Low Oxygen Tension Research Articles

Mitochondrial AOX1a and an H2O2 feed-forward signalling loop regulate flooding tolerance in rice.

Flooding is a widespread natural disaster that causes tremendous yield losses of global food production. Rice is the only cereal capable of growing in aquatic environments. Direct seeding by which seedlings grow underwater is an important cultivation method for reducing rice production cost. Hypoxic germination tolerance and root growth in waterlogged soil are key traits for rice adaptability to flooded environments. Alternative oxidase (AOX) is a non-ATP-producing terminal oxidase in the plant mitochondrial electron transport chain, but its role in hypoxia tolerance had been unclear. We have discovered that AOX1a is necessary and sufficient to promote germination/coleoptile elongation and root development in rice under flooding/hypoxia. Hypoxia enhances endogenous H2O2 accumulation, and H2O2 in turn activates an ensemble of regulatory genes including AOX1a to facilitate the conversion of deleterious reactive oxygen species to H2O2 in rice under hypoxia. We show that AOX1a and H2O2 act interdependently to coordinate three key downstream events, that is, glycolysis/fermentation for minimal ATP production, root aerenchyma development and lateral root emergence under hypoxia. Moreover, we reveal that ectopic AOX1a expression promotes vigorous root and plant growth, and increases grain yield under regular irrigation conditions. Our discoveries provide new insights into a unique sensor-second messenger pair in which AOX1a acts as the sensor perceiving low oxygen tension, while H2O2 accumulation serves as the second messenger triggering downstream root development in rice against hypoxia stress. This work also reveals AOX1a genetic manipulation and H2O2 pretreatment as potential targets for improving flooding tolerance in rice and other crops.

Potential Roles of Hypoxia-Inducible Factor-1 in Alzheimer’s Disease: Beneficial or Detrimental?

The major pathological characteristics of Alzheimer’s disease (AD) include senile plaques and neurofibrillary tangles (NFTs), which are mainly composed of aggregated amyloid-beta (Aβ) peptide and hyperphosphorylated tau protein, respectively. The excessive production of reactive oxygen species (ROS) and neuroinflammation are crucial contributing factors to the pathological mechanisms of AD. Hypoxia-inducible factor-1 (HIF-1) is a transcription factor critical for tissue adaption to low-oxygen tension. Growing evidence has suggested HIF-1 as a potential therapeutic target for AD; conversely, other experimental findings indicate that HIF-1 induction contributes to AD pathogenesis. These previous findings thus point to the complex, even contradictory, roles of HIF-1 in AD. In this review, we first introduce the general pathogenic mechanisms of AD as well as the potential pathophysiological roles of HIF-1 in cancer, immunity, and oxidative stress. Based on current experimental evidence in the literature, we then discuss the possible beneficial as well as detrimental mechanisms of HIF-1 in AD; these sections also include the summaries of multiple chemical reagents and proteins that have been shown to exert beneficial effects in AD via either the induction or inhibition of HIF-1.

MCM proteins are up-regulated in placentas of women with reduced insulin sensitivity.

In the first trimester of pregnancy the human placenta grows rapidly, making it sensitive to changes in the intrauterine environment. To test whether exposure to an environment in utero often associated with obesity modifies placental proteome and function, we performed untargeted proteomics (LC-MS/MS) in placentas from 19 women (gestational age 35-48 days, i.e. 5+0-6+6 weeks). Maternal clinical traits (body mass index, leptin, glucose, C-peptide and insulin sensitivity) and gestational age were recorded. DNA replication and cell cycle pathways were enriched in the proteome of placentas of women with low maternal insulin sensitivity. Driving these pathways were the minichromosome maintenance (MCM) proteins MCM2, MCM3, MCM4, MCM5, MCM6 and MCM7 (MCM-complex). These proteins are part of the pre-replicative complex and participate in DNA damage repair. Indeed, MCM6 and γH2AX (DNA-damage marker) protein levels correlated in first trimester placental tissue (r = 0.514, P<0.01). MCM6 and γH2AX co-localized to nuclei of villous cytotrophoblast cells, the proliferative cell type of the placenta, suggesting increased DNA damage in this cell type. To mimic key features of the intrauterine obesogenic environment, a first trimester trophoblast cell line, i.e., ACH-3P, was exposed to high insulin (10 nM) or low oxygen tension (2.5% O2). There was a significant correlation between MCM6 and γH2AX protein levels, but these were independent of insulin or oxygen exposure. These findings show that chronic exposure in utero to reduced maternal insulin sensitivity during early pregnancy induces changes in the early first trimester placental proteome. Pathways related to DNA replication, cell cycle and DNA damage repair appear especially sensitive to such an in utero environment.

