Proinflammatory and antimicrobial nitric oxide in gingival fluid of diabetic patients with periodontal disease

Endotoxin of Porphyromonas gingivalis amplifies the inflammatory response in hyperglycemia-induced zebrafish through a mechanism involving chitinase-like protein YKL-40 analogs

Porphyromonas gingivalis (P. gingivalis), a key pathogen in periodontal diseases, is also associated with hyperglycemia-associated systemic diseases, including diabetes mellitus (DM). Gingipains are the most important endotoxins of P. gingivalis, and in vivo studies using gingipains are scarce. Zebrafish (Danio rerio) is a vertebrate with high physiological and genetic homology with humans that has multiple co-orthologs for human genes, including inflammation-related proteins. The aim of our study was to determine the effects of gingipain in a hyperglycemia-induced zebrafish model by evaluating inflammation, oxidant-antioxidant status, and the cholinergic system. Adult zebrafish were grouped into the control group (C), hyperglycemia-induced group subjected to 15 days of overfeeding (OF), gingipain-injected group (GP), and gingipain-injected hyperglycemic group (OF + GP). At the end of 15 days, an oral glucose tolerance test (OGTT) was performed, and fasting blood glucose (FBG) levels were measured. Lipid peroxidation (LPO), nitric oxide (NO), glutathione (GSH), glutathione S-transferase, catalase, acetylcholinesterase (AChE), alkaline phosphatase (ALP), and sialic acid (SA) levels were determined spectrophotometrically in the hepatopancreas. The expression levels of tnf-⍺, il-1β, ins, crp, and the acute phase protein YKL-40 analogs chia.5 and chia.6 were evaluated by RT‒PCR. After two weeks of overfeeding, significantly increased weight gain, FBG, and OGTT confirmed that the zebrafish were hyperglycemic. Increased oxidative stress, inflammation, and AChE and ALP activities were observed in both the overfeeding and GP groups. Amplification of inflammation and oxidative stress was evident in the OF + GP group through increased expression of crp, il-1β, chia.5, and chia.6 and increased LPO and NO levels. Our results support the role of gingipains in the increased inflammatory response in hyperglycemia-associated diseases.

Serum nitric oxide concentration in generalized chronic and aggressive periodontitis in the Mexican population is not related to the severity of the disease

Introduction: Periodontitis is an inflammatory disease that affects the supporting tissues of teeth, the effects of excess of nitric oxide, may contribute to the symptoms of periodontitis. Objective: To determine the serum nitric oxide concentration in generalized chronic and aggressive periodontitis patients and to compare it with a healthy subject group from the Mexican population. Materials and methods: A case and control study was performed. Sixty-nine individuals were recruited from the Clínica de Posgrado de Periodoncia of the Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, México. Patients with clinical features of generalized chronic periodontitis (GCP group, n=19), generalized aggressive periodontitis (GAP group, n=11), and a group of healthy subjects (HS group, n=39) were included in the study. Informed consent was obtained from each subject, and serum nitric oxide concentration was measured by an enzyme-linked immunosorbent assay. Results: Nitric oxide concentration in the study groups was greater in the GCP group (462.57 ± 16.57 μmol/L) than in the GAP group (433.84 ± 18.61 μmol/L) and the HS group (422.46 ± 12.07 μmol/L). A comparison using Student’s t-test (one-tailed) between healthy subjects and generalized chronic periodontitis showed borderline significance (p<0.04), whereas no significant differences were observed in HS and GAP groups, with a p-value of 0.64, and the GAP vs. GCP p-value was 0.33. Conclusion: The serum nitric oxide concentration observed in the present study suggests that nitric oxide plays a major role in the inflammatory process, which cannot necessarily be linked to the severity of the disease and periodontal tissue destruction.

Fumarate and nitrite reduction by Prevotella nigrescens and Prevotella buccae isolated from Chronic Periodontitis patients

OBJECTIVE

This study is an investigation of anaerobic nitrite and fumarate reduction/respiration abilities of two characterised Prevotella species namely Prevotella nigrescens (SS6B) and Prevotella buccae (GS6B) isolated from the periodontal pockets of chronic periodontitis (ChP) patients.

