Apolipoprotein E4 (APOE4) is associated with a greater response to neuroinflammation and risk of developing late-onset Alzheimer disease (AD), but the mechanisms for this association are not clear. Activation of calcium-dependent cytosolic phospholipase A2 (cPLA2) is involved in inflammatory signaling and is elevated within plaques of the AD brain. The relation between APOE4 genotype and cPLA2 activity is not known.
Mouse primary astrocytes, mouse and human brain samples differing by APOE genotypes were collected for measuring cPLA2 expression, phosphorylation and activity in relation to measures of inflammation and oxidative stress.
Greater cPLA2 phosphorylation and activity were identified in ApoE4 compared to ApoE3 in primary astrocytes and brains of ApoE-targeted replacement (ApoE-TR) mice. These differences were also demonstrated in brain homogenates from the inferior frontal cortex from AD patients carrying APOE3/4 compared to APOE3/3. Higher cPLA2 activation with APOE4 was associated with greater activation of the MAPK p38 pathway, as well as with higher levels of leukotriene B4 (LTB4), reactive oxygen species (ROS) and inducible nitric oxide synthase (iNOS). Inhibition of cPLA2 reduced LTB4, ROS and iNOS levels in ApoE4 primary astrocytes to those of ApoE3 astrocytes.
Our findings implicate greater activation of cPLA2 signaling system with APOE4, that could represent a potential drug target for mitigating the increased neuroinflammation with APOE4 and AD.

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This is a list of supplementary files associated with this preprint. Click to download.
ApoE4 increases cPLA2 expression in immortalized ApoE astrocytic cultures. A, cPLA2 mRNA levels in immortalized ApoE3 and ApoE4 astrocytes. B, cPLA2 and phosphorylated cPLA2 (p-cPLA2) protein levels in immortalized ApoE3 and ApoE4 astrocytes (left) were detected by western-blot (WB).
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On 10 Feb, 2021
On 01 Feb, 2021
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On 01 Feb, 2021
On 21 Jan, 2021
Received 19 Jan, 2021
Received 17 Jan, 2021
On 13 Jan, 2021
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On 12 Jan, 2021
On 12 Jan, 2021
On 12 Jan, 2021
Posted 14 Sep, 2020
On 14 Oct, 2020
Received 07 Oct, 2020
Received 04 Oct, 2020
On 27 Sep, 2020
Invitations sent on 21 Sep, 2020
On 21 Sep, 2020
On 08 Sep, 2020
On 07 Sep, 2020
On 07 Sep, 2020
On 07 Sep, 2020
On 10 Feb, 2021
On 01 Feb, 2021
On 01 Feb, 2021
On 01 Feb, 2021
On 21 Jan, 2021
Received 19 Jan, 2021
Received 17 Jan, 2021
On 13 Jan, 2021
On 12 Jan, 2021
Invitations sent on 12 Jan, 2021
On 12 Jan, 2021
On 12 Jan, 2021
On 12 Jan, 2021
Posted 14 Sep, 2020
On 14 Oct, 2020
Received 07 Oct, 2020
Received 04 Oct, 2020
On 27 Sep, 2020
Invitations sent on 21 Sep, 2020
On 21 Sep, 2020
On 08 Sep, 2020
On 07 Sep, 2020
On 07 Sep, 2020
On 07 Sep, 2020
Apolipoprotein E4 (APOE4) is associated with a greater response to neuroinflammation and risk of developing late-onset Alzheimer disease (AD), but the mechanisms for this association are not clear. Activation of calcium-dependent cytosolic phospholipase A2 (cPLA2) is involved in inflammatory signaling and is elevated within plaques of the AD brain. The relation between APOE4 genotype and cPLA2 activity is not known.
Mouse primary astrocytes, mouse and human brain samples differing by APOE genotypes were collected for measuring cPLA2 expression, phosphorylation and activity in relation to measures of inflammation and oxidative stress.
Greater cPLA2 phosphorylation and activity were identified in ApoE4 compared to ApoE3 in primary astrocytes and brains of ApoE-targeted replacement (ApoE-TR) mice. These differences were also demonstrated in brain homogenates from the inferior frontal cortex from AD patients carrying APOE3/4 compared to APOE3/3. Higher cPLA2 activation with APOE4 was associated with greater activation of the MAPK p38 pathway, as well as with higher levels of leukotriene B4 (LTB4), reactive oxygen species (ROS) and inducible nitric oxide synthase (iNOS). Inhibition of cPLA2 reduced LTB4, ROS and iNOS levels in ApoE4 primary astrocytes to those of ApoE3 astrocytes.
Our findings implicate greater activation of cPLA2 signaling system with APOE4, that could represent a potential drug target for mitigating the increased neuroinflammation with APOE4 and AD.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9
This is a list of supplementary files associated with this preprint. Click to download.
ApoE4 increases cPLA2 expression in immortalized ApoE astrocytic cultures. A, cPLA2 mRNA levels in immortalized ApoE3 and ApoE4 astrocytes. B, cPLA2 and phosphorylated cPLA2 (p-cPLA2) protein levels in immortalized ApoE3 and ApoE4 astrocytes (left) were detected by western-blot (WB).
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