Association of polymorphisms in pulmonary surfactant protein A1 and A2 genes with high-altitude pulmonary edema

STUDY OBJECTIVES: A potential pathogenetic cofactor for the development of high-altitude pulmonary edema (HAPE) is an increase in capillary permeability, which could occur as a result of an inflammatory reaction and/or free-radical-mediated injury to the lung. Pulmonary surfactant protein A (SP-A), the most abundant surfactant protein, has potent antioxidant properties and protects unsaturated phospholipids and growing cells from oxidative injury. Single-nucleotide polymorphisms (SNPs) in SP-A1 and SP-A2, genes encoding SP-A, have been associated with susceptibility to respiratory distress syndrome, COPD, and pulmonary infections. In view of the protective role of SP-A against inflammatory reactions and oxidative damage, the two underlying mechanisms in development of HAPE, we examined the association of constitutional susceptibility to HAPE with polymorphisms in SP-A1 and SP-A2. DESIGN: A cross-sectional case-control study. SETTING: Blood samples were collected at an altitude (> or = 3,500 m). PARTICIPANTS: Twelve low-altitude native (LAN) subjects with a history of HAPE, 15 healthy LAN sojourners without a history of HAPE (LAN control subjects), and 19 healthy high-altitude natives (HANs) without a history of HAPE (HAN control subjects). MEASUREMENTS: The SNPs in four exons and intermediate introns of the SP-A1 and SP-A2 were screened by polymerase chain reaction and sequencing. Biochemical parameters related to oxidative stress (malondialdehyde and reduced glutathione in RBC) and membrane permeability (circulating levels of lactate dehydrogenase) were measured in plasma. RESULTS: Allele frequencies of three loci in SP-A1 and one in SP-A2 were significantly different between LAN HAPE patients (SP-A1 C1101T: C allele, 36.4% and T allele, 63.6%; SP-A1 T3192C: T allele, 61.1% and C allele, 38.9%; SP-A1 T3234C: T allele, 61.1% and C allele, 38.9%; and SP-A2 A3265C: A allele, 21.4% and C allele, 78.6%) and LAN control subjects (SP-A1 C1101T: C allele, 8.3% and T allele, 91.7%; SP-A1 T3192C: T allele, 15% and C allele, 85%; SP-A1 T3234C: T allele, 15% and C allele, 85%; and SP-A2 A3265C: A allele, 37.5% and C allele, 62.5%) [C1101T odds ratio [OR], 6.3 with 95% confidence interval (CI), 2.8 to 14.3; T3192C OR, 8.9 with 95% CI, 4.5 to 17.6; T3234C OR, 8.9 with 95% CI, 4.5 to 17.6; and A3265C OR, 2.2 with 95% CI, 1.2 to 4.1 (p < or = 0.01)]. Heterozygous individuals, with respect to SP-A1 C1101T and SP-A2 A3265C, showed less severity in oxidative damage in comparison with homozygous subjects (SP-A1 T1101 and SP-A2 C3265). CONCLUSION: The polymorphisms in SP-A1 (C1101T, T3192C, and T3234C) and SP-A2 (A3265C) might be one of the genetic factors contributing to susceptibility to HAPE.     

Heterozygotes of NOS3 polymorphisms contribute to reduced nitrogen oxides in high-altitude pulmonary edema

