Human recombinant interleukin-1 receptor antagonist blocks bone resorption induced by interleukin-1 beta but not interleukin-1 alpha

Dose-Response Relationship between Reach Repetition and Indicators of Inflammation and Movement Dysfunction in a Rat Model of Work-Related Musculoskeletal Disorder

The purpose of this study was to compare the effects of a high or low repetition reaching and grasping task on serum levels of interleukin-1α (IL-1α) and IL-1β and on reach performance in a rat model of work-related musculoskeletal disorder (MSD). Forty-seven rats reached repetitively for 2 hours/day, 3 days/week for 6–8 weeks at a high or low rate. Reach rate and abnormal movement patterns were recorded. Serum was collected at 6 and 8 weeks for ELISA assay of IL-1α and IL-1β. High repetition animals experienced a 2-fold decline in reach rate, strong emergence of a raking movement, and increased IL-1α. IL-1α decreased in the low repetition group. IL-1β decreased in both groups. This model provides evidence that inflammation increases with repetition. At the higher reach rate, persistent IL-1α serum levels indicate chronic inflammation that is attenuated at the lower reach rate. These findings support the use of risk reduction in MSD prevention.

IL-1F5 mediates anti-inflammatory activity in the brain through induction of IL-4 following interaction with SIGIRR/TIR8

Similarity in structure and sequence homology has led to the identification of new members of the interleukin-1 (IL-1) ligand and receptor superfamilies. IL-1F6, IL-1F8 and IL-1F9 have been shown to signal through IL-1R-related protein 2 and IL-1 receptor accessory protein leading to activation of NFkappaB, while IL-1F7 and IL-1F10 interact with the IL-18 receptor and the soluble IL-1 receptor type I respectively. In contrast, identification of a biological role for IL-1F5 has remained elusive, with conflicting data relating to its possible ability to antagonize IL-1F9-stimulated activation of NFkappaB in Jurkat cells transfected with IL-1R-related protein 2. In this study, we set out to investigate a possible role for IL-1F5 in the brain and report that it antagonizes the inflammatory effects of IL-1beta and lipopolysaccharide (LPS) in vivo and in vitro including the inhibitory effect on long-term potentiation (LTP) in rat hippocampus. We demonstrate that IL-1F5 induces IL-4 mRNA and protein expression in glia in vitro and enhances hippocampal expression of IL-4 following intracerebroventricular (i.c.v.) injection. The inhibitory effect of IL-1F5 on LPS-induced IL-1beta is attenuated in cells from IL-4-defective (IL-4-/- mice). Our findings suggest that IL-1F5 mediates anti-inflammatory effects through its ability to induce IL-4 production and that this is a consequence of its interaction with the orphan receptor, single Ig IL-1R-related molecule (SIGIRR)/TIR8, as the effects were not observed in SIGIRR-/- mice. In contrast to its effects in brain tissue, IL-1F5 did not attenuate LPS-induced changes, or up-regulated IL-4 in macrophages or dendritic cells, suggesting that the effect is confined to the brain.

Impact of Increased Occlusal Contact, Interleukin-1 Genotype, and Periodontitis Severity on Gingival Crevicular Fluid IL-1β Levels

BACKGROUND

The study of occlusal therapy in humans with periodontitis is problematic due to potential irreversible bone loss in control subjects. The hypothesis of this pilot investigation was that increased interocclusal contact initiated by short-term occlusal splint disuse would increase tooth mobility and the bone-resorptive cytokine interleukin (IL)-1beta in gingival crevicular fluid (GCF), comparable to IL-1-positive genotype and increased periodontitis severity.

METHODS

Nineteen non-smoking chronic periodontitis patients using nocturnal occlusal splints and undergoing periodontal maintenance in a private practice were evaluated at five time points: 24 hours after continuous splint use; 1, 2, and 3 days after no occlusal splint use; and 14 days after resumption of customary nighttime splint use. Subjects were evaluated to confirm that the plaque index and gingival index were < or = 1.0, and to categorize past periodontitis (moderate or severe) and IL-1 genotype (1A +4845 plus IL-1B +3954). Test sites on two anterior teeth vulnerable to occlusal trauma were sampled for mobility, GCF IL-1beta, and IL-1 receptor antagonist (ra).

