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Baroncelli L, Auel S, Rinne L, Schuster AK, Brand V, Kempkes B, Dietrich K, Müller M. Oral Feeding of an Antioxidant Cocktail as a Therapeutic Strategy in a Mouse Model of Rett Syndrome: Merits and Limitations of Long-Term Treatment. Antioxidants (Basel) 2022; 11:antiox11071406. [PMID: 35883897 PMCID: PMC9311910 DOI: 10.3390/antiox11071406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 07/14/2022] [Accepted: 07/15/2022] [Indexed: 02/01/2023] Open
Abstract
Rett syndrome (RTT) is a severe neurodevelopmental disorder that typically arises from spontaneous germline mutations in the X-chromosomal methyl-CpG binding protein 2 (MECP2) gene. For the first 6–18 months of life, the development of the mostly female patients appears normal. Subsequently, cognitive impairment, motor disturbances, hand stereotypies, epilepsy, and irregular breathing manifest, with previously learned skills being lost. Early mitochondrial impairment and a systemic oxidative burden are part of the complex pathogenesis, and contribute to disease progression. Accordingly, partial therapeutic merits of redox-stabilizing and antioxidant (AO) treatments were reported in RTT patients and Mecp2-mutant mice. Pursuing these findings, we conducted a full preclinical trial on male and female mice to define the therapeutic value of an orally administered AO cocktail composed of vitamin E, N-acetylcysteine, and α-lipoic acid. AO treatment ameliorated some of the microcephaly-related aspects. Moreover, the reduced growth, lowered blood glucose levels, and the hippocampal synaptic plasticity of Mecp2−/y mice improved. However, the first-time detected intensified oxidative DNA damage in Mecp2-mutant cortex persisted. The behavioral performance, breathing regularity, and life expectancy of Mecp2-mutant mice did not improve upon AO treatment. Long-term-treated Mecp2+/− mice eventually became obese. In conclusion, the AO cocktail ameliorated a subset of symptoms of the complex RTT-related phenotype, thereby further confirming the potential merits of AO-based pharmacotherapies. Yet, it also became evident that long-term AO treatment may lose efficacy and even aggravate the metabolic disturbances in RTT. This emphasizes the importance of a constantly well-balanced redox balance for systemic well-being.
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Affiliation(s)
- Laura Baroncelli
- Institut für Neuro- und Sinnesphysiologie, Universitätsmedizin Göttingen, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany; (L.B.); (S.A.); (L.R.); (A.-K.S.); (V.B.); (B.K.); (K.D.)
- Institute of Neuroscience, National Research Council (CNR), via Giuseppe Moruzzi 1, I-56124 Pisa, Italy
- Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, Viale del Tirreno 331, I-56128 Pisa, Italy
| | - Stefanie Auel
- Institut für Neuro- und Sinnesphysiologie, Universitätsmedizin Göttingen, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany; (L.B.); (S.A.); (L.R.); (A.-K.S.); (V.B.); (B.K.); (K.D.)
| | - Lena Rinne
- Institut für Neuro- und Sinnesphysiologie, Universitätsmedizin Göttingen, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany; (L.B.); (S.A.); (L.R.); (A.-K.S.); (V.B.); (B.K.); (K.D.)
| | - Ann-Kathrin Schuster
- Institut für Neuro- und Sinnesphysiologie, Universitätsmedizin Göttingen, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany; (L.B.); (S.A.); (L.R.); (A.-K.S.); (V.B.); (B.K.); (K.D.)
| | - Victoria Brand
- Institut für Neuro- und Sinnesphysiologie, Universitätsmedizin Göttingen, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany; (L.B.); (S.A.); (L.R.); (A.-K.S.); (V.B.); (B.K.); (K.D.)
| | - Belinda Kempkes
- Institut für Neuro- und Sinnesphysiologie, Universitätsmedizin Göttingen, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany; (L.B.); (S.A.); (L.R.); (A.-K.S.); (V.B.); (B.K.); (K.D.)
| | - Katharina Dietrich
- Institut für Neuro- und Sinnesphysiologie, Universitätsmedizin Göttingen, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany; (L.B.); (S.A.); (L.R.); (A.-K.S.); (V.B.); (B.K.); (K.D.)
| | - Michael Müller
- Institut für Neuro- und Sinnesphysiologie, Universitätsmedizin Göttingen, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany; (L.B.); (S.A.); (L.R.); (A.-K.S.); (V.B.); (B.K.); (K.D.)
