Cilostazol inhibits monocytic cell adhesion to vascular endothelium via upregulation of cAMP

Transcriptomic analysis reveals Cilostazol's role in ameliorating cardiovascular disease: Inhibition of monocyte-to-macrophage differentiation and reduction of endothelial cell reactive oxygen species production

Background

Cardiovascular diseases (CVDs) are the leading global cause of death, with atherosclerosis as the primary cause. Chronic inflammation, endothelial dysfunction, and the role of molecules like nitric oxide and reactive oxygen species are crucial in this context. Our previous research indicated that cilostazol and ginkgo biloba extract could enhance the ability of endothelial cells to dissolve blood clots, but the effects of cilostazol on monocytes remain unexplored.

Method

This study utilized peripheral blood mononuclear cells from 10 healthy donors, treated ex vivo with cilostazol. RNA-sequencing, over-representation analysis, xCell stromal cell analysis, and Gene Set Enrichment Analysis were employed to investigate the gene expression changes and biological pathways affected by cilostazol treatment.

Results

The study identified specific gene sets and pathways that were enriched or reduced in response to cilostazol treatment, providing insights into its effects on monocytes and potential therapeutic applications in CVD. The analysis also revealed the potential impact of cilostazol on the stromal cell compartment, further broadening our understanding of its multifaceted role.

Conclusion

The findings offer a nuanced understanding of the advantages and mechanisms of cilostazol in CVD, uncovering novel therapeutic targets and strategies to enhance the clinical application of cilostazol and contributing to the broader implications of this therapy in cardiovascular health.

P-Selectin Glycoprotein Ligand-1 (PSGL-1) Expressing CD4 T Cells Contribute Plaque Instability in Acute Coronary Syndrome

BACKGROUND

Adhesion molecules have essential roles in the development of atherosclerosis. We investigated whether P-selectin glycoprotein ligand-1 (PSGL-1)-expressing CD4 T cells contribute to plaque instability in acute coronary syndrome (ACS).Methods and Results:We studied the adhesion molecules on CD4 T cells from consecutive patients with ACS treated with thrombus-aspirating device and compared them with healthy controls (n=48 each). Blood, thrombi, and plaque samples from the culprit coronary arteries were collected by thrombus aspiration performed during emergency coronary artery angiography. According to flow cytometry results, peripheral CD4 T cells from ACS patients strongly expressed PSGL-1 and integrin β2 (P<0.05 for both) more than those from controls; culprit coronary arteries contained an abundance of PSGL-1⁺(P<0.001) but not integrin β2⁺CD4 T cells. In addition, immunohistochemical analysis of the thrombus-aspirating device samples revealed numerous PSGL-1⁺CD4 T cells in plaques from the culprit lesions. Results from the selectin-binding assay demonstrated that activated PSGL-1⁺CD4 T cells from ACS patients bound to P- or E-selectin after triggering the T-cell receptor, and adhered to endothelial cells under laminar flow conditions (P<0.05 and P<0.05, respectively), inducing their apoptosis (P<0.01) via activated caspase-3, which correlated with PSGL-1 expression (R=0.788, P=0.021) and was suppressed by application of a PSGL-1-specific antibody (P<0.05).

CONCLUSIONS

PSGL-1 contributed to cytotoxic CD4 T cell homing to the culprit coronary artery and promoted plaque instability in ACS.

Divergent Regulation of Actin Dynamics and Megakaryoblastic Leukemia-1 and -2 (Mkl1/2) by cAMP in Endothelial and Smooth Muscle Cells

