Advertisement

Neuroprotection by Minocycline Caused by Direct and Specific Scavenging of Peroxynitrite*

Open AccessPublished:November 16, 2010DOI:https://doi.org/10.1074/jbc.M110.169565
      Minocycline prevents oxidative protein modifications and damage in disease models associated with inflammatory glial activation and oxidative stress. Although the drug has been assumed to act by preventing the up-regulation of proinflammatory enzymes, we probed here its direct chemical interaction with reactive oxygen species. The antibiotic did not react with superoxide or NO radicals, but peroxynitrite (PON) was scavenged in the range of ∼1 μm minocycline and below. The interaction of pharmacologically relevant minocycline concentrations with PON was corroborated in several assay systems and significantly exceeded the efficacy of other antibiotics. Minocycline was degraded during the reaction with PON, and the resultant products lacked antioxidant properties. The antioxidant activity of minocycline extended to cellular systems, because it prevented neuronal mitochondrial DNA damage and glutathione depletion. Maintenance of neuronal viability under PON stress was shown to be solely dependent on direct chemical scavenging by minocycline. We chose α-synuclein (ASYN), known from Parkinsonian pathology as a biologically relevant target in chemical and cellular nitration reactions. Submicromolar concentrations of minocycline prevented tyrosine nitration of ASYN by PON. Mass spectrometric analysis revealed that minocycline impeded nitrations more effectively than methionine oxidations and dimerizations of ASYN, which are secondary reactions under PON stress. Thus, PON scavenging at low concentrations is a novel feature of minocycline and may help to explain its pharmacological activity.

      Introduction

      Minocycline, a semisynthetic tetracycline derivative, has now been in clinical use for almost 40 years and is known for its excellent oral bioavailability and tissue distribution. Its efficient blood brain barrier passage (central nervous system/plasma distribution rate in the range of 0.3–0.6) allows central nervous system levels up to the micromolar range after repeated daily standard oral doses of 100–200 mg (
      • Kelly R.G.
      • Kanegis L.A.
      ,
      • Goulden V.
      • Glass D.
      • Cunliffe W.J.
      ,
      • Saivin S.
      • Houin G.
      ). In addition to its primary application as an antimicrobial agent, the use of minocycline has been considered in the field of neuroprotection (
      • Yong V.W.
      • Wells J.
      • Giuliani F.
      • Casha S.
      • Power C.
      • Metz L.M.
      ,
      • Kim H.S.
      • Suh Y.H.
      ). Its tissue-protective properties have been demonstrated in animal models of stroke, amyotrophic lateral sclerosis, multiple sclerosis, and Parkinson, Alzheimer, and Huntington diseases (
      • Wang C.X.
      • Yang T.
      • Noor R.
      • Shuaib A.
      ,
      • Kriz J.
      • Nguyen M.D.
      • Julien J.P.
      ,
      • Du Y.
      • Ma Z.
      • Lin S.
      • Dodel R.C.
      • Gao F.
      • Bales K.R.
      • Triarhou L.C.
      • Chernet E.
      • Perry K.W.
      • Nelson D.L.
      • Luecke S.
      • Phebus L.A.
      • Bymaster F.P.
      • Paul S.M.
      ,
      • Familian A.
      • Boshuizen R.S.
      • Eikelenboom P.
      • Veerhuis R.
      ,
      • Chen M.
      • Ona V.O.
      • Li M.
      • Ferrante R.J.
      • Fink K.B.
      • Zhu S.
      • Bian J.
      • Guo L.
      • Farrell L.A.
      • Hersch S.M.
      • Hobbs W.
      • Vonsattel J.P.
      • Cha J.H.
      • Friedlander R.M.
      ,
      • Yrjänheikki J.
      • Tikka T.
      • Keinänen R.
      • Goldsteins G.
      • Chan P.H.
      • Koistinaho J.
      ,
      • Tikka T.M.
      • Koistinaho J.E.
      ).
      Some direct neuroprotective actions of minocycline have been demonstrated in vitro (
      • Brundula V.
      • Rewcastle N.B.
      • Metz L.M.
      • Bernard C.C.
      • Yong V.W.
      ,
      • Gieseler A.
      • Schultze A.T.
      • Kupsch K.
