A model for p53-induced apoptosis

The inactivation of the p53 gene in a large proportion of human cancers has inspired an intense search for the encoded protein's physiological and biological properties. Expression of p53 induces either a stable growth arrest or programmed cell death (apoptosis). In human colorectal cancers, the growth arrest is dependent on the transcriptional induction of the protein p21WAF1/CIP1 , but the mechanisms underlying the development of p53-dependent apoptosis are largely unknown. As the most well documented biochemical property of p53 is its ability to activate transcription of genes, we examined in detail the transcripts induced by p53 expression before the onset of apoptosis. Of 7,202 transcripts identified, only 14 (0.19%) were found to be markedly increased in p53-expressing cells compared with control cells. Strikingly, many of these genes were predicted to encode proteins that could generate or respond to oxidative stress, including one that is implicated in apoptosis in plant meristems. These observations stimulated additional biochemical and pharmacological experiments suggesting that p53 results in apoptosis through a three-step process: (1) the transcriptional induction of redox-related genes; (2) the formation of reactive oxygen species; and (3) the oxidative degradation of mitochondrial components, culminating in cell death.

Mitogenic signaling mediated by oxidants in Ras-transformed fibroblasts

NIH 3T3 fibroblasts stably transformed with a constitutively active isoform of p21(Ras), H-RasV12 (v-H-Ras or EJ-Ras), produced large amounts of the reactive oxygen species superoxide (.O2-). .O2- production was suppressed by the expression of dominant negative isoforms of Ras or Rac1, as well as by treatment with a farnesyltransferase inhibitor or with diphenylene iodonium, a flavoprotein inhibitor. The mitogenic activity of cells expressing H-RasV12 was inhibited by treatment with the chemical antioxidant N-acetyl-L-cysteine. Mitogen-activated protein kinase (MAPK) activity was decreased and c-Jun N-terminal kinase (JNK) was not activated in H-RasV12-transformed cells. Thus, H-RasV12-induced transformation can lead to the production of .O2- through one or more pathways involving a flavoprotein and Rac1. The implication of a reactive oxygen species, probably .O2-, as a mediator of Ras-induced cell cycle progression independent of MAPK and JNK suggests a possible mechanism for the effects of antioxidants against Ras-induced cellular transformation.

Molecular cloning of cDNA encoding an unrecognized component of amyloid in Alzheimer disease

A neuropathological hallmark of Alzheimer disease (AD) is a widespread amyloid deposition. We analyzed the entire amino acid sequences in an amyloid preparation and found, in addition to the major beta/A4-protein (A beta) fragment, two unknown peptides. We raised antibodies against synthetic peptides using subsequences of these peptides. These antibodies immunostained amyloid in neuritic and diffuse plaques as well as vascular amyloid. Electron microscopic analysis demonstrated that the immunostaining was localized on amyloid fibrils. We have isolated an apparently full-length cDNA encoding a 140-amino-acid protein within which two previously unreported amyloid sequences are encoded in tandem in the most hydrophobic domain. We tentatively named this 35-amino acid peptide NAC (non-A beta component of AD amyloid) and its precursor NACP. NAC is the second component, after A beta, identified chemically in the purified AD amyloid preparation. Secondary structure predictions indicate that the NAC peptide sequence has a strong tendency to form beta-structures consistent with its association with amyloid. NACP is detected as a M(r) 19,000 protein in the cytosolic fraction of brain homogenates and comigrates on immunoblots with NACP synthesized in Escherichia coli from NACP cDNA. NACP mRNA is expressed principally in brain but is also expressed in low concentrations in all tissues examined except in liver, suggesting its ubiquitous and brain-specific functions. The availability of the cDNA encoding full-length NACP should help to elucidate the mechanisms of amyloidosis in AD.

Nitric oxide functions as a signal in plant disease resistance

Recognition of an avirulent pathogen triggers the rapid production of the reactive oxygen intermediates superoxide (O2-) and hydrogen peroxide (H2O2). This oxidative burst drives crosslinking of the cell wall, induces several plant genes involved in cellular protection and defence, and is necessary for the initiation of host cell death in the hypersensitive disease-resistance response. However, this burst is not enough to support a strong disease-resistance response. Here we show that nitric oxide, which acts as a signal in the immune, nervous and vascular systems, potentiates the induction of hypersensitive cell death in soybean cells by reactive oxygen intermediates and functions independently of such intermediates to induce genes for the synthesis of protective natural products. Moreover, inhibitors of nitric oxide synthesis compromise the hypersensitive disease-resistance response of Arabidopsis leaves to Pseudomonas syringae, promoting disease and bacterial growth. We conclude that nitric oxide plays a key role in disease resistance in plants.

