Requirement of phosphatidylinositol 3-kinase/Akt signaling pathway for regulation of tissue inhibitor of metalloproteinases-3 gene expression by TGF-beta in human chondrocytes.
Transforming growth factor beta (TGF-beta1) induces cartilage extracellular matrix synthesis and tissue inhibitor of metalloproteinases-3 (TIMP-3), an important natural inhibitor of matrix metalloproteinases, aggrecanases and TNF-alpha-converting enzyme, which are implicated in cartilage degradation and joint inflammation. This study tested the hypothesis that Akt/protein kinase B signaling pathway could mediate TGF-beta1 induction of TIMP-3 in human articular chondrocytes. TGF-beta activated phosphorylation of Akt in a delayed and sustained fashion that correlated with TIMP-3 mRNA induction. Phosphatidylinositol kinase (PI3K) inhibitors, Wortmannin and LY294002 and Akt inhibitor (NL-71-101) significantly inhibited TGF-beta-induced Akt phosphorylation, TIMP-3 expression, TIMP-3 promoter (-940 to +376)-driven luciferase activity and Sp1 transcription factor binding. PI3K p85, Akt and Sp1 small interfering RNA (siRNA)-driven knockdown of the respective gene products significantly suppressed TGF-beta-induced TIMP-3 gene expression. TGF-beta-stimulated phosphorylation of p70S6 Kinase and TIMP-3 protein induction was inhibited by rapamycin. Thus TGF-beta induces TIMP-3 gene expression in human chondrocytes partly through PI3K/Akt pathway and Sp1 transcription factor and by translational mechanisms via mammalian target of rapamycin (mTOR) signaling. TGF-beta induction of pro-survival Akt cascade and TIMP-3 may be related to strengthening of cartilage extracellular matrix, increased chondrocyte viability and maintenance of joint tissue integrity.
Qureshi
Hamid Yaqoob
HY
Department of Medicine and Research Centre of Centre Hospitalier de l'Université de Montréal (CRCHUM), Montreal, Quebec, Canada H2L 4M1.
Ahmad
Rasheed
R
Sylvester
Judith
J
Zafarullah
Muhammad
M
D000730:Androstadienes / Q000494:pharmacology; D002358:Cartilage, Articular / Q000166:cytology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism*; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008954:Models, Biological; D009025:Morpholines / Q000494:pharmacology; D051058:Oncogene Protein v-akt / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D010766:Phosphorylation; D015398:Signal Transduction; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000494:pharmacology; D000077191:Wortmannin
D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D019717:Tissue Inhibitor of Metalloproteinase-3; D016212:Transforming Growth Factor beta; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases; D051058:Oncogene Protein v-akt; D000077191:Wortmannin