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      Graded Doses of Recombinant Interleukin-1β Induce Generalized Osteopenia in Rats without Altering Skeletal Growth and Joint Integrity

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          Background: Whereas a primary role of interleukin-1β (IL-1β) in local bone remodelling and articular inflammation has been well established, the effect of prolonged systemic administration of this cytokine on total skeletal Ca, somatic growth and joint tissue has not yet been investigated. Methods: Five groups of 14 rats each, aged 7–8 weeks, had miniosmotic pumps (Alzet 200 µl) implanted and primed to release 100, 200, 500, 1,000 and 2,000 ng/kg/24 h of human recombinant IL-1β (rIL-1β) daily for 14 days. On days 0 and 14 total skeletal mineral content (BMC) was assessed by means of X-ray absorptiometry and vertebral and tibial growth was measured by computer-assisted radiometry. On the same days, blood was drawn and analyzed for rat growth hormone (rGH), insulin-like growth factor (IGF-1), and osteocalcin. Also 24-hour urine was collected for d-pyridinoline (dpd) determinations. Hind- and forepaw diameter as a parameter of joint inflammation was assessed using a micrometric calliper. Subsequently the animals were sacrificed and one tibia dissected for measurement of trabecular volume by computerized histomorphometry. Results: BMC decreased in a dose-dependent manner reaching significance at 1,000 and 2,000 ng/kg (p < 0.03 and 0.04) in close correlation with tibial trabecular volumes (r = 0.84; p < 0.02). Normal vertebral and tibial growth was recorded at all dosages. There was no evidence of joint involvement. Blood rGH and IGF-1 remained normal as did osteocalcin, the latter reflecting lack of osteoblast activation. In contrast dpd increased in a dose-dependent manner indicating enhanced bone matrix turnover. Conclusion: It is concluded that graded infusions of supraphysiological doses of rIL-1β capable of inducing osteopenia did not affect skeletal growth in the absence of articular reaction. This is in contrast with the experience recorded in experimental arthritis in which growth retardation, in addition to osteopenia, may be caused by factors other than circulating IL-1β.

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          Most cited references 31

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          Generalised bone loss in patients with early rheumatoid arthritis.

          Generalised osteoporosis is a feature of established rheumatoid arthritis but whether this is a consequence of treatment, immobility, or disease activity has been unclear. We estimated bone mineral density by dual energy x-ray absorptiometry on 148 patients with early rheumatoid arthritis before treatment with corticosteroids or disease-modifying drugs and 730 normal controls. Scans were done at 12-month intervals in patients and at 0 and 12 months on 50 of the controls matched for menopausal status. At presentation, bone mineral density of patients did not differ from controls. However, patients with disease for less than 6 months had significantly higher spinal bone mineral density than those of longer duration. Over the next 12 months, bone mineral density loss was greater in patients with rheumatoid arthritis compared with controls; significantly so for early disease (eg, -2.4 [0.8] vs -0.6 [0.4] g/cm2, p < 0.05 in the spine and -4.3 [0.8] vs -0.4 [0.5] g/cm2, p < 0.001 in the trochanter). For the lumbar spine, only disease activity was significantly associated with this bone mineral density loss. For patients with active disease over 2 years, mean bone mineral density loss at each site was between 5.5 and 10% (p < 0.01 compared to patients with inactive disease). Suppression of disease activity stabilised this bone loss. In patients with rheumatoid arthritis significant amounts of generalised skeletal bone were lost early in the disease and the loss was associated with disease activity. These findings have implications for the management of patients with rheumatoid arthritis and possibly other inflammatory diseases.
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            Release of multiple hormones by a direct action of interleukin-1 on pituitary cells.

