B Lymphopoiesis is Upregulated after Orchiectomy and is Correlated with Estradiol but not Testosterone Serum Levels in Aged Male Rats

Previous studies have shown that B lymphopoiesis is augmented after androgen withdrawal in male mice. As an analogy to the skeletal system, some effects of androgens on the proliferation of B cells may be mediated via aromatization into estrogens in vivo. The aim of the present study was to assess the effects of androgen withdrawal on B lymphopoiesis in bone marrow of aged male rats sequentially over a period of 9 months, and to correlate the flow-cytometric findings with changes in systemic levels of sex steroids. We first showed that androgen withdrawal is associated with enhanced B lymphopoiesis in bone marrow of 4-month-old male orchiectomized (ORX) rats, and that the changes in the bone marrow B cell compartment in ORX animals can be reversed by testosterone supplementation. In a subsequent, sequential experiment, we found that orchiectomy induced a sustained rise in Thy 1.1⁺/CD45R⁺ bone marrow cells committed for the B cell lineage that lasted for several months in 13-month-old aged rats. In a stepwise model of multiple regression analysis using estradiol, free and total testosterone as independent variables, estradiol was the strongest predictor of the percentage of B precursor cells in bone marrow in aged SHAM and ORX rats. Free and total testosterone did not correlate with B lymphopoiesis in aged SHAM rats. The current experiment has clearly shown that androgen withdrawal upregulates the number of B lineage cells over several months in rat bone marrow. Furthermore, our results provide evidence that estradiol may play an important role as a physiological suppressor of B lymphopoiesis in aged male rats.

Key words:

