Two-photon Imaging of Glutathione Levels in Intact Brain Indicates Enhanced Redox Buffering in Developing Neurons and Cells at the Cerebrospinal Fluid and Blood-Brain Interface
Bibliographic record
Abstract
Glutathione is the major cellular thiol present in mammalian cells and is critical for maintenance of redox homeostasis. However, current assay systems for glutathione lack application to intact animal tissues. To map the levels of glutathione in intact brain with cellular resolution (acute tissue slices and live animals), we have used two-photon imaging of monochlorobimane fluorescence, a selective enzyme-mediated marker for reduced glutathione. Previously, in vitro experiments using purified components and cultured glial cells attributed cellular monochlorobimane fluorescence to a glutathione S-transferase-dependent reaction with GSH. Our results indicate that cells at the cerebrospinal fluid or blood-brain interface, such as lateral ventricle ependymal cells (2.73 ± 0.56 mm; glutathione), meningeal cells (1.45 ± 0.09 mm), and astroglia (0.91 ± 0.08 mm), contain high levels of glutathione. In comparison, layer II cortical neurons contained 20% (0.21 ± 0.02 mm) the glutathione content of nearby astrocytes. Neuronal glutathione labeling increased 250% by the addition of the cell-permeable glutathione precursor N-acetylcysteine indicating that the monochlorobimane level or glutathione S-transferase activity within neurons was not limiting. Regional mapping showed that glutathione was highest in cells lining the lateral ventricles, specifically ependymal cells and the subventricular zone, suggesting a possible function for glutathione in oxidant homeostasis of developing neuronal progenitors. Consistently, developing neurons in the subgranular zone of dentate gyrus contained 3-fold more glutathione than older neurons found in the neighboring granular layer. In conclusion, mapping of glutathione levels in intact brain demonstrates a unique role for enhanced redox potential in developing neurons and cells at the cerebrospinal fluid and blood-brain interface. Glutathione is the major cellular thiol present in mammalian cells and is critical for maintenance of redox homeostasis. However, current assay systems for glutathione lack application to intact animal tissues. To map the levels of glutathione in intact brain with cellular resolution (acute tissue slices and live animals), we have used two-photon imaging of monochlorobimane fluorescence, a selective enzyme-mediated marker for reduced glutathione. Previously, in vitro experiments using purified components and cultured glial cells attributed cellular monochlorobimane fluorescence to a glutathione S-transferase-dependent reaction with GSH. Our results indicate that cells at the cerebrospinal fluid or blood-brain interface, such as lateral ventricle ependymal cells (2.73 ± 0.56 mm; glutathione), meningeal cells (1.45 ± 0.09 mm), and astroglia (0.91 ± 0.08 mm), contain high levels of glutathione. In comparison, layer II cortical neurons contained 20% (0.21 ± 0.02 mm) the glutathione content of nearby astrocytes. Neuronal glutathione labeling increased 250% by the addition of the cell-permeable glutathione precursor N-acetylcysteine indicating that the monochlorobimane level or glutathione S-transferase activity within neurons was not limiting. Regional mapping showed that glutathione was highest in cells lining the lateral ventricles, specifically ependymal cells and the subventricular zone, suggesting a possible function for glutathione in oxidant homeostasis of developing neuronal progenitors. Consistently, developing neurons in the subgranular zone of dentate gyrus contained 3-fold more glutathione than older neurons found in the neighboring granular layer. In conclusion, mapping of glutathione levels in intact brain demonstrates a unique role for enhanced redox potential in developing neurons and cells at the cerebrospinal fluid and blood-brain interface. The tripeptide glutathione (GSH; γ-l-glutamyl-l-cysteinylglycine) is the most abundant low molecular weight thiol in mammalian cells and constitutes a major cellular defense against reactive oxygen species. Deficiency in the GSH system has been linked to neuronal loss during progression of neurodegenerative diseases, such as Parkinson, Alzheimer, Huntington, and amyotrophic lateral sclerosis (1Schulz J.B. Lindenau J. Seyfried J. Dichgans J. Eur. J. Biochem. 