Limits...
Five lipoxygenase hypomethylation mediates the homocysteine effect on Alzheimer ’ s phenotype

View Article: PubMed Central - PubMed

ABSTRACT

Environmental and genetic risk factors are implicated in the pathogenesis of Alzheimer’s disease (AD). However, how they interact and influence its pathogenesis remains to be investigated. High level of homocysteine (Hcy) is an AD risk factor and associates with an up-regulation of the ALOX5 gene. In the current paper we investigated whether this activation is responsible for the Hcy effect on the AD phenotype and the mechanisms involved. Triple transgenic mice were randomized to receive regular chow diet, a diet deficient in folate and B vitamins (Diet), which results in high Hcy, or the Diet plus zileuton, a specific ALOX5 inhibitor, for 7 months. Compared with controls, Diet-fed mice had a significant increase in Hcy levels, memory and learning deficits, up-regulation of the ALOX5 pathway, increased Aβ levels, tau phosphorylation, and synaptic pathology, which were absent in mice treated with zileuton. In vivo and vitro studies demonstrated that the mechanism responsible was the hypomethylation of the ALOX5 promoter. Our findings demonstrate that the up-regulation of the ALOX5 is responsible for the Hcy-dependent worsening of the AD phenotype in a relevant mouse model of the disease. The discovery of this previously unknown cross-talk between these two pathways could afford novel therapeutic opportunities for treating or halting AD.

No MeSH data available.


Related in: MedlinePlus

Diet-induced high Hcy-dependent increase in tau phosphorylation is blocked by zileuton. (A) Representative western blots of soluble and insoluble total tau (HT7), phosphorylated tau at residues S396/S404 (PHF-1), T231/S235 (AT180), at T181 (AT270), and S202/T205 (AT8), in brain cortex homogenates from 3xTg mice receiving vehicle (Ctrl), folate and B vitamins deficient diet (Diet), Diet + zileuton, or zileuton. (B) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). (C) Representative images of brain sections from the same four groups of 3xTg mice immunostained with HT7, AT8, AT180, AT270 antibodies (Scale bar: 100 μm). (D) Representative western blots of cdk5, p35, and p25 in brain cortex homogenates from 3xTg mice treated with vehicle (Ctrl), supplemented diet (Diet), Diet + zileuton, or zileuton. (E) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). Values represent mean ± sem. (n = 5 control, n = 6 Diet, n = 6 Diet + zileuton, n = 5 zileuton).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5382538&req=5

f4: Diet-induced high Hcy-dependent increase in tau phosphorylation is blocked by zileuton. (A) Representative western blots of soluble and insoluble total tau (HT7), phosphorylated tau at residues S396/S404 (PHF-1), T231/S235 (AT180), at T181 (AT270), and S202/T205 (AT8), in brain cortex homogenates from 3xTg mice receiving vehicle (Ctrl), folate and B vitamins deficient diet (Diet), Diet + zileuton, or zileuton. (B) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). (C) Representative images of brain sections from the same four groups of 3xTg mice immunostained with HT7, AT8, AT180, AT270 antibodies (Scale bar: 100 μm). (D) Representative western blots of cdk5, p35, and p25 in brain cortex homogenates from 3xTg mice treated with vehicle (Ctrl), supplemented diet (Diet), Diet + zileuton, or zileuton. (E) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). Values represent mean ± sem. (n = 5 control, n = 6 Diet, n = 6 Diet + zileuton, n = 5 zileuton).

Mentions: Compared with controls, Diet-treated mice had a significant increase in the insoluble tau fraction while there was no change in the level of total soluble tau (Fig. 4A,B). In addition, we found that brains form the same mice had higher levels of tau phosphorylation at specific epitopes: at T231/S235, as recognized by the antibody AT180, and at T181, as recognized by the antibody AT270, but no changes at S396, as recognized by the antibody PHF-13; S396/404, as recognized by the antibody PHF-1; and S202/T205, as recognized by the antibody AT8 (Fig. 4A,B). By contrast, no changes for any of these parameters were observed in the Diet-treated mice receiving zileuton, or zileuton alone when compared with the control group (Fig. 4A,B).


