Transforming growth factor-beta1 (TGFbeta1) stimulates connective tissue growth factor (CCN2/CTGF) expression in human gingival fibroblasts through a RhoA-independent, Rac1/Cdc42-dependent mechanism: statins with forskolin block TGFbeta1-induced CCN2/CTGF expression.
Regulation of connective tissue growth factor (CCN2/CTGF) in gingival fibroblasts is unique and may provide therapeutic opportunities to treat oral fibrotic diseases. RhoA was previously implicated in mediating the expression of CCN2/CTGF. We now present evidence that Rho family GTPases Rac1 and Cdc42 are the principal mediators of the transforming growth factor-beta1 (TGFbeta1)-stimulated expression of CCN2/CTGF in primary human gingival fibroblasts. TGFbeta1 does not stimulate RhoA activation in gingival fibroblasts, and the overexpression of dominant-negative RhoA does not reduce CCN2/CTGF expression in response to TGFbeta1. In contrast, the overexpression of dominant-negative forms of Cdc42 or Rac1 results in a dramatic reduction of CCN2/CTGF protein levels. Lovastatin and a geranylgeranyltransferase inhibitor reduce the TGFbeta1-stimulated levels of CCN2/CTGF protein by approximately 75 and 100%, respectively. We previously demonstrated that JNK1 phosphorylation by TGFbeta1 is also critical for TGFbeta1-induced CCN2/CTGF expression, and forskolin partially reduces levels of phosphorylated JNK1. Inhibition of geranylgeranyltransferase has no effect on levels of JNK phosphorylation in response to TGFbeta1 suggesting Rho-GTPases act independently of JNK1. The combination of lovastatin and forskolin results in a greater inhibitory effect than each agent alone and reduces CCN2/CTGF mRNA and protein expression by greater than 90%. This novel combination has additive inhibitory effects on the TGFbeta1-stimulated expression of CCN2/CTGF in human gingival fibroblasts through the simultaneous disruption of Rho- and JNK1-mediated pathways, respectively. This combination of available therapeutic compounds may therefore be useful in designing treatment strategies for oral fibrotic conditions in which gingival CCN2/CTGF is elevated.
Black
Samuel A
SA
Department of Periodontology and Oral Biology, Division of Oral Biology, Boston University Goldman School of Dental Medicine, Boston, Massachusetts 02118, USA.
Trackman
Philip C
PC
D002467:Cell Nucleus / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology*; D055513:Connective Tissue Growth Factor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism*; D005786:Gene Expression Regulation; D005799:Genes, Dominant; D005881:Gingiva / Q000166:cytology*; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology; D017874:Immediate-Early Proteins / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D008148:Lovastatin / Q000494:pharmacology; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
C526317:CCN2 protein, human; D004791:Enzyme Inhibitors; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; C107953:RAC1 protein, human; D053773:Transforming Growth Factor beta1; C066737:RHOA protein, human; D055513:Connective Tissue Growth Factor; D005576:Colforsin; D008148:Lovastatin; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein