Effects of arachidonic acid, monohydroxyeicosatetraenoic acid and prostaglandins on the release of mucous glycoproteins from human airways in vitro

The physiology of stress and its relationship to mechanisms of disease and therapeutics

Although stress reactions are organized to protect the homeostatic state of animals, they contain elements that may either enhance or diminish susceptibility to disease processes; in many instances, however, stress reactions themselves may induce pathologic change. It is important, therefore, that the veterinary clinician recognize the elements of a stress reaction and understand the mechanisms of disease with which they interact. This article provides a classification of stress stimuli that can be applied when considering interactions between stress reactions and disease processes.

Neonatal adaptation to stress of parturition and dystocia

The fetal animal undergoes a tremendous transition from intrauterine to extrauterine life at parturition. In this article, the maternal-fetal interactions of parturition are discussed with the aim of examining the normal stress reactions of parturition. Dystocia is discussed from the standpoint of additional distress of the newborn, with an aim toward the development of rational therapeutic support.

Studies in the guinea-pig with ICI 185,282: a thromboxane A2 receptor antagonist

The effects of ICI 185,282 (5(Z)-7-([ 2,4,5-cis]-4-O-hydroxyphenyl-2-trifluoromethyl-1, 3-dioxan-5-yl)heptenoic acid) have been studied on guinea-pig platelets and pulmonary smooth muscle in-vitro and in-vivo. When tested on guinea-pig lung parenchyma in-vitro. ICI 185,282 (1 x 10(-7) M) produced a significant shift in U-46619 response curves (concentration ratio of 13:3); the antagonist (1 x 10(-5) M) did not modify histamine responses. When tested on guinea-pig trachea in-vitro ICI 185,282 (1 x 10(-7) M) caused significant inhibition of U-46619 and PGD2 responses (concentration ratios of 8.3 and 14.1, respectively); the antagonist (1 x 10(-5) M proved less effective against contractions of PGF2 alpha, LTD4 and histamine (concentration ratios of 7.0, 1.5 and 1.6). When added to guinea-pig platelet rich plasma in-vitro, ICI 185,282 (x 10(-6), 1 x 10(-5) M) caused concentration-dependent parallel shifts to the right of U-46619 aggregation curves, yielding concentration ratios of 13.6 and 141.9, respectively. In-vitro, addition of ICI 185,282 (x 10(-5) M) to indomethacin-treated pulmonary smooth muscle did not modify resting tone, neither did it induce aggregation or swelling in platelet-rich plasma preparations. When administered orally to guinea-pigs ICI 185,282 (0.1, 0.5 mg kg-1) caused a significant inhibition of U-46619-induced platelet aggregation ex-vivo which persisted greater than or equal to 8 h. In-vivo, a single oral dose of ICI 185,282 (1 mg kg-1) inhibited bronchospasm induced by U-46619, PGD2, PGF2 alpha, arachidonic acid, LTD4 and PAF; responses to histamine were unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of endogenous and exogenous prostaglandins on glycoprotein synthesis and secretion in isolated rabbit gastric mucosa

We studied gastric glycoprotein synthesis and secretion in organ culture before and during cyclooxygenase inhibition and replacement with exogenous prostaglandins (16,16-dimethyl prostaglandin E2 and prostaglandin F2 alpha). Isolated rabbit antral and fundic mucosal explants incorporated [14C]N-acetylglucosamine and [3H]leucine in a linear fashion and steadily secreted labeled proteins and glycoproteins during the 24-h incubation period. On sepharose 4B, greater than 90% of the secreted protein-bound [14C]N-acetylglucosamine was found in the high molecular weight peak. Incorporation of tracer was not influenced by cyclooxygenase inhibition with indomethacin or the addition of exogenous prostaglandins. Secretion of newly formed glycoprotein, however, was significantly inhibited by indomethacin and stimulated by both tested prostaglandins in a concentration-dependent manner. 16,16-Dimethyl prostaglandin E2 caused significant stimulation in concentrations that are well in the physiologic range for endogenous prostaglandin E2, whereas prostaglandin F2 alpha stimulated in 100 times higher concentrations. We conclude that in the isolated gastric mucosa both endogenous and exogenous prostaglandins stimulate mucus secretion. For prostaglandin E2, but not prostaglandin F2 alpha, a role in the physiologic regulation of gastric mucus secretion is probable.

Plasma elevations of histamine and a prostaglandin metabolite in acute asthma

Recent studies of laboratory-provoked asthma have suggested that asthma is an inflammatory disease of lower airways. The purpose of this study was to measure the systemic elaboration of 2 bronchoconstrictive inflammatory mediators during naturally acquired acute asthma utilizing a prospective, serial-sampling protocol. Plasma levels of 13,14-dihydro-15-keto-PGF2 alpha and histamine were measured by radioimmunoassay and radioenzymatic assay, respectively, in 23 children with acute asthma. Mean PG metabolite and histamine values (pg/ml) before (167 +/- 72, 1,029 +/- 378) and 10 to 90 min after (377 +/- 145, 1,000 +/- 489) initial therapy were significantly higher than those of the same children after resolution of asthma (2.9 +/- 0.2, 260 +/- 42) and those of normal children (4.3 +/- 0.9, 240 +/- 14). Peak PG metabolite levels were significantly higher in children who presented with PEFR values (% predicted) less than 40% (1,234 +/- 432) compared with those who presented with greater than 40% (404 +/- 296), and in children with post-therapy improvement in PEFR of less than 20% (1,281 +/- 470) compared with those with greater than 20% (365 +/- 226). Histamine levels were significantly higher in children with post-therapy improvement in PEFR of less than 20% (2,560 +/- 1,600) compared with those with greater than 20% (475 +/- 100), and in hospitalized (3,915 +/- 1,910) compared with nonhospitalized (408 +/- 130) children. Significant differences were not observed on the basis of corticosteroid dependence, allergic disposition, or type of initial therapy. These data suggest a role for histamine and PGF2 alpha in the pathogenesis of airway inflammation in acute asthma.

