Showing papers by "Paul M. Hassoun published in 2009"

Accuracy of Doppler echocardiography in the hemodynamic assessment of pulmonary hypertension.

Abstract: Rationale: Transthoracic Doppler echocardiography is recommended for screening for the presence of pulmonary hypertension (PH). However, some recent studies have suggested that Doppler echocardiographic pulmonary artery pressure estimates may frequently be inaccurate.Objectives: Evaluate the accuracy of Doppler echocardiography for estimating pulmonary artery pressure and cardiac output.Methods: We conducted a prospective study on patients with various forms of PH who underwent comprehensive Doppler echocardiography within 1 hour of a clinically indicated right-heart catheterization to compare noninvasive hemodynamic estimates with invasively measured values.Measurements and Main Results: A total of 65 patients completed the study protocol. Using Bland-Altman analytic methods, the bias for the echocardiographic estimates of the pulmonary artery systolic pressure was −0.6 mm Hg with 95% limits of agreement ranging from +38.8 to −40.0 mm Hg. Doppler echocardiography was inaccurate (defined as being greater ...

Comprehensive Invasive and Noninvasive Approach to the Right Ventricle–Pulmonary Circulation Unit State of the Art and Clinical and Research Implications

Abstract: … And I ask, as the lungs are so close at hand, and in continual motion, and the vessel that supplies them is of such dimensions, what is the use or meaning of this pulse of the right ventricle? And why was nature reduced to the necessity of adding another ventricle for the sole purpose of nourishing the lungs? — —William Harvey, Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus, 1628 There is still no answer to William Harvey’s rhetorical question. He included the right ventricle (RV), its “pulse,” the large pulmonary arteries (PAs), and the lungs in the same sentence, emphasizing the concept of a “unit.” Although Harvey realized the importance of the RV and its interactions with the pulmonary circulation, 4 centuries later, the RV is largely understudied. At the same time, there has been significant progress in our understanding of the pathology of pulmonary vascular disease and, over the past few years, an explosion of clinical therapeutic trials for PA hypertension (PAH).1 This unbalanced approach has generated a number of problems and controversies. For example, it is now becoming apparent that even if experimental therapies improve or reverse PAH pathology, this does not necessarily lead to clinical improvement and prolonged survival unless accompanied by a parallel improvement in RV function. The degree of pulmonary hypertension (ie, PA pressure [PAP]) does not strongly correlate with symptoms or survival, whereas RV mass and size and right atrial pressure reflect functional status and are strong predictors of survival.2 The 6-minute walk test, used as the primary end point in most PAH clinical trials, correlates better with RV function (ie, cardiac output) than with the degree of pulmonary pressure elevation. However, this test is being heavily criticized because of multiple inherent problems and the fact that it does …

Survival in pulmonary hypertension associated with the scleroderma spectrum of diseases: impact of interstitial lung disease.

Abstract: Objective Pulmonary hypertension (PH) is an important cause of mortality in systemic sclerosis (SSc), where it can be isolated (pulmonary arterial hypertension [PAH]) or associated with interstitial lung disease (ILD). This study was undertaken to characterize determinants of survival among SSc patients with either type of PH who received PAH-specific therapy. Methods Consecutive SSc patients with PAH or ILD-associated PH confirmed by right heart catheterization were included in the study. Kaplan-Meier and Cox proportional hazards models were used to compare survival between SSc patients with PAH and those with ILD-associated PH and to identify predictors of survival. Results Fifty-nine patients (39 with PAH and 20 with ILD-associated PH) were identified. The majority (15 of 20 with ILD-associated PH and 27 of 39 with PAH) received an endothelin receptor antagonist as initial therapy. Median followup time was 4.4 years (range 2.7–7.4 years). Survival was significantly worse in SSc patients with ILD-associated PH than in those with PAH (1-, 2-, and 3-year survival rates 82%, 46%, and 39% versus 87%, 79%, and 64%, respectively; P < 0.01 by log rank test). In a multivariable analysis, ILD-associated PH was associated with a 5-fold increase in risk of death compared with PAH. Pulmonary vascular resistance index was also an independent predictor of mortality in the overall cohort (hazard ratio 1.05, P < 0.01) and was a significant univariable risk factor in each group separately. Type of initial PAH therapy and the use of warfarin were not related to survival. Conclusion Survival in SSc complicated by PH remains poor despite currently available treatment options. While therapy may be associated with improved survival in PAH compared with historical controls, the prognosis for patients with ILD-associated PH is particularly grim. Early diagnosis and treatment may improve outcomes since worsening hemodynamic factors were associated with reduced survival.

