L-DOPA-induced neurotoxicity is reduced by the activation of the PI3K signaling pathway

Targeting PI3K by Natural Products: A Potential Therapeutic Strategy for Attention-deficit Hyperactivity Disorder

Attention-Deficit Hyperactivity Disorder (ADHD) is a highly prevalent childhood psychiatric disorder. In general, a child with ADHD has significant attention problems with difficulty concentrating on a subject and is generally associated with impulsivity and excessive activity. The etiology of ADHD in most patients is unknown, although it is considered to be a multifactorial disease caused by a combination of genetics and environmental factors. Diverse factors, such as the existence of mental, nutritional, or general health problems during childhood, as well as smoking and alcohol drinking during pregnancy, are related to an increased risk of ADHD. Behavioral and psychological characteristics of ADHD include anxiety, mood disorders, behavioral disorders, language disorders, and learning disabilities. These symptoms affect individuals, families, and communities, negatively altering educational and social results, strained parent-child relationships, and increased use of health services. ADHD may be associated with deficits in inhibitory frontostriatal noradrenergic neurons on lower striatal structures that are predominantly driven by dopaminergic neurons. Phosphoinositide 3-kinases (PI3Ks) are a conserved family of lipid kinases that control a number of cellular processes, including cell proliferation, differentiation, migration, insulin metabolism, and apoptosis. Since PI3K plays an important role in controlling the noradrenergic neuron, it opens up new insights into research on ADHD and other developmental brain diseases. This review presents evidence for the potential usefulness of PI3K and its modulators as a potential treatment for ADHD.

Mitochondria damaged by Oxygen Glucose Deprivation can be Restored through Activation of the PI3K/Akt Pathway and Inhibition of Calcium Influx by Amlodipine Camsylate

Amlodipine, a L-type calcium channel blocker, has been reported to have a neuroprotective effect in brain ischemia. Mitochondrial calcium overload leads to apoptosis of cells in neurologic diseases. We evaluated the neuroprotective effects of amlodipine camsylate (AC) on neural stem cells (NSCs) injured by oxygen glucose deprivation (OGD) with a focus on mitochondrial structure and function. NSCs were isolated from rodent embryonic brains. Effects of AC on cell viability, proliferation, level of free radicals, and expression of intracellular signaling proteins were assessed in OGD-injured NSCs. We also investigated the effect of AC on mitochondrial structure in NSCs under OGD by transmission electron microscopy. AC increased the viability and proliferation of NSCs. This beneficial effect of AC was achieved by strong protection of mitochondria. AC markedly enhanced the expression of mitochondrial biogenesis-related proteins and mitochondrial anti-apoptosis proteins. Together, our results indicate that AC protects OGD-injured NSCs by protecting mitochondrial structure and function. The results of the present study provide insight into the mechanisms underlying the protective effects of AC on NSCs.

IGF-1 alleviates serum IgG-induced neuronal cytolysis through PI3K signaling in children with opsoclonus-myoclonus syndrome and neuroblastoma

BACKGROUND

Opsoclonus-myoclonus syndrome (OMS) is a rare neurological disorder, usually accompanied by neuroblastoma (NB). There is no targeted treatment and animal model of OMS. We aimed to investigate whether insulin-like growth factor 1 (IGF-1)/phosphoinositide 3-kinase (PI3K) signaling alleviates neuronal cytolysis in pediatric OMS.

METHODS

Cultured rat cerebral cortical neurons and cerebellar neurons were incubated with sera or IgG isolated from sera of children with OMS and NB. Cytolysis and PI3K expression were measured by the lactate dehydrogenase assay and enzyme-linked immunosorbent assay, respectively. Using inhibitors and activators, the effects of IGF-1 and PI3K on cytolysis were investigated.

