Hydrogen sulfide upregulates miR-16-5p targeting PiK3R1 and RAF1 to inhibit neutrophil extracellular trap formation in chickens

Neutrophil microRNAs

Neutrophils are considered 'first-line defence' cells as they can be rapidly recruited to the site of the immune response. As key components of non-specific immune mechanisms, neutrophils use phagocytosis, degranulation, and formation of neutrophil extracellular traps (NETs) to fight pathogens. Recently, immunoregulatory abilities of neutrophils associated with the secretion of several mediators, including cytokines and extracellular vesicles (EVs) containing, among other components, microRNAs (miRNAs), have also been reported. EVs are small structures released by cells into the extracellular space and are present in all body fluids. Microvesicles show the composition and status of the releasing cell, its physiological state, and pathological changes. Currently, EVs have gained immense scientific interest as they act as transporters of epigenetic information in intercellular communication. This review summarises findings from recent scientific reports that have evaluated the utility of miRNA molecules as biomarkers for effective diagnostics or even as start-points for new therapeutic strategies in neutrophil-mediated immune reactions. In addition, this review describes the current state of knowledge on miRNA molecules, which are endogenous regulators of gene expression besides being involved in the regulation of the immune response.

Ozone-oxidized black carbon particles change macrophage fate: Crosstalk between necroptosis and macrophage extracellular traps

The impacts of environmental PM 2.5 on public health have become a major concern all over the world. Many studies have shown that PM 2.5 still poses a threat to public health even at very low levels. Physical or chemical reactions occur between primary particles and other components in the environment, which changes the properties of primary particles. Such newly formed particles with changed properties are called secondary particles. Ozone-oxidized black carbon (oBC) is a key part of PM 2.5 and a representative secondary particle. Macrophages extracellular traps (METs) is a means for macrophages to capture and destroy invading pathogens, thereby exercising innate immunity. Necroptosis is a kind of programmed cell death, which is accompanied by the destruction of membrane integrity, thus inducing inflammatory reaction. However, there is no research on the crosstalk mechanism between necroptosis and MET after oBC exposure. In our study, AO/EB staining, SYTOX Green staining, fluorescent probe, qPCR, Western blot, and immunofluorescence were applied. This experiment found that under normal physiological conditions, when macrophages receive external stimuli (such as pathogens; in our experiment: phorbol 12-myristate 13-acetate (PMA)), they will form METs, capture and kill pathogens, thus exerting innate immune function. However, exposure to oBC can cause necroptosis in macrophages, accompanied by increased levels of reactive oxygen species (ROS) and cytosolic calcium ions, as well as the expression disorder of inflammatory factors and chemokines, and prevent the formation of METs, lose the function of capturing and killing pathogens, and weaken the innate immune function. Notably, inhibition of necroptosis restored the formation of METs, indicating that necroptosis inhibited the formation of METs. This study was the first to explore the crosstalk mechanism between necroptosis and METs after oBC exposure.

Black carbon nanoparticles activate the crosstalk mechanism between necroptosis and macrophage extracellular traps to change macrophages fate

PM2.5 still poses a threat to public health even at very low levels. Black carbon (BC) is a key component of PM2.5. Macrophage extracellular traps (METs) are a means by which macrophages capture and destroy invading pathogens. Necroptosis is an inflammatory programmed cell death. However, there is no research on the crosstalk mechanism between necroptosis and METs after BC exposure. In our study, fluorescence labeling, fluorescent probes, qPCR, and immunofluorescence were applied. Our research found that under normal physiological conditions, when macrophages receive external stimuli (in our experiment, phorbol 12-myristate 13-acetate (PMA)), they will form METs, thus exhibiting innate immune function. However, exposure to BC can cause necroptosis in macrophages accompanied by increased levels of ROS and cytosolic calcium ions as well as altered expression of inflammatory factors and chemokines that prevent the formation of METs, and weakening innate immune function. Notably, inhibition of necroptosis restored the formation of METs, indicating that necroptosis inhibits the formation of METs. Our experiment will enrich the understanding of the mechanism of macrophage injury caused by BC exposure, provide a new direction for studying harmful atmospheric particle toxicity, and propose new therapeutic insights for diseases caused by atmospheric particulate matter. This study is the first to explore the crosstalk mechanism between necroptosis and METs after BC exposure.