Monoclonal antibodies directed against human airway secretions. Localization and characterization of antigens

Cellular mechanisms of normal airway mucus secretion and their alterations in chronic obstructive lung disease are poorly understood. To aid in their study, the authors have produced a panel of monoclonal antibodies directed against various constituents of human airway secretions. Two fusions yielded 401 hybridoma-containing cultures. Supernatants from 150 of these cultures stained human tracheal secretory cells by immunofluorescence. Twenty-nine hybridomas were selected for expansion because they selectively stained a single cell type or displayed another interesting distribution. Antigens were further characterized by their localization in glycol methacrylate sections of human trachea, sensitivity to periodate oxidations, selective affinity for fraction peaks obtained by Sepharose 4B chromatography, and reactivity with molecules of various sizes, as estimated by SDS-PAGE. These antibodies will be useful for 1) quantitative detection of antigens in sputum or lavage samples by immunoassay and 2) purification and biochemical characterization of molecular constituents of airway secretions in health and disease.

U46619 and carbocyclic thromboxane A2-induced increases in tracheal mucous gel layer thickness

U46619 or carbocyclic thromboxane A2 (CTA2) administered intravenously (IV) to rats produced dose-related increases of tracheal mucous gel layer thickness. Significant gel thickening was observed at doses ranging from 3.5 pg to 35 ng and from 500 pg to 50 ng for U46619 and CTA2, respectively. Intravenous treatment with pinane thromboxane A2 (PTA2), a thromboxane antagonist, prior to injection of U46619 or CTA2 attenuated the mucous gel layer response. The effect of PTA2 on U46619 and CTA2 was dose-dependent over the dosage range of PTA2 tested (1.0-31.6 micrograms/kg). PTA2 was equiactive against U46619 and CTA2 stimulated increases in gel thickness (ED50's 6.64 and 6.43 micrograms/kg respectively) suggesting a similar site of action for U46619 and CTA2. Slow reacting substance (SRS) injected IV into rats stimulated mucous gel layer thickening that was also inhibited by pretreatment with PTA2. These findings lend further support for the role of thromboxane in pathophysiologic conditions in which bronchorrhea contributes to the symptomatology.

Inhibition of the 5-lipoxygenase pathway with piriprost (U-60,257) protects normal primates from ozone-induced methacholine hyperresponsive small airways

Weekly exposure to ozone in seven normal Rhesus monkeys led to induction of methacholine hypersensitive airways (RL increases 242 +/- 60% and Cdyn decreases 68 +/- 13% of baseline methacholine responses). It took 19 weeks to establish this hyperresponse that persisted for greater than 15 weeks once ozone was stopped. A second exposure led to similar response peaks in 6 weeks. At the peak of the second response, weekly 1% piriprost exposure before ozone led to a return to baseline that was not different between placebo and piriprost treated animals (9.4 +/- 1.0 and 4.3 +/- 2.9 weeks, placebo and treated, respectively P = 0.09 NS). A statistical difference in the mecholyl response in placebo and piriprost treated groups while on ozone was shown only in the Cdyn measurement (Cdyn% change 68 +/- 13 vs 24 +/- 14, placebo and piriprost, respectively P = 0.03). Off ozone (or return to baseline), a statistical difference could be detected both in RL and Cdyn (RL% changed 151 +/- 41 vs 31.1 +/- 49, P = 0.03, and for Cdyn 62.7 +/- 8 vs 9 +/- 10, P = 0.0006, placebo and piriprost, respectively). We conclude tha the primate provides a chronic model of airways reactivity in which the role of lipoxygenase is implicated because of the beneficial role of piriprost, and further that the ozone lesion is primarily in the smaller airways (possibly and alveolitis).

Dexamethasone inhibits respiratory glycoconjugate secretion from feline airways in vitro by the induction of lipocortin (lipomodulin) synthesis

The effect of glucocorticoids on respiratory glycoconjugate (RGC) secretion was studied in a cat tracheal organ culture system. Dexamethasone (10(-5) to 10(-9) M) added to culture medium for 24 h caused a dose-related reversible inhibition of RCG of as much as 40% with a peak effect at 24 to 60 h after initiation of dexamethasone treatment. A monoclonal antilipocortin antibody added to the cultures blocked the inhibitory effect of dexamethasone on RGC secretion and accelerated the reversal of the dexamethasone effect after discontinuation of dexamethasone treatment. A control antibody without antilipocortin activity had no effect on RGC secretion or dexamethasone-induced inhibition of RGC secretion. Measurement of the concentration of lipocortin in airways revealed a 220% increase after treatment with dexamethasone for 24 h. We conclude that dexamethasone inhibits RGC secretion through the induction of lipocortin synthesis.

