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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

LXR agonists down-regulate expression of pro-inflammatory genes in microglia and astrocytes. Microglial cell line BV2 and astrocytes established from wild type (wt) and LXRdko (dko) mice were pre-treated with LXR ligand GW or vehicle for 18 h prior to LPS treatment (50 ng/ml). Control cells received vehicle only (veh). For GW treated cells (LPS+GW) the ligand was co-applied with LPS. Cells were harvested 24 hours after LPS administration and the mRNA expression measured by RT-QPCR. A: BV-2 cells. Values are fold of vehicle. *, p < 0.05 LPS+GW treated compared to LPS only treated cells. B and C: WT and dko astrocytes were treated with LPS and GW as in A and mRNA expression of iNOS (B) and IL-6 (C) measured by RT-QPCR. Values (means ± SEM) are fold of wild type, vehicle treated cells of at least two independent experiments. Note that unlike in WT cells, GW does not decrease the expression of iNOS and IL-6 in dko cells. (LPS+GW in dko versus LPS+GW in WT, p < 0.01). For all experiments, LXR ligands were applied at 5 μM concentration. Statistics were performed by two-tailed Student's t test.
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Figure 4: LXR agonists down-regulate expression of pro-inflammatory genes in microglia and astrocytes. Microglial cell line BV2 and astrocytes established from wild type (wt) and LXRdko (dko) mice were pre-treated with LXR ligand GW or vehicle for 18 h prior to LPS treatment (50 ng/ml). Control cells received vehicle only (veh). For GW treated cells (LPS+GW) the ligand was co-applied with LPS. Cells were harvested 24 hours after LPS administration and the mRNA expression measured by RT-QPCR. A: BV-2 cells. Values are fold of vehicle. *, p < 0.05 LPS+GW treated compared to LPS only treated cells. B and C: WT and dko astrocytes were treated with LPS and GW as in A and mRNA expression of iNOS (B) and IL-6 (C) measured by RT-QPCR. Values (means ± SEM) are fold of wild type, vehicle treated cells of at least two independent experiments. Note that unlike in WT cells, GW does not decrease the expression of iNOS and IL-6 in dko cells. (LPS+GW in dko versus LPS+GW in WT, p < 0.01). For all experiments, LXR ligands were applied at 5 μM concentration. Statistics were performed by two-tailed Student's t test.

Mentions: Our gene array data show that some genes related to immune response and inflammation, especially those related to the NF-κB cascade – such as Tirap and Serpina3n were down-regulated in APP23 mice after T0 treatment. In AD, CNS inflammation is a result of localized activation of microglia in areas surrounding the amyloid-β plaques and neurofibrillary tangles [32]. In addition, upon injury astrocytes assume an activated state associated with the release of inflammatory mediators [33]. It was shown that LXR ligands inhibit the expression of inflammatory mediators in peripheral peritoneal macrophages in response to lipopolysaccharide (LPS) stimulation [7]. Because the activation of microglia is believed to contribute to neurodegeneration by releasing proinflammatory and cytotoxic factors, including nitric oxide (NO) and IL-1β, we examined the anti-inflammatory effect of LXR ligands in vitro using microglia and astrocytes stimulated with LPS and Aβ. Fig. 4A demonstrates that GW-3965 (GW) (another widely used synthetic LXR agonist), used at 5 μM concentration down-regulated mRNA expression of the pro-inflammatory genes IL-1β, IL-6 and iNOS in the microglial cell line BV2. To examine if the decrease in mRNA expression is LXR dependent we used primary astrocytes derived from wild type and LXRdko mice. As visible from Fig. 4B and 4C, GW inhibited LPS induced up-regulation of iNOS and IL-6 mRNA in wild type but not in dko astrocytes confirming that the down-regulation was LXR dependent. Moreover, there was a statistically significant difference in the expression level of iNOS and IL-6 between GW-treated wild type and dko cells (p < 0.01; compare LPS+GW in wt versus LPS+GW in dko in Fig. 4B and 4C).