RESULTS

The incubation of sera or IgG from children with OMS and NB increased cytolysis in not only cerebellar neurons, but also cerebral cortical neurons. Furthermore, the IGF-1 receptor antagonist NVP-AEW541 exaggerated cytolysis in children with OMS and NB. IGF-1 alleviated cytolysis, which was blocked by the PI3K inhibitor LY294002. Additionally, sera or IgG from children with OMS and NB compensatively elevated PI3K expression. LY294002 exacerbated cytolysis; whereas, the PI3K activator 740 Y-P suppressed cytolysis.

CONCLUSION

IGF-1/PI3K signaling alleviates the cytolysis of cultured neurons induced by serum IgG from children with OMS and NB, which may be innovation therapy targets.

Tracking and protection of transplanted stem cells using a ferrocenecarboxylic acid-conjugated peptide that mimics hTERT

In vivo tracking of transplanted stem cells has been a central aim of stem cell therapy. Although many tracking systems have been introduced, no method has yet been validated for clinical applications. We developed a novel sophisticated peptide (GV1001) that mimics hTERT (human telomerase reverse transcriptase) and analysed its ability to track and protect stem cells after transplantation. Ferrocenecarboxylic acid-conjugated GV1001 (Fe-GV1001) efficiently penetrated stem cells with no adverse effects. Moreover, Fe-GV1001 improved the viability, proliferation, and migration of stem cells under hypoxia. After Fe-GV1001-labelled stem cells were transplanted into the brains of rats after stroke, the labelled cells were easily tracked by MRI. Our findings indicate that Fe-GV1001 can be used for the in vivo tracking of stem cells after transplantation into the brain and can improve the efficacy of stem cell therapy by sustaining and enhancing stem cell characteristics under disease conditions.

Neural stem cells injured by oxidative stress can be rejuvenated by GV1001, a novel peptide, through scavenging free radicals and enhancing survival signals

Oxidative stress is a well-known pathogenic mechanism of a diverse array of neurological diseases, and thus, numerous studies have attempted to identify antioxidants that prevent neuronal cell death. GV1001 is a 16-amino-acid peptide derived from human telomerase reverse transcriptase (hTERT). Considering that hTERT has a strong antioxidant effect, whether GV1001 also has an antioxidant effect is a question of interest. In the present study, we aimed to investigate the effects of GV1001 against oxidative stress in neural stem cells (NSCs). Primary culture NSCs were treated with different concentrations of GV1001 and/or hydrogen peroxide (H2O2) for various time durations. The H2O2 decreased the viability of the NSCs in a concentration-dependent manner, with 200μM H2O2 significantly decreasing both proliferation and migration. However, treatment with GV1001 rescued the viability, proliferation and migration of H2O2-injured NSCs. Consistently, free radical levels were increased in rat NSCs treated with H2O2, while co-treatment with GV1001 significantly reduced these levels, especially the intracellular levels. In addition, GV1001 restored the expression of survival-related proteins and reduced the expression of death-associated ones in NSCs treated with H2O2. In conclusion, GV1001 has antioxidant and neuroprotective effects in NSCs following treatment with H2O2, which appear to be mediated by scavenging free radicals, increasing survival signals and decreasing death signals.

Plumbagin attenuates cancer cell growth and osteoclast formation in the bone microenvironment of mice

AIM

To investigate the effects of plumbagin, a naphthoquinone derived from the medicinal plant Plumbago zeylanica, on human breast cancer cell growth and the cancer cell-induced osteolysis in the bone microenvironment of mice.

METHODS

Human breast cancer cell subline MDA-MB-231SA with the ability to spread and grow in the bone was tested. The cell proliferation was determined using the CCK-8 assay. Apoptosis was detected with Annexin V/PI double-labeled flow cytometry. Red fluorescent protein-labeled MDA-MB-231SArfp cells were injected into the right tibia of female BALB/c-nu/nu mice. Three days after the inoculation, the mice were injected with plumbagin (2, 4, or 6 mg/kg, ip) 5 times per week for 7 weeks. The growth of the tumor cells was monitored using an in vivo imaging system. After the mice were sacrificed, the hind limbs were removed for radiographic and histological analyses.

