Controlled Delivery of 80 mg Aerosol Furosemide Does Not Achieve Consistent Dyspnea Relief in Patients.

PURPOSE: Aerosol furosemide may be an option to treat refractory dyspnea, though doses, methods of delivery, and outcomes have been variable. We hypothesized that controlled delivery of high dose aerosol furosemide would reduce variability of dyspnea relief in patients with underlying pulmonary disease. METHODS: Seventeen patients with chronic exertional dyspnea were recruited. Patients rated recently recalled breathing discomfort on a numerical rating scale (NRS) and the multidimensional dyspnea profile (MDP). They then performed graded exercise using an arm-ergometer. The NRS was completed following each exercise grade, and the MDP was repeated after a pre-defined dyspnea threshold was reached. During separate visits, patients received either aerosol saline or 80 mg of aerosol furosemide in a randomized, double-blind, crossover design. After treatment, graded exercise to the pre-treatment level was repeated, followed by completion of the NRS and MDP. Treatment effect was defined as the difference between pre- and post-treatment NRS at end exercise, expressed in absolute terms as % Full Scale. "Responders" were defined as those showing treatment effect ≥ 20% of full scale. RESULTS: Final analysis included 15 patients. Neither treatment produced a statistically significant change in NRS and there was no significant difference between treatments (p = 0.45). There were four "responders" and one patient whose dyspnea worsened with furosemide; two patients were responders with saline, of whom one also responded to furosemide. No adverse events were reported. CONCLUSIONS: High dose controlled delivery aerosol furosemide was not statistically different from saline placebo at reducing exercise-induced dyspnea. However, a clinically meaningful improvement was noted in some patients.

Lysyl Oxidase-Like 1 Protein Deficiency Protects Mice from Adenoviral Transforming Growth Factor-ß1-induced Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive disease characterized by excessive deposition of extracellular matrix (ECM) in the lung parenchyma. The abnormal ECM deposition slowly overtakes normal lung tissue, disturbing gas exchange and leading to respiratory failure and death. ECM cross-linking and subsequent stiffening is thought to be a major contributor of disease progression and also promotes the activation of transforming growth factor (TGF)-ß1, one of the main profibrotic growth factors. Lysyl oxidase-like (LOXL) 1 belongs to the cross-linking enzyme family and has been shown to be up-regulated in active fibrotic regions of bleomycin-treated mice and patients with IPF. We demonstrate in this study that LOXL1-deficient mice are protected from experimental lung fibrosis induced by overexpression of TGF-ß1 using adenoviral (Ad) gene transfer (AdTGF-ß1). The lack of LOXL1 prevented accumulation of insoluble cross-linked collagen in the lungs, and therefore limited lung stiffness after AdTGF-ß1. In addition, we applied mechanical stretch to lung slices from LOXL1+/+ and LOXL1-/- mice treated with AdTGF-ß1. Lung stiffness (Young's modulus) of LOXL1-/- lung slices was significantly lower compared with LOXL1+/+ lung slices. Moreover, the release of activated TGF-ß1 after mechanical stretch was significantly lower in LOXL1-/- mice compared with LOXL1+/+ mice after AdTGF-ß1. These data support the concept that cross-linking enzyme inhibition represents an interesting therapeutic target for drug development in IPF.

The impact of low-frequency, low-force cyclic stretching of human bronchi on airway responsiveness.