- Correspondence: ; Tel.: +49-551-39-22933
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Janc OA, Müller M. The free radical scavenger Trolox dampens neuronal hyperexcitability, reinstates synaptic plasticity, and improves hypoxia tolerance in a mouse model of Rett syndrome. Front Cell Neurosci 2014; 8:56. [PMID: 24605086 PMCID: PMC3932407 DOI: 10.3389/fncel.2014.00056] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 02/06/2014] [Indexed: 11/13/2022] Open
Abstract
Rett syndrome (RS) causes severe cognitive impairment, loss of speech, epilepsy, and breathing disturbances with intermittent hypoxia. Also mitochondria are affected; a subunit of respiratory complex III is dysregulated, the inner mitochondrial membrane is leaking protons, and brain ATP levels seem reduced. Our recent assessment of mitochondrial function in MeCP2 (methyl-CpG-binding protein 2)-deficient mouse (Mecp2-/y) hippocampus confirmed early metabolic alterations, an increased oxidative burden, and a more vulnerable cellular redox balance. As these changes may contribute to the manifestation of symptoms and disease progression, we now evaluated whether free radical scavengers are capable of improving neuronal and mitochondrial function in RS. Acute hippocampal slices of adult mice were incubated with the vitamin E derivative Trolox for 3–5 h. In Mecp2-/y slices this treatment dampened neuronal hyperexcitability, improved synaptic short-term plasticity, and fully restored synaptic long-term potentiation (LTP). Furthermore, Trolox specifically attenuated the increased hypoxia susceptibility of Mecp2-/y slices. Also, the anticonvulsive effects of Trolox were assessed, but the severity of 4-aminopyridine provoked seizure-like discharges was not significantly affected. Adverse side effects of Trolox on mitochondria can be excluded, but clear indications for an improvement of mitochondrial function were not found. Since several ion-channels and neurotransmitter receptors are redox modulated, the mitochondrial alterations and the associated oxidative burden may contribute to the neuronal dysfunction in RS. We confirmed in Mecp2-/y hippocampus that Trolox dampens neuronal hyperexcitability, reinstates synaptic plasticity, and improves the hypoxia tolerance. Therefore, radical scavengers are promising compounds for the treatment of neuronal dysfunction in RS and deserve further detailed evaluation.
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Affiliation(s)
- Oliwia A Janc
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Georg-August-Universität Göttingen Göttingen, Germany ; Zentrum für Physiologie und Pathophysiologie, Institut für Neuro- und Sinnesphysiologie, Universitätsmedizin, Georg-August-Universität Göttingen Göttingen, Germany
| | - Michael Müller
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Georg-August-Universität Göttingen Göttingen, Germany ; Zentrum für Physiologie und Pathophysiologie, Institut für Neuro- und Sinnesphysiologie, Universitätsmedizin, Georg-August-Universität Göttingen Göttingen, Germany
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Mané M, Müller M. Temporo-spectral imaging of intrinsic optical signals during hypoxia-induced spreading depression-like depolarization. PLoS One 2012; 7:e43981. [PMID: 22952835 PMCID: PMC3430631 DOI: 10.1371/journal.pone.0043981] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 07/27/2012] [Indexed: 11/18/2022] Open
Abstract
Spreading depression (SD) is characterized by a sustained near-complete depolarization of neurons, a massive depolarization of glia, and a negative deflection of the extracellular DC potential. These electrophysiological signs are accompanied by an intrinsic optical signal (IOS) which arises from changes in light scattering and absorption. Even though the underlying mechanisms are unclear, the IOS serves as non-invasive tool to define the spatiotemporal dynamics of SD in brain slices. Usually the tissue is illuminated by white light, and light reflectance or transmittance is monitored. Using a polychromatic, fast-switchable light source we now performed temporo-spectral recordings of the IOS associated with hypoxia-induced SD-like depolarization (HSD) in rat hippocampal slices kept in an interface recording chamber. Recording full illumination spectra (320–680 nm) yielded distinct reflectance profiles for the different phases of HSD. Early during hypoxia tissue reflectance decreased within almost the entire spectrum due to cell swelling. HSD was accompanied by a reversible reflectance increase being most pronounced at 400 nm and 460 nm. At 440 nm massive porphyrin absorption (Soret band) was detected. Hypotonic solutions, Ca2+-withdrawal and glial poisoning intensified the reflectance increase during HSD, whereas hypertonic solutions dampened it. Replacement of Cl- inverted the reflectance increase. Inducing HSD by cyanide distorted the IOS and reflectance at 340–400 nm increased irreversibly. The pronounced changes at short wavelengths (380 nm, 460 nm) and their cyanide sensitivity suggest that block of mitochondrial metabolism contributes to the IOS during HSD. For stable and reliable IOS recordings during HSD wavelengths of 460–560 nm are recommended.
