Decreased forelimb ability in mice intracerebroventricularly injected with low dose 6-hydroxidopamine: A model on the dissociation of bradykinesia from hypokinesia

Bradykinesia and hypokinesia represent well-known motor symptoms of Parkinson's disease (PD). While bradykinesia (slow execution of movements) is present in less affected PD patients and aggravates as the disease severity increases, hypokinesia (reduction of movement) seems to emerge prominently only in the more affected patients. Here we developed a model based on the central infusion of low dose (40μg) 6-hydroxydopamine (6-OHDA) in mice in an attempt to discriminate bradykinesia (accessed through forelimb inability) from hypokinesia (accessed through locomotor and exploratory activities). The potential beneficial effects of succinobucol against 6-OHDA-induced forelimb inability were also evaluated. One week after the beginning of treatment with succinobucol (i.p. injections, 10mg/kg/day), mice received a single i.c.v. infusion of 6-OHDA (40μg/site). One week after 6-OHDA infusion, general locomotor/exploratory activities (open field test), muscle strength (grid test), forelimb skill (single pellet task), as well as striatal biochemical parameters related to oxidative stress and cellular homeostasis (glutathione peroxidase, glutathione reductase and NADH dehydrogenases activities, lipid peroxidation and TH levels), were evaluated. 6-OHDA infusions did not change locomotor/exploratory activities and muscle strength, as well as the evaluated striatal biochemical parameters. However, 6-OHDA infusions caused significant reductions (50%) in the single pellet reaching task performance, which detects forelimb skill inability and can be used to experimentally identify bradykinesia. Succinobucol partially protected against 6-OHDA-induced forelimb inability. The decreased forelimb ability with no changes in locomotor/exploratory behavior indicates that our 6-OHDA-based protocol represents a useful tool to mechanistically study the dissociation of bradykinesia and hypokinesia in PD.

Vascular protectants for the treatment of atherosclerosis

AGI-1067, the monosuccinic acid ester of probucol, is a phenolic antioxidant member of a novel class of agents termed vascular protectants. It has strong antioxidant properties, equipotent to those of probucol, and anti-inflammatory properties. It inhibits gene expression of vascular cell adhesion molecule-1 and monocyte chemotactic protein-1 and has been effective at preventing atherosclerosis in all tested animal models. It also improved luminal dimensions of reference segments in the percutaneous coronary intervention (PCI) vessels in the CART-1 clinical trial, which suggests a direct anti-atherosclerosis effect. Two important trials that test the antioxidant/anti-inflammatory hypothesis are ongoing with AGI-1067: the Canadian Atherosclerosis and Restenosis Trial, which assesses its value for the reduction of both atherosclerosis progression in non-PCI vessels and post-PCI restenosis, and the Aggressive Reduction of Inflammation Stops Events trial, which is evaluating the effects of AGI-1067 on hard cardiovascular outcomes.

AGI-1067, a novel vascular protectant, anti-inflammatory drug and mild antiplatelet agent for treatment of atherosclerosis

Oxidation-sensitive signals play an important role in platelet activation. AGI-1067 is a novel, phenolic, intra- and extracellular antioxidant that inhibits the expression of a number of proinflammatory genes involved in atherosclerosis. AGI-1067 is the metabolically stable monosuccinic acid ester of probucol, and a potent phenolic antioxidant representing a novel class of orally bioavailable compounds termed vascular protectants. AGI-1067 exhibits antioxidant activity equipotent to probucol. In addition, animal studies have demonstrated dual pharmacological activities of AGI-1067: the ability to block the expression of oxidation-sensitive inflammatory genes including genes that code for vascular cell adhesion molecule-1 and monocyte chemotactic protein-1. Importantly, AGI-1067 also exhibits mild antiplatelet properties inhibiting surface expression of various key platelet receptors, the formation of platelet monocyte microparticles and PAR-1 thrombin receptors. AGI-1067 is currently being tested in the late trials, and if proven to improve clinical outcomes (ARISE trial), the drug will ultimately be used in patients with different manifestations of atherosclerosis and atherothrombosis.

Succinobucol induces apoptosis in vascular smooth muscle cells

Probucol inhibits the proliferation of vascular smooth muscle cells in vitro and in vivo, and the drug reduces intimal hyperplasia and atherosclerosis in animals via induction of heme oxygenase-1 (HO-1). Because the succinyl ester of probucol, succinobucol, recently failed as an antiatherogenic drug in humans, we investigated its effects on smooth muscle cell proliferation. Succinobucol and probucol induced HO-1 and decreased cell proliferation in rat aortic smooth muscle cells. However, whereas inhibition of HO-1 reversed the antiproliferative effects of probucol, this was not observed with succinobucol. Instead, succinobucol but not probucol induced caspase activity and apoptosis, and it increased mitochondrial oxidation of hydroethidine to ethidium, suggestive of the participation of H(2)O(2) and cytochrome c. Also, succinobucol but not probucol converted cytochrome c into a peroxidase in the presence of H(2)O(2), and succinobucol-induced apoptosis was decreased in cells that lacked cytochrome c or a functional mitochondrial complex II. In addition, succinobucol increased apoptosis of vascular smooth muscle cells in vivo after balloon angioplasty-mediated vascular injury. Our results suggest that succinobucol induces apoptosis via a pathway involving mitochondrial complex II, H(2)O(2), and cytochrome c. These unexpected results are discussed in light of the failure of succinobucol as an antiatherogenic drug in humans.

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.

[Novel therapy for atherosclerosis and inflammatory vascular disease]

How to manage residual atherosclerosis risk after the statin therapy is a major concern in cardiovascular medicine. In addition to life-style modifications, new drugs against atherosclerotic and inflammatory vascular diseases are expected. In current clinical trials, phospholipase A2 inhibitors(darapladib, varespladib), RVX-208, D-4F, CETP inhibitors (anacetrapib, dalcetrapib), succinobucol are investigated. Some has been failed, but others are still promising. On molecular target basis of PAF-AH, CETP, PON, ABC transporters of A1 and G1, SR-BI, HO-1, potential benefits and side effects are discussed.

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.

Molecular mechanisms underlying the antiatherosclerotic and antidiabetic effects of probucol, succinobucol, and other probucol analogues

PURPOSE OF REVIEW

New therapies for the management of cardiovascular disease remain highly desirable, yet the recently developed agents, such as the cholesterylester transfer protein inhibitor torcetrapib, the antidiabetic agent rosiglitazone, and anti-inflammatory inhibitors of cyclooxygenase-2, have failed. In this review, the more recent developments in the molecular mechanisms underlying the beneficial activities of probucol and related compounds are described.

RECENT FINDINGS

In-vivo and in-vitro studies have revealed that several of the protective activities of probucol can be explained by the ability of this drug to induce the enzyme heme oxygenase-1. It is now apparent that the sulfur atoms, rather than the phenol moieties of probucol, are required for its antiatherogenic and antirestenotic activities. Compounds related to probucol that have improved efficacy without the adverse effects offer promise as novel therapies of cardiovascular disease. Recent results suggest these compounds may also be used for the prevention of type-2 diabetes, a disease that is increasing in prevalence and importance worldwide.

