Immunosuppressive effects of azelastine hydrochloride on contact hypersensitivity and T-cell proliferative response: a comparative study with FK-506

Unique immunomodulatory effects of azelastine on dendritic cells in vitro

Allergic contact dermatitis and atopic dermatitis are among the most common inflammatory skin diseases in western countries, and antigen-presenting cells like dendritic cells (DC) are key players in their pathophysiology. Histamine, an important mediator of allergic reactions, influences DC maturation and cytokine secretion, which led us to investigate the immunomodulatory potential of the well-known histamine H1 receptor antagonists: azelastine, olopatadine, cetirizine, and pyrilamine. Unlike other H1 antihistamines, azelastine decreased lipopolysaccharide-induced tumor necrosis factor α and interleukin-12 secretion from murine bone marrow-derived DC. This effect was independent of histamine receptors H1, H2, or H4 and may be linked to inhibition of the nuclear factor kappa B pathway. Moreover, only azelastine reduced proliferation of allogenic T cells in a mixed leukocyte reaction. We then tested topical application of the H1 antihistamines on mice sensitized against toluene-2,4-diisocyanate, a model of Th2-mediated allergic contact dermatitis. In contrast to the in vitro results, all investigated substances were efficacious in reducing allergic ear swelling. Azelastine has unique effects on dendritic cells and T cell interaction in vitro. However, this did not translate into superior in vivo efficacy for Th2-mediated allergic dermatitis, possibly due to the effects of the antihistamines on other cell types involved in skin inflammation. Future research will have to clarify whether these properties are relevant to in vivo models of allergic inflammation with a different T cell polarization.

Inhibition of IgE-mediated phosphorylation of FcεRIγ protein by antiallergic drugs in rat basophilic leukemia (RBL-2H3) cells: A novel action of antiallergic drugs

We examined the effect of antiallergic drugs, azelastine and epinastine, on the expression of FcepsilonRIalpha, beta, and gamma chains and phosphorylation of the gamma chains in rat basophilic leukemia (RBL-2H3) cells. The cells were cultured for 24 h with IgE treatment in the presence of azelastine or epinastine at the concentration of 10(-5) M. The FcepsilonRIalpha mRNA expression was determined by northern blot analysis. The protein level of FcepsilonRI expressed on the plasma membrane was examined following IgE treatment by immunoprecipitation with anti-IgE light chain, followed by western blot analysis with anti-gamma chain of FcR. Azelastine and epinastine had no effect on the FcepsilonRIalpha, beta and gamma mRNA levels. Although the amount of gamma chain assembled into IgE-bound FcepsilonRI was not changed by treatment with azelastine nor epinastine, phosphorylation levels of gamma chains of IgE-bound FcepsilonRI were inhibited by azelastine. The inhibitory effect of azelastine on the IgE-mediated expression of FcepsilonRIgamma protein is not due to their inhibition of mRNA and protein expression, but due to abrogating phosphorylation of the gamma chains, which is important for initiation of FcepsilonRI signaling cascade elicited by IgE interaction.

Antiallergic drugs, azelastine hydrochloride and epinastine hydrochloride, inhibit ongoing IgE secretion of rat IgE-producing hybridoma FE-3 cells

We asked whether or not antiallergic drugs, azelastine hydrochloride and epinastine hydrochloride, inhibit IgE secretion from IgE-producing hybridoma FE-3 cells. FE-3 cells were cultured in the presence of azelastine or epinastine for 24 h, washed in phosphate-buffered saline , and then recultured in the medium in the absence of the antiallergic drugs. IgE levels in the cultured medium as well as those in the cytoplasm of FE-3 cells were measured by enzyme-linked immunosorbent assay. mRNA levels of Cepsilon, activation-induced cytidine deaminase (AID), XBP-1, and Bip were estimated by northern blot or reverse transcriptase polymerase chain reaction analysis. The activities of nuclear factor-kappa B (NF-kappaB) were analyzed by electrophoretic mobility shift assay (EMSA). Phosphorylation of I kappa B alpha (IkappaBalpha) was analyzed by immunoprecipitation followed by western blot analysis. IgE levels in the cultured medium and in the microsome fraction were lower on the treatment with 10(-5) M azelastine or epinastine than those on the treatment with vehicle. Cepsilon and AID mRNA levels were lower on the treatment with 10(-5) M azelastine than those on the treatment with vehicle, but were not decreased on the treatment with 10(-5) M epinastine. XBP-1 and Bip mRNA levels were not altered following treatment of the antiallergic drugs. Azelastine at 10(-5) M, but not epinastine, reduced DNA binding activity of NF-kappaB and also diminished IkappaBalpha phosphorylation, leading to sustaining IkappaBalpha protein levels. These findings suggest that azelastine exerts its inhibitory effect on the IgE secretion from FE-3 cells through the inhibition of Cepsilon mRNA expression, and that the inhibitory effect of epinastine is, at least in part, due to suppression of IgE synthesis at the post-transcriptional level.

