Expression pattern of candidate cell death effector proteins Bax, Bcl-2, Bcl-X, and c-Jun in sensory and motor neurons following sciatic nerve transection in the rat

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.

Cortical expression of IL1-β, Bcl-2, Caspase-3 and 9, SEMA-3a, NT-3 and P-glycoprotein as biological markers of intrinsic severity in drug-resistant temporal lobe epilepsy

Mesial temporal lobe epilepsy (mTLE) is the most common epilepsy induced by previous cerebral injury, and one out of three mTLE patients develops drug resistance (DR).

AIM

To assess the expression of Bcl-2, Caspase-3, Caspase-9, IL1-β, SEMA-3a, NT-3 and P-glycoprotein in the temporal cortex and their relationship with the progression of mTLE-DR clinical features in patients with mTLE-DR.

METHOD

Tissue samples from 17 patients were evaluated for protein expression by Western blot and the relationships of the evaluated proteins with the clinical features of the mTLE were assessed through hierarchical cluster analysis.

RESULTS

The mTLE-DR group showed significantly higher P-glycoprotein, Bcl-2 and Caspase-9 levels ***p < 0.0001, ****p < 0.0001 and ***p < 0.0002, respectively, than the autopsy control group. Four patient clusters were identified: Clusters 1 and 3 showed relationships among the age of mTLE onset, duration of mTLE-DR, average number of epileptic seizures per week, number of previous antiepileptic drugs (AEDs) and increased expression of Caspase-3, Caspase-9, Neurotrophin-3 and Semaphorin-3a. Clusters 2 and 4 showed relationships among the mTLE onset age, current age, average number of epileptic seizures per week, number of previous AEDs and increased expression of IL1-β, Bcl-2, P-glycoprotein, Caspase-3 and NT-3.

CONCLUSION

The relationships among the clinical data the age of mTLE onset, DR duration, number of previous AEDs, and average number of seizures per week and the expression of proteins involved in neuronal death, neuroinflammation and aberrant connection formation, as which are biological markers in the cerebral temporal cortex, are important factors in the progression and severity of mTLE-DR and support the intrinsic severity hypothesis.

Motor neuron loss in SMA is not associated with somal stress-activated JNK/c-Jun signaling

A pathological hallmark of spinal muscular atrophy (SMA) is severe motor neuron (MN) loss, which results in muscle weakness and often infantile or childhood mortality. Although it is well established that deficient expression of survival motor neuron (SMN) protein causes SMA, the molecular pathways that execute MN cell death are poorly defined. The c-Jun NH2-terminal kinases (JNKs) are stress-activated kinases with multiple substrates including c-Jun, which can be activated during neuronal injury and neurodegenerative disease leading to neuronal apoptosis. Recently, increased JNK-c-Jun signaling was reported in SMA raising the possibility that JNK inhibitors could be a novel treatment for this disease. We examined JNK-c-Jun activity in SMA mouse and human cultured cells and tissues. Anisomycin treatment of human SMA fibroblasts and sciatic nerve ligation in SMA mice provoked robust phosphorylated-c-Jun (p-c-Jun) expression indicating that SMN-deficiency does not prevent activation of the stress-induced JNK-c-Jun signaling pathway. Despite retained capacity to activate JNK-c-Jun, we observed no basal increase of p-c-Jun levels in SMA compared to control cultured cells, human or mouse spinal cord tissues, or mouse MNs during the period of MN loss in severe SMA model mice. In both controls and SMA, ~50% of α-MN nuclei express p-c-Jun with decreasing expression during the early postnatal period. Together these studies reveal no evidence of stress-activated JNK-c-Jun signaling in MNs of SMA mice or human tissues, but do highlight the important role of JNK-c-Jun activity during normal MN development raising caution about JNK antagonism in this pediatric neuromuscular disease.

Gene expression changes in dorsal root ganglia following peripheral nerve injury: roles in inflammation, cell death and nociception

Subsequent to a peripheral nerve injury, there are changes in gene expression within the dorsal root ganglia in response to the damage. This review selects factors which are well-known to be vital for inflammation, cell death and nociception, and highlights how alterations in their gene expression within the dorsal root ganglia can affect functional recovery. The majority of studies used polymerase chain reaction within animal models to analyse the dynamic changes following peripheral nerve injuries. This review aims to highlight the factors at the gene expression level that impede functional recovery and are hence are potential targets for therapeutic approaches. Where possible the experimental model, specific time-points and cellular location of expression levels are reported.

Selected gene profiles of stressed NSC-34 cells and rat spinal cord following peripheral nerve reconstruction and minocycline treatment

The present study was conducted to investigate the effects of minocycline on the expression of selected transcriptional and translational profiles in the rat spinal cord following sciatic nerve (SNR) transection and microsurgical coaptation. The mRNA and protein expression levels of B cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), caspase-3, major histocompatibility complex I (MHC I), tumor necrosis factor-α (TNF-α), activating transcription factor 3 (ATF3), vascular endothelial growth factor (VEGF), matrix metalloproteinase 9 (MMP9), and growth associated protein-43 (GAP-43) were monitored in the rat lumbar spinal cord following microsurgical reconstruction of the sciatic nerves and minocycline treatment. The present study used semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. As a PCR analysis of spinal cord tissue enabled the examination of the expression patterns of all cell types including glia, the motorneuron-like NSC-34 cell line was used to investigate expression level changes in motorneurons. As stressors, oxygen glucose deprivation (OGD) and lipopolysaccharide (LPS) treatment were performed. SNR did not induce significant degeneration of ventral horn motorneurons, whereas microglia activation and synaptic terminal retraction were detectable. All genes were constitutively expressed at the mRNA and protein levels in untreated spinal cord and control cells. SNR significantly increased the mRNA expression levels of all genes, albeit only temporarily. In all genes except MMP9 and GAP-43, the induction was seen ipsilaterally and contralaterally. The effects of minocycline were moderate. The expression levels of MMP9, TNF-α, MHC I, VEGF, and GAP-43 were reduced, whereas those of Bax and Bcl-2 were unaffected. OGD, but not LPS, was toxic for NSC-34 cells. No changes in the expression levels of Bax, caspase-3, MHC I or ATF3 were observed. These results indicated that motorneurons were not preferentially or solely responsible for SNR-mediated upregulation of these genes. MMP9, TNF-α, VEGF and Bcl-2 were stress-activated. These results suggest that a substantial participation of motorneurons in gene expression levels in vivo. Minocycline was also shown to have inhibitory effects. The nuclear factor-κB signalling pathway may be a possible target of minocycline.

Craniocerebral injury promotes the repair of peripheral nerve injury

The increase in neurotrophic factors after craniocerebral injury has been shown to promote fracture healing. Moreover, neurotrophic factors play a key role in the regeneration and repair of peripheral nerve. However, whether craniocerebral injury alters the repair of peripheral nerve injuries remains poorly understood. Rat injury models were established by transecting the left sciatic nerve and using a free-fall device to induce craniocerebral injury. Compared with sciatic nerve injury alone after 6–12 weeks, rats with combined sciatic and craniocerebral injuries showed decreased sciatic functional index, increased recovery of gastrocnemius muscle wet weight, recovery of sciatic nerve ganglia and corresponding spinal cord segment neuron morphologies, and increased numbers of horseradish peroxidase-labeled cells. These results indicate that craniocerebral injury promotes the repair of peripheral nerve injury.

