Adult neuron survival strategies--slamming on the brakes

Tissue plasminogen activator is required for the development of fetal alcohol syndrome in mice

Ethanol exposure during developmental synaptogenesis can lead to brain defects referred to as fetal alcohol syndrome (FAS), which can include mental health problems such as cognitive deficits and mental retardation. In FAS, widespread neuronal death and brain mass loss precedes behavioral and cognitive impairments in adulthood. Because tissue plasminogen activator (tPA) has been implicated in neurodegeneration, we examined whether it mediates FAS. Neonatal WT and tPA-/- mice were injected with ethanol to mimic FAS in humans. In WT mice, ethanol elicited caspase-3 activation, significant forebrain neurodegeneration, and decreased contextual fear conditioning in adults. However, tPA-deficient mice were protected from these neurotoxicities, and this protection could be abrogated by exogenous tPA. Selective pharmacological modulators of NMDA and GABAA receptor pathways revealed that the effects of tPA were mediated by the NR2B subunit of the NMDA receptor. This study identifies tPA as a critical signaling component in FAS.

Effects of propofol on proliferation and anti-apoptosis of neuroblastoma SH-SY5Y cell line: new insights into neuroprotection

Recently, it has been suggested that anesthetic agents may have neuroprotective potency. The notion that anesthetic agents can offer neuroprotection remains controversial. Propofol, which is a short-acting intravenous anesthetic agent, may have potential as a neuroprotective agent. In this study, we tried to determine whether propofol affected the viability of human neuroblastoma SH-SY5Y cells by using the MTT assay. Surprisingly, our results showed that propofol at a dose of 1-10 μM could improve cell proliferation. However, at higher doses (200 μM), propofol appears to be cytotoxic. On the other hand, propofol could up-regulate the expression of key proteins involved in neuroprotection including B-cell lymphoma 2 at a dose range of 1-10 μM, activation of phospho-serine/threonine protein kinase at a dose range of 0.5-10 μM, and activation of phospho-extracellular signal-regulated kinases at a dose range of 5-10 μM. Similarly, we demonstrate that propofol (10 μM) could elevate protein levels of heat shock protein 90 and heat shock protein 70. Therefore, we choose to utilize a 10 μM concentration of propofol to assess neuroprotective activities in our studies. In the following experiments, we used dynorphin A to generate cytotoxic effects on SH-SY5Y cells. Our data indicate that propofol (10 μM) could inhibit the cytotoxicity in SH-SY5Y cells induced by dynorphin A. Furthermore, propofol (10 μM) could decrease the expression of the p-P38 protein as well. These data together suggest that propofol may have the potential to act as a neuroprotective agent against various neurologic diseases. However, further delineation of the precise neuroprotective effects of propofol will need to be examined.

miR-29b is activated during neuronal maturation and targets BH3-only genes to restrict apoptosis

The execution of apoptosis is critical for proper development of the nervous system. However, it is equally important that neurons strictly inhibit apoptosis after development to ensure their survival throughout the lifetime of the organism. Here we show that a microRNA, miR-29b, is markedly induced with neuronal maturation and functions as a novel inhibitor of neuronal apoptosis. The prosurvival function of miR-29b is mediated by targeting genes in the proapoptotic BH3-only family. Our results identify a unique strategy evolved by maturing neurons that uses a single microRNA to inhibit the multiple, redundant BH3-only proteins that are key initiators of apoptosis.

Maldynia: pathophysiology and management of neuropathic and maladaptive pain--a report of the AMA Council on Science and Public Health

BACKGROUND

Because of disparate taxonomic arrays for classification, the American Academy of Pain Medicine has proposed categorizing pain on a neurobiologic basis as eudynia (nociceptive pain), Greek for "good pain," or maldynia (maladaptive pain), Greek for "bad pain." The latter has been viewed as maladaptive because it may occur in the absence of ongoing noxious stimuli and does not promote healing and repair.

OBJECTIVE

To address recent findings on the pathogenesis of pain following neural injury and consider whether the development of maladaptive pain justifies its classification as a disease and to briefly discuss the scope of pharmacologic and non-pharmacologic approaches employed in patients with such pain.

METHODS

English language reports on studies using human subjects were selected from a PubMed search of the literature from 1995 to August 2010 and from the Cochrane Library. Further information was obtained from Internet sites of medical specialty and other societies devoted to pain management.

RESULTS

Neural damage to either the peripheral or central nervous system provokes multiple processes including peripheral and central sensitization, ectopic activity, neuronal cell death, disinhibition, altered gene expression, and abnormal sprouting and cellular connectivity. A series of neuro-immune interactions underlie many of these mechanisms. Imaging studies have shown that such damage is characterized by functional, structural, and chemical changes in the brain. Such pain is maladaptive in the sense that it occurs in the absence of ongoing noxious stimuli and does not promote healing and repair.

CONCLUSION

As defined, maldynia is a multidimensional process that may warrant consideration as a chronic disease not only affecting sensory and emotional processing but also producing an altered brain state based on both functional imaging and macroscopic measurements. However, the absolute clinical value of this definition is not established.

Modulation of the generation of dopaminergic neurons from human neural stem cells by Bcl-X(L): mechanisms of action

Understanding the developmental mechanisms governing dopaminergic neuron generation and maintenance is crucial for the development of neuronal replacement therapeutic procedures, like in Parkinson's disease (PD), but also for research aimed at drug screening and pharmacology. In the present chapter, we review the present situation using stem cells of different origins (pluripotent and multipotent) and summarize current manipulations of stem cells for the enhancement of dopaminergic neuron generation, focusing on the actions of Bcl-X(L). Bcl-X(L) not only enhances dopaminergic neuron survival but also augments the expression of key developmental and maintenance genes, and, through the lengthening of the cell cycle early during differentiation, regulates cell fate decisions, producing a net enhancement of neurogenesis. The relevance of these findings is discussed in the context of basic neurogenesis and also for the development of efficient cell therapy in PD.

