Aspects of prostaglandin function in the lung (second of two parts)

A Randomized Controlled Trial of Intranasal Neuropeptide Y in Patients With Major Depressive Disorder

BACKGROUND

Since about one-third of patients with major depressive disorder (MDD) do not respond adequately to available antidepressants, there is a need for treatments based on novel mechanisms of action. Neuropeptide Y (NPY), a normal brain constituent, is reduced in cerebrospinal fluid of patients with MDD and post-traumatic stress disorder and in corresponding rodent models. Moreover, NPY administered centrally or intranasally rescues pathophysiology in these models. Consequently, we conducted the first, to our knowledge, controlled trial of NPY as a treatment for MDD.

METHODS

Thirty MDD patients on a stable dose of a conventional antidepressant insufflated 6.8 mg NPY (n = 12) or placebo (n = 18) in a double blind randomized fashion. Effects were assessed at baseline, +1 hour, +5 hours, +24 hours, and +48 hours. The primary outcome was change in depression severity measured with the Montgomery-Åsberg Depression Rating Scale (MADRS).

RESULTS

NPY was superior to placebo at +24 hours (change -10.3 [95% CI: -13.8; -6.8]) vs -5.6 (95% CI: -8.4; -2.7); group*time F = 3.26, DF = (1,28), P = .04; Cohen's d = 0.67). At +5 hours MADRS decreased -7.1 ([95% CI: -10.0; -4.2] vs -3.5 [95% CI: -5.8; -1.2]; group*time F = 2.69, DF = (1,28), P = .05; Cohen's d = 0.61). MADRS reduction at +48 hours was not significant.

CONCLUSIONS

Since no results regarding the trajectory of NPY effects existed prior to this study we extrapolated from the known NPY biology and predicted the effects will occur 5-48 hours post insufflation. We chose +48 hours as the primary endpoint and +1, +5, and +24 hours as secondary endpoints. The results, the first of their kind, indicate that insufflated NPY is antidepressant, despite not meeting the primary outcome, and call for dose ranging and repeated NPY insufflation trials.

CLINICAL TRIAL REGISTRATION

EudraCT Number: 2014-000129-19.

Structural and Mutational Analysis of Trypanosoma brucei Prostaglandin H2 Reductase Provides Insight into the Catalytic Mechanism of Aldo-ketoreductases

Trypanosoma brucei prostaglandin F2alpha synthase is an aldo-ketoreductase that catalyzes the reduction of prostaglandin H2 to PGF2alpha in addition to that of 9,10-phenanthrenequinone. We report the crystal structure of TbPGFS.NADP+.citrate at 2.1 angstroms resolution. TbPGFS adopts a parallel (alpha/beta)8-barrel fold lacking the protrudent loops and possesses a hydrophobic core active site that contains a catalytic tetrad of tyrosine, lysine, histidine, and aspartate, which is highly conserved among AKRs. Site-directed mutagenesis of the catalytic tetrad residues revealed that a dyad of Lys77 and His110, and a triad of Tyr52, Lys77, and His110 are essential for the reduction of PGH2 and 9,10-PQ, respectively. Structural and kinetic analysis revealed that His110, acts as the general acid catalyst for PGH2 reduction and that Lys77 facilitates His110 protonation through a water molecule, while exerting an electrostatic repulsion against His110 that maintains the spatial arrangement which allows the formation of a hydrogen bond between His110 and C11 that carbonyl of PGH2. We also show Tyr52 acts as the general acid catalyst for 9,10-PQ reduction, and thus we not only elucidate the catalytic mechanism of a PGH2 reductase but also provide an insight into the catalytic specificity of AKRs.

Prostaglandin production from arachidonic acid and evidence for a 9,11-endoperoxide prostaglandin H2 reductase in Leishmania

Lysates of Leishmania promastigotes can metabolise arachidonic acid to prostaglandins. Prostaglandin production was heat sensitive and not inhibited by aspirin or indomethacin. We cloned and sequenced the cDNA of Leishmania major, Leishmania donovani, and Leishmania tropica prostaglandin F(2alpha) synthase, and overexpressed their respective 34-kDa recombinant proteins that catalyse the reduction of 9,11-endoperoxide PGH(2) to PGF(2alpha). Database search and sequence alignment showed that L. major prostaglandin F(2alpha) synthase exhibits 61, 99.3, and 99.3% identity with Trypanosoma brucei, L. donovani, and L. tropica prostaglandin F(2alpha) synthase, respectively. Using polymerase chain reaction amplification, Western blotting, and immunofluorescence, we have demonstrated that prostaglandin F(2alpha) synthase protein and gene are present in Old World and absent in New World Leishmania, and that this protein is localised to the promastigote cytosol.

