Gasdermin E mediates pyroptotic cell death of neutrophils and macrophages in a zebrafish model of chronic skin inflammation

The inflammasome adaptor pycard is essential for immunity against Mycobacterium marinum infection in adult zebrafish

Inflammasomes regulate the host response to intracellular pathogens including mycobacteria. We have previously shown that the course of Mycobacterium marinum infection in adult zebrafish (Danio rerio) mimics the course of tuberculosis in human. To investigate the role of the inflammasome adaptor pycard in zebrafish M. marinum infection, we produced two zebrafish knockout mutant lines for the pycard gene with CRISPR/Cas9 mutagenesis. Although the zebrafish larvae lacking pycard developed normally and had unaltered resistance against M. marinum, the loss of pycard led to impaired survival and increased bacterial burden in the adult zebrafish. Based on histology, immune cell aggregates, granulomas, were larger in pycard-deficient fish than in wild-type controls. Transcriptome analysis with RNA sequencing of a zebrafish haematopoietic tissue, kidney, suggested a role for pycard in neutrophil-mediated defence, haematopoiesis and myelopoiesis during infection. Transcriptome analysis of fluorescently labelled, pycard-deficient kidney neutrophils identified genes that are associated with compromised resistance, supporting the importance of pycard for neutrophil-mediated immunity against M. marinum. Our results indicate that pycard is essential for resistance against mycobacteria in adult zebrafish.

Gasdermin E as a potential target and biomarker for CRISPR-Cas9-based cancer therapy

Gasdermin E (GSDME), a protein pivotal in mediating pyroptosis, has gained significant attention due to its role in cancer pathogenesis and its potential as a therapeutic target. The advent of CRISPR-Cas9, a precise genome editing tool, has revolutionized cancer therapy by enabling the manipulation of GSDME expression and function. This review explores the interplay of GSDME and CRISPR-Cas9 in cancer, emphasizing GSDME's unique mechanism of cleavage-dependent pore formation in the cell membrane and its emerging applications as both a therapeutic target and a diagnostic biomarker. We discuss the potential and challenges of using GSDME-induced pyroptosis as a therapeutic strategy and how can enhance its efficacy and specificity. We conclude by highlighting promising future research directions in this emerging field.

Ability of short-chain fatty acids to reduce inflammation and attract leucocytes to the inflamed skin of gilthead seabream (Sparus aurata L.)

The aim of the study was to investigate the potential preventive use of short-chain fatty acids (SCFAs) to modulate inflammatory responses in gilthead seabream (Sparus aurata) skin. Initially, in vitro experiments were conducted to evaluate the effects of various concentrations of butyric acid, acetic acid and propionic acid, as well as their combination, on the cytotoxicity and cell viability of three different cell lines. The results determined the safe concentration of SCFAs, which was then used for an in vivo study. Fish were allocated into six groups and administered different combinations of SCFAs via intramuscular injection, followed by an injection of carrageenan as an inflammatory agent. Skin samples were taken from the injection site three hours post-administration and used to analyse gene expression and immunohistochemistry. The results demonstrated that treatment with SCFAs resulted in increased expression of proinflammatory and anti-inflammatory genes and leucocyte markers in the inflamed skin of fish. The highest gene expression and recruitment of acidophilic granulocytes were observed in fish injected with propionic acid and carrageenan. It is concluded that acetic acid is the most effective anti-inflammatory SCFA tested in gilthead seabream exposed to acute inflammation induced by carrageenan injection. Acetic acid exhibited the most pronounced direct anti-inflammatory effect, although propionic acid appeared to play a significant role in several mechanisms contributing to the resolution of inflammation and recruitment of immune cells to the site of carrageenan-inflamed area in gilthead seabream skin.

