Acute mountain sickness, inflammation, and permeability: new insights from a blood biomarker study

Inflammation severity, rather than respiratory failure, is strongly associated with mortality of ARDS patients in high-altitude ICUs

Introduction

In high-altitude cities located above 2,500 m, hospitals face a concerning mortality rate of over 50% among intensive care unit (ICU) patients with acute respiratory distress syndrome (ARDS). This elevated mortality rate is largely due to the absence of altitude-specific medical protocols that consider the unique physiological adaptations of high-altitude residents to hypoxic conditions. This study addresses this critical gap by analyzing demographic, clinical, sex-specific, and preclinical data from ICUs in Bogotá, Colombia (2,650 m) and El Alto, Bolivia (4,150 m).

Methods

A cohort of seventy ARDS patients, aged 18 and older, was evaluated within 24 h of ICU admission. Data collected included demographic information (age, sex), clinical characteristics (primary pathology, weight, height), vital signs, respiratory variables, cardiorespiratory parameters, blood count results, inflammatory markers, severity assessment scores, and comorbidities. Advanced statistical analyses, such as multivariate logistic regression and principal component analysis, were utilized to identify key clinical predictors of ARDS-related mortality.

Results

Our findings indicate that in high-altitude ICUs, monitoring inflammatory markers may be more beneficial for improving ARDS survival rates than emphasizing respiratory failure markers. Unexpectedly, we found no significant differences in clinical outcomes between altitudes of 2,650 and 4,150 m or between male and female patients.

Conclusion

The study concludes that, in high-altitude settings, ARDS patient survival in ICUs is more closely associated with managing inflammatory responses than with focusing solely on respiratory parameters. Further large-scale studies are recommended to validate the impact of inflammatory marker monitoring on survival outcomes in high-altitude ICUs.

Astaxanthin Supplementation Effects in Right Ventricle of Rats Exposed to Chronic Intermittent Hypobaric Hypoxia

In Chile, individuals are commonly exposed to high altitude due to the work shift system, involving days of exposure to high altitude followed by days at sea level over the long term, which can result in chronic intermittent hypobaric hypoxia (CIHH). CIHH can cause high-altitude pulmonary hypertension (HAPH), the principal manifestation of which is right ventricular hypertrophy (RVH), in some cases leading to heart failure and eventually death. Studies have shown the contribution of oxidative stress and inflammation to RVH development. Recently, it was determined that the pigment astaxanthin has high antioxidant capacity and strong anti-inflammatory and cardioprotective effects. Therefore, the aim of this study was to determine the effects of astaxanthin on RVH development in rats subjected to CIHH.

METHODS

Thirty two male Wistar rats were randomly assigned to the following groups (n = 8 per group): the normoxia with vehicle (NX), normoxia with astaxanthin (NX + AS), chronic intermittent hypobaric hypoxia with vehicle (CIHH), and chronic intermittent hypobaric hypoxia with astaxanthin (CIHH + AS) groups. CIHH was simulated by 2 days in a hypobaric chamber followed by 2 days at sea level for 29 days.

RESULTS

Exposure to CIHH induced RVH and increased lipid peroxidation (MDA), Nox2 expression, and SOD activity, however, it decreased pro-IL-1β expression. Astaxanthin restored oxidative stress markers (Nox2 and MDA), increased GPx activity, and decreased RVH compared to CIHH.

CONCLUSION

Astaxanthin alleviates RVH and reduces Nox2 and MDA levels while increasing GPx activity in rats subjected to CIHH. These findings provide new insights of astaxanthin as a new nutraceutical against high-altitude effects.

Impact of Maternal Exercise on Mice Offspring Development, Pulmonary Hypertension, and Vascular Remodeling in Chronic Hypoxia

PURPOSE

Chronic, high-altitude hypoxic exposure increases the risk of high-altitude pulmonary hypertension (PH). Emerging evidence shows maternal exercise may improve offspring resistance to disease throughout life. The purpose of this study is to determine if maternal exercise mitigates chronic hypoxic-induced changes in the offspring indicative of high-altitude PH development.

METHODS

Female adult C57BL/6J mice were randomly allocated to nonexercise or exercise conditions. Exercise consisted of voluntary running wheel exercise for 4 wk during the perinatal period. Three days after birth, the pups remained at low altitude (normoxia) or were exposed to hypobaric hypoxia of 450 mm Hg to simulate ~4500 m of altitude exposure until 8 wk of age. The study consisted of four groups: hypoxia + nonexercise pregnancy, hypoxia + exercise, or the respective normoxia conditions (normoxia + nonexercise or normoxia + exercise). Offspring body size, motor function, right ventricular systolic pressure (RVSP), and cardiopulmonary morphology were assessed after 8 wk in normoxia or hypoxia.

RESULTS

Both hypoxic groups had smaller body sizes, reduced motor function, increased hematocrit, RVSP, muscularization in medium-sized pulmonary arteries, as well as right ventricular hypertrophy and contractility compared with the normoxic groups ( P < 0.05).

CONCLUSIONS

Chronic hypoxia simulating 4500 m attenuated growth, lowered motor function, and elicited PH development. Voluntary maternal exercise did not significantly decrease RVSP in the offspring, which aligned with a lack of effect to attenuate abnormal body size and cardiopulmonary development due to chronic hypoxia. These findings are preliminary in nature, and more powered studies through larger group sizes are required to generalize the results to the population.

Spontaneous and Stimulated Production of Cytokines by Blood Cells Ex Vivo as a Biomarker of Initially High or Low Hypoxia Resistance in Rats

Spontaneous and stimulated production of cytokines by peripheral blood cells obtained from the caudal vein of male Wistar rats was assessed before testing their resistance to oxygen deficiency in a decompression chamber. To study the spontaneous production of cytokines, heparinized blood cells were incubated in a culture medium (24 h, 5% CO2, 37°C) and the content of proinflammatory cytokines IL-6 and TNFα and anti-inflammatory IL-10 in the culture medium was assessed by ELISA. To stimulate cytokine production, blood cells were incubated for 24 h with LPS, phytohemagglutinin, and concanavalin A at final concentrations of 2, 4, and 4 μg, respectively. Two weeks after blood sampling, individual resistance of the animals to hypoxia in a decompression chamber was determined. In animals with low resistance to hypoxia, the levels of spontaneous production of all three cytokines were significantly higher, while after stimulation, the level of IL-1β increased by more than 2 times. The animals with spontaneous production of IL-10>50 pg/ml, IL-6>10 pg/ml, and TNFα>10 pg/ml, as well as with the increase in IL-1β production by more than 2 times upon stimulation were classified as low-resistant. At IL-10<15 pg/ml, IL-6<9 pg/ml, and TNFα<7 pg/ml, as well as the absence of the increase in IL-1β production upon stimulation, they were classified as high-resistant. The identified features of spontaneous and stimulated production of cytokines can be used as non-invasive biomarkers to determine the resistance to hypoxia without exposure to sublethal hypoxia in a decompression chamber.

IL-2, IL-17A and TNF-α hold potential as biomarkers for predicting acute mountain sickness prior to ascent

BACKGROUND

Acute mountain sickness (AMS) is the most prevalent condition resulting from hypobaric hypoxia (HH) at high altitudes. Although evidence suggests the involvement of inflammatory cytokines in AMS development, there is currently a lack of reports on variations in cytokine levels between individuals susceptible to AMS and those resistant to AMS prior to ascending to high altitude. Thus our current study aims to assess the predictive capability for AMS occurrence by evaluating differences in cytokine levels at low altitudes.

METHODS

The present study recruited 48 participants, who ascended from low altitude to middle high-altitude (3700 m) and further to extreme high-altitude (5000 m). Based on Lake Louise Score (LLS) at the two high altitudes, participants were categorized into severe AMS-susceptible (sAMS), moderate AMS-susceptible (mAMS), and non-AMS groups. The Bio-Plex MAGPIX System was employed to measure plasma levels of 11 inflammatory cytokines. Cytokines at low altitude and middle high-altitude were analyzed through receiver operating characteristic (ROC) analysis to obtain area under the ROC curve (AUROC), sensitivity, and specificity.

RESULTS

Based on LLS at 3700 m, we initially categorized the study subjects into the sAMS group (n = 8) and the Non-AMS group (n = 40). Among individuals in the non-AMS group (n = 40) at the altitude of 3700 m, those who developed AMS at the altitude of 5000 m were assigned to the mAMS group (n = 17), whereas those who did not experience AMS were included into the non-AMS group (n = 23). The concentration of TNF-α at low altitude exhibited robust predictive performance for predicting AMS occurrence at the altitude of 3700 m. Among the non-AMS group at the altitude of 3700 m, we identified that the concentration of IL-2 and IL-17A demonstrated high efficacy in predicting the onset of AMS following ascent to 5000 m. In addition, differentially expressed cytokines including IL-17A, TNF-α and IL-2 at low altitude possessed discriminatory potential among the three groups at 5000 m..

CONCLUSION

We posited that the levels of TNF-α, IL-2, IL-17A in serum of low altitude could be considered as potential biomarkers to predict the occurrence of AMS at high altitude.

NEW & NOTEWORTHY

Through the two comparisons at different two altitudes (baseline level and 3700 m), we provided a model to progressively screen individuals who are susceptible and resistant to different high altitudes (3700 m and 5000 m). TNF-α could firstly screen out the AMS susceptible individuals at the altitude of 3700 m. And through its combination with IL-2 and IL-17A, we could further screen out AMS susceptible individuals at the altitude of 5000 m.

