Inflammasome-mediated IL-1β Production Research Articles

Duck hepatitis A virus 1-encoded 2B protein disturbs ion and organelle homeostasis to promote NF-κB/NLRP3-mediated inflammatory response

Previous studies by our group and others have highlighted the critical role of hyperinflammation in the pathogenicity of duck hepatitis A virus 1 (DHAV-1), an avian picornavirus that has caused significant devastation in the duck industry worldwide for decades. However, the precise mechanisms by which DHAV-1 infection regulates the inflammatory responses, particularly the production of IL-1β, remain poorly understood. In this study, we demonstrate that DHAV-1 infection triggers NF-κB- and NLRP3 inflammasome-mediated IL-1β production. Mechanistically, DHAV-1 infection, particularly its replication and translation, disrupts cellular homeostasis of Ca2+, K+, ROS and cathepsin, which act cooperatively as assembly signals for NLRP3 inflammasome activation. By screening DHAV-1-encoded proteins, we identified that the viroporin 2B dominates NF-κB as well as NLRP3 inflammasome activation. Mutation analysis revealed that I43 within the 2B protein is the key amino acid for Ca2+ mobilization and subsequent activation of NF-κB transcriptional activity and NLRP3 inflammasome. Moreover, DHAV-1 infection and the 2B protein activate the MAVS- and MyD88-NF-κB pathways by relay, providing the necessary priming signals for NLRP3 inflammasome activation. In summary, our findings elucidate a mechanism through which DHAV-1 triggers inflammatory responses via NF-κB/NLRP3 inflammasome activation, offering new perspectives on DHAV-1 pathogenesis and informing the development of targeted anti-DHAV-1 treatments.

TLR8-activating miR-146a-3p is an intermediate signal contributing to fetal membrane inflammation in response to bacterial LPS.

Preterm birth is the largest contributor to neonatal morbidity and is often associated with chorioamnionitis, defined as inflammation/infection of the fetal membranes (FMs). Chorioamnionitis is characterised by neutrophil infiltration of the FMs and is associated with elevated levels of the neutrophil chemoattractant, interleukin (IL)-8 and the proinflammatory cytokine, IL-1β. While FMs can respond to infections through innate immune sensors, such as toll-like receptors (TLRs), the downstream mechanisms by which chorioamnionitis arises are not fully understood. A novel group of non-classical microRNAs (miR-21a, miR-29a, miR-146a-3p, Let-7b) function as endogenous danger signals by activating the ssRNA viral sensors TLR7 and TLR8. In this study, the pro-inflammatory roles of TLR7/TLR8-activating miRs were examined as mediators of FM inflammation in response to bacterial lipopolysaccharide (LPS) using an in vitro human FM explant system, an in vivo mouse model of pregnancy, and human clinical samples. Following LPS exposure, miR-146a-3p was significantly increased in both human FM explants and wild-type mouse FMs. Expression of miR-146a-3p was also significantly elevated in FMs from women with preterm birth and chorioamnionitis. FM IL-8 and inflammasome-mediated IL-1β production in response to LPS was dependent on miR-146a-3p and TLR8 downstream of TLR4 activation. In wild-type mice, LPS exposure increased FM IL-8 and IL-1β production and induced preterm birth. In TLR7-/-/TLR8-/- mice, LPS exposure was able to initiate but not sustain preterm birth, and FM inflammation was reduced. Together, we demonstrate a novel signalling mechanism at the maternal-fetal interface in which TLR8-activating miR-146a-3p acts as an intermediate danger signal to drive FM inflammasome-dependent and -independent mechanisms of inflammation and, thus, may play a role in chorioamnionitis and subsequent preterm birth.

