Immune Thrombocytopenia Plasma-Derived Exosomes Impaired Megakaryocyte and Platelet Production through an Apoptosis Pathway

Reduced megakaryocyte (MK) apoptosis and insufficient platelet production play important roles in the pathogenesis of immune thrombocytopenia (ITP). The contribution of plasma-derived exosomes to the decreased platelet count in ITP has not been entirely understood. Here, we found the percentage of apoptotic MKs in patients with ITP was significantly lower than those in healthy volunteers. In the presence of ITP plasma-derived exosomes (ITP-Exo), the apoptosis of MKs was reduced during the process of MK differentiation in vitro, which contributed to the reduced platelet production by Bcl-xL/caspase signaling. Furthermore, in vivo study demonstrated that ITP-Exo administration led to significantly delayed platelet recovery in mice after 3.5 Gy of irradiation. All these findings indicated that ITP-Exo, as a regulator of platelet production, impaired MK apoptosis and platelet production through Bcl-xL/caspase signaling, unveiling new mechanisms for reduced platelet count in ITP.

Apoptotic-like mitochondrial events associated to phosphatidylserine exposure in blood platelets induced by local anaesthetics

Phosphatidylserine exposure in platelets is required for normal haemostasis and is also a hallmark of apoptosis. It results from activation of a phospholipid scramblase, which has been shown to be differently stimulated by Ca2+-influx and during apoptosis, thus suggesting that mitochondria may be involved in phosphatidylserine exposure in platelets. It is also well known that local anaesthetics can expose phosphatidylserine in platelets and affect the mitochondrial metabolism in other cells. Thus, the present study was undertaken to evaluate the specific involvement of mitochondria in phosphatidylserine exposure in platelets. For this purpose, we stimulated phosphatidylserine exposure by local anaesthetics and avoided any external Ca2+-influx by performing all experiments in the absence of added Ca2+. We report that phosphatidylserine exposure, induced by the lipophilic local anaesthetics dibucaine and tetracaine, was accompanied by depolarization of the mitochondrial membrane, cytochrome c release, calpain-processing of caspases 9 and 3 to active enzymes, as well as a prolonged increase in both cytosolic and mitochondrial Ca2+ concentrations. In contrast, in the absence of extracellular Ca2+, the Ca2+-ionophore A23187 induced a smaller transient increase in both cytosolic and mitochondrial Ca2+ concentrations, but did not induce any other phenomena, nor phosphatidylserine exposure. However, phosphatidylserine exposure and depolarization induced by dibucaine still occurred in spite of inhibition of intracellular Ca2+ elevation. Thus we conclude that phosphatidylserine exposure in platelets is associated with mitochondrial apoptotic-like events. Therefore, we propose that mitochondria engagement in an apoptotic pathway in platelets could lead to PS exposure without the participation of Ca2+.

Inner Mitochondrial Membrane Disruption Links Apoptotic and Agonist-Initiated Phosphatidylserine Externalization in Platelets

OBJECTIVE

Phosphatidylserine exposure mediates platelet procoagulant function and regulates platelet life span. Apoptotic, necrotic, and integrin-mediated mechanisms have been implicated as intracellular determinants of platelet phosphatidylserine exposure. Here, we investigate (1) the role of mitochondrial events in platelet phosphatidylserine exposure initiated by these distinct stimuli and (2) the cellular interactions of the procoagulant platelet in vitro and in vivo.

APPROACH AND RESULTS

Key mitochondrial events were examined, including cytochrome c release and inner mitochondrial membrane (IMM) disruption. In both ABT-737 (apoptotic) and agonist (necrotic)-treated platelets, phosphatidylserine externalization was temporally correlated with IMM disruption. Agonist stimulation resulted in rapid cyclophilin D-dependent IMM disruption that coincided with phosphatidylserine exposure. ABT-737 treatment caused rapid cytochrome c release, eventually followed by caspase-dependent IMM disruption that again closely coincided with phosphatidylserine exposure. A nonmitochondrial and integrin-mediated mechanism has been implicated in the formation of a novel phosphatidylserine-externalizing platelet subpopulation. Using image cytometry, this subpopulation is demonstrated to be the result of the interaction of an aggregatory platelet and a procoagulant platelet rather than indicative of a novel intracellular mechanism regulating platelet phosphatidylserine externalization. Using electron microscopy, similar interactions between aggregatory and procoagulant platelets are demonstrated in vitro and in vivo within a mesenteric vein hemostatic thrombus.

CONCLUSIONS

Platelet phosphatidylserine externalization is closely associated with the mitochondrial event of IMM disruption identifying a common pathway in phosphatidylserine-externalizing platelets. The limited interaction of procoagulant platelets and integrin-active aggregatory platelets identifies a potential mechanism for procoagulant platelet retention within the hemostatic thrombus.

[EFFICIENCY OF URSODEOXYCHOLIC ACID APPLICATION IN NONALCOCHOLIC STEATOHEPATITIS]

AIM

to estimate the efficiency of ursodeoxycholic acid (UDHC) in nonalcocholic steatohepatitis (NASH) by analysis of conventional clinical datas, apoptosis and liver perfusion parameters.

MATERIALS AND METHODS

UDHC was used as monotherapy in treatment of 92 NASH patients in daily dose 10-15 mg/kg. We have observed 44 (47.8%) males, 48 (52.2%) females, age was 56.8 ± 7.2 years, BMI was 28.4 ± 2.3 kg/m2, waist circumference was 93.8 ± 8.3 cm. Functional liver tests (ALAT, ASAT, alcaline phosphatase--APh, gamma-glutamyltranspeptidase--GGTP), abdominal ultrasonography and dopplerography of liver blood flow, kaspase-3, 6, 8, 9 genes expression in blood leucocytes were estimated. Periods of controls research and UDCA treatment were: 4-8 weeks in 92 patients, 20-24 weeks in 18 (19.6%) patients and 40-48 weeks in 13 (14.1%) patients.

RESULTS

Significant positive dynamics of liver functional tests and decrease of kaspase-3, 6, 9 genes expression in blood leucocytes were observed over 4-8 weeks, normalization of liver tests--over 20-24 weeks and significant amelioration of venous and arterial liver perfusion parameters--over 40-48 weeks.

CONCLUSION

Ursodeoxycholic acid in daily dose of 10-15 mg/kg in nonalcocholic steatohepatitis caused positive dynamics of cytolytic and cholestasis parameters, leucocytic apoptosis and venous and arterial liver blood flow parameters.

Effects of gamma-hexachlorocyclohexane on apoptosis induced by serum deprivation in PC12 cells

The effects of gamma-hexachlorocyclohexane, one of the endocrine disrupters, widely used for agricultural and medicinal purpose, on apoptosis in PC12 cells were investigated using western blotting analysis and reverse transcriptase-DNA polymerase chain reaction (RT-PCR) method. Apoptosis is a fundamental process necessary for development of individuals and organs. Although gamma -HCH at high concentration did not have an effect on cell viability and apoptosis, DNA fragmentation was slightly enhanced, and apoptotic factors; Bax, Bad, cytochrome c and caspase-3 showed tendency to increase by the addition of a low dose of gamma-HCH to the cell medium. However these changes were not statistically significant. It was concluded that gamma -HCH did not affect on apoptosis in the PC12 cell line system, although gamma -HCH has been reported to induce apoptosis in other cell lines.

Nucleosomal DNA Fragments in Autoimmune Diseases

The inadequate response of immune cells to circulating apoptotic products, such as nucleosomal DNA fragments, is assumed to be a potent stimulus for the production of autoantibodies during the pathogenesis and progression of systemic lupus erythematosus (SLE). Here, we analyzed the levels of circulating nucleosomes, caspases, and C-reactive protein in sera of 244 individuals with various autoimmune diseases (155 with autoimmune hepatic disorders, 25 with ANCA-associated vasculitis, and 64 with various connective tissue diseases), and 32 healthy controls. Nucleosomes and caspase activities were significantly elevated in sera of patients with hepatic autoimmune diseases, connective tissue diseases, and particularly in ANCA-associated vasculitis when compared with healthy individuals. Nucleosomes showed a correlation with caspases, and caspases with C-reactive protein, but nucleosomes did not correlate with C-reactive protein. Serum levels of the apoptotic products, nucleosomes, and caspases are increased in various autoimmune diseases but may not be solely responsible for antinucleosome antibody production in SLE patients. It remains to be clarified whether qualitative changes in nucleosomes are linked with pathogenesis and disease progression in SLE.

