Lipopolysaccharide prevents valproic acid-induced apoptosis via activation of nuclear factor-κB and inhibition of p53 activation

• VPA induces mitochondria-mediated apoptosis in macrophages.
• LPS prevents VPA-induced apoptosis.
• LPS inhibits VPA-induced apoptosis via modulation of NF-κB and p53.
• Various TLR ligands have a preventive effect on VPA-induced apoptosis.

The effect of lipopolysaccharide (LPS) on valproic acid (VPA)-induced cell death was examined by using mouse RAW 264.7 macrophage cells. LPS inhibited the activation of caspase 3 and poly (ADP-ribose) polymerase and prevented VPA-induced apoptosis. LPS inhibited VPA-induced p53 activation and pifithrin-α as a p53 inhibitor as well as LPS prevented VPA-induced apoptosis. LPS abolished the increase of Bax/Bcl-2 ratio, which is a critical indicator of p53-mediated mitochondrial damage, in response to VPA. The nuclear factor (NF)-κB inhibitors, Bay 11-7082 and parthenolide, abolished the preventive action of LPS on VPA-induced apoptosis. A series of toll-like receptor ligands, Pam3CSK4, poly I:C, and CpG DNA as well as LPS prevented VPA-induced apoptosis. Taken together, LPS was suggested to prevent VPA-induced apoptosis via activation of anti-apoptotic NF-κB and inhibition of pro-apoptotic p53 activation. The detailed inhibitory mechanism of VPA-induced apoptosis by LPS is discussed.