BACKGROUND: In vivo, the airways are constantly subjected to oscillatory strain (due to tidal breathing during spontaneous respiration) and (in the event of mechanical ventilation) positive pressure. This exposure is especially problematic for the cartilage-free bronchial tree. The effects of cyclic stretching (other than high-force stretching) have not been extensively characterized. Hence, the objective of the present study was to investigate the functional and transcriptional response of human bronchi to repetitive mechanical stress caused by low-frequency, low-force cyclic stretching. METHODS: After preparation and equilibration in an organ bath, human bronchial rings from 66 thoracic surgery patients were stretched in 1-min cycles of elongation and relaxation over a 60-min period. For each segment, the maximal tension corresponded to 80% of the reference contraction (the response to 3 mM acetylcholine). The impact of cyclic stretching (relative to non-stretched controls) was examined by performing functional assessments (epithelium removal and incubation with sodium channel agonists/antagonists or inhibitors of intracellular pathways), biochemical assays of the organ bath fluid (for detecting the release of pro-inflammatory cytokines), and RT-PCR assays of RNA isolated from tissue samples. RESULTS: The application of low-force cyclic stretching to human bronchial rings for 60 min resulted in an immediate, significant increase in bronchial basal tone, relative to non-cyclic stretching (4.24 ± 0.16 g vs. 3.28 ± 0.12 g, respectively; p < 0.001). This cyclic stimulus also increased the affinity for acetylcholine (-log EC50: 5.67 ± 0.07 vs. 5.32 ± 0.07, respectively; p p < 0.001). Removal of airway epithelium and pretreatment with the Rho-kinase inhibitor Y27632 and inward-rectifier K+ or L-type Ca2+ channel inhibitors significantly modified the basal tone response. Exposure to L-NAME had opposing effects in all cases. Pro-inflammatory pathways were not involved in the response; cyclic stretching up-regulated the early mRNA expression of MMP9 only, and was not associated with changes in organ bath levels of pro-inflammatory mediators. CONCLUSION: Low-frequency, low-force cyclic stretching of whole human bronchi induced a myogenic response rather than activation of the pro-inflammatory signaling pathways mediated by mechanotransduction.

Presión de distensión en el síndrome de dificultad respiratoria aguda (SDRA): su relación con la injuria pulmonar inducida por el ventilador / Distension pressure in acute respiratory distress syndrome (ARDS): its relationship with ventilator-induced lung injury

Existen evidencias que la presión de distensión (ΔP) puede ser un buen predictor del riesgo de muerte en pacientes con sindrome de dificultad respiratoria aguda (SDRA), inclusive con Presión Plateau (PPlat) y volumen tidal (Vt) considerados seguros. Aunque no se pudo establecer una causalidad, se ha sugerido una probable relación entre ΔP y el desarrollo de injuria pulmonar inducida por el ventilador (VILI). Objetivo: Evaluar si ΔP correlaciona con el riesgo de VILI (barotrauma, volutrauma y atelectrauma). Materiales y Métodos: Doce pacientes con SDRA fueron ventilados en VCV con Vt: 6 ml/kg. El nivel de PEEP fue ajustado para obtener una PPlat de 30 cmH2O. Se midieron presiones transpulmonares (PTP) y posteriormente se realizó TAC de tórax en fin de inspiración y de espiración. Los volumenes pulmonares fueron evaluados a partir del análisis de las densidades tomográficas, considerandose hiperinsuflación (HI) al pulmón comprendido entre: -901 a 1000 UH, atelectrauma a la diferencia de pulmón no aireado (NA: -100 a 100 UH) entre ambos tiempos ventilatorio, y distensión pulmonar cíclica (strain) a la diferencia de pulmón hiperinsuflado. Resultados: El ΔP se relacionó de forma inversa con la Cst (r= -0,84, p= 0,0005, IC95% -0,9 a -0,5 y el riesgo de volutrauma (strain: r:-0,86, p=0,0003, IC95:-0,9 a -0,6 e hiperinsuflación: r:-0,78, p 0,002, IC95%: -0,9 a -0,4) y de forma directa con el riesgo de atelectrauma (r:0,89, p=0,0001, IC95% 0,7 a 0,9). No se observó correlación entre ΔP y barotrauma. Conclusiones: En este modelo de SDRA, la presión de distensión estuvo condicionada por la complacencia respiratoria y se encontró directamente relacionada con mayor riesgo de atelectrauma e inversamente asociada al riesgo de volutrauma.

