High-altitude pulmonary edema: review

Salidroside Reduced Ca2+-CaM-CAMKII-Dependent eNOS/NO Activation to Decrease Endothelial Cell Injury Induced by Cold Combined with Hypoxia

To investigate vascular endothelium damage in rats exposed to hypoxic and cold and the effect of salidroside in protecting against this damage. A rat isolated aortic ring hypoxia/cold model was established to simulate exposure to hypoxic and cold. The levels of endothelial cell injury markers were measured by ELISA. TEM was performed to observe the ultrastructure of vascular ring endothelial cells. In vitro assays were performed to verify the effect of salidroside on endothelial cells. CCK-8 and flow cytometry were performed to analyze endothelial cell survival and apoptosis, respectively. Ca2+ concentrations were measured by Flow cytometry, and the expressions of NOS/NO pathway-related proteins were measured by WB. Endothelial cell damage, mitochondrial swelling, autophagy, and apoptosis were increased in the hypoxia group and hypoxia/hypothermia group. All of these effects were inhibited by salidroside. Moreover, exposure to cold combined with hypoxia reduced the NO levels, Ca2+ concentrations and NOS/NO pathway-related protein expression in the hypoxia group and hypoxia/hypothermia group. Salidroside treatment reversed these changes. Salidroside protected against endothelial cell injury induced by cold and hypoxia through reduction of Ca2+-CaM-CAMKII-dependent eNOS/NO activation, thereby preventing mitochondrial damage, reducing ROS levels, and inhibiting apoptosis.

High-Altitude Pulmonary Edema in Two Pediatric Patients with Pre-Existing Lung Disease

BACKGROUND

The illnesses associated with changes in barometric pressure can be classified into three types: acute mountain sickness, high-altitude pulmonary edema (HAPE), and high-altitude cerebral edema. HAPE is a rare form of pulmonary edema that occurs in susceptible individuals after arriving at altitudes over 2500 m above sea level (m). Only a few studies have reported classical HAPE among children with underlying cardiopulmonary comorbidities. In this study, we report two pediatric cases of classical HAPE that occurred immediately upon arriving at Abha city (with an average elevation of 2270 m above sea level). Notably, both patients possessed underlying chronic lung diseases, raising crucial questions about susceptibility factors and the early onset manifestations of HAPE.

CASE

Two pediatric cases of HAPE are presented. The first patient, with a medical history of repaired right congenital diaphragmatic hernia and subsequent right lung hypoplasia, developed HAPE following their ascent to a high altitude. The second patient, diagnosed with diffuse lung disease of unknown etiology, experienced HAPE after a rapid high-altitude ascent. Both patients resided in low-altitude areas prior to ascent. The initial emergency room assessment revealed that both patients had severe hypoxia with respiratory distress that mandated the initiation of respiratory support and 100% oxygen therapy. They required intensive care unit admission, improved after 5 days of hospitalization, and were sent home in good condition.

CONCLUSION

HAPE is a complex, potentially life-threatening high-altitude illness with diverse clinical presentations and variable risk factors. This case report sheds light on a potential predisposition factor-pre-existing lung disease-in children experiencing severe HAPE. While further validation is crucial, this valuable insight opens doors for improved preventative strategies and informed medical decisions for children with pre-existing lung conditions traveling to high altitudes.

Comprehensive viewpoints on heart rate variability at high altitude

OBJECTIVES

Hypoxia is a physiological state characterized by reduced oxygen levels in organs and tissues. It is a common clinicopathological process and a major cause of health problems in highland areas.  Heart rate variability (HRV) is a measure of the balance in autonomic innervation to the heart. It provides valuable information on the regulation of the cardiovascular system by neurohumoral factors, and changes in HRV reflect the complex interactions between multiple systems. In this review, we provide a comprehensive overview of the relationship between high-altitude hypoxia and HRV. We summarize the different mechanisms of diseases caused by hypoxia and explore the changes in HRV across various systems. Additionally, we discuss relevant pharmaceutical interventions. Overall, this review aims to provide research ideas and assistance for in-depth studies on HRV. By understanding the intricate relationship between high-altitude hypoxia and HRV, we can gain insights into the underlying mechanisms and potential therapeutic approaches to mitigate the effects of hypoxia on cardiovascular and other systems.

METHODS

The relevant literature was collected systematically from scientific database, including PubMed, Web of Science, China National Knowledge Infrastructure (CNKI), Baidu Scholar, as well as other literature sources, such as classic books of hypoxia.

RESULTS

There is a close relationship between heart rate variability and high-altitude hypoxia. Heart rate variability is an indicator that evaluates the impact of hypoxia on the cardiovascular system and other related systems. By improving the observation of HRV, we can estimate the progress of cardiovascular diseases and predict the impact on other systems related to cardiovascular health. At the same time, changes in heart rate variability can be used to observe the efficacy of preventive drugs for altitude related diseases.

CONCLUSIONS

HRV can be used to assess autonomic nervous function under various systemic conditions, and can be used to predict and monitor diseases caused by hypoxia at high altitude. Investigating the correlation between high altitude hypoxia and heart rate variability can help make HRV more rapid, accurate, and effective for the diagnosis of plateau-related diseases.

Individual Changes in Respiratory Compliance Upon Immersion May Predict Susceptibility to Immersion Pulmonary Edema

BACKGROUND

Immersion pulmonary edema (IPE) is a frequent diving accident, and it is the primary cause of hospitalization for young military divers during training. The objective of this study was to identify immersion-induced parameters predicting individual susceptibility to IPE.

METHODS

Eighteen experienced male divers having completed at least 100 dives were recruited. Eight divers had previously been hospitalized for IPE (IPE), and the other ten had never developed IPE (non-IPE). The two groups were matched for age, BMI, and number of dives performed. Ventilatory function and overall compliance of the respiratory system (Crs) were measured on land and during head-out-of-water immersion. Subjects also performed 30 min of fin swimming in a channel at 33 m min-1. Following this exercise, the presence of extravascular lung water, revealed by ultrasound lung comets (ULC), was assessed.

