Defective polymorphonuclear leukocyte formyl peptide receptor(s) in juvenile periodontitis

Evaluation of the Genetic Association and Methylation of Immune Response Pathway Genes with the Risk of Chronic Periodontitis in the Uighur Population

Aim: The aim of this study was to explore the possible associations between single nucleotide polymorphisms (SNPs) and DNA methylation levels of seven genes in the inflammatory response pathway with susceptibility to chronic periodontitis (CP) among the Uighur population of the Xinjiang Autonomous Region of China. Methods: A total of 444 eligible subjects (279 CP patients and 165 healthy controls) were enrolled in the study. Genomic DNA was obtained from gingival tissue for genotyping eight SNPs and performing methylation measurements of seven genes. Results: SNP rs2070745 in the formyl peptide receptor 1 (FPR1) gene achieved statistical significance in a standard allelic association analysis for CP (p = 0.02). The frequency of the rs2070745 minor allele G was higher in the cases than in controls (0.367 vs. 0.291). Additionally, rs2070745 was significantly associated with CP under the dominant genetic model (p = 0.03). Using logistic regression analysis, rs2070745 was found to be consistently associated with CP under the additive dominant model, and this association remained significant after covariates were taken into account [odds ratio (OR) = 1.49 (1.09-2.05), p = 0.014; OR = 1.58 (1.04-2.40), p = 0.031, respectively]. No significant gene-gene interactions were identified. Although we did not find a polymorphism in interleukin 6 (IL6) associated with CP in our study, the methylation level of a CpG island region located within the promoter region of IL6 was significantly less in CP patients compared with controls (p < 0.05). Conclusions: The genetic polymorphism rs2070745 in FPR1 and the methylation level of the promoter region of IL6 might be associated with CP in the Uighur population of China.

Formyl peptide receptors in the mucosal immune system

Formyl peptide receptors (FPRs) belong to the G protein-coupled receptor (GPCR) family and are well known as chemotactic receptors and pattern recognition receptors (PRRs) that recognize bacterial and mitochondria-derived formylated peptides. FPRs are also known to detect a wide range of ligands, including host-derived peptides and lipids. FPRs are highly expressed not only in phagocytes such as neutrophils, monocytes, and macrophages but also in nonhematopoietic cells such as epithelial cells and endothelial cells. Mucosal surfaces, including the gastrointestinal tract, the respiratory tract, the oral cavity, the eye, and the reproductive tract, separate the external environment from the host system. In mucosal surfaces, the interaction between the microbiota and host cells needs to be strictly regulated to maintain homeostasis. By sharing the same FPRs, immune cells and epithelial cells may coordinate pathophysiological responses to various stimuli, including microbial molecules derived from the normal flora. Accumulating evidence shows that FPRs play important roles in maintaining mucosal homeostasis. In this review, we summarize the roles of FPRs at mucosal surfaces.

Inhibition of formyl peptide receptors improves the outcome in a mouse model of Alzheimer disease

Background

An important hallmark of Alzheimer’s disease (AD) is the increase of Aβ1-42 burden and its accumulation to senile plaques, leading the reactive gliosis and neurodegeneration. The modulation of glia cell function represents an attractive therapeutic strategy, but is currently limited by an incomplete understanding of its relevance for AD. The chemotactic G-protein coupled formyl peptide receptor (FPR), which is known to modulate Aβ1-42 uptake and signal transduction, might be one candidate molecule regulating glia function in AD. Here, we investigate whether the modulation of FPR exerts beneficial effects in an AD preclinical model.

Methods

To address this question, APP/PS1 double-transgenic AD mice were treated for 20 weeks with either the pro-inflammatory FPR agonist fMLF, the FPR1/2 antagonist Boc2 or the anti-inflammatory FPR2 agonist Ac2-26. Spatial learning and memory were evaluated using a Morris water maze test. Immunohistological staining, gene expression studies, and flow cytometry analyses were performed to study neuronal loss, gliosis, and Aß-load in the hippocampus and cortex, respectively.

Results

FPR antagonism by Boc2-treatment significantly improved spatial memory performance, reduced neuronal pathology, induced the expression of homeostatic growth factors, and ameliorated microglia, but not astrocyte, reactivity. Furthermore, the elevated levels of amyloid plaques in the hippocampus were reduced by Boc2-treatment, presumably by an induction of amyloid degradation.

Conclusions

We suggest that the modulation of FPR signaling cascades might be considered as a promising therapeutic approach for alleviating the cognitive deficits associated with early AD. Additional studies are now needed to address the downstream effectors as well as the safety profile of Boc2.

The formyl peptide fMLF primes platelet activation and augments thrombus formation

Essentials The role of formyl peptide receptor 1 (FPR1) and its ligand, fMLF, in the regulation of platelet function, hemostasis, and thrombosis is largely unknown. Fpr1-deficient mice and selective inhibitors for FPR1 were used to investigate the function of fMLF and FPR1 in platelets. N-formyl-methionyl-leucyl-phenylalanine primes platelet activation and augments thrombus formation, mainly through FPR1 in platelets. Formyl peptide receptor 1 plays a pivotal role in the regulation of platelet function.

BACKGROUND

Formyl peptide receptors (FPRs) play pivotal roles in the regulation of innate immunity and host defense. The FPRs include three family members: FPR1, FPR2/ALX, and FPR3. The activation of FPR1 by its high-affinity ligand, N-formyl-methionyl-leucyl-phenylalanine (fMLF) (a bacterial chemoattractant peptide), triggers intracellular signaling in immune cells such as neutrophils and exacerbates inflammatory responses to accelerate the clearance of microbial infection. Notably, fMLF has been demonstrated to induce intracellular calcium mobilization and chemotaxis in platelets that are known to play significant roles in the regulation of innate immunity and inflammatory responses. Despite a plethora of research focused on the roles of FPR1 and its ligands such as fMLF on the modulation of immune responses, their impact on the regulation of hemostasis and thrombosis remains unexplored.

OBJECTIVE

To determine the effects of fMLF on the modulation of platelet reactivity, hemostasis, and thrombus formation.

METHODS

Selective inhibitors for FPR1 and Fpr1-deficient mice were used to determine the effects of fMLF and FPR1 on platelets using various platelet functional assays.

RESULTS

N-formyl-methionyl-leucyl-phenylalanine primes platelet activation through inducing distinctive functions and enhances thrombus formation under arterial flow conditions. Moreover, FPR1 regulates normal platelet function as its deficiency in mouse or blockade in human platelets using a pharmacological inhibitor resulted in diminished agonist-induced platelet activation.

CONCLUSION

Since FPR1 plays critical roles in numerous disease conditions, its influence on the modulation of platelet activation and thrombus formation may provide insights into the mechanisms that control platelet-mediated complications under diverse pathological settings.

Therapeutic Potential of Annexin A1 in Ischemia Reperfusion Injury

Cardiovascular disease (CVD) continues to be the leading cause of death in the world. Increased inflammation and an enhanced thrombotic milieu represent two major complications of CVD, which can culminate into an ischemic event. Treatment for these life-threatening complications remains reperfusion and restoration of blood flow. However, reperfusion strategies may result in ischemia-reperfusion injury (I/RI) secondary to various cardiovascular pathologies, including myocardial infarction and stroke, by furthering the inflammatory and thrombotic responses and delivering inflammatory mediators to the affected tissue. Annexin A1 (AnxA1) and its mimetic peptides are endogenous anti-inflammatory and pro-resolving mediators, known to have significant effects in resolving inflammation in a variety of disease models. Mounting evidence suggests that AnxA1, which interacts with the formyl peptide receptor (FPR) family, may have a significant role in mitigating I/RI associated complications. In this review article, we focus on how AnxA1 plays a protective role in the I/R based vascular pathologies.

