Paclitaxel Enhances Thrombin-Induced Endothelial Tissue Factor Expression via c-Jun Terminal NH 2 Kinase Activation

A Bayesian network meta-analysis for acute thrombosis after lower extremity artery endovascular treatment

BACKGROUND

Various endovascular treatment devices have been widely used in the lower extremity arterial disease (LEAD). Their patency efficiency for target lesions has been well studied and reported. Comparison of the risk of acute thrombosis events between the different endovascular treatment devices is unclear.

AIMS

To rank the risk of acute thrombosis events when bare metal stents (BMSs), covered stents (CSs), drug-eluting stents (DESs), drug-coated balloons (DCBs), and conventional percutaneous transluminal balloon angioplasty (PTA) are used to treat LEAD through Bayesian network meta-analysis.

METHODS

We performed a network meta-analysis of randomized controlled trials comparing the risk of 1-year postoperative acute thrombosis between BMSs, CSs, DESs, DCBs, and PTA for treating LEAD. Bayesian random models were used for pooled endovascular treatment modality comparisons. We ranked these treatment modalities via the Bayesian method according to their surface under the cumulative ranking curve (SUCRA) and estimated probabilities.

RESULTS

Nineteen studies (38 study arms; 2758 patients) were included. The Bayesian network ranking of treatments indicated that DCB had the lowest risk of acute thrombosis, PTA had the second-lowest risk of thrombosis, and CS, BMS, and DES had the highest risk of thrombosis. Regarding the treatment efficacy, the OR values of the loss of primary patency were significantly lower for DCB (OR = 0.44, 95% CI: 0.30-0.62), DES (OR = 0.36, 95% CI: 0.14-0.94), and CS (OR = 0.31, 95% CI: 0.18,0.56) than for PTA. When BMS was used as a reference, only the OR for CS was significantly lower (OR = 0.41, 95% CI = 0.21-0.82). Correspondingly, the Bayesian ranking of treatments from better to worse target lesion primary patency was CS, DES, DCB, BMS, and PTA.

CONCLUSION

With the available research evidence and according to the network analysis ranking, DES appears to have the highest risk of acute thrombosis and DCB appears to have the lowest risk.

Effect of Paclitaxel on the Hemostatic Potential of the Blood in the Experiment

The duration and severity of prothrombotic effects of the maximum tolerated dose of paclitaxel (40 mg/kg) were evaluated in intact outbred mice. Hemostasis was assessed before and on days 1, 2, 5, 7, 10, 15, 20, and 30 after a single injection of paclitaxel using standard coagulation tests (activated partial thromboplastin time, prothrombin time, fibrinogen concentration, and antithrombin III) and a "global" method, low-frequency piezothromboelastography. A pronounced prothrombotic effect of paclitaxel was revealed starting from the first day postinjection that consisted in intensification of fibrinogenesis up to the 7th day in parallel with activation of the anticoagulant mechanisms. On days 7-30 after paclitaxel administration, decompensation of its anticoagulant activity due to paclitaxel-induced damage to the endothelium was observed with the formation of a procoagulant status of the hemostatic potential of the blood. A single administration of the maximum tolerated dose of paclitaxel forms a powerful thrombogenic stimulus during the first week and provides a long-term/trace procoagulant shift in the hemostasis system (days 10-30).

Interleukin-1β Induces Tissue Factor Expression in A549 Cells via EGFR-Dependent and -Independent Mechanisms

Tissue factor (TF) plays an important role in the progression and angiogenesis of tumor cells. The present study investigated the mechanism of interleukin-1β (IL-1β)-induced TF expression in A549 lung cancer cells. Based on mRNA and protein analyses, including appropriate inhibitor experiments, IL-1β was shown to induce TF expression in a time-dependent manner, mediated by IL-1 receptor-dependent phosphorylation of the mitogen-activated protein kinases (MAPK) p38, p42/44 and c-jun N-terminal kinase (JNK), as well as the Src kinase and the epidermal growth factor receptor (EGFR). Thereby, inhibition of EGFR transactivation by the Src inhibitor PP1 or direct EGFR inhibition by the EGFR tyrosine kinase inhibitor (TKI) erlotinib led to a reduction of IL-1β-induced TF expression and to a suppression of p42/44 MAPK and EGFR activation, while IL-1β-induced p38 MAPK and JNK activation remained unchanged. A knockdown of EGFR by siRNA was associated with decreased IL-1β-mediated p42/44 MAPK activation, which was no longer inhibitable by erlotinib. Concentration-dependent inhibition of IL-1β-induced TF expression was also observed in the presence of gefitinib and afatinib, two other EGFR TKIs. In summary, our results suggest that IL-1β leads to increased TF formation in lung cancer cells via both Src/EGFR/p42/44 MAPK-dependent and EGFR-independent signaling pathways, with the latter mediated via p38 MAPK and JNK.

Coronary Artery Aneurysm after Second-Generation Drug-Eluting Stent Implantation

PURPOSE

We evaluated the incidence, predictors, and prognosis of coronary artery aneurysm (CAA) after second-generation drug-eluting stent (DES) implantation.

MATERIALS AND METHODS

A total of 976 consecutive patients (1245 lesions) who underwent follow-up angiography after second-generation DES implantation were analyzed. Incidence and predictors of CAA were assessed, and clinical prognosis was compared with 34 cases of CAA after first-generation DES implantation using previous CAA registry data.

RESULTS

All 10 cases of CAA (0.80% per lesion) in 10 patients (1.02% per patient) were detected at follow up. Compared to lesions without CAA, those with CAA had greater involvement of the proximal segment (90% vs. 51%, p=0.014), a higher proportion of pre-intervention, a Thrombolysis in Myocardial Infarction score of 0 or 1 flow (80% vs. 16%, p<0.001), more chronic total occlusions (40% vs. 10%, p<0.001), and longer implanted stents (41.9±23.2 mm vs. 28.8±14.8 mm, p=0.006). As for CAA morphology, instances of CAA after second-generation DES were predominantly the single fusiform type (90%), whereas instances of CAA after first-generation DES were multiple saccular (47%) and single saccular (35%) types (p<0.001). Myocardial infarction with stent thrombosis occurred in 5 patients with CAA after first-generation DES (15%), and no adverse events were observed in patients with CAA after second-generation DES over a median follow-up duration of 4.3 years (p=0.047, log-rank).

