Effect of nitric oxide donors on NADPH oxidase signaling pathway in human neutrophils in vitro.

The production of reactive oxygen species (ROS) in activated neutrophils is catalyzed by NADPH oxidase, a multiproteins complex. Various protein kinases including protein kinase C (PKC) and mitogen activated protein kinases (MAPKs) are involved in NADPH oxidase phosphorylation and activation. The main step in the NADPH oxidase activation is phosphorylation of its cytosolic protein p47(phox). We found previously that nitric oxide (NO) donors such as metabolite of molsidomine-SIN-1 and diethylamine/NO significantly impaired the ROS production in activated human neutrophils. In this study, we investigated the effects of both NO donors on NADPH oxidase-linked signaling proteins in activated neutrophils. We found that NO donors decreased the phosphorylation of p47(phox) on tyrosine and serine/threonine residues and PKC on serine residues in neutrophils. Both NO donors did not affect the phosphorylation of MAPKs. NO donors partially but significantly lost their ability to reduce ROS production in the presence of PKC but not MAPKs inhibitors. We show that whereas NO donors have no effect on MAPKs activity, they do decrease PMA- and/or fMLP-induced phosphorylation of p47(phox) and PKC as well as PMA- and fMLP-induced ROS production.

A quantitative method for assessing the sensitizing potency of low molecular weight chemicals using a local lymph node assay: employment of a regression method that includes determination of the uncertainty margins.

Risk assessment of sensitizing chemicals requires, besides hazard identification, the assessment of potency. To examine the sensitizing capacity of low molecular weight chemicals, a murine local lymph node assay (LLNA) was used. The sensitizing capacity of known allergens was quantified by dose-response modeling. At a stimulatory index (SI) of 3, the corresponding estimated concentration was calculated (EC(3)), together with a confidence interval to take account of the quality of the particular data set. We tested ten allergens (ethyl-p-aminobenzoate (benzocaine), diethylamine (DEA), 2,4-dinitrochlorobenzene (DNCB), 2-mercaptobenzothiazole (MBT), 4-ethoxymethylene 2-phenyl oxazol-5-one (oxazolone), phthalic anhydride (PA), toluene diisocyanate (TDI), trimellitic anhydride (TMA), tetramethylthiuramdisulfide (TMTD) and zincdimethyldithiocarbamate (ZDMC)). Oxazolone showed the strongest sensitizing potency followed in this order by DNCB, TDI, TMA, PA, TMTD, ZDMC, MBT, benzocaine and DEA. The approach performed in this study is a way to accurately assess the potency of sensitizing chemicals and thus a possibility for classification.

Occupational contact dermatitis to propacetamol. Allergological and chemical investigations in two new cases.

BACKGROUND AND OBJECTIVE: In 2 new cases of occupational contact dermatitis due to a recently described allergen (propacetamol), a prodrug which is a soluble diethylglycidyl ester of paracetamol, an allergological investigation was performed to elucidate the nature of the allergen involved in the propacetamol contact sensitivity. OBSERVATIONS: Two nurses with eczema of the hands and face had positive patch tests to Pro-Dafalgan. Every day the nurses prepared injections of Pro-Dafalgan (propacetamol dissolved in sodium citrate). The sensitization was due to propacetamol and not to the solvent. To elucidate which part of propacetamol was responsible for the sensitization, the 2 nurses were patch-tested with diethylamine, paracetamol (diluted in different vehicles) and some of their chemical analogues and potential impurities which were all negative. CONCLUSIONS: Propacetamol induces airborne contact dermatitis with no evidence of sensitization to paracetamol or diethylglycine, possibly because of either the presence of unknown impurities and/or an antigenic structure related to the covalent bond of the prodrug.