Cilostazol inhibits modified low-density lipoprotein uptake and foam cell formation in mouse peritoneal macrophages

Therapeutic Potential of Phosphodiesterase Inhibitors for Endothelial Dysfunction- Related Diseases

Cardiovascular diseases (CVD) are considered a major health problem worldwide, being the main cause of mortality in developing and developed countries. Endothelial dysfunction, characterized by a decline in nitric oxide production and/or bioavailability, increased oxidative stress, decreased prostacyclin levels, and a reduction of endothelium-derived hyperpolarizing factor is considered an important prognostic indicator of various CVD. Changes in cyclic nucleotides production and/ or signalling, such as guanosine 3', 5'-monophosphate (cGMP) and adenosine 3', 5'-monophosphate (cAMP), also accompany many vascular disorders that course with altered endothelial function. Phosphodiesterases (PDE) are metallophosphohydrolases that catalyse cAMP and cGMP hydrolysis, thereby terminating the cyclic nucleotide-dependent signalling. The development of drugs that selectively block the activity of specific PDE families remains of great interest to the research, clinical and pharmaceutical industries. In the present review, we will discuss the effects of PDE inhibitors on CVD related to altered endothelial function, such as atherosclerosis, diabetes mellitus, arterial hypertension, stroke, aging and cirrhosis. Multiple evidences suggest that PDEs inhibition represents an attractive medical approach for the treatment of endothelial dysfunction-related diseases. Selective PDE inhibitors, especially PDE3 and PDE5 inhibitors are proposed to increase vascular NO levels by increasing antioxidant status or endothelial nitric oxide synthase expression and activation and to improve the morphological architecture of the endothelial surface. Thereby, selective PDE inhibitors can improve the endothelial function in various CVD, increasing the evidence that these drugs are potential treatment strategies for vascular dysfunction and reinforcing their potential role as an adjuvant in the pharmacotherapy of CVD.

Effect of cilostazol, a phosphodiesterase-3 inhibitor, on coronary artery stenosis and plaque characteristics in patients with type 2 diabetes: ESCAPE study

AIM

To perform a prospective study to evaluate the effect of cilostazol (CTZ) compared with aspirin (acetylsalicylic acid; ASA) in Korean people with diabetes and subclinical coronary atherosclerosis.

MATERIALS AND METHODS

A total of 100 people with diabetes who had mild to moderate coronary atherosclerosis, assessed by coronary computed tomographic angiography (CCTA), were randomly assigned to either 200 mg/d CTZ or 100 mg/d ASA (n = 50 each group). The primary outcome was change in coronary artery stenosis assessed by CCTA after 12 months of treatment. Secondary outcomes included changes in plaque composition, coronary artery calcium score and cardiac markers.

RESULTS

The mean age, body mass index and glycated haemoglobin concentration were 61.5 years, 25.0 kg/m² and 56.8 mmol/mol, respectively, and were well matched between the two groups. Coronary artery stenosis decreased in the CTZ group (from 44.0 ± 2.1% to 40.4 ± 2.5%) but remained unchanged in the ASA group (from 38.9 ± 2.1% to 40.6 ± 2.1%). In the CTZ group, the non-calcified portion of plaques decreased significantly (from 20.6 ± 3.0 to 17.3 ± 3.0 mm³ ), whereas it did not change significantly in the ASA group (15.2 ± 2.8 vs 16.6 ± 2.9 mm³ ). Increases in HDL cholesterol, decreases in triglycerides, liver enzyme and high-sensitivity C-reactive protein levels, and reductions in abdominal visceral fat area and insulin resistance were observed only in the CTZ group.

CONCLUSION

CTZ treatment for 12 months decreased coronary artery stenosis and the non-calcified plaque component. These results suggest that CTZ treatment may be an option for preventing the progression of coronary atherosclerosis in people with diabetes.

