Priming of the neutrophil respiratory burst: role in host defense and inflammation

Prospects of neutrophilic implications against pathobiology of chronic obstructive pulmonary disease: Pharmacological insights and technological advances

Chronic obstructive pulmonary disease (COPD) is a prevalent chronic inflammatory condition that affects the lungs globally. A key feature of this inflammatory response is the migration and aggregation of polymorphonuclear neutrophils (PMNs). The presence of neutrophilic inflammation within the airways is as distinguishing characteristic of COPD. As research advances, PMNs and their products emerge as central players in the airway inflammatory cascade of COPD patients. Their involvement in phagocytosis, degranulation, and the formation of neutrophil extracellular traps (NETs) significantly contributes to the pathogenesis of COPD. Moreover, studies have shown that excessive biological activities of neutrophils in the lungs can result in airway epithelial injury, emphysema, and mucus hypersecretion. Currently, there is growing empirical support for the moderate targeting neutrophils in the clinical management of COPD. This article delves into the pivotal role of neutrophils in COPD, emphasizing the urgency for novel therapeutic approaches that specifically target neutrophils. Additionally, it explores the potential of utilizing single-cell RNA sequencing to further investigate neutrophils and relevant risk genes as potential biomarkers for COPD treatment. By elucidating these mechanisms, this review aims to pave the way for future strategies to modulate neutrophil function, thereby addressing the pressing need for more effective COPD therapies.

Anti-inflammatory effects of heat-killed Lactiplantibacillus argentoratensis BBLB001 on a gut inflammation co-culture cell model and dextran sulfate sodium-induced colitis mouse model

Dysbiosis caused by dietary changes can alter the intestinal bacterial species and is closely associated with inflammatory bowel disease (IBD). Among the possible treatment options, postbiotics, which act to balance the constituent intestinal microflora, have gained substantial attention. Herein, we investigated the anti-inflammatory effects of heat-killed Lactiplantibacillus argentoratensis (hk-LA) BBLB001 isolated from a marine environment using both cell (Caco2/RAW264.7 cell co-culture) and animal (dextran sodium sulfate [DSS]-induced colitis in mice) models. hk-LA BBLB001 markedly reduced IL-8 secretion in Caco-2 cell culture medium after lipopolysaccharide-mediated stimulation of RAW264.7 cells by enhancing the expression of cell adhesion factors.The body weight loss, reduced inflammatory cytokine levels in the serum and colon tissues, colon shortening, and myeloperoxidase activation caused by DSS in mice were alleviated by hk-LA BBLB001. Similar to that in the intestinal cell model, the gene and protein expressions of cell adhesion molecules in the colon tissue were increased upon hk-LA BBLB001 treatment in DSS-induced colitis mice. We observed increased mucin expression and secretory IgA concentration in colon tissues, suggesting that hk-LA BBLB001 intake may benefit pathogen defense and the regulation of intestinal commensal bacteria. Thus, hk-LA BBLB001 may serve as an instrumental postbiotic material in IBD treatment.

NOX2 deficiency promotes GSDME-related pyroptosis by reducing AMPK activation in neutrophils

Nicotinamide adenine dinucleotide phosphate oxidase complex 2 (NOX2) is an effector molecule expressed predominantly in neutrophils. Its deficiency is present in immune disorders, including systemic lupus erythematosus, chronic granulomatous disease, and rheumatoid arthritis. Recent reports indicated that NOX2 regulates autoimmunity and programmed cell death. However, the exact mechanism is unclear. In this study, we explored the effect of NOX2 on neutrophil apoptosis. We demonstrated that NOX2 deficiency caused neutrophil pyroptosis. Mechanistically, the NOX2 inhibitor GSK2795039 application or knockdown of NOX2 components resulted in increased mitochondrial ROS, inhibition of AMP-activated protein kinase (AMPK), and activation of Gasdermin E. AMPK activators, metformin and epigallocatechin gallate, inhibited deficient NOX2-induced pyroptosis. Together, these findings illustrate the involvement of NOX2 in regulating neutrophil death and emphasize its importance in autoimmunity.

Neutrophils in cancer: from biology to therapy

The view of neutrophils has shifted from simple phagocytic cells, whose main function is to kill pathogens, to very complex cells that are also involved in immune regulation and tissue repair. These cells are essential for maintaining and regaining tissue homeostasis. Neutrophils can be viewed as double-edged swords in a range of situations. The potent killing machinery necessary for immune responses to pathogens can easily lead to collateral damage to host tissues when inappropriately controlled. Furthermore, some subtypes of neutrophils are potent pathogen killers, whereas others are immunosuppressive or can aid in tissue healing. Finally, in tumor immunology, many examples of both protumorigenic and antitumorigenic properties of neutrophils have been described. This has important consequences for cancer therapy, as targeting neutrophils can lead to either suppressed or stimulated antitumor responses. This review will discuss the current knowledge regarding the pro- and antitumorigenic roles of neutrophils, leading to the concept of a confused state of neutrophil-driven pro-/antitumor responses.

Synergy of bacteriophage depolymerase with host immunity rescues sepsis mice infected with hypervirulent Klebsiella pneumoniae of capsule type K2

The hypervirulent Klebsiella pneumoniae (hvKp) with K1 and K2 capsular types causes liver abscess, pneumonia, sepsis, and invasive infections with high lethality. The presence of capsular polysaccharide (CPS) resists phagocytic engulfment and contributes to excessive inflammatory responses. Bacteriophage depolymerases can specifically target bacterial CPS, neutralizing its defense. Based on our previous research, we expressed and purified a bacteriophage depolymerase (Dep1979) targeting hvKp with capsule type K2. Interestingly, although Dep1979 lacked direct bactericidal activity in vitro, it exhibited potent antibacterial activity in vivo. Low-dose Dep1979 (0.1 mg/kg) improved the 7-day survival of immunocompetent mice to 100%. Even at 0.01 mg/kg, mice achieved 100% survival at 5 days, although efficacy sharply declined at doses as low as 0.001 mg/kg. Following Dep1979 treatment, reduced expression of inflammatory factors and no apparent tissue damage were observed. However, therapeutic efficacy significantly diminished in immunosuppressed mice. These findings underscore the critical role of Dep1979 in disarming CPS, which synergizes with host immunity to enhance antibacterial activity against hvKp.

Neutrophils in Atopic Dermatitis

Neutrophils have a critical role in inflammation. Recent studies have identified their distinctive presence in certain types of atopic dermatitis (AD), yet their exact function remains unclear. This review aims to compile studies elucidating the role of neutrophils in AD pathophysiology. Proteins released by neutrophils, including myeloperoxidase, elastase, and lipocalin, contribute to pruritus progression in AD. Neutrophilic oxidative stress and the formation of neutrophil extracellular traps may further worsen AD. Elevated neutrophil elastase and high-mobility group box 1 protein expression in AD patients' skin exacerbates epidermal barrier defects. Neutrophil-mast cell interactions in allergic inflammation steer the immunological response toward Th2 imbalance and activate the Th17 pathway, particularly in response to allergens or infections linked to AD. Notably, drugs alleviating pruritic symptoms in AD inhibit neutrophilic inflammation. In conclusion, these findings underscore that neutrophils may be therapeutic targets for AD symptoms, emphasizing their inclusion in AD treatment strategies.

Opuntia ficus-indica cladodes extract inhibits human neutrophil pro-inflammatory functions and protects rats from acetic acid-induced ulcerative colitis

The increased production of reactive oxygen species (ROS) by human neutrophils can lead to oxidative imbalances and several diseases, such as inflammatory bowel disease (IBD). Opuntia ficus-indica (O. ficus-indica) is rich in bioactive substances with anti-inflammatory properties. This study aimed to identify the bioactive compounds present in aqueous cladodes extract (ACE) of O. ficus-indica using high-performance liquid chromatography (HPLC) and to test its effects on human neutrophil inflammatory functions and on ulcerative colitis (UC) induced by acetic acid (Aa) in rats. ROS production and degranulation by neutrophils were assessed by luminol-amplified chemiluminescence, enzymatic techniques, and western blotting. In vivo, the experiment involved seven groups of rats: a negative control group (NaCl), the acetic acid group (Aa), and groups treated with oral sulfasalazine (150 mg/kg) or various doses of ACE for 7 days. Colonic lesions were induced by an intra-rectal Aa injection, and inflammation was assessed. HPLC analysis identified gallic acid, catechin, caffeic acid, and ferulic acid as major compounds in ACE. In vitro, ACE inhibited neutrophil ROS production, including superoxide anion produced by NADPH oxidase, and significantly reduced myeloperoxidase activity and neutrophil degranulation. In vivo, ACE protected rats from Aa-induced histopathological damage of the colonic mucosa, significantly increased catalase, superoxide dismutase and reduced glutathione levels, and significantly suppressed the increases of plasma cytokines (TNF-α and IL-1β) observed in the Aa group. In conclusion, O. ficus-indica ACE has significant anti-inflammatory properties by restoring oxidative balance, indicating that it could be a potential source of therapeutic agents for inflammatory diseases, particularly UC.

