REGULATION OF MACROPHAGE DEHYDROEPIANDROSTERONE-SULFATE METABOLISM BY INFLAMMATORY CYTOKINES

Metabolism of dehydroepiandrosterone sulfate (DHEAS) to dehydroepiandrosterone (DHEA) occurs within specific anatomical compartments in vivo through the actions of the enzyme DHEAS sulfatase. This enzymatic activity facilitates the conversion of hydrophilic DHEAS to the hydrophobic species DHEA, which can then be further metabolized to other steroid hormones. High levels of DHEAS sulfatase reside in tissues where the biological activity of DHEA or its downstream metabolites regulate cellular function. Therefore, control over the activity of DHEAS sulfatase may represent an important regulatory process for the production of DHEA and its metabolites. Homogenous populations of macrophages from normal mice were found to effectively convert DHEAS to DHEA in vitro. DHEAS sulfatase activity could be markedly depressed after exposure of these cells to a variety of nonspecific macrophage activators [i.e. zymosan, polyinosine/cytosine, heat-killed bacteria, or bacterial lipopolysaccharide (LPS)]. Inhibition of DHEAS metabolism was found to require protein synthesis, because temporary abrogation of protein synthesis with cycloheximide eliminated the ability of LPS to depress the conversion of DHEAS to DHEA. Additionally, exposure of LPS-nonresponsive macrophages to supernatants derived from LPS-treated BALB/c macrophages inhibited their ability to convert DHEAS to DHEA. Potent inhibition of sulfatase activity could be achieved by directly exposing murine macrophages to interferon-alpha (IFN alpha), IFN beta, or tumor necrosis factor-alpha, but not interleukin-1, interleukin-6, granulocyte-macrophage colony-stimulating factor, transforming growth factor-beta, platelet-derived growth factor, or the T-cell product IFN gamma. Our results indicate that macrophage metabolism of DHEAS to DHEA is down-regulated after cellular activation. Furthermore, inhibition of DHEAS sulfatase activity appears to be mediated through the actions of the inflammatory cytokines tumor necrosis factor-alpha and IFN alpha/beta.