Potentiation of imatinib by cilostazol in sensitive and resistant gastrointestinal stromal tumor cell lines involves YAP inhibition

Despite the introduction of tyrosine kinase inhibitors, gastrointestinal stromal tumors (GIST) resistance remains a major clinical challenge. We previously identified phosphodiesterase 3A (PDE3A) as a potential therapeutic target expressed in most GIST. The PDE3 inhibitor cilostazol reduced cell viability and synergized with the tyrosine kinase inhibitor imatinib (Gleevec™) in the imatinib-sensitive GIST882 cell line. Here, we found that cilostazol potentiated imatinib also in the imatinib-resistant GIST48 cell line. Cilostazol induced nuclear exclusion, hence inactivation, of the transcriptional co-activator YAP, in a cAMP-independent manner. Verteporfin, a YAP/TEAD interaction inhibitor, reduced by 90% the viability of both GIST882 and GIST48 cells. Our results highlight the potential use of compounds targeting PDE3A or YAP in combined multitherapy to tackle GIST resistance.

Phosphodiesterase 3A: a new player in development of interstitial cells of Cajal and a prospective target in gastrointestinal stromal tumors (GIST)

We previously identified phosphodiesterase 3A (PDE3A) as a marker for interstitial cells of Cajal (ICC) in adult mouse gut. However, PDE3A expression and function during gut development and in ICC-derived gastrointestinal stromal tumors (GIST) remained unknown. Here we found that PDE3A was expressed throughout ICC development and that ICC density was halved in PDE3A-deficient mice. In the human imatinib-sensitive GIST882 cell line, the PDE3 inhibitor cilostazol halved cell viability (IC₅₀ 0.35 μM) and this effect synergized with imatinib (Chou-Talalay's CI₅₀ 0.15). Recently the compound 6-(4-(diethylamino)-3-nitrophenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-one, or DNMDP was found to be cytotoxic selectively for cells expressing both PDE3A and Schlafen12 (SLFN12) (de Waal L et al. Nat Chem Bio 2016), identifying a new, non-catalytic, role for PDE3A. 108 out of 117 (92%) of our human GIST samples displayed both PDE3A and SLFN12 immunoreactivity. GIST882 cells express both PDE3A and SLFN12 and DNMDP decreased their viability by 90%. Our results suggest a role for PDE3A during ICC development and open novel perspectives for PDE3A in targeted GIST therapy, on one hand by the synergism between imatinib and cilostazol, a PDE3 inhibitor already in clinical use for other indications, and, on the other hand, by the neomorphic, druggable, PDE3A-SLFN12 cytotoxic interplay.

Combined therapeutic effect of probucol and cilostazol on endothelial function in patients with silent cerebral lacunar infarcts and hypercholesterolemia: a preliminary study

OBJECTIVE

This study evaluated the efficacy of combined therapy with probucol and cilostazol on endothelial function in silent lacunar cerebral infarcts (SLCI) and mild hypercholesterolemia.

SUBJECTS AND METHODS

Flow-mediated vasodilatation (FMD) and nitroglycerin-induced vasodilatation (NMD) were measured before and after 4 weeks of combined therapy with probucol (500 mg/day) and cilostazol (200 mg/day) in 34 patients with a mean age of 72 ± 7 years (range 57-80 years) with SLCI, mild hypercholesterolemia (low-density lipoprotein cholesterol >100 mg/dl) and impaired endothelial function (FMD <6%). Patients were randomly allocated to one of the following two treatment groups: (1) aspirin (100 mg/day) with behavioral modifications, such as diet and/or exercise therapy (A group or control group, n = 17), and (2) probucol and cilostazol treatment (PC group, n = 17), also with behavioral modifications.

RESULTS

Although the baseline FMD was not different between the two treatment arms (2.7 ± 1.5 vs. 2.6 ± 1.5%, n.s.), the posttreatment FMD was significantly improved in the PC group (from 2.7 ± 1.5 to 3.5 ± 1.7%, p < 0.05) but not in the A group (from 2.6 ± 1.5 to 2.9 ± 1.4%, n.s.). No differences were observed between baseline and posttreatment NMD in either group. The effects of treatments on lipid profiles were more profound in the PC group.