Imeglimin attenuates NLRP3 inflammasome activation by restoring mitochondrial functions in macrophages

Imeglimin is a novel oral antidiabetic drug for treating type 2 diabetes. However, the effect of imeglimin on NLRP3 inflammasome activation has not been investigated yet. Here, we aimed to investigate whether imeglimin reduces LPS-induced NLRP3 inflammasome activation in THP-1 macrophages and examine the associated underlying mechanisms. We analyzed the mRNA and protein expression levels of NLRP3 inflammasome components and IL-1β secretion. Additionally, reactive oxygen species (ROS) generation, mitochondrial membrane potential, and mitochondrial permeability transition pore (mPTP) opening were measured by flow cytometry. Imeglimin inhibited NLRP3 inflammasome-mediated IL-1β production in LPS-stimulated THP-1-derived macrophages. In addition, imeglimin reduced LPS-induced mitochondrial ROS production and mitogen-activated protein kinase phosphorylation. Furthermore, imeglimin restored the mitochondrial function by modulating mitochondrial membrane depolarization and mPTP opening. We demonstrated for the first time that imeglimin reduces LPS-induced NLRP3 inflammasome activation by inhibiting mPTP opening in THP-1 macrophages. These results suggest that imeglimin could be a promising new anti-inflammatory agent for treating diabetic complications.

Isoliquiritigenin inhibits NLRP3 inflammasome activation with CAPS mutations by suppressing caspase-1 activation and mutated NLRP3 aggregation.

The nucleotide-binding oligomerization domain leucine-rich repeat and pyrin domain containing 3 (NLRP3) inflammasome contributes to the development of inflammatory diseases. Cryopyrin-associated periodic syndrome (CAPS) is an autoinflammatory disease caused by NLRP3 gene mutations that results in excessive IL-1β production. We previously identified isoliquiritigenin (ILG), a component of Glycyrrhiza uralensis extracts, as a potent inhibitor of the NLRP3 inflammasome. Here, we aimed to investigate whether ILG inhibits the activation of NLRP3 inflammasome caused by NLRP3 gene mutations. We demonstrated that ILG significantly inhibited NLRP3 inflammasome-mediated lactate dehydrogenase (LDH) release and IL-1β production in two CAPS model THP-1 cell lines, NLRP3-D303N and NLRP3-L353P, in a dose-dependent manner. Interestingly, the NLRP3 inhibitor MCC950 inhibited LDH release and IL-1β production in NLRP3-D303N cells, but not in NLRP3-L353P cells. Western blotting and caspase-1 activity assays showed that ILG, as well as caspase inhibitors, including Z-VAD and YVAD, suppressed caspase-1 activation. Notably, ILG prevented cryo-sensitive foci formation of NLRP3 without affecting the levels of intracellular Ca2+. We concluded that ILG effectively prevents the constitutive activation of the inflammasome associated with NLRP3 gene mutations by inhibiting the aggregation of cryo-sensitive mutated NLRP3.

Cholesterol accumulation in macrophages drives NETosis in atherosclerotic plaques via IL-1β secretion.

Neutrophil extracellular trap formation (NETosis) increases atherosclerotic plaque vulnerability and athero-thrombosis. However, mechanisms promoting NETosis during atherogenesis are poorly understood. We have shown that cholesterol accumulation due to myeloid cell deficiency of the cholesterol transporters ATP Binding Cassette A1 and G1 (ABCA1/G1) promotes NLRP3 inflammasome activation in macrophages and neutrophils and induces prominent NETosis in atherosclerotic plaques. We investigated whether NETosis is a cell-intrinsic effect in neutrophils or is mediated indirectly by cellular crosstalk from macrophages to neutrophils involving IL-1β. We generated mice with neutrophil or macrophage-specific Abca1/g1 deficiency (S100A8CreAbca1fl/flAbcg1fl/fl or CX3CR1CreAbca1fl/flAbcg1fl/fl mice, respectively), and transplanted their bone marrow into low-density lipoprotein receptor knockout mice. We then fed the mice a cholesterol-rich diet. Macrophage, but not neutrophil Abca1/g1 deficiency activated inflammasomes in macrophages and neutrophils, reflected by caspase-1 cleavage, and induced NETosis in plaques. NETosis was suppressed by administering an interleukin (IL)-1β neutralizing antibody. The extent of NETosis in plaques correlated strongly with the degree of neutrophil accumulation, irrespective of blood neutrophil counts, and neutrophil accumulation was decreased by IL-1β antagonism. In vitro, IL-1β or media transferred from Abca1/g1-deficient macrophages increased NETosis in both control and Abca1/Abcg1 deficient neutrophils. This cell-extrinsic effect of IL-1β on NETosis was blocked by an NLRP3 inhibitor. These studies establish a new link between inflammasome-mediated IL-1β production in macrophages and NETosis in atherosclerotic plaques. Macrophage-derived IL-1β appears to increase NETosis both by increasing neutrophil recruitment to plaques and by promoting neutrophil NLRP3 inflammasome activation.

