A multi-omics approach to lignocellulolytic enzyme discovery reveals a new ligninase activity from Parascedosporium putredinis NO1

Lignocellulose, the structural component of plant cells, is a major agricultural byproduct and the most abundant terrestrial source of biopolymers on Earth. The complex and insoluble nature of lignocellulose limits its conversion into value-added commodities, and currently, efficient transformation requires expensive pretreatments and high loadings of enzymes. Here, we report on a fungus from the Parascedosporium genus, isolated from a wheat-straw composting community, that secretes a large and diverse array of carbohydrate-active enzymes (CAZymes) when grown on lignocellulosic substrates. We describe an oxidase activity that cleaves the major β-ether units in lignin, thereby releasing the flavonoid tricin from monocot lignin and enhancing the digestion of lignocellulose by polysaccharidase mixtures. We show that the enzyme, which holds potential for the biorefining industry, is widely distributed among lignocellulose-degrading fungi from the Sordariomycetes phylum.

Mechanistic strategies of microbial communities regulating lignocellulose deconstruction in a UK salt marsh

BACKGROUND

Salt marshes are major natural repositories of sequestered organic carbon with high burial rates of organic matter, produced by highly productive native flora. Accumulated carbon predominantly exists as lignocellulose which is metabolised by communities of functionally diverse microbes. However, the organisms that orchestrate this process and the enzymatic mechanisms employed that regulate the accumulation, composition and permanence of this carbon stock are not yet known. We applied meta-exo-proteome proteomics and 16S rRNA gene profiling to study lignocellulose decomposition in situ within the surface level sediments of a natural established UK salt marsh.

RESULTS

Our studies revealed a community dominated by Gammaproteobacteria, Bacteroidetes and Deltaproteobacteria that drive lignocellulose degradation in the salt marsh. We identify 42 families of lignocellulolytic bacteria of which the most active secretors of carbohydrate-active enzymes were observed to be Prolixibacteracea, Flavobacteriaceae, Cellvibrionaceae, Saccharospirillaceae, Alteromonadaceae, Vibrionaceae and Cytophagaceae. These families secreted lignocellulose-active glycoside hydrolase (GH) family enzymes GH3, GH5, GH6, GH9, GH10, GH11, GH13 and GH43 that were associated with degrading Spartina biomass. While fungi were present, we did not detect a lignocellulolytic contribution from fungi which are major contributors to terrestrial lignocellulose deconstruction. Oxidative enzymes such as laccases, peroxidases and lytic polysaccharide monooxygenases that are important for lignocellulose degradation in the terrestrial environment were present but not abundant, while a notable abundance of putative esterases (such as carbohydrate esterase family 1) associated with decoupling lignin from polysaccharides in lignocellulose was observed.

CONCLUSIONS

Here, we identify a diverse cohort of previously undefined bacteria that drive lignocellulose degradation in the surface sediments of the salt marsh environment and describe the enzymatic mechanisms they employ to facilitate this process. Our results increase the understanding of the microbial and molecular mechanisms that underpin carbon sequestration from lignocellulose within salt marsh surface sediments in situ and provide insights into the potential enzymatic mechanisms regulating the enrichment of polyphenolics in salt marsh sediments. Video Abstract.

Mining the biomass deconstructing capabilities of rice yellow stem borer symbionts

BACKGROUND

Efficient deconstruction of lignocellulosic biomass into simple sugars in an economically viable manner is a prerequisite for its global acceptance as a feedstock in bioethanol production. This is achieved in nature by suites of enzymes with the capability of efficiently depolymerizing all the components of lignocellulose. Here, we provide detailed insight into the repertoire of enzymes produced by microorganisms enriched from the gut of the crop pathogen rice yellow stem borer (Scirpophaga incertulas).

RESULTS

A microbial community was enriched from the gut of the rice yellow stem borer for enhanced rice straw degradation by sub-culturing every 10 days, for 1 year, in minimal medium with rice straw as the main carbon source. The enriched culture demonstrated high cellulolytic and xylanolytic activity in the culture supernatant. Metatranscriptomic and metaexoproteomic analysis revealed a large array of enzymes potentially involved in rice straw deconstruction. The consortium was found to encode genes ascribed to all five classes of carbohydrate-active enzymes (GHs, GTs, CEs, PLs, and AAs), including carbohydrate-binding modules (CBMs), categorized in the carbohydrate-active enzymes (CAZy) database. The GHs were the most abundant class of CAZymes. Predicted enzymes from these CAZy classes have the potential to digest each cell-wall components of rice straw, i.e., cellulose, hemicellulose, pectin, callose, and lignin. Several identified CAZy proteins appeared novel, having an unknown or hypothetical catalytic counterpart with a known class of CBM. To validate the findings, one of the identified enzymes that belong to the GH10 family was functionally characterized. The enzyme expressed in E. coli efficiently hydrolyzed beechwood xylan, and pretreated and untreated rice straw.

CONCLUSIONS

This is the first report describing the enrichment of lignocellulose degrading bacteria from the gut of the rice yellow stem borer to deconstruct rice straw, identifying a plethora of enzymes secreted by the microbial community when growing on rice straw as a carbon source. These enzymes could be important candidates for biorefineries to overcome the current bottlenecks in biomass processing.

Defining functional diversity for lignocellulose degradation in a microbial community using multi-omics studies

BACKGROUND

Lignocellulose is one of the most abundant forms of fixed carbon in the biosphere. Current industrial approaches to the degradation of lignocellulose employ enzyme mixtures, usually from a single fungal species, which are only effective in hydrolyzing polysaccharides following biomass pre-treatments. While the enzymatic mechanisms of lignocellulose degradation have been characterized in detail in individual microbial species, the microbial communities that efficiently breakdown plant materials in nature are species rich and secrete a myriad of enzymes to perform "community-level" metabolism of lignocellulose. Single-species approaches are, therefore, likely to miss important aspects of lignocellulose degradation that will be central to optimizing commercial processes.

RESULTS

Here, we investigated the microbial degradation of wheat straw in liquid cultures that had been inoculated with wheat straw compost. Samples taken at selected time points were subjected to multi-omics analysis with the aim of identifying new microbial mechanisms for lignocellulose degradation that could be applied in industrial pre-treatment of feedstocks. Phylogenetic composition of the community, based on sequenced bacterial and eukaryotic ribosomal genes, showed a gradual decrease in complexity and diversity over time due to microbial enrichment. Taxonomic affiliation of bacterial species showed dominance of Bacteroidetes and Proteobacteria and high relative abundance of genera Asticcacaulis, Leadbetterella and Truepera. The eukaryotic members of the community were enriched in peritrich ciliates from genus Telotrochidium that thrived in the liquid cultures compared to fungal species that were present in low abundance. A targeted metasecretome approach combined with metatranscriptomics analysis, identified 1127 proteins and showed the presence of numerous carbohydrate-active enzymes extracted from the biomass-bound fractions and from the culture supernatant. This revealed a wide array of hydrolytic cellulases, hemicellulases and carbohydrate-binding modules involved in lignocellulose degradation. The expression of these activities correlated to the changes in the biomass composition observed by FTIR and ssNMR measurements.

CONCLUSIONS

A combination of mass spectrometry-based proteomics coupled with metatranscriptomics has enabled the identification of a large number of lignocellulose degrading enzymes that can now be further explored for the development of improved enzyme cocktails for the treatment of plant-based feedstocks. In addition to the expected carbohydrate-active enzymes, our studies reveal a large number of unknown proteins, some of which may play a crucial role in community-based lignocellulose degradation.

Placental Angiogenic and Growth Factors in the Treatment of Chronic Varicose Ulcers: Preliminary Communication

A short-term clinical study on the effect of purified angiogenic and growth factors from human term placenta in the treatment of chronic varicose ulcers was carried out in 18 patients. Patients were randomly allocated to receive a maximum of two dressings containing or not containing these factors. The amount of granulation and epithelial tissue was clinically estimated 48 hours after each application. Patients treated with placental angiogenic and growth factors showed increased granulation and epithelial tissue. These results indicate that placental factors may be used for acceleration of wound healing.

