Cell death and inflammation: the case for IL-1 family cytokines as the canonical DAMPs of the immune system

Necrotizing funisitis is an indicator that intra-amniotic inflammatory response is more severe and amnionitis is more frequent in the context of the extension of inflammation into Wharton's jelly

OBJECTIVE

Necrotizing funisitis (NF) is defined as the presence of an arc (i.e., crescent/band/ring/halos) of infiltrated neutrophils and/or associated debris in Wharton's jelly (WJ) of umbilical-cord (UC). However, no information exists about the comparison in intra-amniotic inflammatory-response (IAIR) and inflammation in extra-placental membranes between the presence and absence of NF in the context of inflammation in WJ among spontaneous preterm births (PTBs). The objective of current study is to examine this issue.

MATERIALS AND METHODS

We examined IAIR and the frequency of amnionitis according to the progression of inflammation in UC (i.e. stage-1, umbilical phlebitis [inflammation in umbilical-vein(UV)] only; stage-2, involvement of at least one umbilical-artery[UA] and either the other UA or UV without extension into WJ; stage-3, the extension of inflammation into WJ without NF; stage-4, the extension of inflammation into WJ with NF) in 120singleton spontaneous PTBs (<37weeks). IAIR was gauged by AF MMP-8 (ng/ml) within 3days before birth.

RESULTS

1) Stage-1, stage-2, stage-3, and stage-4 were present in 20%(24/120), 6%(7/120), 61%(73/120), and 13%(16/120) of cases respectively; 2) AF MMP-8 continuously increased (stage-1 vs. stage-2 vs. stage-3 vs. stage-4; median[ng/ml], range[ng/ml]; 207.2[16.8-1196.5] vs. 444.1[8.5-2608.0] vs. 458.8[0.4-3116.7] vs. 1859.7[912.3-5304.8]; Spearman's rank correlation-test, α = 0.454, P = 0.006), and the frequency of increased AF MMP-8 (≥854.1 ng/ml) elevated (stage-1 vs. stage-2 vs. stage-3 vs. stage-4; 13%[1/8] vs. 33%[1/3] vs. 32%[6/19] vs. 100%[5/5]; Linear-by-linear-association, P = 0.012) with the progression of inflammation in UC; 3) Moreover, there was a stepwise increase in the frequency of amnionitis according to the progression of inflammation in UC (stage-1, 33%[8/24]; stage-2, 43%[3/7]; stage-3, 62%[45/73]; stage-4, 81%[13/16]; Linear-by-linear-association, P = 0.001).

CONCLUSION

NF is an indicator that IAIR is more severe and amnionitis is more frequent in the context of the extension of inflammation into WJ. Therefore, current study confirms that NF is the most advanced stage in the progression of inflammation within UC.

Nasal alum-adjuvanted vaccine promotes IL-33 release from alveolar epithelial cells that elicits IgA production via type 2 immune responses

Aluminum hydroxide salts (alum) have been added to inactivated vaccines as safe and effective adjuvants to increase the effectiveness of vaccination. However, the exact cell types and immunological factors that initiate mucosal immune responses to alum adjuvants are unclear. In this study, the mechanism of action of alum adjuvant in nasal vaccination was investigated. Alum has been shown to act as a powerful and unique adjuvant when added to a nasal influenza split vaccine in mice. Alum is cytotoxic in the alveoli and stimulates the release of damage-associated molecular patterns, such as dsDNA, interleukin (IL)-1α, and IL-33. We found that Ag-specific IgA antibody (Ab) production was markedly reduced in IL-33-deficient mice. However, no decrease was observed in Ag-specific IgA Ab production with DNase I treatment, and no decrease was observed in IL-1α/β or IL-6 production in IL-33-deficient mice. From the experimental results of primary cultured cells and immunofluorescence staining, although IL-1α was secreted by alveolar macrophage necroptosis, IL-33 release was observed in alveolar epithelial cell necroptosis but not in alveolar macrophages. Alum- or IL-33-dependent Ag uptake enhancement and elevation of OX40L expression were not observed. By stimulating the release of IL-33, alum induced Th2 immunity via IL-5 and IL-13 production in group 2 innate lymphoid cells (ILC2s) and increased MHC class II expression in antigen-presenting cells (APCs) in the lung. Our results suggest that IL-33 secretion by epithelial cell necroptosis initiates APC- and ILC2-mediated T cell activation, which is important for the enhancement of Ag-specific IgA Ab production by alum.

Aluminum salts have been used as adjuvants in many vaccines. Aluminum salts induce Th2 immunity and vaccine antigen-specific antibody production aluminum salts elicit adjuvant action via cytokine production. Currently, the mechanisms underlying aluminum salt function in nasal vaccination are unknown, and elucidation of the mechanism is important for the development of particulate adjuvants. This study focused on the cytokines released from dead cells as induced by aluminum salt. This study found that aluminum adjuvant caused release of the cytokine interleukin (IL)-33 from alveolar epithelial cells by inducing necrosis. IL-33 is also crucial for antigen-specific IgA antibody production by nasal vaccination. Aluminum adjuvant also induces alveolar macrophage necrosis, which is not accompanied by IL-33 release. Aluminum salt-induced IL-33 acts as an activator for group 2 innate lymphoid cells and antigen-presenting cells in the lung. This means that by developing an adjuvant that targets the release of IL-33, it may be possible to develop a highly effective nasal vaccine. IL-33 significantly contributes to the efficacy of nasal vaccines and provides new insights into the mechanisms underlying aluminum adjuvants, showing that lung parenchymal tissue, rather than macrophages and lymphocytes, is the source of IL-33.

Traditional herbal formula Wu-Mei-Wan alleviates TNBS-induced colitis in mice by inhibiting necroptosis through increasing RIPK3 O-GlcNAcylation

Background

Accumulating evidence indicated that necroptosis plays an essential role in the pathogenesis of inflammatory bowel disease (IBD). The O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) of necroptotic signal molecule receptor-interacting serine-threonine kinase 3 (RIPK3) was reported to exert a protective effect in gut inflammation. Our recent study suggested traditional Chinese herbal formula Wu-Mei-Wan (WMW) as an effective prescription in mouse colitis. However, the potential mechanisms are not fully understood. Considering the crucial role of necroptosis in the pathogenesis of IBD, therefore, this study was designed to explain whether the anti-colitis effect of WMW is mediated by modulating necroptosis and its related mechanisms.

Methods

The protective effects of WMW on colitis have been determined by detecting colitis mice body weight, disease activity index (DAI), survival rate and colon length. Colonic inflammation was examined by inflammatory cells infiltration and local cytokines levels. After then, we measured the levels of necroptosis and O-GlcNAcylation. C O-immunoprecipitation experiments were used to address whether elevated O-GlcNAcylation can inhibit necroptotic signal transduction in the treatment of WMW. Finally, the key enzymes in O-GlcNAcylation: O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) were examined and molecular docking analysis was used to determine effective natural compounds in the regulation on OGT and OGA activities.

Results

Our results showed that WMW significantly improved mice body weight, survival rate and colon length, decreased DAI in TNBS-induced colitis. WMW obviously alleviated colonic inflammatory responses with reduced macrophages, neutrophils infiltration and local IL-1β, IL-6, TNF-α and IFN-γ levels. It was found that WMW increased colonic O-GlcNAcylation level and inhibited the activation of RIPK1, RIPK3 and MLKL. Then, further experiments revealed that WMW enhanced OGT activity and suppressed OGA activity, thereby increasing RIPK3 O-GlcNAcylation and inhibiting the binding of RIPK3 and MLKL, which led to the inhibition of necroptosis. Additionally, docking analysis demonstrated that hesperidin, coptisine and ginsenoside Rb1 may exert a major role in the regulation on OGT and OGA activities by WMW.

Conclusion

Our work demonstrated that WMW can alleviate TNBS-induced colitis in mice by inhibiting necroptosis through increasing RIPK3 O-GlcNAcylation.

Pulmonary Macrophage Cell Death in Lung Health and Disease

Over the last several decades, our understanding of regulated-cell-death (RCD) pathways has increased dramatically. In addition to apoptosis and accidental cell death (primary necrosis), a diverse spectrum of RCD pathways has been delineated. In the lung, airway macrophages are critical for maintaining the functionality of airways via the clearance of inhaled particles, cell debris, and infectious agents. Exposure of these cells to pathogenic organisms or particles can induce a variety of RCD pathways that promote the release of danger signals into the lung. These responses have evolved to trigger the innate and adaptive arms of the immune system and thus offer protection against pathogens; yet they can also contribute to the development of lung injury and pathogenic immune responses. In this review, we discuss recent studies that suggest a critical role for airway-macrophage RCD pathways in promoting the release of pulmonary danger signals in health and disease.

