Charles A. Hales

Interleukin-6 Overexpression Induces Pulmonary Hypertension

Inflammatory cytokine interleukin (IL)-6 is elevated in the serum and lungs of patients with pulmonary artery hypertension (PAH). Several animal models of PAH cite the potential role of inflammatory mediators. We investigated role of IL-6 in the pathogenesis of pulmonary vascular disease. Indices of pulmonary vascular remodeling were measured in lung-specific IL-6–overexpressing transgenic mice (Tg+) and compared to wild-type (Tg−) controls in both normoxic and chronic hypoxic conditions. The Tg+ mice exhibited elevated right ventricular systolic pressures and right ventricular hypertrophy with corresponding pulmonary vasculopathic changes, all of which were exacerbated by chronic hypoxia. IL-6 overexpression increased muscularization of the proximal arterial tree, and hypoxia enhanced this effect. It also reproduced the muscularization and proliferative arteriopathy seen in the distal arteriolar vessels of PAH patients. The latter was characterized by the formation of occlusive neointimal angioproliferative lesions that worsened with hypoxia and were composed of endothelial cells and T-lymphocytes. IL-6–induced arteriopathic changes were accompanied by activation of proangiogenic factor, vascular endothelial growth factor, the proproliferative kinase extracellular signal-regulated kinase, proproliferative transcription factors c-MYC and MAX, and the antiapoptotic proteins survivin and Bcl-2 and downregulation of the growth inhibitor transforming growth factor-&bgr; and proapoptotic kinases JNK and p38. These findings suggest that IL-6 promotes the development and progression of pulmonary vascular remodeling and PAH through proproliferative antiapoptotic mechanisms.

Gadolinium-Enhanced Magnetic Resonance Angiography for Pulmonary Embolism: A Multicenter Prospective Study (PIOPED III)

BACKGROUND The accuracy of gadolinium-enhanced magnetic resonance pulmonary angiography and magnetic resonance venography for diagnosing pulmonary embolism has not been determined conclusively. OBJECTIVE To investigate performance characteristics of magnetic resonance angiography, with or without magnetic resonance venography, for diagnosing pulmonary embolism. DESIGN Prospective, multicenter study from 10 April 2006 to 30 September 2008. SETTING 7 hospitals and their emergency services. PATIENTS 371 adults with diagnosed or excluded pulmonary embolism. MEASUREMENTS Sensitivity, specificity, and likelihood ratios were measured by comparing independently read magnetic resonance imaging with the reference standard for diagnosing pulmonary embolism. Reference standard diagnosis or exclusion was made by using various tests, including computed tomographic angiography and venography, ventilation-perfusion lung scan, venous ultrasonography, d-dimer assay, and clinical assessment. RESULTS Magnetic resonance angiography, averaged across centers, was technically inadequate in 25% of patients (92 of 371). The proportion of technically inadequate images ranged from 11% to 52% at various centers. Including patients with technically inadequate images, magnetic resonance angiography identified 57% (59 of 104) with pulmonary embolism. Technically adequate magnetic resonance angiography had a sensitivity of 78% and a specificity of 99%. Technically adequate magnetic resonance angiography and venography had a sensitivity of 92% and a specificity of 96%, but 52% of patients (194 of 370) had technically inadequate results. LIMITATION A high proportion of patients with suspected embolism was not eligible or declined to participate. CONCLUSION Magnetic resonance pulmonary angiography should be considered only at centers that routinely perform it well and only for patients for whom standard tests are contraindicated. Magnetic resonance pulmonary angiography and magnetic resonance venography combined have a higher sensitivity than magnetic resonance pulmonary angiography alone in patients with technically adequate images, but it is more difficult to obtain technically adequate images with the 2 procedures.