SUMMARY

The development of derivatives of probucol targeting anti-inflammatory and antioxidant processes, perhaps via induction of heme oxygenase-1, may add to the armamentarium of current agents used in treatment of atherosclerotic disease and diabetes.

Effects of succinobucol (AGI-1067) after an acute coronary syndrome: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Oxidative stress and inflammation are involved in the pathophysiology of atherosclerosis. Our aim was to assess the effects of the antioxidant succinobucol (AGI-1067) on cardiovascular outcomes in patients with recent acute coronary syndromes already managed with conventional treatments.

METHODS

After an acute coronary syndrome occurring 14-365 days before recruitment, 6144 patients were randomly assigned with a computer-generated randomisation list, stratified by study site, to receive succinobucol (n=3078) or placebo (n=3066) in addition to standard of care. Enrolment began in July, 2003; this event-driven trial was stopped in August, 2006, after the prespecified number of primary outcome events had occurred. The composite primary endpoint was time to first occurrence of cardiovascular death, resuscitated cardiac arrest, myocardial infarction, stroke, unstable angina, or coronary revascularisation. Efficacy analyses were done by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00066898.

FINDINGS

All randomised patients were included in the efficacy analyses. Succinobucol had no effect on the primary endpoint (530 events in succinobucol group vs 529 in placebo group; hazard ratio 1.00, 95% CI 0.89-1.13, p=0.96). The composite secondary endpoint of cardiovascular death, cardiac arrest, myocardial infarction, or stroke occurred in fewer patients in the succinobucol group than in the placebo group (207 vs 252 events; 0.81, 0.68-0.98, p=0.029). The tertiary endpoint of new-onset diabetes developed in fewer patients without diabetes at baseline in the succinobucol group than in such patients in the placebo group (30 of 1923 vs 82 of 1950 patients; 0.37, 0.24-0.56, p<0.0001). New-onset atrial fibrillation occurred more often in the succinobucol group than in the placebo group (107 of 2818 vs 55 of 2787 patients; 1.87, 1.67-2.09, p=0.0002). Although the number of patients who reported any treatment emergent adverse event was much the same in the two groups, more patients in the succinobucol group than in the placebo group reported bleeding episodes or anaemia (32 vs 18 and 37 vs ten, respectively) as serious adverse events. Relative to treatment with placebo, succinobucol increased LDL cholesterol and systolic blood pressure, and decreased HDL cholesterol and glycated haemoglobin (p<0.0001 for all).

INTERPRETATION

Although succinobucol had no effect on the primary endpoint, changes in the rates of other clinical outcomes-both beneficial and harmful-will need to be further assessed before succinobucol is used in patients with atherosclerosis or as an antidiabetic agent.

Effects of the antioxidant succinobucol (AGI-1067) on human atherosclerosis in a randomized clinical trial

BACKGROUND

The antioxidant AGI-1067 was shown to reduce experimental atherosclerosis. The present study originally intended to study restenosis as a primary endpoint but was subsequently modified to primarily investigate the effects of AGI-1067 on coronary atherosclerosis.

METHODS AND RESULTS

This placebo-controlled randomized trial assessed the effects of AGI-1067 280 mg qd started before percutaneous coronary intervention (PCI) and administered for 12 months after PCI on atherosclerosis progression as assessed by coronary intravascular ultrasound (IVUS). Among patients with IVUS examinations considered technically adequate both at baseline and follow-up upon central laboratory assessments (n=232), plaque volume was not significantly modified with placebo (least squares mean change: -0.4mm(3), P=0.85 versus baseline), but was significantly reduced by -4.0mm(3) at end of treatment in the AGI-1067 group (P=0.001 versus baseline, P=0.12 versus placebo). LDL-cholesterol varied by -9% and +4% in the placebo and AGI-1067 groups, respectively (P<0.05 between groups), and HDL-cholesterol was reduced by 1% with placebo and 14% with AGI-1067 (P<0.05 between groups). Plasma myeloperoxidase was reduced by 6% with AGI-1067 (P<0.05) but hs-CRP was not significantly different between groups.

CONCLUSIONS

Atherosclerosis regression (-4.0mm(3)) was observed in patients treated with AGI-1067, although this was not significantly different from placebo. The anti-inflammatory effect of AGI-1067 is supported by reduced levels of myeloperoxidase.

Antioxidants: the good, the bad and the ugly

Inflammation has a fundamental role in mediating all stages of atherosclerotic disease. The key role of oxidation in linking lipids and inflammation to atherosclerosis is compelling and is supported by experimental evidence. However, the relevance of the antioxidant hypothesis for the treatment of patients with atherosclerosis has not been definitively proven. Results of randomized trials with 'antioxidant' vitamins have been disappointing, and there are potentially important problems associated with their use, including their potential pro-oxidant effects. Probucol has reduced postpercutaneous coronary intervention (PCI)-restenosis and progression of carotid atherosclerosis in clinical trials. The antioxidant vascular protectant AGI-1067 has also been effective at preventing atherosclerosis in all tested animal models. The nonintervened reference coronary segments of the PCI vessel demonstrated improvements with AGI-1067 in the Canadian Antioxidant Restenosis Trial-1 (CART-1), evidence supportive of a clinical effect on slowing atherosclerosis progression. Two trials test the antioxidant/anti-inflammatory hypothesis with AGI-1067; CART-2 assesses its value for the reduction of both atherosclerosis progression and post-PCI restenosis, and Aggressive Reduction of Inflammation Stops Events (ARISE), which is evaluating its effects on hard cardiovascular outcomes.

Pharmacologic approaches to restenosis prevention

Despite significant advances in technology and technique, coronary restenosis remains the primary limitation of percutaneous transluminal coronary angioplasty (PTCA). Among patients undergoing PTCA, between 20% and 50% of patients who do not receive a stent and 10%-30% of those who do receive a stent develop restenosis within 6 months of the procedure. Drug-eluting stents, which release high local concentrations of antiproliferative or immunosuppressive agents directly into the vessel wall at the site of the lesion, have dramatically reduced the incidence of restenosis in patients undergoing PTCA. However, even with drug-eluting stents, a significant percentage of higher-risk patients develop in-stent restenosis. These data suggest that a role remains for effective, well-tolerated systemic pharmacologic therapies to further reduce the rate of restenosis. To date, the majority of systemic agents tested for restenosis prevention have failed to show significant benefit. Only 2 agents, probucol and cilostazol, have consistently demonstrated efficacy in preventing restenosis. In addition, the investigational agent AGI-1067 has demonstrated promising efficacy in early clinical trials. Together with drug-eluting stents, these therapies may for the first time reduce the rate of restenosis to near zero, even in high-risk patients, such as individuals with diabetes mellitus.