RESULTS

Plumbagin (2.5-20 μmol/L) concentration-dependently inhibited the cell viability and induced apoptosis of MDA-MB-231SA cells in vitro (the IC50 value of inhibition of cell viability was 14.7 μmol/L). Administration of plumbagin to breast cancer bearing mice delayed the tumor growth by 2-3 weeks and reduced the tumor volume by 44%-74%. The in vivo imaging study showed that plumbagin dose-dependently inhibited MDA-MB-231SArfp cell growth in bone microenvironment. Furthermore, X-ray images and micro-CT study demonstrated that plumbagin reduced bone erosion area and prevented a decrease in bone tissue volume. Histological studies showed that plumbagin dose-dependently inhibited the breast cancer cell growth, enhanced the cell apoptosis and reduced the number of TRAcP-positive osteoclasts.

CONCLUSION

Plumbagin inhibits the cell growth and induces apoptosis in human breast cancer cells in mice bone microenvironment, leading to significant reduction in osteolytic lesions caused by the tumor cells.

Novel vaccine peptide GV1001 effectively blocks β-amyloid toxicity by mimicking the extra-telomeric functions of human telomerase reverse transcriptase

GV1001 is a 16-amino-acid vaccine peptide derived from the human telomerase reverse transcriptase sequence. We investigated the effects of GV1001 against β-amyloid (Aβ) oligomer-induced neurotoxicity in rat neural stem cells (NSCs). Primary culture NSCs were treated with several concentrations of GV1001 and/or Aβ₂₅₋₃₅ oligomer for 48 hours. GV1001 protected NSCs against the Aβ₂₅₋₃₅ oligomer in a concentration-dependent manner. Aβ₂₅₋₃₅ concentration dependently decreased viability, proliferation, and mobilization of NSCs and GV1001 treatment restored the cells to wild-type levels. Aβ₂₅₋₃₅ increased free radical levels in rat NSCs while combined treatment with GV1001 significantly reduced these levels. In addition, GV1001 treatment of Aβ₂₅₋₃₅-injured NSCs increased the expression level of survival-related proteins, including mitochondria-associated survival proteins, and decreased the levels of death and inflammation-related proteins, including mitochondria-associated death proteins. Together, these results suggest that GV1001 possesses neuroprotective effects against Aβ₂₅₋₃₅ oligomer in NSCs and that these effects are mediated through mimicking the extra-telomeric functions of human telomerase reverse transcriptase, including the induction of cellular proliferation, anti-apoptotic effects, mitochondrial stabilization, and anti-aging and anti-oxidant effects.

Simvastatin induces neuroprotection in 6-OHDA-lesioned PC12 via the PI3K/AKT/caspase 3 pathway and anti-inflammatory responses

BACKGROUND

In addition to their original applications for lowering cholesterol, statins display multiple neuroprotective effects. Inflammatory reactions and the PI3K/AKT/caspase 3 pathway are strongly implicated in dopaminergic neuronal death in Parkinson's disease (PD). This study aims to investigate how simvastatin affects 6-hydroxydopamine-lesioned PC12 via regulating PI3K/AKT/caspase 3 and modulating inflammatory mediators.

METHODS

6-hydroxydopamine-treated PC12 cells were used to investigate the neuroprotection of simvastatin, its association with the PI3K/AKT/caspase 3 pathway, and antiinflammatory responses. Dopamine transporters (DAT) and tyrosine hydroxylase (TH) were examined in 6-hydroxydopamine-treated PC12 after simvastatin treatment.

RESULTS

Simvastatin-mediated neuroprotection was associated with a robust reduction in the upregulation induced by 6-OHDA of inflammatory mediators including IL-6, COX2, and TNF-α. The downregulated DAT and TH levels in 6-OHDA-lesioned PC12 were restored after simvastatin treatment. Simvastatin reversed 6-OHDA-induced downregulation of PI3K/Akt phosphorylation and attenuated 6-OHDA-induced upregulation of caspase 3 in PC12. Furthermore, the PI3K inhibitor LY294002 pronouncedly abolished the simvastatin-mediated attenuation in caspase 3.