STUDY OBJECTIVES: High-altitude pulmonary edema (HAPE), which develops on exertion under hypoxic conditions, aggravates due to endothelial dysfunction. Repeat events of the disorder suggests of genetic susceptibility. Endothelial nitric oxide synthase gene (NOS3), a regulator of vasodilation, has emerged as a strong candidate marker. In the present study, we investigated G894T, 27-base-pair 4b/4a (variable number of tandem repeat), -922A/G, and -786T/C polymorphisms of NOS3, individually or in combination, for an association with HAPE. DESIGN: A cross-sectional case control study. SETTINGS: Blood samples of HAPE-resistant lowlanders (HAPE-r) were obtained at sea level, and blood samples of patients with HAPE (HAPE-p) were obtained at Sonam Norboo Memorial Hospital, Leh, at 3,500 m. PARTICIPANTS: The study groups consisted of 60 HAPE-r inducted two to three times to altitudes > 3,600 m; and 72 HAPE-p, who had HAPE on their first visit to high altitude. RESULTS: Nitrogen oxides (NOx) at 77.9 +/- 28.6 micromol/L were significantly elevated in HAPE-r as compared to 42.39 +/- 12.93 micromol/L in HAPE-p (p < 0.0001). Genotype distribution of G894T and 4b/4a polymorphisms was significantly different in the two groups (p = 0.001 and 0.009, respectively). Haplotype analysis revealed -922A/G and -786T/C polymorphisms in complete linkage disequilibrium. The wild-type haplotypes G-b (G894T, 4b/4a), G-A (G894T, -922A/G), and G-b-A (G894T, 4b/4a, -922A/G) were significantly overrepresented in HAPE-r (p < 0.0001, p = 0.03, and p = 0.02, respectively). The heterozygote genotype combination GTba as compared to wild-type combination GGbb was significantly higher in HAPE-p (chi2 = 18.62, p = 0.00009; odds ratio, 7.20; 95% confidence interval, 2.82 to 18.38). The combination of four heterozygotes GTbaAGTC was overrepresented in HAPE-p (p = 0.04), whereas the wild-type genotype combination GGbbAATT was overrepresented in HAPE-r (p = 0.002). Furthermore, the GGbb combination correlated with significantly elevated NOx as compared to remaining combinations as a whole in both HAPE-r and HAPE-p (p = 0.01 and 0.004, respectively). CONCLUSIONS: Reduced NOx and combination of heterozygotes associate with the susceptibility to HAPE. The study impels another step toward application of NOx as a diagnostic marker for HAPE. The NOS3 GTba and GTbaAGTC genotype combinations may find application as genetic markers for predicting the risk for HAPE.     

高原肺水肿遗传易感性机制的研究进展

高原肺水肿(high altitude pulmonary edema,HAPE)是一种特发于高原低氧环境的肺水肿,起病急,进展快,危害大[1].调查结果表明,在海拔3700 m以上地区的人群中HAPE发病率为0.4%～2%,多见于从平原快速进入高原者,也可见于久居高原者进入更高海拔地区或在平原居留一段时间重返高原时[2].动物实验和流行病学调查结果均显示,HAPE发病具有种族特异性以及家族和个体易感倾向.西藏高原地区世居藏族HAPE发病率远低于移居汉族,西藏军区总医院曾报道10年间,收治的923例HAPE中,藏族仅占1例,国内也有报道曾患HAPE者再次进入高原地区,HAPE有明显的再发倾向[3-4].     

Inflammatory cytokines in BAL fluid and pulmonary hemodynamics in high-altitude pulmonary edema

To evaluate the pathogenesis of high-altitude pulmonary edema (HAPE), we performed bronchoalveolar lavage (BAL) and pulmonary hemodynamic studies in seven patients with HAPE at its early stage. We measured cell counts, biochemical contents, and concentrations of pro-inflammatory cytokines including interleukin (IL)-1, IL-6, IL-8 and tumor necrosis factor (TNF)-α and of anti-inflammatory cytokines including IL-1 receptor antagonist (ra) and IL-10 in the BAL fluid (BALF). All patients showed increased counts for total cells, alveolar macrophages, neutrophils and lymphocytes, and markedly elevated concentrations of proteins, lactate dehydrogenase, IL-1β, IL-6, IL-8, TNF-α and IL-1ra. The levels of IL-1α and IL-10 were not increased. Patients also showed pulmonary hypertension with normal wedge pressure. Both the driving pressure obtained as pulmonary arterial pressure minus wedge pressure and the Pa_O2 under room air were significantly correlated with the concentrations of IL-6 and TNF-α in the BALF. These findings suggest that the inflammatory cytokines play a role at the early stage of HAPE and might be related to pulmonary hypertension.     

Pulmonary blood flow heterogeneity during hypoxia and high-altitude pulmonary edema

Uneven hypoxic pulmonary vasoconstriction has been proposed to expose parts of the pulmonary capillary bed to high pressure and vascular injury in high-altitude pulmonary edema (HAPE). We hypothesized that subjects with a history of HAPE would demonstrate increased heterogeneity of pulmonary blood flow during hypoxia. A functional magnetic resonance imaging technique (arterial spin labeling) was used to quantify spatial pulmonary blood flow heterogeneity in three subject groups: (1) HAPE-susceptible (n = 5), individuals with a history of physician-documented HAPE; (2) HAPE-resistant (n = 6), individuals with repeated high-altitude exposure without illness; and (3) unselected (n = 6), individuals with a minimal history of altitude exposure. Data were collected in normoxia and after 5, 10, 20, and 30 minutes of normobaric hypoxia FI(O(2)) = 0.125. Relative dispersion (SD/mean) of the signal intensity was used as an index of perfusion heterogeneity. Oxygen saturation was not different between groups during hypoxia. Relative dispersion was not different between groups (HAPE-susceptible 0.94 +/- 0.05, HAPE-resistant 0.94 +/- 0.05, unselected 0.87 +/- 0.06; means +/- SEM) during normoxia, but it was increased by hypoxia in HAPE-susceptible (to 1.10 +/- 0.05 after 30 minutes, p < 0.0001) but not in HAPE-resistant (0.91 +/- 0.05) or unselected subjects (0.87 +/- 0.05). HAPE-susceptible individuals have increased pulmonary blood flow heterogeneity in acute hypoxia, consistent with uneven hypoxic pulmonary vasoconstriction.     