Follicular Development and Expression of the Messenger Ribonucleic Acid for the Inhibin/Activin Subunits in Two Genetic Lines of Turkey Hens that Differ in Total Egg Production

The characterization of the follicular hierarchy and the expression of the mRNA for the inhibin/activin subunits was investigated in the follicles of 2 lines of turkey hens selected for over 40 generations for increased egg production (Egg line) or increased body weight (Growth line). The follicular hierarchies of 6 hens from the Egg and Growth lines were characterized in middle (45 wk of age) and late production (58 wk of age). Relative follicular weights for individual hierarchical follicles (>12 mm), pooled small yellow follicles (5 to 12 mm), and large white follicles (2 to 5 mm) were calculated. Total RNA was extracted for Northern blot analysis from individual granulosa cell layers of the F1 through F4 follicles, and from the combined granulosa and theca layers of small yellow follicles and large white follicles from an additional 6 hens from each genetic line. Egg line hens displayed a more distinct follicular size hierarchy than Growth line hens at 45 and 58 wk. Although total follicular weight relative to body size was greater at 45 and 58 wk of age for the Egg line hens than the Growth line hens, the total number of hierarchical follicles was greater in the Growth line hens at 45 and 58 wk of age. Expression of follistatin and the inhibin beta(B)-subunit was highest in nonhierarchical follicles, whereas the expression of the inhibin alpha- and beta(A)-subunits was highest in the hierarchical follicles. The inhibin alpha- and beta(A)-subunit mRNA expression pattern in the 4 largest follicles of the Growth line hens was not similar to the Egg line hens or characteristic of laying hens that have a high rate of egg production. The unusual inhibin subunit mRNA expression in the largest hierarchical follicles of the Growth line hens may account for their development of an abnormal follicular size hierarchy and for their poor egg production.

Vascular cell adhesion molecule-1: a viable therapeutic target for atherosclerosis?

Atherosclerosis is now well recognised as a chronic inflammatory process which may ultimately lead to myocardial infarction, stroke and peripheral vascular disease. The role of inflammation in the pathogenesis of atherosclerosis has lead to interest in developing therapies that target vascular inflammation. Leucocytes play a key role during atherosclerotic plaque development. Activated vascular endothelium expresses vascular cell adhesion cell molecule-1 (VCAM-1), a member of the adhesion molecule superfamily, to which monocytes and lymphocytes can bind. These inflammatory cells can then move through the endothelium by diapedesis and release cytokines and enzymes, important components in the progression of the lesion. Researchers have demonstrated that the extent of atherosclerotic lesions is significantly reduced in animal models with decreased VCAM-1 expression. VCAM-1 has therefore been identified as a potential anti-inflammatory therapeutic target, the hypothesis being that reduced expression of VCAM-1 will slow the development of atherosclerosis. Succinobucol (AGI-1067), an anti-oxidant compound also capable of inhibiting VCAM-1 gene expression, is an example of such an agent and is currently being investigated in a phase III cardiovascular end-point trial due to report in 2007. If the results are positive, further investigations should derive to what extent blockade of VCAM-1 by succinobucol, rather than its other effects, accounts for the reduction in vascular events.

The in vitro effects of a novel vascular protectant, AGI-1067, on platelet aggregation and major receptor expression in subjects with multiple risk factors for vascular disease

Oxidation-sensitive signals are important in platelet activation. The novel, phenolic, intracellular and extra-cellular antioxidant AGI-1067 inhibits the expression of a number of proinflammatory genes involved in atherosclerosis. The effect of AGI-1067 on human platelets was evaluated. Blood obtained from 20 aspirin-naïve volunteers with multiple risk factors for vascular disease was preincubated with escalating concentrations of AGI-1067 for the assessment of its ex vivo effects on platelet aggregation and expression of major surface receptors flow cytometry, evaluated by flow cytometry. AGI-1067 resulted in significant inhibition of a variety of activation-dependent platelet biomarkers in healthy volunteers, including adenosine diphosphate-induced platelet aggregation and decreased surface platelet expression of glycoprotein IIb/IIIa antigen, activity with PAC-1 antibody, and glycoprotein Ib (CD42b). The effect of AGI-1067 differs from other known antiplatelet agents, suggesting opportunities for therapeutic combination. These data need to be confirmed in subjects receiving orally dosed AGI-1067 to be clinically relevant.

AGI-1067: a novel vascular protectant for prevention of restenosis

OBJECTIVE

To review the synthesis, pharmacology, clinical trials, and adverse effects of AGI-1067, a novel agent for preventing restenosis.

DATA SOURCES

Literature searches were conducted using MEDLINE (1966-July 2005) and International Pharmaceutical Abstracts (1970-July 2005) for English-language articles containing the search terms AGI-1067, AGI 1067, and probucol. In addition, bibliographies from relevant articles were reviewed for additional references.

STUDY SELECTION AND DATA EXTRACTION

All articles identified from data sources were reviewed for relevant information. Applicable information was included in this review.

DATA SYNTHESIS

AGI-1067, a derivative of the lipid-lowering agent probucol, is the first of a new class of drugs termed vascular protectants. It has antioxidant and lipid-lowering effects. In addition, it inhibits inflammatory processes without resultant immunosuppression through its selective inhibition of vascular cell adhesion molecule-1 expression. AGI-1067 also exhibited anti-atherosclerotic effects in preclinical studies. Relatively short-term treatment with AGI-1067 showed positive results compared with probucol in preventing restenosis in patients undergoing percutaneous coronary intervention. AGI-1067 appears to be well tolerated and holds important advantages over probucol in that it has fewer adverse effects on high-density lipoprotein cholesterol and the QT interval.

CONCLUSIONS

The favorable safety profile of AGI-1067 offers potential advantages over its precursor, probucol. Preclinical and clinical studies indicate that it possesses antioxidant, antiinflammatory, and lipid-lowering properties. Ongoing Phase II and III studies will determine AGI-1067's place in therapy for the prevention of restenosis and reduction in cardiovascular events in patients undergoing percutaneous intervention for coronary atherosclerosis.

AGIX-4207 [2-[4-[[1-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]thio]-1-methylethyl]thio]-2,6-bis(1,1-dimethylethyl)phenoxy]acetic acid], a novel antioxidant and anti-inflammatory compound: cellular and biochemical characterization of antioxidant activity and inhibition of redox-sensitive inflammatory gene expression

The pathogenesis of chronic inflammatory diseases, including rheumatoid arthritis, is regulated, at least in part, by modulation of oxidation-reduction (redox) homeostasis and the expression of redox-sensitive inflammatory genes including adhesion molecules, chemokines, and cytokines. AGIX-4207 [2-[4-[[1-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]thio]-1-methylethyl]thio]-2,6-bis(1,1-dimethylethyl)phenoxy]acetic acid] is a novel, orally active, phenolic antioxidant and anti-inflammatory compound with antirheumatic properties. To elucidate its anti-inflammatory mechanisms, we evaluated AGIX-4207 for a variety of cellular, biochemical, and molecular properties. AGIX-4207 exhibited potent antioxidant activity toward lipid peroxides in vitro and displayed enhanced cellular uptake relative to a structurally related drug, probucol. This resulted in potent inhibition of cellular levels of reactive oxygen species in multiple cell types. AGIX-4207 selectively inhibited tumor necrosis factor (TNF)-alpha-inducible levels of the redox-sensitive genes, vascular cell adhesion molecule-1 and monocyte chemoattractant protein-1, with less inhibition of E-selectin, and no effect on intracellular adhesion molecule-1 expression in endothelial cells. In addition, AGIX-4207 inhibited cytokine-induced levels of monocyte chemoattractant protein-1, interleukin (IL)-6, and IL-8 from endothelial cells and human fibroblast-like synoviocytes as well as lipopolysaccharide-induced release of TNF-alpha, IL-1beta, and IL-6 from human peripheral blood mononuclear cells. AGIX-4207 did not inhibit TNF-alpha-induced nuclear translocation of nuclear factor of the kappa-enhancer in B cells (NF-kappaB), suggesting that the mechanism of action is independent of this redox-sensitive transcription factor. Taken together, these results provide a mechanistic framework for understanding the anti-inflammatory and antirheumatic activity of AGIX-4207 and provide further support for the view that inhibition of redox-sensitive inflammatory gene expression is an attractive approach for the treatment of chronic inflammatory diseases.

