Calcium influx, a new potential therapeutic target in the control of neutrophil-dependent inflammatory diseases in bovines

Periparturient Mineral Metabolism: Implications to Health and Productivity

Mineral metabolism, in particular Ca, and to a lesser extent phosphorus (P) and magnesium (Mg), is altered with the onset of lactation because of extensive irreversible loss to synthesize colostrum and milk. The transient reduction in the concentration of Ca in blood, particularly when it lasts days, increases the risk of mineral-related disorders such as hypocalcemia and, to a lesser extent, hypophosphatemia. Although the incidence of clinical hypocalcemia can be reduced by prepartum dietary interventions, subclinical hypocalcemia remains prevalent, affecting up to 60% of the dairy cows in the first 3 d postpartum. More importantly, strong associations exist between hypocalcemia and increased susceptibility to other peripartum diseases and impaired reproductive performance. Mechanistic experiments have demonstrated the role of Ca on innate immune response in dairy cows, which presumably predisposes them to other diseases. Hypocalcemia is not related to inadequate Ca intake as prepartum diets marginal to deficient in Ca reduce the risk of the disease. Therefore, the understanding of how Ca homeostasis is regulated, in particular how calciotropic hormones such as parathyroid hormone and 1,25-dihydroxyvitamin D3, affect blood Ca concentrations, gastrointestinal Ca absorption, bone remodeling, and renal excretion of Ca become critical to develop novel strategies to prevent mineral imbalances either by nutritional or pharmacological interventions. A common method to reduce the risk of hypocalcemia is the manipulation of the prepartum dietary cation-anion difference. Feeding acidogenic diets not only improves Ca homeostasis and reduces hypocalcemia, but also reduces the risk of uterine diseases and improves productive performance. Feeding diets that induce a negative Ca balance in the last weeks of gestation also reduce the risk of clinical hypocalcemia, and recent work shows that the incorporation of mineral sequestering agents, presumably by reducing the absorption of P and Ca prepartum, increases blood Ca at calving, although benefits to production and health remain to be shown. Alternative strategies to minimize subclinical hypocalcemia with the use of vitamin D metabolites either fed prepartum or as a pharmacological agent administered immediately after calving have shown promising results in reducing hypocalcemia and altering immune cell function, which might prove efficacious to prevent diseases in early lactation. This review summarizes the current understanding of Ca homeostasis around parturition, the limited knowledge of the exact mechanisms for gastrointestinal Ca absorption in bovine, the implications of hypocalcemia on the health of dairy cows, and discusses the methods to minimize the risk of hypocalcemia and their impacts on productive performance and health in dairy cows.

E. Coli LPS-induced calcium signaling regulates the expression of hypoxia-inducible factor 1α in periodontal ligament fibroblasts in a non-hypoxia-dependent manner

Periodontitis, an inflammatory disease, can cause significant damage to the oral tissues which support the teeth. During the early development of periodontitis, periodontal ligament fibroblasts (PDLFs) undergo metabolic reprogramming regulated by hypoxia-inducible factor 1α (HIF-1α), which is strongly linked to the progression of inflammation. However, the precise mechanisms by which PDLFs regulate HIF-1α and its associated metabolic reprogramming during early inflammation remain unclear. This study illustrated that brief and low-dose exposure to Escherichia coli (E. coli) lipopolysaccharide (LPS) can serve as a non-hypoxic stimulus, effectively replicating early periodontal inflammatory reactions. This is evidenced by the upregulation of HIF-1α expression and the activation of HIF-1α-mediated crucial glycolytic enzymes, namely lactate dehydrogenase a, pyruvate kinase, and hexokinase 2, concomitant with an augmentation in the inflammatory response within PDLFs. We observed that the effects mentioned and their impact on macrophage polarization were notably attenuated when intracellular and extracellular stores of Ca2+ were depleted using BAPTA-AM and Ca2+-free medium, respectively. Mechanistically, our findings demonstrated that the transcriptional process of HIF-1α is regulated by Ca2+ during E. coli LPS stimulation, mediated through the signal transducer and activator of transcription 3 (STAT3) pathway. Additionally, we observed that the stabilization of intracellular HIF-1α proteins occurs via the endothelin (ET)-1-endothelin A receptor pathway, independent of hypoxia. Taken together, our research outcomes underscore the pivotal involvement of Ca2+ in the onset of early periodontitis by modulating HIF-1α and glycolysis, thereby presenting novel avenues for early therapeutic interventions.

Lanthanide complexes facilitate wound healing by promoting fibroblast viability, migration and M2 macrophage polarization

A tridentate ligand LH3 ((2-hydroxy-3-methoxybenzylidene)-2-(hydroxyimino)propanehydrazide) comprising o-vanillin, hydrazone and oxime donor groups has been employed to prepare a series of tetranuclear Ln(III) complexes. The reaction of ligand LH3 with Ln(NO3)3 [Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er] in MeOH yielded Ln4(LH)6(MeOH)2 (Ln = Sm(1), Eu(2), Gd(3), Tb(4), Ho (6) and Er (7))] whereas the corresponding reaction with Dy(NO3)3 afforded Dy4(LH)4(LH2)2(OH)2 (5). All complexes were characterized by various analytical techniques including single crystal X-ray diffraction, IR spectroscopy, UV-Vis spectroscopy, and elemental analysis. To investigate the potential of these lanthanide complexes for wound healing applications, their effects on fibroblast viability, migration, and M2 macrophage polarization were evaluated. The cytotoxicity assessment revealed that complexes 2(Eu), 4(Tb), 5(Dy), and 7(Er) significantly enhanced fibroblast viability compared to the negative control (NC). In vitro wound healing assay demonstrated that complexes 2(Eu) and 7(Eu) substantially promoted fibroblast migration compared to the NC. Moreover, complex 2(Eu) exhibited significant anti-inflammatory effects by reducing the phagocytic ability of lipopolysaccharide (LPS)-stimulated macrophage cells and attenuating nitric oxide (NO) production. In conclusion, among the series of complexes tested, complex 2(Eu) displayed the most potent anti-inflammatory effect on macrophage cells, while simultaneously promoting fibroblast viability and migration. This unique combination of properties renders complex 2 (Eu) highly promising for wound healing applications.

Phagocyte extracellular traps formation contributes to host defense against Clostridium perfringens infection

Clostridium perfringens (C. perfringens) is an important Gram-positive anaerobic spore-forming pathogen that provokes life-threatening gas gangrene and acute enterotoxaemia, although it colonizes as a component of the symbiotic bacteria in humans and animals. However, the mechanisms by which C. perfringens is cleared from the host remains poorly understood, thereby impeding the development of novel strategies for control this infection. Here, we uncover a beneficial effect of extracellular traps (ETs) formation on bacterial killing and clearance by phagocytes. C. perfringens strain ATCC13124, and wild-type isolates CP1 and CP3 markedly trigger ETs formation in macrophages and neutrophils. As expected, visualization of DNA decorated with histone, myeloperoxidase (MPO) and neutrophils elastase (NE) in C. perfringens-triggered classical ETs structures. Notably, the bacteria-induced ETs formation is an ERK1/2-, P38 MAPK-, store-operated calcium entry (SOCE)-, NADPH oxidase-, histone-, NE-, and MPO-dependent process, and is independent of LDH activity. Meanwhile, the defect of bactericidal activity is mediated by impairing ETs formation in phagocytes. Moreover, In vivo studies indicated that degradation of ETs by DNase I administration leads to a defect in the protection against experimental gas gangrene, with higher mortality rates, exacerbated tissue damage, and more bacterial colonization. Together, these results suggest that phagocyte ETs formation is essential for the host defense against C. perfringens infection.

