Caspase-3 is required for alpha-fodrin cleavage but dispensable for cleavage of other death substrates in apoptosis

Systemic response to Campylobacter jejuni infection by profiling gene transcription in the spleens of two genetic lines of chickens

Campylobacter jejuni (C. jejuni) is a leading cause of human bacterial enteritis worldwide with poultry products being a major source of C. jejuni contamination. The chicken is the natural reservoir of C. jejuni where bacteria colonize the digestive tract of poultry, but rarely cause symptoms of disease. To understand the systemic molecular response mechanisms to C. jejuni infection in chickens, total splenic RNA was isolated and applied to a whole genome chicken microarray for comparison between infected (I) and non-infected (N) chickens within and between genetic lines A and B. There were more total splenic host genes responding to the infection in resistant line A than in susceptible line B. Specifically, genes for lymphocyte activation, differentiation and humoral response, and Ig light and heavy chain were upregulated in the resistant line. In the susceptible line, genes for regulation of erythrocyte differentiation, hemopoiesis, and RNA biosynthetic process were all downregulated. An interaction analysis between genetic lines and treatment demonstrated distinct defense mechanisms between lines: the resistant line promoted apoptosis and cytochrome c release from mitochondria, whereas the susceptible line responded with a downregulation of both functions. This was the first time that such systemic defensive mechanisms against C. jejuni infection have been reported. The results of this study revealed novel molecular mechanisms of the systemic host responses to C. jejuni infection in chickens that warrant further investigation.

Deferasirox protects against iron-induced hepatic injury in Mongolian gerbil

Iron overload is associated with an increased risk of liver complications including fibrosis, cirrhosis, and hepatocellular carcinoma. Deferasirox is a new oral chelator with high iron-binding potency and selectivity. Here we investigate the ability of deferasirox to remove excessive hepatic iron and prevent iron-induced hepatic injury. Adult male Mongolian gerbils were divided into 3 groups (n=5/group)-control, iron overload (100 mg iron-dextran/kg body weight/5 days; intraperitoneal for 10 weeks), and iron overload followed by deferasirox treatment (100 mg deferasirox/kg body weight/d; pulse oral for 1 or 3 months). Compared with the nontreated iron overload group, deferasirox reduced hepatic iron concentration by 44% after 3 months of treatment (P<0.05). Histological analysis of hepatic tissue from the iron overloaded group detected frequent iron deposition, evidence of hepatic damage, and an accumulation of lipid vacuoles. Iron deposition was significantly diminished with deferasirox treatment, and no evidence of lipid accumulation was observed. Immunoblotting demonstrated that iron overload caused approximately 2-fold increase in hepatic ferritin expression (P<0.05), which was 48% lower after 3 months of deferasirox treatment (P<0.05). Deferasirox treatment also was associated with reduced hepatic protein oxidation, superoxide abundance, and cell death. The percentage of terminal deoxynucleotidyl transferase dUTP nick end labeling positive cells in the deferasirox-treated livers was 41% lower than that of iron overloaded group (P<0.05). Similarly, an iron-related increase in the expression of Bax/Bcl2, Bad, and caspase-3 were significantly lower after deferasirox treatment. These findings suggest that deferasirox may confer protection against iron-induced hepatic toxicity.

Emerging roles of DNA-PK besides DNA repair

The DNA-dependent protein kinase (DNA-PK) is a DNA-activated serine/threonine protein kinase, and abundantly expressed in almost all mammalian cells. The roles of DNA-PK in DNA-damage repair pathways, including non-homologous end-joining (NHEJ) repair and homologous recombinant (HR) repair, have been studied intensively. However, the high levels of DNA-PK in human cells are somewhat paradoxical in that it does not impart any increased ability to repair DNA damage. If DNA-PK essentially exceeds the demand for DNA damage repair, why do human cells universally express such high levels of this huge complex? DNA-PK has been recently reported to be involved in metabolic gene regulation in response to feeding/insulin stimulation; our studies have also suggested a role of DNA-PK in the regulation of the homeostasis of cell proliferation. These novel findings expand our horizons about the importance of DNA-PK.

IL-16 effects on A549 lung epithelial cells: dependence on CD9 as an IL-16 receptor?

Interleukin-16 (IL-16) is a pro-inflammatory cytokine released by many types of cells found in the lungs, including normal airway and alveolar epithelial cells. Though a chemotactin for CD4(+) cells and eosinophils, IL-16 also modulates their production of factors that influence inflammatory lung diseases, e.g., asthma and allergic rhinitis. To date, little is known about any potential autocrine-like regulatory effects of IL-16. Using a model human alveolar basal epithelial A549 cell line, the present study sought to assess lung epithelial cell responses to IL-16. Potential induced effects on cell growth/function were assessed using MTT reduction, lactate dehydrogenase release, and 5-bromo-2-deoxyuridine incorporation assays. As IL-16 (at locally high levels) can induce CD4(+) cell death via apoptosis, this potential outcome among the A549 cells was also evaluated using TUNEL and changes in expression of caspase-3 and the pro-apoptotic and anti-apoptotic proteins of Bcl-2 family. The data here indicated that IL-16 inhibited A549 cell growth/function and this was associated with a marked increase in apoptosis characterized by DNA fragmentation, activation of caspase-3, and altered pro-apoptotic protein expression. Since lung epithelial cells lack the CD4 that may bind IL-16, it has been suggested that CD9 may act as an alternate receptor for this cytokine (i.e., an IL-16R). Thus, these studies also sought to determine the extent of CD9 expression on A549 cells and if any/all observed IL-16-induced changes were mediated by CD9. Flow cytometric analyses revealed the cells to be CD9(+)CD4(-). However, neutralization of the purported IL-16R with anti-CD9 antibody could not block the cytotoxic/growth inhibiting effects of IL-16. The only exception appeared to be a mitigation of a chemotactic effect of IL-16; however, studies with an equal amount of non-specific antibody (of same isotype as the anti-CD9) revealed this effect to be artefactual. The neutralization study results thus suggest to us that as-yet undefined pathway(s) exist through which IL-16 may act to exert growth inhibiting/apoptosis-inducing effects on A549 cells, a cell line routinely used as a model for lung epithelial cells.

