High Altitude Polycythemia Research Articles

Macitentan Attenuates Chronic Mountain Sickness in Rats by Regulating Arginine and Purine Metabolism.

Chronic mountain sickness (CMS) is a high altitude complication with high rates of morbidity and mortality. CMS is characterized by high-altitude polycythemia (HAPC) and high-altitude pulmonary hypertension (HAPH). In this study, macitentan, a dual endothelin receptor antagonist, was used to treat CMS, and the induced metabolomics changes were studied. CMS was induced in rats in a hypobaric hypoxia chamber (simulating a 5500 m plateau) for 4 weeks. Macitentan was administered in the third and fourth weeks (30 mg·kg-1·day-1). At the end of the follow-up period, we performed echocardiography, measured hemodynamic parameters and hematocrit, and performed histological staining. Furthermore, ultraperformance liquid chromatography-mass spectrometry (UPLC-MS)-based metabolic analysis was applied to explore metabolic changes associated with hypobaric hypoxia, with or without macitentan. qRT-PCR and kits for the determination of xanthine oxidase (XO) activity were used for validation experiments. Macitentan was effective in attenuating CMS, including CMS-induced right ventricle hypertrophy, HAPC, and HAPH. The levels of 48 metabolites were significantly changed in the CMS model group compared to the control group. Of these changes, 21 were reversed by treatment with macitentan. Enrichment analysis revealed that the purine metabolism pathway, as well as the arginine/proline metabolism pathway, might be the key pathways adjusted by macitentan. Furthermore, we verified macitentan played a beneficial role by directly regulating the expression of arginine1 and arginine2 in the arginine/proline metabolic pathway, and the activity of xanthine oxidase in the purine metabolic pathway. In conclusion, this study demonstrated that macitentan significantly ameliorated CMS in rats, and the mechanism was attributed to the reversion of the disorder in purine and arginine/proline metabolism, via direct regulation of XO activity and arginine1/2 expression. These findings are expected to provide new insights into the therapeutics and mechanism of macitentan in CMS.

Quantitative Proteomics Reveals the Effects of Resveratrol on High-Altitude Polycythemia Treatment.

High-altitude polycythemia (HAPC) is a common plateau chronic disease in which red blood cells are compensatory hyperproliferative due to high altitude hypoxic environment. HAPC severely affects the physical and mental health of populations on the plateau. However, the pathogenesis and treatment of HAPC has been rarely investigated. Here, the hypoxia-induced HAPC model of rat is established, in which hemoglobin concentration significantly increases and platelets clearly decrease. The effect of resveratrol upon hypoxia enables HAPC remission and makes hemoglobin and platelet tend to a normal level. Furthermore, quantitative proteomics is applied to investigate the plasma proteome variation and the underlying molecular regulation during HAPC occurrence and treatment with resveratrol. Hypoxia promotes erythrocyte developing and differentiating and disrupts cytoskeleton organization. Notably, the resveratrol administration reverses the proteome change pattern due to hypoxia and contributes to plateau adaption. Quantitative verification of differentially expressed proteins confirms the roles of resveratrol in HAPC. Resveratrol is expected to be useful for HAPC treatment.

1452-P: High-Altitude Polycythemia Is an Independent Risk Factor for Type 2 Diabetes

Background: According to previous researches, there were several risk factors of type 2 diabetes, including age, overweight or obesity, hypertension, dyslipidemia etc. However, it is not clear whether there are specific diabetes related risk factors in high altitude areas due to the unique low oxygen and low atmospheric pressure environment. Methods: This study is a population-based, cross-sectional epidemiological survey. The permanent Tibetan residents in Lhasa and Shigatse were enrolled in this study, including 1 urban area (10 communities) and 7 rural areas (48 villages). OGTT, HbA1c, blood lipid and blood cell counts were measured in all the subjects. Diabetes was diagnosed according to the WHO criteria. The diagnostic standard of high altitude polycythemia (HAPC) is the universal Qinghai standard (male hemoglobin ≥ 210g/L, female ≥ 190g/L). Results: A total of 1401 subjects were enrolled in this study. The average age was 44.3 ± 15.0 years old, 33.3% were male. The prevalence of diabetes in the study population was 3.6% (5.8% among men and 2.6% among women, p=0.003; 4.4% in rural vs. 2.4% in urban areas, p=0.033). The prevalence of diabetes increased with increasing age (1.9%, 4.7%, and 7.1% among persons who were 18 to 44, 45 to 59, and ≥60 years of age, respectively) and with increasing BMI (0, 2.3%, 4.7%, and 11.3% among persons with a BMI of <18.5, 18.5 to 23.9, 24.0 to 27.9, and ≥28.0, respectively). The prevalence of HAPC was 6.4% (6.2% among men and 6.5% among women, p=0.453). The prevalence of diabetes was significantly higher in HAPC group than in non HAPC group (11.2% vs. 3.1%, P<0.001). After quartile grouping of Hb, the prevalence of diabetes was 1.6%, 1.8%, 4.5% and 6.3% respectively (p=0.001). After adjusting for gender, age, BMI, hypertension, hyperuricemia and hypercholesterolemia, logistic regression analysis indicated that HAPC was an independent risk factor for diabetes (or = 3.514, 95% CI 1.606-7.689, P = 0.002). Conclusion: HAPC is an independent risk factor of type 2 diabetes in Tibet, China. Disclosure Q. Ren: None. X. Lv: None. L. Zhou: None. Y. Luo: None. L. Yang: None. L. Ji: None. Funding Science and Technology Project of Tibet Autonomous Region (CGZH2017000085); National Key Research and Development Program (2016YFC1304901)