Advanced maternal age affects their frozen-thawed embryo susceptibility to high oxygen environment

Preimplantation embryos can experience stress from laboratory interventions and a sub-optimal culture environment. Though research has demonstrated advanced maternal age impairs oocyte quality, the response of embryos derived from such oocytes to vitrification-thawing and culture in a high oxygen (O2) environment in the assisted reproductive technology laboratory is unknown. Therefore, in this study, embryos produced by in vitro fertilization (IVF) using oocytes from two- and eight-month-old Swiss albino mice were vitrified and thawed during their 6–8 cell stage. and cultured at low oxygen (5%) tension (LOT) and high oxygen (20%) tension (HOT). Embryo development, apoptosis, inner cell mass (ICM) outgrowth proliferation ability in vitro and pluripotency were assessed. Embryos from advanced maternal age cultured at HOT showed reduced fertilizing ability (p < 0.05), poor survival post-thawing (p < 0.05), and increased apoptosis (p < 0.01) in comparison to sibling embryos cultured at LOT. Importantly, the extended culture of vitrified-thawed embryos from advanced maternal age led to a significant (p < 0.001) reduction in complete ICM outgrowth formation at HOT in comparison to the LOT environment. The findings of this study suggest that HOT is detrimental to embryos from advanced maternal age, and importantly, vitrified-thawed embryos are more susceptible to stress, which could have negative implications, especially during the peri-implantation developmental period.

Lupus Nephritis: Immune Cells and the Kidney Microenvironment.

Lupus nephritis (LN) is the most common major organ manifestation of the autoimmune disease SLE (lupus), with 10% of those afflicted progressing to ESKD. The kidney in LN is characterized by a significant immune infiltrate and proinflammatory cytokine milieu that affects intrinsic renal cells and is, in part, responsible for the tissue damage observed in LN. It is now increasingly appreciated that LN is not due to unidirectional immune cell activation with subsequent kidney damage. Rather, the kidney microenvironment influences the recruitment, survival, differentiation, and activation of immune cells, which, in turn, modify kidney cell function. This review covers how the biochemical environment of the kidney ( i.e ., low oxygen tension and hypertonicity) and unique kidney cell types affect the intrarenal immune cells in LN. The pathways used by intrinsic renal cells to interact with immune cells, such as antigen presentation and cytokine production, are discussed in detail. An understanding of these mechanisms can lead to the design of more kidney-targeted treatments and the avoidance of systemic immunosuppressive effects and may represent the next frontier of LN therapies.

Immunomodulatory Behavior of Tendon Magnetic Cell Sheets can be Modulated in Hypoxic Environments under Magnetic Stimulus.

Tissue environments play a crucial role in orchestrating cell behavior, guided by a complex interplay of various factors. Long lasting inflammatory signals compromise tendon homeostasis and promote tissue degeneration, while tissue oxygen levels affect local cells' responses with hypoxic environments influencing apoptosis, inflammatory mediators, and matrix production. Recent works have unveiled the therapeutic potential of pulsed electromagnetic field (PEMF) in modulating inflammatory signals expressed by human tendon cells (hTDCs), and in mitigating the hypoxia-induced effects on the regulation of inflammatory cytokines. Thus, we sought to investigate the role of hypoxic environments, namely, 1 and 2% oxygen tension, in the inflammatory profiles of magnetic cell sheets (magCSs) formed by magnetic nanoparticles internalized in contiguous hTDCs with intact cell-cell junctions and deposited matrix. We also aimed to explore the impact of PEMF over hypoxia-treated magCSs, including IL-1β-primed-magCSs, with the objective of harnessing magnetic stimulation to guide abnormal inflammatory cell responses toward efficient treatments supporting tendon regenerative potential. Our findings revealed that low oxygen tensions amplified the expression of hypoxia-associated genes and of inflammatory markers in IL-1β-primed-magCSs with an involvement of the NF-κB signaling pathway. Encouragingly, when PEMF was applied to IL-1β-primed-magCSs under hypoxic conditions, it successfully modulated inflammatory cues by favoring IL-10 and IL-4, via the NF-κB pathway. These results signify the remarkable potential of PEMF in driving proregenerative strategies and opens up new approaches in tendon therapies, highlighting the transformative impact of immunomodulatory magnetic cell sheets.

