Ca2+ influx shutdown during neutrophil apoptosis: importance and possible mechanism

Immunomodulatory effects of a cell processing device to ameliorate dysregulated hyperinflammatory disease states

Cell directed therapy is an evolving therapeutic approach to treat organ dysfunction arising from hyperinflammation and cytokine storm by processing immune cells in an extracorporeal circuit. To investigate the mechanism of action of the Selective Cytopheretic Device (SCD), in vitro blood circuits were utilized to interrogate several aspects of the immunomodulatory therapy. SCD immunomodulatory activity is due to its effects on circulating neutrophils and monocytes in a low ionized calcium (iCa, Ca2+) blood circuit. Activated neutrophils adhere to the SCD fibers and degranulate with release of the constituents of their exocytotic vesicles. Adhered neutrophils in the low iCa environment display characteristics of apoptotic senescence. These neutrophils are subsequently released and returned back to circulation, demonstrating a clear potential for in vivo feedback. For monocytes, SCD treatment results in the selective adhesion of more pro-inflammatory subsets of the circulating monocyte pool, as demonstrated by both cell surface markers and cytokine secretory rates. Once bound, over time a subset of monocytes are released from the membrane with a less inflammatory functional phenotype. Similar methods to interrogate mechanism in vitro have been used to preliminarily confirm comparable findings in vivo. Therefore, the progressive amelioration of circulating leukocyte activation and immunomodulation of excessive inflammation observed in SCD clinical trials to date is likely due to this continuous autologous leukocyte processing.

Rationale and Design of NEUTRALIZE-AKI: A Multicenter, Randomized, Controlled, Pivotal Study to Assess the Safety and Efficacy of a Selective Cytopheretic Device in Patients with Acute Kidney Injury Requiring Continuous Kidney Replacement Therapy

INTRODUCTION

NEUTRALIZE-AKI is a pivotal study to evaluate the safety and effectiveness of the selective cytopheretic device (SCD) in adult patients with acute kidney injury (AKI) requiring continuous kidney replacement therapy (CKRT).

METHODS/DESIGN

This is a two-arm, randomized, open-label, controlled multi-center pivotal US study which will enroll 200 adult patients (age 18-80 years) in the intensive care unit with acute kidney injury requiring CKRT and at least one additional organ failure across 30 clinical centers. Eligible patients will be randomized to CKRT plus SCD therapy versus CKRT alone. Therapy will be administered for up to 10 days, with the hypothesis that the CKRT plus SCD group will demonstrate a lower mortality rate or better rate of renal recovery than the CKRT alone group by day 90. The primary outcome is a composite of dialysis dependence or all-cause mortality at day 90.

CONCLUSION

The SCD is a cell-directed extracorporeal therapy that targets and deactivates pro-inflammatory neutrophils and monocytes, with evidence of efficacy across a variety of critically ill patient populations. Knowledge and experience from many of those studies and other AKI trials were incorporated into the design of this pivotal study, with the aim to investigate the role of effector cell immunomodulation in the intervention of AKI.

Heavy Metals and Essential Elements in Association with Oxidative Stress in Women with Polycystic Ovary Syndrome-A Systematic Review

Altered levels of heavy metals and essential elements have been associated with oxidative stress (OS) and metabolic and hormonal changes in women with polycystic ovary syndrome (PCOS). We aimed to summarize the knowledge on the association of heavy metals and essential elements with OS in PCOS. An electronic literature search using PubMed for studies published between January 2008 and April 2023 was conducted. We evaluated heavy metals and essential elements in relation to OS in PCOS in 15 articles. PCOS women had increased antimonium (Sb), cadmium (Cd), lead (Pb), mercury (Hg), arsenic (As), tellurium (Te), thallium (Tl) and osmium (Os) blood levels and decreased zinc (Zn) blood levels; the results of copper (Cu) blood levels were conflicting. Some studies showed a significant correlation between heavy metals (Sb, Cd, Pb, Hg, As, Te and Tl) and essential elements (Se, Zn, Cr, Ca, Mg and Cu) and markers of OS and chronic inflammation. Heavy metals (Sb, Cd, Pb and Hg) and essential elements (Zn, Cr, Se, Ca, Mg and Cu) were associated with metabolic and hormonal characteristics in PCOS. There might be a possible benefit from supplementation therapy in reducing OS and endocrinological problems related to PCOS. Our review confirmed an association between heavy metals and essential elements with OS in PCOS women. This systematic review is registered in PROSPERO under number CRD42023418453.

2-Hexadecenal Regulates ROS Production and Induces Apoptosis in Polymorphonuclear Leucocytes

2-Hexadecenal (2-HD)-a biologically active long-chain fatty aldehyde formed in organism enzymatically or nonenzymatically in the reaction of free-radical destruction of sphingolipids under the action of hypochlorous acid, producing by myeloperoxidase. This research aimed to study 2-HD effects on polymorphonuclear leukocytes' (PMNLs) functions. It has been shown that at submicromolar concentrations, 2-HD causes an elevation in ROS production by PMNLs. It has been found that such effect is associated with signal transduction pathways modification and expressed in elevation of NADPH oxidase, MPO, and JNK-MAPK contributions to this process. At higher concentrations, 2-HD induces apoptosis, which correlates with a significant increase in free Ca²⁺ in the cytoplasm, a decrease in ROS production, and a decline in mitochondrial potential. Both of these processes are accompanied by cytoskeleton reorganization.

