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Background Allergens are frequently found within or attached to particulate material. For example, house dust mite fecal pellets (HDMFP) contain the major mite allergens, exposure to which have been implicated in the development of asthma. Although several studies have examined the ability of purified allergens to generate inflammatory responses, few studies have investigated whether HDMFP per se, are biologically active. Objective Our objective was to examine the ability of whole HDMFP to stimulate nitric oxide (NO) release from alveolar macrophages. Methods The rat alveolar macrophage cell line, NR8383, was exposed to HDMFP, Der p 1, or Der p 2, and nitrite levels in the culture supernatants were measured with the Griess reagent. NO synthase mRNA expression was determined by RT-PCR. Results HDMFP stimulated the production of NO in a dose-dependent and time-dependent manner, with maximum NO levels measured after 48 hours of exposure. Inclusion of polymyxin B did not influence NO production, suggesting that LPS was not responsible for NO production. HDMFP-mediated NO release was down-modulated after treatment with N G -nitro-l-arginine methyl ester (L-NAME), dexamethasone, EDTA, and cysteine, but not heat treatment. Inducible nitric oxide synthase mRNA was observed 3 hours after HDMFP exposure, with maximum levels after 48 hours. Both purified Der p 1 and Der p 2 induced NO production, and inhibition of the cysteine protease activity of Der p 1 had little effect on NO production. Conclusions HDMFP, Der p 1 and Der p 2 are potent inducers of NO. Neither LPS nor the enzymatic activity of Der p 1 was responsible for NO production observed.

Background: Asthma severity among mite-sensitized individuals appears to be related to the degree of mite allergen exposure. Objectives: The objective of this study was to assess the long-term effectiveness of mite avoidance measures in the homes of asthmatic children in Melbourne, Australia. Methods: The concentration of house dust mite allergen (Der p 1) was measured on the child's mattress surfaces and bedroom floors in 85 homes on 10 occasions over a 16-month period. After the first three visits, all mattresses were covered with a semipermeable encasement, and carpeted bedroom floors were randomly allocated to regular applications of a placebo or an "anti-mite" shampoo. Results: The concentration of Der p 1 recovered was initially high in the carpeted bedrooms ( n = 66) (41.1, 95% confidence interval, 30.7 to 55.0 μg Der p 1 per gm) and mattresses ( n = 85) (39.6, 27.2 to 57.7). During the initial observation period the concentration of mite allergen fell in the treatment, placebo, and parental control groups. During the seven treatment periods, no differences were seen between the Der p 1 concentrations in the groups using the "anti-mite" shampoo, placebo shampoo, or the parental control group (e.g., at visit 4; 12.6, 8.2 to 19.5; 14.8, 8.6 to 25.1; and 12.0, 8.1 to 17.7 μg/gm, respectively). In contrast, the concentration of Der p 1 in samples from uncarpeted floors and mattress encasements was low (4.1, 2.1 to 8.0 μg/gm and 4.2, 2.6 to 6.5 μg/gm, respectively) and insufficient dust for analysis was frequently obtained from these sites. Conclusions: There was no additional benefit from the use of an "anti-mite" shampoo. The absence of carpets and the use of mattress encasements was a useful long-term strategy for mite allergen avoidance.

Extracts of Lepidoglyphus destructor were examined for the presence of digestive enzymes known to be allergenic in the pyroglyphid mites, such as Dermatophagoides pteronyssinus and D. farinae , with particular emphasis on the proteases and carbohydrases. Three serine proteases and one cysteine protease were detected, each with an apparent molecular weight of 25 K as judged by gel filtration. The serine proteases appeared to correspond to the trypsin, chymotrypsin and collagenolytic enzymes previously demonstrated in mites belonging to the genus Dermatophagoides . Chromatofocusing studies showed that each of the serine proteases was polymorphic. Extracts of L. destructor were also found to contain amylase, glucoamylase and an enzyme(s) that lysed Gram-positive bacteria, such as Micrococcus lysodeikticus and Bacillus megatarium . These data indicate that extracts of L. destructor contain a spectrum of digestive enzymes similar to that shown to be present in the Pyroglyphid mites. The allergenicity of such enzymes in L. destructor remains to be determined.

