The NLRP1 inflammasomes

Customized peptidoglycan surfaces to investigate innate immune recognition via surface plasmon resonance

Glycan-protein interactions facilitate some of the most important biomolecular processes in and between cells. They are involved in different cellular pathways, cell-cell interactions and associated with many diseases, making these interactions of great interest. However, their structural and functional diversity poses great challenges in studying them at the molecular level. Surface plasmon resonance (SPR) technology presents great advantages to study glycan-protein interactions due to its superior sensitivity, ability to monitor real-time interactions, relatively simple data interpretation, and most importantly, direct measurement of binding without a need for fluorescent labeling. Here, another dimensionality of SPR in studying glycan-protein interactions is demonstrated via examples of binding between human innate immune receptors and their bacterial peptidoglycan ligands. In order to best resemble interactions in solution, a novel strategy of tethering the carbohydrate at different positions to the biosensor surface is applied to represent the potential displays of the carbohydrate ligand to the receptor. Subsequent kinetic analysis provides insights into the optimized configuration of peptidoglycan fragments for binding with its receptors. The manuscript contains a "how-to guide" to help with the implementation of these methods in other glycan-protein binding systems.

Pyroptosis, and its Role in Central Nervous System Disease

Pyroptosis is an inflammatory form of cell death executed by transmembrane pore-forming proteins known as gasdermins and can be activated in an inflammasome-dependent or -independent manner. Inflammasome-dependent pyroptosis is triggered in response to pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) and has emerged as an important player in the pathogenesis of multiple inflammatory diseases, mainly by releasing inflammatory contents. More recently, numerous studies have revealed the intricate mechanisms of pyroptosis and its role in the development of neuroinflammation in central nervous system (CNS) diseases. In this review, we summarize current understandings of the molecular and regulatory mechanisms of pyroptosis. In addition, we discuss how pyroptosis can drive different forms of neurological diseases and new promising therapeutic strategies targeting pyroptosis that can be leveraged to treat neuroinflammation.

Molecular mechanisms and functions of pyroptosis in inflammation and antitumor immunity

Canonically, gasdermin D (GSDMD) cleavage by caspase-1 through inflammasome signaling triggers immune cell pyroptosis (ICP) as a host defense against pathogen infection. However, cancer cell pyroptosis (CCP) was recently discovered to be activated by distinct molecular mechanisms in which GSDMB, GSDMC, and GSDME, rather than GSDMD, are the executioners. Moreover, instead of inflammatory caspases, apoptotic caspases and granzymes are required for gasdermin protein cleavage to induce CCP. Sufficient accumulation of protease-cleaved gasdermin proteins is the prerequisite for CCP. Inflammation induced by ICP or CCP results in diametrically opposite effects on antitumor immunity because of the differential duration and released cellular contents, leading to contrary effects on therapeutic outcomes. Here, we focus on the distinct mechanisms of ICP and CCP and discuss the roles of ICP and CCP in inflammation and antitumor immunity, representing actionable targets.

ASC Speck Formation after Inflammasome Activation in Primary Human Keratinocytes

Chronic UV irradiation results in many changes in the skin, including hyperplasia, changes in dermal structures, and alteration of pigmentation. Exposure to UVB leads to cutaneous damage, which results in inflammation characterized by increased NF-κB activation and the induction of inflammatory cytokines, such as tumor necrosis factor (TNF), interleukin- (IL-) 1, or IL-8. IL-1 secretion is the result of inflammasome activation which is besides apoptosis, a result of acute UVB treatment. Inflammasomes are cytosolic protein complexes whose formation results in the activation of proinflammatory caspase-1. Key substrates of caspase-1 are IL-1β and IL-18, and the cytosolic protein gasdermin D (GSDMD), which is involved in inflammatory cell death. Here, we demonstrate that UVB-induced inflammasome activation leads to the formation of ASC specks. Our findings show that UVB provokes ASC speck formation in human primary keratinocytes prior to cell death, and that specks are, opposed to the perinuclear cytosolic localization in myeloid cells, formed in the nucleus. Additionally, we showed by RNAi that NLRP1 and not NLRP3 is the major inflammasome responsible for UVB sensing in primary human keratinocytes. Formation of ASC specks indicates inflammasome assembly and activation as their formation in hPKs depends on the presence of NLRP1 and partially on NLRP3. Nuclear ASC specks are not specific for NLRP1/NLRP3 inflammasome activation, as the activation of the AIM2 inflammasome by cytosolic DNA results in ASC specks too. These nuclear ASC specks putatively link cell death to inflammasome activation, possibly by binding of IFI16 (gamma-interferon-inducible protein) to ASC. ASC can interact upon UVB sensing via IFI16 with p53, linking cell death to ASC speck formation.

Vitamin D decreases expression of NLRP1 and NLRP3 ninflammasomes in placental explants from women with preeclampsia cultured with hydrogen peroxide

This study aimed to evaluate the immunomodulatory effect of vitamin D (VD) on the NLRP1 and NLRP3 inflammasomes in placental explants from preeclamptic (PE) and normotensive (NT) pregnant women. Placental explants from eight PE and eight NT pregnant women were cultured with or without hydrogen peroxide (H₂O₂)_, VD or H₂O₂ + VD. Gene and protein expression of NLRP1, NLRP3, HMGB1, caspase-1, IL-1β, TNF-α and IL-18 were determined by qPCR and Western blotting/ELISA. Compared to NT pregnant women, the endogenous gene expression of NLRP1, NLRP3, HMGB1, IL-1β, TNF-α and IL-18 was significantly higher in explants from PE and became decreased after VD treatment. Similarly, VD decreased the protein expression of NLRP1, NLRP3, caspase-1, HMGB1, IL-1β, TNF-α and IL-18 in PE. Placental explants from NT cultured with H₂O₂ showed increased gene and protein expression of NLRP1, NLRP3, caspase-1, IL-1β, TNF-α and HMGB1, while H₂O₂ was also able to increase TNF-α and caspase-1 gene expression in PE. Treatment with H₂O₂ + VD decreased gene/protein expression of NLRP1, NLRP3, caspase-1, HMGB1, IL-1β, TNF-α and IL-18 in PE and NT explants with H₂O₂. NLRP1 and NLRP3 are upregulated in the PE. VD may play an immunomodulatory role in the placental inflammation and downregulates oxidative stress induced in vitro by H₂O_2.

Gasdermin D in pyroptosis

Pyroptosis is the process of inflammatory cell death. The primary function of pyroptosis is to induce strong inflammatory responses that defend the host against microbe infection. Excessive pyroptosis, however, leads to several inflammatory diseases, including sepsis and autoimmune disorders. Pyroptosis can be canonical or noncanonical. Upon microbe infection, the canonical pathway responds to pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), while the noncanonical pathway responds to intracellular lipopolysaccharides (LPS) of Gram-negative bacteria. The last step of pyroptosis requires the cleavage of gasdermin D (GsdmD) at D275 (numbering after human GSDMD) into N- and C-termini by caspase 1 in the canonical pathway and caspase 4/5/11 (caspase 4/5 in humans, caspase 11 in mice) in the noncanonical pathway. Upon cleavage, the N-terminus of GsdmD (GsdmD-N) forms a transmembrane pore that releases cytokines such as IL-1β and IL-18 and disturbs the regulation of ions and water, eventually resulting in strong inflammation and cell death. Since GsdmD is the effector of pyroptosis, promising inhibitors of GsdmD have been developed for inflammatory diseases. This review will focus on the roles of GsdmD during pyroptosis and in diseases.

[Mechanism of high expression of high mobility group protein 1 in a rat model of knee osteoarthritis]

OBJECTIVE

To investigate the molecular mechanism triggering pyroptosis of synovial fibroblast-like synoviocytes(FLSs)and the release of high mobility group protein 1(HMGB1)in a rat model of knee osteoarthritis(KOA).

METHODS

Twelve SD rats were randomized equally into blank control group without any treatment and KOA group with anterior cruciate ligament amputation (ACLT) to induce KOA.HE staining and Mankin score were used to evaluate the damage of knee cartilage.Western blotting was used to detect the expression of pyroptosis-related proteins and HMGB1 in the synovial tissue.In the cell experiment, rat FLSs were treated with PBS (control group), LPS+ATP (to induce cell pyroptosis), or LPS+ATP+siRNAs (to inhibit pyroptosis of the FLSs), and the cellular expressions of apoptosis-related proteins and HMGB1 were detected using Western blotting; the level of HMGB1 in the culture supernatant was detected with ELISA.

