Benign prostatic hyperplasia (BPH) is a common disease among aging males with the etiology remaining unclear. We recently found myosin II was abundantly expressed in rat and cultured human prostate cells with permissive roles in the dynamic and static components. This study aimed to explore the expression and functional activities of myosin II isoforms including smooth muscle myosin II (SMM II) and non-muscle myosin (NMM II) in the hyperplastic prostate. Human prostate cell lines and tissues from normal human and BPH patients were used. H&E, Masson's trichrome, immunohistochemical staining, in vitro organ bath, RT-PCR and Western-blotting were performed. We further created cell models with NMM II isoforms silenced and proliferation, cycle, and apoptosis of prostate cells were determined by CCK-8 assay and flow cytometry. Hyperplastic prostate SM expressed more SM1 and LC17b isoforms compared to their alternatively spliced counterparts, favoring a slower more tonic-type contraction and greater force generation. For BPH group, blebbistatin (BLEB, a selective myosin II inhibitor), exhibited a stronger effect on relaxing phenylephrine (PE) pre-contracted prostate strips and inhibiting PE induced contraction. Additionally, NMMHC-A and NMMHC-B were upregulated in hyperplastic prostate with no change in NMMHC-C. Knockdown of NMMHC-A or NMMHC-B inhibited prostate cell proliferation and induced apoptosis, with no changes in cell cycle. Our novel data demonstrates that expression and functional activities of myosin II isoforms are altered in human hyperplastic prostate, suggesting a new pathological mechanism for BPH. Thus, the myosin II system may provide potential new therapeutic targets for BPH/lower urinary tract symptoms (LUTS).
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