Reciprocal inhibition of p53 and nuclear factor-kappaB transcriptional activities determines cell survival or death in neurons

FABP7 drives an inflammatory response in human astrocytes and is upregulated in Alzheimer's disease

Alzheimer's disease (AD), the most common cause of dementia in the elderly, is characterized by the accumulation of intracellular neurofibrillary tangles, extracellular amyloid plaques, and neuroinflammation. In partnership with microglial cells, astrocytes are key players in the regulation of neuroinflammation. Fatty acid binding protein 7 (FABP7) belongs to a family of conserved proteins that regulate lipid metabolism, energy homeostasis, and inflammation. FABP7 expression is largely restricted to astrocytes and radial glia-like cells in the adult central nervous system. We observed that treatment of primary hippocampal astrocyte cultures with amyloid β fragment 25-35 (Aβ25-35) induces FABP7 upregulation. In addition, FABP7 expression is upregulated in the brain of APP/PS1 mice, a widely used AD mouse model. Co-immunostaining with specific astrocyte markers revealed increased FABP7 expression in astrocytes. Moreover, astrocytes surrounding amyloid plaques displayed increased FABP7 staining when compared to non-plaque-associated astrocytes. A similar result was obtained in the brain of AD patients. Whole transcriptome RNA sequencing analysis of human astrocytes differentiated from induced pluripotent stem cells (i-astrocytes) overexpressing FABP7 identified 500 transcripts with at least a 2-fold change in expression. Gene Ontology enrichment analysis identified (i) positive regulation of cytokine production and (ii) inflammatory response as the top two statistically significant overrepresented biological processes. We confirmed that wild-type FABP7 overexpression induces an NF-κB-driven inflammatory response in human i-astrocytes. On the other hand, the expression of a ligand-binding impaired mutant FABP7 did not induce NF-κB activation. Together, our results suggest that the upregulation of FABP7 in astrocytes could contribute to the neuroinflammation observed in AD.

Emerging role and therapeutic implications of p53 in intervertebral disc degeneration

Lower back pain (LBP) is a common degenerative musculoskeletal disease that imposes a huge economic burden on both individuals and society. With the aggravation of social aging, the incidence of LBP has increased globally. Intervertebral disc degeneration (IDD) is the primary cause of LBP. Currently, IDD treatment strategies include physiotherapy, medication, and surgery; however, none can address the root cause by ending the degeneration of intervertebral discs (IVDs). However, in recent years, targeted therapy based on specific molecules has brought hope for treating IDD. The tumor suppressor gene p53 produces a transcription factor that regulates cell metabolism and survival. Recently, p53 was shown to play an important role in maintaining IVD microenvironment homeostasis by regulating IVD cell senescence, apoptosis, and metabolism by activating downstream target genes. This study reviews research progress regarding the potential role of p53 in IDD and discusses the challenges of targeting p53 in the treatment of IDD. This review will help to elucidate the pathogenesis of IDD and provide insights for the future development of precision treatments.

Electroacupuncture for weight loss by regulating microglial polarization in the arcuate nucleus of the hypothalamus

Electroacupuncture (EA) has a weight loss effect, but the underlying molecular mechanisms of weight loss with EA have not been fully elucidated. This study aimed to investigate the modulatory effects of EA on the phenotype of hypothalamic microglia in obese mice. A total of 50 male C57BL/6J mice were used in this study. There were three groups in this experiment: The conventional diet group (Chow group), the high-fat diet group (HFD group), and the EA intervention group (HFD + EA group). EA was applied at "Tianshu (ST25)", "Guanyuan (RN4)", "Zusanli (ST36)" and "Zhongwan (RN12)" every day for 10 min. Hematoxylin and eosin (H&E) staining, immunohistochemical staining, and real-time PCR were applied in this study. The results showed that EA intervention was associated with a decrease in body weight, food intake, adipose tissue weight, and adipocyte size. At the same time, EA induced microglia to exhibit an M2 phenotype, representing reduced iNOS/TNF-α and increased Arg-1/IL-10/BDNF, which may be due to the promotion of TREM2 expression. EA also reduced microglia enrichment in the hypothalamic arcuate nucleus and declined TLR4 and IL-6, inhibiting microglia-mediated neuroinflammation. In addition, EA treatment promoted POMC expression, which may be associated with reduced food intake and weight loss in obese mice. This work provides novel evidence of EA against obesity. However, further study is necessary of EA as a therapy for obesity.

Transcriptomic, Epigenomic, and Neuroanatomic Signatures Differ in Chronic Prurigo, Atopic Dermatitis, and Brachioradial Pruritus

Scratching and scratch-induced injuries, including neuroanatomical alterations, are key characteristics of chronic pruritus entities of different origins. The aim of this study was to link gene expression (array hybridization, qPCR) with DNA methylation (array hybridization) and neuroanatomy (PGP9.5 staining) in chronic nodular prurigo (CNPG), atopic dermatitis (AD), brachioradial pruritus (BRP), and matched healthy controls. Specific signatures of gene expression and DNA methylation clearly discriminated pruritic lesional skin from nonpruritic skin in CNPG and from healthy skin of volunteers, respectively. Although intraepidermal nerve fiber density was indiscriminately reduced, the level of epidermal branching, assessed by a semiquantitative pattern analysis, differentiated the entities (CNPG > BRP > AD). Correspondingly, repellent SEMA3A showed the highest expression in AD, whereas axonal growth-promoting nerve GF was most prominent in CNPG and BRP. Overexpression of genes for nerve fiber regeneration (NELL2/NFKB/ARTN) was found in AD and CNPG but not in BRP. Our findings suggest that differential branching patterns rather than mere innervation density separate chronic itch conditions and reflect disease-specific local expression profiles. In pruritic dermatoses (AD and CNPG), nerve injury and subsequent sprouting may primarily result from chronic scratching, whereas genuine neuropathy is expected to underlie BRP.

Statins' Effect on Cognitive Outcome After Traumatic Brain Injury: A Systematic Review

Traumatic brain injury (TBI), also known as the "Silent Epidemic," is a growing devastating global health problem estimated to affect millions of individuals yearly worldwide with little public recognition, leading to many individuals living with a TBI-related disability. TBI has been associated with up to five times increase in the risk of dementia among multiple neurologic complications compared with the general population. Several therapies, including statins, have been tried and showed promising benefits for TBI patients. In this systematic review, we evaluated the recent literature that tested the role of statins on neurological and cognitive outcomes such as Alzheimer's Disease and non-Alzheimer's dementia in survivors of TBI with various severities. We conducted a systematic search on PubMed, PubMed Central, MEDLINE, and Google Scholar. MeSH terms and keywords were used to search for full-text randomized clinical trials (RCTs), cross-sectional, case-control, cohort studies, systematic reviews, and animal studies published in English. Inclusion and exclusion criteria were applied, and the articles were subjected to quality appraisal by two reviewers. Our data search retrieved 4948 nonduplicate records. A total of 18 studies were included - nine human studies, and nine animal laboratory trials - after meeting inclusion, eligibility, and quality assessment criteria. Simvastatin was the most tested statin, and the oral route of administration was the most used. Eight human studies showed a significant neuroprotective effect and improvement in the cognitive outcomes, including dementia. Four randomized clinical trials with 296 patients showed that statins play a neuroprotective role and improve cognitive outcomes through different mechanisms, especially their anti-inflammatory effect; they were shown to lower tumor necrosis factor (TNF)-α and C-reactive protein (CRP) levels. Also, they decreased axonal injury and cortical thickness changes. In addition, four cohort studies compared a total of 867.953 patients. One study showed a decrease in mortality in statin-treated patients (p=0.05). Another study showed a reduction in the incidence of Alzheimer's disease and related dementias (RR, 0.77; 95% CI, 0.73-0.81), while one study showed a decreased risk of dementia after concussions by 6.13% (p=0.001). On the other hand, one cohort study showed no significant difference with the use of statins. In eight animal trials, statins showed a significant neuroprotective effect, improved cognitive outcomes, and neurological functions. Different molecular and cellular mechanisms were suggested, including anti-inflammatory effects, promoting angiogenesis, neurogenesis, increasing cerebral blood flow, neurite outgrowth, promoting the proliferation and differentiation of neural stem cells, and reducing axonal injury. On the contrary, one study showed no benefit and actual adverse effect on the cognitive outcome. Most of the studies showed promising neuroprotective effects of statins in TBI patients. Cognitive outcomes, especially dementia, were improved. However, the optimal therapeutic protocol is still unknown. Thus, statins are candidates for more advanced studies to test their efficacy in preventing cognitive decline in patients with TBI.

