Repetitive ozone exposure of young adults: evidence of persistent small airway dysfunction.

Earlier, we found that acute ozone (O3) exposure caused, along with inflammation, greater, more protracted changes in small airway function (isovolumetric V max at intermediate to low lung volumes) than in FVC or FEV1. To test if this distinction prevailed with repetitive O3 exposure, we exposed eight healthy adults on four consecutive days alternatively to filtered air (FA) and O3 (0.25 ppm x 2 h). Isovolumetric FEF25-75, Vmax50, and Vmax75, were grouped into a single value representing small airway function (SAW(grp)); respiratory frequency (f) and tidal volume (VT) were monitored during exercise. On Day 5, peripheral airway resistance (Rp) was measured followed by lavage. All daily spirometric and ventilatory changes declined in magnitude (adapted) after one or more days of O3 exposure. In addition, SAW(grp), f, and VT showed persistent changes beginning with Day 2, denoted either by depression of the preexposure baseline (SAW(grp)) or exaggerated tachypnea during exercise. O3-induced neutrophilia (p = 0.04) was present in lavage fluid. The possible relationship between these persistent changes in small airway function, measured in days, and the likelihood of cumulative injury in the same region if exposure is long term, is unknown.

Tissue prostanoids as biomarkers for chemoprevention of colorectal neoplasia: correlation between prostanoid synthesis and clinical response in familial adenomatous polyposis.

Recent studies indicate that sulindac, a nonsteroidal anti-inflammatory drug (NSAID), lowers mucosal prostanoid levels and regresses colorectal adenomas in patients with familial adenomatous polyposis (FAP). To determine whether they are biomarkers for sulindac-mediated chemoprevention of colorectal adenomas, levels of 5 prostanoids [prostaglandin (PG) D2, PGE2, PGF2alpha, thromboxane B2, and 6-keto-PGF1alpha] in the normal-appearing rectal mucosa from 7 FAP patients with a history of subtotal colectomy and ileorectal anastomosis and 4 FAP patients without surgery, were measured in the absence or presence of exogenously added arachidonic acid before the initiation and at the end of 3 months of sulindac treatment. The addition of arachidonic acid resulted in a uniform increase in the levels of all 5 prostanoids although this increase was selectively attenuated in patients with ileorectal anastomosis who took sulindac. In the latter patients, arachidonic acid also augmented the inhibition of prostanoid synthesis by sulindac. In contrast, sulindac failed to attenuate the increase in prostanoid levels resulting from arachidonic acid in patients without previous surgery. Importantly, when measured in the presence of arachidonic acid, the reduction in the levels of all 5 prostanoids due to sulindac was statistically correlated with a reduction in the size and number of adenomas in the two groups of patients combined. These results suggest that tissue prostanoids measured in the presence of arachidonic acid may serve as sensitive and reliable biomarkers in monitoring the clinical responsiveness of FAP patients undergoing chemoprevention for colorectal neoplasia with NSAIDs.

Size-dependent increase in prostanoid levels in adenomas of patients with familial adenomatous polyposis.

Recent studies indicate that nonsteroidal anti-inflammatory drugs have a chemopreventive effect against colorectal neoplasia. Nonsteroidal anti-inflammatory drugs inhibit cyclooxygenases, principal enzymes that mediate the formation of prostanoids. To determine whether prostanoids are involved in the pathogenesis of colorectal adenomas, we compared the levels of five major stable metabolic products of the cyclooxygenase pathway in the normal-appearing mucosa and in adenomas of patients with familial adenomatosis polyposis. Of 12 patients tested, 6 had elevated levels of at least one prostanoid in the adenomas. More importantly, the relative levels of three prostanoids [prostaglandin (PG)D2, PGE2, and 6-keto-PGF1alpha] were elevated in adenomas compared to normal-appearing mucosa from the same patients, and the resulting ratios were correlated with the size of the adenoma. These results suggest a role for prostanoids in progression of colorectal polyposis in familial adenomatosis polyposis patients.