CONCLUSIONS

Our results demonstrate that simvastatin provides robust neuroprotection against dopaminergic neurodegeneration, partially via antiinflammatory mechanisms and the PI3K/Akt/caspase 3 pathway. These findings contribute to a better understanding of the critical roles of simvastatin in treating PD and might elucidate the molecular mechanisms of simvastatin effects in PD.

The early activation of PI3K strongly enhances the resistance of cortical neurons to hypoxic injury via the activation of downstream targets of the PI3K pathway and the normalization of the levels of PARP activity, ATP, and NAD⁺

Phosphatidylinositol 3-kinase (PI3K) plays several important roles in neuronal survival. Activation of the pathway is essential for the neuroprotective mechanisms of materials that shield neuronal cells from many stressful conditions. However, there have been no reports to date about the effect of the direct activation of the pathway in hypoxic injury of neuronal cells. We investigated whether the direct activation of the PI3K pathway inhibits neuronal cell death induced by hypoxia. Primary cultured cortical neurons (PCCNs) were exposed to hypoxic conditions (less than 1 mol% O2) and/or treated with PI3K activator. Hypoxia reduced the viability of PCCNs in a time-dependent manner, but treatment with PI3K significantly restored viability in a concentration-dependent manner. Among the signaling proteins involved in the PI3K pathway, those associated with survival, including Akt and glycogen synthase kinase-3β, were decreased shortly after exposure to hypoxia and those associated with cell death, including BAX, apoptosis-induced factor, cytochrome c, caspase-9, caspase-3, and poly(ADP-ribose) polymerase (PARP), were increased. However, treatment with PI3K activator normalized the expression levels of those signaling proteins. PARP activity and levels of ATP and NAD(+) altered by hypoxia were also normalized with direct PI3K activation. All these findings suggest that direct and early activation is important for protecting neuronal cells from hypoxic injury.

Plumbagin inhibits cell growth and potentiates apoptosis in human gastric cancer cells in vitro through the NF-κB signaling pathway

AIM

To investigate the effects and underlying mechanisms of plumbagin, a naphthoquinone derived from medicinal plant Plumbago zeylanica, on human gastric cancer (GC) cells.

METHODS

Human gastric cancer cell lines SGC-7901, MKN-28, and AGS were used. The cell viability was examined using CCK-8 viability assay. Cell proliferation rate was determined using both clonogenic assay and EdU incorporation assay. Apoptosis was detected via Annexin V/propidium iodide double-labeled flow cytometry. Western blotting was used to assess the expression of both NF-κB-regulated gene products and TNF-α-induced activation of p65, IκBα, and IKK. The intracellular location of NF-κB p65 was detected using confocal microscopy.

RESULTS

Plumbagin (2.5-40 μmol/L) concentration-dependently reduced the viability of the GC cells. The IC(50) value of plumbagin in SGC-7901, MKN-28, and AGS cells was 19.12, 13.64, and 10.12 μmol/L, respectively. The compound (5-20 μmol/L) concentration-dependently induced apoptosis of SGC-7901 cells, and potentiated the sensitivity of SGC-7901 cells to chemotherapeutic agents TNF-αand cisplatin. The compound (10 μmol/L) downregulated the expression of NF-κB-regulated gene products, including IAP1, XIAP, Bcl-2, Bcl-xL, tumor factor (TF), and VEGF. In addition to inhibition of NF-κB p65 nuclear translocation, the compound also suppressed TNF-α-induced phosphorylation of p65 and IKK, and the degradation of IκBα.

CONCLUSION

Plumbagin inhibits cell growth and potentiates apoptosis in human GC cells through the NF-κB pathway.

Intracellular trafficking and fate of chimeric adenovirus 5/F35 in human B lymphocytes

BACKGROUND

Investigation of the molecular processes that control the development and function of lymphocytes is essential for our understanding of humoral immunity, as well as lymphocyte-associated pathogenesis. Adenovirus-mediated gene transfer provides a powerful tool for investigating these processes. However, we observed variation in transgene expression among normal human peripheral blood B lymphocytes from different donors and at distinct stages of differentiation. It is recognized that efficient gene transfer is highly dependent on the intracellular route by which the viruses travel within the host cell. Thus, we aimed to examine this aspect in the present study.