Innovative hydrogel-based therapies for ischemia-reperfusion injury： bridging the gap between pathophysiology and treatment

Ischemia-reperfusion injury (IRI) commonly occurs in clinical settings, particularly in medical practices such as organ transplantation, cardiopulmonary resuscitation, and recovery from acute trauma, posing substantial challenges in clinical therapies. Current systemic therapies for IRI are limited by poor drug targeting, short efficacy, and significant side effects. Owing to their exceptional biocompatibility, biodegradability, excellent mechanical properties, targeting capabilities, controlled release potential, and properties mimicking the extracellular matrix (ECM), hydrogels not only serve as superior platforms for therapeutic substance delivery and retention, but also facilitate bioenvironment cultivation and cell recruitment, demonstrating significant potential in IRI treatment. This review explores the pathological processes of IRI and discusses the roles and therapeutic outcomes of various hydrogel systems. By categorizing hydrogel systems into depots delivering therapeutic agents, scaffolds encapsulating mesenchymal stem cells (MSCs), and ECM-mimicking hydrogels, this article emphasizes the selection of polymers and therapeutic substances, and details special crosslinking mechanisms and physicochemical properties, as well as summarizes the application of hydrogel systems for IRI treatment. Furthermore, it evaluates the limitations of current hydrogel treatments and suggests directions for future clinical applications.

A key regulator of tumor-associated neutrophils: the CXCR2 chemokine receptor

In recent years, with the advance of research, the role of tumor-associated neutrophils (TANs) in tumors has become a research hotspot. As important effector cells in the innate immune system, neutrophils play a key role in the immune and inflammatory responses of the body. As the first line of defense against bacterial and fungal infections, neutrophils have the ability to kill invading pathogens. In the pathological state of malignant tumors, the phenotype of neutrophils is altered and has an important regulatory function in tumor development. The C-X-C motif chemokine receptor 2(CXCR2) is a key molecule that mediates the migration and aggregation signaling pathway of immune cells, especially neutrophils. This review focuses on the regulation of CXCR2 on TANs in the process of tumorigenesis and development, and emphasizes the application significance of CXCR2 inhibitors in blocking the migration of TANs to tumors.

Catechol-derived Mannich bases: radical regulatory properties, cytotoxicity and interaction with biomolecules

Free radicals are ubiquitous in biological systems, being responsible for pathogenesis of degenerative diseases and participating in vitally important biochemical processes, which are mediated by radical regulatory agents. The effects of the aliphatic amine substituents in the catechol-derived Mannich bases on their antioxidant and pro-oxidant activity were investigated. It has been found that the presence of catechol moiety in the structure of Mannich bases allows them to act as Cu(II) reductants, efficient Fe(II) chelators and potent DPPH radical scavengers. It has been found that the plausible mechanism of the DPPH radical scavenging proceeds via quinone formation, followed by their interaction with ethanol via the Michael addition reaction. In the neutrophil respiratory burst assay, several compounds have demonstrated a weak antioxidant activity at the micromolar level (0.1-10 µM), whereas at the millimolar level (0.1 mМ) a strong pro-oxidant effect has been observed. Additionally, at the highest used concentrations a pronounced cytotoxicity against dermal fibroblasts DF-2 and an immunosuppressive effect against T-lymphocytes have been observed for all the synthesized compounds. It has been demonstrated that the oxidation of catechols in the presence of low-molecular thiols results in the formation of covalent adducts, which provides an insight into their cytotoxicity and detoxification pathways.

Gallic acid attenuates lipopolysaccharide - induced memory deficits, neurochemical changes, and peripheral alterations in purinergic signaling

Neuroinflammation is associated with many neurological disorders. Gallic acid (GA) has attracted significant attention due to its biological properties, such as neuroprotective, anti-inflammatory, and antioxidant effects. In this study, we evaluated the effects of GA in memory, TNF-α levels, oxidative stress, and activities of acetylcholinesterase (AChE), Na+, K+-ATPase and Ca2+-ATPase in the brain of mice exposed to lipopolysaccharide (LPS). Additionally, we evaluated alterations in adenine nucleotides and nucleosides in the serum. Male mice were orally pretreated with vehicle or GA (50 or 100 mg/kg) for 14 days. Between days 8 and 14, the animals also received LPS injection (250 µg/kg) or saline. At the end of the experimental protocol, the animals were submitted to object recognition test, euthanized and cerebral cortex, hippocampus, striatum and blood were collected. LPS induced memory deficits, which were prevented by GA treatment. GA protected against LPS-induced oxidative damage in the cerebral cortex, hippocampus and striatum by reducing reactive oxygen species and nitrite levels, while increasing total thiol content and activities of antioxidant enzymes. GA also prevented LPS-induced alterations in AChE, Na+, K+-ATPase, and Ca2+-ATPase activities in brain structures. LPS elevated TNF-α levels in the hippocampus and cerebral cortex, which were attenuated by GA treatment. Furthermore, LPS caused a reduction in ADP and AMP hydrolysis and an increase in adenosine deamination in the serum, which were also prevented by GA. The effects of GA against neuroinflammation may be attributed to its potent antioxidant and anti-inflammatory properties, which modulate various pathways, including those involved in memory mechanisms.

The neonatal liver hosts a spontaneously occurring neutrophil population, exhibiting distinct spatial and functional characteristics from adults

The elusive nature of the liver immune system in newborns remains an important challenge, casting a shadow over our understanding of how to effectively treat and prevent diseases in children. Therefore, deeper exploration into the intricacies of neonatal immunology might be crucial for improved pediatric healthcare. Using liver intravital microscopy, we unveiled a significant population of granulocytes in the hepatic parenchyma of fetuses and newborns. Utilizing high-dimensional immunophenotyping, we showed dynamic alterations predominantly in granulocytes during neonatal development. Liver intravital microscopy from birth through adulthood captures real-time dynamics, showing a substantial presence of Ly6G+ cells that persisted significantly up to 2 wk of age. Using time-of flight mass cytometry, we characterized neonatal Ly6G+ cells as neutrophils, confirmed by morphology and immunohistochemistry. Surprisingly, the embryonic liver hosts a distinct population of neutrophils established as early as the second gestational week, challenging conventional notions about their origin. Additionally, we observed that embryonic neutrophils occupy preferentially the extravascular space, indicating their early establishment within the liver. Hepatic neutrophils in embryos and neonates form unique cell clusters, persisting during the initial days of life, while reduced migratory capabilities in neonates are observed, potentially compensating with increased reactive oxygen species release in response to stimuli. Finally, in vivo imaging of acute neutrophil behavior in a newborn mouse, subjected to focal liver necrosis, unveils that neonatal neutrophils exhibit a reduced migratory response. The study provides unprecedented insights into the intricate interplay of neutrophils within the liver, shedding light on their functional and dynamic characteristics during development.

Granulocyte colony-stimulating factor mediates bone loss via the activation of IL-1β/JNK signaling pathway in murine Staphylococcus aureus-induced osteomyelitis

Staphylococcus aureus (S. aureus)-induced bone loss is a significant challenge in the treatment of osteomyelitis. Our previous study was the first to confirm that granulocyte colony-stimulating factor (G-CSF) mediates S. aureus-induced bone loss. However, the underlying mechanism remains unknown. The objective of this study was to elucidate this. We found G-CSF mediated BMSC senescence and increased IL-1β concentration of serum and bone marrow in mice after S. aureus infection. Furthermore, we demonstrated that G-CSF promoted the expression of IL1b in murine bone marrow-derived neutrophils. Notably, we identified that IL-1β mediated BMSC (bone marrow mesenchymal stromal cell) senescence in mice after S. aureus infection. Importantly, IL-1β neutralizing antibody effectively alleviated BMSC senescence and bone loss caused by S. aureus infection in mice. In terms of molecular mechanism, we found IL-1β induced BMSC senescence by JNK/P53 and JNK/BCL2 pathways. Collectively, G-CSF promotes IL-1β production which induces BMSC senescence via JNK/P53 and JNK/BCL2 pathways, leading to S. aureus-induced bone loss. This study identified novel targets for preventing and treating S. aureus-induced bone loss in osteomyelitis.

ROS: A "booster" for chronic inflammation and tumor metastasis

Reactive oxygen species (ROS) are a group of highly active molecules produced by normal cellular metabolism and play a crucial role in the human body. In recent years, researchers have increasingly discovered that ROS plays a vital role in the progression of chronic inflammation and tumor metastasis. The inflammatory tumor microenvironment established by chronic inflammation can induce ROS production through inflammatory cells. ROS can then directly damage DNA or indirectly activate cellular signaling pathways to promote tumor metastasis and development, including breast cancer, lung cancer, liver cancer, colorectal cancer, and so on. This review aims to elucidate the relationship between ROS, chronic inflammation, and tumor metastasis, explaining how chronic inflammation can induce tumor metastasis and how ROS can contribute to the evolution of chronic inflammation toward tumor metastasis. Interestingly, ROS can have a "double-edged sword" effect, promoting tumor metastasis in some cases and inhibiting it in others. This article also highlights the potential applications of ROS in inhibiting tumor metastasis and enhancing the precision of tumor-targeted therapy. Combining ROS with nanomaterials strategies may be a promising approach to enhance the efficacy of tumor treatment.

Neutrophils promote the activation of monocytes via ROS to boost systemic antitumor immunity after cryo-thermal therapy

Background

The characteristics of the tumor immunosuppressive microenvironment represent a major challenge that limits the efficacy of immunotherapy. Our previous results suggested that cryo-thermal therapy, a tumor ablation system developed in our laboratory, promotes macrophage M1-type polarization and the complete maturation of DCs to remodel the immunosuppressive environment. However, the cells that respond promptly to CTT have not yet been identified. CTT can cause extensive cell death and the release of danger-associated molecular patterns and antigens. Neutrophils are the first white blood cells recruited to sites of damage and acute inflammation. Therefore, we hypothesized that neutrophils are the initial cells that respond to CTT and are involved in the subsequent establishment of antitumor immunity.

