Serotonin Discharge Regulation by Additional Neurotransmitters of Rat Hippocampus Associated With the Continence Central Circuit.

PURPOSE: The lower urinary tract is believed to be centrally regulated with the involvement of a range of neurotransmitters. The parasympathetic excitatory input to the urinary bladder is suppressed when the serotonergic system is activated, and thereby voiding is blocked. In healthy people, continence is usually underpinned by hippocampal formation (circuit 3). In order to advance knowledge of how serotoninergic neurons and additional nerve fibers were correlated, the purpose of the present work was to research how the discharge of serotonin from hippocampal slices was affected by different neurotransmitters in rat models. METHODS: The adopted procedure involved administration of the central neurotransmitters acetylcholine, norepinephrine, dopamine, N-methyl-D-aspartate (NMDA), gamma-aminobutyric acid (GABA), glycine, and neuropeptide Y as well as monitoring of the alterations in the discharge of [3H]5-hydroxytryptamine (5-HT). Furthermore, to determine whether the effect of the neurotransmitters was influenced by interneuron, tetrodotoxin was also employed. RESULTS: Acetylcholine (10-5M) did not alter [3H]5-HT discharge, whereas more 5-HT was discharged from the hippocampal slices of rats under stimulation by norepinephrine (10-5M) as well as dopamine (10-5M) and tetrodotoxin (10-6M) did not inhibit the discharge. By contrast, tetrodotoxin inhibited the discharge of [3H]5-HT that was exacerbated by NMDA (10-4M). Meanwhile, compared to control, GABA (10-5M), glycine (10-5M), or neuropeptide Y (10-6M) did not alter the [3H]5-HT discharge. CONCLUSION: From the research findings, it can be concluded that 5-HT discharge from rat hippocampus is enhanced by norepinephrine and dopamine through direct effect on the 5-HT neuronal terminal. By contrast, 5-HT discharge is intensified by NMDA by activating interneurons.

Liberation of Serotonin Is Not Unaffected by Acetylcholine in Rat Hippocampus.

PURPOSE: Raised cerebral titers of acetylcholine have notable links with storage symptomatology related to lower urinary tract symptoms. The hippocampus contributes to the normal control of continence in the majority of instances (circuit 3). Owing to synaptic connections with other nerve cells, acetylcholine affects the micturition pathway via the liberation of additional cerebral neurotransmitters. Despite the fact that cerebral serotonin is a key inhibitor of reflex bladder muscle contractions, the influence of acetylcholine on its liberation is poorly delineated. The current research was conducted in order to explore the role of acetylcholine in serotonin liberation from sections of rat hippocampus in order to improve the comprehension of the relationship between cholinergic and serotonergic neurons. METHODS: Hippocampal sections from 6 mature male Sprague-Dawley rats were equilibrated over a 30-minute period in standard incubation medium so as to facilitate [3H]5-hydroxytryptamine (5-HT) uptake. The cerebral neurotransmitter, acetylcholine, was applied to the sections. Aliquots of drained medium solution were utilized in order to quantify the radioactivity associated with [3H]5-HT liberation; any alterations in this parameter were noted. RESULTS: When judged against the controls, [3H]5-HT liberation from the hippocampal sections remained unaltered following the administration of acetylcholine, implying that this agent has no inhibitory action on this process. CONCLUSION: Serotonin liberation from murine hippocampal sections is unaffected by acetylcholine. It is postulated that the bladder micturition reflex responds to acetylcholine through its immediate cholinergic activity rather than by its influence on serotonin release. These pathways are a promising target for the design of de novo therapeutic agents.

A Modified Oxidative Refinement Process for Removing Boron from Molten Silicon Under Enhanced Electromagnetic Force.