Altitude illnesses

Millions of people visit high-altitude regions annually and more than 80 million live permanently above 2,500 m. Acute high-altitude exposure can trigger high-altitude illnesses (HAIs), including acute mountain sickness (AMS), high-altitude cerebral oedema (HACE) and high-altitude pulmonary oedema (HAPE). Chronic mountain sickness (CMS) can affect high-altitude resident populations worldwide. The prevalence of acute HAIs varies according to acclimatization status, rate of ascent and individual susceptibility. AMS, characterized by headache, nausea, dizziness and fatigue, is usually benign and self-limiting, and has been linked to hypoxia-induced cerebral blood volume increases, inflammation and related trigeminovascular system activation. Disruption of the blood-brain barrier leads to HACE, characterized by altered mental status and ataxia, and increased pulmonary capillary pressure, and related stress failure induces HAPE, characterized by dyspnoea, cough and exercise intolerance. Both conditions are progressive and life-threatening, requiring immediate medical intervention. Treatment includes supplemental oxygen and descent with appropriate pharmacological therapy. Preventive measures include slow ascent, pre-acclimatization and, in some instances, medications. CMS is characterized by excessive erythrocytosis and related clinical symptoms. In severe CMS, temporary or permanent relocation to low altitude is recommended. Future research should focus on more objective diagnostic tools to enable prompt treatment, improved identification of individual susceptibilities and effective acclimatization and prevention options.

Potential therapeutic effects of traditional Chinese medicine in acute mountain sickness: pathogenesis, mechanisms and future directions

Background and objectives

Acute mountain sickness (AMS) is a pathology with different symptoms in which the organism is not adapted to the environment that occurs under the special environment of high altitude. Its main mechanism is the organism's tissue damage caused by acute hypobaric hypoxia. Traditional Chinese medicine (TCM) theory focuses on the holistic concept. TCM has made remarkable achievements in the treatment of many mountain sicknesses. This review outlines the pathogenesis of AMS in modern and traditional medicine, the progress of animal models of AMS, and summarizes the therapeutic effects of TCM on AMS.

Methods

Using the keywords "traditional Chinese medicine," "herbal medicine," "acute mountain sickness," "high-altitude pulmonary edema," "high-altitude cerebral edema," "acute hypobaric hypoxia," and "high-altitude," all relevant TCM literature published up to November 2023 were collected from Scopus, Web of Science, PubMed, and China National Knowledge Infrastructure databases, and the key information was analyzed.

Results

We systematically summarised the effects of acute hypobaric hypoxia on the tissues of the organism, the study of the methodology for the establishment of an animal model of AMS, and retrieved 18 proprietary Chinese medicines for the clinical treatment of AMS. The therapeutic principle of medicines is mainly invigorating qi, activating blood and removing stasis. The components of botanical drugs mainly include salidroside, ginsenoside Rg1, and tetrahydrocurcumin. The mechanism of action of TCM in the treatment of AMS is mainly through the regulation of HIF-1α/NF-κB signaling pathway, inhibition of inflammatory response and oxidative stress, and enhancement of energy metabolism.

Conclusion

The main pathogenesis of AMS is unclear. Still, TCM formulas and components have been used to treat AMS through multifaceted interventions, such as compound danshen drip pills, Huangqi Baihe granules, salidroside, and ginsenoside Rg1. These components generally exert anti-AMS pharmacological effects by inhibiting the expression of VEGF, concentration of MDA and pro-inflammatory factors, down-regulating NF-κB/NLRP3 pathway, and promoting SOD and Na + -K + -ATPase activities, which attenuates acute hypobaric hypoxia-induced tissue injury. This review comprehensively analyses the application of TCM in AMS and makes suggestions for more in-depth studies in the future, aiming to provide some ideas and insights for subsequent studies.

B2M is a Biomarker Associated With Immune Infiltration In High Altitude Pulmonary Edema

BACKGROUND

High altitude pulmonary edema (HAPE) is a serious mountain sickness with certain mortality. Its early diagnosis is very important. However, the mechanism of its onset and progression is still controversial.

AIM

This study aimed to analyze the HAPE occurrence and development mechanism and search for prospective biomarkers in peripheral blood.

METHODS

The difference genes (DEGs) of the Control group and the HAPE group were enriched by gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and then GSEA analysis was performed. After identifying the immune-related hub genes, QPCR was used to verify and analyze the hub gene function and diagnostic value with single-gene GSEA and ROC curves, and the drugs that acted on the hub gene was found in the CTD database. Immune infiltration and its association with the hub genes were analyzed using CIBERSORT. Finally, WGCNA was employed to investigate immune invasion cells' significantly related gene modules, following enrichment analysis of their GO and KEGG.

RESULTS

The dataset enrichment analysis, immune invasion analysis and WGCNA analysis showed that the occurrence and early progression of HAPE were unrelated to inflammation. The hub genes associated with immunity obtained with MCODE algorithm of Cytoscape were JAK2 and B2M.. RT-qPCR and ROC curves confirmed that the hub gene B2M was a specific biomarker of HAPE and had diagnostic value, and single-gene GSEA analysis confirmed that it participated in MHC I molecule-mediated antigen presentation ability decreased, resulting in reduced immunity.

CONCLUSION

Occurrence and early progression of high altitude pulmonary edema may not be related to inflammation. B2M may be a new clinical potential biomarker for HAPE for early diagnosis and therapeutic evaluation as well as therapeutic targets, and its decrease may be related to reduced immunity due to reduced ability of MCH I to participate in antigen submission.

The role of hypoxia related hormones responses in acute mountain sickness susceptibility individuals unaccustomed to high altitude

Acute mountain sickness (AMS) is caused by rapid ascent to altitude (>2500 m) and remains a poorly understood pathophysiological condition. Accordingly, we investigated the relationship between acute exposure to high altitude and hypoxia related biochemical proteins. 21 healthy subjects (Female (8) and male (13), Age: 36.7±8.5, BMI: 23.2±3.1) volunteers participated in this project and fasting blood samples were taken before (sea level) and after 1 and 24-h exposure to high altitude (3,550 m). Blood oxygen saturation (SpO2), AMS status (Lake Louise Score) and serum HIF-1, Endothelin-1, VEGF and Orexin-A were measured (via ELISA) at 1, 6 and 24 h after exposure to high altitude. Pre-ascent measurement of hypoxia related proteins (Orexin-A, HIF-1, VEGF and Endothelin-1) where all significantly (<0.05) higher in the AMS-resistant individuals (No-AMS) when compared to AMS susceptible individuals (AMS+). Upon ascent to high altitude, 11 out of 21 volunteers had AMS (10.1±0.6 in AMS+ vs. 0.9±0.6 in No-AMS, P<0.05) and presented with lower resting SpO2 levels (77.7±0.4 vs. 83.5±0.3 respectively, p<0.05). Orexin-A, HIF-1, VEGF and Endothelin-1, significantly increased 24 hrs after exposure to high altitude in both AMS+ and No-AMS. The response of Orexin-A was similar between two groups, also, HIF-1 elevation 24 hrs after exposure to altitude was more in AMS+ (13% vs. 19%), but the increase of VEGF and Endothelin-1, 1 and 24 hrs after exposure to altitude in No-AMS was double that of AMS+. Hypoxia related proteins include Orexin-A, HIF-1, VEGF and Endothelin-1 may play a pathophysiological role in those who are susceptible to AMS.

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.

Prior Ambulatory Mild Coronavirus Disease 2019 Does Not Increase Risk of Acute Mountain Sickness

Small, Elan, Caleb Phillips, William Bunzel, Lakota Cleaver, Nishant Joshi, Laurel Gardner, Rony Maharjan, and James Marvel. Prior ambulatory mild coronavirus disease 2019 does not increase risk of acute mountain sickness. High Alt Med Biol. 24:201-208, 2023. Background: Given its long-term morbidity, understanding how prior coronavirus disease 2019 (COVID-19) may affect acute mountain sickness (AMS) susceptibility is important for preascent risk stratification. The objective of this study was to examine if prior COVID-19 impacts risk of AMS. Materials and Methods: This was a prospective observational study conducted in Lobuje (4,940 m) and Manang (3,519 m), Nepal, from April to May 2022. AMS was defined by the 2018 Lake Louise Questionnaire criteria. COVID-19 severity was defined using the World Health Organization-developed criteria. Results: In the Lobuje cohort of 2,027, 46.2% of surveyed individuals reported history of COVID-19, with 25.7% AMS point-prevalence. There was no significant relationship between prior ambulatory mild COVID-19 and AMS (p = 0.6) or moderate AMS (p = 1.0). In the Manang cohort of 908, 42.8% reported history of COVID-19, with 14.7% AMS point-prevalence. There was no significant relationship between prior ambulatory mild COVID-19 and AMS (p = 0.3) or moderate AMS (p = 0.4). Average months since COVID-19 was 7.4 (interquartile range [IQR] 3-10) for Lobuje, 6.2 (IQR 3-6) for Manang. Both cohorts rarely exhibited moderate COVID-19 history. Conclusions: Prior ambulatory mild COVID-19 was not associated with increased risk of AMS and should not preclude high-altitude travel.

Temporal changes in biomarkers in individuals with and without acute mountain sickness following rapid ascent

BACKGROUND

Field studies have reported conflicting results regarding changes in biomarkers at high altitude. This study measured temporal changes in biomarkers and compared the differences between individuals with and without acute mountain sickness (AMS).

MATERIALS AND METHODS

This study included 34 nonacclimatized healthy participants. Ten-milliliters of blood were collected at four time points: 3 days before ascent (T0), on two successive nights at 3150 m (T1 and T2), and 2 days after descent (T3). Participants were transported by bus from 555 m to 3150 m within 3 hours. AMS was diagnosed using the self-reported Lake Louise Scoring (LLS) questionnaire.

