Recent advances in the mechanisms of NLRP3 inflammasome activation and its inhibitors. Cell Death Dis. 2019;10:128. [PMID: 30755589 PMCID: PMC6372664 DOI: 10.1038/s41419-019-1413-8]

Design, Synthesis, and Biological Evaluation of Ferulic Acid Template-Based Novel Multifunctional Ligands Targeting NLRP3 Inflammasome for the Management of Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia, which arises due to low levels of acetyl and butyrylcholines, an increase in oxidative stress, inflammation, metal dyshomeostasis, Aβ and tau aggregations. The currently available drugs for AD treatment can provide only symptomatic relief without interfering with pathological hallmarks of the disease. In our ongoing efforts to develop naturally inspired novel multifunctional molecules for AD, systematic SAR studies on EJMC-4e were caried out to improve its multifunctional properties. The rigorous medicinal efforts led to the development of 12o, which displayed a 15-fold enhancement in antioxidant properties and a 2-fold increase in the activity against AChE and BChE over EJMC-4e. Molecular docking and dynamics studies revealed the binding sites and stability of the complex of 12o with AChE and BChE. The PAMPA-BBB assay clearly demonstrated that 12o can easily cross the blood-brain barrier. Interestingly, 12o also expresses promising metal chelation activity, while EJMC-4e was found to be devoid of this property. Further, 12o inhibited metal-induced or self Aβ1-42 aggregation. Observing the neuroprotection ability of 12o against H2O2-induced oxidative stress in the PC-12 cell line is noteworthy. Furthermore, 12o also inhibited NLRP3 inflammasome activation and attenuated mitochondrial-induced ROS and MMP damage caused by LPS and ATP in HMC-3 cells. In addition, 12o is able to effectively reduce mitochondrial and cellular oxidative stress in the AD Drosophila model. Finally, 12o could reverse memory impairment in the scopolamine-induced AD mice model, as evident through in vivo and ex vivo studies. These findings suggest that this compound may act as a promising candidate for further improvement in the management of AD.

Gut Microbiota Composition Correlates with Disease Severity in Myelodysplastic Syndrome

The myelodysplastic syndrome (MDS) is a heterogeneous group of clonal disorders of hematopoietic progenitor cells related to ineffective hematopoiesis and an increased risk of transformation to acute myelogenous leukemia. MDS is divided into categories, namely lineage dysplasia (MDS-SLD), MDS with ring sideroblasts (MDS-RS), MDS with multilineage dysplasia (MDS-MLD), MDS with excess blasts (MDS-EB). The International Prognostic Classification System (IPSS) ranks the patients as very low, low, intermediate, high, and very high based on disease evolution and survival rates. Evidence points to toll-like receptor (TLR) abnormal signaling as an underlying mechanism of this disease, providing a link between MDS and immune dysfunction. Microbial signals, such as lipopolysaccharides from gram-negative bacteria, can activate or suppress TLRs. Therefore, we hypothesized that MDS patients present gut microbiota alterations associated with disease subtypes and prognosis. To test this hypothesis, we sequenced the 16S rRNA gene from fecal samples of 30 MDS patients and 16 healthy elderly controls. We observed a negative correlation between Prevotella spp. and Akkermansia spp. in MDS patients compared with the control group. High-risk patients presented a significant increase in the genus Prevotella spp. compared to the other risk categories. There was a significant reduction in the abundance of the genus Akkermansia spp. in high-risk patients compared with low- and intermediate-risk. There was a significant decrease in the genus Ruminococcus spp. in MDS-EB patients compared with controls. Our findings show a new association between gut dysbiosis and higher-risk MDS, with a predominance of gram-negative bacteria.

Crosstalk between autophagy and inflammasomes in ricin-induced inflammatory injury

Ricin (ricin toxin, RT) has the potential to cause damage to multiple organs and systems. Currently, there are no existing antidotes, vaccinations, or effective therapies to prevent or treat RT intoxication. Apart from halting protein synthesis, RT also induces oxidative stress, inflammation and autophagy. To explore the mechanisms of RT-induced inflammatory injury and specific targets of prevention and treatment for RT poisoning, we characterized the role of cross-talk between autophagy and NLRP3 inflammasome in RT-induced damage and elucidated the underlying mechanisms. We showed that RT-induced inflammation was attributed to activation of the TLR4/MyD88/NLRP3 signaling and ROS production, evidenced by increased ASC speck formation and attenuated TXNIP/TRX-1 interaction, as well as pre-treatment with MCC950, MyD88 knockdown and NAC significantly reduced IL-1β, IL-6 and TNF-α mRNA expression. In addition, autophagy is also enhanced in RT-triggered MLE-12 cells. RT elevated the levels of ATG5, p62 and Beclin1 protein, provoked the accumulation of LC3 puncta detected by immunofluorescence staining. Treatment with rapamycin (Rapa) reversed the RT-caused TLR4/MyD88/NLRP3 signaling activation, ASC specks formation as well as the levels of IL-1β, IL-6 and TNF-α mRNA. In conclusion, RT promoted NLRP3 inflammasome activation and autophgay. Inflammation induced by RT was attenuated by autophagy activation, which suppressed the NLRP3 inflammasome. These findings suggest Rapa as a potential therapeutic drug for the treatment of RT-induced inflammation-related diseases.

Octyl gallate has potent anti-inflammasome activity by directly binding to NLRP3 LRR domain

The NOD-, LRR-, and Pyrin domain-containing protein 3 (NLRP3) inflammasome plays key roles in regulating inflammation. Numerous studies show that the abnormal activation of NLRP3 associates with the initiation and progression of various diseases. Hence, the NLRP3 inflammasome may be a promising therapeutic target for these diseases. Octyl gallate (OG) is a small molecule with antioxidant, antimicrobial, antifungal, and anti-inflammatory activities; however, the mechanism underlying its anti-inflammatory activity is still unclear. Here, we developed a screening system for NLRP3-inflammasome inhibitors. A total of 3287 small molecules were screened for inhibitors of nigericin-induced NLRP3 oligomerization. OG was identified as a novel inhibitor. We show that OG directly targets the LRR domain of NLRP3 and thereby blocks the inflammatory cascade of the NLRP3 inflammasome. This contrasts with the mode-of-action of other direct NLRP3 inhibitors, which all bind to the NACHT domain of NLRP3. Interestingly, OG also inhibits the priming step by downregulating the Raf-MEK1/2-ERK1/2 axis. Thus, OG inhibits the NLRP3 inflammasome by two distinct mechanisms. Importantly, OG injection ameliorated the inflammation in mouse models of foot gout and sepsis. Our study identifies OG as a potential therapeutic agent for NLRP3-associated diseases.

Crosstalk between P2Y receptors and cyclooxygenase activity in inflammation and tissue repair

The role of extracellular nucleotides as modulators of inflammation and cell stress is well established. One of the main actions of these molecules is mediated by the activation of purinergic receptors (P2) of the plasma membrane. P2 receptors can be classified according to two different structural families: P2X ionotropic ion channel receptors, and P2Y metabotropic G protein-coupled receptors. During inflammation, damaged cells release nucleotides and purinergic signaling occurs along the temporal pattern of the synthesis of pro-inflammatory and pro-resolving mediators by myeloid and lymphoid cells. In macrophages under pro-inflammatory conditions, the expression and activity of cyclooxygenase 2 significantly increases and enhances the circulating levels of prostaglandin E2 (PGE2), which exerts its effects both through specific plasma membrane receptors (EP1-EP4) and by activation of intracellular targets. Here we review the mechanisms involved in the crosstalk between PGE2 and P2Y receptors on macrophages, which is dependent on several isoforms of protein kinase C and protein kinase D1. Due to this crosstalk, a P2Y-dependent increase in calcium is blunted by PGE2 whereas, under these conditions, macrophages exhibit reduced migratory capacity along with enhanced phagocytosis, which contributes to the modulation of the inflammatory response and tissue repair.

TXNIP/NLRP3 aggravates global cerebral ischemia-reperfusion injury-induced cognitive decline in mice

Global cerebral ischemia/reperfusion (GCI/R) injury poses a risk for cognitive decline, with neuroinflammation considered pivotal in this process. This study aimed to unravel the molecular mechanisms underlying GCI/R injury and propose a potential therapeutic strategy for associated cognitive deficits. Utilizing bioinformatics analysis of a public microarray profile (GSE30655 and GSE80681) in cerebral ischemic mice, it was observed that neuroinflammation emerged as a significant gene ontology item, with an increase in the expression of thioredoxin-interacting protein (TXNIP) and NLRP3 genes. Experimental models involving bilateral occlusion of the common carotid arteries in mice revealed that GCI/R induced cognitive impairment, along with a time-dependent increase in TXNIP and NLRP3 levels. Notably, TXNIP knockdown alleviated cognitive dysfunction in mice. Furthermore, the introduction of adeno-associated virus injection with TXNIP knockdown reduced the number of activated microglia, apoptosis neurons, and levels of oxidative stress and inflammatory cytokines in the hippocampus. Collectively, these findings underscore the significance of TXNIP/NLRP3 in the hippocampus in exacerbating cognitive decline due to GCI/R injury, suggesting that TXNIP knockdown holds promise as a therapeutic strategy.