Inhibition of the NLRP3 inflammasome by progesterone is attenuated by abnormal autophagy induction in endometriotic cyst stromal cells: implications for endometriosis.

The NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome is a cytosolic multi-protein complex that induces inflammation and is known to be regulated negatively by autophagy. Previous studies reported an abnormal induction of autophagy linked to progesterone resistance in human endometriotic cells. Therefore, an aberrant autophagy induction response to progesterone might contribute to the altered inflammatory response observed in endometriotic tissues. To evaluate this hypothesis, we elucidate whether regulation of the NLRP3 inflammasome by ovarian steroids is mediated by autophagy in human endometrial stromal cells (normal endometrial stromal cells (NESCs)) from patients with uterine leiomyoma (presumed normal) and whether abnormal autophagy induction in endometriotic cyst stromal cells (ECSCs) affects NLRP3 inflammasome-induced interleukin-1β (IL-1β) production. Our results show that estrogen enhanced NLRP3 inflammasome activation in NESCs, resulting in increased IL-1β production. Progesterone decreased NLRP3 inflammasome activity with an increase in autophagy induction in estrogen-treated NESCs. Inhibition of NLRP3 inflammasome activity by progesterone was blocked by autophagy inhibition. However, progesterone failed to change NLRP3 inflammasome activity and autophagy induction in estrogen-treated ECSCs. In contrast, dienogest, a specific progesterone receptor agonist, reduced NLRP3 inflammasome-mediated IL-1β production through autophagy induction in ECSCs. Furthermore, autophagy induction was decreased and NLRP3 inflammasome activity was increased in endometriotic tissues, which was reversed by preoperative administration of dienogest. In conclusion, our results suggest that progesterone inhibits NLRP3 inflammasome activation through autophagy in endometrial stromal cells. However, this inhibitory effect is attenuated in endometriotic stromal cells due to an aberrant autophagic response to progesterone, which could lead to an altered inflammatory response in endometriosis.

3β,23-Dihydroxy-12-ene-28-ursolic Acid Isolated from Cyclocarya paliurus Alleviates NLRP3 Inflammasome-Mediated Gout via PI3K-AKT-mTOR-Dependent Autophagy.

Gout is regarded as a painful inflammatory arthritis induced by the deposition of monosodium urate crystals in joints and soft tissues. Nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome-mediated IL-1β production plays a crucial role in the pathological process of gout. Cyclocarya paliurus (CP) tea was found to have an effect on reducing the blood uric acid level of people with hyperuricemia and gout. However, its medicinal ingredients and mechanism for the treatment of gout are still unclear. Thus, this study was designed to investigate the effects of the active triterpenoids isolated from C. paliurus on gout and explore the underlying mechanism. The results showed that compound 2 (3β,23-dihydroxy-12-ene-28-ursolic acid) from C. paliurus significantly decreased the protein expression of IL-1β, caspase-1, pro-IL-1β, pro-caspase-1, and NLRP3. Furthermore, the production of ROS in the intracellular was reduced after compound 2 treatment. However, ROS agonist rotenone remarkably reversed the inhibitory effect of compound 2 on the protein expression of NLRP3 inflammasome. Additionally, the expression level of LC3 and the ratio of LC3II/LC3I were increased, but the expression level of p62 was suppressed by compound 2 whereas an autophagy inhibitor 3-methyladenine (3-MA) significantly abolished the inhibitory effects of compound 2 on the generation of ROS and the protein expression of NLRP3 inflammasome. Moreover, compound 2 could ameliorate the expression ratio of p-PI3K/PI3K, p-AKT/AKT, and p-mTOR/mTOR. Interestingly, mTOR activator MHY-1485 could block the promotion effect of compound 2 on autophagy regulation and inhibitory effect of compound 2 on induction of ROS and IL-1β. In conclusion, these findings suggested that compound 2 may effectively improve NLRP3 inflammasome-mediated gout via PI3K-AKT-mTOR-dependent autophagy and could be further investigated as a potential agent against gout.