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Affiliation(s)
- Maria Mané
- DFG Research Center Molecular Physiology of the Brain (CMPB), Zentrum für Physiologie und Pathophysiologie, Abteilung Neuro- und Sinnesphysiologie, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Michael Müller
- DFG Research Center Molecular Physiology of the Brain (CMPB), Zentrum für Physiologie und Pathophysiologie, Abteilung Neuro- und Sinnesphysiologie, Georg-August-Universität Göttingen, Göttingen, Germany
- * E-mail:
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Schnell C, Janc OA, Kempkes B, Callis CA, Flügge G, Hülsmann S, Müller M. Restraint Stress Intensifies Interstitial K(+) Accumulation during Severe Hypoxia. Front Pharmacol 2012; 3:53. [PMID: 22470344 PMCID: PMC3314232 DOI: 10.3389/fphar.2012.00053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Accepted: 03/12/2012] [Indexed: 11/23/2022] Open
Abstract
Chronic stress affects neuronal networks by inducing dendritic retraction, modifying neuronal excitability and plasticity, and modulating glial cells. To elucidate the functional consequences of chronic stress for the hippocampal network, we submitted adult rats to daily restraint stress for 3 weeks (6 h/day). In acute hippocampal tissue slices of stressed rats, basal synaptic function and short-term plasticity at Schaffer collateral/CA1 neuron synapses were unchanged while long-term potentiation was markedly impaired. The spatiotemporal propagation pattern of hypoxia-induced spreading depression episodes was indistinguishable among control and stress slices. However, the duration of the extracellular direct current potential shift was shortened after stress. Moreover, K+ fluxes early during hypoxia were more intense, and the postsynaptic recoveries of interstitial K+ levels and synaptic function were slower. Morphometric analysis of immunohistochemically stained sections suggested hippocampal shrinkage in stressed rats, and the number of cells that are immunoreactive for glial fibrillary acidic protein was increased in the CA1 subfield indicating activation of astrocytes. Western blots showed a marked downregulation of the inwardly rectifying K+ channel Kir4.1 in stressed rats. Yet, resting membrane potentials, input resistance, and K+-induced inward currents in CA1 astrocytes were indistinguishable from controls. These data indicate an intensified interstitial K+ accumulation during hypoxia in the hippocampus of chronically stressed rats which seems to arise from a reduced interstitial volume fraction rather than impaired glial K+ buffering. One may speculate that chronic stress aggravates hypoxia-induced pathophysiological processes in the hippocampal network and that this has implications for the ischemic brain.
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Affiliation(s)
- Christian Schnell
- DFG Research Center Molecular Physiology of the Brain, Georg-August-Universität Göttingen Göttingen, Germany
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Kron M, Zimmermann JL, Dutschmann M, Funke F, Müller M. Altered responses of MeCP2-deficient mouse brain stem to severe hypoxia. J Neurophysiol 2011; 105:3067-79. [DOI: 10.1152/jn.00822.2010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rett syndrome (RTT) patients suffer from respiratory arrhythmias with frequent apneas causing intermittent hypoxia. In a RTT mouse model (methyl-CpG-binding protein 2-deficient mice; Mecp2−/ y) we recently discovered an enhanced hippocampal susceptibility to hypoxia and hypoxia-induced spreading depression (HSD). In the present study we investigated whether this also applies to infant Mecp2−/ y brain stem, which could become life-threatening due to failure of cardiorespiratory control. HSD most reliably occurred in the nucleus of the solitary tract (NTS) and the spinal trigeminal nucleus (Sp5). HSD susceptibility of the Mecp2−/ y NTS and Sp5 was increased on 8 mM K+-mediated conditioning. 5-HT1A receptor stimulation with 8-hydroxy-2-(di-propylamino)tetralin (8-OH-DPAT) postponed HSD by up to 40%, mediating genotype-independent protection. The deleterious impact of HSD on in vitro respiration became obvious in rhythmically active slices, where HSD propagation into the pre-Bötzinger complex (pre-BötC) immediately arrested the respiratory rhythm. Compared with wild-type, the Mecp2−/ y pre-BötC was invaded less frequently by HSD, but if so, HSD occurred earlier. On reoxygenation, in vitro rhythms reappeared with increased frequency, which was less pronounced in Mecp2−/ y slices. 8-OH-DPAT increased respiratory frequency but failed to postpone HSD in the pre-BötC. Repetitive hypoxia facilitated posthypoxic recovery only if HSD occurred. In 57% of Mecp2−/ y slices, however, HSD spared the pre-BötC. Although this occasionally promoted residual hypoxic respiratory activity (“gasping”), it also prolonged the posthypoxic recovery, and thus the absence of central inspiratory drive, which in vivo would lengthen respiratory arrest. In view of the breathing disorders in RTTs, the increased hypoxia susceptibility of MeCP2-deficient brain stem potentially contributes to life-threatening disturbances of cardiorespiratory control.
