Antibodies directed to the chemotactic factor receptor detect differences between chemotactically normal and defective neutrophils from LJP patients

Unique etiologic, demographic, and pathologic characteristics of localized aggressive periodontitis support classification as a distinct subcategory of periodontitis

BACKGROUND

Localized aggressive periodontitis (LAgP) occurs in 2% of African-American adolescents but only 0.15% of white adolescents. First molars and incisors are affected by rapid onset and progression.

METHODS

This nonsystematic critical review evaluated published data for LAgP and chronic periodontitis (CP), focusing on potential differences in epidemiology, microbiology, immunology, genetics, and response to therapy.

RESULTS

LAgP differs from CP by localization to incisors and first molars, early onset and rapid progression in adolescents and young adults, and a 10-fold higher prevalence in populations of African or Middle Eastern origin, often with strong familial aggregation. The bacterium Aggregatibacter actinomycetemcomitans and hyperresponsive neutrophils are frequently observed. Antibiotic and nonsurgical therapies are highly effective.

CONCLUSIONS

LAgP differs in many ways from the far more common CP that affects older adults. The substantial evidence of dissimilarities summarized in this review strongly supports the classification of LAgP as a distinct form of periodontitis.

PRACTICAL IMPLICATIONS

Classifying LAgP as a distinct subcategory of periodontitis will encourage future research and does not conflict with the newly proposed "staging and grading" system. The silent onset and rapid progression of LAgP make early diagnosis and frequent follow-up with patients essential for effective treatment.

Nupharidine enhances Aggregatibacter actinomycetemcomitans clearance by priming neutrophils and augmenting their effector functions

OBJECTIVES

Nupharidine (6,6'-Dihydroxythiobinupharidine), purified from the aquatic plant Nuphar lutea leaves (Water lily) prompts antimicrobial activity of immune cells. The aim of the study was to test the effect of Nupharidine on neutrophil function against Aggregatibacter actinomycetemcomitans, JP2 clone (Aa-JP2).

METHODS

Neutrophils derived from the human cell line HL60 and human peripheral blood derived from aggressive periodontitis and periodontally healthy subjects were incubated with Nupharidine or vehicle and inoculated with JP2. Bacterial survival was tested using viable counts on blood agar (CFU's). Neutrophils' necrosis/apoptosis, reactive oxygen species (ROS) production, phagocytosis and neutrophil extracellular traps (NET) production following infection were tested, as well as markers of neutrophil priming.

RESULTS

Nupharidine had no direct bactericidal effect on JP2, but it enhanced Aa-JP2 clearance by neutrophils. Nupharidine enhanced neutrophil phagocytosis, ROS production and NET formation during JP2 infection. Furthermore, Nupharidine enhanced the expression of certain markers of neutrophils priming, specifically iCAM1, DECTIN-2 and intracellular IL-1β.

CONCLUSION

Nupharidine was shown to promote neutrophil effector bactericidal functions, boosting Aa-JP2 clearance. The results point to the potential of Nupharidine as an adjunctive agent in the treatment of Aa-JP2 periodontitis, but this should be tested initially using pre-clinical and clinical studies.

Salivary biochemistry in Buffalo: the legacy of Michael J. Levine

The author pays tribute to the contributions of Michael J. Levine to the field of salivary biochemistry.

Isolation and characterization of a human neutrophil aggregation defective mutant of Fusobacterium nucleatum

Fusobacterium nucleatum is known to adhere to human polymorphonuclear neutrophils (PMNs) and cause them to aggregate. In this study, we isolated a spontaneously occurring aggregation defective (AGG(-)) mutant and this mutant will be used for future study of the interactions between this bacterium and human PMN. Genomic DNA fingerprinting by random-primed polymerase chain reaction method revealed a difference between the parent strain and the AGG(-) mutant. This mutant also showed an altered phenotype in both microbicidal and phagocytic assays, suggesting that the bacterial factor involved in the aggregation may also be very important for the phagocytosis and, subsequently, the killing by human PMNs. Further study of this mutant may help to clarify the molecular mechanisms of the interaction between this pathogen and human PMNs.

Single nucleotide polymorphisms of the N-formyl peptide receptor in localized juvenile periodontitis

BACKGROUND

Neutrophils from patients with localized juvenile periodontitis (LJP) exhibit decreased binding and responsiveness to various chemotactic agents, including N-formyl-1-methionyl-1-leucyl-1-phenylalanine (FMLP). This altered reaction of neutrophils is thought to account in part for the increased susceptibility of LJP patients to infections by periodontal organisms. Receptors for FMLP are involved in the activation and the subsequent response to certain chemotactic stimuli.

METHODS

In order to determine if this decreased response is due to a genetic variation in the receptor, we directly compared DNA encoding the FMLP receptor from controls matched for gender and race and LJP patients by single-strand conformation polymorphism analysis (SSCP).

RESULTS

Using this technique, we observed a characteristic SSCP pattern in 29 out of 30 patient samples in the FMLP receptor DNA. This pattern differed from those obtained from the 20 control subjects as well as 31 patients with adult periodontitis. DNA sequencing of 30 patients indicated single nucleotide polymorphisms (SNPs) in the FMLP receptor DNA from the LJP patients when compared to 20 controls (P = 0.0005). Two single nucleotide base alterations were consistently seen: either a thymine to cytosine substitution at base 329 in 17 LJP patients or a cytosine to guanine substitution at base 378 in 5 LJP patients. A combination of both alterations were seen in 7 LJP patients. Both alterations resulted in amino acid changes in the second intracellular loop of the receptor, specifically phenylalanine to serine at residue 110 and cysteine to tryptophan at residue 126. This region of the FMLP receptor has recently been shown to play a role in ligand binding and G-protein activation.

