Publications

Author response: The autophagy protein ATG14 safeguards against unscheduled pyroptosis activation to enable embryo transport during early pregnancy

No abstract is provided for this article.

Toll-like receptor 2 (TLR2) and dectin-1 contribute to the production of IL-12p40 by bone marrow-derived dendritic cells infected with Penicillium marneffei

The present study was designed to elucidate the role of TLR2, TLR4 and dectin-1 in the production of IL-12p40 by bone marrow-derived dendritic cells (BM-DCs) infected with Penicillium marneffei. IL-12p40 production was almost completely abrogated in BM-DCs from TLR2 gene-knockout (KO) and MyD88KO mice, but not from TLR4-defective C3H/HeJ mice compared to those from control mice. Furthermore, BM-DCs from dectin-1KO mice faintly produced IL-12p40 upon stimulation with this fungus. Using a luciferase reporter assay, P. marneffei activated NF-κB in HEK293 cells transfected with the TLR2 gene, but not with the dectin-1 gene, and their co-transfection did not lead to further increase in this response. These results indicate that TLR2 and dectin-1 are essential in sensing P. marneffei for the activation of BM-DCs.

Muramyl Dipeptide Induces NOD2-Dependent Ly6Chigh Monocyte Recruitment to the Lungs and Protects Against Influenza Virus Infection

Bacterial peptidoglycan-derived muramyl dipeptide (MDP) and derivatives have long-recognized antiviral properties but their mechanism of action remains unclear. In recent years, the pattern-recognition receptor NOD2 has been shown to mediate innate responses to MDP. Here, we show that MDP treatment of mice infected with Influenza A virus (IAV) significantly reduces mortality, viral load and pulmonary inflammation in a NOD2-dependent manner. Importantly, the induction of type I interferon (IFN) and CCL2 chemokine was markedly increased in the lungs following MDP treatment and correlated with a NOD2-dependent enhancement in circulating monocytes. Mechanistically, the protective effect of MDP could be explained by the NOD2-dependent transient increase in recruitment of Ly6Chigh "inflammatory" monocytes and, to a lesser extent, neutrophils to the lungs. Indeed, impairment in both Ly6Chigh monocyte recruitment and survival observed in infected Nod2-/- mice treated with MDP was recapitulated in mice deficient for the chemokine receptor CCR2 required for CCL2-mediated Ly6Chigh monocyte migration from the bone marrow into the lungs. MDP-induced pulmonary monocyte recruitment occurred normally in IAV-infected and MDP-treated Ips-1-/- mice. However, IPS-1 was required for improved survival upon MDP treatment. Finally, mycobacterial N-glycolyl MDP was more potent than N-acetyl MDP expressed by most bacteria at reducing viral burden while both forms of MDP restored pulmonary function following IAV challenge. Overall, our work sheds light on the antiviral mechanism of a clinically relevant bacterial-derived compound and identifies the NOD2 pathway as a potential therapeutic target against IAV.

Duet is a novel serine/threonine kinase with Dbl-Homology (DH) and Pleckstrin-Homology (PH) domains

We show here the identification of Duet, a novel molecule bearing serine/threonine kinase, Dbl-Homology (DH), and Pleckstrin-Homology (PH) domains. The kinase domain of Duet shows a homology to that of DAP kinase that is involved in apoptosis, and Duet is autophosphorylated by an in-vitro kinase assay. The DH- and PH-domains are closely related to those of Trio and Kalirin. Duet mRNA is specifically expressed in skeletal muscle. Duet protein was localized to actin-associated cytoskeletal elements. These data suggest a role of Duet in the cytoskeleton-dependent cell function.

Multi-functional roles of Stat3 revealed by conditional gene targeting.

Innate immunity

No abstract is provided for this article.

CCAAT/Enhancer-Binding Protein Homologous Protein (CHOP) Regulates Osteoblast Differentiation

Differentiation of committed osteoblasts is controlled by complex activities involving signal transduction and gene expression, and Runx2 and Osterix function as master regulators for this process. Recently, CCAAT/enhancer-binding proteins (C/EBPs) have been reported to regulate osteogenesis in addition to adipogenesis. However, the roles of C/EBP transcription factors in the control of osteoblast differentiation have yet to be fully elucidated. Here we show that C/EBP homologous protein (CHOP; also known as C/EBPζ) is expressed in bone as well as in mesenchymal progenitors and primary osteoblasts. Overexpression of CHOP reduces alkaline phosphatase activity in primary osteoblasts and suppresses the formation of calcified bone nodules. CHOP-deficient osteoblasts differentiate more strongly than their wild-type counterparts, suggesting that endogenous CHOP plays an important role in the inhibition of osteoblast differentiation. Furthermore, endogenous CHOP induces differentiation of calvarial osteoblasts upon bone morphogenetic protein (BMP) treatment. CHOP forms heterodimers with C/EBPβ and inhibits the DNA-binding activity as well as Runx2-binding activity of C/EBPβ, leading to inhibition of osteocalcin gene transcription. These findings indicate that CHOP acts as a dominant-negative inhibitor of C/EBPβ and prevents osteoblast differentiation but promotes BMP signaling in a cell-type-dependent manner. Thus, endogenous CHOP may have dual roles in regulating osteoblast differentiation and bone formation.

