The anti-androgen hydroxyflutamide and androgens inhibit interleukin-6 production by an androgen-responsive human osteoblastic cell line.
While androgens clearly have significant skeletal effects, the paracrine mediators of androgen action on bone are at present unclear. Interleukin-6 (IL-6) is a candidate cytokine that is produced by osteoblastic lineage cells and promotes osteoclastogenesis and bone resorption. Here, we assessed constitutive as well as IL-1beta- and tumor necrosis factor-alpha (TNF-alpha)-stimulated IL-6 mRNA expression by Northern analysis and protein secretion by immunoassay in a human androgen-responsive osteoblastic cell line (hFOB/AR-6) which contains approximately 4000 androgen receptors (ARs)/nucleus. Treatment with 5alpha-dihydrotestosterone (DHT) dose-dependently inhibited constitutive and TNF-alpha/IL-1beta-stimulated IL-6 mRNA steady-state levels in hFOB/AR-6 cells by 70-80% at 10-7 M. In addition, testosterone also suppressed TNF-alpha/IL-1beta-stimulated IL-6 mRNA levels by 57%, while the adrenal androgen dehydroepiandrosterone had no effect. Of note, the specific AR antagonist, hydroxyflutamide, also inhibited IL-6 mRNA levels by 70%. Consistent with the Northern analyses, treatment with 5alpha-DHT, testosterone, and hydroxyflutamide also inhibited IL-6 protein production by 79%, 62%, and 71%, respectively (p < 0.001), while these agents had no effect on IL-6 soluble receptor levels. Finally, we demonstrated that hydroxyflutamide treatment of hFOB/AR-6 cells markedly inhibited the activation and binding of NF-kappaB (a known stimulator of IL-6 gene transcription) to its response element, thus providing a potential mechanism for its effect on IL-6 production by osteoblasts. These data are consistent with the hypothesis that suppression of osteoblast IL-6 production by androgens may mediate, at least in part, the antiresorptive effects of androgens on bone. Moreover, our findings also indicate that hydroxyflutamide, which is a known AR antagonist in most tissues, may function as a selective AR modulator for effects on IL-6 production by osteoblasts.
Hofbauer
L C
LC
Endocrine Research Unit, Division of Endocrinology and Metabolism, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.
Ten
R M
RM
Khosla
S
S
D000704:Analysis of Variance; D000726:Androgen Antagonists / Q000494:pharmacology*; D000728:Androgens / Q000494:pharmacology*; D002460:Cell Line; D013196:Dihydrotestosterone / Q000494:pharmacology; D005485:Flutamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D015850:Interleukin-6 / Q000096:biosynthesis*; D016328:NF-kappa B / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism; D019899:Paracrine Communication; D011485:Protein Binding; D012333:RNA, Messenger / Q000096:biosynthesis; D013268:Stimulation, Chemical; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D000726:Androgen Antagonists; D000728:Androgens; D007375:Interleukin-1; D015850:Interleukin-6; D016328:NF-kappa B; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D013196:Dihydrotestosterone; C014290:hydroxyflutamide; D005485:Flutamide