Manuel Fischler

Interleukin-6 modulates the expression of the bone morphogenic protein receptor type II through a novel STAT3-microRNA cluster 17/92 pathway.

Dysregulated expression of bone morphogenetic protein receptor type II (BMPR2) is a pathogenetic hallmark of pulmonary hypertension. Downregulation of BMPR2 protein but not mRNA has been observed in multiple animal models mimicking the disease, indicating a posttranscriptional mechanism of regulation. Because microRNAs (miRNAs) regulate gene expression mainly through inhibition of target gene translation, we hypothesized that miRNAs may play a role in the modulation of BMPR2. Performing a computational algorithm on the BMPR2 gene, several miRNAs encoded by the miRNA cluster 17/92 (miR-17/92) were retrieved as potential regulators. Ectopic overexpression of miR-17/92 resulted in a strong reduction of the BMPR2 protein, and a reporter gene system showed that BMPR2 is directly targeted by miR-17-5p and miR-20a. By stimulation experiments, we found that the miR-17/92 cluster is modulated by interleukin (IL)-6, a cytokine involved in the pathogenesis of pulmonary hypertension. Because IL-6 signaling is mainly mediated by STAT3 (signal transducer and activator of transcription 3), the expression of STAT3 was knocked down by small interfering RNA, which abolished the IL-6–mediated expression of miR-17/92. Consistent with these data, we found a highly conserved STAT3-binding site in the promoter region of the miR-17/92 gene (C13orf25). Promoter studies confirmed that IL-6 enhances transcription of C13orf25 through this distinct region. Finally, we showed that persistent activation of STAT3 leads to repressed protein expression of BMPR2. Taken together, we describe here a novel STAT3–miR-17/92—BMPR2 pathway, thus providing a mechanistic explanation for the loss of BMPR2 in the development of pulmonary hypertension.

Both tadalafil and dexamethasone may reduce the incidence of high-altitude pulmonary edema: a randomized trial.