Abstract P4-15-08: Association of OncotypeDX® DCIS ScoreTM results with local recurrence in patients with DCIS treated on accelerated partial breast radiotherapy (APBI) protocols

Background: Ductal carcinoma in situ (DCIS) is a proliferation of malignant epithelial cells of the ducts and terminal lobular units of the breast that do not invade the basement membrane. The incidence of DCIS has increased markedly since the early 1980s, chiefly due to screening mammography. Whole breast radiotherapy has largely been used to treat breast DCIS after lumpectomy. More recently, APBI has increasingly been utilized for breast DCIS. Currently updated American Society of Radiation Oncology (ASTRO) APBI guidelines have included "low risk" DCIS (as defined by RTOG 9804 criteria). The following results further explore clinico-pathologic factors, in addition to the DCIS Score, in order to better define an appropriate DCIS population for APBI.

Methods: An exploratory analysis aimed to retrospectively measure the association between clinico-pathologic factors and the DCIS Score result, an optimized 12-gene expression algorithm, and risk of any local failure (in situ or IBC recurrence) in a cohort of women treated with local excision and APBI on prospective phase II (NCT01185145) and phase III (NCT01185132) clinical trials. Multifocal tumors were described only by local pathology and not determined or defined centrally. The DCIS Score assay was performed by quantitative RT-PCR on formalin-fixed paraffin-embedded DCIS tumor specimens by Genomic Health (Redwood City, CA). Descriptive statistics of the cohort and assay results overall and by clinical trial were derived. Univariable Cox proportional hazards regression was used to determine whether there was an association between local failure and categorized DCIS Score group (≥39 vs <39) or other clinico-pathologic factors on the pooled cohort of clinical trial patients.

Results: This analysis included 104 evaluable patients (N=18 from NCT01185145 and N=86 from NCT01185132). The median age was 60 (range: 41-80), 79% of patients were postmenopausal, and the median span of DCIS was 6 mm (range 2-25 mm). Over two-thirds of the cohort presented with necrosis (71%). The distribution of DCIS Score results ranged from 0 to 82, with 69% of patients having a DCIS Score result <39. The median follow-up time was longer at 8.2 years in NCT01185145 versus 3.0 years in NCT01185132. There was a total of 6 local recurrences. DCIS Score result was significantly associated with local recurrence in univariable modeling (hazard ratio=10.3 for ≥39 vs <39; p=0.0104). None of the other clinico-pathologic characteristics resulted in any significant correlation with locoregional recurrence. All results were highly variable due to the small number of events.

Conclusion: The DCIS Score assay demonstrated risk stratification in this cohort of patients treated with local excision and APBI pooled from two clinical trials. These results are consistent with those recently published by Rakovitch et al (J Natl Cancer Inst 2017). The cohort in this study was dominated by those in the phase III trial. Due to the small number of local recurrence events and limited follow-up time in the phase III trial, caution should be taken when interpreting the results. Further investigations are needed to confirm findings.

Citation Format: Leonard CE, Fryman SP, Turner MP, Bennett JP, Carter DL, Sing AP. Association of OncotypeDX® DCIS ScoreTM results with local recurrence in patients with DCIS treated on accelerated partial breast radiotherapy (APBI) protocols [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-15-08.

Mitochondrial gene replacement in human pluripotent stem cell-derived neural progenitors

Human pluripotent stem cell-derived neural progenitor (hNP) cells are an excellent resource for understanding early neural development and neurodegenerative disorders. Given that many neurodegenerative disorders can be correlated with defects in the mitochondrial genome, optimal utilization of hNP cells requires an ability to manipulate and monitor changes in the mitochondria. Here, we describe a novel approach that uses recombinant human mitochondrial transcription factor A (rhTFAM) protein to transfect and express a pathogenic mitochondrial genome (mtDNA) carrying the G11778A mutation associated with Leber's hereditary optic neuropathy (LHON) disease, into dideoxycytidine (ddC)-treated hNPs. Treatment with ddC reduced endogenous mtDNA and gene expression, without loss of hNP phenotypic markers. Entry of G11778A mtDNA complexed with the rhTFAM was observed in mitochondria of ddC-hNPs. Expression of the pathogenic RNA was confirmed by restriction enzyme analysis of the SfaN1-digested cDNA. On the basis of the expression of neuron-specific class III beta-tubulin, neuronal differentiation occurred. Our results show for the first time that pathogenic mtDNA can be introduced and expressed into hNPs without loss of phenotype or neuronal differentiation potential. This mitochondrial gene replacement technology allows for creation of in vitro stem cell-based models useful for understanding neuronal development and treatment of neurodegenerative disorders.

Structural characterization of a beta-diketone hydrolase from the cyanobacterium Anabaena sp. PCC 7120 in native and product-bound forms, a coenzyme A-independent member of the crotonase suprafamily

The gene alr4455 from the well-studied cyanobacterium Anabaena sp. PCC 7120 encodes a crotonase orthologue that displays beta-diketone hydrolase activity. Anabaena beta-diketone hydrolase (ABDH), in common with 6-oxocamphor hydrolase (OCH) from Rhodococcus sp. NCIMB 9784, catalyzes the desymmetrization of bicyclo[2.2.2]octane-2,6-dione to yield [(S)-3-oxocyclohexyl]acetic acid, a reaction unusual among the crotonase superfamily as the substrate is not an acyl-CoA thioester. The structure of ABDH has been determined to a resolution of 1.5 A in both native and ligand-bound forms. ABDH forms a hexamer similar to OCH and features one active site per enzyme monomer. The arrangement of side chains in the active site indicates that while the catalytic chemistry may be conserved in OCH orthologues, the structural determinants of substrate specificity are different. In the active site of ligand-bound forms that had been cocrystallized with the bicyclic diketone substrate bicyclo[2.2.2]octane-2,6-dione was found the product of the asymmetric enzymatic retro-Claisen reaction [(S)-3-oxocyclohexyl]acetic acid. The structures of ABDH in both native and ligand-bound forms reveal further details about structural variation and modes of coenzyme A-independent activity within the crotonases and provide further evidence of a wider suprafamily of enzymes that have recruited the crotonase fold for the catalysis of reactions other than those regularly attributed to canonical superfamily members.

Field responses of Prunus serotina and Asclepias syriaca to ozone around southern Lake Michigan

Higher ozone concentrations east of southern Lake Michigan compared to west of the lake were used to test hypotheses about injury and growth effects on two plant species. We measured approximately 1000 black cherry trees and over 3000 milkweed stems from 1999 to 2001 for this purpose. Black cherry branch elongation and milkweed growth and pod formation were significantly higher west of Lake Michigan while ozone injury was greater east of Lake Michigan. Using classification and regression tree (CART) analyses we determined that departures from normal precipitation, soil nitrogen and ozone exposure/peak hourly concentrations were the most important variables affecting cherry branch elongation, and milkweed stem height and pod formation. The effects of ozone were not consistently comparable with the effects of soil nutrients, weather, insect or disease injury, and depended on species. Ozone SUM06 exposures greater than 13 ppm-h decreased cherry branch elongation 18%; peak 1-h exposures greater than 93 ppb reduced milkweed stem height 13%; and peak 1-h concentrations greater than 98 ppb reduced pod formation 11% in milkweed.