Relation between defective regulation of arachidonic acid release and symptoms in cystic fibrosis

A hypothesis is formed about the basic defect in CF based on the findings of 1) a defective inhibition of AA release by dexamethasone stimulation of lymphocytes from patients with CF, probably due to a defect in or absence of lipocortin and 2) the essential fatty acid deficiency (EFAD) in CF reported by different authors for 25 years. Both in lymphocytes and fibroblasts from patients with CF increased AA release has been demonstrated. AA, substrate for the eicosanoid system (prostaglandins, leukotrienes, hydroxyeicosatetraenoic acids, thromboxanes), has been shown to increase mucus release, influence chloride transport and the stimulus-secretion coupling (Ca++ balance), all factors suggested as basic defects in CF. The increased release of AA might explain the development of EFAD, since AA is synthesized from linoleic acid. In animals EFAD gives rise to symptoms similar to those in CF, e.g. defect Na transport, liver steatosis, increased caloric need, disturbed insulin release, increased bacterial colonization of airways, and decreased immune response. Regular supplementation with fat emulsion (Intralipid) to CF patients normalizes the renal Na transport and prevents liver steatosis. We suggest that the basic defect in CF is a defect in or absence of lipocortin, causing an increased release of AA, which regulates synthesis in the eicosanoid system. An increase of the products in this system gives rise to the basic signs and symptoms of CF. The resulting EFAD is dependent on the rate of AA turnover and could explain most of the clinical symptoms and the progression of the disease.

The effects of peptides and mediators on mucus secretion rate and smooth muscle tone in the ferret trachea

The effects of a number of peptides and mediators were measured on the secretion rate of tracheal mucus and tracheal smooth muscle tone in the ferret in vitro whole trachea. The comparison of secretion rate and smooth muscle tone, measured simultaneously in the same preparation, shows that there are wide differences in sensitivity between the two systems; there appears to be no relationship between mucus volume output and smooth muscle contraction. The comparison of mucus secretion rate and glycoprotein output in other models and species to these drugs in the same concentrations indicates that there may be mucus glycoprotein output without an increase in volume output.

Arachidonic acid stimulation of mucus production by rat gastric cultured cells

The effect of arachidonic acid (AA) on mucus production (synthesis and secretion) by rat gastric monolayer-cultured cells was investigated. For the study of mucus synthesis, the rate of incorporation of [3H]glucosamine into the cultured cells was measured. The rate of release of glycoprotein into the culture media from the cells, which were incubated in the medium containing [3H]glucosamine for 24 hr in advance, was determined for the study of mucus secretion. Prostaglandins in the medium were measured by radioimmunoassay. AA (10(-4) M) significantly increased mucus synthesis and secretion by the cultured cells (P less than 0.01). PG (E2 and I2) synthesis by the cultured cells was significantly enhanced by AA (10(-4) M) (P less than 0.05). An addition of indomethacin to the culture medium abolished this effect of AA. These results suggested that gastric mucus production was enhanced by AA in vitro and that this effect may be mediated by endogenous PG production.

Mast cell mediators and asthma

Mast cells are found beneath the basement membranes, near blood vessels in the submucosa, adjacent to submucous glands, scattered throughout the muscle bundles, in the interalveolar septa and in the bronchial lumen. The evidence that mast cells and mast cell-derived mediators play a role in allergic and non-allergic asthma is discussed. In allergic individuals, inhalation of specific allergens leads to mast cell degranulation and release of mediators. Many of the pathologic features of asthma may be attributed to the effects of mast cell-derived mediators. Their role is clear in allergic asthma and the presence of mast cell derived mediators in the plasma of individuals with exercise-induced and nocturnal asthma suggests involvement in other forms of asthma as well.

Synthesis of mucous glycoproteins by rabbit tracheal cells in vitro. Modulation by substratum, retinoids and cyclic AMP

One function of airway epithelium is the secretion of mucins, which comprise an important component of the mucous lining layer. We demonstrate that rabbit tracheal epithelial cells grown in primary culture incorporate [3H]glucosamine into material released into the medium which is characterized as mucin by the following criteria: high Mr, monosaccharide composition, ion-exchange behaviour different from that of glycosaminoglycans and oligosaccharides attached via N-acetylgalactosamine. The production of mucin by the cells requires growth on a substratum of collagen gel and is enhanced by retinoids in the extracellular medium. In the presence of retinoids, 8-bromo cyclic AMP and factors present in medium from 3T3 fibroblasts each further stimulate mucin production. These results indicate that an isolated epithelial-cell culture system, in the absence of nervous, mesenchymal or other tissue types, can be used to answer questions about the regulation of mucin production at the cellular level.

Actions of prostaglandins E2 and F2 alpha on release of 14C-labelled mucins from rat submandibular salivary acini in vitro

Mucin secretion was studied in vitro using well-characterized preparations of isolated acini. PGE2 significantly (p less than 0.05) increased release of [14C]-glucosamine labelled mucins at the highest concentration tested (10(-5) M), but was ineffective at lower doses (10(-9)-10(-6) M). PGF2 alpha had no effect on mucin secretion over this concentration range. PGE2 (10(-9)-10(-5) M) did not modify isoproterenol stimulated mucin secretion. The cyclooxygenase inhibitor indomethacin (10(-7)-10(-5) M) did not significantly inhibit either isoproterenol or noradrenaline stimulated mucin secretion. Thus it seems that, although PGE2 significantly increases mucin secretion at a high concentration, it is unlikely that prostaglandins play a major role in modulating beta-adrenergic stimulation of mucin secretion in rat submandibular acinar cells.

