PubMed Health⌕ Search

Biomedical subjects

Paul M Hassoun

Publications and source records attributed to Paul M Hassoun.

At least 19 recordsLinked to original sources
PubMed2006

EGFR-activated signaling and actin remodeling regulate cyclic stretch-induced NRF2-ARE activation.

Cyclic stretch (CS) associated with mechanical ventilation (MV) can cause excessive alveolar and endothelial distention, resulting in lung injury and inflammation. Antioxidant enzymes (AOEs) play a major role in suppressing these effects. The transcription factor Nrf2, via the antioxidant response element (ARE), alleviates pulmonary toxicant- and oxidant-induced oxidative stress by up-regulating the expression of several AOEs. Although gene expression profiling has revealed the induction of AOEs in the lungs of rodents exposed to MV, the mechanisms by which mechanical forces, such as CS, regulate the activation of Nrf2-dependent ARE-transcriptional responses are poorly understood. To mimic mechanical stress associated with MV, we have cultured pulmonary alveolar epithelial and endothelial cells on collagen I-coated BioFlex plates and subjected them to CS. CS exposure stimulated ARE-driven transcriptional responses and subsequent AOE expression. Ectopic expression of a dominant-negative Nrf2 suppressed the CS-stimulated ARE-driven responses. Our findings suggest that actin remodeling is necessary but not sufficient for high-level CS-induced ARE activation in both epithelial and endothelial cells. We also found that inhibition of EGFR activity by a pharmacologic agent ablated the CS-induced ARE transcriptional response in both cell types. Additional studies revealed that amphiregulin, an EGFR ligand, regulates this process. We further demonstrated that the PI3K-Akt pathway acts as the downstream effector of EGFR and regulates CS-induced ARE-activation in an oxidative stress-dependent manner. Collectively, these novel findings suggest that EGFR-activated signaling and actin remodeling act in concert to regulate the CS-induced Nrf2-ARE transcriptional response and subsequent AOE expression.

Actins↗
PubMed2006

Tricuspid annular displacement predicts survival in pulmonary hypertension.

RATIONALE: Right ventricular (RV) function is an important determinant of prognosis in pulmonary hypertension. However, noninvasive assessment of the RV function is often limited by complex geometry and poor endocardial definition. OBJECTIVES: To test whether the degree of tricuspid annular displacement (tricuspid annular plane systolic excursion [TAPSE]) is a useful echo-derived measure of RV function with prognostic significance in pulmonary hypertension. METHODS: We prospectively studied 63 consecutive patients with pulmonary hypertension who were referred for a clinically indicated right heart catheterization. Patients underwent right heart catheterization immediately followed by transthoracic echocardiogram and TAPSE measurement. RESULTS: In the overall cohort, a TAPSE of less than 1.8 cm was associated with greater RV systolic dysfunction (cardiac index, 1.9 vs. 2.7 L/min/m2; RV % area change, 24 vs. 33%), right heart remodeling (right atrial area index, 17.0 vs. 12.1 cm(2)/m), and RV-left ventricular (LV) disproportion (RV/LV diastolic area, 1.7 vs. 1.2; all p < 0.001), versus a TAPSE of 1.8 cm or greater. In patients with pulmonary arterial hypertension (PAH; n = 47), survival estimates at 1 and 2 yr were 94 and 88%, respectively, in those with a TAPSE of 1.8 cm or greater versus 60 and 50%, respectively, in subjects with a TAPSE less than 1.8 cm. The unadjusted risk of death (hazard ratio) in patients with a TAPSE less than 1.8 versus 1.8 cm or greater was 5.7 (95% confidence interval, 1.3-24.9; p = 0.02) for the PAH cohort. For every 1-mm decrease in TAPSE, the unadjusted risk of death increased by 17% (hazard ratio, 1.17; 95% confidence interval, 1.05-1.30; p = 0.006), which persisted after adjusting for other echocardiographic and hemodynamic variables and baseline treatment status. CONCLUSIONS: TAPSE powerfully reflects RV function and prognosis in PAH.

Adult↗
PubMed2006

Mechanical stress activates xanthine oxidoreductase through MAP kinase-dependent pathways.

