Transfection with c-HarasEJModulatesα-actin andα1B-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-rasEJoncogene transfection onα-smooth muscle (SM) actin andα1B-adrenoceptor (ADR) gene expression in vascular (aortic) smooth muscle cells (SMCs). c-Ha-rasEJtransfection of SMCs by lipofection (LF-1) was associated with enhanced DNA synthetic rates relative to vector controls and a significant reduction inα-SM actin andβ/γ-actin mRNAs. Incubation ofras- andneo-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 ofα-actin gene expression. Whileneo-LF-1 cells incubated in 0.1% exhibited increasedα-SM actin mRNA levels relative to 10% serum, slight decreases inα-SM actin were observed inras-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 ofα-SM orβ/γ-actin mRNA expression inneo-LF-1 orras-LF-1 cells. Steady-state mRNA levels ofα1B-ADR were higher inras-LF-1 SMCs relative toneo-LF-1 cells, and stretch increasedα1B-ADR mRNA levels inneo-LF-1, but notras-LF-1 cells. Stretch inhibited [3H]thymidine incorporation into DNA in bothneo- andras-LF-1 cells relative to unstretched counterparts. These results demonstrate that c-Ha-rasEJtransfection is associated with alterations in the expression of genes associated with muscle-specific functions in vascular SMCs and implicate c-Ha-rasin the regulation of phenotypic expression in SMCs.