Proliferation and migration of vascular smooth muscle cells (VSMCs) or endothelial cell (ECs) promote or inhibit, respectively, restenosis after angioplasty, vein graft intimal thickening and atherogenesis. Here we investigated the effects of cAMP-induced cytoskeletal remodelling on the serum response factor (SRF) co-factors Megakaryoblastic Leukemia-1 and -2 (MKL1 and MKL2) and their role in controlling VSMC and EC proliferation and migration. Elevation of cAMP using forskolin, dibutyryl-cAMP (db-cAMP), BAY60-6583 or Cicaprost induced rapid cytoskeleton remodelling and inhibited proliferation and migration in VSMCs but not EC. Furthermore, elevated cAMP inhibited mitogen-induced nuclear-translocation of MKL1 and MKL2 in VSMCs but not ECs. Forskolin also significantly inhibited serum response factor (SRF)-dependent reporter gene (SRE-LUC) activity and mRNA expression of pro-proliferative and pro-migratory MKL1/2 target genes in VSMCs but not in ECs. In ECs, MKL1 was constitutively nuclear and MKL2 cytoplasmic, irrespective of mitogens or cAMP. Pharmacological or siRNA inhibition of MKL1 significantly inhibited the proliferation and migration of VSMC and EC. Our new data identifies and important contribution of MKL1/2 to explaining the strikingly different response of VSMCs and ECs to cAMP elevation. Elucidation of these pathways promises to identify targets for specific inhibition of VSMC migration and proliferation.

Comprehensive analysis of chemokine-induced cAMP-inhibitory responses using a real-time luminescent biosensor

Chemokine receptors are members of the G-protein-coupled receptor (GPCR) family coupled to members of the Gi class, whose primary function is to inhibit the cellular adenylate cyclase. We used a cAMP-related and PKA-based luminescent biosensor (GloSensor™ F-22) to monitor the real-time downstream response of chemokine receptors, especially CX3CR1 and CXCR4, after activation with their cognate ligands CX3CL1 and CXCL12. We found that the amplitudes and kinetic profiles of the chemokine responses were conserved in various cell types and were independent of the nature and concentration of the molecules used for cAMP prestimulation, including either the adenylate cyclase activator forskolin or ligands mediating Gs-mediated responses like prostaglandin E2 or beta-adrenergic agonist. We conclude that the cAMP chemokine response is robustly conserved in various inflammatory conditions. Moreover, the cAMP-related luminescent biosensor appears as a valuable tool to analyze the details of Gi-mediated cAMP-inhibitory cellular responses, even in native conditions and could help to decipher their precise role in cell function.

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.

PSGL-1-expressing CD4 T cells induce endothelial cell apoptosis in perimenopausal women

AIM

Menopause and subsequent estrogen deficiency correlate with the development of atherosclerosis and cardiovascular diseases in women. However, the relationship between estrogen deficiency and development of atherosclerosis with inflammatory infiltrates is not fully understood. We sought to determine whether perimenopausal women (PMW) exhibited T cell dysfunction related to the expression of adhesion molecules and accelerated endothelial cell (EC) apoptosis.

METHODS

Fresh CD4 T cells were isolated from 48 PMW and 54 healthy control women with regular menstrual cycles (CW), and investigated cytotoxicity to ECs by apoptosis assay. The adhesion molecules on CD4 T cells were examined by flow cytometry. CD4 T cell rolling and adhesion on ECs were analyzed by adhesion assay under laminar flow.

RESULTS

CD4 T cells from PMW with low estradiol levels induced significant EC apoptosis (P = 0.0152). Furthermore, cytotoxic CD4 T cells from PMW strongly expressed P-selectin glycoprotein ligand-1 (PSGL-1) and integrin β2 (P < 0.0001 and P = 0.0285, respectively) but not L-selectin or integrin αM when compared to CD4 T cells from CW. Estradiol levels negatively correlated with only PSGL-1 expression (R = -0.781, P = 0.0002), and estradiol treatments inhibited both PSGL-1 expression (P = 0.0133) and T cell-induced EC apoptosis (P = 0.018). An estrogen receptor antagonist inhibited these effects of estradiol (P = 0.0355 and P = 0.0097, respectively). Moreover, PSGL-1 expression correlated with T cell adhesion to ECs under laminar flow conditions (R = 0.636, P = 0.0355) and with EC apoptosis (R = 0.614, P = 0.0196). PSGL-1 specific antibodies effectively suppressed T cell adhesion (P = 0.0057) and EC apoptosis (P = 0.001) indicating that CD4 T cell-mediated EC apoptosis depended on PSGL-1 adhesion in PMW.