Implication of M2 macrophage on NLRP3 inflammasome signaling in mediating the neuroprotective effect of Canagliflozin against methotrexate-induced cognitive impairment

Methotrexate (MTX), a chemotherapeutic antimetabolite, has been linked to cognitive impairment in cancer patients. MTX-induced metabolic pathway disruption may result in decreased antioxidant activity and increased oxidative stress, influencing hippocampal neurogenesis and microglial activation. Nuclear factor-kappa B (NF-κB), an oxidative stress byproduct, has been linked to MTX toxicity via the activation of NLRP3 inflammasome signaling. Macrophage activation and polarization plays an important role in tissue injury. This differentiation may be mediated via either the Toll-like receptor 4 (TLR4) or NLRP3 inflammasome. Interestingly, Canagliflozin (CANA), a sodium-glucose cotransporter 2 (SGLT2) inhibitor has been recently reported to exert anti-inflammatory effects by modulating macrophage polarization balance. This study aimed to investigate CANA's protective effect against MTX-induced cognitive impairment, highlighting the possible involvement of TLR4/ NF-κB crosstalk with NLRP3 inflammasome activation and macrophage polarization. Forty-eight Male Wistar rats were divided into 4 groups; (1) received saline orally for 30 days and intravenously on days 8 and 15. (2) received Canagliflozin (CANA; 20 mg/kg/day; p.o.) for 30 days. (3) received MTX (75 mg/kg, i.v.) on day 8 and 15, then they were injected with four i.p. injections of leucovorin (LCV): the first dose was 6 mg/ kg after 18 h, and the remaining doses were 3 mg/kg after 26, 42, and 50 h of MTX administration. (4) received MTX and LCV as in group 3 in addition to CANA as in group 2. MTX-treated rats showed cognitive deficits in spatial and learning memory as evidenced in the novel object recognition and Morris water maze tests. MTX exerted an oxidative effect which was evident by the increase in MDA and decline in SOD, GSH and GPx. Moreover, it exerted an inflammatory effect via elevated caspase-1, IL-1β and IL-8. CANA treatment restored cognitive ability, reduced MTX-induced oxidative stress and neuroinflammation via attenuation of TLR4/NF-κB/NLRP3 signaling, and rebalanced macrophage polarization by promoting the M2 phenotype. Hence, targeting molecular mechanisms manipulating macrophage polarization may offer novel neuroprotective strategies for preventing or treating MTX-induced immune modulation and its detrimental sequel.

P2X7 receptor antagonists modulate experimental autoimmune neuritis via regulation of NLRP3 inflammasome activation and Th17 and Th1 cell differentiation

BACKGROUND

Guillain-Barré syndrome (GBS), a post-infectious, immune-mediated, acute demyelinating disease of the peripheral nerves and nerve roots, represents the most prevalent and severe acute paralyzing neuropathy. Purinergic P2X7 receptors (P2X7R) play a crucial role in central nervous system inflammation. However, little is known about their role in the immune-inflammatory response within the peripheral nervous system.

METHODS

Initially, we assessed the expression of purinergic P2X7R in the peripheral blood of patients with GBS using flow cytometry and qRT-PCR. Next, we explored the expression of P2 X7R in CD4+ T cells, CD8+ T cells, and macrophages within the sciatic nerves and spleens of rats using immunofluorescence labeling and flow cytometry. The P2X7R antagonist brilliant blue G (BBG) was employed to examine its therapeutic impact on rats with experimental autoimmune neuritis (EAN) induced by immunization with the P0180 - 199 peptide. We analyzed CD4+ T cell differentiation in splenic mononuclear cells using flow cytometry, assessed Th17 cell differentiation in the sciatic nerve through immunofluorescence staining, and examined the expression of pro-inflammatory cytokine mRNA using RT-PCR. Additionally, we performed protein blotting to assess the expression of P2X7R and NLRP3-related inflammatory proteins within the sciatic nerve. Lastly, we utilized flow cytometry and immunofluorescence labeling to examine the expression of NLRP3 on CD4+ T cells in rats with EAN.

RESULTS

P2X7R expression was elevated not only in the peripheral blood of patients with GBS but also in rats with EAN. In rats with EAN, inhibiting P2X7R with BBG alleviated neurological symptoms, reduced demyelination, decreased inflammatory cell infiltration of the peripheral nerves, and improved nerve conduction. BBG also limited the production of pro-inflammatory molecules, down-regulated the expression of P2X7R and NLRP3, and suppressed the differentiation of Th1 and Th17 cells, thus protecting against EAN. These effects collectively contribute to modifying the inflammatory environment and enhancing outcomes in EAN rats.

CONCLUSIONS

Suppression of P2X7R relieved EAN manifestation by regulating CD4+ T cell differentiation and NLRP3 inflammasome activation. This finding underscores the potential significance of P2X7R as a target for anti-inflammatory treatments, advancing research and management of GBS.

Amino Sugar-Enriched Fraction of Korean Red Ginseng Extract Induces the Priming Step of NLRP3 Inflammasome

Intracellular protein complexes, known as inflammasomes, activate caspase-1 and induce the secretion of pro-inflammatory cytokines, namely interleukin (IL)-1β and -18. Korean Red Ginseng extract (RGE) is a known immunomodulator and a potential candidate for the regulation of inflammasomes. The saponins, such as ginsenosides, of RGE inhibit inflammasome signaling, while non-saponin substances containing amino sugars promote the priming step, up-regulating inflammasome components (pro-IL-1β, NLRP3, caspase-1, and Asc). In this study, the amino sugar-enriched fraction (ASEF), which increases only non-saponin components, including amino sugars, without changing the concentration of saponin substances, was used to investigate whether saponin or non-saponin components of RGE would have a greater impact on the priming step. When murine macrophages were treated with ASEF, the gene expression of inflammatory cytokines (IL-1α, TNFα, IL-6, and IL-10) increased. Additionally, ASEF induced the priming step but did not affect the inflammasome activation step, such as the secretion of IL-1β, cleavage of caspase-1, and formation of Asc pyroptosome. Furthermore, the upregulation of gene expression of inflammasome components by ASEF was blocked by inhibitors of Toll-like receptor 4 signaling. Maltol, the main constituent of ASEF, promoted the priming step but inhibited the activation step of the inflammasome, while arginine, sugars, arginine-fructose-glucose, and fructose-arginine, the other main constituents of ASEF, had no effect on either step. Thus, certain amino sugars in RGE, excluding maltol, are believed to be the components that induce the priming step. The priming step that prepares the NLRP3 inflammasome for activation appears to be induced by amino sugars in RGE, thereby contributing to the immune-boosting effects of RGE.

Circadian Influences on Myocardial Ischemia-Reperfusion Injury and Heart Failure

The impact of circadian rhythms on cardiovascular function and disease development is well established, with numerous studies in genetically modified animals emphasizing the circadian molecular clock's significance in the pathogenesis and pathophysiology of myocardial ischemia and heart failure progression. However, translational preclinical studies targeting the heart's circadian biology are just now emerging and are leading to the development of a novel field of medicine termed circadian medicine. In this review, we explore circadian molecular mechanisms and novel therapies, including (1) intense light, (2) small molecules modulating the circadian mechanism, and (3) chronotherapies such as cardiovascular drugs and meal timings. These promise significant clinical translation in circadian medicine for cardiovascular disease. (4) Additionally, we address the differential functioning of the circadian mechanism in males versus females, emphasizing the consideration of biological sex, gender, and aging in circadian therapies for cardiovascular disease.

Mitochondria driven innate immune signaling and inflammation in cancer growth, immune evasion, and therapeutic resistance

Mitochondria play an important and multifaceted role in cellular function, catering to the cell's energy and biosynthetic requirements. They modulate apoptosis while responding to diverse extracellular and intracellular stresses including reactive oxygen species (ROS), nutrient and oxygen scarcity, endoplasmic reticulum stress, and signaling via surface death receptors. Integral components of mitochondria, such as mitochondrial DNA (mtDNA), mitochondrial RNA (mtRNA), Adenosine triphosphate (ATP), cardiolipin, and formyl peptides serve as major damage-associated molecular patterns (DAMPs). These molecules activate multiple innate immune pathways both in the cytosol [such as Retionoic Acid-Inducible Gene-1 (RIG-1) and Cyclic GMP-AMP Synthase (cGAS)] and on the cell surface [including Toll-like receptors (TLRs)]. This activation cascade leads to the release of various cytokines, chemokines, interferons, and other inflammatory molecules and oxidative species. The innate immune pathways further induce chronic inflammation in the tumor microenvironment which either promotes survival and proliferation or promotes epithelial to mesenchymal transition (EMT), metastasis and therapeutic resistance in the cancer cell's. Chronic activation of innate inflammatory pathways in tumors also drives immunosuppressive checkpoint expression in the cancer cells and boosts the influx of immune-suppressive populations like Myeloid-Derived Suppressor Cells (MDSCs) and Regulatory T cells (Tregs) in cancer. Thus, sensing of cellular stress by the mitochondria may lead to enhanced tumor growth. In addition to that, the tumor microenvironment also becomes a source of immunosuppressive cytokines. These cytokines exert a debilitating effect on the functioning of immune effector cells, and thus foster immune tolerance and facilitate immune evasion. Here we describe how alteration of the mitochondrial homeostasis and cellular stress drives innate inflammatory pathways in the tumor microenvironment.