Context Very few trials have evaluated ways to prevent high-altitude pulmonary edema (HAPE). Contribution In this double-blind trial, 29 adults with a history of HAPE were randomly assigned to receive prophylactic tadalafil, dexamethasone, or placebo during a 24-hour ascent and 2-day stay at 4559 m. Compared with placebo recipients, adults taking dexamethasone less often experienced acute mountain sickness and those taking either dexamethasone or tadalafil less often had HAPE. Cautions The trial involved a small number of selected adults who rapidly ascended to a high altitude. Implications Either tadalafil or dexamethasone might help prevent HAPE in mountaineers with a history of pulmonary edema. The Editors Rapid ascent to altitudes greater than 2500 m may cause acute mountain sickness (AMS) and high-altitude pulmonary edema (HAPE). In nonacclimatized mountaineers, the prevalences of AMS and HAPE at 4559 m are approximately 50% and 4%, respectively (1). Individual susceptibility, rate of ascent, and preexposure to high altitude are major, independent determinants of the prevalence of AMS (2). Acute mountain sickness is not a prerequisite for HAPE. Acetazolamide (3, 4) or dexamethasone (5, 6) prophylaxis can prevent AMS, whereas nifedipine prophylaxis can prevent HAPE (7). Whether acetazolamide or dexamethasone also prevents HAPE has not been studied. Exaggerated hypoxic pulmonary vasoconstriction leading to elevated pulmonary capillary pressure (8) is the major pathophysiologic mechanism of HAPE. This elevated pulmonary capillary pressure may be caused by inhomogeneous hypoxic pulmonary vasoconstriction (9), which leads to areas that are subjected to high pressure and flow, consequent mechanical overdistention of pulmonary capillaries, and injury of the bloodgas barrier (10). This phenomenon causes extravasation of fluid, plasma proteins, and blood cells into the interstitial and alveolar spaces (11). Decreased bioavailability of nitric oxide might explain the elevated pulmonary artery pressure (12, 13). Therefore, phosphodiesterase-5 inhibitors are an attractive option to restore impaired effects of nitric oxide in persons susceptible to HAPE (1416). Constitutively impaired sodium and water transport in the lung has been thought to be an additional factor in the pathogenesis of HAPE (17, 18). Hypoxia also decreases water reabsorption from the alveolar space. Direct experimental evidence has been obtained from hypoxia-exposed rats (19), and indirect evidence derives from decreased sodium transport activity in cultured alveolar epithelial cells (20). Prophylactic inhalation of the 2-adrenergic agonist salmeterol to stimulate alveolar sodium transport (17) decreased the incidence of HAPE in susceptible persons. However, other mechanisms of action may also contribute to the preventive effects of salmeterol, because -adrenergics tighten the endothelial barrier and decrease pulmonary artery pressure (21). Dexamethasone may be an alternative therapy to prevent HAPE because it stimulates alveolar sodium and water reabsorption (22); may enhance nitric oxide availability in pulmonary vessels (23, 24); and is effective against AMS (5, 6), which may develop despite use of nifedipine as prophylaxis against HAPE (25). However, HAPE has occurred in persons who received dexamethasone for AMS (26, 27). We sought to test whether prophylaxis with dexamethasone or tadalafil reduces the risk for HAPE in adults with a history of HAPE on rapid ascent to 4559 m. Methods Sample and Setting Mountaineers with a history of HAPE were recruited through announcements in the journals of the Swiss Alpine Club and the German Alpine Club. Four women and 25 men with at least 1 documented episode of HAPE participated after providing written informed consent. Table 1 shows the age and average number of HAPE episodes for each participant. No participant spent more than 4 nights above 2500 m within 30 days before ascent to the Capanna Regina Margherita, Italy (altitude, 4559 m). Table 1. Participant Characteristics Two to 4 weeks before the study at the Capanna Regina Margherita, baseline evaluations were performed in Zrich, Switzerland (altitude, 490 m). For ascent, participants traveled to Alagna, Italy (altitude, 1100 m), ascended to 3200 m by cable car, and continued by foot to the Capanna Gnifetti (altitude, 3600 m), where they spent 1 night. The journey from the cable car arrival station (3200 m) to the Capanna Gnifetti took about 1.5 hours. The next morning, the participants continued to the Capanna Regina Margherita (about 4 hours), where they spent 2 nights. Figure 1 shows the study design. The institutional ethics boards of the University Hospital Zrich and University Hospital Heidelberg approved the study and its protocol, which was consistent with the principles of the Declaration of Helsinki. Figure 1. Flow diagram of the study. Twenty-nine participants were recruited and underwent prealtitude tests, after which they were randomly assigned to treatment groups. *Two participants in the tadalafil group were withdrawn from the study early because they required treatment for severe acute mountain sickness (AMS) with oxygen and dexamethasone before the first night at 4559 m, but high-altitude pulmonary edema (HAPE) was not diagnosed at the time of withdrawal. However, the duration of exposure to 4559 m may not have been long enough to develop HAPE. Randomization and Interventions Medication consisted of white gelatin capsules, identical in appearance, containing placebo; tadalafil, 10 mg (Cialis [Eli Lilly, Geneva, Switzerland]); or dexamethasone, 8 mg (Fortecortin [Merck, Dietikon, Switzerland]). Before the study, the pharmacist at the University Hospital Zrich packaged the medication into numbered bottles, which were assigned to individual participants according to a computer-generated list. Randomization was stratified by the number of previous episodes of HAPE (1 or 2) without blocking. Participants started taking the medication twice daily on the morning of the day before ascent to high altitude and continued intake until the end of the study. Primary End Point and Assessment of HAPE and AMS The primary end point was development of HAPE, which was assessed by clinical examination and chest radiography in each participant after the first and second nights at 4559 m or when HAPE or severe AMS occurred (Figure 1). Two physicians who were blinded to treatment assignment performed clinical examinations according to a predefined checklist in the mornings after the first and second night at 4559 m or when severe AMS or HAPE occurred. High-altitude pulmonary edema was clinically suspected at the appearance of dry cough, orthopnea, or pulmonary rales in at least 1 lung area. A posteroanterior thorax radiograph was then obtained by using a mobile unit (TRS [Siemens, Stockholm, Sweden]) at a fixed distance of 1.4 m at 95 kV and a charge of 3 to 6 mAs. Radiographs were scored retrospectively by a second radiologist who was blinded to other study results. After the lung was divided into 4 quadrants, the following scores were assigned: 1 for a questionable infiltrate, 2 for interstitial edema in less than 50% of the quadrant area, 3 for interstitial edema on 50% or more of the quadrant area, and 4 for alveolar edema. A radiograph showing interstitial or alveolar edema (score >1) in at least 1 quadrant (28) confirmed the diagnosis of HAPE. The severity of AMS was evaluated by clinical examination and was quantified by using the Lake Louise scoring protocol (29). Each participant answered the first 5 questions of the protocol that asked about the severity of headache, gastrointestinal symptoms, fatigue, lightheadedness or dizziness, and insomnia. A score of 0 to 3 points (0 = no symptoms, 1 = mild symptoms, 2 = moderate symptoms, and 3 = severe symptoms) was assigned for each item. In clinical examination, a score of 0 (normal) to 4 points was given for mental status (for which 4 points indicated coma) and ataxia (for which 4 points indicated inability to stand on the heel-to-toe walking test). A score of 1 was given for peripheral edema in 1 location, and a score of 2 was given for edema in more than 1 location. The sum of all points yielded the Lake Louise score (maximum score, 25 points). A Lake Louise score greater than 4 defined AMS (30). To assess possible side effects of the study medications, we separately evaluated the Lake Louise score question that asked for information on headache severity and the degree of insomnia, and we measured blood glucose levels in addition to vital signs. To test for adherence, participants were requested to document medication intake and investigators counted the remaining capsules at each visit. Blood and urine samples were collected to measure cortisol and tadalafil, respectively. Treatment of HAPE and AMS consisted of nifedipine for HAPE, dexamethasone for AMS, and supplemental oxygen for both disorders. Participants who required treatment were withdrawn from the study. Echocardiography and Measurement of Cardiac Output Doppler echocardiography was performed by using an integrated color Doppler system with a 4.0-MHz transducer (Aplio 80 [Toshiba-Medical Systems, Oetwil am See, Switzerland]) while participants were lying in a semi-supine, left-lateral position. Systolic pulmonary artery pressure was calculated from the pressure gradient across the tricuspid valve and measured with continuous-wave Doppler echocardiography by using the modified Bernoulli equation and an estimated right atrial pressure of 7 mm Hg (8). Color flow imaging was used for alignment. The recordings were stored on magneto-optical disk for evaluation by 2 investigators who were blinded to all other data. Averages of at least 3 cardiac cycles were used. Cardiac output was measured by using beat-to-beat stroke volume measurement with impedance cardiography (Task Force Monitor [CNSystems, Graz, Austria]). Nasal Potential Measurements Diffe

