Pyroptotic cell death defends against intracellular pathogens

Mechanisms and Therapeutic Regulation of Pyroptosis in Inflammatory Diseases and Cancer

Programmed Cell Death (PCD) is considered to be a pathological form of cell death when mediated by an intracellular program and it balances cell death with survival of normal cells. Pyroptosis, a type of PCD, is induced by the inflammatory caspase cleavage of gasdermin D (GSDMD) and apoptotic caspase cleavage of gasdermin E (GSDME). This review aims to summarize the latest molecular mechanisms about pyroptosis mediated by pore-forming GSDMD and GSDME proteins that permeabilize plasma and mitochondrial membrane activating pyroptosis and apoptosis. We also discuss the potentiality of pyroptosis as a therapeutic target in human diseases. Blockade of pyroptosis by compounds can treat inflammatory disease and pyroptosis activation contributes to cancer therapy.

NLRP3 Inflammasome and Inflammatory Diseases

Almost all human diseases are strongly associated with inflammation, and a deep understanding of the exact mechanism is helpful for treatment. The NLRP3 inflammasome composed of the NLRP3 protein, procaspase-1, and ASC plays a vital role in regulating inflammation. In this review, NLRP3 regulation and activation, its proinflammatory role in inflammatory diseases, interactions with autophagy, and targeted therapeutic approaches in inflammatory diseases will be summarized.

Overexpressed FOXO3 improves inflammatory status in mice by affecting NLRP3-mediated cell coronation in necrotizing colitis mice

OBJECTIVE

To investigate the relationship between FOXO3 overexpression and NLRP3 and explore the effect of FOXO3 on necrotizing colitis.

METHODS

100 clean grade newborn SD (Sprague Dawley) rats were randomly divided into 4 groups: NEC group, NEC + FOXO3a group, NEC + NC group and control group. NEC rat model was established by hypoxia + hypothermia stimulation; HE staining was used for detection of the inflammation of intestinal tissue. The histological scores of intestinal tissues were histologically scored, generally, there were three types of inflammatory scoring systems including anatomically based systems, severity-based systems and quality of life systems (Lim et al., 2015) and in this study we utilized severity-based systems by HE staining. Human intestinal epithelial cell line was transfected with recombinant plasmid overexpressing FOXO3a and recombinant plasmid overexpressing NLRP3, and divided into control group, LPS group, LPS + NC group, LPS + FOXO3a group and LPS + FOXO3a + NLRP3 group; Caspase-1 was used for the detection of pyroptosis. The expressions of FOXO3a, NLRP3, cleaved Caspase-1 and the expression of TLR4 in TLR4 signaling pathway were detected by RT-qPCR and WB. IL-1β, IL-6, IL-18 and TNF-α were detected by ELISA.

RESULTS

(1) FOXO3a is under-expressed and NLRP3 is highly expressed in NEC neonatal rat intestinal tissue. (2) The inflammatory condition of intestinal tissue in NEC + FOXO3a group was improved compared with NEC group (P < 0.05). (3) FOXO3a was highly expressed in NEC + FOXO3a group. The expression of IL-1β, IL-6, IL-18, SOD and MDA in NEC + FOXO3a group was lower than that in NEC group. (4) The expression of IL-1β, IL-6, IL-18, SOD and MDA in intestinal epithelial cells of LPS + FOXO3a group was lower than other groups. (5) Overexpression of FOXO3a inhibits LPS-induced pyroptotic cell death in intestinal epithelial cells by inhibiting NLRP3.

CONCLUSION

Overexpression of FOXO3 in mice with necrotizing colitis can improve inflammatory conditions in mice by affecting NLRP3-mediated cell caking.

Bioinformatics analyses on the immune status of renal transplant patients, a systemic research of renal transplantation

BACKGROUND

Kidney transplantation is the most effective treatment for end-stage renal disease. Allograft rejections severely affect survivals of allograft kidneys and recipients.

METHODS

Using bioinformatics approaches, the present study was designed to investigate immune status in renal transplant recipients. Fifteen datasets from Gene Expression Omnibus (GEO) were collected and analysed. Analysis of gene enrichment and protein-protein interactions were also used.

RESULTS

There were 40 differentially expressed genes (DEGs) identified in chronic rejection group when compared with stable recipients, which were enriched in allograft rejection module. There were 135 DEGs identified in acute rejection patients, compared with stable recipients, in which most genes were enriched in allograft rejection and immune deficiency. There were 288 DEGs identified in stable recipients when compared to healthy subjects. Most genes were related to chemokine signalling pathway. In integrated comparisons, expressions of MHC molecules and immunoglobulins were increased in both acute and chronic rejection; expressions of LILRB and MAP 4 K1 were increased in acute rejection patients, but not in stable recipients. There were no overlapping DEGs in blood samples of transplant recipients.

CONCLUSION

By performing bioinformatics analysis on the immune status of kidney transplant patients, the present study reports several DEGs in the renal biopsy of transplant recipients, which are requested to be validated in clinical practice.

Orchestration of human macrophage NLRP3 inflammasome activation by Staphylococcus aureus extracellular vesicles

Release of extracellular vesicles (EVs) is a common feature among eukaryotes, archaea, and bacteria. However, the biogenesis and downstream biological effects of EVs released from gram-positive bacteria remain poorly characterized. Here, we report that EVs purified from a community-associated methicillin-resistant Staphylococcus aureus strain were internalized into human macrophages in vitro and that this process was blocked by inhibition of the dynamin-dependent endocytic pathway. Human macrophages responded to S. aureus EVs by TLR2 signaling and activation of NLRP3 inflammasomes through K+ efflux, leading to the recruitment of ASC and activation of caspase-1. Cleavage of pro-interleukin (IL)-1β, pro-IL-18, and gasdermin-D by activated caspase-1 resulted in the cellular release of the mature cytokines IL-1β and IL-18 and induction of pyroptosis. Consistent with this result, a dose-dependent cytokine response was detected in the extracellular fluids of mice challenged intraperitoneally with S. aureus EVs. Pore-forming toxins associated with S. aureus EVs were critical for NLRP3-dependent caspase-1 activation of human macrophages, but not for TLR2 signaling. In contrast, EV-associated lipoproteins not only mediated TLR2 signaling to initiate the priming step of NLRP3 activation but also modulated EV biogenesis and the toxin content of EVs, resulting in alterations in IL-1β, IL-18, and caspase-1 activity. Collectively, our study describes mechanisms by which S. aureus EVs induce inflammasome activation and reveals an unexpected role of staphylococcal lipoproteins in EV biogenesis. EVs may serve as a novel secretory pathway for S. aureus to transport protected cargo in a concentrated form to host cells during infections to modulate cellular functions.

The emerging role of STING-dependent signaling on cell death

STING is a newly identified adaptor protein for sensing cytosolic nucleic acid. It is well established that STING plays a crucial role in innate immune response via inducing production of type I IFN. Emerging evidence suggests that the activation of STING-dependent signaling is also implicated in the process of cell death, such as apoptosis, pyroptosis, necroptosis, and autophagy. Of note, the pro-death outcome is even predominant in certain cell types, like lymphocytes, myeloid cells, and hepatocytes. Given that STING agonists are being tested for enhancing antitumor immune responses, it is necessary to fully understand the outcome of STING activation. The anti-microorganism response mediated by STING has been well described; therefore, we focus on the role of STING-dependent signaling on cell death in this review.

Parenteral Nutrition-Dependent Children With Short-Bowel Syndrome Lack Duodenal-Adaptive Hyperplasia but Show Molecular Signs of Altered Mucosal Function

BACKGROUND

Although adaptive mucosal growth of the remaining small intestine is an essential compensatory mechanism to bowel resection in experimental short-bowel syndrome (SBS), only scarce clinical data are available. We studied structural and molecular mechanisms of intestinal adaptation in children with SBS.

