Hypoxia and Inflammation: Insights From High-Altitude Physiology

A narrative review of periodic breathing during sleep at high altitude: From acclimatizing lowlanders to adapted highlanders

Periodic breathing during sleep at high altitude is almost universal among sojourners. Here, in the context of acclimatization and adaptation, we provide a contemporary review on periodic breathing at high altitude, and explore whether this is an adaptive or maladaptive process. The mechanism(s), prevalence and role of periodic breathing in acclimatized lowlanders at high altitude are contrasted with the available data from adapted indigenous populations (e.g. Andean and Tibetan highlanders). It is concluded that (1) periodic breathing persists with acclimatization in lowlanders and the severity is proportional to sleeping altitude; (2) periodic breathing does not seem to coalesce with poor sleep quality such that, with acclimatization, there appears to be a lengthening of cycle length and minimal impact on the average sleeping oxygen saturation; and (3) high altitude adapted highlanders appear to demonstrate a blunting of periodic breathing, compared to lowlanders, comprising a feature that withstands the negative influences of chronic mountain sickness. These observations indicate that periodic breathing persists with high altitude acclimatization with no obvious negative consequences; however, periodic breathing is attenuated with high altitude adaptation and therefore potentially reflects an adaptive trait to this environment.

Exploring the Blood Biomarkers and Potential Therapeutic Agents for Human Acute Mountain Sickness Based on Transcriptomic Analysis, Inflammatory Infiltrates and Molecular Docking

A high-altitude, low-pressure hypoxic environment has severe effects on the health and work efficiency of its residents, and inadequate preventive measures and adaptive training may lead to the occurrence of AMS. Acute exposure to hypoxia conditions can have a less-favorable physiological effect on the human immune system. However, the regulation of the immune system in high-altitude environments is extremely complex and remains elusive. This study integrated system bioinformatics methods to screen for changes in immune cell subtypes and their associated targets. It also sought potential therapeutically effective natural compound candidates. The present study observed that monocytes, M1 macrophages and NK cells play a crucial role in the inflammatory response in AMS. IL15RA, CD5, TNFSF13B, IL21R, JAK2 and CXCR3 were identified as hub genes, and JAK2 was positively correlated with monocytes; TNFSF13B was positively correlated with NK cells. The natural compound monomers of jasminoidin and isoliquiritigenin exhibited good binding affinity with JAK2, while dicumarol and artemotil exhibited good binding affinity with TNFSF13B, and all are expected to become a potential therapeutic agents.

Evidence of Intraspecific Adaptive Variation in the American Pika (Ochotona princeps) on a Continental Scale Using a Target Enrichment and Mitochondrial Genome Skimming Approach

Montane landscapes present an array of abiotic challenges that drive adaptive evolution amongst organisms. These adaptations can promote habitat specialisation, which may heighten the risk of extirpation from environmental change. For example, higher metabolic rates in an endothermic species may contribute to heightened cold tolerance, whilst simultaneously limiting heat tolerance. Here, using the climate-sensitive American pika (Ochotona princeps), we test for evidence of intraspecific adaptive variation amongst environmental gradients across the Intermountain West of North America. We leveraged results from previous studies on pika adaptation to generate a custom nuclear target enrichment design to sequence several hundred candidate genes related to cold, hypoxia and dietary detoxification. We also applied a 'genome skimming' approach to sequence mitochondrial DNA. Using genotype-environment association tests, we identified rare genomic variants associated with elevation and temperature variation amongst populations. Amongst mitochondrial genes, we identified intraspecific variation in selective signals and significant changes to the amino acid property equilibrium constant, which may relate to electron transport chain efficiency. These results illustrate a complex dynamic of adaptive variation amongst O. princeps where lineages and populations have adapted to unique regional conditions. Some of the clearest signals of selection were in a genetic lineage that includes pikas of the Great Basin region, which is also where recent localised extirpations have taken place and highlights the risk of losing adaptive alleles during environmental change.

JAK2 Mutation Assessment in Thrombotic Events at Unusual Anatomical Sites: Insights from a High-Altitude Cohort

Introduction

Thrombosis stands as a significant contributor to both morbidity and mortality in individuals afflicted with myeloproliferative neoplasms. This retrospective study investigated the association between JAK2 mutations and venous thrombosis at unusual sites, and in young individuals with ischemic stroke, residing at high altitudes in the Aseer region, Saudi Arabia.

Patients and Methods

Data were collected from two high-altitude referral hospitals over three years (2020-2022). Records of all JAK2 mutation tests were reviewed. Those requested as part of evaluation of thrombosis events, without known myeloproliferative neoplasms (MPNs) were analysed.

Results

Among the 208 JAK2 tests, 40 (19.2%) were linked to thrombotic event evaluations. The cohort, with a median age of 41, included 17 (42.7%) males and 23 females, with 57.5% having completely normal complete blood counts (CBC). Thrombotic events were divided between splanchnic vein thrombosis (36.6%) and cerebral thrombosis (34.1%), while the remaining cases involved unprovoked deep vein thromboses/pulmonary embolisms and portal vein thrombosis. Only 2 (5%) participants tested positive for JAK2 mutations: a 17-year-old male diagnosed concurrently with polycythemia vera after renal vein thrombosis and a 31-year-old woman with hepatic vein thrombosis and a normal CBC.

Conclusion

This study reveals that JAK2 mutations are infrequently found in high-altitude patients with unprovoked DVT, PE, or atypical thrombosis. While JAK2 testing is notably relevant for splanchnic vein thrombosis, its routine use for other thrombotic events, particularly with normal CBC results, remains uncertain. Given the study's limitations, further prospective research with larger cohorts is needed to refine guidelines for JAK2 mutation testing in various thrombotic contexts.

Dietary patterns related to attention and physiological function in high-altitude migrants

High altitude exposure negatively affects human attentional function. However, no studies have explored the regulation of attentional and physiological functions from a dietary perspective. A total of 116 Han Chinese students from Tibet University who were born and raised in a plain area and had been living in Tibet for > 2 years were recruited. All participants were male migrants. A food frequency questionnaire, complete blood count, and attention network test were performed on the participants. Pearson's correlation was applied to assess the reliability and validity of the food frequency questionnaire. Principal component analysis was utilized to extract dietary patterns. A linear mixed model was employed to account for individual differences. The results showed that the five main dietary patterns were coarse grain, alcohol, meat, protein, and snacking dietary patterns. Furthermore, individuals who adhered to the coarse grain dietary pattern and had high mean corpuscular hemoglobin showed better attentional performance. Individuals with high alcohol consumption and systemic immune-inflammation index levels exhibited worse attentional performance. These findings imply that high-altitude migrants should include more coarse grains in their daily diet and avoid excessive alcohol consumption to improve attention.

Hypoxia-Induced Inflammation in In Vitro Model of Human Blood-Brain Barrier: Modulatory Effects of the Olfactory Ensheathing Cell-Conditioned Medium

Hypoxia compromises the integrity of the blood-brain barrier (BBB) and increases its permeability, thereby inducing inflammation. Olfactory ensheathing cells (OECs) garnered considerable interest due to their neuroregenerative and anti-inflammatory properties. Here, we aimed to investigate the potential modulatory effects of OEC-conditioned medium (OEC-CM) on the response of human brain microvascular endothelial cells (HBMECs), constituting the BBB, when exposed to hypoxia. HBMECs were utilized to establish the in vitro BBB model. OECs were isolated from mouse olfactory bulbs, and OEC-CM was collected after 48 h of culture. The effect of OEC-CM treatment on the HBMEC viability was evaluated under both normoxic and hypoxic conditions at 6 h, 24 h, and 30 h. Western blot and immunostaining techniques were employed to assess NF-κB/phospho-NF-κB expression. HIF-1α, VEGF-A, and cPLA2 mRNA expression levels were quantified using digital PCR. ELISA assays were performed to measure PGE2, VEGF-A, IL-8 secretion, and cPLA2 specific activity. The in vitro formation of HBMEC capillary-like structures was examined using a three-dimensional matrix system. OEC-CM attenuated pro-inflammatory responses and mitigated the HIF-1α/VEGFA signaling pathway activation in HBMECs under hypoxic condition. Hypoxia-induced damage of the BBB can be mitigated by novel therapeutic strategies harnessing OEC potential.

Acute hypoxic conditions preceding endotoxin administration result in an increased proinflammatory cytokine response in healthy men

Tissues often experience hypoxia at sites of inflammation due to malperfusion, massive immune cell recruitment, and increased oxygen consumption. Organisms adapt to these hypoxic conditions through the transcriptional activation of various genes. In fact, there is significant crosstalk between the transcriptional responses to hypoxia and inflammatory processes. This interaction, named inflammatory hypoxia, plays a crucial role in various diseases including malignancies, chronic inflammatory lung diseases, and sepsis. To further elucidate the crosstalk between hypoxia and inflammation in vivo and assess its potential for innovative therapies, our study aimed at investigating the impact of acute hypoxic conditions on inflammation-induced immune responses. To this end, we exposed healthy human subjects to hypoxia either before (hypoxia priming) or after a single intravenous (i.v.) injection of 0.4 ng/kg LPS. Our data show that hypoxia exposure prior to LPS injection (hypoxia priming) amplified the proinflammatory response. This was reflected by an increase in body temperature, plasma noradrenaline levels, and the production of proinflammatory cytokines (i.e., IL-6 and TNF-α), compared with LPS control conditions. These effects were not observed when participants were exposed to hypoxia after LPS administration, demonstrating that the interaction between hypoxia and inflammation highly depends on the timing of both stimuli. Our findings suggest that acute hypoxia (i.e., hypoxia priming) modulates transient inflammation, leading to an enhanced proinflammatory response in healthy human subjects. This highlights the need for further investigations to understand the pathology of various hypoxia-inducible factor (HIF)-associated inflammatory diseases and to develop suitable, innovative therapies.NEW & NOTEWORTHY To our knowledge, this is the first in vivo study investigating the effects of hypoxia preceding (hypoxia priming) or following LPS administration on the endotoxin-induced inflammatory response in healthy human subjects. The data show that hypoxia priming amplified the proinflammatory response, reflected by an increased body temperature, increased plasma noradrenaline levels, and higher production of proinflammatory cytokines (i.e., IL-6 and TNF-α) compared with LPS control conditions.