The removal of boron is one of the main challenges in the purification of metallurgical grade silicon destined for low-cost photovoltaic applications. However, boron is very difficult to remove in its elemental form due to its large segregation coefficient in silicon and its low vapor pressure. The removal of boron by slag treatment is today regarded as a highly promising method, but its refining efficiency is relatively low. Also, the reduction of boron by plasma treatment exhibits a high refining efficiency, but the processing cost is high due to the large amount of electricity consumed by the process. In this regard, the use of an oxidizing reactive gas in the refinement process offers some advantages both in terms of low energy consumption and promising refinement rates. Boron can be extracted in various gaseous forms as B(x)O(y) and/or B(x)H(z)O(y) phases, but the vapor pressure of B(x)H(z)O(y) is much greater than that of the other specie at a temperature of 1700 K. The present study reports a modified oxidative refining method designed to enhance the vaporization of boron as B(x)H(z)O(y) by blowing gaseous water onto the silicon melt in a segmented crucible to enhance the electromagnetic force, whereby the processing cost can be dramatically reduced due to the use of a reusable quartz crucible in a graphite crucible. An initial boron content of 13 ppm in the metallurgical grade silicon was significantly decreased to 0.3 ppm by the employment of 1.7SLM Ar + 100 ml/h H2O. Also, a mechanism capable of reducing boron based on thermodynamic considerations is proposed.

The effect of bortezomib on expression of inflammatory cytokines and survival in a murine sepsis model induced by cecal ligation and puncture.

PURPOSE: Although the proteasome inhibitor known as bortezomib can modulate the inflammatory process through the nuclear factor-kappa B signaling pathway, the immunomodulatory effect of pre-incubated bortezomib has not been fully evaluated for inflammation by infectious agents. Therefore, we evaluated the effect of bortezomib on the expression of inflammatory cytokines and mediators in macrophage cell lines and on survival in a murine peritonitis sepsis model. MATERIALS AND METHODS: Bortezomib was applied 1 hr before lipopolysaccharide (LPS) stimulation in RAW 264.7 cells. The cecal ligation and puncture (CLP) experiments were performed in C57BL/6J mice. RESULTS: Pre-incubation with bortezomib (25 nM or 50 nM) prior to LPS (50 ng/mL or 100 ng/mL) stimulation significantly recovered the number of viable RAW 264.7 cells compared to those samples without pre-incubation. Bortezomib decreased various inflammatory cytokines as well as nitric oxide production in LPS-stimulated cells. The 7-day survival rate in mice that had received bortezomib at 0.01 mg/kg concentration 1 hr prior to CLP was significantly higher than in the mice that had only received a normal saline solution of 1 mL 1 hr prior to CLP. In addition, the administration of bortezomib at 0.01 mg/kg concentration 1 hr before CLP resulted in a significant decrease in inflammation of the lung parenchyma. Collectively, pretreatment with bortezomib showed an increase in the survival rate and changes in the levels of inflammatory mediators. CONCLUSION: These results support the possibility of pretreatment with bortezomib as a new therapeutic target for the treatment of overwhelming inflammation, which is a characteristic of severe sepsis.

GPR30 mediates anorectic estrogen-induced STAT3 signaling in the hypothalamus.

OBJECTIVE: Estrogen plays an important role in the control of energy balance in the hypothalamus. Leptin-independent STAT3 activation (i.e., tyrosine(705)-phosphorylation of STAT3, pSTAT3) in the hypothalamus is hypothesized as the primary mechanism of the estrogen-induced anorexic response. However, the type of estrogen receptor that mediates this regulation is unknown. We investigated the role of the G protein-coupled receptor 30 (GPR30) in estradiol (E2)-induced STAT3 activation in the hypothalamus. MATERIALS/METHODS: Regulation of STAT3 activation by E2, G-1, a specific agonist of GPR30 and G-15, a specific antagonist of GPR30 was analyzed in vitro and in vivo. Effect of GPR30 activation on eating behavior was analyzed in vivo. RESULTS: E2 stimulated pSTAT3 in cells expressing GPR30, but not expressing estrogen receptor ERα and ERß. G-1 induced pSTAT3, and G-15 inhibited E2-induced pSTAT3 in primary cultures of hypothalamic neurons. A cerebroventricular injection of G-1 increased pSTAT3 in the arcuate nucleus of mice, which was associated with a decrease in food intake and body weight gain. CONCLUSIONS: These results suggest that GPR30 is the estrogen receptor that mediates the anorectic effect of estrogen through the STAT3 pathway in the hypothalamus.

Down-modulation of Bis sensitizes cell death in C6 glioma cells induced by oxygen-glucose deprivation.

