Apoptosis and signal transduction: clues to a molecular mechanism

Evidence of interactions among apoptosis, cell proliferation, and dedifferentiation in the rudiment during whole-organ intestinal regeneration in the sea cucumber

Sea cucumbers have an extraordinary regenerative capability. Under stressful conditions, Holothuria glaberrima can eviscerate their internal organs, including the digestive tract. From the mesentery, a rudiment grows and gives rise to a new intestine within a few weeks. In the last decades, the cellular events that occur during intestinal regeneration have been characterized, including apoptosis, cell proliferation, and muscle cell dedifferentiation. Nevertheless, their contribution to the formation and early growth of the rudiment is still unknown. Furthermore, these cellular events' relationship and potential interdependence remain a mystery. Using modulators to inhibit apoptosis and cell proliferation, we tested whether rudiment growth or other regenerative cellular events like muscle cell dedifferentiation were affected. We found that inhibition of apoptosis by zVAD and cell proliferation by aphidicolin and mitomycin did not affect the overall size of the rudiment seven days post-evisceration (7-dpe). Interestingly, animals treated with aphidicolin showed higher levels of muscle cell dedifferentiation in the distal mesentery, which could act as a compensatory mechanism. On the other hand, inhibition of apoptosis led to a decrease in cell proliferation in the rudiment and a delay in the spatiotemporal progression of muscle cell dedifferentiation throughout the rudiment-mesentery structure. Our findings suggest that neither apoptosis nor cell proliferation significantly contributes to early rudiment growth during intestinal regeneration in the sea cucumber. Nevertheless, apoptosis may play an essential role in modulating cell proliferation in the rudiment (a process known as apoptosis-induced proliferation) and the timing for the progression of muscle cell dedifferentiation. These findings provide new insights into the role and relationship of cellular events during intestinal regeneration in an emerging regeneration model.

The evaluation of anti-breast cancer activity and safety pharmacology of the ethanol extract of Aralia elata Seem. leaves

Aralia elata Seem. is a traditional folk Chinese medicinal plant and its leaves have been used to treat many diseases. We aimed to evaluate the anti-breast cancer activity and safety pharmacology of the ethanol extract of A. elata Seem. leaves (ELE). Cytotoxicity was evaluated on human tumor cell lines by MTT assay in vitro. A tumor bearing-nude mice model was used to assess antitumor activity in vivo. Cell apoptosis was determined by Hoechst 33258 staining, flow cytometry and TUNEL staining. The protein levels were determined by western-blotting and immunohistochemical staining. In safety evaluation, ICR mice and beagle dogs were orally administered ELE at different doses to determine its adverse effects on the central nervous system and cardiorespiratory system. ELE significantly inhibited tumor growth and induced cell apoptosis in MCF-7 cells in vitro and in vivo. The protein levels including caspase-3, caspase-9, bax, bcl-2, PARP, and cytochrome c were significantly changed. For the central nervous system, no treatment-related changes in behavior, motor activity or coordination were observed in mice. For the cardiorespiratory system, no significant differences in cardiorespiratory parameters including heart rate, PR interval, RR interval, P wave duration, QRS duration, QTcF interval, respiratory frequency, tidal volume, body temperature, and blood pressure were observed in beagle dogs between the ELE treatment and control group. In conclusion, ELE possessed anti-breast cancer activity by activating a mitochondrial-mediated apoptotic pathway with high biological safety in animals, which indicates it could be a potential therapeutic agent for treating human breast cancer in the future.

(-)-Syringaresinol-4-O-β-D-glucopyranoside from Cortex Albizziae inhibits corticosterone-induced PC12 cell apoptosis and relieves the associated dysfunction

The neuroprotective effects and potential mechanisms of (-)-Syringaresinol-4-O-β-D-glucopyranoside (SRG), a natural lignan glycoside extracted from Cortex Albizziae, were investigated using corticosterone (CORT)-induced PC12 cells as an in vitro anxiety model. PC12 cells were treated with 100 μM CORT and 5, 10, or 20 μM SRG for 48 h. Cell viability and lactate dehydrogenase (LDH) leakage were measured. Apoptosis were detected using FITC-coupled Annexin V (AV) and propidium iodide (PI) staining flow cytometric analyses and TUNEL assays. Rhodamine 123 and Fluo-3-AM staining flow cytometric analyses were used to detect mitochondrial membrane potential (ΔΨm) and intracellular calcium concentration ([Ca²⁺]_i), respectively. Western blot was used to detect brain-derived neurotrophic factor (BDNF), Bax, Bcl-2, cAMP-response element binding protein (CREB), cytosolic cytochrome c (Cyt c), caspase-3, and cleaved caspase-3. Experimental data showed that SRG promoted cell proliferation, reduced LDH release, inhibited apoptosis, improved ΔΨm values, decreased [Ca²⁺]_i, up-regulated CREB, BDNF, and Bcl-2, down-regulated Bax and Cyt c protein expression levels, and reduced caspase-3 activity. This suggests that SRG has neuroprotective and antiapoptotic effects in the pathogenesis of anxiety disorders, and its mechanisms are partly connecte to inhibition of the mitochondrial apoptotic pathway and activation of pathways involving CREB and BDNF.

Regulator of Cell Cycle (RGCC) Expression During the Progression of Alzheimer's Disease

Unscheduled cell cycle reentry of postmitotic neurons has been described in cases of mild cognitive impairment (MCI) and Alzheimer's disease (AD) and may form a basis for selective neuronal vulnerability during disease progression. In this regard, the multifunctional protein regulator of cell cycle (RGCC) has been implicated in driving G1/S and G2/M phase transitions through its interactions with cdc/cyclin-dependent kinase 1 (cdk1) and is induced by p53, which mediates apoptosis in neurons. We tested whether RGCC levels were dysregulated in frontal cortex samples obtained postmortem from subjects who died with a clinical diagnosis of no cognitive impairment (NCI), MCI, or AD. RGCC mRNA and protein levels were upregulated by ∼50%-60% in MCI and AD compared to NCI, and RGCC protein levels were associated with poorer antemortem global cognitive performance in the subjects examined. To test whether RGCC might regulate neuronal cell cycle reentry and apoptosis, we differentiated neuronotypic PC12 cultures with nerve growth factor (NGF) followed by NGF withdrawal to induce abortive cell cycle activation and cell death. Experimental reduction of RGCC levels increased cell survival and reduced levels of the cdk1 target cyclin B1. RGCC may be a candidate cell cycle target for neuroprotection during the onset of AD.

Effect of a bispidinone analog on mitochondria‑mediated apoptosis in HeLa cells

The present study was carried out to investigate the effect of 2,4,6,8-tetraaryl-3,7-diazabicyclo[3.3.1]nonan-9-one (bispidinone) analogs on the in vitro growth of human cervical carcinoma (HeLa) cells. A series of 11 bispidinone analogs was synthesized with substituents, e.g., fluoro/methyl/ethyl/isopropyl/thiomethyl/methoxy groups, at various positions. These compounds were synthesized to identify which substituent and position induced the strongest cytotoxic effect in cancer cells. Among these synthetics, analog 9, which contains methoxy groups, had the most significant cytotoxic effect on HeLa cells, and its IC50 value was less than 13 µM. A WST-8 assay also showed that analog 9 inhibited the proliferation of HeLa cells. By using DNA content analysis, we found that analog 9 induced sub-G1 and G1 phase arrest in a time-dependent manner. A [3H]-thymidine incorporation assay suggested that analog 9 inhibited DNA replication in HeLa cells. On performing light microscopy, morphological changes such as cellular shrinkage and disruption, which are apoptotic features, were observed in HeLa cells. Annexin V/propidium iodide double staining and rhodamine-123 staining showed that analog 9 induced apoptosis and disrupted the intracellular mitochondrial membrane potential in HeLa cells. The western blot analysis results suggested that analog 9 induced mitochondria-mediated apoptosis. In addition, we have shown that analog 9 may play a role in the Fas signaling apoptotic pathway.

