Green tea extract inhibits chemokine production, but up-regulates chemokine receptor expression, in rheumatoid arthritis synovial fibroblasts and rat adjuvant-induced arthritis

Abstract

Objective. Evaluation of the efficacy of green tea extract (GTE) in regulating chemokine production and chemokine receptor expression in human RA synovial fibroblasts and rat adjuvant-induced arthritis (AIA). Methods. Fibroblasts isolated from human RA synovium were used in the study. Regulated upon activation normal T cell expressed and secreted (RANTES)/CCL5, monocyte chemoattractant protein (MCP)-1/CCL2, growth-regulated oncogene (GRO)a/CXCL1 and IL-8/CXCL8 production was measured by ELISA. Western blotting was used to study the phosphorylation of protein kinase C (PKC)d and c-Jun N-terminal kinases (JNK). Chemokine and chemokine receptor expression was determined by quantitative RT–PCR. The benefit of GTE administration in rat AIA was determined. Results. GTE (2.5–40 mg/ml) inhibited IL-1b-induced MCP-1/CCL2 (10 ng/ml), RANTES/CCL5, GROa/CXCL1 and IL-8/CXCL8 production in human RA synovial fibroblasts (P<0.05). However, GTE inhibited MCP-1/CCL2 and GROa/CXCL1 mRNA synthesis in RA synovial fibroblasts. Furthermore, GTE also inhibited IL-1b-induced phosphorylation of PKCd, the signalling pathway mediating IL-1b-induced chemokine production. Interestingly, GTE preincubation enhanced constitutive and IL-1b-induced CCR1, CCR2b, CCR5, CXCR1 and CXCR2 receptor expression. GTE administration (200 mg/kg/day p.o.) modestly ameliorated rat AIA, which was accompanied by a decrease in MCP-1/CCL2 and GROa/CXCL1 levels and enhanced CCR-1, -2, -5 and CXCR1 receptor expression in the joints of GTE administered rats. Conclusions. Chemokine receptor overexpression with reduced chemokine production by GTE may be one potential mechanism to limit the overall inflammation and joint destruction in RA.