Comparable increase of B-type natriuretic peptide and amino-terminal pro-B-type natriuretic peptide levels in patients with severe sepsis, septic shock, and acute heart failure.

Objective:B-type natriuretic peptide (BNP) and N-terminal pro-BNP measurements are used for the diagnosis of congestive heart failure (HF). However, the diagnostic value of these tests is unknown under septic conditions. We compared patients with severe sepsis or septic shock and patients with acute HF to unravel the influence of the underlying diagnosis on BNP and N-terminal pro-BNP levels. Design:Prospective, clinical study. Setting:Academic medical intensive care unit (ICU). Patients:A total of 249 consecutive patients were screened for the diagnosis of sepsis or HF. Sepsis was defined according to published guidelines. HF was diagnosed in the presence of an underlying heart disease and congestive HF, pulmonary edema, or cardiogenic shock. Interventions:BNP and N-terminal pro-BNP were measured from blood samples that were drawn daily for routine analysis. Measurements and Main Results:We identified 24 patients with severe sepsis or septic shock and 51 patients with acute HF. At admission, the median (range) BNP and N-terminal pro-BNP levels were 572 (13–1,300) and 6,526 (198–70,000) ng/L in patients with sepsis and 581 (6–1,300) and 4,300 (126–70,000) ng/L in patients with HF. The natriuretic peptide levels increased during the ICU stay, but the differences between the groups were not significant. Nine patients with sepsis and eight patients with HF were monitored with a pulmonary artery catheter. Mean (sd) pulmonary artery occlusion pressure were 16 (4.2) and 22 (5.3) mm Hg (p = .02), and cardiac indexes were 4.6 (2.8) and 2.2 (0.6) L/min/m2 (p = .03) in patients with sepsis and HF, respectively. Despite these clear hemodynamic differences BNP and N-terminal pro-BNP levels were not statistically different between the two groups. Conclusion:In patients with severe sepsis or septic shock, BNP and N-terminal pro-BNP values are highly elevated and, despite significant hemodynamic differences, comparable with those found in acute HF patients. It remains to be determined how elevations of natriuretic peptide levels are linked to inflammation and sepsis-associated myocardial dysfunction.

