Anti-inflammatory properties of estrogen. I. In vivo suppression of leukocyte production in bone marrow and redistribution of peripheral blood neutrophils.

We have recently demonstrated that estrogen has differential immunomodulatory properties in mice because it stimulates antibody responses but inhibits T cell-mediated inflammation. In the present study we have examined the influence of estrogen on T cell-independent inflammatory responses. A local inflammation was induced by intradermal injection of olive oil and cholera toxin. Treatment of castrated mice with pharmacological and even physiological doses of estradiol significantly suppressed the inflammatory response, as measured by footpad swelling and documented by histologic examination. Even a single injection of a low dose of estradiol (3.2 micrograms/mouse) given up to 4 days prior to the administration of the phlogistic compound reduced the inflammatory response. Our results demonstrate that the mechanisms whereby estrogen exerts its anti-inflammatory property are probably not mediated by modulation of corticosteroid production. Instead, it is evidenced that estrogen significantly suppresses the bone marrow production of leukocytes and affects the distribution of polymorphonuclear cells in peripheral blood. The possible implications of our results are discussed in the context of the modulation of inflammatory rheumatic diseases.