Psoriasis is characterized by keratinocyte hyperproliferation, erythema, as well as a form of pruritus, involving cutaneous discomfort. There is evidence from both clinical and murine models of psoriasis that chemical or surgical depletion of small-diameter sensory nerves/nociceptors benefits the condition, but the mechanisms are unclear. Hence, we aimed to understand the involvement of sensory nerve mediators using a murine model of psoriasis and associated spontaneous behaviors, indicative of cutaneous discomfort. We have established an Aldara™ model of psoriasis in mice and chemically depleted the small diameter nociceptors in a selective manner. The spontaneous behaviors, in addition to the erythema and skin pathology, were markedly improved. Attenuated inflammation was associated with reduced dermal macrophage influx and production of reactive oxygen/nitrogen species (peroxynitrite and protein nitrosylation). Subsequently, this directly influenced observed behavioral responses. However, the blockade of common sensory neurogenic mechanisms for TRPV1, TRPA1, and neuropeptides (substance P and CGRP) using genetic and pharmacological approaches inhibited the behaviors, but not the inflammation. Thus a critical role of the established sensory TRP-neuropeptide pathway in influencing cutaneous discomfort is revealed, indicating the therapeutic potential of agents that block this pathway. The ongoing inflammation is mediated by a distinct sensory pathway involving macrophage activation.
- TRP channels, neuropeptides, macrophages, oxidative stress, peroxynitrite