Effects of dietary fats on bleomycin-induced pulmonary fibrosis

Bleomycin treatment has been used for the experimental induction of pulmonary fibrosis, but the mechanisms involved are poorly understood. Since alterations in the levels of certain fatty acid metabolites have been associated with bleomycin-induced lung injury, we examined the effects of different dietary fats on the development of bleomycin-induced pulmonary fibrosis. Weanling rats were raised on standard laboratory feed or a diet consisting of a fat-free powder to which was added either coconut oil or beef tallow (25% w/w). After 8 weeks of feeding, animals received either 1.5 units bleomycin or an equivalent volume of saline intratracheally. Bleomycin treatment resulted in significant increases in total lung hydroxyproline content in the groups fed the standard lab diet (p less than 0.001) and beef tallow diet (p less than 0.001), but not in the group receiving the coconut oil diet. Furthermore, the lung hydroxyproline content in bleomycin-treated animals was less with the beef tallow diet compared with standard lab feed (p less than 0.05). Bleomycin treatment resulted in an increase in thiobarbituric acid-reactive products, an index of lipid peroxidation, in lungs from animals fed the standard lab diet, but not in the other diet groups. The percentage of diseased lung, as determined by morphometric analysis, was increased in bleomycin-treated animals from all diet groups (p less than 0.05). We conclude that alterations in dietary fats can reduce the severity of pulmonary fibrosis resulting from bleomycin treatment. Possible mechanisms for this effect include alterations in eicosanoid metabolism or changes in immune or effector cell function.

Pathological regulation of arachidonic acid release in cystic fibrosis: the putative basic defect

The regulation of arachidonic acid release from membrane phospholipids was investigated in lymphocytes from patients with cystic fibrosis as well as control patients. No effect of either dexamethasone or fetal calf serum was seen on arachidonic acid release from cystic fibrosis lymphocytes, in contrast to control lymphocytes. In the latter cells, arachidonic acid release was inhibited by dexamethasone, fetal calf serum, or both. There were no differences in glucocorticoid receptor in lymphocytes from the two groups with regard to Kd and number of binding sites per cell. Furthermore, dexamethasone inhibited the incorporation of thymidine into lymphocytes from either group, indicating a normal functional glucocorticoid receptor. The defective regulation of arachidonic acid, resulting in an increased turnover, can explain many of the findings in cystic fibrosis, and we hypothesize that it is the basic defect causing the disease. The defect occurs at a level after the glucocorticoid receptor, which is functionally normal, and involves either the glucocorticoid-dependent phospholipase-inhibitory protein lipomodulin (lipocortin) or phospholipase A2.

Increased mole fraction of arachidonic acid in bronchial phospholipids in patients with cystic fibrosis

The fatty acid pattern of the phospholipids in the bronchial secretion of patients with cystic fibrosis (CF) showed an increase of the mole fraction of arachidonic acid (AA) in most phospholipid classes compared to normals. Increase of AA in some classes was also found in patients with chronic bronchitis and in patients chronically colonized with Pseudomonas aeruginosa but in the diphosphatidylglycerol, lysophosphatidylethanolamine and sphingomyelin phospholipids, high fractions of AA was found exclusively in CF patients. Arachidonic acid was found to attain the highest ratios in CF in seven of the nine major bronchial phospholipids compared to the controls. There was no difference in the ratio saturated/unsaturated fatty acids between the CF patients and the control groups. A tendency towards unsaturation of the fatty acids in the bronchial secretion seems to be characteristic of infection and inflammation but AA appears to be more markedly increased in CF. Thus, the recorded changes may be characteristic for CF and not secondary to infection and/or inflammation in general, nor to P. aeruginosa colonization.

Prostaglandins, thromboxanes, and leukotrienes in inflammation

Arachidonic acid undergoes two metabolic pathways in leukocytes. The first, catalysis by prostaglandin cyclo-oxygenase, yields the prostaglandin endoperoxides G2 and H2 and thromboxane A2, which induce rapid irreversible aggregation of human platelets and are potent inductors of smooth muscle contraction. The second pathway, catalysis by lipoxygenase, yields various hydroperoxy acids. In platelets, 12-hydroperoxyeicosatetraenoic acid is the predominant product; in polymorphonuclear leukocytes, 5-hydroperoxyeicosatetraenoic acid is formed. These are primarily reduced to 12-hydroxyeicosatetraenoic acid and 5-hydroxyeicosatetraenoic acid. 5-Hydroperoxyeicosatetraenoic acid may also be dehydrated to leukotriene A4. Enzymatic hydrolysis of leukotriene A4 yield leukotriene B4, a potent mediator of leukocyte function. Prostaglandins, thromboxanes, and some hydroxyeicosatetraenoic acids exert chemotactic effects on polymorphonuclear leukocytes. In this respect, leukotriene B4 is the most active compound derived from arachidonic acid. In vivo, adherence of leukocytes to the endothelium of microvessels near inflammatory areas and the sticking phenomenon of these cells are the initial hallmarks of an inflammatory response. In vitro, these responses seem to correspond with leukocyte aggregation and adherence. Leukotriene A4 may also react to form leukotriene C4 (a natural component of slow-reacting substance of anaphylaxis), leukotriene D4, leukotriene E4, and the 11-trans-isomers. All three leukotrienes are virtually unable to induce chemotaxis, enzyme release, or leukocyte aggregation, but they possess biologic properties previously attributed to slow-reacting substances, such as a potent effect on smooth muscle in the peripheral airway and an ability to markedly increase macromolecular permeability in venules. In addition to prolonging bleeding time and causing gastric ulcers, aspirin and other nonsteroidal anti-inflammatory drugs can trigger or aggravate an asthmatic attack. Aspirin can also trigger or aggravate urticaria, probably as a direct effect of thioether leukotrienes rather than from antibody mediation. Many nonsteroidal anti-inflammatory drugs increase formation of slow-reacting substance-A after challenge with allergen, perhaps by inhibiting cyclo-oxygenase, thereby releasing more arachidonic acid for metabolism by lipoxygenase. Alternatively, certain prostaglandins inhibit liberation of arachidonic acid from phospholipids; inhibiting their formation causes release of more arachidonic acid, which must be metabolized by different lipoxygenase pathways, since the cyclo-oxygenase pathway is closed.

