Browsing by Author "Lahm, Tim"
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Item 17β-Estradiol and estrogen receptor α protect right ventricular function in pulmonary hypertension via BMPR2 and apelin(American Society for Clinical Investigation, 2021-03-15) Frump, Andrea L.; Albrecht, Marjorie; Yakubov, Bakhtiyor; Breuils-Bonnet, Sandra; Nadeau, Valérie; Tremblay, Eve; Potus, Francois; Omura, Junichi; Cook, Todd; Fisher, Amanda; Rodriguez, Brooke; Brown, R. Dale; Stenmark, Kurt R.; Rubinstein, C. Dustin; Krentz, Kathy; Tabima, Diana M.; Li, Rongbo; Sun, Xin; Chesler, Naomi C.; Provencher, Steeve; Bonnet, Sebastien; Lahm, Tim; Medicine, School of MedicineWomen with pulmonary arterial hypertension (PAH) exhibit better right ventricular (RV) function and survival than men; however, the underlying mechanisms are unknown. We hypothesized that 17β-estradiol (E2), through estrogen receptor α (ER-α), attenuates PAH-induced RV failure (RVF) by upregulating the procontractile and prosurvival peptide apelin via a BMPR2-dependent mechanism. We found that ER-α and apelin expression were decreased in RV homogenates from patients with RVF and from rats with maladaptive (but not adaptive) RV remodeling. RV cardiomyocyte apelin abundance increased in vivo or in vitro after treatment with E2 or ER-α agonist. Studies employing ER-α–null or ER-β–null mice, ER-α loss-of-function mutant rats, or siRNA demonstrated that ER-α is necessary for E2 to upregulate RV apelin. E2 and ER-α increased BMPR2 in pulmonary hypertension RVs and in isolated RV cardiomyocytes, associated with ER-α binding to the Bmpr2 promoter. BMPR2 is required for E2-mediated increases in apelin abundance, and both BMPR2 and apelin are necessary for E2 to exert RV-protective effects. E2 or ER-α agonist rescued monocrotaline pulmonary hypertension and restored RV apelin and BMPR2. We identified what we believe to be a novel cardioprotective E2/ER-α/BMPR2/apelin axis in the RV. Harnessing this axis may lead to novel RV-targeted therapies for PAH patients of either sex.Item 17β-Estradiol mediates superior adaptation of right ventricular function to acute strenuous exercise in female rats with severe pulmonary hypertension(APS Journals, 2016-08-01) Lahm, Tim; Frump, Andrea L.; Albrecht, Marjorie E.; Fisher, Amanda J.; Cook, Todd G.; Jones, Thomas J.; Yakubov, Bakhtiyor; Whitson, Jordan; Fuchs, Robyn K.; Liu, Aiping; Chesler, Naomi C.; Brown, M. Beth; Medicine, School of Medicine17β-Estradiol (E2) exerts protective effects on right ventricular (RV) function in pulmonary arterial hypertension (PAH). Since acute exercise-induced increases in afterload may lead to RV dysfunction in PAH, we sought to determine whether E2 allows for superior RV adaptation after an acute exercise challenge. We studied echocardiographic, hemodynamic, structural, and biochemical markers of RV function in male and female rats with sugen/hypoxia (SuHx)-induced pulmonary hypertension, as well as in ovariectomized (OVX) SuHx females, with or without concomitant E2 repletion (75 μg·kg−1·day−1) immediately after 45 min of treadmill running at 75% of individually determined maximal aerobic capacity (75% aerobic capacity reserve). Compared with males, intact female rats exhibited higher stroke volume and cardiac indexes, a strong trend for better RV compliance, and less pronounced increases in indexed total pulmonary resistance. OVX abrogated favorable RV adaptations, whereas E2 repletion after OVX markedly improved RV function. E2's effects on pulmonary vascular remodeling were complex and less robust than its RV effects. Postexercise hemodynamics in females with endogenous or exogenous E2 were similar to hemodynamics in nonexercised controls, whereas OVX rats exhibited more severely altered postexercise hemodynamics. E2 mediated inhibitory effects on RV fibrosis and attenuated increases in RV collagen I/III ratio. Proapoptotic signaling, endothelial nitric oxide synthase phosphorylation, and autophagic flux markers were affected by E2 depletion and/or repletion. Markers of impaired autophagic flux correlated