Hydrogen sulfide has a role as an endogenous relaxation factor in the rat prostate

Abstract

ABSTRACT Introduction Hydrogen sulfide (H2S) is the third endogenous gasotransmitter besides carbon monoxide and nitric oxide, and has a wide range of physiological functions such as neuromodulation, vasorelaxation and cytoprotection. Although in human prostate cancer cells, NaHS (a H2S donor) treatment was reported to inhibit proliferation and to elevate secretory function, physiological functions of H2S in the prostate tissue had not been investigated yet. Endogenous H2S is biosynthesized from L-cysteine by cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE). In addition, 3-mercaptopyruvate sulfurtransferase (MPST) synthesizes H2S from 3-mercaptopyruvate (3MP), which is produced from L-cysteine by cysteine aminotransferase (CAT) (CAT/MPST pathway). Recently, a new pathway for endogenous H2S biosynthesis is reported; D-cysteine is metabolized by D-amino acid oxidase (DAO) to 3MP, which is a substrate for MPST to synthesize H2S. Objective We investigated (1) tissue distribution of CBS, CSE, MPST, CAT and DAO, (2) endogenous H2S levels, and (3) effects of NaHS on contractility in the rat prostate. Methods Dorsolateral and ventral prostate (PR-D and PR-V), liver and cerebellum (L and C) were prepared from male Wistar rats (300-400 g) sacrificed with an overdose of sodium pentobarbital (80 mg/kg, ip). (1) Tissue distributions of 5 enzymes were investigated by real-time PCR, western blot and immunohistochemistry. L and C were used for positive controls. (2) H2S contents in the prostate tissues were measured by methylene blue method. (3) By using 1 x 5 mm strips of the prostate tissues, effects of NaHS (1 x 10-9 to 3 x 10-4 M) were evaluated on pre-contracted prostate strips by noradrenaline (10-5 M). Prostate strips were pretreated with propranolol (10-6 M) 30 min before the pre-contraction. Results (1) CBS, MPST and CAT were detected in the prostate. Expression levels of CBS in the PR-D were lower than those in the PR-V, and the levels of MPST in the PR-D were higher than those in the PR-V. In expression levels of CAT, there was no significant difference between two prostate tissues. On the other hand, CSE or DAO was not detected in these tissues. Immunoreactvities of these enzymes were mainly detected in the prostate glandular epithelium. (2) H2S was detected in the prostate tissues. (3) NaHS dose-dependently induced relaxation of pre-contracted PR-D and PR-V strips. There were no significant differences of the EC50 values or relaxation rate against the pre-contractions between two prostate tissues. Conclusion H2S synthesized by CBS- and CAT/MPST-mediated pathways has a role as an endogenous relaxation factor in the rat prostate. Therefore, endogenous H2S might open new avenues of therapeutic interventions for benign prostatic hyperplasia. Disclosure Work supported by industry: no.