Exploring caspase functions in mouse models

Caspases are enzymes with protease activity. Despite being known for more than three decades, caspase investigation still yields surprising and fascinating information. Initially associated with cell death and inflammation, their functions have gradually been revealed to extend beyond, targeting pathways such as cell proliferation, migration, and differentiation. These processes are also associated with disease mechanisms, positioning caspases as potential targets for numerous pathologies including inflammatory, neurological, metabolic, or oncological conditions. While in vitro studies play a crucial role in elucidating molecular pathways, they lack the context of the body's complexity. Therefore, laboratory animals are an indispensable part of successfully understanding and applying caspase networks. This paper aims to summarize and discuss recent knowledge, understanding, and challenges in caspase knock-out mice.

Enhancement of the Tumor Suppression Effect of High-dose Radiation by Low-dose Pre-radiation Through Inhibition of DNA Damage Repair and Increased Pyroptosis

Radiation therapy has been a critical and effective treatment for cancer. However, not all cells are destroyed by radiation due to the presence of tumor cell radioresistance. In the current study, we investigated the effect of low-dose radiation (LDR) on the tumor suppressive effect of high-dose radiation (HDR) and its mechanism from the perspective of tumor cell death mode and DNA damage repair, aiming to provide a foundation for improving the efficacy of clinical tumor radiotherapy. We found that LDR pre-irradiation strengthened the HDR-inhibited A549 cell proliferation, HDR-induced apoptosis, and G2 phase cell cycle arrest under co-culture conditions. RNA-sequencing showed that differentially expressed genes after irradiation contained pyroptosis-related genes and DNA damage repair related genes. By detecting pyroptosis-related proteins, we found that LDR could enhance HDR-induced pyroptosis. Furthermore, under co-culture conditions, LDR pre-irradiation enhances the HDR-induced DNA damage and further suppresses the DNA damage-repairing process, which eventually leads to cell death. Lastly, we established a tumor-bearing mouse model and further demonstrated that LDR local pre-irradiation could enhance the cancer suppressive effect of HDR. To summarize, our study proved that LDR pre-irradiation enhances the tumor-killing function of HDR when cancer cells and immune cells were coexisting.

Bisphenol A Induces Reactive Oxygen Species Production and Apoptosis-Related Gene Expression in Pacific Red Snapper Lutjanus peru Leukocytes

Bisphenol A is one of the most used components of the polycarbonate plastic industry in the word. This contaminant has disrupting effect in cells in in vitro and in vivo in fish. This study evaluated for the first time the cytotoxicity, oxidative stress and apoptosis induced by bisphenol A (BPA) in head-kidney and spleen leukocytes isolated from Pacific red snapper Lutjanus peru. Head-kidney and spleen leukocytes were exposed to 100, 1000 and 10,000 µg/mL of BPA at 2 and 24 h. Results showed cytotoxicity of BPA at 1000 and 10,000 µg/mL. Cell viability > 80% was observed in leukocytes exposed to 100 µg/mL for 2 h; thus, this concentration was selected for the remainder of the study. Reactive oxygen species (ROS) production, analyzed by DCF-DA and NBT assays, significantly increased in those leukocytes exposed to BPA compared to controls after 2 or 24 h. Superoxide dismutase and catalase activities increased in head-kidney leukocytes after 24 h of BPA exposure. Apoptosis was inferred from caspase (casp-1 and casp-3), granzyme A (granz-A) and perforin 1 (perf-1) gene expression, which was significantly up-regulated, at 2 h BPA exposure in head-kidney leukocytes, and from granz-A and perf-1, which were up-regulated, after 24 h BPA exposure in spleen leukocytes. Short cytoplasmic prolongations and membrane blebs, suggestive of apoptosis, were observed by scanning electron microscopy. These data suggest that BPA at 100 µg/mL induces cytotoxicity, oxidative stress, apoptosis in Pacific red snapper head-kidney and spleen leukocytes.

Pathological Impact of Tau Proteolytical Process on Neuronal and Mitochondrial Function: a Crucial Role in Alzheimer's Disease

Tau protein plays a pivotal role in the central nervous system (CNS), participating in microtubule stability, axonal transport, and synaptic communication. Research interest has focused on studying the role of post-translational tau modifications in mitochondrial failure, oxidative damage, and synaptic impairment in Alzheimer's disease (AD). Soluble tau forms produced by its pathological cleaved induced by caspases could lead to neuronal injury contributing to oxidative damage and cognitive decline in AD. For example, the presence of tau cleaved by caspase-3 has been suggested as a relevant factor in AD and is considered a previous event before neurofibrillary tangles (NFTs) formation.Interestingly, we and others have shown that caspase-cleaved tau in N- or C- terminal sites induce mitochondrial bioenergetics defects, axonal transport impairment, neuronal injury, and cognitive decline in neuronal cells and murine models. All these abnormalities are considered relevant in the early neurodegenerative manifestations such as memory and cognitive failure reported in AD. Therefore, in this review, we will discuss for the first time the importance of truncated tau by caspases activation in the pathogenesis of AD and how its negative actions could impact neuronal function.

Microbial gasdermins: More than a billion years of pyroptotic-like cell death

In the recent past, the concept of immunity has been extended to eukaryotic and prokaryotic microorganisms, like fungi and bacteria. The latest findings have drawn remarkable evolutionary parallels between metazoan and microbial defense-related genes, unveiling a growing number of shared transkingdom components of immune systems. One such component is the gasdermin family of pore-forming proteins - executioners of a highly inflammatory immune cell death program in mammals, termed pyroptosis. Pyroptotic cell death limits the spread of intracellular pathogens by eliminating infected cells and coordinates the broader inflammatory response to infection. The microbial gasdermins have similarly been implicated in defense-related cell death reactions in fungi, bacteria and archaea. Moreover, the discovery of the molecular regulators of gasdermin cytotoxicity in fungi and bacteria, has established additional evolutionary links to mammalian pyroptotic pathways. Here, we focus on the gasdermin proteins in microorganisms and their role in organismal defense and provide perspective on this remarkable case study in comparative immunology.

A role for fibroblast-derived SASP factors in the activation of pyroptotic cell death in mammary epithelial cells

In normal tissue homeostasis, bidirectional communication between different cell types can shape numerous biological outcomes. Many studies have documented instances of reciprocal communication between fibroblasts and cancer cells that functionally change cancer cell behavior. However, less is known about how these heterotypic interactions shape epithelial cell function in the absence of oncogenic transformation. Furthermore, fibroblasts are prone to undergo senescence, which is typified by an irreversible cell cycle arrest. Senescent fibroblasts are also known to secrete various cytokines into the extracellular space; a phenomenon that is termed the senescence-associated secretory phenotype (SASP). While the role of fibroblast-derived SASP factors on cancer cells has been well studied, the impact of these factors on normal epithelial cells remains poorly understood. We discovered that treatment of normal mammary epithelial cells with conditioned media from senescent fibroblasts (SASP CM) results in a caspase-dependent cell death. This capacity of SASP CM to cause cell death is maintained across multiple senescence-inducing stimuli. However, the activation of oncogenic signaling in mammary epithelial cells mitigates the ability of SASP CM to induce cell death. Despite the reliance of this cell death on caspase activation, we discovered that SASP CM does not cause cell death by the extrinsic or intrinsic apoptotic pathway. Instead, these cells die by an NLRP3, caspase-1, and gasdermin D-dependent induction of pyroptosis. Taken together, our findings reveal that senescent fibroblasts can cause pyroptosis in neighboring mammary epithelial cells, which has implications for therapeutic strategies that perturb the behavior of senescent cells.

Gasdermin D-mediated pyroptosis: mechanisms, diseases, and inhibitors

Gasdermin D (GSDMD)-mediated pyroptosis and downstream inflammation are important self-protection mechanisms against stimuli and infections. Hosts can defend against intracellular bacterial infections by inducing cell pyroptosis, which triggers the clearance of pathogens. However, pyroptosis is a double-edged sword. Numerous studies have revealed the relationship between abnormal GSDMD activation and various inflammatory diseases, including sepsis, coronavirus disease 2019 (COVID-19), neurodegenerative diseases, nonalcoholic steatohepatitis (NASH), inflammatory bowel disease (IBD), and malignant tumors. GSDMD, a key pyroptosis-executing protein, is linked to inflammatory signal transduction, activation of various inflammasomes, and the release of downstream inflammatory cytokines. Thus, inhibiting GSDMD activation is considered an effective strategy for treating related inflammatory diseases. The study of the mechanism of GSDMD activation, the formation of GSDMD membrane pores, and the regulatory strategy of GSDMD-mediated pyroptosis is currently a hot topic. Moreover, studies of the structure of caspase-GSDMD complexes and more in-depth molecular mechanisms provide multiple strategies for the development of GSDMD inhibitors. This review will mainly discuss the structures of GSDMD and GSDMD pores, activation pathways, GSDMD-mediated diseases, and the development of GSDMD inhibitors.