Docetaxel induces apoptosis in hormone refractory prostate carcinomas during multiple treatment cycles

Caspase-cleaved proteins are released from disintegrated apoptotic cells and can be detected in the circulation. We here addressed whether caspase-cleaved cytokeratin 18 (CK18-Asp396) can be used as a serum biomarker for assessment of the clinical efficiency of chemotherapy in hormone-refractory prostate cancer (HRPC). A total of 82 patients with HRPC were evaluated during 751 treatment cycles, either with estramustine (EMP)/vinorelbine or with EMP/docetaxel. The levels of CK18-Asp396 and of total CK18 were measured in patient serum before and during therapy by ELISA. Docetaxel induced significant increases in serum CK18-Asp396 (P<0.0001) and total CK18 (P<0.0002), suggesting induction of apoptosis. Similarly, vinorelbine induced increases in both CK18-Asp396 and CK18 (P<0.001 and 0.011). In contrast, EMP induced increases in total serum CK18 (P<0.0001), but not in CK18-Asp396 (P=0.13). The amplitudes of docetaxel-induced increases were associated with baseline prostate-specific antigen (PSA) and CK18 serum levels in these patients, consistent with tumoral origin of caspase-cleaved fragments. Docetaxel induced significant increases in CK18-Asp396 during second-, third- and fourth-line therapy and induced increased levels of CK18-Asp396 during treatment cycles 1–8. In contrast, vinorelbine induced significant increases only during cycles 1–3. In a subgroup of 32 patients that received EMP/vinorelbine in second line followed by EMP/docetaxel in third line, docetaxel induced stronger increases than vinorelbine (P=0.008). These results show that the CK18-Asp396 serum marker can be used to assess tumour apoptosis in vivo and suggest that the clinical efficiency of docetaxel in HRPC is due to induction of apoptosis during multiple treatment cycles.

Caspase activation is required for antiviral treatment response in chronic hepatitis C virus infection

Only half of patients with chronic hepatitis C virus (HCV) infection and genotype-1 show a sustained antiviral response to the current antiviral therapy. The reason this treatment fails is unclear, and no reliable marker exists that predicts the treatment outcome. In the present study, we investigated the apoptotic activation of caspases in HCV patients undergoing antiviral therapy with regard to the treatment outcome. We determined caspase activation in sera from patients who were either responding or nonresponding to antiviral therapy by using two novel caspase assays, an immunological and a luminometric enzyme test. We found that compared with nonresponding individuals, responding patients showed significantly (P < .05) increased caspase activity, which was closely correlated with virus elimination (r = 0.81). The cutoff value of serum caspase activity was determined, which correctly predicted the treatment outcome with a sensitivity of 70% and a specificity of 82% (area under the curve 0.845; 95% CI). In conclusion, hepatic caspase activity might play a role in HCV clearance and could also predict the efficacy of antiviral therapy.

Impaired megakaryocytopoiesis in type 2B von Willebrand disease with severe thrombocytopenia

In type 2B von Willebrand disease, there is spontaneous binding of mutated von Willebrand factor (VWF) multimers to platelets. Here we report a family in which severe thrombocytopenia may also be linked to abnormal megakaryocytopoiesis. A heterozygous mutation in the VWF A1 domain gave a R1308P substitution in an interactive site for glycoprotein Ibalpha (GPIbalpha). Electron microscopy showed clusters of platelets in close contact. Binding of antibodies to the GPIbalpha N-terminal domain was decreased, whereas GPIX and GPV were normally detected. In Western blotting (WB), GPIbalpha, alphaIIb, and beta3 were normally present. Proteins involved in Ca(2+) homeostasis were analyzed by quantitating platelet mRNA or by WB. Plasma membrane Ca(2+) ATPase (PMCA)-4b and type III inositol trisphosphate receptor (InsP(3)-R3) were selectively increased. The presence of degradation products of polyadenosine diphosphate (ADP)-ribose polymerase protein (PARP) suggested ongoing caspase-3 activity. These were findings typical of immature normal megakaryocytes cultured from peripheral blood CD34(+) cells with TPO. Significantly, megakaryocytes from the patients in culture produced self-associated and interwoven proplatelets. Immunolocalization showed VWF not only associated with platelets, but already on the megakaryocyte surface and within internal channels. In this family, type 2B VWD is clearly associated with abnormal platelet production.

Peripheral proteasome and caspase activity in Parkinson disease and Alzheimer disease

BACKGROUND

Defects of the ubiquitin-proteasome (UP) system, a multicatalytic complex degrading polyubiquitinated proteins, may intervene in the pathogenesis of neurodegenerative disorders characterized by intracellular formation of protein aggregates such as Parkinson disease (PD) and Alzheimer disease (AD) by inducing proapoptotic conditions.

METHODS

The authors measured the activity of proteolytic UP core, proteasome 20S, and of proapoptotic caspase-3 and -9 in peripheral blood lymphocytes (PBLs) of PD and AD patients to establish whether changes in these systems are detectable peripherally.

RESULTS

Proteasome 20S activity was reduced in PBLs of treated PD patients vs healthy controls (mean +/- SEM: 1.0 +/- 0.1 vs 2.3 +/- 0.2 nmol 7-amino-4-methylcoumarin (AMC)/10(6) cells, p < 0.001), whereas marked increases in caspase-3 activity (1370 +/- 153 vs 586 +/- 104 pmol AMC/10(6) cells, p < 0.001) and caspase-9 activity (873 +/- 86 vs 304 +/- 27 U/10(6) cells, p < 0.001) were found. Increased caspase-9 activity was also detected in PBLs of untreated PD patients (900 +/- 193 U/10(6) cells). PD duration and severity (Unified Parkinson's Disease Rating Scale score) were inversely correlated with proteasome 20S activity and directly correlated with caspase-3 activity. An inverse correlation was also observed in PD patients between caspase-3 activity and proteasome 20S activity. No significant changes in proteasome 20S or caspase activity or correlations between biochemical and clinical variables were found in patients with AD.

CONCLUSIONS

A decrease in proteasome activity, possibly related to caspase activation, is detectable in peripheral blood lymphocytes of patients with Parkinson disease but not patients with Alzheimer disease, suggesting that these variables may be considered for the development of peripheral biomarkers of Parkinson disease.

Circulating fragmented nucleosomal DNA and caspase-3 mRNA in patients with lymphoma and myeloma

Elevated amounts of cell-free nucleic acids are detected in the circulation of cancer patients. The type and pattern of these may vary depending on the origin. Recently, we described the presence of circulating fragmented nucleosomal DNA. In the present study, our aim was to investigate the association between nucleosomal DNA, caspase-3 expression and circulating caspase-3 mRNA, the primary activator of nucleosomal DNA fragmentation. DNA fragmentation was analyzed by gel electrophoresis, and caspase-3 was analyzed by RT-PCR. Plasma samples from 65% of patients were positive for nucleosomal DNA fragmentation, whereas none of the healthy controls showed DNA fragmentation (P = 0.0004). Expression of caspase-3 differed significantly between the cases and controls (P < 0.0001). However, we observed no direct correlation between nucleosomal DNA fragmentation and caspase-3 expression in lymphocytes (P = 0.145). Circulating plasma caspase-3 mRNA was detected by nested RT-PCR, and no significant difference was observed between the patients and the control group (P = 0.5). Our results indicate that caspase-3 expression is increased in lymphocytes from patients. When compared to healthy individuals, no differences were observed in the amount of circulating mRNA. These findings suggest that nucleosomal DNA fragmentation is not correlated with elevated levels of apoptosis and circulating caspase-3 mRNA in circulating tumor cells.

Effects of oral androstenedione on phospholipid fatty acids, ATP, caspase-3, prostaglandin E(2) and C-reactive protein in serum and livers of pregnant and non-pregnant female rats

Androstenedione, a steroidal dietary supplement taken to enhance athletic performance, could affect serum and liver lipid metabolism, induce liver toxicity or alter inflammatory response depending on dose and duration of exposure. Pregnancy could further exaggerate these effects. To examine this, mature female rats were gavaged with 0, 5, 30 or 60 mg/kg/day androstenedione beginning two weeks prior to mating and continuing through gestation day 19. Non-pregnant female rats were gavaged over the same time frame with 0 or 60 mg/kg/day androstenedione. Serum was collected and livers were removed from dams on gestation day 20 and from non-pregnant rats after 5 weeks of treatment. Androstenedione had no effect on serum total cholesterol, triglycerides or HDL-cholesterol, but significantly decreased C-reactive protein in pregnant rats and prostaglandin E(2) in serum of both pregnant and non-pregnant rats. There were treatment related decreases in liver ATP and, to a lesser degree, caspase-3 and no change in alkaline phosphatase of pregnant female rats. Androstenedione decreased docosahexaenoic acid in both serum and liver phospholipids of pregnant female rats. In conclusion, oral androstenedione did not result in overt hepatotoxicity in pregnant female rats, but produced modest changes in lipid metabolism and may impair regeneration of injured hepatic cells or tissue.

