Regulation of superoxide production in neutrophils: role of calcium influx

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.

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.

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.

Apremilast ameliorates acute respiratory distress syndrome by inhibiting neutrophil-induced oxidative stress

BACKGROUND

The pathogenesis of acute respiratory distress syndrome (ARDS) is attributed to the dysregulation of oxidative stress and neutrophil recruitment. We aimed to investigate the anti-inflammatory effects of apremilast on human neutrophils and assess its efficacy for treating ARDS.

METHODS

We analysed superoxide anion generation, integrin expression, and adhesion in activated human neutrophils using spectrophotometry, flow cytometry, and immunofluorescence microscopy. Phosphorylation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) was determined using immunoblotting. A murine lipopolysaccharide (LPS)-induced ARDS model was used to evaluate the therapeutic effects of apremilast.

RESULTS

Apremilast significantly decreased superoxide anion production, reactive oxygen species (ROS) generation, cluster of differentiation (CD)11 b expression, and neutrophil adhesion in formyl-l-methionyl-l-leucyl-l-phenylalanine activated human neutrophils. Apremilast elevated cyclic 3',5'-adenosine monophosphate (cAMP) and protein kinase A (PKA) activity in activated neutrophils. It reduced cellular cAMP-specific phosphodiesterase (PDE) activity and selectively inhibited enzymatic PDE4 activity. The activated cAMP/PKA pathway suppressed the phosphorylation of ERK and JNK as well as Ca2+ mobilization in activated neutrophils. All inhibitory effects of apremilast on activated neutrophils were reversed by a PKA inhibitor. In vivo examinations indicated that apremilast alleviated lung neutrophil infiltration, myeloperoxidase (MPO) activity, pulmonary oedema, and alveolar damage in LPS-induced ARDS.

CONCLUSION

Apremilast inhibits inflammatory responses after neutrophil activation via cAMP/PKA-dependent inhibition of ERK and JNK activation. Our study revealed apremilast suppresses oxidative stress and chemotaxis by selectively inhibiting PDE4 in neutrophils and thus protects against endotoxin-induced ARDS in mice. Apremilast can be used as an alternative off-label drug in treating acute lung damage.

Association of time to metritis diagnosis with circulating concentration of metabolites, minerals, and haptoglobin in Jersey cows

Our objective was to investigate the association of early metritis [EMET, diagnosed at <5 d in milk (DIM)] and late metritis (LMET, diagnosed at ≥5 DIM) with circulating concentrations of energy metabolites, minerals, and haptoglobin (Hp) throughout the first 14 d postpartum. A total of 379 purebred Jersey cows were enrolled in a prospective cohort study from a single herd in west Texas. Cows were examined for metritis using the Metricheck device (Simcro Ltd.) at 4, 7, and 10 DIM. Cows identified by farm employees as possible metritis cases were also evaluated for metritis. Blood samples were collected for analysis of concentrations of Ca, Mg, and glucose at DIM 1 through 5, 7, 10, and 14. Albumin, urea, fructosamine, free fatty acids (FFA), creatinine, and β-hydroxybutyrate (BHB) were analyzed at DIM 3, 5, 7, 10, and 14, and Hp at DIM 1 through 5 and 7. Data were analyzed using the MIXED and PHREG procedures of SAS (SAS Institute Inc.). A series of mixed general linear models accounting for repeated measures were fitted to the data. The independent variables metritis [no metritis (NMET), EMET, and LMET], DIM of analyte assessment, and parity were forced in all models. Multivariable Cox proportional hazard models were built to assess the risk of pregnancy and culling within 150 DIM. The overall metritis incidence was 26.9% (EMET = 49; LMET = 53; NMET = 277). Average concentrations of glucose, Mg, and urea were not associated with metritis. The associations of Ca, creatinine, BHB, and fructosamine with metritis were dependent on the DIM of analyte assessment. Cows categorized as EMET and LMET had, on average, lower albumin and fructosamine compared with NMET cows. Both EMET and LMET cows had, on average, greater BHB than NMET cows. A greater FFA concentration was only observed in cows diagnosed with EMET compared with NMET cows (EMET = 0.58, LMET = 0.52, NMET = 0.48 mmol/L). Additionally, circulating Hp concentration was greater for LMET and EMET compared with NMET cows, and EMET cows had greater Hp compared with LMET cows (EMET = 1.15; LMET = 1.00; NMET = 0.84). In conclusion, several blood biomarkers were temporally associated with early versus late metritis diagnosis in postpartum Jersey cows. No meaningful differences were observed in production, reproduction, or culling between EMET and LMET cows. These results suggest that cows with EMET undergo a more severe degree of inflammation and negative energy balance compared with NMET cows.

The calcium channel modulator 2-APB hydrolyzes in physiological buffers and acts as an effective radical scavenger and inhibitor of the NADPH oxidase 2

2-aminoethoxydiphenyl borate (2-APB) is commonly used as a tool to modulate calcium signaling in physiological studies. 2-APB has a complex pharmacology and acts as activator or inhibitor of a variety of Ca²⁺ channels and transporters. While unspecific, 2-APB is one of the most-used agents to modulate store-operated calcium entry (SOCE) mediated by the STIM-gated Orai channels. Due to its boron core structure, 2-APB tends to readily hydrolyze in aqueous environment, a property that results in a complex physicochemical behavior. Here, we quantified the degree of hydrolysis in physiological conditions and identified the hydrolysis products diphenylborinic acid and 2-aminoethanol by NMR. Notably, we detected a high sensitivity of 2-APB/diphenylborinic acid towards decomposition by hydrogen peroxide to compounds such as phenylboronic acid, phenol, and boric acid, which were, in contrast to 2-APB itself and diphenylborinic acid, insufficient to affect SOCE in physiological experiments. Consequently, the efficacy of 2-APB as a Ca²⁺ signal modulator strongly depends on the reactive oxygen species (ROS) production within the experimental system. The antioxidant behavior of 2-APB towards ROS and its resulting decomposition are inversely correlated to its potency to modulate Ca²⁺ signaling as shown by electron spin resonance spectroscopy (ESR) and Ca²⁺ imaging. Finally, we observed a strong inhibitory effect of 2-APB, i.e., its hydrolysis product diphenylborinic acid, on NADPH oxidase (NOX2) activity in human monocytes. These new 2-APB properties are highly relevant for Ca²⁺ and redox signaling studies and for pharmacological application of 2-APB and related boron compounds.

An increase in the cytosolic concentration of free calcium ions activates the neutrophil NADPH-oxidase provided that the free fatty acid receptor 2 has been allosterically modulated

Signals generated by free fatty acid receptor 2 (FFA2R) can activate the neutrophil NADPH-oxidase without involvement of any orthosteric FFA2R agonist. The initiating signals may be generated by P2Y₂R, the receptor for ATP. An FFA2R specific allosteric modulator (PAM; Cmp58) was required for this response and used to investigate the mechanism by which signals generated by ATP/P2Y₂R activate an FFA2R dependent process. The P2Y₂R induced signal that together with the modulated FFA2R activates neutrophils, was generated downstream of the Gα_q containing G protein coupled to P2Y₂R. A rise in the cytosolic concentration of ionized calcium ([Ca²⁺]_i) was hypothesized to be the important signal. The hypothesis gained support from the finding that the modulator transferred the neutrophils to a Ca²⁺sensitive state. The rise in [Ca²⁺]_i induced by the Ca²⁺ specific ionophore ionomycin, activated the neutrophils provided that an allosteric modulator was bound to FFA2R. The activity of the superoxide generating NADPH-oxidase induced by ionomycin was rapidly terminated and the FFA2Rs could then no longer be activated by the FFA2R agonist propionate or by the signal generated by ATP/P2Y₂R. The non-responding state of FFA2R was, however, revoked by a cross-activating allosteric FFA2R modulator. The [Ca²⁺]_i mediated activation of neutrophils with their FFA2Rs allosterically modulated, represent a unique regulatory receptor crosstalk mechanism by which the activation potency of a G protein coupled receptor is controlled by a receptor-crosstalk signaling system operating from the cytosolic side of the plasma membrane.

Interplay of gut microbiota and oxidative stress: Perspective on neurodegeneration and neuroprotection

Background

Recent research on the implications of gut microbiota on brain functions has helped to gather important information on the relationship between them. Pathogenesis of neurological disorders is found to be associated with dysregulation of gut-brain axis. Some gut bacteria metabolites are found to be directly associated with the increase in reactive oxygen species levels, one of the most important risk factors of neurodegeneration. Besides their morbid association, gut bacteria metabolites are also found to play a significant role in reducing the onset of these life-threatening brain disorders.

Aim of Review

Studies done in the recent past raises two most important link between gut microbiota and the brain: "gut microbiota-oxidative stress-neurodegeneration" and gut microbiota-antioxidant-neuroprotection. This review aims to gives a deep insight to our readers, of the collective studies done, focusing on the gut microbiota mediated oxidative stress involved in neurodegeneration along with a focus on those studies showing the involvement of gut microbiota and their metabolites in neuroprotection.