IL-1β Impacts Vascular Integrity and Lymphatic Function in the Embryonic Omentum.

The chromatin-remodeling enzyme BRG1 (brahma-related gene 1) regulates gene expression in a variety of rapidly differentiating cells during embryonic development. However, the critical genes that BRG1 regulates during lymphatic vascular development are unknown. We used genetic and imaging techniques to define the role of BRG1 in murine embryonic lymphatic development, although this approach inadvertently expanded our study to multiple interacting cell types. We found that omental macrophages fine-tune an unexpected developmental process by which erythrocytes escaping from naturally discontinuous omental blood vessels are collected by nearby lymphatic vessels. Our data indicate that circulating fibrin(ogen) leaking from gaps in omental blood vessels can trigger inflammasome-mediated IL-1β (interleukin-1β) production and secretion from nearby macrophages. IL-1β destabilizes adherens junctions in omental blood and lymphatic vessels, contributing to both extravasation of erythrocytes and their uptake by lymphatics. BRG1 regulates IL-1β production in omental macrophages by transcriptionally suppressing the inflammasome trigger RIPK3 (receptor interacting protein kinase 3). Genetic deletion of Brg1 in embryonic macrophages leads to excessive IL-1β production, erythrocyte leakage from blood vessels, and blood-filled lymphatics in the developing omentum. Altogether, these results highlight a novel context for epigenetically regulated crosstalk between macrophages, blood vessels, and lymphatics.

NLRP3 Inflammasome Activation Enhanced by TRIM25 is Targeted by the NS1 Protein of 2009 Pandemic Influenza A Virus.

Nucleotide-binding domain and leucine-rich repeat-containing protein 3 (NLRP3) inflammasome-mediated interleukin-1 beta (IL-1β) production is one of the crucial responses in innate immunity upon infection with viruses including influenza A virus (IAV) and is modulated by both viral and host cellular proteins. Among host proteins involved, we identified tripartite motif-containing protein 25 (TRIM25) as a positive regulator of porcine NLRP3 inflammasome-mediated IL-1β production. TRIM25 achieved this function by enhancing the pro-caspase-1 interaction with apoptosis-associated speck-like protein containing caspase recruitment domain (ASC). The N-terminal RING domain, particularly residues predicted to be critical for the E3 ligase activity of TRIM25, was responsible for this enhancement. However, non-structural protein 1 (NS1) C-terminus of 2009 pandemic IAV interfered with this action by interacting with TRIM25, leading to diminished association between pro-caspase-1 and ASC. These findings demonstrate that TRIM25 promotes the IL-1β signaling, while it is repressed by IAV NS1 protein, revealing additional antagonism of the NS1 against host pro-inflammatory responses.

Protein-Bound Uremic Toxins Induce Reactive Oxygen Species-Dependent and Inflammasome-Mediated IL-1β Production in Kidney Proximal Tubule Cells.

