Prosurvival role of JAK/STAT and Akt signaling pathways in MPP+-induced apoptosis in neurons

The mechanism of LZ-8-mediated immune response in the mouse model of Parkinson's disease

Parkinson's disease (PD) is associated with microscopic changes in the brain, particularly substantia nigra (SN). Ganoderma lucidum immunoregulatory protein (rLZ-8) is might confer protective effects against PD. We developed a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced murine model of PD and determined the effects of rLZ-8 on molecular and cellular components of SN and whole brain tissue. The levels of SOD, GSH-Px, p-JAK2 and p-STAT3 in the brain tissue and SN were downregulated, while IL-6, IL-1β, and TNF-α and MDA were upregulated. These effects were significantly reversed upon treatment rLZ-8. In summary, oxidative stress and inflammatory response in PD can be alleviated using rLZ-8.

Growth hormone rescue cerebellar degeneration in SCA3 transgenic mice

Spinocerebellar ataxia type 3 (SCA3) is a fatal neurodegenerative disease for which no identified effective treatment or prevention methods exist. However, low-dose growth hormone (GH) therapy, as a potential off-label use, may deter the progress of SCA3. SCA3 15Q and SCA3 84Q transgenic mice harboring a YAC transgene that expresses the human ATXN3 gene with a pathogenic expanded 15 CAG repeat and 84 CAG repeat motif, respectively, were recruited. SCA3 15Q transgenic mice were considered as the healthy control group, whereas low-dose GH- and PBS-treated SCA3 84Q transgenic mice were considered as the study and sham groups, respectively. The SCA3 84Q transgenic mice were administered intraperitoneal injections of GH or PBS weekly from the postnatal age of 9 months-18 months. After 9 months of GH treatment in the SCA3 84Q transgenic mice, all locomotor functions including rotarod test, behavior box analysis were restored. The GH-treated SCA3 84Q transgenic mice revealed more preserved Purkinje cells/cerebellar cortex and less ataxin-3 aggregation, DNA oxidative, cell apoptosis compared with the PBS-treated SCA3 84Q transgenic mice. GH therapy may be one of the potential off-labeled using in the alleviation of SCA3 progression.

Nicotine prevents alpha-synuclein accumulation in mouse and human iPSC-derived dopaminergic neurons through activation of the dopamine D3- acetylcholine nicotinic receptor heteromer

We recently found that in mouse dopaminergic neurons, the heteromer formed by the dopamine D3 receptor (D3R) and the β2 subunit of acetylcholine nicotinic receptor (nAChR) exerts neurotrophic effects when activated by nicotine, leading to neurons with enlarged cell bodies and increased dendrite arborization. Beside this action, we now show that nicotine, by activating the D3R-nAChR heteromer, protects dopaminergic neurons against neuronal injury. In primary cultures of mouse dopaminergic neurons, in fact, the ability of nicotine to inhibit both the pathological accumulation of alpha-synuclein induced by glucose deprivation and the consequent morphological defects were strongly prevented by disrupting the D3R-nAChR heteromer with specific interfering TAT-peptides; the relevance of the phosphoinositide 3-kinase (PI3K) intracellular signaling in mediating nicotine prevention of alpha-synuclein aggregation has been also demonstrated. Moreover, the ability of nicotine in restoring the ubiquitin-proteasome system has been found as a mechanism contributing to the neuroprotective properties of nicotine. By using the proximity ligation assay, we have shown that the D3R-nAChR heteromer is also expressed in human dopaminergic neurons derived from induced pluripotent stem cells. In this human cell model, nicotine exerts neuroprotective effects specifically acting through the D3R-nAChR complex thus indicating that this heteromer is a relevant molecular effector involved in the protection of human dopaminergic neurons.