Hif1α-dependent mitochondrial acute O2 sensing and signaling to myocyte Ca2+ channels mediate arterial hypoxic vasodilation

Vasodilation in response to low oxygen (O2) tension (hypoxic vasodilation) is an essential homeostatic response of systemic arteries that facilitates O2 supply to tissues according to demand. However, how blood vessels react to O2 deficiency is not well understood. A common belief is that arterial myocytes are O2-sensitive. Supporting this concept, it has been shown that the activity of myocyte L-type Ca2+channels, the main ion channels responsible for vascular contractility, is reversibly inhibited by hypoxia, although the underlying molecular mechanisms have remained elusive. Here, we show that genetic or pharmacological disruption of mitochondrial electron transport selectively abolishes O2 modulation of Ca2+ channels and hypoxic vasodilation. Mitochondria function as O2 sensors and effectors that signal myocyte Ca2+ channels due to constitutive Hif1α-mediated expression of specific electron transport subunit isoforms. These findings reveal the acute O2-sensing mechanisms of vascular cells and may guide new developments in vascular pharmacology.

Controlling Pericellular Oxygen Tension in Cell Culture Reveals Distinct Breast Cancer Responses to Low Oxygen Tensions.

In oxygen (O2)-controlled cell culture, an indispensable tool in biological research, it is presumed that the incubator setpoint equals the O2 tension experienced by cells (i.e., pericellular O2). However, it is discovered that physioxic (5% O2) and hypoxic (1% O2) setpoints regularly induce anoxic (0% O2) pericellular tensions in both adherent and suspension cell cultures. Electron transport chain inhibition ablates this effect, indicating that cellular O2 consumption is the driving factor. RNA-seq analysis revealed that primary human hepatocytes cultured in physioxia experience ischemia-reperfusion injury due to cellular O2 consumption. A reaction-diffusion model is developed to predict pericellular O2 tension a priori, demonstrating that the effect of cellular O2 consumption has the greatest impact in smaller volume culture vessels. By controlling pericellular O2 tension in cell culture, it is found that hypoxia vs. anoxia induce distinct breast cancer transcriptomic and translational responses, including modulation of the hypoxia-inducible factor (HIF) pathway and metabolic reprogramming. Collectively, these findings indicate that breast cancer cells respond non-monotonically to low O2, suggesting that anoxic cell culture is not suitable for modeling hypoxia. Furthermore, it is shown that controlling atmospheric O2 tension in cell culture incubators is insufficient to regulate O2 in cell culture, thus introducing the concept of pericellular O2-controlled cell culture.

Diverse and multifunctional roles for perlecan (HSPG2) in repair of the intervertebral disc.

Perlecan is a widely distributed, modular, and multifunctional heparan sulfate proteoglycan, which facilitates cellular communication with the extracellular environment to promote tissue development, tissue homeostasis, and optimization of biomechanical tissue functions. Perlecan-mediated osmotic mechanotransduction serves to regulate the metabolic activity of cells in tissues subjected to tension, compression, or shear. Perlecan interacts with a vast array of extracellular matrix (ECM) proteins through which it stabilizes tissues and regulates the proliferation or differentiation of resident cell populations. Here we examine the roles of the HS-proteoglycan perlecan in the normal and destabilized intervertebral disc. The intervertebral disc cell has evolved to survive in a hostile weight bearing, acidic, low oxygen tension, and low nutrition environment, and perlecan provides cytoprotection, shields disc cells from excessive compressive forces, and sequesters a range of growth factors in the disc cell environment where they aid in cellular survival, proliferation, and differentiation. The cells in mechanically destabilized connective tissues attempt to re-establish optimal tissue composition and tissue functional properties by changing the properties of their ECM, in the process of chondroid metaplasia. We explore the possibility that perlecan assists in these cell-mediated tissue remodeling responses by regulating disc cell anabolism. Perlecan's mechano-osmotic transductive property may be of potential therapeutic application.

Bhlhe40 Regulates Proliferation and Angiogenesis in Mouse Embryoid Bodies under Hypoxia.

