Yongjun Luo

Mitochondrial genome analysis of Ochotona curzoniae and implication of cytochrome c oxidase in hypoxic adaptation.

Pikas originated in Asia and are small lagomorphs native to cold climates. The plateau pika, Ochotona curzoniae is a keystone species on the Qinghai-Tibet Plateau and an ideal animal model for hypoxic adaptation studies. Altered mitochondrial function, especially cytochrome c oxidase activity, is an important factor in modulation of energy generation and expenditure during cold and hypoxia adaptation. In this study, we determined the complete nucleotide sequence of the O. curzoniae mitochondrial genome. The plateau pika mitochondrial DNA is 17,131bp long and encodes the complete set of 37 proteins typical for vertebrates. Phylogenetic analysis based on concatenated heavy-strand encoded protein-coding genes revealed that pikas are closer to rabbit and hare than to rat. This suggests that rabbit or hare would be a good control animal for pikas in cold and hypoxia adaptation studies. Fifteen novel mitochondrial DNA-encoded amino acid changes were identified in the pikas, including three in the subunits of cytochrome c oxidase. These amino acid substitutions potentially function in modulation of mitochondrial complexes and electron transport efficiency during cold and hypoxia adaptation.

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.

Over-starvation aggravates intestinal injury and promotes bacterial and endotoxin translocation under high-altitude hypoxic environment

AIM To study whether over-starvation aggravates intestinal mucosal injury and promotes bacterial and endotoxin translocation in a high-altitude hypoxic environment. METHODS Sprague-Dawley rats were exposed to hypobaric hypoxia at a simulated altitude of 7000 m for 72 h. Lanthanum nitrate was used as a tracer to detect intestinal injury. Epithelial apoptosis was observed with terminal deoxynucleotidyl transferase dUTP nick end labeling staining. Serum levels of diamino oxidase (DAO), malondialdehyde (MDA), glutamine (Gln), superoxide dismutase (SOD) and endotoxin were measured in intestinal mucosa. Bacterial translocation was detected in blood culture and intestinal homogenates. In addition, rats were given Gln intragastrically to observe its protective effect on intestinal injury. RESULTS Apoptotic epithelial cells, exfoliated villi and inflammatory cells in intestine were increased with edema in the lamina propria accompanying effusion of red blood cells. Lanthanum particles were found in the intercellular space and intracellular compartment. Bacterial translocation to mesenteric lymph nodes (MLN) and spleen was evident. The serum endotoxin, DAO and MDA levels were significantly higher while the serum SOD, DAO and Gln levels were lower in intestine (P < 0.05). The bacterial translocation number was lower in the high altitude hypoxic group than in the high altitude starvation group (0.47 ± 0.83 vs 2.38 ± 1.45, P < 0.05). The bacterial translocation was found in each organ, especially in MLN and spleen but not in peripheral blood. The bacterial and endotoxin translocations were both markedly improved in rats after treatment with Gln. CONCLUSION High-altitude hypoxia and starvation cause severe intestinal mucosal injury and increase bacterial and endotoxin translocation, which can be treated with Gln.

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.

Association of Endothelial Nitric Oxide Synthase (eNOS) G894T Polymorphism With High Altitude Pulmonary Edema Susceptibility: A Meta-Analysis

BACKGROUND High altitude pulmonary edema (HAPE) is a potentially deadly disease associated with exposure to altitudes greater than 3000 m. Individuals who have previously experienced HAPE are at a significantly higher risk of recurrence, suggesting an underlying genetic component to HAPE pathogenesis. In a previous nuclear genomic study of individual variation in susceptibility to HAPE, the endothelial nitric oxide synthase (eNOS) gene G894T polymorphism was identified as being associated with HAPE. However, another study found no association. Because of the low incidence of HAPE, sample sizes in current reports have been relatively limited. In this study, the association between the eNOS G894T polymorphism and HAPE was assessed through a meta-analysis of published data. METHODS The literature was searched in PubMed, Web of Science, and Embase for papers published before July 15, 2011. A fixed-effects model and a random-effects model were applied (Revman 5.0) on the basis of heterogeneity, and study quality was assessed in duplicate. RESULTS Five studies with 360 HAPE patients and 469 control subjects were analyzed. There were no significant differences between carriers of the eNOS 894G and 894T polymorphism alleles in terms of the risk of developing HAPE. CONCLUSIONS The eNOS 894G and 894T polymorphism alleles are not associated with HAPE incidence.

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.

The Association of Angiotensin-Converting Enzyme Gene Insertion/Deletion Polymorphisms with Acute Mountain Sickness Susceptibility: A Meta-Analysis

Altitude exposure in nonacclimatized subjects may lead to acute mountain sickness (AMS). AMS is defined as headache upon recent arrival to altitude and may be accompanied by loss of appetite, nausea or vomiting, dizziness, fatigue, and poor sleep. Susceptibility for AMS varies and has been linked to angiotensin-converting enzyme (ACE) gene polymorphisms. We performed a meta-analysis of studies to assess the association between the ACE deletion (D) and insertion (I) alleles and AMS from published data. A fixed effects model was applied and study quality was assessed in duplicate. Five studies with a total of 333 AMS cases and 373 healthy controls were assessed. Our results revealed no significant differences in risk for AMS between carriers of ACE deletion and insertion polymorphism alleles.

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.

High Altitude Medicine Education in China: Exploring a New Medical Education Reform

China has the largest plateau in the world, which includes the whole of Tibet, part of Qinghai, Xinjiang, Yunnan, and Sichuan. The plateau area is about 257.2×10(4) km(2), which accounts for about 26.8% of the total area of China. According to data collected in 2006, approximately twelve million people were living at high altitudes, between 2200 to 5200 m high, on the Qinghai-Tibetan Plateau. Therefore, there is a need for medical workers who are trained to treat individuals living at high altitudes. To train undergraduates in high altitude medicine, the College of High Altitude Military Medicine was set up at the Third Military Medical University (TMMU) in Chongqing in 1999. This is the only school to teach high altitude medicine in China. Students at TMMU study natural and social sciences, basic medical sciences, clinical medical sciences, and high altitude medicine. In their 5(th) year, students work as interns at the General Hospital of Tibet Military Command in Lhasa for 3 months, where they receive on-site teaching. The method of on-site teaching is an innovative approach for training in high altitude medicine for undergraduates. Three improvements were implemented during the on-site teaching component of the training program: (1) standardization of the learning progress; (2) integration of formal knowledge with clinical experience; and (3) coaching students to develop habits of inquiry and to engage in ongoing self-improvement to set the stage for lifelong learning. Since the establishment of the innovative training methods in 2001, six classes of high altitude medicine undergraduates, who received on-site teaching, have graduated and achieved encouraging results. This evidence shows that on-site teaching needs to be used more widely in high altitude medicine education.

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.