Blebbistatin Modulates Prostatic Cell Growth and Contractility through Myosin II Signaling.

OBJECTIVES: To investigate the effect of blebbistatin (BLEB, a selective myosin inhibitor) on regulating contractility and growth of prostate cells and to provide insight into possible mechanisms associated with these actions.

METHODS: BLEB was incubated with cell lines of BPH-1 and WPMY-1 and was intra-prostatically injected into rats. Cell growth was determined by flow cytometry and in vitro organ bath studies were performed to explore smooth muscle (SM) contractility. SM myosin (SMM) isoform (SM1/2, SM-A/B and LC17a/b ) expression was determined via competitive RT-PCR. SM myosin heavy chain (MHC), non-muscle (NM) MHC isoforms (NMMHC-A and NMMHC-B) and proteins related to cell apoptosis were analyzed via Western-blotting.  Masson's trichrome staining was applied to tissue sections.

RESULTS: BLEB dose-dependently trigger apoptosis and retard the growth of BPH-1 and WPMY-1. Consistent with in vitro effect, administration of BLEB to the prostate could decrease rat prostatic epithelial and SM cells via increased apoptosis. Western-blotting confirmed the effects of BLEB on inducing apoptosis through a mechanism involving MLC20 dephosphorylation with downregulation of Bcl-2 and upregulation of BAX and cleaved caspase 3. Meanwhile, NMMHC-A, NMMHC-B and p-MLC20 were found significantly attenuated in BPH-1 and WPMY-1 cells, as well as rat prostate tissues. Additionally, BLEB decreased SM cell number and SM MHC expression, along with attenuated phenylephrine-induced contraction and altered prostate SMM isoform composition with upregulation of SM-B and downregulation of LC17a , favoring a faster contraction.

CONCLUSION: Our novel data demonstrates BLEB regulated myosin expression and functional activity. The mechanism involved MLC20 dephosphorylation and altered SMM isoform composition.