Analysis of circulating metabolites to differentiate Parkinson's disease and essential tremor

Parkinson disease (PD) and essential tremor (ET) are two common adult-onset tremor disorders in which prevalence increases with age. PD is a neurodegenerative condition with progressive disability. In ET, neurodegeneration is not an established etiology. We sought to determine whether an underlying metabolic pattern may differentiate ET from PD. Circulating metabolites in plasma and cerebrospinal fluid were analyzed using gas chromatography-mass spectroscopy. There were several disrupted pathways in PD compared to ET plasma including glycolysis, tyrosine, phenylalanine, tyrosine biosynthesis, purine and glutathione metabolism. Elevated α-synuclein levels in plasma and CSF distinguished PD from ET. The perturbed metabolic state in PD was associated with imbalance in the pentose phosphate pathway, deficits in energy production, and change in NADPH, NADH and nicotinamide phosphoribosyltransferase levels. This work demonstrates significant metabolic differences in plasma and CSF of PD and ET patients.

Hydrogen sulfide facilitates reprogramming and trans-differentiation in 3D dermal fibroblast

The efficiency of cell reprogramming in two-dimensional (2D) cultures is limited. Given that cellular stemness is intimately related to microenvironmental changes, 3D cell cultures have the potential of overcoming this limited capacity by allowing cells to self-organize by aggregation. In 3D space, cells interact more efficiently, modify their cellular topology, gene expression, signaling, and metabolism. It is yet not clear as how 3D culture environments modify the reprogramming potential of fibroblasts. We demonstrate that 3D spheroids from dermal fibroblasts formed under ultra-low attachment conditions showed increased lactate production. This is a requisite for cell reprogramming, increase their expression of pluripotency genes, such as OCT4, NANOG and SOX2, and display upregulated cystathionine-β-synthase (CBS) and hydrogen sulfide (H2S) production. Knockdown of CBS by RNAi suppresses lactic acid and H2S production and concomitantly decreases the expression of OCT4 and NANOG. On the contrary, H2S donors, NaHS and garlic-derived diallyl trisulfide (DATS), promote the expression of OCT4, and support osteogenic trans-differentiation of fibroblasts. These results demonstrate that CBS mediated release of H2S regulates the reprogramming of dermal fibroblasts grown in 3D cultures and supports their trans-differentiation.

Replicative senescence is distinguishable from DNA damage-induced senescence by increased methylation of promoter of rDNA and reduced expression of rRNA

Human fibroblasts become senescent after a limited number of replications or by diverse stresses, such as DNA damage. However, replicative and damage induced senescence are indistinguishable in respect to proliferation cessation and expression of senescence markers, senescence-associated β-galactosidase, p16 and p21. Here, we show that senescence types can be distinguished by reduced levels of 18S, 5.8S and 28S rRNA, in replicative but not induced senescence. We also demonstrate that promoter region of rRNA is hypermethylated in replicative senescence. The findings show that expression level of rRNA or methylation of its promoter can be used to distinguish between senescence types.

Homocysteine and age-associated disorders

There are numerous theories of aging, a process which still seems inevitable. Aging leads to cancer and multi-systemic disorders as well as chronic diseases. Decline in age- associated cellular functions leads to neurodegeneration and cognitive decline that affect the quality of life. Accumulation of damage, mutations, metabolic changes, failure in cellular energy production and clearance of altered proteins over the lifetime, and hyperhomocysteinemia, ultimately result in tissue degeneration. The decline in renal functions, nutritional deficiencies, deregulation of methionine cycle and deficiencies of homocysteine remethylation and transsulfuration cofactors cause elevation of homocysteine with advancing age. Abnormal accumulation of homocysteine is a risk factor of cardiovascular, neurodegenerative and chronic kidney disease. Moreover, approximately 50% of people, aged 65 years and older develop hypertension and are at a high risk of developing cardiovascular insufficiency and incurable neurodegenerative disorders. Increasing evidence suggests inverse relation between cognitive impairment, cerebrovascular and cardiovascular events and renal function. Oxidative stress, inactivation of nitric oxide synthase pathway and mitochondria dysfunction associated with impaired homocysteine metabolism lead to aging tissue degeneration. In this review, we examine impact of high homocysteine levels on changes observed with aging that contribute to development and progression of age associated diseases.