METHODS

Fourteen patients, who had been dependent on parenteral nutrition (PN) since neonatal period for a median (interquartile range)1.4 (0.7-6.5) years, were studied at the age of 1.5 (1.0-6.5) years. Median length of remaining small bowel was 33 (12-60) cm, and 6 patients had their ileocecal valve preserved. Six children without gastrointestinal disorders served as age-matched and gender-matched controls. All patients underwent duodenal biopsies. Mucosal microarchitecture, proliferation, apoptosis, inflammation, and epithelial-barrier function were addressed using histology, immunohistochemistry, and quantitative real-time polymerase chain reaction.

RESULTS

Villus height, crypt depth, enterocyte proliferation, and apoptosis were similar in patients and matched controls. Messenger RNA (mRNA) expression of numerous genes regulating gut epithelial-barrier function (TGFB2, CAV1, CLDN1, MUC2, and NLRC4) was significantly altered. Of various nutrient transporters studied, only expression of SLC2A1 encoding facilitative glucose transporter GLUT1 was increased among patients, whereas RNA expression of genes encoding sodium-dependent glucose, sterol, fatty-acid, and peptide transport remained unchanged.

CONCLUSION

Duodenal mucosal hyperplasia has a limited role in mediating physiological adaptation following intestinal resection among PN-dependent children with SBS. Further clinical studies addressing functional significance of the observed alterations in mucosal RNA expression are warranted.

Polyphyllin VI Induces Caspase-1-Mediated Pyroptosis via the Induction of ROS/NF-κB/NLRP3/GSDMD Signal Axis in Non-Small Cell Lung Cancer

Trillium tschonoskii Maxim (TTM), a traditional Chinese medicine, has been demonstrated to have a potent anti-tumor effect. Recently, polyphyllin VI (PPVI), a main saponin isolated from TTM, was reported by us to significantly suppress the proliferation of non-small cell lung cancer (NSCLC) via the induction of apoptosis and autophagy in vitro and in vivo. In this study, we further found that the NLRP3 inflammasome was activated in PPVI administrated A549-bearing athymic nude mice. As is known to us, pyroptosis is an inflammatory form of caspase-1-dependent programmed cell death that plays an important role in cancer. By using A549 and H1299 cells, the in vitro effect and action mechanism by which PPVI induces activation of the NLRP3 inflammasome in NSCLC were investigated. The anti-proliferative effect of PPVI in A549 and H1299 cells was firstly measured and validated by MTT assay. The activation of the NLRP3 inflammasome was detected by using Hoechst33324/PI staining, flow cytometry analysis and real-time live cell imaging methods. We found that PPVI significantly increased the percentage of cells with PI signal in A549 and H1299, and the dynamic change in cell morphology and the process of cell death of A549 cells indicated that PPVI induced an apoptosis-to-pyroptosis switch, and, ultimately, lytic cell death. In addition, belnacasan (VX-765), an inhibitor of caspase-1, could remarkably decrease the pyroptotic cell death of PPVI-treated A549 and H1299 cells. Moreover, by detecting the expression of NLRP3, ASC, caspase-1, IL-1β, IL-18 and GSDMD in A549 and h1299 cells using Western blotting, immunofluorescence imaging and flow cytometric analysis, measuring the caspase-1 activity using colorimetric assay, and quantifying the cytokines level of IL-1β and IL-18 using ELISA, the NLRP3 inflammasome was found to be activated in a dose manner, while VX-765 and necrosulfonamide (NSA), an inhibitor of GSDMD, could inhibit PPVI-induced activation of the NLRP3 inflammasome. Furthermore, the mechanism study found that PPVI could activate the NF-κB signaling pathway via increasing reactive oxygen species (ROS) levels in A549 and H1299 cells, and N-acetyl-L-cysteine (NAC), a scavenger of ROS, remarkably inhibited the cell death, and the activation of NF-κB and the NLRP3 inflammasome in PPVI-treated A549 and H1299 cells. Taken together, these data suggested that PPVI-induced, caspase-1-mediated pyroptosis via the induction of the ROS/NF-κB/NLRP3/GSDMD signal axis in NSCLC, which further clarified the mechanism of PPVI in the inhibition of NSCLC, and thereby provided a possibility for PPVI to serve as a novel therapeutic agent for NSCLC in the future.

Targeting NLRP3 Inflammasome in Inflammatory Bowel Disease: Putting out the Fire of Inflammation

Inflammatory bowel disease (IBD) is a group of inflammatory conditions of the colon and small intestine, comprised of ulcerative colitis and Crohn's disease. Among the complicated pathogenic factors of IBD, the overaction of inflammatory and immune reaction serves as an important factor. Inflammasome is a form of innate immunity as well as inflammation. Among all kinds of inflammasomes, the NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome is the most studied one, and has been revealed to be involved in the pathogenesis and progression of IBD. Here, in this review, the association between the NLRP3 inflammasome and IBD will be discussed. Furthermore, several NLRP3 inflammasome inhibitors which have been demonstrated to be effective in the alleviation of IBD will be described in this review.

Pyroptosis in Osteoblasts: A Novel Hypothesis Underlying the Pathogenesis of Osteoporosis

Osteoporosis has become a worldwide disease characterized by a reduction in bone mineral density and the alteration of bone architecture leading to an increased risk of fragility fractures. And an increasing number of studies have indicated that osteoblasts undergo a large number of programmed death events by many different causes in osteoporosis and release NLRP3 and interleukin (e.g., inflammatory factors), which play pivotal roles in contributing to excessive differentiation of osteoclasts and result in exaggerated bone resorption. NLRP3 is activated during pyroptosis and processes the precursors of IL-1β and IL-18 into mature forms, which are released into the extracellular milieu accompanied by cell rupture. All of these compounds are the classical factors of pyroptosis. The cellular effects of pyroptosis are commonly observed in osteoporosis. Although many previous studies have focused on the pathogenesis of these inflammatory factors in osteoporosis, pyroptosis has not been previously evaluated. In this review, pyroptosis is proposed as a novel hypothesis of osteoporosis pathogenesis for the first time, thus providing a new direction for the treatment of osteoporosis in the future.

Bnip3 mediates doxorubicin-induced cardiomyocyte pyroptosis via caspase-3/GSDME

AIMS

This study was aimed to investigate the role of GSDME-mediated pyroptosis in cardiac injury induced by Doxorubicin (DOX), and to evaluate the role of BH3-only protein Bcl-2/adenovirus E1B 19-kDa-interacting protein 3 (Bnip3) in regulation of DOX-induced pyroptosis.

MAIN METHODS

HL-1 cardiomyocytes and C57BL/6J mice were treated by DOX to establish DOX-induced cardiotoxicity in vitro and in vivo models, respectively. Cell transfection was applied to regulate the expression of caspase-3, GSDME and Bnip3. Western blot was used for measuring expression of protein level. LDH-cytotoxicity assay was used to detect the LDH release. The Flow cytometry analysis was used to detect the cell death. Echocardiography was used to determine the cardiac function. HE staining was used for observing pathological feature of heart tissues.

KEY FINDINGS

Our results showed that GSDME-mediated pyroptosis was involved in DOX-induced cardiotoxicity in vivo. We showed that HL-1 cardiomyocytes exposed to DOX exhibited morphological features of pyroptosis in vitro. We also showed that DOX induced activation of caspase-3 and eventually triggered GSDME-dependent pyroptosis, which was reduced by the silence or inhibitor of caspase-3. We further showed that knockdown of GSDME inhibited DOX-induced cardiomyocyte pyroptosis in vitro. Finally, DOX increased the expression of Bnip3, whereas silencing of Bnip3 blunted cardiomyocyte pyroptosis induced by DOX, which was regulated through caspase-3 activation and GSDME cleavage.

SIGNIFICANCE

Our findings revealed a novel pathway that cardiomyocyte pyroptosis is regulated through Bnip3-caspase-3-GSDME pathway following DOX treatment, suggesting that Bnip3-dependent pyroptosis may offer a novel therapeutic strategy to reduce cardiotoxicity induced by DOX.

