Genetic interaction of Hsp70 family genes polymorphisms with high-altitude pulmonary edema among Chinese railway constructors at altitudes exceeding 4000 meters

Can acute high-altitude sickness be predicted in advance?

In high-altitude environments, the oxygen and air density are decreased, and the temperature and humidity are low. When individuals enter high-altitude areas, they are prone to suffering from acute mountain sickness (AMS) because they cannot tolerate hypoxia. Headache, fatigue, dizziness, and gastrointestinal reactions are the main symptoms of AMS. When these symptoms cannot be effectively alleviated, they can progress to life-threatening high-altitude pulmonary edema or high-altitude cerebral edema. If the risk of AMS can be effectively assessed before people enter high-altitude areas, then the high-risk population can be promptly discouraged from entering the area, or drug intervention can be established in advance to prevent AMS occurrence and avoid serious outcomes. This article reviews recent studies related to the early-warning biological indicators of AMS to provide a new perspective on the prevention of AMS.

Vitamin D3 improved hypoxia-induced lung injury by inhibiting the complement and coagulation cascade and autophagy pathway

BACKGROUND

Pulmonary metabolic dysfunction can cause lung tissue injury. There is still no ideal drug to protect against hypoxia-induced lung injury, therefore, the development of new drugs to prevent and treat hypoxia-induced lung injury is urgently needed. We aimed to explore the ameliorative effects and molecular mechanisms of vitamin D3 (VD3) on hypoxia-induced lung tissue injury.

METHODS

Sprague-Dawley (SD) rats were randomly divided into three groups: normoxia, hypoxia, and hypoxia + VD3. The rat model of hypoxia was established by placing the rats in a hypobaric chamber. The degree of lung injury was determined using hematoxylin and eosin (H&E) staining, lung water content, and lung permeability index. Transcriptome data were subjected to differential gene expression and pathway analyses. In vitro, type II alveolar epithelial cells were co-cultured with hepatocytes and then exposed to hypoxic conditions for 24 h. For VD3 treatment, the cells were treated with low and high concentrations of VD3.

RESULTS

Transcriptome and KEGG analyses revealed that VD3 affects the complement and coagulation cascade pathways in hypoxia-induced rats, and the genes enriched in this pathway were Fgb/Fga/LOC100910418. Hypoxia can cause increases in lung edema, inflammation, and lung permeability disruption, which are attenuated by VD3 treatment. VD3 weakened the complement and coagulation cascade in the lung and liver of hypoxia-induced rats, characterized by lower expression of fibrinogen alpha chain (Fga), fibrinogen beta chain (Fgb), protease-activated receptor 1 (PAR1), protease-activated receptor 3 (PAR3), protease-activated receptor 4 (PAR4), complement (C) 3, C3a, and C5. In addition, VD3 improved hypoxic-induced type II alveolar epithelial cell damage and inflammation by inhibiting the complement and coagulation cascades. Furthermore, VD3 inhibited hypoxia-induced autophagy in vivo and in vitro, which was abolished by the mitophagy inducer, carbonyl cyanide-m-chlorophenylhydrazone (CCCP).

CONCLUSION

VD3 alleviated hypoxia-induced pulmonary edema by inhibiting the complement and coagulation cascades and autophagy pathways.

Suggestive evidence of CYP4F2 gene polymorphisms with HAPE susceptibility in the Chinese Han population

High altitude pulmonary edema (HAPE) is a common respiratory disease in the high altitude area, which is rapid and harmful. We firstly conducted a case-control study to assess the potential association of CYP4F2 gene polymorphisms with HAPE susceptibility in the Chinese Han population. The study recruited 238 patients with HAPE and 230 healthy controls in Northwest China. Genomic DNA was extracted from blood samples, and gene polymorphisms were detected using the Agena MassARRAY platform. Odds ratios (ORs), 95% confidence intervals (95% CIs), and P-value were used to evaluate the relationship between HAPE risk and CYP4F2 gene polymorphisms. Multi-factor dimension reduction (MDR) was used to assess the optimal interaction of CYP4F2 gene polymorphisms on HAPE risk. We found rs3093193 was shown to reduce the risk of HAPE (OR = 0.70, 95% CI = 0.52-0.93, P = 0.014), while rs12459936 was increased the susceptibility to HAPE (OR = 2.08, 95% CI = 1.33-3.26, P = 0.001). Age stratified analysis revealed that rs3093193 and rs12459936 were correlated with HAPE risk in people at age > 32 years old, and rs3093193 and rs3093110 were correlated with the HAPE risk in people at age ≤ 32 years old. Gender stratification analysis was found that rs3093193, rs12459936, and rs3093110 were all related to HAPE risk in males. A combination of rs12459936 and rs3093110 was the best multi-loci model with the highest testing accuracy. Our study is the first to provide the association between CYP4F2 gene polymorphisms and HAPE risk in the Chinese Han population.

