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Biomedical subjects

S D Revak

Publications and source records attributed to S D Revak.

At least 19 recordsLinked to original sources
PubMed1999

Bronchopulmonary segmental lavage with Surfaxin (KL(4)-surfactant) for acute respiratory distress syndrome.

We performed a trial to assess the safety and tolerability of sequential bronchopulmonary segmental lavage with a dilute synthetic surfactant (Surfaxin) in 12 adults with ARDS. Patients received one of three dosing regimens in which aliquots of Surfaxin were administered via a wedged bronchoscope to each of the 19 bronchopulmonary segments. Suctioning was performed 10-30 s after instillation of individual aliquots. Group 1 patients (n = 3) received one 30-ml aliquot of a 2.5-mg/ml concentration of Surfaxin in each segment, followed by a second 30-ml aliquot with a 10-mg/ml concentration. Group 2 patients (n = 4) received two 30-ml aliquots of the 2.5-mg/ml concentration followed by a third lavage with the 10-mg/ml concentration. Group 3 patients (n = 5) received therapy identical to that received by patients in Group 2 and were eligible for repeat dosing 6 to 24 h later. All patients tolerated the procedure. There were no serious adverse experiences ascribed to either the procedure or the surfactant. In the 96 h after treatment initiation, FI(O(2)) decreased from 0.80 to 0.52 and PEEP decreased from 10.3 to 7.6 cm H(2)O. Bronchoscopic "cleansing" of the lungs with dilute Surfaxin may offer a safe and feasible approach to improving outcomes in patients with ARDS. Wiswell TE, Smith RM, Katz LB, Mastroianni L, Wong DY, Willms D, Heard S, Wilson M, Hite RD, Anzueto A, Revak SD, Cochrane CG. Bronchopulmonary segmental lavage with Surfaxin (KL(4)-surfactant) for acute respiratory distress syndrome.

Bronchoalveolar Lavage↗
PubMed1998

Bronchoalveolar lavage with KL4-surfactant in models of meconium aspiration syndrome.

As a model of the meconium aspiration syndrome (MAS) of human infants, adult rabbits and newborn rhesus monkeys received intratracheal instillation of human meconium to induce pulmonary injury. Injured rabbits were ventilated with 100% O2 and divided into four treatment groups, receiving: 1) bronchoalveolar lavages (BAL) with dilute KL4-Surfactant; 2) lavages with equal volumes of sterile saline; 3) a single intratracheal bolus of KL4-Surfactant, 100 mg/kg; and 4) no treatment. The untreated rabbits developed atelectasis, a fall in pressure-volume levels and in partial pressure of O2 in arterial blood (PaO2) from approximately 500 to < 100 mm Hg, and severe pulmonary inflammation between 3 and 5 h after instillation of meconium. Rabbits treated by BAL with dilute KL4-Surfactant showed rapid and sustained recovery of PaO2 to approximately 300 mm Hg within minutes, a return toward normal pressure-volume levels, and diminished inflammation. Rabbits receiving BAL with saline failed to show recovery, and rabbits treated with a bolus of surfactant intratracheally exhibited a transient response by 1-2 h after treatment, but then returned to the initial atelectatic state. Newborn rhesus monkeys, after receiving human meconium intratracheally before the first breath, developed severe loss of pulmonary function. Treatment of these monkeys 1-5 h after birth with BAL with dilute KL4-Surfactant produced clearing of chest radiographs and a rapid improvement in pulmonary function with ratios of partial pressure of O2 in arterial blood to the fraction of O2 in the inspired air rising into the normal range where they remained through the 20-h period of study. The studies indicate that pulmonary function in two models of severe meconium injury respond rapidly to BAL with dilute KL4-Surfactant.

Animals↗
PubMed1996

The efficacy and safety of KL4-surfactant in preterm infants with respiratory distress syndrome.