RESULTS

In the rat models of KOA, the expressions of pyroptosis-related proteins and HMGB1 in the synovial tissue and Mankin score were significantly increased as compared with those in the control group(P < 0.05).In cultured rat FLSs, the expressions of apoptosis related proteins and HMGB1 were significantly higher in the pyroptosis group than in the control group and in cells transfected with the siRNAs targeting NLRP1, NLRP3, ASC and caspase-1(P < 0.05).The protein level of HMGB1 in the culture supernatant was significantly higher in pyroptosis group than in the control and siRNA groups (P < 0.05).

CONCLUSION

In the pathological process of KOA, NLRPs inflammasome-mediated FLS pyroptosis causes massive release of HMGB1, which is associated with the activation of the downstream molecule caspase-1.

Soluble total antigen derived from Toxoplasma gondii tachyzoites increased the expression levels of NLRP1, NLRP3, NLRC4, AIM2, and the release of mature form of IL1β, but downregulated the expression of IL1β and IL18 genes in THP-1cell line

Toxoplasma gondii (T. gondii) is an intracellular parasitic protozoan infecting homoeothermic animals and about a third of the world's population. Inflammasomes are intracellular multi-protein complex, which are activated by many factors. Inflammasomes are activated during toxoplasmosis; however, there are a lot of obscure aspects. THP-1 monocyte cells were converted to M0 macrophages by PMA and treated by 100 μg/mL soluble total Ag (STAg) derived from T. gondii strain RH for two time points 3 h and 24 h. After total RNA extraction and cDNA synthesis, the expression pattern of NLRP1, NLRP3, NLRC4, AIM2, IL1β, and IL18 was evaluated by relative real-time PCR. In addition, the cytokine release of IL1β and TNFα was evaluated in the supernatant of each well. The results showed statistically significant time-dependent overexpression of inflammasomes. NLRP1 and NLRP3 showed the higher and lower expression, respectively, during 3 h and 24 h after exposure. Both IL1β and IL18 downregulated 3 h after exposure. IL18 presented statistically significant upregulation after 24 h, but IL1β showed statistically significant downregulation after 24 h. The release of IL1β increased after 3 h, but it slightly decreased during 24 h after exposure. The concentration of TNFα showed an insignificant decrease compared to control, while it increased during 24 h after exposure. Taken together, this study suggested that T. gondii STAg induces NLRP1 more than NLRP3, NLRC4, and AIM2. Our findings also proposed that T. gondii STAg downregulates the gene expression of IL1β, but increases the release of this cytokine. It seems that Toxoplasma STAg probably increase the release of IL1β via activating NLRPs and AIM2 to cleave pro-caspase 1 to caspase 1 that leads to conversion of pro IL1β to mature IL1β.

Peripheral leucocyte molecular indicators of inflammation and oxidative stress are altered in dairy cows with embryonic loss

Objective of experiment was to determine whether oxidative stress (OS) and inflammation altered embryonic loss in dairy cows. Blood samples were collected at days 0, 16, 32 and 60 after timed (AI) from 200 Holstein cows to determine embryonic loss based on interferon-stimulated gene-15 (ISG15) mRNA expression (day 16) and ultrasound at day 32 and day 60. Leucocyte expressions of mRNA TLR2, TLR4, TNF-α, IL1B, IL10, STAT3 (inflammation), PTGS2, PTGES (prostaglandin synthesis), and PLA2G4A and ALOX5AP (eicosanoid metabolism) at days 0 and 16 were determined. Plasma redox status for antioxidant enzymatic activities of glutathione peroxidase (GPX), superoxide dismutase (SOD), total antioxidant capacity (TAC), and concentrations of malondialdehyde (MDA) were determined at days 0, 16, 32 and 60. All antioxidant-redox responses were beneficially significant in pregnant cows diagnosed pregnant at day16 and sustained pregnancy to day 60 compared to non-pregnant cows at day16 or pregnant at day16 and lost embryos by days 32 or 60. The leucocyte mRNA expressions of TLR2, TLR4, STAT 3, IL1B, PTGS2, PLA2G4A and ALOX5AP were greater and PTGES was lower at day16 in pregnant cows that lost embryos early (P < 0.05). In conclusion peripheral leucocyte molecular indicators of inflammation and plasma indicators of OS were altered in pregnant cows undergoing embryonic losses compared to cows with a sustained pregnancy.

A Comparative Overview of the Intracellular Guardians of Plants and Animals: NLRs in Innate Immunity and Beyond

Nucleotide-binding domain leucine-rich repeat receptors (NLRs) play important roles in the innate immune systems of both plants and animals. Recent breakthroughs in NLR biochemistry and biophysics have revolutionized our understanding of how NLR proteins function in plant immunity. In this review, we summarize the latest findings in plant NLR biology and draw direct comparisons to NLRs of animals. We discuss different mechanisms by which NLRs recognize their ligands in plants and animals. The discovery of plant NLR resistosomes that assemble in a comparable way to animal inflammasomes reinforces the striking similarities between the formation of plant and animal NLR complexes. Furthermore, we discuss the mechanisms by which plant NLRs mediate immune responses and draw comparisons to similar mechanisms identified in animals. Finally, we summarize the current knowledge of the complex genetic architecture formed by NLRs in plants and animals and the roles of NLRs beyond pathogen detection.

Inflammasomes and Fibrosis

Fibrosis is the final common pathway of inflammatory diseases in various organs. The inflammasomes play an important role in the progression of fibrosis as innate immune receptors. There are four main members of the inflammasomes, such as NOD-like receptor protein 1 (NLRP1), NOD-like receptor protein 3 (NLRP3), NOD-like receptor C4 (NLRC4), and absent in melanoma 2 (AIM2), among which NLRP3 inflammasome is the most studied. NLRP3 inflammasome is typically composed of NLRP3, ASC and pro-caspase-1. The activation of inflammasome involves both "classical" and "non-classical" pathways and the former pathway is better understood. The "classical" activation pathway of inflammasome is that the backbone protein is activated by endogenous/exogenous stimulation, leading to inflammasome assembly. After the formation of "classic" inflammasome, pro-caspase-1 could self-activate. Caspase-1 cleaves cytokine precursors into mature cytokines, which are secreted extracellularly. At present, the "non-classical" activation pathway of inflammasome has not formed a unified model for activation process. This article reviews the role of NLRP1, NLRP3, NLRC4, AIM2 inflammasome, Caspase-1, IL-1β, IL-18 and IL-33 in the fibrogenesis.

The multi-target mechanism of Cyclosporin A in the treatment of vitiligo based on network pharmacology

Network pharmacology is an emerging discipline that designs drugs based on systems biology theory and biological system network analysis. Here, we applied network pharmacology to analyze the multi-target mechanism of Cyclosporin A in the treatment of vitiligo First, we predicted the targets of Cyclosporin A. Second, we obtained the genes related to vitiligo from the database. Third, we constructed the PPI network of the mutual genes between Cyclosporin A and vitiligo and used gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) to analyze. Finally, we verified the prediction of potential targets through a docking study with Cyclosporin A. We found that there were 15 shared target genes between Cyclosporin A and vitiligo. We analyzed these 15 genes by Cytoscape and obtained a network diagram of 885 nodes. Through screening and molecular docking, PRKDC, CUL7, CUL1, HSPA8, HSPA4, and SIRT7 were the most likely multi-target mechanism of Cyclosporin A in the treatment of vitiligo. In our study, Cyclosporin A might not only affect the repair of DNA strands by targeting PRKDC, but also affected the innate and adaptive immune function of vitiligo patients by the targets of CUL1, CUL7, and HSP70. In addition, Cyclosporin A might promote the repigmentation of vitiligo by adjusting the expression of SIRT7.