METHODS

Isolation and identification of the periodontal bacteria from 20 patients showing clinical symptoms of ChP. Characterisation of anaerobic nitrite and fumarate reduction was done in P. nigrescens (SS6B) and P. buccae (GS6B) using reduction assays, inhibition assays with use of specific inhibitors, growth assays and enzyme activity assays. Degenerate PCR was used to detect and amplify nitrite reductase (nrfA) and fumarate reductase (frdA) gene sequences in these Prevotella isolates. In addition, molecular and in silico analysis of the amplified anaerobic reductase gene sequences was performed using NCBI conserved domain analysis, Interpro database and MegaX.

RESULTS

We provided experimental evidence for presence of active nitrite and fumarate reductase activities through enzyme activity, reduction, inhibitor and growth assays. Moreover, we were able to detect presence of 505 bps nrfA gene fragment and 400 bps frdA gene fragment in these Prevotella spp. These fragments show similarity to multiheme ammonia forming cytochrome c nitrite reductases and fumarate reductases flavoprotein subunit, respectively.

CONCLUSION

Anaerobic nitrite and fumarate respiration abilities in P. nigrescens and P. buccae isolates appear to be important for detoxification process and growth, respectively.

Chlorogenic Acid as a Positive Regulator in LPS-PG-Induced Inflammation via TLR4/MyD88-Mediated NF-κB and PI3K/MAPK Signaling Cascades in Human Gingival Fibroblasts

Gingival inflammation is one of the main causes that can be related to various periodontal diseases. Human gingival fibroblast (HGF) is the major constituent in periodontal connective tissue and secretes various inflammatory mediators, such as nitric oxide (NO) and prostaglandin E₂ (PGE₂), upon lipopolysaccharide stimulation. This study is aimed at investigating the anti-inflammatory mechanism of chlorogenic acid (CGA) on Porphyromonas gingivalis LPS- (LPS-PG-) stimulated HGF-1 cells. The concentration of NO and PGE₂, as well as their responsible enzymes, inducible NO synthase (iNOS), and cyclooxygenase-2 (COX-2), was analyzed by Griess reaction, ELISA, and western blot analysis. LPS-PG sharply elevated the production and protein expression of inflammatory mediators, which were significantly attenuated by CGA treatment in a dose-dependent manner. CGA treatment also suppressed activation of Toll-like receptor 4 (TLR4)/myeloid differentiation primary response gene 88 (MyD88) and nuclear factor- (NF-) κB in LPS-PG-stimulated HGF-1 cells. Furthermore, LPS-PG-induced phosphorylation of extracellular regulated kinase (ERK) and Akt was abolished by CGA treatment, while c-Jun N-terminal kinase (JNK) and p38 did not have any effect. Consequently, these results suggest that CGA ameliorates LPS-PG-induced inflammatory responses by attenuating TLR4/MyD88-mediated NF-κB, phosphoinositide-3-kinase (PI3K)/Akt, and MAPK signaling pathways in HGF-1 cells.

The expression of inducible nitric oxide synthase in the gingiva of rats with periodontitis and diabetes mellitus

OBJECTIVE

To ascertain the role of inducible nitric oxide synthase (iNOS) in the periodontitis response during diabetes.

METHODS

Twenty-four male SD rats were randomly divided into four groups: control group (Control), diabetes mellitus group (D), diabetes mellitus plus periodontitis group (DP), and periodontitis group (P). Periodontitis and diabetes were established separately. Then the gingival tissue and alveolar bone were collected. A stereomicroscope was used to evaluate bone loss. The expression of iNOS, TNF-α, and NF-κB in the gingiva was detected by immunohistochemical staining, real-time PCR, and western blot analysis.