METHODS

We analyzed the binding, uptake, intracellular trafficking and fate of CY3-labelled Ad5/F35 vectors in lymphoid cell lines and primary B cells. Furthermore, we decreased protein synthesis levels and rapid endocytosis in a plasma cell line exhibiting a high level of protein synthesis activity and activated transcription and endocytosis in primary B cells, which are less active than plasma cells.

RESULTS

Major differences in intracellular trafficking pattern between B cells and plasma cell line U266 were identified that explain the observed divergence in transgene expression efficiency. Importantly, modification of the transcriptional or translational activity of U266 cells reverted the Ad5/F35 endocytic trafficking to that seen in B cells, with a loss of transgene expression, whereas activation of B cells with phorbol 12-myristate 13-acetate had the opposite effects.

CONCLUSIONS

Taken together, these results suggest that Ad5/F35 is more efficiently transduced in cells with a strong transcriptional activity as a result of differences in intracellular trafficking. This finding extends our current knowledge of the mechanisms of adenovirus-mediated gene transfer.

Neurobehavioral and transcriptional effects of acrylamide in juvenile rats

Acrylamide is a type-2 alkene monomer with established human neurotoxic effects. While the primary source of human exposure to acrylamide is occupational, other exposure sources include food, drinking water, and smoking. In this study, neurobehavioral assays coupled with transcriptional profiling analysis were conducted to assess both behavioral and gene expression effects induced by acrylamide neurotoxicity in juvenile rats. Acrylamide administration in rat pups induced significant characteristic neurotoxic symptoms including increased heel splay, decrease in grip strength, and decrease in locomotor activity. Transcriptome analysis with the Affymetrix Rat Genome 230 2.0 array indicated that acrylamide treatment caused a significant alteration in the expression of a few genes that are involved in muscle contraction, pain, and dopaminergic neuronal pathways. First, expression of the Mylpf gene involved in muscle contraction was downregulated in the spinal cord in response to acrylamide. Second, in sciatic nerves, acrylamide repressed the expression of the opioid receptor gene Oprk1 that is known to play a role in neuropathic pain regulation. Finally, in the cerebellum, acrylamide treatment caused a decrease in the expression of the nuclear receptor gene Nr4a2 that is required for development of dopaminergic neurons. Thus, our work examining the effect of acrylamide at the whole-genome level on a developmental mammalian model has identified a few genes previously not implicated in acrylamide neurotoxicity that might be further developed into biomarkers for assessing the risk of adverse health effects induced by acrylamide exposure.

L-DOPA neurotoxicity is prevented by neuroprotective effects of erythropoietin

The neurotoxicity of L-3,4-dihydroxyphenylalanine (L-DOPA), one of the most important drugs for the treatment of Parkinson's disease, still remains controversial, although much more data on L-DOPA neurotoxicity have been presented. Considering the well known neuroprotective effects of erythropoietin (EPO), the inhibitory effects of EPO on L-DOPA neurotoxicity need to be evaluated. Neuronally differentiated PC12 (nPC12) cells were treated with different concentrations of L-DOPA and/or EPO for 24h. Cell viability was evaluated using trypan blue, 4',6-diamidino-2-phenylindole (DAPI) and TUNEL staining, and cell counting. Free radicals and intracellular signaling protein levels were measured with 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) and Western blotting, respectively. L-DOPA reduced nPC12 cell viability at higher concentrations, but combined treatment with EPO and L-DOPA significantly restored cell viability. Free radicals and hydroxyl radical levels increased by L-DOPA were decreased after combined treatment of L-DOPA and EPO. Levels of survival-related intracellular signaling proteins decreased in nPC12 cells treated with 200 μM L-DOPA but increased significantly in cells treated with 200μM L-DOPA and 5 μM EPO. However, cleaved caspase-3, a death-related protein, increased in nPC12 cells treated with 200 μM L-DOPA but decreased significantly in cells treated with 200 μM L-DOPA and 5 μM EPO. Pretreatment with LY294002, a phosphatidylinositol 3-kinase inhibitor, prior to combined treatment with EPO and L-DOPA almost completely blocked the protective effects of EPO. These results indicate that EPO can prevent L-DOPA neurotoxicity by activating the PI3K pathway as well as reducing oxidative stress.