A role for fibroblast-derived SASP factors in the activation of pyroptotic cell death in mammary epithelial cells

In normal tissue homeostasis, bidirectional communication between different cell types can shape numerous biological outcomes. Many studies have documented instances of reciprocal communication between fibroblasts and cancer cells that functionally change cancer cell behavior. However, less is known about how these heterotypic interactions shape epithelial cell function in the absence of oncogenic transformation. Furthermore, fibroblasts are prone to undergo senescence, which is typified by an irreversible cell cycle arrest. Senescent fibroblasts are also known to secrete various cytokines into the extracellular space; a phenomenon that is termed the senescence-associated secretory phenotype (SASP). While the role of fibroblast derived SASP factors on cancer cells has been well studied, the impact of these factors on normal epithelial cells remains poorly understood. We discovered that treatment of normal mammary epithelial cells with conditioned media (CM) from senescent fibroblasts (SASP CM) results in a caspase-dependent cell death. This capacity of SASP CM to cause cell death is maintained across multiple senescence-inducing stimuli. However, the activation of oncogenic signaling in mammary epithelial cells mitigates the ability of SASP CM to induce cell death. Despite the reliance of this cell death on caspase activation, we discovered that SASP CM does not cause cell death by the extrinsic or intrinsic apoptotic pathway. Instead, these cells die by an NLRP3, caspase-1, and gasdermin D (GSDMD)-dependent induction of pyroptosis. Taken together, our findings reveal that senescent fibroblasts can cause pyroptosis in neighboring mammary epithelial cells, which has implications for therapeutic strategies that perturb the behavior of senescent cells.

Immunoceuticals: Harnessing Their Immunomodulatory Potential to Promote Health and Wellness

Knowledge that certain nutraceuticals can modulate the immune system is not new. These naturally occurring compounds are known as immunoceuticals, which is a novel term that refers to products and systems that naturally improve an individual's immuno-competence. Examples of immunoceuticals include vitamin D3, mushroom glycans, flavonols, quercetin, omega-3 fatty acids, carotenoids, and micronutrients (e.g., zinc and selenium), to name a few. The immune system is a complex and highly intricate system comprising molecules, cells, tissues, and organs that are regulated by many different genetic and environmental factors. There are instances, such as pathological conditions, in which a normal immune response is suboptimal or inappropriate and thus augmentation or tuning of the immune response by immunoceuticals may be desired. With infectious diseases, cancers, autoimmune disorders, inflammatory conditions, and allergies on the rise in both humans and animals, the importance of the use of immunoceuticals to prevent, treat, or augment the treatment of these conditions is becoming more evident as a natural and often economical approach to support wellness. The global nutraceuticals market, which includes immunoceuticals, is a multi-billion-dollar industry, with a market size value of USD 454.55 billion in 2021, which is expected to reach USD 991.09 billion by 2030. This review will provide an overview of the immune system, the importance of immunomodulation, and defining and testing for immunocompetence, followed by a discussion of several key immunoceuticals with clinically proven and evidence-based immunomodulatory properties.

Association of CASP3 rs4647602 Gene Polymorphism with Periodontitis in South Indians of Tamil Ethnicity

Objective: Caspase-3 (CASP3) activation is central to apoptosis and is involved in periodontal disease pathogenesis. CASP3 gene polymorphism in a population may influence the periodontitis disease severity. In this study, we aimed to identify the association of CASP3 (rs4647602) gene polymorphism with periodontitis and to correlate clinical parameters based on genotype and allele distribution in periodontally diseased and healthy South Indian subjects of Tamil ethnicity. Materials and Methods: Allele-specific polymerase chain reaction genotyping were performed to identify CASP3 rs4647602 gene polymorphism in 145 periodontally healthy subjects and 145 periodontitis subjects. The association between gene polymorphism frequencies and the risk of periodontitis were analyzed by Pearson chi-square test, Mann-Whitney U test, t test, logistic regression, and assessed by odds ratio (OR) and 95% confidence interval (95% CI). Results: The statistical test results demonstrated a significant difference in genotype distribution between the two groups (p < 0.001) and the variant GG genotype was associated with a significantly increased risk for periodontitis (OR = 3.55, 95% CI = 1.89-6.68, p < 0.001). Furthermore, all clinical parameters were highly significant to the genotypes in periodontitis subjects (p < 0.05). Conclusion: The present study suggests that the rs4647602 GG genotype of CASP3 is associated with the periodontitis risk in a South Indians of Tamil ethnicity. Clinical Trial Registration Number: (CTRI/2021/03/032412).

Echinacoside Induces Mitochondria-Mediated Pyroptosis through Raf/MEK/ERK Signaling in Non-Small Cell Lung Cancer Cells

Background

Various natural compounds are effective in cancer prevention and treatment with fewer side effects than conventional radiotherapy and chemotherapy. Considering the uncertainty of the antitumor mechanism of Echinacoside (Ech) and the fact that no study on Ech against non-small cell lung cancer (NSCLC) has been explored previously, this study inquired into the anti-NSCLC effect of Ech and explored its potential mechanisms.

Methods

The IC₅₀ to Ech of the NSCLC cells was calculated based on a series of cell viability assays. Different concentrations of Ech were used to treat the cells; the proliferation activity of the cells was evaluated using EdU staining. Mitochondrial membrane potential was detected by JC-1 staining. Levels of cytokines IL-1β and IL-18 were measured by ELISA. GSH and MDA levels were measured by microplate reader. Expression of cytochrome c, NLRP3, caspase-1, IL-1β, c-Myc, c-Fos, and Raf/MEK/ERK pathway proteins was evaluated by western blot. Meanwhile, we used xenograft, immunohistochemical staining, and H&E staining to evaluate the pharmacological effects of Ech in mice in vivo.

Results

ECH inhibited the proliferation of NSCLC cells. Ech increased the expression of pyroptosis-related proteins. Besides, Ech perturbed the mitochondrial membrane potential with the release of mitochondrial cytochrome c, accompanied by increased oxidative stress. Ech inhibited the phosphorylation levels of Raf/MEK/ERK signaling pathway and subsequently reduced c-myc and c-fos protein expression. In addition, Ech effectively restrained the growth of tumors in vivo.

Conclusions

Ech inhibited the Raf/MEK/ERK signaling. Impaired mitochondria activated inflammasome, which in turn led to the pyroptosis of NSCLC cells. These findings can provide some ideas on how to use pyroptosis to treat NSCLC.

A Pyroptosis-Related Gene Panel for Predicting the Prognosis and Immune Microenvironment of Cervical Cancer

Cervical cancer (CC) is one of the most common malignant tumors of the female reproductive system. And the immune system disorder in patients results in an increasing incidence rate and mortality rate. Pyroptosis is an immune system-related programmed cell death pathway that produces systemic inflammation by releasing pro-inflammatory intracellular components. However, the diagnostic significance of pyroptosis-related genes (PRGs) in CC is still unclear. Therefore, we identified 52 PRGs from the TCGA database and screened three Differentially Expressed Pyroptosis-Related Genes (DEPRGs) in the prognosis of cervical cancer: CHMP4C, GZMB, TNF. The least absolute shrinkage and selection operator (LASSO) regression analysis and multivariate COX regression analysis were then used to construct a gene panel based on the three prognostic DEPRGs. The patients were divided into high-and low-risk groups based on the median risk score of the panel. According to the Kaplan-Meier curve, there was a substantial difference in survival rates between the two groups, with the high-risk group’s survival rate being significantly lower than the low-risk group’s. The PCA and t-SNE analyses revealed that the panel was able to differentiate patients into high-and low-risk groups. The area under the ROC curve (AUC) shows that the prognostic panel has high sensitivity and specificity. The risk score could then be employed as an independent prognostic factor using univariate and multivariate COX regression analyses paired with clinical data. The analyses of GO and KEGG functional enrichment of differentially expressed genes (DEGs) in the high-and low-risk groups revealed that these genes were primarily engaged in immune response and inflammatory cell chemotaxis. To illustrate immune cell infiltration in CC patients further, we used ssGSEA to compare immune-related cells and immune pathway activation between the high-and low-risk groups. The link between three prognostic DEPRGs and immune-related cells was still being discussed after evaluating immune cell infiltration in the TCGA cohort with “CIBERSORT.” In addition, the GEPIA database and qRT-PCR analysis were used to verify the expression levels of prognostic DEPRGs. In conclusion, PRGs are critical in tumor immunity and can be utilized to predict the prognosis of CC.