Biochemical analysis of cybrids expressing mitochondrial DNA from Contursi kindred Parkinson's subjects

Complex I activity is reduced in cytoplasmic hybrid (cybrid) cell lines that contain mitochondrial DNA (mtDNA) from sporadic Parkinson's disease (PD) patients. This implies that mtDNA aberration occurs in sporadic PD. To assess the integrity of mtDNA in autosomal dominant PD arising from mutation of the alpha-synuclein gene, we transferred mitochondrial genes from PD-affected members of the Italian-American Contursi kindred to cells previously depleted of their endogenous mtDNA. Unlike cybrid cell lines expressing mtDNA from persons with sporadic or maternally inherited PD, the resultant Contursi cybrid lines did not manifest complex I deficiency, indicating that in Contursi PD mtDNA integrity is relatively preserved. Compared to control cybrids, however, Contursi cybrid lines did show some evidence of oxidative stress. For reasons that are unclear, at least a limited amount of mtDNA damage may nevertheless develop in PD patients with alpha-synuclein mutation.

Transdermal dopaminergic D(2) receptor agonist therapy in Parkinson's disease with N-0923 TDS: a double-blind, placebo-controlled study

N-0923 is a non-ergot, dopaminergic D(2) agonist designed to be transdermally available. It has anti-parkinsonian effects when infused intravenously. An adhesive matrix patch was developed to deliver N-0923 transdermally (N-0923 TDS). In this phase II trial, we evaluated the effectiveness of various doses of N-0923 TDS at replacing levodopa. Eighty-five Parkinson's disease (PD) patients were randomized to placebo or one of four doses of N-0923 TDS for 21 days. Change in daily levodopa dose was the primary efficacy measure. Significantly greater reductions in levodopa dose were achieved as compared to placebo for the two highest doses of N-0923 TDS. Patients treated with 33.5 mg and 67 mg N-0923 TDS decreased levodopa use by 26% and 28%, vs. 7% for placebo. N-0923 TDS was safe and well tolerated.

Chronic reduction in complex I function alters calcium signaling in SH-SY5Y neuroblastoma cells

Sporadic, non-familial Parkinson's disease is characterized by a 15-30% reduction in complex I activity of the electron transport chain. A pharmacological model of reduced complex I activity was created by prolonged treatment of SH-SY5Y cells with low doses (5-20 nM) of rotenone, a selective inhibitor of complex I. Short-term (less than 2 week) exposure to rotenone did not influence calcium signaling, production of reactive oxygen species, or mitochondrial morphology. However, following 2 weeks of rotenone exposure, SH-SY5Y cells showed unusual calcium dynamics, specifically multiple calcium responses to carbachol, a muscarinic agonist. These secondary calcium responses were not seen in control SH-SY5Y cells and were dependent upon calcium influx. Mitochondrial membrane potential was also reduced in low dose rotenone-treated cells. These results demonstrate that a chronic, partial reduction in complex I activity, such as that seen in Parkinson's disease, can alter cell signaling events and perhaps increase the susceptibility of cells to calcium overload and subsequent cell death.

Neurotoxic Abeta peptides increase oxidative stress in vivo through NMDA-receptor and nitric-oxide-synthase mechanisms, and inhibit complex IV activity and induce a mitochondrial permeability transition in vitro

Beta amyloid (Abeta) peptides accumulate in Alzheimer's disease and are neurotoxic possibly through the production of oxygen free radicals. Using brain microdialysis we characterized the ability of Abeta to increase oxygen radical production in vivo. The 1-40 Abeta fragment increased 2,3-dehydroxybenzoic acid efflux more than the 1-28 fragment, in a manner dependent on nitric oxide synthase and NMDA receptor channels. We then examined the effects of Abeta peptides on mitochondrial function in vitro. Induction of the mitochondrial permeability transition in isolated rat liver mitochondria by Abeta(25-35) and Abeta(35-25) exhibited dose dependency and required calcium and phosphate. Cyclosporin A prevented the transition as did ruthenium red, chlorpromazine, or N-ethylmaleimide. ADP and magnesium delayed the onset of mitochondrial permeability transition. Electron microscopy confirmed the presence of Abeta aggregates and swollen mitochondria and preservation of mitochondrial structure by inhibitors of mitochondrial permeability transition. Cytochrome c oxidase (COX) activity was selectively inhibited by Abeta(25-35) but not by Abeta(35-25). Neurotoxic Abeta peptide can increase oxidative stress in vivo through mechanisms involving NMDA receptors and nitric oxide sythase. Increased intracellular Abeta levels can further exacerbate the genetically driven complex IV defect in sporadic Alzheimer's disease and may precipitate mitochondrial permeability transition opening. In combination, our results provide potential mechanisms to support the feed-forward hypothesis of Abeta neurotoxicity.

16-year trends in elements of lichens at Theodore Roosevelt National Park, North Dakota

An epiphytic lichen and a soil lichen in two very closely related genera (Parmelia sulcata and Xanthoparmelia chlorochroa, respectively) were sampled 16 years apart at Theodore Roosevelt National Park in North Dakota and measured for their elemental content. Mercury and cadmium decreased approximately 30% over the time period in both species. Sulfur decreased 8% in the epiphytic species, but increased 20% in the soil lichen. Factor analysis revealed that soil elements were higher in the soil lichen, indicating there was some soil contamination in that species. A relationship between iron and titanium was found only in the soil lichen. Sulfur and mercury were highly enriched in both species relative to the soil, which suggests that the atmosphere is a contributing source of these elements. New baseline values were calculated, 22 elements for both species, although it is not recommended that the soil lichen be sampled in the future.

Mitochondrial dysfunction in cybrid lines expressing mitochondrial genes from patients with progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a neurodegenerative movement disorder of unknown etiology. We hypothesized that mitochondrial DNA (mtDNA) aberration could occur in this disease and contribute to its pathogenesis. To address this we created transmitochondrial cytoplasmic hybrid (cybrid) cell lines expressing mitochondrial genes from persons with PSP. The presence of cybrid mtDNA aberration was screened for by biochemical assay of mitochondrial gene products. Relative to a control cybrid set, complex I activity was reduced in PSP cybrid lines (p<0.005). Antioxidant enzyme activities were elevated in PSP cybrid lines. These data suggest that mtDNA aberration occurs in PSP, causes electron transport chain pathology, and can produce oxidative stress. Further study of mitochondrial dysfunction in PSP may yield insights into why neurodegeneration occurs in this disease.

Disrupted mitochondrial electron transport function increases expression of anti-apoptotic bcl-2 and bcl-X(L) proteins in SH-SY5Y neuroblastoma and in Parkinson disease cybrid cells through oxidative stress

Death of dopamine neurons in Parkinson disease (PD) may arise from consequences of the complex I (C-I) defect in the mitochondrial electron transport chain (ETC). Whether cells activate programmed death (apoptosis) pathways derives, in part, from relative activities of proteins such as bcl-2 and bcl-X(L), that have anti-apoptotic actions. We studied the responses of bcl-2 and bcl-X(L) genes in pharmacologic (acute incubation with methylpyridinium (MPP+)) and mitochondrial transgenic ("cybrid") models of Parkinson disease C-I defects. MPP+ incubation increased levels of bcl-2 and bcl-X(L) proteins in native SH-SY5Y cells but not in rho(0) cells devoid of ETC activity. MPP+ increased bcl-2 mRNA levels by 40% at 8 hr. Confocal microscopic imaging showed that the intracellular distribution of immunoreactive bcl-2 was not significantly associated with mitochondrial membranes at baseline but was associated with mitochondria after 12 hr of MPP+. Immunoreactive bcl-X(L) protein was significantly and equally associated with mitochondrial membranes both at baseline and after MPP+. PD cybrids showed increased basal levels of bcl-2 and bcl-X(L) proteins, similar to the maximum levels found after MPP+ treatment of control SY5Y cells. After MPP+ exposure, bcl-2 protein levels increased in control cybrids but did not increase further in PD cybrids. Both pharmacologically generated and transgenically induced C-I inhibition increases levels of anti-apoptotic bcl proteins, possibly from increased gene transcription. Augmentation of bcl-2 and bcl-X(L) expression may delay neurodegeneration in PD.