Neutrophils: Many Ways to Die

Neutrophils or polymorphonuclear leukocytes (PMN) are key participants in the innate immune response for their ability to execute different effector functions. These cells express a vast array of membrane receptors that allow them to recognize and eliminate infectious agents effectively and respond appropriately to microenvironmental stimuli that regulate neutrophil functions, such as activation, migration, generation of reactive oxygen species, formation of neutrophil extracellular traps, and mediator secretion, among others. Currently, it has been realized that activated neutrophils can accomplish their effector functions and simultaneously activate mechanisms of cell death in response to different intracellular or extracellular factors. Although several studies have revealed similarities between the mechanisms of cell death of neutrophils and other cell types, neutrophils have distinctive properties, such as a high production of reactive oxygen species (ROS) and nitrogen species (RNS), that are important for their effector function in infections and pathologies such as cancer, autoimmune diseases, and immunodeficiencies, influencing their cell death mechanisms. The present work offers a synthesis of the conditions and molecules implicated in the regulation and activation of the processes of neutrophil death: apoptosis, autophagy, pyroptosis, necroptosis, NETosis, and necrosis. This information allows to understand the duality encountered by PMNs upon activation. The effector functions are carried out to eliminate invading pathogens, but in several instances, these functions involve activation of signaling cascades that culminate in the death of the neutrophil. This process guarantees the correct elimination of pathogenic agents, damaged or senescent cells, and the timely resolution of the inflammation that is essential for the maintenance of homeostasis in the organism. In addition, they alert the organism when the immunological system is being deregulated, promoting the activation of other cells of the immune system, such as B and T lymphocytes, which produce cytokines that potentiate the microbicide functions.

Use of the Selective Cytopheretic Device in Critically Ill Children

Introduction

Critically ill children with acute kidney injury (AKI) requiring continuous kidney replacement therapy (CKRT) are at increased risk of death. The selective cytopheretic device (SCD) promotes an immunomodulatory effect when circuit ionized calcium (iCa²⁺) is maintained at <0.40 mmol/l with regional citrate anticoagulation (RCA). In a randomized trial of adult patients on CRRT, those treated with the SCD maintaining an iCa²⁺ <0.40 mmol/l had improved survival/dialysis independence. We conducted a US Food and Drug Administration (FDA)–sponsored study to evaluate safety and feasibility of the SCD in 16 critically ill children.

Methods

Four pediatric intensive care units (ICUs) enrolled children with AKI and multiorgan dysfunction receiving CKRT to receive the SCD integrated post-CKRT membrane. RCA was used to achieve a circuit iCa²⁺ level <0.40 mmol/l. Subjects received SCD treatment for 7 days or CKRT discontinuation, whichever came first.

Results

The FDA target enrollment of 16 subjects completed the study from December 2016 to February 2020. Mean age was 12.3 ± 5.1 years, weight was 53.8 ± 28.9 kg, and median Pediatric Risk of Mortality II was 7 (range 2–19). Circuit iCa²⁺ levels were maintained at <0.40 mmol/l for 90.2% of the SCD therapy time. Median SCD duration was 6 days. Fifteen subjects survived SCD therapy; 12 survived to ICU discharge. All ICU survivors were dialysis independent at 60 days. No SCD-related adverse events (AEs) were reported.

Conclusion

Our data demonstrate that SCD therapy is feasible and safe in children who require CKRT. Although we cannot make efficacy claims, the 75% survival rate and 100% renal recovery rate observed suggest a possible favorable benefit-to-risk ratio.

The effect of prepartum negative dietary cation-anion difference and serum calcium concentration on blood neutrophil function in the transition period of healthy dairy cows