Basal and copper-induced expression of metallothionein isoform 1,2 and 3 genes in epithelial cancer cells: The role of tumor suppressor p53

Metallothioneins (MTs) are a ubiquitous low-molecular weight, cysteine rich proteins with a high affinity for metal ions. The expression and induction of MTs have been associated with protection against DNA damage, oxidative stress, and apoptosis. Our past research had shown that p53 is an important factor in metal regulation of MTs. The present study was undertaken to explore further the interrelationship between p53 and MTs. We investigated whether silencing of p53 could affect expression pattern of basal and copper induced metallothioneins. The silencing of wild-type p53 (wt-p53) in epithelial breast cancer MCF7 cells affected the basal level of MT-2A RNA, whereas the levels of MT-1A and MT-1X RNA remained largely unchanged. The expression of MT-3 was undetectable in MCF7 with either functional or silenced p53. MCF7 cells with silenced wt-p53 failed to upregulate MT-2A in response to copper and showed a reduced sensitivity toward copper induced cell apoptotic death. Similarly in MCF7-E6 and MDA-MB-231 cells, the presence of inactive/mutated p53 halted MT-1A and MT-2A gene expression in response to copper. Constitutive expression of MT-3 RNA was detectable in the presence of mutated p53 (mtp53). Transient transfection of MDA-MB-231 cells with wt-p53 enabled copper induced upregulation of both MT-1A and MT-2A but not basal level of MT-2A, MT-1E, MT-1X and MT-3. Inactivation of p53 in HepG2 cells amplified the basal expression of studied MT isoforms, including MT-3, as well as copper-induced mRNA expression of MTs except MT-1H and MT-3. Presented data demonstrate a direct relation between p53 and MT-1A and MT-2A and they also indicate that wt-p53 might be a negative regulator of MT-3 in epithelial cancer cells.

Dedifferentiation of cancer cells following recovery from a potentially lethal damage is mediated by H2S-Nampt

Recently, we reported that cancer cells that recover from a potentially lethal damage gain new phenotypic features comprised of mitochondrial structural remodeling associated with increased glycolytic dependency and drug resistance. Here, we demonstrate that a subset of cancer cells, upon recovery from a potentially lethal damage, undergo dedifferentiation and express genes, which are characteristic of undifferentiated stem cells. While these cells are competent in maintaining differentiated progeny of tumor, they also exhibit transdifferentiation potential. Dedifferentiation is characterized by accumulation of hydrogen sulfide (H2S), which triggers up-regulation of nicotinamide phosphoribosyltransferase (Nampt) accompanied by changes in the redox state. The molecular events triggered by Nampt include elevated production of NAD(+) and up-regulation of H2S producing enzymes, cystathionine beta synthase (CBS) and cystathionase (CTH) with 3-mercaptopyruvate sulfurtransferase (MST) being detectable only in 3D spheroids. Suppression of Nampt, or inactivation of H2S producing enzymes, all reduce H2S production and reverse the ability of cells to dedifferentiate. Moreover, H2S induced stem cell markers in parental cancer cells in a manner similar to that observed in damage recovered cells. These data suggest of existence of a positive feedback loop between H2S and Nampt that controls dedifferentiation in cancer cells that recover from a potentially lethal damage.