A novel trifluoromethyl benzopyran induces G1 cell cycle arrest and apoptosis in HeLa human cervical carcinoma cells

In the present study, a biologically active 4-(trifluoromethyl)phenyl piperazin moiety was linked to a 2,2- dimethyl -2H-benzopyran template to generate (3R,4S)-2,2-dimethyl-6-nitro-4-(4-(3-(trifluoromethyl)phenyl)piperazin-1-yl) chroman -3-ol (C110g), and the cellular and molecular mechanisms by which C110g exerts cytotoxic effects on the HeLa human cervical cancer cell line were further investigated. C110g suppressed the viability of HeLa cells in both concentration- and time-dependent manner (IC50 of 17 µM) by inducing DNA damage and G1 cell cycle arrest. Characteristic changes in nuclear morphology and Annexin V/PI staining pointed to apoptosis as the mode of cell death. The levels of p53 and p21 were increased in the C110g-treated cells, with a corresponding increase in Bax/Bcl-2 protein ratio. Subsequently, C110g induced the cytoplasmic release of cytochrome c from the mitochondria accompanied by a decreased mitochondrial membrane potential and activation of caspase-3 and -9. These results confirmed that the C110g transduced the apoptotic signal via the mitochondrial pathway. Caspase-8, typically associated with the initiation of the death receptor pathway, was activated, suggesting the extrinsic pathway might also be involved. However, C110g did not result in reactive oxygen species (ROS) generation. Taken together, these findings indicate that the DNA damage-dependent p53-regulated mitochondrial pathway as well as the extrinsic pathway play a crucial role in C110g-induced apoptosis, which provide a better understanding of the molecular mechanisms of trifluoromethyl benzopyrans in cervical cancer.

Cyclin D1 immunoreactivity changes in CA1 pyramidal neurons and dentate granule cells in the gerbil hippocampus after transient forebrain ischemia

OBJECTIVES

Cyclin D1, a member of the G1 cyclin family, plays a critical role in the progression of the cell cycle. In the present study, we investigated chronological alterations in cyclin D1 immunoreactivity and its protein levels in the gerbil hippocampus after ischemia/reperfusion.

METHODS

Chronological alterations in cyclin D1 immunoreactivity and its levels were examined in the gerbil hippocampus after ischemia/reperfusion using immunohistochemistry and western blot analysis.

RESULTS

Changes in cyclin D1 immunoreactivity in the ischemic hippocampus were distinct in pyramidal neurons of the CA1 region and granule cells of the dentate gyrus. Cyclin D1 immunoreactivity in pyramidal neurons of the CA1 region was increased up to 1 day after ischemia/reperfusion, although a transient decrease of cyclin D1 immunoreactivity was detected at 12 hour after ischemia/reperfusion. Thereafter, cyclin D1 immunoreactivity in the CA1 pyramidal neurons was very weak 2 days and disappeared nearly 4 and 7 days after ischemia/reperfusion. However, 4 days after ischemia/reperfusion, the cyclin D1 immunoreactivity in non-pyramidal neurons of the CA1 region was very strong. In the CA2/3 region, cyclin D1 immunoreactivity was higher than that in the CA1 region and not changed after ischemia/reperfusion. In the dentate gyrus, chronological change in cyclin D1 immunoreactivity was observed. Cells in the granule cell layer showed distinct change in cyclin D1 immunoreactivity after ischemia/reperfusion: the cyclin D1 immunoreactivity was lowest at 12 hours and strong 1 and 4 days after ischemia/reperfusion. In addition, change in cyclin D1 protein level was found in the ischemic hippocampus.

CONCLUSION

Our results indicate that cyclin D1 may play an important role in cellular events related with neuronal damage following ischemia/reperfusion.

Neuroblast proliferation on the surface of the adult rat striatal wall after focal ependymal loss by intracerebroventricular injection of neuraminidase

The subventricular zone of the striatal wall of adult rodents is an active neurogenic region for life. Cubic multiciliated ependyma separates the subventricular zone from the cerebrospinal fluid (CSF) and is involved in the control of adult neurogenesis. By injecting neuraminidase from Clostridium perfringens into the right lateral ventricle of the rat, we provoked a partial detachment of the ependyma in the striatal wall. The contralateral ventricle was never affected and was used as the experimental control. Neuraminidase caused widening of the intercellular spaces among some ependymal cells and their subsequent detachment and disintegration in the CSF. Partial ependymal denudation was followed by infiltration of the CSF with macrophages and neutrophils from the local choroid plexus, which ependymal cells never detached after neuraminidase administration. Inflammation extended toward the periventricular parenchyma. The ependymal cells that did not detach and remained in the ventricle wall never proliferated. The lost ependyma was never recovered, and ependymal cells never behaved as neural stem cells. Instead, a scar formed by overlapping astrocytic processes sealed those regions devoid of ependyma. Some ependymal cells at the border of the denudated areas lost contact with the ventricle and became located under the glial layer. Concomitantly with scar formation, some subependymal cells protruded toward the ventricle through the ependymal breaks, proliferated, and formed clusters of rounded ventricular cells that expressed the phenotype of neuroblasts. Ventricular clusters of neuroblasts remained in the ventricle up to 90 days after injection. In the subventricular zone, adult neurogenesis persisted.

Interactions between migratory primordial germ cells and cellular substrates in the mouse

In previous in vitro studies we found that contact between mouse primordial germ cells and other cell types (neighbouring somatic cells or established TM4 or STO cell lines) is crucial for supporting primordial germ cell survival and proliferation and for activating their motility. We have studied primordial germ cell adhesion to different cell monolayers (STO, TM4, COS and F9 cells) as an in vitro model for interactions between primordial germ cells and cellular substrates. The results suggest that these cell interactions are mediated by multiple mechanisms involving Steel factor and its receptor encoded by c-kit, carbohydrates and possibly other unknown factors. We find that Steel factor and leukaemia inhibitory factor are survival rather than proliferation factors for primordial germ cells. Both molecules prevent primordial germ cell death in culture by suppressing apoptosis. Morphological and molecular features of primordial germ cell apoptosis in vitro are reported. Activation of protein kinase C does not promote primordial germ cell proliferation, but compounds known to enhance intracellular levels of cAMP (i.e. dibutyryl cAMP and forskolin) markedly stimulate primordial germ cells to proliferate in culture. We have preliminary results indicating that neuropeptides PACAP-27 and PACAP-28 are possible physiological activators of adenylate cyclase in primordial germ cells.

Systemic chemotherapy for the treatment of metastatic melanoma

The role of systemic chemotherapy in the treatment of patients with metastatic melanoma remains of questionable benefit. Despite encouraging phase II data from multiple institutions that suggested an improved overall response rate for patients treated with the Dartmouth regimen, recently completed phase III trials have failed to demonstrate a significant benefit in survival. Of concern is the fact that there have been relatively few new chemotherapeutic agents in the past several years that have demonstrated any activity in this disease. More recently there has been a shift away from combination chemotherapy to biochemotherapy. However, this approach has yet to be clearly defined as superior. The basis for optimism in the future in this field resides in the realm of molecular oncology. As mechanisms of resistance are identified, new molecules such as antisense oligonucleotides may provide the basis for increasing the sensitivity of melanoma to chemotherapeutic and/or immunotherapeutic treatments.