Our objectives were to assess the effects of a diet with a negative dietary cation-anion difference (DCAD) before calving on phagocytosis (Pc) and oxidative burst (OB) function of circulating neutrophils, and to determine the associations of serum ionized (iCa) and total calcium (tCa) concentrations with Pc and OB in transition dairy cows. We hypothesized that multiparous cows fed a negative DCAD diet prepartum would have greater iCa and tCa, and thus improved Pc and OB. From 3 wk before expected parturition until calving, 38 healthy multiparous cows from 3 farms were assigned to negative DCAD treatment (TRT; -100 mEq/kg of diet dry matter; n = 21) or a control (CON; 95 mEq/kg of dry matter; n = 17) diet. Each farm was on one treatment or the other at a time, but all farms contributed cows to both groups. Urine pH was measured weekly and in TRT was 6.1 ± 0.8 with 80% of 50 samples <7 and 74% ≤ 6.5. Phagocytosis, OB, iCa, and tCa were measured at d -7, 1, and 4 relative to calving. Median fluorescence intensity for Pc (MFIP) and OB (MFIOB), and the shift of percentage of cells active for Pc (PPc) and OB (POB) were measured in isolated, stimulated neutrophils via flow cytometry. Outcomes were assessed with mixed linear regression models accounting for repeated measures. There were no differences between treatments in the 4 neutrophil function outcomes. Although MFIOB varied over time, there were no interactions of treatment with time for any outcome. Serum ionized and tCa did not differ between TRT and CON. The least squares means ± standard deviation for iCa were: d -7, 1.23 ± 0.12 vs. 1.21 ± 0.12; d 1, 1.07 ± 0.12 vs. 1.02 ± 0.12; d 4, 1.16 ± 0.12 vs. 1.17 ± 0.12 mmol/L for TRT and CON, respectively; and for tCa: d -7 2.39 ± 0.25 vs 2.44 ± 0.31; d 1, 2.01 ± 0.25 vs 1.97 ± 0.31; d 4, 2.33 ± 0.25 vs 2.32 ± 0.31 mmol/L, respectively. The proportion of blood samples with tCa <2.15mmol/L at d -7, 1 and 4 was 5, 76, and 13%, respectively, with no differences between TRT and CON. Correlations of iCa or tCa with each of the 4 polymorphonuclear leukocyte (PMN) function outcomes were weak (r < |0.3|). We did not observe the hypothesized differences in aspects of innate immunity in clinically healthy multiparous cows fed a negative DCAD. We underline that cows that experienced clinical disease were excluded from this study, which is important for interpretation of the results.

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.

Regenerative Medicine and Immunomodulatory Therapy: Insights From the Kidney, Heart, Brain, and Lung

Regenerative medicine was initially focused on tissue engineering to replace damaged tissues and organs with constructs derived from cells and biomaterials. More recently, this field of inquiry has expanded into exciting areas of translational medicine modulating the body’s own endogenous processes, to prevent tissue damage in organs and to repair and regenerate these damaged tissues. This review will focus on recent insights derived from studies in which the manipulation of the innate immunologic system may diminish acute kidney injury and enhance renal repair and recovery without the progression to chronic kidney disease and renal failure. The manner in which these interventions may improve acute and chronic organ dysfunction, including the heart, brain, and lung, will also be reviewed.

Anti-tumor Necrosis Factor Alpha (Infliximab) Attenuates Apoptosis, Oxidative Stress, and Calcium Ion Entry Through Modulation of Cation Channels in Neutrophils of Patients with Ankylosing Spondylitis

Ankylosing Spondylitis (AS) is known to be associated with increased neutrophil activation and oxidative stress, however, the mechanism of neutrophil activation is still unclear. We have hypothesized that the antioxidant and anti-tumor necrosis factor properties of infliximab may affect intracellular Ca(2+) concentration in the neutrophils of AS patients. The objective of this study was to investigate the effects of infliximab on calcium signaling, oxidative stress, and apoptosis in neutrophils of AS patients. Neutrophils collected from ten patients with AS and ten healthy controls were used in the study. In a cell viability test, the ideal non-toxic dose and incubation time of infliximab were found as 100 μM and 1 h, respectively. In some experiments, the neutrophils were incubated with the voltage-gated calcium channel (VGCC) blockers verapamil + diltiazem (V + D) and the TRPM2 channel blocker 2-aminoethyl diphenylborinate (2-APB). Intracellular Ca(2+) concentration, lipid peroxidation, apoptosis, caspase 3, and caspase 9 values were high in neutrophils of AS patients and were reduced with infliximab treatment. Reduced glutathione level and glutathione peroxidase activity were low in the patients and increased with infliximab treatment. The intracellular Ca(2+) concentrations were low in 2-APB and V + D groups. In conclusion, the current study suggests that infliximab is useful against apoptotic cell death and oxidative stress in neutrophils of patients with AS, which seem to be dependent on increased levels of intracellular Ca(2+) through activation of TRPM2 and VGCC.

A Multi-Center, Randomized, Controlled, Pivotal Study to Assess the Safety and Efficacy of a Selective Cytopheretic Device in Patients with Acute Kidney Injury

OBJECTIVE

Acute kidney injury (AKI) is a highly morbid condition in critically ill patients that is associated with high mortality. Previous clinical studies have demonstrated the safety and efficacy of the Selective Cytopheretic Device (SCD) in the treatment of AKI requiring continuous renal replacement therapy in the intensive care unit (ICU).

DESIGN, SETTING, PATIENTS

A randomized, controlled trial of 134 ICU patients with AKI, 69 received continuous renal replacement therapy (CRRT) alone and 65 received SCD therapy.

RESULTS

No significant difference in 60-day mortality was observed between the treated (27/69; 39%) and control patients (21/59; 36%, with six patients lost to follow up) in the intention to treat (ITT) analysis. Of the 19 SCD subjects (CRRT+SCD) and 31 control subjects (CRRT alone) who maintained a post-filter ionized calcium (iCa) level in the protocol's recommended range (≤ 0.4 mmol/L) for greater or equal to 90% of the therapy time, 60-day mortality was 16% (3/19) in the SCD group compared to 41% (11/27) in the CRRT alone group (p = 0.11). Dialysis dependency showed a borderline statistically significant difference between the SCD treated versus control CRRT alone patients maintained for ≥ 90% of the treatment in the protocol's recommended (r) iCa target range of ≤ 0.4 mmol/L with values of, 0% (0/16) and 25% (4/16), respectively (P = 0.10). When the riCa treated and control subgroups were compared for a composite index of 60 day mortality and dialysis dependency, the percentage of SCD treated subjects was 16% versus 58% in the control subjects (p<0.01). The incidence of serious adverse events did not differ between the treated (45/69; 65%) and control groups (40/65; 63%; p = 0·86).