LncRNA HOTTIP inhibits cell pyroptosis by targeting miR-148a-3p/AKT2 axis in ovarian cancer

Long noncoding RNA HOTTIP is a crucial regulator in multiple types of cancer, including ovarian cancer (OC). However, the biological roles and underlying mechanisms of HOTTIP in OC have rarely been studied. Hence, this study aimed to investigate the functional correlation between HOTTIP and pyroptosis in OC progression. The expression of HOTTIP in OC tissues and cell lines was characterized by quantitative real-time PCR. Cell proliferation was evaluated using Cell Counting Kit-8 and clone formation assays. Western blot was performed to quantify protein levels. A dual-luciferase reporter assay was used to analyze the molecular interaction among HOTTIP, miR-148a-3p, and AKT2. The expression of HOTTIP was significantly upregulated in OC tissue samples and cell lines. The silencing of HOTTIP led to the inhibition of cell proliferation and NLRP1 inflammasome-mediated pyroptosis. In addition, HOTTIP increased AKT2 expression by negatively regulating miR-148a-3p and then inhibited ASK1/JNK signaling. Further rescue experiments revealed that downregulation of miR-148a-3p and overexpression of AKT2 obviously diminished the effects of HOTTIP downregulation in OC cells. Thus, our study elucidated a novel pyroptosis-related mechanism by which HOTTIP participated in OC progression, which might provide a theoretical reference for clinical treatment.

Inflammasomes in Teleosts: Structures and Mechanisms That Induce Pyroptosis during Bacterial Infection

Pattern recognition receptors (PRRs) play a crucial role in inducing inflammatory responses; they recognize pathogen-associated molecular patterns, damage-associated molecular patterns, and environmental factors. Nucleotide-binding oligomerization domain-leucine-rich repeat-containing receptors (NLRs) are part of the PRR family; they form a large multiple-protein complex called the inflammasome in the cytosol. In mammals, the inflammasome consists of an NLR, used as a sensor molecule, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) as an adaptor protein, and pro-caspase1 (Casp1). Inflammasome activation induces Casp1 activation, promoting the maturation of proinflammatory cytokines, such as interleukin (IL)-1β and IL-18, and the induction of inflammatory cell death called pyroptosis via gasdermin D cleavage in mammals. Inflammasome activation and pyroptosis in mammals play important roles in protecting the host from pathogen infection. Recently, numerous inflammasome-related genes in teleosts have been identified, and their conservation and/or differentiation between their expression in mammals and teleosts have also been elucidated. In this review, we summarize the current knowledge of the molecular structure and machinery of the inflammasomes and the ASC-spec to induce pyroptosis; moreover, we explore the protective role of the inflammasome against pathogenic infection in teleosts.

Somatic Mutation of NLRP Genes in Gastric and Colonic Cancers

Nucleotide-binding and leucine-rich repeat protein (NLRP) genes are involved in inflammasome formation that plays a role in inflammation/host defense and cell death. Both cell death and inflammation are crucial for cancer development, but the roles of NLRPs in cancer are partially known. In this study, we analyzed mononucleotide repeats in coding sequences of NLRP1, NLRP2, NLRP4 and NLRP9, and found 1, 1, 1 and 8 frameshift mutation (s) in gastric (GC) and colonic cancers (CRC), respectively. Five of the 32 high microsatellite instability (MSI-H) GCs (15.5%) and 6 of 113 MSI-H CRCs (5.5%) exhibited the frameshift mutations. There was no NLRP frameshift mutations in microsatellite stable (MSS) GCs and CRCs. We also discovered that 2 of 16 CRCs (12.5%) harbored intratumoral heterogeneity (ITH) of the NLRP9 frameshift mutations in one or more areas. In both GC and CRC with MSI-H, NLRP9 expression in NLRP9-mutated cases was significantly lower than that in NLRP9-non-mutated cases. Our data indicate that NLRP9 is altered at multiple levels (frameshift mutation, mutational ITH and loss of expression), which together could contribute to pathogenesis of MSI-H GC and CRC.

Inflammasome Regulation: Therapeutic Potential for Inflammatory Bowel Disease

Inflammasomes are multiprotein complexes formed to regulate the maturation of pro-inflammatory caspases, in response to intracellular or extracellular stimulants. Accumulating studies showed that the inflammasomes are implicated in the pathogenesis of inflammatory bowel disease (IBD), although their activation is not a decisive factor for the development of IBD. Inflammasomes and related cytokines play an important role in the maintenance of gut immune homeostasis, while its overactivation might induce excess immune responses and consequently cause tissue damage in the gut. Emerging studies provide evidence that some genetic abnormalities might induce enhanced NLRP3 inflammasome activation and cause colitis. In these cases, the colonic inflammation can be ameliorated by blocking NLRP3 activation or its downstream cytokine IL-1β. A number of natural products were shown to play a role in preventing colon inflammation in various experimental colitis models. On the other hand, lack of inflammasome function also causes intestinal abnormalities. Thus, an appropriate regulation of inflammasomes might be a promising therapeutic strategy for IBD intervention. This review aims at summarizing the main findings in these studies and provide an outline for further studies that might contribute to our understanding of the role of inflammasomes in the pathogenesis and therapeutic treatment of IBD.

CARD8 is an inflammasome sensor for HIV-1 protease activity

HIV-1 has high mutation rates and exists as mutant swarms within the host. Rapid evolution of HIV-1 allows the virus to outpace the host immune system, leading to viral persistence. Approaches to targeting immutable components are needed to clear HIV-1 infection. Here, we report that the caspase recruitment domain-containing protein 8 (CARD8) inflammasome senses HIV-1 protease activity. HIV-1 can evade CARD8 sensing because its protease remains inactive in infected cells before viral budding. Premature intracellular activation of the viral protease triggered CARD8 inflammasome-mediated pyroptosis of HIV-1-infected cells. This strategy led to the clearance of latent HIV-1 in patient CD4+ T cells after viral reactivation. Thus, our study identifies CARD8 as an inflammasome sensor of HIV-1, which holds promise as a strategy for the clearance of persistent HIV-1 infection.

Targeting macrophage polarization by Nrf2 agonists for treating various xenobiotics-induced toxic responses

Macrophages can polarize into different phenotypes in response to different microenvironmental stimuli. Macrophage polarization has been assigned to two extreme states, namely proinflammatory M1 and anti-inflammatory M2. Accumulating evidences have demonstrated that M1 polarized macrophages contribute to various toxicants-induced deleterious effects. Switching macrophages from proinflammatory M1 phenotype toward anti-inflammatory M2 phenotype could be a promising approach for treating various inflammatory diseases. Studies in the past few decades have revealed that nuclear factor erythroid 2-related factor 2 (Nrf2) can modulate the polarization of macrophages. Specifically, activation of Nrf2 could block M1 stimuli-induced production of proinflammatory cytokines and chemokines, and shift the polarization of macrophages toward M2 by cross-talking with nuclear factor kappa-B (NF-κB), mitogen-activated protein kinases (MAPKs), peroxisome proliferator-activated receptor γ (PPARγ), and autophagy. Importantly, a great number of studies have confirmed the beneficial effects of natural and synthesized Nrf2 agonists on various inflammatory diseases; however, most of these compounds are far away from clinical application due to lack of characterization and defects of study designs. Interestingly, some endogenous Nrf2 inducers and compounds with dual activities (such as the Nrf2 inducing and CO releasing effects) exhibit potent anti-inflammatory effects, which points out an important direction for future researches.

Neutrophils: Many Ways to Die

Neutrophils or polymorphonuclear leukocytes (PMN) are key participants in the innate immune response for their ability to execute different effector functions. These cells express a vast array of membrane receptors that allow them to recognize and eliminate infectious agents effectively and respond appropriately to microenvironmental stimuli that regulate neutrophil functions, such as activation, migration, generation of reactive oxygen species, formation of neutrophil extracellular traps, and mediator secretion, among others. Currently, it has been realized that activated neutrophils can accomplish their effector functions and simultaneously activate mechanisms of cell death in response to different intracellular or extracellular factors. Although several studies have revealed similarities between the mechanisms of cell death of neutrophils and other cell types, neutrophils have distinctive properties, such as a high production of reactive oxygen species (ROS) and nitrogen species (RNS), that are important for their effector function in infections and pathologies such as cancer, autoimmune diseases, and immunodeficiencies, influencing their cell death mechanisms. The present work offers a synthesis of the conditions and molecules implicated in the regulation and activation of the processes of neutrophil death: apoptosis, autophagy, pyroptosis, necroptosis, NETosis, and necrosis. This information allows to understand the duality encountered by PMNs upon activation. The effector functions are carried out to eliminate invading pathogens, but in several instances, these functions involve activation of signaling cascades that culminate in the death of the neutrophil. This process guarantees the correct elimination of pathogenic agents, damaged or senescent cells, and the timely resolution of the inflammation that is essential for the maintenance of homeostasis in the organism. In addition, they alert the organism when the immunological system is being deregulated, promoting the activation of other cells of the immune system, such as B and T lymphocytes, which produce cytokines that potentiate the microbicide functions.

