Triptolide dysregulates glucose uptake via inhibition of IKKβ-NF-κB pathway by p53 activation in cardiomyocytes

Abstract

Triptolide (TP), a principal bioactive component extracted from traditional Chinese medicine Tripterygium wilfordii Hook. F. (TWHF), has attracted wide attention of its therapeutic effects on inflammation and autoimmune diseases. However, the therapeutic application of TP is hindered by severe cardiomyocyte toxicity and narrow therapeutic window. We previously identified that the p53 was an indispensable contributor in TP-induced myocardial injury. p53 has an inhibitory effect on IKKβ-NF-κB pathway that regulates glucose transporters (GLUT) expression. Based on these evidences, we speculate that p53 mediates TP-disturbed glucose uptake by blocking IKKβ-NF-κB signaling. This study focused on the effect of TP on cardiac glucose uptake and the role of p53 in glucose metabolism in cardiomyocytes, and p53 ^-/- mice. TP treatment depressed glucose consumption and ATP production resulting in myocardial damage. Incubation with ATP (5 mM) remarkably decreased the cellular damage. Immunoblotting and immunofluorescence identified that TP suppressed glucose uptake by restricting IKKβ-NF-κB signaling activation, GLUT1 and GLUT4 expression. p53 inhibition alleviated the cell damage and the compromise of glucose uptake. Mechanistically, p53 antagonist PFTα abolished TP-induced the inhibition of IKKβ, IκBα phosphorylation, p65 nuclear translocation, and GLUT1, GLUT4 expression. Consistently, in acute heart injury models, p53 deficiency upregulated IKKβ-NF-κB activation and GLUT1, GLUT4 protein levels which was also indicated as amelioration of heart histological injury after 1.2 mg kg^-1 TP administration. The present findings indicate that TP-induced p53 overactivation suppresses glucose uptake by inhibiting IKKβ-NF-κB pathway and downregulating NF-κB-dependent GLUT1 and GLUT4 expression.

Keywords: Cardiotoxicity; GLUT; IKKβ; Triptolide; p53.