Valproate Valproic Acid Research Articles

Enhancing transporter activity in heterologous expression systems with SAHA: a 2500-times more potent and odorless alternative to butyrate.

The functional characterization of plasma membrane transport proteins often relies on their heterologous expression in cultured cells. However, some transporters exhibit low activity, hindering meaningful functional assays. Heterologous expression is usually based on strong viral promoters which in living cells are prone to promoter silencing, a major problem. Here, we investigated the efficacy of low-cost histone deacetylase (HDAC) inhibitors in enhancing transporter activity, comparing the established sodium butyrate (the sodium salt of butyric acid) with valproate/valproic acid (VPA) and suberoylanilide hydroxamic acid (SAHA, also known as vorinostat). Using 293 cells stably transfected with pEBTet plasmids containing the CMV promotor to express the transporters SLC16A9, SLC22A15, and OATP1A2, we measured substrate efflux or uptake via LC-MS/MS following overnight preincubation with the HDAC inhibitors. All three compounds markedly stimulated transporter activity. VPA was less effective than butyrate but still surpassed control conditions. SAHA was cytotoxic at 6 μm, but at 2 μm, the enhancement was consistently comparable to 5 mm butyrate. Additionally, SAHA was more cost-effective and devoid of the repulsive odor characteristic of butyrate. Our findings advocate for replacing butyrate with SAHA to enhance heterologously expressed transporter activity. This offers a more efficient and user-friendly alternative for functional assays.

Sodium valproate and 5-aza-2\u2032-deoxycytidine differentially modulate DNA demethylation in G1 phase-arrested and proliferative HeLa cells

Sodium valproate/valproic acid (VPA), a histone deacetylase inhibitor, and 5-aza-2-deoxycytidine (5-aza-CdR), a DNA methyltransferase 1 (DNMT1) inhibitor, induce DNA demethylation in several cell types. In HeLa cells, although VPA leads to decreased DNA 5-methylcytosine (5mC) levels, the demethylation pathway involved in this effect is not fully understood. We investigated this process using flow cytometry, ELISA, immunocytochemistry, Western blotting and RT-qPCR in G1 phase-arrested and proliferative HeLa cells compared to the presumably passive demethylation promoted by 5-aza-CdR. The results revealed that VPA acts predominantly on active DNA demethylation because it induced TET2 gene and protein overexpression, decreased 5mC abundance, and increased 5-hydroxy-methylcytosine (5hmC) abundance, in both G1-arrested and proliferative cells. However, because VPA caused decreased DNMT1 gene expression levels, it may also act on the passive demethylation pathway. 5-aza-CdR attenuated DNMT1 gene expression levels but increased TET2 and 5hmC abundance in replicating cells, although it did not affect the gene expression of TETs at any stage of the cell cycle. Therefore, 5-aza-CdR may also function in the active pathway. Because VPA reduces DNA methylation levels in non-replicating HeLa cells, it could be tested as a candidate for the therapeutic reversal of DNA methylation in cells in which cell division is arrested.

HDAC inhibitors dysregulate neural stem cell activity in the postnatal mouse brain

HDAC inhibitors dysregulate neural stem cell activity in the postnatal mouse brain