MP44-18 INHIBITION OF SMOOTH MUSCLE CONTRACTION BY THE INHIBITOR FOR CYTOHESIN FAMILIY GUANOSINE NUCLEOTIDE EXCHANGE FACTORS, SECIN H3 IN THE HYPERPLASTIC HUMAN PROSTATE

Abstract

INTRODUCTION AND OBJECTIVES: In patients with benign prostatic hyperplasia, smooth muscle contraction and stromal growth in the prostate may both contribute to urethral obstruction and voiding symptoms. Although a context between control of smooth muscle tone and prostate growth may be assumed, molecular mechanisms underlying this connection still represent an enigma. Here, we addressed the role of Src family kinases (SFKs) for contraction of human prostate smooth muscle, and for growth of human stromal cells. METHODS: SFK expression was assessed by RT-PCR, Western blot, and immunofluorescence. Effects of two different SFK inhibitors, AZM475271 and PP2, on contraction were assessed in human prostate tissues obtained from radical prostatectomy. Effects on proliferation, actin organization, and cytotoxicity were examined in cultured stromal cells (WPMY-1). RESULTS: C-Src and Lck were detected by RT-PCR and Western blot in human prostate tissues and WPMY1 cells. Colocalization with calponin in immunofluorescence stainings of prostate sections indicated location to smooth muscle cells. AZM475271 (10 mM) and PP2 (10 mM) inhibited SFK activity in prostate tissues and WPMY-1 cell, being assessed as phospho-SFK content. Both inhibitors significantly inhibited contraction of prostate strips by norepinephrine, by the a1-adrenergic agonist phenylephrine, and by electric field stimulation. This may be explained by cytoskeletal deorganization, which was observed by phalloidin staining of actin filaments in response to AZM475271 and PP2 in WPMY-1 cells. This was paralleled by reduced proliferation of WPMY-1 cells, as indicated by EdU assay. Cytotoxicity was mainly observed at higher concentrations (50 mM or more) and longer incubation, but was minor at 10 mM for 24 h. CONCLUSIONS: Synchronized regulation of smooth muscle tone and growth by SFK-dependent control may explain their concomitant contributions to bladder outlet obstruction in the hyperplastic prostate. Targeting smooth muscle contraction and growth in the prostate at once by single agents may be principally possible.