Protective Role Of Estrogen Against Excessive Erythrocytosis In Monge’s Disease

RationaleChronic mountain sickness (CMS), or Monge’s disease, is an advancing and debilitating syndrome caused by chronic (years) exposure to high altitude hypoxia, as experienced by people living in the Andean region. Excessive erythrocytosis (EE) is one of the critical traits of CMS and this excessive pathobiologic response has deleterious effects since a high hematocrit would increase blood viscosity and reduce blood flow to hypoxia‐sensitive organs (brain and heart), often resulting in myocardial infarction or stroke in young adults. Within the population of Cerro de Pasco in the Andes, CMS prevalence is vastly different between males and females, being rare in females. Of interest is that there is a sharp increase in CMS incidence in females after menopause. This suggests the role of gender and sex hormones in altering disease manifestation.MethodsIn order to understand the molecular basis for polycythemia of high altitude, we have generated a disease in‐the dish‐model by re‐programming fibroblasts and native CD34+ve cells from CMS and non‐CMS subjects and converting them to RBC. Using this in‐vitro platform, we are now studying the interactions between genetic factors and sex hormones (Testosterone, Estrogen and Progesterone) and their effect on RBC production in the CMS and non‐CMS subjects at high altitude.ResultsWhile we found that testosterone increased RBC production somewhat, estrogen in physiologic concentrations (10nM), in sharp contrast, reduced the CD235a (Glycophorin A‐marker of mature RBC) remarkably (from 65.4% in the untreated CMS sample to 11% in the treated CMS) and eliminated the CMS EE phenotype. There was also stage‐specificity since we found that the impact was most severe when estrogen was present at the EB stage. This strongly suggests that estrogen has a protective role against the polycythemia phenotype. To probe further, we studied the effect of estrogen (10nM) on GATA1, a critical link with erythropoiesis. There was a sharp 5 fold decrease in GATA1 (p<0.01) and its target genes such as Alas2 (14 fold, p<0.001) in erythroid cells. This decreased expression resulted in marked reduction (>50%) in RBC production, demonstrating that estrogen constrains RBC production in females.ConclusionOur results demonstrate that estrogen inhibits GATA1 expression and prevents excessive erythropoiesis and Monge’s disease in females at high altitude. We believe that these studies not only shed light on role of sex hormones on hypoxia‐induced excessive erythropoiesis but have a broader application in their regulation of erythropoiesis and related blood disorders.

Erythrocytosis and Performance of HbA1c in Detecting Diabetes on an Oxygen-Deficient Plateau: A Population-based Study.

