Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0034063 (pulmonary edema)
 10,665 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The resolution of alveolar edema is regulated by active sodium and chloride transport across the pulmonary epithelium, including alveolar epithelial type I and II cells as well as distal airway epithelia. Catecholamine-dependent mechanisms can markedly upregulate alveolar fluid clearance even under pathological conditions, an effect that is mediated by both epithelial sodium channel (ENaC) and cystic fibrosis transmembrane conductance regulator (CFTR). Under pathological conditions, impaired alveolar fluid clearance is associated with worse survival in patients with acute lung injury. However, there is some experimental and clinical evidence that cAMP stimulation could accelerate the resolution of pulmonary edema in the presence of acute lung injury. Clinical trials are needed to test this potential therapeutic strategy in patients with acute lung injury.
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PMID:Alveolar epithelium: role in lung fluid balance and acute lung injury. 1622 39

Transepithelial sodium transport via alveolar epithelial Na(+) channels and Na(+),K(+)-ATPase constitutes the driving force for removal of alveolar oedema fluid. Decreased activity of the amiloride-sensitive epithelial Na(+) channel (ENaC) in the apical membrane of alveolar epithelial cells impairs sodium-driven alveolar fluid clearance (AFC) and predisposes to pulmonary oedema. We hypothesized that hyperactivity of ENaC in the distal lung could improve AFC and facilitate the resolution of pulmonary oedema. AFC and lung fluid balance were studied at baseline and under conditions of hydrostatic pulmonary oedema in the beta-Liddle (L) mouse strain harbouring a gain-of-function mutation (R(566)(stop)) within the Scnn1b gene. As compared with wild-type (+/+), baseline AFC was increased by 2- and 3-fold in heterozygous (+/L) and homozygous mutated (L/L) mice, respectively, mainly due to increased amiloride-sensitive AFC. The beta(2)-agonist terbutaline stimulated AFC in +/+ and +/L mice, but not in L/L mice. Acute volume overload induced by saline infusion (40% of body weight over 2 h) significantly increased extravascular (i.e. interstitial and alveolar) lung water as assessed by the bloodless wet-to-dry lung weight ratio in +/+ and L/L mice, as compared with baseline. However, the increase was significantly larger in +/+ than in L/L groups (P=0.01). Volume overload also increased the volume of the alveolar epithelial lining fluid in +/+ mice, indicating the presence of alveolar oedema, but not in L/L mice. Cardiac function as evaluated by echocardiography was comparable in both groups. These data show that constitutive ENaC activation improved sodium-driven AFC in the mouse lung, and attenuated the severity of hydrostatic pulmonary oedema.
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PMID:beta-Liddle mutation of the epithelial sodium channel increases alveolar fluid clearance and reduces the severity of hydrostatic pulmonary oedema in mice. 1743 Sep 90

Hypoxia inhibits Na and lung fluid reabsorption, which contributes to the formation of pulmonary edema. We tested whether dexamethasone prevents hypoxia-induced inhibition of reabsorption by stimulation of alveolar Na transport. Fluid reabsorption, transport activity, and expression of Na transporters were measured in hypoxia-exposed rats and in primary alveolar type II (ATII) cells. Rats were treated with dexamethasone (DEX; 2 mg/kg) on 3 consecutive days and exposed to 10% O(2) on the 2nd and 3rd day of treatment to measure hypoxia effects on reabsorption of fluid instilled into lungs. ATII cells were treated with DEX (1 muM) for 3 days before exposure to hypoxia (1.5% O(2)). In normoxic rats, DEX induced a twofold increase in alveolar fluid clearance. Hypoxia decreased reabsorption (-30%) by decreasing its amiloride-sensitive component; pretreatment with DEX prevented the hypoxia-induced inhibition. DEX increased short-circuit currents (ISC) of ATII monolayers in normoxia and blunted hypoxic transport inhibition by increasing the capacity of Na(+)-K(+)-ATPase and epithelial Na(+) channels (ENaC) and amiloride-sensitive ISC. DEX slightly increased the mRNA of alpha- and gamma-ENaC in whole rat lung. In ATII cells from DEX-treated rats, mRNA of alpha(1)-Na(+)-K(+)-ATPase and alpha-ENaC increased in normoxia and hypoxia, and gamma-ENaC was increased in normoxia only. DEX stimulated the mRNA expression of alpha(1)-Na(+)-K(+)-ATPase and alpha-, beta-, and gamma-ENaC of A549 cells in normoxia and hypoxia (1.5% O(2)) when DEX treatment was begun before or during hypoxic exposure. These results indicate that DEX prevents inhibition of alveolar reabsorption by hypoxia and stimulates the expression of Na transporters even when it is applied in hypoxia.
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PMID:Dexamethasone prevents transport inhibition by hypoxia in rat lung and alveolar epithelial cells by stimulating activity and expression of Na+-K+-ATPase and epithelial Na+ channels. 1787 5

