Add-on effect of probucol in atherosclerotic, cholesterol-fed rabbits treated with atorvastatin

Structure and Dynamics of Oxidized Lipoproteins In Vivo: Roles of High-Density Lipoprotein

Oxidative modification of lipoproteins is implicated in the occurrence and development of atherosclerotic lesions. Earlier studies have elucidated on the mechanisms of foam cell formation and lipid accumulation in these lesions, which is mediated by scavenger receptor-mediated endocytosis of oxidized low-density lipoprotein (oxLDL). Mounting clinical evidence has supported the involvement of oxLDL in cardiovascular diseases. High-density lipoprotein (HDL) is known as anti-atherogenic; however, recent studies have shown circulating oxidized HDL (oxHDL) is related to cardiovascular diseases. A modified structure of oxLDL, which was increased in the plasma of patients with acute myocardial infarction, was characterized. It had two unique features: (1) a fraction of oxLDL accompanied oxHDL, and (2) apoA1 was heavily modified, while modification of apoB, and the accumulation of oxidized phosphatidylcholine (oxPC) and lysophosphatidylcholine (lysoPC) was less pronounced. When LDL and HDL were present at the same time, oxidized lipoproteins actively interacted with each other, and oxPC and lysoPC were transferred to another lipoprotein particle and enzymatically metabolized rapidly. This brief review provides a novel view on the dynamics of oxLDL and oxHDL in circulation.

Effect of Probucol on Proliferation of Leukemia, Multiple Myeloma, Lymphoma, and Fibroblast Cells

Objectives

Probucol is a bisphenol antioxidant with antiinflammatory, antilipidemic and antidiabetic effect. Development and progression of cancer is closely related to chronic inflammation and oxidative stress. Agents that target these processes have been shown to modulate cancer cell proliferation. In this regard, the effect of probucol on proliferation of different cancer cell lines was investigated.

Materials and Methods

Different concentrations of probucol solutions were prepared and applied to the following cancer cell lines: K562S (imatinib sensitive) and K562R (imatinib resistant) chronic myeloid leukemia (CML) cells; U937 histiocytic lymphoma cells; HL60 acute myeloid leukemia cells; U266, H929, and RPMI8226 multiple myeloma cells; and L929 fibroblast cells. Cell viability was conducted by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

Results

Significant toxicity was not exhibited due to probucol treatment (0.1-10 µM) in K562S and K562R CML cells, U937 histiocytic lymphoma cells, HL60 acute myeloid leukemia cells, U266 multiple myeloma cells, and L929 fibroblast cells. However, probucol treatment significantly inhibited the viability of H929 and RPMI8226 multiple myeloma cells at the concentration of 0.5-10 µM and 5-10 µM, respectively.

Conclusion

Probucol treatment slightly inhibited the viability of other cancer cell lines, but significantly inhibited the viability of H929 and RPMI8226 multiple myeloma cells. However, its effect was not potent, since a 50% reduction in cell viability could not be achieved at the concentrations of probucol treatment administered.

Probucol ameliorates EMT and lung fibrosis through restoration of SIRT3 expression