The hemoglobin A1c (HbA1c) test is a standard test for diabetes screening and diagnosis. To evaluate A1c performance for diabetes screening in high-altitude polycythemia compared to a population with a high proportion of people living in an oxygen-deficient environment. A population-based epidemiological survey was conducted. The cities Lhasa and Shigatse were selected. Volunteers were recruited through educational advertisements about diabetes. A total of 1401 Tibetan adults without known diabetes. Oral glucose tolerance test (OGTT), HbA1c, and complete blood cell count were performed. Hemoglobin A1c was evaluated using high-performance liquid chromatography, and serum glucose level, using the hexokinase method. World Health Organization criteria were used to define diabetes and prediabetes. Hemoglobin A1c test performance was evaluated using receiver operating characteristic analysis. The participants' mean age was 44.3 ± 15.0 years; 33.3% of the participants were men and 38.6% lived in urban areas. The prediabetes and diabetes prevalence rates were 7.5% and 3.6%, respectively. The optimal HbA1c cutoff for detecting diabetes was 46 mmol/mol (6.4%), with a sensitivity and specificity of 60.8% and 93.6%, respectively. The cutoff for detecting diabetes was 6.7% (50 mmol/mol) in subjects with high-altitude polycythemia (HAPC). The relationship between red blood cell (RBC) counts and HbA1c was significant (P < 0.001), while there was no correlation between hemoglobin (Hb) and HbA1c (P = 0.085). Multiple linear regression analysis showed that after adjusting for age and fasting serum glucose or 2-hour OGTT (OGTT2h) serum glucose, RBC count and not Hb level was an independent risk factor for HbA1c (β = 0.140, P < 0.001). The optimal HbA1c cutoff for detecting diabetes was 46 mmol/mol (6.4%) in Tibet. Red blood cell count was an independent risk factor for elevated HbA1c, and HAPC may affect the predictive ability of HbA1c.

Whole-Genome Sequencing Identifies the Egl Nine Homologue 3 (egln3/phd3) and Protein Phosphatase 1 Regulatory Inhibitor Subunit 2 (PPP1R2P1) Associated with High-Altitude Polycythemia in Tibetans at High Altitude

Background The hypoxic conditions at high altitudes are great threats to survival, causing pressure for adaptation. More and more high-altitude denizens are not adapted with the condition known as high-altitude polycythemia (HAPC) that featured excessive erythrocytosis. As a high-altitude sickness, the etiology of HAPC is still unclear. Methods In this study, we reported the whole-genome sequencing-based study of 10 native Tibetans with HAPC and 10 control subjects followed by genotyping of selected 21 variants from discovered single nucleotide variants (SNVs) in an independent cohort (232 cases and 266 controls). Results We discovered the egl nine homologue 3 (egln3/phd3) (14q13.1, rs1346902, P = 1.91 × 10−5) and PPP1R2P1 (Protein Phosphatase 1 Regulatory Inhibitor Subunit 2) gene (6p21.32, rs521539, P = 0.012). Our results indicated an unbiased framework to identify etiological mechanisms of HAPC and showed that egln3/phd3 and PPP1R2P1 may be associated with the susceptibility to HAPC. Egln3/phd3b is associated with hypoxia-inducible factor subunit α (HIFα). Protein Phosphatase 1 Regulatory Inhibitor is associated with reactive oxygen species (ROS) and oxidative stress. Conclusions Our genome sequencing conducted in Tibetan HAPC patients identified egln3/phd3 and PPP1R2P1 associated with HAPC.

Network pharmacology research on high frequency use of Tibetan medicine in treatment of HAPC based on data mining

Based on the results of previous data mining,the mechanism of high frequency use of Tibetan medicine in the treatment of high altitude polycythemia(HAPC) was analyzed in this study by network pharmacology. The author obtained the high frequency use data on Tibetan medicine Terminalia chebula,Aucklandia lappa,Crocus sativus and Myristica fragrans for the treatment of HAPC by data mining in the previous period. The first five main active ingredients of each high frequency Tibetan medicine were screened out by reviewing comprehensive literature and TCMSP database. The potential targets of each medicine were screened by PharmMapper and Drug Bank database,and then the targets were imported into MAS 3. 0 database to obtain the corresponding path information. The KEGG database was used for path annotation and GO function enrichment analysis. Finally,Cystoscope 3. 4. 0 software was used to construct " compound-target-path" network for four high-frequency Tibetan medicines. Among them,the target points of four herbs related to HAPC were 16(T. chebula),20(A. lappa),20(C. sativus),and 15(M. fragrans). The common target points included BHMT,F2,ADH5,AKR1 C2,GSK3 B,INSR and PDE4 B,involving pathways related to T. chebula(17),A. lappa(17),C. sativus(24) and M. fragrans(14),and the common pathway was metabolism of xenobiotics by cytochrome P450. The results showed that high-frequency Tibetan medicine had common pathways and targets in treating HAPC,such as T. chebula,A. lappa,C. sativus and M. fragrans.The medicines could reduce hemoglobin and enhance immunity by mediating cell proliferation and oxidative stress,exerting anti-inflammatory effects and participating in regulating blood vessels,showing therapeutic effects for HAPC. In this study,the multi-component,multi-target and multi-pathway mechanism of Tibetan medicine in preventing and treating HAPC was analyzed from the information level,providing a useful reference for further study of Tibetan medicine in preventing and treating plateau diseases from the multi-dimensional perspective.