Increased apoptosis in B-chronic lymphocytic leukemia cells as a result of cyclin D3 down regulation

B-cell chronic lymphocytic leukemia (CLL) is a clonal B cell malignancy of morphologically mature, functionally immature B cells. B-cell CLL cells are known to be resistant to killing by anticancer and other agents. This resistance is associated with alterations in apoptosis and cell cycle regulated genes. In our earlier studies, we have demonstrated that CLL cells have differential expression of genes that are associated with apoptosis and cell cycle regulation, including elevated expression of Bcl-2, DAD-1, Cyclin D3 and cyclin dependent kinase 4 inhibitor. Therefore, in this study, in an attempt to study the role of Cyclin D3 in the resistant behavior of CLL cells, Cyclin D3 was down regulated using antisense oligonucleotide (AS-ODN) in WSU-CLL, a human CLL cell line. The down regulation of Cyclin D3 was confirmed by RT-PCR and flow cytometry techniques. The Cyclin D3 expression down-regulated WSU-CLL cells were then tested for their susceptibility to fludarabine, a chemotherapeutic agent. Our results showed that the Cyclin D3 expression down-regulated WSU-CLL cells were more susceptible to fludarabine mediated killing. Following treatment with fludarabine, there was a significant increase in the number of cells undergoing apoptosis in Cyclin D3 expression down-regulated WSU-CLL cells as determined by Annexin-V assay, cell cycle analysis for DNA content, and cytomorphology. Thus, our results indicate Cyclin D3 down regulation increases the killing of WSU-CLL cells with fludarabine by increasing the number of cells undergoing apoptosis.

Expression of RB C pocket fragments in HSF induces delayed cell cycle progression and sensitizes to apoptosis upon cellular stresses

The retinoblastoma protein (RB) plays an important role in growth suppression through the formation of multiple protein complexes with its target proteins using A/B and C pockets. Even though the A/B and C pockets co-operate for growth suppression, the function of RB in growth arrest is inhibited by the coexpression of RB C fragments with full length RB in the absence of p53, which implies that C pocket fragments are likely to act as a dominant-negative inhibitor of RB function. In contrast, the loss of the RB functions in the presence of p53 triggers a cell cycle arrest or apoptosis by p53-dependent pathways. Thus, it still remains to be elucidated whether the expression of RB C pocket fragments in the presence of p53 induces delayed cell cycle progression and sensitizes cells to apoptosis through p53-dependent pathways. Our results show that the expression of RB C pocket fragments not only induces delayed cell cycle progression, which is mediated by the down-regulation of cyclin A, cyclin E, and E2F-1, but also sensitizes cells to apoptosis through p53-dependent pathways.

A novel beta-lactam antibiotic activates tumor cell apoptotic program by inducing DNA damage

Many of the anticancer drugs in current use are toxic and thus limited in their efficacy. It therefore becomes essential to develop novel chemotherapeutic agents with lower levels of toxicity. The beta-lactam antibiotics have been used for many years to treat bacterial infections with limited or no toxicity. Until now, it has never been shown that beta-lactams could kill tumor cells. Here, for the first time, we have discovered and characterized the apoptosis-inducing properties of a family of novel beta-lactam antibiotics against human leukemia, breast, prostate, and head-and-neck cancer cells. We found that one particular lead compound (lactam 1) with an N-methylthio group was able to induce DNA damage and inhibit DNA replication in Jurkat T cells within a 2-h treatment. This was followed by p38 mitogen-activated protein kinase activation, S phase arrest, and apoptotic cell death. p38 was found to be a central player in beta-lactam-induced apoptosis and resided downstream of DNA damage but upstream of caspase activation. Accompanying caspase-8 activation was cleavage of the pro-apoptotic Bcl-2 family protein Bid, and release of the mitochondrial cytochrome c. This was also associated with activation of caspase-9 and -3. Analogs of lactam 1 in which the N-methylthio group was replaced with other organothio chains exhibited progressive decreased potencies to induce DNA damage, p38 kinase activation, S phase arrest, and apoptosis, demonstrating requirement of the N-methylthio group. Because of the ease of synthesis and structural manipulation, we believe these beta-lactams may have the potential to be developed into anticancer agents.

Inhibition of proteasome function induced apoptosis in gastric cancer

The ubiquitin-proteasome pathway plays a critical role in the degradation of cellular proteins and cell cycle control. Dysregulating the degradation of such proteins should have profound effects on tumor growth and causes cells to undergo apoptosis. The aims of this study are to evaluate the ubiquitin-proteasome pathway in gastric cancer and the potential role of pharmacological inhibition of proteasome on induction of apoptosis in gastric cancer cells. Gastric cancer cell lines AGS (p53 wild-type) and MKN-28 (p53 mutant) were treated with proteasome inhibitor MG132. The results showed that MG132 inhibited cell proliferation in AGS and MKN-28 cells in a time- and dose-dependent manner. The inhibition of cell proliferation was caused by apoptosis which was also time- and dose-dependent. AGS cells were more responsive to MG132 than MKN-28 cells. Induction of apoptosis was preceded by the activation of caspase-3, as measured by a colorimetric caspase-3 cellular activity and Western blotting of the cleavage of caspase-3 and its substrate PARP. Activation of caspase-7 was also exhibited. In addition, z-VAD-fmk, a broad spectrum caspase inhibitor, reversed apoptosis induced by MG132 in AGS and MKN28 cells. Although z-DEVD-fmk, a specific caspase-3 inhibitor, suppressed MG132-induced apoptosis in MKN28 cells, it only partially rescued the apoptotic effect in AGS cells. Caspase-3 activation was the result of release of cytochrome c from mitochondria into the cytosol, as a consequence of upregulation of bax. There were overexpressions of all the proteasome-related proteins p53, p21(waf1) and p27(kip1) at 4 hr after proteasome inhibition which was identified by the accumulation of ubiquitin-tagged proteins. This was accompanied by accumulation of cells at G(1) phase. Our present study suggests that inhibition of proteasome function in gastric cancer cells induces apoptosis and proteasomal inhibitors have potential use as novel anticancer drugs in gastric cancer.

Role of programmed cell death in development

Programmed cell death (PCD) is an integral part of both animal and plant development. In animals, model systems such as Caenorhabditis elegans, Drosophila melanogaster, and mice have shown a general cell death profile of induction, caspase mediation, cell death, and phagocytosis. Tremendous strides have been made in cell death research in animals in the past decade. The ordering of the C. elegans genes Ced-3, 4 and 9, identification of caspase-activated DNase that degrades nuclear DNA during PCD, identification of signal transduction modules involving caspases as well as the caspase-independent pathway, and the involvement of mitochondria are some of the findings of immense value in understanding animal PCDs. Similarly, the caspase inactivation mechanisms of infecting viruses to stall host cell death give a new dimension to the viral infection process. However, plant cell death profiles provide an entirely different scenario. The presence of a cell wall that cannot be phagocytosed, absence of the hallmarks of animal PCDs such as DNA laddering, formation of apoptotic bodies, a cell-death-specific nuclease, a biochemical machinery of killer enzymes such as caspases all point to novel ways of cell elimination. Large gaps in our understanding of plant cell death have prompted speculative inferences and comparisons with animal cell death mechanisms. This paper deals with both animals and plants for a holistic view on cell death in eukaryotes.

