The Early Growth Response Factor-1 Contributes to Interleukin-13 Production by Mast Cells in Response to Stem Cell Factor Stimulation

Targeting glycogen synthase kinase 3 with CHIR99021 negatively regulates allergen-induced mast cell activation

Mast cells are granulated immune sentinels responsible for allergic inflammation. Allergen-induced FcεRI-signaling leads to rapid degranulation in the early-phase and sustained production and release of pro-inflammatory mediators in the late phase. Glycogen synthase kinase 3 (GSK3) is a constitutively active serine/threonine kinase and a central molecular convergence point for several pro-inflammatory pathways. GSK3 inhibition has been shown to reduce inflammation but has not yet been fully characterized in mast cell activation. Therefore, the objective of this study was to evaluate GSK3 as a putative therapeutic target in allergic inflammation using the GSK3 inhibitor, CHIR99021. Here, we found that GSK3 inhibition impaired ROS production and degranulation. Through modulation of MKK4-JNK, c-jun, and NF-κB signaling, GSK3 inhibition reduced the production/release of IL-6, IL-13, TNF, and CCL1, while only the release of CCL2 and CCL3 was impaired. Furthermore, CHIR99021-mediated GSK3 inhibition altered the pro-inflammatory phenotype of mast cells, reducing c-kit receptor levels. This implicated GSK3 in FcεRI signaling, reducing release of IL-6, TNF, and CCL1 when stimulated through FcεRI, while CCL2 and CCL3 remained unaffected, and were increased when stimulated with SCF only. These results identify GSK3 as a potential therapeutic target of utility warranting further consideration in contexts of pathological mast cell activation.

An αvβ3 integrin checkpoint is critical for efficient TH2 cell cytokine polarization and potentiation of antigen-specific immunity

Naive CD4+ T lymphocytes initially undergo antigen-specific activation to promote a broad-spectrum response before adopting bespoke cytokine expression profiles shaped by intercellular microenvironmental cues, resulting in pathogen-focused modular cytokine responses. Interleukin (IL)-4-induced Gata3 upregulation is important for the helper type 2 T cell (TH2 cell) polarization associated with anti-helminth immunity and misdirected allergic inflammation. Whether additional microenvironmental factors participate is unclear. Using whole mouse-genome CRISPR-Cas9 screens, we discovered a previously unappreciated role for αvβ3 integrin in TH2 cell differentiation. Low-level αvβ3 expression by naive CD4+ T cells contributed to pan-T cell activation by promoting T-T cell clustering and IL-2/CD25/STAT5 signaling. Subsequently, IL-4/Gata3-induced selective upregulation of αvβ3 licensed intercellular αvβ3-Thy1 interactions among TH2 cells, enhanced mammalian target of rapamycin (mTOR) signaling, supported differentiation and promoted IL-5/IL-13 production. In mice, αvβ3 was required for efficient, allergen-driven, antigen-specific lung TH2 cell responses. Thus, αvβ3-expressing TH2 cells form multicellular factories to propagate and amplify TH2 cell responses.

The Clusters of Transcription Factors NFATC2, STAT5, GATA2, AP1, RUNX1 and EGR2 Binding Sites at the Induced Il13 Enhancers Mediate Il13 Gene Transcription in Response to Antigenic Stimulation

IL-13 plays a critical role in mediating many biological processes responsible for allergic inflammation. Mast cells express Il13 mRNA and produce IL-13 protein in response to antigenic stimulation. Enhancers are essential in promoting gene transcription and are thought to activate transcription by delivering essential accessory cofactors to the promoter to potentiate gene transcription. However, enhancers mediating Il13 have not been identified. Furthermore, which Il13 enhancers detect signals triggered by antigenic stimulation have not yet been defined. In this study, we identified potential mouse Il13 enhancers using histone modification monomethylation at lysine residue 4 on histone 3 (H3K4me1) chromatin immunoprecipitation sequencing and acetylation at lysine residue 27 on histone 3 (H3K27ac) chromatin immunoprecipitation sequencing. We used Omni-assay for transposase-accessible chromatin sequencing to determine which accessible regions within the potential Il13 enhancers that responded to IgE receptor crosslinking. We also demonstrated that the transcription factor cluster consisting of the NFATC2, STAT5, GATA2, AP1, and RUNX1 binding sites at the proximal Il13 enhancer and the transcription factor cluster consisting of the EGR2 binding site at the distal Il13 E+6.5 enhancer are critical in sensing the signals triggered by antigenic stimulation. Those enhancers, which are responsive to antigenic stimulation and are constitutively active, cooperate to generate greater transcriptional outputs. Our study reveals a novel mechanism underlying how antigenic stimulation induces robust Il13 mRNA expression in mouse mast cells.

Early growth response 1 reduction in peripheral blood involving condylar subchondral bone loss

OBJECTIVES

To detect whether early growth response 1 (EGR1) in peripheral blood leucocytes (PBLs) indicates temporomandibular joint (TMJ) osteoarthritis (OA) lesions.

