Shenggang Sun

A non-transgenic mouse model (icv-STZ mouse) of Alzheimer's disease: similarities to and differences from the transgenic model (3xTg-AD mouse).

Alzheimer’s disease (AD) can be divided into sporadic AD (SAD) and familial AD (FAD). Most AD cases are sporadic and result from multiple etiologic factors, including environmental, genetic, and metabolic factors, whereas FAD is caused by mutations in the presenilins or amyloid-β (Aβ) precursor protein (APP) genes. A commonly used animal model for AD is the 3xTg-AD transgenic mouse model, which harbors mutated presenilin 1, APP, and tau genes and thus represents a model of FAD. There is an unmet need in the field to characterize animal models representing different AD mechanisms, so that potential drugs for SAD can be evaluated preclinically in these animal models. A mouse model generated by intracerebroventricular (icv) administration of streptozocin (STZ), the icv-STZ mouse, shows many aspects of SAD. In this study, we compared the non-cognitive and cognitive behaviors as well as biochemical and immunohistochemical alterations between the icv-STZ mouse and the 3xTg-AD mouse. We found that both mouse models showed increased exploratory activity as well as impaired learning and spatial memory. Both models also demonstrated neuroinflammation, altered synaptic proteins and insulin/IGF-1 (insulin-like growth factor-1) signaling, and increased hyperphosphorylated tau in the brain. The most prominent brain abnormality in the icv-STZ mouse was neuroinflammation, and in the 3xTg-AD mouse it was elevation of hyperphosphorylated tau. These observations demonstrate the behavioral and neuropathological similarities and differences between the icv-STZ mouse and the 3xTg-AD mouse models and will help guide future studies using these two mouse models for the development of AD drugs.

VEGF-expressing human umbilical cord mesenchymal stem cells, an improved therapy strategy for Parkinson’s disease

The umbilical cord provides a rich source of primitive mesenchymal stem cells (human umbilical cord mesenchymal stem cells (HUMSCs)), which have the potential for transplantation-based treatments of Parkinsons Disease (PD). Our pervious study indicated that adenovirus-associated virus-mediated intrastriatal delivery of human vascular endothelial growth factor 165 (VEGF 165) conferred molecular protection to the dopaminergic system. As both VEGF and HUMSCs displayed limited neuroprotection, in this study we investigated whether HUMSCs combined with VEGF expression could offer enhanced neuroprotection. HUMSCs were modified by adenovirus-mediated VEGF gene transfer, and subsequently transplanted into rotenone-lesioned striatum of hemiparkinsonian rats. As a result, HUMSCs differentiated into dopaminergic neuron-like cells on the basis of neuron-specific enolase (NSE) (neuronal marker), glial fibrillary acidic protein (GFAP) (astrocyte marker), nestin (neural stem cell marker) and tyrosine hydroxylase (TH) (dopaminergic marker) expression. Further, VEGF expression significantly enhanced the dopaminergic differentiation of HUMSCs in vivo. HUMSC transplantation ameliorated apomorphine-evoked rotations and reduced the loss of dopaminergic neurons in the lesioned substantia nigra (SNc), which was enhanced significantly by VEGF expression in HUMSCs. These findings present the suitability of HUMSC as a vector for gene therapy and suggest that stem cell engineering with VEGF may improve the transplantation strategy for the treatment of PD.

Potential autophagy enhancers attenuate rotenone-induced toxicity in SH-SY5Y.

Recent studies have shown that autophagy upregulation may be a tractable therapeutic intervention for clearing the disease-causing proteins, including α-synuclein, ubiquitin, and other misfolded or aggregated proteins in Parkinsons disease (PD). In this study, we explored a novel pharmacotherapeutic approach to treating PD by utilizing potential autophagy enhancers valproic acid (VPA) and carbamazepine (CBZ). Pretreatment with VPA (3 mM) and CBZ (50 μM) along with positive control rapamycin (Rap, 0.2 μM) or lithium (LiCl, 10 mM) significantly enhanced cell viability, decreased rotenone-induced nuclear fragmentation and apoptosis, ameliorated the decrease in mitochondrial membrane potential, reduced reactive oxygen species generation in the human neuroblastoma SH-SY5Y cells. Specifically, the numbers of lysosomes and autophagic vacuolar organelles were increased and the microtubule-associated protein 1 light chain 3-II (LC3-II) expression was up-regulated by VPA, CBZ, Rap, and LiCl (53%, 31%, 72%, and 63%), suggesting that these agents activated autophagic pathways. Moreover, pretreatment with the autophagy inhibitor chloroquine (Chl, 10 μM) remarkably strengthened rotenone toxicity in these cells. Our results suggest that VPA and CBZ, the most commonly used anti-epilepsy and mood-stabilizing medications with low-risk and easy administration might be potential therapeutics for PD.