Bone Marrow - Flow Cytometry - B Cells - Androgens - Estrogen

References

• 1 Medina K L, Kincade P W. Pregnancy-related steroids are potential negative regulators of B lymphopoiesis.  Proc Natl Acad Sci USA. 1994;  91 5382-5386
• 2 Medina K L, Smithson G, Kincade P W. Suppression of B lymphopoiesis during normal pregnancy.  J Exp Med. 1993;  178 1507-1515
• 3 Masuzawa T, Miyaura C, Onoe Y, Kusano K, Ohta H, Nozawa S, Suda T. Estrogen deficiency stimulates B lymphopoiesis in mouse bone marrow.  J Clin Invest. 1994;  94 1090-1097
• 4 Erben R G, Raith S, Eberle J, Stangassinger M. Ovariectomy augments B lymphopoiesis and generation of monocyte-macrophage precursors in rat bone marrow.  Am J Physiol Endocrinol Metab. 1998;  274 E476-E483
• 5 Viselli S M, Stanziale S, Shults K, Kovacs W J, Olsen N J. Castration alters peripheral immune function in normal male mice.  Immunology. 1995;  84 337-342
• 6 Viselli S M, Reese K R, Fan J, Kovacs W J, Olsen N J. Androgens alter B cell development in normal male mice.  Cellular Immunology. 1997;  182 99-104
• 7 Wilson C A, Mrose S A, Thomas D W. Enhanced production of B lymphocytes after castration.  Blood. 1995;  85 1535-1539
• 8 Smithson G, Couse J F, Lubahn D B, Korach K S, Kincade P W. The role of estrogen receptors and androgen receptors in sex steroid regulation of B lymphopoiesis.  J Immunol. 1998;  161 27-34
• 9 Smithson G, Medina K, Ponting I, Kincade P W. Estrogen suppresses stromal cell-dependent lymphopoiesis in culture.  J Immunol. 1995;  155 3409-3417
• 10 Anderson F H, Francis R M, Selby P L, Cooper C. Sex hormones and osteoporosis in men.  Calcif Tissue Int. 1998;  62 185-188
• 11 Riggs B L, Khosla S, Melton L J III. A unitary model for involutional osteoporosis: Estrogen deficiency causes both type I and type II osteoporosis in postmenopausal women and contributes to bone loss in aging men.  J Bone Miner Res. 1998;  13 763-773
• 12 Vanderschueren D, Boonen S, Bouillon R. Action of androgens versus estrogens in male skeletal homeostasis.  Bone. 1998;  23 391-394
• 13 Shozu M, Simpson E R. Aromatase expression of human osteoblast-like cells.  Mol Cell Endocrinol. 1998;  139 117-129
• 14 Simpson E R, Bulun S E, Nichols J E, Zhao Y. Estrogen biosynthesis in adipose tissue: Regulation by paracrine and autocrine mechanisms.  J Endocrinol. 1996;  150 Suppl. S51-S57
• 15 Smith E P, Boyd J, Frank G R, Takahashi H, Cohen R M, Specker B, Williams T C, Lubahn D B, Korach K S. Estrogen resistance caused by a mutation in the estrogen- receptor gene in a man.  N Engl J Med. 1994;  331 1056-1061
• 16 Morishima A, Grumbach M M, Simpson E R, Fisher C, Qin K. Aromatase deficiency in male and female siblings caused by a novel mutation and the physiological role of estrogens.  J Clin Endocrinol Metab. 1995;  80 3689-3698
• 17 Korach K S, Couse J F, Curtis S W, Washburn T F, Lindzey J, Kimbro K S, Eddy E M, Migliaccio S, Snedeker S M, Lubahn D B, Schomberg D W, Smith E P. Estrogen receptor gene disruption: molecular characterization and experimental and clinical phenotypes.  Recent Prog Horm Res. 1996;  51 159-186
• 18 Vanderschueren D, Van Herck E, De Coster R, Bouillon R. Aromatization of androgens is important for skeletal maintenance of aged male rats.  Calcif Tissue Int. 1996;  59 179-183
• 19 Vanderschueren D, Van Herck E, Nijs J, Ederveen A GH, De Coster R, Bouillon R. Aromatase inhibition impairs skeletal modeling and decreases bone mineral density in growing male rats.  Endocrinology. 1997;  138 2301-2307
• 20 Mooradian A D, Morley J E, Korenman S G. Biological actions of androgens.  Endocr Rev. 1987;  8 1-28
• 21 Bedrak E, Chap Z, Brown R. Age-related changes in the hypothalamic-pituitary-testicular function of the rat.  Exp Gerontol. 1983;  18 95-104
• 22 Winters S J, Takahashi J. Estrogens and cytosolic estrogen receptors in aged male rats.  J Androl. 1983;  4 171-174
• 23 Coquelin A, Desjardins C. Luteinizing hormone and testosterone secretion in young and old male mice.  Am J Physiol. 1982;  243 E257-E263
• 24 Smith E R, Stefanick M L, Clark J T, Davidson J M. Hormones and sexual behavior in relationship to aging in male rats.  Horm Behav. 1992;  26 110-135
• 25 Gruenewald D A, Hess D L, Wilkinson C W, Matsumoto A M. Excessive testicular progesterone secretion in aged male Fischer 344 rats: a potential cause of age-related gonadotropin suppression and confounding variable in aging studies.  J Gerontol. 1992;  47 B164-B170
• 26 Hunt S V. The presence of Thy-1 on the surface of rat lymphoid stem cells and colony-forming units.  Eur J Immunol. 1979;  9 853-859
• 27 Goldschneider I, Gordon L K, Morris R J. Demonstration of Thy-1 antigen on pluripotent hemopoietic stem cells in the rat.  J Exp Med. 1978;  148 1351-1366
• 28 Hunt S V, Mason D W, Williams A F. In rat bone marrow Thy-1 antigen is present on cells with membrane immunoglobulin and on precursors of peripheral B lymphocytes.  Eur J Immunol. 1977;  7 817-823
• 29 Deenen G J, Hunt S V, Opstelten D. A stathmokinetic study of B lymphocytopoiesis in rat bone marrow: proliferation of cells containing cytoplasmic mu-chains, terminal deoxynucleotidyl transferase and carrying HIS24 antigen.  J Immunol. 1987;  139 702-710
• 30 Kroese F GM, Butcher E C, Lalor P A, Stall A M, Herzenberg L A. The rat B cell system: the anatomical localization of flow cytometry-defined B cell subpopulations.  Eur J Immunol. 1990;  20 1527-1534
• 31 McCarthy K F, Hale M L, Fehnel P L. Purification and analysis of rat hematopoietic stem cells by flow cytometry.  Cytometry. 1987;  8 296-305
• 32 Soares M, Havaux X, Nisol F, Bazin H, Latinne D. Modulation of rat B cell differentiation in vivo by the administration of an anti-mu monoclonal antibody.  J Immunol. 1996;  156 108-118
• 33 Cleland W H, Mendelson C R, Simpson E R. Effects of aging and obesity on aromatase activity of human adipose cells.  J Clin Endocrinol Metab. 1985;  60 174-177
• 34 Erben R G, Eberle J, Stahr K, Goldberg M. Androgen deficiency induces high turnover osteopenia in aged male rats: a sequential histomorphometric study.  J Bone Miner Res. 2000;  15 1085-1098
• 35 Kuiper G G, Enmark E, Pelto-Huikko M, Nilsson S, Gustafsson J A. Cloning of a novel receptor expressed in rat prostate and ovary.  Proc Natl Acad Sci USA. 1996;  93 5925-5930