For instance, MAPK inhibitor significantly reduced the MMP-3 production in HGFs stimulated with IL-1β, but not with epidermal growth factor [23]. In addition, NF-ĸB pathway may be involved in regulation of MMP-3 expression in rabbit dermal fibroblasts, human saphenous vein and rabbit aortic smooth muscle

cells [57, 58]. The present study showed that NF-ĸB signaling is not critically involved in LPS-induced MMP-3 expression in HGFs. Notably, the MAPK pathway but not NF-κB was significantly involved in the regulation of MMP-3 expression in HGFs in both mRNA and protein levels. Previous mTOR inhibitor studies have also proven that the expression of MMP-3 is mainly mediated through P38 MAPK, ERK and tyrosine kinase pathways, but not through NF-κB pathway [23, 59, 60]. Moreover, although a study

reported that the activation of NF-κB could be important for MMP-3 secretion, no consensus NF-κB binding site was identified in the MMP-3 gene promoter [61, 62]. It suggests that NF-κB may regulate the expression of this gene through different binding sites or interacting with other transcription factors [59]. Therefore, within the context and limitations of the present study, it is tempting to speculate that MAPK pathway may be crucial for MMP-3 expression in HGFs in response to P. gingivalis LPS1690. Furthermore, it would be interesting to extend the study to other cells types in human gingiva like gingival epithelial cells to ascertain whether MAPK pathway plays a predominant role in the expression and regulation of MMP-3 in other cells of oral tissues. Lumacaftor chemical structure Conclusions The present study reveals that HGFs significantly express MMP-3 in response to penta-acylated P. gingivalis LPS1690 and hexa-acylated E. coli LPS, but not to the tetra-acylated P. gingivalis LPS1435/1449 in HGFs. Blocking p38 MAPK and ERK pathways significantly down-regulates P. gingivalis LPS1690- and E. coli LPS-induced expression of MMP-3. These findings indicate that the heterogeneous lipid A structures of P. gingivalis LPS differentially modulate

the expression of MMP-3 in HGFs, which may play a role in periodontal pathogenesis. Methods Preparation, purification and identification 17-DMAG (Alvespimycin) HCl of P. gingivalis LPS P. gingivalis LPS was isolated from P. gingivalis ATCC 33277 (the American Type Culture Collection, Rockville, MD). LPS was prepared by the cold MgCl2-Ethanol procedure followed by lipid extraction and conversion to sodium salts as previously described [63, 64]. Optical densities were measured at 280 nm and 260 nm to verify the nucleic acid and protein contamination. LPS preparations were further treated to remove the endotoxin protein and the final protein contamination was less than 0.1% [65]. The fatty acid composition of P. gingivalis LPS was further analysed by Gas chromatographic-mass spectroscopy. Then two separate extractions of P.