Inhibition of lipoprotein lipid oxidation

According to the oxidative modification hypothesis, antioxidants that inhibit the oxidation of low-density lipoprotein (LDL) are expected to attenuate atherosclerosis, yet not all antioxidants that inhibit LDL oxidation in vitro inhibit disease in animal models of atherosclerosis. As with animal studies, a benefit with dietary supplements of antioxidants in general and vitamin E in particular was anticipated in humans, yet the overall outcome of large, randomized controlled studies has been disappointing. However, in recent years it has become clear that the role of vitamin E in LDL oxidation and the relationship between in vitro and in vivo inhibition of LDL oxidation are more complex than previously appreciated, and that oxidative events in addition to LDL oxidation in the extracellular space need to be considered in the context of an antioxidant as a therapeutic drug against atherosclerosis. This review focuses on some of these complexities, proposes a novel method to assess in vitro 'oxidizability' of lipoprotein lipids, and summarizes the present situation of development of antioxidant compounds as drugs against atherosclerosis and related cardiovascular disorders.

Antioxidants and atherosclerosis: Emerging drug therapies

Inflammation has a fundamental role in mediating all stages of atherosclerotic disease. The key role of oxidation in linking lipids and inflammation to atherosclerosis is compelling and supported by experimental evidence. However, the relevance of the antioxidant hypothesis for the treatment of patients with atherosclerosis has not been definitively proven. Probucol has reduced post-percutaneous coronary intervention (PCI) restenosis and progression of carotid atherosclerosis in clinical trials. The antioxidant/vascular protectant AGI-1067 has also been effective at preventing atherosclerosis in all tested animal models. The nonintervened reference coronary segments of the PCI vessel demonstrated improvements with AGI-1067 in the Canadian Antioxidant Restenosis Trial-1 (CART-1), evidence supportive of a clinical effect on slowing atherosclerosis progression. Results of randomized trials with the "antioxidant" vitamins have been disappointing, but there are potentially important problems associated with their use, including their potential pro-oxidant effects. Two important trials that test the antioxidant/anti-inflammatory hypothesis are ongoing with AGI-1067: CART-2, which assesses its value for the reduction of both atherosclerosis progression in non-PCI vessels and post-PCI restenosis; and Aggressive Reduction of Inflammation Stops Events (ARISE), which is evaluating the effects of AGI-1067 on hard cardiovascular outcomes.

NEW DRUGS TO IMPROVE TRANSPLANT OUTCOMES

Fujisawa is committed to improving the outcomes of transplant patients worldwide. Research and development programs are underway for a new modified release dosage form of tacrolimus (MR-4), a new analog of leflunomide (FK 778), and several novel compounds (PG 490-88, AGI 1096) in collaboration with other companies. These programs are targeted to address many of the unmet medical needs in transplantation including (1) improving compliance, (2) reducing chronic rejection, and (3) improving long-term safety by reducing infectious and cardiovascular risk.

Experimental and clinical studies show that the probucol derivative AGI-1067 prevents vascular growth

AGI-1067 is a derivative of probucol that is a promising new development for the treatment of restenosis and possibly atherosclerosis. In monkeys fed a high-fat diet for 1 year, AGI-1067 prevented the development of atherosclerosis. In these monkeys, AGI-1067 lowered plasma levels of low-density lipoprotein (LDL)-cholesterol and, in contrast to probucol, was capable of increasing high-density lipoprotein (HDL)-cholesterol levels. Although AGI1067 did not have marked lipid-lowering effects in two transgenic mouse models (the LDL-receptor-deficient and apolipoprotein-E-deficient models) fed a high-fat chow, it decreased the atherosclerotic lesion area in the aorta. In a mouse model of acute inflammation, the mRNA for the pro-inflammatory vascular cell adhesion molecule-1 and monocyte chemoattractant protein-1 was upregulated and this was inhibited by AGI-1067. AGI-1067 inhibited the TNF-alpha induction of redox-sensitive inflammatory proteins, vascular cell adhesion molecule-1, monocyte chemoattractant protein-1 and Eselectin, in cell culture. In addition, AGI-1067 is an antioxidant. In the Canadian Antioxidant Restenosis Trial (CART-1) of AGI-1067 in percutaneous coronary interventions, AGI-1067 had no effect on LDL-cholesterol but lowered HDL-cholesterol. At 6 months follow up, the lumen area of the percutaneous coronary interventions segments was greater in patients treated with AGI1067 than in untreated patients. Restenosis rates were 37.5% in the placebo group and 26% in the AGI-1067 group. The lumen area of reference segments was reduced in the placebo group but increased with the higher doses of AGI1067. Unlike probucol, AGI-1067 did not alter QTc interval.

Pharmacologic prevention of both restenosis and atherosclerosis progression: AGI-1067, probucol, statins, folic acid and other therapies

PURPOSE OF REVIEW

In this article, the authors intend to provide an update on clinical trials of pharmacologic prevention of restenosis after percutaneous coronary interventions, placed in the perspective of the use of orally administered therapy for the prevention of atherosclerosis progression and clinical events.

RECENT FINDINGS

AGI-1067, the mono-succinic acid ester of probucol, is a phenolic antioxidant member of a novel class of agents termed v-protectants. It has strong antioxidant properties equipotent to those of probucol and antiinflammatory properties. It inhibits gene expression of VCAM-1 and MCP-1 and has been effective at preventing atherosclerosis in all tested animal models including the non-human primate. In the Canadian Antioxidant Restenosis Trial (CART) 1, AGI-1067 and probucol improved lumen dimensions at the site of percutaneous coronary intervention. AGI-1067 also improved luminal dimensions of non-intervened coronary reference segments in the Canadian Antioxidant Restenosis Trial, which suggests a direct antiatherosclerosis effect. Probucol reduced post-percutaneous coronary intervention restenosis and progression of carotid atherosclerosis in other clinical trials. Although statins reduce atherosclerotic events, they do not appear to have a significant effect on restenosis. The failure of folate therapy to protect against restenosis in the Folate After Coronary Intervention Trial (FACIT) occurred despite significant reductions in homocysteine levels.

SUMMARY

Prevention of both post-percutaneous coronary intervention restenosis and atherosclerosis progression with a pharmacologic agent such as AGI-1067 may be an attractive treatment paradigm. Two important trials that test the antioxidant/antiinflammatory hypothesis are ongoing with AGI-1067: the Canadian Atherosclerosis and Restenosis Trial 2, which assesses its value for the reduction of both atherosclerosis progression and post-percutaneous coronary interventions restenosis, and the Aggressive Reduction of Inflammation Stops Events (ARISE) trial which is evaluating its effects on cardiovascular events.