Methods

In this study, we examined the kinetics of neutrophil recruitment after CTT via flow cytometry and immunofluorescence staining and explored the effect of neutrophils on the establishment of systemic antitumor immunity by in vivo neutrophil depletion and in vitro co-culture assays.

Results

We found that CTT led to a rapid and strong proinflammatory neutrophil response, which was essential for the long-term survival of mice. CTT-induced neutrophils promoted the activation of monocytes via reactive oxygen species and further upregulated the expression of IFN-γ and cytotoxic molecules in T and NK cells. Adoptive neutrophil transfer further enhanced the antitumor efficacy of CTT in tumor models of spontaneous and experimental metastasis.

Conclusion

These results reveal the important role of neutrophil‒monocyte interactions in the development of anti-tumor immunity and highlight that CTT could be used as an immunotherapy for targeting neutrophils and monocytes to enhance antitumor immunity.

Structural profiles of the full phagocyte NADPH oxidase unveiled by combining computational biology and experimental knowledge

The phagocyte NADPH oxidase (NOX2) is an enzyme, crucial for innate immune defense, producing reactive oxygen species necessary for pathogen destruction. Its activation requires the assembly of soluble proteins (p47phox, p40phox, p67phox, and Rac) with the membrane-bound flavocytochrome b558 (cytb558). We combined circular-dichroism analyses, with decades of experimental data, to filter structural models of the NADPH oxidase complex generated by the artificial intelligence program AlphaFold2 (AF2). The predicted patterns tend to closely resemble the active states of the proteins, as shown by the compact structure of the cytb558, whose dehydrogenase domain is stabilized closer to the membrane. The modeling of the interaction of p47phox with cytb558, which is the initial assembly and activation steps of the NADPH oxidase, enables us to describe how the C-terminus of p47phox interacts with the cytb558. Combining the AF2 cytb558 -p47phox model and its classical molecular dynamics simulations, we highlighted new hydrophobic lipid insertions of p47phox, particularly at residues Trp80-Phe81 of its PX domain. The AF2 models also revealed the implications of intrinsically disordered regions, such as the fragment between the PX domain and the SH3 regions of p47phox, in ensuring distant protein-protein and membrane-protein interactions. Finally, the AF2 prediction of the cytb558-Trimera model highlighted the importance of leaving Rac1 as a separate protein to reach an active state of the NADPH oxidase complex. Altogether, our step-by-step approach provides a structural model of the active complex showing how disordered regions and specific lipid and protein interactions can enable and stabilize the multi-subunit assembly.

Gut microbiota-derived butyrate improved acute leptospirosis in hamster via promoting macrophage ROS mediated by HDAC3 inhibition

Leptospirosis is a re-emerging worldwide zoonotic disease. Infected patients and animals often exhibit intestinal symptoms. Mounting evidence suggests that host immune responses to bacterial infection are closely associated with intestinal homeostasis. Our previous research has shown that the gut microbiota can protect the host from acute leptospirosis, while the specific bacterial metabolic mediators participating in the pathogenesis remain to be identified. Short-chain fatty acids (SCFAs) are metabolites produced mainly by the gut microbiota that play a role in immune regulation. However, whether SCFAs are the key to protecting the host against leptospirosis and the underlying regulatory mechanisms are unknown. In this study, our results showed that the SCFA butyrate is involved in ameliorating leptospirosis. The depletion of SCFAs by antibiotic cocktail treatment reduced survival time after Leptospira infection while supplementation with butyrate but not acetate or propionate significantly amelioration of leptospirosis. In vitro experiments showed that butyrate treatment enhanced the intracellular bactericidal activity mediated by reactive oxygen species (ROS) production. Mechanistically, butyrate functions as a histone deacetylase 3 inhibitor (HDAC3i) to promote ROS production via monocarboxylate transporter (MCT). The protection of butyrate against acute leptospirosis mediated by ROS was also proven in vivo. Collectively, our data provide evidence that the butyrate-MCT-HDAC3i-ROS signaling axis is a potential therapeutic target for acute leptospirosis. Our work not only interprets the microbial metabolite signaling involved in transkingdom interactions between the host and gut microbiota but also provides a possible target for developing a prevention strategy for acute leptospirosis.

IMPORTANCE

Leptospirosis is a worldwide zoonotic disease caused by Leptospira. An estimated 1 million people are infected with leptospirosis each year. Studies have shown that healthy gut microbiota can protect the host against leptospirosis but the mechanism is not clear. This work elucidated the mechanism of gut microbiota protecting the host against acute leptospirosis. Here, we find that butyrate, a metabolite of gut microbiota, can improve the survival rate of hamsters with leptospirosis by promoting the bactericidal activity of macrophages. Mechanistically, butyrate upregulates reactive oxygen species (ROS) levels after macrophage infection with Leptospira by inhibiting HDAC3. This work confirms the therapeutic potential of butyrate in preventing acute leptospirosis and provides evidence for the benefits of the macrophage-HDAC3i-ROS axis.

LincR-PPP2R5C deficiency enhancing the fungicidal activity of neutrophils in pulmonary cryptococcosis is linked to the upregulation of IL-4

Pulmonary cryptococcosis is a common complication in immunocompromised patients. In a mouse model of pulmonary cryptococcosis, Cryptococcus neoformans induces a type 2 immune response that is detrimental to host protection. Long non-coding RNAs (lncRNAs) have emerged as key players in the pathogenesis of infectious diseases. However, the roles and mechanisms of lncRNAs in fungal infection are largely elusive. In the present study, we aimed to explore the roles of LincR-PPP2R5C in pulmonary cryptococcosis. We observed an increase in the level of LincR-PPP2R5C in the lung tissues of C57BL/6J mice after tracheal infection with C. neoformans. Subsequently, we intratracheally infected LincR-PPP2R5C knockout (KO) mice and wild-type mice with C. neoformans. LincR-PPP2R5C deficiency mitigates C. neoformans infection, which can be demonstrated by extending survival time and decreasing fungal burden in the lung. In the lung tissues of infected LincR-PPP2R5C KO mice, there was a notable increase in the levels of type 2 cytokines [interleukin (IL)-4 and IL-5] and an increase in the number of neutrophils in both the lung tissue and bronchoalveolar lavage fluid. Mechanistically, the lack of LincR-PPP2R5C results in increased protein phosphatase 2A phosphorylation, thereby enhancing the fungicidal activity of neutrophils against Cryptococcus neoformans, with IL-4 playing a synergistic role in this process. Overall, LincR-PPP2R5C deficiency mitigated pulmonary cryptococcosis by increasing the fungicidal activity of neutrophils, which was associated with increased IL-4 levels. Our study presented specific evidence of the role of host-derived lncRNAs in the regulation of C. neoformans infection.

IMPORTANCE

Pulmonary cryptococcosis is a human fungal disease caused by Cryptococcus neoformans, which is common not only in immunocompromised individuals but also in patients with normal immune function. Therefore, studying the control mechanisms of pulmonary cryptococcosis is highly important. Here, we demonstrated that the deletion of LincR-PPP2R5C leads to increased killing of C. neoformans by neutrophils, thereby reducing pulmonary cryptococcal infection. These findings will greatly enhance our understanding of the mechanisms by which lncRNAs regulate the pathogenesis of C. neoformans, facilitating the use of lncRNAs in pulmonary cryptococcosis therapy.

Hordenine Alleviates Lipopolysaccharide-Induced Mastitis by Suppressing Inflammation and Oxidative Stress, Modulating Intestinal Microbiota, and Preserving the Blood-Milk Barrier

Mastitis is a common mammalian disease occurring in the mammary tissue and poses a major threat to agriculture and the dairy industry. Hordenine (HOR), a phenylethylamine alkaloid naturally extracted from malt, has various pharmacological effects, but its role in mastitis is unknown. The aim of this study was to investigate the role of HOR and its underlying mechanism in a lipopolysaccharide (LPS)-induced inflammatory response model of mouse mammary epithelial cells (EpH4-Ev) and mouse mastitis model. The experimental results showed that HOR attenuated LPS-induced mammary tissue damage (from 3.75 ± 0.25 to 1.75 ± 0.25) and restored the integrity of the blood-milk barrier. Further mechanistic studies revealed that HOR inhibited LPS-induced overactivation of the TLR4-MAPK/NF-κB signaling pathway and activated the AMPK/Nrf2/HO-1 signaling pathway. Additionally, HOR altered the composition of the intestinal microbiota in mice, ultimately reducing the extent of inflammatory injury (from 3.33 ± 0.33 to 0.67 ± 0.33) and upregulating the expression of tight junction proteins (ZO-1, occludin, and claudin-3). The findings of this study provide a theoretical basis in the rational use of HOR for the prevention and treatment of mastitis and the maintenance of mammalian mammary gland health.