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)

LXR agonists down-regulate expression of pro-inflammatory genes in microglia and astrocytes. Microglial cell line BV2 and astrocytes established from wild type (wt) and LXRdko (dko) mice were pre-treated with LXR ligand GW or vehicle for 18 h prior to LPS treatment (50 ng/ml). Control cells received vehicle only (veh). For GW treated cells (LPS+GW) the ligand was co-applied with LPS. Cells were harvested 24 hours after LPS administration and the mRNA expression measured by RT-QPCR. A: BV-2 cells. Values are fold of vehicle. *, p < 0.05 LPS+GW treated compared to LPS only treated cells. B and C: WT and dko astrocytes were treated with LPS and GW as in A and mRNA expression of iNOS (B) and IL-6 (C) measured by RT-QPCR. Values (means ± SEM) are fold of wild type, vehicle treated cells of at least two independent experiments. Note that unlike in WT cells, GW does not decrease the expression of iNOS and IL-6 in dko cells. (LPS+GW in dko versus LPS+GW in WT, p < 0.01). For all experiments, LXR ligands were applied at 5 μM concentration. Statistics were performed by two-tailed Student's t test.
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Figure 4: LXR agonists down-regulate expression of pro-inflammatory genes in microglia and astrocytes. Microglial cell line BV2 and astrocytes established from wild type (wt) and LXRdko (dko) mice were pre-treated with LXR ligand GW or vehicle for 18 h prior to LPS treatment (50 ng/ml). Control cells received vehicle only (veh). For GW treated cells (LPS+GW) the ligand was co-applied with LPS. Cells were harvested 24 hours after LPS administration and the mRNA expression measured by RT-QPCR. A: BV-2 cells. Values are fold of vehicle. *, p < 0.05 LPS+GW treated compared to LPS only treated cells. B and C: WT and dko astrocytes were treated with LPS and GW as in A and mRNA expression of iNOS (B) and IL-6 (C) measured by RT-QPCR. Values (means ± SEM) are fold of wild type, vehicle treated cells of at least two independent experiments. Note that unlike in WT cells, GW does not decrease the expression of iNOS and IL-6 in dko cells. (LPS+GW in dko versus LPS+GW in WT, p < 0.01). For all experiments, LXR ligands were applied at 5 μM concentration. Statistics were performed by two-tailed Student's t test.
Mentions: Our gene array data show that some genes related to immune response and inflammation, especially those related to the NF-κB cascade – such as Tirap and Serpina3n were down-regulated in APP23 mice after T0 treatment. In AD, CNS inflammation is a result of localized activation of microglia in areas surrounding the amyloid-β plaques and neurofibrillary tangles [32]. In addition, upon injury astrocytes assume an activated state associated with the release of inflammatory mediators [33]. It was shown that LXR ligands inhibit the expression of inflammatory mediators in peripheral peritoneal macrophages in response to lipopolysaccharide (LPS) stimulation [7]. Because the activation of microglia is believed to contribute to neurodegeneration by releasing proinflammatory and cytotoxic factors, including nitric oxide (NO) and IL-1β, we examined the anti-inflammatory effect of LXR ligands in vitro using microglia and astrocytes stimulated with LPS and Aβ. Fig. 4A demonstrates that GW-3965 (GW) (another widely used synthetic LXR agonist), used at 5 μM concentration down-regulated mRNA expression of the pro-inflammatory genes IL-1β, IL-6 and iNOS in the microglial cell line BV2. To examine if the decrease in mRNA expression is LXR dependent we used primary astrocytes derived from wild type and LXRdko mice. As visible from Fig. 4B and 4C, GW inhibited LPS induced up-regulation of iNOS and IL-6 mRNA in wild type but not in dko astrocytes confirming that the down-regulation was LXR dependent. Moreover, there was a statistically significant difference in the expression level of iNOS and IL-6 between GW-treated wild type and dko cells (p < 0.01; compare LPS+GW in wt versus LPS+GW in dko in Fig. 4B and 4C).

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