Association Between the Polymorphism of Steroid Hormone Metabolism Genes and High-Altitude Pulmonary Edema in the Chinese Han Population

Purpose

Steroid hormone metabolism plays an essential role in high-altitude pulmonary edema (HAPE) progression. This study aimed to investigate the association between polymorphism in seven steroid hormone metabolism genes (STAR, HSD3B1, HSD3B2, CYP17A1, CYP21A2, CYP11B1, and CYP11B2) and HAPE susceptibility among Han Chinese.

Patients and Methods

A total of 41 tagSNPs in the seven genes were genotyped using Sequenom MassARRAY SNP assays from 169 HAPE patients (HAPE-p) and 309 matched Han Chinese individuals resistant to HAPE (HAPE-r). The genotypic and allele frequencies, odds ratios (ORs), and 95% confidence intervals (95% CIs) were calculated.

Results

Four SNPs, including the allele C of rs6203 (p = 0.034, OR [95% CI] = 1.344 [1.022−1.767]) in HSD3B1, allele G of rs3740397 (p = 0.044, OR [95% CI] = 1.314 [1.007−1.714]) and allele C of rs10786712 (p = 0.039, OR [95% CI] = 0.751 [0.572−0.986]) in CYP17A1, and allele T of rs6402 (p = 0.006, OR [95% CI] = 0.504 [0.306−0.830]) in CYP11B1, were significantly associated with HAPE. The distribution of the genotypes of these SNPs also significantly differed between the HAPE-p and HAPE-r groups. Moreover, six haplotypes (the linkage disequilibrium block including rs10883783, rs4919686, rs3740397, rs3824755, and rs10786712) of CYP17A1 were also significantly associated with HAPE.

Conclusion

The four SNPs located in HSD3B1 (rs6203), CYP17A1 (rs3740397 and rs10786712), and CYP11B1 (rs6402) and the six haplotypes of CYP17A1 are likely to have an effect on HAPE.

Toehold probe-based interrogation for haplotype phasing of long nucleic acid strands

The arrangement of multiple single nucleotide polymorphisms (SNPs) in a gene, called a haplotype phase, is increasingly recognized as critical for accurate determination of disease risk and severity. However, conventional toehold-mediated strand displacement reactions are only able to interrogate SNPs, but not phase them since it is not known whether two SNPs in the same copy of the gene (cis) or in different copies of the same gene (trans) will give the same readout. While the rational introduction of an enzyme enables haplotype phasing, the complicated and stable secondary structure of long, single-stranded DNA sequences at room temperature limits its use. Complex nucleic acid structures make the hybridization of the probes difficult. Thus, we designed a molecular method to reveal the relative positions of SNPs located 1.4 kb apart in two copies of a gene by employing a competitive toehold probes and sink strategy at an elevated temperature. As such, we have successfully differentiated 20 nM of the 10 possible diplotypes in a long DNA target with two SNP sites located 1.4 kb apart within an hour without any additional amplification step. This offers a promising technology for accurate and fast haplotype phasing of SNPs that are over multiple kilobases away from each other.

HSPA1A gene polymorphism rs1008438 is associated with susceptibility to acute mountain sickness in Han Chinese individuals

Background

Acute mountain sickness (AMS) usually occurs among non‐acclimated individuals after rapid ascending to high‐altitude environments (generally ≥2,500 m). However, the precise molecular mechanism of AMS remains unclear. Our study aimed to investigate the relationship between several single nucleotide polymorphisms (SNPs) and AMS susceptibility.

Methods

In this work, sequencing data were obtained from 69 AMS patients and 95 matched acclimated Han Chinese individuals from southwest China. Five SNPs (rs1008438, rs150877473, rs1799983, rs2153364, and rs3025039) were systematically investigated in all the participants.

Results

In our study, we found that allele frequencies of “A” (AMS 69.57% vs. non‐AMS 54.74%) and “C” (AMS 30.43% vs. non‐AMS 45.26%) in the HSPA1A gene rs1008438 were significantly different between the AMS and non‐AMS groups (p = .01). Genotypes “CC” and “CA” of the HSPA1A gene (rs1008438) were associated with lower risk of developing AMS than the genotype “AA.” Comparing the genotypes “CC + CA” and “AA,” we also observed that the “CC + CA” genotype of rs1008438 was associated with lower AMS risk.

Conclusions

In our case‐control study, there was a significant association between the rs1008348 polymorphism and AMS susceptibility, suggesting that this particular SNP might be a Han‐specific risk factor for AMS. We believe that this study establishes a foundation for further elucidation of the genetic mechanisms underlying AMS.