CONCLUSION

Although CAAs after second-generation DES implantation were detected at a similar incidence to that for CAAs after first-generation DES implantation, second-generation DES-related CAAs had different morphologies and more benign clinical outcomes versus first-generation DES-related CAAs.

Inhibition of interleukin-1β-induced endothelial tissue factor expression by the synthetic cannabinoid WIN 55,212-2

The role of cannabinoids in thrombosis remains controversial. In view of the primary importance of tissue factor (TF) in blood coagulation and its involvement in the pathology of several cardiovascular, inflammatory and neoplastic diseases, a regulation of this initial procoagulant signal seems to be of particular interest. Using human umbilical vein endothelial cells (HUVEC) the present study investigated the impact of the synthetic cannabinoid WIN 55,212-2 on interleukin (IL)-1β-induced TF expression and activity. WIN 55,212-2 caused a time- and concentration-dependent suppression of IL-1β-induced TF protein accompanied by decreases in TF mRNA and activity. Inhibition of TF protein expression by WIN 55,212-2 was mimicked by its cannabinoid receptor-inactive enantiomer WIN 55,212-3 but not by structurally unrelated phyto-, endo- and synthetic cannabinoids. In addition, the inhibitory effect of WIN 55,212-2 was not reversed by antagonists to cannabinoid receptors (CB₁, CB₂) or transient receptor potential vanilloid 1. Mechanistic approaches revealed WIN 55,212-2 to suppress IL-1β-induced TF expression via inhibition of ceramide formation and via decreased phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinases. Further inhibitor experiments demonstrated neutral sphingomyelinase (nSMase) to confer ceramide generation upon IL-1β treatment with the parallel IL-1β-mediated activation of MAPKs occurring via an nSMase-independent pathway. Finally, a receptor-independent inhibition of IL-1β-induced TF protein by WIN 55,212-2 was confirmed in human blood monocytes. Collectively, this data provide a hitherto unknown receptor-independent anticoagulatory action of the cannabinoid WIN 55,212-2.

Caffeine induces endothelial tissue factor expression via phosphatidylinositol 3-kinase inhibition

Tissue factor (TF) is the key activator of coagulation and is involved in acute coronary syndromes. Caffeine is often reported to increase cardiovascular risk; however, its effect on cardiovascular morbidity and mortality is controversial. Hence, this study was designed to investigate the impact of caffeine on endothelial TF expression in vitro. Caffeine concentration-dependently enhanced TF protein expression and surface activity in human endothelial cells stimulated by tumour necrosis factor (TNF)-α or thrombin. Caffeine inhibited phosphatidylinositol 3-kinase (PI3K) activity and this effect was comparable to that of the known PI3K inhibitor LY294002. Consistently, treatment of endothelial cells with LY294002 enhanced TNF-α induced TF expression to a similar extent as caffeine, and adenoviral expression of the active PI3K mutant (p110) reversed the effect of both caffeine and LY294002 on TF expression. Caffeine and LY294002 increased DNA binding capacity of the transcription factor nuclear factor κB, whereas the activation pattern of mitogen-activated protein kinases (MAPK) remained unaltered. Luciferase reporter assay revealed a caffeine dependent activation of the TF promoter, and RT-PCR revealed a dose dependent increase in TF mRNA levels when stimulated with caffeine in the presence of TNF-α. In conclusion, caffeine enhances TNF-α-induced endothelial TF protein expression as well as surface activity by inhibition of PI3K signalling. Since the caffeine concentrations applied in the present study are within the plasma range measured in humans, our findings indicate that caffeine enhances the prothrombotic potential of endothelial cells and underscore the importance of PI3K in mediating these effects.

Coronary Artery Aneurysms: A Review of the Epidemiology, Pathophysiology, Diagnosis, and Treatment

Coronary artery aneurysms (CAAs) are uncommon and describe a localized dilatation of a coronary artery segment more than 1.5-fold compared with adjacent normal segments. The incidence of CAAs varies from 0.3 to 5.3%. Ever since the dawn of the interventional era, CAAs have been increasingly diagnosed on coronary angiography. Causative factors include atherosclerosis, Takayasu arteritis, congenital disorders, Kawasaki disease (KD), and percutaneous coronary intervention. The natural history of CAAs remains unclear; however, several recent studies have postulated the underlying molecular mechanisms of CAAs, and genome-wide association studies have revealed several genetic predispositions to CAA. Controversies persist regarding the management of CAAs, and emerging findings support the importance of an early diagnosis in patients predisposed to CAAs, such as in children with KD. This review aims to summarize the present knowledge of CAAs and collate the recent advances regarding the epidemiology, etiology, pathophysiology, diagnosis, and treatment of this disease.

The MAP kinase JNK2 mediates cigarette smoke-induced arterial thrombosis

Despite public awareness of its deleterious effects, smoking remains a major cause of death. Indeed, it is a risk factor for atherothrombotic complications and in line with this, the introduction of smoking ban in public areas reduced smoking-associated cardiovascular complications. Nonetheless, smoking remains a major concern, and molecular mechanisms by which it causes cardiovascular disease are not known. Peripheral blood monocytes from healthy smokers displayed increased JNK2 and tissue factor (TF) gene expression compared to non-smokers (n=15, p<0.05). Similarly, human aortic endothelial cells exposed to cigarette smoke total particulate matter (CS-TPM) revealed increased TF expression mediated by JNK2 (n=4; p<0.05). Wild-type and JNK2^-/- mice were exposed to cigarette smoke for two weeks after which arterial thrombosis was investigated. Wild-type mice exposed to smoke displayed reduced time to thrombotic arterial occlusion (n=8; p<0.05) and increased tissue factor activity (n=7; p<0.05) as compared to wild-type controls (n=6), while JNK2^-/-mice exposed to smoke maintained an unaltered thrombotic potential (n=8; p=NS) and tissue factor activity (n=8) comparable to that of JNK2^-/- and wild-type controls (n=6; p=NS). Smoking caused an increased production of reactive oxygen species (ROS) in wild-type but not in JNK2^-/- mice (n=7; p<0.05 for wild-type mice and n=5-6; p=NS for JNK2^-/- mice). In conclusion, the MAP kinase JNK2 mediates cigarette smoke-induced TF activation, arterial thrombosis and ROS production. These results underscore a major role of JNK2 in smoke-mediated thrombus formation and may offer an attractive target to prevent smoke-related thrombosis in those subjects which do not manage quitting.