A H2S-Nampt dependent energetic circuit is critical to survival and cytoprotection from damage in cancer cells

We recently demonstrated that cancer cells that recover from damage exhibit increased aerobic glycolysis, however, the molecular mechanism by which cancer cells survive the damage and show increased aerobic glycolysis remains unknown. Here, we demonstrate that diverse cancer cells that survive hypoxic or oxidative damage show rapid cell proliferation, and develop tolerance to damage associated with increased production of hydrogen sulfide (H₂S) which drives up-regulation of nicotinamide phosphoribosyltransferase (Nampt). Consistent with existence of a H₂S-Nampt energetic circuit, in damage recovered cancer cells, H₂S, Nampt and ATP production exhibit a significant correlation. Moreover, the treatment of cancer cells with H₂S donor, NaHS, coordinately increases Nampt and ATP levels, and protects cells from drug induced damage. Inhibition of cystathionine beta synthase (CBS) or cystathionase (CTH), enzymes which drive generation of H₂S, decreases Nampt production while suppression of Nampt pathway by FK866, decreases H₂S and ATP levels. Damage recovered cells isolated from tumors grown subcutaneously in athymic mice also show increased production of H₂S, Nampt and ATP levels, associated with increased glycolysis and rapid proliferation. Together, these data show that upon recovery from potential lethal damage, H₂S-Nampt directs energy expenditure and aerobic glycolysis in cancer cells, leads to their exponential growth, and causes a high degree of tolerance to damage. Identification of H₂S-Nampt as a pathway responsible for induction of damage tolerance in cancer cells may underlie resistance to therapy and offers the opportunity to target this pathway as a means in treatment of cancer.

Directed differentiation of embryonic P19 cells and neural stem cells into neural lineage on conducting PEDOT-PEG and ITO glass substrates

Differentiation of pluripotent and lineage restricted stem cells such as neural stem cells (NSCs) was studied on conducting substrates of various nature without perturbation of the genome with exogenous genetic material or chemical stimuli. Primary mouse adult neural stem cells (NSCs) and P19 pluripotent embryonal (P19 EC) carcinoma cells were used. Expression levels of neuronal markers β-III-tubulin and neurofilament were evaluated by immunochemistry and flow cytometry. It was shown that the ability of the substrate to induce differentiation directly correlated with its conductivity. Conducting substrates (conducting oxides or doped π-conjugated organic polymers) with different morphology, structure, and conductivity mechanisms all promoted differentiation of NSC and P19 cells into neuronal lineage to a similar degree without use of additional factors such as poly-L-ornithine coating or retinoic acid, as verified by their morphology and upregulation of the neuronal markers but not astrocyte marker GFAP. However, substrates with low conductance below ca. 10(-4) S cm(-2) did not show this ability. Morphology of differentiating cells was visualized by atomic force microscopy. NSCs cells increased β-III-tubulin expression by 95% and P19 cells by over 30%. Our results suggest that the substrate conductivity is a key factor governing the cell fate. Differentiation of P19 cells into neuronal lineage on conducting substrates was attributed to downregualtion of Akt signaling pathway and increase in expression of dual oxidase 1 (DUOX 1).

The role of redox environment in neurogenic development

The dynamic changes of cellular redox elements during neurogenesis allow the control of specific programs for selective lineage progression. There are many redox couples that influence the cellular redox state. The shift from a reduced to an oxidized state and vice versa may act as a cellular switch mechanism of stem cell mode of action from proliferation to differentiation. The redox homeostasis ensures proper functioning of redox-sensitive signaling pathways through oxidation/reduction of critical cysteine residues on proteins involved in signal transduction. This review presents the current knowledge on the relation between changes in the cellular redox environment and stem cell programming in the course of commitment to a restricted neural lineage, focusing on in vivo neurogenesis and in vitro neuronal differentiation. The first two sections outline the main systems that control the intracellular redox environment and make it more oxidative or reductive. The last section provides the background on redox-sensitive signaling pathways that regulate neurogenesis.

p53-mediated regulation of neuronal differentiation via regulation of dual oxidase maturation factor 1