Effects of Atpif1 gene on hemoglobin synthesis in K562 cells

To investigate the effects of mitochondrial ATPase inhibitory factor 1 (Atpif1) on hemoglobin synthesis. Firstly, the K562 cells were divided into 2 groups, hypoxia-treated group and normoxic control group. The K562 cells in hypoxia-treated group were treated with 2% oxygen. The K562 cells in the two groups were collected after cultured for 24, 48 and 72 hours. The proliferation-inhibitory rates of cells were detected by CCK-8 assay. The apoptosis rates of K562 cells were analyzed by flow cytometry. The hemoglobin synthesis of K562 cells was induced by hemin. The gene expressions of Atpif1, Aladelta-aminolevulinate synthase 2 (Alas2) and nuclear factor kappa B (NF-κB) were detected by qRT-PCR. Then, the K562 cells were cultured in hypoxic incubator and divided into blank control group, negative control group and si-Atpif1 group. After sliencing Atpif1 gene, the hemoglobin synthesis and the levels of NF-κB and Alas2 were determined. Compared with the normoxic control group, the proliferation activity of K562 cells was inhibited, the apoptosis rate was increased, and the hemoglobin synthesis was also increased in hypoxia-treated groups. The expressions of Atpif1, Alas2 and NF-κB mRNA of K562 cells were upregulated. Compared with blank control group and negative control group, the content of hemoglobin was decreased, and the levels of NF-κB and Alas2 mRNA were also decreased in si-Atpif1 group. Atpif1 gene is involved in the regulation of hemoglobin synthesis. Exploring its roles in the development of high altitude polycythemia (HAPC) can provide new ideas and therapeutic targets for the prevention and treatment of HAPC.

Plasma proteome profiling of high-altitude polycythemia using TMT-based quantitative proteomics approach

High-altitude polycythemia (HAPC) is one of the classic chronic mountain sicknesses and has been a serious public health problem in high-altitude regions. Despite numerous studies on HAPC via genomics or transcriptomics approaches, the pathogenesis of HAPC is still unclear. Here, we performed a TMT- based comparative quantitative proteomics analysis to reveal the changes of plasma proteomics profiles between HAPC subjects and healthy controls. Of identified 818 proteins, 7 and 12 proteins were up-regulated and down-accumulated, respectively, compared HAPC patients with healthy controls. GO and KEGG pathway analyses revealed the dysregulated proteins were primarily involved in complement and coagulation cascades, inflammation and immune response. ELISA validation demonstrated that C4A, C6 and CALR were down-regulated, and MASP1 and CNDP1 were up-regulated in HAPC patients. By ROC analysis, combinations of these five proteins (i.e., C4A, C6, CALR, MASP1 and CNDP1) resulted in a high AUC value (0.919; 95% CI, 0.817–961; p < .0001) to diagnose HAPC patients. Moreover, CNDP1 seems to be a robust biomarker for HAPC. This study not only provided a comprehensive dataset on overall proteomics changes in HAPC patients compared with healthy controls, but also indicated that CNDP1 can serve as a strong plasma biomarker of HAPC for the diagnostic and therapeutic potential. SignificanceHAPC, one of the classic chronic mountain sicknesses, has been a serious public health problem in high-altitude regions. Despite numerous studies on HAPC via genomics or transcriptomics approaches, the pathogenesis of HAPC is still largely unknown to date. In this study, we addressed this issue by performing TMT-based quantitative analyses of the plasma proteome profiles of HAPC patients and healthy controls. We identified 818 proteins, of which 19 were differentially expressed. Bioinformatics analysis revealed the differentially expressed proteins were mainly involved in complement and coagulation cascades, inflammation and immune response. By ROC analysis, combinations of C4A, C6, CALR, MASP1 and CNDP1 resulted in a high AUC value (0.919, p < .0001) to distinguish HAPC patients from healthy controls. Collectively, the current study provided a comprehensive dataset on overall proteomic changes in HAPC patients for the first time, and it also revealed C4A, C6, CALR, MASP1 and CNDP1 can be served as candidate plasma biomarkers of HAPC for their diagnostic and therapeutic potential.

