Limits...
Role of Liver X Receptor in AD Pathophysiology.

Sandoval-Hernández AG, Buitrago L, Moreno H, Cardona-Gómez GP, Arboleda G - PLoS ONE (2015)

Bottom Line: In the GW3965 treated 3xTg-AD mice we also observed reduction in astrogliosis and increased number of stem and proliferating cells in the subgranular zone of the dentate gyrus.The effect of GW3965 on synaptic function was protein synthesis dependent.Our findings identify alternative functional/molecular mechanisms by which LXR agonists may exert their potential benefits as a therapeutic strategy against AD.

View Article: PubMed Central - PubMed

Affiliation: Grupo de Muerte Celular, Instituto de Genética Universidad Nacional de Colombia, Bogotá, Colombia.

ABSTRACT
Alzheimer's disease (AD) is the major cause of dementia worldwide. The pharmacological activation of nuclear receptors (Liver X receptors: LXRs or Retinoid X receptors: RXR) has been shown to induce overexpression of the ATP-Binding Cassette A1 (ABCA1) and Apolipoprotein E (ApoE), changes that are associated with improvement in cognition and reduction of amyloid beta pathology in amyloidogenic AD mouse models (i.e. APP, PS1: 2tg-AD). Here we investigated whether treatment with a specific LXR agonist has a measurable impact on the cognitive impairment in an amyloid and Tau AD mouse model (3xTg-AD: 12-months-old; three months treatment). The data suggests that the LXR agonist GW3965 is associated with increased expression of ApoE and ABCA1 in the hippocampus and cerebral cortex without a detectable reduction of the amyloid load. We also report that most cells overexpressing ApoE (86±12%) are neurons localized in the granular cell layer of the hippocampus and entorhinal cortex. In the GW3965 treated 3xTg-AD mice we also observed reduction in astrogliosis and increased number of stem and proliferating cells in the subgranular zone of the dentate gyrus. Additionally, we show that GW3965 rescued hippocampus long term synaptic plasticity, which had been disrupted by oligomeric amyloid beta peptides. The effect of GW3965 on synaptic function was protein synthesis dependent. Our findings identify alternative functional/molecular mechanisms by which LXR agonists may exert their potential benefits as a therapeutic strategy against AD.

Show MeSH

Related in: MedlinePlus

GW3965 modulates CA1 fEPSPs and prevents synaptic plasticity impairment mediated by Aβ42-oligomers.(A) Representative examples of evoked fEPSPs changes upon 0,5 μM GW3965 application (Blue dots in B), red arrow before, blue arrow identify fEPSP after 75 min of drug application. (B) Shown are the time-courses of field CA1 fEPSPs evoked every 30 sec (y axis = changes in fEPSP slope over time) after the following treatments: 1) GW3965 (0.1 μM) [GW 0.1 μM—yellow dots]. 2) GW3965 (0.5 μM) [GW 0.5 μM, blue dots] 3) Slices incubated for 60 min with 25 μM anisomycin (ANI) and treated with GW3965 (0.5 μM) [GW+ANI—red dots] 4) Slices incubated for 60 min with 300 μM Cicloheximide (CHX) and treated with 0.5 μM GW3965 [GW+CHX—green dots] and 5) Vehicle treated slices [control—black dots]; n = 4 per group, 3–6 months of age. In all cases a 15 min baseline fEPSP was obtained before pharmacological manipulations and fEPSP slopes were normalized to the first response. (C) Representative traces from B at baseline and 75 min after each treatment, as indicated. (D) Long term potentiation (LTP) was elicited by one train of 100 stimuli at 100 Hz (arrow), fEPSPs were evoked every 30 sec. Shown are normalized fEPSP slope values, the data is presented as mean +/-SEM. Slices were incubated with oligomeric (oAβ42), scrambled (sAβ) or vehicle (control) during 40 min before recording and LTP was induced after 15 min of baseline. [Control-vehicle treated, n = 7- black dots; oAβ42 100nM, n = 4—gray dots; oAβ42 200 nM, n = 5—red dots and sAβ 200 nM, n = 6—purple dots]. (E) Shown are time-courses of fEPSPs responses after high frequency stimulation (HFS) as in D, in slices incubated with GW3965 0.1 μM for 60 min and 200 nM oAβ42 for 40 min [GW+ oAβ42, n = 5—blue dots]. For comparative purposes traces of slices incubated with 200 nM oAβ42 [red dots] and controls [black dots] from D were plotted. (F) Shown are traces of fEPSP responses in slices incubated with GW3965 0.1 μM for 60 min and 200 nM oAβ42 for 40 min. After 30 min of HFS, 25 μM anisomycin (ANI) was added to the bath [GW+ oAβ42+ANI], as indicated by line. (G) Bar graphs and two way ANOVAs analysis of fEPSPs changes from baseline at the 50–60 min interval after HFS in control, oAβ42 200 nM, [GW 0.1 μM + 200 nM oAβ42] and [GW + oAβ42 200nM + ANI 25 μM], ** denotes p<0.01.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4697813&req=5