G(1) phase-dependent expression of bcl-2 mRNA and protein correlates with chemoresistance of human cancer cells

Recent experiments suggest an interconnection between cell proliferation and programmed cell death (apoptosis), although the detailed molecular mechanisms remain unclear. We have hypothesized that expression of some apoptosis regulators is cell cycle-dependent, which in turn influences tumor cell chemosensitivity in a cell cycle-dependent fashion. To test these hypotheses, we synchronized human leukemia Jurkat T, Neo (using aphidicolin), breast cancer MCF-7, normal fibroblast, and simian virus 40-transformed cells (by aphidicolin or serum starvation), and measured levels of several Bcl-2 family proteins. The highest expression of Bcl-2 protein was found in the G(1) phase of all the five cell lines tested. In contrast, levels of Bax protein remained relatively unchanged in four of the cell lines, and levels of Bcl-X(L), Bcl-X(S), and Bak proteins showed little or no cell cycle-dependent changes in Jurkat T cells. Similar to the changes in Bcl-2 protein levels, its mRNA expression was also G(1) phase-specific, whereas the level of a Bcl-2 cleavage activity remained constitutive. When treated with an anticancer drug (etoposide or cisplatin) or the kinase inhibitor staurosporin, the cells containing a high G(1) population and a high Bcl-2 protein level were much more resistant to the induced apoptosis than the cells containing a high S phase population and a low Bcl-2 protein level. Constitutive overexpression of Bcl-2 protein in Jurkat T cells completely blocked the S phase-associated sensitivity to these apoptosis stimuli. The cell cycle-dependent Bcl-2 protein expression seems to contribute to the regulation of chemosensitivity and apoptotic commitment of human tumor cells.

Epithelial cells release proinflammatory cytokines and undergo c-Myc-induced apoptosis on exposure to filarial parasitic sheath protein-Bcl2 mediates rescue by activating c-H-Ras

Circulating filarial proteins elicit strong immunologic reactions in humans leading to the chronic manifestations in human lymphatic filariasis such as lymphatic occlusion, fibrosis, edema, and in some cases, tropical pulmonary eosinophilia. Our earlier studies, in vitro, conclusively prove that filarial parasitic sheath proteins induce apoptosis in HEp2 cells, an epithelial cell line, by a pathway inhibitable by bcl2. The present findings provide evidence that c-myc activation triggers apoptosis in HEp2 cells and that it is also responsible for the burst of abortive proliferation at 6 d of treatment of HEp2 bcl2 cells that overexpress bcl2, with filarial parasitic sheath protein, demonstrating the interplay between the two genes c-myc and bcl2, wherein bcl2 acts by restoring the prosurvival signal to c-myc and keeping its apoptotic tendency in check. This study also indicates that bcl2 upregulates c-H-ras, engaging ras to bring about the suppression of apoptosis through protein tyrosine kinase elevation, thus promoting the survival of the HEp2 bcl2 cells. In addition to the activation of these "signal switches," we also observe that these cells release cytokines like IL-6 and IL-8 through the upregulation of c-fos, when exposed to filarial parasitic sheath protein, reflecting on the immunomodulatory capacity of the epithelium to elicit a host immune response by setting up a chemotactic gradient, attracting inflammatory cells to the site of infection.

A cell-survival factor (N-acetyl-L-cysteine) alters the in vivo fate of constitutively proliferating subependymal cells in the adult forebrain

The adult mouse brain contains a population of constitutively proliferating subependymal cells that surround the lateral ventricle and are the direct progeny of the neural stem cell. Constitutively proliferating cells divide rapidly; 6 days after labeling, 60% of their progeny undergo cell death, 25% migrate to the olfactory bulbs, and 15% continue to proliferate within the subependyma. We have intraventricularly infused a cell survival factor N-acetyl-L-cysteine (NAC), which is known to have survival effects without concomitant proliferative effects on cells in vitro, and examined the resulting fate of cells spared from the normally occurring cell death. NAC infusion for 5 days results in a five-fold increase in the number of retrovirally labeled subependymal cells compared to saline-infused controls. The increase in the number of subependymal cells is directly proportional to the amount of time during which NAC is present and is not due to increased proliferation. While NAC is able to keep all the normally dying progeny alive, the cells spared from death remain confined to the subependyma lining the lateral ventricles and do not migrate to the olfactory bulbs (one normal fate of constitutively proliferating progeny) or into the surrounding brain parenchyma. When animals survive for an additional 6 days following NAC infusion, the number of retrovirally labeled subependymal cells returns to control values, indicating that the continued presence of NAC is necessary for cell survival. These data suggest that preventing cell death is not sufficient to keep all of the progeny of these cells in a proliferative mode.

Downregulation of apoptosis-related genes in keloid tissues

BACKGROUND

Physiologically programmed cell death or apoptosis occurs during the natural balance between cellular proliferation and demise.

MATERIALS AND METHODS

We compared the expression of 64 apoptosis-related genes in keloids and normal scars to investigate the potential role of apoptosis in keloid formation. Two sets of mRNA were isolated from keloids excised from four previously untreated patients and four normal scar patients separately. Human cDNA arrayed hybridization was performed to compare the apoptosis-related gene expression between these two groups. In addition, TUNEL assays were performed to evaluate the percentage of apoptotic cells in keloids (center and periphery) versus normal scars.

RESULTS

Eight of the sixty-four apoptosis-related genes studied were significantly underexpressed in keloid tissue. The underexpressed genes and their relative expression compared with normal scar were defender against cell death 1 (DAD-1) (34.1% of normal scar); nucleoside diphosphate kinase B (c-myc transcription factor) (24.7%); glutathione S-transferase (17.9%); glutathione S-transferase microsomal (28.1%); glutathione peroxidase (47.2%); tumor necrosis factor receptor 1-associated protein (TRADD) (51.0%); 19-kDa interacting protein 3 (NIP3) (36.0%); and cytoplasmic dynein light chain 1 (HDLC1) (47.7%). Spatial analysis of apoptosis using TUNEL assays revealed apoptosis indices of 0.83 for keloid periphery and 0.63 for keloid center.

CONCLUSIONS

In this study we demonstrated underexpression of apoptosis-related genes in human keloid tissue and decreased apoptotic activity in fibroblasts derived from keloids versus normal scars. We hypothesized that keloid fibroblasts fail to undergo physiologically programmed cell death and, thus, continue to produce and secrete connective tissue beyond the period expected in normal scar formation, accounting for the progressive and hypertrophic nature of keloids. This mechanism leads to new possibilities for treatment of keloids through induction of apoptosis.

Proteasome inhibitors as potential novel anticancer agents

Ubiquitin/proteasome-dependent proteolysis plays an essential role in degrading regulatory proteins and thereby controlling processes of cell proliferation and cell death (apoptosis). Most recent experiments using cell cultures and mouse models have demonstrated that proteasome inhibitors induce cancer cell apoptosis and therefore inhibit tumor growth. The proteasome inhibitors have the following unique features: (i) greater apoptosis-inducing potency when tested in various human tumor cell lines than current anticancer drugs; (ii) ability to selectively target transformed and tumor, but not normal, human cells; and (iii) ability to overcome tumor cell resistance to cytotoxic therapies. We suggest that proteasome inhibitors have potential use as novel anticancer agents. Copyright 1999 Harcourt Publishers Ltd.

Increased cyclin D1 in vulnerable neurons in the hippocampus after ischaemia and epilepsy: a modulator of in vivo programmed cell death?