Angiotensin-converting enzyme gene insertion/deletion polymorphism and high-altitude pulmonary edema: An updated meta-analysis

Objective:

The purpose of the study was to investigate the association between angiotensin-converting enzyme gene insertion/deletion polymorphism and high-altitude pulmonary edema.

Methods:

A systematic search for relevant literature was performed in MEDLINE, CNKI, and EMBASE. The pooled odds ratios and their corresponding 95% confidence intervals were calculated in STATA 12.0 software.

Results:

Seven studies, with a total of 304 patients and 564 controls, qualified for the inclusion in the analysis. There was no significant association between angiotensin-converting enzyme insertion/deletion polymorphism and high-altitude pulmonary edema risk in the total population (DD vs II: odds ratio=1.07, 95% confidence interval 0.52–2.24; DI vs II: odds ratio=1.12, 0.85–1.49; dominant model: odds ratio=1.07, 0.83–1.40; recessive model: odds ratio=0.96, 0.53–1.77). Subgroup analysis according to race also revealed no significant correlation between angiotensin-converting enzyme gene insertion/deletion polymorphism and high-altitude pulmonary edema.

Conclusions:

Our findings suggest that angiotensin-converting enzyme insertion/deletion polymorphism does not contribute to the risk of high-altitude pulmonary edema. Larger, well-designed studies are required to further validate these results.

Effect of SNPs in HSP Family Genes, Variation in the mRNA and Intracellular Hsp Levels in COPD Secondary to Tobacco Smoking and Biomass-Burning Smoke

Heat shock proteins (HSP) genes are a superfamily responsible for encoding highly conserved proteins that are important for antigen presentation, immune response regulation, and cellular housekeeping processes. These proteins can be increased by cellular stress related to pollution, for example, smoke from biomass burning and/or tobacco smoking. Single nucleotide polymorphisms (SNPs) in these genes could affect the levels of their proteins, as well as the susceptibility to developing lung diseases, such as chronic obstructive pulmonary disease (COPD), related to the exposure to environmental factors.

Methods: The subjects included were organized into two comparison groups: 1,103 smokers (COPD patients, COPD-S = 360; smokers without COPD, SWOC = 743) and 442 never-smokers who were chronically exposed to biomass smoke (COPD patients, COPD-BS = 244; exposed without COPD, BBES = 198). Eight SNPs in three HSP genes were selected and genotyped: four in HSPA1A, two in HSPA1B, and two in HSPA1L. Sputum expectoration was induced to obtain pulmonary cells and relative quantification of mRNA expression. Subsequently, the intracellular protein levels of total Hsp27, phosphorylated Hsp27 (Hsp27p), Hsp60, and Hsp70 were measured in a sample of 148 individuals selected based on genotypes.

Results: In the smokers’ group, by a dominant model analysis, we found associations between rs1008438 (CA+AA; p = 0.006, OR = 1.52), rs6457452 (CT+TT; p = 0.000015, OR = 1.99), and rs2763979 (CT+TT; p = 0.007, OR = 1.60) and the risk to COPD. Among those exposed to biomass-burning smoke, only rs1008438 (CA+AA; p < 0.01, OR = 2.84) was associated. Additionally, rs1008438 was associated with disease severity in the COPD-S group (AA; p = 0.02, OR = 2.09). An increase in the relative expression level of HSPA1A was found (12-fold change) in the COPD-BS over the BBES group. Differences in Hsp27 and Hsp60 proteins levels were found (p < 0.05) in the comparison of COPD-S vs. SWOC. Among biomass-burning smoke-exposed subjects, differences in the levels of all proteins (p < 0.05) were detected.

Conclusion: SNPs in HSP genes are associated with the risk of COPD and severe forms of the disease. Differences in the intracellular Hsp levels are altered depending on the exposition source.

Metabonomics window into plateau hypoxia

Oxygen deficiency in the plateau environment weakens aerobic metabolism and reduces the energy supply, leading to high-altitude diseases including decreased circulatory function, decreased nutrient and energy supply to tissues and organs, and decreased waste discharge. The involvement of many metabolic pathways is reflected in dramatic changes in levels of endogenous small molecule metabolites. Metabolomics represents a promising technique for mechanistic studies and drug screening, and metabonomics, or quantitative metabolomics, has been increasingly applied to the study of hypoxic diseases and their pathogenesis, as well as to pharmacodynamics at high altitudes. In this article, we review the recent literature on the pathogenesis of altitude hypoxia and the clinical and preclinical metabonomics of drug interventions. Endogenous metabolites and metabolic pathways change significantly under high-altitude hypoxia. Some drug interventions have also been shown to regulate pathway metabolism, and the problems of applying metabonomics to hypoxic diseases at high altitude and the prospects for its future application are summarized.