      • Haroon M.F.
      • Wolf G.
      • Siemen D.
      • Kreutzmann P.
      ). Its beneficial in vivo activities have been suggested to be mainly based on its capacity to dampen glia activation and to reduce the tissue concentration of inflammatory mediators contributing to the degeneration process (
      • Yrjänheikki J.
      • Tikka T.
      • Keinänen R.
      • Goldsteins G.
      • Chan P.H.
      • Koistinaho J.
      ,
      • Wilkins A.
      • Nikodemova M.
      • Compston A.
      • Duncan I.
      ,
      • Yrjänheikki J.
      • Keinänen R.
      • Pellikka M.
      • Hökfelt T.
      • Koistinaho J.
      ,
      • Choi S.H.
      • Lee D.Y.
      • Chung E.S.
      • Hong Y.B.
      • Kim S.U.
      • Jin B.K.
      ,
      • Tomás-Camardiel M.
      • Rite I.
      • Herrera A.J.
      • de Pablos R.M.
      • Cano J.
      • Machado A.
      • Venero J.L.
      ,
      • Cho Y.
      • Son H.J.
      • Kim E.M.
      • Choi J.H.
      • Kim S.T.
      • Ji I.J.
      • Choi D.H.
      • Joh T.H.
      • Kim Y.S.
      • Hwang O.
      ). Accordingly, alterations of cell function by the antibiotic are best described for brain macrophages and microglial cells (
      • Agostini S.
      • Eutamene H.
      • Cartier C.
      • Broccardo M.
      • Improta G.
      • Houdeau E.
      • Petrella C.
      • Ferrier L.
      • Theodorou V.
      • Bueno L.
      ,
      • Bradesi S.
      • Svensson C.I.
      • Steinauer J.
      • Pothoulakis C.
      • Yaksh T.L.
      • Mayer E.A.
      ). The majority of studies describe a reduced up-regulation of inflammatory components, such as surface markers, cytokines, or pro-inflammatory enzymes (
      • Tikka T.
      • Fiebich B.L.
      • Goldsteins G.
      • Keinanen R.
      • Koistinaho J.
      ,
      • Filipovic R.
      • Zecevic N.
      ). The reduced activity of enzymes such as nitric-oxide synthase or peroxidases is generally assumed to account for attenuated nitration of proteins caused by less peroxynitrite formation.
      Apart from this hypothesis on indirect anti-inflammatory effects, relatively little information is available on the biochemical mode of action of minocycline. It has been argued that different targets are relevant in different settings, as suggested by largely varying effective concentrations of the drug (
      • Tikka T.M.
      • Koistinaho J.E.
      ,
      • Yrjänheikki J.
      • Keinänen R.
      • Pellikka M.
      • Hökfelt T.
      • Koistinaho J.
      ,
      • Kraus R.L.
      • Pasieczny R.
      • Lariosa-Willingham K.
      • Turner M.S.
      • Jiang A.
      • Trauger J.W.
      ,
      • Zhu S.
      • Stavrovskaya I.G.
      • Drozda M.
      • Kim B.Y.
      • Ona V.
      • Li M.
      • Sarang S.
      • Liu A.S.
      • Hartley D.M.
      • Wu D.C.
      • Gullans S.
      • Ferrante R.J.
      • Przedborski S.
      • Kristal B.S.
      • Friedlander R.M.
      ). Many studies observed an effect of the antibiotic on phosphorylation and hence the activation status of p38 MAPK, and a correlation of reduced p38 MAPK activation with the observed protective/anti-inflammatory effect was shown (
      • Tikka T.M.
      • Koistinaho J.E.
      ,
      • Lin S.
      • Zhang Y.
      • Dodel R.
      • Farlow M.R.
      • Paul S.M.
      • Du Y.
      ). Other studies focused on a potential role of matrix metalloproteinase inhibition in the actions of minocycline (
      • Brundula V.
      • Rewcastle N.B.
      • Metz L.M.
      • Bernard C.C.
      • Yong V.W.
      ,
      • Machado L.S.
      • Kozak A.
      • Ergul A.
      • Hess D.C.
      • Borlongan C.V.
      • Fagan S.C.
      ). However, a biochemically or pharmacologically defined target has not been characterized in any model system so far.
