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.

The Role of Vascular Endothelial Growth Factor in Human Dental Pulp Cells: Induction of Chemotaxis, Proliferation, and Differentiation and Activation of the AP-1-dependent Signaling Pathway

“…Human dental pulp cells were prepared as described previously (Matsushita et al, 1999). The use of the cells followed a protocol that was reviewed and approved by the Ethical Committee at Kagoshima University Dental School.…”

“…In addition, sufficient consistent information about the effects of VEGF in cell types other than endothelial cells has not yet been obtained. We recently demonstrated that VEGF is spontaneously produced by human pulp cells (HPC) and that the production of this factor is enhanced upon stimulation with lipopolysaccharide (LPS) (Matsushita et al, 1999). More recently, one study indicated that dentin matrix contained VEGF, and it was suggested that release of VEGF from the matrix after injury may also contribute to the overall reparative response of pulp tissue (Roberts-Clark and Smith, 1999 (Masood et al, 1997), were synthesized and purified by Takara Shuzo (Tokyo, Japan).…”

MAPK Signaling Is Required for LPS-induced VEGF in Pulp Stem Cells

“…VEGF has been found to be strongly expressed in teeth developing irreversible pulpitis (Güven et al, 2007); these irreversible vascular changes can affect dentinogenesis and progress to necrosis. LPSsinduced VEGF expression has been demonstrated in human dental pulp fibroblasts (Matsushita et al, 1999) and odontoblast-like cells (Botero et al, 2003…”

Lipoteichoic Acid Up-regulates VEGF Expression in Macrophages and Pulp Cells

“…An increase in vascular density and permeability may become deleterious and contribute to irreversible pulp pathology, since the dental pulp has limited ability to relieve internal pressures (Heyeraas and Berggreen, 1999). It is known that lipopolysaccharides (LPS) from Gram-negative bacteria induce VEGF expression in macrophages (Sakuta et al, 2001), and in a mixed population of pulp cells (Matsushita et al, 1999). However, we do not know if LTA from Gram-positive bacteria has a role in the regulation of angiogenesis.…”