The Formyl Peptide Receptors: Diversity of Ligands and Mechanism for Recognition

The formyl peptide receptors (FPRs) are G protein-coupled receptors that transduce chemotactic signals in phagocytes and mediate host-defense as well as inflammatory responses including cell adhesion, directed migration, granule release and superoxide production. In recent years, the cellular distribution and biological functions of FPRs have expanded to include additional roles in homeostasis of organ functions and modulation of inflammation. In a prototype, FPRs recognize peptides containing N-formylated methionine such as those produced in bacteria and mitochondria, thereby serving as pattern recognition receptors. The repertoire of FPR ligands, however, has expanded rapidly to include not only N-formyl peptides from microbes but also non-formyl peptides of microbial and host origins, synthetic small molecules and an eicosanoid. How these chemically diverse ligands are recognized by the three human FPRs (FPR1, FPR2 and FPR3) and their murine equivalents is largely unclear. In the absence of crystal structures for the FPRs, site-directed mutagenesis, computer-aided ligand docking and structural simulation have led to the identification of amino acids within FPR1 and FPR2 that interact with several formyl peptides. This review article summarizes the progress made in the understanding of FPR ligand diversity as well as ligand recognition mechanisms used by these receptors.

Formylpeptide Receptors Promote the Migration and Differentiation of Rat Neural Stem Cells

Neural stem cells (NSCs) bear characteristics for proliferation, migration and differentiation into three main neural cell type(s): neurons, astrocytes and/or oligodendrocytes. Formylpeptide receptors (Fprs), belonging to the family of G protein-coupled chemoattractant receptors, have been detected on neurons in the central nervous system (CNS). Here, we report that Fpr1 and Fpr2 are expressed on NSCs as detected with immunohistochemistry, RT-PCR and WB assays. In addition, Fpr1 and Fpr2 promoted NSC migration through F-actin polymerization and skewed NSC differentiation to neurons. Our study demonstrates a unique role of Fpr1 and Fpr2 in NSCs and opens a novel window for cell replacement therapies for brain and spinal cord injury.

Intraluminal containment of commensal outgrowth in the gut during infection-induced dysbiosis

Shifts in commensal microbiota composition are emerging as a hallmark of gastrointestinal inflammation. In particular, outgrowth of γ-proteobacteria has been linked to the etiology of inflammatory bowel disease and the pathologic consequences of infections. Here we show that following acute Toxoplasma gondii gastrointestinal infection of mice, control of commensal outgrowth is a highly coordinated process involving both the host response and microbial signals. Notably, neutrophil emigration to the intestinal lumen results in the generation of organized intraluminal structures that encapsulate commensals and limit their contact with the epithelium. Formation of these luminal casts depends on the high-affinity N-formyl peptide receptor, Fpr1. Consequently, after infection, mice deficient in Fpr1 display increased microbial translocation, poor commensal containment, and increased mortality. Altogether, our study describes a mechanism by which the host rapidly contains commensal pathobiont outgrowth during infection. Further, these results reveal Fpr1 as a major mediator of host commensal interaction during dysbiosis.

Innate immune response to oral bacteria and the immune evasive characteristics of periodontal pathogens

Periodontitis is a chronic inflammation of periodontal tissue caused by subgingival plaque-associated bacteria. Periodontitis has long been understood to be the result of an excessive host response to plaque bacteria. In addition, periodontal pathogens have been regarded as the causative agents that induce a hyperinflammatory response from the host. In this brief review, host-microbe interaction of nonperiodontopathic versus periodontopathic bacteria with innate immune components encountered in the gingival sulcus will be described. In particular, we will describe the susceptibility of these microbes to antimicrobial peptides (AMPs) and phagocytosis by neutrophils, the induction of tissue-destructive mediators from neutrophils, the induction of AMPs and interleukin (IL)-8 from gingival epithelial cells, and the pattern recognition receptors that mediate the regulation of AMPs and IL-8 in gingival epithelial cells. This review indicates that true periodontal pathogens are poor activators/suppressors of a host immune response, and they evade host defense mechanisms.

The leukocyte chemotactic receptor FPR1 is functionally expressed on human lens epithelial cells

BACKGROUND

Lens degeneration in Fpr1(-/-) mice prompted us to search for functional FPR1 expression directly on lens epithelial cells.

RESULTS

FPR1 is functionally expressed on human lens epithelial cells but has atypical properties compared with hematopoietic cell FPR1.

CONCLUSION

Lens epithelial cell FPR1 may be involved in development and maintenance of the lens.

SIGNIFICANCE

This is the first link between non-hematopoietic expression of FPR1 and an ophthalmologic phenotype. Formyl peptide receptor 1 (FPR1) is a G protein-coupled chemoattractant receptor expressed mainly on leukocytes. Surprisingly, aging Fpr1(-/-) mice develop spontaneous lens degeneration without inflammation or infection (J.-L. Gao et al., manuscript in preparation). Therefore, we hypothesized that FPR1 is functionally expressed directly on lens epithelial cells, the only cell type in the lens. Consistent with this, the human fetal lens epithelial cell line FHL 124 expressed FPR1 mRNA and was strongly FPR1 protein-positive by Western blot and FACS. Competition binding using FPR1 ligands N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys (Nle = Norleucine), formylmethionylleucylphenylalanine, and peptide W revealed the same profile for FHL 124 cells, neutrophils, and FPR1-transfected HEK 293 cells. Saturation binding with fluorescein-labeled N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys revealed ~2500 specific binding sites on FHL-124 cells (K(D) ~ 0.5 nm) versus ~40,000 sites on neutrophils (K(D) = 3.2 nm). Moreover, formylmethionylleucylphenylalanine induced pertussis toxin-sensitive Ca(2+) flux in FHL 124 cells, consistent with classic G(i)-mediated FPR1 signaling. FHL 124 cell FPR1 was atypical in that it resisted agonist-induced internalization. Expression of FPR1 was additionally supported by detection of the intact full-length open reading frame in sequenced cDNA from FHL 124 cells. Thus, FHL-124 cells express functional FPR1, which is consistent with a direct functional role for FPR1 in the lens, as suggested by the phenotype of Fpr1 knock-out mice.

Membrane-bound proteinase 3 and PAR2 mediate phagocytosis of non-opsonized bacteria in human neutrophils

The molecular mechanisms underlying the non-opsonic phagocytosis of bacteria by neutrophils are poorly understood. We previously reported the efficient uptake of Streptococcus sanguinis by human neutrophils in the absence of opsonins. To characterize the phagocytosis receptor, protein lysates from neutrophils and HL-60 cells were subjected to affinity chromatography using epoxy beads coated with S. sanguinis. Denaturing electrophoresis of the eluted proteins and subsequent mass spectrometry revealed that one of the proteins eluted from neutrophils was proteinase 3 (PR3). Enzymatic cleavage of the glycosylphosphatidylinositol linker of NB1, a co-receptor for membrane-bound PR3 (mPR3), significantly reduced the phagocytosis of S. sanguinis. In addition, the neutralization of mPR3 with antibody reduced both binding and phagocytosis of S. sanguinis. Treatment of neutrophils with a serine proteinase inhibitor indicated that protease activity is required for phagocytosis. Thus, we studied whether protease-activated receptor 2 (PAR2) is involved in signal transmission from mPR3 during this process. Indeed, neutralizing antibodies against PAR2 inhibited phagocytosis and S. sanguinis-induced calcium mobilization desensitized PAR2. Furthermore, the phagocytosis of S. sanguinis and the concomitant activation of Rho family GTPases were inhibited by the intracellular calcium chelator, BAPTA-AM. Collectively, mPR3 acts as a non-opsonic phagocytosis receptor for bacteria probably by activating PAR2 in neutrophils.

