Enhanced bacterial clearance and sepsis resistance in caspase-12-deficient mice

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.

Caspase-12 is Expressed in Purkinje Neurons and Prevents Psychiatric-Like Behavior in Mice

Caspase-12 is a caspase family member for which functions in regulating cell death and inflammation have previously been suggested. In this study, we used caspase-12 lacZ reporter mice to elucidate the expression pattern of caspase-12 in order to obtain an idea about its possible in vivo function. Strikingly, these reporter mice showed that caspase-12 is expressed explicitly in Purkinje neurons of the cerebellum. As this observation suggested a function for caspase-12 in Purkinje neurons, we analyzed the brain and behavior of caspase-12 deficient mice in detail. Extensive histological analyses showed that caspase-12 was not crucial for establishing cerebellum structure or for maintaining Purkinje cell numbers. We then performed behavioral tests to investigate whether caspase-12 deficiency affects memory, motor, and psychiatric functions in mice. Interestingly, while the absence of caspase-12 did not affect memory and motor function, caspase-12 deficient mice showed depression and hyperactivity tendencies, together resembling manic behavior. Next, suggesting a possible molecular mechanistic explanation, we showed that caspase-12 deficient cerebella harbored diminished signaling through the brain-derived neurotrophic factor/tyrosine kinase receptor B/cyclic-AMP response binding protein axis, as well as strongly enhanced expression of the neuronal activity marker c-Fos. Thus, our study establishes caspase-12 expression in mouse Purkinje neurons and opens novel avenues of research to investigate the role of caspase-12 in regulating psychiatric behavior.

Evolution of Caspases and the Invention of Pyroptosis

The protein scaffold that includes the caspases is ancient and found in all domains of life. However, the stringent specificity that defines the caspase biologic function is relatively recent and found only in multicellular animals. During the radiation of the Chordata, members of the caspase family adopted roles in immunity, events coinciding with the development of substrates that define the modern innate immune response. This review focuses on the switch from the non-inflammatory cellular demise of apoptosis to the highly inflammatory innate response driven by distinct members of the caspase family, and the interplay between these two regulated cell death pathways.

Signaling pathways in uric acid homeostasis and gout: From pathogenesis to therapeutic interventions

Uric acid is a product of purine degradation, and uric acid may have multiple physiologic roles, including the beneficial effects as an antioxidant and neuroprotector, maintenance of blood pressure during low salt ingestion, and modulation of immunity. However, overproduction of metabolic uric acid, and/or imbalance of renal uric acid secretion and reabsorption, and/or underexcretion of extrarenal uric acid, e.g. gut, will contribute to hyperuricemia, which is a common metabolic disease. Long-lasting hyperuricemia can induce the formation and deposition of monosodium urate (MSU) crystals within the joints and periarticular structures. MSU crystals further induce an acute, intensely painful, and sterile inflammation conditions named as gout by NLRP3 inflammasome-mediated cleavage of pro-IL-1β to bioactive IL-1β. Moreover, hyperuricemia and gout are associated with multiple cardiovascular and renal disorders, e.g., hypertension, myocardial infarction, stroke, obesity, hyperlipidemia, type 2 diabetes mellitus and chronic kidney disease. Although great efforts have been made by scientists of modern medicine, however, modern therapeutic strategies with a single target are difficult to exert long-term positive effects, and even some of these agents have severe adverse effects. The Chinese have used the ancient classic prescriptions of traditional Chinese medicine (TCM) to treat metabolic diseases, including gout, by multiple targets, for more than 2200 years. In this review, we discuss the current understanding of urate homeostasis, the pathogenesis of hyperuricemia and gout, and both modern medicine and TCM strategies for this commonly metabolic disorder. We hope these will provide the good references for treating hyperuricemia and gout.

Endoplasmic reticulum stress and its role in various neurodegenerative diseases

The Endoplasmic reticulum (ER), a critical cellular organelle, maintains cellular homeostasis by regulating calcium levels and orchestrating essential functions such as protein synthesis, folding, and lipid production. A pivotal aspect of ER function is its role in protein quality control. When misfolded proteins accumulate within the ER due to factors like protein folding chaperone dysfunction, toxicity, oxidative stress, or inflammation, it triggers the Unfolded protein response (UPR). The UPR involves the activation of chaperones like calnexin, calreticulin, glucose-regulating protein 78 (GRP78), and Glucose-regulating protein 94 (GRP94), along with oxidoreductases like protein disulphide isomerases (PDIs). Cells employ the Endoplasmic reticulum-associated degradation (ERAD) mechanism to counteract protein misfolding. ERAD disruption causes the detachment of GRP78 from transmembrane proteins, initiating a cascade involving Inositol-requiring kinase/endoribonuclease 1 (IRE1), Activating transcription factor 6 (ATF6), and Protein kinase RNA-like endoplasmic reticulum kinase (PERK) pathways. The accumulation and deposition of misfolded proteins within the cell are hallmarks of numerous neurodegenerative diseases. These aberrant proteins disrupt normal neuronal signalling and contribute to impaired cellular homeostasis, including oxidative stress and compromised protein degradation pathways. In essence, ER stress is defined as the cellular response to the accumulation of misfolded proteins in the endoplasmic reticulum, encompassing a series of signalling pathways and molecular events that aim to restore cellular homeostasis. This comprehensive review explores ER stress and its profound implications for the pathogenesis and progression of neurodegenerative diseases.

The pathogenesis and potential therapeutic targets in sepsis

Sepsis is defined as "a life-threatening organ dysfunction caused by dysregulated host systemic inflammatory and immune response to infection." At present, sepsis continues to pose a grave healthcare concern worldwide. Despite the use of supportive measures in treating traditional sepsis, such as intravenous fluids, vasoactive substances, and oxygen plus antibiotics to eradicate harmful pathogens, there is an ongoing increase in both the morbidity and mortality associated with sepsis during clinical interventions. Therefore, it is urgent to design specific pharmacologic agents for the treatment of sepsis and convert them into a novel targeted treatment strategy. Herein, we provide an overview of the molecular mechanisms that may be involved in sepsis, such as the inflammatory response, immune dysfunction, complement deactivation, mitochondrial damage, and endoplasmic reticulum stress. Additionally, we highlight important targets involved in sepsis-related regulatory mechanisms, including GSDMD, HMGB1, STING, and SQSTM1, among others. We summarize the latest advancements in potential therapeutic drugs that specifically target these signaling pathways and paramount targets, covering both preclinical studies and clinical trials. In addition, this review provides a detailed description of the crosstalk and function between signaling pathways and vital targets, which provides more opportunities for the clinical development of new treatments for sepsis.

