Fuyu Liu

Hypobaric hypoxia causes deleterious effects on spermatogenesis in rats

The study was conducted to explore the effects of hypobaric hypoxia on spermatogenesis in rats. Adult male Wistar rats were randomly divided into four groups: three hypoxia-exposed groups and one normoxic control group. Rats in the normoxic control group were raised at an altitude of 300 m, while rats in the 5-, 15-, and 30-day hypoxic groups were raised in a hypobaric chamber simulating a high altitude of 5000 m for 5, 15, and 30 days respectively. Flow cytometry was used to detect the DNA content of testicular spermatogenic cells in rats. The apoptosis of germ cells in testis was analyzed by using TUNEL assay. Spermatogenesis was also evaluated by morphology. Flow cytometry analysis revealed that 5-30 days of hypobaric hypoxia exposure significantly reduced the percentage of tetraploid cell population in rat testis. After rats were exposed to hypobaric hypoxia for 30 days, the ratio of haploid and diploid cell populations in testis reduced significantly. Seminiferous tubules with apoptotic germ cell increased after exposure to hypoxia. Most apoptotic germ cells were spermatogonia and spermatocytes. Hypoxia also caused decrease of cellularity of seminiferous epithelium, degeneration and sloughing of seminiferous epithelial cells occasionally. The data suggest that hypobaric hypoxia inhibits the spermatogenesis in rats. Decrease of tetraploid spermatogenic cells (primary spermatocytes) induced by hypoxia is an important approach to suppress spermatogenesis. The apoptosis of primary spermatocytes and spermatogonia may contribute to the loss of tetraploid cell populations.

Silencing of STIM1 attenuates hypoxia-induced PASMCs proliferation via inhibition of the SOC/Ca2+/NFAT pathway

BackgroundStromal interaction molecule 1 (STIM1) is a newly discovered Ca2+ sensor on the endoplasmic reticulum which is an indispensable part in the activation of store-operated Ca2+ channels (SOC). Recent studies demonstrate that SOC of pulmonary smooth muscle cells (PASMCs) were upregulated by chronic hypoxia which contribute to the enhanced pulmonary vasoconstriction and vascular remodeling. However, the exact role of STIM1 in the development of chronic hypoxic pulmonary hypertension(HPH) remains unclear.MethodsIn this study we investigated the cellular distribution and expression of STIM1 by immunofluorescence, qRTPCR and Western blotting methods in Wistar rat distal intrapulmonary arteries under normal and chronic hypobaric hypoxic conditions. In vitro, Wistar rat PASMCs were isolated and cultured. PASMCs were transfected with siRNA targeting STIM1 gene by liposome. The expression of STIM1 protein was detected by Western blotting. [3H]-thymidine ([3H]-TdR) incorporation were performed to detect PASMCs proliferation. The cell cycle was analyzed by flow cytometry. The SOC-mediated Ca2+ influx was calculated by Ca2+ fluorescence imaging and the nuclear translocation of NFATc3 was determined by immunofluorescence and Western blot analysis of nuclear extracts.ResultsWe found that during the development of HPH and the initiation of vascular remodeling, the mRNA and protein expression levels of STIM1 significantly increased in the distal intrapulmonary arteries. Moderate hypoxia significantly promotes PASMCs proliferation and cell cycle progression. Silencing of STIM1 significantly decreased cellular proliferation and delayed the cell cycle progression induced by hypoxia. Silencing of STIM1 also significantly decreased SOC-mediated Ca2+ influx and inhibited the nuclear translocation of NFATc3 in hypoxic PASMCs.ConclusionOur findings suggest that chronic hypobaric hypoxia upregulates the expression of STIM1 in the distal intrapulmonary arteries which plays an important role in the hypoxia-induced PASMCs proliferation via SOC/Ca2+/NFAT pathway and may represent a novel therapeutic target for the prevention of hypoxia pulmonary hypertension.