Are formyl peptide receptors novel targets for therapeutic intervention in ischaemia-reperfusion injury?

Ischaemia–reperfusion (I/R) injury is a common feature of several diseases associated with high morbidity and mortality, such as stroke and myocardial infarction. The damaged tissue displays cardinal signs of inflammation and microvascular injury that, unless resolved, lead to long-term tissue damage with associated dysfunction. Current therapies are limited and are often associated with many side effects. Increasing evidence suggests that members of the formyl peptide receptor (FPR) family, in particular human FPR2/ALX, might have an important role in the pathophysiology of I/R injury. It was recently demonstrated that several peptides and non-peptidyl small-molecule compounds have anti-inflammatory and pro-resolving properties via their action on members of the FPR family. Here I review this evidence and suggest that FPR ligands, particularly in the brain, could be novel and exciting anti-inflammatory therapeutics for the treatment of a variety of clinical conditions, including stroke.

Formylpeptide receptor single nucleotide polymorphism 348T>C and its relationship to polymorphonuclear leukocyte chemotaxis in aggressive periodontitis

BACKGROUND

Aggressive periodontitis (AgP) is associated with impaired polymorphonuclear leukocyte (PMN) chemotaxis toward bacterial N-formylpeptides. Formylpeptide receptors (FPRs) play a major role in guiding PMNs to infection sites. Previous work revealed a significant association between FPR1 single nucleotide polymorphism (SNP) 348T>C and AgP in African Americans. We tested the hypothesis that 348T impairs PMN chemotaxis by decreasing FPR mRNA expression, thereby increasing susceptibility to AgP.

METHODS

Blood samples were obtained from African American subjects (37 AgP cases and 38 controls). Chemotaxis to N-formyl-methionine-leucine-phenylalanine by freshly isolated PMNs was assayed in a modified Boyden chamber. RNA was isolated from PMNs, and FPR1 gene expression was quantified by real-time polymerase chain reaction (PCR). To detect FPR1 5' SNPs, genomic DNA was isolated, and four fragments spanning the FPR1 5' region were PCR-amplified and sequenced. Haplotype associations between SNP 348T>C and 5' SNPs were analyzed.

RESULTS

The homozygous 348T genotype was only found in AgP cases (P = 0.017; odds ratio, 18.9). Subjects with this genotype exhibited a significantly lower PMN chemotactic response relative to controls and to subjects with the 348C/C or 348T/C genotype (P <0.05). There were no significant differences in PMN FPR1 expression among subjects with the 348C/C, 348T/C, and 348T/T genotypes. Eleven FPR1 5' SNPs were detected, but none of the predicted haplotypes reflected associations with AgP or with 348T.

CONCLUSIONS

Although the 348T/T genotype is relatively rare, it is associated with significantly impaired PMN chemotaxis and an increased risk for developing AgP in African Americans. These associations do not seem to be related to significant reductions in FPR1 transcripts in subjects expressing 348T.

PDK1 regulates chemotaxis in human neutrophils

Phosphoinositide-dependent kinase (PDK1) plays a central role in signal transduction mediated by phosphatidylinositol 3-kinases (PI3K) and regulates cellular functions in neutrophils. Neutrophils from individuals diagnosed with localized aggressive periodontitis (LAP) present an in vivo phenotype with depressed chemotaxis. The aim of this study was to test the hypothesis that PDK1 regulates chemotaxis in neutrophils and is responsible for the abnormal neutrophil chemotaxis LAP. Neutrophil chemotaxis was significantly suppressed by the PDK1 inhibitor staurosporine. When cells were transfected with PDK1 siRNA, there was a significant reduction in chemotaxis, while superoxide generation was not significantly affected. In primary neutrophils from persons with LAP, PDK1 expression and activation levels were significantly reduced, and this reduction was associated with the reduced phosphorylation of Akt (Thr308) and chemotaxis. Analysis of these data demonstrates that PDK1 is essential for the chemotactic migration of neutrophils, and in the absence of PDK1, neutrophil chemotaxis is impaired.

Neutrophil formylpeptide receptor single nucleotide polymorphism 348T>C in aggressive periodontitis

BACKGROUND

Neutrophil formylpeptide receptors (FPRs) play an important role in bacterial recognition and chemotaxis. Defective FPR1 expression and impaired polymorphonuclear leukocyte chemotaxis toward bacterial formylpeptides are associated with aggressive periodontitis (AgP). The objective of this study was to determine whether single nucleotide polymorphisms (SNPs) in FPR1 are associated with AgP.

METHODS

Genomic DNA was isolated from blood samples obtained from African Americans (30 subjects with AgP and 33 healthy controls) and Turks (75 subjects with AgP and 63 healthy controls). A highly polymorphic fragment of the FPR1 gene was amplified by polymerase chain reaction and sequenced for analysis of SNPs.

RESULTS

Five previously identified SNPs were detected in African Americans, whereas six were detected in Turkish subjects. The frequency of synonymous SNP c.348T>C was significantly higher in African Americans with AgP than in controls (P = 0.029). The 348T allele was significantly associated with AgP (P = 0.010). Seven of the subjects with AgP, but none of the controls, were homozygous for 348T. FPR1 haplotypes 348T.568A, 348T.576T, and 348T.568A.576T were significantly increased in African Americans with AgP (P <0.02). The Turkish population did not exhibit significant differences in FPR1 SNP frequencies between subjects with AgP and controls.

CONCLUSIONS

FPR1 SNP c.348T>C is associated with AgP in African Americans. Individuals who are homozygous for 348T may have an increased risk for developing this disorder.

International Union of Basic and Clinical Pharmacology. LXXIII. Nomenclature for the formyl peptide receptor (FPR) family

Formyl peptide receptors (FPRs) are a small group of seven-transmembrane domain, G protein-coupled receptors that are expressed mainly by mammalian phagocytic leukocytes and are known to be important in host defense and inflammation. The three human FPRs (FPR1, FPR2/ALX, and FPR3) share significant sequence homology and are encoded by clustered genes. Collectively, these receptors bind an extraordinarily numerous and structurally diverse group of agonistic ligands, including N-formyl and nonformyl peptides of different composition, that chemoattract and activate phagocytes. N-formyl peptides, which are encoded in nature only by bacterial and mitochondrial genes and result from obligatory initiation of bacterial and mitochondrial protein synthesis with N-formylmethionine, is the only ligand class common to all three human receptors. Surprisingly, the endogenous anti-inflammatory peptide annexin 1 and its N-terminal fragments also bind human FPR1 and FPR2/ALX, and the anti-inflammatory eicosanoid lipoxin A4 is an agonist at FPR2/ALX. In comparison, fewer agonists have been identified for FPR3, the third member in this receptor family. Structural and functional studies of the FPRs have produced important information for understanding the general pharmacological principles governing all leukocyte chemoattractant receptors. This article aims to provide an overview of the discovery and pharmacological characterization of FPRs, to introduce an International Union of Basic and Clinical Pharmacology (IUPHAR)-recommended nomenclature, and to discuss unmet challenges, including the mechanisms used by these receptors to bind diverse ligands and mediate different biological functions.