The present study was undertaken to determine if a synthetic peptide, KLLLLKLLLLKLLLLKLLLLK (KL4), in which K = lysine and L = leucine, in an aqueous dispersion of phospholipids (DPPC and POPG), would expand pulmonary alveoli and improve gas exchange in premature human infants with respiratory distress syndrome (RDS). The KL4 peptide was synthesized to resemble the amino acid pattern of surfactant protein B (SP-B). Forty-seven infants with RDS were treated within 4 h of birth with the KL4-peptide/phospholipid mixture, called KL4-Surfactant. The average arterial-to-alveolar oxygen tension ratios (a/A O2) of 39 patients included in efficacy analyses rose from pretreatment values of 0.14 +/- 0.02 (mean +/- SEM) to 0.40 +/- 0.04 (normal value > or = 0.40) by 12 h of age. Mean airway pressures and oxygenation index values fell concomitantly, and expansion of the lungs was observed on radiographs. The median duration of mechanical ventilation was 5.0 d. Of the 39 included infants, 29 required only a single dose. Radiographic data indicate that those patients requiring a second instillation of KL4-Surfactant but not showing a sustained rise in a/A O2 ratios did, in fact, exhibit expansion of alveoli in the lung. There were no RDS-related deaths; the incidence of complications was no higher than found in other comparable published studies. The data demonstrate that the synthetic peptide, KL4, which mimics the hydrophobic and hydrophilic pattern of SP-B, when formulated in an aqueous dispersion with the phospholipids DPPC and POPG, creates a strong and durable surfactant activity as judged by expansion of pulmonary alveoli and improvement of gas exchange in infants with RDS.

Age Factors↗
PubMed1996

Efficacy of synthetic peptide-containing surfactant in the treatment of respiratory distress syndrome in preterm infant rhesus monkeys.

Studies were conducted to assess the efficacy and safety of a synthetic peptide-containing surfactant in the treatment of respiratory distress syndrome (RDS) in preterm (approximately 80% of normal gestation) infant rhesus monkeys. Surfactant was prepared consisting of the phospholipids dipalmitoylphosphatidyl choline and palmitoyl-oleoyl phosphatidyl glycerol and a synthetic peptide modeled after surfactant protein B (SP-B), "KL4-Surfactant" contained a peptide having the sequence KLLLLKLLLLKLLLLKLLLLK, where "K" is lysine and "L" is leucine. The peptide was selected because it mimics the repeating stretches of hydrophobic residues with intermittent basic hydrophilic residues seen in SP-B. KL4-Surfactant was shown to have biophysical activity assessed as the ability to lower surface tension at an air-liquid interface in a pulsating bubble surfactometer. Thirty premature rhesus monkeys were treated shortly after birth with one dose of KL4-Surfactant. The arterial to alveolar oxygen partial pressure ratio (a/A) was found to rise from a pretreatment level of 0.11 +/- 0.01 (mean +/- SEM), indicative of severe RDS, to 0.40 +/- 0.02 at 12-13 h post-treatment. The improvement in oxygenation persisted throughout the study period, with a mean a/A at 22-23 h of 0.45 +/- 0.07. Chest radiographs and gross and microscopic examination of the lungs all confirmed the reversal of the atelectasis seen before treatment. Animals treated with a dose of 200 mg/kg showed a faster, more consistent, and greater response than did a group treated with an average dose of 127 mg/kg. There was no evidence of toxicity after treatment with the higher dose as demonstrated by physiologic, hematologic, biochemical, and pathologic data. The importance of the peptide in the synthetic surfactant was apparent from the results obtained with a control group of nine premature monkeys treated with a non-peptide-containing surfactant; the a/A of this group was 0.15 +/- 0.03 at nine hours of age as compared with a value of 0.38 +/- 0.02 for 30 comparable animals receiving KL4-Surfactant.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1994

Protein-phospholipid interactions in pulmonary surfactant. The Parker B. Francis Lectureship.

SP-B is the protein in pulmonary surfactant with the greatest capacity to augment the phospholipids, ability to resist surface tension, and capability to prevent collapse of pulmonary alveoli. Synthetic peptides derived from the structure of SP-B and simplified analogues of these SP-B-derived peptides were found by tryptophan fluorescence to partition within the phospholipid layer in contact with both polar head groups and acyl side chains of the phospholipids. The intermittent hydrophilic basic residues were found to be essential for full activity, probably because of electrostatic interactions formed with phosphates of the polar head groups. The hydrophobic stretches of residues in SP-B and the related peptides supplement the activity through interaction with the phospholipid acyl side chains. By increasing intermolecular and intramolecular order of the phospholipid layer and thereby stability of the layer, the SP-B analogues provide strong surfactant activity. Simplified peptide analogues of SP-B, dispersed in DPPC and POPG, provide strong surfactant activity in vitro and in the lungs of premature infant rabbits, rhesus monkeys, and humans.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1993

Interactions of model human pulmonary surfactants with a mixed phospholipid bilayer assembly: Raman spectroscopic studies.