Linear Ubiquitination of RIPK1 on Lys 612 Regulates Systemic Inflammation via Preventing Cell Death

Receptor-interacting protein kinase-1 (RIPK1) is a master regulator of the TNF-α-induced cell death program. The function of RIPK1 is tightly controlled by posttranslational modifications, including linear ubiquitin chain assembly complex-mediated linear ubiquitination. However, the physiological function and molecular mechanism by which linear ubiquitination of RIPK1 regulates TNF-α-induced intracellular signaling remain unclear. In this article, we identified Lys627 residue as a major linear ubiquitination site in human RIPK1 (or Lys612 in murine RIPK1) and generated Ripk1^K612R/K612R mice, which spontaneously develop systemic inflammation triggered by sustained emergency hematopoiesis. Mechanistically, without affecting NF-κB activation, Ripk1^K612R/K612R mutation enhances apoptosis and necroptosis activation and promotes TNF-α-induced cell death. The systemic inflammation and hematopoietic disorders in Ripk1^K612R/K612R mice are completely abolished by deleting TNF receptor 1 or both RIPK3 and Caspase-8. These data suggest the critical role of TNF-α-induced cell death in the resulting phenotype in Ripk1^K612R/K612R mice. Together, our results demonstrate that linear ubiquitination of RIPK1 on K612 is essential for limiting TNF-α-induced cell death to further prevent systemic inflammation.

Tissue Homeostasis and Inflammation

There is a growing interest in understanding tissue organization, homeostasis, and inflammation. However, despite an abundance of data, the organizing principles of tissue biology remain poorly defined. Here, we present a perspective on tissue organization based on the relationships between cell types and the functions that they perform. We provide a formal definition of tissue homeostasis as a collection of circuits that regulate specific variables within the tissue environment, and we describe how the functional organization of tissues allows for the maintenance of both tissue and systemic homeostasis. This leads to a natural definition of inflammation as a response to deviations from homeostasis that cannot be reversed by homeostatic mechanisms alone. We describe how inflammatory signals act on the same cellular functions involved in normal tissue organization and homeostasis in order to coordinate emergency responses to perturbations and ultimately return the system to a homeostatic state. Finally, we consider the hierarchy of homeostatic and inflammatory circuits and the implications for the development of inflammatory diseases.

Green pesticide: Tapping to the promising roles of plant secreted small RNAs and responses towards extracellular DNA

The diverse roles of non-coding RNA and DNA in cross-species communication is yet to be revealed. Once thought to only involve intra-specifically in regulating gene expression, the evidence that these genetic materials can also modulate gene expression between species that belong to different kingdoms is accumulating. Plants send small RNAs to the pathogen or parasite when they are being attacked, targeting essential mRNAs for infection or parasitism of the hosts. However, the same survival mechanism is also deployed by the pathogen or parasite to destabilize plant immune responses. In plants, it is suggested that exposure to extracellular self-DNA impedes growth, while to extracellular non-self-DNA induces the modulation of reactive oxygen species, expression of resistance related genes, epigenetic mechanism, or suppression of disease severity. Exploring the potential of secreted RNA and extracellular DNA as a green pesticide could be a promising alternative if we are to provide food for the future global population without further damaging the environment. Hence, some studies on plant secreted RNA and responses towards extracellular DNA are discussed in this review. The precise mode of action of entry and the following cascade of signaling once the plant cell is exposed to secreted RNA or extracellular DNA could be an interesting topic for future research.

Noncanonical Roles of Caspase-4 and Caspase-5 in Heme-Driven IL-1β Release and Cell Death

Excessive release of heme from RBCs is a key pathophysiological feature of several disease states, including bacterial sepsis, malaria, and sickle cell disease. This hemolysis results in an increased level of free heme that has been implicated in the inflammatory activation of monocytes, macrophages, and the endothelium. In this study, we show that extracellular heme engages the human inflammatory caspases, caspase-1, caspase-4, and caspase-5, resulting in the release of IL-1β. Heme-induced IL-1β release was further increased in macrophages from patients with sickle cell disease. In human primary macrophages, heme activated caspase-1 in an inflammasome-dependent manner, but heme-induced activation of caspase-4 and caspase-5 was independent of canonical inflammasomes. Furthermore, we show that both caspase-4 and caspase-5 are essential for heme-induced IL-1β release, whereas caspase-4 is the primary contributor to heme-induced cell death. Together, we have identified that extracellular heme is a damage-associated molecular pattern that can engage canonical and noncanonical inflammasome activation as a key mediator of inflammation in macrophages.

Gasdermin E deficiency attenuates acute kidney injury by inhibiting pyroptosis and inflammation

Pyroptosis, one kind of inflammatory regulated cell death, is involved in various inflammatory diseases, including acute kidney injury (AKI). Besides Gasdermin D (GSDMD), GSDME is a newly identified mediator of pyroptosis via the cleavage of caspase-3 generating pyroptotic GSDME-N. Here, we investigated the role of GSDME in renal cellular pyroptosis and AKI pathogenesis employing GSDME-deficient mice and human tubular epithelial cells (TECs) with the interventions of pharmacological and genetic approaches. After cisplatin treatment, GSDME-mediated pyroptosis was induced as shown by the characteristic pyroptotic morphology in TECs, upregulated GSDME-N expression and enhanced release of IL-1β and LDH, and decreased cell viability. Strikingly, silencing GSDME in mice attenuated acute kidney injury and inflammation. The pyroptotic role of GSDME was also verified in human TECs in vitro. Further investigation showed that inhibition of caspase-3 blocked GSDME-N cleavage and attenuated cisplatin-induced pyroptosis and kidney dysfunction. Moreover, deletion of GSDME also protected against kidney injury induced by ischemia-reperfusion. Taken together, the findings from current study demonstrated that caspase-3/GSDME-triggered pyroptosis and inflammation contributes to AKI, providing new insights into the understanding and treatment of this disease.

Sputum IL-25, IL-33 and TSLP, IL-23 and IL-36 in airway obstructive diseases. Reduced levels of IL-36 in eosinophilic phenotype

INTRODUCTION

Alarmins ((IL-25, IL-33 and thymic stromal lymphopoietin (TSLP)) are known to promote Th2 inflammation and could be associated with eosinophilic airway infiltration. They may also play a role in airway remodeling in chronic airway obstructive diseases such as asthma and chronic obstructive pulmonary disease (COPD). IL-23 and IL-36 were shown to mediate the neutrophilic airway inflammation as seen in chronic airway obstructive diseases.

OBJECTIVES

The purpose of this project was to determine the expression and the production of these cytokines from induced sputum (IS) in patients with chronic airway obstructive diseases including asthmatics and COPD. The relationship of the mediators with sputum inflammatory cellular profile and the severity of airway obstruction was assessed.

METHODS

The alarmins (IL-25, IL-33 and TSLP) as well as IL-23 and IL-36 concentrations were measured in IS from 24 asthmatics and 20 COPD patients compared to 25 healthy volunteers. The cytokines were assessed by ELISA in the IS supernatant and by RT-qPCR in the IS cells.

RESULTS

At protein level, no difference was observed between controls and patients suffering from airway obstructive diseases regarding the different mediators. IL-36 protein level was negatively correlated with sputum eosinophil and appeared significantly decreased in patients with an eosinophilic airway inflammation compared to those with a neutrophilic profile and controls. At gene level, only IL-36, IL-23 and TSLP were measurable but none differed between controls and patients with airway obstructive diseases. IL-36 and IL-23 were significantly increased in patients with an neutrophilic inflammatory profile compared to those with an eosinophilic inflammation and were correlated with sputum neutrophil proportions. None of the mediators were linked to airway obstruction.

CONCLUSIONS

The main finding of our study is that patients with eosinophilic airway inflammation exhibited a reduced IL-36 level which could make them more susceptible to airway infections as IL-36 is implicated in antimicrobial defense. This study showed also an implication of IL-36 and IL-23 in airway neutrophilic inflammation in chronic airway obstructive diseases.

ABIN3 Negatively Regulates Necroptosis-induced Intestinal Inflammation Through Recruiting A20 and Restricting the Ubiquitination of RIPK3 in Inflammatory Bowel Disease

BACKGROUND AND AIMS

There is evidence for a disturbed necroptosis function in many inflammatory diseases, but its role in inflammatory bowel diseases [IBD] and the underlying mechanisms are unclear. Here, we studied the functional significance and molecular mechanisms of ABIN3, a ubiquitin-binding protein, in regulating the ubiquitination and activation of necroptosis in IBD.

METHODS

The expression of necroptosis hallmarks and ABIN3 were assessed in inflamed samples of IBD patients, dextran sodium sulphate [DSS]-induced colitis models, and azoxymethane [AOM]/DSS models in mice. ABIN3 was overexpressed and silenced to explore its function in regulating necroptosis, inflammation, and intestinal barrier function. Immuoprecipitiation [IP] and co-IP assays were performed to investigate the cross-talk between ABIN3 and deubiquitinating enzyme A20, and the mechanisms of coordinating ubiquitination modification to regulate necroptosis.

RESULTS

Excessive necroptosis is an important contributory factor towards the uncontrolled inflammation and intestinal barrier defects in IBD and experimental colitis. Blocking necroptosis by Nec-1s or GSK'872 significantly prevented cell death and alleviated DSS-induced colitis in vivo, whereas in the AOM/DSS model, necroptosis inhibitors aggravated the severity of colitis-associated colon carcinogenesis [CAC]. Mechanistically, ABIN3 is rapidly recruited to the TNF-RSC complex, which interacts and coordinates with deubiquitinating enzyme A20 to control the K63 deubiquitination modification and subsequent activation of the critical necroptosis kinase, RIPK3, to suppress necroptosis.