NLRP3 and AIM2 inflammasomes exacerbate the pathogenic Th17 cell response to eggs of the helminth Schistosoma mansoni

Infection with the helminth Schistosoma mansoni can cause exacerbated morbidity and mortality via a pathogenic host CD4 T cell-mediated immune response directed against parasite egg antigens, with T helper (Th) 17 cells playing a major role in the development of severe granulomatous hepatic immunopathology. The role of inflammasomes in intensifying disease has been reported; however, neither the types of caspases and inflammasomes involved, nor their impact on the Th17 response are known. Here we show that enhanced egg-induced IL-1β secretion and pyroptotic cell death required both caspase-1 and caspase-8 as well as NLRP3 and AIM2 inflammasome activation. Schistosome genomic DNA activated AIM2, whereas reactive oxygen species, potassium efflux and cathepsin B, were the major activators of NLRP3. NLRP3 and AIM2 deficiency led to a significant reduction in pathogenic Th17 responses, suggesting their crucial and non-redundant role in promoting inflammation. Additionally, we show that NLRP3- and AIM2-induced IL-1β suppressed IL-4 and protective Type I IFN (IFN-I) production, which further enhanced inflammation. IFN-I signaling also curbed inflammasome- mediated IL-1β production suggesting that these two antagonistic pathways shape the severity of disease. Lastly, Gasdermin D (Gsdmd) deficiency resulted in a marked decrease in egg-induced granulomatous inflammation. Our findings establish NLRP3/AIM2-Gsdmd axis as a central inducer of pathogenic Th17 responses which is counteracted by IFN-I pathway in schistosomiasis.

The Complexity of Being A20: From Biological Functions to Genetic Associations

A20, encoded by TNFAIP3, is a critical negative regulator of immune activation. A20 is a ubiquitin editing enzyme with multiple domains, each of which mediates or stabilizes a key ubiquitin modification. A20 targets diverse proteins that are involved in pleiotropic immunologic pathways. The complexity of A20-mediated immunomodulation is illustrated by the varied effects of A20 deletion in different cell types and disease models. Clinically, the importance of A20 is highlighted by its extensive associations with human disease. A20 germline variants are associated with a wide range of inflammatory diseases, while somatic mutations promote development of B cell lymphomas. More recently, the discovery of A20 haploinsufficiency (HA20) has provided real world evidence for the role of A20 in immune cell function. Originally described as an autosomal dominant form of Behcet's disease, HA20 is now considered a complex inborn error of immunity with a broad spectrum of immunologic and clinical phenotypes.

Different Anti-inflammatory Drugs on High-Sensitivity C-Reactive Protein in Patients After Percutaneous Coronary Intervention: A Pilot Randomized Clinical Trial

ABSTRACT

Colchicine reduces atherothrombotic cardiovascular events in coronary artery disease because of its anti-inflammatory effect. However, the effects of the other anti-inflammatory drugs in coronary artery disease remain unclear. This study included 132 patients aged 18-80 years who completed the planned percutaneous coronary interventions and were treated with aggressive secondary prevention strategies for 4 weeks. The subjects were randomly assigned to 1 of the following treatment groups for 4 weeks: (1) control: no additional intervention; (2) colchicine: 0.5 mg once a day; (3) tranilast: 0.1 g thrice a day; or (4) oridonin: 0.5 g thrice a day. The primary outcome was the percentage change in high-sensitivity C-reactive protein (hsCRP) levels at the end of 4 weeks. In total, 109 patients completed the study. The mean age was 58.33 years, 81 (74.31%) were male, and 28 (25.69%) were female. The percentage changes in hsCRP after 4 weeks of treatment were -11.62%, -48.28%, -21.60%, and -7.81%, in the control, colchicine, tranilast, and the oridonin groups, respectively. Compared with the control group, only the colchicine group showed significantly greater reduction in hsCRP levels ( P = 0.022). In targeted proteomic analysis, proteins associated with neutrophil activation (azurocidin, myeloperoxidase, and myeloblastin), platelet aggregation (glycoprotein VI), and endothelial damage (galectin-3) were reduced with colchicine therapy. These results show that of 3 anti-inflammatory drugs only colchicine could reduce hsCRP in patients after percutaneous coronary interventions.

Transcutaneous electrical acupoint stimulation attenuated neuroinflammation and oxidative stress by activating SIRT1-induced signaling pathway in MCAO/R rat models

BACKGROUND

Silent information regulator 1 (SIRT1) plays a beneficial role in cerebral ischemic injury. Previous reports have demonstrated that transcutaneous electrical acupoint stimulation (TEAS) exerts a beneficial effect on ischemic stroke; however, whether SIRT1 participates in the underlying mechanism for the neuroprotective effects of TEAS against ischemic brain damage has not been confirmed.

METHODS

The rat models of middle cerebral artery occlusion/reperfusion (MCAO/R) were utilized in the current experiment. After MCAO/R surgery, rats in TEAS, EC and EX group received TEAS intervention with or without the injection of EX527, the SIRT1 inhibitor. Neurological deficit scores, infarct volume, hematoxylin eosin (HE) staining and apoptotic cell number were measured. The results of RNA sequencing were analyzed to determine the differential expression changes of genes among sham, MCAO and TEAS groups, in order to investigate the possible pathological processes involved in cerebral ischemia and explore the protective mechanisms of TEAS. Moreover, oxidative stress markers including MDA, SOD, GSH and GSH-Px were measured with assay kits. The levels of the proinflammatory cytokines, such as IL-6, IL-1β and TNF-α, were detected by ELISA assay, and Iba-1 (the microglia marker protein) positive cells was measured by immunofluorescence (IF). Western blot and IF were utilized to examine the levels of key molecules in SIRT1/FOXO3a and SIRT1/BRCC3/NLRP3 signaling pathways.

RESULTS

TEAS significantly decreased brain infarcted size and apoptotic neuronal number, and alleviated neurological deficit scores and morphological injury by activating SIRT1. The results of RNA-seq and bioinformatic analysis revealed that oxidative stress and inflammation were the key pathological mechanisms, and TEAS alleviated oxidative injury and inflammatory reactions following ischemic stroke. Then, further investigation indicated that TEAS notably attenuated neuronal apoptosis, neuroinflammation and oxidative stress damage in the hippocampus of rats with MCAO/R surgery. Moreover, TEAS intervention in the MCAO/R model significantly elevated the expressions of SIRT1, FOXO3a, CAT, BRCC3, NLRP3 in the hippocampus. Furthermore, EX527, as the inhibitor of SIRT1, obviously abolished the anti-oxidative stress and anti-neuroinflammatory roles of TEAS, as well as reversed the TEAS-mediated elevation of SIRT1, FOXO3a, CAT and reduction of BRCC3 and NLRP3 mediated by following MCAO/R surgery.

CONCLUSIONS

In summary, these findings clearly suggested that TEAS attenuated brain damage by suppressing apoptosis, oxidative stress and neuroinflammation through modulating SIRT1/FOXO3a and SIRT1/BRCC3/NLRP3 signaling pathways following ischemic stroke, which can be a promising treatment for stroke patients.

Therapeutic strategies targeting the NLRP3‑mediated inflammatory response and pyroptosis in cerebral ischemia/reperfusion injury (Review)

Ischemic stroke poses a major threat to human health. Therefore, the molecular mechanisms of cerebral ischemia/reperfusion injury (CIRI) need to be further clarified, and the associated treatment approaches require exploration. The NOD‑like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome serves an important role in causing CIRI, and its activation exacerbates the underlying injury. Activation of the NLRP3 inflammasome triggers the maturation and production of the inflammatory molecules IL‑1β and IL‑18, as well as gasdermin‑D‑mediated pyroptosis and CIRI damage. Thus, the NLRP3 inflammasome may be a viable target for the treatment of CIRI. In the present review, the mechanisms of the NLRP3 inflammasome in the intense inflammatory response and pyroptosis induced by CIRI are discussed, and the therapeutic strategies that target the NLRP3‑mediated inflammatory response and pyroptosis in CIRI are summarized. At present, certain drugs have already been studied, highlighting future therapeutic perspectives.

Fantastic voyage: The journey of NLRP3 inflammasome activation

NLRP3 inflammasome, an intracellular multiprotein complex, can be activated by a range of pathogenic microbes or endogenous hazardous chemicals. Its activation results in the release of cytokines such as IL-1β and IL-18, as well as Gasdermin D which eventually causes pyroptosis. The activation of NLRP3 inflammasome is under strict control and regulation by numerous pathways and mechanisms. Its excessive activation can lead to a persistent inflammatory response, which is linked to the onset and progression of severe illnesses. Recent studies have revealed that the subcellular localization of NLRP3 changes significantly during the activation process. In this review, we review the current understanding of the molecular mechanism of NLRP3 inflammasome activation, focusing on the subcellular localization of NLRP3 and the associated regulatory mechanisms. We aim to provide a comprehensive understanding of the dynamic transportation, activation, and degradation processes of NLRP3.

