Ernesto De Nardin

Systemic Inflammation in Cardiovascular and Periodontal Disease: Comparative Study

ABSTRACT Epidemiological studies have implicated periodontal disease (PD) as a risk factor for the development of cardiovascular disease (CVD). These studies addressed the premise that local infection may perturb the levels of systemic inflammatory mediators, thereby promoting mechanisms of atherosclerosis. Levels of inflammatory mediators in the sera of subjects with only PD, only CVD, both diseases, or neither condition were compared. Subjects were assessed for levels of C-reactive protein (CRP), serum amyloid A (SAA), ceruloplasmin, α1-acid-glycoprotein (AAG), α1-antichymotrypsin (ACT), and the soluble cellular adhesion molecules sICAM-1 and sVCAM by enzyme-linked immunoabsorbent and/or radial immunodiffusion assays. CRP levels in subjects with either condition alone were elevated twofold above subjects with neither disease, whereas a threefold increase was noted in subjects with both diseases (P = 0.0389). Statistically significant increases in SAA and ACT were noted in subjects with both conditions compared to those with one or neither condition (P = 0.0162 and 0.0408, respectively). Ceruloplasmin levels were increased in subjects with only CVD (P = 0.0001). Increases in sVCAM levels were noted in all subjects with CVD (P = 0.0054). No differences in sICAM levels were noted among subject groups. A trend toward higher levels of AAG was noted in subjects with both conditions and for ACT in subjects with only PD. Immunohistochemical examination of endarterectomy specimens of carotid arteries from subjects with atherosclerosis documented SAA and CRP deposition in association with atheromatous lesions. The data support the hypothesis that localized persistent infection may influence systemic levels of inflammatory mediators. Changes in inflammatory mediator levels potentially impact inflammation-associated atherosclerotic processes.

Chemotactic-like receptors and Aβ peptide induced responses in Alzheimer’s Disease

Evidence suggests that beta-amyloid (Abeta) has chemokine-like properties and may act through formyl chemotactic receptors (FPR) to induce pathophysiologically important functional changes in Alzheimers disease (AD) microglia. We have shown that Abeta 1-42, fibrillar Abeta 1-40, and Abeta 25-35 potentiate the release of interleukin-1beta (IL-1beta) from LPS activated human THP-1 monocytes [26] and LPS primed rat microglia. Moreover, Abeta-stimulated IL-1beta secretion seems to be receptor mediated because it is calcium dependent and requires activation of specific G-proteins [27]. Thus, we have evaluated the ability of Abeta 1-42 to mimic formyl chemotactic peptides in stimulating IL-1beta release from THP-1 monocytes. Several of the formyl chemotactic peptides and Abeta 1-42 significantly enhanced IL-1beta production in THP-1 monocytes. In contrast, a formyl chemotactic receptor antagonist inhibited Abeta 1-42-induced IL-1beta release from both human THP-1 monocytes and primary rat microglia. Further, primary rat microglia grown in culture expressed FPR as demonstrated by immunocytochemistry. Given the multiple pathophysiologic roles IL-1beta may play in AD, agents that block Abeta interactions with formyl chemotactic receptors on microglia might be important antiinflammatory therapeutic targets.

Isolation and partial characterization of the formyl peptide receptor components on human neutrophils

The receptor for formylated peptides such as FMLP has been reported to consist of glycoprotein components ranging from 24-95 kDa, and to exhibit both high and low affinity for ligand. Controversy exists on the molecular size and number of these components, and whether the different affinities represent distinct ligand binding sites. In this study, the receptor was found to be comprised of components, of 94, 68, and approximately 40 kDa molecular size. Competitive binding inhibition experiments showed that FMLP bound to the components in the following order from highest to lowest affinity: 68 kDa greater than approximately 40 kDa greater than 94 kDa. Our findings suggest that the FMLP receptor of human neutrophils contains at least three components, and that each component has a different affinity for FMLP.

The Molecular Basis for Neutrophil Dysfunction in Early-Onset Periodontitis*

In recent years, much debate has surrounded the neutrophil defects associated with localized juvenile periodontitis (LJP). Controversy exists on the existence of the defect itself, its genetic nature, and the molecular entities and mechanisms which may be involved in such defects and subsequent biological phenomena. This review attempts to summarize neutrophil functions and their role in periodontal diseases, as well as the observed neutrophil defects reported for LJP. J Periodontol 1996;67:345-354.

Recombinant expression and partial characterization of the human formyl peptide receptor.

