Resolving the Contradictory Functions of Lysine Decarboxylase and Butyrate in Periodontal and Intestinal Diseases

Periodontal disease is a common, bacterially mediated health problem worldwide. Mastication (chewing) repeatedly traumatizes the gingiva and periodontium, causing traces of inflammatory exudate, gingival crevicular fluid (GCF), to appear in crevices between the teeth and gingiva. Inadequate tooth cleaning causes a dentally adherent microbial biofilm composed of commensal salivary bacteria to appear around these crevices where many bacteria grow better on GCF than in saliva. We reported that lysine decarboxylase (Ldc) from Eikenella corrodens depletes the GCF of lysine by converting it to cadaverine and carbon dioxide. Lysine is an amino acid essential for the integrity and continuous renewal of dentally attached epithelium acting as a barrier to microbial products. Unless removed regularly by oral hygiene, bacterial products invade the lysine-deprived dental attachment where they stimulate inflammation that enhances GCF exudation. Cadaverine increases and supports the development of a butyrate-producing microbiome that utilizes the increased GCF substrates to slowly destroy the periodontium (dysbiosis). A long-standing paradox is that acid-induced Ldc and butyrate production support a commensal (probiotic) microbiome in the intestine. Here, we describe how the different physiologies of the respective tissues explain how the different Ldc and butyrate functions impact the progression and control of these two chronic diseases

Zinc chloride inhibits lysine decarboxylase production from Eikenella corrodens in vitro and its therapeutic implications

Objectives Dentifrices containing zinc reduce gingival inflammation and bleeding better than control dentifrices (no zinc). How zinc might work is not understood. We have shown that lysine decarboxylase (LdcE), an enzyme from Eikenella corrodens, converts lysine to cadaverine in dental biofilms. The lack of lysine impairs the dentally attached cell barrier to biofilm, causing biofilm products to leak into junctional epithelium and stimulate inflammation. In year-old beagle dogs, immunization with LdcE, induces antibodies that inhibit LdcE activity and retard gingivitis development. We therefore examined whether a zinc-mediated loss of LdcE activity could explain the beneficial effect of zinc dentifrices. Methods We grew E. corrodens in modified tryptic soy broth with or without zinc chloride, and extracted LdcE from the cell surface using a Potter Elvehjem homogenizer. Results Up to 0.96 mM zinc chloride in the bacterial growth medium did not change cell yield, but reduced the extracted protein content by 41 % (R2 = 0.27, p < 0.05) and LdcE activity/mg extracted protein by 85 % (R2 = 0.90, p < 0.001). In extracts from cells grown without zinc, 78 times this zinc chloride concentration (73 mM) was required to reduce LdcE activity by 75 %. Conclusions Zinc ions inhibit the production of protein with LdcE activity at E. corrodens cell surfaces. The zinc ions may attach to cysteine residues that are unique to the N-terminal region of LdcE by interfering with the non-covalent polypeptide assembly that produces enzyme activity. Clinical significance Zinc ion-mediated inhibition of LdcE assembly may provide a rationale for the improved control of gingival inflammation by zinc dentifrices

Bicarbonate Evokes Reciprocal Changes in Intracellular Cyclic di-GMP and Cyclic AMP Levels in Pseudomonas aeruginosa