The nerve injury and the dying neurons: diagnosis and prevention

Following distal nerve injury significant sensory neuronal cell death occurs in the dorsal root ganglia, while after a more proximal injury, such as brachial plexus injury, a sizeable proportion of spinal motoneurons also undergo cell death. This phenomenon has been undervalued for a long time, but it has a significant role in the lack of functional recuperation, as neuronal cells cannot divide and be replaced, hence the resulting nerve regeneration is usually suboptimal. It is now accepted that this cell death is due to apoptosis, as indicated by analysis of specific genes involved in the apoptotic signalling cascade. Immediate nerve repair, either by direct suturing or nerve grafting, gives a degree of neuroprotection, but this approach does not fully prevent neuronal cell death and importantly it is not always possible. Our work has shown that pharmacological intervention using either acetyl-L-carnitine (ALCAR) or N-acetyl-cysteine (NAC) give complete neuroprotection in different types of peripheral nerve injury. Both compounds are clinically safe and experimental work has defined the best dose, timing after injury and duration of administration. The efficacy of neuroprotection of ALCAR and NAC can be monitored non-invasively using MRI, as demonstrated experimentally and more recently by clinical studies of the volume of dorsal root ganglia. Translation to patients of this pharmacological intervention requires further work, but the available results indicate that this approach will help to secure a better functional outcome following peripheral nerve injury and repair.

New insights into the pathogenesis of spinal muscular atrophy

To clarify the pathomechanism of spinal muscular atrophy (SMA) with mutations in the gene for survival motor neuron (SMN) protein, postmortem neuropathological analyses were performed on spinal cords obtained at autopsy from 2 fetuses with SMA, 5 infants and a low teenager with SMA type 1, and a higher teenager with SMA type 2; the diagnosis of all of them was confirmed clinically and genetically. Histopathologically, it was noted that lower motor neurons (LMNs) in the SMA cases showed immature profiles characterized by fine Nissl bodies restricted to the periphery of small round somata with a few cell processes in the fetal period, and showed small-sized profiles in the postnatal period. LMNs began to reduce in size and number in the fetal period, ballooned neurons (BNs) appeared postnatally, and the remaining LMNs including BNs diminished with age. BNs were filled with phosphorylated neurofilament protein, and morphologically similar to but smaller than typical chromatolytic neurons as axonal reaction. The population of survived LMNs was relatively preserved in an SMA type 2 case, who lived to 17-year-old, as compared to SMA type 1 cases. Immunohistochemical analysis demonstrated expression of Bcl-2, Bax, activated caspase-3 and SMN in the LMNs prominent in the fetal cases. There was no significant difference in staining for these substances between the control and SMA cases. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay revealed no significant signal in the control and SMA cases. Given that downregulation of SMN leads to a failure in neurite outgrowth and neuromuscular contact of LMNs, the present results suggest the involvement of a fetal developmental maturation error as well as a postnatal retrograde dying-back degeneration of LMNs in SMN-mutated SMA.

The expression of corticotropin-releasing factor and its receptors in the spinal cord and dorsal root ganglion in a rat model of neuropathic pain

Corticotropin-releasing factor (CRF) is a peptide involved in the activation of the hypothalamic-pituitary-adrenal (HPA) axis. CRF is distributed not only along the HPA axis but also throughout pain-relevant anatomical sites. CRF elicits potent antinociception at the three main levels of pain transmissions: namely, the brain, spinal cord, and peripheral sensory neurons. The widespread distribution of CRF receptors 1 and 2 in the brain offers several targets wherein CRF could alter pain, some of which may be independent of the HPA axis. In this study, we assessed the expression of CRF and its receptors, CRF receptor type (CRFR)1 and CRFR2, in the spinal dorsal horn and dorsal root ganglion (DRG) in a rat model of neuropathic pain induced by spinal nerve injury (SNI). CRF was expressed in a few DRG neurons and primary afferent fibers in the dorsal horns of naїve rats, and the CRF-positive neurons in DRG and fibers in the spinal dorsal horn were found to have increased after SNI. CRFR1 was not expressed in DRG or the dorsal horn and CRFR2 was expressed weakly in the small neurons in DRG in the naїve rats. After SNI, CRFR1 was expressed in the activated microglia in the ipsilateral dorsal horn, and immunoreaction for CRFR2 was increased in the contralateral DRG following SNI. Consequently, it has been suggested that the increased expression of CRF and CRFR2 in DRG neurons and primary afferent fibers in dorsal horn, and CRFR1 in the activated microglia, may be involved in the mediation of stress responses as well as in microglial activation in the neuropathic pain state following SNI.

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.

Differences in c-jun and nNOS expression levels in motoneurons following different kinds of axonal injury in adult rats

In the peripheral nervous system (PNS), root avulsion causes motoneuron degeneration, but the majority of motoneurons can survive axotomy. In order to study the mechanism of motoneuron degeneration, we compared the expression patterns of c-jun and neuronal nitric oxide synthase (nNOS), the well-known molecular players in PNS regeneration and degeneration, among adult rats having undergone axotomy (Ax), avulsion (Av), or pre-axotomy plus secondary avulsion (Ax + Av) of the brachial plexus. Our results showed that the highest and longest-lasting c-jun activation occurred in Ax, which was much stronger than those in Av and Ax + Av. The time course and intensity of c-jun expression in Ax + Av were similar to those in Av except on day 1, while the pre-axotomy condition resulted in a transient up-regulation of c-jun to a level comparable to that in Ax. Axotomy alone did not induce nNOS expression in motoneurons. Pre-axotomy left-shifted the time course of nNOS induction in Ax + Av compared to that in Av. Motoneuron loss was not evident in Ax, while it was 70% in Av and more than 85% in Ax + Av at 8 weeks postinjury. The survival of motoneurons was positively correlated with c-jun induction, but not with nNOS expression in motoneurons. Moreover, c-jun induction was negatively correlated with nNOS induction in injured motoneurons. Our results indicate that functional crosstalk between c-jun and nNOS might play an important role in avulsion-induced motoneuron degeneration, while c-jun might act as a prerequisite survival factor and nNOS might act as a predictor for the onset of motoneuron degeneration.

Expression of apoptosis-related Bcl-2-family and P53 in human adenocarcinoma of the pancreas

AIM: To investigate the relationships between P53 and Bcl-2 family (Bcl-2, Bax, Bcl-xL, Bcl-xS) expression and apoptosis in human pancreatic carcinoma (PC).

METHODS: The immunohistochemical method was used to detect the expression of P53 protein in a total of 35 patients with PC. The patients were divided into two groups, group 1 with immunonegative P53 (18 cases) and group 2 with immunopositive (17 cases). The expressions of P53, Bcl-2, Bax, Bcl-xL, and Bcl-xS in both groups were detected by Western blot. The apoptosis index (AI) of group 1 was determined by terminal deoxynucleotidyltransferase-mediated UTP end-labeling (TUNEL).

RESULTS: Bcl-2 was remarkably up-regulated in group 2 but down-regulated in group 1 (P = 0.047). Expressions of both Bax and Bcl-xL proteins were up-regulated in those two groups (P = 0.274, 0.334). Bcl-xS was remarkably down-regulated in group 2 but up-regulated in group1 (P = 0.01). The AI of both groups were 12.1 ± 2.47 and 9.1 ± 1.48, respectively (P = 0.023), no correlations were found between AI and expression of Bcl-2 family members, but marked correlations were noted between AI and the Bcl-2/bax ratios (P < 0.01).

CONCLUSION: Bcl-2 family is a group of anti-apoptotic proteins, and Bcl-xS is a pro-apoptotic protein. Both of them are dependent on the regulation of P53 which modulates apoptosis mainly through modifying Bcl-2/Bax ratios.

Pilocarpine-induced status epilepticus in rats involves ischemic and excitotoxic mechanisms

The neuron loss characteristic of hippocampal sclerosis in temporal lobe epilepsy patients is thought to be the result of excitotoxic, rather than ischemic, injury. In this study, we assessed changes in vascular structure, gene expression, and the time course of neuronal degeneration in the cerebral cortex during the acute period after onset of pilocarpine-induced status epilepticus (SE). Immediately after 2 hr SE, the subgranular layers of somatosensory cortex exhibited a reduced vascular perfusion indicative of ischemia, whereas the immediately adjacent supragranular layers exhibited increased perfusion. Subgranular layers exhibited necrotic pathology, whereas the supergranular layers were characterized by a delayed (24 h after SE) degeneration apparently via programmed cell death. These results indicate that both excitotoxic and ischemic injuries occur during pilocarpine-induced SE. Both of these degenerative pathways, as well as the widespread and severe brain damage observed, should be considered when animal model-based data are compared to human pathology.