Colon-targeted S100A8/A9-specific peptide systems ameliorate colitis and colitis-associated colorectal cancer in mouse models

The link between chronic inflammation and cancer development is well acknowledged. Inflammatory bowel disease including ulcerative colitis and Crohn's disease frequently promotes colon cancer development. Thus, control of intestinal inflammation is a therapeutic strategy to prevent and manage colitis-associated colorectal cancer (CRC). Recently, gut mucosal damage-associated molecular patterns S100A8 and S100A9, acting via interactions with their pattern recognition receptors (PRRs), especially TLR4 and RAGE, have emerged as key players in the pathogenesis of colonic inflammation. We found elevated serum levels of S100A8 and S100A9 in both colitis and colitis-associated CRC mouse models along with significant increases in their binding with PRR, TLR4, and RAGE. In this study we developed a dual PRR-inhibiting peptide system (rCT-S100A8/A9) that consisted of TLR4- and RAGE-inhibiting motifs derived from S100A8 and S100A9, and conjugated with a CT peptide (TWYKIAFQRNRK) for colon-specific delivery. In human monocyte THP-1 and mouse BMDMs, S100A8/A9-derived peptide comprising TLR4- and RAGE-interacting motif (0.01, 0.1, 1 μM) dose-dependently inhibited the binding of S100 to TLR4 or RAGE, and effectively inhibited NLRP3 inflammasome activation. We demonstrated that rCT-S100A8/A9 had appropriate drug-like properties including in vitro stabilities and PK properties as well as pharmacological activities. In mouse models of DSS-induced acute and chronic colitis, injection of rCT-S100A8/A9 (50 μg·kg-1·d-1, i.p. for certain consecutive days) significantly increased the survival rates and alleviated the pathological injuries of the colon. In AOM/DSS-induced colitis-associated colorectal cancer (CAC) mouse model, injection of rCT-S100A8/A9 (50 μg·kg-1·d-1, i.p.) increased the body weight, decreased tumor burden in the distal colon, and significantly alleviated histological colonic damage. In mice bearing oxaliplatin-resistant CRC xenografts, injection of rCT-S100A8/A9 (20 μg/kg, i.p., every 3 days for 24-30 days) significantly inhibited the tumor growth with reduced EMT-associated markers in tumor tissues. Our results demonstrate that targeting the S100-PRR axis improves colonic inflammation and thus highlight this axis as a potential therapeutic target for colitis and CRC.

New Insights on NLRP3 Inflammasome: Mechanisms of Activation, Inhibition, and Epigenetic Regulation

Inflammasomes are important modulators of inflammation. Dysregulation of inflammasomes can enhance vulnerability to conditions such as neurodegenerative diseases, autoinflammatory diseases, and metabolic disorders. Among various inflammasomes, Nucleotide-binding oligomerization domain leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) is the best-characterized inflammasome related to inflammatory and neurodegenerative diseases. NLRP3 is an intracellular sensor that recognizes pathogen-associated molecular patterns and damage-associated patterns resulting in the assembly and activation of NLRP3 inflammasome. The NLRP3 inflammasome includes sensor NLRP3, adaptor apoptosis-associated speck-like protein (ASC), and effector cysteine protease procaspase-1 that plays an imperative role in caspase-1 stimulation which further initiates a secondary inflammatory response. Regulation of NLRP3 inflammasome ameliorates NLRP3-mediated diseases. Much effort has been invested in studying the activation, and exploration of specific inhibitors and epigenetic mechanisms controlling NLRP3 inflammasome. This review gives an overview of the established NLRP3 inflammasome assembly, its brief molecular mechanistic activations as well as a current update on specific and non-specific NLRP3 inhibitors that could be used in NLRP3-mediated diseases. We also focused on the recently discovered epigenetic mechanisms mediated by DNA methylation, histone alterations, and microRNAs in regulating the activation and expression of NLRP3 inflammasome, which has resulted in a novel method of gaining insight into the mechanisms that modulate NLRP3 inflammasome activity and introducing potential therapeutic strategies for CNS disorders.

Viroporins Manipulate Cellular Powerhouses and Modulate Innate Immunity

Viruses have a wide repertoire of molecular strategies that focus on their replication or the facilitation of different stages of the viral cycle. One of these strategies is mediated by the activity of viroporins, which are multifunctional viral proteins that, upon oligomerization, exhibit ion channel properties with mild ion selectivity. Viroporins facilitate multiple processes, such as the regulation of immune response and inflammasome activation through the induction of pore formation in various cell organelle membranes to facilitate the escape of ions and the alteration of intracellular homeostasis. Viroporins target diverse membranes (such as the cellular membrane), endoplasmic reticulum, and mitochondria. Cumulative data regarding the importance of mitochondria function in multiple processes, such as cellular metabolism, energy production, calcium homeostasis, apoptosis, and mitophagy, have been reported. The direct or indirect interaction of viroporins with mitochondria and how this interaction affects the functioning of mitochondrial cells in the innate immunity of host cells against viruses remains unclear. A better understanding of the viroporin-mitochondria interactions will provide insights into their role in affecting host immune signaling through the mitochondria. Thus, in this review, we mainly focus on descriptions of viroporins and studies that have provided insights into the role of viroporins in hijacked mitochondria.

Therapeutic effects of a walnut-derived peptide on NLRP3 inflammasome activation, synaptic plasticity, and cognitive dysfunction in T2DM mice

NLRP3 inflammasome activation plays a key role in the development of diabetes-induced cognitive impairment. However, strategies to inhibit NLRP3 inflammasome activation remain elusive. Herein, we evaluated the impact of a walnut-derived peptide, TWLPLPR (TW-7), on cognitive impairment in high-fat diet/streptozotocin-induced type 2 diabetes mellitus (T2DM) mice and explored its underlying mechanisms in high glucose-induced HT-22 cells. In the Morris water maze test, TW-7 alleviated cognitive deficits in mice; this was confirmed at the level of synaptic structure and dendritic spine density in the mouse hippocampus using transmission electron microscopy and Golgi staining. TW-7 increased the expression of synaptic plasticity-related proteins and suppressed the NEK7/NLRP3 inflammatory pathway, as determined by western blotting and immunofluorescence analysis. The mechanism of action of TW-7 was verified in an HT-22 cell model of high glucose-induced insulin resistance. Collectively, TW-7 could regulate T2DM neuroinflammation and synaptic function-induced cognitive impairment by inhibiting NLRP3 inflammasome activation and improving synaptic plasticity.

Covalent Targeting As a Common Mechanism for Inhibiting NLRP3 Inflammasome Assembly

The NLRP3 inflammasome is a cytosolic protein complex important for the regulation and secretion of inflammatory cytokines, including IL-1β and IL-18. Aberrant overactivation of NLRP3 is implicated in numerous inflammatory disorders. However, the activation and regulation of NLRP3 inflammasome signaling remain poorly understood, limiting our ability to develop pharmacologic approaches to target this important inflammatory complex. Here, we developed and implemented a high-throughput screen to identify compounds that inhibit the inflammasome assembly and activity. From this screen, we identify and profile inflammasome inhibition of 20 new covalent compounds across nine different chemical scaffolds, as well as many known inflammasome covalent inhibitors. Intriguingly, our results indicate that NLRP3 possesses numerous reactive cysteines on multiple domains whose covalent targeting blocks the activation of this inflammatory complex. Specifically, focusing on compound VLX1570, which possesses multiple electrophilic moieties, we demonstrate that this compound allows covalent, intermolecular cross-linking of NLRP3 cysteines to inhibit inflammasome assembly. Our results, along with the recent identification of numerous covalent molecules that inhibit NLRP3 inflammasome activation, further support the continued development of electrophilic compounds that target reactive cysteine residues on NLRP3 to regulate its activation and activity.

Extracellular Vesicles in Flaviviridae Pathogenesis: Their Roles in Viral Transmission, Immune Evasion, and Inflammation

The members of the Flaviviridae family are becoming an emerging threat for public health, causing an increasing number of infections each year and requiring effective treatment. The consequences of these infections can be severe and include liver inflammation with subsequent carcinogenesis, endothelial damage with hemorrhage, neuroinflammation, and, in some cases, death. The mechanisms of Flaviviridae pathogenesis are being actively investigated, but there are still many gaps in their understanding. Extracellular vesicles may play important roles in these mechanisms, and, therefore, this topic deserves detailed research. Recent data have revealed the involvement of extracellular vesicles in steps of Flaviviridae pathogenesis such as transmission, immune evasion, and inflammation, which is critical for disease establishment. This review covers recent papers on the roles of extracellular vesicles in the pathogenesis of Flaviviridae and includes examples of clinical applications of the accumulated data.

Crosstalk of HDAC4, PP1, and GSDMD in controlling pyroptosis

Gasdermin D (GSDMD) functions as a pivotal executor of pyroptosis, eliciting cytokine secretion following cleavage by inflammatory caspases. However, the role of posttranslational modifications (PTMs) in GSDMD-mediated pyroptosis remains largely unexplored. In this study, we demonstrate that GSDMD can undergo acetylation at the Lysine 248 residue, and this acetylation enhances pyroptosis. We identify histone deacetylase 4 (HDAC4) as the specific deacetylase responsible for mediating GSDMD deacetylation, leading to the inhibition of pyroptosis both in vitro and in vivo. Deacetylation of GSDMD impairs its ubiquitination, resulting in the inhibition of pyroptosis. Intriguingly, phosphorylation of HDAC4 emerges as a critical regulatory mechanism promoting its ability to deacetylate GSDMD and suppress GSDMD-mediated pyroptosis. Additionally, we implicate Protein phosphatase 1 (PP1) catalytic subunits (PP1α and PP1γ) in the dephosphorylation of HDAC4, thereby nullifying its deacetylase activity on GSDMD. This study reveals a complex regulatory network involving HDAC4, PP1, and GSDMD. These findings provide valuable insights into the interplay among acetylation, ubiquitination, and phosphorylation in the regulation of pyroptosis, offering potential targets for further investigation in the field of inflammatory cell death.