Key Scientific Concepts of Review

This review is focused on three main key concepts. Firstly, the mounting evidences from clinical and preclinical arenas shows the influence of gut microbiota mediated oxidative stress resulting in dysfunctional neurological processes. Therefore, we describe the potential role of gut microbiota influencing the vulnerability of brain to oxidative stress, and a budding causative in Alzheimer's and Parkinson's disease. Secondly, contributing roles of gut microbiota has been observed in attenuating oxidative stress and inflammation via its own metabolites or by producing secondary metabolites and, also modulation in gut microbiota population with antioxidative and anti-inflammatory probiotics have shown promising neuro resilience. Thirdly, high throughput in silico tools and databases also gives a correlation of gut microbiome, their metabolites and brain health, thus providing fascinating perspective and promising new avenues for therapeutic options.

Imperatorin Alleviates Psoriasiform Dermatitis by Blocking Neutrophil Respiratory Burst, Adhesion, and Chemotaxis Through Selective Phosphodiesterase 4 Inhibition

Aim: Neutrophil infiltration and increased oxidative stress are involved in the pathogenesis and severity of psoriasis. Although the therapy of psoriasis remains elusive, targeting treatment to reduce oxidative stress is considered a potential option. Our study demonstrates the anti-inflammatory effects of a natural furocoumarin, imperatorin, on activated human neutrophils and psoriasiform dermatitis in mice. Results: Imperatorin inhibited superoxide anion generation, neutrophil adhesion, and migration in N-formyl-l-methionyl-l-leucyl-l-phenylalanine (fMLF)-stimulated human neutrophils. Further studies showed that imperatorin induced a decrease in cAMP-specific phosphodiesterase (PDE) activity, and increased intracellular cAMP levels and protein kinase A (PKA) activity in human neutrophils. The enzyme activities of PDE4 subtypes, but not PDE3 and PDE7, were inhibited by imperatorin. Furthermore, imperatorin inhibited the phosphorylation of protein kinase B (Akt), extracellular regulated kinase (ERK), and c-Jun N-terminal kinase (JNK), as well as Ca²⁺ mobilization in fMLF-stimulated neutrophils. These suppressive effects of imperatorin on cell responses and signaling were reversed by PKA inhibitor, suggesting that cAMP/PKA is involved in the anti-inflammatory effects of imperatorin. In vivo studies of imiquimod- and interleukin-23-induced mouse psoriasiform dermatitis demonstrated that imperatorin alleviated skin desquamation, epidermal thickening, keratinocyte hyperproliferation, and neutrophil infiltration. Innovation and Conclusion: Our results demonstrate that imperatorin inhibits human neutrophil respiratory burst, adhesion, and migration through the elevation of cAMP/PKA to inhibit Akt, ERK, JNK, and Ca²⁺ mobilization. Imperatorin is a natural inhibitor of PDE4A/B/C and may serve as a lead for developing new therapeutics to treat neutrophilic psoriasis. Antioxid. Redox Signal. 35, 885-903.

Epstein-Barr Virus Promotes Tumor Angiogenesis by Activating STIM1-Dependent Ca2+ Signaling in Nasopharyngeal Carcinoma

Epstein-Barr virus (EBV) promotes tumor angiogenesis in nasopharyngeal carcinoma (NPC) by activating store-operated Ca²⁺ entry. Since such entry has been linked to stromal interaction molecule 1 (STIM1), we examined whether the virus acts via STIM1-dependent Ca²⁺ signaling to promote tumor angiogenesis in NPC. STIM1 expression was detected in NPC cell lines HK1 and CNE2 that were negative or positive for EBV. STIM1 was knocked down in EBV-positive cells using recombinant lentivirus, then cytosolic Ca²⁺ levels were measured based on fluorescence resonance energy transfer. Cells were also exposed to epidermal growth factor (EGF), and secretion of vascular endothelial growth factor (VEGF) was measured using an enzyme-linked immunosorbent assay. Endothelial tube formation was quantified in an in vitro angiogenesis assay. Growth of CNE2-EBV xenografts was measured in mice, and angiogenesis was assessed based on immunohistochemical staining against CD31. Paraffin-embedded NPC tissues from patients were assayed for CD31 and STIM1. EGFR and ERK signaling pathways were assessed in NPC cell lines. STIM1 expression was higher in EBV-positive than in EBV-negative NPC cell lines. STIM1 knockdown in EBV-positive NPC cells significantly reduced Ca²⁺ influx and VEGF production after EGF treatment. STIM1 knockdown also inhibited xenograft growth and angiogenesis. Moreover, CD31 expression level was higher in EBV-positive than EBV-negative NPC tissues, and high expression of CD31 co-localized with high expression of STIM1 in EBV-positive tissues from NPC patients. Viral infection of NPC cells led to higher levels of phosphorylated ERK1/2 after EGF treatment, which STIM1 knockdown partially reversed. Our results suggest that EBV promotes EGF-induced ERK1/2 signaling by activating STIM1-dependent Ca²⁺ signaling, and that blocking such signaling may inhibit EBV-promoted angiogenesis in NPC.

Photoreceptor Cell Calcium Dysregulation and Calpain Activation Promote Pathogenic Photoreceptor Oxidative Stress and Inflammation in Prodromal Diabetic Retinopathy

This study tested the hypothesis that diabetes promotes a greater than normal cytosolic calcium level in rod cells that activates a Ca2+-sensitive protease, calpain, resulting in oxidative stress and inflammation, two pathogenic factors of early diabetic retinopathy. Nondiabetic and 2-month diabetic C57Bl/6J and calpain1 knockout (Capn1-/-) mice were studied; subgroups were treated with a calpain inhibitor (CI). Ca2+ content was measured in photoreceptors using Fura-2. Retinal calpain expression was studied by quantitative RT-PCR and immunohistochemistry. Superoxide and expression of inflammatory proteins were measured using published methods. Proteomic analysis was conducted on photoreceptors isolated from untreated diabetic mice or treated daily with CI for 2 months. Cytosolic Ca2+ content was increased twofold in photoreceptors of diabetic mice as compared with nondiabetic mice. Capn1 expression increased fivefold in photoreceptor outer segments of diabetic mice. Pharmacologic inhibition or genetic deletion of Capn1 significantly suppressed diabetes-induced oxidative stress and expression of proinflammatory proteins in retina. Proteomics identified a protein (WW domain-containing oxidoreductase [WWOX]) whose expression was significantly increased in photoreceptors from mice diabetic for 2 months and was inhibited with CI. Knockdown of Wwox using specific siRNA in vitro inhibited increase in superoxide caused by the high glucose. These results suggest that reducing Ca2+ accumulation, suppressing calpain activation, and/or reducing Wwox up-regulation are novel targets for treating early diabetic retinopathy.

Reactive Oxygen Species and Endothelial Ca2+ Signaling: Brothers in Arms or Partners in Crime?

An increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i) controls virtually all endothelial cell functions and is, therefore, crucial to maintain cardiovascular homeostasis. An aberrant elevation in endothelial can indeed lead to severe cardiovascular disorders. Likewise, moderate amounts of reactive oxygen species (ROS) induce intracellular Ca²⁺ signals to regulate vascular functions, while excessive ROS production may exploit dysregulated Ca²⁺ dynamics to induce endothelial injury. Herein, we survey how ROS induce endothelial Ca²⁺ signals to regulate vascular functions and, vice versa, how aberrant ROS generation may exploit the Ca²⁺ handling machinery to promote endothelial dysfunction. ROS elicit endothelial Ca²⁺ signals by regulating inositol-1,4,5-trisphosphate receptors, sarco-endoplasmic reticulum Ca²⁺-ATPase 2B, two-pore channels, store-operated Ca²⁺ entry (SOCE), and multiple isoforms of transient receptor potential (TRP) channels. ROS-induced endothelial Ca²⁺ signals regulate endothelial permeability, angiogenesis, and generation of vasorelaxing mediators and can be exploited to induce therapeutic angiogenesis, rescue neurovascular coupling, and induce cancer regression. However, an increase in endothelial [Ca²⁺]_i induced by aberrant ROS formation may result in endothelial dysfunction, inflammatory diseases, metabolic disorders, and pulmonary artery hypertension. This information could pave the way to design alternative treatments to interfere with the life-threatening interconnection between endothelial ROS and Ca²⁺ signaling under multiple pathological conditions.