Prostaglandin levels in human colorectal mucosa: effects of sulindac in patients with familial adenomatous polyposis.

Recent evidence suggests that nonsteroidal antiinflammatory drugs (NSAIDs) may prevent colorectal cancer. The mechanism of action of NSAIDs in chemoprevention is unknown but may be linked to their effect on mucosal prostaglandin levels. Levels of five major prostaglandin metabolites were measured by gas chromatography-mass spectrometry in biopsy specimens of flat rectal mucosa from four patients with familial adenomatous polyposis (FAP) before and after sulindac therapy and from five healthy individuals. The prostaglandin present at highest concentration in rectal mucosa from FAP and control subjects was prostaglandin E2. The concentration of thromboxane B2 alone was significantly elevated in FAP patients compared to controls (P = 0.016). In FAP patients treated with sulindac, all prostaglandin metabolite levels were significantly reduced compared to pretreatment levels (P < 0.05) except prostaglandin D2 (P = 0.07). Prostaglandins D2, E2, F2alpha, and 6-keto-F1alpha levels also were significantly reduced in FAP patients on sulindac compared to healthy controls (P < 0.05). However, interpatient heterogeneity of response to sulindac was evident with changes ranging from +19% to -89%, and the patient with the greatest reductions after sulindac developed colorectal cancer after 35 months of therapy. Sulindac treatment, at drug doses shown to regress colorectal adenomas in FAP patients, has heterogeneous effects on the level of major prostaglandins in their rectal mucosa and may not prevent colorectal cancer due to uncoupling of prostaglandin levels and carcinogenesis.

Protective effect of substance P on permeability of airway epithelial cells in culture.

Although substance P (SP) has been shown to mediate microvascular leakage in response to various stimuli, some data suggest that, in contrast, SP may play a protective role in the maintenance of airway epithelial integrity. To investigate the effect of SP on epithelial barrier function, we measured paracellular mannitol flux and the transepithelial potential difference (PD) of human bronchial epithelial (HBE) and canine bronchial epithelial (CBE) cells. Incubation of confluent cell cultures with SP had no effect on baseline flux. However, pretreatment inhibited the flux-enhancing effects of 0.5 ppm ozone by 50% in HBE cells and 40% in CBE cells and inhibited the ozone-induced decrease in PD in CBE cells by 54%. SP-afforded protection was reduced by the neurokinin (NK)-1 receptor antagonist CP-96,345.NK1 and NK3 receptor agonists also inhibited ozone-induced permeability, whereas an NK2 receptor agonist was without significant effect. These data indicate that SP exerts a protective effect on bronchial epithelial barrier function under conditions of challenge, which appears to be mediated in large part through NK1 receptors.

Down-regulation of canine airway mast cell function following exposure to ozone in vivo.

The influence of ozone on the function of airway cells involved in allergic responses is of particular interest due to the increasing prevalence of this environmental oxidant pollutant. In the present studies, the peripheral airways of Ascaris-sensitive dogs were expose to ozone (1 ppm, 5 min) or air (control) and the exposed segments were lavaged 30 min later. The kinetics and magnitude of release of PGD2 and histamine from canine peripheral airway mast cells (PAMC) was determined following in vitro challenge with Ascaris antigen or calcium ionophore approximately 4 h from the time of the in vivo exposures. Histamine content was significantly lower in PAMC retrieved from ozone- versus air-exposed segments (3.0 +/- 0.1 vs. 5.2 +/- 0.5 pg/cell). Absolute release of histamine at 20 min was decreased by 47 and 43% in ozone-exposed cells stimulated with antigen or ionophore, respectively. Maximal synthesis and release of PGD2 in response to antigen (345 +/- 22 pg/10(3) PAMC) or ionophore (1055 +/- 104 pg/10(3) PAMC) was inhibited by 32 and 55%, respectively, in cells from ozone-exposed segments. Inhibition of prostanoid synthesis was not observed in alveolar macrophages in the lavage samples, nor could decreased PGD2 be attributed to enhanced catabolism. These data indicate a differential down-regulatory influence of ozone on subsequent release of granular mediators and newly synthesized PGD2 from PAMC following brief in vivo exposure that lasts for several hours.

