TRANSFECTION WITH C-HA RAS(EJ) MODULATES ALPHA-ACTIN AND ALPHA(1B)-ADRENOCEPTOR GENE-EXPRESSION IN VASCULAR SMOOTH-MUSCLE CELLS

Go-ordinate down-regulation of smooth muscle-specific genes and acquis ition 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 alpha-smooth muscle (SM) actin and alpha(1B)-adrenoceptor (hDR) gene expression in vascular (aortic) smooth muscle cells (SMCs). c-Ha-ras(EJ) transfection of SMCs by lipof ection (LF-1) was associated with enhanced DNA synthetic rates relativ e 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 res trictive serum concentration (0.1%) for 72 h inhibited DNA synthesis i n both cell types, but differentially influenced the pattern of alpha- actin gene expression, While neo-LF-1 cells incubated in 0.1% exhibite d increased alpha-SM actin mRNA levels relative to 10% serum, slight d ecreases in alpha-SM actin were observed in ras-LF-1 cells under the s ame 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-act in mRNA expression in neo-LF-1 or ras-LF-1 cells. Steady-state mRNA le vels 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 [H-3]thymidine incorporation into DNA in both neo- and ras-LF-1 cells relative to unstretched coun terparts, 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. (C) 1997 Academic Pre ss Limited.