alpha-synuclein and Brain-Ischemia

Both Parkinson's disease (PD) and stroke are debilitating conditions that result in neuronal death and loss of neurological functions. These two conditions predominantly affect aging populations with the deterioration of the quality of life for the patients themselves and a tremendous burden to families. While the neurodegeneration and symptomology of PD develop chronically over the years, post-stroke neuronal death and dysfunction develop rapidly in days. Despite the discrepancy in the pathophysiological time frame and severity, both conditions share common molecular mechanisms that include oxidative stress, mitochondrial dysfunction, inflammation, endoplasmic reticulum stress, and activation of various cell death pathways (apoptosis/necrosis/autophagy) that synergistically modulate the neuronal death. Emerging evidence indicates that several proteins associated with early-onset familial PD play critical roles in mediating the neuronal death. Importantly, mutations in the genes encoding Parkin, PTEN-induced putative kinase 1 and DJ-1 mediate autosomal recessive forms of PD, whereas mutations in the genes encoding leucine-rich repeat kinase 2 and α-synuclein are responsible for autosomal dominant PD. This review discusses the significance of these proteins with the emphasis on the role of α-synuclein in mediating post-ischemic brain damage.

Topics: alpha-Synuclein; Apoptosis; Brain Ischemia; Humans; Leucine-Rich Repeat Serine-Threonine Protein Kinase-2; Lewy Bodies; Parkinson Disease; Protein Deglycase DJ-1; Protein Kinases; Protein Processing, Post-Translational; Ubiquitin-Protein Ligases

Topics: alpha-Synuclein; Animals; Brain; Brain Ischemia; Down-Regulation; Endosomes; Infarction, Middle Cerebral Artery; Male; Mice; Mice, Inbred BALB C; Mice, Knockout; Models, Animal; Nedd4 Ubiquitin Protein Ligases; Neurodegenerative Diseases; Neurons; Neuroprotection; Parkinson Disease; Protein Aggregation, Pathological; Protein Processing, Post-Translational; Stroke; Ubiquitin-Protein Ligases; Ubiquitination; Up-Regulation

α-Synuclein is a soluble monomer abundant in the central nervous system. Aggregates of α-synuclein, consisting of higher-level oligomers and insoluble fibrils, have been observed in many chronic neurological diseases and are implicated in neurotoxicity and neurodegeneration. α-Synuclein has recently been shown to aggregate following acute ischemic stroke, exacerbating neuronal damage. Propofol is an intravenous anesthetic that is commonly used during intravascular embolectomy following acute ischemic stroke. While propofol has demonstrated neuroprotective properties following brain injury, the mechanism of protection in the setting of ischemic stroke is unclear. In this study, propofol administration significantly reduced the neurotoxic aggregation of α-synuclein, decreased the infarct area, and attenuated the neurological deficits after ischemic stroke in a mouse model. We then demonstrated that the propofol-induced reduction of α-synuclein aggregation was associated with increased mammalian target of rapamycin/ribosomal protein S6 kinase beta-1 signaling pathway activity and reduction of the excessive autophagy occurring after acute ischemic stroke.

Topics: alpha-Synuclein; Animals; Behavior, Animal; Brain Infarction; Brain Ischemia; Disease Models, Animal; Mice; Mice, Inbred C57BL; Neuroprotective Agents; Propofol; Psychomotor Performance; Stroke

