Effect of loratadine on nitrogen dioxide-induced changes in electrical resistance and release of inflammatory mediators from cultured human bronchial epithelial cells.

BACKGROUND: Recent studies have demonstrated that some antihistamines can attenuate histamine-induced release of inflammatory mediators from bronchial epithelial cells. OBJECTIVE: The purpose of study was to test the hypothesis that loratadine may influence pollution-induced inflammation of the airways by modulating epithelial membrane integrity and the synthesis and/or release of inflammatory mediators from airway epithelial cells. METHODS: We have cultured human bronchial epithelial cell (HBEC) cultures from surgical explants and investigated the effect of loratadine on NO2-induced changes in both electrical resistance of HBEC cultures and release of IL-8, RANTES, and soluble intercellular adhesion molecule-1 (sICAM-1) from these cells after exposure for 6 hours to either air or 400 ppb NO2. RESULTS: Exposure for 6 hours to NO2 significantly decreased the electrical resistance of HBEC cultures by 18.1% from baseline (P <.05). Incubation with 0.25 to 25 micromol/L loratadine did not alter the NO2-induced decrease in the electrical resistance of HBEC cultures. NO2 also significantly increased the release of IL-8 from a control value of 52.5 pg/microgram cellular protein to 81.9 pg/microgram cellular protein (P <.05), RANTES from a control value of 0.023 pg/microgram cellular protein to 0.062 pg/microgram cellular protein (P <.05), and sICAM-1 from a control value of 7.7 pg/microgram cellular protein to 16.3 pg/microgram cellular protein (P <.05). The NO2-induced release of all 3 mediators was significantly attenuated by incubation of HBECs with 25 micromol/L loratadine. Incubation with 2.5 micromol/L loratadine also significantly attenuated the NO2-induced release of RANTES and sICAM-1, but not IL-8. CONCLUSIONS: These results suggest that loratadine has the potential to reduce airway inflammation by modulating the release of inflammatory cytokines from airway epithelial cells.

Inhibitory effect of loratadine on leukotriene B4 production by neutrophils either alone or during interaction with human airway epithelial cells.

Leukotriene B4 (LTB4), an inflammatory mediator, is a potent chemoattractant for neutrophils (PMN) that plays an important role in the late reaction in asthma. Human airway epithelial cells (HAEC) can interact with PMN to increase LTB4 production. The aim of this study was to determine the influence of loratadine, an antihistaminic drug, on the production of LTB4 by PMN either alone or during interaction with transformed HAEC. The effect of tumour necrosis factor-alpha (TNF-alpha) was also examined. LTB4 production was measured by RP-HPLC after cell stimulation with calcium ionophore. Loratadine (0.25-25 microM) induced a significant and dose-dependent decrease of LTB4 production by PMN alone whereas it was up-regulated by TNF-alpha. As reported by others, we confirmed the increase of LTB4 release when PMN were cocultured with HAEC as compared to PMN alone. Addition of loratadine to HAEC before co-culture with PMN induced a significant decrease of LTB4 formation by cell interaction. This effect was noted when HAEC were washed following incubation with loratadine, demonstrating a direct action of the drug on this cell type. Moreover, the TNF-alpha-induced stimulation of LTB4 release that we demonstrated in PMN-HAEC interaction was also inhibited by loratadine. These results indicate that loratadine might reduce inflammatory reaction by a direct effect on PMN LTB4 production but also through an influence on HAEC during interaction with PMN.

Inhibitory activity of loratadine and descarboxyethoxyloratadine on histamine-induced activation of endothelial cells.

BACKGROUND: The allergic inflammatory reaction is characterized by leucocyte adherence and infiltration processes which are controlled by the expression of adhesion molecules on the surface of vascular endothelium. One of the main mediators implicated in allergic reactions is represented by histamine. Histamine is a potent activator of endothelial cells (EC): it induces the expression of P-selectin on the surface of endothelium and the secretion of IL-6 and IL-8. OBJECTIVES: Loratadine (L), a histamine H1-antagonist, and one of its active metabolites, descarboxyethoxyloratadine (DCL), were studied at different concentrations for their ability to reduce the histamine-induced activation of human umbilical vein EC (HUVEC). METHODS: HUVEC were stimulated in the presence of histamine at 10(-6) M, 10(-5) M and 10(-4) M. We assessed by ELISA the expression of P-selectin on EC surface, as well as cytokine production in EC supernatants of 24 h culture. RESULTS: Our results showed that for a 10(-4) M-histamine stimulation, L and DCL have a similar inhibitory effect on P-selectin expression (IC50 = 13 x 10[-9] M and 23 x 10[-9] M, respectively). L and DCL inhibited significantly IL-6 and IL-8 secretion induced by histamine with a more powerful efficiency of the active metabolite. For the dose of 10(-4) M histamine, a 50% inhibition of IL-6 secretion was obtained for a dose of DCL equal to 2.6 x 10(-12) M whereas the same magnitude of effects were only reached for a higher concentration of L (0.3 x 10[-6] M). Similar results were obtained for IL-8 (IC50 = 0.2 x 10[-6] M for L and 10[-9] M for DCL). Analysis of IL-8 mRNA expression by RT-PCR was in accordance with these data. CONCLUSION: These results demonstrate that both L and DCL are active to reduce the histamine-induced activation of EC. Interestingly, DCL seems to be effective at lesser concentrations especially to inhibit cytokine secretion.

