Biomedical subjects

Gabor Szabo

Publications and source records attributed to Gabor Szabo.

At least 19 recordsLinked to original sources

PubMed2026

The transcription factor BACH1 couples chromatin priming and repression to enable macrophage plasticity and adaptation.

Macrophage activation and tissue adaptation involve precise transcriptional control by lineage-determining transcription factors (LDTFs) and stimulus-dependent TFs. The heme-regulated transcriptional repressor BACH1 clusters with myeloid LDTFs in unstimulated macrophages, suggesting a role in shaping macrophage identity and function. We found that BACH1 bound to both inactive and active regulatory regions, including latent enhancers. BACH1 recruited the NuRD complex and had dual functions, establishing early chromatin accessibility while actively repressing transcription. Upon inflammatory stimulation, BACH1 rapidly redistributed in cis to nearby promoters, reshaping chromatin occupancy, motif specificity, and enhancer-promoter interactions. BACH1 constrained 3D chromatin architecture, limiting enhancer mobility and TF complex dynamics. In vivo, Bach1 deletion impaired macrophage polarization and tissue adaptation and limited resilience during systemic and regenerative inflammation. Thus, BACH1 acts as an early chromatin accessibility-priming factor while actively repressing transcription-a regulatory activity that can be defined as pioneer repression-thereby shaping the macrophage epigenome in response to inflammatory and tissue contexts.

Basic-Leucine Zipper Transcription Factors↗

PubMed2007

hORFeome v3.1: a resource of human open reading frames representing over 10,000 human genes.

Complete sets of cloned protein-encoding open reading frames (ORFs), or ORFeomes, are essential tools for large-scale proteomics and systems biology studies. Here we describe human ORFeome version 3.1 (hORFeome v3.1), currently the largest publicly available resource of full-length human ORFs (available at ). Generated by Gateway recombinational cloning, this collection contains 12,212 ORFs, representing 10,214 human genes, and corresponds to a 51% expansion of the original hORFeome v1.1. An online human ORFeome database, hORFDB, was built and serves as the central repository for all cloned human ORFs (http://horfdb.dfci.harvard.edu). This expansion of the original ORFeome resource greatly increases the potential experimental search space for large-scale proteomics studies, which will lead to the generation of more comprehensive datasets.

Animals↗

PubMed2006

Electrostatic couplings in OmpA ion-channel gating suggest a mechanism for pore opening.

The molecular forces that drive structural transitions between the open and closed states of channels and transporters are not well understood. The gate of the OmpA channel is formed by the central Glu52-Arg138 salt bridge, which can open to form alternate ion pairs with Lys82 and Glu128. To gain deeper insight into the channel-opening mechanism, we measured interaction energies between the relevant side chains by double-mutant cycle analysis and correlated these with the channel activities of corresponding point mutants. The closed central salt bridge has a strong interaction energy of -5.6 kcal mol(-1), which can be broken by forming the open-state salt bridge Glu52-Lys82 (DeltaDeltaG(Inter) = -3.5 kcal mol(-1)) and a weak interaction between Arg138 and Glu128 (DeltaDeltaG(Inter) = -0.6 kcal mol(-1)). A covalent disulfide bond in place of the central salt bridge completely blocks the channel. Growth assays indicate that this gating mechanism could physiologically contribute to the osmoprotection of Escherichia coli cells from environmental stress.

Amino Acids↗

PubMed2006

Random mutagenesis of Helicobacter pylori vacA to identify amino acids essential for vacuolating cytotoxic activity.