Bcl-2 interacting cell death suppressor (Bis), also known as Bag3, has been implicated in anti-stress and anti-apoptotic pathways. In a previous study, we observed a significant induction of Bis in reactive astrocytes of the rat hippocampus after transient forebrain ischemia. To investigate the significance of this induction in ischemic injury, the expression of Bis was reduced with siRNA in C6 glioma cells and exposed to oxygen-glucose deprivation (OGD) conditions. Bis knock-down resulted in an increase in the cell death rate of the C6 cells after OGD, accompanied by accumulation of reactive oxygen species. Among the cellular antioxidants, the induction of superoxide dismutase (SOD) activity was significantly interfered within the cells treated with bis siRNA treated cells (bis-kd C6). A Western blot assay revealed that SOD1 expression gradually increased in control cells, which was not observed in bis-kd cells upon OGD treatment. A quantitative analysis of Sod1 and Sod2 transcripts indicated that the induction of Sod1 was more evidently suppressed by the reduction of Bis. As a transcription factor candidate for the Sod1 gene, the activity of NF-kappaB was determined the nuclear translocation of p65, showing that the activation of NF-kappaB was attenuated in bis-kd C6. Supporting this, an overexpression of Bis augments the activation of NF-kappaB and Sod1 mRNA with an increased cell survival under OGD conditions. These results suggest that one of physiological significances of Bis induction in reactive astrocytes after ischemia in vivo is to protect glial cells from oxidative stress, probably via the induction of SOD1, which is related to the activation of NF-kappaB.

Microarray analysis of differentially expressed genes in the brains of tubby mice.

The tubby mouse is characterized by progressive retinal and cochlear degeneration and late-onset obesity. These phenotypes are caused by a loss-of-function mutation in the tub gene and are shared with several human syndromes, suggesting the importance of tubby protein in central nervous system (CNS) functioning. Although evidence suggests that tubby may act as a transcription factor mediating G-protein coupled receptor (GPCR) signaling, any downstream gene regulated by tubby has yet to be identified. To explore potential target genes of tubby with region-specific transcription patterns in the brain, we performed a microarray analysis using the cerebral cortex and hypothalamus of tubby mice. We also validated the changes of gene expression level observed with the microarray analysis using real-time RT-PCR. We found that expression of erythroid differentiation factor 1 (Erdr1) and caspase 1 (Casp1) increased, while p21-activated kinase 1 (Pak1) and cholecystokinin 2 receptor (Cck2r) expression decreased in the cerebral cortex of tubby mice. In the hypothalamic region, Casp 1 was up-regulated and micro-crystallin (CRYM) was down-regulated. Based on the reported functions of the differentially expressed genes, these individual or grouped genes may account for the phenotype of tubby mice. We discussed how altered expression of genes in tubby mice might be understood as the underlying mechanism behind tubby phenotypes.

Zinc Inhibits Amyloid beta Production from Alzheimer's Amyloid Precursor Protein in SH-SY5Y Cells.

Zinc released from excited glutamatergic neurons accelerates amyloid beta (Abeta) aggregation, underscoring the therapeutic potential of zinc chelation for the treatment of Alzheimer's disease (AD). Zinc can also alter Abeta concentration by affecting its degradation. In order to elucidate the possible role of zinc influx in secretase-processed Abeta production, SH-SY5Y cells stably expressing amyloid precursor protein (APP) were treated with pyrrolidine dithiocarbamate (PDTC), a zinc ionophore, and the resultant changes in APP processing were examined. PDTC decreased Abeta40 and Abeta42 concentrations in culture media bathing APP-expressing SH-SY5Y cells. Measuring the levels of a series of C-terminal APP fragments generated by enzymatic cutting at different APP-cleavage sites showed that both beta- and alpha-cleavage of APP were inhibited by zinc influx. PDTC also interfered with the maturation of APP. PDTC, however, paradoxically increased the intracellular levels of Abeta40. These results indicate that inhibition of secretase-mediated APP cleavage accounts -at least in part- for zinc inhibition of Abeta secretion.

hnRNP L binds to CA repeats in the 3'UTR of bcl-2 mRNA.

