Sweet taste receptor agonists attenuate macrophage IL-1β expression and eosinophilic inflammation linked to autophagy deficiency in myeloid cells

BACKGROUND

Eosinophilic inflammation is a hallmark of refractory chronic rhinosinusitis (CRS) and considered a major therapeutic target. Autophagy deficiency in myeloid cells plays a causal role in eosinophilic CRS (ECRS) via macrophage IL-1β overproduction, thereby suggesting autophagy regulation as a potential therapeutic modality. Trehalose is a disaccharide sugar with known pro-autophagy activity and effective in alleviating diverse inflammatory diseases. We sought to investigate the therapeutic potential of autophagy-enhancing agent, trehalose, or related sugar compounds, and the underlying mechanism focusing on macrophage IL-1β production in ECRS pathogenesis.

METHODS

We investigated the therapeutic effects of trehalose and saccharin on macrophage IL-1β production and eosinophilia in the mouse model of ECRS with myeloid cell-specific autophagy-related gene 7 (Atg7) deletion. The mechanisms underlying their anti-inflammatory effects were assessed using specific inhibitor, genetic knockdown or knockout, and overexpression of cognate receptors.

RESULTS

Unexpectedly, trehalose significantly attenuated eosinophilia and disease pathogenesis in ECRS mice caused by autophagy deficiency in myeloid cells. This autophagy-independent effect was associated with reduced macrophage IL-1β expression. Various sugars recapitulated the anti-inflammatory effect of trehalose, and saccharin was particularly effective amongst other sugars. The mechanistic study revealed an involvement of sweet taste receptor (STR), especially T1R3, in alleviating macrophage IL-1β production and eosinophilia in CRS, which was supported by genetic depletion of T1R3 or overexpression of T1R2/T1R3 in macrophages and treatment with the T1R3 antagonist gurmarin.

CONCLUSION

Our results revealed a previously unappreciated anti-inflammatory effect of STR agonists, particularly trehalose and saccharin, and may provide an alternative strategy to autophagy modulation in the ECRS treatment.

Layered Double Hydroxide and Polypeptide Thermogel Nanocomposite System for Chondrogenic Differentiation of Stem Cells

Stem cell therapy for damaged cartilage suffers from low rates of retention, survival, and differentiation into chondrocytes at the target site. To solve these problems, here we propose a two-dimensional/three-dimensional (2D/3D) nanocomposite system. As a new two-dimensional (2D) material, hexagonal layered double hydroxides (LDHs) with a uniform lateral length of 2-3 μm were prepared by a hydrothermal process. Then, tonsil-derived mesenchymal stem cells (TMSCs), arginylglycylaspartic acid-coated LDHs, and kartogenin (KGN) were incorporated into the gel through the thermal-energy-driven gelation of the system. The cells exhibited a tendency to aggregate in the nanocomposite system. In particular, chondrogenic biomarkers of type II collagen and transcription factor SOX 9 significantly increased at both the mRNA and protein levels in the nanocomposite system, compared to the pure thermogel systems. The inorganic 2D materials increased the rigidity of the matrix, slowed down the release of a soluble factor (KGN), and improved cell-material interactions in the gel. The current 2D/3D nanocomposite system of bioactive LDH/thermogel can be a new platform material overcoming drawbacks of hydrogel-based 3D cell culture systems and is eventually expected to be applied as an injectable stem cell therapy.

Autophagy deficiency in myeloid cells exacerbates eosinophilic inflammation in chronic rhinosinusitis

BACKGROUND

Eosinophilic inflammation is a major pathologic feature of chronic rhinosinusitis (CRS) and is frequently associated with severe refractory disease. Prostaglandin (PG) D₂ levels are increased in patients with CRS, and PGD₂ is an important contributing factor to eosinophilic inflammation. Autophagy has a pleiotropic effect on immune responses and disease pathogenesis. Recent studies suggest the potential involvement of autophagy in patients with CRS and the PG pathway.

OBJECTIVE

We sought to investigate whether altered function of autophagy is associated with eosinophilic inflammation and dysregulated production of PGD₂ in patients with CRS.

METHODS

We used myeloid cell-specific deletion of autophagy-related gene 7 (Atg7), which is vital for autophagy, and investigated the effects of impaired autophagy on eosinophilic inflammation in a murine model of eosinophilic chronic rhinosinusitis (ECRS). The effect of autophagy on PGD₂ production and gene expression profiles associated with allergy and the PG pathway were assessed.

RESULTS

We found that impaired autophagy in myeloid cells aggravated eosinophilia, epithelial hyperplasia, and mucosal thickening in mice with ECRS. This aggravation was associated with gene expression profiles that favor eosinophilic inflammation, T_H2 response, mast cell infiltration, and PGD₂ dysregulation. Supporting this, PGD₂ production was also increased significantly by impaired autophagy. Among other myeloid cells, macrophages were associated with autophagy deficiency, leading to increased IL-1β levels. Macrophage depletion or blockade of IL-1 receptor led to alleviation of eosinophilic inflammation and sinonasal anatomic abnormalities associated with autophagy deficiency.

