Transfection with c-Ha ras(EJ) modulates α-actin and α(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-ras(EJ) oncogene transfection on α-smooth muscle (SM) actin and α₁₈-adrenoceptor (ADR) gene expression in vascular (aortic) smooth muscle cells (SMCs). c-Ha-ras(EJ) transfection of SMCs by lipofection (LF-1) was associated with enhanced DNA synthetic rates relative to vector controls and a significant reduction in α-SM actin and β/γ-actin mRNAs. Incubation of ras- and neo-LF-1 SMGs in a restrictive serum concentration (0.1%) for 72 h inhibited DNA synthesis in both cell types, but differentially influenced the pattern of α-actin gene expression. While neo-LF-1 cells incubated in 0.1% exhibited increased α-SM actin mRNA levels relative to 10% serum, slight decreases in α-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 α-SM or β/γ-actin mRNA expression in neo-LF-1 or ras-LF-1 cells. Steady-state mRNA levels of α(1B)-ADR were higher in ras-LF-1 SMCs relative to neo-LF-1 cells, and stretch increased α(1B)-ADR mRNA levels in neo-LF-1, but not ras-LF-1 cells. Stretch inhibited [³H]thymidine incorporation into DNA in both neo- and ras-LF-1 cells relative to unstretched counterparts. These results demonstrate that c-Ha-ras(EJ) 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.