Neurotoxicity and behavioral deficits associated with Septin 5 accumulation in dopaminergic neurons

Septin 5, a parkin substrate, is a vesicle- and membrane-associated protein that plays a significant role in inhibiting exocytosis. The regulatory function of Septin 5 in dopaminergic (DAergic) neurons of substantia nigra (SN), maintained at relatively low levels, has not yet been delineated. As loss of function mutations of parkin are the principal cause of a familial Parkinson's disease, a prevailing hypothesis is that the loss of parkin activity results in accumulation of Septin 5 which confers neuron-specific toxicity in SN-DAergic neurons. In vitro and in vivo models were used to support this hypothesis. In our well-characterized DAergic SN4741 cell model, acute accumulation of elevated levels of Septin 5, but not synphilin-1 (another parkin substrate), resulted in cytotoxic cell death that was markedly reduced by parkin co-transfection. A transgenic mouse model expressing a dominant negative parkin mutant accumulated moderate levels of Septin 5 in SN-DAergic neurons. These mice acquired a progressive l-DOPA responsive motor dysfunction that developed despite a 25% higher than normal level of striatal dopamine (DA) and no apparent loss of DAergic neurons. The phenotype of this animal, increased striatal dopamine and reduced motor function, was similar to that observed in parkin knockout animals, suggesting a common DAergic alteration. These data suggest that a threshold level of Septin 5 accumulation is required for DAergic cell loss and that l-DOPA-responsive motor deficits can occur even in the presence of elevated DA.     

Lipid peroxidation in aging brain and Alzheimer's disease

Lipid peroxidation is one of the major outcomes of free radical-mediated injury that directly damages membranes and generates a number of secondary products, both from fission and endocyclization of oxygenated fatty acids that possess neurotoxic activity. Numerous studies have demonstrated increased lipid peroxidation in brain of patients with Alzheimer's disease (AD) compared with age-matched controls. These data include quantification of fission and endocyclized products such as 4-hydroxy-2-nonenal, acrolein, isoprostanes, and neuroprostanes. Immunohistochemical and biochemical studies have localized the majority of lipid peroxidation products to neurons. A few studies have consistently demonstrated increased cerebrospinal fluid (CSF) levels of isoprostanes in AD patients early in the course of their dementia, and one study has suggested that CSF isoprostanes may improve the laboratory diagnostic accuracy for AD. Similar analyses of control individuals over a wide range of ages indicate that brain lipid peroxidation is not a significant feature of usual aging. Quantification of isoprostanes in plasma and urine of AD patients has yielded inconsistent results. These results indicate that brain lipid peroxidation is a potential therapeutic target in probable AD patients, and that CSF isoprostanes may aid in the assessment of antioxidant experimental therapeutics and the laboratory diagnosis of AD.     

Coenzyme Q 10 as a Possible Treatment for Neurodegenerative Diseases

Coenzyme Q 10 (CoQ 10 ) is an essential cofactor of the electron transport gene as well as an important antioxidant, which is particularly effective within mitochondria. A number of prior studies have shown that it can exert efficacy in treating patients with known mitochondrial disorders. We investigated the potential usefulness of coenzyme Q 10 in animal models of Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and Huntington's disease (HD). It has been demonstrated that CoQ 10 can protect against striatal lesions produced by the mitochondrial toxins malonate and 3-nitropropionic acid. These toxins have been utilized to model the striatal pathology, which occurs in HD. It also protects against 1-methyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity in mice. CoQ 10 significantly extended survival in a transgenic mouse model of ALS. CoQ 10 can significantly extend survival, delay motor deficits and delay weight loss and attenuate the development of striatal atrophy in a transgenic mouse model of HD. In this mouse model, it showed additive efficacy when combined with the N -methyl- d -aspartate (NMDA) receptor antagonist, remacemide. CoQ 10 is presently being studied as a potential treatment for early PD as well as in combination with remacemide as a potential treatment for HD.     

In-cell click labelling of small molecules to determine subcellular localisation

Small molecule fluorometric boron dipyrromethene probes were developed to bind hepatitis C virus-encoded NS5A protein and aid subcellular distribution studies. These molecules did not co-locate with NS5A, therefore alternative ‘silent’ azide reporters were used to obtain a more relevant picture of their distribution. Following pre-incubation with replicon cells, click chemistry was used to append a fluorophore to the azide that confirmed the co-localisation of the small molecule with the NS5A protein, thus providing greater insight into the antiviral mode of action of this chemotype.

Electronic supplementary material

The online version of this article (doi:10.1007/s12154-010-0047-1) contains supplementary material, which is available to authorized users.     

Discovery of PF-184563, a potent and selective V1a antagonist for the treatment of dysmenorrhoea. The influence of compound flexibility on microsomal stability

The V1a receptor has emerged as an attractive target for a range of indications including Raynaud's disease and dysmenorrhoea. As part of an effort to discover a new class of orally active V1a antagonist, we optimised a highly lipophilic, metabolically unstable lead into a range of potent, selective and metabolically stable V1a antagonists. In this communication, we demonstrate the series-dependent effect of limiting the number of rotatable bonds in order to decrease Cytochrome P450-mediated metabolism. This effort culminated in the discovery of PF-184563, a novel, selective V1a antagonist with excellent in vitro and in vivo properties.     