RESULTS

Significant bone loss was observed in the DP and P groups and more extensive bone resorption was discovered in the DP group than in the P group (P < 0.05). The immunohistochemical staining analysis revealed enhanced expression of iNOS located in the gingiva of the three disease groups compared with the control group (P < 0.05). In particular, the level of iNOS was significantly higher in the DP group than in the P group (P < 0.05). This elevated trend of iNOS was further demonstrated by quantitative PCR and western blot analysis. Similarly, the mRNA and protein expression levels of NF-κB in the D, DP, and P groups were significantly higher than those of the control group, as was the level of TNF-α protein (P < 0.05).

CONCLUSIONS

Our results proved diabetes exacerbated alveolar bone resorption in a periodontitis rat model. iNOS may be the inflammatory mediator in the course of periodontal injury promoted by diabetes.

Inducible Nitric Oxide Synthase Polymorphisms and Nitric Oxide Levels in Individuals with Chronic Periodontitis

This study aimed to investigate whether the -1026(A>C)(rs2779249) and +2087(A>G)(2297518) polymorphisms in the NOS2 gene were associated with chronic periodontitis (CP) and with salivary levels of nitrite (NO₂^-) and/or nitrate + nitrite (NOx). A group of 113 mixed-race patients were subjected to periodontal, genetic, and biochemical evaluations (65 CP/48 periodontally healthy subjects). DNA was extracted from oral epithelial cells and used for genotyping by polymerase chain reaction (real-time). Salivary NOx concentrations were determined using an ozone-based chemiluminescence assay. Association of CP with alleles and genotypes of the -1026(A>C) polymorphism was found (X² test, p = 0.0075; 0.0308), but this was not maintained after multiple logistic regression, performed to estimate the effect of covariates and polymorphisms in CP. This analysis demonstrated, after correction for multiple comparisons, that only the female gender was significantly associated with CP. Polymorphisms analyzed as haplotypes were not associated with CP. NOx levels were significantly higher in the control group of heterozygous individuals for both polymorphisms. In conclusion, the female gender was significantly associated with CP, and higher levels of salivary NOx were found in control subjects and associated with the heterozygous state of the NOS2 polymorphisms, reinforcing the potential of NO metabolites as markers of periodontitis status.

Inducible nitric oxide synthase (iNOS) in gingival tissues of chronic periodontitis with and without diabetes: immunohistochemistry and RT-PCR study

BACKGROUND

There is few data concerning the pathogenesis and contribution of inducible nitric oxide synthase (iNOS) in the inflammatory reactions of the periodontium in the course of diabetes. This study evaluated the expression of iNOS in the gingival biopsies of periodontitis patients with and without type 2 diabetes.

METHODS

80 subjects were evaluated in four groups: patients with chronic periodontitis and diabetes, patients with chronic periodontitis, periodontally healthy patients with diabetes, and systemically and periodontally healthy control subjects. Gingival biopsies were subjected to immunohistochemistry as well as reverse transcription polymerase chain reaction (RT-PCR) for determination of iNOS.

RESULTS

All diseased gingival tissues had a significant increase in iNOS expression by immunohistochemistry (P<0.001) compared to controls. There was no significant difference observed between patients with both diabetes and periodontitis and diabetic patients regarding iNOS(+) cells. Meanwhile, these two groups had significantly increased iNOS(+) cells when compared to periodontitis patients (P<0.001). There are significantly higher levels of iNOS mRNA expression of all patient groups compared to controls (P<0.0001). In addition, samples from patients with diabetes and periodontitis showed significantly higher levels of iNOS mRNA expression compared to samples from periodontitis patients and diabetic patients (P<0.0001) yet, without noting statistically significant differences between the latter two groups.

CONCLUSIONS

Although iNOS expression was prominent in the gingiva of patients with diabetes and periodontitis, periodontitis patients and diabetic patients, the higher mRNA for iNOS observed in diabetes and periodontitis may indicate a possible involvement of this mediator in the periodontal destruction of type 2 diabetes.

