Protective Effect of Flavonoids against Methylglyoxal-Induced Oxidative Stress in PC-12 Neuroblastoma Cells and Its Structure-Activity Relationships
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Danyang Zhang1, Xia Li1, Xiaoshi He1
1School of Bioengineering, Dalian University of Technology, Dalian 116024, China.
Abstract:
Methylglyoxal-induced oxidative stress and cytotoxicity are the main factors causing neuronal death-related, diabetically induced memory impairment. Antioxidant and anti-apoptotic therapy are potential intervention strategies. In this study, 25 flavonoids with different substructures were assayed for protecting PC-12 cells from methylglyoxal-induced damage. A structure-activity relationship (SAR) analysis indicated that the absence of the double bond at C-2 and C-3, substitutions of the gallate group at the 3 position, the pyrogallol group at the B-ring, and the R configuration of the 3 position enhanced the protection of flavan-3-ols, and a hydroxyl substitution at the 4' and meta-positions were important for the protection of flavonol. These SARs were further confirmed by molecular docking using the active site of the Keap1-Nrf2 complex as the receptor. The mechanistic study demonstrated that EGCG with the lowest EC50 protected the PC-12 cells from methylglyoxal-induced damage by reducing oxidative stress via the Nrf2/Keap1/HO-1 and Bcl-2/Bax signaling pathways. These results suggested that flavan-3-ols might be a potential dietary supplement for protection against diabetic encephalopathy.
Insights
Flavan-3-ols show promise in protecting brain cells from damage linked to diabetes. This study identifies key structural features that enhance their antioxidant and anti-apoptotic effects, potentially preventing diabetic memory loss.
Area of Science:
- Neuroscience
- Pharmacology
- Biochemistry
Background:
- Diabetic encephalopathy and memory impairment are linked to methylglyoxal-induced oxidative stress and neuronal death.
- Antioxidant and anti-apoptotic therapies are explored as potential interventions for neurodegenerative conditions associated with diabetes.
Purpose of the Study:
- To investigate the protective effects of 25 flavonoids against methylglyoxal-induced damage in PC-12 cells.
- To establish structure-activity relationships (SAR) for flavonoid neuroprotection.
- To elucidate the underlying mechanisms of neuroprotection by potent flavonoids.
Main Methods:
- Assay of 25 flavonoids for cytoprotective activity against methylglyoxal.
- Structure-activity relationship (SAR) analysis to identify key protective structural features.
- Molecular docking studies targeting the Keap1-Nrf2 complex.
- Mechanistic investigation of the Nrf2/Keap1/HO-1 and Bcl-2/Bax signaling pathways.
Main Results:
- Specific structural features, including the absence of a C-2/C-3 double bond and gallate substitution, enhanced flavan-3-ol protection.
- Hydroxyl substitutions at 4' and meta-positions were crucial for flavonol protection.
- Epigallocatechin gallate (EGCG) demonstrated the lowest EC50, indicating potent protection.
- EGCG reduced oxidative stress and modulated Nrf2/Keap1/HO-1 and Bcl-2/Bax pathways.
Conclusions:
- Flavan-3-ols possess significant neuroprotective properties against methylglyoxal-induced damage.
- Detailed SAR provides insights into designing effective neuroprotective flavonoids.
- The Nrf2/Keap1/HO-1 and Bcl-2/Bax pathways are key mediators of EGCG's neuroprotective effects.
- Flavan-3-ols represent a potential dietary supplement strategy for preventing diabetic encephalopathy.
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