Fas-, caspase 8-, and caspase 3-dependent signaling regulates the activity of the aminophospholipid translocase and phosphatidylserine externalization in human erythrocytes

Apoptosis and erythrocyte senescence share the common feature of exposure of phosphatidylserine (PS) in the outer leaflet of the cells. Western analysis showed that mature red cells contain Fas, FasL, Fas-associated death domain (FADD), caspase 8, and caspase 3. Circulating, aged cells showed colocalization of Fas with the raft marker proteins Galpha(s) and CD59; the existence of Fas-associated FasL, FADD and caspase 8; and caspase 8 and caspase 3 activity. Aged red cells had significantly lower aminophospholipid translocase activity and higher levels of PS externalization in comparison with young cells. In support of our contention that caspases play a functional role in the mature red cell, the oxidatively stressed red cell recapitulated apoptotic events, including translocation of Fas into rafts, formation of a Fas-associated complex, and activation of caspases 8 and 3. These events were independent of calpain but dependent on reactive oxygen species (ROS) as evident from the effects of the ROS scavenger N-acetylcysteine. Caspase activation was associated with loss of aminophospholipid translocase activity and with PS externalization. ROS was not generated by treatment of cells with t-butyl hydroperoxide at 10 degrees C, and Fas did not translocate into rafts. Concomitantly, neither formation of a Fas-associated signaling complex nor caspase activation could be observed, supporting the view that translocation of Fas into rafts was the trigger for the chain of events leading to caspase 3 activation. Our data demonstrate for the first time the novel involvement of Fas/caspase 8/caspase 3-dependent signaling in an enucleated cell leading to PS externalization, a central feature of erythrophagocytosis and erythrocyte biology.

The extent of liver steatosis in chronic hepatitis C virus infection is mirrored by caspase activity in serum

Hepatic steatosis is a frequent histological alteration in chronic hepatitis C virus (HCV) infection that sensitizes the liver to cell injury, inflammation, and fibrosis via unclear mechanisms. Although apoptosis has been implicated in various liver diseases, its importance in HCV-associated steatosis is largely unknown. In this study, we investigated the role of caspases, the key regulators of apoptosis, and employed two novel caspase assays, an immunological and a luminometric enzyme test, to detect hepatic caspase activation in sera from HCV patients with different grades of steatosis. Our data show that increased caspase activation can be found not only in liver biopsies, but also in sera from HCV patients with liver steatosis. Patients with steatosis exhibited significantly higher serum levels of caspase activity compared with normal healthy individuals. Moreover, the extent of steatosis closely correlated with serum caspase activity, whereas in particular in cases of low or moderate steatosis, no correlation was found with aminotransferase levels. In conclusion, apoptotic caspase activation is considerably elevated in HCV-associated steatosis. More importantly, our data imply that measurement of caspase activation might be a sensitive serum biomarker to detect liver steatosis in patients with chronic HCV infection and other liver diseases.

Peroxynitrite induces senescence and apoptosis of red blood cells through the activation of aspartyl and cysteinyl proteases

Changes in the oxidative status of erythrocytes can reduce cell lifetime, oxygen transport, and delivery capacity to peripheral tissues and have been associated with a plethora of human diseases. Among reactive oxygen and nitrogen species of importance in red blood cell (RBC) homeostasis, superoxide and nitric oxide radicals play a key role. In the present work, we evaluated subcellular effects induced by peroxynitrite, the product of the fast reaction between superoxide and nitric oxide. Peroxynitrite induced 1) oxidation of oxyhemoglobin to methemoglobin, 2) cytoskeleton rearrangement, 3) ultrastructural alterations, and 4) altered expression of band-3 and decreased expression of glycophorin A. With respect to control cells, this occurred in a significantly higher percentage of human RBC (approximately 40%). The presence of antioxidants inhibited these modifications. Furthermore, besides these senescence-associated changes, other important modifications, absent in control RBC and usually associated with apoptotic cell death, were detected in a small but significant subset of peroxynitrite-exposed RBC (approximately 7%). Active protease cathepsin E and mu-calpain increased; activation of caspase 2 and caspase 3 was detected; and phosphatidylserine externalization, an early marker of apoptosis, was observed. Conversely, inhibition of cathepsin E, mu-calpain, as well as caspase 2 and 3 by specific inhibitors resulted in a significant impairment of erythrocyte "apoptosis" Altogether, these results indicate that peroxynitrite, a milestone of redox-mediated damage in human pathology, can hijack human RBC toward senescence and apoptosis by a mechanism involving both cysteinyl and aspartyl proteases.

Defective lymphocyte caspase-3 expression in type 1 diabetes mellitus

OBJECTIVE

Activation-induced cell death (AICD) is a major mechanism in the regulation of peripheral tolerance and its impairment can determine the development of autoimmunity. In the present study, in order to evaluate the role of caspase-3 in type 1 diabetes mellitus (T1DM) AICD, caspase-3 expression was analyzed in peripheral blood lymphocytes from 37 new onset T1DM patients and from 36 normal control subjects (NC) in resting conditions and after anti-Fas-triggered apoptosis.

METHODS

Caspase-3 expression was determined by semiquantitative RT-PCR and Western blot. Apoptosis was induced in activated lymphocytes by anti-Fas monoclonal antibody and quantified by flow cytometry and morphological analysis.

RESULTS

Caspase-3 mRNA expression was reduced in resting lymphocytes in 18/37 T1DM patients and in 1/36 NC (P < 0.01). Patients studied for both Fas-mediated AICD and caspase-3 mRNA expression revealed that a reduced caspase-3 mRNA expression in resting lymphocytes occurred in all patients showing resistance to Fas-mediated apoptosis (T1DM vs NC, P < 0.02) with the exception of 3 patients who exhibited normal caspase-3 expression levels. Caspase-3 protein analysis confirmed mRNA data and showed an impaired expression of caspase-3 active form in T1DM subjects compared with NC.

CONCLUSIONS

Our data show that defective expression and function of caspase-3 in peripheral lymphocytes of T1DM patients may contribute to the development of AICD resistance in type 1 diabetes.

Expression of Apoptotic and Antiapoptotic Markers in Epithelial Cells in Idiopathic Pulmonary Fibrosis

STUDY OBJECTIVE

Idiopathic pulmonary fibrosis (IPF) is a chronic, usually fatal lung disease of unknown etiology. A common feature is the presence of microscopic areas of epithelial cell dropout. Increased apoptosis of these cells could elucidate the speculative pathogenesis of the disease. Therefore, the aim of our study was to examine the expression of p53, p21, bcl-2, bax, and caspase-3 in association with DNA strand breaks in bronchial and alveolar epithelial cells in lung specimens from IPF patients and control subjects.

PATIENTS AND METHODS

We examined by immunohistochemistry the expression of p53, p21, bax, bcl-2, and caspase-3 in association with DNA strand breaks detected by terminal deoxynucleotide transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling (TUNEL) in bronchial and alveolar epithelial cells in lung specimens taken by biopsy in 12 IPF patients and 10 control subjects. An independent tissue evaluation by two pathologists graded semiquantatively the degree of staining present.

RESULTS

TUNEL was positive in epithelial cells in all IPF patients and only in one control subject. The expression of p53, p21, bax, and caspase-3 was up-regulated in IPF patients compared to control subjects. Bcl-2 was expressed less in IPF patients than in control subjects.

CONCLUSIONS

These results confirm that apoptotic hyperplastic epithelial cells are present in patients with IPF and that the expression of p53, p21, bax, and caspase-3 appears to be up-regulated and that of bcl-2 down-regulated in these cells. The increased expression of proapoptotic molecules in epithelial cells in IPF may be involved in the inadequate and delayed reepithelialization, which in turn contributes to fibroblast proliferation.

Diabetes enhances apoptosis induced by cerebral ischemia

The aim of this study is to explore the mechanism by which diabetes exaggerates cerebral stroke and its outcome. Since ischemia can be related to not only necrosis but apoptosis as well, we compared the development of apoptosis in STZ-diabetic rats and STZ-diabetic rats subjected to occlusion of the middle cerebral artery (MCA). 24-48 hr following MCA occlusion the animals were killed, the brain removed and prepared for evaluation by several indexes of apoptosis: nucleosomal DNA fragmentation, TUNEL staining, activation of caspase-3 and alteration in the expression of Bax and Bcl2. DNA fragmentation was not detected in the cortex of normal and diabetic animals, but was evident following MCA occlusion in diabetic rats. Bax expression was increased in the cortex of normal rats following MCA occlusion and this expression was further increased in the cortex of MCA occluded diabetic rats. Bcl2 expression was not changed in any of the groups. In the hippocampus, DNA fragmentation was not evident in control rats but was observed in diabetic rats. Ischemic injury did not enhance DNA laddering in diabetic animals. The expression of Bax was increased in diabetic rats but was not increased following MCA occlusion. Bcl2 expression was not changed by ischemia in any of the animal models. These data suggest that diabetes may enhance the development of stroke via increased cortical apoptotic activity but this was not additive in the hippocampus following ischemic injury.