Effect of source and amount of vitamin D on function and mRNA expression in immune cells in dairy cows

Objectives were to determine the effect of supplementing 2 sources of vitamin D, cholecalciferol (CH) or calcidiol (CA), at 1 (1mg) or 3 mg/d (3mg) prepartum on concentrations of vitamin D metabolites in plasma, measures of innate immune function, and leukocyte mRNA expression. Parous Holstein cows (n = 99) were assigned to a daily treatment administered as top-dress containing either 1 or 3 mg of CH (CH1 or CH3) or of CA (CA1 or CA3) from 250 d of gestation until calving. Plasma concentrations of vitamin D, immune cell population in blood, cell adhesion markers, and granulocyte phagocytosis and oxidative burst were evaluated pre- and postpartum. The mRNA expression in leukocytes was determined at 270 d of gestation and 3 d postpartum for genes involved in cell migration, pathogen recognition receptors, cell signaling, cytokines, antimicrobial mechanisms, oxidative burst, and Ca and vitamin D metabolism. Concentrations of vitamin D₃ increased in cows fed CH, whereas those of 25-hydroxyvitamin D₃ increased in cows fed CA. Percentage of granulocytes from total leukocytes differed with amount of vitamin D pre- (1mg = 24.5 vs. 3mg = 37.9%) and postpartum (1mg = 22.0 vs. 3mg = 31.0%), thus shifting mononuclear cells in the opposite direction pre- (1mg = 75.5 vs. 3mg = 62.1%) and postpartum (1mg = 78.0 vs. 3mg = 69.0%). Granulocytes displaying phagocytosis (1mg = 69.0 vs. 3mg = 62.9%) and intensity of phagocytosis prepartum (1mg = 7.46 vs. 3mg = 7.28) tended to be less in cows fed 3mg compared with 1mg. During prepartum, CA increased mRNA expression of genes related to cell adhesion and migration (CD44, ICAM1, ITGAL, ITGB1, LGALS8, SELL), pathogen recognition receptor (NOD2, TLR2, TLR6), cell signaling (FOS, JUN, NFKB2), cytokine signaling (IL1B, IL1R1, IL1RN), antimicrobial mechanisms (CTSB, LYZ), and Ca metabolism (ATP2B1, STIM1, TRPV5) compared with CH. Similarly, postpartum, CA increased mRNA expression of genes related to cell adhesion and migration (CXCR2, SELL, TLN1), cell signaling (AKT2), cytokines (CCL2, IL1R1, ILRN), antimicrobial mechanisms (DEFB3), oxidative burst (RAC2), and calcium metabolism (CALM3) compared with CH. Feeding additional vitamin D in the last 3 wk of gestation changed the profile of blood leukocytes and attenuated granulocyte phagocytosis during the transition period, whereas supplementing CA prepartum increased mRNA expression of genes involved in immune cell function, including genes related to pathogen recognition and antimicrobial effects of leukocytes.

Calcium activity in response to nAChR ligands in murine bone marrow granulocytes with different Gr-1 expression

Polymorphonuclear neutrophilic granulocytes (PMNs) are the largest proportion of leukocytes in adult human blood that perform numerous functions, including phagocytosis, degranulation, generation of reactive oxygen species, and NETosis. Excessive neutrophil activity associates with hyperinflammation and tissue damage during pathologies such as inflammatory bowel disease, diabetes mellitus, tuberculosis, and coronavirus disease 2019. Nicotinic acetylcholine receptors (nAChRs) can modulate immune cells, including neutrophils, functions, therefore, nAChR ligands are considered as the potent agents for therapy of inflammation. Earlier it was shown, that about 30% of PMNs from the acute inflammatory site responded to nicotine by calcium spikes. In this study, we studied the generation of calcium spikes in murine granulocytes with different maturity level (evaluated by Gr-1 expression) isolated from bone marrow in response to ligands of nAChRs in control and under chronic nicotine consumption. It was found that nearly 20%-25% cells in the granulocyte population responded to nicotine or selective antagonists of different type of nAChRs (α-cobratoxin, GIC, and Vc1.1). We demonstrated that in the control group Ca2+ -mobilizing activity was regulated through α7 and α9α10 nAChRs in immature granulocytes (Gr-1int ), whereas in mature granulocytes (Gr-1hi ) it was regulated through α7, α3β2, and α9-contained nAChRs. Sensitivity of PMNs to nicotine depended on their maturity level after chronic nicotine consumption. Gr-1int cells responded to nicotine through α7 and α9-contained nAChRs, while Gr-1hi did not respond to nicotine. Thus, calcium response to nAChR ligands in bone marrow PMNs depends on their maturity level.

Mechanism of action of a diterpene alkaloid hypaconitine on cytotoxicity and inhibitory effect of BAPTA-AM in HCN-2 neuronal cells

Hypaconitine, a neuromuscular blocker, is a diterpene alkaloid found in the root of Aconitum carmichaelii. Although hypaconitine was shown to affect various physiological responses in neurological models, the effect of hypaconitine on cell viability and the mechanism of its action of Ca²⁺ handling is elusive in cortical neurons. This study examined whether hypaconitine altered viability and Ca²⁺ signalling in HCN-2 neuronal cell lines. Cell viability was measured by the cell proliferation reagent (WST-1). Cytosolic Ca²⁺ concentrations [Ca²⁺ ]_i was measured by the Ca²⁺ -sensitive fluorescent dye fura-2. In HCN-2 cells, hypaconitine (10-50 μmol/L) induced cytotoxicity and [Ca²⁺ ]_i rises in a concentration-dependent manner. Removal of extracellular Ca²⁺ partially reduced the hypaconitine's effect on [Ca²⁺ ]_i rises. Furthermore, chelation of cytosolic Ca²⁺ with BAPTA-AM reduced hypaconitine's cytotoxicity. In Ca²⁺ -containing medium, hypaconitine-induced Ca²⁺ entry was inhibited by modulators (2-APB and SKF96365) of store-operated Ca²⁺ channels and a protein kinase C (PKC) inhibitor (GF109203X). Hypaconitine induced Mn²⁺ influx indirectly suggesting that hypaconitine evoked Ca²⁺ entry. In Ca²⁺ -free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin abolished hypaconitine-induced [Ca²⁺ ]_i rises. Conversely, treatment with hypaconitine inhibited thapsigargin-induced [Ca²⁺ ]_i rises. However, inhibition of phospholipase C (PLC) with U73122 did not inhibit hypaconitine-induced [Ca²⁺ ]_i rises. Together, hypaconitine caused cytotoxicity that was linked to preceding [Ca²⁺ ]_i rises by Ca²⁺ influx via store-operated Ca²⁺ entry involved PKC regulation and evoking PLC-independent Ca²⁺ release from the endoplasmic reticulum. Because BAPTA-AM loading only partially reversed hypaconitine-induced cell death, it suggests that hypaconitine induced a second Ca²⁺ -independent cytotoxicity in HCN-2 cells.

Dexmedetomidine Alleviates Hypoxia-Induced Synaptic Loss and Cognitive Impairment via Inhibition of Microglial NOX2 Activation in the Hippocampus of Neonatal Rats

BACKGROUND

Perinatal hypoxia is a universal cause of death and neurological deficits in neonates worldwide. Activation of microglial NADPH oxidase 2 (NOX2) leads to oxidative stress and neuroinflammation, which may contribute to hypoxic damage in the developing brain. Dexmedetomidine has been reported to exert potent neuroprotection in several neurological diseases, but the mechanism remains unclear. We investigated whether dexmedetomidine acts through microglial NOX2 to reduce neonatal hypoxic brain damage.

METHODS

The potential role of microglial NOX2 in dexmedetomidine-mediated alleviation of hypoxic damage was evaluated in cultured BV2 microglia and neonatal rats subjected to hypoxia. In vivo, neonatal rats received dexmedetomidine (25 μg/kg, i.p.) 30 min before or immediately after hypoxia (5% O2, 2 h). Apocynin-mediated NOX inhibition and lentivirus-mediated NOX2 overexpression were applied to further assess the involvement of microglial NOX2 activation.

RESULTS

Pre- or posttreatment with dexmedetomidine alleviated hypoxia-induced cognitive impairment, restored damaged synapses, and increased postsynaptic density-95 and synaptophysin protein expression following neonatal hypoxia. Importantly, dexmedetomidine treatment suppressed hypoxia-induced microglial NOX2 activation and subsequent oxidative stress and the neuroinflammatory response, as reflected by reduced 4-hydroxynonenal and ROS accumulation, and decreased nuclear NF-κB p65 and proinflammatory cytokine levels in cultured BV2 microglia and the developing hippocampus. In addition, treating primary hippocampal neurons with conditioned medium (CM) from hypoxia-activated BV2 microglia resulted in neuronal damage, which was alleviated by CM from dexmedetomidine-treated microglia. Moreover, the neuroprotective effect of dexmedetomidine was reversed in NOX2-overexpressing BV2 microglia and diminished in apocynin-pretreated neonatal rats.

CONCLUSION

Dexmedetomidine targets microglial NOX2 to reduce oxidative stress and neuroinflammation and subsequently protects against hippocampal synaptic loss following neonatal hypoxia.

Ion and Water Transport in Neutrophil Granulocytes and Its Impairment during Sepsis

Neutrophil granulocytes are the vanguard of innate immunity in response to numerous pathogens. Their activity drives the clearance of microbe- and damage-associated molecular patterns, thereby contributing substantially to the resolution of inflammation. However, excessive stimulation during sepsis leads to cellular unresponsiveness, immunological dysfunction, bacterial expansion, and subsequent multiple organ dysfunction. During the short lifespan of neutrophils, they can become significantly activated by complement factors, cytokines, and other inflammatory mediators. Following stimulation, the cells respond with a defined (electro-)physiological pattern, including depolarization, calcium influx, and alkalization as well as with increased metabolic activity and polarization of the actin cytoskeleton. Activity of ion transport proteins and aquaporins is critical for multiple cellular functions of innate immune cells, including chemotaxis, generation of reactive oxygen species, and phagocytosis of both pathogens and tissue debris. In this review, we first describe the ion transport proteins and aquaporins involved in the neutrophil ion-water fluxes in response to chemoattractants. We then relate ion and water flux to cellular functions with a focus on danger sensing, chemotaxis, phagocytosis, and oxidative burst and approach the role of altered ion transport protein expression and activity in impaired cellular functions and cell death during systemic inflammation as in sepsis.

