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Caspase-11 is the murine homologue of human caspases-4 and −5 and is involved in mediating the inflammatory response. However, its functions are often confused and misinterpreted with the more important and better described caspase-1. Therefore, this study focused exclusively on the specific roles of caspase-11, both in cartilage formation and in the inflammatory environment. The presence of caspase-11 during mouse limb development and in chondrogenic cell cultures was investigated by immunofluorescence detection. Subsequently, the function of caspase-11 was downregulated and the affected molecules investigated. The expression analysis applied for osteo/chondrogenesis associated factors and inflammatory cytokines. Simultaneously, morphological appearance of the micromass cultures was evaluated. The results revealed that caspase-11 is physiologically present during cartilage development, but its inhibition under physiological conditions has no significant effect on chondrogenic differentiation. However, in an inflammatory environment, inhibition and downregulation of caspase-11 leads to reduced differentiation of cartilage nodules. Additionally, reduced expression of several genes including Col2a1 and Sp7 and conversely increased expression of Mmp9 were observed. In the cytokine expression panel, a significant decrease was found in molecules that, along with the inflammatory function, may also be involved in cartilage differentiation. The findings bring new information about caspase-11 in chondrogenesis and show that its downregulation under inflammatory conditions reduces cartilage formation. • Caspase-11 is expressed during the mouse limb development. • Inhibition of caspase-11 in interleukin-1β induced cultures decrease chondrogenesis. • Inhibition of caspase-11 is accompanied by changes of chondrogenic gene expression. [ABSTRACT FROM AUTHOR]

Inflammatory caspase-11 senses and is activated by intracellular lipopolysaccharide (LPS) leading to pyroptosis that has critical role in defensing against bacterial infection, whereas its excess activation under pathogenic circumstances may cause various inflammatory diseases. However, there are few known drugs that can control caspase-11 activation. We report here that scutellarin, a flavonoid from Erigeron breviscapus , acted as an inhibitor for caspase-11 activation in macrophages. Scutellarin dose-dependently inhibited intracellular LPS-induced release of caspase-11p26 (indicative of caspase-11 activation) and generation of N-terminal fragment of gasdermin D (GSDMD-NT), leading to reduced pyroptosis. It also suppressed the activation of non-canonical nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome as evidenced by reduced apoptosis-associated speck-like protein containing a CARD (ASC) speck formation and decreased interleukin-1 beta (IL-1 β) and caspase-1p10 secretion, whereas the NLRP3-specific inhibitor MCC950 only inhibited IL-1 β and caspase-1p10 release and ASC speck formation but not pyroptosis. Scutellarin also suppressed LPS-induced caspase-11 activation and pyroptosis in RAW 264.7 cells lacking ASC expression. Moreover, scutellarin treatment increased Ser/Thr phosphorylation of caspase-11 at protein kinase A (PKA)-specific sites, and its inhibitory action on caspase-11 activation was largely abrogated by PKA inhibitor H89 or by adenylyl cyclase inhibitor MDL12330A. Collectively, our data indicate that scutellarin inhibited caspase-11 activation and pyroptosis in macrophages at least partly via regulating the PKA signaling pathway. Scutellarin inhibited caspase-11 activation via PKA signaling, thereby suppressing pyroptosis and non-canonical NLRP3 inflammasome activation culminating in reduced release of inflammatory components. Image 1 [ABSTRACT FROM AUTHOR]

Klebsiella pneumoniae ( K. pneumoniae ) is a gram-negative pathogen, and Klebsiella pneumonia is one of the most common nosocomial infections. Canonical NLRP3 and NLRC4 inflammasome was found involved in innate immune response against K. pneumoniae , but the role of caspase-11 in K. pneumoniae infection remains undefined. It was shown that Caspase-11 knockout blocked K. pneumoniae -induced IL-1α and IL-1β secretion and pyroptosis of bone marrow-derived macrophages (BMDMs). Furthermore, caspase-11 −/− mice exhibited impaired neutrophil recruitment and bacterial clearance in the early stage of K. pneumoniae infection, accompanied by a reduction in IL-1α production. Moreover, IL-1α neutralizing antibody pretreatment was found to inhibit neutrophil recruitment and bacterial clearance of wild-type mice. Together, these data suggest that caspase-11/IL-1α pathway plays an important role in defending against K. pneumoniae by recruiting neutrophils in the early stage of infection. [ABSTRACT FROM AUTHOR]