Activation tagging identifies a conserved MYB regulator of phenylpropanoid biosynthesis

Plants produce a wide array of natural products, many of which are likely to be useful bioactive structures. Unfortunately, these complex natural products usually occur at very low abundance and with restricted tissue distribution, thereby hindering their evaluation. Here, we report a novel approach for enhancing the accumulation of natural products based on activation tagging by Agrobacterium-mediated transformation with a T-DNA that carries cauliflower mosaic virus 35S enhancer sequences at its right border. Among approximately 5000 Arabidopsis activation-tagged lines, we found a plant that exhibited intense purple pigmentation in many vegetative organs throughout development. This upregulation of pigmentation reflected a dominant mutation that resulted in massive activation of phenylpropanoid biosynthetic genes and enhanced accumulation of lignin, hydroxycinnamic acid esters, and flavonoids, including various anthocyanins that were responsible for the purple color. These phenotypes, caused by insertion of the viral enhancer sequences adjacent to an MYB transcription factor gene, indicate that activation tagging can overcome the stringent genetic controls regulating the accumulation of specific natural products during plant development. Our findings suggest a functional genomics approach to the biotechnological evaluation of phytochemical biodiversity through the generation of massively enriched tissue sources for drug screening and for isolating underlying regulatory and biosynthetic genes.

Role for neuronally derived fractalkine in mediating interactions between neurons and CX3CR1-expressing microglia

A recently identified chemokine, fractalkine, is a member of the chemokine gene family, which consists principally of secreted, proinflammatory molecules. Fractalkine is distinguished structurally by the presence of a CX3C motif as well as transmembrane spanning and mucin-like domains and shows atypical constitutive expression in a number of nonhematopoietic tissues, including brain. We undertook an extensive characterization of this chemokine and its receptor CX3CR1 in the brain to gain insights into use of chemokine-dependent systems in the central nervous system. Expression of fractalkine in rat brain was found to be widespread and localized principally to neurons. Recombinant rat CX3CR1, as expressed in Chinese hamster ovary cells, specifically bound fractalkine and signaled in the presence of either membrane-anchored or soluble forms of fractalkine protein. Fractalkine stimulated chemotaxis and elevated intracellular calcium levels of microglia; these responses were blocked by anti-CX3CR1 antibodies. After facial motor nerve axotomy, dramatic changes in the levels of CX3CR1 and fractalkine in the facial nucleus were evident. These included increases in the number and perineuronal location of CX3CR1-expressing microglia, decreased levels of motor neuron-expressed fractalkine mRNA, and an alteration in the forms of fractalkine protein expressed. These data describe mechanisms of cellular communication between neurons and microglia, involving fractalkine and CX3CR1, which occur in both normal and pathological states of the central nervous system.

Role of substrates and products of PI 3-kinase in regulating activation of Rac-related guanosine triphosphatases by Vav

Mitogen stimulation of cytoskeletal changes and c-jun amino-terminal kinases is mediated by Rac small guanine nucleotide-binding proteins. Vav, a guanosine diphosphate (GDP)-guanosine triphosphate (GTP) exchange factor for Rac that stimulates the exchange of bound GDP for GTP, bound to and was directly controlled by substrates and products of phosphoinositide (PI) 3-kinase. The PI 3-kinase substrate phosphatidylinositol-4,5-bisphosphate inhibited activation of Vav by the tyrosine kinase Lck, whereas the product phosphatidylinositol-3,4,5-trisphosphate enhanced phosphorylation and activation of Vav by Lck. Control of Vav in response to mitogens by the products of PI 3-kinase suggests a mechanism for Ras-dependent activation of Rac.

Activation tagging in Arabidopsis

Activation tagging using T-DNA vectors that contain multimerized transcriptional enhancers from the cauliflower mosaic virus (CaMV) 35S gene has been applied to Arabidopsis plants. New activation-tagging vectors that confer resistance to the antibiotic kanamycin or the herbicide glufosinate have been used to generate several tens of thousands of transformed plants. From these, over 30 dominant mutants with various phenotypes have been isolated. Analysis of a subset of mutants has shown that overexpressed genes are almost always found immediately adjacent to the inserted CaMV 35S enhancers, at distances ranging from 380 bp to 3.6 kb. In at least one case, the CaMV 35S enhancers led primarily to an enhancement of the endogenous expression pattern rather than to constitutive ectopic expression, suggesting that the CaMV 35S enhancers used here act differently than the complete CaMV 35S promoter. This has important implications for the spectrum of genes that will be discovered by this method.