The temperature dependence and acyl chain packing properties of the binary lipid mixtures of dipalmitoylphosphatidylcholine-d62 (DPPC-d62)/dipalmitoylphosphatidylglycerol (DPPG) multilayers, reconstituted with two synthetic peptides for modeling the membrane behavior of the SP-B protein associated with human pulmonary surfactant, were investigated by vibrational Raman spectroscopy. The synthetic peptides consisted of 21 amino acid residues representing repeating charged units of either lysine or aspartic acid separated by hydrophobic domains consisting of four leucines (KL4 or DL4, respectively). These peptides were designed to mimic the alternating hydrophobic and hydrophilic sequences defining the low molecular weight SP-B protein. Raman spectroscopic parameters consisting of integrated band intensities, line widths, and relative peak height intensity ratios were used to probe the bilayer order/disorder characteristics of the liposomal perturbations reflected by the reconstituted membrane assemblies. Temperature profiles derived from the various Raman intensity parameters for the 3100-2800-cm-1 carbon-hydrogen (C-H) and the 2000-2300-cm-1 carbon-deuterium (C-D) stretching mode regions, spectral intervals representative of acyl chain vibrations, reflected lipid reorganizations specific to peptide interactions with either the DPPC-d62 or DPPG component of the liposome. For the multilamellar surfactant systems composed of either KL4 or DL4 reconstituted with the binary DPPG/DPPC-d62 lipid mixture, the breadth of the gel to liquid crystalline phase transition temperatures TM, defined by acyl chain C-H and C-D stretching mode order/disorder parameters, increased from about 1 degree C in the peptide-free systems to over 10 degrees C. This breadth in TM indicates an increased lipid disorder and a distinct noncooperative chain melting process for the model liposomes. In comparing the interactions of the synthetic peptides with DPPG/DPPC mixtures and with DPPC liposomes alone, the negatively charged DL4 peptide perturbs the DPPG component of the lipid mixture more strongly than the DPPC-d62 component; moreover, the DL4 peptide disrupts the structure of the DPPG lipid domains in the binary mixture to a greater extent than the KL4 peptide. The microdomain heterogeneity of the binary lipid mixture arising from lipid-peptide interactions is discussed in terms of the Raman spectral properties of the multilayers. The Raman data in conjunction with previous bubble surfactometer and animal studies (Cochrane & Revak, 1991) suggest that lipid domain structures are present in functional surfactants and that the dynamic bilayer microheterogeneity induced by the surfactant peptide or protein is essential for pulmonary mechanics.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

Pulmonary surfactant protein B (SP-B): structure-function relationships.

SP-B is a protein in pulmonary surfactant that is, in greatest part, responsible for resistance to surface tension and prevention of collapse of pulmonary alveoli. Peptides of 21 residues, synthesized following the sequence of SP-B or resembling the hydrophobic and hydrophilic domains of SP-B (such as RLLLLRLLLLRLLLLRLLLLR, R, Arg, and L, Leu), enhanced the abilities of phospholipids to reduce surface tension both in vitro and in vivo. Intermittent positively charged residues were essential for this activity. The SP-B-like peptides were found by tryptophan fluorescence to partition within the phospholipid layer in contact with both polar head groups and acyl side chains. These data, together with findings that the SP-B-related peptides increase inter- and intramolecular order of the phospholipid layer, suggest that SP-B resists surface tension by increasing lateral stability of the phospholipid layer.

Amino Acid Sequence↗
PubMed1991

Raman spectroscopic studies of model human pulmonary surfactant systems: phospholipid interactions with peptide paradigms for the surfactant protein SP-B.

The temperature dependence of dipalmitoylphosphatidylcholine (DPPC)/phosphatidylglycerol (PG) multilayers, reconstituted with various synthetic peptides for modeling human lung surfactant, was monitored by vibrational Raman spectroscopy. The synthetic peptides consisted, respectively, of residues 59-81 of the human surfactant protein SP-B and 21 amino acid residue peptides containing repeating units of arginine separated by either four or eight leucines (RL4 or RL8). Each peptide demonstrated the ability to reduce significantly the surface tension of analogues of the phospholipid mixture used in the Raman studies. Raman spectroscopic integrated band intensities and relative peak height intensity ratios, two spectral parameters used to determine bilayer disorder, provided sensitive probes for characterizing multilayer perturbations in the reconstituted liposomes. Temperature profiles derived from the various Raman intensity parameters for the 3100-2800-cm-1 carbon-hydrogen (C-H) stretching mode region, a spectral interval representative of acyl chain vibrations, reflected lipid reorganizations due to the bilayer interactions of these peptides. For the three reconstituted multilamellar surfactant systems, the gel-to-liquid-crystalline phase-transition temperatures Tm, defined by acyl chain C-H stretching mode order/disorder parameters, increased from 35 degrees C in the peptide free system to 37-38 degrees C, indicating increased lipid headgroup constraints for the model liposomes. Although the values of Tm were similar for the three recombinant lipid/peptide assemblies, individual phase-transition cooperativities varied significantly between systems and between spectroscopically derived order/disorder parameters.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

The use of synthetic peptides in the formation of biophysically and biologically active pulmonary surfactants.