RESULTS

In the whole group, the decrease in Crs upon immersion correlated with the immersion-induced alterations to expiratory reserve volume, ERV (r2 = 0.91; p < 0.001), inspiratory reserve volume, IRV (r2 = 0.94; p < 0.001), and tidal volume, Vt, changes (r2 = 0.43; p < 0.003). The number of ULC correlated strongly with immersion-induced changes in ventilatory function (r2 = 0.818; p < 0.001 for ERV, r2 = 0.849; p < 0.001 for IRV, r2 = 0.304; p = 0.0164 for Vt) and reduced Crs (r2 = 0.19; p < 0.001). The variations of ERV, IRV, and Crs at rest induced by head-out-of-water immersion and the number of ULC measured after swimming for 30 min were significantly greater in IPE subjects.

CONCLUSION

In the face of similar immersion stresses, the extent of alterations to ventilatory function and the number of ULCs were very different between individuals but remained statistically correlated. These parameters were significantly greater in divers with a history of IPE. Alterations to pulmonary function and, in particular, to pulmonary compliance induced by head-out-of-water immersion, through their effects on work of breathing appear to allow the identification of divers with a greater susceptibility to developing IPE. Measurement of these parameters could therefore be proposed as a predictive test for the risk of developing IPE.

Mean corpuscular haemoglobin concentration (MCHC): a new biomarker for high-altitude pulmonary edema in the Ecuadorian Andes

Ascent to high altitude (> 3000 m height above sea level or m.a.s.l) exposes people to hypobaric atmospheric pressure and hypoxemia, which provokes mountain sickness and whose symptoms vary from the mild acute mountain sickness to the life-threatening, high-altitude pulmonary edema (HAPE). This study analysed the risk factors underlying HAPE in dwellers and travellers of the Ecuadorian Andes after sojourning over 3000 m height. A group of HAPE patients (N = 58) was compared to a NO HAPE group (N = 713), through demographic (ethnicity, sex, and age), red blood cell parameters (erythrocytes counts, hematocrit, median corpuscular volume, median corpuscular haemoglobin, and median corpuscular haemoglobin concentration (MCHC)), altitude (threshold: 3000 m.a.s.l.), and health status (vital signs) variables. Analysis of Deviance for Generalised Linear Model Fits (logit regression) revealed patterns of significant associations. High-altitude dwellers, particularly children and elder people, were HAPE-prone, while women were more tolerant of HAPE than men. Interestingly, HAPE prevalence was strongly related to an increment of MCH. The residence at middle altitude was inversely related to the odds of suffering HAPE. Ethnicity did not have a significant influence in HAPE susceptibility. Elevated MCHC emerges like a blood adaptation of Andean highlanders to high altitude and biomarker of HAPE risk.

Insight into the Effects of High-Altitude Hypoxic Exposure on Learning and Memory

The earth land area is heterogeneous in terms of elevation; about 45% of its land area belongs to higher elevation with altitude above 500 meters compared to sea level. In most cases, oxygen concentration decreases as altitude increases. Thus, high-altitude hypoxic stress is commonly faced by residents in areas with an average elevation exceeding 2500 meters and those who have just entered the plateau. High-altitude hypoxia significantly affects advanced neurobehaviors including learning and memory (L&M). Hippocampus, the integration center of L&M, could be the most crucial target affected by high-altitude hypoxia exposure. Based on these points, this review thoroughly discussed the relationship between high-altitude hypoxia and L&M impairment, in terms of hippocampal neuron apoptosis and dysfunction, neuronal oxidative stress disorder, neurotransmitters and related receptors, and nerve cell energy metabolism disorder, which is of great significance to find potential targets for medical intervention. Studies illustrate that the mechanism of L&M damaged by high-altitude hypoxia should be further investigated based on the entire review of issues related to this topic.

Protective effects of areca nut polyphenols on hypoxic damage of rat pulmonary microvascular endothelial cells

OBJECTIVE

To investigate the protective effects of areca nut polyphenols on hypoxic damage of rat pulmonary microvascular endothelial cells (PMVECs).

METHODS

Malondialdehyde and superoxide dismutase (SOD) were used to determine the optimal modeling of lung hypoxic injury cells. CCK-8 method was used to detect cell viability for determining the effective dose of areca nut polyphenols. Rat PMVECs were divided into control group, hypoxia model group and areca nut polyphenols group. BCA method was used to detect the protein concentration of each group, and the oxidative stress level in PMVECs was measured. Western blotting was used to detect the expression of inflammatory and apoptosis-related proteins. Immunofluorescence staining was used to detect the expression of occludin and zonula occludens (ZO) 1. Transwell chamber was used to detect transendothelial electrical resistance, and rhodamine fluorescent dye was used to detect PMVECs barrier permeability.

RESULTS

The hypobaric hypoxia-induced cell injury model was established by culturing PMVECs for 48 h at 1% oxygen concentration. The 20 μg/mL areca nut polyphenols significantly reversed the survival rate and the oxidative stress of PMVECs in hypoxia model group (all P<0.05). Areca nut polyphenols had significant inhibitory effect on the up-regulation of inflammation-related proteins, including nuclear factor-κB (NF-κB) and nuclear factor-E2-related factor (Nrf) 2 in hypoxia model group (all P<0.05). And areca nut polyphenols could reduce hypoxia-induced PMVECs apoptosis by down-regulating the expressions of apoptosis-related proteins, including cysteine aspartic acid specific protease (caspase) 3, Bcl-2 associated X protein (Bax) in PMVECs (all P<0.05). In addition, areca nut polyphenols effectively improves the transendothelial electrical resistance and barrier permeability of PMVECs through elevating the expression of occludin and ZO-1 (all P<0.05).