Ability of oral bacteria to induce tissue-destructive molecules from human neutrophils

AIM

The induction of tissue-destructive molecules from neutrophils by periodontopathic bacteria has been suggested as one of the mechanisms of periodontal destruction. The aim of this study was to determine whether the ability to stimulate neutrophils is an authentic characteristic of periodontopathic bacteria.

METHODS

We evaluated, along with phagocytosis, the production of reactive oxygen species (ROS), matrix metalloproteinase-8 (MMP-8), and interleukin-1beta by neutrophils in response to non-periodontopathic Streptococcus sanguinis and periodontopathic bacteria Fusobacterium nucleatum and Treponema denticola, in the absence or presence of antibodies. Phagocytosis, the death of neutrophils, and intracellular ROS production were measured by flow cytometry and the concentrations of MMP-8 and interleukin-1beta secreted into medium were determined by enzyme-linked immunosorbent assay.

RESULTS

S. sanguinis and F. nucleatum induced greater production of ROS, MMP-8, and interleukin-1beta than did T. denticola. The levels of tissue-destructive molecules produced by neutrophils had a positive correlation with phagocytosis. Opsonization of bacteria with antibodies significantly increased phagocytosis and ROS production and release, thus increasing both bacterial clearance and potential tissue damage.

CONCLUSION

The ability of oral bacteria to induce tissue-destructive molecules from neutrophils is not an inherent characteristic of periodontopathic bacteria, which would provide a new insight into the role of neutrophils in periodontal destruction.

Susceptibility of various oral bacteria to antimicrobial peptides and to phagocytosis by neutrophils

BACKGROUND AND OBJECTIVE

The aim of this study was to compare the susceptibility of nonperiodontopathic and periodontopathic bacteria to major defense mechanisms for bacterial clearance in gingival sulcus.

MATERIAL AND METHODS

Twenty strains of 13 oral bacterial species were studied for their susceptibility to phagocytosis by human neutrophils and to the antimicrobial peptides LL-37 and human beta defensin-3. The minimum inhibitory concentrations of LL-37 and human beta defensin-3 were determined by a liquid dilution assay, and susceptibility to phagocytosis was examined by a flow cytometric phagocytosis assay.

RESULTS

The minimum inhibitory concentrations of LL-37 and human beta defensin-3 varied greatly, depending on the strain and species. Although a significant difference between the non- and periodontopathic groups was not observed, the red-complex bacteria were more resistant to LL-37 than the others (p=0.004). The susceptibility of oral bacteria to phagocytosis was quite variable, depending on the species but not on the strains. The periodontopathic bacteria, especially Actinobacillus actinomycetemcomitans and the red-complex triad, were more resistant to phagocytosis than were the nonperiodontopathic bacteria (p=0.0003). In addition, bacteria resistant both to antimicrobial peptides and to phagocytosis were more common in the periodontopathic group.

CONCLUSION

Our results indicate that immune evasion may contribute to the pathogenicity of some periodontopathic bacteria.

Differential activation of polymorphisms of the formyl peptide receptor by formyl peptides

We have investigated the role of two polymorphic sites (R190W and N192K) on the binding and activation of the formyl peptide receptor (FPR) by viral and formyl peptides. WEDWVGWI, a peptide with antiviral activity derived from the membrane proximal region of feline immunodeficiency virus, binds with high affinity to FPR. The three tryptophans in the peptide are all essential for FPR binding, just as they were essential for antiviral activity [S. Giannecchini, A. Di Fenza, A.M. D'Ursi, D. Matteucci, P. Rovero, M. Bendinelli, Antiviral activity and conformational features of an octapeptide derived from the membrane-proximal ectodomain of the feline immunodeficiency virus transmembrane glycoprotein, J. Virol. 77 (2003) 3724]. Formyl-NleWEDWVGWI behaved as a weak partial agonist with FPR W190/N192 but a stronger partial agonist with FPR R190/K192 and FPR R190/N192. Formyl-NleNleWEDWVGWI behaved as a full agonist toward all three FPRs but exhibited a much higher EC(50) with W190/N192 FPR (300+/-45 nM) than for R190/K192 FPR (40+/-3 nM) or R190/N192 (60+/-8 nM). Formyl-MYKWPWYVWL preferentially activated R190/K192 and R190/N192 FPRs by>5 fold compared to W190/N192 FPR. Formyl-MFEDAVAWF, a peptide derived from a protein in Mycobacterium avium subsp. paratuberculosis and formyl-MFTFEPFPTN, a peptide derived from the N-terminus of chemotaxis inhibitory protein of Staphylococcus aureus with an added N-terminal formyl-methionine exhibited the greatest selectivity for R190/K192 and R190/N192 FPRs with approximately 10 fold lower EC(50)s than that observed with FPR W190/N192. Thus, individuals with the W190 polymorphism may display a reduced ability to detect certain formyl peptides.

Roles of the host oxidative immune response and bacterial antioxidant rubrerythrin during Porphyromonas gingivalis infection

The efficient clearance of microbes by neutrophils requires the concerted action of reactive oxygen species and microbicidal components within leukocyte secretory granules. Rubrerythrin (Rbr) is a nonheme iron protein that protects many air-sensitive bacteria against oxidative stress. Using oxidative burst-knockout (NADPH oxidase-null) mice and an rbr gene knockout bacterial strain, we investigated the interplay between the phagocytic oxidative burst of the host and the oxidative stress response of the anaerobic periodontal pathogen Porphyromonas gingivalis. Rbr ensured the proliferation of P. gingivalis in mice that possessed a fully functional oxidative burst response, but not in NADPH oxidase-null mice. Furthermore, the in vivo protection afforded by Rbr was not associated with the oxidative burst responses of isolated neutrophils in vitro. Although the phagocyte-derived oxidative burst response was largely ineffective against P. gingivalis infection, the corresponding oxidative response to the Rbr-positive microbe contributed to host-induced pathology via potent mobilization and systemic activation of neutrophils. It appeared that Rbr also provided protection against reactive nitrogen species, thereby ensuring the survival of P. gingivalis in the infected host. The presence of the rbr gene in P. gingivalis also led to greater oral bone loss upon infection. Collectively, these results indicate that the host oxidative burst paradoxically enhances the survival of P. gingivalis by exacerbating local and systemic inflammation, thereby contributing to the morbidity and mortality associated with infection.

Peptides derived from HIV-1, HIV-2, Ebola virus, SARS coronavirus and coronavirus 229E exhibit high affinity binding to the formyl peptide receptor

Peptides derived from the membrane proximal region of fusion proteins of human immunodeficiency viruses 1 and 2, Coronavirus 229 E, severe acute respiratory syndrome coronavirus and Ebola virus were all potent antagonists of the formyl peptide receptor expressed in Chinese hamster ovary cells. Binding of viral peptides was affected by the naturally occurring polymorphisms at residues 190 and 192, which are located at second extracellular loop-transmembrane helix 5 interface. Substitution of R190 with W190 enhanced the affinity for a severe acute respiratory syndrome coronavirus peptide 6 fold but reduced the affinity for N-formyl-Nle-Leu-Phe by 2.5 fold. A 12 mer peptide derived from coronavirus 229E (ETYIKPWWVWL) was the most potent antagonist of the formyl peptide receptor W190 with a K(i) of 230 nM. Fluorescently labeled ETYIKPWWVWL was effectively internalized by all three variants with EC(50) of approximately 25 nM. An HKU-1 coronavirus peptide, MYVKWPWYVWL, was a potent antagonist but N-formyl-MYVKWPWYVWL was a potent agonist. ETYIKPWWVWL did not stimulate GTPgammaS binding but inhibited the stimulation by formyl-NleLeuPhe. It also blocked beta arrestin translocation and receptor downregulation induced by formyl-Nle-Leu-Phe. This indicates that formyl peptide receptor may be important in viral infections and that variations in its sequence among individuals may affect their likelihood of viral and bacterial infections.

