Platelets as versatile regulators of cutaneous inflammation.

It is generally accepted that the main roles of platelets are to maintain hemostasis and perform thrombosis at sites of injury. However, more recently it has become apparent that platelets also play prominent roles in immune and/or inflammatory processes. Platelets release various kinds and considerable amounts of secretory molecules such as chemokines, monoamines, and cytokine-like factors upon stimulation. They also express a wide variety of immune-related receptors, such as P-selectin and CD40L. Additionally, the hyperaggregability of platelets has been demonstrated in several inflammatory skin diseases. In the last decade, more specific and versatile roles for platelets in the pathophysiology of skin inflammation, such as in atopic dermatitis, have been disclosed, e.g. stimulating keratinocytes, leukocytes, endothelial cells, and other platelets; trafficking leukocytes to skin tissue; inhibiting monocytic apoptosis; inducing fibrosis; provoking itchiness; and regulating inflammation. New anti-platelet strategies directed against the platelet activation process may create new possibilities for the treatment of cutaneous inflammatory diseases such as atopic dermatitis.