Genetic diversity and natural selection in wild fruit flies revealed by whole-genome resequencing

We characterized 26 wild fruit flies comparative population genomics from six different altitude and latitude locations by whole genome resequencing. Genetic diversity was relatively higher in Ganzi and Chongqing populations. We also found 13 genes showing selection signature between different altitude flies and variants related to hypoxia and temperature stimulus, were preferentially selected during the flies evolution. One of the most striking selective sweeps found in all high altitude flies occurred in the region harboring Hsp70Aa and Hsp70Ab on chromosome 3R. Interestingly, these two genes are involved in GO terms including response to hypoxia, unfolded protein, temperature stimulus, heat, oxygen levels. Mutation in HPH gene, a candidate gene in the hypoxia inducible factor pathway, might contributes to hypoxic high-altitude adaptation. Intriguingly, some of the selected genes, primarily utilized in humans, were involved in the response to hypoxia, which could imply a conserved molecular mechanisms underlying high-altitude adaptation between insects and humans.

Evidence for and Against Genetic Predispositions to Acute and Chronic Altitude Illnesses

MacInnis, Martin J., and Michael S. Koehle. Evidence for and against genetic predispositions to acute and chronic altitude illnesses. High Alt Med Biol. 17:281-293, 2016.-Humans exhibit marked variation in their responses to hypoxia, with susceptibility to acute and chronic altitude illnesses being a prominent and medically important example. Many have hypothesized that genetic differences are the cause of these variable responses to hypoxia; however, until recently, these hypotheses were based primarily on small (and sometimes anecdotal) reports pertaining to apparent differences in altitude illness susceptibility between populations, the notion that a history of altitude illness is indicative of subsequent risk, the heritability of hypoxia-related traits, and candidate gene association studies. In the past 5 years, the use of genomic techniques has helped bolster the claim that susceptibility to some altitude illnesses is likely the result of genetic variation. For each of the major altitude illnesses, we summarize and evaluate the evidence stemming from three important characteristics of a genetic trait: (1) individual susceptibility and repeatability across assessments, (2) biogeographical differences and familial aggregation, and (3) association(s) with genetic variants. Evidence to support a genetic basis for susceptibilities to acute mountain sickness (AMS) and high-altitude cerebral edema (HACE) is limited, owing partially to the subjective and unclear phenotype of AMS and the rarity and severity of HACE. In contrast, recent genomic studies have identified genes that influence susceptibility to high-altitude pulmonary edema, chronic mountain sickness, and high-altitude pulmonary hypertension. The collection of more individual, familial, and biogeographical susceptibility data should improve our understanding of the extent to which genetic variation contributes to altitude illness susceptibility, and genomic and molecular investigations have the potential to elucidate the mechanisms that underpin altitude illness susceptibility.

Metabolite Modulation in Human Plasma in the Early Phase of Acclimatization to Hypobaric Hypoxia

The exposure of healthy subjects to high altitude represents a model to explore the pathophysiology of diseases related to tissue hypoxia. We explored a plasma metabolomics approach to detect alterations induced by the exposure of subjects to high altitude. Plasma samples were collected from 60 subjects both on plain and at high altitude (5300 m). Metabolite profiling was performed by gas chromatography-mass spectrometry (GC-MS) and ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOFMS) in conjunction with univariate and multivariate statistical analyses. ELISA assays were further employed to measure the levels of several relevant enzymes together with perturbed metabolic pathways. The results showed that hypobaric hypoxia caused significant and comprehensive metabolic changes, as represented by significant changes of 44 metabolites and 4 relevant enzymes. Using MetaboAnalyst 3.0, it was found that several key metabolic pathways were acutely perturbed. In addition, 5 differentially expressed metabolites in pre-exposure samples from the acute mountain sickness-susceptible (AMS-S) group compared with those from the AMS-resistant (AMS-R) group are identified, which warrant further validation as potential predictive biomarkers for AMS-S individuals. These results provide new insights for further understanding the pathophysiological mechanism of early acclimatization to hypobaric hypoxia and other diseases correlated to tissue hypoxia.

Association of Plasma Heat Shock Protein 70, Interleukin 6, and Creatine Kinase Concentrations in a Healthy, Young Adult Population