Synthetic pulmonary surfactants consisting of mixtures of phospholipids with synthetic peptides based on the amino acid sequence of human surfactant apoprotein SP-B were prepared. These surfactants were analyzed for their ability to lower surface tension on a pulsating bubble surfactometer and for their capacity to improve lung compliance and increase alveolar expansion in a fetal rabbit model of surfactant deficiency. The data demonstrate that several peptides, ranging from 17 to 45 residues in length, matching the carboxy-terminal sequence of the SP-B protein, when appropriately recombined with the phospholipid dipalmitoylphosphatidylcholine and phosphatidylglycerol (3:1), are capable of producing a synthetic surfactant with biophysical and biologic activity approaching that of human surfactant derived from amniotic fluid.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1988

Use of human surfactant low molecular weight apoproteins in the reconstitution of surfactant biologic activity.

Two low molecular weight (LMW) apoproteins were isolated from human pulmonary surfactant. SDS polyacrylamide gel analysis showed one protein (SP 18) to have an apparent molecular weight of 18,000 when unreduced and 9,000 D after reduction. The second protein (SP 9) migrated at approximately 9,000 D in the presence or absence of reducing agents. Both proteins contain a high number of hydrophobic amino acids. The NH2-terminal sequence of SP 18 was determined to be: NH2-phe-pro-ile-pro-leu-pro-tyr-. A cDNA clone isolated from a human adult lung cDNA library contained a long open reading frame encoding at an internal position the human SP 18 amino-terminal sequence. Mixtures of phospholipids (PL) and SP 9 and SP 18 were assessed for their capacity to reduce surface tensions on a pulsating bubble surfactometer. The addition of 1% apoprotein resulted in a reduction of surface tension after 15 s from 42.9 dyn/cm for PL alone to 16.7 and 6.3 dyn/cm for preparations containing SP 9 and SP 18, respectively. In vivo assessment of reconstituted surfactant activity was performed in fetal rabbits. Reconstituted surfactant consisting of PL + 0.5% SP 18 instilled intratracheally at delivery resulted in a marked increase in lung compliance, while the incorporation of 0.5% SP 9 yielded a moderate increase. These data show the ability to produce biologically active surfactant by the addition of isolated LMW apoproteins to defined PL.

Amino Acid Sequence↗
PubMed1986

Reconstitution of surfactant activity using purified human apoprotein and phospholipids measured in vitro and in vivo.

The major apoprotein of human lung surfactant was isolated from amniotic fluid obtained at term gestation. It was found to be a disulfide-linked oligomer composed of polypeptide chains of 35,000 daltons. The monomeric unit was shown to be a glycoprotein, and treatment with peptide: N-glycosidase F resulted in a decrease in molecular weight to 31,000 daltons. The isolated apoprotein could be recombined in the presence of Ca++ with the phospholipids dipalmitoylphosphatidylcholine and phosphatidylglycerol (3:1) at a weight ratio of 1:100. The surface tension (gamma min) measured on a pulsating bubble formed in 4 mg/ml of phospholipids was reduced from 32.3 +/- 2.0 dyn X cm-1 to 18.0 +/- 0.6 dyn X cm-1 after 15 s when 1% apoprotein was present. Reduction of disulfide bonds and deglycosylation of the apoprotein did not alter its ability to lower gamma min. Fetal rabbits of 27 days gestation had instilled intratracheally at delivery, saline, phospholipids, phospholipids plus apoprotein, or natural human surfactant. The latter 2 resulted in increased lung compliance and striking improvement in homogeneous alveolar expansion when the lungs were expanded to 10 cm H2O pressure, fixed, and viewed histologically. This effect was also shown to be independent of the disulfide-dependent oligomeric structure of the apoprotein or its state of glycosylation. The surfactant produced by recombination of the phospholipids with the isolated apoprotein was, therefore, shown to be biophysically active both in vitro and in vivo. These data suggest that apoprotein can be recombined with phospholipids to produce a biologically active surfactant for use in clinical trials of human surfactant replacement.

