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

Succinobucol is a phenolic antioxidant with anti-inflammatory and antiplatelet effects. Given the importance of oxidant stress in modulating platelet-platelet and platelet-vessel wall interactions, the aim of this study was to establish if antioxidant activity was responsible for the antiplatelet activity of succinobucol. Platelet aggregation in response to collagen and adenosine diphosphate (ADP) was studied in rabbit whole blood and platelet-rich plasma using impedance aggregometry. The effect of oxidant stress on aggregation, platelet lipid peroxides, and vascular tone was studied by incubating platelets, washed platelets or preconstricted rabbit iliac artery rings respectively with a combination of xanthine and xanthine oxidase (X/XO). To study the effect of succinobucol in vivo, anaesthetized rats were injected with up to 150 mg/kg succinobucol and aggregation measured in blood removed 15 mins later. Succinobucol (10^-5-10^-4 M) significantly attenuated platelet aggregation to collagen and ADP in whole blood and platelet-rich plasma. X/XO significantly increased aggregation to collagen and platelet lipid peroxides and this was reversed by succinobucol. Addition of X/XO to denuded rabbit iliac arteries caused a dose-dependent relaxation which was significantly inhibited by succinobucol. In vivo administration up to 150 mg/kg had no effect on heart rate or mean arterial blood pressure but significantly inhibited platelet aggregation to collagen ex vivo. In conclusion, succinobucol displays anti-platelet activity in rabbit and rat blood and reverses the increase in platelet aggregation in response to oxidant stress.

Succinobucol's new coat--conjugation with steroids to alter its drug effect and bioavailability

Synthesis, detailed structural characterization (X-ray, NMR, MS, IR, elemental analysis), and studies of toxicity, antioxidant activity and bioavailability of unique potent anti-atherosclerotic succinobucol-steroid conjugates are reported. The conjugates consist of, on one side, the therapeutically important drug succinobucol ([4-{2,6-di-tert-butyl-4-[(1-{[3-tert-butyl-4-hydroxy-5-(propan-2-yl)phenyl]sulfanyl}ethyl)sulfanyl]phenoxy}-4-oxo-butanoic acid]) possessing an antioxidant and anti-inflammatory activity, and on the other side, plant stanol/sterols (stigmastanol, β-sitosterol and stigmasterol) possessing an ability to lower the blood cholesterol level. A cholesterol-succinobucol prodrug was also prepared in order to enhance the absorption of succinobucol through the intestinal membrane into the organism and to target the drug into the place of lipid metabolism-The enterohepatic circulation system. Their low toxicity towards mice fibroblasts at maximal concentrations, their antioxidant activity, comparable or even higher than that of ascorbic acid as determined by direct quenching of the DPPH radical, and their potential for significantly altering total and LDL cholesterol levels, suggest that these conjugates merit further studies in the treatment of cardiovascular or other related diseases. A brief discussion of succinobucol's ability to quench the radicals, supported with a computational model of the electrostatic potential mapped on the electron density surface of the drug, is also presented.

AGI-1067, a novel antioxidant and anti-inflammatory agent, enhances insulin release and protects mouse islets

The antioxidant and anti-inflammatory compound AGI-1067 (succinobucol) has potential as an oral anti-diabetic agent. AGI-1067 reduces H(b)A1c, improves fasting plasma glucose, and reduces new-onset diabetes. We investigated AGI-1067 for possible effects on mouse pancreatic islets in vitro. Pretreatment with 10 microM AGI-1067 increased glucose-stimulated insulin secretion (11 mM) without affecting secretion in basal (3 mM) glucose. AGI-1067 enhanced the intracellular calcium response to glucose stimulation in 7 mM and 11 mM glucose, but had no effect in 28 mM or basal glucose. AGI-1067-pretreated islets also showed enhanced calcium responses to methyl pyruvate and alpha-ketoisocaproate at low doses, but not high doses. The AGI-1067-mediated effects on glucose-stimulated calcium were maintained during continuous diazoxide exposure, suggesting effects on the K(ATP)-channel-independent pathway. AGI-1067 also reduced cytokine-induced islet cell death and expression of iNOS, a key component in cytokine signaling. This is the first report of direct stimulatory and protective effects of a first-in-class potential anti-diabetic agent on pancreatic islets.