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Effects of icariin on phosphodiesterase-5 activity in vitro and cyclic guanosine monophosphate level in cavernous smooth muscle cells

  • Hongxiu Ning
    Affiliations
    Knuppe Molecular Urology Laboratory, Department of Urology, University of California, San Francisco, School of Medicine, San Francisco, California
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  • Zhong-Cheng Xin
    Affiliations
    Andrology Center, Peking University First Hospital, Beijing, China
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  • Guiting Lin
    Affiliations
    Knuppe Molecular Urology Laboratory, Department of Urology, University of California, San Francisco, School of Medicine, San Francisco, California
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  • Lia Banie
    Affiliations
    Knuppe Molecular Urology Laboratory, Department of Urology, University of California, San Francisco, School of Medicine, San Francisco, California
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  • Author Footnotes
    1 T.F. Lue is a paid consultant to Pfizer, Lilly/ICOS, and Bayer/GSK.
    Tom F. Lue
    Footnotes
    1 T.F. Lue is a paid consultant to Pfizer, Lilly/ICOS, and Bayer/GSK.
    Affiliations
    Knuppe Molecular Urology Laboratory, Department of Urology, University of California, San Francisco, School of Medicine, San Francisco, California
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  • Ching-Shwun Lin
    Correspondence
    Reprint requests: Ching-Shwun Lin, M.D., Knuppe Molecular Urology Laboratory, Department of Urology, University of California, San Francisco, School of Medicine, 1657 Scott Street, Room 210, San Francisco, CA 94115.
    Affiliations
    Knuppe Molecular Urology Laboratory, Department of Urology, University of California, San Francisco, School of Medicine, San Francisco, California
    Search for articles by this author
  • Author Footnotes
    1 T.F. Lue is a paid consultant to Pfizer, Lilly/ICOS, and Bayer/GSK.

      Abstract

      Objectives

      To investigate the effect of icariin on the cyclic guanosine monophosphate (cGMP)-hydrolytic activity of phosphodiesterase-5 (PDE5) isoforms and the cGMP levels in cavernous smooth muscle cells treated with sodium nitroprusside (SNP).

      Methods

      PDE5 isoforms (PDE5A1, A2, and A3) were isolated from sf9 insect cells infected with baculoviruses carrying PDE5 isoform cDNA. Icariin was isolated from Epimedii herba. Varying amounts (10−6 to 10−11 M) of icariin or zaprinast were added to reaction mixtures containing PDE5 isoforms and cGMP. The inhibitory effects of icariin and zaprinast were analyzed by GraphPad Software and are expressed as concentration that inhibits 50% (IC50) values. Cavernous smooth muscle cells were isolated from 3-month-old rats, treated with icariin (100 and 200 μM) or zaprinast (200 μM) for 15 minutes, and then with 10 μM SNP for 30, 60, 120, 240, and 360 minutes. The cells were then analyzed for the cGMP concentration using an enzyme immunoassay system.

      Results

      Icariin inhibited PDE5A1, A2, and A3 with an IC50 value of 1.0, 0.75, and 1.1 μM, respectively. The corresponding IC50 values for zaprinast were 0.33, 0.23, and 0.32 μM. Icariin consistently outperformed the control (SNP-only treatment) in maintaining greater cGMP levels, particularly at the greater concentration of 200 μM. In contrast, zaprinast at 200 μM did better than the control only at 60 and 360 minutes.

      Conclusions

      Icariin was inhibitory to all three PDE5 isoforms with similar IC50 values, which were approximately three times greater than those for zaprinast. Icariin was able to enhance cGMP levels in SNP-treated cavernous smooth muscle cells.
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