Ordering the cell death pathway. Differential effects of BCL2, an interleukin-1-converting enzyme family protease inhibitor, and other survival agents on JNK activation in serum/nerve growth factor-deprived PC12 cells

Neuroprotective Strategies for Neurological Disorders by Natural Products: An update

Nature has bestowed mankind with surplus resources (natural products) on land and water. Natural products have a significant role in the prevention of disease and boosting of health in humans and animals. These natural products have been experimentally documented to possess various biological properties such as antioxidant, anti-inflammatory and anti-apoptotic activities. In vitro and in vivo studies have further established the usefulness of natural products in various preclinical models of neurodegenerative disorders. Natural products include phytoconstituents, like polyphenolic antioxidants, found in herbs, fruits, nuts, vegetables and also in marine and freshwater flora. These phytoconstituents may potentially suppress neurodegeneration and improve memory as well as cognitive functions of the brain. Also, they are known to play a pivotal role in the prevention and cure of different neurodegenerative diseases, such as Alzheimer's disease, epilepsy, Parkinson's disease and other neuronal disorders. The large-scale neuro-pharmacological activities of natural products have been documented due to the result of either the inhibition of inflammatory processes, or the up-regulation of various cell survival proteins or a combination of both. Due to the scarcity of human studies on neuroprotective effects of natural products, this review focuses on the various established activities of natural products in in vitro and in vivo preclinical models, and their potential neuro-therapeutic applications using the available knowledge in the literature.

Protein Kinase RNA-Like Endoplasmic Reticulum Kinase-Mediated Bcl-2 Protein Phosphorylation Contributes to Evodiamine-Induced Apoptosis of Human Renal Cell Carcinoma Cells

We investigated the anticancer mechanism of evodiamine (EVO) against the viability of human A498 renal cell carcinoma (RCC) cells in vitro and in vivo. The in vitro study showed that EVO decreased the viability of A498 cells with the occurrence of apoptotic characteristics such as hypodiploid cells, DNA ladders, chromatin-condensed cells, and cleaved caspase (Casp)-3/poly(ADP ribose) polymerase (PARP) proteins. Pharmacological studies using chemical inhibitors of mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) indicated that phosphorylation of the c-Jun N-terminal kinase (JNK) protein participated in EVO-induced cell death of A498 cells, and application of the JNK inhibitor, SP600125 (SP), inhibited EVO-induced cleavage of the Casp-3/PARP proteins and chromatin condensation according to Giemsa staining. EVO disruption of the mitochondrial membrane potential (MMP) with increased protein levels of the phosphorylated Bcl-2 protein (p-Bcl-2) was prevented by JNK inhibitors in A498 cells. A structure-activity relationship study showed that a methyl group at position 14 in EVO was important for its apoptotic effects and increased p-Bcl-2 protein in A498 cells. Furthermore, significant increases in the phosphorylated endoplasmic reticular stress protein, protein kinase RNA-like endoplasmic reticulum kinase (p-PERK at Thr980), by EVO were detected in A498 cells, and the PERK inhibitor, GSK2606414, significantly suppressed EVO-induced apoptosis, p-JNK, p-PERK, and cleaved PARP proteins. The in vivo study showed that EVO significantly reduced RCC growth elicited by a subcutaneous injection of A498 cells, and an increased protein level of p-PERK was observed according to an immunohistochemical analysis. Apoptosis by EVO was also demonstrated in other RCC cells such as 786-O, ACHN, and Caki-1 cells. This is the first study to demonstrate the anti-RCC effect of EVO via apoptosis in vitro and in vivo, and activation of JNK and PERK to induce Bcl-2 protein phosphorylation, which led to disruption of the MMP.

Regeneration after stroke: Stem cell transplantation and trophic factors

Stroke is a leading cause of death and disability worldwide. However, there is only one Food and Drug Administration-approved drug for the treatment of ischemic stroke, i.e., tissue plasminogen activator, and its therapeutic window is limited to within 4.5 h after stroke. Since clinical trials for neuroprotection have failed to demonstrate efficacy, multipotent and pluripotent stem cell transplantations are viable candidates for stroke treatment by providing trophic factor support and/or cell replacement following injury. The goal of this review is to highlight the promise of stem cell transplantation as vehicles for trophic factor delivery. The beneficial effects of different stem cell types as transplants as well as ways to upregulate trophic factors in stem cells are described in this review. Stem cell transplantation has consistently shown beneficial effects in the ischemic stroke model, in part due to the beneficial factors that stem cells release around the stroke injury area, resulting in smaller infarct volumes and regeneration and functional recovery. Upregulation of beneficial factors in stem cells and neural progenitors before transplantation has been shown to be even more effective in treating the stroke injury than stem cells without upregulated factors. However, for both stem cells and genetic engineering, there remain many unanswered questions and potential for improvement. These include modifiable parameters such as the different stem cell types and different factors, as well as the various readouts for investigation, such as various in vivo effects, such as immune system modulation and enhancement of endogenous neurogenesis and angiogenesis.

Toosendanin induces apoptosis through suppression of JNK signaling pathway in HL-60 cells

Toosendanin (TSN), a triterpenoid isolated from Melia toosendan Sieb. et Zucc., has been found to suppress proliferation and induce apoptosis in a variety of human cancer cells. However, the mechanism how TSN induces apoptosis remains poorly understood. In this study, we examined the effects of TSN on the growth, cell cycle arrest, induction of apoptosis and the involved signaling pathway in human promyelocytic leukemia HL-60 cells. Proliferation of HL-60 cells was inhibited in a dose-dependent manner with the IC(50 (48 h)) of 28 ng/mL. The growth inhibition was due primarily to the S phase arrest and cell apoptosis. Cell apoptosis induced by TSN was confirmed by Annexin V-FITC/propidium iodide staining. The increase of the pro-apoptotic protein Bax, cleaved PARP and caspase-3, and the decrease of anti-apoptotic protein Bcl-2 were observed. Western blot analysis indicated that TSN inhibits the CDC42/MEKK1/JNK pathway. Taken together, our study suggested, for the first time, that the pro-apoptotic effects of TSN on HL-60 cells were mediated through JNK signaling pathway.

Neuroprotective effects of N-acetyl-cysteine and acetyl-L-carnitine after spinal cord injury in adult rats

Following the initial acute stage of spinal cord injury, a cascade of cellular and inflammatory responses will lead to progressive secondary damage of the nerve tissue surrounding the primary injury site. The degeneration is manifested by loss of neurons and glial cells, demyelination and cyst formation. Injury to the mammalian spinal cord results in nearly complete failure of the severed axons to regenerate. We have previously demonstrated that the antioxidants N-acetyl-cysteine (NAC) and acetyl-L-carnitine (ALC) can attenuate retrograde neuronal degeneration after peripheral nerve and ventral root injury. The present study evaluates the effects of NAC and ALC on neuronal survival, axonal sprouting and glial cell reactions after spinal cord injury in adult rats. Tibial motoneurons in the spinal cord were pre-labeled with fluorescent tracer Fast Blue one week before lumbar L5 hemisection. Continuous intrathecal infusion of NAC (2.4 mg/day) or ALC (0.9 mg/day) was initiated immediately after spinal injury using Alzet 2002 osmotic minipumps. Neuroprotective effects of treatment were assessed by counting surviving motoneurons and by using quantitative immunohistochemistry and Western blotting for neuronal and glial cell markers 4 weeks after hemisection. Spinal cord injury induced significant loss of tibial motoneurons in L4–L6 segments. Neuronal degeneration was associated with decreased immunostaining for microtubular-associated protein-2 (MAP2) in dendritic branches, synaptophysin in presynaptic boutons and neurofilaments in nerve fibers. Immunostaining for the astroglial marker GFAP and microglial marker OX42 was increased. Treatment with NAC and ALC rescued approximately half of the motoneurons destined to die. In addition, antioxidants restored MAP2 and synaptophysin immunoreactivity. However, the perineuronal synaptophysin labeling was not recovered. Although both treatments promoted axonal sprouting, there was no effect on reactive astrocytes. In contrast, the microglial reaction was significantly attenuated. The results indicate a therapeutic potential for NAC and ALC in the early treatment of traumatic spinal cord injury.