Protein bound-uremic toxins (PBUTs) are not efficiently removed by hemodialysis in chronic kidney disease (CKD) patients and their accumulation leads to various co-morbidities via cellular dysfunction, inflammation and oxidative stress. Moreover, it has been shown that increased intrarenal expression of the NLRP3 receptor and IL-1β are associated with reduced kidney function, suggesting a critical role for the NLRP3 inflammasome in CKD progression. Here, we evaluated the effect of PBUTs on inflammasome-mediated IL-1β production in vitro and in vivo. Exposure of human conditionally immortalized proximal tubule epithelial cells to indoxyl sulfate (IS) and a mixture of anionic PBUTs (UT mix) increased expression levels of NLRP3, caspase-1 and IL-1β, accompanied by a significant increase in IL-1β secretion and caspase-1 activity. Furthermore, IS and UT mix induced the production of intracellular reactive oxygen species, and caspase-1 activity and IL-1β secretion were reduced in the presence of antioxidant N-acetylcysteine. IS and UT mix also induced NF-κB activation as evidenced by p65 nuclear translocation and IL-1β production, which was counteracted by an IKK inhibitor. In vivo, using subtotal nephrectomy CKD rats, a significant increase in total plasma levels of IS and the PBUTs, kynurenic acid and hippuric acid, was found, as well as enhanced urinary malondialdehyde levels. CKD kidney tissue showed an increasing trend in expression of NLRP3 inflammasome components, and a decreasing trend in superoxide dismutase-1 levels. In conclusion, we showed that PBUTs induce inflammasome-mediated IL-1β production in proximal tubule cells via oxidative stress and NF-κB signaling, suggesting their involvement in disease-associated inflammatory processes.

Porphyromonas Gingivalis Infection Induces Synaptic Failure via Increased IL-1β Production in Leptomeningeal Cells.

Studies have reported that synaptic failure occurs before the Alzheimer's disease (AD) onset. The systemic Porphyromonas gingivalis (P. gingivalis) infection is involved in memory decline. We previously showed that leptomeningeal cells, covering the brain, activate glial cells by releasing IL-1β in response to systemic inflammation. In the present study, we focused on the impact of leptomeningeal cells on neurons during systemic P. gingivalis infection. The responses of leptomeningeal cells and cortical neurons to systemic P. gingivalis infection were examined in 15-month-old mice. The mechanism of IL-1β production by P. gingivalis infected leptomeningeal cells was examined, and primary cortical neurons were treated with P. gingivalis infected leptomeningeal cells condition medium (Pg LCM). Systemic P. gingivalis infection increased the expression of IL-1β in leptomeninges and reduced the synaptophysin (SYP) expression in leptomeninges proximity cortex in mice. Leptomeningeal cells phagocytosed P. gingivalis resulting in lysosomal rupture and cathepsin B (CatB) leakage. Leaked CatB mediated NLRP3 inflammasome activation inducing IL-1β secretion in leptomeningeal cells. Pg LCM decreased the expression of synaptic molecules, including SYP, which was inhibited by an IL-1 receptor antagonist pre-treatment. These observations demonstrate that P. gingivalis infection is involved in synaptic failure by inducing CatB/NLRP3 inflammasome-mediated IL-1β production in leptomeningeal cells. The periodontal bacteria-induced synaptic damage may accelerate the onset and cognitive decline of AD.

Hydrogen Peroxide Is Crucial for NLRP3 Inflammasome-Mediated IL-1β Production and Cell Death in Pneumococcal Infections of Bronchial Epithelial Cells

Epithelial cells play a crucial role in detection of the pathogens as well as in initiation of the host immune response. Streptococcus pneumoniae (pneumococcus) is a typical colonizer of the human nasopharynx, which can disseminate to the lower respiratory tract and subsequently cause severe invasive diseases such as pneumonia, sepsis, and meningitis. Hydrogen peroxide (H₂O₂) is produced by pneumococci as a product of the pyruvate oxidase SpxB. However, its role as a virulence determinant in pneumococcal infections of the lower respiratory tract is not well understood. In this study, we investigated the role of pneumococcal-derived H₂O₂ in initiating epithelial cell death by analyzing the interplay between 2 key cell death pathways, namely, apoptosis and pyroptosis. We demonstrate that H₂O₂ primes as well as activates the NLRP3 inflammasome and thereby mediates IL-1β production and release. Furthermore, we show that pneumococcal H₂O₂ causes cell death via the activation of both apoptotic as well as pyroptotic pathways which are mediated by the activation of caspase-3/7 and caspase-1, respectively. However, H₂O₂-mediated IL-1β release itself occurs mainly via apoptosis.

Adenosine synthase A contributes to recurrent Staphylococcus aureus infection by dampening protective immunity.