Mechanism of a methylxanthine drug theophylline-induced Ca2+ signaling and cytotoxicity in AML12 mouse hepatocytes

Theophylline is a methylxanthine drug used in therapy for respiratory diseases. However, the impact of theophylline on Ca²⁺ signaling has not been explored in liver cells. This study examined whether theophylline affected Ca²⁺ homeostasis and its related cytotoxicity in AML12 mouse hepatocytes. Cell viability was measured by the cell viability reagent (WST-1). Cytosolic Ca²⁺ concentration ([Ca²⁺]_i) was measured by the Ca²⁺-sensitive fluorescent dye fura-2. Theophylline (25-125 μM) induced [Ca²⁺]_i rises and cause cytotoxicity in AML12 cells. This cytotoxic response was reversed by chelation of cytosolic Ca²⁺ with BAPTA/AM. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin abolished theophylline-induced [Ca²⁺]_i rises. Conversely, treatment with theophylline also abolished thapsigargin-induced [Ca²⁺]_i rises. However, inhibition of PLC failed to alter theophylline-evoked [Ca²⁺]_i rises. In Ca²⁺-containing medium, modulators of store-operated Ca²⁺ channels inhibited 30% of the [Ca²⁺]_i rises, whereas the PKC modulators had no effect. Furthermore, theophylline-induced Ca²⁺ influx was confirmed by Mn²⁺-induced quench of fura-2 fluorescence. Together, in AML12 cells, theophylline caused Ca²⁺-associated cytotoxicity and induced Ca²⁺ entry through PLC-independent Ca²⁺ release from the endoplasmic reticulum and PKC-insensitive store-operated Ca²⁺ channels. BAPTA-AM with its protective effects may be a potential compound for prevention of theophylline-induced cytotoxicity.

α9α10 nicotinic acetylcholine receptors regulate murine bone marrow granulocyte functions

Polymorphonuclear neutrophilic granulocytes (PMNs) are extremely important in defense of the organism against infections and in inflammatory processes including neuroinflammation and pain sensation. Different subtypes of nicotinic acetylcholine receptors (nAChRs) are involved in modulation of PMN activities. Earlier we determined expression of α2-7, α9, β3, β4 subunits and regulatory role of α7 and α3β2 nAChR subtypes in functions of inflammatory PMNs. Other authors detected mRNA of α9 subunit in bone marrow neutrophils (BM-PMNs). Murine BM-PMNs coming out from the bone marrow, where they develop, to blood were characterized as mature. There was no data for α10 and for the presence of functionally active α9α10 nAChRs in BM-PMNs. Here we detected for the first time mRNA expression of the α10 nAChR subunit in BM-PMNs and confirmed the expression of mRNA for α9 nAChR. With the help of α-conotoxins RgIA and Vc1.1, highly selective antagonists of α9α10 nAChRs, we have revealed participation of α9 and/or α9α10 nAChRs in regulation of cytosolic Ca²⁺ concentration, cell adhesion, and in generation of reactive oxygen species (ROS). Nicotine, choline, RgIA, and Vc1.1 induced Ca²⁺ transients in BM-PMNs, enhanced cell adhesiveness and decreased production of ROS indicating involvement of α9, possibly co-assembled with α10, nAChRs in the BM-PMN activity for recruitment and cytotoxicity.

Effects of oral calcium bolus supplementation on intracellular polymorphonuclear leukocyte calcium levels and functionality in primiparous and multiparous dairy cows

The objectives of this study were (1) to characterize Ca levels and polymorphonuclear leukocyte (PMN) function in primiparous and multiparous animals following oral Ca bolus supplementation, and (2) to determine differential responses of boluses containing a lower dose of Ca than traditionally used in primiparous animals on Ca levels and PMN function. Jersey × Holstein crossbred animals (n = 104) were enrolled within 24 h of parturition. All animals were blocked by time relative to calving and randomly assigned to treatment. The Ca boluses were composed of a mixture of Ca chloride, Ca sulfate, and Ca propionate. For objective 1, animals were assigned to control (CON; no Ca supplementation), or a series of 2 Ca boluses given 24 h apart for a total of 50 g of Ca. Objective 2 treatments included control (CON; no Ca supplementation), a series of 2 Ca boluses given 24 h apart containing 50 g of Ca, or a series of 2 Ca boluses given 24 h apart containing 25 g of Ca. Blood samples were collected on d 1 (<24 h), 2, 3, 5, and 7 relative to parturition. Total serum Ca, serum haptoglobin, PMN intracellular Ca, PMN intracellular Ca after stimulation with an environmental Escherichia coli, PMN L-selectin surface expression, and PMN phagocytic and oxidative burst activities were analyzed. For objective 1 a tendency was detected for a treatment difference on basal intracellular PMN Ca and a treatment difference on E. coli-stimulated intracellular PMN Ca. We detected a parity × DIM effect for PMN oxidative burst intensity. However, no other interactions or parity effects on other functional PMN variables were detectable. In primiparous animals, we found a treatment difference for E. coli-stimulated intracellular PMN Ca among animals given 50 g of Ca but no treatment difference on basal intracellular PMN Ca. The 50 g of Ca treatment increased both PMN phagocytosis and oxidative burst intensities. Supplementing animals with 50 g of oral Ca increased intracellular PMN Ca and influenced PMN function.

Role of the Intracellular Sodium Homeostasis in Chemotaxis of Activated Murine Neutrophils

The importance of the intracellular Ca²⁺ concentration ([Ca²⁺]_i) in neutrophil function has been intensely studied. However, the role of the intracellular Na⁺ concentration ([Na⁺]_i) which is closely linked to the intracellular Ca²⁺ regulation has been largely overlooked. The [Na⁺]_i is regulated by Na⁺ transport proteins such as the Na⁺/Ca²⁺-exchanger (NCX1), Na⁺/K⁺-ATPase, and Na⁺-permeable, transient receptor potential melastatin 2 (TRPM2) channel. Stimulating with either N-formylmethionine-leucyl-phenylalanine (fMLF) or complement protein C5a causes distinct changes of the [Na⁺]_i. fMLF induces a sustained increase of [Na⁺]_i, surprisingly, reaching higher values in TRPM2^−/− neutrophils. This outcome is unexpected and remains unexplained. In both genotypes, C5a elicits only a transient rise of the [Na⁺]_i. The difference in [Na⁺]_i measured at t = 10 min after stimulation is inversely related to neutrophil chemotaxis. Neutrophil chemotaxis is more efficient in C5a than in an fMLF gradient. Moreover, lowering the extracellular Na⁺ concentration from 140 to 72 mM improves chemotaxis of WT but not of TRPM2^−/− neutrophils. Increasing the [Na⁺]_i by inhibiting the Na⁺/K⁺-ATPase results in disrupted chemotaxis. This is most likely due to the impact of the altered Na⁺ homeostasis and presumably NCX1 function whose expression was shown by means of qPCR and which critically relies on proper extra- to intracellular Na⁺ concentration gradients. Increasing the [Na⁺]_i by a few mmol/l may suffice to switch its transport mode from forward (Ca²⁺-efflux) to reverse (Ca²⁺-influx) mode. The role of NCX1 in neutrophil chemotaxis is corroborated by its blocker, which also causes a complete inhibition of chemotaxis.

Effects of maintaining eucalcemia following immunoactivation in lactating Holstein dairy cows

Periparturient hypocalcemia is a common metabolic disorder and it is ostensibly associated with negative health and production outcomes. Acute infection also markedly decreases circulating Ca, but the reasons for and consequences of it on physiological and immunological parameters are unknown. Objectives were to evaluate the effects of maintaining eucalcemia on production, metabolic, and immune variables following an intravenous lipopolysaccharide (LPS) challenge. Twelve multiparous lactating Holstein cows (717 ± 20 kg of body weight; 176 ± 34 d in milk; parity 3 ± 0.2) were enrolled in a study containing 2 experimental periods (P); during P1 (3 d), cows consumed feed ad libitum and baseline values were obtained. At the initiation of P2 (4 d), cows were randomly assigned to 1 of 2 treatments: (1) LPS administered (LPS-Con; 0.5 μg/kg of body weight LPS; n = 6) or (2) LPS administered + eucalcemic clamp (LPS-Ca; 0.5 μg/kg of body weight LPS; Ca infusion; n = 6). Cows were fasted for the first 12 h during P2. After LPS administration, ionized Ca was determined every 15 min for 6 h and every 30 min for an additional 6 h and intravenous Ca infusion was adjusted in LPS-Ca cows to maintain eucalcemia. Blood ionized Ca was decreased 23% for the first 12 h postbolus in LPS-Con cows, and by design, Ca infusion prevented hypocalcemia. To maintain eucalcemia for the 12 h, 13.7 g of Ca was infused. The total Ca deficit (including Ca not secreted into milk) accumulated over the 12 h was 10.4 and 20.2 g for the LPS-Con and LPS-Ca treatments, respectively. Mild hyperthermia (0.8°C) occurred for ∼6 h post-LPS administration relative to P1. From 6 to 7 h postbolus rectal temperature from LPS-Ca cows was increased (0.6°C) relative to LPS-Con cows. On d 1 of P2, milk yield decreased (61%) in both treatments relative to P1. Relative to LPS-Con cows, milk yield decreased (15%) in LPS-Ca cows during P2. Overall, circulating LPS-binding protein continuously increased postbolus, and at 24 h LPS-binding protein levels in LPS-Ca cows were increased (80%) relative to LPS-Con cows. During P2, serum amyloid A increased (4-fold) in both treatments relative to P1. Administering LPS initially decreased circulating neutrophils, then cell counts progressively increased with time. Calcium infusion decreased neutrophil counts (40%) from 9 to 12 h postbolus relative to LPS-Con cows. Neutrophil function, as assessed by oxidative burst and myeloperoxidase production, did not differ due to treatment. In summary, maintaining eucalcemia (via intravenous Ca infusion) during an immune challenge appeared to intensify inflammation and adversely affect lactation performance.

