Differential protein expression and subcellular distribution of TGFbeta1, beta2 and beta3 in cardiomyocytes during pressure overload-induced hypertrophy.

The transforming growth factor beta (TGFbeta) superfamily plays an important role in the myocardial response to hypertrophy. We have investigated the protein expression of TGFbeta1, beta2 and beta3 in left ventricular tissue, and determined their subcellular distribution in myocytes by immunoblotting and immunocytochemistry during the development of left ventricular hypertrophy (LVH), using isoform specific antibodies to TGFbeta1, beta2 and beta3. LVH was produced in rats by aortic constriction (AC) and LV tissue was obtained at days (d)0, 1, 3, 7, 14, 21 and 42 following operation. Compared with age matched sham-operated controls (SH), TGFbeta1 levels in LV tissue of AC rats increased significantly from d1-d14 (P<0.03) concomitant with the adaptive growth of LV tissue. In contrast, TGFbeta3 levels decreased in LV tissue of AC rats from d3 post-operation (significant from d14-d42, P<0.03). No significant difference in TGFbeta2 levels were observed from SH and AC rats after operation. Antibodies to TGFbeta1 stained intercalated disks, sarcolemmal membranes and cytoplasm, but not nuclei, of cardiomyocytes on LV sections from untreated and SH rats. However, a trans-localisation of TGFbeta1 to the nuclei of cardiomyocytes was observed in AC hearts. Antibodies to TGFbeta3 stained T tubules, cytoplasm and the nuclei of cardiomyocytes from untreated and SH rats. However, by d7 post-AC operation, TGFbeta3 expression was lost rapidly from nuclei of cardiomyocytes followed by a reduction in total TGFbeta3 immunofluorescence in myocytes. Antibodies to TGFbeta2 stained sarcolemmal membranes of cardiomyocytes from both SH and AC rats without significant difference between groups. Thus, the differential pattern of protein expression and subcellular distribution of TGFbeta1, beta2 and beta3 in myocytes during the development of LVH suggests that these molecules play different roles in the response of cardiomyocytes to LVH.