Restoration of Akt activity by the bisperoxovanadium compound bpV(pic) attenuates hippocampal apoptosis in experimental neonatal pneumococcal meningitis

Pneumococcal meningitis causes apoptosis of developing neurons in the dentate gyrus of the hippocampus. The death of these cells is accompanied with long-term learning and memory deficits in meningitis survivors. Here, we studied the role of the PI3K/Akt (protein kinase B) survival pathway in hippocampal apoptosis in a well-characterized infant rat model of pneumococcal meningitis. Meningitis was accompanied by a significant decrease of the PI3K product phosphatidylinositol 3,4,5-trisphosphate (PIP(3)) and of phosphorylated (i.e., activated) Akt in the hippocampus. At the cellular level, phosphorylated Akt was decreased in both the granular layer and the subgranular zone of the dentate gyrus, the region where the developing neurons undergo apoptosis. Protein levels and activity of PTEN, the major antagonist of PI3K, were unaltered by infection, suggesting that the observed decrease in PIP(3) and Akt phosphorylation is a result of decreased PI3K signaling. Treatment with the PTEN inhibitor bpV(pic) restored Akt activity and significantly attenuated hippocampal apoptosis. Co-treatment with the specific PI3K inhibitor LY294002 reversed the restoration of Akt activity and attenuation of hippocampal apoptosis, while it had no significant effect on these parameters on its own. These results indicate that the inhibitory effect of bpV(pic) on apoptosis was mediated by PI3K-dependent activation of Akt, strongly suggesting that bpV(pic) acted on PTEN. Treatment with bpV(pic) also partially inhibited the concentration of bacteria and cytokines in the CSF, but this effect was not reversed by LY294002, indicating that the effect of bpV(pic) on apoptosis was independent of its effect on CSF bacterial burden and cytokine levels. These results indicate that the PI3K/Akt pathway plays an important role in the death and survival of developing hippocampal neurons during the acute phase of pneumococcal meningitis.

Synaptic mitochondria in synaptic transmission and organization of vesicle pools in health and disease

Cell types rich in mitochondria, including neurons, display a high energy demand and a need for calcium buffering. The importance of mitochondria for proper neuronal function is stressed by the occurrence of neurological defects in patients suffering from a great variety of diseases caused by mutations in mitochondrial genes. Genetic and pharmacological evidence also reveal a role of these organelles in various aspects of neuronal physiology and in the pathogenesis of neurodegenerative disorders. Yet the mechanisms by which mitochondria can affect neurotransmission largely remain to be elucidated. In this review we focus on experimental data that suggest a critical function of synaptic mitochondria in the function and organization of synaptic vesicle pools, and in neurotransmitter release during intense neuronal activity. We discuss how calcium handling, ATP production and other mitochondrial mechanisms may influence synaptic vesicle pool organization and synaptic function. Given the link between synaptic mitochondrial function and neuronal communication, efforts toward better understanding mitochondrial biology may lead to novel therapeutic approaches of neurological disorders including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and psychiatric disorders that are at least in part caused by mitochondrial deficits.

Differential antiapoptotic effect of erythropoietin on undifferentiated and retinoic acid-differentiated SH-SY5Y cells

Erythropoietin (Epo) is known to have a significant role in tissues outside the hematopoietic system. In this work, we investigated the function of Epo in cells of neuronal origin subjected to differentiation. Treatment of SH-SY5Y cells with all-trans-retinoic acid (atRA) generated differentiated neuron-like cells, observed by increased expression of neuronal markers and morphological changes. Exposure of undifferentiated cells to proapoptotic stimuli such as staurosporine, TNF-alpha, or hypoxia, significantly increased programmed cell death, which was prevented by previous treatment with Epo. In contrast, atRA-differentiated cultures showed cell resistance to apoptosis. No additional effect of Epo was detected in previously differentiated cells. The inhibition of the PI3K/Akt pathway by Ly294002 abrogated the protective effects induced by either Epo or atRA. The effect of atRA was mediated by an increased expression of Bcl-2 whereas the Epo treatment upregulated not only Bcl-2 but also Bcl-xL. This upregulation by Epo was not detected in atRA-differentiated cells, thus confirming the lack of the protective effect of Epo. As expected, assays with AG490, an inhibitor of Jak2, blocked the Epo action only in undifferentiated cells. This reduced neuroprotective function of Epo on SH-SY5Y differentiated cells could be explained at least in part by downregulation of the Epo receptor expression, which was observed in atRA-differentiated cells. This study shows differential cellular protection induced by Epo at two stages of SH-SY5Y differentiation. The results allow us to suggest that this differential cell behavior can be ascribed to the interaction between atRA and the signaling pathways mediated by Epo.

Advances in understanding the molecular basis of FXTAS

Fragile X-associated tremor/ataxia syndrome (FXTAS) is an adult-onset neurodegenerative disorder among carriers of premutation expansions (55-200 CGG repeats) of the fragile X mental retardation 1 (FMR1) gene. The clinical features of FXTAS, as well as other forms of clinical involvement in carriers without FXTAS, are thought to arise from a toxic gain of function of transcriptionally active FMR1 containing expanded CGG repeats. Although the precise mechanisms involved in rCGG toxicity are unknown, here we discuss the latest advances and models that contribute to the understanding of the molecular basis of FXTAS, and the emerging view of FXTAS as the end-stage of a process that begins in early development.

eIF2alpha phosphorylation tips the balance to apoptosis during osmotic stress

Regulation of cell volume is of great importance because persistent swelling or shrinkage leads to cell death. Tissues experience hypertonicity in both physiological (kidney medullar cells) and pathological states (hypernatremia). Hypertonicity induces an adaptive gene expression program that leads to cell volume recovery or apoptosis under persistent stress. We show that the commitment to apoptosis is controlled by phosphorylation of the translation initiation factor eIF2alpha, the master regulator of the stress response. Studies with cultured mouse fibroblasts and cortical neurons show that mutants deficient in eIF2alpha phosphorylation are protected from hypertonicity-induced apoptosis. A novel link is revealed between eIF2alpha phosphorylation and the subcellular distribution of the RNA-binding protein heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1). Stress-induced phosphorylation of eIF2alpha promotes apoptosis by inducing the cytoplasmic accumulation of hnRNP A1, which attenuates internal ribosome entry site-mediated translation of anti-apoptotic mRNAs, including Bcl-xL that was studied here. Hypertonic stress induced the eIF2alpha phosphorylation-independent formation of cytoplasmic stress granules (SGs, structures that harbor translationally arrested mRNAs) and the eIF2alpha phosphorylation-dependent accumulation of hnRNP A1 in SGs. The importance of hnRNP A1 was demonstrated by induction of apoptosis in eIF2alpha phosphorylation-deficient cells that express exogenous cytoplasmic hnRNP A1. We propose that eIF2alpha phosphorylation during hypertonic stress promotes apoptosis by sequestration of specific mRNAs in SGs in a process mediated by the cytoplasmic accumulation of hnRNP A1.

