Abstract
Bone resorption can be caused by excessive differentiation and/or activation of bone‐resorbing osteoclasts. While microbe‐associated molecular patterns can influence the differentiation and ...activation of bone cells, little is known about the role of lipoteichoic acid (LTA), a major cell wall component of Gram‐positive bacteria, in the regulation of bone metabolism. In this study, we investigated the effect of LTA on bone metabolism using wild‐type
Staphylococcus aureus
and the LTA‐deficient mutant strain. LTA‐deficient
S. aureus
induced higher bone loss and osteoclast differentiation than wild‐type
S. aureus
. LTA isolated from
S. aureus
(SaLTA) inhibited osteoclast differentiation from committed osteoclast precursors in the presence of various osteoclastogenic factors by downregulating the expression of NFATc1. Remarkably, SaLTA attenuated the osteoclast differentiation from committed osteoclast precursors of TLR2
−/−
or MyD88
−/−
mice and from the committed osteoclast precursors transfected with paired immunoglobulin‐like receptor B‐targeting siRNA. SaLTA directly interacted with gelsolin, interrupting the gelsolin‐actin dissociation which is a critical process for osteoclastogenesis. Moreover, SaLTA suppressed the mRNA expression of dendritic cell‐specific transmembrane protein, ATPase H
+
transporting V0 subunit D2, and
Integrin
, which encode proteins involved in cell‐cell fusion of osteoclasts. Notably, LTAs purified from probiotics, including
Bacillus subtilis
,
Enterococcus faecalis
, and
Lactobacillus
species, also suppressed Pam2CSK4‐ or RANKL‐induced osteoclast differentiation. Taken together, these results suggest that LTAs have anti‐resorptive activity through the inhibition of osteoclastogenesis by interfering with the gelsolin‐actin dissociation and may be used as effective therapeutic agents for the prevention or treatment of inflammatory bone diseases.
Dental caries is a biofilm-dependent oral disease and Streptococcus mutans is the known primary etiologic agent of dental caries that initiates biofilm formation on tooth surfaces. Although some ...Lactobacillus strains inhibit biofilm formation of oral pathogenic bacteria, the molecular mechanisms by which lactobacilli inhibit bacterial biofilm formation are not clearly understood. In this study, we demonstrated that Lactobacillus plantarum lipoteichoic acid (Lp.LTA) inhibited the biofilm formation of S. mutans on polystyrene plates, hydroxyapatite discs, and dentin slices without affecting the bacterial growth. Lp.LTA interferes with sucrose decomposition of S. mutans required for the production of exopolysaccharide, which is a main component of biofilm. Lp.LTA also attenuated the biding of fluorescein isothiocyanate-conjugated dextran to S. mutans, which is known to have a high affinity to exopolysaccharide on S. mutans. Dealanylated Lp.LTA did not inhibit biofilm formation of S. mutans implying that D-alanine moieties in the Lp.LTA structure were crucial for inhibition. Collectively, these results suggest that Lp.LTA attenuates S. mutans biofilm formation and could be used to develop effective anticaries agents.
Bone‐resorbing osteoclasts are differentiated from macrophages (MΦ) by M‐CSF and RANKL. MΦ can be mainly classified into M1 and M2 MΦ, which are proinflammatory and anti‐inflammatory, respectively, ...but little is known about their osteoclastogenic potential. Here, we investigated the osteoclastogenic potential of MΦ subtypes. When the two MΦ subtypes were differentiated into osteoclasts using M‐CSF and RANKL, M2 MΦ more potently differentiated into osteoclasts than M1 MΦ. M2 MΦ generated with IL‐4 or IL‐10 also showed enhanced osteoclast differentiation compared with M1 MΦ induced by IFN‐γ and lipopolysaccharide. In addition, robust bone‐resorptive capacity and giant actin rings, which are features of mature osteoclasts, were observed in M2, but not M1 MΦ, under the osteoclast differentiation condition. Osteoclast differentiation was significantly increased in CD206+ M2 MΦ but not in CD86+ M1 MΦ. Compared with M1 MΦ, c‐Fms and RANK were highly expressed in M2 MΦ. Enhanced osteoclastogenesis of M2 MΦ was mediated through sustained ERK activation, followed by efficient c‐Fos and NFATc1 induction. Notably, the osteoclastogenic potential of M1 MΦ converted into M2 MΦ by exposure to M‐CSF was higher than that of M2 MΦ converted into M1 MΦ by exposure to GM‐CSF. Silencing IRF5, which is responsible for M1 MΦ polarization, increased osteoclast differentiation by enhancing c‐Fms expression and activation of ERK, c‐Fos, CREB, and NFATc1, which was inhibited by overexpression of IRF5. Collectively, M2 MΦ are suggested to be more efficient osteoclast precursors than M1 MΦ because of the attenuated expression of IRF5.
M2 MΦ were more potent osteoclast precursors than M1 MΦ. Unlike M1 MΦ, M2 MΦ exhibited a high level of c‐Fms and prolonged ERK activation upon stimulation with M‐CSF. Furthermore, M2 MΦ‐derived osteoclasts showed high bone‐resorptive capacity and giant actin ring formation. Interestingly, decreased IRF5 expression in M2 MΦ contributed to enhanced osteoclastogenic potential through induction of c‐Fms, c‐Fos, NFATc1, and CREB.