      The difficulty of finding a protein-binding partner may be explained if minocycline acted by stoichiometric reaction with small molecules and thereby affected a multitude of processes indirectly. Such observations have been made earlier with other widely used drugs such as the analgesic acetaminophen, which has been demonstrated to act as selective scavenger of peroxynitrite (
      • Schildknecht S.
      • Daiber A.
      • Ghisla S.
      • Cohen R.A.
      • Bachschmid M.M.
      ). Because neurodegenerative diseases are always accompanied by inflammatory conditions (
      • Falsig J.
      • van Beek J.
      • Hermann C.
      • Leist M.
      ), the potentially combined direct (on neurons) and indirect actions (prevention of detrimental inflammatory mediator synthesis) of minocycline would explain the good activity seen in animal models of disease. Reactive oxygen species generated in many cells under such conditions comprise H2O2, the hydroxyl radical (OH), nitric oxide (NO), superoxide (), and peroxynitrite (ONOO). The latter anion or the decomposition products (NO2 and OH) of its protonated form, respectively, can modify the structure and function of proteins and enzymes by nitration of tyrosine residues or by methionine sulfoxidation (
      • Pryor W.A.
      • Jin X.
      • Squadrito G.L.
      ,
      • Beckman J.S.
      ). Prominent examples of signal transduction systems regulated by peroxynitrite are the NF-κB pathway (
      • Yakovlev V.A.
      • Barani I.J.
      • Rabender C.S.
      • Black S.M.
      • Leach J.K.
      • Graves P.R.
      • Kellogg G.E.
      • Mikkelsen R.B.
      ) or mitogen-activated kinase cascades (
      • Lin S.
      • Zhang Y.
      • Dodel R.
      • Farlow M.R.
      • Paul S.M.
      • Du Y.
      ,
      • Jope R.S.
      • Zhang L.
      • Song L.
      ). Moreover, disease-specific proteins such as the Parkinson disease-related protein α-synuclein are post-translationally modified by peroxynitrite and become more prone to form intracellular proteinaceous aggregates (
      • Hodara R.
      • Norris E.H.
      • Giasson B.I.
      • Mishizen-Eberz A.J.
      • Lynch D.R.
      • Lee V.M.
      • Ischiropoulos H.
      ).
      A potential role of minocycline as antioxidant has recently been suggested by studies showing that the compound can interfere with a battery of chemical radical generating systems or peroxynitrite (
      • Kraus R.L.
      • Pasieczny R.
      • Lariosa-Willingham K.
      • Turner M.S.
      • Jiang A.
      • Trauger J.W.
      ,
      • Whiteman M.
      • Halliwell B.
      ). However, these studies did not compare defined biologically relevant reactive oxygen species. Also, the effective concentrations of minocycline varied because of the different chemical assay systems used and often were 10–100 μm and higher. In contrast to this, we designed this study to investigate the direct interaction of minocycline with defined biological reactive oxygen species. In particular, we characterized its interaction with peroxynitrite in a pharmacologically relevant range. Our data show a specific interaction with this important intracellular signaling molecule and mediator of neurodegeneration in the submicromolar range. This first description of a molecularly defined target of minocycline may help to explain its broad effects in several different model systems.

      DISCUSSION

      In the present study, we demonstrated that minocycline acts as highly selective scavenger of PON at submicromolar concentrations. This was observed not only in chemically defined assay systems but also in various cellular models, including human neurons. Notably, tetracycline did not show such activity in the low micromolar range, even though it is known that it may scavenge PON in the mm range, similar to most phenolic compounds. No comparative investigations on the interaction of minocycline with biologically relevant radical species have been conducted so far. The high specificity of the antioxidant profile of minocycline is suggested by our findings that the drug interacted neither with NO nor with or H2O2. Interactions with OH were observed but were far less pronounced than with PON. The results suggest that a defined target and mechanism of action has been defined for minocycline.
      The difference observed for the interaction of minocycline versus tetracycline with PON was not found for the OH scavenging capacity of the two antibiotics. This may indicate that the interactions of OH and PON with minocycline are based on different mechanisms. After exposure of minocycline to PON, we were not able to detect a hydroxylated or nitrated derivative of minocycline or another chemically defined metabolite. Instead, decomposition of minocycline was observed. Detailed analysis of the degradation products and their impact on biological systems may contribute to the understanding of the side effects of minocycline.