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Affiliation(s)
- Miriam Kron
- Deutsche Forschungsgemeinschaft Research Center for Molecular Physiology of the Brain, Zentrum für Physiologie und Pathophysiologie, Abteilung Neuro- und Sinnesphysiologie, and
- Bernstein Center for Computational Neuroscience, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Jasper L. Zimmermann
- Deutsche Forschungsgemeinschaft Research Center for Molecular Physiology of the Brain, Zentrum für Physiologie und Pathophysiologie, Abteilung Neuro- und Sinnesphysiologie, and
| | - Mathias Dutschmann
- Deutsche Forschungsgemeinschaft Research Center for Molecular Physiology of the Brain, Zentrum für Physiologie und Pathophysiologie, Abteilung Neuro- und Sinnesphysiologie, and
- Bernstein Center for Computational Neuroscience, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Frank Funke
- Deutsche Forschungsgemeinschaft Research Center for Molecular Physiology of the Brain, Zentrum für Physiologie und Pathophysiologie, Abteilung Neuro- und Sinnesphysiologie, and
| | - Michael Müller
- Deutsche Forschungsgemeinschaft Research Center for Molecular Physiology of the Brain, Zentrum für Physiologie und Pathophysiologie, Abteilung Neuro- und Sinnesphysiologie, and
- Bernstein Center for Computational Neuroscience, Georg-August-Universität Göttingen, Göttingen, Germany
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H(2)O(2)-mediated modulation of cytosolic signaling and organelle function in rat hippocampus. Pflugers Arch 2009; 458:937-52. [PMID: 19430810 PMCID: PMC2719740 DOI: 10.1007/s00424-009-0672-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Revised: 04/06/2009] [Accepted: 04/07/2009] [Indexed: 12/23/2022]
Abstract
Reactive oxygen species (ROS) released from (dys-)functioning mitochondria contribute to normal and pathophysiological cellular signaling by modulating cytosolic redox state and redox-sensitive proteins. To identify putative redox targets involved in such signaling, we exposed hippocampal neurons to hydrogen peroxide (H2O2). Redox-sensitive dyes indicated that externally applied H2O2 may oxidize intracellular targets in cell cultures and acute tissue slices. In cultured neurons, H2O2 (EC50 118 µM) induced an intracellular Ca2+ rise which could still be evoked upon Ca2+ withdrawal and mitochondrial uncoupling. It was, however, antagonized by thapsigargin, dantrolene, 2-aminoethoxydiphenyl borate, and high levels of ryanodine, which identifies the endoplasmic reticulum (ER) as the intracellular Ca2+ store involved. Intracellular accumulation of endogenously generated H2O2—provoked by inhibiting glutathione peroxidase—also released Ca2+ from the ER, as did extracellular generation of superoxide. Phospholipase C (PLC)-mediated metabotropic signaling was depressed in the presence of H2O2, but cytosolic cyclic adenosine-5′-monophosphate (cAMP) levels were not affected. H2O2 (0.2–5 mM) moderately depolarized mitochondria, halted their intracellular trafficking in a Ca2+- and cAMP-independent manner, and directly oxidized cellular nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FADH2). In part, the mitochondrial depolarization reflects uptake of Ca2+ previously released from the ER. We conclude that H2O2 releases Ca2+ from the ER via both ryanodine and inositol trisphosphate receptors. Mitochondrial function is not markedly impaired even by millimolar concentrations of H2O2. Such modulation of Ca2+ signaling and organelle interaction by ROS affects the efficacy of PLC-mediated metabotropic signaling and may contribute to the adjustment of neuronal function to redox conditions and metabolic supply.