Indomethacin increases bronchial reactivity after exposure to subthreshold ozone levels

We investigated the effects of indomethacin on bronchial reactivity after ozone exposure. Guinea pigs in groups of six were treated with indomethacin (30 mg/kg IP) and studied before and 2 h after a 2 h exposure to either 1.5 or 3.0 ppm ozone. These animals were compared to similarly exposed groups that were untreated. Reactivity was determined by measuring specific airway resistance (SRaw) upon intravenous acetylcholine infusion. Prior to ozone exposure, indomethacin had no effect on either SRaw or muscarinic reactivity. In all untreated guinea pigs (n = 12) exposed to 1.5 ppm ozone, there was no significant change in SRaw or muscarinic reactivity. In contrast, all treated animals exposed to 1.5 ppm showed a substantial increase in reactivity. Those treated animals exposed to 3.0 ppm showed significant elevations in SRaw, making interpretations of changes in their reactivity difficult. We conclude that indomethacin treatment increases bronchial reactivity in guinea pigs exposed to subthreshold ozone levels.

Density gradient analysis of secretions produced in vitro by human and canine airway mucosa: identification of lipids and proteoglycans in such secretions

Human and canine airway mucosal explants synthesize and secrete high molecular weight glycoconjugates, incorporating 14C-glucosamine, a radioactive precursor to epithelial glycoprotein. Our examination of secretions produced by several individual specimens, however, did not reveal epithelial glycoprotein of typical buoyant density (1.5 g/ml in CsBr); only a high-density component with features of glycoprotein and proteoglycan. To provide sufficient material for characterization, secretions from several specimens of human and canine explants were separately pooled and subjected to DGU in CsBr. After removal of lipids and proteins, the glycoconjugates were recovered into five fractions of different density. 14C-glucosamine had been incorporated in all five fractions. Fractions 1-4 together accounted for 88% of the radiolabel but gas chromatography indicated that none of these contained epithelial glycoprotein. Their amino acid compositions were similar to those of proteoglycans and electrophoresis confirmed the presence of chondroitin sulfates A, B, C, heparan sulfate and hyaluronic acid. Sugars typical of epithelial glycoprotein were identified only in the glycoconjugate subfraction 5 of lowest density (and also lowest in yield) in which glycosaminoglycans were also identified. By addition of radioactive precursors, 14C acetate, 14C palmitate and 14C mevalonic acid to the culture medium and autoradiography of the secreted lipids we have shown that the tracheal explants actively synthesize lipids. Lipids accounted for a high proportion, almost half by weight, of the explant secretion. While neutral and phospholipids predominate, glycolipids were also identified.

Intravenous SRS-induced increases in tracheal mucous gel layer thickness: evidence for thromboxane involvement

Intravenous (IV) slow reacting substance (SRS) challenge produces bronchoconstriction that can be reduced by cyclooxygenase inhibitors. This report shows that IV SRS challenge also produces significant increases in tracheal mucous gel thickness and that the increases are inhibited by pretreatment with indomethacin (4 mg/kg, PO) or imidazole (10 mg/kg, IV). The increase in gel thickness is preceded by increases in plasma thromboxane B2 (TXB2) levels and the inhibition of gel thickening by imidazole is paralleled by decreases in plasma TXB2 levels. Aerosolized SRS produces increases in tracheal mucous gel thickness which are not inhibited by either indomethacin or imidazole, but are significantly inhibited by FPL-55712. These findings indicate that SRS acts, not only directly to stimulate mucous secretion but also indirectly through an indomethacin and imidazole sensitive mechanism.

Mechanism of action of gonadotropin releasing hormone: role of lipoxygenase products of arachidonic acid in luteinizing hormone release

The mechanism of action of gonadotropin-releasing hormone (GnRH) upon pituitary luteinizing hormone (LH) secretion has not yet been elucidated, but recent evidence has suggested that arachidonic acid or its metabolites are involved in GnRH action. In cultured rat pituitary cells, arachidonic acid and 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) elicited concentration-dependent release of LH with EC50 of about 12 microM. Other lipoxygenase derivatives including 11-, 12- and 15-HETE, had no consistent effect on LH release, and leukotrienes (B4 and C4) exerted only minor stimulatory actions on LH release. The lipoxygenase inhibitors nordihydroguaiaretic acid (NDGA), 5,8,11,14-eicosatetraynoic acid (ETYA), and 3-amino-1-(3-trifluoromethyl phenyl)-2-pyrazoline hydrochloride (BW 755C) caused dose-dependent inhibition of GnRH-induced LH release, with IC50 values of 5, 8.5, and 175 microM, respectively. In contrast, the cyclooxygenase inhibitor, indomethacin, had a biphasic action on GnRH-stimulated LH release, with potentiation of GnRH action at low doses (up to 25 microM) and no effect at higher concentrations. These findings are consistent with the potential role of a 5-lipoxygenase product of arachidonic acid in the mechanism of action of GnRH on pituitary gonadotropin release.