Suppression of the intrinsic apoptosis pathway by synaptic activity

Synaptic activity promotes resistance to diverse apoptotic insults, the mechanism behind which is incompletely understood. We show here that a coordinated downregulation of core components of the intrinsic apoptosis pathway by neuronal activity forms a key part of the underlying mechanism. Activity-dependent protection against apoptotic insults is associated with inhibition of cytochrome c release in most but not all neurons, indicative of anti-apoptotic signaling both upstream and downstream of this step. We find that enhanced firing activity suppresses expression of the proapoptotic BH3-only member gene Puma in a NMDA receptor-dependent, p53-independent manner. Puma expression is sufficient to induce cytochrome c loss and neuronal apoptosis. Puma deficiency protects neurons against apoptosis and also occludes the protective effect of synaptic activity, while blockade of physiological NMDA receptor activity in the developing mouse brain induces neuronal apoptosis that is preceded by upregulation of Puma. However, enhanced activity can also confer resistance to Puma-induced apoptosis, acting downstream of cytochrome c release. This mechanism is mediated by transcriptional suppression of apoptosome components Apaf-1 and procaspase-9, and limiting caspase-9 activity, since overexpression of procaspase-9 accelerates the rate of apoptosis in active neurons back to control levels. Synaptic activity does not exert further significant anti-apoptotic effects downstream of caspase-9 activation, since an inducible form of caspase-9 overrides the protective effect of synaptic activity, despite activity-induced transcriptional suppression of caspase-3. Thus, suppression of apoptotic gene expression may synergize with other activity-dependent events such as enhancement of antioxidant defenses to promote neuronal survival.

Cell Permeable Peptides: A Promising Tool to Deliver Neuroprotective Agents in the Brain

The inability of most drugs to cross the blood-brain barrier and/or plasma membrane limits their use for biomedical applications in the brain. Cell Permeable Peptides (CPPs) overcome this problem and are effective in vivo, crossing the plasma membrane and the blood-brain barrier. CPPs deliver a wide variety of compounds intracellularly in an active form. In fact, many bioactive cargoes have neuroprotective properties, and due to their ability to block protein-protein interactions, offer exciting perspectives in the clinical setting. In this review we give an overview of the Cell Permeable Peptides strategy to deliver neuroprotectants against neurodegeneration in the CNS.

NeuroD6 genomic signature bridging neuronal differentiation to survival via the molecular chaperone network

During neurogenesis, expression of the basic helix-loop-helix NeuroD6/Nex1/MATH-2 transcription factor parallels neuronal differentiation and is maintained in differentiated neurons in the adult brain. To dissect NeuroD6 differentiation properties further, we previously generated a NeuroD6-overexpressing stable PC12 cell line, PC12-ND6, which displays a neuronal phenotype characterized by spontaneous neuritogenesis, accelerated NGF-induced differentiation, and increased regenerative capacity. Furthermore, we reported that NeuroD6 promotes long-term neuronal survival upon serum deprivation. In this study, we identified the NeuroD6-mediated transcriptional regulatory pathways linking neuronal differentiation to survival, by conducting a genome-wide microarray analysis using PC12-ND6 cells and serum deprivation as a stress paradigm. Through a series of filtering steps and a gene-ontology analysis, we found that NeuroD6 promotes distinct but overlapping gene networks, consistent with the differentiation, regeneration, and survival properties of PC12-ND6 cells. By using a gene-set-enrichment analysis, we provide the first evidence of a compelling link between NeuroD6 and a set of heat shock proteins in the absence of stress, which may be instrumental in conferring stress tolerance on PC12-ND6 cells. Immunocytochemistry results showed that HSP27 and HSP70 interact with cytoskeletal elements, consistent with their roles in neuritogenesis and preserving cellular integrity. HSP70 also colocalizes with mitochondria located in the soma, growing neurites, and growth cones of PC12-ND6 cells prior to and upon stress stimulus, consistent with its neuroprotective functions. Collectively, our findings support the notion that NeuroD6 links neuronal differentiation to survival via the network of molecular chaperones and endows the cells with increased stress tolerance.

Disruption of the axon initial segment cytoskeleton is a new mechanism for neuronal injury

Many factors contribute to nervous system dysfunction and failure to regenerate after injury or disease. Here, we describe a previously unrecognized mechanism for nervous system injury. We show that neuronal injury causes rapid, irreversible, and preferential proteolysis of the axon initial segment (AIS) cytoskeleton independently of cell death or axon degeneration, leading to loss of both ion channel clusters and neuronal polarity. Furthermore, we show this is caused by proteolysis of the AIS cytoskeletal proteins ankyrinG and betaIV spectrin by the calcium-dependent cysteine protease calpain. Importantly, calpain inhibition is sufficient to preserve the molecular organization of the AIS both in vitro and in vivo. We conclude that loss of AIS ion channel clusters and neuronal polarity are important contributors to neuronal dysfunction after injury, and that strategies to facilitate recovery must preserve or repair the AIS cytoskeleton.

Neuropathic pain: a maladaptive response of the nervous system to damage

Neuropathic pain is triggered by lesions to the somatosensory nervous system that alter its structure and function so that pain occurs spontaneously and responses to noxious and innocuous stimuli are pathologically amplified. The pain is an expression of maladaptive plasticity within the nociceptive system, a series of changes that constitute a neural disease state. Multiple alterations distributed widely across the nervous system contribute to complex pain phenotypes. These alterations include ectopic generation of action potentials, facilitation and disinhibition of synaptic transmission, loss of synaptic connectivity and formation of new synaptic circuits, and neuroimmune interactions. Although neural lesions are necessary, they are not sufficient to generate neuropathic pain; genetic polymorphisms, gender, and age all influence the risk of developing persistent pain. Treatment needs to move from merely suppressing symptoms to a disease-modifying strategy aimed at both preventing maladaptive plasticity and reducing intrinsic risk.