Bax and Bcl-2 expression and TUNEL labeling in lumbar enlargement of neonatal rats after sciatic axotomy and melatonin treatment

Peripheral axotomy in neonatal rats induces neuronal death. We studied the anti-apoptotic protein Bcl-2 and cell death promoter Bax in spinal cord of neonatal rats after sciatic transection and treatment with melatonin, a neuroprotective substance. Pups were unilaterally axotomized at P2 and received melatonin (1 mg/kg; sc) or vehicle 1 h prior to lesion, immediately after, at 1 h, 2 h and then once daily. Rats were sacrificed at 3 h, 6 h, 24 h, 72 h and 5 days postaxotomy. Intact animals were used as controls. Lumbar enlargement was processed for Nissl staining, immunohistochemistry and RT-PCR for Bax or Bcl-2 and TUNEL reaction. Motoneurons (MN) of lesioned (L) and normal (N) sides were counted, and MN survival ratio (MSR=L/N) was calculated. Bax and Bcl-2 showed cytoplasmic immunoreactivity (IR). Bax IR was noticeable in small cells but less evident in MN. In unlesioned pups, some Bax-positive small cells (B+) and TUNEL-positive nuclei (T+) were mainly seen in the dorsal horn. In lesioned animals given vehicle, Bax mRNA levels and numbers of B+ and T+ were increased in comparison with intact controls at 24 h postaxotomy. The basal IR for Bax in MN was not changed by axotomy. Bcl-2 IR was noted in all cells and, like Bcl-2 mRNA, was unaltered after lesion. Melatonin reduced MN loss at 24 h, 72 h and 5 days and T+ at 24 h after lesion but did not interfere with Bax or Bcl-2 expression. These results suggest that (1) sciatic transection at P2 increases Bax mRNA and the amount of B+ and T+ in the lumbar enlargement, (2) Bax IR in immature MN is not altered by axotomy and (3) melatonin protects MN and dorsal horn cells through a mechanism independent of Bax and Bcl-2.

Proapoptotic multidomain Bcl-2/Bax-family proteins: mechanisms, physiological roles, and therapeutic opportunities

Bcl-2-family proteins are central regulators of cell life and death. At least three major classes of Bcl-2-family proteins have been delineated, including proapoptotic proteins that contain several conserved regions of sequence similarity (termed 'multidomain'). In mammals, the multidomain proteins (MDPs) of the Bcl-2 family include Bax, Bak, and Bok. The founding member of the MDP group of Bcl-2-family proteins was discovered by Stanley Korsmeyer and co-workers, initiating an exciting area of cell death research. The status of current knowledge about the mechanisms and functions of MDPs is reviewed here, and some areas for future research are outlined. Therapeutic opportunities emerging from a growing understanding of MDPs with respect to their three-dimensional structures, biochemical actions, and roles in disease raise hopes that the foundation of basic research laid by Korsmeyer and others will eventually be translated into clinical benefits, leaving a legacy that benefits the world for many decades.

Motorneuron protection by N-acetyl-cysteine after ventral root avulsion and ventral rhizotomy

Motor recovery after proximal nerve injury remains extremely poor, despite advances in surgical care. Several neurobiological hurdles are implicated, the most fundamental being extensive cell death within the motorneuron pool. N-acetyl-cysteine almost completely protects sensory neurons after peripheral axotomy, hence its efficacy in protecting motorneurons after ventral root avulsion/rhizotomy was investigated. In adult rats, the motorneurons supplying medial gastrocnemius were unilaterally pre-labelled with retrograde tracer (true-blue/fluoro-gold), prior to L5 and 6 ventral root avulsion, or rhizotomy. Groups received either intraperitoneal N-acetyl-cysteine (ip, 150 or 750 mg/kg/day), immediate or delayed intrathecal N-acetyl-cysteine treatment (it, 2.4 mg/day), or saline; untreated animals served as controls. Either 4 (avulsion model) or 8 (rhizotomy model) weeks later, the pre-labelled motorneurons' mean soma area and survival were quantified. Untreated controls possessed markedly fewer motorneurons than normal due to cell death (avulsion 53% death; rhizotomy 26% death, P<0.01 vs. normal). Motorneurons were significantly protected by N-acetyl-cysteine after avulsion (ip 150 mg/kg/day 40% death; it 30% death, P<0.01 vs. no treatment), but particularly after rhizotomy (ip 150 mg/kg/day 17% death; ip 750 mg/kg/day 7% death; it 5% death, P<0.05 vs. no treatment). Delaying intrathecal treatment for 1 week after avulsion did not impair neuroprotection, but a 2-week delay was deleterious (42% death, P<0.05 vs. 1-week delay, 32% death). Treatment prevented the decrease in soma area usually found after both types of injury. N-acetyl-cysteine has considerable clinical potential for adjuvant treatment of major proximal nerve injuries, including brachial plexus injury, in order that motorneurons may survive until surgical repair facilitates regeneration.

Spinal cord injury-induced expression of TrkA, TrkB, phosphorylated CREB, and c-Jun in rat lumbosacral dorsal root ganglia

Previous studies have demonstrated increased expression and phosphorylation of tyrosine kinase receptor (TrkA, TrkB) in lumbosacral DRG after chronic (6 weeks) spinal cord (T8-T10) injury. This study examined the effects of acute SCI (48 hours, 2 weeks) on TrkA and TrkB expression and phosphorylation, and CREB and c-Jun expression in DRG. A significant increase in the number of TrkA- (1.5-3-fold; P < or = 0.05), TrkB- (1.3-2.0-fold; P < or = 0.05), and phosphorylated Trk (pTrk)-immunoreactive (1.5-3-fold; P < or = 0.05) cells was observed in the L1, L6, and S1 DRG 48 hours, 2, or 6 weeks after SCI. A significant increase in the number of phosphorylated (p-) CREB-immunoreactive cells was observed in the L1, L2, L6, and S1 DRG 48 hours, 2, or 6 weeks after SCI. The largest changes in p-CREB-immunoreactivity were in L1 and L2 DRG (10-fold; P <or= 0.01) at 48 hours after SCI; however, changes were modest in bladder afferent neurons. After SCI, the overall number of c-Jun-immunoreactive cells in L1, L2, and S1 DRG was dramatically increased (3-10-fold; P < or = 0.01); however, only a low percentage of bladder afferent cells expressed c-Jun-IR before or after SCI. In summary, these results suggest that TrkA or TrkB may be involved in reorganization of micturition pathways after SCI. However, CREB or c-Jun may not be downstream transcription factors in Trk-mediated signaling cascades in micturition reflex pathways after SCI but may play a role in other, nonbladder SCI-induced changes.

Anti-apoptotic action of (2S,3S,4R)-N"-cyano-N-(6-amino-3,4-dihydro-3-hydroxy-2-methyl-2-dimethoxymethyl-2H-benzopyran-4-yl)-N'-benzylguanidine (KR-31378) by suppression of the phosphatase and tensin homolog deleted from chromosome 10 phosphorylation and increased phosphorylation of casein kinase2/Akt/ cyclic AMP response element binding protein via maxi-K channel opening in neuronal cells

This study shows the signaling pathway by which (2S,3S,4R)-N"-cyano-N-(6-amino-3,4-dihydro-3-hydroxy-2-methyl-2-dimethoxymethyl-2H-benzopyran-4-yl)-N'-benzylguanidine (KR-31378) prevents tumor necrosis factor (TNF)-alpha-induced neuronal cell death. KR-31378 restored TNF-alpha-induced decreased cell viability of SK-N-SH. U87-MG cells (PTEN-null glioblastoma cell line) transfected with expression vectors for sense PTEN (phosphatase and tensin homolog deleted from chromosome 10) showed significantly decreased cell viability, which was restored by KR-31378. TNF-alpha-induced increased PTEN phosphorylation and decreased phosphorylation of Akt/cyclic AMP response element-binding protein (CREB) in SK-N-SH cells were concentration-dependently reversed by KR-31378, those of which were antagonized by iberiotoxin, a maxi-K channel blocker. TNF-alpha and apigenin, a casein kinase2 (CK2) inhibitor, showed decreased CK2 phosphorylation and increased PTEN phosphorylation, which were reversed by KR-31378. KR-31378 increased K(+) currents by activating the maxi-K channels in SK-N-SH cells, with suppression of TNF-alpha-induced increase in cytosolic Ca(2+) and elevation of suppressed mitochondrial membrane potential, all of which were antagonized by iberiotoxin. It is suggested that increase in cell viability by KR-31378 is ascribed to the maxi-K channel opening-coupled upregulation of CK2/Akt/CREB phosphorylation and downregulation of PTEN phosphorylation in association with increased Bcl-2 and decreased Bax levels.