Organophosphate pesticide chlorpyrifos impairs STAT1 signaling to induce dopaminergic neurotoxicity: Implications for mitochondria mediated oxidative stress signaling events

The organophosphate (OP) pesticide chlorpyrifos (CPF), used in agricultural settings, induces developmental and neurological impairments. Recent studies using in vitro cell culture models have reported CPF exposure to have a positive association with mitochondria-mediated oxidative stress response and dopaminergic cell death; however, the mechanism by which mitochondrial reactive oxygen species (ROS) contribute to dopaminergic cell death remains unclear. Therefore, we hypothesized that STAT1, a transcription factor, causes apoptotic dopaminergic cell death via mitochondria-mediated oxidative stress mechanisms. Here we show that exposure of dopaminergic neuronal cells such as N27 cells (immortalized murine mesencephalic dopaminergic cells) to CPF resulted in a dose-dependent increase in apoptotic cell death as measured by MTS assay and DNA fragmentation. Similar effects were observed in CPF-treated human dopaminergic neuronal cells (LUHMES cells), with an associated increase in mitochondrial dysfunction. Moreover, CPF (10 μM) induced time-dependent increase in STAT1 activation coincided with the collapse of mitochondrial transmembrane potential, increase in ROS generation, proteolytic cleavage of protein kinase C delta (PKCδ), inhibition of the mitochondrial basal oxygen consumption rate (OCR), with a concomitant reduction in ATP-linked OCR and reserve capacity, increase in Bax/Bcl-2 ratio and enhancement of autophagy. Additionally, by chromatin immunoprecipitation (ChIP), we demonstrated that STAT1 bound to a putative regulatory sequence in the NOX1 and Bax promoter regions in response to CPF in N27 cells. Interestingly, overexpression of non-phosphorylatable STAT1 mutants (STAT1Y701F and STAT1S727A) but not STAT1 WT construct attenuated the cleavage of PKCδ and ultimately cell death in CPF-treated cells. Furthermore, small interfering RNA knockdown demonstrated STAT1 to be a critical regulator of autophagy and mitochondria-mediated proapoptotic cell signaling events after CPF treatment in N27 cells. Finally, oral administration of CPF (5 mg/kg) in postnatal rats (PNDs 27-61) induced motor deficits, and nigrostriatal dopaminergic neurodegeneration with a concomitant induction of STAT1-dependent proapoptotic cell signaling events. Conversely, co-treatment with mitoapocynin (a mitochondrially-targeted antioxidant) and CPF rescued motor deficits, and restored dopaminergic neuronal survival via abrogation of STAT1-dependent proapoptotic cell signaling events. Taken together, our study identifies a novel mechanism by which STAT1 regulates mitochondria-mediated oxidative stress response, PKCδ activation and autophagy. In this context, the phosphorylation of Tyrosine 701 and Serine 727 in STAT1 was found to be essential for PKCδ cleavage. By attenuating mitochondrial-derived ROS, mitoapocynin may have therapeutic applications for reversing CPF-induced dopaminergic neurotoxicity and associated neurobehavioral deficits as well as neurodegenerative diseases.

Systems Biomedicine of Rabies Delineates the Affected Signaling Pathways

The prototypical neurotropic virus, rabies, is a member of the Rhabdoviridae family that causes lethal encephalomyelitis. Although there have been a plethora of studies investigating the etiological mechanism of the rabies virus and many precautionary methods have been implemented to avert the disease outbreak over the last century, the disease has surprisingly no definite remedy at its late stages. The psychological symptoms and the underlying etiology, as well as the rare survival rate from rabies encephalitis, has still remained a mystery. We, therefore, undertook a systems biomedicine approach to identify the network of gene products implicated in rabies. This was done by meta-analyzing whole-transcriptome microarray datasets of the CNS infected by strain CVS-11, and integrating them with interactome data using computational and statistical methods. We first determined the differentially expressed genes (DEGs) in each study and horizontally integrated the results at the mRNA and microRNA levels separately. A total of 61 seed genes involved in signal propagation system were obtained by means of unifying mRNA and microRNA detected integrated DEGs. We then reconstructed a refined protein–protein interaction network (PPIN) of infected cells to elucidate the rabies-implicated signal transduction network (RISN). To validate our findings, we confirmed differential expression of randomly selected genes in the network using Real-time PCR. In conclusion, the identification of seed genes and their network neighborhood within the refined PPIN can be useful for demonstrating signaling pathways including interferon circumvent, toward proliferation and survival, and neuropathological clue, explaining the intricate underlying molecular neuropathology of rabies infection and thus rendered a molecular framework for predicting potential drug targets.

