bcl-2 transgene expression can protect neurons against developmental and induced cell death

Increased Apoptosis in Subcortical Regions of The Visual Pathway in Offspring Born to Diabetic Rats

OBJECTIVE

Diabetes in pregnancy is a prevalent disease that can affect the central nervous system of the fetus by hyperglycemia. This study aimed to investigate the impact of maternal diabetes on neuronal apoptosis in the superior colliculus (SC) and the lateral geniculate nucleus (LGN) in male neonates born to diabetic mothers.

MATERIALS AND METHODS

In this experimental study, female adult rats were separated into three groups: control, diabetic (induced using an intraperitoneal injection of streptozotocin), and insulin-treated diabetic [diabetes controlled by subcutaneous neutral protamine hagedorn (NPH)-insulin injection]. Male neonates from each group were euthanized on 0, 7, and 14 postnatal days (P0, P7, and P14, respectively), and apoptotic cells were identified using TUNEL staining.

RESULTS

The numerical density per unit area (NA) of apoptotic cells was significantly higher in SC and the dorsal LGN (dLGN) in neonates born to the diabetic rats compared to the control group at P0, P7, and P14. However, insulin treatment normalized the number of apoptotic cells.

CONCLUSION

This study demonstrated that maternal diabetes increased apoptosis in dLGN and SC of male neonates at P0, P7, and P14.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Endogenous and imposed determinants of apoptotic vulnerabilities in cancer

The intrinsic apoptosis pathway is controlled by the BCL-2 family of proteins. Although the pro-survival members of this family can help cancer cells evade apoptosis, they may also produce apoptotic vulnerabilities that can potentially be exploited therapeutically. Apoptotic vulnerabilities can be driven by endogenous factors including altered genetics, signaling, metabolism, structure and lineage or differentiation state as well as imposed factors, the most prominent being exposure to anti-cancer agents. The recent development of BH3 mimetics that inhibit pro-survival BCL-2 family proteins has allowed these apoptotic vulnerabilities to be targeted with demonstrable clinical success. Here, we review the key concepts that are vital for understanding, uncovering, and exploiting apoptotic vulnerabilities in cancer for the potential improvement of patient outcomes.

Immature excitatory neurons in the amygdala come of age during puberty

The human amygdala is critical for emotional learning, valence coding, and complex social interactions, all of which mature throughout childhood, puberty, and adolescence. Across these ages, the amygdala paralaminar nucleus (PL) undergoes significant structural changes including increased numbers of mature neurons. The PL contains a large population of immature excitatory neurons at birth, some of which may continue to be born from local progenitors. These progenitors disappear rapidly in infancy, but the immature neurons persist throughout childhood and adolescent ages, indicating that they develop on a protracted timeline. Many of these late-maturing neurons settle locally within the PL, though a small subset appear to migrate into neighboring amygdala subnuclei. Despite its prominent growth during postnatal life and possible contributions to multiple amygdala circuits, the function of the PL remains unknown. PL maturation occurs predominately during late childhood and into puberty when sex hormone levels change. Sex hormones can promote developmental processes such as neuron migration, dendritic outgrowth, and synaptic plasticity, which appear to be ongoing in late-maturing PL neurons. Collectively, we describe how the growth of late-maturing neurons occurs in the right time and place to be relevant for amygdala functions and neuropsychiatric conditions.

The Role of Microglia in Neuroinflammation of the Spinal Cord after Peripheral Nerve Injury

Peripheral nerve injuries induce a pronounced immune reaction within the spinal cord, largely governed by microglia activation in both the dorsal and ventral horns. The mechanisms of activation and response of microglia are diverse depending on the location within the spinal cord, type, severity, and proximity of injury, as well as the age and species of the organism. Thanks to recent advancements in neuro-immune research techniques, such as single-cell transcriptomics, novel genetic mouse models, and live imaging, a vast amount of literature has come to light regarding the mechanisms of microglial activation and alluding to the function of microgliosis around injured motoneurons and sensory afferents. Herein, we provide a comparative analysis of the dorsal and ventral horns in relation to mechanisms of microglia activation (CSF1, DAP12, CCR2, Fractalkine signaling, Toll-like receptors, and purinergic signaling), and functionality in neuroprotection, degeneration, regeneration, synaptic plasticity, and spinal circuit reorganization following peripheral nerve injury. This review aims to shed new light on unsettled controversies regarding the diversity of spinal microglial-neuronal interactions following injury.

Optogenetic Stimulation of Prelimbic Pyramidal Neurons Maintains Fear Memories and Modulates Amygdala Pyramidal Neuron Transcriptome

Fear extinction requires coordinated neural activity within the amygdala and medial prefrontal cortex (mPFC). Any behavior has a transcriptomic signature that is modified by environmental experiences, and specific genes are involved in functional plasticity and synaptic wiring during fear extinction. Here, we investigated the effects of optogenetic manipulations of prelimbic (PrL) pyramidal neurons and amygdala gene expression to analyze the specific transcriptional pathways associated to adaptive and maladaptive fear extinction. To this aim, transgenic mice were (or not) fear-conditioned and during the extinction phase they received optogenetic (or sham) stimulations over photo-activable PrL pyramidal neurons. At the end of behavioral testing, electrophysiological (neural cellular excitability and Excitatory Post-Synaptic Currents) and morphological (spinogenesis) correlates were evaluated in the PrL pyramidal neurons. Furthermore, transcriptomic cell-specific RNA-analyses (differential gene expression profiling and functional enrichment analyses) were performed in amygdala pyramidal neurons. Our results show that the optogenetic activation of PrL pyramidal neurons in fear-conditioned mice induces fear extinction deficits, reflected in an increase of cellular excitability, excitatory neurotransmission, and spinogenesis of PrL pyramidal neurons, and associated to strong modifications of the transcriptome of amygdala pyramidal neurons. Understanding the electrophysiological, morphological, and transcriptomic architecture of fear extinction may facilitate the comprehension of fear-related disorders.

The Transcription Factor LHX1 Regulates the Survival and Directed Migration of POA-derived Cortical Interneurons

The delicate balance of excitation and inhibition is crucial for proper function of the cerebral cortex, relying on the accurate number and subtype composition of inhibitory gamma-aminobutyric (GABA)-expressing interneurons. Various intrinsic and extrinsic factors precisely orchestrate their multifaceted development including the long-range migration from the basal telencephalon to cortical targets as well as interneuron survival throughout the developmental period. Particularly expressed guidance receptors were described to channel the migration of cortical interneurons deriving from the medial ganglionic eminence (MGE) and the preoptic area (POA) along distinct routes. Hence, unveiling the regulatory genetic networks controlling subtype-specific gene expression profiles is key to understand interneuron-specific developmental programs and to reveal causes for associated disorders. In contrast to MGE-derived interneurons, little is known about the transcriptional networks in interneurons born in the POA. Here, we provide first evidence for the LIM-homeobox transcription factor LHX1 as a crucial key player in the post-mitotic development of POA-derived cortical interneurons. By transcriptional regulation of related genes, LHX1 modulates their survival as well as the subtype-specific expression of guidance receptors of the Eph/ephrin family, thereby affecting directional migration and layer distribution in the adult cortex.

Cytotoxic Immunity in Peripheral Nerve Injury and Pain

Cytotoxicity and consequent cell death pathways are a critical component of the immune response to infection, disease or injury. While numerous examples of inflammation causing neuronal sensitization and pain have been described, there is a growing appreciation of the role of cytotoxic immunity in response to painful nerve injury. In this review we highlight the functions of cytotoxic immune effector cells, focusing in particular on natural killer (NK) cells, and describe the consequent action of these cells in the injured nerve as well as other chronic pain conditions and peripheral neuropathies. We describe how targeted delivery of cytotoxic factors via the immune synapse operates alongside Wallerian degeneration to allow local axon degeneration in the absence of cell death and is well-placed to support the restoration of homeostasis within the nerve. We also summarize the evidence for the expression of endogenous ligands and receptors on injured nerve targets and infiltrating immune cells that facilitate direct neuro-immune interactions, as well as modulation of the surrounding immune milieu. A number of chronic pain and peripheral neuropathies appear comorbid with a loss of function of cellular cytotoxicity suggesting such mechanisms may actually help to resolve neuropathic pain. Thus while the immune response to peripheral nerve injury is a major driver of maladaptive pain, it is simultaneously capable of directing resolution of injury in part through the pathways of cellular cytotoxicity. Our growing knowledge in tuning immune function away from inflammation toward recovery from nerve injury therefore holds promise for interventions aimed at preventing the transition from acute to chronic pain.

