Biomedical subjects

Masao Takata

Publications and source records attributed to Masao Takata.

8 recordsLinked to original sources

PubMed2005

Lung-marginated monocytes modulate pulmonary microvascular injury during early endotoxemia.

RATIONALE: The role of monocytes in acute endotoxemia has been ascribed to systemic release of mediators within the central circulation. Little is known about the potential role of "marginated" monocytes in regulating microvascular inflammatory signaling. OBJECTIVES: To investigate whether lung-marginated monocytes can locally activate pulmonary endothelial cells through cell contact-dependent interactions in early endotoxemia. METHODS: Mice were challenged with LPS to produce acute endotoxemia and pulmonary vascular injury. Adoptive transfer of ex vivo LPS-stimulated donor leukocytes to recipient mice was also performed to evaluate cell-associated inflammatory signaling between monocytes and endothelial cells within the lung. Cell suspensions from excised lungs were analyzed by flow cytometry for expression of tumor necrosis factor alpha (TNF-alpha) on monocytes and cell adhesion molecules on endothelial cells. RESULTS: Substantial numbers of monocytes rapidly marginated to the lungs after endotoxin challenge in mice, and lung-marginated monocytes expressed significantly higher levels of membrane TNF than circulating monocytes, due to higher TNF production by the marginated cells. Injection of activated wild-type donor leukocytes to wild-type or TNF receptor double knockout recipients demonstrated that lung-marginated monocytes can induce TNF-dependent upregulation of adhesion molecules on pulmonary endothelial cells. Injection of activated donor leukocytes from TNF knock-in mice that express uncleavable mutant membrane TNF also induced adhesion molecule upregulation in wild-type recipients without a systemic soluble TNF release. CONCLUSIONS: These results reveal a previously unacknowledged role for lung-marginated monocytes in early endotoxemia, exerting local, cell-associated TNF signaling within the pulmonary microcirculation, contributing to the evolution of pulmonary vascular injury.

Animals↗

PubMed2005

Effects of inhaled carbon monoxide on acute lung injury in mice.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are major causes of morbidity and mortality in the intensive care unit, but despite continuing research few effective therapies have been identified. In recent years, inhaled carbon monoxide (CO) has been reported to have cytoprotective effects in several animal models of tissue injury. We therefore evaluated the effects of inhaled CO in three different in vivo mouse models of ALI. Anesthetized C57BL/6 mice were ventilated with oxygen in the presence or absence of CO (500 parts per million) for 1 h before lung injury was induced by lipopolysaccharide (LPS) or oleic acid (OA) administration. Ventilation was then continued with the same gases for a further 2-3 h, with hemodynamic and respiratory parameters monitored throughout. Intratracheal LPS administration induced lung injury with alveolar inflammation (increased lavage fluid neutrophils, total protein, and cytokines). In contrast, intravenous LPS induced a predominantly vascular lung injury, with increased plasma TNF and increased neutrophil activation (surface Mac-1 upregulation and L-selectin shedding) and sequestration within the pulmonary vasculature. Intravenous OA produced deteriorations in lung function, reflected by changes in respiratory mechanics and blood gases and lavage fluid neutrophil accumulation. However, addition of CO to the inspired gas did not produce significant changes in the measured physiological or immunological parameters in the mouse models used in this study. Thus the results do not support the hypothesis that use of inhaled CO is beneficial in the treatment of ALI and ARDS.

Administration, Inhalation↗

PubMed2005

Continuous real-time measurement of tumor necrosis factor-alpha converting enzyme activity on live cells.

Tumor necrosis factor-alpha (TNF) converting enzyme (TACE) is responsible for shedding of various membrane proteins including proinflammatory cytokine TNF. In vivo regulation of TACE is poorly understood mainly due to lack of reliable methodology to measure TACE activity in cell-based assays. Here we report a novel enzyme assay that enables continuous real-time measurement of TACE activity on the surface of live cells. Cells were incubated with a new fluorescent resonance energy transfer peptide consisting of a TACE-sensitive TNF sequence and fluorescein-tetramethylrhodamine (FAM-TAMRA), and enzyme activity was monitored by the rate of increase in fluorescent signal due to peptide cleavage. Validation studies using resting as well as stimulated monocytic cells indicated that the assay was sensitive, reproducible and quantitative. Pharmacological studies with various inhibitors indicated that the observed enzyme activity could largely be ascribed to TACE. Thus, the FAM-TAMRA peptide provides a powerful tool for measurement of constitutive and inducible cellular TACE activity. The principles developed may be applied to analyses of enzyme activity of various sheddases on live cells.