Selective stimulation and blockade of β-adrenergic receptors in the mandibular gland of the red kangaroo, Macropus rufus

Intracarotid infusions of noradrenaline (0.15 nmol · kg⁻¹ · min⁻¹) either alone or accompanied by phentolamine (1.5 nmol · kg⁻¹ · min⁻¹) caused similar-sized increases in salivary protein, magnesium and bicarbonate, and decreases in osmolality, sodium, potassium and chloride whereas intravenous noradrenaline stimulated much smaller responses. Concurrent infusions of the β₁-antagonist, CGP20712A, blocked these noradrenaline-induced changes in salivary composition more effectively than equimolar infusions of the β₂-antagonist, ICI118551, thereby confirming the presence of β₁-adrenoceptors. Intracarotid infusion of salbutamol at 0.15, 0.3 and 1.5 nmol · kg⁻¹ · min⁻¹ caused increasing but qualitatively similar changes in salivary composition, sodium excepted, to intracarotid noradrenaline with 0.3 nmol being most similar quantitatively. Intravenous infusion of salbutamol caused larger changes in salivary composition than equimolar intravenous noradrenaline thereby indicating that the response to salbutamol may, in part, be mediated by reflex increases in general sympathetic tone triggered by lowered blood pressure. Eliminating this hypotensive effect by concurrent intravenous and intracarotid infusions of β₁-(CGP or atenolol) and β₂-(ICI118551) antagonists with intracarotid salbutamol showed that ICI118551 was more potent than the β₁-antagonists thereby demonstrating the presence of β₂-receptors. It was concluded that the kangaroo mandibular has functional β₁- and β₂-adrenoceptor subtypes in both endpieces and excurrent ducts and that the duct system has two populations of cells, each expressing one receptor subtype. Accepted: 26 July 2000     

Methyl sulfides as intermediates in the anaerobic oxidation of methane

While it is clear that microbial consortia containing Archaea and sulfate-reducing bacteria (SRB) can mediate the anaerobic oxidation of methane (AOM), the interplay between these microorganisms remains unknown. The leading explanation of the AOM metabolism is 'reverse methanogenesis' by which a methanogenesis substrate is produced and transferred between species. Conceptually, the reversal of methanogenesis requires low H₂ concentrations for energetic favourability. We used ¹³C-labelled CH₄ as a tracer to test the effects of elevated H₂ pressures on incubations of active AOM sediments from both the Eel River basin and Hydrate Ridge. In the presence of H₂, we observed a minimal reduction in the rate of CH₄ oxidation, and conclude H₂ does not play an interspecies role in AOM. Based on these results, as well as previous work, we propose a new model for substrate transfer in AOM. In this model, methyl sulfides produced by the Archaea from both CH₄ oxidation and CO₂ reduction are transferred to the SRB. Metabolically, CH₄ oxidation provides electrons for the energy-yielding reduction of CO₂ to a methyl group ('methylogenesis'). Methylogenesis is a dominantly reductive pathway utilizing most methanogenesis enzymes in their forward direction. Incubations of seep sediments demonstrate, as would be expected from this model, that methanethiol inhibits AOM and that CO can be substituted for CH₄ as the electron donor for methylogenesis.     

Reduced creatine kinase activity in transgenic amyotrophic lateral sclerosis mice

Creatine (Cr), the substrate of the creatine kinase (CK) isoenzymes, was shown to be neuroprotective in several models of neurodegeneration, including amyotrophic lateral sclerosis (ALS). In order to investigate the mechanism of this beneficial effect, we determined CK activities and mitochondrial respiration rates in tissues from G93A transgenic mice, which overexpress a mutant form of human superoxide dismutase associated with familial ALS (FALS). While respiration rates of mitochondria from G93A transgenic or wild-type control mice isolated from spinal cord showed no difference, a significant and dramatic loss of CK activity could be detected in these tissues. In homogenates from spinal cord of G93A transgenic mice, CK activity decreased to 49% and in mitochondrial fractions to 67% compared to CK activities in wild-type control mice. Feeding the G93A transgenic mice with 2% Cr, the same tissues showed no statistically significant increase of CK activity compared to regular fed G93A transgenic mice. Experiments with isolated mitochondria, however, showed that Cr and adenosine triphosphate (ATP) protected mitochondrial CK activity against peroxynitrite-induced inactivation, which may play a role in tissue damage in neurodegeneration. Our data provide evidence for oxidative damage to the CK system in ALS, which may contribute to impaired energy metabolism and neurodegeneration.     

Increased survival and neuroprotective effects of BN82451 in a transgenic mouse model of Huntington's disease

There is substantial evidence that excitotoxicity and oxidative damage may contribute to Huntington's disease (HD) pathogenesis. We examined whether the novel anti-oxidant compound BN82451 exerts neuroprotective effects in the R6/2 transgenic mouse model of HD. Oral administration of BN82451 significantly improved motor performance and improved survival by 15%. Oral administration of BN82451 significantly reduced gross brain atrophy, neuronal atrophy and the number of neuronal intranuclear inclusions at 90 days of age. These findings provide evidence that novel anti-oxidants such as BN82451 may be useful for treating HD.