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Pharmacological inhibition of O-GlcNAcase (OGA) prevents cognitive decline and amyloid plaque formation in bigenic tau/APP mutant mice.

Yuzwa SA, Shan X, Jones BA, Zhao G, Woodward ML, Li X, Zhu Y, McEachern EJ, Silverman MA, Watson NV, Gong CX, Vocadlo DJ - Mol Neurodegener (2014)

Bottom Line: We treated double transgenic TAPP mice, which express both mutant human tau and amyloid precursor protein (APP), with a highly selective orally bioavailable inhibitor of the enzyme responsible for removing O-GlcNAc (OGA) to increase O-GlcNAc in the brain.We find that increased O-GlcNAc levels block cognitive decline in the TAPP mice and this effect parallels decreased β-amyloid peptide levels and decreased levels of amyloid plaques.The findings provide good support for OGA as a promising therapeutic target to alter disease progression in Alzheimer disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Dr, Burnaby, BC V5A 1S6, Canada. dvocadlo@sfu.ca.

ABSTRACT

Background: Amyloid plaques and neurofibrillary tangles (NFTs) are the defining pathological hallmarks of Alzheimer's disease (AD). Increasing the quantity of the O-linked N-acetylglucosamine (O-GlcNAc) post-translational modification of nuclear and cytoplasmic proteins slows neurodegeneration and blocks the formation of NFTs in a tauopathy mouse model. It remains unknown, however, if O-GlcNAc can influence the formation of amyloid plaques in the presence of tau pathology.

Results: We treated double transgenic TAPP mice, which express both mutant human tau and amyloid precursor protein (APP), with a highly selective orally bioavailable inhibitor of the enzyme responsible for removing O-GlcNAc (OGA) to increase O-GlcNAc in the brain. We find that increased O-GlcNAc levels block cognitive decline in the TAPP mice and this effect parallels decreased β-amyloid peptide levels and decreased levels of amyloid plaques.

Conclusions: This study indicates that increased O-GlcNAc can influence β-amyloid pathology in the presence of tau pathology. The findings provide good support for OGA as a promising therapeutic target to alter disease progression in Alzheimer disease.

Show MeSH

Related in: MedlinePlus

O-GlcNAc levels are increased in the TAPP mouse brain. A. Western blots of total brain homogenates from 0, 200 and 500 mkd Thiamet-G treated TAPP mice reveals that O-GlcNAc levels are vastly increased (RL2 and CTD110.6) while actin indicates equal protein loading. B. Quantification of O-GlcNAc immunoreactivity (CTD110.6) normalized to actin by densitometry of all bands (left panel) or only the low molecular weight (MW) bands (bands <50 kDa, right panel). N =10 in each group. *indicates p <0.05, ***indicates p <0.001, unpaired two-tailed t-test) C. Immunohistochemical (IHC) analysis of 0 and 500 mkd Thiamet-G treated TAPP mice brain tissue reveals that O-GlcNAc levels are increased in all of the hippocampus (A’, E’), cerebellum (B’, F’), pons (C’, G’) and the amygdala (D’, H’).
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Fig2: O-GlcNAc levels are increased in the TAPP mouse brain. A. Western blots of total brain homogenates from 0, 200 and 500 mkd Thiamet-G treated TAPP mice reveals that O-GlcNAc levels are vastly increased (RL2 and CTD110.6) while actin indicates equal protein loading. B. Quantification of O-GlcNAc immunoreactivity (CTD110.6) normalized to actin by densitometry of all bands (left panel) or only the low molecular weight (MW) bands (bands <50 kDa, right panel). N =10 in each group. *indicates p <0.05, ***indicates p <0.001, unpaired two-tailed t-test) C. Immunohistochemical (IHC) analysis of 0 and 500 mkd Thiamet-G treated TAPP mice brain tissue reveals that O-GlcNAc levels are increased in all of the hippocampus (A’, E’), cerebellum (B’, F’), pons (C’, G’) and the amygdala (D’, H’).

