Inhibitory effect of saliva on osteoclastogenesis in vitro requires toll-like receptor 4 signaling

Abstract

ObjectivesSaliva can suppress osteoclastogenesis, but the underlying mechanism has not been discovered yet. Considering that endotoxins suppress osteoclastogenesis in bone marrow cultures and that saliva contains endotoxins, it was reasonable to hypothesize that the impact of saliva on osteoclastogenesis requires toll-like receptor 4 signaling.Material and methodsTo test this hypothesis, we blocked toll-like receptor 4 signaling with TAK-242 in the presence of saliva in murine bone marrow cultures. Osteoclastogenesis was evaluated based on gene expression analysis and histochemical staining for tartrate-resistant acid phosphatase. Resorption was performed on dentine.ResultsWe report that TAK-242 reversed the inhibitory effect of fresh sterile saliva on the formation of multinucleated cells that stained positive for tartrate-resistant acid phosphatase. In line with this finding, TAK-242 increased the expression of the osteoclast functional genes cathepsin K, calcitonin receptor, and tartrate-resistant acid phosphatase in the presence of saliva. TAK-242 also supported the expression of NFATc1, the master regulator of osteoclastogenesis, as well as DC-STAMP and Atp6v0d2, both being cell fusion genes. In support of the hypothesis, depletion of saliva from endotoxin partially reversed the inhibitory effect on osteoclastogenesis. Moreover, salivary pellicle on plastic and titanium did not affect osteoclastogenesis.ConclusionInhibition of toll-like receptor 4 signaling revealed that saliva can contribute to innate immunity by preventing hematopoietic progenitors to become osteoclasts.Clinical relevanceSaliva can activate pattern recognition receptor signaling through endotoxins and other stress factors, indicating the demand for macrophages rather than for osteoclasts.Electronic supplementary materialThe online version of this article (doi:10.1007/s00784-016-2041-7) contains supplementary material, which is available to authorized users.

Oral cell lysates reduce osteoclastogenesis in murine bone marrow cultures

“…DAMPs are molecules released from damaged or dying cells causing an innate immune response (38). DAMPs include but are not limited to extracellular matrix components (39), S100 and heat shock proteins -all of which bind and active TLRs and other pattern recognition receptors (40) -and importantly, LPS as a major TLR4 agonist greatly inhibits osteoclastogenesis in murine in vitro cultures (41,42). There is thus a rational to make DAMPs activating TLR4 signaling in bone marrow cells responsible for the blocking of osteoclastogenesis.…”

Saliva enhances infection of gingival fibroblasts by herpes simplex virus 1

“…In the case of KSHV, an NFκB cascade was activated by LPS, however it is unclear how this response enhanced cell susceptibility to infection [58]. NFκB activation in response to LPS is well documented [61, 62] but data on signal transduction pathways and changes in gene expression in response to saliva’s multiple components are limited [63, 64]. Cell susceptibility to HSV-1 infection is multifactorial but is strongly influenced by the number of entry receptors.…”

Ocenka termometricheskih dannyh kostnoj tkani pri formirovanii vosprinimayushchego materinskogo lozha pod cilindricheskie dental'nye implantaty

“…Установка дентальных имплантатов с применением механотронных устройств получила широкое применение наряду с классическим имплантологическим протоколом [1,2]. Ключевым фактором, ведущим к осложнениям, является несоблюдение стандарта хирургического протокола проведения дентальной имплантации и, как следствие, повышение фокуса температуры в месте сверления костной ткани челюстей [3,4].…”