Prostaglandin production from arachidonic acid and evidence for a 9,11-endoperoxide prostaglandin H2 reductase in Leishmania

Lysates of Leishmania promastigotes can metabolise arachidonic acid to prostaglandins. Prostaglandin production was heat sensitive and not inhibited by aspirin or indomethacin. We cloned and sequenced the cDNA of Leishmania major, Leishmania donovani, and Leishmania tropica prostaglandin F(2alpha) synthase, and overexpressed their respective 34-kDa recombinant proteins that catalyse the reduction of 9,11-endoperoxide PGH(2) to PGF(2alpha). Database search and sequence alignment alignment showed that L. major prostaglandin F(2alpha) synthase exhibits 61, 99.3, and 99.3% identity with Trypanosoma brucei, L. donovani, and L. tropica prostaglandin F(2alpha) synthase, respectively. Using polymerase chain reaction amplification, Western blotting, and immunofluorescence, we have demonstrated that prostaglandin F(2alpha) synthase protein and gene are present in Old World and absent in New World Leishmania, and that this protein is localised to the promastigote cytosol.

Identification of a novel prostaglandin f(2alpha) synthase in Trypanosoma brucei

Members of the genus Trypanosoma cause African trypanosomiasis in humans and animals in Africa. Infection of mammals by African trypanosomes is characterized by an upregulation of prostaglandin (PG) production in the plasma and cerebrospinal fluid. These metabolites of arachidonic acid (AA) may, in part, be responsible for symptoms such as fever, headache, immunosuppression, deep muscle hyperaesthesia, miscarriage, ovarian dysfunction, sleepiness, and other symptoms observed in patients with chronic African trypanosomiasis. Here, we show that the protozoan parasite T. brucei is involved in PG production and that it produces PGs enzymatically from AA and its metabolite, PGH(2). Among all PGs synthesized, PGF(2alpha) was the major prostanoid produced by trypanosome lysates. We have purified a novel T. brucei PGF(2alpha) synthase (TbPGFS) and cloned its cDNA. Phylogenetic analysis and molecular properties revealed that TbPGFS is completely distinct from mammalian PGF synthases. We also found that TbPGFS mRNA expression and TbPGFS activity were high in the early logarithmic growth phase and low during the stationary phase. The characterization of TbPGFS and its gene in T. brucei provides a basis for the molecular analysis of the role of parasite-derived PGF(2alpha) in the physiology of the parasite and the pathogenesis of African trypanosomiasis.

The lack of respiratory effects of the ocular hypotensive drug latanoprost in patients with moderate-steroid treated asthma

The use of beta blockers for glaucoma treatment may cause serious bronchoconstriction in patients with chronic obstructive pulmonary disease. The synthetic prostaglandin (PG) F2 alpha-analogue latanoprost (13,14,dihydro-17-phenyl-18,19,20-trinor-PGF-2-alpha-iso propylester) represents a new class of drugs for glaucoma treatment. In this study the pulmonary tolerability to latanoprost in 12 healthy volunteers and 11 (one withdrawal due to a sty before latanoprost treatment) subjects with moderate but stable steroid-treated intrinsic asthma was examined. Asthmatic subjects received 30 microliters of vehicle (placebo) at the scheduled administration times on baseline day. On a second day, a minimum of one week later, increasing concentrations (0.35, 115 and 350 micrograms/ml) of latanoprost were added to the vehicle and given topically to both eyes. Healthy volunteers were given latanoprost only. ECG, blood pressure, heart rate, forced expiratory volume (FEV1), peak expiratory outflow (PEF) and forced vital capacity (FVC) were recorded immediately prior to and 15, 30, 45 and 60 minutes after latanoprost. Asthmatic patients inhaled salbutamol (0.2 mg) at 60 minutes after the highest latanoprost dose. There were no significant differences in pulmonary function, blood pressure or heart rate after latanoprost in the healthy volunteers. Moreover, all parameters were unaffected in asthmatic patients on the day latanoprost was given compared to the baseline day. Latanoprost did not dampen the bronchodilator response to beta-2-adrenergic stimulation. It is concluded that latanoprost did not affect lung function in healthy subjects or in asthmatics after a total accumulated dose 10 times that clinically recommended for glaucoma treatment. Therefore, latanoprost appears to be safe for glaucoma treatment in patients with steroid-treated stable moderate intrinsic asthma.