Apoptotic caspase-7 activation inhibits non-canonical pyroptosis by GSDMB cleavage

GSDMB is associated with several inflammatory diseases, such as asthma, sepsis and colitis. GZMA is released by cytotoxic lymphocytes and cleaves GSDMB at the K244 site and to induce GSDMB N-terminus dependent pyroptosis. This cleavage of GSDMB is noncell autonomous. In this study, we demonstrated that the GSDMB-N domain (1-91 aa) was important for a novel cell-autonomous function and that GSDMB could bind caspase-4 and promote noncanonical pyroptosis. Furthermore, activated caspase-7 cleaved GSDMB at the D91 site to block GSDMB-mediated promotion of noncanonical pyroptosis during apoptosis. Mechanistically, the cleaved GSDMB-C-terminus (92-417 aa) binds to the GSDMB-N-terminus (1-91 aa) to block the function of GSDMB. During E. coli and S. Typhimurium infection, inhibition of the caspase-7/GSDMB axis resulted in more pyroptotic cells. Furthermore, in a septic mouse model, caspase-7 inhibition or deficiency in GSDMB-transgenic mice led to more severe disease phenotypes. Overall, we demonstrate that apoptotic caspase-7 activation inhibits non-canonical pyroptosis by cleaving GSDMB and provide new targets for sepsis therapy.

Caspases help to spread the message via extracellular vesicles

Cell-cell communication is an essential aspect of multicellular life, key for coordinating cell proliferation, growth, and death in response to environmental changes. Whilst caspases are well-known for facilitating apoptotic and pyroptotic cell death, several recent investigations are uncovering new roles for these enzymes in biological scenarios requiring long-range intercellular signalling mediated by extracellular vesicles (EVs). EVs are small membrane-bound nanoparticles released from cells that may carry and deliver cargo between distant cells, thus helping to coordinate their behaviour. Intriguingly, there is emerging evidence indicating a key contribution of caspases in the biogenesis of EVs, the selection of their cargo content, and EV uptake/function in recipient cells. Here, we discuss the latest findings supporting the interplay between caspases and EVs, and the biological relevance of this molecular convergence for cellular signalling, principally in non-apoptotic scenarios.

Wild oyster population resistance to ocean acidification adversely affected by bacterial infection

The carbon dioxide induced ocean acidification (OA) process is well known to have profound effects on physiology, survival and immune responses in marine organisms, and particularly calcifiers including edible oysters. At the same time, some wild populations could develop a complex and sophisticated immune system to cope with multiple biotic and abiotic stresses, such as bacterial infections and OA, over the long period of coevolution with the environment. However, it is unclear how immunological responses and the underlying mechanisms are altered under the combined effect of OA and bacterial infection, especially in the ecologically and economically important edible oysters. Here, we collected the wild population of oyster species Crassostrea hongkongensis (the Hong Kong oyster) from their native estuarine area and carried out a bacterial challenge with the worldwide pervasive pathogen of human foodborne disease, Vibrio parahaemolyticus, to investigate the host immune responses and molecular mechanisms under the high-CO₂ and low pH-driven OA conditions. The wild population had a high immune resistance to OA, but the resistance is compromised under the combined effect of OA and bacterial infection both in vivo or in vitro. We classified all transcriptomic genes based on expression profiles and functional pathways and identified the specifically switched on and off genes and pathways under combined effect. These genes and pathways were mainly involved in multiple immunological processes including pathogen recognition, immune signal transduction and effectors. This work would help understand how the immunological function and mechanism response to bacterial infection in wild populations and predict the dynamic distribution of human health-related pathogens to reduce the risk of foodborne disease under the future climate change scenario.

Making the head: Caspases in life and death

The term apoptosis, as a way of programmed cell death, was coined a half century ago and since its discovery the process has been extensively investigated. The anatomy and physiology of the head are complex and thus apoptosis has mostly been followed in separate structures, tissues or cell types. This review aims to provide a comprehensive overview of recent knowledge concerning apoptosis-related molecules involved in the development of structures of head with a particular focus on caspases, cysteine proteases having a key position in apoptotic pathways. Since many classical apoptosis-related molecules, including caspases, are emerging in several non-apoptotic processes, these were also considered. The largest organ of the head region is the brain and its development has been extensively investigated, including the roles of apoptosis and related molecules. Neurogenesis research also includes sensory organs such as the eye and ear, efferent nervous system and associated muscles and glands. Caspases have been also associated with normal function of the skin and hair follicles. Regarding mineralised tissues within craniofacial morphogenesis, apoptosis in bones has been of interest along with palate fusion and tooth development. Finally, the role of apoptosis and caspases in angiogenesis, necessary for any tissue/organ development and maintenance/homeostasis, are discussed. Additionally, this review points to abnormalities of development resulting from improper expression/activation of apoptosis-related molecules.

Endoplasmic Reticulum Stress and Cancer: Could Unfolded Protein Response Be a Druggable Target for Cancer Therapy?

Unfolded protein response (UPR) is an adaptive response which is used for re-establishing protein homeostasis, and it is triggered by endoplasmic reticulum (ER) stress. Specific ER proteins mediate UPR activation, after dissociation from chaperone Glucose-Regulated Protein 78 (GRP78). UPR can decrease ER stress, producing an ER adaptive response, block UPR if ER homeostasis is restored, or regulate apoptosis. Some tumour types are linked to ER protein folding machinery disturbance, highlighting how UPR plays a pivotal role in cancer cells to keep malignancy and drug resistance. In this review, we focus on some molecules that have been revealed to target ER stress demonstrating as UPR could be a new target in cancer treatment.

Identification of heptapeptides targeting a lethal bacterial strain in septic mice through an integrative approach

Effectively killing pathogenic bacteria is key for the treatment of sepsis. Although various anti-infective drugs have been used for the treatment of sepsis, the therapeutic effect is largely limited by the lack of a specific bacterium-targeting delivery system. This study aimed to develop antibacterial peptides that specifically target pathogenic bacteria for the treatment of sepsis. The lethal bacterial strain Escherichia coli MSI001 was isolated from mice of a cecal ligation and puncture (CLP) model and was used as a target to screen bacterial binding heptapeptides through an integrative bioinformatics approach based on phage display technology and high-throughput sequencing (HTS). Heptapeptides binding to E. coli MSI001 with high affinity were acquired after normalization by the heptapeptide frequency of the library. A representative heptapeptide VTKLGSL (VTK) was selected for fusion with the antibacterial peptide LL-37 to construct the specific-targeting antibacterial peptide VTK-LL37. We found that, in comparison with LL37, VTK-LL37 showed prominent bacteriostatic activity and an inhibitive effect on biofilm formation in vitro. In vivo experiments demonstrated that VTK-LL37 significantly inhibited bacterial growth, reduced HMGB1 expression, alleviated lesions of vital organs and improved the survival of mice subjected to CLP modeling. Furthermore, membrane DEGP and DEGQ were identified as VTK-binding proteins by proteomic methods. This study provides a novel strategy for targeted pathogen killing, which is helpful for the treatment of sepsis in the era of precise medicine.

