Basic fibroblast growth factor protects against rotenone-induced dopaminergic cell death through activation of extracellular signal-regulated kinases 1/2 and phosphatidylinositol-3 kinase pathways

Diversity of Microglia-Derived Molecules with Neurotrophic Properties That Support Neurons in the Central Nervous System and Other Tissues

Microglia, the brain immune cells, support neurons by producing several established neurotrophic molecules including glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF). Modern analytical techniques have identified numerous phenotypic states of microglia, each associated with the secretion of a diverse set of substances, which likely include not only canonical neurotrophic factors but also other less-studied molecules that can interact with neurons and provide trophic support. In this review, we consider the following eight such candidate cytokines: oncostatin M (OSM), leukemia inhibitory factor (LIF), activin A, colony-stimulating factor (CSF)-1, interleukin (IL)-34, growth/differentiation factor (GDF)-15, fibroblast growth factor (FGF)-2, and insulin-like growth factor (IGF)-2. The available literature provides sufficient evidence demonstrating murine cells produce these cytokines and that they exhibit neurotrophic activity in at least one neuronal model. Several distinct types of neurotrophic activity are identified that only partially overlap among the cytokines considered, reflecting either their distinct intrinsic properties or lack of comprehensive studies covering the full spectrum of neurotrophic effects. The scarcity of human-specific studies is another significant knowledge gap revealed by this review. Further studies on these potential microglia-derived neurotrophic factors are warranted since they may be used as targeted treatments for diverse neurological disorders.

Pharmacological and physiological roles of adipokines and myokines in metabolic-related dementia

Dementia is a detrimental neuropathologic condition with considerable physical, mental, social, and financial impact on patients and society. Patients with metabolic syndrome (MetS), a group of diseases that occur in tandem and increase the risk of neurologic diseases, have a higher risk of dementia. The ratio between muscle and adipose tissue is crucial in MetS, as these contain many hormones, including myokines and adipokines, which are involved in crosstalk and local paracrine/autocrine interactions. Evidence suggests that abnormal adipokine and myokine synthesis and release may be implicated in various MetS, such as atherosclerosis, diabetic mellitus (DM), and dyslipidemia, but their precise role is unclear. Here we review the literature on adipokine and myokine involvement in MetS-induced dementia via glucose and insulin homeostasis regulation, neuroinflammation, vascular dysfunction, emotional changes, and cognitive function.

Changes in the vitreous body after experimental vitreous hemorrhage in rabbit: An interdisciplinary study

PURPOSE

To explore the changes in vitreous body after vitreous hemorrhage and assess its prognosis from the perspective of vitreoretinal interface.

METHODS

The experiment was performed on 32 New Zealand rabbits (64 eyes), weighing 2500-3000 g for 4 months and unlimited gender, which was injected with 0.2 mL of autologous blood into the center of vitreous cavity-the study group (right eyes), and the control one was treated in the same manner with equal volumes of saline. The rabbits were randomly and equally divided into the following four batches according to the days of observation: Days 3, 7, 14, and 30 after injection. IOP and severity grading were evaluated before rabbits' execution and eyeballs were enucleated. The anterior segment was separated to flow out the vitreous body naturally to detect the liquefaction degree and viscosity. Then, chemical composition of electrolytes, PCT and bFGF were determined by colorimetry and enzyme-linked immunosorbent assay (ELISA). Finally, the incidence of posterior vitreous detachment (PVD) was observed after vitreous sampled. The studies were double-blind.

RESULTS

After injection, the extent of vitreous opacity and coagulum size decreased over time. Both the degree of liquefaction and the length of tow differed significantly between two groups at different time points (all p < 0.001). The liquefaction degree in the study group rose obviously from the Day 14, which the viscosity declined significantly on the initial time. Biochemical markers fluctuated temporarily, except for basic fibroblast growth factor (bFGF), which continued to rise and was correlated with the liquefaction degree (r = 0.658, p < 0.001). Besides, the incidence of PVD increased from the 14th day (p < 0.05), and it was highly positively correlated with the number of macrophages (r = 0.934; p < 0.001).

CONCLUSION

After vitreous hemorrhage, the changes of the vitreous body are relatively minor earlier (2-4 weeks), but irreversible later. Specifically, the degree of liquefaction increases with a decrease in viscosity, and the chemotaxis of macrophages and bFGF induce incomplete PVD.

Do Naturally Occurring Antioxidants Protect Against Neurodegeneration of the Dopaminergic System? A Systematic Revision in Animal Models of Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease and is characterized by a significant decrease in dopamine levels, caused by progressive degeneration of the dopaminergic neurons in the nigrostriatal pathway. Multiple mechanisms have been implicated in its pathogenesis, including oxidative stress, neuroinflammation, protein aggregation, mitochondrial dysfunction, insufficient support for neurotrophic factors and cell apoptosis. The absence of treatments capable of slowing or stopping the progression of PD has increased the interest in the natural antioxidant substances present in the diet, since they have multiple beneficial properties and it is possible that they can influence the mechanisms responsible for the dysfunction and death of dopaminergic neurons. Thus, the purpose of this systematic review is to analyze the results obtained in a set of studies carried out in the last years, which describe the neuroprotective, antioxidant and regenerative functions of some naturally occurring antioxidants in experimental models of PD. The results show that the exogenous no enzymatic antioxidants can significantly modify the biochemical and behavioral mechanisms that contribute to the pathophysiology of Parkinsonism in experimental animals. Therefore, it is possible that they may contribute to effective neuroprotection by providing a significant improvement in neuropathological markers. In conclusion, the results of this review suggest that exogenous antioxidants can be promising therapeutic candidates for the prevention and treatment of PD.

Physical Exercise-Induced Myokines in Neurodegenerative Diseases

Neurodegenerative diseases (NDs), such as Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), and amyotrophic lateral sclerosis (ALS), are disorders characterized by progressive degeneration of the nervous system. Currently, there is no disease-modifying treatments for most NDs. Meanwhile, numerous studies conducted on human and animal models over the past decades have showed that exercises had beneficial effects on NDs. Inter-tissue communication by myokine, a peptide produced and secreted by skeletal muscles during exercise, is thought to be an important underlying mechanism for the advantages. Here, we reviewed studies about the effects of myokines regulated by exercise on NDs and their mechanisms. Myokines could exert beneficial effects on NDs through a variety of regulatory mechanisms, including cell survival, neurogenesis, neuroinflammation, proteostasis, oxidative stress, and protein modification. Studies on exercise-induced myokines are expected to provide a novel strategy for treating NDs, for which there are no adequate treatments nowadays. To date, only a few myokines have been investigated for their effects on NDs and studies on mechanisms involved in them are in their infancy. Therefore, future studies are needed to discover more myokines and test their effects on NDs.