CONCLUSION

Our results suggest that impaired autophagy in myeloid cells, particularly macrophages, has a causal role in eosinophilic inflammation and ECRS pathogenesis.

Molecular Strain Typing of Mycobacterium tuberculosis: a Review of Frequently Used Methods

Tuberculosis, caused by the bacterium Mycobacterium tuberculosis, remains one of the most serious global health problems. Molecular typing of M. tuberculosis has been used for various epidemiologic purposes as well as for clinical management. Currently, many techniques are available to type M. tuberculosis. Choosing the most appropriate technique in accordance with the existing laboratory conditions and the specific features of the geographic region is important. Insertion sequence IS6110-based restriction fragment length polymorphism (RFLP) analysis is considered the gold standard for the molecular epidemiologic investigations of tuberculosis. However, other polymerase chain reaction-based methods such as spacer oligonucleotide typing (spoligotyping), which detects 43 spacer sequence-interspersing direct repeats (DRs) in the genomic DR region; mycobacterial interspersed repetitive units-variable number tandem repeats, (MIRU-VNTR), which determines the number and size of tandem repetitive DNA sequences; repetitive-sequence-based PCR (rep-PCR), which provides high-throughput genotypic fingerprinting of multiple Mycobacterium species; and the recently developed genome-based whole genome sequencing methods demonstrate similar discriminatory power and greater convenience. This review focuses on techniques frequently used for the molecular typing of M. tuberculosis and discusses their general aspects and applications.

Natural Killer Cell Deficits Aggravate Allergic Rhinosinusitis in a Murine Model

OBJECTIVE

Defective innate immune functions can contribute to chronic rhinosinusitis (RS). Recently, it has been reported that chronic RS patients show impaired function of natural killer (NK) cells. We investigated the role of NK cells in eosinophilic inflammation in an allergic RS mouse model.

METHODS

Mice sensitized to ovalbumin (OVA) by intraperitoneal injection received nasal challenges with OVA for 5 weeks. NK cell depletion was achieved by intraperitoneal injections of anti-asialo ganglio-N-tetraosylceramide (ASGM1) antibodies 10 days before OVA sensitization and every 5 days thereafter until sacrifice. Sinonasal complex samples were evaluated histologically, and IL-4, IL-5, IL-13, IFN-γ, MIP-2, and eotaxin levels were measured in the nasal lavage fluid. Differential white blood cell counts were also obtained.

RESULTS

Allergic RS mice showed significantly more eosinophilic inflammation in the sinonasal mucosa, elevated levels of IL-4, IL-5, IL-13, and eotaxin in the nasal lavage fluid, and peripheral blood eosinophilia compared to control mice. The depletion of NK cells by anti-ASGM1 treatment induced more prominent eosinophilic inflammation and increased secretion of IL-5 and peripheral blood eosinophilia in allergic RS mice.

CONCLUSION

The depletion of NK cells aggravates allergen-induced sinonasal eosinophilic inflammation, suggesting that impaired NK cell activity may be an exacerbating factor in eosinophilic chronic RS.

Natural killer cells regulate eosinophilic inflammation in chronic rhinosinusitis

Eosinophils play a major pathologic role in the pathogenesis of diverse inflammatory diseases including chronic rhinosinusitis (CRS). Dysregulated production of prostaglandin (PG), particularly PGD₂, is considered to be an important contributing factor to eosinophilic inflammation in CRS primarily through proinflammatory and chemotactic effects on eosinophils. Here, we provide evidence that PGD₂ can promote eosinophilic inflammation through a suppression of Natural killer (NK) cell effector function and NK cell-mediated eosinophil regulation. Eosinophil apoptosis mediated by NK cells was significantly decreased in CRS patients compared with healthy controls. This decrease was associated with NK cell dysfunction and eosinophilic inflammation. Tissue eosinophils were positively correlated with blood eosinophils in CRS patients. In a murine model of CRS, NK cell depletion caused an exacerbation of blood eosinophilia and eosinophilic inflammation in the sinonasal tissue. PGD₂ and its metabolite, but not PGE₂ and a panel of cytokines including TGF-β, were increased in CRS patients compared with controls. Effector functions of NK cells were potently suppressed by PGD₂-dependent, rather than PGE₂-dependent, pathway in controls and CRS patients. Thus, our results suggest decreased NK cell-mediated eosinophil regulation, possibly through an increased level of PGD₂, as a previously unrecognized link between PG dysregulation and eosinophilic inflammation in CRS.