CONCLUSION

Combined treatment with probucol and cilostazol resulted in subacute improvement in FMD/endothelial function in patients with SLCI with mild hypercholesterolemia. This combination therapy has the potential to reduce the risk of cardiovascular events via improvements in endothelial function and lipid profiles.

Rubus coreanusInhibits Oxidized-LDL Uptake by Macrophages Through Regulation of JNK Activation

Oxidized low-density lipoprotein (oxLDL) contributes to atherosclerosis in part by being taken up into macrophages via scavenger receptors and leading to foam cell formation. Herbal compounds that have been used to treat blood stasis (a counterpart of atherosclerosis) for centuries include extracts of medicinal plants in the Rosaceae and Leguminosae families. In this study, we investigated the effect of the unripe Rubus coreanus (Korean black raspberry) fruit extract on oxLDL uptake by murine macrophage cells. In the presence of Rubus coreanus extract (RCE), Dil-labeled oxLDL uptake was inhibited in a dose-dependent manner. SP600125, a specific JNK inhibitor, inhibited the uptake of Dil-oxLDL into macrophages. RCE also inhibited JNK phosphorylation in a time- and dose-dependent manner in macrophages treated with oxLDL. These results indicate that among the mitogen-activated protein kinases, JNK phosphorylation is inhibited by RCE, which is likely the mechanism underlying the RCE-induced inhibition of oxLDL uptake by macrophages.

Cilostazol inhibits accumulation of triglyceride in aorta and platelet aggregation in cholesterol-fed rabbits

Cilostazol is clinically used for the treatment of ischemic symptoms in patients with chronic peripheral arterial obstruction and for the secondary prevention of brain infarction. Recently, it has been reported that cilostazol has preventive effects on atherogenesis and decreased serum triglyceride in rodent models. There are, however, few reports on the evaluation of cilostazol using atherosclerotic rabbits, which have similar lipid metabolism to humans, and are used for investigating the lipid content in aorta and platelet aggregation under conditions of hyperlipidemia. Therefore, we evaluated the effect of cilostazol on the atherosclerosis and platelet aggregation in rabbits fed a normal diet or a cholesterol-containing diet supplemented with or without cilostazol. We evaluated the effects of cilostazol on the atherogenesis by measuring serum and aortic lipid content, and the lesion area after a 10-week treatment and the effect on platelet aggregation after 1- and 10-week treatment. From the lipid analyses, cilostazol significantly reduced the total cholesterol, triglyceride and phospholipids in serum, and moreover, the triglyceride content in the atherosclerotic aorta. Cilostazol significantly reduced the intimal atherosclerotic area. Platelet aggregation was enhanced in cholesterol-fed rabbits. Cilostazol significantly inhibited the platelet aggregation in rabbits fed both a normal diet and a high cholesterol diet. Cilostazol showed anti-atherosclerotic and anti-platelet effects in cholesterol-fed rabbits possibly due to the improvement of lipid metabolism and the attenuation of platelet activation. The results suggest that cilostazol is useful for prevention and treatment of atherothrombotic diseases with the lipid abnormalities.

Ginkgo biloba extract (GbE) enhances the anti-atherogenic effect of cilostazol by inhibiting ROS generation

In this study, the synergistic effect of 6-[4-(1-cyclohexyl- 1H-tetrazol-5-yl) butoxy]-3,4-dihydro-2(1H )-quinolinone (cilostazol) and Ginkgo biloba extract (GbE) was examined in apolipoprotein E (ApoE) null mice. Co-treatment with GbE and cilostazol synergistically decreased reactive oxygen species (ROS) production in ApoE null mice fed a high-fat diet. Co-treatment resulted in a significantly decreased atherosclerotic lesion area compared to untreated ApoE mice. The inflammatory cytokines and adhesion molecules such as monocyte chemoattractant-1 (MCP-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), and VCAM-1 which can initiate atherosclerosis were significantly reduced by the co-treatment of cilostazol with GbE. Further, the infiltration of macrophages into the intima was decreased by co-treatment. These results suggest that co-treatment of GbE with cilostazol has a more potent anti-atherosclerotic effect than treatment with cilostazol alone in hyperlipidemic ApoE null mice and could be a valuable therapeutic strategy for the treatment of atherosclerosis.