Enlarged Right Ventricle Without Shock in Acute Pulmonary Embolism: Prognosis

OBJECTIVE An unsettled issue is the use of thrombolytic agents in patients with acute pulmonary embolism (PE) who are hemodynamically stable but have right ventricular (RV) enlargement. We assessed the in-hospital mortality of hemodynamically stable patients with PE and RV enlargement. METHODS Patients were enrolled in the Prospective Investigation of Pulmonary Embolism Diagnosis II. Exclusions included shock, critical illness, ventilatory support, or myocardial infarction within 1 month, and ventricular tachycardia or ventricular fibrillation within 24 hours. We evaluated the ratio of the RV minor axis to the left ventricular minor axis measured on transverse images during computed tomographic angiography. RESULTS Among 76 patients with RV enlargement treated with anticoagulants and/or inferior vena cava filters, in-hospital deaths from PE were 0 of 76 (0%) and all-cause mortality was 2 of 76 (2.6%). No septal motion abnormality was observed in 49 patients (64%), septal flattening was observed in 25 patients (33%), and septal deviation was observed in 2 patients (3%). No patients required ventilatory support, vasopressor therapy, rescue thrombolytic therapy, or catheter embolectomy. There were no in-hospital deaths caused by PE. There was no difference in all-cause mortality between patients with and without RV enlargement (relative risk=1.04). CONCLUSION In-hospital prognosis is good in patients with PE and RV enlargement if they are not in shock, acutely ill, or on ventilatory support, or had a recent myocardial infarction or life-threatening arrhythmia. RV enlargement alone in patients with PE, therefore, does not seem to indicate a poor prognosis or the need for thrombolytic therapy.

Intracellular glutathione in stretch-induced cytokine release from alveolar type-2 like cells

Objective:  Ventilator‐induced lung injury (VILI) is characterized by release of inflammatory cytokines, but the mechanisms are not well understood. We hypothesized that stretch‐induced cytokine production is dependent on oxidant release and is regulated by intracellular glutathione (GSH) inhibition of nuclear factor κB (NF‐κB) and activator protein‐1 (AP‐1) binding.

Cyclin-Dependent Kinase Inhibitor p27Kip1, But Not p21WAF1/Cip1, Is Required for Inhibition of Hypoxia-Induced Pulmonary Hypertension and Remodeling by Heparin in Mice

Heparin has growth inhibitory effects on pulmonary artery smooth muscle cell (PASMC) in vitro and in vivo. However, the mechanism has not been fully defined. In this study, we investigated the role of cyclin-dependent kinase inhibitors, p21WAF1/cip1 (p21) and p27Kip1 (p27), in the inhibitory effect of heparin on PASMC proliferation in vitro and on hypoxia-induced pulmonary hypertension in vivo using p21 and p27-null mice. In vitro, loss of the p27 gene negated the inhibitory effect of heparin on PASMC proliferation, but p21 was not critical for this inhibition. In vivo, heparin significantly inhibited the development of hypoxia-induced pulmonary hypertension and remodeling, as evidenced by decreased right ventricular systolic pressure, ratio of right ventricular weight to left ventricle plus septum weight, and percent wall thickness of pulmonary artery, in p21+/+, p21−/−, p27+/+, and p27+/−, but not in p27−/− mice. We also observed that hypoxia decreased p27 expression significantly in mouse lung, which was restored by heparin. Heparin inhibited Ki67 proliferative index in terminal bronchial vessel walls in p27+/+ and p27+/−, but not in p27−/− mice exposed to hypoxia. Therefore, we conclude that the cyclin-dependent kinase inhibitor p27, but not p21, is required for the inhibition of hypoxic pulmonary vascular remodeling by heparin.

SPECT in acute pulmonary embolism

The purpose of this review was to evaluate the accuracy of SPECT in acute pulmonary embolism. Sparse data are available on the accuracy of SPECT based on an objective reference test. Several investigations were reported in which the reference standard for the diagnosis of pulmonary embolism was based in part on the results of SPECT or planar ventilation–perfusion (V/Q) imaging. The sensitivity of SPECT in all but one investigation was at least 90%, and specificity also was generally at least 90%. The sensitivity of SPECT in 4 of 5 investigations was higher than that of planar V/Q imaging. The specificity of SPECT was generally higher, equal, or only somewhat lower than that of planar V/Q imaging. Most investigators reported nondiagnostic SPECT V/Q scans in no more than 3% of cases. Methods of obtaining SPECT images, methods of obtaining planar V/Q images, and the criteria for interpretation varied. The general impression is that SPECT is more advantageous than planar V/Q imaging.

Small-airways function in myocardial infarction.

Abstract Small-airways function was measured by closing volumes in 40 patients after uncomplicated acute myocardial infarction who had no evidence of congestive heart failure by physical or radiologic examination. Mean value for closing volume was 125 per cent predicted in 25 patients studied in the first two weeks after infarction as opposed to a mean value of 104 per cent in 14 patients studied in the second two-week period after infarction (p<0.01). Seven patients with elevated closing volumes in the first two weeks after infarction had normal values when re-evaluated four to 12 months later. Acute diuresis with furosemide reduced the elevated closing volumes to normal in two patients studied in the first week after infarction. These findings suggest the occurrence, even in uncomplicated myocardial infarction, of transient left ventricular failure with pulmonary vascular congestion and transudation of fluid into the interstitial space, leading to premature airway closure. (N Engl J Med 290:761–765, 1974)

Protective effect of suberoylanilide hydroxamic acid against LPS-induced septic shock in rodents.

