Summary
The NLRP3 inflammasome, an intracellular sensor consisting of the nucleotide‐binding oligomerization domain‐like receptor family, pyrin domain containing 3 (NLRP3), the adaptor protein ...apoptosis‐associated speck‐like protein containing a caspase‐recruitment domain (ASC), and procaspase‐1, plays critical roles in host defense against microbial pathogens by inducing production of interleukin‐1β (IL‐1β) and IL‐18. Mycoplasma salivarium and Mycoplasma pneumoniae cells activated murine bone marrow‐derived macrophages (BMMs) to induce production of IL‐1α, IL‐1β, and IL‐18. The IL‐1β production‐inducing activities of these mycoplasmas toward BMMs from Toll‐like receptor 2 (TLR2)‐deficient mice were significantly attenuated compared with those from C57BL/6 mice (B6BMMs). This result suggests the possibility that their lipoproteins as TLR2 agonists are involved in the activity. Lipoproteins of M. salivarium and M. pneumoniae (MsLP and MpLP), and the M. salivarium‐derived lipopeptide FSL‐1 induced IL‐1β production by B6BMMs, but not by BMMs from caspase‐1‐, NLRP3‐ or ASC‐deficient mice. The activities of MsLP and MpLP were not downregulated by the proteinase K treatment, suggesting that the active sites are their N‐terminal lipopeptide moieties. B6BMMs internalized the mycoplasmal N‐terminal lipopeptide FSL‐1 at least 30 min after incubation, FSL‐1‐containing endosomes started to fuse with the lysosomes around 2 hours, and then FSL‐1 translocated into the cytosol from LAMP‐1+ endosomes. The artificial delivery of FSL‐1 into the cytosol of B6BMMs drastically enhanced the IL‐1β production‐inducing activity. FSL‐1 as well as the representative NLRP3 inflammasome activator nigericin induced the NLRP3/ASC speck, but FSL‐1 located in a compartment different from the NLRP3/ASC speck.
Summary
Interleukin‐1β (IL‐1β) plays crucial roles in the pathogenesis of periodontal disease. It is produced after the processing of pro‐IL‐1β by caspase‐1, which is activated by the inflammasome‐a ...multiprotein complex comprising nucleotide‐binding domain leucine‐rich repeat‐containing receptor (NLR), the adaptor protein apoptosis‐associated speck‐like protein containing a caspase‐recruitment domain (ASC), and procaspase‐1. Mycoplasma salivarium preferentially inhabits the gingival sulcus and the incidence and number of organisms in the oral cavity increase significantly with the progression of periodontal disease. To initially clarify the association of this organism with periodontal diseases, this study determined whether it induces IL‐1β production by innate immune cells such as dendritic cells or macrophages by using Mycoplasma pneumoniae as a positive control. Both live and heat‐killed M. salivarium and M. pneumoniae cells induced IL‐1β production by XS106 murine dendritic cells as well as pyroptosis. The activities were significantly downregulated by silencing of caspase‐1. Bone‐marrow‐derived macrophage (BMMs) from wild‐type and NLR‐containing protein 3 (NLRP3)‐, ASC‐, and caspase‐1‐deficient mice were examined for IL‐1β production in response to these mycoplasmas. Live M. salivarium and M. pneumoniae cells almost completely lost the ability to induce IL‐1β production by BMMs from ASC‐ and caspase‐1–deficient mice. Their activities toward BMMs from NLRP3‐deficient mice were significantly but not completely attenuated. These results suggest that live M. salivarium and M. pneumoniae cells can activate several types of inflammasomes including the NLRP3 inflammasome. Both M. salivarium and M. pneumoniae cells can activate THP‐1 human monocytic cells to induce IL‐1β production. Hence, the present finding that M. salivarium induces IL‐1β production by dendritic cells and macrophages may suggest the association of this organism with periodontal diseases.