The formation of Pseudomonas aeruginosa biofilms in cystic fibrosis (CF) is one of the most common causes of morbidity and mortality in CF patients. Cyclic di-GMP and cyclic AMP are second messengers regulating the bacterial lifestyle transition in response to environmental signals. We aimed to investigate the effects of extracellular pH and bicarbonate on intracellular c-di-GMP and cAMP levels, and on biofilm formation. P. aeruginosa was inoculated in a brain–heart infusion medium supplemented with 25 and 50 mM NaCl in ambient air (pH adjusted to 7.4 and 7.7 respectively), or with 25 and 50 mM NaHCO3 in 5% CO2 (pH 7.4 and 7.7). After 16 h incubation, c-di-GMP and cAMP were extracted and their concentrations determined. Biofilm formation was investigated using an xCelligence real-time cell analyzer and by crystal violet assay. Our results show that HCO3− exposure decreased c-di-GMP and increased cAMP levels in a dose-dependent manner. Biofilm formation was also reduced after 48 h exposure to HCO3−. The reciprocal changes in second messenger concentrations were not influenced by changes in medium pH or osmolality. These findings indicate that HCO3− per se modulates the levels of c-di-GMP and cAMP, thereby inhibiting biofilm formation and promoting the planktonic lifestyle of the bacteria

Low Biofilm Lysine Content in Refractory Chronic Periodontitis.

BACKGROUND: Chronic periodontitis is controlled without antibiotics by scaling and root planing (SRP) to remove dental biofilm. We previously reported that the epithelial barrier to bacterial proinflammatory products is impaired when biofilm lysine falls below the minimal content of normal blood plasma. We therefore examined whether low biofilm lysine contents were associated with being refractory and requiring antibiotics to supplement SRP therapy. METHODS: Sixteen periodontitis patients and 6 periodontally healthy volunteers (HV), respective mean ages 57+/-6 and 36+/-8 years, were examined. Periodontitis patients received SRP and surgery, and HV received prophylaxis. At quarterly maintenance/prophylaxis visits during the subsequent year, therapeutic response was good (GR, n=9) or poor (PR, n=7; 5 cigarette smokers). Biofilm cadaverine, lysine and other amino acid (AA) contents were determined by liquid chromatography. Cadaverine mole fraction of lysine plus cadaverine (CF) indicated biofilm lysine decarboxylase activity. RESULTS: Biofilm lysine was 0.19+/-0.10 and 0.20+/-0.09 mumol/mg in GR and HV, but 0.07+/-0.03 mumol/mg in PR (Kruskal-Wallis p< 0.01). All AAs were depleted in biofilm from smokers, but only lysine in biofilm from non-smokers. CF was inversely associated with clinical attachment level (CAL) at baseline before therapy in all patients (R2=0.28, p<0.01) and with CAL change after therapy in GR (R2=0.49, p<0.05). Lysine and cadaverine contents discriminated PR from GR and HV (Wilks' Lambda=0.499, p <0.012). CONCLUSIONS: Refractory responses requiring antibiotic therapy result from smoking and/or microbial infections that starve the biofilm and epithelial attachment of lysine. Biofilm CF associates with periodontitis severity pre-therapy and extent of therapeutic response post-therapy

Effect of dentin powder on the antimicrobial properties of hyperpure chlorine-dioxide and its comparision to conventional endodontic disinfecting agents

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Genetic Control of GCF Exudation: Innate Immunity Genes and Periodontitis Susceptibility

Chronic periodontitis is a bacterial infection associated with dentally adherent biofilm (plaque) accumulation and age-related comorbidities. The disease begins as an inflammatory exudate from gingival margins, gingival crevicular fluid (GCF) in response to biofilm lysine. After a week of experimental gingivitis (no oral hygiene), biofilm lysine concentration was linearly related to biofilm accumulation (plaque index) but to GCF as an arch-shaped double curve which separated 9 strong from 6 weak GCF responders (hosts). Host DNA was examined for single nucleotide polymorphisms (SNPs) of alleles reported in 7 periodontitis-associated genes. Across all 15 hosts, an adenine SNP (A) at IL1B-511 (rs16944), was significant for strong GCF (Fisher’s exact test, p p < 0.01). Together with homozygous alternate or reference SNPs at IL10-1082 or CD14-260 in 4 hosts, all hosts were identified as strong or weak GCF responders. The GCF response is therefore a strong or weak genetic trait that indicates strong or weak innate immunity in EG and controllable or uncontrollable periodontal disease, dental implant survival and late-life comorbidities