Dysfunction of neostriatal medium spiny neurons (MSNs) is hypothesized to underlie late-stage motor complications of Parkinson disease (PD). The authors demonstrate shortened dendrite length of MSNs that was similar in four regions of neostriatum in late-stage PD. In contrast, MSN dendrite spine degeneration was unevenly distributed with the greatest loss in caudal putamen. The authors propose that these structural changes in MSN may contribute to late-stage motor complications of PD.

Parkinson's disease (PD)-mimicking drugs and pesticides, and more recently PD-associated gene mutations, have been studied in cell cultures and mammalian models to decipher the molecular basis of PD. Thus far, a dozen of genes have been identified that are responsible for inherited PD. However they only account for about 8% of PD cases, most of the cases likely involving environmental contributions. Environmental manganese (Mn) exposure represents an established risk factor for PD occurrence, and both PD and Mn-intoxicated patients display a characteristic extrapyramidal syndrome primarily involving dopaminergic (DAergic) neurodegeneration with shared common molecular mechanisms. To better understand the specificity of DAergic neurodegeneration, we studied Mn toxicity in vivo in Caenorhabditis elegans. Combining genetics and biochemical assays, we established that extracellular, and not intracellular, dopamine (DA) is responsible for Mn-induced DAergic neurodegeneration and that this process (1) requires functional DA-reuptake transporter (DAT-1) and (2) is associated with oxidative stress and lifespan reduction. Overexpression of the anti-oxidant transcription factor, SKN-1, affords protection against Mn toxicity, while the DA-dependency of Mn toxicity requires the NADPH dual-oxidase BLI-3. These results suggest that in vivo BLI-3 activity promotes the conversion of extracellular DA into toxic reactive species, which, in turn, can be taken up by DAT-1 in DAergic neurons, thus leading to oxidative stress and cell degeneration.

Exposure to excessive manganese (Mn) levels results in neurotoxicity to the extrapyramidal system and the development of Parkinson's disease (PD)-like movement disorder, referred to as manganism. Although the mechanisms by which Mn induces neuronal damage are not well defined, its neurotoxicity appears to be regulated by a number of factors, including oxidative injury, mitochondrial dysfunction and neuroinflammation. To investigate the mechanisms underlying Mn neurotoxicity, we studied the effects of Mn on reactive oxygen species (ROS) formation, changes in high-energy phosphates (HEP), neuroinflammation mediators and associated neuronal dysfunctions both in vitro and in vivo. Primary cortical neuronal cultures showed concentration-dependent alterations in biomarkers of oxidative damage, F 2 -isoprostanes (F 2 -IsoPs) and mitochondrial dysfunction (ATP), as early as 2 hours following Mn exposure. Treatment of neurons with 500 µM Mn also resulted in time-dependent increases in the levels of the inflammatory biomarker, prostaglandin E 2 (PGE 2 ). In vivo analyses corroborated these findings, establishing that either a single or three (100 mg/kg, s.c.) Mn injections (days 1, 4 and 7) induced significant increases in F 2 -IsoPs and PGE 2 in adult mouse brain 24 hours following the last injection. Quantitative morphometric analyses of Golgi-impregnated striatal sections from mice exposed to single or three Mn injections revealed progressive spine degeneration and dendritic damage of medium spiny neurons (MSNs). These findings suggest that oxidative stress, mitochondrial dysfunction and neuroinflammation are underlying mechanisms in Mn-induced neurodegeneration.

