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Kolb TM, Johnston L, Srinath H, Damarla M, Kass DA, Hassoun PM. Abstract 266: Phosphodiesterase 9A Deficiency Does Not Attenuate Chronic-hypoxic Pulmonary Hypertension. Circ Res 2017. [DOI: 10.1161/res.121.suppl_1.266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background:
Phosphodiesterase (PDE) inhibition is a cornerstone of therapy for pulmonary arterial hypertension. A novel role for PDE9A in natriuretic peptide-mediated left ventricular cyclic guanosine monophosphate (cGMP) signaling and remodeling has recently been described. Since cGMP-signaling can promote vaso-relaxation and prevent vascular smooth muscle cell proliferation and cardiac myocyte hypertrophy, we hypothesized that PDE9A deficiency would attenuate right ventricular (RV) and pulmonary vascular remodeling during chronic RV pressure overload.
Methods:
Chronic-hypoxic pulmonary hypertension (CH-PH) was induced in mice lacking PDE9A expression (
Pde9a
-/-
) and wild-type littermates (
Pde9a
+/+
) by exposure to normobaric hypoxia (FiO2 = 10%) for 3 weeks. RV systolic pressures were measured to quantify PH, and RV hypertrophy was quantified as the ratio of RV free wall mass to LV/septal mass (RV/LV+S). Heart, lung, and serum were flash frozen for biochemical analyses.
Results:
In wild-type mice, exposure to chronic hypoxia resulted in significant increases in RV pressure (30 ± 2.4 vs. 20 ± 3.2 mm Hg;
P
= 0.0006) and RV hypertrophy (0.34 ± 0.04 vs. 0.25 ± 0.02;
P
< 0.0001). Serum ANP levels were increased 5-fold with CH-PH (
P
= <0.0001), associated with a 72% reduction in lung
Npr3
receptor expression (responsible for ANP clearance;
P
< 0.0001) but no increase in RV
Nppa
expression. After 3 weeks of CH-PH, tissue levels of cGMP were not increased in lung (993 ± 502 pg/mg vs. 667 ± 210 pg/mg;
P
= 0.27) or RV (47 ± 18 pg/mg vs. 49 ± 13 pg/mg;
P
= 0.88) homogenates. Accordingly, serine-239 phosphorylation of vasodilatory-stimulated phosphoprotein (VASP; a surrogate for protein kinase G activation) was not increased by CH-PH in lung or RV. Expression of
Pde9a
RNA was not increased by CH-PH in lung or RV.
Pde9a
-/-
mice did not have attenuated CH-PH induced increases in RVH (
P
= 0.27, 2-way ANOVA) or RVSP (
P
= 0.23, 2-way ANOVA) when compared to
Pde9a
+/+
mice. In both
Pde9a
-/-
and
Pde9a
+/+
mice, CH-PH was associated with significant increases in lung PDE5A expression.
Conclusions:
In a murine model of chronic RV pressure overload, PDE9A deficiency does not attenuate RV remodeling or PH, despite robust increases in circulating natriuretic peptide levels.
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Leary PJ, Kang S, Kolb TM, Maron BA, Ralph DD, Rao Y, Tedford RJ, Zamanian RT. What's in a side effect? The association between pulmonary vasodilator adverse drug events and clinical outcomes in patients with pulmonary arterial hypertension. Int J Cardiol 2017; 240:386-391. [PMID: 28412029 DOI: 10.1016/j.ijcard.2017.04.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/28/2017] [Accepted: 04/04/2017] [Indexed: 10/19/2022]
Abstract
BACKGROUND Adverse drug events (ADEs) with pulmonary vasodilator use in pulmonary arterial hypertension (PAH) are common. ADEs may contribute to worse quality of life; however, their relationship to prognosis is unknown. The objective of this study was to determine whether common ADEs after initiating subcutaneous treprostinil were associated with prognosis in PAH. METHODS We assembled a retrospective cohort of participants from four clinical trials of treprostinil for PAH, including 908 participants who received subcutaneous treprostinil and 243 who received placebo at the time ADEs were ascertained. The occurrences of four common early ADEs (infusion reactions, headaches, jaw pain, or gastrointestinal side effects) were assessed during the eight weeks after starting the infusion. We used Cox proportional hazards to estimate associations between ADEs and mortality. RESULTS No ADEs related to placebo were associated with mortality. In participants who received treprostinil, infusion reactions, headaches, and jaw pain were not associated with mortality. Gastrointestinal side effects occurring during the first eight weeks following treprostinil infusion were associated with a 57% increase in the hazard of mortality (95% CI: 14-118%). This relationship was unchanged after adjusting for demographic differences and differences in baseline PAH severity. CONCLUSIONS Gastrointestinal ADEs after starting subcutaneous treprostinil were associated with an increased risk for mortality. Increased mortality was not observed with other early ADEs or with gastrointestinal symptoms in participants who were not receiving treprostinil at the time. This hypothesis-generating association suggests ADEs may identify different phenotypes in PAH.
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Bourji KI, Kelemen BW, Mathai SC, Damico RL, Kolb TM, Mercurio V, Cozzi F, Tedford RJ, Hassoun PM. Poor survival in patients with scleroderma and pulmonary hypertension due to heart failure with preserved ejection fraction. Pulm Circ 2017; 7:409-420. [PMID: 28597765 PMCID: PMC5467929 DOI: 10.1177/2045893217700438] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Pulmonary hypertension due to heart failure with preserved ejection fraction (PH-HFpEF) has been poorly studied in patients with systemic sclerosis (SSc). We sought to compare clinical characteristics and survival of SSc patients with PH-HFpEF (SSc-PH-HFpEF) versus pulmonary arterial hypertension (SSc-PAH). We hypothesized that patients with SSc-PH-HFpEF have a similar poor overall prognosis compared with patients with SSc-PAH when matched for total right ventricular load. The analysis included 117 patients with SSc-PH (93 with SSc-PAH versus 24 with SSc-PH-HFpEF) enrolled prospectively in the Johns Hopkins PH Registry. We examined baseline demographics and hemodynamics at diagnostic right heart catheterization (RHC), two-dimensional echocardiographic characteristics, six-minute walking distance (6MWD), treatment modalities, and laboratory values (serum NT-proBNP, creatinine, uric acid, and sodium), and assessed survival. Demographics and clinical features were similar between the two groups. Baseline RHC showed significantly higher pulmonary and right heart pressures in the SSc-PH-HFpEF compared with the SSc-PAH group. Trans-pulmonary gradient (TPG), however, was equally elevated without significant difference between the groups. SSc-PH-HFpEF patients had left atrial enlargement on echocardiography compared with SSc-PAH patients. No significant differences were found between groups for 6MWD, NT-proBNP, and other laboratory values. Although overall median survival time was 4.6 years with no difference in mortality rate between the two groups (SSc-PH-HFpEF versus SSc-PAH: 75% versus 59%; P = 0.26), patients with SSc-PH-HFpEF had a twofold increased risk of death compared with SSc-PAH patients after adjusting for hemodynamics. Concomitant intrinsic pulmonary vascular disease and HFpEF likely contribute to very poor survival in patients with SSc-PH-HFpEF.