Five lipoxygenase hypomethylation mediates the homocysteine effect on Alzheimer ’ s phenotype
Diet-induced high Hcy-dependent increase in tau phosphorylation is blocked by zileuton. (A) Representative western blots of soluble and insoluble total tau (HT7), phosphorylated tau at residues S396/S404 (PHF-1), T231/S235 (AT180), at T181 (AT270), and S202/T205 (AT8), in brain cortex homogenates from 3xTg mice receiving vehicle (Ctrl), folate and B vitamins deficient diet (Diet), Diet + zileuton, or zileuton. (B) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). (C) Representative images of brain sections from the same four groups of 3xTg mice immunostained with HT7, AT8, AT180, AT270 antibodies (Scale bar: 100 μm). (D) Representative western blots of cdk5, p35, and p25 in brain cortex homogenates from 3xTg mice treated with vehicle (Ctrl), supplemented diet (Diet), Diet + zileuton, or zileuton. (E) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). Values represent mean ± sem. (n = 5 control, n = 6 Diet, n = 6 Diet + zileuton, n = 5 zileuton).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5382538&req=5

f4: Diet-induced high Hcy-dependent increase in tau phosphorylation is blocked by zileuton. (A) Representative western blots of soluble and insoluble total tau (HT7), phosphorylated tau at residues S396/S404 (PHF-1), T231/S235 (AT180), at T181 (AT270), and S202/T205 (AT8), in brain cortex homogenates from 3xTg mice receiving vehicle (Ctrl), folate and B vitamins deficient diet (Diet), Diet + zileuton, or zileuton. (B) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). (C) Representative images of brain sections from the same four groups of 3xTg mice immunostained with HT7, AT8, AT180, AT270 antibodies (Scale bar: 100 μm). (D) Representative western blots of cdk5, p35, and p25 in brain cortex homogenates from 3xTg mice treated with vehicle (Ctrl), supplemented diet (Diet), Diet + zileuton, or zileuton. (E) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). Values represent mean ± sem. (n = 5 control, n = 6 Diet, n = 6 Diet + zileuton, n = 5 zileuton).
Mentions: Compared with controls, Diet-treated mice had a significant increase in the insoluble tau fraction while there was no change in the level of total soluble tau (Fig. 4A,B). In addition, we found that brains form the same mice had higher levels of tau phosphorylation at specific epitopes: at T231/S235, as recognized by the antibody AT180, and at T181, as recognized by the antibody AT270, but no changes at S396, as recognized by the antibody PHF-13; S396/404, as recognized by the antibody PHF-1; and S202/T205, as recognized by the antibody AT8 (Fig. 4A,B). By contrast, no changes for any of these parameters were observed in the Diet-treated mice receiving zileuton, or zileuton alone when compared with the control group (Fig. 4A,B).

View Article: PubMed Central - PubMed

ABSTRACT

Environmental and genetic risk factors are implicated in the pathogenesis of Alzheimer&rsquo;s disease (AD). However, how they interact and influence its pathogenesis remains to be investigated. High level of homocysteine (Hcy) is an AD risk factor and associates with an up-regulation of the ALOX5 gene. In the current paper we investigated whether this activation is responsible for the Hcy effect on the AD phenotype and the mechanisms involved. Triple transgenic mice were randomized to receive regular chow diet, a diet deficient in folate and B vitamins (Diet), which results in high Hcy, or the Diet plus zileuton, a specific ALOX5 inhibitor, for 7 months. Compared with controls, Diet-fed mice had a significant increase in Hcy levels, memory and learning deficits, up-regulation of the ALOX5 pathway, increased A&beta; levels, tau phosphorylation, and synaptic pathology, which were absent in mice treated with zileuton. In vivo and vitro studies demonstrated that the mechanism responsible was the hypomethylation of the ALOX5 promoter. Our findings demonstrate that the up-regulation of the ALOX5 is responsible for the Hcy-dependent worsening of the AD phenotype in a relevant mouse model of the disease. The discovery of this previously unknown cross-talk between these two pathways could afford novel therapeutic opportunities for treating or halting AD.

No MeSH data available.


Related in: MedlinePlus