Gallotannin causes differentiation and inflammation via ERK‑1/‑2 and p38 kinase pathways in rabbit articular chondrocytes.

Gallotannin (GT) is a type of tannic acid, derived from plant polyphenols, that is an agonist of plant defense mechanisms. Tannins have two types of structure; condensed tannins are a polymer of flavonoid units, while hydrolysable tannins are carbohydrates. GT is used in medical agents for its anti‑viral, anti‑bacterial and anti‑parasitic effects. The present study investigated the effects of GT on differentiation and inflammation in rabbit articular chondrocytes. GT caused differentiation and inflammatory responses in the rabbit articular chondrocytes. GT treatment induced the expression of type Ⅱ collagen and sulfated proteoglycan, as determined by western blot analysis and alcian blue staining, respectively, in a dose‑ and time‑dependent manner. Additionally, treatment with GT increased the expression of cyclooxygenase‑2 (COX‑2) and the production of prostaglandin E2 (PGE2), as determined by western blot analysis and PGE2 assay. GT was confirmed to cause phosphorylation of ERK‑1/‑2 and p38 kinase. Inhibition of pERK with PD98059 promoted GT‑induced type Ⅱ collagen expression. However, the inhibition of p38 with SB203580 suppressed GT‑induced COX‑2 expression and PGE2 production. In summary, the results demonstrated that GT‑induced ERK‑1/‑2 and p38 kinase have opposite effects on differentiation and inflammation in rabbit articular chondrocytes.