Ischemic stroke, which is caused by a clot that blocks blood flow to the brain, can be severely disabling and sometimes fatal. We previously showed that transient focal ischemia in a rat model induces extensive temporal changes in the expression of cerebral microRNAs, with a sustained decrease in the abundance of miR-7a-5p (miR-7). Here, we evaluated the therapeutic efficacy of a miR-7 mimic oligonucleotide after cerebral ischemia in rodents according to the Stroke Treatment Academic Industry Roundtable (STAIR) criteria. Rodents were injected locally or systemically with miR-7 mimic before or after transient middle cerebral artery occlusion. Decreased miR-7 expression was observed in both young and aged rats of both sexes after cerebral ischemia. Pre- or postischemic treatment with miR-7 mimic decreased the lesion volume in both sexes and ages studied. Furthermore, systemic injection of miR-7 mimic into mice at 30 min (but not 2 hours) after cerebral ischemia substantially decreased the lesion volume and improved motor and cognitive functional recovery with minimal peripheral toxicity. The miR-7 mimic treatment substantially reduced the postischemic induction of α-synuclein (α-Syn), a protein that induces mitochondrial fragmentation, oxidative stress, and autophagy that promote neuronal cell death. Deletion of the gene encoding α-Syn abolished miR-7 mimic-dependent neuroprotection and functional recovery in young male mice. Further analysis confirmed that the transcript encoding α-Syn was bound and repressed by miR-7. Our findings suggest that miR-7 mimics may therapeutically minimize stroke-induced brain damage and disability.

Topics: Administration, Intravenous; alpha-Synuclein; Animals; Apoptosis; Autophagy; Brain Ischemia; Female; Male; Mice, Inbred C57BL; Mice, Knockout; MicroRNAs; Mitochondrial Dynamics; Motor Skills Disorders; Oxidative Stress; Rats; Rats, Inbred SHR; Reperfusion Injury; Stroke

In the present study, we detected the level of oligomeric form of α-synuclein in the red blood cells of ischemic stroke, Parkinson's disease, and normal people and compared the differences to assess the diagnosis potential of α-synuclein in ischemic stroke patients. 86 ischemic stroke, 100 PD, and 102 healthy cases were enrolled in the present study. Total protein amount in the red blood cells were quantified by BCA assay using spectrophotometer. Levels of oligomeric form of α-synuclein were characterized by a sandwich ELISA. Analysis of correlation analysis and receiver operating characteristic curve were conducted. Significant differences were detected in the levels of oligomeric forms of α-synuclein in different samples' blood cells (P < 0.05); the levels of total protein in (188.1 ± 33.9 mmol/L) healthy people were significantly higher than that of PD (147.7 ± 45.0 mmol/L) and ischemic stroke groups (142.9 ± 43.0 mmol/L) (P < 0.05). There was no correlation between the age of patients and level of α-synuclein (R (2) = 0.216 in ischemic stroke group and -0.104 in PD group) and the receiver operating characteristic curve analysis showed a high sensitivity of α-synuclein in discriminating ischemic stroke (sensitivity was 63.7 % and specificity was 9.6 %) and PD (sensitivity was 44.1 % and specificity was 12.5 %) patients from the controls. The levels of oligomeric form of α-synuclein of red blood cells in ischemic stroke and Parkinson's disease patients were both significant higher than normal people. And the level of oligomeric form α-synuclein showed a potential for diagnosis of ischemic stroke in clinic.

Topics: Adult; Aged; Aged, 80 and over; alpha-Synuclein; Analysis of Variance; Brain Ischemia; Enzyme-Linked Immunosorbent Assay; Female; Humans; Male; Middle Aged; Parkinson Disease; ROC Curve; Stroke; Young Adult

α-Synuclein (α-Syn), one of the most abundant proteins in the CNS, is known to be a major player in the neurodegeneration observed in Parkinson's disease. We currently report that transient focal ischemia upregulates α-Syn protein expression and nuclear translocation in neurons of the adult rodent brain. We further show that knockdown or knock-out of α-Syn significantly decreases the infarction and promotes better neurological recovery in rodents subjected to focal ischemia. Furthermore, α-Syn knockdown significantly reduced postischemic induction of phospho-Drp1, 3-nitrotyrosine, cleaved caspase-3, and LC-3 II/I, indicating its role in modulating mitochondrial fragmentation, oxidative stress, apoptosis, and autophagy, which are known to mediate poststroke neuronal death. Transient focal ischemia also significantly upregulated serine-129 (S129) phosphorylation (pα-Syn) of α-Syn and nuclear translocation of pα-Syn. Furthermore, knock-out mice that lack PLK2 (the predominant kinase that mediates S129 phosphorylation) showed better functional recovery and smaller infarcts when subjected to transient focal ischemia, indicating a detrimental role of S129 phosphorylation of α-Syn. In conclusion, our studies indicate that α-Syn is a potential therapeutic target to minimize poststroke brain damage.. Abnormal aggregation of α-synuclein (α-Syn) has been known to cause Parkinson's disease and other chronic synucleinopathies. However, even though α-Syn is linked to pathophysiological mechanisms similar to those that produce acute neurodenegerative disorders, such as stroke, the role of α-Syn in such disorder is not clear. We presently studied whether α-Syn mediates poststroke brain damage and more importantly whether preventing α-Syn expression is neuroprotective and leads to better physiological and functional outcome after stroke. Our study indicates that α-Syn is a potential therapeutic target for stroke therapy.