Fibroblast Growth Factor: Promising Target for Schizophrenia

Schizophrenia is one of the most debilitating mental disorders around the world. It is characterized by neuroanatomical or biochemical changes. The role of the fibroblast growth factors (FGFs) system in schizophrenia has received considerable attention in recent years. Various changes in the gene expression and/or level of FGFs have been implicated in the etiology, symptoms and progression of schizophrenia. For example, studies have substantiated an interaction between FGFs and the signaling pathway of dopamine receptors. To understand the role of this system in schizophrenia, the databases of Open Access Journals, Web of Science, PubMed (NLM), LISTA (EBSCO), and Google Scholar with keywords including fibroblast growth factors, dopamine, schizophrenia, psychosis, along with neurotrophic were searched. In conclusion, the FGF family represent molecular candidates as new drug targets and treatment targets for schizophrenia.

Transcription factor EB overexpression prevents neurodegeneration in experimental synucleinopathies

The synucleinopathies Parkinson’s disease (PD) and Multiple system atrophy (MSA) — characterized by α-synuclein intracytoplasmic inclusions into, respectively, neurons and oligodendrocytes — are associated with impairment of the autophagy-lysosomal pathways (ALP). Increased expression of the master regulator of ALP, transcription factor EB (TFEB), is hypothesized to promote the clearance of WT α-synuclein and survival of dopaminergic neurons. Here, we explore the efficacy of targeted TFEB overexpression either in neurons or oligodendrocytes to reduce the pathological burden of α-synuclein in a PD rat model and a MSA mouse model. While TFEB neuronal expression was sufficient to prevent neurodegeneration in the PD model, we show that only TFEB oligodendroglial overexpression leads to neuroprotective effects in the MSA model. These beneficial effects were associated with a decreased accumulation of α-synuclein into oligodendrocytes through recovery of the ALP machinery. Our study demonstrates that the cell type where α-synuclein aggregates dictates the target of TFEB overexpression in order to be protective, paving the way for adapted therapies.

Targeted overexpression of transcription factor EB (TFEB) decreases accumulation of α-synuclein and prevents neurodegeneration in animal models of synucleinopathies.

Reciprocal stimulating effects of bFGF and FSH on chicken primordial follicle activation through AKT and ERK pathway

Basic fibroblast growth factor (bFGF) and follicle-stimulating hormone (FSH) both play important roles in primordial follicle development. Here we investigated the reciprocal stimulation effects of a cytokine bFGF and FSH on primordial follicle development in the chicken and considered a possible signaling mechanism involving protein kinase B (AKT) and extracellular regulated protein kinase (ERK) pathways. 4-day-old chicken ovaries were treated with bFGF and FSH for 3 days in culture to investigate the effects of bFGF and FSH on primordial follicle development. Methods included HE staining, immunohistochemistry, quantitate real-time PCR, Western blot and immunofluorescence. A correlated change of bFGF receptor (FGFR1) mRNA expression and time course of primordial follicle activation was revealed in the early chick ovaries. A reciprocal stimulation effect on primordial follicle activation was demonstrated for bFGF and FSH, along with accelerated granulosa cells proliferation and decreased cell apoptosis. The promoting effect of bFGF was attenuated by the FGFR1 inhibitor SU5402 where the percentage of growing follicles had decreased. AKT and ERK signaling pathways mediated the action of bFGF and FSH in their promotion of primordial follicle activation. Cytokine bFGF and FSH imposed reciprocal stimulating effects on granulosa cell proliferation and anti-apoptosis to promote primordial follicle activation via the PI3K-AKT and ERK signaling pathways in early chick ovaries.

GRP78/BIP/HSPA5 as a Therapeutic Target in Models of Parkinson's Disease: A Mini Review

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by selective loss of dopamine neurons in the substantia nigra pars compacta of the midbrain. Reports from postmortem studies in the human PD brain, and experimental PD models reveal that endoplasmic reticulum (ER) stress is implicated in the pathogenesis of PD. In times of stress, the unfolded or misfolded proteins overload the folding capacity of the ER to induce a condition generally known as ER stress. During ER stress, cells activate the unfolded protein response (UPR) to handle increasing amounts of abnormal proteins, and recent evidence has demonstrated the activation of the ER chaperone GRP78/BiP (78 kDa glucose-regulated protein/binding immunoglobulin protein), which is important for proper folding of newly synthesized and partly folded proteins to maintain protein homeostasis. Although the activation of this protein is essential for the initiation of the UPR in PD, there are inconsistent reports on its expression in various PD models. Consequently, this review article aims to summarize current knowledge on neuroprotective agents targeting the expression of GRP78/BiP in the regulation of ER stress in experimental PD models.

Overexpression of microRNA-183 promotes apoptosis of substantia nigra neurons via the inhibition of OSMR in a mouse model of Parkinson's disease

The present study aimed to investigate the effect of microRNA-183 (miR-183) on substantia nigra neurons by targeting oncostatin M receptor (OSMR) in a mouse model of Parkinson’s disease (PD). The positive expression rates of OSMR and the apoptosis of substantia nigra neurons were detected by immunohistochemistry and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling, respectively. Substantia nigra neurons in normal and PD mice were cultured in vitro. The association between miR-183 and OSMR was verified using a dual luciferase reporter gene assay. The expression of miR-183 and the phosphoinositide 3-kinase-Akt signaling pathway-associated genes were detected by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. Cell apoptosis was detected by flow cytometry. OSMR is the target gene of miR-183. The number of OSMR-positive cells and the apoptotic rate of substantia nigra neurons were increased in the PD group. Neurons transfected with miR-183 mimic exhibited elevated expression levels of miR-183, B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax) and caspase-9 and increased apoptotic rate, and reduced expression levels of OSMR, Akt, phosphorylated (p-)Akt, glycogen synthase kinase-3 (GSK-3β), p-GSK-3β, Bcl-2, insulin-like growth factor 1 (IGF-1), mammalian target of rapamycin (mTOR) and p-mTOR. The miR-183 inhibitor decreased the expression levels of miR-183, Bax and caspase-9 and the apoptotic rate; however, increased the expression of OSMR, Akt, p-Akt, GSK-3β, p-GSK-3β, Bcl-2, IGF-1, mTOR and p-mTOR. The results of the present study provide evidence that the overexpression of miR-183 promotes the apoptosis of substantia nigra neurons by inhibiting the expression of OSMR.

Microcystin-leucine arginine (MC-LR) induced inflammatory response in bovine sertoli cell via TLR4/NF-kB signaling pathway

Sertoli cells were treated with 0, 20, 40, 60 and 80 μg/L of MC-LR to investigate its toxic effects, mechanism of action and immune response of the cells. Our results revealed that treatment containing 20 μg/L of MC-LR was non-toxic to the cells. Treatments containing 40, 60 and 80 μg/L of MC-LR reduced the cell viability, induced nuclear morphological changes and downregulated the blood-testis barrier constituent proteins within 48 h after treatment. The toll-like receptor 4 (TLR4) and nuclear factor-kappaB (NF-kB) were activated and significantly (P < 0.05) upregulated in cells treated with 40, 60 and 80 μg/L of MC-LR compared to the control. The pro-inflammatory cytokines were upregulated within 48 h after treatment. However commencing from 72 h, upregulation of anti-inflammatory cytokines and expression of blood-testis barrier constituent proteins was observed. This study indicates that MC-LR induced inflammatory response in bovine Sertoli cell via activation of TLR4/NF-kB signaling pathway.