VacA is a secreted toxin that plays a role in Helicobacter pylori colonization of the stomach and may contribute to the pathogenesis of peptic ulcer disease and gastric cancer. In this study, we analyzed a library of plasmids expressing randomly mutated forms of recombinant VacA and identified 10 mutant VacA proteins that lacked vacuolating cytotoxic activity when added to HeLa cells. The mutations included six single amino acid substitutions within an amino-terminal hydrophobic region and four substitutions outside the amino-terminal hydrophobic region. All 10 mutations mapped within the p33 domain of VacA. By introducing mutations into the H. pylori chromosomal vacA gene, we showed that secreted mutant toxins containing V21L, S25L, G121R, or S246L mutations bound to cells and were internalized but had defects in vacuolating activity. In planar lipid bilayer and membrane depolarization assays, VacA proteins containing V21L and S25L mutations were defective in formation of anion-selective membrane channels, whereas proteins containing G121R or S246L mutations retained channel-forming capacity. These are the first point mutations outside the amino-terminal hydrophobic region that are known to abrogate vacuolating toxin activity. In addition, these are the first examples of mutant VacA proteins that have defects in vacuolating activity despite exhibiting channel activities similar to those of wild-type VacA.

Amino Acid Substitution↗

PubMed2006

PUVA treatment of the nasal cavity improves the clinical symptoms of allergic rhinitis and inhibits the immediate-type hypersensitivity reaction in the skin.

We earlier reported that intranasal irradiation with the 308 nm xenon chloride (XeCl) ultraviolet-B laser and irradiation with a combination of ultraviolet-B (UVB), ultraviolet-A (UVA) and visible light (VIS) is highly effective in the treatment of allergic rhinitis and inhibit the immediate-type hypersensitivity reaction in the skin. Since photochemotherapy with 8-methoxypsoralen (8-MOP) plus UVA light (PUVA) is widely used in the treatment of different inflammatory skin disorders due to its immunosuppressive effect, in the present study we investigated the efficacy of intranasal PUVA treatment in allergic rhinitis and the effect of PUVA treatment on the skin prick test (SPT) reaction. An open study was performed in 17 patients with hay fever. Intranasal PUVA therapy was given four times weekly for 3 weeks. The treatment was started with a fluence of 0.5x of the individual minimal phototoxic dose (MPD) and the dosages were gradually increased. Evaluation was based on the symptom scores. The effect of PUVA treatment on the allergen-induced wheal formation was also studied in the SPT. PUVA treatment of the nasal cavity significantly decreased the nasal symptoms of the patients with allergic rhinitis. Treatment of the skin with PUVA also significantly suppressed the allergen-induced wheal formation in the SPT reaction. These data suggest that intranasal PUVA phototherapy is also an effective modality in the treatment of allergic rhinitis.

Administration, Intranasal↗

PubMed2006

Investigation of retrospective respiratory gating techniques for acquisition of thin-slice 4D-Multidetector-computed Tomorgraphy (MDCT) of the lung: Feasibility study in a large animal model.

Respiratory gated 3D-MDCT acquisition of the whole chest over time (4D-MDCT) allow retrospective reconstruction of raw data at any point of the respiratory cycle might be beneficial in severely ill or sedated patients. Aim of this feasibility study was to investigate 2 prototype devices as input for retrospective respiratory gating in order to calculate lung volumes (LVs) and mean lung densities (MLDs) over time. Sixteen-row MDCT data were acquired in 5 ventilated pigs using a laser sensor and charge-coupled devine (CCD) camera and retrospectively reconstructed at every 10% of the respiratory cycle. Semiautomatic segmentation of the 3D data sets was performed, and LV and MLD were calculated. Data acquisition was successful in all cases. The mean difference of LV between maximum inspiration and expiration was 246 and 240 mL (laser and CCD, respectively). The mean difference of MLD between inspiration and expiration was 70 (laser) and 67 (CCD) HU. The lowest MLD was found at the beginning of the respiratory cycle (0%) for laser, and at 90% for CCD. Both gating devices allowed for reliable 4D-MDCT image acquisition. No differences were found for calculated LV and MLD, whereas the respiratory cycle was more precisely detected using the laser based gating device.