with endpoints of RV structure and function. Endogenous and exogenous E2 exerts protective effects on RV function measured immediately after an acute exercise challenge. Harnessing E2's mechanisms may lead to novel RV-directed therapies.Item Acute Exercise Activates Pulmonary eNOS and Lowers Pulmonary Pressure in Rats with Pulmonary Arterial Hypertension(Office of the Vice Chancellor for Research, 2013-04-05) Chingombe, Tsungai J.; Reddy, Jag; Fisher, Amanda; Presson, Robert G.; Lahm, Tim; Petrache, Irina; Brown, Mary BethNO-dependent arterial relaxation is impaired in pulmonary arterial hypertension (PAH). Exercise may be beneficial in PAH, just as it is for systemic vascular disease, via upregulation of endothelial nitric oxide synthase (eNOS) expression and activity. However, exercise-induced cardiac stress in PAH could also promote detrimental RV inflammation. We investigated pulmonary pressure and eNOS, as well inflammatory indicators in the RV, following a single 45 min run bout at moderate intensity in a rat model of PAH. Male Sprague-Dawley rats received either monocrotaline to induce PAH, or saline, for healthy controls. A subset of PAH and healthy controls performed 4 wks of progressive TM familiarization (15-30min, 8-20 m/min) in preparation for their final 45 min run @ 75% of VO2max. Immediately following the run, RV systolic pressure was measured and RV and lung tissues were harvested and cryofixed. eNOS and phosphorylated (at Ser1177) eNOS (p-eNOS) was measured via immunoblotting in lung homogenates and expressed normalized to vinculin. Immunofluorescence for inflammatory markers CD45/68 in cryofixed RV sections evaluated the acute inflammatory response to exercise. MCT reduced VO2max and caused RV hypertrophy (expressed as RV/LV+septum) as consistent with this model. RVSP (normalized by systemic BP) was lower in PAH-Ex vs. unexercised PAH with no difference between exercised and unexercised controls. Greater p-eNOS was measured in PAH-Ex lung compared to unexercised PAH, with no difference between exercised and unexercised controls. PAH-Ex also tended to have greater pulmonary eNOS than their unexercised counterparts. No greater exercise-induced CD45/68 infiltration was observed in RV of PAH compared to that of controls. In rats with moderate MCT-induced PAH, a single exercise bout does not increase acute RV inflammation but lowers pulmonary pressure, possibly mediated in part via pulmonary eNOS activation.Item Assessment of Right Ventricular Function in the Research Setting: Knowledge Gaps and Pathways Forward. An Official American Thoracic Society Research Statement(American Thoracic Society, 2018-08-15) Lahm, Tim; Douglas, Ivor S.; Archer, Stephen L.; Bogaard, Harm J.; Chesler, Naomi C.; Haddad, Francois; Hemnes, Anna R.; Kawut, Steven M.; Kline, Jeffrey A.; Kolb, Todd M.; Mathai, Stephen C.; Mercier, Olaf; Michelakis, Evangelos D.; Naeije, Robert; Tuder, Rubin M.; Ventetuolo, Corey E.; Vieillard-Baron, Antoine; Voelkel, Norbert F.; Vonk-Noordegraaf, Anton; Medicine, School of MedicineBACKGROUND: Right ventricular (RV) adaptation to acute and chronic pulmonary hypertensive syndromes is a significant determinant of short- and long-term outcomes. Although remarkable progress has been made in the understanding of RV function and failure since the meeting of the NIH Working Group on Cellular and Molecular Mechanisms of Right Heart Failure in 2005, significant gaps remain at many levels in the understanding of cellular and molecular mechanisms of RV responses to pressure and volume overload, in the validation of diagnostic modalities, and in the development of evidence-based therapies. METHODS: A multidisciplinary working group of 20 international experts from the American Thoracic Society Assemblies on Pulmonary Circulation and Critical Care, as well as external content experts, reviewed the literature, identified important knowledge gaps, and provided recommendations. RESULTS: This document reviews the knowledge in the field of RV failure, identifies and prioritizes the most pertinent research gaps, and provides