We previously reported that the CA-repeat sequence in the 3'-untranslated region (3'UTR) of bcl-2 mRNA is involved in the decay of bcl-2 mRNA. However, the trans-acting factor for the CA element in bcl-2 mRNA remains unidentified. The heterogeneous nuclear ribonucleoprotein L (hnRNP L), an intron splicing factor, has been reported to bind to CA repeats and CA clusters in the 3'UTR of several genes. We reported herein that the CA repeats of bcl-2 mRNA have the potential to form a distinct ribonuclear protein complex in cytoplasmic extracts of MCF-7 cells, as evidenced by RNA electrophoretic mobility shift assays (REMSA). A super-shift assay using the hnRNP L antibody completely shifted the complex. Immunoprecipitation with the hnRNP L antibody and MCF-7 cells followed by RT-PCR revealed that hnRNP L interacts with endogenous bcl-2 mRNA in vivo. Furthermore, the suppression of hnRNP L in MCF-7 cells by the transfection of siRNA for hnRNP L resulted in a delay in the degradation of RNA transcripts including CA repeats of bcl-2 mRNA in vitro, suggesting that the interaction between hnRNPL and CA repeats of bcl-2 mRNA participates in destabilizing bcl-2 mRNA.

Autocrine function of erythropoietin in IGF-1-induced erythropoietin biosynthesis.

Insulin-like growth factor-1 (IGF-1) and erythropoietin (EPO) are induced in brain cells after brain ischemia and show synergistic neuroprotective effects. In LN215 astrocytoma cells, IGF-1 induced the activation of hypoxia-inducible factor-1, leading to increases in EPO mRNA levels and the secretion of EPO. Interestingly, blocking the potential action of secreted EPO on LN215 cells with EPO antibody, EPO receptor antibody, and soluble EPO receptor significantly suppressed the effect of IGF-1 on the biosynthesis of EPO. Synergistic action between IGF-1 and recombinant human EPO in the astrocytic production of EPO was observed. These data suggest that the IGF-1-EPO production/secretion process initiates a positive feedback loop of EPO biosynthesis in astrocytes, providing a molecular link between the two neuroprotective cytokines.

Calmodulin dynamically regulates the trafficking of the metabotropic glutamate receptor mGluR5.

Metabotropic glutamate receptors (mGluRs) 1-8 are G protein-coupled receptors (GPCRs) that modulate excitatory neurotransmission, neurotransmitter release, and synaptic plasticity. PKC regulates many aspects of mGluR function, including protein-protein interactions, Ca(2+) signaling, and receptor desensitization. However, the mechanisms by which PKC regulates mGluR function are poorly understood. We have now identified calmodulin (CaM) as a dynamic regulator of mGluR5 trafficking. We show that the major PKC phosphorylation site on the intracellular C terminus of mGluR5 is serine 901 (S901), and phosphorylation of this residue is up-regulated in response to both receptor and PKC activation. In addition, S901 phosphorylation inhibits mGluR5 binding to CaM, decreasing mGluR5 surface expression. Furthermore, blocking PKC phosphorylation of mGluR5 on S901 dramatically affects mGluR5 signaling by prolonging Ca(2+) oscillations. Thus, our data demonstrate that mGluR5 activation triggers phosphorylation of S901, thereby directly linking PKC phosphorylation, CaM binding, receptor trafficking, and downstream signaling.

Inhibitory effect of zinc on hypoxic HIF-1 activation in astrocytes.

Hypoxia-inducible factor-1 (HIF-1) regulates the expression of neuroprotective genes such as erythropoietin (EPO). We investigated the mechanism by which zinc, an excitotoxin-like metal, regulates HIF-1 under hypoxic conditions in astrocytes. In hypoxic LN215 cells, HIF-1alpha stabilized and accumulated in the nucleus, resulting in an increase in its DNA-binding activity to the EPO enhancer. Zinc inhibited hypoxia-induced increases in HIF-1 DNA-binding activity and the HIF-1-dependent mRNA expression of EPO. Zinc did not affect hypoxic stabilization of HIF-1alpha. Nuclear migration of HIF-1alpha upon hypoxia was reduced by zinc. Complete blockade of hypoxia-induced assembly of HIF-1alpha-HIF-1beta complex was observed after treatment of zinc. These findings suggest that zinc hampers hypoxia-stimulated HIF-1 activation in astrocytes by inhibiting nuclear HIF-1alpha translocation and subsequently disrupting HIF-1 heterodimerization.

Lithospermic acid B ameliorates the development of diabetic nephropathy in OLETF rats.

