In vivo inhibition of localized bone resorption by human recombinant interleukin-1 receptor antagonist

Cytokine RNA levels in transiliac bone biopsies from healthy early postmenopausal women

The cytokines interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and IL-6 induce osteoclast formation and may contribute to the development of postmenopausal osteoporosis. Cross-sectional studies have suggested that both IL-1 and IL-1ra secretion increase on estrogen withdrawal, and that postmenopausal osteoporosis is associated with an inadequate increase in monocyte IL-1ra secretion with age. We measured cytokine mRNA (IL-1beta, IL-1ra, IL-6, and TNF-alpha) directly in bone biopsies from early postmenopausal women to determine if a lower compensatory increase in IL-1ra mRNA could be demonstrated in women with rapid bone loss after the menopause. Biopsies were obtained from 23 early postmenopausal women (mean age 53.9 years) who participated in a randomized study of hormone replacement therapy (HRT) and risk factors for osteoporosis. Bone mineral density was assessed by duel energy X-ray absorptiometry at 0, 1, 2, and 5 years. Women in the control group were recruited to the biopsy study based on their observed rate of bone loss (upper or lower tertile). Consent was also obtained from 11 participants receiving HRT. Biopsies were taken at 2 years, frozen in nitrogen, and homogenized. Cytokine mRNA was measured by competitive reverse transcriptase polymerase chain reaction. The IL-1ra/IL-1beta mRNA slope for the slow-loss group was steeper (deltaF = 23.3, p < 0.01) than that observed in the fast-loss group, indicating that slower bone loss was associated with higher IL-1ra mRNA levels relative to IL-1beta. During HRT, the IL-1beta mRNA level was inversely correlated with serum estradiol (log r2 = 0.77, p < 0.01), and women with a serum estradiol below 200 pmol/L during HRT had IL-1beta, mRNA levels identical to the control group. In contrast, IL-1ra mRNA was independent of serum estradiol. Histomorphometric analysis revealed weak correlations between IL-1beta mRNA and activation frequency (r2 = 0.26, p = 0.06) and between IL-1ra and volume referent bone resorption rate (r2 = 0.19, p = 0.11). TNF-alpha was not associated with the bone loss rates or with serum estradiol, and only three samples were positive for IL-6 mRNA. The findings support the hypothesis that IL-1beta production within bone increases with declining estrogen levels, and that an increase in II-1ra protects against accelerated bone loss.

Effect of pharmacological sympathectomy on osteoclastic activity in the gerbilline auditory bulla in vivo

Bone destruction causes hearing loss in various middle ear disorders. The mechanisms of such pathological remodeling are unknown. Unilateral surgical sympathectomy is known to induce resorption within mandibular and auditory bulla bone. Explanation of the cause of this effect, however, may be confounded by hemodynamic changes induced by hemicranial sympathectomy and by uncertainty as to the neuroanatomical origins of sympathetic fibers. In this study, gerbils were infused with guanethidine sulfate (GS) to evaluate the in vivo effects of systemic sympatholysis on auditory bone remodeling. In addition, to discount any direct osteolytic effect, GS was assessed of its bone resorbing activity in vitro by means of the calvarial calcium release assay. The in vitro study revealed GS to have no effect on calcium release. The in vivo study revealed GS to increase both the osteoclast surface and number. Guanethidine-induced sympathectomy has thus been shown to increase remodeling in gerbilline auditory bone, while no direct osteolytic effect could be measured in vitro.

Cytokines in rheumatoid arthritis. Potential targets for pharmacological intervention

The ingress of inflammatory leucocytes into the synovium is a crucial step in the pathogenesis of rheumatoid arthritis (RA). Cytokines are mediators involved in the inflammatory events, adhesive mechanisms, angiogenesis and osteopenia associated with RA. Pro- and anti-inflammatory cytokines, growth factors and chemokines all have an important role in these processes. Because the efficacy of currently used antirheumatic therapy is often limited, there is a need for more specific intervention strategies. Anticytokine therapy may include the use of monoclonal antibodies, antagonistic cytokines, soluble cytokine receptors, cytokine receptor antagonists, somatic gene transfer or other approaches. Hopefully, the study of cytokines and their interactions will lead to the development of new immunomodulatory strategies that will benefit patients with RA.

Effect of orthodontic appliance reactivation during the period of peak expansion in the osteoclast population

BACKGROUND

Delays in the appearance ofosteoclasts at compression sites occur following orthodontic appliance reactivation when this is done during the period of osteoclast recruitment. This study examined changes in alveolar bone after appliance reactivation at a time coinciding with the peak expansion of the osteoclast population following the first appliance activation.