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54
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Hsu S, Brusca SB, Rhodes PS, Kolb TM, Mathai SC, Tedford RJ. Use of thermodilution cardiac output overestimates diagnoses of exercise-induced pulmonary hypertension. Pulm Circ 2017; 7:253-255. [PMID: 28680584 PMCID: PMC5448537 DOI: 10.1086/690629] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 12/07/2016] [Indexed: 11/26/2022] Open
Abstract
Two new definitions of exercise-induced pulmonary hypertension (EIPH) have emerged. Both rely on measuring cardiac output (CO), yet this remains unstandardized. In our cohort of patients undergoing invasive cardiopulmonary exercise testing, we found that using thermodilution CO rather than direct Fick CO led to a significant excess of EIPH diagnoses.
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55
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Metkus TS, Mullin CJ, Grandin EW, Rame JE, Tampakakis E, Hsu S, Kolb TM, Damico R, Hassoun PM, Kass DA, Mathai SC, Tedford RJ. Heart Rate Dependence of the Pulmonary Resistance x Compliance (RC) Time and Impact on Right Ventricular Load. PLoS One 2016; 11:e0166463. [PMID: 27861600 PMCID: PMC5115737 DOI: 10.1371/journal.pone.0166463] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 10/28/2016] [Indexed: 12/28/2022] Open
Abstract
Background The effect of heart rate (HR) and body surface area (BSA) on pulmonary RC time and right ventricular (RV) load is unknown. Methods To determine the association of HR and BSA with the pulmonary RC time and measures of RV load, we studied three large patient cohorts including subjects with 1) known or suspected pulmonary arterial hypertension (PAH) (n = 1008), 2) pulmonary hypertension due to left heart disease (n = 468), and 3) end-stage heart failure with reduced ejection fraction (n = 150). To corroborate these associations on an individual patient level, we performed an additional analysis using high-fidelity catheters in 22 patients with PAH undergoing right atrial pacing. Results A faster HR inversely correlated with RC time (p<0.01 for all), suggesting augmented RV pulsatile loading. Lower BSA directly correlated with RC time (p<0.05) although the magnitude of this effect was smaller than for HR. With incremental atrial pacing, cardiac output increased and total pulmonary resistance (TPR) fell. However, effective arterial elastance, its mean resistive component (TPR/heart period; 0.60±0.27 vs. 0.79±0.45;p = 0.048), and its pulsatile component (0.27±0.18 vs 0.39±0.28;p = 0.03) all increased at faster HR. Conclusion Heart rate and BSA are associated with pulmonary RC time. As heart rate increases, the pulsatile and total load on the RV also increase. This relationship supports a hemodynamic mechanism for adverse effects of tachycardia on the RV.
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56
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Kolb TM, Peabody J, Baddoura P, Fallica J, Mock JR, Singer BD, D'Alessio FR, Damarla M, Damico RL, Hassoun PM. Right Ventricular Angiogenesis is an Early Adaptive Response to Chronic Hypoxia-Induced Pulmonary Hypertension. Microcirculation 2016; 22:724-36. [PMID: 26352923 DOI: 10.1111/micc.12247] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Accepted: 09/04/2015] [Indexed: 11/29/2022]
Abstract
OBJECTIVE Myocardial angiogenesis is presumed to play a role in RV adaptation to PH, though definitive evidence and functional correlations are lacking. We aimed to use definitive methods to correlate RV angiogenesis, hypertrophy, and function in a murine PH model. METHODS Mice were exposed to CH for 21 days to induce PH and RV remodeling. We used unbiased stereology and flow cytometry to quantify angiogenesis and myocyte hypertrophy, and pressure-volume loops to measure RV function. RESULTS Within seven days, RV-specific increases in total capillary length (10,576 ± 2574 cm vs. 6822 ± 1379 cm; p = 0.02), surface area (10 ± 3.3 cm(2) vs. 4.9 ± 1.5 cm(2) ; p = 0.01), and volume (0.0013 ± 0.0005 cm(3) vs. 0.0006 ± 0.0001 cm(3) ; p = 0.02) were observed, and RV EC proliferation increased nearly 10-fold. Continued exposure led to progressive RVH without additional angiogenesis. RV function was preserved, but activation of hypoxia-dependent gene expression was observed in both ventricles after 21 days. CONCLUSIONS Early RV remodeling in CH-PH is associated with RV angiogenesis and preserved RV function. Continued CH-PH is associated with RVH but not angiogenesis, leading to biventricular activation of hypoxia-dependent gene expression.