Knowledge of the molecular mechanisms that underlie the regulation of major adaptive responses to an unbalanced oxygen tension is central to understanding tissue homeostasis and disease. Hypoxia-inducible transcription factors (HIFs) coordinate changes in the transcriptome that control these adaptive responses. Here, we focused on the functional role of the transcriptional repressor basic-helix-loop-helix family member e40 (Bhlhe40), which we previously identified in a meta-analysis as one of the most consistently upregulated genes in response to hypoxia across various cell types. We investigated the role of Bhlhe40 in controlling proliferation and angiogenesis using a gene editing strategy in mouse embryonic stem cells (mESCs) that we differentiated in embryoid bodies (EBs). We observed that hypoxia-induced Bhlhe40 expression was compatible with the rapid proliferation of pluripotent mESCs under low oxygen tension. However, in EBs, hypoxia triggered a Bhlhe40-dependent cell cycle arrest in most progenitor cells and endothelial cells within vascular structures. Furthermore, Bhlhe40 knockout increased the basal vascularization of the EBs in normoxia and exacerbated the hypoxia-induced vascularization, supporting a novel role for Bhlhe40 as a negative regulator of blood vessel formation. Our findings implicate Bhlhe40 in mediating key functional adaptive responses to hypoxia, such as proliferation arrest and angiogenesis.

P-609 Impact of low versus air oxygen tension on the oocyte maturation in PCOS women undergoing capacitation IVM: a sibling oocyte pilot study

Abstract Study question Does low or air oxygen tension improve the oocyte maturation rate in biphasic capacitation IVM (CAPA-IVM)? Summary answer Low oxygen tension resulted in a lower maturation rate and two-pronuclei fertilization rate compared with air oxygen tension in the CAPA-IVM culture. What is known already CAPA-IVM, with a pre-maturation step, improves the competence of oocytes matured in-vitro. The current CAPA-IVM culture condition is under air oxygen concentration. However, the impact of oxygen tension on in-vitro oocyte maturation needs to be better understood, and it remains uncertain whether the maturation process aligns with in-vivo conditions. Study design, size, duration A sibling oocyte pilot study of 416 cumulus-oocyte complexes (COCs) recruited from fifteen polycystic ovary syndrome (PCOS) women was performed at IVFMD, My Duc Phu Nhuan Hospital, Ho Chi Minh City, Vietnam from November 2023 to January 2024. The study was approved by the Institutional Ethics Committee (22/23/DD-BVMD, dated October 12th, 2023) and conducted according to Good Clinical Practice and Declaration of Helsinki 2002 principles. All participants provided written informed consent. Participants/materials, setting, methods Women (18–37 years) diagnosed with PCOS undergoing CAPA-IVM were recruited. At collection, COCs from each woman were divided into two groups based on the oxygen tension used in the two steps of CAPA-IVM culture, low oxygen tension (5% O2, 6% CO2 at 37 °C) and air oxygen tension (20% O2, 6% CO2 at 37 °C). Embryos were cultured to blastocyst stage. Primary outcome was the oocyte maturation rate. Secondary outcomes were embryology outcomes. Main results and the role of chance A total of 416 COCs from fifteen eligible women were assigned to the low oxygen (207 COCs) and air oxygen tension (209 COCs) groups. Mean age and body max index were 29.0±2.5 years and 22.6±2.6, respectively. The maturation rate was significantly lower in the low oxygen group compared to the air oxygen group (54.1% vs. 66.5%, p = 0.01, respectively). The two-pronuclei fertilization rate per COC was significantly decreased in the low oxygen group compared to the air oxygen group (35.7% vs. 49.3%, p = 0.005, respectively). Rates of day-3 embryos, blastocyst formation rate, and good quality blastocyst rate were also lower but not significant in the low oxygen tension group as compared to the air oxygen tension group. Limitations, reasons for caution The study’s limitations include a relatively small sample size and a single ethnicity group. There was a lack of data on clinical outcomes after transferring embryos from the study. Wider implications of the findings Oocyte maturation rate and two-pronuclei fertilization rate were significantly lower when oxygen tension was reduced in the process of CAPA-IVM culture. Therefore, air oxygen tension should be considered as a standard for oocyte culture in the pre-maturation step of CAPA-IVM. Trial registration number NCT06087354

P-217 Keep calm and carry on: assessing the effect of below-benchmark vitrified/warmed donor oocyte survival rates in subsequent laboratory and clinical key performance indicators