Tibetan Enriched PKLR Variant Is Beneficial to High Altitude Adaption By Improving Oxygen Delivery

Tibetans have been living at altitudes over 3500 m for ~20,000 years and have developed unique beneficial evolutionary genetic adaptions (PMID:28448578). Our previous study identified selected genetic haplotypes in two genes, EPAS1 (encoding hypoxia-inducible factor 2-alpha [HIF2-a], a transcription factor that mediates the hypoxic response), and EGLN1 (encoding prolyl hydroxylase 2 [PHD2], a principal negative regulator of HIF stability (PMID:25129147). The presence of these two haplotypes correlates with lower hemoglobin levels in Tibetans compared to other highlanders. However, the entire diverse complex of molecular mechanisms of high altitude adaptation is still largely unknown and our study showed that neither EPAS1 nor EGLN1 variants fully explain the mechanism of protection from polycythemia in Tibetans in high altitude (PMID:28233034).We found an enriched haplotype in the PKLR gene (encoding pyruvate kinase [PK] expressed only in liver and red blood cells). The PK enzyme is in the terminal portion of the glycolytic pathway, and its decreased activity leads to accumulation of proximal glycolytic intermediates, including 2,3-diphosphoglycerate (DPG) which shifts the hemoglobin dissociation curve to right (high p50) and increases oxygen release to tissues from a unit of hemoglobin. We hypothesized that Tibetan enriched PKLR variants might improve oxygen delivery to tissues and help explain the protection from polycythemia at high altitude.Genomic analyses revealed that this PKLR haplotype is enriched in Tibetans but is not unique to Tibetans. It has the highest frequency in Tibetans (89%), with a lower prevalence in Chinese and Mongolians (~77%), Kyrgyz (~60 %), Aymara (~44 %), and Colombians (~30 %) and a much lower frequency in Caucasians (11%), perhaps explaining the heterogeneity of responses to hypoxia within and among these populations. Our study of reticulocyte RNA showed that transcript levels of PKLR progressively decrease with increasing altitude in controls and even more in Tibetans with the Tibetan evolutionary selected PKLR haplotype. Tibetans with the PKLR haplotype (heterozygotes and homozygotes) have lower PKLR transcript levels than wild type Tibetans. Because of the paucity of wildtype PKLR haplotype in Tibetans and the challenges of acquiring Tibetan samples in high altitude in China, we collected samples from 125 m (Cheboksary, Chuvashia); 800 m (Bishkek, Kyrgyzstan) and 2640 m (Bogota, Colombia). PK activity, PKLR transcript levels, and ATP decreased at 2640 m compared to 800 m, while p50 increased at 2640 m. PKLR transcript levels correlated with PK activity and ATP and inversely correlated with p50. PK activities also correlated with PKLR transcript levels and ATP and inversely correlated with p50. At 2640 m, PK activity was lower and p50 levels were higher in those with the enriched PKLR haplotype. These results demonstrate that increasing altitude decreases PK activity, resulting in increasing p50 providing a molecular basis for the previously reported improvement of oxygen delivery at high altitude (PMID:17394415).To study the roles of HIFs in the regulation of PKLR gene expression, we also collected samples from Chuvash polycythemia (CP) homozygotes and Chuvash controls. CP homozygotes have a mutation in the VHL gene, a negative regulator of HIFs, that results in augmented HIF levels. CP homozygotes had lower PKLR mRNA in reticulocytes, PK activity, and PKR protein levels in red blood cells compared to controls, while their 2,3 DPG levels were higher. These data confirm that PKLR expression levels are negatively regulated by HIFs.Our findings demonstrate that individuals in high altitudes have lower PKLR transcript levels and PK activity, resulting in high 2,3DPG and p50 which shifts the hemoglobin dissociation curve to right. This decreases affinity of hemoglobin for oxygen, which improves tissue oxygen delivery and as such is another mechanism in Tibetans that protects from high altitude polycythemia. We also demonstrate that HIFs negatively regulate PKLR expression, leading to better oxygen release from hemoglobin at high altitude. DisclosuresKosinski:Agios: Employment, Equity Ownership. Kung:Agios: Employment, Equity Ownership. van Wijk:RR Mechatronics: Research Funding; Agios Pharmaceuticals: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Inhibition of Suicidal Erythrocyte Death by Chronic Hypoxia.