FMLP-receptor DNA was expressed in Escherichia coli. The expressed product could specifically bind FMLP. This is the first-reported expression of a functional FMLP receptor in Escherichia coli. We confirm that receptor glycosylation is not essential for ligand binding. A deletion mutant did not bind FMLP, suggesting that the deleted portion plays a role in ligand binding.

Production of an extracellular toxin by the oral pathogen Campylobacter rectus

The ATCC type strain and six clinical isolates of Campylobacter rectus were tested for toxicity against HL-60 cells and human polymorphonuclear neutrophils (PMNs). After challenge with bacterial cell suspensions and media supernatants for up to 4 h, eukaryotic cell viability was assayed by trypan blue dye exclusion and lactate dehydrogenase release. Cells of the C. rectus type strain were not toxic. However, ethanol and (NH4)2SO4 extracts of culture media supernatants killed HL-60 cells in a time and dose dependent manner with 700 micrograms of supernatant protein killing 100% of HL-60 cells in 4 h. Concentrated media supernatants from clinical isolates also killed 100% of HL-60 cells in 30 to 60 min. The bacterial culture supernatants were toxic to PMNs with clinical isolates killing 70 to 90% of PMNs in 2 to 4 h. SDS-PAGE and immunoblot analysis of the toxic media supernatants revealed C. rectus specific proteins and lipopolysaccharide (LPS). The toxic activity was inhibited by protease, indicating that the toxin was protein. Non-toxic and toxic media supernatants were obtained by altering hemin and fumarate in the growth media. SDS-PAGE analysis of these revealed that all toxic supernatants contained a 104 kDa protein.

Expression and purification of recombinant human N-formyl-L-leucyl-L-phenylalanine (FMLP) receptor: generation of polyclonal antibody against FMLP receptor.

The recombinant formyl peptide receptor has been successfully expressed and purified, utilizing an Escherichia coli expression system. Purification of formyl peptide receptor was performed using gel filtration chromatography and affinity chromatography, and the purified protein migrated at an apparent molecular mass of 36,000 Da. The purified recombinant receptor retained functional activity as determined by a ligand binding assay. The yield of the recombinant purified receptor was approximately 1 mg/2 L of culture, and the binding activity was determined to be approximately 8 nM, which suggests the conclusion that glycosylation does not affect significantly ligand binding of the N-formyl-L-leucyl-L-phenylalanine (FMLP) receptor molecule. The recombinant receptor protein yield was found to be significantly higher than that obtained from neutrophils. The purified recombinant receptor was then utilized to generate antibody against the same. The reaction of the antibody against recombinant formylpeptide receptor and against native formylpeptide receptor on neutrophils was confirmed by western blot analysis and flow cytometric analysis, respectively. The antibody was also used successfully to detect recombinant formylpeptide receptor expression on transfected 293 cells. These results describe for the first time the expression, purification, and characterization of recombinant FMLP receptor with ligand binding activity and the generation of polyclonal antibody against the same. This work also provides a foundation for future biophysical studies of the FMLP receptor molecule, which have not been possible until now.

The Functional Effects of the −455G/A Polymorphism on the IL-6-Induced Expression of the β-fibrinogen Gene may be due to Linkage Disequilibrium with Other Functional Polymorphisms

Elevated plasma fibrinogen levels have been identified as an independent risk factor for coronary heart diseases, stroke and peripheral artery disease. The −455G/A polymorphism in the promoter region of the β-fibrinogen gene has been associated with increased plasma fibrinogen levels. However, the functional effect of this polymorphism has been controversial and other polymorphisms in the fibrinogen gene have also been implicated in higher fibrinogen levels. In this study, we evaluated the transcriptional activity of 4 natural haplotypes and 6 artificial haplotypes in the promoter region of the β-fibrinogen gene. Significantly lower IL-6-induced activity was observed in the −1420A and −148T alleles. In contrast, the −854A allele had significantly higher activity. Artificial haplotypes containing the −1420A, −854A and −148T alleles were also analyzed to confirm individual functional effects. The −1420A and −148T alleles significantly lowered the activities, while the −854A allele significantly raised the activity. From this study we conclude that the −1420G/A, −854G/A and −148C/T polymorphisms in the β-fibrinogen promoter region are functional polymorphisms while the −455G/A polymorphism may not be a functional one, and that the association of the −455G/A polymorphism with higher fibrinogen levels may actually be due to linkage disequilibrium between the −455G/A polymorphism and other truly functional polymorphisms.