MiR-133b ameliorates axon degeneration induced by MPP(+) via targeting RhoA

Increasing evidence suggests that microRNAs (miRs) play a significant role in the pathogenesis of Parkinson's disease (PD). MiR-133b, which is significantly decreased in the PD midbrain, has recently been shown to promote neurite outgrowth and enhance neural functional recovery. However, the role of miR-133b in PD has not been clearly established. Here, using a well-established PD model culture based on the neurotoxin 1-methyl-4-phenyl-pyridinium (MPP(+)), we demonstrated that miR-133b could promote axon outgrowth in dopaminergic neurons (DNs) and ameliorated MPP(+)-induced axon degeneration. Additional experiments suggested that the mechanisms of this miR-133b-mediated effect might rely on RhoA inhibition. We demonstrated that RhoA, an inhibitor of axonal growth, was increased in DNs under MPP(+) treatment, and this increase could be attenuated by miR-133b overexpression. Moreover, we demonstrated that the induced expression of miR-133b could inhibit α-synuclein, which is critically involved in the pathological process of PD. Furthermore, we found that overexpression of miR-133b abrogated the MPP(+)-induced decrease in the Bcl-2/Bax ratio and upregulated phosphorylated Akt (p-Akt), which is a pro-survival kinase. Together these findings reveal novel roles for miR-133b in the pathogenesis of PD and provide new therapeutic avenues for the treatment of the disease.

miR-7 and miR-153 protect neurons against MPP(+)-induced cell death via upregulation of mTOR pathway

Differential expression of microRNAs (miRs) in the brain of patients with neurodegenerative diseases suggests that they may have key regulatory roles in the development of these disorders. Two such miRs, miR-7, and miR-153 have recently been shown to target α-synuclein, a protein critically involved in the pathological process of Parkinson's disease. By using a well-established in culture Parkinson's disease model that of neurotoxin 1-Methyl-4-Phenyl-Pyridinium (MPP⁺), we examined whether miR-7 and miR-153 display neuroprotective properties. Herein, we demonstrate that treatment of cortical neurons with MPP⁺ induced a dose-dependent cell death with apoptotic characteristics. This was reflected in altered intracellular signaling characterized by increased levels of activated kinases p38MAPK and ERK1/2 and reduced levels of activated AKT, p70S6K, and SAPK/JNK. Overexpression of miR-7 or miR-153 by adenoviral transduction protected cortical neurons from MPP⁺-induced toxicity, restored neuronal viability and anti-apoptotic BCL-2 protein levels while attenuated activation of caspase-3. Moreover, both miR-7 and miR-153 interfered with MPP⁺-induced alterations in intracellular signaling pathways in a partially overlapping manner; specifically, they preserved activation of mTOR and SAPK/JNK signaling pathways in the MPP⁺-treated neurons, while miR-153 also attenuated MPP⁺-induced activation of p38MAPK. No major effects were observed in the rest of signaling cascades or proteins investigated. Furthermore, the neuroprotective effect of miR-7 and miR-153 was alleviated when MPP⁺ was co-administered with rapamycin. Taken together, our results suggest that miR-7 and miR-153 protect neurons from cell death by interfering with the MPP⁺-induced downregulation of mTOR signaling.

