INHIBITORY ACTIVITY OF LORATADINE AND DESCARBOETHOXYLORATADINE ON EXPRESSION OF ICAM-1 AND HLA-DR BY NASAL EPITHELIAL-CELLS

Nasal epithelial cells represent the first barrier against noxious age nts and allergens. In allergic rhinitis, these cells are activated and histamine map be involved in this activation. Loratadine and one of i ts active metabolites, descarboethoxyloratadine, were studied for thei r ability to reduce the activation of nasal epithelial cells by histam ine, Nasal turbinates or polyps were removed during surgery from 19 su bjects, and nasal epithelial cells were recovered after enzymatic dige stion, The in vitro activation of epithelial cells with histamine usin g an optimal dose (1 mu M) and an optimal time (24 h) of incubation wa s studied, and the effect of loratadine or descarboethoxyloratadine (1 0 mu M) was investigated. The expression of membrane markers (intercel lular adhesion molecule-1 (ICAM-1) and a human leukocyte class II anti gen (HLA-DR) was assessed by immunocytochemical analysis using alkalin e-antialkaline phosphatase (APAAP) system. The spontaneous expression of both markers was not significantly different in cells recovered Fro m nasal turbinates or polyps, and there was a highly significant incre ase in the numbers of cells expressing ICAM-1 and HLA-DR following inc ubation with histamine, Loratadine or descarboethoxyloratadine signifi cantly blocked these effects. This study shows a new possible antialle rgic effect of H-1-blockers and effects on epithelial cells may be rel evant in vivo.