The p53 transcription factor is involved in cell cycle, apoptosis and differentiation. However, the mechanism of p53 mediated differentiation is not fully understood. Here, we show that recently discovered dual oxidase maturation factor 1 (DUOXA1), which was implicated in neuronal differentiation, is regulated by p53 and may be an important factor in neuronal differentiation. We show that DUOXA1 is highly expressed in mouse neuronal stem cells with intensive nuclear localization. A strong interaction between DUOXA1 and p53 is observed in undifferentiated cells and declines in terminally differentiated neurons. Overexpressed p53 induces marked DUOXA1 expression in P19 cells and intensifies neuronal differentiation in the presence of retinoic acid, which suggests that p53 and DUOXA1 possess a neural differentiation potential. At day 3 of retinoic acid induced differentiation when cells showed a typical morphology of neuronal progenies, CD133 expression was down-regulated. The expression level of CD133 was significantly decreased in p53 over-expressing cells and was accompanied by a substantial increase in the expression level of neurofilament. In conclusion, DUOXA1 is a novel p53-regulated neurogenic factor involved in p53 dependent neuronal differentiation.

Mammalian numb-interacting protein 1/dual oxidase maturation factor 1 directs neuronal fate in stem cells

In this study, we describe a role for the mammalian Numb-interacting protein 1 (Nip1) in regulation of neuronal differentiation in stem cells. The expression of Nip1 was detected in the developing mouse brain, embryonic stem cells, primary neuronal stem cells, and retinoic acid-treated P19 embryonal carcinoma cells. The highest expression of Nip1 was observed in undifferentiated neuronal stem cells and was associated with Duox1-mediated reactive oxygen species ROS production. Ectopic nip1 expression in P19 embryonal carcinoma cells induced neuronal differentiation, and this phenotype was also linked to elevated ROS production. The neuronal differentiation in nip1-overexpressing P19 cells was achieved in a retinoic acid-independent manner and was corroborated by an increase in the expression of the neuronal basic helix-loop-helix transcription factors and neural-lineage cell markers. Furthermore, depletion of nip1 by short hairpin RNA led to a decrease in the expression of neuronal basic helix-loop-helix transcription factors and ROS. However, inhibition of ROS production in nip1-overexpressing P19 cells restricted but did not extinguish neuronal differentiation. Microarray and mass spectrometry analysis identified intermediate filaments as the principal cytoskeletal elements affected by up-regulation of nip1. We show here the first evidence for a functional interaction between Nip1 and a component of the nuclear lamina, lamin A/C. associated with a neuronal-specific phenotype. Taken together, our data reveal an important role for Nip1 in the guidance of neuronal differentiation through ROS generation and modulation of intermediate filaments and implicate Nip1 as a novel intrinsic regulator of neuronal cell fate.

Interplay between Numb and Notch in epithelial cancers: role for dual oxidase maturation factor

Numb and Notch signalling pathways are vitally important in cell fate and differentiation. The outcome of these signalling processes is determined by a delicate balance between opposing effects of Notch and Numb. Imbalance in Numb/Notch regulation was implicated in aberrant differentiation programme and epithelial cancer progression and metastasis. Recent identification of Numb-interacting protein (NIP), which is also known as dual oxidase maturation factor, and was shown to associate with Numb and DUOX and promote their translocation, sheds a new light on how Numb/Notch network may be coordinated in epithelial cancers. Here, a possible link between Numb, Notch and Dual oxidase maturation factor is examined.

