Sadis Matalon

Quantitation of nitrotyrosine levels in lung sections of patients and animals with acute lung injury.

Activated alveolar macrophages and epithelial type II cells release both nitric oxide and superoxide which react at near diffusion-limited rate (6.7 x 10(9) M-1s-1) to form peroxynitrite, a potent oxidant capable of damaging the alveolar epithelium and pulmonary surfactant. Peroxynitrite, but not nitric oxide or superoxide, readily nitrates phenolic rings including tyrosine. We quantified the presence of nitrotyrosine in the lungs of patients with the adult respiratory distress syndrome (ARDS) and in the lungs of rats exposed to hyperoxia (100% O2 for 60 h) using quantitative immunofluorescence. Fresh frozen or paraffin-embedded lung sections were incubated with a polyclonal antibody to nitrotyrosine, followed by goat anti-rabbit IgG coupled to rhodamine. Sections from patients with ARDS (n = 5), or from rats exposed to hyperoxia (n = 4), exhibited a twofold increase of specific binding over controls. This binding was blocked by the addition of an excess amount of nitrotyrosine and was absent when the nitrotyrosine antibody was replaced with nonimmune IgG. In additional experiments we demonstrated nitrotyrosine formation in rat lung sections incubated in vitro with peroxynitrite, but not nitric oxide or reactive oxygen species. These data suggest that toxic levels of peroxynitrite may be formed in the lungs of patients with acute lung injury.

Participation of miR-200 in Pulmonary Fibrosis

Excessive extracellular matrix production by fibroblasts in response to tissue injury contributes to fibrotic diseases, such as idiopathic pulmonary fibrosis (IPF). Epithelial-mesenchymal transition, involving transition of alveolar epithelial cells (AECs) to pulmonary fibroblasts, appears to be an important contributory process to lung fibrosis. Although aberrant expression of microRNAs (miRs) is involved in a variety of pathophysiologic processes, the role of miRs in fibrotic lung diseases is less well understood. In the present study, we found that miR-200a, miR-200b, and miR-200c are significantly down-regulated in the lungs of mice with experimental lung fibrosis. Levels of miR-200a and miR-200c were reduced in the lungs of patients with IPF. miR-200 had greater expression in AECs than in lung fibroblasts, and AECs from mice with experimental pulmonary fibrosis had diminished expression of miR-200. We found that the miR-200 family members inhibit transforming growth factor-β1-induced epithelial-mesenchymal transition of AECs. miR-200 family members can reverse the fibrogenic activity of pulmonary fibroblasts from mice with experimental pulmonary fibrosis and from patients with IPF. Indeed, the introduction of miR-200c diminishes experimental pulmonary fibrosis in mice. Thus, the miR-200 family members participate importantly in fibrotic lung diseases and suggest that restoring miR-200 expression in the lungs may represent a novel therapeutic approach in treating pulmonary fibrotic diseases.

Biochemical characterization of human S-nitrosohemoglobin. Effects on oxygen binding and transnitrosation.

S-Nitrosation of cysteine β93 in hemoglobin (S-nitrosohemoglobin (SNO-Hb)) occurs in vivo, and transnitrosation reactions of deoxygenated SNO-Hb are proposed as a mechanism leading to release of NO and control of blood flow. However, little is known of the oxygen binding properties of SNO-Hb or the effects of oxygen on transnitrosation between SNO-Hb and the dominant low molecular weight thiol in the red blood cell, GSH. These data are important as they would provide a biochemical framework to assess the physiological function of SNO-Hb. Our results demonstrate that SNO-Hb has a higher affinity for oxygen than native Hb. This implies that NO transfer from SNO-Hb in vivo would be limited to regions of extremely low oxygen tension if this were to occur from deoxygenated SNO-Hb. Furthermore, the kinetics of the transnitrosation reactions between GSH and SNO-Hb are relatively slow, making transfer of NO+ from SNO-Hb to GSH less likely as a mechanism to elicit vessel relaxation under conditions of low oxygen tension and over the circulatory lifetime of a given red blood cell. These data suggest that the reported oxygen-dependent promotion of S-nitrosation from SNO-Hb involves biochemical mechanisms that are not intrinsic to the Hb molecule.