Xanthine oxidoreductase (XOR) plays a prominent role in acute lung injury because of its ability to generate reactive oxygen species. We investigated the role of XOR in ventilator-induced lung injury (VILI). Male C57BL/6J mice were assigned to spontaneous ventilation (sham) or mechanical ventilation (MV) with low (7 ml/kg) and high tidal volume (20 ml/kg) for 2 h after which lung XOR activity and expression were measured and the effect of the specific XOR inhibitor allopurinol on pulmonary vascular leakage was examined. In separate experiments, rat pulmonary microvascular endothelial cells (RPMECs) were exposed to cyclic stretch (5% and 18% elongation, 20 cycles/min) for 2 h before intracellular XOR activity measurement. Lung XOR activity was significantly increased at 2 h of MV without changes in XOR expression. There was evidence of p38 MAP kinase, ERK1/2, and ERK5 phosphorylation, but no change in JNK phosphorylation. Evans blue dye extravasation and bronchoalveolar lavage protein concentration were significantly increased in response to MV, changes that were significantly attenuated by pretreatment with allopurinol. Cyclic stretch of RPMECs also caused MAP kinase phosphorylation and a 1.7-fold increase in XOR activity, which was completely abrogated by pretreatment of the cells with specific MAP kinase inhibitors. We conclude that XOR enzymatic activity is significantly increased by mechanical stress via activation of p38 MAP kinase and ERK and plays a critical role in the pathogenesis of pulmonary edema associated with VILI.

Animals↗
PubMed2006

Clinical differences between idiopathic and scleroderma-related pulmonary hypertension.

OBJECTIVE: Pulmonary arterial hypertension related to scleroderma (PAH-Scl) is associated with high morbidity and mortality as well as poorer response to therapy and worse outcomes compared with the idiopathic form of PAH (IPAH). Scleroderma is an autoimmune disease that can affect left and right heart function directly through inflammation and fibrosis and indirectly through systemic and pulmonary hypertension. This study tested the hypothesis that an increased prevalence of left heart disease might explain the higher mortality in patients with PAH-Scl compared with patients with IPAH. METHODS: The study was designed as a retrospective cohort study comparing the baseline clinical data from 91 consecutive patients (41 with IPAH and 50 with PAH-Scl). Cox proportional hazards models were used to predict the effect of clinical covariates on patient survival. RESULTS: Patients with PAH-Scl had a lower mean pulmonary artery pressure (46.6 mm Hg versus 54.4 mm Hg in patients with IPAH; P = 0.002) despite similar levels of cardiac dysfunction (cardiac index 2.2 and 2.1 liters/minute/m(2), respectively; P = 0.19). Echocardiography revealed similar degrees of right ventricular dysfunction in the 2 groups, whereas a predominance of left heart dysfunction was observed in patients with PAH-Scl. One- and three-year survival estimates were 87.8% and 48.9%, respectively, in patients with PAH-Scl and 95.1% and 83.6%, respectively, in those with IPAH. Patients with PAH-Scl were 3.06 times more likely to die than were patients with IPAH, after controlling for the presence of pericardial effusion; there was no significant change in increased risk of death in PAH-Scl after controlling for left heart disease. CONCLUSION: The results confirm that there are significant clinical and survival differences between IPAH and PAH-Scl. The presence of left heart disease, although more common in PAH-Scl, was not predictive of the higher mortality in these patients.

Adult↗
PubMed2005

Inducible nitric oxide synthase contributes to ventilator-induced lung injury.

RATIONALE: Inducible nitric oxide synthase (iNOS) has been implicated in the development of acute lung injury. Recent studies indicate a role for mechanical stress in iNOS and endothelial NOS (eNOS) regulation. OBJECTIVES: This study investigated changes in lung NOS expression and activity in a mouse model of ventilator-induced lung injury. METHODS: C57BL/6J (wild-type [WT]) and iNOS-deficient (iNOS(-/-)) mice received spontaneous ventilation (control) or mechanical ventilation (MV; VT of 7 and 20 ml/kg) for 2 hours, after which NOS gene expression and activity were determined and pulmonary capillary leakage assessed by the Evans blue albumin assay. RESULTS: iNOS mRNA and protein expression was absent in iNOS(-/-) mice, minimal in WT control mice, but significantly upregulated in response to 2 hours of MV. In contrast, eNOS protein was decreased in WT mice, and nonsignificantly increased in iNOS(-/-) mice, as compared with control animals. iNOS and eNOS activities followed similar patterns in WT and iNOS(-/-) mice. MV caused acute lung injury as suggested by cell infiltration and nitrotyrosine accumulation in the lung, and a significant increase in bronchoalveolar lavage cell count in WT mice, findings that were reduced in iNOS(-/-) mice. Finally, Evans blue albumin accumulation in lungs of WT mice was significant (50 vs. 15% increase in iNOS(-/-) mice compared with control animals) in response to MV and was prevented by treatment of the animals with the iNOS inhibitor aminoguanidine. CONCLUSION: Taken together, our results indicate that iNOS gene expression and activity are significantly upregulated and contribute to lung edema in ventilator-induced lung injury.

Animals↗
PubMed2005

Hypoxia alters biophysical properties of endothelial cells via p38 MAPK- and Rho kinase-dependent pathways.

