sphingosine-phosphorylcholine and Pruritus

To elucidate the mechanisms of severe itch in atopic dermatitis, we investigated the role of leukotriene B(4) , a potent itch mediator, in spontaneous itch-related behaviour in NC mice with atopic dermatitis-like skin lesions. Topical application of the BLT leukotriene B(4) receptor antagonist ONO-4057 inhibited spontaneous itch-related behaviour. The concentration of leukotriene B(4) was significantly increased in the lesional skin. The expression levels of 5-lipoxygenase were also elevated in the lesional skin, yet present throughout the epidermis of both healthy and lesional skin. These results suggest a role for leukotriene B(4) in chronic dermatitis-related itch. Sphingosylphosphorylcholine (SPC) was increased in the epidermis of the lesional skin. Moreover, intradermal injection of SPC elicited itch-related behaviours in healthy mice. Because SPC induces itch-related responses through the production of leukotriene B(4) in keratinocytes (J Invest Dermatol, 129, 2009, 2854), these results suggest that an increase in SPC induces leukotriene B(4) -mediated itching in chronic dermatitis. BLT1 receptor and 5-lipoxygenase in the skin may be effective pharmacological targets for the treatment of itch in atopic dermatitis.

Topics: Administration, Topical; Animals; Arachidonate 5-Lipoxygenase; Dermatitis, Atopic; Disease Models, Animal; Leukotriene B4; Mice; Phenylpropionates; Phosphorylcholine; Pruritus; Receptors, Leukotriene B4; Skin; Sphingosine

In atopic dermatitis, the concentration in the skin of sphingosylphosphorylcholine (SPC), which is produced from sphingomyelin by sphingomyelin deacylase, is increased. In the present study, we investigated the itch-eliciting activity of SPC and related substances and the mechanisms of SPC action in mice. An intradermal injection of SPC, but not sphingomyelin and sphingosine, induced scratching, an itch-associated response, which was not suppressed by a deficiency in mast cells or the H(1) histamine receptor antagonist terfenadine. The action of SPC was inhibited by the mu-opioid receptor antagonist naltrexone. SPC action also was inhibited by the 5-lipoxygenase inhibitor zileuton and the leukotriene B(4) antagonist ONO-4057, but not by the cyclooxygenase inhibitor indomethacin. Moreover, SPC action was inhibited by the antiallergic agent azelastine, which suppresses the action and production of leukotriene B(4). Administration of SPC to the skin and to primary cultures of keratinocytes increased leukotriene B(4) production. SPC increased intracellular Ca(2+) ion concentration in primary cultures of dorsal root ganglion neurons and keratinocytes. These results suggest that SPC induces itching through a direct action on primary afferents and leukotriene B(4) production of keratinocytes. Sphingomyelin deacylase and SPC receptors may be previously unreported targets for antipruritic drugs.

Topics: Animals; Calcium; Dermatitis, Atopic; Ganglia, Spinal; Histamine; Histamine H1 Antagonists, Non-Sedating; Injections, Intradermal; Keratinocytes; Leukotriene B4; Male; Mast Cells; Mice; Mice, Inbred ICR; Naltrexone; Narcotic Antagonists; Neurons; Phosphorylcholine; Pruritus; Skin; Sphingomyelins; Sphingosine; Terfenadine

Sphingosylphosphorylcholine (SPC) is upregulated in the stratum corneum of atopic dermatitis patients by sphingomyelin deacylase. We conducted an investigation, both to confirm that intradermal injection of SPC elicits scratching in mice, and to elucidate the detailed mechanism of the SPC-induced itch-scratch response. Intradermal administration of SPC increased the incidence of scratching behavior in a dose-dependent manner. SPC-induced scratching could be suppressed, significantly, by the mu-opoid receptor antagonist, naltrexon, the vaniloid receptor agonist, capsaicin, and the histamine H1 receptor antagonist ketotifen. d-erythro SPC, one of the SPC stereotypes, could elicit the scratch response, but not l-threo SPC. Y-27632 (1 mg/kg, an inhibitor of Rho-associated protein kinase (ROCK)), was found to suppress SPC-induced scratching. Both the stereospecificity of SPC and the involvement of the Rho/ROCK pathway suggested that SPC-induced scratching is related to the receptor.

Topics: Amides; Animals; Antipruritics; Behavior, Animal; Capsaicin; Dose-Response Relationship, Drug; Injections, Intradermal; Ketotifen; Male; Mice; Mice, Inbred ICR; Muscle Relaxants, Central; Naltrexone; Narcotic Antagonists; Phosphorylcholine; Pruritus; Pyridines; rho-Associated Kinases; Sphingosine