CONCLUSION

Areca nut polyphenols can inhibit the hypoxic damage of PMVECs by reducing oxidative stress and apoptosis down-regulating the expression of inflammatory proteins and reducing membrane permeability.

Prevention and Treatment of Life-Threatening COVID-19 May Be Possible with Oxygen Treatment

Most SARS CoV-2 infections probably occur unnoticed or cause only cause a mild common cold that does not require medical intervention. A significant proportion of more severe cases is characterized by early neurological symptoms such as headache, fatigue, and impaired consciousness, including respiratory distress. These symptoms suggest hypoxia, specifically affecting the brain. The condition is best explained by primary replication of the virus in the nasal respiratory and/or the olfactory epithelia, followed by an invasion of the virus into the central nervous system, including the respiratory centers, either along a transneural route, through disruption of the blood-brain barrier, or both. In patients, presenting with early dyspnea, the primary goal of therapy should be the reversal of brain hypoxia as efficiently as possible. The first approach should be intermittent treatment with 100% oxygen using a tight oronasal mask or a hood. If this does not help within a few hours, an enclosure is needed to increase the ambient pressure. This management approach is well established in the hypoxia-related diseases in diving and aerospace medicine and preserves the patient's spontaneous breathing. Preliminary research evidence indicates that even a small elevation of the ambient pressure might be lifesaving. Other neurological symptoms, presenting particularly in long COVID-19, suggest imbalance of the autonomous nervous system, i.e., dysautonomia. These patients could benefit from vagal nerve stimulation.

Methamphetamine exacerbates pathophysiology of traumatic brain injury at high altitude. Neuroprotective effects of nanodelivery of a potent antioxidant compound H-290/51

Military personnel are often exposed to high altitude (HA, ca. 4500-5000m) for combat operations associated with neurological dysfunctions. HA is a severe stressful situation and people frequently use methamphetamine (METH) or other psychostimulants to cope stress. Since military personnel are prone to different kinds of traumatic brain injury (TBI), in this review we discuss possible effects of METH on concussive head injury (CHI) at HA based on our own observations. METH exposure at HA exacerbates pathophysiology of CHI as compared to normobaric laboratory environment comparable to sea level. Increased blood-brain barrier (BBB) breakdown, edema formation and reductions in the cerebral blood flow (CBF) following CHI were exacerbated by METH intoxication at HA. Damage to cerebral microvasculature and expression of beta catenin was also exacerbated following CHI in METH treated group at HA. TiO2-nanowired delivery of H-290/51 (150mg/kg, i.p.), a potent chain-breaking antioxidant significantly enhanced CBF and reduced BBB breakdown, edema formation, beta catenin expression and brain pathology in METH exposed rats after CHI at HA. These observations are the first to point out that METH exposure in CHI exacerbated brain pathology at HA and this appears to be related with greater production of oxidative stress induced brain pathology, not reported earlier.

Might a high hemoglobin mass be involved in non-cardiogenic pulmonary edema? The case of the chronic maladaptation to high-altitude in the Andes

Exposure to hypoxic environments when ascending at high altitudes may cause life-threatening pulmonary edema (HAPE) due to a rapid accumulation of extracellular fluid flooding in the pulmonary alveoli. In Andeans, high-altitude adaptation occurs at the expense of being more prone to chronic mountain sickness: relative hypoventilation, excess pulmonary hypertension, and secondary polycythemia. Because HAPE prevalence is high in the Andes, we posit the hypothesis that a high hemoglobine mass may increase HAPE risk. In support of it, high intrapulmonary hypertension along with hyperviscosity produced by polycytemia may enhance sear forces and intravascular hemolysis, thus leading to increased acellular hemoglobin and the subsequent damage of the alveolar and endothelial barrier. It is proposed to investigate the relationship between the vaso-endothelial homeostasis and erythropoiesis in the maladaptation to high altitude and HAPE. This research is especially important when reentry HAPE, since rheologic properties of blood changes with rapid ascent to high altitudes.

Expression of Aquaporin-1 and Aquaporin-5 in a Rat Model of High-Altitude Pulmonary Edema and the Effect of Hyperbaric Oxygen Exposure

Objective:

To investigate the therapeutic roles of hyperbaric oxygen exposure on high-altitude pulmonary edema and to determine whether aquaporin-1 and aquaporin-5 were involved in the pathogenesis of HAPE in rats.

Methods:

Rats were divided into 5 groups: The control group, the HAPE group (HAPE model), the HBO group (hyperbaric oxygen exposure), the NBO group (normobaric oxygen exposure), and the NA group (normal air exposure). Western blot and real-time PCR were used to analyze the pulmonary expressions of AQP1 and AQP5. The wet-to-dry (W/D) weight ratio and the morphology of the lung were also examined.

Results:

The lung W/D weight ratio in the HAPE group was increased compared with the control group. The injury score in the HBO group was noticeably lower than that in the control group. The mRNA and proteins expressions of AQP1 and AQP5 were significantly downregulated in the HAPE group.

Conclusions:

Oxygen exposure alleviated high-altitude hypobaric hypoxia-induced lung injury in rats. Additionally, HBO therapy had significant advantage on interstitial HAPE.

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.

Acute Lung Edema as a Presentation of Severe Acute Reentry High-Altitude Illness in a Pediatric Patient

Acute high-altitude pulmonary edema (HAPE) is a pathology involving multifactorial triggers that are associated with ascents to altitudes over 2,500 meters above sea level (m). Here, we report two pediatric cases of reentry HAPE, from the city of Huaraz, Peru, located at 3,052 m. The characteristics of both cases were similar, wherein acclimatization to sea level and a subsequent return to the city of origin occurred, and we speculate that it was caused by activation of predisposing factors to HAPE. The diagnosis and management associated with pulmonary hypertension became a determining factor for therapy.