A case of subacute stent thrombosis after drug-coated balloon coronary angioplasty for in-stent restenosis under single anti-platelet therapy

This report describes a case of subacute stent thrombosis (SAT) after drug-coated balloon (DCB). A 79-year-old male was investigated for stable angina. An in-stent restenosis (ISR) lesion was detected by coronary angiography. A skin reaction related to the anti-platelet agent thienopyridine was also observed at this time. Therefore, DCB was used to treat the ISR lesion under single anti-platelet therapy (aspirin). However, 3 days after percutaneous coronary intervention, SAT occurred. OCT did not reveal the underlying cause of SAT. Further data are needed to clarify the optimal duration of dual anti-platelet therapy after DCB.

Effects of Paclitaxel on the Ability of Aspirin and Clopidogrel to Inhibit Platelet Aggregation

The aim of this study was to investigate the effects of different paclitaxel concentrations on platelet aggregation induced by adenosine diphosphate (ADP). This experiment involved platelet suspensions that were obtained from fasting morning blood specimens from healthy adult male volunteers aged 22 to 28 years. The effect of paclitaxel on platelet aggregation induced by ADP and the inhibition rate of platelet aggregation were calculated in 6 groups with varying concentrations of paclitaxel, respectively. The optimal incubation time and concentration of ADP were 10 minutes and 10 μmol/mL, respectively. When the concentration of paclitaxel increased, platelet aggregation induced by ADP increased accordingly. When the concentration of paclitaxel exceeded 0.1 ng/mL, the ability of ADP to induce platelet aggregation increased significantly with increasing paclitaxel concentrations. In all the 3 experimental groups, that is A, C, and AC groups, the ability to inhibit platelet aggregation was weakened as paclitaxel concentration increased. Paclitaxel can enhance platelet aggregation induced by ADP, and this ability was observed to increase as paclitaxel concentration increased. In conclusion, paclitaxel can reduce the ability of aspirin, clopidogrel, and aspirin combined with clopidogrel to inhibit platelet aggregation. Furthermore, the ability to inhibit platelet aggregation was weakened as paclitaxel concentration increased in all 3 experimental groups.

Epigenetic regulation of tissue factor inducibility in endothelial cell senescence

Cellular senescence, a programmed state induced by multiple deleterious triggers, is characterised by permanent cell-cycle exit and altered gene expression and cell morphology. In humans it is considered a tumor suppressor mechanism, mediating removal of damaged or mutated cells from the cell-cycle pool, and may also contribute to the ageing process. In this study, we show that senescent human umbilical vein endothelial cells lose their ability to induce tissue factor (TF), a transmembrane protein with important roles in hemostasis and cancer progression, in response to thrombin or - independently of cell-surface receptors - phorbol-12-myristate-13-acetate. This phenomenon could not be explained by senescence-related alterations in the downstream signal transduction cascade or by accelerated TF mRNA degradation. Rather, using chromatin immuno-precipitation we could show that loss of TF gene inducibility during senescence occurs following chromatin remodelling of the TF promoter resulting from hypo-acetylation of histone H3. These findings were reversible after transduction of presenescent cultures with telomerase reverse transcriptase, enabling late-passage cultures to escape senescence. These results extend the involvement of heterochromatic gene silencing in senescence beyond cell cycle-related genes and suggest a novel anti-cancer mechanism of senescence through inhibition of TF inducibility.

c-Jun N-Terminal Kinases Mediate a Wide Range of Targets in the Metastatic Cascade

Disseminated cancer cells rely on intricate interactions among diverse cell types in the tumor-associated stroma, vasculature, and immune system for survival and growth. Ubiquitous expression of c-Jun N-terminal kinase (jnk) genes in various cell types permits their control of metastasis. In early stages of metastasis, JNKs affect tumor-associated inflammation and angiogenesis as well as tumor cell migration and intravasation. Within the tumor stroma, JNKs are essential for the release of growth factors that promote epithelial-to-mesenchymal transition (EMT) in tumor cells. JNK3, the least ubiquitous isoform, facilitates angiogenesis by increasing endothelial cell migration. Importantly, JNK expression in tumor cells integrates stromal signals to promote tumor cell invasion. However, JNK isoforms differentially regulate migration toward the endothelial barrier. Once tumor cells enter the bloodstream, JNKs increase circulating tumor cell (CTC) survival and homing to tissues. By promoting fibrosis, JNKs improve CTC attachment to the endothelium. Once anchored, JNKs stimulate EMT to facilitate tumor cell extravasation and enhance the secretion of endothelial barrier disrupters. Tumor cells attract barrier-disrupting macrophages by JNK-dependent transcription of macrophage chemoattractant molecules. In the secondary tissue, JNKs are instrumental in the premetastatic niche and stimulate tumor cell proliferation. JNK expression in cancer cells stimulates tissue-remodeling macrophages to improve tumor colonization. However, in T-cells, JNKs alter cytokine production that increases tumor surveillance and inhibits the recruitment of tissue-remodeling macrophages. Therapeutically targeting JNKs for metastatic disease is attractive considering their promotion of metastasis; however, specific JNK tools are needed to determine their definitive actions within the context of the entire metastatic cascade.

PI3K/p110α inhibition selectively interferes with arterial thrombosis and neointima formation, but not re-endothelialization: potential implications for drug-eluting stent design

BACKGROUND

Impaired re-endothelialization and stent thrombosis are a safety concern associated with drug-eluting stents (DES). PI3K/p110α controls cellular wound healing pathways, thereby representing an emerging drug target to modulate vascular homoeostasis after injury.