Caspase mechanisms in the regulation of inflammation

Regulated cell death is defined as genetically encoded pathways that lead towards the demise of cells. In mammals, cell demise can be either inflammatory or non-inflammatory, depending on whether the mechanism of death results in cell rupture or not. Inflammatory cell death can lead towards acute and chronic disease. Therefore, it becomes important to distinguish the mechanisms that result in these different inflammatory cell death outcomes. Apoptosis is a non-inflammatory form of cell death where cells resist rupture. In contrast, pyroptosis and necroptosis are inflammatory forms of cell death principally because of release of pro-inflammatory mediators from cells undergoing lysis. This review focusses on the mechanisms of these different cell death outcomes with specific emphasis on the caspase family of proteolytic enzymes.

PANoptosis: A Unique Innate Immune Inflammatory Cell Death Modality

Innate immunity is the first response to protect against pathogens and cellular insults. Pattern recognition receptors sense pathogen- and damage-associated molecular patterns and induce an innate immune response characterized by inflammation and programmed cell death (PCD). In-depth characterization of innate immune PCD pathways has highlighted significant cross-talk. Recent advances led to the identification of a unique inflammatory PCD modality called PANoptosis, which is regulated by multifaceted PANoptosome complexes that are assembled by integrating components from other PCD pathways. The totality of biological effects observed in PANoptosis cannot be accounted for by any other PCD pathway alone. In this review, we briefly describe mechanisms of innate immune cell death, including molecular mechanisms of PANoptosis activation and regulation. We also highlight the PANoptosomes identified to date and provide an overview of the implications of PANoptosis in disease and therapeutic targeting. Improved understanding of innate immune-mediated cell death, PANoptosis, is critical to inform the next generation of treatment strategies.

Pyroptosis: Role and Mechanisms in Cardiovascular Disease

Cardiovascular disease (CVD) is a common disease that poses a huge threat to human health. Irreversible cardiac damage due to cardiomyocyte death and lack of regenerative capacity under stressful conditions, ultimately leading to impaired cardiac function, is the leading cause of death worldwide. The regulation of cardiomyocyte death plays a crucial role in CVD. Previous studies have shown that the modes of cardiomyocyte death include apoptosis and necrosis. However, another new form of death, pyroptosis, plays an important role in CVD pathogenesis. Pyroptosis induces the amplification of inflammatory response, increases myocardial infarct size, and accelerates the occurrence of cardiovascular disease, and the control of cardiomyocyte pyroptosis holds great promise for the treatment of cardiovascular disease. In this paper, we summarized the characteristics, occurrence and regulation mechanism of pyroptosis are reviewed, and also discussed its role and mechanisms in CVD, such as atherosclerosis (AS), myocardial infarction (MI), arrhythmia and cardiac hypertrophy.

Focus on the Mechanisms and Functions of Pyroptosis, Inflammasomes, and Inflammatory Caspases in Infectious Diseases

Eukaryotic cells can initiate several distinct self-destruction mechanisms to display essential roles for the homeostasis maintenance, development, and survival of an organism. Pyroptosis, a key response mode in innate immunity, also referred to as caspase-1-dependent proinflammatory programmed necrotic cell death activated by human caspase-1/4/5, or mouse caspase-1/11, plays indispensable roles in response to cytoplasmic insults and immune defense against infectious diseases. These inflammatory caspases are employed by the host to eliminate pathogen infections such as bacteria, viruses, protozoans, and fungi. Gasdermin D requires to be cleaved and activated by these inflammatory caspases to trigger the pyroptosis process. Physiological rupture of cells results in the release of proinflammatory cytokines, the alarmins IL-1β and IL-18, symbolizing the inflammatory potential of pyroptosis. Moreover, long noncoding RNAs play direct or indirect roles in the upstream of the pyroptosis trigger pathway. Here, we review in detail recently acquired insights into the central roles of inflammatory caspases, inflammasomes, and pyroptosis, as well as the crosstalk between pyroptosis and long noncoding RNAs in mediating infection immunity and pathogen clearance.

Comprehensive expression analysis with cell-type-specific transcriptome in ALS-linked mutant SOD1 mice: Revisiting the active role of glial cells in disease

Non-cell autonomous mechanisms are involved in the pathogenesis of amyotrophic lateral sclerosis (ALS), an adult neurodegenerative disease characterized by selective motor neuron loss. While the emerging role of glial cells in ALS has been noted, the detailed cell-type-specific role of glial cells has not been clarified. Here, we examined mRNA expression changes using microarrays of the spinal cords of three distinct lines of mutant superoxide dismutase (SOD) 1 transgenic mice, an established ALS model. Our analysis used a transcriptome database of component cell types in the central nervous system (CNS), as well as SOD1 ^G93A cell-type transcriptomes. More than half of the differentially expressed genes (DEGs) were highly expressed in microglia, and enrichment analysis of DEGs revealed that immunological reactions were profoundly involved and some transcription factors were upregulated. Our analysis focused on DEGs that are highly expressed in each cell type, as well as chemokines, caspases, and heat shock proteins. Disease-associated microglial genes were upregulated, while homeostatic microglial genes were not, and galectin-3 (Mac2), a known activated microglial marker, was predicted to be ectopically expressed in astrocytes in mutant SOD1 mice. In mutant SOD1 mice, we developed a prediction model for the pathophysiology of different cell types related to TREM2, apolipoprotein E, and lipoproteins. Our analysis offers a viable resource to understand not only the molecular pathologies of each CNS constituent cell type, but also the cellular crosstalk between different cell types under both physiological and pathological conditions in model mice for various neurodegenerative diseases.

The Role of Caspase-12 in Retinal Bystander Cell Death and Innate Immune Responses against MCMV Retinitis

(1) Background: caspase-12 is activated during cytomegalovirus retinitis, although its role is presently unclear. (2) Methods: caspase-12^−/− (KO) or caspase-12^+/+ (WT) mice were immunosup eyes were analyzed by plaque assay, TUNEL assay, immunohistochemical staining, western blotting, and real-time PCR. (3) Results: increased retinitis and a more extensive virus spread were detected in the retina of infected eyes of KO mice compared to WT mice at day 14 p.i. Compared to MCMV injected WT eyes, mRNA levels of interferons α, β and γ were significantly reduced in the neural retina of MCMV-infected KO eyes at day 14 p.i. Although similar numbers of MCMV infected cells, similar virus titers and similar numbers of TUNEL-staining cells were detected in injected eyes of both KO and WT mice at days 7 and 10 p.i., significantly lower amounts of cleaved caspase-3 and p53 protein were detected in infected eyes of KO mice at both time points. (4) Conclusions: caspase-12 contributes to caspase-3-dependent and independent retinal bystander cell death during MCMV retinitis and may also play an important role in innate immunity against virus infection of the retina.