Hypersensitivity to house dust mite allergens is associated with increased asthma morbidity. Asthma severity appears to be related to the degree of mite allergen exposure. Short-term studies suggest that complete avoidance reduces disease severity.The study was designed to assess the effect of different mattress covers and floor coverings on mite allergen concentrations in the homes of mite-sensitive children with asthma in the city of Melbourne, Australia.Mite allergen Der p 1 concentration was measured on mattress covers, mattress surfaces, and carpeted and uncarpeted floors in 107 dwellings; and measurement was performed on three occasions over a 5-month period. After the first sampling, all mattress covers and impermeable encasements were permanently removed.The initial geometric mean concentrations of Der p 1 (micrograms per gram of fine dust) from the surfaces of sheepskin, wool, and cotton mattress coverings were greater than those from the surfaces of impermeable mattress encasements (116, 113, and 19 vs 0.4) (p0.001); corresponding concentrations on the underlying mattresses were 142, 38, 20, and 0.6, respectively (p0.05 to 0.001). At the end of the study these mattress surface concentrations were 79, 65, 9.7, and 3.1, respectively. In 24 dwellings an uncarpeted room was adjacent to a carpeted room. At each visit the concentration of Der p 1 in uncarpeted rooms was below the reported threshold for sensitization and significantly less than that in the adjacent carpeted room.In homes of children with asthma, "asthmogenic" concentrations of Der p 1 were found on nonencased mattresses and carpeted floors, but the use of impermeable mattress encasements and carpet exclusion were associated with concentrations of Der p 1 below the reported threshold for sensitization.

The effect of histamine on the production of prostaglandin F2 alpha and the actions of prostaglandin F2 alpha on the responsiveness of human isolated bronchial smooth muscle were examined by organ bath techniques using bronchi from lung tissue resected from 18 patients. Following exposure to histamine, epithelium-intact bronchi generated 34.26 +/- 16.3 pg of prostaglandin F2 alpha/mg of tissue and epithelium-denuded preparations produced 32.62 +/- 11.83 pg/mg, suggesting that histamine-induced release of prostaglandin F2 alpha was from non-epithelial sources, presumably smooth muscle. The histamine H2 receptor antagonist ranitidine did not affect the release of prostaglandin F2 alpha, suggesting that its generation may have resulted from histamine H1 receptor activation. Carbachol did not influence prostaglandin F2 alpha generation. Contractile responses to histamine, prostaglandin F2 alpha and carbachol were measured in the presence and absence of the prostaglandin TP receptor antagonist SQ 29,548 ([1 S-[1 alpha,2 beta(5Z),3 beta,4 alpha]]-7-[3[[2-[9-phenylamino)carbonyl]hydrazino] methyl-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid) (0.4 microM). SQ 29,548 abolished responses to prostaglandin F2 alpha suggesting that contractions were mediated via TP receptors. Exposure to SQ 29,548 also produced a 3-fold rightward shift in the concentration-effect curve for histamine (P = 0.01) without influencing the maximum response. SQ 29,548 did not affect responses to carbachol. These results suggest that histamine selectively stimulates the generation of prostaglandin F2 alpha from epithelium-denuded human airway tissue (presumably from the smooth muscle), which in turn, amplifies the contractile responses of human airway smooth muscle to histamine.

