Cellular Responses to Oral Pathogens

Porphyromonas gingivalis lipopolysaccharide increases lipid accumulation by affecting CD36 and ATP-binding cassette transporter A1 in macrophages

Porphyromonas gingivalis lipopolysaccharide (P. gingivalis LPS) promotes macrophage-derived foam cell formation, however, the mechanisms are not well established. In macrophages, lipid uptake is mediated by scavenger receptors including SR-A and CD36, while the cholesterol efflux is mediated by ATP-binding cassette transporter G1 (ABCG1), ABCA1 and SR-BI. We further investigated the mechanisms underlying the dysregulation by P. gingivalis LPS of these regulators resulting in the promotion of lipid accumulation in THP-1-derived macrophages. Our results showed that P. gingivalis LPS exacerbated lipid accumulation in oxidized low-density lipoprotein (oxLDL)-treated macrophages. However, cholesterol efflux was inhibited by P. gingivalis LPS in THP-1-derived macrophages. In oxLDL-untreated macrophages, P. gingivalis LPS treatment caused an increase in CD36 mRNA and protein levels, and a decrease in ABCA1 mRNA and protein levels, while having no effect on SR-A, SR-BI or ABCG1 expression. Upregulation of CD36 by P. gingivalis LPS resulted from activation of c-Jun/AP-1, and this was confirmed by the inhibition of increased CD36 expression after AP-1 inhibition using SP600125. However, the decreased protein stability of ABCA1 by P. gingivalis LPS was a result of increased calpain activity. Moreover, small hairpin RNA (shRNA) targeting heme oxygenase-1 (HO-1) augmented the P. gingivalis LPS-induced atherogenic effects on the expression of c-Jun/AP-1, CD36, ABCA1 and calpain activity. Accordingly, P. gingivalis LPS-regulated promotion of lipid accumulation in foam cells was also exacerbated by HO-1 shRNA. These results indicate that P. gingivalis LPS confers a exacerbation effect on the formation of foam cells by a novel HO-1-dependent mediation of cholesterol efflux and lipid accumulation in macrophages.

Lipoproteins and lipoprotein metabolism in periodontal disease

A growing body of evidence indicates that the incidence of atherosclerosis is increased in subjects with periodontitis - a chronic infection of the oral cavity. This article summarizes the evidence that suggests periodontitis shifts the lipoprotein profile to be more proatherogenic. LDL-C is elevated in periodontitis and most studies indicate that triglyceride levels are also increased. By contrast, antiatherogenic HDL tends to be low in periodontitis. Periodontal therapy tends to shift lipoprotein levels to a healthier profile and also reduces subclinical indices of atherosclerosis. In summary, periodontal disease alters lipoprotein metabolism in ways that could promote atherosclerosis and cardiovascular disease.

Exploring the link between microorganisms and oral cancer: a systematic review of the literature

The majority of cases of oral cancer have been related to tobacco use and heavy alcohol consumption. However, the incidence of oral cavity carcinoma appears to be increasing in many parts of the world in a manner that it is difficult to explain with traditional risk factors alone. Meanwhile, interest in the possible relationships between microorganisms and the different stages of cancer development has been rising and numerous mechanisms by which bacteria and yeast may initiate or promote carcinogenesis are currently under investigation. In particular, a persuasive body of evidence suggests a possible etiological role involving the metabolism and production of carcinogenic products, such as acetaldehyde. Other suggested mechanisms include the induction of chronic inflammation and direct interference with eukaryotic cell cycle and signaling pathways. This review aims to summarize the known associations between microbial infection and cancer and draw attention to how they may relate to oral carcinoma.

Cellular basis of verruciform xanthoma: immunohistochemical and ultrastructural characterization

BACKGROUND

Verruciform xanthoma (VX) holds two basic pathogenic interests: (1) Why and how do macrophage foam cells accumulate exclusively in the sub-basal papillae? and (2) What underlies the disease chronicity? Moreover, an unsolved question is which came first - epithelial hyperplasia or foam cell collection?

MATERIALS AND METHODS

We analyzed 36 oral mucosal lesions to dissect a series of linked cellular changes in VX using immunohistochemical and ultrastructural techniques.

RESULTS

Macrophage scavenger receptor-1 (MSR-1), monocyte chemoattractant protein-1 (MCP-1), CCR2, and oxidized low-density lipoprotein (ox-LDL) were all expressed by foam cells. VX epithelium showed reactivity for MCP-1, HLA-DR and IL8 in varying degrees, and showed a nearly 40% reduction in Langerhans cell density. In sub-epithelial inflammatory infiltrates, CD8+ T cells preponderated (>70%), but only a minority were positive for granzyme B (<1%). Keratinocyte/basal lamina complex exhibited disruption of basal lamina, squamatization and cytolysis of basal cells, fragmentation of desmosomes, and intraepithelial migration of macrophages. In severely inflamed papillae, necrotic foam cells were scavenged by adjacent macrophages.

CONCLUSIONS

Under synergistic regulation of T cells, MCP-1/CCR2-mediated macrophage recruitment in the sub-basal papillae and the lysosomal engulfment of epithelial lipids by MSR-1-bearing macrophages may be central in VX formation. Once developed, ox-LDL-induced foam cell necrosis and macrophage-dependent debris disposal may cyclically perpetuate VX.

Endothelial cell infection and hemostasis

As an important component of the vasculature, endothelial cell lining covers the inner surface of blood vessels and provides an active barrier interface between the vascular and perivascular compartments. In addition to maintaining vasomotor equilibrium and organ homeostasis and communicating with circulating blood cells, the vascular endothelium also serves as the preferred target for a number of infectious agents. This review article focuses on the roles of interactions between vascular endothelial cells and invading pathogens and resultant endothelial activation in the pathogenesis of important human diseases with viral and bacterial etiologies. In this perspective, the signal transduction events that regulate vascular inflammation and basis for endothelial cell tropism exhibited by certain specific viruses and pathogenic bacteria are also discussed.