Modular poly(ethylene glycol) scaffolds provide the ability to decouple the effects of stiffness and protein concentration on PC12 cells

This research focused on developing a modular poly(ethylene glycol) (PEG) scaffold, assembled from PEG microgels and collagen I, to provide an environment to decouple the chemical and mechanical cues within a three-dimensional scaffold. We first characterized the microgel fabrication process, examining the size, polydispersity, swelling ratio, mesh size and storage modulus of the polymer particles. The resulting microgels had a low polydispersity index, PDI=1.08, and a diameter of ~1.6 μm. The mesh size of the microgels, calculated from the swelling ratio, was 47.53 Å. Modular hydrogels (modugels) were then formed by compacting N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride/N-hydroxysuccinimidyl group-activated microgels with PEG-4arm-amine and 0, 1, 10, or 100 μg ml(-1) collagen. The stiffness (G(∗)) of the modugels was not significantly altered with the addition of collagen, allowing for modification of the chemical environment independent from the mechanical properties of the scaffold. PC12 cell aggregation increased in modugels as collagen concentrations increased and cell viability in modugels was improved over bulk PEG hydrogels. Overall, these results indicate that further exploration of modular scaffolds formed from microgels could allow for a better understanding of the relationship between the chemical and mechanical properties and cellular behavior.

Heat-shock protein 90 alpha (HSP90α) modulates signaling pathways towards tolerance of oxidative stress and enhanced survival of hepatocytes of Mugil cephalus

Oxidative stress causes damage at the cellular level and activates a number of signaling pathways. Earlier, we have demonstrated that pollutant-related oxidative stress upregulates heat-shock protein 90 alpha (HSP90α) against stress insult in hepatocytes of Mugil cephalus living in a polluted estuary. However, the impact of pollution-induced HSP90α upregulation on stress tolerance is not clear. Here we propose that the effect of stress resistance depends on the ability of HSP90α to modulate the signaling pathways involving proteins such as apoptosis signal-regulating kinase 1, c-Jun NH(2)-terminal protein kinase 1/2, signal transducers and activators of transcription, extracellular signal-regulated kinase 1/2, protein kinase B, nuclear factor-kappa binding, Ets-like protein 1, and B cell lymphoma-2. In order to investigate this, the activation of HSP90α-associated signaling molecules was examined by Western blotting and immunohistochemistry. The relationship between the protein expression patterns was identified by Spearman's rank correlation analysis. The signaling proteins exhibited differential modulation as revealed from their expression patterns in pollutant-exposed fish hepatocytes, in comparison with the control fish hepatocytes. The results suggested that in spite of the prevalence of oxidative stress in pollutant-exposed fish hepatocytes, the stress-mediated induction of HSP90α enabled the hepatocytes to become stress tolerant and to survive by modulating the actions of key proteins and kinases in the signal transduction pathways.

Tetrandrine induces apoptosis and growth suppression of colon cancer cells in mice

Tetrandrine, a bisbenzylisoquinoline alkaloid, exerts antitumor effects against some cancers. We explored tetrandrine's effects on colon cancer with cultured mouse CT-26 cells and with subcutaneous tumors. Tetrandrine induced apoptosis in concentration- and time-dependent manner. Tetrandrine increased expression of ERK 1/2 and p38 MAPK; inhibition of p38 MAPK reduced tetrandrine-induced apoptosis; inhibition of ERK1/2 did not. Tetrandrine had significant effects on tumors including slower growth and longer animal survival time and higher survival rate. Higher dose and earlier treatment were more effective than lower dose and delayed treatment. TUNEL staining showed prominent tetrandrine-induced apoptosis of tumors. These data suggest that tetrandrine induced significant apoptosis of cultured and subcutaneous CT-26 cells. Tetrandrine-induced apoptosis might be at least partially related to activation of the p38 MAPK signaling pathway.

Protective actions of ovarian hormones in the serotonin system of macaques

The serotonin neurons of the dorsal and medial raphe nuclei project to all areas of the forebrain and play a key role in mood disorders. Hence, any loss or degeneration of serotonin neurons could have profound ramifications. In a monkey model of surgical menopause with hormone replacement and no neural injury, E and P decreased gene expression in the dorsal raphe nucleus of c-jun n-terminal kinase (JNK1) and kynurenine mono-oxygenase (KMO) that promote cell death. In concert, E and P increased gene expression of superoxide dismutase (SOD1), VEGF, and caspase inhibitory proteins that promote cellular resilience in the dorsal raphe nucleus. Subsequently, we showed that ovarian steroids inhibit pivotal genes in the caspase-dependent and caspase-independent pathways in laser-captured serotonin neurons including apoptosis activating factor (Apaf1), apoptosis-inducing factor (AIF) and second mitochondria-derived activator of caspases (Smac/Diablo). SOD1 was also increased specifically in laser-captured serotonin neurons. Examination of protein expression in the dorsal raphe block revealed that JNK1, phosphoJNK1, AIF and the translocation of AIF from the mitochondria to the nucleus decreased with hormone therapy, whereas pivotal execution proteins in the caspase pathway were unchanged. In addition, cyclins A, B, D1 and E were inhibited, which would prevent re-entry into the cell cycle and catastrophic death. These data indicated that in the absence of gross injury to the midbrain, ovarian steroids inhibit the caspase-independent pathway and cell cycle initiation in serotonin neurons. To determine if these molecular actions prevented cellular vulnerability or death, we examined DNA fragmentation in the dorsal raphe nucleus with the TUNEL assay (terminal deoxynucleotidyl transferase nick end labeling). Ovarian steroids significantly decreased the number of TUNEL-positive cells in the dorsal raphe. Moreover, TUNEL staining prominently colocalized with TPH immunostaining, a marker for serotonin neurons. In summary, ovarian steroids increase the cellular resilience of serotonin neurons and may prevent serotonin neuron death in women facing decades of life after menopause. The survival of serotonin neurons would support cognition and mental health.

Role of xanthine oxidoreductase in cardiac nitroso-redox imbalance

Emerging evidence supports the importance of nitroso-redox balance in the cardiovascular system. Xanthine oxidoreductase (XOR) is a major oxidative enzyme and increased XOR activity, leading to both increased production of reactive oxygen species and uric acid, is implicated in heart failure. Within the heart, XOR activity stimulates cardiomyocyte hypertrophy, apoptosis, and impairs matrix structure. The underpinnings of these derangements can be linked not solely to oxidative stress, but may also involve the process of nitroso-redox imbalance. In this regard, XOR interacts with nitric oxide signaling at numerous levels, including a direct protein-protein interaction with neuronal nitric oxide synthase (NOS1) in the sarcoplasmic reticulum. Deficiency or translocation of NOS1 away from this microdomain leads to increased activity of XOR, which in turn impairs excitation-contraction coupling and myofilament calcium sensitivity. There is a mounting abundance of preclinical data supporting beneficial effects of inhibiting XOR, but translation to the clinic continues to be incomplete. A growing understanding of XOR and its role in nitroso-redox imbalance has great potential to lead to improved pathophysiologic insights and possibly therapeutic advances.

CITED2 signals through peroxisome proliferator-activated receptor-gamma to regulate death of cortical neurons after DNA damage

DNA damage is an important initiator of neuronal apoptosis and activates signaling events not yet fully defined. Using the camptothecin-induced DNA damage model in neurons, we previously showed that cyclin D1-associated cell cycle cyclin-dependent kinases (Cdks) (Cdk4/6) and p53 activation are two major events leading to activation of the mitochondrial apoptotic pathway. With gene array analyses, we detected upregulation of Cited2, a CBP (cAMP response element-binding protein-binding protein)/p300 interacting transactivator, in response to DNA damage. This upregulation was confirmed by reverse transcription-PCR and Western blot. CITED2 was functionally important because CITED2 overexpression promotes death, whereas CITED2 deficiency protects. Cited2 upregulation is upstream of the mitochondrial death pathway (BAX, Apaf1, or cytochrome c release) and appears to be independent of p53. However, inhibition of the Cdk4 blocked Cited2 induction. The Cited2 prodeath mechanism does not involve Bmi-1 or p53. Instead, Cited2 activates peroxisome proliferator-activated receptor-gamma (PPARgamma), an activity that we demonstrate is critical for DNA damage-induced death. These results define a novel neuronal prodeath pathway in which Cdk4-mediated regulation of Cited2 activates PPARgamma and consequently caspase.