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Funke F, Kron M, Dutschmann M, Müller M. Infant Brain Stem Is Prone to the Generation of Spreading Depression During Severe Hypoxia. J Neurophysiol 2009; 101:2395-410. [DOI: 10.1152/jn.91260.2008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spreading depression (SD) resembles a concerted, massive neuronal/glial depolarization propagating within the gray matter. Being associated with cerebropathology, such as cerebral ischemia or hemorrhage, epileptic seizures, and migraine, it is well studied in cortex and hippocampus. We have now analyzed the susceptibility of rat brain stem to hypoxia-induced spreading depression-like depolarization (HSD), which could critically interfere with cardiorespiratory control. In rat brain stem slices, severe hypoxia (oxygen withdrawal) triggered HSD within minutes. The sudden extracellular DC potential shift of approximately −20 mV showed the typical profile known from other brain regions and was accompanied by an intrinsic optical signal (IOS). Spatiotemporal IOS analysis revealed that in infant brain stem, HSD was preferably ignited within the spinal trigeminal nucleus and then mostly spread out medially, invading the hypoglossal nucleus, the nucleus of the solitary tract (NTS), and the ventral respiratory group (VRG). The neuronal hypoxic depolarizations underlying the generation of HSD were massive, but incomplete. The propagation velocity of HSD and the associated extracellular K+ rise were also less marked than in other brain regions. In adult brain stem, HSD was mostly confined to the NTS and its occurrence was facilitated by hypotonic solutions, but not by glial poisoning or block of GABAergic and glycinergic synapses. In conclusion, brain stem tissue reliably generates propagating HSD episodes, which may be of interest for basilar-type migraine and brain stem infarcts. The preferred occurrence of HSD in the infant brain stem and its propagation into the VRG may be of importance for neonatal brain stem pathology such as sudden infant death syndrome.
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Fischer M, Reuter J, Gerich FJ, Hildebrandt B, Hägele S, Katschinski D, Müller M. Enhanced hypoxia susceptibility in hippocampal slices from a mouse model of rett syndrome. J Neurophysiol 2008; 101:1016-32. [PMID: 19073793 DOI: 10.1152/jn.91124.2008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rett syndrome is a neurodevelopmental disorder caused by mutations in the X-chromosomal MECP2 gene encoding for the transcriptional regulator methyl CpG binding protein 2 (MeCP2). Rett patients suffer from episodic respiratory irregularities and reduced arterial oxygen levels. To elucidate whether such intermittent hypoxic episodes induce adaptation/preconditioning of the hypoxia-vulnerable hippocampal network, we analyzed its responses to severe hypoxia in adult Rett mice. The occurrence of hypoxia-induced spreading depression (HSD)--an experimental model for ischemic stroke--was hastened in Mecp2-/y males. The extracellular K+ rise during HSD was attenuated in Mecp2-/y males and the input resistance of CA1 pyramidal neurons decreased less before HSD onset. CA1 pyramidal neurons were smaller and more densely packed, but the cell swelling during HSD was unaffected. The intrinsic optical signal and the propagation of HSD were similar among the different genotypes. Basal synaptic function was intact, but Mecp2-/y males showed reduced paired-pulse facilitation and higher field potential/fiber volley ratios, but no increased seizure susceptibility. Synaptic failure during hypoxia was complete in all genotypes and the final degree of posthypoxic synaptic recovery indistinguishable. Cellular ATP content was normal in Mecp2-/y males, but their hematocrit was increased as was HIF-1alpha expression throughout the brain. This is the first study showing that in Rett syndrome, the susceptibility of telencephalic neuronal networks to hypoxia is increased; the underlying molecular mechanisms apparently involve disturbed K+ channel function. Such an increase in hypoxia susceptibility may potentially contribute to the vulnerability of male Rett patients who are either not viable or severely disabled.
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Affiliation(s)
- Marc Fischer
- Deutsche Forschungsgemeinschaft Research Center for Molecular Physiology of the Brain, Zentrum Physiologie und Pathophysiologie, Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany
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