pone.0145467.g009: GW3965 modulates CA1 fEPSPs and prevents synaptic plasticity impairment mediated by Aβ42-oligomers.(A) Representative examples of evoked fEPSPs changes upon 0,5 μM GW3965 application (Blue dots in B), red arrow before, blue arrow identify fEPSP after 75 min of drug application. (B) Shown are the time-courses of field CA1 fEPSPs evoked every 30 sec (y axis = changes in fEPSP slope over time) after the following treatments: 1) GW3965 (0.1 μM) [GW 0.1 μM—yellow dots]. 2) GW3965 (0.5 μM) [GW 0.5 μM, blue dots] 3) Slices incubated for 60 min with 25 μM anisomycin (ANI) and treated with GW3965 (0.5 μM) [GW+ANI—red dots] 4) Slices incubated for 60 min with 300 μM Cicloheximide (CHX) and treated with 0.5 μM GW3965 [GW+CHX—green dots] and 5) Vehicle treated slices [control—black dots]; n = 4 per group, 3–6 months of age. In all cases a 15 min baseline fEPSP was obtained before pharmacological manipulations and fEPSP slopes were normalized to the first response. (C) Representative traces from B at baseline and 75 min after each treatment, as indicated. (D) Long term potentiation (LTP) was elicited by one train of 100 stimuli at 100 Hz (arrow), fEPSPs were evoked every 30 sec. Shown are normalized fEPSP slope values, the data is presented as mean +/-SEM. Slices were incubated with oligomeric (oAβ42), scrambled (sAβ) or vehicle (control) during 40 min before recording and LTP was induced after 15 min of baseline. [Control-vehicle treated, n = 7- black dots; oAβ42 100nM, n = 4—gray dots; oAβ42 200 nM, n = 5—red dots and sAβ 200 nM, n = 6—purple dots]. (E) Shown are time-courses of fEPSPs responses after high frequency stimulation (HFS) as in D, in slices incubated with GW3965 0.1 μM for 60 min and 200 nM oAβ42 for 40 min [GW+ oAβ42, n = 5—blue dots]. For comparative purposes traces of slices incubated with 200 nM oAβ42 [red dots] and controls [black dots] from D were plotted. (F) Shown are traces of fEPSP responses in slices incubated with GW3965 0.1 μM for 60 min and 200 nM oAβ42 for 40 min. After 30 min of HFS, 25 μM anisomycin (ANI) was added to the bath [GW+ oAβ42+ANI], as indicated by line. (G) Bar graphs and two way ANOVAs analysis of fEPSPs changes from baseline at the 50–60 min interval after HFS in control, oAβ42 200 nM, [GW 0.1 μM + 200 nM oAβ42] and [GW + oAβ42 200nM + ANI 25 μM], ** denotes p<0.01.