CONCLUSIONS

ABIN3 regulates inflammatory response and intestinal barrier function by interacting with A20 and coordinating the K63 deubiquitination modification of necroptosis in IBD.

Fluorofenidone Alleviates Renal Fibrosis by Inhibiting Necroptosis Through RIPK3/MLKL Pathway

Cell death and sterile inflammation are major mechanisms of renal fibrosis, which eventually develop into end-stage renal disease. “Necroptosis” is a type of caspase-independent regulated cell death, and sterile inflammatory response caused by tissue injury is strongly related to necrosis. Fluorofenidone (AKF-PD) is a novel compound shown to ameliorate renal fibrosis and associated inflammation. We investigated whether AKF-PD could alleviate renal fibrosis by inhibiting necroptosis. Unilateral ureteral obstruction (UUO) was used to induce renal tubulointerstitial fibrosis in C57BL/6J mice. AKF-PD (500 mg/kg) or necrostatin-1 (Nec-1; 1.65 mg/kg) was administered simultaneously for 3 and 7 days. Obstructed kidneys and serum were harvested after euthanasia. AKF-PD and Nec-1 ameliorated renal tubular damage, inflammatory-cell infiltration, and collagen deposition, and the expression of proinflammatory factors (interlukin-1β, tumor necrosis factor [TNF]-α) and chemokines (monocyte chemoattractant protein-1) decreased. AKF-PD or Nec-1 treatment protected renal tubular epithelial cells from necrosis and reduced the release of lactate dehydrogenase in serum. Simultaneously, production of receptor-interacting protein kinase (RIPK)3 and mixed lineage kinase domain-like protein (MLKL) was also reduced 3 and 7 days after UUO. AKF-PD and Nec-1 significantly decreased the percentage of cell necrosis, inhibiting the phosphorylation of MLKL and RIPK3 in TNF-α- and Z-VAD–stimulated human proximal tubular epithelial (HK-2) cells. In conclusion, AKF-PD and Nec-1 have effective anti-inflammatory and antifibrotic activity in UUO-induced renal tubulointerstitial fibrosis, potentially mediated by the RIPK3/MLKL pathway.

Targeting immunogenic cell death in cancer

Immunogenic cell death (ICD) is a type of cancer cell death triggered by certain chemotherapeutic drugs, oncolytic viruses, physicochemical therapies, photodynamic therapy, and radiotherapy. It involves the activation of the immune system against cancer in immunocompetent hosts. ICD comprises the release of damage-associated molecular patterns (DAMPs) from dying tumor cells that result in the activation of tumor-specific immune responses, thus eliciting long-term efficacy of anticancer drugs by combining direct cancer cell killing and antitumor immunity. Remarkably, subcutaneous injection of dying tumor cells undergoing ICD has been shown to provoke anticancer vaccine effects in vivo. DAMPs include the cell surface exposure of calreticulin (CRT) and heat-shock proteins (HSP70 and HSP90), extracellular release of adenosine triphosphate (ATP), high-mobility group box-1 (HMGB1), type I IFNs and members of the IL-1 cytokine family. In this review, we discuss the cell death modalities connected to ICD, the DAMPs exposed during ICD, and the mechanism by which they activate the immune system. Finally, we discuss the therapeutic potential and challenges of harnessing ICD in cancer immunotherapy.

Regulation of Toll-like receptors Expression in Muscle cells by Exercise-induced Stress

Objective

This study investigates the expression patterns of toll-like receptors (TLRs) and intracellular mediators in horse muscle cells after exercise, and the relationship between TLRS expression in stressed horse muscle cells and immune cell migration toward them.

Methods

The expression patterns of the TLRs (TLR2, TLR4, and TLR8) and downstream signaling pathway-related genes (myeloid differentiation primary response 88 [MYD88]; activating transcription factor 3 [ATF3]) are examined in horse tissues, and horse peripheral blood mononuclear cells (PBMCs), polymorphonuclear cells (PMNs) and muscles in response to exercise, using the quantitative reverse transcription-polymerase chain reaction (qPCR). Expressions of chemokine receptor genes, i.e., C-X-C motif chemokine receptor 2 (CXCR2) and C-C motif chemokine receptor 5 (CCR5), are studied in PBMCs and PMNs. A horse muscle cell line is developed by transfecting SV-T antigen into fetal muscle cells, followed by examination of muscle-specific genes. Horse muscle cells are treated with stressors, i.e., cortisol, hydrogen peroxide (H₂O₂), and heat, to mimic stress conditions in vitro, and the expression of TLR4 and TLR8 are examined in stressed muscle cells, in addition to migration activity of PBMCs toward stressed muscle cells.

Results

The qPCR revealed that TLR4 message was expressed in cerebrum, cerebellum, thymus, lung, liver, kidney, and muscle, whereas TLR8 expressed in thymus, lung, and kidney, while TLR2 expressed in thymus, lung, and kidney. Expressions of TLRs, i.e., TLR4 and TLR8, and mediators, i.e., MYD88 and ATF3, were upregulated in muscle, PBMCs and PMNs in response to exercise. Expressions of CXCR2 and CCR5 were also upregulated in PBMCs and PMNs after exercise. In the muscle cell line, TLR4 and TLR8 expressions were upregulated when cells were treated with stressors such as cortisol, H₂O₂, and heat. Migration of PBMCs toward stressed muscle cells was increased by exercise and oxidative stresses, and combinations of these. Treatment with methylsulfonylmethane (MSM), an antioxidant on stressed muscle cells, reduced migration of PBMCs toward stressed muscle cells.

Conclusion

In this study, we have successfully cultured horse skeletal muscle cells, isolated horse PBMCs, and established an in vitro system for studying stress-related gene expressions and function. Expression of TLR4, TLR8, CXCR2, and CCR5 in horse muscle cells was higher in response to stressors such as cortisol, H₂O₂, and heat, or combinations of these. In addition, migration of PBMCs toward muscle cells was increased when muscle cells were under stress, but inhibition of reactive oxygen species by MSM modulated migratory activity of PBMCs to stressed muscle cells. Further study is necessary to investigate the biological function(s) of the TLR gene family in horse muscle cells.

Oxyphospholipids in Cardiovascular Calcification

Mineralization of cardiovascular structures including blood vessels and heart valves is a common feature. We postulate that ectopic mineralization is a response-to-injury in which signals delivered to cells trigger a chain of events to restore and repair tissues. Maladaptive response to external or internal signals promote the expression of danger-associated molecular patterns, which, in turn, promote, when expressed chronically, a procalcifying gene program. Growing evidence suggest that danger-associated molecular patterns such as oxyphospholipids and small lipid mediators, generated by enzyme activity, are involved in the transition of vascular smooth muscle cells and valve interstitial cells to an osteoblast-like phenotype. Understanding the regulation and the molecular processes underpinning the mineralization of atherosclerotic plaques and cardiac valves are providing valuable mechanistic insights, which could lead to the development of novel therapies. Herein, we provide a focus account on the role oxyphospholipids and their mediators in the development of mineralization in plaques and calcific aortic valve disease.

Determining the effector response to cell death

Cell death occurs when a pathogen invades a host organism or the organism is subjected to sterile injury. Thus, cell death is often closely associated with the induction of an immune response. Furthermore, cell death can occur as a consequence of the immune response and precedes the tissue renewal and repair responses that are initiated by innate immune cells during resolution of an immune response. Beyond immunity, cell death is required for development, morphogenesis and homeostasis. How can such a ubiquitous event as cell death trigger such a wide range of context-specific effector responses? Dying cells are sensed by innate immune cells using specialized receptors and phagocytosed through a process termed efferocytosis. Here, we outline a general principle whereby signals within the dead cell as well as the environment are integrated by specific efferocytes to define the appropriate effector response.

Necroptosis in Intestinal Inflammation and Cancer: New Concepts and Therapeutic Perspectives

Necroptosis is a caspases-independent programmed cell death displaying intermediate features between necrosis and apoptosis. Albeit some physiological roles during embryonic development such tissue homeostasis and innate immune response are documented, necroptosis is mainly considered a pro-inflammatory cell death. Key actors of necroptosis are the receptor-interacting-protein-kinases, RIPK1 and RIPK3, and their target, the mixed-lineage-kinase-domain-like protein, MLKL. The intestinal epithelium has one of the highest rates of cellular turnover in a process that is tightly regulated. Altered necroptosis at the intestinal epithelium leads to uncontrolled microbial translocation and deleterious inflammation. Indeed, necroptosis plays a role in many disease conditions and inhibiting necroptosis is currently considered a promising therapeutic strategy. In this review, we focus on the molecular mechanisms of necroptosis as well as its involvement in human diseases. We also discuss the present developing therapies that target necroptosis machinery.