RESULTS

Compared with T0, significant increases in E-selectin and decreases in vascular endothelial growth factor (VEGF) levels were observed at high altitude. Significantly increased C-reactive protein (CRP), monocyte chemoattractant protein-1 (MCP-1), and S100 calcium-binding protein B (S100B) levels were observed at T2, and significantly decreased vascular cell adhesion molecule-1 (VCAM-1) levels were observed at T3. Eighteen (53%) participants developed AMS. Changes in E-selectin, CRP, MCP-1, and S100B levels were independent of AMS. Relative to individuals without AMS, those with AMS had significantly higher atrial natriuretic peptide (ANP) and VCAM-1 levels and lower plasminogen activator inhibitor-1 (PAI-1) levels at T1 and higher brain natriuretic peptide and lower VEGF and PAI-1 levels at T3. LLSs were positively correlated with ANP and VCAM-1 levels and negatively correlated with PAI-1 levels measured at T1.

CONCLUSIONS

After acute ascent, individuals with and without AMS exhibited different trends in biomarkers associated with endothelial cell activation and natriuretic peptides.

IGFBP-6 Network in Chronic Inflammatory Airway Diseases and Lung Tumor Progression

The lung is an accomplished organ for gas exchanges and directly faces the external environment, consequently exposing its large epithelial surface. It is also the putative determinant organ for inducing potent immune responses, holding both innate and adaptive immune cells. The maintenance of lung homeostasis requires a crucial balance between inflammation and anti-inflammation factors, and perturbations of this stability are frequently associated with progressive and fatal respiratory diseases. Several data demonstrate the involvement of the insulin-like growth factor (IGF) system and their binding proteins (IGFBPs) in pulmonary growth, as they are specifically expressed in different lung compartments. As we will discuss extensively in the text, IGFs and IGFBPs are implicated in normal pulmonary development but also in the pathogenesis of various airway diseases and lung tumors. Among the known IGFBPs, IGFBP-6 shows an emerging role as a mediator of airway inflammation and tumor-suppressing activity in different lung tumors. In this review, we assess the current state of IGFBP-6's multiple roles in respiratory diseases, focusing on its function in the inflammation and fibrosis in respiratory tissues, together with its role in controlling different types of lung cancer.

Hypoxia briefly increases diuresis but reduces plasma volume by fluid redistribution in women

We have recently reported that hypobaric hypoxia (HH) reduces plasma volume (PV) in men by decreasing total circulating plasma protein (TCPP). Here, we investigated whether this applies to women and whether an inflammatory response and/or endothelial glycocalyx shedding could facilitate the TCCP reduction. We further investigated whether acute HH induces a short-lived diuretic response that was overlooked in our recent study, where only 24-h urine volumes were evaluated. In a strictly controlled crossover protocol, 12 women underwent two 4-day sojourns in a hypobaric chamber: one in normoxia (NX) and one in HH equivalent to 3,500-m altitude. PV, urine output, TCPP, and markers for inflammation and glycocalyx shedding were repeatedly measured. Total body water (TBW) was determined pre- and postsojourns by deuterium dilution. PV was reduced after 12 h of HH and thereafter remained 230-330 mL lower than in NX (P < 0.0001). Urine flow was 45% higher in HH than in NX throughout the first 6 h (P = 0.01) but lower during the second half of the first day (P < 0.001). Twenty-four-hour urine volumes (P ≥ 0.37) and TBW (P ≥ 0.14) were not different between the sojourns. TCPP was lower in HH than in NX at the same time points as PV (P < 0.001), but inflammatory or glycocalyx shedding markers were not consistently increased. As in men, and despite initially increased diuresis, HH-induced PV contraction in women is driven by a loss of TCPP and ensuing fluid redistribution, rather than by fluid loss. The mechanism underlying the TCPP reduction remains unclear but does not seem to involve inflammation or glycocalyx shedding.NEW & NOTEWORTHY This study is the first to investigate the mechanisms underlying plasma volume (PV) contraction in response to hypoxia in women while strictly controlling for confounders. PV contraction in women has a similar time course and magnitude as in men and is driven by the same mechanism, namely, oncotically driven redistribution rather than loss of fluid. We further report that hypoxia facilitates an increase in diuresis, that is, however, short-lived and of little relevance for PV regulation.

Steroid utility, immunotherapy, and brain tumor management: an update on conflicting therapies

Steroid use is a widely accepted practice for both the treatment and prevention of tumor-induced edema, but there are many unknowns regarding their current clinical utility with modern anti-tumor therapies. This decreases edema and relieves the symptomatic mass effect. There are clearly understood benefits and commonly accepted complications of methylprednisolone (MP) use, but the topic is recently controversial. With immunotherapy advancing, a robust immune response is crucial for full therapeutic efficacy. The immunosuppression of MP may interfere with future and current therapeutics relying on the integrity of the patient's immune system. This further emphasizes the need for alternative agents to effectively treat tumor-induced cerebral edema. This review highlights the current clinical utility of steroids to treat brain tumor-related edema and the underlying pathophysiology. It also reviews details regarding different steroid formulations and dosing. Research available regarding concurrent steroid use with immunotherapy is detailed next, followed by alternatives to steroids and barriers to their adoption. Finally, this paper discusses pre-clinical findings and emerging treatments aimed to augment or replace steroid use.

Inflammatory gene expression during acute high‐altitude exposure

Abstract

The molecular signalling pathways that regulate inflammation and the response to hypoxia share significant crosstalk and appear to play major roles in high‐altitude acclimatization and adaptation. Several studies demonstrate increases in circulating candidate inflammatory markers during acute high‐altitude exposure, but significant gaps remain in our understanding of how inflammation and immune function change at high altitude and whether these responses contribute to high‐altitude pathologies, such as acute mountain sickness. To address this, we took an unbiased transcriptomic approach, including RNA sequencing and direct digital mRNA detection with NanoString, to identify changes in the inflammatory profile of peripheral blood throughout 3 days of high‐altitude acclimatization in healthy sea‐level residents (n = 15; five women). Several inflammation‐related genes were upregulated on the first day of high‐altitude exposure, including a large increase in HMGB1 (high mobility group box 1), a damage‐associated molecular pattern (DAMP) molecule that amplifies immune responses during tissue injury. Differentially expressed genes on the first and third days of acclimatization were enriched for several inflammatory pathways, including nuclear factor‐κB and Toll‐like receptor (TLR) signalling. Indeed, both TLR4 and LY96, which encodes the lipopolysaccharide binding protein (MD‐2), were upregulated at high altitude. Finally, FASLG and SMAD7 were associated with acute mountain sickness scores and peripheral oxygen saturation levels on the first day at high altitude, suggesting a potential role of immune regulation in response to high‐altitude hypoxia. These results indicate that acute high‐altitude exposure upregulates inflammatory signalling pathways and might sensitize the TLR4 signalling pathway to subsequent inflammatory stimuli.

Key points

Inflammation plays a crucial role in the physiological response to hypoxia.

High‐altitude hypoxia exposure causes alterations in the inflammatory profile that might play an adaptive or maladaptive role in acclimatization.

In this study, we characterized changes in the inflammatory profile following acute high‐altitude exposure.

We report upregulation of novel inflammation‐related genes in the first 3 days of high‐altitude exposure, which might play a role in immune system sensitization.

These results provide insight into how hypoxia‐induced inflammation might contribute to high‐altitude pathologies and exacerbate inflammatory responses in critical illnesses associated with hypoxaemia.

Proteomic and clinical biomarkers for acute mountain sickness in a longitudinal cohort

Ascending to high-altitude by non-high-altitude natives is a well-suited model for studying acclimatization to extreme environments. Acute mountain sickness (AMS) is frequently experienced by visitors. The diagnosis of AMS mainly depends on a self-questionnaire, revealing the need for reliable biomarkers for AMS. Here, we profiled 22 AMS symptom phenotypes, 65 clinical indexes, and plasma proteomic profiles of AMS via a combination of proximity extension assay and multiple reaction monitoring of a longitudinal cohort of 53 individuals. We quantified 1069 proteins and validated 102 proteins. Via differential analysis, machine learning, and functional association analyses. We found and validated that RET played an important role in the pathogenesis of AMS. With high-accuracies (AUCs > 0.9) of XGBoost-based models, we prioritized ADAM15, PHGDH, and TRAF2 as protective, predictive, and diagnostic biomarkers, respectively. Our findings shed light on the precision medicine for AMS and the understanding of acclimatization to high-altitude environments.

Preliminary Intermittent Hypoxia Training Alleviates the Damage of Sustained Normobaric Hypoxia on Human Hematological Indexes and Cerebral White Matter

Zhang, Guangbo, Yanzhao Zhou, Zhengtao Cao, Xiang Cheng, Xiangpei Yue, Tong Zhao, Ming Zhao, Yongqi Zhao, Ming Fan, and Lingling Zhu. Preliminary intermittent hypoxia training alleviates the damage of sustained normobaric hypoxia on human hematological indexes and cerebral white matter. High Alt Med Biol. 00:000-000, 2022. Study Objectives: We aimed to examine the effects of preliminary intermittent hypoxia training (IHT) on human hematological indexes and cerebral white matter (WM) after exposure to a simulated altitude of 4,300 m. Methods: We recruited 20 young healthy volunteers. Participants were then randomized to either the IHT group (n = 10) or the control group (n = 10). We measured the physiological function of the control group at sea level and after exposure to a simulated altitude of 4,300 m, respectively. The IHT group performed the above tests at three time points: before and after hypoxia training, and after exposure to a simulated altitude of 4,300 m, respectively. Results: We found that mean SpO₂ during day 10 of hypoxia training showed a significant increase compared with mean SpO₂ on day 1 (88.3% ± 1.5% vs. 90.0% ± 1.6%, p < 0.05), and erythrocyte P₅₀ of post-training was significantly increased compared with pretraining (37.8 ± 2.9 mmHg vs. 45.9 ± 6.4 mmHg, p < 0.05). Mean SpO₂ measures after acute exposure to high altitude exhibited a significant difference, with the IHT group showing significantly greater SpO₂ than the control group (73.8% ± 3.7% vs. 77.4% ± 3.2%, p < 0.05), and the Lake Louise Score was also lower than the control group (2.55 ± 2.1 vs. 6.67 ± 2.5, p < 0.05). After daily IHT, brain-derived neurotrophic factor plasma levels of participants in the IHT group did not change but significantly increased in response to high-altitude hypoxia (103.5% ± 70.4% vs. 29.7% ± 73.2%, p < 0.05). Interleukin-10 (IL-10) plasma level did not change before and after IHT in the IHT group, whereas the IL-10 plasma level of the control group after high-altitude exposure was significantly higher. Furthermore, we found that fractional anisotropy values in the left corticospinal tract and splenium of the corpus callosum in the IHT group were significantly higher than those in the control group after high-altitude hypoxia. Conclusions: These results demonstrate that IHT alleviates the damage of sustained normobaric hypoxia on human hematological indexes and cerebral WM.