Abstract Study question When we experience below benchmark donor oocyte survival rates, are the laboratory and clinical outcomes of the recipient cycle affected? Summary answer Donor-oocyte cryo-survival rates below the benchmark (95-100%) result in slightly lower laboratory KPIs, equivalent live birth rates (LBR) and lower cumulative LBR (CLBR) per cycle. What is known already The use of vitrified/warmed donor oocytes allows overcoming many logistic challenges, but it is hindered by the loss of oocytes due to degeneration after warming. The 2012 Vienna Consensus established the benchmark rate of oocyte survival at 95-100%, competency level at &amp;gt; 85%. Results of &amp;lt; 85% cryo-survival are considered below competency, &amp;lt;70% can be considered poor, and &amp;lt;50% very poor. Below-benchmark rates of survival may not only limit the number of donor oocytes for the cycle, but they can also translate into lower per-oocyte cycle KPIs if the lower survival correlates with lower performance of the surviving oocytes. Study design, size, duration We analyzed 12690 vitrified-warmed donor oocyte recipient cycles, encompassing a total 144793 vitrified/warmed donor oocytes, carried out in a network of European private IVF units from 2018-2022. Cycles with PGT-A and spermatozoa from testicular biopsy were excluded. The primary endpoint of the study was the blastocyst utilization rate per 2PN zygote. Secondary endpoints were fertilization rate, live birth rate after the first single blastocyst transfer (SET-LBR) of each cycle, and cumulative LBR (CLBR). Participants/materials, setting, methods In all cases, fertilization was carried out by ICSI, and embryos were cultured to the blastocyst stage at low oxygen tension. Blastocysts with good or fair quality (A, B &amp; C by ASEBIR Criteria) were considered usable (transferred + cryopreserved blastocyts / zygotes). Differences in proportions were analyzed using chi-square and the adjusted odds ratio (OR) was calculated using multivariable logistic regression. Main results and the role of chance Baseline donor and patient characteristics such as age, stimulation duration and dose, total donor oocytes per cycle, male factor, and fresh/frozen/donor spem were compared between groups and adjusted for when necessary. The mean number of warmed oocytes per cycle was 11.4±3.22 with a mean survival rate of 89.2%. More oocytes per cycle were consumed in the lower survival groups, yet the total oocytes available for ICSI was smaller in the below competency, poor and very poor survival groups. There were differences in the proportion of usable blastocysts per zygote amongst the survival rate groups (benchmark: 48.9%; competence: 47.0%, below-competence: 46.0%; poor: 43.6%; very-poor:43.6%, p &amp;lt; 0.001). Fertilization rates also differed between survival groups (benchmark: 76.9%; competence: 76.5%, below-competence: 75.6%; poor: 74.7%; very-poor:75.4%, p &amp;lt; 0.001) The adjusted odds ratio of live birth on the first SET of the cycle was not lower to the benchmark survival group in all the lower survival groups (Benchmark: 40.9%; Competence: OR:0.995; 95%CI:0.971-1.018; below-competence: OR:0.996; 95%CI:0.970-1.023; poor: OR:1.044; 95%CI:1.003-1.086, and very-poor: OR:1.069; 95%CI:0.976-1.170). The CLBR decreased in lower survival groups, with 80.8% for the benchmark survival group, 80.3% (p = 0.539) for competence, 76.2% (p &amp;lt; 0.001) for below-competence, 72.5% (p &amp;lt; 0.001) for poor, and 74.8% (p = 0.056) for very-poor. Limitations, reasons for caution These results are limited to a donor-oocyte population. Wider implications of the findings Lower oocyte-cryo-survival rates resulted in a lower total number of usable blastocysts obtained for the recipient, and consequently, lower CLBR. However, the competence of surviving oocytes is encouraging, with laboratory KPIs in very close range irrespectively of the cohort survival rates, and similar implantation potential of the obtained blastocysts. Trial registration number not applicable

Hypoxia Promotes the Stemness of Mesangiogenic Progenitor Cells and Prevents Osteogenic but not Angiogenic Differentiation