      Minocycline demonstrated neuroprotective properties in a variety of chronic neurodegenerative diseases such as Alzheimer disease, Parkinson disease, and amyothrophic lateral sclerosis (
      • Wang C.X.
      • Yang T.
      • Noor R.
      • Shuaib A.
      ,
      • Kriz J.
      • Nguyen M.D.
      • Julien J.P.
      ,
      • Du Y.
      • Ma Z.
      • Lin S.
      • Dodel R.C.
      • Gao F.
      • Bales K.R.
      • Triarhou L.C.
      • Chernet E.
      • Perry K.W.
      • Nelson D.L.
      • Luecke S.
      • Phebus L.A.
      • Bymaster F.P.
      • Paul S.M.
      ,
      • Familian A.
      • Boshuizen R.S.
      • Eikelenboom P.
      • Veerhuis R.
      ,
      • Chen M.
      • Ona V.O.
      • Li M.
      • Ferrante R.J.
      • Fink K.B.
      • Zhu S.
      • Bian J.
      • Guo L.
      • Farrell L.A.
      • Hersch S.M.
      • Hobbs W.
      • Vonsattel J.P.
      • Cha J.H.
      • Friedlander R.M.
      ,
      • Yrjänheikki J.
      • Tikka T.
      • Keinänen R.
      • Goldsteins G.
      • Chan P.H.
      • Koistinaho J.
      ,
      • Tikka T.M.
      • Koistinaho J.E.
      ). However, no clearly defined molecular target of minocycline action has been described that would explain the wide spectrum of activities of the drug. Our findings that PON is a direct target and chemical interaction partner of minocycline in biological assay systems suggest that this mechanism may be relevant in pathological situations and may contribute to solve the riddle of minocycline action. Neurodegenerative diseases treated with minocycline are all accompanied by an inflammatory activation of glial cells and apoptotic cell death. These processes have been reported to be blocked by minocycline (
      • Tikka T.
      • Fiebich B.L.
      • Goldsteins G.
      • Keinanen R.
      • Koistinaho J.
      ,
      • Filipovic R.
      • Zecevic N.
      ). Therefore, the question of an involvement of PON under such conditions arises. In this regard, it is important to be aware of the Janus-faced nature of PON in biological systems, because it can act as a harmful cellular oxidant when generated at high fluxes but importantly also serves as an intracellularly formed signaling molecule affecting several cellular pathways under normal conditions (
      • Schildknecht S.
      • Ullrich V.
      ).

      Minocycline as a Scavenger of Pathologically Relevant PON Concentrations

      PON at concentrations sufficient to act as oxidant in the brain primarily occurs following inflammatory activation of glial cells (
      • Arimoto T.
      • Bing G.
      ). Under such conditions, DNA damage or nitration of proteins can be observed in vivo (
      • Iravani M.M.
      • Kashefi K.
      • Mander P.
      • Rose S.
      • Jenner P.
      ,
      • Su J.H.
      • Deng G.
      • Cotman C.W.
      ). DNA damage was therefore investigated in the present study in a first step by exposure of plasmid DNA to Sin-1-generated fluxes of PON. A concentration-dependent formation of 8-oxo-deoxyguanosine was found and was completely prevented by 5 μm minocycline. This concentration corresponds to the range that can be expected in the brain following repeated standard oral doses of minocycline in clinical studies or animal experiments. The DNA damage was not detected after NO or treatment (not shown). To study the impact of PON on DNA in intact cells, the deletion of a defined segment of mitochondrial DNA was investigated. This study revealed that DNA damage by PON was prevented in a concentration-dependent manner by minocycline. For investigations on the impact of minocycline on the nitration of protein targets, we chose ASYN that is known to be nitrated in patients with Parkinson disease and in animal models of Parkinson disease (
      • Giasson B.I.
      • Duda J.E.
      • Murray I.V.
      • Chen Q.
      • Souza J.M.
      • Hurtig H.I.
      • Ischiropoulos H.
      • Trojanowski J.Q.
      • Lee V.M.
