Upregulated expression of substance P in basophils of the patients with chronic spontaneous urticaria: induction of histamine release and basophil accumulation by substance P.

Human basophils have been implicated in the pathogenesis of chronic spontaneous urticaria (CSU), and substance P (SP) is a possible candidate as histamine-releasing factor in some patients with CSU. However, little is known of relationship between basophils and SP in CSU. In the present study, we investigated expression of SP and NK1R on basophils from patients with CSU, and influence of SP on basophil functions by using flow cytometry analysis, basophil challenge, and mouse sensitization model techniques. The results showed that plasma SP level and basophil numbers in CSU patients were higher than that in HC subject. The percentages of SP+ and NK1R+ basophils were markedly elevated in CSU blood in comparison with HC blood. Once added, SP induced up to 41.2 % net histamine release from basophils of CSU patients, which was comparable with that provoked by anti-IgE, and fMLP. It appeared that SP induced dramatic increase in blood basophil numbers of mice following peritoneal injection. Ovalbumin (OVA)-sensitized mice had much more SP+ and NK1R+ basophils in blood than non-sensitized mice. In conclusion, the elevated plasma concentration of SP, upregulated expression of SP and NK1R on basophils, and the ability of SP in induction of basophil degranulation and accumulation indicate strongly that SP is most likely a potent proinflammatory mediator, which contributes greatly to the pathogenesis of CSU through basophils. Inhibitors of SP and blockers of NK1R are likely useful agents for treatment of CSU.