Increased expression and activation of CD30 induce apoptosis in human blood eosinophils

Eosinophils are one of the major effector cells in asthma, and controlling the number and survival of eosinophils might attenuate the severity of asthma. This result could be achieved by inducing eosinophil apoptosis. Apoptosis allows the removal of cells without inducing an inflammatory response. Our knowledge of the factors involved in regulating eosinophil apoptosis remains limited. CD30 molecule has been associated with T cell-negative selection and in TCR-mediated apoptosis. In this study we examined the expression and role of CD30 in apoptosis of human blood eosinophils. Percentage of apoptotic eosinophils was determined by annexin V-propidium iodide labeling, and CD30 expression was examined by flow cytometry. Spontaneous apoptosis was induced by serum deprivation, and survival was conferred by incubating cells with 10% FBS and IL-5. CD30 surface expression was up-regulated in eosinophils incubated for 24 h as compared with freshly isolated eosinophils, and both CD30 expression and eosinophil apoptosis increased in a time-dependent manner. We also measured CD30 mRNA expression by quantitative real-time RT-PCR and determined that CD30 transcripts increased in eosinophils undergoing apoptosis only under serum deprivation conditions. The agonistic CD30 Abs, Ber-H8 and HeFi-1, significantly enhanced eosinophil apoptosis. FBS and IL-5 failed to inhibit or suppress the CD30 agonistic-induced apoptosis. These data support the role of CD30 activation in eosinophil apoptosis. This research will help in furthering our understanding of eosinophil apoptosis and therefore might contribute to the development of better therapeutic modalities in the treatment and/or cure of allergic inflammation in bronchial asthma.

p38-MAPK signals survival by phosphorylation of caspase-8 and caspase-3 in human neutrophils

Neutrophil apoptosis occurs both in the bloodstream and in the tissue and is considered essential for the resolution of an inflammatory process. Here, we show that p38-mitogen-activated protein kinase (MAPK) associates to caspase-8 and caspase-3 during neutrophil apoptosis and that p38-MAPK activity, previously shown to be a survival signal in these primary cells, correlates with the levels of caspase-8 and caspase-3 phosphorylation. In in vitro experiments, immunoprecipitated active p38-MAPK phosphorylated and inhibited the activity of the active p20 subunits of caspase-8 and caspase-3. Phosphopeptide mapping revealed that these phosphorylations occurred on serine-364 and serine-150, respectively. Introduction of mutated (S150A), but not wild-type, TAT-tagged caspase-3 into primary neutrophils made the Fas-induced apoptotic response insensitive to p38-MAPK inhibition. Consequently, p38-MAPK can directly phosphorylate and inhibit the activities of caspase-8 and caspase-3 and thereby hinder neutrophil apoptosis, and, in so doing, regulate the inflammatory response.

Effects of homocysteine on apoptosis-related proteins and anti-oxidant systems in isolated human lymphocytes

Homocysteine (Hcy) is a nonprotein-forming sulphur amino acid that plays an important role in remethylation and trans-sulphuration processes. In recent years, it has been suggested that increased levels of plasma Hcy may play a role in the pathogenesis of various diseases, particularly at the cardiovascular level. The pathogenic mechanism of hyperhomocysteinemia, however, has not been clarified. Because oxygen radicals can be generated by the auto-oxidation of this amino acid, it has been suggested that Hcy may cause cellular damage through oxidative mechanisms, ultimately leading to apoptotic cell death. In this study, we sought to investigate the effects of Hcy on oxidative damage and antioxidant agent levels, as well as on apoptosis-related proteins and apoptosis occurrence in human cells. For this purpose, we measured levels of Bcl-2, caspase-3 and caspase-9 activity, Cu/Zn superoxide dismutase, reduced glutathione, lipid peroxidation [malondialdehyde and 4-hydroxy-2 (E)-nonenal concentrations], apoptotic single-stranded DNA and nuclear changes in human isolated lymphocytes exposed to increasing concentrations of Hcy. Incubation with Hcy did not induce significant changes in any of these biomarkers. Therefore, our results do not support the existence of a direct link between increased levels of Hcy and the occurrence of a pro-apoptotic state mediated by enhanced oxidative stress.

Effect of octreotide on apoptosis-related proteins in rat Kupffer cells: a possible anti-tumour mechanism

BACKGROUND

Octreotide may prolong survival in patients with hepatocellular carcinoma, through an as yet unidentified mechanism. Kupffer cells play a key role in antitumour activity. Kupffer cell apoptosis is of major importance for the maintenance of this antitumour activity.

MATERIALS AND METHODS

We studied the in vitro effects of octreotide in the RNA expression of apoptotic and antiapoptotic proteins in isolated rat Kupffer cells, before and after exposure to lipopolysaccharide (LPS). Apoptotic and antiapoptotic gene expression was assessed using a semi-quantitative multiplex RT-PCR measuring bax, bcl-xS, bcl-2 and bcl-xL. LICE (caspase-3) mRNA was used as a measure of apoptosis.

RESULTS

Unstimulated Kupffer cells exhibited increased proapoptotic gene expression in a time-dependent manner, paralleled by a similar increase of LICE. LPS stimulation decreased the expression of proapoptotic bax and bcl-xS mRNA without effecting the antiapoptotic proteins. A decrease of LICE expression became significant at 48 hours. Octreotide showed a reduction of proapoptotic proteins, accompanied by an early increase and a late reduction of antiapoptotic proteins and a net decrease of LICE expression. A combination of LPS and octreotide produced a similar effect with the exception of a late increase of LICE expression, probably caused by a late increase of bax and bcl-xS.

CONCLUSION

LPS and octreotide reverse the observed increased apoptosis of cultured Kupffer cells by influencing both proapoptotic and antiapoptotic proteins. Therefore, the antitumour effect of octreotide in hepatocellular carcinoma may, in part, be explained by its antiapoptotic effect on Kupffer cells.

Protection against concanavalin A–induced hepatocyte apoptosis by molsidomine is time-dependent

BACKGROUND

Viral hepatitis and autoimmune liver diseases cause hepatocyte apoptosis. Concanavalin A (Con A)-induced hepatitis resembles human viral hepatitis and autoimmune hepatitis. The role of nitric oxide (NO) in liver injury was controversial in different liver injury models. We hypothesize both endogenous and exogenous NO protect liver against Con A-induced liver injury. Molsidomine is metabolized into SIN-1 by the liver, and SIN-1 subsequently generates NO. So, molsidomine was used as a NO donor in this study.

STUDY DESIGN

To study a protective role of endogenous NO in Con A-induced liver injury, mice were pretreated with a specific inducible nitric oxide synthase (iNOS) inhibitor, L-N(6)-(1-iminoethyl)-lysine (L-NIL), before Con A challenge. To study a time-dependent protection against Con A-induced liver injury, animals were either given molsidomine, a NO donor, before or after Con A administration. Serum alanine aminotranferase (ALT) was analyzed. Liver samples were subjected to DNA fragmentation assay, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling stain, Western blot analysis, and caspase activity assays.

RESULTS

Animals pretreated with L-NIL had significantly increased serum ALT levels compared with those challenged with Con A alone; but pretreatment with molsidomine dramatically decreased ALT levels in L-NIL-pretreated animals or in animals that received Con A alone. Administration of molsidomine 30 minutes before or 1, 2, and 3 hours after Con A injection significantly reduced serum ALT levels and attenuated hepatocyte apoptosis from caspase inactivation. The ALT reduction was associated with inhibition of both caspase-3 and caspase-8 activation and reduction of hepatocyte apoptosis.

CONCLUSIONS

Endogenous NO plays an important protective role against Con A-induced liver injury by reducing hepatocyte apoptosis. Administration of a NO donor early after Con A injection protects the liver from injury. This is the first study demonstrating a time-dependent inhibition of liver injury induced by Con A administration.

Decreased levels of CD95 and caspase-8 mRNA in multiple sclerosis patients with gadolinium-enhancing lesions on MRI

Magnetic resonance imaging (MRI) allows examining inflammation and central nervous system (CNS) tissue damage in patients suffering from multiple sclerosis (MS), a demyelinating disease of the CNS. Using real-time PCR, we quantified mRNA levels of apoptosis regulators CD95, CD95 ligand, caspase-8, -10 and cellular FLICE-inhibitory protein (cFLIP), and cytokines IL-10 and TNF-alpha in blood mononuclear cells of MS patients at the time of MRI examination. Patients with detectable gadolinium-enhancing lesions had lower expression of CD95 and caspase-8 (P<0.05). Lesion load and brain atrophy did not correlate with expression levels of any of the target molecules studied. Disease duration correlated positively with both FLIP/caspase-8 and CD95/CD3 ratios (P<0.05). These results support the notion that the CD95-dependent pathway plays a complex role in the regulation of survival of activated immune cells in MS.

