Coronavirus subgenomic minus-strand RNAs and the potential for mRNA replicons

The genome of the porcine transmissible gastroenteritis coronavirus is a plus-strand, polyadenylylated, infectious RNA molecule of approximately 20 kilobases. During virus replication, seven subgenomic mRNAs are generated by what is thought to be a leader-priming mechanism to form a 3'-coterminal nested set. By using radiolabeled, strand-specific, synthetic oligodeoxynucleotide probes in RNA blot hybridization analyses, we have found a minus-strand counterpart for the genome and for each subgenomic mRNA species in the cytoplasm of infected cells. Subgenomic minus strands were found to be components of double-stranded replicative forms and in numbers that surpass full-length antigenome. We propose that subgenomic mRNA replication, in addition to leader-primed transcription, is a significant mechanism of mRNA synthesis and that it functions to amplify mRNAs. It is a mechanism of amplification that has not been described for any other group of RNA viruses. Subgenomic replicons may also function in a manner similar to genomes of defective interfering viruses to lead to the establishment of persistent infections, a universal property of coronaviruses.

Analysis of the steps involved in Dengue virus entry into host cells

The initial steps of dengue viral entry have been divided into adsorption and penetration using acid glycine treatment to inactivate extracellular virus after attachment to baby hamster kidney (BHK) cells but prior to penetration. First, we showed that virus infection was accomplished within 2 h after adsorption. Second, the assay was used to examine the properties of dengue envelope E protein-specific monoclonal antibodies (MAbs), lectins, and heparin. We found that three MAbs, 17-2, 46-9, and 51-3, may neutralize dengue 2 virus (DEN-2) through inhibition of not only viral attachment but also of penetration. However, one MAb, 56-3.1, interfered specifically with attachment. Therefore, the functional domains of E protein involved in attachment and penetration may be different. Moreover, studies with lectins indicated that carbohydrates, especially alpha-mannose residues, present on the virion glycoproteins may contribute to binding and penetration of the virus into BHK and mosquito C6/36 cells. Finally, virus infectivity was inhibited by heparin through its blocking effects at both virus attachment and penetration. This suggests that cell surface heparan sulfate functions in both viral attachment and penetration of DEN-2 virus. In conclusion, our results further elucidated some aspects of the dengue virus entry process.

Eugenol suppressed the expression of lipopolysaccharide-induced proinflammatory mediators in human macrophages

Eugenol is commonly used as an analgesic agent during acute pulpitis and is a major component of root canal sealers. Despite the frequent applications of eugenol in the practice of dentistry, little is known about the role of eugenol under the status of inflammation. This study was aimed to investigate the influence of eugenol on human macrophages (U937) under the stimulation of lipopolysaccharide (LPS). Eugenol was shown to block the release of the bone resorbing mediators, including interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and prostaglandin E2 from LPS-stimulated macrophages. In contrast, eugenol alone did not alter the expression levels of these proinflammatory mediators in macrophages. Consistent with downregulation of bone-resorbing mediators, eugenol suppressed the messenger RNA expression of LPS-induced IL-1beta, TNF-alpha, and cyclooxygenase-2 in macrophages. The results suggest a potential anti-inflammatory effect of eugenol in the acute inflamed pulps and apical periodontitis.

The 9-kDa hydrophobic protein encoded at the 3' end of the porcine transmissible gastroenteritis coronavirus genome is membrane-associated

The open reading frame potentially encoding a 78 amino acid, 9101 Da hydrophobic protein (HP) and, mapping at the 3' end of the porcine transmissible gastroenteritis coronavirus (TGEV) genome, was shown to be expressed during virus replication. The cloned HP gene was placed in a plasmid under control of the T7 RNA polymerase promoter and in vitro translation of transcripts generated in vitro yielded a 9.1-kDa protein that was immunoprecipitable with porcine hyperimmune anti-TGEV serum. Antiserum raised in rabbits against a 31 amino acid synthetic polypeptide that represented the central hydrophilic region of HP specifically immunoprecipitated HP from TGEV-infected cells. HP was further shown to become associated with microsomal membranes during synthesis in vitro and was found to be closely associated with the endoplasmic reticulum and cell surface membranes in infected cells. The intracellular location of HP suggests that it may play a role in the membrane association of replication complexes or in virion assembly.