Copy number variation and population-specific immune genes in the model vertebrate zebrafish

Copy number variation in large gene families is well characterized for plant resistance genes, but similar studies are rare in animals. The zebrafish (Danio rerio) has hundreds of NLR immune genes, making this species ideal for studying this phenomenon. By sequencing 93 zebrafish from multiple wild and laboratory populations, we identified a total of 1513 NLRs, many more than the previously known 400. Approximately half of those are present in all wild populations, but only 4% were found in 80% or more of the individual fish. Wild fish have up to two times as many NLRs per individual and up to four times as many NLRs per population than laboratory strains. In contrast to the massive variability of gene copies, nucleotide diversity in zebrafish NLR genes is very low: around half of the copies are monomorphic and the remaining ones have very few polymorphisms, likely a signature of purifying selection.

Zebrafish: A trending model for gut-brain axis investigation

Zebrafish (Danio rerio) has ascended as a pivotal model organism in the realm of gut-brain axis research, principally owing to its high-throughput experimental capabilities and evolutionary alignment with mammals. The inherent transparency of zebrafish embryos facilitates unprecedented real-time imaging, affording unparalleled insights into the intricate dynamics of bidirectional communication between the gut and the brain. Noteworthy are the structural and functional parallels shared between the zebrafish and mammalian gut-brain axis components, rendering zebrafish an invaluable model for probing the molecular and cellular intricacies inherent in this critical physiological interaction. Recent investigations in zebrafish have systematically explored the impact of gut microbiota on neurodevelopment, behaviour, and disease susceptibility, underscoring the model's prowess in unravelling the multifaceted influence of microbial communities in shaping gut-brain interactions. Leveraging the genetic manipulability inherent in zebrafish, researchers have embarked on targeted explorations of specific pathways and molecular mechanisms, providing nuanced insights into the fundamental functioning of the gut-brain axis. This comprehensive review synthesizes pivotal findings and methodological advancements derived from zebrafish-based gut-brain axis research, accentuating the model's potential to significantly advance our understanding of this complex interplay. Furthermore, it underscores the translational significance of these insights, offering promising avenues for the identification of therapeutic targets in neuro-gastroenterological disorders and psychiatric conditions intricately linked with gut-brain interactions.

Guarea microcarpa C. DC. extract inhibits NLRP3 inflammasome by suppressing its ATPase activity

ETHNOPHARMACOLOGICAL RELEVANCE

Guarea genus comprises tropical and subtropical terrestrial herbs inhabiting Central and South America. These plants, including Guarea guidonia (L.) Sleumer, have anti-inflammatory, analgesic, antibacterial, antiviral, and immune-enhancing properties.

AIM OF THE STUDY

Although various species of the Guarea genus are known for their medicinal properties, comprehensive data on their anti-inflammatory effects remain limited. Therefore, we investigated the NLRP3 inflammasome-inhibiting effects of the Guarea genus in this study.

MATERIALS AND METHODS

To evaluate the anti-inflammatory activities of 18 members of the Guarea genus, we treated NLRP3 inflammasome activators with their extracts in LPS-primed J774A.1 and THP-1 cells. Cell viability was determined by water soluble tetrazolium salt (WST) and cytokine production, protein expression, and nuclear fractionation were determined by western blotting. Reactive oxygen species (ROS) production and apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) oligomerization were measured using confocal microscopic analysis. Inflammation-induced zebrafish was used in the in vivo experiments.

RESULTS

Among the 18 Guarea members tested, Guarea microcarpa C. DC. extract (GM) exhibited no cytotoxicity and specifically suppressed the activation of the NLRP3 inflammasome, but not of the AIM2 or NLRC4 inflammasomes, by inhibiting the ATPase activity of NLRP3. This was achieved without affecting NF-κB signaling, potassium efflux, or intracellular ROS production, all of which are involved in NLRP3 activation. The reduced ATPase activity of NLRP3 led to decreased ASC oligomerization. Furthermore, GM exhibited anti-inflammatory effects in vivo. Additionally, GM treatment alleviated inflammation at the organismal level in an LPS-induced inflammation model using zebrafish embryos.