Several observations suggest that delayed neuronal death in ischaemia, epilepsy and other brain disorders includes an apoptotic component, involving programmed cell death (PCD). PCD is hypothesized to result, in part, from aberrant control of the cell cycle. Because they are instrumental in mitosis, cyclins D are key markers to evaluate whether neurons indeed progress into the cell cycle in situations of pathology. Therefore, we investigated in rat brains, the expression of cyclins D in the delayed neuronal death that occurs following transient global ischaemia and kainate-induced seizures. Following a four-vessel occlusion insult, quantitative in situ hybridization revealed a highly significant and persistent 100% increase of cyclin D1 mRNA in the vulnerable pyramidal neurons of the CA1 hippocampal region. Ischaemia also induced a smaller and transient cyclin D1 mRNA increase in the resistant CA3 area and dentate gyrus. In contrast, the cyclin D2 and D3 mRNAs, expressed constitutively in the adult rat hippocampus, were not upregulated. Following kainate-induced seizures, cyclin D1 mRNA was induced in the vulnerable CA3 region, and to a lesser extent, in non-vulnerable regions. Cyclin D1 immunohistochemistry revealed increased protein levels in the cytoplasm and nucleus of neurons commited to die after ischaemia. Double labelling experiments indicate that cyclin D1 is also expressed in reactive astrocytes but not in microglial cells. Finally, we report that in neurons, cyclin D1 expression peaks before nuclear condensation and the appearance of DNA fragmentation. We propose that cyclin D1, when expressed at high levels in lesioned neurons, may act as a modulator of apoptosis.

Identification of a neuronal calmodulin-binding peptide, CAP-19, containing an IQ motif

Neurons produce polypeptides which can bind the calcium-poor or pre-activated form of calmodulin. It is expected that this class of peptide will serve an important role in maintaining cellular homeostasis since it would modulate calcium-dependent target regulation and redirect intracellular signaling. The lack of conserved sequence has made the identification of these peptides difficult, consequently leading us to exploit their property of binding calcium-poor calmodulin as a means of finding new species. A new peptide termed Calmodulin-Associated Peptide-19 (CAP-19) was purified and characterized. The protein-sequence information was employed in order to recover a cDNA clone from rat which included the entire reading frame for the peptide. Like its counterparts, neuromodulin (GAP-43), neurogranin (RC3) and PEP-19, it contains an IQ motif although the remainder of the peptide is quite different. Northern blot analysis of ribonucleic acid (RNA) from animals of differing ages indicated that the message appears at birth and then persists into adulthood. Antibodies to synthetic peptide were employed for localizing CAP-19. The results indicated that the peptide was localized to neurons in several brain regions. CAP-19 is similar to other calmodulin-binding proteins in that the domain spanning the IQ motif was demonstrated to participate in binding to calmodulin. Database searching showed CAP-19 to be homologous to the silkworm protein, multiprotein bridging factor 1 (MBF1). This homology suggests a potential new role for calmodulin-associated proteins in cellular homeostasis.

Monoamine and iron-related toxicity: from "serotonin-binding proteins" to lipid peroxidation and apoptosis in PC12 cells

1. Monoamines do not form coordination bonds with a preformed iron-serotonin-binding protein (SBP) complex, as initially believed. Instead, metals oxidize the monoamines either directly (manganese, copper) or by oxygen free radical formation (iron), the oxidation products bind covalently to SBP and the conjugates are able to undergo redox cycling. These interactions are denoted as a "molecular oxidative mechanism." 2. Dopamine in combination with iron induces lipid peroxidation and apoptosis in PC12 cells by a stress oxidative-Ca2+ independent mechanism. 3. Dopamine-iron cytotoxicity may have relevance to an understanding of the mechanism by which dopaminergic neurons are eroded in some neurodegenerative disorders.

H-7-induced apoptosis in the cells of a Drosophila neuronal cell line through affecting unidentified H-7-sensitive substance(s)

The present study was undertaken to reveal underlying mechanisms of apoptosis in neurons using clonal neuronal cells, ML-DmBG2-c2, derived from Drosophila larval central nervous system 1-(5-Isoquinolinesulfonyl)-2-methylpiperazine (H-7), a protein kinase inhibitor, induced cell death with typical features of apoptosis such as internucleosomal DNA fragmentation, nuclear condensation and apoptotic bodies in the cells. Though H-7 is known to inhibit cAMP-dependent protein kinase (PKA), protein kinase C (PKC), cGMP-dependent protein kinase (PKG), myosin light chain kinase (MLCK), and casein kinase I (CKI), specific inhibitors for these kinases such as H-89, calphostin C, ML-9, or CKI-7 did not induce apoptosis in the cells. Other kinases such as tyrosine kinase. PI3-kinase and Ca2+/CaM kinase II so far examined in the present study were interpreted not to be involved in the apoptotic cascade. Therefore, it is concluded that an H-7-sensitive substance(s) other than these kinases is responsible for the apoptosis in the neuronal cells. Caspase inhibitors prevented apoptosis in the cells treated with H-7. These results suggest that caspase(s) is involved downstream of the H-7-sensitive point in the cascade of the apoptosis.

Activity-dependent regulation of [Ca2+]i in avian cochlear nucleus neurons: roles of protein kinases A and C and relation to cell death

Neurons of the cochlear nucleus, nucleus magnocellularis (NM), of young chicks require excitatory afferent input from the eighth nerve for maintenance and survival. One of the earliest changes seen in NM neurons after deafferentation is an increase in intracellular calcium concentration ([Ca2+]i). This increase in [Ca2+]i is due to loss of activation of metabotropic glutamate receptors (mGluR) that activate second-messenger cascades involved in [Ca2+]i regulation. Because mGluRs are known to act via the phospholipase C and adenylate cyclase signal transduction pathways, the goal of this study was to determine the roles of protein kinases A (PKA) and C (PKC) activities in the regulation of NM neuron [Ca2+]i by eighth nerve stimulation. Additionally, we sought to determine the relationship between increased [Ca2+]i and cell death as measured by propidium iodide incorporation. [Ca2+]i of individual NM neurons in brain stem slices was monitored using fura-2 ratiometric fluorescence imaging. NM field potentials were monitored in experiments in which the eighth nerve was stimulated. Five hertz orthodromic stimulation maintained NM neuron [Ca2+]i at approximately 110 nM for 180 min. In the absence of stimulation, NM neuron [Ca2+]i increased steadily to a mean of 265 nM by 120 min. This increase was attenuated by superfusion of PKC activators phorbol-12,13-myristate acetate (100 nM) or dioctanoylglycerol (50 microM) and by activators of PKA: 1 mM 8-bromoadenosine-3',5'-cyclophosphate sodium (8-Br-cAMP), 50 microM forskolin or 100 microM Sp-adenosine 3',5'-cyclic monophosphothioate triethylamine. Inhibition of PKA (100 microM Rp-cAMPS) or PKC (50 nM bisindolymaleimide or 10 microM U73122) during continuous orthodromic stimulation resulted in an increase in NM neuron [Ca2+]i that exceeded 170 and 180 nM, respectively, by 120 min. Nonspecific kinase inhibition with 1 microM staurosporine during stimulation resulted in an [Ca2+]i increase that was greater in magnitude than that seen with either PKA or PKC inhibition alone, equal to that seen in the absence of stimulation, but much smaller than that seen with inhibition of mGluRs. In addition, manipulations that resulted in a [Ca2+]i increase >/=250 nM resulted in an increase in number and percentage of propidium iodide-labeled NM neurons. These results suggest that eighth nerve activity maintains [Ca2+]i of NM neurons at physiological levels in part via mGluR-mediated activation of PKA and PKC and that increases in [Ca2+]i due to activity deprivation or interruption of the PKA and PKC [Ca2+]i regulatory mechanisms are predictive of subsequent cell death.