6-(7-Nitro-2,1,3-benzoxadiazol-4-ylthio)hexanol, a specific glutathione S-transferase inhibitor, overcomes the multidrug resistance (MDR)-associated protein 1-mediated MDR in small cell lung cancer

In the present work, we have investigated the antitumor activity of 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio)hexanol (NBDHEX) on aggressive small cell lung cancer. NBDHEX not only is cytotoxic toward the parental small cell lung cancer H69 cell line (LC(50) of 2.3 +/- 0.6 micromol/L) but also overcomes the multidrug resistance of its variant, H69AR, which overexpresses the ATP-binding cassette transporter multidrug resistance-associated protein 1 (MRP1; LC(50) of 4.5 +/- 0.9 micromol/L). Drug efflux experiments, done in the presence of a specific inhibitor of MRP1, confirmed that NBDHEX is not a substrate for this export pump. Interestingly, NBDHEX triggers two different types of cell death: a caspase-dependent apoptosis in the H69AR cells and a necrotic phenotype in the parental H69 cells. The apoptotic pathway triggered by NBDHEX in H69AR cells is associated with c-Jun NH(2)-terminal kinase and c-Jun activation, whereas glutathione oxidation and activation of p38(MAPK) is observed in the NBDHEX-treated H69 cells. In contrast to the parental cells, the higher propensity to die through apoptosis of the H69AR cell line may be related to the lower expression of the antiapoptotic protein Bcl-2. Therefore, down-regulation of a factor crucial for cell survival makes H69AR cells more sensitive to the cytotoxic action of NBDHEX, which is not a MRP1 substrate. We have previously shown that NBDHEX is cytotoxic toward P-glycoprotein-overexpressing tumor cell lines. Therefore, NBDHEX seems a very promising compound in the search for new molecules able to overcome the ATP-binding cassette family of proteins, one of the major mechanisms of multidrug resistance in cancer cells.

Required roles of Bax and JNKs in central and peripheral nervous system death of retinoblastoma-deficient mice

Retinoblastoma-deficient mice show massive neuronal damage and deficits in both CNS and PNS tissue. Previous work in the field has shown that death is regulated through distinct processes where CNS tissue undergoes death regulated by the tumor suppressor p53 and the apoptosome component, APAF1. Death in the PNS, however, is independent of p53 and reliant on the death protease, caspase 3. In the present study, we more carefully delineated the common and distinct mechanisms of death regulation by examining the stress-activated kinases, JNK2 and 3, the conserved Bcl-2 member Bax, and the relationship among these elements including p53. By use of genetic modeling, we show that death in various regions of the CNS and DRGs of the PNS is reliant on Bax. In the CNS, Bax acts downstream of p53. The relevance of the JNKs is more complex, however. Surprisingly, JNK3 deficiency by itself does not inhibit c-Jun phosphorylation and instead, aggravates death in both CNS and PNS tissue. However, JNK2/3 double deficiency blocks death due to Rb loss in both the PNS and CNS. Importantly, the relationships between JNKs, p53, and Bax exhibit regional differences. In the medulla region of the hindbrain in the CNS, JNK2/3 deficiency blocks p53 activation. Moreover, Bax deficiency does not affect c-Jun phosphorylation. This indicates that a JNK-p53-Bax pathway is central in the hindbrain. However, in the diencephalon regions of the forebrain (thalamus), Bax deficiency blocks c-Jun activation, indicating that a Bax-JNK pathway of death is more relevant. In the DRGs of the PNS, a third pathway is present. In this case, a JNK-Bax pathway, independent of p53, regulates damage. Accordingly, our results show that a death regulator Bax is common to death in both PNS and CNS tissue. However, it is regulated by or itself regulates different effectors including the JNKs and p53 depending upon the specific region of the nervous system.

Prolyl hydroxylase inhibitors delay neuronal cell death caused by trophic factor deprivation

Nerve growth factor (NGF) serves a critical survival-promoting function for developing sympathetic neurons. Following removal of NGF, sympathetic neurons undergo apoptosis characterized by the activation of c-Jun N-terminal kinases (JNKs), up-regulation of BH3-only proteins including BcL-2-interacting mediator of cell death (BIM)(EL), release of cytochrome c from mitochondria, and activation of caspases. Here we show that two small-molecule prolyl hydroxylase inhibitors frequently used to activate hypoxia-inducible factor (HIF) - ethyl 3,4-dihydroxybenzoic acid (DHB) and dimethyloxalylglycine (DMOG) - can inhibit apoptosis caused by trophic factor deprivation. Both DHB and DMOG blocked the release of cytochrome c from mitochondria after NGF withdrawal, whereas only DHB blocked c-Jun up-regulation and phosphorylation. DHB, but not DMOG, also attenuated the induction of BIM(EL) in NGF-deprived neurons, suggesting a possible mechanism whereby DHB could inhibit cytochrome c release. DMOG, on the other hand, was substantially more effective at stabilizing HIF-2alpha and inducing expression of the HIF target gene hexokinase 2 than was DHB. Thus, while HIF prolyl hydroxylase inhibitors can delay cell death in NGF-deprived neurons, they do so through distinct mechanisms that, at least in the case of DHB, are partly independent of HIF stabilization.

Acquisition of apoptotic resistance in cadmium-transformed human prostate epithelial cells: Bcl-2 overexpression blocks the activation of JNK signal transduction pathway

BACKGROUND

We have recently shown that cadmium can induce malignant transformation of the human prostate epithelial cell line (RWPE-1) and that these cadmium-transformed prostate epithelial (CTPE) cells acquire apoptotic resistance concurrently with malignant phenotype.

OBJECTIVE

The present study was designed to define the mechanism of acquired apoptotic resistance in CTPE cells.

METHODS

Various molecular events associated with apoptosis were assessed in control and CTPE cells that were obtained after 8 weeks of continuous cadmium exposure.

RESULTS

Compared with control, CTPE cells showed a generalized resistance to apoptosis induced by cadmium, cisplatin, or etoposide. Signal-regulated mitogen-activated protein kinases, extracellular signal-regulated kinases 1 and 2, c-Jun N-terminal kinases (JNK1 and JNK2), and p38 were phosphorylated in a cadmium concentration-dependent fashion in CTPE and control cells. However, phosphorylated JNK1/2 levels and JNK kinase activity were much lower in CTPE cells. The pro-apoptotic gene Bax showed lower transcript and protein levels, whereas the anti-apoptotic gene Bcl-2 showed higher levels in CTPE cells. The ratio of Bcl-2/Bax, a key determinant in apoptotic commitment, increased more than 4-fold in CTPE cells. In Bcl-2-transfected PT-67 cells, phosphorylated JNK1/2 levels were much lower after apoptogenic stimulus, and apoptosis induced by cadmium or etoposide was reduced compared with control. Mutation of tyrosine to serine at the 21st amino acid of the Bcl-2 protein BH4 domain resulted in a loss both of suppression of JNK1/2 phosphorylation and its anti-apoptotic function.

CONCLUSIONS

CTPE cells become resistant to apoptosis during malignant transformation, and disruption of the JNK pathway and Bcl-2 overexpression play important roles in this resistance. Bcl-2 BH4 domain is required for modulating JNK phosphorylation and anti-apoptotic function.