CONCLUSION

Our results demonstrate the anti-inflammatory effects of GM via suppressing the NLRP3 inflammasome. Therefore, GM can be a potential therapeutic candidate for various inflammatory diseases caused by aberrant NLRP3 inflammasome activation.

Gasdermin E (GSDME)-A New Potential Marker of Psoriasis and Its Metabolic Complications: The First Combined Study on Human Serum, Urine and Tissue

Psoriasis is a frequent and incurable skin disease whose pathogenesis is still not fully understood. It is characterized by immune disturbances leading to hyperproliferation and improper differentiation of keratinocytes. Gasdermin E (GSDME) is a protein from the gasdermin family involved in the processes of inflammation and cell death based on apoptosis, necroptosis and pyroptosis. It has never been studied in psoriatics' sera or urine before. Our study enrolled 60 patients with psoriasis and 30 volunteers without dermatoses as controls. Serum and urinary GSDME concentrations were examined by ELISA and tissue expression of GSDME by immunohistochemistry. Serum GSDME concentration was significantly higher in patients than controls (p < 0.05). There were no differences in urinary GSDME concentrations between patients and controls. GSDME expression was significantly higher in the psoriatic plaque than non-lesional patients' skin and compared to controls (both p < 0.001). There was no correlation between serum GSDME or its lesional expression and psoriasis severity, age or disease duration. GSDME serum concentration was significantly negatively correlated with BMI, triglycerides and glucose concentrations. The obtained results suggest the engagement of GSDME in psoriasis pathogenesis. It could potentially become a new non-invasive psoriasis marker. Considering its pro-apoptotic influence, GSDME could be compensatively elevated to direct cells towards apoptosis, whereas under other circumstances, it may lead to pyroptosis and sustain inflammation. GSDME may exert a protective influence on the metabolic complications in psoriasis which requires further studies.

Pyroptosis in fish research: A promising target for disease management

Pyroptosis is a newly discovered programmed cell death pathway that plays an essential role in the host's defense against pathogenic infections. This process is orchestrated by inflammasomes, which are intricate multiprotein complexes that orchestrate the activation of caspase and instigate the liberation of proinflammatory cytokines. Additionally, gasdermin family proteins execute their role by forming pores in the cell membrane, ultimately leading to cell lysis. In recent years, pyroptosis has emerged as a promising target for disease management in fish, particularly in the context of infectious diseases. In this review, we provide an overview of the current understanding regarding the role of pyroptosis in fish, focusing on its involvement in host-pathogen interactions and its potential as a therapeutic target. We also highlighted the latest advancements in the field development of pyroptosis inhibitors and their potential applications in fish disease management. Subsequently, we deliberate on the obstacles and future prospects for pyroptosis research in fish, emphasizing the necessity of conducting more comprehensive investigations to unravel the intricate regulatory mechanisms governing this process across diverse fish species and environmental contexts. Finally, this review will also highlight the current limitations and future perspectives of pyroptosis research in aquaculture.

Silica crystals activate toll-like receptors and inflammasomes to promote local and systemic immune responses in zebrafish

Silica crystals are potent activators of the inflammasome that cause a fibrotic lung disease, called silicosis, with no effective treatment available. We report here that injection of silica crystals into the hindbrain ventricle of zebrafish embryos led to the initiation of local and systemic immune responses driven through both Toll-like receptors (TLR)- and inflammasome-dependent signaling pathways, followed by induction of pro-fibrotic markers. Genetic and pharmacological analysis revealed that the Nlrp3 inflammasome regulated silica crystal-induced inflammation and pyroptotic cell death, but not emergency myelopoiesis. In addition, Cxcl8a/Cxcr2-dependent recruitment of myeloid cells to silica crystals was required to promote emergency myelopoiesis and systemic inflammation. The zebrafish model of silicosis developed here shed light onto the molecular mechanisms involved in the activation of the immune system by silica crystals.