METHODS AND RESULTS

PI3K/p110α was inhibited by treatment with the small molecule inhibitor PIK75 or a specific siRNA. Arterial thrombosis, neointima formation, and re-endothelialization were studied in a murine carotid artery injury model. Proliferation and migration of human vascular smooth muscle cell (VSMC) and endothelial cell (EC) were assessed by cell number and Boyden chamber, respectively. Endothelial senescence was evaluated by the β-galactosidase assay, endothelial dysfunction by organ chambers for isometric tension. Arterial thrombus formation was delayed in mice treated with PIK75 when compared with controls. PIK75 impaired arterial expression and activity of tissue factor (TF) and plasminogen activator inhibitor-1 (PAI-1); in contrast, plasma clotting and platelet aggregation did not differ. In VSMC and EC, PIK75 inhibited expression and activity of TF and PAI-1. These effects occurred at the transcriptional level via the RhoA signalling cascade and the transcription factor NFkB. Furthermore, inhibition of PI3K/p110α with PIK75 or a specific siRNA selectively impaired proliferation and migration of VSMC while sparing EC completely. Treatment with PIK75 did not induce endothelial senescence nor inhibit endothelium-dependent relaxations. In line with this observation, treatment with PIK75 selectively inhibited neointima formation without affecting re-endothelialization following vascular injury.

CONCLUSION

Following vascular injury, PI3K/p110α inhibition selectively interferes with arterial thrombosis and neointima formation, but not re-endothelialization. Hence, PI3K/p110α represents an attractive new target in DES design.

Local insulin application on the carotid artery inhibits neointima formation

Anti-mitogenic agents currently used to prevent restenosis in drug-eluting stents delay re-endothelialization. Delayed re-endothelialization is now considered as the main cause of late stent thrombosis with drug-eluting stents, which emphasizes the need for new treatments. We have shown that systemic insulin treatment decreases neointimal growth and accelerates re-endothelialization after arterial injury in a rat model of restenosis. However, systemic insulin treatment cannot be given to non-diabetic individuals because of the risk of hypoglycemia. Thus, we investigated whether local insulin treatment is also effective in reducing neointimal growth after arterial injury. Rats were given local vehicle or local insulin delivered via Pluronic gel applied around the carotid artery immediately following balloon injury. Plasma glucose and systemic insulin levels were not affected by local insulin treatment. Insulin decreased intimal area at 28 days (P < 0.05) and also inhibited vascular smooth muscle cell migration by 60% at 4 days (P < 0.05). NPH (a longer-lasting insulin) also decreased neointimal area. These results indicate that local insulin treatment can lead to decreased restenosis, suggesting a protective vascular effect of insulin in vivo and that local insulin treatment, possibly via insulin-eluting stents, may be clinically relevant.

Contemporary analysis of incidence and outcomes of stent thrombosis presenting as ST elevation myocardial infarction in a primary percutaneous coronary intervention cohort

There are limited data about the effectiveness of primary percutaneous coronary intervention (PPCI) for stent thrombosis treatment. We aimed to evaluate the prevalence and outcomes of PPCI in patients with ST elevation acute myocardial infarction (STEMI) due to stent thrombosis, and comparing the outcomes with patients treated for de novo coronary thrombosis. This was an observational cohort study of 2,935 patients who underwent PPCI from 2003 to 2011 with follow-up for a median of 3.0 years (interquartile range 1.2 to 4.6). The primary end point was the first major adverse cardiac event (MACE) defined as death, nonfatal myocardial infarction, stroke, or target vessel revascularization. Stent thrombosis overall accounted for 6.6% (194 of 2,935) of all STEMIs with a proportion that increased over time (3.3% in 2004 to 9.4% in 2011). A total of 34.5% were early, 30.9% late stent thrombosis, and 34.5% were very late stent thrombosis. Indications for the original intervention were elective in 27.8%, after acute coronary syndrome (non-STEMI or unstable angina) in 21.1%, and after PPCI in 51.1%. Patients with stent thrombosis had higher rates of hypertension, hypercholesterolemia, diabetes, renal dysfunction, and previous myocardial infarction or coronary artery bypass surgery compared with patients with native artery occlusion. MACE rates were higher in patients with stent thrombosis compared with patients with native artery occlusions (40.9%, 95% confidence interval [CI] 31.1 to 50.6 vs 15.1%, 95% CI 12.5 to 18.3; p <0.0001). The poor outcome of stent thrombosis was particularly associated with early and late stent thromboses. Very late stent thrombosis appears to be a relatively less serious event, with similar outcomes to native vessel thromboses (MACE very late stent thrombosis 16.5%, 95% CI 8.2 to 28.6 vs native 15.1%, 95% CI 12.5 to 18.3, p = 0.245). In conclusion, stent thrombosis accounts for an increasing proportion of STEMI and is associated with worse outcomes compared with native artery occlusion.

Impact of stent mis-sizing and mis-positioning on coronary fluid wall shear and intramural stress

Stent deployments with geographical miss (GM) are associated with increased risk of target-vessel revascularization and periprocedural myocardial infarction. The aim of the current study was to investigate the underlying biomechanical mechanisms for adverse events with GM. The hypothesis is that stent deployment with GM [longitudinal GM, or LGM (i.e., stent not centered on the lesion); or radial GM, RGM (i.e., stent oversizing)] results in unfavorable fluid wall shear stress (WSS), WSS gradient (WSSG), oscillatory shear index (OSI), and intramural circumferential wall stress (CWS). Three-dimensional computational models of stents and plaque were created using a computer-assisted design package. The models were then solved with validated finite element and computational fluid dynamic packages. The dynamic process of large deformation stent deployment was modeled to expand the stent to the desired vessel size. Stent deployed with GM resulted in a 45% increase in vessel CWS compared with stents that were centered and fully covered the lesion. A 20% oversized stent resulted in 72% higher CWS than a correct sized stent. The linkages between the struts had much higher stress than the main struts (i.e., 180 MPa vs. 80 MPa). Additionally, LGM and RGM reduced endothelial WSS and increased WSSG and OSI. The simulations suggest that both LGM and RGM adversely reduce WSS but increase WSSG, OSI, and CWS. These findings highlight the potential mechanical mechanism of the higher adverse events and underscore the importance of stent positioning and sizing for improved clinical outcome.

