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Biomedical subjects

Patricia A Thistlethwaite

Publications and source records attributed to Patricia A Thistlethwaite.

At least 19 recordsLinked to original sources
PubMed2006

Pulmonary artery smooth muscle cells from normal subjects and IPAH patients show divergent cAMP-mediated effects on TRPC expression and capacitative Ca2+ entry.

Pulmonary vascular remodeling due to overgrowth of pulmonary artery smooth muscle cells (PASMC) is a major cause for the elevated vascular resistance in patients with idiopathic pulmonary arterial hypertension (IPAH). Increased cytosolic Ca(2+) concentration, resulting from enhanced capacitative Ca(2+) entry (CCE) and upregulated transient receptor potential (TRP) channel expression, is involved in stimulating PASMC proliferation. The current study was designed to determine the impact of cAMP, a second messenger that we hypothesized would blunt aspects of PASMC activity, as a possible contributor to IPAH pathophysiology. Short-term (30 min) pretreatment with forskolin (FSK; 10 muM), a direct activator of adenylyl cyclase, in combination with the cyclic nucleotide phosphodiesterase inhibitor isobutylmethylxanthine (IBMX; 200 muM), attenuated CCE in PASMC from normal subjects, patients without pulmonary hypertension (NPH), and patients with IPAH. The FSK-mediated CCE inhibition was independent of protein kinase A (PKA), because the PKA inhibitor H89 negligibly affected the decrease in CCE produced by cAMP. By contrast, longer (4 h) treatment with FSK (with IBMX) attenuated CCE in normal and NPH PASMC but enhanced CCE in IPAH PASMC. This enhancement of CCE was abolished by PKA inhibition and associated with an upregulation of TRPC3. In addition, cAMP increased TRPC1 mRNA expression in IPAH (but not in normal or NPH) PASMC, an effect blunted by H89. Furthermore, iloprost, a prostacyclin analog that increases cAMP, downregulated TRPC3 expression in IPAH PASMC and FSK-mediated cAMP increase inhibited IPAH PASMC proliferation. Although a rapid rise in cellular cAMP decreases CCE by a PKA-independent mechanism, sustained cAMP increase inhibits CCE in normal and NPH PASMC but increases CCE via a PKA-dependent pathway in IPAH PASMC. The divergent effect of cAMP on CCE parallels effects on TRPC expression. The results suggest that the combined use of a PKA inhibitor and cAMP-elevating drugs may provide a novel approach for treatment of IPAH.

Adult↗
PubMed2006

Expression and activity of cAMP phosphodiesterase isoforms in pulmonary artery smooth muscle cells from patients with pulmonary hypertension: role for PDE1.

Pulmonary hypertension (PHT) is associated with increased vascular resistance due to sustained contraction and enhanced proliferation of pulmonary arterial smooth muscle cells (PASMC); the abnormal tone and remodeling in the pulmonary vasculature may relate, at least in part, to decreased cyclic nucleotide levels. Cyclic nucleotide phosphodiesterases (PDEs), of which 11 families have been identified, catalyze the hydrolysis of cAMP and cGMP. We tested the hypothesis that PASMC isolated from patients with PHT, either idiopathic pulmonary arterial hypertension (IPAH) or secondary pulmonary hypertension (SPH), have increased expression and activity of PDE isoforms that reduce the responsiveness of agents that raise cellular cAMP. Real-time PCR and immunoblotting demonstrated that the expression of PDE1A, PDE1C, PDE3B, and PDE5A was enhanced in PASMC from both IPAH and SPH patients compared with control PASMC. Consistent with this enhanced expression of PDEs, agonist-stimulated cAMP levels were significantly reduced in IPAH and SPH PASMC unless a PDE inhibitor was present. The use of specific PDE inhibitors revealed that an increase in PDE1 and PDE3 activity largely accounted for reduced agonist-induced cAMP levels and increased proliferation in IPAH and SPH PASMC. Treatment with PDE1C-targeted small interference RNA enhanced cAMP accumulation and inhibited cellular proliferation to a greater extent in PHT PASMC than controls. The results imply that an increase in PDE isoforms, in particular PDE1C, contributes to decreased cAMP and increased proliferation of PASMC in patients with PHT. PDE1 isoforms may provide novel targets for the treatment of both primary and secondary forms of the disease.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2006

Outcomes of pulmonary endarterectomy for treatment of extreme thromboembolic pulmonary hypertension.