The role of fibroblast growth factor 2 in drug addiction

Fibroblast growth factor 2 (FGF2) is a member of the FGF-family, which consists of 22 members, with four known FGF receptors (five in humans). Over the last 30 years, FGF2 has been extensively studied for its role in cell proliferation, differentiation, growth, survival and angiogenesis during development, as well as for its role in adult neurogenesis and regenerative plasticity. Over the past decade, FGF2 has been implicated in learning and memory, as well as in several neuropsychiatric disorders, including anxiety, stress, depression and drug addiction. In this review, we present accumulating evidence indicating the involvement of FGF2 in neuroadaptations caused by drugs of abuse, namely, amphetamine, cocaine, nicotine and alcohol. Moreover, evidence suggests that FGF2 is a positive regulator of alcohol and drug-related behaviors. Thus, although additional studies are yet required, we suggest that reducing FGF2 activity may provide a novel therapeutic approach for substance use disorders.

Growth Factors and Neuroglobin in Astrocyte Protection Against Neurodegeneration and Oxidative Stress

Neurodegenerative diseases, such as Parkinson and Alzheimer, are among the main public health issues in the world due to their effects on life quality and high mortality rates. Although neuronal death is the main cause of disruption in the central nervous system (CNS) elicited by these pathologies, other cells such as astrocytes are also affected. There is no treatment for preventing the cellular death during neurodegenerative processes, and current drug therapy is focused on decreasing the associated motor symptoms. For these reasons, it has been necessary to seek new therapeutical procedures, including the use of growth factors to reduce α-synuclein toxicity and misfolding in order to recover neuronal cells and astrocytes. Additionally, it has been shown that some growth factors are able to reduce the overproduction of reactive oxygen species (ROS), which are associated with neuronal death through activation of antioxidative enzymes such as catalase, superoxide dismutase, glutathione peroxidase, and neuroglobin. In the present review, we discuss the use of growth factors such as PDGF-BB, VEGF, BDNF, and the antioxidative enzyme neuroglobin in the protection of astrocytes and neurons during the development of neurodegenerative diseases.

Overexpression of TFEB Drives a Pleiotropic Neurotrophic Effect and Prevents Parkinson's Disease-Related Neurodegeneration

The possible implication of transcription factor EB (TFEB) as a therapeutic target in Parkinson's disease has gained momentum since it was discovered that TFEB controls lysosomal biogenesis and autophagy and that its activation might counteract lysosomal impairment and protein aggregation. However, the majority of putative direct targets of TFEB described to date is linked to a range of biological processes that are not related to the lysosomal-autophagic system. Here, we assessed the effect of overexpressing TFEB with an adeno-associated viral vector in mouse substantia nigra dopaminergic neurons. We demonstrate that TFEB overexpression drives a previously unknown bona fide neurotrophic effect, giving rise to cell growth, higher tyrosine hydroxylase levels, and increased dopamine release in the striatum. TFEB overexpression induces the activation of the mitogen-activated protein kinase 1/3 (MAPK1/3) and AKT pro-survival pathways, phosphorylation of mTORC1 effectors 4E-binding protein 1 (4E-BP1) and S6 kinase B1 (S6K1), and increased protein synthesis. We show that TFEB overexpression prevents dopaminergic cell loss and counteracts atrophy and the associated protein synthesis decline in the MPTP mouse model of Parkinson's disease. Our results suggest that increasing TFEB activity might prevent neuronal death and restore neuronal function in Parkinson's disease and other neurodegenerative diseases through different mechanisms.

Impaired Wnt signaling in dopamine containing neurons is associated with pathogenesis in a rotenone triggered Drosophila Parkinson's disease model

Parkinson’s disease, which is the one of the most common neurodegenerative movement disorder, is characterized by a progressive loss of dopamine containing neurons. The mechanisms underlying disease initiation and development are not well understood and causative therapies are currently not available. To elucidate the molecular processes during early stages of Parkinson’s disease, we utilized a Drosophila model. To induce Parkinson’s disease-like phenotypes, we treated flies with the pesticide rotenone and isolated dopamine producing neurons of animals that were at an early disease stage. Transcriptomic analyses revealed that gene ontologies associated with regulation of cell death and neuronal functions were significantly enriched. Moreover, the activities of the MAPK/EGFR- and TGF-β signaling pathways were enhanced, while the Wnt pathway was dampened. In order to evaluate the role of Wnt signaling for survival of dopaminergic neurons in the disease model, we rescued the reduced Wnt signaling activity by ectopic overexpression of armadillo/β-catenin. This intervention rescued the rotenone induced movement impairments in the Drosophila model. Taken together, this initial study showed a highly relevant role of Wnt signaling for dopamine producing neurons during pathogenesis in Parkinson’s disease and it implies that interfering with this pathway might by a suitable therapeutic option for the future.

Effect of moxibustion on mTOR-mediated autophagy in rotenone-induced Parkinson's disease model rats

Defects in autophagy-mediated clearance of α-synuclein may be one of the key factors leading to progressive loss of dopaminergic neurons in the substantia nigra. Moxibustion therapy for Parkinson's disease has been shown to have a positive effect, but the underlying mechanism remains unknown. Based on this, we explored whether moxibustion could protect dopaminergic neurons by promoting autophagy mediated by mammalian target of rapamycin (mTOR), with subsequent elimination of α-syn. A Parkinson's disease model was induced in rats by subcutaneous injection of rotenone at the back of their necks, and they received moxibustion at Zusanli (ST36), Guanyuan (CV4) and Fengfu (GV16), for 10 minutes at every point, once per day, for 14 consecutive days. Model rats without any treatment were used as a sham control. Compared with the Parkinson's disease group, the moxibustion group showed significantly greater tyrosine hydroxylase immunoreactivity and expression of light chain 3-II protein in the substantia nigra, and their behavioral score, α-synuclein immunoreactivity, the expression of phosphorylated mTOR and phosphorylated ribosomal protein S6 kinase (p-p70S6K) in the substantia nigra were significantly lower. These results suggest that moxibustion can promote the autophagic clearance of α-syn and improve behavioral performance in Parkinson's disease model rats. The protective mechanism may be associated with suppression of the mTOR/p70S6K pathway.