Expression of ICAM-1 in airway epithelium after acute ozone exposure in the mouse.

We investigated the time course and regional distribution of the expression of intercellular adhesion molecule-1 (ICAM-1) on airway epithelial cells and the polymorphonuclear leukocyte (PMN) inflammatory response in the lung after acute exposure to ozone (O3). C57BL/6J mice were exposed to air or 2 ppm O3 for 3 h and killed immediately or 3, 6, 9, or 21 h after exposure. Expression of ICAM-1 was examined by immunohistochemical staining of frozen sections. PMN influx was evaluated by lavage and by histochemical staining of myeloperoxidase (MPO) and measurement of tissue MPO activity. ICAM-1 expression exhibited regional selectivity and temporal patterns that were unique to each region. Upregulation of ICAM-1 expression on the epithelial cells in the trachea, and to a lesser extent in the lobar and segmental bronchi, was observed 3-9 h after exposure and remained present at 21 h. Enhanced ICAM-1 expression in bronchioles and terminal bronchiole/alveolar duct regions was evident earlier (immediately to 3 h after exposure) but returned to baseline levels by 21 and 9 h, respectively. Maximal ICAM-1 expression and PMN influx in the lung parenchyma were concurrently observed at 3 h, followed by transepithelial migration of PMNs to the airway lumen. These results demonstrate regional variations in airway inflammatory activity and are supportive of the notion that upregulation of ICAM-1 on the airway epithelium may play a role in local regulation of PMN influx to the airways after acute O3 exposure.

Specific binding of endothelin-1 to canine tracheal epithelial cells in culture.

We have studied the binding of endothelin-1 (ET-1) to cultured canine tracheal epithelial cells. A single specific binding site for 125I-labeled ET-1 was identified with an apparent dissociation constant (Kd) of 0.2 nM, maximal binding sites (Bmax) of 6.7 x 10(3) sites/cell, and half-maximal inhibition (IC50) of 0.3 nM during a 2-h incubation period. The binding of 125I-ET-1 to these cells was inhibited by the presence of unlabeled ET-1, ET-2, or BQ-123, whereas ET-3 and sarafotoxin S6c did not compete for this binding site. These binding characteristics are consistent with those of the ETA receptor. At 37 degrees C, specific binding continuously increased over 18 h, while at 4 degrees C, it reached a plateau by 2 h. The increase in binding at 37 degrees C was not associated with DNA synthesis but was dependent upon protein synthesis, suggesting that epithelial binding sites were produced continuously under these incubation conditions. Our results indicate that canine tracheal epithelial cells possess specific binding sites for ET-1 with characteristics similar to those of the ETA receptor subtype. Because these cells are demonstrated to both release and bind ET-1, the results further suggest that ET-1 is involved in paracrine and/or autocrine control mechanisms in the airway epithelium.

The effects of ozone on immune function.

A review of the literature reveals that ozone (O3) exposure can either suppress or enhance immune responsiveness. These disparate effects elicited by O3 exposure depend, in large part, on the experimental design used, the immune parameters examined as well as the animal species studied. Despite the apparent contradictions, a general pattern of response to O3 exposure can be recognized. Most studies indicate that continuous O3 exposure leads to an early (days 0-3) impairment of immune responsiveness followed, with continued exposures, by a form of adaptation to O3 that results in a re-establishment of the immune response. The effects of O3 exposure on the response to antigenic stimulation also depend on the time at which O3 exposure occurred. Whereas O3 exposure prior to immunization is without effect on the response to antigen, O3 exposure subsequent to immunization suppresses the response to antigen. Although most studies have focused on immune responses in the lung, numerous investigators have provided functional and anatomical evidence to support the hypothesis that O3 exposure can have profound effects on systemic immunity.

The 5-lipoxygenase pathway in cultured human intestinal epithelial cells.