Structural basis of C3b binding by glycoprotein C of herpes simplex virus

Glycoproteins C (gC) from herpes simplex virus type 1 (HSV-1) and HSV-2, gC-1 and gC-2, bind the human complement fragment C3b, although the two glycoproteins differ in their abilities to act as C3b receptors on infected cells and in their effects on the alternative complement pathway. Previously, we identified three regions of gC-2 (I, II, and III) which are important for C3b binding. In this study, our goal was to identify C3b-binding sites on gC-1 and to continue our analysis of gC-2. We constructed a large panel of mutants by using the cloned gC-1 and gC-2 genes. Most of the mutant proteins were transported to the surface of transiently transfected L cells and reacted with one or more monoclonal antibodies to discontinuous epitopes. By using 31 linker insertion mutants spread across the coding region of gC-1, we identified four regions in the ectodomain of gC-1 which are important for C3b binding, three of which are similar in position to C3b-binding regions I, II, and III of gC-2. Region III shares some similarities with the short consensus repeat found in CR1, the human complement receptor. These were, in part, the targets for construction of 20 single amino acid changes in region III of gC-1 and gC-2. These mutants identified similarities and differences in the C3b-binding properties of gC-1 and gC-2 and suggest that the amino half of region III is more important for C3b binding. However, our results do not support the concept of a structural relationship between the short consensus repeat of CR1 and gC, since mutations of some of the conserved residues, including three of four cysteines in region III, had no effect on C3b binding. Finally, we constructed four deletion mutants of gC-1, including one which lacked residues 33 to 123, as well as residues 367 to 449. This severely truncated molecule, lacking four cysteines and five potential N-linked glycosylation sites, was transported to the cell surface and retained its ability to bind monoclonal antibodies as well as C3b. Thus, the four distinct C3b-binding regions of gC-1 and several epitopes within two different antigenic sites are localized within residues 124 to 366.

The interaction of glycoprotein C of herpes simplex virus types 1 and 2 with the alternative complement pathway

Glycoprotein C (gC) of herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2) binds the human complement fragment C3b, but the two proteins differ in their ability to bind C3b on infected cell surfaces. In addition, gC-1, but not gC-2, accelerates the decay of the alternative pathway C3 convertase, thereby affecting later steps of the complement cascade. Previously, we constructed linker insertion and deletion mutants of gC-1 and gC-2 and used transient transfection to express mutant proteins in uninfected cells. In spite of the differences between gC-1 and gC-2, C3b binding was localized to residues within the central portion of both proteins, encompassing the first four cysteines. For gC-1, deletion mutants lacking amino acids 33 to 123 or 367 to 469 or lacking both regions still bound C3b. We recombined these deleted forms of gC-1 into gC-39, an HSV-1 strain lacking the gC gene. The altered forms of gC-1 were incorporated into virions, expressed on the surface of infected cells, and bound C3b. We used these proteins to investigate the structural basis for the inhibitory action of gC-1 on the complement cascade. We found that gC-1 does not inhibit formation of the alternative pathway C3 convertase. This convertase is stabilized by the serum protein properdin. Purified gC-1, but not gC-2, inhibits the binding of properdin to C3b, suggesting that this destabilizes the convertase. The mutant lacking amino acids 367 to 449 was able to inhibit properdin binding to a limited extent when present at high concentrations, although it bound to C3b more weakly than wild-type gC. In contrast, the protein lacking amino acids 33 to 123 was unable to inhibit properdin binding to C3b. Thus, gC-1 contains two structural domains, one for C3b binding, residues 124 to 366, and another, residues 33 to 133, which interferes with properdin binding to C3b.

