Antioxidant and Cytoprotective Effects of Oligomeric and Polymeric Procyanidin Fractions from Defatted Grape Seed in PC12 Cells

Procyanidins: A promising anti-diabetic agent with potential benefits on glucose metabolism and diabetes complications

Diabetes mellitus (DM) is a complex disease with alarming worldwide health implications and high mortality rates, largely due to its complications such as cardiovascular disease, nephropathy, neuropathy, and retinopathy. Recent research has shown that procyanidins (PC), a type of flavonoid, have strong antioxidant and free radical elimination effects, and may be useful in improving glucose metabolism, enhancing pancreatic islet cell activity, and decreasing the prevalence of DM complications. This review article presents a systematic search for peer-reviewed articles on the use of PC in the treatment of DM, without any language restrictions. The article also discusses the potential for PC to sensitise DM medications and improve their efficacy. Recent in vivo and in vitro studies have demonstrated promising results in improving the biological activity and bioavailability of PC for the treatment of DM. The article concludes by highlighting the potential for novel materials and targeted drug delivery methods to enhance the pharmacokinetics and bioactivity of PC, leading to the creation of safer and more effective anti-DM medications in the future.

Protective effect of gamma-aminobutyric acid against oxidative stress by inducing phase II enzymes in C2C12 myoblast cells

In this study, the cytoprotective effect of gamma-aminobutyric acid (GABA) via inducing phase II enzymes in C2C12 myoblasts was evaluated. The highest concentration of GABA (100 μM) significantly increased the cell viability by approximately 90% in hydrogen peroxide-induced C2C12 cells. The treatment with GABA (100 μM) effectively decreased the glutathione (GSH) depletion and the activities of antioxidant enzymes such as catalase (CAT) and superoxide dismutase (SOD). And, reactive oxygen species (ROS) levels were effectively reduced by about 50% in GABA-treated cells. In addition, the protein expression of phase II enzymes, such as NADPH:quinone oxidoreductase 1 and heme oxygenase-1 was significantly increased by GABA treatment. Moreover, GABA treatment increased the nuclear factor erythroid 2-related factor 2 (Nrf2) protein expression in the nucleus of C2C12 myoblasts. Altogether, the results in this study indicate that GABA possesses the cytoprotective effects against oxidative insults by regulating the GSH levels, CAT and SOD activities, ROS scavenging activities, and expression of phase II enzymes through the activation of Nrf2 in C2C12 cells. Hence, this study suggests that the GABA supplementation could be effective in alleviating oxidative stress-induced muscle damage. PRACTICAL APPLICATIONS: GABA exists in the germ and bran layers of rice and is well-known as the inhibitory neurotransmitter in the central nervous system. GABA also has various health beneficial effects, such as preventing chronic alcohol-related diseases and lowering blood pressure. The present study shows the cytoprotective effect of GABA against oxidative stress in C2C12 myoblasts, and suggests that GABA has great potential as a functional food ingredient for attenuating oxidative stress-induced muscle damage.

Protective Effect of Grape Seed Procyanidins against H2 O2 -Induced Oxidative Stress in PC-12 Neuroblastoma Cells: Structure-Activity Relationships

To establish a structure-activity relationship for procyanidins, we verified the cyto-protective effect of 13 grape seed procyanidins, ranging from monomers to trimers against H₂ O₂ -induced oxidative stress in PC-12 neuroblastoma cells. Our study demonstrated some procyanidins were able to significantly protect PC-12 cells from the H₂ O₂ -induced cytotoxicity suggesting they possess neuroprotective effects against oxidative stress. Procyanidins' protective effects against oxidative stress mainly depended on their polymerization degree in addition to their structural features. A positive correlation was found between procyanidins' polymerization degree and the protective effect against oxidative stress in PC-12 cells. The presence of 3- or 3'-galloylated groups in the C-ring of procyanidin molecules significantly increased their protective activity as well. These results demonstrated that galloylated high-molecular-mass procyanidins would be of more interesting as promising antioxidant natural compounds. This work for the first time demonstrated the structure-activity relationships of 13 procyanidins' antioxidative stress activity, which could have a significant impact on future development of procyanidins for healthy food products or drugs to treat disease such as neurodegenerative disorders.