OBJECTIVE: Pulmonary endarterectomy is the operation of choice for thromboembolic pulmonary hypertension. As the largest referral center for thromboembolic pulmonary hypertension in the world, we are frequently asked whether patients with extreme pulmonary hypertension (pulmonary artery systolic pressure >100 mm Hg) can safely undergo this operation with therapeutic benefit. METHODS: To determine whether patients with pulmonary artery systolic pressures of greater than 100 mm Hg have favorable outcomes after pulmonary endarterectomy, we reviewed the outcomes of 743 patients who underwent this operation between 1999 and 2004. We compared hemodynamic and outcome parameters of 65 patients (group 1: 26 male and 39 female patients; mean age, 49.5 years) who had preoperative pulmonary artery systolic pressures of greater than 100 mm Hg with 678 patients (group 2: 314 male and 364 female patients; mean age, 50.3 years) with preoperative pulmonary artery systolic pressures of less than 100 mm Hg. RESULTS: Group 1 patients had a greater overall diminution in pulmonary vascular resistance (mean decrease: 926.7 +/- 511.1 vs 546.4 +/- 365.1 dynes x sec x cm(-5), P < .01) and reduction in pulmonary artery systolic pressure (mean decrease: 50.5 +/- 18.7 vs 27.2 +/- 18.6 mm Hg, P < .05), with similar improvement in cardiac output (mean increase: 1.53 +/- 1.47 vs 1.55 +/- 1.58 L/min) compared with values seen in group 2 patients. Although length of hospital stay was similar for the 2 groups, overall perioperative survival was slightly lower in group 1 patients (89.2% [58/65] for group 1 vs 96.5% [654/678] for group 2). Patients with extreme pulmonary hypertension manifest a higher rate of postoperative reperfusion edema, leading to longer days of intubation compared with group 2 patients. CONCLUSIONS: Pulmonary endarterectomy can be performed safely in patients with severe thromboembolic pulmonary hypertension. The magnitude of preoperative pulmonary artery systolic pressure or pulmonary vascular resistance is not a contraindication for surgical intervention. Indeed, patients with extreme pulmonary hypertension might benefit the most from this operation.

Adolescent↗
PubMed2006

Venovenous extracorporeal life support after pulmonary endarterectomy: indications, techniques, and outcomes.

BACKGROUND: Pulmonary endarterectomy is the accepted therapy for thromboembolic pulmonary hypertension. A recognized complication of this surgery is the postoperative development of reperfusion edema, a potentially fatal cause of respiratory failure. Because reperfusion edema can be a reversible process, temporizing support measures may be life saving. METHODS: We retrospectively reviewed our experience with venovenous extracorporeal life support (V-V ECLS) from July 1990 to February 2006, in 20 adult patients (mean age 50.5 +/- 14.5 years) presenting with potentially reversible respiratory failure after pulmonary endarterectomy. This subset of patients comprised 1.12% of our total pulmonary endarterectomy experience during that time (1,790 cases). RESULTS: Overall in-hospital survival was 30.0% for patients requiring ECLS support after pulmonary endarterectomy versus 94.2% for patients who underwent pulmonary endarterectomy alone during the same timeframe. V-V ECLS was instituted at a mean of 86.8 hours after surgery. The mean duration of V-V ECLS was 123.4 +/- 71.3 hours. The most common cause of death in ECLS patients after pulmonary endarterectomy was pulmonary hemorrhage. Survival was greater in patients cannulated within 120 hours of surgery (46.2% survival; 6 of 13 patients) compared with those cannulated after 120 hours (0 of 7 patients). Multiple logistic regression identified long duration of mechanical ventilation pre-ECLS and severity of preoperative pulmonary hypertension together as predictors of mortality. CONCLUSIONS: A small subset of patients undergoing pulmonary endarterectomy develop temporary life-threatening respiratory failure secondary to severe reperfusion edema. In those patients with satisfactory hemodynamic outcome, V-V ECLS is a therapeutic option when all other conventional strategies have been exhausted.

