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Estriol preserves synaptic transmission in the hippocampus during autoimmune demyelinating disease.

Ziehn MO, Avedisian AA, Dervin SM, O'Dell TJ, Voskuhl RR - Lab. Invest. (2012)

Bottom Line: Neuropathological experiments demonstrated that there were decreased levels of pre- and post-synaptic proteins in the hippocampus, diffuse loss of myelin staining and atrophy of the pyramidal layers of hippocampal cornu ammonis 1 (CA1).Estriol treatment prevented decreases in excitatory synaptic transmission and lessened the effect of EAE on PPF.Cross-modality correlations revealed that deficits in excitatory synaptic transmission were significantly correlated with reductions in trans-synaptic protein binding partners known to modulate excitatory synaptic transmission.

View Article: PubMed Central - PubMed

Affiliation: Interdepartmental Program of Neuroscience, University of California, Los Angeles, Los Angeles, CA, USA.

ABSTRACT
Cognitive deficits occur in over half of multiple sclerosis patients, with hippocampal-dependent learning and memory commonly impaired. Data from in vivo MRI and post-mortem studies in MS indicate that the hippocampus is targeted. However, the relationship between structural pathology and dysfunction of the hippocampus in MS remains unclear. Hippocampal neuropathology also occurs in experimental autoimmune encephalomyelitis (EAE), the most commonly used animal model of MS. Although estrogen treatment of EAE has been shown to be anti-inflammatory and neuroprotective in the spinal cord, it is unknown if estrogen treatment may prevent hippocampal pathology and dysfunction. In the current study we examined excitatory synaptic transmission during EAE and focused on pathological changes in synaptic protein complexes known to orchestrate functional synaptic transmission in the hippocampus. We then determined if estriol, a candidate hormone treatment, was capable of preventing functional changes in synaptic transmission and corresponding hippocampal synaptic pathology. Electrophysiological studies revealed altered excitatory synaptic transmission and paired-pulse facilitation (PPF) during EAE. Neuropathological experiments demonstrated that there were decreased levels of pre- and post-synaptic proteins in the hippocampus, diffuse loss of myelin staining and atrophy of the pyramidal layers of hippocampal cornu ammonis 1 (CA1). Estriol treatment prevented decreases in excitatory synaptic transmission and lessened the effect of EAE on PPF. In addition, estriol treatment prevented several neuropathological alterations that occurred in the hippocampus during EAE. Cross-modality correlations revealed that deficits in excitatory synaptic transmission were significantly correlated with reductions in trans-synaptic protein binding partners known to modulate excitatory synaptic transmission. To our knowledge, this is the first report describing a functional correlate to hippocampal neuropathology in any MS model. Furthermore, a treatment was identified that prevented both deficits in synaptic function and hippocampal neuropathology.