The impact of influenza pulmonary infection and inflammation on vagal bronchopulmonary sensory neurons

Influenza A virus (IAV) is rapidly detected in the airways by the immune system, with resident parenchymal cells and leukocytes orchestrating viral sensing and the induction of antiviral inflammatory responses. The airways are innervated by heterogeneous populations of vagal sensory neurons which also play an important role in pulmonary defense. How these neurons respond to IAV respiratory infection remains unclear. Here, we use a murine model to provide the first evidence that vagal sensory neurons undergo significant transcriptional changes following a respiratory IAV infection. RNA sequencing on vagal sensory ganglia showed that IAV infection induced the expression of many genes associated with an antiviral and pro-inflammatory response and this was accompanied by a significant increase in inflammatory cell recruitment into the vagal ganglia. Assessment of gene expression in single-vagal sensory neurons confirmed that IAV infection induced a neuronal inflammatory phenotype, which was most prominent in bronchopulmonary neurons, and also evident in some neurons innervating other organs. The altered transcriptome could be mimicked by intranasal treatment with cytokines and the lung homogenates of infected mice, in the absence of infectious virus. These data argue that IAV pulmonary infection and subsequent inflammation induces vagal sensory ganglia neuroinflammation and this may have important implications for IAV-induced morbidity.

Human Caspase 12 Enhances NF-κB Activity through Activation of IKK in Nasopharyngeal Carcinoma Cells

Human nasopharyngeal carcinoma (NPC) is a highly invasive cancer associated with proinflammation. Caspase-12 (Casp12), an inflammatory caspase, is implicated in the regulation of NF-κB-mediated cellular invasion via the modulation of the IκBα protein in NPC cells. However, the effect mechanisms of Casp12 need to be elucidated. NPC cells were transfected with the full length of human Casp12 cDNA (pC12) and the effect of human Casp12 (hCasp12) on the NF-κB activity was investigated. We found ectopic expression of hCasp12 increased the NF-κB activity accompanied by an increased p-IκBα expression and a decreased IκBα expression. Treatment of BMS, a specific IKK inhibitor, and pC12-transfected cells markedly decreased the NF-κB activity and ameliorated the expression level of IκBα reduced by hCasp12. Co-immunoprecipitation assays validated the physical interaction of hCasp12 with IKKα/β, but not with NEMO. Furthermore, the NF-κB activity of ΔCasp12-Q (a mutated catalytic of hCasp12) transfected cells was concentration-dependently induced, but lower than that of hCasp12-transfected cells. Importantly, the hCasp12-mediated NF-kB activity was enhanced by TNFα stimulation. That indicated a role of the catalytic motif of hCasp12 in the regulation of the NF-κB activity. This study indicated hCasp12 activated the NF-κB pathway through the activation of IKK in human NPC cells.

New Insights into Pathomechanisms and Treatment Possibilities for Lung Silicosis

Inhalation of silica particles is an environmental and occupational cause of silicosis, a type of pneumoconiosis. Development of the lung silicosis is a unique process in which the vicious cycle of ingestion of inhaled silica particles by alveolar macrophages and their release triggers inflammation, generation of nodular lesions, and irreversible fibrosis. The pathophysiology of silicosis is complex, and interactions between the pathomechanisms have not been completely understood. However, elucidation of silica-induced inflammation cascades and inflammation-fibrosis relations has uncovered several novel possibilities of therapeutic targeting. This article reviews new information on the pathophysiology of silicosis and points out several promising treatment approaches targeting silicosis-related pathways.

Khoe-San Genomes Reveal Unique Variation and Confirm the Deepest Population Divergence in Homo sapiens

The southern African indigenous Khoe-San populations harbor the most divergent lineages of all living peoples. Exploring their genomes is key to understanding deep human history. We sequenced 25 full genomes from five Khoe-San populations, revealing many novel variants, that 25% of variants are unique to the Khoe-San, and that the Khoe-San group harbors the greatest level of diversity across the globe. In line with previous studies, we found several gene regions with extreme values in genome-wide scans for selection, potentially caused by natural selection in the lineage leading to Homo sapiens and more recent in time. These gene regions included immunity-, sperm-, brain-, diet-, and muscle-related genes. When accounting for recent admixture, all Khoe-San groups display genetic diversity approaching the levels in other African groups and a reduction in effective population size starting around 100,000 years ago. Hence, all human groups show a reduction in effective population size commencing around the time of the Out-of-Africa migrations, which coincides with changes in the paleoclimate records, changes that potentially impacted all humans at the time.

The antimicrobial peptide YD attenuates inflammation via miR-155 targeting CASP12 during liver fibrosis

The antimicrobial peptide APKGVQGPNG (named YD), a natural peptide originating from Bacillus amyloliquefaciens CBSYD1, exhibited excellent antibacterial and antioxidant properties in vitro. These characteristics are closely related to inflammatory responses which is the central trigger for liver fibrosis. However, the therapeutic effects of YD against hepatic fibrosis and the underlying mechanisms are rarely studied. In this study, we show that YD improved liver function and inhibited the progression of liver fibrosis by measuring the serum transaminase activity and the expression of α-smooth muscle actin and collagen I in carbon tetrachloride-induced mice. Then we found that YD inhibited the level of miR-155, which plays an important role in inflammation and liver fibrosis. Bioinformatics analysis and luciferase reporter assay indicate that Casp12 is a new target of miR-155. We demonstrate that YD significantly decreases the contents of inflammatory cytokines and suppresses the NF-κB signaling pathway. Further studies show that transfection of the miR-155 mimic in RAW264.7 cells partially reversed the YD-mediated CASP12 upregulation, the downregulated levels of inflammatory cytokines, and the inactivation of the NF-κB pathways. Collectively, our study indicates that YD reduces inflammation through the miR-155–Casp12–NF-κB axis during liver fibrosis and provides a promising therapeutic candidate for hepatic fibrosis.

Sequential ubiquitination of NLRP3 by RNF125 and Cbl-b limits inflammasome activation and endotoxemia

Aberrant NLRP3 inflammasome activation contributes to the development of endotoxemia. The importance of negative regulation of NLRP3 inflammasomes remains poorly understood. Here, we show that the E3 ubiquitin ligase Cbl-b is essential for preventing endotoxemia induced by a sub-lethal dose of LPS via a caspase-11/NLRP3-dependent manner. Further studies show that NLRP3 undergoes both K63- and K48-linked polyubiquitination. Cbl-b binds to the K63-ubiquitin chains attached to the NLRP3 leucine-rich repeat domain (LRR) via its ubiquitin-associated region (UBA) and then targets NLRP3 at K496 for K48-linked ubiquitination and proteasome-mediated degradation. We also identify RNF125 as an additional E3 ubiquitin ligase that initiates K63-linked ubiquitination of the NLRP3 LRR domain. Therefore, NLRP3 is sequentially ubiquitinated by K63- and K48-linked ubiquitination, thus keeping the NLRP3 inflammasomes in check and restraining endotoxemia.

