TLR4, RAGE, and p-JNK/JNK mediated inflammatory aggression in osteoathritic human chondrocytes are counteracted by redox-sensitive phenolic olive compounds: Comparison with ibuprofen

Nutritional Epigenomics: Bioactive Dietary Compounds in the Epigenetic Regulation of Osteoarthritis

Nutritional epigenomics is exceptionally important because it describes the complex interactions among food compounds and epigenome modifications. Phytonutrients or bioactive compounds, which are secondary metabolites of plants, can protect against osteoarthritis by suppressing the expression of inflammatory and catabolic mediators, modulating epigenetic changes in DNA methylation, and the histone or chromatin remodelling of key inflammatory genes and noncoding RNAs. The combination of natural epigenetic modulators is crucial because of their additive and synergistic effects, safety and therapeutic efficacy, and lower adverse effects than conventional pharmacology in the treatment of osteoarthritis. In this review, we have summarized the chondroprotective properties of bioactive compounds used for the management, treatment, or prevention of osteoarthritis in both human and animal studies. However, further research is needed into bioactive compounds used as epigenetic modulators in osteoarthritis, in order to determine their potential value for future clinical applications in osteoarthritic patients as well as their relation with the genomic and nutritional environment, in order to personalize food and nutrition together with disease prevention.

Anti-inflammatory effects of Olive (olea europaea L.) fruit extract in LPS-stimulated RAW264.7 cells via MAPK and NF-κB signal pathways

BACKGROUND

Olive is an evergreen tree of Oleaceae Olea with numerous bioactive components. While the anti-inflammatory properties of olive oil and the derivatives are well-documented, there remains a dearth of in-depth researches on the immunosuppressive effects of olive fruit water extract. This study aimed to elucidate the dose-effect relationship and underlying molecular mechanisms of olive fruit extract in mediating anti-inflammatory responses.

METHODS AND RESULTS

The impacts of olive fruit extract on the release of nitric oxide (NO), tumor necrosis factor (TNF-α), interleukins-6 (IL-6) and reactive oxygen species (ROS) were assessed in RAW264.7 cells induced by lipopolysaccharide (LPS). For deeper understanding, the expression of genes encoding inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), TNF-α and IL-6 was quantitatively tested. Additionally, the expression patterns of MAPK and NF-κB pathways were further observed to analyze the action mechanisms. Results suggested that olive fruit extract (200, 500, 1000 µg/mL) markedly exhibited a dose-dependent reduction in the generation of NO, TNF-α, IL-6 and ROS, as well as the expression of correlative genes studied. The activation of ERK, JNK, p38, IκB-α and p65 were all suppressed when p65 nuclear translocation was further restricted by olive fruit extract in NF-κB and MAPK signal pathways.

CONCLUSIONS

Olive fruit extract targeted imposing restrictions on the signal transduction of key proteins in NF-κB and MAPK pathways, and thereby lowered the level of inflammatory mediators, which put an enormous hindrance to inflammatory development. Accordingly, it is reasonable to consider olive fruit as a potent ingredient in immunomodulatory products.

Effects of Oleuropein and Hydroxytyrosol on Inflammatory Mediators: Consequences on Inflammaging

Aging is associated with a low-grade, systemic inflammatory state defined as "inflammaging", ruled by the loss of proper regulation of the immune system leading to the accumulation of pro-inflammatory mediators. Such a condition is closely connected to an increased risk of developing chronic diseases. A number of studies demonstrate that olive oil phenolic compound oleuropein and its derivative hydroxytyrosol contribute to modulating tissue inflammation and oxidative stress, thus becoming attractive potential candidates to be used in the context of nutraceutical interventions, in order to ameliorate systemic inflammation in aging subjects. In this review, we aim to summarize the available data about the anti-inflammatory properties of oleuropein and hydroxytyrosol, discussing them in the light of molecular pathways involved in the synthesis and release of inflammatory mediators in inflammaging.