LncRNA KLF3-AS1 in human mesenchymal stem cell-derived exosomes ameliorates pyroptosis of cardiomyocytes and myocardial infarction through miR-138-5p/Sirt1 axis

AIM

Myocardial infarction (MI) is a severe disease with increased mortality and disability rates, posing heavy economic burden for society. Exosomes were uncovered to mediate intercellular communication after MI. This study aims to explore the effect and mechanism of lncRNA KLF3-AS1 in exosomes secreted by human mesenchymal stem cells (hMSCs) on pyroptosis of cardiomyocytes and MI.

METHODS

Exosomes from hMSCs were isolated and identified. Exosomes from hMSCs with transfection of KLF3-AS1 for overexpression were injected into MI rat model or incubated with hypoxia cardiomyocytes. Effect of KLF3-AS1 on MI area, cell viability, apoptosis, and pyroptosis was determined. The relationship among miR-138-5p, KLF3-AS1, and Sirt1 was verified by dual-luciferase reporter assay. Normal cardiomyocytes were transfected with miR-138-5p inhibitor or sh-Sirt1 to clarify whether alteration of miR-138-5p or sh-Sirt1 can regulate the effect of KLF3-AS1 on cardiomyocytes.

RESULTS

Exosomes from hMSCs were successfully extracted. Transfection of KLF3-AS1 exosome in rats and incubation with KLF3-AS1 exosome in hypoxia cardiomyocytes both verified that overexpression of KLF3-AS1 in exosomes leads to reduced MI area, decreased cell apoptosis and pyroptosis, and attenuated MI progression. KLF3-AS1 can sponge miR-138-5p to regulate Sirt1 expression. miR-138-5p inhibitor transfection and KLF3-AS1 exosome incubation contribute to attenuated pyroptosis and MI both in vivo and in vitro, while transfection of sh-Sirt1 could reverse the protective effect of exosomal KLF3-AS1 on hypoxia cardiomyocytes.

CONCLUSION

LncRNA KLF3-AS1 in exosomes secreted from hMSCs by acting as a ceRNA to sponge miR-138-5p can regulate Sirt1 so as to inhibit cell pyroptosis and attenuate MI progression.

Fiery Cell Death: Pyroptosis in the Central Nervous System

Pyroptosis ('fiery death') is an inflammatory type of regulated cell death (RCD), which occurs downstream of inflammasome activation. Pyroptosis is mediated directly by the recently identified family of pore-forming proteins known as gasdermins, the best characterized of which is gasdermin D (GSDMD). Recent investigations implicate pyroptosis in the pathogenesis of multiple neurological diseases. In this review, we discuss molecular mechanisms that drive pyroptosis, evidence for pyroptosis within the CNS, and emerging therapeutic strategies for its inhibition in the context of neurological disease.

Retinal Pigment Epithelium Cell Death Is Associated With NLRP3 Inflammasome Activation by All-trans Retinal

Purpose

Visual (retinoid) cycle anomalies induce aberrant build-up of all-trans retinal (atRAL) in the retinal pigment epithelium (RPE), which is a cause of RPE atrophy in Stargardt disease type 1 and age-related macular degeneration. NLR family pyrin domain containing 3 (NLRP3) inflammasome activation is implicated in the etiology of age-related macular degeneration. Here, we elucidated the relationship between NLRP3 inflammasome activation and atRAL-induced death of RPE cells.

Methods

Cellular toxicities were assessed by MTS or MTT assays. Expression levels of mRNAs and proteins were determined by quantitative reverse transcription-polymerase chain reaction, Western blotting, or enzyme-linked immunosorbent assay. Fluorescence microscopy was used to examine intracellular signals. Ultrastructural features of organelles were examined by transmission electron microscope.

Results

Abnormal accumulation of atRAL was associated with a significant increase in the proportion of human ARPE-19 cells exhibiting features of apoptosis and Caspase-3/gasdermin E (GSDME)-mediated pyroptosis. These cells also exhibited elevated expression of NLRP3, ASC, cleaved Caspase-1/poly ADP-ribose polymerase (PARP)/Caspase-3/GSDME, interleukin-1β (IL-1β), and IL-18, as well as NLRP3 inflammasome-related genes (IL1B and IL18). After exposure of human ARPE-19 cells to excess atRAL, reactive oxygen species (ROS) (including mitochondrial ROS) and cathepsins released from lysosomes transmitted signals leading to NLRP3 inflammasome activation. Suppressing the production of ROS, NLRP3 inflammasome, Caspase-1, cathepsin B, or cathepsin D protected ARPE-19 cells against atRAL-associated cytotoxicity. Damage to mitochondria, lysosomes, and endoplasmic reticulum in atRAL-exposed ARPE-19 cells was partially alleviated by treatment with MCC950, a selective NLRP3 inflammasome inhibitor.

Conclusions

Aberrant build-up of atRAL promotes the death of RPE cells via NLRP3 inflammasome activation.

Research progresses of molecular mechanism of pyroptosis and its related diseases

Pyroptosis is a newly discovered untypical form of programmed cell death by inflammatory response, which is dependent on the classic pathway of Caspase-1 and the non-canonical pathway of Caspase-11 in mice or orthologue Caspase-4/-5 in Humans. It has been found that the Gasdermin family of protein is a key molecule in the formation of membrane pores of pyroptosis. After being cleaved by inflammatory caspases, it releases a N-terminal fragment with perforating activity to trigger pyroptosis. That pyroptosis is closely related to the occurrence and development of certain diseases. Now, the molecular mechanism of pyroptosis and pyroptosis-related diseases are reviewed.

Inhibition of PRMT5 Attenuates Oxidative Stress-Induced Pyroptosis via Activation of the Nrf2/HO-1 Signal Pathway in a Mouse Model of Renal Ischemia-Reperfusion Injury

Background

Extensive evidence has demonstrated that oxidative stress, pyroptosis, and proinflammatory programmed cell death are related to renal ischemia/reperfusion (I/R) injury. However, the underlying mechanism remains to be illustrated. Protein arginine methylation transferase 5 (PRMT5), which mediates arginine methylation involved in the regulation of epigenetics, exhibits a variety of biological functions and essential roles in diseases. The present study investigated the role of PRMT5 in oxidative stress and pyroptosis induced by I/R injury in a mouse model and in a hypoxia/reoxygenation (H/R) model of HK-2 cells.

Methods

C57 mice were used as an animal model. All mice underwent right nephrectomy, and the left renal pedicles were either clamped or not. Renal I/R injury was induced by ligating the left renal pedicle for 30 min followed by reperfusion for 24 h. HK-2 cells were exposed to normal conditions or stimulation through H/R. EPZ015666(EPZ)—a selective potent chemical inhibitor—and small interfering RNA (siRNA) were administered to suppress the function and expression of PRMT5. The levels of urea nitrogen and creatinine in the serum and renal tissue injury were assessed. Immunohistochemistry, western blotting, and reverse transcription-polymerase chain reaction were used to evaluate pyroptosis-related proteins including nod-like receptor protein-3, ASC, caspase-1, caspase-11, GSDMD-N, and interleukin-1β. Cell apoptosis and cell viability were detected through flow cytometry, and the levels of reactive oxygen species (ROS) and hydrogen peroxide (H₂O₂) were measured. Ki-67 was used to assess the proliferation of renal tubular epithelium. In addition, the activity of malondialdehyde and superoxide dismutase was determined.

Results

I/R or H/R induced an increase in the expression of PRMT5. Inhibition of PRMT5 by EPZ alleviated oxidative stress and I/R- or H/R-induced pyroptosis. In renal tissue, the application of EPZ promoted the proliferation of tubular epithelium. In addition, H/R-induced pyroptosis in HK-2 cells was dependent on oxidative stress in vitro. Administration of either EPZ or siRNA led to decreased expression of pyroptosis-related proteins. Inhibition of PRMT5 also attenuated the I/R- or H/R-induced oxidative stress in vivo and in HK-2 cells, respectively. It also resulted in a distinct decrease in the levels of malondialdehyde and H₂O₂, and an apparent increase in superoxide dismutase activity in mouse renal tissue. Moreover, it led to a significant decrease in the levels of ROS and H₂O₂ in HK-2 cells. When activated, NF-E2-related factor/heme oxygenase-1 (Nrf2/HO-1)—a key regulator of various cytoprotective proteins that withstand oxidative damage—can decrease the generation of ROS. Nrf2/HO-1 was downregulated during I/R in tissues and H/R in HK-2 cells, and this effect was reversed by the PRMT5 inhibitor. Furthermore, the expressions of Nrf2 and HO-1 proteins were markedly upregulated by EPZ or siRNA against PRMT5.

