Quantification of active caspase 3 in apoptotic cells

Design and synthesis of novel 2-S-alkylated Quinazolinones as dual BRAFV600E and EGFR inhibitors in melanoma: Mechanistic insights from apoptosis and cell cycle modulation

Melanoma, an aggressive and highly metastatic form of skin cancer, remains challenging to treat due to its resistance to conventional therapies and frequent mutations in the BRAF signaling pathway. In this study, we report the design and synthesis of a novel series of thirteen quinazolinone derivatives, featuring a phenyl thiazole moiety linked via a triazole acetamide spacer. These compounds were developed as potential dual inhibitors of BRAFV600E and EGFR, which should offer a promising therapeutic strategy for melanoma treatment. The antiproliferative activity of these compounds was evaluated against the NCI-60 cell line panel, with six compounds advancing to a five-dose screening. Three compounds, 7k, 7l, and 7m, exhibited broad-spectrum anticancer activity, with mean growth inhibition (GI%) exceeding 100 %. Compound 7l demonstrated exceptional efficacy against melanoma subpanels (GI% = 152 %) and potent dual kinase inhibition, with IC50 values of 0.048 μM against B-RAFV600E and 0.037 μM against EGFR. In vitro studies of compound 7l revealed significant cytotoxicity against MALME-3 M (IC50 = 3.16 μM) and LOX-IMVI (IC50 = 2.50 μM) melanoma cell lines, with minimal toxicity towards normal Vero cells. Cell cycle analysis showed G1-phase arrest and disrupted DNA synthesis in melanoma cells, while apoptosis assays demonstrated a dramatic increase in early apoptotic cells from 7.28 % to 40.69 %. Compound 7l modulated key apoptotic markers, increasing the BAX/Bcl-2 ratio by 14.42-fold and elevating caspase 3 and 9 levels, indicating its potential to overcome drug resistance and enhance therapeutic efficacy in melanoma treatment.

Highly sensitive detection of caspase-3 activity based on peptide-modified organic electrochemical transistor biosensors

Caspase-3 is an important proteolytic enzyme that cleaves several key substrates in apoptotic processes, resulting in DNA fragmentation, the degradation of nuclear proteins, and the formation of apoptotic bodies. However, it is challenging to detect caspase-3 due to its low expression levels in cells. In this work, organic electrochemical transistors (OECTs) are used in the detection of caspase-3 for the first time. A self-assembled monolayer of the peptide is bonded to the Au gate electrode (GE) of an OECT via gold-sulphur bonds. It is found that the transfer curve of the transistor shifts to a lower gate voltage due to the modulation of the surface potential of the GE by the peptides. Then, the device is used in the detection of caspase-3 in aqueous solutions and shows a detection limit of 0.1 pM. Due to its high sensitivity, the device can detect caspase-3 in induced apoptotic HeLa cells. The system is low-cost, conveniently used and applicable for biological and medical monitoring where caspase-3 detection and quantification are required.

Fluorogenic Substrates for In Situ Monitoring of Caspase-3 Activity in Live Cells

The in situ detection of caspase-3 activity has applications in the imaging and monitoring of multiple pathologies, notably cancer. A series of cell penetrating FRET-based fluorogenic substrates were designed and synthesised for the detection of caspase-3 in live cells. A variety of modifications of the classical caspase-3 and caspase-7 substrate sequence Asp-Glu-Val-Asp were carried out in order to increase caspase-3 affinity and eliminate caspase-7 cross-reactivity. To allow cellular uptake and good solubility, the substrates were conjugated to a cationic peptoid. The most selective fluorogenic substrate 27, FAM-Ahx-Asp-Leu-Pro-Asp-Lys(MR)-Ahx, conjugated to the cell penetrating peptoid at the C-terminus, was able to detect and quantify caspase-3 activity in apoptotic cells without cross-reactivity by caspase-7.

Ameliorative Effects of Curcumin on Fibrinogen-Like Protein-2 Gene Expression, Some Oxido-Inflammatory and Apoptotic Markers in a Rat Model of l-Arginine-Induced Acute Pancreatitis

The aim of the study was to investigate the ameliorative effects of curcumin on fibrinogen like protein-2 (fgl-2), some oxido-inflammatory and apoptotic markers in rat-induced acute pancreatitis (AP). Seventy-five albino rats were divided into control group, l-arginine (l-Arg)-induced AP group, curcumin pre-treated group before AP induction, curcumin post-treated group after AP induction, and curcumin injected group only. AP group showed severe necrotizing pancreatitis confirmed by histopathological changes and elevations in serum amylase and lipase activities, levels of epithelial neutrophil-activating peptide 78, tissue content of protein carbonyls, levels of tumor necrosis factor α, and caspase-3 as well as myeloperoxidase activity. Significant elevation in pancreatic fgl-2 mRNA expression was detected in AP group. Improvement of all parameters was detected with increase of caspase-3 in both curcumin-treated groups that confirmed curcumin ameliorative effects against AP through induction of apoptosis and inhibition of micro-thrombosis, inflammation, and oxidative stress.