Prion protein prevents Bax-mediated cell death in the absence of other Bcl-2 family members inSaccharomyces cerevisiae

Although there is no consensus regarding the normal function of the prion protein, increasing evidence points towards a role in cellular protection against cell death. We have previously shown that prion protein is a potent inhibitor of Bax-induced apoptosis in human primary neurons and in the breast carcinoma MCF-7 cells. Here, we used the yeast Saccharomyces cerevisiae to investigate if the neuroprotective function of prion protein requires other members of the Bcl-2 family given that S. cerevisiae lacks Bcl-2 genes but undergoes a mitochondrial-dependent apoptotic cell death upon exogenous expression of Bax protein. We show that Bax induces cell death and growth inhibition in S. cerevisiae. Prion protein prevents Bax-mediated cell death. Prion protein overcomes Bax-mediated growth arrest in S phase but cannot overcome population growth inhibition because the cells then accumulate in G(2)/M phase. We conclude that prion protein does not require other Bcl-2 family proteins to protect against Bax-mediated cell death.

Expression of c-Jun and Bcl-2 Family Proteins in Apoptotic Photoreceptors of RCS Rats

PURPOSE

To determine if c-Jun and Bcl-2 family proteins play a role in photoreceptor apoptosis in Royal College of Surgeons (RCS) rats.

METHODS

RCS and Sprague-Dawley rats were used. Cryosections of retinas harvested at various postnatal periods were immunostained with antibodies against c-Jun, Bcl-2, and Bax. Double staining with TdT-dUTP nick-end labeling (TUNEL) or propidium iodide (PI) and antibodies was also done. To study the time course of gene and protein expression, semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblotting analyses were carried out.

RESULTS

TUNEL-positive photoreceptors of RCS rats were stained strongly with antibodies against c-Jun and Bax. The number of immunoreactive cells increased on days 21 and 28 after birth (P21 and P28) and decreased on P45. Semiquantitative RT-PCR analysis showed that mRNAs for c-Jun and Bax were upregulated at P21 and P28, but those for Bcl-2 were unchanged. On immunoblotting, a 43-kDa band was revealed by the anti-c-Jun antibody and a 21-kDa band, by the anti-Bax antibody. Protein expression of c-Jun and Bax were increased at both P21 and P28. The temporal profiles of immunoreactivity, protein expression, and mRNA expression were similar.

CONCLUSION

c-Jun and Bax may play a role in photoreceptor apoptosis in RCS rats.

Thiol reducing compounds prevent human amylin-evoked cytotoxicity

Human amylin (hA) is a small fibrillogenic protein that is the major constituent of pancreatic islet amyloid, which occurs in most subjects with type-2 diabetes mellitus (T2Dm). There is growing evidence that hA toxicity towards islet beta-cells is responsible for their gradual loss of function in T2Dm. Preventing hA-mediated cytotoxicity has been proposed as a route to halt the progression of this disease, although this has not yet been demonstrated in vivo. The aim of our studies, in which we show that a small number of hA-treated cells exhibit intracellular accumulation of reactive oxygen species (ROS), was to evaluate the role of oxidative stress in the mechanism of hA-mediated cytotoxicity. Here we report that catalase and n-propyl gallate, antioxidants that are thought to act mainly as free radical scavengers, afford RINm5F cells only limited protection against hA-mediated toxicity. By contrast, the thiol antioxidants, N-acetyl-L-cysteine (NAC), GSH and dithiothreitol, which not only react with ROS, but also modulate the cellular redox potential by increasing intracellular levels of GSH and/or by acting as thiol reducing agents, afford almost complete protection and inhibit the progression of hA-evoked apoptosis. We also show that hA treatment is not associated with changes in intracellular GSH levels and that inhibition of GSH biosynthesis has no effect on either hA-mediated cytotoxicity or NAC-mediated protection. These results indicate that, in addition to the induction of oxidative stress, hA appears to mediate cytotoxicity through signalling pathways that are sensitive to the actions of thiol antioxidants.

JNK activation contributes to DP5 induction and apoptosis following traumatic spinal cord injury

Growing evidence suggests that cells undergo apoptosis after spinal cord injury (SCI). However, little is known about the early events that trigger apoptosis in the contused cord. The BH3-only subfamily of pro-apoptotic regulators (e.g., bim, bad, and dp5) is recognized as initiators of the apoptotic cascade, and is subject to stringent control, both at the transcriptional and post-translational level. In the current study, we studied upstream events regulating trauma-induced apoptosis in the spinal cord. Within 1 h after SCI in rats, DP5 was induced, while Bim and Bad levels remained unchanged. In parallel, SCI also activated the stress-induced c-Jun N-terminal kinase (JNK), leading to the phosphorylation of c-Jun, with a similar temporal profile. Immunohistochemical analysis revealed that p-JNK and DP5 colocalized to neurons and oligodendrocytes undergoing apoptosis in the injured cord, but were absent in uninjured spinal cord. Furthermore, inhibition of JNK activity with in vivo delivery of SP600125 or a jnk1 antisense oligodeoxynucleotide (ODN) attenuated DP5 induction and caspase-3 activation. These results suggest that JNK activation contributes to trauma-induced DP5 expression and subsequent apoptosis in SCI.

The basic helix-loop-helix transcription factor Nex-1/Math-2 promotes neuronal survival of PC12 cells by modulating the dynamic expression of anti-apoptotic and cell cycle regulators

The basic helix-loop-helix transcription factor Nex1/Math-2 belongs to the NeuroD subfamily, which plays a critical role during neuronal differentiation and maintenance of the differentiated state. Previously, we demonstrated that Nex1 is a key regulatory component of the nerve growth factor (NGF) pathway. Further supporting this hypothesis, this study shows that Nex1 has survival-inducing properties similar to NGF, as Nex1-overexpressing PC12 cells survive in the absence of trophic factors. We dissected the molecular mechanism by which Nex1 confers neuroprotection upon serum removal and found that constitutive expression of Nex1 maintained the expression of specific G1 phase cyclin-dependent kinase inhibitors and concomitantly induced a dynamic expression profile of key anti-apoptotic regulators. This study provides the first evidence of the underlying mechanism by which a member of the NeuroD-subfamily promotes an active anti-apoptotic program essential to the survival of neurons. Our results suggest that the survival program may be viewed as an integral component of the intrinsic programming of the differentiated state.

Preliminary array analysis reveals novel genes regulated by ovarian steroids in the monkey raphe region

We hypothesize that ovarian hormones may improve serotonin neuron survival. We sought the effect of estradiol (E) and progesterone (P) on novel gene expression in the macaque dorsal raphe region with Affymetrix array analysis. Nine spayed rhesus macaques were treated with either placebo, E or E+P via Silastic implant for 1 month prior to euthanasia (n=3 per treatment). RNA was extracted from a small block of midbrain containing the dorsal raphe and examined on an Agilent Bioanalyzer. The RNA from each monkey was labeled and hybridized to an Affymetrix HG_U95AV Human GeneChip Array. After filtering and sorting, 25 named genes remained that were regulated by E, and 24 named genes remained that were regulated by supplemental P. These genes further sorted into functional categories that would promote neuronal plasticity, transmitter synthesis, and trafficking, as well as reduce apoptosis. The relative abundance of four pivotal genes was examined in all nine animals with quantitative RT-PCR and normalized by glyceraldehyde 3-phosphate dehydrogenase (GAPDH). E+/-P caused a significant threefold reduction in JNK-1 (a pro-apoptosis gene, p<0.007); and a significant sixfold decrease in kynurenine mono-oxygenase (produces neurotoxic quinolones, p<0.05). GABA-A receptor (alpha3 subunit; benzodiazepine site) and E2F1 (interferes with cytokine signaling) were unaffected by E, but increased sevenfold (p<0.02) and fourfold (p<0.009), respectively, upon treatment with P. In summary, subsets of genes related to tissue remodeling or apoptosis were up- or down-regulated by E and P in a tissue block containing the dorsal raphe. These changes could promote cellular resilience in the region where serotonin neurons originate.

c-Jun N-terminal Kinase 3 Deficiency Protects Neurons from Axotomy-induced Death in Vivo through Mechanisms Independent of c-Jun Phosphorylation

Both the transcription factor c-Jun and the c-Jun N-terminal kinases (JNKs) have been associated with neuronal loss in several death paradigms. JNK are key regulators of c-Jun and a common accepted model has been that JNKs mediate neuronal death through modulation of c-Jun activation. In the present study, we examined whether JNK2 and -3 (JNK members most associated with neuronal loss) deficiency can rescue neuronal loss caused by facial and sciatic nerve axotomy in the neonate in vivo. JNK2, JNK3, and JNK2/3 double-deficient neurons displayed significantly less death in the facial nerves of the CNS when compared with controls. JNK2 and JNK2/3 double-deficient animals also showed reduced c-Jun phosphorylation and induction following axotomy, consistent with the model that JNK acts to regulate death by activating c-Jun. Of significance, however, protection of facial nerves in JNK3-deficient animals was not accompanied by reduction in c-Jun activation. These results suggest that JNKs can mediate death independently of c-Jun. Importantly, the lack of correlation between JNK3 deficiency and c-Jun induction was not universal. In a sciatic axotomy model of neuronal injury in the neonate, death of DRG neurons was also reduced by JNK3 deficiency. However, in this case, c-Jun activation was also eliminated.