Immunomodulatory Potential of Diuretics

In this review, diuretics and their immunomodulatory functions are described. The effects on the immune response of this group of drugs are reported in patients suffering from hypertension and under experimental conditions involving animal models and cell line studies. The pathogenesis of hypertension is strongly connected to chronic inflammation. The vast majority of diuretics modulate the immune response, changing it in favor of the anti-inflammatory response, but depending on the drug, these effects may differ. This topic is significantly important in medical practice regarding the treatment of patients who have coexisting diseases with chronic inflammatory pathogenesis, including hypertension or chronic heart failure. In patients with metabolic syndrome, allergies, or autoimmune disorders, the anti-inflammatory effect is favorable, because of the overstimulation of their immune system. Otherwise, in the geriatric population, it is important to find the proper anti- and pro-inflammatory balance to avoid an enhancement of immune response suppression, which can result in reducing the risk of serious infections that can occur due to the age-diminished function of the immune system. This article is intended to facilitate the selection of an antihypertensive drug that depends on the patient's immune situation.

Acute Mountain Sickness Following Incremental Trekking to High Altitude: Correlation With Plasma Vascular Endothelial Growth Factor Levels and the Possible Effects of Dexamethasone and Acclimatization Following Re-exposure

Purpose: The recognition and treatment of high-altitude illness (HAI) is increasingly important in global emergency medicine. High altitude related hypobaric hypoxia can lead to acute mountain sickness (AMS), which may relate to increased expression of vascular endothelial growth factor (VEGF), and subsequent blood-brain barrier (BBB) compromise. This study aimed to establish the relationship between AMS and changes in plasma VEGF levels during a high-altitude ascent. VEGF level changes with dexamethasone, a commonly used AMS medication, may provide additional insight into AMS.

Methods: Twelve healthy volunteers ascended Mt Fuji (3,700 m) and blood samples were obtained at distinct altitudes for VEGF analysis. Oxygen saturation (SPO2) measurements were also documented at the same time-point. Six out of the 12 study participants were prescribed dexamethasone for a second ascent performed 48 h later, and blood was again collected to establish VEGF levels.

Results: Four key VEGF observations could be made based on the data collected: (i) the baseline VEGF levels between the two ascents trended upwards; (ii) those deemed to have AMS in the first ascent had increased VEGF levels (23.8–30.3 pg/ml), which decreased otherwise (23.8–30.3 pg/ml); (iii) first ascent AMS participants had higher VEGF level variability for the second ascent, and similar to those not treated with dexamethasone; and (iv) for the second ascent dexamethasone participants had similar VEGF levels to non-AMS first ascent participants, and the variability was lower than for first ascent AMS and non-dexamethasone participants. SPO2 changes were unremarkable, other than reducing by around 5% irrespective of whether measurement was taken for the first or second ascent.

Conclusion: First ascent findings suggest a hallmark of AMS could be elevated VEGF levels. The lack of an exercise-induced VEGF level change strengthened the notion that elevated plasma VEGF was brain-derived, and related to AMS.

Association of ischemic electrocardiographic changes in high-altitude areas with coronary angiography

BACKGROUND

Soldiers native to lowlands, while sojourning at high altitude (HA), are referred to tertiary care centers with electrocardiographic (ECG) abnormalities. Exposure to HA may precipitate myocardial ischemia in subjects with underlying coronary artery disease (CAD). Conversely, it may produce physiological ECG changes mimicking those of CAD, causing a diagnostic dilemma. This study sought to correlate the presence of CAD on coronary angiography (CAG) with a putative diagnosis of CAD based on clinical findings and ECG.

METHODS

A prospective study was conducted on patient's from HA areas, referred for evaluation for CAD to a single center at near-sea-level. Thirty-five minimally symptomatic/asymptomatic soldiers with ECG changes suggestive of CAD, underwent CAG. Correlation was sought between ECG and CAG evidence of CAD.

RESULTS

The association of CAD on CAG with clinical and ECG diagnosis of CAD was not significant, 4 of the 35 soldiers (11.4%) showing CAG evidence of CAD (chi square 3.849, p = 0.697). The association between symptoms and coronary artery lesions was, also, not significant, only four of twenty-three (17.4%) minimally symptomatic subjects having CAD on CAG.

CONCLUSION

Insignificant numbers of previously healthy persons, who present with minimal symptoms and ECG changes suggestive of CAD while sojourning at HA, have coronary artery involvement on CAG. Those with incidental ECG changes, without symptomatology, do not have CAD on CAG.

The impact of hypoxia on blood-brain, blood-CSF, and CSF-brain barriers

The blood-brain barrier (BBB), blood-cerebrospinal fluid (CSF) barrier (BCSFB), and CSF-brain barriers (CSFBB) are highly regulated barriers in the central nervous system comprising complex multicellular structures that separate nerves and glia from blood and CSF, respectively. Barrier damage has been implicated in the pathophysiology of diverse hypoxia-related neurological conditions, including stroke, multiple sclerosis, hydrocephalus, and high-altitude cerebral edema. Much is known about the damage to the BBB in response to hypoxia, but much less is known about the BCSFB and CSFBB. Yet, it is known that these other barriers are implicated in damage after hypoxia or inflammation. In the 1950s, it was shown that the rate of radionucleated human serum albumin passage from plasma to CSF was five times higher during hypoxic than normoxic conditions in dogs, due to BCSFB disruption. Severe hypoxia due to administration of the bacterial toxin lipopolysaccharide is associated with disruption of the CSFBB. This review discusses the anatomy of the BBB, BCSFB, and CSFBB and the impact of hypoxia and associated inflammation on the regulation of those barriers.

Gain-of-function Tibetan PHD2D4E;C127S variant suppresses monocyte function: A lesson in inflammatory response to inspired hypoxia

Background

We have previously described an evolutionarily selected Tibetan prolyl hydroxylase-2 (PHD2^D4E;C127S) variant that degrades the hypoxia-inducible factor (HIFα) more efficiently and protects these highlanders from hypoxia-triggered elevation in haemoglobin concentration. High altitude is known to cause acute mountain sickness (AMS) and high-altitude pulmonary edema (HAPE) in a section of rapidly ascending non-acclimatised lowlanders. These morbidities are often accompanied by inflammatory response and exposure to hypobaric hypoxia is presumed to be the principal causative agent. We have investigated whether PHD2^D4E;C127S variant is associated with prevention of hypoxia-mediated inflammatory milieu in Tibetan highlanders and therefore identify a potential target to regulate inflammation.

Methods

We genotyped the Tibetans using DNA isolated from whole blood. Thereafter immunophenotying was performed on PBMCs from homozygous PHD2^D4E;C127S and PHD2^WT individuals using flow cytometry. RNA isolated from these individuals was used to evaluate the peripheral level of important transcripts associated with immune as well as hypoxia response employing the nCounter technology. The ex-vivo findings were validated by generating monocytic cell lines (U937 cell line) expressing PHD2^D4E;C127S and PHD2^WT variants post depletion of endogenous PHD2. We had also collected whole blood samples from healthy travellers and travellers afflicted with AMS and HAPE to evaluate the significance of our ex-vivo and in vitro findings. Hereafter, we also attempted to resolve hypoxia-triggered inflammation in vitro as well as in vivo by augmenting the function of PHD2 using alpha-ketoglutarate (αKG), a co-factor of PHD2.

Findings

We report that homozygous PHD2^D4E;C127S highlanders harbour less inflammatory and patrolling monocytes in circulation as compared to Tibetan PHD2^WT highlanders. In response to in vitro hypoxia, secretion of IL6 and IL1β from PHD2^D4E;C127S monocytes, and their chemotactic response compared to the PHD2^WT are compromised, corresponding to the down-modulated expression of related signalling molecules RELA, JUN, STAT1, ATF2 and CXCR4. We verified these functional outcomes in monocytic U937 cell line engineered to express PHD2^D4E;C127S and confirmed the down-modulation of the signalling molecules at protein level under hypoxia. In contrast, non-Tibetan sojourners with AMS and HAPE at high altitude (3,600 m above sea level) displayed significant increase in these inflammatory parameters. Our data henceforth underline the role of gain-of-function of PHD2 as the rate limiting factor to harness hyper-activation of monocytes in hypoxic environment. Therefore upon pre-treatment with αKG, we observed diminished inflammatory response of monocytes in vitro and reduction in leukocyte infiltration to the lungs in mice exposed to normobaric hypoxia.

Interpretation

Our report suggests that gain-of-function PHD2 ^D4E;C127S variant can therefore protect against inflammation elicited by hypobaric hypoxia. Augmentation of PHD2 activity therefore may be an important method to alleviate inflammatory response to inspired hypoxia.

Funding

This study is supported by the Department of Biotechnology, Government of India.

