Low-molecular-weight heparin inhibits hypoxic pulmonary hypertension and vascular remodeling in guinea pigs.

RATIONALE: We have shown previously that antiproliferative unfractionated heparins block hypoxia-induced pulmonary arterial hypertension (PAH) and vascular remodeling, and hypothesized that low-molecular-weight heparins (LMWHs) would too. OBJECTIVES: To determine the potential role and mechanisms of dalteparin and enoxaparin (two LMWHs) in inhibiting hypoxic PAH and vascular remodeling. METHODS: Male Hartley guinea pigs were exposed for 10 days to normobaric 10% oxygen with dalteparin (5 mg/kg), enoxaparin (5 mg/kg), or with an equivalent volume of normal saline solution. Normoxic control animals (n = 5) received room air for 10 days. Bovine pulmonary artery smooth-muscle cells (PASMCs) were grown in 10% fetal bovine serum without heparin, with dalteparin (1 microg/mL) or with enoxaparin (1 microg/mL). MEASUREMENTS: Pulmonary arterial pressure (PAP), cardiac index, right ventricular heart weight divided by left ventricular plus septum weight (RV/LV+S), hematocrit, percentage of wall thickness of intraacinar vessels (%WT-IA), percentage of wall thickness of terminal bronchiole vessels (%WT-TA), and the percentage of thick-walled vessels (%Thick) were determined. In PASMCs, expression of p27 and cell growth were compared because in mice whole heparin depends on p27 for its antiproliferative action. MAIN RESULTS: In hypoxic animals, hematocrit, PAP, total pulmonary vascular resistance index, RV/LV+S, %WT-IA, %WT-TA, and %Thick all rose significantly vs normoxic control animals (p < 0.05); cardiac index was unchanged. Dalteparin but not enoxaparin significantly reduced PAP, total pulmonary vascular resistance index, and RV/LV + S (p < 0.05 vs hypoxia alone); inhibited PASMC growth; and upregulated p27 expression. Enoxaparin moderately reduced vascular remodeling, which did not translate into less pulmonary hypertension. CONCLUSIONS: Not all LMWHs are the same. Dalteparin was more effective than enoxaparin in inhibiting pulmonary hypertension and vascular remodeling in hypoxic guinea pigs.

Predictors of survival in severe, early onset COPD.

STUDY OBJECTIVES: Multiple risk factors for mortality in patients with COPD have been described, but most studies have involved older, primarily male subjects. The purpose of this study was to determine the mortality rate and predictors of survival in subjects with severe, early onset COPD. DESIGN, SETTING, AND PARTICIPANTS: The cohort of 139 probands in the Boston Early-Onset COPD Study was recruited from lung transplant and general pulmonary clinics between September 1994 and July 2002. Subjects were < 53 years old, had an FEV(1) of < 40% of predicted, did not have severe alpha(1)-antitrypsin deficiency, and had not undergone lung transplantation. The initial evaluation included a standardized respiratory questionnaire, spirometry, and a blood sample. A follow-up telephone interview was conducted between May and December 2002. MEASUREMENTS AND RESULTS: Subjects were young (mean age at enrollment, 47.9 years) and had severe airflow obstruction (mean baseline FEV(1), 19.4% predicted). A total of 72.7% of the subjects were women (p < 0.0001 [comparison to equal gender distribution]). The median estimated survival time was 7.0 years from the time of study enrollment, determined by the Kaplan-Meier method. The majority of deaths were due to cardiorespiratory illness. In a multivariable Cox proportional hazards model, adjusting for age, gender, and baseline FEV(1), lifetime cigarette consumption (hazard ratio [HR], 1.20 [per 10 pack-years]; 95% confidence interval [CI], 1.02 to 1.40) and recent smoking status (HR, 2.50; 95% CI, 1.03 to 6.05) were both significant predictors of mortality. CONCLUSION: In this cohort, recent smoking status predicted increased mortality independent of the effects of lifetime smoking intensity. Smoking cessation may confer a survival benefit even among patients with very severe COPD.

Thrombospondin-1 null mice are resistant to hypoxia-induced pulmonary hypertension.

BACKGROUND AND OBJECTIVE: Chronic hypoxia induces pulmonary hypertension in mice. Smooth muscle cell hyperplasia and medial thickening characterize the vasculature of these animals. Thrombospondin-1 null (TSP-1(-/-)) mice spontaneously develop pulmonary smooth muscle cell hyperplasia and medial thickening. In addition, TSP-1 produced by the pulmonary endothelium inhibits pulmonary artery smooth muscle cell growth. Based on these observations we sought to describe the pulmonary vascular changes in TSP-1(-/-) mice exposed to chronic hypoxia. METHODS: We exposed TSP-1(-/-) and wild type (WT) mice to a fraction of inspired oxygen (FiO2) of 0.1 for up to six weeks. Pulmonary vascular remodeling was evaluated using tissue morphometrics. Additionally, right ventricle systolic pressures (RVSP) and right ventricular hypertrophy by right ventricle/left ventricle + septum ratios (RV/LV+S) were measured to evaluate pulmonary hypertensive changes. Finally, acute pulmonary vasoconstriction response in both TSP-1(-/-) and WT mice was evaluated by acute hypoxia and U-46619 (a prostaglandin F2 analog) response. RESULTS: In hypoxia, TSP-1(-/-) mice had significantly lower RVSP, RV/LV+S ratios and less pulmonary vascular remodeling when compared to WT mice. TSP-1(-/-) mice also had significantly lower RVSP in response to acute pulmonary vasoconstriction challenges than their WT counterparts. CONCLUSION: TSP-1(-/-) mice had diminished pulmonary vasoconstriction response and were less responsive to hypoxia-induced pulmonary hypertension than their wild type counterparts. This observation suggests that TSP-1 could play an active role in the pathogenesis of pulmonary hypertension associated with hypoxia.