Dipeptidyl peptidase IV and quorum sensing signaling in biofilm-related virulence of Prevotella aurantiaca.

Biofilm formation and dipeptidyl peptidase IV (DPPIV) enzyme activity contribute to the virulence of oral bacteria, and these virulence factors are partly regulated by quorum sensing signaling system. We recently demonstrated that estradiol regulates growth properties and DPPIV activity of Prevotella intermedia, Prevotella nigrescens, and Prevotella pallens. Here, we examined the DPPIV dependency of biofilm formation of Prevotella aurantiaca. Three strains (two clinical strains AHN 37505 and 37552 and the type strain CCUG 57723) were incubated in three estradiol concentrations (30, 90, and 120 nmol/L). Regulation of DPPIV activity, biofilm and fimbria formation, and coaggregation of bacterial strains were analyzed after incubation with four concentrations (10 nM, 100 nM, 1 µM, 10 µM) of dihydroxy-2,3-pentaedione (DPD), the universal precursor of autoinducer -2 (AI-2), and analogs (ethyl-DPD, butyl-DPD, and isobutyl-DPD) for 24 h. Estradiol enhanced the planktonic growth, coaggregation, and biofilm formation of P. aurantiaca strains. The whole cell extract of AHN 37505 had the highest DPPIV activity, followed by CCUG 57723 and AHN 37552. Inhibition of DPPIV activity with di-isopropylfluorophosphate suppressed the effect of estradiol on biofilm formation. At 100 nM and 10 µM concentrations of DPD, butyl DPD, and isobutyl DPD, biofilm formation of P. aurantiaca was significantly inhibited. Fimbriae formation was enhanced up to concentrations of 100 nM and 1 µM followed by a significant inhibition at higher concentrations of DPD and all analogs. A slight but significant inhibitory effect of DPD and analogs on DPPIV activity was observed. Our results indicate that DPPIV plays a key role in the estradiol-regulated biofilm formation of P. aurantiaca. Quorum sensing autoinducer DPD and C1-alkyl analogs could inhibit biofilm-related virulence of P. aurantiaca.

Morphological and functional adaptations of Fusobacterium nucleatum exposed to human neutrophil Peptide-1.

BACKGROUND AND OBJECTIVE: We recently demonstrated that Fusobacterium nucleatum can resist to human neutrophil peptide (HNP)-1 by decreasing its membrane permeability and increasing its proliferation and biofilm formation. In this continuation study, we aimed to further evaluate and explain these resistance properties by determining the morphological and functional adaptations of F. nucleatum, using transmission electron microscopy (TEM). MATERIALS AND METHODS: Cultures of the type strain of F. nucleatum (ssp. nucleatum ATCC 25586) and two clinical strains (ssp. polymorphum AHN 9910 and ssp. nucleatum AHN 9508) were incubated without (0 µg/ml) or with four different test concentrations of recombinant HNP-1 (1, 5, 10 and 20 µg/ml). Membrane morphology and thickness, and cell (visualized by TEM), planktonic growth (measured in colony forming units), and biofilm formation (measured as total mass) were analyzed. Scrambled HNP-1 was used in planktonic growth and biofilm formation studies as a negative control. RESULTS: TEM analyses revealed a decrease in the outer membrane surface corrugations and roughness of the strain AHN 9508 with increasing HNP-1 concentrations. In higher concentrations of HNP-1, the strain AHN 9910 showed thicker outer membranes with a number of associated rough vesicles attached to the outer surface. Intracellular granules became increasingly visible in the strain ATCC 25586 with increasing peptide concentrations. With increased concentrations of HNP-1, planktonic growth of the two clinical strains was significantly enhanced (P < 0.001) and of the type strain significantly suppressed (P < 0.01). HNP-1 decreased the biofilm formation of the two clinical strains, AHN 9910 (P < 0.01) and 9508 (P < 0.001) significantly. Scrambled HNP-1 showed no effect on planktonic growth or biofilm formation of the tested strains. DISCUSSION: F. nucleatum has the ability to withstand the lethal effects of HNP-1, and the ultrastructural changes on bacterial membrane and cytoplasm may play role in this adaptive process.

Commentary on the article 'Understanding Muslim patients: cross-sectional dental hygiene care'.

I have read with interest the article ''Understanding Muslim patients: cross-sectional dental hygiene care'' by ML Sirois et al. In the time that I see their article as a faithful, unbiased image showing a Muslim's religious life and conduct from the oral and systemic health perspective, I still have two main concerns about certain facts which were denoted with imprecise connotations. These are related to food and Ramadan fasting.

Human neutrophil peptide-1 affects matrix metalloproteinase-2, -8 and -9 secretions of oral squamous cell carcinoma cell lines in vitro.

OBJECTIVES: The present study aimed to investigate the effect of HNP-1 on the matrix metalloproteinase (MMP)-2, -8 and -9 secretions of two oral squamous cell carcinoma (OSCC) cell lines (UT-SCC-43A and UT-SCC-43B). DESIGN: In all experiments, the two OSCC cell lines were incubated with graded concentrations (0, 1, 5, and 10 µg/ml) of HNP-1 for 24 and 48 h. Cell viability was measured using a colorimetric proliferation test and cell death was analyzed with a colorimetric cytotoxicity detection kit. Enzyme activity of MMP-2 and MMP-9 was detected by using gelatin zymography, and molecular weight forms of MMP-8 were determined by Western-blot and a densitometric quantitation method. RESULTS: Both cell lines showed a significant increase in LDH toxicity at 24h (UT-SCC-43A: p=0.005 & UT-SCC-43B: p=0.014). Reduced gelatinolytic activities of proMMP-2 were detected in UT-SCC-43B cell line after 24 and 48 h of incubation with HNP-1 (1 µg/ml: p<0.001, 5 µg/ml: p<0.001, and 10 µg/ml: p=0.0225). MMP-8 levels of both cell lines decreased at 200-250 kDa after 24h of incubation, while after 48 h only UT-SCC-43B decreased at 45-50 kDa. CONCLUSIONS: Our results indicate that HNP-1 suppresses the secretion of MMP-2, -8, and -9 in OSCC cell lines.