Amiloride-sensitive epithelial sodium channel (ENaC) is a major sodium channel in the lung facilitating fluid absorption. ENaC is composed of alpha-, beta-, and gamma-subunits, and the alpha-subunit is indispensable for ENaC function in the lung. In human lungs, the alpha-subunit is expressed as various splice variants. Among them, alpha(1)- and alpha(2)-subunits are two major variants with different upstream regulatory sequences that possess similar channel characteristics when tested in Xenopus oocytes. Despite the importance of alpha-ENaC, little was known about the relative abundance of its variants in lung epithelial cells. Furthermore, lung infection and inflammation are often accompanied by reduced alpha-ENaC expression, oxidative stress, and pulmonary edema. However, it was not clear how oxidative stress affects expression of alpha-ENaC variants. In this study, we examined relative expression levels of alpha-subunit variants in four human lung epithelial cell lines. We also tested the hypothesis that oxidative stress inhibits alpha-ENaC expression. Our results show that both alpha(1)- and alpha(2)-ENaC variants are expressed in the cells we tested, but relative abundance varies. In the two monolayer-forming cell lines, H441 and Calu-3, alpha(2)-ENaC is the predominant variant. We also show that H(2)O(2) specifically suppresses alpha(1)- and alpha(2)-ENaC variant expression in H441 and Calu-3 cells in a dose-dependent fashion. This suppression is achieved by inhibition of their promoters and is attenuated by dexamethasone. These data demonstrate the importance of the alpha(2)-subunit variant and suggest that glucocorticoids and antioxidants may be useful in correcting infection/inflammation-induced lung fluid imbalance.
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PMID:ENaC alpha-subunit variants are expressed in lung epithelial cells and are suppressed by oxidative stress. 1790 53

The epithelial Na(+) channel (ENaC) is a major regulator of salt and water reabsorption in a number of epithelial tissues. Abnormalities in ENaC function have been directly linked to several human disease states including Liddle's syndrome, psuedohypoaldosteronism, and cystic fibrosis and may be implicated in states as diverse as salt-sensitive hypertension, nephrosis, and pulmonary edema. ENaC activity in epithelial cells is highly regulated both by open probability and number of channels. Open probability is regulated by a number of factors, including proteolytic processing, while ENaC number is regulated by cellular trafficking. This review discusses current understanding of apical membrane delivery, cell surface stability, endocytosis, retrieval, and recycling of ENaC and the molecular partners that have so far been shown to participate in these processes. We review known sites and mechanisms of hormonal regulation of trafficking by aldosterone, vasopressin, and insulin. While many details of the regulation of ENaC trafficking remain to be elucidated, knowledge of these mechanisms may provide further insights into ENaC activity in normal and disease states.
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PMID:Regulation of the epithelial sodium channel by membrane trafficking. 1850 77

Among the multiple organ disorders caused by the severe acute respiratory syndrome coronavirus (SARS-CoV), acute lung failure following atypical pneumonia is the most serious and often fatal event. We hypothesized that two of the hydrophilic structural coronoviral proteins (S and E) would regulate alveolar fluid clearance by decreasing the cell surface expression and activity of amiloride-sensitive epithelial sodium (Na(+)) channels (ENaC), the rate-limiting protein in transepithelial Na(+) vectorial transport across distal lung epithelial cells. Coexpression of either S or E protein with human alpha-, beta-, and gamma-ENaC in Xenopus oocytes led to significant decreases of both amiloride-sensitive Na(+) currents and gamma-ENaC protein levels at their plasma membranes. S and E proteins decreased the rate of ENaC exocytosis and either had no effect (S) or decreased (E) rates of endocytosis. No direct interactions among SARS-CoV E protein with either alpha- or gamma-ENaC were indentified. Instead, the downregulation of ENaC activity by SARS proteins was partially or completely restored by administration of inhibitors of PKCalpha/beta1 and PKCzeta. Consistent with the whole cell data, expression of S and E proteins decreased ENaC single-channel activity in oocytes, and these effects were partially abrogated by PKCalpha/beta1 inhibitors. Finally, transfection of human airway epithelial (H441) cells with SARS E protein decreased whole cell amiloride-sensitive currents. These findings indicate that lung edema in SARS infection may be due at least in part to activation of PKC by SARS proteins, leading to decreasing levels and activity of ENaC at the apical surfaces of lung epithelial cells.
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PMID:SARS-CoV proteins decrease levels and activity of human ENaC via activation of distinct PKC isoforms. 1911