Leukotrienes (LTs), the 5-lipoxygenase (5-LOX) metabolites of arachidonic acid, have roles in many biological processes relevant to the gastrointestinal tract, including intestinal inflammation. We screened two well-known human intestinal epithelial cell lines, HT29 and Caco-2, for evidence of LT-associated enzyme transcripts and LT synthesis. Northern blot analysis of total RNA from both intestinal lines demonstrated high levels of transcripts for LTA4 hydrolase, a multisubstrate enzyme that converts the 5-LOX metabolite, LTA4, to LTB4. With total RNA, the 5-LOX transcript was detected only in HT29. Caco-2 failed to show 5-LOX message even with poly A-containing RNA, although the transcript could be amplified with the polymerase chain reaction. Messenger RNA for FLAP, the 5-lipoxygenase-activating protein, was detectable in both cell lines, but only with poly A-containing RNA. In a sonicated cell preparation, HT29, but not Caco-2, revealed detectable levels of 5-HETE and LTB4. These results suggest that certain intestinal epithelial cells possess a limited capacity to synthesize LTs.

Modulation of bronchial epithelial cell barrier function by in vitro ozone exposure.

The epithelial cells lining the small, peripheral airways function as important targets for the action of inspired ozone. Loss of epithelial barrier integrity in these regions is a common element in ozone-induced airway inflammation. To investigate the direct effect of ozone on epithelial barrier function, canine bronchial epithelial (CBE) cells grown with an air interface were exposed for 3 hr to 0.2, 0.5, or 0.8 ppm ozone or to air. Mannitol flux, used as an index of paracellular permeability, increased above air controls by 461%, 774%, and 1172% at the three ozone concentrations, respectively. Transcellular electrical resistance exhibited a dose-related decrease. The immediate effect of 0.8 ppm ozone on permeability was significantly inhibited by preincubation for 48 hr in the presence of 1 ng/ml vitamin E (33%) or 1 microM vitamin A (34%). Responses to 0.5 ppm or 0.8 ppm were inhibited by pretreatment of the cells with 0.1 microM of the actin polymerizing agent phalloidin (34% and 25% inhibition, respectively). The increases in permeability induced by 0.2 and 0.5 ppm ozone were attenuated by 54% and 22%, respectively, at 18 hr after exposure, whereas that to 0.8 ppm was further enhanced by 42% at this time. The effects of ozone are modulated by the availability of antioxidants to the cells and appear to be associated with cytoskeletal dysfunction in CBE cells. The data are consistent with a loss of barrier function linked to a direct oxidative effect of ozone on individual CBE cells and indicate that the reversible or progressive nature of this effect is dose dependent.

Comparison of the toxic effects of hydrogen peroxide and ozone on cultured human bronchial epithelial cells.

In this study, we compared the cytotoxic and genotoxic effects of hydrogen peroxide and ozone on cultured human airway epithelial cells in primary culture. Both agents caused a dose-dependent loss in the replicative ability of epithelial cells and at higher levels of exposure caused acute cytotoxicity as measured by release of lactate dehydrogenase. Differences were seen, however, between the agents' effects with regard to induction of DNA single strand breaks as measured by alkaline elution:; whereas single-strand breaks were detected in significant amounts at concentration of hydrogen peroxide that cause acute cytotoxicity, none were detected at any of the levels of ozone exposure examined. A difference was also seen in the ability of the iron chelator deferoxamine to protect cells from the effect of the two oxidants. Preincubation of cultures with deferoxamine appreciably attenuated the toxicity of hydrogen peroxide but not of ozone. These data suggest that ozone has significant toxic effects on bronchial epithelial cells not mediated through the generation of hydrogen peroxide or hydroxyl radical. Furthermore, the data indicate that the inhibiting action of ozone on cell replicative ability is not mediated through a mechanism related to DNA single strand breaks.

Soluble intracellular adhesion molecule 1 in bronchoalveolar lavage fluid of allergic subjects following segmental antigen challenge.