Negative dietary cation-anion difference and amount of calcium in prepartum diets: Effects on milk production, blood calcium, and health

Acidogenic prepartum diets with negative dietary cation-anion difference (DCAD) induce compensated metabolic acidosis, which stimulates calcium (Ca) mobilization before calving and decreases clinical and subclinical hypocalcemia postpartum. This strategy is often combined with limiting dietary Ca concentrations, which historically has been used to mobilize Ca prepartum to prepare cows for lactation. Supplemental dietary Ca in combination with a negative DCAD formulation that does not reverse the effect of compensated metabolic acidosis may be beneficial. Our objective was to determine the effects of prepartum dietary strategies on dry matter intake (DMI), milk production, peripartal Ca status, and health during the transition period in multiparous Holstein cows (n = 81). Treatments during the last 28 d before calving were: (1) positive DCAD diet, +6 mEq/100 g of DM, target urine pH >7.5, low dietary Ca (0.40% DM; CON); (2) negative DCAD diet, -24 mEq/100 g of DM, target urine pH 5.5 to 6.0, low dietary Ca (0.40% DM; ND); or (3) negative DCAD diet, -24 mEq/100 g of DM, target urine pH 5.5 to 6.0, , high dietary Ca (2.0% DM; NDCA). Preplanned treatment contrasts were: (1) CON versus (ND and NDCA), and (2) ND versus NDCA. Individual DMI were recorded daily. Cows were milked 3 times daily, with individual DMI and milk yield summarized by week. Whole blood sampled at calving and 24 h, 48 h, and 4 d after calving was analyzed for ionized Ca concentration, and serum was analyzed for total Ca. Prepartum urine pH for cows fed ND or NDCA averaged 5.7, whereas cows fed CON remained >7.5. During the 3 wk before calving, cows fed CON had greater DMI than cows fed ND or NDCA, with NDCA greater than ND. Postpartum DMI (% of body weight) tended to be less for cows fed CON than for those fed ND or NDCA prepartum. Thresholds for subclinical hypocalcemia were ionized Ca <1.0 mM at 24 h, and total Ca ≤2.125 mM at 48 h after calving. On average, blood Ca for cows fed CON indicated subclinical hypocalcemia, whereas blood Ca for cows fed ND or NDCA was greater than subclinical hypocalcemia thresholds for both ionized Ca and total Ca. No milk production differences were detected. Cows fed CON had an elevated adverse health score (calculated by assigning numerical values to recorded health events) and tended to have an elevated somatic cell count during the fresh period compared with cows fed ND or NDCA. Overall, an acidogenic diet prepartum without or with high Ca improved postpartum Ca status and health. Supplementation of additional Ca to the acidogenic diet had little effect.

Protective effect of cabergoline on mitochondrial oxidative stress-induced apoptosis is mediated by modulations of TRPM2 in neutrophils of patients with endometriosis

Calcium ion (Ca²⁺) signaling in endometriosis (ENDO) is associated with increased neutrophil activation and oxidative stress. A Ca²⁺ signaling modulator and antioxidant actions of cabergoline (CBG) in some cells were recently reported. TRPM2 cation channel is activated by reactive oxygen species (ROS). Antioxidant action of CGB via inhibition of ROS may modulate the channel. We aimed to investigate the effect of CBG on TRPM2 inhibition in serum and neutrophils of patients with ENDO. The serum and neutrophil samples were grouped into healthy samples (no treatment), ENDO and ENDO + CBG treated groups (n = 10 in each). In some experiments, the neutrophils were also incubated with TRPM2 (ACA) and PARP-1 (PJ34) blockers. The values of intracellular ROS, Ca²⁺ concentration, mitochondrial membrane depolarization, lipid peroxidation, apoptosis, and caspase - 3, caspase - 9, PARP-1 and TRPM2 expressions were high in the neutrophils of patients with ENDO, although antioxidant levels (reduced glutathione, glutathione peroxidase, vitamin A, and vitamin E) were low in the neutrophils and serum from these patients. However, markers for apoptosis, oxidative stress, and mitochondrial dysfunction were reduced with CBG, ACA and PJ34 treatments, although the antioxidant levels were increased in the serum and neutrophils following treatment with CBG. Taken together, our current results suggest that CBG are useful antagonists against apoptosis and mitochondrial oxidative stress via inhibition of TRPM2 in neutrophils of patients with ENDO.

Refocusing the Brain: New Approaches in Neuroprotection Against Ischemic Injury

A new era for neuroprotective strategies is emerging in ischemia/reperfusion. This has forced to review the studies existing to date based in neuroprotection against oxidative stress, which have undoubtedly contributed to clarify the brain endogenous mechanisms, as well as to identify possible therapeutic targets or biomarkers in stroke and other neurological diseases. The efficacy of exogenous administration of neuroprotective compounds has been shown in different studies so far. However, something must be missing to get these treatments successfully applied in the clinical environment. Here, the mechanisms involved in neuronal protection against physiological level of ROS and the main neuroprotective signaling pathways induced by excitotoxic and ischemic stimuli are reviewed. Also, the endogenous ischemic tolerance in terms of brain self-protection mechanisms against subsequent cerebral ischemia is revisited to highlight how the preconditioning has emerged as a powerful tool to understand these phenomena. A better understanding of endogenous defense against exacerbated ROS and metabolism in nervous cells will therefore aid to design pharmacological antioxidants targeted specifically against oxidative damage induced by ischemic injury, but also might be very valuable for translational medicine.

Targeting the Endothelial Ca2+ Toolkit to Rescue Endothelial Dysfunction in Obesity Associated-Hypertension

BACKGROUND

Obesity is a major cardiovascular risk factor which dramatically impairs endothelium- dependent vasodilation and leads to hypertension and vascular damage. The impairment of the vasomotor response to extracellular autacoids, e.g., acetylcholine, mainly depends on the reduced Nitric Oxide (NO) bioavailability, which hampers vasorelaxation in large conduit arteries. In addition, obesity may affect Endothelium-Dependent Hyperpolarization (EDH), which drives vasorelaxation in small resistance arteries and arterioles. Of note, endothelial Ca2+ signals drive NO release and trigger EDH.

METHODS

A structured search of bibliographic databases was carried out to retrieve the most influential, recent articles on the impairment of vasorelaxation in animal models of obesity, including obese Zucker rats, and on the remodeling of the endothelial Ca2+ toolkit under conditions that mimic obesity. Furthermore, we searched for articles discussing how dietary manipulation could be exploited to rescue Ca2+-dependent vasodilation.

RESULTS

We found evidence that the endothelial Ca2+ could be severely affected by obese vessels. This rearrangement could contribute to endothelial damage and is likely to be involved in the disruption of vasorelaxant mechanisms. However, several Ca2+-permeable channels, including Vanilloid Transient Receptor Potential (TRPV) 1, 3 and 4 could be stimulated by several food components to stimulate vasorelaxation in obese individuals.

CONCLUSION

The endothelial Ca2+ toolkit could be targeted to reduce vascular damage and rescue endothelium- dependent vasodilation in obese vessels. This hypothesis remains, however, to be probed on truly obese endothelial cells.

A membrane-tethering pepducin derived from formyl peptide receptor 3 shows strong therapeutic effects against sepsis

Formyl peptide receptors (FPRs) are G protein-coupled receptors mainly expressed in inflammatory myeloid cells. Previous reports demonstrated that human neutrophils express only FPR1 and FPR2 but not FPR3. Here, we found that FPR3 is expressed in sepsis patient derived neutrophils and Fpr3 is expressed in the mouse neutrophils. To test the role of Fpr3 in neutrophil activity, we synthesized Fpr3 pepducins and successfully developed an agonistic pepducin that stimulates Fpr3, eliciting calcium increase and chemotactic migration of neutrophils. We also found that administration of an Fpr3 pepducin in an experimental mouse sepsis model significantly increased the survival rate. The pepducin markedly inhibited lung injury, splenocyte apoptosis, and inflammatory cytokine production. Bacterial counts were significantly decreased by the pepducin in septic mice. Based on these results, we suggest that FPR3 can be regarded as a new target to control sepsis, and the newly generated Fpr3-based pepducin can be used for the development of anti-septic agents.