Cloning and characterization of the 5'UTR of the rat anti-apoptotic Bcl-w gene

The anti-apoptotic Bcl-w regulator, which is expressed in the developing and mature brain, not only promotes neuronal survival, but also neuronal differentiation. However, its transcriptional regulation remains to be elucidated due to a lack of knowledge of the Bcl-w promoter. Here, we report the mapping and characterization of the rat Bcl-w promoter, which is highly conserved between the human, mouse, and rat species. Using a series of 5' and 3' deletions, we mapped the TATA-less minimal Bcl-w promoter and showed that it is under a combinatorial regulation with the neurogenic bHLH transcription factor NeuroD6 mediating its activation, validating our previous finding of increased expression of the Bcl-w protein in stably transfected PC12-NeuroD6 cells. Upon stress, NeuroD6 promotes colocalization of Bcl-w with mitochondria and endoplasmic reticulum. Finally, we provide the first evidence of Bcl-w localization in the growth cones of differentiating neuronal cells, suggestive of a potential synaptic neuroprotective role.

Stem cell-based cell therapy in neurological diseases: a review

Human neurological disorders such as Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis (ALS), Alzheimer's disease, multiple sclerosis (MS), stroke, and spinal cord injury are caused by a loss of neurons and glial cells in the brain or spinal cord. Cell replacement therapy and gene transfer to the diseased or injured brain have provided the basis for the development of potentially powerful new therapeutic strategies for a broad spectrum of human neurological diseases. However, the paucity of suitable cell types for cell replacement therapy in patients suffering from neurological disorders has hampered the development of this promising therapeutic approach. In recent years, neurons and glial cells have successfully been generated from stem cells such as embryonic stem cells, mesenchymal stem cells, and neural stem cells, and extensive efforts by investigators to develop stem cell-based brain transplantation therapies have been carried out. We review here notable experimental and preclinical studies previously published involving stem cell-based cell and gene therapies for Parkinson's disease, Huntington's disease, ALS, Alzheimer's disease, MS, stroke, spinal cord injury, brain tumor, and lysosomal storage diseases and discuss the future prospects for stem cell therapy of neurological disorders in the clinical setting. There are still many obstacles to be overcome before clinical application of cell therapy in neurological disease patients is adopted: 1) it is still uncertain what kind of stem cells would be an ideal source for cellular grafts, and 2) the mechanism by which transplantation of stem cells leads to an enhanced functional recovery and structural reorganization must to be better understood. Steady and solid progress in stem cell research in both basic and preclinical settings should support the hope for development of stem cell-based cell therapies for neurological diseases.

N-acetylcysteine alters apoptotic gene expression in axotomised primary sensory afferent subpopulations

Novel approaches are required in peripheral nerve injury management because current surgical techniques, which do not address axotomy-induced neuronal death, lead to deficient sensory recovery. Sensory neuronal death has functional preference with cutaneous neurons dying in great numbers whilst muscle afferents survive axotomy. This offers the potential of comparing similar cell types that suffer distinct fates upon nerve injury. Here, a novel approach, combining in vivo rat nerve injury model with laser microdissection and quantitative real-time polymerase chain reaction, identifies crucial disparities in apoptotic gene expression attributable to subpopulations of differing sensory modalities and examines the response to N-acetylcysteine (NAC) therapy. We show that axotomised muscle afferent neurons survive injury due to a neuroprotective response which markedly downregulates Bax and caspase-3 mRNA. In contrast, axotomised cutaneous sensory neurons significantly upregulate caspase-3 and alter both Bcl-2 and Bax expression such that pro-apoptotic Bax predominates. N-Acetylcysteine (NAC) intervention promotes neuroprotection of cutaneous sensory neurons through considerable upregulation of Bcl-2 and downregulation of both Bax and caspase-3 mRNA. The data presented identifies differential activation of apoptotic genes in axotomised neuronal subpopulations. Furthermore, NAC therapy instigates apoptotic gene expression changes in axotomised neurons, thereby offering pharmacotherapeutic potential in the clinical treatment of nerve injury.

Cyp46-mediated cholesterol loss promotes survival in stressed hippocampal neurons

Aged neurons constitute an outstanding example of survival robustness, outliving the accumulation of reactive oxygen species (ROS) derived from various physiological activities. Since during aging hippocampal neurons experience a progressive loss of membrane cholesterol and, by virtue of this, a gradual and sustained increase in the activity of the survival receptor tyrosine kinase TrkB, we have tested in this study if cholesterol loss is functionally associated to survival robustness during aging. We show that old neurons that did not undergo the cholesterol drop, upon knockdown of the cholesterol hydroxylating enzyme Cyp46, presented low TrkB activity and increased apoptotic levels. In further agreement, inducing cholesterol loss in young neurons led to the early appearance of TrkB activity. In vivo, Cyp46 knockdown led to the appearance of damaged hippocampal neurons in old mice exposed to exogenous stressful stimuli. Cholesterol loss seems therefore to contribute to neuronal survival in conditions of prominent stress, either acute or chronic. The relevance of this pathway in health and disease is discussed.

CREB activation in the rapid, intermediate, and delayed ischemic preconditioning against hypoxic-ischemia in neonatal rat

Ischemic preconditioning (IP) is a defense program in which exposure to sublethal ischemia followed by a period of reperfusion results in subsequent resistance to severe ischemic insults. Very few in vivo IP models have been established for neonatal brain. We examined whether rapid, intermediate, and delayed IP against hypoxic-ischemia (HI) could be induced in neonatal brain, and if so, whether the IP involved phosphorylation of cAMP response element-binding protein (pCREB) after HI. Postnatal day 7 rat pups were subjected to HI at 2 h (2-h IP), 6 h (6-h IP), or 22 h (22-h IP) after IP. We found all three IP groups had significantly reduced neuronal damage and TUNEL-(+) cells 24 h post-HI than no-IP group. Compared with control, the no-IP group had significant decreases of pCREB and mitochondria Bcl-2 levels in the ipsilateral cortex 24 h post-HI. In contrast, the three IP groups had increased pCREB and mitochondria Bcl-2 levels, and significant differences were found between three IP and no-IP groups. The increases of cleavage of caspase-3 and poly (ADP-ribose) polymerase and of cells with nuclear apoptosis inducing factor post-HI in no-IP group were all significantly reduced in three IP groups. The increases of caspase-3 and calpain-mediated proteolysis of a-spectrin post-HI were significantly reduced only in 22-h IP group. Furthermore, all three IP groups had long-term neuroprotection at behavioral and pathological levels compared with no-IP group. In conclusion, IP, rapid, intermediate, or delayed, in neonatal rat brain activates CREB, up-regulates Bcl-2, induces extensive brakes on caspase-dependent and -independent apoptosis after HI, and provides long-term neuroprotection.