Protective effects of the resveratrol analog piceid in dopaminergic SH-SY5Y cells

Age-related motor deficits, such as loss of balance and coordination, are caused, in part, by loss of dopaminergic neurons. Oxidative stress is known to play a role in this neuronal loss. Resveratrol, a natural antioxidant with anticancer and anti-inflammatory potential, has been shown to protect dopaminergic-like cells (SH-SY5Y) against oxidative stress. However, the low bioavailability of resveratrol makes it worthwhile to explore newer compounds with similar properties. Piceid (RV8), an analog of resveratrol, has greater bioavailability than resveratrol, and our studies found that piceid (10, 20, 30 µM) protects SH-SY5Y cells against oxidative stress. Our investigations also found that the neuroprotection afforded by piceid was decreased when the MAP kinases, ERK1/2 and ERK5, were independently inhibited. Since oxidative stress is considered a master operator of apoptosis, our study also scrutinized dopamine-induced apoptosis and whether caspase-3/7 and Bcl-2 are involved, following piceid pretreatment followed by dopamine exposure. Our findings suggested that piceid pretreatment inhibited the dopamine-induced increase in caspase-3/7 activity and dopamine-induced loss of Bcl-2 expression. Overall, these findings suggest that the neuroprotective effects of piceid are mediated via the activation of ERK1/2, ERK5, and inhibition of apoptosis caused by oxidative stress.

α-Tocopherol at Nanomolar Concentration Protects Cortical Neurons against Oxidative Stress

The aim of the present work is to study the mechanism of the α-tocopherol (α-T) protective action at nanomolar and micromolar concentrations against H₂O₂-induced brain cortical neuron death. The mechanism of α-T action on neurons at its nanomolar concentrations characteristic for brain extracellular space has not been practically studied yet. Preincubation with nanomolar and micromolar α-T for 18 h was found to increase the viability of cortical neurons exposed to H₂O₂; α-T effect was concentration-dependent in the nanomolar range. However, preincubation with nanomolar α-T for 30 min was not effective. Nanomolar and micromolar α-T decreased the reactive oxygen species accumulation induced in cortical neurons by the prooxidant. Using immunoblotting it was shown that preincubation with α-T at nanomolar and micromolar concentrations for 18 h prevented Akt inactivation and decreased PKCδ activation induced in cortical neurons by H₂O₂. α-T prevented the ERK1/2 sustained activation during 24 h caused by H₂O₂. α-T at nanomolar and micromolar concentrations prevented a great increase of the proapoptotic to antiapoptotic proteins (Bax/Bcl-2) ratio, elicited by neuron exposure to H₂O₂. The similar neuron protection mechanism by nanomolar and micromolar α-T suggests that a “more is better” approach to patients’ supplementation with vitamin E or α-T is not reasonable.

Microtubule: A Common Target for Parkin and Parkinson’s Disease Toxins

Parkinson’s disease (PD) is characterized by the selective loss of nigral dopaminergic (DA) neurons, which have long axons enriched with microtubules. Depolymerization of microtubules by PD toxins such as rotenone disrupts vesicular transport. The ensuing accumulation of vesicles in the cell body leads to increased cytosolic concentration of dopamine due to leakage of the vesicles. Elevated oxidative stress induced by dopamine oxidation may thus trigger the selective demise of DA neurons. Many strategies have been developed to protect DA neurons by stabilizing microtubules either directly or through intracellular signaling cascades. On the other hand, parkin, one of the most frequently mutated genes in PD, encodes for a protein-ubiquitin E3 ligase that strongly binds to microtubules. Parkin stabilizes microtubules through three domains that provide strong and independent interactions with tubulin and microtubules. These interactions anchor parkin on microtubules and may facilitate its E3 ligase activity on misfolded proteins transported along microtubules. Thus, parkin and rotenone, two prominent genetic and environmental factors linked to PD, act in an opposing manner on the same molecular target in the cell, microtubules, whose destruction underlies the selective vulnerability of dopaminergic neurons.

Human Basic Fibroblast Growth Factor Inhibits Tau Phosphorylation via the PI3K/Akt-GSK3β Signaling Pathway in a 6-Hydroxydopamine-Induced Model of Parkinson's Disease

BACKGROUND

Basic fibroblast growth factor (bFGF) has been increasingly investigated due to its neuroprotection in neurodegenerative disorders. Because there are still no cures for any of these disorders, it is crucial to identify new therapeutic targets and screen potential drugs. The increased phosphorylation of tau at Ser396 leads to intracellular tau accumulation, which forms neurofibrillary tangles in Parkinson's disease (PD). In this study, neuroprotection by bFGF was observed, and the mechanisms related to its regulation of phosphorylated tau were investigated.

METHODS

bFGF-loaded liposome carriers were intranasally administered to rats. The neuroprotective effects of bFGF were assessed in a PD model induced by 6-hydroxydopamine (6-OHDA) in vivo and in vitro. The phosphorylation of tau was measured, and the PI3K/Akt-GSK3β signaling pathway was investigated.

RESULTS

Our study demonstrated that liposomes markedly assisted in the delivery of bFGF to the striatum and substantia nigra of rats and enhanced the neuroprotective effects of bFGF on dopaminergic neurons. bFGF treatment significantly ameliorated the behavioral deficits induced by 6-OHDA, rescued the loss of tyrosine hydroxylase-positive neurons and increased the number of Nissl bodies. bFGF reduced the phosphorylation of tau and GSK3β and increased the phosphorylation of PI3K/Akt.

CONCLUSION

Liposomes markedly assisted in the delivery of bFGF to the brain and enhanced the neuroprotective effects of bFGF by inhibiting the phosphorylation of tau. bFGF down-regulated the phosphorylation of tau by increasing the phosphorylation of GSK3β via the PI3K/Akt signaling pathway. These findings provide a new vision of bFGF as a potential therapy for PD.

Inhibition of p38 pathway-dependent MPTP-induced dopaminergic neurodegeneration in estrogen receptor alpha knockout mice

Approximately, 7-10 million people in the world suffer from Parkinson's disease (PD). Recently, increasing evidence has suggested the protective effect of estrogens against nigrostriatal dopaminergic damage in PD. In this study, we investigated whether estrogen affects 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced behavioral impairment in estrogen receptor alpha (ERα)-deficient mice. MPTP (15mg/kg, four times with 1.5-h interval)-induced dopaminergic neurodegeneration was evaluated in ERα wild-type (WT) and knockout (KO) mice. Larger dopamine depletion, behavioral impairments (Rotarod test, Pole test, and Gait test), activation of microglia and astrocytes, and neuroinflammation after MPTP injection were observed in ERα KO mice compared to those in WT mice. Immunostaining for tyrosine hydroxylase (TH) after MPTP injection showed fewer TH-positive neurons in ERα KO mice than WT mice. Levels of dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC, metabolite of dopamine) were also lowered in ERα KO mice after MPTP injection. Interestingly, a higher immunoreactivity for monoamine oxidase (MAO) B was found in the substantia nigra and striatum of ERα KO mice after MPTP injection. We also found an increased activation of p38 kinase (which positively regulates MAO B expression) in ERα KO mice. In vitro estrogen treatment inhibited neuroinflammation in 1-methyl-4-phenyl pyridium (MPP+)-treated cultured astrocyte cells; however, these inhibitory effects were removed by p38 inhibitor. These results indicate that ERα might be important for dopaminergic neuronal survival through inhibition of p38 pathway.