      ). Here, ASYN was nitrated by PON in a cell-free system as well as in cells, and it was prevented by submicromolar concentrations of minocycline. Although pretreatment with minocycline or uric acid completely prevented nitration of the three C-terminal tyrosines, minocycline did not prevent the oxidation of the two methionine residues present in ASYN. Nitration of tyrosine primarily occurs via attack by the NO2 radical that originates from the decomposition of peroxynitrous acid (
      • van der Vliet A.
      • Eiserich J.P.
      • O'Neill C.A.
      • Halliwell B.
      • Cross C.E.
      ), and minocycline may directly interact with this specific radical. Our findings are consistent with the view that methionine oxidation is mediated by a different radical species. Others reported that OH, as another degradation product of peroxynitrous acid, plays no significant role in methionine oxidation (
      • Pryor W.A.
      • Jin X.
      • Squadrito G.L.
      ). Instead, a two electron oxidation by an interaction with the electrophilic nitrogen of peroxynitrous acid and the sulfur atom of methionine has been proposed and thus could be responsible for the observations made in our study (
      • Perrin D.
      • Koppenol W.H.
      ,
      • Schöneich C.
      ). The neutralization of OH may be relevant in pathological situations favoring the Fenton reaction, as for example in the iron-rich substantia nigra in Parkinson disease. The effect of OH scavenging would become pharmacologically relevant only at higher concentrations of minocycline (>10 μm), that are likely to be reached in several animal studies described in the literature (
      • Du Y.
      • Ma Z.
      • Lin S.
      • Dodel R.C.
      • Gao F.
      • Bales K.R.
      • Triarhou L.C.
      • Chernet E.
      • Perry K.W.
      • Nelson D.L.
      • Luecke S.
      • Phebus L.A.
      • Bymaster F.P.
      • Paul S.M.
      ).

      Minocycline as Scavenger of Physiological PON Concentrations

      Pathologically high concentrations of PON are usually found under conditions when the inducible isoform of nitric-oxide synthase (NOS-2) is the source of NO. When minocycline is considered as a scavenger of PON in its role as signaling molecule, the question arises regarding how NO is generated in the absence of NOS-2 expression. The significance of the constitutively expressed brain isoform NOS-1 has been underestimated for a long time, although it has been known that NOS-1 contributes to brain damage associated with DNA lesions or PARP activation (
      • Su J.H.
      • Deng G.
      • Cotman C.W.
      ,
      • Schulz J.B.
      • Matthews R.T.
      • Klockgether T.
      • Dichgans J.
      • Beal M.F.
      ,
      • Leist M.
      • Nicotera P.
      ). Recent findings indicated nitration of proteins in activated cells in the absence of inducible NOS-2 (
      • Imam S.Z.
      • el-Yazal J.
      • Newport G.D.
      • Itzhak Y.
      • Cadet J.L.
      • Slikker Jr., W.
      • Ali S.F.
      ). NOS-1 activity is mainly regulated by levels of cytosolic free Ca2+, and hence, Ca2+ becomes a key regulator in the endogenous formation of PON. Glutamate excitotoxicity represents a classical model of elevated cytosolic Ca2+ levels (
      • Nicotera P.
      • Leist M.
      • Manzo L.
      ), and in such models, minocycline concentrations in the low nanomolar range have been reported to be neuroprotective (
      • Yrjänheikki J.
      • Tikka T.
      • Keinänen R.
      • Goldsteins G.
      • Chan P.H.
      • Koistinaho J.
      ). Similar observations were made in 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)/1-Methyl-4-phenylpyridinium (MPP+) models that are also characterized by disturbed cellular Ca2+ homeostasis (
      • Kass G.E.
      • Wright J.M.
      • Nicotera P.
      • Orrenius S.
      ). Further indirect evidence for a role of PON scavenging by minocycline comes from experiments in which cerebellar granule cells were treated with subtoxic concentrations of an NO donor and MPP+ that together allow formation of PON (
      • Du Y.
      • Ma Z.
      • Lin S.
      • Dodel R.C.
      • Gao F.
      • Bales K.R.
      • Triarhou L.C.
      • Chernet E.
      • Perry K.W.
      • Nelson D.L.
      • Luecke S.
      • Phebus L.A.
      • Bymaster F.P.
      • Paul S.M.