Hypoxia alters the barrier function of the endothelial cells that line the pulmonary vasculature, but underlying biophysical mechanisms remain unclear. Using rat pulmonary microvascular endothelial cells (RPMEC) in culture, we report herein changes in biophysical properties, both in space and in time, that occur in response to hypoxia. We address also the molecular basis of these changes. At the level of the single cell, we measured cell stiffness, the distribution of traction forces exerted by the cell on its substrate, and spontaneous nanoscale motions of microbeads tightly bound to the cytoskeleton (CSK). Hypoxia increased cell stiffness and traction forces by a mechanism that was dependent on the activation of Rho kinase. These changes were followed by p38-mediated decreases in spontaneous bead motions, indicating stabilization of local cellular-extracellular matrix (ECM) tethering interactions. Cells overexpressing phospho-mimicking small heat shock protein (HSP27-PM), a downstream effector of p38, exhibited decreases in spontaneous bead motions that correlated with increases in actin polymerization in these cells. Together, these findings suggest that hypoxia differentially regulates endothelial cell contraction and cellular-ECM adhesion.

Animals↗
PubMed2005

Long-term outcome of bosentan treatment in idiopathic pulmonary arterial hypertension and pulmonary arterial hypertension associated with the scleroderma spectrum of diseases.

BACKGROUND: Bosentan improves clinical outcomes in pulmonary arterial hypertension (PAH), particularly in the idiopathic (IPAH) subset. Scant data are available regarding PAH associated with the scleroderma spectrum of diseases (APAH-SSD). Here we review our experience with bosentan in these 2 groups. METHODS: Included were all patients at our center with either IPAH or APAH-SSD in whom bosentan was the first-line, single-agent therapy with at least 6 months of follow-up. Changes in the World Health Organization (WHO) functional class from baseline to the most recent follow-up on monotherapy were compared between the 2 groups, as well as overall survival and time to a composite end point of hepatotoxicity requiring discontinuation, use of additional therapy, or death. RESULTS: Nineteen IPAH and 17 APAH-SSD subjects with similar baseline clinical characteristics and a median follow-up 9 months (range, 6-44) were analyzed. In IPAH subjects, WHO class improved from 3.1 +/- 0.5 at baseline to 2.4 +/- 0.8 (p = 0.005). No change occurred in the APAH-SSD group: 2.9 +/- 0.3 vs. 2.8 +/- 0.8; p = 0.5. Hepatotoxicity requiring discontinuation developed in 6 patients (17%). Seven (37%) IPAH and 8 SSD patients (47%) reached the composite end point (p = NS). Overall survival at 1 and 2 years was 100% and 100% vs 87% and 79% for IPAH and APAH-SSD patients, respectively (p = 0.075). CONCLUSIONS: First-line bosentan monotherapy is associated with long-term improvement in functional class and good overall survival in patients with WHO class III IPAH. Most APAH-SSD patients experienced stability or decline in functional class and tended to have a higher mortality.

Adult↗
PubMed2004

Sphingosine 1-phosphate reduces vascular leak in murine and canine models of acute lung injury.

Excessive mechanical stress is a key component of ventilator-associated lung injury, resulting in profound vascular leak and an intense inflammatory response. To extend our in vitro observations concerning the barrier-protective effects of the lipid growth factor sphingosine 1-phosphate (Sph 1-P), we assessed the ability of Sph 1-P to prevent regional pulmonary edema accumulation in clinically relevant rodent and canine models of acute lung injury induced by combined intrabronchial endotoxin administration and high tidal volume mechanical ventilation. Intravenously delivered Sph 1-P significantly attenuated both alveolar and vascular barrier dysfunction while significantly reducing shunt formation associated with lung injury. Whole lung computed tomographic image analysis demonstrated the capability of Sph 1-P to abrogate significantly the accumulation of extravascular lung water evoked by 6-hour exposure to endotoxin. Axial density profiles and vertical density gradients localized the Sph 1-P response to transitional zones between aerated and consolidated lung regions. Together, these results indicate that Sph 1-P represents a novel therapeutic intervention for the prevention of pulmonary edema related to inflammatory injury and increased vascular permeability.

Acute Disease↗
PubMed2004

Protective effects of sphingosine 1-phosphate in murine endotoxin-induced inflammatory lung injury.

Our prior in vitro studies indicate that sphingosine 1-phosphate (S1P), a phospholipid angiogenic factor, produces endothelial cell barrier enhancement through ligation of endothelial differentiation gene family receptors. We hypothesized that S1P may reduce the vascular leak associated with acute lung injury and found that S1P infusion produced a rapid and significant reduction in lung weight gain (more than 50%) in the isolated perfused murine lung. The effect of S1P was next assessed in a murine model of LPS-mediated microvascular permeability and inflammation with marked increases in parameters of lung injury at both 6 and 24 hours after intratracheal LPS. Each parameter assessed was significantly reduced by intravenous S1P (1 microM final) and in selected experiments by the S1P analogue FTY720 (0.1 mg/kg, intraperitoneally) delivered 1 hour after LPS. S1P produced an approximately 40-50% reduction in LPS-mediated extravasation of Evans blue dye albumin, bronchoalveolar lavage protein content, and lung tissue myeloperoxidase activity (reflecting phagocyte infiltration). Consistent with systemic barrier enhancement, S1P significantly decreased Evans blue dye albumin extravasation and myeloperoxidase content in renal tissues of LPS-treated mice. These studies indicate that S1P significantly decreases pulmonary/renal vascular leakage and inflammation in a murine model of LPS-mediated acute lung injury and may represent a novel therapeutic strategy for vascular barrier dysfunction.

