TLRs are key sensors for conserved bacterial molecules and play a critical role in host defense against invading pathogens. Although the roles of TLRs in defense against pathogen infection and in maintaining gut immune homeostasis have been studied, the precise functions of different TLRs in response to pathogen infection in the gut remain elusive. The present study investigated the role of TLR signaling in defense against the Gram-negative bacterial pathogen The results indicated that TLR9-deficient mice were more susceptible to infection compared with wild-type and TLR2- or TLR4-deficient mice, as indicated by more severe intestinal damage and the highest bacterial load. TLR9 deficiency in intestinal epithelial cells (IECs) augmented the activation of NF-κB and NLRP3 inflammasomes significantly, resulting in increased secretion of IL-1β. IL-1β increased the expression of NKG2D on intestinal intraepithelial lymphocytes and NKG2D ligands on IECs, resulting in higher susceptibility of IECs to cytotoxicity of intestinal intraepithelial lymphocytes and damage to the epithelial barrier. We proposed that TLR9 regulates the NF-κB-NLRP3-IL-1β pathway negatively in -induced NKG2D-mediated intestinal inflammation and plays a critical role in defense against infection and in the protection of intestinal integrity.

bToll-like receptors (TLRs) are evolutionarily conserved host proteins that are essential for effective host defense against pathogens. However, recent studies suggest that some TLRs can negatively regulate immune responses. We observed here that TLR2 and TLR9 played opposite roles in regulating innate immunity against oral infection of Salmonella enterica serovar Typhimurium in mice. While TLR9 ؊/؊ mice exhibited shortened survival, an increased cytokine storm, and more severe Salmonella hepatitis than wild-type (WT) mice, TLR2 ؊/؊ mice exhibited the opposite phenomenon. Further studies demonstrated that TLR2 deficiency and TLR9 deficiency in macrophages both disrupted NK cell cytotoxicity against S. Typhimurium-infected macrophages by downregulating NK cell degranulation and gamma interferon (IFN-␥) production through decreased macrophage expression of the RAE-1 NKG2D ligand. But more importantly, we found that S. Typhimurium-infected TLR2 ؊/؊ macrophages upregulated inducible nitric oxide synthase (iNOS) expression, resulting in a lower bacterial load than that in WT macrophages in vitro and livers in vivo as well as low proinflammatory cytokine levels. In contrast, TLR9 ؊/؊ macrophages showed decreased reactive oxygen species (ROS) expression concomitant with a high bacterial load in the macrophages and in livers of TLR9؊/؊ macrophages were also more susceptible than WT macrophages to S. Typhimurium-induced necroptosis in vitro, likely contributing to bacterial spread and transmission in vivo. Collectively, these findings indicate that TLR2 negatively regulates anti-S. Typhimurium immunity, whereas TLR9 is vital to host defense and survival against S. Typhimurium invasion. TLR2 antagonists or TLR9 agonists may thus serve as potential anti-S. Typhimurium therapeutic agents. During the early stages of infection, the innate immune system serves as the first line of defense against microbial replication and spread before an adaptive response is mounted (1). As one mechanism to elicit a rapid and appropriate innate immune response against pathogen infection, pattern recognition receptors (PRRs) evolved in the host to recognize various microbial molecular patterns. In response, pathogens evolved to use many different tactics, including subversion of some of these host antimicrobial immune mechanisms, in order to ensure their multiplication, survival, and persistence in the host (2). This ongoing interplay between host innate immune responses and pathogen virulence factors largely determines the outcome of most infections.As the most widely studied PRRs, Toll-like receptors (TLRs) play a crucial role in pathogen recognition and the induction of immune responses. Currently, 11 and 13 TLRs have been identified in humans and mice, respectively. They are widely expressed on many cell types, such as macrophages, neutrophils, dendritic cells (DCs), and mucosal epithelial cells. TLR signaling results in the induction of reactive oxygen species (ROS) and the activation of the transcription factor NF-B, which in turn induce...

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BackgroundHepatocellular carcinoma (HCC) is one of the most common malignant cancer worldwide. Importantly, the precise mechanisms causing HCC pathogenicity are still unknown. The identification of potential oncogenes plays significant roles in finding novel therapeutic targets for human HCC.PurposeWDR12 (WD repeat protein 12), a member of WD repeats family, plays crucial roles in the ribosome biogenesis pathway. However, Whether WDR12 contributes to HCC development remains unknown. The objective of this study was to elucidate the role of WDR12 in HCC development.MethodsThe expression level of WDR12 in HCC tissues and adjacent non-tumor tissues were detected form Gene Expression Omnibus (GEO) database. The expression level of WDR12 in HCC cell lines were examined by RT-PCR and western blot. Kaplan-Meier analysis were used to analyze the effect of WDR12 level on overall and disease-free survival of HCC patients. To examine whether WDR12 supports development of HCC, we inhibited expression of WDR12 by using an shRNA-encoding lentivirus system. Effects of WDR12 knockdown were evaluated on cell-growth, cell-proliferation and cell-migration. The mechanisms involved in HCC cells growth, proliferation and migration were analyzed by western blot assay.ResultsIn silico analysis of HCC data sets showed that elevated expression of WDR12 correlated with high serum AFP level, high vascular invasion, high histologic grade and high TNM stage in HCC patients. Furthermore, up-regulated expression of WDR12 significantly correlated with the short overall survival and recurrence time of HCC patients. The shRNA-mediated knockdown of WDR12 expression resulted in reduced proliferation and migration of HepG2 and Huh-7 cells. Notably, inhibition of WDR12 resulted in decreased phosphorylation of AKT, mTOR and S6K1.ConclusionOur study indicates that WDR12 contributes to HCC propagation, and indicates that suppression of WDR12 may be a potential strategy for human HCC treatment.