intravitreal injection of MCC950 was given, and then autophagy and apoptosis markers were assessed. Retinal autophagy, apoptosis, and related pathways were evaluated by western blot, immunofluorescent labeling, transmission electron microscopy, and TUNEL assay. Autophagic activity in Müller glia after NLRP3 inflammasome inhibition, together with its influence on photoreceptor death, was studied using western blot, immunofluorescence staining, mRFP-GFP-LC3 adenovirus transfection, cell viability, proliferation, and apoptosis assays. Results showed that activation of NLRP3 inflammasome in Müller glia was detected in OIR model. MCC950 could improve impaired retinal autophagic flux and attenuate retinal apoptosis while it regulated the retinal AMPK/mTOR/ULK-1 pathway. Suppressed autophagy and depressed proliferation capacity resulting from hypoxia was promoted after MCC950 treatment in Müller glia. Inhibition of AMPK and ULK-1 pathway significantly interfered with the MCC950-induced autophagy activity, indicating MCC950 positively modulated autophagy through AMPK/mTOR/ULK-1 pathway in Müller cells. Furthermore, blockage of autophagy in Müller glia significantly induced apoptosis in the cocultured 661W photoreceptor cells, whereas MCC950 markedly preserved the density of photoreceptor cells. These findings substantiated the therapeutic potential of MCC950 against impaired autophagy and subsequent apoptosis under hypoxia. Such protective effect might involve the modulation of AMPK/mTOR/ULK-1 pathway. Targeting NLRP3 inflammasome in Müller glia could be beneficial for photoreceptor survival under hypoxic conditions.

Characterization of HIF-1α Knockout Primary Human Natural Killer Cells including Populations in Allogeneic Glioblastoma

Enhancing immune cell functions in tumors remains a major challenge in cancer immunotherapy. Natural killer cells (NK) are major innate effector cells with broad cytotoxicity against tumors. Accordingly, NK cells are ideal candidates for cancer immunotherapy, including glioblastoma (GBM). Hypoxia is a common feature of solid tumors, and tumor cells and normal cells adapt to the tumor microenvironment by upregulating the transcription factor hypoxia-inducible factor (HIF)-1α, which can be detrimental to anti-tumor effector immune cell function, including that of NK cells. We knocked out HIF-1α in human primary NK cells using clustered regularly interspaced short palindromic repeat (CRISPR)-associated protein 9 (Cas9). Then, cellular characterizations were conducted in normoxic and hypoxic conditions. Electroporating two HIF-1α-targeting guide RNA–Cas9 protein complexes inhibited HIF-1α expression in expanded NK cells. HIF-1α knockout human NK cells, including populations in hypoxic conditions, enhanced the growth inhibition of allogeneic GBM cells and induced apoptosis in GBM-cell-derived spheroids. RNA-sequencing revealed that the cytotoxicity of HIF-1α knockout NK cells could be related to increased perforin and TNF expression. The results demonstrated that HIF-1α knockout human NK cells, including populations, enhanced cytotoxicity in an environment mimicking the hypoxic conditions of GBM. CRISPR–Cas9-mediated HIF-1α knockout NK cells, including populations, could be a promising immunotherapeutic alternative in patients with GBM.

Mycobacterium tuberculosis produces D-serine under hypoxia to limit CD8+ T cell-dependent immunity in mice.

Adaptation to hypoxia is a major challenge for the survival of Mycobacterium tuberculosis (Mtb) in vivo. Interferon (IFN)-γ-producing CD8+ T cells contribute to control of Mtb infection, in part by promoting antimicrobial activities of macrophages. Whether Mtb counters these responses, particularly during hypoxic conditions, remains unknown. Using metabolomic, proteomic and genetic approaches, here we show that Mtb induced Rv0884c (SerC), an Mtb phosphoserine aminotransferase, to produce D-serine. This activity increased Mtb pathogenesis in mice but did not directly affect intramacrophage Mtb survival. Instead, D-serine inhibited IFN-γ production by CD8+ T cells, which indirectly reduced the ability of macrophages to restrict Mtb upon co-culture. Mechanistically, D-serine interacted with WDR24 and inhibited mTORC1 activation in CD8+ T cells. This decreased T-bet expression and reduced IFN-γ production by CD8+ T cells. Our findings suggest an Mtb evasion mechanism where pathogen metabolic adaptation to hypoxia leads to amino acid-dependent suppression of adaptive anti-TB immunity.

