title: Green tea polyphenol epigallocatechin-3-gallate inhibits advanced glycation end product-induced expression of tumor necrosis factor-alpha and matrix metalloproteinase-13 in human chondrocytes.
abstract: BACKGROUND
  The major risk factor for osteoarthritis (OA) is aging, but the mechanisms underlying this risk are only partly understood. Age-related accumulation of advanced glycation end products (AGEs) can activate chondrocytes and induce the production of proinflammatory cytokines and matrix metalloproteinases (MMPs). In the present study, we examined the effect of epigallocatechin-3-gallate (EGCG) on AGE-modified-BSA (AGE-BSA)-induced activation and production of TNFalpha and MMP-13 in human OA chondrocytes.
  
  
  METHODS
  Human chondrocytes were derived from OA cartilage by enzymatic digestion and stimulated with in vitro-generated AGE-BSA. Gene expression of TNFalpha and MMP-13 was measured by quantitative RT-PCR. TNFalpha protein in culture medium was determined using cytokine-specific ELISA. Western immunoblotting was used to analyze the MMP-13 production in the culture medium, phosphorylation of mitogen-activated protein kinases (MAPKs), and the activation of NF-kappaB. DNA binding activity of NF-kappaB p65 was determined using a highly sensitive and specific ELISA. IkappaB kinase (IKK) activity was determined using an in vitro kinase activity assay. MMP-13 activity in the culture medium was assayed by gelatin zymography.
  
  
  RESULTS
  EGCG significantly decreased AGE-stimulated gene expression and production of TNFalpha and MMP-13 in human chondrocytes. The inhibitory effect of EGCG on the AGE-BSA-induced expression of TNFalpha and MMP-13 was mediated at least in part via suppression of p38-MAPK and JNK activation. In addition, EGCG inhibited the phosphorylating activity of IKKbeta kinase in an in vitro activity assay and EGCG inhibited the AGE-mediated activation and DNA binding activity of NF-kappaB by suppressing the degradation of its inhibitory protein IkappaBalpha in the cytoplasm.
  
  
  CONCLUSIONS
  These novel pharmacological actions of EGCG on AGE-BSA-stimulated human OA chondrocytes provide new suggestions that EGCG or EGCG-derived compounds may inhibit cartilage degradation by suppressing AGE-mediated activation and the catabolic response in human chondrocytes.
authors.affiliation: Department of Pathology, School of Medicine, University of South Carolina, Columbia, SC 29209, USA. zafar.rasheed@uscmed.sc.edu
authors.forename: Zafar
authors.initials: Z
authors.lastname: Rasheed
authors.forename: Arivarasu N
authors.initials: AN
authors.lastname: Anbazhagan
authors.forename: Nahid
authors.initials: N
authors.lastname: Akhtar
authors.forename: Sangeetha
authors.initials: S
authors.lastname: Ramamurthy
authors.forename: Frank R
authors.initials: FR
authors.lastname: Voss
authors.forename: Tariq M
authors.initials: TM
authors.lastname: Haqqi
mesh_terms: D000368:Aged; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D017127:Glycation End Products, Advanced / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D006801:Humans; D008297:Male; D053509:Matrix Metalloproteinase 13 / Q000096:biosynthesis; D061965:Matrix Metalloproteinase Inhibitors; D008875:Middle Aged; D010636:Phenols / Q000494:pharmacology; D059808:Polyphenols; D011480:Protease Inhibitors / Q000494:pharmacology; D012710:Serum Albumin, Bovine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D013662:Tea; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000096:biosynthesis
chemical_list: D005419:Flavonoids; D017127:Glycation End Products, Advanced; D061965:Matrix Metalloproteinase Inhibitors; D010636:Phenols; D059808:Polyphenols; D011480:Protease Inhibitors; D013662:Tea; D014409:Tumor Necrosis Factor-alpha; C081628:advanced glycation end products-bovine serum albumin; D012710:Serum Albumin, Bovine; D002392:Catechin; C045651:epigallocatechin gallate; D053509:Matrix Metalloproteinase 13