Cell death or survival: Molecular and connectional conditions for olivocochlear neurons after axotomy

We aimed to determine whether rat olivocochlear neurons survive axotomy inflicted through cochlear ablation, or if they degenerate. To estimate their intrinsic potential for axonal regeneration, we investigated the expression of the transcription factor c-Jun and the growth-associated protein-43 (GAP43). Axonal tracing studies based on application of Fast Blue into the cochlea and calcitonin gene-related peptide immunostaining revealed that many, but not all, lateral olivocochlear neurons in the ipsilateral lateral superior olive degenerated upon cochleotomy. A decrease of their number was noticed 2 weeks after the lesion, and 2 months postoperative the population was reduced to approximately one quarter (27-29%) of its original size. No further reduction took place at longer survival times up to 1 year. Most or all shell neurons and medial olivocochlear neurons survived axotomy. Following cochleotomy, 56-60% of the lateral olivocochlear neurons in the ipsilateral lateral superior olive were found to co-express c-Jun and GAP43. Only a small number of shell and medial olivocochlear neurons up-regulated c-Jun expression, and only a small number of shell neurons expressed GAP43. Up-regulation of c-Jun and GAP43 in lateral olivocochlear neurons upon axotomy suggests that they have an intrinsic potential to regenerate after axotomy, but cell counts based on the markers Fast Blue and calcitonin gene-related peptide indicate that this potential cannot be exploited and degeneration is induced instead. The survival of one quarter of the axotomized lateral olivocochlear neurons and of all, or almost all, shell and medial olivocochlear neurons appeared to depend on connections of these cells to other regions than the cochlea by means of axon collaterals, which remained intact after cochleotomy.

Midkine expression in rat spinal motor neurons following sciatic nerve injury

Midkine (MK), a heparin-binding growth factor, is produced in the developing and damaged nervous system. However, the role of MK in peripheral nerve injury has not been clarified. Here, we investigated MK expression in lumbar spinal motor neurons after rat sciatic nerve injury by immunohistochemical, in situ hybridization, and Western blot analyses. The rat sciatic nerve showed complete degeneration after local freezing. Numerous regenerated myelinated and thin nerve fibers were observed 3 weeks after injury. Intense MK immunoreactivity was detected in the ipsilateral spinal motor neurons of the anterior horn of the lumbar spinal cord after 1 day and in ipsilateral and contralateral spinal motor neurons from 4 days to 1 week after injury. It decreased after 2 weeks and again transiently increased in spinal motor neurons after 3 weeks. MK was found in the motor neurons and axon of the sciatic nerve. However, it was not detected in normal neurons and axon. In situ hybridization showed the expression of MK mRNA in lumbar spinal motor neurons of the anterior horn, but it was not present in Schwann cells or non-neuronal cells. Low-density lipoprotein receptor-related protein (LRP) immunoreactivity, a cell membrane receptor of MK, was observed in anterior horn motor neurons, but receptor-type protein tyrosine phosphatase zeta (PTPzeta) immunoreactivity as a signaling receptor complex of MK was not observed. LRP and PTPzeta immunoreactivities were observed in Schwann cells of the injured and uninjured sciatic nerve. Our findings suggest that MK is synthesized, released, and taken up in anterior horn motor neurons in an autocrine fashion with LRP. MK may have a role in degeneration and regeneration after peripheral nerve injury.

Motoneuron resistance to apoptotic cell death in vivo correlates with the ratio between X-linked inhibitor of apoptosis proteins (XIAPs) and its inhibitor, XIAP-associated factor 1

Apoptotic cell death occurs in motoneurons in the neonate but not in the adult after a lesion of a peripheral nerve. To investigate the molecular basis for this difference, we have analyzed the expression and localization of inhibitors of apoptosis proteins (IAPs) and their inhibitors X-linked IAP (XIAP)-associated factor 1 (XAF1), Smac/DIABLO, and Omi/HtrA2 in motoneurons at both ages. Quantitative immunohistochemical and immunoblotting analysis of these proteins in motoneurons revealed an increase in IAP expression [XIAP, neuronal apoptosis inhibitory protein, human IAP1 (HIAP1), and HIAP2] during postnatal development as opposed to XAF1, which decreased during the same period; there was no significant alteration in either Smac/DIABO or Omi/HtrA2. The regulation of IAPs and XAF1 varied after axotomy of the sciatic nerve; in the neonate, there was a significant loss of IAP in the injured motoneurons as opposed to the adult, in which there was only a moderate decrease. By overexpressing exogenous IAPs in neonatal axotomized motoneurons, it was possible to delay motoneuron cell death (Perrelet et al., 2000, 2002). In opposition, the overexpression of exogenous XAF1 in adult motoneurons totally abrogated the natural resistance of these cells to axotomy. The degradation in the adult, induced by XAF1, could be overcome by simultaneously expressing high levels of exogenous XIAP in adult motoneurons. These experiments suggest that it may be the ratio between XAF1 and XIAP that confers the resistance of adult motoneurons to axotomy. In addition, the regulation in the levels of IAPs and XAF1 may be essential in the cell death mechanism of injured motoneurons.

Sensory neuroprotection, mitochondrial preservation, and therapeutic potential of N-acetyl-cysteine after nerve injury

Neuronal death is a major factor in many neuropathologies, particularly traumatic, and yet no neuroprotective therapies are currently available clinically, although antioxidants and mitochondrial protection appear to be fruitful avenues of research. The simplest system involving neuronal death is that of the dorsal root ganglion after peripheral nerve trauma, where the loss of approximately 40% of primary sensory neurons is a major factor in the overwhelmingly poor clinical outcome of the several million nerve injuries that occur each year worldwide. N-acetyl-cysteine (NAC) is a glutathione substrate which is neuroprotective in a variety of in vitro models of neuronal death, and which may enhance mitochondrial protection. Using TdT uptake nick-end labelling (TUNEL), optical disection, and morphological studies, the effect of systemic NAC treatment upon L4 and 5 primary sensory neuronal death after sciatic nerve transection was investigated. NAC (150 mg/kg/day) almost totally eliminated the extensive neuronal loss found in controls both 2 weeks (no treatment 21% loss, NAC 3%, P=0.03) and 2 months after axotomy (no treatment 35% loss, NAC 3%, P=0.002). Glial cell death was reduced (mean number TUNEL positive cells 2 months after axotomy: no treatment 51/ganglion pair, NAC 16/ganglion pair), and mitochondrial architecture was preserved. The effects were less profound when a lower dose was examined (30 mg/kg/day), although significant neuroprotection still occurred. This provides evidence of the importance of mitochondrial dysregulation in axotomy-induced neuronal death in the peripheral nervous system, and suggests that NAC merits investigation in CNS trauma. NAC is already in widespread clinical use for applications outside the nervous system; it therefore has immediate clinical potential in the prevention of primary sensory neuronal death, and has therapeutic potential in other neuropathological systems.

Bcl-2 family regulation of neuronal development and neurodegeneration

Neuronal cell death is a key feature of both normal nervous system development and neuropathological conditions. The Bcl-2 family, via its regulation of both caspase-dependent and caspase-independent cell death pathways, is uniquely positioned to critically control neuronal cell survival. Targeted gene disruptions of specific bcl-2 family members and the generation of transgenic mice overexpressing anti- or pro-apoptotic Bcl-2 family members have confirmed the importance of the Bcl-2 family in the nervous system. Data from studies of human brain tissue and experimental animal models of neuropathological conditions support the hypothesis that the Bcl-2 family regulates cell death in the mature nervous system and suggest that pharmacological manipulation of Bcl-2 family action could prove beneficial in the treatment of human neurological conditions such as stroke and neurodegenerative diseases.