Variations of baseline plasma concentrations of creatine kinase (CK), heat shock protein 70 (HSP70), and interleukin 6 (IL-6) have been reported. We report categorical associations which may influence these protein levels. Methods. Blood was harvested for DNA and plasma protein analysis from 567 adults. Mean protein levels of CK, HSP70, and IL-6 were compared by sex, ethnicity, genetic variants-CKMM Nco1 (rs1803285), HSPA1B +A1538G (rs1061581), and IL6 G-174C (rs1800795)-self-reported history of exercise, oral contraceptive use, and dietary supplement use. Results. SNP major allele frequencies for CKMM, HSPA1B, and IL6 were 70% A, 57% A, and 60%. Mean CK statistically differed by sex, ethnicity, oral contraceptives, and caffeine. Plasma HSP70 differed by caffeine and protein. Mean IL-6 concentration differed by sex, ethnicity, and genotype. Plasma IL-6 was significantly lower (29%) in males (1.92 ± 0.08 pg/mL) and higher (29%) among African Americans (2.85 ± 0.50 pg/mL) relative to the others. IL6 G-174C GG genotype (2.23 ± 0.14 pg/mL) was 19% greater than CG or CC genotypes. Conclusion. Differences in baseline CK and IL-6 plasma protein concentrations are associated with genetics, sex, ethnicity, and the use of oral contraceptives, caffeine, and protein supplements in this young and athletic population.

Fever, immunity, and molecular adaptations

The heat shock response (HSR) is an ancient and highly conserved process that is essential for coping with environmental stresses, including extremes of temperature. Fever is a more recently evolved response, during which organisms temporarily subject themselves to thermal stress in the face of infections. We review the phylogenetically conserved mechanisms that regulate fever and discuss the effects that febrile-range temperatures have on multiple biological processes involved in host defense and cell death and survival, including the HSR and its implications for patients with severe sepsis, trauma, and other acute systemic inflammatory states. Heat shock factor-1, a heat-induced transcriptional enhancer is not only the central regulator of the HSR but also regulates expression of pivotal cytokines and early response genes. Febrile-range temperatures exert additional immunomodulatory effects by activating mitogen-activated protein kinase cascades and accelerating apoptosis in some cell types. This results in accelerated pathogen clearance, but increased collateral tissue injury, thus the net effect of exposure to febrile range temperature depends in part on the site and nature of the pathologic process and the specific treatment provided.

High altitude pulmonary edema in an experienced mountaineer. possible genetic predisposition

High altitude pulmonary edema (HAPE) is a form of high altitude illness characterized by cough, dyspnea upon exertion progressing to dyspnea at rest and eventual death, seen in patients who ascend over 2,500 meters, particularly if that ascent is rapid. This case describes a patient with no prior history of HAPE and extensive experience hiking above 2,500 meters who developed progressive dyspnea and cough while ascending to 3,200 meters. His risk factors included rapid ascent, high altitude, male sex, and a possible genetic predisposition for HAPE.

Association between heat shock protein 70 gene polymorphisms and clinical outcomes in intensive care unit patients with sepsis

Objective:

The objective of the following study is to evaluate the associations between single nucleotide polymorphisms (SNPs) in the Heat Shock Protein 70 (HSP70) gene, gene expression of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) and medical intensive care unit (MICU) stay and organ failure in sepsis.

Materials and Methods:

MICU patients with sepsis were genotyped for rs1061581, rs2227956, rs1008438 and rs1043618 polymorphisms in HSP70 gene using polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis or allele-specific PCR. Messenger ribonucleic acid (mRNA) expression of IL-6 and TNF-α were quantitated in peripheral blood lymphocytes. Outcomes were recorded.

Results:

108 patients (48 male) aged 40.7 ± 16.0 (mean ± standard deviation) years included H1N1 infection (36), scrub typhus (29) and urosepsis (12). Seventy-one (65.7%) had dysfunction of three or more organ systems, 66 patients (61.1%) were treated by mechanical ventilation, 21 (19.4%) needed dialysis. ICU stay was 9.3 ± 7.3 days. Mortality was 38.9%. One or more SNPs were noted in 101/108 (93.5%) and organ failure was noted in only 1/7 patients without a single SNP. The A allelotypes of rs1061581 and rs1008438 were associated with hematological dysfunction (P = 0.03 and 0.07) and longer ICU stay (P = 0.05 and 0.04), whereas IL-6 and TNF-α mRNA levels were associated with central nervous system dysfunction.

Conclusions:

HSP70 genotypes may determine some adverse outcomes in patients with sepsis.

Polymorphisms of the tissue inhibitor of metalloproteinase 3 gene are associated with resistance to high-altitude pulmonary edema (HAPE) in a Japanese population: a case control study using polymorphic microsatellite markers

Introduction

High-altitude pulmonary edema (HAPE) is a hypoxia-induced, life-threatening, high permeability type of edema attributable to pulmonary capillary stress failure. Genome-wide association analysis is necessary to better understand how genetics influence the outcome of HAPE.

Materials and Methods

DNA samples were collected from 53 subjects susceptible to HAPE (HAPE-s) and 67 elite Alpinists resistant to HAPE (HAPE-r). The genome scan was carried out using 400 polymorphic microsatellite markers throughout the whole genome in all subjects. In addition, six single nucleotide polymorphisms (SNPs) of the gene encoding the tissue inhibitor of metalloproteinase 3 (TIMP3) were genotyped by Taqman® SNP Genotyping Assays.