Protection of crayfish glial cells but not neurons from photodynamic injury by nerve growth factor

Photodynamic treatment that causes intense oxidative stress and cell death is currently used in neurooncology. However, along with tumor cells, it may damage healthy neurons and glia. In order to study photodynamic effect on normal nerve and glial cells, we used crayfish stretch receptor, a simple system consisting of only two identified sensory neurons surrounded by glial cells. Photodynamic treatment induced firing abolition and necrosis of neurons as well as necrosis and apoptosis of glial cells. Nerve growth factor but not brain-derived neurotrophic factor or epidermal growth factor protected glial cells but not neurons from photoinduced necrosis and apoptosis. Inhibitors of tyrosine kinases or protein kinase JNK eliminated anti-apoptotic effect of nerve growth factor in photosensitized glial cells but not neurons. Therefore, these signaling proteins were involved in the anti-apoptotic activity of nerve growth factor. These data indicate the possible presence of receptors capable of recognizing murine nerve growth factor in crayfish glial cells. Thus, intercellular signaling mediated by nerve-growth-factor-like neurotrophin, receptor tyrosine kinase, and JNK may be involved in crayfish glia protection from apoptosis induced by photodynamic treatment.

Stanniocalcin-1 acts in a negative feedback loop in the prosurvival ERK1/2 signaling pathway during oxidative stress

Mammalian Stanniocalcin-1 (STC1) is a glycoprotein that has been implicated in various biological processes including angiogenesis. Aberrant STC1 expression has been reported in breast, ovarian and prostate cancers, but the significance of this is not well understood. Here, we report that oxidative stress caused a 40-fold increase in STC1 levels in mouse embryo fibroblasts (MEFs). STC1-/- MEFs were resistant to growth inhibition and cell death induced by H(2)O(2) or by 20% O(2) (which is hyperoxic for most mammalian cells); this is the first phenotype reported for STC1-null cells. STC1-/- cells had higher levels of activated MEK and ERK1/2 than their wild-type (WT) counterparts, and these levels were all reduced by stable expression of exogenous STC1 in STC1-/- cells. Furthermore, pharmacological inhibition by PD98059 or UO126 of MEK and therefore of ERK1/2 activation restored sensitivity of STC1-/- cells to oxidative stress. We also found that H(2)O(2)-induced STC1 expression in WT cells was abolished by inhibition of ERK1/2 activation. Thus, the ERK1/2 signaling pathway upregulates STC1 expression, which in turn downregulates the level of activated MEK and consequently ERK1/2 in a novel negative feedback loop. Therefore, STC1 expression downregulates prosurvival ERK1/2 signaling and reduces survival under conditions of oxidative stress.

Mechanisms to explain wasting of muscle and fat in cancer cachexia

PURPOSE OF REVIEW

To describe the most relevant recent findings concerning the molecular mechanisms involved in both fat and muscle tissues in cachectic cancer patients.

RECENT FINDINGS

Relevant progress has been made in the mechanism of signalling protein metabolism in skeletal muscle. PI3K has a dual role inhibiting protein degradation by inhibition of Atrogin-1 and MuRF1 gene expression and facilitating AKT phosphorylation, leading to increased protein synthesis. Interestingly, Caspase-3 activity is intimately associated with myofibrillar protein degradation in muscle tissue. With respect to fat metabolism, increased lipolysis in human cancer cachexia seems to be directly connected to increased hormone-sensitive lipase activity.

SUMMARY

The results and findings described in this review represent important progress in wasting disease mechanisms and may provide hints for future therapeutic approaches in cancer cachexia.

Manganese activates the mitochondrial apoptotic pathway in rat astrocytes by modulating the expression of proteins of the Bcl-2 family

Manganese induces the central nervous system injury leading to manganism, by mechanisms not completely understood. Chronic exposure to manganese generates oxidative stress and induces the mitochondrial permeability transition. In the present study, we characterized apoptotic cell death mechanisms associated with manganese toxicity in rat cortical astrocytes and demonstrated that (i) Mn treatment targets the mitochondria and induces mitochondrial membrane depolarization followed by cytochrome c release to the cytoplasm, (ii) Mn induces both effector caspases 3/7 and 6 as well as PARP-1 cleavage and (iii) Mn shifts the balance of cell death/survival of Bcl-2 family proteins to favor the apoptotic demise of astrocytes. Our model system using cortical rat astrocytes treated with Mn would emerge as a good tool for investigations aimed to elucidate the role of apoptosis in manganism.

Driving GDNF expression: the green and the red traffic lights

Glial cell line-derived neurotrophic factor (GDNF) is widely recognized as a potent survival factor for dopaminergic neurons of the nigrostriatal pathway that degenerate in Parkinson's disease (PD). In animal models of PD, GDNF delivery to the striatum or the substantia nigra protects dopaminergic neurons against subsequent toxin-induced injury and rescues previously damaged neurons, promoting recovery of the motor function. Thus, GDNF was proposed as a potential therapy to PD aimed at slowing down, halting or reversing neurodegeneration, an issue addressed in previous reviews. However, the use of GDNF as a therapeutic agent for PD is hampered by the difficulty in delivering it to the brain. Another potential strategy is to stimulate the endogenous expression of GDNF, but in order to do that we need to understand how GDNF expression is regulated. The aim of this review is to do a comprehensive analysis of the state of the art on the control of endogenous GDNF expression in the nervous system, focusing mainly on the nigrostriatal pathway. We address the control of GDNF expression during development, in the adult brain and after injury, and how damaged neurons signal glial cells to up-regulate GDNF. Pharmacological agents or natural molecules that increase GDNF expression and show neuroprotective activity in animal models of PD are reviewed. We also provide an integrated overview of the signalling pathways linking receptors for these molecules to the induction of GDNF gene, which might also become targets for neuroprotective therapies in PD.

Neuron and gliocyte death induced by photodynamic treatment: signal processes and neuron-glial interactions

The mechanisms of photodynamic (PD) damage to neurons and gliocytes are discussed. The spike reactions of neurons are described, with stimulation at high concentrations of photosensitizer and inhibition at low concentrations, accompanying necrosis. Glial cells developed both necrosis and apoptosis. Local laser inactivation of neurons increased light-induced apoptosis of gliocytes, i.e., neurons maintained gliocyte survival. Inter-and intracellular signaling plays an important role in the photolesioning of these cells. Studies using inhibitors and activators of signal proteins demonstrated the involvement of the Ca(2+)-dependent, adenylate cyclase, and tyrosine kinase pathways in the responses of neurons and gliocytes to PD treatment. Pharmacological modulation may alter the selectivity of PD neuron and gliocyte damage and the efficacy of PD treatment.