Alzheimer's disease cybrids replicate beta-amyloid abnormalities through cell death pathways

Alzheimer's disease (AD) is characterized by the deposition in brain of beta-amyloid (Abeta) peptides, elevated brain caspase-3, and systemic deficiency of cytochrome c oxidase. Although increased Abeta deposition can result from mutations in amyloid precursor protein or presenilin genes, the cause of increased Abeta deposition in sporadic AD is unknown. Cytoplasmic hybrid ("cybrid") cells made from mitochondrial DNA of nonfamilial AD subjects show antioxidant-reversible lowering of mitochondrial membrane potential (delta(gYm), secrete twice as much Abeta(1-40) and Abeta(1-42), have increased intracellular Abeta(1-40) (1.7-fold), and develop Congo red-positive Abeta deposits. Also elevated are cytoplasmic cytochrome c (threefold) and caspase-3 activity (twofold). Increased AD cybrid Abeta(1-40) secretion was normalized by inhibition of caspase-3 or secretase and reduced by treatment with the antioxidant S(-)pramipexole. Expression of AD mitochondrial genes in cybrid cells depresses cytochrome c oxidase activity and increases oxidative stress, which, in turn, lowers delta(psi)m. Under stress, cells with AD mitochondrial genes are more likely to activate cell death pathways, which drive caspase 3-mediated Abeta peptide secretion and may account for increased Abeta deposition in the AD brain. Therapeutic strategies for reducing neurodegeneration in sporadic AD can address restoration of delta(psi)m and reduction of elevated Abeta secretion.

Interaction among mitochondria, mitogen-activated protein kinases, and nuclear factor-kappaB in cellular models of Parkinson's disease

Oxidative stress induced by acute complex I inhibition with 1-methyl-4-phenylpyridinium ion activated biphasically the stress-activated c-Jun N-terminal kinase (JNK) and the early transcription factor nuclear factor-kappaB (NF-kappaB) in SH-SY5Y neuroblastoma cells. Early JNK activation was dependent on mitochondrial adenine nucleotide translocator (ANT) activity, whereas late-phase JNK activation and the cleavage of signaling proteins Raf-1 and mitogen-activated protein kinase (MAPK) kinase (MEK) kinase (MEKK)-1 appeared to be ANT-independent. Early NF-kappaB activation depended on MEK, later activation required an intact electron transport chain (ETC), and Parkinson's disease (PD) cybrid (mitochondrial transgenic cytoplasmic hybrid) cells had increased basal NF-kappaB activation. Mitochondria appear capable of signaling ETC impairment through MAPK modules and inducing protective NF-kappaB responses, which are increased by PD mitochondrial genes amplified in cybrid cells. Irreversible commitment to apoptosis in this cell model may derive from loss of Raf-1 and cleavage/activation of MEKK-1, processes reported in other models to be caspase-mediated. Therapeutic strategies that reduce mitochondrial activation of proapoptotic MAPK modules, i.e., JNK, and enhance survival pathways, i.e., NF-kappaB, may offer neuroprotection in this debilitating disease.

Abnormal mitochondrial morphology in sporadic Parkinson's and Alzheimer's disease cybrid cell lines

Diseases linked to defective mitochondrial function are characterized by morphologically abnormal, swollen mitochondria with distorted cristae. Several lines of evidence now suggest that sporadic forms of Parkinson's disease (PD) and Alzheimer's disease (AD) are linked to mitochondrial dysfunction arising from defects in mitochondrial DNA (mtDNA). Human neuroblastoma (SH-SY5Y) cells that are deficient in mtDNA (Rho(0)) were repopulated with mitochondria from AD or PD patients or age-matched controls. These cytoplasmic hybrid (cybrid) cell lines differ only in the source of their mtDNA. Differences between cybrid cell lines therefore arise from differences in mtDNA and provide a model for the study of how impaired mitochondrial function alters the mitochondria themselves and how these changes adversely affect the neuronal cells they occupy. Cybrid cell mitochondria were labeled with the mitochondrial membrane potential-sensitive dye, JC-1. Analysis of these JC-1 labeled mitochondria by confocal microscopy revealed that mitochondrial membrane potential was significantly reduced in both PD and AD cybrid cells when compared with controls. Ultrastructural examination showed that control cybrid cells contained small, morphologically normal, round or oval mitochondria with a dark matrix and regular distribution of cristae. PD cybrid cells contained a significant and increased percentage of mitochondria that were enlarged or swollen and had a pale matrix with few remaining cristae (0.26-0.65 microm(2)). AD cybrid cells also contained a significantly increased percentage of enlarged or swollen mitochondria (0.25-5.0 microm(2)) that had a pale matrix and few remaining cristae. Other pathological features such as crystal-like intramitochondrial inclusions and cytoplasmic inclusion bodies were also found in PD and AD cybrids. These observations suggest that transfer of PD or AD mtDNA into Rho(0) cells was sufficient to produce pathological changes in mitochondrial ultrastructure that are similar to those seen in other mitochondrial disorders. These data were reported in abstract form (Trimmer et al., 1998, Soc. Neurosci. Abstr. 24: 476).

Heavy metals in wild rice from northern Wisconsin

Wild rice grain samples from various parts of the world have been found to have elevated concentrations of heavy metals, raising concern for potential effects on human health. It was hypothesized that wild rice from north-central Wisconsin could potentially have elevated concentrations of some heavy metals because of possible exposure to these elements from the atmosphere or from water and sediments. In addition, no studies of heavy metals in wild rice from Wisconsin had been performed, and a baseline study was needed for future comparisons. Wild rice plants were collected from four areas in Bayfield, Forest, Langlade, Oneida, Sawyer and Wood Counties in September, 1997 and 1998 and divided into four plant parts for elemental analyses: roots, stems, leaves and seeds. A total of 194 samples from 51 plants were analyzed across the localities, with an average of 49 samples per part depending on the element. Samples were cleaned of soil, wet digested, and analyzed by ICP for Ag, As, Cd, Cr, Cu, Hg, Mg, Pb, Se and Zn. Roots contained the highest concentrations of Ag, As, Cd, Cr, Hg, Pb, and Se. Copper was highest in both roots and seeds, while Zn was highest just in seeds. Magnesium was highest in leaves. Seed baseline ranges for the 10 elements were established using the 95% confidence intervals of the medians. Wild rice plants from northern Wisconsin had normal levels of the nutritional elements Cu, Mg and Zn in the seeds. Silver, Cd, Hg, Cr, and Se were very low in concentration or within normal limits for food plants. Arsenic and Pb, however, were elevated and could pose a problem for human health. The pathway for As, Hg and Pb to the plants could be atmospheric.

Characterization of cybrid cell lines containing mtDNA from Huntington's disease patients

Electron transport chain (ETC) dysfunction may arise from mitochondrial genetic, nuclear genetic, or toxic etiologies. Cytoplasmic hybrid (cybrid) systems can help distinguish between these possibilities by facilitating expression of suspect mitochondrial DNA (mtDNA) within a nuclear and environmentally controlled context. Perpetuation of ETC dysfunction in cybrids is consistent with an mtDNA pathogenesis while defect correction is not. We previously used cybrids to screen sporadic Parkinson's disease, Alzheimer's disease, and amyotrophic lateral sclerosis patients for mtDNA mutation with positive results. To further address the fidelity of these experiments, we created and characterized cybrids expressing mtDNA from persons with Huntington's disease (HD), an autosomal dominant, nuclear DNA-determined disorder in which mitochondrial ETC functioning is abnormal. On ETC, oxidative stress, and calcium homeostasis assays HD cybrid lines were indistinguishable from control cybrid lines. These data support the use of the cybrid technique for mtDNA mutation screening in candidate diseases.