Inflammasome activation and evasion by bacterial pathogens

Innate immune system plays an essential role in combating infectious diseases by recognizing invading pathogens and activating host defense response. Inflammasomes complexes are a central component of the cytosolic innate immune surveillance and are vital in host defense against bacterial pathogens. Bacterial products or pathogen-induced modifications in the intracellular environment are sensed by the inflammasome receptors that form complexes that serve as a platform for caspase-1-dependent or caspase-11-dependent induction of pyroptosis and secretion of cytokines, IL-1β and IL-18. However, several pathogenic bacteria have developed strategies to evade inflammasome activation. This review highlights the recent advances in the mechanism of inflammasome activation by bacterial pathogens and some of the bacterial evasion strategies of inflammasome activation.

Endosymbiotic RNA virus inhibits Leishmania-induced caspase-11 activation

New World species of the intracellular protozoan parasites of the Leishmania genus can cause mucocutaneous leishmaniases. The presence of an endosymbiotic Leishmania RNA virus (LRV) in Leishmania guyanensis (L.g.) promotes disease exacerbation and the development of mucocutaneous disease. It was previously reported that LRV blocks the NLRP3 inflammasome, but additional mechanisms remain unclear. Here, we investigated whether LRV interferes with the inflammasome via caspase-11, which induces non-canonical NLRP3 activation and was reported to be activated by Leishmania. By using macrophages and mice, we found that LRV inhibits caspase-11 activation and IL-1β release by L.g. in a TLR3- and ATG5-dependent manner. Moreover, LRV exacerbates disease in C57BL/6 mice but not in Casp11 ^-/- , Nlrp3 ^-/- , and 129 mice, a mouse strain that is naturally mutant for caspase-11. These results demonstrate that LRV interferes with caspase-11 activation by Leishmania, expanding our understanding about the mechanisms by which LRV promotes disease exacerbation.

Structure, Activation and Regulation of NLRP3 and AIM2 Inflammasomes

The inflammasome is a three-component (sensor, adaptor, and effector) filamentous signaling platform that shields from multiple pathogenic infections by stimulating the proteolytical maturation of proinflammatory cytokines and pyroptotic cell death. The signaling process initiates with the detection of endogenous and/or external danger signals by specific sensors, followed by the nucleation and polymerization from sensor to downstream adaptor and then to the effector, caspase-1. Aberrant activation of inflammasomes promotes autoinflammatory diseases, cancer, neurodegeneration, and cardiometabolic disorders. Therefore, an equitable level of regulation is required to maintain the equilibrium between inflammasome activation and inhibition. Recent advancement in the structural and mechanistic understanding of inflammasome assembly potentiates the emergence of novel therapeutics against inflammasome-regulated diseases. In this review, we have comprehensively discussed the recent and updated insights into the structure of inflammasome components, their activation, interaction, mechanism of regulation, and finally, the formation of densely packed filamentous inflammasome complex that exists as micron-sized punctum in the cells and mediates the immune responses.

Role of Microgliosis and NLRP3 Inflammasome in Parkinson's Disease Pathogenesis and Therapy

Parkinson's disease (PD) is a neurodegenerative disorder marked primarily by motor symptoms such as rigidity, bradykinesia, postural instability and resting tremor associated with dopaminergic neuronal loss in the Substantia Nigra pars compacta (SNpc) and deficit of dopamine in the basal ganglia. These motor symptoms can be preceded by pre-motor symptoms whose recognition can be useful to apply different strategies to evaluate risk, early diagnosis and prevention of PD progression. Although clinical characteristics of PD are well defined, its pathogenesis is still not completely known, what makes discoveries of therapies capable of curing patients difficult to be reached. Several theories about the cause of idiopathic PD have been investigated and among them, the key role of inflammation, microglia and the inflammasome in the pathogenesis of PD has been considered. In this review, we describe the role and relation of both the inflammasome and microglial activation with the pathogenesis, symptoms, progression and the possibilities for new therapeutic strategies in PD.

Landscape of T Cells Transcriptional and Metabolic Modules During HIV Infection Based on Weighted Gene Co-expression Network Analysis

Human immunodeficiency virus (HIV) causes acquired immunodeficiency syndrome (AIDS). HIV infection affects the functions and metabolism of T cells, which may determine the fate of patients; however, the specific pathways activated in different T-cell subtypes (CD4⁺ and CD8⁺ T cells) at different stages of infection remain unclear. We obtained transcriptome data of five individuals each with early HIV infection, chronic progressive HIV infection, and no HIV infection. Weighted gene co-expression network analysis was used to evaluate changes in gene expression to determine the antiviral response. An advanced metabolic algorithm was then applied to compare the alterations in metabolic pathways in the two T-cell subtypes at different infection stages. We identified 23 and 20 co-expressed gene modules in CD4⁺ T and CD8⁺ T cells, respectively. CD4⁺ T cells from individuals in the early HIV infection stage were enriched in genes involved in metabolic and infection-related pathways, whereas CD8⁺ T cells were enriched in genes involved in cell cycle and DNA replication. Three key modules were identified in the network common to the two cell types: NLRP1 modules, RIPK1 modules, and RIPK2 modules. The specific role of NLRP1 in the regulation of HIV infection in the human body remains to be determined. Metabolic functional analysis of the two cells showed that the significantly altered metabolic pathways after HIV infection were valine, leucine, and isoleucine degradation; beta-alanine metabolism; and PPAR signaling pathways. In summary, we found the core gene expression modules and different pathways activated in CD4⁺ and CD8⁺ T cells, along with changes in their metabolic pathways during HIV infection progression. These findings can provide an overall resource for establishing biomarkers to facilitate early diagnosis and potential guidance for new targeted therapeutic strategies.

Bushen Huoxue Acupuncture Inhibits NLRP1 Inflammasome-Mediated Neuronal Pyroptosis in SAMP8 Mouse Model of Alzheimer's Disease

BACKGROUND

It was indicated that nucleotide-binding oligomerisation domain‑like receptor protein 1 (NLRP1) inflammasome-mediated pyroptosis is involveg in the progression of Alzheimer's disease (AD). This study was designed to explore the effect of Bushen Huoxue Acupuncture on cognitive defect and NLRP1 inflammasome-mediated pyroptosis in AD mouse.

METHODS

Senescence-accelerated mouse prone 8 (SAMP8) mice were used as a model of AD. Bushen Huoxue Acupuncture was performed in four acupoints: "Baihui acupoint" (GV20), "Shenshu acupoint" (BL23), "Xuehai acupoint" (SP10), and "Geshu acupoint" (BL17). Morris water maze test was performed to evaluate the cognitive function of the mouse. The levels of Aβ_1-40, Aβ_1-42, IL-1β, and IL-18 were examined by ELISA assay. Neuronal apoptosis and damage in hippocampal tissues were measured using TUNEL and Nissl staining, respectively. The expression of NLRP1, ASC, cleaved caspase-1, IL-1β, and IL-18 was examined using Western blot.

RESULTS

Bushen Huoxue Acupuncture improved the learning and memory deficits of AD mouse. Meanwhile, Bushen Huoxue Acupuncture decreased the production of Aβ in hippocampal tissues of SAMP8 mice and attenuated the neuronal apoptosis and damage. Furthermore, Bushen Huoxue Acupuncture inhibited NLRP1 inflammasome activation in SAMP8 mice.

CONCLUSION

Bushen Huoxue Acupuncture could notably attenuate the cognitive defect of mouse AD model and inhibit NLRP1 inflammasome-mediated pyroptosis.