2000; 267: 4904-4911Crossref PubMed Scopus (1033) Google Scholar, 2Bains J.S. Shaw C.A. Brain Res. Brain Res. Rev. 1997; 25: 335-358Crossref PubMed Scopus (623) Google Scholar, 3Perry G. Avila J. Espey M.G. Wink D.A. Atwood C.S. Smith M.A. Science. 2001; 291: 595-597Crossref PubMed Google Scholar), as well as acute conditions such as spinal cord injury (4Kamencic H. Griebel R.W. Lyon A.W. Paterson P.G. Juurlink B.H. FASEB J. 2001; 15: 243-250Crossref PubMed Scopus (91) Google Scholar) and stroke (5Liu T.H. Beckman J.S. Freeman B.A. Hogan E.L. Hsu C.Y. Am. J. Physiol. 1989; 256: H589-H593PubMed Google Scholar, 6Kinouchi H. Epstein C.J. Mizui T. Carlson E. Chen S.F. Chan P.H. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 11158-11162Crossref PubMed Scopus (533) Google Scholar, 7Yu Z.F. Bruce-Keller A.J. Goodman Y. Mattson M.P. J. Neurosci. Res. 1998; 53: 613-625Crossref PubMed Scopus (286) Google Scholar). Although reactive oxygen species accumulation has been implicated in these disorders, of GSH levels in has been to and that in neuronal and glial or brain used for GSH in cultured cells and tissue monochlorobimane used glutathione two-photon spinal cerebrospinal used glutathione two-photon spinal cerebrospinal S. H. H. G. G. PubMed Scopus Google Scholar), a that to reduced GSH by glutathione that have that GSH in cells of intact and by two-photon with A.J. J. 2000; PubMed Scopus Google Scholar). we a in intact mammalian brain to GSH levels in tissues. GSH in brain of species using have been A.J. 1997; Google Scholar). However, these results tissue the GSH is that such as Eur. J. Neurosci. PubMed Scopus Google Scholar) lack for GSH or the of in to animal cultured brain cells by that contain high levels of GSH such as present at in than in cerebrospinal fluid in J. 2000; PubMed Scopus Google Scholar). we that is a for GSH labeling in brain and used to GSH content in brain at the cellular In the a of with and the reaction and GSH is and by a we have for using H. T.H. Biochem. Res. PubMed Scopus Google Scholar), we imaging in to of GSH such as by and to brain slices and of live we have found that GSH is in lateral ependymal and neurons in dentate neurons in slices by at a level of fluorescence, suggesting that and ependymal a role in brain was or and as a in and at was as a in and at was and as a in and at used in and and GSH using a ± and ± Although these for of the within the the of and fluorescence the with the fluorescence in GSH and with of purified and was using a a reaction of the of was GSH and in the of a GSH and used to that was of and was The contained within in vitro cells and with two-photon using to used brain tissues. of was used in in brain Brain brain slices or and the brain was the and in mm) was at by with and with a and to a at for at The slices in spinal fluid mm) with and slices to a and with with and was to the system at a of To we with for in experiments by the of and in with the The and at the of animal for in imaging as S. J. T.H. J. Neurosci. 