Normal cell surface expression and selective loss of functions resulting from Phe110 to Ser and Cys126 to Trp substitutions in the formyl peptide receptor

The N-formyl peptide receptor (FPR) is a G protein-coupled chemoattractant receptor that mediates diverse leukocyte functions when stimulated by bacteria-derived N-formyl peptides such as fMet-Leu-Phe (fMLF). Impaired neutrophil responsiveness to fMLF parallels increased susceptibility to periodontal microorganisms among patients with localized juvenile periodontitis (LJP). To determine whether the recently identified FPR mutations in LJP patients are responsible for selective loss of receptor-mediated functions, we prepared and analyzed RBL-2H3 cells expressing FPR bearing Phe110 to Ser (FPR-F110S) or Cys-126 to Trp (FPR-C126W) replacement as well as a FPR double mutant (FPR-FSCW). All mutant receptors were expressed normally on the cell surface, but were unable to mediate release of beta-hexosaminidase upon fMLF stimulation. FPR-C126W effectively mediated fMLF uptake, an indication of receptor-mediated endocytosis, whereas FPR-F110S and FSCW exhibited markedly reduced ability to uptake fMLF. Both FPR-F110S and FPR-C126W were defective in chemotaxis and displayed reduced Ca2+ mobilization, but mutation at both positions partially restored the ability to respond to fMLF in chemotaxis assay and was nearly normal in Ca2+ mobilization assay. All mutants exhibited diminished accumulation of inositol phosphates. FPR-F110S displayed a delayed and significantly reduced ERK phosphorylation whereas FPR-FSCW nearly lost the ability to phosphorylate ERK. Taken together, these results indicate compromised signaling capabilities due to the FPR mutations, but the loss of function is selective and could be partially rescued by mutations at both positions.

Alterations of gene expression in human neutrophils induced by smoking cessation

OBJECTIVE

The purpose of the present study was to investigate the effect of smoking cessation on the peripheral neutrophil mRNA expression levels for inflammatory cytokines, chemokine, growth factor and matrix metalloproteinase (MMP).

MATERIAL AND METHODS

Sixteen male smokers (aged 22-39 [25.3+/-4.0] years), with no clinical signs of periodontal and systemic diseases, were recruited. The experiment was performed before (baseline) and at 1, 4 and 8 weeks after smoking cessation. The status of smoking and smoking cessation was verified by exhaled carbon monoxide (CO) concentration and serum cotinine concentration. Neutrophils were isolated from each subjects' peripheral blood, then the cell was stimulated with N-formyl-methionyl-leucyl-phenylalanine (FMLP). The mRNA expression levels for interleukin (IL)-1 beta, IL-8, tumor necrosis factor (TNF)-alpha, vascular endothelial growth factor (VEGF) and MMP-8 were analyzed by semiquantitative reverse transcription-polymerase chain reactions. The same experiment was performed on 11 non-smoking controls (four female and seven male), aged 23-27 (24.4+/-1.2) years.

RESULTS

Eleven of 16 smokers successfully completed smoking cessation for 8 weeks. At 1 day after smoking cessation, there was a statistically significantly lower CO concentration than at baseline (p<0.01). Also, cotinine concentration markedly decreased at the second measurement, which was taken at 1 week. All of the analyzed mRNA expression levels of neutrophils from smokers were statistically significantly lower than that in non-smokers (p<0.01: IL-1 beta, IL-8, VEGF; p<0.05: TNF-alpha, MMP-8). The MMP-8 mRNA levels were statistically significantly increased at 8 weeks after smoking cessation compared with the baseline (p<0.05). Although the other mRNA expression levels were also elevated gradually from the baseline, they did not reach the statistically significant levels at 8 weeks after smoking cessation.

CONCLUSION

The results showed that the neutrophil transcript levels in smokers were generally lower than those in non-smokers, which could be related to an impairment of neutrophils by smoking effects. The significant increase of MMP-8 mRNA levels were associated with the effects of smoking cessation, while recovery of the other mRNA levels seemed to require a bit longer period beyond 8 weeks after smoking cessation.

A molecular defect in intracellular lipid signaling in human neutrophils in localized aggressive periodontal tissue damage

Host defense mechanisms are impaired in patients with congenital neutrophil (polymorphonuclear neutrophils (PMN)) defects. Impaired PMN chemotaxis is observed in localized aggressive periodontitis (LAP), a familial disorder characterized by destruction of the supporting structures of dentition. In the present studies, we sought evidence for molecular events underlying this aberrant human PMN phenotype. To this end, PMN transendothelial migration and superoxide anion generation were assessed with LAP patients and asymptomatic family members, as well as patients with other chronic mucosal inflammation. PMN from LAP patients showed decreased transmigration across vascular endothelial monolayers (18 +/- 12% of control, n = 4) and increased superoxide anion generation (358 +/- 37%, p = 0.003). Gene expression was analyzed using oligonucleotide microarrays and fluorescence-based kinetic PCR. cDNA microarray and kinetic-PCR analysis revealed diminished RNA expression of leukocyte-type diacylglycerol (DAG) kinase alpha in PMN from LAP patients (4.6 +/- 1.7 relative units, n = 6, p = 0.007) compared with asymptomatic individuals (51 +/- 27 relative units, n = 7). DAG kinase activity was monitored by DAG phosphorylation and individual DAG molecular species were quantified using liquid chromatography and tandem mass spectrometry-based lipidomics. DAG kinase activity was also significantly decreased (73 +/- 2%, p = 0.007) and correlated with increased accumulation of 1,2-diacyl-sn-3-glycerol substrates (p = 0.01). These results implicate defects in both PMN transendothelial migration and PMN DAG kinase alpha signaling as disordered functions in LAP. Moreover, they identify a potential molecular lesion in PMN signal transduction that may account for their aberrant responses and tissue destruction in this disease.

Mutations of F110 and C126 of the formyl peptide receptor interfere with G-protein coupling and chemotaxis

BACKGROUND

Localized aggressive periodontitis (LAgP) is a disease characterized by rapid loss of alveolar bone in teeth of otherwise healthy patients. Neutrophils from LAgP patients have been shown to exhibit diminished chemotaxis and low levels of formyl peptide receptor (FPR) surface expression. A recent study has associated LAgP with 2 polymorphisms in the FPR: 110Phe-->Ser and 126Cys-->Trp.

METHODS

We transfected Chinese hamster ovary cells with wtFPR, FPR-110Phe-->Ser, FPR-126Cys-->Trp, or FPR-110Phe-->Ala and determined their surface expression of FPR, their ligand binding affinity, their G-protein coupling, and their chemotaxis toward N-formyl-methionyl-leucyl-phenylalanine (FMLP).