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

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-alpha (TNF-alpha), interleukin (IL)-1beta, 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-alpha-responsive and nuclear factor-kappaB (NF-kappaB)-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-kappaB. These studies suggest that the anti-inflammatory and antiatherosclerotic properties of AGI-1067 may be due to selective inhibition of redox-sensitive 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.

AGI-1067: a multifunctional phenolic antioxidant, lipid modulator, anti-inflammatory and antiatherosclerotic agent

To explore the therapeutic efficacy and potential mechanisms of action of a new class of antiatherosclerotic drugs, AGI-1067 [mono[4-[[1-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]thio]-1-methylethyl]thio]-2,6-bis(1,1-dimethylethyl)phenyl] ester] (butanedioc acid) was tested in several animal models of atherosclerosis. AGI-1067, a novel phenolic antioxidant, was well tolerated in a 1-year study in hypercholesterolemic cynomolgus monkeys. It lowered low-density lipoprotein cholesterol (LDLc) by 41 and 90% at oral doses of 50 and 150 mg/kg, respectively and increased high-density lipoprotein cholesterol (HDLc) by 107% at the higher dose. In contrast, another phenolic antioxidant, probucol, had a modest LDLc-lowering effect (15% at 250 mg/kg) while decreasing HDLc (37% at 150 mg/kg). Histopathology of the aortas and coronary arteries revealed no atherosclerosis in the AGI-1067 (150 mg/kg) group and minimal-to-moderate atherosclerosis in the vehicle and probucol (150 mg/kg) groups. AGI-1067 also inhibited atherosclerosis in LDL receptor-deficient (LDLr -/-) mice and apolipoprotein E-deficient (ApoE -/-) mice even in the absence of a lipid-lowering effect. In LDLr -/- mice, AGI-1067 reduced aortic atherosclerosis by 49%. In ApoE -/- mice, AGI-1067 reduced atherosclerosis by 25, 41, and 49% in the arch, thoracic, and abdominal regions of the aorta. AGI-1067 also reduced vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1) mRNA levels in lungs of lipopolysaccharide-stimulated mice. At the cellular level, AGI-1067 inhibited tumor necrosis factor-alpha-inducible expression of VCAM-1, MCP-1, and E-selectin in human aortic endothelial cells (IC50 values = 6, 10, and 25 microM, respectively). These data show that AGI-1067 can inhibit atherosclerosis not only via its lipid-lowering effects but also by having direct anti-inflammatory effects on the vessel wall and suggest that it may be a novel therapeutic agent for coronary artery disease.

Chemistry and pharmacology of vascular protectants: a novel approach to the treatment of atherosclerosis and coronary artery disease

This review addresses the role of oxidative stress in the pathology of atherosclerosis and why it is now believed that atherosclerosis is not only a disease of oxidative stress but also of chronic inflammation. Perhaps more importantly, this review also describes the vascular protectant (V-protectant) technology platform originated at AtheroGenics, Inc., from which a series of inhibitory compounds has emerged to treat a number of chronic inflammatory diseases, including atherosclerosis. In atherosclerosis, these drugs not only act as antioxidants, but also as lipid modulators, inhibitors of inflammation, and inhibitors of gene expression. It is also important to understand the basis for considering vascular cell adhesion molecule-1 (VCAM-1) as a reduction-oxidation-sensitive protein, which has a key role in the early phases of atherosclerosis. The review concludes with a description of the design and chemistry of AtheroGenics' lead clinical development compound, AGI-1067, and an analysis of its preclinical in vitro and in vivo profile. AGI-1067 is a novel, potent antioxidant with anti-inflammatory properties. It inhibits gene expression of VCAM-1 and monocyte chemoattractant protein-1, decreases low-density lipoprotein cholesterol levels, and prevents atherosclerosis in a number of animal models. AGI-1067 is currently undergoing clinical trials as an antiatherosclerotic agent.

Clinical results with AGI-1067: a novel antioxidant vascular protectant

A large body of evidence points to oxidative stress as an important trigger in the complex chain of events leading to atherosclerosis. Reactive oxygen species have also been implicated in the pathophysiology of restenosis after percutaneous coronary interventions (PCI). The powerful antioxidant probucol has been shown to prevent coronary restenosis after balloon angioplasty in the MultiVitamins and Probucol (MVP) trial and other clinical studies. Probucol has also induced regression of carotid atherosclerosis in the Fukuoka Atherosclerosis Trial (FAST). However, prolongation of the QT interval with probucol remains a long-term safety concern. AGI-1067, a metabolically stable analog of probucol, is a vascular protectant (V-protectant) with strong antioxidant properties, equipotent to those of probucol. This V-protectant has been effective at preventing atherosclerosis in all tested animal models, including the low-density lipoprotein receptor-deficient and apolipoprotein E-knockout mice and the hypercholesterolemic primate. AGI-1067 improved luminal dimensions of the PCI site and reduced restenosis in the Canadian Antioxidant Restenosis Trial (CART-1). In contrast to probucol, AGI-1067 did not induce prolongation of the QT interval. AGI-1067 also improved luminal dimensions of the reference segments in the PCI vessels in CART-1, an effect that suggests a direct antiatherosclerosis effect. This has potentially important implications, as local approaches to prevent restenosis, such as coated stents, are not expected to prevent atherosclerosis progression, myocardial infarction, and cardiovascular death. Considering that oxidative stress and inflammation may persist for a prolonged period after stenting, treatment with AGI-1067 for the entire period of risk after PCI (instead of only 4 weeks in CART-1) may result in enhanced protection against luminal renarrowing in the ongoing multicenter CART-2 trial. Because the ultimate goal of therapy for patients with coronary artery disease must remain prevention of disease progression and atherosclerosis-related events, CART-2 will test the value of AGI-1067 for the reduction of both post-PCI restenosis and atherosclerosis progression.

Effects of AGI-1067 and probucol after percutaneous coronary interventions

BACKGROUND

AGI-1067, a metabolically stable modification of probucol, is an equipotent antioxidant to probucol but is pharmacologically distinct. In a multicenter trial, we studied whether AGI-1067 reduces restenosis assessed by intravascular ultrasound (IVUS) after percutaneous coronary intervention (PCI) compared with placebo and probucol used as a positive control.

METHODS AND RESULTS

Two weeks before PCI, 305 patients were randomly assigned to 1 of 5 treatment groups: placebo, probucol 500 mg BID, or AGI-1067 70, 140, or 280 mg once daily. Patients were treated for 2 weeks before and 4 weeks after PCI. Baseline and 6-month follow-up IVUS were interpreted by a blinded core laboratory. Stents were used in 85% of patients. Luminal area at the PCI site at follow-up was 2.66+/-1.58 mm2 for placebo, 3.69+/-2.69 mm2 for probucol, 2.75+/-1.76 mm2 for AGI-1067 70 mg, 3.17+/-2.26 mm2 for AGI-1067 140 mg, and 3.36+/-2.12 mm2 for AGI-1067 280 mg (P=0.02 for the dose-response relationship; P< or =0.05 for AGI-1067 280 mg and probucol versus placebo). There was a mean narrowing of 5.3 mm3 of reference segment lumen in the placebo group and an enlargement in the AGI-1067 140- and 280-mg groups at follow-up (P=0.05 for 140 mg). An increase in QTc interval >60 ms occurred in 4.8% of placebo patients, 17.4% of probucol patients, and 4.8%, 2.4%, and 2.5% of patients in the AGI-1067 groups (P=0.02).