Gastric myoelectrical activity in patients with Parkinson's disease: evidence of a primary gastric abnormality

Parkinson's disease patients may experience various gastrointestinal symptoms; however, the exact pathophysiology of these symptoms is not fully understood. Therefore, the aim of this study was to investigate the pattern of gastric myoelectrical activity in patients with Parkinson's disease. Eleven patients with Parkinson's disease and 10 healthy subjects participated in the study. Patients were stratified as "receiving dopaminergic therapy" (N = 5) and "off therapy" (N = 6). Gastric myoelectrical activity was measured by means of surface electrogastrography (EGG) for 30 min before and for 90 min after a standardized meal. The dominant frequency, postprandial EGG power change, and the percentage of normal 2-4 cycles/min (cpm) slow-wave activity in the three groups were calculated and compared. The mean postprandial EGG power increase in the untreated patients was smaller than in the treated patients (-3.11 +/- 1.01 and 1.17 +/- 1.96 dB; P = 0.072). Moreover, both of these values were significantly decreased when compared to the control group (untreated vs control: -3.11 +/- 1.01 vs 8.01 +/- 1.86 dB; P = 0.04 and treated vs control: 1.17 +/- 1.96 vs 8.01 +/- 1.86 dB; P = 0.02). The percentage of normal 2-4 cpm slow waves in untreated patients was not different from the treated patients (82.6 +/- 6.6% vs 75.8 +/- 13.6%, P = NS) or from the control group (88.2 +/- 5.4%, P = NS). The dominant frequency after the meal was similar to that in the fasting state both in the untreated (3.3 +/- 0.1 vs 3.2 +/- 0.2 cpm; P = NS) and treated patients (3.2 +/- 0.1 vs 3.1 +/- 0.1 cpm, P = NS), whereas the dominant frequency significantly increased postprandially in the control group (2.88 +/- 0.12 vs 3.05 +/- 0.16; P < 0.05). Abnormalities in gastric myoelectrical activity in untreated Parkinson's disease patients reflect direct involvement of the gastrointestinal tract by the primary disease process. EGG can be regarded as a useful diagnostic tool in evaluating gastrointestinal involvement in neurodegenerative diseases.

Characterization and time course of MPP+ -induced apoptosis in human SH-SY5Y neuroblastoma cells

A genetic defect in complex I of the mitochondrial electron transport chain (ETC) is implicated in the etiology of Parkinson's disease (PD), and has been studied in hybrid mitochondrial transgene cells based on the SH-SY5Y neuroblastoma. We sought to characterize further the mechanisms and time course of cell death in cultures of human SH-SY5Y neuroblastoma cells exposed to the ETC complex I inhibitor methylpyridinium ion (MPP+). We verify previous reports that apoptosis occurs after MPP+ exposure in SH-SY5Y cells. Nuclear pyknosis, the end stage of apoptosis, is evident after 18-hr exposure to 5 mM MPP+ and reversible until 10 hr, providing a temporal window within which to look for molecular and physiological correlates of MPP+-induced apoptosis. We then looked for mitochondrial correlates of MPP+ induced apoptosis in SH-SY5Y cells. Using flow cytometry, we found that MPP+ -induced increased reactive oxygen species (ROS) and lactate production consistent with inhibition of the ETC. Rho(o) cells, lacking a functional ETC, showed no ROS production, compensatory lactate production or apoptosis after exposure to MPP+. Finally, we show a collapse in ROS production and mitochondrial potential that is temporally correlated with irreversibility of MPP+ -induced apoptosis.

Pramipexole--a new dopamine agonist for the treatment of Parkinson's disease

Although L-DOPA is the current 'gold standard' for treatment of Parkinson's disease, its effectiveness fades rapidly and its use results in serious motor fluctuations (on-off, wearing off, freezing, involuntary movements) for most patients with Parkinson's disease. Pramipexole is an aminothiazole dopamine agonist with selective actions at dopamine receptors belonging to the D2 subfamily, where it possesses full activity similar to dopamine itself. Pramipexole's preferential affinity for the D3 receptor subtype could contribute to efficacy in the treatment of both the motor and psychiatric symptoms of Parkinson's disease. Both in vitro and in vivo studies in animals suggest that pramipexole possesses numerous neuroprotective properties, including dopamine autoreceptor agonist properties, antioxidant properties, ability to block the mitochondrial permeability transition pore and the ability to stimulate the release of trophic factors. Clinical studies have demonstrated that pramipexole has excellent pharmacokinetic properties and that it is an effective monotherapy in treating early Parkinson's disease and an effective adjunctive therapy with L-DOPA in treating late Parkinson's disease. In addition, pramipexole has demonstrated efficacy in a clinical trial for the treatment of major depression. In the early disease studies, pramipexole was able to retard the need for L-DOPA treatment for several years. Thus, a new 'L-DOPA-sparing' paradigm for treating Parkinson's disease may now be possible, whereby patients are initially treated with pramipexole and L-DOPA is added only as necessary.

Visualization of cyclosporin A and Ca2+-sensitive cyclical mitochondrial depolarizations in cell culture

Mitochondria not only facilitate chemiosmotic energy transduction, but also are excitable organelles that are important participants in intracellular Ca2+ signaling and are obligate participants in the active cell death cascade known as apoptosis. Underlying these functions is the cyclosporin A (CSA)-sensitive mitochondrial permeability transition pore (MTP), which can open transiently in a low conductance mode (MTPL) to relieve excess Ca2+, and irreversibly during the initiation of apoptosis. Here we image for the first time CSA- and Ca2+-sensitive cyclical mitochondrial depolarizations in cultures of the SH-SY5Y human neuroblastoma cell. In addition, we show that mitochondrial transmembrane potential (DeltaPsi) increases in response to CSA, indicating a baseline channel activity. Moreover, networks of mitochondria are shown to behave as an excitable system that may use Ca2+ as a diffusible messenger to recruit neighboring mitochondria to depolarize. We propose that these depolarizations represent MTPL activity. Our data further reinforce the notion that mitochondria are excitable organelles and suggest coordinated activation of MTPL.

The parkinsonian neurotoxin MPP+ opens the mitochondrial permeability transition pore and releases cytochrome c in isolated mitochondria via an oxidative mechanism

The mitochondrial transition pore (MTP) is implicated as a mediator of cell injury and death in many situations. The MTP opens in response to stimuli including reactive oxygen species and inhibition of the electron transport chain. Sporadic Parkinson's disease (PD) is characterized by oxidative stress and specifically involves a defect in complex I of the electron transport chain. To explore the possible involvement of the MTP in PD models, we tested the effects of the complex I inhibitor and apoptosis-inducing toxin N-methyl-4-phenylpyridinium (MPP+) on cyclosporin A (CsA)-sensitive mitochondrial swelling and release of cytochrome c. In the presence of Ca2+ and Pi, MPP+ induced a permeability transition in both liver and brain mitochondria. MPP+ also caused release of cytochrome c from liver mitochondria. Rotenone, a classic non-competitive complex I inhibitor, completely inhibited MPP(+)-induced swelling and release of cytochrome c. The MPP(+)-induced permeability transition was synergistic with nitric oxide and the adenine nucleotide translocator inhibitor atractyloside, and additive with phenyl arsine oxide cross-linking of dithiol residues. MPP(+)-induced pore opening and cytochrome c release were blocked by CsA, the Ca2+ uniporter inhibitor ruthenium red, the hydrophobic disulfide reagent N-ethylmaleimide, butacaine, and the free radical scavenging enzymes catalase and superoxide dismutase. MPP+ neurotoxicity may derive from not only its inhibition of complex I and consequent ATP depletion, but also from its ability to open the MTP and to release mitochondrial factors including Ca2+ and cytochrome c known to be involved in apoptosis.