Deacetylation of p53 after nerve growth factor treatment in PC12 cells as a post-translational modification mechanism of neurotrophin-induced tumor suppressor activation

The tumor suppressor protein p53 is a transcription factor that regulates the response to cellular insults such as DNA damage and growth factor withdrawal. Transcriptional activity of p53 requires post-translational modification by phosphorylation and acetylation. This study used site-specific antibodies to demonstrate that nerve growth factor (NGF) treatment of PC12 cells results in p53 deacetylation at lysine (Lys) 382. Histone deacetylase (HDAC) activity, measured by a direct fluorescent assay, was increased after NGF treatment and peaked before p53 deacetylation. Inhibition of HDAC by trichostatin blocked the deacetylation of p53 and its transcriptional activity toward a reporter gene construct. Comparison of PC12 with PC12 cells containing a temperature-sensitive, dominant-negative construct showed that p53 deacetylation required functional p53. Inhibitors of MAP kinase that block p53 transactivation and inhibitors of TrkA receptor also abolished HDAC activation, indicating that deacetylation of p53 is an NGF-dependent post-translational mechanism of p53 activation. Finally, NGF or serum withdrawal did not lead to p53 deacetylation. A model is proposed in which the acetylation status of Lys 382 of p53 discriminates between cell cycle arrest and apoptosis.

Nerve growth factor receptor signaling induces histone acetyltransferase domain-dependent nuclear translocation of p300/CREB-binding protein-associated factor and hGCN5 acetyltransferases

The transcriptional coactivators, p300/CREB-binding protein-associated factor (PCAF) and hGCN5, are recruited to chromatin-remodeling complexes on enhancers of various gene promoters in response to growth factor stimulation. However, the molecular mechanisms by which surface receptor signals modulate the assembly of nuclear transcription complexes are not fully understood. Here we report that nerve growth factor receptor signaling induces nuclear translocation of PCAF and hGCN5 dependent upon the phosphorylation of Ser and Thr residues within their histone acetyltransferase domains, which requires activation of PI3K, Rsk2(pp90), and MSK-1. Neurotrophin stimulation induces p53(K320) acetylation by PCAF and transcriptionally activates p53-responsive enhancer elements within the p21(WAF/CIP1) promoter associated with G(1)/S arrest during neuronal differentiation. Most importantly, these findings represent the first evidence for signal-dependent nuclear translocation of PCAF and hGCN5 acetyltransferases and allude to a novel mechanism for ligand/receptor modulation of nuclear chromatin-remodeling complexes in neurons.

Neuroprotective actions of eicosapentaenoic acid on lipopolysaccharide-induced dysfunction in rat hippocampus

Eicosapentaenoic acid (EPA) protects hippocampus from age-related and irradiation-induced changes that lead to impairment in synaptic function; the evidence suggests that this is due to its anti-inflammatory effects, specifically preventing changes induced by the proinflammatory cytokine, interleukin-1beta (IL-1beta). In this study, we have investigated the possibility that EPA may prevent the effects of lipopolysaccharide (LPS) administration, which have been shown to lead to deterioration of synaptic function in rat hippocampus. The data indicate that treatment of hippocampal neurones with EPA abrogated the LPS-induced increases in phosphorylation of the mitogen-activated protein kinase, c-Jun N-terminal kinase (JNK), the transcription factor, c-Jun and the mitochondrial protein, Bcl-2. In parallel, we report that intraperitoneal administration of LPS to adult rats increases phosphorylation of JNK, c-Jun and Bcl-2 in hippocampal tissue and that these changes are coupled with increased IL-1beta concentration. Treatment of rats with EPA abrogates these effects and also blocks the LPS-induced impairment in long-term potentiation in perforant path-granule cell synapses that accompanies these changes. We propose that the neuroprotective effect of EPA may be dependent on its ability to inhibit the downstream consequences of JNK activation.

Noncytotoxic ribonuclease, RNase T1, induces tumor cell death via hemagglutinating virus of Japan envelope vector

Several ribonucleases, including onconase and alpha-sarcin, are known to be toxic to tumor cells. On the other hand, although its structure is related to that of alpha-sarcin, RNase T1 is noncytotoxic because of its inability to internalize into tumor cells. In this study, we internalized RNase T1 into human tumor cells via a novel gene transfer reagent, hemagglutinating virus of Japan (HVJ) envelope vector, which resulted in cell death. This cytotoxicity was drastically increased by pretreatment of HVJ envelope vector with protamine sulfate, and was stronger than that of onconase, which is in phase III human clinical trials as a nonmutagenic cancer chemotherapeutic agent. Furthermore, internalized RNase T1 induced apoptotic cell death programs. Because its cytotoxicity is unfortunately not specific to tumor cells, it cannot at present be developed as an anticancer drug. However, we believe that RNase T1 incorporated in HVJ envelope vector will be a unique anticancer drug if HVJ envelope vector can be targeted to tumor cells.

Basic fibroblast growth factor-induced cell death is effected through sustained activation of p38MAPK and up-regulation of the death receptor p75NTR

Basic fibroblast growth factor (bFGF) induces cell death in cells of the Ewing's sarcoma family of tumors in vivo and in vitro. In this study we demonstrate that this is dependent on the rapid and sustained activation of p38(MAPK), in contrast to the transient activation of p38(MAPK) associated with bFGF-induced cell proliferation. Stem cell factor-induced survival of TC-32 cells was also associated with transient activation of p38(MAPK). Inhibition of p38(MAPK) by SB202190 and p38(MAPK) small interfering RNA reduces bFGF-induced death in TC-32 cells, consistent with the hypothesis that activation of p38(MAPK) is essential for induction of death by bFGF. This appears to be dependent on sustained activation of p38(MAPK), demonstrated by inhibition of bFGF-induced cell death following addition of SB202190 to TC-32 cells 5 min after exposure to bFGF (20 ng/ml) and activation of p38(MAPK). Prolonged activation of p38(MAPK) is accompanied by a rapid and sustained phosphorylation of Ras and ERK; inhibition of ERK phosphorylation using the MEK-1 inhibitor PD98059 rescued approximately 30% of cells from bFGF-induced death suggesting ERK plays a secondary role in the induction of death. This hypothesis is supported by observations in the A673 cell line; bFGF induced sustained activation of ERK and transient activation of p38(MAPK), which was not associated with cell death. These data demonstrate that sustained activation of p38(MAPK) is essential for activation of the death cascade following exposure of Ewing's sarcoma family of tumors cells to bFGF and provide evidence that activation of p38(MAPK) results in an up-regulation of the death receptor p75(NTR).

