Selective Inhibition of Endothelial and Monocyte Redox-Sensitive Genes by AGI-1067: A Novel Antioxidant and Anti-Inflammatory Agent

Abstract

Atherosclerosis is a disease of oxidative stress and inflammation. AGI-1067 [butanedioic acid, mono[4-[[1-[[3,5-bis(1,1-dimethylethyl)-4-,hydroxyphenyl]thio]-1-methylethyl]thio]-2,6-bis (1,1-dimethylethyl)phenyl] ester] is a metabolically stable derivative of, yet pharmacologically distinct from, the antioxidant drug probucol. It is a member of a novel class of orally active, antioxidant, anti-inflammatory compounds termed vascular protectants and exhibits antiatherosclerotic properties in multiple animal models and in humans. To elucidate its antiatherosclerotic mechanisms, we have evaluated several cellular and molecular properties of AGI-1067 in vitro. AGI-1067 exhibited potent lipid peroxide antioxidant activity comparable with probucol yet demonstrated significantly enhanced cellular uptake over that observed with probucol. AGI-1067, but not probucol, inhibited basal levels of reactive oxygen species (ROS) in cultured primary human endothelial cells and both basal and hydrogen peroxide-induced levels of ROS in the promonocytic cell line, U937. Furthermore, AGI-1067 inhibited the inducible expression of the redox-sensitive genes, vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1, in endothelial cells as well as tumor necrosis factor-␣ (TNF-␣), interleukin (IL)-1␤, and IL-6 production in peripheral blood mononuclear cells, whereas probucol had no effect. cDNA array hybridization experiments demonstrated that AGI-1067 selectively inhibited the expression of only a subset of TNF-␣-responsive and nuclear factor-B (NF-B)-inducible genes in endothelial cells. The inhibitory effect of AGI-1067 on inducible VCAM-1 gene expression occurred at the transcriptional level, yet AGI-1067 had no effect on the activation of the redox-sensitive transcription factor NF-B. These studies suggest that the anti-inflammatory and antiatherosclerotic properties of AGI-1067 may be due to selective inhibition of redoxsensitive endothelial and monocyte inflammatory gene expression. These studies provide a molecular basis for understanding the mechanism of action of this new class of therapeutic antiatherosclerotic compounds.

Activation of Nrf2/ARE pathway protects endothelial cells from oxidant injury and inhibits inflammatory gene expression

“…However, diphenylene iodonium did not inhibit TNF-␣ induced-NF-B nuclear translocation or activation of NF-B transcriptional activity (39). We have also shown (24,25) that two phenolic antioxidants, although quite effective at inhibiting VCAM-1 and MCP-1 expression, had no effect on NF-B activation.…”

Unconjugated Bilirubin Inhibits VCAM-1-Mediated Transendothelial Leukocyte Migration

“…That bilirubin is a key mediator of the cytoprotective effects of HO is supported by a number of in vitro (26, 66 -69) and in vivo (21,24,70) studies demonstrating that bilirubin ameliorates cellular oxidative damage. One of the ways in which bilirubin has been shown to inhibit tissue injury is by preventing the induction of NO synthase and consequent increases in NO levels (24).…”

“…Because the generation of ROS appears to be critical to VCAM-1 signaling, oxygen radical scavengers would be expected to block this process. In this regard, antioxidants have been shown to inhibit leukocyte infiltration in murine nephritis (19) and asthma (20) models, and to decrease cytokine production (21) by cultured endothelial cells.…”

An investigation of the antiplatelet effects of succinobucol (AGI-1067)

“…Succinobucol inhibits cytokine release by monocytes and expression of proinflammatory cell adhesion molecules by endothelial cells (ECs) [4]. However, it has not fulfilled early clinical promise due to deleterious changes in lipid profiles and increased incidence of atrial fibrillation [5].…”