Clinical Conundrum: Return to High Altitude After Cerebral Venous Sinus Thrombosis.

Luks, Andrew M., Thomas G. DeLoughery, Jeffrey H. Gertsch, and Suzy Stokes. Clinical conundrum: return to high altitude after cerebral venous sinus thrombosis. High Alt Med Biol. 00:00-00, 2024.

Effects of acute hypoxia exposure and acclimation on the thermal tolerance of an imperiled Canadian minnow.

Elevated water temperatures and low dissolved oxygen (hypoxia) are pervasive stressors in aquatic systems that can be exacerbated by climate change and anthropogenic activities, and there is growing interest in their interactive effects. To explore this interaction, we quantified the effects of acute and long-term hypoxia exposure on the critical thermal maximum (CTmax) of Redside Dace (Clinostomus elongatus), a small-bodied freshwater minnow with sparse populations in the Great Lakes Basin of Canada and designated as Endangered under Canada's Species at Risk Act. Fish were held at 18°C and acclimated to four levels of dissolved oxygen (>90%, 60%, 40%, and 20% air saturation). CTmax was measured after 2 and 10 weeks of acclimation and after 3.5 weeks of reoxygenation, and agitation behavior was quantified during CTmax trials. Aquatic surface respiration behavior was also quantified at 14 weeks of acclimation to oxygen treatments. Acute hypoxia exposure decreased CTmax in fish acclimated to normoxia (>90% air saturation), but acclimation to hypoxia reduced this effect. There was no effect of acclimation oxygen level on CTmax when measured in normoxia, and there was no effect of exposure time to hypoxia on CTmax. Residual effects of hypoxia acclimation on CTmax were not seen after reoxygenation. Agitation behavior varied greatly among individuals and was not affected by oxygen conditions. Fish performed aquatic surface respiration with low frequency, but performed it earlier when acclimated to higher levels of oxygen. Overall, this work sheds light on the vulnerability of fish experiencing acute hypoxia and heat waves concurrently.

Obesity hypoventilation syndrome, literature review.

Obesity is a global health concern that has been increasing over the years, and it is associated with several pathophysiological changes affecting the respiratory system, including alveolar hypoventilation. Obesity hypoventilation syndrome (OHS) is one of the six subtypes of sleep-hypoventilation disorders. It is defined as the presence of obesity, chronic alveolar hypoventilation leading to daytime hypercapnia and hypoxia, and sleep-disordered breathing. The existence of a sleep disorder is one of the characteristics that patients with OHS present. Among them, 90% of patients have obstructive sleep apnea (OSA), and the remaining 10% of patients with OHS have non-obstructive sleep hypoventilation without OSA or with mild OSA. This review aims to provide a comprehensive understanding of the epidemiological and pathophysiological impact of OHS and to highlight its clinical features, prognosis, and severity, as well as the available treatment options.

Hypoxia and inflammation induce synergistic transcriptome turnover in macrophages.

Macrophages are effector immune cells that experience substantial changes to oxygenation when transiting through tissues, especially when entering tumors or infected wounds. How hypoxia alters gene expression and macrophage effector function at the post-transcriptional level remains poorly understood. Here, we use TimeLapse-seq to measure how inflammatory activation modifies the hypoxic response in primary macrophages. Nucleoside recoding sequencing allows the derivation of steady-state transcript levels, degradation rates, and transcriptional synthesis rates from the same dataset. We find that hypoxia produces distinct responses from resting and inflammatory macrophages. Hypoxia induces destabilization of mRNA transcripts, though inflammatory macrophages substantially increase mRNA degradation compared to resting macrophages. Increased RNA turnover results in the upregulation of ribosomal protein genes and downregulation of extracellular matrix components in inflammatory macrophages. Pathways regulated by mRNA decay in vitro are differentially regulated in tumor-associated macrophages implying that mixed stimuli could induce post-transcriptional regulation of macrophage function in solid tumors.

Metabolic Theory of Preeclampsia: Implications for Maternal Cardiovascular Health.

