Porphyromonas gingivalis lipopolysaccharide induces tumor necrosis factor‐α and interleukin‐6 secretion, and CCL25 gene expression, in mouse primary gingival cell lines: interleukin‐6‐driven activation of CCL2

Abstract

Background and Objective Porphyromonas gingivalis infection is strongly associated with periodontitis. Although P. gingivalis is known to elicit a strong inflammatory response, details of that remain fragmentary. To understand the local response to P. gingivalis, primary cell lines derived from mouse gingival tissues were exposed to P. gingivalis or E. coli lipopolysaccharide (LPS), and cytokine production for interleukin-6 (IL-6) and tumor necrosis factor-α (TNFα were measured. CCL25 gene expression was measured by real-time PCR. Cells stimulated with combinations of IL-6, soluble IL-6 receptor (sIL-6R), and/or soluble gp130 (sgp130) were assayed for CCL2 and TNFα secretion. Methods Primary cell lines were generated from mouse gingival tissues. Enzyme-linked assays were used to determine cytokine levels, and real-time PCR was used to quantify CCL25 gene expression. Results Exposure to P. gingivalis but not E. coli LPS resulted in significantly elevated levels of both IL-6 and TNFα, and P. gingivalis LPS-stimulation also upregulated CCL25 gene expression. In one of three experiments, IL-6 induced CCL2 secretion, whereas IL-6 with sIL-6R induced CCL2 secretion in all three experiments, suggesting that both direct IL-6 signaling and IL-6 trans-signaling may be involved. However, because sgp130 did not inhibit trans-signaling, and because direct stimulation of gingival cells with sgp130 resulted in CCL2 secretion, the possibility exists that sgp130 forms binary complexes with soluble IL-6R that promote direct IL-6 stimulation. Conclusion These findings define a pathway in which exposure of gingival cells to P. gingivalis induces the release of IL-6 and TNFα; IL-6 in turn induces CCL2 secretion.

Palatal mucosa derived fibroblasts present an adaptive behavior regarding cytokine secretion when grafted onto the gingival margin

“…This could give us some information about possible post transcriptional modifications that can alter production of cytokines. Previous studies [8,14,15,27,28] have shown that fibroblasts exposed to bacterial stimuli such as LPS showed significant IL-6 expression, indicating the importance of this cytokine in the host immune and inflammatory response in periodontitis, but the present investigation also revealed increased IL-6 secretion at 48 h for both subtypes of fibroblasts. Here, there was IL-6 constitutive secretion by unstimulated cells from the palatal mucosa and also from the marginal gingival graft, being statistically significant for the latter.…”

Differential Production of Macrophage Inflammatory Protein‐1α, Stromal‐Derived Factor‐1, and IL‐6 by Human Cultured Periodontal Ligament and Gingival Fibroblasts Challenged With Lipopolysaccharide From P. gingivalis

“…An upregulation in IL‐6 mRNA expression by human gingival fibroblasts was detected in a concentration‐dependent manner when these cells were stimulated with IL‐1β and TNF‐α 43 . In the same manner, primary cell cultures derived from murine gingival tissue were exposed to LPS from P. gingivalis , and IL‐6 production was significantly elevated as was the TNF‐α secretion 44 . The induction of IL‐6 mRNA expression when cells were challenged by LPS was statistically significant for periodontal ligament fibroblasts, 45 highlighting the important participation of this molecule in the inflammatory events of both tissues.…”

Potassium is a key signal in host-microbiome dysbiosis in periodontitis

“…Increased levels of IL-6 have been detected in the crevicular fluid of active sites compared with healthy sites of patients with refractory periodontitis [62] and exposure to lipopolysaccharide from the P . gingivalis induces elevated levels of IL-6 and TNF-α in primary gingival mouse cell lines [63]. Nonetheless, it has also been shown that IL-6 inhibits production of TNF-α in culture human monocytes, as a part of a TNF-α/IL-6 regulatory circuit [64].…”