Digitoxin elicits anti-inflammatory and vasoprotective properties in endothelial cells: Therapeutic implications for the treatment of atherosclerosis?

Abstract

Pro-inflammatory processes initiated in the endothelium represent a crucial step in the pathogenesis of inflammatory cardiovascular disease, such as atherosclerosis. Recent observations pointed to potential anti-inflammatory properties of the cardiac glycoside digitoxin. Therefore, the present study investigated potential anti-inflammatory and vasoprotective properties of digitoxin as well as the underlying signaling pathways affected in endothelial cells (EC). Digitoxin, employing therapeutical concentrations used in patients (3–30 nM), potently inhibited the IL-1β-induced expression of MCP-1 and VCAM-1 in EC and the capacity of corresponding cell culture supernatants on monocyte migration as well as monocyte adhesion to endothelial monolayers, respectively. Furthermore, digitoxin prevented the IL-1β-induced activation of p44/42-MAPK and NF-κB without affecting activation of JNK and p38-MAPK. Inhibition of NF-κB signaling but not p44/42-MAPK mimicked the observed inhibitory effects of digitoxin on MCP-1 expression and monocyte migration. Moreover, digitoxin inhibited NF-κB signaling at the level of TAK-1/IKK. Additionally, digitoxin prevented TNF-α-induced apoptosis in EC accompanied by activation of Akt. Blockade of PI-3-kinase, activator of Akt, prevented the anti-apoptotic properties of digitoxin and impaired its inhibitory action on NF-κB signaling and MCP-1 expression. Finally, digitoxin activated endothelial NO-synthase, which was blocked by inhibition of PI-3-kinase, Ca 2+/Calmodulin-dependent-proteinkinase-II and chelation of intracellular calcium. Digitoxin elicits anti-inflammatory and vasoprotective properties by blocking NF-κB and activating PI-3-kinase/Akt signaling as well as Ca 2+/Calmodulin-dependent-proteinkinase-II in EC. These observations indicate a potential therapeutical application of digitoxin in the treatment of cardiovascular diseases, such as atherosclerosis.