Regulation of apoptosis in health and disease: the balancing act of BCL-2 family proteins

The loss of vital cells within healthy tissues contributes to the development, progression and treatment outcomes of many human disorders, including neurological and infectious diseases as well as environmental and medical toxicities. Conversely, the abnormal survival and accumulation of damaged or superfluous cells drive prominent human pathologies such as cancers and autoimmune diseases. Apoptosis is an evolutionarily conserved cell death pathway that is responsible for the programmed culling of cells during normal eukaryotic development and maintenance of organismal homeostasis. This pathway is controlled by the BCL-2 family of proteins, which contains both pro-apoptotic and pro-survival members that balance the decision between cellular life and death. Recent insights into the dynamic interactions between BCL-2 family proteins and how they control apoptotic cell death in healthy and diseased cells have uncovered novel opportunities for therapeutic intervention. Importantly, the development of both positive and negative small-molecule modulators of apoptosis is now enabling researchers to translate the discoveries that have been made in the laboratory into clinical practice to positively impact human health.

Anti-apoptotic BCL-2 family members in development

Almost 30 years ago it was first appreciated that anti-apoptotic B-cell lymphoma-2 (BCL-2) prevents the induction of apoptosis not only in malignant cells, but also in normal cellular lineages. This critical observation has rapidly evolved from merely identifying new BCL-2 family members to understanding how their biochemical interactions trigger the cell death process, and, more recently, to pharmacological inhibition of anti-apoptotic BCL-2 function in disease. Indeed, the proper regulation of apoptosis is important in many aspects of life including development, homeostasis, and disease biology. To better understand these processes, scientists have used many tools to assess the contribution of individual anti-apoptotic BCL-2 family members. This review will focus on the prominent roles for BCL-2 and other pro-survival family members in promoting the development of mammals during early embryogenesis, neurogenesis, and hematopoiesis.

Expression of apoptosis-regulatory genes in the hippocampus of rat neonates born to mothers with diabetes

Diabetes during pregnancy impairs the development of the central nervous system (CNS) and causes cognitive and behavioral abnormalities in offspring. However, the exact mechanism by which the maternal diabetes affects the development of the brain remains to be elucidated. The aim of the present study was to investigate the effects of maternal diabetes in pregnancy on the expression of Bcl-2 and Bax genes and the numerical density of degenerating dark neurons (DNs) in the hippocampus of offspring at the first postnatal two weeks. Wistar female rats were maintained diabetic from a week before pregnancy through parturition and male offspring was sacrificed at P0, P7, and P14. Our findings demonstrated a significant down-regulation in the hippocampal expression of Bcl-2 in the diabetic group newborns (P < 0.05). In contrast, the mRNA expression of Bax was markedly up-regulated in the offspring born to diabetic dams at all of studied time-points (P < 0.05). Moreover, we found a striking increase in the numerical density of DNs in the various subfields of hippocampus of diabetic group pups (P < 0.05). The results of the present study revealed that maternal hyperglycemia during gestational period may result in disturbances in the expression of Bcl-2 and Bax genes as two important genes in neuronal apoptosis regulation and induces the production of DNs in the developing hippocampus of neonatal rats. These disturbances may be a reason for the cognitive, structural, and behavioral anomalies observed in offspring born to diabetic mothers. Furthermore, the control of maternal glycaemia by insulin administration in most cases normalized these negative impacts.

Neuroprotective effect and mechanism of Mu-Xiang-You-Fang on cerebral ischemia-reperfusion injury in rats

ETHNOPHARMACOLOGICAL RELEVANCE

The present study is to investigate the neuroprotective effect of Mu-Xiang-You-Fang (MXYF), a classic Traditional Chinese Medicine used by Chinese minorities to treat stroke, on cerebral ischemia-reperfusion (I/R) injury and the related signaling pathways.

MATERIALS AND METHODS

Male Sprague-Dawley rats were divided into 6 groups: sham group, I/R group, nimodipine and MXYF (58, 116 and 232mg/kg respectively) groups. Cerebral ischemia model was induced by middle cerebral artery occlusion for 2h followed by reperfusion for 48h. Neurological functional score was evaluated according to the method of Zea longa's score and the infarct area was determined by 2,3,5-triphenyltetrazolium chloride (TTC) staining at 48h after reperfusion. The protein expression of cytochrome c (cyt-c), Bcl-2, Bax, caspase-9, caspase-3 and caspase-7 were analyzed by western blot and the mRNA expression of Caspase-9, Caspase-3 and Caspase-7 were determined by the reverse transcription-polymerase chain reaction.

RESULTS

Oral administration of MXYF (116 and 232mg/kg) significantly reduced the neurological functional score and attenuated the cerebral infarct area. Western blot analysis showed that the expression of Bcl-2 is enhanced and Bax expression is inhibited after treatment with MXYF (116 and 232mg/kg), leading to significant increase of the ratio between Bcl-2 and Bax. Furthermore, the protein expression of cyt-c, caspase-9, caspase-3 and caspase-7 was significantly inhibited while the mRNA expression of caspase-9, caspase-3 and caspase-7 but not cyt-c was markedly inhibited in the MXYF (116 and 232mg/kg) treatment groups compared with the I/R group.

CONCLUSIONS

The above data suggested that MXYF has potential neuroprotective activities by the regulation of apoptotic pathway, MXYF is a promising agent in treatment of stroke.

Neuroprotective Effects of Engineered Polymeric Nasal Microspheres Containing Hydroxypropyl-β-cyclodextrin on β-Amyloid (1-42)-Induced Toxicity

β-Amyloid (Aβ) plaques are the key neurotoxic assemblies in Alzheimer disease. It has been suggested that an interaction occurs between membrane cholesterol and Aβ aggregation in the brain. Cyclodextrins can remove cholesterol from cell membranes and change receptor function. This study aimed to investigate the effect of hydroxypropyl-β-cyclodextrin (HP-CD) polymeric microspheres, based on chitosan or sodium alginate, on the levels of lipid peroxidation, reactive oxygen species production, and mitochondrial function in brain synaptosomes. The effect of microspheres on DNA fragmentation, the expression of Bcl-2, Bax, and Apex1 mRNAs in rat hippocampus after Aβ(1-42) peptide-induced neurotoxicity was also evaluated. Comparison with HP-CD raw material was performed. Aβ(1-42) treatment significantly decreased the mitochondrial activity of Apex1 and Bcl-2 mRNAs, induced DNA fragmentation, and increased mRNA levels of Bax. Treatment with HP-CD microspheres against Aβ(1-42) significantly reduced DNA fragmentation and increased the Bcl-2/Bax mRNA ratio and mitochondrial function. In addition, HP-CD microspheres used against Aβ(1-42) decreased the levels of lipid peroxidation and reactive oxygen species production. These results indicate that nasally administered spray-dried HP-CD microspheres are able to provide protection against Aβ(1-42)-induced neurotoxicity, due to the suppressed levels of oxidative stress and apoptotic signals in the rat hippocampus.

Manual acupuncture at the SJ5 (Waiguan) acupoint shows neuroprotective effects by regulating expression of the anti-apoptotic gene Bcl-2

Acupuncture at the SJ5 (Waiguan) acupoint has neuroprotective effects in cerebral infarction, but the underlying mechanism remains poorly understood. Here, we analyzed gene expression in healthy rat cerebellum using a pathway-focused DNA microarray to screen 113 genes associated with 18 signal transduction pathways. After 20 minutes of acupuncture at SJ5, the expression of Bcl-2 and Birc1b mRNA was markedly increased. This was confirmed by real-time reverse transcription PCR. Furthermore, western blot analysis showed that Bcl-2 protein expression remained high in the cerebellum until at least 2 hours after cessation of acupuncture. These findings indicate that acupuncture at SJ5 exerts neuroprotective effects by regulating the expression of anti-apoptotic gene Bcl-2.

