Stress, the neuroendocrine system and mast cells: current understanding of their role in psoriasis.

Psychological stress can activate the hypothalamic-pituitary-adrenal axis and sensory nerves in the brain and skin, resulting in the release of neuroendocrine and neural mediators such as, corticotropin-releasing hormone, neuropeptides, neurotrophins and α-melanocyte-stimulating hormone. These factors can activate mast cells to release proinflammatory mediators and some of them, for example, histamine, tryptase and nerve growth factor, can stimulate sensory C-fibers. Since corticotropin-releasing hormone, sensory nerves and mast cell numbers are increased in the psoriatic lesion, a feedforward loop can exist potentiating the inflammation. Studies in rats and mice have shown that mast cells are activated during standardized stress through corticotropin-releasing hormone and sensory nerves. Therefore, the role of stress, the neuroendocrine system and mast cells in psoriasis is discussed in this article.