This study was undertaken to determine the relationship of soluble intercellular adhesion molecule 1 (sICAM-1) levels in bronchoalveolar lavage (BAL) fluid during allergic airway inflammation to those in the vascular compartment and to cellular components in the BAL fluids. A group of 11 allergic subjects underwent initial bronchoscopy during which a control BAL was performed and normal saline (NS) and specific antigen (Ag) were administered to two sublobar segments. A second bronchoscopy was performed 17 to 21 h later, and the NS and Ag segments were lavaged. Blood was drawn before each bronchoscopic procedure. The mean concentration of sICAM-1 in BAL fluid from NS-challenged segments was 59.2 +/- 7.6 ng/ml and was not different from that in unchallenged segments (51.5 +/- 5.6 ng/ml). In BAL fluid from Ag-challenged segments, mean concentrations of sICAM-1 increased significantly to 97.5 +/- 12.5 ng/ml. Segmental antigen challenge was associated with a small but statistically significant increase in sICAM-1 concentrations in serum. The concentrations of sICAM-1 in BAL fluid after antigen challenge exceeded levels that could be accounted for by passive transudation from the circulation, based upon the magnitude of increases in BAL albumin concentrations. The levels of sICAM-1 in BAL from Ag-challenged segments were correlated significantly with the total white cell, lymphocyte, neutrophil, and eosinophil counts in BAL fluids. These results are supportive of the notion that the local release of sICAM-1 may play a role in allergen-induced inflammatory processes in the airways.

Physiologic modulation of bronchial epithelial cell barrier function by polycationic exposure.

Bronchial epithelial cells provide a functional barrier to the movement of water and solutes between the luminal and interstitial compartments of the lung. Barrier integrity can be compromised by a variety of factors, including polycationic proteins released by inflammatory cells. We investigated the characteristics of epithelial barrier function and its modulation by cationic stimuli in canine bronchial epithelial (CBE) cells grown in culture. Morphologic characteristics were examined, and barrier function was assessed by measurements of transepithelial mannitol flux (flux) and electrical resistance (RT) during a stable, 3- to 14-day culture period. CBE cultures exhibited progressive mucociliary differentiation and contained nonciliated, ciliated, and neutral and acidic mucin-secretory cells. The synthetic polycation, poly-L-lysine (PLL), from 2.5 to 10 micrograms/ml, caused dose-related increases in flux and decreases in RT that were not accompanied by detectable release of lactate dehydrogenase (LDH) or changes in histochemical appearance. The effect on RT spontaneously reversed over a 15-h recovery period. The action of PLL on flux was not attenuated by treatment of the cells to stabilize cytoskeletal contractile elements but was immediately attenuated by the addition of heparin to the challenged cells. These results indicate that modulation of the barrier integrity of bronchial epithelial cells by cationic proteins, such as those released by inflammatory cells, represents a physiologic process that may be regulated by endogenous anionic factors.

Endothelin-1 induces stimulation of prostaglandin synthesis in cells obtained from canine airways by bronchoalveolar lavage.

Endothelin-1 (ET-1), a potent mediator released by airway epithelial cells, often exerts its effects in the lung through stimulation of arachidonic acid (AA) metabolism. To investigate its range of influence, we studied the action of ET-1 on the synthesis and release of thromboxane (TX)B2, prostaglandin (PG)D2, and histamine from canine airway cells obtained by bronchoalveolar lavage (BAL). ET-1 (10(-10), 10(-9) and 10(-8)M) stimulated production of TXB2 and PGD2 by BAL cell preparations in a dose-related manner in the absence of measurable histamine release. Release of TXB2 was 10-fold higher than that of PGD2. The effect of ET-1 on AA metabolism in alveolar macrophages was evaluated in preparations of purified (greater than 99%) cells labelled for 20-22 hrs with 3H-AA prior to stimulation. ET-1 (10(-8), 10(-7), 10(-6)M) induced significant, dose-related release of 3H-AA and its metabolites from alveolar macrophages, to levels 350% above control. These studies indicate that low levels of ET-1 can stimulate AA metabolism in resident luminal airway cells, including alveolar macrophages, and suggest that the function of these luminal cells may be modulated by the epithelium, in vivo, through the release of this peptide into the airways.