Mentions: At the functional level, AD has been proposed to be characterized by early synaptic abnormalities [37]. AD mouse models display changes in synaptic structure, function and plasticity at a young age, [38,39]. It has also been hypothesized that synaptic dysfunction is a major cause of the cognitive deficits observed in AD [27,29,40]. Because GW3965 improved cognitions in an hippocampus-dependent paradigm such as MWM, we tested whether the drug had any effect on hippocampus synaptic transmission. Acute application of 0.5 μM GW3965, produced a gradual potentiation of single fEPSPs evoked from Schaeffer collateral to CA1 neurons every 30 sec (Fig 9A), which was prevented by the protein synthesis inhibitors anisomycin or cyclohexemide [41] (Fig 9B and 9C). Interestingly 0.1 μM GW3965 did not significantly affected fEPSP amplitude or slope (Fig 9B and 9C), while 1 μM was synaptotoxic (not shown). As it has been reported before [42] also in a dose dependent manner, bath application of oligomeric Aβ42 (oAβ42) peptides at 200 nM concentration in hippocampal brain slices of WT mice inhibited the induction of long term potentiation of the Schaeffer collateral-CA1 synapses, a proposed electrophysiological correlate to learning and memory (Fig 9D). No significant effect on LTP induction or maintenance was observed with 100 nM (oAβ42) peptides or scrambled control Aβ peptides (Fig 9D). Since for the LTP paradigm it is necessary to obtain a baseline fEPSP for 15 min (see methods for details) we used 0.1 μM GW3965 co-incubation with oAβ42, as shown in (Fig 9E and 9G), GW3965 at this concentration rescued LTP function. These experiments suggest that GW3965 at 0.1 μM independently of the acute effect on fEPSP amplitude or slope can rescue LTP. We also rule out that the slice incubation with 200 nM oAβ42 or 0.1 μM GW3965+ 200 nM oAβ42 had any effect on basal fEPSP amplitude or slope for the time of the recording (S4 File). We then asked whether the effect of GW3965 on LTP modulation by oAβ42 required protein synthesis. Since LTP induction has been shown to be protein synthesis dependent [43,44], anisomycin was used to block protein synthesis 30 min after LTP was induced, as shown in (Fig 9F). The effect of GW was not affected by this treatment. These experiments are consistent with the observations made by other groups, that LTP induction is protein synthesis dependent, but not its maintenance (for the time we studied here). The experiments also suggest that once the effect of GW3965 is established (during the incubation period) then it is independent of protein synthesis. This does not imply that protein synthesis is not required during its initial effect. [45–47].


Role of Liver X Receptor in AD Pathophysiology.

Sandoval-Hernández AG, Buitrago L, Moreno H, Cardona-Gómez GP, Arboleda G - PLoS ONE (2015)

GW3965 modulates CA1 fEPSPs and prevents synaptic plasticity impairment mediated by Aβ42-oligomers.(A) Representative examples of evoked fEPSPs changes upon 0,5 μM GW3965 application (Blue dots in B), red arrow before, blue arrow identify fEPSP after 75 min of drug application. (B) Shown are the time-courses of field CA1 fEPSPs evoked every 30 sec (y axis = changes in fEPSP slope over time) after the following treatments: 1) GW3965 (0.1 μM) [GW 0.1 μM—yellow dots]. 2) GW3965 (0.5 μM) [GW 0.5 μM, blue dots] 3) Slices incubated for 60 min with 25 μM anisomycin (ANI) and treated with GW3965 (0.5 μM) [GW+ANI—red dots] 4) Slices incubated for 60 min with 300 μM Cicloheximide (CHX) and treated with 0.5 μM GW3965 [GW+CHX—green dots] and 5) Vehicle treated slices [control—black dots]; n = 4 per group, 3–6 months of age. In all cases a 15 min baseline fEPSP was obtained before pharmacological manipulations and fEPSP slopes were normalized to the first response. (C) Representative traces from B at baseline and 75 min after each treatment, as indicated. (D) Long term potentiation (LTP) was elicited by one train of 100 stimuli at 100 Hz (arrow), fEPSPs were evoked every 30 sec. Shown are normalized fEPSP slope values, the data is presented as mean +/-SEM. Slices were incubated with oligomeric (oAβ42), scrambled (sAβ) or vehicle (control) during 40 min before recording and LTP was induced after 15 min of baseline. [Control-vehicle treated, n = 7- black dots; oAβ42 100nM, n = 4—gray dots; oAβ42 200 nM, n = 5—red dots and sAβ 200 nM, n = 6—purple dots]. (E) Shown are time-courses of fEPSPs responses after high frequency stimulation (HFS) as in D, in slices incubated with GW3965 0.1 μM for 60 min and 200 nM oAβ42 for 40 min [GW+ oAβ42, n = 5—blue dots]. For comparative purposes traces of slices incubated with 200 nM oAβ42 [red dots] and controls [black dots] from D were plotted. (F) Shown are traces of fEPSP responses in slices incubated with GW3965 0.1 μM for 60 min and 200 nM oAβ42 for 40 min. After 30 min of HFS, 25 μM anisomycin (ANI) was added to the bath [GW+ oAβ42+ANI], as indicated by line. (G) Bar graphs and two way ANOVAs analysis of fEPSPs changes from baseline at the 50–60 min interval after HFS in control, oAβ42 200 nM, [GW 0.1 μM + 200 nM oAβ42] and [GW + oAβ42 200nM + ANI 25 μM], ** denotes p<0.01.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4697813&req=5