CONCLUSION

SCD therapy may improve mortality and reduce dialysis dependency in a tightly controlled regional hypocalcaemic environment in the perfusion circuit.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01400893 http://clinicaltrials.gov/ct2/show/NCT01400893.

Selenium reduces oxidative stress and calcium entry through TRPV1 channels in the neutrophils of patients with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common inflammatory disease with an uncertain pathogenesis, although one consistent finding is increased neutrophil activity. It has been recently reported that the essential antioxidant element selenium has protective effects on oxidative stress and cytosolic Ca(2+) concentrations in human neutrophil. We aimed to investigate the effects of selenium on oxidative stress and Ca(2+) levels through TRPV1 channels in neutrophils from patients with PCOS. Blood samples were obtained for neutrophil isolation from ten female patients with PCOS and ten healthy female subjects. Neutrophils isolated from PCOS group were investigated in four settings: (1) PCOS, (2) after incubation with TRPV1 channel blocker capsazepine (CPZ), (3) after incubation with selenium (sodium selenite), and (4) with combination (CPZ + selenium) exposure. Intracellular free Ca(2+) concentrations were higher in the patients than those in the controls, although their levels were reduced after CPZ and selenium incubations. The cytosolic Ca(2+) concentrations in neutrophils obtained from PCOS group were further decreased after incubation with CPZ + selenium, as compared with those exposed to neither agent. Lipid peroxidation levels were higher in the PCOS group than those in the control although neutrophil glutathione peroxidase (GSH-Px) and reduced glutathione (GSH) values were decreased. The lipid peroxidation level was lower in the CPZ and selenium groups than that in the PCOS group although GSH and GSH-Px values were higher in the treatment with selenium and CPZ. In conclusion, we observed the importance of Ca(2+) influx into the neutrophils through TRPV1 channels in the pathogenesis of the patients with PCOS. The selenium appeared to provide a protective effect against oxidative stress and Ca(2+) entry through modulation of neutrophil TRPV1 calcium channels.

Hypericum perforatum modulates apoptosis and calcium mobilization through voltage-gated and TRPM2 calcium channels in neutrophil of patients with Behcet's disease

Behcet's disease (BD) is a chronic, inflammatory, and multisystemic condition although its pathogenesis is uncertain. Main component of St. John's wort (Hypericum perforatum, HP) is hyperforin and induces antiinflammatory and antioxidant properties. We aimed to investigate effects of HP on oxidative stress, apoptosis, and cytosolic-free Ca²⁺ [Ca²⁺](i) concentration in neutrophil of BD patients. Nine new-diagnosed active patients with BD and nine control subjects were included in the study. Disease activity was considered by clinical findings. Neutrophil samples were obtained from the patients and controls. The neutrophils from patients were divided into three subgroups and were incubated with HP, voltage-gated calcium channel (VGCC) blockers, (verapamil+dilitiazem) and non-specific TRPM2 channel blocker (2-aminoethyl diphenylborinate, 2-APB), respectively. The neutrophils were stimulated by fMLP as a Ca²⁺-concentration agonist and oxidative stress former. Caspase-3, caspase-9, apoptosis, lipid peroxidation, and [Ca²⁺](i) values were high in the patient groups, although cell viability, glutathione (GSH), and glutathione peroxidase (GSH-Px) values were low in patient group. However, the [Ca²⁺](i), caspase-3, and caspase-9 values decreased markedly in patient+HP group although GSH and GSH-Px values increased in the group. The [Ca²⁺](i) concentration was also decreased in the patient group by V+D, 2-APB, and HP incubations. In conclusion, we observed the importance of neutrophil Ca²⁺ entry, apoptosis, and oxidative stress through gating VGCC and TRPM2 channels in the neutrophils in the pathogenesis and activation of the patients with BD. HP induced protective effects on oxidative stress by modulating Ca²⁺ influx in BD patients.

Cell-based approaches for the treatment of systemic inflammation

Acute and chronic solid organ failures are costly disease processes with high mortality rates. Inflammation plays a central role in both acute and chronic organ failure, including heart, lung and kidney. In this regard, new therapies for these disorders have focused on inhibiting the mediators of inflammation, including cytokines and free radicals, with little or no success in clinical studies. Recent novel treatment strategies have been directed to cell-based rather than mediator-based approaches, designed to immunomodulate the deleterious effects of inflammation on organ function. One approach, cell therapy, replaces cells that were damaged in the acute or chronic disease process with stem/progenitor technology, to rebalance excessive inflammatory states. As an example of this approach, the use of an immunomodulatory role of renal epithelial progenitor cells to treat acute renal failure (ARF) and multiorgan failure arising from acute kidney injury is reviewed. A second therapeutic pathway, cell processing, does not incorporate stem/progenitor cells in the device, but rather biomimetic materials that remove and modulate the primary cellular components, which promote the worsening organ tissue injury associated with inflammation. The use of an immunomodulating leukocyte selective cytopheretic inhibitory device is also reviewed as an example of this cell processing approach. Both of these unconventional strategies have shown early clinical efficacy in pilot clinical trials and may transform the therapeutic approach to organ failure disorders.

