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Background: Increased reactive oxygen species and estrogen deficiency contribute to the pathophysiology of postmenopausal osteoporosis. Reactive oxygen species contribute to bone degradation and is necessary for RANKLinduced osteoclast differentiation. In postmenopausal bone loss, reactive oxygen species can also activate immune cells to further enhance bone resorption. Here, we investigated the role of reactive oxygen species in ovariectomyinduced osteoporosis in mice deficient in Ncf1, a subunit for the NADPH oxidase 2 and a well-known regulator of the immune system. Methods: B10.Q wild-type (WT) mice and mice with a spontaneous point mutation in the Ncf1-gene (Ncf1*/*) were ovariectomized (ovx) or sham-operated. After 4 weeks, osteoclasts were generated ex vivo, and bone mineral density was measured using peripheral quantitative computed tomography. Lymphocyte populations, macrophages, pre-osteoclasts and intracellular reactive oxygen species were analyzed by flow cytometry. Results: After ovx, Ncf1*/*-mice formed fewer osteoclasts ex vivo compared to WT mice. However, trabecular bone mineral density decreased similarly in both genotypes after ovx. Ncf1*/*-mice had a larger population of preosteoclasts, whereas lymphocytes were activated to the same extent in both genotypes. Conclusion: Ncf1*/*-mice develop fewer osteoclasts after ovx than WT mice. However, irrespective of genotype, bone mineral density decreases after ovx, indicating that a compensatory mechanism retains bone degradation after ovx. [ABSTRACT FROM AUTHOR]

Background: Collagen-induced arthritis (CIA) is an often-used murine model for human rheumatoid arthritis (RA). Earlier studies have shown potent anti-arthritic effects with the female sex hormone estradiol and the selective estrogen receptor modulator (SERM) raloxifene in CIA in DBA/1-mice. B10.Q-ncf1*/*mice are B10.Q mice with a mutated Ncf1 gene. In B10.Q-ncf1*/*mice, CIA develops as a chronic relapsing disease, which more accurately mimics human RA. We investigated the role of endogenous and exogenous sex steroids and raloxifene in the course of this model of chronic arthritis. We also examined whether treatment would prevent the development of inflammation-triggered generalized osteoporosis. Methods: Female B10.Q-ncf1*/*mice were sham-operated or ovariectomized, and CIA was induced. 22 days later, when 30% of the mice had developed arthritis, treatment with raloxifene, estradiol or vehicle was started, and the clinical disease was evaluated continuously. Treatment was continued until day 56 after immunization. At termination of the experiment (day 73), bone mineral density (BMD) was analyzed, paws were collected for histological examination, and sera were analyzed for markers of cartilage turnover and pro-inflammatory cytokines. Results: Raloxifene and estradiol treatment, as well as endogenous estrogen, decreased the frequency of arthritis, prevented joint destruction and countered generalized osteoporosis. These effects were associated with lower serum levels of the pro-inflammatory cytokine IL-6. Conclusions: This is the first study to show that raloxifene and estradiol can ameliorate established erosive arthritis and inflammation-triggered osteoporosis in this chronic arthritis model. We propose that treatment with raloxifene could be a beneficial addition to the treatment of postmenopausal RA. [ABSTRACT FROM AUTHOR]

Background: Estrogens and androgens have extensive effects on the immune system, for example they suppress both T and B lymphopoiesis in thymus and bone marrow. Submandibular glands are sexually dimorphic in rodents, resulting in larger granular convoluted tubules in males compared to females. The aim of the present experiments was to investigate the estrogenic and androgenic effects of 4-estren-3 α ,17β-diol (estren) on thymus, bone marrow and submandibular glands, and compare the effects to those of 17β-estradiol (E2) and 5 α -dihydrotestosterone (DHT), respectively. Estrogen receptors (ERs) were blocked by treatment of mice with the ER-antagonist ICI 182,780; also, knock-out mice lacking one or both ERs were used. Results: As expected, the presence of functional ERs was mandatory for all the effects of E2. Similar to DHT-treatment, estren-treatment resulted in decreased thymus weight, as well as decreased frequency of bone marrow B cells. Treatment with estren or DHT also resulted in a shift in submandibular glands towards an androgen phenotype. All the effects of estren and DHT were independent of ERs. Conclusion: Our study is the first to show that estren has similar effects as the androgen DHT on lymphopoiesis in thymus and bone marrow, and on submandibular glands, and that these effects are independent of estrogen receptors. This supports the hypothesis of estren being able to signal through the androgen receptor. [ABSTRACT FROM AUTHOR]