Disruption of Nrf2 Impairs the Resolution of Hyperoxia-Induced Acute Lung Injury and Inflammation in Mice

Abstract: Aberrant tissue repair and persistent inflammation following oxidant-mediated acute lung injury (ALI) can lead to the development and progression of various pulmonary diseases, but the mechanisms underlying these processes remain unclear. Hyperoxia is widely used in the treatment of pulmonary diseases, but the effects of this oxidant exposure in patients undergoing recovery from ALI are not clearly understood. Nrf2 has emerged as a crucial transcription factor that regulates oxidant stress through the induction of several detoxifying enzymes and other proteins. Using an experimental model of hyperoxia-induced ALI, we have examined the role of oxidant stress in resolving lung injury and inflammation. We found that when exposed to sublethal (72 h) hyperoxia, Nrf2-deficient, but not wild-type mice, succumbed to death during recovery. When both genotypes were exposed to a shorter period of hyperoxia-induced ALI (48 h), the lungs of Nrf2-deficient mice during recovery exhibited persistent cellular injury, impaired alveolar and endothelial cell regeneration, and persistent cellular infiltration by macrophages and lymphocytes. Glutathione (GSH) supplementation in Nrf2-deficient mice immediately after hyperoxia remarkably restored their ability to recover from hyperoxia-induced damage in a manner similar to that of wild-type mice. Thus, the results of the present study indicate that the Nrf2-regulated transcriptional response and, particularly GSH synthesis, is critical for lung tissue repair and the resolution of inflammation in vivo and suggests that a dysfunctional Nrf2-GSH pathway may compromise these processes in vivo.

The Triterpenoid CDDO-Imidazolide Confers Potent Protection against Hyperoxic Acute Lung Injury in Mice

Abstract: Rationale: Oxygen supplementation (e.g., hyperoxia) is used to support critically ill patients with noninfectious and infectious acute lung injury (ALI); however, hyperoxia exposure can potentially further contribute to and/or perpetuate preexisting ALI. Thus, developing novel therapeutic agents to minimize the side effects of hyperoxia is essential to improve the health of patients with severe ALI and respiratory dysfunction. We have previously shown that mice with a genetic disruption of the Nrf2 transcription factor, which squelches cellular stress by up-regulating the induction of several antioxidant enzymes and proteins, have greater susceptibility to hyperoxic lung injury. Moreover, we have recently demonstrated that Nrf2-deficiency impairs the resolution of lung injury and inflammation after nonlethal hyperoxia exposure. Objectives: To test the hypothesis that amplification of endogenous Nrf2 activity would prevent or dampen ALI induced by hyperoxia. Methods: Here, we tested our hypothesis using a synthetic triterpenoid compound CDDO-imidazole (CDDO-Im) (1-[2-cyano-3-,12-dioxooleana-1,9(11)-dien-28-oyl] imidazole) in Nrf2-sufficient and Nrf2-deficient mice subjected to hyperoxia-induced ALI. Measurements and Main Results: We demonstrate that oral administration of CDDO-Im at a dose of 30 μmol/kg body weight during the hyperoxic exposure is sufficient to markedly attenuate hyperoxia-induced ALI in Nrf2-sufficient but not Nrf2-deficient mice. This protection by the CDDO-Im against hyperoxic insult was accompanied by increased levels of Nrf2-regulated cytoprotective gene expression and reduced levels of DNA damage in the lung. Conclusions: These results suggest that up-regulation of Nrf2 signaling by CDDO-Im or its analogs may provide a novel therapeutic strategy to minimize the adverse effects of hyperoxia.

