Short-term administration of 17-beta estradiol to outbred male CD-1 mice induces changes in the immune system, but not in reproductive organs.
The magnitude of an immune response to many foreign and/or self-antigens is known to be gender-dependent and influenced by sex hormones. While the immune consequences of long-term exposure (3 to 5 months) to natural 17-beta estradiol in an inbred mouse model (e.g., C57BL/6, Balb/c) are relatively well-documented, the immunological effects of shorter-term 17-beta estradiol exposure in an outbred mouse model (CD-1) have not been thoroughly evaluated. The male outbred-CD-1 mouse is considered to be less 17-beta estradiol-responsive (in terms of reproductive changes) compared to the inbred mouse. In the present study, CD-1 male mice were dosed with vehicle, or 17-beta estradiol at 2 or 4 micrg/100 g body weight on alternate days over a 7-day period. The immune changes in the developmental organ (thymus) and mature lymphoid organ (spleen) were determined. Thymic organ weight/body weight ratio and thymocyte cellularity decreased with increasing dose of 17-beta estradiol, reaching significance at the 4 microg dose. Although 17-beta estradiol decreased thymocyte numbers, no differences were noted in the relative percentages of major thymocyte subsets (CD4+CD8-, CD4-CD8+, CD4+CD8+, CD4- CD8-) and no evidence of enhanced apoptosis was found. In contrast to the diminished thymocyte numbers, 17-beta estradiol increased splenic lymphocyte cellularity, especially in mice given 4 microg 17-beta estradiol dose. The functionality of splenocytes from mice exposed to 17-beta estradiol was also altered. Supernatants from Con-A activated splenocytes from 17-beta estradiol-treated mice had increased IFN-gamma and decreased IL-4 levels (p < 0.05 at the 4 microg dose). This increase in IFN-gamma in 17-beta estradiol-treated mice was not due to an increase in the relative percentages of T cells, since they were comparable to relative percentages of T cells from oil-treated control mice. In addition, supernatants from cultured splenocytes (both Con A-activated and unstimulated) also had significantly higher levels of nitric oxide activity, especially at the 4 microg 17-beta estradiol dose. These results indicate that short-term 17-beta estradiol treatment in outbred mice, at relatively modest doses (2-4 microg/100 g body weight), altered both thymocytes and splenocytes. These 17-beta estradiol-induced immune changes are compelling, since in these mice, post-17-beta estradiol exposure did not demonstrate robust changes in the male reproductive system (testicular and seminal vesical weights to body weight ratios).
Karpuzoglu-Sahin
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E
Center for Molecular Medicine and Infectious Diseases, Department of Biomedical Sciences and Pathobiology, Virginia Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia 24060-0342, USA.
Gogal
R M
RM
Hardy
C
C
Sponenberg
P
P
Ahmed
S Ansar
SA
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D005837:Genitalia, Male / Q000187:drug effects*; D007107:Immune System / Q000187:drug effects* / Q000276:immunology; D007136:Immunoglobulins / Q000097:blood; D007371:Interferon-gamma / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008297:Male; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D013154:Spleen / Q000187:drug effects / Q000276:immunology; D013950:Thymus Gland / Q000187:drug effects / Q000276:immunology
D007136:Immunoglobulins; D015847:Interleukin-4; D009569:Nitric Oxide; D004958:Estradiol; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse