ABSTRACT
Airway epithelial damage, increased Th2 inflammatory response, and impaired immune regulatory T cell function are important mechanisms for the development of asthma.Indoleamine 2, 3-dioxygenase(IDO) is induced by LPS and IFN-γ, which regulates the differentiation of naive T cells into CD4 + CD25 + regulatory T cells(Treg)and induces immune tolerance.It can inhibit eosinophilic airway inflammation.Decreased IDO activity may promote the development of asthma.Tryptophan metabolites act on AhR receptors to promote the production of IL-22 and enhance the integrity of the epithelium and its resistance to infection.The Th17/Treg balance induced by specific immunotherapy could be altered, and Treg cell proliferation was observed.Tryptophan metabolites can reduce airway inflammation and inflammatory cytokine infiltration.D-tryptophan can promote the diversity of intestinal flora, increase the number of Treg in lung and colon, reduce Th2 reaction, and reduce airway hyperresponsiveness.Tryptophan and its metabolites, IDO and D-tryptophan play an important role in the occurrence, development and specific immunotherapy of asthma.
ABSTRACT
Biofilm genesis by Pseudomonas and Staphylococcus sp is associated with biofouling in natural settings. D-Tryptophan (DTrp) inhibits bacterial biofilms and have been proposed for biofouling control applications. In this study, D-Trp significantlyinhibited Pseudomonas mendocina and Staphylococcus aureus cell attachment (biofilm formation) rates on polystyrene96-well microtiter plates in comparison with L-Tryptophan (L-Trp) and mixtures of D-/L-Tryptophan (D-/L-Trp). Theinhibitory effect was greater on P. mendocina, where the rate of cell adherence was declined to 8.7 9 105 cells/h from8.0 9 106 cells/h (control) in P. mendocina. In S. aureus it was declined to 4.2 9 107 cells/h from 9.2 9 107 cells/h(control) at 1 mM concentration. It hindered the intracellular communication and adherence in both the strains, as confirmed by SEM and real time PCR analysis. Addition of D-Trp to preformed biofilms also caused partial disassembly. Intraand interbacterial aggregation were decreased subsequently upon treatment with D-Trp. It repressed the genes involved incell–cell communication, which could be responsible for the diminished biofilm formation of the selected strains. HenceD-Tryptophan has proved to be an effective strategy to control biofilm and may support in the development of surfacecoating technologies.
ABSTRACT
Objective To investigate the effects of D-tryptophan (D-Trp) on the formation of Streptococcus mutans (S. mutans) biofilm and the dispersal of 24 h-old biofilm, and the drug susceptibility of S. mutans against chlorhexidine (CHX) under the role of D-Trp. Methods Optical density assay was used to evaluate the growth curve of S. mutans exposed to 5.0 mmol/L D-Trp for 28 h. The non-treated group was not added with D-Trp. After treatment with 1.0, 2.5 and 5.0 mmol/L D-Trp, crystal violet staining was used to observe the changes of S. mutans biofilm formation in treatment group and non-treatment group. Crystal violet staining and confocal laser scanning microscopy (CLSM) were applied to illustrate the effects of 1.0, 2.5 and 5.0 mmol/L D-Trp on the dispersal of 24 h-old S. mutans biofilm. Resazurin sodium was used to indicate the effect of 5.0 mmol/L D- Trp on the minimum inhibitory concentration (MIC) and the minimum biofilm inhibitory concentration (MBIC) of treatment groups and negative control group. Results The growth curves of planktonic S. mutans within 28 h was consistent in treatment group and the non-treated group, both attained exponential phase after 4 h and reached stationary phase at 22 h. Notably, when compared with non-treated group, the biomass of S. mutans biofilm was increased with time from 0 to 72 h after treatment with 1.0, 2.5 and 5.0 mmol/L D-Trp. And at the same time point, the biomass was significantly less in each subgroup of treatment group than that of non-treated group (P<0.05). Crystal violet staining demonstrated that values of biomass(OD570)were less in treatment groups treated with 1.0, 2.5 and 5.0 mmol/L D-Trp than those of non-treated group (P<0.01). CLSM also showed that bacteria was adhered to the surface of media intreatment groups treated with 1.0, 2.5 and 5.0 mmol/L D-Trp. The values of biomass were lower in treatment groups than those of non-treated group (P<0.01). The MIC against S. mutans was 0.073 mg/L in both experimental group and negative control group. The values of MBIC were 0.293 mg/L and 2.344 mg/L in experimental group and negative control group, respectively. Under the action of 5.0 mmol/L D-Trp, the MBIC of S. mutans was reduced to 1/8. Conclusion Results indicate that D-Trp may inhibit the formation of S. mutans biofilm and promote the dispersal of biofilm already formed. D-Trp may further help CHX exert its bactericidal activity to S. mutans.