Divergences of the RLR Gene Families across Lophotrochozoans: Domain Grafting, Exon-Intron Structure, Expression, and Positive Selection

Invertebrates do not possess adaptive immunity but have evolved a variety of unique repertoires of innate immune sensors. In this study, we explored the immune diversity and specificity of invertebrates based on the lophotrochozoan RLRs, a major component in antiviral immune recognition. By annotating RLRs in the genomes of 58 representative species across metazoan evolution, we explored the gene expansion of RLRs in Lophotrochozoa. Of note, the N-terminal domains of lophotrochozoan RLRs showed the most striking diversity which evolved independently by domain grafting. Exon–intron structures were revealed to be prevalent in the domain grafting of lophotrochozoan RLRs based on an analysis of sibling paralogs and orthologs. In more than half of the cases, the mechanism of ‘exonization/pseudoexonization’ led to the generation of non-canonical N-terminal domains. Transcriptomic studies revealed that many non-canonical RLRs display immune-related expression patterns. Two of these RLRs showed obvious evidence of positive selection, which may be the result of host defense selection pressure. Overall, our study suggests that the complex and unique domain arrangement of lophotrochozoan RLRs might result from domain grafting, exon–intron divergence, expression diversification, and positive selection, which may have led to functionally distinct lophotrochozoan RLRs.

The Caspase Homologues in Scallop Chlamys farreri and Their Expression Responses to Toxic Dinoflagellates Exposure

The cysteine aspartic acid-specific protease (caspase) family is distributed across vertebrates and invertebrates, and its members are involved in apoptosis and response to cellular stress. The Zhikong scallop (Chlamys farreri) is a bivalve mollusc that is well adapted to complex marine environments, yet the diversity of caspase homologues and their expression patterns in the Zhikong scallop remain largely unknown. Here, we identified 30 caspase homologues in the genome of the Zhikong scallop and analysed their expression dynamics during all developmental stages and following exposure to paralytic shellfish toxins (PSTs). The 30 caspase homologues were classified as initiators (caspases-2/9 and caspases-8/10) or executioners (caspases-3/6/7 and caspases-3/6/7-like) and displayed increased copy numbers compared to those in vertebrates. Almost all of the caspase-2/9 genes were highly expressed throughout all developmental stages from zygote to juvenile, and their expression in the digestive gland and kidney was slightly influenced by PSTs. The caspase-8/10 genes were highly expressed in the digestive gland and kidney, while PSTs inhibited their expression in these two organs. After exposure to different Alexandrium PST-producing algae (AM-1 and ACDH), the number of significantly up-regulated caspase homologues in the digestive gland increased with the toxicity level of PST derivatives, which might be due to the higher toxicity of GTXs produced by AM-1 compared to the N-sulphocarbamoyl analogues produced by ACDH. However, the effect of these two PST-producing algae strains on caspase expression in the kidney seemed to be stronger, possibly because the PST derivatives were transformed into highly toxic compounds in scallop kidney, and suggested an organ-dependent response to PSTs. These results indicate the dedicated control of caspase gene expression and highlight their contribution to PSTs in C. farreri. This work provides a further understanding of the role of caspase homologues in the Zhikong scallop and can guide future studies focussing on the role of caspases and their interactions with PSTs.

Polaryzacja mikrogleju i makrofagów w wybranych chorobach degeneracyjnych i zapalnych układu nerwowego

Makrofagi to komórki efektorowe układu odpornościowego zdolne do polaryzacji, czyli zmiany fenotypu powiązanej ze zmianą aktywności. Można wyróżnić: polaryzację klasyczną (M1), która służy obronie przed patogenami, a makrofagi M1 mają aktywność ogólnie prozapalną, oraz polaryzację alternatywną (M2), która sprzyja wygaszaniu stanu zapalnego i regeneracji tkanki. Makrofagi zasiedlają niemal cały organizm, więc zjawisko ich polaryzacji ma wpływ na wiele procesów zachodzących w różnych tkankach. W układzie nerwowym reprezentacją osiadłych makrofagów jest mikroglej. Jednak w wielu sytuacjach patologicznych w mózgu pojawiają się także makrofagi rekrutowane z monocytów krążących we krwi. Choroby neurodegeneracyjne, urazy i choroby autoimmunologiczne są związane z reakcją układu odpornościowego, która może mieć istotny wpływ na dalszy przebieg choroby i na tempo regeneracji tkanki. Polaryzacja makrofagów ma w związku z tym znaczenie w chorobach centralnego układu nerwowego. Aktywność komórek M1 i M2 może bowiem różnie wpływać na przeżywalność neuronów i oligodendrocytów, na wzrost aksonów, na proces demielinizacji czy na szczelność bariery krew–mózg. Wynika to z różnic między fenotypami w wytwarzaniu reaktywnych form tlenu i tlenku azotu, wydzielaniu cytokin i czynników wzrostu, bezpośrednich oddziaływaniach na sąsiednie komórki i zdolnościach do fagocytozy. W artykule omówiono to zagadnienie w: udarze mózgu, urazie rdzenia kręgowego, chorobie Alzheimera, stwardnieniu zanikowym bocznym i stwardnieniu rozsianym. W wielu spośród tych patologii obserwuje się gradient czasowy lub przestrzenny rozmieszczenia w tkance poszczególnych fenotypów mikrogleju i/lub makrofagów. Wydaje się zatem, że zmiany polaryzacji makrofagów mogą potencjalnie sprzyjać regeneracji tkanki lub hamować rozwój chorób neurodegeneracyjnych.

Neuroprotective Effects of Hesperetin in Regulating Microglia Polarization after Ischemic Stroke by Inhibiting TLR4/NF-κB Pathway

This study aimed to explore the influence of hesperidin on the polarization of microglia to clarify the key mechanism of regulating the polarization of M2 microglia. C57BL/6 mice were randomly divided into middle cerebral artery occlusion model group (MCAO group), MCAO + hesperidin treatment group (MCAO + hesperidin group), and sham group (sham operation group). The mice were assessed with neurological scores for their functional status. 2,3,5-Triphenyltetrazole chloride (TTC) was used to determine the volume of cerebral infarction. Hematoxylin and eosin (H&E) staining was performed to detect brain loss. The system with 1% O2, 5% CO2, and 92% N2 was applied to establish BV2 in vitro model induced by MCAO. TNF-α, IL-1β, TGF-β, and IL-10 levels of cytokines in the supernatant were detected by ELISA. RT-qPCR was used to detect mRNA levels of M1 iNOS, CD11b, CD32, and CD86, and mRNA levels of M2 CD206, Arg-1, and TGF-β. The Iba-1, iNOS, and Arg-1 of microglia and protein levels of TLR4 and p-NF-κB related to the pathway were detected by Western blot. After treatment with hesperidin, BV2 cells induced by MCAO in vitro can reduce the proinflammatory cytokines of TNF-α and IL-1β significantly, further upregulating anti-inflammatory cytokines of TGF-β, IL-10 while inhibiting TLR4 and p-NF-κB expression. The MCAO-induced BV2 cells treated by TLR-4 inhibitor TAK-242 and NF-κB inhibitor BAY 11-7082 had similar polarization effects to those treated with hesperidin. This study found that hesperetin gavage treatment can improve the neurological deficit and regulate the polarization of microglia in MCAO mice. In vitro experiments further verified that hesperidin plays a neuroprotective role by inhibiting the TLR4-NF-κB pathway, thus providing new targets and strategies for neuroprotection and nerve repair after ischemic stroke.