Caspase-12 Is Present During Craniofacial Development and Participates in Regulation of Osteogenic Markers

Caspases are evolutionary conserved proteases traditionally known as participating in apoptosis and inflammation but recently discovered also in association with other processes such as proliferation or differentiation. This investigation focuses on caspase-12, ranked among inflammatory caspases but displaying other, not yet defined functions. A screening analysis pointed to statistically significant (P < 0.001) increase in expression of caspase-12 in a decisive period of mandibular bone formation when the original mesenchymal condensation turns into vascularized bone tissue. Immunofluorescence analysis confirmed the presence of caspase-12 protein in osteoblasts. Therefore, the osteoblastic cell line MC3T3-E1 was challenged to investigate any impact of caspase-12 on the osteogenic pathways. Pharmacological inhibition of caspase-12 in MC3T3-E1 cells caused a statistically significant decrease in expression of some major osteogenic genes, including those for alkaline phosphatase, osteocalcin and Phex. This downregulation was further confirmed by an alkaline phosphatase activity assay and by a siRNA inhibition approach. Altogether, this study demonstrates caspase-12 expression and points to its unknown physiological engagement in bone cells during the course of craniofacial development.

Mechanism of inositol-requiring enzyme 1-alpha inhibition in endoplasmic reticulum stress and apoptosis in ovarian cancer cells

IRE1α endonuclease is a key regulator of endoplasmic reticulum (ER) stress that controls cell survival/apoptosis in cancers. Inhibition of IRE1α endonuclease leads to decreased splice XBP1 which decreases cell proliferation and increases cell death in cancer cells. Therefore, this study investigated the effects and mechanism of STF-083010 (an IRE1α inhibitor) on the cell growth/apoptosis of ovarian malignant cells via the XBP1-CHOP-Bim pathway following the induction of ER stress (ERS). ERS in OVCAR3 and SKOV3 cells was measured using Thioflavin T staining. The expression of ER stress response genes was evaluated by QRT-PCR. The levels of XBP1(s), PERK, phospho-PERK, p-PP2A, ATF4, BIP/GRP78, CHOP, and Bim proteins were evaluated using western blotting. Cell viability and apoptosis in STF-083010 and Tunicamycin (Tm) co-treated cells were assessed using BrdU, MTT, Annexin V-FITC/PI staining, and caspases-12 and -3 activity assays. The results showed increased XBP1, CHOP, and ATF-4 mRNA expression levels as well as high protein aggregation in STF-083010 and Tm co-treated cells. The IRE1α inhibitor down-regulated sXBP1 and BIP proteins, while XBP-1, p-PERK, ATF-4, CHOP, and Bim proteins were up-regulated. STF-083010 reduced cell proliferation and induced apoptosis through the activation of caspases-12 and -3 and Bax/Bcl-2 protein expression. In summary, the present data revealed the effects of STF-083010 in ER stress and apoptosis as well as signaling via XBP1/CHOP/Bim mediators. Thus, STF-083010 is proposed as a new target for the control of ERS in ovarian cancer cells.

Caspases in Cell Death, Inflammation, and Pyroptosis

Caspases are a family of conserved cysteine proteases that play key roles in programmed cell death and inflammation. In multicellular organisms, caspases are activated via macromolecular signaling complexes that bring inactive procaspases together and promote their proximity-induced autoactivation and proteolytic processing. Activation of caspases ultimately results in programmed execution of cell death, and the nature of this cell death is determined by the specific caspases involved. Pioneering new research has unraveled distinct roles and cross talk of caspases in the regulation of programmed cell death, inflammation, and innate immune responses. In-depth understanding of these mechanisms is essential to foster the development of precise therapeutic targets to treat autoinflammatory disorders, infectious diseases, and cancer. This review focuses on mechanisms governing caspase activation and programmed cell death with special emphasis on the recent progress in caspase cross talk and caspase-driven gasdermin D-induced pyroptosis.

Chemical chaperones improve the functional recovery of stunned myocardium by attenuating the endoplasmic reticulum stress

AIM

Myocardial ischaemia/reperfusion (I/R) produces structural and functional alterations depending on the duration of ischaemia. Brief ischaemia followed by reperfusion causes reversible contractile dysfunction (stunned heart) but long-lasting ischaemia followed by reperfusion can result in irreversible injury with cell death. Events during I/R can alter endoplasmic reticulum (ER) function leading to the accumulation of unfolded/misfolded proteins. The resulting ER stress induces activation of several signal transduction pathways, known as unfolded protein response (UPR). Experimental evidence shows that UPR contributes to cell death in irreversible I/R injury; however, there is still uncertainty for its occurrence in the stunned myocardium. This study investigated the ER stress response and its functional impact on the post-ischaemic cardiac performance of the stunned heart.

METHODS

Perfused rat hearts were subjected to 20 minutes of ischaemia followed by 30 minutes of reperfusion. UPR markers were evaluated by qRT-PCR and western blot. Post-ischaemic mechanical recovery was measured in absence and presence of two chemical chaperones: tauroursodeoxycholic acid (TUDCA) and 4-phenylbutyric acid (4-PBA).

RESULTS

Analysis of mRNA and protein levels of various ER stress effectors demonstrated that different UPR signalling cascades, involving both pro-survival and pro-apoptotic pathways, are activated. Inhibition of the UPR with chemical chaperones improved the post-ischaemic recovery of cardiac mechanical function without affecting the I/R-induced increase in oxidative stress.

CONCLUSION

Our results suggest that prevention of ER stress by chemical chaperones could be a therapeutic tool to limit deterioration of the contractile function in clinical settings in which the phenomenon of myocardial stunning is present.

Inflammasomes and their regulation in periodontal disease: A review

Interleukin-1β (IL-1β), which is secreted by host tissues leading to periodontal tissue inflammation, is a major pro-inflammatory cytokine in the pathogenesis of periodontal disease. The conversion of pro-IL-1β into its biologically active form is controlled by multiprotein complexes named as inflammasomes, which are key regulator of host defense mechanisms and inflammasome involved diseases, including the periodontal diseases. Inflammasomes are regulated by different proteins and processes, including pyrin domain (PYD)-only proteins (POPs), CARD-only proteins (COPs), tripartite motif family proteins (TRIMs), autophagy, and interferons. A review of in vitro, in vivo, and clinical data from these publications revealed that several inflammasomes including (NOD)-like receptor (NLR) pyrin domain-containing 3 (NLRP3) and absent in melanoma 2 (AIM2) have been found to be involved in periodontal disease pathogenesis. To the best of our knowledge, the current article provides the first review of the literature focusing on studies that evaluated both inflammasomes and their regulators in periodontal disease. An upregulation for inflammasomes and a downregulation of inflammasome regulator proteins including POPs, COPs, and TRIMs have been reported in periodontal disease. Although interferons (types I and II) and autophagy have been found to be involved in periodontal disease, their possible role in inflammasome activation has not evaluated yet. Modulating the excessive inflammatory response by the use of inflammasome regulators may have potential in the management of periodontal disease.