El abordaje homeopático de la tos / The homeopathic approach cough

El organismo humano posee distintos mecanismos de defensa natural para sus diversos sistemas, los que son conocidos como signos clínicos o lo que Hahnemann llamaba en los §6 y 7 del Organon la expresión de la fuerza vital. La tos es un fenómeno producido por un mecanismo reflejo que emerge en los receptores vagales situados a lo largo del tracto respiratorio. Se han descrito tres tipos diferentes de receptores, los receptores de estiramiento de adaptación lenta (REAL), receptores de estiramiento de adaptación rápida (REAR) y las fibras C. Este reflejo tusígeno consiste en tres fases: inspiratoria, compresiva y espiratoria. Es importante tener muy en cuenta que la tos es tan sólo un síntoma de un cuadro clínico complejo e individual que se desarrolla en la totalidad del organismo. Incluso la medicina convencional reconoce que la tos, aunque puede ser un síntoma problemático, es una forma de curación del cuerpo; en este sentido, se debe hacer lo posible por no erradicarla, menos aún en menores de seis años, a través de antitusígenos de venta libre.

Human organism has different natural defense mechanisms for its various systems,these mechanisms are known as clinical signs or what Hahnemann called in § 6and 7 of Organon “expression of the vital force”. Cough is a phenomenon caused by a reflection mechanism emerges vagal receptors along the respiratory tract have been described three types of receptors, slowly adapting stretch receptors (SARs), rapidly adapting stretch receptors (RARs) and C-fibers. This cough reflex consists of three phases, the first “inspiratory”, “compression” and “expiratory”. It is important to bear in mind that the cough is just a symptom of a complex clinical picture and individual that develops in the whole organism, even conventional medicine recognizes that cough, but can be a troubling symptom, it is a form of healing the body, in this regard, it should be possible not eradicate it, even less in children under six years antitussives through counter.

Interaction of cyclic mechanical stretch and toll-like receptor 4-mediated innate immunity in rat alveolar type II cells.

BACKGROUND AND OBJECTIVE: In cases of infection-induced acute lung injury, mechanical ventilation might be necessary to maintain oxygenation. Although low tidal volume ventilation is applied, alveolar over-distension may occur and result in ventilator-induced lung injury. In this study, we investigate (i) the influence of lipopolysaccharide (LPS) stimulation on high-amplitude stretching; and (ii) the effect of stretching on LPS-mediated immune response in isolated rat alveolar type II cells. METHODS: Type II cells were incubated with LPS and stretched for 24 h on elastic membranes. Initially we examined apoptosis and lactic acid dehydrogenase release in LPS-treated stretched cells. Furthermore we determined toll-like receptor (TLR) 4 expression, TLR4 signalling by analysis of nuclear factor κB (NF-κB) activation and the secretion of inflammatory cytokines (monocyte chemoattractant protein-1, macrophage inflammatory protein-2, interleukin-1 beta, tumour necrosis factor alpha). RESULTS: Our results show that LPS increases apoptosis and cytotoxicity in high amplitude stretched cells. Stretching and LPS activate NF-κB. The LPS influence is the prevailing one while no synergistic effects were observed by additional stretching. LPS stimulates an increased secretion of the inflammatory mediators only. Stretching had no influence on cytokines secretion. CONCLUSIONS: We conclude that activation of TLR4 mediated immunity intensifies cell damage caused by stretching whereas in return stretching had no influence on TLR4 mediated innate immunity.

[The different types of dyspnoea]. / 4 soorten dyspneu.

Dyspnoea can be classified into four types with each arising by means of a different mechanism. Air hunger originates from chemoreflex activity. It is inhibited by pulmonary inflation, probably through a reflex induced by stretch receptors in the large airways. The feeling of increased work of breathing particularly occurs during volitional breathing and is augmented by every cause of increased work of breathing or muscle weakness. This feeling is probably induced by activity of the cerebral motor cortex. Tightness of the chest can be due to bronchospasm. This feeling possibly arises from stimulation of 'slowly adapting receptors' in the large airways, which are closely connected to smooth muscle cells. There are indications that tachypnoea can result from the stimulation of pulmonary C fibres. Possible stimuli are pulmonary venous congestion and the intravenous administration of adenosine. Recognizing and understanding the different types of dyspnoea is relevant to the interpretation and treatment of this symptom.

Imaging and characterization of stretch-induced ATP release from alveolar A549 cells.