Pulmonary fibrosis is a progressive fibrotic lung disease with a paucity of therapeutic options. Here we investigated the potential roles of probucol, a cholesterol-lowering drug with potent anti-oxidation properties, on pulmonary epithelial-mesenchymal transition (EMT) and fibrosis. We found that bleomycin-induced lung fibrosis was associated with increased transforming growth factor (TGF)-β1, α-smooth muscle actin (α-SMA) and decreased E-cadherin expression in lung tissues, indicating EMT formation. Bleomycin treatment resulted in an induction of oxidative stress in lung tissues. Probucol treatment attenuated bleomycin-induced TGF-β1 production, EMT and pulmonary fibrosis, meanwhile it suppressed bleomycin-induced oxidative stress. Bleomycin treatment resulted in decreases in protein expressions of Sirtuin 3 (SIRT3) in the lung, which were restored by ROS scavenger NAC and probucol treatment, suggesting that probucol might restore SIRT3 expression by suppressing bleomycin-induced oxidative stress. In the mouse alveolar type II epithelial cell line MLE-12, probucol treatment leads to an increase in SIRT3 expression in bleomycin-treated AT-II cells, which might contribute to the inhibitory effect of probucol on EMT through suppressing hypoxia inducible factor (HIF)-1α/TGF-β1 pathway. In addition, probucol inhibited bleomycin-induced macrophage infiltration in the lung. Bleomycin decreased SIRT3 protein expression, whereas increased HIF-1α activation and TGF-β1 release in the mouse macrophage cell line RAW264.7, which were attenuated by probucol treatment. Taken together, the present study suggests that probucol may ameliorate EMT and lung fibrosis through restoration of SIRT3 expression. The data obtained in this study provides proof for the idea that probucol may be a potential therapeutic option for the treatment of pulmonary fibrosis.

Effects of atorvastatin and/or probucol on recovery of atherosclerosis in high-fat-diet-fed apolipoprotein E-deficient mice

INTRODUCTION

We have investigated the possible effects and mechanism of atorvastatin, a statin, and/or probucol, a powerful antioxidant used to lower cholesterol before 1995, on the atherosclerosis development.

METHODS

Apolipoprotein-E-deficient (ApoE^-/-) mice fed with the high fat diet were randomly divided into 3 groups (n = 10/each group): Placebo, Atorvastatin (10 mg/ kg/d), and atorvastatin (10 mg/kg/d) plus probucol (10 mg/kg/d) groups. C57BL/6 J mice were fed with normal diet as the control group (n = 10). Animals were sacrificed 10 weeks after the intervention. To evaluate the experimental atherosclerosis, blood tests were used for measuring serum lipoprotein profile, Western blots for endoplasmic reticulum (ER) stress protein expression, H&E staining for plaque lesions, immunohistology for macrophages, inflammatory cytokines, innate immune receptor TLR-4, transcription factor NF-κB, and atherosclerosis plaques.

RESULTS

Compared with the control group, ApoE^-/- mice in the placebo group showed with the significantly (p < 0.05) higher levels of serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL) and oxidized low density lipoprotein (ox-LDL), PERK, GRP78, CHOP, IL-1β, TNF-α and NF-κB, but with the lower levels of high-density lipoprotein cholesterol (HDL) and TLR-4, and also the increase in macrophages and the aortic media collagen, and the decrease in the elastic fibers (p < 0.01). Treatment with atorvastatin recovered all these features (p < 0.05 or p < 0.01) near to the levels in the control group. In addition, the combination of atorvastatin and probucol has shown the slightly stronger effect than the use of atorvastatin alone without statistical significances when comparing most bio-markers of atherosclerosis, but with significant differences in the reduction of the plaque lesion areas and macrophages (p < 0.05).

CONCLUSIONS

Atorvastatin and/or probucol suppresses ER stress and increase the level of TLR-4, which lowers NF-κB, resulting in the recovery of atherosclerosis in the ApoE^-/- mouse model.

The effects of seed from Linum usitatissimum cultivar with increased phenylpropanoid compounds and hydrolysable tannin in a high cholesterol-fed rabbit

Background

Dietary fat is considered one of the most important factors associated with blood lipid metabolism and plays a significant role in the cause and prevention of atherosclerosis that has been widely accepted as an inflammatory disease of the vascular system. The aim of the present study was to evaluate the effect of genetically modified flaxseed (W86) rich in phenylpropanoid compounds and hydrolysable tannin in high cholesterol-induced atherosclerosis rabbit models compared to parental cultivar Linola.

