Butyrate-enhanced TNFalpha-induced apoptosis is associated with inhibition of NF-kappaB.

ABSTRACT

BACKGROUND: Tumor necrosis factor (TNFalpha)-induced apoptosis is limited by concomitant activation of nuclear factor kappa B (NF-kappaB)-dependent anti-apoptotic genes. Butyrate inhibits NF-kappaB activation so that co-treatment with butyrate effectively enhances TNFalpha-induced apoptosis. In this context, the inhibition of NF-kappaB activation and subsequent modulation of (NF-kappaB)-dependent genes was assessed MATERIALS AND METHODS: Human colon adenocarcinoma cells (SW620) were incubated with TNFalpha and butyrate. Apoptosis was determined by annexin V/propidium iodide staining and flow cytometry. NF-kappaB activation was detected by electrophoretic mobility shift assay. The expression of NF-kappaB-dependent genes was assessed by RNase protection assay (RPA) RESULTS: The TNFalpha/butyrate combination yielded an additive increase in the number of apoptotic cells. NF-kappaB nuclear translocation was successfully inhibited by co-incubation with butyrate. However, the expression pattern of NF-kappaB-dependent genes remained essentially unchanged CONCLUSION: Butyrate enhances TNFalpha-induced apoptosis in the human adenocarcinoma cell line SW620. This additive effect may, at least in part, be mediated by the inhibition of NF-kappaB activation, presumably by impairing the anti-apoptotic properties of NF-kappaB.