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Inhibition of soluble tumor necrosis factor ameliorates synaptic alterations and Ca2+ dysregulation in aged rats.

Sama DM, Mohmmad Abdul H, Furman JL, Artiushin IA, Szymkowski DE, Scheff SW, Norris CM - PLoS ONE (2012)

Bottom Line: To determine if altered TNF/TNFR1 interactions contribute to key brain aging biomarkers, aged rats received chronic (4-6 week) intracranial infusions of XPro1595: a soluble dominant negative TNF that preferentially inhibits TNFR1 signaling.Aged rats treated with XPro1595 showed improved Morris Water Maze performance, reduced microglial activation, reduced susceptibility to hippocampal long-term depression, increased protein levels for the GluR1 type glutamate receptor, and lower L-type voltage sensitive Ca(2+) channel (VSCC) activity in hippocampal CA1 neurons.The results suggest that diverse functional changes associated with brain aging may arise, in part, from selective alterations in TNF signaling.

View Article: PubMed Central - PubMed

Affiliation: Graduate Center for Gerontology, University of Kentucky, Lexington, Kentucky, United States of America.

ABSTRACT
The role of tumor necrosis factor α (TNF) in neural function has been investigated extensively in several neurodegenerative conditions, but rarely in brain aging, where cognitive and physiologic changes are milder and more variable. Here, we show that protein levels for TNF receptor 1 (TNFR1) are significantly elevated in the hippocampus relative to TNF receptor 2 (TNFR2) in aged (22 months) but not young adult (6 months) Fischer 344 rats. To determine if altered TNF/TNFR1 interactions contribute to key brain aging biomarkers, aged rats received chronic (4-6 week) intracranial infusions of XPro1595: a soluble dominant negative TNF that preferentially inhibits TNFR1 signaling. Aged rats treated with XPro1595 showed improved Morris Water Maze performance, reduced microglial activation, reduced susceptibility to hippocampal long-term depression, increased protein levels for the GluR1 type glutamate receptor, and lower L-type voltage sensitive Ca(2+) channel (VSCC) activity in hippocampal CA1 neurons. The results suggest that diverse functional changes associated with brain aging may arise, in part, from selective alterations in TNF signaling.

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XPro1595 reduces L-VSCC activity in CA1 neurons of aged rats. A, Left panel, Cartoon illustration of a partially dissociated hippocampal slice in which CA1 is “unzipped” along stratum pyramidale to expose CA1 neurons for patch clamp recording. Right panel, Photomicrograph showing a glass micropipette tip patched onto a CA1 pyramidal neuron in an “unzipped” slice. B, Three representative L-VSCC current traces and the average ensemble current (bottom trace) in cell attached patches from aged rats treated for six weeks (intrahippocampal delivery) with vehicle or XPro1595 (0.08 mg/kg/day). Traces were taken from 45–50 consecutive step depolarizations (150 ms duration) from −70 to +10 mV. C, Mean ± SEM current (I) densities (pA/μm2) for each treatment group are shown. XPro1595 significantly reduced VSCC I density nearly three-fold (* p<0.05). D–E, Representative Western blots (D) and mean+SEM protein levels (E) for the major pore-forming L-VSCC subunits (CaV1.2 and CaV1.3) from hippocampal membrane fractions. The Na/K-ATPase served as loading control. XPro1595 did not significantly alter either CaV1.2 (p = 0.17) or CaV1.3 (p = 0.63) levels.
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pone-0038170-g005: XPro1595 reduces L-VSCC activity in CA1 neurons of aged rats. A, Left panel, Cartoon illustration of a partially dissociated hippocampal slice in which CA1 is “unzipped” along stratum pyramidale to expose CA1 neurons for patch clamp recording. Right panel, Photomicrograph showing a glass micropipette tip patched onto a CA1 pyramidal neuron in an “unzipped” slice. B, Three representative L-VSCC current traces and the average ensemble current (bottom trace) in cell attached patches from aged rats treated for six weeks (intrahippocampal delivery) with vehicle or XPro1595 (0.08 mg/kg/day). Traces were taken from 45–50 consecutive step depolarizations (150 ms duration) from −70 to +10 mV. C, Mean ± SEM current (I) densities (pA/μm2) for each treatment group are shown. XPro1595 significantly reduced VSCC I density nearly three-fold (* p<0.05). D–E, Representative Western blots (D) and mean+SEM protein levels (E) for the major pore-forming L-VSCC subunits (CaV1.2 and CaV1.3) from hippocampal membrane fractions. The Na/K-ATPase served as loading control. XPro1595 did not significantly alter either CaV1.2 (p = 0.17) or CaV1.3 (p = 0.63) levels.