Abstract Mechano-transduction at cellular and tissue levels often involves ATP release and activation of the purinergic signalling cascade. In the lungs, stretch is an important physical stimulus but its impact on ATP release, the underlying release mechanisms and transduction pathways are poorly understood. Here, we investigated the effect of unidirectional stretch on ATP release from human alveolar A549 cells by real-time luciferin-luciferase bioluminescence imaging coupled with simultaneous infrared imaging, to monitor the extent of cell stretch and to identify ATP releasing cells. In subconfluent (<90%) cell cultures, single 1 s stretch (10-40%)-induced transient ATP release from a small fraction (1.5%) of cells that grew in number dose-dependently with increasing extent of stretch. ATP concentration in the proximity (150 µm) of releasing cells often exceeded 10 µm, sufficient for autocrine/paracrine purinoreceptor stimulation of neighbouring cells. ATP release responses were insensitive to the putative ATP channel blockers carbenoxolone and 5-nitro-2-(3-phenylpropyl-amino) benzoic acid, but were inhibited by N-ethylmaleimide and bafilomycin. In confluent cell cultures, the maximal fraction of responding cells dropped to <0.2%, but was enhanced several-fold in the wound/scratch area after it was repopulated by new cells during the healing process. Fluo8 fluorescence experiments revealed two types of stretch-induced intracellular Ca(2+) responses, rapid sustained Ca(2+) elevations in a limited number of cells and delayed secondary responses in neighbouring cells, seen as Ca(2+) waves whose propagation was consistent with extracellular diffusion of released ATP. Our experiments revealed that a single >10% stretch was sufficient to initiate intercellular purinergic signalling in alveolar cells, which may contribute to the regulation of surfactant secretion and wound healing.

High altitude simulation, substance P and airway rapidly adapting receptor activity in rabbits.

To investigate whether there is a change in airway rapidly adapting receptor (RAR) activity during high altitude exposure, rabbits were placed in a high altitude simulation chamber (barometric pressure, 429 mm Hg). With 12 h exposure, when there was pulmonary congestion, an increase in basal RAR activity was observed. With 36 h exposure, when there was alveolar edema, there was a further increase in basal RAR activity. In these backgrounds, there was an increase in the sensitivity of the RARs to substance P (SP). To assess whether there was an increase in lung SP level, neutral endopeptidase activity was determined which showed a decrease in low barometric pressure exposed groups. It is concluded that along with the SP released, pulmonary congestion and edema produced, respectively by different durations of low barometric pressure exposure cause a progressive increase in RAR activity which may account for the respiratory symptoms reported in climbers who are unacclimatized.

Transient in utero nicotine exposure stimulates mechanosensory-dependent lung development.

Nicotine receptors are present in the developing lung yet their function is unknown. The transient role of nicotine receptors in lung development has not been addressed. In this study, nicotine's direct effect on smooth muscle contraction, necessary for mechanosensory-dependent fetal lung development, is examined after transient nicotine stimulation to determine the relationship between nicotine exposure, smooth muscle contraction, and fetal lung development. Rat fetuses at 16 days' gestation were exposed in utero to 5 different concentrations of nicotine or control injected directly into the amniotic fluid. Specific concentrations of in utero nicotine increased the phosphorylated Western blot analysis and immunohistochemistry of muscle contraction proteins. Respiratory function tests on nicotine-exposed rat pups showed a statistically significant decrease in airway resistance earlier in life compared to control and an upward shift of the pressure-volume curve pointing towards a structural maturation of the in utero nicotine-exposed lung. These results are consistent with transient nicotine exposure during intrauterine life stimulating stretch-induced lung organogenesis by altering phosphorylation of muscle contraction proteins. The increase in smooth muscle phosphorylation may stimulate stretch-induced lung organogenesis, which affects lung development and accelerates lung maturation in rats.

Stretch magnitude and frequency-dependent actin cytoskeleton remodeling in alveolar epithelia.