The alveolar epithelium plays a critical role in resolving pulmonary edema. We thus hypothesized that its function might be upregulated in rats with heart failure, a condition that severely challenges the lung's ability to maintain fluid balance. Heart failure was induced by left coronary artery ligation. Echocardiographic and cardiovascular hemodynamics confirmed its development at 16 wk postligation. At that time, alveolar fluid clearance was measured by an increase in protein concentration over 1 h of a 5% albumin solution instilled into the lungs. Baseline alveolar fluid clearance was similar in heart failure and age-matched control rats. Terbutaline was added to the instillate to determine whether heart failure rats responded to beta-adrenoceptor stimulation. Alveolar fluid clearance in heart failure rats was increased by 194% after terbutaline stimulation compared with a 153% increase by terbutaline in control rats. To determine the mechanisms responsible for this accelerated alveolar fluid clearance, we measured ion transporter expression (ENaC, Na-K- ATPase, CFTR). No significant upregulation was observed for these ion transporters in the heart failure rats. Lung morphology showed significant alveolar epithelial type II cell hyperplasia in heart failure rats. Thus, alveolar epithelial type II cell hyperplasia is the likely explanation for the increased terbutaline-stimulated alveolar fluid clearance in heart failure rats. These data provide evidence for previously unrecognized mechanisms that can protect against or hasten resolution of alveolar edema in heart failure.
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PMID:Beta-adrenoceptor stimulation of alveolar fluid clearance is increased in rats with heart failure. 1959 57

The lung possesses specific transport systems that intra- and extracellularly maintain salt and fluid balance necessary for its function. At birth, the lungs rapidly transform into a fluid (Na(+))-absorbing organ to enable efficient gas exchange. Alveolar fluid clearance, which mainly depends on sodium transport in alveolar epithelial cells, is an important mechanism by which excess water in the alveoli is reabsorbed during the resolution of pulmonary edema. In this review, we will focus and summarize on the role of ENaC in alveolar lung liquid clearance and discuss recent data from mouse models with altered activity of epithelial sodium channel function in the lung, and more specifically in alveolar fluid clearance. Recent data studying mice with hyperactivity of ENaC or mice with reduced ENaC activity clearly illustrate the impaired lung fluid clearance in these adult mice. Further understanding of the physiological role of ENaC and its regulatory proteins implicated in salt and water balance in the alveolar cells may therefore help to develop new therapeutic strategies to improve gas exchange in pulmonary edema.
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PMID:Importance of ENaC-mediated sodium transport in alveolar fluid clearance using genetically-engineered mice. 2005 45

Hypoxia impairs alveolar fluid clearance by inhibition of Na(+) reabsorption, and also impairs beta(2) adrenergic signaling in alveolar epithelium. Since both are major rescue mechanisms preventing pulmonary edema, we studied whether acute and prolonged treatment with terbutaline would prevent hypoxic inhibition of ion transport. Short circuit currents (ISC) were measured on normoxic and hypoxic (1.5% O(2); 24h) primary rat alveolar type II (ATII) cells in absence and presence of terbutaline (1 to 100 microM, 24h). Control and pre-treated cells were stimulated acutely with terbutaline. Transepithelial transport was measured as short circuit current (ISC) in Ussing chambers. Terbutaline induced a rapid decrease ISC (-20%) followed by a slow raise. The transient change in ISC was not inhibited by amiloride but was prevented after Cl(-) depletion indicating a Cl(-) current. The slow increase after this transient was amiloride-sensitive indicating a Na(+) current. Total ISC, its amiloride-sensitive component, and the transient decrease upon terbutaline stimulation were decreased by hypoxia. 24h treatment with terbutaline stimulated these currents in normoxia and hypoxia, although stimulation was less in the latter. 24h treatment with terbutaline increased the capacity of Na(+)/K(+)-ATPase and ENaC as measured after permeabilization with amphotericin. These changes were not paralleled by altered mRNA expression. Acutely applied terbutaline induced a 4-fold increase in cAMP formation in normoxia; terbutaline-induced cAMP-formation was impaired by hypoxia (-20%). Pre-treatment with terbutaline for 24h decreased terbutaline-induced cAMP formation by 85%. Despite this desensitization, addition of terbutaline to terbutaline pre-treated cells caused a larger increase in Cl(-) and Na(+) transport both in normoxia and hypoxia than in non pre-treated cells. These results indicate that beta(2) adrenergic stimulation increased Na(+)- and Cl(-) transport in ATII cells even in hypoxia thus restoring normal reabsorption.
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PMID:Beta2-adrenergic stimulation blunts inhibition of epithelial ion transport by hypoxia of rat alveolar epithelial cells. 2005 51

Lung complications during malaria infection can range from coughs and impairments in gas transfer to the development of acute respiratory distress syndrome (ARDS). Infecting C57BL/6 mice with Plasmodium berghei K173 strain (PbK) resulted in pulmonary oedema, capillaries congested with leukocytes and infected red blood cells (iRBCs), and leukocyte infiltration into the lungs. This new model of malaria-associated lung pathology, without any accompanying cerebral complications, allows the investigation of mechanisms leading to the lung disease. The activity of the amiloride-sensitive epithelial sodium channel (ENaC) in alveolar epithelial cells is decreased by several respiratory tract pathogens and this is suggested to contribute to pulmonary oedema. We show that PbK, a pathogen that remains in the circulation, also decreased the activity and expression of ENaC, suggesting that infectious agents can have indirect effects on ENaC activity in lung epithelial cells. The reduced ENaC activity may contribute to the pulmonary oedema induced by PbK malaria.
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PMID:Reduced activity of the epithelial sodium channel in malaria-induced pulmonary oedema in mice. 2081 46


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