Roscovitine, olomoucine, purvalanol: inducers of apoptosis in maturing cerebellar granule neurons

Cyclin-dependent kinases (CDKs) mediate proliferation and neuronal development, while aberrant CDK activity is associated with cancer and neurodegeneration. Consequently, pharmacologic inhibitors, such as 2,6,9-trisubstituted purines, which potently inhibit CDKs 1, 2, and 5, were developed to combat these pathologies. One agent, R-roscovitine (CYC202), has advanced to clinical trials as a potential cancer therapy. In primary neuronal cultures, these agents have been used to delineate the physiologic and pathologic functions of CDKs, and associated signaling pathways. Herein we demonstrate that three 2,6,9-trisubstituted purines: olomoucine, roscovitine, and purvalanol, used at concentrations ascribed by others to potently inhibit CDKs 1, 2, and 5, are powerful triggers of death in maturing cerebellar granule neurons, assessed by loss of mitochondrial reductive capacity and differential staining with fluorescent indicators of living/dead neurons. Based on several criteria, including delayed time course and establishment of an irreversible commitment point of death, pyknotic cell and nuclear morphology, and caspase-3 cleavage, the death process is apoptotic. However, pharmacological and biochemical data indicate that apoptosis is independent of CDK 1, 2, or 5 inhibition. This is based on the pattern of changes in c-jun mRNA, c-Jun protein, and Ca(2+)/cAMP response element binding protein (CREB) phosphorylation, and also, the ineffectiveness of structurally distinct CDK 1, 2, and 5 inhibitors butyrolactone-1 and PNU112445A to induce apoptosis. Collectively, our results, and those of others, indicate that the CDK regulation of transcription (CDKs 7 and 9) should be examined as a target of these agents, and as an indirect mediator of neuronal fate.

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.

Resveratrol Suppresses the Angiogenesis and Tumor Growth of Gliomas in Rats

PURPOSE

We wanted to investigate the antitumor effects and effect on angiogenesis of resveratrol in rat RT-2 gliomas.

EXPERIMENTAL DESIGN

RT-2 glioma cells were treated with resveratrol, and then cytotoxicity was assayed, apoptosis was measured by flow-activated cell sorter flow cytometry, and expression of vascular endothelial growth factor was measured by reverse transcription-PCR. Tumor size, animal survival time, and survival rate were followed in resveratrol-treated rats with s.c. or intracerebral gliomas. Furthermore, in vitro proliferation was assayed to explore the effect of resveratrol on the proliferation of ECV304 human umbilical vein endothelial cells. Expression of CD31 in resveratrol-treated gliomas was followed immunohistochemically to study the effect of resveratrol on the glioma-induced angiogenesis.

RESULTS

Resveratrol was demonstrated to exert cytotoxic effects and induce glioma cell apoptosis in a concentration- and time-dependent manner (P < 0.05). Resveratrol (40 mg/kg/day) exerted significant antitumor effects on s.c. tumors, including slower tumor growth rate, longer animal survival time, and higher animal survival rate (P < 0.05). In contrast, resveratrol affected intracerebral tumors at only an increased dose (100 mg/kg/day), prolonging animal survival (P < 0.05) without affecting survival rate. The expression of vascular endothelial growth factor in the glioma cells and the proliferation of ECV304 cells were inhibited by resveratrol in a concentration-dependent manner. Immunohistochemical analyses showed that the s.c. gliomas from resveratrol-treated rats had fewer microvessel densities than did control rats (P < 0.01).

CONCLUSIONS

Resveratrol caused significant glioma cell cytotoxicity and apoptosis, exerted antitumor effects on the s.c. and intracerebral gliomas, and inhibited angiogenesis in s.c. gliomas. Thus, resveratrol might be considered a possible treatment strategy for gliomas.

Activation of c-Jun N-terminal kinase 1 and caspase 3 in the tamoxifen-induced apoptosis of rat glioma cells

PURPOSE

The mechanisms of the antitumor effects of tamoxifen upon gliomas are still unclear. In this study, we investigated the role of c-Jun N-terminal kinase-1 (JNK1) and caspase 3 in the tamoxifen-induced apoptosis of rat glioma cells.

METHODS

Glioma cells were treated with tamoxifen, followed by a cytotoxicity assay to study its effects on the cells, and then a flow-activated cell sorter (FACS) analysis was performed to analyze the cellular apoptosis of the glioma cells. The expression of JNK1 and phospho-specific JNK1 in glioma cells treated with tamoxifen was investigated by Western blot analysis. The activity of caspase 3 in glioma cells was analyzed by caspase activity assay.

RESULTS

Tamoxifen was demonstrated to exert cytotoxic effects upon and induced apoptosis of the glioma cells in a concentration- and time-dependent manner (P<0.05). Western blot analysis demonstrated that tamoxifen increased the expression of phospho-specific JNK1 in glioma cells, and an increasing concentration of tamoxifen induced an increasing expression of phospho-specific JNK1. Four-hour 50-microM tamoxifen treatment increased the expression of phospho-specific JNK1 to 3.2 times that of the control level in glioma cells. Tamoxifen also increased the activity of caspase 3 in glioma cells. Pretreatment of glioma cells with the antisense oligonucleotide (OGN) of JNK1 immediately prior to tamoxifen treatment suppressed the expression of phospho-specific JNK1 and the activity of caspase 3. The apoptosis fraction of glioma cells induced by 4-h treatment with 50 microM tamoxifen was decreased from 51% to 28% by pretreatment with the antisense OGN of JNK1 (P<0.003), and to 20% by pretreatment with caspase 3 inhibitor (DEVD-CHO) (P<0.0008).

CONCLUSIONS

The results suggest that the tamoxifen-induced apoptosis of rat glioma cells is related to the activation of the JNK1/caspase 3 signaling pathway; however, the confirmation of the occurrence of such activation in vivo needs further investigation.

Lipopolysaccharide-induced increase in signalling in hippocampus is abrogated by IL-10--a role for IL-1 beta?

Parenterally administered lipopolysaccharide (LPS) increases the concentration of the pro-inflammatory cytokine interleukin-1beta (IL-1beta) in the rat hippocampus and evidence suggests that this effect plays a significant role in inhibiting long-term potentiation (LTP). The anti-inflammatory cytokine IL-10, antagonizes certain effects of IL-1beta, so if the effects of LPS are mediated through an increase in IL-1beta, it might be predicted that IL-10 would also abrogate the effect of LPS. Here, we report that IL-10 reversed the inhibitory effect of LPS on LTP and the data couple this with an inhibitory effect on the LPS-induced increase in IL-1beta. LPS treatment increased hippocampal expression of IL-1 receptor Type I protein. Consistent with the LPS-induced increases in IL-1beta concentration and receptor expression, were downstream changes which included enhanced phosphorylation of IRAK and the stress-activated kinases, JNK and p38; these LPS-induced changes were reversed by IL-10, which concurs with the idea that these events are triggered by increased activation of IL-1RI by IL-1beta. We provide evidence which indicates that LPS treatment leads to evidence of cell death and this was reversed in hippocampus prepared from LPS-treated rats which received IL-10. The evidence is therefore consistent with the idea that IL-10 acts to protect neuronal tissue from the detrimental effects induced by LPS.

Pathways of survival induced by NGF and extracellular ATP after growth factor deprivation

In a previous work we demonstrated that extracellular adenosine-5'-triphosphate (ATP), acting on P2 receptors, exerts neuritogenic and trophic effects on the phaeochromocytoma PC12 cell line. These actions are comparable to those sustained by nerve growth factor (NGF) and involve several overlapping pathways. In this work, we describe some of the mechanisms recruited by ATP and NGF in maintaining PC12 cell survival after serum deprivation. We show that both ATP and NGF upregulate the expression of the stress-induced heat shock protein HSP70 and HSP90, whilst glucose-response protein GRP75 and GRP78 are not affected. In parallel with NGF, ATP prevents the cleavage and activation of caspase-2 and inhibits the release of cytochrome c from mitochondria into the cytoplasm. Finally, neither NGF, nor ATP directly modulate the expression of P2 receptors in the induction of cell survival. Our data contribute to dissect the biological mechanisms activated by extracellular purines exerting trophic actions and to establish that survival and neurite outgrowth lie on different mechanistic pathways.