Inhibition of Endoplasmic Reticulum Stress is Involved in the Neuroprotective Effect of bFGF in the 6-OHDA-Induced Parkinson's Disease Model

Parkinson's disease (PD) is a progressive neurodegenerative disorder with complicated pathophysiologic mechanisms. Endoplasmic reticulum (ER) stress appears to play a critical role in the progression of PD. We demonstrated that basic fibroblast growth factor (bFGF), as a neurotropic factor, inhibited ER stress-induced neuronal cell apoptosis and that 6-hydroxydopamine (6-OHDA)-induced ER stress was involved in the progression of PD in rats. bFGF administration improved motor function recovery, increased tyrosine hydroxylase (TH)-positive neuron survival, and upregulated the levels of neurotransmitters in PD rats. The 6-OHDA-induced ER stress response proteins were inhibited by bFGF treatment. Meanwhile, bFGF also increased expression of TH. The administration of bFGF activated the downstream signals PI3K/Akt and Erk1/2 in vivo and in vitro. Inhibition of the PI3K/Akt and Erk1/2 pathways by specific inhibitors partially reduced the protective effect of bFGF. This study provides new insight towards bFGF translational drug development for PD involving the regulation of ER stress.

FGF9-induced changes in cellular redox status and HO-1 upregulation are FGFR-dependent and proceed through both ERK and AKT to induce CREB and Nrf2 activation

Our previous studies demonstrated that fibroblast growth factor 9 (FGF9) protects cortical and dopaminergic neurons from 1-methyl-4-phenylpyridinium (MPP(+))-induced oxidative insult by upregulation of γ-glutamylcysteine synthetase (γ-GCS) and heme oxygenase-1 (HO-1). However, the mechanisms responsible for FGF9-induced γ-GCS and HO-1 upregulation remain uncharacterized. In the present study, we demonstrate the signaling pathways by which FGF9 upregulates HO-1 and γ-GCS expression. We found that FGF9-induced HO-1 and γ-GCS expression was prevented by PD173014, an inhibitor of the FGF receptor (FGFR). FGF9 treatment induced the phosphorylation of FGFR downstream signals of extracellular signal-regulated kinase 1/2 (ERK1/2) and AKT in a dose- and time-dependent manner. The inhibition of MEK/ERK1/2 or PI3K/AKT activity by U0126 or wortmannin, but not the inhibition of phospholipase Cγ by U73122, prevented FGF9-induced γ-GCS and HO-1 upregulation, changes in cellular redox status, and neuroprotection against MPP(+) toxicity in primary cortical and dopaminergic neurons. Furthermore, FGF9 treatment enhanced the promoter activity of the cAMP-response element binding protein (CREB) and nuclear factor erythroid-derived 2-like 2 (Nrf2), and this phenomenon was blocked by PD173014 or U0126 or wortmannin. Knockdown of CREB and Nrf2 by shRNA blocked FGF9-induced γ-GCS and HO-1 upregulation, but not ERK and AKT phosphorylation. An in vivo study consistently showed that FGF9 overexpression using a lentivirus delivery system induced ERK1/2 phosphorylation and HO-1 upregulation and protected dopaminergic neurons against MPP(+) toxicity in rat substantia nigra. These results indicate that FGF9-induced HO-1 and γ-GCS upregulation is mediated by binding to FGFR and activation of two parallel downstream signaling pathways, ERK and AKT, which reconverge to induce CREB and Nrf2 transcriptional activity.

Meloxicam inhibits fipronil-induced apoptosis via modulation of the oxidative stress and inflammatory response in SH-SY5Y cells

Oxidative stress and inflammatory responses have been identified as key elements of neuronal cell apoptosis. In this study, we investigated the mechanisms by which inflammatory responses contribute to apoptosis in human neuroblastoma SH-SY5Y cells treated with fipronil (FPN). Based on the cytotoxic mechanism of FPN, we examined the neuroprotective effects of meloxicam against FPN-induced neuronal cell death. Treatment of SH-SY5Y cells with FPN induced apoptosis via activation of caspase-9 and -3, leading to nuclear condensation. In addition, FPN induced oxidative stress and increased expression of cyclooxygenase-2 (COX-2) and tumor necrosis factor-α (TNF-α) via inflammatory stimulation. Pretreatment of cells with meloxicam enhanced the viability of FPN-exposed cells through attenuation of oxidative stress and inflammatory response. FPN activated mitogen activated protein kinase (MAPK) and inhibitors of MAPK abolished FPN-induced COX-2 expression. Meloxicam also attenuated FPN-induced cell death by reducing MAPK-mediated pro-inflammatory factors. Furthermore, we observed both nuclear accumulation of p53 and enhanced levels of cytosolic p53 in a concentration-dependent manner after FPN treatment. Pretreatment of cells with meloxicam blocked the translocation of p53 from the cytosol to the nucleus. Together, these data suggest that meloxicam may exert anti-apoptotic effects against FPN-induced cytotoxicity by both attenuating oxidative stress and inhibiting the inflammatory cascade via inactivation of MAPK and p53 signaling.

Computer-aided targeting of the PI3K/Akt/mTOR pathway: toxicity reduction and therapeutic opportunities

The PI3K/Akt/mTOR pathway plays an essential role in a wide range of biological functions, including metabolism, macromolecular synthesis, cell growth, proliferation and survival. Its versatility, however, makes it a conspicuous target of many pathogens; and the consequential deregulations of this pathway often lead to complications, such as tumorigenesis, type 2 diabetes and cardiovascular diseases. Molecular targeted therapy, aimed at modulating the deregulated pathway, holds great promise for controlling these diseases, though side effects may be inevitable, given the ubiquity of the pathway in cell functions. Here, we review a variety of factors found to modulate the PI3K/Akt/mTOR pathway, including gene mutations, certain metabolites, inflammatory factors, chemical toxicants, drugs found to rectify the pathway, as well as viruses that hijack the pathway for their own synthetic purposes. Furthermore, this evidence of PI3K/Akt/mTOR pathway alteration and related pathogenesis has inspired the exploration of computer-aided targeting of this pathway to optimize therapeutic strategies. Herein, we discuss several possible options, using computer-aided targeting, to reduce the toxicity of molecularly-targeted therapy, including mathematical modeling, to reveal system-level control mechanisms and to confer a low-dosage combination therapy, the potential of PP2A as a therapeutic target, the formulation of parameters to identify patients who would most benefit from specific targeted therapies and molecular dynamics simulations and docking studies to discover drugs that are isoform specific or mutation selective so as to avoid undesired broad inhibitions. We hope this review will stimulate novel ideas for pharmaceutical discovery and deepen our understanding of curability and toxicity by targeting the PI3K/Akt/mTOR pathway.