Keeping the host alive - lessons from obligate intracellular bacterial pathogens

Mammals have evolved sophisticated host cell death signaling pathways as an important immune mechanism to recognize and eliminate cell intruders before they establish their replicative niche. However, intracellular bacterial pathogens that have co-evolved with their host have developed a multitude of tactics to counteract this defense strategy to facilitate their survival and replication. This requires manipulation of pro-death and pro-survival host signaling pathways during infection. Obligate intracellular bacterial pathogens are organisms that absolutely require an eukaryotic host to survive and replicate, and therefore they have developed virulence factors to prevent diverse forms of host cell death and conserve their replicative niche. This review encapsulates our current understanding of these host-pathogen interactions by exploring the most relevant findings of Anaplasma spp., Chlamydia spp., Rickettsia spp. and Coxiella burnetii modulating host cell death pathways. A detailed comprehension of the molecular mechanisms through which these obligate intracellular pathogens manipulate regulated host cell death will not only increase the current understanding of these difficult-to-study pathogens but also provide insights into new tools to study regulated cell death and the development of new therapeutic approaches to control infection.

Apoptosis, Pyroptosis, and Necroptosis-Oh My! The Many Ways a Cell Can Die

Cell death is an essential process in all living organisms and occurs through different mechanisms. The three main types of programmed cell death are apoptosis, pyroptosis, and necroptosis, and each of these pathways employs complex molecular and cellular mechanisms. Although there are mechanisms and outcomes specific to each pathway, they share common components and features. In this review, we discuss recent discoveries in these three best understood modes of cell death, highlighting their singularities, and examining the intriguing notion that common players shape different individual pathways in this highly interconnected and coordinated cell death system. Understanding the similarities and differences of these cell death processes is crucial to enable targeted strategies to manipulate these pathways for therapeutic benefit.

Host cell death during infection with Chlamydia: a double-edged sword

The phylum Chlamydiae constitutes a group of obligate intracellular bacteria that infect a remarkably diverse range of host species. Some representatives are significant pathogens of clinical or veterinary importance. For instance, Chlamydia trachomatis is the leading infectious cause of blindness and the most common bacterial agent of sexually transmitted diseases. Chlamydiae are exceptionally dependent on their eukaryotic host cells as a consequence of their developmental biology. At the same time, host cell death is an integral part of the chlamydial infection cycle. It is therefore not surprising that the bacteria have evolved exquisite and versatile strategies to modulate host cell survival and death programs to their advantage. The recent introduction of tools for genetic modification of Chlamydia spp., in combination with our increasing awareness of the complexity of regulated cell death in eukaryotic cells, and in particular of its connections to cell-intrinsic immunity, has revived the interest in this virulence trait. However, recent advances also challenged long-standing assumptions and highlighted major knowledge gaps. This review summarizes current knowledge in the field and discusses possible directions for future research, which could lead us to a deeper understanding of Chlamydia's virulence strategies and may even inspire novel therapeutic approaches.

Development and Application of Activity-based Fluorescent Probes for High-Throughput Screening

High-throughput screening facilitates the rapid identification of novel hit compounds; however, it remains challenging to design effective high-throughput assays, partially due to the difficulty of achieving sensitivity in the assay techniques. Among the various analytical methods that are used, fluorescence-based assays dominate owing to their high sensitivity and ease of operation. Recent advances in activity-based sensing/imaging have further expanded the availability of fluorescent probes as monitors for high-throughput screening of result outputs. In this study, we have reviewed various activity-based fluorescent probes used in high-throughput screening assays, emphasizing their structure-related working mechanisms. Moreover, we have explored the possibility of the development of additional and better probes to boost hit identification and drug development against various targets.

Inhalable Jojoba Oil Dry Nanoemulsion Powders for the Treatment of Lipopolysaccharide- or H2O2-Induced Acute Lung Injury

Jojoba (Simmondsia chinensis (Link) C.K. Schneid) is a dioecious plant in desert and semi-desert areas, e.g., the Ismailia Desert in Egypt. Jojoba oil (JJBO) is a natural slight yellow oil with the functions of skin barrier repairing and wound healing, which is dermally applied as a traditional medication or cosmetic in the Middle East. The objective of this study was to prepare JJBO dry nanoemulsion powders (JNDs) and investigate their anti-acute lung injury effects. JJBO nanoemulsions (JNEs) were prepared and then lyophilized to JNDs and the properties and simulated lung deposition were measured. Rat acute lung injury (ALI) models were established after intratracheal (i.t.) administration of lipopolysaccharide (LPS) or hydrogen peroxide (H₂O₂). JNDs and dexamethasone (DXM) solutions were also i.t. administered to the rats. The pathological states of lung tissues were checked. Inflammatory and oxidative factors in the lung tissues were determined using ELISA methods. NF-κB p65 and caspase-3 were measured with a Western blotting method and an immunohistochemical method, respectively. JNDs had an appropriate mass median aerodynamic diameter (MMAD) of 4.17 µm and a fine particle fraction (FPF) of 39.11%. JNDs showed higher anti-inflammatory effect on LPS-induced ALI than DXM with a decrease in total protein content and down-regulation of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6) and NF-κB p65. JNDs also showed higher anti-inflammatory and anti-oxidation effect on H₂O₂-induced ALI than DXM with elimination of reactive oxygen species (ROS), increasing of superoxide dismutase (SOD), decrease in of lipid peroxide malondialdehyde (MDA) and glutathione (GSH), and inhibition of caspase-3 expression. Moreover, i.t. JNDs attenuated bleeding and infiltrations of the inflammatory cells in the two ALI models. JNDs are a promising natural oil-contained inhalable medication for the treatment of LPS- or H₂O₂-induced ALI.

Cryptotanshinone ameliorates CUS-induced depressive-like behaviors in mice

Objectives

Cryptotanshinone (CPT), a natural quinoid diterpene, isolated from Salvia miltiorrhiza, has shown various pharmacological properties. However, its effect on chronic unpredictable stress (CUS)-induced depression phenotypes and the underlying mechanism remain unclear. Therefore, the aim of this study was to investigate whether CPT could exert an antidepressant effect.

Methods

We investigated the effects of CPT in a CUS-induced depression model and explored whether these effects were related to the anti-inflammatory and neurogenesis promoting properties by investigating the expression levels of various signaling molecules at the mRNA and protein levels.

Results

Administration of CPT improved depression-like behaviors in CUS-induced mice. CPT administration increased the levels of doublecortin-positive cells and reversed the decrease in the expression levels of brain-derived neurotrophic factor (BDNF)/tyrosine kinase receptor B (TrkB) signaling transduction, as well as the downstream functional proteins, phosphorylated extracellular regulated protein kinases (p-ERK), and cyclic adenosine monophosphate (cAMP)-response element-binding protein levels (p-CREB) in hippocampus. CPT treatment also inhibited the activation of microglia and suppressed M1 microglial polarization, while promoting M2 microglial polarization by monitoring the expression levels of arginase 1 (Arg-1) and inducible nitric oxide synthase (iNOS), and further inhibited the expression of proinflammatory cytokines, including interleukin (IL)-1, IL-6, and tumor necrosis factor-α (TNF-α), and increased the expression of the anti-inflammatory cytokine IL-10 by regulating nuclear factor-κB (NF-κB) activation.

Conclusions

CPT relieves the depressive-like state in CUS-induced mice by enhancing neurogenesis and inhibiting inflammation through the BDNF/TrkB and NF-κB pathways and could therefore serve as a promising candidate for the treatment of depression.

Immune modulating effects of receptor interacting protein 2 (RIP2) in autoinflammation and immunity

Receptor-interacting protein 2 (RIP2) is a kinase that is involved in downstream signaling of nuclear oligomerization domain (NOD)-like receptors NOD1 and 2 sensing bacterial peptidoglycans. RIP2-deficiency or targeting of RIP2 by pharmaceutical inhibitors partially ameliorates inflammatory diseases by reducing pro-inflammatory signaling in response to peptidoglycans. However, RIP2 is widely expressed and interacts with several other proteins suggesting additional functions outside the NOD-signaling pathway. In this review, we discuss the immunological functions of RIP2 and its possible role in autoinflammation and immunity.

