Nitric oxide production by alveolar macrophages in response to house dust mite fecal pellets and the mite allergens, Der p 1 and Der p 2.
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.
D000485:Allergens / Q000008:administration & dosage*; D000818:Animals; D039741:Antigens, Dermatophagoides / Q000008:administration & dosage*; D060829:Arthropod Proteins; D002460:Cell Line; D003546:Cysteine Endopeptidases; D003907:Dexamethasone / Q000494:pharmacology; D004391:Dust; D004492:Edetic Acid / Q000494:pharmacology; D005243:Feces; D016676:Macrophages, Alveolar / Q000276:immunology* / Q000378:metabolism*; D008925:Mites; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000235:genetics; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats
D000485:Allergens; D039741:Antigens, Dermatophagoides; D060829:Arthropod Proteins; C451163:Dermatophagoides pteronyssinus antigen p 2; D004391:Dust; D012333:RNA, Messenger; D009569:Nitric Oxide; D003907:Dexamethasone; D004492:Edetic Acid; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496322:Nos1 protein, rat; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat; D003546:Cysteine Endopeptidases; C451162:Dermatophagoides pteronyssinus antigen p 1; D019331:NG-Nitroarginine Methyl Ester