BACKGROUND AND PURPOSEBones are widely innervated, suggesting an important role for the sympathetic regulation of bone metabolism, although there are controversial studies. We investigated the effects of propranolol in a model of experimental periodontal disease. EXPERIMENTAL APPROACHRats were assigned as follows: animals without ligature; ligated animals receiving vehicle and ligated animals receiving 0.1, 5 or 20 mg·kg -1 propranolol. After 30 days, haemodynamic parameters were measured by cardiac catheterization. Gingival tissues were removed and assessed for IL-1b, TNF-a and cross-linked carboxyterminal telopeptides of type I collagen (CTX) by ELISA, or intercellular adhesion molecule 1 (ICAM-1), receptor activator of NF-k B ligand (RANKL) and osteoprotegerin (OPG) by Western blot analysis. Sections from the mandibles were evaluated for bone resorption. Also, we analysed the ability of propranolol to inhibit osteoclastogenesis in vitro. RESULTSPropranolol at 0.1 and 5 mg·kg -1 reduced the bone resorption as well as ICAM-1 and RANKL expression. However, only 0.1 mg·kg -1 reduced IL-1b, TNF-a and CTX levels as well as increased the expression of OPG, but did not alter any of the haemodynamic parameters. Propranolol also suppressed in vitro osteoclast differentiation and resorptive activity by inhibiting the nuclear factor of activated T cells (NFATc)1 pathway and the expression of tartrate-resistant acid phosphatase (TRAP), cathepsin K and MMP-9. CONCLUSIONS AND IMPLICATIONSLow doses of propranolol suppress bone resorption by inhibiting RANKL-mediated osteoclastogenesis as well as inflammatory markers without affecting haemodynamic parameters. AbbreviationsAP, arterial pressure; BD, bone density; CTX, cross-linked carboxyterminal telopeptides of type I collagen; DMEM, Dulbecco's modified Eagle medium; DTT, dithiothreitol; FBS, fetal bovine serum; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; ICAM-1, intercellular adhesion molecule 1; LVEDP, left ventricular end-diastolic pressure; LVSP, left ventricular systolic pressure; NFAT, nuclear factor of activated T cells; OPG, osteoprotegerin; OVX, ovariectomized; RANKL, receptor activator of NF-k B ligand; SaM-1, human periosteum-derived osteoblastic cells; SaOS-2, human osteosarcoma-derived cells; SHR, spontaneous hypertensive rats; TBST, Tris-buffered saline-Tween; TRAP, tartrate-resistant acid phosphatase BJP British Journal of Pharmacology

Rheumatoid arthritis (RA) and periodontal disease (PD) are prevalent chronic inflammatory disorders that affect bone structures. Individuals with RA are more likely to experience PD, but how disease in joints could induce PD remains unknown. This study aimed to experimentally mimic clinical parameters of RA-induced PD and to provide mechanistic findings to explain this association. Chronic Ag-induced arthritis (AIA) was triggered by injection of methylated BSA in the knee joint of immunized mice. Anti–TNF-α was used to assess the role of this cytokine. Intra-articular challenge induced infiltration of cells, synovial hyperplasia, bone resorption, proteoglycan loss, and increased expression of cytokines exclusively in challenged joints. Simultaneously, AIA resulted in severe alveolar bone loss, migration of osteoclasts, and release of proinflammatory cytokines in maxillae. Anti–TNF-α therapy prevented the development of both AIA and PD. AIA did not modify bacterial counts in the oral cavity. PD, but not AIA, induced by injection of Ag in immunized mice was decreased by local treatment with antiseptic, which decreased the oral microbiota. AIA was associated with an increase in serum C-reactive protein levels and the expression of the transcription factors RORγ and Foxp3 in cervical lymph nodes. There were higher titers of anti-collagen I IgG, and splenocytes were more responsive to collagen I in AIA mice. In conclusion, AIA-induced PD was dependent on TNF-α and the oral microbiota. Moreover, PD was associated with changes in expression of lymphocyte transcription factors, presence of anti-collagen Abs, and increased reactivity to autoantigens.

Periodontal disease (PD) is a chronic inflammatory and alveolar bone destructive disease triggered by microorganisms from the oral biofilm. Oral inoculation of mice with the periodontopathogen Aggregatibacter actinomycetemcomitans (Aa) induces marked alveolar bone loss and local production of inflammatory mediators, including Macrophage Migration Inhibitory Factor (MIF). The role of MIF for alveolar bone resorption during PD is not known. In the present study, experimental PD was induced in BALB/c wild-type mice (WT) and MIF knockout mice (MIF⁻/⁻) through oral inoculation of Aa. Despite enhanced number of bacteria, MIF⁻/⁻ mice had reduced infiltration of TRAP-positive cells and reduced alveolar bone loss. This was associated with decreased neutrophil accumulation and increased levels of IL-10 in periodontal tissues. TNF-α production was similar in both groups. In vitro, LPS from Aa enhanced osteoclastic activity in a MIF-dependent manner. In conclusion, MIF has role in controlling bacterial growth in the context of PD but contributes more significantly to the progression of bone loss during PD by directly affecting differentiation and activity of osteoclasts.

Irinotecan is a useful chemotherapeutic for the treatment of various cancers. Irinotecan treatment is associated with mucositis, which clearly limits the use of the drug. Mechanisms that account for mucositis are only partially known. This study assessed mechanisms and the role of inflammasome activation in irinotecan-induced mucositis. Mucositis in mice was induced by irinotecan injection in C57BL/6 wild-type, gp91phox(-/-), il-18(-/-), casp-1(-/-), and asc(-/-) mice once a day for 4 consecutive days. In some experiments, mice received apocynin to inhibit NADPH oxidase (NOX), IL-1 receptor antagonist, or IL-18 binding protein to prevent activation of IL-1 and IL-18 receptors, respectively. Mice were euthanized 7 days after the beginning of irinotecan treatment, and small intestines were collected for analysis. Irinotecan treatment resulted in increased IL-1β and IL-18 production in ileum and NOX-2-dependent oxidative stress. gp91phox(-/-) and apocynin-treated mice had diminished oxidative stress and less severe mucositis. Furthermore, treatment with apocynin decreased caspase-1 activation and IL-1β and IL-18 production in the ileum. asc(-/-) and casp-1(-/-) mice also had less intestinal injury and decreased IL-1β and IL-18 production. Finally, both the absence of IL-18 and IL-1β resulted in reduced inflammatory response and attenuated intestinal injury. NOX-2-derived oxidative stress mediates inflammasome activation and inflammasome-dependent production of IL-1β and IL-18, which mediate tissue injury during irinotecan-induced mucositis in mice.

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