Small Molecule Active Site Directed Tools for Studying Human Caspases

Caspases are proteases of clan CD and were described for the first time more than two decades ago. They play critical roles in the control of regulated cell death pathways including apoptosis and inflammation. Due to their involvement in the development of various diseases like cancer, neurodegenerative diseases, or autoimmune disorders, caspases have been intensively investigated as potential drug targets, both in academic and industrial laboratories. This review presents a thorough, deep, and systematic assessment of all technologies developed over the years for the investigation of caspase activity and specificity using substrates and inhibitors, as well as activity based probes, which in recent years have attracted considerable interest due to their usefulness in the investigation of biological functions of this family of enzymes.

Fas Activated Serine-Threonine Kinase Domains 2 (FASTKD2) mediates apoptosis of breast and prostate cancer cells through its novel FAST2 domain

Background

Expression of NRIF3 (Nuclear Receptor Interacting Factor-3) rapidly and selectively leads to apoptosis of breast cancer cells. This occurs through binding of NRIF3 or its 30 amino acid Death Domain-1 (DD1) region to the transcriptional repressor, DIF-1 (DD1 Interacting Factor-1). DIF-1 acts in a wide variety of breast cancer cells but not other cell types to repress the pro-apoptotic gene, FASTKD2. Expression of NRIF3 or DD1 inactivates the DIF-1 repressor leading to rapid derepression of FASTKD2, which initiates apoptosis within 5–8 h of expression. Although FASTKD2 is an inner mitochondrial membrane protein, it does not require mitochondrial localization to initiate apoptosis.

Methods

Androgen dependent LNCaP cells as well as two androgen independent LNCaP cell lines (LNCaP-AI and LNCaP-abl) were studied and LNCaP-AI cells were engineered to conditionally express DD1 or the inactive DD1-S28A with 4-hydroxytamoxifen. Apoptosis was assessed by TUNEL assay. FASTKD2 is related to 4 other proteins encoded in the human genome (FASTKD1, 3, 4, 5). All contain a poorly conserved putative bipartite kinase domain designated as FAST1_FAST2. We examined whether expression of any of the other FASTKD isoforms leads to apoptosis and sought to identify the region of FASTKD2 necessary to initiate the apoptotic pathway.

Results

Of the FASTKD1-5 isoforms only expression of FASTKD2 leads to apoptosis. Although, the NRIF3/DD1/DIF-1 pathway does not mediate apoptosis of a wide variety of non-breast cancer cell lines, because of certain similarities and gene signatures between breast and prostate cancer we explored whether the NRIF3/DD1/DIF-1/FASTKD2 pathway mediates apoptosis of prostate cancer cells. We found that the pathway leads to apoptosis in LNCaP cells, including the two androgen-independent LNCaP cell lines that are generally resistant to apoptosis. Lastly, we identified that FASTKD2-mediated apoptosis is initiated by the 81 amino acid FAST2 region.

Conclusions

The NRIF3/DIF-1/FASTKD2 pathway acts as a “death switch” in breast and prostate cancer cells. Deciphering how this pathway is regulated and how FASTKD2 initiates the apoptotic response will allow for the development of therapeutic agents for the treatment of androgen-independent prostate cancer or Tamoxifen-unresponsive Estrogen Receptor negative tumors as well as metastatic breast or prostate cancer.

Garlic-derived compound S-allylmercaptocysteine inhibits cell growth and induces apoptosis via the JNK and p38 pathways in human colorectal carcinoma cells

S-allylmercaptocysteine (SAMC) is an active compound that is derived from garlic and has been demonstrated to possess antitumor properties in vitro. The present study aimed to investigate the effect of SAMC and determine the underlying mechanism of this effect on human colorectal carcinoma cells. The SW620 cells were cultured with various concentrations of SAMC and cell viability was detected using an MTT assay. Analysis of apoptosis was performed using terminal deoxynucleotidyl-transferase-mediated deoxyuridine triphosphate nick end labeling. The c-Jun N-terminal kinase (JNK) and p38 mitogen activated protein kinase (p38) signaling pathways were investigated by polymerase chain reaction. SAMC was observed to reduce cell viability in a dose- and time-dependent manner, partially through the induction of apoptosis in human colorectal carcinoma cells. At the molecular level, SAMC induces apoptosis through JNK and p38 signaling pathways, increasing tumor protein p53 (p53) and Bax activation in the SW620 cells. The most effective concentration of SAMC for the induction of SW620 cell apoptosis was found to be 400 μM, which was confirmed through cell viability assays and apoptosis analysis. The current study indicated that SAMC inhibits cell proliferation and induces apoptosis of SW620 cells via the JNK and p38 pathways. The results from the current study demonstrated that SAMC must be further investigated as a novel preventive or therapeutic agent for the treatment of colorectal carcinoma, and potentially for use in other tumor types.

