The effects of tumour necrosis factor-alpha on bone cells involved in periodontal alveolar bone loss; osteoclasts, osteoblasts and osteocytes

Periodontitis is the most common bone loss pathology in adults and if left untreated is responsible for premature tooth loss. Cytokines, such as tumour necrosis factor-α (TNFα), involved in the chronic inflammatory response within the periodontal gingiva, significantly influence the normal bone remodelling processes. In this review, the effects of TNFα on bone metabolism in periodontitis are evaluated in relation to its direct and indirect actions on bone cells including osteoclasts, osteoblasts and osteocytes. Evidence published to date suggests a potent catabolic role for TNFα through the stimulation of osteoclastic bone resorption as well as the suppression of osteoblastic bone formation and osteocytic survival. However, the extent and timing of TNFα exposure in vitro and in vivo greatly influences its effect on skeletal cells, with contradictory anabolic activity observed with TNFα in a number of studies. None the less, it is evident that managing the chronic inflammatory response in addition to the deregulated bone metabolism is required to improve periodontal and inflammatory bone loss treatments‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬.K. Algate, D.R. Haynes, P.M. Bartold, T.N. Crotti, M.D. Cantle

Class I and II histone deacetylase expression in human chronic periodontitis gingival tissue

Histone deacetylase inhibitors (HDACi) are being considered to treat chronic inflammatory diseases at low doses. Currently HDACi that are more specific are being developed to target particular HDACs; therefore, this study aimed to determine levels and distribution of class I and II HDAC in human gingival samples obtained from patients with chronic periodontitis.Gingival biopsies were obtained from patients with and without (mild inflammation, no bone loss) periodontitis. Total RNA was isolated for real-time quantitative polymerase chain reaction to determine expression of HDACs 1-10. Immunohistochemistry was used to determine protein distribution of HDACs 1, 5, 8 and 9. Factor VIII, CD3 and tartrate resistant acid phosphatase (TRAP) were detected in serial sections to identify blood vessels, lymphocytes, pre-osteoclasts and osteoclasts cells respectively. Tumour necrosis factor α (TNF-α) expression was also assessed.mRNA for HDAC 1, 5, 8 and 9 were significantly upregulated in chronic periodontitis gingival tissues compared to non-periodontitis samples (p < 0.05). Significantly higher HDAC 1 protein expression was observed in chronic periodontitis samples (p < 0.05), and was associated with CD3, TRAP and TNF-α-positive cells. HDAC 1, 5, 8 and 9 were expressed strongly by the factor VIII-positive microvasculature in the chronic periodontitis gingival tissues.HDAC 1, 5, 8 and 9 expression was higher in gingival tissues from patients with chronic periodontitis compared to non-periodontitis samples. Results suggest that these HDACs could therefore be targeted with specific acting HDACi.M. D. Cantley, A. Dharmapatni, K. Algate, T. N. Crotti, P. M. Bartold, D. R. Hayne

Semaphorin-3a, neuropilin-1 and plexin-A1 in prosthetic-particle induced bone loss

Abstract not availableS. Saad, A.A.S.S.K. Dharmapatni, T.N. Crotti, M.D. Cantley, K. Algate, D.M. Findlay, G.J. Atkins, D.R. Hayne

Histone deacetylases 1 and 2 inhibition suppresses cytokine production and osteoclast bone resorption in vitro

First published: 21 June 2019The regulation of epigenetic factors is an emerging therapeutic target of immune function in a variety of osteolytic pathologies. Histone deacetylases (HDAC) modify core histone proteins and transcriptional processes, in addition to nonhistone protein activity. The activated immune response in rheumatoid arthritis, periodontitis, and prosthetic implant particle release stimulates the catabolic activity of osteoclasts. In this study, we investigated the effects of novel therapeutic agents targeting HDAC isozymes (HDAC 1, 2, and 5), previously shown to be upregulated in inflammatory bone disorders, in cytokine-stimulated human monocytes and osteoclasts in vitro. Inhibiting HDAC 1 and 2 significantly reduced gene expression of IL-1β, TNF, MCP-1, and MIP-1α in TNF-stimulated monocytes, while suppressing secretions of IL-1β, IL-10, INF-γ, and MCP-1 (P < .05). Osteoclast formation and bone resorption were also significantly diminished with HDAC 1 and 2 inhibition, through reduced NFATc1 expression and osteoclast specific target genes, TRAF6, CTR, TRAP, and Cathepsin K (P < .05). Similar trends were observed when inhibiting HDAC 1 and to a lesser extent, HDAC 2, in isolation. However, their combined inhibition had the greatest anti-inflammatory and antiosteoclastic effects. Targeting HDAC 5 had minimal effects on these processes investigated in this study, whereas a broad acting HDACi, 1179.4b, had widespread suppressive outcomes. This study demonstrates that targeting HDACs is a potent and effective way of regulating the inflammatory and catabolic processes in human monocytes and osteoclasts. It also demonstrates the importance of targeting individual HDACs with an overall aim to improve efficiency and reduce any potential off target effects.Kent Algate, David Haynes, Tracy Fitzsimmons, Ornella Romeo, Florence Wagner, Edward Holson, Robert Reid, David Fairlie, Peter Bartold, Melissa Cantle

Pharmacological characterization of neurogenic responses of the sheep isolated internal anal sphincter

1. The aim of the study was to establish the nature of the neurogenic responses of the sheep isolated anal sphincter. 2. Isolated strips of sheep internal anal sphincter develop intrinsic contractile tone following the application of stretch tension. On transmural stimulation (1–20 Hz, 10 V pulse strength, 0.5 ms pulse width, 1 s every 180 s) transient relaxations were observed. 3. The amplitude of the relaxations were frequency-dependent reaching a maximal response at 10–20 Hz and were inhibited by tetrodotoxin (0.3 μM). Neither atropine (0.3 μM) nor phentolamine (1 μM) affected control responses. 4. The nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 100 μM) and the selective inhibitor of soluble guanylyl cyclase ODQ, (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one) (1 μM) completely inhibited the neurogenic relaxations and uncovered contractions that were abolished by 1 μM phentolamine and 0.1 μM prazosin. The effect of L-NAME, but not that of ODQ, was partially reversed by the addition of L-arginine (1 mM). 5. Sodium nitroprusside (10 nM–10 μM) caused concentration-dependent inhibition of myogenic tone and this effect was significantly reduced by ODQ. Calcium-free Krebs-Henseleit solution also reduced myogenic tone by 85%. 6. Transmural electrical stimulation of the sheep isolated internal anal sphincter causes a transient relaxation of myogenic tone that appears to involve nitric oxide from non-adrenergic, non-cholinergic nerves and, to a lesser degree, noradrenaline from sympathetic nerves. The characteristics of the preparation compares well with that of human tissue and may prove to be a suitable animal based model for further studies