ab22108

Effects of physiological concentrations of steroid hormones and interleukin-11 on basal and stimulated production of interleukin-8 by human osteoblast-like cells with different functional profiles

A. Dovio¹, M.L. Sartori¹, R.G. Masera¹, L. Peretti², L. Perotti³, A. Angeli¹

¹Internal Medicine Unit, Department of Clinical and Biological Sciences, University of Turin, Orbassano (TO), Italy; and the ²Pathology Unit and 3Internal Medicine Unit, A.S.O. S. Croce e Carle, Cuneo, Italy.

ABSTRACT
Objective
IL-8 is a CXC chemokine involved in the pathogenesis of articular damage in rheumatoid arthritis. Local hyperproduction of IL-8 has been suggested to play a role in subchondral bone loss, since it suppresses osteoblast activity and promotes osteoclasts recruitment. Osteoblasts are a source of IL-8; its secretion is regulated by a number of hormones and cytokines. The aim of the present study was to evaluate the single and combined effects of physiological concentrations of cortisol, 17b-estradiol and IL-11 upon basal and IL-1b-inducible production of IL-8 in two human osteoblast-like cell lines, Saos-2 and MG-63.

Methods
Cells were incubated with cortisol (0.01 to 1 mM), 17b-estradiol (10 to 1000 pg/ml), IL-11 (1 to 100 ng/ml), in presence or absence of IL-1b (10 ng/ml), for 20 h. Combinations of 17b-estradiol and cortisol, and of IL-11 and cortisol, were also tested. After incubation, IL-8 levels in supernatants were measured by ELISA.

Results
Cortisol dose-dependently inhibited spontaneous IL-8 secretion in both cell lines, although statistical significance was attained in the MG-63 cells only (P < 0.01); no effect of 17b-estradiol was apparent. With regard to IL-1b-inducible production, cortisol dose-dependently inhibited IL-8 release in both cell lines (P < 0.01); 17b-estradiol resulted in only a non-significant decrease in Saos-2, but not in MG-63 cells. 17b-estradiol did not alter the effects of cortisol in experiments involving co-incubation. IL-11 did not have any effect on spontaneous IL-8 release, but exerted a significant inhibitory effect on IL-1b-inducible release in MG-63 cells (P < 0.05); no additional effect was observed upon the degree of cortisol-dependent inhibition.

Conclusion
Cortisol is a potent physiological inhibitor of IL-8 production by osteoblast-like cells. The results of the present study support the use of exogenous supplemental glucocorticoids to prevent the deleterious effects of excess IL-8. The estrogenic milieu and local concentrations of IL-11 have little if any effect on the IL-8-dependent mechanisms of disease.

Key words
Cortisol, estradiol, IL-11, IL-8, osteoblast, rheumatoid arthritis.

This work was supported by grants from MURST (Rome-Italy), Cassa di Risparmio di Cuneo, Cassa di Risparmio di Saluzzo, Fondazione Rossini.
Please address correspondence and reprint requests to: Alberto Angeli, MD, PhD, Internal Medicine Unit, Department of Clinical and Biological Sciences,
University of Turin - Regione Gonzole 10, 10043 Orbassano (TO) - Italy.
E-mail: alberto.angeli@unito.it