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57
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Mock JR, Kolb TM, Illei PB, Yang SC, Lederman HM, Merlo CA. Bronchus-associated Lymphoid Tissue in Kabuki Syndrome with Associated Hyper-IgM Syndrome/Common Variable Immunodeficiency. Am J Respir Crit Care Med 2016; 194:514-5. [PMID: 27275756 PMCID: PMC5803647 DOI: 10.1164/rccm.201511-2305im] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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58
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Hsu S, Houston BA, Tampakakis E, Bacher AC, Rhodes PS, Mathai SC, Damico RL, Kolb TM, Hummers LK, Shah AA, McMahan Z, Corona-Villalobos CP, Zimmerman SL, Wigley FM, Hassoun PM, Kass DA, Tedford RJ. Right Ventricular Functional Reserve in Pulmonary Arterial Hypertension. Circulation 2016; 133:2413-22. [PMID: 27169739 PMCID: PMC4907868 DOI: 10.1161/circulationaha.116.022082] [Citation(s) in RCA: 132] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 04/28/2016] [Indexed: 01/02/2023]
Abstract
BACKGROUND Right ventricular (RV) functional reserve affects functional capacity and prognosis in patients with pulmonary arterial hypertension (PAH). PAH associated with systemic sclerosis (SSc-PAH) has a substantially worse prognosis than idiopathic PAH (IPAH), even though many measures of resting RV function and pulmonary vascular load are similar. We therefore tested the hypothesis that RV functional reserve is depressed in SSc-PAH patients. METHODS AND RESULTS RV pressure-volume relations were prospectively measured in IPAH (n=9) and SSc-PAH (n=15) patients at rest and during incremental atrial pacing or supine bicycle ergometry. Systolic and lusitropic function increased at faster heart rates in IPAH patients, but were markedly blunted in SSc-PAH. The recirculation fraction, which indexes intracellular calcium recycling, was also depressed in SSc-PAH (0.32±0.05 versus 0.50±0.05; P=0.039). At matched exercise (25 W), SSc-PAH patients did not augment contractility (end-systolic elastance) whereas IPAH did (P<0.001). RV afterload assessed by effective arterial elastance rose similarly in both groups; thus, ventricular-vascular coupling declined in SSc-PAH. Both end-systolic and end-diastolic RV volumes increased in SSc-PAH patients to offset contractile deficits, whereas chamber dilation was absent in IPAH (+37±10% versus +1±8%, P=0.004, and +19±4% versus -1±6%, P<0.001, respectively). Exercise-associated RV dilation also strongly correlated with resting ventricular-vascular coupling in a larger cohort. CONCLUSIONS RV contractile reserve is depressed in SSc-PAH versus IPAH subjects, associated with reduced calcium recycling. During exercise, this results in ventricular-pulmonary vascular uncoupling and acute RV dilation. RV dilation during exercise can predict adverse ventricular-vascular coupling in PAH patients.
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59
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Hassoun PM, Zamanian RT, Damico R, Lechtzin N, Khair R, Kolb TM, Tedford RJ, Hulme OL, Housten T, Pisanello C, Sato T, Pullins EH, Corona-Villalobos CP, Zimmerman SL, Gashouta MA, Minai OA, Torres F, Girgis RE, Chin K, Mathai SC. Ambrisentan and Tadalafil Up-front Combination Therapy in Scleroderma-associated Pulmonary Arterial Hypertension. Am J Respir Crit Care Med 2016; 192:1102-10. [PMID: 26360334 DOI: 10.1164/rccm.201507-1398oc] [Citation(s) in RCA: 128] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Scleroderma-associated pulmonary arterial hypertension (SSc-PAH) is a rare disease characterized by a very dismal response to therapy and poor survival. We assessed the effects of up-front combination PAH therapy in patients with SSc-PAH. METHODS In this prospective, multicenter, open-label trial, 24 treatment-naive patients with SSc-PAH received ambrisentan 10 mg and tadalafil 40 mg daily for 36 weeks. Functional, hemodynamic, and imaging (cardiac magnetic resonance imaging and echocardiography) assessments at baseline and 36 weeks included changes in right ventricular (RV) mass and pulmonary vascular resistance as co-primary endpoints and stroke volume/pulmonary pulse pressure ratio, tricuspid annular plane systolic excursion, 6-minute walk distance, and N-terminal pro-brain natriuretic peptide as secondary endpoints. RESULTS At 36 weeks, we found that treatment had resulted in significant reductions in median (interquartile range [IQR]) RV mass (28.0 g [IQR, 20.6-32.9] vs. 32.5 g [IQR, 23.2-41.4]; P < 0.05) and median pulmonary vascular resistance (3.1 Wood units [IQR, 2.0-5.7] vs. 6.9 Wood units [IQR, 4.0-12.9]; P < 0.0001) and in improvements in median stroke volume/pulmonary pulse pressure ratio (2.6 ml/mm Hg [IQR, 1.8-3.5] vs. 1.4 ml/mm Hg [IQR 8.9-2.4]; P < 0.0001) and mean ( ± SD) tricuspid annular plane systolic excursion (2.2 ± 0.12 cm vs. 1.65 ± 0.11 cm; P < 0.0001), 6-minute walk distance (395 ± 99 m vs. 343 ± 131 m; P = 0.001), and serum N-terminal pro-brain natriuretic peptide (647 ± 1,127 pg/ml vs. 1,578 ± 2,647 pg/ml; P < 0.05). CONCLUSIONS Up-front combination therapy with ambrisentan and tadalafil significantly improved hemodynamics, RV structure and function, and functional status in treatment-naive patients with SSc-PAH and may represent a very effective therapy for this patient population. In addition, we identified novel hemodynamic and imaging biomarkers that could have potential value in future clinical trials. Clinical trial registered with www.clinicaltrials.gov (NCT01042158).
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60
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Fallica J, Varela L, Johnston L, Kim B, Serebreni L, Wang L, Damarla M, Kolb TM, Hassoun PM, Damico R. Macrophage Migration Inhibitory Factor: A Novel Inhibitor of Apoptosis Signal-Regulating Kinase 1-p38-Xanthine Oxidoreductase-Dependent Cigarette Smoke-Induced Apoptosis. Am J Respir Cell Mol Biol 2016; 54:504-14. [PMID: 26390063 PMCID: PMC4821049 DOI: 10.1165/rcmb.2014-0403oc] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 09/08/2015] [Indexed: 12/29/2022] Open
Abstract
Cigarette smoke (CS) exposure is the leading cause of emphysema. CS mediates pathologic emphysematous remodeling of the lung via apoptosis of lung parenchymal cells resulting in enlargement of the airspaces, loss of the capillary bed, and diminished surface area for gas exchange. Macrophage migration inhibitory factor (MIF), a pleiotropic cytokine, is reduced both in a preclinical model of CS-induced emphysema and in patients with chronic obstructive pulmonary disease, particularly those with the most severe disease and emphysematous phenotype. MIF functions to antagonize CS-induced DNA damage, p53-dependent apoptosis of pulmonary endothelial cells (EndoCs) and resultant emphysematous tissue remodeling. Using primary alveolar EndoCs and a mouse model of CS-induced lung damage, we investigated the capacity and molecular mechanism(s) by which MIF modifies oxidant injury. Here, we demonstrate that both the activity of xanthine oxidoreductase (XOR), a superoxide-generating enzyme obligatory for CS-induced DNA damage and EndoC apoptosis, and superoxide concentrations are increased after CS exposure in the absence of MIF. Both XOR hyperactivation and apoptosis in the absence of MIF occurred via a p38 mitogen-activated protein kinase-dependent mechanism. Furthermore, a mitogen-activated protein kinase kinase kinase family member, apoptosis signal-regulating kinase 1 (ASK1), was necessary for CS-induced p38 activation and EndoC apoptosis. MIF was sufficient to directly suppress ASK1 enzymatic activity. Taken together, MIF suppresses CS-mediated cytotoxicity in the lung, in part by antagonizing ASK1-p38-XOR-dependent apoptosis.
