Lipopolysaccharide Enhances the Production of Vascular Endothelial Growth Factor by Human Pulp Cells in Culture

Abstract

We investigated whether vascular endothelial growth factor (VEGF) production by human pulp cells (HPC) is regulated by lipopolysaccharide (LPS) in relation to the pathogenesis of pulpitis. Although HPC incubated with medium alone only marginally expressed VEGF mRNA and produced a low level of VEGF as detected by enzyme-linked immunosorbent assay, the VEGF mRNA expression and VEGF production were markedly enhanced upon stimulation with LPS from Escherichia coli. Prevotella intermedia LPS, phorbol 12-myristate 13-acetate, and interleukin-6 also induced VEGF mRNA expression in HPC. A simian virus 40-infected HPC line also exhibited increased VEGF mRNA expression in response to E. coli LPS, but lung and skin fibroblasts did not. Fetal bovine serum (FBS) increased the sensitivity of HPC to LPS in a dose-dependent manner. HPC did not express membrane CD14 on their surfaces. However, the anti-CD14 monoclonal antibody MY4 inhibited VEGF induction upon stimulation with LPS in HPC cultures in the presence of 10% FBS but not in the absence of FBS. LPS augmented the VEGF production in HPC cultures in the presence of recombinant human soluble CD14 (sCD14). To clarify the mechanisms of VEGF induction by LPS, we examined the possible activation of the transcription factor AP-1 in HPC stimulated with LPS, by a gel mobility shift assay. AP-1 activation in HPC was clearly observed, whereas that in skin fibroblasts was not. The AP-1 inhibitor curcumin strongly inhibited LPS-induced VEGF production in HPC cultures. In addition, a protein synthesis inhibitor, cycloheximide, inhibited VEGF mRNA accumulation in response to LPS. These results suggest that the enhanced production of VEGF in HPC induced by LPS takes place via an sCD14-dependent pathway which requires new protein synthesis and is mediated in part through AP-1 activation.

Effect of lipopolysaccharides on vascular endothelial growth factor expression in mouse pulp cells and macrophages

“…We observed that odontoblast-like cells and macrophages, but not undifferentiated pulp cells, exposed to bacterial LPS consistently upregulate VEGF synthesis. While the results obtained from cell lines should be interpreted with caution, our experiments confirmed a previous report that demonstrated that VEGF was up-regulated in a mixed population of human dental pulp cells exposed to LPS (27), and suggest that odontoblasts and macrophages may be the cell populations responsible, in part, for the previously reported upregulation of VEGF expression induced by LPS.…”

“…In the current study, 0-20 lg ml )1 E. coli LPS or 0-80 lg ml )1 P. intermedia LPS were used to challenge the cells. Other studies have used a range of 0.01-100 lg ml )1 LPS (27,44), which is believed to be within a range of LPS relevant to pulp pathologies (45). A previous investigation has evaluated the effect of LPS from Porphyromonas endodontalis, Porphyromonas gingivalis, Fusobacterium nucleatum, and E. coli on DNA content, protein synthesis, and alkaline phosphatase activity in dental pulp cells (44).…”

“…Bacterial LPS enhances VEGF expression by a mixed population of dental pulp cells in vitro (27) and a recent paper analysed the expression of VEGF in both healthy and inflamed dental pulps in vivo (28). However, it is not known if LPS stimulation has a direct effect on VEGF expression by odontoblasts or undifferentiated pulp cells.…”

Effects of cranberry components on human aggressive periodontitis gingival fibroblasts

“…Lipopolysaccharide activates the NF-jB and MAPK/AP-1 signaling pathways and their associated inflammatory gene expression in fibroblasts, including human gingival fibroblasts (24,43). However, lipopolysaccharide activation of AP-1 in human gingival fibroblasts is controversial, and Jin et al recently reported that in normal human gingival fibroblasts, Escherichia coli lipopolysaccharide stimulated NF-jB, but not AP-1 (45,46). The IL-6 gene promoter is under the regulation of AP-1 and NF-jB, and can contain binding sites for other transcription factors in some types of cells (47,48); both AP-1 and NF-jB are involved in IL-1-stimulation of IL-6 in human gingival fibroblasts (13,24,47,49).…”

Catechins inhibit vascular endothelial growth factor production and cyclooxygenase‐2 expression in human dental pulp cells

“…It has been demonstrated that the increase of VEGF expression is consistent with enhanced vascularization during dental pulp inflammation (Tran-Hung et al 2006). The dental pulp cells can also produce VEGF in response to lipopolysaccharide (LPS; Matsushita et al 1999) and pro-inflammatory cytokines such as interleukin (IL)-1 (Chu et al 2004). These previous reports suggested that dental pulp cells play a role in the aetiology of pulpitis through the production of VEGF.…”