Adult↗
PubMed2006

Molecular biology of chronic thromboembolic pulmonary hypertension.

Recent efforts have seen major advances in elucidating the mechanisms underlying pulmonary arterial hypertension. However, chronic thromboembolic pulmonary hypertension (CTEPH) often has been excluded from these studies. Consequently, whereas the clinical, radiographic, and hemodynamic characteristics of CTEPH have been well described, there remains a deficit in our understanding of the cellular, molecular, and genetic mechanisms underlying CTEPH. Furthermore, although prior venous thromboembolism may act as the inciting event, it is still unclear what predisposes some patients to develop CTEPH. CTEPH has two major pathogenic components. The first is the primary obstruction of central pulmonary arteries by accumulation of thrombotic material. The second is characterized by severe pulmonary vascular remodeling, similar to that seen in idiopathic pulmonary arterial hypertension. Other articles in this series describe the pathological, surgical, and therapeutic aspects of CTEPH. Here, we review the potential molecular and cellular mechanisms that may contribute to the pathogenesis of CTEPH.

Chronic Disease↗
PubMed2006

Outcomes of pulmonary endarterectomy surgery.

Chronic thromboembolic pulmonary hypertension has emerged as one of the leading causes of severe pulmonary hypertension. This disease is estimated to occur in approximately 1 to 5% of all patients who have previously developed an acute pulmonary embolism, although the true prevalence is suspected to be much higher. Chronic thromboembolic pulmonary hypertension is characterized by intraluminal thrombus organization, fibrous stenosis, and vascular remodeling of pulmonary vessels. Pulmonary endarterectomy is an operation that is considered curative for thromboembolic pulmonary hypertension and is therefore superior to transplantation for this condition. This article focuses on the surgical outcomes of patients undergoing pulmonary endarterectomy for chronic thromboembolic pulmonary hypertension and discusses the currently known factors that affect survival after this operation.

Aged↗
PubMed2006

Lung cancer and radiofrequency ablation.

Radiofrequency (RF) ablation is a recently developed technique for image-guided local destruction of selected tumors. Because the lung is a common site for cancer and usually has substantial functional reserve, RF ablation of lung cancers is an attractive option for minimally invasive treatment. The primary goal of the present review is to describe the natural history, staging systems, and conventional therapies for primary and secondary treatment of lung cancer, as well as the results of RF ablation in animal models and in humans for pulmonary applications, to clarify the appropriate role and limitations of this technology. The secondary goals are to review the principles of how RF works and to describe RF ablation techniques to familiarize interventionalists who may consider incorporating this technology into their practice and inform diagnostic radiologists of expected imaging findings and clinicians of their patients' anticipated courses and outcomes.

Animals↗
PubMed2005

Hypoxia-inducible factor 1-alpha reduces infarction and attenuates progression of cardiac dysfunction after myocardial infarction in the mouse.

OBJECTIVES: The aim of this research was to test whether constitutive expression of hypoxia-inducible factor 1-alpha (HIF-1alpha) influences infarction size and cardiac performance after myocardial infarction. BACKGROUND: A major question in clinical medicine is whether infarction size and border zone remodeling of the heart can be influenced by the overexpression of specific genes in the peri-infarction region. METHODS: We investigated the role of constitutive HIF-1alpha expression in acute myocardial infarction using a transgenic model. Transgenic mice containing the HIF-1alpha gene under the control of the alpha-myosin heavy chain promoter were constructed. Myocardial infarction was produced by coronary ligation in HIF-1alpha transgenic mice and control animals. Extent of infarction was then quantitated by two-dimensional and M-mode echocardiography as well as by molecular and pathologic analysis of heart samples in infarct, peri-infarct, and remote heart regions at serial time points. RESULTS: Constitutive overexpression of HIF-1alpha in the murine heart resulted in attenuated infarct size and improved cardiac function 4 weeks after myocardial infarction. Significantly, we found an increase in both capillary density as well as vascular endothelial growth factor and inducible nitric oxide synthase expression in peri-infarct and infarct regions in the hearts of constitutive HIF-1alpha-expressing animals compared to control animals. CONCLUSIONS: These observations suggest the involvement of HIF-1alpha in myocardial remodeling and peri-infarct vascularization. Our results show that supranormal amounts of this peptide protect against extension of infarction and improve border zone survival in myocardial infarction.