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61
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Corona-Villalobos CP, Kamel IR, Rastegar N, Damico R, Kolb TM, Boyce DM, Sager AES, Skrok J, Shehata ML, Vogel-Claussen J, Bluemke DA, Girgis RE, Mathai SC, Hassoun PM, Zimmerman SL. Bidimensional measurements of right ventricular function for prediction of survival in patients with pulmonary hypertension: comparison of reproducibility and time of analysis with volumetric cardiac magnetic resonance imaging analysis. Pulm Circ 2015; 5:527-37. [PMID: 26401254 DOI: 10.1086/682229] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 02/23/2015] [Indexed: 01/03/2023] Open
Abstract
We tested the hypothesis that bidimensional measurements of right ventricular (RV) function obtained by cardiac magnetic resonance imaging (CMR) in patients with pulmonary arterial hypertension (PAH) are faster than volumetric measures and highly reproducible, with comparable ability to predict patient survival. CMR-derived tricuspid annular plane systolic excursion (TAPSE), RV fractional shortening (RVFS), RV fractional area change (RVFAC), standard functional and volumetric measures, and ventricular mass index (VMI) were compared with right heart catheterization data. CMR analysis time was recorded. Receiver operating characteristic curves, Kaplan-Meier, Cox proportional hazard (CPH), and Bland-Altman test were used for analysis. Forty-nine subjects with PAH and 18 control subjects were included. TAPSE, RVFS, RVFAC, RV ejection fraction, and VMI correlated significantly with pulmonary vascular resistance and mean pulmonary artery pressure (all P < 0.05). Patients were followed up for a mean (± standard deviation) of 2.5 ± 1.6 years. Kaplan-Meier curves showed that death was strongly associated with TAPSE <18 mm, RVFS <16.7%, and RVFAC <18.8%. In CPH models with TAPSE as dichotomized at 18 mm, TAPSE was significantly associated with risk of death in both unadjusted and adjusted models (hazard ratio, 4.8; 95% confidence interval, 2.0-11.3; P = 0.005 for TAPSE <18 mm). There was high intra- and interobserver agreement. Bidimensional measurements were faster (1.5 ± 0.3 min) than volumetric measures (25 ± 6 min). In conclusion, TAPSE, RVFS, and RVFAC measures are efficient measures of RV function by CMR that demonstrate significant correlation with invasive measures of PAH severity. In patients with PAH, TAPSE, RVFS, and RVFAC have high intra- and interobserver reproducibility and are more rapidly obtained than volumetric measures. TAPSE <18 mm by CMR was strongly and independently associated with survival in PAH.
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62
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Kolb TM, Singer B, D’Alessio F, Damarla M, Damico RL, Hassoun PM, Semenza GL, Shimoda LA. Abstract 378: Endothelial Cell Hypoxia-inducible Factor (HIF) Activity is Necessary for Right Ventricular Remodeling in a Murine Model of Chronic-hypoxic Pulmonary Hypertension. Circ Res 2015. [DOI: 10.1161/res.117.suppl_1.378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Introduction:
Pulmonary hypertension induced myocardial remodeling is required to minimize RV wall stress as pulmonary arterial pressures increase. Myocardial angiogenesis is presumed to play an integral role in early RV remodeling, though molecular regulators remain undefined. Endothelial cell (EC) expression of HIF-1 is necessary for adaptive LV remodeling during chronic pressure overload, with loss of EC-specific HIF-1 activity associated with reduced LV capillary density. We hypothesized that EC HIF activity may also be necessary for adaptive RV remodeling and angiogenesis in a model of chronic RV pressure overload.
Methods:
We used a murine model of chronic hypoxic pulmonary hypertension (CH-PH) to induce RV remodeling. Conditional transgenic mice lacking expression of the obligate HIF-1α/HIF-2α co-factor ARNT (aryl hydrocarbon receptor nuclear translocator) in Tie2+ lineage cells (
ARNT
fl/fl
;
Tie2-Cre
+/-
) and
ARNT
fl/fl
;Tie2-Cre
-/-
controls were exposed to normobaric hypoxia (10% FiO
2
) for 1-5 weeks. We measured RV hypertrophy (RVH), RV systolic pressure (RVSP), and myocardial EC proliferation (flow cytometry) as a marker for sprouting angiogenesis.
Results:
After three weeks of CH-PH, RVH was observed in
ARNT
fl/fl
;Tie2-Cre
-/-
control mice, as anticipated (0.332±0.02 vs. 0.231±0.02;
P
< 0.05). CH-PH induced RVH in
ARNT
fl/fl
;Tie2-Cre
-/-
mice was associated with an early (1 week) increase in RV EC proliferation (vs. LV, 4.5±1.3% vs.1.8±0.5%;
P
< 0.05). Conversely,
ARNT
fl/fl
;
Tie2
-
Cre
+/-
mice did not develop RVH after 3 weeks of CH ( 0.222±0.01 vs. 0.241±0.02;
P
= NS), and early RV EC proliferation was attenuated (vs. LV, 2.9±1.2% vs. 1.5±0.3%;
P
= NS). Despite similar increases in CH-PH induced RVSP after 3 weeks, after 5 weeks RVSP normalized in
ARNT
fl/fl
;
Tie2
-
Cre
+/-
mice, but remained elevated in
ARNT
fl/fl
;Tie2-Cre
-/-
controls.