Predictive Value of Basal Exhaled Nitric Oxide and Carbon Monoxide for Acute Mountain Sickness

OBJECTIVE The purpose of this study was to examine the relationship between acute mountain sickness (AMS) and the fraction of exhaled nitric oxide (Fe(NO)) and carbon monoxide (Fe(CO)) before ascent to high altitude and to evaluate their predictive value for AMS. METHODS A total of 314 healthy young male recruits were voluntarily enrolled. Before ascent to an elevation of 4300 m, their Fe(NO) and Fe(CO) values, demographic factors, drinking and smoking history, vital capacity, and forced vital capacity were obtained. The investigators followed the subjects in the first exposure week to obtain their Lake Louise Score (LLS) each day. Subjects with LLS > 4, headache, and at least 1 other symptom were diagnosed with AMS, and the highest LLS of each individual during 7 days was considered the final LLS score. RESULTS The AMS group had lower Fe(NO) (P = .003) and Fe(CO) (P < .001) values, and a lower smoking rate (P < .001) than the non-AMS group. Mean Fe(NO) and Fe(CO) values were 11.03 ppb (95% CI, 9.07 to 12.98) and 4.39 ppm (95% CI, 3.76 to 5.02), respectively, in the AMS group, and 14.74 ppb (95% CI, 13.25 to 16.23) and 6.10 ppm (95% CI, 5.49 to 6.72), respectively, in the non-AMS group (P < .0001). Using linear regression, both Fe(NO) and Fe(CO) were found to be significantly associated with the groups maximal LLS. Using logistic regression, Fe(NO) and Fe(CO) were also found to be significantly associated with AMS. CONCLUSIONS Basal Fe(NO) and Fe(CO) are significantly negatively correlated with AMS development. However, the gases have only modest predictive value for the development of AMS.

Rare Mitochondrial DNA Polymorphisms are Associated with High Altitude Pulmonary Edema (HAPE) Susceptibility in Han Chinese

BACKGROUND The role of genetics in determining an individuals susceptibility to high altitude pulmonary edema (HAPE) is unclear. However a number of genetic polymorphisms have recently been found to be overrepresented in patients with HAPE. Changes at the mitochondrial level may play an important role in the human bodys adaptation to hypoxia. Polymorphisms of mitochondrial DNA (mtDNA) have been shown to be responsible for differences in organelle function. Therefore, the frequency of mtDNA 3397A/G and 3552T/A polymorphisms were studied to determine their potential role in HAPE. OBJECTIVES To further study the role of mtDNA 3397A/G and 3552T/A variations of reduced nicotinamide adenosine dinucleotide dehydrogenase 1 in HAPE susceptibility. METHODS The single-nucleotide polymorphisms of mtDNA 3397 and 3552 in patients with HAPE (n = 132) and their matched control subjects (n = 233) were studied using polymerase chain reaction sequencing. RESULTS The frequency of mtDNA 3397G in the HAPE group (2.3%) was significantly higher than that of the control group (0%; P = .021; odds ratio, 2.806; 95% confidence interval, 2.443 to 3.223). The frequency of mtDNA 3552A in the HAPE group (6.8%) also was significantly higher than in the control group (1.7%; P = .012; odds ratio, 4.198; 95% confidence interval, 1.264 to 13.880). CONCLUSIONS In this study, we present the first evidence of differences in mtDNA polymorphism frequencies between HAPE victims and healthy Han Chinese. Genotypes of mtDNA 3397G and 3552A were correlated with HAPE susceptibility. This result could contribute to defining the role of the mitochondrial genome in the pathogenesis of HAPE.

Mitochondrial nt3010G-nt3970C haplotype is implicated in high-altitude adaptation of Tibetans

Tibetans are well adapted to living and thriving in high-altitude environments. Mitochondria are central links to oxygen consumption, and variations in mitochondrial DNA (mtDNA) could play a role in high-altitude adaptation. Alleles at several polymorphic sites in mtDNA define common haplotypes, or haplogroups, including some that have been implicated in the risk of developing certain diseases. However, few reports have determined whether relationships exist between haplogroups and high-altitude adaptation in the Tibetan population. The D4 haplogroup is a major haplogroup of the Han Chinese. In the present study, genotypes of 12 polymorphisms were determined in members of a Tibetan population (n = 72), low altitude-Han (la-Han, n = 144), and high altitude-Han (ha-Han, n = 227) populations using polymerase chain reaction–restriction fragment length polymorphism and polymerase chain reaction–ligase detection reaction assays. The mitochondrial haplogroup D4 was negatively associated with high-altitude adaptation in Tibetans (P = 0.001 vs. la-Han, OR = 0.166, 95% CI = 0.048–0.567; P = 0.009 vs. ha-Han OR = 0.232, 95% CI = 0.069–0.778). The frequency of the nt3010G-nt3970C haplotype was significantly higher in Tibetans than in la-Han (P = 0.000) and ha-Han (P = 0.001) subjects. Findings in the present study suggest that unique mitochondrial variations determine a genetic background that is associated with high-altitude adaptation in the Tibetan population.

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.