Sodium nitroprusside in treating acute high-altitude pulmonary edema]

Sodium nitroprusside (NP) alone Was given to the 39 cases with acute high-altitude pulmonary edema (AHPE). 33 of them (84.6%) fully recovered and 6 (15.38%) obviously improved in 72 hours. The total efficacy was 100%. There was obvious improvement in the cardiac pumping and contractile function as well as total peripheral resistance. The mean pulmonary artery pressure (MPAP) decreased from 52.22 +/- 7.51mmHg to 25.13 +/- 10.36mmHg in 3 to 5 hours after the first dose. Strophanthin K was given to another 11 cases with AHPE, But none fully recovered or obviously improved. During the 72 hours of treatment, 4 improved slightly, 4 showed no therapeutic effect and 3 became worse. The heart rate was reduced obviously and cardiac contractile function strengthened while the cardiac pumping function and total peripheral resistance had no change. Vasodilator therapy is a new method for AHPE treatment and this study shows that the NP is an ideal drug in treating AHPE and that dilation of the small pulmonary arteries by NP may explain its efficacy.     

不同氧流量氧疗对高原肺水肿的治疗效果分析

目的　探讨不同氧流量氧疗对高原肺水肿的临床治疗效果。方法　 75例高原肺水肿患者随机分成 3组 ,在常规治疗的基础上分别给予不同氧流量吸氧治疗 ,观察比较其治疗后肺部音消失时间、胸片阴影消失时间、临床治愈时间。结果　高氧流量氧疗组肺部音消失时间、胸片阴影消失时间、临床治愈时间明显短于低氧流量氧疗组。结论　根据高原肺水肿的病理生理特点 ,及时诊断、积极给予吸氧治疗可明显提高高原肺水肿的治愈率。     

Augmented sympathetic activation during short-term hypoxia and high-altitude exposure in subjects susceptible to high-altitude pulmonary edema

BACKGROUND: Pulmonary hypertension is a hallmark of high-altitude pulmonary edema and may contribute to its pathogenesis. Cardiovascular adjustments to hypoxia are mediated, at least in part, by the sympathetic nervous system, and sympathetic activation promotes pulmonary vasoconstriction and alveolar fluid flooding in experimental animals. METHODS AND RESULTS: We measured sympathetic nerve activity (using intraneural microelectrodes) in 8 mountaineers susceptible to high-altitude pulmonary edema and 7 mountaineers resistant to this condition during short-term hypoxic breathing at low altitude and at rest at a high-altitude laboratory (4559 m). We also measured systolic pulmonary artery pressure to examine the relationship between sympathetic activation and pulmonary vasoconstriction. In subjects prone to pulmonary edema, short-term hypoxic breathing at low altitude evoked comparable hypoxemia but a 2- to 3-times-larger increase in the rate of the sympathetic nerve discharge than in subjects resistant to edema (P<0.001). At high altitude, in subjects prone to edema, the increase in the mean+/-SE sympathetic firing rate was >2 times larger than in those resistant to edema (36+/-7 versus 15+/-4 bursts per minute, P<0.001) and preceded the development of lung edema. We observed a direct relationship between sympathetic nerve activity and pulmonary artery pressure measured at low and high altitude in the 2 groups (r=0.83, P<0.0001). CONCLUSIONS: With the use of direct measurements of postganglionic sympathetic nerve discharge, these data provide the first evidence for an exaggerated sympathetic activation in subjects prone to high-altitude pulmonary edema both during short-term hypoxic breathing at low altitude and during actual high-altitude exposure. Sympathetic overactivation may contribute to high-altitude pulmonary edema.     