[A study on the heterogeneous apoptosis of lymphocytes, eosinophils, and neutrophils from peripheral blood of asthmatic patients]

OBJECTIVES

To observe different responsiveness of lymphocytes, eosinophils, and neutrophils from peripheral blood of asthmatic patients to dexamethasone and montelukast-induced apoptosis and to explore the roles of Fas antigen and caspase-3 in the heterogeneity of cell apoptosis.

METHODS

Lymphocytes, eosinophils, and neutrophils were isolated from peripheral blood of 18 asthmatic patients. Cells were incubated in vitro and treated with dexamethasone and leukotriene receptor antagonist montelukast respectively. Cell apoptosis rates and Fas expression rates were examined by flowcytometry whereas caspase-3 levels in these cells were detected by enzyme linked immunosorbent assay (ELISA).

RESULTS

(1) Apoptosis rates: in vitro lymphocytes, eosinophils and neutrophils were compromised of spontaneous apoptosis at lower rates [(6.9 +/- 0.7)%, (31 +/- 11)% and (32 +/- 30)%, respectively]. With induction of dexamethasone, the apoptosis rates were (17.1 +/- 10.8)%, (44 +/- 22)% and (35 +/- 24)%. Montelukast markedly elevated the apoptosis rates of these three cells [(22.5 +/- 17.6)%, (50 +/- 27)% and (55 +/- 22)%, respectively] (compared to control, P < 0.01, < 0.05, > 0.05, respectively). (2) Fas expression: lymphocytes, eosinophils and neutrophils expressed low levels of Fas antigen at baseline [(1.50 +/- 0.07)%, (2.20 +/- 0.10)% and (1.21 +/- 0.09)%, respectively]. Dexamethasone induced Fas antigen expression levels of these cells of (6.58 +/- 2.10)%, (7.52 +/- 3.20)% and (3.24 +/- 2.34)%, and montelukast induced the expression levels of (5.06 +/- 1.66, 7.45 +/- 2.63, 3.03 +/- 2.47, P < 0.01, < 0.01, > 0.05, respectively). (3) caspase-3 levels: lymphocytes, eosinophils and neutrophils expressed constitutive caspase-3 levels of [(3.3 +/- 2.9) ng/L, (5 +/- 4) ng/L and (4.3 +/- 2.6) ng/L, respectively]. The dexamethasone induced caspase-3 levels were (6.7 +/- 3.1) ng/L, (6 +/- 3) ng/L and (3.1 +/- 1.8) ng/L. The montelukast induced levels were (5.2 +/- 3.7) ng/L, (8 +/- 4) ng/L, and (3.1 +/- 2.0) ng/L (compared to control, P < 0.01, < 0.01, > 0.05, respectively). It was demonstrated that dexamethasone and montelukast significantly induced apoptosis of lymphocytes and eosinophils which were assocreased with increased expression of Fas antigen and caspase-3. Dexamethasone was incapable of inducing neutrophils to apoptosis and had no significant effects on Fas expression and caspase-3 activity. Neutrophils underwent significant apoptosis after montelukast treatment, however, the induction was unlikely to be regulated by Fas and caspase-3 pathway.

CONCLUSIONS

In asthmatic inflammatory modulating and effective cells, neutrophils is distinct from lymphocytes and eosinophils in profile of apoptosis induced by glucocorticoids and leukotriene receptor antagonist. The signal pathway contributing neutrophil apoptosis heterogeneity may involve deficient caspase cascade or Fas/FasL.

Bisindolylmaleimide IX is a potent inducer of apoptosis in chronic lymphocytic leukaemic cells and activates cleavage of Mcl-1

New agents are required for the treatment of chronic lymphocytic leukaemia (CLL). We show here that a protein kinase C inhibitor, bisindolylmaleimide IX, is a potent inducer of apoptosis in CLL cells, and investigate the mechanisms by which this is induced. Bisindolylmaleimide IX induced a conformational change and subcellular redistribution of Bax from the cytosol to the mitochondria, resulting in the release of the proapoptotic mediators cytochrome c, Smac and Omi/HtrA2 from the mitochondrial inner membrane space. This was followed by the activation of caspase-9 as the apical caspase and subsequent activation of effector caspases. CLL cells undergoing apoptosis showed a rapid caspase-mediated cleavage of Mcl-1, an antiapoptotic member of the Bcl-2 family implicated in CLL survival and poor prognosis. This cleavage was mediated primarily by caspase-3. Cleavage of Mcl-1 may provide a feed-forward amplification loop, resulting in the rapid induction of apoptosis. Bisindolylmaleimide IX or a related derivative may be of clinical use in the treatment of CLL.

Apoptotic markers are increased in platelets stored at 37 degrees C

BACKGROUND

PLTs for transfusion lose viability during storage in blood banking. This loss of viability is accelerated at 37 degrees C, as is the risk of bacterial contamination, and has led to the selection of 22 degrees C as the routine storage temperature. Because PLTs contain an intact apoptotic mechanism, we sought to determine whether PLTs undergo apoptosis during storage and whether storage at 37 degrees C accelerated this process.

STUDY DESIGN AND METHODS

PLT-rich plasma from PLT concentrates was stored at 37 or 22 degrees C in small aliquots or whole bags, with and without cell-permeable caspase inhibitors. Number of PLTs, pH, LDH level, and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium activity were analyzed over time. PLT lysates were prepared and tested for the presence and activation of apoptotic proteins by enzyme assay and Western blotting.

RESULTS

PLT viability was greatly reduced after 1 to 2 days of storage at 37 degrees C; however, signs of apoptosis were evident by 3 hours after temperature shift. In temperature-stressed PLTs only, a gradual rise in caspase-3 activity was detected that correlated with the appearance of the 17- to 20-kDa cleavage products of caspase-3. Gelsolin, a caspase-3 substrate, underwent cleavage within the same time frame. Bcl-xL and caspase-2 also declined significantly; caspase-9 activity rose. Specific caspase inhibitors could prevent caspase activation but did not improve PLT cellular viability at 37 degrees C.

CONCLUSIONS

PLTs contain apoptotic proteins that are activated during PLT storage at 37 degrees C and may account for the rapid decline in PLT cellular viability. Although ineffective here, inhibition of PLT apoptosis may improve PLT cellular viability.

Apoptotic neutrophils in the circulation of patients with glycogen storage disease type 1b (GSD1b)

Glycogen storage disease type 1b (GSD1b) is a rare autosomal recessive disorder characterized by hypoglycemia, hepatomegaly, and growth retardation, and associated-for unknown reasons- with neutropenia and neutrophil dysfunction. In 5 GSD1b patients in whom nicotin-amide adenine dinucleotide phosphate-oxidase activity and chemotaxis were defective, we found that the majority of circulating granulocytes bound Annexin-V. The neutrophils showed signs of apoptosis with increased caspase activity, condensed nuclei, and perinuclear clustering of mitochondria to which the proapoptotic Bcl-2 member Bax had translocated already. Granulocyte colony-stimulating factor (G-CSF) addition to in vitro cultures did not rescue the GSD1b neutrophils from apoptosis as occurs with G-CSF-treated control neutrophils. Moreover, the 2 GSD1b patients on G-CSF treatment did not show significantly lower levels of apoptotic neutrophils in the bloodstream. Current understanding of neutrophil apoptosis and the accompanying functional demise suggests that GSD1b granulocytes are dysfunctional because they are apoptotic.

Presentation of nitric oxide regulates monocyte survival through effects on caspase-9 and caspase-3 activation

In the absence of survival factors, blood monocytes undergo spontaneous apoptosis, which involves the activation of caspase-3. Although nitric oxide can block caspase-3 activation and promote cell survival, it can also induce apoptosis. We hypothesized that nitrosothiols that promote protein S-nitrosylation would reduce caspase-3 activation and cell survival, whereas nitric oxide donors (such as 1-propamine 3-(2-hydroxy-2-nitroso-1-propylhydrazine (PAPA) NONOate and diethylamine (DEA) NONOate) that do not target thiol residues would not. Using human monocytes as a model, we observed that nitrosothiol donors S-nitrosoglutathione and S-nitroso-N-acetylpenicillamine suppressed caspase-9 and caspase-3 activity and DNA fragmentation. In contrast, PAPA or DEA NONOate did not promote monocyte survival events and appeared to inhibit monocyte survival induced by macrophage colony-stimulating factor. The caspase-3-selective inhibitor DEVD-fluoromethyl ketone reversed DNA fragmentation events, and the caspase-9 inhibitor LEHD-fluoromethyl ketone reversed caspase-3 activity in monocytes treated with PAPA or DEA NONOate in the presence of macrophage colony-stimulating factor. These results were not caused by differences in glutathione levels or the kinetics of nitric oxide release. Moreover, S-nitrosoglutathione and S-nitroso-N-acetylpenicillamine directly blocked the activity of recombinant caspase-3, which was reversed by the reducing agent dithiothreitol, whereas PAPA or DEA NONOate did not block the enzymatic activity of caspase-3. These data support the hypothesis that nitrosylation of protein thiol residues by nitric oxide is critical for promoting the survival of human monocytes.

