In vivo and in vitro effects of an apolipoprotein e mimetic peptide on amyloid-ß pathology.

BACKGROUND: Apolipoprotein E (ApoE) is the major apolipoprotein present in the high-density lipoprotein-like particles in the central nervous system (CNS). ApoE is involved in various protective functions in CNS including cholesterol transport, anti-inflammatory, and antioxidant effects. An ApoE peptide would be expected to exert protective effects on neuroinflammation. OBJECTIVE: To determine the effects of an ApoE mimetic peptide Ac-hE18A-NH2 on amyloid-ß pathology. METHOD: Using human APP/PS1ΔE9 transgenic mice and in vitro studies, we have evaluated the effect of an ApoE mimetic peptide, Ac-hE18A-NH2, on amyloid plaque deposition and inflammation. RESULTS: Administration of Ac-hE18A-NH2 to APP/PS1ΔE9 mice for 6 weeks (50 µg/mouse, 3 times a week) significantly improved cognition with a concomitant decrease in amyloid plaque deposition and reduced activated microglia and astrocytes, and increased brain ApoE levels. Oligomeric Aß42 (oAß42) and oxidized PAPC (ox-PAPC) inhibited secretion of ApoE in U251 cells, a human astrocyte cell line, and this effect was ameliorated in the presence of peptide Ac-hE18A-NH2. The peptide also increased Aß42 uptake in a cell line of human macrophages. CONCLUSIONS: Peptide Ac-hE18A-NH2 attenuates the effects of oxidative stress on ApoE secretion, inhibits amyloid plaque deposition, and thus could be beneficial in the treatment of Alzheimer's disease.

Two apolipoprotein E mimetic peptides with similar cholesterol reducing properties exhibit differential atheroprotective effects in LDL-R null mice.

OBJECTIVE: We investigated two apoE mimetic peptides with similar long-term plasma cholesterol reducing abilities for their effects on atherosclerotic lesions in Western diet-fed female LDL-receptor (LDL-R) null mice. METHODS AND RESULTS: Single doses of peptides Ac-hE18A-NH(2) and mR18L were administered retro-orbitally to LDL-R null mice on Western diet and plasma cholesterol was measured at 10 min, 4 h, and 24 h post administration. Peptide mR18L and not Ac-hE18A-NH(2) reduced plasma cholesterol levels significantly at 4 h post administration. However, multiple administrations (100 µg/mouse twice weekly for 8 weeks) resulted in a similar reduction in plasma cholesterol. Only the plasma from the Ac-hE18A-NH(2) group had significantly reduced reactive oxygen species levels at the end of the treatment protocol. Both mR18L and Ac-hE18A-NH(2) showed reduced atherosclerotic lesion areas. However, peptide Ac-hE18A-NH(2) was significantly more effective in inhibiting atherosclerosis. Both peptides reduced total plaque macrophage load compared to the saline treated animals, with peptide Ac-hE18A-NH(2) having a greater reduction. Incubation of HepG2 cells and THP-1 monocyte-derived macrophages with both peptides in the presence of oxidized phospholipid showed that Ac-hE18A-NH(2) promotes the secretion of apoE from the cells whereas mR18L does not. CONCLUSIONS: Despite similar reductions in plasma cholesterol levels, Ac-hE18A-NH(2) was more effective in inhibiting lesions than mR18L, possibly due to its ability to promote the secretion of apoE from hepatocytes and macrophages.

Apolipoprotein E mimetic is more effective than apolipoprotein A-I mimetic in reducing lesion formation in older female apo E null mice.

OBJECTIVE: The apolipoprotein E mimetic peptide Ac-hE18A-NH(2), capable of reducing plasma cholesterol and possessing anti-inflammatory properties, was compared with the well-studied anti-atherogenic apoA-I mimetic peptide 4F for reducing lesion formation in female apoE null mice with already existing lesions. METHODS AND RESULTS: In initial experiments, Ac-hE18A-NH(2) was administered retro-orbitally two or three times weekly for 6-8 weeks, while peptide 4F was administered intraperitoneally every day for the same period. Age matched controls were injected with saline every day. At the end of the treatment period, plasma cholesterol levels of Ac-hE18A-NH(2) administered mice were significantly lower than in 4F and control mice. However, both 4F and Ac-hE18A-NH(2) showed reduced lesion areas in en face lesion analysis to a similar extent compared to the control group, while paraoxonase-1 (PON-1) activity was increased only in the Ac-hE18A-NH(2) group. In the third experiment, both peptides were administered at the same dose, frequency, and route of administration. The reduction in en face lesions with Ac-hE18A-NH(2) was significantly greater than the 4F and control groups, although lesions in 4F-treated mice were also significantly reduced compared with controls. Both peptide groups had significantly reduced plasma lipid hydroperoxides, but only the Ac-hE18A-NH(2) group had significantly reduced serum amyloid A levels. HDL and plasma inflammatory indices were significantly reduced in both peptide groups compared with controls. CONCLUSIONS: Although both peptides had similar anti-inflammatory properties, Ac-hE18A-NH(2) was more effective in inhibiting lesions than 4F at the same dose, frequency, and route of administration, perhaps due to its cholesterol reducing properties.

Two adjacent domains (141-150 and 151-160) of apoE covalently linked to a class A amphipathic helical peptide exhibit opposite atherogenic effects.