Common patterns of bcl-2 family gene expression in two traumatic brain injury models

Cell death/survival following traumatic brain injury (TBI) may be a result of alterations in the intracellular ratio of death and survival factors. Bcl-2 family genes mediate both cell survival and the initiation of cell death. Using lysate RNase protection assays, mRNA expression of the anti-cell death genes Bcl-2 and Bcl-xL, and the pro-cell death gene Bax, was evaluated following experimental brain injuries in adult male Sprague-Dawley rats. Both the lateral fluid-percussion (LFP) and the lateral controlled cortical impact (LCI) models of TBI showed similar patterns of gene expression. Anti-cell death bcl-2 and bcl-xL mRNAs were attenuated early and tended to remain depressed for at least 3 days after injury in the cortex and hippocampus ipsilateral to injury. Pro-cell death bax mRNA was elevated in these areas, usually following the decrease in anti-cell death genes. These common patterns of gene expression suggest an important role for Bcl-2 genes in cell death and survival in the injured brain. Understanding the regulation of these genes may facilitate the development of new therapeutic strategies for a condition that currently has no proven pharmacologic treatments.

Enhanced functional recovery after proximal nerve root injury by vector-mediated gene transfer

In order to test the functional implication of herpes simplex virus (HSV) vector-mediated gene transfer after axonal injury, we injected replication-incompetent HSV vectors coding for the anti-apoptotic peptide Bcl-2 and the glial cell-derived neurotrophic factor (GDNF), separately or in combination into ventral spinal cord 30 min after a crush injury to the proximal spinal root that was combined with moderate mechanical traction. HSV-mediated expression of Bcl-2 or GDNF enhanced functional recovery assessed by histologic, electrophysiologic, and behavioral parameters up to 5 months after injury. The most sensitive measure of distal motor function, the sciatic function index, was significantly improved in animals injected with the two vectors together. These results suggest an approach to root trauma that might be used to enhance functional recovery after injury.

Temporal alterations in cellular Bax:Bcl-2 ratio following traumatic brain injury in the rat

Cell death/survival following CNS injury may be a result of alterations in the intracellular ratio of death and survival factors. Using immunohistochemistry, Western analysis and in situ hybridization, the expression of the anti-cell death protein, Bcl-2, and the pro-cell death protein, Bax, was evaluated following lateral fluid-percussion (FP) brain injury of moderate severity (2.3-2.6 atm) in adult male Sprague-Dawley rats. By 2 h post-injury, a marked reduction of cellular Bcl-2-immunoreactivity (IR) and a mild decrease in cellular Bax IR were observed in the temporal and occipital cortices, and in the hippocampal CA3 ipsilateral to the site of impact. These decreases in Bcl-2 and Bax IR appeared to precede the overt cell loss in these regions that was evident at 24 h. Immunoblot analysis supported the immunohistochemical data, with a modest but significant reduction in the intensities of both the Bcl-2 and Bax protein bands at 2 h (p < 0.05 compared to sham levels). However, the Bax:Bcl-2 ratio increased significantly at 2 h (2.28 +/- 0.13) and remained elevated up to 7 days (2.05 +/- 0.13) post-injury compared to sham-injured control tissue (1.62 +/- 0.10, p < 0.05). Furthermore, cortical, but not hippocampal, levels of Bax protein increased by 25% (p < 0.05 compared to sham-injured controls) at 24 h post-injury, and returned to control levels by 7 days. In situ hybridization analysis of Bax mRNA revealed increased cellular grain density in the injured cortex (p < 0.05 compared to sham-injured brains), but not in the CA3 region of the injured hippocampus. No injury-induced changes in the expression of Bcl-2 mRNA were observed in any brain region. Taken together, these data suggest that the association between regional post-traumatic cell death and alterations in the cellular ratio of Bcl-2 and Bax may be, in part, due to alterations in mRNA and/or protein expression of the Bcl-2 family of proteins.

Up-regulation of phosphorylated CREB but not c-Jun in bladder afferent neurons in dorsal root ganglia after cystitis

We examined the changes of two transcription factors, CREB and c-Jun, in dorsal root ganglia (DRG) after acute (8 or 48 hours) or chronic (10 days) cyclophosphamide (CYP)-induced cystitis. Results showed an increase in the number of p-CREB-immunoreactive (-IR) cells in the L1 and L2 DRG (5-7-fold; P < or = 0.05) as well as L6 and S1 DRG (2-4-fold; P < or = 0.05) after acute and chronic cystitis. The number of p-CREB-IR cells in the L4-L5 DRG was not altered with cystitis. The number of c-Jun-IR cells increased in the L1-L2 DRG (L1: 10-fold; L2: 8-fold; P < or = 0.05) only with chronic cystitis, although it increased in the L6-S1 DRG with CYP-induced cystitis of acute (2-3-fold; P < or = 0.05) and chronic (6-10-fold; P < or = 0.05) duration. After CYP treatment, the percentage of bladder afferent cells expressing p-CREB immunoreactivity (3-7-fold; P < or = 0.05) increased in L1, L2, L6, and S1 DRG. The increase occurred 8 hours post-CYP injection and was maintained with chronic cystitis. There were few c-Jun-IR cells in the bladder afferent population. These results demonstrate that CYP induces p-CREB and c-Jun expression in DRG in a time-dependent manner. However, c-Jun expression is not associated with bladder afferent neurons. Resiniferatoxin reduced CYP-induced up-regulation of p-CREB in DRG, suggesting that cystitis can reveal an altered CREB phosphorylation that may be mediated by capsaicin-sensitive bladder afferents. Colocalization of p-CREB and Trk receptor(s) showed that a subpopulation of p-CREB-IR cells expressed p-Trk with cystitis. These results suggest that up-regulation of p-CREB may be mediated by a neurotrophin/Trk signaling pathway.

Replicate high-density rat genome oligonucleotide microarrays reveal hundreds of regulated genes in the dorsal root ganglion after peripheral nerve injury

BACKGROUND

Rat oligonucleotide microarrays were used to detect changes in gene expression in the dorsal root ganglion (DRG) 3 days following sciatic nerve transection (axotomy). Two comparisons were made using two sets of triplicate microarrays, naïve versus naïve and naïve versus axotomy.

RESULTS

Microarray variability was assessed using the naïve versus naïve comparison. These results support use of a P < 0.05 significance threshold for detecting regulated genes, despite the large number of hypothesis tests required. For the naïve versus axotomy comparison, a 2-fold cut off alone led to an estimated error rate of 16%; combining a >1.5-fold expression change and P < 0.05 significance reduced the estimated error to 5%. The 2-fold cut off identified 178 genes while the combined >1.5-fold and P < 0.05 criteria generated 240 putatively regulated genes, which we have listed. Many of these have not been described as regulated in the DRG by axotomy. Northern blot, quantitative slot blots and in situ hybridization verified the expression of 24 transcripts. These data showed an 83% concordance rate with the arrays; most mismatches represent genes with low expression levels reflecting limits of array sensitivity. A significant correlation was found between actual mRNA differences and relative changes between microarrays (r2 = 0.8567). Temporal patterns of individual genes regulation varied.

CONCLUSIONS

We identify parameters for microarray analysis which reduce error while identifying many putatively regulated genes. Functional classification of these genes suggest reorganization of cell structural components, activation of genes expressed by immune and inflammatory cells and down-regulation of genes involved in neurotransmission.