Dichloroacetonitrile induces oxidative stress and developmental apoptotic imbalance in mouse fetal brain

Dichloroacetonitrile (DCAN) is one of the disinfection by-products of chlorination of drinking water. Limited mechanistic studies exist on the developmental toxicity of haloacetonitriles (HANs). The present study was designed to investigate the potential adverse effects of maternal exposure to DCAN on mouse fetal brain. Based on initial dose-response experiment, DCAN (14 mg/kg/day) was administered orally to pregnant mice at gestation day (GD) 6, till GD 15. Maternal exposure to DCAN resulted in redox imbalance in fetal cortex and cerebellum, characterized by significant decrease in reduced glutathione (GSH), and elevation of malondialdehyde (MDA) level and superoxide dismutase (SOD) activity. Further, DCAN induced apoptosis indicated by significant enhancement of DNA fragmentation and active caspase-3 level in fetal cortex and cerebellum. Neuronal degeneration was indicated by positive cupric silver staining. In conclusion, maternal exposure to DCAN adversely affects mouse fetal brain as evidenced by induction of oxidative stress, apoptotic imbalance and neurodegeneration.

Mechanisms of cardioprotective effect of aged garlic extract against Doxorubicin-induced cardiotoxicity

Aged garlic has been extensively studied and has been shown to have a number of medicinal properties, including immunomodulatory, hepatoprotective, antimutagenic, anticarcinogenic, and antioxidant effects. The objective of this study was to investigate the mechanisms of the cardioprotective effect of aged garlic extract (AGE), a widely used herbal medicine with potent antioxidant activity, against doxorubicin-induced cardiotoxicity. Moreover, the study investigated if the cardioprotective effect of AGE might be at the expense of the antitumor effect of the anticancer drug doxorubicin (DOX). Primary cultured neonatal rat cardiac myocytes were treated with DOX, AGE, and their combination for 24 hours. DOX increased p53 and caspase 3 activity-induced apoptotic cell death, whereas AGE pretreatment suppressed the action of DOX. AGE pretreatment did not interfere with the cytotoxic activity of DOX, but it increased the DOX uptake into tumor cells and increased the long term survivors of tumor-bearing mice from 30% to 70%. In conclusion, DOX impairs viability of cardiac myocytes, at least partially by activating the p53-mediated apoptotic signaling. AGE can effectively and extensively counteract this action of DOX and may potentially protect the heart from severe toxicity of DOX. At the same time, AGE did not interfere with antitumor activity of DOX.

A constitutively active and uninhibitable caspase-3 zymogen efficiently induces apoptosis

The caspase-3 zymogen has essentially zero activity until it is cleaved by initiator caspases during apoptosis. However, a mutation of V266E in the dimer interface activates the protease in the absence of chain cleavage. We show that low concentrations of the pseudo-activated procaspase-3 kill mammalian cells rapidly and, importantly, this protein is not cleaved nor is it inhibited efficiently by the endogenous regulator XIAP (X-linked inhibitor of apoptosis). The 1.63 Å (1 Å = 0.1 nm) structure of the variant demonstrates that the mutation is accommodated at the dimer interface to generate an enzyme with substantially the same activity and specificity as wild-type caspase-3. Structural modelling predicts that the interface mutation prevents the intersubunit linker from binding in the dimer interface, allowing the active sites to form in the procaspase in the absence of cleavage. The direct activation of procaspase-3 through a conformational switch rather than by chain cleavage may lead to novel therapeutic strategies for inducing cell death.

Pharmacologic modification to resuscitation fluid after thermal injury--is drotrecogin alfa the answer to arrest burn depth progression?

HYPOTHESIS

The addition of drotrecogin alfa (DA), an anti-inflammatory useful in septic shock, to standard burn shock resuscitation fluids will protect burned, injured skin from further injury.

METHODS

Anesthetized animals were subjected to a standardized burn pattern by applying a branding iron to 10 different locations on the back of the rat for 1 seconds to 14 seconds, creating a range of burn depths and severities.

DESIGN

Animal burn shock and resuscitation model.

PARTICIPANTS

Thirty-one male adult Sprague-Dawley rats.

INTERVENTIONS

Control animals were resuscitated with lactated Ringer's solution (LRS) at 2 mL/kg/percent total body surface area/24 h; experimental animals received LRS plus DA 24 microg/kg/h (LRS + DA).

OUTCOME MEASURES

Perfusion to each burned area was assessed using a laser Doppler imaging technology. Punch biopsies at each burned area were stained with hematoxylin and eosin and assessed for burn depth and for inflammation using previously reported measures. Samples from 14 animals were stained for terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and caspase-3 (apoptosis markers).