Striatal Akt/GSK3 signaling pathway in the development of L-Dopa-induced dyskinesias in MPTP monkeys

L-Dopa treatment, the gold standard therapy for Parkinson's disease, is hampered by motor complications such as dyskinesias. Recently, impairment of striatal Akt/GSK3 signaling was proposed to play a role in the mechanisms implicated in development of L-Dopa-induced dyskinesias in a rodent model of Parkinson's disease. The present experiment investigated in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) monkeys, the effects on Akt/GSK3 of chronic L-Dopa treatment inducing dyskinesias compared to L-Dopa with CI-1041 (NMDA receptor antagonist) or a low dose of cabergoline (dopamine D2 receptor agonist) preventing dyskinesias. The extensive dopamine denervation induced by MPTP was associated with a decrease by about half of phosphorylated Akt(Ser473) levels in posterior caudate nucleus, anterior and posterior putamen; smaller changes were observed for phosphorylated Akt(Thr308) levels that did not reach statistical significance. Dopamine depletion reduced phosphorylated GSK3beta(Ser9) levels, mainly in posterior putamen whereas pGSK3beta(Tyr216) and pGSK3alpha(Ser21) were unchanged. In posterior caudate nucleus, anterior and posterior putamen of dyskinetic L-Dopa-treated MPTP monkeys, pAkt(Ser473) and pGSK3beta(Ser9) were elevated whereas L-Dopa+cabergoline treated MPTP monkeys without dyskinesias had lower values in posterior striatum as vehicle-treated MPTP monkeys. In non-dyskinetic MPTP monkeys treated with L-Dopa+CI-1041, putamen pAkt(Ser473) and pGSK3beta(Ser9) levels remained elevated as in dyskinetic monkeys while in posterior caudate nucleus, these levels were low as vehicle-treated and lower than L-Dopa treated MPTP monkeys. Extent of phosphorylation of Akt and GSK3beta in putamen correlated positively with dyskinesias scores of MPTP monkeys; these correlations were higher with dopaminergic drugs (L-Dopa, cabergoline) suggesting implication of additional mechanisms and/or signaling molecules in the NMDA antagonist antidyskinetic effect. In conclusion, our results showed that in MPTP monkeys, loss of striatal dopamine decreased Akt/GSK3 signaling and that increased phosphorylation of Akt and GSK3beta was associated with L-Dopa-induced dyskinesias.

Inhibition of NGF-induced neurite outgrowth of rat pheochromocytoma cells (PC12) following administration of dioxyamphetamine

Amphetamine analogs are known to induce not only neurotoxicity at serotonergic axon terminals but also neocortical neuronal degeneration. However, a much less studied aspect involves the impact of amphetamine exposure on neuronal development. The present study investigated whether pretreatment of PC12 cells with dioxyamphetamine (DA) alters differentiation of PC12 cells by NGF and, if so, which components of the Ras/Raf/MEK/ERK pathway known to be involved in the differentiation response to NGF are particularly affected. Though exposure of PC12 cells to DA 1h prior to NGF treatment resulted in apopotosis, several PC12 cells survived. However, neurite outgrowth of these NGF-responsive cells was repressed. Immunoblots of whole cell extracts revealed a strong induction rather than inhibition of ERK phosphorylation up to 48h after DA/NGF treatment. Our results indicate that NGF-mediated neurite outgrowth was inhibited by pretreatment with DA, and this blockage of NGF-induced neuritogenesis was not due to an inhibition of ERK phosphorylation.