Microarray analysis suggests the involvement of proteasomes, lysosomes, and matrix metalloproteinases in the response of motor neurons to root avulsion

We used microarray analysis of RNA expression from punch samples from ventral horn of spinal cord to identify alterations in gene expression in motor neurons 3 days after proximal spinal root avulsion, a traumatic injury that results in the death of 80% of the motor neurons. This analysis identified the anticipated increases in expression of genes coding for proteins involved in the apoptosis cascades and abortive cell cycle re-entry, as well as decreases in expression of genes coding for proteins related to neuronal functional activity, including groups of genes related to energy metabolism, transporter proteins, ion channels, and receptors. It was also found that cathepsins, metalloproteinases, and proteasome-related protein products were highly up-regulated in motor neurons following axotomy. Each of these products represent pathways that have been implicated in other models of neuronal damage, but which have not previously been described as a response to axotomy.

A new millenium for spinal cord regeneration: growth-associated genes

INTRODUCTION

Neurons surviving spinal cord injury undergo extensive reorganization that may result in the formation of functional synaptic contacts. Many neurons, however, fail to activate the necessary mechanisms for successful regeneration. In this review, we discuss the implications of growth cone genes that we have correlated with successful spinal cord axonal regeneration.

METHOD

Factors that inhibit regeneration, and activation of genes that promote it are discussed.

RESULTS/DISCUSSION

The early progress n understanding mechanisms that seem to promote or inhibit regeneration in the central nervous system may have significant clinical utility in the future.

Simultaneous expression of c-Jun and p53 in retinal ganglion cells of adult rat retinal slice cultures

PURPOSE

To determine whether the apoptosis-associated transcription factor c-Jun and the regulator protein p53 are expressed together during retinal ganglion cell (RGC) death in slice cultures of adult rat retina, and whether c-Jun expression or p53 expression is altered by glutamate.

METHODS

Newborn rat RGCs were retrogradely labeled by Di-I microinjections into the superior colliculus. Retinas were isolated 2 to 4 months later, cut into 200 microm-thick slices. These slices were cultured with 0-300 microM glutamate in the presence or absence of MK801. Survival was assessed using Sytox green and ethidium homodimer. Cultures also were immunostained for Thy-1, c-Jun and/or p53. The linear density of stained RGCs was determined by confocal laser microscopy.

RESULTS

RGCs in freshly-isolated adult retina slices did not express either c-Jun or p53. By 12 hours in vitro, 12.0 +/- 3.1 cells/mm of RGCs expressed c-Jun and 18.5 +/- 3.5 cells/mm of RGCs expressed p53 in control cultures. Exposure to glutamate increased both c-Jun and p53 positive RGCs in dose-dependent manner, and decreased survival in the RGC layer. Following double staining, up to 58% of cells in the RGC layer simultaneously expressed both c-Jun and p53. Time-course analysis showed that peak c-Jun expression preceded peak p53 expression in control and glutamate-treated cultures.

CONCLUSIONS

The simultaneous expression of both c-Jun and p53 in the cultured adult rat slices raises the possibility that each may contribute to the mechanism of RGC death. This is supported by the increased p53 and c-Jun inductions in the presence of glutamate.

Bcl-2 and GDNF delivered by HSV-mediated gene transfer after spinal root avulsion provide a synergistic effect

Proximal spinal nerve injury results in the death of motor neurons in ventral horn. We have previously demonstrated this cell death can be prevented by HSV-mediated transfer of the gene coding for the antiapoptotic peptide Bcl-2 7 days prior to injury, but that expression of Bcl-2 does not preserve ChAT expression in the lesioned cells. In the current study, we examined two related issues: whether Bcl-2 delivered by HSV-mediated gene transfer 30 min after injury could similarly protect motor neurons from cell death, and whether the additional HSV-mediated expression of the glial cell derived neurotrophic factor (GDNF) could improve the result. At 30 min after avulsion of the L4, L5, and L6 spinal nerves, replication defective genomic HSV-based vectors coding for Bcl-2, GDNF, a reporter transgene (lacZ), or the Bcl-2 and GDNF vectors together were injected into spinal cord. Transduction of motor neurons with either the Bcl-2-expressing vector or the GDNF-expressing vector resulted in a substantial increase in the number of surviving motor neurons, and coinjection of the two vectors together resulted in cell survival that was similar to the result obtained with either vector alone. Neither the Bcl-2-expressing vector nor the GDNF-expressing vector delivered alone protected choline acetyltransferase (ChAT) expression in lesioned neurons. However, simultaneous injection of the Bcl-2- and the GDNF-expressing vectors together resulted in a substantial increase in the number of ChAT in cells in the lesioned ventral horn. Together, these findings suggest an approach to improving cell survival and regeneration following proximal root injury.

Pathobiology of neuropathic pain

This review deals with physiological and biological mechanisms of neuropathic pain, that is, pain induced by injury or disease of the nervous system. Animal models of neuropathic pain mostly use injury to a peripheral nerve, therefore, our focus is on results from nerve injury models. To make sure that the nerve injury models are related to pain, the behavior was assessed of animals following nerve injury, i.e. partial/total nerve transection/ligation or chronic nerve constriction. The following behaviors observed in such animals are considered to indicate pain: (a) autotomy, i.e. self-attack, assessed by counting the number of wounds implied, (b) hyperalgesia, i.e. strong withdrawal responses to a moderate heat stimulus, (c) allodynia, i.e. withdrawal in response to non-noxious tactile or cold stimuli. These behavioral parameters have been exploited to study the pharmacology and modulation of neuropathic pain. Nerve fibers develop abnormal ectopic excitability at or near the site of nerve injury. The mechanisms include unusual distributions of Na(+) channels, as well as abnormal responses to endogenous pain producing substances and cytokines such as tumor necrosis factor alpha (TNF-alpha). Persistent abnormal excitability of sensory nerve endings in a neuroma is considered a mechanism of stump pain after amputation. Any local nerve injury tends to spread to distant parts of the peripheral and central nervous system. This includes erratic mechano-sensitivity along the injured nerve including the cell bodies in the dorsal root ganglion (DRG) as well as ongoing activity in the dorsal horn. The spread of pathophysiology includes upregulation of nitric oxide synthase (NOS) in axotomized neurons, deafferentation hypersensitivity of spinal neurons following afferent cell death, long-term potentiation (LTP) of spinal synaptic transmission and attenuation of central pain inhibitory mechanisms. In particular, the efficacy of opioids at the spinal level is much decreased following nerve injury. Repeated or prolonged noxious stimulation and the persistent abnormal input following nerve injury activate a number of intracellular second messenger systems, implying phosphorylation by protein kinases, particularly protein kinase C (PKC). Intracellular signal cascades result in immediate early gene (IEG) induction which is considered as the overture of a widespread change in protein synthesis, a general basis for nervous system plasticity. Although these processes of increasing nervous system excitability may be considered as a strategy to compensate functional deficits following nerve injury, its by-product is widespread nervous system sensitization resulting in pain and hyperalgesia. An important sequela of nerve injury and other nervous system diseases such as virus attack is apoptosis of neurons in the peripheral and central nervous system. Apoptosis seems to induce neuronal sensitization and loss of inhibitory systems, and these irreversible processes might be in common to nervous system damage by brain trauma or ischemia as well as neuropathic pain. The cellular pathobiology including apoptosis suggests future strategies against neuropathic pain that emphasize preventive aspects.

Electrical stimulation of cerebellar fastigial nucleus protects rat brain, in vitro, from staurosporine-induced apoptosis

Electrical stimulation of the cerebellar fastigial nucleus (FN) elicits a prolonged ( approximately 10 days) and substantial (50-80%) protection against ischemic and excitotoxic injuries. The mechanism(s) of protection are unknown. We investigated whether FN stimulation directly protects brain cells against apoptotic cell death in an in vitro rat brain slice culture model. Rats were electrically stimulated in FN or, as control, the cerebellar dentate nucleus (DN). Coronal slices through the forebrain were explanted, exposed to staurosporine, harvested, and analyzed for caspase-3 activity by a fluorescence assay. FN, but not DN, stimulation significantly reduced staurosporine-induced caspase-3 activity by 39 +/- 7% at 3 h, 31 +/- 3% at 6 h and 26 +/- 4% at 10 h of incubation. Immunocytochemistry revealed FN-specific reductions in activated caspase-3 mainly in glial-like cells throughout the forebrain. FN stimulation also results in a 56.5% reduction in cytochrome c release upon staurosporine incubation. We conclude that neuroprotection elicited from FN stimulation can directly modify the sensitivity of brain cells to apoptotic stimuli and thereby suppress staurosporine induced apoptosis in adult rat brain slices. This model indicates that neuroprotection can be studied in vitro and provides new insight into the potential role of glial cells in ischemic protection of neurons induced by FN stimulation.