The stem cell niche in the bone marrow is a hypoxic environment, where the low oxygen tension preserves the pluripotency of stem cells. We have identified mesangiogenic progenitor cells (MPC) exhibiting angiogenic and mesenchymal differentiation capabilities in vitro. The effect of hypoxia on MPC has not been previously explored. In this study, MPCs were isolated from volunteers' bone marrow and cultured under both normoxic and hypoxic conditions (3% O2). MPCs maintained their characteristic morphology and surface marker expression (CD18 + CD31 + CD90-CD73-) under hypoxia. However, hypoxic conditions led to reduced MPC proliferation in primary cultures and hindered their differentiation into mesenchymal stem cells (MSCs) upon exposure to differentiative medium. First passage MSCs derived from MPC appeared unaffected by hypoxia, exhibiting no discernible differences in proliferative potential or cell cycle. However, hypoxia impeded the subsequent osteogenic differentiation of MSCs, as evidenced by decreased hydroxyapatite deposition. Conversely, hypoxia did not impact the angiogenic differentiation potential of MPCs, as demonstrated by spheroid-based assays revealing comparable angiogenic sprouting and tube-like formation capabilities under both hypoxic and normoxic conditions. These findings indicate that hypoxia preserves the stemness phenotype of MPCs, inhibits their differentiation into MSCs, and hampers their osteogenic maturation while leaving their angiogenic potential unaffected. Our study sheds light on the intricate effects of hypoxia on bone marrow-derived MPCs and their differentiation pathways.Graphical

Branched chain α-ketoacids aerobically activate HIF1α signaling in vascular cells.

Hypoxia-inducible factor 1α (HIF1α) is a master regulator of numerous biological processes under low oxygen tensions. Yet, the mechanisms and biological consequences of aerobic HIF1α activation by intrinsic factors, particularly in primary cells remain elusive. Here, we show that HIF1α signaling is activated in several human primary vascular cells under ambient oxygen tensions, and in vascular smooth muscle cells (VSMCs) of normal human lung tissue, which contributed to a relative resistance to further enhancement of glycolytic activity in hypoxia. Mechanistically, aerobic HIFα activation is mediated by paracrine secretion of three branched chain α-ketoacids (BCKAs), which suppress prolyl hydroxylase domain-containing protein 2 (PHD2) activity via direct inhibition and via lactate dehydrogenase A (LDHA)-mediated generation of L-2-hydroxyglutarate (L2HG). Metabolic dysfunction induced by BCKAs was observed in the lungs of rats with pulmonary arterial hypertension (PAH) and in pulmonary artery smooth muscle cells (PASMCs) from idiopathic PAH patients. BCKA supplementation stimulated glycolytic activity and promoted a phenotypic switch to the synthetic phenotype in PASMCs of normal and PAH subjects. In summary, we identify BCKAs as novel signaling metabolites that activate HIF1α signaling in normoxia and that the BCKA-HIF1α pathway modulates VSMC function and may be relevant to pulmonary vascular pathobiology.

Do middle-aged patients with onset of idiopathic scoliosis before the age of 10 years who have reduced pulmonary function have a risk for rapid decline – a comparative study

Back groundKnowledge concerning pulmonary function in adult patients with onset of idiopathic scoliosis before age 10 is sparse. A long-term follow-up (FU, mean 26 years, > 12 years after treatment) of pulmonary function (PF) in patients treated with brace or surgery due to idiopathic scoliosis with onset before the age of 10 was earlier performed. To evaluate whether a more severe reduction in pulmonary function leads to more rapid deterioration within a four-year period, this study was performed.MethodsTwenty patients with the most reduced pulmonary function and 19 out of those with normal PF found at the long-term FU were reexamined 4 years later to evaluate further changes in pulmonary function. Patients underwent spirometry and arterial blood gas analysis and answered pulmonary symptom questionnaires.Results70% of the reduced pulmonary function group had undergone surgery vs. 26% of the normal group. The mean age (47 vs. 43 years) at this FU and curve size (37° vs. 35°) at the 26-year FU were similar. The decline in forced vital capacity (FVC) % of predicted was similar in both groups over the four-year period, from 67 to 65% in the reduced PF group vs. 96 to 94% in the normal PF group. The total lung capacity (TLC) % of predicted did not change over time in either group. No patient reported worsening dyspnea symptoms. Only one patient in the reduced PF group showed low arterial oxygen tension, 8.4 kPa, not signifying respiratory insufficiency.ConclusionThe age-related decline in FVC and TLC % of predicted did not differ between those with reduced and those with normal pulmonary function at the 26-year follow-up. Thus, these data do not infer increased rate of decline in the most deteriorated patients.

Mass Spectrometric Analysis of Purine Intermediary Metabolism Indicates Cyanide Induces Purine Catabolism in Rabbits.