Nitric oxide synthase generates superoxide and nitric oxide in arginine-depleted cells leading to peroxynitrite-mediated cellular injury

Besides synthesizing nitric oxide (NO), purified neuronal NO synthase (nNOS) can produce superoxide (.O2-) at lower L-Arg concentrations. By using electron paramagnetic resonance spin-trapping techniques, we monitored NO and .O2- formation in nNOS-transfected human kidney 293 cells. In control transfected cells, the Ca2+ ionophore A23187 triggered NO generation but no .O2- was seen. With cells in L-Arg-free medium, we observed .O2- formation that increased as the cytosolic L-Arg levels decreased, while NO generation declined. .O2- formation was virtually abolished by the specific NOS blocker, N-nitro-L-arginine methyl ester (L-NAME). Nitrotyrosine, a specific nitration product of peroxynitrite, accumulated in L-Arg-depleted cells but not in control cells. Activation by A23187 was cytotoxic to L-Arg-depleted, but not to control cells, with marked lactate dehydrogenase release. The cytotoxicity was largely prevented by either superoxide dismutase or L-NAME. Thus, with reduced L-Arg availability NOS elicits cytotoxicity by generating .O2- and NO that interact to form the potent oxidant peroxynitrite. Regulating arginine levels may provide a therapeutic approach to disorders involving .O2-/NO-mediated cellular injury.

A tunable topological insulator in the spin helical Dirac transport regime

Helical Dirac fermions-charge carriers that behave as massless relativistic particles with an intrinsic angular momentum (spin) locked to its translational momentum-are proposed to be the key to realizing fundamentally new phenomena in condensed matter physics. Prominent examples include the anomalous quantization of magneto-electric coupling, half-fermion states that are their own antiparticle, and charge fractionalization in a Bose-Einstein condensate, all of which are not possible with conventional Dirac fermions of the graphene variety. Helical Dirac fermions have so far remained elusive owing to the lack of necessary spin-sensitive measurements and because such fermions are forbidden to exist in conventional materials harbouring relativistic electrons, such as graphene or bismuth. It has recently been proposed that helical Dirac fermions may exist at the edges of certain types of topologically ordered insulators-materials with a bulk insulating gap of spin-orbit origin and surface states protected against scattering by time-reversal symmetry-and that their peculiar properties may be accessed provided the insulator is tuned into the so-called topological transport regime. However, helical Dirac fermions have not been observed in existing topological insulators. Here we report the realization and characterization of a tunable topological insulator in a bismuth-based class of material by combining spin-imaging and momentum-resolved spectroscopies, bulk charge compensation, Hall transport measurements and surface quantum control. Our results reveal a spin-momentum locked Dirac cone carrying a non-trivial Berry's phase that is nearly 100 per cent spin-polarized, which exhibits a tunable topological fermion density in the vicinity of the Kramers point and can be driven to the long-sought topological spin transport regime. The observed topological nodal state is shown to be protected even up to 300 K. Our demonstration of room-temperature topological order and non-trivial spin-texture in stoichiometric Bi(2)Se(3).M(x) (M(x) indicates surface doping or gating control) paves the way for future graphene-like studies of topological insulators, and applications of the observed spin-polarized edge channels in spintronic and computing technologies possibly at room temperature.

Superoxide generation from endothelial nitric-oxide synthase. A Ca2+/calmodulin-dependent and tetrahydrobiopterin regulatory process