OBJECTIVE: We recently described anti-atherogenic properties of the dual domain peptide Ac-hE18A-NH(2) derived by covalently linking the heparin binding domain 141-150 of apoE to 18A, a class A amphipathic helical peptide. In this paper we have compared the properties of Ac-hE18A-NH(2) with the non-heparin binding 151-160 region of apoE linked to 18A (Ac-nhE18A-NH(2)). METHODS AND RESULTS: Both peptides were highly helical in solution and in association with lipids. Ac-hE18A-NH(2) and not Ac-nhE18A-NH(2) enhanced uptake of low density lipoprotein (LDL) in HepG2 cells. While Ac-hE18A-NH(2) retarded the electrophoretic mobility of LDL, Ac-nhE18A-NH(2) slightly enhanced mobility. Ac-hE18A-NH(2) reduced monocyte association with endothelial cells, while Ac-nhE18A-NH(2) increased it. Ac-hE18A-NH(2) also reduced lipid hydroperoxide content of LDL while Ac-nhE18A-NH(2) increased it. A single administration of Ac-hE18A-NH(2) (100 µg/mouse) into apoE null mice dramatically reduced cholesterol (from 600 mg/dL to 180 mg/dL at 5 min and to 60 mg/dL at 5h) while Ac-nhE18A-NH(2) had no effect. Administration (100 µg/mouse/day, three days a week) into apoE null mice for six weeks showed Ac-hE18A-NH(2) group having a moderate aortic sinus lesion reduction compared with the control group (-15.1%), while the Ac-nhE18A-NH(2) administered group had increased lesion area (+33.0% vs controls and 36.1% vs Ac-hE18A-NH(2)). Plasma from mice administered Ac-hE18A-NH(2) for six weeks showed a significant reduction in plasma cholesterol and triglyceride levels and increase in paraoxonase-1 (PON-1) activity compared to controls, while Ac-nhE18A-NH(2) caused no change in plasma cholesterol and decreased PON-1 activity. CONCLUSION: It is proposed that Ac-hE18A-NH(2) reduced lesion progression in apoE null mice due to its anti-inflammatory and lipoprotein clearing properties, while Ac-nhE18A-NH(2) exhibited pro-atherogenic effects.

Oral administration of L-mR18L, a single domain cationic amphipathic helical peptide, inhibits lesion formation in ApoE null mice.

We have shown that Ac-hE18A-NH2, a dual-domain cationic apolipoprotein-mimetic peptide, reduces plasma cholesterol levels in dyslipidemic mice. Two single-domain cationic peptides based on the lytic class L peptide 18L were developed to test the hypothesis that a single-domain cationic amphipathic peptide can reduce atherosclerosis in apolipoprotein (apo)E null mice when orally administered. To incorporate anti-inflammatory properties, aromatic residues were clustered in the nonpolar face similar to peptide 4F, resulting in modified 18L (m18L). To reduce lytic properties, the Lys residues of 18L were replaced with Arg with the resulting peptide called modified R18L (mR18L). Biophysical studies showed that mR18L had stronger interactions with lipids than did m18L. Peptide mR18L was also more effective than m18L in promoting LDL uptake by HepG2 cells. ApoE null mice received normal chow or chow containing m18L or mR18L for six weeks. A significant reduction in plasma cholesterol and aortic sinus lesion area was seen only in the mR18L group. Plasma from mice administered mR18L, unlike those from the control and m18L groups, did not enhance monocyte adhesion to endothelial cells. Thus oral administration of mR18L reduces plasma cholesterol and lesion formation and inhibits monocyte adhesion.

Oral apolipoprotein A-I mimetic peptide improves cognitive function and reduces amyloid burden in a mouse model of Alzheimer's disease.

Recent evidence indicates that inflammation may significantly contribute to the pathogenesis of Alzheimer's disease (AD). Since the apo A-I mimetic peptide D-4F has been shown to inhibit atherosclerotic lesion formation and regress already existing lesions (in the presence of pravastatin) and the peptide also decreases brain arteriole inflammation, we undertook a study to evaluate the efficacy of oral D-4F co-administered with pravastatin on cognitive function and amyloid beta (A beta) burden in the hippocampus of APPSwe-PS1 Delta E9 mice. Three groups of male mice were administered D-4F and pravastatin, Scrambled D-4F (ScD-4F, a control peptide) and pravastatin in drinking water, while drinking water alone served as control. The escape latency in the Morris Water Maze test was significantly shorter for the D-4F+statin administered animals compared to the other two groups. While the hippocampal region of the brain was covered with 4.2+/-0.5 and 3.8+/-0.6% of A beta load in the control and ScD-4F+statin administered groups, in the D-4F+statin administered group A beta load was only 1.6+/-0.1%. Furthermore, there was a significant decrease in the number of activated microglia (p<0.05 vs the other two groups) and activated astrocytes (p<0.05 vs control) upon oral D-4F+statin treatment. Inflammatory markers TNFalpha and IL-1 beta levels were decreased significantly in the D-4F+statin group compared to the other two groups (for IL-1 beta p<0.01 vs the other two groups and for TNF-alpha p<0.001 vs control) and the expression of MCP-1 were also less in D-4F+statin administered group compared to the other two groups. These results suggest that the apo A-I mimetic peptide inhibits amyloid beta deposition and improves cognitive function via exerting anti-inflammatory properties in the brain.