GM1 ganglioside activates ERK1/2 and Akt downstream of Trk tyrosine kinase and protects PC12 cells against hydrogen peroxide toxicity

Ganglioside GM1 at micro- and nanomolar concentrations was shown to increase the viability of pheochromocytoma PC12 cells exposed to hydrogen peroxide and diminish the accumulation of reactive oxygen species and oxidative inactivation of Na(+),K(+)-ATPase, the effects of micromolar GM1 being more pronounced than those of nanomolar GM1. These effects of GM1 were abolished by Trk receptor tyrosine kinase inhibitor and diminished by MEK1/2, phosphoinositide 3-kinase and protein kinase C inhibitors. Hydrogen peroxide activates Trk tyrosine kinase; Akt and ERK1/2 are activated downstream of this protein kinase. GM1 was found to activate Trk receptor tyrosine kinase in PC12 cells. GM1 (100 nM and 10 µM) increased the basal activity of Akt, but did not change Akt activity in cells exposed to hydrogen peroxide. Basal ERK1/2 activity in PC12 cells was increased by GM1 at a concentration of 10 µM, but not at nanomolar concentrations. Activation of ERK1/2 by hydrogen peroxide was enhanced by GM1 at a concentration of 10 µM and to a lesser extent at a concentration of 100 nM. Thus, the protective and metabolic effects of GM1 ganglioside on PC12 cells exposed to hydrogen peroxide appear to depend on the activation of Trk receptor tyrosine kinase and downstream activation of Akt and ERK1/2.

Microglial displacement of inhibitory synapses provides neuroprotection in the adult brain

Microglia actively survey the brain microenvironment and play essential roles in sculpting synaptic connections during brain development. While microglial functions in the adult brain are less clear, activated microglia can closely appose neuronal cell bodies and displace axosomatic presynaptic terminals. Microglia-mediated stripping of presynaptic terminals is considered neuroprotective, but the cellular and molecular mechanisms are poorly defined. Using 3D electron microscopy, we demonstrate that activated microglia displace inhibitory presynaptic terminals from cortical neurons in adult mice. Electrophysiological recordings further establish that the reduction in inhibitory GABAergic synapses increased synchronized firing of cortical neurons in γ-frequency band. Increased neuronal activity results in the calcium-mediated activation of CaM kinase IV, phosphorylation of CREB, increased expression of antiapoptotic and neurotrophic molecules and reduced apoptosis of cortical neurons following injury. These results indicate that activated microglia can protect the adult brain by migrating to inhibitory synapses and displacing them from cortical neurons.

Microglia play essential roles in sculpting synaptic connections during brain development but their role in the adult brain is less clear. Here the authors show that activated microglia can prophylactically protect the adult rodent brain from injury by migrating to and displacing inhibitory synapses from cortical neurons.

FGF-2 induces neuronal death through upregulation of system xc-

The cystine/glutamate antiporter (system xc-) transports cystine into cell in exchange for glutamate. Fibroblast growth factor-2 (FGF-2) upregulates system xc- selectively on astrocytes, which leads to increased cystine uptake, the substrate for glutathione production, and increased glutamate release. While increased intracellular glutathione can limit oxidative stress, the increased glutamate release can potentially lead to excitotoxicity to neurons. To test this hypothesis, mixed neuronal and glial cortical cultures were treated with FGF-2. Treatment with FGF-2 for 48 h caused a significant neuronal death in these cultures. Cell death was not observed in neuronal-enriched cultures, or astrocyte-enriched cultures, suggesting the toxicity was the result of neuron-glia interaction. Blocking system xc- eliminated the neuronal death as did the AMPA/kainate receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[f]quinoxaline-2,3-dione (NBQX), but not the NMDA receptor antagonist memantine. When cultures were exposed directly to glutamate, both NBQX and memantine blocked the neuronal toxicity. The mechanism of this altered profile of glutamate receptor mediated toxicity by FGF-2 is unclear. The selective calcium permeable AMPA receptor antagonist 1-naphthyl acetyl spermine (NASPM) failed to offer protection. The most likely explanation for the results is that 48 h FGF-2 treatment induces AMPA/kainate receptor toxicity through increased system xc- function resulting in increased release of glutamate. At the same time, FGF-2 alters the sensitivity of the neurons to glutamate toxicity in a manner that promotes selective AMPA/kainate receptor mediated toxicity.

Gelatin nanostructured lipid carriers-mediated intranasal delivery of basic fibroblast growth factor enhances functional recovery in hemiparkinsonian rats

Lipid nanoparticles with solid matrix have been given increasing attention due to their biodegradable status and ability to entrap a variety of biologically active compounds. In this study, new phospholipid-based gelatin nanoparticles encapsulating basic fibroblast growth factor (bFGF) were developed to target the brain via nasal administration. Treatment effects were assessed by quantifying rotational behavior, monoamine neurotransmitter levels and tyrosine hydroxylase expression in 6-hydroxydopamine induced hemiparkinsonian rats. The gelatin nanostructured lipid carriers (GNLs) were prepared by a water-in-water emulsion method and then freeze-dried. The GNLs possessed better profile than gelatin nanoparticles (GNs), with particle size 143±1.14nm and Zeta potential -38.2±1.2mV. The intranasal GNLs efficiently enriched exogenous bFGF in olfactory bulb and striatum without adverse impact on the integrity of nasal mucosa and showed obvious therapeutic effects on hemiparkinsonian rats. Thus, GNLs are attractive carriers for nose-to-brain drug delivery, especially for unstable macromolecular drugs such as bFGF.

FROM THE CLINICAL EDITOR

This team of authors reports the development of phospholipid-based gelatin nanoparticles encapsulating basic fibroblast growth factor to target the brain via intranasal administration. A rat model of hemiparkinsonism was applied demonstrating a good safety profile and an obvious therapeutic effect.

Impairment of Atg5-dependent autophagic flux promotes paraquat- and MPP⁺-induced apoptosis but not rotenone or 6-hydroxydopamine toxicity

Controversial reports on the role of autophagy as a survival or cell death mechanism in dopaminergic cell death induced by parkinsonian toxins exist. We investigated the alterations in autophagic flux and the role of autophagy protein 5 (Atg5)-dependent autophagy in dopaminergic cell death induced by parkinsonian toxins. Dopaminergic cell death induced by the mitochondrial complex I inhibitors 1-methyl-4-phenylpyridinium (MPP⁺) and rotenone, the pesticide paraquat, and the dopamine analog 6-hydroxydopamine (6-OHDA) was paralleled by increased autophagosome accumulation. However, when compared with basal autophagy levels using chloroquine, autophagosome accumulation was a result of impaired autophagic flux. Only 6-OHDA induced an increase in autophagosome formation. Overexpression of a dominant negative form of Atg5 increased paraquat- and MPP⁺-induced cell death. Stimulation of mammalian target of rapamycin (mTOR)-dependent signaling protected against cell death induced by paraquat, whereas MPP⁺-induced toxicity was enhanced by wortmannin, a phosphoinositide 3-kinase class III inhibitor, rapamycin, and trehalose, an mTOR-independent autophagy activator. Modulation of autophagy by either pharmacological or genetic approaches had no effect on rotenone or 6-OHDA toxicity. Cell death induced by parkinsonian neurotoxins was inhibited by the pan caspase inhibitor (Z-VAD), but only caspase-3 inhibition was able to decrease MPP⁺-induced cell death. Finally, inhibition of the lysosomal hydrolases, cathepsins, increased the toxicity by paraquat and MPP⁺, supporting a protective role of Atg5-dependent autophagy and lysosomes degradation pathways on dopaminegic cell death. These results demonstrate that in dopaminergic cells, Atg5-dependent autophagy acts as a protective mechanism during apoptotic cell death induced by paraquat and MPP⁺ but not during rotenone or 6-OHDA toxicity.