Conclusion

PRMT5 is involved in ischemia- and hypoxia-induced oxidative stress and pyroptosis in vitro and in vivo. Inhibition of PRMT5 may ameliorate renal I/R injury by suppressing oxidative stress and pyroptosis via the activation of the Nrf2/HO-1 pathway, as well as promoting the proliferation of tubular epithelium. Therefore, PRMT5 may be a promising therapeutic target.

Characterization of the NLRP1 inflammasome response in bovine species

Inflammasomes act as sensors of infection or damage to initiate immune responses. While extensively studied in rodents, understanding of livestock inflammasomes is limited. The NLRP1 inflammasome sensor in rodents is activated by Toxoplasma gondii, Bacillus anthracis lethal toxin (LT), and potentially other zoonotic pathogens. LT activates NLRP1 by N-terminal proteolysis, inducing macrophage pyroptosis and a pro-inflammatory cytokine response. In contrast, NLRP1 in macrophages from humans and certain rodent strains is resistant to LT cleavage, and pyroptosis is not induced. Evolution of NLRP1 sequences towards those leading to pyroptosis is of interest in understanding innate immune responses in different hosts. We characterized NLRP1 in cattle (Bos taurus) and American bison (Bison bison). Bovine NLRP1 is not cleaved by LT, and cattle and bison macrophages do not undergo toxin-induced pyroptosis. Additionally, we found a predicted Nlrp1 splicing isoform in cattle macrophages lacking the N-terminal domain. Resistance to LT in bovine and human NLRP1 correlates with evolutionary sequence similarity to rodents. Consistent with LT-resistant rodents, bovine macrophages undergo a slower non-pyroptotic death in the presence of LPS and LT. Overall, our findings support the model that NLRP1 activation by LT requires N-terminal cleavage, and provide novel information on mechanisms underlying immune response diversity.

Pyroptosis: A new frontier in cancer

Pyroptosis is an inflammatory form of cell death triggered by certain inflammasomes, leading to the cleavage of gasdermin D (GSDMD) and activation of inactive cytokines like IL-18 and IL-1β. Pyroptosis has been reported to be closely associated to some diseases like atherosclerosis and diabetic nephropathy. Recently, some studies found that pyroptosis can influence the proliferation, invasion and metastasis of tumor, which regulated by some non-coding RNAs and other molecules. Hence, we provided an overview of morphological and molecular characteristics of pyroptosis. We also focus on mechanism of regulating pyroptosis in tumor cells as well as the potential roles of pyroptosis in cancer to explore potential diagnostic markers in cancers contributing to the prevention and treatment in cancers.

The role of interleukin-18 in pancreatitis and pancreatic cancer

Originally described as an interferon (IFN)-γ-inducing factor, interleukin (IL)-18 has been reported to be involved in Th1 and Th2 immune responses, as well as in activation of NK cells and macrophages. There is convincing evidence that IL-18 plays an important role in various pathologies (i.e. inflammatory diseases, cancer, chronic obstructive pulmonary disease, Crohn's disease and others). Recently, IL-18 has also been shown to execute specific effects in pancreatic diseases, including acute and chronic pancreatitis, as well as pancreatic cancer. The aim of this study was to give a profound review of recent data on the role of IL-18 and its potential as a therapeutic target in pancreatic diseases. The existing data on this topic are in part controversial and will be discussed in detail. Future studies should aim to confirm and clarify the role of IL-18 in pancreatic diseases and unravel their molecular mechanisms.

Immunological recovery failure in cART-treated HIV-positive patients is associated with reduced thymic output and RTE CD4+ T cell death by pyroptosis

Despite more than three decades of studies and advances in combination antiretroviral therapy (cART) against human immunodeficiency virus (HIV), the mechanisms that precisely determine immune reconstitution failure have not been completely elucidated yet. Thus, this study aimed to investigate the thymic function, immune activation, and cell death by pyroptosis and apoptosis in virologically suppressed HIV-positive patients receiving cART. Immunophenotyping analyses were performed in 57 cART-treated HIV-infected patients with undetectable plasma viral load, who were classified as immunological nonresponders (INR = 29) and immunologic responders (IR = 28). Sociodemographic and clinical data were also assessed from medical records. Twelve healthy volunteers were also included in this study. The INR showed lower pretreatment CD4+ T cell count that remained low even after 1 yr of treatment, lower CD4/CD8 ratio, lower percentage of recent thymic emigrant (RTE) CD4+ T cell (CD45RA+CD31+) and naïve CD4+ T cell (CD45RA+CD62L+), higher levels of effector memory CD4+ T cells (CD45RA-CD62L-), and higher pyroptosis levels of RTE CD4+ T cells (CD31+FLICA-Caspase1+) when compared with IR. Our findings indicate that reduced thymic function and RTE CD4+ T cell death by pyroptosis are the major mechanisms of immunological recovery failure in HIV-infected patients receiving cART.

WDR90 is a new component of the NLRC4 inflammasome involved in Salmonella Typhimurium resistance

Inflammasomes are pivotal cytosolic molecular platforms involved in infection resistance. As multiprotein complexes, they consist of NOD-like receptors (NLRs), the adaptor proteins apoptosis-associated speck-like protein containing a CARD (ASC) and the effector molecules caspase-1 and caspase-11, whose assembly and activation depends on homotypic interactions. Here we describe WD repeat containing protein 90 (WDR90) as a new inflammasome component. We found that zebrafish wdr90 is highly induced by guanylate binding protein 4 (Gbp4) independently of inflammasome activation and caspase-1 activity. This gene encodes an evolutionarily conserved protein with unknown functions that contains several WD40 domains, which are involved in coordinating multiprotein complex assembly. Functional studies in zebrafish larvae showed that forced expression of wdr90 increased caspase-1 activity and inflammasome-dependent resistance to Salmonella enterica serovar Typhimurium infection. Wdr90 acted upstream of zebrafish caspase a (Caspa), the functional homolog of mammalian caspase-1, and Asc. Reconstitution experiments of the human inflammasome in HEK293 cells demonstrated that WDR90 was able to physically interact with and to alter the cellular distribution of NLRC4, but not of NLRP3 and AIM2. These results highlight the complexity of the inflammasome and the interest of studying fish immunity to understand not only the evolution of the immune system but also human immunity.

Screening of Sera from Patients with Pancreatitis by an Apoptosis Assay of Skin-derived Cells

Background/Aims

An excessive inflammatory response is typical in acute pancreatitis and a significant cause of early mortality in severe acute pancreatitis. This is believed to be caused by inflammatory molecules or upregulated cytokine levels in the serum of patients. The aim of this study was to identify the serum-mediated apoptosis-inducing effects in acute pancreatitis patients.

Methods

A skin tissue-derived cell line, BJ, was treated for 24 hours with the sera of 22 healthy volunteers (control) and 71 acute pancreatitis patients (22 with gallstone pancreatitis, 16 with alcoholic pancreatitis, and 11 with pancreatitis with other causes) collected at the time of hospital admission (active) and discharge (resolved). Apoptosis was analyzed by flow cytometry.

Results

The average percentage of living cells, early apoptotic cells, and late apoptotic cells ranged from 78.8% to 85.0%, 5.5% to 7.3%, and 7.7% to 13.1%, respectively. The number of live cells increased significantly using the serum from the resolved state of gallstone-induced pancreatitis. In addition, the number of early apoptotic cells increased significantly using the serum from the resolved state of pancreatitis with other causes. The number of late apoptotic cells decreased significantly with the serum from the resolved state compared to the active state of gallstone- and alcohol-induced pancreatitis.

Conclusions

Serum samples from patients with pancreatitis induced a change in the apoptosis profiles of skin-derived cells. These results indicate changes in the serum components in patients with acute pancreatitis.