Asbestos inhalation induces reactive nitrogen species and nitrotyrosine formation in the lungs and pleura of the rat.

To determine whether asbestos inhalation induces the formation of reactive nitrogen species, three groups of rats were exposed intermittently over 2 wk to either filtered room air (sham-exposed) or to chrysotile or crocidolite asbestos fibers. The rats were killed at 1 or 6 wk after exposure. At 1 wk, significantly greater numbers of alveolar and pleural macrophages from asbestos-exposed rats than from sham-exposed rats demonstrated inducible nitric oxide synthase protein immunoreactivity. Alveolar macrophages from asbestos-exposed rats also generated significantly greater nitrite formation than did macrophages from sham-exposed rats. Strong immunoreactivity for nitrotyrosine, a marker of peroxynitrite formation, was evident in lungs from chrysotile- and crocidolite-exposed rats at 1 and 6 wk. Staining was most evident at alveolar duct bifurcations and within bronchiolar epithelium, alveolar macrophages, and the visceral and parietal pleural mesothelium. Lungs from sham-exposed rats demonstrated minimal immunoreactivity for nitrotyrosine. Significantly greater quantities of nitrotyrosine were detected by ELISA in lung extracts from asbestos-exposed rats than from sham-exposed rats. These findings suggest that asbestos inhalation can induce inducible nitric oxide synthase activation and peroxynitrite formation in vivo, and provide evidence of a possible alternative mechanism of asbestos-induced injury to that thought to be induced by Fenton reactions.

Upregulation of Alveolar Epithelial Active Na+ Transport Is Dependent on β2-Adrenergic Receptor Signaling

Abstract— Alveolar epithelial β-adrenergic receptor (βAR) activation accelerates active Na+ transport in lung epithelial cells in vitro and speeds alveolar edema resolution in human lung tissue and normal and injured animal lungs. Whether these receptors are essential for alveolar fluid clearance (AFC) or if other mechanisms are sufficient to regulate active transport is unknown. In this study, we report that mice with no β1- or β2-adrenergic receptors (β1AR−/−/β2AR−/−) have reduced distal lung Na,K-ATPase function and diminished basal and amiloride-sensitive AFC. Total lung water content in these animals was not different from wild-type controls, suggesting that βAR signaling may not be required for alveolar fluid homeostasis in uninjured lungs. Comparison of isoproterenol-sensitive AFC in mice with β1- but not β2-adrenergic receptors to β1AR−/−/β2AR−/− mice indicates that the β2AR mediates the bulk of β-adrenergic–sensitive alveolar active Na+ transport. To test the necessity of βAR signaling in acute lung injury, β1AR−/−/β2AR−/−, β1AR+/+/β2AR−/−, and β1AR+/+/β2AR+/+ mice were exposed to 100% oxygen for up to 204 hours. β1AR−/−/β2AR−/− and β1AR+/+/β2AR−/− mice had more lung water and worse survival from this form of acute lung injury than wild-type controls. Adenoviral-mediated rescue of β2-adrenergic receptor (β2AR) function into the alveolar epithelium of β1AR−/−/β2AR−/− and β1AR+/+/β2AR−/− mice normalized distal lung β2AR function, alveolar epithelial active Na+ transport, and survival from hyperoxia. These findings indicate that βAR signaling may not be necessary for basal AFC, and that β2AR is essential for the adaptive physiological response needed to clear excess fluid from the alveolar airspace of normal and injured lungs.

Differential induction of c-fos, c-jun, and apoptosis in lung epithelial cells exposed to ROS or RNS.