Reduction of soluble ICAM-1 levels in nasal secretion by H1-blockers in seasonal allergic rhinitis.

ICAM-1, a transmembrane glycoprotein promoting adhesion in immunologic and inflammatory reactions, was found to be increased on nasal epithelial cells of patients with allergic rhinitis. Loratadine, an H1-blocker, was found to reduce in vitro the expression of ICAM-1 on nasal epithelial cells. A double-blind, parallel-group study was carried out during the pollen season to compare the effect of two H1-blockers, cetirizine (10 mg OD) and loratadine (10 mg OD), on the release of soluble ICAM-1 in nasal secretions. A group of untreated patients was used as a control group. sICAM-1 was measured by enzyme immunoassay before and after 2 weeks of treatment. Symptoms were significantly decreased in the actively treated groups. sICAM-1 levels were unchanged in the control group but were significantly reduced in the two treated groups (P < 0.015, Wilcoxon's W test). This study shows that two H1-blockers, loratadine and cetirizine, have a similar effect on sICAM-1 released in nasal secretions during the pollen season.

Antihistamines and production of granulocyte-macrophage colony-stimulating factor and interleukin-8 by human bronchial epithelial cells in vitro: evaluation of the effects of loratadine and cetirizine.

1. In this study, we compared the effects of two antihistamine drugs on the production of granulocyte-macrophage colony-stimulating factor and interleukin-8 by human bronchial epithelial cells in vitro. 2. Cytokine production was assessed by the use of an enzyme-linked immunosorbent assay. 3. Epithelial cells spontaneously released both cytokines and tumor necrosis factor alone induced a significant increase in this production but loratadine and cetirizine had no effect at the various concentrations studied. 4. The antihistamines have no effect and this suggests that histamine plays no role in cytokine production under these conditions.

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 agents and allergens. In allergic rhinitis, these cells are activated and histamine may be involved in this activation. Loratadine and one of its active metabolites, descarboethoxyloratadine, were studied for their ability to reduce the activation of nasal epithelial cells by histamine. Nasal turbinates or polyps were removed during surgery from 19 subjects, and nasal epithelial cells were recovered after enzymatic digestion. The in vitro activation of epithelial cells with histamine using an optimal dose (1 microM) and an optimal time (24 h) of incubation was studied, and the effect of loratadine or descarboethoxyloratadine (10 microM) was investigated. The expression of membrane markers (intercellular adhesion molecule-1 (ICAM-1) and a human leukocyte class II antigen (HLA-DR) was assessed by immunocytochemical analysis using an alkaline-antialkaline phosphatase (APAAP) system. The spontaneous expression of both markers was not significantly different in cells recovered from nasal turbinates or polyps, and there was a highly significant increase in the numbers of cells expressing ICAM-1 and HLA-DR following incubation with histamine. Loratadine or descarboethoxyloratadine significantly blocked these effects. This study shows a new possible antiallergic effect of H1-blockers and suggests that their effects on epithelial cells may be relevant in vivo.

In vitro inhibition, by loratadine and descarboxyethoxyloratadine, of histamine release from human basophils, and of histamine release and intracellular calcium fluxes in rat basophilic leukemia cells (RBL-2H3).

The effect of the H1-antihistamine drug loratadine and its active metabolite descarboxyethoxyloratadine upon histamine release was examined on anti-immunoglobulin E (IgE) triggered human basophils and 2,4-dinitrophenyl (DNP) triggered rat basophilic leukemia (RBL-2H3) cells. In both experimental systems, dose-dependent inhibition of histamine release was observed at descarboxyethoxyloratadine and loratadine doses above 2 and 7 microM, respectively. In the RBL-2H3 experimental system, inhibition by loratadine increased when the concentration of extracellular Ca2+ was reduced from 1.8 to 0.45 mM. We further investigated the effect of loratadine and descarboxyethoxyloratadine on the increase in cytosolic calcium concentration (Ca2+)i, an early step in biochemical events leading to exocytosis. The effect of these two drugs upon (Ca2+)i changes was measured using the fluorescent probe fura-2 loaded into RBL-2H3 cells passively sensitized with DNP-specific IgE. Both drugs inhibited, in a dose-dependent manner (2.5-25 microM), the (Ca2+)i rise induced by DNP-BSA challenge in sensitized RBL cells, a process observed in both the presence and absence of extracellular Ca2+. Loratadine also inhibited the Mn2+ influx into these cells, thus reflecting the Ca2+ influx. These results suggest that loratadine and descarboxyethoxyloratadine impair the increase in (Ca2+)i following cell activation by decreasing both the influx of extracellular Ca2+ and the release of Ca2+ from intracellular stores.