Enterococcus faecalis
, a Gram-positive bacterium commonly isolated in patients with refractory apical periodontitis, invades dentin tubules easily and forms biofilms. Bacteria in biofilms, which ...contribute to recurrent and/or chronic inflammatory diseases, are more resistant to antimicrobial agents than planktonic cells and easily avoid phagocytosis. Although
Lactobacillus plantarum
lipoteichoic acid (Lp.LTA) is associated with biofilm formation, the effect of Lp.LTA on biofilm formation by
E. faecalis
is not clearly understood. In this study, we investigated whether Lp.LTA inhibits
E. faecalis
biofilm formation. The degree of biofilm formation was determined by using crystal violet assay and LIVE/DEAD bacteria staining. The quantification of bacterial growth was determined by measuring the optical density at 600 nm with a spectrophotometer. Formation of biofilms on human dentin slices was observed under a scanning electron microscope.
E. faecalis
biofilm formation was reduced by Lp.LTA treatment in a dose-dependent manner. Lp.LTA inhibited biofilm development of
E. faecalis
at the early stage without affecting bacterial growth. LTA from other
Lactobacillus
species such as
Lactobacillus acidophilus, Lactobacillus casei
, or
Lactobacillus rhamnosus
GG also inhibited
E. faecalis
biofilm formation. In particular, among LTAs from various lactobacilli, Lp.LTA showed the highest inhibitory effect on biofilms formed by
E. faecalis
. Interestingly, LTAs from lactobacilli could remove the biofilm preformed by
E. faecalis
. These inhibitory effects were also observed on the surface of human dentin slices. In conclusion, Lactobacillus species LTA inhibits biofilm formation caused by
E. faecalis
and it could be used as an anti-biofilm agent for prevention or treatment against
E. faecalis
-associated diseases.
Enterococci are Gram-positive facultative anaerobic bacteria that colonize the oral cavity and gastrointestinal tract. Enterococcal infections, mainly caused by
Enterococcus faecalis
and
Enterococcus ...faecium
, include apical periodontitis, endocarditis, and bloodstream infections. Recently, vancomycinresistant Enterococci are considered major pathogens that are common but difficult to treat, especially in nosocomial settings. Moreover,
E. faecalis
is closely associated with recurrent endodontic infections and failed endodontic treatment. In this study, we investigated the effects of short-chain fatty acids (SCFAs), acetate, propionate, and butyrate, which are metabolites fermented by gut microbiota, on the growth of Enterococci. Enterococci were cultured in the presence or absence of acetate, propionate, or butyrate, and the optical density at 600 nm was measured to determine bacterial growth. The minimum inhibitory concentration/minimum bactericidal concentration test was conducted. Bacteria were treated with a SCFA, together with clinically used endodontic treatment methods such as triple antibiotics (metronidazole, minocycline, and ciprofloxacin) and chlorhexidine gluconate (CHX) to determine the effects of combination treatment. Of the SCFAs, propionate had a bacteriostatic effect, inhibiting the growth of
E. faecalis
in a dose-dependent manner and also that of clinical strains of
E. faecalis
isolated from dental plaques. Meanwhile, acetate and butyrate had minimal effects on
E. faecalis
growth. Moreover, propionate inhibited the growth of other Enterococci including
E. faecium
. In addition, combination treatment of propionate and triple antibiotics led to further growth inhibition, whereas no cooperative effect was observed at propionate plus CHX. These results indicate that propionate attenuates the growth of Enterococci, suggesting propionate as a potential agent to control Enterococcal infections, especially when combined with triple antibiotics.
Probiotics in livestock feed supplements are considered a replacement for antibiotics that enhance gastrointestinal immunity. Although bacterial cell wall components have been proposed to be ...associated with probiotic function, little evidence demonstrates that they are responsible for probiotic functions in livestock. The present study demonstrated that lipoteichoic acid (LTA) of
(Lp.LTA) confers anti-inflammatory responses in porcine intestinal epithelial cell line, IPEC-J2. A synthetic analog of viral double-stranded RNA, poly I:C, dose-dependently induced IL-8 production at the mRNA and protein levels in IPEC-J2 cells. Lp.LTA, but not lipoprotein or peptidoglycan from
, exclusively suppressed poly I:C-induced IL-8 production. Compared with LTAs from other probiotic
strains including
,
, and
GG, Lp.LTA had higher potential to suppress poly I:C-induced IL-8 production. Dealanylated or deacylated Lp.LTA did not suppress poly I:C-induced IL-8 production, suggesting that D-alanine and lipid moieties in the Lp.LTA structure were responsible for the inhibition. Furthermore, Lp.LTA attenuated the phosphorylation of ERK and p38 kinase as well as the activation of NF-κB, resulting in decreased IL-8 production. Taken together, these results suggest that Lp.LTA acts as an effector molecule to inhibit viral pathogen-induced inflammatory responses in porcine intestinal epithelial cells.
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