Hypoxia and Inflammation: Insights From High-Altitude Physiology

The key regulators of the transcriptional response to hypoxia and inflammation (hypoxia inducible factor, HIF, and nuclear factor-kappa B, NF-κB, respectively) are evolutionarily conserved and share significant crosstalk. Tissues often experience hypoxia and inflammation concurrently at the site of infection or injury due to fluid retention and immune cell recruitment that ultimately reduces the rate of oxygen delivery to tissues. Inflammation can induce activity of HIF-pathway genes, and hypoxia may modulate inflammatory signaling. While it is clear that these molecular pathways function in concert, the physiological consequences of hypoxia-induced inflammation and how hypoxia modulates inflammatory signaling and immune function are not well established. In this review, we summarize known mechanisms of HIF and NF-κB crosstalk and highlight the physiological consequences that can arise from maladaptive hypoxia-induced inflammation. Finally, we discuss what can be learned about adaptive regulation of inflammation under chronic hypoxia by examining adaptive and maladaptive inflammatory phenotypes observed in human populations at high altitude. We aim to provide insight into the time domains of hypoxia-induced inflammation and highlight the importance of hypoxia-induced inflammatory sensitization in immune function, pathologies, and environmental adaptation.

High-altitude cerebral edema: its own entity or end-stage acute mountain sickness?

High-altitude cerebral edema (HACE) and acute mountain sickness (AMS) are neuropathologies associated with rapid exposure to hypoxia. However, speculation remains regarding the exact etiology of both HACE and AMS and whether they share a common mechanistic pathology. This review outlines the basic principles of HACE development, highlighting how edema could develop from 1) a progression from cytotoxic swelling to ionic edema or 2) permeation of the blood brain barrier (BBB) with or without ionic edema. Thereafter, discussion turns to the available neuroimaging literature in the context of cytotoxic, ionic, or vasogenic edema in both HACE and AMS. Although HACE is clearly caused by an increase in brain water of ionic and/or vasogenic origin, there is very little evidence that this type of edema is present when AMS develops. However, cerebral vasodilation, increased intracranial blood volume, and concomitant intracranial fluid shifts from the extracellular to the intracellular space, as interpreted from changes in diffusion indices within white matter, are observed consistently in persons acutely exposed to hypoxia and with AMS. Therefore, herein we explore the idea that intracellular swelling occurs alongside AMS, and is a critical precursor to extracellular ionic edema formation. We propose that this process produces a subtle modulation of the BBB, which either together with or independent of vasogenic edema provides a transvascular segue from the end-stage of AMS to HACE. Ultimately, this review seeks to shed light on the possible processes underlying HACE pathophysiology, and thus highlights potential avenues for future prevention and treatment.

High-altitude illnesses: Old stories and new insights into the pathophysiology, treatment and prevention

Areas at high-altitude, annually attract millions of tourists, skiers, trekkers, and climbers. If not adequately prepared and not considering certain ascent rules, a considerable proportion of those people will suffer from acute mountain sickness (AMS) or even from life-threatening high-altitude cerebral (HACE) or/and pulmonary edema (HAPE). Reduced inspired oxygen partial pressure with gain in altitude and consequently reduced oxygen availability is primarily responsible for getting sick in this setting. Appropriate acclimatization by slowly raising the hypoxic stimulus (e.g., slow ascent to high altitude) and/or repeated exposures to altitude or artificial, normobaric hypoxia will largely prevent those illnesses. Understanding physiological mechanisms of acclimatization and pathophysiological mechanisms of high-altitude diseases, knowledge of symptoms and signs, treatment and prevention strategies will largely contribute to the risk reduction and increased safety, success and enjoyment at high altitude. Thus, this review is intended to provide a sound basis for both physicians counseling high-altitude visitors and high-altitude visitors themselves.

The oxygen cascade in patients treated with hemodialysis and native high-altitude dwellers: lessons from extreme physiology to benefit patients with end-stage renal disease

Patients treated with hemodialysis (HD) repeatedly undergo intradialytic low arterial oxygen saturation and low central venous oxygen saturation, reflecting an imbalance between upper body systemic oxygen supply and demand, which are associated with increased mortality. Abnormalities along the entire oxygen cascade, with impaired diffusive and convective oxygen transport, contribute to the reduced tissue oxygen supply. HD treatment impairs pulmonary gas exchange and reduces ventilatory drive, whereas ultrafiltration can reduce tissue perfusion due to a decline in cardiac output. In addition to these factors, capillary rarefaction and reduced mitochondrial efficacy can further affect the balance between cellular oxygen supply and demand. Whereas it has been convincingly demonstrated that a reduced perfusion of heart and brain during HD contributes to organ damage, the significance of systemic hypoxia remains uncertain, although it may contribute to oxidative stress, systemic inflammation, and accelerated senescence. These abnormalities along the oxygen cascade of patients treated with HD appear to be diametrically opposite to the situation in Tibetan highlanders and Sherpa, whose physiology adapted to the inescapable hypobaric hypoxia of their living environment over many generations. Their adaptation includes pulmonary, vascular, and metabolic alterations with enhanced capillary density, nitric oxide production, and mitochondrial efficacy without oxidative stress. Improving the tissue oxygen supply in patients treated with HD depends primarily on preventing hemodynamic instability by increasing dialysis time/frequency or prescribing cool dialysis. Whether dietary or pharmacological interventions, such as the administration of L-arginine, fermented food, nitrate, nuclear factor erythroid 2-related factor 2 agonists, or prolyl hydroxylase 2 inhibitors, improve clinical outcome in patients treated with HD warrants future research.

Influence of Zinc on the Acute Changes in Erythropoietin and Proinflammatory Cytokines with Hypoxia

Baranauskas, Marissa N., Joseph Powell, Alyce D. Fly, Bruce J. Martin, Timothy D. Mickleborough, Hunter L. Paris, and Robert F. Chapman. Influence of zinc on the acute changes in erythropoietin and proinflammatory cytokines with hypoxia. High Alt Med Biol. 22: 148-156, 2021. Background: Considerable, unexplained, interindividual variability characterizes the erythropoietin (EPO) response to hypoxia, which can impact hematological acclimatization for individuals sojourning to altitude. Zinc supplementation has the potential to alter EPO by attenuating increases in inflammation and oxidative stress. Yet, the application of such an intervention has not been evaluated in humans. In this proof-of-concept study, we aimed to evaluate the EPO and inflammatory responses to acute hypoxia in human participants following chronic zinc supplementation. Methods: Nine physically active participants (men n = 5, women n = 4, age 28 ± 4 years, height 176 ± 11 cm, mass 77 ± 21 kg) were exposed to 12 hours of normobaric hypoxia simulating an altitude of 3,000 m (F_iO₂ = 0.14) before and after 8 weeks of supplementation with 40 mg/day of elemental zinc from picolinate. Blood samples for subsequent analysis of serum zinc, EPO, superoxide dismutase (extracellular superoxide dismutase [EC-SOD]), C-reactive protein (CRP), and proinflammatory cytokines were obtained pre- and postsupplementation and exposure to hypoxia. Results: After zinc supplementation, EPO increased by 64.9 ± 36.0% (mean ± standard deviation) following 12 hours of hypoxia, but this response was not different from presupplementation (70.8 ± 46.1%). Considerable interindividual (range: -1% to +208%) variability was apparent in the acute EPO response. While most markers of inflammation did not change with hypoxia, interleukin-6 concentrations increased from 1.17 ± 0.05 to 1.97 ± 0.32 pg/ml during the final 6 hours. The acute EPO response at 12 hours was not related to changes in serum zinc, EC-SOD, CRP, or proinflammatory cytokines. Conclusions: Zinc supplementation does not influence the acute EPO or inflammatory response with short-term exposure to moderate levels of normobaric hypoxia (3,000 m) in apparently healthy young adults.

Differences in Tolerance to Hypoxia: Physiological, Biochemical, and Molecular-Biological Characteristics

Hypoxia plays an important role in the development of many infectious, inflammatory, and tumor diseases. The predisposition to such disorders is mostly provided by differences in basic tolerance to oxygen deficiency, which we discuss in this review. Except the direct exposure of different-severity hypoxia in decompression chambers or in highland conditions, there are no alternative methods for determining organism tolerance. Due to the variability of the detection methods, differences in many parameters between tolerant and susceptible organisms are still not well-characterized, but some of them can serve as biomarkers of susceptibility to hypoxia. At the moment, several potential biomarkers in conditions after hypoxic exposure have been identified both in experimental animals and humans. The main potential biomarkers are Hypoxia-Inducible Factor (HIF)-1, Heat-Shock Protein 70 (HSP70), and NO. Due to the different mechanisms of various high-altitude diseases, biomarkers may not be highly specific and universal. Therefore, it is extremely important to conduct research on hypoxia susceptibility biomarkers. Moreover, it is important to develop a method for the evaluation of organisms' basic hypoxia tolerance without the necessity of any oxygen deficiency exposure. This can contribute to new personalized medicine approaches' development for diagnostics and the treatment of inflammatory and tumor diseases, taking into account hypoxia tolerance differences.

No Relevant Analogy Between COVID-19 and Acute Mountain Sickness

Berger, Marc Moritz, Peter H. Hackett, and Peter Bärtsch. No relevant analogy between COVID-19 and acute mountain sickness. High Alt Med Biol. 21:315-318, 2020.-Clinicians and scientists have suggested therapies for coronavirus disease-19 (COVID-19) that are known to be effective for other medical conditions. A recent publication suggests that pathophysiological mechanisms underlying acute mountain sickness (a syndrome of nonspecific neurological symptoms typically experienced by nonacclimatized individuals at altitudes >2500 m) may overlap with the mechanisms causing COVID-19. In this short review, we briefly evaluate this mistaken analogy and demonstrate that this concept is not supported by scientific evidence.