Inhibition of canine tracheal smooth muscle by mediators from cultured bronchial epithelial cells.

To determine the effect of mediators released from cultured canine bronchial epithelial cells on contraction of canine tracheal smooth muscle, we treated smooth muscle strips with piperazine-N,N'-bis(2-ethanesulfonic acid) buffer "conditioned" by 5 h incubation with cultures of 4- to 5-day-old cultured epithelial cells. Pretreatment of tracheal smooth muscle with conditioned buffer for 5 min resulted in a significant shift to the right of the contractile dose-response curve to histamine in the range of 10(-8) to 5 x 10(-4) M. In addition, conditioned buffer induced a dose-related relaxation of the muscle precontracted by histamine (5 microM). Relaxant activity was also evident against tissues precontracted by 5-hydroxytryptamine or methacholine. Lipid extraction of conditioned buffer reduced its activity to that of the fresh buffer control. Prior treatment of the cells in culture with the cyclooxygenase inhibitor, sodium meclofenamate (4 microM), markedly reduced the relaxant effect of the conditioned buffer, whereas prior treatment with MK-886, an inhibitor of 5-lipoxygenase, did not alter relaxant activity. Analysis of prostanoids released into the buffer by epithelial cells indicated the presence of prostaglandin E2 (PGE2) and 6-ketoprostaglandin F1 alpha, the former in concentrations sufficient to account for the effect of conditioned buffer on precontracted tracheal muscle. Prostaglandin I2 appeared to have a synergistic effect on PGE2-induced relaxation. We conclude that canine bronchial epithelial cells exhibit baseline release of a relaxant lipid factor(s) that can both inhibit and reverse the contraction of tracheal smooth muscle by histamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Ozone reduces murine alveolar and peritoneal macrophage phagocytosis: the role of prostanoids.

Continuous ozone exposure (0.5 ppm, 1-14 days) reduced the phagocytic activity of murine alveolar and peritoneal macrophages. The response of peritoneal macrophages to ozone was virtually indistinguishable from the response of alveolar macrophages. When added exogenously, prostaglandin E2 (PGE2) inhibited alveolar and peritoneal macrophage phagocytosis. To test the hypothesis that prostanoids mediated the effects of ozone on macrophages, PGE levels of bronchoalveolar lavage fluid (BALF) and the phagocytic activity of macrophages from ozone-exposed mice pretreated with cyclooxygenase inhibitors were measured. PGE levels in BALF were increased following ozone exposure, with high levels of PGE associated with large decreases in phagocytic activity. Pretreatment with indomethacin and d-naproxen completely inhibited ozone-induced increases in PGE recovered by BAL and the suppression of peritoneal macrophage phagocytic activity. The inactive enantiomer of naproxen, l-naproxen, was without effect. Indomethacin partially inhibited ozone-induced suppression of alveolar macrophage phagocytic activity. These observations suggest that prostanoids play a key role in the response to ozone.

Contractile responses of guinea pig trachea to oxybarbiturates and thiobarbiturates.

To determine what mechanisms are involved in barbiturate-induced tracheal constriction and whether a relationship exists between barbiturate structure and the ability of the barbiturate to induce constriction, we compared the effects of thiamylal, thiopental, methohexital, pentobarbital, and phenobarbital at increasing airway tone in an intact guinea pig tracheal preparation in the presence and absence of cyclooxygenase and thromboxane synthetase inhibition. Whole tracheas were suspended between two cannulas in 50-ml tissue baths and perfused at a constant flow rate with Krebs-Henseleit solution. The contractile responses were assessed by measuring the pressure differential between the tracheal inlet and outlet ports. Barbiturates were added to the bath of each trachea, which was washed between each drug. Each drug was added to produce final bath concentrations of 10(-6), 10(-5), 10(-4), 10(-3), and 3 x 10(-3) M. Tracheas were also pretreated with meclofenamate (10(-6) M) (a cyclooxygenase inhibitor) and UK 37,248 (10(-8) to 10(-5) M) and OKY 046 (10(-9) to 10(-6) M) (thromboxane synthetase inhibitors), and the thiamylal protocol was repeated. All data were normalized to a concentration of carbachol (2 x 10(-6) M) that has been shown to produce maximum constriction in this preparation. Thiamylal and thiopental produced constriction beginning at 10(-4) M and reached a maximum at 10(-3) M (P less than 0.0001). Methohexital, pentobarbital, and phenobarbital did not produce any significant change in airway tone. Pretreatment with meclofenamate (10(-6) M), UK 37,248 (5 x 10(-5) M), and OKY 046 (10(-6) M) prevented thiamylal-induced tracheal constriction.(ABSTRACT TRUNCATED AT 250 WORDS)