Effects of single and multiple treatments with L-dihydroxyphenylalanine (L-DOPA) on dopamine receptor-G protein interactions and supersensitive immediate early gene responses in striata of rats after reserpine treatment or with unilateral nigrostriatal lesions

We studied effects of L-dihydroxyphenylalanine (L-DOPA) treatment in rats following reserpine treatment or unilateral 6-hydroxydopamine (6-OHDA) injections into medial forebrain bundle. Quantitative in situ hybridization for mRNA's coding for the zinc finger immediate early gene (IEG) zif/268 or Jun family IEG jun b revealed that single L-DOPA injections accentuated IEG expression 3- to 7-fold in the dopamine (DA)-depleted striatum. This increased IEG response did not derive from any alterations in DA receptor-G protein coupling, assayed by DA stimulation of 35S-guanosine-5' (gamma-thio) triphosphate (35S-GTP-gamma-S) binding to striatal sections. Reserpine treatment increased both basal and maximal striatal DA-stimulated 35S-GTP-gamma-S binding. The augmented IEG responses to single L-DOPA treatments involved dependency on both D1 and D2 receptors and acutely to N-methyl-D-aspartate (NMDA) channels. Repetitive L-DOPA treatments yielded persistently elevated (zif/268) or additionally up-regulated (jun b) IEG response in the denervated striatum and down-regulated IEG responses in the control striatum. Degraded L-DOPA responses and appearance of involuntary movements after chronic L-DOPA use in advanced Parkinson's disease may derive from these IEG changes.

An evaluation of the role of mitochondria in neurodegenerative diseases: mitochondrial mutations and oxidative pathology, protective nuclear responses, and cell death in neurodegeneration

There is mounting evidence for mitochondrial involvement in neurodegenerative diseases including Alzheimer's and Parkinson's disease and amyotrophic lateral sclerosis. Mitochondrial DNA mutations, whether inherited or acquired, lead to impaired electron transport chain (ETC) functioning. Impaired electron transport, in turn, leads to decreased ATP production, formation of damaging free-radicals, and altered calcium handling. These toxic consequences of ETC dysfunction lead to further mitochondrial damage including oxidation of mitochondrial DNA, proteins, and lipids, and opening of the mitochondrial permeability transition pore, an event linked to cell death in numerous model systems. Although protective nuclear responses such as antioxidant enzymes and bcl-2 may be induced to combat these pathological changes, such a vicious cycle of increasing oxidative damage may insidiously damage neurons over a period of years, eventually leading to neuronal cell death. This hypothesis, a synthesis of the mitochondrial mutations and oxidative stress hypotheses of neurodegeneration, is readily tested experimentally, and clearly points out many potential therapeutic targets for preventing or ameliorating these diseases.

Matrilineal inheritance of complex I dysfunction in a multigenerational Parkinson's disease family

Recent data suggesting complex I dysfunction in Parkinson's disease (PD) arises from mitochondrial DNA (mtDNA) mutation does not conclusively answer whether the responsible genetic lesion is inherited (primary) or somatic (secondary). To address this question, we identified a family in which multiple members over three generations are affected with PD through exclusively maternal lines. Cytoplasmic hybrids (cybrids) were created for 15 family members over two generations by transferring each individual's mtDNA to mtDNA-depleted human neuroblastoma cells. Eight of the 15 cybrid lines contained mtDNA obtained from maternally descended family members and seven contained mtDNA from paternally descended family members. After 6 weeks of culture, cybrid cell lines were assayed for complex I activity and oxidative stress, and mitochondrial morphology was analyzed by electron microscopy. Compared with the cybrid lines containing mtDNA from paternal descendants, cybrid lines containing mtDNA from maternal descendants had lower complex I activity, increased reactive oxygen species production, increased radical scavenging enzyme activities, and more abnormal mitochondrial morphologic features. These findings were present in cybrid lines containing mtDNA from maternal descendants with PD as well as in currently asymptomatic young maternal descendants, and support a precedent for inherited mtDNA mutation in some persons with PD.

MPP+ induced SH-SY5Y apoptosis is potentiated by cyclosporin A and inhibited by aristolochic acid

In experiments investigating the role of the mitochondrial transition pore (MTP) in apoptosis induced by the Parkinsonism producing toxin N-methyl pyridinium ion (MPP+), we attempted to block possible MTP opening with cyclosporin A (CSA) alone or in combination with the phospholipase A2 (PLA2) inhibitor aristolochic acid (ARA). Paradoxically, CSA potentiated rather than inhibited MPP+ induced apoptosis. Aristolochic acid alone inhibited MPP+ induced apoptosis at 24 h but did not alter mitochondrial effects of MPP+, suggesting that ARA inhibits MPP+ induced apoptosis downstream of the initiation event. ARA may prove to be another useful tool for understanding apoptosis.

Pallidotomy improves motor responses and widens the levodopa therapeutic window in Parkinson's disease

Stereotactic posteroventral pallidotomy (PVP) as a treatment for Parkinson's disease (PD) symptoms has been increasingly used in moderate-advanced disease. We examined the pharmacodynamic responses of PD patients to single oral levodopa doses and intravenous levodopa infusions before and after PVP surgery. Nine subjects with advanced PD received a single oral dose and ramped intravenous levodopa infusions before and 3-5 weeks after unilateral PVP. Timed motor tasks, Unified Parkinson's Disease Rating Scale (UPDRS) evaluations, and ordinal dyskinesia rating were performed after oral levodopa and during i.v. levodopa infusions. Serum prolactin and dopa levels were measured during the levodopa infusions. Overall timed motor but not motor UPDRS scores were improved after PVP in both the worst ("off") and best ("on") states. Contralateral but not ipsilateral limb dyskinesias were substantially reduced at all serum (dopa) levels after PVP. Ipsilateral and contralateral timed motor performance at low serum (dopa) levels was improved by PVP. Walking speeds at all serum (dopa) levels were not changed by PVP. Serum prolactin was reduced equally by increasing (dopa) preoperatively and postoperatively. PVP significantly and favorably altered oral and intravenous levodopa pharmacodynamics by improving bilateral limb motor function and contralateral dyskinesia but did not alter walking speed. PVP appears to widen significantly the therapeutic window for levodopa in PD.

Mitochondria in sporadic amyotrophic lateral sclerosis

Mitochondria are abnormal in persons with amyotrophic lateral sclerosis (ALS) for unknown reasons. We explored whether aberration of mitochondrial DNA (mtDNA) could play a role in this by transferring mitochondrial DNA (mtDNA) from ALS subjects to mtDNA-depleted human neuroblastoma cells. Resulting ALS cytoplasmic hybrids (cybrids) exhibited abnormal electron transport chain functioning, increases in free radical scavenging enzyme activities, perturbed calcium homeostasis, and altered mitochondrial ultrastructure. Recapitulation of defects previously observed in ALS subjects and ALS transgenic mice by expression of ALS mtDNA support a pathophysiologic role for mtDNA mutation in some persons with this disease.

Potentiation of D2-dopamine receptor-mediated suppression of zif 268 by non-competitive NMDA receptor antagonists in reserpinized rats

Striatopallidal output neurons, which coexpress D2-dopamine receptors and NMDA receptors, are logically a potential site of interaction between corticostriatal glutamatergic input and dopaminergic systems. Recent hypotheses about the etiology of schizophrenia have implicated both excitatory amino acid and dopamine systems. The present study was designed to examine, in vivo, the interaction between D2-dopamine receptors and NMDA receptors in the regulation of the expression of the early immediate genes (IEGs), zif 268 and jun B, in striatopallidal neurons. We tested whether coadministration of NMDA antagonists interacted with the actions of the D2 agonist, quinpirole, on IEG expression following dopamine depletion with reserpine. When rats were pretreated with the non-competitive NMDA receptor antagonists, MK 801 (1 mg/kg) or PCP (20 mg/kg), together with quinpirole, the quinpirole reversal of reserpine induction of zif 268 mRNA was potentiated in all regions examined. MK 801 alone had no significant effect on reserpine induction of zif 268 mRNA. Pretreatment with the competitive NMDA receptor antagonist, CPP (5 mg/kg), did not significantly alter the dose response of zif 268 mRNA expression to quinpirole in any region. There was no significant effect of MK 801 on jun B mRNA expression, either on the response to quinpirole or when administered alone with reserpine. Our findings provide evidence of an interaction between the NMDA receptor channel system and the D2-dopamine system on a molecular level in striatopallidal neurons carrying output from the basal ganglia.