CEP11004, a novel inhibitor of the mixed lineage kinases, suppresses apoptotic death in dopamine neurons of the substantia nigra induced by 6-hydroxydopamine

There is much evidence that the kinase cascade which leads to the phosphorylation of c-jun plays an important signaling role in the mediation of programmed cell death. We have previously shown that c-jun is phosphorylated in a model of induced apoptotic death in dopamine neurons of the substantia nigra in vivo. To determine the generality and functional significance of this response, we have examined c-jun phosphorylation and the effect on cell death of a novel mixed lineage kinase inhibitor, CEP11004, in the 6-hydroxydopamine model of induced apoptotic death in dopamine neurons. We found that expression of total c-jun and Ser73-phosphorylated c-jun is increased in this model and both colocalize with apoptotic morphology. CEP11004 suppresses apoptotic death to levels of 44 and 58% of control values at doses of 1.0 and 3.0 mg/kg, respectively. It also suppresses, to approximately equal levels, the number of profiles positive for the activated form of capase 9. CEP11004 markedly suppresses striatal dopaminergic fiber loss in these models, to only 22% of control levels. We conclude that c-jun phosphorylation is a general feature of apoptosis in living dopamine neurons and that the mixed lineage kinases play a functional role as up-stream mediators of cell death in these neurons.

The transcriptional repressor HBP1 is a target of the p38 mitogen-activated protein kinase pathway in cell cycle regulation

The p38 mitogen-activated protein (MAP) kinase signaling pathway participates in both apoptosis and G1 arrest. In contrast to the established role in apoptosis, the documented induction of G1 arrest by activation of the p38 MAP kinase pathway has attracted recent attention with reports of substrates that are linked to cell cycle regulation. Here, we identify the high-mobility group box protein HBP1 transcriptional repressor as a new substrate for p38 MAP kinase. Our previous work had shown that HBP1 inhibits G1 progression in cell and animal models, and thus indicated that HBP1 could be a relevant substrate for p38 MAP kinase in cell cycle regulation. In the present work, a p38 MAP kinase docking site (amino acids [aa] 81 to 125) and a p38 MAP kinase phosphorylation site (serine 401) were identified in the HBP1 protein. Furthermore, the docking and phosphorylation sites on HBP1 were specific for p38 MAP kinase. In defining the role of p38 MAP kinase regulation, the inhibition of p38 MAP kinase activity was shown to decrease HBP1 protein levels by triggering protein instability, as manifested by a decrease in protein half-life. Consistently, a decrease in protein levels was accompanied by a decrease in overall DNA binding activity. A mutation of the p38 MAP kinase phosphorylation site at aa 401 [(S-A)401HBP1] also triggered HBP1 protein instability. While protein stability was compromised by mutation, the specific activities of (S-A)401HBP1 and of wild-type HBP1 appeared comparable for transcriptional repression. This comparison of transcription-specific activity highlighted that p38 MAP kinase regulated HBP1 protein levels but not the intrinsic activity for DNA binding or for transcriptional repression. Finally, p38 MAP kinase-mediated regulation of the HBP1 protein also contributed to the regulation of G1 progression. Together, our work supports a molecular framework in which p38 MAP kinase activity contributes to cell cycle inhibition by increasing HBP1 and other G1 inhibitory factors by regulating protein stability.

Inhibition of apoptosis signal-regulating kinase 1 by nitric oxide through a thiol redox mechanism

Nitric oxide is an endogenous thiol-reactive molecule that modulates the functions of many regulatory proteins by a thiol-redox mechanism. NO has now been shown to inhibit the activation of apoptosis signal-regulating kinase 1 (ASK1) in murine fibrosarcoma L929 cells through such a mechanism. Exposure of L929 cells to interferon-gamma resulted in the endogenous production of NO and in inhibition of the activation of ASK1 by hydrogen peroxide. The interferon-gamma-induced inhibition of ASK1 activity was blocked by N(G)-nitro-l-arginine, an inhibitor of NO synthase. Furthermore, the NO donor S-nitro-N-acetyl-dl-penicillamine (SNAP) inhibited ASK1 activity in vitro, and this inhibition was reversed by thiol-reducing agents such as dithiothreitol and beta-mercaptoethanol. SNAP did not inhibit the kinase activities of MKK3, MKK6, or p38 in vitro. The inhibition of ASK1 by interferon-gamma was not changed by 1H- (1,2,4)oxadiazolo[4,3-alpha]quinoxalin-1-one, an inhibitor of guanylyl cyclase nor was it mimicked by 8-bromo-cyclic GMP. Site-directed mutagenesis revealed that replacement of cysteine 869 of ASK1 by serine rendered this protein resistant to the inhibitory effects both of interferon-gamma in intact cells and of SNAP in vitro. Co-immunoprecipitation data showed that NO production inhibited a binding of ASK1, but not ASK1(C869S), to MKK3 or MKK6. Moreover, interferon-gamma induced the S-nitrosylation of endogenous ASK1 in L929 cells. Together, these results suggest that NO mediates the interferon-gamma-induced inhibition of ASK1 in L929 cells through a thiolredox mechanism.

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.

Ebselen inhibits NO-induced apoptosis of differentiated PC12 cells via inhibition of ASK1-p38 MAPK-p53 and JNK signaling and activation of p44/42 MAPK and Bcl-2

Ebselen, a selenium-containing heterocyclic compound, prevents ischemia-induced cell death. However, the molecular mechanism through which ebselen exerts its cytoprotective effect remains to be elucidated. Using sodium nitroprusside (SNP) as a nitric oxide (NO) donor, we show here that ebselen potently inhibits NO-induced apoptosis of differentiated PC12 cells. This was associated with inhibition of NO-induced phosphatidyl Serine exposure, cytochrome c release, and caspase-3 activation by ebselen. Analysis of key apoptotic regulators during NO-induced apoptosis of differentiated PC12 cells showed that ebselen blocks the activation of the apoptosis signaling-regulating kinase 1 (ASK1), and inhibits phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-jun N-terminal protein kinase (JNK). Moreover, ebselen inhibits NO-induced p53 phosphorylation at Ser15 and c-Jun phosphorylation at Ser63 and Ser73. It appears that inhibition of p38 MAPK and p53 phosphorylation by ebselen occurs via a thiol-redox-dependent mechanism. Interestingly, ebselen also activates p44/42 MAPK, and inhibits the downregulation of the antiapoptotic protein Bcl-2 in SNP-treated PC12 cells. Together, these findings suggest that ebselen protects neuronal cells from NO cytotoxicity by reciprocally regulating the apoptotic and antiapoptotic signaling cascades.

Transient transfection protects PC6-3 cells from apoptosis induced by nerve growth factor deprivation

Some mammalian neurons undergo apoptosis after neurotrophin deprivation. We studied neuronally differentiated PC6-3 pheochromocytoma cells, which are highly dependent on nerve growth factor for survival. We found that transient transfection with green fluorescent protein or beta-galactosidase protected cells from apoptosis induced by nerve growth factor deprivation. Individual transfection reagent components did not produce increased viability of nerve growth factor-deprived cells. This apparent neuroprotective effect from transient transfection was specific to neurotrophin deprivation, as cells treated with H(2)O(2) or staurosporine were not protected. To determine the mechanism of neuroprotection after transfection, the transfection status of identified groups of cells was assessed both before and after nerve growth factor deprivation. The results were consistent with a model whereby cells that are transfected but not yet expressing the transfected protein are relatively protected from nerve growth factor deprivation. We suggest that apoptosis induced by neurotrophin deprivation may interact with processes of transient transfection and expression of foreign genes in neuronal cells. Not only should these interactions be considered in transient transfection studies of neurotrophin-deprived neurons, but also their elucidation could lead to novel methods for achieving neuroprotection.

Activation of p38 plays a pivotal role in the inhibitory effect of lipopolysaccharide and interleukin-1 beta on long term potentiation in rat dentate gyrus

Lipopolysaccharide (LPS), a component of the cell wall of Gram-negative bacteria, has been shown to induce profound changes both peripherally and centrally. It has recently been reported that intraperitoneal injection of LPS inhibited long term potentiation (LTP) in perforant path-granule cell synapses and that this effect was coupled with an increase in the concentration of the proinflammatory cytokine, interleukin-1 beta (IL-1 beta). The LPS-induced effects were abrogated by inhibition of caspase-1, suggesting that IL-1 beta may mediate the effects of LPS. Here we report that the inhibition of LTP induced by LPS and IL-1 beta was coupled with stimulation of the stress-activated protein kinase p38 in hippocampus and entorhinal cortex and that this effect was abrogated by the p38 inhibitor SB203580, while the effect of LPS was markedly attenuated in C57BL/6 IL-1RI-/- mice. The data also indicate that activation of the transcription factor, nuclear factor kappa B (NF kappa B), may play a role, since the inhibitory effect of LPS and IL-1 beta on LTP was attenuated by the NF kappa B inhibitor, SN50; consistently, LPS and IL-1 beta led to activation of NF kappa B in entorhinal cortex. We suggest that one consequence of these LPS and IL-1 beta-induced changes is a compromise in glutamate release in dentate gyrus, which was coupled with the inhibition of LTP. The evidence is consistent with the idea that the LPS-induced impairment in LTP is mediated by IL-1 beta and is a consequence of activation of p38.