In vivo Bcl-2 oncogene neuronal expression in the rat spinal cord

STUDY DESIGN

An acute mechanical rat spinal cord injury model was used to investigate in vivo Bcl-2 oncogene overexpression in neuronal tissue.

OBJECTIVES

To introduce the Bcl-2 oncogene in vivo by a recombinant adenovirus vector into rat spinal cord tissue, and to investigate any potential protective effect on neural tissue in the zone of injury in a rat spinal cord model.

SUMMARY OF BACKGROUND DATA

The Bcl-2 oncogene inhibits apoptotic and necrotic neural cell death in vitro by regulating an antioxidant pathway at sites of free radical generation. Thus, overexpression of the Bcl-2 oncogene may have a role in limiting the secondary injury cascade of spinal cord injury through its regulation of antioxidants.

METHODS

After confirmation of Bcl-2 gene expression in vitro and in vivo in the rat spinal cord, a weight-drop spinal cord injury model was performed on seven rats with prior Bcl-2 inoculation, and on seven rats with prior B-gal inoculation (controls).

RESULTS

In vivo Bcl-2 expression was documented by immunostaining. After spinal cord harvest, quantification of percentage preserved tissue at the spinal cord injury site suggested that Bcl-2 overexpression confers neuroprotection.

CONCLUSIONS

In vivo Bcl-2 oncogene overexpression was successfully induced in neuronal tissue. After Bcl-2 oncogene expression in the rat spinal cord, the zone of microscopic injury was diminished. Further investigation of the Bcl-2 oncogene for potentially enhancing neuronal survival after spinal cord injury appears indicated.

Accelerated entry into S phase associated with up-regulation of cyclin D1 as a mechanism for granulocyte colony-stimulating factor (G-CSF)-induced apoptosis of murine myeloid leukemia cells

We previously reported that injection of recombinant granulocyte colony-stimulating factor (G-CSF) suppressed the development of leukemia in mice transplanted with C2M-A5 (C2M) myeloid leukemia cells and that the anti-leukemic effect of G-CSF was ascribed to the induction of apoptosis of C2M cells. These observations make a striking contrast with other previous reports on the biological activities of G-CSF. In the present study, in order to further clarify the G-CSF-induced apoptosis of C2M cells, we studied the effects of G-CSF on the cell cycle as well as the molecular events involving D-type cyclines and their cyclin-dependent kinases (cdk) in G-CSF-treated C2M cells. Cell cycle analysis revealed that G-CSF treatment of C2M cells resulted in accelerated entry from the first gap (G1) phase into the DNA synthesis (S) phase. Western blotting disclosed that G-CSF treatment resulted in down-regulation of cyclin D2 and cdk2 and up-regulation of cyclin D1 and cdk4. The reciprocal relationship between the up-regulation of cyclin D1 and down-regulation of cyclin D2 was closely associated with accelerated entry into S phase and subsequent apoptosis of C2M cells. These results suggest that G-CSF-induced apoptosis of C2M cells might be ascribed to imbalanced cell cycle progression due to deregulated expression of D-type cyclins and their cdks.

Inhibition of cyclin D1 expression and induction of apoptosis by inostamycin in small cell lung carcinoma cells

Previously, we demonstrated that inostamycin, an inhibitor of phosphatidylinositol turnover, caused cell cycle arrest at the G1 phase, inhibiting the expression of cyclins D1 and E in normal cells. In the present study, we examined the effects of inostamycin on cell cycle progression and apoptosis in human small cell lung carcinoma Ms-1 cells. Treatment of exponentially proliferating Ms-1 cells with low concentrations of inostamycin caused cells to accumulate in the G1 phase. We found that inostamycin decreased cyclin D1, and increased cyclin-dependent kinase inhibitors such as p21WAF1 and p27KIP1 in Ms-1 cells. On the other hand, higher concentrations of inostamycin induced morphological apoptosis and DNA fragmentation in Ms-1 cells without affecting the expression of p53, Bcl-2 and Bax. Inostamycin-induced apoptosis was suppressed by an inhibitor of caspase-3, and a 17 kDa fragment of activated caspase-3 was detected following inostamycin treatment. Therefore, caspase-3(-like) would appear to be involved in inostamycin-induced apoptosis. On the other hand, an inhibitor of caspase-3(-like) proteases did not affect the inhibitory effect of inostamycin on cyclin D1 expression, suggesting that caspase-3(-like) proteases were not responsible for inostamycin-induced G1 arrest.

ZIP kinase, a novel serine/threonine kinase which mediates apoptosis

We have identified a novel serine/threonine kinase, designated ZIP kinase, which mediates apoptosis. ZIP kinase contains a leucine zipper structure at its C terminus, in addition to a kinase domain at its N terminus. ZIP kinase physically binds to ATF4, a member of the activating transcription factor/cyclic AMP-responsive element-binding protein (ATF/CREB) family, through interaction between their leucine zippers. The leucine zipper domain is necessary for the homodimerization of ZIP kinase as well as for the activation of kinase. Immunostaining study showed that ZIP kinase localizes in the nuclei. Overexpression of intact ZIP kinase but not catalytically inactive kinase mutants led to the morphological changes of apoptosis in NIH 3T3 cells, suggesting that the cell death-inducing activity of ZIP kinase depends on its intrinsic kinase activity. Interestingly, the catalytic domain of ZIP kinase is closely related to that of death-associated protein kinase (DAP kinase), which is a mediator of apoptosis induced by gamma interferon. Therefore, both ZIP and DAP kinases represent a novel kinase family, which mediates apoptosis through their catalytic activities.

Soluble Fas (Apo-1) levels in cerebrospinal fluid of multiple sclerosis patients

CSF and serum levels of soluble Fas were studied in MS patients, in patients with various neurological diseases and in healthy controls. We did not detect differences in serum sFas levels between MS patients and controls. In CSF, despite sFas levels being similar in all patients studied, a statistically significant correlation between sFas CSF/sFas serum ratio and BBB damage (expressed as albumin CSF/albumin serum ratio) was detected in non-MS neurological disease, but not in MS patients. The normalized ratio (sFas CSF/sFas serum)/(Alb CSF/Alb serum) was significantly increased in MS patients compared to patients with non-inflammatory neurological disease suggesting an intrathecal synthesis of soluble Fas in MS. The percentage of apoptotic mononuclear cells was higher in CSF as compared to peripheral blood; moreover a lower proportion of apoptotic cells was found in CSF of MS patients. The findings lend support to the involvement of sFas in MS pathogenesis and suggest that a lower apoptosis in CSF may be a feature of the disease.

Use of the herpes amplicon system as a vehicle for somatic gene transfer

The study of herpes virus biology has produced two vector delivery strategies which exploit the highly evolved neuronal tropism and life cycle regulation exhibited by this class of viruses. Amplicon and recombinant herpes simplex virus systems show promise for use in gene transfer to the nervous system and although neither vector has been used in clinical trials to date, their application to gene delivery and perturbation of neuronal physiology have been well established. We will review the properties of the herpes amplicon system, and demonstrate its utility in neuroscience applications.

