Limits...
Expression profiling in APP23 mouse brain: inhibition of Abeta amyloidosis and inflammation in response to LXR agonist treatment.

Lefterov I, Bookout A, Wang Z, Staufenbiel M, Mangelsdorf D, Koldamova R - Mol Neurodegener (2007)

Bottom Line: Additional treatment experiments demonstrated an increase of soluble apolipoproteins E and A-I and a decrease of insoluble Abeta.The results show that LXR agonists could alleviate AD pathology by acting on amyloid deposition and brain inflammation.An increased understanding of the LXR controlled regulation of Abeta aggregation and clearance systems will lead to the development of more specific and powerful agonists targeting LXR for the treatment of AD.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15219, USA. iliyal@pitt.edu.

ABSTRACT

Background: Recent studies demonstrate that in addition to its modulatory effect on APP processing, in vivo application of Liver X Receptor agonist T0901317 (T0) to APP transgenic and non-transgenic mice decreases the level of Abeta42. Moreover, in young Tg2576 mice T0 completely reversed contextual memory deficits. Compared to other tissues, the regulatory functions of LXRs in brain remain largely unexplored and our knowledge so far is limited to the cholesterol transporters and apoE. In this study we applied T0 to APP23 mice for various times and examined gene and protein expression. We also performed a series of experiments with primary brain cells derived from wild type and LXR knockout mice subjected to various LXR agonist treatments and inflammatory stimuli.

Results: We demonstrate an upregulation of genes related to lipid metabolism/transport, metabolism of xenobiotics and detoxification. Downregulated genes are involved in immune response and inflammation, cell death and apoptosis. Additional treatment experiments demonstrated an increase of soluble apolipoproteins E and A-I and a decrease of insoluble Abeta. In primary LXRwt but not in LXRalpha-/-beta-/- microglia and astrocytes LXR agonists suppressed the inflammatory response induced by LPS or fibrillar Abeta.

Conclusion: The results show that LXR agonists could alleviate AD pathology by acting on amyloid deposition and brain inflammation. An increased understanding of the LXR controlled regulation of Abeta aggregation and clearance systems will lead to the development of more specific and powerful agonists targeting LXR for the treatment of AD.

No MeSH data available.


Related in: MedlinePlus

Transcriptional regulation of apoE and ABCA1 expression by LXR in brain, glia and neurons. A: 7-month old APP23 mice were treated with 50 mg/kg T0 for 24 hours. Total RNA was extracted separately from cortices and hippocampi and mRNA expression of ABCA1, apoE and ABCG1 were determined by RT-QPCR; h-v, (black bars) – vehicle treatment, hippocampi; h-T0, (white bars) – T0 treatment, hippocampi, c-v (grey bars), vehicle treatment, cortex; c-T0 (hatched bars), T0 treatment, cortex. B, C and D: Primary neurons, astrocytes and microglia were established from wild type (wt) and LXRα-/-β-/- double knockout mice (dko). Cells were treated with 10 μM T0 for 24 hours and mRNA expression of ABCA1 (B) and apoE (D) measured by RT-QPCR. Values are means ± SEM and represent fold of vehicle for the corresponding genotype. C: ABCA1 protein level in wild type (wt) and LXRα-/-β-/- (dko) neurons was determined by WB. The level of ABCA1 was normalized to the level of GAPDH, and presented (means ± SEM) as fold of vehicle of the corresponding genotype in the graph bellow.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2214725&req=5

Figure 3: Transcriptional regulation of apoE and ABCA1 expression by LXR in brain, glia and neurons. A: 7-month old APP23 mice were treated with 50 mg/kg T0 for 24 hours. Total RNA was extracted separately from cortices and hippocampi and mRNA expression of ABCA1, apoE and ABCG1 were determined by RT-QPCR; h-v, (black bars) – vehicle treatment, hippocampi; h-T0, (white bars) – T0 treatment, hippocampi, c-v (grey bars), vehicle treatment, cortex; c-T0 (hatched bars), T0 treatment, cortex. B, C and D: Primary neurons, astrocytes and microglia were established from wild type (wt) and LXRα-/-β-/- double knockout mice (dko). Cells were treated with 10 μM T0 for 24 hours and mRNA expression of ABCA1 (B) and apoE (D) measured by RT-QPCR. Values are means ± SEM and represent fold of vehicle for the corresponding genotype. C: ABCA1 protein level in wild type (wt) and LXRα-/-β-/- (dko) neurons was determined by WB. The level of ABCA1 was normalized to the level of GAPDH, and presented (means ± SEM) as fold of vehicle of the corresponding genotype in the graph bellow.