Caused by fungus, fungal keratitis is a kind of infections corneal disease with high rate of blindness, which patients are mainly farmers in developing contries. Interleukin, as important proinflammatory cytokines, involve in immune defense process against fungal infection of cornea. The expression of interleukin in the pathogenesis of fungal keratitis, especially the main source of its cells, is not clear and the cell signaling pathways which regulate the synthesis and modification of interleukin is still unknown. Caspase-11 was obtained and cultured. And the ELISA and Westernblot methods were used to explore the regulatory effect of Caspse-11 on Interleukin-1β in the fungal keratitis. neutrophils were the main cell lineage of IL-1β to take part in the innate anti-fungi immunity in the cornea; IL-1β generation induced by fungal infection might not be through the pre-excitation in the classical signal pathway; TLR4/TRIF pathway was not involved in pro-IL-1β generation; while Dectin-1/syk pathway was involved in IL-1β generation in the fungal keratitis; Caspase-l participated in the modification of IL-1β to change from the precursor into the mature body; but NLRP3 inflammasome and ASC inflammasome were not involved in IL-1β generation; Caspase-11 was involved in IL-1β generation through regulating the modified process of Caspase-l to turning from precursor into mature body. TLR4/TRIF pathway and NLRP3 inflammasome and ASC inflammasome are not involved in the pro-IL-1β generation, while Caspase-l, Caspase-11 and Dectin-1/syk pathway are involved in the IL-1β generation. [ABSTRACT FROM AUTHOR]

Interferons and the IL-1 family of cytokines have important roles in host defense against invading viruses and bacteria. Inflammasomes, multimeric cytosolic sensors of infection, are required for IL-1β and IL-18 processing and release. Interferons, IL-1β, and IL-18 are also implicated in autoimmune disease and chronic inflammation. Although independent but complementary pathways induce these cytokine subsets during infection, in some circumstances the cross-talk between these key inflammatory mediators is a particular requirement for effective host defense. In this review we will summarize recent discoveries concerning the potentiation of inflammasome responses by type I interferons, particularly in patients with gram-negative bacterial infections, and reflect on the molecular mechanisms of IFN-β's immunosuppressive effects through modulation of inflammasome and IL-1β signaling in patients with tuberculosis and multiple sclerosis. [ABSTRACT FROM AUTHOR]

Maternal high-fat diet (HFD) has been shown to promote the development of insulin resistance (IR) in adult offspring; however, the underlying mechanisms remain unclear. Eight-week-old female wild-type mice (C57BL/6) were fed either an HFD or a normal diet (ND), one week prior to mating, and the diet was continued throughout gestation and lactation. Eight-week-old male offspring of both groups were fed an HFD for 8 weeks. Offspring of HFD-fed dams (O-HFD) exhibited significantly impaired insulin sensitivity compared with the offspring of ND-fed dams (O-ND). The adipocyte size of the eWAT increased significantly in O-HFD and was accompanied by abundant crown-like structures (CLSs), as well as a higher concentration of interleukin 1β (IL-1β) in the eWAT. Treatment with an inflammasome inhibitor, MCC950, completely abrogated the enhanced IR in O-HFD. However, ex vivo caspase-1 activity in eWAT revealed no difference between the two groups. In contrast, noncanonical inflammasome activation of caspase-11 was significantly augmented in O-HFD compared with O-ND, suggesting that membrane pore formation, but not cleavage of pro-IL-1β by caspase-1, is augmented in O-HFD. To examine the membrane pore formation, we performed metabolic activation of bone marrow-derived macrophages (BMDMs). The percentage of pore formation assessed by ethidium bromide staining was significantly higher in BMDMs of O-HFD, accompanied by an enhanced active caspase-11 expression. Consistently, the concentration of IL-1β in culture supernatants was significantly higher in the BMDMs from O-HFD than those from O-ND. These findings demonstrate that maternal HFD exaggerates diet-induced IR in adult offspring by enhancing noncanonical caspase-11-mediated inflammasome activation. • Maternal HFD increases the vulnerability to HFD-induced IR in adult offspring. • Maternal HFD augments inflammasome activation in eWAT in adult offspring. • Treatment with an inflammasome inhibitor abrogates IR in offspring of HFD-fed dam. • Maternal HFD augments the noncanonical inflammasome activation pathway of caspase-11. • Maternal HFD augments IL-1β release from BMDMs by enhancing membrane pore formation. [ABSTRACT FROM AUTHOR]

Summary Sepsis is a life-threatening condition caused by pathogen infection and associated with pyroptosis. Pyroptosis occurs upon activation of proinflammatory caspases and their subsequent cleavage of gasdermin D (GSDMD), resulting in GSDMD N-terminal fragments that form membrane pores to induce cell lysis. Here, we show that antioxidant defense enzyme glutathione peroxidase 4 (GPX4) and its ability to decrease lipid peroxidation, negatively regulate macrophage pyroptosis, and septic lethality in mice. Conditional Gpx4 knockout in myeloid lineage cells increases lipid peroxidation-dependent caspase-11 activation and GSDMD cleavage. The resultant N-terminal GSDMD fragments then trigger macrophage pyroptotic cell death in a phospholipase C gamma 1 (PLCG1)-dependent fashion. Administration of the antioxidant vitamin E that reduces lipid peroxidation, chemical inhibition of PLCG1, or genetic Caspase-11 deletion or Gsdmd inactivation prevents polymicrobial sepsis in Gpx4 −/− mice. Collectively, this study suggests that lipid peroxidation drives GSDMD-mediated pyroptosis and hence constitutes a potential therapeutic target for lethal infection. [ABSTRACT FROM AUTHOR]