Herpes simplex virus vector-mediated expression of Bcl-2 protects spinal motor neurons from degeneration following root avulsion

Proximal axotomy in adult animals results in delayed death of motor neurons. Features characteristic of both necrosis and apoptosis have been described in motor neurons of the spinal cord following proximal avulsion of the ventral roots. We have previously demonstrated that a genomic herpes simplex virus (HSV)-based vector expressing the anti-apoptotic peptide Bcl-2 protects dopaminergic neurons of the substantia nigra from neurotoxin-induced apoptotic cell death and preserves the neurotransmitter phenotype of those cells. In this study we examined whether the same vector could protect adult rat lumbar motor neurons from cell death following proximal ventral root avulsion. Injection of the Bcl-2-expressing vector 1 week prior to root avulsion increased the survival of lesioned motor neurons, determined by retrograde Fluorogold labeling, by 50%. The Bcl-2-expressing vector did not preserve choline acetyltransferase neurotransmitter phenotype of the lesioned cells. These results shed light on the mechanism of cell death following axonal injury, and have implications for developing an effective treatment for the clinical problem of proximal root avulsion.

Co-induction of nitric oxide synthase, bcl-2 and growth-associated protein-43 in spinal motoneurons during axon regeneration in the lizard tail

In lizards, tail loss transects spinal nerves and the cut axons elongate in the regrowing tail, providing a natural paradigm of robust regenerative response of injured spinal motoneurons. We previously ascertained that these events involve nitric oxide synthase induction in the axotomized motoneurons, suggesting a correlation of this enzyme with regeneration-associated gene expression. Here we investigated, in lizards, whether the cell death repressor Bcl-2 protein and growth-associated protein-43 (GAP-43) were also induced in motoneurons that innervate the regenerated tail in the first month post-caudotomy. Single and multiple immunocytochemical techniques, and quantitative image analysis, were performed. Nitric oxide synthase, GAP-43 or Bcl-2 immunoreactivity was very low or absent in spinal motoneurons of control lizards with intact tail. Nitric oxide synthase and GAP-43 were induced during the first month post-caudotomy in more than 75% of motoneurons which innnervate the regenerate. Bcl-2 was induced in approximately 95% of these motoneurons at five and 15days, and in about 35% at one month. The intensity of Bcl-2 and GAP-43 immunostaining peaked at five days, and nitric oxide synthase at 15days; immunoreactivity to these proteins was still significantly high at one month. Immunofluorescence revealed co-localization of nitric oxide synthase, GAP-43 and Bcl-2 in the vast majority of motoneurons at five and 15days post-caudotomy. These findings demonstrate that co-induction of nitric oxide synthase, Bcl-2 and GAP-43 may be part of the molecular repertoire of injured motoneurons committed to survival and axon regeneration, and strongly favor a role of nitric oxide synthase in motoneuron plasticity.

Prevention of death of axotomized hypoglossal neurones and promotion of regeneration by chitin grafting

1. Chitin is known to promote skin wound healing. In this study, chitin, prepared from Zuwai crab shell, was used as a bridge between the proximal and distal stumps of cut hypoglossal nerves in shrews. We compared the effects of chitin on the regeneration of transected right hypoglossal nerve axons, with those of porcine dermis, bovine dermal aterocollagen, and autologous nerve bundles. 2. To assess the survival of neurones, the size of neuronal cell body, and number of motoneurones were determined in the absence of any bridged material and in the presence of porcine dermis, bovine dermal aterocollagen, chitin, or autologous nerve bundles as a bridge. 3. Our results revealed a significantly better outcome in chitin and autologous nerve bridged groups; the size of neuronal cell body and number of hypoglossal neurones were higher than in the other groups. Chitin also enhanced the regeneration of neurones; the number of horseradish peroxide positive neurones indicative of repaired axonal processes was significantly higher in chitin and autologous nerve-bridged groups than in other groups. 4. Our results demonstrated that the use of chitin sheet or autograft successfully prevented the death of severed neurones and promoted the regeneration of the lesioned nerve. Although the mechanisms underlying the effects of chitin are still unknown, chitin seems to be a potentially useful biocompatible material for nerve repair and regeneration.

Alteration of the Bcl-x/Bax ratio in a transgenic mouse model of amyotrophic lateral sclerosis: evidence for the implication of the p53 signaling pathway

Molecular mechanisms promoting neuronal death in amyotrophic lateral sclerosis (ALS) were investigated using transgenic mice that overexpressed the G86R mutated form of the Cu/Zn superoxide dismutase (SOD1) gene. We observed: (i) alteration of the Bcl-x/Bax ratio and (ii) activation of the transcription factor p53, as deduced from its location within neuron nuclei. We further demonstrated that ectopic expression of the G86R mutant SOD1 in PC12 cells enhanced both p53 expression and phosphorylation, leading to transcriptional stimulation of p53-responsive genes. These findings provide evidence that the p53 signaling pathway is activated in SOD1-linked familial ALS and may play a causative role in spinal cord neuron apoptosis by modulating the Bcl-x/Bax ratio.

Adenovirus-mediated transfer of Bcl-X(L) protects neuronal cells from Bax-induced apoptosis

Bax-mediated apoptosis in neurons is involved in many pathologic conditions affecting the central nervous system, including degenerative diseases, stroke, and trauma. Two molecules belonging to the Bcl-2 family, Bcl-2 and Bcl-X(L), protect cells from Bax-induced apoptosis and show distinct expression patterns in adult neurons, with downregulated Bcl-2 and highly upregulated Bcl-X(L) expression. To investigate the biological functions of these two molecules in Bax-mediated apoptosis in neurons, we transduced various levels of Bcl-X(L) or Bcl-2 via adenoviral vectors into nerve growth factor (NGF)-treated PC12 cells. Overexpression of Bax induced drastic apoptosis in NGF-treated PC12 cells. Bcl-X(L) expressed at a wide range of levels conferred a high level of protection against Bax-mediated apoptosis. In contrast, Bcl-2 at various levels conferred far less protection against apoptosis. Moreover, Bcl-X(L) protected PC12 cells from apoptosis induced by NGF withdrawal. These data indicate that Bcl-X(L)-mediated protection is the major pathway that suppresses apoptosis in NGF-treated PC12 cells and that Bcl-X(L) would be a more relevant target of manipulation in future treatment strategies, including gene therapies.

Survival- and death-promoting events after transient cerebral ischemia: phosphorylation of Akt, release of cytochrome C and Activation of caspase-like proteases

Release of cytochrome c (cyt c) into cytoplasm initiates caspase-mediated apoptosis, whereas activation of Akt kinase by phosphorylation at serine-473 prevents apoptosis in several cell systems. To investigate cell death and cell survival pathways, the authors studied release of cyt c, activation of caspase, and changes in Akt phosphorylation in rat brains subjected to 15 minutes of ischemia followed by varying periods of reperfusion. The authors found by electron microscopic study that a portion of mitochondria was swollen and structurally altered, whereas the cell membrane and nuclei were intact in hippocampal CA1 neurons after 36 hours of reperfusion. In some neurons, the pattern of immunostaining for cyt c changed from a punctuate pattern, likely representing mitochondria, to a more diffuse cytoplasmic localization at 36 and 48 hours of reperfusion as examined by laser-scanning confocal microscopic study. Western blot analysis showed that cyt c was increased in the cytosolic fraction in the hippocampus after 36 and 48 hours of reperfusion. Consistently, caspase-3-like activity was increased in these hippocampal samples. As demonstrated by Western blot using phosphospecific Akt antibody, phosphorylation of Akt at serine-473 in the hippocampal region was highly increased during the first 24 hours but not at 48 hours of reperfusion. The authors conclude that transient cerebral ischemia activates both cell death and cell survival pathways after ischemia. The activation of Akt during the first 24 hours conceivably may be one of the factors responsible for the delay in neuronal death after global ischemia.