Neuroprotection requires the functions of the RNA-binding protein HuR

Alterations in the functions of neuronal RNA-binding proteins (RBPs) can contribute to neurodegenerative diseases. However, neurons also express a set of widely distributed RBPs that may have developed specialized functions. Here, we show that the ubiquitous member of the otherwise neuronal Elavl/Hu family of RNA-binding proteins, Elavl1/HuR, has a neuroprotective role. Mice engineered to lack exclusively HuR in the hippocampal neurons of the central nervous system (CNS), maintain physiologic levels of neuronal Elavls and develop a partially diminished seizure response following strong glutamatergic excitation; however, they display an exacerbated neurodegenerative response subsequent to the initial excitotoxic event. This response was phenocopied in hippocampal cells devoid of ionotropic glutamate receptors in which the loss of HuR results in enhanced mitochondrial dysfunction, oxidative damage and programmed necrosis solely after glutamate challenge. The molecular dissection of HuR and nElavl mRNA targets revealed the existence of a HuR-restricted posttranscriptional regulon that failed in HuR-deficient neurons and is involved in cellular energetics and oxidation defense. Thus, HuR acts as a specialized controller of oxidative metabolism in neurons to confer protection from neurodegeneration.

Genes showing altered expression in the medial preoptic area in the highly social maternal phenotype are related to autism and other disorders with social deficits

Background

The mother-child relationship is the most fundamental social bond in mammals, and previous studies indicate that the medial preoptic area (MPOA) contributes to this increase in sociability. It is possible that the same genes that lead to elevated sociability in one condition (the maternal state) might also be dysregulated in some disorders with social deficits (e.g. autism). In this study, we examined whether there was enrichment (greater than chance overlap) for social deficit disorder related genes in MPOA microarray results between virgin and postpartum female mice. We utilized microarrays to assess large scale gene expression changes in the MPOA of virgin and postpartum mice. The Modular Single Set Enrichment Test (MSET) was used to determine if mental health disorder related genes were enriched in significant microarray results. Additional resources, such as ToppCluster, NIH DAVID, and weighted co-expression network analysis (WGCNA) were used to analyze enrichment for specific gene clusters or indirect relationships between significant genes of interest. Finally, a subset of microarray results was validated using quantitative PCR.

Results

Significant postpartum MPOA microarray results were enriched for multiple disorders that include social deficits, including autism, bipolar disorder, depression, and schizophrenia. Together, 98 autism-related genes were identified from the significant microarray results. Further, ToppCluser and NIH DAVID identified a large number of postpartum genes related to ion channel activity and CNS development, and also suggested a role for microRNAs in regulating maternal gene expression. WGCNA identified a module of genes associated with the postpartum phenotype, and identified indirect links between transcription factors and other genes of interest.

Conclusion

The transition to the maternal state involves great CNS plasticity and increased sociability. We identified multiple novel genes that overlap between the postpartum MPOA (high sociability) and mental health disorders with low sociability. Thus, the activity or interactions of the same genes may be altering social behaviors in different directions in different conditions. Maternity also involves elevated risks for disorders, including depression, psychosis, and BPD, so identification of maternal genes common to these disorders may provide insights into the elevated vulnerability of the maternal brain.

Lycopene inhibits ischemia/reperfusion-induced neuronal apoptosis in gerbil hippocampal tissue

Plant lycopene exhibits antioxidant activity in animal tissues. Transient cerebral ischemia/reperfusion in Mongolian gerbils resulted in delayed neuronal death in hippocampal regions. We examined the antioxidant effects of lycopene because we expected lycopene to attenuate ischemia-related neuronal damage by controlling apoptosis at the gene level. The gerbils were divided into two groups: the normal feeding (control) group that received normal market food (MF) and the lycopene group that received MF containing lycopene (5 mg in 100 g MF food). After 1.5-2.0 months (when body weight were 60-65 g), the lycopene level was 38.2 ± 17.6 ng/ml in serum and 11.9 ± 4.0 μg/g-wet weight tissue in the liver. Levels of B cell leukemia-2, an apoptosis-suppressing protein, decreased in control animal brains 1, 3, and 7 days after surgery, whereas the levels increased in lycopene-treated animal brains. Moreover, cysteinyl aspartate-specific protease-3 activity increased gradually after ischemia, but was suppressed in the lycopene-treated animal brains 7 days after surgery. Finally, hippocampal superoxide dismutase (SOD) activity decreased in the control group 3 h after ischemia and, gradually increased thereafter, whereas it was significantly elevated in the lycopene group. Thus, orally administered lycopene is accumulated in the body, and provided protections against ischemia/reperfusion-induced brain injury by inducing an increase in SOD activity and inhibiting apoptosis.

Early differential cell death and survival mechanisms initiate and contribute to the development of OPIDN: a study of molecular, cellular, and anatomical parameters

Organophosphorus-ester induced delayed neurotoxicity (OPIDN) is a neurodegenerative disorder characterized by ataxia progressing to paralysis with a concomitant central and peripheral, distal axonapathy. Diisopropylphosphorofluoridate (DFP) produces OPIDN in the chicken that results in mild ataxia in 7-14 days and severe paralysis as the disease progresses with a single dose. White leghorn layer hens were treated with DFP (1.7 mg/kg, sc) after prophylactic treatment with atropine (1mg/kg, sc) in normal saline and eserine (1mg/kg, sc) in dimethyl sulfoxide. Control groups were treated with vehicle propylene glycol (0.1 ml/kg, sc), atropine in normal saline and eserine in dimethyl sulfoxide. The hens were euthanized at different time points such as 1, 2, 5, 10 and 20 days, and the tissues from cerebrum, midbrain, cerebellum, brainstem and spinal cord were quickly dissected and frozen for mRNA (northern) studies. Northern blots were probed with BCL2, GADD45, beta actin, and 28S RNA to investigate their expression pattern. Another set of hens was treated for a series of time points and perfused with phosphate buffered saline and fixative for histological studies. Various staining protocols such as Hematoxylin and Eosin (H&E); Sevier-Munger; Cresyl echt Violet for Nissl substance; and Gallocynin stain for Nissl granules were used to assess various patterns of cell death and degenerative changes. Complex cell death mechanisms may be involved in the neuronal and axonal degeneration. These data indicate altered and differential mRNA expressions of BCL2 (anti apoptotic gene) and GADD45 (DNA damage inducible gene) in various tissues. Increased cell death and other degenerative changes noted in the susceptible regions (spinal cord and cerebellum) than the resistant region (cerebrum), may indicate complex molecular pathways via altered BCL2 and GADD45 gene expression, causing the homeostatic imbalance between cell survival and cell death mechanisms. Semi quantitative analysis revealed that the order of severity of damage declines from the spino-cerebellar, ventral, and dorsal tract respectively, suggesting neuroanatomical specificity. Thus, early activation of cell death and cell survival processes may play significant role in the clinical progression and syndromic clinical feature presentation of OPIDN.

Bcl-2 in suppressing neuronal apoptosis after spinal cord injury

BACKGROUND

Apoptosis plays an important role in central neural diseases and trauma. B-cell lymphoma/Leukemia-2 (Bcl-2) can inhibit apoptosis in a wide variety of cells including neurons. In this experiment, by studying Bcl-2 over-expression transgenic (TG) mice subjected to spinal cord injury (SCI), we investigated whether Bcl-2 could reduce posttraumatic neuronal apoptosis, reduce the range of damage, and improve the behavioral functional recovery after contusive SCI.

METHODS

Nine Bcl-2 TG mice and nine control mice were subjected to SCI of moderate severity at T10, with the use of weight dropping (WD) method (impact force 2.5×3.0 g/cm). At times up to 1 day, 7 days and 14 days after SCI, functional deficits were evaluated with Basso, Beattie, and Bresnahan (BBB) scales, and apoptosis of neurons was investigated by using the TUNEL method. Another three control mice only underwent lamina opening, but were not subjected to SCI, to provide blank comparison.