JNK is activated but does not mediate hippocampal neuronal apoptosis in experimental neonatal pneumococcal meningitis

Pneumococcal meningitis is associated with caspase 3-dependent apoptosis of recently post-mitotic immature neurons in the dentate gyrus of the hippocampus. The death of these cells is implicated in the learning and memory deficits in patients surviving the disease. The stress-activated protein kinase c-Jun N-terminal kinase (JNK) has been shown to be an important mediator of caspase 3-dependent neuronal apoptosis. However, whether JNK is involved in hippocampal apoptosis caused by pneumococcal meningitis has so far not been investigated. Here we show in a neonatal rat model of pneumococcal meningitis that JNK3 but not JNK1 or JNK2 is activated in the hippocampus during the acute phase of infection. At the cellular level, JNK3 activation was accompanied in the dentate gyrus by markedly increased phosphorylation of its major downstream target c-Jun in early immature (Hu-positive) neurons, but not in migrating (doublecortin-positive) neurons, the cells that do undergo apoptosis. These findings suggested that JNK may not be involved in pneumococcal meningitis-induced hippocampal apoptosis. Indeed, although intracerebroventricular administration of D-JNKI-1 or AS601245 (two highly specific JNK inhibitors) inhibited c-Jun phosphorylation and protein expression in the hippocampus, hippocampal apoptosis was unaffected. Collectively, these results demonstrate that JNK does not mediate hippocampal apoptosis in pneumococcal meningitis, and that JNK may be involved in processes unrelated to apoptosis in this disease.

Ro5-4864 promotes neonatal motor neuron survival and nerve regeneration in adult rats

The translocator protein (18 kDa; TSPO), formerly known as the peripheral benzodiazepine receptor, is an outer mitochondrial membrane protein that associates with the mitochondrial permeability transition pore to regulate both steroidogenesis and apoptosis. TSPO expression is induced in adult dorsal root ganglion (DRG) sensory neurons after peripheral nerve injury and a TSPO receptor ligand, Ro5-4864, enhances DRG neurite growth in vitro and axonal regeneration in vivo. We have now found that TSPO is induced in neonatal motor neurons after peripheral nerve injury and have evaluated its involvement in neonatal and adult sensory and motor neuron survival, and in adult motor neuron regeneration. The TSPO ligand Ro5-4864 rescued cultured neonatal DRG neurons from nerve growth factor withdrawal-induced apoptosis and protected neonatal spinal cord motor neurons from death due to sciatic nerve axotomy. However, Ro5-4864 had only a small neuroprotective effect on adult facial motor neurons after axotomy, did not delay onset or prolong survival in SOD1 mutant mice, and failed to protect adult DRG neurons from sciatic nerve injury-induced death. In contrast, Ro5-4864 substantially enhanced adult facial motor neuron nerve regeneration and restoration of function after facial nerve axotomy. These data indicate a selective sensitivity of neonatal sensory and motor neurons to survival in response to Ro5-4864, which highlights that survival in injured immature neurons cannot necessarily predict success in adults. Furthermore, although Ro5-4864 is only a very weak promoter of survival in adult neurons, it significantly enhances regeneration and functional recovery in adults.

Priming of CD8+ T cells during central nervous system infection with a murine coronavirus is strain dependent

Virus-specific CD8(+) T cells are critical for protection against neurotropic coronaviruses; however, central nervous system (CNS) infection with the recombinant JHM (RJHM) strain of mouse hepatitis virus (MHV) elicits a weak CD8(+) T-cell response in the brain and causes lethal encephalomyelitis. An adoptive transfer model was used to elucidate the kinetics of CD8(+) T-cell priming during CNS infection with RJHM as well as with two MHV strains that induce a robust CD8(+) T-cell response (RA59 and SJHM/RA59, a recombinant A59 virus expressing the JHM spike). While RA59 and SJHM/RA59 infections resulted in CD8(+) T-cell priming within the first 2 days postinfection, RJHM infection did not lead to proliferation of naïve CD8(+) T cells. While all three viruses replicated efficiently in the brain, only RA59 and SJHM/RA59 replicated to appreciable levels in the cervical lymph nodes (CLN), the site of T-cell priming during acute CNS infection. RJHM was unable to suppress the CD8(+) T-cell response elicited by RA59 in mice simultaneously infected with both strains, suggesting that RJHM does not cause generalized immunosuppression. RJHM was also unable to elicit a secondary CD8(+) T-cell response in the brain following peripheral immunization against a viral epitope. Notably, the weak CD8(+) T-cell response elicited by RJHM was unique to CNS infection, since peripheral inoculation induced a robust CD8(+) T-cell response in the spleen. These findings suggest that the failure of RJHM to prime a robust CD8(+) T-cell response during CNS infection is likely due to its failure to replicate in the CLN.

Detrimental effects of aging on outcome from traumatic brain injury: a behavioral, magnetic resonance imaging, and histological study in mice

Considerable evidence indicates that outcomes from traumatic brain injury (TBI) are worse in the elderly, but there has been little preclinical research to explore potential mechanisms. In this study, we examined the age-related effects on outcome in a mouse model of controlled cortical impact (CCI) injury. We compared the responses of adult (5-6 months old) and aged (21-24 months old) male mice following a moderate lateral CCI injury to the sensorimotor cortex. Sensorimotor function was evaluated with the rotarod, gridwalk and spontaneous forelimb behavioral tests. Acute edema was assessed from hyperintensity on T2-weighted magnetic resonance images. Blood-brain barrier opening was measured using anti-mouse immunoglobulin G (IgG) immunohistochemistry. Neurodegeneration was assessed by amino-cupric silver staining, and lesion cavity volumes were measured from histological images. Indicators of injury were generally worse in the aged than the adult mice. Acute edema, measured at 24 and 48 h post-injury, resolved more slowly in the aged mice (p < 0.01). Rotarod recovery (p < 0.05) and gridwalk deficits (p < 0.01) were significantly worse in aged mice. There was greater (p < 0.01 at 3 days) and more prolonged post-acute opening of the blood-brain barrier in the aged mice. Neurodegeneration was greater in the aged mice (p < 0.01 at 3 days). In contrast, lesion cavity volumes, measured at 3 days post-injury, were not different between injured groups. These results suggest that following moderate controlled cortical impact injury, the aged brain is more vulnerable than the adult brain to neurodegeneration, resulting in greater loss of function. Tissue loss at the impact site does not explain the increased functional deficits seen in the aged animals. Prolonged acute edema, increased opening of the blood-brain barrier and increased neurodegeneration found in the aged animals implicate secondary processes in age-related differences in outcome.