Effects of 12 Weeks of Combined Exercise Training in Normobaric Hypoxia on Arterial Stiffness, Inflammatory Biomarkers, and Red Blood Cell Hemorheological Function in Obese Older Women

BACKGROUND/OBJECTIVES

The present study examined the effect of 12-week combined exercise training in normobaric hypoxia on arterial stiffness, inflammatory biomarkers, and red blood cell (RBC) hemorheological function in 24 obese older women (mean age: 67.96 ± 0.96 years).

METHODS

Subjects were randomly divided into two groups (normoxia (NMX; n = 12) and hypoxia (HPX; n = 12)). Both groups performed aerobic and resistance exercise training programs three times per week for 12 weeks, and the HPX group performed exercise programs in hypoxic environment chambers during the intervention period. Body composition was estimated using bioelectrical impedance analysis equipment. Arterial stiffness was measured using an automatic waveform analyzer. Biomarkers of inflammation and oxygen transport (tumor necrosis factor alpha, interleukin 6 (IL-6), erythropoietin (EPO), and vascular endothelial growth factor (VEGF)), and RBC hemorheological parameters (RBC deformability and aggregation) were analyzed.

RESULTS

All variables showed significantly more beneficial changes in the HPX group than in the NMX group during the intervention. The combined exercise training in normobaric hypoxia significantly reduced blood pressure (systolic blood pressure: p < 0.001, diastolic blood pressure: p < 0.001, mean arterial pressure: p < 0.001, pulse pressure: p < 0.05) and brachial-ankle pulse wave velocity (p < 0.001). IL-6 was significantly lower in the HPX group than in the NMX group post-test (p < 0.001). Also, EPO (p < 0.01) and VEGF (p < 0.01) were significantly higher in the HPX group than in the NMX group post-test. Both groups showed significantly improved RBC deformability (RBC EI_3Pa) (p < 0.001) and aggregation (RBC AI_3Pa) (p < 0.001).

CONCLUSIONS

The present study suggests that combined exercise training in normobaric hypoxia can improve inflammatory biomarkers and RBC hemorheological parameters in obese older women and may help prevent cardiovascular diseases.

p53 lysine-lactylated modification contributes to lipopolysaccharide-induced proinflammatory activation in BV2 cell under hypoxic conditions

p53 has diversity functions in regulation of transcription, cell proliferation, cancer metastasis, etc. Recent studies have shown that p53 and nuclear factor-κB (NF-κB) co-regulate proinflammatory responses in macrophages. However, the role of p53 lysine lactylation (p53Kla) in mediating proinflammatory phenotypes in microglia under hypoxic conditions remains unclear. In the current study, we investigated the proinflammatory activation exacerbated by hypoxia and the levels of p53Kla in microglial cells. BV2 cells, an immortalized mouse microglia cell line, were divided into control, lipopolysaccharide (LPS)-induced, hypoxia (Hy), and LPS-Hy groups. The protein expression levels of p53 and p53Kla and the activation of microglia were compared among the four groups. Sodium oxamate and mutant p53 plasmids were transfected into BV2 cells to detect the effect of p53Kla on microglial proinflammatory activation. LPS-Hy stimulation significantly upregulated p53Kla levels in both the nucleus and the cytoplasm of BV2 cells. In contrast, the p53 protein levels were downregulated. LPS-Hy stimulation upregulated phosphorylated p65 protein levels in nuclear and activated the NF-κB pathway in BV2 cells, resulting in increased expression of pro-inflammatory cytokines (iNOS, IL6, IL1β, TNFα), enhanced cell viability, and concomitantly, increased cytotoxicity. In conclusion, p53 lysine-lactylated modification contributes to LPS-induced proinflammatory activation in BV2 cells under hypoxia through NF-κB pathway and inhibition of lactate production may alleviate neuroinflammatory injury.

The role of oxidative stress and neuroinflammatory mediators in the pathogenesis of high-altitude cerebral edema in rats

High-altitude environments present extreme conditions characterized by low barometric pressure and oxygen deficiency, which can disrupt brain functioning and cause edema formation. The objective of the present study is to investigate several biomolecule expressions and their role in the development of High Altitude Cerebral Edema in a rat model. Specifically, the study focuses on analyzing the changes in total arginase, nitric oxide, and lipid peroxidation (MDA) levels in the brain following acute hypobaric hypoxic exposure (7620 m, SO2=8.1 %, for 24 h) along with the histopathological assessment. The histological examination revealed increased TNF-α activity, and an elevated number of mast cells in the brain, mainly in the hippocampus and cerebral cortex. The research findings demonstrated that acute hypobaric hypoxic causes increased levels of apoptotic cells, shrinkage, and swelling of neurons, accompanied by the formation of protein aggregation in the brain parenchyma. Additionally, the level of nitric oxide and MDA was found to have increased (p<0.0001), however, the level of arginase decreased indicating active lipid peroxidation and redox imbalance in the brain. This study provides insights into the pathogenesis of HACE by evaluating some biomolecules that play a pivotal role in the inflammatory response and the redox landscape in the brain. The findings could have significant implications for understanding the neuronal dysfunction and the pathological mechanisms underlying HACE development.

Exposure to normobaric hypoxia shapes the acute inflammatory response in human whole blood cells in vivo

Cells of the immune defence, especially leukocytes, often have to perform their function in tissue areas that are characterized by oxygen deficiency, so-called hypoxia. Physiological hypoxia significantly affects leukocyte function and controls the innate and adaptive immune response mainly through transcriptional gene regulation via the hypoxia-inducible factors (HIFs). Multiple pathogens including components of bacteria, such as lipopolysaccharides (LPS) trigger the activation of leukocytes. HIF pathway activation enables immune cells to adapt to both hypoxic environments in physiological and inflammatory settings and modulates immune cell responses through metabolism changes and crosstalk with other immune-relevant signalling pathways. To study the mutual influence of both processes in vivo, we used a human endotoxemia model, challenging participants with an intravenous LPS injection post or prior to a 4-h stay in a hypoxic chamber with normobaric hypoxia of 10.5% oxygen. We analysed changes in gene expression in whole blood cells and determined inflammatory markers to unveil the crosstalk between both processes. Our investigations showed differentially altered gene expression patterns of HIF and target genes upon in vivo treatment with LPS and hypoxia. Further, we found evidence for effects of hypoxic priming upon inflammation in combination with immunomodulatory effects in whole blood cells in vivo. Our work elucidates the complex interplay of hypoxic and inflammatory HIF regulation in human immune cells and offers new perspectives for further clinical research.

Network pharmacology and in vivo experimental studies reveal the protective effects of 6-hydroxygenistein against hypobaric hypoxia-induced brain injury

Hypobaric hypoxia-induced brain injury (HHBI) is a progressive neurodegenerative disease that has still not been effectively treated. There are several different mechanisms involved in HHBI. Among them, oxidative stress and inflammation response predominate. 6-hydroxygenistein (4',5,6,7-tetrahydroxyisoflavone, 6-OHG) is a hydroxylated derivative of genistein with excellent antioxidant activity, however, the protective effects and underlying mechanisms against HHBI have not been clarified. In the present study, we aimed to explore the mechanisms of action of 6-OHG on HHBI using network pharmacology and experimental validation. Network pharmacology analysis revealed 186 candidate targets through the intersection of the targets of 6-OHG and related genes in HHBI, which were mainly enriched in oxidative stress and inflammation response. Moreover, key targets of 6-OHG against HHBI, namely Nrf2 and NF-κB, were screened and found to be closely related to oxidative stress and inflammation response. Subsequent in vivo experiments revealed that 6-OHG treatment attenuated oxidative stress and inflammation response, prevented energy disorder and apoptosis as well as maintained the BBB integrity in HHBI mice. In addition, 6-OHG administration up-regulated the expressions of Nrf2 and HO-1 and down-regulated the expressions of NF-κB and NLRP3, thereby inhibiting oxidative stress and inflammation response. Hence, the present study demonstrates that 6-OHG protects against HHBI by stimulating the Nrf2/HO-1 signaling pathway and suppressing the NF-κB/NLRP3 signaling pathway.

The cytoprotective effect of Gymnema inodorum leaf extract against hypoxia-induced cardiomyocytes injury

Ischemic heart disease stands out as a major global contributor to mortality, with the initiation of hypoxia, marked by reduced oxygen availability, disrupting the balance of reactive oxygen species (ROS), leading to cellular injury. Exploring antioxidants derived from medicinal plants is becoming more interesting as a potential alternative treatment, especially for mitigating myocardial injury. Thus, this study aimed to assess the cytoprotective efficacy of Gymnema inodorum leaf extract (GIE) in a rat cardiac myoblast, H9c2, subjected to an in vitro hypoxia. The cell viability, intracellular ROS production and the expression of inflammatory cytokines were quantified, and hypoxia-induced cell morphology changes were observed using confocal fluorescence microscopy. The results showed that GIE notably enhanced cell viability, preserving membrane integrity, when compared with the hypoxic group. Remarkably, GIE significantly reduced hypoxia-induced intracellular ROS production, attributable to its inherent antioxidant properties. Furthermore, GIE significantly reduced interleukin (IL)-1β, interleukin (IL)-6 mRNA expression level and tended to reduce tumor necrosis factor-α (TNF-α) mRNA expression. In conclusion, these findings underscore the potential of GIE in mitigating hypoxia-induced myocardial injury, highlighting its robust antioxidant and anti-inflammatory attributes.