METHODS

Orthodontic appliances were activated with 40 g on maxillary molars followed by a reactivation with the same force after 4 days in one group and sham reactivation in the other. Rats were killed at 0, 1, 3, 6, and 10 days thereafter. Orthodontic movement was measured cephalometrically. TRAP and interleukin-1 alpha (IL-1alpha) were measured biochemically, and changes in osteoclasts and root resorption were assessed at both compression and tension sites histomorphometrically.

RESULTS

Teeth in the reactivated group displayed more initial displacement than controls but no more tooth movement 10 days following appliance reactivation. Also, increases in osteoclast numbers and surface percent, as well as alveolar bone Tartrate-resistant acid phosphatase (TRAP), became evident in the treated animals only 10 days after reactivation. However, IL-1alpha was elevated in alveolar bone within 1 hr following appliance reactivation but returned to baseline by day 1. There were no treatment-related difference in nuclear number per osteoclast or trabecular surface per osteoclast. Significant treatment-related increases in root resorption were evident at compression sites by day 10.

CONCLUSIONS

These findings indicate that after appliance reactivation during the height of osteoclastic stimulation, a second cohort of osteoclasts can be recruited, but only after a delay of several days. This delay is not due to a failure to produce IL-1alpha in the tissues.

Pre- and post-treatment serum levels of cytokines IL-1beta, IL-6, and IL-1 receptor antagonist in celiac disease. Are they related to the associated osteopenia?

OBJECTIVE

Decreased bone mineral density is a common finding in untreated celiac disease patients. However, the precise pathophysiology of osteopenia remains incompletely understood. Pathological features of gluten sensitivity are associated with local release of proinflammatory and antiinflammatory cytokines. We investigated the serum levels of IL-1beta, IL-6, and IL-1 receptor antagonist in celiac patients and correlated them with bone density measurements.

METHODS

We assessed serum samples of 16 female patients at the time of diagnosis (on an unrestricted diet) and after a mean time of 37 months on a gluten-free diet. At the same time, bone mineral density in the lumbar spine and total skeleton was determined by DEXA.

RESULTS

Untreated patients had high serum levels of IL-1beta and IL-6 and normal IL-1-RA. Treatment produced a decrease in median IL-1beta levels (p = NS) and a significant diminution of IL-6 (p < 0.05). On the contrary, IL-1-RA increased significantly after treatment (p < 0.05). Baseline lumbar spine Z-score and IL-6 levels exhibited a significant inverse correlation (r = -0.61; p < 0.01). Patients with more severe baseline osteopenia (< -2 Z-scores) had a significantly lower IL-1-RA than those with less bone compromise (> -2 Z-scores).

CONCLUSIONS

Our data demonstrate that the inflammatory process observed in active celiac disease is associated with high serum levels of IL-1beta and IL-6 and normal levels of IL-1-RA. Treatment significantly reduces both proinflammatory cytokines and significantly increases the antiinflammatory one. We also suggest that these cytokines might have a role in the osteopenia associated with celiac disease.

Cytokines and T-lymphocyte subsets in healthy post-menopausal women: estrogen retards bone loss without affecting the release of IL-1 or IL-1ra

Interleukin (IL)-1 is a potent inducer of bone resorption, and an increased secretion of the IL-1 agonists IL-1 alpha and IL-1 beta relative to the IL-1 receptor antagonist (IL-1ra) has been proposed as a mechanism leading to post-menopausal osteoporosis. T-lymphocytes are capable of secreting bone resorptive cytokines and have also been linked with bone metabolism and the development of osteoporosis. Cytokine secretion from whole blood cell cultures was compared between two randomized groups of healthy early post-menopausal women (mean age 52.5 yrs, N = 91) and lymphocyte subsets were quantitated by flow cytometry. One group received cyclic estrogen-gestagen replacement therapy (ERT) while the other group was untreated. In spite of a significant bone maintaining effect of ERT, the basal and LPS-stimulated secretion of IL-1 alpha, IL-1 beta, and IL-1ra was identical in the two groups. There was no association between cytokine release and bone mass or loss assessed over 2 yrs. The only exception was a weak estrogen-independent correlation between basal IL-1ra secretion and bone loss (r = -0.21, p < 0.05). Flow cytometry did not confirm a relationship between CD4/CD8 T-cell ratios and bone density or loss, and there was no effect of ERT on lymphocyte subsets. The number of CD3+ CD56+ T-cells showed a highly significant negative correlation with femoral and lumbar bone density in untreated women (r = -0.42, p < 0.01) similar to that found in patients with established osteoporosis, indicating that these adherent mononuclear cells may be important in the pathophysiology of post-menopausal bone loss. The possibility that IL-1ra acts as an independent bone-sparing factor unrelated to estrogen withdrawal warrants further investigation. In conclusion, ERT maintains bone without affecting the release of the IL-1 family of cytokines in whole blood cultures.

