Limits...
Colony-stimulating factor 1 receptor inhibition prevents microglial plaque association and improves cognition in 3xTg-AD mice.

Dagher NN, Najafi AR, Kayala KM, Elmore MR, White TE, Medeiros R, West BL, Green KN - J Neuroinflammation (2015)

Bottom Line: Microglia are dependent upon colony-stimulating factor 1 receptor (CSF1R) signaling for their survival in the adult brain, with administration of the dual CSF1R/c-kit inhibitor PLX3397 leading to the near-complete elimination of all microglia brainwide.Aβ levels and plaque loads were not altered, but microglia in treated mice no longer associated with plaques, revealing a role for the CSF1R in the microglial reaction to plaques, as well as in mediating cognitive deficits.We find that inhibition of CSF1R alone is sufficient to eliminate microglia and that sustained microglial elimination is concentration-dependent.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology and Behavior, Institute for Memory Impairments and Neurological Disorders, University of California, 3208 Biological Sciences III, Irvine, CA, 92697-4545, USA. ndagher53@gmail.com.

ABSTRACT

Background: Microglia are dependent upon colony-stimulating factor 1 receptor (CSF1R) signaling for their survival in the adult brain, with administration of the dual CSF1R/c-kit inhibitor PLX3397 leading to the near-complete elimination of all microglia brainwide. Here, we determined the dose-dependent effects of a specific CSF1R inhibitor (PLX5622) on microglia in both wild-type and the 3xTg-AD mouse model of Alzheimer's disease.

Methods: Wild-type mice were treated with PLX5622 for up to 21 days, and the effects on microglial numbers were assessed. 3xTg-AD mice were treated with PLX5622 for 6 or 12 weeks and effects on microglial numbers and pathology subsequently assessed.

Results: High doses of CSF1R inhibitor eliminate most microglia from the brain, but a 75% lower-dose results in sustained elimination of ~30 of microglia in both wild-type and 3xTg-AD mice. No behavioral or cognitive deficits were found in mice either depleted of microglia or treated with lower CSF1R inhibitor concentrations. Aged 3xTg-AD mice treated for 6 or 12 weeks with lower levels of PLX5622 resulted in improved learning and memory. Aβ levels and plaque loads were not altered, but microglia in treated mice no longer associated with plaques, revealing a role for the CSF1R in the microglial reaction to plaques, as well as in mediating cognitive deficits.

Conclusions: We find that inhibition of CSF1R alone is sufficient to eliminate microglia and that sustained microglial elimination is concentration-dependent. Inhibition of the CSF1R at lower levels in 3xTg-AD mice prevents microglial association with plaques and improves cognition.

No MeSH data available.


Related in: MedlinePlus

Chronic lower-dose CSF1R inhibition prevents microglia associating with plaques. Immunofluorescent staining was performed on 3 months treated and control 3xTg-AD mice for 6E10, which recognizes Aβ plaques and IBA1. a–f Representative 10× images are shown of control and treated mice. g–l Representative 63× images are shown of control and treated mice, centered on an area dense with plaques. m Quantification of the number of microglia associated with a plaque and normalized to plaque diameter revealed a 70 % decrease in treated animals as compared to untreated animals. *Indicates significance (p < 0.05) by unpaired Students t test. Error bars indicate SEM
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4522109&req=5

Fig7: Chronic lower-dose CSF1R inhibition prevents microglia associating with plaques. Immunofluorescent staining was performed on 3 months treated and control 3xTg-AD mice for 6E10, which recognizes Aβ plaques and IBA1. a–f Representative 10× images are shown of control and treated mice. g–l Representative 63× images are shown of control and treated mice, centered on an area dense with plaques. m Quantification of the number of microglia associated with a plaque and normalized to plaque diameter revealed a 70 % decrease in treated animals as compared to untreated animals. *Indicates significance (p < 0.05) by unpaired Students t test. Error bars indicate SEM

Mentions: However, stark differences were seen in the microglia that are associated with plaques—in vehicle-treated animals, microglia were densely packed around plaques and displayed an activated morphology (Fig. 7a–c). Mice treated with PLX5622 showed comparable plaque load, but microglia were not associated with plaques to the same extent (Fig. 7d–f), suggesting that low doses of PLX5622 do not fully eliminate microglia but alter their response to inflammatory stimuli, such as plaques. Indeed, closeup z-stacks showed a clear association of microglia with plaques in untreated 3xTg-AD mice (Fig. 7g–i) but a lack of association in PLX5622-treated mice (Fig. 7j–l). Quantification of the number of microglia associated with a plaque and normalized to plaque diameter revealed a 70 % reduction in microglia associated with plaques. To explore the possibility that this lower dose of CSF1R inhibitor could be selectively killing plaque-associated microglia, we performed immunostaining for active caspase-3, as an indicator of cell death. However, no increased microglial cell death was seen in PLX5622-treated mice in areas adjacent to plaques (data not shown). This suggests that the reduction in the number of microglia associated with plaques is due to altered microglial behavior, although it is possible that susceptible plaque-associated microglia are already dead and no further cells are going through the cell death process at this point.Fig. 7


Colony-stimulating factor 1 receptor inhibition prevents microglial plaque association and improves cognition in 3xTg-AD mice.