Apoptotic activity in stored human platelets

BACKGROUND

Platelets possess some of the machinery required for apoptotic cell death. However, disruption of mitochondria function, implicated in several models of cell death, has not been extensively studied in platelets. Mitochondrial viability and several other measures of apoptotic death in stored and experimentally stressed platelets were evaluated.

MATERIALS AND METHODS

Platelet mitochondrial transmembrane potentials (Deltapsim) were studied by staining platelets with JC-1, a dye that fluoresces at different wavelengths based on the state of mitochondrial polarization. Annexin V binding, a measure of phosphatidylserine (PS) exposure, and CD62P expression, an indicator of platelet activation, were determined by flow cytometry. Caspase-3 activity was measured with an enzyme assay and by Western blotting. Experimental platelet stressors included storage for 7 days, azide exposure, calcium ionophore stimulation, and plasma deprivation.

RESULTS

As measured by flow cytometry, Deltapsim values were similar in freshly drawn platelets and in platelet concentrates stored for up to 7 days. However, compared to fresh platelets, stored platelet concentrates had significantly increased PS exposure (3.1 vs. 5.1%, p = 0.015), CD62P expression (6.5 vs. 13.5%, p = 0.0067), and caspase-3 activity. Azide exposure, which decreased ATP release 20 to 30 percent, did not affect the Deltapsim. Stressed platelets exhibited higher degrees of mitochondrial depolarization in response to calcium ionophore stimulation than platelets that were not stressed. Plasma deprivation also resulted in significant alterations in Deltapsim, PS exposure, and CD62P expression.

CONCLUSIONS

Platelet mitochondria maintain Deltapsim when stored for up to 7 days under standard blood bank storage conditions. Therefore, changes in platelet mitochondria Deltapsim do not correlate with downstream markers of apoptotic death such as caspase activation and PS exposure.

The triterpenoid CDDO induces apoptosis in refractory CLL B cells

Chronic lymphocytic leukemia (CLL) cells develop chemo-resistance over time. Most anticancer agents function through induction of apoptosis, and therefore resistance against these agents is likely to be caused by selection for CLL cells with defects in the particular apoptosis pathway that is triggered by these drugs. Anticancer agents that function through alternative apoptotic pathways might therefore be useful in treating chemo-resistant CLL. Triterpenoids represent a class of naturally occurring and synthetic compounds with demonstrated antitumor activity. We examined the effects of CDDO (triterpenoid 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid) on CLL B cells in vitro. CDDO induced apoptosis in a dose-dependent manner in all (n = 30) CLL samples tested, including previously untreated and chemo-resistant CLL specimens. CDDO induced rapid proteolytic processing of caspase-8, but not caspase-9, in CLL B cells, suggesting activation of a mitochondria-independent pathway. CDDO-induced apoptosis of CLL B cells was blocked by cytokine response modifier A (CrmA), a suppressor of caspase-8, but not by X-linked inhibitor of apoptosis protein-baculovirus IAP repeat-3 (XIAP-BIR3), a fragment of XIAP, which selectively inhibits caspase-9. Examination of CDDO effects on expression of several apoptosis-relevant genes demonstrated significant reductions in the levels of caspase-8 homolog Fas-ligand interleukin-1-converting enzyme (FLICE)-inhibitory protein (c-FLIP), an endogenous antagonist of caspase-8. However, reductions of FLIP achieved by FLIP antisense oligonucleotides were insufficient for triggering apoptosis, indicating that CDDO has other targets in CLL B cells besides FLIP. These data suggest that the synthetic triterpenoid CDDO should be further explored as a possible therapeutic agent for treatment of chemo-resistant CLL.

Modulation of inflammation by vasoactive intestinal peptide and bombesin: lack of effects on neutrophil apoptosis

Inhibition of neutrophil apoptosis has been identified as a prominent feature in chronic inflammation, parenchymal damage, and unresolved organ dysfunction. Lung injury animal models suggest that the neuropeptides vasoactive intestinal peptide and bombesin are protective. Therefore, in vitro effects of VIP and bombesin on apoptosis of normal human neutrophils were tested. For measuring effects on cell survival and apoptosis, trypan dye exclusion, colorimetric MTT assay to assess cell survival, and caspase-3 assay and annexin-V binding for analysing apoptosis rates were used. Foetal calf serum, Fas ligand, and tumour necrosis factor-alpha served as modulatory control agents; survival-promoting and apoptosis-inducing activities of the respective agents were confirmed. Vasoactive intestinal peptide and bombesin, however, failed to significantly affect cell death in neutrophils. Data suggest that direct regulation of neutrophil apoptosis is unlikely to be among the mechanisms of lung-protective actions of VIP and bombesin.

Activation of platelet caspases by TNF and its consequences for kinetics

TNF is known to induce a thrombocytopenia, due to a reduced platelet life span. Injection of TNF (10 microg) to mice did markedly increase the number of platelet-derived microparticles in plasma, most pronounced 1h after injection. Injection of TNF induced a transient activation of platelet caspases, -1, -3, -6, -8, -9, as seen by the binding of caspases probes detected by flow cytometry, most pronounced 1h after injection. Activation of caspase-3 was also evidenced by antibodies. Injection of the caspases inhibitor ZVAD-fmk decreased TNF-induced generation of microparticles and thrombocytopenia, indicating a causal role of caspases in platelet fragmentation. Activation of platelet caspases was also evident in platelets exposed to TNF in vitro, indicating that TNF acts on platelets directly. Comparison of platelets from +/+, TNFR1 -/- and TNFR2 -/- mice showed that caspases are activated mainly by the TNFR1. These observations indicate that TNF activates platelet caspases via the TNFR1, which results in platelet fragmentation and thrombocytopenia.

Granulocytes from patients with paroxysmal nocturnal hemoglobinuria and normal individuals have the same sensitivity to spontaneous apoptosis

OBJECTIVE

The aim of this study was to determine whether granulocytes from patients with paroxysmal nocturnal hemoglobinuria (PNH) are more or less intrinsically sensitive to spontaneous apoptosis than granulocytes from healthy individuals. Resistance to apoptosis has been suggested as an explanation for the proliferation or selection of PNH clones.

PATIENTS AND METHODS

Peripheral blood granulocytes from five patients with PNH, five patients with myelodysplastic syndrome (MDS), and five healthy volunteers were cultured in the absence of serum. Spontaneous apoptosis of the granulocytes was assessed every 6 hours by flow cytometry. The expression levels of CD16b, CD95, and granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor also were studied by flow cytometry, and caspase-3 activity was measured by fluorometry.

RESULTS

There were no significant differences in the proportion or absolute numbers of apoptotic and apoptotic/dead granulocytes between the cells from PNH patients and healthy individuals, whereas those from MDS patients showed significantly lower frequencies of apoptotic granulocytes compared with normal controls. The proportion of CD16b(-) granulocytes was not significantly different among the three groups during in vitro culture. CD95 and GM-CSF receptor was not significantly increased in cultured granulocytes or noncultured granulocytes from, respectively, patients with PNH and normal controls. Caspase-3 activity significantly decreased in cultured granulocytes from MDS patients, but not in granulocytes from PNH patients.

CONCLUSIONS

Granulocytes from PNH patients did not display a reduced sensitivity to spontaneous apoptosis, suggesting that the apoptosis of blood cells in PNH may not be an important factor in proliferation or selection of PNH clones. These findings are in agreement with the normal lifespan of granulocytes in vivo.

Evaluation of oxidative stress during apoptosis and necrosis caused by carbon tetrachloride in rat liver

After 12, 18, and 24 h of oral administration of carbon tetrachloride (as a 1:1 mixture with mineral oil: 4 ml/kg body weight) to rats, the activity of caspase-3-like protease in the liver increased significantly compared to that in the control group that was given mineral oil (4 ml/kg). In plasma, the activity of caspase-3 was barely detectable in the control rat, but increased significantly 24 h after drug administration along with a dramatic increase in glutamate oxaloacetate transaminase. These results indicate that carbon tetrachloride causes apoptosis in the liver by activating caspase-3, which is released to plasma by secondary necrosis. After 18 and 24 h of carbon tetrachloride administration, the liver concentration of hydrophilic vitamin C was decreased significantly, while that of hydrophobic vitamin E was not affected. The plasma concentration of vitamins C and E was not influenced significantly. These results suggest that carbon tetrachloride induces oxidative stress mainly in the aqueous phase of the liver cell.