RESULTS

Increasing branding iron contact times worsened perfusion, burn depth, and apoptotic ratios. There was no correlation between inflammatory markers and burn contact time. The addition of DA leads to worse perfusion, deeper burns, worse inflammation, and decreased apoptotic ratios.

CONCLUSIONS

Laser Doppler imaging is a useful technology to assess burn depth. The addition of DA to traditional resuscitation fluids for burn shock is deleterious to the injured, burned skin. Modifying the traditional burn shock resuscitation fluids, although intellectually attractive, needs to be rigorously studied.

Caspase substrates: easily caught in deep waters?

Caspases are key players in various cellular processes, such as apoptosis, proliferation and differentiation, and in pathological conditions including cancer and inflammation. Although caspases preferentially cleave C-terminal of aspartic acid residues, their action is restricted generally to one or a few sites per protein substrate. Caspase-specific substrate recognition appears to be determined by the substrate sequences adjacent to the scissile bond. Knowledge of these substrates and the generated fragments is crucial for a thorough understanding of the functional implications of caspase-mediated proteolysis. In addition, insight into the cleavage specificity might assist in designing inhibitors that target disease-related caspase activities. Here, we critically review recently published procedures used to generate a proteome-wide view of caspase substrates.

Assessment of cell engineering strategies for improved therapeutic protein production in CHO cells

Recombinant glycoprotein therapeutics have proven to be invaluable pharmaceuticals for the treatment of various diseases. Chinese hamster ovary (CHO) cells are widely used in industry for the production of these proteins. Several strategies for engineering CHO cells for improved protein production have been tried with considerable results. The focus has mainly been to increase the specific productivity and to extend the culture longevity by preventing programmed cell death. These CHO cell engineering strategies, particularly those developed in Korea, are reviewed here.

Apoptosis-associated caspase activation assays

Caspases are aspartate-directed cysteine proteases that cleave a diverse group of intracellular substrates to contribute to various manifestations of apoptosis. These proteases are synthesized as inactive precursors and are activated as a consequence of signaling induced by a wide range of physiological and pathological stimuli. Caspase activation can be detected by measurement of catalytic activity, immunoblotting for cleavage of their substrates, immunolabeling using conformation-sensitive antibodies or affinity labeling followed by flow cytometry or ligand blotting. Here we describe methods for each of these assays, identify recent improvements in these assays and outline the strengths and limitations of each approach.

RETRACTED: Stimulation of sensory neurons by capsaicin increases tissue levels of IGF-I, thereby reducing reperfusion-induced apoptosis in mice

Calcitonin gene-related peptide (CGRP) increases insulin-like growth factor-I (IGF-I) production in fetal rat osteoblasts in vitro, suggesting that stimulation of sensory neurons might increase IGF-I production, thereby preventing apoptosis. We examined whether stimulation of sensory neurons by capsaicin might reduce reperfusion-induced hepatic apoptosis by increasing IGF-I production. Administration of capsaicin increased tissue levels of IGF-I and IGF-I mRNA in various organs in wild-type (WT) mice, but not in CGRP-knock-out (CGRP-/-) mice. Administration of CGRP increased tissue levels of IGF-I and IGF-I mRNA in both WT and CGRP-/- mice. Increases in hepatic tissue levels of TNF, serum levels of transaminases, hepatic apoptosis and hepatic tissue levels of caspase-3 after hepatic ischemia/reperfusion (I/R) were more marked in CGRP-/- mice than in WT mice. Hepatic IGF-I levels were increased in WT mice after reperfusion, while they were not changed in CGRP-/- mice. Although administration of capsaicin enhanced increases in IGF-I levels and reduced reperfusion-induced events in WT mice, it had no effect in CGRP-/- mice. Administration of CGRP and IGF-I reduced reperfusion-induced effects in both strains of mice. These observations suggested that capsaicin-induced sensory neuron activation, which leads to release of CGRP, might increase IGF-I production, thereby reducing reperfusion-induced liver injury by reducing apoptosis.

Agonistic monoclonal antibody against CD40 receptor decreases lymphocyte apoptosis and improves survival in sepsis

Sepsis causes a marked apoptosis-induced depletion of lymphocytes. The degree of lymphocyte apoptosis during sepsis strongly correlates with survival. CD40, a member of the TNFR family, is expressed on APCs and has potent antiapoptotic activity. In this study we determined whether an agonistic Ab against CD40 could protect lymphocytes from sepsis-induced apoptosis. Secondly, we examined potential antiapoptotic mechanisms of the putative protection. Lastly, we aimed to determine whether anti-CD40 treatment could improve survival in sepsis. CD1 mice were made septic by the cecal ligation and puncture method and treated postoperatively with anti-CD40 Ab. Treatment with anti-CD40 completely abrogated sepsis-induced splenic B cell death and, surprisingly, decreased splenic and thymic T cell death as well (p < 0.001). To investigate the mechanism of protection of anti-CD40 therapy on T cells, CD40 receptor expression was examined. As anticipated, the CD40 receptor was constitutively expressed on B cells, but, unexpectedly, splenic and thymic T cells were found to express CD40 receptor during sepsis. Furthermore, CD4+CD8- T cells were the predominant subtype of T cells expressing CD40 receptor during sepsis. Additionally, the antiapoptotic protein Bcl-x(L) was found to be markedly increased in splenic B and T cells as well as in thymic T cells after treatment with anti-CD40 Ab (p < 0.0025). Lastly, mice that were made septic in a double injury model of sepsis had improved survival after treatment with anti-CD40 as compared with controls (p = 0.05). In conclusion, anti-CD40 treatment increases Bcl-x(L), provides nearly complete protection against sepsis-induced lymphocyte apoptosis, and improves survival in sepsis.