            Exposure to bacterial endotoxins has long been known to stimulate the release of anterior pituitary hormones; administration of endotoxin was at one time a common clinical test of anterior pituitary function. Endotoxin is a potent stimulus for production of the endogenous pyrogenic protein, interleukin-1 (IL-1), by macrophages and monocytes. The possibility that IL-1 has a direct effect on the secretion of hormones by rat pituitary cells in a monolayer culture was investigated. Recombinant human IL-1 beta stimulated the secretion of adrenocorticotropic hormone, luteinizing hormone, growth hormone, and thyroid-stimulating hormone. Increased hormone secretion into culture supernatants was found with IL-1 concentrations ranging from 10(-9) M to 10(-12) M. Prolactin secretion by the monolayers was inhibited by similar doses. These concentrations of IL-1 are within the range reported for IL-1 in serum, suggesting that IL-1 generated peripherally by mononuclear immune cells may act directly on anterior pituitary cells to modulate hormone secretion in vivo. Incubation of IL-1 solutions with antibody to IL-1 neutralized these actions. These pituitary effects of IL-1 suggest that this monokine may be an important regulator of the metabolic adaptations to infectious stressors.
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              Interleukin-1beta and TNF-alpha act in synergy to inhibit longitudinal growth in fetal rat metatarsal bones.

              We hypothesized that pro-inflammatory cytokines can act locally in the growth plate to impair longitudinal growth. In a model of cultured fetal rat metatarsal bones, we found that IL-1beta and TNF-alpha act in synergy to inhibit longitudinal growth, an effect linked to decreased proliferation and increased apoptosis of growth plate chondrocytes. IGF-I could partially reverse all these effects. Children with chronic inflammatory conditions, such as Crohn's disease or rheumatoid arthritis, experience impaired longitudinal growth. The inflammatory process itself, which includes upregulation of the pro-inflammatory cytokines interleukin (IL)-1beta, IL-6, and TNF-alpha, is believed to be at least partly responsible for the poor growth in these patients. This study aimed to clarify whether these cytokines can act locally in the growth plate to suppress longitudinal growth and whether any negative effects can be reversed by insulin-like growth factor-I (IGF-I). The effects of cytokines on longitudinal bone growth were studied in fetal (day E20) rat metatarsal bones kept in culture. After a 7-day culture, the bones were sectioned, and chondrocyte proliferation was assessed by bromodeoxyuridine (BrdU) incorporation and apoptosis by TUNEL. When added separately, IL-1beta and TNF-alpha impaired longitudinal bone growth only at a high concentration (100 ng/ml each; p < 0.05 versus control). In contrast, when added in combination, IL-1beta and TNF-alpha potently inhibited growth at far lower concentrations (from 3 ng/ml each; p < 0.001 versus control) and also decreased chondrocyte proliferation and increased apoptosis. Growth failure induced by the combination of IL-1beta and TNF-alpha (10 ng/ml each) could be counteracted by anti-IL-1beta (100 ng/ml; p < 0.001), anti-TNF-alpha (100 ng/ml; p < 0.001), or IGF-I (100 ng/ml; p < 0.01). IL-6 did not affect longitudinal growth even when added in combination with IL-1beta or TNF-alpha (10 ng/ml each). We show that IL-1beta and TNF-alpha act in synergy to locally suppress longitudinal growth, an effect that can be partially reversed by IGF-I. Although growth hormone (GH)/IGF-I may improve longitudinal growth in children with chronic inflammatory diseases, our results suggest that the inflammatory process itself must be targeted to achieve normal growth.

                Author and article information

                Horm Res Paediatr
                Hormone Research in Paediatrics
                S. Karger AG
                October 2005
                13 October 2005
                : 64
                : 2
                : 88-95
                aOsteoporosis Policlinic, University Hospital of Bern, Bern, and bNovartis Pharma AG, Basel, Switzerland; cUniversity Hospital, Rotterdam, The Netherlands
                88169 Horm Res 2005;64:88–95
                © 2005 S. Karger AG, Basel

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                Page count
                Figures: 3, Tables: 2, References: 48, Pages: 8
                Original Paper


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