RESULTS

The mean functional scores for the control mice (5.05 ±0.35) were lower than those for the Bcl-2 TG mice (5.45 ±0.15), although the unpaired T-test revealed no significant difference (P=0.67). On the other hand, the number of TUNEL positive neurons and integrated option density (IOD) scores for the Bcl-2 TG mice were both significantly lower than those for the control mice (P<0.05).

CONCLUSIONS

This experiment suggests that overexpression of Bcl-2 may suppress neuronal apoptosis after SCI. Bcl-2 may be an important factor within the central nervous system that can relieve the damage after trauma.

Neural precursor death is central to the pathogenesis of intestinal aganglionosis in Ret hypomorphic mice

The RET tyrosine kinase is required for the migration, proliferation, and survival of the enteric neural crest-derived cells (ENCCs) that form the enteric nervous system (ENS). Hypomorphic RET alleles cause intestinal aganglionosis [Hirschsprung disease (HSCR)], in which delayed migration and successive nonapoptotic ENCC death are considered to be major contributory factors. The significance of ENCC death in intestinal aganglionosis, however, has remained unclear. We show that elevated expression of Bcl-xL inhibits ENCC death in both Ret-null and hypomorphic states. However, the rescued Ret-null mice showed ENS malfunction with reduced nitric oxide synthase expression in colonic neurons, revealing the requirement of RET for neuronal differentiation. In contrast, the inhibition of cell death allows morphologically and functionally normal ENS formation in Ret hypomorphic mice. These results indicate that ENCC death is a principal cause of intestinal aganglionosis in a Ret hypomorphic state, and suggest that the inhibition of cell death is a route to the prevention of HSCR.

Overexpression of Bcl-2 in vascular endothelium inhibits the microvascular lesions of diabetic retinopathy

Recent studies on the pathogenesis of diabetic retinopathy have focused on correcting adverse biochemical alterations, but there have been fewer efforts to enhance prosurvival pathways. Bcl-2 is the archetypal member of a group of antiapoptotic proteins. In this study, we investigated the ability of overexpressing Bcl-2 in vascular endothelium to protect against early stages of diabetic retinopathy. Transgenic mice overexpressing Bcl-2 regulated by the pre-proendothelin promoter were generated, resulting in increased endothelial Bcl-2. Diabetes was induced with streptozotocin, and mice were sacrificed at 2 months of study to measure superoxide generation, leukostasis, and immunohistochemistry, and at 7 months to assess retinal histopathology. Diabetes of 2 months duration caused a significant decrease in expression of Bcl-2 in retina, upregulation of Bax in whole retina and isolated retinal microvessels, and increased generation of retinal superoxide and leukostasis. Seven months of diabetes caused a significant increase in the number of degenerate (acellular) capillaries in diabetic animals. Furthermore, overexpression of Bcl-2 in the vascular endothelium inhibited the diabetes-induced degeneration of retinal capillaries and aberrant superoxide generation, but had no effect on Bax expression or leukostasis. Therefore, overexpression of Bcl-2 in endothelial cells inhibits the capillary degeneration that is characteristic of the early stages of diabetic retinopathy, and this effect seems likely to involve inhibition of oxidative stress.

Oxidative stress triggers neuronal caspase-independent death: endonuclease G involvement in programmed cell death-type III

To characterize neuronal death, primary cortical neurons (C57/Black 6 J mice) were exposed to hydrogen peroxide (H2O2) and staurosporine. Both caused cell shrinkage, nuclear condensation, DNA fragmentation and loss of plasma membrane integrity. Neither treatment induced caspase-7 activity, but caspase-3 was activated by staurosporine but not H2O2. Each treatment caused redistribution from mitochondria of both endonuclease G (Endo G) and cytochrome c. Neurons knocked down for Endo G expression using siRNA showed reduction in both nuclear condensation and DNA fragmentation after treatment with H2O2, but not staurosporine. Endo G suppression protected cells against H2O2-induced cell death, while staurosporine-induced death was merely delayed. We conclude that staurosporine induces apoptosis in these neurons, but severe oxidative stress leads to Endo G-dependent death, in the absence of caspase activation (programmed cell death-type III). Therefore, oxidative stress triggers in neurons a form of necrosis that is a systematic cellular response subject to molecular regulation.

The Bcl-2 family in autoimmune and degenerative disorders

Members of the Bcl-2 family are essential regulators of programmed cell death and thus play a major role in the development and function of many tissues. The balance between pro-survival and pro-apoptotic members of the family decides whether a cell will live or die. This mechanism allows organisms to get rid of cells that are no longer needed or have become dangerous. Deregulation of apoptosis is a major contributing factor in the development of many diseases. A deeper understanding of how the Bcl-2 family proteins orchestrate death in normal and pathologic conditions is thus relevant not only for disease etiology, but also to try to prevent these various disorders. Experiments with transgenic and gene-ablated mice have helped elucidate the function of the different members of the Bcl-2 family and their physiological roles. The present review highlights the role of Bcl-2 family members in autoimmune and degenerative disorders, with a particular focus on the mouse models that have been used to study their function.

Transgenic expression of human equilibrative nucleoside transporter 1 in mouse neurons

Transgenic mice that express human equilibrative nucleoside transporter subtype 1 (hENT1) under the control of a neuron-specific enolase promoter have been generated. Southern blot and PCR revealed the presence of the transgene in five founder mice. Mice from each founder line were examined by reverse transcriptase (RT)-PCR and found to express hENT1 in RNA isolated from whole brain, cerebral cortex, striatum, hippocampus, and cerebellum but not liver, kidney, heart, lung or skeletal muscle. Cortical synaptosomes prepared from transgenic mice had significantly increased [(3)H]adenosine uptake and [(3)H]nitrobenzylthioinosine binding, relative to samples from wild-type mice. In behavioral tests, transgenic mice had altered responses to caffeine and ethanol, two drugs that inhibit and enhance, respectively, adenosine receptor activity. Caffeine-induced locomotor stimulation was attenuated whereas the hypnotic effect of ethanol was enhanced in transgenic mice. Caffeine was more potent in inhibiting ethanol-induced motor incoordination in wild-type than in transgenic mice. No differences in expression of mouse genes for adenosine receptors, nucleoside transporters, or purine metabolizing enzymes were detected by RT-PCR analyses. These data indicate that expression of hENT1 in neurons does not trigger adaptive changes in expression of adenosine-related genes. Instead, hENT1 expression affects dynamic changes in endogenous adenosine levels, as revealed by altered behavioral responses to drugs that affect adenosine receptor signalling.

Genetic modulation of apoptotic pathways fails to alter disease course in tripeptidyl-peptidase 1 deficient mice

Late-infantile neuronal ceroid lipofuscinosis (LINCL) is a fatal, incurable neurodegenerative disease of children caused by the loss of the lysosomal protein tripeptidyl-peptidase 1 (TPP1). Previous studies have suggested that Bcl-2-dependent apoptotic pathways are involved in neuronal cell death in LINCL patients and, as a result, anti-apoptotic treatments that increase Bcl-2 activity have been proposed as a potential therapeutic approach. In this study, we have directly investigated whether targeting anti-apoptotic pathways may be of value in LINCL in a mouse model of this disease that lacks TPP1 and which recapitulates many aspect of the human disease, including a greatly shortened life-span. Our approach was to genetically modify apoptotic pathways and determine the effects of these changes on the severe neurodegenerative phenotype of the LINCL mouse. LINCL mice were generated that either lacked the pro-apoptotic p53 or had increased levels of anti-apoptotic Bcl-2, changes that would exacerbate or ameliorate neuronal death, respectively, should pathways involving these proteins be important. Neither modification affected the shortened life-span of the LINCL mouse. These results suggest that either neuronal death in LINCL does not occur via apoptosis or that it occurs via apoptotic pathways not involving p53 or Bcl-2. Alternatively, pathways involving p53 and/or Bcl-2 may be involved in neuronal death under normal circumstances but may not be the only routes to this end. Importantly, our findings suggest that targeting pathways of cell death involving p53 or Bcl-2 do not represent useful directions for developing effective treatment.