      ). In all of these models, minocycline demonstrated neuroprotective effects, and we suggest that at least some of its protective properties may originate from a direct scavenging of the intracellular signaling molecule PON.
      In chronic neurodegenerative disorders, PON signaling may be involved in the assembly of the mitochondrial permeability transition pore complex, leading to cytochrome c release (
      • Wilkins A.
      • Nikodemova M.
      • Compston A.
      • Duncan I.
      ). Moreover, PON is pivotally involved in the activation of signaling cascades such as p38 MAPK or NF-κB (
      • Lin S.
      • Zhang Y.
      • Dodel R.
      • Farlow M.R.
      • Paul S.M.
      • Du Y.
      ,
      • Yakovlev V.A.
      • Barani I.J.
      • Rabender C.S.
      • Black S.M.
      • Leach J.K.
      • Graves P.R.
      • Kellogg G.E.
      • Mikkelsen R.B.
      ,
      • Jope R.S.
      • Zhang L.
      • Song L.
      ). It might therefore be speculated that scavenging of PON contributes to the observations on an inhibition of cytochrome c release as well as the repeatedly described inhibitory effect on the p38 signaling cascade and on induction of pro-inflammatory enzymes such as NOS-2 or COX-2 in glial cells.
      In this work, we have demonstrated that minocycline is a selective and potent scavenger of PON. The compound protected cells from exogenously added PON. Under such conditions that, for example, reflect the situation of inflammatory glia activation and its impact on neurons in the brain, relatively high concentrations of the antibiotic in the micromolar range are required to scavenge PON sufficiently fast to achieve protection. In contrast, considering the role of endogenous low levels of PON as intracellular signaling molecules under chronic pathological conditions, and the excellent penetration of biological membranes by minocycline, nanomolar concentrations might be sufficient to interrupt chronic processes that would ultimately lead to cell death.

      Acknowledgments

      We are particularly thankful to Prof. V. Ullrich for fruitful discussions and careful reading of the manuscript.

      REFERENCES

        • Kelly R.G.
        • Kanegis L.A.
        Toxicol. Appl. Pharmacol. 1967; 11: 171-183
        • Goulden V.
        • Glass D.
        • Cunliffe W.J.
        Br. J. Dermatol. 1996; 134: 693-695
        • Saivin S.
        • Houin G.
        Clin. Pharmacokinet. 1988; 15: 355-366
        • Yong V.W.
        • Wells J.
        • Giuliani F.
        • Casha S.
        • Power C.
        • Metz L.M.
        Lancet Neurol. 2004; 3: 744-751
        • Kim H.S.
        • Suh Y.H.
        Behav. Brain Res. 2009; 196: 168-179
        • Wang C.X.
        • Yang T.
        • Noor R.
        • Shuaib A.
        BMC Neurol. 2002; 2: 2
        • Kriz J.
        • Nguyen M.D.
        • Julien J.P.
        Neurobiol. Dis. 2002; 10: 268-278
        • Du Y.
        • Ma Z.
        • Lin S.
        • Dodel R.C.
        • Gao F.
        • Bales K.R.
        • Triarhou L.C.
        • Chernet E.
        • Perry K.W.
        • Nelson D.L.
        • Luecke S.
        • Phebus L.A.
        • Bymaster F.P.
        • Paul S.M.
        Proc. Natl. Acad. Sci. U.S.A. 2001; 98: 14669-14674
        • Familian A.
        • Boshuizen R.S.
        • Eikelenboom P.
        • Veerhuis R.
        Glia. 2006; 53: 233-240
        • Chen M.
        • Ona V.O.
        • Li M.
        • Ferrante R.J.
        • Fink K.B.
        • Zhu S.
        • Bian J.
        • Guo L.
        • Farrell L.A.
        • Hersch S.M.
        • Hobbs W.
        • Vonsattel J.P.
        • Cha J.H.
        • Friedlander R.M.
        Nat. Med. 2000; 6: 797-801
        • Yrjänheikki J.
        • Tikka T.
        • Keinänen R.
        • Goldsteins G.
        • Chan P.H.
        • Koistinaho J.
        Proc. Natl. Acad. Sci. U.S.A. 1999; 96: 13496-13500
        • Tikka T.M.