Background: Staphylococcus aureus is a common human pathogen capable of causing diverse illnesses with possible recurrent infections. Although recent studies have highlighted the role of cellular immunity in recurrent infections, the mechanism by which S. aureus evades host responses remains largely unexplored.Methods: This study utilizes in vitro and in vivo infection experiments to investigate difference of pro-inflammatory responses and subsequent adaptive immune responses between adsA mutant and WT S. aureus strain infection.Findings: We demonstrated that adenosine synthase A (AdsA), a potent S. aureus virulence factor, can alter Th17 responses by interfering with NLRP3 inflammasome-mediated IL-1β production. Specifically, S. aureus virulence factor AdsA dampens Th1/Th17 immunity by limiting the release of IL-1β and other Th polarizing cytokines. In particular, AdsA obstructs the release of IL-1β via the adenosine/A2aR/NLRP3 axis. Using a murine infection model, pharmacological inhibition of A2a receptor enhanced S. aureus-specific Th17 responses, whereas inhibition of NLRP3 and caspase-1 downregulated these responses. Our results showed that AdsA contributes to recurrent S. aureus infection by restraining protective Th1/Th17 responses.Interpretation: Our study provides important mechanistic insights for therapeutic and vaccination strategies against S. aureus infections.

AKT Regulates NLRP3 Inflammasome Activation by Phosphorylating NLRP3 Serine 5.

The cytosolic pattern recognition receptor NLRP3 senses host-derived danger signals and certain microbe-derived products in both humans and rodents. NLRP3 activation assembles an inflammasome complex that contains the adapter proteins ASC and caspase-1, whose activation triggers the maturation and release of the proinflammatory cytokines IL-1β and IL-18. S5 phosphorylation of NLRP3 prevents its oligomerization and activation, whereas dephosphorylation of this residue by the phosphatase PP2A allows NLRP3 activation. However, the protein kinase that mediates NLRP3 S5 phosphorylation is unknown. In this study, we show that AKT associates with NLRP3 and phosphorylates it on S5, limiting NLRP3 oligomerization. This phosphorylation event also stabilizes NLRP3 by reducing its ubiquitination on lysine 496, which inhibits its proteasome-mediated degradation by the E3 ligase Trim31. Pharmacologic manipulation of AKT kinase activity reciprocally modulates NLRP3 inflammasome-mediated IL-1β production. Inhibition of AKT reduced IL-1β production following the i.p. injection of LPS into mice. We propose that AKT, Trim31, and PP2A together modulate NLRP3 protein levels and the tendency to oligomerize, thereby setting a tightly regulated threshold for NLRP3 activation.

TET2-Loss-of-Function-Driven Clonal Hematopoiesis Exacerbates Experimental Insulin Resistance in Aging and Obesity

SUMMARYHuman aging is frequently accompanied by the acquisition of somatic mutations in the hematopoietic system that induce clonal hematopoiesis, leading to the development of a mutant clone of hematopoietic progenitors and leukocytes. This somatic-mutation-driven clonal hematopoiesis has been associated with an increased incidence of cardiovascular disease and type 2 diabetes, but whether this epidemiological association reflects a direct, causal contribution of mutant hematopoietic and immune cells to age-related metabolic abnormalities remains unexplored. Here, we show that inactivating mutations in the epigenetic regulator TET2, which lead to clonal hematopoiesis, aggravate age- and obesity-related insulin resistance in mice. This metabolic dysfunction is paralleled by increased expression of the pro-inflammatory cytokine IL-1β in white adipose tissue, and it is suppressed by pharmacological inhibition of NLRP3 inflammasome-mediated IL-1β production. These findings support a causal contribution of somatic TET2 mutations to insulin resistance and type 2 diabetes.

