Toxicological insight from AP-1 silencing study on proliferation, migration, and dedifferentiation of rat vascular smooth muscle cell.

There has an effective way to prevent intimal hyperplasia on vascular smooth muscle cell (VSMC) proliferation in grafted veins. The activator protein-1 (AP-1) transcription factor plays an important role in cardiovascular generation and angioplasty. Once activated, AP-1 binds its specific DNA sequence to promote the proliferation of VSMC, differentiation, and migration. The objectives of this study were to determine toxicological effects of AP-1 silencing study on proliferation, migration, and dedifferentiation of rat vascular smooth muscle cell. To suppress the expression of AP-1 gene, AP-1 siRNA was used to interfere post-transcription in rat primary VSMCs. To observe the expression of SM α-actin and downstream genes of AP-1, the activity of cell matrix metal proteinases and the migration ability of VSMC was examined by a modified Boyden chamber assay. Effects of AP-1 siRNA on proliferation and differentiation in rat VSMCs were evaluated by cell cycle analysis, DNA synthesis, MTT-test, and immunofluorescence. The results showed that the level of SM α-actin protein expression was increased. AP-1 siRNA also significantly decreased the MTT extinction value, DNA synthesis, PCNA expression, and the cell migration velocity when compared to the control group. AP-1 siRNA also clearly arrested cell cycle of VSM at the G0/G1 phase. Zymographic and Western blotting analyses showed that AP-1 siRNA suppressed serum-induced MMP-2 expression. These data suggest that the AP-1 siRNA was able to effectively inhibit the proliferation, migration, and dedifferentiation of smooth muscle cells. Thus, AP-1 siRNA provides a novel method to prevent intimal hyperplasia in blood vessel angioplasty.

Altered AP-1 (activating protein-1) activity and c-jun activation in T cells exposed to the amide class herbicide 3,4-dichloropropionanilide (DCPA).

3,4-Dichloropropionanilide (DCPA), the active ingredient of some postemergence herbicides, has been demonstrated to inhibit several immune system functions including cytokine production by T cells. The central role of cytokines in regulating the immune response suggests a possible mechanism by which DCPA inhibits the immune system. Since interleukin (IL)-2 is critical in regulating many immune functions, we chose to investigate the effect of DCPA on this cytokine. Using the human T lymphoma line, Jurkat, stimulated with phorbol-12-myristate acetate (PMA) and the calcium ionophore A23187 (Io), we determined that DCPA exposure decreased IL-2 secretion and mRNA levels in a dose dependent manner. We hypothesized that DCPA affected one or more of the transcription factors that regulate IL-2 gene transcription. Activating protein 1(AP-1) is a transcription factor that has been demonstrated to be required for optimal IL-2 gene transcription. Electrophoretic mobility shift assays (EMSAs) demonstrated a decreased level of AP-1 DNA binding activity in DCPA-exposed Jurkat cells compared to control cells from 30 min to 2 h after stimulation. The altered AP-1 DNA binding kinetics was associated with a decrease in c-jun protein in these cells at 1 and 2 h after exposure and a decreased level of phosphorylated c-jun at 1-4 h after exposure. These results suggest a possible mechanism for DCPA-induced IL-2 inhibition; alteration in the activation of the c-jun component of AP-1.