Topical glucocorticoid augments scratching behaviour in dinitrofluorobenzene-sensitized mice by the induction of substance P

Topical glucocorticoid (GC) is commonly applied in atopic dermatitis treatment. However, the chronic use of GC may be associated with significant side effects. In this study, we investigated whether long-term epicutaneous application of GC modulates scratching behaviour in dinitrofluorobenzene (DNFB) contact-sensitized mice. After challenge with DNFB, scratching behaviour was increased in DNFB-sensitized mice treated with GC in contrast to control mice. In addition, reverse transcriptase-polymerase chain reaction analysis demonstrated that the expression of preprotachykinin-A (PPT-A) mRNA, a precursor of substance P (SP), and inducible nitric oxide synthase (iNOS) mRNA in mice, to which GC was applied, was only observed. In order to evaluate the factors responsible for the augmented scratching behaviour, we injected various cytokines (interleukin-1alpha (IL-1alpha), IL-2, IL-3 and tumour necrosis factor-alpha (TNF-alpha)) subcutaneously into the ear of DNFB contact-sensitized mice before DNFB challenge. Among the cytokines, only IL-3 and TNF-alpha significantly increased scratching behaviour in DNFB contact dermatitis mice. Furthermore, PPT-A mRNA was only expressed in mice pre-injected with IL-3 before challenge, but not in those pre-injected with other cytokines. Taken together, our results suggest that topical GC may augment the itching sensation in DNFB-sensitized mice through modulation of iNOS and SP induced by IL-3.

Stress response, tachykinin, and cutaneous inflammation

In the last decade, several new aspects of glucocorticoid (GC)-actions on immune cells have been recognized. This recognition has been largely obtained through clinical observations of stress-induced exacerbations of certain dermatologic diseases. To clarify whether GC modulates cutaneous inflammatory reactions besides its known anti-inflammatory effect, first we examined the effect of long-term application of topical GC on several kinds of inflammatory responses induced in the murine model and demonstrated that these regimens significantly augmented the classical contact sensitivity reaction, the croton oil-induced irritant reaction, and the IgE-mediated biphasic cutaneous reaction. In addition, large dose topical steroid and its withdrawal enhanced scratching behavior in hapten-challenged mice. This augmented scratching behavior correlated with the induction of preprotachykinin mRNA expression in the challenged skin. In an in vitro experiment, a low-dose, stress-induced level of glucocorticoid significantly upregulated hapten-induced proinflammatory cytokine (IL1alpha) production by murine keratinocyte cell line Pam 212 and induced substance P peptide production from cultured human keratinocytes. Our results suggest that unsuitable use of GC in addition to stress-induced GC may modulate immune function in the skin through aberrant production of tachykinin, such as substance P or other epidermal cell derived cytokines.

[Pharmacological profile and clinical effect of tacrolimus ointment (Protopic ointment) for atopic dermatitis]

Atopic dermatitis (AD) is thought to be induced by a complex of various allergic reactions and T cells are implicated in its etiology. Since tacrolimus strongly inhibits T cell activation, tacrolimus ointment has been developed as a novel drug for AD throughout the world. Tacrolimus inhibits mast cell and eosinophil activation and antigen presenting activity of Langerhans cells in vitro. In the in vivo experimental animal models of AD, such as contact and spontaneous dermatitis in mice and repeated hapten treated skin inflammation in rats, tacrolimus ointment showed inhibitory activity. In clinical studies with AD patients in Japan, USA and Europe, tacrolimus ointment showed a marked effect. In comparative studies in Japan, it showed the same efficacy as a strong class steroid ointment on eczema at the trunk and extremities and superior efficacy at the face and neck compared to a medium class steroid. The most prominent adverse event is experienced at the local application site with reactions such as a burning sensation and erythema. Systemic side effects were rarely observed. While there is a possibility of skin infections when using tacrolimus, skin atrophy, even after long term treatment, was not observed. Thus tacrolimus ointment could be an efficient alternative to steroid ointment for AD.

