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Fulltext AIM2 Inflammasome-Mediated Pyroptosis in Enterovirus A71-Infected Neuronal Cells Restricts Viral Replication

Yogarajah T, Ong KC, Perera D, Wong KT

Sci Rep, 2017 07 19;7(1):5845.
PMID: 28724943 DOI: 10.1038/s41598-017-05589-2

Encephalomyelitis is a well-known complication of hand, foot, and mouth disease (HFMD) due to Enterovirus 71 (EV71) infection. Viral RNA/antigens could be detected in the central nervous system (CNS) neurons in fatal encephalomyelitis but the mechanisms of neuronal cell death is not clearly understood. We investigated the role of absent in melanoma 2 (AIM2) inflammasome in neuronal cell death, and its relationship to viral replication. Our transcriptomic analysis, RT-qPCR, Western blot, immunofluorescence and flow cytometry studies consistently showed AIM2 gene up-regulation and protein expression in EV-A71-infected SK-N-SH cells. Downstream AIM2-induced genes, CARD16, caspase-1 and IL-1β were also up-regulated and caspase-1 was activated to form cleaved caspase-1 p20 subunits. As evidenced by 7-AAD positivity, pyroptosis was confirmed in infected cells. Overall, these findings have a strong correlation with decreases in viral titers, copy numbers and proteins, and reduced proportions of infected cells. AIM2 and viral antigens were detected by immunohistochemistry in infected neurons in inflamed areas of the CNS in EV-A71 encephalomyelitis. In infected AIM2-knockdown cells, AIM2 and related downstream gene expressions, and pyroptosis were suppressed, resulting in significantly increased virus infection. These results support the notion that AIM2 inflammasome-mediated pyroptosis is an important mechanism of neuronal cell death and it could play an important role in limiting EV-A71 replication.

Matched MeSH terms: Caspase 1/metabolism
Genetic disruption of the inflammasome adaptor ASC has minimal impact on the pathogenesis of Duchenne muscular dystrophy in mdx mice

Lau YS, Zhao L, Zhang C, Li H, Han R

Life Sci, 2020 Jul 10.
PMID: 32659370 DOI: 10.1016/j.lfs.2020.118069

AIM: Up-regulation of inflammasome proteins was reported in dystrophin-deficient muscles. However, it remains to be determined whether inflammasome activation plays a role in the pathogenesis of Duchenne muscular dystrophy. This study was therefore set out to investigate whether genetic disruption of the inflammasome pathway impacts the disease progression in mdx mice.
MAIN METHODS: Mice deficient in both dystrophin and ASC (encoded by Pycard [PYD And CARD Domain Containing]) were generated. The impact of ASC deficiency on muscular dystrophy of mdx mice were assessed by measurements of serum cytokines, Western blot, real-time PCR and histopathological staining.
KEY FINDINGS: The pro-inflammatory cytokines such as TNF-α, IL-6, KC/GRO and IL-10 were markedly increased in the sera of 8-week-old mdx mice compared to WT. Western blotting showed that P2X7, caspase-1, ASC and IL-18 were upregulated. Disruption of ASC and dystrophin expression in the mdx/ASC-/- mice was verified by Western blot analysis. Histopathological analysis did not find significant alterations in the muscular dystrophy phenotype in mdx/ASC-/- mice as compared to mdx mice.
SIGNIFICANCE: Taken together, our results show that disruption of the central adaptor ASC of the inflammasome is insufficient to alleviate muscular dystrophy phenotype in mdx mice.

Matched MeSH terms: Caspase 1
GC-MS metabolomics revealed protocatechuic acid as a cytotoxic and apoptosis-inducing compound from black rice brans

Yuliana ND, Tuarita MZ, Khatib A, Laila F, Sukarno S

Food Sci Biotechnol, 2020 Jun;29(6):825-835.
PMID: 32523792 DOI: 10.1007/s10068-019-00725-2

GC-MS metabolomics was used to discriminate the phytochemicals profile of Indonesian white, red, and black rice brans, and Japanese white rice brans. This technique was used for the first time to identify compounds in rice brans having cytotoxic activity against WiDr colon cancer cells. Orthogonal Projection to the Latent Structure (OPLS) analysis showed that protocatechuic acid (PA) was a discriminating factor found in black rice brans which strongly correlated with its cytotoxicity (IC50 8.53 ± 0.26 µM). Real time-PCR data demonstrated that PA cytotoxicity at different concentrations (1, 5, 10, 25 and 50 µg/mL) was mediated through different pathways. Bcl-2 expression was downregulated at all tested concentrations indicating apoptosis stimulation. At 1-10 ppm concentration, PA activated both intrinsic and extrinsic apoptosis pathways since the expression of p53, Bax, caspase-8, and caspase-9 were upregulated. At a higher dose (25 and 50 µg/mL), PA possibly involved in pyroptosis-mediated pro-inflammatory cell death by upregulating the expression of caspase-1 and caspase-7.