Ambient NO2 hinders neutrophil extracellular trap formation in rats: Assessment of the role of neutrophil autophagy

NO₂ has been known to impair immunity and exacerbate susceptibility to infectious diseases. However, scant notice has been taken of the effect of NO₂ on neutrophils. Neutrophil extracellular traps (NETs) formation is necessary for NETosis development by neutrophils as an immune system against pathogens. By analyzing the morphology and signature components of NETs, we focused for the first time on finding that 10 ppm of NO₂ exposure for 15 consecutive days can hinder the formation of NETs. Next, we used NO₂ in vivo derivatives to probe the mechanism for NETs formation in vitro. Our findings showed that NO₂ suppression of respiratory burst levels and mitogen-activated protein kinase (MAPK)/Phosphoinositide 3-kinase (PI3K)-protein kinase B (AKT) signaling was related to NO₂ reduction in NETs formation. Inhibition of phorbol myristate acetate (PMA)-induced NETs formation by NO₂ hindered autophagy, as evidenced by increased mTOR protein expression, decreased LC3 protein expression, and reduced autophagic vesicles. By activating mTOR-mediated autophagy, rapamycin (Rapa) reduced the inhibition of PMA-induced NETs by NO₂. This study will provide valuable insights into the mechanisms of immunotoxicity of NO₂, new insights into the etiology of diseases linked to NETs formation, and a theoretical basis for protection against such illnesses.

1,4-Naphthoquinone-Coated Black Carbon, a Kind of Atmospheric Fine Particulate Matter, Affects Macrophage Fate: New Insights into Crosstalk between Necroptosis and Macrophage Extracellular Traps

1,4-Naphthoquinone-coated BC (1,4 NQ-BC) is an important component of PM_2.5 and a representative secondary particle. However, there is no research on the crosstalk mechanism between necroptosis and macrophage extracellular traps (METs) after 1,4 NQ-BC exposure. In this study, we treated RAW264.7 cells with 50, 100, and 200 mg/L 1,4 NQ-BC for 24 h, with 10 μM necrostatin-1 for 24 h, and with 2.5 μM phorbol 12-myristate 13-acetate (PMA) for 3 h. Our experiment revealed that under normal physiological conditions, when macrophages receive external stimuli (such as pathogens; in this experiment, PMA), they will form METs and capture and kill pathogens, thus exerting innate immune function. However, exposure to 1,4 NQ-BC can cause necroptosis in macrophages, accompanied by increased levels of reactive oxygen species (ROS) and cytosolic calcium ions, as well as the expression disorder of inflammatory factors and chemokines, prevent the formation of METs, lead to loss of the function of capturing and killing pathogens, and weaken the innate immune function. Notably, inhibition of necroptosis restored the formation of METs, indicating that necroptosis inhibited the formation of METs. Our study was the first to explore the crosstalk mechanism between necroptosis and METs. This experiment will enrich the mechanism of macrophage injury caused by 1,4 NQ-BC exposure.

Neutrophil Extracellular Traps in Cerebral Ischemia/Reperfusion Injury: Friend and Foe

