Toll-like receptor 4 in rat prostate: modulation by testosterone and acute bacterial infection in epithelial and stromal cells.

The prostate gland is the most inflammation-prone organ in the male reproductive tract. However, little information is available regarding the immunobiology of this gland. Toll-like receptor 4 (TLR4) is considered to be a major sensor of danger signals and a key trigger of the innate immune responses. TLRs have also been implicated in the development of different inflammatory diseases in organs in which epithelial-stromal interactions are critical for homeostasis. The purpose of this work was to evaluate the presence and regulation of TLR4 in the rat prostate. Western blot and immunocytochemical studies revealed that constitutive expression of TLR4 in the rat ventral prostate was localized in the epithelial cells, mainly associated with the rough endoplasmic reticulum, as well as in smooth muscle cells in the stroma. In addition, increased concentrations of TLR4 were found in castrated rats, predominantly in hypertrophied smooth muscle cells. On the other hand, using a bacterial prostatitis model, we observed an increment in the TLR4 cytoplasmic content and migration of this receptor to the apical plasmatic membranes of epithelial cells at 24 h and 48 h post-infection. These findings suggest that the prostate gland is able to recognize pathogens and to initiate immune responses. In addition, TLR4 appears to be implicated in the vital stromal-epithelial interactions that maintain prostate homeostasis during prostatitis, as well as following androgen deprivation.