RESULTS

FPR-110Phe-->Ser mutants failed to show any significant surface expression or chemotaxis toward FMLP. FPR-126Cys-->Trp mutants exhibited slightly lower than normal binding affinity, markedly lower G-protein coupling response, and markedly lower chemotaxis toward FMLP than that observed with wtFPR. We also analyzed another FPR-Phe110 mutant, FPR-110Phe-->Ala, to ascertain what the effect of mutating this residue might be in a mutant that could be expressed on the cell surface. The FPR-110Phe-->Ala mutant demonstrated markedly lower surface expression, normal ligand binding affinity, markedly lower G-protein coupling, and markedly lower chemotaxis toward FMLP.

CONCLUSIONS

Our data substantiate the hypothesis that the chemotactic defects observed in LAgP patients are due at least in part to molecular alterations in the FPR. The FPR-110Phe-->Ser polymorphism appears to be more defective than the FPR-126Cys-->Trp polymorphism, indicating that patients with the former polymorphism might be expected to exhibit a more severe form of aggressive periodontitis.

Effects of safrole on the defensive functions of human neutrophils

The effects of safrole on the defensive functions of human neutrophils were examined. At the concentrations employed in this study, safrole did not significantly affect the viability of peripheral blood neutrophils as verified by their ability to exclude trypan blue dye. However, exposure of neutrophils to safrole inhibited their bactericidal activity against oral pathogens, including Actinobacillus actinomycetemcomitans and Streptococcus mutans, in a dose dependent manner. In addition, safrole inhibited the production of bactericidal superoxide anion by neutrophils as measured by cytochrome c reduction. In conclusion, the results demonstrated that safrole reduced the antibacterial activity and the superoxide anion production of neutrophils. Inhibition of the defensive functions of neutrophils may be one possible mechanism by which safrole compromises the oral health.

Evaluation of human leukocyte N-formylpeptide receptor (FPR1) SNPs in aggressive periodontitis patients

Polymorphonuclear neutrophils (PMNs) are attracted to sites of infection by N-formylpeptide (fMLP) chemoattractants. The high-affinity fMLP receptor (FPR1) of phagocytic cells interacts with bacterial fMLP and mediates chemotaxis, degranulation, and superoxide production. These cellular functions are disrupted in PMN from aggressive periodontitis (AP) patients. Two FPR1 gene single nucleotide polymorphisms (SNPs), c.329T>C and c.378C>G, have been associated with a localized form of AP in African-American patients. To evaluate the generality of these SNPs in AP patients, we sequenced a 363 bp interval of the FPR1 gene in an ethnically diverse group of patients (n=111) and controls (n=115). Neither c.329T>C nor c.378C>G were detected in the 452 alleles sequenced. Six SNPs were identified including two located in the FPR1 second extracellular loop that were significantly associated with the AP phenotype in African-American patients (p.R190W, P=0.0033; and p.N192K, P=0.0018). These two SNPs show three predominant haplotypes, each associated with a different disease risk in African-Americans. These data do not support the hypothesis that the FPR1 SNPs c.329T>C and c.378C>G play an etiologic role in aggressive periodontitis, but do suggest that SNPs in the second extracellular loop may be etiologically important.

Defective Gi protein coupling in two formyl peptide receptor mutants associated with localized juvenile periodontitis

The formyl peptide receptor (FPR) is a prototypical chemoattractant receptor expressed in neutrophils. It is well known that the FPR couples to G(i) proteins to activate phospholipase C, chemotaxis, and cytotoxic cell functions, but the in vivo role of the FPR in man has remained elusive. Recently, F110S and C126W mutations of the FPR have been associated with localized juvenile periodontitis. We studied FPR-F110S and FPR-C126W in comparison with wild-type FPR (FPR-WT) by coexpressing epitope-tagged versions of these receptors with the G protein Galpha(i2)beta(1)gamma(2) in Sf9 insect cells. FPRs were efficiently expressed in Sf9 membranes as assessed by immunoblotting using the beta(2)-adrenoreceptor as a standard. FPR-C126W differed from FPR-WT and FPR-F110S in migration on SDS-polyacrylamide gels and tunicamycin-sensitive glycosylation. FPR-WT efficiently reconstituted high-affinity agonist binding and agonist- and inverse agonist-regulated guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) binding to Galpha(i2)beta(1)gamma(2). In contrast, FPR-F110S only weakly reconstituted agonist-stimulated GTPgammaS binding, and FPR-C126W was completely inefficient. Collectively, our data show almost complete and complete loss of G(i) protein coupling in FPR-F110S and FPR-C126W, respectively. The severe functional defects in FPR-F110S and FPR-C126W contrast with the discrete clinical symptoms associated with these mutations, indicating that loss of FPR function in host defense is, for the most part, readily compensated.

Contrasting evolution of the human leukocyte N-formylpeptide receptor subtypes FPR and FPRL1R

N-formylpeptides are phagocyte chemoattractants that act by binding to two structurally related receptors, FPR (formylpeptide receptor) and FPRL1R (FPR-like-1 receptor), which are encoded by the human genes FPR1 and FPRL1. Single nucleotide polymorphisms (SNPs) in the FPR coding region have been reported and two have been associated with the disease juvenile periodontitis; however, their frequency and linkage relationships are unknown. Here we systematically analyzed polymorphism in the open reading frames of FPR1 and FPRL1 by direct sequencing of cloned alleles from random blood donors from North America. For FPR1 we detected five non-synonymous SNPs and two synonymous SNPs in a sample of 26 chromosomes one each from 17 Caucasian and nine black random blood donors. Although all five non-synonymous SNPs were common in Caucasians, Blacks, and Asians, notable differences in allele frequency were found for each SNP in the different racial groups, suggesting differential selective pressures. We found that the FPR1 polymorphisms are linked in 15 common haplotypes. No polymorphisms were detected in FPRL1 after sampling 44 chromosomes from 36 random blood donors from the same three racial groups. Thus FPR1 and FPRL1, though they originated from a common gene, appear to have undergone markedly different evolutionary events.

Heterogeneity of host immunological risk factors in patients with aggressive periodontitis

BACKGROUND

The pathogenesis of early-onset periodontitis (EOP) can be explained by various host risk factors. Previous studies have focused on a single (among many possible) immunological risk factor and the association among the factors has not been assessed. We comprehensively investigated the associations among multiple host immunological risk factors in EOP patients to further elucidate their role in the pathogenesis of EOP.

METHODS

Sixty-eight EOP patients (50 generalized EOP, 18 localized EOP), 51 EOP-suspected patients (S-EOP), 43 adult periodontitis (AP) patients, and 36 periodontally healthy subjects (HS) participated in this cross-sectional study. We examined peripheral neutrophil functions, phenotypic and functional characterization of peripheral lymphocytes (lymphocyte subsets, T-cell proliferative activity), cytokine productivity (interleukin [IL]-1, IL-2, tumor necrosis factor [TNF]-alpha, interferon [IFN]-gamma, IL-4 and IL-6), serum immunoglobulin G (IgG) antibody titers against 12 periodontal bacteria, and HLA class II genotypes.