25: PubMed Scopus Google Scholar). In with of with as Proc. Natl. Acad. Sci. U. S. A. 1998; PubMed Scopus Google Scholar), and in was to animal was at using a was used to a the at of and the that the was to the with To the the and the was with 2000; Scholar). The cortical and with in or a and with a in and in to a of and to the brain of was using a by a to using and by using was used in with the was at and fluorescence was using for the and for the and used as at and the and was at the two-photon imaging of the lateral ventricle cortical and for the was at than that at the of and by and labeling and two-photon slices with in for with and with against in in or in for at The contained and in with the slices with and in for in at slices with and with two-photon was using To and a or was The fluorescence was to to a or of was used with as ± of is the of for GSH levels in intact is in the of GSH. In a reaction by GSH is to a with fluorescence J.B. Res. 1991; Google Scholar, Res. 1991; Google Scholar). has for such as and low for low molecular weight or A.J. J. 2001; PubMed Google Scholar). a we the of for the reduced of GSH in in vitro experiments using purified to the In the of addition of GSH to in a in of purified in a in the fluorescence indicating that is reaction The with is the fluorescence is the fluorescence and is the of the The level of the in vitro reaction was to the of GSH and not the was to the The of the and for and of The of reaction the of for labeling GSH. in brain slices and in we to that to and activity was not a is a S. H. H. G. G. PubMed Scopus Google Scholar) and is in brain such as neurons and glial cells Rev. PubMed Scopus Google Scholar), a labeling in brain the of cellular GSH content by the fluorescence of the Our experiments have by that labeling of been with the GSH have a reduced fluorescence at the reaction H. T.H. Biochem. Res. PubMed Scopus Google Scholar). 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PubMed Scopus Google Scholar) layer II neurons well as and has a of labeling than not indicating of and within cells by the as we to that was a suggesting that and by to the that addition of to the in contain high levels of GSH. with GSH in that of GSH content and in such as Parkinson, Alzheimer, and (1Schulz J.B. Lindenau J. Seyfried J. Dichgans J. Eur. J. Biochem. 2000; 267: 4904-4911Crossref PubMed Scopus (1033) Google Scholar, 2Bains J.S. Shaw C.A. Brain Res. Brain Res. Rev. 1997; 25: 335-358Crossref PubMed Scopus (623) Google Scholar, 3Perry G. Avila J. Espey M.G. Wink D.A. Atwood C.S. Smith M.A. Science. 2001; 291: 595-597Crossref PubMed Google Scholar, J. S. J. Neurosci. Res. 2001; PubMed Scopus Google Scholar, S. H. T.H. J. PubMed Scopus Google Scholar, T.H. J. Neurosci. 25: PubMed Scopus Google Scholar). In of the role of GSH in cells A.J. 1997; Google Scholar, D.A. G. H. T.H. J. Neurosci. PubMed Google Scholar, Proc. Natl. Acad. Sci. U. S. A. 1997; PubMed Scopus Google Scholar), has been in to GSH content by using Biochem. PubMed Scopus Google Scholar, PubMed Scopus Google Scholar, Biochem. PubMed Scopus Google Scholar). However, using or tissue for GSH levels in intact with against GSH potential in GSH in to Eur. J. Neurosci. PubMed Scopus Google Scholar). The to GSH at the cellular level using two-photon imaging with and and a cellular in labeling in a assay for GSH. However, is to that by the of two-photon to E. E. J. S. J. Neurosci. 2001; PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). GSH in we for the of by the fluorescence of at by tissue is and to have fluorescence in brain Brain experiments by E. E. J. S. J. Neurosci. 2001; PubMed Scopus Google Scholar) and and PubMed Scopus Google Scholar) found that fluorescence by two-photon reduced by for tissue to the a of for brain slices of to we to and 2000; Scholar), two-photon fluorescence by at in in at the we have and for the in GSH levels is that not cellular and that or of not to a to in labeling we have that of the two-photon imaging to the assay of GSH results that and not using the cells and conditions we potential is that the labeling is a of the GSH content of a of GSH to a and not a of GSH To GSH content at within the to and for of and with is in the of GSH the of GSH as we have with H. T.H. Biochem. Res. PubMed Scopus Google Scholar). is that a used brain slices or in at Although these and to we that two-photon imaging of labeling in brain slices is or imaging for GSH. GSH in Brain has been well that in GSH levels neurons and in brain 2000; PubMed Scopus Google Scholar). However, the GSH in neurons has not been M.A. Google Scholar, J.S. T. T. A. Hogan