Animals↗
PubMed2005

Gene transfer of a TIE2 receptor antagonist prevents pulmonary hypertension in rodents.

OBJECTIVES: Overexpression of angiopoietin 1 in the lung has been associated with human pulmonary hypertension. We hypothesized that inhibiting angiopoietin 1 signaling in the lung by administration of a receptor antagonist would block the development of pulmonary hypertensive vasculopathy in rodent models. METHODS: We injected 2 and 4 x 10(10) genomic particles of adeno-associated virus containing an extracellular fragment of the TIE2 receptor (AAV-sTIE2) into the pulmonary artery of 60 rats by using adeno-associated virus-lacZ and carrier-injected rats as control animals. Pulmonary hypertension was then induced by each of the following methods: (1) monocrotaline (group 1); (2) angiopoietin 1 expression in pulmonary vascular smooth muscle by adeno-associated virus gene transfer (group 2); or (3) oxygen deprivation (group 3). Animals were sacrificed at serial time points. At each time point, pulmonary artery pressures were measured, and pulmonary angiography was performed. Lungs were harvested for pathologic-molecular analysis. RESULTS: Each rodent pulmonary hypertension model demonstrated a significant increase in pulmonary artery pressures compared with that seen in control animals (P < .01). Administration of AAV-sTIE2 prevented pulmonary hypertension in the monocrotaline and angiopoietin 1 groups (from 44.6 +/- 2.1 to 18.8 +/- 1.9 mm Hg in the monocrotaline group and from 31.2 +/- 3.7 to 18.2 +/- 1.8 mm Hg in the angiopoietin 1 group, P < .001) but did not affect pulmonary hypertension in the hypoxia group. Pathologic analysis of group 1 and 2 lungs treated with AAV-sTIE2 demonstrated absence of smooth muscle cell proliferation within arterioles. Pulmonary angiography confirmed a lack of small pulmonary vessel occlusion in group 1 and 2 animals treated with AAV-sTIE2. CONCLUSIONS: Molecular blocking of the interaction between angiopoietin 1 and its endothelial receptor, TIE2, in the lung prevents pulmonary hypertension in 2 animal models of the disease. These experiments suggest a new strategy for understanding pulmonary hypertension based on the molecular biology of the pulmonary vascular wall.

Angiopoietin-1↗
PubMed2005

Divergent effects of BMP-2 on gene expression in pulmonary artery smooth muscle cells from normal subjects and patients with idiopathic pulmonary arterial hypertension.

Bone morphogenetic proteins (BMPs) inhibit proliferation and induce apoptosis in pulmonary artery smooth muscle cells (PASMCs) from normal subjects. Dysfunction of BMP signaling due to mutations in and/or down-regulation of BMP receptors has been implicated in idiopathic pulmonary arterial hypertension (IPAH). The authors examined whether BMP differentially regulates gene expression in PASMCs from normal subjects and IPAH patients using the Affymetrix microarray analysis. BMP-2 treatment (200 nM for 24 hours) altered expression levels of 6206 genes in normal and IPAH PASMCs. Of these genes, 1063 were regulated oppositely by BMP-2: 523 genes were down-regulated by BMP-2 in normal PASMCs but up-regulated in IPAH PASMCs, whereas 540 genes were up-regulated by BMP-2 in normal PASMCs but down-regulated in IPAH PASMCs. The divergent effects of BMP-2 on gene expression profiles indicate that PASMCs may undergo significant phenotypic changes in IPAH patients during development of the disease. The transition of the antiproliferative effect of BMP-2 in normal PASMCs to its proliferative effect in IPAH patients is attributed potentially to its differential effect on expression patterns of various genes that are involved in cell proliferation and apoptosis. Among the 6206 BMP-2-sensitive genes, there are more than 1800 genes whose expression levels were negatively (correlation coefficient, r, <-0.9) or positively (with r >+ 0.9) correlated with the pulmonary arterial pressure. These results suggest that BMP-mediated gene regulation is significantly altered in PASMCs from IPAH patients and mRNA expression changes in BMP-regulated genes may be involved in the development of IPAH.