Measurement of quality of life in pulmonary hypertension and its significance.

Until recently, assessment of patients with pulmonary hypertension has mainly relied on functional and haemodynamic parameters. Health-related quality of life (HRQOL), however, has become increasingly important in defining overall health status. The present study investigated the performance and clinical relevance of the Minnesota Living with Heart Failure (MLHF) questionnaire by prospectively studying 48 patients with either pulmonary arterial hypertension (n = 26) or chronic thromboembolic pulmonary hypertension (n = 22). The MLHF scores were correlated to various clinical and haemodynamic parameters. Prognostic outcome was evaluated by calculating the time taken to reach an adverse clinical event defined as death, lung transplantation or pulmonary endarterectomy. The reliability of test–re-test and internal consistency of this HRQOL tool was high. The MLHF score and its physical subscore correlated moderately to well with functional and haemodynamic parameters, except in the case of pulmonary artery pressures. Both scores significantly improved during vasodilator therapy. This figure was surpassed only by the New York Heart Association/World Health Organization functional class. A multivariate analysis of all variables revealed that the MLHF score was the sole factor predicting subsequent outcome. The Minnesota Living with Heart Failure questionnaire is highly reproducible, consistent, and a moderately valid and responsive tool in assessing health-related quality of life in pulmonary hypertension. Moreover, it is a significant predictor of outcome in these patients.

Sleep-related breathing disorders in patients with pulmonary hypertension.

BACKGROUND Cheyne-Stokes respiration (CSR) and central sleep apnea (CSA) are common in patients with left-heart failure. We investigated the hypothesis that sleep-disordered breathing is also prevalent in patients with right ventricular dysfunction due to pulmonary hypertension (PH). METHODS We studied 38 outpatients (median age, 61 years; quartiles, 51 to 72) with pulmonary arterial hypertension (n = 23) or chronic thromboembolic PH (n = 15). New York Heart Association (NYHA) class was II to IV, and median 6-min walk distance was 481 m (quartiles, 429 to 550). In-laboratory polysomnography (n = 22) and ambulatory cardiorespiratory sleep studies (n = 38) including pulse oximetry were performed. Quality of life and sleepiness by the Epworth sleepiness score were assessed. RESULTS The median apnea/hypopnea index was 8 events/h (quartiles, 4 to 19), with 8 central events (quartiles, 4 to 17), and 0 obstructive events (quartiles, 0 to 0.3) per hour. Seventeen patients (45%) had > or = 10 apnea/hypopnea events/h. Comparison of 13 patients with > or = 10 CSR/CSA events/h with 21 patients with < 10 CSR/CSA events/h (excluding 4 patients with > or = 10 obstructive events/h from this analysis) revealed no difference in regard to hemodynamics, NYHA class, and Epworth sleepiness scores. However, patients with > or = 10 CSR/CSA events/h had a reduced quality of life in the physical domains. Ambulatory cardiorespiratory sleep studies accurately predicted > or = 10 apnea/hypopnea events/h during polysomnography in patients who underwent both studies (area under the receiver operating characteristic curve, 0.93; SE +/- 0.06; p = 0.002). The corresponding value for pulse oximetry was 0.63 +/- 0.14 (p = not significant). CONCLUSIONS In patients with PH, CSR/CSA is common, but obstructive sleep apnea also occurs. Sleep-related breathing disorders are not associated with excessive sleepiness but affect quality of life. They should be evaluated by polysomnography or cardiorespiratory sleep studies because pulse oximetry may fail to detect significant sleep apnea.