A phenotypic model recapitulating the neuropathology of Parkinson's disease

This study was undertaken to develop a phenotypic model recapitulating the neuropathology of Parkinson's disease (PD). Such a model would show loss of dopamine in the basal ganglia, appearance of Lewy bodies, and the early stages of motor dysfunction. The model was developed by subcutaneously injecting biodegradable microspheres of rotenone, a complex I inhibitor in 8-9 month old, ovariectomized Long-Evans rats. Animals were observed for changes in body weight and motor activity. At the end of 11-12 weeks animals were euthanized and the brains examined for histopathological changes. Rotenone treated animals gain weight and appear normal and healthy as compared to controls but showed modest hypokinesia around 5-6 weeks posttreatment. Animals showed loss of dopaminergic (DA) neurons and the appearance of putative Lewy bodies in the substantia nigra. Neuroinflammation and oxidative stress were evidenced by the appearance of activated microglia, iron precipitates, and 8-oxo-2'-deoxyguanosine a major product of DNA oxidation. The dorsal striatum, the projection site of midbrain DA neurons, showed a significant reduction in tyrosine hydroxylase immunostaining, together with an increase in reactive astrocytes, an early sign of DA nerve terminal damage. Levels of vesicular monoamine transporter 2 (VMAT2) were significantly reduced in the dorsal striatum; however, there was an unexpected increase in dopamine transporter (DAT) levels. Old, ovariectomized females treated with rotenone microspheres present with normal weight gain and good health but a modest hypokinesia. Accompanying this behavioral phenotype are a constellation of neuropathologies characteristic of PD that include loss of DA neurons, microglia activation, oxidative damage to nuclear DNA, iron deposition, and appearance of putative Lewy bodies. This phenotypic model recapitulating the neuropathology of Parkinson's disease could provide insight into early mechanisms of pathogenesis and could aid in the identification of biomarkers to identify patients in early stage, PD.

Valproic acid ameliorates C. elegans dopaminergic neurodegeneration with implications for ERK-MAPK signaling

Parkinson's disease (PD) is a currently incurable neurodegenerative disorder that affects the aging population. The loss of dopaminergic neurons in the substantia nigra is one of the pathological features of PD. The precise causes of PD remain unresolved but evidence supports both environmental and genetic contributions. Current efforts for the treatment of PD are directed toward the discovery of compounds that show promise in impeding age-dependent neurodegeneration in PD patients. Alpha-synuclein (α-Syn) is a human protein that is mutated in specific populations of patients with familial PD. Overexpression of α-Syn in animal models of PD replicates key symptoms of PD, including neurodegeneration. Here, we use the nematode Caenorhabditis elegans as a model system, whereby α-Syn toxicity causes dopaminergic neurodegeneration, to test the capacity of valproic acid (VA) to protect neurons. The results of our study showed that treatment of nematodes with moderate concentrations of VA significantly protects dopaminergic neurons against α-Syn toxicity. Consistent with previously established knowledge related to the mechanistic action of VA in the cell, we showed through genetic analysis that the neuroprotection conferred by VA is inhibited by cell-specific depletion of the C. elegans ortholog of the MAP extracellular signal-regulated kinase (ERK), MPK-1, in the dopaminergic neurons. These findings suggest that VA may exert its neuroprotective effect via ERK-MAPK, or alternately could act with MAPK signaling to additively provide dopaminergic neuroprotection.

JNK and p38 MAPK regulate oxidative stress and the inflammatory response in chlorpyrifos-induced apoptosis

To investigate mechanisms of neuronal cell death in response to chlorpyrifos (CPF), a pesticide, we evaluated the regulation of ROS and COX-2 in human neuroblastoma SH-SY5Y cells treated with CPF. CPF treatment produced cytotoxic effects that appeared to involve an increase in ROS. In addition, CPF treatment activated MAPK pathways including JNK, ERK1/2, and p38 MAPK, and MAPK inhibitors abolished the cytotoxicity and reduced ROS generation. Our data demonstrate that CPF induced apoptosis involving MAPK activation through ROS production. Furthermore, after the CPF treatment, COX-2 expression increased. Interestingly, JNK and p38 MAPK inhibitors attenuated the CPF-induced COX-2 expression while an ERK1/2 inhibitor did not. These findings suggest that pathways involving JNK and p38 MAPK, but not ERK1/2, mediated apoptosis and are involved in the inflammatory response. In conclusion, the JNK and p38 MAPK pathways might be critical mediators in CPF-induced neuronal apoptosis by both generating ROS and up-regulating COX-2.

Reactive oxygen species regulated mitochondria-mediated apoptosis in PC12 cells exposed to chlorpyrifos

Reactive oxidative species (ROS) generated by environmental toxicants including pesticides could be one of the factors underlying the neuronal cell damage in neurodegenerative diseases. In this study we found that chlorpyrifos (CPF) induced apoptosis in dopaminergic neuronal components of PC12 cells as demonstrated by the activation of caspases and nuclear condensation. Furthermore, CPF also reduced the tyrosine hydroxylase-positive immunoreactivity in substantia nigra of the rat. In addition, CPF induced inhibition of mitochondrial complex I activity. Importantly, N-acetyl cysteine (NAC) treatment effectively blocked apoptosis via the caspase-9 and caspase-3 pathways while NAC attenuated the inhibition of mitochondrial complex I activity as well as the oxidative metabolism of dopamine (DA). These results demonstrated that CPF-induced apoptosis was involved in mitochondrial dysfunction through the production of ROS. In the response of cellular antioxidant systems to CPF, we found that CPF treatment increased HO-1 expression while the expression of CuZnSOD and MnSOD was reduced. In addition, we found that CPF treatment activated MAPK pathways, including ERK 1/2, the JNK, and the p38 MAP kinase in a time-dependent manner. NAC treatment abolished MAPK phosphorylation caused by CPF, indicating that ROS are upstream signals of MAPK. Interestingly, MAPK inhibitors abolished cytotoxicity and reduced ROS generation by CPF treatment. Our results demonstrate that CPF induced neuronal cell death in part through MAPK activation via ROS generation, suggesting its potential to generate oxidative stress via mitochondrial damage and its involvement in oxidative stress-related neurodegenerative disease.