Lithospermic acid B (LAB), an active component isolated from Salvia miltiorrhizae, has been reported to have renoprotective effects in type 1 diabetic animal models. In the present study we investigated the effects of LAB on the prevention of diabetic nephropathy in type 2 diabetic Otsuka Long-Evans-Tokushima Fatty (OLETF) rats. LAB (20 mg/kg) was given orally once daily to 10-week-old male OLETF rats for 28 weeks. Treatment of OLETF rats with LAB had little effects on body weight and blood glucose levels. Treatment with LAB resulted in significant reduction in blood pressure. LAB markedly attenuated albuminuria and significantly lowered levels of lipid peroxidation, monocyte chemoattractant protein-1 (MCP-1), and transforming growth factor-beta (TGF-beta1) expression in renal tissues of OLETF rats. In addition, LAB inhibited the progression of glomerular hypertrophy, mesangial expansion, and expansion of the extracellular matrix in the renal cortex. Collectively, these results suggest that LAB has beneficial effects on the diabetic nephropathy in OLETF rats by decreasing blood pressure, oxidative stress, and MCP-1 expression. Our results suggest that LAB might be a new therapeutic agent for the prevention of nephropathy in type 2 diabetes.

Adsorption of water on mesoporous silica for heat management: effect of pore structure.

As a potential adsorbent for humidity control, the mesoporous silica, SBA-15, with various pore sizes that was synthesized hydrothermally at different temperatures was examined by measuring the rate of water adsorption under ambient condition, 2.53 kPa H2O and 30 degrees C. The adsorption saturation quantity and the diffusion coefficient of water were changed consistently with the micropore fraction in SBA-15 obtained from the t-plot method. The diffusion of water into the SBA-15 was very similar to that on either zeolite A or Y because of the presence of complimentary pore.

Heparin Attenuates the Expression of TNFalpha-induced Cerebral Endothelial Cell Adhesion Molecule.

Heparin is a well-known anticoagulant widely used in various clinical settings. Interestingly, recent studies have indicated that heparin also has anti-inflammatory effects on neuroinflammation-related diseases, such as Alzheimer's disease and meningitis. However, the underlying mechanism of its actions remains unclear. In the present study, we examined the anti-inflammatory mechanism of heparin in cultured cerebral endothelial cells (CECs), and found that heparin inhibited the tumor necrosis factor alpha(TNFalpha)-induced and nuclear factor kappa B (NF-kappaB)-dependent expression of adhesion molecules, such as intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), which are crucial for inflammatory responses. Heparin selectively interfered with NF-kappaB DNA-binding activity in the nucleus, which is stimulated by TNFalpha. In addition, non-anticoagulant 2,3-O desulfated heparin (ODS) prevented NF-kappaB activation by TNFalpha, suggesting that the anti-inflammatory mechanism of heparin action in CECs lies in heparin's ability to inhibit the expression of cell adhesion molecules, as opposed to its anticoagulant actions.

DYRK1A-mediated hyperphosphorylation of Tau. A functional link between Down syndrome and Alzheimer disease.

Most individuals with Down syndrome show early onset of Alzheimer disease (AD), resulting from the extra copy of chromosome 21. Located on this chromosome is a gene that encodes the dual specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A). One of the pathological hallmarks in AD is the presence of neurofibrillary tangles (NFTs), which are insoluble deposits that consist of abnormally hyperphosphorylated Tau. Previously it was reported that Tau at the Thr-212 residue was phosphorylated by Dyrk1A in vitro. To determine the physiological significance of this phosphorylation, an analysis was made of the amount of phospho-Thr-212-Tau (pT212) in the brains of transgenic mice that overexpress the human DYRK1A protein (DYRK1A TG mice) that we recently generated. A significant increase in the amount of pT212 was found in the brains of DYRK1A transgenic mice when compared with age-matched littermate controls. We further examined whether Dyrk1A phosphorylates other Tau residues that are implicated in NFTs. We found that Dyrk1A also phosphorylates Tau at Ser-202 and Ser-404 in vitro. Phosphorylation by Dyrk1A strongly inhibited the ability of Tau to promote microtubule assembly. Following this, using mammalian cells and DYRK1A TG mouse brains, it was demonstrated that the amounts of phospho-Ser-202-Tau and phospho-Ser-404-Tau are enhanced when DYRK1A amounts are high. These results provide the first in vivo evidence for a physiological role of DYRK1A in the hyperphosphorylation of Tau and suggest that the extra copy of the DYRK1A gene contributes to the early onset of AD.

Heparin inhibits NF-kappaB activation and increases cell death in cerebral endothelial cells after oxygen-glucose deprivation.