Animals↗
PubMed1985

Experimental pulmonary inflammatory injury in the monkey.

Inflammatory pulmonary injury was induced in Macaca mulatta rhesus monkeys by the intrabronchial instillation of the formylated peptide norleu-leu-phe (FNLP) or phorbol myristate acetate (PMA). Indicators of pulmonary injury included an increase in mean protein content of bronchoalveolar lavage (BAL) fluid from 0.51 mg/ml in untreated animals to 3.74 mg/ml and 6.64 mg/ml in FNLP- and PMA-treated animals, respectively, the appearance of a diffuse pulmonary infiltrate in chest roentgenograms, and histologic evidence of a predominantly neutrophilic leukocytic infiltration. Concomitant with the appearance of pulmonary injury was the generation of proteases and oxidants in the BAL fluids. Neutrophil elastase, bound to alpha 1-protease inhibitor (alpha 1-PI), was found to increase from 0.47 micrograms/ml in untreated monkeys to 0.99 micrograms/ml in FNLP-treated animals and 1.23 micrograms/ml in monkeys receiving PMA. Radioiodinated human prekallikrein, instilled for 2 min into the inflammatory site and retrieved by lavaging, was found to have undergone proteolytic cleavage; this cleavage was not consistently inhibitable with the inclusion of antibody to elastase. BAL fluids were shown to contain an amidolytic activity when tested on the synthetic substrate H-D-pro-phe-arg-pNA. This activity was partially inhibitable with known inhibitors of active Hageman factor and kallikrein. beta-Glucuronidase levels in the BAL fluids increased from 0.85 U/ml to 4.36 U/ml and 8.25 U/ml in FNLP- and PMA-treated animals, respectively. Myeloperoxidase (MPO) levels also increased from 1.37 OD U/ml X min to 16.59 and 30.47 OD U/ml X min in the same groups of animals. Oxidant generation was also assessed in several different ways. The specific activity of the oxidant-sensitive inhibitor alpha 1-PI recovered in the BAL fluid decreased from 0.80 in control samples to 0.57 and 0.65 in FNLP- and PMA-treated animals. That this inactivation was due to oxidant injury of the molecule was confirmed by the return to full activity of four out of five BAL samples after their incubation with the reducing agent dithiothreitol in the presence of methionine sulfoxide peptide reductase. The specific activity of catalase in the BAL fluids of animals given 3-amino, 1,2,4 triazole (AT) 1 h before lavaging showed drops from 0.97 in untreated monkeys to 0.04 in FNLP-treated and 0.49 in PMA-treated monkeys. MPO levels also fell in the AT-treated injured animals from 16.59 to 0.85 delta OD/min X ml in FNLP animals in the absence and presence of AT, and 30.47 to 0.60 delta OD/min X ml in PMA-treated animals. Inhibition of MPO by AT was shown in vitro to be H2O2 dependent. Total glutathione levels in the BAL fluids did not change appreciably after FNLP or PMA treatment. These studies present substantial evidence of the generation of both proteases and oxidants during the establishment of acute pulmonary inflammatory injury in an experimental primate model.

Animals↗
PubMed1984

Proteases and oxidants in experimental pulmonary inflammatory injury.

We have examined various biochemical parameters of pulmonary inflammation in experimental animals. Intrabronchial instillation of glucose oxidase-glucose (GO/G) to produce oxidants or formylated norleu-leu-phe (FNLP) or phorbol myristate acetate (PMA) as leukocytic stimuli induced severe acute pulmonary injury in New Zealand white rabbits. PMA also induced inflammation when administered intravenously. Each stimulus induced transudation of protein from the vascular space into the pulmonary tissues, and an influx of leukocytes during the 4-6 h period of the experiment. Pathophysiologic changes were measured by edema formation (transudation of 125I-bovine serum albumin), and histologic examination. Biochemical analysis was performed by measuring concentrations of potentially injurious agents in bronchoalveolar lavage (BAL) fluid. Increased acid protease and myeloperoxidase levels were found in the BAL fluid after administration of either of the stimuli. Evidence of oxidant generation in vivo was obtained in two different ways. In the first, specific activities for catalase were measured in the BAL fluid in the presence or absence of 3-amino, 1,2,4 triazole (AT), injected at intervals before obtaining BAL fluid. In the presence of AT, specific activities for catalase dropped to 0.22 after a double instillation of FNLP and to 0.15 in the presence of GO/G. In neutrophil-depleted FNLP animals, catalase was not greatly inhibited by AT (sp act 0.90). In the second, intracellular levels of total glutathione (GSH + GSSG) in whole lung tissue and alveolar macrophages decreased when stimuli of neutrophils were administered. Intrabronchially instilled PMA, e.g., caused a drop of glutathione in whole lung tissue from the control value of 2.3 mumol GSH equivalent/100 mg dry wt to 0.54 mumol GSH equivalent/100 mg dry wt at 4 h. Neutrophil depletion and superoxide dismutase protected from this effect. From these results, we conclude that O-2 or its metabolites can initiate severe pulmonary injury as shown by the effect of GO/G and that, during development of pulmonary injury, stimulated neutrophils generate oxidants and release proteolytic enzymes into the surrounding tissues.