Objective
Roles of aging or immune responses mediated by Toll‐like receptors and natural killer cell in the onset or progression of human candidiasis remain unclear. This study was designed to ...elucidate the roles using peripheral blood mononuclear cells from healthy donors and patients with oral candidiasis.
Subjects and methods
Subjects tested were healthy volunteers and patients who visited Dental Clinical Division of Hokkaido University Hospital. The patients with oral candidiasis included 39 individuals (25–89 years of age) with major complaints on pain in oral mucosa and/or dysgeusia. Healthy volunteers include students (25–35 years of age) and teaching staffs (50–65 years of age) of Hokkaido University Graduate School of Dental Medicine.
Results
Functions of Toll‐like receptors 2 and 4 were downregulated significantly and the natural killer activity was slightly, but not significantly downregulated in aged healthy volunteers compared with healthy young volunteers. Functions of Toll‐like receptors 2 and 4 and the natural killer activity were significantly downregulated in patients with oral candidiasis compared with healthy volunteers.
Conclusion
Downregulation of functions of Toll‐like receptors 2 and 4 as well as natural killer activity is suggested to be associated with the onset or progression of oral candidiasis in human.
The activities to induce TNF-alpha production by a monocytic cell line, THP-1, and ICAM-1 expression and IL-6 production by human gingival fibroblasts were detected in plural membrane lipoproteins of ...Mycoplasma salivarium. Although SDS-PAGE of the lipoproteins digested by proteinase K did not reveal any protein bands with molecular masses higher than approximately10 kDa, these activities were detected in the front of the gel. A lipoprotein with a molecular mass of 44 kDa (Lp44) was purified. Proteinase K did not affect the ICAM-1 expression-inducing activity of Lp44, but lipoprotein lipase abrogated the activity. These results suggested that the proteinase K-resistant and low molecular mass entity, possibly the N-terminal lipid moiety, played a key role in the expression of the activity. The N-terminal lipid moiety of Lp44 was purified from Lp44 digested with proteinase K by HPLC. Judging from the structure of microbial lipopeptides as well as the amino acid sequence and infrared spectrum of Lp44, the structure of the N-terminal lipid moiety of Lp44 was speculated to be S-(2, 3-bisacyloxypropyl)-cysteine-GDPKHPKSFTEWV-. Its analogue, S-(2, 3-bispalmitoyloxypropyl)-cysteine-GDPKHPKSF, was synthesized. The lipopeptide was similar to the N-terminal lipid moiety of Lp44 in the infrared spectrum and the ICAM-1 expression-inducing activity. Thus, this study suggested that the active entity of Lp44 was its N-terminal lipopeptide moiety, the structure of which was very similar to S-(2, 3-bispalmitoyloxypropyl)-cysteine-GDPKHPKSF.
Summary
The chronic hepatitis B virus (HBV) carrier exhibits ongoing replication of HBV and expresses abundant amounts of HBV‐related antigens in the liver. However, HBV‐specific immune responses are ...either absent or narrowly focused in these subjects. With the postulation that impaired functional abilities of liver dendritic cells (DCs) might be responsible for this, we assessed the functions of liver DCs in HBV transgenic mice (HBV‐TM), an animal model of the HBV carrier state. Liver DCs were isolated from normal C57BL/6 mice and HBV‐TM without the use of cytokines or growth factors. Lymphoproliferative assays were conducted to evaluate the ability of liver DCs to induce the proliferation of allogenic T lymphocytes and hepatitis B surface antigen (HBsAg)‐enriched T lymphocytes. Liver DCs were stimulated with viral and bacterial products to assess their cytokine‐producing capacities. In comparison to liver DCs from normal C57BL/6 mice, liver DCs from HBV‐TM exhibited significantly decreased T cell proliferation‐inducing capacities in allogenic mixed leucocyte reaction (P < 0·05) and HBsAg‐enriched T lymphocytes proliferation assays (P < 0·05). Liver DCs from HBV‐TM produced significantly lower levels of interleukin‐12p70, tumour necrosis factor‐alpha, interferon‐gamma, and interleukin‐6 (P < 0·05) compared to liver DCs from normal C57BL/6 mice. This study provides evidence that liver DCs from HBV‐TM had impaired ability to induce both innate and adaptive immune responses. This might account for a weak and almost undetectable HBV‐specific immune response in chronic HBV carriers. This inspires hope that up‐regulation of the functions of liver DCs in situ may have therapeutic implications in chronic HBV carriers.