CONCLUSIONS

This study suggests that a molecular alteration in the second intracellular loop of the FMLP receptor molecules in LP patients may play a role in the decreased chemotactic activity reported for some LJP patients.

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.

Alterations in phagocyte function and periodontal infection

A review of phagocytic cells-polymorphonuclear leukocytes and monocytes-in the inflammatory process is presented. Examples of phagocyte defect-related pathology serve as a framework for understanding the role of these cells in periodontal infection. The role of alterations in neutrophil function in localized juvenile periodontitis is presented as a model system for understanding periodontal pathology as a result of host-related functional abnormalities. Two topical alternative hypotheses for periodontal breakdown are presented in which macrophage control of the chronic lesion is altered by an absence of T cells or the influence of bacterial superantigens.

Immunological, genetic, and microbiological study of family members manifesting early-onset periodontitis

From the standpoint of host-parasite interactions, family studies help us understand the host defensive factors and the molecular mechanisms involved in the periodontal immune response. In this study, we report the immunological profile of host-defensive functions, human leukocyte antigen (HLA) phenotypes, and the microflora of a mother (rapidly progressive periodontitis), an older son (periodontally healthy), a younger son (localized juvenile periodontitis), and a daughter (localized juvenile periodontitis). We examined the peripheral neutrophil functions, phenotypic and functional analysis of peripheral lymphocytes, serum immunoglobulin G (IgG) antibody titers against periodontopathic bacteria, serological type of HLA class II antigens, and bacterial flora in all periodontal pockets. The results showed that Actinobacillus actinomycetemcomitans was dominant in the pockets of all subjects. The mother and two sons showed a depressed neutrophil chemotaxis to N-formyl-methionyl-leucyl-phenylalanine. All subjects except the older son exhibited low T4/T8 ratios. The mother and daughter had raised levels of IgG titers to Porphyromonas gingivalis. All subjects had HLA phenotypes of DRw52 and DQ1 in common. We found that the family members had similar disorders in certain defensive functions. This family has been a model for our understanding of the host defensive factors in the development of early-onset periodontitis.

Disorders of neutrophil function

Major bacterial infections are most commonly associated with agranulocytosis or an abnormality of immunoglobulins or complement. Occasionally, repeated infections cannot be attributed to these relatively common causes. In such cases, a quantitative abnormality in neutrophil function should be sought. Complete evaluation of neutrophil function, including: chemotaxis, adhesion, aggregation, phagocytosis, granule content and degranulation, respiratory burst activity and bacterial killing is expensive and requires the services of a specialized laboratory. However, preliminary screening of a patient with a predisposition towards infection can be carried out using simple and inexpensive methods. These include examination of blood films, chemotaxis assay, NBT test and peroxidase staining. For final diagnosis and determination of genetic transmission and treatment, specific tests are indicated. Investigation of neutrophil functions may be useful for the diagnosis of congenital and acquired neutrophil disorders. These assays may also be useful in research, diagnosis and follow up of non-infectious diseases with active inflammatory component.

Influence of gingival crevicular washing on the expression of polymorphonuclear leukocyte membrane receptors before and after periodontal therapy

Extensive data demonstrate that polymorphonuclear leukocytes (PMN) are the predominant cell type involved in periodontal disease and that gingival crevicular fluid constituents are influenced by the inflamed gingiva. The aim of the present study was to evaluate the ability of gingival crevicular washing (GCW) (a dilution of gingival crevicular fluid) from periodontal sites in different clinical conditions of modulating the PMN membrane receptors involved in motility, adhesion and phagocytosis before and after periodontal treatment. 10 patients affected by adult periodontitis (AP) were selected. From each patient, 2 test sites (TS) were chosen on the basis of a probing depth > 5 mm and attachment loss, and 2 control sites (CS) with probing depth < 3 mm without. Modifications of membrane receptor density of PMN from healthy donors incubated with GCW harvested from TS and CS was evaluated using fluorescent probes and flow cytometry. Compared to CS-GCW, TS-GCW before therapy increased the expression of the beta 2 integrin CD11b and the chemotactic receptor for the oligopeptide N-formyl methionyl leucyl phenylalanine (FMLP-R) while it reduced the expression of L-selectin. GCW collected from the same TS after the successful completion of periodontal treatment did not influence PMN receptors, indicating that the clinical improvement paralleled the disappearance of the PMN modulating capability contained in TS-GCW before therapy. In conclusion, the present data illustrate the relevant modifications occurring at PMN membrane in chronic adult periodontitis exerted by GCW obtained by a simple fluid collection technique. Thus, monitoring gingival crevicular fluid PMN activating capability may help disclose the presence of chronic periodontitis and may be useful in assessing successful treatment.

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.

Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

Subjects of the past decade in the dental literature are reflected in this year's Committee report. We note the decrease in the prevalence of caries, the influence of dental implants, the advancements in dental materials, and the continued efforts to control adhesive events in the oral cavity. This year we included comments from and about many significant review articles published this past year. The Committee continues to be concerned about the quality of some of the work reported and the quality of the reporting. We have attempted to select the distinguished work, that which provides new information to our profession. The subjects covered include pulp biology, caries prevention, periodontics, implants, craniomandibular function and dysfunction, occlusion, and dental materials.

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.