Results

The results were analyzed using case-control comparisons. Whole genome scanning revealed that allele frequencies in nine markers were statistically different between HAPE-s and HAPE-r subjects. The SNP genotyping of the TIMP3 gene revealed that the derived allele C of rs130293 was associated with resistance to HAPE [odds ratio (OR) = 0.21, P = 0.0012) and recessive inheritance of the phenotype of HAPE-s (P = 0.0012). A haplotype CAC carrying allele C of rs130293 was associated with resistance to HAPE.

Discussion

This genome-wide association study revealed several novel candidate genes associated with susceptibility or resistance to HAPE in a Japanese population. Among those, the minor allele C of rs130293 (C/T) in the TIMP3 gene was linked to resistance to HAPE; while, the ancestral allele T was associated with susceptibility to HAPE.

Genetic variations of HSPA1A, the heat shock protein levels, and risk of atherosclerosis

HSPA1A is a serum and intracellular heat shock protein with antiapoptotic and antithrombotic properties. The present study examines the hypothesis that a decrease in the synthesis of this protein in relation to certain polymorphisms of the regulatory region of the HSPA1A gene can define a vascular disease risk phenotype. A randomly selected population was studied and stratified into groups according to the degree of vascular risk. After applying the Task Force Chart to 452 people, the subjects were divided into three groups: group 0 (no vascular risk factor or risk < 5%), n = 239; group 1 (moderate (10-20%) risk, with no clinical cardiovascular disease), n = 161; and group 2 (overt atherosclerosis), n = 52. Serum and intragranulocytic HSPA1A was quantified, and direct Sanger sequencing was performed in all subjects. An analysis was made of the association of two single nucleotide polymorphisms (db rs1008438 -110A/C and db rs1043618 +190 G/C) with circulating and intragranulocytic HSPA1A and the risk of atherosclerosis. The atherosclerotic subjects showed significantly lower circulating HSPA1A levels than the other groups, regardless of the genotype. The patients with CC genotype for both polymorphisms showed significantly lower intragranulocytic HSPA1A levels than the other genotypes. Serum HSPA1A concentrations could be proposed as a biomarker of cardiovascular disease. CC homozygosis for polymorphisms db rs1008438 and db rs1043618 is associated with a decrease in the intragranulocytic production of HSPA1A. Given the antiatherogenic functions of intracellular HSPA1A, the -110A and +190 G alleles could constitute potential genetic biomarkers of a less severe clinical phenotype for the risk of developing atherosclerosis.

The genetics of altitude tolerance: the evidence for inherited susceptibility to acute mountain sickness

OBJECTIVE

Acute mountain sickness (AMS) has become a significant environmental health issue as improvements in transportation, "environmental tourism," and resource development lure more people to the highlands. Whether there is a genetic contribution to AMS susceptibility is a central question in high-altitude medicine. This article provides a systematic review of the evidence supporting such an innate predisposition.

METHODS

Scientific literature databases were screened using the terms "acute mountain sickness/AMS" and "altitude illness" combined with the terms "DNA," "gene," "genetic," or "polymorphism."

RESULTS

Sixteen genes from a variety of pathways have been tested for association with AMS and variants in eight showed positive associations suggesting that AMS is an environmentally mediated polygenic disorder.

CONCLUSIONS

The data suggest that genotype contributes to capacity to rapidly and efficiently acclimatize to altitude; nevertheless, the mechanisms by which this occurs have yet to be elucidated.

Association of angiotensin-converting enzyme gene insertion/deletion polymorphism with high-altitude pulmonary oedema: a meta-analysis

Background and objective: High-altitude pulmonary oedema (HAPE) is a non-cardiogenic hydrostatic oedema involving a genetic component. Considering the low incidence of HAPE, sample sizes in current reports are relatively limited. We aimed to assess the association between the angiotensin-converting enzyme (ACE) I/D polymorphism and HAPE via a meta-analysis of published and unpublished data.

Materials and methods: We searched PubMed, CBM, CNKI, and Cochrane Library Database before 20 November 2010. A random-effects model was applied (STATA) and study quality was assessed in duplicate.

Results: A total of five studies including 305 cases and 662 controls were meta-analysed. The summary odds ratio (OR) indicated that no significant differences in risk of developing HAPE were found between carriers of ACE D and I alleles (OR = 1.20; 95% confidence interval (CI), 0.98–1.48; p = 0.084). Lack of association persisted for genotypes under the recessive mode. However, genotype association under the dominant mode showed D allele carriers significantly conferred a 1.55-fold increased HAPE risk compared with II genotype carriers (95% CI, 1.15–2.08; p = 0.004). Funnel plot and Egger’s test suggested no evidence of publication bias.