Mentions: To better understand how Thiamet-G prevents impairment of cognitive performance, we first verified that O-GlcNAc levels were increased in treated animals (Figure 2). Immunoblotting with O-GlcNAc antibodies CTD110.6 and RL2 revealed dramatically increased O-GlcNAc levels in both the 200 and 500 mkd treated TAPP mice compared to the 0 mkd control TAPP mice (Figure 2A). We performed densitometric quantification of the O-GlcNAc immunoreactivity of the CTD110.6 antibody based on either all of the immunoreactive bands or only the low molecular weight (<50 kDa) immunoreactive bands (Figure 2B). This analysis revealed a trend toward lower O-GlcNAc levels in the 200 mkd TAPP mice group compared to the 500 mkd TAPP mice group when considering all of the immunoreactive bands. When only the low molecular weight bands are considered, O-GlcNAc levels were roughly 20% lower in the 200 mkd TAPP mice (p <0.05). These analyses reveal that there is a dose dependent effect of Thiamet-G on the levels of O-GlcNAc. We also performed immunohistochemistry (IHC) using the O-GlcNAc antibodies (CTD110.6 and RL2) on animals from the 0 and 500 mkd Thiamet-G treatment groups. The hippocampus and the cerebelleum have been previously shown to have high levels of expression of both OGA and OGT [31, 32] and O-GlcNAc levels in these structures, along with the pons and the amygdala, were particularly increased in the 500 mkd Thiamet-G treatment group (Figure 2C). Previously, we have shown that Thiamet-G does not block tau hyperphosphorylation in the transgenic parental JNPL3 mouse model [20]. We confirmed that this was also the case in the double transgenic TAPP mice by immunoblot (Figure 3A) and IHC (Figure 3B) analyses using various phosphorylation state-specific tau antibodies. Even though dramatically increased O-GlcNAc levels were observed (Figure 2) immunoblot analyses revealed that Thiamet-G treatment actually slightly increased the total amount of tau (92e) and the extent to which tau was phosphorylated but this did not reach statistical significance. In our previous study of JNPL3 mice [20], we found that Thiamet-G treatment reduced the amount of sarkosyl insoluble tau, which is known to correlate with the amount of fibrillar tau in 9 month old mice JNPL3 mice [33]. In a blinded experiment we therefore probed whether Thiamet-G can also reduce the amount of sarkosyl insoluble tau in the double transgenic TAPP mice. We observed a strong trend of less sarkosyl insoluble tau in the 500 mkd Thiamet-G treatment group (32% reduction), which was consistent in magnitude with our earlier JNPL3 study, although this difference did not reach statistical significance in the TAPP mice (Figure 4).Figure 2


Pharmacological inhibition of O-GlcNAcase (OGA) prevents cognitive decline and amyloid plaque formation in bigenic tau/APP mutant mice.

Yuzwa SA, Shan X, Jones BA, Zhao G, Woodward ML, Li X, Zhu Y, McEachern EJ, Silverman MA, Watson NV, Gong CX, Vocadlo DJ - Mol Neurodegener (2014)

O-GlcNAc levels are increased in the TAPP mouse brain. A. Western blots of total brain homogenates from 0, 200 and 500 mkd Thiamet-G treated TAPP mice reveals that O-GlcNAc levels are vastly increased (RL2 and CTD110.6) while actin indicates equal protein loading. B. Quantification of O-GlcNAc immunoreactivity (CTD110.6) normalized to actin by densitometry of all bands (left panel) or only the low molecular weight (MW) bands (bands <50 kDa, right panel). N =10 in each group. *indicates p <0.05, ***indicates p <0.001, unpaired two-tailed t-test) C. Immunohistochemical (IHC) analysis of 0 and 500 mkd Thiamet-G treated TAPP mice brain tissue reveals that O-GlcNAc levels are increased in all of the hippocampus (A’, E’), cerebellum (B’, F’), pons (C’, G’) and the amygdala (D’, H’).
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4232697&req=5