Faculty Opinions recommendation of Negative regulation of the NLRP3 inflammasome by A20 protects against arthritis.

StreptococcusResponse to Group B Role of Lipoteichoic Acid in the

No abstract is provided for this article.

Recognition of RNA virus by RIG-I results in activation of CARD9 and inflammasome signaling for interleukin 1β production

No abstract is provided for this article.

Papillomavirus-Like Particles Stimulate Murine Bone Marrow-Derived Dendritic Cells To Produce Alpha Interferon and Th1 Immune Responses via MyD88

Dendritic cells (DCs) link innate and adaptive immunity by sensing pathogens or vaccinogens and signaling a variety of defense responses. Since human papillomavirus type 16 L1 virus-like particles (HPV16 VLPs) induce a potent, protective immune response after vaccination, we examined their recognition by DCs. HPV16 VLPs cause phenotypic maturation of murine bone marrow-derived DCs (BMDCs), and immunization of mice with HPV16 VLP-loaded BMDCs or HPV16 VLPs alone induced T helper 1 (Th1)-biased immune responses. Analysis of transcriptional responses of murine BMDCs by microarray suggested that alpha/beta interferon (IFN-α/β) transcripts and numerous proinflammatory cytokines and chemokines are up regulated in response to HPV16 VLPs. Indeed, the induction of IFN-α, IFN-γ, and interleukin-12 (IL-12) production by BMDCs after stimulation with HPV16 VLPs was demonstrated by quantitative enzyme-linked immunosorbent assay. Many microbial products that induce proinflammatory responses are recognized via Toll-like receptor (TLR) signaling through the key adaptor protein MyD88 and activation of NF-κB, nuclear factor of activated T cells (NF-AT), and activating protein 1 (AP-1). Reporter assays indicated that HPV16 VLPs activated NF-κB-, NF-AT-, and AP-1-dependent transcription in the RAW264.7 macrophage cell line. Knockdown of MyD88 transcripts by small interfering RNA in the RAW264.7 macrophage cell line inhibited the activation of NF-κB-, NF-AT- and AP-1-dependent transcription by HPV16 VLP. Furthermore, MyD88 −/− BMDCs failed to up regulate IL-12 and IFN-α and -γ in response to HPV16 VLPs. Finally, Th1-biased immune responses to HPV16 VLPs are dramatically impaired in MyD88 and IFN-α/β receptor-deficient mice. This implicates TLR recognition as central to immune recognition of HPV16 L1 VLPs.

Resveratrol inhibits the acetylated α-tubulin-mediated assembly of the NLRP3-inflammasome

With its adaptor protein apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), Nod-like receptor family, pyrin domain containing 3 (NLRP3) forms the inflammasome and mediates inflammatory innate immune responses. Development of an anti-inflammatory drug targeting the NLRP3-inflammasome is urgently required because its aberrant activation often causes inflammatory diseases, including gout. We show that resveratrol, a natural polyphenol in grapes and wine, is a safe and effective phytochemical that inhibits NLRP3-inflammasome activation. Resveratrol inhibits the accumulation of acetylated α-tubulin caused by mitochondrial damage in macrophages stimulated with inducers of the NLRP3-inflammasome. Consequently, resveratrol inhibits the acetylated-α-tubulin-mediated spatial arrangement of mitochondria and their subsequent contact with the endoplasmic reticulum (ER), causing insufficient assembly of ASC on the mitochondria and NLRP3 on the ER. These findings indicate that resveratrol targets the generation of an optimal site for the assembly of NLRP3 and ASC, thus inhibiting NLRP3-inflammasome activation. Therefore, resveratrol could be an effective medication for the treatment of NLRP3-related inflammatory diseases.

IL-18 Improves the Early Antimicrobial Host Response to Pneumococcal Pneumonia

To determine the role of endogenous IL-18 during pneumonia, IL-18 gene-deficient (IL-18−/−) mice and wild-type (WT) mice were intranasally inoculated with Streptococcus pneumoniae, the most common causative agent of community-acquired pneumonia. Infection with S. pneumoniae increased the expression of IL-18 mRNA and was associated with elevated concentrations of both precursor and mature IL-18 protein within the lungs. IL-18−/− mice had significantly more bacteria in their lungs and were more susceptible for progressing to systemic infection at 24 and 48 h postinoculation. Similarly, treatment of WT mice with anti-IL-18 was associated with enhanced outgrowth of pneumococci. In contrast, the clearance of pneumococci from lungs of IL-12−/− mice was unaltered when compared with WT mice. Furthermore, anti-IL-12 did not influence bacterial clearance in either IL-18−/− or WT mice. These data suggest that endogenous IL-18, but not IL-12, plays an important role in the early antibacterial host response during pneumococcal pneumonia.