The Expression of Hypoxia-Inducible Factor-1 Alpha (HIF-1α) as a Potential Target for Hypoxic Therapy in COVID-19 Cases

Background: The cellular response to hypoxia is characterized by the stabilization of the HIF-1α protein, which will form a transcription factor that activates genes for low oxygen adaptation. Positive cases of COVID-19 are often characterized by hypoxia, especially in patients with comorbidities. This hypoxic condition will mediate drug resistance or weaken the patient's condition, resulting in lengthening treatment time and even causing death. This study aims to analyze the cellular expression of the HIF-1α gene in patients confirmed positive for COVID-19 with the alpha, beta, delta, and omicron variants. Methods: The research design used was observational, with parameters measuring HIF-1 mRNA expression (RT-PCR, protein (ELISA), and its correlation. The samples used were nose-throat swabs from COVID-19 patients. Results: The expression of HIF-1α mRNA and protein levels produced in variants of COVID-19 patients was compared with controls (times; ng/mL): alpha (0.53; 18.08), beta (0.92; 19.98), delta (0.65; 25.83), and omicron (0.73; 19.85) (Kruskal-Wallis test, p <0.01). The correlation between mRNA expression of HIF-1α and HIF-1α proteins was found to be significantly negative (Pearson Correlation test R = -0.589). Conclusion: In this study, it was found that a decrease in HIF-1α mRNA expression (the result of transcription) increased the levels of HIF-1α protein (the result of translation) and stable HIF-1α expression. Moreover, cellular hypoxia occurred in patients with confirmed positive for COVID-19, with the alpha, beta, delta, and omicron variants. This study can be used as a basis for therapy to control viruses that cause hypoxia in the future. result: The expression of HIF-1α mRNA and protein levels produced in variants of COVID-19 patients compared with controls (times; ng/mL): alpha (0.53; 18.08), beta (0.92; 19.98), delta (0.65 ; 25.83), omicron (0.73; 19.85) (Kruskal Wallis test, p <0.01); The correlation between mRNA expression of HIF-1α and HIF-1α proteins obtained strong negative results (Pearson Correlation test R = -0.589 ).

DKK2 Promotes the progression of oral squamous cell carcinoma through the PI3K/AKT signaling pathway.

This study aimed to investigate the impact of Dickkopf 2 (DKK2) on the progression of oral squamous cell carcinoma (OSCC) and explore its role in the PI3K/AKT signaling transduction pathway. The study initially examined the expression of the DKK2 gene in OSCC tissues and normal tissues. Simultaneously, the expression of DKK2 in HOK cells and OSCC cells was verified, and changes in DKK2 expression under hypoxic conditions were detected. DKK2 overexpression and knockdown were performed in SCC-15 and CAL-27 cells. Subsequently, the effects of DKK2 on the proliferation, migration and invasion of OSCC were detected. Western blotting was employed to detect the expression of key proteins in the DKK2/PI3K/AKT signaling axis before and after transfection, and further explore the relevant molecular mechanisms. Compared to normal tissues, DKK2 expression was elevated in OSCC tissues. The expression of DKK2 in the SCC-15 and CAL-27 cell lines was higher than that in HOK cells, and hypoxic conditions could promote DKK2 expression. DKK2 overexpression promoted cell proliferation, migration, and invasion, while DKK2 knockdown inhibited these processes. DKK2 overexpression activated the PI3K/AKT pathway, while DKK2 knockdown suppressed this pathway. This study suggests that hypoxic conditions enhance the expression of DKK2 in OSCC. DKK2 regulates the proliferation, migration, and invasion of OSCC through the PI3K/AKT signaling pathway.

NPTX1 Mediates the Facilitating Effects of Hypoxia-Stimulated Human Adipocytes on Adipose-Derived Stem Cell Activation and Autologous Adipose Graft Survival Rate.

Autologous adipose tissue is an ideal material for soft tissue filling and transplantation; however, high volumes of fat absorption over time lead to a relatively low overall survival percentage. The survival and differentiation of adipose-derived stem cells (ADSCs) in the transplanted microenvironment might improve adipose graft survival. Adipocytes have been reported to affect ADSC activation. However, its underlying mechanisms remain unclear. Human ADSCs were incubated in a culture medium supplemented with hypoxic or normoxic conditioned culture medium (CM) derived from human adipocytes. Neuronal Pentraxin 1 (NPTX1) was overexpressed or knocked down in human adipocytes using an overexpression vector (NPTX1 OE) or small interfering RNA (siRNA) transfection, respectively. ADSC differentiation and paracrine secretion were assessed. Nude mice were implanted with human adipocytesand ADSCs. The adipose tissue was subsequently evaluated by histological analysis. CM from hypoxic-stimulated human adipocytes significantly facilitated the differentiation ability and paracrine levels of ADSCs. NPTX1 was significantly up-regulated in human adipocytes exposed to hypoxic conditions. In vitro, CM derived from hypoxia-stimulated human adipocytes or NPTX1-overexpressing human adipocytes exposed to normoxia promoted ADSC differentiation and paracrine; after silencing NPTX1, the facilitating effects of hypoxia-treated human adipocytes on ADSC activation were eliminated. Similarly, in vivo, the NPTX1 OE + normoxia-CM group saw improved histological morphology and fat integrity, less fibrosis and inflammation, and increased vessel numbers compared with the OE NC + normoxia-CM group; the adipocyte grafts of the si-NC + hypoxia-CM group yielded the most improved histological morphology, fat integrity, and the most vessel numbers. However, these enhancements of ADSC activation and adipose graft survival were partially abolished by NPTX1 knockdown in human adipocytes. NPTX1 might mediate the facilitating effects of hypoxia-stimulated human adipocytes on ADSC activation, thereby improving adipose tissue survival rate after autologous fat transplantation and the effectiveness of autologous fat transplantation through promoting ADSC activation. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Characteristic Differences between Freeze-dried Tenogenic Secretomes and Freeze-dried Crude Secretomes of Mesenchymal Stem Cells under Hypoxic Conditions