Cyclosporin A increases resting mitochondrial membrane potential in SY5Y cells and reverses the depressed mitochondrial membrane potential of Alzheimer's disease cybrids

Alzheimer's disease (AD) brains exhibit oxidative stress and a biochemical defect of complex IV (cytochrome oxidase, COX) of the mitochondrial electron transport chain (ETC). This defect can be transferred through mitochondrial DNA (mtDNA) into clonal SY5Y cells depleted of their mtDNA. The resulting cytoplasmic hybrids or "cybrids" retain the complex IV defect and exhibit oxidative stress. We measured the mitochondrial membrane potential (delta psi m) in AD and control cybrids via H3-tetraphenylphosphonium ion (H3-TPP+) accumulation. AD cybrids exhibited a significant (about 30%) decrease in H3-TPP+ accumulation relative to controls. Acute treatment of normal SY5Ys with azide, a COX inhibitor, moderately decreased H3-TPP+ retention and strongly inhibited COX activity in a dose-dependent manner. As the mitochondrial transition pore (MTP) can be activated by reactive oxygen species and ETC inhibitors, and its opening causes delta psi m dissipation, we tested the effects of the MTP inhibitor cyclosporin A (CsA) on TPP+ accumulation. 5mM CsA increased basal H3-TPP+ accumulation in SY5Y cells about 10-fold, corresponding to about a 2-fold increase in delta psi m. In the AD cybrids, CsA increased the apparent delta psi m to the same final levels as it did in controls. These results indicate that low-conductance MTP activity contributes significantly to resting delta psi m in SY5Y cells. We propose the novel hypothesis that the COX defect and resulting oxidative stress in AD may pathologically activate the MTP, resulting in lower delta psi m and the release of mitochondrial factors involved in apoptosis.

Early morning dystonia in Parkinson's disease

We interviewed 383 patients with PD regarding disease onset and medication history and evaluated them using the Unified Parkinson's Disease Rating Scale. Sixteen percent of the sample reported the occurrence of early morning dystonia (EMD). Patients with EMD had been taking levodopa for a longer time, were taking higher daily levodopa doses, demonstrated more disability in carrying out their activities of daily living, exhibited dystonia more often before initiation of levodopa treatment, and experienced more peak-dose and diphasic dyskinesias with levodopa therapy.

Pramipexole reduces reactive oxygen species production in vivo and in vitro and inhibits the mitochondrial permeability transition produced by the parkinsonian neurotoxin methylpyridinium ion

Sporadic Parkinson's disease is associated with a defect in the activity of complex I of the mitochondrial electron transport chain. This electron transport chain defect is transmitted through mitochondrial DNA, and when expressed in host cells leads to increased oxygen free radical production, increased antioxidant enzyme activities, and increased susceptibility to programmed cell death. Pramipexole, a chemically novel dopamine agonist used for the treatment of Parkinson's disease symptoms, possesses antioxidant activity and is neuroprotective toward substantia nigral dopamine neurons in hypoxic-ischemic and methamphetamine models. We found that pramipexole reduced the levels of oxygen radicals produced by methylpyridinium ion (MPP+) both when incubated with SH-SY5Y cells and when perfused into rat striatum. Pramipexole also exhibited a concentration-dependent inhibition of opening of the mitochondrial transition pore induced by calcium and phosphate or MPP+. These results suggest that pramipexole may be neuroprotective in Parkinson's disease by attenuating intracellular processes such as oxygen radical generation and the mitochondrial transition pore opening, which are associated with programmed cell death.

Differential hydroxylation of salicylate in core and penumbra regions during focal reversible cerebral ischemia

BACKGROUND AND PURPOSE

Free radical-mediated damage during and/or after cerebral ischemia is thought to participate in the elaboration of stroke-related injury. To elucidate the role of this mechanism in cerebral damage, the study presented herein sought to clarify the spatial and temporal features of the free radical response to transient ischemia. With use of a reproducible model of in vivo focal ischemia/reperfusion, the time course of salicylate hydroxylation was measured in ischemic core and penumbra regions.

METHODS

Transient focal cerebral ischemia was produced in Sprague-Dawley rats by occluding both carotid arteries and one middle cerebral artery for 3 hours, followed by reperfusion. Cerebral reperfusion was confirmed by visual inspection and iodo[14C]antipyrine autoradiography. A microdialysis probe was placed stereotactically in either the ischemic core or ischemic penumbra of the frontoparietal cortex; the probe was perfused with salicylate, and dialysate samples were analyzed by high-performance liquid chromatography for salicylate hydroxylation products.

RESULTS

Salicylate hydroxylation was significantly increased during ischemia and was further increased during 6 hours of reperfusion in the penumbra compared with sham controls. In comparison, a delayed increase in hydroxylation was observed within the ischemic core region only after 3 hours of reperfusion.

CONCLUSION

A differential generation of salicylate hydroxylation occurs in core and penumbra regions in association with focal ischemia/reperfusion of the rat neocortex. The early and progressive response in the penumbra suggests that free radical mechanisms may be continuously active in the aggravation of injury in the ischemic penumbra during ischemia and reperfusion. In contrast, the relatively delayed onset of hydroxylation in the core region indicates that this mechanism participates primarily in the late stages of ischemic injury in densely ischemic tissue. These findings are consistent with the concept that the role of free radicals in cerebral injury may differ qualitatively and/or quantitatively in areas of total and partial cerebral perfusion.

Elevated reactive oxygen species and antioxidant enzyme activities in animal and cellular models of Parkinson's disease

The dopaminergic neurotoxin N-methyl,4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) causes a syndrome in primates and humans which mimics Parkinson's disease (PD) in clinical, pathological, and biochemical findings, including diminished activity of complex I in the mitochondrial electron transport chain. Reduced complex I activity is found in sporadic PD and can be transferred through mitochondrial DNA, suggesting a mitochondrial genetic etiology. We now show that MPTP treatment of mice and N-methylpyridinium (MPP+) exposure of human SH-SY5Y neuroblastoma cells increases oxygen free radical production and antioxidant enzyme activities. Cybrid cells created by transfer of PD mitochondria exhibit similar characteristics; however, PD cybrids' antioxidant enzyme activities are not further increased by MPP+ exposure, as are the activities in control cybrids. PD mitochondrial cybrids are subject to metabolic and oxidative stresses similar to MPTP parkinsonism and provide a model to determine mechanisms of oxidative damage and cell death in PD.

Cybrids in Alzheimer's disease: a cellular model of the disease?

The mitochondrial electron transport chain enzyme cytochrome c oxidase (COX) is defective in patients with sporadic Alzheimer's disease (AD). This defect arises from the mutation of mitochondrial DNA (mtDNA). To develop a tissue culture system that would express this genetically derived bioenergetic lesion and permit characterization of its functional consequences, we depleted Ntera2/D1 (NT2) teratocarcinoma cells of endogenous mtDNA and repopulated them with platelet mtDNA from AD patients. Cytochrome c oxidase activity was depressed in the resulting AD cytoplasmic hybrids (cybrids) compared with cybrids prepared with mtDNA from non-AD controls. Reactive oxygen species (ROS) production and free radical scavenging enzyme activities were significantly elevated in AD cybrids. A COX defect in NT2 AD cybrid lines indicates that AD patients possess mtDNA COX gene mutations that are sufficient for determining this biochemical lesion. Expression of unique functional characteristics (increased ROS production and free radical scavenging enzyme activities) relevant to neurodegeneration demonstrates the utility of these cells in defining AD pathophysiology at a cellular level. This in vitro tissue culture model of AD may prove useful in drug screening.

Loss of cell surface microvilli on rat basophilic leukaemia cells precedes secretion and can be mimicked using the calmodulin antagonist trifluoperazine

OBJECTIVE

We studied changes in cell surface morphology following treatment with secretagogue or trifluoperazine in a mast cell model.

