Health economic evaluation of blended collaborative care for older multimorbid heart failure patients: study protocol.

BACKGROUND: Integrated care, in particular the 'Blended Collaborative Care (BCC)' strategy, may have the potential to improve health-related quality of life (HRQoL) in multimorbid patients with heart failure (HF) and psychosocial burden at no or low additional cost. The ESCAPE trial is a randomised controlled trial for the evaluation of a BCC approach in five European countries. For the economic evaluation of alongside this trial, the four main objectives were: (i) to document the costs of delivering the intervention, (ii) to assess the running costs across study sites, (iii) to evaluate short-term cost-effectiveness and cost-utility compared to providers' usual care, and (iv) to examine the budgetary implications. METHODS: The trial-based economic analyses will include cross-country cost-effectiveness and cost-utility assessments from a payer perspective. The cost-utility analysis will calculate quality-adjusted life years (QALYs) using the EQ-5D-5L and national value sets. Cost-effectiveness will include the cost per hospital admission avoided and the cost per depression-free days (DFD). Resource use will be measured from different sources, including electronic medical health records, standardised questionnaires, patient receipts and a care manager survey. Uncertainty will be addressed using bootstrapping. DISCUSSION: The various methods and approaches used for data acquisition should provide insights into the potential benefits and cost-effectiveness of a BCC intervention. Providing the economic evaluation of ESCAPE will contribute to a country-based structural and organisational planning of BCC (e.g., the number of patients that may benefit, how many care managers are needed). Improved care is expected to enhance health-related quality of life at little or no extra cost. TRIAL REGISTRATION: The study follows CHEERS2022 and is registered at the German Clinical Trials Register (DRKS00025120).

Reliability of peripheral arterial tonometry in patients with heart failure, diabetic nephropathy and arterial hypertension.

Endothelial dysfunction plays a major role in cardiovascular diseases and pulse amplitude tonometry (PAT) offers a non-invasive way to assess endothelial dysfunction. However, data about the reliability of PAT in cardiovascular patient populations are scarce. Thus, we evaluated the test-retest reliability of PAT using the natural logarithmic transformed reactive hyperaemia index (LnRHI). Our cohort consisted of 91 patients (mean age: 65±9.7 years, 32% female), who were divided into four groups: those with heart failure with preserved ejection fraction (HFpEF) ( n=25), heart failure with reduced ejection fraction (HFrEF) ( n=22), diabetic nephropathy ( n=21), and arterial hypertension ( n=23). All subjects underwent two separate PAT measurements at a median interval of 7 days (range 4-14 days). LnRHI derived by PAT showed good reliability in subjects with diabetic nephropathy (intra-class correlation (ICC) = 0.863) and satisfactory reliability in patients with both HFpEF (ICC = 0.557) and HFrEF (ICC = 0.576). However, in subjects with arterial hypertension, reliability was poor (ICC = 0.125). We demonstrated that PAT is a reliable technique to assess endothelial dysfunction in adults with diabetic nephropathy, HFpEF or HFrEF. However, in subjects with arterial hypertension, we did not find sufficient reliability, which can possibly be attributed to variations in heart rate and the respective time of the assessments. Clinical Trial Registration Identifier: NCT02299960.

Impact of cyclin-dependent kinase CDK4 inhibition on eryptosis.

BACKGROUND/AIMS: The cyclin-dependent kinase 4 (CDK4) participates in the regulation of apoptosis of nucleated cells by altering transcriptional regulation of genes governing cell proliferation and cell death. Similar to apoptosis of nucleated cells, erythrocytes may enter eryptosis, which is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine (PS) exposure at the cell surface. As mature erythrocytes lack nuclei, acute stimulation of eryptosis cannot result from altered gene expression. Eryptosis is triggered by isotonic cell shrinkage following Cl- removal (replacement with the impermeant organic anion gluconate) or by oxidative stress (exposure to 0.3 mM tertbutyl-hydroperoxide [tBOOH]). The present study explored whether CDK4 is expressed in erythrocytes and whether the CDK4 inhibitors II (NSC625987) and III (ryuvidine) influence eryptosis. METHODS: Western blotting was utilized for determination of the presence of CDK4 protein in human erythrocytes, and FACS analysis to determine Fluo3 fluorescence (reflecting cytosolic Ca2+), annexin-V-binding (reflecting PS-exposure) and forward scatter (reflecting cell volume). RESULTS: CDK4 protein was present in human erythrocytes. Cl- removal was followed by decrease of forward scatter and increase of both annexin-V-binding and Fluo3 fluorescence, an effect significantly curtailed by CDK4 inhibitors II and III. Furthermore, CDK4 inhibition blunted enhanced PS-exposure elicited by tBOOH treatment. CONCLUSIONS: The present observations disclose the presence of CDK4 protein in human erythrocytes and the suppression of suicidal erythrocyte death by pharmacological inhibition of CDK4.