A phosphodiesterase 3 inhibitor, K-134, improves hindlimb skeletal muscle circulation in rat models of peripheral arterial disease

OBJECTIVE

Cilostazol is a phosphodiesterase (PDE)3 inhibitor used to treat peripheral arterial disease with intermittent claudication, as there is clinical evidence that it improves treadmill exercise capacity. However, details of the mechanism underlying this enhanced walking capacity remain to be elucidated.

METHODS

Based on the hypothesis that PDE3 inhibitors improve peripheral microcirculation in the hindlimbs via vascular smooth muscle relaxation and antiplatelet effects, we examined the effects of a more potent and selective PDE3 inhibitor, K-134, in rat models of peripheral arterial disease (PAD).

RESULTS

In a hindlimb ischemia model established by bilateral femoral artery occlusion, oral administration of K-134 for 27 days significantly increased blood flow in hindlimb skeletal muscle after exercise induced by electrical stimulation of the sciatic nerve. Moreover, K-134 enlarged the luminal area of intramuscular arteries and prevented rarefaction of capillary density in the gastrocnemius muscle. These effects were observed without pre-administration on the day following the last administration, suggesting that vasodilatory, antiplatelet and angiogenic activities of K-134 were indirectly responsible for the long-term beneficial effects. In fact, K-134 dose-dependently induced relaxation of rat femoral arteries in vitro, and inhibited rat platelet aggregation ex vivo. Interestingly, in a laurate-induced peripheral vascular injury model, oral administration of K-134 for 6 days prevented progression of hindlimb necrosis.

CONCLUSION

These findings suggest that the beneficial effects of PDE3 inhibitors on walking capacity are due to increased hindlimb skeletal muscle blood flow via intramuscular artery enlargement, and that K-134 is a promising drug for PAD associated with platelet hyperaggregability.

Effect of cilostazol on the progression of carotid intima-media thickness: a meta-analysis of randomized controlled trials

BACKGROUND

It has been well established that cilostazol has anti-proliferative effect against in-stent restenosis. However, it remains unclear whether cilostazol can prevent the progression of carotid atherosclerosis.

METHODS AND RESULTS

We performed a meta-analysis of all relevant randomized controlled trials (RCTs) to evaluate the effect of cilostazol on the progression of carotid intima-media thickness (IMT). Five RCTs with 698 patients [597 subjects with type 2 diabetes mellitus (T2DM)] were included in this study. Cilostazol was associated with a significant reduction in the progression of carotid IMT (WMD, -0.08mm, 95% CI -0.13, -0.04; P=0.00003). Subgroup analysis shows that cilostazol monotherapy or addition to dual antiplatelet therapy (aspirin and clopidogrel) was superior to placebo (WMD, -0.04mm, 95% CI -0.05, -0.03; P<0.00001), no antiplatelet medication (WMD, -0.12mm, 95% CI -0.21, -0.03; P=0.008), aspirin monotherapy (WMD, -0.06mm, 95% CI -0.12, 0.00; P=0.04) or dual antiplatelet therapy (WMD, -0.16mm, 95% CI -0.30, -0.02; P=0.03) in preventing the progression of carotid IMT. Cilostazol resulted in a significant decrease in total cholesterol (WMD -8.47mg/dl, 95% CI -14.18, -2.75; P=0.004) and LDL-C (WMD -8.25mg/dl, 95% CI -14.15, -2.36; P=0.006) and favorable trends in reducing triglyceride (WMD -15.83mg/dl, 95% CI -32.14, 0.48; P=0.06).

CONCLUSION

It suggests that cilostazol may have beneficial effects in preventing the progression of carotid atherosclerosis and improving pro-atherogenic lipid profile, especially in patients with T2DM. Whether the anti-atherosclerotic effect of cilostazol is independent of improving pro-atherogenic dyslipidemia is worth further investigation.