Trophoblast fusion

The villous trophoblast of the human placenta is the epithelial cover of the fetal chorionic villi floating in maternal blood. This epithelial cover is organized in two distinct layers, the multinucleated syncytiotrophoblast directly facing maternal blood and a second layer of mononucleated cytotrophoblasts. During pregnancy single cytotrophoblasts continuously fuse with the overlying syncytiotrophoblast to preserve this end-differentiated layer until delivery. Syncytial fusion continuously supplies the syncytiotrophoblast with compounds of fusing cytotrophoblasts such as proteins, nucleic acids and lipids as well as organelles. At the same time the input of cytotrophoblastic components is counterbalanced by a continuous release of apoptotic material from the syncytiotrophoblast into maternal blood. Fusion is an essential step in maintaining the syncytiotrophoblast. Trophoblast fusion was shown to be dependant on and regulated by multiple factors such as fusion proteins, proteases and cytoskeletal proteins as well as cytokines, hormones and transcription factors. In this chapter we focus on factors that may be involved in the fusion process of trophoblast directly or that may prepare the cytotrophoblast to fuse.

Iron-induced cardiac damage: role of apoptosis and deferasirox intervention

Excess cardiac iron levels are associated with cardiac damage and can result in increased morbidity and mortality. Here, we hypothesize that elevations in tissue iron can activate caspase-dependent signaling, which leads to increased cardiac apoptosis and fibrosis, and that these alterations can be attenuated by iron chelation. Using an iron-overloaded gerbil model, we show that increased cardiac iron is associated with reduced activation of Akt (Ser473 and Thr308), diminished phosphorylation of the proapoptotic regulator Bad (Ser136), and an increased Bax/Bcl-2 ratio. These iron-overload-induced alterations in Akt/Bad phosphorylation and Bax/Bcl-2 ratio were coupled with increased activation of the downstream caspase-9 (40/38- and 17-kDa fragments) and apoptosis executioner caspase-3 (19- and 17-kDa fragments), which were accompanied by evidence of elevated cytoskeletal α-fodrin cleavage (150- and 120-kDa fragments), discontinuity of myocardial membrane dystrophin immunoreactivity, increases in the number of terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive cells (nucleic DNA fragmentation), and cardiac fibrosis. We demonstrate that the administration of deferasirox, a tridentate iron chelator, is associated with diminished tissue iron deposition, attenuated activation of caspases, reduced α-fodrin cleavage, improved membrane integrity, decreased TUNEL reactivity, and attenuated cardiac fibrosis. These results suggest that the activation of caspase-dependent signaling may play a role in the development of iron-induced cardiac apoptosis and fibrosis, and deferasirox, via a reduction in cardiac tissue iron levels, may be useful for decreasing the extent of iron-induced cardiac damage.

Melody, an ENU mutation in Caspase 3, alters the catalytic cysteine residue and causes sensorineural hearing loss in mice

Progeny from the Harwell N-ethyl-N-nitrosourea (ENU) recessive mutagenesis screen were assessed for auditory defects. A pedigree was identified with multiple progeny lacking response to a clickbox test. Auditory brainstem response (ABR) analysis showed that homozygous mutant mice were profoundly deaf and the line was named melody. We subsequently mapped this mutation to a 6-Mb region on chromosome 8 and identified a point mutation in melody that results in a C163S substitution in the catalytic site of Caspase 3, a cysteine protease involved in apoptosis. Melody fails to complement a null Caspase-3 mutant. Scanning electron microscopy (SEM) has revealed disorganised sensory hair cells and hair cell loss. Histological analysis of melody has shown degeneration of spiral ganglion cells in homozygote mice, with a gradient of severity from apical to basal turns. Melody heterozygotes also show evidence of loss of spiral ganglion neurons, suggesting that the C163S mutation may show dominant negative effects by binding and sequestering proteins at the active site. The melody line provides a new model for studying the role of Caspase 3 in deafness and a number of other pathways and systems.

The release of high mobility group box 1 in apoptosis is triggered by nucleosomal DNA fragmentation

High mobility group box 1 (HMGB1) initially identified as a non-histone chromosomal protein, which mainly functions as chromatin structure and transcriptional regulation, has been recently reported to be secreted into extracellular milieu in necrosis and apoptosis, and act as a proinflammatory mediator. However, the mechanism by which apoptotic cells release HMGB1 is not clear. In this study, we found that staurosporine (apoptosis-inducer)-induced HMGB1 release was associated with nucleosomal DNA fragmentation catalyzed by caspase-activated DNase (CAD) in WEHI-231 cells. Importantly, this event was effectively attenuated by the treatment of a pan-caspase inhibitor, Z-VAD-fmk, and by the inhibition of CAD-mediated DNA fragmentation by the expression of caspase-resistant inhibitor of CAD (ICAD-CR). In WEHI-231/ICAD-CR and WEHI-231/Puro cells, DNase γ-catalyzed nucleosomal DNA fragmentation occurred by anti-IgM antibody treatment was critical for HMGB1 release. Furthermore, in DNase γ stably-expressing HeLa S3 cells (HeLa S3/γ), the release of HMGB1 accompanied with nucleosomal DNA fragmentation was more apparent than that in parental HeLa S3 cells in which DNA fragmentation was scarcely observed. Taken together, these date suggest that nucleosomal DNA fragmentation catalyzed by CAD or DNase γ plays a pivotal role in HMGB1 release.

Multifunctional roles of gelsolin in health and diseases

Gelsolin, a Ca(2+) -regulated actin filament severing, capping, and nucleating protein, is an ubiquitous, multifunctional regulator of cell structure and metabolism. More recent data show that gelsolin can act as a transcriptional cofactor in signal transduction and its own expression and function can be influenced by epigenetic changes. Here, we review the functions of the plasma and cytoplasmic forms of gelsolin, and their manifold impacts on cancer, apoptosis, infection and inflammation, cardiac injury, pulmonary diseases, and aging. An improved understanding of the functions and regulatory mechanisms of gelsolin may lead to new considerations of this protein as a potential biomarker and/or therapeutic target.

Substituted E-3-(3-indolylmethylene)-1,3-dihydroindol-2-ones with antitumor activity. In depth study of the effect on growth of breast cancer cells

The synthesis of new substituted E-3-(3-indolylmethylene)-1,3-dihydroindol-2-ones is reported. The antitumor activity was evaluated according to protocols available at the National Cancer Institute (NCI), Bethesda, MD. Structure-activity relationships are discussed. The action of selected compounds was investigated in MCF-7 breast cancer cells. The ability of these derivatives to inhibit cellular proliferation was accompanied by increased level of p53 and its transcriptional targets p21 and Bax, interference in the cell cycle progression with cell accumulation in the G2/M phase, and activation of apoptosis.

