Inhibition of cutaneous contact hypersensitivity in the mouse with systemic or topical spiperone: topical application of spiperone produces local immunosuppression without inducing systemic neuroleptic effects

Spiperone enhances intracellular calcium level and inhibits the Wnt signaling pathway

BACKGROUND

Wnt signaling affects fundamental development pathways by regulating cell proliferation and differentiation. Aberrant activation of Wnt/beta-catenin signaling promotes the development of several cancers and is an attractive target for chemopreventive and chemotherapeutic agents.

RESULTS

In order to identify the novel antagonists for the Wnt/beta-catenin pathway, we employed a cell-based Wnt reporter system (TOPflash) to screen a library of 960 known drugs. We identified spiperone, a psychotropic drug, as a novel Wnt inhibitor, which specifically blocks canonical Wnt signaling prior to the activation of beta-catenin. The Wnt inhibitory function of spiperone is not associated with its dopamine-, serotonin- and sigma-receptor antagonist properties. Instead, spiperone increases intracellular calcium levels in a similar manner to thapsigargin, that also impedes Wnt signal transduction. Inhibition of protein kinase C had no effect on spiperone-mediated antagonism of Wnt signaling.

CONCLUSION

Spiperone is a calcium regulator. It inhibits Wnt signaling by enhancing intracellular calcium levels.

The skin as a mirror of the soul: exploring the possible roles of serotonin

Serotonin (5-hydroxytryptamine; 5-HT) is an important mediator of bidirectional interactions between the neuroendocrine system and the skin. The rate of synthesis of 5-HT from l-tryptophan can be enhanced by brain-derived neuronal growth factor, cytokines, exposure to ultraviolet light and steroids. The major source of 5-HT in the skin are platelets, which, upon aggregation, release this biogenic amine. Moreover, the epidermal and dermal skin express the enzymes required for the transformation of tryptophan to 5-HT, and certain skin cells, such as melanocytes, have been demonstrated to produce 5-HT. In addition, rodent mast cells produce 5-HT, but human mast cells have not yet been fully examined in this respect. Skin cells express functionally active, membrane-bound receptors for 5-HT, as well as proteins that transport 5-HT. The interactions of 5-HT with these various proteins determines the nature, magnitude and duration of serotonergic responses. The immune and vasculature systems in the skin are traditional targets for bioregulation by 5-HT. Moreover, recent findings indicate that keratinocytes, melanocytes and dermal fibroblasts also respond to this amine in various ways. Thus, mammalian skin is both a site for the production of and a target for bioregulation by 5-HT. This indicates that agonists and antagonists directed towards specific 5-HT receptors could be useful in connection with treatment of skin diseases. Based on our increasing knowledge concerning these receptors and their plasticity, future research will focus on the development of serotonergic drugs that exert metabotrophic effects on the cells of the skin without affecting the central nervous system.

Increased and prolonged inflammation and angiogenesis in delayed-type hypersensitivity reactions elicited in the skin of thrombospondin-2--deficient mice

Angiogenesis and enhanced microvascular permeability are hallmarks of a large number of inflammatory diseases. Although up-regulation of proangiogenic factors such as vascular endothelial growth factor and interleukin-8 have been previously reported in inflamed tissue, the biologic role of endogenous inhibitors of angiogenesis in inflammation has remained unclear. To investigate the biologic role of the potent angiogenesis inhibitor thrombospondin-2 (TSP-2) in the control of cutaneous inflammation, delayed-type hypersensitivity reactions were elicited in the ear skin of wild-type and TSP-2-deficient mice by topical sensitization and challenge with oxazolone. Cutaneous TSP-2 expression was up-regulated in the inflamed skin of wild-type mice, predominantly in dermal fibroblasts and microvessels. Lack of TSP-2 resulted in a significantly enhanced inflammatory response with increased angiogenesis, edema formation, and inflammatory infiltration. Ear swelling and inflammation persisted for more than 2 weeks in TSP-2-deficient mice, as compared with 1 week in wild-type mice. Although baseline vascular permeability was unchanged, significantly enhanced microvascular leakage was found in the inflamed skin of TSP-2-deficient mice. Moreover, the fraction of rolling leukocytes was significantly increased in the untreated skin of TSP-2-deficient mice. These results reveal an important role of TSP-2 in limiting the extent and the duration of edema formation, angiogenesis, and inflammatory cell infiltration during acute and chronic inflammation.

Haloperidol and spiperone potentiate murine splenic B cell proliferation

The neuroleptics haloperidol and spiperone potentiated anti-mu induced murine B-lymphocyte proliferation in vitro and lowered the threshold of anti-mu antibody needed to trigger proliferation. Because haloperidol and spiperone are best known for actions at D2, 5HT2, alpha 1 and sigma (sigma) receptors, a series of agonists and antagonists of these receptors were tested. Dopamine and norepinephrine inhibited, and serotonin (5HT) enhanced B-cell proliferation. Spiperone opposed the suppression of proliferation by dopamine and norepinephrine. However, antagonists of D1, D2, D3, D5, 5HT2, 5HT1A, and alpha 1 receptors did not mimic the effect of haloperidol and spiperone. Furthermore, a series of sigma agonists failed to affect B-cell proliferation. Therefore it is likely that the effects of haloperidol and spiperone are not due to actions at known dopamine, 5HT, alpha 1, or sigma receptors. These findings indicate neuroleptics act not only in the CNS, but also directly on B-lymphocytes of the immune system. The pharmacological site of this action is not clear at this time.

Effect of coadministration of corticosteroids on the development of contact sensitization

BACKGROUND

Transdermal administration of drugs can increase patient compliance and reduce side effects, but it can also cause contact sensitization. Corticosteroids frequently are used to suppress the local immune response; however, their use as a pretreatment for transdermal system application sites is not practical.

OBJECTIVE

Our purpose was to determine the feasibility of suppressing contact sensitization by delivering a corticosteroid with the transdermal delivery systems.

METHODS

Materials were applied continuously for 3 weeks to the same (protocol SS) or different (protocol AS) skin sites. Skin flux and appearance of sensitization were determined.

RESULTS

Coadministration of hydrocortisone reduced the incidence of sensitization by d-chlorpheniramine and benzoyl peroxide from 45% to 7.5% and from 20% to 2.3%, respectively, under protocol SS. Under protocol AS, sensitization by d-chlorpheniramine was reduced from 15% to 1%. Frequent exposure to the sensitizer plus corticosteroid induced tolerance to the sensitizer.

CONCLUSION

Sensitization by moderately immunogenic drugs after any length of exposure may be reduced to acceptable levels by the coadministration of hydrocortisone.

Horizons in pharmacologic intervention in allergic contact dermatitis

The treatment of allergic contact dermatitis remains a major challenge. Current management strategies consist of elimination of the allergen when possible and therapy for symptoms with topical or systemic corticosteroids. With increasing exposure of the human skin to environmental antigens and haptens, more selective treatment options are needed. Advances in the elucidation of the skin immune system and of the cellular and molecular events in immunologic processes may allow targeted methods of controlling delayed hypersensitivity reactions. This review focuses on mechanisms of established therapeutic agents and new developments, such as FK 506 (tacrolimus), pentoxifylline, and vitamin D3 derivative, for suppression of any phase of allergic contact dermatitis.