CONCLUSIONS

PSGL-1-expressing cytotoxic CD4 T cells are abundant in PMW with low estradiol levels may contribute to T cell-mediated atherosclerotic development.

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.

Andrographolide inhibits ICAM-1 expression and NF-κB activation in TNF-α-treated EA.hy926 cells

Several lines of evidence indicate that inflammation and endothelial cell dysfunction are important initiating events in atherosclerosis. Tumor necrosis factor-α (TNF-α), a pro-inflammatory cytokine, induces the expression of cell adhesion molecules and results in monocyte adherence and atheromatous plaque formation. Andrographolide (AP) is a major bioactive diterpene lactone in Andrographis paniculata that has anti-inflammatory activity. A previous study demonstrated the role of heme oxygenase 1 (HO-1) in the inhibition of TNF-α-induced ICAM-1 expression by AP. The present study investigated the effect of AP on the IKK/NF-κB signaling pathway, which mediates TNF-α-induced ICAM-1 expression in EA.hy926 cells. Similar to the previous study, AP inhibited TNF-α-induced ICAM-1 mRNA and protein levels, its expression on the cell surface, and subsequent adhesion of HL-60 cells to EA.hy926 cells. AP inhibited TNF-α-induced κB inhibitor (IκB) kinase (IKK) and IκBα activation, p65 nuclear translocation, NF-κB and DNA binding activity, and promoter activity of ICAM-1. Although AP increased the intracellular cAMP concentration and induced the phosphorylation of cAMP response element-binding protein (CREB), knocking down CREB protein expression by transfecting the cells with CREB-specific small interfering RNA did not relieve the inhibition of ICAM-1 expression by AP. Taken together, these results suggest that AP down-regulates TNF-α-induced ICAM-1 expression at least in part via attenuation of activation of NF-κB in EA.hy926 cells rather than through activation of CREB. The results suggest that AP may have potential as a cardiovascular-protective agent.

Cilostazol inhibits cytokine-induced tetrahydrobiopterin biosynthesis in human umbilical vein endothelial cells

AIMS

Cilostazol, a type III phosphodiesterase inhibitor, is utilized for the treatment of intermittent claudication and is considered to have the beneficial effects against the atherogenic process. In the present study, we examined the effects of cilostazol on BH(4) biosynthesis in HUVEC treated with a mixture of the pro-inflammatory cytokines IFN-γ and TNF-α.

METHODS

Isolated HUVECs were grown to confluence and treated with IFN-γ (300 units/mL) and TNF-α (300 units/mL) for 16 h in order to stimulate BH(4) biosynthesis. The BH(4) levels were measured by HPLC. The mRNA expression of GTP cyclohydrolase I (GTPCH), the rate-limiting enzyme of BH(4) biosynthesis, and GTPCH feedback regulatory protein (GFRP) were quantified by real-time PCR. The GTPCH protein expression was assessed by western blot analysis.

RESULTS

Cilostazol significantly reduced the BH(4) levels in cytokine-stimulated HUVEC. Cilostazol produced a concomitant increase in the cAMP levels in HUVEC. Cilostazol decreased the GTPCH activity as well as the expression of GTPCH mRNA and protein. 8-bromo-cAMP (8Br-cAMP), a cell-permeable cAMP analogue, did not reproduce the effects of cilostazol. Cilostazol did not affect the cytokine-induced inhibition of GFRP mRNA expression.

CONCLUSIONS

We conclude that cilostazol inhibited cytokine-stimulated BH(4) biosynthesis via a cAMP-independent mechanism in HUVEC. Our data indicate that cilostazol reduced GTPCH activity and did so by suppressing the GTPCH protein levels.