Mitochondrial-nuclear p53 trafficking controls neuronal susceptibility in stroke

Stroke is a major cause of death and long-term disability in the adult. Neuronal apoptosis plays an essential role in the pathophysiology of ischemic brain damage and impaired functional recovery after stroke. The tumor suppressor protein p53 regulates key cellular processes, including cell cycle arrest, DNA repair, senescence, and apoptosis. Under cellular stress conditions, p53 undergoes post-translational modifications, which control protein localization, stability, and proapoptotic activity. After stroke, p53 rapidly accumulates in the ischemic brain, where it activates neuronal apoptosis through both transcriptional-dependent and -independent programs. Over the last years, subcellular localization of p53 has emerged as an important regulator of ischemia-induced neuronal apoptosis. Upon an ischemic insult, p53 rapidly translocates to the mitochondria and interacts with B-cell lymphoma-2 family proteins, which activate the mitochondrial apoptotic program, with higher efficacy than through its activity as a transcription factor. Moreover, the identification of a human single nucleotide polymorphism at codon 72 of the Tp53 gene that controls p53 mitochondrial localization and cell susceptibility to apoptosis supports the important role of the p53 mitochondrial program in neuronal survival and functional recovery after stroke. In this article, we review the relevance of mitochondrial and nuclear localization of p53 on neuronal susceptibility to cerebral ischemia and its impact on functional outcome of stroke patients.

The AAA + ATPase Thorase is neuroprotective against ischemic injury

Neuronal preconditioning in vitro or in vivo with a stressful but non-lethal stimulus leads to new protein expression that mediates a profound neuroprotection against glutamate excitotoxicity and experimental stroke. The proteins that mediate neuroprotection are relatively unknown and under discovery. Here we find that the expression of the AAA + ATPase Thorase is induced by preconditioning stimulation both in vitro and in vivo. Thorase provides neuroprotection in an ATP-dependent manner against oxygen-glucose deprivation (OGD) neurotoxicity or glutamate N-Methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity in vitro. Knock-down of Thorase prevents the establishment of preconditioning induced neuroprotection against OGD or NMDA neurotoxicity. Transgenic overexpression of Thorase provides neuroprotection in vivo against middle cerebral artery occlusion (MCAO)-induced stroke in mice, while genetic deletion of Thorase results in increased injury in vivo following stroke. These results define Thorase as a neuroprotective protein and understanding Thorase signaling could offer a new therapeutic strategy for the treatment of neurologic disorders.

MAPKs and NF-κB-mediated acrylamide-induced neuropathy in rat striatum and human neuroblastoma cells SY5Y

Acrylamide (ACR) is a potent neurotoxin that can be produced during high-temperature food processing, but the underlying toxicological mechanism remains unclear. In this study, the detrimental effects of ACR on the striatal dopaminergic neurons and the roles of mitogen-activated protein kinases (MAPKs) and nuclear factor κB (NF-κB) in ACR-induced neuronal apoptosis were investigated. Acute ACR exposure caused dopaminergic neurons loss and apoptosis as revealed by decreased tyrosine hydroxylase (TH)-positive cells and TH protein level and increased terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive cells in the striatum. ACR-decreased glutathione content, increased levels of malondialdehyde, proinflammatory cytokines tumor necrosis factor α, and interleukin 6. In addition, nuclear NF-κB and MAPKs signaling pathway with c-Jun N-terminal kinase (JNK) and p38 were activated by ACR. Specific inhibitors were used to explore the roles of MAPKs and NF-κB pathways in ACR-induced apoptosis in SH-SY5Y cells. Pretreatment with JNK-specific inhibitors SP600125 markedly upregulated the reduced B-cell lymphoma 2 (Bcl-2) content and downregulated the increased Bcl-2-associated X protein (Bax) level and thereby eventually reduced the proportions of early and late apoptotic cells induced by ACR, while p38 suppression by SB202190 only reversed the decrease in Bcl-2 expression. Inhibition of NF-κB by BAY 11-7082 markedly upregulated Bax level and decreased Bcl-2 expression, and eventually increasing the proportions of neuronal apoptosis compared with that in ACR alone. These results suggested that JNK contributed to ACR-induced apoptosis, while NF-κB acted as a protective regulator in response to ACR-induced neuropathy. This study helps to offer a deeper insight into the mechanism of ACR-induced neuropathy.

Tamoxifen overrides autophagy inhibition in Beclin-1-deficient glioma cells and their resistance to adenovirus-mediated oncolysis via upregulation of PUMA and BAX

Autophagy is an evolutionarily conserved process regulating cellular homeostasis via digestion of dysfunctional proteins and whole cellular organelles by mechanisms, involving their enclosure into double-membrane vacuoles that are subsequently fused to lysosomes. Glioma stem cells utilize autophagy as a main mechanism of cell survival and stress response. Most recently, we and others demonstrated induction of autophagy in gliomas in response to treatment with chemical drugs, such as temozolomide (TMZ) or oncolytic adenoviruses (Ads). As autophagy has been implicated in the mechanism of Ad-mediated cell killing, autophagy deficiency in some glioma tumors could be the reason for their resistance to oncolysis. Despite the observed connection, the exact relationship between autophagy-activating cell signaling and adenoviral infection remains unclear. Here, we report that inhibition of autophagy in target glioma cells induces their resistance to killing by oncolytic agent CRAd-S-5/3. Furthermore, we found that downregulation of autophagy inducer Beclin-1 inhibits replication-competent Ad-induced oncolysis of human glioma by suppressing cell proliferation and inducing premature senescence. To overcome the autophagy-deficient state of such glioma cells and restore their susceptibility to oncolytic Ad infection, we propose treating glioma tumors with an anticancer drug tamoxifen (TAM) as a means to induce apoptosis in Ad-targeted cancer cells via upregulation of BAX/PUMA genes. In agreement with the above hypothesis, our data suggest that TAM improves susceptibility of Beclin-1-deficient glioma cells to CRAd-S-5/3 oncolysis by means of activating autophagy and pro-apoptotic signaling pathways in the target cancer cells.

Exploring the selective vulnerability in Alzheimer disease using tissue specific variant analysis

The selective vulnerability of distinct regions of the brain is a critical factor in neurodegenerative disorders. In Alzheimer's disease (AD), neurons in hippocampus situated in medial temporal lobe are immensely damaged. Identifying tissue-specific variants is essential in order to perceive the selective vulnerability in AD. In current work, we aligned mRNA-seq data with HG19/HG38 genomic assembly and identified specific variations present in temporal, frontal and other lobes of the AD using sequence alignment map tools. We compared the results with the genome-wide association and gene expression quantitative trait loci studies of the various neurological disorders. We also distinguished variants and epitranscriptomic modifications through the RNA-modification database and evaluated the variant effect in the coding/UTR regions. In addition, we developed genetic and functional interaction networks to understand the relationship between predicted vulnerable variations and differentially expressed genes. We found that genes involved in gliogenesis, intermediate filament organization are altered in the temporal lobe. Oxidative phosphorylation, and calcium ion homeostasis are modified in the frontal lobe, and protein degradation, apoptotic signaling are altered in other lobes. From this study, we propose that disruption of glial cell structural integrity, defective gliogenesis, and failure in glia-neuron communication are the primary factors for selective vulnerability.