Effect of quercetin-rich onion peel extracts on arterial thrombosis in rats

The aim of this study was to examine whether oral supplementation of quercetin-rich onion peel extract (OPE) influences blood coagulation and arterial thrombosis in Sprague-Dawley (SD) rats. 24 male rats, 5 weeks old, were divided into three groups with different diets (C: control, 2mg OPE: chow diet with 2mg OPE supplementation, 10mg OPE: chow diet with 10mg OPE supplementation) for 6 weeks. Blood coagulation parameters including prothrombin time (PT), activated partial thromboplastin time (aPTT) and platelet aggregation were examined. The OPE did not affect blood cholesterol levels but significantly decreased blood triglyceride and glucose levels. PT, aPTT and platelet aggregation were not significantly different among all tested groups. However, in vivo arterial thrombosis was significantly delayed in groups that were fed 2mg and 10mg OPE diets compared to the control group. In addition, the OPE greatly diminished thrombin-induced expression of tissue factor in human umbilical vein endothelial cells (HUVECs), a coagulation initiator. In addition, extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) signaling pathways activated by thrombin treatment were prevented by the OPE pre-treatment. These results indicate that OPE may have anti-thrombotic effects through restricting the induced expression of tissue factor via down-regulating mitogen-activated protein kinase (MAPK) activation upon coagulation stimulus, leading to the prolongation of time for arterial thrombosis.

Free fatty acids inhibit TM-EPCR expression through JNK pathway: an implication for the development of the prothrombotic state in metabolic syndrome

Metabolic syndrome is associated with significant hypercoagulable prothrombotic tendency; however, the mechanism for the prothrombotic state is not completely understood. We hypothesize that higher circulating plasma free fatty acids (FFAs) in metabolic syndrome inhibit the endothelial thrombomodulin (TM)-endothelial protein C receptor (EPCR) pathway, thereby promoting thrombus formation. Human umbilical vein endothelial cells were cultured in media supplemented with various doses of palmitic acid (PA), in the presence or absence of JNK inhibitor, and the expression of TM and EPCR was measured by western blot. The thrombotic state of high fat fed C57BL/6J mice was examined by tail bleeding time and deep venous thrombosis (DVT) model. As a result, PA inhibited the expression of TM and EPCR in endothelial cells, and this effect was blunted by inhibiting JNK signaling. High fat diet fed mice had higher level of circulating FFAs and exhibited prothrombotic state, evidenced by increased tail bleeding time and enlarged thrombotic size in DVT model, compared to the control diet fed mice. Hence, FFAs inhibit TM-EPCR-Protein C system in endothelial cells through activating JNK signaling, which may be a mechanism for the prothrombotic state in metabolic syndrome.

Endogenous cannabinoid receptor CB1 activation promotes vascular smooth-muscle cell proliferation and neointima formation

Percutaneous transluminal angioplasty is frequently used in patients with severe arterial narrowing due to atherosclerosis. However, it induces severe arterial injury and an inflammatory response leading to restenosis. Here, we studied a potential activation of the endocannabinoid system and the effect of FA amide hydrolase (FAAH) deficiency, the major enzyme responsible for endocannabinoid anandamide degradation, in arterial injury. We performed carotid balloon injury in atherosclerosis-prone apoE knockout (apoE(-/-)) and apoE(-/-)FAAH(-/-) mice. Anandamide levels were systemically elevated in apoE(-/-) mice after balloon injury. ApoE(-/-)FAAH(-/-) mice had significantly higher baseline anandamide levels and enhanced neointima formation compared with apoE(-/-) controls. The latter effect was inhibited by treatment with CB1 antagonist AM281. Similarly, apoE(-/-) mice treated with AM281 had reduced neointimal areas, reduced lesional vascular smooth-muscle cell (SMC) content, and proliferating cell counts. The lesional macrophage content was unchanged. In vitro proliferation rates were significantly reduced in CB1(-/-) SMCs or when treating apoE(-/-) or apoE(-/-)FAAH(-/-) SMCs with AM281. Macrophage in vitro adhesion and migration were marginally affected by CB1 deficiency. Reendothelialization was not inhibited by treatment with AM281. In conclusion, endogenous CB1 activation contributes to vascular SMC proliferation and neointima formation in response to arterial injury.

The effect of short-term intra-arterial delivery of paclitaxel on neointimal hyperplasia and the local thrombotic environment after angioplasty

PURPOSE

To evaluate the effects of short-term intra-arterial delivery of paclitaxel on neointimal hyperplasia and the local thrombotic environment after angioplasty.

METHODS

An experimental common carotid artery injury model was established in 60 rats, which were divided into experimental groups (40 rats) and controls (20 rats). Local intra-arterial administration of paclitaxel was applied at 2 doses (90 and 180 μg/30 μl), and the effects of short-term delivery of paclitaxel on neointimal hyperplasia and the expression of tissue factor (TF), plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (t-PA) were evaluated at days 15 and 30 by hematoxylin and eosin staining and immunohistochemistry.

RESULTS

At 15 and 30 days after injury, neointimal thickness and area, the ratio of intimal area to medial area and the stenotic rate were all significantly decreased in the group provided the high concentrations (180 μg/30 μl) of paclitaxel for 2 min or 10 min and in the group provided the low concentration (90 μg/30 μl) of paclitaxel for 10 min (p < 0.05). At 30 days after injury, there were no significant changes in TF expression among all experimental groups. PAI-1 expression increased in the neointima of the high concentration 10 min group (p < 0.05), while t-PA expression decreased in the neointima of the high concentration 2 min group (p < 0.05).

CONCLUSION

In the rat common carotid artery injury model, the short-term delivery of paclitaxel could effectively inhibit neointimal hyperplasia in the long term, with very little influence on the local expression of TF and PAI-1.

Impact of lesion length and vessel size on clinical outcomes after percutaneous coronary intervention with everolimus- versus paclitaxel-eluting stents pooled analysis from the SPIRIT (Clinical Evaluation of the XIENCE V Everolimus Eluting Coronary Stent System) and COMPARE (Second-generation everolimus-eluting and paclitaxel-eluting stents in real-life practice) Randomized Trials

OBJECTIVES

The aim of this study was to investigate the impact of reference vessel diameter (RVD) and lesion length (LL) on the relative safety and efficacy of everolimus-eluting stents (EES) and paclitaxel-eluting stents (PES).

BACKGROUND

Lesion length and RVD are well-known predictors of adverse events after percutaneous coronary intervention.