Topics: alpha-Synuclein; Animals; Brain Infarction; Brain Ischemia; Caspase 3; Death-Associated Protein Kinases; Disease Models, Animal; Gene Expression Regulation; Male; Mice; Mice, Transgenic; Microtubule-Associated Proteins; Motor Activity; PC12 Cells; Protein Serine-Threonine Kinases; Rats; Rats, Inbred SHR; RNA, Small Interfering; Stroke; Tyrosine

Sirtuin deacetylases regulate diverse cellular pathways and influence disease processes. Our previous studies identified the brain-enriched sirtuin-2 (SIRT2) deacetylase as a potential drug target to counteract neurodegeneration. In the present study, we characterize SIRT2 inhibition activity of the brain-permeable compound AK7 and examine the efficacy of this small molecule in models of Parkinson's disease, amyotrophic lateral sclerosis and cerebral ischemia. Our results demonstrate that AK7 is neuroprotective in models of Parkinson's disease; it ameliorates alpha-synuclein toxicity in vitro and prevents 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopamine depletion and dopaminergic neuron loss in vivo. The compound does not show beneficial effects in mouse models of amyotrophic lateral sclerosis and cerebral ischemia. These findings underscore the specificity of protective effects observed here in models of Parkinson's disease, and previously in Huntington's disease, and support the development of SIRT2 inhibitors as potential therapeutics for the two neurodegenerative diseases.

Topics: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; alpha-Synuclein; Amyotrophic Lateral Sclerosis; Animals; Benzamides; Brain Ischemia; Cell Line; Disease Models, Animal; Humans; Male; Mice; Neuroprotective Agents; Parkinson Disease; Sirtuin 2; Small Molecule Libraries; Sulfonamides

Alpha-synuclein oligomerization and aggregation are considered to have a role in the pathogenesis of neurodegenerative diseases. However, despite numerous in vitro studies, the impact of aggregates in the intact brain is unclear. In vitro, oxidative/nitrative stress and acidity induce α-synuclein oligomerization. These conditions favoring α-synuclein fibrillization are present in the ischemic brain, which may serve as an in vivo model to study α-synuclein aggregation. In this study, we show that 30-minute proximal middle cerebral artery (MCA) occlusion and 72 hours reperfusion induce oligomerization of wild-type α-synuclein in the ischemic mouse brain. The nonamyloidogenic isoform β-synuclein did not form oligomers. Alpha-synuclein aggregates were confined to neurons and colocalized with ubiquitin immunoreactivity. We also found that 30 minutes proximal MCA occlusion and 24 hours reperfusion induced larger infarcts in C57BL/6(Thy1)-h[A30P]alphaSYN transgenic mice, which have an increased tendency to form synuclein fibrils. Trangenics also developed more selective neuronal necrosis when subjected to 20 minutes distal MCA occlusion and 72 hours reperfusion. Enhanced 3-nitrotyrosine immunoreactivity in transgenic mice suggests that oxidative/nitrative stress may be one of the mechanisms mediating aggregate toxicity. Thus, the increased vulnerability of transgenic mice to ischemia suggests that α-synuclein aggregates not only form during ischemia but also negatively impact neuronal survival, supporting the idea that α-synuclein misfolding may be neurotoxic.