Elevated plasma atrial natriuretic factor and vasopressin in high-altitude pulmonary edema

A diagnosis of acute high-altitude pulmonary edema was made in five male skiers (age, 35.0 +/- 1.8 years) by history and physical examination and was confirmed by a characteristic chest radiogram showing alveolar infiltrates associated with a normal cardiac silhouette. Five healthy age- and sex-matched subjects with similar physical activity at the same altitude served as controls. Plasma sodium was 135.0 +/- 1.5 mmol/L in the acutely ill patients compared with 144.0 +/- 3.3 mmol/L in the controls (P less than 0.025). Mean plasma atrial natriuretic factor immunoreactivity averaged 17.6 +/- 5.6 pmol/L in patients with high-altitude pulmonary edema compared with 6.8 +/- 0.7 pmol/L in the controls at the same altitude (P less than 0.05). Elevated atrial natriuretic factor levels normalized to 7.5 +/- 1.9 pmol/L (P less than 0.05) during recovery in Denver (altitude, 1600 meters) 24 hours later. Plasma arginine vasopressin levels were 1.8 +/- 0.37 pmol/L in patients with high-altitude pulmonary edema at diagnosis compared with 0.92 +/- 0.28 pmol/L in controls (P = 0.07). The inappropriately elevated arginine vasopressin levels decreased to 1.29 +/- 0.37 pmol/L during recovery (P less than 0.025), but the lowered plasma sodium concentration had not normalized by discharge within 24-hours of transfer to Denver and averaged 135.8 +/- 1.2 mmol/L. The pathophysiologic implications of these findings are discussed.     

Chest ultrasonography for the diagnosis and monitoring of high-altitude pulmonary edema

BACKGROUND: The comet-tail technique of chest ultrasonography has been described for the diagnosis of cardiogenic pulmonary edema. This is the first report describing its use for the diagnosis and monitoring of high-altitude pulmonary edema (HAPE), the leading cause of death from altitude illness. METHODS: Eleven consecutive patients presenting to the Himalayan Rescue Association clinic in Pheriche, Nepal (4,240 m) with a clinical diagnosis of HAPE underwent one to three chest ultrasound examinations using the comet-tail technique to determine the presence of extravascular lung water (EVLW). Seven patients with no evidence of HAPE or other altitude illness served as control subjects. All examinations were read by a blinded observer. RESULTS: HAPE patients had higher comet-tail score (CTS) [mean +/- SD, 31 +/- 11 vs 0.86 +/- 0.83] and lower oxygen saturation (O(2)Sat) [61 +/- 9.2% vs 87 +/- 2.8%] than control subjects (p < 0.001 for both). Mean CTS was higher (35 +/- 11 vs 12 +/- 6.8, p < 0.001) and O(2)Sat was lower (60 +/- 11% vs 84 +/- 1.6%, p = 0.002) at hospital admission than at discharge for the HAPE patients with follow-up ultrasound examinations. Regression analysis showed CTS was predictive of O(2)Sat (p < 0.001), and for every 1-point increase in CTS O(2)Sat fell by 0.67% (95% confidence interval, 0.41 to 0.93%, p < 0.001). CONCLUSIONS: The comet-tail technique effectively recognizes and monitors the degree of pulmonary edema in HAPE. Reduction in CTS parallels improved oxygenation and clinical status in HAPE. The feasibility of this technique in remote locations and rapid correlation with changes in EVLW make it a valuable research tool.     

Clinical features of patients with high-altitude pulmonary edema in Japan

Clinical studies were performed in 27 consecutive patients with high-altitude pulmonary edema who were transported from the mountains to Shinshu University Hospital, Matsumoto, Japan. The altitude of onset was 2,680 m to 3,190 m above sea level. Symptoms included marked dyspnea, cough, and stridor. Physical findings included cyanosis, tachycardia, and rales. Neurologic disturbances, which were seen in 17 patients, included headache, vomiting, memory disturbance, clouding of consciousness, or coma. Chest roentgenograms revealed patchy infiltrates throughout the pulmonary fields, often in an asymmetric pattern, and enlargement of the right ventricle. Hemodynamic studies by right cardiac catheterization showed that high-altitude pulmonary edema was noncardiogenic. Scintiscans of the lungs with technetium-99m-macroaggregated albumin (99mTc-MAA) performed in one patient showed decreased perfusion of 99mTc-MAA in the area of infiltrates. Pulmonary edema fluid collected through the endotracheal tube in two patients was rich in protein. Computerized tomograms of the brain showed small ventricles and cisterns, disappearance of sulci, and diffuse low density of the cerebrum, indicating cerebral edema in eight of nine cases. Retinal hemorrhage and papilledema were observed in five patients.