Patchy Vasoconstriction Versus Inflammation: A Debate in the Pathogenesis of High Altitude Pulmonary Edema

High altitude pulmonary edema (HAPE) occurs in individuals rapidly ascending at altitudes greater than 2,500 m within one week of arrival. HAPE is characterized by orthopnea, breathlessness at rest, cough, and pink frothy sputum. Several mechanisms to describe the pathophysiology of HAPE have been proposed in different kinds of literature where most of the mechanisms are reported to be activated before a drop in oxygen saturation levels. The majority of the current studies favor diffuse hypoxic pulmonary vasoconstriction (HPV) as a pathophysiological basis for HAPE. However, some of the studies described inflammation in the lungs and genetic basis as the pathophysiology of HAPE. So, there is a major disagreement regarding the exact pathophysiology of HAPE in the current literature, which raises a question as to what is the exact pathophysiology of HAPE. So, we reviewed 23 different articles which include clinical trials, review articles, randomized controlled trials (RCTs), and original research published from 2010 to 2020 to find out widely accepted pathophysiology of HAPE. In our study, we found out sympathetic stimulation, reduced nitric oxide (NO) bioavailability, increased endothelin, increased pulmonary artery systolic pressure (PASP) resulting in diffuse HPV, and reduced reabsorption of interstitial fluid to be the most important determinants for the development of HAPE. Similarly, with the evaluation of the role of inflammatory mediators like C-reactive protein (CRP) and interleukin (IL-6), we found out that inflammation in the lungs seems to modulate but not cause the process of development of HAPE. Genetic basis as evidenced by increased transcription of certain gene products seems to be another promising hypoxic change leading to HAPE. However, comprehensive studies are still needed to decipher the pathophysiology of HAPE in greater detail.

Effect of 8 days of exercise-heat acclimation on aerobic exercise performance of men in hypobaric hypoxia

Exercise-heat acclimation (EHA) induces adaptations that improve tolerance to heat exposure. Whether adaptations from EHA can also alter responses to hypobaric hypoxia (HH) conditions remains unclear. This study assessed whether EHA can alter time-trial performance and/or incidence of acute mountain sickness (AMS) during HH exposure. Thirteen sea-level (SL) resident men [SL peak oxygen consumption (V̇o_2peak) 3.19 ± 0.43 L/min] completed steady-state exercise, followed by a 15-min cycle time trial and assessment of AMS before (HH1; 3,500 m) and after (HH2) an 8-day EHA protocol [120 min; 5 km/h; 2% incline; 40°C and 40% relative humidity (RH)]. EHA induced lower heart rate (HR) and core temperature and plasma volume expansion. Time-trial performance was not different between HH1 and HH2 after 2 h (106.3 ± 23.8 vs. 101.4 ± 23.0 kJ, P = 0.71) or 24 h (107.3 ± 23.4 vs. 106.3 ± 20.8 kJ, P > 0.9). From HH1 to HH2, HR and oxygen saturation, at the end of steady-state exercise and time-trial tests at 2 h and 24 h, were not different (P > 0.05). Three of 13 volunteers developed AMS during HH1 but not during HH2, whereas a fourth volunteer only developed AMS during HH2. Heat shock protein 70 was not different from HH1 to HH2 at SL [1.9 ± 0.7 vs. 1.8 ± 0.6 normalized integrated intensities (NII), P = 0.97] or after 23 h (1.8 ± 0.4 vs. 1.7 ± 0.5 NII, P = 0.78) at HH. Our results indicate that this EHA protocol had little to no effect-neither beneficial nor detrimental-on exercise performance in HH. EHA may reduce AMS in those who initially developed AMS; however, studies at higher elevations, having higher incidence rates, are needed to confirm our findings.

Tetrahydrocurcumin mitigates acute hypobaric hypoxia-induced cerebral oedema and inflammation through the NF-κB/VEGF/MMP-9 pathway

High-altitude cerebral oedema (HACE) is a potentially fatal manifestation of high-altitude sickness and is caused partly by inflammation and the blood-brain barrier disruption. Tetrahydrocurcumin (THC) has been reported to exert effective antioxidative and anti-inflammatory effects; This study sought to elucidate the underlying mechanism of THC in mitigating HACE using a mouse model. Our results revealed that prophylactic administration of THC (40 mg/kg) for 3 days significantly alleviated the increase in brain water content (BWC), interleukin-1β (IL-1β) and TNF-α levels caused by acute hypobaric hypoxia (AHH). Additionally, superoxide dismutase (SOD) activity was increased by THC to enhance the ability to resist hypoxia. Histological and ultrastructural analysis of the cerebrum revealed that THC administration mitigated AHH-induced pericellular oedema and reduced the perivascular space, resulting in the simultaneous remission of oedema and protection of mitochondria in the cerebrum. In vitro, astrocytes exposed to hypoxia (4% O₂ ) for 24 hr exhibited and increase in IL-1β expression followed by an increase in vascular endothelial growth factor (VEGF) levels. Furthermore, THC administration remarkably downregulated VEGF, matrix metallopeptidase-9 (MMP-9), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) expression, both in vivo and in vitro. Our data highlight the potential prophylactic activity of THC in HACE, it effectively mitigates AHH-induced cerebral oedema and inflammation is associated with the inhibition of the NF-κB/ VEGF/MMP-9 pathways.

Reduced inflammatory and phagocytotic responses following normobaric hypoxia exercise despite evidence supporting greater immune challenge

This study examined changes in immune markers following sustained treadmill exercise in normobaric hypoxia. Ten subjects performed 1 h of treadmill exercise (65% maximal oxygen uptake) under normoxic (NORM: fraction of inspired oxygen (F_IO₂) = 20.9%) and normobaric hypoxic (HYP: F_IO₂ = 13.5%) conditions. Blood samples, collected before, after (Post), 1 h after (1-Post), and 4 h after (4-Post) exercise, were assayed for plasma cytokines (interleukin (IL)-1RA/IL-1β/IL-8/tumor necrosis factor alpha (TNF-α)) and markers of leukocyte activation (macrophage inflammatory protein-1β (MIP-1β)/myeloperoxidase (MPO)/soluble intercellular adhesion molecule-1 (sICAM-1)) using ELISA. Pro- to anti-inflammatory cytokine ratios (TNF-α/IL-1RA; IL-1β/IL-1RA) were calculated. Peripheral blood mononuclear cells (PBMC) were analyzed for changes in inflammatory status (phosphorylated nuclear factor kappa B/nuclear factor kappa B) using Western Blot. Data were analyzed with 2-way (condition × time) repeated-measure ANOVAs with Newman-Keuls post hoc tests. MIP-1β was elevated at 1-Post HYP exercise (+11%; p < 0.01) but did not increase following exercise in NORM. TNF-α/IL-1RA and IL-1β/IL-1RA ratios were both reduced (p < 0.05) following HYP exercise (-16% and -52%, respectively, at 1-Post and -7% and -32%, respectively, at 4-Post). IL-8 increased (p < 0.05) at Post and 1-Post NORM (+33% and +57%, respectively) and HYP (+60% and +83%, respectively) exercise, but was not different between conditions (p > 0.05). Interestingly, plasma sICAM-1 did not increase (p > 0.05) following NORM exercise but was increased (p < 0.05) at Post (+17%), 1-Post (+16%), and 4-Post (+14%) HYP exercise. There was also a delayed peak in plasma MPO concentrations following HYP exercise and PBMC exhibited a reduced (p < 0.05) inflammatory capacity at Post (-38%) and 1-Post (-49%). Novelty Following HYP exercise, participants exhibited (i) circulatory bias towards anti-inflammation; (ii) elevated sICAM; (iii) delayed peak in plasma MPO; and (iv) diminished inflammatory response in PBMC. Collectively, these data suggest immunosuppression. This is undesirable, given that elevated MIP-1β (reported here) and elevated intestinal fatty acid binding protein (reported previously) both suggest higher lipopolysaccharide concentrations following HYP exercise.

The Role of Salivary miR-134-3p and miR-15b-5p as Potential Non-invasive Predictors for Not Developing Acute Mountain Sickness

Background

Acute mountain sickness (AMS) is a crucial public health problem for high altitude travelers. Discriminating individuals who are not developing (AMS resistance, AMS−) from developing AMS (AMS susceptibility, AMS+) at baseline would be vital for disease prevention. Salivary microRNAs (miRNAs) have emerged as promising non-invasive biomarkers for various diseases. Thus, the aim of our study was to identify the potential roles of salivary miRNAs in identifying AMS− individuals pre-exposed to high altitude. Moreover, as hypoxia is the triggering factor for AMS, present study also explored the association between cerebral tissue oxygenation indices (TOI) and AMS development after exposed to high altitude, which was the complementary aim.

Methods

In this study, 124 healthy men were recruited, and were exposed at simulated high altitude of 4,500 m. Salivary miR-134-3p and miR-15b-5p were measured at baseline (200 m). AMS was diagnosed based on Lake Louise Scoring System at 4,500 m. The measurements of physiological parameters were recorded at both the altitudes.

Results

Salivary miR-134-3p and miR-15b-5p were significantly up-regulated in AMS− individuals as compared to the AMS+ (p < 0.05). In addition, the combination of these miRNAs generated a high power for discriminating the AMS− from AMS+ at baseline (AUC: 0.811, 95% CI: 0.731−0.876, p < 0.001). Moreover, the value of cerebral TOIs at 4,500 m were significantly higher in AMS− individuals, compared to AMS+ (p < 0.01).

Conclusion

Our study reveals for the first time that salivary miR-134-3p and miR-15b-5p can be used as non-invasive biomarkers for predicting AMS− individuals pre-exposed to high altitude.