Purines are the building blocks of DNA/RNA, energy substrates, and cofactors. Purine metabolites, including ATP, GTP, NADH, and coenzyme A, are essential molecules in diverse biological processes such as energy metabolism, signal transduction, and enzyme activity. When purine levels increase, excess purines are either recycled to synthesize purine metabolites or catabolized to the end product uric acid. Purine catabolism increases during states of low oxygen tension (hypoxia and ischemia), but this metabolic pathway is incompletely understood in the context of histotoxic hypoxia (i.e., inhibition of oxygen utilization despite normal oxygen tension). In rabbits exposed to cyanide-a classical histotoxic hypoxia agent-we demonstrated significant increases in several concordant metabolites in the purine catabolic pathway (including plasma levels of uric acid, xanthosine, xanthine, hypoxanthine, and inosine) via mass spectrometry-based metabolite profiling. Pharmacological inhibition of the purine catabolic pathway with oxypurinol mitigated the deleterious effects of cyanide on skeletal muscle cytochrome c oxidase redox state, measured by non-invasive diffuse optical spectroscopy. Finally, plasma uric acid levels correlated strongly with those of lactic acid, an established clinical biomarker of cyanide exposure, in addition to a tissue biomarker of cyanide exposure (skeletal muscle cytochrome c oxidase redox state). Cumulatively, these findings not only shed light on the in vivo role(s) of cyanide but also have implications in the field of medical countermeasure (MCM) development.

Dynamics of transcription is affected by oxygen tension and developmental speed during invitro production of bovine embryos.

This study examines the impact of oxygen tension and embryo kinetics on gene transcription dynamics in pathways crucial for embryonic preimplantation development, including lipid metabolism, carbohydrate transport and metabolism, mitochondrial function, stress response, apoptosis and transcription regulation. Bovine embryos were generated invitro and allocated into two groups based on oxygen tension (20% or 5%) at 18 h post insemination (hpi). At 40 hpi, embryos were categorized into Fast (≥4 cells) or Slow (2 cells) groups, resulting in four experimental groups: FCL20, FCL5, SCL20 and SCL5. Embryo collection also occurred at 72 hpi (16-cell stage; groups FMO20, FMO5, SMO20 and SMO5) and at 168 hpi (expanded blastocyst (BL) stage; groups FBL20, FBL5, SBL20 and SBL5). Pools of three embryos per group were analysed in four replicates using inventoried TaqMan assays specific for Bos taurus, targeting 93 genes. Gene expression patterns were analysed using the K-means algorithm, revealing three main clusters: genes with low relative abundance at the cleavage (CL) and 16-cell morula (MO) stages but increased at the BL stage (cluster 1); genes with higher abundances at CL but decreasing at MO and BL (cluster 2); and genes with low levels at CL, higher levels at MO and decreased levels at BL (cluster 3). Within each cluster, genes related to epigenetic mechanisms, cell differentiation events and glucose metabolism were particularly influenced by differences in developmental kinetics and oxygen tension. Fast-developing embryos, particularly those cultured under low oxygen tension, exhibited transcript dynamics more closely resembling that reported invivo-produced embryos.

Unraveling the evolutionary marathon: improved mitochondrial bioenergetics in CMP-Neu5Ac hydroxylase gene deleted (Cmah−/−) mouse skeletal myofibers

Objective: Humans are unique among hominids in that they are endurance athletes. Inactivation of the CMP-Neu5Ac hydroxylase (CMAH) gene, which encodes a hydroxylase converting sialic acid Neu5Ac to Neu5Gc, is thought to contribute to this exceptional capacity for endurance running. Recently, our group demonstrated improved fatigue resistance and preserved intracellular O2, estimated by NAD(P)H levels in contracting mouse Cmah−/− flexor digitorum brevis (FDB) single fibers under low oxygen tension. Hypothesis: Effcient regulation of mitochondrial oxygen consumption contributes to improved skeletal myofiber fatigue resistance in Cmah−/− mice. Methods: The mitochondrial bioenergetic potential of permeabilized FDB and soleus fiber bundles from wild type (WT) and Cmah−/− mice was evaluated using a physiological creatine kinase clamp method and high-resolution respirometer. Experiments were conducted with pyruvate and malate with or without branched chain amino acids (BCAAs) as the substrates. Respiratory chain conductance and maximal respiration were measured. Results: FDB Cmah−/− fibers from male but not female mice revealed an increase conductance above WT fibers independent of substrate (male: genotype, p=0.006, substrate, ns; female: genotype, ns, substrate, ns). Maximal respiration was also increased only in male FDBs fibers and was even greater when BCAAs were included in the respiration media. (male: genotype, p=0.003, substrate, p=0.0007, interaction, p=0.002.; female: genotype, ns, substrate, ns). Soleus Cmah−/− fibers from male and female mice revealed an increase conductance above WT fiber bundles that was also greater in the presence of BCAAs but only for male mice (male: genotype, p=0.003, substrate, p=0.05.; female: genotype, p=0.009, substrate, ns). Maximal respiration was increased only in male Cmah−/− soleus fibers independent of substrate. (male: genotype, p=0.002, substrate, ns.; female: genotype, ns, substrate, ns). Summary: Fibers from both the FDB and soleus of male Cmah−/− mice have a greater capacity for mitochondrial respiration under a metabolically active state that is similar to myofibers stimulated to repeatedly contraction in a hypoxic environment. Conclusion: These data suggest that effcient regulation of mitochondrial respiration utilizing BCAAs as a substrate, particularly in males, could contribute to an elite endurance phenotype. This project was funded through the UC San Diego Academic Senate Grant. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Multicenter, phase 1 study of etavopivat (FT-4202) treatment for up to 12 weeks in patients with sickle cell disease