Strategies for Targeting the NLRP3 Inflammasome in the Clinical and Preclinical Space

Inhibiting the NLRP3 inflammasome mediates inflammation in an extensive number of preclinical models. As excitement in this field has grown, several companies have recently initiated testing of direct NLRP3 inhibitors in the clinic. At the same time, the NLRP3 inflammasome is part of a larger pro-inflammatory pathway, whose modulation is also being explored. Multiple targets in this pathway are already impinged upon by molecules that have been through clinical trials. These data, informed by the growing mechanistic understanding of the NLRP3 inflammasome in the preclinical space, provide a rich backdrop to assess the current state of the field. Here we explore attempts to inhibit the NLRP3 inflammasome in light of clinical and preclinical data around efficacy and safety.

Double-Stranded RNA Dependent Kinase R Regulates Antibacterial Immunity in Sepsis

Double-stranded RNA dependent kinase R (PKR) is originally identified as an intracellular sensor of viral infection, but its role in bacterial infection remains largely unknown. Here we report that PKR was an important regulator of antibacterial immunity in sepsis. Genetic deletion of PKR or pharmacological inhibition of its kinase activity markedly increased bacterial loads, organ injury, and mortality in polymicrobial infection induced by cecal ligation and puncture (CLP). In contrast, PKR deficiency or inhibition did not affect bacterial loads, organ injury, or mortality when mice were systemically challenged with Escherichia coli, an abundant microbe in the gastrointestinal tract. PKR deficiency or inhibition markedly decreased the release of interleukin (IL)-1β after CLP. Defect in IL-1 signaling phenocopied PKR deficiency or inhibition in CLP-induced bacterial sepsis. Taken together, these findings identified a critical role of the PKR signaling pathway in antibacterial immunity.

Insight Into Inflammasome Signaling: Implications for Toxoplasma gondii Infection

Inflammasomes are multimeric protein complexes regulating the innate immune response to invading pathogens or stress stimuli. Recent studies have reported that nucleotide-binding leucine-rich repeat-containing (NLRs) proteins and DNA sensor absent in melanoma 2 (AIM2) serve as inflammasome sentinels, whose stimulation leads to the proteolytic activation of caspase-1, proinflammatory cytokine secretion, and pyroptotic cell death. Toxoplasma gondii, an obligate intracellular parasite of phylum Apicomplexans, is reportedly involved in NLRP1, NLRP3 and AIM2 inflammasomes activation; however, mechanistic evidence regarding the activation of these complexes is preliminary. This review describes the current understanding of inflammasome signaling in rodent and human models of T. gondii infection.

Taming the Autophagy as a Strategy for Treating COVID-19

Currently, an efficient treatment for COVID-19 is still unavailable, and people are continuing to die from complications associated with SARS-CoV-2 infection. Thus, the development of new therapeutic approaches is urgently needed, and one alternative is to target the mechanisms of autophagy. Due to its multifaceted role in physiological processes, many questions remain unanswered about the possible advantages of inhibiting or activating autophagy. Based on a search of the literature in this field, a novel analysis has been made to highlight the relation between the mechanisms of autophagy in antiviral and inflammatory activity in contrast with those of the pathogenesis of COVID-19. The present analysis reveals a remarkable coincidence between the uncontrolled inflammation triggered by SARS-CoV-2 and autophagy defects. Particularly, there is conclusive evidence about the substantial contribution of two concomitant factors to the development of severe COVID-19: a delayed or absent type I and III interferon (IFN-I and IFN-III) response together with robust cytokine and chemokine production. In addition, a negative interplay exists between autophagy and an IFN-I response. According to previous studies, the clinical decision to inhibit or activate autophagy should depend on the underlying context of the pathological timeline of COVID-19. Several treatment options are herein discussed as a guide for future research on this topic.

A deep dive into UV-based phototherapy: Mechanisms of action and emerging molecular targets in inflammation and cancer

UV-based phototherapy (including psoralen plus UVA (PUVA), UVB and UVA1) has a long, successful history in the management of numerous cutaneous disorders. Photoresponsive diseases are etiologically diverse, but most involve disturbances in local (and occasionally systemic) inflammatory cells and/or abnormalities in keratinocytes that trigger inflammation. UV-based phototherapy works by regulating the inflammatory component and inducing apoptosis of pathogenic cells. This results in a fascinating and complex network of simultaneous events-immediate transcriptional changes in keratinocytes, immune cells, and pigment cells; the emergence of apoptotic bodies; and the trafficking of antigen-presenting cells in skin-that quickly transform the microenvironment of UV-exposed skin. Molecular elements in this system of UV recognition and response include chromophores, metabolic byproducts, innate immune receptors, neurotransmitters and mediators such as chemokines and cytokines, antimicrobial peptides, and platelet activating factor (PAF) and PAF-like molecules that simultaneously shape the immunomodulatory effects of UV and their interplay with the microbiota of the skin and beyond. Phototherapy's key effects-proapoptotic, immunomodulatory, antipruritic, antifibrotic, propigmentary, and pro-prebiotic-promote clinical improvement in various skin diseases such as psoriasis, atopic dermatitis (AD), graft-versus-host disease (GvHD), vitiligo, scleroderma, and cutaneous T-cell lymphoma (CTCL) as well as prevention of polymorphic light eruption (PLE). As understanding of phototherapy improves, new therapies (UV- and non-UV-based) are being developed that will modify regulatory T-cells (Treg), interact with (resident) memory T-cells and /or utilize agonists and antagonists as well as antibodies targeting soluble molecules such as cytokines and chemokines, transcription factors, and a variety of membrane-associated receptors.

Deubiquitinase enzyme STAMBP plays a broad role in both Toll-like and Nod-like receptor mediated inflammation

The innate immune system in mammals include pattern recognition receptors (PRRs), which initiate immune responses to microbial infection via several mechanisms. These PRRs include cell surface Toll-like receptors (TLRs) and cytosolic Nod-like receptors (NLRs) that recognizes extracellular and intracellular danger signals respectively. NLRs are poised to respond specifically to pathogens that access the host cell cytosol. The molecular mechanisms by which NLRs are activated to form inflammasomes and exert downstream inflammatory responses remain poorly understood. Additionally, very little is known about the regulation of cytosolic pathogen sensory NLR family members, except for NLRP3. Recently a deubiquitinase known as STAMBP has been implicated as a regulator of NLRP7 inflammasome assembly. We have investigated the role of STAMBP in regulation of other inflammasome components and its broader role in inflammation using genetic removal of STAMBP protein from cells using CRISPR/Cas9 gene editing and challenging these gene edited cells with an inflammatory stimuli. Our study demonstrated that STAMBP has a critical role in inflammation both in the context of NLR pathway, through NLRP stabilization and TLR pathway, through JNK signaling and downstream cytokine production. The findings indicate that STAMBP has a wider role in inflammation than previously thought to be the case.

Peptidome analysis of cerebrospinal fluid in neonates with hypoxic-ischemic brain damage

Hypoxic-ischemic brain injury (HIBD) causes neonatal death and serious neurological disability; however, there are currently no promising therapies for it excepting cooling. Therefore, in this study, we used peptidome analysis to identify differentially expressed peptides in cerebrospinal fluid (CSF) of neonates with HIBD or controls, which may give a foundation for finding new promising drugs of neonatal HIBD. CSF samples were collected from neonates with HIBD (n = 4) or controls (n = 4). ITRAQ LC-MS/MS was used to identify differentially expressed peptides between two groups. A total of 35 differentially expressed peptides from 25 precursor proteins were identified. The 2671.5 Da peptide (HSQFIGYPITLFVEKER), one of the down-regulated peptides in neonatal HIBD, is a fragment of heat shock protein 90-alpha (HSP90α/HSP90AA1). Results of bioinformatics analysis showed that HSP90α/HSP90AA1 was located in the protein-protein interaction (PPI) network hub and was involved in the NOD-LIKE receptor (NLR) signaling pathway. This peptide, we named it Hypoxic-Ischemic Brain Damage Associated Peptide (HIBDAP), is a hydrophilic peptide with high stability and has a long half-life of 3.5 h in mammalian reticulocytes. It was demonstrated that TAT-HIBDAP could successfully enter PC12 cells and further into the nucleus. After HIBDAP pretreatment and 6 h of OGD treatment, low concentrations of HIBDAP increased the survival rate of cells, except 40 μM had a toxic effect. Safe concentrations of HIBDAP reduced pyroptosis of PC12 cells under OGD, except 20 μM had no effect, by suppressing expressions of NLRP3, ASC and Caspase-1 except NLRP1. The results of our study identified the characterization and expression profiles of peptides in CSF of neonatal HIBD. Several meaningful peptides such as HIBDAP may play significant roles in neonatal HIBD and provide new therapeutic targets for neonatal HIBD.