Involvement of purinergic 2X4 receptor in glycoprotein 120-induced pyroptosis in dorsal root ganglia

Pyroptosis is a type of programmed cell death, displaying caspase-1-dependent and pro-inflammatory features. Purinergic 2X₄ (P2X₄ ) receptor activation in response to high-adenosine triphosphate release can induce inflammation. Envelope glycoprotein 120 (gp120) of human immunodeficiency virus type 1 is considered one of the primary pathogens leading to neuronal injury. In this study, we investigated the possible role of P2X₄ receptor activation in gp120-triggered pyroptosis in cultured satellite glial cells (SGCs) of rat dorsal root ganglia (DRG). MTS assay, TdT-mediated dUTP Nick-end labeling assay, real-time RT-PCR, and western blotting et al. methods were used. The results indicated that the expression of P2X₄ receptor in SGCs of DRG was up-regulated upon cultured with gp120 for 24 h. The highest decrease in viability of SGCs due to gp120 treatment was accompanied by marked increases of positive pyroptosis cells and cellular lactate dehydrogenase release, elevated levels of interleukin-1β, interleukin-18, active caspase-1 and NOD-like receptor family, pyrin domain containing 1, and enhanced phosphorylation of p38MAPK. These abnormal changes because of gp120 were significantly inhibited and cell viability was markedly improved when SGCs of DRG were treated with short hairpin RNAs targeting P2X₄ receptor. Our data suggest that silencing of P2X₄ receptor may act effectively against gp120-induced pyroptosis mediated by the activation of NOD-like receptor family, pyrin domain containing 1 inflammasome and caspase-1 signaling in SGCs of DRG.

Emerging insights into molecular mechanisms underlying pyroptosis and functions of inflammasomes in diseases

Pyroptosis is a form of necrotic and inflammatory programmed cell death, which could be characterized by cell swelling, pore formation on plasma membranes, and release of proinflammatory cytokines (IL-1β and IL-18). The process of pyroptosis presents as dual effects: protecting multicellular organisms from microbial infection and endogenous dangers; leading to pathological inflammation if overactivated. Two pathways have been found to trigger pyroptosis: caspase-1 mediated inflammasome pathway with the involvement of NLRP1-, NLRP3-, NLRC4-, AIM2-, pyrin-inflammasome (canonical inflammasome pathway) and caspase-4/5/11-mediated inflammasome pathway (noncanonical inflammasome pathway). Gasdermin D (GSDMD) has been proved to be a substrate of inflammatory caspases (caspase-1/4/5/11), and the cleaved N-terminal domain of GSDMD oligomerizes to form cytotoxic pores on the plasma membrane. Here, we mainly reviewed the up to date mechanisms of pyroptosis, and began with the inflammasomes as the activator of caspase-1/caspase-11, 4, and 5. We further discussed these inflammasomes functions in diseases, including infectious diseases, sepsis, inflammatory autoimmune diseases, and neuroinflammatory diseases.

Neuroprotective effect of glycosides in Buyang Huanwu Decoction on pyroptosis following cerebral ischemia-reperfusion injury in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Buyang Huanwu Decoction (BYHWD) is used in classical traditional Chinese medicine to prevent and treat cerebral ischemia. Glycosides, which are effective components extracted from BYHWD, mainly include astragaloside IV, paeoniflorin, and amygdalin. These glycosides are the primary pharmacologically effective constituents of BYHWD that act against cerebral ischemic nerve injury; however, the mechanism of action of BYHWD is still unclear.

AIM OF THE STUDY

The present study aimed to determine the effect of BYHWD glycosides on pyroptosis after cerebral ischemia reperfusion injury and explore whether its mechanism involves the classical pyroptosis pathway mediated by NLRP3.

MATERIAL AND METHODS

Adult male Sprague-Dawley rats (n = 140) were randomly divided into seven groups: sham, cerebral ischemia and reperfusion (I/R), glycosides (0.064 g/kg, 0.128 g/kg, and 0.256 g/kg), BYHWD, and AC-YVAD-CMK (caspase-1 inhibitor). A rat model of cerebral I/R was established via classic middle cerebral artery occlusion (MCAO) for 2 h, followed by 24-h reperfusion. Neurological function was estimated using neurological defect scores. Brain infarct volumes were determined by 2,3,5-triphenyltetrazolium chloride (TTC) staining, and nerve cell damage was evaluated by Nissl staining. Pyroptosis was detected using TUNEL and caspase-1 immunofluorescence double staining. Protein expression of NLRP3, ASC, caspase-1, pro-caspase-1, and IL-1β was analyzed using Western blot analysis.

RESULTS

Glycosides improved neurological dysfunction, alleviated neuronal damage, and inhibited neuronal pyroptosis. The 0.128 g/kg glycosides group showed the most significant effects. Furthermore, we observed that this group showed significant inhibition of the expression of NLRP3, ASC, pro-caspase-1, caspase-1, and IL-1β proteins of the NLRP3-mediated classical pathway of pyroptosis.

CONCLUSIONS

Glycosides exert neuroprotective effects by inhibiting pyroptosis of neurons after cerebral I/R injury. The underlying mechanism of action is closely related to the regulation of the classical pyroptosis pathway by NLRP3.

Pyroptosis in Liver Disease: New Insights into Disease Mechanisms

There has been increasing interest in pyroptosis as a novel form of pro-inflammatory programmed cell death. The mechanism of pyroptosis is significantly different from other forms of cell death in its morphological and biochemical features. Pyroptosis is characterized by the activation of two different types of caspase enzymes—caspase-1 and caspase-4/5/11, and by the occurrence of a proinflammatory cytokine cascade and an immune response. Pyroptosis participates in the immune defense mechanisms against intracellular bacterial infections. On the other hand, excessive inflammasome activation can induce sterile inflammation and eventually cause some diseases, such as acute or chronic hepatitis and liver fibrosis. The mechanism and biological significance of this novel form of cell death in different liver diseases will be evaluated in this review. Specifically, we will focus on the role of pyroptosis in alcoholic and non-alcoholic fatty liver disease, as well as in liver failure. Finally, the therapeutic implications of pyroptosis in liver diseases will be discussed.

Nigericin Promotes NLRP3-Independent Bacterial Killing in Macrophages

Altered microbiota has been associated with a number of diseases, including inflammatory bowel diseases, diabetes, and cancer. This dysregulation is thought to relate the host inflammatory response to enteric pathogens. Macrophages play a key role in host response to microbes and are involved in bacterial killing and clearance. This process is partially mediated through the potassium efflux-dependent, cytosolic, PYCARD-containing inflammasome protein complex. Surprisingly, we discovered an alternative mechanism for bacterial killing, independent of the NLRP3 inflammasome/PYCARD. Using the NLRP3 inflammasome-deficient Raw 264.7 and PYCARD-deficient J77 macrophages, which both lack PYCARD, we found that the potassium efflux activator nigericin enhances bacterial killing. Macrophage response to nigericin was examined by RT gene profiling and subsequent qPCR, which demonstrated altered expression of a series of genes involved in the IL-18 bacterial killing pathway. Based on our results we propose a model of bacterial killing, unrelated to NLRP3 inflammasome activation in macrophage cells. Improving understanding of the molecular pathways driving bacterial clearance within macrophage cells will aid in the development of novel immune-targeted therapeutics in a number of diseases.

Induction of Pyroptosis and Its Implications in Cancer Management

Pyroptosis is a gasdermins mediated programmed cell death, which has been widely studied in inflammatory disease models. Recently, there are growing evidences that pyroptosis can be chemically induced in cancer cells without any bacterial or viral infection. Pyroptosis may affect all stages of carcinogenesis and has become a new topic in cancer research. In this review, we first briefly introduced pyroptosis. In the subsequent section, we discussed the induction of pyroptosis in cancer and its potential role as a promising target for cancer therapy. In addition, the biological characteristics of gasdermin D (GSDMD) and gasdermin E (GSDME), two important pyroptosis substrates, and their prognostic role in cancer management were reviewed. These results help us to understand the pathogenesis of cancer and develop new drugs, which based on pyroptosis modulation, for cancer patients.