Comparison of the salivary and the serum nitric oxide levels in chronic and aggressive periodontitis: a biochemical study

BACKGROUND AND OBJECTIVES

Nitric oxide (NO) is a ubiquitous intercellular messenger molecule with important cardiovascular, neurological, and immune functions. In addition, it has been postulated that the pharmacological inhibition of NO or its actions may be therapeutically valuable in the disease management. The levels of nitric oxide may provide clues about the severity and the state of the underlying disease process. It could be an inflammatory biomarker that may enable clinicians to direct the environmentally based prevention or treatment programmes and to establish whether NO plays a role in the pathogenesis of periodontitis or not. Hence, the aim of the present study was to evaluate the salivary and the serum levels of NO in generalized chronic and aggressive periodontitis. The Study Design: Unstimulated whole saliva and serum samples were collected from a total of 60 subjects who were in the age group of 18-45 years, who participated in this study. They were divided into three equal groups with 20 subjects in each group; group A (healthy controls), group B (chronic periodontitis) and group C (aggressive periodontitis). The clinical parameters were assessed, based on the oral hygiene index simplified (OHI-S), the gingival index (GI), the probing pocket depth and the clinical attachment loss (CAL). A biochemical analysis was performed to evaluate and compare the salivary and the serum nitric oxide levels of the above groups. Statistical Analysis and Results: The statistical comparisons were done under the Griess Reaction. There were statistically significant salivary and serum levels of NO in the groups of periodontitis (group B and C) as compared to those in the healthy controls (group A). A significant positive correlation was found between the values of the salivary and the serum NO levels in chronic and aggressive periodontitis.

CONCLUSION

Nitric oxide is a potent modulator of the inflammatory disease processes and under pathological conditions, NO has damaging effects. As there is a paucity in the studies which have compared chronic and aggressive periodontitis, this study paved an interest for combining the serum and the salivary analysis in comparing the levels of nitric oxide in chronic and aggressive periodontitis.

The sociodemographic characteristics, periodontal health status, and subgingival microbiota of patients with chronic periodontitis and type 2 diabetes mellitus: a case-control study in a Chinese population

BACKGROUND

In China, chronic periodontitis (CP) is common in patients with type 2 diabetes mellitus (T2DM). The purpose of this study is to identify the sociodemographic characteristics associated with such patients and to assess the periodontal health status and subgingival microbiota of patients with CP and T2DM (T2DMCP) in the Chinese population.

METHODS

A total of 150 patients with T2DMCP and 306 patients with CP without any systemic disease completed questionnaires, underwent clinical periodontal examinations and participated in diabetes-related parameter examinations. Subgingival plaques were obtained to determine the prevalence and amounts of selected oral bacterial species using polymerase chain reaction (PCR) and real-time PCR, respectively.

RESULTS

The income level and mean body mass index (BMI) of the patients with T2DMCP were significantly higher than those of the patients with CP. Additionally, the patients with T2DMCP were more likely to be urban residents, and they had significantly more severe periodontitis than did the patients with CP. In the patients with T2DMCP, the prevalence and amounts of Treponema denticola and Tannerella forsythia were significantly higher than those in the patients with CP. Finally, compared with the patients with CP, the patients with T2DMCP had a significantly lower prevalence and amount of Prevotella intermedia.

CONCLUSIONS

Compared with the patients with CP, the patients with T2DMCP were more likely to be urban residents and generally had higher incomes, higher mean BMI, and poorer periodontal health status. Higher levels of T. denticola and T. forsythia and lower levels of P. intermedia were identified in the subgingival plaque of the patients with T2DMCP.

Association between periodontitis and salivary nitric oxide metabolites among community elderly Koreans

BACKGROUND

Nitric oxide (NO) is known to play an important role in many biologic systems, although the relationship between NO metabolites and periodontitis remains controversial. Moreover, little evidence of an association between salivary NO (S-NO) and periodontitis in the general population has been reported. This study aims to investigate the relationship between S-NO and periodontitis in an elderly Korean population.

METHODS

A cross-sectional study was conducted using participants and salivary samples from Sunchang Elderly Cohort Study. The total number of final participants was 242 (91 males and 151 females; 48 to 93 years old). Periodontitis was determined by a clinical attachment loss of >6 mm at six probe points on 12 index teeth. NO was measured in unstimulated saliva via the Griess reaction. Sociodemographic status, general/oral health, and health-related behaviors were investigated as confounders. Bivariate analysis and multivariable linear regression analyses including confounders were applied.