Role of contrast media on oxidative stress, Ca(2+) signaling and apoptosis in kidney

Contrast media (CM)-induced nephropathy is a common cause of iatrogenic acute renal failure. The aim of the present review was to discuss the mechanisms and risk factors of CM, to summarize the controlled studies evaluating measures for prevention and to conclude with evidence-based strategies for prevention. A review of the relevant literature and results from recent clinical studies as well as critical analyses of published systematic reviews used MEDLINE and the Science Citation Index. The cytotoxicity induced by CM leads to apoptosis and death of endothelial and tubular cells and may be initiated by cell membrane damage together with reactive oxygen species (ROS) and inflammation. Cell damage may be aggravated by factors such as tissue hypoxia, properties of individual CM such as ionic strength, high osmolarity and/or viscosity. Clinical studies indeed support this possibility, suggesting a protective effect of ROS scavenging with the administration of N-acetylcysteine, ascorbic acid erdosteine, glutathione and bicarbonate infusion. The interaction between extracellular Ca(2+), which plays a central role in intercellular contacts and production of ROS, and the in vitro toxicity of CM was also reviewed. The current review addresses the role of oxidative stress in the pathogenesis of CM in the kidney as well as current and potential novel treatment modalities for the prevention of neutrophil activation and CM-induced kidney degeneration in patients. ROS production through CM-induced renal hypoxia may exert direct tubular and vascular endothelial injury. Preventive strategies via antioxidant supplementation include inhibition of ROS generation or scavenging.

Cell-based strategies for the treatment of kidney dysfunction: a review

Conventional treatment of acute and chronic renal diseases has focused on solute removal. Novel strategies aim to treat the multifactorial disease states of acute kidney injury and chronic kidney disease by mitigating inflammation. Cell-based technologies for the treatment of kidney dysfunction fall under two broad categories: cell therapy and cell processing. Cell therapy utilizes cells that are isolated, cultured outside of the body, and reintroduced as therapy, leveraging beneficial metabolic and synthetic functions. For example, renal tubule cells have been used to provide gluconeogenesis, ammoniagenesis, metabolism of glutathione, catabolism of important peptide hormones, growth factors, and cytokines critical to multiorgan homeostasis and immunomodulation to treat renal dysfunction. Cell processing focuses on altering the characteristics of cell populations inside the body to provide therapy. The selective cytopheretic device is an example of this novel therapeutic strategy that aims to modulate the innate immune response during organ dysfunction, additional organ injury, by binding and deactivating leukocytes. In this review, both cell therapy and cell processing approaches will be discussed in the context of acute kidney injury and chronic renal disease.

Non-ionic contrast media induces oxidative stress and apoptosis through Ca²⁺ influx in human neutrophils

Non-ionic contrast media (CM) can induce tissue kidney injury via activation of phagocytosis and oxidative stress, although the mechanisms of injury via neutrophils are not clear. We investigated the effects of CM on oxidative stress and Ca²⁺ concentrations in serum and neutrophils of humans. Ten migraine patients were used in the study. Serum and neutrophil samples from patients' peripheral blood were obtained before (control) and 30 min after non-ionic (iopromide) CM injection. The neutrophils were incubated with non specific transient receptor potential 2 (TRPM2) channel blocker, 2-aminoethoxydiphenyl borate (2-APB), and voltage gated Ca²⁺ channel blockers, verapamil plus diltiazem. Serum and neutrophil lipid peroxidation, apoptosis and intracellular Ca²⁺ concentrations levels were higher in the CM group than in controls. The neutrophilic reduced glutathione (GSH) and glutathione peroxidase (GSH-Px) levels as well as serum vitamin E and β-carotene concentrations were lower in the CM group than in controls. Neutrophil lipid peroxidation levels were lower in the CM+2-APB and CM+verapamil-diltiazem groups than in the CM group, although GSH, GSH-Px and intracellular Ca²⁺ values increased in the CM+2-APB and CM+verapamil-diltiazem groups. However, caspase-3, caspase-9, vitamin A and vitamin C values were unaltered by CM treatment. In conclusion, we observed that CM induced oxidative stress and Ca²⁺ influx by decreasing vitamin E, β-carotene and Ca²⁺ release levels in human serum and neutrophils. However, we observed protective effects of Ca²⁺ channel blockers on Ca²⁺ influx in neutrophils.