6-Gingerol attenuates macrophages pyroptosis via the inhibition of MAPK signaling pathways and predicts a good prognosis in sepsis

BACKGROUND

Sepsis is a major cause of death for ICU patients. Sepsis development depends heavily on the presence of mature IL-1β cytokine. This study evaluates the potential therapeutic properties of a bioactive compound known as 6-gingerol on sepsis. This compound has previously been demonstrated to possess anti-inflammatory properties both in vivo and in vitro.

METHODS

C57BL/6 mice was used to establish models of sepsis by means of cecal ligation and puncture (CLP). Upon treatment with 6-gingerol, we assessed the survival rate of mice and measured the levels of key pro-inflammatory cytokines in serum and colon tissues. Sepsis pathogenesis was further explored using the RAW264.7 cell line and bone marrow-derived macrophages (BMDMs) treated with ATP and lipopolysaccharide (LPS). The impact of 6-gingerol on pyroptosis was also examined. In addition, we assessed the role of MAPK signaling in 6-gingerol-induced effects in BMDMs and RAW264.7 cells.

RESULTS

In CLP mice, 6-gingerol significantly ameliorated sepsis development, which was associated with the reduction of serum IL-1β. In BMDMs and RAW264.7 cells, 6-gingerol strongly attenuated pyroptosis as well as the release of caspase-1p20, HMGB1, mature IL-1β, IL-18 in response to ATP and LPS treatment. 6-Gingerol conferred these effects by blocking MAPK activation. Exposure to an ERK agonist (EGF) reversed effects of 6-gingerol, causing pyroptosis, LDH and caspase-1p20 release.

CONCLUSIONS

By targeting MAPK signaling, 6-gingerol significantly suppressed secretion of pro-inflammatory cytokines and inhibited macrophage cells pyroptosis resulting in overall inhibition of sepsis development.

The role of pyroptosis in cancer: pro-cancer or pro-"host"?

Programmed cell death (PCD) refers to the way in which cells die depending on specific genes encoding signals or activities. Apoptosis, autophagy, and pyroptosis are all mechanisms of PCD. Among these mechanisms, pyroptosis is mediated by the gasdermin family, accompanied by inflammatory and immune responses. The relationship between pyroptosis and cancer is complex, and the effects of pyroptosis on cancer vary in different tissues and genetic backgrounds. On one hand, pyroptosis can inhibit the occurrence and development of tumors; on the other hand, as a type of proinflammatory death, pyroptosis can form a suitable microenvironment for tumor cell growth and thus promote tumor growth. In addition, the induction of tumor pyroptosis is also considered a potential cancer treatment strategy. Studies have shown that DFNA5 (nonsyndromic hearing impairment protein 5)/GSDME (Gasdermin-E) mRNA methylation results in lower expression levels of DFNA5/GSDME in most tumor cells than in normal cells, making it difficult to activate the pyroptosis in most tumor cells. During the treatment of malignant tumors, appropriate chemotherapeutic drugs can be selected according to the expression levels of DFNA5/GSDME, which can be upregulated in tumor cells, thereby increasing the sensitivity to chemotherapeutic drugs and reducing drug resistance. Therefore, induced pyroptosis may play a predominant role in the treatment of cancer. Here, we review the latest research on the anti- and protumor effects of pyroptosis and its potential applications in cancer treatment.

Sodium butyrate alleviates high-glucose-induced renal glomerular endothelial cells damage via inhibiting pyroptosis

We recently found that Sodium butyrate (NaB) possesses anti-inflammatory effects in diabetic nephropathy (DN) mouse model and in high-glucose induced mouse glomerular mesangial cells. Pyroptosis is a programmed cell death accompanied with the release of pro-inflammatory factors. Gasdermin D (GSDMD) is a novel discovered pivotal executive protein of pyroptosis, which can be cleaved by inflammatory caspases. The aim of our study is to verify if NaB have some effects against high-glucose induces pyroptosis in renal Glomerular endothelial cells (GECs). For this aim, human GECs were cultured and exposed to high-glucose. Exogenous NaB, caspase 1 inhibitor Ac-YVAD-CMK (A-Y-C) or knockdown GSDMD by siRNA were used. We found high glucose could increase Propidium Iodide (PI) positive cells and elevate release of lactate dehydrogenase (LDH), Interleukin 1 beta (IL-1β) and Interleukin 18 (IL-18); protein levels of GSDMD, GSDMD N-terminal domain (GSDMD-N) and cleaved-caspase-1 were also elevated. Effect of NaB on LDH release and PI positive cells was further enhanced by inhibiting caspase 1-GSDMD. In addition, high glucose-induced nuclear factor kappa-B (NF-κB)/NF-κB inhibitor α (IκB-α) signaling pathway was reversed by NaB or A-Y-C administration. In conclusion, NaB could ameliorate high-glucose induced GECs via caspase1-GSDMD canonical pyroptosis pathway; and NF-κB/IκB-α signaling pathway was involved in it.

Gasdermin D in peripheral myeloid cells drives neuroinflammation in experimental autoimmune encephalomyelitis

The NLRP3 inflammasome is critical for EAE pathogenesis; however, the role of gasdermin D (GSDMD), a newly identified pyroptosis executioner downstream of NLRP3 inflammasome, in EAE has not been well defined. Here, we observed that the levels of GSDMD protein were greatly enhanced in the CNS of EAE mice, especially near the areas surrounding blood vessels. GSDMD was required for the pathogenesis of EAE, and GSDMD deficiency in peripheral myeloid cells impaired the infiltration of immune cells into the CNS, leading to the suppression of neuroinflammation and demyelination. Furthermore, the loss of GSDMD reduced the activation and differentiation of T cell in the secondary lymphoid organs and prevented T cell infiltration into CNS of EAE. The administration of inflammasome-related cytokines partially rescued the impairment of pathogenesis of EAE in GSDMD KO mice. Collectively, these findings provide the first demonstration of GSDMD in peripheral myeloid cells driving neuroinflammation during EAE pathogenesis.

Caspase-11-dependent IL-1α release boosts Th17 immunity against Paracoccidioides brasiliensis

The granulomatous lesion resulting from infection with the fungus Paracoccidioides brasiliensis is characterized by a compact aggregate of mature cells, surrounded by a fibroblast- and collagen-rich content. Granuloma formation requires signaling elicited by inflammatory molecules such as members of the interleukin-1 family. Two members of this family have been thoroughly studied, namely IL-1α and IL-1β. In this study, we addressed the mechanisms underlying IL-1α secretion and its functional role on the host resistance to fungal infection. We found that, the expression of caspase-11 triggered by P. brasiliensis infection of macrophages depends on IFN-β production, because its inhibition reduced procaspase-11 levels. Curiously, caspase-11 deficiency did not impair IL-1β production, however caspase-11 was required for a rapid pore-mediated cell lysis. The plasma membrane rupture facilitated the release of IL-1α, which was necessary to induce NO production and restrict fungal replication. Furthermore, P. brasiliensis-infected macrophages required IL-1α to produce optimal levels of IL-6, a major component of Th17 lymphocyte differentiation. Indeed, IL-1α deficiency accounted for a significant reduction of Th17 lymphocytes in lungs of infected mice, correlating with diminished neutrophil infiltration in the lungs. Strikingly, we identified that IL-1α directly reprograms the transcriptional profile of Th17-committed lymphocytes, increasing cellular proliferation, as for boosting IL-17 production by these cells. Beyond neutrophil chemotaxis in vivo, IL-17 also amplified IL-1α production by infected macrophages in vitro, endorsing a critical amplification loop of the inflammatory response. Therefore, our data suggest that the IFN-β/caspase-11/IL-1α pathway shapes a protective antifungal Th17 immunity, revealing a molecular mechanism underlying the cross-talk between innate and adaptive immunity.