Role of Caspase-1 in the Pathogenesis of Inflammatory-Associated Chronic Noncommunicable Diseases

Caspase-1 is the first and extensively studied inflammatory caspase that is activated through inflammasome assembly. Inflammasome is a cytosolic formation of multiprotein complex that aimed to start inflammatory response against infections or cellular damages. The process leads to an auto-activation of caspase-1 and consequent maturation of caspase-1 target molecules such as interleukin (IL)-1β and IL-18. Recently, the role of caspase-1 and inflammasome in inflammatory-induced noncommunicable diseases (NCDs) like obesity, diabetes mellitus (DM), cardiovascular diseases (CVDs), cancers and chronic respiratory diseases have widely studied. However, their reports are distinct and even they have reported contrasting role of caspase-1 in the development and progression of NCDs. A few studies have reported that caspase-1/inflammasome assembley has a protective role in the initiation and progression of these diseases through the activation of the noncanonical caspase-1 target substrates like gasdermin-D and regulation of immune cells. Conversely, others have revealed that caspase-1 has a direct/indirect effect in the development and progression of several NCDs. Therefore, in this review, we systematically summarized the role of caspase-1 in the development and progression of NCDs, especially in obesity, DM, CVDs and cancers.

CRID3, a blocker of apoptosis associated speck like protein containing a card, ameliorates murine spinal cord injury by improving local immune microenvironment

Background

After spinal cord injury (SCI), destructive immune cell subsets are dominant in the local microenvironment, which are the important mechanism of injury. Studies have shown that inflammasomes play an important role in the inflammation following SCI, and apoptosis-associated speck-like protein containing a card (ASC) is the adaptor protein shared by inflammasomes. Therefore, we speculated that inhibiting ASC may improve the local microenvironment of injured spinal cord. Here, CRID3, a blocker of ASC oligomerization, was used to study its effect on the local microenvironment and the possible role in neuroprotection following SCI.

Methods

Murine SCI model was created using an Infinite Horizon impactor at T9 vertebral level with a force of 50 kdynes and CRID3 (50 mg/kg) was intraperitoneally injected following injury. ASC and its downstream molecules in inflammasome signaling pathway were measured by western blot. The immune cell subsets were detected by immunohistofluorescence (IHF) and flow cytometry (FCM). The spinal cord fibrosis area, neuron survival, myelin preservation, and functional recovery were assessed.

Results

Following SCI, CRID3 administration inhibited inflammasome-related ASC and caspase-1, IL-1β, and IL-18 activation, which consequently suppressed M1 microglia, Th1 and Th1Th17 differentiation, and increased M2 microglia and Th2 differentiation. Accordingly, the improved histology and behavior have also been found.

Conclusions

CRID3 may ameliorate murine SCI by inhibiting inflammasome activation, reducing proinflammatory factor production, restoring immune cell subset balance, and improving local immune microenvironment, and early administration may be a promising therapeutic strategy for SCI.

Pharmacological Transection of Brain-Spinal Cord Communication Blocks Pain-Induced Hemorrhage and Locomotor Deficits after Spinal Cord Injury in Rats

Spinal cord injury (SCI) is often accompanied by additional tissue damage (polytrauma), which engages pain (nociceptive) fibers. Prior research has shown that nociceptive input can increase cell death, expand the area of hemorrhage, and impair long-term recovery. The current study shows that these adverse effects can be blocked by the sodium channel blocker lidocaine applied rostral to a contusion injury. Rats received a lower thoracic (T12) contusion injury, and noxious electrical stimulation (shock) was applied to the tail 24 h later. Immediately before shock treatment, a pharmacological transection was performed by slowly infusing lidocaine at T2. Long-term locomotor recovery was assessed over the next 21 days. Noxious electrical stimulation impaired locomotor recovery, and this effect was blocked by rostral lidocaine. Next, the acute effect of lidocaine was assessed. Tissue was collected 3 h after noxious stimulation, and the extent of hemorrhage was evaluated by assessing hemoglobin content using Western blotting. Nociceptive stimulation increased the extent of hemorrhage. Lidocaine applied at T2 before, but not immediately after, stimulation blocked this effect. A similar pattern of results was observed when lidocaine was applied at the site of injury by means of a lumbar puncture. The results show that a pharmacological transection blocks nociception-induced hemorrhage and exacerbation of locomotor deficits.

6-Gingerol attenuates microglia-mediated neuroinflammation and ischemic brain injuries through Akt-mTOR-STAT3 signaling pathway

Neuroinflammation is critical for the pathogenesis of ischemia brain damage. Over-activated microglia-mediated inflammation plays a very important role in ischemia cerebral injuries. 6-Gingerol, obtained from edible ginger (Zingiber Officinale) exhibits protective effects against inflammation. In this study, we found that 6-Gingerol could reduce the size of infarction (P = 0.0184) and improve neurological functions (P = 0.04) at the third day after ischemic brain injury in vivo. Since 6-Gingerol has the anti-inflammatory effects, we further investigated its impacts on neuroinflammation mediated by microglia both in vivo and in vitro. We found that the levels of pro-inflammatory cytokines Interleukin-1 beta (IL-1β, P = 0.0213), Interleukin-6 (IL-6, P = 0.0316), and inducible NO synthase (iNOS, P = 0.0229) in the infarct penumbra were lower in 6-Gingerol treated groups. Furthermore, microglia induced pro-inflammatory cytokines, such as IL-6, IL-1β, incremental intercellular nitric oxide (NO), as well as iNOS were blocked by the treatment of 6-Gingerol in lipopolysaccharide (LPS) stimulated microglia. In terms of mechanism, 6-Gingerol potently suppressed phosphorylation of serine-threonine protein kinase (Akt) - mammalian target of rapamycin (mTOR) - signal transducer and activator of transcription 3 (STAT3) in LPS-treated microglia. Taken together, the present study suggested that 6-Gingerol improved cerebral ischemia injury by suppressing microglia-mediated neuroinflammation by down-regulating Akt-mTOR-STAT3 pathway.

Caspase-1 Engages Full-Length Gasdermin D through Two Distinct Interfaces That Mediate Caspase Recruitment and Substrate Cleavage

The recognition and cleavage of gasdermin D (GSDMD) by inflammatory caspases-1, 4, 5, and 11 are essential steps in initiating pyroptosis after inflammasome activation. Previous work has identified cleavage site signatures in substrates such as GSDMD, but it is unclear whether these are the sole determinants for caspase engagement. Here we report the crystal structure of a complex between human caspase-1 and the full-length murine GSDMD. In addition to engagement of the GSDMD N- and C-domain linker by the caspase-1 active site, an anti-parallel β sheet at the caspase-1 L2 and L2' loops bound a hydrophobic pocket within the GSDMD C-terminal domain distal to its N-terminal domain. This "exosite" interface endows an additional function for the GSDMD C-terminal domain as a caspase-recruitment module besides its role in autoinhibition. Our study thus reveals dual-interface engagement of GSDMD by caspase-1, which may be applicable to other physiological substrates of caspases.

The Arg/N-Degron Pathway-A Potential Running Back in Fine-Tuning the Inflammatory Response?

Recognition of danger signals by a cell initiates a powerful cascade of events generally leading to inflammation. Inflammatory caspases and several other proteases become activated and subsequently cleave their target proinflammatory mediators. The irreversible nature of this process implies that the newly generated proinflammatory fragments need to be sequestered, inhibited, or degraded in order to cancel the proinflammatory program or prevent chronic inflammation. The Arg/N-degron pathway is a ubiquitin-dependent proteolytic pathway that specifically degrades protein fragments bearing N-degrons, or destabilizing residues, which are recognized by the E3 ligases of the pathway. Here, we report that the Arg/N-degron pathway selectively degrades a number of proinflammatory fragments, including some activated inflammatory caspases, contributing in tuning inflammatory processes. Partial ablation of the Arg/N-degron pathway greatly increases IL-1β secretion, indicating the importance of this ubiquitous pathway in the initiation and resolution of inflammation. Thus, we propose a model wherein the Arg/N-degron pathway participates in the control of inflammation in two ways: in the generation of inflammatory signals by the degradation of inhibitory anti-inflammatory domains and as an “off switch” for inflammatory responses through the selective degradation of proinflammatory fragments.