Mentions: We interpret the increased level of brain apolipoproteins after T0 treatment as a combined effect of increased apoE and ABCA1 mRNA levels. The up-regulation of ABCA1 increases cholesterol efflux and consequently the lipidation of brain apoE and apoA-I, thus decreasing their catabolism. We were surprised, however, that the apoE mRNA up-regulation in the brain was rather small, even though statistically significant (Fig. 2A). One reason for this might be that LXR regulation is different in different brain areas. To test this hypothesis we treated 7 month old APP23 mice with T0 at a dose of 50 mg/kg body weight for 24 hours and examined the expression of several LXR target genes separately in the cortex and hippocampus (Fig. 3A). We specifically chose genes that have been previously implicated in the regulation of cholesterol efflux in brain – ABCA1, apoE and ABCG1. As shown in Fig. 3A, whereas T0 increased ABCA1 mRNA similarly in the cortex and hippocampus, apoE mRNA up-regulation was higher in the cortex than in the hippocampus. We did not find a corresponding change in apoE protein level in T0 treated mice as compared to vehicle treated ones (data not shown). Another reason for the smaller increase of apoE mRNA after T0 treatment might be that LXR ligands effectively up-regulate apoE mRNA expression only in a subset of brain cells. To examine this we treated primary astrocytic, microglial and neuronal cultures with T0 and examined ABCA1 and apoE mRNA expression. Fig. 3B shows that T0 (used at 10 μM concentration in this experiment) up-regulates ABCA1 expression in all three cell types in a similar way. To confirm that the observed effect is LXR dependent, we performed a series of experiments with wild type cells and cells obtained from LXRα-/-β-/- double knockout (LXRdko) mice. We found that ABCA1 mRNA and protein levels were increased only in wild type cells (Fig. 3B and 3C, wt versus dko) confirming that the effect is LXR specific. In contrast, the LXR agonist up-regulated apoE mRNA expression only in astrocytes and microglia but not in neurons (Fig. 3D). Fig. 3D demonstrates that T0 increased apoE mRNA only in wild type astrocytes, confirming that apoE up-regulation was also LXR dependent. Therefore, whereas LXRs regulate ABCA1 in all brain cell types, their effect on apoE is cell-type specific which could explain the relatively small increase of apoE mRNA isolated from a total brain fraction.


Expression profiling in APP23 mouse brain: inhibition of Abeta amyloidosis and inflammation in response to LXR agonist treatment.

Lefterov I, Bookout A, Wang Z, Staufenbiel M, Mangelsdorf D, Koldamova R - Mol Neurodegener (2007)

Transcriptional regulation of apoE and ABCA1 expression by LXR in brain, glia and neurons. A: 7-month old APP23 mice were treated with 50 mg/kg T0 for 24 hours. Total RNA was extracted separately from cortices and hippocampi and mRNA expression of ABCA1, apoE and ABCG1 were determined by RT-QPCR; h-v, (black bars) – vehicle treatment, hippocampi; h-T0, (white bars) – T0 treatment, hippocampi, c-v (grey bars), vehicle treatment, cortex; c-T0 (hatched bars), T0 treatment, cortex. B, C and D: Primary neurons, astrocytes and microglia were established from wild type (wt) and LXRα-/-β-/- double knockout mice (dko). Cells were treated with 10 μM T0 for 24 hours and mRNA expression of ABCA1 (B) and apoE (D) measured by RT-QPCR. Values are means ± SEM and represent fold of vehicle for the corresponding genotype. C: ABCA1 protein level in wild type (wt) and LXRα-/-β-/- (dko) neurons was determined by WB. The level of ABCA1 was normalized to the level of GAPDH, and presented (means ± SEM) as fold of vehicle of the corresponding genotype in the graph bellow.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2214725&req=5

