Effects of dexamethasone or methotrexate on chitinolytic activity in nasal polyps

Chitin is a recognition element for tissue infiltration by innate cells implicated in allergy and immunity. This process can be negatively regulated by vertebrate chitinases. Chitinolytic activity is significantly increased in nasal polyps (NPs) compared with that in normal turbinate mucosa. Dexamethasone (DEX) or methotrexate (MTX) is an effective treatment for chronic inflammatory diseases. The aim of this study was to investigate the effects of DEX or MTX on chitinolytic activity in organ-cultured NPs.

NP tissues were cultured using an air-liquid interface culture model. Cultures were maintained for 24 hours in the absence or presence of DEX (10 or 100 micromolar) or MTX (10 or 100 micromolar). Acidic mammalian chitinase (AMCase) and chitotriosidase (ChT) activities in tissue samples were measured at a range of pH values by using the fluorogenic substrate 4-methylumbelliferyl-beta-(D)-N,N',N″-triacetyl-chitotriose.

AMCase and ChT chitinolytic activities were significantly lower in NPs treated with 100 micromolar DEX or 100 micromolar MTX than that in fresh or untreated NPs. AMCase chitinolytic activity tended to be lower in DEX-treated polyps than in MTX-treated polyps, although the difference was not statistically significant.

DEX or MTX reduced chitinolytic activity in NPs. We suggest that DEX or MTX may inhibit the growth of NPs via local regulation of NP chitinolytic activity.