Type 2 Diabetes Alters Intracellular Ca2+ Handling in Native Endothelium of Excised Rat Aorta

An increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i) plays a key role in controlling endothelial functions; however, it is still unclear whether endothelial Ca²⁺ handling is altered by type 2 diabetes mellitus, which results in severe endothelial dysfunction. Herein, we analyzed for the first time the Ca²⁺ response to the physiological autacoid ATP in native aortic endothelium of obese Zucker diabetic fatty (OZDF) rats and their lean controls, which are termed LZDF rats. By loading the endothelial monolayer with the Ca²⁺-sensitive fluorophore, Fura-2/AM, we found that the endothelial Ca²⁺ response to 20 µM and 300 µM ATP exhibited a higher plateau, a larger area under the curve and prolonged duration in OZDF rats. The “Ca²⁺ add-back” protocol revealed no difference in the inositol-1,4,5-trisphosphate-releasable endoplasmic reticulum (ER) Ca²⁺ pool, while store-operated Ca²⁺ entry was surprisingly down-regulated in OZDF aortae. Pharmacological manipulation disclosed that sarco-endoplasmic reticulum Ca²⁺-ATPase (SERCA) activity was down-regulated by reactive oxygen species in native aortic endothelium of OZDF rats, thereby exaggerating the Ca²⁺ response to high agonist concentrations. These findings shed new light on the mechanisms by which type 2 diabetes mellitus may cause endothelial dysfunction by remodeling the intracellular Ca²⁺ toolkit.

Effects of ORAI calcium release-activated calcium modulator 1 (ORAI1) on neutrophil activity in dairy cows with subclinical hypocalcemia1

Hypocalcemia in dairy cows is often associated with inflammation-related disorders such as metritis and mastitis. The protein encoded by the Ca2+ release-activated calcium modulator 1 (ORAI1) gene is a membrane Ca2+ channel subunit that is activated when Ca2+ stores are depleted. Polymorphonuclear neutrophils (PMNL) have a crucial role in the defense against infection through migration, adhesion, chemotaxis, phagocytosis, and reactive oxygen species (ROS) production in response to pathogens. Whether hypocalcemia affects the activity of PMNL and if ORAI1 is involved remains unknown. To address this, PMNL were isolated at 3 d of calving from dairy cows diagnosed as clinically healthy (n = 20, CONTROL) or with plasma concentration of calcium < 2.0 mmol/L as a criterion for diagnosis of subclinical hypocalcemia (n = 20, HYPOCAL). PMNL isolated from both groups of cows were treated with or without the sarcoendoplasmic Ca2+ ATPase inhibitor thapsigargin, Ca2+ ionophore Ionomycin, and ORAI1 blocker 2APB. The intracellular Ca2+ concentration, ORAI1 abundance, ROS, phagocytosis rate, migration, and adhering capacity of treated PMNL were evaluated. Some of the in vitro assays also included use of small interfering ORAI1 RNA (siORAI1), 100 nM 1,25(OH)2D3, or 100 nM parathyroid hormone (PTH). Intracellular Ca2+ concentration was markedly lower in HYPOCAL. In addition, ORAI1 was detected in PMNL plasma membrane via FACS and was markedly lower in cows with HYPOCAL. Migration, adhesion capacity, and phagocytosis rate of PMNL were lower in response to HYPOCAL. Furthermore, plasma and PMNL concentration of nucleosome assembly protein (NAP2) and pro-platelet basic protein (CXCL7) was markedly lower with HYPOCAL. All these changes were associated with lower ROS production by PMNL. Thapsigargin and ionomycin treatment in vitro increased ORAI1 expression, migration of PMNL, adhering capacity, phagocytosis rate, and ROS production; conversely, those effects were abrogated by siORAI1 and ORAI1 inhibitor 2APB treatment. Also cytosolic Ca2+ concentration and ORAI1 abundance were increased by 1,25(OH)2D3 and PTH supplementation. Overall, the data indicate that failure of PMNL to uptake Ca2+ due to downregulation of ORAI1 during subclinical hypocalcemia is a factor contributing to impaired PMNL function. In addition, plasma PTH or 1,25(OH)2D3 could regulate ORAI1 and also participate in the regulation of PMNL activity.

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.

Modulator role of infliximab and methotrexate through the transient receptor potential melastatin 2 (TRPM2) channel in neutrophils of patients with rheumatoid arthritis: a pilot study

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic, systemic, inflammatory disease causing symmetric polyarthritis. In this study, we aimed to investigate the effects of infliximab (INF) and methotrexate (MTX) on apoptosis, oxidative stress, and calcium signaling in the neutrophils of RA patients.

MATERIAL AND METHODS

Neutrophils were isolated from 10 patients with newly diagnosed RA and 10 healthy controls. They were divided into four groups (control, RA, RA + MTX, RA + INF) and incubated with MTX and INF. In the cell viability (MTT) test, the ideal non-toxic dose and incubation time of MTX were found to be 0.1 mM and 1 h, respectively. The neutrophils were also incubated with the TRPM2 channel blocker N-(p-amylcinnamoyl) anthranilic acid (ACA).

RESULTS

Intracellular free Ca²⁺ concentration, intracellular reactive oxygen species (ROS) production, mitochondrial depolarization, lipid peroxidation, apoptosis, and caspase 3 and caspase 9 activities were found to be significantly higher in the neutrophils of RA patients compared to controls. MTT, reduced glutathione (GSH) level, and glutathione peroxidase (GSHPx) activity were significantly lower in the neutrophils of RA patients. However, MTT, GSH and GSHPx values were detected to be significantly increased with INF and MTX therapies. The Ca²⁺ concentrations were further decreased by the ACA therapy.

CONCLUSIONS

Our results suggest that INF and MTX are useful antagonists in apoptosis and mitochondrial oxidative stress in the neutrophils of RA patients. INF and MTX decreased the Ca²⁺ concentration through inhibition of the TRPM2 channel in the neutrophils of RA patients. It may be a new pathway in the mechanisms of anti-rheumatic drugs.

Calcium Release from Endoplasmic Reticulum Involves Calmodulin-Mediated NADPH Oxidase-Derived Reactive Oxygen Species Production in Endothelial Cells

Background: Previous studies demonstrated that calcium/calmodulin (Ca²⁺/CaM) activates nicotinamide adenine dinucleotide phosphate oxidases (NOX). In endothelial cells, the elevation of intracellular Ca²⁺ level consists of two components: Ca²⁺ mobilization from the endoplasmic reticulum (ER) and the subsequent store-operated Ca²⁺ entry. However, little is known about which component of Ca²⁺ increase is required to activate NOX in endothelial cells. Here, we investigated the mechanism that regulates NOX-derived reactive oxygen species (ROS) production via a Ca²⁺/CaM-dependent pathway. Methods: We measured ROS production using a fluorescent indicator in endothelial cells and performed phosphorylation assays. Results: Bradykinin (BK) increased NOX-derived cytosolic ROS. When cells were exposed to BK with either a nominal Ca²⁺-free or 1 mM of extracellular Ca²⁺ concentration modified Tyrode’s solution, no difference in BK-induced ROS production was observed; however, chelating of cytosolic Ca²⁺ by BAPTA/AM or the depletion of ER Ca²⁺ contents by thapsigargin eliminated BK-induced ROS production. BK-induced ROS production was inhibited by a CaM inhibitor; however, a Ca²⁺/CaM-dependent protein kinase II (CaMKII) inhibitor did not affect BK-induced ROS production. Furthermore, BK stimulation did not increase phosphorylation of NOX2, NOX4, and NOX5. Conclusions: BK-induced NOX-derived ROS production was mediated via a Ca²⁺/CaM-dependent pathway; however, it was independent from NOX phosphorylation. This was strictly regulated by ER Ca²⁺ contents.

Propofol inhibits endogenous formyl peptide-induced neutrophil activation and alleviates lung injury

Critically ill patients have a high risk of sepsis. Various studies have demonstrated that propofol has anti-inflammatory effects that may benefit critically ill patients who require anesthesia. However, the mechanism and therapeutic effect remain incompletely understood. Our previous data suggest that propofol can act as a formyl peptide receptor 1 (FPR1) antagonist. Here, we hypothesize that propofol mitigates sepsis-induced acute lung injury (ALI) by inhibiting mitochondria-derived N-formyl peptide-mediated neutrophil activation. Oxidative stress caused by activated neutrophils is involved in the pathogenesis of ALI. In human neutrophils, propofol competitively reduced the release of superoxide and associated reactive oxygen species induced by fMMYALF, a human mitochondria-derived N-formyl peptide, suggesting that propofol effectively suppresses neutrophilic oxidative stress. In addition, propofol significantly inhibited fMMYALF-induced elastase release, chemotaxis, calcium mobilization, and phosphorylation of protein kinase B and mitogen-activated protein kinases. These results indicate that propofol suppresses neutrophil activation by blocking the interaction between endogenous N-formyl peptide and its receptor, FPR1, thus inhibiting downstream signaling. Furthermore, propofol alleviated alveolar wall disruption, edematous changes, and neutrophil infiltration in lipopolysaccharide-induced ALI in mice. Noticeably, propofol improved the survival of sepsis mice. This study indicates that the anti-neutrophil effects of propofol may benefit critically ill septic patients.

