Honokiol, a constituent of Magnolia species, inhibits adrenergic contraction of human prostate strips and induces stromal cell death

PurposeSmooth muscle contraction and prostate growth are important targets for medical therapy of lower urinary tract symptoms (LUTS) in patients with benign prostatic hyperplasia. Honokiol and Magnolol are lignan constituents of Magnolia species, which are used in traditional Asian medicine. Here, we examined effects of honokiol and magnolol on contraction of human prostate tissue and on growth of stromal cells.MethodsProstate tissues were obtained from radical prostatectomy. Contraction of prostate strips was examined in organ bath studies. Effects in stromal cells were assessed in cultured immortalized human prostate stromal cells (WPMY-1). Ki-67 mRNA was assessed by reverse transcription-polymerase chain reaction, and proliferation by a fluorescence 5-ethynyl-2′-deoxyuridine assay.ResultsHonokiol (100 μM) reduced noradrenaline-induced contractions, which was significant at 10- to 100-μM noradrenaline. Honokiol reduced phenylephrine-induced contractions, which was significant at 3- to 100-μM phenylephrine. Honokiol reduced electric field stimulation-induced contractions very slightly. In WPMY-1 cells, honokiol (24 hours) induced cell death. Magnolol (100 μM) was without effects on contraction, and cellular viability.ConclusionsHonokiol inhibits smooth muscle contraction in the human prostate, and induces cell death in cultured stromal cells. Because prostate smooth muscle tone and prostate growth may cause LUTS, it appears possible that honokiol improves voiding symptoms.