Conclusions: Our results supported the notion that ACE D allele carriers were at significant increased risk of developing HAPE.

Evidence for a genetic basis for altitude illness: 2010 update

Altitude illness refers to a group of environmentally mediated pathophysiologies. Many people will suffer acute mountain sickness shortly after rapidly ascending to a moderately hypoxic environment, and an unfortunate few will develop potentially fatal conditions such as high altitude pulmonary edema or high altitude cerebral edema. Some individuals seem to be predisposed to developing altitude illness, suggesting an innate contribution to susceptibility. The implication that there are altitude-sensitive and altitude-tolerant individuals has stimulated much research into the contribution of a genetic background to the efficacy of altitude acclimatization. Although the effect of altitude attained and rate of ascent on the etiology of altitude illness is well known, there are only tantalizing, but rapidly accumulating, clues to the genes that may be involved. In 2006, we reviewed what was then known about the genetics of altitude illness. This article updates that review and attempts to tabulate all the available genetic data pertaining to these conditions. To date, 58 genes have been investigated for a role in altitude illness. Of these, 17 have shown some association with the susceptibility to, or the severity of, these conditions, although in many cases the effect size is small or variable. Caution is recommended when evaluating the genes for which no association was detected, because a number of the investigations reviewed in this article were insufficiently powered to detect small effects. No study has demonstrated a clear-cut altitude illness gene, but the accumulating data are consistent with a polygenic condition with a strong environmental component. The genes that have shown an association affect a variety of biological pathways, suggesting that either multiple systems are involved in altitude pathophysiology or that gene-gene interactions play a role. Although numerous studies have been performed to investigate specific genes, few have looked for evidence of heritability or familial transmission, or for epidemiological patterns that would be consistent with genetically influenced conditions. Future trends, such as genome-wide association studies and epigenetic analysis, should lead to enhanced understanding of the complex interactions within the genome and between the genome and hypoxic environments that contribute to an individual's capacity to acclimatize rapidly and effectively to altitude.

Endothelial nitric oxide synthase gene polymorphisms associated with susceptibility to high altitude pulmonary edema in Chinese railway construction workers at Qinghai-Tibet over 4 500 meters above sea level

OBJECTIVE

To examine whether the polymorphisms of endothelial nitric oxide synthase (eNOS) gene are associated with the susceptibility to high altitude pulmonary edema (HAPE) in Chinese railway construction workers at Qinghai-Tibet where the altitude is over 4 500 m above sea level.

METHODS

A case-control study was conducted including 149 HAPE patients in the construction workers and 160 healthy controls randomly recruited from their co-workers, matching the patients in ethnicity, age, sex, lifestyle, and working conditions. Three polymorphisms of eNOS gene, T-786C in promoter, 894G/T in exon 7, and 27bp variable number tandem repeat (VNTR) in intron 4, were genotyped using polymerase chain reaction (PCR) and confirmed with DNA sequencing.

RESULTS

The frequencies of 894T allele and heterozygous G/T of the 894G/T variant were significantly higher in HAPE patients group than in the control group (P=0.0028 and P=0.0047, respectively). However, the frequencies of the T-786C in promoter and the 27bp VNTR in intron 4 were not significantly different between the two groups. Haplotypic analysis revealed that the frequencies of two haplotypes (H3,T-T-b, b indicates 5 repeats of 27 bp VNTR; H6, C-G-a, a indicates 4 repeats of 27 bp VNTR) were significantly higher in HAPE patients (both Pü0.0001). On the contrary, the frequencies of H1 (T-G-b) and H2 (T-G-a) were lower in HAPE patients than in healthy controls (both Pü0.001).

CONCLUSIONS

Two haplotypes (T-T-b and C-G-a) may be strongly associated with susceptibility to HAPE. Compared with the individual alleles of eNOS gene, the interaction of multiple genetic markers within a haplotype may be a major determinant for the susceptibility to HAPE.

Polymorphisms in the Hsp70 gene locus are genetically associated with systemic lupus erythematosus

BACKGROUND

Heat shock proteins (Hsps) play a role in the delivery and presentation of antigenic peptides and are thought to be involved in the pathogenesis of multifactorial diseases.

OBJECTIVE

To investigate genes encoding cytosolic Hsp70 proteins for associations of allelic variants with systemic lupus erythematosus (SLE).

METHODS

Case-control studies of two independent Caucasian SLE cohorts were performed. In a haplotype-tagging single-nucleotide polymorphism approach, common variants of HspA1L, HspA1A and HspA1B were genotyped and principal component analyses were performed for the cohort from the Oklahoma Medical Research Foundation (OMRF). Relative quantification of mRNA was carried out for each Hsp70 gene in healthy controls. Conditional regression analysis was performed to determine if allelic variants in Hsp70 act independently of HLA-DR3.

