Effect of transplantation of c17.2 cells transfected with interleukin-10 gene on intracerebral immune response in rat model of Parkinson's disease

Disease mechanisms as subtypes: Immune dysfunction in Parkinson's disease

In recent years, the contraposition between inflammatory and neurodegenerative processes has been increasingly challenged. Inflammation has been emphasized as a key player in the onset and progression of Parkinson disease (PD) and other neurodegenerative disorders. The strongest indicators of the involvement of the immune system derived from evidence of microglial activation, profound imbalance in phenotype and composition of peripheral immune cells, and impaired humoral immune responses. Moreover, peripheral inflammatory mechanisms (e.g., involving the gut-brain axis) and immunogenetic factors are likely to be implicated. Even though several lines of preclinical and clinical studies are supporting and defining the complex relationship between the immune system and PD, the exact mechanisms are currently unknown. Similarly, the temporal and causal connections between innate and adaptive immune responses and neurodegeneration are unsettled, challenging our ambition to define an integrated and holistic model of the disease. Despite these difficulties, current evidence is providing the unique opportunity to develop immune-targeted approaches for PD, thus enriching our therapeutic armamentarium. This chapter aims to provide an extensive overview of past and present studies that explored the implication of the immune system in neurodegeneration, thus paving the road for the concept of disease modification in PD.

Concise Review: Innate and Adaptive Immune Recognition of Allogeneic and Xenogeneic Cell Transplants in the Central Nervous System

Over the last 30 years, numerous allogeneic and xenogeneic cell grafts have been transplanted into the central nervous system (CNS) of mice and men in an attempt to cure neurological diseases. In the early studies, human or porcine embryonic neural cells were grafted in the striatum of animals or patients in an attempt to replace lost neurons. Although the immune-privileged status of the brain as a recipient organ was widely accepted, it rapidly became evident that CNS-grafted allogeneic and xenogeneic cells could be recognized and rejected by the immune system, resulting in poor neural graft survival and limited functional recovery. Since then, the CNS transplantation field has witnessed a sharp rise in the number of studies in which allogeneic and xenogeneic neural or mesenchymal stem cells (NSCs or MSCs, respectively) are transplanted, predominantly aiming at providing trophic stimulation and promoting endogenous repair of the brain. Interestingly, in many recent NSC and MSC-based publications functional improvement was used as the principal measure to evaluate the success of cell transplantation, while the fate of transplanted cells remained largely unreported. In this review, we first attempt to understand why primary neural cell isolates were largely substituted for NSCs and MSCs in cell grafting studies. Next, we review the current knowledge on the immune mechanisms involved in the recognition and rejection of allogeneic and xenogeneic cellular grafts in the CNS. Finally, we propose strategies to reduce graft immunogenicity and to improve graft survival in order to design improved cell-based CNS therapies. Stem Cells Translational Medicine 2017;6:1434-1441.

Aging-related 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurochemial and behavioral deficits and redox dysfunction: improvement by AK-7

Aging is a prominent risk factor for the occurrence and progression of Parkinson disease (PD). Aging animals are more significant for PD research than young ones. It is promising to develop effective treatments for PD through modulation of aging-related molecules. Sirtuin 2 (SIRT2), a strong deacetylase highly expressed in the brain, has been implicated in the aging process. In our present study, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 12mg/kg once daily) was observed to bring about significant behavioral deficits and striatal dopamine depletion in aging male and female mice, while it did not do so in young animals. MPTP did not cause significant reduction in striatal 5-hydroxytryptamine content in aging male and female mice. Furthermore, we observed that MPTP treatment resulted in significant reduction in GSH content and significant increase in MDA content and SIRT2 expression in the substantia nigra (SN) of aging mice, while it did not do so in young animals. Importantly, we observed that AK-7 (a selective SIRT2 inhibitor) significantly improved behavior abnormality and neurochemical deficits in aging male and female mice treated with MPTP. Significant increase in GSH content and significant decrease in MDA content were also observed in the SN of aging male and female mice co-treated with MPTP and AK-7 compared with the MPTP-treated animals. Our results indicated that MPTP induce aging-related neurochemical and behavioural deficits and dysfunction of redox network in male and female mice and AK-7 may be neuroprotective in PD through modulating redox network.

Behavioral and Neurochemical Deficits in Aging Rats with Increased Neonatal Iron Intake: Silibinin's Neuroprotection by Maintaining Redox Balance

Aging is a critical risk factor for Parkinson's disease. Silibinin, a major flavonoid in Silybum marianum, has been suggested to display neuroprotective properties against various neurodegenerative diseases. In the present study, we observed that neonatal iron (120 μg/g body weight) supplementation resulted in significant abnormality of behavior and depletion of striatal dopamine (DA) in the aging male and female rats while it did not do so in the young male and female rats. No significant change in striatal serotonin content was observed in the aging male and female rats with neonatal supplementation of the same dose of iron. Furthermore, we found that the neonatal iron supplementation resulted in significant increase in malondialdehyde (MDA) and decrease in glutathione (GSH) in the substantia nigra (SN) of the aging male and female rats. No significant change in content of MDA and GSH was observed in the cerebellum of the aging male and female rats with the neonatal iron supplementation. Interestingly, silibinin (25 and 50 mg/kg body weight) treatment significantly and dose-dependently attenuated depletion of striatal DA and improved abnormality of behavior in the aging male and female rats with the neonatal iron supplementation. Moreover, silibinin significantly reduced MDA content and increased GSH content in the SN of the aging male and female rats. Taken together, our results indicate that elevated neonatal iron supplementation may result in neurochemical and behavioral deficits in the male and female rats with aging and silibinin may exert dopaminergic neuroprotection by maintaining redox balance.