Cerebral ischemic injury, one of the leading causes of morbidity and mortality worldwide, triggers various central nervous system (CNS) diseases, including acute ischemic stroke (AIS) and chronic ischemia-induced Alzheimer's disease (AD). Currently, targeted therapies are urgently needed to address neurological disorders caused by cerebral ischemia/reperfusion injury (CI/RI), and the emergence of neutrophil extracellular traps (NETs) may be able to relieve the pressure. Neutrophils are precursors to brain injury following ischemic stroke and exert complicated functions. NETs extracellularly release reticular complexes of neutrophils, i.e., double-stranded DNA (dsDNA), histones, and granulins. Paradoxically, NETs play a dual role, friend and foe, under different conditions, for example, physiological circumstances, infection, neurodegeneration, and ischemia/reperfusion. Increasing evidence indicates that NETs exert anti-inflammatory effects by degrading cytokines and chemokines through protease at a relatively stable and moderate level under physiological conditions, while excessive amounts of NETs release (NETosis) irritated by CI/RI exacerbate the inflammatory response and aggravate thrombosis, disrupt the blood-brain barrier (BBB), and initiates sequential neuron injury and tissue damage. This review provides a comprehensive overview of the machinery of NETs formation and the role of an abnormal cascade of NETs in CI/RI, as well as other ischemia-induced neurological diseases. Herein, we highlight the potential of NETs as a therapeutic target against ischemic stroke that may inspire translational research and innovative clinical approaches.

Selenium mitigates the inhibitory effect of TBBPA on NETs release by regulating ROS/MAPK pathways-induced carp neutrophil apoptosis and necroptosis

Tetrabromobisphenol A (TBBPA) is one of the most common and persistent organic pollutants found in the environment. When TBBPA is ingested by organisms through various pathways and stored in the body, it shows obvious harmful effects. Selenium (Se) works as an antioxidant in the body, allowing it to withstand the poisonous effects of dangerous substances. The effects and mechanisms of Se and TBBPA on carp neutrophil immune function, apoptosis, and necroptosis, however, are unknown. As a result, we created TBBPA exposure and Se antagonism models using carp neutrophils as study objects, and we investigated the expression of genes implicated in extracellular traps (NETs), cytokines, apoptosis, and necroptosis. The findings demonstrated that extracellular traps neutrophils in the TBBPA group displayed the inhibition of NETs, apoptosis, and necrosis, as well as an increase in Reactive oxygen species (ROS) levels and activation of the MAPK pathway. The expression of genes related to the mitochondrial apoptosis pathway (Bax, Cyt-c, Bcl-2 and Caspase-3) and necroptosis pathway (MLKL, RIPK1, RIPK3, Caspase-8 and FADD) were activated. The expression of inflammatory factors IL-1 and TNF-α were increased, and the expression of IL-2 and IFN-γ were decreased. But an appropriate concentration of Se can mitigate the effects of TBBPA. Our results suggest that Se can mitigate the inhibitory effect of TBBPA on NETs release by regulating apoptosis and necroptosis of carp neutrophil via ROS/MAPK pathways. These results provide a basis information for exploring the toxicity of TBBPA, and enrich the anti-toxicity mechanism of trace element Se in the body.

Quantitative proteomics reveals tissue-specific toxic mechanisms for acute hydrogen sulfide-induced injury of diverse organs in pig

Hydrogen sulfide (H₂S) is a highly toxic gas in many environmental and occupational places. It can induce multiple organ injuries particularly in lung, trachea and liver, but the relevant mechanisms remain poorly understood. In this study, we used a TMT-based discovery proteomics to identify key proteins and correlated molecular pathways involved in the pathogenesis of acute H₂S-induced toxicity in porcine lung, trachea and liver tissues. Pigs were subjected to acute inhalation exposure of up to 250 ppm of H₂S for 5 h for the first time. Changes in hematology and biochemical indexes, serum inflammatory cytokines and histopathology demonstrated that acute H₂S exposure induced organs inflammatory injury and dysfunction in the porcine lung, trachea and liver. The proteomic data showed 51, 99 and 84 proteins that were significantly altered in lung, trachea and liver, respectively. Gene ontology (GO) annotation, KEGG pathway and protein-protein interaction (PPI) network analysis revealed that acute H₂S exposure affected the three organs via different mechanisms that were relatively similar between lung and trachea. Further analysis showed that acute H₂S exposure caused inflammatory damages in the porcine lung and trachea through activating complement and coagulation cascades, and regulating the hyaluronan metabolic process. Whereas antigen presentation was found in the lung but oxidative stress and cell apoptosis was observed exclusively in the trachea. In the liver, an induced dysfunction was associated with protein processing in the endoplasmic reticulum and lipid metabolism. Further validation of some H₂S responsive proteins using western blotting indicated that our proteomics data were highly reliable. Collectively, these findings provide insight into toxic molecular mechanisms that could potentially be targeted for therapeutic intervention for acute H₂S intoxication.

