The effect of substance P on peripheral blood mononuclear cells in patients with atopic dermatitis

Background: There is increasing evidence that neuropeptides, especially substance P (SP), may be involved in the pathogenesis of atopic dermatitis (AD). Objective: We performed this study to determine more precisely the role of SP in AD. Methods: We separated peripheral blood mononuclear cells (PBMCs) from AD patients and normal controls, and measured proliferation response and cytokine release after adding SP (10(-11), 10(-10) and 10(-9) M). We also compared substance P receptor expression by semi-quantitative RT-PCR. Results: PBMCs from AD patients proliferated at significantly higher rates (ca. by 30%). Semi-quantitative RT-PCR showed that the level of expression of SP receptor increased in AD patients versus normal controls. IL-4 release from PBMCs was significantly higher in AD patients, white IFN-gamma release from PBMCs was significantly Lower in AD patients. Different concentrations of SP did not cause any difference in IL-4 and IFN-gamma secretions. However, TNF-alpha release from PBMCs in AD patients increased significantly at 10(-10) and 10(-9) M of SP compared to SP (-) control. IL-10 release from PBMCs increased significantly in AD patients with 10(-9) M of SP compared to SP (-) control. Conclusion: SP might aggravate AD by increasing the production of TNF-alpha and IL-10 rather than by affecting IL-4 and IFN-gamma. This different immune response is considered to be the result of upregutated SP receptor in AD. (C) 2003 Japanese Society for Investigative Dermatology. Published by Elsevier Science Ireland Ltd. ALL rights reserved.