It has been previously shown that besides synthesizing nitric oxide (NO), neuronal and inducible NO synthase (NOS) generates superoxide (O-2) under conditions of L-arginine depletion. However, there is controversy regarding whether endothelial NOS (eNOS) can also produce O-2. Moreover, the mechanism and control of this process are not fully understood. Therefore, we performed electron paramagnetic resonance spin-trapping experiments to directly measure and characterize the O-2 generation from purified eNOS. With the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), prominent signals of O-2 adduct, DMPO-OOH, were detected from eNOS in the absence of added tetrahydrobiopterin (BH4), and these were quenched by superoxide dismutase. This O-2 formation required Ca2+/calmodulin and was blocked by the specific NOS inhibitor N-nitro-L-arginine methyl ester (L-NAME) but not its non-inhibitory enantiomer D-NAME. A parallel process of Ca2+/calmodulin-dependent NADPH oxidation was observed which was also inhibited by L-NAME but not D-NAME. Pretreatment of the enzyme with the heme blockers cyanide or imidazole also prevented O-2 generation. BH4 exerted dose-dependent inhibition of the O-2 signals generated by eNOS. Conversely, in the absence of BH4 L-arginine did not decrease this O-2 generation. Thus, eNOS can also catalyze O-2 formation, and this appears to occur primarily at the heme center of its oxygenase domain. O-2 synthesis from eNOS requires Ca2+/calmodulin and is primarily regulated by BH4 rather than L-arginine.

Complex Optical Surfaces Formed by Replica Molding Against Elastomeric Masters

Complex, optically functional surfaces in organic polymers can be fabricated by replicating relief structures present on the surface of an elastomeric master with an ultraviolet or thermally curable organic polymer, while the master is deformed by compression, bending, or stretching. The versatility of this procedure for fabricating surfaces with complex, micrometer- and submicrometer-scale patterns was demonstrated by the production of (i) diffraction gratings with periods smaller than the original grating; (ii) chirped, blazed diffraction gratings (where the period of a chirped grating changes continuously with position) on planar and curved surfaces; (iii) patterned microfeatures on the surfaces of approximately hemispherical objects (for example, an optical surface similar to a fly's eye); and (iv) arrays of rhombic microlenses. These topologically complex, micropatterned surfaces are difficult to fabricate with other techniques.

Superoxide and peroxynitrite generation from inducible nitric oxide synthase in macrophages

Superoxide (O-2) and nitric oxide (NO) act to kill invading microbes in phagocytes. In macrophages NO is synthesized by inducible nitric oxide synthase (iNOS, NOS 2) from L-arginine (L-Arg) and oxygen; however, O-2 was thought to be produced mainly by NADPH oxidase. Electron paramagnetic resonance (EPR) spin trapping experiments performed in murine macrophages demonstrate a novel pathway of O-2 generation. It was observed that depletion of cytosolic L-Arg triggers O-2 generation from iNOS. This iNOS-mediated O-2 generation was blocked by the NOS inhibitor N-nitro-L-arginine methyl ester or by L-Arg, but not by the noninhibitory enantiomer N-nitro-D-arginine methyl ester. In L-Arg-depleted macrophages iNOS generates both O-2 and NO that interact to form the potent oxidant peroxynitrite (ONOO-), which was detected by luminol luminescence and whose formation was blocked by superoxide dismutase, urate, or L-Arg. This iNOS-derived ONOO- resulted in nitrotyrosine formation, and this was inhibited by iNOS blockade. iNOS-mediated O-2 and ONOO- increased the antibacterial activity of macrophages. Thus, with reduced L-Arg availability iNOS produces O-2 and ONOO- that modulate macrophage function. Due to the existence of L-Arg depletion in inflammation, iNOS-mediated O-2 and ONOO- may occur and contribute to cytostatic/cytotoxic actions of macrophages.

Thrombocytopenia caused by the development of antibodies to thrombopoietin

Thrombocytopenia developed in some individuals treated with a recombinant thrombopoietin (TPO), pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF). Three of the subjects who developed severe thrombocytopenia were analyzed in detail to determine the cause of their thrombocytopenia. Except for easy bruising and heavy menses, none of these subjects had major bleeding episodes; none responded to intravenous immunoglobulin or prednisone. Bone marrow examination revealed a marked reduction in megakaryocytes. All 3 thrombocytopenic subjects had antibody to PEG-rHuMGDF that cross-reacted with endogenous TPO and neutralized its biological activity. All anti-TPO antibodies were immunoglobulin G (IgG), with increased amounts of IgG4; no IgM antibodies to TPO were detected at any time. A quantitative assay for IgG antibody to TPO was developed and showed that the antibody concentration varied inversely with the platelet count. Anti-TPO antibody recognized epitopes located in the first 163 amino acids of TPO and prevented TPO from binding to its receptor. In 2 subjects, endogenous TPO levels were elevated, but the TPO circulated as a biologically inactive immune complex with anti-TPO IgG; the endogenous TPO in these complexes had an apparent molecular weight of 95 000, slightly larger than the full-length recombinant TPO. None of the subjects had atypical HLA or platelet antigens, and the TPO cDNA was normal in both that were sequenced. Treatment of one subject with cyclosporine eliminated the antibody and normalized the platelet count. These data demonstrate a new mechanism for thrombocytopenia in which antibody develops to TPO; because endogenous TPO is produced constitutively, thrombocytopenia ensues.