Biscaesalmins A and B from Caesalpinia minax, highly oxidized dimeric cassane diterpenoids as interleukin-1β inhibitors

To search naturally occurring interleukin-1β (IL-1β) inhibitors, biscaesalmins A (1) and B (2), two highly oxidized dimeric cassane diterpenoids with a newly formed alicyclic skeleton, have been isolated from the traditional Chinese medicine Kushilian (Caesalpinia minax). Their full structures were determined by comprehensive spectroscopic analysis and quantum chemical TD-DFT (time-dependent density functional theory) calculation. Biosynthetically, 1 and 2 were formed via an intermolecular [4 + 2] Diels-Alder cycloaddition of two monomers, affording an additional six-membered carbon ring linkage. Compounds 1 and 2 inhibited nitric oxide production on lipopolysaccharide-stimulated THP-1 macrophages, with IC50 values being at 1.20 ± 0.23 and 2.30 ± 0.15 μmol/L, respectively. Furthermore, compound 1 inhibited NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasome-mediated IL-1β production and blocked the migration of macrophages towards adipocyte conditioned medium. Biscaesalmins A and B might be candidates for treating inflammation-related metabolic diseases.

5-Heptadecylresorcinol, a Biomarker for Whole Grain Rye Consumption, Ameliorates Cognitive Impairments and Neuroinflammation in APP/PS1 Transgenic Mice.

5-heptadecylresorcinol (AR-C17) is a biomarker for whole grain rye consumption, which is also an important active component with potential health benefits. The aim of this study is to investigate the protective effect of AR-C17 on cognitive deficits in amyloid precursor protein (APP)/PS1 transgenic mice. Cognitive function is evaluated using Morris water maze test. The result shows that oral administration of AR-C17 (150mg kg-1 day-1 ) for 5 months can ameliorate APP/PS1 transgenic mice memory impairment and improve learning ability. Moreover, AR-C17 treatment can notably reduce β-amyloid plaques accumulation and tau hyperphosphorylation while enhancing a disintegrin and metalloprotease 10 (ADAM10), postsynaptic density protein-95 (PSD-95), and synaptophysin protein expression in APP/PS1 transgenic mice. Furthermore, AR-C17 treatment reduces neuroinflammation by inhibiting microglial activation and astrogliosis as well as decreasing NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome-mediated IL-1β production and activating the sirtuin 3 (SIRT3)/superoxide dismutase 2 (SOD2) signaling pathway. Additionally, AR-C17 consumption significantly modulated gut dysbiosis in APP/PS1 transgenic mice through improving the relative abundance of Akkermansia and Lactobacillus while reducing the abundance of Clostridium and Desulfovibr according to16S rRNA analysis. AR-C17 can be applied as a potential functional food ingredient to ameliorate cognitive impairments and prevent Alzheimer's disease.

Microtubule-Mediated NLRP3 Inflammasome Activation Is Independent of Microtubule-Associated Innate Immune Factor GEF-H1 in Murine Macrophages

Inflammasomes are intracellular multiple protein complexes that mount innate immune responses to tissue damage and invading pathogens. Their excessive activation is crucial in the development and pathogenesis of inflammatory disorders. Microtubules have been reported to provide the platform for mediating the assembly and activation of NLRP3 inflammasome. Recently, we have identified the microtubule-associated immune molecule guanine nucleotide exchange factor-H1 (GEF-H1) that is crucial in coupling microtubule dynamics to the initiation of microtubule-mediated immune responses. However, whether GEF-H1 also controls the activation of other immune receptors that require microtubules is still undefined. Here we employed GEF-H1-deficient mouse bone marrow-derived macrophages (BMDMs) to interrogate the impact of GEF-H1 on the activation of NLRP3 inflammasome. NLRP3 but not NLRC4 or AIM2 inflammasome-mediated IL-1β production was dependent on dynamic microtubule network in wild-type (WT) BMDMs. However, GEF-H1 deficiency did not affect NLRP3-driven IL-1β maturation and secretion in macrophages. Moreover, α-tubulin acetylation and mitochondria aggregations were comparable between WT and GEF-H1-deficient BMDMs in response to NLRP3 inducers. Further, GEF-H1 was not required for NLRP3-mediated immune defense against Salmonella typhimurium infection. Collectively, these findings suggest that the microtubule-associated immune modulator GEF-H1 is dispensable for microtubule-mediated NLRP3 activation and host defense in mouse macrophages.