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Related in: MedlinePlus

Excitatory synaptic transmission and paired-pulse facilitation are altered during EAE(A) Input/output (IO) curves were created by comparing fiber volley amplitude (FV Amp; mV) to field excitatory postsynaptic potential (fEPSP; mV/ms) during four different stimulation intensities of presynaptic fiber stimulation that caused fEPSP responses of 25, 50, 75 and 100% maximal fEPSP amplitude. One-way ANOVA analyses demonstrated that placebo-treated EAE (EAE+PLAC; black star, dashed black line) fEPSP responses were significantly reduced at each point along the IO curve (percentage of maximal fEPSP slope: 25, 50 75 and 100%) in comparison to healthy controls (NL; black squares, solid black line), p < 0.05. With estriol treatment during EAE, (EAE+ESTRIOL; gray triangle, dashed gray line), the IO curve followed a similar trajectory to healthy controls. (B) A histogram demonstrating decreased maximal fEPSP responses in placebo-treated EAE compared to healthy controls, and maximal fEPSPs in estriol-treated EAE mice that were not significantly different from controls. One-way ANOVA revealed a significant effect of disease on maximal fEPSP slope (p = 0.0029) and follow up Bonferroni tests indicated that placebo-treated EAE mice (EAE+PLAC; n = 15 slices from 5 mice) were significantly different from healthy controls (NL, n = 7 slices from 3 mice; ** p < 0.01) and also significantly different from estriol-treated EAE (EAE+ESTRIOL, n = 16 slices from 5 mice; * p < 0.05). (C) Paired-pulse facilitation was increased in the hippocampal CA1 region of placebo-treated EAE mice. Paired presynaptic fiber stimulation pulses were delivered with varying inter-pulse intervals (25, 50, 100, 200 and 275 ms) to elicit postsynaptic responses with amplitudes that were then compared. At an inter-pulse interval of 25ms, one-way ANOVA demonstrated that condition had a significant effect on paired-pulse facilitation, (p = 0.0178). Bonferroni post-hoc analysis showed that placebo-treated mice (EAE+PLAC; black star, dashed black line, n = 12 slices from 5 mice) had significantly greater paired-pulse facilitation (* p < 0.05) compared to healthy controls (NL; black square, solid black line, n = 6 slices from 3 mice). Estriol-treated mice (EAE+ESTRIOL; gray triangle, dashed gray line, n = 11 slices from 5 mice) also had significantly increased PPF compared to healthy controls. (D) Sample waveforms depict representative paired-pulse responses recorded from animals in each experimental condition at a 25ms inter-pulse interval (NL: black solid line; EAE+PLAC: dashed black line; and EAE+ESTRIOL: gray dashed line). (E) Neither the post-tetanic potentiation (PTP; the first response after high-frequency stimulation), nor the early phase of LTP were significantly affected by EAE, as analyzed by one-way ANOVAs. Furthermore, one-way ANOVA’s revealed that estriol treatment during EAE did not have an effect on PTP or eLTP.
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Figure 2: Excitatory synaptic transmission and paired-pulse facilitation are altered during EAE(A) Input/output (IO) curves were created by comparing fiber volley amplitude (FV Amp; mV) to field excitatory postsynaptic potential (fEPSP; mV/ms) during four different stimulation intensities of presynaptic fiber stimulation that caused fEPSP responses of 25, 50, 75 and 100% maximal fEPSP amplitude. One-way ANOVA analyses demonstrated that placebo-treated EAE (EAE+PLAC; black star, dashed black line) fEPSP responses were significantly reduced at each point along the IO curve (percentage of maximal fEPSP slope: 25, 50 75 and 100%) in comparison to healthy controls (NL; black squares, solid black line), p < 0.05. With estriol treatment during EAE, (EAE+ESTRIOL; gray triangle, dashed gray line), the IO curve followed a similar trajectory to healthy controls. (B) A histogram demonstrating decreased maximal fEPSP responses in placebo-treated EAE compared to healthy controls, and maximal fEPSPs in estriol-treated EAE mice that were not significantly different from controls. One-way ANOVA revealed a significant effect of disease on maximal fEPSP slope (p = 0.0029) and follow up Bonferroni tests indicated that placebo-treated EAE mice (EAE+PLAC; n = 15 slices from 5 mice) were significantly different from healthy controls (NL, n = 7 slices from 3 mice; ** p < 0.01) and also significantly different from estriol-treated EAE (EAE+ESTRIOL, n = 16 slices from 5 mice; * p < 0.05). (C) Paired-pulse facilitation was increased in the hippocampal CA1 region of placebo-treated EAE mice. Paired presynaptic fiber stimulation pulses were delivered with varying inter-pulse intervals (25, 50, 100, 200 and 275 ms) to elicit postsynaptic responses with amplitudes that were then compared. At an inter-pulse interval of 25ms, one-way ANOVA demonstrated that condition had a significant effect on paired-pulse facilitation, (p = 0.0178). Bonferroni post-hoc analysis showed that placebo-treated mice (EAE+PLAC; black star, dashed black line, n = 12 slices from 5 mice) had significantly greater paired-pulse facilitation (* p < 0.05) compared to healthy controls (NL; black square, solid black line, n = 6 slices from 3 mice). Estriol-treated mice (EAE+ESTRIOL; gray triangle, dashed gray line, n = 11 slices from 5 mice) also had significantly increased PPF compared to healthy controls. (D) Sample waveforms depict representative paired-pulse responses recorded from animals in each experimental condition at a 25ms inter-pulse interval (NL: black solid line; EAE+PLAC: dashed black line; and EAE+ESTRIOL: gray dashed line). (E) Neither the post-tetanic potentiation (PTP; the first response after high-frequency stimulation), nor the early phase of LTP were significantly affected by EAE, as analyzed by one-way ANOVAs. Furthermore, one-way ANOVA’s revealed that estriol treatment during EAE did not have an effect on PTP or eLTP.