Change in caspase-3-like protease in the liver and plasma during rat liver regeneration following partial hepatectomy

Recent studies have shown that many factors orchestrate liver regeneration after a two-thirds partial hepatectomy (PH). However, the termination mechanism in liver regeneration has not been thoroughly studied. In this paper, we report that the activity of liver caspase-3-like protease, which is specifically activated in apoptosis, increases 18, 36, and 48 hr after PH during maximal hepatocyte proliferative activity. This is the first study that shows the activation of an apoptosis-executing enzyme during physiological liver regeneration. These results suggest that apoptosis is induced in each surge of DNA synthesis as the termination mechanism. When phenoxybenzamine, an alpha-blocker that has been reported to inhibit DNA synthesis during liver regeneration, was injected 8 hr after PH, the caspase-3-like activity in the liver peaked at 15 hr after PH and the enzyme activity also increased in plasma at 18 and 24 hr after PH in sharp contrast to the case of normal regeneration. These results indicate that extensive apoptosis is caused by phenoxybenzamine and that the secondary necrosis of apoptotic cells results in the increase of caspase-3-like protease activity in the plasma.

The mechanism of apoptosis in human platelets during storage

BACKGROUND

Although it is usually involved only in nucleated cells (NCs), artificially enucleated cells also lose viability by a programmed process of cell death called apoptosis. Because platelets undergo loss of viability during storage, an attempt was made to determine whether platelets contained the apoptotic mechanisms and whether it was activated during platelet storage.

STUDY DESIGN AND METHODS

Platelet viability was measured by reduction of a tetrazolium dye (MTS) and annexin V binding. Members of the death receptor, caspase, and Bcl-2 families were detected by RNase protection assay and Western blotting. Caspase 3 activation was measured by enzyme and Western blot assays and by cleavage of gelsolin.

RESULTS

After 5 days of storage under standard blood banking conditions, platelets display biochemical signs of apoptosis by losing MTS activity and increasing the amount of phosphatidylserine on their surface. The mRNA and the proenzyme for several members of the caspase, death receptor, and Bcl-2 families are expressed at high levels in platelets. An increase in caspase 3 activity and the amount of the biologically active p17 subunit of active caspase 3 were observed to coincide with the appearance of apoptotic markers during storage. These effects were not due to platelet activation. The caspase 3 substrate, gelsolin, began to undergo proteolysis after 3 to 4 days of storage, and the addition of the caspase inhibitor z-VAD-fmt substantially inhibited this process.

CONCLUSION

Platelets contain many of the components of the apoptotic mechanism and show activation of caspase 3 and consequent cleavage of gelsolin during storage, independent of platelet activation. Evaluation of the mechanism of apoptosis in platelets may provide a basis for developing novel strategies to enhance platelet viability during storage.

Functional protection by acute phase proteins alpha(1)-acid glycoprotein and alpha(1)-antitrypsin against ischemia/reperfusion injury by preventing apoptosis and inflammation

BACKGROUND

Ischemia followed by reperfusion (I/R) causes apoptosis, inflammation, and tissue damage leading to organ malfunction. Ischemic preconditioning can protect against such injury. This study investigates the contribution of the acute phase proteins alpha(1)-acid glycoprotein (AGP) and alpha(1)-antitrypsin (AAT) to the protective effect of ischemic preconditioning in the kidney.

METHODS AND RESULTS

Exogenous AGP and AAT inhibited apoptosis and inflammation after 45 minutes of renal I/R in a murine model. AGP and AAT administered at reperfusion prevented apoptosis at 2 hours and 24 hours, as evaluated by the presence of internucleosomal DNA cleavage, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling, and the determination of renal caspase-1- and caspase-3-like activity. AGP and AAT exerted anti-inflammatory effects, as reflected by reduced renal tumor necrosis factor-alpha expression and neutrophil influx after 24 hours. In general, these agents improved renal function. Similar effects were observed when AGP and AAT were administered 2 hours after reperfusion but to a lesser extent and without functional improvement. Moreover, I/R elicited an acute phase response, as reflected by elevated serum AGP and serum amyloid P (SAP) levels after 24 hours, and increased hepatic acute phase protein mRNA levels after 18 hours of renal reperfusion.

CONCLUSIONS

We propose that the antiapoptotic and anti-inflammatory effects of AGP and AAT contribute to the delayed type of protection associated with ischemic preconditioning and other insults. This mechanism is potentially involved in the course of many clinical conditions associated with I/R injury. Moreover, exogenous administration of these proteins may provide new therapeutic means of treatment.

Inhibition of anti-Fas antibody-induced hepatitis by aminoguanidine in mice

Aminoguanidine is an inhibitor of inducible nitric oxide synthase (iNOS) and is of potential clinical usefulness. Treatment of mice with anti-Fas antibodies (150 microg/kg, i.v.) induced elevation of plasma alanine aminotransferase activity at 4 h and this elevation was inhibited by pretreatment of mice with aminoguanidine (3, 10 and 30 mg/kg, i.p.). The anti-Fas antibody-induced elevation of caspase-3 activity was inhibited by aminoguanidine (30 mg/kg, i.p.), but the addition of aminoguanidine to the cytosol up to 10(-4) M did not inhibit the caspase-3 activity in vitro. Thus, aminoguanidine prevents anti-Fas antibody-induced hepatitis by affecting the apoptotic pathway upstream of caspase-3 activation.

Altered caspase expression results in delayed neutrophil apoptosis in acute pancreatitis

Acute pancreatitis (AP) may lead to the development of multiple organ dysfunction syndrome (MODS), especially in severe cases. Resolution of such inflammatory responses is dependent on neutrophil apoptosis. Delays in this apoptotic response are associated with persistent inflammation and subsequent tissue damage. The aim of this study is to determine the effects of AP on neutrophil apoptosis and to investigate the underlying mechanisms involved. Neutrophils and serum were isolated from control (n=10) and from patients with AP (mild, n=35, and severe, n=5). Neutrophil apoptosis was assessed by propidium iodide DNA staining using flow cytometry. Caspase, glutathione-S-transferase (GST), and Mcl-1 protein expression were assessed by SDS-PAGE western blotting. Serum interleukin (IL)-1beta and granulocyte-macrophage colony-stimulating factor (GM-CSF) levels were measured by ELISA. Neutrophils isolated from patients with AP show a significant delay in spontaneous neutrophil apoptosis. Serum factors contributed to this delay with increases in IL-1beta and GM-CSF. Isolated neutrophils were resistant to Fas antibody-induced apoptosis. Caspases represent a central mechanism for spontaneous and Fas antibody-induced neutrophil apoptosis. Procaspase 3 expression was decreased in mild and severe cases, but this effect was independent of serum factors. Increases in GST expression may also contribute to the antiapoptotic effect. Altered caspase expression may represent an additional factor contributing to delayed neutrophil apoptosis. This may contribute to the development of AP and its related complications.

Neutrophil apoptosis is delayed in patients with inflammatory bowel disease

Delayed neutrophil apoptosis is a feature of persistent acute inflammation. Neutrophil-mediated damage has been shown to be associated with the development of inflammatory bowel disease (IBD). Persistence of these cells both at the colonic site and circulation may further contribute to IBD. The aims of this study were to determine whether neutrophils isolated from IBD patients delay apoptosis and to investigate possible mechanisms involved in this delay. We studied 20 patients with IBD, 13 with Crohn's disease, and 7 with ulcerative colitis, all of whom were undergoing intestinal resection for symptomatic disease. Seventeen patients undergoing elective resection of colon cancer acted as operative controls. Systemic, mesenteric arterial, and mesenteric venous blood was harvested. Neutrophils isolated from patients with IBD showed decreased spontaneous apoptosis compared to cancer patients. Mesenteric venous serum of IBD patients contributed to this delay, which contained higher concentrations of interleukin-8 (IL-8). Pro-caspase 3 expression was also reduced in IBD neutrophils, which may contribute to decreased spontaneous and Fas antibody-induced apoptosis. Neutrophil apoptosis may be altered in Crohn's disease and ulcerative colitis through release of anti-apoptotic cytokines and altered caspase expression. The alterations in cell death mechanisms may lead to persistence of the inflammatory response associated with IBD.

Increase of caspase-3 activity in rat liver and plasma by thioacetamide

Twelve and twenty-four hours after intraperitoneal administration of thioacetamide (200 mg/kg body weight) to rats, caspase-3 activity in the liver and plasma of the treated rats increased significantly compared with that of the control group. These results demonstrated that thioacetamide caused apoptosis, which involved activation of caspase-3, although there may be a number of pathways to apoptosis in the liver that may or may not involve the activation of this protein. The results also indicated that the activated caspase-3 was released in plasma along with glutamate-oxaloacetate transaminase (GOT) by successive necrosis. This is the first study that shows an increase of caspase-3 activity in plasma.