Figure 3: Transcriptional regulation of apoE and ABCA1 expression by LXR in brain, glia and neurons. A: 7-month old APP23 mice were treated with 50 mg/kg T0 for 24 hours. Total RNA was extracted separately from cortices and hippocampi and mRNA expression of ABCA1, apoE and ABCG1 were determined by RT-QPCR; h-v, (black bars) – vehicle treatment, hippocampi; h-T0, (white bars) – T0 treatment, hippocampi, c-v (grey bars), vehicle treatment, cortex; c-T0 (hatched bars), T0 treatment, cortex. B, C and D: Primary neurons, astrocytes and microglia were established from wild type (wt) and LXRα-/-β-/- double knockout mice (dko). Cells were treated with 10 μM T0 for 24 hours and mRNA expression of ABCA1 (B) and apoE (D) measured by RT-QPCR. Values are means ± SEM and represent fold of vehicle for the corresponding genotype. C: ABCA1 protein level in wild type (wt) and LXRα-/-β-/- (dko) neurons was determined by WB. The level of ABCA1 was normalized to the level of GAPDH, and presented (means ± SEM) as fold of vehicle of the corresponding genotype in the graph bellow.
Mentions: We interpret the increased level of brain apolipoproteins after T0 treatment as a combined effect of increased apoE and ABCA1 mRNA levels. The up-regulation of ABCA1 increases cholesterol efflux and consequently the lipidation of brain apoE and apoA-I, thus decreasing their catabolism. We were surprised, however, that the apoE mRNA up-regulation in the brain was rather small, even though statistically significant (Fig. 2A). One reason for this might be that LXR regulation is different in different brain areas. To test this hypothesis we treated 7 month old APP23 mice with T0 at a dose of 50 mg/kg body weight for 24 hours and examined the expression of several LXR target genes separately in the cortex and hippocampus (Fig. 3A). We specifically chose genes that have been previously implicated in the regulation of cholesterol efflux in brain – ABCA1, apoE and ABCG1. As shown in Fig. 3A, whereas T0 increased ABCA1 mRNA similarly in the cortex and hippocampus, apoE mRNA up-regulation was higher in the cortex than in the hippocampus. We did not find a corresponding change in apoE protein level in T0 treated mice as compared to vehicle treated ones (data not shown). Another reason for the smaller increase of apoE mRNA after T0 treatment might be that LXR ligands effectively up-regulate apoE mRNA expression only in a subset of brain cells. To examine this we treated primary astrocytic, microglial and neuronal cultures with T0 and examined ABCA1 and apoE mRNA expression. Fig. 3B shows that T0 (used at 10 μM concentration in this experiment) up-regulates ABCA1 expression in all three cell types in a similar way. To confirm that the observed effect is LXR dependent, we performed a series of experiments with wild type cells and cells obtained from LXRα-/-β-/- double knockout (LXRdko) mice. We found that ABCA1 mRNA and protein levels were increased only in wild type cells (Fig. 3B and 3C, wt versus dko) confirming that the effect is LXR specific. In contrast, the LXR agonist up-regulated apoE mRNA expression only in astrocytes and microglia but not in neurons (Fig. 3D). Fig. 3D demonstrates that T0 increased apoE mRNA only in wild type astrocytes, confirming that apoE up-regulation was also LXR dependent. Therefore, whereas LXRs regulate ABCA1 in all brain cell types, their effect on apoE is cell-type specific which could explain the relatively small increase of apoE mRNA isolated from a total brain fraction.

Bottom Line: Additional treatment experiments demonstrated an increase of soluble apolipoproteins E and A-I and a decrease of insoluble Abeta.The results show that LXR agonists could alleviate AD pathology by acting on amyloid deposition and brain inflammation.An increased understanding of the LXR controlled regulation of Abeta aggregation and clearance systems will lead to the development of more specific and powerful agonists targeting LXR for the treatment of AD.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15219, USA. iliyal@pitt.edu.

ABSTRACT

Background: Recent studies demonstrate that in addition to its modulatory effect on APP processing, in vivo application of Liver X Receptor agonist T0901317 (T0) to APP transgenic and non-transgenic mice decreases the level of Abeta42. Moreover, in young Tg2576 mice T0 completely reversed contextual memory deficits. Compared to other tissues, the regulatory functions of LXRs in brain remain largely unexplored and our knowledge so far is limited to the cholesterol transporters and apoE. In this study we applied T0 to APP23 mice for various times and examined gene and protein expression. We also performed a series of experiments with primary brain cells derived from wild type and LXR knockout mice subjected to various LXR agonist treatments and inflammatory stimuli.

Results: We demonstrate an upregulation of genes related to lipid metabolism/transport, metabolism of xenobiotics and detoxification. Downregulated genes are involved in immune response and inflammation, cell death and apoptosis. Additional treatment experiments demonstrated an increase of soluble apolipoproteins E and A-I and a decrease of insoluble Abeta. In primary LXRwt but not in LXRalpha-/-beta-/- microglia and astrocytes LXR agonists suppressed the inflammatory response induced by LPS or fibrillar Abeta.

Conclusion: The results show that LXR agonists could alleviate AD pathology by acting on amyloid deposition and brain inflammation. An increased understanding of the LXR controlled regulation of Abeta aggregation and clearance systems will lead to the development of more specific and powerful agonists targeting LXR for the treatment of AD.

No MeSH data available.


Related in: MedlinePlus