Prevention, diagnosis and treatment are the watchwords in stroke research, for basic neuroscientists and clinicians alike. This 2002 book, from the 22nd Princeton Conference on Cerebrovascular ...Disease, contains contributions from outstanding investigators on numerous topics in stroke research. The contents cover the status and future directions of stroke pathophysiology, diagnosis and treatment, with special emphasis on the molecular and cellular mechanisms of ischaemic cell death and repair, and clinical issues including imaging, risk factors and therapeutic strategies in stroke. Available in both print and online formats, this survey of the basic and clinical science of stroke is an essential resource for all involved in advancing knowledge of cerebrovascular disease.
Doc number: 34 Abstract Background: Missense mutations and multiplications of the α-synuclein gene cause autosomal dominant familial Parkinson's disease (PD). α-Synuclein protein is also a major ...component of Lewy bodies, the hallmark pathological inclusions of PD. Therefore, α-synuclein plays an important role in the pathogenesis of familial and sporadic PD. To model α-synuclein-linked disease in vivo , transgenic mouse models have been developed that express wild-type or mutant human α-synuclein from a variety of neuronal-selective heterologous promoter elements. These models exhibit a variety of behavioral and neuropathological features resembling some aspects of PD. However, an important deficiency of these models is the observed lack of robust or progressive nigrostriatal dopaminergic neuronal degeneration that is characteristic of PD. Results: We have developed conditional α-synuclein transgenic mice that can express A53T, E46K or C-terminally truncated (1-119) human α-synuclein pathological variants from the endogenous murine ROSA26 promoter in a Cre recombinase-dependent manner. Using these mice, we have evaluated the expression of these α-synuclein variants on the integrity and viability of nigral dopaminergic neurons with age. Expression of A53T α-synuclein or truncated αSyn119 selectively in nigrostriatal pathway dopaminergic neurons for up to 12 months fails to precipitate dopaminergic neuronal loss in these mice. However, αSyn119 expression in nigral dopaminergic neurons for up to 12 months causes a marked reduction in the levels of striatal dopamine and its metabolites together with other subtle neurochemical alterations. Conclusion: We have developed and evaluated novel conditional α-synuclein transgenic mice with transgene expression directed selectively to nigrostriatal dopaminergic neurons as a potential new mouse model of PD. Our data support the pathophysiological relevance of C-terminally truncated α-synuclein species in vivo . The expression of αSyn119 in the mouse nigrostriatal dopaminergic pathway may provide a useful model of striatal dopamine depletion and could potentially provide a presymptomatic model of PD perhaps representative of the earliest derangements in dopaminergic neuronal function observed prior to neuronal loss. These conditional α-synuclein transgenic mice provide novel tools for evaluating and dissecting the age-related effects of α-synuclein pathological variants on the function of the nigrostriatal dopaminergic pathway or other specific neuronal populations.
Parkinson disease is a common neurodegenerative disorder characterized by the loss of dopaminergic neurons and the presence of intracytoplasmic-ubiquitinated inclusions (Lewy bodies). Mutations in ...alpha-synuclein (A53T, A30P) and parkin cause familial Parkinson disease. Both these proteins are found in Lewy bodies. The absence of Lewy bodies in patients with parkin mutations suggests that parkin might be required for the formation of Lewy bodies. Here we show that parkin interacts with and ubiquitinates the alpha-synuclein-interacting protein, synphilin-1. Co-expression of alpha-synuclein, synphilin-1 and parkin result in the formation of Lewy-body-like ubiquitin-positive cytosolic inclusions. We further show that familial-linked mutations in parkin disrupt the ubiquitination of synphilin-1 and the formation of the ubiquitin-positive inclusions. These results provide a molecular basis for the ubiquitination of Lewy-body-associated proteins and link parkin and alpha-synuclein in a common pathogenic mechanism through their interaction with synphilin-1.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Nitric oxide (NO) is an endogenous gas that functions as a neurotransmitter. Because NO is very labile with a half-life of less than 5 sec, most functional studies of NO have manipulated its ...synthetic enzyme, NO synthase (NOS). Three isoforms of NOS have been identified: (1) in the endothelial lining of blood vessels (eNOS), (2) an inducible form found in macrophages (iNOS), and (3) in neurons (nNOS). Most pharmacological studies to date have blocked all three isoforms of NOS. Previous studies using such agents have revealed that NO might be necessary for photic entrainment of circadian rhythms; general NOS inhibitors attenuate phase shifts of free-running behavior, light-induced c-fos expression in the suprachiasmatic nucleus (SCN), and phase shifts of neural firing activity in SCN maintained in vitro. To assess the specific role of nNOS in mediating entrainment of circadian rhythms, mice with targeted deletion of the gene encoding the neuronal isoform of NOS (nNOS–/–) were used. Wild-type (WT) and nNOS–/– mice initially were entrained to a 14:10 light:dark (LD) cycle. After 3 weeks, the LD cycle was either phase advanced or phase delayed. After an additional 3 weeks, animals were held in either constant dim light or constant dark. WT and nNOS–/– animals did not differ in their ability to entrain to the LD cycle, phase shift locomotor activity, or free run in constant conditions. Animals held in constant dark were killed after light exposure during either the subjective day or subjective night to assess c-fos induction in the SCN. Light exposure during the subjective night increased c-fos expression in the SCN of both WT and nNOS–/– mice relative to animals killed after light exposure during the subjective day. Taken together, these findings suggest that NO from neurons might not be necessary for photic entrainment.