ABSTRACT Introduction: Tendons that are crucial for movement are struggling with self-healing. Regenerative medicine has been using mesenchymal stem cells (MSCs) and their secretomes, and it offers promise. These secretomes, rich in growth factors, aid tissue healing. Tenogenic secretomes target tendon-specific healing, while crude ones provide a broader view of MSC signaling. The study aims to enhance targeted interventions in tendon regeneration and improve the quality of life for those with tendon-related issues. Methods: This laboratory study compares freeze-dried tenogenic and crude secretomes of MSCs under hypoxic conditions for regenerative potential. Stem cells from adipose tissue undergo isolation, culture, and multiplication then treated in hypoxic conditions. Characterization, Interleukin-6 (IL-6) and Interleukin-10 (IL-10) analysis with enzyme-linked immunosorbent assay (ELISA) follow. The results, including organoleptic, pH, and scanning electron microscope assessments, were presented descriptively. Statistical analysis will enhance understanding. Results: Physical characteristics (odor, color, and pH) are similar in both groups. Tenogenic secretome has a more concave surface, potentially aiding cell migration compared to the crude secretome. There were significant differences in cytokine levels (P = 0.001). IL-6 levels expressed from tenogenic secretome were 10.2 ± 2.432 pg/mL compared to the crude one which 18.3 ± 3.175 pg/mL. Levels of IL-10 expressed from tenogenic and crude secretomes were 309.2 ± 50.973 pg/mL and 200.1 ± 32.030, respectively. Conclusion: The tenogenic secretome and crude secretome exhibit no differences in physical characteristics but differ in surface morphology. The concave surface of the tenogenic secretome facilitates cell migration more than the crude secretome. Under hypoxic conditions, the tenogenic secretome shows lower pro-inflammatory (IL-6) and higher anti-inflammatory (IL-10) effects than the crude secretome.

Correlation of C-Reactive Proteins With Chronic Periodontitis. A Prospective Study

Abstract Context: The C-reactive protein (CRP) is an acute-phase reactant protein that is produced in response to various inflammatory and noxious stimuli that include exposure to heat, traumatic conditions, varieties of infectious processes, and conditions of hypoxia. Estimation of CRP levels in serum samples helps in providing important information related to the diagnosis, monitoring, and treatment of inflammatory processes and various associated diseases. Materials and Methods: This prospective longitudinal study was designed to evaluate serum CRPs in subjects who were selected for study participation after fitting into inclusion criteria, which were as follows: a) study participants who were clinically diagnosed with chronic generalized periodontitis along with periodontal pocket depths of ≥5 mm and also radiographic alveolar bone loss; b) subjects within the age range of 35 to 55 years; and c) no smoking habit or use of tobacco in any other form. Results: Patients were assessed for clinical parameters such as gingival index, sulcular bleeding index, mean depth of periodontal pocket, and loss of clinical attachment. Blood was collected at required visits, and CRP was evaluated. Study evaluation periods were baseline (day 0), day 14 (2nd appointment), and day 45 (3rd appointment). Results: Statistically significant reductions in both clinical and serum CRP levels were obtained at subsequent appointments. Conclusion: This study has demonstrated and supported the evidence that serum CRPs act as a biomarker in determining the prognosis of chronic periodontitis patients after nonsurgical periodontal treatment.

Changes in hypoxic and hypercapnic ventilatory responses at high altitude measured using rebreathing methods.

Ventilatory responses to hypoxia and hypercapnia play a vital role in maintaining gas exchange homeostasis, and in adaptation to high-altitude environments. This study investigates the mechanisms underlying sensitization of hypoxic and hypercapnic ventilatory responses (HVR and HCVR, respectively) in individuals acclimatized to moderate high altitude (3800 m). Thirty-one participants underwent chemoreflex testing using the Duffin modified rebreathing technique. Measures were taken at sea level and after 2 days of acclimatization to high altitude. Ventilatory recruitment thresholds (VRT), HCVR, and HVR were quantified. Acclimatization to high altitude resulted in increased HVR (p<0.001) and HCVR (p<0.001), as expected. We also observed that the decrease in VRT under hypoxic test conditions significantly contributed to the elevated HVR at high altitude since the change in VRT across hyperoxic and hypoxic test conditions was greater at high altitude compared to baseline sea level tests (p=0.043). Pre-VRT ventilation also increased at high altitude (p<0.001), but the change did not differ between oxygen conditions. Taken together, this data suggests that the increase in HVR at high altitude is at least partially driven by a larger decrease in the VRT in hypoxia versus hyperoxia at high altitude compared to sea level. This study highlights the intricacies of respiratory adaptations during acclimatization to moderate high altitude, shedding light on the roles of the VRT, baseline respiratory drive, and two-slope HCVR in this process. These findings contribute to our understanding of how the human respiratory control responds to hypoxic and hypercapnic challenges at high altitude.