        • Koistinaho J.E.
        J. Immunol. 2001; 166: 7527-7533
        • Brundula V.
        • Rewcastle N.B.
        • Metz L.M.
        • Bernard C.C.
        • Yong V.W.
        Brain. 2002; 125: 1297-1308
        • Gieseler A.
        • Schultze A.T.
        • Kupsch K.
        • Haroon M.F.
        • Wolf G.
        • Siemen D.
        • Kreutzmann P.
        Biochem. Pharmacol. 2009; 77: 888-896
        • Wilkins A.
        • Nikodemova M.
        • Compston A.
        • Duncan I.
        Neuron Glia Biol. 2004; 1: 297-305
        • Yrjänheikki J.
        • Keinänen R.
        • Pellikka M.
        • Hökfelt T.
        • Koistinaho J.
        Proc. Natl. Acad. Sci. U.S.A. 1998; 95: 15769-15774
        • Choi S.H.
        • Lee D.Y.
        • Chung E.S.
        • Hong Y.B.
        • Kim S.U.
        • Jin B.K.
        J. Neurochem. 2005; 95: 1755-1765
        • Tomás-Camardiel M.
        • Rite I.
        • Herrera A.J.
        • de Pablos R.M.
        • Cano J.
        • Machado A.
        • Venero J.L.
        Neurobiol. Dis. 2004; 16: 190-201
        • Cho Y.
        • Son H.J.
        • Kim E.M.
        • Choi J.H.
        • Kim S.T.
        • Ji I.J.
        • Choi D.H.
        • Joh T.H.
        • Kim Y.S.
        • Hwang O.
        Neurotox. Res. 2009; 16: 361-371
        • Agostini S.
        • Eutamene H.
        • Cartier C.
        • Broccardo M.
        • Improta G.
        • Houdeau E.
        • Petrella C.
        • Ferrier L.
        • Theodorou V.
        • Bueno L.
        Gastroenterology. 2010; 139: 553-563
        • Bradesi S.
        • Svensson C.I.
        • Steinauer J.
        • Pothoulakis C.
        • Yaksh T.L.
        • Mayer E.A.
        Gastroenterology. 2009; 136: 1339-1348
        • Tikka T.
        • Fiebich B.L.
        • Goldsteins G.
        • Keinanen R.
        • Koistinaho J.
        J. Neurosci. 2001; 21: 2580-2588
        • Filipovic R.
        • Zecevic N.
        Exp. Neurol. 2008; 211: 41-51
        • Kraus R.L.
        • Pasieczny R.
        • Lariosa-Willingham K.
        • Turner M.S.
        • Jiang A.
        • Trauger J.W.
        J. Neurochem. 2005; 94: 819-827
        • Zhu S.
        • Stavrovskaya I.G.
        • Drozda M.
        • Kim B.Y.
        • Ona V.
        • Li M.
        • Sarang S.
        • Liu A.S.
        • Hartley D.M.
        • Wu D.C.
        • Gullans S.
        • Ferrante R.J.
        • Przedborski S.
        • Kristal B.S.
        • Friedlander R.M.
        Nature. 2002; 417: 74-78
        • Lin S.
        • Zhang Y.
        • Dodel R.
        • Farlow M.R.
        • Paul S.M.
        • Du Y.
        Neurosci. Lett. 2001; 315: 61-64
        • Machado L.S.
        • Kozak A.
        • Ergul A.
        • Hess D.C.
        • Borlongan C.V.
        • Fagan S.C.
        BMC Neurosci. 2006; 7: 56
        • Schildknecht S.
        • Daiber A.
        • Ghisla S.
        • Cohen R.A.
        • Bachschmid M.M.
        FASEB J. 2008; 22: 215-224
        • Falsig J.
        • van Beek J.
        • Hermann C.
        • Leist M.
        J. Neurosci. Res. 2008; 86: 1434-1447
        • Pryor W.A.
        • Jin X.
        • Squadrito G.L.
        Proc. Natl. Acad. Sci. U.S.A. 1994; 91: 11173-11177
        • Beckman J.S.
        Chem. Res. Toxicol. 1996; 9: 836-844
        • Yakovlev V.A.
        • Barani I.J.
        • Rabender C.S.
        • Black S.M.
        • Leach J.K.