RESULTS

On analysis of common genetic variants of HspA1L, HspA1A and HspA1B, a haplotype significantly associated with SLE in the Erlangen-SLE cohort was identified, which was confirmed in the OMRF cohort. Depending on the cohorts, OR ranging from 1.43 to 1.88 and 2.64 to 3.16 was observed for individuals heterozygous and homozygous for the associated haplotype, respectively. Patients carrying the risk haplotype or the risk allele more often displayed autoantibodies to Ro and La in both cohorts. In healthy controls bearing this haplotype, the amount of HspA1A mRNA was significantly increased, whereas total Hsp70 protein concentration was not altered.

CONCLUSIONS

Allelic variants of the Hsp70 genes are significantly associated with SLE in Caucasians, independently of HLA-DR3, and correlate with the presence of autoantibodies to Ro and La. Hence, the Hsp70 gene locus appears to be involved in SLE pathogenesis.

No association between alleles of the bradykinin receptor-B2 gene and acute mountain sickness

The pathophysiological mechanism(s) of the development of acute mountain sickness (AMS) is still unclear. Although the chance of developing AMS and the severity of the condition are influenced by ascent rate and altitude attained, previous history is a reliable predictor of subsequent affliction, and some individuals and families are clearly predisposed, suggesting a genetic component to susceptibility. As the vasodilator bradykinin may be involved in acclimatization to altitude, we hypothesized that variants in genes encoding components of this pathway might play a role in AMS susceptibility. We tested this by looking for associations between two functional polymorphisms (the in/del polymorphism +9/−9 [rs5810761] and the single-nucleotide polymorphism C − 58T [rs1799722]) of BDKRB2 (the gene encoding the bradykinin receptor B2) and susceptibility to AMS in an altitude-exposed Nepalese population. Lowland attendees ( n = 233) at a religious festival at 4380 m in the Nepalese Himalaya were recruited and assessed for AMS by clinical evaluation and Lake Louise score (LLS). Those with a clinical diagnosis of AMS and an LLS ≥3 were designated AMS+ ( n = 100) and those without a diagnosis of AMS and with an LLS <3 were categorized as AMS− ( n = 117). DNA was prepared from buccal cells, genotyped for the two polymorphisms and allele frequencies compared between the two cohorts. No association was found between alleles at either polymorphism and susceptibility to AMS ( P > 0.50), although C − 58T heterozygotes were significantly more common ( P < 0.001, χ2 = 49.6) in the subjects than would be predicted if the population was in Hardy–Weinberg equilibrium. The results of our association study do not support the hypothesis that variants in BDKRB2 influence altitude tolerance in a lowland Nepalese population; however, the deviation from Hardy–Weinberg equilibrium observed for the C − 58T polymorphism could be explained by self-selection for altitude tolerance in the festival attendees.

Neural networks for modeling gene-gene interactions in association studies

Background

Our aim is to investigate the ability of neural networks to model different two-locus disease models. We conduct a simulation study to compare neural networks with two standard methods, namely logistic regression models and multifactor dimensionality reduction. One hundred data sets are generated for each of six two-locus disease models, which are considered in a low and in a high risk scenario. Two models represent independence, one is a multiplicative model, and three models are epistatic. For each data set, six neural networks (with up to five hidden neurons) and five logistic regression models (the null model, three main effect models, and the full model) with two different codings for the genotype information are fitted. Additionally, the multifactor dimensionality reduction approach is applied.

Results

The results show that neural networks are more successful in modeling the structure of the underlying disease model than logistic regression models in most of the investigated situations. In our simulation study, neither logistic regression nor multifactor dimensionality reduction are able to correctly identify biological interaction.

Conclusions

Neural networks are a promising tool to handle complex data situations. However, further research is necessary concerning the interpretation of their parameters.

Neural networks for modeling gene-gene interactions in association studies

BACKGROUND

Our aim is to investigate the ability of neural networks to model different two-locus disease models. We conduct a simulation study to compare neural networks with two standard methods, namely logistic regression models and multifactor dimensionality reduction. One hundred data sets are generated for each of six two-locus disease models, which are considered in a low and in a high risk scenario. Two models represent independence, one is a multiplicative model, and three models are epistatic. For each data set, six neural networks (with up to five hidden neurons) and five logistic regression models (the null model, three main effect models, and the full model) with two different codings for the genotype information are fitted. Additionally, the multifactor dimensionality reduction approach is applied.

RESULTS

The results show that neural networks are more successful in modeling the structure of the underlying disease model than logistic regression models in most of the investigated situations. In our simulation study, neither logistic regression nor multifactor dimensionality reduction are able to correctly identify biological interaction.

CONCLUSIONS

Neural networks are a promising tool to handle complex data situations. However, further research is necessary concerning the interpretation of their parameters.