Colchicine modulates oxidative stress in serum and neutrophil of patients with Behçet disease through regulation of Ca²⁺ release and antioxidant system

Behçet disease (BD) is a chronic, inflammatory, and multisystemic condition with an uncertain pathogenesis. One of the major immunologic findings in BD pathogenesis is increase in activity of neutrophil. An increase in the cytosolic free Ca²⁺[Ca²⁺](i) concentration that induces Ca²⁺ signaling is an important step that participates in the neutrophil activation and reactive oxygen species production that leads to tissue damage in body cells. We aimed to investigate the effects of colchicine on oxidative stress and Ca²⁺ release in serum and neutrophil of BD patients with active and inactive periods. Twelve Behçet patients (6 active and 6 inactive) and 6 control subject were included in the study. Disease activity was considered by clinical findings. Serum and neutrophil samples were obtained from the patients and control subjects. Neutrophils from patients with active BD were divided into three subgroups and were incubated with colchicine, verapamil + diltiazem, and colchicine + verapamil + diltiazem, respectively. Erythrocyte sedimentation rate, leucocytes counts, serum C-reactive protein, neutrophil, and serum lipid peroxidation and intracellular Ca²⁺ release levels were higher in active and inactive groups than in the control group, although their levels were lower in active group than in inactive group. However, neutrophil Ca²⁺ release levels were decreased in colchicine, verapamil + diltiazem, and colchicine + verapamil + diltiazem groups group compared to active group. Serum glutathione, vitamin A, vitamin E, and β-carotene concentrations were lower in active and inactive groups than in the control group, although serum vitamin E and β-carotene concentrations were higher in the inactive group than in the active group. Neutrophil and serum glutathione peroxidase activity within the three groups did not change. In conclusion, we observed the importance of Ca²⁺ influx into the neutrophils and oxidative stress in the pathogenesis and activation of the patients with BD. Colchicine induced protective effects on oxidative stress by modulating Ca²⁺ influx in BD patients.

Why are Neutrophils Polymorphonuclear?

Most cells in the human body have a spherical or ovoid nucleus. The mature human neutrophil, unlike most other cells exhibits a distinctly non-spherical nucleus, which is segmented into three to five lobes. The possible mechanisms underlying this segmented nuclear shape have been explored. The structure of the nuclear envelope, composition of lamins and lamin-B receptor seems to have an important role in shaping the nucleus. Being the first line of defense, neutrophils migrate rapidly to the site of infection and destroy the invading pathogen. This requires negotiation through narrow capillaries, transmigration across the vessel wall and passage through tight tissue spaces. Segmented shape confers increased nuclear flexibility, thereby easing the migration of neutrophils through narrow channels. The segmented shape of the nucleus may also play a role in intranuclear chromatin organization and gene expression. The unique shape of the neutrophil nucleus seems to be an adaptation to facilitate its function.

Colchicine modulates oxidative stress in serum and leucocytes from remission patients with Family Mediterranean Fever through regulation of Ca²+ release and the antioxidant system

We investigated the effects of colchicine on oxidative stress and Ca²+ release in serum and polymorphonuclear leucocytes (PMNs) of Familial Mediterranean Fever (FMF) patients with attack, remission and unremission periods. Eighteen FMF patients and six age-matched healthy subjects in four groups were used. The first group was a control. The second group included patients with active FMF. The third and fourth groups were patients with remission and unremission, respectively. Colchicine (1.5 mg/day) was given to the third and fourth groups for 1 month. PMN cells, serum lipid peroxidation and intracellular Ca²+-release levels in the attack and unremission groups were higher than in those in controls, although they were lower in the remission group than in the attack group. Serum vitamin E and β-carotene concentrations were higher in the remission group than in the control and attack groups. However, PMN, serum lipid peroxidation and Ca²+-release levels were further increased in the unremission group compared to the attack group. Glutathione peroxidase, reduced glutathione and vitamin A values in the four groups did not change by FMF and colchicine. In conclusion, we observed that colchicine induced protective effects on oxidative stress by modulating vitamin E, β-carotene and Ca²+-release levels in FMF patients with a remission period.

Constitutive neutrophil apoptosis: mechanisms and regulation

Neutrophil constitutive death is a critical cellular process for modulating neutrophil number and function, and it plays an essential role in neutrophil homeostasis and the resolution of inflammation. Neutrophils die due to programmed cell death or apoptosis. In this article, we review recent studies on the mechanism of neutrophil apoptosis. The involvement of caspase, calpain, reactive oxygen species, cellular survival/death signaling pathways, mitochondria, and BCL-2 family member proteins are discussed. The fate of neutrophils can be influenced within the inflammatory microenvironment. We summarize the current understanding regarding the modulation of neutrophil apoptotic death by various extracellular stimuli such as proinflammatory cytokines, cell adhesion, phagocytosis, red blood cells, and platelets. The involvement of neutrophil apoptosis in infectious and inflammatory diseases is also addressed.