Fetal chronic hypoxia does not affect urinary presepsin levels in newborns at birth

OBJECTIVES

Early sepsis detection and diagnosis still constitutes an open issue since the accuracy of standard-of care parameters is biased by a series of perinatal factors including hypoxia. Therefore, we aimed at investigating the effect of fetal chronic hypoxia insult on urine levels of a promising new marker of sepsis, namely presepsin (P-SEP).

METHODS

We conducted a prospective case-control study in 22 cases of early-intrauterine growth restriction (E-IUGR) compared with 22 small-for-gestational-age (SGA) newborns and 66 healthy controls. P-SEP urine samples were collected over the first 72 h from birth. Blood culture and C-reactive protein (CRP) blood levels were measured in E-IUGR and SGA infants. Perinatal standard monitoring parameters and main outcomes were also recorded.

RESULTS

No significant urinary P-SEP differences (p>0.05, for all) were observed among studied groups. Moreover, no significant correlations (p>0.05, for both) between urinary P-SEP and blood CRP levels in both E-IUGR and SGA groups (R=0.08; R=0.07, respectively) were observed.

CONCLUSIONS

The present results showing the lack of influence of fetal chronic hypoxia on urinary P-SEP levels offer additional data to hypothesize the possible use of urinary P-SEP measurement in neonates in daily clinical practice. Further multicenter prospective data are needed, including infants with early-onset sepsis.

Analysis of Ferritin, Hepcidin, Zinc, C-Reactive Protein and IL-6 Levels in COVID-19 in Patients Living at Different Altitudes in Peru

BACKGROUND

Despite great scientific efforts, understanding the role of COVID-19 clinical biomarkers remains a challenge.

METHODS

A cross-sectional descriptive study in two Peruvian cities at different altitudes for comparison: Lima and Huaraz. In each place, three groups were formed, made up of 25 patients with COVID-19 in the ICU, 25 hospitalized patients with COVID-19 who did not require the ICU, and 25 healthy subjects as a control group. Five biomarkers were measured: IL-6, hepcidin, ferritin, C-reactive protein, and zinc using ELISA assays.

RESULTS

Ferritin, C-reactive protein, and IL-6 levels were significantly higher in the ICU and non-ICU groups at both study sites. In the case of hepcidin, the levels were significantly higher in the ICU group at both study sites compared to the non-ICU group. Among the groups within each study site, the highest altitude area presented statistically significant differences between its groups in all the markers evaluated. In the lower altitude area, differences were only observed between the groups for the zinc biomarker.

CONCLUSION

COVID-19 patients residing at high altitudes tend to have higher levels of zinc and IL-6 in all groups studied compared to their lower altitude counterparts.

Histone deacetylase Sir2 promotes the systemic Candida albicans infection by facilitating its immune escape via remodeling the cell wall and maintaining the metabolic activity

Histone deacetylation affects Candida albicans (C. albicans) pathogenicity by modulating virulence factor expression and DNA damage. The histone deacetylase Sir2 is associated with C. albicans plasticity and maintains genome stability to help C. albicans adapt to various environmental niches. However, whether Sir2-mediated chromatin modification affects C. albicans virulence is unclear. The purpose of our study was to investigate the effect of Sir2 on C. albicans pathogenicity and regulation. Here, we report that Sir2 is required for C. albicans pathogenicity, as its deletion affects the survival rate, fungal burden in different organs and the extent of tissue damage in a mouse model of disseminated candidiasis. We evaluated the impact of Sir2 on C. albicans virulence factors and revealed that the Sir2 null mutant had an impaired ability to adhere to host cells and was more easily recognized by the innate immune system. Comprehensive analysis revealed that the disruption of C. albicans adhesion was due to a decrease in cell surface hydrophobicity rather than the differential expression of adhesion genes on the cell wall. In addition, Sir2 affects the distribution and exposure of mannan and β-glucan on the cell wall, indicating that Sir2 plays a role in preventing the immune system from recognizing C. albicans. Interestingly, our results also indicated that Sir2 helps C. albicans maintain metabolic activity under hypoxic conditions, suggesting that Sir2 contributes to C. albicans colonization at hypoxic sites. In conclusion, our findings provide detailed insights into antifungal targets and a useful foundation for the development of antifungal drugs.

IMPORTANCE

Candida albicans (C. albicans) is the most common opportunistic fungal pathogen and can cause various superficial infections and even life-threatening systemic infections. To successfully propagate infection, this organism relies on the ability to express virulence-associated factors and escape host immunity. In this study, we demonstrated that the histone deacetylase Sir2 helps C. albicans adhere to host cells and escape host immunity by mediating cell wall remodeling; as a result, C. albicans successfully colonized and invaded the host in vivo. In addition, we found that Sir2 contributes to carbon utilization under hypoxic conditions, suggesting that Sir2 is important for C. albicans survival and the establishment of infection in hypoxic environments. In summary, we investigated the role of Sir2 in regulating C. albicans pathogenicity in detail; these findings provide a potential target for the development of antifungal drugs.

16α-OHE1 alleviates hypoxia-induced inflammation and myocardial damage via the activation of β2-Adrenergic receptor

OBJECTIVE

Myocardial injuries resulting from hypoxia are a significant concern, and this study aimed to explore potential protective strategies against such damage. Specifically, we sought to investigate the cardioprotective effects of 16α-hydroxyestrone (16α-OHE1).

METHODS

Male Sprague‒Dawley (SD) rats were subjected to hypoxic conditions simulating high-altitude exposure at 6000 m in a low-pressure chamber for 7 days. Before and during hypoxic exposure, estradiol (E2) and various doses of 16α-OHE1 were administered for 14 days. Heart weight/body weight (HW/BW), myocardial structure, Myocardial injury indicators and inflammatory infiltration in rats were measured. H9C2 cells cultured under 5% O2 conditions received E2 and varying doses of 16α-OHE1; Cell viability, apoptosis, inflammatory infiltration, and Myocardial injury indicators were determined. Expression levels of β2AR were determined in rat hearts and H9C2 cells. The β2AR inhibitor, ICI 118,551, was employed to investigate β2AR's role in 16α-OHE1's cardioprotective effects.

RESULTS

Hypoxia led to substantial myocardial damage, evident in increased heart HW, CK-MB, cTnT, ANP, BNP, structural myocardial changes, inflammatory infiltration, and apoptosis. Pre-treatment with E2 and 16α-OHE1 significantly mitigated these adverse changes. Importantly, the protective effects of E2 and 16α-OHE1 were associated with the upregulation of β2AR expression in both rat hearts and H9C2 cells. However, inhibition of β2AR by ICI 118,551 in H9C2 cells nullified the protective effect of 16α-OHE1 on myocardium.

CONCLUSION

Our findings suggest that 16α-OHE1 can effectively reduce hypoxia-induced myocardial injury in rats through β2ARs, indicating a promising avenue for cardioprotection.

Intermittent Versus Sustained Hypoxemia from Sleep-disordered Breathing: Outcomes in Patients with Chronic Lung Disease and High Altitude

In a variety of physiologic and pathologic states, people may experience both chronic sustained hypoxemia and intermittent hypoxemia ("combined" or "overlap" hypoxemia). In general, hypoxemia in such instances predicts a variety of maladaptive outcomes, including excess cardiovascular disease or mortality. However, hypoxemia may be one of the myriad phenotypic effects in such states, making it difficult to ascertain whether adverse outcomes are primarily driven by hypoxemia, and if so, whether these effects are due to intermittent versus sustained hypoxemia.

Low- and moderate-intensity aerobic exercise improves the physiological acclimatization of lowlanders on the Tibetan plateau

This study investigates whether exercise as a strategy for improving physical fitness at sea level also offers comparable benefits in the unique context of high altitudes (HA), considering the physiological challenges of hypoxic conditions. Overall, 121 lowlanders who had lived on the Tibetan Plateau for >2 years and were still living at HA during the measurements were randomly classified into four groups. Each individual of the low-intensity (LI), moderate-intensity (MI), and high-intensity (HI) groups performed 20 sessions of aerobic exercise at HA (3680 m) over 4 weeks, while the control group (CG) did not undergo any intervention. Physiological responses before and after the intervention were observed. The LI and MI groups experienced significant improvement in cardiopulmonary fitness (0.27 and 0.35 L/min increases in peak oxygen uptake [V ˙ $\dot{\mathrm{V}}$ O2peak], both p < 0.05) after exercise intervention, while the hematocrit (HCT) remained unchanged (p > 0.05). However, HI exercise was less efficient for cardiopulmonary fitness of lowlanders (0.02 L/min decrease inV ˙ $\dot{\mathrm{V}}$ O2peak, p > 0.05), whereas both the HCT (1.74 %, p < 0.001) and glomerular filtration rate (18.41 mL/min, p < 0.001) increased with HI intervention. Therefore, LI and MI aerobic exercise, rather than HI, can help lowlanders in Tibet become more acclimated to the HA by increasing cardiopulmonary function and counteracting erythrocytosis.

Association of Polymorphism with Periodontitis and Salivary Levels of Hypoxia-Inducible Factor-1α

OBJECTIVE

 This investigation aims to investigate the association between HIF-1α genetic polymorphism and periodontitis and examine and contrast the levels of HIF-1α present in the saliva of subjects afflicted with periodontitis and in the control group. Additionally, this study aims to establish diagnostic proficiency of this biomarker in distinguishing between periodontal health and disease.

