Critical Role for Tumor Necrosis Factor–related Apoptosis-inducing Ligand in Immune Surveillance Against Tumor Development

Natural killer (NK) cells and interferon (IFN)-γ have been implicated in immune surveillance against tumor development. Here we show that tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) plays a critical role in the NK cell–mediated and IFN-γ–dependent tumor surveillance. Administration of neutralizing monoclonal antibody against TRAIL promoted tumor development in mice subcutaneously inoculated with a chemical carcinogen methylcholanthrene (MCA). This protective effect of TRAIL was at least partly mediated by NK cells and totally dependent on IFN-γ. In the absence of TRAIL, NK cells, or IFN-γ, TRAIL-sensitive sarcomas preferentially emerged in MCA-inoculated mice. Moreover, development of spontaneous tumors in p53+/− mice was also promoted by neutralization of TRAIL. These results indicated a substantial role of TRAIL as an effector molecule that eliminates developing tumors

Tumor Necrosis Factor–Related Apoptosis-Inducing Ligand (Trail) Contributes to Interferon γ–Dependent Natural Killer Cell Protection from Tumor Metastasis

Tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) is expressed by in vitro activated natural killer (NK) cells, but the relevance of this observation to the biological function of NK cells has been unclear. Herein, we have demonstrated the in vivo induction of mouse TRAIL expression on various tissue NK cells and correlated NK cell activation with TRAIL-mediated antimetastatic function in vivo. Expression of TRAIL was only constitutive on a subset of liver NK cells, and innate NK cell control of Renca carcinoma hepatic metastases in the liver was partially TRAIL dependent. Administration of therapeutic doses of interleukin (IL)-12, a powerful inducer of interferon (IFN)-γ production by NK cells and NKT cells, upregulated TRAIL expression on liver, spleen, and lung NK cells, and IL-12 suppressed metastases in both liver and lung in a TRAIL-dependent fashion. By contrast, α-galactosylceramide (α-GalCer), a powerful inducer of NKT cell IFN-γ and IL-4 secretion, suppressed both liver and lung metastases but only stimulated NK cell TRAIL-mediated function in the liver. TRAIL expression was not detected on NK cells from IFN-γ–deficient mice and TRAIL-mediated antimetastatic effects of IL-12 and α-GalCer were strictly IFN-γ dependent. These results indicated that TRAIL induction on NK cells plays a critical role in IFN-γ–mediated antimetastatic effects of IL-12 and α-GalCer

The Yersinia pestis Effector YopM Inhibits Pyrin Inflammasome Activation

Type III secretion systems (T3SS) are central virulence factors for many pathogenic Gram-negative bacteria, and secreted T3SS effectors can block key aspects of host cell signaling. To counter this, innate immune responses can also sense some T3SS components to initiate anti-bacterial mechanisms. The Yersinia pestis T3SS is particularly effective and sophisticated in manipulating the production of pro-inflammatory cytokines IL-1beta and IL-18, which are typically processed into their mature forms by active caspase-1 following inflammasome formation. Some effectors, like Y. pestis YopM, may block inflammasome activation. Here we show that YopM prevents Y. pestis induced activation of the Pyrin inflammasome induced by the RhoA-inhibiting effector YopE, which is a GTPase activating protein. YopM blocks YopE-induced Pyrin-mediated caspase-1 dependent IL-1beta/IL-18 production and cell death. We also detected YopM in a complex with Pyrin and kinases RSK1 and PKN1, putative negative regulators of Pyrin. In contrast to wild-type mice, Pyrin deficient mice were also highly susceptible to an attenuated Y. pestis strain lacking YopM, emphasizing the importance of inhibition of Pyrin in vivo. A complex interplay between the Y. pestis T3SS and IL-1beta/IL-18 production is evident, involving at least four inflammasome pathways. The secreted effector YopJ triggers caspase-8- dependent IL-1beta activation, even when YopM is present. Additionally, the presence of the T3SS needle/translocon activates NLRP3 and NLRC4-dependent IL-1beta generation, which is blocked by YopK, but not by YopM. Taken together, the data suggest YopM specificity for obstructing the Pyrin pathway, as the effector does not appear to block Y. pestis-induced NLRP3, NLRC4 or caspase-8 dependent caspase-1 processing. Thus, we identify Y. pestis YopM as a microbial inhibitor of the Pyrin inflammasome. The fact that so many of the Y. pestis T3SS components are participating in regulation of IL-1beta/IL-18 release suggests that these effects are essential for maximal control of innate immunity during plague