Methods

Twenty-Eight White New Zealand white rabbits aged 6 months were randomly divided into four groups, control group, high cholesterol group (10 g/kg), Linola flaxseed group (100 g/kg) and W86 flaxseed group (100 g/kg). The rabbits were fed a normal diet or a high cholesterol diet for 10 weeks. Levels of blood lipids, hematological values, total antioxidative status and superoxide dismutase activity in serum were determined. Moreover, body weight and feed intake were measured after sixth and tenth weeks. After each stage of the experiment atherogenic indexes (non-HDL-C/HDL-C, LDL-C/HDL-C, and atherogenic index of plasma) was calculated.

Results

The intake of a dyslipidaemic diet negatively influenced lipid profile in rabbits at the 10 weeks of feeding. W86 flaxseed significantly decreased total cholesterol, LDL-C, VLDL-C and TG serum levels in cholesterolemic rabbits compared with parental Linola after 10 weeks. Atherogenic indexes decreased over time with a significant difference between the diets and they were the best for W86 flaxseed. Similarly, the experimental addition of W86 significantly decreased atherogenic predictors such as heterophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and the mean platelet volume-to-lymphocyte ratio. In rabbits, W86 flaxseed increased the activity of superoxide dismutase and total antioxidative status compared to Linola.

Conclusions

Results of the presented study suggest that the addition of W86 flaxseed alleviate serum lipid changes in high cholesterolemic diet-administered rabbits. W86 flaxseed significantly reduced atherogenic indexes, as compared with the Linola and indicate that W86 flaxseed more effectively red CVD risk factors during hypercholesterolemia. Moreover, the presented result suggested that W86 flaxseed can be a part of a heart-healthy and antiatherogenic diet for the human.

Electronic supplementary material

The online version of this article (10.1186/s12944-018-0726-4) contains supplementary material, which is available to authorized users.

Atorvastatin as a Promising Crystallization Inhibitor of Amorphous Probucol: Dielectric Studies at Ambient and Elevated Pressure

The aim of this article was to check the physical stability of the amorphous form of probucol at both standard storage and manufacturing conditions. Our studies clearly show that disordered form of the examined, cholesterol lowering, agent stored at ambient pressure does not reveal any tendency toward recrystallization. The physical stability of neat probucol stored at ambient pressure has been investigated (i) at room temperature by means of X-ray diffraction technique (XRD) as well as (ii) at T = 333 K by means of broadband dielectric spectroscopy (BDS). Due to the fact that compression is an important stage of drugs manufacturing we additionally performed physical stability tests of amorphous probucol at elevated pressure. The recrystallization tendency of the examined pharmaceutical has been tracked online from the initial and further up to a few hours after compression by means of the high pressure BDS technique. These experiments indicate that even very small pressure applied during the sample compression immediately induce its recrystallization. Since, the sensitivity on pressure eliminates probucol from the group of physically stable amorphous APIs, its stabilization is required. Taking into account that there are many scientific reports describing the positive effect of coadministration of probucol with the drug atorvastatin, we used the latter as probucol's crystallization inhibitor.

Probucol in Albuminuric Type 2 Diabetes Mellitus Patients on Renin–Angiotensin System Blockade

Objective—

To determine the effect of probucol on urine albumin excretion in type 2 diabetes mellitus patients with albuminuria using angiotensin-converting enzyme inhibitors or angiotensin receptor blockers.

Approach and Results—

This was a 16-week, phase II, randomized, placebo-controlled, parallel-group study in type 2 diabetes mellitus patients with a urinary albumin/creatinine ratio of ≥300 mg/g using angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, conducted in 17 tertiary referral hospitals. Eligible patients were randomized to probucol 250 mg/d (n=44), probucol 500 mg/d (n=41), and placebo (n=41) groups in a ratio of 1:1:1 after block randomization procedures, keeping the treatment assignment blinded to the investigators, patients, and study assistants. The primary end point was change in the geometric mean of urinary albumin/creatinine ratio from baseline to week 16 ( ClinicalTrials.gov identifier NCT01726816). The study was started on November 8, 2012, and completed on March 24, 2014. The least squares mean change±SE from baseline in urinary albumin/creatinine ratio at week 16 was −7.2±639.5 mg/g in the probucol 250 mg/d group (n=43; P =0.2077 versus placebo group), 9.3±587.4 mg/g in the probucol 500 mg/d group (n=40; P =0.1975 versus placebo group), and 259.0±969.1 mg/g in the placebo group (n=41). Although the majority of subjects were on statins, probucol treatment significantly lowered total cholesterol and low-density lipoprotein cholesterol levels. QT prolongation occurred in one and two subjects in control and probucol 250 mg/d groups, respectively.