Alterations in eicosanoid production by rat alveolar type II cells isolated after silica-induced lung injury

Although alveolar type II cells in primary culture have been shown to produce eicosanoids and exposure of type II cells to silica in vitro alters eicosanoid production, the production of eicosanoids by alveolar type II cells isolated after acute lung injury in vivo has not been evaluated. Therefore, we investigated the production of arachidonic acid (AA) metabolites by alveolar type II cells isolated after silica-induced lung injury. Alveolar type II cells were isolated from rats 14 days after intratracheal silica instillation and from untreated animals. Type II cells were separated into normotrophic and hypertrophic populations by centrifugal elutriation, and secreted eicosanoids were determined under basal and stimulated conditions by enzyme immunoassay on the day of isolation and after 1 day in culture. Under basal conditions, freshly isolated type II cells from silica-treated animals produced more prostaglandin (PG) E2 than 6-keto-PGF1 alpha or thromboxane B2 (TxB2). Production of all three prostanoids increased with increasing cell size. The calcium ionophore A23187 stimulated a less than 2-fold increase in PGE2 and 6-keto-PGF1 alpha production in all groups of cells. In contrast, this calcium ionophore greatly enhanced TxB2 and leukotriene C4 (LTC4) production by normotrophic type II cells from both untreated and silica-treated animals. Incubation with exogenous AA suggested that the increased capability of the hypertrophic cells to synthesize PGE2 and TxB2 was due primarily to an increase in arachidonate availability. The hypertrophic type II cells also appear to have increased prostacyclin synthase activity. There were no differences in the catabolism of PGE2 between the normotrophic and the hypertrophic type II cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Catecholamines inhibit leukotriene formation and decrease leukotriene/prostaglandin ratio

Adrenaline, noradrenaline, isoprenaline, and to a lesser extent dopamine inhibit the release of leukotriene (LT) B2 from calcium ionophore-stimulated human polymorphonuclear leukocytes, while the release of prostaglandin (PG) E2 is proportionally elevated. The inactivity of salbutamol, a noncatechol adrenergic beta 2-receptor agonist, and the inability of propranolol to antagonize the effects of adrenaline, suggest the mediation through beta-receptor independent mechanisms. Neither are alpha-1-receptors involved, as prazosin, a specific antagonist, fails to inhibit the reaction. As the principles for biochemical regulation of LT- and PG-production are met by catecholamines in several tissues, the mechanism is considered to be of general physiological importance. Catecholamines may function as coenzymes/antioxidants which, by altering the redox state of the enzyme iron or heme, decrease the LT/PG ratio thus protecting the organism against tissue anaphylaxis and other LT-related pathophysiology.

The effect of diclofenac acid (Voltaren) on bleomycin-induced pulmonary fibrosis in hamsters

Bleomycin is an anti-neoplastic compound which produces a time- and dose-dependent pulmonary fibrosis. The mechanisms which cause this fibrosis are not known. However, the ability of bleomycin to modulate prostaglandin synthesis, degradation and circulating levels appears to be central to the fibrosis. Previous studies, which have attempt to modulate bleomycin-induced fibrosis by prevention of prostaglandin synthesis have conflicting results. Therefore, the present study was designed to determine the effects of diclofenac acid, a nonsteroidal anti-inflammatory compound, on the development of bleomycin-induced pulmonary fibrosis. Diclofenac acid pretreatment and daily injections prevented lung collagen accumulation after intratracheal bleomycin. In addition diclofenac acid treatment resulted in significantly lower lung collagen level after intratracheal bleomycin at 14 and 21 days when compared with bleomycin alone. These data indicate that diclofenac acid treatment inhibits bleomycin-induced lung fibrosis possible through the prevention of prostaglandins synthesis.