Topics: alpha-Synuclein; Animals; Blotting, Western; Brain Ischemia; Cell Survival; Disease Susceptibility; Drug Resistance; Endopeptidase K; Immunohistochemistry; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neurons; Tissue Distribution; Ubiquitin

In this study, we examined changes in the level and immunoreactivity of alpha-synuclein in the hippocampal CA1 region of adult (6 months old) and aged (24 months old) gerbils after 5 min of transient forebrain ischemia. The delayed neuronal death of CA1 pyramidal cells in adult gerbils was severer than that in aged gerbils 4 days after ischemia/reperfusion. Alpha-synuclein immunoreactivity in the CA1 region of adult and aged gerbils significantly changed after ischemia. In control animals, alpha-synuclein immunoreactivity and level in the aged-gerbil CA1 region were higher than those in the adult-gerbil CA1 region. In both adult and aged gerbils, alpha-synuclein immunoreactivity and level started to increase 3h after ischemia, and they were highest 1 day after ischemia. Thereafter, alpha-synuclein immunoreactivity and level decreased with time after ischemia. We also observed the effects of Cu,Zn-superoxide dismutase (SOD1) on ischemic damage using the Pep-1 transduction domain. Alpha-synuclein level in the CA1 region was lower in Pep-1-SOD1-treated adult and aged gerbils than in vehicle-treated adult and aged gerbils. We conclude that neuronal loss in the hippocampal CA1 region of adult gerbils was more prominent than that in aged gerbils 4 days after ischemia/reperfusion. The higher level of alpha-synuclein in the aged-gerbil CA1 region than that in the adult-gerbil CA1 region may be associated with the earlier induction of reactive oxygen species, and Pep-1-SOD1 potentially and reversibly inhibits the accumulation of alpha-synuclein in the CA1 region after transient ischemia.

Topics: Aging; alpha-Synuclein; Animals; Brain Ischemia; Cell Death; Disease Models, Animal; Down-Regulation; Gerbillinae; Hippocampus; Immunohistochemistry; Male; Nerve Degeneration; Protein Structure, Tertiary; Pyramidal Cells; Reactive Oxygen Species; Reperfusion Injury; Superoxide Dismutase; Time Factors

An anti-alpha-synuclein (alpha-SYN) monoclonal antibody produced in our laboratory was used to investigate the effect of repeated acute hypoxic treatments on the expression of alpha-SYN in the mouse cerebral cortex. Western blot analysis showed that the expression levels of alpha-SYN in the cortex changed accordingly upon hypoxic exposure times, as that the alpha-synuclein level significantly increased after the first hypoxic exposure and then dropped down to the background level after the fourth hypoxic exposure. Immunohistochemical staining revealed that the alpha-SYN-immunopositive substance was localized not only in the nerve endings, but also within the nuclei of some neurons. The cell density of the neurons with alpha-SYN immunopositive nuclei was increased significantly after the first hypoxic exposure but returned back to control levels after the fourth hypoxic exposure. Our results indicate that both of the alpha-SYN expression level in the brain and the number of the neurons with alpha-SYN positive nuclei are affected by the repeated acute hypoxic treatments and that this modification is hypoxic time-dependent. The mechanism and the physiological significance underlying these changes need to be further investigated.

Topics: alpha-Synuclein; Animals; Brain; Brain Ischemia; Cerebral Cortex; Ischemic Preconditioning; Mice; Mice, Inbred BALB C; Nerve Tissue Proteins; Neurons; Phosphoproteins; Random Allocation; Synucleins

Alpha-synuclein, a presynaptic protein, is markedly included in Lewy bodies (LB) in Parkinson's and LB diseases. In this study, neuronal loss and the activation of glial cells such as microglia and astrocytes were induced by neurodegenerative insults such as the injection of kainic acid and occlusion of the middle cerebral artery. In contrast, immunoreactivity for alpha-synuclein did not change even at 7 days after these insults. These results suggest that alpha-synuclein protein may be so scarcely scavenged by glial cells that it readily condenses in neurodegenerative regions.

Topics: alpha-Synuclein; Animals; Brain; Brain Ischemia; Cell Death; Kainic Acid; Male; Nerve Degeneration; Nerve Tissue Proteins; Neurons; Rats; Rats, Wistar; Synucleins; Time Factors