BTG2 acts as an inducer of muscle stem cell senescence.

BACKGROUND: Muscle aging is associated with muscle stem cell (MuSC) senescence, a process of whose DNA damage accumulation is considered as one of the leading causes. BTG2 had been identified as a mediator of genotoxic and cellular stress signaling pathways, however, its role in senescence of stem cells, including MuSC, remains unknown. METHOD: We first compared MuSCs isolated from young and old mice to evaluate our in vitro model of natural senescence. CCK8 and EdU assays were utilized to assess the proliferation capacity of the MuSCs. Cellular senescence was further assessed at biochemical levels by SA-ß-Gal and γHA2.X staining, and at molecular levels by quantifying the expression of senescence-associated genes. Next, by performing genetic analysis, we identified Btg2 as a potential regulator of MuSC senescence, which was experimentally validated by Btg2 overexpression and knockdown in primary MuSCs. Lastly, we extended our research to humans by analyzing the potential links between BTG2 and muscle function decline in aging. RESULTS: BTG2 is highly expressed in MuSCs from elder mice showing senescent phenotypes. Overexpression and knockdown of Btg2 stimulates and prevents MuSCs senescence, respectively. In humans, high level of BTG2 is associated with low muscle mass in aging, and is a risk factor of aging-related diseases, such as diabetic retinopathy and HDL cholesterol. CONCLUSION: Our work demonstrates BTG2 as a regulator of MuSC senescence and may serve as an intervention target for muscle aging.

Mycobacterium tuberculosis PPE60 antigen drives Th1/Th17 responses via Toll-like receptor 2-dependent maturation of dendritic cells.

Targeting of Mycobacterium tuberculosis (MTB) PE/PPE antigens that induce type 1 helper T cell (Th1) and Th17 responses represents a crucial strategy for the development of tuberculosis (TB) vaccines. However, only a few PE/PPE antigens induce these responses. Here, we sought to determine how the cell wall-associated antigen PPE60 (Rv3478) activates dendritic cell (DC) maturation and T-cell differentiation. We observed that PPE60 induces DC maturation by augmenting the protein expression of cluster of differentiation 80 (CD80) and CD86 and major histocompatibility complex (MHC) class I and MHC class II on the cell surface. PPE60 also stimulated the production of tumor necrosis factor-α (TNFα), interleukin (IL)-1ß, IL-6, IL-12p70, and IL-23p19 but not IL-10. This induction was mediated by Toll-like receptor 2 (TLR2) and followed by activation of p38, c-Jun N-terminal kinase (JNK), and NF-κB signaling. PPE60 enhanced MHC-II expression and promoted antigen processing by DCs in a TLR2-dependent manner. Moreover, PPE60-stimulated DCs directed naïve CD4+ T cells to produce IFN-γ, IL-2, and IL-17A, expanding the Th1 and Th17 responses, along with activation of T-bet and RAR-related orphan receptor C (RORγt) but not GATA-3. Moreover, PPE60 activated the NLRP3 inflammasome followed by caspase-1-dependent IL-1ß and IL-18 synthesis in DCs. Of note, pharmacological inhibition of NLRP3 activation specifically attenuated IFN-γ and IL-17A secretion into the supernatant from CD4+ T cells cocultured with PPE60-activated DCs. These findings indicate that PPE60 induces Th1 and Th17 immune responses by activating DCs in a TLR2-dependent manner, suggesting PPE60's potential for use in MTB vaccine development.

A novel prognostic model based on immunogenic cell death-related genes for improved risk stratification in hepatocellular carcinoma patients.

PURPOSE: Hepatocellular carcinoma (HCC) is a prevalent primary malignant tumor with increasing incidence and mortality rates in recent years. The treatment options for advanced HCC are very limited. Immunogenic cell death (ICD) plays an important role in cancer, in particular immunotherapy. However, the specific ICD genes and their prognostic values in HCC remain to be investigated. METHODS: The TCGA-LIHC datasets were obtained from TCGA database, LIRI-JP datasets were obtained from ICGC database, and immunogenic cell death (ICD) genes datasets were obtained from previous literature. WGCNA analysis identifies ICD-related genes. Functional analysis was used to investigate the biological characteristics of ICD-related genes. Univariate Cox analysis and least absolute shrinkage and selection operator (LASSO) Cox regression analysis was used to select prognostic ICD-related genes and construct a prognostic risk score. Prognostic independence of ICD risk scores was determined by univariate and multivariate Cox regression analyses. A nomogram was then constructed and the diagnostic value was assessed using decision curve analysis. Immune infiltration analysis and drug sensitivity analysis were used to investigate immune cell enrichment and drug response in HCC patients classified as low or high risk based on their risk score. RESULTS: Most of the ICD genes were differentially expressed in normal and HCC patients, and some ICD genes were differentially expressed in different clinical groups. A total of 185 ICD-related genes were identified by WGCNA. Prognostic ICD-related genes were selected using a univariate Cox analysis. A model comprising nine prognosis ICD-related gene biomarkers was developed. Patients was divided into high-risk and low-risk groups, and patients in high-risk groups had poorer outcomes. Meanwhile, the reliability of the model was verified by external independent data. The Independent prognostic value of the risk score in HCC was investigated by univariate and multivariate Cox analyses. Diagnostic nomogram was constructed to predict prognosis. Through immune infiltration analysis, we found that some innate and adaptive immune cells were significantly different between low- and high-risk groups. CONCLUSION: We developed and validated a novel prognostic predictive classification system for HCC based on nine ICD-related genes. In addition, immune-related predictions and model could help predict the outcomes of HCC and could provide a reference for clinical practice.

The Mycobacterium tuberculosis glycoprotein Rv1016c protein inhibits dendritic cell maturation, and impairs Th1 /Th17 responses during mycobacteria infection.

The myobacterial factors and the associated mechanism by which Mycobacterium tuberculosis (Mtb) evades the host immune surveillance system remain widely unexplored. Here, we found that overexpressing Rv1016c, a mannosylated protein of M. tuberculosis in BCG (rBCG-Rv1016c) led to increased virulence of the recombined BCG in the severe-combined immunodeficient (SCID) mice model and to a loss of protective efficacy in a zebrafish-M. marinum model, compared to wild type BCG. Further investigations on the effects of rBCG-Rv1016c on the host innate immunity revealed that rBCG-Rv1016c decreased the production of cytokines IL-2, IL-12p70, TGF-ß, IL-6 as well as of the co-stimulatory molecules CD80, CD86, MHC-I and MHC-II by the infected DCs. These effects were mimicked by rBCG-Rv1016cHis, which carried an extra 6-His tag at the C-terminus of Rv1016c. Relatively to BCG infected DCs, the rBCG-Rv1016c-infected DCs failed to polarize naïve T cells to Th1- and Th17-type cells to secret IFN-γ and IL-17. Additionally, T lymphocytes from BCG- infected mice showed significantly less proliferation and production of IFN-γ and IL-17. Similarly, rBCG-Rv1016c mice released a higher level of IL-10 in response to rBCG-Rv1016c stimulation than wild type BCG infected mice. Furthermore, DCs from TLR-2 knockout mice showed no reduction in IL-6, IL-12 p70 and TGF-ß secretion in response to rBCG-Rv1016c infection, compared to DCs infected with BCG. We propose that Rv1016c interferes in differentiation of the DCs by targeting suppressor of cytokine signaling (SOCS) 1 and SOCS3 expression, which subsequently leads to the reduction in STAT-1 and STAT-6 phosphorylation. These findings open new perspectives regarding the immunosuppressive strategies adopted by Mtb to survive in the host.