Association between betel quid chewing, periodontal status and periodontal pathogens

The present investigation examined whether an association exists between betel quid chewing and signs of periodontal disease and determined the prevalence of Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis by polymerase chain reaction. The periodontal status of 34 betel quid chewers and 32 non-betel quid chewers were compared. A significantly higher prevalence of bleeding on probing was found in betel quid chewers than non-chewers among the subjects with higher plaque level, greater gingival inflammation, deeper probing depth or greater attachment loss. Also, the results suggested that betel quid chewers may harbor higher levels of infection with A. actinomycetemcomitans and P. gingivalis than non-betel quid chewers. The association persists after adjusting for severity of the clinical parameters. In conclusion, betel quid chewing was associated with a higher prevalence of bleeding on probing where higher clinical levels of disease existed, and with a likelihood of subgingival infection with A. actinomycetemcomitans and P. gingivalis.

Association between human herpesviruses and the severity of periodontitis

BACKGROUND

Herpesviruses may play roles in the development of periodontal diseases. The present study evaluated the relationships between herpesviruses and the severity of periodontitis.

METHODS

Periodontal status in terms of gingival inflammation, bleeding on probing, probing depth, and clinical attachment loss of 20 participants was evaluated. The presence of herpes simplex virus (HSV), human cytomegalovirus (HCMV), or Epstein-Barr virus type 1 (EBV-1) in six subgingival plaques from each participant was examined by nested-polymerase chain reaction techniques.

RESULTS

Among the 120 sites examined, the prevalence of HCMV (51.7%) was higher than HSV (30.8%) followed by EBV-1 (4.2%). The prevalence of HSV or HCMV was significantly higher in the subgroups that had lower plaque index (<1). However, the prevalence of HSV was significantly higher in the subgroup that had higher gingival index (> or =2), positive bleeding on probing, deeper probing depth (> or =4 mm), or higher clinical attachment loss (> or =4 mm). Moreover, the prevalence of EBV-1 was significantly higher in the subgroup that had higher probing depth (> or =4 mm). Coinfection of HSV and HCMV was significantly associated with the sites that had higher gingival index (> or =2) or positive bleeding on probing. Coinfection of any two herpesviruses was also associated with higher probing depth (> or =4 mm) or higher clinical attachment loss (> or =4 mm).

CONCLUSIONS

This study demonstrated that HSV is related to the severity of periodontal diseases in terms of clinical attachment loss. Coinfection of any two herpesviruses may also play roles.

PI3K/Akt signaling mediated apoptosis blockage and viral gene expression in oral epithelial cells during herpes simplex virus infection

Phosphatidylinositol 3-kinases (PI3Ks) function in the anti-apoptotic pathway, and are commonly exploited by various viruses to accomplish the viral life cycle. This study examined the role of the PI3K pathway in human oral epithelial cells following herpes simplex virus type 1 (HSV-1) infection. The results showed that HSV-1 induced the phosphorylation of Akt and glycogen synthase kinase 3 (GSK-3). Phosphorylation of Akt, but not GSK-3, induced by HSV-1 was PI3K-dependent. The expression of HSV-1 immediate-early genes may be involved in the initial phosphorylation of Akt and GSK-3. Inhibition of HSV-1-induced PI3K activity increased DNA fragmentation and cleavage of poly ADP-ribose polymerase (PARP), caspase 3 and caspase 7 compared with infected alone. Inhibition of PI3K attenuated the expression of HSV-1-infected cell protein 0 (ICP0), but not thymidine kinase (TK) and viral replication. Collectively, these data suggested that, in oral epithelial cells, the HSV-1-induced PI3K/Akt activation was involved in the regulation of apoptosis blockage and viral gene expression.

Osteoblastic response to collagen scaffolds varied in freezing temperature and glutaraldehyde crosslinking