Dexamethasone But Not Tadalafil Improves Exercise Capacity in Adults Prone to High-Altitude Pulmonary Edema

RATIONALE Whether pulmonary hypertension at high altitude limits exercise capacity remains uncertain. OBJECTIVES To gain further insight into the pathophysiology of hypoxia induced pulmonary hypertension and the resulting reduction in exercise capacity, we investigated if the reduction in hypoxic pulmonary vasoconstrictive response with corticosteroids or phosphodiesterase-5 inhibition improves exercise capacity. METHODS A cardiopulmonary exercise test and echocardiography to estimate systolic pulmonary artery pressure were performed in 23 subjects with previous history of high altitude pulmonary edema, known to be associated with enhanced hypoxic vasoconstriction. Subjects were randomized to dexamethasone 8 mg twice a day, tadalafil 10 mg twice a day, or placebo (double-blinded), starting the day before ascent. MEASUREMENTS AND MAIN RESULTS Measurements were performed at low and high (i.e., 4,559 m) altitude. Altitude exposure decreased maximum oxygen uptake and oxygen saturation, increased pulmonary artery pressure, and altered oxygen uptake kinetics. Compared with placebo, dexamethasone improved maximum oxygen uptake (% predicted 74 +/- 13%; tadalafil 63 +/- 13%, placebo 61 +/- 11%; P < 0.05), oxygen kinetics (mean response time 41 +/- 13 s; tadalafil 46 +/- 6 s, placebo 45 +/- 10 s; P < 0.05), and reduced the ventilatory equivalent for CO(2) (42 +/- 4; tadalafil 49 +/- 4, placebo 50 +/- 5; P < 0.01). Peak oxygen saturation did not differ significantly between the three groups (dexamethasone 66 +/- 7%, placebo 62 +/- 7%, tadalafil 69 +/- 5%; P = 0.08). During echocardiography at low-intensity exercise (40% of peak power), dexamethasone compared with placebo resulted in lower pulmonary artery pressure (47 +/- 9 mm Hg; tadalafil 57 +/- 11 mm Hg, placebo 68 +/- 23 mm Hg; P = 0.05) and higher oxygen saturation (74 +/- 7%; tadalafil 67 +/- 3%, placebo 61 +/- 20; P < 0.02). CONCLUSIONS Corticosteroids, but not phosphodiesterase-5 inhibition, partially prevented the limitation of exercise capacity in subjects with intense hypoxic pulmonary vasoconstriction at high altitude.

Reference values for the 6-minute walk test in healthy children and adolescents in Switzerland

BackgroundThe six-minute walk test (6MWT) is a simple, low tech, safe and well established, self-paced assessment tool to quantify functional exercise capacity in adults. The definition of normal 6MWT in children is especially demanding since not only parameters like height, weight and ethnical background influence the measurement, but may be as crucial as age and the developmental stage. The aim of this study is establishing reference values for the 6MWT in healthy children and adolescents in Switzerland and to investigate the influence of age, anthropometrics, heart rate, blood pressure and physical activity on the distance walked.MethodsChildren and adolescents between 5–17 years performed a 6MWT. Short questionnaire assessments about their health state and physical activities. anthropometrics and vitals were measured before and after a 6-minute walk test and were previously defined as secondary outcomes.ResultsAge, height, weight and the heart rate after the 6MWT all predicted the distance walked according to different regression models: age was the best single predictor and mostly influenced walk distance in younger age, anthropometrics were more important in adolescents and females. Heart rate after the 6MWT was an important distance predictor in addition to age and outreached anthropometrics in the majority of subgroups assessed.ConclusionsThe 6MWT in children and adolescents is feasible and practical. The 6MWT distance depends mainly on age; however, heart rate after the 6MWT, height and weight significantly add information and should be taken into account mainly in adolescents. Reference equations allow predicting 6-minute walk test distance and may help to better assess and compare outcomes in young patients with cardiovascular and respiratory diseases and are highly warranted for different populations.