Dietary fish oil inhibits bleomycin-induced pulmonary fibrosis in the rat

Intratracheal bleomycin induces pulmonary fibrosis in experimental animals, but the mechanisms involved are poorly understood. Since altered levels of fatty acid metabolites are associated with bleomycin-induced lung injury, we examined the effects of a change in dietary fat on bleomycin-induced fibrosis. Previously we have shown that an essential fatty acid-deficient diet can reduce the severity of bleomycin-induced pulmonary fibrosis. The present study examined the effect of replacement of usual dietary fat with menhaden oil, rich in eicosapentaenoic acid, on the development of pulmonary fibrosis. Weanling rats were raised on a standard laboratory diet or a diet consisting of a fat-free powder to which was added 25% (w/w) of menhaden oil. After 8 weeks of feeding, the animals received either 1.5 units of bleomycin or an equivalent volume of saline intratracheally. In animals receiving the laboratory diet, bleomycin treatment produced a 44% increase in total lung protein content when compared to saline-treated controls (p less than 0.001) and a 77% increase in total lung hydroxyproline content (p less than 0.01). In contrast, bleomycin-treated animals receiving the menhaden oil diet had only small increases, which did not reach statistical significance, in protein and hydroxyproline content in the lung. Bronchoalveolar lavage cellularity did not differ among the treatment groups, but the percentage of lavage macrophages was slightly diminished in bleomycin-treated animals receiving the laboratory diet. Cellular differentials of lavage fluid did not differ significantly between bleomycin- and saline-treated animals receiving the menhaden oil diet. Bleomycin-induced histologic changes, quantitated by morphometric analysis, were significantly reduced with the menhaden oil diet. We conclude that a diet rich in eicosapentaenoic acid can significantly ameliorate bleomycin-induced pulmonary fibrosis, possibly via alterations in eicosanoid metabolism.

Endotoxin-induced hyperreactivity of the guinea-pig isolated trachea coincides with decreased prostaglandin E2 production by the epithelial layer

1. Pretreatment of guinea-pigs with endotoxin (1 mg kg-1 b.w., i.p., 4 days before the experiments) results in respiratory airway hyperreactivity in vitro. Dose-response curves with either arecoline or histamine on isolated tracheae from these animals display increased maximal contractions, and decreased EC50 values. 2. Tracheae denuded of epithelium respond with a similar hyperreactivity to histamine as observed in preparations from endotoxin pretreated animals. Removal of the epithelial layer of tracheae from endotoxin pretreated guinea-pigs did not additionally affect the histamine dose-response curve. 3. The cyclo-oxygenase inhibitor indomethacin (10 microM) induces histamine hyperreactivity which is equal in intact and epithelium-denuded tracheae from saline or endotoxin pretreated guinea-pigs. Similar results are obtained with the combined lipoxygenase/cyclo-oxygenase inhibitor nordihydroguaiaretic acid (10 microM). 4. Histamine (0.1 mM) induces an increase in prostaglandin E2 (PGE2) formation by the tracheal spiral in vitro, which is reduced by 34% by endotoxin pretreatment, and by about 60% following epithelium removal irrespective of endotoxin pretreatment. 5. Arachidonic acid (AA, 22 microM) stimulation of the guinea-pig trachea in vitro induces a relaxation, and an increase in PGE2 production. In preparations lacking the epithelium, AA induces a contraction which coincides with a 60% reduced increase in PGE2 formation. These effects are not altered by endotoxin pretreatment. 6. It is concluded that the endotoxin-induced respiratory airway hyperreactivity may be caused by a disturbed ability of epithelial cells to synthesize PGE2. The decreased formation of this prostaglandin is rather the consequence of a diminished liberation of AA from the phospholipid stores than a dysfunction of the cyclo-oxygenase enzyme.

A new role for histamine H2-receptors in asthmatic airways

Histamine tachyphylaxis develops with repeated inhalation of histamine in asthmatic subjects, and this appears to be due to the release of inhibitory prostaglandins. The purpose of this study was to determine whether histamine H2-receptors are also involved in the development of this protective effect in the airways. Seven subjects with mild asthma were studied on 2 days separated by at least 1 wk. On both days, three histamine inhalation tests were performed, separated by 1 h. The response was expressed as the provocative concentration of histamine causing a 20% decrease in FEV1 (histamine PC20). Before each study day subjects were pretreated with placebo or cimetidine (300 mg twice a day) for 3 days in a double-blind, randomized, crossover study. Cimetidine pretreatment had no effect on either baseline FEV1 or on baseline histamine PC20 (p = 0.461). After pretreatment with placebo, histamine tachyphylaxis occurred in all subjects; the mean PC20 increased from 3.01 mg/ml (%SD, 1.44) to 4.88 mg/ml (%SD, 1.68) and to 6.84 mg/ml (%SD, 1.68). Cimetidine pretreatment prevented histamine tachyphylaxis; the mean PC20 was 2.72 mg/ml (%SD, 1.77), 3.03 mg/ml (%SD, 1.73), and 3.56 mg/ml (%SD, 1.59) with repeated tests. These values differed significantly from placebo for both the second (p = 0.014) and third (p = 0.001) tests. This study demonstrated that cimetidine pretreatment prevents histamine tachyphylaxis and suggests that histamine tachyphylaxis occurs through stimulation of histamine H2-receptors in the airway.