Sexual differentiation of vasopressin innervation of the brain: cell death versus phenotypic differentiation

In most vertebrates studied, males have more vasopressin (VP) cells in the bed nucleus of the stria terminalis, or homologous vasotocin cells in nonmammalian species, than females. Previous research excluded differential cell birth and migration as likely mechanisms underlying this difference, leaving just differential cell death and phenotypic differentiation of existing cells. To differentiate between these remaining possibilities, we compared VP cell number in wild-type mice vs. mice overexpressing the anti-cell death factor, Bcl-2. All animals were gonadectomized in adulthood and given testosterone capsules. Three weeks later, brains were processed for in situ hybridization to identify VP cells. Bcl-2 overexpression increased VP cell number in both sexes but did not reduce the sex difference. We repeated this experiment in mice with a null mutation of the pro-cell death gene, Bax, and obtained similar results; cell number was increased in Bax(-/-) mice of both sexes, but males had about 40% more VP cells, regardless of Bax gene status. Taken together, cell death is unlikely to account for the sex difference in VP cell number, leaving differentiation of cell phenotype as the most likely underlying mechanism. We also used immunocytochemistry to examine VP projections in Bcl-2-overexpressing mice. As expected, males showed denser VP-immunoreactive fibers than females in the lateral septum, a projection area of the bed nucleus of the stria terminalis. However, even though Bcl-2 overexpression increased VP cell number, it did not affect fiber density. Thus, a compensatory mechanism may control total septal innervation regardless of the number of contributing cells.

Effect of hypoxia on expression of apoptotic proteins in nuclear, mitochondrial and cytosolic fractions of the cerebral cortex of newborn piglets: the role of nuclear Ca++ -influx

We have shown that hypoxia results in increased influx of nuclear Ca++ and increased expression of nuclear apoptotic proteins. The present study tests the hypothesis that hypoxia alters the distribution of pro-apoptotic proteins Bad and Bax, and the anti-apoptotic proteins Bcl-xl, and Bcl-2 in the nuclear, mitochondrial and cytosolic compartments of the cerebral cortex of newborn piglets and the administration of Clonidine, an inhibitor of high affinity nuclear Ca++ -ATPase, will prevent the hypoxia-induced increase in apoptotic proteins' expression. Studies were conducted in 19 newborn piglets, 6 normoxic (Nx), 7 hypoxic and 6 Clonidine-treated hypoxic (Hx-Clo). Tissue hypoxia was documented biochemically by measuring cerebral tissue ATP and phosphocreatine (PCr) levels. Bax and Bad protein expression increased in all the three compartments during hypoxia, while there was no significant change in the expression of anti-apoptotic proteins Bcl-2 and Bcl-xl. In Clonidine pretreated hypoxic group, the hypoxia-induced increased expression of pro-apoptotic proteins Bad and Bax was prevented in all the three fractions. We conclude that hypoxia results in increased expression of pro-apoptotic proteins in nuclear, mitochondrial and cytosolic compartments and that the increased expression of pro-apoptotic proteins during hypoxia is nuclear Ca++ -influx-dependent. We propose that during hypoxia the increased ratio of (pro-apoptotic Bad and Bax/anti-apoptotic Bcl-xl and Bcl-2) in all the three compartments, will lead to altered mitochondrial and nuclear membrane permeability as well as caspase-9 activation in the cytosolic compartment.

Pathological apoptosis in the developing brain

More than half of the initially-formed neurons are deleted in certain brain regions during normal development. This process, whereby cells are discretely removed without interfering with the further development of remaining cells, is called programmed cell death (PCD). The term apoptosis is used to describe certain morphological manifestations of PCD. Many of the effectors of this developmental cell death program are highly expressed in the developing brain, making it more susceptible to accidental activation of the death machinery, e.g. following hypoxia-ischemia or irradiation. Recent evidence suggests, however, that activation and regulation of cell death mechanisms under pathological conditions do not exactly mirror physiological, developmentally regulated PCD. It may be argued that the conditions after e.g. ischemia are not even compatible with the execution of PCD as we know it. Under pathological conditions cells are exposed to various stressors, including energy failure, oxidative stress and unbalanced ion fluxes. This results in parallel triggering and potential overshooting of several different cell death pathways, which then interact with one another and result in complex patterns of biochemical manifestations and cellular morphological features. These types of cell death are here called "pathological apoptosis," where classical hallmarks of PCD, like pyknosis, nuclear condensation and caspase-3 activation, are combined with non-PCD features of cell death. Here we review our current knowledge of the mechanisms involved, with special focus on the potential for therapeutic intervention tailored to the needs of the developing brain.

Exacerbation of apoptosis of cortical neurons following traumatic brain injury in par-4 transgenic mice

Traumatic brain injury (TBI) is a significant clinical problem, yet few effective strategies for treating it have emerged. People that sustain and survive a TBI are left with significant cognitive, behavioral, and communicative disabilities. Apoptotic neuronal death occurs following TBI. Prostate apoptosis response-4 (Par-4) is a death domain-containing protein initially characterized as a critical regulator of apoptosis in prostate cancer cells. We have recently generated and characterized Par-4 transgenic mice in which the expression of the par-4 transgene was limited to cells of neuronal lineage. We now provide evidence that, in cortical neurons from these mice, Par-4 drastically increases apoptotic neuronal death in both in vitro and in vivo models of TBI. In vitro experiments were performed in 7-day-old primary cultures of cortical neurons using a previously published, scratch-induced mechanical trauma model. Neurons that overexpress Par-4 showed not only a significant decrease in overall neuron survival after TBI compared to wild-type cells, but also exhibited a sharper decrease in mitochondrial transmembrane potential, a higher degree of free radical accumulation, and earlier activation of caspase-3 than wild-type cells did. In vivo experiments were performed utilizing a weight drop TBI model. A significantly increased volume of cortical injury and exacerbated activation of caspase-3 were observed in Par-4 transgenic mice when compared to those in wild-type mice. These data suggests that aberrant Par-4 expression exacerbates neuronal cell death following TBI by altering mitochondrial function, enhancing oxidative damage, and execution of apoptosis via caspase activation.

WITHDRAWN: Bcl-2 Upregulation is Significantly Enhanced in the Hippocampus of Normal Aging Mice After an Acute Challenge Elicited by Pro-inflammatory Cytokines Circulating in the Cerebrospinal Fluid

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Differential expression of apoptotic proteins following hypoxia-induced CREB phosphorylation in the cerebral cortex of newborn piglets

The present study investigates the correlation between the hypoxia-induced phosphorylation of cyclic AMP response element binding protein and the expression of apoptotic proteins (proapoptotic proteins Bax and Bad and antiapoptotic proteins Bcl-2 and Bcl-xl) during hypoxia in the cerebral cortex of newborn piglets. Piglets were divided into normoxic (Nx) and hypoxic (Hx, FiO(2)=0.06 for 1 h) groups. Cerebral tissue hypoxia was documented by ATP and phosphocreatine (PCr) levels. Ser(133) phosphorylation of cyclic AMP response element binding (CREB) protein was determined by Western blot analysis using a specific anti-phosphorylated Ser(133)-CREB protein antibody. The expression of apoptotic proteins was determined by using specific anti-Bax, anti-Bad, anti-Bcl-2 and anti-Bcl-xl antibodies. ATP and PCr values (mumoles/g brain) in Hx were significantly different from Nx (ATP: 4.40 +/- 0.39 in Nx vs. 1.19 +/- 0.44 in Hx, P<0.05 vs. Nx; PCr: 3.60 +/- 0.40 in Nx vs. 0.70 +/- 0.31 in Hx, P<0.05 vs. Nx). Ser(133) phosphorylated CREB protein (OD x mm(2)) was 74.55 +/- 4.75 in Nx and 127.13 +/- 19.36 in Hx (P<0.05 vs. Nx). The expression of proapoptotic proteins Bax and Bad increased and strongly correlated with the increase in CREB protein phosphorylation (correlation coefficient r=0.82 and r=0.85, respectively). The expression of antiapoptotic proteins Bcl-2 and Bcl-xl did not show correlation with CREB protein phosphorylation. We conclude that cerebral hypoxia results in differential regulation of CREB protein-mediated expression of proapoptotic and antiapoptotic proteins in the cerebral cortex of newborn piglets. We propose that the increased expression of proapoptotic vs antiapoptotic genes will lead to an increased potential for apoptotic programmed cell death in the Hx newborn brain.

