Interleukin-6 (IL-6) and/or soluble IL-6 receptor down-regulation of human type II collagen gene expression in articular chondrocytes requires a decrease of Sp1.Sp3 ratio and of the binding activity of both factors to the COL2A1 promoter.
Type II collagen is composed of alpha1(II) chains encoded by the COL2A1 gene. Alteration of this cartilage marker is a common feature of osteoarthritis. Interleukin-6 (IL-6) is a pro-inflammatory cytokine that needs a soluble form of receptor called sIL-6R to exert its effects in some cellular models. In that case, sIL-6R exerts agonistic action. This mechanism can make up for the partial or total absence of membrane-anchored IL-6 receptors in some cell types, such as chondrocytes. Our study shows that IL-6, sIL-6R, or both inhibit type II collagen production by rabbit articular chondrocytes through a transcriptional control. The cytokine and/or sIL-6R repress COL2A1 transcription by a -63/-35 sequence that binds Sp1.Sp3. Indeed, IL-6 and/or sIL-6R inhibit Sp1 and Sp3 expression and their binding activity to the 63-bp promoter. In chromatin immunoprecipitation experiments, IL-6.sIL-6R induced an increase in Sp3 recruitment to the detriment of Sp1. Knockdown of Sp1.Sp3 by small interference RNA and decoy strategies were found to prevent the IL-6- and/or sIL-6R-induced inhibition of COL2A1 transcription, indicating that each of these Sp proteins is required for down-regulation of the target gene and that a heterotypic Sp1.Sp3 complex is involved. Additionally, Sp1 was shown to interact with Sp3 and HDAC1. Indeed, overexpression of a full-length Sp3 cDNA blocked the Sp1 up-regulation of the 63-bp COL2A1 promoter activity, and by itself, inhibits COL2A1 transcription. We can conclude that IL-6, sIL-6R, or both in combination decrease both the Sp1.Sp3 ratio and DNA-binding activities, thus inhibiting COL2A1 transcription.
Laboratoire de Biochimie du Tissu Conjonctif, Université de Caen/Basse-Normandie, IFR ICORE 146, Faculté de Médecine, CHU niveau 3, Avenue de la Côte de Nacre, 14032 Caen Cedex, France.
Benoît
B
Porée
Magdalini
M
Kypriotou
Christos
C
Chadjichristos
Gallic
G
Beauchef
Emmanuelle
E
Renard
Florence
F
Legendre
Martine
M
Melin
Sylviane
S
Gueret
Daniel-Jean
DJ
Hartmann
Frédéric
F
Malléin-Gerin
Jean-Pierre
JP
Pujol
Karim
K
Boumediene
Philippe
P
Galéra
D000818:Animals; D002358:Cartilage, Articular / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism* / Q000473:pathology; D024043:Collagen Type II / Q000096:biosynthesis* / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D008954:Models, Biological; D010003:Osteoarthritis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic; D011817:Rabbits; D019947:Receptors, Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D051705:Sp3 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
C499177:COL2A1 protein, human; D024043:Collagen Type II; C508600:IL6 protein, human; D015850:Interleukin-6; D019947:Receptors, Interleukin-6; C497121:SP3 protein, human; D016329:Sp1 Transcription Factor; D051705:Sp3 Transcription Factor