Parkinson's disease ͉ PI3K͞PTEN͞Akt signaling ͉ reactive oxygen species P arkinson's disease (PD) is the most common movement disorder and the second most common neurodegenerative disease. The movement abnormality in PD arises from deficiency of brain dopamine (DA) contents and the degeneration of dopaminergic neurons in the substantia nigra. The most common forms of PD are sporadic with no known cause. Nevertheless, postmortem studies have identified common features associated with sporadic PD, including defects in mitochondrial complex I function, oxidative damage, and abnormal protein aggregation (1).The contribution of genetic factors in the pathogenesis of PD, although initially controversial, has been firmly established by recent human genetic studies. At least 10 distinct loci (PARK1 to -11) have been linked to rare familial forms of PD (2). It is anticipated that understanding the molecular lesions associated with these familial PD (FPD) genes will shed light on the pathogenesis of the sporadic forms of the disease. To date, five unequivocal FPD genes have been molecularly cloned. These include ␣-Synuclein (␣-Syn), Parkin, DJ-1, PINK-1, and dardarin. Biochemical and biophysical studies of ␣-Syn and Parkin have primarily linked dysfunction of these genes to aberrant protein folding and ubiquitin-proteasome dysfunction. Intriguingly, in vivo genetic and in vitro cell culture studies have revealed their connection to mitochondrial dysfunction and oxidative stress, reinforcing the involvement of these processes in PD pathogenesis in general (3).DJ-1 encodes a conserved protein belonging to the ThiJ͞PfpI͞ DJ-1 superfamily. The exact molecular function of DJ-1 is still unclear. Human DJ-1 was initially discovered as a candidate oncoprotein that could transform cells in cooperation with activated ras (4), and it was later found as a component of an RNA-binding protein complex and was associated with male infertility (4-6). Under oxidative stress conditions, DJ-1 was modified by oxidation, and the modified form associated with mitochondria in cultured cells (7-10). Knocking down DJ-1 expression with small interfering RNA (siRNA) resulted in susceptibility to oxidative stress, endoplasmic reticulum stress, and proteasome inhibition (11). Recent analyses of DJ-1 knockout mice have shed light on the physiological function of DJ-1 in mammals. DJ-1-deficient mice were found to have nigrostriatal dopaminergic dysfunction, motor deficits, and hypersensitivity to the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine (MPTP) and oxidative stress stimuli (12)(13)(14). In mammalian cells, DJ-1 was found to regulate the phosphorylation status of protein kinase B (PKB)͞Akt through the tumor suppressor PTEN (15). The relevance of this novel finding of DJ-1 function to PD pathogenesis remains to be explored.As an alternative approach to understanding the role of DJ-1 dysfunction in PD pathogenesis, we have used Drosophila as a model system. We inhibited the function of a Drosophila DJ-1 homologue (DJ-1A) by transgenic RN...

The solution properties of the surfactants dodecyl-, tetradecyl-, and hexadecyl(cetyl)trimethylammonium bromide (DTAB, TTAB, and CTAB, respectively) as well as hexadecylpyridinium chloride (CPC) in pure and mixed states (binary and ternary combinations) have been studied. The critical micelle concentration (cmc), counterion binding, aggregation number, polarity, thermodynamics of micellization, interfacial adsorption, etc., have been quantitatively estimated by surface tension, conductance, spectrophotometry, fluorescence, and calorimetric methods. The micellar compositions, activities of the components in the micelle, and their mutual interactions have been estimated from Rubingh's theory. The surfactant mixtures have been found to be nonideal, with a lower degree of counterion association compared to pure states, but possess more or less comparable micellar polarity and energetic parameters.