CONCLUSIONS

AGI-1067 and probucol reduce restenosis after PCI. In contrast to probucol, AGI-1067 did not cause prolongation of the QTc interval and improved lumen dimensions of reference segments, suggestive of a direct effect on atherosclerosis.

Immunomodulation with DiNAC-- a new approach to the treatment of atherosclerosis?

Not all antioxidants reduce atherosclerosis. This may be because atherosclerosis has an autoimmune, inflammatory pathogenesis. As probucol is both an antioxidant and an immunomodulatory drug, it may be the immunomodulatory effect that underlies its ability to reduce atherosclerosis. N,N-Diacetyl-L-cystine is not an antioxidant but is immunomodulatory. In the Watanabe-heritable hyperlipidaemic rabbit model of familial hypercholesterolaemia, N,N-diacetyl-L-cystine treatment does not lower lipid levels but it does reduce atherosclerosis. Immunomodulation may be a new approach to the treatment of atherosclerosis.

[Antioxidant effect of novel probucol analogs and their combinations with alpha-tocopherol]

The antioxidant and antiradical activities of sulfur containing phenols which are analogues of probucol in comparison with alpha-tocopherol and BHT were tested using initiated methyl oleate oxidation model. The antioxidant effect linearly increased with increasing concentration of phenols. The ability of investigated phenols to destroy and reduced accumulation of hydroperoxides is revealed. The combined inhibitory effects of composition most effective researched antioxidant--CO-3--with alpha-tocopherol for the first time are described.

The in vitro and ex vivo antioxidant properties, and hypolipidemic activity of CGP 2881

This report describes the in vitro and ex vivo antioxidant properties of a new antioxidant, CGP 2881. This compound is structurally similar to probucol, in that both compounds contain bis-tertiary butyl phenyl groups. However, CGP 2881 consistently inhibited CuSO4 (Cu2+)- and macrophage (MO)-induced oxidation of human low density lipoproteins (LDL) more potently than equimolar concentrations of probucol. CGP 2881 (1 mumol/l) prolonged the lag phase of diene formation during Cu(2+)-induced LDL oxidation by 3.4 versus 1.5-fold prolongation with 1 mumol/l probucol (P < 0.05 vs CGP 2881). The IC50 for inhibiting the formation of Cu(2+)-induced thiobarbituric acid-reactive substances (TBARS) was 0.15 mumol/l for CGP 2881, versus approximately 10 mumol/l for probucol. The IC50 for MO-induced oxidation of LDL (TBARS) was 0.64 mumol/l. In contrast, 1 mumol/l probucol failed to inhibit MO-induced oxidation of LDL. Treatment of cholic acid/cholesterol-fed rats with CGP 2881 (50 mg/kg per day, orally for 5 days) inhibited ex vivo Cu(2+)-induced oxidation (TBARS) of the very low density lipoproteins (VLDL) + LDL lipoprotein fraction by 93% versus vehicle controls (P < 0.0001), and prolonged the lag phase for Cu(2+)-induced diene formation by 3.4-fold over vehicle-treated controls. Five days of orally administered CGP 2881 reduced plasma total cholesterol and LDL cholesterol levels to 55 and 54% of vehicle-treated controls, respectively (P < 0.05). In contrast, probucol had no appreciable effect on plasma total cholesterol or LDL cholesterol levels, unless administered for longer than 5 days. Treatment of hypercholesterolemic rabbits with 50 mg/kg per day orally for 5-12 days delayed the lag phase of diene formation during LDL oxidation by 4.3-fold over controls. However, the relative antioxidant potencies of CGP 2881 and probucol seen with oral administration to hypercholesterolemic rabbits were reversed when the compounds were given intravenously. In addition, the effects of these antioxidants were potentiated when given to normocholesterolemic rabbits compared to hypercholesterolemic animals. These data establish that CGP 2881 demonstrates hypolipidemic activity and is a substantially more potent antioxidant than probucol (in vitro and ex vivo). CGP 2881 may be useful as a new antioxidant tool in the effort to better understand the atherogenicity of oxidized LDL (oxLDL).

MDL 29311, a phenolic antioxidant, interferes with the interaction of apoC with VLDL: a possible explanation for its triglyceride-lowering effect

MDL 29311 is an antioxidant that lowers plasma triglycerides and raises high density lipoprotein (HDL) cholesterol in rats. It lowers triglycerides in rats by enhancing the clearance of very low density lipoprotein (VLDL) by the liver (Sheetz, M. J., et al. 1994. Metabolism. 43: 232-240). In this paper, the possibility that MDL 29311 enhances VLDL clearance by altering the apolipoprotein (apo) content of lipoproteins is examined. Treatment of rats with 1% MDL 29311 in the diet for 7 days lowered plasma triglycerides and markedly increased total lipoprotein-associated apoE. The increase in apoE was confined to the HDL fraction; no increase in VLDL-associated apoE was detected. No apparent alterations in the amount of total lipoprotein-associated apoC were observed, although there was a decrease in VLDL-associated apoC-II and C-III-0. Consistent with this finding, the amount of 125I-labeled apoC transferred from HDL to VLDL in plasma from MDL 29311-treated rats was only 40% of the amount transferred in control plasma. Sepharose 6B gel filtration of mixtures of 125I-labeled apoC with increasing concentrations of MDL 29311 in the absence of plasma or lipid revealed that proportionally increasing amounts of the 125I-labeled apoC eluted in a high molecular weight (HMW) complex with MDL 29311. An HMW complex was not formed when MDL 29311 was mixed with 125I-labeled soybean trypsin inhibitor. The 125I-labeled apoC in the HMW complex bound to VLDL only 20% as well as uncomplexed 125I-labeled apoC. MDL 29311 also caused the dissociation of 125I-labeled apoC from VLDL at concentrations of MDL 29311 similar to those obtained in vivo. Other phenolic antioxidants related to MDL 29311 caused the formation of HMW 125I-labeled apoC-containing complexes to an extent proportional to their abilities to lower triglycerides in rats. These studies support the hypothesis that MDL 29311 lowers triglycerides in rats by interfering with apoC association with VLDL, thereby relieving the apoC-mediated inhibition of hepatic VLDL uptake.

Interactions of MDL 29,311 and probucol metabolites with cholesteryl esters

The hypothesis that the efficacy of hydrophobic antioxidants in animal models of atherogenesis may, in part, be related to physical effects on cholesteryl esters in cells was probed with analogs and metabolites of probucol. The interactions of an effective bis-thiomethane analog (MDL 29,311) and selected metabolites of probucol with cholesteryl oleate were examined by differential scanning calorimetry and polarized light microscopy. Like probucol, MDL 29,311 and the bisphenol metabolite decrease the liquid-crystalline phase transition enthalpy of cholesteryl oleate with increasing concentrations. At 20 mol%, no transition is detectable. By contrast, the spiroquinone metabolite of probucol and the diphenoquinone metabolite common to both molecules have minimal effects on the liquid-crystalline transitions of cholesteryl oleate. At 20 mol%, neither compound has as great an effect as 1 mol% MDL 29,311. Consistent with their effects on dry cholesteryl oleate, MDL 29,311 and the bisphenol metabolite convert lipid inclusions in cells supplemented with cholesterol to an isotropic physical state similar to that observed with probucol. The number of anisotropic inclusions in the cells decreases with increasing concentration in the medium in the range of 50 to 250 micrograms/mL. In cells fed with the spiroquinone or diphenoquinone metabolites, the lipid inclusions are liquid-crystalline and resemble those observed with cholesterol-fed controls. These data are interpreted in terms of a model in which hydrophobic antioxidants closely related to probucol disrupt the packing of cellular cholesteryl esters.