Preeclampsia (PE) is a multisystemic disorder of pregnancy that not only causes perinatal mortality and morbidity but also has a long-term toll on the maternal and fetal cardiovascular system. Women diagnosed with PE are at greater risk for the subsequent development of hypertension, ischemic heart disease, cardiomyopathy, cerebral edema, seizures, and end-stage renal disease. Although PE is considered heterogeneous, inefficient extravillous trophoblast migration leading to deficient spiral artery remodeling and increased uteroplacental vascular resistance is the likely initiation of the disease. The principal pathophysiology is placental hypoxia, causing subsequent oxidative stress, leading to mitochondrial dysfunction, mitophagy, and immunological imbalance. The damage imposed on the placenta in turn results in the 'stress response' categorized by the dysfunctional release of vasoactive components including oxidative stressors, pro-inflammatory factors, and cytokines into the maternal circulation. These bioactive factors have deleterious effects on systemic endothelial cells and coagulation leading to generalized vascular dysfunction and hypercoagulability. A better understanding of these metabolic factors may lead to novel therapeutic approaches to prevent and treat this multisystemic disorder. In this review, we connect the hypoxic-oxidative stress and inflammation involved in the pathophysiology of PE to the resulting persistent cardiovascular complications in preeclamptic patients.

A Fe2O3/CNx cascade nanoreactor with dual-enzyme-mimetic activities for cancer hypoxia relief to amplify chemo/photodynamic therapy.

Reactive oxygen species (ROS)-mediated therapeutic strategies, including chemodynamic therapy (CDT), photodynamic therapy (PDT), and their combination, are effective for treating cancer. Developing a nanoreactor with combined functions of catalase (CAT) and peroxidase (POD) that can simultaneously convert excess H2O2 in tumors into O2 required for type II PDT and hydroxyl radicals (•OH) for CDT can help achieve combined therapy. Here, we reported on a safe Fe2O3/CNx nanoreactor with dual enzyme simulated activity, in which CNx sheet was the carrier and reducing agent to convert Fe2O3 to Fe2+. After modified by MgO2 and photosensitizer Ce6, MgO2-Fe2O3/CNx-Ce6 (MFCC) platform integrated multiple functions, including photosensitizer delivery, compensated H2O2 continuous supply, relieve of hypoxia, generation of •OH and consumption of GSH into a single formulation. Under 660 nm irradiation for 4 min, MFCC actives more ROS to conduct PDT/CDT, leading to the remarkable reduced survival rate of breast cancer cells to 14 %. Due to the enhanced permeability and retention (EPR) effect, MFCC can retain and accumulate at the tumor site of mice for a longer period that inhibit the expression of tumor angiogenic factors, suppress tumor neovascularization, and suppress the proliferation and growth of tumor cells.

Aptamer Functionalized Hypoxia-potentiating Agent and Hypoxia-inducible Factor Inhibitor Combined with Hypoxia-activated Prodrug for Enhanced Tumor Therapy.

Triple-negative breast cancer (TNBC) is the most lethal subtype of breast cancer. Hypoxia-activated prodrugs (HAPs) have shown promise as potential therapeutic agents for TNBC. While increasing hypoxia levels may promote the HAP activation, it raises concerns regarding HIF1α-dependent drug resistance. It is desirable to develop a targeted approach that enhances tumor hypoxia for HAP activation without promoting HIF1α-dependent drug resistance in TNBC treatment. Herein, we proposed a multi-responsive carrier-free self-assembled nanomedicine named AQ4N@CA4T1ASO. This nanomedicine first targeted tumors by the TNBC-targeting aptamers (T1), and then disassembled in the reductive and acidic conditions within tumors. The released Combretastatin 4 (CA4) could exacerbate hypoxia, thereby promoting the conversion of inactive Banoxantrone (AQ4N) to its active form, AQ4. Simultaneously, the released antisense oligonucleotide (ASO) could attenuate hypoxia-induced HIF1α mRNA expression, thereby sensitizing the tumor to chemotherapy. Overall, this smart nanomedicine represents a profound targeted therapy strategy, combining "hypoxia-potentiating, hypoxia-activated, chemo-sensitization" approaches for TNBC treatment. In vivo study demonstrated significant suppression of tumor growth, highlighting the promising potential of this nanomedicine for future clinical translation.