Bovine sperm samples induce different NET phenotypes in a NADPH oxidase-, PAD4-, and Ca++-dependent process†

Deposition of sperm during artificial insemination in the bovine female reproductive tract results in early host innate immune reactions of polymorphonuclear neutrophils (PMNs). Furthermore, sperm-mediated neutrophil extracellular trap (NET) formation (NETosis) was recently reported to occur in different mammalian species, including humans. We, here, investigated the interactions of bovine PMN with different semen-derived samples and analyzed in more depth molecular aspects of this effector mechanism. Overall, confrontation of PMN with sperm/cell preparation (SCP) resulted in a rapid and dose-dependent NET formation leading to effective spermatozoa entrapment. Thereby, spermatozoa induced different phenotypes of NETs. Immunostaining analyses revealed the presence of histones (H3), neutrophil elastase (NE), and pentraxin (PTX) in sperm-triggered NET structures. Fresh SCP strongly induced NETosis than frozen-thawed ones. The level of NETosis was not related to spermatozoa viability. SCP as well as purified sperm cells (SCs) and supernatant (SN) induce NETosis, although the reaction in SC was lower. Enhanced levels of oxygen consumption and proton leak in PMN revealed sperm SNs but not purified SCs as PMN activators. Functional inhibition experiments revealed sperm-triggered NETosis as an NADPH oxidase- and peptidylarginine deiminase 4-dependent process and proved to be dependent on intra- and extracellular Ca++ influxes while myeloperoxidase activity and as ERK1/2- and PI3K-related signaling pathways did not seem to play a pivotal role in this effector mechanism. From these findings, we speculate that sperm-derived NETosis might also occur in vivo during artificial insemination and might therefore play a role related to reduced fertility.

The effect of bovine vaccines against respiratory viruses administered either intranasal or intramuscular on broncho-alveolar fluid cells of heifers

Background

The knowledge on bovine vaccines against respiratory viruses on bronchoalveolar fluid cells is scarce.

Objective

To compare the effects of a commercial intranasal (IN) and intramuscular (IM) vaccine against bovine respiratory disease (BRD) complex viruses on bronchoalveolar fluid cells of healthy heifers.

Methods

21 healthy heifers were assigned to three treatment groups: control (CO, N = 7), intranasally vaccinated (IN) (n = 7), and intramuscularly vaccinated (IM) (n = 7). The IN group received 1 mL of the commercial vaccine in each nostril once containing attenuated BoHV-1, bPIV-3, and BRSV. The IM group was vaccinated with two doses of 2 mL with an interval of 21 days of the commercial vaccine containing attenuated BoHV-1, bPIV-3, and BRSV plus inactivated BVDV. At day 0 (D0), before the first vaccine dose, and at D3, D7, and D21, after the last vaccine dose, airway bronchoscopy was performed to observe local irritation and collect bronchoalveolar lavage fluid (BALF). The bronchoalveolar count, cytological evaluation, bronchoalveolar cell oxidative metabolism, and total bronchoalveolar IgA and IgG were measured.

Results

The IN vaccine increased neutrophil cellularity at D7 and D21 and total IgA at D3 in BALF. Total IgA in BALF also increased at D3 and oxidative metabolism of bronchoalveolar cells at D21 lowered compared to the CO group. Following IM vaccination there was no alteration of immunoglobulins or cell oxidative metabolism in BALF. Both vaccines reduced the number of alveolar macrophages.

Conclusion

Both vaccines induced bronchoalveolar inflammation during the establishment of the vaccine immunity, which was more expressive in the IN protocol.

Eimeria ninakohlyakimovae casts NOX-independent NETosis and induces enhanced IL-12, TNF-α, IL-6, CCL2 and iNOS gene transcription in caprine PMN

Eimeria ninakohlyakimovae represents a highly pathogenic coccidian parasite causing severe haemorrhagic typhlocolitis in goat kids worldwide. NETosis was recently described as an efficient defense mechanism of polymorphonuclear neutrophils (PMN) acting against different parasites in vitro and in vivo. In vitro interactions of caprine PMN with parasitic stages of E. ninakohlyakimovae (i. e. oocysts and sporozoites) as well as soluble oocyst antigens (SOA) were analyzed at different ratios, concentrations and time spans. Extracellular DNA staining was used to illustrate classical molecules induced during caprine NETosis [i. e. histones (H3) and neutrophil elastase (NE)] via antibody-based immunofluorescence analyses. Functional inhibitor treatments with DPI and DNase I were applied to unveil role of NADPH oxidase (NOX) and characterize DNA-backbone composition of E. ninakohlyakimovae-triggered caprine NETosis. Scanning electron microscopy (SEM)- and immunofluorescence-analyses demonstrated that caprine PMN underwent NETosis upon contact with sporozoites and oocysts of E. ninakohlyakimovae, ensnaring filaments which firmly entrapped parasites. Detailed co-localization studies of E. ninakohlyakimovae-induced caprine NETosis revealed presence of PMN-derived DNA being adorned with nuclear H3 and NE corroborating molecular characteristics of NETosis. E. ninakohlyakoimovae-induced caprine NETosis was found to be NOX-independent since DPI inhibition led to a slight decrease of NETosis. Exposure of caprine PMN to vital E. ninakohlyakimovae sporozoites as well as SOA resulted in up-regulation of IL-12, TNF-α, IL-6, CCL2 and iNOS gene transcription in stimulated PMN. Since vital E. ninakohlyakimovae-sporozoites induced caprine NETosis, this effective entrapment mechanism might reduce initial sporozoite epithelial host cell invasion during goat coccidiosis ultimately resulting in less macromeront formation and reduced merozoites I production.

Effects of injectable calcitriol on mineral metabolism and postpartum health and performance in dairy cows