HIF-1α-induced expression of the m6A reader YTHDF1 inhibits the ferroptosis of nucleus pulposus cells by promoting SLC7A11 translation.

The nucleus pulposus is in a hypoxic environment in the human body, and when intervertebral disc degeneration (IVDD) occurs, the hypoxic environment is disrupted. Nucleus pulposus cell (NPC) ferroptosis is one of the causes of IVDD. N6-methyladenosine (m6A) and its reader protein YTHDF1 regulate cellular activities by affecting RNA metabolism. However, the regulation of ferroptosis in NPCs by m6A-modified RNAs under hypoxic conditions has not been as well studied. In this study, through invitro and invivo experiments, we explored the underlying mechanism of HIF-1α and YTHDF1 in regulating ferroptosis in NPCs. The results indicated that the overexpression of HIF-1α or YTHDF1 suppressed NPC ferroptosis; conversely, the knockdown of HIF-1α or YTHDF1 increased ferroptosis levels in NPCs. Luciferase reporter assays and chromatin immunoprecipitation demonstrated that HIF-1α regulated YTHDF1 transcription by directly binding to its promoter region. Polysome profiling results showed that YTHDF1 promoted the translation of SLC7A11 and consequently the expression of the anti-ferroptosis protein GPX4 by binding to m6A-modified SLC7A11 mRNA. In conclusion, HIF-1α-induced YTHDF1 expression reduces NPC ferroptosis and delays IVDD by promoting SLC7A11 translation in a m6A-dependent manner.

#2940 Expression and modulation of SGLT2 in human podocytes. Not all in tubule

Abstract Background and Aims Inhibitors of the sodium-glucose cotransporter type 2 (iSGLT2) modify important non-glycemic pathways that lead to the protection of target organs. Its renoprotective pleiotropic effects in CKD, associated or not with diabetes, justifies further studies to elucidate the mechanisms of action (MoA) of these drugs. Although the co-transporter SGLT2 is mostly expressed in the proximal tubule, its location and function in other cells, that can be potential therapeutic targets for inhibitor drugs, has not been well studied. We explored the presence of SGLT2 in human podocyte cells and whether it is modified in different situations of cellular stress. Method Differentiated immortalized human podocytes were cultured under different experimental conditions for 24 or 48 h: Normoxia (Control); Normoxia + High concentration of glucose (HG); Hypoxia(1%)+2 h Reoxygenation(H) and the combination H + HG. Cells were also incubated with 0.1 uM Dihydrotestosterone (DHT). SGLT2 gene expression was determined by quantitative PCR and SGLT2 protein was detected by Western Blot (WB) and immunofluorescence (IF). Results Sglt2 gene expression was detected in human podocytes in culture, with an increase of expression after 24 h of exposure to HG. Protein expression by WB showed a trend to increase after 48h of exposure to HG and hypoxia, which was significant with co-incubation with DHT. HG plus DHT also increased the protein expression of SGLT2 under normoxic conditions. The IF measured by intensity of area did not show an increase in the protein expression of the transporter under HG incubation. However, protein expression increased under all hypoxic conditions: Control 50.05 ± 3, Hypoxia 140 ± 16.3 (p &amp;lt; 0.05 vs control) and HG + Hypoxia 253 ± 21.29 (p &amp;lt; 0.001 vs control). Conclusion Our data suggest that podocyte may be one of the therapeutic targets on which the iSGLT2 is acting. The experimental conditions described did not show differences in the expression of the transporter before the single stimulus of glucose, but they did under hypoxia and the combination Hypoxia-high glucose. In addition, co-incubation with testosterone seems to enhance the expression. Studying the MoA of iSGLT2 will open better comprehension of the kidney pathophysiology, particularly in the podocytopathies, regardless of diabetes.