O-GlcNAc signaling: implications for stress-induced adaptive response pathway in the tumor microenvironment.

The tumor microenvironment (TME) consists of tumor cells, non-tumor cells, extracellular matrix, and signaling molecules, which can contribute to tumor initiation, progression, and therapy resistance. In response to starvation, hypoxia, and drug treatments, tumor cells undergo a variety of deleterious endogenous stresses, such as hypoxia, DNA damage, and oxidative stress. In this context, to survive the difficult situation, tumor cells evolve multiple conserved adaptive responses, including metabolic reprogramming, DNA damage checkpoints, homologous recombination, up-regulated antioxidant pathways, and activated unfolded protein responses. In the last decades, the protein O-GlcNAcylation has emerged as a crucial causative link between glucose metabolism and tumor progression. Here, we discuss the relevant pathways that regulate the above responses. These pathways are adaptive adjustments induced by endogenous stresses in cells. In addition, we systematically discuss the role of O-GlcNAcylation-regulated stress-induced adaptive response pathways (SARPs) in TME remodeling, tumor progression, and treatment resistance. We also emphasize targeting O-GlcNAcylation through compounds that modulate OGT or OGA activity to inhibit tumor progression. It seems that targeting O-GlcNAcylated proteins to intervene in TME may be a novel approach to improve tumor prognosis.

Combining neuromodulation strategies in spinal cord injury gait rehabilitation: A proof of concept, randomized, crossover trial.

OBJECTIVE: To evaluate if acute intermittent hypoxia (AIH) coupled with transcutaneous spinal cord stimulation (tSCS) enhance task-specific training and lead to superior and more sustained gait improvements as compared to each of these strategies used in isolation in persons with chronic, incomplete spinal cord injury (SCI). DESIGN: Proof of concept, randomized crossover trial SETTING: Outpatient, rehabilitation hospital INTERVENTIONS: Ten participants completed 3 intervention arms: 1) AIH, tSCS, and gait training (AIH + tSCS), 2) tSCS plus gait training (SHAM AIH + tSCS), and 3) gait training alone (SHAM + SHAM). Each arm consisted of 5 consecutive days of intervention with a minimum of a 4-week washout between arms. The order of arms was randomized. The study took place from December 3, 2020 to January 4, 2023. MAIN OUTCOME MEASURES: 10-meter walk test (10MWT) at self-selected velocity (SSV) and fast velocity (FV), 6-minute walk test (6MWT), Timed Up and Go (TUG) SECONDARY OUTCOME MEASURES: Isometric ankle plantarflexion and dorsiflexion torque RESULTS: TUG improvements were 3.44 seconds (95% CI: 1.24-5.65) significantly greater in the AIH + tSCS arm than the SHAM AIH + tSCS arm at post-intervention (POST) and 3.31 seconds (95% CI: 1.03-5.58) greater than the SHAM + SHAM arm at 1-week follow up. SSV was 0.08 m/s (95% CI: 0.02-0.14) significantly greater following the AIH + tSCS arm than the SHAM AIH + tSCS at POST. Although not significant, the AIH + tSCS arm also demonstrated the greatest average improvements compared to the other two arms at POST and 1WK for the 6MWT, FV, and ankle plantarflexion torque. CONCLUSIONS: This pilot study is the first to demonstrate that combining these three neuromodulation strategies leads to superior improvements in the TUG and SSV for individuals with chronic incomplete SCI and warrants further investigation.

Optimizing selective withdrawal strategies to mitigate hypoxia under water-level reduction in Germany's largest drinking water reservoir.