pone.0145467.g009: GW3965 modulates CA1 fEPSPs and prevents synaptic plasticity impairment mediated by Aβ42-oligomers.(A) Representative examples of evoked fEPSPs changes upon 0,5 μM GW3965 application (Blue dots in B), red arrow before, blue arrow identify fEPSP after 75 min of drug application. (B) Shown are the time-courses of field CA1 fEPSPs evoked every 30 sec (y axis = changes in fEPSP slope over time) after the following treatments: 1) GW3965 (0.1 μM) [GW 0.1 μM—yellow dots]. 2) GW3965 (0.5 μM) [GW 0.5 μM, blue dots] 3) Slices incubated for 60 min with 25 μM anisomycin (ANI) and treated with GW3965 (0.5 μM) [GW+ANI—red dots] 4) Slices incubated for 60 min with 300 μM Cicloheximide (CHX) and treated with 0.5 μM GW3965 [GW+CHX—green dots] and 5) Vehicle treated slices [control—black dots]; n = 4 per group, 3–6 months of age. In all cases a 15 min baseline fEPSP was obtained before pharmacological manipulations and fEPSP slopes were normalized to the first response. (C) Representative traces from B at baseline and 75 min after each treatment, as indicated. (D) Long term potentiation (LTP) was elicited by one train of 100 stimuli at 100 Hz (arrow), fEPSPs were evoked every 30 sec. Shown are normalized fEPSP slope values, the data is presented as mean +/-SEM. Slices were incubated with oligomeric (oAβ42), scrambled (sAβ) or vehicle (control) during 40 min before recording and LTP was induced after 15 min of baseline. [Control-vehicle treated, n = 7- black dots; oAβ42 100nM, n = 4—gray dots; oAβ42 200 nM, n = 5—red dots and sAβ 200 nM, n = 6—purple dots]. (E) Shown are time-courses of fEPSPs responses after high frequency stimulation (HFS) as in D, in slices incubated with GW3965 0.1 μM for 60 min and 200 nM oAβ42 for 40 min [GW+ oAβ42, n = 5—blue dots]. For comparative purposes traces of slices incubated with 200 nM oAβ42 [red dots] and controls [black dots] from D were plotted. (F) Shown are traces of fEPSP responses in slices incubated with GW3965 0.1 μM for 60 min and 200 nM oAβ42 for 40 min. After 30 min of HFS, 25 μM anisomycin (ANI) was added to the bath [GW+ oAβ42+ANI], as indicated by line. (G) Bar graphs and two way ANOVAs analysis of fEPSPs changes from baseline at the 50–60 min interval after HFS in control, oAβ42 200 nM, [GW 0.1 μM + 200 nM oAβ42] and [GW + oAβ42 200nM + ANI 25 μM], ** denotes p<0.01.
Mentions: At the functional level, AD has been proposed to be characterized by early synaptic abnormalities [37]. AD mouse models display changes in synaptic structure, function and plasticity at a young age, [38,39]. It has also been hypothesized that synaptic dysfunction is a major cause of the cognitive deficits observed in AD [27,29,40]. Because GW3965 improved cognitions in an hippocampus-dependent paradigm such as MWM, we tested whether the drug had any effect on hippocampus synaptic transmission. Acute application of 0.5 μM GW3965, produced a gradual potentiation of single fEPSPs evoked from Schaeffer collateral to CA1 neurons every 30 sec (Fig 9A), which was prevented by the protein synthesis inhibitors anisomycin or cyclohexemide [41] (Fig 9B and 9C). Interestingly 0.1 μM GW3965 did not significantly affected fEPSP amplitude or slope (Fig 9B and 9C), while 1 μM was synaptotoxic (not shown). As it has been reported before [42] also in a dose dependent manner, bath application of oligomeric Aβ42 (oAβ42) peptides at 200 nM concentration in hippocampal brain slices of WT mice inhibited the induction of long term potentiation of the Schaeffer collateral-CA1 synapses, a proposed electrophysiological correlate to learning and memory (Fig 9D). No significant effect on LTP induction or maintenance was observed with 100 nM (oAβ42) peptides or scrambled control Aβ peptides (Fig 9D). Since for the LTP paradigm it is necessary to obtain a baseline fEPSP for 15 min (see methods for details) we used 0.1 μM GW3965 co-incubation with oAβ42, as shown in (Fig 9E and 9G), GW3965 at this concentration rescued LTP function. These experiments suggest that GW3965 at 0.1 μM independently of the acute effect on fEPSP amplitude or slope can rescue LTP. We also rule out that the slice incubation with 200 nM oAβ42 or 0.1 μM GW3965+ 200 nM oAβ42 had any effect on basal fEPSP amplitude or slope for the time of the recording (S4 File). We then asked whether the effect of GW3965 on LTP modulation by oAβ42 required protein synthesis. Since LTP induction has been shown to be protein synthesis dependent [43,44], anisomycin was used to block protein synthesis 30 min after LTP was induced, as shown in (Fig 9F). The effect of GW was not affected by this treatment. These experiments are consistent with the observations made by other groups, that LTP induction is protein synthesis dependent, but not its maintenance (for the time we studied here). The experiments also suggest that once the effect of GW3965 is established (during the incubation period) then it is independent of protein synthesis. This does not imply that protein synthesis is not required during its initial effect. [45–47].