Vitamin D-Rich Diet in Mice Modulates Erythrocyte Survival.

BACKGROUND/AIMS: Epidemiological evidence suggests that vitamin D deficiency is associated with anemia. The potent metabolite 1,25(OH)2 vitamin D3 [1,25(OH)2D3] activates various signaling cascades regulating a myriad of cellular functions including suicidal cell death or apoptosis. Suicidal death of erythrocytes or eryptosis is characterized by cell shrinkage and cell membrane scrambling leading to phosphatidylserine (PS) externalization. Stimulation of eryptosis may limit lifespan of circulating erythrocytes and thus cause anemia. In the present study, we explored the effect of a high vitamin D diet (10,000 I.U. vitamin D for 14 days) in mice on eryptosis. METHODS: Plasma concentrations of erythropoietin were estimated using an immunoassay kit, blood count using an electronic hematology particle counter, relative reticulocyte numbers using Retic-COUNT® reagent, PS exposure at the cell surface from annexin V binding, cell volume from forward scatter, and cytosolic Ca(2+) ([Ca(2+)]i) from Fluo3-fluorescence in FACS analysis. RESULTS: Vitamin D treatment decreased mean corpuscular volume, reticulocyte count, and plasma erythropoietin levels. Vitamin D treatment slightly but significantly decreased forward scatter but did not significantly modify spontaneous PS exposure and [Ca(2+)]i of freshly drawn erythrocytes. Vitamin D treatment augmented the stimulation of PS exposure and cell shrinkage following exposure to hyperosmotic shock (addition of 550 mM sucrose) or energy depletion (glucose removal) without significantly modifying [Ca(2+)]i. CONCLUSIONS: The present observations point to a subtle effect of exogenous vitamin D supplementation on erythrocyte survival.

Stimulation of eryptosis by cryptotanshinone.

BACKGROUND/AIMS: Cryptotanshinone, a component of Salvia miltiorrhiza Bunge roots, may trigger suicidal death or apoptosis of tumor cells and has thus been recommended for the prevention and treatment of malignancy. On the other hand, Cryptotanshinone has been shown to counteract apoptosis of neurons and hepatocytes. Similar to apoptosis of nucleated cells, erythrocytes may enter eryptosis, a suicidal death characterized by cell shrinkage and phosphatidylserine translocation to the erythrocyte surface. Eryptosis may be triggered by increase of cytosolic Ca(2+)-activity ([Ca(2+)]i). The present study explored whether Cryptotanshinone stimulates eryptosis. METHODS: Forward scatter was taken as measure of cell volume, annexin V binding for identification of phosphatidylserine-exposing erythrocytes and Fluo3-fluorescence for determination of [Ca(2+)]i. RESULTS: A 48 h exposure of human erythrocytes to Cryptotanshinone (10 µM) was followed by significant decrease of forward scatter, significant increase of the percentage annexin-V-binding cells and significant increase of [Ca(2+)]i. The effect of Cryptotanshinone (1 µM) on annexin-V-binding was virtually abrogated by removal of extracellular Ca(2+). CONCLUSION: Cryptotanshinone is a powerful stimulator of suicidal erythrocyte death or eryptosis, which is effective mainly, if not exclusively, by stimulation of Ca(2+) entry.

Integrated care for older multimorbid heart failure patients: protocol for the ESCAPE randomized trial and cohort study.

