In vitro modulation of steroid 5alpha-reductase activity by phospholipases in epithelium and stroma of human benign prostatic hyperplasia.
Membrane components, such as phospholipids, play an important role in the regulation of prostatic 5alpha-reductase activity. To describe in more detail the impact of such regulation on 5alpha-reductase activity, epithelial and stromal cell homogenates of human BPH were treated with phospholipases to specifically alter the structure of cellular phospholipid components. Phospholipase A(2) (PLA(2)) was used to alter the structure of the nonpolar, hydrophobic region of the membrane bilayer. Various types of phospholipase C (PLC) affect the polar, hydrophilic region of phospholipids. In epithelium and stroma, 5alpha-reductase activity was dose-dependently inhibited by PLA(2) and PLC type III. In epithelium and stroma, the mean IC(50) values of PLA(2) were 9.4 +/- 1.1 and 13.9 +/- 2.6 [U/mg protein +/- SEM], respectively. The mean IC(50) values of PLC type III in epithelium and stroma were 4.5 +/- 1.2 and 1.7 +/- 0.2 [U/mg protein +/- SEM], respectively. In epithelium as well as in stroma, 5alpha-reductase activity was more greatly inhibited by PLC type III than by PLA(2). Both in epithelium and stroma, PLA(2) significantly decreased the V(max) of 5alpha-reductase whereas its K(m) remained unaffected. A similar decrease in V(max) was found with PLC type III in epithelium and stroma. Furthermore, the K(m) of epithelial 5alpha-reductase increased significantly following the addition of PLC type III. The two phospholipases, with their specific substrate affinities and sites of hydrolysis, exhibited significantly different effects on 5alpha-reductase, indicating that 5alpha-reductase activity is not unspecifically affected by modification of the hydrophilic milieu. Rather, 5alpha-reductase activity is specifically modulated by various phospholipids and/or phospholipolysis mediated degradation products. These findings suggest that the structural composition of the lipid environment plays a fundamental role in the post-translational regulation of 5alpha-reductase activity in the epithelium and stroma of human BPH. Thus, changes in membrane phospholipid content seem to be instrumental in the expression of DHT-dependent processes.
Weisser
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H
Institute of Clinical Chemistry, Transfusion and Laboratory Medicine, University Clinic Bergmannsheil, Bürkle-de-la-Camp-Platz 1, D-44789, Bochum, Germany. heike.weisser@ruhr-uni-bochum.de
Ziemssen
T
T
Krieg
M
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D004848:Epithelium / Q000201:enzymology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D010741:Phospholipases A / Q000378:metabolism*; D011470:Prostatic Hyperplasia / Q000201:enzymology*; D013251:Steroid Isomerases / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism*
D010741:Phospholipases A; D010738:Type C Phospholipases; D013251:Steroid Isomerases; C022660:steroid delta-isomerase