NLRP3 inflammasome in endothelial dysfunction

Inflammasomes are a class of cytosolic protein complexes. They act as cytosolic innate immune signal receptors to sense pathogens and initiate inflammatory responses under physiological and pathological conditions. The NLR-family pyrin domain-containing protein 3 (NLRP3) inflammasome is the most characteristic multimeric protein complex. Its activation triggers the cleavage of pro-interleukin (IL)-1β and pro-IL-18, which are mediated by caspase-1, and secretes mature forms of these mediators from cells to promote the further inflammatory process and oxidative stress. Simultaneously, cells undergo pro-inflammatory programmed cell death, termed pyroptosis. The danger signals for activating NLRP3 inflammasome are very extensive, especially reactive oxygen species (ROS), which act as an intermediate trigger to activate NLRP3 inflammasome, exacerbating subsequent inflammatory cascades and cell damage. Vascular endothelium at the site of inflammation is actively involved in the regulation of inflammation progression with important implications for cardiovascular homeostasis as a dynamically adaptable interface. Endothelial dysfunction is a hallmark and predictor for cardiovascular ailments or adverse cardiovascular events, such as coronary artery disease, diabetes mellitus, hypertension, and hypercholesterolemia. The loss of proper endothelial function may lead to tissue swelling, chronic inflammation, and the formation of thrombi. As such, elimination of endothelial cell inflammation or activation is of clinical relevance. In this review, we provided a comprehensive perspective on the pivotal role of NLRP3 inflammasome activation in aggravating oxidative stress and endothelial dysfunction and the possible underlying mechanisms. Furthermore, we highlighted the contribution of noncoding RNAs to NLRP3 inflammasome activation-associated endothelial dysfunction, and outlined potential clinical drugs targeting NLRP3 inflammasome involved in endothelial dysfunction. Collectively, this summary provides recent developments and perspectives on how NLRP3 inflammasome interferes with endothelial dysfunction and the potential research value of NLRP3 inflammasome as a potential mediator of endothelial dysfunction.

miRNA-141 Induced Pyroptosis in Intervertebral Disk Degeneration by Targeting ROS Generation and Activating TXNIP/NLRP3 Signaling in Nucleus Pulpous Cells

The role and mechanism of pyroptosis in intervertebral disk (IVD) degeneration are unclear. MicroRNAs (miRNAs) regulate the viability and function of nucleus pulposus cells (NPCs) in IVDs and are related to pyroptosis. We performed microarray analyses of normal and degenerated nucleus pulposus (NP) to assess the role of pyroptosis and identify key miRNAs in IVD degeneration. We also evaluated the underlying mechanism of miRNA-mediated pyroptosis in NPCs. In addition, we demonstrated the preventative effects of miRNAs on IVD degeneration in a rat model. The levels of the pyroptosis-related proteins cleaved caspase-1, N-terminal gasdermin D (GSDMD), interleukin (IL)-1β, and IL-18 in the degenerative NP were significantly higher than those in the normal NP. miRNA-141 was significantly upregulated in the degenerated NP. miR-141 mimic suppressed the matrix synthesis function of NPCs. By contrast, reactive oxygen species (ROS) generation, and the expression of TXNIP and NLRP3 were significantly downregulated by an miR-141 inhibitor. Furthermore, the miRNA-141 inhibitor prevented the degeneration of IVDs in vivo. Our findings suggest that miRNA-141 induces pyroptosis and extracellular matrix (ECM) catabolism in NPCs by increasing ROS generation and activating TXNIP/NLRP3 signaling. miRNA-141-regulated pyroptosis may be a novel therapeutic target for IVD degeneration.

Contribution of inflammasome complex in inflammatory-related eye disorders and its implications for anti-inflammasome therapy

Inflammasome complex is regarded as a major molecular regulator that exerts a significant function in caspase-1 activation and consequently, the development of cytokines like interleukin-1β (IL-1β) and interleukin-18 (IL-18). The secretion of these cytokines may induce inflammation. The role of inflammasomes in the pathologic process of eye-related illnesses like glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy has been well studied over the past decade. However, the detailed pathogenic mechanism of inflammasomes in these retinal diseases is still unknown. Therefore, further investigation and understanding various aspects of inflammasome complexes as well as their pivotal roles in the immunopathology of human ocular illnesses are essential. The present review aims to describe the significant involvement of inflammasomes in the immunopathology of important inflammatory retinal illnesses, including glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy focusing on anti-inflammasome therapy as a promising approach in the treatment of inflammation-related eye diseases.

The Role of Protein Tyrosine Phosphatases in Inflammasome Activation

Inflammasomes are multi-protein complexes that mediate the activation and secretion of the inflammatory cytokines IL-1β and IL-18. More than half a decade ago, it has been shown that the inflammasome adaptor molecule, ASC requires tyrosine phosphorylation to allow effective inflammasome assembly and sustained IL-1β/IL-18 release. This finding provided evidence that the tyrosine phosphorylation status of inflammasome components affects inflammasome assembly and that inflammasomes are subjected to regulation via kinases and phosphatases. In the subsequent years, it was reported that activation of the inflammasome receptor molecule, NLRP3, is modulated via tyrosine phosphorylation as well, and that NLRP3 de-phosphorylation at specific tyrosine residues was required for inflammasome assembly and sustained IL-1β/IL-18 release. These findings demonstrated the importance of tyrosine phosphorylation as a key modulator of inflammasome activity. Following these initial reports, additional work elucidated that the activity of several inflammasome components is dictated via their phosphorylation status. Particularly, the action of specific tyrosine kinases and phosphatases are of critical importance for the regulation of inflammasome assembly and activity. By summarizing the currently available literature on the interaction of tyrosine phosphatases with inflammasome components we here provide an overview how tyrosine phosphatases affect the activation status of inflammasomes.

Gaussian Embedding for Large-scale Gene Set Analysis

Gene sets, including protein complexes and signaling pathways, have proliferated greatly, in large part as a result of high-throughput biological data. Leveraging gene sets to gain insight into biological discovery requires computational methods for converting them into a useful form for available machine learning models. Here, we study the problem of embedding gene sets as compact features that are compatible with available machine learning codes. We present Set2Gaussian, a novel network-based gene set embedding approach, which represents each gene set as a multivariate Gaussian distribution rather than a single point in the low-dimensional space, according to the proximity of these genes in a protein-protein interaction network. We demonstrate that Set2Gaussian improves gene set member identification, accurately stratifies tumors, and finds concise gene sets for gene set enrichment analysis. We further show how Set2Gaussian allows us to identify a previously unknown clinical prognostic and predictive subnetwork around NEFM in sarcoma, which we validate in independent cohorts.

CD147 Aggravated Inflammatory Bowel Disease by Triggering NF-κB-Mediated Pyroptosis

BACKGROUND

Pyroptosis, a novel form of inflammatory programmed cell death, was recently found to be a cause of mucosal barrier defect. In our pervious study, CD147 expression was documented to increase in intestinal tissue of inflammatory bowel disease (IBD).

OBJECTIVE

The aim of this study was to determine the function of serum CD147 in pyroptosis.

METHODS

The study group consisted of 96 cases. The centration of CD147, IL-1β, and IL-18 levels in serum was assessed by ELISA. Real-time PCR and WB were performed to analyze the effect of CD147 on pyroptosis.