Sun ginseng protects endothelial progenitor cells from senescence associated apoptosis

Endothelial progenitor cells (EPC) are a population of cells that circulate in the blood stream. They play a role in angiogenesis and, therefore, can be prognostic markers of vascular repair. Ginsenoside Rg₃ prevents endothelial cell apoptosis through the inhibition of the mitochondrial caspase pathway. It also affects estrogen activity, which reduces EPC senescence. Sun ginseng (SG), which is heat-processed ginseng, has a high content of ginsenosides. The purpose of this study was to investigate the protective effects of SG on senescence-associated apoptosis in EPCs. In order to isolate EPCs, mononuclear cells of human blood buffy coats were cultured and characterized by their uptake of acetylated low-density lipoprotein (acLDL) and their binding of Ulex europaeus agglutinin I (ulex-lectin). Flow cytometry with annexin-V staining was performed in order to assess early and late apoptosis. Senescence was determined by β-galactosidase (β-gal) staining. Staining with 4′-6-Diamidino-2-phenylindole verified that most adherent cells (93±2.7%) were acLDL-positive and ulex-lectin-positive. The percentage of β-gal-positive EPCs was decreased from 93.8±2.0% to 62.5±3.6% by SG treatment. A fluorescence-activated cell sorter (FACS) analysis showed that 4.9% of EPCs were late apoptotic in controls. Sun ginseng decreased the apoptotic cell population by 39% in the late stage of apoptosis from control baseline levels. In conclusion, these results show antisenescent and antiapoptotic effects of SG in human-derived EPCs, indicating that SG can enhance EPC-mediated repair mechanisms.

AG490 improves the survival of human myoblasts in vitro and in vivo

Cell therapies consist in transplanting healthy cells into a disabled tissue with the goal to repopulate it and restore its function at least partially. In muscular diseases, most of the time, myoblasts are chosen for their expansion capacity in culture. Nevertheless, cell transplantation has limitations, among them, death of the transplanted cells, during the days following the graft. One possibility to counteract this problem is to enhance the proliferation of the transplanted myoblasts before their fusion with the existing muscle fibers. AG490 is a specific inhibitor of janus tyrosine kinase 2 (JAK2). The hypothesis is to block myoblast differentiation with AG490, thus permitting their proliferation. The inhibition of myoblast fusion by AG490 was confirmed in this study by gene expression and with a myosin heavy chain staining (MyHC). Moreover, cell survival was estimated by flow cytometry. AG490 was found to protect myoblasts in vitro from apoptosis induced by H(2)O(2) or by preventing attachment of cells to their substrate. Finally, in an in vivo model of muscle regeneration, when AG490 was coinjected with the myoblasts their survival was increased by 45% at 5 days after their transplantation.

Involvement of Stat3 in mouse brain development and sexual dimorphism: a proteomics approach

Although the role of STAT3 in cell physiology and tissue development has been largely investigated, its involvement in the development and maintenance of nervous tissue and in the mechanisms of neuroprotection is not yet known. The potentially wide range of STAT3 activities raises the question of tissue- and gender-specificity as putative mechanisms of regulation. To explore the function of STAT3 in the brain and the hypothesis of a gender-linked modulation of STAT3, we analyzed a neuron-specific STAT3 knockout mouse model investigating the influence of STAT3 activity in brain protein expression pattern in both males and females in the absence of neurological insult. We performed a proteomic study aimed to reveal the molecular pathways directly or indirectly controlled by STAT3 underscoring its role in brain development and maintenance. We identified several proteins, belonging to different neuronal pathways such as energy metabolism or synaptic transmission, controlled by STAT3 that confirm its crucial role in brain development and maintenance. Moreover, we investigated the different processes that could contribute to the sexual dimorphic behavior observed in the incidence of neurological and mental disease. Interestingly both STAT3 KO and gender factors influence the expression of several mitochondrial proteins conferring to mitochondrial activity high importance in the regulation of brain physiology and conceivable relevance as therapeutic target.