Inhibition of p53 prevents diabetic cardiomyopathy by preventing early-stage apoptosis and cell senescence, reduced glycolysis, and impaired angiogenesis

Elevated tumor suppressor p53 expression has been associated with heart diseases, including the diabetic heart. However, its precise role in the pathogenesis of diabetic cardiomyopathy (DCM) remains unclear. We hypothesized that the development of DCM is attributed to up-regulated p53-mediated both early cardiac cell death and persistent cell senescence, glycolytic and angiogenetic dysfunctions. The present study investigated the effect of p53 inhibition with its specific inhibitor pifithrin-α (PFT-α) on the pathogenesis of DCM and its associated mechanisms. Type 1 diabetes was induced with multiple low doses of streptozotocin. Both hyperglycemic and age-matched control mice were treated with and without PFT-α five times a week for 2 months and then sacrificed at 3 and 6 months post-diabetes. Treatment with PFT-α significantly prevented the progression of diabetes-induced cardiac remodeling and dysfunction (i.e., DCM). Mechanistically, the inhibition of p53 prevented the cardiac apoptosis during early-stage diabetes (0.5 month), attenuated diabetes-induced cell senescence (3 and 6 months), and improved both glycolytic and angiogenic defects by increasing hypoxia-induced factor (HIF)-1α protein stability and upregulating HIF-1α transcription of specific target genes at 3 and 6 months after diabetes. Therefore, the targeted inhibition of p53 in diabetic individuals may provide a novel approach for the prevention of DCM.

Small chaperons and autophagy protected neurons from necrotic cell death

Neuronal necrosis occurs during early phase of ischemic insult. However, our knowledge of neuronal necrosis is still inadequate. To study the mechanism of neuronal necrosis, we previously established a Drosophila genetic model of neuronal necrosis by calcium overloading through expression of a constitutively opened cation channel mutant. Here, we performed further genetic screens and identified a suppressor of neuronal necrosis, CG17259, which encodes a seryl-tRNA synthetase. We found that loss-of-function (LOF) CG17259 activated eIF2α phosphorylation and subsequent up-regulation of chaperons (Hsp26 and Hsp27) and autophagy. Genetically, down-regulation of eIF2α phosphorylation, Hsp26/Hsp27 or autophagy reduced the protective effect of LOF CG17259, indicating they function downstream of CG17259. The protective effect of these protein degradation pathways indicated activation of a toxic protein during neuronal necrosis. Our data indicated that p53 was likely one such protein, because p53 was accumulated in the necrotic neurons and down-regulation of p53 rescued necrosis. In the SH-SY5Y human cells, tunicamycin (TM), a PERK activator, promoted transcription of hsp27; and necrosis induced by glutamate could be rescued by TM, associated with reduced p53 accumulation. In an ischemic stroke model in rats, p53 protein was also increased, and TM treatment could reduce the p53 accumulation and brain damage.

Sex differences in vascular physiology and pathophysiology: estrogen and androgen signaling in health and disease

Sex differences between women and men are often overlooked and underappreciated when studying the cardiovascular system. It has been long assumed that men and women are physiologically similar, and this notion has resulted in women being clinically evaluated and treated for cardiovascular pathophysiological complications as men. Currently, there is increased recognition of fundamental sex differences in cardiovascular function, anatomy, cell signaling, and pathophysiology. The National Institutes of Health have enacted guidelines expressly to gain knowledge about ways the sexes differ in both normal function and diseases at the various research levels (molecular, cellular, tissue, and organ system). Greater understanding of these sex differences will be used to steer future directions in the biomedical sciences and translational and clinical research. This review describes sex-based differences in the physiology and pathophysiology of the vasculature, with a special emphasis on sex steroid receptor (estrogen and androgen receptor) signaling and their potential impact on vascular function in health and diseases (e.g., atherosclerosis, hypertension, peripheral artery disease, abdominal aortic aneurysms, cerebral aneurysms, and stroke).

TNFα drives mitochondrial stress in POMC neurons in obesity

Consuming a calorically dense diet stimulates microglial reactivity in the mediobasal hypothalamus (MBH) in association with decreased number of appetite-curbing pro-opiomelanocortin (POMC) neurons; whether the reduction in POMC neuronal function is secondary to the microglial activation is unclear. Here we show that in hypercaloric diet-induced obese mice, persistently activated microglia in the MBH hypersecrete TNFα that in turn stimulate mitochondrial ATP production in POMC neurons, promoting mitochondrial fusion in their neurites, and increasing POMC neuronal firing rates and excitability. Specific disruption of the gene expressions of TNFα downstream signals TNFSF11A or NDUFAB1 in the MBH of diet-induced obese mice reverses mitochondrial elongation and reduces obesity. These data imply that in a hypercaloric environment, persistent elevation of microglial reactivity and consequent TNFα secretion induces mitochondrial stress in POMC neurons that contributes to the development of obesity.

Combining Oncolytic Virotherapy with p53 Tumor Suppressor Gene Therapy

Oncolytic virus (OV) therapy utilizes replication-competent viruses to kill cancer cells, leaving non-malignant cells unharmed. With the first U.S. Food and Drug Administration-approved OV, dozens of clinical trials ongoing, and an abundance of translational research in the field, OV therapy is poised to be one of the leading treatments for cancer. A number of recombinant OVs expressing a transgene for p53 (TP53) or another p53 family member (TP63 or TP73) were engineered with the goal of generating more potent OVs that function synergistically with host immunity and/or other therapies to reduce or eliminate tumor burden. Such transgenes have proven effective at improving OV therapies, and basic research has shown mechanisms of p53-mediated enhancement of OV therapy, provided optimized p53 transgenes, explored drug-OV combinational treatments, and challenged canonical roles for p53 in virus-host interactions and tumor suppression. This review summarizes studies combining p53 gene therapy with replication-competent OV therapy, reviews preclinical and clinical studies with replication-deficient gene therapy vectors expressing p53 transgene, examines how wild-type p53 and p53 modifications affect OV replication and anti-tumor effects of OV therapy, and explores future directions for rational design of OV therapy combined with p53 gene therapy.

3-Hydroxybutyrate regulates energy metabolism and induces BDNF expression in cerebral cortical neurons

During fasting and vigorous exercise, a shift of brain cell energy substrate utilization from glucose to the ketone 3-hydroxybutyrate (3OHB) occurs. Studies have shown that 3OHB can protect neurons against excitotoxicity and oxidative stress, but the underlying mechanisms remain unclear. Neurons maintained in the presence of 3OHB exhibited increased oxygen consumption and ATP production, and an elevated NAD⁺ /NADH ratio. We found that 3OHB metabolism increases mitochondrial respiration which drives changes in expression of brain-derived neurotrophic factor (BDNF) in cultured cerebral cortical neurons. The mechanism by which 3OHB induces Bdnf gene expression involves generation of reactive oxygen species, activation of the transcription factor NF-κB, and activity of the histone acetyltransferase p300/EP300. Because BDNF plays important roles in synaptic plasticity and neuronal stress resistance, our findings suggest cellular signaling mechanisms by which 3OHB may mediate adaptive responses of neurons to fasting, exercise, and ketogenic diets.

Conditional abrogation of Atm in osteoclasts extends osteoclast lifespan and results in reduced bone mass

Ataxia-telangiectasia mutated (ATM) kinase is a central component involved in the signal transduction of the DNA damage response (DDR) and thus plays a critical role in the maintenance of genomic integrity. Although the primary functions of ATM are associated with the DDR, emerging data suggest that ATM has many additional roles that are not directly related to the DDR, including the regulation of oxidative stress signaling, insulin sensitivity, mitochondrial homeostasis, and lymphocyte development. Patients and mice lacking ATM exhibit growth retardation and lower bone mass; however, the mechanisms underlying the skeletal defects are not fully understood. In the present study, we generated mutant mice in which ATM is specifically inactivated in osteoclasts. The mutant mice did not exhibit apparent developmental defects but showed reduced bone mass due to increased osteoclastic bone resorption. Osteoclasts lacking ATM were more resistant to apoptosis and showed a prolonged lifespan compared to the controls. Notably, the inactivation of ATM in osteoclasts resulted in enhanced NF-κB signaling and an increase in the expression of NF-κB-targeted genes. The present study reveals a novel function for ATM in regulating bone metabolism by suppressing the lifespan of osteoclasts and osteoclast-mediated bone resorption.