Reactive oxygen (ROS) or nitrogen (RNS) species can affect epithelial cells to cause acute damage and an array of pulmonary diseases. The goal of this study was to determine patterns of early response gene expression and functional end points of exposure to nitric oxide (NO ⋅), H2O2, or peroxynitrite (ONOO-) in a line of rat lung epithelial (RLE) cells. Our focus was on c- fos and c- jun protooncogenes, as these genes play an important role in proliferation or apoptosis, possible end points of exposure to reactive metabolites in lung. Our data demonstrate that NO ⋅ generated by spermine 1,3-propanediamine N-{4-[1-(3-aminopropyl)-2-hydroxy-2-nitrosohydrazino]butyl} or S-nitroso- N-acetylpenicillamine as well as H2O2cause increased c- fos and c- jun mRNA levels, nuclear proteins, and complexes binding the activator protein-1 recognition sequence in RLE cells. These agents also lead to apoptosis and increased membrane permeability. In contrast, exogenously administered ONOO- or 3-morpholinosydnonimine do not induce protooncogenes or apoptosis in RLE cells despite nitration of tyrosines. We conclude that ROS and RNS can elicit distinct molecular and phenotypic responses in a target cell of pulmonary disease.Reactive oxygen (ROS) or nitrogen (RNS) species can affect epithelial cells to cause acute damage and an array of pulmonary diseases. The goal of this study was to determine patterns of early response gene expression and functional end points of exposure to nitric oxide (NO.), H2O2, or peroxynitrite (ONOO-) in a line of rat lung epithelial (RLE) cells. Our focus was on c-fos and c-jun protooncogenes, as these genes play an important role in proliferation or apoptosis, possible end points of exposure to reactive metabolites in lung. Our data demonstrate that NO. generated by spermine 1,3-propanediamine N-14-[1-(3-aminopropyl)-2-hydroxy-2-nitrosohydrazino]-butyl] or S-nitroso-N-acetylpenicillamine as well as H2O2 cause increased c-fos and c-jun mRNA levels, nuclear proteins, and complexes binding the activator protein-1 recognition sequence in RLE cells. These agents also lead to apoptosis and increased membrane permeability. In contrast, exogenously administered ONOO- or 3-morpholinosydnonimine do not induce protooncogenes or apoptosis in RLE cells despite nitration oftyrosines. We conclude that ROS and RNS can elicit distinct molecular and phenotypic responses in a target cell of pulmonary disease.

Role of Pulmonary Surfactant in the Development and Treatment of Adult Respiratory Distress Syndrome

The goal of this article has been to examine the role of pulmonary surfactant system alterations in the development of ARDS, and the potential efficacy of surfactant replacement therapy in ARDS and ARDS-type injuries. Data from patients with ARDS and animal models with ARDS-type injuries clearly indicate the existence of a surfactant-deficient state. However, in contrast to neonatal RDS, this deficiency generally does not represent the primary pathogenic factor. The diversity of the disorders associated with ARDS has made it impossible to develop a single-animal model that can be used to test potential therapeutic measures. The ARDS animal models that have been developed are equally diverse, and represent the wide variations in severity and time-course seen clinically. Nevertheless, almost all of the lung injury models show indications of surfactant abnormality, which is caused mainly by biophysical inhibition of surfactant activity by the large amounts of proteinaceous edema found in the injured lungs. In some cases, this surfactant dysfunction is further compounded by a quantitative surfactant deficiency brought about by metabolic alterations of the type II pneumocytes. It is important to note that all of the lung injury models studied thus far have shown significant improvements in pulmonary mechanics and arterial oxygenation after treatment with exogenous surfactant. Such results are consistent with biophysical studies that suggest that increasing the effective surfactant concentration in the lung should mitigate the effects of both quantitative and functional surfactant deficiencies. Although animal studies suggest that surfactant replacement therapy might be efficacious in ARDS, there is a good deal of experimental work that still needs to be done.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced cell-surface stability of rescued DeltaF508 cystic fibrosis transmembrane conductance regulator (CFTR) by pharmacological chaperones.

