Transfection with c-Ha rasEJ modulates alpha-actin and alpha 1B-adrenoceptor gene expression in vascular smooth muscle cells.

Co-ordinate down-regulation of smooth muscle-specific genes and acquisition of unregulated proliferative characteristics have been proposed as hallmarks of the atherosclerotic process. In the present study, we have evaluated this reciprocal relationship by examining the impact of c-Ha-rasEJ oncogene transfection on alpha-smooth muscle (SM) actin and alpha 1B-adrenoceptor (ADR) gene expression in vascular (aortic) smooth muscle cells (SMCs), c-Ha-rasEJ transfection of SMCs by lipofection (LF-1) was associated with enhanced DNA synthetic rates relative to vector controls and a significant reduction in alpha-SM actin and beta/gamma-actin mRNAs. Incubation of ras- and neo-LF-1 SMCs in a restrictive serum concentration (0.1%) for 72 h inhibited DNA synthesis in both cell types, but differentially influenced the pattern of alpha-actin gene expression. While neo-LF-1 cells incubated in 0.1% exhibited increased alpha-SM actin mRNA levels relative to 10% serum, slight decreases in alpha-SM actin were observed in ras-LF-1 cells under the same conditions. Cyclical stretch of randomly cycling cells, seeded on a flexible elastin substrate at a rate of 100 cycles/min for 72 h, did not significantly influence the pattern of alpha-SM or beta/gamma-actin mRNA expression in neo-LF-1 or ras-LF-1 cells. Steady-state mRNA levels of alpha 1B-ADR were higher in ras-LF-1 SMCs relative to neo-LF-1 cells, and stretch increased alpha 1B-ADR mRNA levels in neo-LF-1, but not ras-LF-1 cells. Stretch inhibited [1H]thymidine incorporation into DNA in both neo- and ras-LF-1 cells relative to unstretched counterparts. These results demonstrate that c-Ha-rasEJ transfection is associated with alterations in the expression of genes associated with muscle-specific functions in vascular SMCs and implicate c-Ha-ras in the regulation of phenotypic expression in SMCs.