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Lipopolysaccharide-binding protein and CD14 in human gingiva

by Ren, Lei

Abstract (Summary)
(Uncorrected OCR) Abstract of thesis entitled Lipopolysaccharide-binding protein and CD14 in human gingiva Submitted by Lei Ren for the degree of Doctor of Philosophy at The University of Hong Kong in May 2005 Human periodontitis is an infectious disease characterized by the destruction of periodontal tissues. Bacterial lipopolysaccharide (LPS) acts as a potent stimulus to a variety of host cells mainly through lipopolysaccharide-binding protein (LBP) and CD14, the two key pattern recognition receptors (PRRs) in innate immunity, which subsequently elicits inflammatory responses to bacterial challenge. The present studies aimed to i) investigate the expression profiles of LBP and CD14 in human gingival tissues; ii) elucidate the interrelationship and the implications of PRRs including toll like receptors (TLRs) in periodontal health and disease; iii) investigate the associations of PRRs and cytokines in various periodontal conditions; iv) examine the roles of LBP in E. coli LPS induced expression of pro- and anti-inflammatory cytokines by human gingival fibroblast (HGF). Gingival biopsies were collected from 44 subjects with chronic periodontitis, including periodontal pocket tissues (PoTs) and clinically healthy gingival tissues (HT-Ps), and from 15 periodontally healthy subjects as controls (HT-Cs). Immunohistochemistry, TEM, ELISA and RT-PCR were employed to detect the expression of LBP, CD14, TLR-2 and -4 and cytokines in gingival tissues and cultured HGFs from periodontally healthy subjects in both in vivo and in vitro studies. In vivo study showed that i) the novel finding of LBP in human gingiva was mainly confined to the cytoplasm of granular and keratinized layers of gingival epithelium; ii) mCD14-positive cells were mainly confined to the gingival epithelium-connective tissue interface; iii) the mean expression levels of LBP and mCD14 in healthy controls were significantly higher than those in the patients, respectively. LBP and mCD14 peptides were co-detected in over 90% of gingival tissues, while their mRNAs were co-detected in over 55% of the tissues. Positive correlations existed between LBP and mCD14 expression; iv) In PoTs, mCD14 was detected on macrophages as well as on dendritic cells. TLR-2 was frequently detected in both pocket epithelia and macrophage-like cells of connective tissues; while TLR-4 was predominantly detected in connective tissues. No similar expression profiles were detected in HT-Ps and HT-Cs. In vitro study found that E. coli LPS up-regulated the expression of IL-6 and IL-1?in a dose dependent manner and it induced the expression of MD-2, TLR-2 and -4 mRNAs by HGFs as well. rhLBP significantly down-regulated the basal or E. coli LPS enhanced expression of both mRNAs and peptides of CD14, IL-6 and IL-1?but not MD-2 by HGFs. The up-regulated expression of TLR-2 and -4 no longer existed in the presence of rhLBP. No expression of LBP, IL-10 and IL-1ra mRNAs were detected in HGFs. These results imply that LBP and mCD14 expression in human gingiva may be interrelated. Altered cellular expression profiles of the PRRs in periodontal pocket tissues imply that these molecules may play a role in periodontal pathogenesis. LBP could inhibit the basal or E. coli LPS induced expression of PRRs and pro-inflammatory cytokines by HGFs. The present study suggests that LBP, CD14 and TLRs might contribute to periodontal homeostasis.
Bibliographical Information:

Advisor:

School:The University of Hong Kong

School Location:China - Hong Kong SAR

Source Type:Master's Thesis

Keywords:endotoxins gums diseases periodontal disease

ISBN:

Date of Publication:01/01/2005

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