Store-operated calcium entry mediates intracellular alkalinization, ERK1/2, and Akt/PKB phosphorylation in bovine neutrophils

Neutrophil's responses to G protein-coupled chemoattractants are highly dependent on store-operated calcium (Ca(2+)) entry (SOCE). Platelet-activating factor (PAF), a primary chemoattractant, simultaneously increases cytosolic-free Ca(2+), intracellular pH (pH(i)), ERK1/2, and Akt/protein kinase B (PKB) phosphorylation. In this study, we looked at the efficacy of several putative SOCE inhibitors and whether SOCE mediates intracellular alkalinization, ERK1/2, and Akt/PKB phosphorylation in bovine neutrophils. We demonstrated that the absence of external Ca(2+) and the presence of EGTA reduced the intracellular alkalinization and ERK1/2 phosphorylation induced by PAF, apparently via SOCE influx inhibition. Next, we tested the efficacy of several putative SOCE inhibitors such as 2-aminoethoxydiphenyl borate (2-APB), capsaicin, flufenamic acid, 1-{beta-[3-(4-methoxy-phenyl)propoxy]-4-methoxyphenethyl}-1H-imidazole hydrochloride (SK&F 96365), and N-(4-[3,5-bis(trifluoromethyl)-1H-pyrazol-1-yl]phenyl)-4-methyl-1,2,3-thiadiazole-5-carboxamide (BTP2) on Ca(2+) entry induced by PAF or thapsigargin. 2-APB was the most potent SOCE inhibitor, followed by capsaicin and flufenamic acid. Conversely, SK&F 96365 reduced an intracellular calcium ([Ca(2+)](i)) peak but SOCE partially. BTP2 did not show an inhibitory effect on [Ca(2+)](i) following PAF stimuli. 2-APB strongly reduced the pH(i) recovery, whereas the effect of flufenamic acid and SK&F 96365 was partial. Capsaicin and BTP2 did not affect the pH(i) changes induced by PAF. Finally, we observed that 2-APB reduced the ERK1/2 and Akt phosphorylation completely, whereas the inhibition with flufenamic acid was partial. The results suggest that 2-APB is the most potent SOCE inhibitor and support a key role of SOCE in pH alkalinization and PI-3K-ERK1/2 pathway control. Finally, 2-APB could be an important tool to characterize Ca(2+) signaling in neutrophils.

Mitochondria in neutrophil apoptosis

Central in the regulation of the short life span of neutrophils are their mitochondria. These organelles hardly contribute to the energy status of neutrophils but play a vital role in the apoptotic process. Not only do the mitochondria contain cytotoxic proteins that are released during apoptosis and contribute to caspase activation, but they also act as sensors of the metabolic and redox state of the cell and as scavengers of free Ca2+. The balance of the expression and activity of the proapoptotic and antiapoptotic members of the Bcl-2 family of proteins determines the life span of neutrophils, because these proteins are essential for the formation of a permeability transition pore in the mitochondria and also seem to control the release of Ca2+ from the endoplasmic reticulum and thereby mitochondrial energy metabolism.

Human galectin-1, -2, and -4 induce surface exposure of phosphatidylserine in activated human neutrophils but not in activated T cells

Cellular turnover is associated with exposure of surface phosphatidylserine (PS) in apoptotic cells, leading to their phagocytic recognition and removal. But recent studies indicate that surface PS exposure is not always associated with apoptosis. Here we show that several members of the human galectin family of glycan binding proteins (galectins-1, -2, and -4) induce PS exposure in a carbohydrate-dependent fashion in activated, but not resting, human neutrophils and in several leukocyte cell lines. PS exposure is not associated with apoptosis in activated neutrophils. The exposure of PS in cell lines treated with these galectins is sustained and does not affect cell viability. Unexpectedly, these galectins bind well to activated T lymphocytes, but do not induce either PS exposure or apoptosis, indicating that galectin's effects are cell specific. These results suggest novel immunoregulatory contribution of galectins in regulating leukocyte turnover independently of apoptosis.

Defective chemoattractant-induced calcium signalling in S100A9 null neutrophils

The S100 family member S100A9 and its heterodimeric partner, S100A8, are cytosolic Ca2+ binding proteins abundantly expressed in neutrophils. To understand the role of this EF-hand-containing complex in Ca2+ signalling, neutrophils from S100A9 null mice were investigated. There was no role for the complex in buffering acute cytosolic Ca2+ elevations. However, Ca2+ responses to inflammatory agents such as chemokines MIP-2 and KC and other agonists are altered. For S100A9 null neutrophils, signalling at the level of G proteins is normal, as is release of Ca2+ from the IP(3) receptor-gated intracellular stores. However MIP-2 and FMLP signalling in S100A9 null neutrophils was less susceptible than wildtype to PLCbeta inhibition, revealing dis-regulation of the signalling pathway at this level. Downstream of PLCbeta, there was reduced intracellular Ca2+ release induced by sub-maximal levels of chemokines. Conversely the response to FMLP was uncompromised, demonstrating different regulation compared to MIP-2 stimulation. Study of the activity of PLC product DAG revealed that chemokine-induced signalling was susceptible to inhibition by elevated DAG with S100A9 null cells showing enhanced inhibition by DAG. This study defines a lesion in S100A9 null neutrophils associated with inflammatory agonist-induced IP3-mediated Ca2+ release that is manifested at the level of PLCbeta.