Profiling of bisenoic prostaglandins and thromboxane B2 in bronchoalveolar fluid from the lower respiratory tract of human subjects by combined capillary gas chromatography-mass spectrometry

Methods for the profiling of prostaglandin D2 (PGD2), prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), 15(S),9 alpha,11 beta-trihydroxyprosta-5Z,13E-dien-1-oic acid (9 alpha,11 beta-PGF2), 6-keto-prostaglandin F1 alpha (6kPGF1 alpha), and thromboxane B2 (TxB2) in bronchoalveolar lavage (BAL) fluids from human subjects by combined capillary gas chromatography-mass spectrometry are described. Aliquots (5 ml) of BAL fluid obtained using a standardized lavage protocol were extracted on octadecylsilyl silica cartridges after addition of 0.8 to 2.0 nanograms of tetradeuterated analogs of PGE2, PGF2 alpha, and 6kPGF1 alpha as internal standards. Eluted analytes and internal standards were prepared for vapor phase analysis by sequential reactions resulting in the formation of methyloxime-pentafluorobenzyl ester-trimethylsilyl ether derivatives. The derivatized analytes were detected by simultaneous monitoring of ions at six different masses characteristic for each of the derivatized prostanoids. The samples were of adequate purity for identification and quantitation of each of the prostanoids with detection limits of 0.1 to 0.2 picograms of each analyte per milliliter of BAL fluid. The time required for analysis of each sample was approximately 30 minutes. Standard curves of unlabeled species of the six prostanoids extracted after addition to BAL fluid were linear over a range from subpicogram to nanogram quantities. The differences between the amounts of prostanoid added and the amounts of prostanoid measured were typically less than 19%, and the intra-assay coefficients of variation for repeated measurements of a single sample were less than 20%. PGE2, PGD2, PGF2 alpha, and TxB2 were detectable in BAL fluids from normal subjects with levels of each of these compounds being less than 2.6 picograms/ml. BAL fluids from patients with lung disease presented qualitative and quantitative profiles of prostanoids markedly different than those from normal subjects. These analytical methods provide a basis for in vivo comparisons of prostanoid profiles in the lower respiratory tract of man and should be readily adaptable for use in a variety of clinical studies.

The effect of bleomycin on lung metabolism of prostaglandin E2 in hamster

Lung is a major site of prostaglandin synthesis and degradation. One site of metabolism has been shown to be the endothelial cell. Metabolism of prostaglandins has been shown to be influenced by both physiological and pathological mechanism. Furthermore, it has been suggested that a relationship might exist between pulmonary disease and the lung's ability to synthesize and/or degrade prostaglandins. Therefore, we evaluated if bleomycin-induced fibrosis, a model of human pulmonary fibrosis, affects the ability of lung to metabolize prostaglandins. Single pass metabolism of prostaglandin E2 was evaluated in an isolated, perfused and ventilated lung of hamsters at 5 and 500 nM concentrations 4,7,14,21 and 28 days after intratracheal bleomycin. The metabolism of prostaglandin E2 was not changed at the 5 nM level, but was significantly decreased at 500 nM level on day 14 and day 28 after intratracheal bleomycin. The results suggest that intratracheal bleomycin causes alterations in prostaglandin metabolism; the mechanism(s) is unknown but may be related to endothelial cell damage and possible changes in alveolar-capillary surface area.