IL18 gene polymorphism and its influence on CD4+ T-cell recovery in HIV-positive patients receiving antiretroviral therapy

BACKGROUND

Pyroptosis has been reported to be critical in human immunodeficiency virus type 1 (HIV-1) pathogenesis and acquired immunodeficiency syndrome (AIDS) progression. Even after achieving viral suppression to undetectable levels during antiretroviral therapy (ART), exacerbated CD4+ T-cell death by pyroptosis has been suggested as one of the main causes of immunological non-response. Thus, variants in genes of pyroptosis pathway were studied in individuals with poor CD4+ T-cell reconstitution under antiretroviral therapy against HIV-1.

METHODS

248 virologically suppressed ART-treated patients, 126 immunological non-responders (INR) and 122 immunological responders (IR) were recruited. Genotyping was performed using TaqMan probe-based realtime PCR platform. Genotype-guided flow cytometry analysis with general and recent thymic emigrant (RTE) CD4+ T-cells in pyroptosis was performed based on associated polymorphisms.

RESULTS

Both IL18 rs187238 G allele and GG genotype were associated as protection factors against poor CD4+ T-cell recovery (OR = 0.22; 95%CI = 0.50-0.77; P = .010 and OR = 0.58; 95%CI = 0.36-0.93; P = .022, respectively). It was demonstrated a statistical association between IL18 rs187238 genotypes of ART-treated patients and death by Caspase-1 levels (P = .020). The GG genotype showed lower pyroptotic RTE CD4+ T-lymphocytes levels in the ART-treated groups comparing with CC (P = .029) and CG (P = .018) genotypes, suggesting that the G allele presence may be related to a lower IL-18 production and thus reduced dead CD4+ T-cells levels by Caspase-1.

CONCLUSION

We observed that IL18 G variant allele and genotype were associated with a better immunological response, which may influence on immunological recovery of HIV-positive patients receiving antiretroviral therapy, and low Caspase-1 activity levels was observed on GG genotype when compared CC genotypes.

Interleukin-18 binding protein attenuates renal injury of adriamycin-induced mouse nephropathy

Nephrotic syndrome is one of the most common kidney diseases in children, most of which were caused by minimal change disease, which could be typically reversible with the use of corticosteroid therapy in steroid-sensitive nephrotic syndrome. At the same time, there still exist some side effects caused by drugs and steroid-resistant nephrotic syndrome. It's urgent to investigate more accurate treatment to improve the situation. In this study, we chose mice model by adriamycin to observe the effect of IL-18BP intervention. It was shown that (1) weak general conditions appeared after adriamycin administration; (2) Proteinuria showed up after adriamycin-administration and then decreased with IL-18 binding protein intervention; (3) the level of triglyceride, cholesterol, IL-18, IFN-γ, and TNF-α in the IL-18 binding protein intervening group were significantly lower than those in the adriamycin-minimal change disease MCD group (all P < 0.01), and the levels of serum total protein, albumin, and IL-4 were significantly higher than those in the adriamycin-minimal change disease MCD group (P < 0.05, P < 0.01, P < 0.05); (4) ultramicrostructural examination demonstrated wide fusion of foot processes of glomerular epithelial cells in adriamycin-minimal change disease MCD mice, while only focal fusion occurred in IL-18 binding protein intervening mice. In conclusion, IL-18BP repaired the proteinurine, histopathological injury of kidney, and the induction of serum cytokines in mice models of minimal change disease induced by adriamycin.

Role of dendritic cells in the host response to biomaterials and their signaling pathways

Strategies to enhance, inhibit, or qualitatively modulate immune responses are important for diverse biomedical applications such as vaccine adjuvant, drug delivery, immunotherapy, cell transplant, tissue engineering, and regenerative medicine. However, the clinical efficiency of these biomaterial systems is affected by the limited understanding of their interaction with complex host microenvironments, for example, excessive foreign body reaction and immunotoxicity. Biomaterials and biomedical devices implanted in the body may induce a highly complicated and orchestrated series of host responses. As macrophages are among the first cells to infiltrate and respond to implanted biomaterials, the macrophage-mediated host response to biomaterials has been well studied. Dendritic cells (DCs) are the most potent antigen-presenting cells that activate naive T cells and bridge innate and adaptive immunity. The potential interaction of DCs with biomaterials appears to be critical for exerting the function of biomaterials and has become an important, developing area of investigation. Herein, we summarize the effects of the physicochemical properties of biomaterials on the immune function of DCs together with their receptors and signaling pathways. This review might provide a complete understanding of the interaction of DCs with biomaterials and serve as a reference for the design and selection of biomaterials with particular effects on targeted cells. STATEMENT OF SIGNIFICANCE: Biomaterials implanted in the body are increasingly applied in clinical practice. The performance of these implanted biomaterials is largely dependent on their interaction with the host immune system. As antigen-presenting cells, dendritic cells (DCs) directly interact with biomaterials through pattern recognition receptors (PRRs) recognizing "biomaterial-associated molecular patterns" and generate a battery of immune responses. In this review, the physicochemical properties of biomaterials that regulate the immune function of DCs together with their receptors and signaling pathways of biomaterial-DC interactions are summarized and discussed. We believe that knowledge of the interplay of DC and biomaterials may spur clinical translation by guiding the design and selection of biomaterials with particular effects on targeted cell for tissue engineering, vaccine delivery, and cancer therapy.

Cell Death in the Kidney

Apoptotic cell death is usually a response to the cell's microenvironment. In the kidney, apoptosis contributes to parenchymal cell loss in the course of acute and chronic renal injury, but does not trigger an inflammatory response. What distinguishes necrosis from apoptosis is the rupture of the plasma membrane, so necrotic cell death is accompanied by the release of unprocessed intracellular content, including cellular organelles, which are highly immunogenic proteins. The relative contribution of apoptosis and necrosis to injury varies, depending on the severity of the insult. Regulated cell death may result from immunologically silent apoptosis or from immunogenic necrosis. Recent advances have enhanced the most revolutionary concept of regulated necrosis. Several modalities of regulated necrosis have been described, such as necroptosis, ferroptosis, pyroptosis, and mitochondrial permeability transition-dependent regulated necrosis. We review the different modalities of apoptosis, necrosis, and regulated necrosis in kidney injury, focusing particularly on evidence implicating cell death in ectopic renal calcification. We also review the evidence for the role of cell death in kidney injury, which may pave the way for new therapeutic opportunities.

The in vitro Mycobacterium bovis BCG Moreau infection of human monocytes that induces Caspase-1 expression, release and dependent cell death is mostly reliant upon cell integrity

Background

Caused by Mycobacterium tuberculosis, tuberculosis (TB) is an extremely contagious disease predominantly affecting the lungs. TB is found worldwide and has a major impact on public health safety primarily due to its high mortality rate. Applied for over a hundred years as a preventive measure, Mycobacterium bovis BCG remains the only available TB vaccine. Only one seminal study about the apoptotic pathways induced by this vaccine in the monocytic lineage of the host cell has found the effects of BCG on regulation of apoptosis. The aim of this study was to explore beyond that pioneer study the pathway related to the in vitro cell-death pattern and the inflammatory response to the BCG vaccine in human monocytes.

Methods

Cohorts of HIV-negative volunteers were enrolled: adult Healthy Donors (HD) and neonates’ Umbilical Cord Blood (UCB) individuals. Host mononuclear cells were infected with the M. bovis Moreau strain of BCG vaccine at 16, 24, 48, and 72 h. The Real-Time RT-PCR for TRADD, Bcl-2, and Caspases-1 and -3 were performed, and supernatants were assayed in parallel for Caspase-1, NLRP3, HO-1, and IL-1β levels whereas caspases were assessed intracellularly. The effect of a BCG infection in monocytes was characterized via a metabolic activity assay by LDH release profiles.

Results

Overall, the BCG vaccine induced significantly higher Caspase-1 and Bcl-2 mRNA levels in both the HD and UCB groups (p-value ≤0.05). In addition, a significant increase solely in Caspase-1 protein levels was also noted in both HD and UCB (p-value ≤0.05) notwithstanding the absence of any damaged cell membranes.

Conclusions

Our data directly corroborate other findings showing that BCG Moreau led to an increased secretion of IL-1β but not IL-18, two Caspase-1-activated cytokines, and are also in support of the model that the BCG Moreau infection of human mononuclear cells may induce a cell-death pattern involving Caspase-1 activation.