Effects of Pressure, Hypoxia, and Hyperoxia on Neutrophil Granulocytes

Background: The application of normo- and hyperbaric O2 is a common therapy option in various disease patterns. Thereby, the applied O2 affects the whole body, including the blood and its components. This study investigates influences of pressure and oxygen fraction on human blood plasma, nutrient media, and the functions of neutrophil granulocytes (PMNs). Methods: Neutrophil migration, reactive oxygen species (ROS) production, and NETosis were examined by live cell imaging. The treatment of various matrices (Roswell Park Memorial Institute 1640 medium, Dulbecco's Modified Eagle's Medium, H2O, human plasma, and isolated PMNs) with hyperbaric oxygen (HBO) was performed. In addition, the expression of different neutrophil surface epitopes (CD11b, CD62L, CD66b) and the oxidative burst were investigated by flow cytometry (FACS). The application of cold atmospheric plasma (CAP) to normoxic and normobaric culture media served as a positive control. Soluble reaction products such as H2O2, reactive nitrogen species (RNS: NO2- and NO3-), and ROS-dependent dihydrorhodamine oxidation were quantified by fluoro- and colorimetric assay kits. Results: Under normobaric normoxia, PMNs migrate slower and shorter in comparison with normobaric hyper- or hypoxic conditions and hyperbaric hyperoxia. The pressure component has less effect on the migration behavior of PMNs than the O2 concentration. Individual PMN cells produce prolonged ROS at normoxic conditions. PMNs showed increased expression of CD11b in normobaric normoxia, lower expression of CD62L in normobaric normoxia, and lower expression of CD66b after HBO and CAP treatment. Treatment with CAP increased the amount of ROS and RNS in common culture media. Conclusions: Hyperbaric and normobaric O2 influences neutrophil functionality and surface epitopes in a measurable way, which may have an impact on disorders with neutrophil involvement. In the context of hyperbaric experiments, especially high amounts of H2O2 in RPMI after hyperbaric oxygen should be taken into account. Therefore, our data support a critical indication for the use of normobaric and hyperbaric oxygen and conscientious and careful handling of oxygen in everyday clinical practice.

Probiotic Consortia Protect the Intestine Against Radiation Injury by Improving Intestinal Epithelial Homeostasis

PURPOSE

Radiation-induced intestinal injury (RIII) commonly occur during abdominal-pelvic cancer radiation therapy; however, no effective prophylactic or therapeutic agents are available to manage RIII currently. This study aimed to clarify the potential of probiotic consortium supplementation in alleviating RIII.

METHODS AND MATERIALS

Male C57BL/6J mice were orally administered a probiotic mixture comprising Bifidobacterium longum BL21, Lactobacillus paracasei LC86, and Lactobacillus plantarum Lp90 for 30 days before exposure to 13 Gy of whole abdominal irradiation. The survival rates, clinical scores, and histologic changes in the intestines of mice were assessed. The impacts of probiotic consortium treatment on intestinal stem cell proliferation, differentiation, and epithelial barrier function; oxidative stress; and inflammatory cytokines were evaluated. A comprehensive examination of the gut microbiota composition was conducted through 16S rRNA sequencing, while changes in metabolites were identified using liquid chromatography-mass spectrometry.

RESULTS

The probiotic consortium alleviated RIII, as reflected by increased survival rates, improved clinical scores, and mitigated mucosal injury. The probiotic consortium treatment exhibited enhanced therapeutic effects at the histologic level compared with individual probiotic strains, although there was no corresponding improvement in survival rates and colon length. Moreover, the probiotic consortium stimulated intestinal stem cell proliferation and differentiation, enhanced the integrity of the intestinal epithelial barrier, and regulated redox imbalance and inflammatory responses in irradiated mice. Notably, the treatment induced a restructuring of the gut microbiota composition, particularly enriching short-chain fatty acid-producing bacteria. Metabolomic analysis revealed distinctive metabolic changes associated with the probiotic consortium, including elevated levels of anti-inflammatory and antiradiation metabolites.

CONCLUSIONS

The probiotic consortium attenuated RIII by modulating the gut microbiota and metabolites, improving inflammatory symptoms, and regulating oxidative stress. These findings provide new insights into the maintenance of intestinal health with probiotic consortium supplementation and will facilitate the development of probiotic-based therapeutic strategies for RIII in clinical practice.

Novel quinazoline sulfonamide-based scaffolds modulate methicillin-resistant Staphylococcus aureus (MRSA) pneumonia in immunodeficient irradiated model: Regulatory role of TGF-β

A library of new quinazoline pharmacophores bearing benzenesulfonamide moiety was designed and synthesized. Compounds 3a-n were screened for their in vitro antimicrobial activity against eight multidrug-resistant clinical isolates. Compounds 3d and 3n exhibited prominent antibacterial activity, specifically against MRSA. After exhibiting relative in vitro and in vivo safety, compound 3n was selected to assess its anti-inflammatory activity displaying promising COX-2 inhibitory activity compared to Ibuprofen. In vivo experimental MRSA pneumonia model was conducted on immunodeficient (irradiated) mice to reveal the antimicrobial and anti-inflammatory responses of compound 3n compared to azithromycin (AZ). Treatment with compound 3n (10 and 20 mg/kg) as well as AZ resulted in a significant decrease in bacterial counts in lung tissues, suppression of serum C-reactive protein (CRP), lung interleukin-6 (IL-6), myeloperoxidase activity (MPO) and transforming growth factor-β (TGF-β). Compound 3n showed a non-significant deviation of lung TGF-β1 from normal values which in turn controlled the lung inflammatory status and impacted the histopathological results. Molecular docking of 3n showed promising interactions inside the active sites of TGF-β and COX-2. Our findings present a new dual-target quinazoline benzenesulfonamide derivative 3n, which possesses significant potential for treating MRSA-induced pneumonia in an immunocompromised state.

PiRNA hsa_piR_019914 Promoted Chondrocyte Anabolic Metabolism By Inhibiting LDHA-Dependent ROS Production

OBJECTIVES

Osteoarthritis (OA) is the most common joint disease. The occurrence and progression of OA are regulated by epigenetics. A large number of studies have shown the important regulatory role of noncoding RNAs in joint diseases. As the largest class of noncoding small RNAs, the importance of piRNAs in many diseases, especially cancer, has been increasingly recognized. However, few studies have explored the role of piRNAs in OA. Our study showed that hsa_piR_019914 decreased significantly in OA. This study aimed to demonstrate the role of hsa_piR_019914 as a potential biological target of OA in chondrocytes.

DESIGN

The GEO database and bioinformatics analysis were used for a series of screenings, and the OA model using human articular chondrocytes (C28/I2 cells), SW1353 cells under inflammatory factor stimulation was used to determine that hsa_piR_019914 was significantly downregulated in OA. Overexpression or inhibition of hsa_piR_019914 in C28/I2 cells was achieved by transfecting mimics or inhibitors. The effect of hsa_piR_019914 on the biological function of chondrocytes was verified by qPCR, flow cytometry, and colony formation assays in vitro. The target gene of hsa_piR_019914, lactate dehydrogenase A (LDHA), was screened by small RNA sequencing and quantitative polymerase chain reaction (qPCR), LDHA was knocked out in C28/I2 cells by the transfection of siRNA LDHA, and the relationship between hsa_piR_019914, LDHA, and reactive oxygen species (ROS) production was verified by flow cytometry.

RESULTS

The piRNA hsa-piR-019914 was significantly downregulated in osteoarthritis (OA). Hsa-piR-019914 reduced inflammation-mediated chondrocyte apoptosis and maintained cell proliferation and clone formation in vitro. Hsa-piR-019914 reduced the production of LDHA-dependent ROS through targeted regulation of LDHA expression, maintained chondrocyte-specific gene expression of ACAN and COL2, and inhibited the gene expression of MMP3 and MMP13.

CONCLUSIONS

Collectively, this study showed that hsa_piR_019914 was negatively correlated with the expression of LDHA, which mediates ROS production. Under the stimulation of inflammatory factors, overexpression of hsa_piR_019914 had a protective effect on chondrocytes in vitro, and the absence of hsa_piR_019914 exacerbated the negative effect of inflammation on chondrocytes. Studies on piRNAs provide new therapeutic interventions for OA.

The peptidyl-prolyl isomerase Pin1 controls GM-CSF-induced priming of NADPH oxidase in human neutrophils and priming at inflammatory sites

The production of superoxide anions and other reactive oxygen species (ROS) by neutrophils is necessary for host defense against microbes. However, excessive ROS production can induce cell damage that participates in the inflammatory response. Superoxide anions are produced by the phagocyte NADPH oxidase, a multicomponent enzyme system consisting of two transmembrane proteins (gp91phox/NOX2 and p22phox) and four soluble cytosolic proteins (p40phox, p47phox, p67phox and the small G proteins Rac1/2). Stimulation of neutrophils by various agonists, such as the bacterial peptide formyl-Met-Leu-Phe (fMLF), induces NADPH oxidase activation and superoxide production, a process that is enhanced by the pro-inflammatory cytokines such as GM-CSF. The pathways involved in this GM-CSF-induced up-regulation or priming are not fully understood. Here we show that GM-CSF induces the activation of the prolyl cis/trans isomerase Pin1 in human neutrophils. Juglone and PiB, two selective Pin1 inhibitors, were able to block GM-CSF-induced priming of ROS production by human neutrophils. Interestingly, GM-CSF induced Pin1 binding to phosphorylated p47phox at Ser345. Neutrophils isolated from synovial fluid of patients with rheumatoid arthritis are known to be primed. Here we show that Pin1 activity was also increased in these neutrophils and that Pin1 inhibitors effectively inhibited ROS hyperproduction by the same cells. These results suggest that the prolyl cis/trans isomerase Pin1 may control GM-CSF-induced priming of ROS production by neutrophils and priming of neutrophils in synovial fluid of rheumatoid arthritis patients. Pharmacological targeting of Pin1 may be a valuable approach to the treatment of inflammation.

Enhanced effect of limb remote ischemic postconditioning combined with paeoniflorin on alleviating cerebral ischemic injury via neutrophil NADPH pathway

BACKGROUND

Limb remote ischemic postconditioning (LRIP) and paeoniflorin (PF) both can ameliorate cerebral ischemia reperfusion (I/R) injury. At present, whether LRIP combined with PF can achieve better therapeutic effect is unknown.

PURPOSE

This study explored the alleviating effect and mechanism of LRIP in combination with PF on cerebral I/R injury in rats.