a prioritized pathway for addressing these preclinical and clinical questions. The group identified knowledge gaps and research opportunities in three major topic areas: 1) optimizing the methodology to assess RV function in acute and chronic conditions in preclinical models, human studies, and clinical trials; 2) analyzing advanced RV hemodynamic parameters at rest and in response to exercise; and 3) deciphering the underlying molecular and pathogenic mechanisms of RV function and failure in diverse pulmonary hypertension syndromes. CONCLUSIONS: This statement provides a roadmap to further advance the state of knowledge, with the ultimate goal of developing RV-targeted therapies for patients with RV failure of any etiology.Item Association of premature menopause with incident pulmonary hypertension: A cohort study(PLOS, 2021-03-10) Honigberg, Michael C.; Patel, Aniruddh P.; Lahm, Tim; Wood, Malissa J.; Ho, Jennifer E.; Kohli, Puja; Natarajan, Pradeep; Medicine, School of MedicineBackground: Several forms of pulmonary hypertension (PH) disproportionately affect women. Animal and human studies suggest that estradiol exerts mixed effects on the pulmonary vasculature. Whether premature menopause represents a risk factor for PH is unknown. Methods and findings: In this cohort study, women in the UK Biobank aged 40-69 years who were postmenopausal and had complete data available on reproductive history were included. Premature menopause, defined as menopause occurring before age 40 years. Postmenopausal women without premature menopause served as the reference group. The primary outcome was incident PH, ascertained by appearance of a qualifying ICD code in the participant's UK Biobank study record. Of 136,715 postmenopausal women included, 5,201 (3.8%) had premature menopause. Participants were followed up for a median of 11.1 (interquartile range 10.5-11.8) years. The primary outcome occurred in 38 women (0.73%) with premature menopause and 409 (0.31%) without. After adjustment for age, race, ever-smoking, body-mass index, systolic blood pressure, antihypertensive medication use, non-high-density lipoprotein cholesterol, cholesterol-lowering medication use, C-reactive protein, prevalent type 2 diabetes, obstructive sleep apnea, heart failure, mitral regurgitation, aortic stenosis, venous thromboembolism, forced vital capacity (FVC), the forced expiratory volume in 1 second-to-FVC ratio, use of menopausal hormone therapy, and hysterectomy status, premature menopause was independently associated with PH (hazard ratio 2.13, 95% CI 1.31-3.23, P<0.001). In analyses of alternate menopausal age thresholds, risk of PH appeared to increase progressively with younger age at menopause (Ptrend <0.001), with 4.8-fold risk in women with menopause before age 30 years (95% CI 1.82-12.74, P = 0.002). Use of menopausal hormone therapy did not modify the association of premature menopause with PH. Conclusions: Premature menopause may represent an independent risk factor for PH in women. Further investigation of the role of sex hormones in PH is needed in animal and human studies to elucidate pathobiology and identify novel therapeutic targets.Item At the X-Roads of Sex and Genetics in Pulmonary Arterial Hypertension(MDPI, 2020-11) Cirulis, Meghan M.; Dodson, Mark W.; Brown, Lynn M.; Brown, Samuel M.; Lahm, Tim; Elliott, Greg; Medicine, School of MedicineGroup 1 pulmonary hypertension (pulmonary arterial hypertension; PAH) is a rare disease characterized by remodeling of the small pulmonary arteries leading to progressive elevation of pulmonary vascular resistance, ultimately leading to right ventricular failure and death. Deleterious mutations in the serine-threonine receptor bone morphogenetic protein receptor 2 (BMPR2; a central mediator of bone morphogenetic protein (BMP) signaling) and female sex are known risk factors for the development of PAH in humans. In this narrative review, we explore the complex interplay between the BMP and estrogen signaling pathways, and the potentially synergistic mechanisms by which these signaling cascades