Top Five Stories of the Cellular Landscape and Therapies of Atherosclerosis: Current Knowledge and Future Perspectives

Atherosclerosis (AS) is characterized by impairment and apoptosis of endothelial cells, continuous systemic and focal inflammation and dysfunction of vascular smooth muscle cells, which is documented as the traditional cellular paradigm. However, the mechanisms appear much more complicated than we thought since a bulk of studies on efferocytosis, transdifferentiation and novel cell death forms such as ferroptosis, pyroptosis, and extracellular trap were reported. Discovery of novel pathological cellular landscapes provides a large number of therapeutic targets. On the other side, the unsatisfactory therapeutic effects of current treatment with lipid-lowering drugs as the cornerstone also restricts the efforts to reduce global AS burden. Stem cell- or nanoparticle-based strategies spurred a lot of attention due to the attractive therapeutic effects and minimized adverse effects. Given the complexity of pathological changes of AS, attempts to develop an almighty medicine based on single mechanisms could be theoretically challenging. In this review, the top stories in the cellular landscapes during the initiation and progression of AS and the therapies were summarized in an integrated perspective to facilitate efforts to develop a multi-targets strategy and fill the gap between mechanism research and clinical translation. The future challenges and improvements were also discussed.

L-ergothioneine reduces mitochondrial-driven NLRP3 activation in gestational diabetes mellitus

BACKGROUND

Maternal hyperglycaemia has a significant impact on placental metabolism and mitochondrial function. The NLRP3 inflammasome is responsive to endogenous signals of mitochondrial dysfunction. We tested our hypothesis that mitochondrial dysfunction orchestrates activation of the NLRP3 inflammasome and contributes to inflammation in gestational diabetes mellitus (GDM).

METHODS

Fasting blood, omental and placental tissue were collected on the day of caesarean section from nulliparous women with normal glucose tolerant (NGT) (n = 30) and GDM (n = 27) pregnancies. Cell-free mitochondrial DNA (cf-mtDNA) copy number was quantified by real-time PCR. M1-like (CD14+CD86+CD206-) and M2-like (CD14+CD86+CD206+) macrophage populations were characterized by flow cytometry. Immunoblotting for protein expression of NLRP3, ASC and caspase-1 was performed in maternal BMI and age-matched tissue samples. IL-1β and IL-18 were measured by multiplex ELISA. Placental explants from GDM participants were cultured for 24 h with 1 mM L-ergothioneine (antioxidant) and 1 µM MCC950 (NLRP3 inhibitor).

RESULTS

Cf-mtDNA copy numbers were significantly higher in GDM compared to NGT participants (p = 0.002). Placental populations of CD14+ (p = 0.02) and CD14+CD86+CD206- (p = 0.03) macrophages produced significantly increased levels of mitochondrial superoxide in GDM compared to NGT participants. Placental production of IL-18 (p = 0.04) was significantly increased in GDM. This increase in placental IL-18 was attenuated by treatment with 1 µM MCC950 (p = 0.0005), and 1 mM L-ergothioneine (p = 0.007).

CONCLUSION

Placental inflammation is significantly increased in women with GDM. Furthermore, this increase may be initiated by elevated production of mitochondrial superoxide by macrophage subpopulations and orchestrated by the NLRP3 inflammasome. The mitochondrial antioxidant, L-ergothioneine, ameliorates NLRP3-induced placental inflammation in GDM, identifying a potential therapeutic role.

Discovery of novel oridonin sulfamide derivatives as potent NLRP3 inhibitors by a visible-light photocatalysis-enabled peripheral editing

The progress of organicsyntheticmethod can promote late-stage lead compound modification and novel active compound discovery. Molecular editing technology in the field of organic synthesis, including peripheral and skeletal editing, facilitates rapid access to molecular diversity of a lead compound. Peripheral editing of CH bond activation is gradually used in lead optimization to afford novel active scaffolds and chemical space exploitation. To develop oridonin derivatives with high anti-inflammatory potency, novel oridonin sulfamides had been designed and synthesized by a scaffoldhopping strategy based on a visible-light photocatalysis peripheral editing. All novel compounds revealed measurable inhibition of IL-1β and low cytotoxicity in THP-1 cells. The docking study indicated that the best active compound ZM640 was accommodated in thebinding site of NLRP3 with two hydrogen bond interaction. These preliminary results confirm that α, β-unsaturated carbonyl of oridonin is not essential for NLRP3 inhibitory effect. This new oridonin scaffold has its potential to be further developed as a promising class of NLRP3 inhibitors.

Impact of fasting & ketogenic interventions on the NLRP3 inflammasome: A narrative review

Overactivation of the NLRP3 inflammasome is implicated in chronic low-grade inflammation associated with various disease states, including obesity, type 2 diabetes, atherosclerosis, Alzheimer's disease, and Parkinson's disease. Emerging evidence, mostly from cell and animal models of disease, supports a role for ketosis in general, and the main circulating ketone body beta-hydroxybutyrate (BHB) in particular, in reducing NLRP3 inflammasome activation to improve chronic inflammation. As a result, interventions that can induce ketosis (e.g., fasting, intermittent fasting, time-restricted feeding/eating, very low-carbohydrate high-fat ketogenic diets) and/or increase circulating BHB (e.g., exogenous ketone supplementation) have garnered increasing interest for their therapeutic potential. The purpose of the present review is to summarize our current understanding of the literature on how ketogenic interventions impact the NLRP3 inflammasome across human, rodent and cell models. Overall, there is convincing evidence that ketogenic interventions, likely acting through multiple interacting mechanisms in a cell-, disease- and context-specific manner, can reduce NLRP3 inflammasome activation. The evidence supports a direct effect of BHB, although it is important to consider the myriad of other metabolic responses to fasting or ketogenic diet interventions (e.g., elevated lipolysis, low insulin, stable glucose, negative energy balance) that may also impact innate immune responses. Future research is needed to translate promising findings from discovery science to clinical application.

KLF4 interacts with TXNIP to modulate the pyroptosis in ulcerative colitis via regulating NLRP3 signaling

INTRODUCTION

Ulcerative colitis (UC) is one of the most common diseases in the gastrointestinal tract related to abnormal inflammation. Pyroptosis, which is characterized by the formation of inflammasome, activation of caspase-1, and separation of N- and C-terminus of gasdermin D (GSDMD), and may be involved in the pathogenesis of IBD. Krüppel-like factor 4 (KLF4) is a zinc finger transcription factor expressed in differentiated epithelial cells. KLF4 mediates proinflammatory signaling in macrophages. Here, we tested whether KLF4 is functional in pyroptosis of UC.

METHODS

In human UC tissues and/or lipopolysaccharide (LPS)/adenosine 5-triphosphate (ATP) stimulation human colon epithelial cells, KLF4, TXNIP, Cleave-Caspase-1, and GSDMD expression were detected through quantitative reverse transcription polymerase chain reaction (PCR), immunohistochemical and western blot assay. Interleukin (IL)-1β and IL-18 levels were quantified by enzyme-linked immunosorbent assay. We successfully constructed a KLF4-silenced colon epithelial cell line using an adenovirus vector. We apply the UCSC and JASPAR to predict the KLF4 binding sites in the promoter region of TXNIP.

RESULTS

In human UC tissues and/or LPS/ATP stimulation human colon epithelial cells, KLF4, TXNIP, Caspase-1, and GSDMD expression level were significantly elevated via quantitative reverse transcription PCR, immunohistochemical and western blot assay. Moreover, We identified that there is an interaction between KLF4 and TXNIP through Yeast double hybrid assay and CO-IP assay. We successfully constructed a KLF4-silenced human intestinal epithelial cell line. In LPS/ATP stimulation KLF4-silenced human intestinal epithelial cells, KLF4, TXNIP, Cleave Caspase-1, ASC, and GSDMD expression level were significantly decreased via quantitative reverse transcription PCR.

CONCLUSION

Our results confirm that KLF4 can positively regulate the expression of TXNIP and regulate the pyroptosis process of UC through the TXNIP/NLRP3 pathway.

RNA-seq revealed the anti-pyroptotic effect of suramin by suppressing NLRP3/caspase-1/GSDMD pathway in LPS-induced MH-S alveolar macrophages

BACKGROUND

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), acting as one common sepsis-associated organ injury, induces uncontrolled and self-amplifies pulmonary inflammation. Given the lack of clinically effective approaches, the mortality rate of it still remains high. Suramin(SUR), as an antiparasitic drug initially, was found to ameliorate sepsis associated ALI in our previous work. However, the underlying mechanism of its protective effects has not been clarified. Pyroptosis, categorized as an inflammatory form of programmed cell death, could aggravate lung inflammatory responses via inducing alveolar macrophages (AM) pyroptosis.

METHODS

MH-S AM cell line was stimulated with or without lipopolysaccharide (LPS) or suramin, and the differential expression genes (DEGs) were excavated using RNA sequencing (RNA-seq). To identify the regulatory roles of these genes, pyroptosis-related genes (PRGs), GO/KEGG and GSEA analysis were conducted. We also performed WB, qRTPCR and ELISA to validate the RNA-seq results and further expound the protective effect of suramin.