J. 2000; PubMed Scopus Google Scholar, 1998; PubMed Scopus Google Scholar). in to the or conditions of the of lateral ventricle ependymal cells contain the highest level of GSH. of the contain GSH than astrocytes. H. S. S. J. Neurosci. PubMed Google Scholar) have that high is in and in ependymal of these in with to for GSH and to the brain against The have in defense and have been for role at the H. J. PubMed Scopus Google Scholar, Brain Res. Brain Res. Rev. PubMed Scopus Google Scholar, J. Neurosci. PubMed Scopus Google Scholar). Our a the possible role of the in the brain against have used in vitro of and meningeal cells to more the of In Neurosci. we found that cultured meningeal cells levels of and increased GSH to with astrocytes. is with the high level of meningeal labeling in imaging experiments and with meningeal cells more in against than H. T.H. Biochem. Res. PubMed Scopus Google Scholar). results that in of the cells we have and to redox and neuronal In addition to the developing neurons in brain contained high levels with in vitro a for high levels of thiol in neurons for T.H. FASEB J. PubMed Scopus Google Scholar). In the brain major is to the subventricular zone and the subgranular zone of the dentate gyrus G. Neurosci. PubMed Scopus Google Scholar). Our results indicate that contain high levels of GSH. In dentate neurons in the of granular layer contain GSH at a level than the precursor cells the neurons in the lateral of the granular layer contain levels of GSH. that neurons in of and contain high GSH. that during the of neurons most of GSH content and to to with is with the of M.A. Google Scholar) GSH in the system by cellular and that neuronal and glial cells contain most neurons the of GSH content by that neurons GSH content as in with J. S. J. Neurosci. Res. 2001; PubMed Scopus Google Scholar, S. J. PubMed Scopus Google Scholar). low level of GSH content in neurons unique to T.H. FASEB J. PubMed Scopus Google Scholar, J.B. J. PubMed Scopus Google Scholar, J. J. PubMed Scopus Google Scholar, J. Neurosci. 2001; PubMed Google Scholar, T.H. J. PubMed Scopus Google Scholar). the high of is that have GSH and GSH to such as reduced to levels of GSH. to GSH is and by neurons for thiol and A. PubMed Scopus Google Scholar). neurons with a GSH or function at a more potential is for a or of GSH within the of of the intact brain to by two-photon imaging to a for labeling cells in the in The of labeling for in was by with marker A. PubMed Scopus Google Scholar). the to GSH content in live The GSH system the brain is such as during the GSH H. A. H. H. Brain Res. 1991; PubMed Scopus Google Scholar, S. J. Smith J. PubMed Scopus Google Scholar). by disorders, such as J.B. J. PubMed Scopus Google Scholar) and J. Neurosci. PubMed Google Scholar). indicate a role for GSH and in the of brain H. H. J. Neurosci. 25: PubMed Scopus Google Scholar). However, in most the GSH system to these tissue cellular is possible that these have to the GSH levels during T. H. Chan P.H. Am. J. Physiol. Google Scholar, A. H. 1998; PubMed Scopus Google Scholar, Y. 1991; PubMed Scopus Google Scholar, A. Scholar). Our to animal of and with of J. Chan Chen Y. Neurosci. PubMed Scopus Google Scholar, A. S. A. T. J. PubMed Scopus Google Scholar) to GSH levels in brain have used of the to systems as a for stroke S. H. T.H. J. PubMed Scopus Google Scholar, T.H. J. Neurosci. 25: PubMed Scopus Google Scholar). In used to and the cellular of GSH by as well as that the GSH system PubMed Scopus Google Scholar, Scopus Google Scholar). we S. J. T.H. J. Neurosci. 25: PubMed Scopus Google Scholar) and PubMed Scopus Google Scholar, Scopus Google Scholar) have used two-photon to the of and of cortical brain Our to GSH levels in with two-photon of and unique the brain with the In conclusion, we have to GSH content in intact brain these imaging we the that meningeal and lateral ventricle ependymal cells a role in brain redox homeostasis.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".