Alveolar epithelial cells (AEC) maintain integrity of the blood-gas barrier with gasket-like intercellular tight junctions (TJ) that are anchored internally to the actin cytoskeleton. We hypothesize that stretch rapidly reorganizes actin (<10 min) into a perijunctional actin ring (PJAR) in a manner that is dependent on magnitude and frequency of the stretch, accompanied by spontaneous movement of actin-anchored receptors at the plasma membrane. Primary AEC monolayers were stretched biaxially to create a change in surface area (DeltaSA) of 12%, 25%, or 37% in a cyclic manner at 0.25 Hz for up to 60 min, or held tonic at 25% DeltaSA for up to 60 min, or left unstretched. By 10 min of stretch PJARs were evident in 25% and 37% DeltaSA at 0.25 Hz, but not for 12% DeltaSA at 0.25 Hz, or at tonic 25% DeltaSA, or with no stretch. Treatment with 1 muM jasplakinolide abolished stretch-induced PJAR formation, however. As a rough index of remodeling rate, we measured spontaneous motions of 5-mum microbeads bound to actin focal adhesion complexes on the apical membrane surfaces; within 1 min of exposure to DeltaSA of 25% and 37%, these motions increased substantially, increased with increasing stretch frequency, and were consistent with our mechanistic hypothesis. With a tonic stretch, however, the spontaneous motion of microbeads attenuated back to unstretched levels, whereas PJAR remained unchanged. Stretch did not increase spontaneous microbead motion in human alveolar epithelial adenocarcinoma A549 monolayers, confirming that this actin remodeling response to stretch was a cell-type specific response. In summary, stretch of primary rat AEC monolayers forms PJARs and rapidly reorganized actin binding sites at the plasma membrane in a manner dependent on stretch magnitude and frequency.

Mechanical stretch promotes fetal type II epithelial cell differentiation via shedding of HB-EGF and TGF-alpha.

The mechanisms by which mechanical forces promote fetal lung development are not fully understood. Here, we investigated differentiation of fetal type II epithelial cells via the epidermal growth factor receptor (EGFR) in response to mechanical strain. First, we showed that incubation of embryonic day (E) 19 fetal type II cells with recombinant heparin-binding EGF-like growth factor (HB-EGF) or transforming growth factor (TGF)-alpha, but not with amphiregulin (AR), betacellulin (BTC) or epiregulin (EPR), increased fetal type II cell differentiation, as measured by surfactant protein B/C mRNA and protein levels. Next, we demonstrated that 5% cyclic stretch of E19 monolayers transfected with plasmid encoding alkaline phosphatase (AP)-tagged ligands shed mature HB-EGF and TGF-alpha into the supernatant and promoted type II cell differentiation. Release of these ligands was also observed in E19 cells subjected to higher degrees of cyclic strain, but not in cells exposed to continuous stretch. Interestingly, the addition of fibroblasts to type II cell cultures did not enhance release of HB-EGF. Whereas HB-EGF shedding was also detected in E18 cells exposed to 5% cyclic stretch, release of this ligand after 2.5% sustained stretch was restricted to cells isolated on E18 of gestation. In addition, mechanical stretch released EGF, AR and BTC. We conclude that mechanical stretch promotes fetal type II cell differentiation via ectodomain shedding of HB-EGF and TGF-alpha. The magnitude of shedding varied depending on gestational age, ligand, and strain protocol. These studies provide novel mechanistic information potentially relevant to fetal lung development and to mechanical ventilation-induced lung injury.

Origins of the inhibiting effects of nasal CPAP on nonnutritive swallowing in newborn lambs.