Objectives were to determine the effects of an injectable formulation of calcitriol on Ca concentration, risk of clinical diseases, and performance in dairy cows. Cows were blocked by lactation number (1 vs. >1) and calving sequence and, within block, assigned randomly within 6 h of calving to receive subcutaneously vehicle only (CON, n = 450) or 200 (CAL200, n = 450) or 300 μg of 1α,25-dihydroxyvitamin D₃ (CAL300, n = 450). Cows were fed the same acidogenic diet prepartum. Blood was sampled before treatment administration and again during the first 11 d postpartum and analyzed for concentrations of ionized Ca (iCa), total Ca (tCa), Mg (tMg), and P (tP), β-hydroxybutyrate, carboxylated osteocalcin (cOC), and undercarboxylated osteocalcin (uOC). Cows were evaluated for diseases in the first 60 d postpartum. Reproduction and survival were monitored for the first 300 d postpartum. Calcitriol increased concentration of blood iCa (CON = 1.12 vs. CAL200 = 1.23 vs. CAL300 = 1.27 mM), plasma tCa (CON = 2.29 vs. CAL200 = 2.44 vs. CAL300 = 2.46 mM), and plasma tP (CON = 1.72 vs. CAL200 = 2.21 vs. CAL300 = 2.28 mM), and differences were observed during the first 5 d postpartum for iCa and tCa, and the first 7 d postpartum for tP. Concentrations of tMg were lower in calcitriol-treated cows than in CON cows (CON = 0.81 vs. CAL200 = 0.78 vs. CAL300 = 0.75 mM), and differences were observed during the first 5 d postpartum. Calcitriol increased plasma concentrations of cOC (CON = 14.5 vs. CAL200 = 23.0 vs. CAL300 = 19.8 ng/mL) and uOC (CON = 1.6 vs. CAL200 = 3.4 vs. CAL300 = 2.6 ng/mL). Prevalence of subclinical hypocalcemia was less in calcitriol-treated cows (CON = 19.0 vs. CAL200 = 4.7 vs. CAL300 = 9.3%); however, benefits on health were only observed in overconditioned cows (n = 270/1,350). Calcitriol reduced incidence of retained placenta (CON = 14.3 vs. CAL200 = 5.1 vs. CAL300 = 5.9%), puerperal metritis (CON = 12.7 vs. CAL200 = 6.1 vs. CAL300 = 2.5%), and morbidity (CON = 72.1 vs. CAL200 = 57.4 vs. CAL300 = 56.9%) in cows with BCS greater than 3.50, but no benefit on health was observed in cows with BCS equal to or less than 3.50 at parturition. Milk yield did not differ among treatments. Pregnancy at first AI did not differ, but pregnancy rate after the first AI was slower for calcitriol-treated cows because of reduced insemination rate and pregnancy per AI. We found that CAL200 reduced death but increased culling in cows without calving problems. Collectively, results indicate that treatment with calcitriol at parturition was effective in improving concentrations of iCa, tCa, and tP, which reduced the risk of hypocalcemia. Pregnancy rate was reduced by calcitriol treatment, and benefits on health performance were limited to overconditioned cows. Thus, treatment of all cows is not supported, and proper identification of cohorts of cows that benefit from postpartum interventions that increase blood calcitriol or calcium is needed.

Extracellular Traps Released by Neutrophils from Cats are Detrimental to Toxoplasma gondii Infectivity

Toxoplasma gondii is the causative agent of toxoplasmosis, an infectious disease that affects over 30% of the human world population, causing fatal infections in immunocompromised individuals and neonates. The life cycle of T. gondii is complex, and involves intermediate hosts (birds and mammals) and definitive hosts (felines, including domestic cats). The innate immune repertoire against the parasite involves the production of neutrophil extracellular traps (NET), and neutrophils from several intermediate hosts produce NET induced by T. gondii. However, the mechanisms underlying NET release in response to the parasite have been poorly explored. Therefore, the aims of this study were to investigate whether neutrophils from cats produce NET triggered by T. gondii and to understand the mechanisms thereby involved. Neutrophils from cats were stimulated with T. gondii tachyzoites and NET-derived DNA in the supernatant was quantified during the time. The presence of histone H1 and myeloperoxidase was detected by immunofluorescence. We observed that cat neutrophils produce both classical and rapid/early NET stimulated by T. gondii. Inhibition of elastase, intracellular calcium, and phosphatidylinositol 3-kinase (PI3K)-δ partially blocked classical NET release in response to the parasite. Electron microscopy revealed strands and networks of DNA in close contact or completely entrapping parasites. Live imaging showed that tachyzoites are killed by NET. We conclude that the production of NET is a conserved strategy to control infection by T. gondii amongst intermediate and definitive hosts.

Nanotechnology-based Drug Delivery, Metabolism and Toxicity

BACKGROUND

Nanoparticles (NPs) are being used extensively owing to their increased surface area, targeted delivery and enhanced retention. NPs have the potential to be used in many disease conditions. Despite widespread use, their toxicity and clinical safety still remain a major concern.

OBJECTIVE

The purpose of this study was to explore the metabolism and toxicological effects of nanotherapeutics.

METHODS

Comprehensive, time-bound literature search was done covering the period from 2010 till date. The primary focus was on the metabolism of NP including their adsorption, degradation, clearance, and bio-persistence. This review also focuses on updated investigations on NPs with respect to their toxic effects on various in vitro and in vivo experimental models.

RESULTS

Nanotechnology is a thriving field of biomedical research and an efficient drug delivery system. Further their applications are under investigation for diagnosis of disease and as medical devices.

CONCLUSION

The toxicity of NPs is a major concern in the application of NPs as therapeutics. Studies addressing metabolism, side-effects and safety of NPs are desirable to gain maximum benefits of nanotherapeutics.

Post-Translational Protein Deimination Signatures in Serum and Serum-Extracellular Vesicles of Bos taurus Reveal Immune, Anti-Pathogenic, Anti-Viral, Metabolic and Cancer-Related Pathways for Deimination

The bovine immune system is known for its unusual traits relating to immunoglobulin and antiviral responses. Peptidylarginine deiminases (PADs) are phylogenetically conserved enzymes that cause post-translational deimination, contributing to protein moonlighting in health and disease. PADs also regulate extracellular vesicle (EV) release, forming a critical part of cellular communication. As PAD-mediated mechanisms in bovine immunology and physiology remain to be investigated, this study profiled deimination signatures in serum and serum-EVs in Bos taurus. Bos EVs were poly-dispersed in a 70-500 nm size range and showed differences in deiminated protein cargo, compared with whole sera. Key immune, metabolic and gene regulatory proteins were identified to be post-translationally deiminated with some overlapping hits in sera and EVs (e.g., immunoglobulins), while some were unique to either serum or serum-EVs (e.g., histones). Protein-protein interaction network analysis of deiminated proteins revealed KEGG pathways common for serum and serum-EVs, including complement and coagulation cascades, viral infection (enveloped viruses), viral myocarditis, bacterial and parasitic infections, autoimmune disease, immunodeficiency intestinal IgA production, B-cell receptor signalling, natural killer cell mediated cytotoxicity, platelet activation and hematopoiesis, alongside metabolic pathways including ferroptosis, vitamin digestion and absorption, cholesterol metabolism and mineral absorption. KEGG pathways specific to EVs related to HIF-1 signalling, oestrogen signalling and biosynthesis of amino acids. KEGG pathways specific for serum only, related to Epstein-Barr virus infection, transcription mis-regulation in cancer, bladder cancer, Rap1 signalling pathway, calcium signalling pathway and ECM-receptor interaction. This indicates differences in physiological and pathological pathways for deiminated proteins in serum-EVs, compared with serum. Our findings may shed light on pathways underlying a number of pathological and anti-pathogenic (viral, bacterial, parasitic) pathways, with putative translatable value to human pathologies, zoonotic diseases and development of therapies for infections, including anti-viral therapies.

Histone H2A and Bovine Neutrophil Extracellular Traps Induce Damage of Besnoitia besnoiti-Infected Host Endothelial Cells but Fail to Affect Total Parasite Proliferation

Besnoitia besnoiti tachyzoites infect and develop in bovine endothelial cells in vivo and trigger the release of neutrophil extracellular traps (NETs) from bovine polymorphonuclear neutrophils (PMN). The purpose of this study was to analyze if pure B. besnoiti tachyzoite-triggered NETs would damage endothelial host cells and subsequently influence intracellular development and proliferation of B. besnoiti tachyzoites in primary bovine endothelial cells. For comparison purposes, isolated A23187-induced NETs were also used. Thus, we here evaluated endothelial host cell damage triggered by histone 2A (H2A) and B. besnoiti tachyzoite-induced NET preparations and furthermore estimated the effects of PMN floating over B. besnoiti-infected endothelium under physiological flow conditions on endothelial host cell viability. Overall, all treatments (H2A, B. besnoiti-triggered NETs and floating PMN) induced endothelial cell death of B. besnoiti-infected host cells. However, though host cell damage led to significantly altered intracellular parasite development with respect to parasitophorous vacuole diameter and numbers, the total proliferation of the parasite over time was not significantly affected by these treatments thereby denying any direct effect of NETs on intracellular B. besnoiti replication.