RESULTS

624 DEGs were identified between control (CON) and lipopolysaccharide (LPS) groups, and enrichment analysis of these genes revealed significantly enriched pathways that related to immune system and signal transduction. Meanwhile, 500 DEGs were identified in LPS/SUR+LPS group. In addition to the pathways mentioned above, IL-17 pathway and C-type lectin receptor signaling pathway were also enriched. All 6 pathways were connected with pyroptosis. Concurrently, the "DESeq2" R package was used to identify differentially expressed PRGs. Nod1, Nod2, interleukin (IL)-1b, IL-6, tumor necrosis factor (TNF), NLRP3 were upregulated under LPS stimulation. Then, in SUR+LPS group, Nod2, IL-6, IL-1b, NLRP3 were downregulated. The validation results of WB, qRT-PCR, and ELISA showed: the protein and mRNA expression levels of NLRP3, caspase-1, GSDMD and the concentrations of IL-1b, IL-18 were decreased when treated with suramin and LPS.

CONCLUSION

Suramin could inhibit NLRP3/caspase-1/GSDMD canonical pyroptosis pathway in LPS-induced MH-S alveolar macrophages.

The transcriptomic landscape of canonical activation of NLRP3 inflammasome from bone marrow-derived macrophages

The NLRP3 inflammasome has gained significant attention due to its participation in diverse cellular processes. Nevertheless, the detailed framework of the canonical NLRP3 inflammasome assembly still remains unrevealed. This study aims to elucidate the transcriptomic landscape of the various stages involved in the canonical activation of the NLRP3 inflammasome in BMDMs by integrating RNA-seq, bioinformatics, and molecular dynamics analyses. The model for the canonical activation of the NLRP3 inflammasome was confirmed through morphological observations, functional assessments (ELISA and LDH), and protein detection (western blot). Subsequently, cells were subjected to RNA sequencing following three groups: control, priming (LPS 500 ng/ml, 4 h), and activation (LPS 500 ng/ml, 4 h; ATP 5 mM, 1 h). A total of 9116 differentially expressed genes (DEGs) were identified, which exerted regulatory effects on various pathways, including cell metabolism, ion fluxes, post-translational modifications, and organelles. Subsequently, six hub genes (Sirt3, Stat3, Syk, Trpm2, Tspo, and Txnip) were identified via integrating literature review and database screening. Finally, the three-dimensional structures of these six hub proteins were obtained using the MD-optimized RoseTTAFold and Gromacs simulations (at least 200 ns). In summary, our research offers novel insights into the transcriptomic-level understanding of the assembly of the canonical NLRP3 inflammasome.

Mitochondrial Mechanisms in Immunity and Inflammatory Conditions: Beyond Energy Management

Significance: The growing importance of mitochondria in the immune response and inflammation is multifaceted. Unraveling the different mechanisms by which mitochondria have a relevant role in the inflammatory response beyond the energy management of the process is necessary for improving our understanding of the host immune defense and the pathogenesis of various inflammatory diseases and syndromes. Critical Issues: Mitochondria are relevant in the immune response at different levels, including releasing activation molecules, changing its structure and function to accompany the immune response, and serving as a structural base for activating intermediates as NLRP3 inflammasome. In this scientific journey of dissecting mitochondrial mechanisms, new questions and interesting aspects arise, such as the involvement of mitochondrial-derived vesicles in the immune response with the putative role of preventing uncontrolled situations. Recent Advances: Researchers are continuously rethinking the role of mitochondria in acute and chronic inflammation and related disorders. As such, mitochondria have important roles as centrally positioned signaling hubs in regulating inflammatory and immune responses. In this review, we present the current understanding of mitochondrial mechanisms involved, beyond the largely known mitochondrial dysfunction, in the onset and development of inflammatory situations. Future Directions: Mitochondria emerge as an interesting and multifaceted platform for studying and developing pharmaceutical and therapeutic approaches. There are many ongoing studies aimed to describe the effects of specific mitochondrial targeted molecules and treatments to ameliorate the consequences of exacerbated inflammatory components of pathologies and syndromes, resulting in an open area of increasing research interest.

High-Density Lipoproteins at the Interface between the NLRP3 Inflammasome and Myocardial Infarction

Despite significant therapeutic advancements, morbidity and mortality following myocardial infarction (MI) remain unacceptably high. This clinical challenge is primarily attributed to two significant factors: delayed reperfusion and the myocardial injury resulting from coronary reperfusion. Following reperfusion, there is a rapid intracellular pH shift, disruption of ionic balance, heightened oxidative stress, increased activity of proteolytic enzymes, initiation of inflammatory responses, and activation of several cell death pathways, encompassing apoptosis, necroptosis, and pyroptosis. The inflammatory cell death or pyroptosis encompasses the activation of the intracellular multiprotein complex known as the NLRP3 inflammasome. High-density lipoproteins (HDL) are endogenous particles whose components can either promote or mitigate the activation of the NLRP3 inflammasome. In this comprehensive review, we explore the role of inflammasome activation in the context of MI and provide a detailed analysis of how HDL can modulate this process.

SARS-CoV-2 ORF3a Protein as a Therapeutic Target against COVID-19 and Long-Term Post-Infection Effects

The COVID-19 pandemic caused by SARS-CoV-2 has posed unparalleled challenges due to its rapid transmission, ability to mutate, high mortality and morbidity, and enduring health complications. Vaccines have exhibited effectiveness, but their efficacy diminishes over time while new variants continue to emerge. Antiviral medications offer a viable alternative, but their success has been inconsistent. Therefore, there remains an ongoing need to identify innovative antiviral drugs for treating COVID-19 and its post-infection complications. The ORF3a (open reading frame 3a) protein found in SARS-CoV-2, represents a promising target for antiviral treatment due to its multifaceted role in viral pathogenesis, cytokine storms, disease severity, and mortality. ORF3a contributes significantly to viral pathogenesis by facilitating viral assembly and release, essential processes in the viral life cycle, while also suppressing the body's antiviral responses, thus aiding viral replication. ORF3a also has been implicated in triggering excessive inflammation, characterized by NF-κB-mediated cytokine production, ultimately leading to apoptotic cell death and tissue damage in the lungs, kidneys, and the central nervous system. Additionally, ORF3a triggers the activation of the NLRP3 inflammasome, inciting a cytokine storm, which is a major contributor to the severity of the disease and subsequent mortality. As with the spike protein, ORF3a also undergoes mutations, and certain mutant variants correlate with heightened disease severity in COVID-19. These mutations may influence viral replication and host cellular inflammatory responses. While establishing a direct link between ORF3a and mortality is difficult, its involvement in promoting inflammation and exacerbating disease severity likely contributes to higher mortality rates in severe COVID-19 cases. This review offers a comprehensive and detailed exploration of ORF3a's potential as an innovative antiviral drug target. Additionally, we outline potential strategies for discovering and developing ORF3a inhibitor drugs to counteract its harmful effects, alleviate tissue damage, and reduce the severity of COVID-19 and its lingering complications.

Colchicine ameliorates myocardial injury induced by coronary microembolization through suppressing pyroptosis via the AMPK/SIRT1/NLRP3 signaling pathway

BACKGROUND

Coronary microembolization(CME)is a common complication in acute coronary syndrome and percutaneous coronary intervention, which is closely related to poor prognosis. Pyroptosis, as an inflammatory programmed cell death, has been found to be associated with CME-induced myocardial injury. Colchicine (COL) has potential benefits in coronary artery disease due to its anti-inflammatory effect. However, the role of colchicine in pyroptosis-related CME-induced cardiomyocyte injury is unclear. This study was carried out to explore the effects and mechanisms of colchicine on myocardial pyroptosis induced by CME.

METHODS

The CME animal model was constructed by injecting microspheres into the left ventricle with Sprague-Dawley rats, and colchicine (0.3 mg/kg) pretreatment seven days before and on the day of modeling or compound C(CC)co-treatment was given half an hour before modeling. The study was divided into 4 groups: Sham group, CME group, CME + COL group, and CME + COL + CC group (10 rats for each group). Cardiac function, serum myocardial injury markers, myocardial histopathology, and pyroptosis-related indicators were used to evaluate the effects of colchicine.

RESULTS

Colchicine pretreatment improved cardiac dysfunction and reduced myocardial injury induced by CME. The main manifestations were the improvement of left ventricular systolic function, the decrease of microinfarction area, and the decrease of mRNA and protein indexes related to pyroptosis. Mechanistically, colchicine increased the phosphorylation level of adenosine monophosphate-activated protein kinase (AMPK), promoted the expression of silent information regulation T1 (SIRT1), and inhibited the expression of NOD-like receptor pyrin containing 3 (NLRP3) to reduce myocardial pyroptosis. However, after CC co-treatment with COL, the effect of colchicine was partially reversed.

CONCLUSION

Colchicine improves CME-induced cardiac dysfunction and myocardial injury by inhibiting cardiomyocyte pyroptosis through the AMPK/SIRT1/NLRP3 signaling pathway.

Molecular Foundations of Inflammatory Diseases: Insights into Inflammation and Inflammasomes

Inflammatory diseases are a global health problem affecting millions of people with a wide range of conditions. These diseases, including inflammatory bowel disease (IBD), rheumatoid arthritis (RA), osteoarthritis (OA), gout, and diabetes, impose a significant burden on patients and healthcare systems. A complicated interaction between genetic variables, environmental stimuli, and dysregulated immune responses shows the complex biological foundation of various diseases. This review focuses on the molecular mechanisms underlying inflammatory diseases, including the function of inflammasomes and inflammation. We investigate the impact of environmental and genetic factors on the progression of inflammatory diseases, explore the connection between inflammation and inflammasome activation, and examine the incidence of various inflammatory diseases in relation to inflammasomes.