Conclusions:
These preliminary findings confirm that EC-specific HIF activity is necessary for CH-PH induced RVH, and suggest that reduced EC proliferation (and potentially angiogenesis) may contribute to abrogated RV remodeling in
ARNT
fl/fl
;
Tie2
-
Cre
+/-
mice. We hypothesize that late normalization of RVSP in these mice may be indicative of premature RV failure.
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63
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Kelemen BW, Mathai SC, Tedford RJ, Damico RL, Corona-Villalobos C, Kolb TM, Chaisson NF, Harris TH, Zimmerman SL, Kamel IR, Kass DA, Hassoun PM. Right ventricular remodeling in idiopathic and scleroderma-associated pulmonary arterial hypertension: two distinct phenotypes. Pulm Circ 2015; 5:327-34. [PMID: 26064458 DOI: 10.1086/680356] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 10/13/2014] [Indexed: 11/03/2022] Open
Abstract
Patients with scleroderma (SSc)-associated pulmonary arterial hypertension (PAH) have worse survival than patients with idiopathic PAH (IPAH). We hypothesized that the right ventricle (RV) adapts differently in SSc-PAH versus IPAH. We used cardiac magnetic resonance imaging (cMRI) and hemodynamic characteristics to assess the relationship between RV morphology and RV load in patients with SSc-PAH and IPAH. In 53 patients with PAH (35 with SSc-PAH and 18 with IPAH) diagnosed by right heart catheterization (RHC), we examined cMRIs obtained within 48 hours of RHC and compared RV morphology between groups. Regression analysis was used to assess the association between diagnosis (IPAH vs. SSc-PAH) and RV measurements after adjusting for age, sex, race, body mass index (BMI), left ventricular (LV) mass, and RV load. There were no significant differences in unadjusted comparisons of cMRI measurements between the two groups. Univariable regression showed RV mass index (RVMI) was linearly associated with measures of RV load in both the overall cohort and within each group. Multivariable linear regression models revealed a significant interaction between disease type and RVMI adjusting for pulmonary vascular resistance (PVR), age, sex, race, BMI, and LV mass. This model showed a decreased slope in the relationship between RVMI and PVR in the SSc-PAH group compared with the IPAH group. RVMI varies linearly with measures of RV load. After adjusting for multiple potential confounders, patients with SSc-PAH demonstrated significantly less RV hypertrophy with increasing PVR than patients with IPAH. This difference in adaptive hypertrophy may in part explain previously observed decreased contractility and poorer survival in SSc-PAH.
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64
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Damico R, Kolb TM, Valera L, Wang L, Housten T, Tedford RJ, Kass DA, Rafaels N, Gao L, Barnes KC, Benza RL, Rand JL, Hamid R, Loyd JE, Robbins IM, Hemnes AR, Chung WK, Austin ED, Drummond MB, Mathai SC, Hassoun PM. Serum endostatin is a genetically determined predictor of survival in pulmonary arterial hypertension. Am J Respir Crit Care Med 2015; 191:208-18. [PMID: 25489667 DOI: 10.1164/rccm.201409-1742oc] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
RATIONALE Pulmonary arterial hypertension (PAH) is a medically incurable disease resulting in death from right ventricular (RV) failure. Both pulmonary vascular and RV remodeling are linked to dynamic changes in the microvasculature. Therefore, we hypothesized that circulating angiostatic factors could be linked to outcomes and represent novel biomarkers of disease severity in PAH. OBJECTIVES We sought to determine the relationship of a potent angiostatic factor, endostatin (ES), with disease severity and mortality in PAH. Furthermore, we assessed genetic predictors of ES expression and/or function and their association with outcomes in PAH. METHODS We measured levels of serum ES in two independent cohorts of patients with PAH. Contemporaneous clinical data included New York Heart Association functional class, 6-minute-walk distance, invasive hemodynamics, and laboratory chemistries. MEASUREMENTS AND MAIN RESULTS Serum ES correlated with poor functional status, decreased exercise tolerance, and invasive hemodynamics variables. Furthermore, serum ES was a strong predictor of mortality. A loss-of-function, missense variant in the gene encoding ES, Col18a1, was linked to lower circulating protein and was independently associated with reduced mortality. CONCLUSIONS Our data link increased expression of ES to disease severity in PAH and demonstrate a significant relationship with adverse outcomes. Circulating ES levels can be genetically influenced, implicating ES as a genetically determined modifier of disease severity impacting on survival. These observations support serum ES as a potential biomarker in PAH with the capacity to predict poor outcomes. More importantly, this study implicates Col18a1/ES as a potential new therapeutic target in PAH.
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Painschab MS, Malpartida GE, Dávila-Roman VG, Gilman RH, Kolb TM, León-Velarde F, Miranda JJ, Checkley W. Association between serum concentrations of hypoxia inducible factor responsive proteins and excessive erythrocytosis in high altitude Peru. High Alt Med Biol 2015; 16:26-33. [PMID: 25760230 DOI: 10.1089/ham.2014.1086] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Painschab, Matthew S., Gary E. Malpartida, Victor G. Davila-Roman, Robert H. Gilman, Todd M. Kolb, Fabiola Leon-Velarde, J. Jaime Miranda, and William Checkley. Association between serum concentrations of hypoxia inducible factor responsive proteins and excessive erythrocytosis in high altitude Peru. High Alt Med Biol 16:26-33, 2015.-Long-term residence at high altitude is associated with the development of chronic mountain sickness (CMS), which is characterized by excessive erythrocytosis (EE). EE occurs under chronic hypoxia, and a strongly selected mutation in hypoxia-inducible factor 2α (HIF2A) has been found in native Tibetans that correlates with having a normal hemoglobin at high altitude. We sought to evaluate differences in plasma levels of four HIF-responsive proteins in 20 participants with EE (hemoglobin >21 g/dL in men and >19 in women) and in 20 healthy, age- and sex-matched participants without EE living at high altitude in Puno, Peru. We performed ELISA to measure plasma levels of the four HIF-responsive proteins: vascular endothelial growth factor (VEGF), soluble VEGF receptor 1 (sVEGF-R1), endothelin-1, and erythropoietin. As a secondary aim, we evaluated the association between HIF-responsive proteins and echocardiography-estimated pulmonary artery systolic pressure (PASP) in a subset of 26 participants. sVEGF-R1 was higher in participants with vs. without EE (mean 107 pg/mL vs. 90 pg/mL; p=0.007). Although plasma concentrations of endothelin-1, VEGF, and erythropoietin were higher in participants with vs. without EE, they did not achieve statistical significance (all p>0.25). Both sVEGF-R1 (p=0.04) and erythropoietin (p=0.04) were positively associated with PASP after adjustment for age, sex, and BMI. HIF-responsive proteins may play a pathophysiological role in altitude-related, chronic diseases but our results did not show consistent changes in all measured HIF-responsive proteins. Larger studies are needed to evaluate for additional genetic and environmental risk factors.