Lipopeptide PAM3CYS4 Synergizes N-Formyl-Met-Leu-Phe (fMLP)-Induced Calcium Transients in Mouse Neutrophils

N-Formyl-Met-Leu-Phe (fMLP), a mimic of N-formyl oligopeptides that are released from bacteria, is a potent leukocyte chemotactic factor. It induces intracellular calcium ([Ca]i) transient that is important for various neutrophil biological functions, e.g., adhesion, ROS, and cytokine productions. Toll-like receptors (TLRs), an essential part of host innate immunity, regulate neutrophil activities, but their role in [Ca]i signaling is less clear. In the present study, we examined the effect of several TLR ligands, including Pam3Cys4 (TLR1/2), lipopolysaccharide (LPS, TLR4), and lipoteichoic acid (LTA, TLR2/6), on calcium signaling and on the fMLP-induced [Ca]i transients in mouse neutrophils loaded with Fura-2/AM. We found that unlike fMLP, the three TLR ligands tested did not elicit any detectable Ca flux. However, Pam3Cys4, but not LPS or LTA, markedly synergized the fMLP-induced [Ca]i transients, and had no effect on the host component keratinocyte-derived cytokine (KC)- or C5a-induced calcium flux. The effect of Pam3Cys4 on the fMLP-induced [Ca]i transients is by enhancing extracellular Ca influx, not intracellular Ca release. Surprisingly, deletion of TLR2 or MyD88 in neutrophils had no impact on the Pam3Cys4's effect, suggesting a TLR2-MyD88-independent mechanism. Finally, using the pan PKC activator and inhibitor, we demonstrated that PKC negatively regulated fMLP-induced [Ca]i transients and that inhibition of PKC did not prohibit Pam3Cys4's synergistic effect on the fMLP-induced calcium influx. In conclusion, the present study identified a novel synergistic effect of Pam3Cys4 on fMLP-induced [Ca]i transients, a process important for many neutrophil biological functions.

Bioinorganics and Wound Healing

Wound dressings and the healing enhancement (increasing healing speed and quality) are two components of wound care that lead to a proper healing. Wound care today consists mostly of providing an optimal environment by removing waste and necrotic tissues from a wound, preventing infections, and keeping the wounds adequately moist. This is however often not enough to re-establish the healing process in chronic wounds; with the local disruption of vascularization, the local environment is lacking oxygen, nutrients, and has a modified ionic and molecular concentration which limits the healing process. This disruption may affect cellular ionic pumps, energy production, chemotaxis, etc., and will affect the healing process. Biomaterials for wound healing range from simple absorbents to sophisticated bioactive delivery vehicles. Often placing a material in or on a wound can change multiple parameters such as pH, ionic concentration, and osmolarity, and it can be challenging to pinpoint key mechanism of action. This article reviews the literature of several inorganic ions and molecules and their potential effects on the different wound healing phases and their use in new wound dressings.

Pinniped- and Cetacean-Derived ETosis Contributes to Combating Emerging Apicomplexan Parasites (Toxoplasma gondii, Neospora caninum) Circulating in Marine Environments

Leukocytes play a major role in combating infections either by phagocytosis, release of antimicrobial granules, or extracellular trap (ET) formation. ET formation is preceded by a certain leukocyte cell death form, known as ETosis, an evolutionarily conserved mechanism of the innate immune system also observed in marine mammals. Besides several biomolecules and microbial stimuli, marine mammal ETosis is also trigged by various terrestrial protozoa and metazoa, considered nowadays as neozoan parasites, which are circulating in oceans worldwide and causing critical emerging marine diseases. Recent studies demonstrated that pinniped- and cetacean-derived polymorphonuclear neutrophils (PMNs) and monocytes are able to form different phenotypes of ET structures composed of nuclear DNA, histones, and cytoplasmic peptides/proteases against terrestrial apicomplexan parasites, e.g., Toxoplasma gondii and Neospora caninum. Detailed molecular analyses and functional studies proved that marine mammal PMNs and monocytes cast ETs in a similar way as terrestrial mammals, entrapping and immobilizing T. gondii and N. caninum tachyzoites. Pinniped- and cetacean leukocytes induce vital and suicidal ETosis, with highly reliant actions of nicotinamide adenine dinucleotide phosphate oxidase (NOX), generation of reactive oxygen species (ROS), and combined mechanisms of myeloperoxidase (MPO), neutrophil elastase (NE), and DNA citrullination via peptidylarginine deiminase IV (PAD4).This scoping review intends to summarize the knowledge on emerging protozoans in the marine environment and secondly to review limited data about ETosis mechanisms in marine mammalian species.

Docosahexaenoic acid and TUG-891 activate free fatty acid-4 receptor in bovine neutrophils

Fatty acids are well known metabolic intermediaries but also have a role in the immune response. Long-chain fatty acids such as omega-6 and -9 activate neutrophil function through free fatty acid (FFA)-1 receptor in bovines. Although omega-3 has also been suggested to influence neutrophil function, the details remain unclear. The goal of this study was to determine the presence of the bovine FFA4 receptor and its effect on neutrophil responses. We treated bovine neutrophils with the natural and synthetic agonists of FFA4 receptor docosahexaenoic acid (DHA) and TUG-891, respectively, and assessed oxidative and no oxidative response. We detected protein and mRNA FFA4 receptor expression through immunofluorescence, immunoblot, and RT-PCR analysis. DHA and TUG-891 both increased intracellular calcium mobilisation in bovine neutrophils, with 50% effective concentrations of 99 μM and 73 μM, respectively, which was partially reduced after treatment with the FFA4 antagonist AH7614. Furthermore, DHA and TUG-891 increased matrix metalloproteinase (MMP)-9 granules release and superoxide production. AH7614 and the intracellular calcium chelator BAPTA-AM decreased the superoxide production induced by TUG-891 and by both DHA and TUG-891, respectively, suggesting a key role of intracellular calcium in FFA4 agonists-induced superoxide production. These results highlight an important mechanism of bovine neutrophil responses mediated via FFA4 receptor, which can further inform the development of new formulations for DHA-enriched feed supplements to enhance innate immunity in dairy cattle.

Assessment of the oxidative metabolism of calves’ bronchoalveolar cells: comparison between NBT and fluorimetric techniques

ABSTRACT: Evaluation of alveolar macrophage functions of cattle is an important tool in order to assess whether measures taken during the cattle husbandry can decrease the respiratory tract defense. The aim of this study was to determine whether dexamethasone used at therapeutic dose can affect the oxidative metabolism of alveolar macrophages of cattle. This was evaluated by two tests, the fluorometric and colorimetric. The similarity of the results was studied, using alveolar macrophages of six healthy cattle, obtained from bronchoalveolar lavage on a basal and an immunosuppressant moment after the application of dexamethasone. For the fluorometric test, alveolar macrophages were incubated with Staphylococcus aureus and 2’-7’dichlorohidroflurescein, and analyzed by flow cytometer. For the colorimetric test, alveolar macrophages were incubated with Phorbol 12- miristate-13 acetate and nitroblue tetrazolium, dissolved and analyzed in a spectrophotometer. It was noted that dexamethasone therapeutic dose (0.05 mg/kg) reduced the functions of alveolar macrophages from healthy bovine. This result was observed by both tests with the difference that the flow cytometry assay was more informative for identifying which specific cellular function has been compromised.

