Na super(+)/Ca super(2)+ Exchanger Activity Modulates Connective Tissue Growth Factor mRNA Expression in Transforming Growth Factor beta 1- and Des-Arg super(10)-kallidin-stimulated Myofibroblasts

• Published in: The Journal of biological chemistry Vol. 280; no. 15; pp. 14378 - 14384
• Main Authors: Romero, Jose R, Rivera, Alicia, Lanca, Vasco, Bicho, Manuel DP, Conlin, Paul R, Ricupero, Dennis A
• Format: Journal Article
• Language: English
• Published: 01.04.2005
• ISSN: 0021-9258; 1083-351X

Transforming growth factor (TGF)- beta and des-Arg super(10)-kallidin stimulate the expression of connective tissue growth factor (CTGF), a matrix signaling molecule that is frequently overexpressed in fibrotic disorders. Because the early signal transduction events regulating CTGF expression are unclear, we investigated the role of Ca super(2+) homeostasis in CTGF mRNA expression in TGF- beta 1- and des-Arg super(10)-kallidin-stimulated human lung myofibroblasts. Activation of the kinin B1 receptor with des-Arg super(10)-kallidin stimulated a rise in cytosolic Ca super(2+) that was extracellular Na super(+)-dependent and extracellular Ca super(2+)-dependent. The des-Arg super(10)-kallidin-stimulated increase of cytosolic Ca super(2+) was blocked by KB-R7943, a specific inhibitor of Ca super(2+) entry mode operation of the plasma membrane Na super(+)/Ca super(2+) exchanger. TGF- beta 1 similarly stimulated a KB-R7943-sensitive increase of cytosolic Ca super(2+) with kinetics distinct from the des-Arg super(10)-kallidin-stimulated Ca super(2+) response. We also found that KB-R7943 or 2',4'-dichlorobenzamil, an amiloride analog that inhibits the Na super(+)/Ca super(2+) exchanger activity, blocked the TGF- beta 1- and des-Arg super(10)-kallidin-stimulated increases of CTGF mRNA. Pretreatment with KB-R7943 also reduced the basal and TGF- beta 1-stimulated levels of alpha 1(I) collagen and alpha smooth muscle actin mRNAs. These data suggest that, in addition to regulating ion homeostasis, Na super(+)/Ca super(2+) exchanger acts as a signal transducer regulating CTGF, alpha 1(I) collagen, and alpha smooth muscle actin expression. Consistent with a more widespread role for Na super(+)/Ca super(2+) exchanger in fibrogenesis, we also observed that KB-R7943 likewise blocked TGF- beta 1-stimulated levels of CTGF mRNA in human microvascular endothelial and human osteoblast-like cells. We conclude that Ca super(2+) entry mode operation of the Na super(+)/Ca super(2+) exchanger is required for des-Arg super(10)-kallidin- and TGF- beta 1-stimulated fibrogenesis and participates in the maintenance of the myofibroblast phenotype.