Native incretins prevent the development of atherosclerotic lesions in apolipoprotein E knockout mice

AIMS/HYPOTHESIS

Several lines of evidence suggest that incretin-based therapies suppress the development of cardiovascular disease in type 2 diabetes. We investigated the possibility that glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) can prevent the development of atherosclerosis in Apoe (-/-) mice.

METHODS

Apoe (-/-) mice (17 weeks old) were administered GLP-1(7-36)amide, GLP-1(9-36)amide, GIP(1-42) or GIP(3-42) for 4 weeks. Aortic atherosclerosis, oxidised LDL-induced foam cell formation and related gene expression in exudate peritoneal macrophages were determined.

RESULTS

Administration of GLP-1(7-36)amide or GIP(1-42) significantly suppressed atherosclerotic lesions and macrophage infiltration in the aortic wall, compared with vehicle controls. These effects were cancelled by co-infusion with specific antagonists for GLP-1 and GIP receptors, namely exendin(9-39) or Pro(3)(GIP). The anti-atherosclerotic effects of GLP-1(7-36)amide and GIP(1-42) were associated with significant decreases in foam cell formation and downregulation of CD36 and acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT-1) in macrophages. GLP-1 and GIP receptors were both detected in Apoe (-/-) mouse macrophages. Ex vivo incubation of macrophages with GLP-1(7-36)amide or GIP(1-42) for 48 h significantly suppressed foam cell formation. This effect was wholly abolished in macrophages pretreated with exendin(9-39) or (Pro(3))GIP, or with an adenylate cyclase inhibitor, MDL12,330A, and was mimicked by incubation with an adenylate cyclase activator, forskolin. The inactive forms, GLP-1(9-36)amide and GIP(3-42), had no effects on atherosclerosis and macrophage foam cell formation.

CONCLUSIONS/INTERPRETATION

Our study is the first to demonstrate that active forms of GLP-1 and GIP exert anti-atherogenic effects by suppressing macrophage foam cell formation via their own receptors, followed by cAMP activation. Molecular mechanisms underlying these effects are associated with the downregulation of CD36 and ACAT-1 by incretins.

Cilostazol inhibits matrix invasion and modulates the gene expressions of MMP-9 and TIMP-1 in PMA-differentiated THP-1 cells

The invasion of monocytes into the subendothelium space plays an important role in the early stage of atherosclerosis. Cilostazol, a specific phosphodiesterase type III (PDE3) inhibitor, has been shown to exhibit anti-atherosclerotic effect. The present study aimed to investigate the modulating effects of cilostazol on monocyte invasion and the gene expressions of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in phorbol 12-myristate 13-acetate (PMA)-differentiated THP-1. We found that PMA significantly increased the invasive ability and the MMP-9 activity of THP-1 cells, as analyzed by matrix invasion assay and gelatin zymography, respectively. The increased expression of MMP-9 was demonstrated at both the RNA and protein levels by RT/real-time PCR and western blot analysis. These changes were markedly inhibited by cilostazol in a dose-dependent manner, which also could be observed when cAMP analog was used. On the contrary, the expression of TIMP-1, an inhibitor of MMP-9, was significantly upregulated by cilostazol dose dependently at both the RNA and protein levels. Reverse zymography further confirmed the increase of TIMP-1 activity after cilostazol treatment. The increase of TIMP-1 by cilostazol, however, was not cAMP-dependent. Cilostazol reduced the MMP-9 promoter activity and suppressed the nuclear translocation of NF-κB, indicating that the inhibitory effect of cilostazol is at the transcriptional level. In conclusion, the present study provides an additional mechanism underlying the anti-atherosclerotic effect of cilostazol by inhibiting the monocyte invasion and modulating the gene expressions of MMP-9 and TIMP-1 in monocytes upon differentiating to macrophages.