Poly(ethylene glycol) (PEG)-mediated fusion of phosphatidylcholine model membranes has been shown to mimic the protein-mediated biomembrane process [Lee, J., and Lentz, B. R. (1998) Proc. Natl. Acad. Sci. U.S.A. 95, 9274-9279]. Unlike the simple model membranes used in this earlier study, the lipid composition of fusogenic biomembranes is quite complex. The purpose of this paper was to examine PEG-mediated fusion of highly curved (SUV) and largely uncurved (LUV) membrane vesicles composed of different lipids in order to identify lipid compositions that produce highly fusogenic membranes. Starting with liposomes composed of five lipids with different physical properties, dioleoylphosphatidylcholine (DOPC), dioleoylphosphatidylethanolamine (DOPE), dioleoylphosphatidylserine (DOPS), bovine brain sphingomyelin (SM), and cholesterol (CH), we systematically varied the composition and tested for the extent of PEG-mediated fusion after 5 min of treatment. We found that a vesicle system composed of four lipids, DOPC/DOPE/SM/CH, fused optimally at a 35/30/15/20 molar ratio. Each lipid seemed to play a part in optimizing the membrane for fusion. PE disrupted outer leaflet packing as demonstrated with TMA-DPH lifetime, C(6)-NBD-PC partitioning, and DPH anisotropy measurements, and thus significantly enhanced fusion and rupture, without significantly altering interbilayer approach (X-ray diffraction). An optimal ratio of PC/PE (35/30) produced a balance between fusion and rupture. CH and SM, when present at an optimal ratio of 3/4 in vesicles containing the optimal PC/PE ratio, reduced rupture without significantly reducing fusion. This optimal CH/SM ratio also enhanced outer leaflet packing, suggesting that fusion is dependent not only on outer leaflet packing but also on the properties of the inner leaflet. Addition of CH without SM enhanced rupture relative to fusion, while SM alone reduced both rupture and fusion. The optimal lipid composition is very close to the natural synaptic vesicle composition, suggesting that the synaptic vesicle composition is optimized with respect to fusogenicity.

Parkinson disease (PD) is a neurodegenerative disease characterized by progressive dopaminergic neurodegeneration in the substantia nigra pars compacta (SNc) area. The present study was undertaken to evaluate the neuroprotective effect of β-caryophyllene (BCP) against rotenone-induced oxidative stress and neuroinflammation in a rat model of PD. In the present study, BCP was administered once daily for 4 weeks at a dose of 50 mg/kg body weight prior to a rotenone (2.5 mg/kg body weight) challenge to mimic the progressive neurodegenerative nature of PD. Rotenone administration results in oxidative stress as evidenced by decreased activities of superoxide dismutase, catalase, and depletion of glutathione with a concomitant rise in lipid peroxidation product, malondialdehyde. Rotenone also significantly increased pro-inflammatory cytokines in the midbrain region and elevated the inflammatory mediators such as cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in the striatum. Further, immunohistochemical analysis revealed loss of dopaminergic neurons in the SNc area and enhanced expression of ionized calcium-binding adaptor molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP), indicators of microglia activation, and astrocyte hypertrophy, respectively, as an index of inflammation. However, treatment with BCP rescued dopaminergic neurons and decreased microglia and astrocyte activation evidenced by reduced Iba-1 and GFAP expression. BCP in addition to attenuation of pro-inflammatory cytokines and inflammatory mediators such as COX-2 and iNOS, also restored antioxidant enzymes and inhibited lipid peroxidation as well as glutathione depletion. The findings demonstrate that BCP provides neuroprotection against rotenone-induced PD and the neuroprotective effects can be ascribed to its potent antioxidant and anti-inflammatory activities.

α-Synuclein, an intrinsically-disordered protein associated with Parkinson’s disease, interacts with mitochondria, but the details of this interaction are unknown. We probed the interaction of α-synuclein and its A30P variant with lipid vesicles by using fluorescence anisotropy and 19F nuclear magnetic resonance. Both proteins interact strongly with large unilamellar vesicles whose composition is similar to that of the inner mitochondrial membrane, which contains cardiolipin. However, the proteins have no affinity for vesicles mimicking the outer mitochondrial membrane, which lacks cardiolipin. The 19F data show that the interaction involves α-synuclein’s N-terminal region. These data indicate that the middle of the N-terminal region, which contains the KAKEGVVAAAE repeats, is involved in binding, probably via electrostatic interactions between the lysines and cardiolipin. We also found that the strength of α-synuclein binding depends on the nature of the cardiolipin acyl side chains. Eliminating one double bond increases affinity, while complete saturation dramatically decreases affinity. Increasing the temperature increases the binding of wild-type, but not the A30P variant. The data are interpreted in terms of the properties of the protein, cardiolipin demixing within the vesicles upon binding of α-synuclein, and packing density. The results advance our understanding of α-synuclein’s interaction with mitochondrial membranes.