RESULTS

After controlling for age, sex, education, salivary flow rate, number of teeth, smoking status, physical activity, hypertension, and diabetes, three metabolites of S-NO (total NO, nitrite, and nitrate) were independently associated with the percentage of probe points exhibiting periodontitis. Of these linear associations, total NO was found to have the strongest correlation with periodontitis (partial r = 0.181, P = 0.009). These associations were most pronounced in females (except for nitrate), non-smokers, those without hypertension, and those without diabetes.

CONCLUSIONS

Our data suggest that high concentrations of S-NO are associated with severe periodontitis. Thus, S-NO may serve as a potential biologic marker for detecting and monitoring periodontitis.

Estimation of nitric oxide as an inflammatory marker in periodontitis

Nitric oxide (NO) is not only important in host defense and homeostasis but it is also regarded as harmful and has been implicated in the pathogenesis of a wide variety of inflammatory and autoimmune diseases. The presence of NO in periodontal disease may reflect the participation of an additional mediator of bone resorption responsible for disease progression. The aim of this study was to assess the level of NO in serum in chronic periodontitis, and correlate these levels with the severity of periodontal disease. Sixty subjects participated in the study and were divided into two groups. NO levels were assayed by measuring the accumulation of stable oxidative metabolite, nitrite with Griess reaction. Results showed subjects with periodontitis had significantly high nitrite in serum than healthy subjects. NO production is increased in periodontal disease, this will enable us to understand its role in disease progression and selective inhibition of NO may be of therapeutic utility in limiting the progression of periodontitis.

Periodontal nitric oxide pathway alteration due to precompetition anxiety in handball players

BACKGROUND

Psychologic and physical stress is known to be related with periodontal disorders. The objective of this study is to investigate salivary and gingival crevicular fluid (GCF) nitric oxide (NO) metabolism and its association with the periodontal reaction to precompetition anxiety in competitive athletes.

METHODS

A total of 18 elite male handball players participated in this study. The anxiety level of participants was determined by using a competitive state anxiety inventory-2 (CSAI-2). Periodontal clinical measurements, saliva, and GCF samples were obtained before the application of the CSAI-2 during the half-season break and just before the league championship match. NO-level, arginase, and NO synthase (NOS) activities were analyzed in saliva samples; NO and basic fibroblast growth factor (FGF-b) levels were analyzed in GCF samples.

RESULTS

The CSAI-2 was significantly different between the two evaluation time points. GCF NO and FGF-b levels increased before the championship match, whereas saliva levels did not change. The plaque index and gingival index (GI) increased at the evaluation just before the championship match. The difference in the GI was statistically significant.

CONCLUSION

The competitive stress of athletes may lead to a gingival/periodontal disturbance accompanied by an altered NO metabolism in saliva and GCF.

Systemic use of selective iNOS inhibitor 1400W or non-selective NOS inhibitor l-NAME differently affects systemic nitric oxide formation after oral Porphyromonas gingivalis inoculation in mice

OBJECTIVE

Nitric oxide synthase (NOS) inhibitors are reported to protect against the local tissue damage in gingivitis and periodontal disease by reducing nitroxidative stress during inflammation, but their systemic effects are not well investigated.

DESIGN

NOS inhibitors systemic effects were investigated in a murine chronic oral inoculation model using live Porphyromonas gingivalis ATCC 33277 (0.3 ml; 10(9)cfu/ml) or sterile broth (0.3 ml). Organ nitric oxide (NO) and plasma nitrite/nitrate (NOx) were determined in mice treated with non-selective NOS inhibitor l-NAME (50mg/kg/24h i.p.) or selective iNOS inhibitor 1400W (10mg/kg/6h i.p.) for the last 5 days of the experiment. Differences between groups were evaluated by nonparametric Wilcoxon's rank-sum one-sided two-sample test and the results compared to those obtained from sham-treated (sterile broth) sham-inoculated animals (water for injection i.p./6h).