Cilostazol reduces MCP-1-induced chemotaxis and adhesion of THP-1 monocytes by inhibiting CCR2 gene expression

The chemotaxis and adhesion of monocytes to the injured endothelium in the early atherosclerosis is important. Cilostazol, a specific phosphodiesterase type III inhibitor, is known to exhibit anti-atherosclerotic effects mediated by different mechanisms. This study aimed to investigate the modulating effect of cilostazol on the MCP-1-induced chemotaxis and adhesion of monocytes. The gene expression of CCR2, the major receptor of MCP-1 in THP-1 monocytes, was also analyzed. The chemotaxis of monocytes toward MCP-1 was investigated using the transwell filter assay. Cilostazol dose-dependently inhibited the MCP-1-induced chemotaxis of monocytes which was shown to be cAMP-dependent. Using western blot analysis and flow cytometry method, we demonstrated the decrease of CCR2 protein at the cell membrane of monocytes by cilostazol treatment. Results from RT/real-time PCR confirmed the decrease of CCR2 mRNA expression by cilostazol which was also mediated by cAMP. Similar inhibition was also noted in human peripheral monocytes. The post-CCR2 signaling pathways including p44/42 and p38 MAPK were examined by western blot analysis. Result confirmed the inhibitory effect of cilostazol on the phosphorylation of p44/42 and p38 MAPK after MCP-1 stimulation. The activation of monocytes after MCP-1 treatment exhibited enhanced adhesion to vascular endothelial cells which was dose-dependently suppressed by cilostazol. Together, cilostazol was demonstrated, for the first time, to inhibit the CCR2 gene expression and MCP-1-induced chemotaxis and adhesion of monocytes which might therefore reduce the infiltration of monocytes during the early atherosclerosis. The present study provides an additional molecular mechanism underlying the anti-atherosclerotic effects of cilostazol.

Study design and rationale of "Synergistic effect of combination therapy with cilostazol and ProbUcol on plaque stabilization and lesion REgression (SECURE)" study: a double-blind randomised controlled multicenter clinical trial

Background

Probucol, a cholesterol-lowering agent that paradoxically also lowers high-density lipoprotein cholesterol has been shown to prevent progression of atherosclerosis. The antiplatelet agent cilostazol, which has diverse antiatherogenic properties, has also been shown to reduce restenosis in previous clinical trials. Recent experimental studies have suggested potential synergy between probucol and cilostazol in preventing atherosclerosis, possibly by suppressing inflammatory reactions and promoting cholesterol efflux.

Methods/design

The Synergistic Effect of combination therapy with Cilostazol and probUcol on plaque stabilization and lesion REgression (SECURE) study is designed as a double-blind, randomised, controlled, multicenter clinical trial to investigate the effect of cilostazol and probucol combination therapy on plaque volume and composition in comparison with cilostazol monotherapy using intravascular ultrasound and Virtual Histology. The primary end point is the change in the plaque volume of index intermediate lesions between baseline and 9-month follow-up. Secondary endpoints include change in plaque composition, neointimal growth after implantation of stents at percutaneous coronary intervention target lesions, and serum levels of lipid components and biomarkers related to atherosclerosis and inflammation. A total of 118 patients will be included in the study.

Discussion

The SECURE study will deliver important information on the effects of combination therapy on lipid composition and biomarkers related to atherosclerosis, thereby providing insight into the mechanisms underlying the prevention of atherosclerosis progression by cilostazol and probucol.

Trial registration number

ClinicalTrials (NCT): NCT01031667

Cilostazol enhances macrophage reverse cholesterol transport in vitro and in vivo

OBJECTIVE

Recent failure of an HDL-cholesterol raising strategy using a cholesteryl ester transfer protein inhibitor highlights the importance of the anti-atherogenic function rather than plasma concentration of HDL. Cilostazol, a selective inhibitor of phosphodiesterase 3, has been widely used in patients with atherosclerotic diseases and is known to increase HDL-cholesterol. However, it remains unclear whether cilostazol enhances anti-atherogenic properties by promoting reverse cholesterol transport (RCT), a major anti-atherogenic function of HDL.