Animals↗

PubMed2006

Free-breathing three-dimensional computed tomography of the lung using prospective respiratory gating: charge-coupled device camera and laser sensor device in an animal experiment.

PURPOSE: The aim was to investigate the feasibility and image quality of prospective respiratory gating for 3-D computed tomography (CT) of the lung. MATERIAL AND METHODS: Eight anesthetized pigs underwent prospectively gated multidetector computed tomography using 2 devices: a charge-coupled device (CCD) camera and a laser sensor. The output signal of both gating devices was connected to the scanner instead of ECG unit. Inspiratory and expiratory images were obtained during "free-breathing" and analyzed in MPR mode for sharpness of bronchi, diaphragm and lung using a 4-point-score (1, excellent to 4, severe artifacts). RESULTS: The CCD camera worked in all animals. Using the laser sensor, only 50% of expiratory scans could be acquired. All acquired images showed excellent sharpness (CCD camera vs. laser sensor) for trachea (1.1 +/- 0.3 vs. 1.3 +/- 0.5), bronchi (1.4 +/- 0.7 vs. 1.8 +/- 0.6), lung fissures (1.0 vs. 1.1 +/- 0.3), and lung parenchyma (1.0 +/- 0.2 vs. 1.4 +/- 0.6), and minor to major artifacts for diaphragm (1.5 +/- 0.8 vs. 2.0 +/- 1.0, P < 0.05) and pericardial lung structures (1.9 +/- 0.7 vs. 2.3 +/- 0.5). CONCLUSION: High image quality for inspiratory and expiratory scans was achieved by free-breathing 3-D CT of the lung using noncontact prospective respiratory gating.

Animals↗

PubMed2005

S100A1 gene therapy preserves in vivo cardiac function after myocardial infarction.

Myocardial infarction (MI) represents an enormous clinical challenge as loss of myocardium due to ischemic injury is associated with compromised left ventricular (LV) function often leading to acute cardiac decompensation or chronic heart failure. S100A1 was recently identified as a positive inotropic regulator of myocardial contractility in vitro and in vivo. Here, we explore the strategy of myocardial S100A1 gene therapy either at the time of, or 2 h after, MI to preserve global heart function. Rats underwent cryothermia-induced MI and in vivo intracoronary delivery of adenoviral transgenes (4 x 10(10) pfu). Animals received saline (MI), the S100A1 adenovirus (MI/AdS100A1), a control adenovirus (MI/AdGFP), or a sham operation. S100A1 gene delivery preserved global in vivo LV function 1 week after MI. Preservation of LV function was due mainly to S100A1-mediated gain of contractility of the remaining, viable myocardium since contractile parameters and Ca(2+) transients of isolated MI/AdS100A1 myocytes were significantly enhanced compared to myocytes isolated from both MI/AdGFP and sham groups. Moreover, S100A1 gene therapy preserved the cardiac beta-adrenergic inotropic reserve, which was associated with the attenuation of GRK2 up-regulation. Also, S100A1 overexpression reduced cardiac hypertrophy 1 week post-MI. Overall, our data indicate that S100A1 gene therapy provides a potential novel treatment strategy to maintain contractile performance of the post-MI heart.

Adenoviridae↗

PubMed2005

Mimicry of a host anion channel by a Helicobacter pylori pore-forming toxin.

Bacterial pore-forming toxins have traditionally been thought to function either by causing an essentially unrestricted flux of ions and molecules across a membrane or by effecting the transmembrane transport of an enzymatically active bacterial peptide. However, the Helicobacter pylori pore-forming toxin, VacA, does not appear to function by either of these mechanisms, even though at least some of its effects in cells are dependent on its pore-forming ability. Here we show that the VacA channel exhibits two of the most characteristic electrophysiological properties of a specific family of cellular channels, the ClC channels: an open probability dependent on the molar ratio of permeable ions and single channel events resolvable as two independent, voltage-dependent transitions. The sharing of such peculiar properties by VacA and host ClC channels, together with their similar magnitudes of conductance, ion selectivities, and localization within eukaryotic cells, suggests a novel mechanism of toxin action in which the VacA pore largely mimics the electrophysiological behavior of a host channel, differing only in the membrane potential at which it closes. As a result, VacA can perturb, but not necessarily abolish, the homeostatic ionic imbalance across a membrane and so change cellular physiology without necessarily jeopardizing vitality.