RESULTS

Repeated ingestion of P. gingivalis resulted in generalized production of NO in organs and NOx in plasma, the levels of both typically being reduced in P. gingivalis-inoculated-1400W-treated mice, whilst the use of l-NAME was largerly ineffective, even promoting NO/NOx formation. Application of either inhibitor to sham-inoculated animals enhanced NO/NOx formation, due only in part to the repeated i.p. injections.

CONCLUSIONS

The systemic use of 1400W or l-NAME differently affects systemic nitric oxide formation in mice orally challenged with P. gingivalis, but the sequelae of such an intervention should be evaluated further.

Nitric oxide synthase in gingival tissues of patients with chronic periodontitis and with and without diabetes

BACKGROUND

The purpose of this study was to evaluate the expression of inducible nitric oxide synthase (iNOS) in the gingival tissues of periodontitis patients with and without type 2 diabetes to assess whether NO plays a role in the severity of periodontitis in patients with diabetes. Patients with diabetes and healthy patients were used as controls.

METHODS

A total of 80 patients were evaluated in four groups (with 20 subjects each): patients with chronic periodontitis and diabetes (12 males and eight females; mean age, 52.1 +/- 6.9 years), patients with chronic periodontitis who were otherwise healthy (12 males and eight females; mean age, 43.1 +/- 8.9 years), periodontally healthy patients with diabetes (12 males and eight females; mean age 50.9 +/- 6.3 years), and systemically and periodontally healthy control subjects (12 males and eight females; mean age 29.8 +/- 9.2 years). Periodontal parameters were recorded. Immunohistochemistry was used to detect inflammation and iNOS expression in gingival tissues.

RESULTS

Although periodontal parameters were slightly higher in periodontitis compared to diabetic periodontitis, immunohistochemical parameters were higher in diabetic periodontitis compared to periodontitis. All periodontal parameters were higher in patients with periodontitis and with/without diabetes compared to controls and patients with diabetes. All immunohistochemical parameters were higher in patients with diabetes and periodontitis compared to patients with only diabetes or periodontitis, but there was no difference between the latter two groups. There was a correlation between the expression of iNOS and inflammatory cells in controls, patients with diabetes, and patients with periodontitis but not in patients with diabetes and periodontitis.

CONCLUSIONS

Inflammation and iNOS expression were more prominent in the gingiva of the patients with both diabetes and periodontitis. However, iNOS expression did not seem to have an additional detrimental effect on the course of periodontitis in patients with diabetes compared to those with periodontitis alone.

Interleukin-6 released from fibroblasts is essential for up-regulation of matrix metalloproteinase-1 expression by U937 macrophages in coculture: cross-talking between fibroblasts and U937 macrophages exposed to high glucose

Matrix metalloproteinases (MMPs) play a key role in periodontal disease. Although it is known that macrophages and fibroblasts are co-localized and express MMPs in the diseased periodontal tissue, the effect of interaction between these two cell types on MMP expression has not been well elucidated. Furthermore although it is known that diabetes is associated with accelerated periodontal tissue destruction, it remains unknown whether hyperglycemia, a major metabolic abnormality in diabetes, regulates MMP expression by affecting the cross-talking between fibroblasts and macrophages. In this study, human gingival fibroblasts and U937 macrophages were cocultured in a two-compartment transwell culture system, and the cells were treated with normal or high glucose. We found that coculture of fibroblasts and U937 macrophages led to an augmentation of MMP-1 expression by U937 macrophages, and high glucose further enhanced this augmentation. Similar observations were also made in the coculture of fibroblasts and human primary monocytes. We also found that interleukin 6 (IL-6) released by fibroblasts was essential for the augmentation of MMP-1 expression by U937 macrophages. Furthermore our results showed that high glucose, IL-6, and lipopolysaccharide had a synergistic effect on MMP-1 expression. Finally our study indicated that MAPK pathways and activator protein-1 transcription factor were involved in the coculture- and high glucose-augmented MMP-1 expression. In conclusion, this study demonstrates that IL-6 derived from fibroblasts is essential for MMP-1 up-regulation by cross-talking between fibroblasts and U937 macrophages exposed to high glucose, revealing an IL-6-dependent mechanism in MMP-1 up-regulation.