Regenerative repair of Pifithrin-α in cerebral ischemia via VEGF dependent manner

Promoting regenerative repair, including neurogenesis and angiogenesis, may provide a new therapeutic strategy for treatment of stroke. P53, a well-documented transcription factor, has been reported to be involved in cerebral ischemia and also serves as an important regulator of vascular endothelial growth factor (VEGF). However, the role of p53 in endogenous regenerative repair after brain ischemia is poorly understood. In this study, we investigated the effects of PFT-α, a specific p53 inhibitor on neurogenesis and angiogenesis improvement and associated signal pathways in rats impaired by cerebral artery occlusion (MCAo). PFT-α induced neuroprotection, reduced infarct volume and neurological functional impairment after ischemic stroke. More importantly, neurogenesis and angiogenesis were greatly enhanced by PFT-α, and accompanied by increased expression of VEGF. Moreover, we got consistent results in neural stem cells (NSCs) isolated from fetal rats. In contrast, application of the anti-VEGF neutralizing antibody (RB-222) partially reversed PFT-α-induced neuroprotection and rescued p53 expression. Noteworthily, inhibition of p53 after ischemic stroke in these rats improved their outcomes via promotion of regenerative repair. In conclusion, PFT-α could serve as a promising therapeutic strategy for ischemic stroke by promoting regenerative repair.

Feedback modulation of neural network synchrony and seizure susceptibility by Mdm2-p53-Nedd4-2 signaling

Background

Neural network synchrony is a critical factor in regulating information transmission through the nervous system. Improperly regulated neural network synchrony is implicated in pathophysiological conditions such as epilepsy. Despite the awareness of its importance, the molecular signaling underlying the regulation of neural network synchrony, especially after stimulation, remains largely unknown.

Results

In this study, we show that elevation of neuronal activity by the GABA(A) receptor antagonist, Picrotoxin, increases neural network synchrony in primary mouse cortical neuron cultures. The elevation of neuronal activity triggers Mdm2-dependent degradation of the tumor suppressor p53. We show here that blocking the degradation of p53 further enhances Picrotoxin-induced neural network synchrony, while promoting the inhibition of p53 with a p53 inhibitor reduces Picrotoxin-induced neural network synchrony. These data suggest that Mdm2-p53 signaling mediates a feedback mechanism to fine-tune neural network synchrony after activity stimulation. Furthermore, genetically reducing the expression of a direct target gene of p53, Nedd4-2, elevates neural network synchrony basally and occludes the effect of Picrotoxin. Finally, using a kainic acid-induced seizure model in mice, we show that alterations of Mdm2-p53-Nedd4-2 signaling affect seizure susceptibility.

Conclusion

Together, our findings elucidate a critical role of Mdm2-p53-Nedd4-2 signaling underlying the regulation of neural network synchrony and seizure susceptibility and reveal potential therapeutic targets for hyperexcitability-associated neurological disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/s13041-016-0214-6) contains supplementary material, which is available to authorized users.

Reciprocal regulation of p53 and NF-κB by diacylglycerol kinase ζ

Diacylglycerol kinase (DGK) participates in lipid mediated-signal transduction. It phosphorylates diacylglycerol (DG) to phosphatidic acid (PA), thereby regulating the balanced control of these second messenger actions. Previous reports have described that one DGK family, DGKζ, is closely involved in stress responses under various conditions. Cellular stress response, a physiological process enabling cells to cope with an altered environment, is finely tuned through various signaling cascades and their molecular crosstalk. The major components of stress response are p53 and NF-κB. p53 generally serves as a proapoptotic transcriptional factor, whereas NF-κB promotes resistance to programmed cell death under most circumstances. Recent studies have suggested that DGKζ facilitates p53 degradation in cytoplasm through ubiquitin proteasome system and that DGKζ deletion upregulates p53 protein levels under basal and DNA-damage conditions. Counter-intuitively, however, DGKζ deletion suppresses p53 transcriptional activity despite increased p53 levels. In contrast, DGKζ knockdown engenders enhancement of NF-κB pathway in response to cytokines such as TNF-α and IL-1β. In response to these cytokines, DGKζ downregulation accelerates phosphorylation of the p65 subunit and its nuclear translocation, thereby enhancing NF-κB transcriptional activity. Furthermore, DGKζ deficiency is shown to promote increased association of p65 subunit with the transcriptional cofactor CBP. It is particularly interesting that this association is observed even under basal conditions in the absence of stimulation. These findings suggest that DGKζ plays a role in sequestration of the limiting pool of CBP/p300 between the NF-κB p65 subunit and p53, and that DGKζ downregulation shifts CBP/p300 toward the NF-κB subunit to regulate reciprocally antagonistic phenotypes of these transcription factors.

Pifithrin-α provides neuroprotective effects at the level of mitochondria independently of p53 inhibition

Impaired mitochondrial integrity and function are key features of intrinsic death pathways in neuronal cells. Therefore, key regulators of intrinsic death pathways acting upstream of mitochondria are potential targets for therapeutic approaches of neuroprotection. The tumor suppressor p53 is a well-established regulator of cellular responses towards different kinds of lethal stress, including oxidative stress. Recent reports suggested that p53 may affect mitochondrial integrity and function through both, transcriptional activation of mitochondria-targeted pro-death proteins and direct effects at the mitochondrial membrane. In the present study, we compared the effects of pharmacological inhibition of p53 by pifithrin-α with those of selective p53 gene silencing by RNA interference. Using MTT assay and real-time cell impedance measurements we confirmed the protective effect of both strategies against glutamate-induced oxidative stress in immortalized mouse hippocampal HT-22 neurons. Further, we observed full restoration of mitochondrial membrane potential and inhibition of glutamate-induced mitochondrial fragmentation by pifithrin-α which was, in contrast, not achieved by p53 gene silencing. Downregulation of p53 by siRNA decreased p53 transcriptional activity and reduced expression levels of p21 mRNA, while pifithrin-α did not affect these endpoints. These results suggest a neuroprotective effect of pifithrin-α which occurred at the level of mitochondria and independently of p53 inhibition.

Hypothalamic innate immune reaction in obesity

Findings from rodent and human studies show that the presence of inflammatory factors is positively correlated with obesity and the metabolic syndrome. Obesity-associated inflammatory responses take place not only in the periphery but also in the brain. The hypothalamus contains a range of resident glial cells including microglia, macrophages and astrocytes, which are embedded in highly heterogenic groups of neurons that control metabolic homeostasis. This complex neural-glia network can receive information directly from blood-borne factors, positioning it as a metabolic sensor. Following hypercaloric challenge, mediobasal hypothalamic microglia and astrocytes enter a reactive state, which persists during diet-induced obesity. In established mouse models of diet-induced obesity, the hypothalamic vasculature displays angiogenic alterations. Moreover, proopiomelanocortin neurons, which regulate food intake and energy expenditure, are impaired in the arcuate nucleus, where there is an increase in local inflammatory signals. The sum total of these events is a hypothalamic innate immune reactivity, which includes temporal and spatial changes to each cell population. Although the exact role of each participant of the neural-glial-vascular network is still under exploration, therapeutic targets for treating obesity should probably be linked to individual cell types and their specific signalling pathways to address each dysfunction with cell-selective compounds.

An unexpected inhibition of antiviral signaling by virus-encoded tumor suppressor p53 in pancreatic cancer cells

Virus-encoded tumor suppressor p53 transgene expression has been successfully used in vesicular stomatitis virus (VSV) and other oncolytic viruses (OVs) to enhance their anticancer activities. However, p53 is also known to inhibit virus replication via enhanced type I interferon (IFN) antiviral responses. To examine whether p53 transgenes enhance antiviral signaling in human pancreatic ductal adenocarcinoma (PDAC) cells, we engineered novel VSV recombinants encoding human p53 or the previously described chimeric p53-CC, which contains the coiled-coil (CC) domain from breakpoint cluster region (BCR) protein and evades the dominant-negative activities of endogenously expressed mutant p53. Contrary to an expected enhancement of antiviral signaling by p53, our global analysis of gene expression in PDAC cells showed that both p53 and p53-CC dramatically inhibited type I IFN responses. Our data suggest that this occurs through p53-mediated inhibition of the NF-κB pathway. Importantly, VSV-encoded p53 or p53-CC did not inhibit antiviral signaling in non-malignant human pancreatic ductal cells, which retained their resistance to all tested VSV recombinants. To the best of our knowledge, this is the first report of p53-mediated inhibition of antiviral signaling, and it suggests that OV-encoded p53 can simultaneously produce anticancer activities while assisting, rather than inhibiting, virus replication in cancer cells.