Phosphodiesterases as targets for intermittent claudication

Intermittent claudication (IC) is one of the most frequent forms of lower extremity peripheral arterial disease (PAD) and is most commonly caused by arterial atherosclerosis. Its clinical manifestation includes fatigue, discomfort, or pain occurring in limb muscles due to exercise-induced ischemia, thus limiting the ability of IC patients to walk and exercise. In addition to lifestyle changes (diet, exercise, and smoking cessation), pharmacological treatments are needed. Pathologically, atherosclerotic lesions cause a mismatch in oxygen supply and metabolic demand in the leg muscles during walking/exercise. This subjects the muscles to repeated ischemia and reperfusion injury that can alter structure and oxidative metabolism, resulting in insufficient utilization of oxygen supply. Despite extensive research efforts, cilostazol and pentoxifylline are the only drugs indicated for relieving the symptoms of IC, with cilostazol demonstrating significant improvement in walking distance and quality of life in these patients. Originally developed as a PDE3 inhibitor, cilostazol was later found to have several other pharmacological actions, and its success has been attributed to its multifactorial actions on platelets, endothelium, smooth muscle, and lipid profiles. Using cilostazol as an example, we discuss the rationales and pitfalls of targeting PDEs in IC, and potential strategies for the development of new and more effective pharmacological treatments.

Inhibitory effects of cilostazol on proliferation of vascular smooth muscle cells (VSMCs) through suppression of the ERK1/2 pathway

AIM

The abnormal proliferation of vascular smooth muscle cells (VSMCs) in arterial walls is an important pathogenic factor of vascular disorders such as atherosclerosis and restenosis after angioplasty. During atherogenesis or in response to vessel injury, VSMC proliferation is induced by a number of peptide growth factors released from platelets and VSMCs. Cilostazol is a phosphodiesterase (PDE) 3 inhibitor that increases intracellular cAMP levels and decreases intracellular Ca(2+) levels, inhibiting platelet aggregation and inducing vasodilatation. Cilostazol is also known to have an inhibitory effect on the proliferation of VSMCs, but the anti-proliferative mechanism of cilostazol in VSMCs has not yet been established. In the present study, we investigated whether the anti-proliferative mechanism of cilostazol is associated with the suppression of extracellular signal-regulated kinases (ERK) and phosphatidylinositol 3 kinase (PI3K) signaling pathways.

METHODS

To confirm the anti-proliferative effects of cilostazol on VSMCs, VSMCs were induced to proliferate by serum-induced mitogenesis and then were treated with cilostazol for 24 h. And, to investigate whether the anti-proliferative mechanism of cilostazol in VSMCs involves the suppression of the ERK and PI3K pathways, expression of the phosphorylated forms of ERK1/2, Raf, Akt, and glycogen synthase kinase (GSK)-3 were evaluated by western blot.

RESULTS

Cilostazol inhibited VSMC proliferation in a dose-dependent manner. Phosphorylated ERK1/2 and Raf were significantly reduced in a dose-dependent manner, whereas phosphorylated Akt and GSK-3 were not changed.

CONCLUSION

These results suggest that suppression of the ERK pathway but not the PI3K pathway is an important mechanism in the anti-proliferative effect of cilostazol on VSMCs.

The integrin co-activator Kindlin-3 is expressed and functional in a non-hematopoietic cell, the endothelial cell

Integrin activation is crucial for numerous cellular responses, including cell adhesion, migration, and survival. Recent studies in mice have specifically emphasized the vital role of kindlin-3 in integrin activation. Kindlin-3 deficiency in humans also has now been documented and includes symptoms of bleeding, frequent infections, and osteopetrosis, which are consequences of an inability to activate beta1, beta2, and beta3 integrins. To date, kindlin-3 was thought to be restricted to hematopoietic cells. In this article, we demonstrate that kindlin-3 is present in human endothelial cells derived from various anatomical origins. The mRNA and protein for KINDLIN-3 was detected in endothelial cells by reverse transcription-PCR and Western blots. When subjected to sequencing by mass spectrometry, the protein was identified as authentic kindlin-3 and unequivocally distinguished from KINDLIN-1 and KINDLIN-2 or any other known protein. By quantitative real time PCR, the level of kindlin-3 in endothelial cells was 20-50% of that of kindlin-2. Using knockdown approaches, we show that kindlin-3 plays a role in integrin-mediated adhesion of endothelial cells. This function depends upon the integrin and substrate and is distinct from that of kindlin-2. Formation of tube-like structures in Matrigel also was impaired by kindlin-3 knockdown. Mechanistically, the distinct functions of the kindlins can be traced to differences in their subcellular localization in integrin-containing adhesion structures. Thus, the prevailing view that individual kindlins exert their functions in a cell type-specific manner must now be modified to consider distinct functions of the different family members within the same cell type.