ADAM Proteins↗

PubMed2004

Pulmonary inflammation induced by high-stretch ventilation is mediated by tumor necrosis factor signaling in mice.

Although high-stretch mechanical ventilation has been demonstrated to induce lung inflammation, the roles of soluble mediators, in particular TNF, remain controversial. We have previously shown in mice that high-stretch ventilation, in the absence of preceding lung injury, induces expression of bioactive TNF in lung lavage fluid early in the course of injury, but the biological significance of this, if any, has yet to be determined. We therefore investigated the pulmonary inflammatory response to a transient period of high-stretch ventilation in anesthetized mice lacking TNF receptors and mice treated with anti-TNF antibodies. A standardized stretch-induced lung injury (assessed by lung mechanics, blood gases, and lavage protein content), followed by noninjurious low-stretch ventilation for 3 h, produced significant alveolar neutrophil infiltration in wild-type mice. However, neutrophil recruitment was substantially attenuated in TNF receptor double knockout mice and in wild-type mice treated with intratracheal anti-TNF antibody. This attenuation was not associated with decreased concentrations of neutrophil attractant CXC chemokines (macrophage inflammatory protein-2 and keratinocyte-derived chemokine) in lavage fluid. In contrast to intratracheal antibody, intravenous anti-TNF antibody did not reduce neutrophil infiltration, suggesting that the role of TNF signaling is localized within the alveolar space and does not require decompartmentalization of TNF into the circulation. These findings provide the first direct evidence that pulmonary inflammation induced by high-stretch ventilation without underlying lung injury possesses a significant TNF-dependent component. The results suggest a potential for regional anti-TNF treatment in attenuating stretch-induced pulmonary inflammation.

Animals↗

PubMed2004

Mechanisms of early pulmonary neutrophil sequestration in ventilator-induced lung injury in mice.

Polymorphonuclear leukocytes (PMN) play an important role in ventilator-induced lung injury (VILI), but the mechanisms of pulmonary PMN recruitment, particularly early intravascular PMN sequestration during VILI, have not been elucidated. We investigated the physiological and molecular mechanisms of pulmonary PMN sequestration in an in vivo mouse model of VILI. Anesthetized C57/BL6 mice were ventilated for 1 h with high tidal volume (injurious ventilation), low tidal volume and high positive end-expiratory pressure (protective ventilation), or normal tidal volume (control ventilation). Pulmonary PMN sequestration analyzed by flow cytometry of lung cell suspensions was substantially enhanced in injurious ventilation compared with protective and control ventilation, preceding development of physiological signs of lung injury. Anesthetized, spontaneously breathing mice with continuous positive airway pressure demonstrated that raised alveolar pressure alone does not induce PMN entrapment. In vitro leukocyte deformability assay indicated stiffening of circulating leukocytes in injurious ventilation compared with control ventilation. PMN sequestration in injurious ventilation was markedly inhibited by administration of anti-L-selectin antibody, but not by anti-CD18 antibody. These results suggest that mechanical ventilatory stress initiates pulmonary PMN sequestration early in the course of VILI, and this phenomenon is associated with stretch-induced inflammatory events leading to PMN stiffening and mediated by L-selectin-dependent but CD18-independent mechanisms.

Animals↗

PubMed2004

Prolonged nitric oxide inhalation during recovery from chronic hypoxia does not decrease nitric oxide-dependent relaxation in pulmonary arteries.

STUDY OBJECTIVE: To investigate the effects of long-term nitric oxide (NO) inhalation on the recovery process of right ventricular hypertrophy (RVH) and functional alterations in the NO-cyclic guanosine monophosphate (cGMP) relaxation pathway in rat conduit pulmonary arteries (PAs) in established chronic hypoxic pulmonary hypertension. MATERIALS AND METHODS: A total of 35 rats were exposed to chronic hypobaric hypoxia (380 mm Hg, 10% oxygen), and 39 rats were exposed to air for 10 days. Both groups were then exposed to 3 or 10 days of NO 10 ppm, NO 40 ppm, or air (control groups for each NO concentration), resulting in a total of 16 groups. Acetylcholine- and sodium nitroprusside (SNP)-induced relaxation were evaluated in precontracted PA rings. RVH was assessed by heart weight ratio of right ventricle to left ventricle plus septum. RESULTS: NO inhalation had no effect on either the regression of RVH or the recovery process of impaired relaxation induced by acetylcholine or SNP in a endothelium-intact hypertensive conduit extrapulmonary artery or intrapulmonary artery (IPA). In a normal endothelium-intact conduit IPA, 40 ppm NO inhalation for 10 days partially augmented SNP-induced relaxation, but not that induced by acetylcholine. CONCLUSION: Continuous NO inhalation did not affect the regression process of either established RVH or the impaired endogenous NO-cGMP relaxation cascade in a conduit PA in rats during the recovery period after chronic hypoxia.