Inhibiting Caspase-12 Mediated Inflammasome Activation protects against Oxygen-Glucose Deprivation Injury in Primary Astrocytes

Stroke is one of the leading causes of death worldwide. Accumulating evidence suggests that NLRP3 inflammasome activation plays an important role in ischemic stroke injury. However, the existence of the NLRP3 inflammasome in astrocytes remains controversial. In this study, we demonstrated the presence of the NLRP3 inflammasome in primary mouse astrocytes and investigated the role of caspase-12 in NLRP3 inflammasome activation and cell injury in an in vitro astrocyte oxygen-glucose deprivation (OGD) model. Astrocytes exposed to 2, 3, and 4 h of OGD exhibited increased cell injury and apoptosis, and the protein levels of caspase-12, cleaved caspase-3, NLRP3 inflammasome components, and IL-1β were also significantly elevated. Interestingly, pretreatment with the caspase-12-specific inhibitor Z-ATAD-FMK attenuated cell injury and apoptosis and decreased the levels of NLRP3, caspase-1, IL-1β, and cleaved caspase-3 in the OGD group. In conclusion, Z-ATAD-FMK protected astrocytes against OGD-induced cell death and inhibited NLPR3-inflammasome activation. Our results indicate that caspase-12 and its potential regulation of NLRP3 inflammasome activation might be a promising target for treatment of ischemic stroke.

Regulatory roles of ginseng on inflammatory caspases, executioners of inflammasome activation

Inflammation is an immune response that protects against pathogens and cellular stress. The hallmark of inflammatory responses is inflammasome activation in response to various stimuli. This subsequently activates downstream effectors, that is, inflammatory caspases such as caspase-1, 4, 5, 11, and 12. Extensive efforts have been made on developing effective and safe anti-inflammatory therapeutics, and ginseng has long been traditionally used as efficacious and safe herbal medicine in treating various inflammatory and inflammation-mediated diseases. Many studies have successfully shown that ginseng plays an anti-inflammatory role by inhibiting inflammasomes and inflammasome-activated inflammatory caspases. This review discusses the regulatory roles of ginseng on inflammatory caspases in inflammatory responses and also suggests new research areas on the anti-inflammatory function of ginseng, which provides a novel insight into the development of ginseng as an effective and safe anti-inflammatory herbal medicine.

Proteostasis In The Endoplasmic Reticulum: Road to Cure

The endoplasmic reticulum (ER) is an interconnected organelle that is responsible for the biosynthesis, folding, maturation, stabilization, and trafficking of transmembrane and secretory proteins. Therefore, cells evolve protein quality-control equipment of the ER to ensure protein homeostasis, also termed proteostasis. However, disruption in the folding capacity of the ER caused by a large variety of pathophysiological insults leads to the accumulation of unfolded or misfolded proteins in this organelle, known as ER stress. Upon ER stress, unfolded protein response (UPR) of the ER is activated, integrates ER stress signals, and transduces the integrated signals to relive ER stress, thereby leading to the re-establishment of proteostasis. Intriguingly, severe and persistent ER stress and the subsequently sustained unfolded protein response (UPR) are closely associated with tumor development, angiogenesis, aggressiveness, immunosuppression, and therapeutic response of cancer. Additionally, the UPR interconnects various processes in and around the tumor microenvironment. Therefore, it has begun to be delineated that pharmacologically and genetically manipulating strategies directed to target the UPR of the ER might exhibit positive clinical outcome in cancer. In the present review, we summarize recent advances in our understanding of the UPR of the ER and the UPR of the ER-mitochondria interconnection. We also highlight new insights into how the UPR of the ER in response to pathophysiological perturbations is implicated in the pathogenesis of cancer. We provide the concept to target the UPR of the ER, eventually discussing the potential of therapeutic interventions for targeting the UPR of the ER for cancer treatment.

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

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

Broken heart: A matter of the endoplasmic reticulum stress bad management?

Cardiovascular diseases are the number one cause of morbidity and mortality in the United States and worldwide. The induction of the endoplasmic reticulum (ER) stress, a result of a disruption in the ER homeostasis, was found to be highly associated with cardiovascular diseases such as hypertension, diabetes, ischemic heart diseases and heart failure. This review will discuss the latest literature on the different aspects of the involvement of the ER stress in cardiovascular complications and the potential of targeting the ER stress pathways as a new therapeutic approach for cardiovascular complications.

Linking the Endoplasmic Reticulum to Parkinson's Disease and Alpha-Synucleinopathy

Accumulation of misfolded proteins is a central paradigm in neurodegeneration. Because of the key role of the endoplasmic reticulum (ER) in regulating protein homeostasis, in the last decade multiple reports implicated this organelle in the progression of Parkinson's Disease (PD) and other neurodegenerative illnesses. In PD, dopaminergic neuron loss or more broadly neurodegeneration has been improved by overexpression of genes involved in the ER stress response. In addition, toxic alpha-synuclein (αS), the main constituent of proteinaceous aggregates found in tissue samples of PD patients, has been shown to cause ER stress by altering intracellular protein traffic, synaptic vesicles transport, and Ca²⁺ homeostasis. In this review, we will be summarizing evidence correlating impaired ER functionality to PD pathogenesis, focusing our attention on how toxic, aggregated αS can promote ER stress and cell death.

Inflammatory caspase regulation: maintaining balance between inflammation and cell death in health and disease

Members of the mammalian inflammatory caspase family, including caspase-1, caspase-4, caspase-5, caspase-11, and caspase-12, are key regulators of the innate immune response. Most studies to date have focused on the role of caspase-1 in the maturation of the proinflammatory cytokine interleukin-1β and its upstream regulation by the inflammasome signaling complexes. However, an emerging body of research has supported a role for caspase-4, caspase-5, and caspase-11 in both regulating caspase-1 activation and inducing the inflammatory form of cell death called pyroptosis. This inflammatory caspase pathway appears essential for the regulation of cytokine processing. Consequently, insight into this noncanonical pathway may reveal important and, to date, understudied targets for the treatment of autoinflammatory disorders where the inflammasome pathway is dysregulated. Here, we will discuss the mechanisms of inflammasome and inflammatory caspase activation and how these pathways intersect to promote pathogen clearance.