The interfacial and bulk properties of sodium deoxycholate (NaDC) and polyoxyethylene tert-octylphenyl ether (Triton X-100, TX-100) and their binary mixtures in aqueous solution have been investigated by means of surface tension, conductance, calorimetric, and fluorescence methods. The experimental results are utilized to evaluate critical micelle concentration (cmc), counterion binding, mean aggregation number, thermodynamics of micellization, interfacial adsorption, and the microenvironment of the surfactant systems. The enthalpy of micellization ( m~) has been found to be negligible for TX-100 and mixed combinations containing its higher proportion. The entropy of micellization (ASOM) is the predominant factor in the micellization process.The polarity of the mixed micelles obtained from 11/ 13 and the lifetime of the pyrene monomer fluorescence shows that the solubilization site of pyrene changes with mole fraction. The concentration dependence of Z1/Z3 indicates that the mixed micellar size and composition vary with total surfactant concentration, and the initial micelles near the cmc contain higher mole fractions of TX-100 compared to the experimental ones. The mean aggregation number is seen to decrease with the increase of the mole fraction of NaDC in the mixed micelle. The composition of the mixed systems have been estimated using regular solution theory, excess thermodynamic quantities, and the molecular thermodynamic model. The mole fractions of NaDC in micelles are found to be lower than those of analytical mole fractions.

BackgroundParkinson disease (PD) is a movement disorder affecting 1 % of people over the age of 60. The etiology of the disease is unknown; however, accumulating evidence suggests that mitochondrial defects, oxidative stress, and neuroinflammation play important roles in developing the disease. Current medications for PD can only improve its symptoms, but are unable to halt its progressive nature. Although many therapeutic approaches are available, new drugs are urgently needed for the treatment of PD. Thus, the present study was undertaken to investigate the neuroprotective potential of nerolidol, a sesquiterpene alcohol, on a rotenone-induced experimental model of PD, where male Wistar rats intraperitoneally received rotenone (ROT) at a dose of 2.5 mg/kg of body weight once daily for 4 weeks.ResultsNerolidol, which has antioxidant and anti-inflammatory properties, was injected intraperitoneally at 50 mg/kg of body weight, once daily for 4 weeks, and at 30 min prior to ROT administration. ROT administration significantly reduced the activities of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), and the level of the antioxidant tripeptide glutathione (GSH). Moreover, ROT increased the levels of the lipid peroxidation product malondialdehyde (MDA), proinflammatory cytokines (IL-1β, IL-6, and TNF-α), and inflammatory mediators (COX-2 and iNOS) in rat brain tissues. Immunostaining of brain tissue sections revealed a significant increase in the number of activated astrocytes (GFAP) and microglia (Iba-1), along with the concomitant loss of dopamine (DA) neurons in the substantia nigra pars compacta and dopaminergic nerve fibers in the striatum of ROT-treated rats. As expected, nerolidol supplementation to ROT-injected rats significantly increased the level of SOD, CAT, and GSH, and decreased the level of MDA. Nerolidol also inhibited the release of proinflammatory cytokines and inflammatory mediators. Finally, nerolidol treatment prevented ROT-induced glial cell activation and the loss of dopaminergic neurons and nerve fibers, and ultimately attenuated ROT-induced dopaminergic neurodegeneration.ConclusionOur findings are the first to show that the neuroprotective effect of nerolidol is mediated through its anti-oxidant and anti-inflammatory activities, which strongly supports its therapeutic potential for the treatment of PD.

The fusion peptides of HIV and influenza virus are crucial for viral entry into a host cell. We report the membrane-perturbing and structural properties of fusion peptides from the HA fusion protein of influenza virus and the gp41 fusion protein of HIV. Our goals were to determine: 1), how fusion peptides alter structure within the bilayers of fusogenic and nonfusogenic lipid vesicles and 2), how fusion peptide structure is related to the ability to promote fusion. Fluorescent probes revealed that neither peptide had a significant effect on bilayer packing at the water-membrane interface, but both increased acyl chain order in both fusogenic and nonfusogenic vesicles. Both also reduced free volume within the bilayer as indicated by partitioning of a lipophilic fluorophore into membranes. These membrane ordering effects were smaller for the gp41 peptide than for the HA peptide at low peptide/lipid ratio, suggesting that the two peptides assume different structures on membranes. The influenza peptide was predominantly helical, and the gp41 peptide was predominantly antiparallel beta-sheet when membrane bound, however, the depths of penetration of Trps of both peptides into neutral membranes were similar and independent of membrane composition. We previously demonstrated: 1), the abilities of both peptides to promote fusion but not initial intermediate formation during PEG-mediated fusion and 2), the ability of hexadecane to compete with this effect of the fusion peptides. Taken together, our current and past results suggest a hypothesis for a common mechanism by which these two viral fusion peptides promote fusion.