Caspase-11 contributes to pulmonary host defense against Klebsiella pneumoniae and local activation of coagulation

Klebsiella (K.) pneumoniae is a common cause of gram-negative pneumonia and sepsis. Caspase-11 is an intracellular receptor for lipopolysaccharide and regulates pyroptosis, a specific form of inflammatory cell death, which aids in host defense against intracellular gram-negative bacteria. Recently, caspase-11 has also been implicated in blood coagulation. Previously, we found that local fibrin formation contributes to protective immunity against Klebsiella infection of the lung. The aim of the present study was to determine the role of caspase-11 in host defense during K. pneumoniae-evoked pneumonia and sepsis. Therefore, we infected wild-type and caspase-11-deficient (Casp11^-/-) mice with a low-dose K. pneumoniae via the airways to induce a gradually evolving pneumosepsis. Casp11^-/- mice displayed increased bacterial numbers in the lung 12 h and 48 h after inoculation. Analysis of pulmonary IL-1α, IL-1β, and TNF levels showed reduced IL-1α levels in bronchoalveolar lavage fluid and increased TNF levels in the lung of Casp11^-/- mice at 48 h after inoculation. Lung γH2AX staining (marker for cell death), lung pathology and neutrophil influx in the lung, as well as bacterial dissemination and organ damage, however, were not altered in Casp11^-/- mice after Klebsiella infection. Strikingly, analysis of cross-linked fibrin and D-dimer (markers for coagulation) revealed significantly less fibrin formation in the lungs of Casp11^-/- mice at either time point after Klebsiella infection. These data reveal that caspase-11 contributes to protective immunity against K. pneumoniae possibly by activation of blood coagulation in the lung.

NLRP3 level in cerebrospinal fluid of patients with neuromyelitis optica spectrum disorders: Increased levels and association with disease severity

BACKGROUND

Neuromyelitis optica spectrum disorder (NMOSD) and MS are the most common autoimmune inflammatory demyelinating diseases of the CNS. However, the mechanisms of pathogenesis are still unclear. nucleotide-binding leucine-rich repeat (NLR) family pyrin domain containing 3 (NLRP3), an important protein of the innate immune system that is activated by mitochondrial DNA (mtDNA), has been reported to be associated with various autoimmune disorders.

OBJECTIVE

To assess the levels of cerebrospinal fluid (CSF) NLRP3, mtDNA and inflammation-associated cytokines (IL-1β, IL-6 and IL-17) in patients with NMOSD and MS, and to examine the correlations between these factors.

METHODS

28 NMOSD patients, 15 MS patients, and 16 controls with non-inflammatory neurological diseases were recruited. NLRP3 inflammasome, IL-1β, IL-6 and IL-17 were measured by ELISA. CSF extracellular mtDNA was measured by qPCR. The severity of clinical presentation was evaluated by EDSS score.

RESULTS

CSF levels of NLRP3, mtDNA, IL-1β, IL-6 and IL-17 were higher in NMOSD patients than in controls. Elevated CSF NLRP3, mtDNA and IL-6 were found in MS patients compared with controls. CSF NLRP3 and IL-6 levels were significantly higher in NMOSD patients than in MS patients. The EDSS scores of NMOSD patients during relapse were positively correlated with CSF NLRP3 and mtDNA.

CONCLUSION

Our findings suggest that CSF levels of the NLRP3 inflammasome may serve as a diagnostic biomarker for distinguishing NMOSD and MS. Pyroptosis mediated by the NLRP3 inflammasome following mitochondrial damage may play an important role in the pathogenesis of these neuroinflammatory disorders, especially NMOSD.

Caspase-1 as a regulatory molecule of lipid metabolism

Caspase-1 is an evolutionarily conserved inflammatory mediated enzyme that cleaves and activates inflammatory cytokines. It can be activated through the assembly of inflammasome and its major effect is to activate the pro-inflammatory cytokines; interleukin 1β (IL-1β) and interluekine-18 (IL-18). In addition to IL-1β and IL-8, several lines of evidence showed that caspase-1 targets the substrates that are involved in different metabolic pathways, including lipid metabolism. Caspase-1 regulates lipid metabolism through cytokine dependent or cytokine independent regulation of genes that involved in lipid metabolism and its regulation. To date, there are several reports on the role of caspase-1 in lipid metabolism. Therefore, this review is aimed to summarize the role of caspase-1 in lipid metabolism and its regulation.

Regulation of efferocytosis by caspase-dependent apoptotic cell death in atherosclerosis

During the growing process of the atherosclerotic lesions, lipid-filled macrophage foam cells form, accumulate, and ultimately undergo apoptotic death. If the apoptotic foam cells are not timely removed, they may undergo secondary necrosis, and form a necrotic lipid core which renders the plaque unstable and susceptible to rupture. Therefore, the non-lipid-filled fellow macrophages, as the main phagocytic cells in atherosclerotic lesions, need to effectively remove the apoptotic foam cells. In general, in apoptotic macrophages, caspases are the central regulators of several key processes required for their efficient efferocytosis. The processes include the generation of "Find-Me" signals (such as adenosine triphosphate/uridine triphosphate, fractalkine, lysophosphatidylcholine, and sphingosine-1-phosphate) for the recruitment of viable macrophages, generation of the "Eat-Me" signals (for example, phosphatidylserine) for the engulfment process, and, finally, release of anti-inflammatory mediators (including transforming factor β and interleukin-10) as a tolerance-enhancing and an anti-inflammatory response, and for the motile behavior of the apoptotic cell. The caspase-dependent mechanisms are operative also in apoptotic macrophages driving the atherogenesis. In this review, we explore the role of the molecular pathways related to the caspase-dependent events in efferocytosis in the context of atherosclerosis. Understanding of the molecular mechanisms of apoptotic cell death in atherosclerotic lesions is essential when searching for new leads to treat atherosclerosis.

NLRP3 Inflammasome Mediated Interleukin-1β Production in Cancer-Associated Fibroblast Contributes to ALA-PDT for Cutaneous Squamous Cell Carcinoma

Background

Long-term tumor control following PDT is a result of its direct effect on tumor and vasculature in combination with induction of inflammatory-reactions upregulating the immune system. When PDT induces necrosis of tumors and vascular system, an immune cascade can be initiated to release all kinds of cytokines including IL1β. This further leads to the activation of inflammatory-cells and hence death of tumor cells.

Methods

Ultraviolet irradiation was used to induce cSCC mice model, gene chip was used to screen inflammatory cytokines, qPCR, ELISA and implanted tumor mice model were used to verify the changes and important role of interleukin-1β, and WB preliminarily explored the production mechanism of interleukin-1β.

Results

Inflammatory cytokines and receptors transcript screening identify IL1r1 as the top4. After ALA-PDT, IL1r1 and IL1β increased in patients' biopsies, principally in mesenchymal cells. In vivo, the inhibition of ALA-PDT on tumor growth of cutaneous squamous cell carcinoma (cSCC) mice in the group with intralesional injection of anti-IL1β mAb or caspase1-inhibitor was significantly weaker than the control groups. Furthermore, NLRP3-inflammasome and p-p65/p65 were elevated after ALA-PDT mediated IL1β production in cancer-associated-fibroblasts.

Discussion

By means of activating NLRP3-inflammasome with IL1β production in CAFs, PDT stimulates local acute-inflammatory-response, which further promotes PDT effect for cSCC.

Necrosis Contributes to the Development of Hypertension in Male, but Not Female, Spontaneously Hypertensive Rats

Necrosis is a pathological form of cell death that induces an inflammatory response, and immune cell activation contributes to the development and maintenance of hypertension. Necrosis was measured in kidney, spleen, and aorta of 12- to 13-week-old male and female SHRs (spontaneously hypertensive rats); male SHRs had greater renal necrotic cell death than female SHRs. Because male SHRs have a higher blood pressure (BP) and a more proinflammatory T-cell profile than female SHRs, the current studies tested the hypothesis that greater necrotic cell death in male SHRs exacerbates increases in BP and contributes to the proinflammatory T-cell profile. Male and female SHRs were randomized to receive vehicle or Necrox-5-a cell permeable inhibitor of necrosis-from 6 to 12 weeks of age or from 11 to 13 weeks of age. In both studies, Necrox-5 decreased renal necrosis and abolished the sex difference. Treatment with Necrox-5 beginning at 6 weeks of age attenuated maturation-induced increases in BP in male SHR; BP in female SHR was not altered by Necrox-5 treatment. Necrox-5 decreased proinflammatory renal T cells in both sexes, although sex differences were maintained. Administration of Necrox-5 for 2 weeks in SHR with established hypertension resulted in a small but significant decrease in BP in males with no effect in females. These results suggest that greater necrotic cell death in male SHR exacerbates maturation-induced increases in BP with age contributing to sex differences in BP. Moreover, although necrosis is proinflammatory, it is unlikely to explain sex differences in the renal T-cell profile.