Mouse macrophages capture and kill Giardia lamblia by means of releasing extracellular trap

Giardia lamblia is one of the most prevalent parasites residing in the duodenum of human and many other mammals throughout the world which is transmitted via ingested cysts through contaminated food or water. The severity of disease may depend on multiple parasite and host factors. Commonly, children and immunologically compromised persons like AIDS patient exhibit severe diarrhea, malabsorption and weight loss, however, there are also some infected people who are asymptomatic or only exhibit mild clinical symptoms and can shed the Giardia cysts in the environment. Although many studies have indicated that the innate immune system is important for Giardia defense, however, whether the innate immune responses such extracellular traps (ETs) could be induced by G. lamblia is still unclear. In recent years, macrophage extracellular traps (METs) have been described as an effective defense mechanism against invading microorganisms. In the present study, the formation of METs triggered by G. lamblia trophozoites was investigated. The formation of METs induced by G. lamblia trophozoites of mouse macrophage was observed with Scanning Electron Microscopy (SEM). The main components DNA, H3 histone and MPO were confirmed by Sytox orange staining, DNase1 digestion, immunofluorescence staining and fluorescence confocal microscopy. Inhibitor assays suggested that G. lamblia trophozoites triggered METs formation through ERK1/2 and p38 MAPK signal pathways and was Store-operated Ca²⁺ entry (SOCE) dependent. In addition, the process of METs formation triggered by G. lamblia trophozoites was also time and dose-dependent. Furthermore, the production of Reactive Oxygen Species (ROS) in macrophages stimulated with G. lamblia trophozoites significantly increased whereas no significant changes were observed about LDH activity.

Bovine neutrophils in health and disease

Bovine neutrophils have similarities to those of other species with respect to mechanisms of their activation and migration into tissue, modulation of immune responses and the balance between microbial killing and host tissue damage. However, bovine neutrophils have biochemical and functional differences from those of other species, which may yield insights about the comparative biology of neutrophils. Neutrophils play protective and harmful roles in the infectious diseases of cattle that occur at times of transition: respiratory disease in beef calves recently arrived to feedlots and mastitis and other diseases of postparturient dairy cows. An important research focus is the mechanisms by which risk factors for these diseases affect neutrophil function and thereby lead to disease and the prospect of genetic or pharmacologic improvement of disease resistance. Further, in keeping with the One Health paradigm, cattle can be considered a model for studying the role of neutrophils in naturally occurring diseases caused by host-adapted pathogens and are thus an intermediary between studies of mouse models and investigations of human disease. Finally, the study of bovine neutrophils is important for agriculture, to understand the pathogenesis of these production-limiting diseases and to develop novel methods of disease prevention that improve animal health and reduce the reliance on antimicrobial use.

Molecular analyses on Neospora caninum-triggered NETosis in the caprine system

Neospora caninum is an obligate intracellular protozoan parasite causing serious reproductive disorders in large and small ruminants worldwide. Polymorphonuclear neutrophils (PMN) react against multiple invading pathogens through different mechanisms including the release of neutrophil extracellular traps (NETs). Here, in vitro interactions of caprine PMN and N. caninum tachyzoites were studied. Scanning electron microscopic- and immunofluorescence-analyses demonstrated that caprine PMN undergo NETosis upon contact with tachyzoites of N. caninum, extruding filaments that entrap parasites. Detailed co-localization studies of N. caninum tachyzoite-induced NETs revealed the presence of PMN-derived DNA being decorated with histones (H1, H2A/H2B, H3,H4) and neutrophil elastase (NE) corroborating the molecular characteristics of classical mammalian NETs. As a new result for parasite-induced NETosis, we identified pentraxin and cathepsin B in N. caninum-triggered NETs. Nonetheless, functional inhibition assays revealed that during caprine NET formation triggered by N. caninum different molecular signaling pathways are induced, when compared to other apicomplexan parasites or host species. As such, N. caninum-induced NETosis appears to be influenced by MPO but independent of NADPH oxidase, SOCE, ERK1/2 and p38 MAPK activities. Furthermore, the inhibition of PMN autophagy via blockage of the PI3K-mediated signaling pathway failed to influence tachyzoite-induced NETosis. Since N. caninum-tachyzoites induced caprine NETosis, this effector mechanism should be considered as an early host immune response during acute caprine neosporosis.

Bovine Polymorphonuclear Neutrophils Cast Neutrophil Extracellular Traps against the Abortive Parasite Neospora caninum

Neospora caninum represents a relevant apicomplexan parasite causing severe reproductive disorders in cattle worldwide. Neutrophil extracellular trap (NET) generation was recently described as an efficient defense mechanism of polymorphonuclear neutrophils (PMN) acting against different parasites. In vitro interactions of bovine PMN with N. caninum were analyzed at different ratios and time spans. Extracellular DNA staining was used to illustrate the typical molecules of NETs [i.e., histones (H3), neutrophil elastase (NE), myeloperoxidase (MPO), pentraxin] via antibody-based immunofluorescence analyses. Functional inhibitor treatments were applied to reveal the role of several enzymes [NADPH oxidase (NOX), NE, MPO, PAD4], ATP-dependent P2Y2 receptor, store-operated Ca⁺⁺entry (SOCE), CD11b receptor, ERK1/2- and p38 MAPK-mediated signaling pathway in tachyzoite-triggered NETosis. N. caninum tachyzoites triggered NETosis in a time- and dose-dependent manner. Scanning electron microscopy analyses revealed NET structures being released by bovine PMN and entrapping tachyzoites. N. caninum-induced NET formation was found not to be NOX-, NE-, MPO-, PAD4-, ERK1/2-, and p38 MAP kinase-dependent process since inhibition of these enzymes led to a slight decrease of NET formation. CD11b was also identified as a neutrophil receptor being involved in NETosis. Furthermore, N. caninum-triggered NETosis depends on Ca⁺⁺ influx as well as neutrophil metabolism since both the inhibition of SOCE and of P2Y2-mediated ATP uptake diminished NET formation. Host cell invasion assays indicated that PMN-derived NETosis hampered tachyzoites from active host cell invasion, thereby inhibiting further intracellular replication. NET formation represents an early and effective mechanism of response of the innate immune system, which might reduce initial infection rates during the acute phase of cattle neosporosis.

Cellular and Molecular Mechanisms of Autoimmunity and Lupus Nephritis

Autoimmunity involves immune responses directed against self, which are a result of defective self/foreign distinction of the immune system, leading to proliferation of self-reactive lymphocytes, and is characterized by systemic, as well as tissue-specific, inflammation. Numerous mechanisms operate to ensure the immune tolerance to self-antigens. However, monogenetic defects or genetic variants that weaken immune tolerance render susceptibility to the loss of immune tolerance, which is further triggered by environmental factors. In this review, we discuss the phenomenon of immune tolerance, genetic and environmental factors that influence the immune tolerance, factors that induce autoimmunity such as epigenetic and transcription factors, neutrophil extracellular trap formation, extracellular vesicles, ion channels, and lipid mediators, as well as costimulatory or coinhibitory molecules that contribute to an autoimmune response. Further, we discuss the cellular and molecular mechanisms of autoimmune tissue injury and inflammation during systemic lupus erythematosus and lupus nephritis.