Conclusions—

Four months of probucol up to 500 mg/d failed to reduce urinary albumin excretion.

Dietary cholesterol atherogenic changes in juvenile rabbits

Atherosclerotic lesion formation starts during fetal development and progresses with age after adolescence. However, atherogenesis during the juvenile period has not been studied thoroughly. In this study, we examined the atherogenic susceptibility of juvenile rabbits to cholesterol feeding. Male New Zealand White rabbits aged 8 (younger group) and 12 (older group) weeks were fed a 0.5% cholesterol-containing diet for 8 weeks, and then their aortic atherosclerotic lesion areas were evaluated. Plasma concentrations of total cholesterol, triglycerides, and phospholipids did not differ between the two groups; however, plasma concentrations of high-density lipoprotein cholesterol were 23% lower in the younger than in the older group. Atherosclerotic lesion areas were significantly larger in the younger group (32±21%). However, only moderate changes were observed in these areas in the older group (3.3±0.3%). Histological examination showed marked intimal thickening and macrophage accumulation in the aortic lesions of rabbits in the younger group. To the best of our knowledge, this is the first study to show that dietary cholesterol-induced atherogenic changes markedly occur during a short period in juvenile rabbits.

Asymmetric Dimethylarginine Limits the Efficacy of Simvastatin Activating Endothelial Nitric Oxide Synthase

Background

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of endothelial nitric oxide synthase (eNOS), is considered a risk factor for the pathogenesis of cardiovascular diseases. Simvastatin, a lipid‐lowering drug with other pleiotropic effects, has been widely used for treatment of cardiovascular diseases. However, little is known about the effect and underlying molecular mechanisms of ADMA on the effectiveness of simvastatin in the vascular system.

Methods and Results

We conducted a prospective cohort study to enroll 648 consecutive patients with coronary artery disease for a follow‐up period of 8 years. In patients with plasma ADMA level ≥0.49 μmol/L (a cut‐off value from receiver operating characteristic curve), statin treatment had no significant effect on cardiovascular events. We also conducted randomized, controlled studies using in vitro and in vivo models. In endothelial cells, treatment with ADMA (≥0.5 μmol/L) impaired simvastatin‐induced nitric oxide (NO) production, endothelial NO synthase (eNOS) phosphorylation, and angiogenesis. In parallel, ADMA markedly increased the activity of NADPH oxidase (NOX) and production of reactive oxygen species (ROS). The detrimental effects of ADMA on simvastatin‐induced NO production and angiogenesis were abolished by the antioxidant, N‐acetylcysteine, NOX inhibitor, or apocynin or overexpression of dimethylarginine dimethylaminohydrolase 2 (DDAH‐2). Moreover, in vivo, ADMA administration reduced Matrigel plug angiogenesis in wild‐type mice and decreased simvastatin‐induced eNOS phosphorylation in aortas of apolipoprotein E–deficient mice, but not endothelial DDAH‐2‐overexpressed aortas.

Conclusions

We conclude that ADMA may trigger NOX‐ROS signaling, which leads to restricting the simvastatin‐conferred protection of eNOS activation, NO production, and angiogenesis as well as the clinical outcome of cardiovascular events.

Did we abandon probucol too soon?