CD200-CD200R Interaction: An Important Regulator After Stroke

The high mortality and morbidity rate of stroke is a chronic problem that plagues human society. The activation of microglia is one of the principal reasons why neuroinflammation induces cerebral dysfunction. Because of their vital functions in the regulation of neuroinflammation, microglia constitute an important target for stroke. Given that there is an innate self-preservation mechanism between neurons and microglia, the transmembrane glycoproteins on the surface of their membranes, namely CD200 and CD200R, have become a popular topic of research. Numerous studies have demonstrated that CD200-CD200R interaction, microglial activation, and poststroke neuroinflammatory damage are inextricably linked. In this review, we describe the above relationship from a new perspective. We specifically focus on neuroinflammation after stroke. The role of crosstalk of CD200-CD200R inhibitory immune ligand receptors in immune regulation will also be illustrated. Thus, we will see how poststroke injury can be influenced by the CD200-CD200R crosstalk. Finally, we will discuss the possibility of clinical application of the result of CD200-CD200R interaction to manage neuroinflammatory injury after stroke.

Opportunities and challenges for the development of covalent chemical immunomodulators

Compounds that react irreversibly with cysteines have reemerged as potent and selective tools for altering protein function, serving as chemical probes and even clinically approved drugs. The exquisite sensitivity of human immune cell signaling pathways to oxidative stress indicates the likely, yet still underexploited, general utility of covalent probes for selective chemical immunomodulation. Here, we provide an overview of immunomodulatory cysteines, including identification of electrophilic compounds available to label these residues. We focus our discussion on three protein classes essential for cell signaling, which span the 'druggability' spectrum from amenable to chemical probes (kinases), somewhat druggable (proteases), to inaccessible (phosphatases). Using existing inhibitors as a guide, we identify general strategies to guide the development of covalent probes for selected undruggable classes of proteins and propose the application of such compounds to alter immune cell functions.

Gasdermin D Protects from Melioidosis through Pyroptosis and Direct Killing of Bacteria

Gasdermin D (GSDMD) cleavage by caspase-1 or caspase-11 inflammasomes triggers pyroptosis, a lytic form of cell death protective against intracellular bacteria. In this study, we examine the role of GSDMD in a mouse model of melioidosis. Gsdmd^-/- mice were more susceptible than wild-type mice to intranasal infection with Burkholderia thailandensis Production of IL-18, but not IL-1β, was decreased in Gsdmd^-/- infected mice. Despite lower IL-18, IFN-γ was produced in similar amounts in wild-type and Gsdmd^-/- mice. In vitro, secretion of both IL-1β and IL-18 by macrophages or dendritic cells infected with B. thailandensis was dependent on GSDMD. Surprisingly, wild-type or GSDMD-deficient neutrophils secreted similar amounts of IL-1β, suggesting these cells may be the source of the GSDMD-independent IL-1β detected in vivo. Recombinant GSDMD was able to directly kill B. thailandensis in vitro upon processing by active caspase-1. Moreover, bacteria harvested from wild-type, but not Gsdmd^-/- , macrophages were more susceptible to the microbicidal effect of hydrogen peroxide or human β-defensin-3. Finally, we provide evidence that pyroptosis of in vitro infected macrophages is directly microbicidal. Taken together, these results indicate that the protective action of GSDMD in melioidosis is primarily due to induction of pyroptosis and direct killing of bacteria rather than production of cytokines.

Effects of cross-fostering and developmental exposure to mixtures of environmental contaminants on hepatic gene expression in prepubertal 21 days old and adult male Sprague-Dawley rats

The notion that adverse health effects produced by exposure to environmental contaminants (EC) may be modulated by the presence of non-chemical stressors is gaining attention. Previously, our lab demonstrated that cross-fostering (adoption of a litter at birth) acted as a non-chemical stressor that amplified the influence of developmental exposure to EC on the glucocorticoid stress-response in adult rats. Using liver from the same rats, the aim of the current study was to investigate whether cross-fostering might also modulate EC-induced alterations in hepatic gene expression profiles. During pregnancy and nursing, Sprague-Dawley dams were fed cookies laced with corn oil (control, C) or a chemical mixture (M) composed of polychlorinated biphenyls (PCB), organochlorine pesticides (OCP), and methylmercury (MeHg), at 1 mg/kg/day. This mixture simulated the contaminant profile reported in maternal human blood. At birth, some control and M treated litters were cross-fostered to form two additional groups with different biological/nursing mothers (CC and MM). The hepatic transcriptome was analyzed by DNA microarray in male offspring at postnatal days 21 and 78-86. Mixture exposure altered the expression of detoxification and energy metabolism genes in both age groups, but with different sets of genes affected at day 21 and 78-86. Cross-fostering modulated the effects of M on gene expression pattern (MM vs M), as well as expression of energy metabolism genes between control groups (CC vs C). In conclusion, while describing short and long-term effects of developmental exposure to EC on hepatic transcriptomes, these cross-fostering results further support the consideration of non-chemical stressors in EC risk assessments.

Exhaustive acute exercise-induced ER stress is attenuated in IL-6-knockout mice

The endoplasmic reticulum (ER) stress and inflammation relationship occurs at different levels and is essential for the adequate homeostatic function of cellular systems, becoming harmful when chronically engaged. Intense physical exercise enhances serum levels of interleukin 6 (IL-6). In response to a chronic exhaustive physical exercise protocol, our research group verified an increase of the IL-6 concentration and ER stress proteins in extensor digitorium longus (EDL) and soleus. Based on these results, we hypothesized that IL-6-knockout mice would demonstrate a lower modulation in the ER stress proteins compared to the wild-type mice. To clarify the relationship between exercise-induced IL-6 increased and ER stress, we studied the effects of an acute exhaustive physical exercise protocol on the levels of ER stress proteins in the skeletal muscles of IL-6-knockout (KO) mice. The WT group displayed a higher exhaustion time compared to the IL-6 KO group. After 1 h of the acute exercise protocol, the serum levels of IL-6 and IL-10 were enhanced in the WT group. Independent of the experimental group, the CHOP and cleaved caspase 12/total caspase 12 ratio in EDL as well as ATF6 and CHOP in soleus were sensitive to the acute exercise protocol. Compared to the WT group, the oscillation patterns over time of BiP in EDL and soleus as well as of peIF2-alpha/eIF2-alpha ratio in soleus were attenuated for the IL-6 KO group. In conclusion, IL-6 seems to be related with the ER stress homeostasis, once knockout mice presented attenuation of BiP in EDL and soleus as well as of pEiF2-alpha/EiF2-alpha ratio in soleus after the acute exhaustive physical exercise protocol.

Interaction between caspase-3 and caspase-5 in the stretch-induced programmed cell death in the human periodontal ligament cells

In our previous studies, programmed cell death (PCD) was induced in human periodontal ligament (PDL) cells, through activation of caspase-3 and upregulation of CASP5 gene (encoding caspase-5 protein), in response to mechanical stretch loading. The aim of this study is to explore the relationship between the inflammatory caspase, caspase-5, and the apoptotic executioner protein, caspase-3, in human PDL cells. Here, we found that cyclic stretching upregulated the activity and the protein expression level of caspase-3 and -5 and the addition of the caspase-3 inhibitor or caspase-5 inhibitor significantly inhibited the stretch-induced PCD. Meanwhile, the inhibition of caspase-5 inhibited the activation of caspase-3 and vice versa. The result of coimmunoprecipitation also demonstrated that the expression of caspase-3 was immunoprecipitated with caspase-5. Thus, our study revealed that the in vitro application of cyclic stretching induced PCD by activation of caspase-3 and -5 in human PDL cells, and these two caspases could interact with each other after mechanical stretch loading. The study may facilitate further studies on the mechanism of stretch-induced PCD and help us understand the force-related periodontal homeostasis and remodeling better.