Water-level reduction frequently occurs in deep reservoirs, but its effect on dissolved oxygen concentration is not well understood. In this study we used a well-established water quality model to illustrate effects of water level dynamics on oxygen concentration in Rappbode Reservoir, Germany. We then systematically elucidated the potential of selective withdrawal to control hypoxia under changing water levels. Our results documented a gradual decrease of hypolimnetic oxygen concentration under decreasing water level, and hypoxia occurred when the initial level was lower than 410 m a.s.l (71 m relative to the reservoir bottom). We also suggested that changes of hypoxic region, under increasing hypolimnetic withdrawal discharge, followed a unimodal trajectory with the maximum hypoxic area projected under the discharge between 3 m3/sec and 4 m3/sec. Besides, our results illustrated the extent of hypoxia was most effectively inhibited if the withdrawal strategy was applied at the end of stratification with the outlet elevation at the deepest part of the reservoir. Moreover, hypoxia can be totally avoided under a hybrid elevation withdrawal strategy using surface withdrawal during early and mid stratification, and deep withdrawal at the end of stratification. We further confirmed the decisive role of thermal structure in the formation of hypoxia under water-level reduction and withdrawal strategies. We believe the conclusions from this study can be applied to many deep waters in the temperate zone, and the results should guide stakeholders to mitigate negative impacts of hypoxia on aquatic ecosystems.

Inhibition of hypoxia-inducible factors suppresses subretinal fibrosis.

Age-related macular degeneration (AMD) is a common cause of vision loss. The aggressive form of AMD is associated with ocular neovascularization and subretinal fibrosis, representing a responsive outcome against neovascularization mediated by epithelial-mesenchymal transition of retinal pigment epithelium (RPE) cells. A failure of the current treatment (anti-vascular endothelial growth factor therapy) has also been attributed to the progression of subretinal fibrosis. Hypoxia-inducible factors (HIFs) increase gene expressions to promote fibrosis and neovascularization. HIFs act as a central pathway in the pathogenesis of AMD. HIF inhibitors may suppress ocular neovascularization. Nonetheless, further investigation is required to unravel the aspects of subretinal fibrosis. In this study, we used RPE-specific HIFs or von Hippel-Lindau (VHL, a regulator of HIFs) conditional knockout (cKO) mice, along with pharmacological HIF inhibitors, to demonstrate the suppression of subretinal fibrosis. Fibrosis was suppressed by treatments of HIF inhibitors, and similar suppressive effects were detected in RPE-specific Hif1a/Hif2a- and Hif1a-cKO mice. Promotive effects were observed in RPE-specific Vhl-cKO mice, where fibrosis-mediated pathologic processes were evident. Marine products' extracts and their component taurine suppressed fibrosis as HIF inhibitors. Our study shows critical roles of HIFs in the progression of fibrosis, linking them to the potential development of therapeutics for AMD.

Activation of the hypoxia response in the aging cerebrovasculature protects males against cognitive impairment.

Alzheimer's disease (AD) is a neurodegenerative disorder with a distinct sex bias. Age-related vascular alterations, a hallmark of AD onset and progression, are consistently associated with sexual dimorphism. Here, we conducted an integrative meta-analysis of 335,803 single-nucleus transcriptomes and 667 bulk transcriptomes from the vascular system in AD and normal aging to address the underlying sex-dependent vascular aging in AD. All vascular cell types in male AD patients exhibited an activated hypoxia response and downstream signaling pathways including angiogenesis. The female AD vasculature is characterized by increased antigen presentation and decreased angiogenesis. We further confirmed that these sex-biased alterations in the cerebral vascular emerged and were primarily determined in the early stages of AD. Sex-stratified analysis of normal vascular aging revealed that angiogenesis and various stress-response genes were downregulated concurrently with female aging. Conversely, the hypoxia response increased steadily in males upon aging. An investigation of upstream driver transcription factors (TFs) revealed that altered communication between estrogen receptor alpha (ESR1) and hypoxia induced factors during menopause contributes to the inhibition of angiogenesis during normal female vascular aging. Additionally, inhibition of CREB1, a TF that targets estrogen, is also related to female AD. Overall, our study revealed a distinct cerebral vascular profile in females and males, and revealed novel targets for precision medicine therapy for AD.