MATERIALS AND METHODS

 This study entailed the collection of venous blood samples and unstimulated saliva samples from a total of 160 participants, encompassing 80 individuals diagnosed with periodontitis and 80 periodontitis-free individuals. The periodontal parameters were evaluated, involving the measurement of clinical attachment loss, the probing pocket depth, and the bleeding on probing percentage. Subsequently, genetic analysis of HIF-1α using polymerase chain reaction (PCR) technique, DNA sequencing, and enzyme-linked immunosorbent assays was conducted.

RESULTS

 The genetic analysis of 352 bp of the HIF-1α gene revealed the presence of 66 single-nucleotide polymorphisms (SNPs) in control samples, whereas 78 SNPs were found in periodontitis sample. The nucleotide A was replaced with a C nucleotide at position 207 of the amplified PCR fragments. The homozygous AA pattern was predominant in the control group, with significant differences between the two groups. In contrast, the homozygous CC pattern was more dominant in the periodontitis group, with significant differences between the two groups. The analysis of Hardy-Weinberg equilibrium for the comparison between the observed and the expected genotypes showed significant differences between the observed and the expected values in the control and periodontitis groups, as well as the total sample. The highest mean values of the measured periodontal parameters were found in the periodontitis group (clinical attachment loss = 4.759, probing pocket depth = 4.050, and bleeding on probing = 30.950) with statistically significant differences between the groups. The periodontitis group showed significantly higher salivary HIF-1α levels compared to control group (p < 0.001). Besides, HIF-1α is a good biomarker in distinguishing between periodontal health and periodontitis.

CONCLUSION

 rs1951795 SNP of HIF-1α has no significant impact on the progression of periodontitis and the salivary level HIF-1α. Periodontitis results in a notable elevation in HIF-1α salivary levels, with an outstanding diagnostic ability to distinguish between periodontitis and periodontal health.

Live Microscopy of Multicellular Spheroids with the Multimodal Near-Infrared Nanoparticles Reveals Differences in Oxygenation Gradients

Assessment of hypoxia, nutrients, metabolite gradients, and other hallmarks of the tumor microenvironment within 3D multicellular spheroid and organoid models represents a challenging analytical task. Here, we report red/near-infrared (NIR) emitting cell staining with O2-sensitive nanoparticles, which enable measurements of spheroid oxygenation on a conventional fluorescence microscope. Nanosensor probes, termed "MMIR" (multimodal infrared), incorporate an NIR O2-sensitive metalloporphyrin (PtTPTBPF) and deep red aza-BODIPY reference dyes within a biocompatible polymer shell, allowing for oxygen gradient quantification via fluorescence ratio and phosphorescence lifetime readouts. We optimized staining techniques and evaluated the nanosensor probe characteristics and cytotoxicity. Subsequently, we applied nanosensors to the live spheroid models based on HCT116, DPSCs, and SKOV3 cells, at rest, and treated with drugs affecting cell respiration. We found that the growth medium viscosity, spheroid size, and formation method influenced spheroid oxygenation. Some spheroids produced from HCT116 and dental pulp stem cells exhibited "inverted" oxygenation gradients, with higher core oxygen levels than the periphery. This contrasted with the frequently encountered "normal" gradient of hypoxia toward the core caused by diffusion. Further microscopy analysis of spheroids with an "inverted" gradient demonstrated metabolic stratification of cells within spheroids: thus, autofluorescence FLIM of NAD(P)H indicated the formation of a glycolytic core and localization of OxPhos-active cells at the periphery. Collectively, we demonstrate a strong potential of NIR-emitting ratiometric nanosensors for advanced microscopy studies targeting live and quantitative real-time monitoring of cell metabolism and hypoxia in complex 3D tissue models.

Ultrastructural and immunohistochemical evaluation of hyperplastic soft tissues surrounding dental implants in fibular jaws

In reconstructive surgery, complications post-fibula free flap (FFF) reconstruction, notably peri-implant hyperplasia, are significant yet understudied. This study analyzed peri-implant hyperplastic tissue surrounding FFF, alongside peri-implantitis and foreign body granulation (FBG) tissues from patients treated at the Department of Oral and Maxillofacial Surgery, Seoul National University Dental Hospital. Using light microscopy, pseudoepitheliomatous hyperplasia, anucleate and pyknotic prickle cells, and excessive collagen deposition were observed in FFF hyperplastic tissue. Ultrastructural analyses revealed abnormal structures, including hemidesmosome dilation, bacterial invasion, and endoplasmic reticulum (ER) swelling. In immunohistochemical analysis, unfolded protein-response markers ATF6, PERK, XBP1, inflammatory marker NFκB, necroptosis marker MLKL, apoptosis marker GADD153, autophagy marker LC3, epithelial-mesenchymal transition, and angiogenesis markers were expressed variably in hyperplastic tissue surrounding FFF implants, peri-implantitis, and FBG tissues. NFκB expression was higher in peri-implantitis and FBG tissues compared to hyperplastic tissue surrounding FFF implants. PERK expression exceeded XBP1 significantly in FFF hyperplastic tissue, while expression levels of PERK, XBP1, and ATF6 were not significantly different in peri-implantitis and FBG tissues. These findings provide valuable insights into the interconnected roles of ER stress, necroptosis, apoptosis, and angiogenesis in the pathogenesis of oral pathologies, offering a foundation for innovative strategies in dental implant rehabilitation management and prevention.

Interleukin 6 at menstruation promotes the proliferation and self-renewal of endometrial mesenchymal stromal/stem cells through the WNT/β-catenin signaling pathway

Background

At menstruation, the functional layer of the human endometrium sheds off due to the trigger of the release of inflammatory factors, including interleukin 6 (IL-6), as a result of a sharp decline in progesterone levels, leading to tissue breakdown and bleeding. The endometrial mesenchymal stem-like cells (CD140b+CD146+ eMSC) located in the basalis are responsible for the cyclical regeneration of the endometrium after menstruation. Endometrial cells from the menstruation phase have been proven to secrete a higher amount of IL-6 and further enhance the self-renewal and clonogenic activity of eMSC. However, the IL-6-responsive mechanism remains unknown. Thus, we hypothesized that IL-6 secreted from niche cells during menstruation regulates the proliferation and self-renewal of eMSC through the WNT/β-catenin signaling pathway.

Methods

In this study, the content of IL-6 across the menstrual phases was first evaluated. Coexpression of stem cell markers (CD140b and CD146) with interleukin 6 receptor (IL-6R) was confirmed by immunofluorescent staining. In vitro functional assays were conducted to investigate the effect of IL-6 on the cell activities of eMSC, and the therapeutic role of these IL-6- and WNT5A-pretreated eMSC on the repair of injured endometrium was observed using an established mouse model.

Results

The endometrial cells secrete a high amount of IL-6 under hypoxic conditions, which mimic the physiological microenvironment in the menstruation phase. Also, the expression of IL-6 receptors was confirmed in our eMSC, indicating their capacity to respond to IL-6 in the microenvironment. Exogenous IL-6 can significantly enhance the self-renewal, proliferation, and migrating capacity of eMSC. Activation of the WNT/β-catenin signaling pathway was observed upon IL-6 treatment, while suppression of the WNT/β-catenin signaling impaired the stimulatory role of IL-6 on eMSC activities. IL-6- and WNT5A-pretreated eMSC showed better performance during the regeneration of the injured mouse endometrium.

Conclusion

We demonstrate that the high level of IL-6 produced by endometrial cells at menstruation can induce the stem cells in the human endometrium to proliferate and migrate through the activation of the WNT/β-catenin pathway. Treatment of eMSC with IL-6 and WNT5A might enhance their therapeutic potential in the regeneration of injured endometrium.

History of Diversification and Adaptation from North to South Revealed by Genomic Data: Guanacos from the Desert to Sub-Antarctica

The increased availability of quality genomic data has greatly improved the scope and resolution of our understanding of the recent evolutionary history of wild species adapted to extreme environments and their susceptibility to anthropogenic impacts. The guanaco (Lama guanicoe), the largest wild ungulate in South America, is a good example. The guanaco is well adapted to a wide range of habitats, including the Sechura Desert, the high Andes Mountains to the north, and the extreme temperatures and conditions of Navarino Island to the south. Guanacos also have a long history of overexploitation by humans. To assess the evolutionary impact of these challenging habitats on the genomic diversity, we analyzed 38 genomes (∼10 to 16×) throughout their extensive latitudinal distribution from the Sechura and Atacama Desert to southward into Tierra del Fuego Island. These included analyses of patterns of unique differentiation in the north and geographic region further south with admixture among L. g. cacsilensis and L. g. guanicoe. Our findings provide new insights on the divergence of the subspecies ∼800,000 yr BP and document two divergent demographic trajectories and to the initial expansion of guanaco into the more southern portions of the Atacama Desert. Patagonian guanacos have experienced contemporary reductions in effective population sizes, likely the consequence of anthropogenic impacts. The lowest levels of genetic diversity corresponded to their northern and western limits of distribution and some varying degrees of genetic differentiation. Adaptive genomic diversity was strongly linked with environmental variables and was linked with colonization toward the south followed by adaptation.