Expression of SKP1 mRNA and protein in rat brain during postnatal development

We previously isolated the cell cycle element SKP1 as a candidate plasticity gene in the rat visual cortex. Here, we studied the expression and localization of SKP1 mRNA and protein in rat brain. We found a high level of expression for the SKP1 gene in the cortex at different postnatal ages. SKP1 mRNA levels remained stable from P2 (postnatal day 2) to adulthood. SKP1 mRNA expression was also detected in several other brain areas. Skp1p (SKP1 protein) immunohistochemistry showed nuclear staining in a large majority of neurones. The pyramidal cells in the hippocampus, as well as cortical cells were stained. The presence of Skp1p in post-mitotic neurones suggests that this protein is involved in processes other than the cell cycles other target proteins and functions in neurones are currently under investigation.

1-(5-Isoquinolinesulfonyl)-2-methylpiperazine induces apoptosis in human neuroblastoma cells, SH-SY5Y, through a p53-dependent pathway

We have studied the effect of 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), a protein kinase inhibitor, on the regulation of apoptosis in the human neuroblastoma cell line, SH-SY5Y. H-7 (20-100 microM) induced apoptosis in these cells characterized by DNA fragmentation and chromatin condensation. Immunoblot analyses were performed with specific antibody against BCL-2, BCL-XS/L, BAX, JUNB, c-JUN, ICH-1L, c-FOS, RB, CDK-2, and p53. H-7 treatment did not significantly alter the level of these proteins with the exception of p53. H-7, but not staurosporine, caused a dramatic nuclear accumulation of p53. The kinetics of nuclear accumulation of p53 correlates well with the kinetics of induction of apoptosis. The effect of H-7 was further assessed in a group of human cell lines. Only cell lines harboring the wild-type p53 gene were responsive to the stimulatory effect of H-7 on nuclear accumulation of p53. Furthermore, cell lines carrying a mutated p53 gene were resistant to the cytotoxic effect of H-7. The ability of H-7 in mediating apoptosis in the SH-SY5Y line expressing a dominant negative mutant of p53 was significantly diminished. Taken together, these data strongly suggest that a p53-dependent mechanism contributes to the cytotoxicity of H-7 in human neuroblastoma cells.

Linkage between reovirus-induced apoptosis and inhibition of cellular DNA synthesis: role of the S1 and M2 genes

The mammalian reoviruses are capable of inhibiting cellular DNA synthesis and inducing apoptosis. Reovirus strains type 3 Abney (T3A) and type 3 Dearing (T3D) inhibit cellular DNA synthesis and induce apoptosis to a substantially greater extent than strain type 1 Lang (T1L). We used T1L x T3A and T1L x T3D reassortant viruses to identify viral genes associated with differences in the capacities of reovirus strains to elicit these cellular responses to viral infection. We found that the S1 and M2 genome segments determine differences in the capacities of both T1L x T3A and T1L x T3D reassortant viruses to inhibit cellular DNA synthesis and to induce apoptosis. These genes encode viral outer-capsid proteins that play important roles in viral attachment and disassembly. To extend these findings, we used field isolate strains of reovirus to determine whether the strain-specific differences in inhibition of cellular DNA synthesis and induction of apoptosis are also associated with viral serotype, a property determined by the S1 gene. In these experiments, type 3 field isolate strains were found to inhibit cellular DNA synthesis and to induce apoptosis to a greater extent than type 1 field isolate strains. Statistical analysis of these data indicate a significant correlation between the capacity of T1L x T3A and T1L x T3D reassortant viruses and field isolate strains to inhibit cellular DNA synthesis and to induce apoptosis. These findings suggest that reovirus-induced inhibition of cellular DNA synthesis and induction of apoptosis are linked and that both phenomena are induced by early steps in the viral replication cycle.

Cyclin D3 sensitizes tumor cells to tumor necrosis factor-induced, c-Myc-dependent apoptosis

c-Myc is an important mediator of apoptosis in cytokine- or serum-deprived cells and sensitizes various cell types to tumor necrosis factor alpha (TNF) cytotoxicity. However, downstream mediators of c-Myc-dependent apoptosis are largely unknown. In this study, we investigated whether one or more cyclins which, like c-Myc, are important regulators of the cell cycle are involved in TNF-induced apoptosis downstream of c-Myc. Cyclin D3 and c-Myc levels in HeLa and fibrosarcoma cells correlated with sensitivity of these cells to TNF-induced apoptosis, as both proteins were highly expressed in TNF-sensitive HeLa D98 cells and HT-1080 fibrosarcoma cells but not in their TNF-resistant counterparts, HeLa H21 and SS-HT-1080 cells, respectively. All other cyclins tested were equally expressed in all tumor cell lines. Reduction in the expression of c-Myc by dexamethasone or inhibition of the transcriptional activity of c-Myc by introduction of a dominant negative form of c-Myc into TNF-sensitive HeLa D98 cells strongly suppressed the expression of cyclin D3 (but none of the other cyclins) and rendered the cells resistant to TNF-induced apoptosis. Conversely, introduction of the c-myc gene into TNF-resistant, c-Myc- and cyclin D3-deficient HeLa H21 cells resulted in enhanced cyclin D3 expression and TNF killing. When cyclin D3 expression in HeLa cells was altered by sense or antisense cyclin D3 cDNA, there was a concomitant alteration in their susceptibility to TNF-induced apoptosis without any change in c-Myc levels. Overall, our results show that cyclin D3 sensitizes tumor cells to TNF-induced apoptosis and indicate that the expression of c-Myc and expression of cyclin D3 in HeLa and in HT-1080 fibrosarcoma cells are closely linked.

Chlorambucil in chronic lymphocytic leukemia: mechanism of action

Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries but the clinical presentation and rate of disease progression are highly variable. When treatment is required the most commonly used therapy is the nitrogen mustard alkylating agent, chlorambucil (CLB), with or without prednisone. Although CLB has been used in the treatment of CLL for forty years the exact mechanism of action of this agent in CLL is still unclear. Studies in proliferating model tumor systems have demonstrated that CLB can bind to a variety of cellular structures such as membranes, RNA, proteins and DNA; however, DNA crosslinking appears to be most important for antitumor activity in these systems. In addition, a number of different mechanisms can contribute to CLB resistance in these tumor models including increased drug metabolism, DNA repair and CLB detoxification resulting from elevated levels of glutathione (GSH) and glutathione S-transferase (GST) activity. However, unlike tumor models in vitro, CLL cells are generally not proliferating and studies in CLL cells have raised questions about the hypothesis that DNA crosslinking is the major mechanism of antitumor action for CLB in this disease. CLB induces apoptosis in CLL cells and this appears to correlate with the clinical effects of this agent. Thus, alkylation of cellular targets other than DNA, which can also induce apoptosis, may contribute to the activity of CLB. Alterations in genes such as p53, mdm-2, bcl-2 and bax which control entry into apoptosis may cause drug resistance. Loss of wild-type p53 by mutation or deletion occurs in 10 to 15% of CLL patients and appears to correlate strongly with poor clinical response to CLB. The induction of apoptosis by CLB is paralleled by an increase in P53 and Mdm-2 but this increase in not observed in patients with p53 mutations indicating that with high drug concentrations CLB can produce cell death through P53 independent pathways. The level of Mdm-2 mRNA in the CLL cells is not a useful predictor of drug sensitivity. In addition, although Bax and Bcl-2 are important regulators of apoptosis and the levels of these proteins are elevated in CLL cells compared with normal B cells, the levels of Bax and Bcl-2, or the Bax:Bcl-2 ratio, are not important determinants of drug sensitivity in this leukemia. Finally, whereas CLB and nucleoside analogs may produce cell death in CLL by a P53 dependent pathway other agents, such as dexamethasone or vincristine, may act through P53-independent pathways.