Stereotaxical Infusion of Rotenone: A Reliable Rodent Model for Parkinson's Disease

A clinically-related animal model of Parkinsons disease (PD) may enable the elucidation of the etiology of the disease and assist the development of medications. However, none of the current neurotoxin-based models recapitulates the main clinical features of the disease or the pathological hallmarks, such as dopamine (DA) neuron specificity of degeneration and Lewy body formation, which limits the use of these models in PD research. To overcome these limitations, we developed a rat model by stereotaxically (ST) infusing small doses of the mitochondrial complex-I inhibitor, rotenone, into two brain sites: the right ventral tegmental area and the substantia nigra. Four weeks after ST rotenone administration, tyrosine hydroxylase (TH) immunoreactivity in the infusion side decreased by 43.7%, in contrast to a 75.8% decrease observed in rats treated systemically with rotenone (SYS). The rotenone infusion also reduced the DA content, the glutathione and superoxide dismutase activities, and induced alpha-synuclein expression, when compared to the contralateral side. This ST model displays neither peripheral toxicity or mortality and has a high success rate. This rotenone-based ST model thus recapitulates the slow and specific loss of DA neurons and better mimics the clinical features of idiopathic PD, representing a reliable and more clinically-related model for PD research.

Morin exerts neuroprotective actions in Parkinson disease models in vitro and in vivo.

AbstractAim:To investigate the neuroprotective effects of morin on 1-methyl-4-phenylpyridinium ion (MPP+)-induced apoptosis in neuronal differentiated PC12 cells as well as in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson disease (PD).Methods:PC12 cells were challenged with MPP+ in the presence or absence of morin. Cell viability was determined using MTT assay. Cell apoptosis was measured using flow cytometry. Generation of reactive oxygen species (ROS) was assayed using fluorescence assay. In an MPTP mouse model of PD, behavioral deficits, striatal dopamine content, and number of dopaminergic neurons were measured.Results:MPP+ induced apoptosis and ROS formation in PC12 cells. Concomitant treatment with morin (5-50 μmol/L) significantly attenuated the loss of cell viability and apoptosis when compared with MPP+ treatment alone. Morin also attenuated ROS formation induced by MPP+. MPTP induced permanent behavioral deficits and nigrostriatal lesions in mice. When administered prior to MPTP, morin (20 to 100 mg/kg) attenuated behavioral deficits, dopaminergic neuronal death and striatal dopamine depletion in the MPTP mouse model.Conclusion:The findings suggest that morin has neuroprotective actions both in vitro and in vivo, and may provide a novel therapeutic agent for the treatment of PD and other neurodegenerative diseases.

Dl-3-n-butylphthalide, a natural antioxidant, protects dopamine neurons in rotenone models for Parkinson's disease

In the absence of a cure for Parkinsons disease, development of preventive medications for this devastating disease is particularly encouraged. Dl-3-n-butylphthalide (NBP), an established natural antioxidant for clinical stroke treatment in China, can reportedly reduce beta-amyloid-induced neuronal toxicity in cultured neuronal cells, and attenuate neurodegenerative changes in aged rats. However, whether or not NBP confers neuroprotection in parkinsonian models is still unknown. In this study, we investigated the effects of NBP in rotenone models for Parkinsons diseases. In a cellular model, pretreatment with NBP enhanced cell viability by decreasing nuclear fragmentation, retaining mitochondrial membrane potential, and preventing reactive oxygen species (ROS) from generation. In a rodent model, 2-week treatment with NBP was able to ameliorate apomorphine-evoked rotations by 48% and rescue dopaminergic (DA) neurons by 30% and striatal DA terminal by 49%. Furthermore, NBP upregulated the vesicular monoamine transporter 2 gene expression in vitro and in vivo. Together, NBP protects DA neurons likely by reducing oxidative stress, offering an alternative neuroprotective medication for Parkinsons disease.

Involvement of glyceraldehyde-3-phosphate dehydrogenase in rotenone-induced cell apoptosis: relevance to protein misfolding and aggregation.