DAMPs in Unilateral Ureteral Obstruction

Damage-associated molecular patterns (DAMPs) are released from tubular and interstitial cells in the kidney after unilateral ureteral obstruction (UUO). DAMPs are recognized by pattern recognition receptors (PRRs), which mediate the initiation of an immune response and the release of inflammatory cytokines. The animal model of UUO is used for various purposes. UUO in adult mice serves as a model for accelerated renal fibrosis, which is a hallmark of progressive renal disease. UUO in adult mice enables to study cell death, inflammation, and extracellular matrix deposition in the kidney. Neonatal UUO is a model for congenital obstructive nephropathies. It studies inflammation, apoptosis, and interstitial fibrosis in the neonatal kidney, when nephrogenesis is still ongoing. Following UUO, several DAMPs as well as DAMP receptors are upregulated. In adult UUO, soluble uric acid is upregulated and activates the NOD-like receptor family, pyrin domain containing-3 (NLRP3) inflammasome, which promotes fibrosis, apoptosis, and reactive oxygen species (ROS) injury. Further DAMPs associated with UUO are uromodulin, members of the IL-1 family, and necrotic cell DNA, all of which promote sterile inflammation. In neonatal UUO, the receptor for advanced glycation endproducts (RAGE) is highly upregulated. RAGE is a ligand for several DAMPs, including high mobility group box 1 (HMGB1) and S100 proteins, which play an important role in renal fibrosis. Additionally, necroptosis is an important mechanism of cell death, besides apoptosis, in neonatal UUO. It is highly inflammatory due to release of cytokines and specific DAMPs. The release and recognition of DAMPs initiate sterile inflammation, which makes them good candidates to develop and improve diagnostic and therapeutic strategies in renal fibrosis and congenital obstructive nephropathies.

COVID-19 and the Heart and Vasculature: Novel Approaches to Reduce Virus-Induced Inflammation in Patients With Cardiovascular Disease

The coronavirus disease 2019 (COVID-19) pandemic presents an unprecedented challenge and opportunity for translational investigators to rapidly develop safe and effective therapeutic interventions. Greater risk of severe disease in COVID-19 patients with comorbid diabetes mellitus, obesity, and heart disease may be attributable to synergistic activation of vascular inflammation pathways associated with both COVID-19 and cardiometabolic disease. This mechanistic link provides a scientific framework for translational studies of drugs developed for treatment of cardiometabolic disease as novel therapeutic interventions to mitigate inflammation and improve outcomes in patients with COVID-19.

Necroptosis in Hepatosteatotic Ischaemia-Reperfusion Injury

While liver transplantation remains the sole treatment option for patients with end-stage liver disease, there are numerous limitations to liver transplantation including the scarcity of donor livers and a rise in livers that are unsuitable to transplant such as those with excess steatosis. Fatty livers are susceptible to ischaemia-reperfusion (IR) injury during transplantation and IR injury results in primary graft non-function, graft failure and mortality. Recent studies have described new cell death pathways which differ from the traditional apoptotic pathway. Necroptosis, a regulated form of cell death, has been associated with hepatic IR injury. Receptor-interacting protein kinase 3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL) are thought to be instrumental in the execution of necroptosis. The study of hepatic necroptosis and potential therapeutic approaches to attenuate IR injury will be a key factor in improving our knowledge regarding liver transplantation with fatty donor livers. In this review, we focus on the effect of hepatic steatosis during liver transplantation as well as molecular mechanisms of necroptosis and its involvement during liver IR injury. We also discuss the immune responses triggered during necroptosis and examine the utility of necroptosis inhibitors as potential therapeutic approaches to alleviate IR injury.

Revisiting Cell Death Responses in Fibrotic Lung Disease: Crosstalk between Structured and Non-Structured Cells

Fibrosis is a life-threatening disorder caused by excessive formation of connective tissue that can affect several critical organs. Innate immune cells are involved in the development of various disorders, including lung fibrosis. To date, several hematopoietic cell types have been implicated in fibrosis, including pro-fibrotic monocytes like fibrocytes and segregated-nucleus-containing atypical monocytes (SatMs), but the precise cellular and molecular mechanisms underlying its development remain unclear. Repetitive injury and subsequent cell death response are triggering events for lung fibrosis development. Crosstalk between lung structured and non-structured cells is known to regulate the key molecular event. We recently reported that RNA-binding motif protein 7 (RBM7) expression is highly upregulated in the fibrotic lung and plays fundamental roles in fibrosis development. RBM7 regulates nuclear degradation of NEAT1 non-coding RNA, resulting in sustained apoptosis in the lung epithelium and fibrosis. Apoptotic epithelial cells produce CXCL12, which leads to the recruitment of pro-fibrotic monocytes. Apoptosis is also the main source of autoantigens. Recent studies have revealed important functions for natural autoantibodies that react with specific sets of self-antigens and are unique to individual diseases. Here, we review recent insights into lung fibrosis development in association with crosstalk between structured cells like lung epithelial cells and non-structured cells like migrating immune cells, and discuss their relevance to acquired immunity through natural autoantibody production.

Alarmins from conjunctival fibroblasts up-regulate matrix metalloproteinases in corneal fibroblasts

AIM

To explore the effects of alarmins produced by necrotic human conjunctival fibroblasts on the release of matrix metalloproteinases (MMPs) by human corneal fibroblasts (HCFs).

METHODS

A necrotic cell supernatant (NHCS) was prepared by subjecting human conjunctival fibroblasts to three cycles of freezing and thawing. The amounts of interleukin (IL)-1β and tumor necrosis factor (TNF)-α in NHCS were determined by enzyme-linked immunosorbent assays. HCFs exposed to NHCS or other agents in culture were assayed for the release of MMPs as well as for intracellular signaling by immunoblot analysis. The abundance of MMP mRNAs in HCFs was examined by reverse transcription and real-time polymerase chain reaction analysis.

RESULTS

NHCS increased the release of MMP-1 and MMP-3 by HCFs as well as the amounts of the corresponding mRNAs in the cells. NHCS also induced activation of mitogen-activated protein kinase (MAPK) signaling pathways mediated by extracellular signal-regulated kinase (ERK), p38, and c-Jun NH₂-terminal kinase (JNK) as well as elicited that of the nuclear factor (NF)-κB signaling pathway by promoting phosphorylation of the endogenous NF-κB inhibitor IκB-α. Inhibitors of MAPK and NF-κB signaling as well as IL-1 and TNF-α receptor antagonists attenuated the NHCS-induced release of MMP-1 and MMP-3 by HCFs. Furthermore, IL-1β and TNF-α were both detected in NHCS, and treatment of HCFs with these cytokines induced the release of MMP-1 and MMP-3 in a concentration-dependent manner.

CONCLUSION

Alarmins, including IL-1β and TNF-α, produced by necrotic human conjunctival fibroblasts triggered MMP release in HCFs through activation of MAPK and NF-κB signaling. IL-1β and TNF-α are therefore potential therapeutic targets for the amelioration of corneal stromal degradation in severe ocular burns.

Neutrophil Extracellular Trapping Network Promotes the Pathogenesis of Neutrophil-associated Asthma through Macrophages

Asthma is a complex airway inflammatory disease that can be roughly classified into eosinophilic phenotype and non-eosinophilic phenotype. Most of the latter manifested as airway inflammation dominated by neutrophil infiltration, namely neutrophil-dominated asthma (NA). Neutrophil extracellular trapping (NETs) is a newly discovered antimicrobial mechanism of neutrophils; however, NETs can not only resist killing pathogenic microorganisms, but also promote tissue damage and autoimmune response. In the present study, we successfully established NA model in C57BL/6 mice and observed the increased formation of NETs. In NA mice, the free DNA abundance, the airway resistance, the cell numbers (total cell number, macrophage number, and neutrophil number), and inflammatory cytokine levels were significantly increased while the lung dynamic compliance was significantly reduced. After DNase I treatment, the above indexes in NA mice were all improved. In NA mice, either treatment with macrophage scavenger or IL-1β neutralizing antibody also improved the above-described indexes. In vitro, in human peripheral blood-derived neutrophils, PMA treatment significantly increased the formation of NETs. Furthermore, in macrophages differentiated from THP-1 monocytes, LPS or isolated NETs both significantly increased the levels of cytokines. In conclusion, NETs can stimulate macrophages to secrete IL-1β, which promotes neutrophils infiltration in the airway; infiltrated neutrophils, in turn, generates NETs, which can amplify the tissue damage caused by NETs and macrophages, inducing and aggravating NA.

Salidroside protects mice against CCl4-induced acute liver injury via down-regulating CYP2E1 expression and inhibiting NLRP3 inflammasome activation

Salidroside (Sal), a natural phenolic compound isolated from Rhodiola sachalinensis, has been utilized as anti-inflammatory and antioxidant for centuries, however, its effects against liver injury and the underlying mechanisms are unclear. This study was designed to evaluate the protective effects and underlying mechanisms of Sal on carbon tetrachloride (CCl4)-induced acute liver injury (ALI) in mice. C57BL/6 mice were pretreated with Sal before CCl4 injection, the serum and liver tissue were collected to evaluate liver damage and molecular indices. The results showed that Sal pretreatment dose-dependently attenuated CCl4-induced acute liver injury, as indicated by lowering the activities of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and inhibiting hepatic pathological damage and apoptosis. In addition, Sal alleviated CCl4-primed oxidative stress and inflammatory response by restoring hepatic glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), and inhibiting cytokines. Finally, Sal also down-regulated the expression of cytochrome P4502E1 (CYP2E1), and Nod-like receptor protein 3 (NLRP3) inflammasome activation in the liver of mice by CCl4. Our study demonstrates that Sal exerts its hepatoprotective effects on ALI through its antioxidant and anti-inflammatory effects, which might be mediated by down-regulating CYP2E1 expression and inhibiting NLRP3 inflammasome activation.