increase the risk of developing PAH. A comprehensive understanding of these tangled pathways may reveal therapeutic targets to prevent or slow the progression of PAH.Item Beet-ing Muscle Dysfunction and Exercise Intolerance in Pulmonary Hypertension(2019-10) Long, Gary Marshall; Coggan, Andrew R.; Brown, Mary Beth; Lahm, Tim; Avin, Keith; Arnold, BrentBackground: Pulmonary Hypertension (PH) is a devastating disease characterized by pulmonary arterial remodeling, right ventricular dysfunction and ultimately right heart failure. Increased emphasis has been given to skeletal muscle dysfunction in PH, and to its implication in the severe exercise intolerance that is a hallmark of the condition. In this dissertation, skeletal muscle blood flow was measured via the microsphere technique at rest and during exercise (Aim 1), with an acute dose of dietary nitrate via beetroot juice (BRJ) gavage used to determine if supplementation could improve muscle blood flow and alter energetics (Aim 2). VO2max, voluntary running and grip strength tests were used to determine the effect of disease on performance, and to test for an ergogenic effect of BRJ vs. placebo (PL) in healthy and PH rats (Aim 3). Methods: A prospective, randomized, counterbalanced, placebo-controlled trial was used to examine the aforementioned aims across four groups; PH rats (induced with monocrotaline, MCT, 60mg/kg, s.q., 4 weeks) supplemented with BRJ (MCT BRJ, n=9); PH rats supplemented with placebo (MCT PL, n=9); healthy control rats (vehicle, s.q.) supplemented with BRJ (CON BRJ, n=8); healthy control rats supplemented with placebo (CON PL, n=9). Results: Monocrotaline induced a severe PH phenotype evidenced by increased RV wall thickness, RV hypertrophy, RVSP and reduced cardiac output and stroke volume compared to controls (p=<0.001). MCT rats demonstrated lower muscle blood flow at rest, and more prominently during exercise compared to controls (p=0.007-0.047), regardless of supplementation. MCT rats displayed a greater reliance on anaerobic metabolism, demonstrated by increased blood lactate accumulation (p=<0.001), and this was significantly related to reduced blood flow during exercise (r=-0.5879, p=0.001). BRJ supplementation resulted in increased plasma nitrate and nitrite compared to PL (p=<0.001), but at the skeletal muscle level, only nitrate was increased after BRJ. BRJ did not have a significant effect on blood flow, with no improvement during exercise shown vs. PL. Similarly, BRJ did not significantly improve exercise function in MCT or CON rats. Conclusion: MCT rats demonstrated a reduction in muscle blood flow, with BRJ supplementation not resulting in improved flow or exercise performance.Item Cardiac and Skeletal Muscle Lipotoxicity in a Rat Model of Pulmonary Arterial Hypertension(Office of the Vice Chancellor for Research, 2015-04-17) Dave, Priya; Cooney, Sean; Lahm, Tim; Brown, Mary BethPatients with Pulmonary Arterial Hypertension (PAH)experience shift from aerobic to anaerobic respiration in cardiac and skeletal muscle myocytes. This shift can be identified histologically by an increased presence of the glucose transporter Glut 1 in the tissue, indicating increased reliance on cytoplasmic glycolysis. Previous studies have demonstrated that in patients with diabetes, an increase in Glut 1 is accompanied by an increase in fat storage in the cell. Excessive myocyte fat storage may contribute to tissue and systemic inflammation and has therefore been termed ‘lipotoxicity’. This study tested the hypothesis in a PAH rat model that an increase in cardiac and skeletal muscle Glut 1 abundance would be associated with an increase in fat storage in the cell. Oil Red O staining was performed to assay for lipotoxicity in cryosections of right ventricle and soleus muscle tissue, imaged using brightfield microscopy. The experiment was conducted using tissue from a moderately severe PAH phenotype produced by monocrotaline(60 mg/kg) injection, as well as from saline injected control animals. Lipids have been observed in the first few samples tested with Oil Red