Caspase-9 holoenzyme is a specific and optimal procaspase-3 processing machine

Caspase-9 activation is critical for intrinsic cell death. The activity of caspase-9 is increased dramatically upon association with the apoptosome, and the apoptosome bound caspase-9 is the caspase-9 holoenzyme (C9Holo). In this study, we use quantitative enzymatic assays to fully characterize C9Holo and a leucine-zipper-linked dimeric caspase-9 (LZ-C9). We surprisingly show that LZ-C9 is more active than C9Holo for the optimal caspase-9 peptide substrate LEHD-AFC but is much less active than C9Holo for the physiological substrate procaspase-3. The measured Km values of C9Holo and LZ-C9 for LEHD-AFC are similar, demonstrating that dimerization is sufficient for catalytic activation of caspase-9. The lower activity of C9Holo against LEHD-AFC may be attributed to incomplete C9Holo assembly. However, the measured Km of C9Holo for procaspase-3 is much lower than that of LZ-C9. Therefore, in addition to dimerization, the apoptosome activates caspase-9 by enhancing its affinity for procaspase-3, which is important for procaspase-3 activation at the physiological concentration.

Correlating the fractional inhibition of caspase-3 in NT2 cells with apoptotic markers using an active-caspase-3 enzyme-linked immunosorbent assay

A rapid and quantitative method for measuring the activity and fractional inhibition of enzymes within their natural cellular environment remains an unmet need in drug discovery. We describe the use of a nonradioactive quantitative enzyme-linked immunosorbent assay (ELISA) for measuring intracellular caspase activity that is amenable to robotic automation. The ELISA specifically detects active-caspase-3 and was used to correlate the in-cell activity of caspase-3 with the progress of caspase-3-mediated events under varying concentrations of caspase-3 inhibitors in NT2 cells. We examined the cleavage of endogenous substrates (poly(ADP-ribose)polymerase and alphaII-spectrin), the extent of DNA fragmentation, and the autocatalytic removal of the caspase-3 prodomain as markers of caspase-3 activity. To impart inhibition of the downstream markers, a greater level of caspase-3 inhibition was required. Although the functional markers were found not to accurately predict intracellular caspase-3 activity, we found that the inhibition of intracellular caspase-3 was highly correlated (R(2) = 0.96) to the inhibition of DNA fragmentation. Also, by comparing the potency of the different inhibitors against the intracellular enzyme versus the purified enzyme, the effects of inhibitor functional groups on whole-cell activity were addressed.

β2-Adrenergic receptor stimulation in vivo induces apoptosis in the rat heart and soleus muscle

High doses of the β2-adrenergic receptor (AR) agonist clenbuterol can induce necrotic myocyte death in the heart and slow-twitch skeletal muscle of the rat. However, it is not known whether this agent can also induce myocyte apoptosis and whether this would occur at a lower dose than previously reported for myocyte necrosis. Male Wistar rats were given single subcutaneous injections of clenbuterol. Immunohistochemistry was used to detect myocyte-specific apoptosis (detected on cryosections via a caspase 3 antibody and confirmed with annexin V, single-strand DNA labeling, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling). Myocyte apoptosis was first detected at 2 h and peaked 4 h after clenbuterol administration. The lowest dose of clenbuterol to induce cardiomyocyte apoptosis was 1 μg/kg, with peak apoptosis (0.35 ± 0.05%; P < 0.05) occurring in response to 5 mg/kg. In the soleus, peak apoptosis (5.8 ± 2%; P < 0.05) was induced by the lower dose of 10 μg/kg. Cardiomyocyte apoptosis was detected throughout the ventricles, atria, and papillary muscles. However, this damage was most abundant in the left ventricular subendocardium at a point 1.6 mm, that is, approximately one-quarter of the way, from the apex toward the base. β-AR antagonism (involving propranolol, bisoprolol, or ICI 118551) or reserpine was used to show that clenbuterol-induced myocardial apoptosis was mediated through neuromodulation of the sympathetic system and the cardiomyocyte β1-AR, whereas in the soleus direct stimulation of the myocyte β2-AR was involved. These data show that, when administered in vivo, β2-AR stimulation by clenbuterol is detrimental to cardiac and skeletal muscles even at low doses, by inducing apoptosis through β1- and β2-AR, respectively.

