Sodium butyrate increases the effect of the photodynamic therapy: a mechanism that involves modulation of gene expression and differentiation in astrocytoma cells.

OBJECTIVES: In order to evaluate the improvement of the photodynamic therapy (PDT) due to sodium butyrate (NaBu), its effectiveness in U373-MG and D54-MG astrocytoma cell lines was evaluated. METHODS: Cells were exposed to delta-aminolevulinic acid (δ-ALA) as a precursor to endogenous photosensitizer protoporphyrin IX (PpIX). In both astrocytoma cells, an important increase by ALA was observed in uroporphyrinogen synthetase gene expression: 1.8- and 52-fold for D54-MG and U373-MG cells, respectively. After irradiation, they showed 16.67 and 28.9% of mortality in U373-MG and D54-MG, respectively. These mortalities increased to 70.62 and 96.7% when U373-MG and D54-MG cells, respectively, were exposed 24 h to 8 mM NaBu, before to PpIX induction. NaBu induced expression of caspase-3, caspase-9, and Bcl-2 and increased Bax in U373-MG cells. ALA-induced morphological changes are compatible to differentiation. CONCLUSIONS: Genes and differentiation induced mainly by NaBu improve cell death performed by PDT in astrocytoma cells. These facts prove the synergistic effect of NaBu on cytotoxic damage induced by PDT.