METHODS

Middle cerebral artery occlusion (MCAO) surgery was performed on rats except Sham group. Then PF (2.5 mg/kg, 5 mg/kg, 10 mg/kg) was administrated by intraperitoneal injection 10 min before the start of reperfusion. LRIP was operated on the left femoral artery at 0 h of reperfusion. Behavioral testing was used to assess neurological impairment, while TTC staining was used to examine infarct volume. Protein expression of MyD88, TRAF6, p38-MAPK and phosphorylation of p47phox in neutrophils from rat peripheral blood were tested by Western blot. Rat bone marrow neutrophils were extracted and incubated for 24 h with serum from rats after LRIP combined with PF. p38 MAPK inhibitor group was administrated SB203580 while the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor group was administrated Apocynin. Neutrophils were stimulated by fMLP (10 μM). Reactive oxygen species (ROS) production and protein expression of MyD88, TRAF6, p38 MAPK, and p47phox (ser 304 and ser 345) were detected.

RESULTS

LRIP combined with PF (5 mg/kg) reduced cerebral infarct volume, ameliorated neurological deficit score (NDS), decreased fMLP-stimulated ROS release and downregulated the protein expression of MyD88, TRAF6, p38-MAPK and phosphorylation of p47phox (ser 304 and ser 345) in neutrophils.

CONCLUSION

The protective effect of LRIP combined with PF on cerebral I/R injury was better than either alone. Taken together, we provided solid evidence to demonstrate that the combination of LRIP and PF had potential to alleviate cerebral I/R injury, which was regulated by MyD88-TRAF6-p38 MAPK pathway and neutrophil NADPH oxidase pathway.

Drug repurposing of cyclin-dependent kinase inhibitors for neutrophilic acute respiratory distress syndrome and psoriasis

BACKGROUND

Neutrophilic inflammation, characterized by dysregulated neutrophil activation, triggers a variety of inflammatory responses such as chemotactic infiltration, oxidative bursts, degranulation, neutrophil extracellular traps (NETs) formation, and delayed turnover. This type of inflammation is pivotal in the pathogenesis of acute respiratory distress syndrome (ARDS) and psoriasis. Despite current treatments, managing neutrophil-associated inflammatory symptoms remains a significant challenge.

AIM OF REVIEW

This review emphasizes the role of cyclin-dependent kinases (CDKs) in neutrophil activation and inflammation. It aims to highlight the therapeutic potential of repurposing CDK inhibitors to manage neutrophilic inflammation, particularly in ARDS and psoriasis. Additionally, it discusses the necessary precautions for the clinical application of these inhibitors due to potential off-target effects and the need for dose optimization.

KEY SCIENTIFIC CONCEPTS OF REVIEW

CDKs regulate key neutrophilic functions, including chemotactic responses, degranulation, NET formation, and apoptosis. Repurposing CDK inhibitors, originally developed for cancer treatment, shows promise in controlling neutrophilic inflammation. Clinical anticancer drugs, palbociclib and ribociclib, have demonstrated efficacy in treating neutrophilic ARDS and psoriasis by targeting off-label pathways, phosphoinositide 3-kinase (PI3K) and phosphodiesterase 4 (PDE4), respectively. While CDK inhibitors offer promising therapeutic benefits, their clinical repurposing requires careful consideration of off-target effects and dose optimization. Further exploration and clinical trials are necessary to ensure their safety and efficacy in treating inflammatory conditions.

(Chemical) Roles of HOCl in Rheumatic Diseases

Chronic rheumatic diseases such as rheumatoid arthritis (RA) are characterized by a dysregulated immune response and persistent inflammation. The large number of neutrophilic granulocytes in the synovial fluid (SF) from RA patients leads to elevated enzyme activities, for example, from myeloperoxidase (MPO) and elastase. Hypochlorous acid (HOCl), as the most important MPO-derived product, is a strong reactive oxygen species (ROS) and known to be involved in the processes of cartilage destruction (particularly regarding the glycosaminoglycans). This review will discuss open questions about the contribution of HOCl in RA in order to improve the understanding of oxidative tissue damaging. First, the (chemical) composition of articular cartilage and SF and the mechanisms of cartilage degradation will be discussed. Afterwards, the products released by neutrophils during inflammation will be summarized and their effects towards the individual, most abundant cartilage compounds (collagen, proteoglycans) and selected cellular components (lipids, DNA) discussed. New developments about neutrophil extracellular traps (NETs) and the use of antioxidants as drugs will be outlined, too. Finally, we will try to estimate the effects induced by these different agents and their contributions in RA.

Impact of polystyrene nanoplastics on apoptosis and inflammation in zebrafish larvae: Insights from reactive oxygen species perspective

In recent years, there has been a growing focus on the toxicity and mortality induced by nanoplastics (NPs) in aquatic organisms. However, studies investigating mechanisms underlying oxidative stress (OS), apoptosis, and inflammation induced by NPs in fish remain limited. This study observed that polystyrene NPs (PS-NPs) were accumulated into zebrafish larvae and zebrafish embryonic fibroblast (ZF4 cells), accompanied by the occurrence of pathological damage both at the cellular and tissue-organ level. Additionally, the transcriptional up-regulation of NADPH oxidases (NOXs) and subsequent excessive generation of reactive oxygen species (ROS) resulted in notable changes in the relative mRNA and protein expression levels associated with antioxidant oxidase systems in larvae. Furthermore, the study identified the impact of NPs on mitochondrial ultrastructural, resulting in mitochondrial depolarization and downregulation of mRNA expression related to the electron transport chain due to excessive ROS generation. Short-term exposure to NPs also triggered apoptosis and inflammation in zebrafish larvae, evident from significant up-regulation in mRNA expressions of proapoptotic factors and NF-κB proinflammatory signaling pathway, as well as increased transcription and protein levels of pro-inflammatory factors in larvae. Inhibition of intracellular excessive ROS effectively reduced the induction of apoptosis, NF-κB P65 nuclear migration levels, and cytokine secretion, underscoring OS as a pivotal factor throughout the process of apoptosis and inflammatory responses induced by NPs. This research significantly advances our comprehension of biological effects and underlying mechanisms of NPs in freshwater fish.

Ribosomal proteins: the missing piece in the inflammation puzzle?

Ribosomal proteins (RPs) are constituents of macromolecular machinery, ribosome that translates genetic information into proteins. Besides ribosomal functions, RPs are now getting appreciated for their 'moonlighting'/extra-ribosomal functions modulating many cellular processes. Accumulating evidence suggests that a number of RPs are involved in inflammation. Though acute inflammation is a part of the innate immune response, uncontrolled inflammation is a driving factor for several chronic inflammatory diseases. An in-depth understanding of inflammation regulation has always been valued for the better management of associated diseases. Hence, this review first outlines the common livelihood of RPs and then provides a comprehensive account of five RPs that significantly contribute to the inflammation process. Finally, we discuss the possible therapeutic uses of RPs against chronic inflammatory diseases.

Tumor mutational burden adjusted by neutrophil-to-lymphocyte ratio serves as a potential biomarker for atezolizumab-treated patients with extensive stage small cell lung cancer

BACKGROUND

There is a desperate for the identification of more accurate and efficient biomarkers for ICI responses in patients with SCLC.

METHODS

The data of our study was obtained from IMpower133 study. A total of 202 patients with SCLC received the treatment of placebo plus carboplatin plus etoposide (EC) while a total of 201 patients with SCLC received the treatment of atezolizumab plus EC. Overall survival (OS) was compared using Kaplan Meier analyses. Univariate and multivariate Cox regression analysis were used to determine independent prognostic variables affecting OS in patients with SCLC.

RESULTS

We have demonstrated that a higher TMB adjusted by a lower neutrophil-to-lymphocyte ratio (NLR) is significantly correlated with improved OS, in patients with SCLC subject to either atezolizumab or placebo (P = 0.001 for atezolizumab and P = 0.034 for placebo). Moreover, Cox model showed that TMB < 10 mut/Mb adjusted by NLR ≥ median was an independent factor of OS for atezolizumab-treated SCLC patients (hazard ratio [HR], 2.82; 95% confidence interval; 1.52-5.24; P = 0.001). Both univariate and multivariate cox regression analysis showed that for patients with SCLC harboring low NLR and high TMB, survival is significantly longer in those treated with atezolizumab than those treated with placebo. Survival benefit is significantly higher in atezolizumab-treated patients with SCLC than those treated with placebo (P = 0.018 for TMB cutoff = 10 mut/Mb, P = 0.034 for TMB cutoff = 16 mut/Mb).

CONCLUSION

Our findings provide a promising insight into the utility of NLR-adjusted TMB in the prognosis and immune responses in patients with SCLC.