637. Β-Lactam (BL) Antibiotics Promote an IL-1β Response in Patients with Staphylococcus aureus Bacteremia (SaB)

BackgroundBL therapy has been associated with reduced SaB duration compared with non-BL therapy. It has been shown that patients with SaB who fail to generate increased serum IL-1β are at risk for prolonged SaB (> 4 days duration), a predictor of mortality. This suggests a major role for the IL-1β host response in prompt clearance of SaB. Furthermore, BL result in reduced peptidoglycan cross-linking, reduced peptidoglycan O-acetylation, and increased alpha-toxin expression, all of which have independently been shown to enhance IL-1β release. This study aims to show that BL therapy results in a more robust IL-1β host response compared with non-BL therapy to explain, in part, more rapid SaB clearance.MethodsFifty-nine patients (47 MRSA and 12 MSSA) with diverse SaB sources, including endovascular, extravascular (e.g., pneumonia), and catheter-related infections were included. In the first 48 hours, patients were treated with either BL, including oxacillin, ceftaroline, or cefazolin (n = 24), vs. non-BL vancomycin or daptomycin (n = 35). IL-1β concentrations were determined by ELISA on serum samples obtained on Days 1, 3 and Day 7 after bacteremia onset and compared between groups by Mann–Whitney U test.ResultsPatients in BL and non-BL groups had similar IL-1β concentrations on Day 1 of bacteremia (median BL 6.1 pg/mL vs. non-BL 2.8 pg/mL, P = 0.090). BL-treated patients had significantly higher IL-1β serum concentrations on Day 3 (median 7.54 mg/mL vs. 1.9 pg/mL; P = 0.007) and Day 7 (12.52 pg/mL vs. 1.56 pg/mL, P = 0.016) when compared with non-BL-treated patients. BL therapy resulted in 23% and 105% increase in IL-1β at Days 3 and 7, respectively, while non-BL treatment resulted in 32% and 44% reduction in IL-1β. The median duration of SaB was similar between BL and non-BL-treated patients (2.5 vs. 2.0 days, respectively, P = 0.590).ConclusionGiven that a lack of inflammasome-mediated IL-1β production is associated with prolonged SaB, the significant increases in IL-1β levels in patients treated with BL has important therapeutic implications. Previously observed reduced duration of MRSA bacteremia with the addition of BL to vancomycin may have its basis on enhancing IL-1β release. A therapeutic regimen of vancomycin or daptomycin in combination with BL to treat MRSA bacteremia and use of BL therapy in MSSA bacteremia is strongly advised to improve outcomes based on these results.Disclosures G. Sakoulas, Allergan: Consultant and Speaker, Consulting fee and Speaker honorarium. Sunovion: Speaker, Speaker honorarium. The Medicines Company: Speaker, Consulting fee. Paratek Pharmaceuticals: Consultant, Consulting fee. Cidara Therapeutics: Scientific Advisor, None. Arsanis Pharmaceuticals: Scientific Advisor, None. W. Rose, Merck: Grant Investigator, Research grant.

Tannic acid inhibits NLRP3 inflammasome-mediated IL-1β production via blocking NF-κB signaling in macrophages

The NLRP3 inflammasome rapidly responds to many infections and stress signals and is involved in the pathogenesis of numerous inflammatory disease processes. Tannic acid plays a role in antioxidant, antifungal and antitumor activities. Here, we reported that tannic acid inhibited NLRP3 inflammasome activation by blocking NF-κB signaling to suppress IL-1β secretion. We found that the BMDMs (bone marrow-derived macrophages cells) pre-treated with tannic acid blocked caspase-1 cleavage and inhibited IL-1β secretion in a NLRP3-dependent manner, and suppressed NF-κB signaling activation by inhibiting NF-κB/P65 nuclear localization, suggesting that tannic acid inhibited NLRP3 inflammasome activation. These investigations revealed that tannic acid inhibited NLRP3 inflammasome activation via blocking NF-κB signaling in macrophages, providing us with evidence that tannic acid may be a potent inhibitor for NLRP3-driven diseases.