ESCAPE: Evaluation of a patient-centred biopsychosocial blended collaborative care pathway for the treatment of multimorbid elderly patients. THERAPEUTIC AREA: Healthcare interventions for the management of older patients with multiple morbidities. AIMS: Multi-morbidity treatment is an increasing challenge for healthcare systems in ageing societies. This comprehensive cohort study with embedded randomized controlled trial tests an integrated biopsychosocial care model for multimorbid elderly patients. HYPOTHESIS: A holistic, patient-centred pro-active 9-month intervention based on the blended collaborative care (BCC) approach and enhanced by information and communication technologies can improve health-related quality of life (HRQoL) and disease outcomes as compared with usual care at 9 months. METHODS: Across six European countries, ESCAPE is recruiting patients with heart failure, mental distress/disorder plus ≥2 medical co-morbidities into an observational cohort study. Within the cohort study, 300 patients will be included in a randomized controlled assessor-blinded two-arm parallel group interventional clinical trial (RCT). In the intervention, trained care managers (CMs) regularly support patients and informal carers in managing their multiple health problems. Supervised by a clinical specialist team, CMs remotely support patients in implementing the treatment plan-customized to the patients' individual needs and preferences-into their daily lives and liaise with patients' healthcare providers. An eHealth platform with an integrated patient registry guides the intervention and helps to empower patients and informal carers. HRQoL measured with the EQ-5D-5L as primary endpoint, and secondary outcomes, that is, medical and patient-reported outcomes, healthcare costs, cost-effectiveness, and informal carer burden, will be assessed at 9 and ≥18 months. CONCLUSIONS: If proven effective, the ESCAPE BCC intervention can be implemented in routine care for older patients with multiple morbidities across the participating countries and beyond.

OSR1-sensitive regulation of Na+/H+ exchanger activity in dendritic cells.

The oxidative stress-responsive kinase 1 (OSR1) is activated by WNK (with no K kinases) and in turn stimulates the thiazide-sensitive Na-Cl cotransporter (NCC) and the furosemide-sensitive Na-K-2Cl cotransporter (NKCC), thus contributing to transport and cell volume regulation. Little is known about extrarenal functions of OSR1. The present study analyzed the impact of decreased OSR1 activity on the function of dendritic cells (DCs), antigen-presenting cells linking innate and adaptive immunity. DCs were cultured from bone marrow of heterozygous WNK-resistant OSR1 knockin mice (osr(KI)) and wild-type mice (osr(WT)). Cell volume was estimated from forward scatter in FACS analysis, ROS production from 2',7'-dichlorodihydrofluorescein-diacetate fluorescence, cytosolic pH (pH(i)) from 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein fluorescence, and Na(+)/H(+) exchanger activity from Na(+)-dependent realkalinization following ammonium pulse and migration utilizing transwell chambers. DCs expressed WNK1, WNK3, NCC, NKCC1, and OSR1. Phosphorylated NKCC1 was reduced in osr(KI) DCs. Cell volume and pH(i) were similar in osr(KI) and osr(WT) DCs, but Na(+)/H(+) exchanger activity and ROS production were higher in osr(KI) than in osr(WT) DCs. Before LPS treatment, migration was similar in osr(KI) and osr(WT) DCs. LPS (1 µg/ml), however, increased migration of osr(WT) DCs but not of osr(KI) DCs. Na(+)/H(+) exchanger 1 inhibitor cariporide (10 µM) decreased cell volume, intracellular reactive oxygen species (ROS) formation, Na(+)/H(+) exchanger activity, and pH(i) to a greater extent in osr(KI) than in osr(WT) DCs. LPS increased cell volume, Na(+)/H(+) exchanger activity, and ROS formation in osr(WT) DCs but not in osr(KI) DCs and blunted the difference between osr(KI) and osr(WT) DCs. Na(+)/H(+) exchanger activity in osr(WT) DCs was increased by the NKCC1 inhibitor furosemide (100 nM) to values similar to those in osr(KI) DCs. Oxidative stress (10 µM tert-butyl-hydroperoxide) increased Na(+)/H(+) exchanger activity in osr(WT) DCs but not in osr(KI) DCs and reversed the difference between genotypes. Cariporide virtually abrogated Na(+)/H(+) exchanger activity in both genotypes and blunted LPS-induced cell swelling and ROS formation in osr(WT) mice. In conclusion, partial OSR1 deficiency influences Na(+)/H(+) exchanger activity, ROS formation, and migration of dendritic cells.

Enhanced suicidal erythrocyte death in mice carrying a loss-of-function mutation of the adenomatous polyposis coli gene.