MATERIALS AND METHODS

Egr1 mRNA expression levels in PBLs were detected in eight malocclusion patients without temporomandibular disorder (TMD) signs and 16 malocclusion patients with clinical TMD signs with (eight) or without (eight) imaging signs of TMJ OA. Twelve 6-week-old rats were randomized to a control group and a unilateral anterior crossbite (UAC) group and were sampled at 4 weeks. The Egr1 mRNA expression levels in PBLs and protein expression levels in different orofacial tissues were measured.

RESULTS

Patients with TMD signs with/without TMJ OA diagnosis showed lower Egr1 mRNA expression levels in PBLs than patients without TMD signs. The lower Egr1 mRNA expression was also found in the PBLs of UAC rats, which were induced to exhibit early histo-morphological signs of TMJ OA lesions. In subchondral bone of UAC rats, EGR1 protein expression was decreased, co-localization of EGR1 with osterix or dentin matrix protein-1 was identified, and the number of EGR1 and osterix double-positive cells was reduced (all p < .05).

CONCLUSION

Egr1 reduction in PBLs potentially indicates subchondral bone OA lesions at an early stage.

Effects of anticholinergic agent on miRNA profiles and transcriptomes in a murine model of allergic rhinitis

Anticholinergic agent, ipratropium bromide (IB) ameliorates symptoms of allergic rhinitis (AR) using neuroimmunologic mechanisms. However, the underlying molecular mechanism remains largely unclear. In the present study, 27 mice with AR induced by ovalbumin were randomly allocated to one of three groups: Model group, model group with IB treatment for 2 weeks, and model group with IB treatment for 4 weeks. Allergic symptoms were evaluated according to symptoms scores. Differentially expressed genes [microRNAs (miRNAs) and messenger RNAs (mRNAs)] of nasal mucosa were identified by microarray analysis. The expression levels of candidate genes were measured by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The data indicates that the symptoms scores in allergic mice were significantly reduced by IB treatment. In the nasal mucosa of allergic mice with IB treatment, 207 mRNAs and 87 miRNAs were differentially expressed, when compared with the sham group. IB treatment significantly downregulated the expression levels of interleukin-4Rα and prostaglandin D2 synthase, whereas the leukemia inhibitory factor, A20 and nuclear receptor subfamily 4, group A, member 1 expression levels were upregulated. Similarly, the expression levels of mmu-miR-124-3p/5p, −133b-5p, −133a-3p/5p, −384-3p, −181a-5p, −378a-5p and −3071-5p were significantly increased. RT-qPCR data further validated these mRNA and miRNA expression levels. Thus, IB treatment regulated expression of allergic immune-associated mRNAs and miRNAs of the nasal mucosa in allergic mice, which may be associated with ameliorated nasal allergic symptoms.

Loss of transcription factor early growth response gene 1 results in impaired endochondral bone repair

Transcription factors that play a role in ossification during development are expected to participate in postnatal fracture repair since the endochondral bone formation that occurs in embryos is recapitulated during fracture repair. However, inherent differences exist between bone development and fracture repair, including a sudden disruption of tissue integrity followed by an inflammatory response. This raises the possibility that repair-specific transcription factors participate in bone healing. Here, we assessed the consequence of loss of early growth response gene 1 (EGR-1) on endochondral bone healing because this transcription factor has been shown to modulate repair in vascularized tissues. Model fractures were created in ribs of wild type (wt) and EGR-1(-/-) mice. Differences in tissue morphology and composition between these two animal groups were followed over 28 post fracture days (PFDs). In wt mice, bone healing occurred in healing phases characteristic of endochondral bone repair. A similar healing sequence was observed in EGR-1(-/-) mice but was impaired by alterations. A persistent accumulation of fibrin between the disconnected bones was observed on PFD7 and remained pronounced in the callus on PFD14. Additionally, the PFD14 callus was abnormally enlarged and showed increased deposition of mineralized tissue. Cartilage ossification in the callus was associated with hyper-vascularity and -proliferation. Moreover, cell deposits located in proximity to the callus within skeletal muscle were detected on PFD14. Despite these impairments, repair in EGR-1(-/-) callus advanced on PFD28, suggesting EGR-1 is not essential for healing. Together, this study provides genetic evidence that EGR-1 is a pleiotropic regulator of endochondral fracture repair.

Mast cell transcription factors--regulators of cell fate and phenotype

Transcription factors have a key role in mast cell differentiation and response of differentiated mast cells to external stimuli. During differentiation of progenitor cells to mast cells, a role for different GATA transcription factors in combination with PU.1 expression and downregulation of C/EBPα has been described. Notch pathway has been proposed to have a role in mast cell development. The microphthalmia-associated transcription factor expression is upregulated in later stages of mast cells differentiation, but it is not expressed in the closely related basophiles. In differentiated mast cells, there is a role for transcription factors both in determining the specific mast cell phenotype and in the response to immune stimuli such as IgE-Ag. A large number of transcription factors, including AP-1 family proteins, microphthalmia-associated transcription factor and STAT5, are modulated by these stimuli. These transcription factors and related protein modulators form a complex transcription factor network. They can form stimuli regulated specific heterodimers and common inhibitors can move from one protein to another. Transcription factors are the key regulators of mast cell physiology. Modulation of key transcription by such means as the therapeutic siRNA may hopefully allow us to modulate mast cell function, obtaining clinical benefit in a variety of diseases. This article is part of a Special Issue entitled: Mast cells in inflammation.