Consequences of epigenetic derepression in facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD), a common hereditary myopathy, is caused either by the contraction of the D4Z4 macrosatellite repeat at the distal end of chromosome 4q to a size of 1 to 10 repeat units (FSHD1) or by mutations in D4Z4 chromatin modifiers such as Structural Maintenance of Chromosomes Hinge Domain Containing 1 (FSHD2). These two genotypes share a phenotype characterized by progressive and often asymmetric muscle weakening and atrophy, and common epigenetic alterations of the D4Z4 repeat. All together, these epigenetic changes converge the two genetic forms into one disease and explain the derepression of the DUX4 gene, which is otherwise kept epigenetically silent in skeletal muscle. DUX4 is consistently transcriptionally upregulated in FSHD1 and FSHD2 skeletal muscle cells where it is believed to exercise a toxic effect. Here we provide a review of the recent literature describing the progress in understanding the complex genetic and epigenetic architecture of FSHD, with a focus on one of the consequences that these epigenetic changes inflict, the DUX4-induced immune deregulation cascade. Moreover, we review the latest therapeutic strategies, with particular attention to the potential of epigenetic correction of the FSHD locus.

GSDME-Dependent Incomplete Pyroptosis Permits Selective IL-1α Release under Caspase-1 Inhibition

Pyroptosis is a form of regulated cell death that is characterized by gasdermin processing and increased membrane permeability. Caspase-1 and caspase-11 have been considered to be essential for gasdermin D processing associated with inflammasome activation. In the present study, we found that NLRP3 inflammasome activation induces delayed necrotic cell death via ASC in caspase-1/11-deficient macrophages. Furthermore, ASC-mediated caspase-8 activation and subsequent gasdermin E processing are necessary for caspase-1-independent necrotic cell death. We define this necrotic cell death as incomplete pyroptosis because IL-1β release, a key feature of pyroptosis, is absent, whereas IL-1α release is induced. Notably, unprocessed pro-IL-1β forms a molecular complex to be retained inside pyroptotic cells. Moreover, incomplete pyroptosis accompanied by IL-1α release is observed under the pharmacological inhibition of caspase-1 with VX765. These findings suggest that caspase-1 inhibition during NLRP3 inflammasome activation modulates forms of cell death and permits the release of IL-1α from dying cells.

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NLRP3 inflammasome induces necrotic cell death in the absence of caspase-1/11

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ASC initiates GSDME-dependent pyroptosis via caspase-8

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IL-1α, but not IL-1β, is released during Casp1/11-independent pyroptosis

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Pharmacological inhibition of caspase-1 permits IL-1α release during pyroptosis

The clearance of dead cells by efferocytosis

Multiple modes of cell death have been identified, each with a unique function and each induced in a setting-dependent manner. As billions of cells die during mammalian embryogenesis and daily in adult organisms, clearing dead cells and associated cellular debris is important in physiology. In this Review, we present an overview of the phagocytosis of dead and dying cells, a process known as efferocytosis. Efferocytosis is performed by macrophages and to a lesser extent by other 'professional' phagocytes (such as monocytes and dendritic cells) and 'non-professional' phagocytes, such as epithelial cells. Recent discoveries have shed light on this process and how it functions to maintain tissue homeostasis, tissue repair and organismal health. Here, we outline the mechanisms of efferocytosis, from the recognition of dying cells through to phagocytic engulfment and homeostatic resolution, and highlight the pathophysiological consequences that can arise when this process is abrogated.

Minocycline prevents neuronal hyperexcitability and neuroinflammation in medial prefrontal cortex, as well as memory impairment caused by repeated toluene inhalation in adolescent rats

Toluene can be intentionally misused by adolescents to experience psychoactive effects. Toluene has a complex mechanism of action and broad behavioral effects, among which memory impairment is reported consistently. We have previously reported that repeated toluene inhalation (8000 ppm) increases layer 5 prelimbic pyramidal cells' excitability in the medial prefrontal cortex (mPFC) of adolescent rats. Toluene also produces reactive oxygen species (ROS), which activate glial cells. Here, we tested the hypothesis that the anti-inflammatory agent minocycline would decrease toluene's effects because it inhibits NF-κB (nuclear factor enhancer of the kappa light chains of activated B cells) and reduces pro-inflammatory cytokine and ROS production. Our results show that minocycline (50 mg/kg, ip, for 10 days) prevents the hyperexcitability of mPFC neurons observed after repeated 8000 ppm toluene exposure (30 min/day, 2×/day for 10 days). Minocycline prevents toluene-induced hyperexcitability by a mechanism that averts the loss of the slow calcium-dependent potassium current, and normalizes mPFC neurons' firing frequency. These effects are accompanied by significant decreased expression of astrocytes and activated microglia in the mPFC, reduced NLRP3 inflammasome activation and mRNA expression levels of the pro-inflammatory cytokine interleukin 1β (IL-1β), as well as increased mRNA expression of the anti-inflammatory cytokine transforming growth factor β (TGF-β). Minocycline also prevents toluene-induced memory impairment in adolescent rats in the passive avoidance task and the temporal order memory test in which the mPFC plays a central role. These results show that neuroinflammation produces several effects of repeated toluene administration at high concentrations, and minocycline can significantly prevent them.

Complement: Bridging the innate and adaptive immune systems in sterile inflammation

The complement system is a collection of soluble and membrane-bound proteins that together act as a powerful amplifier of the innate and adaptive immune systems. Although its role in infection is well established, complement is becoming increasingly recognized as a key contributor to sterile inflammation, a chronic inflammatory process often associated with noncommunicable diseases. In this context, damaged tissues release danger signals and trigger complement, which acts on a range of leukocytes to augment and bridge the innate and adaptive immune systems. Given the detrimental effect of chronic inflammation, the complement system is therefore well placed as an anti-inflammatory drug target. In this review, we provide a general outline of the sterile activators, effectors, and targets of the complement system and a series of examples (i.e., hypertension, cancer, allograft transplant rejection, and neuroinflammation) that highlight complement's ability to bridge the 2 arms of the immune system.

A Review of the Anti-Inflammatory Effects of Rosmarinic Acid on Inflammatory Diseases

Inflammatory diseases are caused by abnormal immune responses and are characterized by an imbalance of inflammatory mediators and cells. In recent years, the anti-inflammatory activity of natural products has attracted wide attention. Rosmarinic acid (RosA) is a water-soluble phenolic compound that is an ester of caffeic acid and 3, 4-dihydroxyphenyl lactic acid. It is discovered in many plants, like those of the Boraginaceae and Lamiaceae families. RosA has a wide range of pharmacological effects, including anti-oxidative, anti-apoptotic, anti-tumorigenic, and anti-inflammatory effects. The anti-inflammatory effects of RosA have been revealed through in vitro and in vivo studies of various inflammatory diseases like arthritis, colitis, and atopic dermatitis. This article mainly describes the preclinical research of RosA on inflammatory diseases and depicts a small amount of clinical research data. The purpose of this review is to discuss the anti-inflammatory effects of RosA in inflammatory diseases and its underlying mechanism.

TRAIL Receptors Serve as Stress-Associated Molecular Patterns to Promote ER-Stress-Induced Inflammation

Inflammation triggered by infection or cellular necrosis is initiated by a battery of pattern-recognition receptors, such as Toll-like receptors or IL-1 family receptors. Diverse forms of cell stress, such as ER stress or mitochondrial stress, can also promote inflammatory responses that contribute to the chronic inflammation observed in cancer, obesity, and other conditions. However, the molecular mechanisms of cell-stress-induced inflammation are poorly understood. Here, we show that ER stress initiated NF-κB activation and inflammation through transcriptional upregulation and ligand-independent activation of TRAIL receptors. ER-stress-induced TRAIL receptor activation resulted in caspase-8/FADD/RIPK1-dependent NF-κB activation and inflammatory cytokine production. Silencing or deletion of TRAIL receptors, or their downstream effectors caspase-8, FADD, or RIPK1, suppressed ER-stress-induced inflammation. Furthermore, chemotherapeutic stress-induced inflammatory responses were blunted in DR5/TRAIL-R null animals. We propose that, upon ER stress, TRAIL receptors serve as "stress-associated molecular patterns (SAMPs)" coupling ER stress to NF-κB-dependent inflammation.

A novel role of NLRP3-generated IL-1β in the acute-chronic transition of peripheral lipopolysaccharide-elicited neuroinflammation: implications for sepsis-associated neurodegeneration

BACKGROUND

Sepsis-associated acute brain inflammation, if unresolved, may cause chronic neuroinflammation and resultant neurodegenerative diseases. However, little is known how the transition from acute to chronic neuroinflammation, which is critical for the following progressive neurodegeneration, occurs in sepsis. The goal of this study was to investigate potential immune factors regulating the transition process using a widely used endotoxemia LPS mouse model. This model shows distinct acute and chronic phases of neuroinflammation and recapitulates many cardinal features of Parkinson's disease, thus, providing a unique opportunity for studying phase transition of neuroinflammation.