Susceptibility to high-altitude pulmonary edema is associated with increased pulmonary arterial stiffness during exercise

High-altitude pulmonary edema (HAPE), a reversible form of capillary leak, is a common consequence of rapid ascension to high altitude and a major cause of death related to high-altitude exposure. Individuals with a prior history of HAPE are more susceptible to future episodes, but the underlying risk factors remain uncertain. Previous studies have shown that HAPE-susceptible subjects have an exaggerated pulmonary vasoreactivity to acute hypoxia, but incomplete data are available regarding their vascular response to exercise. To examine this, seven HAPE-susceptible subjects and nine control subjects (HAPE-resistant) were studied at rest and during incremental exercise at sea level and at 3,810 m altitude. Studies were conducted in both normoxic (inspired Po₂ = 148 Torr) and hypoxic (inspired Po₂ = 91 Torr) conditions at each location. Here, we report an expanded analysis of previously published data, including a distensible vessel model that showed that HAPE-susceptible subjects had significantly reduced small distal artery distensibility at sea level compared with HAPE-resistant control subjects [0.011 ± 0.001 vs. 0.021 ± 0.002 mmHg^-1; P < 0.001). Moreover, HAPE-susceptible subjects demonstrated constant distensibility over all conditions, suggesting that distal arteries are maximally distended at rest. Consistent with having increased distal artery stiffness, HAPE-susceptible subjects had greater increases in pulmonary artery pulse pressure with exercise, which suggests increased proximal artery stiffness. In summary, HAPE-susceptible subjects have exercise-induced increases in proximal artery stiffness and baseline increases in distal artery stiffness, suggesting increased pulsatile load on the right ventricle.NEW & NOTEWORTHY In comparison to subjects who appear resistant to high-altitude pulmonary edema, those previously symptomatic show greater increases in large and small artery stiffness in response to exercise. These differences in arterial stiffness may be a risk factor for the development of high-altitude pulmonary edema or evidence that consequences of high-altitude pulmonary edema are long-lasting after return to sea level.

Effect of different high altitudes on vascular endothelial function in healthy people

BACKGROUND

The aim of the study was to provide a theoretical basis for the early diagnosis and prediction of acute altitude sickness, to provide a better entry mode for healthy people from plain areas to plateau areas, and to preliminarily clarify the possible mechanism of this approach.

METHODS

We measured endothelin-1 (ET-1), asymmetric dimethylarginine (ADMA), vascular endothelial growth factor (VEGF), nitric oxide (NO), and hypoxia-inducible factor 1 (HIF-1) levels in each sample and determined flow-mediated dilation (FMD) values using a portable OMRON color Doppler with a 7.0- to 12.0-MHz linear array probe. We used the Lewis Lake score to diagnose acute mountain sickness (AMS) and to stratify the disease severity.

RESULTS

We found no cases of AMS at any of the studied elevation gradients. We found significant differences in FMD values between individuals when at 400 m above sea level and when at 2200, 3200, and 4200 m above sea level (P < .05) but found no significant differences among those at 2200, 3200, and 4200 m. Our variance analysis showed that serum ET-1, VEGF, ADMA, NO, and HIF-1 levels in individuals at ≥3000 m and those at subplateau and plain areas (<3000 m) significantly differed (P < .05). The level of these factors also significantly differed between individuals at elevation gradients of plateau areas (3260 m vs 4270 m) (P < .05). We found no significant differences in serum ET-1, VEGF, and ADMA levels between individuals at the plateau (2260 m) and plain (400 m) areas (P > .05). NO and HIF-1 levels were significantly different in serum samples from individuals between the plateau (2260 m) and plain (400 m) areas (P < .05). However, with increasing altitude, the NO level gradually increased, whereas ET-1, ADMA, VEGF, and HIF-1 levels showed a decreasing trend. With the increase of altitude, there is no correlation between the trend of FMD and hematologic-related factors such as VEGF, NO, and HIF-1.

CONCLUSION

A healthy young male population ascending to a high-altitude area experiences a low incidence of AMS. Entering an acute plateau exposure environment from different altitude gradients may weaken the effect of acute highland exposure on vascular endothelial dysfunction in healthy individuals. Changes in serum ET-1, VEGF, ADMA, NO, and HIF-1 levels in healthy young men may be related to the body's self-regulation and protect healthy individuals from AMS. A short stay in a subplateau region may initiate an oxygen-free preconditioning process in healthy individuals, thereby protecting them from AMS. Noninvasive brachial artery endothelial function test instead of the detection of invasive hematologic-related factors for early diagnosis and prediction of the occurrence and severity of acute high-altitude disease is still lack of sufficient theoretical basis.

Effects of Hypobaric Hypoxia on Endothelial Function and Adiponectin Levels in Airforce Aviators

Background: Hypobaric hypoxia (HH) increases the risk of high altitude-related illnesses (HARI). The pathophysiological mechanism(s) involved are still partially unknown. Altered vascular reactivity as consequence of endothelial dysfunction during HH might play a role in this phenomenon. Adiponectin exerts protective effect on cardiovascular system since it modulates NO release, antagonizing endothelial dysfunction. Aims of this study, performed in a selected population of airforce aviators, were (1) to investigate whether exposure to acute HH might be associated with endothelial dysfunction and (2) to evaluate whether adiponectin might be involved in modulating this phenomenon. Methods: Twenty aviators were exposed to acute HH in a hypobaric chamber by simulating altitude of 8000 and then 6000 m for 2 hours. Vascular reactivity was evaluated by the EndoPAT test immediately before and after the HH; salivary and blood adiponectin levels were measured. Results: EndoPAT performed immediately after HH divided pilots in two groups: 12 pilots with preserved vascular reactivity and 8 pilots with reduction of vascular reactivity, indicating that HH exposure might cause endothelial dysfunction. Salivary and blood adiponectin levels increased post-HH in a time-dependent manner in all aviators, but the significant increase was observed only in those with preserved vascular reactivity suggesting that HH stimulated release of adiponectin that, in turn, by exerting a protective effect, might reduce endothelial dysfunction. Conclusions: Acute HH may cause endothelial dysfunction due, at least in part, to reduced release of adiponectin. This phenomenon might be involved in pathophysiology of HARI.