Innate Immunity against Bacterial Infection following Hyperoxia Exposure Is Impaired in NRF2-Deficient Mice

Abstract: Oxygen supplementation is used as therapy to support critically ill patients with severe respiratory impairment. Although hyperoxia has been shown to enhance the lung susceptibility to subsequent bacterial infection, the mechanisms underlying enhanced susceptibility remain enigmatic. We have reported that disruption of NF-E2-related factor 2 (Nrf2), a master transcription regulator of various stress response pathways, enhances susceptibility to hyperoxia-induced acute lung injury in mice, and have also demonstrated an association between a polymorphism in the NRF2 promoter and increased susceptibility to acute lung injury. In this study, we show that Nrf2-deficient (Nrf2(-/-)) but not wild-type (Nrf2(+/+)) mice exposed to sublethal hyperoxia succumbed to death during recovery after Pseudomonas aeruginosa infection. Nrf2-deficiency caused persistent bacterial pulmonary burden and enhanced levels of inflammatory cell infiltration as well as edema. Alveolar macrophages isolated from Nrf2(-/-) mice exposed to hyperoxia displayed persistent oxidative stress and inflammatory cytokine expression concomitant with diminished levels of antioxidant enzymes, such as Gclc, required for glutathione biosynthesis. In vitro exposure of Nrf2(-/-) macrophages to hyperoxia strongly diminished their antibacterial activity and enhanced inflammatory cytokine expression compared with Nrf2(+/+) cells. However, glutathione supplementation during hyperoxic insult restored the ability of Nrf2(-/-) cells to mount antibacterial response and suppressed cytokine expression. Thus, loss of Nrf2 impairs lung innate immunity and promotes susceptibility to bacterial infection after hyperoxia exposure, ultimately leading to death of the host.

Resistin-Like Molecule-β in Scleroderma-Associated Pulmonary Hypertension

Abstract: Scleroderma is a systemic, mixed connective tissue disease that can impact the lungs through pulmonary fibrosis, vascular remodeling, and the development of pulmonary hypertension and right heart failure. Currently, little is known about the molecular mechanisms that drive this condition, but we have recently identified a novel gene product that is up-regulated in a murine model of hypoxia-induced pulmonary hypertension. This molecule, known as hypoxia-induced mitogenic factor (HIMF), is a member of the newly described resistin gene family. We have demonstrated that HIMF has mitogenic, angiogenic, vasoconstrictive, inflammatory, and chemokine-like properties, all of which are associated with vascular remodeling in the lung. Here, we demonstrate that the human homolog of HIMF, resistin-like molecule (RELM)-β, is expressed in the lung tissue of patients with scleroderma-associated pulmonary hypertension and is up-regulated compared with normal control subjects. Immunofluorescence colocalization revealed that RELM-β is expressed in the endothelium and vascular smooth muscle of remodeled vessels, as well as in plexiform lesions, macrophages, T cells, and myofibroblast-like cells. We also show that addition of recombinant RELM-β induces proliferation and activation of ERK1/2 in primary cultured human pulmonary endothelial and smooth muscle cells. These results suggest that RELM-β may be involved in the development of scleroderma-associated pulmonary hypertension.

Mitogen activated protein kinase activated protein kinase 2 regulates actin polymerization and vascular leak in ventilator associated lung injury.

Abstract: Mechanical ventilation, a fundamental therapy for acute lung injury, worsens pulmonary vascular permeability by exacting mechanical stress on various components of the respiratory system causing ventilator associated lung injury. We postulated that MK2 activation via p38 MAP kinase induced HSP25 phosphorylation, in response to mechanical stress, leading to actin stress fiber formation and endothelial barrier dysfunction. We sought to determine the role of p38 MAP kinase and its downstream effector MK2 on HSP25 phosphorylation and actin stress fiber formation in ventilator associated lung injury. Wild type and MK2−/− mice received mechanical ventilation with high (20 ml/kg) or low (7 ml/kg) tidal volumes up to 4 hrs, after which lungs were harvested for immunohistochemistry, immunoblotting and lung permeability assays. High tidal volume mechanical ventilation resulted in significant phosphorylation of p38 MAP kinase, MK2, HSP25, actin polymerization, and an increase in pulmonary vascular permeability in wild type mice as compared to spontaneous breathing or low tidal volume mechanical ventilation. However, pretreatment of wild type mice with specific p38 MAP kinase or MK2 inhibitors abrogated HSP25 phosphorylation and actin polymerization, and protected against increased lung permeability. Finally, MK2−/− mice were unable to phosphorylate HSP25 or increase actin polymerization from baseline, and were resistant to increases in lung permeability in response to HVT MV. Our results suggest that p38 MAP kinase and its downstream effector MK2 mediate lung permeability in ventilator associated lung injury by regulating HSP25 phosphorylation and actin cytoskeletal remodeling.