Anaphylatoxin C3a enhances mucous glycoprotein release from human airways in vitro

Because C3a may be generated during the course of pulmonary inflammatory reactions, we investigated the ability of C3a to affect mucous glycoprotein (MGP) secretion from cultured human airways. C3a, but not C3a des Arg, caused a dose-related increase in MGP release (maximal after 4-6 h), with as little as 15 micrograms of C3a per milliliter stimulating a 40% increase. The experimental evidence suggested that immunologically specific C3a was required for the secretagogue actions, as monospecific anti-C3a inhibited the reaction, as well as specifically absorbing the secretagogue from solution. Moreover, it appeared that C3a does not require mast cell activation, eicosanoid generation, or macrophage-derived mucus secretagogue synthesis for its effect, since (a) no evidence of histamine release accompanied C3a-induced MGP release, and dibutyryl cAMP failed to affect C3a-induced MGP release, while reducing the actions of reversed anaphylaxis; (b) MGP release caused by C3a was not influenced by eicosatetraynoic acid or specific cyclooxygenase inhibitors, and no leukotrienes were detectable on the supernatants of C3a-stimulated airways; and (c) cycloheximide failed to affect C3a secretion-stimulating actions. Thus, C3a is a potent mucus secretagogue, and, possibly, acts directly as a glandular stimulant. It seems likely that C3a generated in the course of pulmonary inflammation might contribute to the mucus secretion associated with pulmonary infections.

Prostaglandins and other arachidonic acid metabolites in the middle ear fluids

Prostaglandins (PGs) and other arachidonic acid (AA) metabolites have been recognized as mediators of inflammation and bone resorption, chemotactic agent to polymorphonuclear leukocytes (PMN), and regulators of inflammatory response. Although assays of some PGs in the middle ear fluid (MEF) were reported, there has been no report on comprehensive assay of PGs and other AA metabolites in MEF. Concentrations of PGs were measured by radioimmunoassay in human MEF. The data on human MEF were analyzed according to age group. In addition, levels of lipoxygenase-products, 5- and 15-hydroxyeicosatetraenoic acid (HETE) and leukotriene (LT)C4 were measured in human MEF. Levels of PGE2 in MEF from human serous otitis media (SOM) were highest in younger age group (below the age of 10) then the levels drop down to lower level in older age group. In human mucoid otitis media (MOM) the levels of PGE2 are lower than SOM in younger age group then become higher than SOM in older age group. Levels of 6-keto-PGF1 alpha were higher in SOM than in MOM overall. The age breakdown of data showed progressive increase in the 6-keto-PGF1 alpha levels with older age group. Levels of TxB2 in SOM were higher than in MOM overall. The age breakdown of SOM data remained almost the same in all the age groups but the MOM data showed lowest levels in 6-10 year-old group and highest in 11-15 year-old group. Concentrations of 15-HETE in human MOM were over two times higher than in SOM. LTC4 levels in MOM were higher than SOM.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergen-induced release of sulphidopeptide leukotrienes (SRS-A) and LTB4 in allergic rhinitis

Leukotrienes are a recently discovered group of arachidonic acid-derived lipid mediators. Using radioimmunoassay and high pressure liquid chromatography (HPLC), we have identified the SRS-A sulphidopeptide leukotrienes (LTC4, LTD4 and LTE4) in nasal washings from patients with allergic rhinitis who underwent nasal challenge with specific allergen. Smaller, but significant, amounts of LTB4 were also detected. The concentrations of nasal leukotrienes were directly related to the dose of allergen, and were recovered in washings in a time-dependent fashion after challenge. When the patients were subjected to methacholine nasal challenge on a control day, we found only negligible amounts of either the sulphidopeptide leukotrienes or LTB4. These findings support the view that LTC4, LTD4 and LTE4 might contribute to the pathogenesis of allergic rhinitis as a result of their recognized effects on mucous hypersecretion and vasopermeability, and that the potent chemoattractant LTB4 might be involved in the subsequent infiltration of inflammatory cells.

Human monocyte-derived mucus secretagogue

Human peripheral monocytes were stimulated with opsonized zymosan or protein A-containing Staphylococcus aureus to examine whether factors might be released that were capable of stimulating mucous glycoprotein release from cultured human airways, as has recently been described with human pulmonary macrophages. While the supernatant from monocytes exposed to opsonized zymosan or protein A-containing S. aureus caused an impressive activity was found in the control samples that were cultured in parallel and exposed to nonactivated zymosan or S. aureus that was deficient in protein A. The responsible factor was termed monocyte-derived mucus secretagogue (MMS). The maximum MMS release was reached 4-8 h after stimulation, and the amount of MMS released was dependent on the dose of opsonized zymosan added. Chromatographic analyses of MMS indicate that its molecular weight was approximately 2,000 and that the isoelectric point (pI) was 5.2, with a smaller second peak of 7.4 on isoelectric focusing. MMS itself was not detected in monocyte lysates, nor was it formed by monocytes treated with the protein synthesis inhibitor, cycloheximide, before exposure to activating particles. MMS was not a prostaglandin, could not be extracted into organic solvents, and is probably not an eicosanoid. Based on these observations, we conclude that stimulated human peripheral monocytes synthesize a small, acidic molecule, termed MMS, that is capable of stimulating human airways to secrete mucus and in nearly every respect is identical to pulmonary macrophage-derived MMS.