Comparison of an automated repetitive sequence-based PCR microbial typing system with IS6110-restriction fragment length polymorphism for epidemiologic investigation of clinical Mycobacterium tuberculosis isolates in Korea

Tuberculosis remains a severe public health problem worldwide. Presently, genotyping is used for conducting epidemiologic and clinical studies on tuberculosis cases. We evaluated the efficacy of the repetitive sequence-based PCR (rep-PCR)-based DiversiLab™ system (bioMérieux, France) over the IS6110-restriction fragment length polymorphism analysis for detecting Mycobacterium tuberculosis. In all, 89 clinical M. tuberculosis isolates collected nationwide from Korea were used. The DiversiLab system allocated the 89 isolates to 8 groups with 1 unique isolate when a similarity level of 95% was applied. Seventy-six isolates of the Beijing family and 13 isolates of non-Beijing family strains were irregularly distributed regardless of rep-PCR groups. The DiversiLab system generated a rapid, sensitive, and standardized result. It can be used to conduct molecular epidemiologic studies to identify clinical M. tuberculosis isolates in Korea.

Application of single-nucleotide polymorphism and mycobacterial interspersed repetitive units-variable number of tandem repeats analyses to clinical Mycobacterium tuberculosis isolates from Korea

Background

Single-nucleotide polymorphism (SNP) analysis is a powerful strategy for large-scale molecular population studies examining phylogenetic relationships among bacterial strains. Mycobacterial interspersed repetitive units-variable number of tandem repeats (MIRU-VNTR) can be easily digitized to share data among laboratories. This study applied SNP and MIRU-VNTR analyses for molecular strain typing of Mycobacterium tuberculosis isolates collected throughout Korea.

Methods

We studied 102 clinical M. tuberculosis isolates, including 6 paired strains, collected from 11 university hospitals in Korea in 2008 and 2009. SNPs were detected using hairpin primer assays, and then, MIRU-VNTR analysis was performed.

Results

Thirty-five SNPs contained polymorphisms that helped differentiate the 96 tested isolates. The isolates were classified into 15 clusters. The Beijing family strains were distributed within closely related clusters in the SNP dendrogram. For MIRU-VNTR analysis, the 96 isolates were divided into 12 groups. The discriminatory index in 8 of these groups (MIRU-10, -23, -26, and -31; ETR-A, -B, -C, and -F) was high (Hunter-Gaston diversity index > 0.6). Unlike the SNP method, MIRU-VNTR analysis did not identify any notable localizations of Beijing or non-Beijing family isolates in specific clusters.

Conclusions

SNP and MIRU-VNTR analyses are surrogate molecular strain-typing methods for M. tuberculosis in Korea where Beijing family isolates are predominant.

IS6110-restriction fragment length polymorphism and spoligotyping analysis of Mycobacterium tuberculosis clinical isolates for investigating epidemiologic distribution in Korea

The Beijing family of Mycobacterium tuberculosis has been emerging in the world. However, there are few nationwide data of genotypic distribution in Korea. This study aimed to identify the genotypic diversity of clinical isolates of M. tuberculosis and to demonstrate the population of Beijing family in Korea. We collected 96 clinical M. tuberculosis isolates from 11 university hospitals nationwide in Korea from 2008 to 2009. We observed 24 clusters in IS6110-RFLP analysis and 19 patterns in spoligotyping. Seventy-five isolates were confirmed to be Beijing family. Two isolates of the K strain and 12 isolates of the K family strain were also found. We found that drug resistance phenotypes were more strongly associated with Beijing family than non-Beijing family (P=0.003). This study gives an overview of the distribution of genotypes of M. tuberculosis in Korea. These findings indicate that we have to pay more attention to control of M. tuberculosis strains associated with the Beijing family.

Strain typing of Mycobacterium tuberculosis isolates from Korea by mycobacterial interspersed repetitive units-variable number of tandem repeats

BACKGROUND

Mycobacterium tuberculosis is one of the most clinically significant infectious agents. Especially during mass outbreaks, accurate identification and monitoring are required. The proportion of Beijing family members is very high among infecting strains, and spoligotyping is not suitable for strain typing. Therefore, we studied the homogeneity of isolates using the mycobacterial interspersed repetitive units-variable number of tandem repeats (MIRU-VNTR) method and identified its utility for carrying out molecular epidemiologic analysis.

METHODS

Eighty-one clinical M. tuberculosis isolates that had previously been analyzed by spoligotyping were used in this study. We used the 12 standard MIRU loci and further four exact tandem repeat (ETR) loci (ETR-A, -B, -C, and -F). Four strains each of randomly selected Beijing and Beijing-like families were subjected to IS6110- restriction fragment length polymorphism analysis.

RESULTS

All 81 samples showed amplification products of all VNTR loci, and all of them showed differences in at least one locus. The calculation of the Hunter-Gaston diversity index (HGDI) for MIRU-VNTR gave the value of 0.965. Discriminatory index in the six loci (MIRU-10, -16, -26, -31, -39, and ETR-F) were found to be highly discriminated (HGDI >0.6). Beijing and Beijing-like family isolates were discriminated into different MIRU-VNTR types.

CONCLUSIONS

MIRU-VNTR analysis by using well-selected loci can be useful in discriminating the clinical M. tuberculosis isolates in areas where the Beijing family is predominant.