Evaluation of apoptotic pathways in dorsal root ganglion neurons following peripheral nerve injury

Peripheral nerve injuries induce significant sensory neuronal cell death in the dorsal root ganglia (DRG); however, the role of specific apoptotic pathways is still unclear. In this study, we performed peripheral nerve transection on adult rats, after which the corresponding DRGs were harvested at 7, 14, and 28 days after injury for subsequent molecular analyses with quantitative reverse transcription-PCR, western blotting, and immunohistochemistry. Nerve injury led to increased levels of caspase-3 mRNA and active caspase-3 protein in the DRG. Increased expression of caspase-8, caspase-12, caspase-7, and calpain suggested that both the extrinsic and the endoplasmic reticulum (ER) stress-mediated apoptotic pathways were activated. Phosphorylation of protein kinase R-like ER kinase further implied the involvement of ER-stress in the DRG. Phosphorylated protein kinase R-like ER kinase was most commonly associated with isolectin B4 (IB4)-positive neurons in the DRG and this may provide an explanation for the increased susceptibility of these neurons to die following nerve injury, likely in part because of an activation of the ER-stress response.

Evodiamine Augments NLRP3 Inflammasome Activation and Anti-bacterial Responses Through Inducing α-Tubulin Acetylation

Evodiamine is a major ingredient of the plant Evodia rutaecarpa, which has long been used for treating infection-related diseases including diarrhea, beriberi and oral ulcer, but the underlying mechanism is unclear. Here we aimed to explore whether evodiamine influenced NLRP3 (NLR family, pyrin containing domain 3) inflammasome activation in macrophages, which is a critical mechanism for defending the host against pathogenic infections. We uncovered that evodiamine dose-dependently enhanced NLRP3 inflammasome activation in lipopolysaccharide-primed macrophages, as indicated by increased interleukin (IL)-1β production and caspase-1 cleavage, accompanied by increased ASC speck formation and pyroptosis. Mechanistically, evodiamine induced acetylation of α-tubulin around the microtubule organization center (indicated by γ-tubulin) in lipopolysaccharide-primed macrophages. Such evodiamine-mediated increases in NLRP3 activation and pyroptosis were attenuated by activators of α-tubulin deacetylase, resveratrol and NAD⁺, or dynein-specific inhibitor ciliobrevin A. Small interfering RNA knockdown of αTAT1 (the gene encoding α-tubulin N-acetyltransferase) expression, which reduced α-tubulin acetylation, also diminished evodiamine-mediated augmentation of NLRP3 activation and pyroptosis. Evodiamine also enhanced NLRP3-mediated production of IL-1β and neutrophil recruitment in vivo. Moreover, evodiamine administration evidently improved survival of mice with lethal bacterial infection, accompanied by increased production of IL-1β and interferon-γ, decreased bacterial load, and dampened liver inflammation. Resveratrol treatment reversed evodiamine-induced increases of IL-1β and interferon-γ, and decreased bacterial clearance in mice. Collectively, our results indicated that evodiamine augmented the NLRP3 inflammasome activation through inducing α-tubulin acetylation, thereby conferring intensified innate immunity against bacterial infection.

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.

Exercise training modifies gut microbiota with attenuated host responses to sepsis in wild-type mice

This study investigated the effects of exercise preconditioning-induced modification in gut microbiota composition and host responses to cecal ligation and puncture (CLP)-induced sepsis. Four-week-old C57BL/6N male mice were randomly assigned to either CLP ( n = 30) or CLP-exercise (CLP+Exe; n = 30) groups. Prior to CLP-induced sepsis, the CLP+Exe mice were subjected to 8 wk of treadmill running. Fecal samples were collected and analyzed by 16S rRNA amplification sequencing to assess gut microbiota composition. Diversity analyses such as principal coordinates analysis and rarefaction curves showed that exercise preconditioning was associated with differences in gut microbiota community structure and species richness. Exercise preconditioning-induced differences in gut microbiota composition were also evident at the family level of taxonomic analysis, with the dominant phyla being Bacteriodetes, Firmicutes, Verrucomicrobia, and, to a lesser extent, Cyanobacteria. Compared with control mice, preconditioned mice had a higher survival rate and less organ damage during the acute phase of sepsis, secondary to attenuation of the host response to septic shock. The current findings suggest that exercise preconditioning-induced modification in gut microbiota composition may lead to an attenuated host response to CLP-induced sepsis in wild-type mice, as shown by increased survival and less organ damage, as well as the establishment of a balance between pro- and anti-inflammatory responses.-Kim, D., Kang, H. Exercise training modifies gut microbiota with attenuated host responses to sepsis in wild-type mice.

Deoxynivalenol Impairs Porcine Intestinal Host Defense Peptide Expression in Weaned Piglets and IPEC-J2 Cells

Host defense peptides (HDPs) are efficient defense components of the innate immune system, playing critical roles in intestinal homeostasis and protection against pathogens. This study aims to investigate the interference effects of DON on the intestinal porcine HDPs expression in piglets and intestinal porcine epithelial cell line (IPEC-J2) cells, and elucidate the underlying mechanisms through which it functions. In an animal experiment, intestinal HDPs were determined in weaned piglets fed control and 1.28 mg/kg or 2.89 mg/kg DON-contaminated diets. Dietary exposure to DON significantly decreased piglet average daily gain, increased intestinal permeability and depressed the expression of porcine β-defensin1 (pBD1), pBD2, pBD3, epididymis protein 2 splicing variant C (pEP2C), PMAP23, and proline/arginine-rich peptide of 39 amino acids (PR39) in the intestine (p < 0.05). In IPEC-J2 cells, DON decreased cell viability and inhibited the expression of pBD1, pBD3, pEP2C, PG1-5, and PR39 (p < 0.05). NOD2, key regulator that is responsible for HDPs production, was markedly downregulated, whereas caspase-12 was activated in the presence of DON. In conclusion, DON induced caspase-12 activation and inhibited the NOD2-mediated HDPs production, which led to an impaired intestinal barrier integrity of weaned piglets. Our study provides a promising target for future therapeutic strategies to prevent the adverse effects of DON.

The Role of NLRP3 and IL-1β in the Pathogenesis of Inflammatory Bowel Disease

It is logical to assume that a major pro-inflammatory mechanism, i.e., the NLRP3 inflammasome would play a prominent role in the pathogenesis of the Inflammatory Bowel Disease (IBD) in humans. However, while both studies of murine models of gut disease and patients provide data that the main cytokine product generated by this inflammasome, IL-1β, does in fact contribute to inflammation in IBD, there is no evidence that IL-1β plays a decisive or prominent role in "ordinary" patients with IBD (Crohn's disease). On the other hand, there are several definable point mutations that result in over-active NLRP3 inflammasome activity and in these cases, the gut inflammation is driven by IL-1β and is treatable by biologic agents that block the effects of this cytokine.