METHODS

C57BL/6 J, NLRP3-/-, and IL-1R1-/- mice were employed. Mild and severe endotoxemia were produced by LPS ip injection at 1 or 5 mg/kg. Neuroinflammation in vitro and in vivo was assessed with proinflammatory cytokine expression by qPCR or ELISA and microglial activation by immunohistochemical analysis. Neurodegeneration was measured by manual and stereological counts of nigral dopaminergic neurons and immunohistochemical analysis of protein nitrosylation and α-synuclein phosphorylation.

RESULTS

LPS-elicited initial increases in mouse brain mRNA levels of TNFα, IL-6, IL-1β, and MCP-1, and nigral microglial activation were not dose-related. By contrast, the delayed increase in brain mature IL-1β levels was dependent on LPS doses and protracted nigral microglial activation was only observed in high dose of LPS-treated mice. LPS-elicited increase in brain mature IL-1β but not IL-1α level was NLRP3-dependent. After high dose LPS treatment, deficiency of NLRP3 or IL-1R1 did not prevent the initiation of acute neuroinflammation but abolished chronic neuroinflammation. Genetic or pharmacological inhibition of the NLRP3-IL-1β axis repressed LPS-stimulated upregulation of chronic neuroinflammatory mediators including MHC-II, NOX2, and Mac1, and protected dopaminergic neurons. Ten months after LPS-elicited severe endotoxemia, nigral persisted microglial activation, elevated nitrosylated proteins and phosphorylated α-synuclein, and significant neuronal degeneration developed in wild-type mice but not in NLRP3-/- or IL-1R1-/- mice.

CONCLUSIONS

This study uncovers a novel role of the NLRP3-IL-1β signaling pathway in gauging the severity of sepsis-associated inflammation and determining whether acute neuroinflammation will resolve or transition to low grade chronic neuroinflammation. These findings also provide novel targets for developing therapy for severe systemic infection-related neurodegeneration.

The Coming Decade of Cell Death Research: Five Riddles

Active cell death, in its many forms, is a fundamental biological process. Studies over the past several decades have explored the functions and consequences of cellular demise and elucidated several of the key cell death pathways. Here, I pose five questions, or riddles, that might provide a guide to the next decade of cell death research. Focusing mainly on four types of active cell death (apoptosis, necroptosis, pyroptosis, and ferroptosis) mainly in mammals, this Perspective explores the possible research directions that might answer these riddles, or at least prompt new ones.

Reactive fibrosis precedes doxorubicin-induced heart failure through sterile inflammation

Aims

Doxorubicin (DOX)‐induced heart failure has a poor prognosis, and effective treatments have not been established. Because DOX shows cumulative cardiotoxicity, we hypothesized that minimal cardiac remodelling occurred at the initial stage in activating cardiac fibroblasts. Our aim was to investigate the initial pathophysiology of DOX‐exposed cardiac fibroblasts and propose prophylaxis.

Methods and results

An animal study was performed using a lower dose of DOX (4 mg/kg/week for 3 weeks, i.p.) than a toxic cumulative dose. Histological analysis was performed with terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labelling assay, picrosirius red staining, and immunohistochemical staining. The mechanism was analysed in vitro with a low dose of DOX, which did not induce cell apoptosis. Microarray analysis was performed. Differentially expressed genes were confirmed by enrichment analysis. Mitochondrial damage was assessed by mitochondrial membrane potential. The production of inflammatory cytokines and fibrosis markers was assessed by western blot, quantitative polymerase chain reaction, and ELISA. A phosphokinase antibody array was performed to detect related signalling pathways. Low‐dose DOX did not induced cell death, and fibrosis was localized to the perivascular area in mice. Microarray analysis suggested that DOX induced genes associated with the innate immune system and inflammatory reactions, resulting in cardiac remodelling. DOX induced mitochondrial damage and increased the expression of interleukin‐1. DOX also promoted the expression of fibrotic markers, such as alpha smooth muscle actin and galectin‐3. These responses were induced through stress‐activated protein kinase/c‐Jun NH2‐terminal kinase signalling. A peroxisome proliferator‐activated receptor (PPARγ) agonist attenuated the expression of fibrotic markers through suppressing stress‐activated protein kinase/c‐Jun NH2‐terminal kinase. Furthermore, this molecule also suppressed DOX‐induced early fibrotic responses in vivo.

Conclusions

Low‐dose DOX provoked reactive fibrosis through sterile inflammation evoked by the damaged mitochondria.

Spontaneous embryo resorption in the mouse is triggered by embryonic apoptosis followed by rapid removal via maternal sterile purulent inflammation

Background

In normal mammalian development a high percentage of implantations is lost by spontaneous resorption. This is a major problem in assisted reproduction and blastocyst transfer. Which embryo will be resorbed is unpredictable. Resorption is very fast, so that with conventional methods only final haemorrhagic stages are encountered.

Here we describe the histology and immunohistochemistry of 23 spontaneous embryo resorptions between days 7 and 13 of murine development, which were identified by high-resolution ultrasound (US) in a previous study.

Results

In the early resorptions detected at day 7, the embryo proper was replaced by maternal haemorrhage and a suppurate focus of maternal neutrophils. In the decidua maternal macrophages transformed to foam cells and formed a second focus of tissue dissolution.

In the late resorptions detected at day 9, the embryo underwent apoptosis without involvement of maternal cells. The apoptotic embryonic cells expressed caspase 3 and embryonic blood cells developed a macrophage like phenotype. Subsequently, the wall of the embryonic vesicle ruptured and the apoptotic embryo was aborted into the uterine lumen. Abortion was initiated by degeneration of the embryonic lacunar trophoblast and dissolution of the maternal decidua capsularis via sterile inflammation and accompanied by maternal haemorrhage, invasion of the apoptotic embryo by maternal neutrophils, and contraction rings of the uterine muscle layers.

Conclusions

We conclude that spontaneous resorption starts with endogenous apoptosis of the embryo without maternal contribution. After break down of the foetal-maternal border, the apoptotic embryo is invaded by maternal neutrophils, aborted into the uterine lumen, and rapidly resorbed. We assume that the innate maternal unspecific inflammation is elicited by disintegrating apoptotic embryonic cells.

Graphical abstract

Investigating Macrophages Plasticity Following Tumour-Immune Interactions During Oncolytic Therapies

Over the last few years, oncolytic virus therapy has been recognised as a promising approach in cancer treatment, due to the potential of these viruses to induce systemic anti-tumour immunity and selectively killing tumour cells. However, the effectiveness of these viruses depends significantly on their interactions with the host immune responses, both innate (e.g., macrophages, which accumulate in high numbers inside solid tumours) and adaptive (e.g., \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {CD8}^{+}$$\end{document}CD8+ T cells). In this article, we consider a mathematical approach to investigate the possible outcomes of the complex interactions between two extreme types of macrophages (M1 and M2 cells), effector \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {CD8}^{+}$$\end{document}CD8+ T cells and an oncolytic Vesicular Stomatitis Virus (VSV), on the growth/elimination of B16F10 melanoma. We discuss, in terms of VSV, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {CD8}^{+}$$\end{document}CD8+ and macrophages levels, two different types of immune responses which could ensure tumour control and eventual elimination. We show that both innate and adaptive anti-tumour immune responses, as well as the oncolytic virus, could be very important in delaying tumour relapse and eventually eliminating the tumour. Overall this study supports the use mathematical modelling to increase our understanding of the complex immune interaction following oncolytic virotherapies. However, the complexity of the model combined with a lack of sufficient data for model parametrisation has an impact on the possibility of making quantitative predictions.

Emerging Roles of 5-Lipoxygenase Phosphorylation in Inflammation and Cell Death

5-Lipoxygenase (ALOX5) is an iron-containing and nonheme dioxygenase that catalyzes the peroxidation of polyunsaturated fatty acids such as arachidonic acid. ALOX5 is the rate-limiting enzyme for the biosynthesis of leukotrienes, a family of proinflammatory lipid mediators derived from arachidonic acid. ALOX5 also make great contributions to mediating lipid peroxidation. In recent years, it has been discovered that ALOX5 plays a central role in cell death including apoptosis, pyroptosis, and ferroptosis, a newly discovered type of cell death. According to the previous studies, ALOX5 can regulate cell death in two ways: one is inflammation and the other is lipid peroxidation. Meanwhile, it has been shown that ALOX5 activity is regulated by several factors including protein phosphorylation, ALOX5-interactng protein, redox state, and metal ions such as iron and calcium. In this review, we aim to summarize the knowledge on the emerging roles of ALOX5 protein phosphorylation in the regulation of cell death and inflammation in order to explore a potential target for human diseases.