Correlative Quantitative Raman Chemical Imaging and MCR–ALS in Mouse NASH Model Reveals Direct Relationships between Diet and Resultant Liver Pathology

Raman imaging has the capability to provide unlabeled, spatially aware analysis of chemical components, with no a priori assumptions. Several lifestyle diseases such as nonalcoholic steatohepatitis (NASH) can appear in the liver as changes in the nature, abundance, and distribution of lipids, proteins, and other biomolecules and are detectable by Raman imaging. In order to identify which of these liver-associated changes occur as a direct result of the diet and which are secondary effects, we developed correlative imaging and analysis of diet and liver samples. Oleic acid was found to be a direct contributor to NASH liver composition, whereas protein and collagen distributions were found to be affected in a manner consistent with early fibrotic transformation, as a secondary consequence of the high-fat diet.

B cells enhance early innate immune responses during bacterial sepsis

Microbes activate pattern recognition receptors to initiate adaptive immunity. T cells affect early innate inflammatory responses to viral infection, but both activation and suppression have been demonstrated. We identify a novel role for B cells in the early innate immune response during bacterial sepsis. We demonstrate that Rag1−/− mice display deficient early inflammatory responses and reduced survival during sepsis. Interestingly, B cell–deficient or anti-CD20 B cell–depleted mice, but not α/β T cell–deficient mice, display decreased inflammatory cytokine and chemokine production and reduced survival after sepsis. Both treatment of B cell–deficient mice with serum from wild-type (WT) mice and repletion of Rag1−/− mice with B cells improves sepsis survival, suggesting antibody-independent and antibody-dependent roles for B cells in the outcome to sepsis. During sepsis, marginal zone and follicular B cells are activated through type I interferon (IFN-I) receptor (IFN-α/β receptor [IFNAR]), and repleting Rag1−/− mice with WT, but not IFNAR−/−, B cells improves IFN-I–dependent and –independent early cytokine responses. Repleting B cell–deficient mice with the IFN-I–dependent chemokine, CXCL10 was also sufficient to improve sepsis survival. This study identifies a novel role for IFN-I–activated B cells in protective early innate immune responses during bacterial sepsis.

Immune stimulation mediated by autoantigen binding sites within small nuclear RNAs involves Toll-like receptors 7 and 8

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the production of autoantibodies to certain cellular macromolecules, such as the small nuclear ribonucleoprotein particles (snRNPs), which had been considered to be passive targets of the autoimmune response. SLE is also characterized by the increased expression of type I interferon (IFN), which appears to be associated with the development and severity of disease. Here, we show that specific, highly conserved RNA sequences within snRNPs can stimulate Toll-like receptors (TLRs) 7 and 8 as well as activate innate immune cells, such as plasmacytoid dendritic cells (pDCs), which respond by secreting high levels of type I IFN. SLE patient sera containing autoantibodies to snRNPs form immune complexes that are taken up through the Fc receptor gammaRII and efficiently stimulate pDCs to secrete type I IFNs. These results demonstrate that a prototype autoantigen, the snRNP, can directly stimulate innate immunity and suggest that autoantibodies against snRNP may initiate SLE by stimulating TLR7/8.

Role of prostaglandin E2-EP2/EP4 signaling in the development of photosensitivity in pellagra

No abstract is provided for this article.

Targeted disruption of ATF4 discloses its essential role in the formation of eye lens fibres

Background : Activating transcription factor‐4 (ATF4)—also termed CREB2, C/ATF, and TAXREB67—is a basic‐leucine zipper (bZip) transcription factor that belongs to the ATF/CREB family. In addition to its own family members, ATF4 can also form heterodimers with other related but distinct bZIP proteins such as the C/EBP, AP‐1 and Maf families, which may give rise to a variety of combinatorial diversity in gene regulation. In order to assess the in vivo essential role of ATF4, we have generated mice lacking ATF4 by gene targeting. Results : ATF4‐deficient mice exhibited severe microphthalmia. Although ATF4‐deficient eyes revealed a normal gross lens structure up to embryonic day 14.5, later on the ATF4‐deficient lens, degenerated due to apoptosis without the formation of lens secondary fibre cells. Retinal development was normal in the mutant mice. The lens‐specific expression of ATF4 in the mutant mice led not only to the recovery of lens secondary fibres but also to the induction of hyperplasia of these fibres. Conclusion : These results demonstrated that ATF4 is essential for the later stages of lens fibre cell differentiation.