Mentions: Excitatory synaptic transmission in the hippocampus during EAE has not been previously investigated. Synaptic transmission is dependent on functional and appropriately located synaptic protein families. Thus, basal synaptic transmission and paired-pulse facilitation were assessed using in vitro hippocampal slices. To determine if EAE caused an effect in excitatory synaptic transmission, input/output (IO) relationships were compared in hippocampal slices from the right hemispheres of mice in each experimental group. The amplitude of presynaptic fiber volleys and the slope of the EPSPs evoked by different intensities of Schaffer Collateral fiber stimulation were analyzed. Here, hippocampal slices from placebo-treated EAE mice had a significantly altered IO curve compared to those from healthy controls (Fig 2A). Hippocampal slices from EAE mice had FV Amps and fEPSP slopes that were both decreased by nearly 50%, suggesting that basal synaptic transmission was significantly impaired during EAE. When treated with estriol, however, hippocampal slices from mice with EAE displayed input/output relationships more similar to healthy controls, (Fig 2A-B). When maximal fEPSP slopes were compared across the three groups, there was a significant deficit in postsynaptic responses in slices from EAE mice compared to healthy controls, and this decrease in the postsynaptic response was prevented with estriol treatment (Fig 2B). Next, to examine short-term plasticity we measured paired-pulse facilitation (PPF) at Schaffer collateral fiber inputs onto CA1 pyramidal cells. Paired-pulse facilitation is inversely correlated with the probability of neurotransmitter release from presynaptic terminals, such that an increase in PPF is indicative of a decrease in transmitter release probability, whereas a decrease in PPF is indicative of an increase in transmitter release probability. Compared to healthy controls, placebo-treated EAE mice displayed significantly increased PPF at the shortest paired-pulse interval tested (Fig 2C-D). Interestingly, although PPF in slices from estriol-treated EAE mice was also significantly elevated compared to healthy controls, the increase tended to be lower than placebo-treated EAE mice at the same time interval (Fig 2C-D). Since hippocampal slices from placebo-treated EAE mice had significantly increased paired-pulse ratios, our results suggest that EAE caused a decrease in the probability of presynaptic neurotransmitter release. With estriol treatment during EAE there was a trend of partially restored release probability. To examine if EAE impaired synaptic plasticity, long-term potentiation (LTP) was induced with high frequency stimulation (HFS, 2x100Hz) in hippocampal slices from mice in each condition. Two separate components of LTP were analyzed: post-tetanic potentiation (PTP; the immediate potentiated response of each slice after HFS stimulation), and early phase LTP (eLTP; the average of the last five minutes of LTP in each slice). When compared across groups, PTP was not significantly affected by disease, or by estriol treatment during disease. eLTP was also unaffected by EAE or estriol treatment during EAE (Fig 2E).


Estriol preserves synaptic transmission in the hippocampus during autoimmune demyelinating disease.

Ziehn MO, Avedisian AA, Dervin SM, O'Dell TJ, Voskuhl RR - Lab. Invest. (2012)

Excitatory synaptic transmission and paired-pulse facilitation are altered during EAE(A) Input/output (IO) curves were created by comparing fiber volley amplitude (FV Amp; mV) to field excitatory postsynaptic potential (fEPSP; mV/ms) during four different stimulation intensities of presynaptic fiber stimulation that caused fEPSP responses of 25, 50, 75 and 100% maximal fEPSP amplitude. One-way ANOVA analyses demonstrated that placebo-treated EAE (EAE+PLAC; black star, dashed black line) fEPSP responses were significantly reduced at each point along the IO curve (percentage of maximal fEPSP slope: 25, 50 75 and 100%) in comparison to healthy controls (NL; black squares, solid black line), p < 0.05. With estriol treatment during EAE, (EAE+ESTRIOL; gray triangle, dashed gray line), the IO curve followed a similar trajectory to healthy controls. (B) A histogram demonstrating decreased maximal fEPSP responses in placebo-treated EAE compared to healthy controls, and maximal fEPSPs in estriol-treated EAE mice that were not significantly different from controls. One-way ANOVA revealed a significant effect of disease on maximal fEPSP slope (p = 0.0029) and follow up Bonferroni tests indicated that placebo-treated EAE mice (EAE+PLAC; n = 15 slices from 5 mice) were significantly different from healthy controls (NL, n = 7 slices from 3 mice; ** p < 0.01) and also significantly different from estriol-treated EAE (EAE+ESTRIOL, n = 16 slices from 5 mice; * p < 0.05). (C) Paired-pulse facilitation was increased in the hippocampal CA1 region of placebo-treated EAE mice. Paired presynaptic fiber stimulation pulses were delivered with varying inter-pulse intervals (25, 50, 100, 200 and 275 ms) to elicit postsynaptic responses with amplitudes that were then compared. At an inter-pulse interval of 25ms, one-way ANOVA demonstrated that condition had a significant effect on paired-pulse facilitation, (p = 0.0178). Bonferroni post-hoc analysis showed that placebo-treated mice (EAE+PLAC; black star, dashed black line, n = 12 slices from 5 mice) had significantly greater paired-pulse facilitation (* p < 0.05) compared to healthy controls (NL; black square, solid black line, n = 6 slices from 3 mice). Estriol-treated mice (EAE+ESTRIOL; gray triangle, dashed gray line, n = 11 slices from 5 mice) also had significantly increased PPF compared to healthy controls. (D) Sample waveforms depict representative paired-pulse responses recorded from animals in each experimental condition at a 25ms inter-pulse interval (NL: black solid line; EAE+PLAC: dashed black line; and EAE+ESTRIOL: gray dashed line). (E) Neither the post-tetanic potentiation (PTP; the first response after high-frequency stimulation), nor the early phase of LTP were significantly affected by EAE, as analyzed by one-way ANOVAs. Furthermore, one-way ANOVA’s revealed that estriol treatment during EAE did not have an effect on PTP or eLTP.
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Related In: Results  -  Collection