A mechanism for sympathectomy-induced bone resorption in the middle ear

BACKGROUND

Recent investigations have demonstrated a link between sympathectomy and osteoclast-mediated bone resorption. The exact nature of this link, however, is unknown. We hypothesize that substance P, a potent vasoconstrictive neuropeptide found in peripheral sensory fibers, including those innervating bone, is the mediator of this phenomenon. To test this theory, the effects of substance P on in vitro calcium release from cultured neonatal mouse calvaria were assessed. In addition, an in vivo study was conducted whereby gerbils were injected with capsaicin to eliminate substance P-containing fibers before sympathectomy with 6-hydroxydopamine. If the effects of 6-hydroxydopamine were eliminated by prior administration of capsaicin, the role of sensory nerves in sympathectomy-induced resorption would be strongly implicated.

IN VITRO STUDY

Substance P at 10(-8) mol/L was incubated with eight newborn Swiss-Webster mouse hemicalvarial explants and compared with explants incubated in control media alone. The neonatal mice were euthanized at day 3, and their hemicalvaria were preincubated in 2 ml of stock media without treatment for 24 hours at 36.5 degrees C as a stabilization period. After the stabilization period, the stock media were replaced with 2 ml of fresh control media or media containing substance P at 10(-8) mol/L. A similar experiment was performed with the addition of indomethacin at 5 x 10(-7). The explants were then incubated for 72 hours with gassing every 12 hours with a mixture of O2, N2, and CO2. At the end of the 72-hour period, the media were analyzed for calcium content by atomic absorption spectrophotometry and compared by one-way analysis of variance with Bonferroni-corrected post hoc tests.

IN VIVO STUDY

Forty-eight Mongolian gerbils were placed into four groups: group 1 received intraperitoneal injections of 6-hydroxydopamine at 75 micrograms/gm body weight on days 1, 2, 6, 7, and 8; group 2 received identical injections of hydroxydopamine, but 12 hours after receiving subdermal injections of capsaicin at 50 micrograms/gm body weight; group 3 received only subdermal injections of capsaicin; and group 4 received only saline injections to serve as controls. Seven days after treatment, the animals were euthanized, and the ventral wall of each animal's right bulla was resected and quantified for osteoclast number and surface with a computer-based histomorphometry system. Analysis was then made by one-way analysis of variance with Bonferroni-corrected post hoc tests.

RESULTS

The results of the in vitro study revealed that substance P at 10(-8) mol/L (11.05 +/- 3.37 micrograms/ml) induced significant calcium release from cultured neonatal mouse calvaria when compared with control bone incubated in base media alone (0.92 +/- 2.85 micrograms/ml, p < 0.01). The process was completely inhibited by 5.0 x 10(-7) indomethacin. The results of the in vivo study showed 6-hydroxydopamine treatment significantly increased both the osteoclast number (NOc/TL = 3.14 +/- 1.33/mm) and the osteoclast surface (OcS/BS = 16.04% +/- 6.95%) of bone when compared with bone from saline-treated controls (NOc/TL = 1.77 +/- 0.79/mm, p < 0.01; OcS/BS = 8.88% +/- 4.15%, p < 0.01). These 6-hydroxydopamine-induced increases were eliminated, however, in animals pretreated with capsaicin before sympathectomy (NOc/TL = 1.86 +/- 0.68/mm, p > 0.05; OcS/BS = 9.92 +/- 3.73, p > 0.05), whereas treatment with capsaicin alone had no effect when compared with bone from saline-treated controls (NOc/TL = 2.02 +/- 0.50/mm, p > 0.05; OcS/BS = 10.28% +/- 2.62%, p > 0.05). Substance P has thus been shown to induce calcium release from membranous bone in vitro, whereas capsaicin, a substance P-specific sensory neurolytic chemical, eliminates the in vivo osteoclast-inductive effects of 6-hydroxydopamine when given 12 hours before treatment. The results indicate that substance P is capable of inducing resorption and that substance P-containing sensory ne