The present study investigated the mechanism by which continuous positive airway pressure (CPAP) suppresses nonnutritive swallowing (NNS) during quiet sleep (QS) in newborn lambs. Eighteen full-term lambs were chronically instrumented and evenly distributed into three separate groups to determine the extent to which modulation of NNS may be attributed to stimulation of upper airway and/or bronchopulmonary mechanoreceptors. Six lambs were tracheotomized, six other lambs underwent a two-step bilateral intrathoracic vagotomy, and the remaining six lambs underwent chronic laryngotracheal separation (isolated upper airway group). Forty-eight hours after surgery, each nonsedated lamb underwent polysomnographic recordings on three consecutive days. States of alertness, NNS and respiratory movements were recorded. Results demonstrate that a CPAP of 6 cmH(2)O inhibited NNS during QS while administered directly on the lower airways and that bivagotomy prevented this inhibition. However, application of CPAP on the upper airways only also inhibited NNS during QS. Finally, the application of a CPAP of 6 cmH(2)O had no systematic effect on NNS-breathing coordination (assessed by the respiratory phase preceding and following NNS). In conclusion, our results suggest that bronchopulmonary receptors are implicated in the inhibiting effects of nasal CPAP of 6 cmH(2)O on NNS in all our experimental conditions, whereas upper airway receptors are only implicated in certain conditions.

Hipotensão pós-exercício: mecanismos e infl uências do exercício físico / Post-exercise hypotension: mechanisms and infl uences of physical exercise

Imediatamente após um período de exercício físico dinâmico, a pressão arterial diminui para níveis inferiores aos observados pré-exercício. Foi observado em indivíduos hipertensos, resposta de hipotensão pós-exercício de 11 mmHg e 4 mmHg para as pressões arteriais sistólica e diastólica, respectivamente , mas não verifi caram reduções signifi cantes nos indivíduos normotensos. Com relação ao efeito da intensidade do exercício foi verifi cado em hipertensos idosos, que o exercício físico mais intenso (70% do consumo pico de oxigênio) provocava diminuição da pressão arterial maior que uma sessão menos intensa (40% do consumo pico de oxigênio). As respostas de pressão arterial, freqüência cardíaca e resistência vascular periférica pós-exercício não apresentam sempre um padrão coerente ao esperado pelo controle barorrefl exo. Dessa forma, torna-se importante verifi car o efeito do exercício físico no controle barorrefl exo cardiopulmonar. Foi observado que após uma sessão aguda de exercício físico, ocorre diminuição da atividade nervosa simpática muscular com diminuição concomitante da resistência vascular periférica. Isto indica alteração no controle barorrefl exo arterial, pois o fl uxo simpático está diminuído para um nível de pressão arterial idêntico. Portanto, estas modifi cações na sensibilidade dos barorreceptores arteriais estão relacionados a mecanismos neurais e vasculares. Com isso, pode-se notar que a hipotensão pós-exercício pode ser infl uenciada por diversos mecanismos, sendo que os mesmos ainda necessitam de maiores investigações, por isso o intuito da realização dessa revisão.

Immediately after a dynamic physical exercise, blood pressure decreases to lower levels compared with pre-exercise. In hypertensive subjects was observed post-exercise hypotension reply of 11 mmHg and 4 mmHg for systolic and diastolic blood pressure, respectively, but was not verifi ed signifi cant reductions in normotensive individuals. In older hypertensive subjects, it was noted that the most intensive physical exercise (70% of the oxygen consumption peak) provoked a higher reduction on blood pressure than another light intensive (40% of the oxygen consumption peak). Blood pressure, heart rate and peripheral vascular resistance’s post-exercise reply do not present a coherent standard answer for the barorefl ex control expected frequently. Thus, it becomes important to verify the effect of physical exercise in cardiopulmonary barorefl ex control. It was observed that post-exercise, the sympathetic muscular nervous activity reduces with concomitant diminishes of the peripheral vascular resistance. This indicates that there is an alteration in arterial barorefl ex control, because the sympathetic fl ow is decreased for an identical level of blood pressure. So, these modifi cations in the sensibility of arterial baroreceptors are related with neural and vascular mechanisms. Therefore, we can observe that the post-exercise hypotension might be infl uenced by several mechanisms, which still need additional investigations; so, this is the intention of the present review.

Retention of lung distension information in pump cell spike trains.