Casein-derived tripeptide, Val-Pro-Pro (VPP), modulates monocyte adhesion to vascular endothelium

AIM

A food-derived bioactive tripeptide, Val-Pro-Pro (VPP), has been shown to possess angiotensin I-converting enzyme (ACE) inhibitory activity and foods containing such peptides exhibit an anti-hypertensive effect in clinical settings.

METHODS

The present study focused on the effect of VPP on monocyte adhesion to endothelium under flow conditions using phorbol 12-myristate 13-acetate (PMA)-stimulated monocytic THP-1 cells.

RESULTS

Pre-incubation of THP-1 cells with VPP (1 mM, 24 hours) significantly decreased the PMA-induced adhesion of THP-1 cells (p<0.05) to human umbilical vein endothelial cells (HUVECs). PMA-induced up-regulation of beta1 and beta2 integrin activation in THP-1 cells was downregulated by VPP, which significantly suppressed only the PMA-induced phosphorylation of JNK (p<0.05) in THP-1 cells. In addition, preincubation of THP-1 with SP600125, a specific inhibitor of JNK, resulted in significant reduction of the PMA-induced adhesion of THP-1. Interestingly, another tripeptide with comparable ACE inhibitory activity, Leu-Gly-Pro (LGP), failed to reduce the PMA-induced adhesion of THP-1, suggesting a distinct anti-inflammatory effect of VPP on THP-1 adhesion.

CONCLUSION

These observations suggest that VPP moderates monocyte adhesion to inflamed endothelia via attenuation of the JNK pathway in monocytes, which might contribute to the primary prevention of atherosclerosis.

Polymorphisms of fractalkine receptor CX3CR1 gene in patients with symptomatic and asymptomatic carotid artery stenosis

AIM

The chemokine fractalikine is expressed in vascular endothelium, exerting a pro-atherogenic effect. Two single-nucleotide polymorphisms of the CX3CR1 gene (T280M and V249I) affect frac-talkine receptor expression and function. We aimed to assess the prevalence of CX3CR1 polymor-phisms and the association with ischemic cerebrovascular attacks in a cohort of carotid atheromatous disease patients and age-matched controls.

METHODS

Using PCR-RFLP, we analyzed allelotypes for T280M and V249I in 150 patients with and 151 controls without carotid atherosclerosis assessed using carotid duplex ultrasound; the subjects were patients admitted for any reason to a tertiary hospital. Genotype data were compared with modifiable risk factors for cerebrovascular disease and the reason for admission, using ischemic stroke as an endpoint. Stroke types associated with carotid atherosclerosis were analysed separately.

RESULTS

The M280 allelic frequency was lower among carotid atherosclerosis patients than controls (0.15 versus 0.23, adjusted OR 0.47, 95% CI 0.30-0.74). Absence of M280 allele was an indepen-dent factor associated with carotid atherosclerosis (OR 3.70, 95% CI 1.92-7.14), stronger than hypertension, dyslipidemia, diabetes and cigarette smoking. The I249 allele was also under-repre-sented in carotid atherosclerosis; this was not statistically significant. T280M and V249I genotypes were not associated with admission due to ischemic stroke of the large vessel subtype (TOAST classi-fication, 73 episodes), whereas carotid atherosclerosis, previous ischemic event, age, hypertension, diabetes, hyperlipidemia and cigarette smoking were all independently associated.

CONCLUSIONS

The M280 fractalkine receptor gene allele is associated with a lower risk of carotid ath-eromatous disease, independent from the modifiable cerebrovascular risk factors.