IntroductionPreconditioning to ischemic tolerance is a phenomenon in which brief episodes of a subtoxic insult induce a robust protection against a lethal ischemic insult. The beneficial effects of ...preconditioning were first demonstrated in the heart. It is now clear that preconditioning can induce ischemic tolerance in a variety of organ systems, including the brain. Preconditioning stimuli are quite diverse, ranging from transient ischemic episodes, spreading depression, hypoxia, anoxia, chemical inhibition of oxidative phosphorylation exposure to excitotoxins and cytokines.There are two temporally and mechanistically distinct types of protection afforded by preconditioning stimuli; acute and delayed. Acute preconditioning is protein synthesis independent, mediated by post-translational protein modifications. Acute preconditioning is short lived, of the order of minutes to hours. Delayed preconditioning requires new protein synthesis and is sustained for days to weeks. Elucidation of the molecular mechanisms that are involved in preconditioning and ischemic tolerance might lead to the identification of drugs that mimic this protective response and improve the prognosis of patients at risk for ischemic injury.Neuronal ischemic preconditioning was first reported by Kitagawa and coworkers in gerbils subjected to sublethal transient global ischemia. CA1 hippocampal neurons exhibited reduced neuronal death after a severe ischemic insult 24 to 48 hours later. In the brain, ischemic preconditioning is mediated largely through the activation of the N-methyl-d-aspartate (NMDA) receptors through increases in intracellular calcium and requires new protein synthesis.
BACKGROUND AND PURPOSE: Previous studies have demonstrated that the immunosuppressant FK506 provides neuroprotection in experimental brain injury and suggest that this action may be mediated by ...suppression of neuronal nitric oxide synthase activation that occurs after ischemic depolarization. We sought to determine whether FK506 reduces histological injury after middle cerebral artery occlusion (MCAO) in the rat and whether the neuroprotective effect is mediated via suppression of in vivo nitric oxide (NO) production during ischemia or early reperfusion. METHODS: Under controlled conditions of normoxia, normocarbia, and normothermia, halothane-anesthetized male Wistar rats were subjected to 2 hours of MCAO by the intraluminal occlusion technique in a blinded, randomized experimental trial. Ipsilateral parietal cortical laser-Doppler flowmetry was monitored throughout ischemia. Animals were randomly assigned to 4 pretreatment groups: intravenous FK506 0.3 mg/kg or 1. 0 mg/kg, vehicle (cremaphor), or an equivalent volume of saline administered 30 minutes before MCAO. Infarction volume was assessed by a triphenyltetrazolium chloride staining at 22 hours of reperfusion. In separate experiments, microdialysis probes were placed bilaterally into the striatum. Rats were perfused with artificial cerebrospinal fluid containing 3 micromol/L 14C- L-arginine for 3 hours and then subjected to 2 hours of right MCAO. Intravenous 0.3 mg/kg FK506 or cremaphor was given 30 minutes before right MCAO. Right-left differences between 14C-L-citrulline in the effluent were assumed to reflect differences in NO production. RESULTS: All values are mean+/-SE. FK506 at 0.3 mg/kg reduced infarction volume in cortex: 40+/-12 mm3 compared with saline (109+/-15 mm3) and cremaphor vehicle (148+/-23) (P<0.05). Striatal infarction was also reduced by low-dose FK506: 16+/-4 mm3 versus 36+/-4 mm3 and 34+/-4 mm3 in saline and vehicle groups, respectively (P<0.05). High-dose treatment reduced infarction volume in cortex (61+/-14 mm3, P<0.05 from saline and vehicle groups) and in striatum (22+/-5 mm3, P<0.05 from saline and vehicle groups). 14C-L-citrulline recovery via microdialysis was markedly enhanced in ischemic compared with nonischemic striatum. However, ischemia-evoked 14C-L-citrulline recovery was not different in FK506-treated rats compared with vehicle-treated animals. CONCLUSIONS: These data demonstrate that FK506 provides robust neuroprotection against transient focal cerebral ischemia in the rat. The mechanism of protection in vivo is not through attenuation of ischemia-evoked NO production during MCAO and early reperfusion.
Parkinson's disease (PD) is a common progressive neurodegenerative disorder caused by the loss of dopaminergic neurons in the substantia nigra. Although mutations in alpha-synuclein have been ...identified in autosomal dominant PD, the mechanism by which dopaminergic neural cell death occurs remains unknown. Proteins encoded by two other genes in which mutations cause familial PD, parkin and UCH-L1, are involved in regulation of the ubiquitin-proteasome pathway, suggesting that dysregulation of the ubiquitin-proteasome pathway is involved in the mechanism by which these mutations cause PD. We established inducible PC12 cell lines in which wild-type or mutant alpha-synuclein can be de-repressed by removing doxycycline. Differentiated PC12 cell lines expressing mutant alpha-synuclein showed decreased activity of proteasomes without direct toxicity. Cells expressing mutant alpha-synuclein showed increased sensitivity to apoptotic cell death when treated with sub-toxic concentrations of an exogenous proteasome inhibitor. Apoptosis was accompanied by mitochondrial depolarization and elevation of caspase-3 and -9, and was blocked by cyclosporin A. These data suggest that expression of mutant alpha-synuclein results in sensitivity to impairment of proteasome activity, leading to mitochondrial abnormalities and neuronal cell death.
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