Respiratory control requires feedback signals from the viscera, including mechanoreceptors and chemoreceptors. We previously showed that typical pulmonary stretch receptor (PSR) spike trains provide the central nervous system with approximately 31% of the theoretical maximum information regarding the amplitude of lung distension. However, it is unknown whether the spatiotemporal convergence of many PSR inputs onto second-order neurons (e.g., pump cells) results in more, or less, information about the stimulus carried by second-order cell spike trains. We recorded pump cell activity in adult, anesthetized, paralyzed, artificially ventilated rabbits during continuous manipulation of ventilator rate and volume to test the hypothesis that less information is carried by spike trains of individual pump cells than PSRs. Using previously developed analytic methods, we quantified the information carried by the pump cell spike trains and compared it with the same values derived from PSR data. Our results provide evidence that rejects our hypothesis: pump cells as a group did not carry significantly less information about the lung distension stimulus than PSRs, although that trend was implied by the data. By comparing the response variances with the theoretical minimum, we discovered that the trend toward information loss depends on response strength, with higher mean responses associated with larger response variances in pump cells than in PSRs. Thus spatiotemporal integration may result in information loss within certain analytic/stimulus parameters, but this is counterbalanced by the consistency of pump cell responses during brief integration times and/or low stimulus amplitudes, resulting in retention of total information.

Stretch-activated signaling pathways responsible for early response gene expression in fetal lung epithelial cells.

High-tidal volume ventilation has been shown to increase the expression of several inflammation-associated genes prior to overt physiologic lung injury. Herein, using an in vitro stretch system, we investigated the mechanotransduction pathways involved in ventilation-induced expression of these early response genes (i.e., early growth response gene (Egr)1, heat-shock protein (HSP)70, and the pro-inflammatory cytokines interleukin (IL)-1beta, IL-6, and MIP-2). Mechanical stretch of fetal lung epithelial cells activated various signaling pathways, resulting in transient or progressive increases in gene expression of the early response genes. The transient increase in Egr1 and IL-6 expression was mediated via p44/42 mitogen-activated protein kinase (p44/42 MAPK), while nuclear factor-kappaB (NF-kappaB) was responsible for the sustained and progressive increase in expression of HSP70 and MIP-2. Blockage of Egr-1 expression did not affect the upregulation of IL-6, HSP70, MIP-2, and itself by stretch. Inhibition of calcium mobilization abolished stretch-induced p44/42 MAPK activation and NF-kappaB nuclear translocation as well as increased expression of all early response genes. Similar results were obtained with an inhibitor of Ras. These results suggest that mechanical stretch of fetal lung epithelial cells evokes a complex network of signaling molecules, which diverge downstream to regulate the temporal expression of a unique set of early response genes, but upstream converge at calcium. Thus, calcium mobilization may be a point of hierarchical integration of mechanotransduction in lung epithelial cells.

Activations of mitogen-activated protein kinase and nuclear factor-kappaB by mechanical stretch result in ventilation-induced lung injury.

Mechanical ventilation is an important therapeutic technique for patients with respiratory failure. Nonetheless, it may cause or worsen lung injury. The specific triggers for cytokine release and the cellular origins of the inflammatory mediators in ventilation-induced lung injury (VILI) have yet to be defined. With the development of cytomechanics, we can study the lung cell response to mechanical strain. The initial step is mechanosensation, including stretch-activated ionchannels and the ECM-integrin-cytoskeleton pathway. Several intracellular signaling pathways then are activated and eventually result in increased transcription of specific genes. Mitogen-activated protein kinase cascade, nuclear factor(NF)-kappaB, PKC are all activated by mechanical stretch. But the mechanisms regulating lung stretch-induced cytokine production are still unclear. I hypotheses mechanical stretch initiate specific genes transcription, then the cytokines stimulate the cell again. This formed a positive feed back loop, which caused VILI. These studies may lead to the identification of new targets for therapeutic interventions and help to develop less aggressive ventilation strategies for patients with acute respiratory failure.

[Relationship of stress index with lung recruitment and gas exchange in dogs with acute respiratory distress syndrome].