Primary neurons become less susceptible to coxsackievirus B5 following maturation: the correlation with the decreased level of CAR expression on cell surface

Coxsackievirus B (CVB) is one of the major pathogens of aseptic meningitis and meningioencephalitis, particularly in newborn infants. To analyze the influence of neural maturation on susceptibility to CVB infection, we prepared immature and mature neurons from 16-day-old BALB/c embryonic cortex. In contrast to immature neurons, mature neurons were less susceptible to CVB5 infection, as indicated by the decrease of cytopathic features. In mature neurons, progeny virus production was significantly hindered, and virus capsid protein VP1 synthesis and virus genome amplification were concomitantly reduced. In addition, the expression of coxsackievirus and adenovirus receptor (CAR), the major receptor of CVB5, was down-regulated in mature neurons. The antibody treatment specific to CAR significantly attenuated CVB5 susceptibility of immature neurons. These findings demonstrate that mature neurons become less susceptible to CVB by the decrease of CAR level. Thus, the data strongly support the idea that the level of virus receptor in neurons is one of the crucial determinants in the age-dependency of CVB virulence in central nervous system.

Apoptosis signalling is essential and precedes protein degradation in wasting skeletal muscle during catabolic conditions

Activation of skeletal muscle proteolysis leads to wasting in many types of catabolic/chronic diseases. Protein breakdown is basically accomplished by the activation of the ubiquitin-proteasome system. Interestingly, several publications have shown that DNA fragmentation also occurs in skeletal muscle tissue during catabolism. The present review suggests that activation of apoptosis precedes protein breakdown associated with muscle wasting. In addition, the role of the different proteolytic systems and their relation with apoptosis is emphasized. Altogether, the data presented could be used for the design of new approaches for the treatment of muscle wasting diseases.

Cell death is associated with reduced base excision repair during chronic alcohol administration in adult rat brain

The cell death cascades in different brain regions namely hippocampus and frontal cortex of rats fed with 10% (v/v) ethanol for 12 weeks, was examined. After Western blotting, different cell death associated proteins displayed differential activation in the two regions observed. In hippocampus, activated caspase-3 and caspase-7 resulted in subsequent cleavage of poly(ADP-ribose) polymerase-1 (PARP-1). Cytochrome c release to cytosol and apoptosis inducing factor (AIF) translocation to nucleus was marginal. B-cell leukemia/lymphoma-2 (Bcl-2) translocation to cytosol was significant whereas Bcl-2-associated X protein (Bax) and Bcl-associated death protein (Bad) were largely located in cytosol. Further, upregulation of N-methyl D-aspartate receptor subunit 1 (NMDAR1), N-methyl D-aspartate receptor subunit 2B (NMDAR2B), N-methyl D-aspartate receptor subunit 2C (NMDAR2C) and activation of calpains were observed. In frontal cortex, caspase-3 activation, cleavage of PARP-1 and nuclear translocation of AIF were more pronounced. Moreover, cytochrome c release to cytosol, Bcl-2 translocation to cytosol was evident. However, levels of Bax, Bad, NMDA receptor subunits, and calpains were unaffected. Apoptosis was further substantiated by in situ staining for terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL). Results of the current study revealed that frontal cortex exhibits a higher level of ethanol-induced apoptosis relative to hippocampus. DNA polymerase beta assay and immunoblot showed significant loss in base excision repair in ethanol treated group.

BH3-only proteins Bid and Bim(EL) are differentially involved in neuronal dysfunction in mouse models of Huntington's disease

Apoptosis, a cell death mechanism regulated by Bcl-2 family members, has been proposed as one of the mechanisms leading to neuronal loss in Huntington's disease (HD). Here we examined the regulation of Bcl-2 family proteins in three different mouse models of HD with exon 1 mutant huntingtin: the R6/1, the R6/1:BDNF+/-, and the Tet/HD94 in which the huntingtin transgene is controlled by the tetracycline-inducible system. Our results disclosed an increase in the levels of the BH3-only proteins Bid and Bim(EL) in the striatum of HD mouse models that was different depending on the stage of the disease. At 16 weeks of age, Bid was similarly enhanced in the striatum of R6/1 and R6/1:BDNF+/- mice, whereas Bim(EL) protein levels were enhanced only in R6/1:BDNF+/- mice. In contrast, at later stages of the disease, both genotypes displayed increased levels of Bid and Bim(EL) proteins. Furthermore, Bax, Bak, Bad, Bcl-2, and Bcl-x(L) proteins were not modified in any of the points analyzed. We next explored the potential reversibility of this phenomenon by analyzing conditional Tet/HD94 mice. Constitutive expression of the transgene resulted in increased levels of Bid and Bim(EL) proteins, and only the Bid protein returned to wild-type levels 5 months after mutant huntingtin shutdown. In conclusion, our results show that enhanced Bid protein levels represent an early mechanism linked to the continuous expression of mutant huntingtin that, together with enhanced Bim(EL), may be a reporter of the progress and severity of neuronal dysfunction.

The C. elegans protein CEH-30 protects male-specific neurons from apoptosis independently of the Bcl-2 homolog CED-9

The developmental control of apoptosis is fundamental and important. We report that the Caenorhabditis elegans Bar homeodomain transcription factor CEH-30 is required for the sexually dimorphic survival of the male-specific CEM (cephalic male) sensory neurons; the homologous cells of hermaphrodites undergo programmed cell death. We propose that the cell-type-specific anti-apoptotic gene ceh-30 is transcriptionally repressed by the TRA-1 transcription factor, the terminal regulator of sexual identity in C. elegans, to cause hermaphrodite-specific CEM death. The established mechanism for the regulation of specific programmed cell deaths in C. elegans is the transcriptional control of the BH3-only gene egl-1, which inhibits the Bcl-2 homolog ced-9; similarly, most regulation of vertebrate apoptosis involves the Bcl-2 superfamily. In contrast, ceh-30 acts within the CEM neurons to promote their survival independently of both egl-1 and ced-9. Mammalian ceh-30 homologs can substitute for ceh-30 in C. elegans. Mice lacking the ceh-30 homolog Barhl1 show a progressive loss of sensory neurons and increased sensory-neuron cell death. Based on these observations, we suggest that the function of Bar homeodomain proteins as cell-type-specific inhibitors of apoptosis is evolutionarily conserved.