Pulmonary hypertension in Switzerland: treatment and clinical course

BACKGROUND The prognosis of pulmonary hypertension (PH), especially idiopathic pulmonary arterial hypertension (IPAH), has improved during the recent years. The Swiss Registry for PH represents the collaboration of the various centres in Switzerland dealing with PH and serves as an important tool in quality control. The objective of the study was to describe the treatment and clinical course of this orphan disease in Switzerland. METHODS We analyzed data from 222 of 252 adult patients, who were included in the registry between January 1999 and December 2004 and suffered from either PAH, PH associated with lung diseases or chronic thromboembolic PH (CTEPH) with respect to the following data: NYHA class, six-minute walking distance (6-MWD), haemodynamics, treatments and survival. RESULTS If compared with the calculated expected figures the one, two and three year mean survivals in IPAH increased from 67% to 89%, from 55% to 78% and from 46% to 73%, respectively. Most patients (90%) were on oral or inhaled therapy and only 10 patients necessitated lung transplantation. Even though pulmonary endarterectomy (PEA) was performed in only 7 patients during this time, the survival in our CTEPH cohort improved compared with literature data and seems to approach outcomes usually seen after PEA. The 6-MWD increased maximally by 52 m and 59 m in IPAH and CTEPH, respectively, but in the long term returned to or below baseline values, despite the increasing use of multiple specific drugs (overall in 51% of IPAH and 29% of CTEPH). CONCLUSION Our national registry data indicate that the overall survival of IPAH and presumably CTEPH seems to have improved in Switzerland. Although the 6-MWD improved transiently, it decreased in the long term despite specific and increasingly combined drug treatment. Our findings herewith underscore the progressive nature of the diseases and the need for further intense research in the field.

Genetic polymorphisms of the serotonin transporter, but not the 2a receptor or nitric oxide synthetase, are associated with pulmonary hypertension in chronic obstructive pulmonary disease.

Background: Pulmonary hypertension (PH) is prognosti- cally important in chronic obstructive pulmonary disease (COPD). Since PH only weakly correlates with hypoxemia, other factors must play a role. Objective: To investigate whether polymorphisms of the serotonin transporter (5HTT), serotonin-2a receptor (5HTR2a) and endothelial nitric oxide synthetase (eNOS) are related to PH in COPD. Methods: In 59 COPD patients who underwent right heart catheterization, 6-min walking distance, NYHA functional class, pulmonary function tests, blood gases and 5HTT, 5HTR2a and eNOS (4ab and T298C) polymorphisms were determined. Results: Forty-nine COPD patients in NYHA functional class III–IV were included. Ten were excluded due to comorbid causes of PH (mainly chronic thromboembolic). PH (mPAP ≧25 mm Hg) was present in 55% and usually mild, but out of proportion (mPAP ≧40 mm Hg) in 12%. Patients with PH had significantly higher frequencies of the 5HTT-L-allele (52%) compared to individuals without PH (36%), and LL homozygote patients had more severe PH. In patients with out-of-proportion PH, the L-allelic frequency was even 75%. We found no association of 5HTR2a and eNOS polymorphism with PH in COPD. Conclusions: In this COPD cohort we confirm that PH is frequent and usually mild, but out of proportion in a subgroup. We found a significant association of the L-allelic variant of 5HTT with PH overall and especially in out-of-proportion PH. These findings may point towards a role of the serotonin system in COPD-PH and warrant further studies.

Tobacco Smoke: A Risk Factor for Pulmonary Arterial Hypertension?: A Case-Control Study

BACKGROUND Smoking is a well-known risk factor for cardiovascular, lung, and many other diseases. Smoking can induce pulmonary arterial hypertension (PAH) in animal models; PAH is common in smokers with COPD and thereby not correlated with the degree of airway obstruction. The impact of tobacco smoke exposure on the development of PAH in humans is not known. METHODS In a case-control study we assessed smoking and secondhand smoke exposure in all patients with PAH and chronic thromboembolic pulmonary hypertension (CTEPH) seen at our pulmonary hypertension clinic from 2002 until July 2008. Data from patients with PAH were compared with CTEPH and healthy control subjects from the Swiss Health Survey 2007. RESULTS Ninety-one patients with PAH were compared with 64 patients with CTEPH and 18,747 control subjects (women 58, 36, 10,331, respectively). Tobacco smoking was significantly more common in PAH compared with CTEPH and control subjects. This difference could be attributed to men. Patients with PAH also smoked longer and more heavily compared with patients with CTEPH. In addition, secondhand smoke exposure was significantly longer in nonsmokers with PAH compared with control subjects. CONCLUSION Our data indicate that tobacco smoke exposure may be a risk factor for men with PAH. Considering smoking as a risk factor for PAH will have implications in counseling patients and especially their hitherto unaffected relatives. Further research on the pathogenetic role of smoking in PAH is warranted.