Pulmonary phenotypes associated with genetic variation in telomere-related genes

PURPOSE OF REVIEW

Genomic mutations in telomere-related genes have been recognized as a cause of familial forms of idiopathic pulmonary fibrosis (IPF). However, it has become increasingly clear that telomere syndromes and telomere shortening are associated with various types of pulmonary disease. Additionally, it was found that also single nucleotide polymorphisms (SNPs) in telomere-related genes are risk factors for the development of pulmonary disease. This review focuses on recent updates on pulmonary phenotypes associated with genetic variation in telomere-related genes.

RECENT FINDINGS

Genomic mutations in seven telomere-related genes cause pulmonary disease. Pulmonary phenotypes associated with these mutations range from many forms of pulmonary fibrosis to emphysema and pulmonary vascular disease. Telomere-related mutations account for up to 10% of sporadic IPF, 25% of familial IPF, 10% of connective-tissue disease-associated interstitial lung disease, and 1% of COPD. Mixed disease forms have also been found. Furthermore, SNPs in TERT, TERC, OBFC1, and RTEL1, as well as short telomere length, have been associated with several pulmonary diseases. Treatment of pulmonary disease caused by telomere-related gene variation is currently based on disease diagnosis and not on the underlying cause.

SUMMARY

Pulmonary phenotypes found in carriers of telomere-related gene mutations and SNPs are primarily pulmonary fibrosis, sometimes emphysema and rarely pulmonary vascular disease. Genotype-phenotype relations are weak, suggesting that environmental factors and genetic background of patients determine disease phenotypes to a large degree. A disease model is presented wherever genomic variation in telomere-related genes cause specific pulmonary disease phenotypes whenever triggered by environmental exposure, comorbidity, or unknown factors.

Association between the IL1R2 rs2072472 polymorphism and high-altitude pulmonary edema risk

Aim

High‐altitude pulmonary edema (HAPE), as a multifactorial disease, is caused by stress failure and involves both environmental and genetic factors. Study shows that IL‐1 receptors can selectively decrease the oxygen arterial hypertension and influence the blood coagulation. So we evaluated whether genetic polymorphisms in IL1R1 and 1L1R2 genes are associated with the risk of HAPE in Chinese Han population.

Methods

Ten susceptible SNPs in the IL1R1 and IL1R2 genes were genotyped among 265 HAPE cases and 303 controls using the Agena MassARRAY platform. The associations of the SNP frequencies with HAPE were analyzed by chi‐square (χ²) test/Fisher's test. The genetic models were used to evaluate associations.

Results

In the allele model, we found that rs2072472 was significantly associated with a 0.73‐fold decreased risk of HAPE (OR = 0.73, 95% CI = 0.55–0.97, p = 0.033). In the genetic model analysis, the rs2072472 in IL1R2 gene was associated with a 0.32‐fold decreased risk of HAPE in the codominant model, 0.67‐fold decreased risk of HAPE in the dominant model, 0.36‐fold decreasing the risk of HAPE in the recessive model, and 0.66‐fold decreased risk of HAPE in the log‐additive model, respectively. We found three candidate SNPs (rs11674595, rs4851527, and rs719250) in the IL1R2 gene have shown strong linkage, and none of the haplotypes was significantly associated with risk of HAPE.

Conclusion

These findings suggested that IL1R2 polymorphisms may contribute to the protection of HAPE.

Lung Ultrasound Is Accurate for the Diagnosis of High-Altitude Pulmonary Edema: A Prospective Study

Objective

The aim of this study was to assess the diagnostic accuracy of lung ultrasonography (LUS) for high-altitude pulmonary edema (HAPE).

Background

LUS has proven to be a reliable tool for the diagnosis of pulmonary diseases, including pneumonia, acute respiratory distress syndrome (ARDS), and pneumothorax. LUS also has potential for the diagnosis of HAPE. However, the actual diagnostic value of LUS for HAPE is still unknown. Our objective was to determine the feasibility of using LUS for the diagnosis of HAPE.

Materials and Methods

A prospective clinical research study of adult HAPE patients was conducted. LUS and chest X-ray (CXR) were performed in patients with suspected HAPE before and after treatment, and pulmonary moist rales were recorded concurrently. The diagnostic value of LUS, CXR, and moist rales for HAPE (i.e., their sensitivity, specificity, and positive and negative predictive values) were assessed, and the results were compared. The gold standard was the final diagnosis.

Results

In total, 148 patients were enrolled in the study, 126 of which were diagnosed with HAPE (85.14%). Before treatment, the diagnostic accuracy of LUS for HAPE was as follows: sensitivity, 98.41% (95% confidence interval (CI) 100.60-96.23%); specificity, 90.91% (95% CI 102.92-78.90%). LUS had higher sensitivity (0.98 vs. 0.81, P < 0.01 using the McNemar test) than moist rales for the diagnosis of HAPE. LUS also had higher sensitivity than CXR (0.98 vs. 0.93, P < 0.05 using the McNemar test). After treatment, LUS was consistent with CXR in 96.55% of HAPE patients, and the concordance between LUS and CXR was high (k statistic = 0.483 P ≤ 0.001; 95% CI -0.021 to -0.853).

Conclusion

The results indicate that LUS is a reliable method for the diagnosis and surveillance of HAPE. This trial is registered with Chinese Clinical Trial Registry (No. ChiCTR-DDD-16009841).