Recombinant analogs of a novel milk pro-apoptotic peptide, lactaptin, and their effect on cultured human cells

We recently isolated and characterized a human milk peptide, lactaptin, which induced apoptosis of cultured human MCF-7 cells. Lactaptin was identified as a proteolytic fragment of human kappa-casein. Here, we generated two recombinant analogs of the peptide, RL1 and RL2, containing truncated and complete amino acid sequences of lactaptin, respectively. Analogs were produced in E.coli, purified and assayed for biological activity on cultured human MCF-7 cells. RL1 was shown to induce only a small decrease in cell viability, whereas RL2 lowered the viability of MCF-7 cells by 60%. This reduction in MCF-7 cell viability was associated with apoptosis, which was indicated by phosphatidilserine externalization and caspase-7 activation. The viability of A549 and Hep-2 cells was also reduced by RL2, albeit to a lesser degree than seen with MCF-7 cells; this reduced viability was not accompanied by apoptosis. Non-malignant human mesenchymal stem cells (MSC) were completely resistant to RL2 action.

Multifunctional nanoparticles delivering small interfering RNA and doxorubicin overcome drug resistance in cancer

Drug resistance is a major challenge to the effective treatment of cancer. We have developed two nanoparticle formulations, cationic liposome-polycation-DNA (LPD) and anionic liposome-polycation-DNA (LPD-II), for systemic co-delivery of doxorubicin (Dox) and a therapeutic small interfering RNA (siRNA) to multiple drug resistance (MDR) tumors. In this study, we have provided four strategies to overcome drug resistance. First, we formed the LPD nanoparticles with a guanidinium-containing cationic lipid, i.e. N,N-distearyl-N-methyl-N-2-(N'-arginyl) aminoethyl ammonium chloride, which can induce reactive oxygen species, down-regulate MDR transporter expression, and increase Dox uptake. Second, to block angiogenesis and increase drug penetration, we have further formulated LPD nanoparticles to co-deliver vascular endothelial growth factor siRNA and Dox. An enhanced Dox uptake and a therapeutic effect were observed when combined with vascular endothelial growth factor siRNA in the nanoparticles. Third, to avoid P-glycoprotein-mediated drug efflux, we further designed another delivery vehicle, LPD-II, which showed much higher entrapment efficiency of Dox than LPD. Finally, we delivered a therapeutic siRNA to inhibit MDR transporter. We demonstrated the first evidence of c-Myc siRNA delivered by the LPD-II nanoparticles down-regulating MDR expression and increasing Dox uptake in vivo. Three daily intravenous injections of therapeutic siRNA and Dox (1.2 mg/kg) co-formulated in either LPD or LPD-II nanoparticles showed a significant improvement in tumor growth inhibition. This study highlights a potential clinical use for the multifunctional nanoparticles with an effective delivery property and a function to overcome drug resistance in cancer. The activity and the toxicity of LPD- and LPD-II-mediated therapy are compared.

Activation of B cell apoptotic pathways in the course of Francisella tularensis infection

Francisella tularensis is a facultative intracellular, gram-negative bacterium that induces apoptosis in macrophages and B cells. Here we show apoptotic pathways that are activated in the Ramos human B cell line in the course of F. tularensis infection. Live bacteria F. tularensis FSC200 activate caspases 8, 9 and 3, as well as Bid; release cytochrome c and apoptosis-inducing factor from mitochondria; and induce depolarization of mitochondrial membrane potential in the Ramos cell line, thus leading these cells to apoptosis. Unlike live bacteria, killed F. tularensis FSC200 bacteria activated only caspase 3, and did not cause apoptosis of Ramos cells as measured by annexin V. Killed bacteria also caused accumulation of anti-apoptotic protein Bclx(L) in mitochondrial membranes. Thus, live F. tularensis activates both caspase pathways (receptor-mediated and intrinsic) as well as caspase-independent mitochondrial death.

Targeting activated integrin alphavbeta3 with patient-derived antibodies impacts late-stage multiorgan metastasis

Advanced metastatic disease is difficult to manage and specific therapeutic targets are rare. We showed earlier that metastatic breast cancer cells use the activated conformer of adhesion receptor integrin alphavbeta3 for dissemination. We now investigated if targeting this form of the receptor can impact advanced metastatic disease, and we analyzed the mechanisms involved. Treatment of advanced multi-organ metastasis in SCID mice with patient-derived scFv antibodies specific for activated integrin alphavbeta3 caused stagnation and regression of metastatic growth. The antibodies specifically localized to tumor lesions in vivo and inhibited alphavbeta3 ligand binding at nanomolar levels in vitro. At the cellular level, the scFs associated rapidly with high affinity alphavbeta3 and dissociated extremely slowly. Thus, the scFvs occupy the receptor on metastatic tumor cells for prolonged periods of time, allowing for inhibition of established cell interaction with natural alphavbeta3 ligands. Potential apoptosis inducing effects of the antibodies through interaction with caspase-3 were studied as potential additional mechanism of treatment response. However, in contrast to a previous concept, neither the RGD-containing ligand mimetic scFvs nor RGD peptides bound or activated caspase-3 at the cellular or molecular level. This indicates that the treatment effects seen in the animal model are primarily due to antibody interference with alphavbeta3 ligation. Inhibition of advanced metastatic disease by treatment with cancer patient derived single chain antibodies against the activated conformer of integrin alphavbeta3 identifies this form of the receptor as a suitable target for therapy.

Quercetin protects rat liver against lead-induced oxidative stress and apoptosis

Quercetin, a flavonoid, effectively improved the lead-induced histology changes including structure damage and leukocyte infiltration in rat liver. The present study was designed to explore the protective mechanism of quercetin against lead-induced hepatic injury. We found that quercetin markedly decreased the MDA and H(2)O(2) levels and lowered the GSH/GSSG ratio in the liver of lead-treated rat. Moreover, quercetin markedly restored Cu/Zn-SOD, Mn-SOD, CAT and GPx activities and upregulated mRNA expression levels of these proteins in the liver of lead-treated rat. Western blot analysis showed that quercetin significantly inhibited apoptosis by modulating the ratio of Bax to Bcl-2 expression and suppressing the expression of phosphorylated JNK1/2 and cleaved caspase-3 in the liver of lead-treated rat. In conclusion, these data suggest that quercetin protects the rat liver from lead-induced injury by attenuating lipid peroxidation, renewing the activities of antioxidant enzymes and inhibiting apoptosis.