Topical glucocorticoids application induced an augmentation in the expression of IL-1alpha while inhibiting the expression of IL-10 in the epidermis in murine contact hypersensitivity

The repeated application of glucocorticoids (GC) on the skin augmented the inflammatory response of both allergic and irritant contact dermatitis in our studies. In order to further clarify the mechanism of such an augmentation of contact hypersensitivity (CHS), we investigated the modulatory effects of cytokines in the epidermis after the administration of GC at challenged sites in CHS. Diflucortolone valerate was applied to BALB/c mice on alternate days for a total of nine times. On day 12, they were contact sensitized with dinitrofluorobenzene (DNFB). Next, on day 17, one day after the last application of GC, they were challenged with DNFB on the ear. The whole challenged ear lobes were removed after a hapten challenge and then were analysed by the RT-PCR method or underwent an immunohistochemical analysis. To clarify the modulatory effects of cytokines in vivo, DNFB sensitized mice pre-treated with GC were injected with rIL-10, IL-1 receptor antagonist (ra) and anti-IL-1alpha monoclonal antibody (mAb) and thereafter were challenged with DNFB. A RT-PCR analysis has demonstrated IL-10 mRNA to be detected in the challenged skin of non-GC-pretreated mice but not in that of GC-pre-treated mice after challenge. On the other hand, the expression of IL-1alpha mRNA in the challenged skin of mice pretreated with GC was more strongly detected that that in mice without GC-pretreatment. Furthermore, an immuno-histochemical analysis in the challenge showed the expression of IL-10 in the skin showed the expression of IL-10 in the challenged epidermis of the non-GC-pretreated mice but not in the GC-pretreated mice and IL-1alpha was also strongly expressed in the epidermis of the GC-pretreated mice. A subcutaneous injection of anti-IL-1alpha mAb or IL-1 ra inhibited the augmented CHS reaction in the GC-pretreated mice. A subcutaneous injection of rIL-10 also inhibited the augmentation of the CHS reaction in the GC-pretreated mice; however, no such inhibition was observed in the non-GC-pretreated mice. These results indicated that both an up-regulation of IL-1alpha production and the inhibition of the IL-10 production in the epidermis at the challenged skin sites in the GC-pretreated mice appear to play a critical role in the GC-induced augmentation of murine CHS.

Glucocorticoids augment the chemically induced production and gene expression of interleukin-1alpha through NF-kappaB and AP-1 activation in murine epidermal cells

To clarify the mechanism of the glucocorticoid-induced augmentation of skin response, we attempted to demonstrate the modulatory effect of glucocorticoids on the regulation of cytokines produced by keratinocytes stimulated with various chemicals in vitro. Haptens, irritants, and a superantigen (staphylococcal enterotoxin B) induced a significant release of interleukin-1alpha and tumor necrosis factor alpha, but not interleukin-10, from a murine keratinocyte cell line, Pam 212 cells. Glucocorticoids (10(-6)-10(-12) M) significantly augmented the production of interleukin-1alpha by Pam 212 cells at both the protein and mRNA levels when stimulated by either haptens or irritants, but not by staphylococcal enterotoxin B, whereas glucocorticoids alone had no effect. In contrast, glucocorticoids had no effect on the production of tumor necrosis factor alpha and interleukin-10 by chemically stimulated Pam 212 cells. Electrophoretic mobility shift assays revealed that chemical stimulation induced NF-kappaB activation in Pam 212 cells; however, augmented NF-kappaB activation by 10(-6)-10(-8) M of glucocorticoids was observed in Pam 212 cells stimulated by both haptens and irritants, but not by staphylococcal enterotoxin B. Furthermore, pyrrolidine dithiocarbamate inhibited the hapten-induced interleukin-1alpha production and NF-kappaB expression by Pam 212 cells. Pyrrolidine dithiocarbamate did not completely abrogate the hapten-induced interleukin-1alpha production augmented by glucocorticoids, however. To determine the effect on transcription factors other than NF-kappaB, AP-1 activity was examined by electrophoretic mobility shift assays. Hapten was founded to induce AP-1 activation in Pam 212 cells. In addition, AP-1 activation was augmented in the hapten-stimulated Pam 212 cells in the presence of 10(-8)-10(-10) M of glucocorticoids. The augmented inflammatory reaction by glucocorticoids may therefore reflect the augmentation of interleukin-1alpha production by keratinocytes mediated through the NF-kappaB and AP-1 pathway.