Bcl-2 Inhibition to Overcome Resistance to Chemo- and Immunotherapy

Abstract: According to the World Health Organization (WHO), cancer is a leading cause of death worldwide. The identification of novel targets for cancer treatment is an area of intense work that has led Bcl-2 over-expression to be proposed as one of the hallmarks of cancer and Bcl-2 inhibition as a promising strategy for cancer treatment. In this review, we describe the different pathways related to programmed cell death, the role of Bcl-2 family members in apoptosis resistance to anti-cancer treatments, and the potential utility of Bcl-2 inhibitors to overcome resistance to chemo- and immunotherapy.

The inflammasome in leprosy skin lesions: an immunohistochemical evaluation

Objective

Leprosy is a chronic infectious disease presenting with a spectrum of clinical manifestations that correspond to the type of immune response that develops in the host. Factors that may be involved in this process include inflammasomes, cytosolic proteins responsible for the activation of caspase 1, IL-1β and IL-18 secretion, and induction of a type of death called pyroptosis.

Patients and methods

We evaluated the expression of inflammasome markers (nucleotide-binding oligomerization domain-like receptor containing pyrin domain 1 [NLRP1], nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 [NLRP3], caspase 1, IL-1β, and IL-18) by immunohistochemistry in 43 samples of skin lesions of leprosy patients from the groups indeterminate (I) leprosy (13 patients), tuberculoid (TT) leprosy (15 patients), and lepromatous leprosy (LL; 15 patients).

Results

The evaluated markers were most upregulated in LL lesions, followed by lesions of TT leprosy and I leprosy. Differences were statistically significant between the I leprosy and LL leprosy forms and between the I leprosy and TT leprosy forms. Positive and significant correlations were found between IL-18 and caspase 1 in LL (r=0.7516, P=0.0012) and TT leprosy (r=0.7366, P=0.0017). In I leprosy, correlations were detected between caspase 1 and IL-1β (r=0.6412, P=0.0182), NLRP1 and IL-18 (r=0.5585, P=0.473), NLRP3 and IL-18 (r=0.6873, P=0.0094), and NLRP1 and NLRP3 (r=0.8040, P=0.0009).

Conclusion

The expression of inflammasome markers in LL lesions indicates the ineffectiveness of this protein complex in controlling the infection. Caspase 1 may be involved in the pyroptotic cell death in the lepromatous form of the disease. Inflammasomes may act together in the initial phase of I leprosy; this phenomenon may influence the clinical outcome of the disease.

Up-regulation of TRAF2 inhibits chondrocytes apoptosis in lumbar facet joint osteoarthritis

Tumor necrosis factor receptor-associated factor 2 (TRAF2) has been demonstrated that it plays a significant role in cell death receptor signal transduction. The purpose of this study was to investigate the expression of TRAF2 and its possible role in FJOA. We observed an up-regulation of TRAF2 in FJOA by immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) compared to normal tissues. In vitro, we used TNF-α to stimulate Human SW1353 chondrosarcoma cells to establish the chondrocytes injury model. Western blot analysis revealed significant expression of TRAF2 and cleaved caspase-3/8 in SW1353 cells. Co-localization of TRAF2/cleaved caspase-3/8 was detected in the cells injury model by double-labeling immunofluorescent staining. We demonstrated a possible anti-apoptotic effect of TRAF2 in chondrocyte apoptosis in FJOA by knockdown of its expression with siRNA. Moreover, TRAF2 knockdown was demonstrated to enhance TNF-α-induced apoptosis by flow cytometry assay. In conclusion, our results show that the up-regulation of TRAF2 may play an important role in the inhibition of chondrocyte apoptosis of FJOA.

Mechanism of gasdermin D recognition by inflammatory caspases and their inhibition by a gasdermin D-derived peptide inhibitor

The inflammasomes are signaling platforms that promote the activation of inflammatory caspases such as caspases-1, -4, -5, and -11. Recent studies identified gasdermin D (GSDMD) as an effector for pyroptosis downstream of the inflammasome signaling pathways. Cleavage of GSDMD by inflammatory caspases allows its N-terminal domain to associate with membrane lipids and form pores that induce pyroptotic cell death. Despite the important role of GSDMD in pyroptosis, the molecular mechanisms of GSDMD recognition and cleavage by inflammatory caspases that trigger pyroptosis are poorly understood. Here, we demonstrate that the catalytic domains of inflammatory caspases can directly bind to both the full-length GSDMD and its cleavage site peptide, FLTD. A GSDMD-derived inhibitor, N-acetyl-Phe-Leu-Thr-Asp-chloromethylketone (Ac-FLTD-CMK), inhibits GSDMD cleavage by caspases-1, -4, -5, and -11 in vitro, suppresses pyroptosis downstream of both canonical and noncanonical inflammasomes, as well as reduces IL-1β release following activation of the NLRP3 inflammasome in macrophages. By contrast, the inhibitor does not target caspase-3 or apoptotic cell death, suggesting that Ac-FLTD-CMK is a specific inhibitor for inflammatory caspases. Crystal structure of caspase-1 in complex with Ac-FLTD-CMK reveals extensive enzyme-inhibitor interactions involving both hydrogen bonds and hydrophobic contacts. Comparison with other caspase-1 structures demonstrates drastic conformational changes at the four active-site loops that assemble the catalytic groove. The present study not only contributes to our understanding of GSDMD recognition by inflammatory caspases but also reports a specific inhibitor for these caspases that can serve as a tool for investigating inflammasome signaling.

Perilla aldehyde attenuates CUMS-induced depressive-like behaviors via regulating TXNIP/TRX/NLRP3 pathway in rats

BACKGROUND

Current evidence supports that inflammatory reaction in the hippocampus is a potential cause of major depressive disorder (MDD). Perilla aldehyde (PAH), a major constituent from Perilla frutescens, has been reported to have anti-inflammatory and anti-oxidant activity. The aim of this study is to explore the antidepressant-like effect and the underlying mechanism of PAH on the rats model induced by chronic unpredictable mild stress (CUMS).

METHODS

CUMS rats model was built to tested their depressive-like behaviors. The levels of pro-inflammatory cytokines were tested. Proteins were analyzed by Western blot and Immunohistochemistry.

RESULTS

We found that treatment with PAH (20, 40 mg/kg) and fluoxetine (FLU, 10 mg/kg) significantly improved the sucrose consumption, immobility time in forced swim test (FST), as well as locomotor activity in open-field test (OFT). The levels of pro-inflammatory cytokines in hippocampus were also suppressed effectively by PAH and FLU administration. Western blot analysis showed the up-regulated levels of TXNIP, NLRP3, Cleaved caspase-1 and p-NF-κB p65 in the hippocampus in rats exposed to CUMS paradigm, while different degrees of down-regulation in their expression were detected after PAH (20, 40 mg/kg) and FLU (10 mg/kg) treatment respectively. The results from histopathological examination further demonstrated that PAH (20, 40 mg/kg) and FLU (10 mg/kg) treatment reversed the alteration of TRX, NLRP3 and Cleaved caspase-1 induced by CUMS procedure.

CONCLUSIONS

Our results demonstrated that PAH exhibited antidepressant-like effect in CUMS-induced rats model of depression, which might be mediated by TXNIP/TRX/NLRP3 pathway.

Learning on the Fly: The Interplay between Caspases and Cancer

The ease of genetic manipulation, as well as the evolutionary conservation of gene function, has placed Drosophila melanogaster as one of the leading model organisms used to understand the implication of many proteins with disease development, including caspases and their relation to cancer. The family of proteases referred to as caspases have been studied over the years as the major regulators of apoptosis: the most common cellular mechanism involved in eliminating unwanted or defective cells, such as cancerous cells. Indeed, the evasion of the apoptotic programme resulting from caspase downregulation is considered one of the hallmarks of cancer. Recent investigations have also shown an instrumental role for caspases in non-lethal biological processes, such as cell proliferation, cell differentiation, intercellular communication, and cell migration. Importantly, malfunction of these essential biological tasks can deeply impact the initiation and progression of cancer. Here, we provide an extensive review of the literature surrounding caspase biology and its interplay with many aspects of cancer, emphasising some of the key findings obtained from Drosophila studies. We also briefly describe the therapeutic potential of caspase modulation in relation to cancer, highlighting shortcomings and hopeful promises.