Aggregation of spectrin and PKCtheta is an early hallmark of fludarabine/mitoxantrone/dexamethasone-induced apoptosis in Jurkat T and HL60 cells

It has been shown that changes in spectrin distribution in early apoptosis preceded changes in membrane asymmetry and phosphatidylserine (PS) exposure. PKCtheta was associated with spectrin during these changes, suggesting a possible role of spectrin/PKCtheta aggregation in regulation of early apoptotic events. Here we dissect this hypothesis using Jurkat T and HL60 cell lines as model systems. Immunofluorescent analysis of alphaIIbetaII spectrin arrangement in Jurkat T and HL60 cell lines revealed the redistribution of spectrin and PKCtheta into a polar aggregate in early apoptosis induced by fludarabine/mitoxantrone/dexamethasone (FND). The appearance of an alphaIIbetaII spectrin fraction that was insoluble in a non-ionic detergent (1% Triton X-100) was observed concomitantly with spectrin aggregation. The changes were observed within 2 h after cell exposure to FND, and preceded PS exposure. The changes seem to be restricted to spectrin and not to other cytoskeletal proteins such as actin or vimentin. In studies of the mechanism of these changes, we found that (i) neither changes in apoptosis regulatory genes (e.g., Bcl-2 family proteins) nor changes in cytoskeleton-associated proteins were detected in gene expression profiling of HL60 cells after the first hour of FND treatment, (ii) caspase-3, -7, -8, and -10 had minor involvement in the early apoptotic rearrangement of spectrin/PKCtheta, and (iii) spectrin aggregation was shown to be partially dependent on PKCtheta activity. Our results indicate that spectrin/PKCtheta aggregate formation is related to an early stage in drug-induced apoptosis and possibly may be regulated by PKCtheta activity. These findings indicate that spectrin/PKCtheta aggregation could be considered as a hallmark of early apoptosis and presents the potential to become a useful diagnostic tool for monitoring efficiency of chemotherapy as early as 24 h after treatment.

Possible molecular mechanisms underlying age-related cardiomyocyte apoptosis in the F344XBN rat heart

Despite advances in treatment, age-related cardiac dysfunction still remains a leading cause of cardiovascular death. Recent data have suggested that increases in cardiomyocyte apoptosis may be involved in the pathological remodeling of heart. Here, we examine the effects of aging on cardiomyocyte apoptosis in 6-, 30-, and 36-month-old Fischer344 x Brown Norway F1 hybrid rats (F344XBN). Compared with 6-month hearts, aged hearts exhibited increased TdT-mediated dUTP nick end labeling-positive nuclei, caspase-3 activation, caspase-dependent cleavage of alpha-fodrin and diminished phosphorylation of protein kinase B/Akt (Thr 308). These age-dependent increases in cardiomyocyte apoptosis were associated with alterations in the composition of the cardiac dystrophin glycoprotein complex and elevated cytoplasmic IgG and albumin immunoreactivity. Immunohistochemical analysis confirmed these data and demonstrated qualitative differences in localization of dystrophin-glycoprotein complex (DGC) molecules with aging. Taken together, these data suggest that aging-related increases in cardiac apoptotic activity model may be due, at least in part, to age-associated changes in DGC structure.

Downregulation of ANP32B, a novel substrate of caspase-3, enhances caspase-3 activation and apoptosis induction in myeloid leukemic cells

The acidic leucine-rich nuclear phosphoprotein 32 (ANP32)B has been reported to regulate gene expression by acting as a histone chaperone or modulate messenger RNA trafficking by serving as a HuR ligand. However, its exact cellular functions are poorly understood. By utilizing a proteomics-based approach, in this work, we identify that the human ANP32B protein is cleaved during apoptosis induction by NSC606985, a novel camptothecin analog. Further investigation shows that various apoptosis inducers cause a decrease of full-length ANP32B in multiple cell lines with a concomitant increase of an approximately 17 kDa fragment. The proteolytic cleavage of ANP32B is inhibited by a specific caspase-3 inhibitor Z-DEVD-fmk, and it cannot be seen in NSC606985-induced death of caspase-3-deficient MCF-7 cells. In vitro caspase cleavage assay and mutagenesis experiment reveal that ANP32B is a direct substrate of caspase-3 and it is primarily cleaved at the sequence of Ala-Glu-Val-Asp, after Asp-163. Additionally, the reduced expression of endogenous ANP32B by specific small interfering RNA enhances caspase-3 activation and apoptosis induction by NSC606985 and etoposide. These results suggest that ANP32B is a novel substrate for caspase-3 and acts as a negative regulator for apoptosis, the mechanism of which remains to be explored.

Okadaic acid induces DNA fragmentation via caspase-3-dependent and caspase-3-independent pathways in Chinese hamster ovary (CHO)-K1 cells

DNA fragmentation is a hallmark of apoptosis that occurs in a variety of cell types; however, it remains unclear whether caspase-3 is required for its induction. To investigate this, we produced caspase-3 knockout Chinese hamster ovary (CHO)-K1 cells and examined the effects of gene knockout and treatment with caspase-3 inhibitors. Okadaic acid (OA) is a potent inhibitor of the serine/threonine protein phosphatases (PPs) PP1 and PP2A, which induce apoptotic cellular reactions. Treatment of caspase-3(-/-) cells with OA induced DNA fragmentation, indicating that caspase-3 is not an essential requirement. However, in the presence of benzyloxycarbonyl-Asp-Glu-Val-Asp (OMe) fluoromethylketone (z-DEVD-fmk), DNA fragmentation occurred in CHO-K1 cells but not in caspase-3(-/-) cells, suggesting that caspase-3 is involved in OA-induced DNA fragmentation that does not utilize DEVDase activity. In the absence of caspase-3, DEVDase activity may play an important role. In addition, OA-induced DNA fragmentation was reduced but not blocked in CHO-K1 cells, suggesting that caspase-3 is involved in caspase-independent OA-induced DNA fragmentation. Furthermore, OA-induced cleavage of caspase-3 and DNA fragmentation were blocked by pretreatment with the wide-ranging serine protease inhibitor 4-(2-aminoethyl)-benzenesulfonyl fluoride hydrochloride. These results suggest that serine proteases regulate DNA fragmentation upstream of caspase-3.

