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VU0155069 inhibits inflammasome activation independent of phospholipase D1 activity.

ABSTRACT: The inflammasome is a specialized multiprotein oligomer that regulates IL-1? production. Although regulation of the inflammasome is related to crucial inflammatory disorders such as sepsis, pharmacological inhibitors that effectively inhibit inflammasome activity are limited. Here, we evaluated the effects of a phospholipase D1 (PLD1)-selective inhibitor (VU0155069) against sepsis and inflammasome activation. VU0155069 strongly enhances survival rate in cecal ligation and puncture (CLP)-induced sepsis by inhibiting lung inflammation, leukocyte apoptosis, and the production of proinflammatory cytokines, especially IL-1?. VU0155069 also significantly blocked IL-1? production, caspase-1 activation, and pyroptosis caused by several inflammasome-activating signals in the bone marrow-derived macrophages (BMDMs). However, VU0155069 did not affect LPS-induced activation of signaling molecules such as MAPK, Akt, NF-?B, and NLRP3 expression in the BMDMs. VU0155069 also failed to affect mitochondrial ROS generation and calcium increase caused by nigericin or ATP, and subsequent ASC oligomerization caused by several inflammasome-activating signals. VU0155069 indirectly inhibited caspase-1 activity caused by LPS?+?nigericin in BMDMs independent of PLD1 activity. We demonstrated that a PLD1 inhibitor, VU0155069, shows anti-septic activity as well as inflammasome-inhibiting effects. Our results suggest that VU0155069 can be considered a novel inflammasome inhibitor.

SUBMITTER: Lee SK

PROVIDER: S-EPMC6778193 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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VU0155069 inhibits inflammasome activation independent of phospholipase D1 activity.

Lee Sung Kyun SK Kim Ye Seon YS Bae Geon Ho GH Lee Ha Young HY Bae Yoe-Sik YS

Scientific reports 20191004 1

The inflammasome is a specialized multiprotein oligomer that regulates IL-1β production. Although regulation of the inflammasome is related to crucial inflammatory disorders such as sepsis, pharmacological inhibitors that effectively inhibit inflammasome activity are limited. Here, we evaluated the effects of a phospholipase D1 (PLD1)-selective inhibitor (VU0155069) against sepsis and inflammasome activation. VU0155069 strongly enhances survival rate in cecal ligation and puncture (CLP)-induced ...[more]

PMID: 31586128

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Project description: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-1β 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-1β/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-1β/IL-18 production is evident, involving at least four inflammasome pathways. The secreted effector YopJ triggers caspase-8- dependent IL-1β activation, even when YopM is present. Additionally, the presence of the T3SS needle/translocon activates NLRP3 and NLRC4-dependent IL-1β 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-1β/IL-18 release suggests that these effects are essential for maximal control of innate immunity during plague.

Project description:Canonical inflammasomes are innate immune protein scaffolds that enable the activation of inflammatory caspase-1, and subsequently the processing and release of interleukin (IL)-1β, IL-18, and danger signals, as well as the induction of pyroptotic cell death. Inflammasome assembly and activation occurs in response to sensing of infectious, sterile and self-derived molecular patterns by cytosolic pattern recognition receptors, including the Nod-like receptor NLRP3. While these responses are essential for host defense, excessive and uncontrolled NLRP3 inflammasome responses cause and contribute to a wide spectrum of inflammatory diseases, including gout. A key step in NLRP3 inflammasome assembly is the sequentially nucleated polymerization of Pyrin domain (PYD)- and caspase recruitment domain (CARD)-containing inflammasome components. NLRP3 triggers polymerization of the adaptor protein ASC through PYD-PYD interactions, but ASC polymerization then proceeds in a self-perpetuating manner and represents a point of no return, which culminates in the activation of caspase-1 by induced proximity. In humans, small PYD-only proteins (POPs) lacking an effector domain regulate this key process through competitive binding, but limited information exists on their physiological role during health and disease. Here we demonstrate that POP1 expression in macrophages is sufficient to dampen MSU crystal-mediated inflammatory responses in animal models of gout. Whether MSU crystals are administered into a subcutaneous airpouch or into the ankle joint, the presence of POP1 significantly reduces neutrophil infiltration. Also, airpouch exudates have much reduced IL-1β and ASC, which are typical pro-inflammatory indicators that can also be detected in synovial fluids of gout patients. Exogenous expression of POP1 in mouse and human macrophages also blocks MSU crystal-induced NLRP3 inflammasome assembly, resulting in reduced IL-1β and IL-18 secretion. Conversely, reduced POP1 expression in human macrophages enhances IL-1β secretion. We further determined that the mechanism for the POP1-mediated inhibition of NLRP3 inflammasome activation is through its interference with the crucial NLRP3 and ASC interaction within the inflammasome complex. Strikingly, administration of an engineered cell permeable version of POP1 was able to ameliorate MSU crystal-mediated inflammation in vivo, as measured by neutrophil infiltration. Overall, we demonstrate that POP1 may play a crucial role in regulating inflammatory responses in gout.

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VU0155069 inhibits inflammasome activation independent of phospholipase D1 activity.

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VU0155069 inhibits inflammasome activation independent of phospholipase D1 activity.

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