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. 2021 Jan 19;11(1):126.
doi: 10.3390/biom11010126.

Glycyl-L-Prolyl-L-Glutamate Pseudotripeptides for Treatment of Alzheimer's Disease

Hasan Turkez  1 , Ivana Cacciatore  2 , Lisa Marinelli  2 , Erika Fornasari  2 , Mehmet Enes Aslan  3 , Kenan Cadirci  4 , Cigdem Yuce Kahraman  5 , Ozge Caglar  3 , Abdulgani Tatar  5 , Giuseppe Di Biase  2 , Ahmet Hacimuftuoglu  6 , Antonio Di Stefano  2 , Adil Mardinoglu  7   8
Affiliations

Glycyl-L-Prolyl-L-Glutamate Pseudotripeptides for Treatment of Alzheimer's Disease

Hasan Turkez et al. Biomolecules. .

Abstract

So far, there is no effective disease-modifying therapies for Alzheimer's Disease (AD) in clinical practice. In this context, glycine-L-proline-L-glutamate (GPE) and its analogs may open the way for developing a novel molecule for treating neurodegenerative disorders, including AD. In turn, this study was aimed to investigate the neuroprotective potentials exerted by three novel GPE peptidomimetics (GPE1, GPE2, and GPE3) using an in vitro AD model. Anti-Alzheimer potentials were determined using a wide array of techniques, such as measurements of mitochondrial viability (MTT) and lactate dehydrogenase (LDH) release assays, determination of acetylcholinesterase (AChE), α-secretase and β-secretase activities, comparisons of total antioxidant capacity (TAC) and total oxidative status (TOS) levels, flow cytometric and microscopic detection of apoptotic and necrotic neuronal death, and investigating gene expression responses via PCR arrays involving 64 critical genes related to 10 different pathways. Our analysis showed that GPE peptidomimetics modulate oxidative stress, ACh depletion, α-secretase inactivation, apoptotic, and necrotic cell death. In vitro results suggested that treatments with novel GPE analogs might be promising therapeutic agents for treatment and/or or prevention of AD.

Keywords: Alzheimer’s disease; gene expressions; glycine-proline-glutamate peptidomimetics; in vitro cell culture model; neurotoxicity.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Design and development of GPEs peptidomimetics starting from native GPE.
Figure 2
Figure 2
(A) Undifferentiated SHSY5Y cells, (B) differentiated SHSY5Y cells using a combination of RA+BDNF. (40× magnifications) and (C) cell cycle analysis via flow cytometry. Statistical analysis was performed using a one-way ANOVA followed by Tukey’s post-hoc test. Symbol (*) used for statistically significant (p < 0.05) change in each cell cycle phase.
Figure 3
Figure 3
The neuroprotective effects of GPE, MEM, GPE1, GPE2, and GPE3 against in vitro Aβ1-42-exposure (MTT assay; % cell viability) (n = 5). Statistical analysis was performed using a one-way ANOVA followed by Tukey’s post-hoc test. Symbol (*) represents a statistically significant (p < 0.05) increase in cell viability compared to beta-amyloid.
Figure 4
Figure 4
The neuroprotective effects of GPE, MEM, GPE1, GPE2, and GPE3 against in vitro Aβ1-42-exposure (LDH assay results converted to % of cell viabilities) (n = 5). Statistical analysis was performed using a one-way ANOVA followed by Tukey’s post-hoc test. Symbol (*) represents a statistically significant (p < 0.05) increase in cell viability compared to beta-amyloid.
Figure 5
Figure 5
The effects of novel GPEs applications on Aβ1-42-induced AChE activity (n = 5). Statistical analysis was performed using a one-way ANOVA followed by Tukey’s post-hoc test. Symbol (*) represents a statistically significant (p < 0.05) decrease in AChE activity compared to beta-amyloid.
Figure 6
Figure 6
Effects of GPE and GPE3 on apoptosis and necrosis in cellular model of AD (Hoechst 33258) (n = 5), (A) Untreated group, (B) Aβ1-42 (20 µM), (C) GPE3 (50 µM) + Aβ1-42, (D) GPE (50 µM) + Aβ1-42. Red arrows indicate necrotic cells with damaged chromosomal structures.
Figure 7
Figure 7
Flow cytometric analysis of Annexin V-FITC (FL1)/PI (FL2) double-labeled cells in a cellular model of AD (n = 5), (A) negative control, (B) Aβ1-42, (C) MEM (50 µM) + Aβ1-42, (D) GPE3 (50 µM) + Aβ1-42, (E) All experimental groups were shown in one graph. Statistical analysis was performed using a one-way ANOVA followed by Tukey’s post-hoc test. Symbol (*) represents a statistically significant (p < 0.05) increase in cell viability compared to beta-amyloid application.
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