Electronic supplementary material

The online version of this article (10.1186/s12950-019-0223-1) contains supplementary material, which is available to authorized users.

Activation of Pyroptotic Cell Death Pathways in Cancer: An Alternative Therapeutic Approach

Cancer can be considered the result of a series of genetic variations that lead to a normal cell being transformed into a malignant one while avoiding cell death-atypical characteristics of tumor development. Although a large number of genomics and epigenetic alterations have been identified in cells undergoing apoptotic, autophagic or necrotic cell death, the treatment of cancer remains thought-provoking. Pyroptosis is differentiated from other types of programmed cell death and is mainly activated by Caspase-1. To initiate pyroptosis, cells receive specific "death" messages, produce cytokines, swell, burst, and ultimately die. The deficiency of Caspase-1 expression may lead to inflammation-mediated tumor progression. Hence, the molecular mechanisms for the Caspase-1 activation in tumor tissues are yet to be exploited extensively. This review aims to summarise the latest discoveries about pyroptosis and its new exciting role in inducing cancer cell death.

Virome and Inflammasomes, a Finely Tuned Balance with Important Consequences for the Host Health

BACKGROUND

The virome is a network of viruses normally inhabiting humans. It forms a conspicuous portion of the so-called microbiome, once generically referred to as resident flora. Indeed, viruses infecting humans without leading to clinical disease are increasingly recognized as part of the microbiome and have an impact on the development of our immune system. In addition, they activate inflammasomes, multiprotein complexes that assemble in cells and that are responsible for the downstream effects of sensing pathogens.

OBJECTIVE

This review aims at summarizing the evidence on the role of the virome in modulating inflammation and emphasizes evidence for Anelloviruses as useful molecular markers to monitor inflammatory processes and immune system competence.

METHOD

We carried out a review of the literature published in the last 5 years and summarized older literature to take into account ground-breaking discoveries concerning inflammasome assembly and virome.

RESULTS

A massive amount of data recently emerging demonstrate that the microbiome closely reflects what we eat, and many other unexpected variables. Composition, location, and amount of the microbiome have an impact on innate and adaptive immune defences. Viruses making up the virome contribute to shaping the immune system. Anelloviruses, the best known of such viruses, are present in most human beings, persistently without causing apparent disease. Depending on their interplay with such viruses, inflammasomes instruct host defences to tolerate or forfeit a specific microorganism.

CONCLUSION

The virome plays an important role in shaping human immune defences and contributes to inflammatory processes by quenching or increasing them.

Nlrc3-like is required for microglia maintenance in zebrafish

Microglia are tissue-resident macrophages residing in the central nervous system (CNS) and play critical roles in removing cellular debris and infectious agents as well as regulating neurogenesis and neuronal activities. Yet, the molecular basis underlying the establishment of microglia pool and the maintenance of their homeostasis in the CNS remain largely undefined. Here we report the identification and characterization of a mutant zebrafish, which harbors a point mutation in the nucleotide-binding oligomerization domain (NOD) like receptor gene nlrc3-like, resulting in the loss of microglia in a temperature sensitive manner. Temperature shift assay reveals that the late onset of nlrc3-like deficiency leads to excessive microglia cell death. Further analysis shows that the excessive microglia death in nlrc3-like deficient mutants is attributed, at least in part, to aberrant activation of canonical inflammasome pathway. Our study indicates that proper regulation of inflammasome cascade is critical for the maintenance of microglia homeostasis.

Caspase-11 Mediates Pyroptosis of Tubular Epithelial Cells and Septic Acute Kidney Injury

BACKGROUND/AIMS

Acute kidney injury (AKI) is a serious complication of sepsis and has a high morbidity and mortality rate. Caspase-11 induces pyroptosis, a form of programmed cell death that plays a critical role in endotoxic shock, but its role in tubular epithelial cell death and whether it contributes to sepsis-associated AKI remains unknown.

METHODS

The caspase-11-/- mouse received an intraperitoneal injection of lipopolysaccharide (LPS, 40 mg/kg body weight). Caspase-11-/- renal tubular epithelial cells (RTECs) form C57BL caspase-11-/- mice were treated with LPS in vitro. The IL-1β ELISA kit and Scr assay kit were used to measure the level of interleukin-1β and serum creatinine. Annexin V-FITC assay and TUNEL staining assay were used to detect the cell death in different groups in vitro and in vivo. Western blot was performed to analyze the protein expression of caspase-11 and Gsdmdc1.

RESULTS

LPS-induced sepsis results in lytic death of RTECs, accompanied by increased expression of the pyroptosis-related proteins caspase-11 and Gsdmd. However, the increase in pyroptosis-related protein expression induced by LPS was attenuated with caspase-11 knockout, both in vitro and in vivo. Furthermore, when challenged with lethal doses of systemic LPS, pathologic abnormalities in renal structure, increased serum and kidney interleukin-1β, increased serum creatinine, and animal death were observed in wild-type mice but prevented in caspase-11-/- mice.

CONCLUSIONS

Caspase-11-induced pyroptosis of RTECs is a key event during septic AKI, and targeting of caspase-11 in RTECs may serve as a novel therapeutic target in septic AKI.

Divergent Roles for the IL-1 Family in Gastrointestinal Homeostasis and Inflammation

Inflammatory disorders of the gastro-intestinal tract are a major cause of morbidity and significant burden from a health and economic perspective in industrialized countries. While the incidence of such conditions has a strong environmental component, in particular dietary composition, epidemiological studies have identified specific hereditary mutations which result in disequilibrium between pro- and anti-inflammatory factors. The IL-1 super-family of cytokines and receptors is highly pleiotropic and plays a fundamental role in the pathogenesis of several auto-inflammatory conditions including rheumatoid arthritis, multiple sclerosis and psoriasis. However, the role of this super-family in the etiology of inflammatory bowel diseases remains incompletely resolved despite extensive research. Herein, we highlight the currently accepted paradigms as they pertain to specific IL-1 family members and focus on some recently described non-classical roles for these pathways in the gastrointestinal tract. Finally, we address some of the shortcomings and sources of variance in the field which to date have yielded several conflicting results from similar studies and discuss the potential effect of these factors on data interpretation.

NLRP3/Caspase-1 Pathway-Induced Pyroptosis Mediated Cognitive Deficits in a Mouse Model of Sepsis-Associated Encephalopathy

Sepsis-associated encephalopathy (SAE) is a common complication that leads to long-term cognitive impairments and increased mortality in sepsis survivors. The mechanisms underlying this complication remain unclear and an effective intervention is lacking. Accumulating evidence suggests the nucleotide-binding domain-like receptor protein3 (NLRP3)/caspase-1 pathway is involved in several neurodegenerative diseases. Thus, we hypothesized that the NLRP3/caspase-1 pathway is involved in NLRP3-mediated pyroptosis, maturation and release of inflammatory cytokines, and cognitive deficits in SAE. We used the NLRP3 inhibitor MCC950 and the caspase-1 inhibitor Ac-YVAD-CMK to study the role of the NLRP3/caspase-1 pathway in pyroptosis and cognitive deficits in a mouse model of SAE. Mice were randomly assigned to one of six groups: sham+saline, sham+MCC950, sham+Ac-YVAD-CMK, cecal ligation and puncture (CLP)+saline, CLP+MCC950, and CLP+Ac-YVAD-CMK. Surviving mice underwent behavioral tests or had hippocampal tissues collected for histochemical analysis and biochemical assays. Our results show that CLP-induced hippocampus-dependent memory deficits are accompanied by increased NLRP3 and caspase-1 positive cells, and augmented protein levels of NLRP3, caspase-1, gasdermin-D, and pro-inflammatory cytokines in the hippocampus. In addition, administration of MCC950 or Ac-YVAD-CMK rescues cognitive deficits and ameliorates increased hippocampal NLRP3-mediated neuronal pyroptosis and pro-inflammatory cytokines. Our results suggest that the NLRP3/caspase-1 pathway-induced pyroptosis mediates cognitive deficits in a mouse model of SAE.