Transcriptional profiling in the livers of rats after hypobaric hypoxia exposure

Ascent to high altitude feels uncomfortable in part because of a decreased partial pressure of oxygen due to the decrease in barometric pressure. The molecular mechanisms causing injury in liver tissue after exposure to a hypoxic environment are widely unknown. The liver must physiologically and metabolically change to improve tolerance to altitude-induced hypoxia. Since the liver is the largest metabolic organ and regulates many physiological and metabolic processes, it plays an important part in high altitude adaptation. The cellular response to hypoxia results in changes in the gene expression profile. The present study explores these changes in a rat model. To comprehensively investigate the gene expression and physiological changes under hypobaric hypoxia, we used genome-wide transcription profiling. Little is known about the genome-wide transcriptional response to acute and chronic hypobaric hypoxia in the livers of rats. In this study, we carried out RNA-Sequencing (RNA-Seq) of liver tissue from rats in three groups, normal control rats (L), rats exposed to acute hypobaric hypoxia for 2 weeks (W2L) and rats chronically exposed to hypobaric hypoxia for 4 weeks (W4L), to explore the transcriptional profile of acute and chronic mountain sickness in a mammal under a controlled time-course. We identified 497 differentially expressed genes between the three groups. A principal component analysis revealed large differences between the acute and chronic hypobaric hypoxia groups compared with the control group. Several immune-related and metabolic pathways, such as cytokine-cytokine receptor interaction and galactose metabolism, were highly enriched in the KEGG pathway analysis. Similar results were found in the Gene Ontology analysis. Cogena analysis showed that the immune-related pathways were mainly upregulated and enriched in the acute hypobaric hypoxia group.

The plasma level changes of VEGF and soluble VEGF receptor-1 are associated with high-altitude pulmonary edema

Hypoxia-induced plasma levels of VEGF and sFlt-1 are responsible for increased vascular permeability occurred in both brain and pulmonary edema. Currently, it remains unclear the exact roles of VEGF and sFlt-1 in High Altitude Pulmonary Edema (HAPE) pathogenesis. In this study, plasma levels of VEGF and sFlt-1 from 10 HAPE and 10 non-HAPE subjects were measured and compared. The results showed that plasma levels of both VEGF and sFlt-1 in HAPE patients were significantly increased as compared to the non-HAPE group. Interestingly, increased plasma levels of these two protein factors were markedly reduced after treatments. As compared to VEGF, sFlt-1 was much more affected by hypoxia and treatments, suggesting this factor was a key factor contributed to HAPE pathogenesis. Importantly, the ratio of sFlt-1 and VEGF in group of either non-HAPE or HAPE after recovery was significantly lower than the ratio in HAPE patients prior to treatments. Our findings suggested that sFlt-1 was a key factor that involved in HAPE pathogenesis and the sFlt-1/VEGF ratio could be used as a sensitive diagnostic marker for HAPE. J. Med. Invest. 65:64-68, February, 2018.

Increased Cytokines at High Altitude: Lack of Effect of Ibuprofen on Acute Mountain Sickness, Physiological Variables, or Cytokine Levels

Lundeberg, Jenny, John R. Feiner, Andrew Schober, Jeffrey W. Sall, Helge Eilers, and Philip E. Bickler. Increased cytokines at high altitude: lack of effect of ibuprofen on acute mountain sickness, physiological variables or cytokine levels. High Alt Med Biol. 19:249-258, 2018.

INTRODUCTION

There is no consensus on the role of inflammation in high-altitude acclimatization.

AIMS

To determine the effects of a nonsteroidal anti-inflammatory drug (ibuprofen 400 mg every 8 hours) on blood cytokines, acclimatization, acute mountain sickness (AMS, Lake Louise Score), and noninvasive oxygenation in brain and muscle in healthy volunteers.

MATERIALS AND METHODS

In this double-blind study, 20 volunteers were randomized to receive ibuprofen or placebo at sea level and for 48 hours at 3800 m altitude. Arterial, brain, and leg muscle saturation with near infrared spectroscopy, pulse oximetry, and heart rate were measured. Blood samples were collected for cytokine levels and cytokine gene expression.

RESULTS

All of the placebo subjects and 8 of 11 ibuprofen subjects developed AMS at altitude (p = 0.22, comparing placebo and ibuprofen). On arrival at altitude, the oxygen saturation as measured by pulse oximetry (S_pO₂) was 84.5% ± 5.4% (mean ± standard deviation). Increase in blood interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α), and granulocyte-macrophage colony-stimulating factor (GM-CSF) levels occurred comparably in the placebo and ibuprofen groups (all not significant, univariate test by Wilcoxon rank sum). Increased IL-6 was associated with higher AMS scores (p = 0.002 by Spearman rank correlation). However, we found no difference or association in AMS score and blood or tissue oxygenation between the ibuprofen and placebo groups.

CONCLUSIONS

We found that ibuprofen, at the package-recommended adult dose, did not have a significant effect on altitude-related increases in cytokines, AMS scores, blood, or tissue oxygenation in a population of healthy subjects with a high incidence of AMS.

Plasma proteomic study of acute mountain sickness susceptible and resistant individuals

Although extensive studies have focused on the development of acute mountain sickness (AMS), the exact mechanisms of AMS are still obscure. In this study, we used isobaric tags for relative and absolute quantitation (iTRAQ) proteomic analysis to identify novel AMS-associated biomarkers in human plasma. After 9 hours of hypobaric hypoxia the abundance of proteins related to tricarboxylic acid (TCA) cycle, glycolysis, ribosome, and proteasome were significantly reduced in AMS resistant (AMS-) group, but not in AMS susceptible (AMS+) group. This suggested that AMS- individuals could reduce oxygen consumption via repressing TCA cycle and glycolysis, and reduce energy consumption through decreasing protein degradation and synthesis compared to AMS+ individuals after acute hypoxic exposure. The inflammatory response might be decreased resulting from the repressed TCA cycle. We propose that the ability for oxygen consumption reduction may play an important role in the development of AMS. Our present plasma proteomic study in plateau of the Han Chinese volunteers gives new data to address the development of AMS and potential AMS correlative biomarkers.

Hematological Risk Factors for High-Altitude Headache in Chinese Men Following Acute Exposure at 3,700 m

Background: High-altitude headache (HAH) is a notably common disorder affecting the daily life of travelers ascending to high altitude. Hematological parameters are important clinical examinations for various diseases. Today, hematological characteristics of HAH remain unrevealed. Above all, we aimed to ascertain hematological characteristics and independent risk factors/predictors associated with HAH before and after exposure at 3,700 m.

Methods: Forty five healthy men were enrolled in present study. Demographic and clinical data, physiological and hematological parameters were collected 3 days before the ascent and after acute exposure at 3,700 m.

Results: HAH patients featured significantly lower white blood cell count (WBC), neutrophil count (NEU#) and percentage (NEU%), and higher percentage of lymphocyte (LYM%) at 3,700 m and significantly lower NEU#, reticulocyte count (RET#) and percentage (RET%) at sea level (all P < 0.05). HAH severity was significantly and negatively associated with WBC, NEU#, and NEU% at 3,700 m and RET# at sea level, whereas was positively associated with LYM% at 3,700 m (all P < 0.05). Moreover, we have found that RET# at sea level and NEU% at 3,700 m was an independent predictor and risk factor for HAH, respectively.

Conclusion: The present study is the first to examine the hematological characteristics of HAH. Furthermore, lower RET# at sea level and lower NEU% at 3,700 m is a novel independent predictor and risk factor for HAH, respectively.

Interventions for preventing high altitude illness: Part 1. Commonly-used classes of drugs

BACKGROUND

High altitude illness (HAI) is a term used to describe a group of cerebral and pulmonary syndromes that can occur during travel to elevations above 2500 metres (8202 feet). Acute hypoxia, acute mountain sickness (AMS), high altitude cerebral oedema (HACE) and high altitude pulmonary oedema (HAPE) are reported as potential medical problems associated with high altitude. In this review, the first in a series of three about preventive strategies for HAI, we assess the effectiveness of six of the most recommended classes of pharmacological interventions.

OBJECTIVES

To assess the clinical effectiveness and adverse events of commonly-used pharmacological interventions for preventing acute HAI.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OVID), Embase (OVID), LILACS and trial registries in January 2017. We adapted the MEDLINE strategy for searching the other databases. We used a combination of thesaurus-based and free-text terms to search.

SELECTION CRITERIA

We included randomized-controlled and cross-over trials conducted in any setting where commonly-used classes of drugs were used to prevent acute HAI.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as expected by Cochrane.

MAIN RESULTS

We included 64 studies (78 references) and 4547 participants in this review, and classified 12 additional studies as ongoing. A further 12 studies await classification, as we were unable to obtain the full texts. Most of the studies were conducted in high altitude mountain areas, while the rest used low pressure (hypobaric) chambers to simulate altitude exposure. Twenty-four trials provided the intervention between three and five days prior to the ascent, and 23 trials, between one and two days beforehand. Most of the included studies reached a final altitude of between 4001 and 5000 metres above sea level. Risks of bias were unclear for several domains, and a considerable number of studies did not report adverse events of the evaluated interventions. We found 26 comparisons, 15 of them comparing commonly-used drugs versus placebo. We report results for the three most important comparisons: Acetazolamide versus placebo (28 parallel studies; 2345 participants)The risk of AMS was reduced with acetazolamide (risk ratio (RR) 0.47, 95% confidence interval (CI) 0.39 to 0.56; I2 = 0%; 16 studies; 2301 participants; moderate quality of evidence). No events of HAPE were reported and only one event of HACE (RR 0.32, 95% CI 0.01 to 7.48; 6 parallel studies; 1126 participants; moderate quality of evidence). Few studies reported side effects for this comparison, and they showed an increase in the risk of paraesthesia with the intake of acetazolamide (RR 5.53, 95% CI 2.81 to 10.88, I2 = 60%; 5 studies, 789 participants; low quality of evidence). Budenoside versus placebo (2 parallel studies; 132 participants)Data on budenoside showed a reduction in the incidence of AMS compared with placebo (RR 0.37, 95% CI 0.23 to 0.61; I2 = 0%; 2 studies, 132 participants; low quality of evidence). Studies included did not report events of HAPE or HACE, and they did not find side effects (low quality of evidence). Dexamethasone versus placebo (7 parallel studies; 205 participants)For dexamethasone, the data did not show benefits at any dosage (RR 0.60, 95% CI 0.36 to 1.00; I2 = 39%; 4 trials, 176 participants; low quality of evidence). Included studies did not report events of HAPE or HACE, and we rated the evidence about adverse events as of very low quality.