Pulmonary arterial hypertension complicating connective tissue diseases.

Abstract: Pulmonary arterial hypertension (PAH) may complicate diverse connective tissue diseases (CTDs) such as systemic sclerosis (SSc), systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and mixed CTD (MCTD) and is an important cause of morbidity and mortality in this context. From a histological standpoint, the pulmonary vascular lesions in PAH complicating CTD are similar to those observed in idiopathic PAH (IPAH). However, prognosis and responsiveness to therapy are distinctly worse in PAH associated with CTD. PAH is most common in SSc (affecting up to 20% of patients with SSc), and most of the data regarding incidence, clinical features, and therapy of CTD-associated PAH are derived from patients with SSc (scleroderma). Although PAH may involve other CTDs, data are more limited (primarily small, uncontrolled series and case reports). Treatment strategies for PAH associated with CTD are similar to but are distinctly less effective than those for IPAH. Lung transplantation may be offered for a subset of patients with CTD-associated PAH, but results are less favorable than for IPAH due to comorbidities and specific complications associated with CTD (e.g., esophageal involvement, aspiration with SSc).

Activated protein C protects against ventilator-induced pulmonary capillary leak.

Abstract: The coagulation system is central to the pathophysiology of acute lung injury. We have previously demonstrated that the anticoagulant activated protein C (APC) prevents increased endothelial permea...

Interactive effects of mechanical ventilation and kidney health on lung function in an in vivo mouse model

Abstract: We hypothesized that the influence of acute kidney injury (AKI) on the sensitivity of the lung to an injurious process varies with the severity of the injurious process. Thus, we thought that AKI would exacerbate lung injury from low degrees of lung trauma but attenuate lung injury from higher degrees of lung trauma. C57BL/6 mice underwent AKI (30-min kidney ischemia) or sham surgery, followed at 24 h by 4 h of spontaneous breathing (SB), mechanical ventilation with low tidal volume (7 ml/kg, LTV), or mechanical ventilation with high tidal volume (30 ml/kg, HTV). Compared with LTV, median bronchoalveolar lavage (BAL) protein leak was significantly lower with SB and greater with HTV in both sham and AKI mice. Compared with LTV, median Evans blue dye-labeled albumin extravasation in lungs (L-EBD) was also significantly lower with SB and greater with HTV. L-EBD showed a significant interaction between ventilatory mode and kidney health, such that AKI attenuated the L-EBD rise seen in HTV vs. LTV sham mice. An interaction between ventilatory mode and kidney health could also be seen in BAL neutrophil number (PMN). Thus, AKI attenuated the BAL PMN rise seen in HTV vs. LTV sham mice. These data support the presence of a complex interaction between mechanical ventilation and AKI in which the sensitivity of the lung to trauma varies with the magnitude of the trauma and may involve a modification of pulmonary neutrophil activity by AKI.

Therapy for pulmonary arterial hypertension associated with systemic sclerosis.

Abstract: Purpose of reviewSystemic sclerosis is commonly complicated by pulmonary arterial hypertension (PAH-SSc) and is a leading cause of death in this population. We will review existing challenges and recent advances in the treatment of this disease.Recent findingsTraditionally employed outcome measures

Therapies for scleroderma-related pulmonary arterial hypertension

Abstract: Pulmonary arterial hypertension (PAH), a common complication of systemic sclerosis, carries a very severe prognosis and is one of the leading causes of death in patients who suffer from it. Indeed, response to modern medical therapy has been disappointing in scleroderma-related PAH compared with other forms of PAH from the WHO group 1 classification of diseases, despite similar histological changes involving the pulmonary vasculature. This review discusses specific features of scleroderma-related PAH, currently available and US FDA-approved therapy for this syndrome, as well as potential future therapeutic developments based on newly acquired knowledge of this disorder.

Pulmonary hypertension: role of septomarginal trabeculation and moderator band complex assessed by cardiac magnetic resonance imaging

Abstract: In the right ventricle (RV), the septomarginal trabecula (SMT) arises as a muscular band originating from the interventricular septum (IVS) at the lower segment of the crista supraventricularis. It forms a functional unit with the moderator band, which attaches to the lateral free wall of the RV [1, 2]. Strategically situated between the RV inflow and outflow tracts, the whole unit serves to help emptying blood into the pulmonary trunk during systole. Thus, it should be anticipated that the SMT may undergo changes in RV hypertrophy secondary to chronic pulmonary hypertension.