α-Hemolysin-mediated endothelial injury contributes to the development of Staphylococcus aureus-induced dermonecrosis.

Staphylococcus aureus α-hemolysin (Hla) is a pore-forming toxin critical for the pathogenesis of skin and soft tissue infections, which causes the pathognomonic lesion of cutaneous necrosis (dermonecrosis) in mouse models. To determine the mechanism by which dermonecrosis develops during S. aureus skin infection, mice were given control serum, Hla-neutralizing antiserum, or an inhibitor of Hla receptor [A-disintegrin and metalloprotease 10 (ADAM10) inhibitor] followed by subcutaneous infection by S. aureus, and the lesions were evaluated using immunohistochemistry and immunofluorescence. Hla induced apoptosis in the vascular endothelium at 6 hours post-infection (hpi), followed by apoptosis in keratinocytes at 24 hpi. The loss of vascular endothelial (VE)-cadherin expression preceded the loss of epithelial-cadherin expression. Hla also induced hypoxia in the keratinocytes at 24 hpi following vascular injury. Treatment with Hla-neutralizing antibody or ADAM10 inhibitor attenuated early cleavage of VE-cadherin, cutaneous hypoxia, and dermonecrosis. These findings suggest that Hla-mediated vascular injury with cutaneous hypoxia underlies the pathogenesis of S. aureus-induced dermonecrosis.

Hypoxia-induced Semaphorin 3A promotes the development of endometriosis through regulating macrophage polarization.

BACKGROUND: Semaphorin 3A (Sema3A) is a member of neural guidance factor family well-known for inducing the collapse of nerve cell growth cone and regulating nerve redistribution. It also has been characterized as an immunoregulatory and tumor promoting factor. Our previous study showed that Sema3A was involved in the regulation of sympathetic innervation and neuropathic pain of endometriosis. Nevertheless, the role of Sema3A in the development of endometriosis and its potential upstreaming factor are still not clear. METHODS: Histology experiments were carried to detect the expression of Sema3A, hypoxia -inducible factor 1α (HIF-1α) and the distribution of macrophages. Cell experiments were used to explore the effect of Sema3A on the proliferation and migration of endometrial stromal cells (ESCs) and to confirm the regulatory action of HIF-1α on Sema3A. In vivo experiments were carried out to explore the role of Sema3A on the development of endometriosis. RESULTS: Sema3A was highly expressed in endometriotic lesions and could enhanced the proliferation and migration abilities of ESCs. Aberrant macrophage distribution was found in endometriotic lesions. Sema3A also promoted the differentiation of monocytes into anti-inflammatory macrophages, so indirectly mediating the proliferation and migration of ESCs. Hypoxic microenvironment induced Sema3A mRNA and protein expression in ESCs via HIF-1α. Administration of Sema3A promoted the development of endometriosis in a mouse model. CONCLUSIONS: Sema3A, which is regulated by HIF-1α, is a promoting factor for the development of endometriosis. Targeting Sema3A may be a potential treatment strategy to control endometriotic lesions.

Revisiting reactive oxygen species production in hypoxia.

Cellular responses to hypoxia are crucial in various physiological and pathophysiological contexts and have thus been extensively studied. This has led to a comprehensive understanding of the transcriptional response to hypoxia, which is regulated by hypoxia-inducible factors (HIFs). However, the detailed molecular mechanisms of HIF regulation in hypoxia remain incompletely understood. In particular, there is controversy surrounding the production of mitochondrial reactive oxygen species (ROS) in hypoxia and how this affects the stabilization and activity of HIFs. This review examines this controversy and attempts to shed light on its origin. We discuss the role of physioxia versus normoxia as baseline conditions that can affect the subsequent cellular response to hypoxia and highlight the paucity of data on pericellular oxygen levels in most experiments, leading to variable levels of hypoxia that might progress to anoxia over time. We analyze the different outcomes reported in isolated mitochondria, versus intact cells or whole organisms, and evaluate the reliability of various ROS-detecting tools. Finally, we examine the cell-type and context specificity of oxygen's various effects. We conclude that while recent evidence suggests that the effect of hypoxia on ROS production is highly dependent on the cell type and the duration of exposure, efforts should be made to conduct experiments under carefully controlled, physiological microenvironmental conditions in order to rule out potential artifacts and improve reproducibility in research.

