The vitamin D receptor agonist elocalcitol inhibits IL-8-dependent benign prostatic hyperplasia stromal cell proliferation and inflammatory response by targeting the RhoA/Rho kinase and NF-kB pathways

BACKGROUND Benign prostatic hyperplasia (BPH) is characterized by an important inflammatory component. Stimulation of human prostate stromal cells from BPH tissues with proinflammatory cytokines leads to secretion of IL‐8, a chemokine involved in BPH pathogenesis. The vitamin D receptor (VDR) agonist elocalcitol can arrest prostate growth in BPH patients, but its mechanism of action in this pathology is still incompletely understood. METHODS IL‐8 levels were measured by real‐time RT‐PCR and ELISA. NF‐κB translocation and COX‐2 expression were evaluated by confocal microscopy. RhoA and Rho‐kinase (ROCK) gene expression and functional activity were studied by real‐time RT‐PCR, immuno‐kinase assays, Western blot analysis, confocal microscopy, and cell invasion. RESULTS Stimulation of BPH cells with IL‐8 activates the calcium‐sensitizing RhoA/ROCK pathway, as demonstrated by the increased membrane translocation of RhoA and by phosphorylation of the ROCK substrate myosin phosphatase target subunit 1 (MYPT‐1). In agreement with these data, C3 exoenzyme, a selective RhoA inhibitor, inhibits IL‐8‐induced invasion of BPH cells. The VDR agonist elocalcitol significantly inhibits IL‐8 production by BPH cells stimulated with inflammatory cytokines, and IL‐8‐induced proliferation of BPH cells. In addition, elocalcitol inhibits IL‐8‐induced membrane translocation of RhoA and MYPT‐1 phosphorylation in BPH cells, and inhibits dose‐dependently their IL‐8‐dependent invasion. The inhibition induced by elocalcitol of IL‐8 production by BPH cells is accompanied by decreased COX‐2 expression and PGE2 production and by arrest of NF‐κB p65 nuclear translocation, associated with inhibition of the RhoA/ROCK pathway. CONCLUSIONS These data provide a mechanistic explanation for the anti‐proliferative and anti‐inflammatory properties of elocalcitol in BPH cells. Prostate 69:480–493, 2009. © 2008 Wiley‐Liss, Inc.