Taming the neutrophil: calcium clearance and influx mechanisms as novel targets for pharmacological control

Neutrophils are relatively insensitive to the anti-inflammatory actions of conventional chemotherapeutic agents, including corticosteroids, emphasizing the requirement for novel pharmacological strategies to control the potentially harmful proinflammatory activities of these cells. In the case of commonly-occurring inflammatory diseases of the airways, the neutrophil is the primary mediator of inflammation in conditions such as chronic obstructive pulmonary disease, cystic fibrosis, acute respiratory distress syndrome, bronchiectasis and non-eosinophilic bronchial asthma. Recent insights into the mechanisms utilized by neutrophils to restore Ca(2+) homeostasis following activation with Ca(2+)-mobilizing, proinflammatory stimuli have facilitated the identification of novel targets for anti-inflammatory chemotherapy in these cells. The most amenable of these from a chemotherapeutic perspective, is the cyclic AMP-dependent protein kinase-modulated endomembrane Ca(2+)-ATPase which promotes clearance of the cation from the cytosol of activated neutrophils. Second generation type 4 phosphodiesterase inhibitors and adenosine receptor agonists operative at the level of subtype A2A adenosine receptors, which are currently undergoing clinical and preclinical assessment respectively, hold promise as pharmacologic modulators during the restoration of Ca(2+) homeostasis. If this promise is realized, it may result in novel chemotherapeutic strategies for the control of hyperacute and chronic inflammatory conditions in which neutrophils are primary offenders. Alternative, potential future targets include the Na(+), Ca(2+)-exchanger and store-operated Ca(2+) channels, which cooperate in the refilling of intracellular Ca(2+) stores.

Adherence of Staphylococcus epidermidis to extracellular matrix proteins and effects of fibrinogen-bound bacteria on oxidase activity and apoptosis in neutrophils

Staphylococcus epidermidis often causes foreign-body infections such as those associated with hip prostheses, but the underlying pathogenic mechanisms are not fully understood. We performed spectrophotometry to study the ability of S. epidermidis to bind to immobilised fibrinogen, fibronectin, vitronectin, and collagen. The strains were isolated from infected hip prostheses or from normal flora and the well-known protein-binding strain Staphylococcus aureus Cowan was used as positive control. We also analysed the interaction between neutrophils and a fibrinogen-bound prosthesis-derived strain of S. epidermidisby measuring chemiluminescence to determine the neutrophil oxidative response and binding of annexin V to indicate neutrophil apoptosis. We found that binding of S. epidermidis to extracellular matrix proteins varied under different growth conditions, and that prosthesis isolates adhered better to vitronectin than did strains from normal flora. The oxidative response caused by fibrinogen-bound S. epidermidis was not above the background level, which was in marked contrast to the distinct response induced by fibrinogen-associated S. aureus Cowan. Furthermore, fibrinogen-adhering S. epidermidis retarded neutrophil apoptosis. We conclude that surface-bound S. epidermidis induces only a weak inflammatory response, which in combination with the ability of the adherent bacteria to retard neutrophil apoptosis may contribute to low-grade inflammation and loosening of prostheses.

Deimination of Histone H2A and H4 at Arginine 3 in HL-60 Granulocytes

Interplay of various covalent modifications of histone tails has an essential role in regulation of chromatin function. Peptidylarginine deiminase (PADI) 4 deiminates protein arginine to citrulline in a Ca(2+)-dependent manner and is present in the nucleus of granulocyte-differentiated HL-60 cells. When these cells are treated with the calcium ionophore A23187, core histone deimination occurs. To determine the deimination sites of histones, histone species were purified by reverse-phase high-performance liquid chromatography (RP-HPLC) from the cells. Immunoblotting using antimodified citrulline antibody indicated that histones H2A, H3, and H4 but not H2B were deiminated. H2A and H4 were digested with Staphylococcus aureus V8 protease, and the digests were separated by RP-HPLC. Immuno dot-blotting and mass spectrometry showed that the deiminated residues were present in H2A (1-56) and H4 (1-52) regions but not in other regions. The H2A peptide (1-56) was digested with alpha-chymotrypsin, and the deiminated peptide was separated from the corresponding nondeiminated peptide by RP-HPLC. The deiminated residue was found to be limited to residues 1-23. Similarly, digestion of the H4 peptide (1-52) with endoproteinase Asp-N and separation of the deiminated peptide from the nondeiminated peptide indicated that the deiminated residue was limited to residues 1-23. Mass spectrometry of lysylendopeptidase digests of the H2A (1-23) and H4 (1-23) peptides showed that deimination occurred at arginine 3 of the N-terminal sequence Ac-SGRGK common to H2A and H4. These results suggest that PADI4 deiminates only a restricted site of target proteins in cells. Deimination of histones is discussed in relation to chromatin structure and function.

Signalling shutdown strategies in aging immune cells

It is important for the resolution of inflammation that the number and activity of immune cells are reduced. Clearance of immune cells may be achieved by apoptosis and phagocytosis of cell fragments by macrophages. However, signalling shutdown by immune cells committed to apoptosis occurs early in the progression of these cells towards fragmentation and, it could be argued, is a key feature of apoptosis. There is surprisingly little known about the mechanisms that underlie this signalling shutdown, in particular the shutdown of Ca(2+) influx. The consequences and the potential mechanisms by which Ca(2+) influx shutdown is achieved are discussed. In addition, the potential consequences for cell signalling of cytochrome c release from mitochondria and of phosphatidyl-serine externalization are discussed. The aim of the review is therefore to highlight the evidence for various signalling shutdown strategies in immune cells that may limit their activity during progression towards apoptosis.