Collagen sponges are widely used scaffolds in bone engineering. To form bone, the osteoblastic cells undergo proliferation, differentiation, and mineralization stages in the scaffold. Crosslinking and freezing temperature are two important variables in fabricating collagen sponges. The purpose of this study was to examine the osteoblastic responses to collagen sponges prepared with or without glutaraldehyde crosslinking at different freezing temperatures (-20 degrees C or -80 degrees C). MC3T3-E1 osteoblastic cells were cultured in differently prepared sponges. Osteoblastic responses examined included cell numbers, osteocalcin expression, and calcium deposition. Cell numbers were measured by DNA content. Osteocalcin expression was determined by RT-PCR and real-time RT-PCR. Calcium deposition was assayed by ortho-cresophthalein complexone method and von Kossa stain. The osteoblastic cells grown in all collagen sponges did not show apparent signs of cytotoxicity. Collagen sponges differed in freezing temperatures resulted in similar osteoblastic responses. Glutaraldehyde-crosslinked sponges demonstrated less cell-mediated contraction and more cell numbers at day 7 (p < 0.005). However, they showed lower osteocalcin expression at day 7 (p < 0.05) and less calcium deposition at day 21 (p < 0.001). In summary, different freezing temperatures played a minor role in osteoblastic responses. Glutaraldehyde crosslinking process, though improved the dimensional stability of collagen sponges, might compromise the osteoblastic differentiation and mineralization.

The influence of membrane exposure on the outcomes of guided tissue regeneration: clinical and microbiological aspects

The aim of the present study was to evaluate the influence of membrane exposure on guided tissue regeneration (GTR). Thirty patients with 2-wall or 3-wall intraosseous defects were treated with GTR. Periodontal index, gingival index, bleeding on probing, probing depth, clinical attachment level and recession were assessed at the baseline examination, as well as immediately prior to and six months after GTR. The numbers of Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans on the retrieved expanded polytetrafluoroethylene (e-PTFE) membranes were assessed using polymerase chain reaction. The results showed that 26.3% of the membrane exposure sites had zero attachment gain. The membrane exposure sites tended to achieve a smaller clinical attachment gain and had significantly greater marginal tissue recession ( p = 0.006). In addition, the exposed membranes harbored significantly more A. actinomycetemcomitans than the non-exposed membranes (p = 0.029). In conclusion, membrane exposure resulted in a poor GTR outcome. The amount of A. actinomycetemcomitans on the exposed membrane may be a major contributing factor to the outcome of GTR.

Effects of areca nut extracts on the functions of human neutrophils in vitro

Aqueous extracts of ripe areca nut without husk (ripe ANE) and fresh and tender areca nut with husk (tender ANE) were examined for their effects on the defensive functions of human neutrophils. Exposure of peripheral blood neutrophils to ripe ANE and tender ANE inhibited their bactericidal activity against oral pathogens, including Actinobacillus actinomycetemcomitans and Streptococcus mutans, in a dose-dependent manner. At the concentrations tested, ripe and tender ANEs did not significantly affect the viability of neutrophils as verified by their ability to exclude trypan blue dye. However, both ANEs inhibited the production of bactericidal superoxide anion by neutrophils as measured by cytochrome c reduction. Moreover, the ripe ANE inhibited neutrophils more effectively than did tender ANE. Arecoline, a major alkaloid of areca nut, only exhibited an inhibitory effect on the functions of neutrophils when high concentrations were used. Therefore, arecoline could not be used to explain the inhibitory effects observed for ANEs. In conclusion, our results demonstrated that ripe and tender ANEs reduced the antibacterial activity and the superoxide anion production of neutrophils. This effect may contribute to a less efficient elimination of bacteria from the periodontal environment. Inhibition of the antimicrobial functions of neutrophils may alter the microbial ecology of the oral cavity, and this may be one possible mechanism by which areca nut compromises the oral health of users of areca nut products.

Inhibitory effects of tea catechin epigallocatechin-3-gallate against biofilms formed from Streptococcus mutans and a probiotic lactobacillus strain

OBJECTIVE

Effects of tea catechin epigallocatechin-3-gallate (EGCG) against biofilm formation by Streptococcus mutans and probiotic Lactobacillus casei in Yakult^® (LcY) were examined.

DESIGN

Biofilms were formed by S. mutans alone (Sm) and co-culture of S. mutans and LcY (Sm + LcY) in the absence or presence of EGCG. The biomass of biofilms, which were sonicated or not, was measured by the crystal violet assay. Biofilm morphology was observed by scanning electron microscopy. Bacterial viability and extracellular polysaccharides were determined by SYTO9/propidium iodide and dextran-conjugated fluorescein staining, respectively, and confocal microscopy. Gene expression of glucosyltransferase was determined by quantitative polymerase chain reaction.