Adult↗
PubMed2004

Enhanced expression of transient receptor potential channels in idiopathic pulmonary arterial hypertension.

Pulmonary vascular medial hypertrophy caused by excessive pulmonary artery smooth muscle cell (PASMC) proliferation is a major cause for the elevated pulmonary vascular resistance in patients with idiopathic pulmonary arterial hypertension (IPAH). Increased Ca(2+) influx is an important stimulus for PASMC proliferation. Transient receptor potential (TRP) channel genes encode Ca(2+) channels that are responsible for Ca(2+) entry during cell proliferation. Normal human PASMC expressed multiple canonical TRP (TRPC) isoforms; TRPC6 was highly expressed and TRPC3 was minimally expressed. The protein expression of TRPC6 in normal PASMC closely correlated with the expression of Ki67, suggesting that TRPC6 expression is involved in the transition of PASMC from quiescent phase to mitosis. In lung tissues and PASMC from IPAH patients, the mRNA and protein expression of TRPC3 and -6 were much higher than in those from normotensive or secondary pulmonary hypertension patients. Inhibition of TRPC6 expression with TRPC6 small interfering RNA markedly attenuated IPAH-PASMC proliferation. These results demonstrate that expression of TRPC channels correlates with the progression of the cell cycle in PASMC. TRPC channel overexpression may be partially responsible for the increased PASMC proliferation and pulmonary vascular medial hypertrophy in IPAH patients.

Adult↗
PubMed2004

Bosentan inhibits transient receptor potential channel expression in pulmonary vascular myocytes.

Bosentan, a dual endothelin receptor blocker, has been used clinically to treat idiopathic pulmonary arterial hypertension (IPAH). However, the mechanism of its antiproliferative effect on pulmonary artery smooth muscle cells (PASMCs) remains unclear. A rise in cytoplasmic Ca2+ stimulates PASMC proliferation and the canonical transient receptor potential (TRPC) channels are an important pathway for Ca2+ entry during PASMC proliferation. Bosentan (20-50 microM) significantly inhibited endothelin-1- or platelet-derived growth factor (PDGF)-mediated PASMC growth and [3H]thymidine uptake. In PASMCs, endothelin-1 (1 microM) and PDGF (10 ng/ml) both upregulated protein expression of TRPC6, whereas bosentan markedly downregulated TRPC6 protein levels. Furthermore, TRPC6 expression in PASMCs from patients with IPAH was greater than in normal PASMCs, and the antiproliferative effect of bosentan was significantly enhanced in IPAH-PASMCs in comparison with normal PASMCs. These observations demonstrate that the antiproliferative effect of bosentan on PASMCs involves the downregulation of TRPC6 channels via a mechanism possibly independent of endothelin receptor blockade. The greater effect of bosentan on IPAH-PASMCs than on normal PASMCs suggests that increased TRPC6 expression and function may be involved in the overgrowth of PASMCs in patients with IPAH.

Animals↗
PubMed2004

Molecular biology of primary pulmonary hypertension.

Primary pulmonary hypertension (PPH) is a rare but often fatal condition characterized by pulmonary artery remodeling leading to chronic elevation of pulmonary artery pressure in the absence of causes. The pathophysiology of PPH is not completely understood, but a number of recent studies have elucidated many possible gentic, hormonal, and environmental factors. Current treatment options slow the progression of the disease but do not halt it. The study of molecular mechanisms that result from mutations in onmental and hormonal modifiers holds great promise for the development of novel therapies that may halt the progression of the disease.