METHODS

Patient-level data were pooled from the randomized SPIRIT (Clinical Evaluation of the XIENCE V Everolimus Eluting Coronary Stent System) II, III, IV and COMPARE (Second-generation everolimus-eluting and paclitaxel-eluting stents in real-life practice) trials. Quantitative angiographic core laboratory data were available for 6,183 patients randomized to EES (n = 3,944) or PES (n = 2,239). Long lesions and small vessels were defined as LL >median (13.4 mm) and RVD ≤median (2.65 mm), respectively. Major adverse cardiac events (MACE) (consisting of cardiac death, myocardial infarction, or ischemia-driven target lesion revascularization) were assessed at 2 years, according to stent type in 3 groups: short lesions in large vessels (group A, n = 1,297); long lesions or small vessels but not both (group B, n = 2,981); and long lesions in small vessels (group C, n = 1,905).

RESULTS

The pooled 2-year MACE rates were 5.6%, 8.2%, and 10.4% in Groups A, B, and C, respectively (p < 0.0001). There was no significant interaction between lesion group and stent type (p = 0.64), indicating lower MACE with EES compared with PES regardless of LL and RVD. However, the absolute difference was largest in Groups B and C. In Group A, 2-year MACE rates were not significantly different between EES and PES (4.8% vs. 7.0%, respectively, p = 0.11). In contrast, EES was associated with lower 2-year rates of MACE in Group B (6.6% vs. 11.2%, p < 0.01) and in Group C (9.1% vs. 12.7%, p = 0.008) as well as lower rates of myocardial infarction, target lesion revascularization, and stent thrombosis. Multivariable analysis confirmed EES versus PES as an independent predictor of freedom from MACE in Groups B and C.

CONCLUSIONS

Patients with short lesions in large vessels have low rates of MACE at 2 years after treatment with either EES or PES. In higher-risk patients with long lesions and/or small vessels, EES results in significant improvements in both clinical safety and efficacy outcomes. (A Clinical Evaluation of the XIENCE V Everolimus Eluting Coronary Stent System in the Treatment of Patients With de Novo Native Coronary Artery Lesions; NCT00180310; SPIRIT III: A Clinical Evaluation of the Investigational Device XIENCE V Everolimus Eluting Coronary Stent System [EECSS] in the Treatment of Subjects With de Novo Native Coronary Artery Lesions; NCT00180479; SPIRIT IV Clinical Trial: Clinical Evaluation of the XIENCE V Everolimus Eluting Coronary Stent System in the Treatment of Subjects With de Novo Native Coronary Artery Lesions; NCT00307047; A Randomized Controlled Trial of Everolimus-eluting Stents and Paclitaxel-eluting Stents for Coronary Revascularization in Daily Practice: The COMPARE Trial; NCT01016041).

Peroxisome proliferator-activated receptor-gamma agonists suppress tissue factor overexpression in rat balloon injury model with paclitaxel infusion

The role and underlying mechanisms of rosiglitazone, a peroxisome proliferator-activated receptor-gamma (PPAR-γ) agonist, on myocardial infarction are poorly understood. We investigated the effects of this PPAR-γ agonist on the expression of tissue factor (TF), a primary molecule for thrombosis, and elucidated its underlying mechanisms. The PPAR-γ agonist inhibited TF expression in response to TNF-α in human umbilical vein endothelial cells, human monocytic leukemia cell line, and human umbilical arterial smooth muscle cells. The overexpression of TF was mediated by increased phosphorylation of mitogen-activated protein kinase (MAPK), which was blocked by the PPAR-γ agonist. The effective MAPK differed depending on each cell type. Luciferase and ChIP assays showed that transcription factor, activator protein-1 (AP-1), was a pivotal target of the PPAR-γ agonist to lower TF transcription. Intriguingly, two main drugs for drug-eluting stent, paclitaxel or rapamycin, significantly exaggerated thrombin-induced TF expression, which was also effectively blocked by the PPAR-γ agonist in all cell types. This PPAR-γ agonist did not impair TF pathway inhibitor (TFPI) in three cell types. In rat balloon injury model (Sprague-Dawley rats, n = 10/group) with continuous paclitaxel infusion, the PPAR-γ agonist attenuated TF expression by 70±5% (n = 4; P<0.0001) in injured vasculature. Taken together, rosiglitazone reduced TF expression in three critical cell types involved in vascular thrombus formation via MAPK and AP-1 inhibitions. Also, this PPAR-γ agonist reversed the paclitaxel-induced aggravation of TF expression, which suggests a possibility that the benefits might outweigh its risks in a group of patients with paclitaxel-eluting stent implanted.

Eosinophilic responses to stent implantation and the risk of Kounis hypersensitivity associated coronary syndrome

The use of drug eluting stents constitutes a major breakthrough in current interventional cardiology because it is more than halves the need of repeat interventions. It is incontrovertible that coronary stents, in general, have been beneficial for the vast majority of patients. A small increase in thrombosis, following DES implantation, is offset by a diminished risk of complications associated with repeat vascularization. However, late and, especially, very late stent thrombosis is a much feared complication because it is associated with myocardial infarction with increased mortality. Despite that stent thrombosis is thought to be multifactorial, so far clinical reports and reported pathology findings in patients died from coronary stent thrombosis as well as animal studies and experiments, point toward a hypersensitivity inflammation. The stented and thrombotic areas are infiltrated by interacting, via bidirectional stimuli inflammatory cells including eosinophils, macrophages, T-cells and mast cells. Stented regions constitute an ideal surrounding for endothelial damage and dysfunction, together with hemorheologic changes and turbulence as well as platelet dysfunction, coagulation and fibrinolytic disturbances. Drug eluting stent components include the metal strut which contains nickel, chromium, manganese, titanium, molybdenum, the polymer coating and the impregnated drugs which for the first generation stents are: the antimicrotubule antineoplastic agent paclitaxel and the anti-inflammatory, immunosuppressive and antiproliferative agent sirolimus. The newer stents which are called cobalt-chromiun stents and elute the sirolimus analogs everolimus and zotarolimus both contain nickel and other metals. All these components constitute an antigenic complex inside the coronary arteries which apply chronic, continuous, repetitive and persistent inflammatory action capable to induced Kounis syndrome and stent thrombosis. Allergic inflammation goes through three phases, the early phase, the late phase and the chronic phase and these three phases correspond temporally with early (acute and sub acute), late and very late stent thrombosis. Bioabsorbable allergy free poly lactic acid self expanding stents, nickel free stainless steel materials, stent coverage with nitric oxide donors and antibodies with endothelial progenitor cell capturing abilities as well as stents eluting anti-inflammatory and anti-allergic agents might be the solution of this so feared and devastating stent complication.