Mediators, initiating the inflammatory response, released in organ culture by full-thickness human skin explants exposed to the irritant, sulfur mustard.

Mediators released from injured human skin that initiate the inflammatory response have not been adequately identified. Organ culture of full-thickness skin explants enables us to do so, because injury to the skin can be made in vitro, eliminating the rapid leakage of serum and infiltration of leukocytes that occur in vivo. In our studies, the military vesicant sulfur mustard (SM) (10 microliters of a 0.01 to 1.0% dilution) was topically applied to injure the epidermis of the explant. Then, the explants were cultured in small Petri dishes, usually for 18 h at 36 degrees C, and the organ-culture fluids were assayed for various inflammatory mediators. We found that the culture fluids from SM-exposed and control explants contained similar amounts of angiotensin-converting enzyme, trypsin-like and chymotrypsin-like proteases, acid phosphatase, beta-glucuronidase, beta-galactosidase, lysozyme, deoxyribonuclease, ribonuclease, interleukin 1, and lactic dehydrogenase. However, the culture fluids from SM-exposed explants contained increased amounts of histamine and plasminogen-activating activity, and often prostaglandin E2, when compared to culture fluids from control explants. After 3 to 4 d in culture, full-thickness human skin explants, when exposed to 0.2% SM (but not when exposed to 1.0% SM), sometimes showed separation of the epidermis and increased collagenase activity (i.e., hydroxyproline release). Thus, histamine (from local mast cells), and prostaglandin E2 and plasminogen-activating activity (probably from both mast cells and epidermal cells) are apparently involved in early mediation of the inflammatory response.

Acute topical steroid administration blocks mast cell increase and the late asthmatic response of the canine peripheral airways.

Previous studies indicated that mast cell number increased after airway exposure to Ascaris suum antigen (Ag). The following two series of experiments were performed to test the hypothesis that this phenomenon may be associated with the Ag-induced late-phase bronchoconstriction (LAR). In the first, two bronchoscopes wedged in airway segments of two contralateral lobes of 16 dogs were used to deliver 0.26, 2.6, or 26 micrograms of Ag to one lobe; the other served as a control. After the observation of a LAR, Ag and control lobes plus one unexposed tissue sample were collected and prepared for histologic examination. The data showed that the incidence, time of onset, and magnitude of the LAR were dose-related. In the second series of experiments, performed in 14 dogs, the tracheal mucosal surface was surgically exposed to allow 80 micrograms of beclomethasone dipropionate to be sprayed on one half while the other half was left untreated. Pledgets saturated with 0.2 microgram of Ag were placed on both sides 1 h later. Then two bronchoscopes were used to pretreat airways of two contralateral lobes to 40 micrograms of either the steroid or the vehicle. One hour later, both airways were exposed to 2.6 micrograms of aerosolized Ag. Of these 14 dogs monitored for peripheral airway responses, seven demonstrated a LAR in the vehicle-treated airway. In all seven dogs, the LAR was absent in the steroid-treated airway even though the cellular profiles of the two airways did not significantly differ. In seven additional dogs, the bronchoscopic procedure was performed as previously described. However, these dogs were killed 1 h after Ag exposure.(ABSTRACT TRUNCATED AT 250 WORDS)