Innate immunity and glucocorticoids: potential regulatory mechanisms in epididymal biology

Inflammation is a primordial host response to invasion by pathogens or tissue injury. During infection, microbes can activate immune cells through pattern-recognition receptors, such as Toll-like receptors, an evolutionarily conserved family of receptors that mediate innate immunity in a wide range of organisms. Infection also triggers an increase in glucocorticoid levels as part of the stress response. The scenario indicates that these signals have to be well integrated to mount an effective host response to infection and injury. The mechanisms by which innate and adaptive immunity are regulated, as well as the intersection of these responses with glucocorticoids and the glucocorticoid receptor (GR) in the epididymis, an organ essential for the transport, maturation, storage, and protection of the spermatozoa, are not well understood. In this review we bring together recent data demonstrating the cellular and biochemical machinery involved in the response of the adult rat epididymis to a bacterial product challenge. We also illustrate the basic aspects of the expression, localization, function, and regulation of the GR by steroid hormones (androgens and glucocorticoids) within the epididymis. We conclude with considerations of controversial or still unanswered topics about GR, now emerging as a regulatory step in epididymal biology, its functional relationship with androgens and androgen receptor, and the innate immune response of the epididymis. How these topics may be of interest as part of future research in the area, and how they ultimately can help us to better understand the epididymal function under noninflammatory and inflammatory conditions, are also discussed.