Chromatin modification of Apaf-1 restricts the apoptotic pathway in mature neurons

Although apoptosis has been extensively studied in developing neurons, the dynamic changes in this pathway after neuronal maturation remain largely unexplored. We show that as neurons mature, cytochrome c– mediated apoptosis progresses from inhibitor of apoptosis protein–dependent to –independent regulation because of a complete loss of Apaf-1 expression. However, after DNA damage, mature neurons resynthesize Apaf-1 through the cell cycle–related E2F1 pathway and restore their apoptotic potential. Surprisingly, we find that E2F1 is sufficient to induce Apaf-1 expression in developing but not mature neurons. Rather, Apaf-1 up-regulation in mature neurons requires both chromatin derepression and E2F1 transcriptional activity. This differential capacity of E2F1 to induce Apaf-1 transcription is because of the association of the Apaf-1 promoter with active chromatin in developing neurons and repressed chromatin in mature neurons. These data specifically illustrate how the apoptotic pathway in mature neurons becomes increasingly restricted by a novel mechanism involving the regulation of chromatin structure.

MPP(+)-induced cytotoxicity in neuroblastoma cells: Antagonism and reversal by guanosine

Guanosine exerts neuroprotective effects in the central nervous system. Apoptosis, a morphological form of programmed cell death, is implicated in the pathophysiology of Parkinson's disease (PD). MPP(+), a dopaminergic neurotoxin, produces in vivo and in vitro cellular changes characteristic of PD, such as cytotoxicity, resulting in apoptosis. Undifferentiated human SH-SY5Y neuroblastoma cells had been used as an in vitro model of Parkinson's disease. We investigated if extracellular guanosine affected MPP(+)-induced cytotoxicity and examined the molecular mechanisms mediating its effects. Exposure of neuroblastoma cells to MPP(+) (10 muM-5 mM for 24-72 h) induced DNA fragmentation in a time-dependent manner (p < 0.05). Administration of guanosine (100 muM) before, concomitantly with or, importantly, after the addition of MPP(+) abolished MPP(+)-induced DNA fragmentation. Addition of MPP(+) (500 muM) to cells increased caspase-3 activity over 72 h (p < 0.05), and this was abolished by pre- or co-treatment with guanosine. Exposure of cells to pertussis toxin prior to MPP(+) eliminated the anti-apoptotic effect of guanosine, indicating that this effect is dependent on a Gi protein-coupled receptor, most likely the putative guanosine receptor. The protection by guanosine was also abolished by the selective inhibitor of the enzyme PI-3-K/Akt/PKB (LY294002), confirming that this pathway plays a decisive role in this effect of guanosine. Neither MPP(+) nor guanosine had any significant effect on alpha-synuclein expression. Thus, guanosine antagonizes and reverses MPP(+)-induced cytotoxicity of neuroblastoma cells via activation of the cell survival pathway, PI-3-K/Akt/PKB. Our results suggest that guanosine may be an effective pharmacological intervention in PD.

Opposite regulation of oligodendrocyte apoptosis by JNK3 and Pin1 after spinal cord injury

Although oligodendrocytes undergo apoptosis after spinal cord injury, molecular mechanisms responsible for their death have been unknown. We report that oligodendrocyte apoptosis is regulated oppositely by c-Jun N-terminal kinase 3 (JNK3) and protein interacting with the mitotic kinase, never in mitosis A I (Pin1), the actions of which converge on myeloid cell leukemia sequence-1 (Mcl-1). Activated after injury, JNK3 induces cytochrome c release by facilitating the degradation of Mcl-1, the stability of which is maintained in part by Pin1. Pin1 binds Mcl-1 at its constitutively phosphorylated site, Thr163Pro, and stabilizes it by inhibiting ubiquitination. After injury JNK3 phosphorylates Mcl-1 at Ser121Pro, facilitating the dissociation of Pin1 from Mcl-1. JNK3 thus induces Mcl-1 degradation by counteracting the protective binding of Pin1. These results are confirmed by the opposing phenotypes observed between JNK3-/- and Pin1-/- mice: oligodendrocyte apoptosis and cytochrome c release are reduced in JNK3-/- but elevated in Pin1-/- mice. This report thus unveils a mechanism by which cytochrome c release is under the opposite control of JNK3 and Pin1, regulators for which the activities are intricately coupled.

Bcl-XL modulates the differentiation of immortalized human neural stem cells

Understanding basic processes of human neural stem cell (hNSC) biology and differentiation is crucial for the development of cell replacement therapies. Bcl-X(L) has been reported to enhance dopaminergic neuron generation from hNSCs and mouse embryonic stem cells. In this work, we wanted to study, at the cellular level, the effects that Bcl-X(L) may exert on cell death during differentiation of hNSCs, and also on cell fate decisions and differentiation. To this end, we have used both v-myc immortalized (hNS1 cell line) and non-immortalized neurosphere cultures of hNSCs. In culture, using different experimental settings, we have consistently found that Bcl-X(L) enhances neuron generation while precluding glia generation. These effects do not arise from a glia-to-neuron shift (changes in fate decisions taken by precursors) or by only cell death counteraction, but, rather, data point to Bcl-X(L) increasing proliferation of neuronal progenitors, and inhibiting the differentiation of glial precursors. In vivo, after transplantation into the aged rat striatum, Bcl-X(L) overexpressing hNS1 cells generated more neurons and less glia than the control ones, confirming the results obtained in vitro. These results indicate an action of Bcl-X(L) modulating hNSCs differentiation, and may be thus important for the future development of cell therapy strategies for the diseased mammalian brain.

A protocol describing pharynx counts and a review of other assays of apoptotic cell death in the nematode worm Caenorhabditis elegans

Studies of the nematode worm Caenorhabditis elegans have provided important insights into the genetics of programmed cell death (PCD), and revealed molecular mechanisms conserved from nematodes to humans. The organism continues to offer opportunities to investigate the processes of apoptosis under very well-defined conditions and at single-cell resolution in living animals. Here, a survey of the common methods used to study the process of PCD in C. elegans is described. Detailed instructions are provided for one standard method--the counting of extra cells of the anterior pharynx--a quantitative technique that can be used to detect even very subtle alterations in the progression of apoptotic cell death.