In Su Kim

Cellular and Molecular Mediators of Neuroinflammation in the Pathogenesis of Parkinson’s Disease

Neuroinflammation is a host-defense mechanism associated with restoration of normal structure and function of the brain and neutralization of an insult. Increasing neuropathological and biochemical evidence from the brains of individuals with Parkinsons disease (PD) provides strong evidence for activation of neuroinflammatory pathways. Microglia, the resident innate immune cells, may play a major role in the inflammatory process of the diseased brain of patients with PD. Although microglia forms the first line of defense for the neural parenchyma, uncontrolled activation of microglia may directly affect neurons by releasing various molecular mediators such as inflammatory cytokines (tumor necrosis factor-α, interleukin [IL]-6, and IL-1β), nitric oxide, prostaglandin E2, and reactive oxygen and nitrogen species. Moreover, recent studies have reported that activated microglia phagocytose not only damaged cell debris but also intact neighboring cells. This phenomenon further supports their active participation in self-enduring neuronal damage cycles. As the relationship between PD and neuroinflammation is being studied, there is a realization that both cellular and molecular mediators are most likely assisting pathological processes leading to disease progression. Here, we discuss mediators of neuroinflammation, which are known activators released from damaged parenchyma of the brain and result in neuronal degeneration in patients with PD.

The role of free radicals in the aging brain and Parkinson's Disease: convergence and parallelism.

Free radical production and their targeted action on biomolecules have roles in aging and age-related disorders such as Parkinson’s disease (PD). There is an age-associated increase in oxidative damage to the brain, and aging is considered a risk factor for PD. Dopaminergic neurons show linear fallout of 5–10% per decade with aging; however, the rate and intensity of neuronal loss in patients with PD is more marked than that of aging. Here, we enumerate the common link between aging and PD at the cellular level with special reference to oxidative damage caused by free radicals. Oxidative damage includes mitochondrial dysfunction, dopamine auto-oxidation, α-synuclein aggregation, glial cell activation, alterations in calcium signaling, and excess free iron. Moreover, neurons encounter more oxidative stress as a counteracting mechanism with advancing age does not function properly. Alterations in transcriptional activity of various pathways, including nuclear factor erythroid 2-related factor 2, glycogen synthase kinase 3β, mitogen activated protein kinase, nuclear factor kappa B, and reduced activity of superoxide dismutase, catalase and glutathione with aging might be correlated with the increased incidence of PD.

Protective effects of Gastrodia elata Blume on MPP+-induced cytotoxicity in human dopaminergic SH-SY5Y cells.

AIM OF THE STUDY Gastrodia elata (GE) Blume (Orchidaceae) has been traditionally used as a folk medicine in Oriental countries since centuries for their variety of therapeutic benefits. This study is an attempt to investigate the protective effects of GE extract against MPP(+)-induced cytotoxicity in human dopaminergic SH-SY5Y cells and explore the neuroprotective mechanisms involved. MATERIALS AND METHODS Human dopaminergic SH-SY5Y cells were used to demonstrate the protective effects of GE against multiple parameters such as MPP(+)-induced cell viability, oxidative damage, expression of Bcl-2 and Bax, caspase-3 and poly(ADP-ribose) polymerase proteolysis. RESULTS GE effectively attenuated the cytotoxicity and improved cell viability in a dose-dependent manner. GE was effective in inhibiting both, the increased production of reactive oxygen species (ROS) and increase in Bax/Bcl-2 ratio, cleaved caspase-3 and PARP proteolysis. CONCLUSION Data from this study suggests the protective effects of GE on MPP(+)-induced cytotoxicity in dopaminergic cells, which may be ascribed to its significant anti-oxidative and anti-apoptotic properties, thus, GE might prove to be a valuable therapeutic agent for the treatment of various neurodegenerative diseases including progressive Parkinsons disease (PD).

Reactive oxygen species and inhibitors of inflammatory enzymes, NADPH oxidase, and iNOS in experimental models of Parkinson's disease.