METHODS AND RESULTS

We observed that treatment of THP-1 macrophages, human monocyte-derived macrophages, and RAW264.7 cells with cilostazol increased ABCA1 and ABCG1 expression in a concentration-dependent manner, translating into enhanced apoA-I- and HDL-mediated cholesterol efflux from the macrophages. However, other cyclic AMP (cAMP)-elevating agents did not increase ABCA1 gene expression in THP-1 macrophages. Cilostazol did not change intracellular cAMP levels in THP-1 macrophages and RAW264.7 cells, and a protein kinase A (PKA) inhibitor did not affect cilostazol-induced ABCA1 and ABCG1 expression. To further investigate RCT in vivo, (3)H-cholesterol-labeled and acetyl LDL-loaded RAW264.7 cells were intraperitoneally injected into mice and the appearance of the (3)H-tracer was monitored in plasma, liver, and feces. Supporting the in vitro data, cilostazol was found to significantly increase (3)H-tracer levels in both plasma and feces.

CONCLUSIONS

These findings indicate that cilostazol might provide anti-atherosclerotic effects by promoting RCT through increased ABCA1/G1 expression in macrophages.

Cilostazol protects mice against endotoxin shock and attenuates LPS-induced cytokine expression in RAW 264.7 macrophages via MAPK inhibition and NF-kappaB inactivation: not involved in cAMP mechanisms

Cilostazol, a phosphodiesterase 3 inhibitor, is a platelet aggregation inhibitor and vasodilator that is useful for treating intermittent claudication. Experimental studies have shown that cilostazol has potent anti-inflammatory effects. In the present study, we examined the effect of cilostazol on lipopolysaccharide (LPS)-induced inflammatory cytokines in macrophages and endotoxin shock in mice. Our results indicate that cilostazol inhibits LPS-stimulated up-regulation of pro-inflammatory cytokines in a concentration-dependent manner without appreciable cytotoxicity in RAW 264.7 cells. Cilostazol did not enhance intracellular cyclic AMP (cAMP) levels. To further elucidate the mechanism responsible for the inhibition of production of pro-inflammatory mediators by cilostazol, we examined the effect of cilostazol on LPS-stimulated nuclear factor-kappaB (NF-kappaB) activation and phosphorylation of mitogen-activated protein kinases (MAPK). Our results clearly indicated that cilostazol treatment reduced on of MAPK phosphorylation and NF-kappaB activity, and that the inhibitory effect of cilostazol is independent of the cAMP pathway. In an animal model, cilostazol protected c57BL/6 mice from LPS-induced endotoxin shock, possibly through inhibition of the production of pro-inflammatory cytokines. In conclusion, cilostazol inhibits LPS-stimulated production of pro-inflammatory cytokines and protects mice from endotoxin shock, suggesting that cilostazol may be a novel therapeutic agent for the prevention of various inflammatory diseases.

Cilostazol Attenuates 4-hydroxynonenal-enhanced CD36 Expression on Murine Macrophages via Inhibition of NADPH Oxidase-derived Reactive Oxygen Species Production

Although anti-atherogenic effects of cilostazol have been suggested, its effects on the expression of SR in macrophages are unclear. This study investigated the role of cilostazol on CD36 expression of murine macrophages enhanced by HNE, a byproduct of lipid peroxidation. The stimulation of macrophages with HNE led to an increased expression of CD36, which was significantly attenuated by NAC, an antioxidant. Moreover, the increased production of ROS by HNE was completely abolished by NADPH oxidase inhibitors, DPI and apocynin, as well as by the 5-LO inhibitor, MK886, but not by inhibitors for other oxidases. This suggested that NADPH-oxidase and 5-LO were major sources of ROS induced by HNE. In addition, HNE-enhanced expression of CD36 was reduced by these inhibitors, which indicated a role for NADPH oxidase and 5-LO on CD36 expression. In our present study, cilostazol was a significant inhibitor of ROS production, as well as CD36 expression induced by HNE. An increase in NADPH oxidase activity by HNE was significantly attenuated by cilostazol, however cilostazol had no effect on HNE-enhanced 5-LO activity. Together, these results suggest that cilostazol attenuates HNE-enhanced CD36 expression on murine macrophages thorough inhibition of NADPH oxidase-derived ROS generation.