Regulatory roles of sex hormones in cutaneous biology and immunology

Recent studies have revealed that sex hormones manifest a variety of biological and immunological effects in the skin. Pregnancy, menstruation and the menopause modulate the natural course of psoriasis, indicating a female hormone-induced regulation of skin inflammation. Estrogen in vitro down-regulates the production of the neutrophil, type 1 T cell and macrophage-attracting chemokines, CXCL8, CXCL10, CCL5, by keratinocytes, and suppresses IL-12 production and antigen-presenting capacity while enhancing anti-inflammatory IL-10 production by dendritic cells. These data indicate that estrogen may attenuate inflammation in psoriatic lesions. Estrogen, alone or together with progesterone, prevents or reverses skin atrophy, dryness and wrinkles associated with chronological or photo-aging. Estrogen and progesterone stimulate proliferation of keratinocytes while estrogen suppresses apoptosis and thus prevents epidermal atrophy. Estrogen also enhances collagen synthesis, and estrogen and progesterone suppress collagenolysis by reducing matrix metalloproteinase activity in fibroblasts, thereby maintaining skin thickness. Estrogen maintains skin moisture by increasing acid mucopolysaccharide or hyaluronic acid levels in the dermis. Progesterone increases sebum secretion. Estrogen accelerates cutaneous wound healing stimulating NGF production in macrophages, GM-CSF production in keratinocytes and bFGF and TGF-beta1 production in fibroblasts, leading to the enhancement of wound re-innervation, re-epithelialization and granulation tissue formation. In contrast, androgens prolong inflammation, reduce deposition of extracellular matrix in wounds, and reduce the rate of wound healing. Estrogen enhances VEGF production in macrophages, an effect that is antagonized by androgens and which may be related to the development of granuloma pyogenicum during pregnancy. These regulatory effects of sex steroids may be manipulated as therapeutic or prophylactic measures in psoriasis, aging, chronic wounds or granuloma pyogenicum.