Neonatal ethanol exposure alters bcl-2 family mRNA levels in the rat cerebellar vermis

BACKGROUND

The objective of the present work was to determine whether ethanol-induced cerebellar cell death during development is related to alterations in the expression of bcl-2 family genes.

METHODS

Rats were exposed to ethanol or control conditions during the neonatal period and transcript levels of bcl-2 family members relative to cyclophilin were determined. Pups exposed in parallel were taken for cerebellar cell counts.

RESULTS

Ethanol exposure during the first postnatal week significantly reduced Purkinje and granule cell numbers by postnatal day 21 (P21). Acute first postnatal week ethanol exposure up-regulated mRNA transcripts encoding the cell death-promoting molecules bax and bcl-xs as measured on P4. An additional day of exposure on P5 resulted in no further alterations in bcl-2 family transcripts, likely because Purkinje cell death was detectable as early as P5. To determine whether proapoptotic gene expression changes were specific to first postnatal week ethanol neurotoxicity, we examined bcl-2 family mRNA levels in rats exposed to ethanol during a developmental period of cerebellar insusceptibility, the second postnatal week. Exposure on P7 to P8 produced no change in cerebellar cell number, but also resulted in increased levels of bax, although only after 2-day ethanol exposure and not after acute exposure on P7.

CONCLUSIONS

These data implicate altered expression of proapoptotic members of the bcl-2 gene family in acute ethanol-mediated cerebellar cell death during the first postnatal week. They also suggest that the differential survival of cerebellar neurons after ethanol exposure during more mature developmental stages may be related to more successful suppression of proapoptotic processes.

Estrogen and NGF synergistically protect terminally differentiated, ERalpha-transfected PC12 cells from apoptosis

The potential cytoprotective effects of the gonadal steroid estrogen, acting via its receptor (ER) on target neurons, are of considerable interest in aging, disease, and trauma. In this study, we examined the effects of estrogen on a prototypical neuronal-like cell, namely, nerve growth factor (NGF) differentiated PC12 cells when these cells are placed into an apoptosis-inducing environment. A clonal line of PC12 cells stably transfected to express full-length rat ERalpha mRNA and protein (PCER cells), as well as control cells (vector DNA transfected: PCCON cells), were differentiated into neurite bearing cells by 14 days of NGF treatment. Reverse transcription polymerase chain reaction (RT-PCR) and immunocytochemistry for ERalpha revealed that terminally differentiated PCER cells continue to show robust ER mRNA and protein expression after differentiation. PCCON cells do not express ERalpha either before or after NGF-induced differentiation. After differentiation, serum and NGF withdrawal from wild type PC12 cells is well known to induce cell death via apoptotic mechanisms. We challenged differentiated PCER and PCCON cells with serum-free media and assessed the effects of various treatments on cell survival and apoptosis using trypan blue staining and quantitative TUNEL staining. When differentiated PCER cells were treated with 17beta-estradiol (E2) plus NGF during a 2-day serum-free media challenge, cell survival was significantly greater, and the apoptotic index was significantly lower, than when PCER cells were treated with NGF only during the challenge. No additional improvement in cell survival, and no further reduction in apoptosis, was observed in non-ER expressing cells (PCCON) by E2 plus NGF treatment over that obtained by NGF alone. The effects of E2 on the expression of several apoptosis-related genes in this system were also examined. We found that E2 treatment of differentiated PCER cells in serum-free media increased the levels of Bcl-XL mRNA and reduced the levels of BAD mRNA relative to those in vehicle-treated PCER cells, and also relative to those in PCCON cells. Thus, estrogen's protective effects on PCER cells appear to, at least partly, involve a modulation of apoptosis-regulating genes.

Reciprocal changes in the expression of Bcl-2 and Bax in hypoglossal nucleus after axotomy in adult rats: possible involvement in the induction of neuronal cell death

Numerous studies of neonatal neuronal development in mammals have revealed that neuronal cell death following axotomy is apoptotic in nature. In adult animals, however, neuronal cell death following axonal injury may or may not exhibit features of apoptosis. Bcl-2 and Bax have been identified as inhibitor and promoter proteins, respectively, of apoptosis. To investigate the relationship between these proteins and neuronal cell death following axotomy in adult animals, we performed axotomy of the right hypoglossal nerve in adult male Wistar rats, and sacrificed the rats at various intervals after axotomy. We analyzed the expression of Bcl-2 and Bax immunohistochemically in the hypoglossal nuclei of the adult rats following axotomy. Our analysis showed an increase in the percentage of Bax-positive motoneurons relative to the total number of motoneurons in the hypoglossal nucleus on the axotomy side at three days after axotomy. In contrast, a low percentage of Bcl-2-positive motoneurons to the total number of motoneurons was noted at the same time interval after axotomy. Quantitative analysis of the signal intensity for Bcl-2 and Bax in individual neurons showed that Bax immunostaining significantly increased 7 days after axotomy, while the intensity of Bcl-2 immunostaining decreased in most of Bcl-2-positive neurons. Our results confirmed the occurrence of motoneuron cell death in adult rats after axotomy, and that a close temporal relationship exists between the reciprocal changes in Bcl-2/Bax expression and the loss of motoneurons. These results indicate the possible involvement of the Bcl-2/Bax system in the induction of neuronal cell apoptosis after axotomy in adult rats.

Motor neuron degeneration is attenuated in bax-deficient neurons in vitro

Apoptosis plays a major role in motor neuron survival during developmental cell death, after axotomy, and in motor neuron diseases. Bax is the first member of the bcl-2 family shown to promote apoptosis. In the present study, we used the bax-deficient mouse model to determine the role of bax in motor neuron survival in vitro by using dissociated spinal cord cultures. This system enables the maturation of individual motor neurons in a controlled in vitro environment. Motor neurons were identified by using the antineurofilament antibody SMI-32 and the antitranscription factor antibody Islet1. Both antibodies labeled large motor neurons in wild-type and bax-null cultures. Differentiated wild-type cultures exhibited a reduction in long-term cultures of two- and fivefold in the number of SMI-32- and Islet1-positive cells, respectively. The reduction in the number of motor neurons was attenuated in bax -/- cultures. Bax deficiency also attenuated serum withdrawal- and kainate-induced apoptosis in motor neurons. For comparison, necrotic cell death led to significant motor neuron cell death in both wild-type and bax -/- cultures. In addition, bax deficiency did not induce proliferation of motor neuron precursors in vitro. This study indicates for the first time that bax has a dominant role in the survival of long-term cultured motor neurons.

A review of the pathophysiology of cervical spondylotic myelopathy with insights for potential novel mechanisms drawn from traumatic spinal cord injury

Cervical spondylotic myelopathy (CSM) is the most common cause of spinal cord dysfunction. Despite advances in diagnosis and surgical treatment, many patients still have severe permanent neurologic deficits caused by this condition. An improved understanding of the pathophysiology of cervical spondylotic myelopathy, particularly at a cellular and molecular level, may allow improved treatments in the future. A detailed review of articles in the literature pertaining to cervical spondylotic myelopathy was supplemented by an analysis of relevant mechanisms of spinal cord injury. The pathologic course of cervical spondylotic myelopathy is characterized by early involvement of the corticospinal tracts and later destruction of anterior horn cells, demyelination of lateral and dorsolateral tracts, and relative preservation of anterior columns. Static and mechanical factors and ischemia are critical to the development of cervical spondylotic myelopathy. Free radical-and cation-mediated cell injury, glutamatergic toxicity, and apoptosis may be of relevance to the pathophysiology of cervical spondylotic myelopathy. To date, research in cervical spondylotic myelopathy has focused exclusively on the role of mechanical factors and ischemia. Fundamental research at a cellular and molecular level, particularly in the areas of glutamatergic toxicity and apoptosis may result in clinically relevant treatments for this condition.