PURPOSE OF REVIEW

Probucol is a potent antioxidative drug that has been used for prevention and treatment of atherosclerotic cardiovascular diseases and xanthoma. Probucol has been used as a lipid-lowering drug for a long time especially in Japan, although Western countries quitted its use because of the reduction in serum HDL-cholesterol (HDL-C). This review highlights both basic and clinical studies that provide new insights into the pleiotropic effects of probucol.

RECENT FINDINGS

Recently, the mechanisms for the pharmacologic actions of probucol have been elucidated at the molecular level with a special focus on HDL metabolism and its functions. Probucol enhances plasma cholesteryl ester transfer protein activity and hepatic scavenger receptor class B type I, causing a decrease in HDL-C. It also accelerates the antioxidative function of HDL via increase in paraoxonase 1 activity. Recent retrospective analyses of probucol-treated patients with heterozygous familial hypercholesterolemia and those after coronary revascularization demonstrated a strong beneficial effect of probucol on secondary prevention of cardiovascular events and mortality.

SUMMARY

Probucol has pleiotropic and beneficial therapeutic effects on cardiovascular system. Although statins are effective for lowering LDL-cholesterol (LDL-C) and reducing coronary heart disease risk, probucol should be considered as an option in case statins are not effective.

Combined use of probucol and cilostazol with atorvastatin attenuates atherosclerosis in moderately hypercholesterolemic rabbits

Background

Atherosclerotic cardiovascular disease is one of the major diseases that seriously impacts human health. Combined drug therapy may be efficacious in delaying the occurrence of cardiovascular events.

Aim

The current study was designed to investigate whether combined use of probucol (an anti-oxidant agent) with cilostazol (a platelet aggregation inhibitor) would increase the inhibitory effect of statins (a lipid-lowering agent) on atherosclerosis in moderately hypercholesterolemic rabbits.

Methods and Results

Thirty Japanese white rabbits were fed with a high cholesterol diet for 12 weeks, which was supplemented with either 0.005 % atorvastatin alone or 0.005 % atorvastatin plus 0.3 % probucol and 0.3 % cilostazol. Except for high-density lipoprotein cholesterol, no difference was found in plasma lipids among vehicle, statin, and the combined treatment group. However, atherosclerotic lesions were significantly reduced by statin treatment compared with vehicle. Moreover, we found that the anti-atherogenic effect of statin was further enhanced by the combined treatment, which was due to increased anti-inflammatory and anti-oxidant properties.

Conclusions

These data demonstrated that combined drug treatment exhibits potent athero-protective effects via pleiotropic functions, such as anti-inflammatory and anti-oxidative stress, which is independent of the lipid-lowering effect.

Emerging risk biomarkers in cardiovascular diseases and disorders

Present review article highlights various cardiovascular risk prediction biomarkers by incorporating both traditional risk factors to be used as diagnostic markers and recent technologically generated diagnostic and therapeutic markers. This paper explains traditional biomarkers such as lipid profile, glucose, and hormone level and physiological biomarkers based on measurement of levels of important biomolecules such as serum ferritin, triglyceride to HDLp (high density lipoproteins) ratio, lipophorin-cholesterol ratio, lipid-lipophorin ratio, LDL cholesterol level, HDLp and apolipoprotein levels, lipophorins and LTPs ratio, sphingolipids, Omega-3 Index, and ST2 level. In addition, immunohistochemical, oxidative stress, inflammatory, anatomical, imaging, genetic, and therapeutic biomarkers have been explained in detail with their investigational specifications. Many of these biomarkers, alone or in combination, can play important role in prediction of risks, its types, and status of morbidity. As emerging risks are found to be affiliated with minor and microlevel factors and its diagnosis at an earlier stage could find CVD, hence, there is an urgent need of new more authentic, appropriate, and reliable diagnostic and therapeutic markers to confirm disease well in time to start the clinical aid to the patients. Present review aims to discuss new emerging biomarkers that could facilitate more authentic and fast diagnosis of CVDs, HF (heart failures), and various lipid abnormalities and disorders in the future.