S 12340: a potent inhibitor of the oxidative modification of low-density lipoprotein in vitro and ex vivo in WHHL rabbits

Oxidative modification of low-density lipoprotein (LDL) is thought to play a key role in the formation of foam cells and in the initiation and progression of the atherosclerotic plaque. After evaluation of a large number of original drugs, S 12340 was found to be the most potent compound in inhibiting in a dose-dependent manner the human LDL oxidative modification induced either by copper ions or by cultured endothelial cells. Both the electrophoretic mobility and the thiobarbituric acid reactive substances returned to almost normal values in the presence of 0.5 microM of S 12340. Watanabe heritable hyperlipidemic rabbits were treated orally for 3 days or for 1 month with S 12340 to evaluate the potential protective effect of the compound on LDL oxidative modification induced ex vivo. Purified LDL from placebo and treated rabbits were submitted to oxidation, and S 12340 was effectively able to protect LDL in a dose-dependent manner and at doses as low as 10 mg/kg/day. Purified LDL from animals sacrificed at various times after oral administration of S 12340 were protected against oxidation for at least 6 h after the last administration of the compound. These findings are in good agreement with the plasma and LDL levels of S 12340 in these WHHL rabbits. S 12340, probucol and vitamin E were all able to decrease the optical density of the 1,1-diphenyl-2-picrylhydrazyl solution, demonstrating their free radical scavenging properties. The pharmacological properties of the compound suggest that S 12340 may be of potential interest for a new therapeutic approach to atherosclerosis.

MDL 29311, an analog of probucol, decreases triglycerides in rats by increasing hepatic clearance of very-low-density lipoprotein

MDL 29311 is an analog of probucol that shares probucol's antioxidant and antiatherogenic properties. When fed to rats as a 1% dietary admixture, MDL 29311 decreased triglyceride levels by 65% without affecting total or high-density lipoprotein (HDL) cholesterol levels. Under the same conditions, probucol decreased triglyceride levels by 23% and total cholesterol levels by 29% (with a corresponding decrease in HDL cholesterol level). MDL 29311 treatment did not affect the rate of triglyceride entry into the plasma. However, MDL 29311-treated rats cleared in vivo-labeled very-low-density lipoprotein (VLDL)-associated [3H]-triglyceride ([3H]-VLDL) over threefold faster than control rats. This increase in clearance led to increased levels of [3H]-lipid in liver and decreased [3H]-lipid in fat, muscle, diaphragm, and kidney of MDL 29311-treated rats 1.5 to 2.0 minutes after injection of [3H]-VLDL. MDL 29311 treatment had no effect on lipoprotein lipase (LPL) or hepatic triglyceride lipase (H-TGL) activities, or on plasma apolipoprotein (apo) C-II-dependent LPL activation. Intravenously injected [3H]-VLDL was allowed to circulate in MDL 29311-treated or control rats for 1 minute, and the undiluted plasma was then perfused through rat livers in a recirculating system. The [3H] in MDL 29311 plasma was cleared threefold faster (t1/2, 1.3 v 3.8 minutes) than the [3H] in control plasma by control livers. Conversely, the [3H] in control plasma was cleared slowly (t1/2 = 3.5 minutes) by the livers of MDL 29311-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

[The effect of probucol and its new analog on cholesterol and lipoprotein metabolism in rabbit cultured hepatocytes]

The effects of the well-known hypolipidemic drug probucol and its new analog K5 on cholesterol and bile acid metabolism in cultured rabbit hepatocytes have been studied. Probucol (100 microM) inhibited by 24-28% the [2-14C]acetate incorporation into cholesterol. In contrast, the probucol analog K5 used at the same concentration did not affect the cholesterol synthesis but reduced by 44-55% the VLDL-apolipoprotein B (apo-B) secretion into the culture medium. Neither of the drugs influenced the [14C]leucine incorporation into cellular proteins. In addition, probucol (100 microM) stimulated by 29-64% the specific uptake of 125I-labelled LDL into the cells and increased the glycocholic and taurocholic acid synthesis by 29-93% and 45-77%, respectively, the total bile acid synthesis from [4-14C]cholesterol synthesis being increased by 25-36%. K5 had no appreciable effect on this process. The data obtained suggest that the enhanced specific uptake of LDL into hepatocytes as well as the slight inhibition of cholesterol synthesis and stimulation of cholesterol conversion into bile acids can, at least partly, account for the hypolipodemic effect of probucol. The observed reduction in the secretion of the hepatocyte apo-B containing lipoprotein by the probucol analog K5 suggests it to be a potentially hypolipodemic compound.

Antioxidant MDL 29,311 prevents diabetes in nonobese diabetic and multiple low-dose STZ-injected mice

Recent investigations suggest a role for antioxidants in preventing IDDM. MDL 29,311 (4,4'-[methylenebis(thio)]bis](1,1- dimethylethyl)]-phenol) is an analogue of the antioxidant probucol. Administered as a 1% dietary admixture to female nonobese diabetic mice from 4 to 24 wk of age, MDL reduced the prevalence of diabetes from 49 to 4% at 24 wk of age (n = 50-61/group). Discontinuation of treatment at 24 wk of age did not result in a rapid onset of diabetes. Probucol (1%) did not prevent diabetes. Initiating MDL treatment at 4 or 8 wk of age was more effective (19 and 17%, respectively, compared with 60% in control mice) than initiating treatment at 12 wk of age (30% diabetic; n = 28-35/group). A lower dose of MDL (0.1%), started at 4 wk of age, decreased the prevalence of diabetes to 36%. Histopathology indicated that MDL did not prevent insulitis. MDL (0.1%) also was evaluated in combination with immunosuppressants. Compared with control mice (65% diabetic), the combination of MDL and deflazacort was more effective (21% diabetic) than either agent alone (39% diabetic for MDL and 59% diabetic for deflazacort), whereas the effectiveness of MDL, cyclosporin, and MDL plus cyclosporin was similar (39, 38, and 34% diabetic, respectively). In another model of IDDM, the multiple-low-dose streptozocin-injected mouse, MDL (1%) also reduced the prevalence of diabetes when administered beginning 8 wk before streptozocin (55% diabetic vs. 100% of control mice; n = 20-25/group). Probucol (1%) was ineffective. MDL appears effective in preventing the onset of disease in two mouse models of IDDM.