AbstractEtavopivat is an investigational, once daily, oral, selective erythrocyte pyruvate kinase (PKR) activator. A multicenter, randomized, placebo-controlled, double-blind, 3-part, phase 1 study was conducted to characterize the safety and clinical activity of etavopivat. Thirty-six patients with sickle cell disease (SCD) were enrolled into 4 cohorts: 1 single-dose, 2 multiple ascending doses, and 1 open-label (OL). In the OL cohort, 15 patients (median age 33.0 years [range, 17-55]) received 400 mg etavopivat once daily for 12 weeks; 14 patients completed treatment. Consistent with the mechanism of PKR activation, increases in adenosine triphosphate and decreases in 2,3-diphosphoglycerate were observed and sustained over 12 weeks’ treatment. This translated clinically to an increase in hemoglobin (Hb; mean maximal increase 1.6 g/dL [range, 0.8-2.8]), with >1 g/dL increase in 11 (73%) patients during treatment. In addition, the oxygen tension at which Hb is 50% saturated was reduced (P = .0007) with a concomitant shift in point of sickling (P = .0034) to lower oxygen tension in oxygen-gradient ektacytometry. Hemolysis markers (absolute reticulocyte count, indirect bilirubin, and lactate dehydrogenase) decreased from baseline, along with matrix metalloproteinase-9 and erythropoietin. In the OL cohort, adverse events (AEs) were mostly grade 1/2, consistent with underlying SCD; 5 patients had serious AEs. Vaso-occlusive pain episode was the most common treatment-emergent AE (n = 7) in the OL cohort. In this, to our knowledge, the first study of etavopivat in SCD, 400 mg once daily for 12 weeks was well tolerated, resulting in rapid and sustained increases in Hb, improved red blood cell physiology, and decreased hemolysis. This trial was registered at www.ClinicalTrials.gov as #NCT03815695.

Efficacy of mesenchymal stem cells cultured low oxygen tension ameliorates apoptotic inhibitors, viability, and differentiation of ovarian tissue: A study in a rat model with ovarian failure

Background In cases of ovarian failure due to malnutrition, stem cell therapy is ineffective due to the lack of viability and differentiation of transplanted cells, resulting in low adaptation and survival rates. This study aimed to investigate whether stem cells cultured under low oxygen (O2) tension improve the adaptability and viability of cells in rats with ovarian failure. Methods After four days of culturing mesenchymal stem cells (MSCs) in 21% oxygen (normoxia) as the T2 group and 1% oxygen (low O2 or hypoxia) as the T1 group, 200 million bone marrow-derived MSCs per rat were transplanted into female rats with ovarian failure (15 rats per treatment group). A total of 15 fertile and 15 infertile rats were categorized as the C+ and C− groups, respectively. Results The slight increase gradually in cells expressing HSP70, VEGF-1, and GDF-9 was reported in C+, T2, T1, and C− groups, respectively. Caspase-3 expression was reported to decrease gradually in C+, T2, T1, and C− groups. Meanwhile, Graafian follicle count was reported to increase gradually in C+, T2, T1, and C− groups, respectively. Conclusions Based on those parameters, MSCs cultured under low O2 tension were more effective than those cultured under normoxic conditions as a treatment for female rats with ovarian failure.