Arrest of apoptosis in auditory neurons: implications for sensorineural preservation in cochlear implantation

HYPOTHESIS

The JNK/c-Jun cell death pathway is a major pathway responsible for the loss of oxidative stress-damaged auditory neurons.

BACKGROUND

Implantation of patients with residual hearing accentuates the need to preserve functioning sensorineural elements. Although some auditory function may survive electrode insertion, the probability of initiating an ongoing loss of auditory neurons and hair cells is unknown. Cochlear implantation can potentially generate oxidative stress, which can initiate the cell death of both auditory neurons and hair cells.

METHODS

Dissociated cell cultures of P4 rat auditory neurons identified the apoptotic pathway initiated by oxidative stress insults (e.g., loss of trophic factor support) and characterized this pathway by arresting translation of pathway-specific mRNA with antisense oligonucleotide treatment and with the use of pathway specific inhibitors. The presence or absence of apoptosis-specific protein and changes in the level of neuronal survival measured the efficacy of these interventional strategies.

RESULTS

These in vitro studies identified the JNK/c-Jun cascade as a major initiator of apoptosis of auditory neurons in response to oxidative stress. Neurons pretreated with c-jun antisense oligonucleotide and exposed to high levels of oxidative stress were rescued from apoptosis, whereas neurons in treatment control cultures died. Treatment of oxidative-stressed cultures with either curcumin, a MAPKKK pathway inhibitor, or PD-098059, a MEK1 inhibitor, blocked loss of neurons via the JNK/c-Jun apoptotic pathway.

CONCLUSION

Blocking the JNK/c-Jun cell death pathway is a feasible approach to treating oxidative stress-induced apoptosis within the cochlea and may have application as an otoprotective strategy during cochlear implantation.

Interleukin-1 receptor antagonist exerts agonist activity in the hippocampus independent of the interleukin-1 type I receptor

Interleukin-1 receptor antagonist (IL-1ra) selectively and competitively inhibits the actions of IL-1 at its receptors and has not been reported to have agonist activity. This study demonstrates that stimulation of synaptosomes with IL-1ra in vitro, mimicked the effects of IL-1 beta by decreasing glutamate release and increasing JNK phosphorylation. These effects of IL-1ra, but not IL-1 beta, were maintained in IL-1 type I receptor (IL-1RI) defective mice. IL-1 beta blocked these IL-1ra-induced effects suggesting that it may also act independently of IL-1RI in some circumstances. Furthermore, IL-1ra mimicked the inhibitory effect of IL-1 beta on long-term potentiation (LTP) in the hippocampus. These data, taken together with our findings that IL-1ra binds to hippocampal synaptosomes in the absence of IL-1RI, provide evidence that IL-1ra exerts agonist activity in the hippocampus independent of IL-1RI.

Nitric oxide-mediated cytoprotection of hepatocytes from glucose deprivation-induced cytotoxicity: involvement of heme oxygenase-1

Heme oxygenase-1 (HO-1) is the rate-limiting enzyme in heme catabolism, which leads to the generation of carbon monoxide (CO), biliverdin, and free iron. One of 3 mammalian HO isoforms, HO-1, is a stress-responsive protein and known to modulate such cellular functions as cytokine production, cell proliferation, and apoptosis to protect organs and tissues from acute injury. Although nitric oxide (NO)-mediated cytoprotective effects against cytotoxicity induced by glucose deprivation have been well recognized, the underlying mechanisms remain to be elucidated. Thus, we investigate the involvement of HO-1 in the cytoprotective effects of NO. Deprivation of glucose markedly reduced the viability of BNL CL.2 cells and primary rat hepatocytes. Pretreatment with NO donor, sodium nitroprusside (SNP), protected hepatocytes from glucose deprivation-induced cytotoxicity; zinc protoporphyrin (ZnPP) IX, an inhibitor of HO, was found to block the SNP-induced cytoprotection. SNP increased the induction of HO-1 protein as well as its activity in hepatocytes. A cytoprotective effect comparable to SNP was observed when the cells were transfected with HO-1 gene or preincubated with another HO-1 inducer, hemin. Additional experiments revealed the involvement of CO in the cytoprotective effect of SNP/HO-1 in BNL CL.2 cells. CO mediated cytoprotective effect through suppression of ERK MAPK activation. In conclusion, our results show that SNP protects hepatocytes from glucose deprivation-induced cytotoxicity through up-regulation of HO-1. Thus, HO-1 might be an important cellular target of NO donor with clinical implications for the prevention of acute liver injury in several pathological conditions.

Activation of mitogen-activated protein kinase pathways during the death of PC12 cells is dependent on the state of differentiation

PC12 cells that are differentiated with NGF and cAMP become totally dependent on these factors for their survival, unlike those that are differentiated with NGF alone. We have asked whether the MAP Kinases, ERKs, JNKs and p38s play a role in the cell death induced by withdrawal of trophic factors on NGF- and NGF/cAMP-differentiated PC12 cells. By Western-blot analyses with antibodies directed against the activated forms of these kinases, we show that when the trophic factors were withdrawn, ERK phosphorylation was reduced to very low levels within 1 h in both cases. Changes in the other enzymes were observed only in the NGF/cAMP-differentiated cells, in which the JNK phosphorylation increased about 160% by 6 h and that of p38 increased linearly to at least 18-fold throughout the cell death process. The increases in p38 and JNK phosphorylation were implicated in the death of the cells, since the p38 inhibitor PD169316 and the JNK inhibitor SP600125 were protective. These results demonstrate that the state of differentiation of PC12 cells, a model for the differentiation of sympathetic neurons, determines their vulnerability to cell death by modifying the state of phosphorylation and the regulation of specific kinases implicated in signal transduction pathways that are responsible for the survival or the death of these cells.

JNK phosphorylation of Bim-related members of the Bcl2 family induces Bax-dependent apoptosis

The c-Jun NH(2)-terminal kinase (JNK) is activated when cells are exposed to environmental stress, including UV radiation. Gene disruption studies demonstrate that JNK is essential for UV-stimulated apoptosis mediated by the mitochondrial pathway by a Bax/Bak-dependent mechanism. Here, we demonstrate that JNK phosphorylates two members of the BH3-only subgroup of Bcl2-related proteins (Bim and Bmf) that are normally sequestered by binding to dynein and myosin V motor complexes. Phosphorylation by JNK causes release from the motor complexes. These proapoptotic BH3-only proteins therefore provide a molecular link between the JNK signal transduction pathway and the Bax/Bak-dependent mitochondrial apoptotic machinery.

IL-1beta-dependent neurological effects of the whole cell pertussis vaccine: a role for IL-1-associated signalling components in vaccine reactogenicity

Immunization with the whole cell pertussis vaccine (Pw), but not the acellular pertussis vaccine (Pa), is associated with a number of neurological side effects. Previously, we have demonstrated a role for interleukin-1beta (IL-1beta) in Pw reactogenicity. Here we report that parenteral Pw administration resulted in a concomitant increase IL-1 type I receptor (IL-1RI) mRNA and a decrease in IL-1 type II receptor (IL-1RII) mRNA expression in the murine hypothalamus. These Pw-induced changes were accompanied by an increase in caspase-1 and interleukin-1beta (IL-1beta), and were associated with increased activity of the stress-activated kinase, p38. In contrast, immunization with Pa failed to activate pro-inflammatory IL-1 responses but resulted in increased IL-1 receptor antagonist (IL-1ra) production. These results suggest that the neurological effects of Pw are associated with central activation of IL-1beta and IL-1-associated signalling components.