MCC950/CRID3 potently targets the NACHT domain of wild-type NLRP3 but not disease-associated mutants for inflammasome inhibition

The nucleotide-binding-domain (NBD)-and leucine-rich repeat (LRR)-containing (NLR) family, pyrin-domain-containing 3 (NLRP3) inflammasome drives pathological inflammation in a suite of autoimmune, metabolic, malignant, and neurodegenerative diseases. Additionally, NLRP3 gain-of-function point mutations cause systemic periodic fever syndromes that are collectively known as cryopyrin-associated periodic syndrome (CAPS). There is significant interest in the discovery and development of diarylsulfonylurea Cytokine Release Inhibitory Drugs (CRIDs) such as MCC950/CRID3, a potent and selective inhibitor of the NLRP3 inflammasome pathway, for the treatment of CAPS and other diseases. However, drug discovery efforts have been constrained by the lack of insight into the molecular target and mechanism by which these CRIDs inhibit the NLRP3 inflammasome pathway. Here, we show that the NAIP, CIITA, HET-E, and TP1 (NACHT) domain of NLRP3 is the molecular target of diarylsulfonylurea inhibitors. Interestingly, we find photoaffinity labeling (PAL) of the NACHT domain requires an intact (d)ATP-binding pocket and is substantially reduced for most CAPS-associated NLRP3 mutants. In concordance with this finding, MCC950/CRID3 failed to inhibit NLRP3-driven inflammatory pathology in two mouse models of CAPS. Moreover, it abolished circulating levels of interleukin (IL)-1 beta and IL-18 in lipopolysaccharide (LPS)-challenged wild-type mice but not in Nlrp3(L351P) knock-in mice and ex vivo-stimulated mutant macrophages. These results identify wild-type NLRP3 as the molecular target of MCC950/CRID3 and show that CAPS-related NLRP3 mutants escape efficient MCC950/CRID3 inhibition. Collectively, this work suggests that MCC950/CRID3-based therapies may effectively treat inflammation driven by wild-type NLRP3 but not CAPS-associated mutants

Requirement of Cell–Cell Contact in the Induction of Jurkat T Cell Apoptosis: The Membrane-Anchored but Not Soluble Form of FasL Can Trigger Anti-CD3-Induced Apoptosis in Jurkat T Cells

Fas ligand (FasL) has been shown to be processed by the action of certain metalloproteinase and released from the cell surface. However, it is unclear whether death of Fas-sensitive target cells is mediated by a membrane-bound form of FasL (mFasL) or by a soluble form of FasL (sFasL). In the present study, we demonstrated that JCaM, a p56lck-deficient mutant of Jurkat, underwent Fas-dependent apoptosis only upon physical contact with anti-CD3-stimulated Jurkat cells or with human FasL- expressing transfectant (hFas/L5178Y). Recombinant FasL or sFasL-containing supernatant failed to induce apoptosis in both Jurkat and JCaM. Moreover, addition of a metalloproteinase inhibitor, which led to the accumulation of mFasL in hFas/L5178Y, was found to augment apoptosis in both Jurkat and JCaM. These findings indicate that, in a physiologic setting represented by the activation-induced cell death in Jurkat T cells, cell–cell contact appears to be required for the induction of Fas-mediated killing