Reprogramming Glioblastoma Cells into Non-Cancerous Neuronal Cells as a Novel Anti-Cancer Strategy

Glioblastoma Multiforme (GBM) is an aggressive brain tumor with a high mortality rate. Direct reprogramming of glial cells to different cell lineages, such as induced neural stem cells (iNSCs) and induced neurons (iNeurons), provides genetic tools to manipulate a cell’s fate as a potential therapy for neurological diseases. NeuroD1 (ND1) is a master transcriptional factor for neurogenesis and it promotes neuronal differentiation. In the present study, we tested the hypothesis that the expression of ND1 in GBM cells can force them to differentiate toward post-mitotic neurons and halt GBM tumor progression. In cultured human GBM cell lines, including LN229, U87, and U373 as temozolomide (TMZ)-sensitive and T98G as TMZ-resistant cells, the neuronal lineage conversion was induced by an adeno-associated virus (AAV) package carrying ND1. Twenty-one days after AAV-ND1 transduction, ND1-expressing cells displayed neuronal markers MAP2, TUJ1, and NeuN. The ND1-induced transdifferentiation was regulated by Wnt signaling and markedly enhanced under a hypoxic condition (2% O2 vs. 21% O2). ND1-expressing GBM cultures had fewer BrdU-positive proliferating cells compared to vector control cultures. Increased cell death was visualized by TUNEL staining, and reduced migrative activity was demonstrated in the wound-healing test after ND1 reprogramming in both TMZ-sensitive and -resistant GBM cells. In a striking contrast to cancer cells, converted cells expressed the anti-tumor gene p53. In an orthotopical GBM mouse model, AAV-ND1-reprogrammed U373 cells were transplanted into the fornix of the cyclosporine-immunocompromised C57BL/6 mouse brain. Compared to control GBM cell-formed tumors, cells from ND1-reprogrammed cultures formed smaller tumors and expressed neuronal markers such as TUJ1 in the brain. Thus, reprogramming using a single-factor ND1 overcame drug resistance, converting malignant cells of heterogeneous GBM cells to normal neuron-like cells in vitro and in vivo. These novel observations warrant further research using patient-derived GBM cells and patient-derived xenograft (PDX) models as a potentially effective treatment for a deadly brain cancer and likely other astrocytoma tumors.

#1738 Renal endogenous hepcidin alleviates ferroptosis of collecting duct in ischemia/reperfusion induced AKI

Abstract Background and Aims Recent studies have demonstrated that urinary and serum hepcidin predicted the incidence of acute kidney injury (AKI) among critically ill patients. As an endogenous acute phase hormone, hepcidin is synthesized not only by the liver but also secreted by distal nephron. However, the autocrine impact of hepcidin secreted by distal nephron on collecting duct cells in AKI remains poorly understood. Method We determined the expression and location of hepcidin in murine kidney in different severity of bilateral ischemia/reperfusion (bIRI) induced AKI model with ischemic duration for 20 min and 32 min. The effect of renal endogenous hepcidin was explored in cultured M-1 (Murine Cortical collecting duct) exposed to hypoxia/reoxygenation (H/R), as well as in bIRI mice with collecting duct-specific overexpression of hepcidin. Transgenic mice were generated by genetic cross between Hepcidin floxed mice which knocked the gene fragment of CAG-LSL-mHamp-flag-WPRE-PolyA into H11 locus and Cdh16-cre mice. Mechanistically, RNA-seq was performed in M-1 cells under H/R condition. Results The expression of renal endogenous hepcidin was significantly elevated in bIRI32min mice compared to both bIRI20min and sham group, suggesting that augmented secretion of hepcidin was induced by more severe AKI. Interestingly, renal endogenous hepcidin was mainly localized to distal convoluted tubule and collecting tubule as indicated by its co-staining with AQP2 and Calbindin-D28k in the kidney. To investigate the role of hepcidin in collecting duct, M-1 cells were cultured under hypoxia condition. We observed remarkable ferroptosis in collecting duct cells other than apoptosis nor necroptosis. Subsequently, hepcidin knockdown further exacerbated ferroptosis under H/R condition, as evidenced by an upregulation of PTGS2 expression and downregulation of GXP4 expression, lower proportion of GSH/GSSG ratio as well as enhanced lipid peroxide accumulation and production of Fe2+. Then, RNA-seq data revealed that hepcidin knockdown promoted the enrichment of genes related to oxidative stress and glutathione metabolic pathway which may be responsible for the deterioration of ferroptosis. To investigate the role of hepcidin in vivo, bIRI induced AKI was established in Cdh16-cre+Hepcidinflox/+ mice. We observed remarkable overexpression of Hepcidin-Flag localized to collecting duct and interstium area. Impressively, Cdh16-cre+Hepcidinflox/+ mice showed ameliorated renal dysfunction adrenal tubule injury histologically. Ferroptosis of renal was alleviated in Cdh16-cre+Hepcidinflox/+ mice as confirmed by an upregulation of GPX4 expression and downregulation of PTGS2, ACSL4, FPN expression, higher proportion of GSH/GSSG ratio, as well as reduced lipid peroxide accumulation and production of Fe2+ by Lipofluo (lipid peroxides) and FerroOrange (Fe2+) staining on frozen section of kidney. Ferroptosis of the collecting duct was alleviated as indicated by downregulation of PTGS2 expression which co-staining with AQP2. To demonstrate the beneficial role of hepcidin, exogenous hepcidin was applied to bIRI induced AKI mice to strengthen the endogenous protective response. Conclusion Renal endogenous hepcidin is induced in the distal tubule and collecting duct after AKI as a protective response via alleviating ferroptosis of collecting duct. Hepcidin may represent a novel therapeutic approach to promote tubule repair by targeting ferroptosis for AKI.