RESULTS

In this study, our results showed that CD147 induced cell pyroptosis in intestinal epithelial cells (IECs) by enhancement of IL-1β and IL-18 expression and secretion in IECs, which is attributed to activation of inflammasomes, including caspase-1 and GSDMD as well as GSDME, leading to aggregate inflammatory reaction. Mechanically, CD147 promoted phosphorylation of NF-κB p65 in IECs, while inhibition of NF-κB activity by the NF-κB inhibitor BAY11-7082 reversed the effect of CD147 on IL-1β and IL-18 secretion. Most importantly, serum CD147 level is slightly clinically correlated with IL-1β, but not IL-18 level.

CONCLUSION

These findings revealed a critical role of CD147 in the patients with IBD, suggesting that blockade of CD147 may be a novel therapeutic strategy for the patients with IBD.

Immunostimulatory efficacy and protective potential of putative TgERK7 protein in mice experimentally infected by Toxoplasma gondii

The extracellular signal-regulated kinases (ERKs) serve as important determinants of cellular signal transduction pathways, and hence may play important roles during infections. Previous work suggested that putative ERK7 of Toxoplasma gondii is required for efficient intracellular replication of the parasite. However, the antigenic and immunostimulatory properties of TgERK7 protein remain unknown. The objective of this study was to produce a recombinant TgERK7 protein in vitro and to evaluate its effect on the induction of humoral and T cell-mediated immune responses against T. gondii infection in BALB/c mice. Immunization using TgERK7 mixed with Freund's adjuvants significantly increased the ratio of CD3e⁺CD4⁺ T/CD3e⁺CD8a⁺ T lymphocytes in spleen and elevated serum cytokines (IFN-γ, IL-2, IL-4, IL-10, IL-12p70, IL-23, MCP-1, and TNF-α) in immunized mice compared to control mice. On the contrary, immunization did not induce high levels of serum IgG antibodies. Five predicted peptides of TgERK7 were synthesized and conjugated with KLH and used to analyze the antibody specificity in the sera of immunized mice. We detected a progressive increase in the antibody level only against TgERK7 peptide A (DEVDKHVLRKYD). Antibody raised against this peptide significantly decreased intracellular proliferation of T. gondii in vitro, suggesting that peptide A can potentially induce a protective antibody response. We also showed that immunization improved the survival rate of mice challenged with a virulent strain and significantly reduced the parasite cyst burden within the brains of chronically infected mice. Our data show that TgERK7-based immunization induced TgERK7 peptide A-specific immune responses that can impart protective immunity against T. gondii infection. The therapeutic potential of targeting ERK7 signaling pathway for future toxoplasmosis treatment is warranted.

Cepharanthine attenuates cerebral ischemia/reperfusion injury by reducing NLRP3 inflammasome-induced inflammation and oxidative stress via inhibiting 12/15-LOX signaling

Cepharanthine (CEP) is a potential candidate for treatment of cerebral ischemia/reperfusion (I/R) injury, due to its anti-inflammatory and anti-oxidative properties. To investigate the effect of CEP on cerebral I/R injury, we established a mouse model of transient middle cerebral artery occlusion (tMCAO) and a microglia cell model of oxygen and glucose deprivation/reoxygenation (OGD/R). Administration of CEP attenuated neurological deficits, reduced infarct volume and edema, and decreased microglia activation in MCAO mice. Immunofluorescence staining showed an up-regulation in NLR Family Pyrin Domain Containing 3 (NLRP3) immunoreactivity in Iba1-labled microglia together with total Iba1 and NLRP3 expression in the brain following tMCAO, while down-regulated by CEP treatment. In both tMCAO-induced mice and OGD/R-treated BV-2 cells, CEP exhibited dose-dependent inhibition on the expression of NLRP3, ASC and cleaved caspase-1. Importantly, CEP attenuated tMCAO or OGD/R-induced overproduction of M1 microglia-regulated pro-inflammation cytokines IL-1β and IL-18, suggesting that CEP might involve in suppressing microglia polarization to M1 phenotype in vivo and in vitro. Moreover, CEP dose-dependently inhibited tMCAO-induced arachidonate 15 lipoxygenase (ALOX15) together with Iba1-labled microglia. The subsequent ALOX15-mediated oxidative stress was decreased by CEP treatment in vivo and in vitro, as evidenced by reduced ROS generation and MDA level, and increased SOD activity. Taken together, we demonstrate that CEP attenuates cerebral I/R injury probably by inhibiting microglia activation and NLRP3 inflammasome-induced inflammation and reducing oxidative stress via suppressing 12/15-LOX signaling.

Characterization of the inflammasome component SmASC in turbot (Scophthalmus maximus)

Apoptosis-associated speck-like protein containing a C-terminal caspase recruit domain (ASC) is an important adapter protein in the inflammasome complex that mediates inflammatory caspase activation and host innate immunity in mammals. However, the function of inflammasome components in lower vertebrate remains poorly understood. In this study, full length of SmASC was cloned from turbot (Scophthalmus maximus). Through bioinformatic analysis, we found that SmASC shares relatively high identity with ASC in bony fish. Furthermore, we found that the intact SmASC can form an oligomeric speck-like structure, while the PYD segment of SmASC can form the filamentous structure. Moreover, expression of SmASC was induced after intraperitoneal injection of Edwardsiella piscicida (E. piscicida) in vivo. To further explore the role of SmASC during infection, we constructed SmASC knockdown and overexpression models by administration of siRNA and overexpression plasmids in vivo, respectively. Expression of SmASC decreased the propagation of E. piscicida in different immune organs. In summary, our results characterize the function of SmASC in S. maximus, suggesting that the SmASC plays a critical role in turbot immune responses.

Role of inflammasomes in the pathogenesis of periodontal disease and therapeutics

Inflammasomes are a group of multimolecular intracellular complexes assembled around several innate immune proteins. Recognition of a diverse range of microbial, stress and damage signals by inflammasomes results in direct activation of caspase‐1, which subsequently induces the only known form of secretion of active interleukin‐1β and interleukin‐18. Although the importance of interleukin‐1β in the periodontium is not questioned, the impact of inflammasomes in periodontal disease and its potential for therapeutics in periodontology is still in its very early stages. Increasing evidence in preclinical models and human data strongly implicate the involvement of inflammasomes in a number of inflammatory, autoinflammatory and autoimmune disorders. Here we review: (a) the currently known inflammasome functions, (b) clinical/preclinical data supporting inflammasome involvement in the context of periodontal and comorbid diseases and (c) potential therapies targeting inflammasomes. To clarify further the inflammasome involvement in periodontitis, we present analyses of data from a large clinical study (n = 5809) that measured the gingival crevicular fluid‐interleukin‐1β and grouped the participants based on current periodontal disease classifications. We review data on 4910 European‐Americans that correlate 16 polymorphisms in the interleukin‐1B region with high gingival crevicular fluid‐interleukin‐1β levels. We show that inflammasome components are increased in diseased periodontal tissues and that the caspase‐1 inhibitor, VX‐765, inhibits ~50% of alveolar bone loss in experimental periodontitis. The literature review further supports that although patients clinically present with the same phenotype, the disease that develops probably has different underlying biological pathways. The current data indicate that inflammasomes have a role in periodontal disease pathogenesis. Understanding the contribution of different inflammasomes to disease development and distinct patient susceptibility will probably translate into improved, personalized therapies.

Inflammasome activation by NLRP1 and NLRC4 in patients with coronary stenosis

OBJECTIVE AND DESIGN

We performed an experimental, analytical and prospective study to evaluate the systemic activation of inflammasome in atherosclerosis' patients, in order to shed light into responsible mechanisms for plaque formation.

SUBJECTS

We included sixty individuals distributed into 3 groups: 2 groups based on the report from the angiography (severe lesions - SL and primary lesions - PL) and 1 group enclosing healthy individuals (HC).

METHODS

The expression assays of inflammasome genes NLRP1, NLRC4, CASP-1 and IL-1β were performed using Real Time qPCR, with specific Taqman Assays. IL-1β serum levels were analysed by commercial kit. Were applied the Shapiro-Wilk and Student's T-test as statistical tests. Statistical significance was set to p ≤ 0.05.