Loss-of-function mutations in human adenomatous polyposis coli (APC) lead to multiple colonic adenomatous polyps eventually resulting in colonic carcinoma. Similarly, heterozygous mice carrying defective APC (apc(Min/+)) suffer from intestinal tumours. The animals further suffer from anaemia, which in theory could result from accelerated eryptosis, a suicidal erythrocyte death triggered by enhanced cytosolic Ca(2+) activity and characterized by cell membrane scrambling and cell shrinkage. To explore, whether APC-deficiency enhances eryptosis, we estimated cell membrane scrambling from annexin V binding, cell size from forward scatter and cytosolic ATP utilizing luciferin-luciferase in isolated erythrocytes from apc(Min/+) mice and wild-type mice (apc(+/+)). Clearance of circulating erythrocytes was estimated by carboxyfluorescein-diacetate-succinimidyl-ester labelling. As a result, apc(Min/+) mice were anaemic despite reticulocytosis. Cytosolic ATP was significantly lower and annexin V binding significantly higher in apc(Min/+) erythrocytes than in apc(+/+) erythrocytes. Glucose depletion enhanced annexin V binding, an effect significantly more pronounced in apc(Min/+) erythrocytes than in apc(+/+) erythrocytes. Extracellular Ca(2+) removal or inhibition of Ca(2+) entry with amiloride (1 mM) blunted the increase but did not abrogate the genotype differences of annexin V binding following glucose depletion. Stimulation of Ca(2+) -entry by treatment with Ca(2+) -ionophore ionomycin (10 µM) increased annexin V binding, an effect again significantly more pronounced in apc(Min/+) erythrocytes than in apc(+/+) erythrocytes. Following retrieval and injection into the circulation of the same mice, apc(Min/+) erythrocytes were more rapidly cleared from circulating blood than apc(+/+) erythrocytes. Most labelled erythrocytes were trapped in the spleen, which was significantly enlarged in apc(Min/+) mice. The observations point to accelerated eryptosis and subsequent clearance of apc(Min/+) erythrocytes, which contributes to or even accounts for the enhanced erythrocyte turnover, anaemia and splenomegaly in those mice.

Rapamycin sensitive ROS formation and Na(+)/H(+) exchanger activity in dendritic cells.

Rapamycin, a widely used immunosuppressive drug, has been shown to interfere with the function of dendritic cells (DCs), antigen-presenting cells contributing to the initiation of primary immune responses and the establishment of immunological memory. DC function is governed by the Na(+)/H(+) exchanger (NHE), which is activated by bacterial lipopolysaccharides (LPS) and is required for LPS-induced cell swelling, reactive oxygen species (ROS) production and TNF-α release. The present study explored, whether rapamycin influences NHE activity and/or ROS formation in DCs. Mouse DCs were treated with LPS in the absence and presence of rapamycin (100 nM). ROS production was determined from 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) fluorescence, cytosolic pH (pH(i)) from 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) fluorescence, NHE activity from the Na(+)-dependent realkalinization following an ammonium pulse, cell volume from forward scatter in FACS analysis, and TNF-α production utilizing ELISA. In the absence of LPS, rapamycin did not significantly modify cytosolic pH, NHE activity or cell volume but significantly decreased ROS formation. LPS stimulated NHE activity, enhanced forward scatter, increased ROS formation, and triggered TNF-α release, effects all blunted in the presence of rapamycin. NADPH oxidase inhibitor Vas-2870 (10 µM) mimicked the effect of rapamycin on LPS induced stimulation of NHE activity and TNF-α release. The effect of rapamycin on TNF-α release was also mimicked by the antioxidant ROS scavenger Tempol (30 µM) and partially reversed by additional application of tert-butylhydroperoxide (10 µM). In conclusion, in DCs rapamycin disrupts LPS induced ROS formation with subsequent inhibition of NHE activity, cell swelling and TNF-α release.

Effect of casein kinase 1α activator pyrvinium pamoate on erythrocyte ion channels.

Pharmacological modification of protein kinase CK1 (casein kinase 1) has previously been shown to influence suicidal erythrocyte death or eryptosis, which is triggered by activation of Cl(-)-sensitive Ca(2+)-permeable cation channels. Ca(2+) entering through those channels stimulates cell membrane scrambling and opens Ca(2+)-activated K(+)-channels resulting in KCl exit and thus cell shrinkage. The specific CK1-inhibitor D4476 (1 µM) blunted, whereas the specific CK1 αactivator pyrvinium pamoate (10 µM) enhanced cell membrane scrambling. The substances were at least partially effective through modification of cytosolic Ca(2+)-activity. The present study explored, whether pyrvinium pamoate indeed influences Cl(-)-sensitive cation-channels in erythrocytes. As a result, removal of Cl(-)increased Fluo3-fluorescence (reflecting cytosolic Ca(2+)-activity), triggered cell membrane scrambling (apparent from annexin-V-binding), and decreased forward scatter (pointing to cell shrinkage). Pyrvinium pamoate significantly augmented the effect of Cl(-)-removal on Fluo3 fluorescence and annexin-V-binding, but blunted the effect on forward scatter. According to whole cell patch clamp recording, Cl(-)removal activated a cation current, which was significantly enhanced by pyrvinium pamoate. Pyrvinium pamoate inhibited Ca(2+)-activated K(+)-channels. Ca(2+)-ionophore ionomycin (1 µM) decreased forward scatter, an effect significantly blunted by pyrvinium pamoate. In conclusion, pyrvinium pamoate activates Cl(-)-sensitive Ca(2+)-permeable cation channels with subsequent Ca(2+)-entry and inhibits Ca(2+)-activated K(+)-channels thus blunting the stimulating effect of Ca(2+) on those channels, K(+)-exit and thus cell shrinkage.