Post-trauma administration of the pifithrin-α oxygen analog improves histological and functional outcomes after experimental traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. Programmed death of neuronal cells plays a crucial role in acute and chronic neurodegeneration following TBI. The tumor suppressor protein p53, a transcription factor, has been recognized as an important regulator of apoptotic neuronal death. The p53 inactivator pifithrin-α (PFT-α) has been shown to be neuroprotective against stroke. A previous cellular study indicated that PFT-α oxygen analog (PFT-α (O)) is more stable and active than PFT-α. We aimed to investigate whether inhibition of p53 using PFT-α or PFT-α (O) would be a potential neuroprotective strategy for TBI. To evaluate whether these drugs protect against excitotoxicity in vitro, primary rat cortical cultures were challenged with glutamate (50mM) in the presence or absence of various concentrations of the p53 inhibitors PFT-α or PFT-α (O). Cell viability was estimated by LDH assay. In vivo, adult Sprague Dawley rats were subjected to controlled cortical impact (CCI, with 4m/s velocity, 2mm deformation). Five hours after injury, PFT-α or PFT-α (O) (2mg/kg, i.v.) was administered to animals. Sensory and motor functions were evaluated by behavioral tests at 24h after TBI. The p53-positive neurons were identified by double staining with cell-specific markers. Levels of mRNA encoding for p53-regulated genes (BAX, PUMA, Bcl-2 and p21) were measured by reverse transcription followed by real time-PCR from TBI animals without or with PFT-α/PFT-α (O) treatment. We found that PFT-α(O) (10 μM) enhanced neuronal survival against glutamate-induced cytotoxicity in vitro more effectively than PFT-α (10 μM). In vivo PFT-α (O) treatment enhanced functional recovery and decreased contusion volume at 24h post-injury. Neuroprotection by PFT-α (O) treatment also reduced p53-positive neurons in the cortical contusion region. In addition, p53-regulated PUMA mRNA levels at 8h were significantly reduced by PFT-α (O) administration after TBI. PFT-α (O) treatment also decreased phospho-p53 positive neurons in the cortical contusion region. Our data suggest that PFT-α (O) provided a significant reduction of cortical cell death and protected neurons from glutamate-induced excitotoxicity in vitro, as well as improved neurological functional outcome and reduced brain injury in vivo via anti-apoptotic mechanisms. The inhibition of p53-induced apoptosis by PFT-α (O) provides a useful tool to evaluate reversible apoptotic mechanisms and may develop into a novel therapeutic strategy for TBI.

Interaction of p53 with prolyl isomerases: Healthy and unhealthy relationships

BACKGROUND

The p53 protein family, comprising p53, p63 and p73, is primarily involved in preserving genome integrity and preventing tumor onset, and also affects a range of physiological processes. Signal-dependent modifications of its members and of other pathway components provide cells with a sophisticated code to transduce a variety of stress signaling into appropriate responses. TP53 mutations are highly frequent in cancer and lead to the expression of mutant p53 proteins that are endowed with oncogenic activities and sensitive to stress signaling.

SCOPE OF REVIEW

p53 family proteins have unique structural and functional plasticity, and here we discuss the relevance of prolyl-isomerization to actively shape these features.

MAJOR CONCLUSIONS

The anti-proliferative functions of the p53 family are carefully activated upon severe stress and this involves the interaction with prolyl-isomerases. In particular, stress-induced stabilization of p53, activation of its transcriptional control over arrest- and cell death-related target genes and of its mitochondrial apoptotic function, as well as certain p63 and p73 functions, all require phosphorylation of specific S/T-P motifs and their subsequent isomerization by the prolyl-isomerase Pin1. While these functions of p53 counteract tumorigenesis, under some circumstances their activation by prolyl-isomerases may have negative repercussions (e.g. tissue damage induced by anticancer therapies and ischemia-reperfusion, neurodegeneration). Moreover, elevated Pin1 levels in tumor cells may transduce deregulated phosphorylation signaling into activation of mutant p53 oncogenic functions.

GENERAL SIGNIFICANCE

The complex repertoire of biological outcomes induced by p53 finds mechanistic explanations, at least in part, in the association between prolyl-isomerases and the p53 pathway. This article is part of a Special Issue entitled Proline-directed foldases: Cell signaling catalysts and drug targets.

Toxic effects of mildly elevated homocysteine concentrations in neuronal-like cells

Epidemiological and experimental evidence indicated that hyperhomocysteinemia is associated with neurodegeneration. However, homocysteine neurotoxic effects have been so far investigated mostly by employing homocysteine concentrations (≥100 µM) much higher than homocysteine mean plasma levels (20 µM) observed in patients with neurodegenerative disorders. While evaluating the effects of a prolonged exposure to ~20 µM homocysteine in neuronal-like differentiated SH-SY5Y cells, we observed a 35% loss of cell viability and a four-fold increase in reactive oxygen species levels in cells incubated with homocysteine for five days compared with controls. Moreover, homocysteine increased by 30% and around two-fold, respectively, the Comet-positive cell number and DNA damage indexes (tail length, T-DNA, olive tail moment) compared with controls. Cell response to homocysteine-induced DNA damage involved the up-regulation of Bax and, at a greater extent, Bcl-2, but not caspase-3, in association with a p53-independent increase of p21 levels; concomitantly, also p16 levels were increased. When looking at time-dependent changes in cyclin expression, we found that a significant up-regulation of cyclins D1, A1, E1, but not B1, concomitant with p21 down-regulation, occurred in cells incubated with homocysteine for three days. However, in line with the observed increase of p21 and p16 levels, a five days incubation with homocysteine induced cyclin down-regulation accompanied by a strong reduction of phosphorylated pRB amounts. These results suggest that, when prolonged, the exposure of neuronal-like cells to mildly elevated homocysteine concentrations triggers oxidative and genotoxic stress involving an early induction of cyclins, that is late repressed by G1-S check-point regulators.

Cognitive impairments accompanying rodent mild traumatic brain injury involve p53-dependent neuronal cell death and are ameliorated by the tetrahydrobenzothiazole PFT-α

With parallels to concussive mild traumatic brain injury (mTBI) occurring in humans, anesthetized mice subjected to a single 30 g weight drop mTBI event to the right parietal cortex exhibited significant diffuse neuronal degeneration that was accompanied by delayed impairments in recognition and spatial memory. To elucidate the involvement of reversible p53-dependent apoptosis in this neuronal loss and associated cognitive deficits, mice were subjected to experimental mTBI followed by the systemic administration of the tetrahydrobenzothiazole p53 inactivator, PFT-α, or vehicle. Neuronal loss was quantified immunohistochemically at 72 hr. post-injury by the use of fluoro-Jade B and NeuN within the dentate gyrus on both sides of the brain, and recognition and spatial memory were assessed by novel object recognition and Y-maze paradigms at 7 and 30 days post injury. Systemic administration of a single dose of PFT-α 1 hr. post-injury significantly ameliorated both neuronal cell death and cognitive impairments, which were no different from sham control animals. Cellular studies on human SH-SY5Y cells and rat primary neurons challenged with glutamate excitotoxicity and H₂O₂ induced oxidative stress, confirmed the ability of PFT-α and a close analog to protect against these TBI associated mechanisms mediating neuronal loss. These studies suggest that p53-dependent apoptotic mechanisms underpin the neuronal and cognitive losses accompanying mTBI, and that these are potentially reversible by p53 inactivation.

Current overview of functions of FoxO proteins, with special regards to cellular homeostasis, cell response to stress, as well as inflammation and aging

FoxO transcription factors act at the interconnections between metabolic pathways inducible by many important signal transducers and mediators, such as p53, Ikk-β, NFKB, Akt, sirtuins, PTEN, and others. This may account for a crucial significance of disruptions in FoxO functions both in many kinds of diseases (including cancer, chronic inflammatory diseases, degenerative diseases, obesity, polymetabolic syndrome) and in some disease-like conditions (such as inflammaging, cachexia related to chronic inflammation, cancer-promotion by some chronic inflammatory responses, and the aging process itself). This paper reviews complex interactions between FoxOs and other signal transducers, trying to pinpoint how exactly disruptions of FoxO functions may occur, and how they may contribute to occurrence, development or complications of the conditions mentioned above.

