Objectives: The branched-chain fatty acid, valproic acid (VPA), is the most commonly used anti-epileptic drug for treating generalized epilepsy. Recently antiproliferative effects of VPA have been described in human cancer cells, and phase I trials for the treatment of solid tumors have been initiated. In cardiologic patients, increased cell proliferation and migration from the media into the subendothelial space are the key events causing restenosis after coronary angioplasty and stenting. This study investigates the effect of VPA on proliferation and migration in human coronary vascular cells.
Methods and results: The theoretical clinical relevance of the data is estimated with a SI/MPL-ratio, which is defined as the relationship between a significant effect in vitro (SI) and the maximal plasma level in vivo (MPL). Dilution of VPA: Aqua dest, MPL in vivo: 100 μg/ml. Cell culture: HUVEC, human umbilical endothelial cells; HCAEC, human coronary artery endothelial cells; HCMSMC, human coronary media smooth muscle cells. Proliferation assay: HUVEC, HCAEC, and HCMSMC were seeded as described. At day 1, after seeding the cell number was calculated in a cell counter. VPA was added in six different concentrations ranging between 50 and 300 μg/ml. At day 3, the medium and agent were renewed, and after another 2 days, the cell number was calculated in relation with the cell number at day 1. Cell toxicity: Cytotoxic effects of VPA were studied in concentrations ranging from 50 to 300 μg/ml. Migration assay: migration of HCMSMC after incubation with VPA in concentrations ranging from 50 to 300 μg/ml was studied for a period of 24 h. Proliferation assay: strong dose-dependent antiproliferative effects were detected after 5 days of incubation with all the three tested cell types. In HUVEC, significant antiproliferative effects were found with VPA in concentrations of 100 μg/ml (P<0.05, SI/MPL-ratio: 1.0) and more. In HCAEC and HCMSMC, significant antiproliferative effects were detected after incubation with VPA in the concentrations of 50 μg/ml (HCAEC: P<0.01, SI/MPL ratio: 0.5; HCMSMC: P<0.001, SI/MPL-ratio: 0.5). Migration assay: no effect on cell migration was detected after incubation of HCMSMC for a period of 48 h with VPA in concentrations ranging from 50 to 300 μg/ml. Cell toxicity: in HUVEC, HCAEC, and HCMSMC significant toxic effects were detected in all the VPA concentrations studied.
Conclusion: Significant dose-dependent antiproliferative effects of VPA with SI/MPL ratios of 0.5 identify the drug as a promising candidate for both systemic and local therapy of postinterventional restenosis. The partial cytotoxic effects, however, may restrict the use of VPA to local high-dose devices such as drug eluting stents.