Identification of Hypoxia-ALCAMhigh Macrophage- Exhausted T Cell Axis in Tumor Microenvironment Remodeling for Immunotherapy Resistance.

Although hypoxia is known to be associated with immune resistance, the adaptability to hypoxia by different cell populations in the tumor microenvironment and the underlying mechanisms remain elusive. This knowledge gap has hindered the development of therapeutic strategies to overcome tumor immune resistance induced by hypoxia. Here, bulk, single-cell, and spatial transcriptomics are integrated to characterize hypoxia associated with immune escape during carcinogenesis and reveal a hypoxia-based intercellular communication hub consisting of malignant cells, ALCAMhigh macrophages, and exhausted CD8+ T cells around the tumor boundary. A hypoxic microenvironment promotes binding of HIF-1α complex is demonstrated to the ALCAM promoter therefore increasing its expression in macrophages, and the ALCAMhigh macrophages co-localize with exhausted CD8+ T cells in the tumor spatial microenvironment and promote T cell exhaustion. Preclinically, HIF-1ɑ inhibition reduces ALCAM expression in macrophages and exhausted CD8+ T cells and potentiates T cell antitumor function to enhance immunotherapy efficacy. This study reveals the systematic landscape of hypoxia at single-cell resolution and spatial architecture and highlights the effect of hypoxia on immunotherapy resistance through the ALCAMhigh macrophage-exhausted T cell axis, providing a novel immunotherapeutic strategy to overcome hypoxia-induced resistance in cancers.

A critical influence of HIF-1 on MMP-9 and Galectin-3 in oral lichen planus.

OBJECTIVE: Oral lichen planus carries a risk for malignancy. The pathogenesis of the disease is mediated by various inflammatory mediators. Several mediators could be responsible for the oncogenic behavior in certain cases. Hypoxia-inducible factor-1a (HIF-1), and its possible correlation to Galactin-3 (Gal-3) and matrix metalloproteinase-9 (MMP-9) over expression represents an important indicator for malignant transformation. The investigation of these factors may present evidence-based information on malignant transformation of the disease. SUBJECTS AND METHODS: The study investigated the expression of HIF-1, Gla-3 and MMP-9 in tissue samples of OLP compared to control subjects of un-inflamed gingival overgrowth. 20 biospecimen were allocated in each group. RESULTS: Immunohistochemical findings of OLP showed immunoreactivity for Galectin 3, HIF1a and MMP-9 by most of the epithelial cells. There was a positive correlation between HIF1α and MMP-9, r = 0.9301 (P-value < 0.00001). A positive correlation was detected between Galectin 3 and MMP-9, r = 0.7292 (P-value = 0.000264) between Galectin 3 and HIF1α, r = 0.5893 (P-value = 0.006252). CONCLUSION: These findings confirm the hypothesis that the adaptive pathways to hypoxia as Gal 3 and MMP-9 expressions and their HIF-1 may play a crucial role in carcinogenesis of OLP.

Beyond Legal Boundaries: Public and Clinician Perspectives on Treatment Withdrawal in Infants With Poor Neurological Prognosis.