SAP binds to CD22 and regulates B cell inhibitory signaling and calcium flux

The signaling lymphocyte activation molecule (SLAM)-associated protein (SAP or SH2D1A) is an important regulator of immune function which, when mutated or deleted, causes the X-linked lymphoproliferative syndrome (XLP). Because B cell lymphoma is a major phenotype of XLP, it is important to understand the function of SAP in B cells. Here we report that SAP is expressed endogenously in mouse splenic B cells, is inducibly expressed in the human BJAB cells, and co-localizes and interacts with CD22. We also show that SAP binding to the inhibitory immunoreceptor CD22 regulates calcium mobilization in B cells. Moreover, forced expression of SAP leads to constitutive CD22 tyrosine phosphorylation and decreased Ca(2+) response in B cells. Biochemical analysis reveals that, in response to IgM cross-linking, the phosphorylation of Syk, Blnk, or PLCgamma2 and their interactions with one another were either diminished or completely abolished in SAP-expressing cells compared to cells that lack SAP. Collectively our work identifies a novel role for SAP in B cells and extends its function to inhibitory immunoreceptor signaling and calcium mobilization.

P53 mediated regulation of metallothionein transcription in breast cancer cells

Recent studies have shown that only breast cancer epithelial cells with intact p53 can induce metallothionein (MT) synthesis after exposure to metals. In this study, the potential role of p53 on regulation of MT was investigated. Results demonstrate that zinc and copper increased metal response elements (MREs) activity and MTF-1 expression in p53 positive MN1 and parental MCF7 cells. However, inactivation of p53 by treatment with pifithrin-alpha or the presence of inactive p53 inhibited MRE-dependent reporter gene expression in response to metals. MTF-1 levels remained unchanged after treatment with zinc in cells with nonfunctional p53. The introduction of wild-type p53 in MDD2 cells, containing nonfunctional p53, enhanced the ability of zinc to increase MRE-dependent reporter gene expression. The cellular level of p21Cip1/WAF1 was increased in MDD2 cells after p53 transfection, confirming the presence of active p53. The treatment of MN1 and parental MCF7 with trichostatin A led to a sixfold increase in the MRE activity in response to zinc. On the contrary, MRE activity remained unaltered in MDD2 cells with inactive p53. The above results demonstrate that activation of p53 is an important factor in metal regulation of MT.

Stimulation of phosphoinositide 3-kinase/Akt signaling by copper and zinc ions: mechanisms and consequences

The phosphoinositide 3'-kinase (PI3K)/Akt signaling cascade controls cellular processes such as apoptosis and proliferation. Moreover, it is a mediator of insulin effects on target cells and as such is a major regulator of fuel metabolism. The PI3K/Akt cascade was demonstrated to be activated by stressful stimuli, including heat shock and reactive oxygen species (ROS). This minireview focuses on activation of the pathway by exposure of cells to heavy metal ions, Cu2+ and Zn2+. It is hypothesized that stimulation of PI3K/Akt is the molecular mechanism underlying the known insulin-mimetic effects of copper and zinc ions. Following a brief summary of PI3K/Akt signaling and of activation of the cascade by Cu2+ and Zn2+, mechanisms of metal-induced PI3K/Akt activation are discussed with a focus on the role of ROS and of cellular thiols (glutathione, thioredoxin) and protein tyrosine phosphatases in Cu2+ and Zn2+ signaling. Finally, consequences of metal-induced PI3K/Akt activation are discussed, focusing on the modulation of FoxO-family transcription factors by Cu2+ and Zn2+.

The role of SLAM family receptors in immune cell signaling

The signaling lymphocyte-activating molecule (SLAM) family immunoreceptors are expressed in a wide array of immune cells, including both T and B lymphocytes. By virtue of their ability to transduce tyrosine phosphorylation signals through the so-called ITSM (immunoreceptor tyrosine-based switch motif) sequences, they play an important part in regulating both innate and adaptive immune responses. The critical role of the SLAM immunoreceptors in mediating normal immune reactions was highlighted in recent findings that SAP, a SLAM-associated protein, modulates the activities of various immune cells through interactions with different members of the SLAM family expressed in these cells. Importantly, mutations or deletions of the sap gene in humans result in the X-linked lymphoproliferative syndrome. In this review, we summarize current knowledge and survey the latest developments in signal transduction events triggered by the activation of SLAM family receptors in different cell types.