Gene expression profiling of high altitude polycythemia in Han Chinese migrating to the Qinghai-Tibetan plateau

Chronic mountain sickness (CMS) is a condition in which the hematocrit is increased above the normal level in residents at high altitude. High altitude polycythemia (HAPC) is the most characteristic sign of CMS. However, the pathogenesis of HAPC is poorly understood. The present study aimed to investigate the gene expression profile of HAPC in Han Chinese migrating to the Qinghai-Tibetan Plateau and to identify the pathogenetic mechanisms. A total of 9 differentially expressed genes were identified in HAPC patients using microarrays: 5 were up-regulated and 4 were down-regulated. Functional analysis of the array data revealed that cell division cycle 42 (CDC42) and the human immune response may be key features underlying the mechanism and development of HAPC.

Mitochondrial genome sequence of the Tibetan wild ass (Equus kiang)

The Tibetan wild ass, or kiang (Equus kiang) is endemic to the cold and hypoxic (4000–7000 m above sea level) climates of the montane and alpine grasslands of the Tibetan Plateau. We report here the complete nucleotide sequence of the E. kiang mitochondrial genome. Our results show that E. kiang mitochondrial DNA is 16,634 bp long, and predicted to encode all the 37 genes that are typical for vertebrates.

An EPAS1 Haplotype Is Associated With High Altitude Polycythemia in Male Han Chinese at the Qinghai-Tibetan Plateau

BACKGROUND Hemoglobin concentration at high altitude is considered an important marker of high altitude adaptation, and native Tibetans in the Qinghai-Tibetan plateau show lower hemoglobin concentrations than Han people who have emigrated from plains areas. Genetic studies revealed that EPAS1 plays a key role in high altitude adaptation and is associated with the low hemoglobin concentration in Tibetans. Three single nucleotide polymorphisms (rs13419896, rs4953354, rs1868092) of noncoding regions in EPAS1 exhibited significantly different allele frequencies in the Tibetan and Han populations and were associated with low hemoglobin concentrations in Tibetans. METHODS To explore the hereditary basis of high altitude polycythemia (HAPC) and investigate the association between EPAS1 and HAPC in the Han population, these 3 single nucleotide polymorphisms were assessed in 318 male Han Chinese HAPC patients and 316 control subjects. Genotyping was performed by high resolution melting curve analysis. RESULTS The G-G-G haplotype of rs13419896, rs4953354, and rs1868092 was significantly more frequent in HAPC patients than in control subjects, whereas no differences in the allele or genotype frequencies of the 3 single nucleotide polymorphisms were found between HAPC patients and control subjects. Moreover, genotypes of rs1868092 (AA) and rs4953354 (GG) that were not observed in the Chinese Han in the Beijing population were found at frequencies of 1.6% and 0.9%, respectively, in our study population of HAPC patients and control subjects. CONCLUSIONS Carriers of this EPAS1 haplotype (G-G-G, rs13419896, rs4953354, and rs1868092) may have a higher risk for HAPC. These results may contribute to a better understanding of the pathogenesis of HAPC in the Han population.

Interaction of CARD14, SENP1 and VEGFA polymorphisms on susceptibility to high altitude polycythemia in the Han Chinese population at the Qinghai–Tibetan Plateau

High altitude polycythemia (HAPC) is a serious public health problem among Han Chinese immigrants to the Qinghai-Tibetan Plateau. This study aims to explore the genetic basis of HAPC in the Han Chinese population. 484 male subjects (234 patients and 250 controls) were enrolled in this study. Genotyping was performed for polymorphisms of I/D in ACE, C1772T and G1790A in exon 12 of HIF-1α, rs2567206 in CYP1B1, rs726354 in SENP1, rs3025033 in VEGFA, rs7251432 in HAMP, rs2075800 in HSPA1L and rs8065364 in CARD14. Gene-gene interaction was assessed by multifactor dimensionality reduction. A significant association was seen between CARD14 polymorphism rs8065364 and risk of HAPC development in male Han Chinese, and the C allele of rs8065364 was a risk factor (odds ratio (OR)=1.59, 95% confidence interval (95% CI)=1.21-2.08). Gene-gene interaction analysis indicated that a synergistic relationship existed between rs3025033 and rs8065364 (1.00%), rs3025033 and rs726354 (0.18%), and rs726354 and rs8065364 (0.17%). The combination of rs8065364 in CARD14, rs3025033 in VEGFA and rs726354 in SENP1 was the best model to predict HAPC development in this study (testing accuracy=0.6183, p=0.0010, cross-validated consistency=10/10). Genetic interactions of SNPs in CARD14, SENP1 and VEGFA might represent a functional mechanism in the pathogenesis of HAPC.