Induction of programmed erythrocyte death by gambogic acid.

Gambogic acid, a xanthone from Garcinia hanburyi, stimulates apoptosis and has thus anticancer potency. Similar to apoptosis of nucleated cells, erythrocytes may undergo apoptosis-like suicidal death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling leading to phosphatidylserine-exposure at the cell surface. Eryptosis could be triggered by increase of cytosolic Ca(2+)-activity ([Ca(2+)](i)), ceramide formation, ATP-depletion and caspase activation. The present study explored, whether gambogic acid triggers eryptosis of human erythrocytes. [Ca(2+)](i )was estimated utilizing Fluo-3 fluorescence, cell volume from forward scatter, phosphatidylserine-exposure from annexin-V-binding, hemolysis from hemoglobin release, ceramide abundance utilizing antibodies, and cytosolic ATP with luciferin- luciferase. A 48 h exposure to gambogic acid (500 nM) significantly increased [Ca(2+)](i), stimulated ceramide formation, decreased forward scatter and increased annexin-V-binding. Gambogic acid exposure was followed by a slight but significant increase of hemolysis. Gambogic acid did not significantly modify cytosolic ATP-concentration. Removal of extracellular Ca(2+) slightly, but significantly blunted the effect of gambogic acid (500 nM) on annexin-V-binding. The present observations disclose a novel effect of gambogic acid, i.e. stimulation of suicidal death of human erythrocytes or eryptosis, paralleled by Ca(2+)-entry, ceramide formation, cell shrinkage and phosphatidylserine-exposure.

Effect of thymoquinone on cytosolic pH and Na+/H+ exchanger activity in mouse dendritic cells.

The anti-inflammatory Nigella sativa component thymoquinone compromises the function of dendritic cells (DCs), key players in the regulation of innate and adaptive immunity. DC function is regulated by the Na(+)/H(+) exchanger (NHE), which is stimulated by lipopolysaccharides (LPS) and required for LPS-induced cell swelling, reactive oxygen species (ROS) production, TNF-α release and migration. Here we explored, whether thymoquinone influences NHE activity in DCs. To this end, bone marrow derived mouse DCs were treated with LPS in the absence and presence of thymoquinone (10 µM). Cytosolic pH (pH(i)) was determined from 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) fluorescence, NHE activity from the Na(+)-dependent realkalinization following an ammonium pulse, cell volume from forward scatter in FACS analysis, ROS production from 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) fluorescence, TNF-α production utilizing ELISA and DC migration with transwell migration assays. As a result, exposure of DCs to LPS (1 µg/ml) led within 4 hours to transient increase of NHE activity. Thymoquinone did not significantly modify cytosolic pH or cellular NHE activity in the absence of LPS, but abrogated the effect of LPS on NHE activity. Accordingly, in the presence of thymoquinone LPS-treatment resulted in cytosolic acidification. LPS further increased forward scatter and ROS formation, effects similarly abrogated by thymoquinone. Again, in the absence of LPS, thymoquinone did not significantly modify ROS formation and cell volume. LPS further triggered TNF-α release and migration, effects again blunted in the presence of thymoquinone. NHE1 inhibitor cariporide (10 µM) blunted LPS induced TNF-α release and migration. The effects of thymoquinone on NHE activity and migration were reversed upon treatment of the cells with t-butyl hydroperoxide (TBOOH, 5 µM). In conclusion, thymoquinone blunts LPS induced NHE activity, cell swelling, oxidative burst, cytokine release and migration of bone marrow derived murine dendritic cells. NHE inhibition may thus contribute to the antiinflammatory action of thymoquinone.

Protein kinase CK1α regulates erythrocyte survival.