Hypoxia Exacerbates Inflammatory Acute Lung Injury via the Toll-Like Receptor 4 Signaling Pathway

Acute lung injury (ALI) is characterized by non-cardiogenic diffuse alveolar damage and often leads to a lethal consequence, particularly when hypoxia coexists. The treatment of ALI remains a challenge: pulmonary inflammation and hypoxia both contribute to its onset and progression and no effective prevention approach is available. Here, we aimed to investigate the underlying mechanism of hypoxia interaction with inflammation in ALI and to evaluate hypoxia-inducible factor 1 alpha (HIF-1α)—the crucial modulator in hypoxia—as a potential therapeutic target against ALI. First, we developed a novel ALI rat model induced by a combined low-dose of lipopolysaccharides (LPS) with acute hypoxia. Second, we used gene microarray analysis to evaluate the inflammatory profiles of bronchi alveolar lavage fluid cells of ALI rats. Third, we employed an alveolar macrophage cell line, NR8383 as an in vitro system together with a toll-like receptor 4 (TLR4) antagonist TAK-242, to verify our in vivo findings from ALI animals. Finally, we tested the therapeutic effects of HIF-1α augmentation against inflammation and hypoxia in ALI. We demonstrated that (i) LPS upregulated inflammatory genes, tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6), in the alveolar macrophages of ALI rats, which were further enhanced when ALI combined with hypoxia; (ii) hypoxia exposure could further enhance the upregulation of alveolar macrophageal TLR4 that was noticed in LPS-induced inflammatory ALI, conversely, TLR4 antagonist TAK-242 could suppress the macrophageal expression of TLR4 and inflammatory cytokines, including TNF-α, IL-1β, and IL-6, suggesting that the TLR4 signaling pathway as a central link between inflammation and hypoxia in ALI; (iii) manipulation of HIF-1α in vitro could suppress TLR4 expression induced by combined LPS and hypoxia, via suppressing promoter activity of the TLR4 gene; (iv) preconditioning augmentation of HIF-1α in vivo by HIF hydroxylase inhibitor, DMOG excreted protection against inflammatory, and hypoxic processes in ALI. Together, we see that hypoxia can exacerbate inflammation in ALI via the activation of the TLR4 signaling pathway in alveolar macrophages and predispose impairment of the alveolar-capillary barrier in the development of ALI. Targeting HIF-1α can suppress TLR4 expression and macrophageal inflammation, suggesting the potential therapeutic and preventative value of HIF-1α/TLR4 crosstalk pathway in ALI.

Genome-wide association study of high-altitude pulmonary edema in a Han Chinese population

A two-stage genome-wide association study (GWAS) was performed to identify and analyze genes and single nucleotide polymorphisms (SNPs) associated with high-altitude pulmonary edema (HAPE) in a Han Chinese patient population. In the first stage, DNA samples from 68 patients with recurrent HAPE were scanned using Affymetrix SNP Array 6.0 Chips, and allele frequencies were compared to those of 84 HapMap CHB samples to identify candidate SNPs. In the second stage, the 77 identified candidate SNPs were examined in an independent cohort of samples from 199 HAPE patients and 304 controls. Associations between SNPs and HAPE risk were tested using various genetic models. Of the 77 original SNPs, 7 were found to be associated with HAPE susceptibility in the second stage of the study. GO and pathway enrichment analysis of the 7 SNPs revealed 5 adjacent genes involved in various processes, including regulation of nucleoside diphosphate metabolism, thyroid hormone catabolism, and low-density lipoprotein receptor activity. These results suggest the identified SNPs and genes may contribute to the physiopathology of HAPE.

Angiotensin II receptor 1 gene variants are associated with high-altitude pulmonary edema risk

Previous studies demonstrated that Angiotensin II Receptor 1 (AGTR1) may play an important role in the development of high-altitude pulmonary edema. We envisaged a role for AGTR1 gene variants in the pathogenesis of HAPE and investigated their potential associations with HAPE in a Han Chinese population. We genotyped seven AGTR1 polymorphisms in 267 patients with diagnosed HAPE and 304 controls and evaluated their association with risk of HAPE. Statistically significant associations were found for the single nucleotide polymorphisms (SNPs) rs275651 (p = 0.017; odds ratio [OR] = 0.65) and rs275652 (p = 0.016; OR = 0.64). Another SNP rs10941679 showed a marginally significant association after adjusting for age and sex in the additive genetic model (adjusted OR = 1.44, 95% CI = 1.01-2.04, p = 0.040). Haplotype analysis confirmed that the haplotype "AG" was associated with a 35% reduction in the risk of developing HAPE, while the haplotype "AA" increased the risk of developing HAPE by 44%. These results provide the first evidence linking genetic variations in AGTR1 with HAPE risk in Han Chinese individuals.

Association between single nucleotide polymorphisms in ADRB2, GNB3 and GSTP1 genes and high-altitude pulmonary edema (HAPE) in the Chinese Han population

High altitude pulmonary edema (HAPE) occurs mainly under conditions such as high altitude, rapid ascent, or hypoxia. Previous studies suggest that ADRB2, GNB3, TH, and GSTP1 polymorphisms are associated with various lung diseases. We evaluated whether those polymorphisms are associated with the risk of HAPE in a Chinese Han population. ADRB2, GNB3, TH and GSTP1 polymorphisms were genotyped using a Sequenom MassARRAY. Logistic regression, adjusted for age and gender, was used to evaluate the association between the genotypes and the risk of HAPE by computing odds ratios (ORs) and 95% confidence intervals (95% CIs). The results revealed that GNB3 rs4963516 allele ''G'' (G vs T: OR = 0.70, 95% CI = 0.55-0.90, p = 0.006) was associated with HAPE risk. The ADRB2 rs1042718 alleles had a 1.29-fold (95%CI = 1.00-1.66; p = 0.045) increased risk of HAPE, and the GSTP1 rs749174 alleles had a 0.71-fold (95%CI = 0.52-0.99; p = 0.042) decreased risk of HAPE. Co-dominant and dominant models of GNB3 rs4963516 decreased the risk of HAPE (p = 0.023 and p = 0.008, respectively). Our results indicate GNB3 and GSTP1 polymorphisms may protect against HAPE progression, while ADRB2 polymorphisms are associated with an increased risk of HAPE.