The actin filament cross-linker L-plastin confers resistance to TNF-alpha in MCF-7 breast cancer cells in a phosphorylation-dependent manner

We used a tumour necrosis factor (TNF)-α resistant breast adenocarcinoma MCF-7 cell line to investigate the involvement of the actin cytoskeleton in the mechanism of cell resistance to this cytokine. We found that TNF resistance correlates with the loss of cell epithelial properties and the gain of a mesenchymal phenotype, reminiscent of an epithelial-to-mesenchymal transition (EMT). Morphological changes were associated with a profound reorganization of the actin cytoskeleton and with a change in the repertoire of expressed actin cytoskeleton genes and EMT markers, as revealed by DNA microarray-based expression profiling. L-plastin, an F-actin cross-linking and stabilizing protein, was identified as one of the most significantly up-regulated genes in TNF-resistant cells. Knockdown of L-plastin in these cells revealed its crucial role in conferring TNF resistance. Importantly, overexpression of wild-type L-plastin in TNF-sensitive MCF-7 cells was sufficient to protect them against TNF-mediated cell death. Furthermore, we found that this effect is dependent on serine-5 phosphorylation of L-plastin and that non-conventional protein kinase C isoforms and the ceramide pathway may regulate its phosphorylation state. The protective role of L-plastin was not restricted to TNF-α resistant MCF-7 cells because a correlation between the expression of L-plastin and the resistance to TNF-α was observed in other breast cancer cell lines. Together, our study discloses a novel unexpected role of the actin bundling protein L-plastin as a cell protective protein against TNF-cytotoxicity.

Activation of the extrinsic apoptotic pathway by TNF-alpha in human salivary gland (HSG) cells in vitro, suggests a role for the TNF receptor (TNF-R) and intercellular adhesion molecule-1 (ICAM-1) in Sjögren's syndrome-associated autoimmune sialadenitis

Studies suggest that apoptosis plays a major role in destruction of salivary glands in Sjögren's syndrome. We hypothesise that apoptosis results in the exposure of cryptic T cell epitopes and an autoimmune response which is pathway-specific.

OBJECTIVE

To activate the extrinsic or intrinsic apoptotic pathway to examine morphology, adhesion molecules, markers of antigen processing, and autoantigens on apoptotic bodies in vitro.

METHODS

Tumor necrosis factor-alpha (TNF-alpha) or staurosporine, a protein kinase inhibitor, was used to trigger the extrinsic or intrinsic apoptotic pathway in a Human Salivary Gland cell line (HSG), in vitro. Activated genes were profiled by cDNA array. Apoptotic bodies were visualised using light and SEM. Proteins were evaluated by immunofluorescence and confirmed by functional binding assays with Jurkat lymphocytes.

RESULTS

TNF-alpha-triggered extrinsic apoptosis resulted in "sticky" aggregated, apoptotic bodies which displayed cleaved alpha-fodrin autoantigen. In contrast, intrinsic apoptosis induced by staurosporine, resulted in dispersed cell blebs which were alpha-fodrin-negative. cDNA arrays revealed that TNF-alpha, but not staurosporine, upregulated transcriptional expression of Intercellular Adhesion Molecule-1 (ICAM-1) and Macrophage Inflammatory Protein-3 (CCL20).

CONCLUSION

The apoptotic pathway controls morphological, structural and functional properties of apoptotic bodies. Collectively, TNF-alpha-dependent activation of the extrinsic apoptotic pathway leads to upregulation of ICAM-1 and CCL20 in HSG in vitro. This suggests that pathogenesis in Sjögren's syndrome may involve a TNF-controlled cross-talk between apoptotic ductal and CCL20-attracted dendritic cells via the CD137/CD137L signalling pathway.

Ursolic acid triggers apoptosis and Bcl-2 downregulation in MCF-7 breast cancer cells

In this report we determine the ability of ursolic acid (UA) to induce apoptosis and to modulate glucocorticoid receptor (GR) and Activator Protein-1 (AP-1) in MCF-7 cells. The UA-induced apoptosis (53 microM), the PARP cleavage, and the decrease in Bcl-2 protein (53 microM) support the notion that UA induces apoptosis through the intrinsic mitochondrial pathway. UA binds GR (relative binding affinity: 2.57) and translocates GR into nucleus, suggesting its potential as a GR modulator. UA had no effect on GRE- or TRE-driven gene expression. In summary, UA is a GR modulator and may be considered as a potential anticancer agent in breast cancer.

Nitro-aspirin inhibits MCF-7 breast cancer cell growth: effects on COX-2 expression and Wnt/beta-catenin/TCF-4 signaling

There is current evidence implicating the Wnt/beta-catenin/TCF pathway in breast cancer. We investigated the effect of para- and meta-positional isomers of nitric oxide-releasing aspirin (NO-ASA), and aspirin (ASA) on MCF-7 human breast cancer cell growth and beta-catenin/TCF signaling. The p- and m-NO-ASA isomers strongly inhibited cell growth and beta-catenin/TCF transcriptional activity compared to ASA; the IC50s for growth inhibition were 57+/-4, 193+/-10 and >5000microM, and for transcriptional inhibition they were 12+/-1.8, 75+/-6.5 and >5000microM for p-, m-NO-ASA and ASA, respectively. p-NO-ASA reduced the expression of Wnt/beta-catenin downstream target gene cyclin D1, and total cellular beta-catenin levels. COX-2 expression was induced by p-NO-ASA, protein kinase C inhibitors reversed this induction. p-NO-ASA blocked the cell cycle transition at S to G2/M phase. These studies suggest a targeted chemopreventive/chemotherapeutic potential for NO-ASA against breast cancer.

Pulsed-laser creation and characterization of giant plasma membrane vesicles from cells

Femtosecond-pulsed laser irradiation was found to initiate giant plasma membrane vesicle (GPMV) formation on individual cells. Laser-induced GPMV formation resulted from intracellular cavitation and did not require the addition of chemical stressors to the cellular environment. The viscosity, structure, and contents of laser-induced GPMVs were measured with fluorescence microscopy and single-particle tracking. These GPMVs exhibit the following properties: (1) GPMVs grow fastest immediately after laser irradiation; (2) GPMVs contain barriers to free diffusion of incorporated fluorescent beads; (3) materials from both the cytoplasm and surrounding media flow into the growing GPMVs; (4) the GPMVs are surrounded by phospholipids, including phosphatidylserine; (5) F-actin is incorporated into the vesicles; and (6) caspase activity is not essential for GPMV formation. The effective viscosity of 65 nm polystyrene nanoparticles within GPMVs ranged from 32 to 434 cP. The nanoparticle diffusion was commonly affected by relatively large, macromolecular structures within the bleb.