Sunitinib enhances neuronal survival in vitro via NF-κB-mediated signaling and expression of cyclooxygenase-2 and inducible nitric oxide synthase

BACKGROUND

Angiogenesis is tightly linked to inflammation and cancer. Regulation of angiogenesis is mediated primarily through activation of receptor tyrosine kinases, thus kinase inhibitors represent a new paradigm in anti-cancer therapy. However, these inhibitors have broad effects on inflammatory processes and multiple cell types. Sunitinib is a multitarget receptor tyrosine kinase inhibitor, which has shown promise for the treatment of glioblastoma, a highly vascularized tumor. However, there is little information as to the direct effects of sunitinib on brain-derived neurons. The objective of this study is to explore the effects of sunitinib on neuronal survival as well as on the expression of inflammatory protein mediators in primary cerebral neuronal cultures.

METHODS

Primary cortical neurons were exposed to various doses of sunitinib. The drug-treated cultures were assessed for survival by MTT assay and cell death by lactate dehydrogenase release. The ability of sunitinib to affect NF-κB, COX2 and NOS2 expression was determined by western blot. The NF-κB inhibitors dicoumarol, SN50 and BAY11-7085 were employed to assess the role of NF-κB in sunitinib-mediated effects on neuronal survival as well as COX2 and NOS2 expression.

RESULTS

Treatment of neuronal cultures with sunitinib caused a dose-dependent increase in cell survival and decrease in neuronal cell death. Exposure of neurons to sunitinib also induced an increase in the expression of NF-κB, COX2 and NOS2. Inhibiting NF-κB blunted the increase in cell survival and decrease in cell death evoked by sunitinib. Treatment of cell cultures with both sunitinib and NF-κB inhibitors mitigated the increase in COX2 and NOS2 caused by sunitinib.

CONCLUSIONS

Sunitinib increases neuronal survival and this neurotrophic effect is mediated by NF-κB. Also, the inflammatory proteins COX2 and NOS2 are upregulated by sunitinib in an NF-κB-dependent manner. These data are in agreement with a growing literature suggesting beneficial effects for inflammatory mediators such as NF-κB, COX2 and NOS2 in neurons. Further work is needed to fully explore the effects of sunitinib in the brain and its possible use as a treatment for glioblastoma. Finally, sunitinib may be useful for the treatment of a range of central nervous system diseases where neuronal injury is prominent.

Peroxiredoxin 2 battles poly(ADP-ribose) polymerase 1- and p53-dependent prodeath pathways after ischemic injury

BACKGROUND AND PURPOSE

Ischemic/reperfusion neuronal injury is characterized by accumulation of reactive oxygen species and oxidative DNA damage, which can trigger cell death by various signaling pathways. Two of these modes of death include poly(ADP-ribose) polymerase 1-mediated death or p53- and Bax-mediated apoptosis. The present study tested the hypothesis that peroxiredoxin 2 (PRX2) attenuates DNA damage-mediated prodeath signaling using in vitro and in vivo models of ischemic injury. The impact of this peroxide scavenger on p53- and poly(ADP-ribose) polymerase 1-mediated ischemic death is unknown.

METHODS

Neuronal PRX2 overexpression in primary cortical cultures and transgenic mice was combined with the poly(ADP-ribose) polymerase 1 inhibitor AG14361. AG14361 was also applied to p53 and Bax knockout cultures and mice and combined with the JNK inhibitor SP600125. DCF fluorescence, apurinic/apyrimidinic sites, single-strand breaks, Comet tail-length, nicotinamide adenine dinucleotide depletion, and viability were assessed in response to oxygen-glucose deprivation in cultures or transient focal cerebral ischemia in mice.

RESULTS

PRX2 attenuated reactive oxygen species, DNA damage, nicotinamide adenine dinucleotide depletion, and cell death. PRX2 knockdown exacerbated neuronal death after oxygen and glucose deprivation. PRX2 ameliorated poly(ADP-ribose) polymerase 1, p53, Bax, and caspase activation after ischemia. AG14361 reduced ischemic cell death in wild-type and p53 or Bax knockout cultures and animals but had no additional effect in PRX2-overexpressing mice. AG14361 and p53 knockout elicited additive effects with SP600125 on viability in vitro. Our findings support the existence of multiple parallel prodeath pathways with some crosstalk.

CONCLUSIONS

The promising therapeutic candidate PRX2 can clamp upstream DNA damage and efficiently inhibit multiple prodeath cascades operating in both parallel and interactive fashions.

Apoptosis induced by trimethyltin chloride in human neuroblastoma cells SY5Y is regulated by a balance and cross-talk between NF-κB and MAPKs signaling pathways

Trimethyltin chloride (TMT) has been known as a classic neurotoxicant which can cause serious neuronal degeneration diseases. Nuclear factor κB (NF-κB) and mitogen-activated protein kinases (MAPKs) signaling pathways play pivotal role in the central nerves system. In the present study, the intracellular pathways involved in TMT-induced apoptosis on human neuroblastoma cells SY5Y (SH-SY5Y) were investigated. We observed high level of nuclear NF-κB p65 submit, activated JNK, ERK, and p38 by TMT exposure. In contrast, low level of Bcl-2 and XIAP (two known NF-κB-regulated endogenous anti-apoptotic molecules) was present. To further investigate the role of these pathways and the relationship between them, specific inhibitors were used and the alteration of each pathway was evaluated. Pretreatment with MG132, an inhibitor of proteasome activity, and BAY11-7082, an inhibitor of IκBα phosphorylation, both inhibited NF-κB p65 translocation and significantly promoted apoptosis. NF-κB inhibition also induced down-expression of Bcl-2 and XIAP, exaggerated JNK phosphorylation, and ERK inhibition. SP600125 and U0126, by blocking the phosphorylation of c-Jun and MEK1/2, inhibited JNK and ERK phosphorylation, respectively, and attenuated apoptosis significantly. JNK and ERK inhibition also induced IκBα degradation and NF-κB p65 translocation, leading to expression of Bcl-2 and XIAP. The detrimental role of MG132 and BAY11-7082 appears related to the exaggerated JNK phosphorylation. The SP600125 and U0126 neuroprotection appears related to NF-κB-regulated transcriptional control of Bcl-2 and XIAP. These results suggest that the cross-talk and a balance between NF-κB and MAPKs may be involved in TMT-induced apoptosis on SH-SY5Y cells.

Pifithrin-α enhances the survival of transplanted neural stem cells in stroke rats by inhibiting p53 nuclear translocation

AIMS

To examine a novel strategy to enhance the survival of grafted neural stem cells (NSCs) in stroke model.

METHODS

Using a cell counting kit-8 (CCK-8) and TUNEL assay to test the protective effects of p53 inhibitor, pifithrin-α (PFT-α), on oxygen glucose deprivation (OGD) in NSCs. We compared the effects of vehicle + NSCs and FFT-α + NSCs on the efficacy of transplantation in stroke rat model using behavioral analysis, immunohistochemistry, etc.

RESULTS

Pifithrin-α increased viability and decreased apoptosis in NSCs after OGD in vitro. By in vivo studies, we showed that the best recovery of neurological function in the stroke rats and the maximum survival of grafted NSCs were found in the PFT-α + NSCs group. Twelve hours after cell transplantation, p53 was localized to the nuclei of grafted NSCs in the vehicle + NSCs group but was primarily localized to the cytoplasm in the PFT-α + NSCs group. The p53-upregulated modulator of apoptosis (PUMA) was highly expressed among the grafted cells in the vehicle + NSCs group compared with that in the PFT-α + NSCs group.

CONCLUSION

Our results indicate that PFT-α enhances the survival of grafted NSCs through the inhibition of p53 translocation into the nucleus.