O staining, and results are still pending as a larger sample size is currently being collected.Item A case report of hepatopulmonary syndrome in hereditary hemorrhagic telangiectasia (HHT): Not all right-to-left shunting in HHT is due to pulmonary arteriovenous malformations(Wolters Kluwer, 2018-08) Krishnan, Sheila; Lahm, Tim; Medicine, School of MedicineRATIONALE: Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by abnormal vessel growth that results in telangiectasias and arteriovenous malformations (AVMs) in the skin, mucosa, and viscera. Up to 30% of patients with HHT exhibit pulmonary AVMs (PAVMs), clinically manifesting as right-to-left shunting and hypoxemia. PATIENT CONCERNS: We report an unusual and novel case of a patient with HHT who lacked clinical sequelae of portal hypertension but presented to clinic with hypoxemia without dyspnea. DIAGNOSES: Diagnostic workup revealed noncardiac right-to-left shunting due to hepatopulmonary syndrome (HPS) from HHT-induced portal hypertension rather than PAVMs. The diagnosis was confirmed by the absence of PAVMs on chest computed tomography and evidence of elevated portal pressures as noted by the presence of small esophageal varices on upper endoscopy and histologic findings on liver biopsy. INTERVENTION: Due to the patient's mild symptoms, no further intervention was required. He was closely followed up in the outpatient setting for changes in symptoms and underwent annual screening for development of PAVMs. OUTCOMES: The patient continues to do well clinically. He has not experienced worsening hypoxemia or dyspnea and has not developed PAVMs. LESSONS: Given that management of hypoxemia in HPS drastically differs from that of hypoxemia due to PAVMs, this case demonstrates the importance of evaluating HHT patients for HPS if they exhibit impaired oxygenation and noncardiac right-to-leftshunting in the setting of hepatic arteriovenous shunting.Item Derivation of a screening tool to identify patients with right ventricular dysfunction or tricuspid regurgitation after negative computerized tomographic pulmonary angiography of the chest(University of Chicago Press Journals, 2015-03) Kline, Jeffrey A.; Russell, Frances M.; Lahm, Tim; Mastouri, Ronald A.; Department of Medicine, IU School of MedicineMany dyspneic patients who undergo computerized tomographic pulmonary angiography (CTPA) for presumed acute pulmonary embolism (PE) have no identified cause for their dyspnea yet have persistent symptoms, leading to more CTPA scanning. Right ventricular (RV) dysfunction or overload can signal treatable causes of dyspnea. We report the rate of isolated RV dysfunction or overload after negative CTPA and derive a clinical decision rule (CDR). We performed secondary analysis of a multicenter study of diagnostic accuracy for PE. Inclusion required persistent dyspnea and no PE. Echocardiography was ordered at clinician discretion. A characterization of isolated RV dysfunction or overload required normal left ventricular function and RV hypokinesis, or estimated RV systolic pressure of at least 40 mmHg. The CDR was derived from bivariate analysis of 97 candidate variables, followed by multivariate logistic regression. Of 647 patients, 431 had no PE and persistent dyspnea, and 184 (43%) of these 431 had echocardiography ordered. Of these, 64 patients (35% [95% confidence interval (CI): 28%-42%]) had isolated RV dysfunction or overload, and these patients were significantly more likely to have a repeat CTPA within 90 days (P = .02, [Formula: see text] test). From univariate analysis, 4 variables predicted isolated RV dysfunction: complete right bundle branch block, normal CTPA scan, active malignancy, and CTPA with infiltrate, the last negatively. Logistic regression found only normal CTPA scanning significant. The final rule (persistent dyspnea + normal CTPA scan) had a positive predictive value of 53% (95% CI: 37%-69%). We conclude that a simple CDR consisting of persistent dyspnea plus a normal CTPA scan predicts a high probability of isolated RV dysfunction or overload on echocardiography.