Protein kinase CK1 (casein kinase 1) isoforms are involved in the regulation of various physiological functions including apoptosis. The specific CK1 inhibitor D4476 may either inhibit or foster apoptosis. Similar to apoptosis of nucleated cells, eryptosis, the suicidal death of erythrocytes, is paralleled by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Triggers of eryptosis include increase of cytosolic Ca(2+) activity following energy depletion (removal of glucose) or oxidative stress (exposure to the oxidant tert-butyl hydroperoxide [TBOOH]). Western blotting was utilized to verify that erythrocytes express the protein kinase CK1α, and FACS analysis to determine whether the CK1 inhibitor D4476 and CK1α activator pyrvinium pamoate modify forward scatter (reflecting cell volume), annexin V binding (reflecting phosphatidylserine exposure), and Fluo3 fluorescence (reflecting cytosolic Ca(2+) activity). As a result, both, human and murine erythrocytes express CK1 isoform α. Glucose depletion (48 hours) and exposure to 0.3 mM TBOOH (30 minutes) both decreased forward scatter, increased annexin V binding and increased Fluo3 fluorescence. CK1 inhibitor D4476 (10 µM) significantly blunted the decrease in forward scatter, the increase in annexin V binding and the increase in Fluo 3 fluorescence. (R)-DRF053, another CK1 inhibitor, similarly blunted the increase in annexin V binding upon glucose depletion. The CK1α specific activator pyrvinium pamoate (10 µM) significantly enhanced the increase in annexin V binding and Fluo3 fluorescence upon glucose depletion and TBOOH exposure. In the presence of glucose, pyrvinium pamoate slightly but significantly increased Fluo3 fluorescence. In conclusion, CK1 isoform α participates in the regulation of erythrocyte programmed cell death by modulating cytosolic Ca(2+) activity.

Tanshinone IIA stimulates erythrocyte phosphatidylserine exposure.

Tanshinone IIA, an antimicrobial, antioxidant, antianaphylactic, antifibrotic, vasodilating, antiatherosclerotic, organo-protective and antineoplastic component from the rhizome of Salvia miltiorrhiza, is known to trigger apoptosis of tumor cells. Tanshinone IIA is effective in part through mitochondrial depolarization and altered gene expression. Erythrocytes lack mitochondria and nuclei but may undergo eryptosis, an apoptosis-like suicidal cell death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Eryptosis is triggered by increase of cytosolic Ca(2+) activity, ATP depletion and ceramide formation. The present study explored, whether tanshinone IIA elicits eryptosis. Cytosolic Ca(2+)-concentration was determined from Fluo3-fluorescence, cell volume from forward scatter, phosphatidylserine exposure from binding of fluorescent annexin V, hemolysis from hemoglobin concentration in the supernatant, ATP concentration utilizing luciferin-luciferase and ceramide formation utilizing fluorescent anticeramide antibodies. Clearance of circulating erythrocytes was estimated by CFSE-labeling. A 48 h exposure to tanshinone IIA (≥10 µM) significantly increased cytosolic Ca(2+)-concentration, decreased ATP concentration (25 µM), increased lactate concentration (25 µM), increased ceramide formation (25 µM), decreased forward scatter, increased annexin-V-binding and increased (albeit to a much smaller extent) hemolysis. The effect of 25 µM tanshinone IIA on annexin-V binding was partially reversed in the nominal absence of Ca(2+). Labelled tanshinone IIA-treated erythrocytes were more rapidly cleared from the circulating blood in comparison to untreated erythrocytes. The present observations reveal a completely novel effect of tanshinone IIA, i.e. triggering of Ca(2+) entry, ATP depletion and ceramide formation in erythrocytes, events eventually leading to eryptosis with cell shrinkage and cell membrane scrambling.

Enhanced erythrocyte membrane exposure of phosphatidylserine following sorafenib treatment: an in vivo and in vitro study.

BACKGROUND: Sorafenib (Nexavar(®)), a polytyrosine kinase inhibitor, stimulates apoptosis and is thus widely used for chemotherapy in hepatocellular carcinoma (HCC). Hematological side effects of Nexavar(®) chemotherapy include anemia. Erythrocytes may undergo apoptosis-like suicidal death or eryptosis, which is characterized by cell shrinkage and phosphatidylserine-exposure at the cell surface. Signaling leading to eryptosis include increase in cytosolic Ca(2+)activity ([Ca(2+)](i)), formation of ceramide, ATP-depletion and oxidative stress. The present study explored, whether sorafenib triggers eryptosis in vitro and in vivo. METHODS: [Ca(2+)](i )was estimated from Fluo3-fluorescence, cell volume from forward scatter, phosphatidylserine-exposure from annexin-V-binding, hemolysis from hemoglobin release, ceramide with antibody binding-dependent fluorescence, cytosolic ATP with a luciferin-luciferase-based assay, and oxidative stress from 2',7' dichlorodihydrofluorescein diacetate (DCFDA) fluorescence. RESULTS: A 48 h exposure of erythrocytes to sorafenib (≥0.5 µM) significantly increased Fluo 3 fluorescence, decreased forward scatter, increased annexin-V-binding and triggered slight hemolysis (≥5 µM), but did not significantly modify ceramide abundance and cytosolic ATP. Sorafenib treatment significantly enhanced DCFDA-fluorescence and the reducing agents N-acetyl-L-cysteine and tiron significantly blunted sorafenib-induced phosphatidylserine exposure. Nexavar(®) chemotherapy in HCC patients significantly enhanced the number of phosphatidylserine-exposing erythrocytes. CONCLUSIONS: The present observations disclose novel effects of sorafenib, i.e. stimulation of suicidal erythrocyte death or eryptosis, which may contribute to the pathogenesis of anemia in Nexavar(®)-based chemotherapy.