Effects of type II collagen hydrolysates on osteoarthritis through the NF-κB, Wnt/β-catenin and MAPK pathways

Osteoarthritis (OA), a degenerative disease, has attracted extensive attention all over the world. In this study, a rat model involving medial meniscus resection (MMx) and anterior to medial collateral ligament (ACL) operation was successfully established to study the effects of bovine cartilage hydrolysates rich in type II collagen peptides (BIIP) on cartilage protection. The results of histological analysis indicated that oral administration of BIIP at doses of 200 and 500 mg kg^-1 d^-1 ameliorated cartilage degeneration. Moreover, the potential targets of BIIP affecting OA in vivo were studied by proteomics, and the effects of BIIP on OA through signaling pathways, such as NF-κB, Wnt/β-catenin and MAPK, were further explored at mRNA and protein levels. BIIP downregulated the expression of IL-6, RUNX2, NF-κB p65, HIF-2α, β-catenin and p-JNK, which may be the main factor leading to the prevention of OA. These results suggest that BIIP can be used as a novel potential substance of functional foods to exert chondroprotective action.

S-Allylcysteine Inhibits Chondrocyte Inflammation to Reduce Human Osteoarthritis via Targeting RAGE, TLR4, JNK and Nrf2 Signaling: Comparison with Colchicine

Discovery of new pharmacological agents is needed to control the progression of osteoarthritis (OA) characterized by progressive joint cartilage damage. Human OA chondrocyte cultures (OAC) were either applied to S-Allyl cysteine (SAC), a sulfur-containing amino acid derivative, or colchicine, an ancient anti-inflammatory therapeutic, for 24 hours. SAC or colchicine did not change viability at 1 nM-10 µM but inhibited p-JNK/pan-JNK. While SAC seems to be more effective, both agents inhibited reactive oxygen species (ROS), 3-nitrotyrosine (3-NT), lipid-hydroperoxides (LPO), advanced lipoxidation end-products (ALEs as 4-hydroxy-2-nonenal, HNE) and advanced glycation end-products (AGEs), and increased glutathione-peroxidase (GPx) and type-II-collagen (COL2). IL-1β, IL-6 and osteopontin (OPN) were more strongly inhibited by SAC than in colchicine. In contrast, TNF-α was inhibited only by SAC, and COX2 only by colchicine. Casp-1/ICE, GM-CSF, receptor for advanced glycation end-products (RAGE) and toll-like receptors (TLR4) were inhibited by both agents, but bone morphogenetic protein 7 (BMP7) was partially inhibited by SAC while induced by colchicine. The nuclear factor erythroid 2-related factor 2 (Nrf2) was induced by SAC; in contrast it was inhibited by colchicine. Although exerting opposite effects on TNF-α, COX2, BMP7 and Nrf2, SAC and colchicine exhibit anti-osteoarthritic properties in OAC by modulating redox sensitive inflammatory signaling.

Dietary Interventions with Polyphenols in Osteoarthritis: A Systematic Review Directed from the Preclinical Data to Randomized Clinical Studies

Osteoarthritis (OA) is the most common form of arthritis and a major cause of limited functionality and thus a decrease in the quality of life of the inflicted. Given the fact that the existing pharmacological treatments lack disease-modifying properties and their use entails significant side effects, nutraceuticals with bioactive compounds constitute an interesting field of research. Polyphenols are plant-derived molecules with established anti-inflammatory and antioxidant properties that have been extensively evaluated in clinical settings and preclinical models in OA. As more knowledge is gained in the research field, an interesting approach in the management of OA is the additive and/or synergistic effects that polyphenols may have in an optimized supplement. Therefore, the aim of this review was to summarize the recent literature regarding the use of combined polyphenols in the management of OA. For that purpose, a PubMed literature survey was conducted with a focus on some preclinical osteoarthritis models and randomized clinical trials on patients with osteoarthritis from 2018 to 2021 which have evaluated the effect of combinations of polyphenol-rich extracts and purified polyphenol constituents. Data indicate that combined polyphenols may be promising for the treatment of osteoarthritis in the future, but more clinical trials with novel approaches in the identification of the in-between relationship of such constituents are needed.