Background: Dust mites have been shown to contain a serine protease distinct from the previously reported trypsin and chymotrypsin. The latter enzymes have been shown to be allergens, but the allergenic importance of the former is unknown. Objective: This study was performed to isolate and characterize the novel mite serine protease and determine its allergenicity. Methods: The mite serine protease was isolated from feces-enriched extracts of Dermatophagoides pteronyssinus by ion-exchange chromatography and affinity chromatography, and its physicochemical properties were determined. The allergenicity of the protease was assessed by using the RAST. Results: The protease was enzymatically similar to chymotrypsin and cathepsin G–like enzymes from a variety of sources and was shown to cleave collagen. It had a molecular mass of 23,780 d. N-terminal sequence analysis (18 residues) indicated homology with the mite tryptic allergen, Der p 3, and the chymotryptic allergen, Der p 6. RAST analyses showed that the frequencies of reactivity to the novel allergen and to Der p 1, Der p 2, Der p 3, and Der p 6 were 92%, 97%, 100%, 97%, and 65%, respectively ( n = 35). RAST inhibition studies showed some cross-reactivity between the protease and Der p 3 but not Der p 6. Conclusions: A novel mite serine protease was isolated from D. pteronyssinus and found to be a major allergen. This allergen has been tentatively designated Der p 9. (J ALLERGY CLIN IMMUNOL 1996;98:739-47.)

The effects of exogenous prostaglandin E2 and prostacyclin on the function of epithelium-intact and epithelium-denuded human bronchial smooth muscle and the role of these mediators in the inhibition of histamine-induced contraction was examined using bronchi obtained from 22 patients undergoing thoracotomy. Under resting tension, a variable biphasic contraction-relaxation or monophasic relaxation was observed following the cumulative addition of exogenous prostaglandin E2 or prostacyclin. Cumulative addition of these mediators to pre-contracted bronchi produced incomplete relaxation, irrespective of the presence of epithelium. Addition of prostaglandin E2, at a concentration equating to that produced after histamine stimulation (1.2 x 10(-9)M), produced a reduction (24%) in the maximum contractile response (Emax) to a subsequent histamine challenge (P < 0.03). However, a similar response was not observed after the addition of prostacyclin at a concentration similar to that produced endogenously (6.5 x 10(-10)M). The combined addition of both mediators resulted in a significant reduction (26%) in the Emax to histamine (P < 0.02) but this effect was not statistically different to that of prostaglandin E2 alone. The addition of supramaximal concentrations (1 microM) of each prostanoid, either alone or in combination, did not inhibit responses to histamine. These data suggest that whilst prostaglandin E2 does not act as a direct acting relaxant agonist, it may inhibit histamine-induced muscle contraction and thereby contribute to the observed tachyphylaxis to this mediator. In contrast, prostacyclin appears to be of little importance in modulating human bronchial smooth muscle responses to histamine either directly or by enhancing responses to prostaglandin E2. The inhibitory effect of prostaglandin E2 appears to be concentration-dependent and suggests a bimodal action of this mediator in human airways.

The role of the bronchial epithelium and inhibitory prostaglandins in the induction of histamine tachyphylaxis in human isolated bronchial smooth muscle was investigated using bronchi obtained from 14 patients who had been treated with non-steroidal anti-inflammatory drugs (NSAID) for > 2 months and from 14 untreated patients. Epithelium-intact bronchial strips from untreated patients demonstrated tachyphylaxis to histamine with the maximum response (Emax) reduced by 30 +/- 5% (P < 0.02) and the EC50 increased 1.86-fold (P < 0.02). Tachyphylaxis was not observed in epithelium-denuded strips. In epithelium-intact bronchial preparations from NSAID treated patients, the mean initial maximum tension generated in response to histamine was significantly greater than that for bronchial preparations from untreated patients (P < 0.05). In NSAID-treated patients, both epithelium-intact and denuded preparations failed to demonstrate tachyphylaxis. The generation of prostaglandin E2 and prostacyclin was assessed by radio-immunoassay using bronchi from untreated patients (n = 8). In epithelium-intact bronchial preparations, the generation of both prostaglandin E2 and prostacyclin was significantly increased by histamine exposure (P < 0.05) and was completely inhibited by indomethacin. However, the selective histamine H2 receptor antagonist, ranitidine, selectively inhibited the synthesis of prostaglandin E2 alone. Production of both prostaglandins was not altered by exposure to acetylcholine. These results suggest that prostaglandin E2 and prostacyclin are released primarily from the epithelium in response to histamine and may be specifically involved in inhibiting human bronchial smooth muscle responsiveness to this mediator. Significantly, the release of prostaglandin E2 appears to be selectively controlled by histamine H2 receptors, resident on the epithelium.