Proteinases of Pseudomonas aeruginosa evoke mucin release by tracheal epithelium

We have determined the potential of exoproducts from pathogenic bacteria to stimulate the release of high molecular weight mucins from goblet cells of airway epithelium in a rabbit tracheal explant system. Culture supernatants from proteolytic strains of Pseudomonas aeruginosa and Serratia marcescens, but not supernatants from a number of non-proteolytic strains, released mucins from goblet cells. Highly purified elastase and alkaline proteinase from P. aeruginosa stimulated goblet cell mucin release in a dose-dependent fashion. Lipopolysaccharide, exotoxin A, and alginate of P. aeruginosa did not possess mucin release properties. Proteolytic activity was required for mucin release by P. aeruginosa elastase, but such release in goblet cells was not mediated by cyclic AMP. Morphologic studies suggested rapid release of mucins from goblet cells was response to elastase by a process resembling apocrine secretion. Several nonbacterial proteinases mimicked the effect of Pseudomonas proteases. These studies provide support for the hypothesis that bacterial and other play a role in the pathogenesis of mucus hypersecretion in acute and chronic lung infections.

Analysis of human nasal mucous glycoproteins

Human nasal turbinates were cultured in the presence of 3H-glucosamine, which is incorporated into nasal mucous glycoproteins. Nasal mucous glycoprotein was then characterized biochemically, and the effects of various neurohormones and immunologic stimulation on mucous glycoprotein release were analyzed. Fractionation of nasal mucous glycoprotein by gel filtration chromatography revealed a molecular size range of 2 to 200 X 10(5) (as judged by protein markers) but displayed a single, acidic charge, as reflected both in a narrow elution pattern from DEAE-cellulose and a sharp isoelectric focusing point of 2.6. Highly enriched nasal mucous glycoprotein preparations consisted of 80 per cent carbohydrate and 20 per cent protein (by weight) and included enzymatically cleavable carbohydrate side chains with molecular weights of 1,600 to 1,800. Thus, nasal mucous glycoproteins are a family of molecules that express uniform acidic charge characteristics and a wide range of molecular sizes. Cholinergic stimulation of atropine-inhibitable muscarinic receptors increased nasal mucous glycoprotein release in a dose-related manner, as did alpha-adrenergic stimulation. However, beta-adrenergic stimulation did not affect mucous glycoprotein release. Immunologic stimulation of nasal mast cells by either reversed anaphylaxis or antigen challenge after passive sensitization caused both histamine release and increased mucous glycoprotein release. Thus, nasal turbinates provide an accessible source of tissue for the analysis of nasal mucus secretion and mast cell degranulation and may provide a model for the study of pharmacologic approaches to the universally experienced discomfort of rhinorrhea.

Production of mucous glycoproteins by nasal turbinates in vitro

An in vitro system of human nasal turbinate tissue culture has been developed. Nasal turbinate tissue resected during surgery for nasal obstruction is dissected free of bone, placed on absorbable gelatin sponges, and cultured with CMRL-1066 medium containing antibiotics. Viability of explants may be demonstrated both physiologically and histologically through a period of 4 weeks. 3H-glucosamine added to the medium is biosynthetically incorporated into mucous glycoprotein (MGP). Gel filtration column chromatography on Sephacryl S-1000 in 6M urea in 0.005M phosphate buffer demonstrates human turbinate MGP to fractionate with 85% of the radiolabel filtered and 15% excluded by the column. The excluded MGP fractionates with globular proteins of greater than 20 X 10(6) daltons, while the fractions that enter the column filter with molecular sizes of 0.4 X 10(6) to 20 X 10(6) daltons. MGP synthesized by human lung airways has comparable sizing characteristics, suggesting a similarity in upper and lower airway mucus chemistry.

Prostaglandin-generating factor of anaphylaxis induces mucous glycoprotein release and the formation of lipoxygenase products of arachidonate from human airways

The effects of prostaglandin-generating factor of anaphylaxis (PGF-A) upon the lipoxygenation of arachidonic acid and the promotion of mucous glycoprotein secretion by human airways were analyzed concurrently in order to determine the role that lipoxygenase products play in the secretion of mucus which accompanies immediate hypersensitivity reactions of airways. PGF-A enhanced both mucous glycoprotein release and the 5- and 15-lipoxygenation of arachidonic acid as well as the formation of leukotriene B4 (LTB4) with similar dose-response relationships. The capacity of PGF-A to stimulate mucous glycoprotein release was inhibited by ETYA but not by indomethacin, suggesting that PGF-A stimulated lipoxygenase products may be involved. Lipoxygenase products of arachidonic acid thus may serve as mediators of the enhancement of mucus secretion from human airways in response to PGF-A.

Effects of prostaglandins E1, E2, and F2 alpha on mucin secretion from human bronchi in vitro

The effects of three prostaglandins on the output of 35S labelled mucus glycoproteins (mucins), from explants of human bronchial tissue suspended in Ussing chambers, have been investigated. Prostaglandin F2 alpha, added to the Krebs-Henseleit solution bathing both luminal and submucosal sides of the tissue, significantly increased mucin output at concentrations of 0.1 and 1.0 micrograms/ml (0.28 and 2.8 microM), 11 preparations being used for each dose. Since prostaglandin F2 alpha has been shown to be released from human airways challenged by antigen, it may be important in the regulation of mucus secretion in these circumstances. Prostaglandins E1 and E2 had no significant effects on mucin output even at the highest concentration (1.0 micrograms/ml), though in half the tissues tested PGE2 stimulated secretion consistently. These results contrast with the findings in a previous study, which showed an inhibition of mucin output by PGE2.

