Neuroendocrine immune mechanisms in rheumatic diseases. An overview and future implications

Perspectives on the relationship of adrenal steroids to rheumatoid arthritis

An expanded model of RA is presented that incorporates cumulative multifactorial processes operating over a prolonged physiological phase prior to initial clinical manifestations. During this phase, progressive imbalances in the homeostasis of core neuroendocrine, immunological, and microvascular systems are believed to occur. Normal adrenal function plays an essential role in helping to maintain homeostasis of core systems in health. In RA, chronic adrenal hypocompetence is suspected to occur in a minority subset of females who have younger clinical onset and males who have associated low serum testosterone levels. Chronic, relative glucocorticoid insufficiency is believed to contribute to development of inflammatory manifestations in RA patients. Androgenic deficiencies, particularly of gonadal origin in males, may also contribute to RA, particularly its decreased anabolic features. Precise influences of hypocompetent adrenal steroid function on long-term modeling of the immunological compartment and control of microvascular activation processes are not well understood. These complex mechanisms need to be elucidated for better understanding of the physiopathogenesis of RA. Nevertheless, at a clinical level, sufficient data are currently available to endorse further controlled studies of early clinical onset patients and prospective investigations to determine more definitively the roles of adrenal (and gonadal) steroids in subsets of RA patients and unaffected susceptible persons in the population.

Enhancement of splenic-macrophage Fcgamma receptor expression by treatment with estrogens

Splenic-macrophage Fcgamma receptors (FcgammaRs) participate in the pathophysiologies of immune-complex diseases and in host defense against infection. Modulation of macrophage FcgammaR expression is an immuno-therapeutic target. Glucocorticoids, sex steroids, and dopaminergic drugs modulate macrophage FcgammaR expression. Previous data indicate that estradiol increases macrophage FcgammaR expression. Nevertheless, the effects of clinically used estrogens upon macrophage FcgammaR expression are unknown. We assessed the effects of treatment with commonly used estrogens on the expression of macrophage FcgammaRs using a guinea pig experimental model. Six estrogens have been studied: ethynylestradiol (Et), mestranol (M), chlortianisene (Ct), promestriene, 17-epiestriol, and 17beta-estradiol. Following in vivo treatment of guinea pigs, we determined the clearance of immunoglobulin G (IgG)-sensitized erythrocytes in vivo, the binding of IgG-sensitized erythrocytes by isolated splenic macrophages, and splenic-macrophage FcgammaR cell surface expression. Estrogens enhance the clearance of IgG-sensitized erythrocytes by increasing splenic-macrophage FcgammaR expression. Et, M, and Ct were more effective than the other estrogens. Flow cytometry and fluorescence microscopy with monoclonal antibodies demonstrated that estrogens increase the cell surface expression of FcgammaR1 and -2 more than that of FcgammaR2. These data indicate that treatment with commonly used estrogens enhances the clearance of IgG-sensitized cells by improving splenic-macrophage FcgammaR expression.