Caspase 2 and caspase 3 as predictors of complete remission and survival in adults with acute lymphoblastic leukemia

Dysregulation of apoptosis is an important mechanism in leukemogenesis. Caspases are cysteine proteases that play a major role in the activation of apoptotic pathways and chemotherapy-induced cell death. High levels of inactive, uncleaved caspase 2 and caspase 3 have recently been associated with poor survival in patients with acute myelogenous leukemia. We hypothesized a similarly significant role for caspase 2 and caspase 3 in patients with acute lymphoblastic leukemia. We determined levels of uncleaved caspase 2 and caspase 3 by quantitative Western blot analysis in peripheral blood samples of 45 adults with newly diagnosed ALL. We evaluated patient prognostic variables and caspase levels using multivariate logistic and Cox regression models to determine their impact on complete remission rate and overall survival probability. Levels of caspase 2 and, to a lesser degree, caspase 3 were highly associated with cytogenetic abnormalities, with lower levels in the diploid group (P = 0.016 and P = 0.10, respectively). No association between either caspase level and the percentage of bone marrow blasts was found. A high level of caspase 3 (>0.37 as determined graphically) was significantly associated with achieving complete remission (CR; P = 0.006). A multivariate logistic regression analysis including age, WBC count, percentage of peripheral and marrow blasts, hemoglobin, albumin, lactate dehydrogenase, bilirubin, and creatinine determined that a high level of caspase 3 was the most significant predictor of CR (P = 0.025, adjusted), with albumin the only other significant variable (P = 0.031). Caspase 2 levels were not associated with probability of CR. In a multivariate Cox model for survival, however, levels of caspase 2 above 0.37 were associated with a lower survival probability than were levels below that threshold (P = 0.064). High levels of caspase 3 may have a significant effect on achieving CR. Because of the limited power (n = 45) of our study, the significance of caspase 2 and caspase 3 on overall survival remains to be validated by further investigations.

Spontaneous human monocyte apoptosis utilizes a caspase-3-dependent pathway that is blocked by endotoxin and is independent of caspase-1

Apoptosis is an important mechanism for regulating the numbers of monocytes and macrophages. Caspases (cysteine-aspartate-specific proteases) are key molecules in apoptosis and require proteolytic removal of prodomains for activity. Caspase-1 and caspase-3 have both been connected to apoptosis in other model systems. The present study attempted to delineate what role these caspases play in spontaneous monocyte apoptosis. In serum-free conditions, monocytes showed a commitment to apoptosis as early as 4 h in culture, as evidenced by caspase-3-like activity. Apoptosis, as defined by oligonucleosomal DNA fragmentation, was prevented by a generalized caspase inhibitor, z-VAD-FMK, and the more specific caspase inhibitor, z-DEVD-FMK. The caspase activity was specifically attributable to caspase-3 by the identification of cleavage of procaspase-3 to active forms by immunoblots and by cleavage of the fluorogenic substrate DEVD-AFC. In contrast, a caspase-1 family inhibitor, YVAD-CMK, did not protect monocytes from apoptosis, and the fluorogenic substrate YVAD-AFC failed to show an increase in activity in apoptotic monocytes. When cultured with LPS (1 microgram/ml), monocyte apoptosis was prevented, as was the activation of caspase-3. Unexpectedly, LPS did not change baseline caspase-1 activity. These findings link spontaneous monocyte apoptosis to the proteolytic activation of caspase-3.

Role of caspase in a subset of human platelet activation responses

Platelets function to protect the integrity of the vascular wall. A subset of platelet activation responses that are especially important for thrombus formation include exposure of phosphatidylserine and release of microparticles, which generate procoagulant surfaces. The resemblance of these platelet activation processes to events occurring in nucleated cells undergoing apoptosis suggests a possible role for caspases, which are major effector enzymes of nucleated cell apoptosis. We demonstrate here the presence of caspase-3 in human platelets and its activation by physiological platelet agonists. Using cell-permeable specific inhibitors, we demonstrate a role for a caspase-3-like protease in the agonist-induced (collagen plus thrombin or Ca2+ ionophore) platelet activation events of phosphatidylserine exposure, microparticle release, and cleavage of moesin, a cytoskeletal-membrane linker protein. The role of caspase-3 in platelet activation is restricted rather than global, because other activation responses, alpha granule secretion, shape change, and aggregation were unaffected by caspase-3 inhibitors. Experiments with two classes of protease inhibitors show that caspase-3 function is distinct from that of calpain, which is also involved in late platelet activation events. These findings show novel functions of caspase and provide new insights for understanding of platelet activation.

Bcl-Xl- and Bax-alpha-mediated regulation of apoptosis of human neutrophils via caspase-3

In this study, a mechanism is reported which determines the lifetime of polymorphonuclear neutrophils (PMN). In human PMN freshly isolated from the circulation, expression of bcl-Xl, bax-alpha, and bak, members of the bcl-2 family of apoptosis-associated genes, was found using the reverse transcription-polymerase chain reaction technique. In contrast, no expression of bcl-2 was seen in PMN, whereas the myeloid cell line HL-60 was positive for bcl-2 mRNA. Two gene products, Bcl-Xl and Bax-alpha, which are known to function as the regulatory machinery of programmed cell death (apoptosis), were detected at the protein level in PMN. Moreover, differential expression of these proteins was found upon induction or prevention of apoptosis by cytokines: Whereas induction of apoptosis by tumor necrosis factor-alpha was associated with a reduction of expression of the anti-apoptotic Bcl-Xl protein, prevention of apoptosis by granulocyte-macrophage colony-stimulating factor led to a downregulation of expression of the death-promoting Bax-alpha protein. This shift of balance of anti- and pro-apoptotic proteins was found to control caspase-3 activity which, in turn, downregulated Bcl-Xl expression in PMN undergoing apoptosis. Thus, cytokines can affect the ratio of Bax-alpha/Bcl-Xl expression in human PMN and modulate the subsequent activity of caspase-3, which functions as executer of the programmed cell death and may promote apoptosis by a positive feed-forward mechanism that downregulates Bcl-Xl.

Caspase 2 and caspase 3 protein levels as predictors of survival in acute myelogenous leukemia

Because caspase activation is an essential step in programmed cell death (apoptosis) and cytotoxic drug-induced apoptosis is mediated by caspase 2 and caspase 3, we hypothesized that caspase 2 and 3 levels predict clinical outcome in acute myelogenous leukemia (AML). Using quantitative Western blot analysis, we studied the levels of nonactivated (uncleaved) caspase 2 and 3 in peripheral blood low-density cells from 185 patients with newly diagnosed AML. We also measured the level of activated (cleaved) caspase 3 in 41 randomly selected samples from the 185 patients. Finally, we analyzed the effect of caspase 2 and 3 levels and other prognostic variables on patient survival using a multivariate Cox model. We found that median levels of nonactivated caspase 2 and 3 were higher in AML than in normal peripheral blood cells (P < .001 and P <.02, respectively). There was no association between caspase level and either the percentage of peripheral blasts or any specific type of leukemia cell cytogenetic abnormalities. When the effect of each uncleaved caspase was considered individually, a high level of uncleaved caspase 3 (P = .04), but not of caspase 2 (P = .16), was associated with decreased survival. Conversely, a high level of cleaved caspase 3 denoted improved survival and correlated with the inactivation of the DNA-repair enzyme poly(ADP-ribose) polymerase. Thus, cleaved caspase 3 could stimulate the apoptotic cascade further, and lack of its activation likely caused an accumulation of the uncleaved caspase. Although uncleaved caspase 2 level per se had no prognostic significance, the interactive effect of high levels of both uncleaved caspase 2 and 3 denoted very poor survival (P < .001) and had the largest effect of all prognostic variables (P < .001; estimated relative risk, 2.49; 95% confidence interval, 1.59 to 3. 90). Taken together, caspase 2 and caspase 3 protein levels obtained at diagnosis may constitute a reliable prognostic factor in AML.

Are caspases involved in the death of cells with a transcriptionally inactive nucleus? Sperm and chicken erythrocytes

We show that mouse sperm die spontaneously within 1–2 days in culture and that treatment with either staurosporine (STS) and cycloheximide (CHX) or a peptide caspase inhibitor does not accelerate or delay the cell death. Chicken erythrocytes, by contrast, are induced to die by either serum deprivation or treatment with STS and CHX, and embryonic erythrocytes are more sensitive than adult erythrocytes to both treatments. Although these erythrocyte deaths display a number of features that are characteristic of apoptosis, they are not blocked, or even delayed, by peptide caspase inhibitors, and most of the cells die without apparently activating caspases. A small proportion of the dying erythrocytes do activate caspase-3, but even these cells, which seem to be the least mature erythrocytes, die just as quickly in the presence of caspase inhibitors. Our findings raise the possibility that both mouse sperm and chicken erythrocytes have a death programme that may not depend on caspases and that chicken erythrocytes lose caspases as they mature. Chicken erythrocytes may provide a useful ‘stripped down’ cell system to try to identify the protein components of such a death programme, which may serve to back-up the conventional caspase-dependent suicide mechanism in many cell types.