Interaction of metallothionein with tumor suppressor p53 protein

Previous reports have shown that metallothionein (MT) may modulate p53 activity through zinc exchange. However, little is known on a direct interaction between MT and p53 in cells. The results demonstrate an interaction between MT and p53 can occur in vitro. The complex between MT and p53 was observed in breast cancer epithelial cells with both wild and inactive type of p53. Furthermore, it was shown that wt-p53 was preferentially associated with Apo-MT. Our data suggest that co-expression of MT and p53 and their complex formation in tumor cells may be involved in regulation of apoptosis in these cells.

Inhibition of extracellular signal regulated kinase (ERK) leads to apoptosis inducing factor (AIF) mediated apoptosis in epithelial breast cancer cells: the lack of effect of ERK in p53 mediated copper induced apoptosis

Recent studies have shown that MEK/ERK-mediated signals play a major role in regulation of activity of p53 tumor suppressor protein. In this study, we investigated whether or not there is functional interaction between p53 and MEK/ERK pathways in epithelial breast cancer cells exposed to copper or zinc. We demonstrated that expression of wild-type p53 induced by copper or zinc significantly reduced phosphorylation of extracellular signal regulated kinase (ERK) in epithelial breast cancer MCF7 cells. Mutation or suppression of p53 in MDA-MB231 and MCF7-E6 cells, respectively, resulted in a strong ERK phosphorylation in the presence of metals. Weak ERK phosphorylation in MCF7 cells induced by copper or zinc was linked to mitochondrial disruption and apoptosis. Furthermore, inhibition of ERK through addition of PD98059 stimulated p53 activation in MCF7 cells and also led to upregulation of p53 downstream targets, p21 and Bax, which is a proapototic member of Bcl-2 family triggering mitochondrial pore opening. Moreover, blockage of the MEK/ERK pathway caused a breakdown of the mitochondrial membrane potential accompanied by an elevation in the ROS production. Disruption of p53 expression attenuated the depolarization of the mitochondrial membrane and ROS generation. Furthermore, PD98059 initiated apoptosis inducing factor (AIF) translocation from mitochondria to the nucleus in MCF7 cells; which are depleted in caspase 3. Interestingly, repression of MEK/ERK pathway did not intensify the cell stress caused by metal toxicity. Therefore, these findings demonstrate that MEK/ERK pathway plays an important role in downregulation of p53 and cell survival. Inhibition of ERK can lead to apoptosis via nuclear relocation of AIF. However, metal-induced activation of p53 and mitochondrial depolarization appears to be independent of ERK. Our data suggest that copper induces apoptosis through depolarization of mitochondrial membrane with release of AIF, and this process is MEK/ERK independent.

Role of p53 and reactive oxygen species in apoptotic response to copper and zinc in epithelial breast cancer cells

Previous studies revealed that cells may differ in their response to metal stress depending on their p53 status; however, the sequence of events leading to copper-induced apoptosis is still unclear. Exposure of copper (10 and 25 microM) and zinc (10 and 25 microM) caused activation of p53 in ER+/p53+ human epithelial breast cancer MCF7 cells and resulted in up-regulation of p21. Transactivation of p53 in MCF7 cells also led to increase in expression of Bax, proapototic Bcl-2 family member, triggering mitochondrial pore opening, and PIG3 (p53-induced gene 3 product), and also generation of intracellular reactive oxygen species (ROS). The treatment of MCF7 cells with either copper or zinc for 4 h also caused decrease in mitochondrial membrane potential (Delta psi(m)), accompanied by an elevation in the ROS production and redistribution of p53 into mitochondria. The loss of Delta psi(m) was correlated with accumulation of Annexin V positive apoptotic cells. However, the release of apoptosis inducing factor (AIF) and its translocation into nucleus was observed only in MCF7 cells treated with copper. In MDA-MB-231 (ER-/p53-) and MCF7-E6 (ER+/p53-) cells, both p53 and p21 protein levels were not altered in the presence of metals. These cells were resistant to metals, and there was no alteration in Delta psi(m). Copper treatment did not result in accumulation of ROS in these cell lines with an inactive p53 even after exposure to 50 microM of copper for 6 h, indicating a key role for p53 in the ROS generation. Pretreatment of MCF7 cells with p53 inhibitor, pifithrin-alpha, resulted in decrease of copper and zinc induced ROS production to the control level, suppression of both Bax expression and AIF release. Therefore, the activation of p53 seems to play a crucial role in copper and zinc induced generation of ROS in epithelial breast cancer cells, and expression of downstream targets of p53, such as PIG3 and Bax, responsible for increased generation of the intracellular ROS, as well as disruption of mitochondrial integrity. Our data suggest that copper induces apoptosis in MCF-7 cells with no caspases through the depolarization of mitochondrial membrane with release of AIF and its translocation into the nucleus. The results demonstrate that a functional p53 is required for the execution of apoptosis in epithelial cells.