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Bourji KI, Khair RM, Damico RL, Kolb TM, Mathai SC, Hassoun PM. Vascular Receptor Autoantibodies in Pulmonary Arterial Hypertension. Am J Respir Crit Care Med 2015; 191:602. [DOI: 10.1164/rccm.201412-2267le] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Fallica J, Boyer L, Kim B, Serebreni L, Varela L, Hamdan O, Wang L, Simms T, Damarla M, Kolb TM, Bucala R, Mitzner W, Hassoun PM, Damico R. Macrophage migration inhibitory factor is a novel determinant of cigarette smoke-induced lung damage. Am J Respir Cell Mol Biol 2014; 51:94-103. [PMID: 24490973 DOI: 10.1165/rcmb.2013-0371oc] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Cigarette smoke (CS) is the most common cause of chronic obstructive pulmonary diseases (COPD), including emphysema. CS exposure impacts all cell types within the airways and lung parenchyma, causing alveolar tissue destruction through four mechanisms: (1) oxidative stress; (2) inflammation; (3) protease-induced degradation of the extracellular matrix; and (4) enhanced alveolar epithelial and endothelial cell (EC) apoptosis. Studies in human pulmonary ECs demonstrate that macrophage migration inhibitory factor (MIF) antagonizes CS-induced apoptosis. Here, we used human microvascular ECs, an animal model of emphysema (mice challenged with chronic CS), and patient serum samples to address both the capacity of CS to alter MIF expression and the effects of MIF on disease severity. We demonstrate significantly reduced serum MIF levels in patients with COPD. In the murine model, chronic CS exposure resulted in decreased MIF mRNA and protein expression in the intact lung. MIF deficiency (Mif(-/-)) potentiated the toxicity of CS exposure in vivo via increased apoptosis of ECs, resulting in enhanced CS-induced tissue remodeling. This was linked to MIF's capacity to protect against double-stranded DNA damage and suppress p53 expression. Taken together, MIF appears to antagonize CS-induced toxicity in the lung and resultant emphysematous tissue remodeling by suppressing EC DNA damage and controlling p53-mediated apoptosis, highlighting a critical role of MIF in EC homeostasis within the lung.
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Damarla M, Parniani AR, Johnston L, Maredia H, Serebreni L, Hamdan O, Sidhaye VK, Shimoda LA, Myers AC, Crow MT, Schmidt EP, Machamer CE, Gaestel M, Rane MJ, Kolb TM, Kim BS, Damico RL, Hassoun PM. Mitogen-activated protein kinase-activated protein kinase 2 mediates apoptosis during lung vascular permeability by regulating movement of cleaved caspase 3. Am J Respir Cell Mol Biol 2014; 50:932-41. [PMID: 24304496 DOI: 10.1165/rcmb.2013-0361oc] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Apoptosis is a key pathologic feature in acute lung injury. Animal studies have demonstrated that pathways regulating apoptosis are necessary in the development of acute lung injury, and that activation of p38 mitogen-activated protein kinase (MAPK) is linked to the initiation of the apoptotic cascade. In this study, we assessed the role of the MAPK-activated protein kinase (MK) 2, one of p38 MAPK's immediate downstream effectors, in the development of apoptosis in an animal model of LPS-induced pulmonary vascular permeability. Our results indicate that wild-type (WT) mice exposed to LPS demonstrate increased apoptosis, as evidenced by cleavage of caspase 3 and poly (ADP-ribose) polymerase 1 and increased deoxynucleotidyl transferase-mediated dUDP nick-end labeling staining, which is accompanied by increases in markers of vascular permeability. In contrast, MK2(-/-) mice are protected from pulmonary vascular permeability and apoptosis in response to LPS. Although there was no difference in activation of caspase 3 in MK2(-/-) compared with WT mice, interestingly, cleaved caspase 3 translocated to the nucleus in WT mice while it remained in the cytosol of MK2(-/-) mice in response to LPS. In separate experiments, LPS-induced apoptosis in human lung microvascular endothelial cells was also associated with nuclear translocation of cleaved caspase 3 and apoptosis, which were both prevented by MK2 silencing. In conclusion, our data suggest that MK2 plays a critical role in the development of apoptosis and pulmonary vascular permeability, and its effects on apoptosis are in part related to its ability to regulate nuclear translocation of cleaved caspase 3.
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Blanco I, Mathai S, Shafiq M, Boyce D, M Kolb T, Chami H, K Hummers L, Housten T, Chaisson N, L Zaiman A, M Wigley F, J Tedford R, A Kass D, Damico R, E Girgis R, M Hassoun P. Severity of systemic sclerosis-associated pulmonary arterial hypertension in African Americans. Medicine (Baltimore) 2014; 93:177-185. [PMID: 25181310 PMCID: PMC4602454 DOI: 10.1097/md.0000000000000032] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
African Americans (AA) with systemic sclerosis (SSc) have a worse prognosis compared to Americans of European descent (EA). We conducted the current study to test the hypothesis that AA patients with SSc have more severe disease and poorer outcomes compared to EA patients when afflicted with pulmonary arterial hypertension (PAH). We studied 160 consecutive SSc patients with PAH diagnosed by right heart catheterization, comparing demographics, hemodynamics, and outcomes between AA and EA patients. The cohort included 29 AA and 131 EA patients with similar baseline characteristics except for increased prevalence of diffuse SSc in AA. AA patients had worse functional class (FC) (80% FC III-IV vs 53%; p = 0.02), higher brain natriuretic peptide (NT-pro-BNP) (5729 ± 9730 pg/mL vs 1892 ± 2417 pg/mL; p = 0.02), more depressed right ventricular function, a trend toward lower 6-minute walk distance (263 ± 111 m vs 333 ± 110 m; p = 0.07), and worse hemodynamics (cardiac index 1.95 ± 0.58 L/min/m vs 2.62 ± 0.80 L/min/m; pulmonary vascular resistance 10.3 ± 6.2 WU vs 7.6 ± 5.0 WU; p < 0.05) compared with EA patients. Kaplan-Meier survival estimates for AA and EA patients, respectively, were 62% vs 73% at 2 years and 26% vs 44% at 5 years (p > 0.05). In conclusion, AA patients with SSc-PAH are more likely to have diffuse SSc and to present with significantly more severe PAH compared with EA patients. AA patients also appear to have poorer survival, though larger studies are needed to investigate this association definitively.