Gelsolin regulates cardiac remodeling after myocardial infarction through DNase I-mediated apoptosis

Gelsolin, a calcium-regulated actin severing and capping protein, is highly expressed in murine and human hearts after myocardial infarction and is associated with progression of heart failure in humans. The biological role of gelsolin in cardiac remodeling and heart failure progression after injury is not defined. To elucidate the contribution of gelsolin in these processes, we randomly allocated gelsolin knockout mice (GSN(-/-)) and wild-type littermates (GSN(+/+)) to left anterior descending coronary artery ligation or sham surgery. We found that GSN(-/-) mice have a surprisingly lower mortality, markedly reduced hypertrophy, smaller late infarct size, less interstitial fibrosis, and improved cardiac function when compared with GSN(+/+) mice. Gene expression and protein analysis identified significantly lower levels of deoxyribonuclease (DNase) I and reduced nuclear translocation and biological activity of DNase I in GSN(-/-) mice. Absence of gelsolin markedly reduced DNase I-induced apoptosis. The association of hypoxia-inducible factor (HIF)-1alpha with gelsolin and actin filaments cleaved by gelsolin may contribute to the higher activation of DNase. The expression pattern of HIF-1alpha was similar to that of gelsolin, and HIF-1alpha was detected in the gelsolin complex by coprecipitation and HIF-1alpha bound to the promoter of DNase I in both gel-shift and promoter activity assays. Furthermore, the phosphorylation of Akt at Ser473 and expression of Bcl-2 were significantly increased in GSN(-/-) mice, suggesting that gelsolin downregulates prosurvival factors. Our investigation concludes that gelsolin is an important contributor to heart failure progression through novel mechanisms of HIF-1alpha and DNase I activation and downregulation of antiapoptotic survival factors. Gelsolin inhibition may form a novel target for heart failure therapy.

C-jun N-terminal kinase regulates the interaction between 14-3-3 and Bad in ethanol-induced cell death

Activation of the c-jun N-terminal kinase (JNK) is known to be an important step during ethanol-induced cell death, but it has yet to be identified how JNK regulates apoptosis. Therefore, we investigated the mechanism by which JNK induces cell death following ethanol treatment. Ethanol (6 g/kg, 20% in saline) was administered subcutaneously to postnatal 7 day rat pups. Twelve hours after the first ethanol administration, rat pups were decapitated, and extracts of total protein from cerebral cortices were prepared. Ethanol exposure induced phosphorylation of JNK but did not affect the expression levels of pro- and antiapoptotic proteins. Furthermore, interactions of phospho-JNK (p-JNK) with 14-3-3 as well as with Bad were enhanced in the cerebral cortices of ethanol-treated rats. Pretreatment with JNK inhibitor (SP600125) of SH-SY5Y cells inhibited JNK phosphorylation and interaction between p-JNK and 14-3-3 resulting from ethanol. Furthermore, 14-3-3 interaction with Bad was diminished in the cerebral cortices of ethanol-treated rats. These findings suggest that JNK induces Bad release from 14-3-3 by inhibiting their interaction. After this event, Bad binds to Bcl-xL, releasing Bax from Bcl-xL and leading to cell death. We hypothesize that JNK may play an important role during ethanol-induced cell death via the inhibition of antiapoptotic function of 14-3-3 as well as activation of proapoptotic function of Bad.

Trace amounts of copper exacerbate beta amyloid-induced neurotoxicity in the cholesterol-fed mice through TNF-mediated inflammatory pathway

Evidence has been gathered to suggest that trace amounts of copper induce neurotoxicity by interaction with elevated cholesterol in diet. Step-through task and Morris water maze task were used to evaluate cognitive function in the animals. Although a 16-week copper treatment alone in mice showed no significant change in learning and memory performances, cholesterol treatment significantly induced learning and memory impairments, which could be exacerbated by the co-treatment with copper. Immunohistochemical studies revealed that trace amounts of copper further stimulated the amyloid precursor protein (APP) upregulation and contributed to amyloid beta-peptide (Abeta) deposition in the brain of cholesterol-fed mice. Western blot analysis showed that copper also increased the protein expression levels of tumor necrosis factor-alpha (TNF-alpha) and the degradation of IkappaB proteins in the brain of cholesterol-fed mice. Furthermore, increased production of high inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) expressions were detected in the hippocampus and cerebral cortex of copper and cholesterol co-treated mice by immunohistochemical analysis. These findings suggest that trace amounts of copper could induce APP upregulation, activate inflammatory pathway and exacerbate neurotoxicity in cholesterol-fed mice.

Possible involvement of caspase-6 and -7 but not caspase-3 in the regulation of hypoxia-induced apoptosis in tube-forming endothelial cells

We recently reported that a broad-spectrum caspase inhibitor zVAD-fmk failed, while p38 inhibitor SB203580 succeeded, to prevent chromatin condensation and nuclear fragmentation induced by hypoxia in tube-forming HUVECs. In this study, we investigated the reasons for zVAD-fmk's inability to inhibit these morphological changes at the molecular level. The inhibitor effectively inhibited DNA ladder formation and activation of caspase-3 and -6, but it surprisingly failed to inhibit caspase-7 activation. On the other hand, SB203580 successfully inhibited all of these molecular events. When zLEHD-fmk, which specifically inhibits initiator caspase-9 upstream of caspase-3, was used, it inhibited caspase-3 activation but failed to inhibit caspase-6 and -7 activation. It also failed to inhibit hypoxia-induced chromatin condensation, nuclear fragmentation and DNA ladder formation. Taken together, our results indicate that, during hypoxia, caspase-7 is responsible for chromatin condensation and nuclear fragmentation while caspase-6 is responsible for DNA ladder formation.

hScrib, a human homologue of Drosophila neoplastic tumor suppressor, is a novel death substrate targeted by caspase during the process of apoptosis

hScrib, human homologue of Drosophila neoplastic tumor suppressor, was identified as a target of human papillomavirus E6 oncoprotein for the ubiquitin-mediated degradation. Here, we report that hScrib is a novel death substrate targeted by caspase. Full-length hScrib was cleaved by caspase during death ligands-induced apoptosis, which generates a p170 C-terminal fragments in Hela cells. In vitro cleavage assay using recombinant caspases showed that hScrib is cleaved by the executioner caspases. DNA damage-induced apoptosis caused loss of expression of full-length hScrib, which was recovered by addition of capase-3 inhibitor in HaCat cells. TUNEL positive apoptotic cells, which were identified 4 h after UV irradiation in HaCat cells, showed loss of hScrib expression at the adherens junction. Mutational analysis identified the caspase-dependent cleavage site of hScrib at the position of Asp-504. Although MDCK cells transfected with GFP-fused wild-type hScrib showed loss of E-cadherin expression and shrinkage of cytoplasm by UV irradiation, cells transfected with hScrib with Ala substitution of Asp-504 showed resistance to caspase-dependent cleavage of hScrib and intact expression of E-cadherin. These results indicate that caspase-dependent cleavage of hScrib is a critical step for detachment of cell contact during the process of apoptosis.