Anions↗

PubMed2005

SCAMP2 interacts with Arf6 and phospholipase D1 and links their function to exocytotic fusion pore formation in PC12 cells.

SNAP receptor (SNARE)-mediated fusion is regarded as a core event in exocytosis. Exocytosis is supported by other proteins that set up SNARE interactions between secretory vesicle and plasma membranes or facilitate fusion pore formation. Secretory carrier membrane proteins (SCAMPs) are candidate proteins for functioning in these events. In neuroendocrine PC12 cells, SCAMP2 colocalizes on the cell surface with three other proteins required for dense-core vesicle exocytosis: phospholipase D1 (PLD1), the small GTPase Arf6, and Arf6 guanine nucleotide exchange protein ARNO. Arf6 and PLD1 coimmunoprecipitate (coIP) with SCAMP2. These associations have been implicated in exocytosis by observing enhanced coIP of Arf6 with SCAMP2 after cell depolarization and in the presence of guanosine 5'-O-(3-thio)triphosphate and by inhibition of coIP by a SCAMP-derived peptide that inhibits exocytosis. The peptide also suppresses PLD activity associated with exocytosis. Using amperometry to analyze exocytosis, we show that expression of a point mutant of SCAMP2 that exhibits decreased association with Arf6 and of mutant Arf6 deficient in activating PLD1 have the same inhibitory effects on early events in membrane fusion. However, mutant SCAMP2 also uniquely inhibits fusion pore dilation. Thus, SCAMP2 couples Arf6-stimulated PLD activity to exocytosis and links this process to formation of fusion pores.

ADP-Ribosylation Factor 6↗

PubMed2005

Increased aortic wall stress in aortic insufficiency: clinical data and computer model.

OBJECTIVE: The study was aimed at determining which cardiac pathologies are associated with increased longitudinal stress in the aorta and therefore may be responsible for the intimal transverse tears seen in aortic dissections. METHODS: Aortic root contrast injections were analyzed in 90 cardiac patients to measure the downward motion of the annulus during a cardiac cycle. A finite element model of the pressurized aortic root, arch and supra-aortic vessels was created to assess the influence of the aortic root motion on the aortic wall stress. RESULTS: The axial displacement of the aortic root ranged from 0 to 14 mm. A multivariate analysis showed that aortic insufficiency (AI) grade, hypokinesis of the left ventricle (HKI), and myocardial hypertrophy (HTR) were 3 independent variables which correlated with the axial displacement of the aortic root (DISP), such that ARM (mm)=5.379 (P<0.0001) +1.186 x AI grade (P=0.0016) - 1.611 x HKI (P=0.0078) - 1.399 x HTR (P=0.0355) with R2=0.23. The major finding of the stress analysis was that in the ascending aorta, at approximately 2 cm above the sino-tubular junction, the longitudinal stress due to aortic root motion was 32% higher in patients with AI than in patients without AI, thereby increasing the risk of transverse intimal rupture. CONCLUSIONS: Cardiac patients with AI are likely to experience enhanced longitudinal stress in the ascending aorta due to increased aortic root motion. Thus, these patients should be targeted and their aortic root movement monitored because it may be an important risk factor for aortic dissection.

Adult↗

PubMed2005

Rhinophototherapy: a new therapeutic tool for the management of allergic rhinitis.