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MESH Headings
- Adult
- Black or African American
- Autoantibodies/blood
- Cardiac Catheterization/methods
- Echocardiography/methods
- Exercise Test/methods
- Familial Primary Pulmonary Hypertension
- Female
- Humans
- Hypertension, Pulmonary/blood
- Hypertension, Pulmonary/diagnosis
- Hypertension, Pulmonary/ethnology
- Hypertension, Pulmonary/etiology
- Hypertension, Pulmonary/physiopathology
- Kaplan-Meier Estimate
- Male
- Middle Aged
- Natriuretic Peptide, Brain/blood
- Outcome Assessment, Health Care
- Peptide Fragments/blood
- Prevalence
- Prognosis
- Scleroderma, Systemic/blood
- Scleroderma, Systemic/complications
- Scleroderma, Systemic/diagnosis
- Scleroderma, Systemic/ethnology
- Scleroderma, Systemic/physiopathology
- Severity of Illness Index
- United States/epidemiology
- Ventricular Dysfunction, Right/etiology
- Ventricular Dysfunction, Right/physiopathology
- White People
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Kolb TM, King LS, Pearse DB. A 32-year-old woman with dyspnea, lung cysts, and previous pneumothoraces. Chest 2014; 144:1964-1968. [PMID: 24297131 DOI: 10.1378/chest.13-0902] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
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Stephens RS, Servinsky LE, Rentsendorj O, Kolb TM, Pfeifer A, Pearse DB. Protein kinase G increases antioxidant function in lung microvascular endothelial cells by inhibiting the c-Abl tyrosine kinase. Am J Physiol Cell Physiol 2014; 306:C559-69. [PMID: 24401847 DOI: 10.1152/ajpcell.00375.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Oxidant injury contributes to acute lung injury (ALI). We previously reported that activation of protein kinase GI (PKGI) posttranscriptionally increased the key antioxidant enzymes catalase and glutathione peroxidase 1 (Gpx-1) and attenuated oxidant-induced cytotoxicity in mouse lung microvascular endothelial cells (MLMVEC). The present studies tested the hypothesis that the antioxidant effect of PKGI is mediated via inhibition of the c-Abl tyrosine kinase. We found that activation of PKGI with the cGMP analog 8pCPT-cGMP inhibited c-Abl activity and decreased c-Abl expression in wild-type but not PKGI(-/-) MLMVEC. Treatment of wild-type MLMVEC with atrial natriuretic peptide also inhibited c-Abl activation. Moreover, treatment of MLMVEC with the c-Abl inhibitor imatinib increased catalase and GPx-1 protein in a posttranscriptional fashion. In imatinib-treated MLMVEC, there was no additional effect of 8pCPT-cGMP on catalase or GPx-1. The imatinib-induced increase in antioxidant proteins was associated with an increase in extracellular H2O2 scavenging by MLMVEC, attenuation of oxidant-induced endothelial barrier dysfunction, and prevention of oxidant-induced endothelial cell death. Finally, in the isolated perfused lung, imatinib prevented oxidant-induced endothelial toxicity. We conclude that cGMP, through activation of PKGI, inhibits c-Abl, leading to increased key antioxidant enzymes and resistance to lung endothelial oxidant injury. Inhibition of c-Abl by active PKGI may be the downstream mechanism underlying PKGI-mediated antioxidant signaling. Tyrosine kinase inhibitors may represent a novel therapeutic approach in oxidant-induced ALI.
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Abstract
Right ventricular (RV) dysfunction arises in chronic lung disease when chronic hypoxemia and disruption of pulmonary vascular beds increase ventricular afterload. RV dysfunction is defined by hypertrophy with preserved myocardial contractility and cardiac output. RV hypertrophy seems to be a common complication of chronic and advanced lung disease. RV failure is rare, except during acute exacerbations of chronic lung disease or when multiple comorbidities are present. Treatment is targeted at correcting hypoxia and improving pulmonary gas exchange and mechanics. There are no data supporting the use of pulmonary hypertension-specific therapies for patients with RV dysfunction secondary to chronic lung disease.
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Kolb TM, Damico RL, Hassoun PM. Linking new and old concepts: inflammation meets the Warburg phenomenon in pulmonary arterial hypertension. J Mol Med (Berl) 2012; 89:729-32. [PMID: 21735043 DOI: 10.1007/s00109-011-0783-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Kolb TM, Duan L, Davis MA. Tsc2 Expression Increases the Susceptibility of Renal Tumor Cells to Apoptosis. Toxicol Sci 2005; 88:331-9. [PMID: 16150885 DOI: 10.1093/toxsci/kfi310] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Although the precise role for the tuberous sclerosis complex-2 tumor suppressor gene (Tsc2) in tumor suppression is not clear, many studies have implicated Tsc2 in the regulation of cell differentiation, cell cycle control, GTPase activity, transcription, polycystin-1 localization, and translation initiation. We propose that Tsc2 also increases susceptibility to apoptosis, and that this functional role may contribute to the tumor suppressor activity of Tsc2. We previously characterized the apoptotic response of a Tsc2-null renal tumor cell line (ERC-18) to the tumor promoter okadaic acid (OKA). In the present study, we expressed Tsc2 in ERC-18 cells and compared the effect of Tsc2 expression on apoptotic induction. Tsc2 expression increased the susceptibility of ERC-18 cells to apoptosis induced by OKA and the phosphatidylinositol-3' kinase inhibitor, LY294002. In addition, Tsc2 expression abrogated OKA-induced cell detachment of ERC-18 cells. These results indicate that the OKA-induced, caspase-independent detachment previously observed in ERC-18 cells is Tsc2-dependent, and may support an additional role for the Tsc2 in regulating cell adhesion.