Cytokines activate caspase-3 in insulinoma cells of diabetes-prone NOD mice directly and via upregulation of Fas

In type 1 diabetes, autoimmune inflammation of pancreatic islets of Langerhans ('insulitis') results in destruction of insulin-producing beta cells. Cytokines released from islet-infiltrating mononuclear cells are known to be cytotoxic both directly and by upregulating Fas for FasL-induced apoptosis. To investigate the role of caspase-3, a major effector of apoptosis in beta-cell death, we asked whether cytokine- and/or FasL-induced apoptosis was associated with increased activity of caspase-3 in NIT-1 insulinoma cells and islets of autoimmune diabetes-prone NOD mice. Measurement of caspase-3 activity using a fluorogenic cleavage assay was validated in NOD mouse thymocytes undergoing dexamethasone (Dex)-induced apoptosis. For cytokine-induced apoptosis, NIT-1 cells or islets were exposed to IL-1 beta and IFN-gamma for 24 h. Caspase-3-like activity was increased 2.1+/-0.7 and 2.4+/-0.9-fold in lysates of cytokine-treated NIT-1 cells and NOD mouse islets, respectively. However, NIT-1 cells exhibited 2.1% (4.7 pg active caspase-3/microg protein) and islets 0.8% (1.9 pg active caspase-3/microg protein) of the active caspase-3 content observed in Dex-treated thymocytes (225.1 pg active caspase-3/microg protein). After 24 h cytokine-exposure, the percentage of Fas-positive NIT-1 cells increased from 1.4+/-1.1 to 29.7+/-11.6%. Addition of FasL for a further 3 h increased caspase-3-like activity an additional 1.8-fold in cytokine-treated NIT-1 cells. In summary, exposure of NOD mouse insulinoma cells or islets to IL-1 beta and IFN-gamma for 24 h induced caspase-3-like activity that, in the case of insulinoma cells at least, can be further enhanced by interaction of cytokine-induced Fas receptor with FasL. Compared to thymocytes, insulinoma cells and islets from NOD mice were characterised by low basal and cytokine-induced caspase-3 activity.

Bacterial cupredoxin azurin as an inducer of apoptosis and regression in human breast cancer

Azurin, a copper-containing redox protein released by the pathogenic bacterium Pseudomonas aeruginosa, is highly cytotoxic to the human breast cancer cell line MCF-7, but is less cytotoxic toward p53-negative (MDA-MB-157) or nonfunctional p53 cell lines like MDD2 and MDA-MB-231. The purpose of this study was to investigate the underlying mechanism of the action of bacterial cupredoxin azurin in the regression of breast cancer and its potential chemotherapeutic efficacy. Azurin enters into the cytosol of MCF-7 cells and travels to the nucleus, enhancing the intracellular levels of p53 and Bax, thereby triggering the release of mitochondrial cytochrome c into the cytosol. This process activates the caspase cascade (including caspase-9 and caspase-7), thereby initiating the apoptotic process. Our results indicate that azurin-induced cell death stimuli are amplified in the presence of p53. In vivo injection of azurin in immunodeficient mice harboring xenografted human breast cancer cells in the mammary fat pad leads to statistically significant regression (85%, P = 0.0179, Kruskal-Wallis Test) of the tumor. In conclusion, azurin blocks breast cancer cell proliferation and induces apoptosis through the mitochondrial pathway both in vitro and in vivo, thereby suggesting a potential chemotherapeutic application of this bacterial cupredoxin for the treatment of breast cancer.

Allicin (from garlic) induces caspase-mediated apoptosis in cancer cells

Garlic (Allium sativum) has been used for centuries for treating various ailments, and its consumption is said to reduce cancer risk and its extracts and components effectively block experimentally induced tumors. Allicin, the major component present in freshly crushed garlic, is one of the most biologically active compounds of garlic. We found that allicin inhibited the growth of cancer cells of murine and human origin. Allicin induced the formation of apoptotic bodies, nuclear condensation and a typical DNA ladder in cancer cells. Furthermore, activation of caspases-3, -8 and -9 and cleavage of poly(ADP-ribose) polymerase were induced by allicin. The present results demonstrating allicin-induced apoptosis of cancer cells are novel since allicin has not been shown to induce apoptosis previously. Our results also provide a mechanistic basis for the antiproliferative effects of allicin and partly account for the chemopreventive action of garlic extracts reported by earlier workers.