Protective effect of S12340 on cardiac cells exposed to oxidative stress

Oxidative stress induced by reactive oxygen species is one aspect of the deleterious mechanisms involved in myocardial post-ischemic reperfusion injury. The antioxidant properties of the new molecule S12340 (8-[3-(3,5-diterbutyl-4-hydroxyphenyl-thio)propyl]-1-oxa-2- oxo-3,8-diazaspiro[4.5]decane) were evaluated using three successive in vitro approaches mimicking the cardiac cell damages induced by reactive oxygen species released into the reperfused myocardium. (i) The effects of S12340 on lipid peroxidation were evaluated using an original cell-free model of non-enzymatic peroxidation of 1.32 mM arachidonic acid induced by reactive oxygen species generated photochemically. S12340 (13.2 microM) inhibited by 29% the rate of oxidative fragmentation of monohydroperoxidized arachidonic acid into aldehydic products. (ii) S12340 (10 microM) inhibited by 96% and 58% the oxidative necrosis of cultured rat cardiomyocytes induced by xanthine oxidase (20 mU/ml) and monohydroperoxidized arachidonic acid (30 microM), respectively. (iii) Superfusion of guinea-pig papillary muscle with monohydroperoxidized arachidonic acid (20 microM) resulted in marked alterations of their electrophysiological and mechanical activities. These modifications, maximal 15-17 min after the addition of lipid hydroperoxide, were completely abolished by S12340 (30 microM).

HLA-DQA1 and DQB1 gene polymorphisms in type I diabetic patients from central Italy and their use for risk prediction

Susceptibility to type I diabetes has been shown to be highly correlated with the presence of an amino acid other than Asp at position 57 of the DQ beta-chain (non-Asp57) and also with the presence of an Arg at position 52 of the DQ alpha-chain (Arg52). In this study we analyzed the DQA1 and DQB1 gene polymorphisms in 65 patients from central Italy and 93 randomly selected control subjects. Polymerase chain reaction amplification of DNA encoding the first polymorphic domain of the DQB1 and DQA1 chains was performed, and DQB1 gene polymorphism was evaluated by dot blot analysis using 11 sequence-specific oligonucleotide probes. For DQA1 typing, a new simple procedure based on allele-specific amplification and analysis of heteroduplex DNA molecules formed by the annealing of mismatched allelic strands was used. This technique allows the discrimination of Arg52 and non-Arg52 DQA1 alleles. We then calculated by logistic regression the contribution of these genetic markers to the development of diabetes. Frequencies and odds ratios relative to the amino acid in position 57 of the DQ beta-chain and the amino acid in position 52 of the DQ alpha-chain showed that the highest odds ratio (odds ratio = 161; 95% confidence interval 19-1386) was that of the homozygous combination of the two susceptibility markers (non-Asp57 and Arg52).(ABSTRACT TRUNCATED AT 250 WORDS)

MDL 29311. Antioxidant with marked lipid- and glucose-lowering activity in diabetic rats and mice

MDL 29311, an analogue of probucol, administered to rats as a 1% dietary admixture for 2 wk before and 5 days after intravenous injection of 40 mg/kg of ALX significantly (P < 0.05) reduced plasma glucose (6.9 +/- 0.3 vs. 19.2 +/- 1.3 mM) and serum triglyceride (0.17 +/- 0.01 vs. 1.82 +/- 0.39 mM) levels in overnight-fasted ALX-plus-MDL 29311-administered rats vs. ALX-administered rats. A cross-over study indicated that MDL 29311 did not attenuate the diabetogenic action of ALX, but rather, directly lowered glucose and triglycerides. In rats injected intravenously with 45, 65, or 85 mg/kg of STZ and then administered control or MDL 29311 diet for 7 days, MDL 29311 decreased fasted plasma glucose to nondiabetic levels, decreased fasted and nonfasted plasma triglycerides by 49-79%, but did not affect plasma insulin levels. In STZ-induced (65 mg/kg) diabetic rats, MDL 29311 attenuated the increase in plasma nonesterified fatty acids during an 18-h fast; had little or no effect on glucagon, pyruvate, lactate, beta-hydroxybutyrate, acetoacetate, or cholesterol; and did not induce hypoglycemia in rats fasted up to 64 h. In nonfasted hyperinsulinemic db/db mice treated for 10 wk, MDL 29311 significantly lowered glucose levels by 14-40%, triglyceride levels by 31-63% and GHb from 8.0 to 5.4%, and had no consistent effect on plasma insulin levels. Because of its marked glucose- and lipid-lowering activity in both nonfasted hyperinsulinemic and fasted insulinopenic animals, MDL 29311 merits additional investigation as a potential antidiabetic agent.

[Synthetic antioxidant correction for disorders of the regulatory and microcirculatory systems in the early stages of experimental atherosclerosis]

The influence of synthetic antioxidants (AOs) on hypothalamo-hypophyseal neuro-secretory system (HHNS), sympatho-adrenal system and microcirculatory bad in early stages of atherogenesis in rabbits (Anichkov's model) was studied. Correction of lipid metabolism and lipid peroxidation (LP) activation by AOs was accompanied by disappearing of structural changes in regulatory and microcirculatory systems, regression of atheromatosis in great arteries. Stabilization effect of AOs on neurons and erythrocytes membrane structures was noticed. Some distinctions in mechanism of action between mexidol and fenbutol were found. Thus, regulatory and microcirculatory disturbances, which appear on early atherogenesis stages and is the basis of chronic noninfectious pathology in different target-organs is reversible, for example trough LP correction.

Ascorbate and phenolic antioxidant interactions in prevention of liposomal oxidation

Efficient prevention of membrane lipid peroxidation by vitamin E (alpha-tocopherol) may involve its regeneration by vitamin C (ascorbate). Conceivably, the efficacy of antioxidants designed as therapeutic agents could be enhanced if a similar regeneration were favorable; thus, a model membrane system was developed which allowed assessment of interaction of phenolic antioxidants with ascorbate and ascorbyl-6-palmitate. Ascorbate alone (50-200 microM) potentiated oxidation of soybean phosphatidylcholine liposomes by Fe2+/histidine-Fe3+, an effect which was temporally related to reduction of Fe3+ generated during oxidation. Addition of 200 microM ascorbate to alpha-tocopherol-containing liposomes (0.1 mol%) resulted in marked, synergistic protection. Accordingly, in the presence but not absence of ascorbate, alpha-tocopherol levels were maintained relatively constant during Fe2+/histidine-Fe3+ exposure. Probucol (4,4'-[(1-methylethylidine)bis(thio)]bis[2,6-bis(1,1- dimethylethyl)]phenol), an antioxidant which prevents oxidation of low density lipoproteins, and its analogues MDL 27,968 (4,4'-[(1-methylethylidene)bis(thio)]bis[2,6- dimethyl]phenol) and MDL 28,881 (2,6-bis(1,1-dimethylethyl)-4-[(3,7,11- trimethyldodecyl)thio]phenol) prevented oxidation but exhibited no synergy with ascorbate. Ascorbyl-6-palmitate itself was an effective antioxidant but did not interact synergistically with any of the phenolic antioxidants. Differential scanning calorimetry revealed significant differences among the antioxidants in their effect on the liquid-crystalline phase transition of dipalmitoyl phosphatidylcholine (DPPC) liposomes. Both alpha-tocopherol and MDL 27,968 significantly reduced the phase transition temperature and the enthalpy of the transition. MDL 28,881 had no effect while probucol was intermediate. The potential for ascorbate or its analogues to interact with phenolic antioxidants to provide a more effective antioxidant system appears to be dictated by structural features and by the location of the antioxidants in the membrane.