Animals↗
PubMed2004

Hypoxia decreases expression of soluble guanylate cyclase in cultured rat pulmonary artery smooth muscle cells.

Nitric oxide (NO) has an important role in modulating the pulmonary vascular tone. NO acts, in part, by stimulating soluble guanylate cyclase (sGC) to synthesize the intracellular second messenger cyclic GMP. In vascular smooth muscle cells, sGC is a heterodimer composed of alpha1 and beta1 subunits. The objective of this study was to test whether oxygen concentration regulates sGC expression in cultured rat pulmonary artery smooth muscle cells (rPaSMC). rPaSMC were exposed to 0, 3, and 20% oxygen for 1-48 h, and sGC subunit mRNA levels were measured. Compared with rPaSMC exposed to 20% oxygen, sGC alpha1 and beta1 subunit mRNA levels were markedly decreased in rPaSMC exposed to 0% and 3% oxygen. The decrease in sGC subunit mRNA levels in hypoxic rPaSMC was detected as early as 6 h of exposure. Compared with rPaSMC exposed to 20% oxygen, exposure of rPaSMC to 3% oxygen progressively decreased sGC subunit protein levels at 24 and 48 h. There was also a 30% and 50% decrease in sGC enzyme activity in cells exposed to hypoxia for 24 and 48 h (P < 0.05 and P < 0.001, respectively, as compared with cells maintained in normoxia). These results demonstrate that hypoxia decreases sGC expression in cultured pulmonary artery smooth muscle cells and suggest that, in hypoxic vascular smooth muscle, decreased cyclic GMP synthesis may limit the vasodilator response to NO.

Animals↗
PubMed2004

Activation of the STAT pathway in acute lung injury.

Acute lung injury (ALI) is a devastating clinical problem with a mortality as high as 60%. It is now appreciated that ALI represents a cytokine excess state that involves the microvasculature of multiple organs. The signal transducers and activators of transcription (STAT) family of transcription factors activate critical mediators of cytokine responses, but there is limited knowledge about their role in mediating ALI. In the present study, we demonstrate that the STAT transcription factors are activated rapidly in the lungs after intraperitoneal and intranasal LPS administration in mice. We also demonstrated that LPS activates both the STAT kinases, Src and JAK, in the lung with kinetics that are consistent with STAT activation. LPS treatment resulted in STAT3 activation throughout the resident lung cells, as well as in the recruited inflammatory cells. Whereas direct LPS treatment did not lead to STAT activation in cultured epithelial or endothelial cells, IL-6 activated STAT3 in both of these cell types. Furthermore, IL-6 was induced by LPS in serum and in the lung with kinetics consistent with STAT3 activation, suggesting that IL-6 may be one mechanism of STAT activation by LPS. In addition, STAT activation required reactive oxygen species, as the overexpression of catalase in mice prevented LPS-mediated STAT activation in the lung. STATs may be a common pathway for mediating ALI, regardless of the inciting factor, as STAT activation also occurred in both a gastric acid aspiration and acute pancreatitis model of ALI. Finally, STATs are activated in the lung long before signs of ALI are present, suggesting that the STAT transcription factors may play a role in initiating the inflammatory response seen in the lung.

Acute Disease↗
PubMed2004

Severe respiratory muscle weakness related to long-term colchicine therapy.

We report a case of colchicine-induced myopathy, in which the initial presenting and predominant clinical feature was respiratory muscle dysfunction; there was also chronic renal failure and electromyographically-measured myopathy. Discontinuation of colchicine led to marked improvement. Colchicine discontinuation was the only therapy performed (other medications were unchanged), and within 3 weeks the patient had regained motor function and resumed daily activities. Myopathy from primary biliary cirrhosis was ruled out. In contrast to acute colchicine intoxication, chronic colchicine toxicity is related to prolonged use rather than colchicine serum level, so colchicine serum level was not measured and did not affect the decision to discontinue colchicine. Although the diagnosis was not confirmed by muscle biopsy, we believe the typical presentation and the rapid improvement after withdrawing colchicine confirm the diagnosis. We conclude that long-term colchicine therapy, especially in the setting of chronic renal failure, can produce symptomatic respiratory muscle weakness.

Colchicine↗