Bone Morphogenetic Protein Receptors, Type II↗
PubMed2004

Pulmonary thromboendarterectomy surgery.

Considerable progress has been made over the past decade in understanding the etiology, prevalence, natural history, and therapeutic approach to chronic thromboembolic pulmonary hypertension. Pulmonary endarterectomy is now widely recognized as the definitive treatment for chronic pulmonary hypertension resulting from thromboembolic disease. This article focuses on the surgical treatment of chronic thromboembolic pulmonary hypertension.

Chronic Disease↗
PubMed2004

Differential myocardial gene delivery by recombinant serotype-specific adeno-associated viral vectors.

Recombinant cross-packaging of adeno-associated virus (AAV) genome of one serotype into other AAV serotypes has the potential to optimize tissue-specific gene transduction and expression in the heart. To evaluate the role of AAV1 to 5 virion shells on AAV2 transgene transduction, we constructed hybrid vectors in which each serotype capsid coding domain was cloned into a common vector backbone containing AAV2 replication genes. Constructs were tested for expression in: (1) adult murine heart in vivo using direct injection of virus, (2) neonatal and adult murine ventricular cardiomyocytes in vitro, and (3) adult human ventricular cardiomyocytes in vitro, using green fluorescent protein (GFP) as the measurable transgene. Serotype 1 virus demonstrated the highest transduction efficiency in adult murine cardiomyocytes both in vitro and in vivo, while serotype 2 virus had the greater transduction efficiency in neonatal cardiomyocytes in vitro. Prolonged in vivo myocardial GFP expression was observed for up to 12 months using serotype 1 and 2 vectors only. In human cardiomyocytes, serotype 1 vector was superior in transduction efficiency, followed by types 2, 5, 4, and 3. These data establish a hierarchy for efficient serotype-specific vector transduction in myocardial tissue. AAV1 serotype packaging results in more efficient transduction of genes in the murine and human adult heart, compared to other AAV serotypes. Our results suggest that adult human cardiac gene therapy may be enhanced by the use of serotype 1-specific AAV vectors.

Animals↗
PubMed2004

A new animal model for pulmonary hypertension based on the overexpression of a single gene, angiopoietin-1.

BACKGROUND: Angiopoietin-1 gene expression in human pulmonary hypertensive lungs is directly proportional to increasing pulmonary vascular resistance. We hypothesized that targeted overexpresssion of angiopoietin-1 in the lung would cause persistent pulmonary hypertension in an animal model. METHODS: We injected 2 x 10(10) genomic particles of adeno-associated virus-angiopoietin-1 (AAV-Ang-1) into the right ventricular outflow tract of 30 Fischer rats while using adeno-associated virus-lacZ (AAV-lacZ) injected rats and carrier-injected rats as our control groups. All animals underwent survival surgery and were sacrificed at serial timepoints postgene delivery. At each timepoint, pulmonary artery pressures were measured and pulmonary angiography using the Microfil polymer perfusion technique was performed. The lungs were harvested for pathologic analysis, mRNA analysis, Western blot assays, and in situ RNA hybridization to localize gene expression. RESULTS: Pulmonary artery pressures of AAV-Ang-1 injected rats were significantly increased compared with the control groups (p < 0.01) at all timepoints. Pathologic analysis of AAV-Ang-1 lung specimens demonstrated increased smooth muscle cell proliferation within the medial layer of arterioles with obliteration of small vessels similar to that seen in human pulmonary hypertension. Angiograms of AAV-Ang-1 injected lungs showed blunting of small peripheral arterioles consistent with advanced pulmonary hypertension. In situ RNA hybridization localized angiopoietin-1 expression to the vascular wall of small-caliber pulmonary vessels. Protein and mRNA assays confirmed persistent angiopoietin-1 expression in the lung for up to 60 days postgene delivery. CONCLUSIONS: Overexpression of angiopoietin-1 using an adeno-associated virus vector causes pulmonary hypertension in rats. These data provide a novel physiologic animal model for pulmonary hypertension.

Angiopoietin-1↗