Background/Aims: High-altitude polycythemia is defined by the increase of hematocrit and hemoglobin at high altitudes caused by production of excessive erythrocytes. Eryptosis is a process by which mature erythrocytes undergo self-destruction sharing several features with apoptosis. However, the eryptosis in high-altitude hypobaric hypoxia is unknown. Thus, the main purpose of this study was to investigate whether chronic hypoxia affected eryptosis and, if so, by what mechanisms. Methods: Biotin labeling technology was utilized to study the survival of red blood cells in chronic hypoxia. Flow cytometry was used to determine the volume of mature erythrocytes from forward scatter, phosphatidylserine scrambling from annexin-V-binding, intracellular Ca2+ from Fluo-3-AM, reactive oxygen species (ROS) abundance from ROS-probe, and ceramide and CD47 abundance utilizing specific antibodies. Results: The volume of mature erythrocytes was significantly changed, and the percentage of annexin-V-binding cells was significantly decreased under chronic hypobaric hypoxia. Erythrocyte survival was improved under chronic hypoxia, and chronic hypoxia resulted in a decrease in intracellular Ca2+in vivo and influenced eryptosis which was induced by the Ca2+-ionophore ionomycin (1 μM, 60 minutes) in vitro. Chronic hypoxia also resulted in an increase in CD47 and ceramide abundance, but it had no effect on ROS formation. Conclusions: Chronic hypobaric hypoxia can inhibit eryptosis by decreasing intracellular Ca2+ and increasing integrin-associated protein CD47.

Associations of high-altitude polycythemia with polymorphisms in PIK3CD and COL4A3 in Tibetan populations

BackgroundHigh-altitude polycythemia (HAPC) is a chronic high-altitude disease that can lead to an increase in the production of red blood cells in the people who live in the plateau, a hypoxia environment, for a long time. The most frequent symptoms of HAPC include headache, dizziness, breathlessness, sleep disorders, and dilation of veins. Although chronic hypoxia is the main cause of HAPC, the fundamental pathophysiologic process and related molecular mechanisms responsible for its development remain largely unclear yet.Aim/methodsThis study aimed to explore the related hereditary factors of HAPC in the Chinese Han and Tibetan populations. A total of 140 patients (70 Han and 70 Tibetan) with HAPC and 60 healthy control subjects (30 Han and 30 Tibetan) were recruited for a case-control association study. To explore the genetic basis of HAPC, we investigated the association between HAPC and both phosphatidylinositol-4,5-bisphosphonate 3-kinase, catalytic subunit delta gene (PIK3CD) and collagen type IV α3 chain gene (COL4A3) in Chinese Han and Tibetan populations.Results/conclusionUsing the unconditional logistic regression analysis and the false discovery rate (FDR) calculation, we found that eight SNPs in PIK3CD and one SNP in COL4A3 were associated with HAPC in the Tibetan population. However, in the Han population, we did not find any significant association. Our study suggested that polymorphisms in the PIK3CD and COL4A3 were correlated with susceptibility to HAPC in the Tibetan population.

Excessive Iron Availability Caused by Disorders of Interleukin-10 and Interleukin-22 Contributes to High Altitude Polycythemia.

Background: Because the pathogenesis of high altitude polycythemia (HAPC) is unclear, the aim of the present study was to explore whether abnormal iron metabolism is involved in the pathogenesis of HAPC and the possible cause.Methods: We examined the serum levels of iron, total iron binding capacity, soluble transferrin receptor (sTfR), ferritin, and hepcidin as well as erythropoietin (EPO) and inflammation-related cytokines in 20 healthy volunteers at sea level, 36 healthy high-altitude migrants, and 33 patients with HAPC. Mice that were exposed to a simulated hypoxic environment at an altitude of 5,000 m for 4 weeks received exogenous iron or intervention on cytokines, and the iron-related and hematological indices of peripheral blood and bone marrow were detected. The in vitro effects of some cytokines on hematopoietic cells were also observed.Results: Iron mobilization and utilization were enhanced in people who had lived at high altitudes for a long time. Notably, both the iron storage in ferritin and the available iron in the blood were elevated in patients with HAPC compared with the healthy high-altitude migrants. The correlation analysis indicated that the decreased hepcidin may have contributed to enhanced iron availability in HAPC, and decreased interleukin (IL)-10 and IL-22 were significantly associated with decreased hepcidin. The results of the animal experiments confirmed that a certain degree of iron redundancy may promote bone marrow erythropoiesis and peripheral red blood cell production in hypoxic mice and that decreased IL-10 and IL-22 stimulated iron mobilization during hypoxia by affecting hepcidin expression.Conclusion: These data demonstrated, for the first time, that an excess of obtainable iron caused by disordered IL-10 and IL-22 was involved in the pathogenesis of some HAPC patients. The potential benefits of iron removal and immunoregulation for the prevention and treatment of HAPC deserve further research.