BACKGROUND: Phototherapy has a profound immunosuppressive effect and is able to inhibit hypersensibility reactions in the skin. OBJECTIVE: We evaluated whether phototherapy using a combination of UV-B (5%), UV-A (25%), and visible light (70%), referred to as mUV/VIS, is effective in treating allergic rhinitis. METHODS: We conducted a randomized, double-blind study, in 49 patients with hay fever. The study was performed during the ragweed season. Each intranasal cavity was illuminated 3 times a week for 3 weeks with mUV/VIS or with low-intensity visible light. Symptom scores, inflammatory cells, and their mediators were assessed in nasal lavages. In vitro effects of mUV/VIS irradiation on T-cell and eosinophil apoptosis and its inhibitory effect on mediator release from basophils were examined. RESULTS: Rhinophototherapy was tolerated well and resulted in a significant improvement of clinical symptoms for sneezing (P < .016), rhinorrhea (P < .007), nasal itching (P < .014), and total nasal score (P < .004). None of the scores improved significantly in the control group. Scores for nasal obstruction slightly improved after mUV/VIS treatment and significantly increased in the control group (P < .017). In the nasal lavage, phototherapy significantly reduced the number of eosinophils and the level of eosinophil cationic protein and IL-5. In vitro irradiation of T cells and eosinophils with mUV/VIS light dose-dependently induced apoptosis. Furthermore, mUV/VIS irradiation inhibited the mediator release from RBL-2H3 basophils. CONCLUSION: These results suggest that phototherapy is an effective modality to treat allergic rhinitis and offer new options for the treatment of immune-mediated mucosal diseases.

Apoptosis↗

PubMed2005

Are there surgical implications to aortic root motion?

BACKGROUND AND AIM OF THE STUDY: By increasing the longitudinal stress in the ascending aorta, downward movement of the aortic root might promote the proximal transverse tears seen in aortic dissections. The study aim was to evaluate the influence of five common cardiac conditions on the magnitude of aortic root displacement in cardiac patients. METHODS: Aortic root contrast injections were analyzed in 90 patients (mean age 68 years) to measure downward motion of the root perpendicular to the plane of the sinotubular junction (STJ). RESULTS: Displacement of the aortic root ranged from 0 to 14 mm (mean 4.8 mm). Patients with aortic insufficiency (AI) showed increased aortic root movement (7.3 versus 4.3 mm, p = 0.003), whereas those with left ventricular hypokinesis (3.7 versus 5.5 mm, p = 0.014) or with myocardial hypertrophy (3.8 versus 5.1 mm, p = 0.073) exhibited reduced downward movement. These variables were independent, and correlated with the magnitude of aortic root motion. A stress analysis of the aortic root, arch and branches of the arch determined that the longitudinal stress approximately 2 cm above the STJ, in the outer curve of the aorta, was increased by 32% in patients with AI compared to patients without AI. CONCLUSION: Patients with cardiac conditions associated with increased aortic root motion such as AI may be at greater risk of aortic dissection because of increased longitudinal stress in the ascending aorta. Therefore, AI should be used as an indicator and aortic root displacement monitored to prevent the risk of aortic dissection.

Adult↗

PubMed2004

Intranasal irradiation with the xenon chloride ultraviolet B laser improves allergic rhinitis.

We earlier reported that the 308 nm xenon chloride (XeCl) ultraviolet B (UVB) laser is highly effective for the treatment of inflammatory skin diseases. Since UVB irradiation has been shown to exert both local and systemic immunosuppression, we investigated the clinical efficacy of UVB irradiation in allergic rhinitis. In an open study, groups of patients with severe allergic rhinitis received intranasal irradiation with a 308 nm XeCl UVB excimer laser for two weeks. In the low-dose group (n=10), treatment was given twice weekly, starting with 0.25x the individual minimal erythema dose (MED), whereas patients in the medium-dose group (n=8) were treated four times weekly, starting with 0.4x MED. In each group, the dosage was gradually increased. Evaluation was based on the symptom scores. The effect of the XeCl laser on the skin prick test reaction was also studied. In the low-dose group, seven patients completed the study, and there was no improvement in the nasal symptoms. In the medium-dose group, the XeCl UVB irradiation significantly inhibited the rhinorrhoea, the sneezing, the nasal obstruction and the total nasal score (p<0.05). The XeCl UVB excimer laser also inhibited the allergen-induced skin prick test in a dose-dependent manner. These results suggest that the XeCl UVB excimer laser might serve as a new therapeutic tool in the treatment of allergic rhinitis.