Delineating three-dimensional behavior of uveal melanoma cells under anchorage independent or dependent conditions

BackgroundAlthough rare, uveal melanoma (UM) is a life-threatening malignancy. Understanding its biology is necessary to improve disease outcome. Three-dimensional (3D) in vitro culture methods have emerged as tools that incorporate physical and spatial cues that better mimic tumor biology and in turn deliver more predictive preclinical data. Herein, we comprehensively characterize UM cells under different 3D culture settings as a suitable model to study tumor cell behavior and therapeutic intervention.MethodsSix UM cell lines were tested in two-dimensional (2D) and 3D-culture conditions. For 3D cultures, we used anchorage-dependent (AD) methods where cells were embedded or seeded on top of basement membrane extracts and anchorage-free (AF) methods where cells were seeded on agarose pre-coated plates, ultra-low attachment plates, and on hanging drops, with or without methylcellulose. Cultures were analyzed for multicellular tumor structures (MCTs) development by phase contrast and confocal imaging, and cell wellbeing was assessed based on viability, membrane integrity, vitality, apoptotic features, and DNA synthesis. Vascular endothelial growth factor (VEGF) production was evaluated under hypoxic conditions for cell function analysis.ResultsUM cells cultured following anchorage-free methods developed MCTs shaped as spheres. Regardless of their sizes and degree of compaction, these spheres displayed an outer ring of viable and proliferating cells, and a core with less proliferating and apoptotic cells. In contrast, UM cells maintained under anchorage-dependent conditions established several morphological adaptations. Some remained isolated and rounded, formed multi-size irregular aggregates, or adopted a 2D-like flat appearance. These cells invariably conserved their metabolic activity and conserved melanocytic markers (i.e., expression of Melan A/Mart-1 and HMB45). Notably, under hypoxia, cells maintained under 3D conditions secrete more VEGF compared to cells cultured under 2D conditions.ConclusionsUnder an anchorage-free environment, UM cells form sphere-like MCTs that acquire attributes reminiscent of abnormal vascularized solid tumors. UM cells behavior in anchorage-dependent manner exposed diverse cells populations in response to cues from an enriched extracellular matrix proteins (ECM) environment, highlighting the plasticity of UM cells. This study provides a 3D cell culture platform that is more predictive of the biology of UM. The integration of such platforms to explore mechanisms of ECM-mediated tumor resistance, metastatic abilities, and to test novel therapeutics (i.e., anti-angiogenics and immunomodulators) would benefit UM care.

Mild hyperthermia enhanced synergistic uric acid degradation and multiple ROS elimination for an effective acute gout therapy.

Acute gouty is caused by the excessive accumulation of Monosodium Urate (MSU) crystals within various parts of the body, which leads to a deterioration of the local microenvironment. This degradation is marked by elevated levels of uric acid (UA), increased reactive oxygen species (ROS) production, hypoxic conditions, an upsurge in pro-inflammatory mediators, and mitochondrial dysfunction. In this study, we developed a multifunctional nanoparticle of polydopamine-platinum (PDA@Pt) to combat acute gout by leveraging mild hyperthermia to synergistically enhance UA degradation and anti-inflammatory effect. Herein, PDA acts as a foundational template that facilitates the growth of a Pt shell on the surface of its nanospheres, leading to the formation of the PDA@Pt nanomedicine. Within this therapeutic agent, the Pt nanoparticle catalyzes the decomposition of UA and actively breaks down endogenous hydrogen peroxide (H2O2) to produce O2, which helps to alleviate hypoxic conditions. Concurrently, the PDA component possesses exceptional capacity for ROS scavenging. Most significantly, Both PDA and Pt shell exhibit absorption in the Near-Infrared-II (NIR-II) region, which not only endow PDA@Pt with superior photothermal conversion efficiency for effective photothermal therapy (PTT) but also substantially enhances the nanomedicine's capacity for UA degradation, O2 production and ROS scavenging enzymatic activities. This photothermally-enhanced approach effectively facilitates the repair of mitochondrial damage and downregulates the NF-κB signaling pathway to inhibit the expression of pro-inflammatory cytokines. The multifunctional nanomedicine PDA@Pt exhibits exceptional efficacy in UA reduction and anti-inflammatory effects, presenting a promising potential therapeutic strategy for the management of acute gout.

Hypoxia-inducible factor-1α attenuates renal podocyte injury in male rats in a simulated high-altitude environment by upregulating Krüppel-like factor 4 expression.