Acetylcholine↗

PubMed2003

High tidal volume upregulates intrapulmonary cytokines in an in vivo mouse model of ventilator-induced lung injury.

Mechanical ventilation has been demonstrated to exacerbate lung injury, and a sufficiently high tidal volume can induce injury in otherwise healthy lungs. However, it remains controversial whether injurious ventilation per se, without preceding lung injury, can initiate cytokine-mediated pulmonary inflammation. To address this, we developed an in vivo mouse model of acute lung injury produced by high tidal volume (Vt) ventilation. Anesthetized C57BL6 mice were ventilated at high Vt (34.5 +/- 2.9 ml/kg, mean +/- SD) for a duration of 156 +/- 17 min until mean blood pressure fell below 45 mmHg (series 1); high Vt for 120 min (series 2); or low Vt (8.8 +/- 0.5 ml/kg) for 120 or 180 min (series 3). High Vt produced progressive lung injury with a decrease in respiratory system compliance, increase in protein concentration in lung lavage fluid, and lung pathology showing hyaline membrane formation. High-Vt ventilation was associated with increased TNF-alpha in lung lavage fluid at the early stage of injury (series 2) but not the later stage (series 1). In contrast, lavage fluid macrophage inflammatory protein-2 (MIP-2) was increased in all high-Vt animals. Lavage fluid from high-Vt animals contained bioactive TNF-alpha by WEHI bioassay. Low-Vt ventilation induced minimal changes in physiology and pathology with negligible TNF-alpha and MIP-2 proteins and TNF-alpha bioactivity. These results demonstrate that high-Vt ventilation in the absence of underlying injury induces intrapulmonary TNF-alpha and MIP-2 expression in mice. The apparently transient nature of TNF-alpha upregulation may help explain previous controversy regarding the involvement of cytokines in ventilator-induced lung injury.

Animals↗

PubMed2003

Pressure-flow relationship and longitudinal distribution of pulmonary vascular resistance in heartworm-infected dogs.

The pressure-flow relationships and the longitudinal distributions of pulmonary vascular resistance in normal and heartworm-infected (HWI) dogs were compared in an isolated, blood perfused preparation. The pulmonary circulation was partitioned into pulmonary arterial, middle, and venous segment based on the concept of a five element lumped model. The pulmonary arterial pressure-flow relationships were found to be non-linear and convex to the pressure axis in both normal and HWI lungs. The pressure-flow relationships of the pulmonary arterial and venous segment were linear and these slopes in the HWI lungs were significantly higher than the normal lungs. The pressure gradient of the middle segment was increased as flow increased at lower flow range, however, it was not increased during higher perfusion range in both lungs. At higher flow, the pressure gradient of the middle segment in the HWI lungs was significantly higher than the normal lungs. These results suggest that the ohmic resistance was almost equal to the sum of the two slopes of the pressure-flow relationships of the pulmonary arterial and venous segment because the pressure gradient of the middle segment was not altered as flow increased during higher perfusion rate. Because the slopes of the pressure-flow relationships of the pulmonary arterial and venous segment were increased with heartworm infection, the ohmic resistance of HWI lungs would be higher than normal lungs. The intercept pressure on the pressure axis of the linear portion of the pulmonary arterial pressure-flow relationship, a critical closing pressure, was regarded as pressure gradient of the middle segment during higher perfusing rate because the intercept pressures of pressure-flow relationships of pulmonary arterial and venous segment were almost equal to zero. Therefore, the critical closing pressure of HWI lungs would be higher than normal lungs. The pulmonary hypertension of filariasis appears to be due to an increase in ohmic resistance and elevated critical closing pressure.

Animals↗