Effects of intratracheal administration of bleomycin on prostaglandins and thromboxane-B2 and collagen levels of the lung in hamsters

The effects of intratracheal administration of one unit of bleomycin on the lung levels of different prostaglandins (PGs), thromboxane B2 (TxB2), and total collagen were investigated in hamsters in two separate sets of this study. Averaging the values from two sets, the lung levels of 6-keto-PGF1 alpha (stable metabolite of PGI2), TxB2 (stable metabolite of TXA2), PFG2 alpha, and PGE in bleomycin-treated animals were increased by 11-, 7.5-, 7-, and 3-fold over the saline control at 14 days post treatment, respectively. The total lung collagen content in bleomycin-treated animals was significantly increased to 180% of the control during the same period. A number of possibilities for a marked variation in the levels of rise for different PGs and TxB2 and their significance in bleomycin-induced lung fibrosis have been discussed. It was concluded from the findings of the present study that there is a relationship between the lung levels of various metabolites of arachidonic acid cascade and bleomicin-induced increases in the synthesis and accumulation of lung collagen. The nature of this relationship, however, remains to be elucidated.

Prostaglandin F2 alpha increases responsiveness of pulmonary airways in dogs

We studied the effect of prostaglandin F2 alpha (PGF2 alpha) on the responsiveness of pulmonary airways in dogs. Airway responsiveness was assessed by determining the bronchoconstrictor response to increasing concentrations of acetylcholine aerosol delivered to the airways. In each of five dogs, we determined responsiveness during treatment with physiologic saline, histamine, or PGF2 alpha aerosols. The doses of histamine and PGF2 alpha were determined by establishing the largest dose of each which could be given to the dog without causing bronchoconstriction (subthreshold doses). We found that airway responsiveness was not significantly different during histamine treatment than after saline, however, responsiveness increased during treatment with PGF2 alpha. In addition, the hyperresponsiveness induced by PGF2 alpha was prevented by pretreatment with the ganglion blocking drug hexamethonium (5 mg/kg given intravenously). The results show that PGF2 alpha specifically increases the responsiveness of pulmonary airways in doses that do not cause bronchoconstriction, and suggest that the hyperresponsiveness involves a neural mechanism such as increased responsiveness of airway sensory nerves.

Release of arachidonate cascade products by the rabbit bladder; neurophysiological significance?

The endogenous production of prostaglandins and thromboxane A2 by the rabbit urinary bladder was assessed by radioimmunoassay in a relatively intact system and in the absence of substrate. PGE2 and PGI2 (prostacyclin) were the main prostaglandins released whereas PGF2 alpha ratio of 5:1 and a PGI2 to PGF2 alpha ratio of 3:1 were observed. This qualitative pattern was independent of bladder area. In addition, prostaglandin release by the bladder body was significantly greater than by the bladder base at all incubation times. The physiological implications of these experimental observations are discussed.

The in vitro synthesis and degradation of prostaglandins during the development of bleomycin-induced pulmonary fibrosis in hamsters

Subsequent to optimization of conditions for enzyme assay, we examined the in vitro synthesis and degradation of prostaglandins by the lung during the development of bleomycin-induced pulmonary fibrosis in hamsters. It was found that the microsomal protein content on a per lung basis was significantly increased to 144, 129, 134, and 121% of control (2.3 mg protein/lung) at 4, 7, 14 and 21 days post-treatment, respectively. The synthesis of PGD2 was significantly elevated to 10.2, 10.8, and 12.5 nmoles/lung at 7, 21 and 28 days, respectively, as compared to the control value of 5.6 nmoles/lung. Significant increases in PGF2 alpha synthesis from the control value of 3.3 nmoles/lung to 5.2, 8.2 and 5.5 nmoles/lung were found at 4, 7 and 21 days post-treatment, respectively. The synthesis of PGE2 also showed significant increases above the control value of 6.1 nmoles/lung to 10.5, 12.2 and 11.0 nmoles/lung at 7, 21 and 28 days post-treatment, respectively. Similarly, the synthesis of 6-keto-PGF1 alpha was significantly increased to 7.4, 7.5 and 8.6 nmoles/lung at 7, 21 and 28 days post-treatment, respectively, as compared to the control value of 4.4 nmoles/lung. The synthesis of TxB2 was also significantly increased from the control value of 3.9 nmoles/lung to 7.5 and 6.4 nmoles/lung at 7 and 21 days post-treatment, respectively. Accompanying the increased synthesis of prostaglandins in general, the in vitro degradation of PGF2 alpha was significantly increased from the control value of 71.1 nmoles/lung to 173.5, 131.7 and 143.3 nmoles/lung at 2, 4 and 7 days after bleomycin treatment, respectively. We conclude that bleomycin-induced pulmonary fibrosis leads to changes in prostaglandin synthesis and degradation possibly as a result of an accompanying inflammatory response and resident cellular proliferation.