Immune consequences of exercise in hypoxia: A narrative review

Immune outcomes are key mediators of many health benefits of exercise and are determined by exercise type, dose (frequency/duration, intensity), and individual characteristics. Similarly, reduced availability of ambient oxygen (hypoxia) modulates immune functions depending on the hypoxic dose and the individual capacity to respond to hypoxia. How combined exercise and hypoxia (e.g., high-altitude training) sculpts immune responses is not well understood, although such combinations are becoming increasingly popular. Therefore, in this paper, we summarize the impact on immune responses of exercise and of hypoxia, both independently and together, with a focus on specialized cells in the innate and adaptive immune system. We review the regulation of the immune system by tissue oxygen levels and the overlapping and distinct immune responses related to exercise and hypoxia, then we discuss how they may be modulated by nutritional strategies. Mitochondrial, antioxidant, and anti-inflammatory mechanisms underlie many of the adaptations that can lead to improved cellular metabolism, resilience, and overall immune functions by regulating the survival, differentiation, activation, and migration of immune cells. This review shows that exercise and hypoxia can impair or complement/synergize with each other while regulating immune system functions. Appropriate acclimatization, training, and nutritional strategies can be used to avoid risks and tap into the synergistic potentials of the poorly studied immune consequences of exercising in a hypoxic state.

Huangqi Baihe Granules alleviate hypobaric hypoxia-induced acute lung injury in rats by suppressing oxidative stress and the TLR4/NF-κB/NLRP3 inflammatory pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Huangqi Baihe Granules (HQBHG) are a modified formulation based on the traditional recipe "Huangqi Baihe porridge" and the Dunhuang medical prescription "Cistanche Cistanche Soup." The Herbal medicine moistens the lungs and tones the kidneys in addition to replenishing Qi and feeding Yin, making it an ideal choice for enhancing adaptability to high-altitude hypoxic environments.

AIM OF THE STUDY

The purpose of this study was to examine a potential molecular mechanism for the treatment and prevention of hypoxic acute lung injury (ALI) in rats using Huangqi Baihe Granules.

MATERIALS AND METHODS

The HCP-III laboratory animal low-pressure simulation chamber was utilized to simulate high-altitude environmental exposure and establish an ALI model in rats. The severity of lung damage was evaluated using a battery of tests that included spirometry, a wet/dry lung ratio, H&E staining, and transmission electron microscopy. Using immunofluorescence, the amount of reactive oxygen species (ROS) in lung tissue was determined. Superoxide dismutase (SOD), glutathione (GSH), malondialdehyde (MDA), and myeloperoxidase (MPO) levels in lung tissue were determined using this kit. Serum levels of proinflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1 beta (IL-1 beta), and antiinflammatory cytokines like interleukin-10 (IL-10) were measured using an enzyme-linked immunosorbent assay kit. Gene expression changes in lung tissue were identified using transcriptomics, and the relative expression of proteins and mRNA involved in the toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB p65)/Nod-like receptor protein 3 (NLRP3) pathway were determined using western blotting and quantitative real-time PCR.

RESULTS

HQBHG was shown to enhance lung function considerably, decrease the wet/dry ratio of the lungs, attenuate lung tissue damage, suppress ROS and MDA formation, and increase SOD activity and GSH expression. The research also demonstrated that HQBHG inhibited the activation of the TLR4/NF-κB p65/NLPR3 signaling pathway in lung tissue, reducing the release of downstream pro-inflammatory cytokines.

CONCLUSIONS

HQBHG exhibits potential therapeutic effects against ALI induced by altitude hypoxia through suppressing oxidative stress and inflammatory response. This suggests it may be a novel drug for treating and preventing ALI.

NF-κB in the Radiation Response of A549 Non-Small Cell Lung Cancer Cells to X-rays and Carbon Ions under Hypoxia

Cellular hypoxia, detectable in up to 80% of non-small cell lung carcinoma (NSCLC) tumors, is a known cause of radioresistance. High linear energy transfer (LET) particle radiation might be effective in the treatment of hypoxic solid tumors, including NSCLC. Cellular hypoxia can activate nuclear factor κB (NF-κB), which can modulate radioresistance by influencing cancer cell survival. The effect of high-LET radiation on NF-κB activation in hypoxic NSCLC cells is unclear. Therefore, we compared the effect of low (X-rays)- and high (12C)-LET radiation on NF-κB responsive genes' upregulation, as well as its target cytokines' synthesis in normoxic and hypoxic A549 NSCLC cells. The cells were incubated under normoxia (20% O2) or hypoxia (1% O2) for 48 h, followed by irradiation with 8 Gy X-rays or 12C ions, maintaining the oxygen conditions until fixation or lysis. Regulation of NF-κB responsive genes was evaluated by mRNA sequencing. Secretion of NF-κB target cytokines, IL-6 and IL-8, was quantified by ELISA. A greater fold change increase in expression of NF-κB target genes in A549 cells following exposure to 12C ions compared to X-rays was observed, regardless of oxygenation status. These genes regulate cell migration, cell cycle, and cell survival. A greater number of NF-κB target genes was activated under hypoxia, regardless of irradiation status. These genes regulate cell migration, survival, proliferation, and inflammation. X-ray exposure under hypoxia additionally upregulated NF-κB target genes modulating immunosurveillance and epithelial-mesenchymal transition (EMT). Increased IL-6 and IL-8 secretion under hypoxia confirmed NF-κB-mediated expression of pro-inflammatory genes. Therefore, radiotherapy, particularly with X-rays, may increase tumor invasiveness in surviving hypoxic A549 cells.

Mechanism of hypoxia-induced damage to the mechanical property in human erythrocytes-band 3 phosphorylation and sulfhydryl oxidation of membrane proteins

Introduction: The integrity of the erythrocyte membrane cytoskeletal network controls the morphology, specific surface area, material exchange, and state of erythrocytes in the blood circulation. The antioxidant properties of resveratrol have been reported, but studies on the effect of resveratrol on the hypoxia-induced mechanical properties of erythrocytes are rare. Methods: In this study, the effects of different concentrations of resveratrol on the protection of red blood cell mor-phology and changes in intracellular redox levels were examined to select an appropriate concentration for further study. The Young's modulus and surface roughness of the red blood cells and blood viscosity were measured via atomic force microsco-py and a blood rheometer, respectively. Flow cytometry, free hemoglobin levels, and membrane lipid peroxidation levels were used to characterize cell membrane damage in the presence and absence of resveratrol after hypoxia. The effects of oxida-tive stress on the erythrocyte membrane proteins band 3 and spectrin were further investigated by immunofluorescent label-ing and Western blotting. Results and discussion: Resveratrol changed the surface roughness and Young's modulus of the erythrocyte mem-brane, reduced the rate of eryptosis in erythrocytes after hypoxia, and stabilized the intracellular redox level. Further data showed that resveratrol protected the erythrocyte membrane proteins band 3 and spectrin. Moreover, resistance to band 3 pro-tein tyrosine phosphorylation and sulfhydryl oxidation can protect the stability of the erythrocyte membrane skeleton net-work, thereby protecting erythrocyte deformability under hypoxia. The results of the present study may provide new insights into the roles of resveratrol in the prevention of hypoxia and as an antioxidant.

Hypobaric hypoxia aggravates osteoarthritis via the alteration of the oxygen environment and bone remodeling in the subchondral zone

A high prevalence of osteoarthritis (OA) has been observed among individuals living at high altitudes, and hypobaric hypoxia (HH) can cause bone mass and strength deterioration. However, the effect of HH on OA remains unclear. In this study, we aimed to explore the impact of HH on OA and its potential mechanisms. A rat knee OA model was established by surgery, and the rats were bred in an HH chamber simulating a high-altitude environment. Micro-computed tomography (Micro-CT), histological analysis, and RNA sequencing were performed to evaluate the effects of HH on OA in vivo. A hypoxic co-culture model of osteoclasts and osteoblasts was also established to determine their effects on chondrogenesis in vitro. Cartilage degeneration significantly worsened in the HH-OA group compared to that in the normoxia-OA (N-OA) group, 4 weeks after surgery. Micro-CT analysis revealed more deteriorated bone mass in the HH-OA group than in the N-OA group. Decreased hypoxia levels in the cartilage and enhanced hypoxia levels in the subchondral bone were observed in the HH-OA group. Furthermore, chondrocytes cultured in a conditioned medium from the hypoxic co-culture model showed decreased anabolism and extracellular matrix compared to those in the normoxic model. RNA sequencing analysis of the subchondral bone indicated that the glycolytic signaling pathway was highly activated in the HH-OA group. HH-related OA progression was associated with alterations in the oxygen environment and bone remodeling in the subchondral zone, which provided new insights into the pathogenesis of OA.

A proteomics study of rheumatoid arthritis patients on etanercept identifies putative biomarkers associated with clinical outcome measures

OBJECTIVES

Biologic DMARDs (bDMARDs) are widely used in patients with RA, but response to bDMARDs is heterogeneous. The objective of this work was to identify pretreatment proteomic biomarkers associated with RA clinical outcome measures in patients starting bDMARDs.

METHODS

Sequential window acquisition of all theoretical fragment ion spectra mass spectrometry (SWATH-MS) was used to generate spectral maps of sera from patients with RA before and after 3 months of treatment with the bDMARD etanercept. Protein levels were regressed against RA clinical outcome measures, i.e. 28-joint DAS (DAS28) and its subcomponents and DAS28 <2.6 (i.e. remission). The proteins with the strongest evidence for association were analysed in an independent, replication dataset. Finally, subnetwork analysis was carried out using the Disease Module Detection algorithm and biological plausibility of identified proteins was assessed by enrichment analysis.

RESULTS

A total of 180 patients with RA were included in the discovery dataset and 58 in the validation dataset from a UK-based prospective multicentre study. Ten individual proteins were found to be significantly associated with RA clinical outcome measures. The association of T-complex protein 1 subunit η with DAS28 remission was replicated in an independent cohort. Subnetwork analysis of the 10 proteins from the regression analysis identified the ontological theme, with the strongest associations being with acute phase and acute inflammatory responses.

CONCLUSION

This longitudinal study of 180 patients with RA commencing etanercept has identified several putative protein biomarkers of treatment response to this drug, one of which was replicated in an independent cohort.