Transplantation of human neural stem cells exerts neuroprotection in a rat model of Parkinson's disease

Neural stem cells (NSCs) possess high potencies of self-renewal and neuronal differentiation. We explored here whether transplantation of human NSCs cloned by v-myc gene transfer, HB1.F3 cells, is a feasible therapeutic option for Parkinson's disease. In vivo, green fluorescent protein-labeled HB1.F3 cells (200,000 viable cells in 3 microl of PBS) when stereotaxically transplanted (same-day lesion-transplant paradigm) into the 6-hydroxydopamine-lesioned striatum of rats significantly ameliorated parkinsonian behavioral symptoms compared with controls (vehicle, single bolus, or continuous minipump infusion of trophic factor, or killed cell grafts). Such graft-derived functional effects were accompanied by preservation of tyrosine hydroxylase (TH) immunoreactivity along the nigrostriatal pathway. Grafted HB1.F3 cells survived in the lesioned brain with some labeled with neuronal marker mitogen-activated protein 2 and decorated with synaptophysin-positive terminals. Furthermore, endogenous neurogenesis was activated in the subventricular zone of transplanted rats. To further explore the neuroprotective mechanisms underlying HB1.F3 cell transplantation, we performed cell culture studies and found that a modest number of HB1.F3 cells were TH and dopamine and cAMP-regulated phosphoprotein 32 positive, although most cells were nestin positive, suggesting a mixed population of mature and immature cells. Administration of the HB1.F3 supernatant to human derived dopaminergic SH-SY5Y cells and fetal rat ventral mesencephalic dopaminergic neurons protected against 6-hydroxydopamine neurotoxicity by suppressing apoptosis through Bcl-2 upregulation, which was blocked by anti-stem cell factor antibody alone, the phosphatidylinositol 3-kinase/Akt inhibitor LY294002 [2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one] alone, or a combination of both. These results suggest that HB1.F3 cell transplantation exerts neuroprotective effects against dopaminergic depletion in vitro and in vivo because of trophic factor secretion and neuronal differentiation.

Cooperative effects ofbcl-2and AAV-mediated expression of CNTF on retinal ganglion cell survival and axonal regeneration in adult transgenic mice

We used a gene therapy approach in transgenic mice to assess the cooperative effects of combining anti-apoptotic and growth-promoting stimuli on adult retinal ganglion cell (RGC) survival and axonal regeneration following intraorbital optic nerve injury. Bi-cistronic adeno-associated viral vectors encoding a secretable form of ciliary neurotrophic factor and green fluorescent protein (AAV-CNTF-GFP) were injected into eyes of mice that had been engineered to over-express the anti-apoptotic protein bcl-2. For comparison this vector was also injected into wildtype (wt) mice, and both mouse strains were injected with control AAV encoding GFP. Five weeks after optic nerve injury we confirmed that bcl-2 over-expression by itself promoted the survival of axotomized RGCs, but in contrast to previous reports we also saw regeneration of some mature RGC axons beyond the optic nerve crush. AAV-mediated expression of CNTF in adult retinas significantly increased the survival and axonal regeneration of RGCs following axotomy in wt and bcl-2 transgenic mice; however, the effects were greatest in the transgenic strain. Compared with AAV-GFP-injected bcl-2 mice, RGC viability was increased by about 50% (mean, 36 738 RGCs per retina), and over 1000 axons per optic nerve regenerated 1-1.5 mm beyond the crush. These findings exemplify the importance of using a multifactorial therapeutic approach that enhances both neuroprotection and regeneration after central nervous system injury.

Gene therapy and transplantation in CNS repair: The visual system

Normal visual function in humans is compromised by a range of inherited and acquired degenerative conditions, many of which affect photoreceptors and/or retinal pigment epithelium. As a consequence the majority of experimental gene- and cell-based therapies are aimed at rescuing or replacing these cells. We provide a brief overview of these studies, but the major focus of this review is on the inner retina, in particular how gene therapy and transplantation can improve the viability and regenerative capacity of retinal ganglion cells (RGCs). Such studies are relevant to the development of new treatments for ocular conditions that cause RGC loss or dysfunction, for example glaucoma, diabetes, ischaemia, and various inflammatory and neurodegenerative diseases. However, RGCs and associated central visual pathways also serve as an excellent experimental model of the adult central nervous system (CNS) in which it is possible to study the molecular and cellular mechanisms associated with neuroprotection and axonal regeneration after neurotrauma. In this review we present the current state of knowledge pertaining to RGC responses to injury, neurotrophic and gene therapy strategies aimed at promoting RGC survival, and how best to promote the regeneration of RGC axons after optic nerve or optic tract injury. We also describe transplantation methods being used in attempts to replace lost RGCs or encourage the regrowth of RGC axons back into visual centres in the brain via peripheral nerve bridges. Cooperative approaches including novel combinations of transplantation, gene therapy and pharmacotherapy are discussed. Finally, we consider a number of caveats and future directions, such as problems associated with compensatory sprouting and the reformation of visuotopic maps, the need to develop efficient, regulatable viral vectors, and the need to develop different but sequential strategies that target the cell body and/or the growth cone at appropriate times during the repair process.

Bcl-2 over-expression fails to prevent age-related loss of calretinin positive neurons in the mouse dentate gyrus

BACKGROUND

Cognitive performance declines with increasing age. Possible cellular mechanisms underlying this age-related functional decline remain incompletely understood. Early studies attributed this functional decline to age-related neuronal loss. Subsequent studies using unbiased stereological techniques found little or no neuronal loss during aging. However, studies using specific cellular markers found age-related loss of specific neuronal types. To test whether there is age-related loss of specific neuronal populations in the hippocampus, and subsequently, whether over-expression of the B-cell lymphoma protein-2 (Bcl-2) in these neurons could delay possible age-related neuronal loss, we examined calretinin (CR) positive neurons in the mouse dentate gyrus during aging.

RESULT

In normal mice, there was an age-related loss of CR positive cells in the dentate gyrus. At the same region, there was no significant decrease of total numbers of neurons, which suggested that age-related loss of CR positive cells was due to the decrease of CR expression in these cells instead of cell death. In the transgenic mouse line over-expressing Bcl-2 in neurons, there was an age-related loss of CR positive cells. Interestingly, there was also an age-related neuronal loss in this transgenic mouse line.

CONCLUSION

These data suggest an age-related loss of CR positive neurons but not total neuronal loss in normal mice and this age-related neuronal change is not prevented by Bcl-2 over-expression.

Protective effect against 17beta-estradiol on neuronal apoptosis in hippocampus tissue following transient ischemia/recirculation in mongolian gerbils via down-regulation of tissue transglutaminase activity

We analyzed the protective effect of 17beta-estradiol (17beta-ED) injection against delayed neuronal death in the hippocampus tissue of the brain in Mongolian gerbils after transient ischemia/recirculation treatment, especially in relation with bcl-2 gene expression and enzymatic activity changes of caspase-3 and tissue transglutaminase (tTGase). Daily intraperitoneal injection of 17beta-ED to the animal after the ischemia stimulated the expression of an apoptosis suppressor gene, bcl-2, in the hippocampal tissue for a week. The gradually increasing apoptotic enzyme activity of caspase-3 and increased number of TUNEL positive fragmented neuronal nuclei caused by ischemic attack in the gerbil brain were clearly suppressed by 17beta-ED administration. The reduced activity and enzyme protein of tTGase, a neurodegenerative marker of apoptosis in the hippocampus after ischemia, were also restored to nearly normal levels by 17beta-ED injection. These results suggest that daily 17beta-ED administration to the gerbil after transient ischemic insult with progressing neuronal deteriorative changes in hippocampus tissue can effectively prevent apoptotic changes through a molecular cascade involving gene expression regulation.