Inactivation of prostaglandins in the perfused rat lung

Inactivation in the isolated perfused rat lung of prostaglandins (PG) D2, E1, F2 alpha, I2 and the metabolites 6-keto PGF1 alpha (=6KF1 alpha) and 13, 14-dihydro-15-keto PGF2 alpha (= KH2F2 alpha) was studied using 5 min perfusion of 7-10 ng/ml PG in Krebs' solution containing 0.02 microCi/ml tritiated PG and 4.5% bovine serum albumin (BSA). The parameters measured were (a) extent of inactivation (F2 alpha greater than E1 greater than D2 greater than 6KF1 alpha greater than I2; KH2F2 alpha unchanged), (b) the accumulation of PG within the lung measured as tissue to medium ratio (F2 alpha = D2 greater than E1 greater than 6KF1 alpha greater than I1 - KH2F2 alpha) and (c) rate of equilibration of PG within the lung measured as "wash-in t 1/2" (D2 greater than F2 alpha greater than E1 greater than I2 = 6KF1 alpha = KH2F2 alpha). Removal of sodium ions produced a small decrease in PGD2 and PGE1 breakdown but not of PGF2 alpha whereas breakdown of all PGs was markedly inhibited at 5 degrees. Removal of BSA enhanced PGE1 and PGI2 breakdown but not that of PGF2 alpha. Addition of 10% BSA inhibited PGE1 breakdown but not that of PGF2 alpha. Binding of PGs to 4.5% BSA was PGE1 = KH2F2 alpha greater than D2 greater than F2 alpha, and increased at 10% BSA or after removal of sodium ions. These data support the view that PGs must be taken up into pulmonary cells by a transmembrane carrier process as a prerequisite for enzymatic breakdown. The metabolites are then released back into the pulmonary circulation.

Allergen tachyphylaxis of guinea pigs in vivo; a prostaglandin E mediated phenomenon?

Ovalbumin (OA) sensitized guinea pigs were repeatedly challenged with 1% OA in saline nebulized ultrasonically at the 0, 10, 20, 60 and 70th min. The intensity of bronchial obstruction was measured by body plethysmography. The first three challenges (0. 10, 20 min) caused strong asthmatic reactions in all animals, the last two (60, 70 min) only mild one in 10 out of 15 animals. The development of this "tachyphylaxis" was markedly reduced by pretreatment of the animals with cyclooxygenase inhibitors (indomethacin 10 mg/kg intraperitoneally resp, acetylsalicylic acid 10 mg/kg orally 2 h before tests). The effect of both inhibitors (i.e. inhibition of tachyphylaxis) was abolished by supplementing prostaglandin E2 as aerosol simultaneously to the allergen (100-200 ng per inhalation). The results suggest that allergen tachyphylaxis we have observed in vivo might be due to synthesis of cyclooxygenase products, e.g. prostaglandin E.

Indomethacin inhibition of intralipid-induced lung dysfunction

Intralipid-related pulmonary alterations have been attributed to hyperlipemia. To better quantitate and explain these alterations, Intralipid (0.4 gm/kg over one hour) was infused into three groups of rabbits and saline into a fourth group. Group I had normal lung function; Groups II-IV were pretreated with oleic acid and Group III also received indomethacin. Serum triglyceride (TG) levels, arterial (a) and end-tidal (A) PCO2 and PO2 were measured at baseline and then hourly for six hours. There was no ventilatory deterioration in Group I despite a peak TG level of 638 mg/dl. In Group II there was an Intralipid-related PaO2 decrease of 11-13 mmHg (p less than .01) and a delta AaPO2 increase of 16 mmHg (p less than .01); both returned to baseline without significant TG normalization. Since indomethacin prevented these PaO2 and delta AaPO2 changes despite a significant TG increase, the effects of Intralipid appear not to be TG-related but rather to be related to PG-mediated alterations in pulmonary vasomotor tone. Our results are most consistent with a net increase in vasodilating prostaglandins and resultant hypoxemia secondary to unblocking of baseline hypoxic vasoconstriction.