Extracellular vesicles derived from human umbilical cord mesenchymal stem cells alleviate rat hepatic ischemia-reperfusion injury by suppressing oxidative stress and neutrophil inflammatory response

Mesenchymal stem cells (MSCs) have been reported to exert therapeutic effects on immunoregulation, tissue repair, and regeneration from the bench to the bedside. Increasing evidence demonstrates that extracellular vesicles (EVs) derived from MSCs could contribute to these effects and are considered as a potential replacement for stem cell-based therapies. However, the efficacy and underlying mechanisms of EV-based treatment in hepatic ischemia-reperfusion injury (IRI) remain unclear. Here, we demonstrated that human umbilical cord MSC-EVs (huc-MSC-EVs) could protect against IRI-induced hepatic apoptosis by reducing the infiltration of neutrophils and alleviating oxidative stress in hepatic tissue in vivo. Meanwhile, huc-MSC-EVs reduced the respiratory burst of neutrophils and prevented hepatocytes from oxidative stress-induced cell death in vitro. Interestingly, we found that the mitochondria-located antioxidant enzyme, manganese superoxide dismutase (MnSOD), was encapsulated in huc-MSC-EVs and reduced oxidative stress in the hepatic IRI model. Knockdown of MnSOD in huc-MSCs decreased the level of MnSOD in huc-MSC-EVs and attenuated the antiapoptotic and antioxidant capacities of huc-MSC-EVs, which could be partially rescued by MnSOD mimetic manganese (III) 5,10,15,20-tetrakis (4-benzoic acid) porphyrin (MnTBAP). In summary, these findings provide new clues to reveal the therapeutic effects of huc-MSC-EVs on hepatic IRI and evaluate their preclinical application.-Yao, J., Zheng, J., Cai, J., Zeng, K., Zhou, C., Zhang, J., Li, S., Li, H., Chen, L., He, L., Chen, H., Fu, H., Zhang, Q., Chen, G., Yang, Y., Zhang, Y. Extracellular vesicles derived from human umbilical cord mesenchymal stem cells alleviate rat hepatic ischemia-reperfusion injury by suppressing oxidative stress and neutrophil inflammatory response.

Dysregulated Calcium Homeostasis in Cystic Fibrosis Neutrophils Leads to Deficient Antimicrobial Responses

Cystic fibrosis (CF), one of the most common human genetic diseases worldwide, is caused by a defect in the CF transmembrane conductance regulator (CFTR). Patients with CF are highly susceptible to infections caused by opportunistic pathogens (including Burkholderia cenocepacia), which induce excessive lung inflammation and lead to the eventual loss of pulmonary function. Abundant neutrophil recruitment into the lung is a key characteristic of bacterial infections in CF patients. In response to infection, inflammatory neutrophils release reactive oxygen species and toxic proteins, leading to aggravated lung tissue damage in patients with CF. The present study shows a defect in reactive oxygen species production by mouse Cftr^-/- , human F508del-CFTR, and CF neutrophils; this results in reduced antimicrobial activity against B. cenocepacia Furthermore, dysregulated Ca²⁺ homeostasis led to increased intracellular concentrations of Ca²⁺ that correlated with significantly diminished NADPH oxidase response and impaired secretion of neutrophil extracellular traps in human CF neutrophils. Functionally deficient human CF neutrophils recovered their antimicrobial killing capacity following treatment with pharmacological inhibitors of Ca²⁺ channels and CFTR channel potentiators. Our findings suggest that regulation of neutrophil Ca²⁺ homeostasis (via CFTR potentiation or by the regulation of Ca²⁺ channels) can be used as a new therapeutic approach for reestablishing immune function in patients with CF.

Combination ART-Induced Oxidative/Nitrosative Stress, Neurogenic Inflammation and Cardiac Dysfunction in HIV-1 Transgenic (Tg) Rats: Protection by Mg

Chronic effects of a combination antiretroviral therapy (cART = tenofovir/emtricitatine + atazanavir/ritonavir) on systemic and cardiac oxidative stress/injury in HIV-1 transgenic (Tg) rats and protection by Mg-supplementation were assessed. cART (low doses) elicited no significant effects in normal rats, but induced time-dependent oxidative/nitrosative stresses: 2.64-fold increased plasma 8-isoprostane, 2.0-fold higher RBC oxidized glutathione (GSSG), 3.2-fold increased plasma 3-nitrotyrosine (NT), and 3-fold elevated basal neutrophil superoxide activity in Tg rats. Increased NT staining occurred within cART-treated HIV-Tg hearts, and significant decreases in cardiac systolic and diastolic contractile function occurred at 12 and 18 weeks. HIV-1 expression alone caused modest levels of oxidative stress and cardiac dysfunction. Significantly, cART caused up to 24% decreases in circulating Mg in HIV-1-Tg rats, associated with elevated renal NT staining, increased creatinine and urea levels, and elevated plasma substance P levels. Strikingly, Mg-supplementation (6-fold) suppressed all oxidative/nitrosative stress indices in the blood, heart and kidney and substantially attenuated contractile dysfunction (>75%) of cART-treated Tg rats. In conclusion, cART caused significant renal and cardiac oxidative/nitrosative stress/injury in Tg-rats, leading to renal Mg wasting and hypomagnesemia, triggering substance P-dependent neurogenic inflammation and cardiac dysfunction. These events were effectively attenuated by Mg-supplementation likely due to its substance P-suppressing and Mg’s intrinsic anti-peroxidative/anti-calcium properties.

Biosensors for spatiotemporal detection of reactive oxygen species in cells and tissues

Redox biology has become a major issue in numerous areas of physiology. Reactive oxygen species (ROS) have a broad range of roles from signal transduction to growth control and cell death. To understand the nature of these roles, accurate measurement of the reactive compounds is required. An increasing number of tools for ROS detection is available; however, the specificity and sensitivity of these tools are often insufficient. Furthermore, their specificity has been rarely evaluated in complex physiological conditions. Many ROS probes are sensitive to environmental conditions in particular pH, which may interfere with ROS detection and cause misleading results. Accurate detection of ROS in physiology and pathophysiology faces additional challenges concerning the precise localization of the ROS and the timing of their production and disappearance. Certain ROS are membrane permeable, and certain ROS probes move across cells and organelles. Targetable ROS probes such as fluorescent protein-based biosensors are required for accurate localization. Here we analyze these challenges in more detail, provide indications on the strength and weakness of current tools for ROS detection, and point out developments that will provide improved ROS detection methods in the future. There is no universal method that fits all situations in physiology and cell biology. A detailed knowledge of the ROS probes is required to choose the appropriate method for a given biological problem. The knowledge of the shortcomings of these probes should also guide the development of new sensors.

Alkaline pH Promotes NADPH Oxidase-Independent Neutrophil Extracellular Trap Formation: A Matter of Mitochondrial Reactive Oxygen Species Generation and Citrullination and Cleavage of Histone

pH is highly variable in different tissues and affects many enzymatic reactions in neutrophils. In response to calcium ionophores such as A23187 and ionomycin, neutrophils undergo nicotinamide adenine dinucleotide phosphate oxidase (NOX)-independent neutrophil extracellular trap (NET) formation (NETosis). However, how pH influences calcium-dependent Nox-independent NET formation is not well understood. We hypothesized that increasing pH promotes Nox-independent NET formation by promoting calcium influx, mitochondrial reactive oxygen species (mROS) generation, histone citrullination, and histone cleavage. Here, we show that stimulating human neutrophils isolated from peripheral blood with calcium ionophore A23187 or ionomycin in the media with increasing extracellular pH (6.6, 6.8, 7.0, 7.2, 7.4, 7.8) drastically increases intracellular pH within in 10-20 min. These intracellular pH values are much higher compared to unstimulated cells placed in the media with corresponding pH values. Raising pH slightly drastically increases intracellular calcium concentration in resting and stimulated neutrophils, respectively. Like calcium, mROS generation also increases with increasing pH. An mROS scavenger, MitoTempo, significantly suppresses calcium ionophore-mediated NET formation with a greater effect at higher pH, indicating that mROS production is at least partly responsible for pH-dependent suppression of Nox-independent NETosis. In addition, raising pH increases PAD4 activity as determined by the citrullination of histone (CitH3) and histone cleavage determined by Western blots. The pH-dependent histone cleavage is reproducibly very high during ionomycin-induced NETosis compared to A23187-induced NETosis. Little or no histone cleavage was noted in unstimulated cells, at any pH. Both CitH3 and cleavage of histones facilitate DNA decondensation. Therefore, alkaline pH promotes intracellular calcium influx, mROS generation, PAD4-mediated CitH3 formation, histone 4 cleavage and eventually NET formation. Calcium-mediated NET formation and CitH3 formation are often related to sterile inflammation. Hence, understanding these important mechanistic steps helps to explain how pH regulates NOX-independent NET formation, and modifying pH may help to regulate NET formation during sterile inflammation or potential damage caused by compounds such as ionomycin, secreted by Streptomyces, a group of Gram-positive bacteria well known for producing antibiotics.