Aging-related rotenone-induced neurochemical and behavioral deficits: role of SIRT2 and redox imbalance, and neuroprotection by AK-7

Aging is one of the strongest risk factors for Parkinson’s disease (PD). SIRT2 has been implicated in the aging process. It is pertinent to investigate the role of SIRT2 in aging-related dopaminergic neurotoxicity and to develop effective therapeutic strategies for PD through the use of aging animals. In this study, we observed that rotenone induced significant behavior abnormality and striatal dopamine depletion in aging rats, while it did not do so in young rats. No significant change in striatal serotonin level was observed in the aging rats after rotenone administration. There was also aging-related rotenone-induced increase in substantia nigra (SN) SIRT2 expression in the rats. In addition, there was aging-related rotenone-induced SN malondialdehyde (MDA) increase and glutathione (GSH) decrease in the rats. No significant changes in cerebellar SIRT2, MDA, or GSH levels were observed in the aging rats after rotenone administration. Striatal dopamine content was significantly inversely correlated with SN SIRT2 expression in the rats. AK-7 significantly diminished striatal dopamine depletion and improved behavior abnormality in the rotenone-treated aging rats. Furthermore, AK-7 significantly decreased MDA content and increased GSH content in the SN of rotenone-treated aging rats. Finally, the effect of AK-7 on dopaminergic neurons and redox imbalance was supported by the results from primary mesencephalic cultures. Our study helps to elucidate the mechanism for the participation of aging in PD and suggests that SN SIRT2 may be involved in PD neurodegeneration, that AK-7 may be neuroprotective in PD, and that maintaining redox balance may be one of the mechanisms underlying neuroprotection by AK-7.

Inhibition of Sirtuin 2 exerts neuroprotection in aging rats with increased neonatal iron intake

Impaired iron homeostasis may cause damage to dopaminergic neurons and is critically involved in the pathogenesis of Parkinson's disease. At present, very little is understood about the effect of neonatal iron intake on behavior in aging animals. Therefore, we hypothesized that increased neonatal iron intake would result in significant behavior abnormalities and striatal dopamine depletion during aging, and Sirtuin 2 contributes to the age-related neurotoxicity. In the present study, we observed that neonatal iron intake (120 μg/g per day) during postnatal days 10–17 resulted in significant behavior abnormalities and striatal dopamine depletion in aging rats. Furthermore, after AK-7 (a selective Sirtuin 2 inhibitor) was injected into the substantia nigra at postnatal 540 days and 570 days (5 μg/side per day), striatal dopamine depletion was significantly diminished and behavior abnormality was improved in aging rats with neonatal iron intake. Experimental findings suggest that increased neonatal iron intake may result in Parkinson's disease-like neurochemical and behavioral deficits with aging, and inhibition of Sirtuin 2 expression may be a neuroprotective measure in Parkinson's disease.

Changes in surface expression of N-methyl-D-aspartate receptors in the striatum in a rat model of Parkinson's disease

BACKGROUND

N-methyl-D-aspartate (NMDA) receptors play a central role in glutamatergic synaptic transmission in the mammalian brain and are linked to the pathophysiology and symptomatology of Parkinson's disease (PD). However, changes in NMDA receptor expression in distinct subcellular compartments in PD have not been elucidated. In this study, we investigated changes in subcellular expression of NMDA receptors in striatal neurons in a rodent PD model.

METHODS

Intracranial injection of the neurotoxin 6-hydroxydopamine (6-OHDA) was selectively lesioned into the nigrostriatal dopaminergic pathway in adult Sprague Dawley rats, which is a common rat model of PD. A surface receptor crosslinking assay was conducted to examine the response of individual NMDA receptor subunits to dopamine depletion in isolated and confined surface and intracellular compartments of striatal neurons.

RESULTS

In PD rats where 6-OHDA was selectively lesioned, surface expression of NMDA receptor GluN1 subunits as detected by surface protein crosslinking assays was increased in the striatum. In contrast, intracellular levels of GluN1 were decreased in the lesioned region. The NMDA receptor GluN2B subunit was elevated in its abundance in the surface pool of the lesioned striatum, while intracellular GluN2B levels were not altered. GluN2A subunits in both surface and intracellular fractions remained stable. In addition, total cellular levels of striatal GluN1 and GluN2A were not changed in lesioned tissue, while total GluN2B proteins showed an increase.

CONCLUSION

These results demonstrate the differential sensitivity of principal NMDA receptor subunits to dopamine depletion. GluN1 and GluN2B expression in the distinct surface compartment underwent upregulation in striatal neurons after selective lesions of the dopaminergic pathway by 6-OHDA.