MATERIALS AND METHODS

Rat basophilic leukaemia (RBL) cells were treated with antigen and or the calmodulin antagonist, 0-50 microM trifluoperazine (TFP). The release of a secretory granule enzyme, beta-hexosaminidase, into the external medium was used as a measure of secretion. Quantitation of cell surface microvilli was determined by using a computer with input from a digitising tablet from scanning electron micrographs. Cytoskeletal proteins present in microvilli were analysed by confocal immunofluorescence.

RESULTS

When RBL cells are stimulated to secrete with an antigen, the cell surface is transformed from a microvillous morphology to a ruffled one. The cell surface rearrangement preceded beta-hexosaminidase secretion: the majority of microvilli disappeared rapidly after stimulation (t1/2 of 39 s) whereas secretion can only be measured after a lag of 47 s. The calmodulin antagonist, TFP did not inhibit antigen-induced secretion or loss of microvilli, however TFP alone caused a similar loss of microvilli but was unable to stimulate or potentiate secretion. The microvilli mostly disappeared within 30 s, and a half-maximal effect occurred at approximately 8 microM TFP. Using immunofluorescence, calmodulin was localized to punctate structures on the dorsal cell surface which presumably correspond to the microvilli, and which also stained for F-actin and myosin I.

CONCLUSIONS

Loss of cell surface microvilli on RBL cells precedes secretion and could reflect a cytoskeletal rearrangement which facilitates fusion of secretory granules with the membrane. It can be mimicked using trifluoperazine and we suggest it may involve calmodulin-binding components of the microvillus cytoskeleton such as myosin I.

Efficacy of pramipexole, a novel dopamine agonist, as monotherapy in mild to moderate Parkinson's disease. The Pramipexole Study Group

A total of 335 patients with early Parkinson's disease (PD) were enrolled in a multicenter, randomized, double-blind trial designed to assess the efficacy and safety of pramipexole. Entry was restricted to patients with idiopathic PD who were not receiving levodopa. Pramipexole was administered according to an ascending dose schedule up to 4.5 mg/d. During the 7-week dose-escalation phase, each subject was titrated to his or her maximally tolerated dose of study medication. This was followed by a 24-week period of maintenance therapy. The mean daily dose during the maintenance period was 3.8 mg. Pramipexole significantly reduced the severity of PD symptoms and signs compared with placebo, as measured by decreases in parts II (Activities of Daily Living) and III (Motor Examination) of the Unified Parkinson's Disease Rating Scale at week 24 compared with baseline (p < or = 0.0001). Differences between the active drug and placebo groups emerged at week 3 (1.5 mg/d) in the ascending-dose interval and persisted throughout the maintenance phase (p < or = 0.0001). The majority of patients completed the study (pramipexole 83%, placebo 80%). In the assessment of adverse events, nausea, insomnia, constipation, somnolence, and visual hallucinations occurred more frequently in the pramipexole treatment group compared with placebo patients. No clinically significant changes were noted in blood pressure or pulse rate. Overall, these results indicate that pramipexole is safe and effective in the treatment of early PD.

Mitochondrial toxins in models of neurodegenerative diseases. II: Elevated zif268 transcription and independent temporal regulation of striatal D1 and D2 receptor mRNAs and D1 and D2 receptor-binding sites in C57BL/6 mice during MPTP treatment

Sporadic Parkinson's disease (PD) may arise from a defect in complex I of the mitochondrial electron transport chain (ETC), transmitted through mitochondrial DNA mutations. The N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of experimental PD is believed to arise from loss of complex I activity in dopamine (DA) neurons after accumulation of MPP+, a potent complex I inhibitor and the two electron monoamine oxidase B oxidation product of MPTP. Acute MPP+ infusion into striatum, possibly mimicking the in vivo situation after MPTP treatment, increases release of DA and production of hydroxyl radical (-OH). We treated C57BL/6 mice with MPTP and followed the expression of the immediate-early gene zif268 in striatum as a marker of DA synaptic activity, determined the pharmacology of its activation during MPTP toxicity, and assayed the time course of MPTP effects on striatal DA transporter (DAT), and D1 and D2 DA receptor-binding sites and their mRNAs. MPTP (24 mg/kg b.i.d. for 4 doses) increased striatal zif268 expression, with peak effects observed 24 h after starting MPTP. Increased striatal zif268 was dependent mainly on DA D1 and to a lesser extent on non-NMDA glutamate receptors and was not altered by inhibition of nitric oxide synthase (NOS). Our MPTP schedule resulted in a loss of about one-third of nigral DA neurons. We observed with [3H]mazindol autoradiography that loss of striatal DAT sites after starting MPTP was heterogenous and greatest in centromedial striatum, reached a maximum at 48 h and showed a slight recovery at 2 weeks. Striatal D1 and D2 receptor-binding sites (measured with [3H]SCH23390 and [3H]spiperone binding, respectively) and mRNA levels for D1 and D2 receptors (determined with quantitative in situ hybridization) were altered after MPTP treatment in temporally independent manners. MPTP toxicity to the nigrostriatal system likely induces substantial striatal DA release in vivo and stimulates transcription of at least one major IEG, zif268, in striatal neurons. Increased striatal zif268 expression after MPTP appears to derive mainly from DA released onto D1 receptors, not by a NO-dependent process which has been described in striatal neurons in vitro. The rapid loss of striatal DA terminals after MPTP treatment alters D1 and D2 receptor sites independently of changes in their mRNA levels. Increased D1 and D2 gene transcription in this model may depend on re-innervation by DA terminals of striatal neurons and likely is not related to the increased zif268 transcription observed after MPTP.

Mitochondrial toxins in models of neurodegenerative diseases. I: In vivo brain hydroxyl radical production during systemic MPTP treatment or following microdialysis infusion of methylpyridinium or azide ions

Mitochondrial electron transport chain (ETC) function is selectively reduced in multiple tissues, including brain, from patients with Parkinson's disease (PD) and Alzheimer's disease (AD). The ETC defects are specific to each illness, involve complex I in PD and complex IV in AD, are transferable with mitochondrial DNA (mtDNA) and lead to increased production of reactive oxygen species (ROS) in mtDNA-deficient clonal neuronal cells hybridized with mtDNA ('cybrids') from PD or AD patients. C57BL/6 mice treated with MPTP developed elevated tissue hydroxyl radical ('OH) levels in striatum and ventral midbrain but not cerebellum. In brain microdialysis in awake rats, striatal 'OH output increased 3-5-fold after infusion of methylpyridinium ion (MPP+), a complex I inhibitor, or sodium azide, a complex IV inhibitor. Elevated 'OH after MPP+ was blocked stereospecifically by infusion of the nitric oxide synthase (NOS) inhibitor nitro-L-arginine or by the NMDA channel blocker MK801. Neither NOS inhibition nor NMDA blockade altered azide-induced 'OH production. ETC inhibition in vivo increases production of toxic 'OH, but the underlying mechanisms vary as a function of which ETC complex is inhibited. These results support the concept of developing oxygen free radical scavengers for both AD and PD and further suggest that inhibition of NOS and blockade of NMDA receptor function may alter progression of idiopathic PD.

Expression of serotonin transporter mRNA in rat brain: presence in neuronal and non-neuronal cells and effect of paroxetine

The expression of serotonin transporter mRNA in rat brain was-examined by in situ hybridisation. Hybridisation was observed in cells of the known serotonergic nuclei and no other neuronal populations. It was also associated with ependymal cells of the aqueduct which may indicate a specialisation of this part of the ventricular system in anatomical and neurophysiological terms. The effect of the selective serotonin reuptake inhibitor paroxetine on neuronal expression of the serotonin transporter mRNA was examined. Quantitation at the cellular level in the dorsal and median raphe nuclei was carried out by analysis of the mean number of silver grains per cell in autoradiographed sections. No significant change (P > 0.1) in serotonin transporter mRNA expression was observed following 21 day administration of paroxetine (5 mg/kg per day).