RESULTS

Tooth mobility remained low during the 3-day period when patients were not wearing their occlusal appliance. GCF IL-1beta decreased after not wearing the appliances (P = 0.016), especially at 48 hours. At this time, genotype-positive subjects had higher levels of GCF IL-1beta/IL-1ra than genotype-negative subjects (P = 0.045), and patients who had experienced severe periodontitis had higher IL-1beta levels than moderate periodontitis subjects (P = 0.004).

CONCLUSIONS

These findings suggest that short-term discontinuation of occlusal splint therapy in non-smoking periodontitis patients undergoing periodontal maintenance does not result in potential signs of early occlusal trauma (increasing mobility or GCF IL-1beta). Longer-term studies may be needed to determine appropriate therapy applications for periodontitis-susceptible patients with definable occlusal discrepancies and/or parafunction.

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.

Adenoviral transduction of human osteoblastic cell cultures: a new perspective for gene therapy of bone diseases

This article confirms the susceptibility of osteoblastic cells to adenoviral transduction. Osteoblasts were harvested from human cancellous bone. Cells were transduced, using various amounts of adenoviral vectors carrying the cDNA encoding interleukin-1 receptor antagonist (IL-1 Ra), or the marker genes beta-galactosidase and luciferase. Expression of the transgenes and the biological activity of IL-1 Ra produced by gene transfer were measured quantitatively in a time-course by ELISA. The rate of transduction was 100% after exposure to 1 x 10(7) infective particles of adeno-LacZ. No expression of IL-1Ra was seen after transduction with adeno-IL-1Ra at titers of 1 x 10(4) and less. However, after transduction at titers of 1 x 10(7), infective particles cells expressed IL-1 Ra consistently for 72 days, with levels up to 1 microg IL-1 Ra/1 x 10(6) cells/ 48 hours. None of the control samples expressed detectable levels of IL-1 Ra. The biological activity of the transgenic IL-1 Ra was demonstrated by its ability to suppress successfully IL-1-induced nitric oxide synthesis by rabbit articular chondrocytes. After transduction with 1 x 10(7) infective particles of the adenoluciferase vector, up to 81,000 Units transgenic luciferase/x 10(6) osteoblastic cells were measured 2 days after gene transfer. Our results show that adenovirus transduces osteoblastic cells at a high rate in vitro.

Cytochrome P-450 inhibition blocks bone resorption in vitro and in vivo

Although the cyclooxygenase and lipoxygenase pathways of arachidonic acid metabolism have been shown to lead to osteoclastic resorption, the cytochrome P450 pathway has not been implicated. We investigated the effects of the cytochrome P450 pathway in IL-1beta-induced calcium release from cultured mouse calvaria in vitro in the presence of clotrimazole, a cytochrome P450 inhibitor, or L-N(G)-arginine methyl ester, a nitric oxide synthase inhibitor. Clotrimazole inhibited calcium release in a dose-dependent manner; however, L-N(G)-arginine methyl ester did not inhibit resorption. These results suggest that cytochrome P450 may be another possible mediator of IL-1beta-induced bone resorption in vitro. In the in vivo portion of the study, clotrimazole was administered in the gerbil model of adaptive bone modeling. Clotrimazole inhibited osteoclast surface; however, it did not reduce the osteoclast number, mean erosion surface per osteoclast, mineralization surface, or mineral-apposition rate. These results suggest that clotrimazole may inhibit the activation of osteoclasts and that cytochrome P450-dependent enzymes may be related to osteoclast activation in vivo.

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.

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

Interleukin-1 (IL-1) has been implicated as a primary mediator of bone remodeling; it is a powerful activator of bone resorption both in vivo and in vitro. However, there is no direct evidence that IL-1 plays a role in physiological bone modeling or remodeling. Interleukin-1 receptor antagonist (IL-1ra) is a member of the IL-1 family, which bind to IL-1 receptors and blocks the action of IL-1 alpha and IL-1 beta. We have previously shown that IL-1ra blocks IL-1-induced bone resorption in vitro. Evidence is reported here that human recombinant IL-1ra (hrIL-1ra) inhibits strain-induced modeling in the gerbil auditory bulla while having no significant effect on apposition rate. Pressurization of the auditory bulla to 10 mm Hg above atmospheric pressure increased osteoclast surface from 3.62 to 19.14%. Infusion of hrIL-1ra during pressurization resulted in significant inhibition of osteoclast surface on the pressurized side. These findings suggest that IL-1 is a physiological mediator of bone modeling and that hrIL-1ra inhibits resorption but not apposition in the auditory bulla model.