CD73/adenosine axis exerts cardioprotection against hypobaric hypoxia-induced metabolic shift and myocarditis in a sex-dependent manner

BACKGROUND

Clinical and experimental studies have shown that the myocardial inflammatory response during pathological events varies between males and females. However, the cellular and molecular mechanisms of these sex differences remain elusive. CD73/adenosine axis has been linked to anti-inflammatory responses, but its sex-specific cardioprotective role is unclear. The present study aimed to investigate whether the CD73/adenosine axis elicits sex-dependent cardioprotection during metabolic changes and myocarditis induced by hypobaric hypoxia.

METHODS

For 7 days, male and female mice received daily injections of the CD73 inhibitor adenosine 5'- (α, β-methylene) diphosphate (APCP) 10 mg/kg/day while they were kept under normobaric normoxic and hypobaric hypoxic conditions. We evaluated the effects of hypobaric hypoxia on the CD73/adenosine axis, myocardial hypertrophy, and cardiac electrical activity and function. In addition, metabolic homeostasis and immunoregulation were investigated to clarify the sex-dependent cardioprotection of the CD73/adenosine axis.

RESULTS

Hypobaric hypoxia-induced cardiac dysfunction and adverse remodeling were more pronounced in male mice. Also, male mice had hyperactivity of the CD73/adenosine axis, which aggravated myocarditis and metabolic shift compared to female mice. In addition, CD73 inhibition triggered prostatic acid phosphatase ectonucleotidase enzymatic activity to sustain adenosine overproduction in male mice but not in female mice. Moreover, dual inhibition prostatic acid phosphatase and CD73 enzymatic activities in male mice moderated adenosine content, alleviating glycolytic shift and proinflammatory response.

CONCLUSION

The CD73/adenosine axis confers a sex-dependent cardioprotection. In addition, extracellular adenosine production in the hearts of male mice is influenced by prostatic acid phosphatase and tissue nonspecific alkaline phosphatase.

Comparative Molecular and Biological Characteristic of the Systemic Inflammatory Response in Adult and Old Male Wistar Rats with Different Resistance to Hypoxia

Morphological, molecular, and biological features of the systemic inflammatory response induced by LPS administration were assessed in adult and old male Wistar rats with high and low resistance to hypoxia. In 6 h after LPS administration, mRNA expression levels of Hif1a, Vegf, Nfkb, and level of IL-1β protein in old rats were higher than in adult rats regardless of hypoxia tolerance. The morphometric study showed that the number of neutrophils in the interalveolar septa of the lungs was significantly higher in low-resistant adult and old rats 6 h after LPS administration. Thus, in old male Wistar rats, systemic inflammatory response is more pronounced than in adult rats and depends on the initial tolerance to hypoxia, which should be considered when developing new approaches to the therapy of systemic inflammatory response in individuals of different ages.

Intermittent hypoxia preconditioning can attenuate acute hypoxic injury after a sustained normobaric hypoxic exposure: A randomized clinical trial

BACKGROUND

Intermittent hypoxia (IH) is emerging as a cost-effective nonpharmacological method for vital organ protection. We aimed to assess the effects of a short-term moderate intermittent hypoxia preconditioning protocol (four cycles of 13% hypoxia lasting for 10 min with 5-min normoxia intervals) on acute hypoxic injury induced by sustained hypoxic exposure (oxygen concentration of 11.8% for 6 h).

METHODS

One hundred healthy volunteers were recruited and randomized to the IH group and the control group to receive IH or sham-IH preconditioning for 5 days, respectively, and then were sent to a hypoxic chamber for simulated acute high-altitude exposure (4500 m).

RESULTS

The overall incidence of acute mountain sickness was 27% (27/100), with 14% (7/50) in the IH group and 40% (20/50) in the control group (p = 0.003). After 6-h simulated high-altitude exposure, the mean Lake Louise Score was lower in the IH group as compared to controls (1.30 ± 1.27 vs. 2.04 ± 1.89, p = 0.024). Mean peripheral oxygen saturations (SpO2 ) and intracranial pressure (ICP) measures after acute hypoxic exposure exhibited significant differences, with the IH group showing significantly greater SpO2 values (85.47 ± 5.14 vs. 83.10 ± 5.15%, p = 0.026) and lower ICP levels than the control group (115.59 ± 32.15 vs. 130.36 ± 33.83 mmH2 O, p = 0.028). IH preconditioning also showed greater effects on serum protein gene product 9.5 (3.89 vs. 29.16 pg/mL; p = 0.048) and C-reactive protein (-0.28 vs. 0.41 mg/L; p = 0.023).

CONCLUSION

The short-term moderate IH improved the tolerance to hypoxia and exerted protection against acute hypoxic injury induced by exposure to sustained normobaric hypoxia, which provided a novel method and randomized controlled trial evidence to develop treatments for hypoxia-related disease.

Hypoxia and its effect on the cellular system

Eukaryotic cells utilize oxygen for different functions of cell organelles owing to cellular survival. A balanced oxygen homeostasis is an essential requirement to maintain the regulation of normal cellular systems. Any changes in the oxygen level are stressful and can alter the expression of different homeostasis regulatory genes and proteins. Lack of oxygen or hypoxia results in oxidative stress and formation of hypoxia inducible factors (HIF) and reactive oxygen species (ROS). Substantial cellular damages due to hypoxia have been reported to play a major role in various pathological conditions. There are different studies which demonstrated that the functions of cellular system are disrupted by hypoxia. Currently, study on cellular effects following hypoxia is an important field of research as it not only helps to decipher different signaling pathway modulation, but also helps to explore novel therapeutic strategies. On the basis of the beneficial effect of hypoxia preconditioning of cellular organelles, many therapeutic investigations are ongoing as a promising disease management strategy in near future. Hence, the present review discusses about the effects of hypoxia on different cellular organelles, mechanisms and their involvement in the progression of different diseases.

In silico screening of phytoconstituents as potential anti-inflammatory agents targeting NF-κB p65: an approach to promote burn wound healing

Chronic burn wounds are frequently characterised by a prolonged and dysregulated inflammatory phase that is mediated by over-activation of NF-κB p65. Synthetic wound healing drugs used for treatment of inflammation are primarily associated with several shortcomings which reduce their therapeutic index. In this scenario, phytoconstituents that exhibit multifaceted biological activities including anti-inflammatory effects have emerged as a promising therapeutic alternative. However, identification and isolation of phytoconstituents from medicinal herbs is a cumbersome method that is linked to profound uncertainty. Hence, present study aimed to identify prospective phytoconstituents as inhibitors of RHD of NF-κB p65 by utilizing in silico approach. Virtual screening of 2821 phytoconstituents was performed against protein model. Out of 2821 phytoconstituents, 162 phytoconstituents displayed a higher binding affinity (≤ -8.0 kcal/mol). These 162 phytoconstituents were subjected to ADMET predictions, and 15 of them were found to satisfy Lipinski's rule of five and showed favorable pharmacokinetic properties. Among these 15 phytoconstituents, 5 phytoconstituents with high docking scores i.e. silibinin, bismurrayaquinone A, withafastuosin B, yuccagenin, (+)-catechin 3-gallate were selected for molecular dynamics (MD) simulation analysis. Results of MD simulation indicated that withafastuosin B, (+)-catechin 3-gallate and yuccagenin produced a compact and stable complex with protein without significant variations in conformation. Relative binding energy analysis of best hit molecules indicate that withafastuosin B, and (+)-catechin 3-gallate exhibit high binding affinity with target protein among other lead molecules. Findings of study suggest that these phytoconstituents could serve as promising anti-inflammatory agents for treatment of burn wounds by inhibiting the RHD of NF-κB p65.Communicated by Ramaswamy H. Sarma.

Respiratory tract infection: an unfamiliar risk factor in high-altitude pulmonary edema

The dramatic changes in physiology at high altitude (HA) as a result of the characteristic hypobaric hypoxia condition can modify innate and adaptive defense mechanisms of the body. As a consequence, few sojourners visiting HA with mild or asymptomatic infection may have an enhanced susceptibility to high-altitude pulmonary edema (HAPE), an acute but severe altitude sickness. It develops upon rapid ascent to altitudes above 2500 m, in otherwise healthy individuals. Though HAPE has been studied extensively, an elaborate exploration of the HA disease burden and the potential risk factors associated with its manifestation are poorly described. The present review discusses respiratory tract infection (RTI) as an unfamiliar but important risk factor in enhancing HAPE susceptibility in sojourners for two primary reasons. First, the symptoms of RTI s resemble those of HAPE. Secondly, the imbalanced pathways contributing to vascular dysfunction in HAPE also participate in the pathogenesis of the infectious processes. These pathways have a crucial role in shaping host response against viral and bacterial infections and may further worsen the clinical outcomes at HA. Respiratory tract pathogenic agents, if screened in HAPE patients, can help in ascertaining their role in disease risk and also point toward their association with the disease severity. The microbial screenings and identifications of pathogens with diseases are the foundation for describing potential molecular mechanisms underlying host response to the microbial challenge. The prior knowledge of such infections may predict the manifestation of disease etiology and provide better therapeutic options.

Hypoxia-Inducible Factor and Oxidative Stress in Tendon Degeneration: A Molecular Perspective

Tendinopathy is a debilitating condition marked by degenerative changes in the tendons. Its complex pathophysiology involves intrinsic, extrinsic, and physiological factors. While its intrinsic and extrinsic factors have been extensively studied, the role of physiological factors, such as hypoxia and oxidative stress, remains largely unexplored. This review article delves into the contribution of hypoxia-associated genes and oxidative-stress-related factors to tendon degeneration, offering insights into potential therapeutic strategies. The unique aspect of this study lies in its pathway-based evidence, which sheds light on how these factors can be targeted to enhance overall tendon health.