Summary
This study was designed to determine whether oral streptococci modulate the growth and functions of regulatory T cells. Heat‐killed cells of wild‐type strains of Streptococcus gordonii and ...Streptococcus mutans induced the Toll‐like receptor 2 (TLR2) ‐mediated nuclear factor‐κB (NF‐κB) activation, but their lipoprotein‐deficient strains did not. Stimulation with these streptococci resulted in a significant increase in the frequency of CD4+ CD25+ Foxp3+ regulatory T cells in splenocytes derived from both TLR2+/+ and TLR2−/− mice, but the level of increase in TLR2+/+ splenocytes was stronger than that in TLR2−/− splenocytes. Both strains of S. gordonii enhanced the proliferation of CD4+ CD25+ Foxp3+ regulatory T cells isolated from TLR2+/+ mice at the same level as those from TLR2−/− mice in an interleukin‐2‐independent manner. However, wild‐type and lipoprotein‐deficient strains of both streptococci did not enhance the suppressive activity of the isolated regulatory T cells in vitro, but rather inhibited it. TLR ligands also inhibited the suppressive activity of the regulatory T cells. Inhibition of the suppressive activity was recovered by the addition of anti‐IL‐6 antibody. Pretreatment of antigen‐presenting cells with the NF‐κB inhibitor BAY11‐7082 enhanced the suppressive activity of the regulatory T cells. These results suggested that interleukin‐6 produced by antigen‐presenting cells inhibits the suppressive activity of the regulatory T cells. Wild‐type strain, but not lipoprotein‐deficient strain, of S. gordonii reduced the frequency of CD4+ CD25+ Foxp3+ regulatory T cells in the acute infection model, whereas both strains of S. gordonii increased it in the chronic infection model mice. Hence, this study suggests that oral streptococci are capable of modulating the growth and functions of regulatory T cells in vitro and in vivo.
•IL-1β was induced in DCs and macrophages with C. albicans direct contact.•The induction in DCs was irrespective of the morphology of C. albicans.•The induction in macrophages needed direct contact ...with live C. albicans.•The induction in macrophages needed form change of C. albicans from yeast to hyphae.
The purpose of this study is to elucidate differences in the mechanism of the IL-1β release-inducing activity of Candida albicans toward dendritic cells and macrophages because IL-1β is one of the proinflammatory cytokines which is crucial in host defense against candidiasis.
Two C. albicans strains were used in this study. One strain is uridine-auxotrophic (CAI4) that needs uridine to grow and form hyphae, and another is a strain without any specific auxotrophy (pACT1-GFP), which forms hyphae naturally by culturing with serum components. Murine macrophage and dendritic cell lines were primed with LPS and then stimulated with C. albicans CAI4 or pACT1-GFP.
Both strains of C. albicans induced IL-1β release from dendritic cells, and C. albicans pACT1-GFP induced IL-1β release but CAI4 induced little amounts in macrophages. These differences were suggested to be due to the difference in the amount of extracellular ATP released in the cell culture supernatants induced by C. albicans CAI4 or pACT1-GFP. For induction of IL-1β release from both macrophages and dendritic cells by C. albicans, direct contacts of the microbes with cells were required. In addition, macrophages required morphological change of C. albicans from yeast to hyphae for induction of IL-1β release, whereas dendritic cells did not require it. Dead C. albicans could induce IL-1β release from dendritic cells, but could not from macrophages.
There are different mechanisms by which C. albicans induces IL-1β release from dendritic cells and macrophages.
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