RESULTS

While 250 μg/ml EGCG significantly decreased the biomass and acid production of Sm biofilms, 500 μg/ml EGCG was required to inhibit Sm + LcY biofilm formation and acid production. EGCG decreased the amount of live bacteria present in both Sm and Sm + LcY biofilms. The level of dead bacteria in Sm + LcY biofilms was higher than in Sm biofilms when formed in the presence of 250 μg/ml EGCG. EGCG decreased levels of extracellular polysaccharides in Sm and Sm + LcY biofilms. The extent of biofilm removal by sonication was not different between Sm and Sm+LcY biofilms formed in the absence or presence of 62.5 or 125 μg/ml EGCG. The level of Sm gtfB and gtfD expression in Sm + LcY biofilms was higher than those in the Sm biofilms when formed in the presence of EGCG at 250 μg/ml.

CONCLUSION

The results indicated that LcY might interfere the inhibitory effects of EGCG against biofilm formation by S. mutans.

Attachment of Periodontal Ligament Cells to Chlorhexidine-Loaded Guided Tissue Regeneration Membranes

BACKGROUND

Early exposure of a guided tissue regeneration (GTR) membrane in the oral cavity results in bacterial contamination, which may lead to failure or incomplete regeneration. Incorporation of antimicrobial agents in GTR membranes may be valuable to control membrane-associated infection during GTR therapy. The purpose of this study was to evaluate whether the incorporation of chlorhexidine into various GTR membranes improves the attachment of periodontal ligament cells in the presence of Actinobacillus actinomycetemcomitans.

METHODS

The possible effects of chlorhexidine on the viability of primary human periodontal ligament (PDL) cells were determined using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide (MTT), which measures cellular metabolic activity. An expanded polytetrafluoroethylene (ePTFE) membrane, glycolide fiber membrane, and collagen membrane were loaded with chlorhexidine and characterized. Attachment of PDL cells to the chlorhexidine-loaded membranes with or without A. actinomycetemcomitans was examined using scanning electron microscopy (SEM) analysis.

RESULTS

Relative cellular viability of PDL cells was reduced to approximately 50% when 15 microg/ml (0.0015%) of chlorhexidine was used. Chlorhexidine released from the coated GTR membranes inhibited the growth of A. actinomycetemcomitans. At the concentration used in this study, chlorhexidine incorporated into the GTR membranes did not interfere with the attachment of PDL cells. The inhibitory effects of A. actinomycetemcomitans on cellular attachment were reduced using chlorhexidine-loaded membranes, including ePTFE, glycolide fiber, and collagen membranes.

CONCLUSIONS

These results suggest that incorporation of chlorhexidine into GTR membranes is beneficial in reducing bacterial effects on cellular attachment. The future application of chlorhexidine-loaded membranes during GTR therapy may be of value.

Permeability of Streptococcus mutans and Actinobacillus actinomycetemcomitans Through guided tissue regeneration membranes and their effects on attachment of periodontal ligament cells

BACKGROUND

Microbial colonization on barrier materials used in guided tissue regeneration (GTR) may adversely affect treatment outcomes. The purposes of this study were: 1) to compare the invasion of Streptococcus mutans and Actinobacillus actinomycetemcomitans through 3 GTR membranes, composed of expanded polytetrafluoroethylene (ePTFE; non-resorbable), a glycolide fiber composite, and type I collagen (both bioabsorbable), and 2) to explore the effects of bacteria on the attachment of periodontal ligament (PDL) fibroblasts onto these membranes.

METHODS

Bacterial permeability was analyzed using a tube capped with a GTR membrane as a septum and filled with media. The tube was then placed in a bigger tube inoculated with S. mutans or A. actinomycetemcomitans. The passage of bacteria through the membranes into the inner tube was monitored. For cellular attachment experiments, primary human PDL cells were placed onto the GTR membranes with or without bacteria. Attached cells were analyzed by scanning electron microscopy (SEM) analysis.