Misfolded proteins destined for the cell surface are recognized and degraded by the ERAD [ER (endoplasmic reticulum) associated degradation] pathway. TS (temperature-sensitive) mutants at the permissive temperature escape ERAD and reach the cell surface. In this present paper, we examined a TS mutant of the CFTR [CF (cystic fibrosis) transmembrane conductance regulator], CFTR DeltaF508, and analysed its cell-surface trafficking after rescue [rDeltaF508 (rescued DeltaF508) CFTR]. We show that rDeltaF508 CFTR endocytosis is 6-fold more rapid (approximately 30% per 2.5 min) than WT (wild-type, approximately 5% per 2.5 min) CFTR at 37 degrees C in polarized airway epithelial cells (CFBE41o-). We also investigated rDeltaF508 CFTR endocytosis under two further conditions: in culture at the permissive temperature (27 degrees C) and following treatment with pharmacological chaperones. At low temperature, rDeltaF508 CFTR endocytosis slowed to WT rates (20% per 10 min), indicating that the cell-surface trafficking defect of rDeltaF508 CFTR is TS. Furthermore, rDeltaF508 CFTR is stabilized at the lower temperature; its half-life increases from <2 h at 37 degrees C to >8 h at 27 degrees C. Pharmacological chaperone treatment at 37 degrees C corrected the rDeltaF508 CFTR internalization defect, slowing endocytosis from approximately 30% per 2.5 min to approximately 5% per 2.5 min, and doubled DeltaF508 surface half-life from 2 to 4 h. These effects are DeltaF508 CFTR-specific, as pharmacological chaperones did not affect WT CFTR or transferrin receptor internalization rates. The results indicate that small molecular correctors may reproduce the effect of incubation at the permissive temperature, not only by rescuing DeltaF508 CFTR from ERAD, but also by enhancing its cell-surface stability.

Characterization of antioxidant activities of pulmonary surfactant mixtures

Instillation of intratracheal surfactant is known to limit the morbidity and mortality of patients and animals with oxidant-induced lung injury. In this study we quantified the antioxidant properties of natural lung surfactant (NLS), consisting of 90% lipid and 10% protein, and of calf lung surfactant extract (CLSE) consisting of 99% lipid and 1% protein. NLS, but not CLSE, contained significant amounts of superoxide dismutase (SOD) and catalase activities (7 U SOD/mumol phospholipid (PL) and 1 U catalase/mumol PL). More than 90% of the SOD activity was abolished by 1 mM KCN, suggesting that this was the CuZn form of the enzyme. In addition, NLS significantly reduced extracellular H2O2 without losing its ability to reach minimum surface tensions below 1 dyn/cm upon dynamic compression. The NLS scavenging of H2O2 could not be accounted for by albumin. The presence of catalase and SOD activities in NLS was also verified by activity stains of proteins separated by native polyacrylamide gel electrophoresis. Intratracheal instillation of 7 ml of NLS (308 mumol PL) into rabbits significantly increased SOD content in type II cells isolated 12 h later. It is concluded that, in addition to promoting alveolar stability, instillation of pulmonary surfactant may offer significant protection to the alveolar epithelium by scavenging extracellularly generated partially reduced oxygen species and by enhancing intracellular antioxidant enzyme content.

δ-subunit confers novel biophysical features to αβγ- human epithelial sodium channel (ENaC) via a physical interaction

Native amiloride-sensitive Na+ channels exhibit a variety of biophysical properties, including variable sensitivities to amiloride, different ion selectivities, and diverse unitary conductances. The molecular basis of these differences has not been elucidated. We tested the hypothesis that co-expression of δ-epithelial sodium channel (ENaC) underlies, at least in part, the multiplicity of amiloride-sensitive Na+ conductances in epithelial cells. For example, the δ-subunit may form multimeric channels with αβγ-ENaC. Reverse transcription-PCR revealed that δ-ENaC is co-expressed with αβγ-subunits in cultured human lung (H441 and A549), pancreatic (CFPAC), and colonic epithelial cells (Caco-2). Indirect immunofluorescence microscopy revealed that δ-ENaC is co-expressed with α-, β-, and γ-ENaC in H441 cells at the protein level. Measurement of current-voltage that cation selectivity ratios for the revealed relationships Na+/Li+/K+/Cs+/Ca2+/Mg2+, the apparent dissociation constant (Ki) for amiloride, and unitary conductances for δαβγ-ENaC differed from those of both αβγ- and δβγ-ENaC (n = 6). The contribution of the δ subunit to PLi/PNa ratio and unitary Na+ conductance under bi-ionic conditions depended on the injected cRNA concentration. In addition, the EC50 for proton activation, mean open and closed times, and the self-inhibition time of δαβγ-ENaC differed from those of αβγ- and δβγ-ENaC. Co-immunoprecipitation of δ-ENaC with α- and γ-subunits in H441 and transfected COS-7 cells suggests an interaction among these proteins. We, therefore, concluded that the interactions of δ-ENaC with other subunits could account for heterogeneity of native epithelial channels.