Reactive oxygen species (ROSs) are emerging as important players in the etiology of neurodegenerative disorders including Parkinsons disease (PD). Out of several ROS-generating systems, the inflammatory enzymes nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and inducible nitric oxide synthase (iNOS) were believed to play major roles. Mounting evidence suggests that activation of NADPH oxidase and the expression of iNOS are directly linked to the generation of highly reactive ROS which affects various cellular components and preferentially damage midbrain dopaminergic neurons in PD. Therefore, appropriate management or inhibition of ROS generated by these enzymes may represent a therapeutic target to reduce neuronal degeneration seen in PD. Here, we have summarized recently developed agents and patents claimed as inhibitors of NADPH oxidase and iNOS enzymes in experimental models of PD.

Recent Advances on the Neuroprotective Potential of Antioxidants in Experimental Models of Parkinson’s Disease

Parkinson’s disease (PD), a neurodegenerative movement disorder of the central nervous system (CNS) is characterized by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta region of the midbrain. Although the etiology of PD is not completely understood and is believed to be multifactorial, oxidative stress and mitochondrial dysfunction are widely considered major consequences, which provide important clues to the disease mechanisms. Studies have explored the role of free radicals and oxidative stress that contributes to the cascade of events leading to dopamine cell degeneration in PD. In general, in-built protective mechanisms consisting of enzymatic and non-enzymatic antioxidants in the CNS play decisive roles in preventing neuronal cell loss due to free radicals. But the ability to produce these antioxidants decreases with aging. Therefore, antioxidant therapy alone or in combination with current treatment methods may represent an attractive strategy for treating or preventing the neurodegeneration seen in PD. Here we summarize the recent discoveries of potential antioxidant compounds for modulating free radical mediated oxidative stress leading to neurotoxicity in PD.

Chrysanthemum morifolium Ramat (CM) extract protects human neuroblastoma SH-SY5Y cells against MPP+-induced cytotoxicity

ETHNOPHARMACOLOGICAL RELEVANCE Chrysanthemum morifolium Ramat (Asteraceae) has (CM) long been used in Korean and Chinese traditional herbal medicines with numerous therapeutic applications. AIM OF THE STUDY To evaluate the neuroprotective activities of Chrysanthemum morifolium (CM) extract against 1-methyl-4-phenylpridinium ions (MPP(+)), Parkinsonian toxin through oxidative stress and impaired energy metabolism, in human SH-SY5Y neuroblastoma cells and the underlying mechanisms. MATERIALS AND METHODS The effects of CM against MPP(+)-induced cytotoxicity and neuronal cell viability, oxidative damage, the expression of Bcl-2 and Bax, caspase-3 and poly(ADP-ribose) polymerase (PARP) proteolysis were evaluated by using SH-SY5Y neuroblastoma cells. RESULTS CM effectively inhibited the cytotoxicity and improved cell viability. CM also attenuated the elevation of reactive oxygen species (ROS) level, increase in Bax/Bcl-2 ratio, cleavage of caspase-3 and PARP proteolysis. CONCLUSION These results demonstrate that CM possesses potent neuroprotective activity and therefore, might be a potential candidate in neurodegenerative diseases such as Parkinsons disease.

Inflexin attenuates proinflammatory responses and nuclear factor-κB activation in LPS-treated microglia

Activated microglia participate in neuroinflammation which contribute to neuronal damage. Suppression of microglial activation would have therapeutic benefits, which lead to alleviation of the progression of neurodegeneration. In this study, the inhibitory effects of inflexin, a putative antiinflammatory agent isolated from Isodon excisus (Max.) Kudo (Labiateae), on the production of proinflammatory mediators were investigated in the lipopolysaccharide (LPS)-stimulated microglia. Inflexin significantly inhibited the release of nitric oxide (NO). Consistently, both the mRNA and the protein levels for the inducible NO synthase were decreased by inflexin in a concentration-dependent manner. Inflexin also inhibited the expression of cyclooxygenase (COX)-2, but not the COX-1 and effectively reduced the LPS-induced expression of proinflammatory cytokines in a dose-dependent manner. Furthermore, inflexin inhibited the degradation of IkappaB-alpha and the activation of NF-kappaB, p65 and Akt, while the MAPKs signal pathway was not affected. Our data suggest that inflexin was able to suppress neuroinflammation via inhibition of NF-kappaB activation and Akt pathway indicating that inflexin may be developed as a potent therapeutic agent in treating neuroinflammatory diseases.