Prevalence and risk factors of chronic mountain sickness in Pamirs plateau

To investigate the prevalence of chronic mountain sickness (CMS) and its predisposing factors in Pamirs plateau and analysis clinical feature and risk factors. Eight hundred and twenty-four individuals in Pamirs plateau were surveyed used Qinghai CMS scoring system. Demographics, BP, SaO2, heart rate and specified symptoms of CMS were recorded, Hb level was estimated. Overall CMS prevalence was 22.08%, including 21.84% mild and 0.24% moderate without severe patient. Gender, nation, age, immigration time, altitude, occupation and accommodation mode were risk factors for CMS (P<0.05 or P<0.01), CMS prevalence was higher than HAPC rate both in male and female (χ2=90.59 and 44.13, P<0.01). Multiple linear regression analysis showed age, BMI, SaO2 and systolic pressure correlated with CMS (P<0.01). Chronic mountain sickness prevalence in Pamirs plateau is rather high but high altitude polycythemia prevalence is low, so the disease type is high altitude deterioration. Work and exercise more reasonable to avoid overtiredness, oxygen inhalation to raise blood oxygen saturation, control blood pressure and resting therapy can improve CMS symptom and decrease prevalence.

Investigation of the differences between the Tibetan and Han populations in the hemoglobin–oxygen affinity of red blood cells and in the adaptation to high-altitude environments

ABSTRACTObjective: High altitude is characterized by low oxygen pressure, resulting in multiple adaptive responses. Tibetans who have lived in the plateau for thousands of years have developed unique phenotypes, such as downregulation of the HIF pathway through EPAS1 and EGLN1 gene mutation. However, the changes of hemoglobin–oxygen affinity under hypoxia environment remain elusive.Methods: A blood cell analyzer and a blood oxygen analyzer were used to conduct routine blood tests and measure the oxygen affinity P50 in in the Han population that rapidly entered the plateau (for 3–7 days), the plateau-acclimatized Han population (residing for 30 days on the plateau), the plateau Han population (more than 10 years on the plateau), and the Tibetan population.Results: The Han population that rapidly entered the plateau had increasing higher P50 values, RBCs counts and hemoglobin (HGB) levels, while the acclimatized Han population, the plateau Han population and Tibetan all had significantly lower P50 values. However, there were no significant differences in the RBCs counts and HGB levels between the plateau Han, Tibetan populations and the Han population of the plains.Discussion: The adaptability of the Tibetan and plateau Han populations to the plateau was mainly due to the strong affinity of HGB for oxygen, which provided sufficient oxygen for tissues and organs.Conclusions: The change of P50 could be a feature of the adaptation to the plateau and to avoid altitude sickness, such as high-altitude polycythemia and dyspnea.

Natural Selection on Genes Related to Cardiovascular Health in High-Altitude Adapted Andeans

The increase in red blood cell mass (polycythemia) due to the reduced oxygen availability (hypoxia) of residence at high altitude or other conditions is generally thought to be beneficial in terms of increasing tissue oxygen supply. However, the extreme polycythemia and accompanying increased mortality due to heart failure in chronic mountain sickness most likely reduces fitness. Tibetan highlanders have adapted to high altitude, possibly in part via the selection of genetic variants associated with reduced polycythemic response to hypoxia. In contrast, high-altitude-adapted Quechua- and Aymara-speaking inhabitants of the Andean Altiplano are not protected from high-altitude polycythemia in the same way, yet they exhibit other adaptive features for which the genetic underpinnings remain obscure. Here, we used whole-genome sequencing to scan high-altitude Andeans for signals of selection. The genes showing the strongest evidence of selection-including BRINP3, NOS2, and TBX5-are associated with cardiovascular development and function but are not in the response-to-hypoxia pathway. Using association mapping, we demonstrated that the haplotypes under selection are associated with phenotypic variations related to cardiovascular health. We hypothesize that selection in response to hypoxia in Andeans could have vascular effects and could serve to mitigate the deleterious effects of polycythemia rather than reduce polycythemia itself.

Elevated pentose phosphate pathway is involved in the recovery of hypoxia‑induced erythrocytosis.