Caspases in metabolic disease and their therapeutic potential

Caspases, a family of cysteine-dependent aspartate-specific proteases, are central to the maintenance of cellular and organismal homoeostasis by functioning as key mediators of the inflammatory response and/or apoptosis. Both metabolic inflammation and apoptosis play a central role in the pathogenesis of metabolic disease such as obesity and the progression of nonalcoholic steatohepatisis (NASH) to more severe liver disease. Obesity and nonalcoholic fatty liver disease (NAFLD) are the leading global health challenges associated with the development of numerous comorbidities including insulin resistance, type-2 diabetes and early mortality. Despite the high prevalence, current treatment strategies including lifestyle, dietary, pharmaceutical and surgical interventions, are often limited in their efficacy to manage or treat obesity, and there are currently no clinical therapies for NAFLD/NASH. As mediators of inflammation and cell death, caspases are attractive therapeutic targets for the treatment of these metabolic diseases. As such, pan-caspase inhibitors that act by blocking apoptosis have reached phase I/II clinical trials in severe liver disease. However, there is still a lack of knowledge of the specific and differential functions of individual caspases. In addition, cross-talk between alternate cell death pathways is a growing concern for long-term caspase inhibition. Evidence is emerging of the important cell-death-independent, non-apoptotic functions of caspases in metabolic homoeostasis that may be of therapeutic value. Here, we review the current evidence for roles of caspases in metabolic disease and discuss their potential targeting as a therapeutic strategy.

Araloside C Prevents Hypoxia/Reoxygenation-Induced Endoplasmic Reticulum Stress via Increasing Heat Shock Protein 90 in H9c2 Cardiomyocytes

Araloside C (AsC) is a cardioprotective triterpenoid compound that is mainly isolated from Aralia elata. This study aims to determine the effects of AsC on hypoxia-reoxygenation (H/R)-induced apoptosis in H9c2 cardiomyocytes and its underlying mechanisms. Results demonstrated that pretreatment with AsC (12.5 μM) for 12 h significantly suppressed the H/R injury in H9c2 cardiomyocytes, including improving cell viability, attenuating the LDH leakage and preventing cardiomyocyte apoptosis. AsC also inhibited H/R-induced ER stress by reducing the activation of ER stress pathways (PERK/eIF2α and ATF6), and decreasing the expression of ER stress-related apoptotic proteins (CHOP and caspase-12). Moreover, AsC greatly improved the expression level of HSP90 compared with that in the H/R group. The use of HSP90 inhibitor 17-AAG and HSP90 siRNA blocked the above suppression effect of AsC on ER stress-related apoptosis caused by H/R. Taken together, AsC could reduce H/R-induced apoptosis possibly because it attenuates ER stress-dependent apoptotic pathways by increasing HSP90 expression.

Role of Inflammasomes in Neuroimmune and Neurodegenerative Diseases: A Systematic Review

Inflammasomes are multiprotein complexes that can sense pathogen-associated molecular patterns and damage-associated molecular signals. They are involved in the initiation and development of inflammation via activation of IL-1β and IL-18. Many recent studies suggest a strong correlation between inflammasomes and neurological diseases, such as multiple sclerosis (MS), Alzheimer's disease (AD), and Parkinson's disease (PD). Several components of inflammasomes, such as nucleotide-binding oligomerization domain- (NOD-) like receptor, absent in melanoma 2- (AIM2-) like receptors (ALRs), apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and caspase-1, as well as the upstream factors and downstream effectors, are associated with the initiation and development of MS and its animal model, experimental autoimmune encephalomyelitis. Additionally, inflammasomes affect the efficacy of interferon-β therapy in patients with MS. Finally, the strong association of inflammasomes with AD and PD needs to be further studied. In this review of latest literatures, we comprehensively tease out diverse roles of different kinds of inflammasomes in neuroimmune and neurodegenerative diseases, especially in the perspective of double roles involved in pathogenesis, and identify future research priorities.

Human genetics of infectious diseases: Unique insights into immunological redundancy

For almost any given human-tropic virus, bacterium, fungus, or parasite, the clinical outcome of primary infection is enormously variable, ranging from asymptomatic to lethal infection. This variability has long been thought to be largely determined by the germline genetics of the human host, and this is increasingly being demonstrated to be the case. The number and diversity of known inborn errors of immunity is continually increasing, and we focus here on autosomal and X-linked recessive traits underlying complete deficiencies of the encoded protein. Schematically, four types of infectious phenotype have been observed in individuals with such deficiencies, each providing information about the redundancy of the corresponding human gene, in terms of host defense in natural conditions. The lack of a protein can confer vulnerability to a broad range of microbes in most, if not all patients, through the disruption of a key immunological component. In such cases, the gene concerned is of low redundancy. However, the lack of a protein may also confer vulnerability to a narrow range of microbes, sometimes a single pathogen, and not necessarily in all patients. In such cases, the gene concerned is highly redundant. Conversely, the deficiency may be apparently neutral, conferring no detectable predisposition to infection in any individual. In such cases, the gene concerned is completely redundant. Finally, the lack of a protein may, paradoxically, be advantageous to the host, conferring resistance to one or more infections. In such cases, the gene is considered to display beneficial redundancy. These findings reflect the current state of evolution of humans and microbes, and should not be considered predictive of redundancy, or of a lack of redundancy, in the distant future. Nevertheless, these observations are of potential interest to present-day biologists testing immunological hypotheses experimentally and physicians managing patients with immunological or infectious conditions.

Endoplasmic reticulum stress in the heart: insights into mechanisms and drug targets

The endoplasmic reticulum (ER) serves several essential cellular functions including protein synthesis, protein folding, protein translocation, calcium homoeostasis and lipid biosynthesis. Physiological or pathological stimuli, which disrupt ER homoeostasis and disturb its functions, lead to an accumulation of misfolded and unfolded proteins, a condition referred to as ER stress. ER stress triggers the unfolded protein response to restore the homoeostasis of ER, through activating transcriptional and translational pathways. However, prolonged ER stress will lead to cell dysfunction and apoptosis. Recent evidence revealed that ER stress is involved in the development and progression of various heart diseases, such as cardiac hypertrophy, ischaemic heart diseases and heart failure. Therefore, improved understanding of the molecular mechanisms of ER stress in heart disease will help to investigate more potential targets for new therapeutic interventions and drug discovery.

LINKED ARTICLES

This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

An updated view on the functions of caspases in inflammation and immunity

The binary classification of mammalian caspases as either apoptotic or inflammatory is now obsolete. Emerging data indicate that all mammalian caspases are intricately involved in the regulation of inflammation and immunity. They participate in embryonic and adult tissue homeostasis, control leukocyte differentiation, activation and effector functions, and mediate innate and adaptive immunity signaling. Caspases also promote host resistance by regulating anti-oxidant defense and pathogen clearance through regulation of phagosomal maturation, actin dynamics and phagosome-lysosome fusion. Beyond apoptosis, they regulate inflammatory cell death, eliciting rapid pyroptosis of infected cells, while inhibiting necroptosis-mediated tissue destruction and chronic inflammation. In this review, we describe the cellular and molecular mechanisms underlying non-apoptotic functions of caspases in inflammation and immunity and provide an updated view of their functions as central regulators of tissue homeostasis and host defense.