RESULTS

The ePTFE membrane had the best barrier effects followed by the collagen membrane and then the glycolide fiber composite membrane. Moreover, S. mutans passed through these membranes faster than A. actinomycetemcomitans. The attachment of PDL cells on the 3 membranes was also varied. The ePTFE membrane was the worst substrate for PDL fibroblast attachment. Moreover, both bacteria influenced the cellular attachment on the GTR membranes.

CONCLUSIONS

Differences in the behavior of 3 GTR membranes penetrated by S. mutans and A. actinomycetemcomitans were demonstrated. The results suggest that attachment of PDL cells was affected on bacterial-contaminated GTR membranes, which may alter healing following membrane exposure.

Porphyromonas gingivalis GroEL induces osteoclastogenesis of periodontal ligament cells and enhances alveolar bone resorption in rats

Porphyromonas gingivalis is a major periodontal pathogen that contains a variety of virulence factors. The antibody titer to P. gingivalis GroEL, a homologue of HSP60, is significantly higher in periodontitis patients than in healthy control subjects, suggesting that P. gingivalis GroEL is a potential stimulator of periodontal disease. However, the specific role of GroEL in periodontal disease remains unclear. Here, we investigated the effect of P. gingivalis GroEL on human periodontal ligament (PDL) cells in vitro, as well as its effect on alveolar bone resorption in rats in vivo. First, we found that stimulation of PDL cells with recombinant GroEL increased the secretion of the bone resorption-associated cytokines interleukin (IL)-6 and IL-8, potentially via NF-κB activation. Furthermore, GroEL could effectively stimulate PDL cell migration, possibly through activation of integrin α1 and α2 mRNA expression as well as cytoskeletal reorganization. Additionally, GroEL may be involved in osteoclastogenesis via receptor activator of nuclear factor κ-B ligand (RANKL) activation and alkaline phosphatase (ALP) mRNA inhibition in PDL cells. Finally, we inoculated GroEL into rat gingiva, and the results of microcomputed tomography (micro-CT) and histomorphometric assays indicated that the administration of GroEL significantly increased inflammation and bone loss. In conclusion, P. gingivalis GroEL may act as a potent virulence factor, contributing to osteoclastogenesis of PDL cells and resulting in periodontal disease with alveolar bone resorption.

Bacterial penetration through antibiotic-loaded guided tissue regeneration membranes

BACKGROUND

This study compared bacterial penetration through guided tissue regeneration (GTR) membranes impregnated with antibiotics.

METHODS

Three barrier membranes, expanded polytetrafluoroethylene (ePTFE) membrane, collagen membrane, and glycolide fiber composite membrane, were loaded with amoxicillin or tetracycline. The penetration of Streptococcus mutans and Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) through the GTR membranes was achieved using a device consisting of an inner tube and an outer bottle filled with culture media.

RESULTS

The penetration of S. mutans or A. actinomycetemcomitans into the inner tubes significantly decreased with all of the antibiotic-loaded membranes compared to membranes without antibiotics. However, differences were found in the behavior of the three membranes. The antibiotic-loaded ePTFE membranes showed the best barrier effect. Moreover, the inhibitory effect of tetracycline on S. mutans was greater than that of amoxicillin for all GTR membranes. Furthermore, the inhibitory effect of tetracycline on A. actinomycetemcomitans was lower than that of amoxicillin with the glycolide fiber membrane.

CONCLUSIONS

The results showed that penetration of S. mutans and A. actinomycetemcomitans through amoxicillin- or tetracycline-loaded ePTFE membrane, glycolide fiber membrane, and collagen membrane was delayed and/or reduced. Thus, incorporation of an antibiotic into the membrane may be of value when controlling membrane-associated infection during GTR therapy.

Modulation of Phagocytosis, Chemotaxis, and Adhesion of Neutrophils by Areca Nut Extracts

BACKGROUND

A higher prevalence of periodontal diseases among areca chewers than non-areca chewers has been demonstrated. Neutrophils, representing the first line of the host defense mechanism against microbial infection, play important roles in maintaining periodontal health. This study determined the possible effects of areca nut on phagocytosis, chemotaxis, and adhesion of human neutrophils.