Caspase polymorphisms and genetic susceptibility to multiple myeloma

Multiple myeloma is a haematological malignency, characterized by clonal expansion of plasma cells. However, little is known about the cause of multiple myeloma. Cancer cells must avoid apoptosis to ensure unregulated tumour formation and growth. The highly conserved caspase cascade is essential to the regulation of the apoptotic pathway. To examine if five single nucleotide polymorphisms (SNPs) in four caspase genes [CASP3 Ex8-280 C > A (rs6948), CASP3 Ex8 + 567 T > C (rs1049216), CASP8 Ex14-271 A > T (rs13113), CASP9 Ex5 + 32 G > A (rs1052576), CASP10 Ex3-171 A > G (rs39001150)] alter multiple myeloma risk, we conducted a population-based case-control study of women (128 cases; 516 controls) in Connecticut. Compared to individuals with the TT genotype of CASP3 Ex8 + 567 T > C, subjects with the CC genotype had a five-fold decreased risk of multiple myeloma (odds ratio (OR)(CC) = 0.2, 95% confidence interval (CI) = 0.0-1.0). Further, individuals with the AG and AA genotypes of CASP9 Ex5 + 32 G > A also experienced a decreased risk of multiple myeloma (OR(AG) = 0.8, 95% CI = 0.5-1.3; OR(AA) = 0.5, 95% CI = 0.3-0.9; p-trend = 0.02). While no previous study has evaluated the association between caspase genes and multiple myeloma, studies have found associations with lung, breast, esophageal, gastric, colorectal and cervical cancers. Our parallel study of non-Hodgkin lymphoma, which utilized the same controls, found strong evidence that caspase genes play a key role in lymphogenesis. The protective associations observed in two key caspase genes suggest that genetic variation in CASP genes may play an important role in the aetiology of multiple myeloma.

A potent reporter applicable to the monitoring of caspase-3-dependent proteolytic cleavage

In this study, we developed a chimeric caspase-3 substrate (GST:DEVD:EGFP) comprised of glutathione-S transferase (GST) and enhanced green fluorescent protein (EGFP) with a specialized linker peptide harboring the caspase-3 cleavage sequence, DEVD. Using this reporter, we assessed the proteolytic cleavage of the artificial caspase-3 substrate for caspase-3. The common feature of this approach is that the presence of the DEVD sequence between GST and EGFP allows for caspase-3-dependent cleavage after the Asp (D) residue, resulting in the elimination of EGFP from the GST:DEVD:EGFP reporter. To the best of our knowledge, this study reports the first application employing a chimeric protein substrate, with the similar accuracy level compared to the conventional methods such as fluorometric assays. As a result, using this GST:DEVD:EGFP reporter, caspase-3 activation based on proteolytic properties could be monitored via a variety of bioanalytical techniques such as immunoblot analysis, glutathione-agarose bead assay, and on-chip visualization, providing both technical and economical advantages over the extensively utilized fluorogenic peptide assay. Our results convincingly showed that this versatile reporter (GST:DEVD:EGFP) constitutes a useful system for the monitoring of caspase-3 activation, potentially enabling the monitoring of the proteolytic activities of different intra-cellular proteases via the substitution of the cleavage sequence within the same schematic construct.

Glutamate-induced losses of oligodendrocytes and neurons and activation of caspase-3 in the rat spinal cord

The toxicity of released glutamate contributes substantially to secondary cell death following spinal cord injury (SCI). In this work, the extent and time courses of glutamate-induced losses of neurons and oligodendrocytes are established. Glutamate was administered into the spinal cords of anesthetized rats at approximately the concentration and duration of its release following SCI. Cells in normal tissue, in tissue exposed to artificial cerebrospinal fluid and in tissue exposed to glutamate were counted on a confocal system in control animals and from 6 h to 28 days after treatment to assess cell losses. Oligodendrocytes were identified by staining with antibody CC-1 and neurons by immunostaining for Neuronal Nuclei (NeuN) or Neurofilament H. The density of oligodendrocytes declined precipitously in the first 6 h after exposure to glutamate, and then relatively little from 24 h to 28 days post-exposure. Similarly, neuron densities first declined rapidly, but at a decreasing rate, from 0 h to 72 h post-glutamate exposure and did not change significantly from 72 h to 28 days thereafter. The nuclei of many cells strongly and specifically stained for activated caspase-3, an indicator of apoptosis, in response to exposure to glutamate. Caspase-3 was localized to the nucleus and may participate in apoptotic cell death. However, persistence of caspase-3 staining for at least a week after exposure to glutamate during little to no loss of oligodendrocytes and neurons demonstrates that elevation of caspase-3 does not necessarily lead to rapid cell death. Beyond about 48 h after exposure to glutamate, locomotor function began to recover while cell numbers stabilized or declined slowly, demonstrating that functional recovery in the experiments presented involves processes other than replacement of oligodendrocytes and/or neurons.

Isoform B of myosin II heavy chain mediates actomyosin contractility during TNFalpha-induced apoptosis

Cells that are treated long-term with TNFalpha or short-term with TGFalpha together with cycloheximide (CHX) undergo apoptosis. Cell shrinkage and detachment during apoptosis is dependent on actomyosin contractility. Myosin II heavy chain (MHCII) isoforms have shared and distinct functions. Here, we investigated whether the involvement of MHCII isoforms A and B (MHCIIA and MHCIIB, respectively) in cell shrinkage and detachment differs during apoptosis. We show that TNFalpha induces caspase-dependent MHCIIA degradation, whereas MHCIIB levels and association with the cytoskeleton remained virtually unchanged in TtT/GF cells and NIH 3T3 fibroblasts. MHCIIA proteolysis also occurred in fibroblasts that lack MHCIIB when treated with TNFalpha and CHX together. The absence of MHCIIB did not affect cell death rate. However, MHCIIB-/- cells showed more resistance to TNFalpha-induced actin disassembly, cell shrinkage and detachment than wild-type fibroblasts, indicating the participation of MHCIIB in these events. Moreover, inhibition of atypical PKCzeta, which targets MHCIIB but not MHCIIA, blocked TNFalpha-induced shrinkage and detachment in TtT/GF cells and wild-type fibroblasts, but the inhibitory effect was significantly reduced in MHCIIB-/- fibroblasts. TNFalpha treatment increased cytoskeleton-associated myosin light chain (MLC) phosphorylation but did not induce actin cleavage. In conclusion, our results demonstrate that MHCIIB, together with MLC phosphorylation and actin, constitute the actomyosin cytoskeleton that mediates contractility during apoptosis.