A novel antimicrobial peptide isolated from centipede Scolopendra subspinipes mutilans stimulates neutrophil activity through formyl peptide receptor 2

In this study, we identified scolopendrasin X, a novel antimicrobial peptide (AMP), from centipede Scolopendra subspinipes mutilans. Scolopendrasin X strongly stimulated mouse neutrophils, resulting in intracellular calcium increase, chemotactic migration through pertussis toxin-sensitive G-protein and phospholipase C pathway, and increased superoxide anion production in neutrophils. Target receptor for scolopendrasin X, formyl peptide receptor (FPR)2 mediated scolopendrasin X-induced neutrophil activation. Moreover, scolopendrasin X significantly blocked inflammatory cytokine production induced by lipopolysaccharide in mouse neutrophils. Taken together, our results suggest that the novel AMP scolopendrasin X can be used as a material to regulate neutrophil activity through FPR2.

TRPC3 Channels in Cardiac Fibrosis

Cardiac stiffness, caused by interstitial fibrosis due to deposition of extracellular matrix proteins, is thought as a major clinical outcome of heart failure with preserved ejection fraction (HFpEF). Canonical transient receptor potential (TRPC) subfamily proteins are components of Ca²⁺-permeable non-selective cation channels activated by receptor stimulation and mechanical stress, and have been attracted attention as a key mediator of maladaptive cardiac remodeling. How TRPC-mediated local Ca²⁺ influx encodes a specific signal to induce maladaptive cardiac remodeling has been long obscure, but our recent studies suggest a pathophysiological significance of channel activity-independent function of TRPC proteins for amplifying redox signaling in heart. This review introduces the current understanding of the physiological and pathophysiological roles of TRPCs, especially focuses on the role of TRPC3 as a positive regulator of reactive oxygen species (PRROS) in heart. We have revealed that TRPC3 stabilizes NADPH oxidase 2 (Nox2), a membrane-bound reactive oxygen species (ROS)-generating enzyme, by forming stable protein complex with Nox2, which leads to amplification of mechanical stress-induced ROS signaling in cardiomyocytes, resulting in induction of fibrotic responses in cardiomyocytes and cardiac fibroblasts. Thus, the TRPC3 function as PRROS will offer a new therapeutic strategy for the prevention or treatment of HFpEF.

Epic Immune Battles of History: Neutrophils vs. Staphylococcus aureus

Neutrophils are the most abundant leukocytes in human blood and the first line of defense after bacteria have breached the epithelial barriers. After migration to a site of infection, neutrophils engage and expose invading microorganisms to antimicrobial peptides and proteins, as well as reactive oxygen species, as part of their bactericidal arsenal. Ideally, neutrophils ingest bacteria to prevent damage to surrounding cells and tissues, kill invading microorganisms with antimicrobial mechanisms, undergo programmed cell death to minimize inflammation, and are cleared away by macrophages. Staphylococcus aureus (S. aureus) is a prevalent Gram-positive bacterium that is a common commensal and causes a wide range of diseases from skin infections to endocarditis. Since its discovery, S. aureus has been a formidable neutrophil foe that has challenged the efficacy of this professional assassin. Indeed, proper clearance of S. aureus by neutrophils is essential to positive infection outcome, and S. aureus has developed mechanisms to evade neutrophil killing. Herein, we will review mechanisms used by S. aureus to modulate and evade neutrophil bactericidal mechanisms including priming, activation, chemotaxis, production of reactive oxygen species, and resolution of infection. We will also highlight how S. aureus uses sensory/regulatory systems to tailor production of virulence factors specifically to the triggering signal, e.g., neutrophils and defensins. To conclude, we will provide an overview of therapeutic approaches that may potentially enhance neutrophil antimicrobial functions.

Mechanisms of the Immunological Effects of Volatile Anesthetics: A Review

Volatile anesthetics (VAs) have been in clinical use for a very long time. Their mechanism of action is yet to be fully delineated, but multiple ion channels have been reported as targets for VAs (canonical VA targets). It is increasingly recognized that VAs also manifest effects outside the central nervous system, including on immune cells. However, the literature related to how VAs affect the behavior of immune cells is very limited, but it is of interest that some canonical VA targets are reportedly expressed in immune cells. Here, we review the current literature and describe canonical VA targets expressed in leukocytes and their known roles. In addition, we introduce adhesion molecules called β2 integrins as noncanonical VA targets in leukocytes. Finally, we propose a model for how VAs affect the function of neutrophils, macrophages, and natural killer cells via concerted effects on multiple targets as examples.

6-Hydroxy-5,7-dimethoxy-flavone suppresses the neutrophil respiratory burst via selective PDE4 inhibition to ameliorate acute lung injury

Over-activated neutrophils produce enormous oxidative stress and play a key role in the development of acute and chronic inflammatory diseases. 6-Hydroxy-5,7-dimethoxy-flavone (UFM24), a flavone isolated from the Annonaceae Uvaria flexuosa, showed inhibitory effects on human neutrophil activation and salutary effects on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. UFM24 potently inhibited superoxide anion (O₂^•-) generation, reactive oxidants, and CD11b expression, but not elastase release, in N-formyl-l-methionyl-l-leucyl-l-phenylalanine (fMLF)-activated human neutrophils. However, UFM24 failed to scavenge O₂^•- and inhibit the activity of subcellular NADPH oxidase. fMLF-induced phosphorylation of protein kinase B (Akt) was inhibited by UFM24. Noticeably, UFM24 increased cyclic adenosine monophosphate (cAMP) concentration and protein kinase (PK) A activity in activated human neutrophils. PKA inhibitors significantly reversed the inhibitory effects of UFM24, suggesting that the effects of UFM24 were through cAMP/PKA-dependent inhibition of Akt activation. Additionally, activity of cAMP-related phosphodiesterase (PDE)4, but not PDE3 or PDE7, was significantly reduced by UFM24. Furthermore, UFM24 attenuated neutrophil infiltration, myeloperoxidase activity, and pulmonary edema in LPS-induced ALI in mice. In conclusion, our data demonstrated that UFM24 inhibits oxidative burst in human neutrophils through inhibition of PDE4 activity. UFM24 also exhibited significant protection against endotoxin-induced ALI in mice. UFM24 has potential as an anti-inflammatory agent for treating neutrophilic lung damage.

TRPM2 ion channels regulate macrophage polarization and gastric inflammation during Helicobacter pylori infection

Calcium signaling in phagocytes is essential for cellular activation, migration, and the potential resolution of infection or inflammation. The generation of reactive oxygen species (ROS) via activation of NADPH (nicotinamide adenine dinucleotide phosphate)-oxidase activity in macrophages has been linked to altered intracellular calcium concentrations. Because of its role as an oxidative stress sensor in phagocytes, we investigated the function of the cation channel transient receptor potential melastatin 2 (TRPM2) in macrophages during oxidative stress responses induced by Helicobacter pylori infection. We show that Trpm2^-/^- mice, when chronically infected with H. pylori, exhibit increased gastric inflammation and decreased bacterial colonization compared with wild-type (WT) mice. The absence of TRPM2 triggers greater macrophage production of inflammatory mediators and promotes classically activated macrophage M1 polarization in response to H. pylori. TRPM2-deficient macrophages upon H. pylori stimulation are unable to control intracellular calcium levels, which results in calcium overloading. Furthermore, increased intracellular calcium in TRPM2^-/^- macrophages enhanced mitogen-activated protein kinase and NADPH-oxidase activities, compared with WT macrophages. Our data suggest that augmented production of ROS and inflammatory cytokines with TRPM2 deletion regulates oxidative stress in macrophages and consequently decreases H. pylori gastric colonization while increasing inflammation in the gastric mucosa.

Amitriptyline modulated Ca2+ signaling and induced Ca2+-independent cell viability in human osteosarcoma cells

Amitriptyline is a widely used tricyclic antidepressant, which acts primarily as a serotonin–norepinephrine reuptake inhibitor. This study examined the effect of amitriptyline on Ca2+ homeostasis and its related mechanism in MG63 human osteosarcoma cells. Amitriptyline evoked cytosolic-free Ca2+ concentrations ([Ca2+]i) rises concentration dependently. Amitriptyline-evoked Ca2+ entry was confirmed by Mn2+-induced quench of fura-2 fluorescence. This entry was inhibited by Ca2+ entry modulators nifedipine, econazole, SKF96365, the protein kinase C (PKC) activator phorbol 12-myristate 13 acetate but was not affected by the PKC inhibitor GF109203X. In Ca2+-free medium, treatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin (TG) inhibited amitriptyline-evoked [Ca2+]i rises by 95%. Conversely, treatment with amitriptyline abolished TG-evoked [Ca2+]i rises. Inhibition of phospholipase C (PLC) with U73122 inhibited amitriptyline-evoked [Ca2+]i rises by 70%. Amitriptyline killed cells at 200–500 μM in a concentration-dependent fashion. Chelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid/AM did not reverse amitriptyline-induced cytotoxicity. Collectively, our data suggest that in MG63 cells, amitriptyline induced [Ca2+]i rises by evoking PLC-dependent Ca2+ release from the endoplasmic reticulum and Ca2+ entry via PKC-regulated store-operated Ca2+ entry. Amitriptyline also induced Ca2+-disassociated cell death.

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.