PRACTICAL APPLICATION

This work evaluated the protective effect of procyanidins against oxidative stress in PC-12 neuroblastoma cells and established their activity-structure relationships, which provides useful cellular evidence for the further investigating the structure-optimizing and function-exploiting of procyanidins.

Oligomeric Procyanidins (OPCs) Inhibit Procollagen Type I Secretion of Fibroblasts

Wound healing is composed of a complex process that requires harmonies of various cell populations where fibroblasts play the main role. Oligomeric procyanidins (OPC) are main components of grape (Vitis vinifera) seed extracts, and recent studies showed OPC's effects on inflammation, cell migration, and proliferation. We investigated the effect of OPC on fibroblasts to regulate wound healing process. Human dermal fibroblast known as Hs27 cells were treated with various concentrations of OPC (0, 2.5, 5, 10, and 20 μg/μl). Cell cytotoxicity was evaluated by the Cell Counting Kit assay, and the expression levels of secreted procollagen were analyzed. Procollagen levels in OPC treated cells exposed to transforming growth factor beta 1 (TGF-β1) or ascorbic acid were evaluated using Western blot and immunocytochemistry. Relative mRNA expressions of procollagen, molecular chaperone such as HSP47, P4H were determined by real-time PCR in OPC treated cells. OPC showed no cytotoxicity on Hs27 cells at every concentration but inhibited procollagen secretion in a dose-dependent manner. The inhibitory effect also appeared under TGF-β1 induced collagen overproduction. Immunocytochemistry showed that higher levels of intracytoplasmic procollagen were accumulated in TGF-β1 treatment group, whereas ascorbic acid induced a release of accumulated procollagen under OPC treatment. The mRNA expressions of procollagen, molecular chaperone were not affected by OPC, but procollagen level was increased when exposed to TGF-β1. OPC inhibits procollagen secretion from fibroblasts with no effects on cell proliferations even under the environment of TGF-β1-induced collagen overproduction. OPC could regulate the diseases and symptoms of abnormal overabundant collagen production.

Synthetic chalcones with potent antioxidant ability on H₂O₂-induced apoptosis in PC12 cells

Chalcone derivatives (E)-3-(4-hydroxy-3-methoxyphenyl)-1-(4-methoxyphenyl) prop-2-en-1-one and (E)-3-(4-hydroxyphenyl)-1-(4-methoxyphenyl) prop-2-en-1-one (Compounds 1 and 2) have been demonstrated to be potent anti-inflammatory agents in our previous study. In light of the relationship of intracellular mechanisms between anti-inflammatories and antioxidants, we further designed and synthesized a series of chalcone derivatives based on 1 and 2, to explore their antioxidant efficacy. The majority of the derivatives exhibited strong protective effects on PC12 (PC12 rat pheochromocytoma) cells exposed to H₂O₂, and all compounds were nontoxic. A preliminary structure-activity relationship was proposed. Compounds 1 and 1d ((E)-2-methoxy-4-(3-(4-methoxyphenyl)-3-oxoprop-1-en-1-yl) phenyl acrylate) exerted the action in a good dose-dependent manner. Quantitative RT-PCR (qRT-PCR) and western blot analysis showed that 1 and 1d significantly improve the expression of nuclear factor erythroid 2 p45-related factor 2 (Nrf2)-dependent antioxidant genes g-Glutamylcysteine Ligase Catalytic Subunit (GCLC) and heme oxygenase-1 (HO-1) and their corresponding proteins (γ-glutamyl cysteine synthase (γ-GCS) and HO-1) in PC12 cells. Inhibition of GCLC and HO-1 by specific inhibitors, l-buthionine-S-sulfoximine (BSO) and zinc protoporphyrin (ZnPP), respectively, partially reduce the protective effect of 1 and 1d. These data present a series of novel chalcone analogs, especially compounds 1 and 1d, as candidates for treating oxidative stress-related disease by activating the Nrf2-antioxidant responsive element (ARE) pathway.