In a recent study published in the journal Dr Antioxidants, Researchers have investigated the mechanisms by which resveratrol, a natural phenolic compound, may prevent and reduce Alzheimer’s disease (AD). They used the BV2 microglial cell line established from C57BL/g transgenic murine models to elucidate the mechanistic benefits of resveratrol against glia activation by proinflammatory monomeric C-reactive protein (mCRP). Their results highlight that resveratrol inhibits lipopolysaccharides (LPS) and MCRP-induced cyclooxygenase-2, thereby preventing the release of proinflammatory cytokines. It further promotes the expression of antioxidant enzymes, viz the cat And Sod2. Together, these findings provide a mechanistic basis for resveratrol’s benefits in fighting and controlling AD.
Study: Resveratrol activates antioxidant defense mechanisms in cellular models of Alzheimer’s disease inflammation. Image credit: Aimee Lee Studios/Shutterstock
What is Resveratrol?
Resveratrol, commonly found in red grapes and their derivatives (eg, red wine), is a natural phenolic compound belonging to the stilbene family. Extensive pre-clinical studies on metabolism have revealed its potent anti-inflammatory, anti-neurodegenerative, antioxidant and anti-aging properties. It is a common compound synthesized by more than 70 known plant species as a stress-response mechanism.
Recent studies of resveratrol in animal models have shown that trans-Resveratrol is able to cross the blood-brain barrier, suggesting that it may exert neuroprotective functions. This is compounded by the fact that older men and women who drink moderately have a consistently lower dementia risk than lifelong abstainers. Unfortunately, the human body does not manufacture resveratrol, and therapeutic doses (150-250 mg/d) can only be achieved through oral supplementation.
Scientists have attempted to elucidate the effects of these compounds on neurodegenerative and non-neural medical conditions to arrive at the mechanistic underpinnings. However, Resveratrol’s mechanism of action in humans remains a mystery, given the inconclusive results of the aforementioned studies. The compound is both hormetic and hydrophobic, limiting its absorption and bioavailability. Researchers have overcome this by developing novel nanocarrier-based delivery systems showing significant promise in cancer- and neurotherapy. Murine models have also suggested that resveratrol can significantly reduce oxidative stress and improve neurodegenerative outcomes through tumor necrosis factor α (TNFα) downregulation. However, these claims remain to be tested.
Understanding the mechanisms by which resveratrol exerts its neuroprotective benefits may allow the development of new interventions aimed at preventing or managing Alzheimer’s disease (AD). This will further inform future clinical trials of safe dose ranges, given that the chemical can be cytotoxic at high concentrations.
About the study
In the present study, researchers attempted to evaluate the antioxidant protection mechanism of resveratrol using BV2 microglia, which are activated by monomeric C-reactive protein (mCRP). MCRP activation and overexpression are important features of most inflammation-activated diseases, and its prevention may delay or reverse AD-like conditions that may progress to some extent due to inflammatory stress.
Schematic representation of the protective mechanisms of resveratrol against the proinflammatory agents mCRP and LPS.
The BV2 cell line used here was established from C57BL/6 transgenic mouse microglia, an established model for studying brain inflammation. MCRP was prepared from purified CRP protein by urea/ethylenediaminetetraacetic acid (EDTA) chelation, followed by dialysis. Escherichia coli 026:B26 was used as a lipopolysaccharide (LPS) strain. Resveratrol treatment in these primary cell cultures varied between 10–50 µM. mCRP assays used mCRP at 50 µg/mL. To avoid astrocyte damage, primary glial cultures were not subjected to nutrient (serum) starvation.
Nitric oxide generation by glial cultures was determined using the colorimetric Griess reaction. Enzyme-linked immunosorbent assay (ELISA) was used to detect and quantify tumor necrosis factor-alpha (TNF-α) and interleukin one-beta (IL1 ß) expressed in ng/mL and pg/mL, respectively. Western blotting assay was used to detect and identify other protein products produced by BV2 cells. BV2 cell RNA was then extracted and subjected to real-time quantitative polymerase chain reaction (qPCR) to determine relative gene expression.
Finally, immunofluorescence assay was used to measure the effect of Resveratrol on the expression of BV2 cells. Statistical analysis included two-way analysis of variance (ANOVA) and the Shapiro-Wilk test.
Resveratrol has been shown to significantly inhibit and reduce TNF-α production induced by mCRP and LPS, explaining and validating its anti-inflammatory properties. The compound was further observed to suppress the activation of the nitric oxide pathway, preventing the generation of reactive oxygen species (ROS).
Activation of the NLR family pyrin domain containing 3 (NLRP3) gene has also been shown to be inhibited by Resveratrol. NLRP3 is the gene responsible for the production of cryopyrin protein, an important microglia cell sensor inflammasome that is activated during oxidative stress. Nuclear factor-κB (NF-κB) and Nos2 were found to be up-regulated upon addition of resveratrol. Finally, Resveratrol has been found to stimulate the expression of antioxidant genes, including Sirt1 and Nfe2I2.
In summary, anti-AD effects of resveratrol have been shown to be due to a combination of oxidation suppression and antioxidant expression.
In the current study, researchers investigated the mechanisms by which resveratrol, a plant metabolite found in more than 70 species, may promote positive neurodegenerative outcomes, particularly in AD. They used a combination of in vitro cell culture, ELISAs, Western blotting and qPCR and revealed that resveratrol both suppressed the generation of ROS and enhanced the expression of antioxidant-protective genes.
“Resveratrol BV2 protects against microglia polarization in an activated phenotype induced by two critical proinflammatory agents, LPS and mCRP. NLRP3 inflammasome and COX-2 in this novel in vitro model. SIRT1, Nrf2, and NF-ĸB pathways account for resveratrol’s protective mechanism against mCRP. Modulation is required that reduces downstream inflammatory mediators and, in particular, resistance mechanisms against induced antioxidant enzymes. The proinflammatory phenotype by mCRP was confirmed in primary mixed glial cultures.”
These results highlight the potential of resveratrol in future AD preclinical trials. Resveratrol and similar plant-derived metabolites may allow the development of future clinical interventions against currently incurable diseases such as AD. However, extensive clinical trials are needed to evaluate the efficacy of resveratrol on other oxidation-induced genes and to arrive at safe doses for human use.
- Bartra, C., Yuan, Y., Vuraić, K., Slevin, M., Pastorello, Y., Suñol, C., & Sanfeliu, C. (2024). Resveratrol activates antioxidant defense mechanisms in cellular models of Alzheimer’s disease inflammation. Antioxidants13(2), 177, DOI – 10.3390/antiox13020177, https://www.mdpi.com/2076-3921/13/2/177