SARS-CoV-2 Infection to Premature Neuronal Aging and Neurodegenerative Diseases: Is there any Connection with Hypoxia?

The pandemic of coronavirus disease-2019 (COVID-19), caused by SARS-CoV-2, has become a global concern as it leads to a spectrum of mild to severe symptoms and increases death tolls around the world. Severe COVID-19 results in acute respiratory distress syndrome, hypoxia, and multi- organ dysfunction. However, the long-term effects of post-COVID-19 infection are still unknown. Based on the emerging evidence, there is a high possibility that COVID-19 infection accelerates premature neuronal aging and increases the risk of age-related neurodegenerative diseases in mild to severely infected patients during the post-COVID period. Several studies correlate COVID-19 infection with neuronal effects, though the mechanism through which they contribute to the aggravation of neuroinflammation and neurodegeneration is still under investigation. SARS-CoV-2 predominantly targets pulmonary tissues and interferes with gas exchange, leading to systemic hypoxia. The neurons in the brain require a constant supply of oxygen for their proper functioning, suggesting that they are more vulnerable to any alteration in oxygen saturation level that results in neuronal injury with or without neuroinflammation. We hypothesize that hypoxia is one of the major clinical manifestations of severe SARS-CoV-2 infection; it directly or indirectly contributes to premature neuronal aging, neuroinflammation, and neurodegeneration by altering the expression of various genes responsible for the survival of the cells. This review focuses on the interplay between COVID-19 infection, hypoxia, premature neuronal aging, and neurodegenerative diseases and provides a novel insight into the molecular mechanisms of neurodegeneration.

More severe initial manifestations and worse short-term functional outcome of intracerebral hemorrhage in the plateau than in the plain

Intracerebral hemorrhage (ICH) is one of the most devastating forms of stroke. However, studies on ICH at high altitude are insufficient. We aimed to compare the initial manifestations, imaging features and short-term functional outcomes of ICH at different altitudes, and further explore the effect of altitude on the severity and prognosis of ICH. We retrospectively recruited ICH patients from January 2018 to July 2021 from two centers at different altitudes in China. Information regarding to clinical manifestations, neuroimages, and functional outcomes at discharge were collected and analyzed. Association between altitude and initial severity, neuroimages, and short-term prognosis of ICH were also investigated. A total of 724 patients with 400 lowlanders and 324 highlanders were enrolled. Compared with patients from the plain, those at high altitude were characterized by more severe preliminary manifestations (P < 0.0001), larger hematoma volume (P < 0.001) and poorer short-term functional outcome (P < 0.0001). High altitude was independently associated with dependency at discharge (adjusted P = 0.024), in-hospital mortality (adjusted P = 0.049) and gastrointestinal hemorrhage incidence (adjusted P = 0.017). ICH patients from high altitude suffered from more serious initial manifestations and worse short-term functional outcome than lowlanders. Control of blood pressure, oxygen supplementation and inhibition of inflammation may be critical for ICH at high altitude.

Nanocurcumin attenuates pyroptosis and inflammation through inhibiting NF-κB/GSDMD signal in high altitude-associated acute liver injury

Exposure to a hypobaric hypoxic environment at high altitudes can lead to liver injury, and mounting evidence indicates that pyroptosis and inflammation play important roles in liver injury. Curcumin (Cur) can inhibit pyroptosis and inflammation. Therefore, our purpose here was to clarify the mechanism underlying the protective effect of nanocurcumin (Ncur) and Cur in a rat model of high altitude-associated acute liver injury. Eighty healthy rats were selected and exposed to different altitudes (6000 or 7000 m) for 0, 24, 48, or 72 h. Fifty normal healthy rats were divided into normal control, high-altitude control, salidroside (40 mg/kg [Sal-40]), Cur (200 mg/kg [Cur-200]), and Ncur (25 mg/kg [Ncur-25]) groups and exposed to a high-altitude hypobaric hypoxic environment (48 h, 7000 m). Serum-liver enzyme activities (alanine transaminase, aspartate transaminase, and lactate dehydrogenase were detected and histopathology of liver injury was evaluated by hematoxylin and eosin staining, and inflammatory factors were detected in liver tissues by enzyme-linked immunosorbent assays. Pyroptosis-associated proteins (gasdermin D, gasdermin D N-terminal [GSDMD-N], pro-Caspase-1, and cleaved-Caspase-1 [cleaved-Casp1]) and inflammation-associated proteins (nuclear factor-κB [NF-κB], phospho-NF-κB [P-NF-κB], and high-mobility group protein B1 [HMGB1]) levels were analyzed by immunoblotting. Ncur and Cur inhibited increased serum-liver enzyme activities, alleviated liver injury in rats caused by high-altitude hypobaric hypoxic exposure, and downregulated inflammatory factors, including tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and IL-18, in rat liver tissues. The level of P-NF-κB, GSDMD-N, cleaved-Casp1, and HMGB1 in rat liver tissues increased significantly after high-altitude exposure. Ncur and Cur downregulated P-NF-κB, GSDMD-N, cleaved-Casp-1, and HMGB1. Ncur and Cur may inhibit inflammatory responses and pyroptosis in a rat model of high altitude-associated acute liver injury.

Molecular pathways of NF-ĸB and NLRP3 inflammasome as potential targets in the treatment of inflammation in diabetic wounds: A review

Diabetic wounds are slow healing wounds characterized by disordered healing processes and frequently take longer than three months to heal. One of the defining characteristics of impaired diabetic wound healing is an abnormal and unresolved inflammatory response, which is primarily brought on by abnormal macrophage innate immune signaling activation. The persistent inflammatory state in a diabetic wound may be attributed to inflammatory pathways such as nuclear factor kappa B (NF-ĸB) and nod-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, which have long been associated with inflammatory diseases. Despite the available treatments for diabetic foot ulcers (DFUs) that include debridement, growth factor therapy, and topical anti-bacterial agents, successful wound healing is still hampered. Further understanding of the molecular mechanism of these pathways could be useful in designing potential therapeutic targets for diabetic wound healing. This review provides an update and novel insights into the roles of NF-ĸB and NLRP3 pathways in the molecular mechanism of diabetic wound inflammation and their potential as therapeutic targets in diabetic wound healing.

Topically applied pH-responsive nanogels for alkyl radical-based therapy against psoriasiform hyperplasia

Phototherapy is a conventional antipsoriatic approach based on oxygen-relevant generation of oxidative stress to inhibit keratinocyte hyperproliferation. However, this therapy can be restricted due to local hypoxia in psoriatic lesions. The generation of alkyl radicals is oxygen-independent and suppresses hyperproliferation. Herein, we established alkyl radical-based therapy to treat psoriatic hyperplasia. Because alkyl radicals are short-lived compounds, we loaded 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (AIPH) as a precursor of alkyl radicals into the chitosan nanogels to improve stability. The present study presented a topically applied nanogel that led to a pH-responsive network sensitive to skin pH. This pH responsiveness of the nanogels allowed fast alkyl radical release in the target site. The physicochemical properties of the prepared nanogels were determined through size, zeta potential, scanning electron microscopy, and absorption spectroscopy. The antipsoriatic activity was examined with keratinocyte- and animal-based studies. The nanogels displayed a smooth and spherical morphology with a hydrodynamic diameter of 215 nm. This size was largely increased as the environmental pH increased to 6. The nanogels heated at 44 °C produced alkyl radicals to induce keratinocyte death through the necrosis pathway. Bioimaging demonstrated that topically applied nanogels could deliver alkyl radicals into the epidermis. This targeting was accompanied by the accumulation of free radicals in the epidermis according to the 2',7'-dichlorodihydrofluorescein diacetate assay. The imiquimod-stimulated psoriasiform animal model indicated a remarkable reduction in erythema, scaling, and overexpressed cytokines upon topical treatment of the nanogels. The transepidermal water loss of the psoriasiform skin was inhibited from 51.7 to 27.0 g/m2/h, suggesting barrier function recovery by the nanocarriers. The nanogels lowered hyperplasia by decreasing the epidermal thickness from 212 to 89 μm. The incorporation of 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) as a pH-sensitive fluorescence dye in the nanogels could be used to diagnose the severity of the psoriasiform plaque due to the stronger fluorescence of HPTS in skin with lower pH (psoriasiform skin pH = 4.4) than in healthy skin (pH = 4.9). It was possible to deliver the prepared nanogels into the epidermis to restrain hyperplasia without causing cutaneous irritation.

Dexamethasone prophylaxis protects from acute high-altitude illness by modifying the peripheral blood mononuclear cell inflammatory transcriptome

Acute high-altitude (HA) exposure can induce several pathologies. Dexamethasone (DEX) can be taken prophylactically to prevent HA disease, but the mechanism by which it acts in this setting is unclear. We studied the transcriptome of peripheral blood mononuclear cells (PBMCs) from 16 subjects at low altitude (LA, 225 m) and then 3 days after acute travel to HA (3500 m) during the India-Leh-Dexamethasone-Expedition-2020 (INDEX2020). Half of the participants received oral DEX prophylaxis 4 mg twice daily in an unblinded manner, starting 1 day prior to travel to HA, and 12 h prior to the first PBMC collection. PBMC transcriptome data were obtained from 16 subjects, half of whom received DEX. The principal component analysis demonstrated a clear separation of the groups by altitude and treatment. HA exposure resulted in a large number of gene expression changes, particularly in pathways of inflammation or the regulation of cell division, translation, or transcription. DEX prophylaxis resulted in changes in fewer genes, particularly in immune pathways. The gene sets modulated by HA and DEX were distinct. Deconvolution analysis to assess PBMC subpopulations suggested changes in B-cell, T-cell, dendritic cell, and myeloid cell numbers with HA and DEX exposures. Acute HA travel and DEX prophylaxis induce significant changes in the PBMC transcriptome. The observed benefit of DEX prophylaxis against HA disease may be mediated by suppression of inflammatory pathways and changing leukocyte population distributions.