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Figure 2: Excitatory synaptic transmission and paired-pulse facilitation are altered during EAE(A) Input/output (IO) curves were created by comparing fiber volley amplitude (FV Amp; mV) to field excitatory postsynaptic potential (fEPSP; mV/ms) during four different stimulation intensities of presynaptic fiber stimulation that caused fEPSP responses of 25, 50, 75 and 100% maximal fEPSP amplitude. One-way ANOVA analyses demonstrated that placebo-treated EAE (EAE+PLAC; black star, dashed black line) fEPSP responses were significantly reduced at each point along the IO curve (percentage of maximal fEPSP slope: 25, 50 75 and 100%) in comparison to healthy controls (NL; black squares, solid black line), p < 0.05. With estriol treatment during EAE, (EAE+ESTRIOL; gray triangle, dashed gray line), the IO curve followed a similar trajectory to healthy controls. (B) A histogram demonstrating decreased maximal fEPSP responses in placebo-treated EAE compared to healthy controls, and maximal fEPSPs in estriol-treated EAE mice that were not significantly different from controls. One-way ANOVA revealed a significant effect of disease on maximal fEPSP slope (p = 0.0029) and follow up Bonferroni tests indicated that placebo-treated EAE mice (EAE+PLAC; n = 15 slices from 5 mice) were significantly different from healthy controls (NL, n = 7 slices from 3 mice; ** p < 0.01) and also significantly different from estriol-treated EAE (EAE+ESTRIOL, n = 16 slices from 5 mice; * p < 0.05). (C) Paired-pulse facilitation was increased in the hippocampal CA1 region of placebo-treated EAE mice. Paired presynaptic fiber stimulation pulses were delivered with varying inter-pulse intervals (25, 50, 100, 200 and 275 ms) to elicit postsynaptic responses with amplitudes that were then compared. At an inter-pulse interval of 25ms, one-way ANOVA demonstrated that condition had a significant effect on paired-pulse facilitation, (p = 0.0178). Bonferroni post-hoc analysis showed that placebo-treated mice (EAE+PLAC; black star, dashed black line, n = 12 slices from 5 mice) had significantly greater paired-pulse facilitation (* p < 0.05) compared to healthy controls (NL; black square, solid black line, n = 6 slices from 3 mice). Estriol-treated mice (EAE+ESTRIOL; gray triangle, dashed gray line, n = 11 slices from 5 mice) also had significantly increased PPF compared to healthy controls. (D) Sample waveforms depict representative paired-pulse responses recorded from animals in each experimental condition at a 25ms inter-pulse interval (NL: black solid line; EAE+PLAC: dashed black line; and EAE+ESTRIOL: gray dashed line). (E) Neither the post-tetanic potentiation (PTP; the first response after high-frequency stimulation), nor the early phase of LTP were significantly affected by EAE, as analyzed by one-way ANOVAs. Furthermore, one-way ANOVA’s revealed that estriol treatment during EAE did not have an effect on PTP or eLTP.
Mentions: Excitatory synaptic transmission in the hippocampus during EAE has not been previously investigated. Synaptic transmission is dependent on functional and appropriately located synaptic protein families. Thus, basal synaptic transmission and paired-pulse facilitation were assessed using in vitro hippocampal slices. To determine if EAE caused an effect in excitatory synaptic transmission, input/output (IO) relationships were compared in hippocampal slices from the right hemispheres of mice in each experimental group. The amplitude of presynaptic fiber volleys and the slope of the EPSPs evoked by different intensities of Schaffer Collateral fiber stimulation were analyzed. Here, hippocampal slices from placebo-treated EAE mice had a significantly altered IO curve compared to those from healthy controls (Fig 2A). Hippocampal slices from EAE mice had FV Amps and fEPSP slopes that were both decreased by nearly 50%, suggesting that basal synaptic transmission was significantly impaired during EAE. When treated with estriol, however, hippocampal slices from mice with EAE displayed input/output relationships more similar to healthy controls, (Fig 2A-B). When maximal fEPSP slopes were compared across the three groups, there was a significant deficit in postsynaptic responses in slices from EAE mice compared to healthy controls, and this decrease in the postsynaptic response was prevented with estriol treatment (Fig 2B). Next, to examine short-term plasticity we measured paired-pulse facilitation (PPF) at Schaffer collateral fiber inputs onto CA1 pyramidal cells. Paired-pulse facilitation is inversely correlated with the probability of neurotransmitter release from presynaptic terminals, such that an increase in PPF is indicative of a decrease in transmitter release probability, whereas a decrease in PPF is indicative of an increase in transmitter release probability. Compared to healthy controls, placebo-treated EAE mice displayed significantly increased PPF at the shortest paired-pulse interval tested (Fig 2C-D). Interestingly, although PPF in slices from estriol-treated EAE mice was also significantly elevated compared to healthy controls, the increase tended to be lower than placebo-treated EAE mice at the same time interval (Fig 2C-D). Since hippocampal slices from placebo-treated EAE mice had significantly increased paired-pulse ratios, our results suggest that EAE caused a decrease in the probability of presynaptic neurotransmitter release. With estriol treatment during EAE there was a trend of partially restored release probability. To examine if EAE impaired synaptic plasticity, long-term potentiation (LTP) was induced with high frequency stimulation (HFS, 2x100Hz) in hippocampal slices from mice in each condition. Two separate components of LTP were analyzed: post-tetanic potentiation (PTP; the immediate potentiated response of each slice after HFS stimulation), and early phase LTP (eLTP; the average of the last five minutes of LTP in each slice). When compared across groups, PTP was not significantly affected by disease, or by estriol treatment during disease. eLTP was also unaffected by EAE or estriol treatment during EAE (Fig 2E).