Differences in biological activation of arachidonic acid in perfused lungs from guinea pig, rat and man

Arachidonic acid (AA) perfused through the pulmonary circulation of isolated lungs from guinea pig was metabolised to more myotropic metabolites than it was in rat or hjman lungs. There was more rabbit aorta contracting activity in effluent following AA in guinea-pig lungs than in rat or human lungs. This correlated with the amount of thromboxane B2-like material identified by t.l.c. following 14C-AA infusion. The release of cyclooxygenase products by guinea-pig SRS-A was observed only in guinea-pig lungs and not in rat or human lungs. The calcium ionophore A23187 released cyclo-oxygenase products from the lungs of all three species but rat and human lungs released less and required more ionophore for relase. There are important quantitative and qualitative differences in the activation of exogenous or endogenous AA between guinea-pig lungs and those from rat and human. The rat lung provides a better model than guinea-pig lung for AA metabolism in human lung.

Pulmonary vascular response to prostacyclin in fetal lambs

Eighteen prostacyclin injections (19.4 +/- 1.5 micrograms/kg) were performed in five chronically instrumented, intact fetal lambs in order to study the effects on pulmonary blood flow. These resulted in a brief period of bradycardia followed by a more prolonged period of increased pulmonary blood flow. In this latter phase, pulmonary blood flow increased from a baseline value of 49 +/- 4 ml/(kg min) to 122 +/- 10 ml/(kg min). Systolic/diastolic pulmonary arterial pressure simultaneously fell from 73 +/- 2/48 +/- 1 to 68 +/- 2/42 +/- 1 mm Hg. Flow through the ductus arteriosus was unchanged and right ventricular output increased to account for the increased pulmonary blood flow. Thus, prostacyclin causes pulmonary vasodilation in intact fetal lambs and may participate in the control of fetal pulmonary blood flow and the circulatory adjustments to extra-uterine life.

The effect of histamine-1 and histamine-2 antagonists on airway responses to histamine in the rhesus monkey

This study used rhesus monkeys with consistent respiratory responses to aerosolized histamine. Two systems of histamine challenge were evolved to study the effects of histamine antagonists on the histamine-induced respiratory response. One system consisted of administering increasing subreactive concentrations of histamine until an airway response (H) occurred. This threshold histamine dose was repeated (H'). The pulmonary function changes occurring with the H' challenge were less intense than those with H. M, a histamine-2 receptor antagonist, when given before the H' dose was associated with a potentiated H' response compared with the threshold H response. This provides evidence for histamine-2 receptor sites in rhesus monkey airways. A second system used duplicate histamine challenges with a known reactive dose of histamine. In this system, the pulmonary function changes occurring with the repeated challenge (H') were greater than with the first reactive challenge dose (H). This H' response was inhibited partially with diphenhydramine, a histamine-1 receptor antagonist. These two systems of histamine challenge provide an experimental model for evaluating pharmacologic alteration of histamine-induced respiratory responses. There is evidence for the existence of histamine-1 and histamine-2 receptor sites in the airways of the rhesus monkey.

Prostaglandin production by type II alveolar epithelial cells

Prostaglandin production was studied in fetal and adult type II alveolar epithelial cells. Two culture systems were employed, fetal rat lung organotypic cultures consisting of fetal type II cells and monolayer cultures of adult lung type II cells. Dexamethasone, thyroxine, prolactin and insulin, hormones which influence lung development, each reduced the production of prostaglandin E and F alpha by the organotypic cultures. The fetal cultures produced relatively large quantities of prostaglandin E and F alpha and smaller quantities of 6-keto-prostaglandin F1 alpha and thromboxane B2. However, prostaglandin E2 production was predominant. In contrast, the adult type II cells in monolayer culture produced predominantly prostacyclin (6-keto-prostaglandin F1 alpha) along with smaller quantities of prostaglandin E2 and F2 alpha. The type II cells were relatively unresponsive to prostaglandins. Exogenously added prostaglandin E, had no effect on cell growth, and only a minimal effect on cyclic AMP levels in the monolayer cultures.

Dramatic pyrexic and cardiovascular response to intravaginal prostaglandin E2

The efficacy of prostaglandin E2 (PGE2) for the induction of labor in pregnancies complicated by IUFD or missed abortion has been demonstrated. Gastrointestinal and pyrexic side effects are frequently observed. The following report describes two patients with documented IUFD who experienced a dramatic pyrexic and cardiovascular response to the intravaginal PGE2. In addition, evidence will be provided to account for this unusual pharmacologic reaction, as well as provide a method of managing this unusual side effect.