BACKGROUND: Despite medical advancements in neonatal survival rates, many children have poor neurological outcomes. Because the law in Korea restricts the withdrawal of life-sustaining treatment to only cases of imminent death, treatment discontinuation may not be an option, even in patients with poor neurological prognosis. This study investigated the opinions of the general population and clinicians regarding life-sustaining treatment withdrawal in such cases using hypothetical scenarios. METHODS: We conducted a cross-sectional study on the general population and clinicians using a web-based questionnaire. The sample of the general population from an online panel comprised 500 individuals aged 20-69 years selected by quota sampling. The clinician sample comprised 200 clinicians from a tertiary university hospital. We created hypothetical vignettes and questionnaire items to assess attitudes regarding mechanical ventilation withdrawal for an infant at risk of poor neurological prognosis due to birth asphyxia at 2 months and 3 years after the incidence. RESULTS: Overall, 73% of the general population and 74% of clinicians had positive attitudes toward mechanical ventilator withdrawal at 2 months after birth asphyxia. The proportion of positive attitudes toward mechanical ventilator withdrawal was increased in the general population (84%, P < 0.001) and clinicians (80.5%, P = 0.02) at 3 years after birth asphyxia. Religion, spirituality, the presence of a person with a disability in the household, and household income were associated with the attitudes of the general population. In the multivariable logistic regression analysis of the general population, respondents living with a person with a disability or having a disability were more likely to find the withdrawal of the ventilator at 2 months and 3 years after birth asphyxia not permissible. Regarding religion, respondents who identified as Christians were more likely to find the ventilator withdrawal at 2 months after birth asphyxia unacceptable. CONCLUSION: The general population and clinicians shared the perspective that the decision to withdraw life-sustaining treatment in infants with a poor neurological prognosis should be considered before the end of life. A societal discussion about making decisions centered around the best interest of pediatric patients is warranted.

Survival strategies of aerobic methanotrophs under hypoxia in methanogenic lake sediments.

BACKGROUND: Microbial methane oxidation, methanotrophy, plays a crucial role in mitigating the release of the potent greenhouse gas methane from aquatic systems. While aerobic methanotrophy is a well-established process in oxygen-rich environments, emerging evidence suggests their activity in hypoxic conditions. However, the adaptability of these methanotrophs to such environments has remained poorly understood. Here, we explored the genetic adaptability of aerobic methanotrophs to hypoxia in the methanogenic sediments of Lake Kinneret (LK). These LK methanogenic sediments, situated below the oxidic and sulfidic zones, were previously characterized by methane oxidation coupled with iron reduction via the involvement of aerobic methanotrophs. RESULTS: In order to explore the adaptation of the methanotrophs to hypoxia, we conducted two experiments using LK sediments as inoculum: (i) an aerobic "classical" methanotrophic enrichment with ambient air employing DNA stable isotope probing (DNA-SIP) and (ii) hypoxic methanotrophic enrichment with repeated spiking of 1% oxygen. Analysis of 16S rRNA gene amplicons revealed the enrichment of Methylococcales methanotrophs, being up to a third of the enriched community. Methylobacter, Methylogaea, and Methylomonas were prominent in the aerobic experiment, while hypoxic conditions enriched primarily Methylomonas. Using metagenomics sequencing of DNA extracted from these experiments, we curated five Methylococcales metagenome-assembled genomes (MAGs) and evaluated the genetic basis for their survival in hypoxic environments. A comparative analysis with an additional 62 Methylococcales genomes from various environments highlighted several core genetic adaptations to hypoxia found in most examined Methylococcales genomes, including high-affinity cytochrome oxidases, oxygen-binding proteins, fermentation-based methane oxidation, motility, and glycogen use. We also found that some Methylococcales, including LK Methylococcales, may denitrify, while metals and humic substances may also serve as electron acceptors alternative to oxygen. Outer membrane multi-heme cytochromes and riboflavin were identified as potential mediators for the utilization of metals and humic material. These diverse mechanisms suggest the ability of methanotrophs to thrive in ecological niches previously thought inhospitable for their growth. CONCLUSIONS: Our study sheds light on the ability of enriched Methylococcales methanotrophs from methanogenic LK sediments to survive under hypoxia. Genomic analysis revealed a spectrum of genetic capabilities, potentially enabling these methanotrophs to function. The identified mechanisms, such as those enabling the use of alternative electron acceptors, expand our understanding of methanotroph resilience in diverse ecological settings. These findings contribute to the broader knowledge of microbial methane oxidation and have implications for understanding and potential contribution methanotrophs may have in mitigating methane emissions in various environmental conditions.