We have recently found that suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, improves survival in a lethal model of hemorrhagic shock in rats. The purpose of the present study was to determine whether SAHA treatment would prevent LPS-induced septic shock and improve the survival in a murine model. C57BL/6J mice were randomly divided into two groups. Experimental mice were given intraperitoneal SAHA (50 mg/kg) in vehicle dimethyl sulfoxide fluid (n = 10). The control mice (n = 10) received vehicle dimethyl sulfoxide only. They were injected with LPS (20 mg/kg, i.p.) 2 h later, and the animals from the treatment group were given a second dose of SAHA. Survival was monitored during the next 7 days. In a parallel study, mice treated with or without SAHA were subjected to LPS insult while normal (sham) mice serviced as controls. 1) Lungs were harvested at 3 and 48 h for analysis of gene expression and pathologic changes, respectively; 2) spleens were isolated for analysis of neutrophilic cell population. In addition, RAW264.7 mouse macrophages were cultured to assess the effects of SAHA on LPS-induced inflammation in vitro. All mice in the control group that were subjected to LPS challenge died in less than 48 h. However, SAHA-treated animals displayed a significantly higher 1-week survival rate (87.5%) compared with the control group (0%). Moreover, LPS insult decreased the acetylation of histone proteins (H2A, H2B, and H3), elevated the levels of TNF-&agr; in vivo (circulation) and in vitro (culture medium), increased the neutrophilic cell population in the spleen, enhanced the expression of TNF-&agr; and IL-1&bgr; genes in lung tissue, and augmented the pulmonary neutrophil infiltration. In contrast, SAHA treatment markedly attenuated all of these LPS-induced alterations. We report for the first time that administration of SAHA (50 mg/kg) significantly attenuates a variety of inflammatory markers and improves long-term survival after a lethal LPS insult.

Oxidant stress mediates inflammation and apoptosis in ventilator-induced lung injury

Background and objective:  Ventilator‐induced lung injury (VILI) leads to airway epithelial cell apoptosis and lung inflammation. High tidal volume ventilation in vivo has been shown to induce MIP‐2 production, lung neutrophil sequestration and apoptotic airway cell death. This study aimed to determine the effect of N‐acetylcysteine (NAC), a scavenger of oxygen radicals, on lung inflammation and apoptosis in an in vivo model of VILI.

High-molecular-weight hyaluronan – a possible new treatment for sepsis-induced lung injury: a preclinical study in mechanically ventilated rats

IntroductionMechanical ventilation with even moderate-sized tidal volumes synergistically increases lung injury in sepsis and has been associated with proinflammatory low-molecular-weight hyaluronan production. High-molecular-weight hyaluronan (HMW HA), in contrast, has been found to be anti-inflammatory. We hypothesized that HMW HA would inhibit lung injury associated with sepsis and mechanical ventilation.MethodsSprague–Dawley rats were randomly divided into four groups: nonventilated control rats; mechanical ventilation plus lipopolysaccharide (LPS) infusion as a model of sepsis; mechanical ventilation plus LPS with HMW HA (1,600 kDa) pretreatment; and mechanical ventilation plus LPS with low-molecular-weight hyaluronan (35 kDa) pretreatment. Rats were mechanically ventilated with low (7 ml/kg) tidal volumes. LPS (1 or 3 mg/kg) or normal saline was infused 1 hour prior to mechanical ventilation. Animals received HMW HA or low-molecular-weight hyaluronan via the intraperitoneal route 18 hours prior to the study or received HMW HA (0.025%, 0.05% or 0.1%) intravenously 1 hour after injection of LPS. After 4 hours of ventilation, animals were sacrificed and the lung neutrophil and monocyte infiltration, the cytokine production, and the lung pathology score were measured.ResultsLPS induced lung neutrophil infiltration, macrophage inflammatory protein-2 and TNFα mRNA and protein, which were decreased in the presence of both 1,600 kDa and 35 kDa hyaluronan pretreatment. Only 1,600 kDa hyaluronan completely blocked both monocyte and neutrophil infiltration and decreased the lung injury. When infused intravenously 1 hour after LPS, 1,600 kDa hyaluronan inhibited lung neutrophil infiltration, macrophage inflammatory protein-2 mRNA expression and lung injury in a dose-dependent manner. The beneficial effects of hyaluronan were partially dependent on the positive charge of the compound.ConclusionsHMW HA may prove to be an effective treatment strategy for sepsis-induced lung injury with mechanical ventilation.