Zeolitic imidazole framework-8 loaded gelatin methacryloyl microneedles: A transdural and controlled-release drug delivery system attenuates neuroinflammation after spinal cord injury

Spinal cord injury (SCI) is a matter of significant clinical concern, often treated through early surgical decompression along with methylprednisolone sodium succinate (MPSS). However, the side effects and the unsatisfactory focal concentration of MPSS have limited its further applications. To address this limitation, herein, a versatile drug delivery system of zeolitic imidazole framework-8 (ZIF-8) and gelatin methacryloyl microneedles (GelMA MNs) was developed for stable, transdural, and controlled sustained release of drugs in SCI. The microneedles were used to create tiny pores in the dura mater, allowing for the direct administration of drugs into the spinal cord. ZIF-8 provided a secondary extended release once they were separated from the microneedles. To attenuate the neuroinflammation, MPSS was selected. Such a combination of ZIF-8 and GelMA MNs was able to prolong the release period of MPSS to five days. The system showed transdural capacity, reduction of M1 polarization, and decrease in NLRP3-positive inflammasome and proinflammatory cytokines. In vivo studies indicated that this novel drug delivery strategy could constrict the inflammatory microenvironment, reduce glial scar formation, and promote neural regeneration. Thus, this versatile drug delivery system provides an up-and-coming alternative for stable, transdural, and controlled sustained release of drugs to those suffering from SCI.

The Neuro-Inflammatory Microenvironment: An Important Regulator of Stem Cell Survival in Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disease, characterized by progressive memory loss and cognitive impairment due to excessive accumulation of extracellular amyloid-β plaques and intracellular neurofibrillary tangles. Although decades of research efforts have been put into developing disease-modifying therapies for AD, no "curative" drug has been identified. As a central player in neuro-inflammation, microglia play a key role inbrain homeostasis by phagocytosing debris and regulating the balance between neurotoxic and neuroprotective events. Typically, the neurotoxic phenotype of activated microglia is predominant in the impaired microenvironment of AD. Accordingly, transitioning the activity state of microglia from pro-inflammatory to anti-inflammatory can restore the disrupted homeostatic microenvironment. Recently, stem cell therapy holds great promise as a treatment for AD; however, the diminished survival of transplanted stem cells has resulted in a disappointing long-term outcome for this treatment. This article reviews the functional changes of microglia through the course of AD-associated homeostatic deterioration. We summarize the possible microglia-associated therapeutic targets including TREM2, IL-3Rα, CD22, C5aR1, CX3CR1, P2X7R, CD33, Nrf2, PPAR-γ, CSF1R, and NLRP3, each of which has been discussed in detail. The goal of this review is to put forth the notion that microglia could be targeted by either small molecules or biologics to make the brain microenvironment more amenable to stem cell implantation and propose a novel treatment strategy for future stem cell interventions in AD.

Vasculitis and the NLRP3 inflammasome

PURPOSE OF REVIEW

Vasculitis are a group of heterogeneous conditions characterized by chronic inflammation of blood vessels, leading to tissue destruction and organ failure. Vasculitis is an inflammatory process in which immune effector cells infiltrate blood vessels and surrounding tissues. The involvement of inflammasomes seems to occur during inflammatory processes.

RECENT FINDINGS

Studies have emphasized that genetic susceptibility is an important aspect of the pathogenesis of vasculitis. The innate immune system is a major contributor to these inflammatory diseases, suggesting that the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome plays a key role. NLRP3 activation causes the assembly of a large multiprotein and leads to the secretion of bioactive interleukin (IL)-1β and IL-18 as well as the induction of inflammatory cell death, termed pyroptosis. Accumulating evidence confirms the involvement of this cascade in sterile inflammatory diseases and other vascular diseases.

SUMMARY

In this review, we will summarize the current state of knowledge regarding the role of NLRP3 inflammasome in vascular diseases, and discuss the potential of the NLRP3 inflammasome as a therapeutic target.

Targeting NLRP3 Inflammasome: Structure, Function, and Inhibitors

Inflammasomes are multimeric protein complexes that can detect various physiological stimuli and danger signals. As a result, they perform a crucial function in the innate immune response. The NLRP3 inflammasome, as a vital constituent of the inflammasome family, is significant in defending against pathogen invasion and preserving cellhomeostasis. NLRP3 inflammasome dysregulation is connected to various pathological conditions, including inflammatory diseases, cancer, and cardiovascular and neurodegenerative diseases. This profile makes NLRP3 an applicable target for treating related diseases, and therefore, there are rising NLRP3 inhibitors disclosed for therapy. Herein, we summarized the updated advances in the structure, function, and inhibitors of NLRP3 inflammasome. Moreover, we aimed to provide an overview of the existing products and future directions for drug research and development.

Pyridaben induces apoptosis and inflammation in bovine mammary epithelial cells by disturbance of calcium homeostasis and upregulation of MAPK cascades

Pyridaben is a widely used pyridazinone insecticide used to protect crops against insects and mites. The toxicity of pyridaben has been reported in mice, zebrafish, the human reproductive system, nervous system, and respiratory system. Pyridaben can also be ingested by dairy cattle through feed. However, the toxicity of pyridaben in cattle has not been investigated on. Thus, this study focuses on demonstrating the toxicity of pyridaben in the bovine mammary glands and with the generation milk in the bovine mammary epithelial cells, as it is crucial to the continuance of the amount and the quality of the milk produced. We started by analyzing the intracellular toxicity along with the impact of pyridaben on the cell cycle distribution and the transcription of associated genes. Pyridaben treatment induced cell cycle arrest accompanied the disruption in G1 and S phases with imbalanced cytosolic and mitochondrial calcium ion homeostasis, and caused a destruction of mitochondrial membrane potential. This eventually led to apoptosis of MAC-T cells. We also investigated in the impact that pyridaben has on MAPK signaling proteins, where phosphorylation of ERK1/2, JNK, and p38 were upregulateed. Moreover, examination of the effect of pyridaben in the inflammatory genes revealed hyperactivation of the inflammatory gene transcription. This is the first research to assess the negative outcomes that pyridaben could impose on dairy cattle and milk production.

Inhibition of the interaction between microglial adenosine 2A receptor and NLRP3 inflammasome attenuates neuroinflammation posttraumatic brain injury

AIMS

Adenosine 2A receptor (A2A R) is widely expressed in the brain and plays important roles in neuroinflammation, and the nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) inflammasome is a crucial component of the innate immune system while the regulation of A2A R on it in the central nervous system (CNS) has not been clarified.

METHODS

The effects of microglial A2A R on NLRP3 inflammasome assembly and activation were investigated in wild-type, A2A R- or NLRP3-knockout primary microglia with pharmacological treatment. Microglial A2A R or NLRP3 conditional knockout mice were used to interrogate the effects of this regulation on neuroinflammation posttraumatic brain injury (TBI).

RESULTS

We found that A2A R directly interacted with NLRP3 and facilitated NLRP3 inflammasome assembly and activation in primary microglia while having no effects on mRNA levels of inflammasome components. Inhibition of the interaction via A2A R agonist or knockout attenuated inflammasome assembly and activation in vitro. In the TBI model, microglial A2A R and NLRP3 were co-expressed at high levels in microglia next to the peri-injured cortex, and abrogating of this interaction by microglial NLRP3 or A2A R conditional knockout attenuated the neurological deficits and neuropathology post-TBI via reducing the NLRP3 inflammasome activation.

CONCLUSION

Our results demonstrated that inhibition of the interaction between A2A R and NLRP3 in microglia could mitigate the NLRP3 inflammasome assembly and activation and ameliorate the neuroinflammation post-TBI. It provides new insights into the effects of A2A R on neuroinflammation regulation post-TBI and offers a potential target for the treatment of NLRP3 inflammasome-related CNS diseases.

Regulation of cellular senescence by innate immunity

During the COVID-19 pandemic, the interplay between the processes of immunity and senescence is drawing more and more intensive attention. SARS-CoV-2 infection induces senescence in lung cells, failure to clear infected cells and increased presence of inflammatory factors could lead to a cytokine storm and acute respiratory disease syndrome (ARDS), which together with aging and age-associated disease lead to 70% of COVID-19-related deaths. Studies on how senescence initiates upon viral infection and how to restrict excessive accumulation of senescent cells to avoid harmful inflammation are crucially important. Senescence can induce innate immune signaling, and innate immunity can engage cell senescence. Here, we mainly review the innate immune pathways, such as cGAS-STING, TLRs, NF-κB, and NLRP3 inflammasome, participating in the senescence process. In these pathways, IFN-I and inflammatory factors play key roles. At the end of the review, we propose the strategies by which we can improve the immune function and reduce inflammation based on these findings.

Acetyl-11-Keto-β-Boswellic Acid Accelerates the Repair of Spinal Cord Injury in Rats by Resisting Neuronal Pyroptosis with Nrf2

The primary aim of this study is to delve into the potential of Acetyl-11-keto-β-boswellic acid (AKBA) in ameliorating neuronal damage induced by acute spinal cord injury, as well as to unravel the intricate underlying mechanisms. A cohort of 40 Sprague-Dawley rats was meticulously categorized into four groups. Following a seven-day oral administration of AKBA, damaged spinal cord samples were meticulously procured for Nissl staining and electron microscopy to assess neuronal demise. Employing ELISA, immunofluorescence, Western blot (WB), and quantitative polymerase chain reaction (qPCR), the modulatory effects of AKBA within the context of spinal cord injury were comprehensively evaluated. Furthermore, employing an ex vivo extraction of spinal cord neurons, an ATP + LPS-induced pyroptotic injury model was established. The model was subsequently subjected to Nrf2 inhibition, followed by a battery of assessments involving ELISA, DCFH-DA staining, flow cytometry, immunofluorescence, and WB to decipher the effects of AKBA on the spinal cord neuron pyroptosis model. By engaging the Nrf2-ROS-NLRP3 pathway, AKBA exerted a repressive influence on the expression of the pyroptotic initiator protein Caspase-1, thereby mitigating the release of GSDMD and alleviating pyroptosis. Additionally, AKBA demonstrated the ability to attenuate the release of IL-18 and IL-1β, curbing neuronal loss and expediting the restorative processes within the context of spinal cord injury. Our study elucidates that AKBA can reduce spinal cord neuronal apoptosis, providing a basis for the development of AKBA as a clinical treatment for spinal cord injury.

