Anthocyanin Extracted from Black Soybean Seed Coats Prevents Autoimmune Arthritis by Suppressing the Development of Th17 Cells and Synthesis of Proinflammatory Cytokines by Such Cells, via Inhibition of NF-κB

The anti-arthritic effects of AEBS were associated with decreases in Th17 cell numbers, and the levels of proinflammatory cytokines synthesized by such cells, mediated via suppression of NF-κB signaling. Additionally, AEBS suppressed osteoclastogenesis and reduced oxidative stress levels.

CIA was induced in DBA/1J mice. Cytokine levels were measured via enzyme-linked immunosorbent assays. Joints were assessed in terms of arthritis incidence, clinical arthritis scores, and histological features. The extent of oxidative stress in affected joints was determined by measuring the levels of nitrotyrosine and inducible nitric oxide synthase. NF-κB activity was assayed by measuring the ratio of phosphorylated IκB to total IκB via Western blotting. Th17 cells were stained with antibodies against CD4, IL-17, and STAT3. Osteoclast formation was assessed via TRAP staining and measurement of osteoclast-specific mRNA levels.

CIA was induced in DBA/1J mice. Cytokine levels were measured via enzyme-linked immunosorbent assays. Joints were assessed in terms of arthritis incidence, clinical arthritis scores, and histological features. The extent of oxidative stress in affected joints was determined by measuring the levels of nitrotyrosine and inducible nitric oxide synthase. NF-κB activity was assayed by measuring the ratio of phosphorylated IκB to total IκB via Western blotting. Th17 cells were stained with antibodies against CD4, IL-17, and STAT3. Osteoclast formation was assessed via TRAP staining and measurement of osteoclast-specific mRNA levels.

In the CIA model, AEBS decreased the incidence of arthritis, histological inflammation, cartilage scores, and oxidative stress. AEBS reduced the levels of proinflammatory cytokines in affected joints of CIA mice and suppressed NF-κB signaling. AEBS decreased Th17 cell numbers in spleen of CIA mice. Additionally, AEBS repressed differentiation of Th17 cells and expression of Th17-associated genes in vitro, in both splenocytes of naïve DBA/1J mice and human PBMCs. In vitro, the numbers of both human and mouse tartrate-resistant acid phosphatase+ (TRAP) multinucleated cells fell, in a dose-dependent manner, upon addition of AEBS. Conclusions: The anti-arthritic effects of AEBS were associated with decreases in Th17 cell numbers, and the levels of proinflammatory cytokines synthesized by such cells, mediated via suppression of NF-κB signaling. Additionally, AEBS suppressed osteoclastogenesis and reduced oxidative stress levels.