Topical pimecrolimus in the treatment of human allergic contact dermatitis

BACKGROUND

Contact dermatitis is a common clinical problem, with prevalent sensitizers being cosmetics, metals, medicines, and plants. Plants of the Toxicodendron species cause allergic contact dermatitis (ACD) in 50% to 70% of the population. Pimecrolimus is an ascomycin macrolactam developed for the treatment of inflammatory skin diseases and approved by the US Food and Drug Administration for atopic dermatitis. There are studies supporting the effectiveness of macrolactams when administered before antigen challenge, but there are no studies describing the effectiveness of these drugs in the treatment of established human ACD.

OBJECTIVE

To investigate the effect of topical pimecrolimus in the treatment of Toxicodendron-induced ACD once rash is evident.

METHODS

Poison ivy tincture was applied to the bilateral anterior forearms of 12 subjects with Finn Chambers (Allerderm Diagnostic Products, Petaluma, CA). After dermatitis was evident, volunteers treated each arm twice daily with either 1% topical pimecrolimus cream or placebo in a blinded fashion. Outcomes measured were a dermatitis grading score and time to rash and itch resolution.

RESULTS

The median +/- SEM time for rash resolution was 16.55 +/- 1.59 days in the treatment group and 16.27 +/- 1.82 days in the placebo group (P = 0.601). The median time for itch resolution was 4.73 +/- 1.56 days in the treatment group and 4.91 +/- 1.59 days in the placebo group (P = 0.167). The average dermatitis score was 2.26 +/- 0.17 in the treatment group and 2.32 +/- 0.15 in the placebo group (P = 0.62).

CONCLUSIONS

The application of topical pimecrolimus is ineffective in the treatment of ongoing Toxicodendron-induced ACD.

Anti-allergic drug olopatadine suppresses murine contact hypersensitivity and downmodulates antigen-presenting ability of epidermal Langerhans cells

Olopatadine hydrochloride is an H1-receptor-blocker but has other anti-allergic pharmacological potencies. We investigated whether olopatadine inhibits murine contact hypersensitivity, focussing on its modulatory action on epidermal Langerhans cells serving as antigen-presenting cells. While BALB/c mice were sensitized and challenged epicutaneously with hapten, they were administered intraperitoneally with olopatadine. Olopatadine at 1 or 0.2 mg/kg of weight significantly suppressed the sensitivity when injected at least once before sensitization or challenge. In olopatadine-injected mice, the ability of Langerhans cells to present hapten to primed T cells was reduced with decreased expression of MHC class II and co-stimulatory molecules. Langerhans cells exposed in vitro to 10(-5) or 10(-6) M olopatadine had less antigen-presenting activity than control, whereas neither T cell proliferation nor keratinocyte production of IL-1alpha and IP-10 was affected at these doses. These findings suggest that olopatadine downmodulates contact hypersensitivity at least partly by interfering with the antigen-presenting ability of Langerhans cells.

Inhibition of collagen expression by azelastine hydrochloride in cultured skin fibroblasts from normal individuals and scleroderma patients

The effects of azelastine hydrochloride on cell proliferation and collagen synthesis in cultured human skin fibroblasts were studied. Azelastine inhibited cell proliferation during proliferating cell phases. Azelastine was found to inhibit collagen synthesis without altering cell proliferation during quiescent phases. It did not alter the ratio of type I to III collagen synthesis. Northern blot analysis of collagen chain mRNAs revealed that the levels of alpha1 (I), alpha1 (III) and alpha1 (VI) mRNAs were reduced by azelastine treatment, whereas the level of alpha2 (VI), alpha3 (VI) mRNAs were not significantly changed. These results suggest that azelastine modulates collagen synthesis at a pretranslational level. Azelastine inhibited collagen synthesis in fibroblasts from scleroderma patients to the same extent as in normal skin fibroblasts. This drug may be useful in the treatment of fibrotic diseases.