        • Graves P.R.
        • Kellogg G.E.
        • Mikkelsen R.B.
        Biochemistry. 2007; 46: 11671-11683
        • Jope R.S.
        • Zhang L.
        • Song L.
        Arch. Biochem. Biophys. 2000; 376: 365-370
        • Hodara R.
        • Norris E.H.
        • Giasson B.I.
        • Mishizen-Eberz A.J.
        • Lynch D.R.
        • Lee V.M.
        • Ischiropoulos H.
        J. Biol. Chem. 2004; 279: 47746-47753
        • Whiteman M.
        • Halliwell B.
        Free Radic. Res. 1997; 26: 49-56
        • Moreno-Villanueva M.
        • Pfeiffer R.
        • Sindlinger T.
        • Leake A.
        • Müller M.
        • Kirkwood T.B.
        • Bürkle A.
        BMC Biotechnol. 2009; 9: 39
        • Wenzel P.
        • Schuhmacher S.
        • Kienhöfer J.
        • Müller J.
        • Hortmann M.
        • Oelze M.
        • Schulz E.
        • Treiber N.
        • Kawamoto T.
        • Scharffetter-Kochanek K.
        • Münzel T.
        • Bürkle A.
        • Bachschmid M.M.
        • Daiber A.
        Cardiovasc. Res. 2008; 80: 280-289
        • Koch H.
        • Wittern K.P.
        • Bergemann J.
        J. Invest. Dermatol. 2001; 117: 892-897
        • Schildknecht S.
        • Pöltl D.
        • Nagel D.M.
        • Matt F.
        • Scholz D.
        • Lotharius J.
        • Schmieg N.
        • Salvo-Vargas A.
        • Leist M.
        Toxicol. Appl. Pharmacol. 2009; 241: 23-35
        • Lotharius J.
        • Falsig J.
        • van Beek J.
        • Payne S.
        • Dringen R.
        • Brundin P.
        • Leist M.
        J. Neurosci. 2005; 25: 6329-6342
        • Yakes F.M.
        • Van Houten B.
        Proc. Natl. Acad. Sci. U.S.A. 1997; 94: 514-519
        • Schildknecht S.
        • Ullrich V.
        Arch. Biochem. Biophys. 2009; 484: 183-189
        • Arimoto T.
        • Bing G.
        Neurobiol. Dis. 2003; 12: 35-45
        • Iravani M.M.
        • Kashefi K.
        • Mander P.
        • Rose S.
        • Jenner P.
        Neuroscience. 2002; 110: 49-58
        • Su J.H.
        • Deng G.
        • Cotman C.W.
        Brain Res. 1997; 774: 193-199
        • Giasson B.I.
        • Duda J.E.
        • Murray I.V.
        • Chen Q.
        • Souza J.M.
        • Hurtig H.I.
        • Ischiropoulos H.
        • Trojanowski J.Q.
        • Lee V.M.
        Science. 2000; 290: 985-989
        • van der Vliet A.
        • Eiserich J.P.
        • O'Neill C.A.
        • Halliwell B.
        • Cross C.E.
        Arch. Biochem. Biophys. 1995; 319: 341-349
        • Perrin D.
        • Koppenol W.H.
        Arch. Biochem. Biophys. 2000; 377: 266-272
        • Schöneich C.
        Biochim. Biophys. Acta. 2005; 1703: 111-119
        • Schulz J.B.
        • Matthews R.T.
        • Klockgether T.
        • Dichgans J.
        • Beal M.F.
        Mol. Cell. Biochem. 1997; 174: 193-197
        • Leist M.
        • Nicotera P.
        Exp. Cell Res. 1998; 239: 183-201
        • Imam S.Z.
        • el-Yazal J.
        • Newport G.D.
        • Itzhak Y.
        • Cadet J.L.
        • Slikker Jr., W.
        • Ali S.F.
        Ann. N.Y. Acad. Sci. 2001; 939: 366-380
        • Nicotera P.
        • Leist M.
        • Manzo L.
        Trends Pharmacol. Sci. 1999; 20: 46-51
        • Kass G.E.
        • Wright J.M.
        • Nicotera P.
        • Orrenius S.
        Arch. Biochem. Biophys. 1988; 260: 789-797