Activation of GSDMD contributes to acute kidney injury induced by cisplatin

Cisplatin is one of the most effective antitumor agents, but its clinical use is highly limited by its severe side effects, especially nephrotoxicity. Recently, the active form of gasdermin D (GSDMD), termed GSDMD-N, was identified to mediate pyroptotic inflammatory cell death in several diseases. However, the role of the GSDMD-N fragment in cisplatin-induced acute kidney injury (AKI) remains unclear. In the present study, we found that pyroptosis was induced by cisplatin in both mouse kidney tissues and renal tubular epithelial cells, accompanied by increased expression of the GSDMD-N fragment. In GSDMD knockout mice with cisplatin-induced AKI, we found that cisplatin-induced loss of renal function, renal tubular injury, and inflammation was significantly attenuated compared with wild-type mice. Furthermore, the GSDMD-N fragment was overexpressed by an established rapid plasmid tail vein injection approach to evaluate the role of this cleaved form of GSDMD in AKI. As expected, mice with GSDMD-N fragment overexpression in the kidney were more susceptible to cisplatin-induced AKI than control mice, as evidenced by further elevated serum levels of blood urea nitrogen and creatinine, aggravated renal pathology, increased expression of neutrophil gelatinase-associated lipocalin and kidney injury molecule-1, and enhanced renal inflammatory cytokine secretion, which indicates a pathogenic role of GSDMD-N in cisplatin-induced AKI by triggering cell pyroptosis. Similar results were also observed in renal tubular epithelial cells overexpressing the GSDMD-N fragment. Thus these findings suggested that the activation of GSDMD contributes to cisplatin-induced AKI, possibly through triggering pyroptosis.

DAMPs and NETs in Sepsis

Sepsis is a deadly inflammatory syndrome caused by an exaggerated immune response to infection. Much has been focused on host response to pathogens mediated through the interaction of pathogen-associated molecular patterns (PAMPs) and pattern recognition receptors (PRRs). PRRs are also activated by host nuclear, mitochondrial, and cytosolic proteins, known as damage-associated molecular patterns (DAMPs) that are released from cells during sepsis. Some well described members of the DAMP family are extracellular cold-inducible RNA-binding protein (eCIRP), high mobility group box 1 (HMGB1), histones, and adenosine triphosphate (ATP). DAMPs are released from the cell through inflammasome activation or passively following cell death. Similarly, neutrophil extracellular traps (NETs) are released from neutrophils during inflammation. NETs are webs of extracellular DNA decorated with histones, myeloperoxidase, and elastase. Although NETs contribute to pathogen clearance, excessive NET formation promotes inflammation and tissue damage in sepsis. Here, we review DAMPs and NETs and their crosstalk in sepsis with respect to their sources, activation, release, and function. A clear grasp of DAMPs, NETs and their interaction is crucial for the understanding of the pathophysiology of sepsis and for the development of novel sepsis therapeutics.

The Diversification of Cell Death and Immunity: Memento Mori

Why do cells have so many ways to die? Why does "cellular suicide" exist at all? In the war against pathogens and rogue cells, organisms developed cellular suicide as a last resort. Fighting an evolutionary arms race, cell death pathways have adapted and multiplied to cover the complexity of the foes the immune system faces. In this review, we discuss the different types of cell death, the underlying signaling events, and their unequal ability to trigger an immune response. We also comment on how to use our knowledge of cell death signaling to improve the efficacy of cancer treatment. We argue that cell death is integral to the immune response and acts as a beacon, a second messenger, that guides both immune system and tissue micro-environment to ensure tissue repair and homeostasis. Memento mori-"remember you must die"-as failure to do so opens the way to chronic infection and cancer.

Cytotoxicity and Apoptosis Induction of Coumarins and Carbazole Alkaloids from Clausena harmandiana

Seven compounds, carbazole alkaloids (heptaphylline, 7-methoxyheptaphylline, 7-methoxymukonal) and coumarins (clausarin, dentatin, nordentatin, and xanthoxyletin), were isolated from the root bark of Clausena harmandiana. Antioxidation, cytotoxicity and apoptosis induction were evaluated in vitro. Results showed that clausarin exerted the highest DPPH radical scavenging and 7-methoxymukonal had the highest ferric reducing antioxidant power. In contrary, dentatin was the least DPPH radical scavenger, and heptaphylline was the least reducing antioxidant power. The isolated compounds showed different cytotoxicity. The hepatocellular carcinoma (HepG2) was generally more sensitive to the isolated compounds than lung cancer (SK-LU-1), colon cancer (HCT-116), and noncancerous (Vero) cell lines, respectively. Clausarin possessed the highest cytotoxicity selectively against cancer cell lines tested. 7-Methoxymukonal and 7-methoxyheptaphylline exhibited less cytotoxicity only in HepG2 cells and were inactive in the SK-LU-1 and HCT116 cells. Despite xantoxyletin possessing low antioxidant and low cytotoxic activity, it induced the highest apoptosis percentage with the lowest necrosis percentage of HepG2 cells after 24 h. In conclusion, xantoxyletin primarily show potential anticancer activity. The root bark of C. harmandiana is a good source of bioactive compounds or the lead for the development of new pharmaceutical agent.

Extracellular Neutrophil Proteases Are Efficient Regulators of IL-1, IL-33, and IL-36 Cytokine Activity but Poor Effectors of Microbial Killing

Neutrophil granule proteases are thought to function as anti-microbial effectors, cooperatively hydrolyzing microorganisms within phagosomes, or upon deployment into the extracellular space. However, evidence also suggests that neutrophil proteases play an important role in the coordination and escalation of inflammatory reactions, but how this is achieved has been obscure. IL-1 family cytokines are important initiators of inflammation and are typically released via necrosis but require proteolytic processing for activation. Here, we show that proteases liberated from activated neutrophils can positively or negatively regulate the activity of six IL-1 family cytokines (IL-1α, IL-1β, IL-33, IL-36α, IL-36β, and IL-36γ) with exquisite sensitivity. In contrast, extracellular neutrophil proteases displayed very poor bactericidal activity, exhibiting 100-fold greater potency toward cytokine processing than bacterial killing. Thus, in addition to their classical role as phagocytes, neutrophils play an important immunoregulatory role through deployment of their granule proteases into the extracellular space to process multiple IL-1 family cytokines.

Neutrophils as a Protagonist and Target in Chronic Rhinosinusitis

Neutrophils have traditionally been acknowledged as the first immune cells that are recruited to inflamed tissues during acute inflammation. By contrast, their importance in the context of chronic inflammation has been studied in less depth. Neutrophils can be recruited and are largely present in the nasal mucosa of patients with chronic rhinosinusitis (CRS) both in Asians and in Caucasians. Increased infiltration of neutrophils in patients with CRS has been linked to poor corticosteroid response and disease prognosis. Meanwhile, tissue neutrophils may possess specific phenotypic features distinguishing them from resting blood counterparts and are endowed with particular functions, such as cytokines and chemokines production, thus may contribute to the pathogenesis of CRS. This review aims to summarize our current understanding of the pathophysiologic mechanisms of CRS, with a focus on the roles of neutrophils. We discuss recruitment, function, and regulation of neutrophils in CRS and outline the potential therapeutic strategies targeting neutrophils.

Antibiotic administration can eradicate intra-amniotic infection or intra-amniotic inflammation in a subset of patients with preterm labor and intact membranes

BACKGROUND

Intra-amniotic infection is present in 10% of patients with an episode of preterm labor, and is a risk factor for impending preterm delivery and neonatal morbidity/mortality. Intra-amniotic inflammation is often associated with intra-amniotic infection, but is sometimes present in the absence of detectable microorganisms. Antibiotic treatment of intra-amniotic infection has traditionally been considered to be ineffective. Intra-amniotic inflammation without microorganisms has a prognosis similar to that of intra-amniotic infection.

OBJECTIVE

To determine whether antibiotics can eradicate intra-amniotic infection or intra-amniotic inflammation in a subset of patients with preterm labor and intact membranes.

MATERIALS AND METHODS

The study population consisted of women who met the following criteria: 1) singleton gestation between 20 and 34 weeks; 2) preterm labor and intact membranes; 3) transabdominal amniocentesis performed for the evaluation of the microbiologic/inflammatory status of the amniotic cavity; 4) intra-amniotic infection and/or intra-amniotic inflammation; and 5) received antibiotic treatment that consisted of ceftriaxone, clarithromycin, and metronidazole. Follow-up amniocentesis was performed in a subset of patients. Amniotic fluid was cultured for aerobic and anaerobic bacteria and genital mycoplasmas, and polymerase chain reaction was performed for Ureaplasma spp. Intra-amniotic infection was defined as a positive amniotic fluid culture or positive polymerase chain reaction, and intra-amniotic inflammation was suspected when there was an elevated amniotic fluid white blood cell count or a positive result of a rapid test for matrix metalloproteinase-8. For this study, the final diagnosis of intra-amniotic inflammation was made by measuring the interleukin-6 concentration in stored amniotic fluid (>2.6 ng/mL). These results were not available to managing clinicians. Treatment success was defined as eradication of intra-amniotic infection and/or intra-amniotic inflammation or delivery ≥37 weeks.