ADAPTIVE ROLES OF PROGRAMMED CELL DEATH DURING NERVOUS SYSTEM DEVELOPMENT

The programmed cell death (PCD) of developing cells is considered an essential adaptive process that evolved to serve diverse roles. We review the putative adaptive functions of PCD in the animal kingdom with a major focus on PCD in the developing nervous system. Considerable evidence is consistent with the role of PCD in events ranging from neurulation and synaptogenesis to the elimination of adult-generated CNS cells. The remarkable recent progress in our understanding of the genetic regulation of PCD has made it possible to perturb (inhibit) PCD and determine the possible repercussions for nervous system development and function. Although still in their infancy, these studies have so far revealed few striking behavioral or functional phenotypes.

Transgenic mice that overexpress the anti-apoptotic Bcl-2 protein have improved histological outcome but unchanged behavioral outcome after traumatic brain injury

Increasing evidence suggests that apoptosis is a contributing factor to neuronal cell death in traumatic brain injury (TBI). There is increased expression, cleavage and activation of caspases as well as other proteins known to regulate apoptosis in neurons after TBI. These proteins include the proto-oncogene Bcl-2 which belongs to a family of proteins with both pro- and anti-apoptotic properties. To investigate the role of apoptosis in TBI and the importance of Bcl-2 protein on the severity and outcome of injury, Bcl-2 overexpressing transgenic and wild-type control mice were subjected to the controlled cortical impact model of TBI. There was no significant difference in the cleavage of caspase-3 or caspase-9 detected by Western blotting of hippocampal samples from transgenic or wild-type mice after TBI. Bcl-2 transgenic mice had smaller contusion volumes and increased numbers of surviving neurons in CA2 but not other regions of hippocampus compared to wild-type controls. By contrast, there was no difference in motor function determined by the round beam balance and wire grip tests between transgenic and wild-type mice after TBI. Cognitive function assessed by the Morris water maze was also not different between groups. These results suggest that overexpression of Bcl-2 is only partially neuroprotective and other members of this protein family may prove to be more important in protecting neurons from cell death.

Effect of nitric oxide synthase inhibition during post-hypoxic reoxygenation on Bax and Bcl-2 protein expression and DNA fragmentation in neuronal nuclei of newborn piglets

Previous studies have shown that cerebral tissue hypoxia results in increased generation of oxygen-free radicals including nitric oxide (NO), expression of the proapoptotic protein Bax and fragmentation of nuclear DNA. The present study tests the hypothesis that post-hypoxic reoxygenation for 6 h following hypoxia (FiO2=0.06 for 1 h) results in continued hypoxia-induced, NO-mediated expression of the Bax protein and nuclear DNA fragmentation in the cerebral cortex of newborn piglets. Piglets were divided into normoxic (Nx), hypoxic (Hx, FiO2=0.06 for 1 h), hypoxic with 6 h reoxygenation (Hx+reox) and hypoxic with 6 h reoxygenation injected with 7-nitroindazole sodium salt (7-NINA), a selective nNOS inhibitor, immediately after hypoxia (Hx+7-NINA). Cerebral tissue hypoxia was documented by levels of ATP and phosphocreatine (PCr). Bax and Bcl-2 were analyzed by Western blot and DNA fragmentation was determined by agarose gel electrophoresis. ATP and PCr values in Hx, Hx+reox and Hx+7-NINA were significantly different from Nx (P<0.05 vs. Nx). Bax protein (ODxmm2) was 128.9+/-38.7 in Nx; 223.6+/-45.8 in Hx (P<0.05 vs. Nx); 340.5+/-73.2 in Hx+reox (P<0.05 vs. Nx, Hx and Hx+7-NINA); and 202.2+/-34.8 in Hx+7-NINA (P=NS vs. Hx). Bcl-2 protein (ODxmm2) was 14.9+/-2.7 in Nx, 12.4+/-2.1 in Hx, (P<0.05 vs. Nx), 15.7+/-3.8 in Hx+reox, (P<0.05 vs. Hx) and 13.1+/-2.2 in Hx+7-NINA (P=NS among groups). Nuclear DNA fragmentation (ODxmm2) was 147+/-15 in Nx; 797+/-84 in Hx (P<0.05 vs. Nx); 1134+/-127 in Hx+reox (P<0.05 vs. Nx, Hx and Hx+7-NINA); and 778+/-146 in Hx+7-NINA (P=NS vs. Hx, P<0.05 vs. Hx+reox). The results show that post-hypoxic reoxygenation results in increased expression of Bax protein without affecting Bcl-2 protein and increased fragmentation of nuclear DNA, which are prevented by 7-NINA. We conclude that during post-hypoxic reoxygenation the increase in Bax protein expression and fragmentation of nuclear DNA are mediated by NO derived from nNOS. We propose that in addition to NO-mediated nuclear DNA damage, the hypoxia-induced increased ratio of Bax/Bcl-2 protein will lead to caspase-activated cascade of hypoxic neuronal death during post-hypoxic reoxygenation.

Hypoxia-induced Bax and Bcl-2 protein expression, caspase-9 activation, DNA fragmentation, and lipid peroxidation in mitochondria of the cerebral cortex of newborn piglets: the role of nitric oxide

The present study tests the hypothesis that cerebral hypoxia results in increased ratio of Bax/Bcl-2, activation of caspase-9, lipid peroxidation, and DNA fragmentation in mitochondria of the cerebral cortex of newborn piglets and that the inhibition of nitric oxide synthase by N-nitro-L-arginine during hypoxia will prevent the events leading to mitochondrial DNA fragmentation. To test this hypothesis, six piglets, 3-5 days old, were divided into three groups: normoxic (n=5), hypoxic (n=5), and hypoxic-nitric oxide synthase (n=4). Hypoxic animals were exposed to a FiO2 of 0.6 for 60 min. Nitric oxide synthase (40 mg/kg) was infused over 60 min prior to hypoxia. Tissue hypoxia was confirmed by measuring levels of ATP and phosphocreatine. Cerebral cortical tissue mitochondria were isolated and purified using a discontinuous ficoll gradient. Mitochondrial Bax and Bcl-2 proteins were determined by Western blot. Caspase-9 activity in mitochondria was determined spectro-fluorometrically using fluorogenic substrate for caspase-9. Fluorescent compounds, an index of mitochondrial membrane lipid peroxidation, were determined spectrofluorometrically. Mitochondrial DNA was isolated and separated by electrophoresis on 1% agarose gel and stained with ethidium bromide. ATP levels (micromol/g brain) were 4.52+/-0.34 in normoxic, 1.18+/-0.29 in hypoxic (P<0.05) and 1.00+/-0.26 in hypoxic-nitric oxide synthase animals (P<0.05 vs. normoxic). Phosphocreatine levels (micromol/g brain) were 3.61+/-0.33 in normoxic, 0.70+/-0.20 in hypoxic (P<0.05 vs. normoxic) and 0.57+/-0.14 in hypoxic-nitric oxide synthase animals (P<0.05 vs. normoxic, P=NS vs. hypoxic). Bax density in mitochondrial membranes was 160+/-28 in normoxic and 324+/-65 in hypoxic (P<0.001 vs. normoxic). Bcl-2 density mitochondria was 96+/-18 in normoxic and 98+/-20 in hypoxic (P=NS vs. normoxic). Mitochondrial caspase-9 activity (nmol/mg protein/h) was 1.32+/-0.23 in normoxic and 2.25+/-0.24 in hypoxic (P<0.01 vs. normoxic). Levels of fluorescent compounds (microg of quinine sulfate/g protein) were 12.48+/-4.13 in normoxic and 37.92+/-7.62 in hypoxic (P=0.003 vs. normoxic). Densities (ODxmm2) of low molecular weight DNA fragments were 143+/-38 in normoxic, 365+/-152 in hypoxic, (P<0.05 vs. normoxic) and 163+/-25 in hypoxic-nitric oxide synthase animals (P<0.05 vs. hypoxic, P=NS vs. normoxic). The data demonstrate that hypoxia results in increased mitochondrial proapoptotic protein Bax, increased mitochondrial caspase-9 activity, increased mitochondrial lipid peroxidation, and increased fragmentation of DNA in mitochondria of the cerebral cortex of newborn piglets. The administration of a nitric oxide synthase inhibitor, nitric oxide synthase, prior to hypoxia prevented fragmentation of mitochondrial DNA, indicating that the hypoxia-induced mitochondrial DNA fragmentation is NO-mediated. We propose that NO free radicals generated during hypoxia lead to NO-mediated altered expression of Bax leading to increased ratio of pro-apoptotic/anti-apoptotic protein resulting in modification of mitochondrial membrane, and subsequently Ca2+-influx and fragmentation of mitochondrial DNA.