The hallmarks of Parkinsons disease (PD) are the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and the presence of intracellular inclusion bodies in surviving neurons. Although the specific etiology and pathogenesis of sporadic PD remains unknown, neuronal death was proven to be associated with mitochondrial dysfunction and protein misfolding. However, molecular links between mitochondrial dysfunction and protein misfolding remains obscure. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a classical glycolytic enzyme, is responsible for carbohydrate metabolism under normal circumstances. When translocated to the nucleus, GAPDH promotes neuron apoptosis in several neurodegenerative disorders. But it seems that GAPDH translocation is not the sole mechanism responsible for neuronal apoptosis. We found that rotenone, a common mitochondrial complex I inhibitor used to produce experimental parkinsonism, cannot only induce GAPDH translocation but also trigger intermolecular disulfide bonding and result in the formation of intracytoplasmic aggregates of GAPDH. This suggests a link between mitochondrial dysfunction and protein misfolding, and sheds light on the pathophysiology of Lewy body formation in Parkinsons disease.

Favorable effects of VEGF gene transfer on a rat model of Parkinson disease using adeno-associated viral vectors.

Vascular endothelial growth factor (VEGF) is a specific angiogenic peptide, which has been identified to play a critical role in neurodegeneration, and has beneficial effects on neurons. In this study, we investigated whether neurodegeneration in a rat model of Parkinson disease could be prevented by VEGF gene transfer mediated by adeno-associated virus (AAV) vectors. Our results demonstrated that a single injection of a VEGF-expressing AAV vector into striatum improved the rotational behavior of rat Parkinson disease models, and promoted the survival of dopaminergic neurons and fibers. Meanwhile, AAV-VEGF injection significantly increased the reactive astrocytes and the levels of glial cell line-derived neurotrophic factor in striatum, but did not induce extra angiogenesis and remarkable disorder of blood-brain barrier. We thus conclude that intrastriatal delivery of VEGF gene mediated by AAV has favorable effects on the dopaminergic neurons in a rat Parkinson disease model.

Edaravone guards dopamine neurons in a rotenone model for Parkinson's disease.

3-methyl-1-phenyl-2-pyrazolin-5-one (edaravone), an effective free radical scavenger, provides neuroprotection in stroke models and patients. In this study, we investigated its neuroprotective effects in a chronic rotenone rat model for Parkinsons disease. Here we showed that a five-week treatment with edaravone abolished rotenones activity to induce catalepsy, damage mitochondria and degenerate dopamine neurons in the midbrain of rotenone-treated rats. This abolishment was attributable at least partly to edaravones inhibition of rotenone-induced reactive oxygen species production or apoptotic promoter Bax expression and its up-regulation of the vesicular monoamine transporter 2 (VMAT2) expression. Collectively, edaravone may provide novel clinical therapeutics for PD.

Rapamycin decreases tau phosphorylation at Ser214 through regulation of cAMP-dependent kinase.

Preventing or reducing tau hyperphosphorylation is considered to be a therapeutic strategy in the treatment of Alzheimers disease (AD). Rapamycin may be a potential therapeutic agent for AD, because the rapamycin-induced autophagy may enhance the clearance of the hyperphosphorylated tau. However, recent rodent studies show that the protective effect of rapamycin may not be limited in the autophagic clearance of the hyperphosphorylated tau. Because some tau-related kinases are targets of the mammalian target of rapamycin (mTOR), we assume that rapamycin may regulate tau phosphorylation by regulating these kinases. Our results showed that in human neuroblastoma SH-SY5Y cells, treatment with rapamycin induced phosphorylation of the type IIα regulatory (RIIα) subunit of cAMP-dependent kinase (PKA). Rapamycin also induced nuclear translocation of the catalytic subunits (Cat) of PKA and decreases in tau phosphorylation at Ser214 (pS214). The above effects of rapamycin were prevented by pretreatment with the mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) inhibitor U0126. In addition, these effects of rapamycin might not depend on the level of tau expression, because similar results were obtained in both the non-tau-expressing wild type human embryonic kidney 293 (HEK293) cells and HEK293 cells stably transfected with the longest isoform of recombinant human tau (tau441; HEK293/tau441). These findings suggest that rapamycin decreases pS214 via regulation of PKA. Because tau phosphorylation at Ser214 may prime tau for further phosphorylation by other kinases, our findings provide a novel possible mechanism by which rapamycin reduces or prevents tau hyperphosphorylation.