Supplemental Data S1

Abstract: Supplemental Figure S1 AOX genes from N. attenuata are highly homologous to AOX1a gene from Arabidopsis thaliana. (A) Deduced NaAOX1 (AY422688) and NaAOX2 (AY422689) protein sequences were aligned with AtAOX1a protein from A. thaliana (AT3G22370.1). Asterisks show conserved amino acids in all three proteins. (B) The accumulation of AOX transcripts in local treated leaves was determined by microarrays (n=3) after elicitation of the leaves with wounding (W+W) or simulated herbivory (W+OS); control plants remained untreated. Control and W+OS samples were harvested at 0.5, 1, 5, 9, 12, 17 and 21 h post treatment; samples from W+W treatment were collected at 1, 5 and 17 h post treatment.

Janus-faced signaling of cGMP in acute lung injury

Abstract: The effect of increasing pulmonary endothelial cGMP concentration on endothelial function in acute lung injury appears to depend on 1) the presence of specific cGMP targets, 2) intracellular cGMP compartmentalization and 3) the timing of the increase in cGMP relative to the injury onset [1-4]. For example, we recently showed that pretreatment of pulmonary artery endothelial monolayers with 8pCPT-cGMP attenuated oxidant-induced barrier dysfunction by a cGMP-dependent kinase-1 (cGKI)-dependent mechanism [1,2]. More recently, however, we found that the increase in endogenous lung cGMP resulting from increased NO production in a ventilator-induced lung injury (VILI) mouse model caused lung endothelial barrier dysfunction [4]. The injurious effect of sGC-derived cGMP in VILI was mediated by the simultaneous generation of phosphodiesterase 2A (PDE2A), which was stimulated by cGMP to hydrolyze cAMP. Interestingly, in the same model, pretreatment with BAY 41-2272 (1.5 μM) to stimulate sGC before injurious tidal volume ventilation attenuated VILI. Recent evidence suggests that endothelial apoptosis may contribute to VILI [5] so we wondered if the protective effect of increasing lung endothelial cGMP before injury could be mediated by an anti-apoptotic effect of cGMP signalling. Mouse lung microvascular endothelial cells (MLMVEC) were isolated and purified by flow cytometry and shown to express cGK1 by Western blot and phosphorylation of VASP Ser235. A 6 hr pretreatment with 8pCPT-cGMP (50 μM), significantly attenuated H2O2-induced cell death assessed by flow cytometry (Annexin-, 7AAD-) and nuclear condensation. A similar protection was not observed in human pulmonary artery endothelial cells (HPAEC) which lack cGK1 expression in vitro. Restoration of cGK1 expression in HPAEC resulted in cGMP-mediated protection against oxidant cell death suggesting a cGK1-mediated effect. To determine if this protective effect was upstream of apoptotic signaling, MLMVEC from C57BL6 mice were treated with 8p-CPT-cGMP (50 uM) before exposure to increasing concentrations of H2O2. The extracellular H2O2 concentration ([H2O2]ext) was continuously measured with a H2O2 electrode. Compared with untreated cells, wildtype MLMVEC pre-treated with 8p-CPT-cGMP for 2 or 4 hrs (but not 30 min) significantly decreased the maximal Δ[H2O2]ext by 33 ± 11, 32 ± 10 and 25 ± 10% in cells exposed to 20, 50, and 100 μM H2O2, respectively (N = 8, P < 0.01). Consistent with this effect, 8pCPT-cGMP pretreatment attenuated H2O2-induced H2DCF fluorescence as well as p38MAPK and Akt phosphorylation suggesting that intracellular H2O2 concentration was also decreased. MLMVEC isolated from cGK1-/- mice failed to enhance H2O2 uptake suggesting cGK1-mediated signaling was responsible. An assessment of the major H2O2 degrading enzyme systems revealed a significant cGMP-mediated increase in catalase expression without an increase in catalase mRNA suggesting a post-translational effect. We conclude that the effects of cGMP signalling on lung endothelial function in acute lung injury are complex and include both injurious and protective mechanisms depending on the specific downstream signalling pathways that are present. Activation of lung microvascular endothelial cell cGK1 by cGMP protects against oxidant-mediated cell death possibly through an increase in endothelial antioxidant function.