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Kolb TM, Davis MA. The Tumor Promoter 12-O-Tetradecanoylphorbol 13-acetate (TPA) Provokes a Prolonged Morphologic Response and ERK Activation in Tsc2-Null Renal Tumor Cells. Toxicol Sci 2004; 81:233-42. [PMID: 15178807 DOI: 10.1093/toxsci/kfh183] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Loss of tumor suppressor function dramatically alters the cellular response to chemicals. The phorbol ester tumor promoter, 12-O-tetradecanoylphorbol 13-acetate (TPA), stimulates cell proliferation through rapid activation of protein kinase C (PKC), followed by gradual degradation of the kinase. TPA also activates the GTPase Rap1 in some cell types. The tumor suppressor protein Tsc2 has a proposed GTPase activating protein (GAP) function for Rap1, providing a common mechanistic target for Tsc2 and TPA. We compared the cellular response of Tsc2-null (ERC-18) and Tsc2-competent (NRK-52E) renal epithelial cells to TPA treatment. Treatment of ERC-18 cells with 100 ng/ml TPA for 24 h resulted in loss of cell-cell contact, retraction of the cell periphery and rounding. These changes were reversed 1 h after treatment in NRK-52E cells and were apparent 24 h after treatment of ERC-18 cells. Expression of Tsc2 in ERC-18 cells abrogated the prolonged morphologic response. TPA treatment rapidly increased phosphorylation of ERK, a reported downstream effector of both PKC and Rap1, in ERC-18 cells, but induced weak Rap1 activation. TPA-induced ERK phosphorylation was prolonged in ERC-18 cells compared to NRK-52E cells and expression of Tsc2 in ERC-18 cells did not inhibit prolonged ERK activation. The selective PKC inhibitor, bisindolylmaleimide VIII, however, inhibited TPA-induced changes in morphology and ERK activation. These results imply that TPA-induced changes in morphology and ERK activation are mediated primarily through PKC and not Rap1 in renal epithelial cells. These data also imply that Tsc2 expression modulates TPA-induced changes in renal epithelial cell morphology via an ERK-independent mechanism.
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Kolb TM, Chang SH, Davis MA. Biochemical and morphological events during okadaic acid-induced apoptosis of Tsc2-null ERC-18 cell line. Toxicol Pathol 2002; 30:235-46. [PMID: 11950167 DOI: 10.1080/019262302753559579] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Several tumor suppressor genes have been shown to regulate cellular susceptibility to proliferation or apoptotic cell death. An essential first step in studies with the long-range goal of determining the effect of a tumor suppressor gene on cellular susceptibility to apoptosis is careful characterization of the cell's response to an apoptotic stimulus. The goals of this study were to characterize the apoptotic response of a tuberous sclerosis complex-2 (Tsc2) tumor suppressor gene-null cell line, to establish valid biochemical events that can be used as apoptosis markers, and to determine how these events correlate with apoptosis-specific morphologic changes. For characterization of apoptosis, we treated Tsc2-null renal epithelial tumor cells (ERC-18) with okadaic acid (OKA, 0.1-0.25 microM), and measured the biochemical and morphologic events during the apoptotic response. Electron microscopic and immunocytochemical evaluation showed an early loss of microvilli and a loss of vinculin and talin staining from focal adhesions within 1 hour. During the first 2 hours of treatment with 0.25 microM OKA, ERC-18 cells rounded and approximately 50% detached from the culture vessel with minimal membrane bleb formation. Phosphatidylserine externalization, chromatin margination and fragmentation, cytochrome C release, and caspase-3 and -7 cleavage were evident at 6 hours. Maximal membrane bleb formation occurred between 6 and 10 hours. Cells progressed to secondary oncotic necrosis between 10 and 24 hours of OKA treatment. Almost all cells had an oncotic phenotype after 24 hours, and 17.5% lost cell membrane integrity. A small subpopulation (< or = 5%) of OKA-treated cells underwent primary oncotic necrosis within 6 hours. Interestingly, the caspase-3 and -7 inhibitor Z-DEVD-FMK did not inhibit or delay OKA-induced apoptosis in these cells. Our results suggest a complex apoptotic model involving 2 or more potentially parallel death pathways. Although caspase-3 and -7 cleavage occurs during apoptosis in this model, this cleavage may not independently regulate cell death in ERC-18 cells. Therefore, measurement of apoptosis in this model requires analysis of both biochemical and morphologic events.
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Kolb TM. Ultrasound boosts cancer detection in dense breasts. DIAGNOSTIC IMAGING 2000; 22:103-4, 107-11. [PMID: 11148953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
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Kolb TM, Lichy J, Newhouse JH. Occult cancer in women with dense breasts: detection with screening US--diagnostic yield and tumor characteristics. Radiology 1998; 207:191-9. [PMID: 9530316 DOI: 10.1148/radiology.207.1.9530316] [Citation(s) in RCA: 369] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE To evaluate bilateral screening ultrasound (US) in the detection of otherwise occult masses and cancer in women with dense breasts and normal mammographic and physical examination findings. MATERIALS AND METHODS Of 11,220 consecutive patients prospectively examined, all 3,626 women with dense breasts and normal mammographic and physical examination findings underwent physician-performed screening US. The size and stage of cancers detected with US alone were compared with those of cancers detected on mammograms, at physical examination, or both, in the remainder of the patients. RESULTS In the group of 3,626 women, 11 surgically proved cancers in 11 women (prevalence, 0.30%) were identified with US alone. These cancers were not statistically significantly different in mean surgical size and stage from those of 61 nonpalpable, mammographically detected cancers and were smaller and lower in stage than 64 palpable cancers (P < .01) that were diagnosed in the remainder of the population. In the women with dense breasts, overall cancer detection increased by 17% (from 63 to 74 tumors), and the number of tumors detected only with imaging increased by 37% (from 30 to 41 tumors). CONCLUSION Screening US can depict small, early-stage, otherwise occult cancers similar in size and stage to mammographically identified nonpalpable cancers and smaller and lower in stage than palpable cancers in dense breasts.
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