Mentions: Age-related alterations in short and long-lasting forms of synaptic plasticity appear to be strongly linked to the activity of L-VSCCs [37], [41], which is increased in CA1 pyramidal neurons during aging [13], [25], [42], [43]. We previously reported that blockade of L-VSCCs prevents the induction of LTD in aged animals [37], much like what is seen with TNF blockade (Figure 3D). Interestingly, TNF has been shown to potentiate L-VSCC activity in neuronal cultures [11], suggesting that blockade of TNF/TNFR1 signaling may reduce L-VSCC activity in aged rats. To test this possibility, an additional cohort of aged rats received intrahippocampal perfusions of vehicle (n = 12) or XPro1595 (0.08 mg/kg/day; n = 14) across six weeks, followed by extraction of hippocampi for preparation of “zipper slices” as described [13], [25]. Cleanly exposed CA1 neurons (Figure 5A) were sealed with a glass micropipette containing recording solution and the potent L-VSCC agonist Bay-K 8644 to maximize the probability of L-VSCC openings. L-VSCC activity was recorded in cell-attached patch mode from a total of 53 cells (25 vehicle, 28 XPro1595). Maximal L-VSCC activity was elicited by step depolarizations from −70 to +10 mV, and averaged across 45–50 sweeps. Maximal peak L-VSCC current densities (pA/μm2 of membrane) in two or more patches from the same rat were averaged to produce a single data point for each rat. Average L-VSCC current (I) density (pA/μM2) was then compared across groups using an unpaired t-test. As shown in Figure 5C, XPro1595-treated aged rats exhibited a 3-fold decrease in cell-attached L-VSCC current density (p<0.05), suggesting that TNF/TNFR1 signaling potentiates, or is permissive for L-VSCC activity in aged rats.


Inhibition of soluble tumor necrosis factor ameliorates synaptic alterations and Ca2+ dysregulation in aged rats.

Sama DM, Mohmmad Abdul H, Furman JL, Artiushin IA, Szymkowski DE, Scheff SW, Norris CM - PLoS ONE (2012)

XPro1595 reduces L-VSCC activity in CA1 neurons of aged rats. A, Left panel, Cartoon illustration of a partially dissociated hippocampal slice in which CA1 is “unzipped” along stratum pyramidale to expose CA1 neurons for patch clamp recording. Right panel, Photomicrograph showing a glass micropipette tip patched onto a CA1 pyramidal neuron in an “unzipped” slice. B, Three representative L-VSCC current traces and the average ensemble current (bottom trace) in cell attached patches from aged rats treated for six weeks (intrahippocampal delivery) with vehicle or XPro1595 (0.08 mg/kg/day). Traces were taken from 45–50 consecutive step depolarizations (150 ms duration) from −70 to +10 mV. C, Mean ± SEM current (I) densities (pA/μm2) for each treatment group are shown. XPro1595 significantly reduced VSCC I density nearly three-fold (* p<0.05). D–E, Representative Western blots (D) and mean+SEM protein levels (E) for the major pore-forming L-VSCC subunits (CaV1.2 and CaV1.3) from hippocampal membrane fractions. The Na/K-ATPase served as loading control. XPro1595 did not significantly alter either CaV1.2 (p = 0.17) or CaV1.3 (p = 0.63) levels.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3362564&req=5