Mitochondrial complex I inhibitor rotenone-induced toxicity and its potential mechanisms in Parkinson's disease models

The etiology of Parkinson's disease (PD) is attributed to both environmental and genetic factors. The development of PD reportedly involves mitochondrial impairment, oxidative stress, α-synuclein aggregation, dysfunctional protein degradation, glutamate toxicity, calcium overloading, inflammation and loss of neurotrophic factors. Based on a link between mitochondrial dysfunction and pesticide exposure, many laboratories, including ours, have recently developed parkinsonian models by utilization of rotenone, a well-known mitochondrial complex I inhibitor. Rotenone models for PD appear to mimic most clinical features of idiopathic PD and recapitulate the slow and progressive loss of dopaminergic (DA) neurons and the Lewy body formation in the nigral-striatal system. Notably, potential human parkinsonian pathogenetic and pathophysiological mechanisms have been revealed through these models. In this review, we summarized various rotenone-based models for PD and discussed the implied etiology of and treatment for PD.

Insulin-like growth factor-I mediates neuroprotection in proteasome inhibition-induced cytotoxicity in SH-SY5Y cells

The proteasome is an enzyme complex responsible for targeted intracellular proteolysis. Alterations in proteasome-mediated protein clearance have been implicated in the pathogenesis of aging, Alzheimer's disease (AD) and Parkinson's disease (PD). In such diseases, proteasome inhibition may contribute to formation of abnormal protein aggregates, which in turn activate intracellular unfolded protein responses that cause oxidative stress and apoptosis. In this study, we investigated the protective effect of Insulin-like Growth Factor-I (IGF-1) for neural SH-SY5Y cells treated with the proteasomal inhibitor, Epoxomicin. In SH-SY5Y cells, Epoxomicin treatment results in accumulation of intracellular ubiquitinated proteins and cytochrome c release from damaged mitochondria, leading to cell death, in Epoxomicin time- and dose-dependent manner. In cells treated with small amounts of IGF-1, the same dosages of Epoxomicin reduced both mitochondrial damage (cytochrome c release) and reduced caspase-3 activation and PARP cleavage, both of which are markers of apoptosis. Notably, however, IGF-1-treated SH-SY5Y cells still contained ubiquitinated protein aggregates. This result indicates that IGF-1 blocks the downstream apoptotic consequences of Epoxomicin treatment leading to decreased proteasome function. Clues as to the mechanism for this protective effect come from (a) increased AKT phosphorylation observed in IGF-1-protected cells, vs. cells exposed to Epoxomicin without IGF-1, and (b) reduction of IGF-1 protection by pretreatment of the cells with LY294002 (an inhibitor of PI3-kinase). Together these findings suggest that activation of PI3/AKT pathways by IGF-1 is involved in IGF-1 neuroprotection against apoptosis following proteasome inhibition.

Exercise inhibits neuronal apoptosis and improves cerebral function following rat traumatic brain injury

Exercise is reported to inhibit neuronal apoptotic cell death in the hippocampus and improve learning and memory. However, the effect of exercise on inhibition of neuronal apoptosis surrounding the area of damage after traumatic brain injury (TBI) and the improvement of cerebral dysfunction following TBI are unknown. Here, we investigate the effect of exercise on morphology and cerebral function following TBI in rats. Wistar rats received TBI by a pneumatic controlled injury device were randomly divided into two groups: (1) non-exercise group and (2) exercise group. The exercise group ran on a treadmill for 30 min/day at 22 m/min for seven consecutive days. Immunohistochemical and behavioral studies were performed following TBI. The number of single-stranded DNA (ssDNA)-positive cells around the damaged area early after TBI was significantly reduced in the exercise group compared with the non-exercise group (P < 0.05). Furthermore, most ssDNA-positive cells in the non-exercise group co-localized with neuronal cells. However, in the exercise group, a few ssDNA-positive cells co-localized with neurons. In addition, there was a significant increase in neuronal cell number and improvement in cerebral dysfunction after TBI in the exercise group compared with the non-exercise group (P < 0.05). These results indicate that exercise following TBI inhibits neuronal degeneration and apoptotic cell death around the damaged area, which results in improvement of cerebral dysfunction. In summary, treadmill running improved cerebral dysfunction following TBI, indicating its potential as an effective clinical therapy. Therefore, exercise therapy (rehabilitation) in the early phase following TBI is important for recuperation from cerebral dysfunction.

JNK3-mediated apoptotic cell death in primary dopaminergic neurons

Investigation of mechanisms responsible for dopaminergic neuron death is critical for understanding the pathogenesis of Parkinson's disease, yet this is often quite challenging technically. Here, we describe detailed methods for culturing primary mesencephalic dopaminergic neurons and examining the activation of c-Jun N-terminal protein Kinase (JNK) in these cultures. We utilized immunocytochemistry and computerized analysis to quantify the number of surviving dopaminergic neurons and JNK activation in dopaminergic neurons. TUNEL staining was used to quantify apoptotic cell death. siRNA was used to specifically inhibit JNK3, the neural specific isoform of JNK. Our data implicate the activation of JNK3 in rotenone-induced dopaminergic neuron apoptosis.

Protein S protects neurons from excitotoxic injury by activating the TAM receptor Tyro3-phosphatidylinositol 3-kinase-Akt pathway through its sex hormone-binding globulin-like region

The anticoagulant factor protein S (PS) protects neurons from hypoxic/ischemic injury. However, molecular mechanisms mediating PS protection in injured neurons remain unknown. Here, we show mouse recombinant PS protects dose-dependently mouse cortical neurons from excitotoxic NMDA-mediated neuritic bead formation and apoptosis by activating the phosphatidylinositol 3-kinase (PI3K)-Akt pathway (EC(50) = 26 ± 4 nm). PS stimulated phosphorylation of Bad and Mdm2, two downstream targets of Akt, which in neurons subjected to pathological overstimulation of NMDA receptors (NMDARs) increased the antiapoptotic Bcl-2 and Bcl-X(L) levels and reduced the proapoptotic p53 and Bax levels. Adenoviral transduction with a kinase-deficient Akt mutant (Ad.Akt(K179A)) resulted in loss of PS-mediated neuronal protection, Akt activation, and Bad and Mdm2 phosphorylation. Using the TAM receptors tyrosine kinases Tyro3-, Axl-, and Mer-deficient neurons, we showed that PS protected neurons lacking Axl and Mer, but not Tyro3, suggesting a requirement of Tyro3 for PS-mediated protection. Consistent with these results, PS dose-dependently phosphorylated Tyro3 on neurons (EC(50) = 25 ± 3 nm). In an in vivo model of NMDA-induced excitotoxic lesions in the striatum, PS dose-dependently reduced the lesion volume in control mice (EC(50) = 22 ± 2 nm) and protected Axl(-/-) and Mer(-/-) transgenic mice, but not Tyro3(-/-) transgenic mice. Using different structural PS analogs, we demonstrated that the C terminus sex hormone-binding globulin-like (SHBG) domain of PS is critical for neuronal protection in vitro and in vivo. Thus, our data show that PS protects neurons by activating the Tyro3-PI3K-Akt pathway via its SHGB domain, suggesting potentially a novel neuroprotective approach for acute brain injury and chronic neurodegenerative disorders associated with excessive activation of NMDARs.