Neutrophil Oxidative Burst Profile Is Related to a Satisfactory Response to Itraconazole and Clinical Cure in Feline Sporotrichosis

Despite the central role of cats in the transmission and amplification of Sporothrix, studies regarding immune response in feline sporotrichosis are scarce. In cats with sporotrichosis, neutrophil-rich lesions are usually associated to good general condition and lower fungal burden. However, the role of neutrophils in anti-Sporothrix immunity has been little explored in cats. Thus, the aim of this study was to evaluate the neutrophil oxidative burst in the blood of cats with sporotrichosis. Cats with sporotrichosis included in the study were treated with itraconazole (ITZ) alone or combined with potassium iodide (KI). The neutrophil oxidative burst was evaluated through a flow-cytometry-based assay using dihydrorhodamine 123 (background) and stimulation with Zymosan and heat-killed Sporothrix yeasts. The cure rate was 50.0% in cats under treatment with ITZ monotherapy and 90.9% in cats treated with ITZ + KI (p = 0.014), endorsing the combination therapy as an excellent alternative for the treatment of feline sporotrichosis. Higher percentages of Sporothrix-stimulated neutrophils were associated with good general condition (p = 0.003). Higher percentages of Sporothrix- (p = 0.05) and Zymosan-activated (p = 0.014) neutrophils before and early in the treatment were related to clinical cure in ITZ-treated cats. The correlation between oxidative burst and successful use of KI could not be properly assessed given the low number of failures (n = 2) in this treatment group. Nasal mucosa involvement, typically linked to treatment failure, was related to lower percentages of activated neutrophils in the background at the treatment outcome (p = 0.02). Our results suggest a beneficial role of neutrophils in feline sporotrichosis and a positive correlation between neutrophil activation and the cure process in ITZ-treated cats.

Exploring the Impact of French Raw-Milk Cheeses on Oxidative Process Using Caenorhabditis elegans and Human Leukocyte Models

Fermented foods, including cheeses, have garnered increased interest in recent years for their potential health benefits. This study explores the biological properties of eight French raw-milk cheeses-goat cheese, Saint-Nectaire, Cantal, Bleu d'Auvergne, Roquefort, Comté, Brie de Meaux, and Epoisses-on oxidative processes using both in vivo (Caenorhabditis elegans) and in vitro (human leukocytes) models. A cheese fractionation protocol was adapted to study four fractions for each cheese: a freeze-dried fraction (FDC) corresponding to whole cheese, an apolar (ApE), and two polar extracts (W40 and W70). We showed that all cheese fractions significantly improved Caenorhabditis elegans (C. elegans) survival rates when exposed to oxidative conditions by up to five times compared to the control, regardless of the fractionation protocol and the cheese type. They were also all able to reduce the in vivo accumulation of reactive oxygen species (ROS) by up to 70% under oxidative conditions, thereby safeguarding C. elegans from oxidative damage. These beneficial effects were explained by a reduction in ROS production up to 50% in vitro in human leukocytes and overexpression of antioxidant factor-encoding genes (daf-16, skn-1, ctl-2, and sod-3) in C. elegans.

Direct Interaction of Minocycline to p47phox Contributes to its Attenuation of TNF-α-Mediated Neuronal PC12 Cell Death: Experimental and Simulation Validation

Minocycline, a repurposed approved medication, shows promise in treating neurodegeneration. However, the specific pathways targeted by minocycline remain unclear despite the identification of molecular targets. This study explores minocycline's potential protective effects against TNF-α-mediated neuronal death in PC12 cells, with a focus on unraveling its interactions with key molecular targets. The study begins by exploring minocycline's protective role against TNF-α-mediated neuronal death in PC12 cells, showcasing a substantial reduction in cleaved caspase-3 expression, DNA fragmentation, and intracellular ROS levels following minocycline pretreatment. Subsequently, a comprehensive analysis utilizing pull-down assays, computational docking, mutation analysis, molecular dynamics simulations, and free energy calculations is conducted to elucidate the direct interaction between minocycline and p47phox-the organizer subunit of NADPH oxidase-2 (NOX2) complex. Computational insights, including a literature survey and analysis of key amino acid residues, reveal a potential binding site for minocycline around Trp193 and Cys196. In silico substitutions of Trp193 and Cys196 further confirm their importance in binding with minocycline. These integrated findings underscore minocycline's protective mechanisms, linking its direct interaction with p47phox to the modulation of NOX2 activity and attenuation of NOX-derived ROS generation. Minocycline demonstrates protective effects against TNF-α-induced PC12 cell death, potentially linked to its direct interaction with p47phox. This interaction leads to a reduction in NOX2 complex assembly, ultimately attenuating NOX-derived ROS generation. These findings hold significance for researchers exploring neuroprotection and the development of p47phox inhibitors.

Membrane potential dynamics of C5a-stimulated neutrophil granulocytes

Neutrophil granulocytes play a crucial role in host defense against invading pathogens and in inflammatory diseases. The aim of this study was to elucidate membrane potential dynamics during the initial phase of neutrophil activation and its relation to migration and production of reactive oxygen species (ROS). We performed ROS production measurements of neutrophils from healthy C57BL/6J mice after TNFα-priming and/or C5a stimulation. The actin cytoskeleton was visualized with fluorescence microscopy. Furthermore, we combined migration assays and measurements of membrane potential dynamics after stimulating unprimed and/or TNFα-primed neutrophils with C5a. We show that C5a has a concentration-dependent effect on ROS production and chemokinetic migration. Chemokinetic migration and chemotaxis are impaired at C5a concentrations that induce ROS production. The actin cytoskeleton of unstimulated and of ROS-producing neutrophils is not distributed in a polarized way. Inhibition of the phagocytic NADPH oxidase NOX2 with diphenyleneiodonium (DPI) leads to a polarized distribution of the actin cytoskeleton and rescues chemokinetic migration of primed and C5a-stimulated neutrophils. Moreover, C5a evokes a pronounced depolarization of the cell membrane potential by 86.6 ± 4.2 mV starting from a resting membrane potential of -74.3 ± 0.7 mV. The C5a-induced depolarization occurs almost instantaneously (within less than one minute) in contrast to the more gradually developing depolarization induced by PMA (lag time of 3-4 min). This initial depolarization is accompanied by a decrease of the migration velocity. Collectively, our results show that stimulation with C5a evokes parallel changes in membrane potential dynamics, neutrophil ROS production and motility. Notably, the amplitude of membrane potential dynamics is comparable to that of excitable cells.

Transcriptomic insights into vibrio-induced mortality in the clam Meretrix petechialis under high temperature

In this study, we investigate the mortality of the clam Meretrix petechialis facing a vibrio challenge under different temperatures and the underlying molecular mechanisms. Our experiment distinctly revealed that clam mortality was predominantly observed under high temperature, highlighting the critical impact of thermal stress on clam susceptibility to infection. Using RNA-seq, we further compared the global transcriptional response to vibrio in clam gills between high and low temperatures. Compared to other groups, the differentially expressed genes in vibrio-challenged group at high temperature associated with immunity, oxidative stress, and membrane transport. Key results show a weakened immune response in clams at high temperature, especially in the TNF signaling pathway, and a decrease in membrane transport efficiency, notably in SLC proteins. Additionally, high temperature enhanced pro-inflammatory related unsaturated fatty acid metabolism, leading to increased oxidative damage. This was further evidenced by our biochemical assays, which showed significantly higher levels of lipid peroxidation and protein carbonylation in clams at high temperature, indicating heightened oxidative damage. RT-PCR validation of selected DEGs corroborated the RNA-seq findings. Our findings contribute to the understanding of more frequent shellfish mortality in summer, emphasizing the role of temperature in pathogen response, elucidating the molecular mechanisms underlying the synergistic effect of pathogen and high temperature stresses. The key genes identified provide potential targets for resistance-assisted breeding. This research has significant implications for bivalve aquaculture and their physiology, particularly in light of global climate changes affecting marine ecosystems.

Neutrophil Virucidal Activity Against SARS-CoV-2 Is Mediated by Neutrophil Extracellular Traps

BACKGROUND

Inflammation in the lungs and other vital organs in COVID-19 is characterized by the presence of neutrophils and a high concentration of neutrophil extracellular traps (NETs), which seems to mediate host tissue damage. However, it is not known whether NETs could have virucidal activity against SARS-CoV-2.

METHODS

We investigated whether NETs could prevent SARS-CoV-2 replication in neutrophils and epithelial cells and what the consequence of NETs degradation would be in K18-humanized ACE2 transgenic mice infected with SARS-CoV-2.

RESULTS

Here, by immunofluorescence microscopy, we observed that viral particles colocalize with NETs in neutrophils isolated from patients with COVID-19 or healthy individuals and infected in vitro. The inhibition of NETs production increased virus replication in neutrophils. In parallel, we observed that NETs inhibited virus abilities to infect and replicate in epithelial cells after 24 hours of infection. Degradation of NETs with DNase I prevented their virucidal effect in vitro. Using K18-humanized ACE2 transgenic mice, we observed a higher viral load in animals treated with DNase I. However, the virucidal effect of NETs was not dependent on neutrophil elastase or myeloperoxidase activity.

CONCLUSIONS

Our results provide evidence of the role of NETosis as a mechanism of SARS-CoV-2 viral capture and inhibition.

Histone H3 posttranslational modified enzymes defined neutrophil plasticity and their vulnerability to IL-10 in the course of the inflammation

BACKGROUND

Neutrophils are a heterogeneous population capable of antimicrobial functions associated with pre-activation/activation and tissue regeneration. The specific polarisation of immune cells is mediated by the modification of 'chromatin landscapes', which enables differentiated access and activity of regulatory elements that guarantee their plasticity during inflammation No specific pattern within histone posttranslational modifications (PTMs) controlling this plasticity has been identified.

METHODS

Using the in vitro model of inflammation, reflecting different states of neutrophils from resting, pre-activated cells to activated and reducing tissue regeneration, we have analysed 11 different histone posttranslational modifications (PTMs), PTM enzymes associated with remodelling neutrophil chromatin, and H3K4me3 ChIP-Seq Gene Ontology analysis focusing on the processes related to histone PTMs. These findings were verified by extrapolation to adequate clinical status, using neutrophils derived from the patients with sepsis (systemic septic inflammation with LPS-stimulated neutrophils), neuromyelitis optical spectrum disorders (aseptic inflammation with pre-activated neutrophils) and periodontitis (local self-limiting septic inflammation with IL-10-positive neutrophils).