Molecular effects of activated BV-2 microglia by mitochondrial toxin 1-methyl-4-phenylpyridinium

Microglia plays an important role in inflammation-mediated neurodegeneration. Compelling evidence supports the hypothesis that microglial activation contributes to the pathogenesis of various neurodegenerative diseases. However, little is known about the molecular outcome of activated microglia. In this report, we investigate the molecular consequences of MPP(+) toxin-induced activated BV-2 microglia. Intoxication of specific mitochondrial toxin methyl-4-phenylpyridinium iodide ion (MPP(+)) to BV-2 cells induced significant mitochondrial dysfunction and increased the reactive oxygen species generation, caspase-3 activation, and poly ADP ribose polymerase proteolysis. Further, MAC-1 immunostaining in the midbrain of mice revealed a decrease in activated microglia at day 4 after intoxication with MPP(+). From this study, it was confirmed that BV-2 microglia respond to the mitochondrial toxin MPP(+) which may lead to apoptotic cell death. Understanding of the mechanistic basis of apoptotic elimination of activated microglia may help to develop new strategies for the treatment of neurodegenerative diseases.

A novel synthetic compound PHID (8-Phenyl-6a, 7, 8, 9, 9a, 10-hexahydro-6H-isoindolo [5, 6-g] quinoxaline-7, 9-dione) protects SH-SY5Y cells against MPP(+)-induced cytotoxicity through inhibition of reactive oxygen species generation and JNK signaling.

1-Methyl-4-phenylpyridinium ion (MPP(+)), a neurotoxin selective to dopaminergic neurons and an inhibitor of mitochondrial complex I, has been widely used as an etiologic model of Parkinsons disease. In this study, we investigated the protective effects of a novel synthetic compound, 8-Phenyl-6a,7,8,9,9a,10-hexahydro-6H-isoindolo[5,6-g]quinoxaline-7,9-dione (PHID), on MPP(+)-induced cytotoxicity in SH-SY5Y cells. MPP(+) induced apoptosis characterized by generation of reactive oxygen species, caspase-3 activation, poly ADP ribose polymerase proteolysis and increase in Bax/Bcl-2 ratio were blocked by PHID in a dose-dependent fashion. Furthermore, MPP(+)-mediated activation of stress-activated protein kinase/c-Jun N-terminal kinase (JNK) was also inhibited by PHID in a dose-dependent manner. The results indicate that PHID protects against MPP(+)-induced apoptosis by blocking reactive oxygen species stimulation and JNK signaling pathways in SH-SY5Y cells, implicating the novel compound in the prevention of progressive neurodegenerative diseases such as Parkinsons disease.

Genome-wide temporal responses of human neuroblastoma SH-SY5Y cells to MPP+ neurotoxicity

The development of a stable and reliable dopaminergic (DAergic) neuronal injury model is particularly necessary for studying the pathogenesis of Parkinson’s disease (PD) and developing therapeutic strategies. As SH-SY5Y cells express the dopamine transporter (DAT), a protein expressed in DAergic neurons within the central nervous system, SH-SY5Y cells has been widely used in studies of mechanisms of 1-methyl-4-phenyl-pyridinium (MPP+)-induced neurotoxicity and the pathogenesis underlying MPP+-induced PD mimics. However, the genome-wide time dependent gene expression change of neuroblastoma SH-SY5Y cells by MPP+ toxicity has not been characterized. Here, we carried out a time series microarray experiment consisting of eight time points including time 0 (control) and 0.5, 1.5, 3, 6, 9, 12, and 24 h after MPP+ treatment using IIlumina human HT-12 expression v.4 bead array. The differentially expressed genes from time series microarray data were identified using the EDGE (Extraction of Differential Gene Expression) software package. In this study, 79 and 838 genes are considered significant at a 0.1% and 1% false-discovery rate level, respectively. Gene ontology (GO) analysis of these genes was carried out with the GOrilla web-server interactive software. GO terms such as the mitochondrial part (GO:0044429), the protein-DNA complex assembly (GO:0065004), and the nucleosome assembly (GO:0006334) had significant enrichment scores. Collectively, the information of time dependent gene expression might provide insight into the regulatory mechanisms induced by MPP+ toxicity in human neuroblastoma SH-SY5Y cells.