Background: Collagen-induced arthritis (CIA) is an often-used murine model for human rheumatoid arthritis (RA). Earlier studies have shown potent anti-arthritic effects with the female sex hormone estradiol and the selective estrogen receptor modulator (SERM) raloxifene in CIA in DBA/1-mice. B10.Q-ncf1*/*mice are B10.Q mice with a mutated Ncf1 gene. In B10.Q-ncf1*/*mice, CIA develops as a chronic relapsing disease, which more accurately mimics human RA. We investigated the role of endogenous and exogenous sex steroids and raloxifene in the course of this model of chronic arthritis. We also examined whether treatment would prevent the development of inflammation-triggered generalized osteoporosis.Methods: Female B10.Q-ncf1*/*mice were sham-operated or ovariectomized, and CIA was induced. 22 days later, when 30% of the mice had developed arthritis, treatment with raloxifene, estradiol or vehicle was started, and the clinical disease was evaluated continuously. Treatment was continued until day 56 after immunization. At termination of the experiment (day 73), bone mineral density (BMD) was analyzed, paws were collected for histological examination, and sera were analyzed for markers of cartilage turnover and pro-inflammatory cytokines.Results: Raloxifene and estradiol treatment, as well as endogenous estrogen, decreased the frequency of arthritis, prevented joint destruction and countered generalized osteoporosis. These effects were associated with lower serum levels of the pro-inflammatory cytokine IL-6.Conclusions: This is the first study to show that raloxifene and estradiol can ameliorate established erosive arthritis and inflammation-triggered osteoporosis in this chronic arthritis model. We propose that treatment with raloxifene could be a beneficial addition to the treatment of postmenopausal RA. [ABSTRACT FROM AUTHOR]

Introduction: Postmenopausal patients with rheumatoid arthritis (RA) are often treated with corticosteroids. Loss of estrogen, the inflammatory disease and exposure to corticosteroids all contribute to the development of osteoporosis. Therefore, our aim was to investigate if addition of the selective estrogen receptor modulator raloxifene, or estradiol, could prevent loss of bone mineral density in ovariectomized and dexamethasone treated mice with collagen-induced arthritis (CIA)., Methods: Female DBA/1-mice were ovariectomized or sham-operated, and CIA was induced. Treatment with dexamethasone (Dex) (125 μg/d), estradiol (E2) (1 μg/d) or raloxifene (Ral) (120 μg/day) alone, or the combination of Dex + E2 or Dex + Ral, was started after disease onset, and continued until termination of the experiments. Arthritic paws were collected for histology and one of the femoral bones was used for measurement of bone mineral density., Results: Dex-treatment alone protected against arthritis and joint destruction, but had no effect on osteoporosis in CIA. However, additional treatment with either Ral or E2 resulted in completely preserved bone mineral density., Conclusions: Addition of raloxifene or estradiol to dexamethasone-treatment in experimental postmenopausal polyarthritis prevents generalized bone loss.

Generalized osteoporosis in postmenopausal rheumatoid arthritis (RA) is caused both by estrogen deficiency and by the inflammatory disease. The relative importance of each of these factors is unknown. The aim of this study was to establish a murine model of osteoporosis in postmenopausal RA, and to evaluate the relative importance and mechanisms of menopause and arthritis-related osteoporosis. To mimic postmenopausal RA, DBA/1 mice were ovariectomized, followed by the induction of type II collagen-induced arthritis. After the mice had been killed, paws were collected for histology, one femur for bone mineral density (BMD) and sera for analyses of markers of bone resorption (RatLaps; type I collagen cross-links, bone formation (osteocalcin) and cartilage destruction (cartilage oligomeric matrix protein), and for the evaluation of antigen-specific and innate immune responsiveness. Ovariectomized mice displayed more severe arthritis than sham-operated controls. At termination of the experiment, arthritic control mice and non-arthritic ovariectomized mice displayed trabecular bone losses of 26% and 22%, respectively. Ovariectomized mice with arthritis had as much as 58% decrease in trabecular BMD. Interestingly, cortical BMD was decreased by arthritis but was not affected by hormonal status. In addition, markers of bone resorption and cartilage destruction were increased in arthritic mice, whereas markers of bone formation were increased in ovariectomized mice. This study demonstrates that the loss of endogenous estrogen and inflammation contribute additively and equally to osteoporosis in experimental postmenopausal polyarthritis. Markers of bone remodeling and bone marrow lymphocyte phenotypes indicate different mechanisms for the development of osteoporosis caused by ovariectomy and arthritis in this model.