High plasma interleukin-6 is associated with drug-eluting stent thrombosis: possible role of inflammatory cytokines in the development of stent thrombosis from the Korea Stent Thrombosis Registry

BACKGROUND

Inflammation might contribute to the development of stent thrombosis (ST). The association between inflammatory cytokine concentrations and drug-eluting ST were evaluated.

METHODS AND RESULTS

Among the 123 ST patients enrolled in the multicenter Korea Stent Thrombosis registry, plasma samples were available in 41 patients. The patients' clinical characteristics and plasma concentrations of monocyte chemoattractant protein-1, tumor necrosis factor-alpha, and interleukin (IL)-6 were compared with 81 matched controls. Although the concentrations of 3 cytokines were higher in the ST group, they did not have significant differences. When divided into quartiles, the proportion of patients with the highest quartile of IL-6 was higher in the ST group than in the control group (44% vs. 16%, P = 0.001), and the highest IL-6 quartile was an independent predictor of ST for both early (adjusted hazard ratio [HR] 6.96; 95% confidence interval [CI] 1.75-27.66) and late ST (adjusted HR 4.71; 95%CI 1.06-20.92). In addition, the highest IL-6 quartile was an independent predictor of ST in those on clopidogrel (adjusted HR 7.70; 95%CI 1.97-30.13) but not in those who were off clopidogrel.

CONCLUSIONS

Highest IL-6 quartile was associated with ST, especially in clopidogrel users regardless of the time of ST, suggesting the involvement of inflammatory cytokines in ST.

The evolving role of inflammatory biomarkers in risk assessment after stent implantation

The main adverse reactions to coronary stents are in-stent restenosis (ISR) and stent thrombosis. Along with procedural factors, individual susceptibility to these events plays an important role. In particular, inflammatory status, as assessed by C-reactive protein levels, predicts the risk of ISR after bare-metal stent implantation, although it does not predict the risk of stent thrombosis. Conversely, C-reactive protein levels fail to predict the risk of ISR after drug-eluting stent (DES) implantation, although they appear to predict the risk of stent thrombosis. Of note, DES have abated ISR rates occurring in the classical 1-year window, but new concern is emerging regarding late restenosis and thrombosis. The pathogenesis of these late events seems to be related to delayed healing and allergic reactions to polymers, a process in which eosinophils seem to play an important role by enhancing restenosis and thrombosis. The identification of high-risk individuals based on biomarker assessment may be important for the management of patients receiving stent implantation. In this report, we review the evolving role of inflammatory biomarkers in predicting the risk of ISR and stent thrombosis.

How safe and how good are drug-eluting stents?

Percutaneous transluminal coronary angioplasty revolutionized therapy for coronary artery disease. This early promise of a viable alternative to surgical treatment of coronary artery disease was thwarted by the high rates of angiographic restenosis. The advent of stenting reduced the rates of restenosis, although it was hindered by the new problem of in-stent restenosis. It was demonstrated that in-stent restenosis was the result of a new pathology in the form of neointimal hyperplasia, which was a maladaptive healing response to bare-metal stent implantation. Recently, the introduction of drug-eluting stents (DES) technology has offered a new solution to the problem of restenosis. Current evidence suggests that although DES have reduced restenosis rates, important concerns have been raised regarding increased stent thrombosis, myocardial infarction and death. The purpose of this article is to examine the efficacy and safety data of DES as highlighted in recent publications and to further discuss the biomolecular mechanisms of accelerated endothelization and stent thrombosis. In addition, we will examine some of the newer stent technologies available.

The Management of Antiplatelet Therapy in Patients With Coronary Stents Undergoing Noncardiac Surgery

Whereas the development of coronary stents has been a major breakthrough in the treatment of coronary artery disease, stent thrombosis, associated with myocardial infarction and death, has introduced a new challenge in the care of patients with coronary stents undergoing noncardiac surgery. This review presents the authors’ recommendations regarding the optimal management of such patients. Elective surgery should be postponed for at least 6 weeks and optimally 3 months for a bare-metal stent and at least 1 year for a drug-eluting stent. On the other hand, managing a patient undergoing non-elective surgery is more difficult and necessitates a case-by-case assessment of bleeding risk versus thrombotic risk based on patient comorbidities, type of stents present, details of the coronary intervention, and type of surgical procedure. Patients with a risk of bleeding that outweighs the risk of stent thrombosis should discontinue at least clopidogrel, whereas all other patients should continue dual antiplatelet therapy throughout the perioperative period.

Increased serum vWF and sVCAM-1 levels are associated with late or very late angiographic stent thrombosis after sirolimus-eluting stent implantation

BACKGROUND

This study sought to examine whether circulatory levels of endothelial dysfunction biomarkers [vascular cell adhesion molecule (sVCAM-1), intercellular adhesion molecule (sICAM-1), sE-selectin, von Willebrand factor (vWF), tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI-1)] are associated with occurrence of late or very late stent thrombosis (ST) after percutaneous coronary intervention with sirolimus-eluting stent implantation, and to assess the possible influence of genetic variants of these proteins on ST.

METHODS

Serum levels of sVCAM-1, sICAM-1, sE-selectin, vWF, t-PA and PAI-1 were measured, and polymorphisms of vWF (-1234C/T, -1185A/G and -1051G/A), t-PA (insertion/deletion) and PAI-1 genes (4G/5G) were determined in 41 patients who experienced at least one episode of late or very late ST. Eighty-two patients without ST randomly selected from the same study period served as controls.

RESULTS

Serum levels of vWF, sVCAM-1 and sICAM-1 were significantly increased in patients with ST than in controls (all P<0.01). No significant difference was observed in the genotype and allele distribution of the vWF, t-PA and PAI-1 gene polymorphisms. Multivariable logistic regression analysis showed that vWF, sVCAM-1, discontinuation of clopidogrel therapy and left ventricular ejection fraction of less than 50% were independent determinants of late ST.

CONCLUSION

Increased serum vWF and sVCAM-1 levels are associated with late ST, suggesting that endothelial dysfunction contributes to the development of late or very late ST.