pone-0038170-g005: XPro1595 reduces L-VSCC activity in CA1 neurons of aged rats. A, Left panel, Cartoon illustration of a partially dissociated hippocampal slice in which CA1 is “unzipped” along stratum pyramidale to expose CA1 neurons for patch clamp recording. Right panel, Photomicrograph showing a glass micropipette tip patched onto a CA1 pyramidal neuron in an “unzipped” slice. B, Three representative L-VSCC current traces and the average ensemble current (bottom trace) in cell attached patches from aged rats treated for six weeks (intrahippocampal delivery) with vehicle or XPro1595 (0.08 mg/kg/day). Traces were taken from 45–50 consecutive step depolarizations (150 ms duration) from −70 to +10 mV. C, Mean ± SEM current (I) densities (pA/μm2) for each treatment group are shown. XPro1595 significantly reduced VSCC I density nearly three-fold (* p<0.05). D–E, Representative Western blots (D) and mean+SEM protein levels (E) for the major pore-forming L-VSCC subunits (CaV1.2 and CaV1.3) from hippocampal membrane fractions. The Na/K-ATPase served as loading control. XPro1595 did not significantly alter either CaV1.2 (p = 0.17) or CaV1.3 (p = 0.63) levels.
Mentions: Age-related alterations in short and long-lasting forms of synaptic plasticity appear to be strongly linked to the activity of L-VSCCs [37], [41], which is increased in CA1 pyramidal neurons during aging [13], [25], [42], [43]. We previously reported that blockade of L-VSCCs prevents the induction of LTD in aged animals [37], much like what is seen with TNF blockade (Figure 3D). Interestingly, TNF has been shown to potentiate L-VSCC activity in neuronal cultures [11], suggesting that blockade of TNF/TNFR1 signaling may reduce L-VSCC activity in aged rats. To test this possibility, an additional cohort of aged rats received intrahippocampal perfusions of vehicle (n = 12) or XPro1595 (0.08 mg/kg/day; n = 14) across six weeks, followed by extraction of hippocampi for preparation of “zipper slices” as described [13], [25]. Cleanly exposed CA1 neurons (Figure 5A) were sealed with a glass micropipette containing recording solution and the potent L-VSCC agonist Bay-K 8644 to maximize the probability of L-VSCC openings. L-VSCC activity was recorded in cell-attached patch mode from a total of 53 cells (25 vehicle, 28 XPro1595). Maximal L-VSCC activity was elicited by step depolarizations from −70 to +10 mV, and averaged across 45–50 sweeps. Maximal peak L-VSCC current densities (pA/μm2 of membrane) in two or more patches from the same rat were averaged to produce a single data point for each rat. Average L-VSCC current (I) density (pA/μM2) was then compared across groups using an unpaired t-test. As shown in Figure 5C, XPro1595-treated aged rats exhibited a 3-fold decrease in cell-attached L-VSCC current density (p<0.05), suggesting that TNF/TNFR1 signaling potentiates, or is permissive for L-VSCC activity in aged rats.

Bottom Line: To determine if altered TNF/TNFR1 interactions contribute to key brain aging biomarkers, aged rats received chronic (4-6 week) intracranial infusions of XPro1595: a soluble dominant negative TNF that preferentially inhibits TNFR1 signaling.Aged rats treated with XPro1595 showed improved Morris Water Maze performance, reduced microglial activation, reduced susceptibility to hippocampal long-term depression, increased protein levels for the GluR1 type glutamate receptor, and lower L-type voltage sensitive Ca(2+) channel (VSCC) activity in hippocampal CA1 neurons.The results suggest that diverse functional changes associated with brain aging may arise, in part, from selective alterations in TNF signaling.

View Article: PubMed Central - PubMed

Affiliation: Graduate Center for Gerontology, University of Kentucky, Lexington, Kentucky, United States of America.

ABSTRACT
The role of tumor necrosis factor α (TNF) in neural function has been investigated extensively in several neurodegenerative conditions, but rarely in brain aging, where cognitive and physiologic changes are milder and more variable. Here, we show that protein levels for TNF receptor 1 (TNFR1) are significantly elevated in the hippocampus relative to TNF receptor 2 (TNFR2) in aged (22 months) but not young adult (6 months) Fischer 344 rats. To determine if altered TNF/TNFR1 interactions contribute to key brain aging biomarkers, aged rats received chronic (4-6 week) intracranial infusions of XPro1595: a soluble dominant negative TNF that preferentially inhibits TNFR1 signaling. Aged rats treated with XPro1595 showed improved Morris Water Maze performance, reduced microglial activation, reduced susceptibility to hippocampal long-term depression, increased protein levels for the GluR1 type glutamate receptor, and lower L-type voltage sensitive Ca(2+) channel (VSCC) activity in hippocampal CA1 neurons. The results suggest that diverse functional changes associated with brain aging may arise, in part, from selective alterations in TNF signaling.

Show MeSH
Related in: MedlinePlus