ERK/p38/ROS burst responses to environmentally relevant concentrations of diphenyl phosphate-evoked neutrophil extracellular traps formation: Assessing the role of autophagy

Organophosphorus compounds were proposed to impair immune surveillance and increase the total burden of pathogens. However, scarce attention has been paid to the effects of organophosphate flame retardants (OPFRs) on neutrophils. Previous literature outlined that neutrophil extracellular traps (NETs) death (NETosis) is associated with autophagy-related signaling. Here we found that 20 μM diphenyl phosphate (DPHP) could promote NETs formation via assessing markers of NETs and the morphological changes. Concurrently, flow cytometry and western blot analysis revealed that DPHP-triggered NETs formation was associated with reactive oxygen species (ROS) burst and activation of extracellular signal-regulated kinase (ERK) and p38. Additionally, the results revealed that autophagy occurred in DPHP-triggered NETs formation, manifested as enhanced LC3B protein expressions and reduced p62 protein expressions. Mechanism dissection revealed that inhibition of autophagy by 3-methyladenine (3-MA) alleviated the ROS burst and subsequent NETosis caused by DPHP. Conversely, autophagy enhancer Rapamycin (Rapa) augmented the above effects of DPHP, including the generation of ROS and NETosis. Collectively, these data suggested ERK/p38 signaling and ROS burst might be an important cause of DPHP-triggered NETs formation, while suppression of excessive autophagy could rescue these actions. These observations provided a theoretical basis for the treatment and prevention of OPFRs-induced immunotoxicity.

Environmental Stress in Chickens and the Potential Effectiveness of Dietary Vitamin Supplementation

Environmental stressors can promote the vulnerability of animals to infections; it is therefore, essential to understand how stressors affect the immune system, the adaptive capacity of animals to respond, and effective techniques in managing stress. This review highlights scientific evidence regarding environmental stress challenge models and the potential effectiveness of vitamin supplementation. The major environmental stressors discussed are heat and cold stress, feed restriction, stocking density, and pollutants. Much work has been done to identify the effects of environmental stress in broilers and layers, while few involved other types of poultry. Studies indicated that chickens' performance, health, and welfare are compromised when challenged with environmental stress. These stressors result in physiological alterations, behavioral changes, decreased egg and meat quality, tissue and intestinal damage, and high mortalities. The application of vitamins with other nutritional approaches can help in combating these environmental stressors in chickens. Poultry birds do not synthesize sufficient vitamins during stressful periods. It is therefore suggested that chicken diets are supplemented with vitamins when subjected to environmental stress. Combination of vitamins are considered more efficient than the use of individual vitamins in alleviating environmental stress in chickens.

METTL3 regulates PM2.5-induced cell injury by targeting OSGIN1 in human airway epithelial cells

N⁶-methyladenosine (m⁶A) is implicated in alteration of cellular biological processes caused by exogenous environmental factors. However, little is known about the role of m⁶A in airborne fine particulate matter (PM_2.5)-induced adverse effects. Thus, we investigated the role of m⁶A modification in PM_2.5-induced airway epithelial cell injury. We observed a methyltransferase-like 3 (METTL3)-dependent induction of m⁶A modification after PM_2.5 treatment in HBE and A549 cells. METTL3 knockdown attenuated PM_2.5-induced apoptosis and arrest of cell cycle. mRNA sequencing and RNA N⁶-methyladenosine binding protein immunoprecipitation (Me-RIP) assay identified m⁶A-modified oxidative stress induced growth inhibitor 1 (OSGIN1) as the target gene of METTL3. Knockdown of METTL3 resulted a shorter mRNA half-life of OSGIN1 by catalyzing its m⁶A modification. Knockdown of METTL3 or OSGIN1 attenuated cell apoptosis, arrest of cell cycle and autophagy induced by PM_2.5. In conclusion, METTL3 may mediate PM_2.5-induced cell injury by targeting OSGIN1 in human airway epithelial cells. Our work uncovered a critical role of METTL3 in PM_2.5-induced airway epithelial cell injury and provided insight into the vital role of m⁶A modification in PM_2.5-induced human hazards.