Fig2: O-GlcNAc levels are increased in the TAPP mouse brain. A. Western blots of total brain homogenates from 0, 200 and 500 mkd Thiamet-G treated TAPP mice reveals that O-GlcNAc levels are vastly increased (RL2 and CTD110.6) while actin indicates equal protein loading. B. Quantification of O-GlcNAc immunoreactivity (CTD110.6) normalized to actin by densitometry of all bands (left panel) or only the low molecular weight (MW) bands (bands <50 kDa, right panel). N =10 in each group. *indicates p <0.05, ***indicates p <0.001, unpaired two-tailed t-test) C. Immunohistochemical (IHC) analysis of 0 and 500 mkd Thiamet-G treated TAPP mice brain tissue reveals that O-GlcNAc levels are increased in all of the hippocampus (A’, E’), cerebellum (B’, F’), pons (C’, G’) and the amygdala (D’, H’).
Mentions: To better understand how Thiamet-G prevents impairment of cognitive performance, we first verified that O-GlcNAc levels were increased in treated animals (Figure 2). Immunoblotting with O-GlcNAc antibodies CTD110.6 and RL2 revealed dramatically increased O-GlcNAc levels in both the 200 and 500 mkd treated TAPP mice compared to the 0 mkd control TAPP mice (Figure 2A). We performed densitometric quantification of the O-GlcNAc immunoreactivity of the CTD110.6 antibody based on either all of the immunoreactive bands or only the low molecular weight (<50 kDa) immunoreactive bands (Figure 2B). This analysis revealed a trend toward lower O-GlcNAc levels in the 200 mkd TAPP mice group compared to the 500 mkd TAPP mice group when considering all of the immunoreactive bands. When only the low molecular weight bands are considered, O-GlcNAc levels were roughly 20% lower in the 200 mkd TAPP mice (p <0.05). These analyses reveal that there is a dose dependent effect of Thiamet-G on the levels of O-GlcNAc. We also performed immunohistochemistry (IHC) using the O-GlcNAc antibodies (CTD110.6 and RL2) on animals from the 0 and 500 mkd Thiamet-G treatment groups. The hippocampus and the cerebelleum have been previously shown to have high levels of expression of both OGA and OGT [31, 32] and O-GlcNAc levels in these structures, along with the pons and the amygdala, were particularly increased in the 500 mkd Thiamet-G treatment group (Figure 2C). Previously, we have shown that Thiamet-G does not block tau hyperphosphorylation in the transgenic parental JNPL3 mouse model [20]. We confirmed that this was also the case in the double transgenic TAPP mice by immunoblot (Figure 3A) and IHC (Figure 3B) analyses using various phosphorylation state-specific tau antibodies. Even though dramatically increased O-GlcNAc levels were observed (Figure 2) immunoblot analyses revealed that Thiamet-G treatment actually slightly increased the total amount of tau (92e) and the extent to which tau was phosphorylated but this did not reach statistical significance. In our previous study of JNPL3 mice [20], we found that Thiamet-G treatment reduced the amount of sarkosyl insoluble tau, which is known to correlate with the amount of fibrillar tau in 9 month old mice JNPL3 mice [33]. In a blinded experiment we therefore probed whether Thiamet-G can also reduce the amount of sarkosyl insoluble tau in the double transgenic TAPP mice. We observed a strong trend of less sarkosyl insoluble tau in the 500 mkd Thiamet-G treatment group (32% reduction), which was consistent in magnitude with our earlier JNPL3 study, although this difference did not reach statistical significance in the TAPP mice (Figure 4).Figure 2

Bottom Line: We treated double transgenic TAPP mice, which express both mutant human tau and amyloid precursor protein (APP), with a highly selective orally bioavailable inhibitor of the enzyme responsible for removing O-GlcNAc (OGA) to increase O-GlcNAc in the brain.We find that increased O-GlcNAc levels block cognitive decline in the TAPP mice and this effect parallels decreased β-amyloid peptide levels and decreased levels of amyloid plaques.The findings provide good support for OGA as a promising therapeutic target to alter disease progression in Alzheimer disease.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Dr, Burnaby, BC V5A 1S6, Canada. dvocadlo@sfu.ca.

ABSTRACT

Background: Amyloid plaques and neurofibrillary tangles (NFTs) are the defining pathological hallmarks of Alzheimer's disease (AD). Increasing the quantity of the O-linked N-acetylglucosamine (O-GlcNAc) post-translational modification of nuclear and cytoplasmic proteins slows neurodegeneration and blocks the formation of NFTs in a tauopathy mouse model. It remains unknown, however, if O-GlcNAc can influence the formation of amyloid plaques in the presence of tau pathology.

Results: We treated double transgenic TAPP mice, which express both mutant human tau and amyloid precursor protein (APP), with a highly selective orally bioavailable inhibitor of the enzyme responsible for removing O-GlcNAc (OGA) to increase O-GlcNAc in the brain. We find that increased O-GlcNAc levels block cognitive decline in the TAPP mice and this effect parallels decreased β-amyloid peptide levels and decreased levels of amyloid plaques.

Conclusions: This study indicates that increased O-GlcNAc can influence β-amyloid pathology in the presence of tau pathology. The findings provide good support for OGA as a promising therapeutic target to alter disease progression in Alzheimer disease.

Show MeSH
Related in: MedlinePlus