Matched MeSH terms: Caspase 1
Fulltext Aberrant Inflammasome Activation Characterizes Tuberculosis-Associated Immune Reconstitution Inflammatory Syndrome

Tan HY, Yong YK, Shankar EM, Paukovics G, Ellegård R, Larsson M, et al.

J Immunol, 2016 05 15;196(10):4052-63.
PMID: 27076678 DOI: 10.4049/jimmunol.1502203

Tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) complicates combination antiretroviral therapy (cART) in up to 25% of patients with HIV/TB coinfection. Monocytes and IL-18, a signature cytokine of inflammasome activation, are implicated in TB-IRIS pathogenesis. In this study, we investigated inflammasome activation both pre- and post-cART in TB-IRIS patients. HIV/TB patients exhibited higher proportions of monocytes expressing activated caspase-1 (casp1) pre-cART, compared with HIV patients without TB, and patients who developed TB-IRIS exhibited the greatest increase in casp1 expression. CD64(+) monocytes were a marker of increased casp1 expression. Furthermore, IL-1β, another marker of inflammasome activation, was also elevated during TB-IRIS. TB-IRIS patients also exhibited greater upregulation of NLRP3 and AIM2 inflammasome mRNA, compared with controls. Analysis of plasma mitochondrial DNA levels showed that TB-IRIS patients experienced greater cell death, especially pre-cART. Plasma NO levels were lower both pre- and post-cART in TB-IRIS patients, providing evidence of inadequate inflammasome regulation. Plasma IL-18 levels pre-cART correlated inversely with NO levels but positively with monocyte casp1 expression and mitochondrial DNA levels, and expression of IL-18Rα on CD4(+) T cells and NK cells was higher in TB-IRIS patients, providing evidence that IL-18 is a marker of inflammasome activation. We propose that inflammasome activation in monocytes/macrophages of HIV/TB patients increases with ineffective T cell-dependent activation of monocytes/macrophages, priming them for an excessive inflammatory response after cART is commenced, which is greatest in patients with TB-IRIS.

Matched MeSH terms: Caspase 1/metabolism
1'-Acetoxychavicol acetate inhibits NLRP3-dependent inflammasome activation via mitochondrial ROS suppression

Sok SPM, Ori D, Wada A, Okude H, Kawasaki T, Momota M, et al.

Int Immunol, 2021 06 18;33(7):373-386.
PMID: 33830232 DOI: 10.1093/intimm/dxab016

The nucleotide-binding oligomerization domain-like receptor (NLR) family pyrin domain containing (NLRP) 3 inflammasome is a multiprotein complex that triggers Caspase-1-mediated IL-1β production and pyroptosis, and its dysregulation is associated with the pathogenesis of inflammatory diseases. 1'-Acetoxychavicol acetate (ACA) is a natural compound in the rhizome of tropical ginger Alpinia species with anti-microbial, anti-allergic and anti-cancer properties. In this study, we found that ACA suppressed NLRP3 inflammasome activation in mouse bone marrow-derived macrophages and human THP-1 monocytes. ACA inhibited Caspase-1 activation and IL-1β production by NLRP3 agonists such as nigericin, monosodium urate (MSU) crystals, and ATP. Moreover, it suppressed oligomerization of the adapter molecule, apoptosis-associated speck-like protein containing a CARD (ASC), and Caspase-1-mediated cleavage of pyroptosis executor Gasdermin D. Mechanistically, ACA inhibited generation of mitochondrial reactive oxygen species (ROS) and prevented release of oxidized mitochondrial DNA, which trigger NLRP3 inflammasome activation. ACA also prevented NLRP3 inflammasome activation in vivo, as evidenced in the MSU crystal-induced peritonitis and dextran sodium sulfate-induced colitis mouse models accompanied by decreased Caspase-1 activation. Thus, ACA is a potent inhibitor of the NLRP3 inflammasome for prevention of NLRP3-associated inflammatory diseases.

Matched MeSH terms: Caspase 1/metabolism