Diazoxide protects rat vascular endothelial cells against hypoxia and cold-induced damage

The present study aimed to examine the effects of hypoxia and cold on vascular endothelial cells (VECs), as well as the protective ability of novel VECs-protective drugs against these injuries. A rat model simulating exposure to hypoxia and cold at high altitude environments was established. Based on these animal experiments, rat aortic VECs were established as injury models and exposed to hypoxia and/or adrenaline (ADR) in vitro. The results revealed that hypoxia significantly altered the levels of nitric oxide and vascular endothelial growth factor, while the cold temperature significantly increased the release of ADR and noradrenaline. Exposure to hypoxia combined with cold temperature significantly affected all these indices. In vitro experiments demonstrated that hypoxia, ADR (which was used to simulate cold in the animal experiments) and the combination of the two factors resulted in damage to the VECs and endothelial dysfunction. In addition, the results also showed that diazoxide, a highly selective mitoK_ATP opener, protected VECs against these injuries. In conclusion, hypoxia and cold temperature induced endothelial cell dysfunction and endocrine disorders, respectively. Improving endothelial function using diazoxide may be an effective therapeutic strategy in patients with altitude-associated disorders. However, the potential for clinical application requires further study.

HMOX1 Promoter Microsatellite Polymorphism Is Not Associated With High Altitude Pulmonary Edema in Han Chinese

OBJECTIVE

To investigate the relationship between microsatellite polymorphism in the Heme oxygenase-1 (HMOX1) gene promoter and high-altitude pulmonary edema (HAPE) in Han Chinese.

METHODS

Eighty-three construction workers who developed HAPE 2 to 7 days after arrival at Yushu (3800 m) in Qinghai, China, and 145 matched healthy subjects were included in this study. The amplification and labeling of the polymerase chain reaction products for capillary electrophoresis were performed to identify HMOX1 genotype frequency. The alleles were classified as short (S: <25 [GT]n repeats) and long (L: ≥25 [GT]n repeats) alleles.

RESULTS

Patients with HAPE have significantly higher white blood cell count, heart rate, and mean pulmonary artery pressure, but lower hemoglobin and arterial oxygen saturation than healthy subjects without HAPE. The numbers of (GT)n repeats in the HMOX1 gene promoter show a bimodal distribution. However, there is no significant difference in the genotype frequency and allele frequency between patients with HAPE and healthy subjects without HAPE. Chi-square test analysis reveals that the genotype frequency of (GT)n repeats is not associated with HAPE.

CONCLUSION

The microsatellite polymorphism in the HMOX1 gene promoter is not associated with HAPE in Han Chinese in Qinghai, China.

Dissecting Low Atmospheric Pressure Stress: Transcriptome Responses to the Components of Hypobaria in Arabidopsis

Controlled hypobaria presents biology with an environment that is never encountered in terrestrial ecology, yet the apparent components of hypobaria are stresses typical of terrestrial ecosystems. High altitude, for example, presents terrestrial hypobaria always with hypoxia as a component stress, since the relative partial pressure of O₂ is constant in the atmosphere. Laboratory-controlled hypobaria, however, allows the dissection of pressure effects away from the effects typically associated with altitude, in particular hypoxia, as the partial pressure of O₂ can be varied. In this study, whole transcriptomes of plants grown in ambient (97 kPa/pO₂ = 21 kPa) atmospheric conditions were compared to those of plants transferred to five different atmospheres of varying pressure and oxygen composition for 24 h: 50 kPa/pO₂ = 10 kPa, 25 kPa/pO₂ = 5 kPa, 50 kPa/pO₂ = 21 kPa, 25 kPa/pO₂ = 21 kPa, or 97 kPa/pO₂ = 5 kPa. The plants exposed to these environments were 10 day old Arabidopsis seedlings grown vertically on hydrated nutrient plates. In addition, 5 day old plants were also exposed for 24 h to the 50 kPa and ambient environments to evaluate age-dependent responses. The gene expression profiles from roots and shoots showed that the hypobaric response contained more complex gene regulation than simple hypoxia, and that adding back oxygen to normoxic conditions did not completely alleviate gene expression changes in hypobaric responses.

Hypoxic Pulmonary Vasoconstriction: From Molecular Mechanisms to Medicine

Hypoxic pulmonary vasoconstriction (HPV) is a homeostatic mechanism that is intrinsic to the pulmonary vasculature. Intrapulmonary arteries constrict in response to alveolar hypoxia, diverting blood to better-oxygenated lung segments, thereby optimizing ventilation/perfusion matching and systemic oxygen delivery. In response to alveolar hypoxia, a mitochondrial sensor dynamically changes reactive oxygen species and redox couples in pulmonary artery smooth muscle cells (PASMC). This inhibits potassium channels, depolarizes PASMC, activates voltage-gated calcium channels, and increases cytosolic calcium, causing vasoconstriction. Sustained hypoxia activates rho kinase, reinforcing vasoconstriction, and hypoxia-inducible factor (HIF)-1α, leading to adverse pulmonary vascular remodeling and pulmonary hypertension (PH). In the nonventilated fetal lung, HPV diverts blood to the systemic vasculature. After birth, HPV commonly occurs as a localized homeostatic response to focal pneumonia or atelectasis, which optimizes systemic Po2 without altering pulmonary artery pressure (PAP). In single-lung anesthesia, HPV reduces blood flow to the nonventilated lung, thereby facilitating thoracic surgery. At altitude, global hypoxia causes diffuse HPV, increases PAP, and initiates PH. Exaggerated or heterogeneous HPV contributes to high-altitude pulmonary edema. Conversely, impaired HPV, whether due to disease (eg, COPD, sepsis) or vasodilator drugs, promotes systemic hypoxemia. Genetic and epigenetic abnormalities of this oxygen-sensing pathway can trigger normoxic activation of HIF-1α and can promote abnormal metabolism and cell proliferation. The resulting pseudohypoxic state underlies the Warburg metabolic shift and contributes to the neoplasia-like phenotype of PH. HPV and oxygen sensing are important in human health and disease.