RESULTS

Physiological activation of neutrophils comprises a pre-activation characterised by histone H3K27ac and H3K4me1, which position enhancers; direct LPS exposure is induced explicitly by H3K4me3 which marked Transcription Start Site (TSS) regions and low-level of H3K9me3, H3K79me2 and H3K27me3 which, in turn, marked repressed genes. Contrary to antimicrobial action, IL-10 positively induced levels of H3S10p and negatively H3K9me3, which characterised processes related to the activation of genes within heterochromatin mediated by CHD1 and H3K9me3 specific demethylase JMJD2A. IL-10 protects changes within histone PTMs induced by TNF or LPS that affected H3K4me3-specific methyltransferase SETD1A and MLL1. Neutrophils previously exposed to inflammatory factors become unvulnerable to IL-10 because previous LPS stimulation interrupts TSS regions marked by H3K4me3 of CHD1 and JMJD2A genes. Therefore, LPS-activated neutrophils are disabled to induce CHD1/JMJD2A enzymes by IL-10, making this process irreversible. Because transcription of JMJD2A and CHD1 also depends on TSS positioning by H3K4me3, neutrophils before LPS stimulation become insensitive to IL-10.

CONCLUSION

Neutrophils, once pre-activated by TNF or directly stimulated by LPS, become insensitive to the anti-inflammatory effects of IL-10, and vice versa; IL-10 protects neutrophils against these proinflammatory stimuli. This phenomenon is responsible for disturbing the natural process of resolving inflammation and tissue regeneration.

Endothelial ERG programs neutrophil transcriptome for sustained anti-inflammatory vascular niche

Neutrophils (PMNs) reside as a marginated pool within the vasculature, ready for deployment during infection. However, how endothelial cells (ECs) control PMN extravasation and activation to strengthen tissue homeostasis remains ill-defined. Here, we found that the vascular ETS-related gene (ERG) is a generalized mechanism regulating PMN activity in preclinical tissue injury models and human patients. We show that ERG loss in ECs rewired PMN-transcriptome, enriched for genes associated with the CXCR2-CXCR4 signaling. Rewired PMNs compromise mice survival after pneumonia and induced lung vascular inflammatory injury following adoptive transfer into naïve mice, indicating their longevity and inflammatory activity memory. Mechanistically, EC-ERG restricted PMN extravasation and activation by upregulating the deubiquitinase A20 and downregulating the NFκB-IL8 cascade. Rescuing A20 in EC-Erg -/- endothelium or suppressing PMN-CXCR2 signaling rescued EC control of PMN activation. Findings deepen our understanding of EC control of PMN-mediated inflammation, offering potential avenues for targeting various inflammatory diseases.

Highlights

ERG regulates trans-endothelial neutrophil (PMN) extravasation, retention, and activationLoss of endothelial (EC) ERG rewires PMN-transcriptomeAdopted transfer of rewired PMNs causes inflammation in a naïve mouse ERG transcribes A20 and suppresses CXCR2 function to inactivate PMNs.

In brief/blurb

The authors investigated how vascular endothelial cells (EC) control polymorphonuclear neutrophil (PMN) extravasation, retention, and activation to strengthen tissue homeostasis. They showed that EC-ERG controls PMN transcriptome into an anti-adhesive and anti-inflammatory lineage by synthesizing A20 and suppressing PMNs-CXCR2 signaling, defining EC-ERG as a target for preventing neutrophilic inflammatory injury.

Identification of early events in nitrogen mustard pulmonary toxicity that are independent of infiltrating inflammatory cells using precision cut lung slices

Nitrogen mustard (NM; mechlorethamine) is a cytotoxic vesicant known to cause acute lung injury which can progress to chronic disease. Due to the complex nature of NM injury, it has been difficult to analyze early responses of resident lung cells that initiate inflammation and disease progression. To investigate this, we developed a model of acute NM toxicity using murine precision cut lung slices (PCLS), which contain all resident lung cell populations. PCLS were exposed to NM (1-100 μM) for 0.5-3 h and analyzed 1 and 3 d later. NM caused a dose-dependent increase in cytotoxicity and a reduction in metabolic activity, as measured by LDH release and WST-1 activity, respectively. Optimal responses were observed with 50 μM NM after 1 h incubation and these conditions were used in further experiments. Analysis of PCLS bioenergetics using an Agilent Seahorse showed that NM impaired both glycolytic activity and mitochondrial respiration. This was associated with injury to the bronchial epithelium and a reduction in methacholine-induced airway contraction. NM was also found to cause DNA damage in bronchial epithelial cells in PCLS, as measured by expression of γ-H2AX, and to induce oxidative stress, which was evident by a reduction in glutathione levels and upregulation of the antioxidant enzyme catalase. Cleaved caspase-3 was also upregulated in airway smooth muscle cells indicating apoptotic cell death. Characterizing early events in NM toxicity is key in identifying therapeutic targets for the development of efficacious countermeasures.

Programmable stopped-flow injection analysis: A comparative study on the effects of adenosine and its aptamer on respiratory burst of salivary and circulatory neutrophils

Neutrophils play a pivotal role in innate immunity by releasing ROS through respiratory bursts to neutralize various pathogenic factors. However, excessive ROS release can cause tissue damage. Adenosine is an endogenous anti-inflammatory molecule inhibiting respiratory burst to protect the host. Adenosine aptamers with antibody-like properties and good stability are expected to act as adenosine antagonists with functional modulation capability. This study compares the effects of adenosine and its aptamer on the respiratory bursts of salivary polymorphonuclear leukocytes and circulating polymorphonuclear leukocytes using a programmable stopped-flow injection approach, ensuring rapid and efficient analysis while maintaining the neutrophils' viability. The results show that primed salivary polymorphonuclear leukocytes exhibit specificities that differ from circulating polymorphonuclear leukocytes. Adenosine aptamer can function as an inhibitory antagonist that distinguishes between physiologically controlled and excessive priming of neutrophils, showing potential application prospects in immunotherapy.

Neutrophil Infiltration and Function in the Pathogenesis of Inflammatory Airspace Disease

Neutrophils are an important cell type often considered the body's first responders to inflammatory insult or damage. They are recruited to the tissue of the lungs in patients with inflammatory airspace diseases and have unique and complex functions that range from helpful to harmful. The uniqueness of these functions is due to the heterogeneity of the inflammatory cascade and retention in the vasculature. Neutrophils are known to marginate, or remain stagnant, in the lungs even in nondisease conditions. This review discusses the ways in which the recruitment, presence, and function of neutrophils in the airspace of the lungs are unique from those of other tissues, and the complex effects of neutrophils on pathogenesis. Inflammatory mediators produced by neutrophils, such as neutrophil elastase, proresolving mediators, and neutrophil extracellular traps, dramatically affect the outcomes of patients with disease of the lungs.

Integrating Artificial DNAzymes with Natural Enzymes on 2D MOF Hybrid Nanozymes for Enhanced Treatment of Bacteria-Infected Wounds

Removal of invasive bacteria is critical for proper wound healing. This task is challenging because these bacteria can trigger intense oxidative stress and gradually develop antibiotic resistance. Here, the use of a multienzyme-integrated nanocatalytic platform is reported for efficient bacterial clearance and mitigation of inflammatory responses, constructed by physically adsorbing natural superoxide dismutase (SOD), in situ reduction of gold nanoparticles (Au NPs), and incorporation of a DNAzyme on 2D NiCoCu metal-organic frameworks (DNAzyme/SOD/Au@NiCoCu MOFs, termed DSAM), which can adapt to infected wounds. O2 and H2O2 replenishment is achieved and alleviated the hypoxic microenvironment using the antioxidant properties of SOD. The H2O2 produced during the reaction is decomposed by peroxidase (POD)-like activity enhanced by Au NPs and DNAzyme, releasing highly toxic hydroxyl radicals (•OH) to kill the bacteria. In addition, it possesses glutathione peroxidase (GPx)-like activity, which depletes GSH and prevents •OH loss. Systematic antimicrobial tests are performed against bacteria using this multienzyme-integrated nanoplatform. A dual-mode strategy involving natural enzyme-enhanced antioxidant capacity and artificial enzyme-enhanced •OH release to develop an efficient and novel enzyme-integrated therapeutic platform is integrated.

Neutrophils versus Protozoan Parasites: Plasmodium, Trichomonas, Leishmania, Trypanosoma, and Entameoba

Neutrophils are the most abundant polymorphonuclear granular leukocytes in human blood and are an essential part of the innate immune system. Neutrophils are efficient cells that eliminate pathogenic bacteria and fungi, but their role in dealing with protozoan parasitic infections remains controversial. At sites of protozoan parasite infections, a large number of infiltrating neutrophils is observed, suggesting that neutrophils are important cells for controlling the infection. Yet, in most cases, there is also a strong inflammatory response that can provoke tissue damage. Diseases like malaria, trichomoniasis, leishmaniasis, Chagas disease, and amoebiasis affect millions of people globally. In this review, we summarize these protozoan diseases and describe the novel view on how neutrophils are involved in protection from these parasites. Also, we present recent evidence that neutrophils play a double role in these infections participating both in control of the parasite and in the pathogenesis of the disease.