Anticholinesterase compounds, organophosphates (OPs) and carbamates (CMs) are commonly used for a variety of purposes in agriculture and in human and veterinary medicine. They exert their toxicity in mammalian system primarily by virtue of acetylcholinesterase (AChE) inhibition at the synapses and neuromuscular junctions, leading into the signs of hypercholinergic preponderance. However, the mechanism(s) involved in brain/muscle damage appear to be linked with alteration in antioxidant and the scavenging system leading to free radical-mediated injury. OPs and CMs cause excessive formation of F2-isoprostanes and F4-neuroprostanes, in vivo biomarkers of lipid peroxidation and generation of reactive oxygen species (ROS), and of citrulline, a marker of NO/NOS and reactive nitrogen species (RNS) generation. In addition, during the course of these excitatory processes and inhibition of AChE, a high rate of ATP consumption, coupled with the inhibition of oxidative phosphorylation, compromise the cell's ability to maintain its energy levels and excessive amounts of ROS and RNS may be generated. Pretreatment with N-methyl D-aspartate (NMDA) receptor antagonist memantine, in combination with atropine sulfate, provides significant protection against inhibition of AChE, increases of ROS/RNS, and depletion of high-energy phosphates induced by DFP/carbofuran. Similar antioxidative effects are observed with a spin trapping agent, phenyl-N-tert-butylnitrone (PBN) or chain breaking antioxidant vitamin E. This review describes the mechanisms involved in anticholinesterase-induced oxidative/nitrosative injury in target organs of OPs/CMs, and protection by various agents.

Increase in prostaglandin (PG) E 2 levels and oxidative damage are associated with diseases of brain that involve activation of innate immunity. We tested the hypothesis that cerebral oxidative damage resulting from activation of innate immunity with intracerebroventricular (icv) lipopolysaccharide (LPS) is dependent on PGE 2 -mediated signaling. We measured two quantitative in vivo biomarkers of lipid peroxidation: F 2 -isoprostanes (IsoPs) that derive from arachidonic acid (AA) that is uniformly distributed in all cell types in brain, and F 4 -neuroprostanes (NeuroPs) that derive from docosahexaenoic acid (DHA) that is highly concentrated in neuronal membranes. LPS stimulated delayed elevations in cerebral F 2 -IsoPs and F 4 -NeuroPs that were completely suppressed by indomethacin or ibuprofen pre-treatment. LPS-induced cerebral oxidative damage was abolished by disruption of subtype 2 receptor for PGE 2 (EP 2 ). In contrast, initial oxidative damage from icv kainic acid (KA) was more rapid than with LPS also was completely suppressed by indomethacin or ibuprofen pre-treatment but was independent of EP 2 receptor activation. The protective effect of deleting the EP 2 receptor was not associated with changes in cerebral eicosaniod production, but was partially related to reduced induction of nitric oxide synthase (NOS) activity. These results suggest the EP 2 receptor as a therapeutic target to limit oxidative damage from activation of innate immunity in cerebrum. Keywords: excitotoxicityinnate immunity, isoprostanes, neuroprostanes, NSAIDs, prostaglandin E 2 . J. Neurochem. Coincident cerebral oxidative damage and elevated prostaglandin (PG) E 2 levels are characteristic of several degenerative and destructive diseases of brain including stroke, epilepsy, Alzheimer's disease, HIV-associated dementia, and Creutzfeldt-Jakob disease (Griffin et al. 1994;Pace and Leaf 1995;Montine et al. 1998Montine et al. , 1999aMontine et al. , 1999bPaoletti et al. 1998;Thornhill and Smith 1998;Minghetti et al. 2000). PGE 2 potently modulates neurodegeneration and oxidative damage in several model systems; however, some have concluded that PGE 2 is neuroprotective while others have proposed that PGE 2 promotes neuronal damage (Akaike et al. 1994;Cazevielle et al. 1994;Minghetti et al. 1997aMinghetti et al. , 1997bMinghetti et al. , 1998Bezzi et al. 1998; Kraig 1998, 1999;Levi et al. 1998;Paoletti et al. 1998;Thornhill and Smith 1998;Aloisi et al. 1999;Kelley et al. 1999;Sanzgiri et al. 1999;Drachman and Rothstein 2000;Hewett et al. 2000). Most in vivo studies suggest that PGE 2 contributes to oxidative damage and neurodegeneration, while most in vitro studies indicate that PGE 2 has neuroprotective activity. There are several possible explanations for these disparate results.Cell culture models typically are limited by use of supraphysiologic concentrations of PGE 2 , by the absence of some of the PGE 2 receptor (EP) subtypes, and by disruption of paracrine interactions between neurons and glia. In vivo studies have rel...