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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.


Diet-induced high Hcy brain level affects synaptic integrity and neuroinflammation. (A) Representative western blot analyses of post-synaptic density protein 95 (PSD-95), synaptophysin (SYP), and microtubule-associated protein 2 (MAP2) in brain cortex homogenates of controls (ctrl), folate and B vitamins deficient diet (Diet), Diet + zileuton, or zileuton-treated 3xTg mice. (B) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). (C) Representative images of brain sections from 3xTg mice receiving vehicle (Ctrl), supplemented diet (Diet), Diet + zileuton, or zileuton alone immunostained with PDS-95, synaptophysin, and MAP2 antibodies (Scale bar: 100 μm) (D) Representative western blots of GFAP and CD45 in brain cortex homogenates from controls (Ctrl), Diet, Diet + zileuton, or zileuton-treated 3xTg mice. (E) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). Values represent mean ± s.e.m. (n = 5 control, n = 6 Diet, n = 6 Diet + zileuton, n = 5 zileuton).
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f5: Diet-induced high Hcy brain level affects synaptic integrity and neuroinflammation. (A) Representative western blot analyses of post-synaptic density protein 95 (PSD-95), synaptophysin (SYP), and microtubule-associated protein 2 (MAP2) in brain cortex homogenates of controls (ctrl), folate and B vitamins deficient diet (Diet), Diet + zileuton, or zileuton-treated 3xTg mice. (B) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). (C) Representative images of brain sections from 3xTg mice receiving vehicle (Ctrl), supplemented diet (Diet), Diet + zileuton, or zileuton alone immunostained with PDS-95, synaptophysin, and MAP2 antibodies (Scale bar: 100 μm) (D) Representative western blots of GFAP and CD45 in brain cortex homogenates from controls (Ctrl), Diet, Diet + zileuton, or zileuton-treated 3xTg mice. (E) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). Values represent mean ± s.e.m. (n = 5 control, n = 6 Diet, n = 6 Diet + zileuton, n = 5 zileuton).

Mentions: Next, we investigated the effect of the Diet with and without zileuton on synaptic integrity markers. Compared with controls, steady state levels of two distinct synaptic proteins, synaptophysin and post-synaptic protein-95 (PDS-95), but not MAP-2, were significantly decreased in the mice administered the Diet (Fig. 5A,B). By contrast, mice on the same Diet but simultaneously treated with zileuton had levels of these proteins no different from controls (Fig. 5A,B). Immunohistochemical staining results were consistent with these observations (Fig. 5C). In addition, we observed that compared with controls Diet-treated mice had a significant increase in GFAP and CD45 immunoreactivities, which was blunted in mice that with the Diet also received zileuton (Fig. 5D,E). Zileuton alone had no significant effect on both synaptic integrity and neuroinflammatory markers (Fig. 5A–E).


Five lipoxygenase hypomethylation mediates the homocysteine effect on Alzheimer ’ s phenotype
Diet-induced high Hcy brain level affects synaptic integrity and neuroinflammation. (A) Representative western blot analyses of post-synaptic density protein 95 (PSD-95), synaptophysin (SYP), and microtubule-associated protein 2 (MAP2) in brain cortex homogenates of controls (ctrl), folate and B vitamins deficient diet (Diet), Diet + zileuton, or zileuton-treated 3xTg mice. (B) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). (C) Representative images of brain sections from 3xTg mice receiving vehicle (Ctrl), supplemented diet (Diet), Diet + zileuton, or zileuton alone immunostained with PDS-95, synaptophysin, and MAP2 antibodies (Scale bar: 100 μm) (D) Representative western blots of GFAP and CD45 in brain cortex homogenates from controls (Ctrl), Diet, Diet + zileuton, or zileuton-treated 3xTg mice. (E) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). Values represent mean ± s.e.m. (n = 5 control, n = 6 Diet, n = 6 Diet + zileuton, n = 5 zileuton).
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Related In: Results  -  Collection

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f5: Diet-induced high Hcy brain level affects synaptic integrity and neuroinflammation. (A) Representative western blot analyses of post-synaptic density protein 95 (PSD-95), synaptophysin (SYP), and microtubule-associated protein 2 (MAP2) in brain cortex homogenates of controls (ctrl), folate and B vitamins deficient diet (Diet), Diet + zileuton, or zileuton-treated 3xTg mice. (B) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). (C) Representative images of brain sections from 3xTg mice receiving vehicle (Ctrl), supplemented diet (Diet), Diet + zileuton, or zileuton alone immunostained with PDS-95, synaptophysin, and MAP2 antibodies (Scale bar: 100 μm) (D) Representative western blots of GFAP and CD45 in brain cortex homogenates from controls (Ctrl), Diet, Diet + zileuton, or zileuton-treated 3xTg mice. (E) Densitometric analyses of the immunoreactivities to the antibodies shown in the previous panel (*p < 0.05). Values represent mean ± s.e.m. (n = 5 control, n = 6 Diet, n = 6 Diet + zileuton, n = 5 zileuton).
Mentions: Next, we investigated the effect of the Diet with and without zileuton on synaptic integrity markers. Compared with controls, steady state levels of two distinct synaptic proteins, synaptophysin and post-synaptic protein-95 (PDS-95), but not MAP-2, were significantly decreased in the mice administered the Diet (Fig. 5A,B). By contrast, mice on the same Diet but simultaneously treated with zileuton had levels of these proteins no different from controls (Fig. 5A,B). Immunohistochemical staining results were consistent with these observations (Fig. 5C). In addition, we observed that compared with controls Diet-treated mice had a significant increase in GFAP and CD45 immunoreactivities, which was blunted in mice that with the Diet also received zileuton (Fig. 5D,E). Zileuton alone had no significant effect on both synaptic integrity and neuroinflammatory markers (Fig. 5A–E).

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.