The effects of estrogen in ischemic stroke

Stroke is a leading cause of death and the most common cause of long-term disability in the USA. Women have a lower incidence of stroke compared with men throughout most of the lifespan which has been ascribed to protective effects of gonadal steroids, most notably estrogen. Due to the lower stroke incidence observed in pre-menopausal women and robust preclinical evidence of neuroprotective and anti-inflammatory properties of estrogen, researchers have focused on the potential benefits of hormones to reduce ischemic brain injury. However, as women age, they are disproportionately affected by stroke, coincident with the loss of estrogen with menopause. The risk of stroke in elderly women exceeds that of men and it is clear that in some settings estrogen can have pro-inflammatory effects. This review will focus on estrogen and inflammation and its interaction with aging.

Simvastatin attenuates axonal injury after experimental traumatic brain injury and promotes neurite outgrowth of primary cortical neurons

The beneficial effects of simvastatin on experimental traumatic brain injury (TBI) have been demonstrated in previous studies. In this study, we investigated the effects of simvastatin on axonal injury and neurite outgrowth after experimental TBI and explored the underlying mechanisms. Wistar rats were subjected to controlled cortical impact or sham surgery. Saline or simvastatin was administered for 14 days. A modified neurological severity score (mNSS) test was performed to evaluate functional recovery. Immunohistochemistry studies using synaptophysin, neurofilament H (NF-H) and amyloid-β precursor protein (APP) were performed to examine synaptogenesis and axonal injury. Primary cortical neurons (PCNs) were subjected to oxygen glucose deprivation (OGD) followed by various treatments. Western blot analysis was utilized to assess the activation of phosphatidylinositol-3 kinase (PI-3K)/Akt/mammalian target of rapamycin (mTOR) and glycogen synthase kinase 3β (GSK-3β)/adenomatous polyposis coli (APC) pathways. Simvastatin decreased the density of APP-positive profiles and increased the density of NF-H -positive profiles. Simvastatin reduced mNSS, which was correlated with the increase of axonal density. Simvastatin treatment stimulated the neurite outgrowth of PCNs after OGD, which was attenuated by LY294002 and enhanced by lithium chloride (LiCl). Simvastatin activated Akt and mTOR, inactivated GSK-3β and dephosphorylated APC in the injured PCNs. Our data suggest that simvastatin reduces axonal injury, enhances neurite outgrowth and promotes neurological functional recovery after experimental TBI. The beneficial effects of simvastatin on neurite outgrowth may be mediated through manipulation of the PI-3K/Akt/mTOR and PI-3K/GSK-3β/APC pathways.

p53 at the crossroads between cancer and neurodegeneration

Aging, dementia, and cancer share a critical set of altered cellular functions in response to DNA damage, genotoxic stress, and other insults. Recent data suggest that the molecular machinery involved in maintaining neural function in neurodegenerative disease may be shared with oncogenic pathways. Cancer and neurodegenerative diseases may be influenced by common signaling pathways regulating the balance of cell survival versus death, a decision often governed by checkpoint proteins. This paper focuses on one such protein, p53, which represents one of the most extensively studied proteins because of its role in cancer prevention and which, furthermore, has been recently shown to be involved in aging and Alzheimer disease (AD). The contribution of a conformational change in p53 to aging and neurodegenerative processes has yet to be elucidated. In this review we discuss the multiple functions of p53 and how these correlate between cancer and neurodegeneration, focusing on various factors that may have a role in regulating p53 activity. The observation that aging and AD interfere with proteins controlling duplication and cell cycle may lead to the speculation that, in senescent neurons, aberrations in proteins generally dealing with cell cycle control and apoptosis could affect neuronal plasticity and functioning rather than cell duplication.

Ginsenoside F2 induces apoptosis accompanied by protective autophagy in breast cancer stem cells

Ginsenoside F2 (F2) was assessed for its antiproliferative activity against breast cancer stem cells (CSCs). F2 induced apoptosis in breast CSCs by activating the intrinsic apoptotic pathway and mitochondrial dysfunction. Concomitantly, F2 induced the formation of acidic vesicular organelles, recruitment of GFP-LC3-II to autophagosomes, and elevation of Atg-7 levels, suggesting that F2 initiates an autophagic progression in breast CSCs. Treatment with an inhibitor of autophagy enhanced F2-induced cell death. Our findings provide new insights into the anti-cancer activity of F2 and may contribute to the rational use and pharmacological study of F2.

A small molecule binding to the coactivator CREB-binding protein blocks apoptosis in cardiomyocytes

As a master transcription factor in cellular responses to external stress, tumor suppressor p53 is tightly regulated. Excessive p53 activity during myocardial ischemia causes irreversible cellular injury and cardiomyocyte death. p53 activation is dependent on lysine acetylation by the lysine acetyltransferase and transcriptional coactivator CREB-binding protein (CBP) and on acetylation-directed CBP recruitment for p53 target gene expression. Here, we report a small molecule ischemin, developed with a structure-guided approach to inhibit the acetyl-lysine binding activity of the bromodomain of CBP. We show that ischemin alters post-translational modifications on p53 and histones, inhibits p53 interaction with CBP and transcriptional activity in cells, and prevents apoptosis in ischemic cardiomyocytes. Our study suggests small molecule modulation of acetylation-mediated interactions in gene transcription as a new approach to therapeutic interventions of human disorders such as myocardial ischemia.

KCa2 channels activation prevents [Ca2+]i deregulation and reduces neuronal death following glutamate toxicity and cerebral ischemia

Exacerbated activation of glutamate receptor-coupled calcium channels and subsequent increase in intracellular calcium ([Ca2+]i) are established hallmarks of neuronal cell death in acute and chronic neurological diseases. Here we show that pathological [Ca2+]i deregulation occurring after glutamate receptor stimulation is effectively modulated by small conductance calcium-activated potassium (KCa2) channels. We found that neuronal excitotoxicity was associated with a rapid downregulation of KCa2.2 channels within 3 h after the onset of glutamate exposure. Activation of KCa2 channels preserved KCa2 expression and significantly reduced pathological increases in [Ca2+]i providing robust neuroprotection in vitro and in vivo. These data suggest a critical role for KCa2 channels in excitotoxic neuronal cell death and propose their activation as potential therapeutic strategy for the treatment of acute and chronic neurodegenerative disorders.

NF-kappaB signaling in neurite growth and neuronal survival

The nuclear factor kappa B (NF-kappaB) transcription factor system plays multiple roles in the function of the nervous system during development and postnatal physiology. In the developing nervous system, neurite outgrowth could be regulated by both canonical and alternative NF-kappaB signaling pathways. The degree and site of NF-kappaB activation could promote or inhibit neuronal survival in a complex, signal and subunit-dependent manner. The significance and mechanistic basis of some of NF-kappaB activity in neurons have remained controversial. We discuss our current understanding and recent findings with regard to the roles of NF-kappaB in the neurite outgrowth and neuronal survival, and how NF-kappaB activation is associated with the pathophysiology of ischemic/ traumatic injuries and neurodegenerative diseases.

p53-mediated neuronal cell death in ischemic brain injury

p53 is a key modulator of cellular stress responses. It is activated in the ischemic areas of brain, and contributes to neuronal apoptosis. In various stroke models, p53 deficiency or applications of p53 inhibitors can significantly attenuate brain damage. p53-mediated neuronal apoptosis occurs through various molecular mechanisms. The transcriptional pathway is an important mechanism through which p53 induces neuronal apoptosis by up-regulating the expression of its target gene p21(WAF), Peg3/Pw1 or p53-up-regulated modulator of apoptosis (PUMA). In addition, p53 disrupts NF-kappaB binding to p300 and blocks NF-kappaB-mediated survival signaling. On the other hand, the transcription-independent pathway mechanism is also of great importance. In this pathway, p53 is translocated to mitochondrial and mediates the release of cytochrome c. In both pathways, p53 seems to play a key role in post-ischemic brain damage and has become a therapeutic target against stroke pathology.