RESULTS

G-EOP, S-EOP, and AP patient groups showed significantly lower percentages of pan T cells and CD8-positive cells (P < 0.02) compared with the HS group. L-EOP patients showed depressed IL-4 and TNF-alpha productivity compared with the HS group (P < 0.02). The EOP group showed significantly elevated antibody levels against Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Treponema denticola, and Fusobacterium nucleatum compared with the HS group (P < 0.05). The frequency with DQB1*0503 was significantly higher in the EOP patient group than the HS group (P = 0.045) due to the higher frequency in L-EOP patients than the HS group (P = 0.035). There were wide interindividual variations in each of the tests among patient and HS groups; however, EOP patients showed wider intradiagnostic group variations in certain host defensive cell functions than the other groups. There were some EOP patients who showed extremely low or high values in some tests; the EOP patients could be further divided into subgroups according to their host defensive and immunological profiles. However, there was heterogeneity in some of the other host immunological tests even in the subgroups.

CONCLUSIONS

The association of host immunological risk factors in EOP patients is widely varied and more complex than previously thought. These results indicate the difficulty of explaining the pathogenesis of EOP based on a single host risk factor and also emphasize the importance of critical assessment of not only EOP patient groups, but also individual patients.

The Fcgamma receptor genotype as a risk factor for generalized early-onset periodontitis in Japanese patients

BACKGROUND

Genetic polymorphisms of immunoglobulin G (IgG) Fc receptors (FcgammaR) were recently shown to be associated with recurrence rates of adult periodontitis (AP). The purpose of this study was to evaluate whether FcgammaR polymorphisms are also associated with generalized early-onset periodontitis (G-EOP) in Japanese patients.

METHODS

Thirty-eight Japanese patients with G-EOP and 83 Japanese patients with AP were identified according to established clinical criteria, including measurements of probing depth, clinical attachment level, and alveolar bone level. FcgammaR genotypes for 3 bi-allelic polymorphisms were determined in these G-EOP and AP patients and 104 race-matched healthy controls by means of allele-specific polymerase chain reactions.

RESULTS

There was a significant difference in the distribution of FcgammaRIIIb genotypes between G-EOP patients and healthy controls (P = 0.02). Additionally, a significant over-representation of FcgammaRIIIb-NA2 allele was observed in G-EOP patients as compared to AP patients and controls (P= 0.02, P= 0.009, respectively). Moreover, we found a strong association between G-EOP and the composite genotype comprising FcgammaRIIIb-NA2 and FcgammaRIIIa-158F (G-EOP versus controls: odds ratio 2.4, 95% CI 1.0-6.0, chi2 = 4.13, P= 0.04).

CONCLUSIONS

This study indicates that the FcgammaRIIIb-NA2 allele and possibly FcgammaRIIIa-158F could be associated with susceptibility to G-EOP in Japanese patients.

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.

A potential role of an intracellular signaling defect in neutrophil functional abnormalities and promotion of tissue damage in patients with localized juvenile periodontitis

Localized juvenile periodontitis is a destructive form of periodontal inflammatory disease which has its onset at puberty. The etiopathology of the disease is still unclear but neutrophils have been suggested to play a major role both in the production and development of the disorder. About 70% of the patients with localized juvenile periodontitis exhibit neutrophil functional abnormalities, such as decreased chemotaxis and phagocytosis. Interestingly, it has been frequently reported that the same hypoactive cells show an enhanced respiratory burst response and increased adhesion. Several possible mechanisms explaining neutrophil anomalies in localized juvenile periodontitis have been proposed. These include the presence of soluble serum factors capable of modulating neutrophil function, altered cell-surface receptor expression and/or function, and a change in the post-receptor signaling events. Recently, a growing evidence has accumulated showing that the diacylglycerol metabolism could be altered in neutrophils from patients with localized juvenile periodontitis. This change, which may be due to a defect in a major diacylglycerol metabolizing enzyme, diacylglycerol kinase, results in enhanced accumulation of diacylglycerol in activated cells. Because diacylglycerol is an endogenous activator of protein kinase C, the increased and prolonged generation of diacylglycerol could lead to abnormal pattern of protein kinase C-regulated neutrophil functions, explaining the parallel hypo- and hyperactivities.

Evidence of an association between functional abnormalities and defective diacylglycerol kinase activity in peripheral blood neutrophils from patients with localized juvenile periodontitis

Peripheral neutrophils from patients with localized juvenile periodontitis (LJP) show functional abnormalities, such as impaired locomotion and enhanced respiratory burst activity. A defect in intracellular signalling mechanism has been proposed to be responsible for some changes, but direct evidence is lacking. In this study we have determined the activity of diacylglycerol (DAG) kinase, an enzyme controlling the DAG/protein kinase C (PKC) pathway, in crude cytosolic and membrane fractions of neutrophils from 5L JP patients and age and gender-matched normal individuals. No difference was observed in the DAG kinase activity in subcellular fractions from unstimulated cells between the 2 groups. When normal neutrophils were stimulated with N formyl-methionyl-leucyl-phenylalanine (FMLP), the enzyme activity was markedly increased in both subcellular fractions. In contrast, neutrophils from 3 of the 5 LJP patients tested completely failed to rise the DAG kinase activity upon chemoattractant stimulation. These data indicate that in some LJP patients the neutrophil DAG kinase may be defective. To examine whether a decrease in DAG kinase activity could account for some neutrophil abnormalities seen in LJP, normal neutrophils were treated with R59022, a DAG kinase inhibitor, that has been shown to reduce DAG kinase activity in human neutrophils. Upon stimulation with FMLP, R59022-treated normal neutrophils showed significantly reduced chemotactic response and enhanced respiratory burst activity, two typical functional abnormalities featured by LJP cells. It is concluded that a defect in DAG kinase may cause, through an abnormal accumulation of the endogenous PKC activator DAG some of the functional changes observed in neutrophils from LJP patients.

Children, adolescents and periodontal diseases

OBJECTIVES

This manuscript attempts to critically review current literature regarding the natural history, aetiology and pathogenesis of the common periodontal diseases to affect children and adolescents. The logic behind the emergence of a new classification in the early 1990s is explained and potential problems with the interpretation of such systems outlined.

DATA SOURCES

The manuscript focuses upon recent developments, reported in the international periodontal literature, aimed at unraveling the molecular basis for this group of diseases. The concept of one disease type progressing with time to another disease within the same individual is discussed, and early data presented that indicate the possibility of microbial transmission from deciduous to permanent dentition's within a subject.

CONCLUSIONS

It is concluded that differing classification systems for adolescent and childhood periodontal diseases may lead to confusion within the dental profession, unless the clinical and molecular basis for such diseases is fully understood. Further advances in basic research using molecular biology tools should assist in our understanding of the aetiopathology at a molecular level and hopefully lead to the development of new treatment strategies.

Generalized prepubertal periodontitis. A report of 4 cases with the immunological findings

The clinical and immunological data from 4 patients with generalized prepubertal periodontitis are presented. The peripheral blood neutrophil chemotaxis was measured using zymosan activated sera as the chemoattractant. All of the 4 patients have shown depressed neutrophil chemotaxis compared to those of the healthy controls. Peripheral blood lymphocyte subpopulations were analysed by double-coloured flow cytometry using monoclonal antibodies for the receptors CD2, CD3, CD4, CD8, CD19, CD29, CD45RA+, 34,29dK, CD56. CD11b/CD18. Lymphocytes bearing CD3 receptors showed a significant decrease compared to those of the controls. Natural killer cells were lowered in 3 of the 4 cases. All of the patients showed a higher increase in CD11b/CD18 expression. The evaluation of CD11b/CD18 receptor in peripheral blood leukocytes may be of help explaining the rôle of neutrophils in the pathogenesis of the disease.