An uncleavable procaspase-3 mutant has a lower catalytic efficiency but an active site similar to that of mature caspase-3

We have examined the enzymatic activity of an uncleavable procaspase-3 mutant (D9A/D28A/D175A), which contains the wild-type catalytic residues in the active site. The results are compared to those for the mature caspase-3. Although at pH 7.5 and 25 degrees C the K(m) values are similar, the catalytic efficiency (k(cat)) is approximately 130-fold lower in the zymogen. The mature caspase-3 demonstrates a maximum activity at pH 7.4, whereas the maximum activity of procaspase-3 occurs at pH 8.3. The pK(a) values of both catalytic groups, H121 and C163, are shifted to higher pH for procaspase-3. We developed limited proteolysis assays using trypsin and V8 proteases, and we show that these assays allow the examination of amino acids in three of five active site loops. In addition, we examined the fluorescence emission of the two tryptophanyl residues in the active site over the pH range of 2.5-9 as well as the response to several quenching agents. Overall, the data suggest that the major conformational change that occurs upon maturation results in formation of the loop bundle among loops L4, L2, and L2'. The pK(a) values of both catalytic groups decrease as a result of the loop movements. However, loop L3, which comprises the bulk of the substrate binding pocket, does not appear to be unraveled and solvent-exposed, even at lower pH.

Morphological and biochemical aspects of apoptosis, oncosis and necrosis

Recent investigations have demonstrated the need for a precise differentiation of various forms of cell death such as apoptosis, oncosis, necrosis and programmed cell death. Apoptosis is marked by cellular shrinking, condensation and margination of the chromatin and ruffling of the plasma membrane with eventually breaking up of the cell in apoptotic bodies. Cell death marked by cellular swelling should be called oncosis, whereas the term necrosis refers to the morphological alterations appearing after cell death. Apoptosis and oncosis are therefore pre-mortal processes, while necrosis is a post-mortal condition. The term programmed cell death refers to the 'fixed' pathway followed by dying cells, whether or not with the characteristic morphology of apoptosis. Three mechanisms are actually known to be involved in the apoptotic process: a receptor-ligand mediated mechanism, a mitochondrial pathway and a mechanism in which the endoplasmic reticulum plays a central role. All three mechanisms activate caspases which are responsible for the characteristic morphological changes observed during apoptosis. A review of the different methods used for detecting apoptotic cells demonstrates that most of these techniques are not entirely specific.

Evaluation of caspase activity in apoptotic cells

A family of cysteine proteases, the caspases, plays a central role in the initiation and execution phases of apoptosis. Upon activation, these enzymes cleave specific substrates and thereby mediate many of the typical biochemical and morphological changes in apoptotic cells, such as cell shrinkage, chromatin condensation, DNA fragmentation and plasma membrane blebbing. Hence, the detection of activated caspases can be used as a biochemical marker for apoptosis. Here we review a set of methods available for characterizing and quantifying the activation of caspases, including immunoblotting, cleavage of synthetic substrates, affinity labeling and confocal microscopy. Each method is described in general terms and the advantages and disadvantages of each technique are discussed.

Photogenotoxicity of mammalian cells: a review of the different assays for in vitro testing

During the past several years, phototoxicity has been studied at the molecular level, and these studies have provided new insights in the field of DNA lesion characterization, DNA repair and cell response to ultraviolet (UV)-induced stress. The development of new antibiotics and antiinflammatory drugs has highlighted the necessity to develop the assessment of phototoxicity in the safety evaluation of new chemical compounds. This paper aims at reviewing the known molecular mechanisms of the cellular response to UV-induced stress, the in vitro methods that can be proposed and used to screen for toxicity of sunlight and the photosensitization process resulting from the activation of drugs by light. UV sources, biological systems and endpoints of interest in that particular objective are listed. Phototoxic effects span from the cytotoxic-apoptotic effect to the induction of primary DNA damage, DNA repair and a variety of stress genes acting on the cell cycle and the fate of the cell. Ultimately, it can lead to the induction of hereditary DNA modification. A variety of assays are proposed to specifically address all these particular consequences of UV-induced toxicity.

Inhibition of sodium butyrate-induced apoptosis in recombinant Chinese hamster ovary cells by constitutively expressing antisense RNA of caspase-3

Sodium butyrate (NaBu) can enhance the expression of genes controlled by some of the mammalian promoters, but it can also inhibit cell growth and induce cellular apoptosis. Thus, the beneficial effect of using a higher concentration of NaBu on a foreign protein expression is compromised by its cytotoxic effect on cell growth. To overcome this cytotoxic effect of NaBu, the expression vector of antisense RNA of caspase-3 was constructed and transfected to recombinant Chinese hamster ovary (rCHO) cells producing a humanized antibody. Using this antisense RNA strategy, rCHO cells (B3) producing a low level of caspase-3 proenzyme were established. When batch cultures of both B3 cells and control cells transfected with antisense RNA-deficient plasmid were performed in the absence of NaBu, both cells showed similar profiles of cell growth and antibody production. Compared with control cell culture, under the condition of 5 mM NaBu addition at the exponential growth phase, expression of antisense RNA of caspase-3 significantly suppressed the NaBu-induced apoptosis of B3 cells and extended culture longevity by >2 days if the culture was terminated at cell viability of 50%. However, compared with control cell culture, the final antibody concentration of B3 cell culture was not increased in the presence of NaBu, which may be due to the loss of cellular metabolic capability resulted from the depolarization of mitochondrial membrane. Taken together, this study suggests that, although expression of antisense RNA of caspase-3 does not improve antibody productivity of rCHO cells, it can suppress NaBu-induced apoptotic cell death of rCHO cells and thereby may reduce problems associated with cellular disintegration.