Template-assisted self-assembly: a practical route to complex aggregates of monodispersed colloids with well-defined sizes, shapes, and structures

This paper describes a strategy that combines physical templating and capillary forces to assemble monodispersed spherical colloids into uniform aggregates with well-controlled sizes, shapes, and structures. When an aqueous dispersion of colloidal particles was allowed to dewet from a solid surface that had been patterned with appropriate relief structures, the particles were trapped by the recessed regions and assembled into aggregates whose structures were determined by the geometric confinement provided by the templates. We have demonstrated the capability and feasibility of this approach by assembling polystyrene beads and silica colloids (> or =150 nm in diameter) into complex aggregates that include polygonal or polyhedral clusters, linear or zigzag chains, and circular rings. We have also been able to generate hybrid aggregates in the shape of HF or H2O molecules that are composed of polymer beads having different diameters, polymer beads labeled with different organic dyes, and a combination of polymeric and inorganic beads. These colloidal aggregates can serve as a useful model system to investigate the hydrodynamic and optical scattering properties of colloidal particles having nonspherical morphologies. They should also find use as the building blocks to generate hierarchically self-assembled systems that may exhibit interesting properties highly valuable to areas ranging from photonics to condensed matter physics.

Signaling by proinflammatory cytokines: oligomerization of TRAF2 and TRAF6 is sufficient for JNK and IKK activation and target gene induction via an amino-terminal effector domain

Interleukin-1 (IL-1) and tumor necrosis factor (TNF-alpha) stimulate transcription factors AP-1 and NF-kappaB through activation of the MAP kinases JNK and p38 and the IkappaB kinase (IKK), respectively. The TNF-alpha and IL-1 signals are transduced through TRAF2 and TRAF6, respectively. Overexpressed TRAF2 or TRAF6 activate JNK, p38, or IKK in the absence of extracellular stimulation. By replacing the carboxy-terminal TRAF domain of TRAF2 and TRAF6 with repeats of the immunophilin FKBP12, we demonstrate that their effector domains are composed of their amino-terminal Zn and RING fingers. Oligomerization of the TRAF2 effector domain results in specific binding to MEKK1, a protein kinase capable of JNK, p38, and IKK activation, and induction of TNF-alpha and IL-1 responsive genes. TNF-alpha also enhances the binding of native TRAF2 to MEKK1 and stimulates the kinase activity of the latter. Thus, TNF-alpha and IL-1 signaling is based on oligomerization of TRAF2 and TRAF6 leading to activation of effector kinases.

Involvement of reactive oxygen intermediates in cyclooxygenase-2 expression induced by interleukin-1, tumor necrosis factor-alpha, and lipopolysaccharide

Reactive oxygen intermediates (ROIs) play an important role in inflammatory processes as mediators of injury and potentially in signal transduction leading to gene expression. Cyclooxygenase (COX) is a rate-limiting enzyme in prostanoid biosynthesis, and its recently cloned inducible form, COX-2, is induced by proinflammatory cytokines. This study linked ROIs to the signaling pathways that induce COX-2 expression. The hydroxyl radical scavengers DMSO (1%), as well as di- and tetramethylthiourea, inhibited IL-1-, TNF alpha-, and LPS-induced COX-2 expression in rat mesangial cells. The suppression of COX-2 mRNA expression correlated with the COX-2 protein level. In comparison with the prolonged induction of the inducible gene encoding protein-tyrosine phosphatase by hydrogen peroxide, the COX-2 gene was only transiently induced. Protein-tyrosine phosphatase is also induced by heat shock and chemical stress, whereas COX-2 is not. Superoxide was a more potent inducer for COX-2 than hydrogen peroxide. In addition, NADPH stimulated COX-2 expression, and an inhibitor of NADPH oxidase blocked COX-2 expression induced by TNF alpha. COX-2 and KC gene expression costimulated by IL-1 were inhibited differentially by the scavengers. These studies demonstrate that oxidant stress is a specific and important inducer of COX-2 gene expression. This induction may contribute to the deleterious amplification of prostanoids in inflammation and compound the direct effects of ROI production.