Apoptosis: a programmed cell death involved in ovarian and uterine physiology

Apoptosis is a form of programmed cell death which occurs through the activation of a cell-intrinsic suicide machinery. The biochemical machinery responsible for apoptosis is expressed in most, if not all, cells. Contrary to necrosis, an accidental form of cell death, apoptosis does not induce inflammatory reaction noxious for the vicinity. Apoptosis is primarily a physiologic process necessary to remove individual cells that are no longer needed or that function abnormally. Apoptosis plays a major role during development, homeostasis. Many stimuli can trigger apoptotic cell death, but expression of genes can modulate the sensibility of the cell. The aim of this review is to summarise current knowledge of the molecular mechanisms of apoptosis and its roles in human endometrium and ovary physiology.

Possible involvement of protein kinase C-epsilon in phorbol ester-induced growth inhibition of human lymphoblastic cells

Sustained activation of members of the protein kinase C (PKC) family is known to influence the growth and differentiation of various cell types, however, the specific roles for individual isoforms mediating these cellular events have yet to be elucidated. Activation of PKC by phorbol esters leads to growth inhibition in certain cell lines. The HT58 human B lymphoblastic cell may serve as a cellular model system to investigate the participation of individual isoforms in the initial events of growth arrest induced by phorbol ester. Determination of cell cycle and investigation of apoptosis were performed by flow cytometric measurements. Phorbol ester-induced translocation and down-regulation of the conventional alpha, beta and the novel epsilon isoforms of PKC were demonstrated by Western blot analysis. At lower concentrations (o.5 ng/ml) phorbol myristate acetate (PMA) stimulated a G1 arrest with retention of viability in the human HT58 B lymphoblastic cell. The protein kinase inhibitor staurosporine at a concentration of 25 nM did not significantly alter HT58 cell viability. However, staurosporine (25 nM) induced apoptosis in cells preincubated for 4 hr with 0.5-1.0 ng/ml PMA. The translocation of PKC-epsilon was observed within 39 min exposure to 0.5 ng/ml PMA. After a 4 hr treatment, evidence for down-regulation and and altered phosphorylation state of PKC-epsilon was seen. In contrast, the conventional alpha and beta isoforms were practically uneffected by this PMA treatment. At higher PMA concentrations (50 ng/ml) the alpha and beta isoforms showed a significant down-regulation. The preferential alterations in PKC-epsilon observed under the conditions required for PMA to influence the growth and survival of HT58 cells suggest a role for the Ca(2+)-independent epsilon isoform in mediating the initial events of the phorbol ester stimulated cellular responses.

Tumor necrosis factor alpha is a powerful apoptotic inducer in lymphoid leukemic cells expressing the P-170 glycoprotein

Multidrug resistance (MDR) is a phenomenon by which tumor cells exposed to a single anti-proliferative agent acquire resistance to other structurally and functionally unrelated drugs. The classical form of MDR is caused by a plasma-membrane protein currently named P-glycoprotein or P-170 encoded by the human mdr-1 gene in its functional isoform. In vitro cell lines expressing P-170 usually also present phenotypic and functional alterations. In the present study we report that the cytotoxicity mediated by tumor necrosis factor alpha (TNF alpha) in MDR variants of the human T-lymphoblastoid CEM cell line is associated with apoptosis (programmed cell death). Susceptibility of MDR cells to apoptosis was increased upon cycloheximide + TNF alpha sequential treatment, whereby the impairment of protein synthesis due to the former agent was followed by the effect of cytokine exposure. Massive apoptosis of P-170-positive cells, but not of controls, was also obtained by depletion of nutrients (i.e., serum starvation). In contrast, TNF-alpha exerted a similar apoptotic effect in epithelial (MCF-7) or myeloma (S8226) drug-sensitive/ -resistant cell pairs. However, the MDR variant of myeloma S8226 was more sensitive to the cytostatic effect of TNF alpha than the parental drug-sensitive cell line. These results suggest that the presence of the MDR phenotype may be associated with increased histotype-dependent cell susceptibility to specific, protein-synthesis-independent, apoptotic pathways.

The cellular derivation and the life span of the myofibroblast

The presence of myofibroblasts in granulation tissue and various fibrotic settings is well established. Recent work on this cell has shown that myofibroblasts derive mainly from local fibroblasts, but also from pericytes and smooth muscle cells as well as from specialized cells such as perisinusoidal stellate cells of the liver and mesangial cells of the kidney glomerulus. During the healing of an open wound, myofibroblasts disappear by means of apoptosis when the wound is closed and granulation tissue gradually transforms into scar tissue. The possibility exists that an altered regulation of this process leads to the development of a hypertrophic scar.

Dose-dependent effects of berberine on cell cycle pause and apoptosis in Balb/c 3T3 cells

In determining the morphological appearance of Balb/c 3T3 cells from berberine-treated (100 and 200 micrograms/ml) cultures by light microscopy demonstrated that the high berberine concentration (200 micrograms/ml) treatment was associated with the accumulation of numerous apoptotic cells, as identified by condensed nuclei and decrease in cell size. On the other hand, accumulation of cells in G2/M phase instead of induction of apoptosis was observed after 48-72 h of 100 micrograms/ml berberine treatment. Berberine was found mainly in cytoplasm during berberine-induced (100 micrograms/ml) cell cycle G2/M arrest, while it was highly concentrated in nuclei in the induction of apoptosis under high dose of berberine (200 micrograms/ml) treatment. Further addition of berberine (100-200 micrograms/ml) had little effect on the induction of apoptosis in the cells that had already been exposed to 100 micrograms/ml of berberine for 48 h. Our results suggest that there may exist in Balb/c 3T3 cells an important threshold for regulation of cell cycle pause and induction of apoptosis, that is dose-dependent.

Mitotic mechanisms in Alzheimer's disease?

The mechanism(s) leading to widespread hyper-phosphorylation of proteins in Alzheimer's disease (AD) are unknown. We have characterized seven new monoclonal antibodies recognizing independent phospho-epitopes in the paired helical filament proteins (PHF) found in AD brain. These antibodies show pronounced immunoreactivity with cultured human neuroblastoma cells that are in the M phase of cell division, but have no discernible reactivity with interphase cells. Immunoreactivity with these antibodies does not localize to the microtubule spindles or chromosomes in M phase, but is confined to the surrounding cytoplasm. Similar staining in M phase is observed with cultured cells of various tissue types and species. Cells arrested in M phase with the microtubule depolymerizing agent, nocodazole, show marked increases in immunoreactivity with the antibodies by immunofluorescence staining, ELISA, and immunoblotting. In neuroblastoma cells, the appearance of the TG/MC phospho-epitopes coincides with activation of mitotic protein kinases, but not with the activity of the neuronal specific cyclin-dependent kinase, cdk5. These data suggest that the TG/MC epitopes are conserved mitotic phospho-epitopes produced as a result of increased mitotic kinase activity. To investigate this possibility in AD, we examined the staining of human brain tissue with MPM-2, a marker antibody for mitotic phospho-epitopes. It was found that MPM-2 reacts strongly with neurofibrillary tangles, neuritic processes, and neurons in AD but has no staining in normal human brain. Our data suggest that accumulation of phospho-epitopes in AD may result from activation of mitotic posttranslational mechanisms which do not normally operate in mature neurons of brain.