Developmental expression of Bis protein in the cerebral cortex and hippocampus of rats

Bis (Bcl-2 interacting death suppressor), identified as a Bcl-2-binding protein, has been suggested to have diverse functions in addition to binding to Bcl-2, thereby regulating cell death. To investigate the potential role of Bis in the developing brain, the spatiotemporal expression of Bis protein was studied in the rat forebrain during prenatal and early postnatal development using immunohistochemistry. Initial expression of Bis was detected in the medial telencephalic wall of the lateral ventricle, the area most likely corresponded to the cortical hem from the earliest age examined (E13). There was an abrupt increase of immunoreactive neurons in the cortex and hippocampus during the first postnatal week, which declined thereafter. Two populations of Bis-immunoreactive neurons can be clearly distinguished in the developing forebrain: a population of differentiating and postmitotic neurons coexpressing Bis and microtubule-associated protein-2 (MAP-2), and a population of neurons with the characteristic morphology of Cajal-Retzius cells located exclusively in the marginal zone/layer I of the cortex and in the hippocampal equivalents of the marginal zone. The latter neurons were colabeled with reelin, a marker for Cajal-Retzius cells. While Bis expression in the cerebral cortex and hippocampus exists only transiently by P14, considerable expression was found to be maintained in the rostral migratory stream and the subventricular zone of the lateral ventricle, where Bis-immunoreactive cells were glutamine synthetase-positive glial cells. Our results suggest that Bis may contribute to the developmental processes, including the differentiation and maturation of specific neuronal populations in relation to Bcl-2 in the developing rat forebrain.

Deconvoluting the structural and drug-recognition complexity of the G-quadruplex-forming region upstream of the bcl-2 P1 promoter

The human bcl-2 gene contains a GC-rich region upstream of the P1 promoter that has been shown to be critically involved in the regulation of bcl-2 gene expression. We have demonstrated that the guanine-rich strand of the DNA in this region can form any one of three distinct intramolecular G-quadruplex structures. Mutation and deletion analysis permitted isolation and identification of three overlapping DNA sequences within this element that formed the three individual G-quadruplexes. Each of these was characterized using nondenaturing gel analysis, DMS footprinting, and circular dichroism. The central G-quadruplex, which is the most stable, forms a mixed parallel/antiparallel structure consisting of three tetrads connected by loops of one, seven, and three bases. Three different G-quadruplex-interactive agents were found to further stabilize these structures, with individual selectivity toward one or more of these G-quadruplexes. Collectively, these results suggest that the multiple G-quadruplexes identified in the promoter region of the bcl-2 gene are likely to play a similar role to the G-quadruplexes in the c-myc promoter in that their formation could serve to modulate gene transcription. Last, we demonstrate that the complexity of the G-quadruplexes in the bcl-2 promoter extends beyond the ability to form any one of three separate G-quadruplexes to each having the capacity to form either three or six different loop isomers. These results are discussed in relation to the biological significance of this G-quadruplex-forming element in modulation of bcl-2 gene expression and the inherent complexity of the system where different G-quadruplexes and loop isomers are possible.

Bcl-2 expression mediated by Cre/loxP system in olfactory epithelium

To study the Bcl-2 expression mediated by the Cre/loxP recombination system and its effect on prevention of apoptosis in olfactory epithelium. Adenoviral vectors with cassette for Bcl-2 (AxCALNLBcl-2) and Cre recombinase (AxCANCre) were applied to mouse olfactory epithelium by intranasal instillation. The effect of exogenous Bcl-2 expression on prevention of apoptosis of olfactory receptor neurons was investigated using an apoptosis model induced by bulbectomy. The Bcl-2 product was expressed not only in the olfactory receptor neurons but also in the supporting cells. Although statistical analysis did not show significant difference, the number of apoptotic cells in the infected olfactory epithelium on post-bulbectomy day 2 was lower than that of control and the number of survived mature olfactory receptor neurons in the infected olfactory epithelium on post-bulbectomy day 5 was higher than that of control. Although further studies are required for clinical application, the results of our study suggest that this strategy may be able to deliver exogenous Bcl-2 for the treatment of degeneration of olfactory receptor neurons.

Glucocorticoid modulatory element-binding protein 1 binds to initiator procaspases and inhibits ischemia-induced apoptosis and neuronal injury

Caspases are divided into two classes: initiator caspases, which include caspase-8 and -9 and possess long prodomains, and effector caspases, which include caspase-3 and -7 and possess short prodomains. Recently, we demonstrated that glucocorticoid modulatory element-binding protein 1 (GMEB1) interacts with the prodomain of procaspase-2, thereby disrupting its autoactivation and the induction of apoptosis. Here we show that GMEB1 is also capable of binding to procaspase-8 and -9. GMEB1 attenuated the Fas-mediated activation of these caspases and the subsequent apoptosis. The knockdown of endogenous GMEB1 using RNA interference revealed that cells with decreased GMEB1 expression are more sensitive to stress and undergo accelerated apoptosis. Transgenic mice expressing a neurospecific GMEB1 had smaller cerebral infarcts and less brain swelling than wild-type mice in response to transient focal ischemia. These results suggest that GMEB1 is an endogenous regulator that selectively binds to initiator procaspases and inhibits caspase-induced apoptosis.

LIM kinase 2 is widely expressed in all tissues

The LIM kinase family includes two proteins: LIMK1 and LIMK2. These proteins have identical genomic structure and overall amino acid identity of 50%. Both proteins regulate actin polymerization via phosphorylation and inactivation of the actin depolymerizing factors ADF/cofilin. Although the function of endogenous LIMK1 is well established, little is known about the function of the endogenous LIMK2 protein. To understand the specific role of endogenous LIMK2 protein, we examined its expression in embryonic and adult mice using a rat monoclonal antibody, which recognizes specifically the PDZ domain of LIMK2 but not that of LIMK1. Immunoblotting and immunoprecipitation analyses of mouse tissues and human and mouse cell lines revealed widespread expression of the 75-kDa LIMK2 protein. Immunofluorescence analysis demonstrated that the cellular localization of LIMK2 is different from that of LIMK1. LIMK2 protein is found in the cytoplasm localized to punctae and is not enriched within focal adhesions like LIMK1. Immunohistochemical studies revealed that LIMK2 is widely expressed in embryonic and adult mouse tissues and that its expression pattern is similar to that of LIMK1 except in the testes. We have also demonstrated that endogenous LIMK1 and LIMK2 form heterodimers, and that LIMK2 does not always interact with the same proteins as LIMK1.

Increased generation of granule cells in adult Bcl-2-overexpressing mice: a role for cell death during continued hippocampal neurogenesis

Programmed cell death is an important mechanism during brain development in order to control neuronal cell numbers and to correctly form neuronal circuitries. Programmed cell death is also present in neurogenic regions of the adult brain, and a significant portion of the adult-born cells is eliminated during the first months of maturation. We here address the question whether overexpression of the anti-apoptotic protein Bcl-2 would improve the survival of neural progenitor cells and, as a consequence, increase neurogenesis in the adult hippocampus. Transgenic animals, which express human Bcl-2 under the neuron-specific enolase promoter (NSE-huBcl-2), show a significant reduction of apoptotic cells in the hippocampal granule cell layer to about half of the wild-type level. These apoptotic cells are almost exclusively found in the zone of hippocampal progenitor activity and frequently co-label with the neuronal progenitor marker doublecortin (DCX). The rate of adult neurogenesis is doubled in the dentate gyrus of Bcl-2-overexpressing mice as demonstrated by quantification of progenitor cells using DCX and new neurons using bromodeoxyuridine (BrdU)/neuronal nuclei antigen (NeuN) double-labelling. The effect of Bcl-2 is limited to the late phase of progenitor maturation, as proliferation and early-phase progenitor cells were not affected. The increased level of neurogenesis leads to a significantly higher total number of granule cells in the dentate gyrus. These results underline the importance of developmental cell death during neurogenesis in the adult brain.