Canine Neutrophil Extracellular Traps Release Induced by the Apicomplexan Parasite Neospora caninum In Vitro

Neosporosis is considered as one of the main causes of abortion and severe economic losses in dairy industry. The Canis genus serving as one of the confirmed definitive hosts of the apicomplexan parasite Neospora caninum (N. caninum) plays a critical role in its life cycle. However, the effects of N. caninum on its definitive hosts of neutrophils extracellular traps (NETs) formation remain unclear. In the present study, N. caninum tachyzoite-induced canine NETs formation was observed by scanning electron microscopy (SEM). Visualization of DNA decorated with H3, neutrophil elastase (NE), and myeloperoxidase (MPO) within N. caninum tachyzoite-induced NETs were examined using fluorescence confocal microscopy analyses. Furthermore, the formation of canine NETs was quantified using Sytox Green staining, and the LDH levels in supernatants were examined by an LDH Cytotoxicity Assay^® kit. The results clearly showed that NETs-like structures were induced by N. caninum tachyzoites, and the major components within these structures induced by N. caninum tachyzoite were further confirmed by fluorescence confocal microscopy visualization. These results suggest that N. caninum tachyzoites strongly induced NETs formation in canine polymorphonuclear neutrophils (PMN). In functional inhibition assays, the blockings of NADPH oxidase, NE, MPO, SOCE, ERK 1/2, and p38 MAPK signaling pathways significantly inhibited N. caninum tachyzoite-induced NETs formation. To our knowledge, this study is the first to report the formation of NETs in canine PMN against N. caninum infection.

A Novel Strategy for TNF-Alpha Production by 2-APB Induced Downregulated SOCE and Upregulated HSP70 in O. tsutsugamushi-Infected Human Macrophages

Orientia (O.) tsutsugamushi-induced scrub typhus is endemic across many regions of Asia and the Western Pacific, where an estimated 1 million cases occur each year; the majority of patients infected with O. tsutsugamushi end up with a cytokine storm from a severe inflammatory response. Previous reports have indicated that blocking tumor necrosis factor (TNF)-α reduced cell injury from a cytokine storm. Since TNF-α production is known to be associated with intracellular Ca2+ elevation, we examined the effect of store-operated Ca2+ entry (SOCE) inhibitors on TNF-α production in O. tsutsugamushi-infected macrophages. We found that 2-aminoethoxydiphenyl borate (2-APB), but not SKF96365, facilitates the suppression of Ca2+ mobilization via the interruption of Orai1 expression in O. tsutsugamushi-infected macrophages. Due to the decrease of Ca2+ elevation, the expression of TNF-α and its release from macrophages was repressed by 2-APB. In addition, a novel role of 2-APB was found in macrophages that causes the upregulation of heat shock protein 70 (HSP70) expression associated with ERK activation; upregulated TNF-α production in the case of knockdown HSP70 was inhibited with 2-APB treatment. Furthermore, elevated HSP70 formation unexpectedly did not help the cell survival of O. tsutsugamushi-infected macrophages. In conclusion, the parallelism between downregulated Ca2+ mobilization via SOCE and upregulated HSP70 after treatment with 2-APB against TNF-α production was found to efficiently attenuate an O. tsutsugamushi-induced severe inflammatory response.

Far beyond Phagocytosis: Phagocyte-Derived Extracellular Traps Act Efficiently against Protozoan Parasites In Vitro and In Vivo

Professional mononuclear phagocytes such as polymorphonuclear neutrophils (PMN), monocytes, and macrophages are considered as the first line of defence against invasive pathogens. The formation of extracellular traps (ETs) by activated mononuclear phagocytes is meanwhile well accepted as an effector mechanism of the early host innate immune response acting against microbial infections. Recent investigations showed evidence that ETosis is a widely spread effector mechanism in vertebrates and invertebrates being utilized to entrap and kill bacteria, fungi, viruses, and protozoan parasites. ETs are released in response to intact protozoan parasites or to parasite-specific antigens in a controlled cell death process. Released ETs consist of nuclear DNA as backbone adorned with histones, antimicrobial peptides, and phagocyte-specific granular enzymes thereby producing a sticky extracellular matrix capable of entrapping and killing pathogens. This review summarizes recent data on protozoa-induced ETosis. Special attention will be given to molecular mechanisms of protozoa-induced ETosis and on its consequences for the parasites successful reproduction and life cycle accomplishment.

Inhibition of neutrophil superoxide generation by shikonin is associated with suppression of cellular Ca(2+) fluxes

Shikonin, an anti-inflammatory compound of “Shikon”, inhibits the neutrophil superoxide (O₂^•−) generation by NADPH oxidase 2 (Nox2); however, the mechanisms of how shikonin affects Nox2 activity remained unclear. We aimed to elucidate the relationship between the inhibition of Nox2 activity and influences on intracellular Ca²⁺ concentration ([Ca²⁺]_i) by shikonin. For this purpose, we used a simultaneous monitoring system for detecting changes in [Ca²⁺]_i (by fluorescence) and O₂^•− generation (by chemiluminescence) and evaluated the effects of shikonin on neutrophil-like HL-60 cells stimulated with N-formyl-l-methionyl-l-leucyl-l-phenylalanine (fMLP). Since fMLP activates Nox2 by elevation in [Ca²⁺]_i via fluxes such as inositol 1,4,5-trisphosphate-induced Ca²⁺ release (IICR) and store-operated Ca²⁺ entry (SOCE), we also evaluated the effects of shikonin on IICR and SOCE. Shikonin dose-dependently inhibited the fMLP-induced elevation in [Ca²⁺]_i and O₂^•− generation (IC₅₀ values of 1.45 and 1.12 µM, respectively) in a synchronized manner. Analyses of specific Ca²⁺ fluxes showed that shikonin inhibits IICR and IICR-linked O₂^•− generation (IC₅₀ values: 0.28 and 0.31 µM for [Ca²⁺]_i and O₂^•−, respectively), as well as SOCE and SOCE-linked O₂^•− generation (IC₅₀ values: 0.39 and 0.25 µM for [Ca²⁺]_i and O₂^•−, respectively). These results suggested that shikonin inhibits the O₂^•− generation by Nox2 in fMLP-stimulated neutrophils by targeting Ca²⁺ fluxes such as IICR and SOCE.

Butyric acid stimulates bovine neutrophil functions and potentiates the effect of platelet activating factor

Increased short-chain fatty acid (SCFA) production is associated with subacute ruminal acidosis (SARA) and activation of inflammatory processes. In humans and rodents, SCFAs modulate inflammatory responses in the gut via free fatty acid receptor 2 (FFA2). In bovines, butyric acid is one of the most potent FFA2 agonists. Its expression in bovine neutrophils has recently been demonstrated, suggesting a role in innate immune response in cattle. This study aimed to evaluate if butyric acid modulates oxidative and non-oxidative functions or if it can potentiate other inflammatory mediators in bovine neutrophils. Our results showed that butyric acid can activate bovine neutrophils, inducing calcium (Ca(2+)) influx and mitogen-activated protein kinase (MAPK) phosphorylation, two second messengers involved in FFA2 activation. Ca(2+) influx induced by butyric acid was dependent on the extracellular and intracellular Ca(2+) source and phospholipase C (PLC) activation. Butyric acid alone had no significant effect on reactive oxygen species (ROS) production and chemotaxis; however, a priming effect on platelet-activating factor (PAF), a potent inflammatory mediator, was observed. Butyric acid increased CD63 expression and induced the release of neutrophil granule markers matrix metalloproteinase-9 (MMP-9) and lactoferrin. Finally, we observed that butyric acid induced neutrophil extracellular trap (NET) formation without affecting cellular viability. These findings suggest that butyric acid, a component of the ruminal fermentative process, can modulate the innate immune response of ruminants.