Effects of miltefosine on various biochemical parameters in a panel of tumor cell lines with different sensitivities

We investigated endocytosis activity, uptake of miltefosine (hexadecylphosphocholine), phospholipid and cholesterol content, the cell cycle, and apoptosis in 13 tumor cell lines (MCF7, MCF7/ADR, KB-3-1, KB-8-5, KB-C1, HeLa, HeLa-MDR1-G185, HeLa-MDR1-V185, CCRF/CEM, CCRF/VCR1000, CCRF/ADR5000, HL-60, HL-60/AR) with different sensitivities to treatment with the antitumor phospholipid analogues miltefosine and D-21266 (octadecyl-(N,N-dimethyl-piperidino-4-yl)-phosphate). In this panel of cell lines, MDR1 (multidrug resistance gene 1)- and MRP1 (multidrug resistance-associated protein)-expressing cells were found to be slightly more resistant to both compounds than sensitive parental cells. No correlation was found between resistance to miltefosine and endocytosis, intracellular concentration of miltefosine, the phospholipid and cholesterol content, induction of apoptosis, or cell cycle alterations in all the cell lines tested. Wild-type p53 containing WMN Burkitt's lymphoma cells and wild type p53-deficient CA46 exhibited similar sensitivities to miltefosine. The low percentage of apoptosis induced in MCF7 cells lacking caspase 3 indicated that caspase 3 seems to play an essential role in miltefosine-induced apoptosis.

Measurement of proteases using chemiluminescence-resonance-energy-transfer chimaeras between green fluorescent protein and aequorin

Homogeneous assays, without a separation step, are essential for measuring chemical events in live cells and for drug discovery screens, and are desirable for making measurements in cell extracts or clinical samples. Here we demonstrate the principle of chemiluminescence resonance energy transfer (CRET) as a homogeneous assay system, using two proteases as models, one extracellular (alpha-thrombin) and the other intracellular (caspase-3). Chimaeras were engineered with aequorin as the chemiluminescent energy donor and green fluorescent protein (GFP) or enhanced GFP as the energy acceptors, with a protease linker (6 or 18 amino acid residues) recognition site between the donor and acceptor. Flash chemiluminescent spectra (20--60 s) showed that the spectra of chimaeras matched GFP, being similar to that of luminous jellyfish, justifying their designation as 'Rainbow' proteins. Addition of the protease shifted the emission spectrum to that of aequorin in a time- and dose-dependent manner. Separation of the proteolysed fragments showed that the ratio of green to blue light matched the extent of proteolysis. The caspase-3 Rainbow protein was able to provide information on the specificity of caspases in vitro and in vivo. It was also able to monitor caspase-3 activation in cells provoked into apoptosis by staurosporine (1 or 2 microM). CRET can also monitor GFP fluor formation. The signal-to-noise ratio of our Rainbow proteins is superior to that of fluorescence resonance energy transfer, providing a potential platform for measuring agents that interact with the reactive site between the donor and acceptor.

Expression of active caspase-3 in mitotic and postmitotic cells of the rat forebrain

Active caspase-3 immunoreactivity was detected in the rat forebrain proliferative regions at birth and remained high in these areas for about 2 weeks, during which period labeled cells were present centroperipherally across the olfactory bulb. By the end of the third postnatal week, only a small number of immunolabeled cells remained in these forebrain structures. Active caspase-3 immunolabeling was localized mostly to cell nuclei and co-localized partially with TuJ1 and NeuN immunoreactivity, but not with glial fibrially acidic protein, OX-42, gamma-aminobutyric acid, or terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL)-positive labeling. Active caspase-3 and 5-bromo-2'-deoxyuridine (BrdU) double-labeled nuclei were seen in the proliferative regions after 2 hours and in the periglomerular region of the bulb after 7 days following BrdU injections. Examination of the cells with electron microscopy confirmed that the active caspase-3-containing nuclei in the proliferative regions often had infoldings and appeared to be undergoing division. Some of the cells with active caspase-3-labeled nuclei in the bulb had synapses on their somata or dendrites. Labeled dendritic spines and a few axon terminals were also observed in the olfactory bulb. Taken together, it appears that a wave of active caspase-3-positive cells are dividing in the proliferative zones and then migrating to the bulb as they differentiate into neurons. Therefore, active caspase-3 may play a role in cellular processes such as neuronal differentiation, migration, and plasticity, in addition to its role in cell death.