Selective inhibition of the NLRP3 inflammasome protects against acute ethanol-induced cardiotoxicity in an FBXL2-dependent manner

Binge drinking exerts cardiac toxicity through various mechanisms, including oxidative stress and inflammation. NLRP3 inflammasomes possess both pro- and anti-inflammatory properties, although the role of NLRP3 in ethanol-induced cardiotoxicity remains unknown. This study is designed to examine the role of NLRP3 inflammasome in acute ethanol cardiotoxicity and the underlying mechanisms of action. Nine- to twelve-week-old adult male C57BL/6 mice are administered with ethanol (1.5 g/kg, twice daily, i.p.) for 3 days. A cohort of control and ethanol-challenged mice are treated with the NLRP3 inhibitor MCC950 (10 mg/kg/day, i.p., days 1 and 3). Myocardial geometry and function are monitored using echocardiography and cardiomyocyte edge-detection techniques. Levels of NLRP3 inflammasome, mitophagy and apoptosis are evaluated by western blot analysis and immunofluorescence techniques. Acute ethanol challenge results in abnormally higher cardiac systolic function, in conjunction with deteriorated cardiac diastolic function and cardiomyocyte contractile function. Levels of NLRP3 inflammasome and apoptosis are elevated, and mitophagy flux is blocked (elevated Pink1-Parkin and LC3B along with diminished p62 and Rab7) in mice receiving acute ethanol challenge. Although MCC950 does not elicit a notable effect on myocardial function, apoptosis or inflammasome activation in the absence of ethanol exposure, it effectively rescues acute ethanol cardiotoxicity, as manifested by restored myocardial and cardiomyocyte functional homeostasis, suppressed NLRP3 inflammasome activation and apoptosis, and improved mitophagy flux. Our data further suggest that FBXL2, an E3 ubiquitin ligase associated with mitochondrial homeostasis and mitophagy, is destabilized due to proteasomal degradation of caspase-1 by ethanol-induced hyperactivation of NLRP3-caspase-1 inflammasome signaling, resulting in mitochondrial injury and apoptosis. These findings denote a role for NLRP3 inflammasome in acute ethanol exposure-induced cardiotoxicity in an FBXL2-dependent manner and the therapeutic promise of targeting NLRP3 inflammasome for acute ethanol cardiotoxicity.

Short-term and repeated exposure to particulate matter sizes from Imperial Valley, California to induce inflammation and asthmatic-like symptoms in mice

Imperial Valley, California has become increasingly hot, dry, and polluted over the past decade. Particulate matter (PM) levels are amongst the highest in this State, associated with significantly higher asthma prevalence among children in the region compared to national and state averages. The present study was performed to test the hypothesis that Imperial Valley PM by size and chemical composition might possess allergenic properties following introduction into murine lungs without prior sensitization to a known allergen with size fraction as a determining factor. In acute exposure experiments, BALB/c male mice were administered a single 50-μl oropharyngeal aspiration of nanopure water (H2O; control) or a stock 1 μg/μl PM solution. In sub-acute exposure experiments, male and female mice were treated with a total of six 16.6-μl intranasal instillations of H2O or stock PM solution over the course of 14 days. In all experiments, pulmonary function tests were performed 24 hr after the final instillation followed by necropsies for the collection of biological samples. Inflammatory responses measured via cellularity in histopathological tissue sections as well as significant, marked influxes of eosinophils and lymphocytes were noted in the bronchoalveolar lavage fluid in mice administered PM compared to control. Allergic responses, including airway hyperresponsiveness and significantly increased expression of IL-1ß, were found in male mice exposed to either PM2.5 or ultrafine (PMUF). A combination of all three size fractions of PM from Imperial Valley initiated atopic and asthmatic-like symptoms in the lungs of mice in the absence of additional allergen or preexisting condition.

Regulation of alveolar macrophage death in pulmonary fibrosis: a review

Pulmonary fibrosis (PF) is a disease in which excessive extracellular matrix (ECM) accumulation occurs in pulmonary mesenchyme, which induces the destruction of alveolar structures and poor prognosis. Macrophage death is responsible for ECM accumulation after alveolar epithelial injury in PF. Depending on the local micro-environments, macrophages can be polarized to either classically activated (M1) or alternatively activated (M2) macrophage phenotypes. In general, M1 macrophages can promote inflammation and sterilization, stop the continuous damage process and prevent excessive repair, while M2 macrophages are anti-inflammatory and promote tissue repair, and excessive M2 macrophage activity may inhibit the absorption and degradation of ECM. Emerging evidence has revealed that death forms such as pyroptosis mediated by inflammasome affect polarization direction and ultimately lead to the development of PF. Pharmacological manipulation of macrophages death signals may serve as a logical therapeutic strategy for PF. This review will focus on the current state of knowledge regarding the regulation and underlying mechanisms of macrophages and their mediators in the influence of macrophage death on the development of PF. We expect to provide help in developing effective therapeutic strategies in clinical settings.

Mechanisms of NLRP3 inflammasome activation and the development of peptide inhibitors

The Nucleotide-binding domain leucine-rich repeat and pyrin domain containing receptor 3 (NLRP3), a member of the nucleotide-binding oligomerization domain (NOD) like receptors (NLRs) family, plays an important role in the innate immune response against pathogen invasions. NLRP3 inflammasome consisting of NLRP3 protein, the adapter protein apoptosis-associated speck-like protein containing a caspase recruitment domain (CARD) (ASC), and the effector protein pro-caspase-1, is central to this process. Upon activation, NLRP3 inflammasome initiates the release of inflammatory cytokines and triggers a form of cell death known as pyroptosis. Dysregulation or inappropriate activation of NLRP3 has been implicated in various human diseases, including type 2 diabetes, colitis, depression, and gout. Consequently, understanding the mechanism underlying NLRP3 inflammasome activation is critical for the development of therapeutic drugs. In the pursuit of potential therapeutic agents, peptides present several advantages over small molecules. They offer higher selectivity, increased potency, reduced toxicity, and fewer off-target effects. The advancements in molecular biology have expanded the opportunities for applying peptides in medicine, unlocking their vast medical potential. This review begins by providing a comprehensive summary of recent research progress regarding the mechanisms governing NLRP3 inflammasome activation. Subsequently, we offer an overview of current peptide inhibitors capable of modulating the NLRP3 inflammasome activation pathway.

miR-141-3p alleviates ulcerative colitis by targeting SUGT1 to inhibit colonic epithelial cell pyroptosis

Ulcerative colitis (UC) is a chronic and recurrent inflammatory disease of the colon that result in the destruction and inflammation of the colonic mucosa. Current research has established a strong correlation between pyroptosis of colonic epithelial cells and the onset and progression of UC. In addition, miRNAs have been implicated in the development and progression of UC and pyroptosis. This aimed of this study was to identify specific miRNAs that could inhibit pyroptosis in colon epithelial cells and alleviate UC. Lipopolysaccharide (LPS) was used to induce inflammation in FHC normal colonic epithelial cells to construct an enteritis cell model and downregulated expression levels of miRNAs were detected in inflammatory bowel disease mucosal tissue model. Pyroptosis indicators were detected using Cell Counting Kit-8, flow cytometry, ELISA, qPCR, western blot, and immunofluorescence, and miRNA target genes were predicted by miRDB, TargetScan, pyroptosis pathway from KEGG, and double luciferase assay was used for verification. The effect of miR-141-3p on colitis was observed in the mouse DSS colitis model. The results showed that miR-141-3p was the most significantly downregulated miRNA in LPS-induced FHC cells, and promoted the proliferation of LPS-induced FHC cells and suppressed their apoptosis. In addition, miR-141-3p decreased the expression of pyroptosis-related proteins such as NLRP3, caspase-1, N-GSDMD, and the other proteins, as well as the release of IL-18 and IL-1β inflammatory factors. Conversely, the miR-141-3p inhibitor promoted LPS-induced FHC pyroptosis. Dual luciferase experiments confirmed that miR-141-3p could target the HSP90 molecular chaperone SUGT1. Further experiments demonstrated that SUGT1 overexpression could restore the inhibitory effect of miR-141-3p on pyroptosis, while SUGT1 knockdown could alleviate the promotion of pyroptosis induced by miR-141-3p inhibitor. Furthermore, miR-141-3p alleviated the inflammatory phenotype of mouse colonic mucosa in the mouse DSS colitis model. Therefore, miR-141-3p inhibits LPS-induced pyroptosis of colonic epithelial cells by targeting SUGT1. miR-141-3p could also alleviate DSS-induced colitis in mice, suggesting that miR-141-3p may become a nucleic acid drug for the treatment of UC.