Influence of Valproic Acid on Cytokine Expression of Spleen Cells and Acute Graft-Versus-Host-Disease in a Murine Model.

Inhibition of histone deacetylase, one of the mechanisms for the immunologic changes by antiepileptic drugs, induces gene expression which, in turn, alters cytokine secretion. Valproic acid (VPA), the most commonly used antiepileptic drug, inhibits TNF-α and IL-6 secretion induced by PHA in THP-1 cells, a human monocytic leukemia cell line. We examined the changes in cytokine secretion induced by differing concentrations of VPA and whether VPA could prevent lethal GVHD in murine allogeneic bone marrow transplantation (BMT).

For the evaluation of inhibitory effect of VPA, C3H/He (H-2^k) splenocytes, irradiated BALB/c (H-2^d) splenocytes, and PHA were cocultured with 0.1 mM, 1 mM, and 10 mM VPA. Concentrations of 0.1 mM and 1 mM VPA did not inhibit cell proliferation but 95% was inhibited at 10 mM. Apoptosis was induced more than 99% cells with 10 mM VPA but less than 5% of cells with 0.1 mM, and 1 mM. RT-PCR was performed to evaluate the changes and concentrations of each cytokine. TNF-α and IL-1β secretion, determined by the RNA quantity, was inhibited significantly more at 1 mM VPA than 0.1 mM (P<0.05). Decrease in IFN-γ concentration and increase in TGF-β concentration were significantly more at 1 mM VPA than 0.1 mM (P<0.05). However, differences in IFN-γ and TGF-β secretion, determined by the RNA quantity, were not statistically significant. Lethally irradiated BALB/c mice were transplanted with C3H/He bone marrow cells and splenocytes. Recipients were given 30 mg/kg and 100 mg/kg VPA intraperitoneally once daily from day −3 to day +14, respectively, whereas controls received phosphate buffered saline. There were no significant differences in the GVHD severity and mortality.

These results show that VPA inhibits the secretion of inflammatory cytokines and stimulates the secretion of an antiinflammtory cytokine without inhibition of cell proliferation. Although lethal GVHD was not prevented or controlled in a major and minor histocompatibility complex-mismatched murine allogeneic BMT model, further investigations concerning the effects of VPA on GVHD prevention using a congeneic murine model should be performed.