AUTHORS' CONCLUSIONS

Our assessment of the most commonly-used pharmacological interventions suggests that acetazolamide is an effective pharmacological agent to prevent acute HAI in dosages of 250 to 750 mg/day. This information is based on evidence of moderate quality. Acetazolamide is associated with an increased risk of paraesthesia, although there are few reports about other adverse events from the available evidence. The clinical benefits and harms of other pharmacological interventions such as ibuprofen, budenoside and dexamethasone are unclear. Large multicentre studies are needed for most of the pharmacological agents evaluated in this review, to evaluate their effectiveness and safety.

Efficacy of ibuprofen on prevention of high altitude headache: A systematic review and meta-analysis

OBJECTIVE

Ibuprofen is used to prevent high altitude headache (HAH) but its efficacy remains controversial. We conducted a systematic review and meta-analysis of randomized, placebo-controlled trials (RCTs) of ibuprofen for the prevention of HAH.

METHODS

Studies reporting efficacy of ibuprofen for prevention of HAH were identified by searching electronic databases (until December 2016). The primary outcome was the difference in incidence of HAH between ibuprofen and placebo groups. Risk ratios (RR) were aggregated using a Mantel-Haenszel random effect model. Heterogeneity of included trials was assessed using the I2 statistics.

RESULTS

In three randomized-controlled clinical trials involving 407 subjects, HAH occurred in 101 of 239 subjects (42%) who received ibuprofen and 96 of 168 (57%) who received placebo (RR = 0.79, 95% CI 0.66 to 0.96, Z = 2.43, P = 0.02, I2 = 0%). The absolute risk reduction (ARR) was 15%. Number needed to treat (NNT) to prevent HAH was 7. Similarly, The incidence of severe HAH was significant in the two groups (RR = 0.40, 95% CI 0.17 to 0.93, Z = 2.14, P = 0.03, I2 = 0%). Severe HAH occurred in 3% treated with ibuprofen and 10% with placebo. The ARR was 8%. NNT to prevent severe HAH was 13. Headache severity using a visual analogue scale was not different between ibuprofen and placebo. Similarly, the difference between the two groups in the change in SpO2 from baseline to altitude was not different. One included RCT reported one participant with black stools and three participants with stomach pain in the ibuprofen group, while seven participants reported stomach pain in the placebo group.

CONCLUSIONS

Based on a limited number of studies ibuprofen seems efficacious for the prevention of HAH and may therefore represent an alternative for preventing HAH with acetazolamide or dexamethasone.

Regulation of blood volume in lowlanders exposed to high altitude

Humans ascending to high altitude (HA) experience a reduction in arterial oxyhemoglobin saturation and, as a result, arterial O₂ content ([Formula: see text]). As HA exposure extends, this reduction in [Formula: see text] is counteracted by an increase in arterial hemoglobin concentration. Initially, hemoconcentration is exclusively related to a reduction in plasma volume (PV), whereas after several weeks a progressive expansion in total red blood cell volume (RCV) contributes, although often to a modest extent. Since the decrease in PV is more rapid and usually more pronounced than the expansion in RCV, at least during the first weeks of exposure, a reduction in circulating blood volume is common at HA. Although the regulation of hematological responses to HA has been investigated for decades, it remains incompletely understood. This is not only related to the large number of mechanisms that could be involved and the complexity of their interplay but also to the difficulty of conducting comprehensive experiments in the often secluded HA environment. In this review, we present our understanding of the kinetics, the mechanisms and the physiological relevance of the HA-induced reduction in PV and expansion in RCV.

IL-10 Dysregulation in Acute Mountain Sickness Revealed by Transcriptome Analysis

Acute mountain sickness (AMS), which may progress to life-threatening high-altitude cerebral edema, is a major threat to millions of people who live in or travel to high altitude. Although studies have revealed the risk factors and pathophysiology theories of AMS, the molecular mechanisms of it do not comprehensively illustrate. Here, we used a system-level methodology, RNA sequencing, to explore the molecular mechanisms of AMS at genome-wide level in 10 individuals. After exposure to high altitude, a total of 1,164 and 1,322 differentially expressed transcripts were identified in AMS and non-AMS groups, respectively. Among them, only 328 common transcripts presented between the two groups. Immune and inflammatory responses were overrepresented in participants with AMS, but not in non-AMS individuals. Anti-inflammatory cytokine IL10 and inflammation cytokines IF17F and CCL8 exhibited significantly different genetic connectivity in AMS compared to that of non-AMS individuals based on network analysis. IL10 was downregulated and both IF17F and CCL8 were upregulated in AMS individuals. Moreover, the serum concentration of IL10 significantly decreased in AMS patients after exposure to high altitude (p = 0.001) in another population (n = 22). There was a large negative correlation between the changes in IL10 concentration, r(22) = −0.52, p = 0.013, and Lake Louise Score. Taken together, our analysis provides unprecedented characterization of AMS transcriptome and identifies that genes involved in immune and inflammatory responses were disturbed in AMS individuals by high-altitude exposure. The reduction of IL10 after exposure to high altitude was associated with AMS.

Drug Use and Misuse in the Mountains: A UIAA MedCom Consensus Guide for Medical Professionals

Donegani, Enrico, Peter Paal, Thomas Küpper, Urs Hefti, Buddha Basnyat, Anna Carceller, Pierre Bouzat, Rianne van der Spek, and David Hillebrandt. Drug use and misuse in the mountains: a UIAA MedCom consensus guide for medical professionals. High Alt Med Biol. 17:157-184, 2016.-Aims: The aim of this review is to inform mountaineers about drugs commonly used in mountains. For many years, drugs have been used to enhance performance in mountaineering. It is the UIAA (International Climbing and Mountaineering Federation-Union International des Associations d'Alpinisme) Medcom's duty to protect mountaineers from possible harm caused by uninformed drug use. The UIAA Medcom assessed relevant articles in scientific literature and peer-reviewed studies, trials, observational studies, and case series to provide information for physicians on drugs commonly used in the mountain environment. Recommendations were graded according to criteria set by the American College of Chest Physicians.

RESULTS

Prophylactic, therapeutic, and recreational uses of drugs relevant to mountaineering are presented with an assessment of their risks and benefits.

CONCLUSIONS

If using drugs not regulated by the World Anti-Doping Agency (WADA), individuals have to determine their own personal standards for enjoyment, challenge, acceptable risk, and ethics. No system of drug testing could ever, or should ever, be policed for recreational climbers. Sponsored climbers or those who climb for status need to carefully consider both the medical and ethical implications if using drugs to aid performance. In some countries (e.g., Switzerland and Germany), administrative systems for mountaineering or medication control dictate a specific stance, but for most recreational mountaineers, any rules would be unenforceable and have to be a personal decision, but should take into account the current best evidence for risk, benefit, and sporting ethics.

Soluble Urokinase-Type Plasminogen Activator Receptor Plasma Concentration May Predict Susceptibility to High Altitude Pulmonary Edema

Introduction. Acute exposure to high altitude induces inflammation. However, the relationship between inflammation and high altitude related illness such as high altitude pulmonary edema (HAPE) and acute mountain sickness (AMS) is poorly understood. We tested if soluble urokinase-type plasminogen activator receptor (suPAR) plasma concentration, a prognostic factor for cardiovascular disease and marker for low grade activation of leukocytes, will predict susceptibility to HAPE and AMS. Methods. 41 healthy mountaineers were examined at sea level (SL, 446 m) and 24 h after rapid ascent to 4559 m (HA). 24/41 subjects had a history of HAPE and were thus considered HAPE-susceptible (HAPE-s). Out of the latter, 10/24 HAPE-s subjects were randomly chosen to suppress the inflammatory cascade with dexamethasone 8 mg bid 24 h prior to ascent. Results. Acute hypoxic exposure led to an acute inflammatory reaction represented by an increase in suPAR (1.9 ± 0.4 at SL versus 2.3 ± 0.5 at HA, p < 0.01), CRP (0.7 ± 0.5 at SL versus 3.6 ± 4.6 at HA, p < 0.01), and IL-6 (0.8 ± 0.4 at SL versus 3.3 ± 4.9 at HA, p < 0.01) in all subjects except those receiving dexamethasone. The ascent associated decrease in PaO₂ correlated with the increase in IL-6 (r = 0.46, p < 0.001), but not suPAR (r = 0.27, p = 0.08); the increase in IL-6 was not correlated with suPAR (r = 0.16, p = 0.24). Baseline suPAR plasma concentration was higher in the HAPE-s group (2.0 ± 0.4 versus 1.8 ± 0.4, p = 0.04); no difference was found for CRP and IL-6 and for subjects developing AMS. Conclusion. High altitude exposure leads to an increase in suPAR plasma concentration, with the missing correlation between suPAR and IL-6 suggesting a cytokine independent, leukocyte mediated mechanism of low grade inflammation. The correlation between IL-6 and PaO₂ suggests a direct effect of hypoxia, which is not the case for suPAR. However, suPAR plasma concentration measured before hypoxic exposure may predict HAPE susceptibility.