Differential regulation of signal transduction pathways in wild type and mutated p53 breast cancer epithelial cells by copper and zinc

Previous studies have suggested that cells may differ in their response to metal stress. This study was undertaken to investigate the role of PI3K/Akt signaling pathway in metal resistance in human breast cancer epithelial cells with different p53 and estrogen receptor status. Exposure to copper and zinc increased Akt phosphorylation with its nuclear localization only in MDA-MB-231 cells with no estrogen receptor and mutated p53. Cyclin D1 expression and cell-cycle progression followed the metal-induced Akt phosphorylation. Treatment with LY294002 abrogated these effects, suggesting the essential role of PI3-kinase. In contrast, in MCF-7 cells with wild type p53 and estrogen receptor, there was no change in Akt activation, while suppression of p53 activity by pifithrin-alpha increased phosphorylation of Akt after the treatment with copper. In MCF-7 cells, the metal treatment increased the phosphorylation of p53 at serine 15, up-regulated p21 expression, and resulted in cell-cycle arrest in G1 phase with apoptosis. These results demonstrate that copper-induced apoptosis in MCF-7 cells is p53 dependent, whereas the metal resistance in MDA-MB-231 cells may be due to activation of Akt in the absence of a functional p53.

Copper ions strongly activate the phosphoinositide-3-kinase/Akt pathway independent of the generation of reactive oxygen species

Copper is implicated in metabolic disorders, such as Wilson's disease or Alzheimer's disease. Analysis of signaling pathways regulating cellular survival and function in response to a copper stress is crucial for understanding the pathogenesis of such diseases. Exposure of human skin fibroblasts or HeLa cells to Cu(2+) resulted in a dose- and time-dependent activation of the antiapoptotic kinase Akt/protein kinase B, starting at concentrations as low as 3 microM. Only Cu(II), but not Cu(I), had this effect. Activation of Akt was accompanied by phosphorylation of a downstream target of Akt, glycogen synthase kinase-3. Inhibitors of phosphoinositide-3-kinase (PI3K) completely blocked activation of Akt by Cu(2+), indicating a requirement of PI3K for Cu(2+)-induced activation of Akt. Indeed, cellular PI3K activity was strongly enhanced after exposure to Cu(2+). Copper ions may lead to the formation of reactive oxygen species, such as hydrogen peroxide. Activation of Akt by hydrogen peroxide or growth factors is known to proceed via the activation growth factor receptors. In line with this, pretreatment with inhibitors of growth factor receptor tyrosine kinases blocked activation of Akt by hydrogen peroxide and growth factors, as did a src-family tyrosine kinase inhibitor or the broad-spectrum tyrosine kinase inhibitor genistein. Activation of Akt by Cu(2+), however, remained unimpaired, implying (i) that tyrosine kinase activation is not involved in Cu(2+) activation of Akt and (ii) that activation of the PI3K/Akt pathway by Cu(2+) is initiated independently of that induced by reactive oxygen species. Comparison of the time course of the oxidation of 2',7'-dichlorodihydrofluorescein in copper-treated cells with that of Akt activation led to the conclusion that production of hydroperoxides cannot be an upstream event in copper-induced Akt activation. Rather, both activation of Akt and generation of ROS are proposed to occur in parallel, regulating cell survival after a copper stress.