Bottom Line: Neuropathological experiments demonstrated that there were decreased levels of pre- and post-synaptic proteins in the hippocampus, diffuse loss of myelin staining and atrophy of the pyramidal layers of hippocampal cornu ammonis 1 (CA1).Estriol treatment prevented decreases in excitatory synaptic transmission and lessened the effect of EAE on PPF.Cross-modality correlations revealed that deficits in excitatory synaptic transmission were significantly correlated with reductions in trans-synaptic protein binding partners known to modulate excitatory synaptic transmission.

View Article: PubMed Central - PubMed

Affiliation: Interdepartmental Program of Neuroscience, University of California, Los Angeles, Los Angeles, CA, USA.

ABSTRACT
Cognitive deficits occur in over half of multiple sclerosis patients, with hippocampal-dependent learning and memory commonly impaired. Data from in vivo MRI and post-mortem studies in MS indicate that the hippocampus is targeted. However, the relationship between structural pathology and dysfunction of the hippocampus in MS remains unclear. Hippocampal neuropathology also occurs in experimental autoimmune encephalomyelitis (EAE), the most commonly used animal model of MS. Although estrogen treatment of EAE has been shown to be anti-inflammatory and neuroprotective in the spinal cord, it is unknown if estrogen treatment may prevent hippocampal pathology and dysfunction. In the current study we examined excitatory synaptic transmission during EAE and focused on pathological changes in synaptic protein complexes known to orchestrate functional synaptic transmission in the hippocampus. We then determined if estriol, a candidate hormone treatment, was capable of preventing functional changes in synaptic transmission and corresponding hippocampal synaptic pathology. Electrophysiological studies revealed altered excitatory synaptic transmission and paired-pulse facilitation (PPF) during EAE. Neuropathological experiments demonstrated that there were decreased levels of pre- and post-synaptic proteins in the hippocampus, diffuse loss of myelin staining and atrophy of the pyramidal layers of hippocampal cornu ammonis 1 (CA1). Estriol treatment prevented decreases in excitatory synaptic transmission and lessened the effect of EAE on PPF. In addition, estriol treatment prevented several neuropathological alterations that occurred in the hippocampus during EAE. Cross-modality correlations revealed that deficits in excitatory synaptic transmission were significantly correlated with reductions in trans-synaptic protein binding partners known to modulate excitatory synaptic transmission. To our knowledge, this is the first report describing a functional correlate to hippocampal neuropathology in any MS model. Furthermore, a treatment was identified that prevented both deficits in synaptic function and hippocampal neuropathology.

Show MeSH
Related in: MedlinePlus