Adolescent↗

PubMed2004

NDP kinase moves into developing primary cilia.

Inmunofluorescence staining of murine NIH3T3 fibroblasts grown at high density shows that conventional nucleoside diphosphate (NDP) kinases A and B localize to a sensory organelle, the primary cilium. Similar results are obtained with Xenopus A6 kidney epithelial cells, suggesting that NDP kinases are a universal component of the primary cilium. The translocation of NDP kinase into primary cilia depends on size, taking place only when cilia reach a critical length of 5-6 microm. In mature cilia, NDP kinases are distributed along the ciliary shaft in a punctate pattern that is distinct from the continuous staining observed with acetylated alpha-tubulin, a ciliary marker and axonemal component. Isolation of a fraction enriched in primary cilia from A6 cells led to the finding that ciliary NDP kinase is enzymatically active, and is associated with the membrane and the matrix, but not the axoneme. In contrast, acetylated alpha-tubulin is found in the axoneme and, to a lesser extent, in the membrane. Based on the tightly regulated translocation process and the subciliary distribution pattern of NDP kinase, we propose that it plays a role in the elongation and maintenance of primary cilia by its ability to regenerate the GTP utilized by ciliary microtubule turnover and transmembrane signaling.

Animals↗

PubMed2003

Receptor activation regulates cortical, but not vesicular localization of NDP kinase.

We used immunofluorescence techniques to determine the localization of nucleoside diphosphate (NDP) kinase in NIH-3T3 fibroblasts. We found that cytoplasmic NDP kinase can be separated into two populations according to subcellular localization and response to extracellular stimuli. Specifically, within minutes of stimulation of resting fibroblasts with serum, growth factors or bombesin, a portion of NDP kinase becomes associated with membrane ruffles and lamellipodia. Another pool of NDP kinase accumulates independently of stimulation around intracellular vesicles. Transfection of cells with activated Rac mimics, whereas expression of dominant negative Rac inhibits, the effects of extracellular stimulation on the translocation of NDP kinase to the cell cortex. Neither Rac mutant affects the vesicle-associated pool. Association of NDP kinase with vesicles depends on microtubule integrity and is disrupted by nocodazole. In cell-free assays NDP kinase binds tightly to membrane vesicles associated with taxol-stabilized microtubules. Binding of NDP kinase to this fraction is reduced by ATP and abolished by GTP, as well as guanine nucleotides that are NDP kinase substrates. Thus, the localization of the two NDP kinase pools identified here is regulated independently by distinct cellular components: the appearance of cortical NDP kinase is a consequence of Rac activation, whereas vesicular NDP kinase is responsive to microtubule dynamics and nucleotides, in particular GTP. These results suggest that in fibroblasts NDP kinase participates in Rac-related cortical events and in GTP-dependent processes linked to intracellular vesicle trafficking.

Animals↗

PubMed2003

Essential role of a GXXXG motif for membrane channel formation by Helicobacter pylori vacuolating toxin.