Oxidative stress in rheumatoid arthritis leukocytes: suppression by rutin and other antioxidants and chelators

The enhanced production of superoxide ion and peroxynitrite by bloodstream neutrophils and of superoxide ion by monocytes from rheumatoid arthritis (RA) patients was registered. It was suggested that NADPH oxidase together with NO synthase were the major sources of superoxide ion in RA neutrophils, while in RA monocytes superoxide ion was produced by NADPH oxidase and mitochondria. Among the different free radical inhibitors studied (antioxidant enzymes, SOD and catalase; free radical scavengers, bioflavonoid rutin and mannitol; and the iron chelator desferrioxamine), SOD and rutin were the most efficient suppressors of oxygen radical overproduction by RA neutrophils, while mannitol and desferrioxamine were inactive. Thus, in contrast to Fanconi anemia (FA) leukocytes (Korkina LG et al., J Leukocyte Biol 1992;52:357-62), iron-catalyzed hydroxyl radical formation was unimportant in RA leukocytes, which mainly produced superoxide ion. Natural non-toxic bioflavonoid rutin (vitamin P) inhibited oxygen radical overproduction in both RA and FA in an equally efficient manner and therefore may be considered as a useful supporting pharmaceutical agent for the treatment of "free radical" pathologies.

Direct enzymatic reduction of lucigenin decreases lucigenin-amplified chemiluminescence produced by superoxide ion

The interaction of superoxide ion with lucigenin produces chemiluminescence (CL), which is widely used for the detection of this radical anion. However, in many biological systems lucigenin may be directly reduced to its semiquinone by some enzymes. We found that if the direct reduction of lucigenin takes place, it decreases superoxide production due to the competition with one-electron reduction of dioxygen to superoxide ion. Comparison of two methods of superoxide detection (lucigenin-amplified CL and cytochrome c reduction) showed that there are excellent correlations between the results obtained by the two methods. Hence, lucigenin-amplified CL remains a sensitive and reliable assay of superoxide detection.

Enhancement of antioxidant and anti-inflammatory activities of bioflavonoid rutin by complexation with transition metals

The antioxidant and anti-inflammatory activities of two transition metal complexes of bioflavonoid rutin, Fe(rut)Cl(3) and Cu(rut)Cl(2), were studied. It was found that Cu(rut)Cl(2) was a highly efficient in vitro and ex vivo free radical scavenger that sharply decreased (by 2-30 times compared to the parent rutin): oxygen radical production by xanthine oxidase, rat liver microsomes, and rat peritoneal macrophages; the formation of thiobarbituric acid-reactive products in microsomal lipid peroxidation; and the generation of oxygen radicals by broncho-alveolar cells from bleomycin-treated rats. The copper-rutin complex was also a superior inhibitor of inflammatory and fibrotic processes (characterized by such parameters as macrophage/neutrophil ratio, wet lung weight, total protein content, and hydroxyproline concentration) in the bleomycin-treated rats. The antioxidant activity of Fe(rut)Cl(3) was much lower and in some cases approached that of rutin. Fe(rut)Cl(3) also stimulated to some degree spontaneous oxygen radical production by macrophages. We suggested that the superior antioxidant and anti-inflammatory activity of the copper-rutin complex is a consequence of its acquiring the additional superoxide-dismuting copper center. The inhibitory activity of Fe(rut)Cl(3) was lower, probably due to the partial reduction into Fe(rut)Cl(2) in the presence of biological reductants; however, similarly to the copper-rutin complex, this complex efficiently suppressed lung edema.