Previous studies have shown that podocyte injury is involved in the development of proteinuria in rats under hypobaric hypoxia conditions. Prolyl hydroxylase inhibitors (PHIs) may reduce proteinuria. This study aimed to further investigate whether the protective effects of hypoxia-inducible factor 1α (HIF1α) on podocyte injury induced by hypobaric hypoxia are related to Krüppel-like factor 4 (KLF4). Rats were housed in a low-pressure oxygen chamber to simulate a high-altitude environment (5000m), and a PHI was intraperitoneally injected. Urinary protein electrophoresis was performed and the morphology of the podocytes was observed by electron microscopy. Rat podocytes were cultured under 1% O2, and siRNA was used to interfere with KLF4 expression. The protein expression levels of HIF1α, KLF4, CD2-associated protein (CD2AP) and nephrin were determined by western blotting. Compared with those in the experimental group, the rats in the intervention group on day 14 had lower urinary protein levels, increased protein expression levels of CD2AP and nephrin, and reduced podocyte injury. The results of in vitro experiments showed that the protein expression levels of KLF4, CD2AP and nephrin were greater in the PHI intervention group and lower in the HIF1α inhibitors group than in the low-oxygen group. The protein expression of CD2AP and nephrin in the siKLF4-transfected podocytes treated with PHI and HIF1α inhibitors did not differ significantly from that in the low-oxygen group. HIF1α may be involved in reducing progressive high-altitude proteinuria by regulating KLF4 expression and contributing to the repair of podocyte injury induced by hypobaric hypoxia.

Hypoxia-induced SENP3 promotes chemosensitivity and mitochondrial fission via deSUMOylation of Drp1.

The study aimed to investigate the effect of the SUMOylation status of Drp1 on mitochondrial fission in CDDP-treated HNSCC cells cultured under hypoxic conditions. The effect of hypoxia on the chemosensitivity of HNCC cells was evaluated by flow cytometry and CCK-8 assays. The biological function of SUMO-specific peptidase 3 (SENP3) was evaluated by loss-of-function assays both in vitro and in vivo. SENP3-regulated deSUMOylation of Drp1 were performed with co-IP assays. SENP3 expression correlated with chemosensitivity in clinical HNSCC samples subjected to hypoxic conditions. Hypoxia-induced ROS increased HIF-1α/SENP3 expression and mitochondrial fission in CDDP-treated HNSCC cells, and these effects were reversed by NAC treatment. SENP3 knockdown reversed hypoxia-induced mitochondrial fission and inhibited HNSCC cell apoptosis, which decreased CDDP sensitivity. Furthermore, hypoxia-induced SENP3 deconjugated SUMO2 from Drp1. Our findings revealed that hypoxia-induced SENP3 facilitates CDDP sensitivity and mitochondrial fission via deSUMOylation of Drp1.

Hypobaria During Aeromedical Evacuation and Systemic Inflammation after Porcine Traumatic Brain Injury.

Traumatic brain injury (TBI)-related morbidity is caused largely by secondary injury resulting from hypoxia, excessive sympathetic drive, and uncontrolled inflammation. Aeromedical evacuation (AE) is utilized by the military for transport of wounded soldiers to higher levels of care. We hypothesized that the hypobaric, hypoxic conditions of AE may exacerbate uncontrolled inflammation following TBI that could contribute to more severe TBI-related secondary injury. Thirty-six female pigs were used to test TBI vs. TBI sham, hypoxia vs. normoxia, and hypobaria vs. ground conditions. TBI was induced by controlled cortical injury, hypobaric conditions of 12,000 feet were established in an altitude chamber, and hypoxic exposure was titrated to 85% SpO2 while at altitude. Serum cytokines, UCH-L1 and TBI biomarkers were analyzed via ELISA. Gross analysis and staining of cortex and hippocampus tissue was completed for glial fibrillary acidic protein (GFAP) and phosphorylated tau (p-tau). Serum IL-1b, IL-6, and TNFα were significantly elevated following TBI in pigs exposed to altitude-induced hypobaria/hypoxia, as well as hypobaria alone, compared to ground level/normoxia. No difference in TBI biomarkers following TBI or hypobaric, hypoxic exposure was noted. No difference in brain tissue GFAP or p-tau when comparing the most different conditions of sham TBI+ground/normoxia to the TBI+hypobaria/hypoxia group was noted. The hypobaric environment of AE induces systemic inflammation following TBI. Severe inflammation may play a role in exacerbating secondary injury associated with TBI and contribute to worse neurocognitive outcomes. Measures should be taken to minimize barometric and oxygenation changes during AE following TBI.

Impact of nocturnal hypoxia on glycaemic control, appetite, gut microbiota and inflammation in adults with type 2 diabetes mellitus: A single-blind cross-over trial.

