Norepinephrine activates P44 and P42 MAPK in human prostate stromal and smooth muscle cells but not in epithelial cells

BACKGROUND: In vascular smooth muscle cells, alpha1-adrenergic stimulation increases DNA synthesis and cell proliferation via activation of p44/42 (ERK1/2) MAPK. We examined whether norepinephrine (NE) activates MAPK and stimulates the proliferation of prostatic epithelial and non-epithelial cells. METHODS: Human prostatic epithelial cells, stromal cells, and smooth muscle cells were purchased from BioWhittaker (Walkersville, MD). After reaching a semi-confluent condition, the cells were cultured in RPMI-1640 without serum for 1 day. At 10 min after adding NE (10(-6) or 10(-7) M) to the medium, the cells were collected. Cell lysate was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) followed by Western blot using anti-phospho-p44/42 and anti-p44/42 antibodies. The activation of p44/42 was estimated by the ratio of phospho-p44/42 to total p44/42. Cell proliferation was evaluated by (3)H-thymidine uptake assay. After reaching a semi-confluent condition, the cells were cultured in RPMI-1640 containing 0.5% FCS with or without NE (10(-6) or 10(-7) M) for 16 hr followed by a (3)H-thymidine uptake period (24 hr). RESULTS: P44/42 MAPK was significantly activated by NE in non-epithelial cells (stromal cells and smooth muscle cells) while not in epithelial cells. The uptake of (3)H-thymidine was significantly increased by NE in both non-epithelial cells, which was inhibited by alpha1-adrenoceptor antagonists. CONCLUSIONS: These results suggest that NE may stimulate the proliferation of non-epithelial prostatic cells, which may be involved in the pathogenesis of BPH.