Clinical and immunological findings in 2 siblings with Papillon-Lefèvre syndrome

Rapid and severe destruction of periodontal tissues in early childhood has been reported both in systemically healthy children and in children with systemic disorders. In this study, the clinical and immunological findings of two siblings in a family with Papillon-Lefèvre syndrome are presented. The peripheral blood lymphocytes were analyzed using a double colored flow cytometry and adequate monoclonal antibodies to CD2, CD3, CD4, CD5, CD8, CD11b, CD16, CD19, and HLA-DR receptors. CD11b expression was found to be higher in both siblings (35% and 37%). The elevated CD11b expression may be related to a defect in neutrophils. The expression of natural killer cells was found to be higher in one patient but the results were in normal range. The CD2+, CD3+, CD4+, CD5+, CD8+, and CD19+ lymphocytes were in normal range in both patients. We think that the depressed chemotaxis of peripheral neutrophils, and higher expression of HLA-DR and CD11b molecules in peripheral leukocytes were useful in explaining the pathogenesis of the Papillon-Lefèvre syndrome.

Inhibition of neutrophil and monocyte defensive functions by nicotine

To learn more about the effects of smokeless tobacco on the defensive functions of neutrophils, we studied the influence of nicotine on these cells in vitro, looking at their bactericidal activity against oral pathogens, and at their ability to produce microbicidal reactive oxygen species (oxygen radicals). Exposure of human blood neutrophils to nicotine (0.01% to 0.1%) inhibited their ability to kill Actinomyces naeslundii, Actinobacillus actinomycetemcomitans, and Fusobacterium nucleatum. Although these concentrations of nicotine are high, such concentrations are relevant to phagocytes in the gingival sulcus, because smokeless tobacco contains 0.5% to 3.5% nicotine by dry weight. Nicotine had no such inhibitory effect when the killing assay was performed in an anaerobic environment, implying that nicotine preferentially affected oxygen-dependent killing mechanisms. To further investigate the effects of nicotine on production of oxygen radicals, neutrophils were primed with lipopolysaccharide and triggered with f-met-leu-phe or phorbol ester in the presence of nicotine. Nicotine inhibited production of superoxide anion (measured by reduction of cytochrome c) and hydrogen peroxide (measured by oxidation of phenol red). Nicotine inhibition of superoxide production was reversible by washing away the nicotine. By observing that nicotine inhibited the reduction of cytochrome c by reagent potassium superoxide, we determined that nicotine directly absorbed superoxide. In addition, by examining nicotine inhibition of the uptake of oxygen by neutrophils, we determined that nicotine also interfered with the production of oxygen radicals by these cells. Nicotine also inhibited production of superoxide and interleukin-1 beta by monocytes. Nicotine did not affect the viability of neutrophils and monocytes, as determined by their ability to exclude trypan blue dye. Inhibition of the aerobic antimicrobial functions of neutrophils and monocytes by nicotine may alter the microbial ecology of the oral cavity, and this might be one mechanism by which nicotine compromises the oral health of users of tobacco products.

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 sE-selectin and L-selectin on the regulation of cell migration during chronic periodontitis

Soluble endothelial leukocyte adhesion molecule-1 (sE-selectin) levels in peripheral blood (PB) and gingival capillary blood (GCB) of both healthy donors (HD) and patients with adult periodontitis (AP) were assayed by ELISA. Binding of sE-selectin to polymorphonuclear neutrophils (PMN) from PB, GCB and crevicular fluid (GF), and expression of L-selectin and sialyl-Lewisx (sLex) on these cells were analyzed by immunofluorescence and flow cytometry. No significantly enhanced serum levels of sE-selectin in patients with AP, compared to HD (28 +/- 5 ng/ml vs 19 +/- 3 ng/ml, respectively), and no differences in the concentration of sE-selectin in GCB (16 +/- 1 ng/ml vs 16 +/- 2 ng/ml, respectively) were observed. On PB-PMN no significant differences in the expression of L-selectin and sLex were found and binding of sE-selectin to PB-PMN was comparable between HD and patients with AP. Binding of sE-selectin to GCB-PMN was significantly higher in patients with AP compared to HD (mean channel fluorescence (MCF) = 88.5 +/- 13.2 vs MCF = 24.2 +/- 5.3, respectively). The expression of sLex on GCB-PMN did not differ significantly between the two groups. A significant decrease in the expression of the adhesion molecule L-selectin on GCB-PMNs compared to PB-PMN was found in patients with AP but not in HD. CF-PMN showed decreased expression of both L-selectin and sLex compared to PMN from PB and GCB, both in HD and patients with AP. Taken together, these data suggest that PMN from patients with AP had reduced selectin-mediated adhesive capabilities to inflamed gingival endothelium.

Diacylglycerol in peripheral blood neutrophils from patients with localized juvenile periodontitis

Neutrophils from patients with localized juvenile periodontitis (LJP) show several functional abnormalities. Recently, it has become increasingly apparent that the reason for these changes lies in part at the post receptor level of cellular metabolism. In this study we have analyzed intracellular diacylglycerol (DAG), a second messenger and an endogenous activator of protein kinase C, in unstimulated and agonist-stimulated neutrophils, from five LJP patients showing a chemotaxis defect and matched normal individuals. No difference was observed in the basal cellular DAG between the two groups. In neutrophils from LJP patients the DAG levels increased by 67% and 111% from the basal level following stimulation with N-formyl-methionyl-leucyl-phenylalanine (FMLP) and unopsonized zymosan particles, respectively, while in control cells the mean increases were 36% and 65%, respectively. Incubation with serum-opsonized zymosan particles produced an identical rise in DAG in both groups. These data indicate that the stimulation of receptors for FMLP and unopsonized zymosan may produce an enhanced accumulation of DAG in neutrophils from LJP patients. In addition to DAG mass analysis, we determined the effect of R59022, a DAG-kinase inhibitor, on zymosan-stimulated luminol-amplified chemiluminescence (CL) of neutrophils. In control cells R59022 significantly enhanced unopsonized zymosan induced CL, but it had no effect on cells from LJP patients, suggesting a possible change in the regulation of DAG-kinase in LJP.

Increased respiratory burst activity is associated with normal expression of IgG-Fc-receptors and complement receptors in peripheral neutrophils from patients with juvenile periodontitis

The respiratory burst activity in peripheral neutrophils from nine patients with localized juvenile periodontitis (LJP) and age- and sex-matched healthy controls was studied by measuring the intensity of luminol-enhanced chemiluminescence (CL) induced by unopsonized and three differently opsonized zymosan particles, formyl-methionyl-leucyl-phenylalanine (FMLP) or phorbol myristate acetate (PMA). The neutrophils from LJP patients showed in general more intense CL with all activators than did their controls. Particularly, the CL response induced by unopsonized zymosan particles and FMLP were significantly higher (p < 0.05 and 0.001). When comparisons were made between female LJP patients (n = 6) and matched controls, also serum-opsonized and IgG-opsonized zymosan particles produced CL was significantly increased (p < 0.05). In order to determine whether the elevated CL responses to zymosan particles were due to altered levels of the interacting receptors on neutrophil surface, an immunofluorescence analysis of the expression of IgG-Fc-receptors (FcR) and complement receptors (CR) was performed with flow cytometry. No significant difference in the expression of FcRII, FcRIII, CR1 and CR3 was detected in LJP group compared to controls. Since the elevated CL responses can not be explained by changes in receptor numbers it is hypothesized that the increased respiratory burst activity in LJP may be caused by altered post receptor signalling pathway.