A novel indazole derivative, compound Cyy-272, attenuates LPS-induced acute lung injury by inhibiting JNK phosphorylation

Acute lung injury (ALI) is a diffuse lung dysfunction disease characterized by high prevalence and high mortality. Thus far, no effective pharmacological treatment has been made for ALI in clinics. Inflammation is critical to the development of ALI. Therefore, anti-inflammation may be a potential therapy strategy for ALI. Indazole-containing derivatives, representing one of the most important heterocycles in drug molecules, are endowed with a broad range of biological properties, such as anti-cancer and anti-inflammation. In the current study, we investigated the biological effects of Cyy-272, a newly synthesized indazole compound, on LPS-induced ALI both in vivo and in vitro. Results show that Cyy-272 can inhibit the release of inflammatory cytokines in LPS-stimulated macrophage and alleviate LPS induced ALI. Further experiment revealed that Cyy-272 exhibit anti-inflammation activity by inhibiting JNK phosphorylation. Overall, our studies show that an indazole derivative, Cyy-272, is effective in suppressing LPS-induced JNK activation and inflammatory signaling.

Micro RNA (miRNA) Differential Expression and Exposure to Crude-Oil-Related Compounds

This review summarizes studies on miRNA differential regulation related to exposure to crude oil and 20 different crude oil chemicals, such as hydrocarbons, sulphur, nitrogen, and metal- containing compounds. It may be interesting to explore the possibility of using early post-transcriptional regulators as a potential novel exposure biomarker.

Crude oil has been defined as a highly complex mixture of solids, liquids, and gases. Given the toxicological properties of the petroleum components, its extraction and elaboration processes represent high-risk activities for the environment and human health, especially when accidental spills occur. The effects on human health of short-term exposure to petroleum are well known, but chronic exposure effects may variate depending on the exposure type (i.e., work, clean-up activities, or nearby residence).

As only two studies are focused on miRNA differential expression after crude-oil exposure, this review will also analyse the bibliography concerning different crude-oil or Petroleum-Related Compounds (PRC) exposure in Animalia L. kingdom and how it is related to differential miRNA transcript levels. Papers include in vitro, animal, and human studies across the world.

A list of 10 miRNAs (miR-142-5p, miR-126-3p, miR-24-3p, miR-451a, miR-16-5p, miR-28-5p, let-7b-5p, miR-320b, miR-27a-3p and miR-346) was created based on bibliography analysis and hypothesised as a possible “footprint” for crude-oil exposure. miRNA differential regulation can be considered a Big-Data related challenge, so different statistical programs and bioinformatics tools were used to have a better understanding of the biological significate of the most interesting data.

MicroRNAs as New Regulators of Neutrophil Extracellular Trap Formation

Neutrophil extracellular traps (NETs) are formed after neutrophils expelled their chromatin content in order to primarily capture and eliminate pathogens. However, given their characteristics due in part to DNA and different granular proteins, NETs may induce a procoagulant response linking inflammation and thrombosis. Unraveling NET formation molecular mechanisms as well as the intracellular elements that regulate them is relevant not only for basic knowledge but also to design diagnostic and therapeutic tools that may prevent their deleterious effects observed in several inflammatory pathologies (e.g., cardiovascular and autoimmune diseases, cancer). Among the potential elements involved in NET formation, several studies have investigated the role of microRNAs (miRNAs) as important regulators of this process. miRNAs are small non-coding RNAs that have been involved in the control of almost all physiological processes in animals and plants and that are associated with the development of several pathologies. In this review, we give an overview of the actual knowledge on NETs and their implication in pathology with a special focus in cardiovascular diseases. We also give a brief overview on miRNA biology to later focus on the different miRNAs implicated in NET formation and the perspectives opened by the presented data.