High altitude residents have a lower incidence of type 2 diabetes mellitus (T2DM). Therefore, we examined the effect of repeated overnight normobaric hypoxic exposure on glycaemic control, appetite, gut microbiota and inflammation in adults with T2DM. Thirteen adults with T2DM [glycated haemoglobin (HbA1c): 61.1±14.1mmolmol-1; aged 64.2±9.4years; four female] completed a single-blind, randomised, sham-controlled, cross-over study for 10 nights, sleeping when exposed to hypoxia (fractional inspired O2 [ ]=0.155; ∼2500m simulated altitude) or normoxic conditions ( =0.209) in a randomised order. Outcome measures included: fasted plasma [glucose]; [hypoxia inducible factor-1α]; [interleukin-6]; [tumour necrosis factor-α]; [interleukin-10]; [heat shock protein 70]; [butyric acid]; peak plasma [glucose] and insulin sensitivity following a 2h oral glucose tolerance test; body composition; appetite indices ([leptin], [acyl ghrelin], [peptide YY], [glucagon-like peptide-1]); and gut microbiota diversity and abundance [16S rRNA amplicon sequencing]. During intervention periods, accelerometers measured physical activity, sleep duration and efficiency, whereas continuous glucose monitors were used to assess estimated HbA1c and glucose management indicator and time in target range. Overnight hypoxia was not associated with changes in any outcome measure (P>0.05 with small effect sizes) except fasting insulin sensitivity and gut microbiota alpha diversity, which exhibited trends (P=0.10; P=0.08 respectively) for a medium beneficial effect (d=0.49; d=0.59 respectively). Ten nights of overnight moderate hypoxic exposure did not significantly affect glycaemic control, gut microbiome, appetite, or inflammation in adults with T2DM. However, the intervention was well tolerated and a medium effect-size for improved insulin sensitivity and reduced alpha diversity warrants further investigation. KEY POINTS: Living at altitude lowers the incidence of type 2 diabetes mellitus (T2DM). Animal studies suggest that exposure to hypoxia may lead to weight loss and suppressed appetite. In a single-blind, randomised sham-controlled, cross-over trial, we assessed the effects of 10 nights of hypoxia (fractional inspired O2 ∼0.155) on glucose homeostasis, appetite, gut microbiota, inflammatory stress ([interleukin-6]; [tumour necrosis factor-α]; [interleukin-10]) and hypoxic stress ([hypoxia inducible factor 1α]; heat shock protein 70]) in 13 adults with T2DM. Appetite and inflammatory markers were unchanged following hypoxic exposure, but an increased insulin sensitivity and reduced gut microbiota alpha diversity were associated with a medium effect-size and statistical trends, which warrant further investigation using a definitive large randomised controlled trial. Hypoxic exposure may represent a viable therapeutic intervention in people with T2DM and particularly those unable or unwilling to exercise because barriers to uptake and adherence may be lower than for other lifestyle interventions (e.g. diet and exercise).

DYNAMIC CHANGES IN HISTOLOGICAL AND MORPHOMETRIC INDICATORS OF THE LUNGS IN SEXUALLY IMMATURE RATS DURING SIMULATION OF PARTIAL TRACHEAL STENOSIS

Introduction. The morphological features of the respiratory system in laryngomalacia remain insufficiently understood, particularly regarding structural, cytological, and functional alterations. The aim of this study is to investigate the morphological characteristics of the respiratory compartment in the lungs of sexually immature rats, conduct a morphometric assessment of lung tissue density, analyze the dynamics of erythrocyte mass and collagen accumulation, and identify correlations between these parameters. Materials and Methods: The study involved sexually immature male Wistar rats aged 25-28 days and weighing 40-55 g. Partial tracheal stenosis was induced in experimental animals using a developed method, restricting the tracheal lumen by 20-25%. The stenosis was maintained for 7 and 21 days in different groups. In one group, tracheal stenosis was relieved after 7 days by removing the compressive ligature. Histological, histochemical, and morphometric methods were employed to study changes in lung tissue. Results. Pathological changes in lung tissue during hypoxia were characterized by an increase in the number of different types of cells and erythrocyte mass, especially on the 21st day of the experiment and the removal of ligatures from the trachea in experimental animals. Disturbances in the microcirculation of the lung acini were manifested by a sharp increase in blood filling of the microvessels and expansion of their lumen. In this case, the process of erythrocyte penetration into the lumen of the alveoli was sometimes noted. The results of histochemical detection of collagen indicate that in the lung tissue of experimental animals there is no activation of fibrogenetic processes, which would be accompanied by a simultaneous increase in the specific density of collagen. Indicators characterizing the lung tissue (number of cells, their specific density) made it possible to evaluate the corresponding correlations. At the same time, they were not associated with the level of collagen or erythrocyte density in the studied loci of the respiratory system of experimental sexually immature rats. A significant increase in the specific density of erythrocyte mass in lung tissue did not depend on the duration of the experiment. Removal of the ligature and restoration of the tracheal lumen did not significantly affect the restoration of alveolar acini and the spectrum of identified cells. In addition, an increase in the specific density of lung tissue was observed. Conclusion. The findings of this study contribute to deeper understanding of lung damage in children with laryngomalacia and associated respiratory system ventilation impairment. The observed reactive changes in lung connective tissue and collagen synthesis during hypoxia do not necessarily indicate the development of respiratory system fibrosis. However, longer exposure to hypoxic conditions may increase the risk of fibrosis in children.