Heparin is a classic anticoagulant that is commonly used in the treatment of acute ischemic stroke (AIS). Its use remains controversial, however, due to the risk of cerebral hemorrhagic transformation. In addition to anticoagulant effects, diverse effects on transcription factors can be caused by heparin. Among the transcription factors potentially affected is nuclear factor kappa B (NF-kappaB), a protein that is reportedly related to the survival of cerebral endothelial cells. We investigated the effect of heparin on NF-kappaB activation and cell death following oxygen-glucose deprivation (OGD), an experimental model of AIS. We subjected bEnd.3 cells from a murine cerebral microvascular endothelial cell line to OGD. We examined the effect of heparin on OGD-induced NF-kappaB activation and its mechanism of action, using electrophoretic mobility shift assays, reporter gene analysis, real-time RT-PCR, Western blot analysis, and confocal microscopy. We also measured the effect of heparin on OGD-induced cell death using an MTT assay. Heparin inhibited both tumor necrosis factor alpha- and OGD-induced NF-kappaB activation. Heparin was taken up by endocytosis and then entered the nucleus. Heparin did not affect the nuclear translocation of NF-kappaB, but instead inhibited the DNA binding of NF-kappaB in the nucleus. Cells were more susceptible to OGD-induced cell death after heparin treatment. Besides producing an anticoagulation effect, heparin also inhibits NF-kappaB activation, resulting in increased susceptibility to OGD-induced cell death. This effect may be responsible for hemorrhagic transformation in patients following heparin treatment for AIS.

Activation of NF-kappaB is involved in 6-hydroxydopamine-but not MPP+ -induced dopaminergic neuronal cell death: its potential role as a survival determinant.

The nuclear factor-kappaB (NF-kappaB) family plays an important role in the control of the apoptotic response. Its activation has been demonstrated in both neurons and glial cells in many neurological disorders. In the present study, we specifically examined whether and to what extent NF-kappaB activation is involved in culture models of Parkinson's disease following exposure of MN9D dopaminergic neuronal cells to 6-hydroxydopamine (6-OHDA) and 1-methyl-4-phenyl-4-phenylpyridinium ion (MPP(+)). Both analysis by immunocytochemistry and of immunoblots revealed that NF-kappaB-p65 was translocated into the nuclei following 6-OHDA but not MPP(+)-treatment. A time-dependent activation of NF-kappaB induced by 6-OHDA but not MPP(+) was also demonstrated by an electrophoretic mobility shift assay. A competition assay indicated that not only NF-kappaB-p65 but also -p50 is involved in 6-OHDA-induced NF-kappaB activity. Co-treatment with an antioxidant, N-acetyl-l-cysteine, blocked 6-OHDA-induced activation of NF-kappaB signaling. In the presence of an NF-kappaB inhibitor, pyrrolidine dithiocarbamate (PDTC), 6-OHDA-induced cell death was accelerated while PDTC did not affect MPP(+)-induced cell death. Our data may point to a drug-specific activation of NF-kappaB as a survival determinant for dopaminergic neurons.

Pyrrolidine dithiocarbamate and zinc inhibit proteasome-dependent proteolysis.

Proteasomes play important roles in a variety of cellular processes such as cell cycle progression, signal transduction and immune responses. Proteasome activity is important in maintaining rapid turnover of short-lived proteins, as well as preventing accumulation of misfolded or damaged proteins. Alteration in ubiquitin-proteasome function may be detrimental to its crucial role in maintaining cellular homeostasis. Here, we have found that treatment of pyrrolidine dithiocarbamate (PDTC), a zinc ionophore, resulted in the accumulation of several proteasome substrates including p53 and p21 in HeLa cells. The PDTC effect was due to an extended half-life of these proteins through the mobilization of zinc. PDTC and/or zinc also increased fluorescence intensity of Ub(G76V)-GFP fusion protein that is degraded rapidly by the ubiquitin-proteasome system. Treatment of cells with zinc induced formation of ubiquitinated inclusions in the centrosome, a histological marker of proteasome inhibition. Western blotting showed zinc-induced increase in laddering bands of polyubiquitin-conjugated proteins. In vitro study, zinc inhibited the ubiquitin-independent proteasomal degradations of p21 and alpha-synuclein. These results suggest that zinc may modulate cell functions through its action on the turnover of proteins that are susceptible to proteasome-dependent proteolysis.