Helicobacter pylori secretes a toxin, VacA, that can form anion-selective membrane channels. Within a unique amino-terminal hydrophobic region of VacA, there are three tandem GXXXG motifs (defined by glycines at positions 14, 18, 22, and 26), which are characteristic of transmembrane dimerization sequences. The goals of the current study were to investigate whether these GXXXG motifs are required for membrane channel formation and cytotoxicity and to clarify the role of membrane channel formation in the biological activity of VacA. Six different alanine substitution mutations (P9A, G13A, G14A, G18A, G22A, and G26A) were introduced into the unique hydrophobic region located near the amino terminus of VacA. The effects of these mutations were first analyzed using the TOXCAT system, which permits the study of transmembrane oligomerization of proteins in a natural membrane environment. None of the mutations altered the capacity of ToxR-VacA-maltose-binding protein fusion proteins to insert into a membrane, but G14A and G18A mutations markedly diminished the capacity of the fusion proteins to oligomerize. We then introduced the six alanine substitution mutations into the vacA chromosomal gene of H. pylori and analyzed the properties of purified mutant VacA proteins. VacA-G13A, VacA-G22A, and VacA-G26A induced vacuolation of HeLa cells, whereas VacA-P9A, VacA-G14A, and VacA-G18A did not. Subsequent experiments examined the capacity of each mutant toxin to form membrane channels. In a planar lipid bilayer assay, VacA proteins containing G13A, G22A, and G26A mutations formed anion-selective membrane channels, whereas VacA proteins containing P9A, G14A, and G18A mutations did not. Similarly, VacA-G13A, VacA-G22A, and VacA-G26A induced depolarization of HeLa cells, whereas VacA-P9A, VacA-G14A, and VacA-G18A did not. These data indicate that an intact proline residue and an intact G(14)XXXG(18) motif within the amino-terminal hydrophobic region of VacA are essential for membrane channel formation, and they also provide strong evidence that membrane channel formation is essential for VacA cytotoxicity.

Anion Transport Proteins↗

PubMed2003

Inhaled nitric oxide inhibits platelet-leukocyte interactions in patients with acute respiratory distress syndrome.

INTRODUCTION: In addition to its effects on platelet function, recent studies suggest that inhaled nitric oxide (NO) also influences the function of circulating leukocytes. Therefore, the aim of this work was to investigate the formation of platelet-leukocyte aggregates (PLAs) and platelet and leukocyte cell surface receptor expression during NO therapy in patients with acute respiratory distress syndrome. METHODS: In 16 patients responding to NO therapy with an improvement in oxygenation (NO group) and in four nonresponders (control), platelet P-selectin expression, platelet fibrinogen binding, the expression CD11a on leukocytes, and the formation of PLAs were investigated at 0, 60, 120, and 180 mins of therapy or at corresponding time points by means of flow cytometry. In addition, PLA was investigated in 30 healthy volunteers during NO inhalation, in five mechanically ventilated patients without acute respiratory distress syndrome and without NO inhalation, and during NO incubation in platelet-rich plasma of ten healthy volunteers in vitro. RESULTS: NO therapy inhibited PLA formation at 60 (13% +/- 4% in the NO group vs. 19% +/- 7% in the control group, p <.01) and 120 mins (14% +/- 4% vs. 18% +/- 7%, p <.05) and slightly decreased CD11a expression at 60 mins (152 +/- 22 arbitrary units vs. 187 +/- 36 arbitrary units, p <.05). Furthermore, besides inhibiting platelet fibrinogen binding, NO also led to a significant inhibition of P-selectin expression at 120 (38% +/- 4% vs. 43% +/- 5%, p <.05) and 180 mins (34% +/- 5% vs. 43% +/- 6%, p <.01), demonstrating a significant correlation between changes in P-selectin expression and PLA formation. In contrast, PLA formation was not influenced by mechanical ventilation in patients without acute respiratory distress syndrome. These results were further supported by additional studies showing inhibition of PLA formation in healthy volunteers as well. CONCLUSIONS: NO-dependent inhibition of PLA formation in patients with acute respiratory distress syndrome can be explained by the inhibition in platelet P-selectin expression. Thus, this study provides rational evidence of systemic antileukocytic and antiplatelet properties of NO therapy in the clinical setting.

Administration, Inhalation↗