METHODS

Aqueous extracts of ripe areca nut without husk (rANE) and fresh and tender areca nut with husk (tANE) were examined for their effects on neutrophil phagocytosis using flow cytometry and confocal laser scanning microscopy. The effects of rANE and tANE on chemotaxis and adhesion of neutrophils to human aortic endothelial cells were examined using fluorescence-labeled neutrophils.

RESULTS

Both rANE and tANE inhibited the phagocytic activity of neutrophils in a dose-dependent manner. The levels of internalized fluorescent bacteria in neutrophils decreased after ANE treatment. However, exposure of neutrophils to rANE and tANE stimulated the chemotaxis activity of neutrophils to N-formyl-Met-Leu-Phe (fMLP) and enhanced adhesion of neutrophils to human aortic endothelial cells in a dose-dependent manner. Moreover, treatment of neutrophils with rANE was more effective than incubation with tANE.

CONCLUSIONS

Components of areca nut inhibited phagocytosis activity of neutrophils but enhanced chemotaxis and adhesion of neutrophils. Alterations in functions of neutrophils may lead to signs of clinical diseases associated with areca chewing. The components in ANEs that are responsible for these observations remain to be elucidated.

Inhibitory Effects of Areca Nut Extracts on Phagocytosis ofActinobacillus actinomycetemcomitansATCC 33384 by Neutrophils

BACKGROUND

Areca quid chewers have a higher prevalence of periodontal disease than non-chewers. Little is known about the influence of areca quid on the immune system. This study was to determine the possible effects of the areca nut on phagocytic activity of human neutrophils.

METHODS

Aqueous extracts of ripe areca nut without husk (rANE), fresh and tender areca nut with husk (tANE), a major alkaloid (arecoline), and a phenolic component ([+]-catechin) of areca nut were examined for their effects on cellular viability using trypan blue exclusion assay. The possible effects on the phagocytic activity of neutrophils against a periodontal pathogen, Actinobacillus actinomycetemcomitans ATCC 33384, were determined using flow cytometry and confocal laser scanning microscopy.

RESULTS

At the concentrations tested, rANE, tANE, arecoline, and (+)-catechin did not significantly affect viability of neutrophils. However, rANE, tANE, arecoline, and (+)-catechin inhibited the phagocytic activity of neutrophils in a dose-dependent manner. Approximately 50% of the relative phagocytic activity of neutrophils was affected when 50 microg/ml of rANE, 400 microg/ml of tANE, 20,000 microg/ml of arecoline, or 2,500 microg/ml of (+)- catechin was used. Decreased levels of internalized fluorescent bacteria were also demonstrated. However, arecoline or (+)-catechin alone could not be used to explain the inhibitory effects observed for rANE and tANE.

CONCLUSIONS

Components of areca nut reduced the uptake of A. actinomycetemcomitans ATCC 33384 by human neutrophils. The inhibition of areca nut on phagocytosis of neutrophils may be one possible mechanism by which the areca nut compromises the periodontal health of areca quid chewers.

Bacterial adhesion to antibiotic-loaded guided tissue regeneration membranes - a scanning electron microscopy study

BACKGROUND/PURPOSE

Bacterial contamination of sites undergoing guided tissue regeneration (GTR) therapy may reduce the efficiency of periodontal regeneration. This study compared bacterial adhesion onto various GTR membranes incorporated with antibiotics.

METHODS

Three barrier membranes, including expanded polytetrafluoroethylene (ePTFE) membrane, collagen membrane, and glycolide fiber membrane, were loaded with tetracycline or amoxicillin. The adhesion of Streptococcus mutans and Aggregatibacter actinomycetemcomitans onto the GTR membranes with or without antibiotics was analyzed using the scanning electron microscopy (SEM) analysis.

RESULTS

The SEM analysis showed no apparent alteration in the physical structure of the membranes loaded with antibiotics. Both S. mutans and A. actinomycetemcomitans attached best on the collagen membranes, followed by the ePTFE membranes, and then the glycolide fiber membranes without antibiotics. Moreover, higher numbers of bacteria were observed on the fibril areas than on the laminar areas of the ePTFE membranes. The amounts of attached bacteria on the GTR membranes increased after longer incubation. Incorporation of tetracycline or amoxicillin greatly reduced the adhesion of S. mutans and A. actinomycetemcomitans onto all of the GTR membranes examined.