Animals↗
PubMed1984

Biochemical factors in pulmonary inflammatory disease.

Various biochemical events taking place during pulmonary inflammation were examined in the bronchoalveolar lavage (BAL) fluids from patients with acute respiratory distress syndrome (ARDS) and in experimental animal models. In patients with ARDS, active neutrophil elastase was found in the BAL fluids. In these fluids, inactivation of the major elastase inhibitor alpha 1-protease inhibitor (alpha 1-PI) occurred. This was caused by oxidation of a methionine residue at the active site of the alpha 1-PI, and offered indirect evidence of oxidation occurring in the inflamed pulmonary tissues. Studies with experimental animals have been initiated to gain understanding of the relative roles of proteases, oxidants, arachidonate metabolites, complement and contact system components, and other mediators in the pathogenesis of pulmonary inflammation. Intrabronchial instillation of glucose oxidase/glucose to produce oxidants or formylated norleucylleucylphenylalanine or phorbol myristate acetate as leukocytic stimuli induced severe acute pulmonary injury in New Zealand white rabbits and rhesus monkeys. The injury was accompanied by leukocytic protease (acid cathepsins) release in rabbit lungs and oxidant formation, and could be inhibited by neutrophil depletion. Oxidant formation was demonstrated by the inactivation of catalase by 3-amino-1,2,4-triazole in the presence of H2O2, a drop in intracellular glutathione levels, and in the rhesus monkey by inactivation of alpha 1-PI.

Animals↗
PubMed1983

The plasma contact system in atopic asthma.

An in vitro test for the rate of appearance of kallikrein in plasma due to contact system activation by dextran sulfate at 0 degree C was applied to plasmas of 19 atopic asthma patients and 19 age- and sex-matched controls without atopy. The average prekallikrein activation rate was markedly higher in the plasmas of the atopic patients. Mean endogenous heparin levels were also elevated.

Adolescent↗
PubMed1983

Pathogenesis of the adult respiratory distress syndrome. Evidence of oxidant activity in bronchoalveolar lavage fluid.

Evidence is presented indicating that oxidants are generated in lungs of patients with the adult respiratory distress syndrome (ARDS). The evidence was derived from observations that alpha-1-PI, recovered in bronchoalveolar lavage (BAL) fluid, had been inactivated by oxidation, presumably oxidation of the methionyl residue in the reaction site of the molecule. This was indicated by findings that activity of the alpha-1-PI could be restored by exposure to the reducing agent, dithiothreitol in the presence of methionyl sulfoxide peptide reductase. The amount of activity restored was proportional to the amount of inactive alpha-1-PI present at 52,000 D. Oxidation of the 52,000-D alpha-1-PI was also revealed by the finding that the inactive molecule was subject to proteolytic cleavage to 47,000 D when exposed to porcine pancreatic elastase, a characteristic of alpha-1-PI with oxidized methionyl residues in the reactive site. Inactivation of the alpha-1-PI in vivo also resulted from complexing to an active enzyme, shown previously to be neutrophil elastase, and from proteolytic cleavage in vivo, that produced a fragment of 47,000 mol wt. In contrast to that in BAL fluids, the alpha-1-PI in plasma of patients with respiratory distress syndrome was found to be greater than 90% active in 14 of 22 cases and 50-90% active in 8 cases. This suggested that for the most part, alpha-1-PI was inactivated after leaving the vessels and entering the lung. The circulating alpha-1-PI in patients with the respiratory distress syndrome was found to be equally susceptible to oxidative inactivation as alpha-1-PI from normal individuals. It seems improbable therefore that patients develop ARDS because of labile alpha-1-PI inhibitor.

Adult↗