Nicotine-induced survival signaling in lung cancer cells is dependent on their p53 status while its down-regulation by curcumin is independent

Background

Lung cancer is the most lethal cancer and almost 90% of lung cancer is due to cigarette smoking. Even though nicotine, one of the major ingredients of cigarette smoke and the causative agent for addiction, is not a carcinogen by itself, several investigators have shown that nicotine can induce cell proliferation and angiogenesis. We observed that the proliferative index of nicotine is different in the lung cancer cell lines H1299 (p53-/-) and A549 (p53+/+) which indicates that the mode of up-regulation of survival signals by nicotine might be different in cells with and without p53.

Results

While low concentrations of nicotine induced activation of NF-κB, Akt, Bcl2, MAPKs, AP1 and IAPs in H1299, it failed to induce NF-κB in A549, and compared to H1299, almost 100 times higher concentration of nicotine was required to induce all other survival signals in A549. Transfection of WT-p53 and DN-p53 in H1299 and A549 respectively, reversed the mode of activation of survival signals. Curcumin down-regulated all the survival signals induced by nicotine in both the cells, irrespective of their p53 status. The hypothesis was confirmed when lower concentrations of nicotine induced NF-κB in two more lung cancer cells, Hop-92 and NCI-H522 with mutant p53 status. Silencing of p53 in A549 using siRNA made the cells susceptible to nicotine-induced NF-κB nuclear translocation as in A549 DN-p53 cells.

Conclusions

The present study reveals a detrimental role of nicotine especially in lung cancer patients with impaired p53 status and identifies curcumin as a potential chemopreventive.

Hypoxia-inducible factor 1alpha determines gastric cancer chemosensitivity via modulation of p53 and NF-kappaB

BACKGROUND

Reduced chemosensitivity of solid cancer cells represents a pivotal obstacle in clinical oncology. Hence, the molecular characterization of pathways regulating chemosensitivity is a central prerequisite to improve cancer therapy. The hypoxia-inducible factor HIF-1alpha has been linked to chemosensitivity while the underlying molecular mechanisms remain largely elusive. Therefore, we comprehensively analysed HIF-1alpha's role in determining chemosensitivity focussing on responsible molecular pathways.

METHODOLOGY AND PRINCIPAL FINDINGS

RNA interference was applied to inactivate HIF-1alpha or p53 in the human gastric cancer cell lines AGS and MKN28. The chemotherapeutic agents 5-fluorouracil and cisplatin were used and chemosensitivity was assessed by cell proliferation assays as well as determination of cell cycle distribution and apoptosis. Expression of p53 and p53 target proteins was analyzed by western blot. NF-kappaB activity was characterized by means of electrophoretic mobility shift assay. Inactivation of HIF-1alpha in gastric cancer cells resulted in robust elevation of chemosensitivity. Accordingly, HIF-1alpha-competent cells displayed a significant reduction of chemotherapy-induced senescence and apoptosis. Remarkably, this phenotype was completely absent in p53 mutant cells while inactivation of p53 per se did not affect chemosensitivity. HIF-1alpha markedly suppressed chemotherapy-induced activation of p53 and p21 as well as the retinoblastoma protein, eventually resulting in cell cycle arrest. Reduced formation of reactive oxygen species in HIF-1alpha-competent cells was identified as the molecular mechanism of HIF-1alpha-mediated inhibition of p53. Furthermore, loss of HIF-1alpha abrogated, in a p53-dependent manner, chemotherapy-induced DNA-binding of NF-kappaB and expression of anti-apoptotic NF-kappaB target genes. Accordingly, reconstitution of the NF-kappaB subunit p65 reversed the increased chemosensitivity of HIF-1alpha-deficient cells.

CONCLUSION AND SIGNIFICANCE

In summary, we identified HIF-1alpha as a potent regulator of p53 and NF-kappaB activity under conditions of genotoxic stress. We conclude that p53 mutations in human tumors hold the potential to confound the efficacy of HIF-1-inhibitors in cancer therapy.

Nuclear factor-κB expression is predictive of overall survival in patients with cutaneous melanoma

Nuclear factor (NF)- κB is one of the most important transcription factors that plays a crucial role in the regulation of a wide spectrum of genes involved in modulating the cell cycle, apoptosis, cell growth, angiogenesis, inflammation and the tissue invasiveness of highly malignant cells. NF-κB activity has been found to be constitutively elevated in a number of human tumors from either a haematological or solid origin, such as melanomas. In several studies, NF-κB activation was shown to be an adverse prognostic factor, and in melanoma it was proposed as an event that promotes tumor progression. This study aimed to evaluate whether NF-κB activation in tumor tissues, assessed by the expression of the NF-κB p65 subunit, has an effect on the survival of melanoma patients. The expression of NF-κB was immunohistochemically investigated, and the correlation with survival was analyzed. Furthermore, the immunostaining for p53 and survivin was evaluated, and the relationship of these apoptotic and anti-apoptotic factors with NF-κB expression was analyzed. Kaplan-Meier analysis showed that patients with low levels of NF-κB in the nuclei of tumor cells had a significantly longer survival compared to those with high levels. Multivariate analysis confirmed the predictive value of nuclear NF-κB, showing that its expression maintains significance after the model was adjusted using clinicopathological factors. The results demonstrate the correlation of NF-κB p65 nuclear staining with the disease-specific 5-year survival of melanoma patients and suggest that nuclear NF-κB p65 may be promising as an early independent prognostic factor in patients with primary cutaneous melanoma.

p53 and NF-κB: different strategies for responding to stress lead to a functional antagonism

The p53 transcription factor responds to a variety of intrinsic stresses, such as DNA damage, hypoxia, and even oncogene activation. NF-κB responds to a large number of extrinsic stresses such as cytokine activation and infectious diseases. The p53 tumor suppressor limits the consequences of stress by initiating cell death, senescence, or cell cycle arrest and promotes metabolic patterns in the cell to favor oxidative phosphorylation. NF-κB, the oncogene, promotes cell division, which initiates the innate and adaptive immune responses utilizing large amounts of glucose in aerobic glycolysis, resulting in the synthesis of substrates for cell division. Thus these two transcription factors, both of which have evolved to respond to different types of stress, have adopted opposite strategies and cannot function in the same cell at the same time. On activation of one of these transcription factors, the other is inactivated. This is achieved at several places in the p53 and NF-κB pathways where regulatory proteins act on both p53 and NF-κB with opposite functional consequences. These internodal sites create core regulatory circuits essential for integrating two central pathways in cells.

Inhibition of extracellular signal-regulated kinases 1/2 provides neuroprotection in spinal cord ischemia/reperfusion injury in rats: relationship with the nuclear factor-kappaB-regulated anti-apoptotic mechanisms

Previously we demonstrated benefits of inhibiting the extracellular signal-regulated kinases 1/2 (ERK1/2) signaling pathway in spinal cord ischemia/reperfusion (I/R) injury. To further identify the underlying mechanisms, we investigated the impact of ERK inhibition on apoptosis and cellular protective mechanisms against cell death. Spinal cord I/R injury induced ERK1/2 phosphorylation, followed by neuronal loss through caspase 3-mediated apoptosis. Pre-treatment with U0126, a specific inhibitor of MAPK/ERK kinases 1/2 (MEK1/2), inhibited ERK1/2 phosphorylation, and significantly attenuated apoptosis and increased neuronal survival. MEK/ERK inhibition also induced I-kappaB phosphorylation and enhanced nuclear factor (NF)-kappaB/DNA binding activity, leading to expression of cellular inhibitors of apoptosis protein 2 (c-IAP2), a known nuclear factor-kappaB (NF-kappaB)-regulated endogenous anti-apoptotic molecule. Pyrrolidine dithiocarbamate, an NF-kappaB inhibitor, by blocking I-kappaB phosphorylation, NF-kappaB activation, and c-IAP2 synthesis, abolished the protective effects of U0126. The MEK/ERK pathway appears to mediate cellular death following I/R injury. The U0126 neuroprotection appears related to NF-kappaB-regulated transcriptional control of c-IAP2. MEK/ERK inhibition at the initial stage of I/R injury may cause changes in c-IAP2 gene expression or c-IAP2/caspase 3 interactions, resulting in long lasting therapeutic effects. Future research should focus on the possible cross-talk between the MEK/ERK pathway and the NF-kappaB transcriptional cascade.