Cloning two isoforms of rat cyclooxygenase: differential regulation of their expression

Two isoforms of cyclooxygenase (COX) have been identified in eukaryotic cells: COX-1 encoded by a 2.8-kb mRNA, and a mitogen-inducible COX-2 encoded by a 4-kb mRNA. We have cloned the COX-1 and COX-2 cDNAs from the cDNA library constructed from lipopolysaccharide (LPS)-stimulated rat peritoneal macrophages. The deduced amino acid sequence showed that COX-1 contained 602 amino acids, whereas COX-2 contained 604 amino acids. There is 95% conservation of the nucleotide sequence in the open reading frame of COX-1 between the rat and the mouse, while the homology of the 3' untranslated region is 68% except for a 150 bp segment adjacent to the stop codon which is nonhomologous with the mouse. Transfection of both COX cDNAs into Cos-7 cells resulted in increased COX activity. In rat vascular smooth muscle cells, interleukin-1 beta selectively increased the expression of COX-2, but not that of COX-1, as assessed by enzyme activity, immunoprecipitation of COX proteins, and mRNA analysis. Only the brain among tissues tested exhibits basal expression of COX-2 as the major form of the enzyme. However, COX-2 mRNA was expressed in vivo in the lung and kidney, but not in the heart, after systemic administration of LPS, suggesting that COX-2 but not COX-1 plays a major role in producing COX-derived products of arachidonic acid during endotoxic shock. Thus, the two COX isoforms were differentially expressed, and COX-2 was selectively induced in response to inflammatory stimuli in rats.

Controlling cell attachment on contoured surfaces with self-assembled monolayers of alkanethiolates on gold

This paper describes a method based on experimentally simple techniques--microcontact printing and micromolding in capillaries--to prepare tissue culture substrates in which both the topology and molecular structure of the interface can be controlled. The method combines optically transparent contoured surfaces with self-assembled monolayers (SAMs) of alkanethiolates on gold to control interfacial characteristics; these tailored interfaces, in turn, control the adsorption of proteins and the attachment of cells. The technique uses replica molding in poly(dimethylsiloxane) molds having micrometer-scale relief patterns on their surfaces to form a contoured film of polyurethane supported on a glass slide. Evaporation of a thin (< 12 nm) film of gold on this surface-contoured polyurethane provides an optically transparent substrate, on which SAMs of terminally functionalized alkanethiolates can be formed. In one procedure, a flat poly(dimethylsiloxane) stamp was used to form a SAM of hexadecanethiolate on the raised plateaus of the contoured surface by contact printing hexadecanethiol [HS(CH2)15CH3]; a SAM terminated in tri(ethylene glycol) groups was subsequently formed on the bare gold remaining in the grooves by immersing the substrate in a solution of a second alkanethiol [HS(CH2)11(OCH2CH2)3OH]. Then this patterned substrate was immersed in a solution of fibronectin, the protein adsorbed only on the methyl-terminated plateau regions of the substrate [the tri(ethylene glycol)-terminated regions resisted the adsorption of protein]; bovine capillary endothelial cells attached only on the regions that adsorbed fibronectin. A complementary procedure confined protein adsorption and cell attachment to the grooves in this substrate.

Oxidative stress induces amyloid-like aggregate formation of NACP/alpha-synuclein in vitro

The precursor of non-amyloid beta protein component of Alzheimer's disease amyloid (NACP/alpha-synuclein), found in Lewy bodies of Parkinson's disease (PD), is a presynaptic protein genetically linked to some familial types PD. Mechanisms of abnormal NACP/alpha-synuclein aggregation in neurodegenerative diseases are unclear. Since oxidative stress might play a role in PD pathogenesis, we investigated the role of iron and peroxide in NACP/alpha-synuclein aggregation. Immunoblot analysis showed that human NACP/alpha-synuclein (but not beta-synuclein) aggregated in the presence of ferric ion and was inhibited by the iron chelator deferoxamine. Ferrous ion was not effective by itself, but it potentially aggregated NACP/alpha-synuclein in the presence of hydrogen peroxide. NACP/ alpha-synuclein aggregates displayed strong thioflavine-S and congo-red reactivity, reminiscent of amyloid. This study suggests that NACP/alpha-synuclein aggregation might be closely related to oxidative reactions which may play a critical role in neurodegeneration in disorders with Lewy bodies.