Dagher NN, Najafi AR, Kayala KM, Elmore MR, White TE, Medeiros R, West BL, Green KN - J Neuroinflammation (2015)

Chronic lower-dose CSF1R inhibition prevents microglia associating with plaques. Immunofluorescent staining was performed on 3 months treated and control 3xTg-AD mice for 6E10, which recognizes Aβ plaques and IBA1. a–f Representative 10× images are shown of control and treated mice. g–l Representative 63× images are shown of control and treated mice, centered on an area dense with plaques. m Quantification of the number of microglia associated with a plaque and normalized to plaque diameter revealed a 70 % decrease in treated animals as compared to untreated animals. *Indicates significance (p < 0.05) by unpaired Students t test. Error bars indicate SEM
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4522109&req=5

Fig7: Chronic lower-dose CSF1R inhibition prevents microglia associating with plaques. Immunofluorescent staining was performed on 3 months treated and control 3xTg-AD mice for 6E10, which recognizes Aβ plaques and IBA1. a–f Representative 10× images are shown of control and treated mice. g–l Representative 63× images are shown of control and treated mice, centered on an area dense with plaques. m Quantification of the number of microglia associated with a plaque and normalized to plaque diameter revealed a 70 % decrease in treated animals as compared to untreated animals. *Indicates significance (p < 0.05) by unpaired Students t test. Error bars indicate SEM
Mentions: However, stark differences were seen in the microglia that are associated with plaques—in vehicle-treated animals, microglia were densely packed around plaques and displayed an activated morphology (Fig. 7a–c). Mice treated with PLX5622 showed comparable plaque load, but microglia were not associated with plaques to the same extent (Fig. 7d–f), suggesting that low doses of PLX5622 do not fully eliminate microglia but alter their response to inflammatory stimuli, such as plaques. Indeed, closeup z-stacks showed a clear association of microglia with plaques in untreated 3xTg-AD mice (Fig. 7g–i) but a lack of association in PLX5622-treated mice (Fig. 7j–l). Quantification of the number of microglia associated with a plaque and normalized to plaque diameter revealed a 70 % reduction in microglia associated with plaques. To explore the possibility that this lower dose of CSF1R inhibitor could be selectively killing plaque-associated microglia, we performed immunostaining for active caspase-3, as an indicator of cell death. However, no increased microglial cell death was seen in PLX5622-treated mice in areas adjacent to plaques (data not shown). This suggests that the reduction in the number of microglia associated with plaques is due to altered microglial behavior, although it is possible that susceptible plaque-associated microglia are already dead and no further cells are going through the cell death process at this point.Fig. 7

Bottom Line: Microglia are dependent upon colony-stimulating factor 1 receptor (CSF1R) signaling for their survival in the adult brain, with administration of the dual CSF1R/c-kit inhibitor PLX3397 leading to the near-complete elimination of all microglia brainwide.Aβ levels and plaque loads were not altered, but microglia in treated mice no longer associated with plaques, revealing a role for the CSF1R in the microglial reaction to plaques, as well as in mediating cognitive deficits.We find that inhibition of CSF1R alone is sufficient to eliminate microglia and that sustained microglial elimination is concentration-dependent.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology and Behavior, Institute for Memory Impairments and Neurological Disorders, University of California, 3208 Biological Sciences III, Irvine, CA, 92697-4545, USA. ndagher53@gmail.com.

ABSTRACT

Background: Microglia are dependent upon colony-stimulating factor 1 receptor (CSF1R) signaling for their survival in the adult brain, with administration of the dual CSF1R/c-kit inhibitor PLX3397 leading to the near-complete elimination of all microglia brainwide. Here, we determined the dose-dependent effects of a specific CSF1R inhibitor (PLX5622) on microglia in both wild-type and the 3xTg-AD mouse model of Alzheimer's disease.

Methods: Wild-type mice were treated with PLX5622 for up to 21 days, and the effects on microglial numbers were assessed. 3xTg-AD mice were treated with PLX5622 for 6 or 12 weeks and effects on microglial numbers and pathology subsequently assessed.

Results: High doses of CSF1R inhibitor eliminate most microglia from the brain, but a 75% lower-dose results in sustained elimination of ~30 of microglia in both wild-type and 3xTg-AD mice. No behavioral or cognitive deficits were found in mice either depleted of microglia or treated with lower CSF1R inhibitor concentrations. Aged 3xTg-AD mice treated for 6 or 12 weeks with lower levels of PLX5622 resulted in improved learning and memory. Aβ levels and plaque loads were not altered, but microglia in treated mice no longer associated with plaques, revealing a role for the CSF1R in the microglial reaction to plaques, as well as in mediating cognitive deficits.

Conclusions: We find that inhibition of CSF1R alone is sufficient to eliminate microglia and that sustained microglial elimination is concentration-dependent. Inhibition of the CSF1R at lower levels in 3xTg-AD mice prevents microglial association with plaques and improves cognition.

No MeSH data available.


Related in: MedlinePlus