Abstract

Mechanical overload may change cardiac structure through angiotensin II-dependent and angiotensin II-independent mechanisms. We investigated the effects of mechanical strain on the gene expression of tenascin-C, a prominent extracellular molecule in actively remodeling tissues, in neonatal rat cardiac myocytes. Mechanical strain induced tenascin-C mRNA (3.9 +/- 0.5-fold, p < 0.01, n = 13) and tenascin-C protein in an amplitude-dependent manner but did not induce secreted protein acidic and rich in cysteine nor fibronectin. RNase protection assay demonstrated that mechanical strain induced all three alternatively spliced isoforms of tenascin-C. An angiotensin II receptor type 1 antagonist inhibited mechanical induction of brain natriuretic peptide but not tenascin-C. Antioxidants such as N-acetyl-L-cysteine, catalase, and 1, 2-dihydroxy-benzene-3,5-disulfonate significantly inhibited induction of tenascin-C. Truncated tenascin-C promoter-reporter assays using dominant negative mutants of IkappaBalpha and IkappaB kinase beta and electrophoretic mobility shift assays indicated that mechanical strain increases tenascin-C gene transcription by activating nuclear factor-kappaB through reactive oxygen species. Our findings demonstrate that mechanical strain induces tenascin-C in cardiac myocytes through a nuclear factor-kappaB-dependent and angiotensin II-independent mechanism. These data also suggest that reactive oxygen species may participate in mechanically induced left ventricular remodeling.