Understanding autoimmunity: The ion channel perspective

Ion channels are integral membrane proteins that orchestrate the passage of ions across the cell membrane and thus regulate various key physiological processes of the living system. The stringently regulated expression and function of these channels hold a pivotal role in the development and execution of various cellular functions. Malfunction of these channels results in debilitating diseases collectively termed channelopathies. In this review, we highlight the role of these proteins in the immune system with special emphasis on the development of autoimmunity. The role of ion channels in various autoimmune diseases is also listed out. This comprehensive review summarizes the ion channels that could be used as molecular targets in the development of new therapeutics against autoimmune disorders.

The calcium-activated potassium channel KCa3.1 plays a central role in the chemotactic response of mammalian neutrophils

AIM

Neutrophils are the first cells to arrive at sites of injury. Nevertheless, many inflammatory diseases are characterized by an uncontrolled infiltration and action of these cells. Cell migration depends on volume changes that are governed by ion channel activity, but potassium channels in neutrophil have not been clearly identified. We aim to test whether KCa3.1 participates in neutrophil migration and other relevant functions of the cell.

METHODS

Cytometer and confocal measurements to determine changes in cell volume were used. Cells isolated from human, mouse and horse were tested for KCa3.1-dependent chemotaxis. Chemokinetics, calcium handling and release of reactive oxygen species were measured to determine the role of KCa3.1 in those processes. A mouse model was used to test for neutrophil recruitment after acute lung injury in vivo.

RESULTS

We show for the first time that KCa3.1 is expressed in mammalian neutrophils. When the channel is inhibited by a pharmacological blocker or by genetic silencing, it profoundly affects cell volume regulation, and chemotactic and chemokinetic properties of the cells. We also demonstrated that pharmacological inhibition of KCa3.1 did not affect calcium entry or reactive oxygen species production in neutrophils. Using a mouse model of acute lung injury, we observed that Kca3.1(-/-) mice are significantly less effective at recruiting neutrophils into the site of inflammation.

CONCLUSIONS

These results demonstrate that KCa3.1 channels are key actors in the migration capacity of neutrophils, and its inhibition did not affect other relevant cellular functions.

Effect of the synthetic Toll-like receptor ligands LPS, Pam3CSK4, HKLM and FSL-1 in the function of bovine polymorphonuclear neutrophils

Toll-like receptors (TLR) are a family of pattern recognition receptors that sense microbial associated molecular patterns (MAMP) such as microbial membrane components and nucleic acids of bacterial origin. Polymorphonuclear neutrophils (PMN) are the first cell of the innate immune system to arrive at the site of infection or injury and elicit oxidative and non-oxidative microbicidal mechanisms. Observations in human and mouse suggest that TLR ligands can induce direct responses in PMN. So far, there is no information of the effect of synthetic TLR ligands on the response of bovine PMN. The objective of this study was to evaluate the functional response of bovine PMN incubated with four synthetic TLR ligands: ultrapure LPS (TLR4), Pam(3)CSK(4) (TLR2/1), HKLM (TLR2) and FSL-1 (TLR2/6). The results show that all the ligands increment cells size as identified by changes in the FSC-SSC as part of the flow cytometric analysis. Interestingly, only Pam(3)CSK(4) consistently induced a calcium influx, increased ROS production and secretion of gelatinase granules, whereas no response was seen using other ligands. Furthermore, exposure of bovine PMN to ultrapure LPS, Pam(3)CSK(4), HKLM or FSL-1 for 24 hours did not impact on apoptosis of these cells. Our data provide evidence for a selective response of bovine PMNs to TLR ligands.

Harbour seal (Phoca vitulina) PMN and monocytes release extracellular traps to capture the apicomplexan parasite Toxoplasma gondii

Extracellular traps (ETs) are composed of nuclear DNA as backbone adorned with histones, cytoplasmic antimicrobial peptides/proteins which are released from a range of vertebrate and invertebrate host immune cells in response to several invading pathogens. Until now this ancient novel innate defence mechanism has not been demonstrated in any marine mammal. Interactions of harbour seal (Phoca vitulina)-PMN and -monocytes with viable tachyzoites of Toxoplasma gondii were investigated in this respect in vitro. For the demonstration and quantification of harbour seal PMN- and monocyte-derived ETs, extracellular DNA was stained with Sytox Orange. Fluorescence assays as well as scanning electron microscopy (SEM) analyses demonstrated PMN- and monocyte-promoted ET formation rapidly being induced upon contact with T. gondii-tachyzoites. The co-localisation of extracellular DNA decorated with histones (H3), neutrophil elastase (NE) and myeloperoxidase (MPO) in parasite entrapping structures confirmed the classical characteristics of PMN- and monocyte-promoted ETs. Exposure of harbour seal PMN and monocytes to viable tachyzoites resulted in a significant induction of ETs when compared to negative controls. Harbour seal-ETs were efficiently abolished by DNase I treatment and were reduced after PMN and monocytes pre-incubation with the NADPH oxidase inhibitor diphenilane iodondium. Tachyzoites of T. gondii were firmly entrapped and immobilised within harbour seal-ET structures. To our best knowledge, we here report for the first time on T. gondii-induced ET formation in harbour seal-PMN and -monocytes. Our results strongly indicate that PMN- and monocyte-triggered ETs represent a relevant and ancient conserved effector mechanism of the pinniped innate immune system as reaction against the pathogenic protozoon T. gondii and probably against other foreign pathogens occurring in the ocean environment.

The impact of cationic solid lipid nanoparticles on human neutrophil activation and formation of neutrophil extracellular traps (NETs)

Cationic solid lipid nanoparticles (cSLNs) are extensively employed as the nanocarriers for drug/gene targeting to tumors and the brain. Investigation into the possible immune response of cSLNs is still lacking. The aim of this study was to evaluate the impact of cSLNs upon the activation of human polymorphonuclear neutrophil cells (PMNs). The cytotoxicity, pro-inflammatory mediators, Ca(2+) mobilization, mitogen-activated protein kinases (MAPKs), and neutrophil extracellular traps (NETs) as the indicators of PMN stimulation were examined in this work. The cSLNs presented a diameter of 195 nm with a zeta potential of 44 mV. The cSLNs could interact with the cell membrane to produce a direct membrane lysis and the subsequent cytotoxicity according to lactate dehydrogenase (LDH) elevation. The interaction of cSLNs with the membrane also triggered a Ca(2+) influx, followed by the induction of oxidative stress and degranulation. The cationic nanoparticles elevated the levels of superoxide anion and elastase by 24- and 9-fold, respectively. The PMN activation by cSLNs promoted the phosphorylation of p38 and Jun-N-terminal kinases (JNK) but not extracellular signal-regulated kinases (ERK). The imaging of scanning electron microscopy (SEM) and immunofluorescence demonstrated the production of NETs by cSLNs. This phenomenon was not significant for the neutral SLNs (nSLNs), although histones in NETs also increased after treatment of nSLNs. Our results suggest an important role of cSLNs in governing the activation of human neutrophils.