Hexavalent chromium-induced erythrocyte membrane phospholipid asymmetry.

Hexavalent (VI) chromium is a global contaminant with cytotoxic activity. Chromium (VI) induces oxidative stress, inflammation, cell proliferation, malignant transformation and may trigger carcinogenesis and at the same time apoptosis. The toxic effects of chromium (VI) at least partially result from mitochondrial injury and DNA damage. Erythrocytes lack mitochondria and nuclei but may experience an apoptosis-like suicidal cell death, i.e. eryptosis, which is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Eryptosis may result from increase of cytosolic Ca(2+) activity, ATP depletion and/or ceramide formation. The present study explored, whether chromium (VI) triggers eryptosis. Fluo-3-fluorescence was employed to determine cytosolic Ca(2+)-concentration, forward scatter to estimate cell volume, binding of fluorescent annexin V to detect phosphatidylserine exposure, hemoglobin concentration in the supernatant to quantify hemolysis, luciferin-luciferase to determine cytosolic ATP concentration and fluorescent anti-ceramide antibodies to uncover ceramide formation. A 48 h exposure to chromium (VI) (≥10 µM) significantly increased cytosolic Ca(2+)-concentration, decreased ATP concentration (20 µM), decreased forward scatter, increased annexin V-binding and increased (albeit to a much smaller extent) hemolysis. Chromium (VI) did not significantly modify ceramide formation. The effect of 20 µM chromium (VI) on annexin V binding was partially reversed in the nominal absence of Ca(2+). The present observations disclose a novel effect of chromium (VI), i.e. Ca(2+) entry and cytosolic ATP depletion in erythrocytes, effects resulting in eryptosis with cell shrinkage and cell membrane scrambling.

Inhibition of the heterotetrameric K+ channel KCNQ1/KCNE1 by the AMP-activated protein kinase.

The heterotetrameric K(+)-channel KCNQ1/KCNE1 is expressed in heart, skeletal muscle, liver and several epithelia including the renal proximal tubule. In the heart, it contributes to the repolarization of cardiomyocytes. The repolarization is impaired in ischemia. Ischemia stimulates the AMP-activated protein kinase (AMPK), a serine/threonine kinase, sensing energy depletion and stimulating several cellular mechanisms to enhance energy production and to limit energy utilization. AMPK has previously been shown to downregulate the epithelial Na(+) channel ENaC, an effect mediated by the ubiquitin ligase Nedd4-2. The present study explored whether AMPK regulates KCNQ1/KCNE1. To this end, cRNA encoding KCNQ1/KCNE1 was injected into Xenopus oocytes with and without additional injection of wild type AMPK (AMPKα1 + AMPKß1 + AMPKγ1), of the constitutively active (γR70Q)AMPK (α1ß1γ1(R70Q)), of the kinase dead mutant (αK45R)AMPK (α1(K45R)ß1γ1), or of the ubiquitin ligase Nedd4-2. KCNQ1/KCNE1 activity was determined in two electrode voltage clamp experiments. Moreover, KCNQ1 abundance in the cell membrane was determined by immunostaining and subsequent confocal imaging. As a result, wild type and constitutively active AMPK significantly reduced KCNQ1/KCNE1-mediated currents and reduced KCNQ1 abundance in the cell membrane. Similarly, Nedd4-2 decreased KCNQ1/KCNE1-mediated currents and KCNQ1 protein abundance in the cell membrane. Activation of AMPK in isolated perfused proximal renal tubules by AICAR (10 mM) was followed by significant depolarization. In conclusion, AMPK is a potent regulator of KCNQ1/KCNE1.

Inhibition of suicidal erythrocyte death by blebbistatin.