As a typical model of hypoxia-induced excessive erythrocytosis, high altitude polycythemia (HAPC) results in microcirculation disturbance, aggravates tissue hypoxia and results in a severe clinical outcome, without any effective intervention methods except for returning to an oxygen-rich environment. The present study aimed to explore potential therapeutic targets which may participate in the recovery of HAPC by studying the mechanisms of reducing the hemoglobin (HB) concentration during re-oxygenation. A total of 14 and 13 subjects were recruited over a 5,300 m distance and 5,170 m area. The patients were classified into HAPC or control groups based on their HB value. Plasma samples were collected on the day when they finished their stay in plateau for a year, and on the 180th day following their reaching in plain. Metabolic profiling was conducted by UPLC-QTOF/MS. MetaboAnalyst platform was performed to explore the most perturbed metabolic pathways. A panel of differential metabolites were obtained in the recovery phase of HAPC and control groups. The present study identified the uniquely upregulated pentose phosphate pathway in HAPC subjects, along with a significantly decreased HB level. The findings were verified via a direct comparison between HAPC and control subjects at a high altitude. An increased pentose phosphate pathway was identified in control groups compared with HAPC subjects. An elevated pentose phosphate pathway may therefore participate in the recovery of HAPC, whereas a downregulated pentose phosphate pathway may contribute to hypoxia-induced erythrocytosis. The results of the present study provide potential therapeutic strategies and novel insights into the pathogenesis of hypoxia-induced polycythemia.

GW28-e0446 Traditional Tibetan medicine Corydalis hendersonii exerts anti-myocardial ischemia effect by attenuating inflammation and fibrosis in acute myocardial infarction mice

Corydalis hendersonii Hemsl. (CH) has been used for centuries in China largely for the treatment of high altitude polycythemia, hypertension, hepatitis, edema, gastritis, and other infectious diseases, but never employed for coronary heart diseases. The current study is to investigate the

Associations of high altitude polycythemia with polymorphisms in EPAS1, ITGA6 and ERBB4 in Chinese Han and Tibetan populations.

High altitude polycythemia (HAPC) is a common chronic disease at high altitude, which is characterized by excessive erythrocytosis (females, hemoglobin ≥ 190 g/L; males, hemoglobin ≥ 210 g/L). It is the most common disease in chronic mountain sickness casued primarily by persistent arterial hypoxia and ventilatory impairment. However, the disease is still unmanageable and related molecular mechanisms remain largely unclear. This study aims to explore the genetic basis of HAPC in the Chinese Han and Tibetan populations. Subjects were screened for HAPC using the latest approved diagnostic criteria. To explore the hereditary basis of HAPC and investigate the association between three genes (EPAS1, ITGA6, ERBB4) and HAPC in Chinese Han and Tibetan populations. We enrolled 100 patients (70 Han, 30 Tibetan) with HAPC and 100 healthy control subjects (30 Han, 70 Tibetan). Subjects were screened for HAPC using the latest approved diagnostic criteria combined with excessive erythrocytosis and clinical symptoms. Analysis of variance was used to evaluate the impact of polymorphism on HAPC based on genetic variation. The Chi-squared test and analyses of genetic models, rs75591953 and rs75984373 in EPAS1, rs6744873 in ITGA6, rs17335043 in ERBB4 showed associations with reduced HAPC susceptibility in Han populations. Additionally, in Tibetan populations, rs3749148 in ITGA6, rs934607 and rs141267844 in ERBB4 showed a reduced risk of HAPC, whereas rs6710946 in ERBB4 increased the risk of HAPC. Our study suggest that the polymorphisms in the EPAS1, ITGA6 and ERBB4 correlate with susceptibility to HAPC.

Mechanism of apoptosis involved in gastric mucosal lesions in Tibetans with high-altitude polycythemia.

The Tibetan high plateau is a low-oxygen environment, which may cause the pathogenesis of high-altitude polycythemia (HAPC). Gastric mucosal lesions (GML) are a common complication of HAPC. The molecular mechanisms involved in HAPC-induced GML have remained to be fully elucidated and were therefore investigated in the present study. Gastric tissues of patients with heavy, HAPC-induced GML and healthy controls were assessed by ultrastructural and histopathological analysis. In addition, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis were used to detect cell apoptosis in the gastric mucosa tissues. Moreover, the expression of genes associated with the phosphoinositide-3 kinase (PI3K) pathway was assessed by RT-qPCR to investigate the mechanism of cell apoptosis in HAPC-induced GML. The results revealed a significant increase in the number of red blood cells, gastric vessels and the diameter of gastric mucosal vessels in HAPC-induced GML patients compared with those in healthy controls. In addition, more red blood cells were distributed in gastric tissue not only at the vascular level but also in the tissue space. The number of vacuoles was increased in the gastric mucosal cells. Furthermore, a significant increase in apoptosis of the gastric mucosal cells was identified. The expression of phosphatase and tensin homolog was significantly higher in gastric mucosa from patients with HAPC-induced GML compared with that in the healthy controls. All of the pathologic changes suggested that significant cell apoptosis occurred in the HAPC-induced GML tissues, which may be associated with the PI3K pathway. These findings may provide novel insight for the treatment of gastric lesions caused by HAPC in the future.