RESULTS

Upregulation of NLRP1 (+3.47 FC, p = 0.0001), NLRC4 (+7.06 FC, p = 6.792 × 10^-09) and IL-1β (+2.43 FC, p = 0.005) was observed in all atherosclerosis patients when compared to HC. According to stenosis severity, patients with primary lesions showed upregulation of inflammasome genes NLRP1 (+2.87 FC, p = 0.0008), NLRC4 (+6.34 FC, p = 4.134 × 10^-07) and IL-1β (+3.39 FC, p = 0.0012) with respect to the HC group. No statistical difference was found in IL-1β serum levels according the assessed groups.

CONCLUSIONS

Inflammasome activation in atherosclerosis's patients can be systemic altered and may be triggered by NLRP1 and NLRC4 receptors. IL-1β gene expression was identified in our study as an important systemic detectable marker of plaque severity.

Inflammasome Activation in Response to Intracellular Protozoan Parasites

Inflammasomes are cytosolic complexes that assemble in response to cellular stress or upon sensing microbial molecules, culminating in cytokine processing and an inflammatory form of cell death called pyroptosis. Inflammasomes are usually composed of a sensor molecule, an adaptor protein, and an inflammatory caspase, such as Caspase-1, which cleaves and activates multiple substrates, including Gasdermin-D, pro-IL-1β, and pro-IL-18. Ultimately, inflammasome activation promotes inflammation and restriction of the microbial infection. In recent years, many studies have addressed the role of inflammasomes during fungal, bacterial, viral, and parasitic diseases, revealing sophisticated aspects of the host-pathogen interaction. In this review, we summarize recent advances on inflammasome activation in response to intracellular parasites, including Leishmania spp., Plasmodium spp., Trypanosoma cruzi, and Toxoplasma gondii.

Exploring the ring potential of 2,4-diaminopyrimidine derivatives towards the identification of novel caspase-1 inhibitors in Alzheimer's disease therapy

Pro-inflammatory activation of caspase-1 in the neurodegenerative pathway has been associated with age-dependent cognitive impairment and Alzheimer's disease (AD) in humans. A recent report highlighted 2,4-diaminopyrimidine ring as an essential fragment in the inhibition of human caspase-1. However, the role of the ring and its enzyme inhibitory mechanism is not thoroughly investigated at the molecular level. The purpose of this study is therefore in twofold: (1) to understand the enzyme binding mechanism of the 2,4-diaminopyrimidine ring and (2) to search for more potent caspase-1 inhibitors that contain the ring, using integrative per-residue energy decomposition (PRED) pharmacophore modeling. Ligand interaction profile of a reference compound revealed a peculiar hydrogen formation of the amino group of 2,4-diaminopyrimidine with active site residue Arg341, possibly forming the bases for its inhibitory prowess against caspase-1. A generated pharmacophore model for structure-based virtual screening identified compounds, ZINC724667, ZINC09908119, and ZINC09933770, as potential caspase-1 inhibitors that possessed desirable pharmacokinetic and physiochemical properties. Further analyses revealed active site residues, Arg179, Ser236, Cys285, Gln283, Ser339, and Arg341, as crucial to inhibitor binding by stabilizing and forming hydrogen bonds, hydrophobic, and pi-pi interactions with the 2,4-diaminopyrimidine rings. Common interaction patterns of the hits could have accounted for their selective and high-affinity ligand binding, which was characterized by notable disruptions in caspase-1 structural architecture. These compounds could further be explored as potential leads in the development of novel caspase-1 inhibitors.

Pyroptosis: The missing puzzle among innate and adaptive immunity crosstalk

Pyroptosis is a newly discovered programmed cell death with inflammasome formation. Pattern recognition receptors that identify repetitive motifs of prospective pathogens such as LPS of gram-negative bacteria are crucial to pyroptosis. Upon stimulation by pathogen-associated molecular patterns or damage-associated molecular patterns, proinflammatory cytokines, mainly IL-1 family members IL-1β and IL-18, are released through pyroptosis specific pore-forming protein, gasdermin D. Even though IL-1 family members are mainly involved in innate immunity, they can be factors in adaptive immunity. Given the importance of IL-1 family members in health and diseases, deciphering the role of pyroptosis in the regulation of innate and adaptive immunity is of great importance, especially with the recent progress in identifying the exact mechanism of such a pathway. In this review, we will focus on how the innate inflammatory mediators can regulate the adaptive immune system and vice versa via pyroptosis.

Cellular Stress and General Pathological Processes

From the viewpoint of the general pathology, most of the human diseases are associated with a limited number of pathogenic processes such as inflammation, tumor growth, thrombosis, necrosis, fibrosis, atrophy, pathological hypertrophy, dysplasia and metaplasia. The phenomenon of chronic low-grade inflammation could be attributed to non-classical forms of inflammation, which include many neurodegenerative processes, pathological variants of insulin resistance, atherosclerosis, and other manifestations of the endothelial dysfunction. Individual and universal manifestations of cellular stress could be considered as a basic element of all these pathologies, which has both physiological and pathophysiological significance. The review examines the causes, main phenomena, developmental directions and outcomes of cellular stress using a phylogenetically conservative set of genes and their activation pathways, as well as tissue stress and its role in inflammatory and para-inflammatory processes. The main ways towards the realization of cellular stress and its functional blocks were outlined. The main stages of tissue stress and the classification of its typical manifestations, as well as its participation in the development of the classical and non-classical variants of the inflammatory process, were also described. The mechanisms of cellular and tissue stress are structured into the complex systems, which include networks that enable the exchange of information with multidirectional signaling pathways which together make these systems internally contradictory, and the result of their effects is often unpredictable. However, the possible solutions require new theoretical and methodological approaches, one of which includes the transition to integral criteria, which plausibly reflect the holistic image of these processes.

Cellular Interplay as a Consequence of Inflammatory Signals Leading to Liver Fibrosis Development

Inflammation has been known to be an important driver of fibrogenesis in the liver and onset of hepatic fibrosis. It starts off as a process meant to protect the liver from further damage, but it can become the main promoter of liver fibrosis. There are many inflammation-related pathways activated during liver fibrosis that lead to hepatic stellate cells (HSCs) activation and collagen-deposition in the liver. Such events are mostly modulated upstream of HSCs and involve signals from hepatocytes and innate immune cells. One particular event is represented by cell death during liver injury that generates multiple inflammatory signals that further trigger sterile inflammation and enhancement of inflammatory response. The assembly of inflammasome that responds to danger-associated molecular patterns (DAMPs) stimulates the release of pro-inflammatory cytokines and at the same time, initiates programmed cell death called pyroptosis. This review focuses on cellular and molecular mechanisms responsible for initiation and progress of inflammation in the liver.

miR-590-3p Inhibits Pyroptosis in Diabetic Retinopathy by Targeting NLRP1 and Inactivating the NOX4 Signaling Pathway

Purpose

To elucidate the mechanism whereby miR-590-3p regulates pyroptosis in diabetic retinopathy (DR).

Methods

Human retinal microvascular endothelial cells (HRMECs) incubated with high glucose (HG) were used to establish cell models, and the expression levels of miR-590-3p, caspase-1, IL-1β, NLRP1, NOX4, TXNIP, NLRP3, and ROS were determined. Additionally, miR-590-3p was altered using a mimic or an inhibitor, and siRNAs targeting NLRP1 and NOX4 were applied to explore the regulatory mechanism of miR-590-3p in DR. The relationships between miR-590-3p and NLRP1/NOX4 also were investigated using a luciferase reporter assay. Furthermore, vitreous tissue samples were collected to confirm pyroptosis in clinical DR.

Results

Downregulated miR-590-3p and upregulated NLRP1/NOX4 levels were observed in a cell culture model of DR. Inhibiting miR-590-3p upregulated NLRP1, the NOX4/ROS/TXNIP/NLRP3 pathway, and caspase-1. NLRP1 and NOX4 were confirmed as direct target genes of miR-590-3p. The overexpression of miR-590-3p or knockdown of NLRP1 and NOX4 increased cell activity and suppressed pyroptosis. Intriguingly, the upregulation of IL-1β induced the downregulation of miR-590-3p by lowering the DNA promoter activity of pri-miR-590.

Conclusions

HG induced pyroptosis in a cell culture model of DR, and the downregulation of miR-590-3p promoted pyroptotic death by targeting NLRP1 and activating the NOX4/ROS/TXNIP/NLRP3 pathway via an IL-1β-mediated positive feedback loop.