Systematic review and meta-analysis of nasal potential difference in hypoxia-induced lung injury

Nasal potential difference (NPD), a well-established in vivo clinical test for cystic fibrosis, reflects transepithelial cation and anion transport in the respiratory epithelium. To analyze whether NPD can be applied to diagnose hypoxic lung injury, we searched PubMed, EMBASE, Scopus, Web of Science, Ovid MEDLINE, and Google Scholar, and analyzed data retrieved from eleven unbiased studies for high altitude pulmonary edema (HAPE) and respiratory distress syndrome (RDS) using the software RevMan and R. There was a significant reduction in overall basal (WMD -5.27 mV, 95% CI: -6.03 to -4.52, P < 0.00001, I(2) = 42%), amiloride-sensitive (ENaC) (-2.87 mV, 95% CI: -4.02 to -1.72, P < 0.00001, I(2) = 51%), and -resistant fractions (-3.91 mV, 95% CI: -7.64 to -0.18, P = 0.04, I(2) = 95%) in lung injury patients. Further analysis of HAPE and RDS separately corroborated these observations. Moreover, SpO2 correlated with ENaC-associated NPD positively in patients only, but apparently related to CFTR-contributed NPD level inversely. These correlations were confirmed by the opposite associations between NPD values and altitude, which had a negative regression with SpO2 level. Basal NPD was significantly associated with amiloride-resistant but not ENaC fraction. Our analyses demonstrate that acute lung injury associated with systemic hypoxia is characterized by dysfunctional NPD.

Acute mountain sickness among tourists visiting the high-altitude city of Lhasa at 3658 m above sea level: a cross-sectional study

BACKGROUND

Traveling to Tibet implies a risk for developing acute mountain sickness (AMS), and the size of this problem is likely increasing due to the rising number of tourists. No previous study on AMS has been conducted among the general tourist population in Tibet. Thus, the aim of this study was to estimate the prevalence and determinants of AMS in a large tourist population visiting Lhasa.

METHODS

A sample of 2385 tourists was recruited from seven randomly selected hotels in Lhasa between June and October 2010. Within three days of their first arrival, the participants filled in a questionnaire based on the Lake Louise Scoring System (LLSS) about AMS-related symptoms and potential contributing factors. AMS was defined as the presence of headache and a cumulative Lake Louise Score ≥4. After estimating the prevalence of AMS, a Log-Binomial Model was applied to analyse the relationship between AMS and selected risk factors.

RESULTS

The prevalence of AMS was 36.7 % (95 % CI: 34.6-38.7 %) and was not dependent on tourists' country of origin. Among the participants who developed AMS, 47.6 % reported that they experienced symptoms within the first 12 h after arriving in Lhasa, and 79.0 % reported that they had to reduce their activity level. A poor or average health condition (adjusted PR 1.63, 95 % CI 1.38-1.93), an age below 55 years (adjusted PR 1.29, 95 % CI 1.04-1.60), a rapid ascent to Lhasa (adjusted PR 1.17, 95 % CI 1.02-1.34) were independent AMS risk factors, while smoking (adjusted PR 0.75, 95 % CI 0.59-0.96) and pre-exposure to high altitude (adjusted PR 0.71, 95 % CI 0.60-0.84) reduced the risk of AMS.

CONCLUSIONS

AMS is commonly experienced by tourists visiting Lhasa Tibet, and often affects their activities. The tourists' country of origin did not seem to affect their risk of AMS, and their age was inversely related to AMS. Subjects planning to visit a high-altitude area should be prepared for experiencing AMS-related problems, and consider preventive measures such as pre-exposure or a gradual ascent to high altitudes.

Diffuse alveolar hemorrhage from systemic lupus erythematosus misdiagnosed as high altitude pulmonary edema

A 26-year-old woman presented with dyspnea and dry cough soon after arriving on the Qinghai-Tibet Plateau (3650 m). Chest radiograph showed diffuse patchy infiltrates. The initial diagnosis was high altitude pulmonary edema (HAPE). However, the patient had no sputum or moist rales, and supplemental oxygen and intravenous aminophylline produced no improvement. Chest HRCT revealed symmetric and diffuse ground glass opacities. Further examination found anemia, leukopenia, urine abnormalities, and increased erythrocyte sedimentation rate. Antibodies for ds-DNA and ANA were positive. Hemoptysis and arthralgia developed after a few days. Finally the patient was diagnosed with diffuse alveolar hemorrhage secondary to systemic lupus erythemetosus.

CONCLUSION

When considering a diagnosis of HAPE, careful attention to physical signs, and a clinical course that is atypical for HAPE should prompt evaluation for other disease processes; HRCT can be useful in this setting.

Three plasma metabolite signatures for diagnosing high altitude pulmonary edema

High-altitude pulmonary edema (HAPE) is a potentially fatal condition, occurring at altitudes greater than 3,000 m and affecting rapidly ascending, non-acclimatized healthy individuals. However, the lack of biomarkers for this disease still constitutes a bottleneck in the clinical diagnosis. Here, ultra-high performance liquid chromatography coupled with Q-TOF mass spectrometry was applied to study plasma metabolite profiling from 57 HAPE and 57 control subjects. 14 differential plasma metabolites responsible for the discrimination between the two groups from discovery set (35 HAPE subjects and 35 healthy controls) were identified. Furthermore, 3 of the 14 metabolites (C8-ceramide, sphingosine and glutamine) were selected as candidate diagnostic biomarkers for HAPE using metabolic pathway impact analysis. The feasibility of using the combination of these three biomarkers for HAPE was evaluated, where the area under the receiver operating characteristic curve (AUC) was 0.981 and 0.942 in the discovery set and the validation set (22 HAPE subjects and 22 healthy controls), respectively. Taken together, these results suggested that this composite plasma metabolite signature may be used in HAPE diagnosis, especially after further investigation and verification with larger samples.