Cationic additives in nanosystems activate cytotoxicity and inflammatory response of human neutrophils: lipid nanoparticles versus polymeric nanoparticles

This report compares the effect of lipid and polymeric nanoparticles upon human neutrophils in the presence of cationic surfactants. Nanostructured lipid carriers and poly(lactic-co-glycolic) acid nanoparticles were manufactured as lipid and polymeric systems, respectively. Some cytotoxic and proinflammatory mediators such as lactate dehydrogenase (LDH), elastase, O₂^•−, and intracellular Ca²⁺ were examined. The nanoparticles showed a size of 170–225 nm. Incorporation of cetyltrimethylammonium bromide or soyaethyl morpholinium ethosulfate, the cationic surfactant, converted zeta potential from a negative to a positive charge. Nanoparticles without cationic surfactants revealed a negligible change on immune and inflammatory responses. Cationic surfactants in both nanoparticulate and free forms induced cell death and the release of mediators. Lipid nanoparticles generally demonstrated a greater response compared to polymeric nanoparticles. The neutrophil morphology observed by electron microscopy confirmed this trend. Cetyltrimethylammonium bromide as the coating material showed more significant activation of neutrophils than soyaethyl morpholinium ethosulfate. Confocal microscope imaging displayed a limited internalization of nanoparticles into neutrophils. It is proposed that cationic nanoparticles interact with the cell membrane, triggering membrane disruption and the following Ca²⁺ influx. The elevation of intracellular Ca²⁺ induces degranulation and oxidative stress. The consequence of these effects is cytotoxicity and cell death. Caution should be taken when selecting feasible nanoparticulate formulations and cationic additives for consideration of applicability and toxicity.

In silico assessment of S100A12 monomer and dimer structural dynamics: implications for the understanding of its metal-induced conformational changes

Changes in the concentration of different ions modulate several cellular processes, such as Ca(2+) and Zn(2+) in inflammation. Upon activation of immune system effector cells, the intracellular Ca(2+) concentration rises propagating the activation signal, leading to degranulation and generation of reactive oxygen species, which increases the Zn(2+) intracellular concentration as a consequence of the cellular antioxidant machinery. In this context, S100A12 is of special interest because it is a pro-inflammatory protein expressed in neutrophils whose structure and function are modulated by both Ca(2+) and Zn(2+). The current hypothesis about its mechanism of action was built based on biochemical and crystallographic data. However, there are missing connections between molecular structure and the way in which many events are concatenated at the triggering and along the inflammatory process. In this work we use molecular dynamics simulations to describe how variations in Zn(2+) and Ca(2+) concentrations modulate the structural dynamics of the calcium-free S100A12 dimer and monomer, which was not considered a part of the mechanism of action before. Our results suggest that (i) Zn(2+) have a determinant role in the dimerization step, as well as in the unbinding of the Na(+) complexed to the N-terminal EF-hand; (ii) the N-terminal EF-hand domain is the first to bind Ca(2+), and not the C-terminal, as usually accepted; and that (iii) Ca(2+) modulates the structural dynamics of H-III.

Cationic surfactants in the form of nanoparticles and micelles elicit different human neutrophil responses: a toxicological study

Cationic surfactants are an ingredient commonly incorporated into nanoparticles for clinical practicability; however, the toxicity of cationic surfactants in nanoparticles is not fully elucidated. We aimed to evaluate the inflammatory responses of cationic nanobubbles and micelles in human neutrophils. Soyaethyl morpholinium ethosulfate (SME) and hexadecyltrimethyl-ammonium bromide (CTAB) are the two cationic surfactants employed in this study. The zeta potential of CTAB nanobubbles was 80 mV, which was the highest among all formulations. Nanobubbles, without cationic surfactants, showed no cytotoxic effects on neutrophils in terms of inflammatory responses. Cationic nanobubbles caused a concentration-dependent cytotoxicity of degranulation (elastase release) and membrane damage (release of lactate dehydrogenase, LDH). Among all nanoparticles and micelles, CTAB-containing nanosystems showed the greatest inflammatory responses. A CTAB nanobubble diluent (1/150) increased the LDH release 80-fold. Propidium iodide staining and scanning electron microscopy (SEM) verified cell death and morphological change of neutrophils treated by CTAB nanobubbles. SME, in a micelle form, strengthened the inflammatory response more than SME-loaded nanobubbles. Membrane interaction and subsequent Ca(2+) influx were the mechanisms that triggered inflammation. The information obtained from this work is beneficial in designing nanoparticulate formulations for balancing clinical activity and toxicity.

Propionate induces the release of granules from bovine neutrophils

Short-chain fatty acids (SCFA) are produced by bacterial fermentation in the rumen of cattle and are the primary energy source in ruminants. Propionate is one of the main SCFA and it can exert multiple effects on the inflammatory process and neutrophil function via calcium (Ca(2+)) release, reactive oxygen species, and intracellular pH changes. However, currently no evidence has shown whether propionate can induce granule release from bovine neutrophils. The purpose of this study was to analyze the effect of propionate on granule release and to evaluate the expression of two G-protein coupled receptors-GPR41 and GPR43-that are activated by propionate. Neutrophil degranulation was assessed by quantifying the release of the neutrophil enzymes myeloperoxidase (MPO), lactoferrin, and matrix metalloprotease-9 (MMP-9) as markers of azurophil, specific granules, and gelatinase granules, respectively. Isolated bovine neutrophils were treated with millimolar concentrations of propionate (0.3, 3 and 30mM), and the cell-free supernatants were recovered. The stimulation of neutrophils with 0.3mM propionate induced the release of lactoferrin and MMP-9 as revealed by ELISA and gelatin zymography, respectively. Propionate at 30mM induced the release of MPO as demonstrated using an enzymatic assay. The role of intracellular Ca(2+) influx and the signaling pathways that may regulate the propionate effect on granules release were also determined. Reverse transcription (RT)-PCR and real-time PCR were performed to analyze the expression of GPR41 and GPR43 mRNA in bovine neutrophils. Both mRNA were detected, whereas the expression of GPR43 was higher than that of GPR41, and the synthetic agonists for this receptor, phenylacetamides 1 and 2, caused an increase in intracellular Ca(2+), lactoferrin, and MMP-9 release. These results support that propionate-induced granule release is mediated by intracellular Ca(2+) influx and activation of extracellular signal-regulated kinase ERK 1/2. We also propose a potential role of GPR43 in propionate-induced granule release from bovine neutrophils that may be involved in regulatory effects of propionate in the innate immune response in cattle.

Immune complexes isolated from patients with pulmonary tuberculosis modulate the activation and function of normal granulocytes

Circulating immune complexes (ICs) are associated with the pathogenesis of several diseases. Very little is known about the effect of ICs on the host immune response in patients with tuberculosis (TB). The effects of ICs isolated from patients with TB in modulating the release of calcium, cytokines, and granular proteins were studied in normal granulocytes, as were their chemotactic, phagocytic, and oxidative burst processes. ICs from TB patients induced decreased production of cytokines and platelet-activating factor (PAF) from normal granulocytes. ICs from TB patients also induced enhanced chemotaxis and phagocytosis but caused diminished oxidative burst. This was accompanied by an increased release in intracellular calcium. On the other hand, ICs from TB patients induced increased release of the granular proteins human neutrophil peptides 1 to 3 (HNP1-3). Thus, ICs from patients with TB exhibit a profound effect on granulocyte function with activation of certain effector mechanisms and dampening of others.