RESULTS

Of 62 patients with intra-amniotic infection and/or intra-amniotic inflammation, 50 received the antibiotic regimen. Of those patients, 29 were undelivered for ≥7 days and 19 underwent a follow-up amniocentesis. Microorganisms were identified by culture or polymerase chain reaction of amniotic fluid obtained at admission in 21% of patients (4/19) who had a follow-up amniocentesis, and were eradicated in 3 of the 4 patients. Resolution of intra-amniotic infection/inflammation was confirmed in 79% of patients (15/19), and 1 other patient delivered at term, although resolution of intra-amniotic inflammation could not be confirmed after a follow-up amniocentesis. Thus, resolution of intra-amniotic inflammation/infection or term delivery (treatment success) occurred in 84% of patients (16/19) who had a follow-up amniocentesis. Treatment success occurred in 32% of patients (16/50) with intra-amniotic infection/inflammation who received antibiotics. The median amniocentesis-to-delivery interval was significantly longer among women who received the combination of antibiotics than among those who did not (11.4 days vs 3.1 days: P = .04).

CONCLUSION

Eradication of intra-amniotic infection/inflammation after treatment with antibiotics was confirmed in 79% of patients with preterm labor, intact membranes, and intra-amniotic infection/inflammation who had a follow-up amniocentesis. Treatment success occurred in 84% of patients who underwent a follow-up amniocentesis and in 32% of women who received the antibiotic regimen.

An Omics Approach to Extracellular Vesicles from HIV-1 Infected Cells

Human Immunodeficiency Virus-1 (HIV-1) is the causative agent of Acquired Immunodeficiency Syndrome (AIDS), infecting nearly 37 million people worldwide. Currently, there is no definitive cure, mainly due to HIV-1's ability to enact latency. Our previous work has shown that exosomes, a small extracellular vesicle, from uninfected cells can activate HIV-1 in latent cells, leading to increased mostly short and some long HIV-1 RNA transcripts. This is consistent with the notion that none of the FDA-approved antiretroviral drugs used today in the clinic are transcription inhibitors. Furthermore, these HIV-1 transcripts can be packaged into exosomes and released from the infected cell. Here, we examined the differences in protein and nucleic acid content between exosomes from uninfected and HIV-1-infected cells. We found increased cyclin-dependent kinases, among other kinases, in exosomes from infected T-cells while other kinases were present in exosomes from infected monocytes. Additionally, we found a series of short antisense HIV-1 RNA from the 3' LTR that appears heavily mutated in exosomes from HIV-1-infected cells along with the presence of cellular noncoding RNAs and cellular miRNAs. Both physical and functional validations were performed on some of the key findings. Collectively, our data indicate distinct differences in protein and RNA content between exosomes from uninfected and HIV-1-infected cells, which can lead to different functional outcomes in recipient cells.

Control of cell death-associated danger signals during cornification prevents autoinflammation of the skin

The function of the skin as a barrier to the environment is mainly achieved by the outermost layers of the epidermis. In the granular layer, epidermal keratinocytes undergo the last steps of their terminal differentiation program resulting in cornification. The coordinated conversion of living keratinocytes into corneocytes, the building blocks of the cornified layer, represents a unique form of programmed cell death. Recent studies have identified numerous genes that are specifically expressed in terminally differentiated keratinocytes and, surprisingly, this genetic program does not only include mediators of cornification but also suppressors of pyroptosis, another mode of programmed cell death. Pyroptosis is activated by inflammasomes, leads to the release of interleukin-1 (IL-1) family cytokines, and thereby activates inflammation. In addition, inhibitors of potentially pro-inflammatory proteases and enzymes removing danger-associated cytoplasmic DNA are expressed in differentiated keratinocytes. We propose the concept of cornification as an inherently hazardous process in which damaging side effects are actively suppressed by protective mechanisms. In support of this hypothesis, loss-of-function mutations in epidermal protease inhibitors and IL-1 family antagonists suffice to induce autoinflammation. Similarly, exogenous disturbances of either cornification or its accompanying control mechanisms may be starting points for skin inflammation. Further studies into the relationship between cornification, pyroptosis and other forms of cell death will help to define the initiation phase of inflammatory skin diseases and offer new targets for disease prevention and therapy.

IL-33trap is a novel IL-33-neutralizing biologic that inhibits allergic airway inflammation

BACKGROUND

The emergence of IL-33 as a key molecular player in the development and propagation of widespread inflammatory diseases, including asthma and atopic dermatitis, has established the need for effective IL-33-neutralizing biologics.

OBJECTIVE

Here we describe the development and validation of a new antagonist of IL-33, termed IL-33trap, which combines the extracellular domains of the IL-33 receptor (ST2) and its coreceptor, IL-1 receptor accessory protein, into a single fusion protein.

METHODS

We produced and purified recombinant IL-33trap from human cells and analyzed its IL-33-binding affinity and IL-33 antagonistic activity in cultured cells and mice. IL-33trap activity was also benchmarked with a recombinant soluble ST2 corresponding to the naturally occurring IL-33 decoy receptor. Finally, we studied the effect of IL-33trap in the Alternaria alternata mouse model of allergic airway inflammation.

RESULTS

In vitro IL-33trap binds IL-33 and inhibits IL-33 activity to a much stronger degree than soluble ST2. Furthermore, IL-33trap inhibits eosinophil infiltration, splenomegaly, and production of signature cytokines in splenic lymphocytes and lung tissue on IL-33 injection. Finally, administration of IL-33trap at the time of allergen challenge inhibits inflammatory responses in a preclinical mouse model of acute allergic airway inflammation.

CONCLUSIONS

IL-33trap is a novel IL-33 antagonist that outperforms the natural IL-33 decoy receptor and shows anti-inflammatory activities in a preclinical mouse model of acute allergic airway inflammation when administered at the time of allergen challenge.

Keeping Cell Death in Check: Ubiquitylation-Dependent Control of TNFR1 and TLR Signaling

Pro-inflammatory signaling pathways, induced by pathogens, tissue damage or cytokines, depend on the ubiquitylation of various subunits of receptor signaling complexes, controlled by ubiquitin ligases and deubiquitinases. Ubiquitylation sets the stage for the activation of kinases within these receptor complexes, which ultimately regulate pro-inflammatory gene expression. The receptors, which transduce pro-inflammatory signals, can often induce cell death, which is controlled by ubiquitylation as well. In this review, we discuss the key role of ubiquitylation in pro-inflammatory signaling by TNFR1 and TLRs and its role in setting the threshold for cell death induced by these pro-inflammatory triggers.

RIP1/RIP3-regulated necroptosis as a target for multifaceted disease therapy (Review)

Necroptosis is a type of programmed cell death with necrotic morphology, occurring in a variety of biological processes, including inflammation, immune response, embryonic development and metabolic abnormalities. The current nomenclature defines necroptosis as cell death mediated by signal transduction from receptor‑interacting serine/threonine kinase (RIP) 1 to RIP3 (hereafter called RIP1/RIP3). However, RIP3‑dependent cell death would be a more precise definition of necroptosis. RIP3 is indispensable for necroptosis, while RIP1 is not consistently involved in the signal transduction. Notably, deletion of RIP1 even promotes RIP3‑mediated necroptosis under certain conditions. Necroptosis was previously thought as an alternate process of cell death in case of apoptosis inhibition. Currently, necroptosis is recognized to serve a pivotal role in regulating various physiological processes. Of note, it mediates a variety of human diseases, such as ischemic brain injury, immune system disorders and cancer. Targeting and inhibiting necroptosis, therefore, has the potential to be used for therapeutic purposes. To date, research has elucidated the suppression of RIP1/RIP3 via effective inhibitors and highlighted their potential application in disease therapy. The present review focused on the molecular mechanisms of RIP1/RIP3‑mediated necroptosis, explored the functions of RIP1/RIP3 in necroptosis, discussed their potential as a novel therapeutic target for disease therapy, and provided valuable suggestions for further study in this field.

A high concentration of fetal fibronectin in cervical secretions increases the risk of intra-amniotic infection and inflammation in patients with preterm labor and intact membranes

Objective To determine whether the risk of intra-amniotic infection/inflammation and spontaneous preterm delivery (SPTD) varies as a function of the concentration of cervical fetal fibronectin (fFN) in patients with preterm labor and intact membranes. Methods This prospective study included 180 patients with preterm labor and intact membranes who had a sample collected for quantitative fFN measurement and underwent amniocentesis. Amniotic fluid was cultured for aerobic and anaerobic bacteria and genital mycoplasmas. Intra-amniotic inflammation was defined as an amniotic fluid matrix metalloproteinase-8 concentration >23 ng/mL. Results (1) The prevalence of intra-amniotic infection/inflammation and SPTD within 7 days was 32.2% (58/180) and 33.9% (61/178), respectively; (2) The higher the fFN concentration, the greater the risk of intra-amniotic infection/inflammation and SPTD within 7 days (P<0.001, respectively); (3) An fFN concentration 150 ng/mL had a better diagnostic performance than an fFN 50 ng/mL in the identification of intra-amniotic infection/inflammation and SPTD within 7 days; (4) Among the patients with an fFN <50 ng/mL, intra-amniotic infection/inflammation was identified in 7.6% (6/79) of patients and 66.7% (4/6) delivered within 7 days. Conclusion The higher the concentration of fFN, the greater the risk of intra-amniotic infection/inflammation and SPTD in patients with preterm labor and intact membranes.