Bottom Line: In the GW3965 treated 3xTg-AD mice we also observed reduction in astrogliosis and increased number of stem and proliferating cells in the subgranular zone of the dentate gyrus.The effect of GW3965 on synaptic function was protein synthesis dependent.Our findings identify alternative functional/molecular mechanisms by which LXR agonists may exert their potential benefits as a therapeutic strategy against AD.

View Article: PubMed Central - PubMed

Affiliation: Grupo de Muerte Celular, Instituto de Genética Universidad Nacional de Colombia, Bogotá, Colombia.

ABSTRACT
Alzheimer's disease (AD) is the major cause of dementia worldwide. The pharmacological activation of nuclear receptors (Liver X receptors: LXRs or Retinoid X receptors: RXR) has been shown to induce overexpression of the ATP-Binding Cassette A1 (ABCA1) and Apolipoprotein E (ApoE), changes that are associated with improvement in cognition and reduction of amyloid beta pathology in amyloidogenic AD mouse models (i.e. APP, PS1: 2tg-AD). Here we investigated whether treatment with a specific LXR agonist has a measurable impact on the cognitive impairment in an amyloid and Tau AD mouse model (3xTg-AD: 12-months-old; three months treatment). The data suggests that the LXR agonist GW3965 is associated with increased expression of ApoE and ABCA1 in the hippocampus and cerebral cortex without a detectable reduction of the amyloid load. We also report that most cells overexpressing ApoE (86±12%) are neurons localized in the granular cell layer of the hippocampus and entorhinal cortex. In the GW3965 treated 3xTg-AD mice we also observed reduction in astrogliosis and increased number of stem and proliferating cells in the subgranular zone of the dentate gyrus. Additionally, we show that GW3965 rescued hippocampus long term synaptic plasticity, which had been disrupted by oligomeric amyloid beta peptides. The effect of GW3965 on synaptic function was protein synthesis dependent. Our findings identify alternative functional/molecular mechanisms by which LXR agonists may exert their potential benefits as a therapeutic strategy against AD.

Show MeSH
Related in: MedlinePlus