Autoimmunity and glaucoma

Elevated intraocular pressure does not explain glaucoma in all patients, but there is information that autoimmune mechanisms may be involved in this disorder. This review attempts to reveal the findings about specific changes in autoantibody profiles in glaucoma patients and their possible role in glaucoma. Considering that these changes in natural autoimmunity can be found consistently among different study populations, it might be a promising new tool for glaucoma detection.

Immunological mechanisms in glaucoma

Glaucoma is one of the most frequent causes of blindness worldwide. The elevated intraocular pressure does not explain glaucoma in all patients but can be considered as a risk factor of the disease. There are some evidences that autoimmune mechanisms may be involved in this disorder. This review attempts to demonstrate the findings about autoimmune mechanisms in glaucoma patients. Consistent up- and down-regulations in the autoantibody profiles against ocular antigens are present in glaucoma patients. These changes in natural autoimmunity could be found in independent study populations and might be a promising tool for glaucoma detection.

Implication of caspases and subcellular compartments in tert-butylhydroperoxide induced apoptosis

Oxidative stress has been implicated in many physiopathologies including neurodegenerative diseases, cancer, cardiovascular and respiratory diseases, and in mechanisms of action of environmental toxicants. tert-butylhydroperoxide (t-BHP) is an organic lipid hydroperoxide analogue, which is commonly used as a pro-oxidant for evaluating mechanisms involving oxidative stress in cells and tissues. This study investigates mechanisms of apoptosis induced by oxidative stress in hepatocytes, in particular, the involvement of caspases and subcellular compartments. Freshly isolated hepatocytes were exposed to 0.4 mM t-BHP during 1 h. A general caspase inhibitor, Boc-D-FMK, reduced t-BHP-induced apoptosis (chromatin condensation), confirming the involvement of caspases in apoptosis. A caspase-9 inhibitor, Z-LEHD-FMK, also reduced t-BHP-induced apoptosis, suggesting that caspase-9 plays a critical role in this process. Procaspase-9 underwent cleavage in mitochondria and translocation to the nucleus, where increased caspase-9 activity was detected. The caspase-9 substrates, caspase-3 and caspase-7, were not activated. Caspase-7 was translocated from the cytosol to the endoplasmic reticulum (ER), where it underwent processing; however, enzymatic activity of caspase-7 was inhibited by t-BHP. t-BHP caused cleavage of procaspase-12 at the ER and its subsequent translocation to the nucleus, where increased caspase-12 activity was found. t-BHP caused translocation of calpain from the cytosol to the ER. Calpain inhibition reduced chromatin condensation and caspase-12 activity in the nucleus, suggesting that calpain is involved in caspase-12 activation and apoptosis. This study demonstrates that caspase-9 and caspase-12 are activated in t-BHP-induced apoptosis in hepatocytes. We highlight the importance of subcellular compartments such as mitochondria, ER and nuclei in the apoptotic process.

Caspase-mediated cleavage of HuR in the cytoplasm contributes to pp32/PHAP-I regulation of apoptosis

The RNA-binding protein HuR affects cell fate by regulating the stability and/or the translation of messenger RNAs that encode cell stress response proteins. In this study, we delineate a novel regulatory mechanism by which HuR contributes to stress-induced cell death. Upon lethal stress, HuR translocates into the cytoplasm by a mechanism involving its association with the apoptosome activator pp32/PHAP-I. Depleting the expression of pp32/PHAP-I by RNA interference reduces both HuR cytoplasmic accumulation and the efficiency of caspase activation. In the cytoplasm, HuR undergoes caspase-mediated cleavage at aspartate 226. This cleavage activity is significantly reduced in the absence of pp32/PHAP-I. Substituting aspartate 226 with an alanine creates a noncleavable isoform of HuR that, when overexpressed, maintains its association with pp32/PHAP-I and delays the apoptotic response. Thus, we propose a model in which HuR association with pp32/PHAP-I and its caspase-mediated cleavage constitutes a regulatory step that contributes to an amplified apoptotic response.

Prostaglandin-induced VASP phosphorylation controls alpha II-spectrin breakdown in apoptotic cells

In pathological conditions, the inflammatory mediator prostaglandin E2 (PGE2) has been shown to induce apoptosis through a cAMP-dependent pathway. However, underlying mechanisms have remained illusive. Irrespective whether apoptosis is induced by the intrinsic or extrinsic pathway, the cysteine protease caspase-3 becomes activated and cleaves many key proteins including spectrins. Cleavage of the plasma membrane-associated spectrins leads to cell shrinkage, membrane blebbing, the formation of apoptotic bodies, and irreversible cell death. Recently, we identified a novel interaction between alpha II-spectrin and vasodilator-stimulated phosphoprotein (VASP), which is abrogated by the cAMP-dependent protein kinase (PKA)-mediated phosphorylation of VASP. In the present study we investigated whether VASP binding to alpha II-spectrin affects spectrin breakdown in PGE2-induced apoptosis. PGE2 dose- and time-dependently triggered VASP phosphorylation. Following induction of apoptosis, caspase-3-mediated alpha II-spectrin breakdown and membrane blebbing were markedly delayed in wild-type as compared to VASP-deficient endothelial cells. This suggests that VASP binding to alpha II-spectrin attenuates alpha II-spectrin cleavage in apoptotic cells and that PGE2-induced VASP phosphorylation regulates this process. Our findings may therefore provide the molecular basis for PGE2-induced apoptosis in pathological events.

Involvement of the calcium-dependent proteolytic system in skeletal muscle aging

Aging is associated with a progressive and involuntary loss of muscle mass also known as sarcopenia. This condition represents a major public health concern with high socio-economics implications. Although sarcopenia is well documented, the aetiology of this condition still remains poorly understood. Calpains are ubiquitous proteases regulated in part by a specific inhibitor, calpastatin. They are well known to have major implications in muscle growth and differentiation. The aim of the present study was to determine if this proteolytic system could be involved in the phenotype associated with sarcopenia. Calpains and calpastatin levels, subcellular distributions and activities were compared between muscles from 3 and 24 months old rats. Altogether, the results we obtained showed an overall increase in calpain activities associated with muscle aging. These findings suggest that the calcium-dependent proteolytic system is indeed involved in sarcopenia.