CONCLUSION

Incorporation of tetracycline or amoxicillin greatly reduced adhesion of S. mutans or A. actinomycetemcomitans on the ePTFE, glycolide fiber, or collagen membranes. This finding indicates that it is valuable and effective to use the antibiotic-loaded GTR membranes for periodontal regeneration therapy.

Sequences regulating poly(A) site selection within the adenovirus major late transcription unit influence the interaction of constitutive processing factors with the pre-mRNA

The adenovirus major late transcription unit (MLTU) encodes five families of mRNAs, L1 to L5, each distinguished by a unique poly(A) site. Use of the promoter-proximal L1 poly(A) site predominates during early infection, whereas poly(A) site choice shifts to the promoter-distal sites during late infection. A mini-MLTU containing only the L1 and L3 poly(A) sites has been shown to reproduce this processing switch. In vivo analysis has revealed that sequences extending 5' and 3' of the L1 core poly(A) site are required for efficient processing as well as for regulated expression. By replacement of the L1 core poly(A) site with that of the ground squirrel hepatitis virus poly(A) site, we now demonstrate that the L1 flanking sequences can enhance the processing of a heterologous poly(A). Upon recombination of the chimeric L1-ground squirrel hepatitis virus poly(A) site onto the viral chromosome, the L1 flanking sequences were also found to be sufficient to reproduce the processing switch during the course of viral infection. Subsequent in vitro analysis has shown that the L1 flanking sequences function to enhance the stability of binding of cleavage and polyadenylation specificity factor to the core poly(A) site. The impact of L1 flanking sequences on the binding of cleavage and polyadenylation specificity factor suggests that the regulation of the MLTU poly(A) site selection is mediated by the interaction of constitutive processing factors.

Areca nut extracts modulated expression of alkaline phosphatase and receptor activator of nuclear factor kappaB ligand in osteoblasts

OBJECTIVES

Areca chewers have a higher prevalence of periodontal diseases than non-chewers. This study was to determine the possible effects of ripe areca nut extracts (rANE) on viability and gene expression of alkaline phosphatase (ALP), receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) in human osteoblasts.

METHODS

The effects of rANE on cell viability of osteoblast-like MG63 cells were determined using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide (MTT) that measures metabolic activity. Gene expression of ALP, RANKL and OPG was examined using reverse transcription-polymerase chain reaction. ALP activity and RANKL protein were further examined using substrate assay and confocal laser scanning microscopy, respectively.

RESULTS

Relative viability was reduced to approximately 50% when 25 microg/ml of rANE was used. The expression of OPG mRNA in MG63 cells was not altered by rANE. However, decreased levels of mRNA and enzyme activity of ALP were observed. Moreover, the expressions of mRNA and protein of RANKL were stimulated by rANE in a dose-dependent manner.

CONCLUSIONS

The rANE affected morphology and viability of osteoblasts. We also present novel evidence demonstrating that areca nut may compromise the periodontal health of areca chewers by suppression of ALP gene expression and elevation of RANKL gene expression in osteoblasts.

Eugenol Modulates Cyclooxygenase-2 Expression Through the Activation of Nuclear Factor Kappa B in Human Osteoblasts

Because eugenol is a major component of root canal sealers and retrograde filling materials, its effects on periapical bone healing are therefore of concern. In this study, the effects of eugenol on the activation of nuclear factor kappa B (NF-kappaB) and the expression of cyclooxygenase-2 (COX-2) in human osteoblasts were investigated. The results showed that eugenol activated the nuclear translocation of NF-kappaB. In addition, COX-2 protein expression in osteoblasts was induced by eugenol in a dose-dependent manner. Furthermore, the eugenol-modulated COX-2 expression was inhibited by an NF-kappaB inhibitor, N-acetylcysteine. Taken together, eugenol might induce COX-2 expression through the activation of NF-kappaB in human osteoblasts. These results suggest that eugenol might be involved in periapical healing by impairing the functions of osteoblasts.