Blebbistatin, a myosin II inhibitor, interferes with myosin-actin interaction and microtubule assembly. By influencing cytoskeletal dynamics blebbistatin counteracts apoptosis of several types of nucleated cells. Even though lacking nuclei and mitochondria, erythrocytes may undergo suicidal cell death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Triggers of eryptosis include energy depletion and osmotic shock, which enhance cytosolic Ca(2+) activity with subsequent Ca(2+)-sensitive cell shrinkage and cell membrane scrambling. The present study explored the effect of blebbistatin on eryptosis. Cell membrane scrambling was estimated from binding of annexin V to phosphatidylserine at the erythrocyte surface, cell volume from forward scatter in fluorescence-activated cell sorting analysis and cytosolic Ca(2+) concentration from Fluo3 fluorescence. Exposure to blebbistatin on its own (1-50 µM) did not significantly modify cytosolic Ca(2+) concentration, forward scatter, or annexin V binding. Glucose depletion (48 h) was followed by a significant increase of Fluo3 fluorescence and annexin V binding, effects significantly blunted by blebbistatin (Fluo3 fluorescence ≥ 25 µM, annexin V binding ≥ 10 µM). Osmotic shock (addition of 550 mM sucrose) again significantly increased Fluo3 fluorescence and annexin binding, effects again significantly blunted by blebbistatin (Fluo3 fluorescence ≥ 25 µM, annexin V binding ≥ 25 µM). The present observations disclose a novel effect of blebbistatin, i.e., an influence on Ca(2+) entry and suicidal erythrocyte death following energy depletion and osmotic shock.

Proteome analysis of erythrocytes lacking AMP-activated protein kinase reveals a role of PAK2 kinase in eryptosis.

Activation of AMP-activated protein kinase (AMPK) upon energy depletion stimulates energy production and limits energy utilization. Erythrocytes lacking AMPK are susceptible to suicidal cell death (eryptosis). A hallmark of eryptosis is cell membrane scrambling with phosphatidylserine exposure at the erythrocyte surface, which can be identified from annexin V-binding. AMPKα1-deficient mice (ampk(-/-)) suffer from anemia due to accelerated clearance of erythrocytes from circulating blood. To determine the link between AMPK and the eryptotic phenotype, we performed a global proteome analysis of erythrocytes from ampk(-/-) mice and wild-type mice using high-accuracy mass spectrometry and label-free quantitation and measured changes of expression levels of 812 proteins. Notably, the p21-activated kinase 2 (PAK2), previously implicated in apoptosis, was detected as downregulated in erythrocytes of ampk(-/-) mice, pointing to its potential role in eryptosis. To validate this, we showed that specific inactivation of PAK2 with the inhibitor IPA3 in human and murine ampk(+/+) erythrocytes increases the binding of annexin V and augments the stimulating effect of glucose deprivation on annexin V-binding. Inhibition of PAK2 failed to significantly modify annexin V-binding in ampk(-/-) erythrocytes, showing that AMPK and PAK2 exert similar phenotypes upon inactivation in erythrocytes. This study presents the first large-scale analysis of protein expression in erythrocytes from AMPKα1-deficient mice and reveals a role of PAK2 kinase in eryptosis.

Dicoumarol activates Ca2+-permeable cation channels triggering erythrocyte cell membrane scrambling.

Dicoumarol, a widely used anticoagulant, may cause anemia, which may result from enhanced erythrocyte loss due to bleeding or due to accelerated erythrocyte death. Erythrocytes may undergo suicidal death or eryptosis, characterized by cell shrinkage and phospholipid scrambling of the cell membrane. Eryptosis may be triggered by increase of cytosolic Ca(2+)-activity ([Ca(2+)](i)). The present study explored, whether dicoumarol induces eryptosis. [Ca(2+)](i) was estimated from Fluo3-fluorescence, cation channel activity utilizing whole cell patch clamp, cell volume from forward scatter, phospholipid scrambling from annexin-V-binding, and hemolysis from haemoglobin release. Exposure of erythrocytes for 48 hours to dicoumarol (=10 µM) significantly increased [Ca(2+)](i), enhanced cation channel activity, decreased forward scatter, triggered annexin-V-binding and elicited hemolysis. Following exposure to 30 µM dicoumarol, annexin-V-binding affected approximately 15%, and hemolysis 2% of treated erythrocytes. The stimulation of annexin-V-binding by dicoumarol was abrogated in the nominal absence of Ca(2+). In conclusion, dicoumarol stimulates suicidal death of erythrocytes by stimulating Ca(2+) entry and subsequent triggering of Ca(2+) dependent cell membrane scrambling.