OBJECTIVE: To determine the relationship of stress index with lung recruitment and gas exchange in dogs with acute respiratory distress syndrome (ARDS). METHODS: The ARDS model was induced by infusion of oleic acid intravenously in anesthetized dogs. During volume control ventilation with constant inspiratory flow, the pressure-time (P-t) curve was fitted to a power equation: P = a.time(b)+c, where coefficient b (stress index) describes the shape of the curve: b = 1, straight curve; b < 1, progressive increase in slope; and b > 1, progressive decrease in slope. Tidal volume (V(T)) was 6 ml/kg, and positive end-expiratory pressure (PEEP) was set to obtain a b value between 0.9 and 1.1 before (b = 1) and after (b = 1 after recruiting maneuver) application of a recruiting maneuver (RM). PEEP was changed to obtain 0.6 < b < 0.8 and 1.1 < b < 1.3. Experimental condition sequence was random. Recruited volume (RV) was measured by static pressure-volume curve method. Hemodynamics, pulmonary mechanics and gas exchange were observed at the same time. RESULTS: At b = 1 without RM, the PEEP was (5.0 +/- 3.0) cm H2O, the RV was (27 +/- 15) ml, and the RV increased to (166 +/- 84) ml significantly at b = 1 after RM [PEEP (10.8 +/- 2.3) cm H2O (1 cm H2O = 0.098 kPa), q = 3.18, P < 0.01]. At 1.1 < b < 1.3 after RM, the PEEP was (16.8 +/- 1.1) cm H2O and the RV was (262 +/- 57) ml, which was higher than that at b = 1 after RM (q = 2.54, P = 0.023). At 0.6 < b < 0.8 after RM, the PEEP was (5.6 +/- 2.2) cm H2O and the RV was lower than that at b = 1 after RM (q = 2.85, P = 0.013). The partial pressure of oxygen in arterial blood (PaO2) in b = 1, 0.6 < b < 0.8 and 1.1 < b < 1.3 after RM were (319 +/- 49) mm Hg (1 mm Hg = 0.133 kPa), (246 +/- 57) mm Hg and (314 +/- 27) mm Hg respectively, which was higher than the PaO2 at b = 1 without RM [(153 +/- 64) mm Hg, all q = 2.81, all P < 0.05]. The PaO2 at 0.6 < b < 0.8 was lower than that at b = 1 after RM (q = 2.81, P = 0.005), while there was no significant difference between the PaO2 at 1.1 < b < 1.3 and that at b = 1 after RM. The peak airway pressure and plateau pressure at 1.1 < b < 1.3 were higher than those at b = 1 after RM (q = 6.02, 5.72, all P < 0.05). CONCLUSION: In the b = 1 after RM, there were better PaO2 and lower airway pressure, suggesting that b = 1 after RM may be a good indicator for PEEP titration.

Effect of ouabain on the afterhyperpolarization of slowly adapting pulmonary stretch receptors in the rat lung.

In anesthetized, artificially ventilated rats with one vagus nerve section, the purposes of the present study were to investigate whether release from phasic consecutive hyperinflations (inflation volume=3 tidal volumes) results in the afterhyperpolarization (AHP) of the slowly adapting pulmonary stretch receptor (SAR) activity and whether the effect of ouabain, a Na+-K+ ATPase inhibitor, alters AHP of the SAR activity seen after release from maintained inflations. Release from 10 consecutive phasic hyperinflations did not cause any significant inhibition of SAR activity. Release from maintained inflations (for approximately 10 and 15 cmH2O) for 5 s produced the induction of disappearance of SAR activity, corresponding with the AHP. Intravenous administration of ouabain (20 and 40 microg/kg) had no significant effects on the responses of SAR activity and SAR adaptation index (AI) to maintained inflations, but ouabain treatment with at 40 microg/kg resulted in a significant increase in the SAR activity after stopping the respirator and significantly attenuated the AHP of the SAR activity. In the immunohistochemical study, we found Na+-K+ ATPase alpha3-subunit-isoforms-like immunoreactivity in SAR terminals, forming leaflike extensions in the intrapulmonary bronchioles at different diameters, and those terminals were buried in the smooth muscle. In the same sections, the alpha1 subunit immunoreactivity of SAR terminals was not found. These results suggest that the mechanism of generating the AHP of SARs is mainly mediated by the activation of Na+-K+ ATPase alpha3 subunit isoform.