Effect of exogenous nitric oxide on murine immune response induced by Aggregatibacter actinomycetemcomitans lipopolysaccharide

BACKGROUND AND OBJECTIVE

Elevated nitric oxide (NO) has been associated with destructive periodontal disease. The aim of the present study was to test the hypothesis that exogenous NO may inhibit a protective immune response to Aggregatibacter actinomycetemcomitans lipopolysaccharide (LPS) in a murine model.

MATERIAL AND METHODS

Mice of the BALB/c strain were sham immunized, immunized with A. actinomycetemcomitans LPS, treated with S-nitroso-N-acetyl penicillamine (SNAP; a NO donor) and immunized with A. actinomycetemcomitans LPS or treated with SNAP plus 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO) and immunized with A. actinomycetemcomitans LPS. All animals were then challenged subcutaneously with viable A. actinomycetemcomitans. The serum-specific immunoglobulin G (IgG) subclasses and both interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) as well as splenic inducible nitric oxide synthase (iNOS) activity before and after bacterial challenge were assessed. The diameter of skin lesions was determined. Groups of mice were treated with l-N(6)-(1-iminoethyl)-lysine (l-NIL), an iNOS inhibitor, or 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ), a guanylyl cyclase inhibitor, prior to injections with SNAP and/or A. actinomycetemcomitans LPS, and the skin lesions were assessed.

RESULTS

Treatment with SNAP increased the iNOS activity, suppressed both serum-specific IgG2a and IFN-gamma levels, and delayed the healing of the lesions. These SNAP-induced immune alterations were restored by treatment with carboxy-PTIO. Pretreatment with l-NIL resulted in partial healing, whereas pretreatment with ODQ induced a delayed healing of the lesions.

CONCLUSION

The present study suggests that exogenous NO may suppress a protective T helper 1-like murine immune response to A. actinomycetemcomitans LPS by an endogenous NO-independent but a cyclic GMP-dependent mechanism.

Porphyromonas gingivalis, gamma interferon, and a proapoptotic fibronectin matrix form a synergistic trio that induces c-Jun N-terminal kinase 1-mediated nitric oxide generation and cell death

During infection and inflammation, bacterial and inflammatory proteases break down extracellular matrices into macromolecular fragments. Fibronectin fragments are associated with disease severity in arthritis and periodontitis. The mechanisms by which these fragments contribute to disease pathogenesis are unclear. One likely mechanism is that fibronectin fragments induce apoptosis of resident cells, which can be further modulated by nitric oxide. Nitric oxide levels are increased at inflammatory sites in periodontitis patients. The aim of this study was to examine whether a proapoptotic fibronectin matrix (AFn) exerts its action by inducing nitric oxide and whether priming by bacterial and inflammatory components exacerbates this mechanism. Our data demonstrate that AFn increased the levels of nitric oxide and inducible nitric oxide synthase (iNOS) dose and time dependently in periodontal ligament (PDL) cells. These effects and apoptosis were inhibited by iNOS suppression and enhanced by iNOS overexpression. Nitric oxide and iNOS induction were paralleled by increased c-Jun N-terminal kinase 1 (JNK-1) phosphorylation. JNK-1 overexpression enhanced the expression of nitric oxide and iNOS, whereas inhibiting JNK-1 by small interfering RNA or a kinase mutant reversed these findings. Priming PDL cells with Porphyromonas gingivalis, its lipopolysaccharide (LPS), or gamma interferon (IFN-gamma) further increased nitric oxide levels and apoptosis. Escherichia coli and Streptococcus mutans induced lesser effects. Gingival fibroblasts and neutrophils responded to a lesser degree to these stimuli, whereas keratinocytes were resistant to apoptosis. Thus, proapoptotic matrices trigger nitric oxide release via JNK-1, promoting further apoptosis in host cells. LPS and IFN-gamma accentuate this mechanism, suggesting that during inflammation, the affected matrices and bacterial and inflammatory components combined exert a greater pathogenic effect on host cells.