Human pulmonary macrophage-derived mucus secretagogue

Human pulmonary macrophages (PM) obtained from surgically removed human lung tissue released a factor after exposure to activated zymosan that caused cultured human airways to release increased amounts of radiolabeled mucous glycoproteins. The factor was released maximally after 4-8 h of zymosan exposure and caused a dose-related increase in glycoprotein release; it was termed macrophage-derived mucus secretagogue (MMS). MMS release was produced in a dose-dependent fashion by activated but not by nonactivated zymosan. The activation of zymosan was C3 dependent, and C3b-coated Sepharose was also an effective stimulant. The data suggested that cell surface activation of the PM was a sufficient stimulus to cause MMS release and that both C3-dependent activation as well as Fc receptor activation were effective. The synthesis of MMS was sensitive to cycloheximide, and no active MMS was detectable intracellularly. To determine if MMS might be one of the oxidative derivatives of arachidonic acid, PM were incubated with cyclooxygenase and lipoxygenase inhibitors before activation. These maneuvers did not influence MMS generation. MMS-rich supernatants were then extracted into organic solvents or exposed to lipophilic resin; in both cases, MMS remained in the aqueous phase. Thus, MMS is not a derivative of arachidonic acid. Sequential fractionation of MMS on ultramembrane and gel filtration followed by isoelectric focusing and gel filtration indicated that MMS is a small (approximately 2000 daltons), acidic (pI, 5.15) molecule. Therefore, surface activation of human PM results in the synthesis and release of a small acidic molecule that causes airway mucous glands to secrete increased quantities of mucous glycoproteins.

Respiratory tract fluids: analysis of content and contemporary use in understanding lung diseases

Respiratory tract fluid, produced from an enormous area spanning the mucosa of the nose to the alveolar surface, is a complex mixture of serum transudate and locally secreted proteins and glycomucoproteins and of inflammatory and immune effector cells intermingled. Its analysis is important in understanding the pathogenesis of respiratory diseases and remains essential for the clinical diagnosis of most lung disorders. Many basic facts about the formation and composition of this fluid remain unknown, and little information exists about absorptive mechanisms along the airways. Respiratory fluid is not homogeneous but has unique regional characteristics that are becoming better appreciated as more selective sampling methods are devised. Above all, it is a dynamic substance in healthy airways and diseased ones, and any specimen is just a point-in-time sample that can change in composition, often making serial analysis and comparisons necessary. Nasal fluids currently have limited diagnostic application except in allergic rhinitis. Expectorant (sputum) telescopes fluid and cells from all areas and is not from a specific locale, so the trend is to retrieve more selective and regional specimens of airways fluids. Technology largely does not exist to collect area specimens, except for bronchoalveolar lavage, which generally samples the alveolar surface. Clearly, bronchoalveolar lavage fluid analysis has been the favored way to characterize the peripheral air-spaces for the past 10 years or so, and most of this monograph has been devoted to normal data derived from lavage specimens and to a few examples of lung disease that reflect this burgeoning application. In many respects, results obtained from lavage fluid are virtually in catalogue form at present, and it remains to the future to know how some of the observations will help make diagnosis better or elucidate pathogenic mechanisms. Generally, bronchoalveolar lavage fluid analysis has led to better concepts of immunopathology of many diseases and provided new ways to monitor the evolution of certain diseases, especially the diffuse interstitial lung disorders, but development of specific criteria for diagnosis has been less rewarding. However, certain patterns of lymphocyte-predominant alveolitis, suggesting sarcoidosis or hypersensitivity diseases, recognition of specific T lymphocyte defects and opportunistic microorganisms as in AIDS, and the use of microprobe electron analysis to identify cellular particulates all point to more precision of diagnosis. Alveolar proteinosis and histiocytosis X may be detected from lavage fluid components. The prospects are truly exciting.(ABSTRACT TRUNCATED AT 400 WORDS)

Human bronchial explants in long-term culture: establishing a baseline for secretion

A serum-free culture medium was employed to evaluate both qualitative and quantitative aspects of secreted proteins derived from human bronchial explants over a period of 26 to 50 d. It was found that protein and hexose were secreted at a reasonably constant rate during this period. Viability of explants was assessed by histological examination, attachment to scored grids of the petri dish, incorporation of labeled precursors into tissue proteins, and by fluorographic analysis of the sodium dodecyl sulfate-polyacrylamide gel pattern of the secreted material. This culture system is useful as a model for the study of secretory products and processes and how they are affected by various stimuli.

Plasma prostaglandin activities in some immuno-inflammatory diseases

In the present study the relationship between plasma prostaglandins (PGs) level and the immuno-inflammatory reactions, known to accompany bronchial asthma and/or schistosomiasis infection, was investigated. It was found that plasma PGF2 alpha increased significantly above the control values in 30 asthmatics, 30 schistosomal and 30 asthmatic schistosomal patients. Plasma PGE increased also together with that of PGF2 alpha which is considered to be useful for the protection of the patient against the injurious effects of the infection, due to the known opposing actions of PGE to those of PGF2 alpha.