MiR-1696/GPx3 axis is involved in oxidative stress mediated neutrophil extracellular traps inhibition in chicken neutrophils

As an important immune mechanism of neutrophils, the release of Web-like chromatin structures known as neutrophil extracellular traps (NETs) can rapidly locate and capture invading pathogens, which has received sustained attention. There are still some fundamental questions surrounding established studies on the mechanism of balance between reactive oxygen species (ROS) dependent release and neutrophil antioxidant response. Glutathione peroxidase 3 (GPx3) is an important antioxidant protein and has been identified can regulate the immune response. However, the effect of GPx3 on the NETs formation and microRNA in this process remain poorly understood. In the present study, we used chicken peripheral blood neutrophils treated with Phorbol-12-myristate-13-acetate (PMA) for 3 h as NETs formation model. The result of morphological observation showed that GPx3 inactivation compromised the release of NETs. Further analysis revealed that knockdown of GPx3 significantly disturbed oxidative balance by inhibiting antioxidant enzymes activity and increasing H₂ O₂ content. Quantitative analysis of NETs-related genes found that the phosphorylation level of mitogen-activated protein kinase (MAPK) pathway genes (ERK, JNK, and p38) and expression of phosphoinositide-3-kinase (PI3K)/AKT pathway genes (PI3K and AKT) were suppressed with the downregulation of GPx3. Meanwhile, we identified that miR-1696 can target GPx3 expression by using dual luciferase reporter system. Additionally, overexpression of miR-1696 can not only inhibit the formation of NETs by restraining the expression of GPx3, interfering with the generation of ROS and activation of the MAPK and PI3K/AKT pathways, but also reducing the release of PMA-induced NETs promoted by overexpression of GPx3. These results provide evidence that miR-1696 targeted GPx3 activities in neutrophils could be used to regulate the NETs formation stimulated by PMA.

Hydrogen sulfide: An endogenous regulator of the immune system

Hydrogen sulfide (H₂S) is now recognized as an endogenous signaling gasotransmitter in mammals. It is produced by mammalian cells and tissues by various enzymes - predominantly cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) - but part of the H₂S is produced by the intestinal microbiota (colonic H₂S-producing bacteria). Here we summarize the available information on the production and functional role of H₂S in the various cell types typically associated with innate immunity (neutrophils, macrophages, dendritic cells, natural killer cells, mast cells, basophils, eosinophils) and adaptive immunity (T and B lymphocytes) under normal conditions and as it relates to the development of various inflammatory and immune diseases. Special attention is paid to the physiological and the pathophysiological aspects of the oral cavity and the colon, where the immune cells and the parenchymal cells are exposed to a special "H₂S environment" due to bacterial H₂S production. H₂S has many cellular and molecular targets. Immune cells are "surrounded" by a "cloud" of H₂S, as a result of endogenous H₂S production and exogenous production from the surrounding parenchymal cells, which, in turn, importantly regulates their viability and function. Downregulation of endogenous H₂S producing enzymes in various diseases, or genetic defects in H₂S biosynthetic enzyme systems either lead to the development of spontaneous autoimmune disease or accelerate the onset and worsen the severity of various immune-mediated diseases (e.g. autoimmune rheumatoid arthritis or asthma). Low, regulated amounts of H₂S, when therapeutically delivered by small molecule donors, improve the function of various immune cells, and protect them against dysfunction induced by various noxious stimuli (e.g. reactive oxygen species or oxidized LDL). These effects of H₂S contribute to the maintenance of immune functions, can stimulate antimicrobial defenses and can exert anti-inflammatory therapeutic effects in various diseases.