Extreme environments and human health: From the immune microenvironments to immune cells

Exposure to extreme environments causes specific acute and chronic physiological responses in humans. The adaptation and the physiological processes under extreme environments predominantly affect multiple functional systems of the organism, in particular, the immune system. Dysfunction of the immune system affected by several extreme environments (including hyperbaric environment, hypoxia, blast shock, microgravity, hypergravity, radiation exposure, and magnetic environment) has been observed from clinical macroscopic symptoms to intracorporal immune microenvironments. Therefore, simulated extreme conditions are engineered for verifying the main influenced characteristics and factors in the immune microenvironments. This review summarizes the responses of immune microenvironments to these extreme environments during in vivo or in vitro exposure, and the approaches of engineering simulated extreme environments in recent decades. The related microenvironment engineering, signaling pathways, molecular mechanisms, clinical therapy, and prevention strategies are also discussed.

Protective effects of epigallocatechin-3-gallate counteracting the chronic hypobaric hypoxia-induced myocardial injury in plain-grown rats at high altitude

Exposure to hypobaric hypoxia (HH) environment causes stress to the body, especially the oxygen-consuming organs. Chronic HH conditions have adverse effects on the myocardium. Thus, we conducted this experiment and aim to evaluate such adverse effects and explore the therapeutic role of epigallocatechin-3-gallate (EGCG) in rats' heart under chronic HH conditions. For that purpose, we transported rats from plain to a real HH environment at high altitude for establishing the HH model. At high altitude, animals were treated with EGCG while the salidroside was used as the positive control. General physiological data were collected, and routine blood test results were analyzed. Cardiac magnetic resonance (CMR) was examined to assess the structural and functional changes of the heart. Serum levels of cardiac enzymes and pro-inflammatory cytokines were examined. Oxidative markers in the left ventricle (LV) were detected. Additionally, ultrastructural and histopathological changes and apoptosis of the LV were assessed. Furthermore, the antioxidant stress-relevant proteins nuclear factor E2-related factor 2 (Nrf2) and the heme oxygenase-1 (HO-1) were detected. The experiment revealed that EGCG treatment decreased HH-induced elevation of cardiac enzymes and relieved mitochondrial damage of the LV. Notably, EGCG treatment significantly alleviated oxidative stress in the LV and inflammatory response in the blood. Western blot confirmed that EGCG significantly upregulated Nrf2 and HO-1. Therefore, EGCG may be considered a promising natural compound for treating the HH-induced myocardial injuries.

Pretreatment with Notoginsenoside R1 attenuates high-altitude hypoxia-induced cardiac injury via activation of the ERK1/2-P90RSK-Bad signaling pathway in rats

High-altitude cardiac injury (HACI) is one of the common tissue injuries caused by high-altitude hypoxia that may be life threatening. Notoginsenoside R1 (NG-R1), a major saponin of Panax notoginseng, exerts anti-oxidative, anti-inflammatory, and anti-apoptosis effects, protecting the myocardium from hypoxic injury. This study aimed to investigate the protective effect and molecular mechanism of NG-R1 against HACI. We simulated a 6000 m environment for 48 h in a hypobaric chamber to create a HACI rat model. Rats were pretreated with NG-R1 (50, 100 mg/kg) or dexamethasone (4 mg/kg) for 3 days and then placed in the chamber for 48 h. The effect of NG-R1 was evaluated by changes in Electrocardiogram parameters, histopathology, cardiac biomarkers, oxidative stress and inflammatory indicators, key protein expression, and immunofluorescence. U0126 was used to verify whether the anti-apoptotic effect of NG-R1 was related to the activation of ERK pathway. Pretreatment with NG-R1 can improve abnormal cardiac electrical conduction and alleviate high-altitude-induced tachycardia. Similar to dexamethasone, NG-R1 can improve pathological damage, reduce the levels of cardiac injury biomarkers, oxidative stress, and inflammatory indicators, and down-regulate the expression of hypoxia-related proteins HIF-1α and VEGF. In addition, NG-R1 reduced cardiomyocyte apoptosis by down-regulating the expression of apoptotic proteins Bax, cleaved caspase 3, cleaved caspase 9, and cleaved PARP1 and up-regulating the expression of anti-apoptotic protein Bcl-2 through activating the ERK1/2-P90RSK-Bad pathway. In conclusion, NG-R1 prevented HACI and suppressed apoptosis via activation of the ERK1/2-P90RSK-Bad pathway, indicating that NG-R1 has therapeutic potential to treat HACI.

Global REACH 2018: High Altitude-Related Circulating Extracellular Microvesicles Promote a Proinflammatory Endothelial Phenotype In Vitro

Brewster, L. Madden, Anthony R. Bain, Vinicius P. Garcia, Noah M. DeSouza, Michael M. Tymko, Jared J. Greiner, and Philip N. Ainslie. Global REACH 2018: high altitude-related circulating extracellular microvesicles promote a proinflammatory endothelial phenotype in vitro. High Alt Med Biol. 24:223-229, 2023. Introduction: Ascent to high altitude (HA) can induce vascular dysfunction by promoting a proinflammatory endothelial phenotype. Circulating microvesicles (MVs) can mediate the vascular endothelium and inflammation. It is unclear whether HA-related MVs are associated with endothelial inflammation. Objectives: We tested the hypothesis that MVs derived from ascent to HA induce a proinflammatory endothelial phenotype. Methods: Ten healthy adults (8 M/2 F; age: 28 ± 2 years) residing at sea level (SL) were studied before and 4-6 days after rapid ascent to HA (4,300 m). MVs were isolated and enumerated from plasma by centrifugation and flow cytometry. Human umbilical vein endothelial cells were treated with MVs collected from each subject at SL (MV-SL) and at HA (MV-HA). Results: Circulating MV number significantly increased at HA (26,637 ± 3,315 vs. 19,388 ± 1,699). Although intracellular expression of total nuclear factor kappa beta (NF-κB; 83.4 ± 6.7 arbitrary units [AU] vs. 90.2 ± 6.9 AU) was not affected, MV-HA resulted in ∼55% higher (p < 0.05) active NF-κB (129.6 ± 19.8 AU vs. 90.7 ± 10.5 AU) expression compared with MV-SL. In addition, MV-HA induced higher interleukin (IL)-6 (63.9 ± 3.9 pg/ml vs. 53.3 ± 3.6 pg/ml) and IL-8 (140.2 ± 3.6 pg/ml vs. 120.7 ± 3.8 pg/ml) release compared with MV-SL, which was blunted with NF-κB blockade. Conclusions: Circulating extracellular MVs increase at HA and induce endothelial inflammation, potentially contributing to altitude-related vascular dysfunction.

Crosstalk between hypoxic cellular micro-environment and the immune system: a potential therapeutic target for infectious diseases

There are overwhelming reports on the promotional effect of hypoxia on the malignant behavior of various forms of cancer cells. This has been proposed and tested exhaustively in the light of cancer immunotherapy. However, there could be more interesting functions of a hypoxic cellular micro-environment than malignancy. There is a highly intricate crosstalk between hypoxia inducible factor (HIF), a transcriptional factor produced during hypoxia, and nuclear factor kappa B (NF-κB) which has been well characterized in various immune cell types. This important crosstalk shares common activating and inhibitory stimuli, regulators, and molecular targets. Impaired hydroxylase activity contributes to the activation of HIFs. Inflammatory ligands activate NF-κB activity, which leads to the expression of inflammatory and anti-apoptotic genes. The eventual sequelae of the interaction between these two molecular players in immune cells, either bolstering or abrogating functions, is largely cell-type dependent. Importantly, this holds promise for interesting therapeutic interventions against several infectious diseases, as some HIF agonists have helped prevent immune-related diseases. Hypoxia and inflammation are common features of infectious diseases. Here, we highlighted the role of this crosstalk in the light of functional immunity against infection and inflammation, with special focus on various innate and adaptive immune cells. Particularly, we discussed the bidirectional effects of this crosstalk in the regulation of immune responses by monocytes/macrophages, dendritic cells, neutrophils, B cells, and T cells. We believe an advanced understanding of the interplay between HIFs and NF-kB could reveal novel therapeutic targets for various infectious diseases with limited treatment options.

Mechanisms of Atrial Fibrillation in Obstructive Sleep Apnoea

Obstructive sleep apnoea (OSA) is a strong independent risk factor for atrial fibrillation (AF). Emerging clinical data cite adverse effects of OSA on AF induction, maintenance, disease severity, and responsiveness to treatment. Prevention using continuous positive airway pressure (CPAP) is effective in some groups but is limited by its poor compliance. Thus, an improved understanding of the underlying arrhythmogenic mechanisms will facilitate the development of novel therapies and/or better selection of those currently available to complement CPAP in alleviating the burden of AF in OSA. Arrhythmogenesis in OSA is a multifactorial process characterised by a combination of acute atrial stimulation on a background of chronic electrical, structural, and autonomic remodelling. Chronic intermittent hypoxia (CIH), a key feature of OSA, is associated with long-term adaptive changes in myocyte ion channel currents, sensitising the atria to episodic bursts of autonomic reflex activity. CIH is also a potent driver of inflammatory and hypoxic stress, leading to fibrosis, connexin downregulation, and conduction slowing. Atrial stretch is brought about by negative thoracic pressure (NTP) swings during apnoea, promoting further chronic structural remodelling, as well as acutely dysregulating calcium handling and electrical function. Here, we provide an up-to-date review of these topical mechanistic insights and their roles in arrhythmia.