Eugenol Inhibits Neutrophils Myeloperoxidase In Vitro and Attenuates LPS-Induced Lung Inflammation in Mice

Eugenol (Eug) is a polyphenol extracted from the essential oil of Syzygium aromaticum (L.) Merr. and Perry (Myrtaceae). The health benefits of eugenol in human diseases were proved in several studies. This work aims to evaluate the effect of eugenol on lung inflammatory disorders. For this, using human neutrophils, the antioxidant activity of eugenol was investigated in vitro. Furthermore, a model of LPS-induced lung injury in mice was used to study the anti-inflammatory effect of eugenol in vivo. Results showed that eugenol inhibits luminol-amplified chemiluminescence of resting neutrophils and after stimulation with N-formyl-methionyl-leucyl-phenylalanine (fMLF) peptide or phorbol myristate acetate (PMA). This effect was dose dependent and was significant from a low concentration of 0.1 µg/mL. Furthermore, eugenol inhibited myeloperoxidase (MPO) activity without affecting its degranulation. Eugenol has no scavenging effect on hydrogen peroxide (H2O2) and superoxide anion (O2-). Pretreatment of mice with eugenol prior to the administration of intra-tracheal LPS significantly reduced neutrophil accumulation in the bronchoalveolar lavage fluid (BALF) and decreased total proteins concentration. Moreover, eugenol clearly inhibited the activity of matrix metalloproteinases MMP-2 (21%) and MMP-9 (28%), stimulated by LPS administration. These results suggest that the anti-inflammatory effect of eugenol against the LPS-induced lung inflammation could be exerted via inhibiting myeloperoxidase and metalloproteinases activity. Thus, eugenol could be a promising molecule for the treatment of lung inflammatory diseases.

Neutrophils and Anesthetic Drugs: Implications in Onco-Anesthesia

Apart from being a significant line of defense in the host defense system, neutrophils have many immunological functions. Although there are not many publications that accurately present the functions of neutrophils in relation to oncological pathology, their activity and implications have been studied a lot recently. This review aims to extensively describe neutrophils functions'; their clinical implications, especially in tumor pathology; the value of clinical markers related to neutrophils; and the implications of neutrophils in onco-anesthesia. This review also aims to describe current evidence on the influence of anesthetic drugs on neutrophils' functions and their potential influence on perioperative outcomes.

Hesperetin regulates the intestinal flora and inhibits the TLR4/NF-κB signaling axis to protect the blood-milk barrier and prevent mastitis

The World Health Organization recommends breastfeeding for 6 months, but mastitis, a common disease during lactation, presents a major obstacle to fulfilling this recommendation. Maternal nutrient intake during lactation has been shown to be related to mastitis. Therefore, this study aimed to explore the effect of hesperetin, a phytonutrient, on mastitis. The oral administration of hesperetin to lipopolysaccharide (LPS)-induced mastitis mice alleviated their pathological damage, reduced the secretion of pro-inflammatory cytokines, and maintained the integrity of their blood-milk barrier. Moreover, our results showed that oral administration of hesperetin regulates the composition of the intestinal flora of mice. Fecal microbial transplantation (FMT) from the mice of hesperetin group alleviated LPS-induced mastitis in recipient mice. In additional, hesperetin attenuated the inflammatory response and increased the expression of tight junction proteins (TJs) in LPS-stimulated mouse mammary epithelial cells (mMECs). Through network pharmacological analysis and further research, we demonstrated hesperetin inhibits the expression of TLR4 and the activation of NF-κB signaling. In conclusion, hesperetin protects the blood-milk barrier and improve mastitis by regulating intestinal flora and inhibiting the activation of TLR4/NF-κB signaling axis. This study provides a theoretical basis for lactating females to consume hesperetin as a supplement to prevent mastitis and maintain mammary health.

IL-17RA-Mediated Epithelial Cell Activity Prevents Severe Inflammatory Response to Helicobacter pylori Infection

Helicobacter pylori is a Gram-negative pathogen that colonizes the stomach, induces inflammation, and drives pathological changes in the stomach tissue, including gastric cancer. As the principal cytokine produced by Th17 cells, IL-17 mediates protective immunity against pathogens by inducing the activation and mobilization of neutrophils. Whereas IL-17A is largely produced by lymphocytes, the IL-17 receptor is expressed in epithelial cells, fibroblasts, and hematopoietic cells. Loss of the IL-17RA in mice results in impaired antimicrobial responses to extracellular bacteria. In the context of H. pylori infection, this is compounded by extensive inflammation in Il17ra-/- mice. In this study, Foxa3creIl17rafl/fl (Il17raΔGI-Epi) and Il17rafl/fl (control) mice were used to test the hypothesis that IL-17RA signaling, specifically in epithelial cells, protects against severe inflammation after H. pylori infection. The data indicate that Il17raΔGI-Epi mice develop increased inflammation compared with controls. Despite reduced Pigr expression, levels of IgA increased in the gastric wash, suggesting significant increase in Ag-specific activation of the T follicular helper/B cell axis. Gene expression analysis of stomach tissues indicate that both acute and chronic responses are significantly increased in Il17raΔGI-Epi mice compared with controls. These data suggest that a deficiency of IL-17RA in epithelial cells is sufficient to drive chronic inflammation and hyperactivation of the Th17/T follicular helper/B cell axis but is not required for recruitment of polymorphonuclear neutrophils. Furthermore, the data suggest that fibroblasts can produce chemokines in response to IL-17 and may contribute to H. pylori-induced inflammation through this pathway.

Neutrophil Extracellular DNA Traps in Response to Infection or Inflammation, and the Roles of Platelet Interactions

Neutrophils present the host's first line of defense against bacterial infections. These immune effector cells are mobilized rapidly to destroy invading pathogens by (a) reactive oxygen species (ROS)-mediated oxidative bursts and (b) via phagocytosis. In addition, their antimicrobial service is capped via a distinct cell death mechanism, by the release of their own decondensed nuclear DNA, supplemented with a variety of embedded proteins and enzymes. The extracellular DNA meshwork ensnares the pathogenic bacteria and neutralizes them. Such neutrophil extracellular DNA traps (NETs) have the potential to trigger a hemostatic response to pathogenic infections. The web-like chromatin serves as a prothrombotic scaffold for platelet adhesion and activation. What is less obvious is that platelets can also be involved during the initial release of NETs, forming heterotypic interactions with neutrophils and facilitating their responses to pathogens. Together, the platelet and neutrophil responses can effectively localize an infection until it is cleared. However, not all microbial infections are easily cleared. Certain pathogenic organisms may trigger dysregulated platelet-neutrophil interactions, with a potential to subsequently propagate thromboinflammatory processes. These may also include the release of some NETs. Therefore, in order to make rational intervention easier, further elucidation of platelet, neutrophil, and pathogen interactions is still needed.

Electroacupuncture Attenuates Ventilator-Induced Lung Injury by Modulating the Nrf2/HO-1 Pathway

INTRODUCTION

Ventilator-induced lung injury (VILI) is the most common complication associated with mechanical ventilation. Electroacupuncture (EA) has shown potent anti-inflammatory effects. This study aimed to investigate the effects of EA on VILI and explore the underlying mechanisms.

METHODS

Male C57BL/6 mice were subjected to high tidal volume ventilation to induce VILI. Prior to mechanical ventilation, mice received treatment with EA, nonacupoint EA, or EA combined with zinc protoporphyrin.

RESULTS

EA treatment significantly improved oxygenation, as indicated by increased PaO2 levels in VILI mice. Moreover, EA reduced lung injury score, lung wet/dry weight ratio, and protein concentration in bronchoalveolar lavage fluid. EA also decreased the expression of pro-inflammatory cytokines including interleukin (IL)-1β, IL-6, tumor necrosis factor-α, IL-18, chemokine keratinocyte chemoattractant, macrophage inflammatory protein 2, and malondialdehyde. Furthermore, EA increased the activities of antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase in VILI mice. At the molecular level, EA upregulated the expression of Nrf2 (nucleus) and heme oxygenase -1, while down-regulating the expression of p-NF-κB p65, NLR Family Pyrin Domain Containing 3, Cleaved Caspase-1, and ASC in VILI mice. Notably, the effects of EA were reversed by zinc protoporphyrin treatment, nonacupoint EA did not affect the aforementioned indicators of VILI.

CONCLUSIONS

EA alleviates VILI by inhibiting the NLR Family Pyrin Domain Containing three inflammasome through activation of the Nrf2/HO-1 pathway.

Synthetic Antimicrobial Peptides Fail to Induce Leucocyte Innate Immune Functions but Elicit Opposing Transcriptomic Profiles in European Sea Bass and Gilthead Seabream

Antimicrobial peptides (AMPs) are promising molecules in diverse fields, including aquaculture. AMPs possess lytic effects on a wide range of pathogens, resulting in a potential replacement for traditional antimicrobials in aquaculture. In addition, they also have modulatory effects on host immune responses. Thus, the objective of this work was to evaluate the immunomodulatory capability of three known synthetic AMPs derived from European sea bass, NK-lysin (Nkl), hepcidin (Hamp), and dicentracin (Dic), in head-kidney cell suspensions from European sea bass and gilthead seabream. The tested peptides were neither cytotoxic for European sea bass nor gilthead seabream cells and failed to modulate the respiratory burst and phagocytosis activities. However, they modified the pattern of transcription of immune-related genes differently in both species. Peptides were able to promote the expression of marker genes for anti-inflammatory (il10), antiviral (mx, irf3), cell-mediated cytotoxicity (nccrp1, gzmb), and antibody responses (ighm) in European sea bass, with the Nkl peptide being the most effective. Contrary to this, the effects of those peptides on gilthead seabream mainly resulted in the suppression of immune responses. To conclude, European sea bass-derived peptides can be postulated as potential tools for immunostimulation in European sea bass fish farms, but more efforts are required for their universal use in other species.