Paclitaxel potentiates inflammatory cytokine-induced prothrombotic molecules in endothelial cells

To overcome the limitations of balloon expandible metal stent-induced neointimal smooth muscle cell proliferation, drug-coated stent devices have been developed. Drug eluting stents release high concentrations of antiproliferative agents, such as paclitaxel, to reduce neointimal hyperplasia. The proinflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), is known to cause severe endothelial dysfunction and accelerate atherosclerotic lesion progression. The interaction of TNF-alpha and paclitaxel on the release of prothrombotic molecules was examined in endothelial cells. Treatment of endothelial cells with paclitaxel had no direct effect on tissue factor (TF) expression, but TNF-alpha increased TF. Cotreatment of paclitaxel with TNF-alpha markedly augmented the release of TF. TNF-alpha induced release of plasminogen activator inhibitor but no synergism occurred with paclitaxel. Treatment of endothelial cells with paclitaxel and TNF-alpha reduced expression of thrombomodulin and protein C receptor. Tissue factor pathway inhibitor expression was reduced by prolonged treatment with either paclitaxel or TNF-alpha. The adhesion molecule, CD62 E, was induced by TNF-alpha; however, CD31, CD62 P, and CD106 were not affected by paclitaxel and TNF-alpha. Apoptosis was not observed with cotreatment of endothelial cells with paclitaxel and TNF-alpha. CD59-positive microparticles were released in response to TNF-alpha, but the release was not augmented by paclitaxel. Paclitaxel and TNF-alpha increased the nitrotyrosination of proteins. These findings indicate that paclitaxel enhances TNF-alpha-induced release of TF, and downregulated thrombomodulin, increased protein nitration, which may subsequently favor prothrombotic intimal surface.

JNK-ATF-2 inhibits thrombomodulin (TM) expression by recruiting histone deacetylase4 (HDAC4) and forming a transcriptional repression complex in the TM promoter

Thrombomodulin (TM) is an important vascular protective molecule that has anticoagulant, anti-inflammatory and anti-apoptotic properties. TM is downregulated in many thrombotic and vascular diseases. However, the mechanisms responsible for TM suppression are not completely understood. In this study, we investigated the mechanism involved in fatty acid-induced suppression of TM expression in human aortic endothelial cells. We found that palmitic acid inhibited TM expression through the JNK and p38 pathways. ATF-2, a JNK and p38 target transcription factor, was involved in the suppression. ATF-2 can bind to the TM promoter, recruit HDAC4 and form a transcriptional repression complex in the promoter, which may lead to chromatin condensation and transcriptional arrest. This study provides novel insight into TM down-regulation by stress signaling pathways.

Amphetamines induce tissue factor and impair tissue factor pathway inhibitor: role of dopamine receptor type 4

AIMS

Amphetamine intake is associated with acute vascular syndromes. Since these events are caused by arterial thrombosis and this in turn is triggered by tissue factor (TF), this study examines whether amphetamines regulate TF in human endothelial cells.

METHODS AND RESULTS

Amphetamine (10(-7)-10(-4) mol/L) enhanced thrombin- and tumour necrosis factor (TNF)-alpha-induced as well as basal TF expression (P = 0.029, 0.0003, and 0.003 at maximal concentration), and TNF-alpha-induced plasminogen activator inhibitor (PAI)-1 expression (P = 0.003), whereas tissue factor pathway inhibitor expression was impaired (P = 0.008). Similarly, 3,4-methylenedioxymethamphetamine (10(-7)-10(-4) mol/L) enhanced TF expression (P = 0.046). These effects were paralleled by an increased TF activity (P = 0.002); moreover, clotting time of human plasma was accelerated by supernatant from amphetamine-treated cells (P = 0.03). Amphetamine enhanced TF mRNA expression via phosphorylation of the mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinase (ERK) and p38 (P = 0.03 and 0.033), but not c-Jun NH(2)-terminal kinase (JNK; P = 0.81). The effect of amphetamine on TF expression was abrogated by the dopamine D4 receptor antagonists L-745,870 and L-750,667, but not D2 or D3 receptor antagonists; furthermore, L-745,870 blunted the amphetamine-induced activation of ERK and p38, but not JNK.

CONCLUSION

Amphetamines induce endothelial TF expression via stimulation of dopamine D4 receptor and activation of the MAPKs p38 and ERK. These effects occur at clinically relevant amphetamine concentrations and may account for the increased incidence of acute vascular syndromes after amphetamine consumption.

Tissue factor in cardiovascular disease pathophysiology and pharmacological intervention

Tissue factor (TF) is the major trigger of the coagulation cascade and thereby crucially involved in the maintenance of vascular hemostasis. By binding factor VIIa, the resulting TF:VIIa complex activates the coagulation factors IX and X ultimately leading to fibrin and clot formation. In the vessel wall, TF expression and activity is detectable in vascular smooth muscle cells and fibroblasts and, at a much lower level, in endothelial cells and can be induced by various stimuli including cytokines. In addition, TF is found in the bloodstream in circulating cells such as monocytes, in TF containing microparticles, and as a soluble splicing isoform. Besides its well-known extracellular role as a trigger of coagulation, TF also functions as a transmembrane receptor, and TF-dependent intracellular signaling events regulate the expression of genes involved in cellular responses such as proliferation and migration. TF indeed appears to be involved in the pathogenesis of neointima formation and tumor growth, and increased levels of TF have been detected in patients with cardiovascular risk factors or coronary artery disease as well as in those with cancer. Therefore, pharmacological or genetic inhibition of TF may be an attractive target for the treatment of cardiovascular disease and cancer. Different strategies for inhibition of TF have been developed such as inhibition of TF synthesis and blockade of TF action. Clinical applications of such strategies need to be tested in appropriate trials, in particular for evaluating the advantages of targeted versus systemic delivery of the inhibitors.

DMSO inhibits human platelet activation through cyclooxygenase-1 inhibition. A novel agent for drug eluting stents?

BACKGROUND

DMSO is routinely infused together with hematopoietic cells in patients undergoing myeloablative therapy and was recently found to inhibit smooth muscle cells proliferation and arterial thrombus formation in the mouse by preventing tissue factor (TF), a key activator of the coagulation cascade. This study was designed to investigate whether DMSO prevents platelet activation and thus, whether it may represent an interesting agent to be used on drug eluting stents.

METHODS AND RESULTS

Human venous blood from healthy volunteers was collected in citrated tubes and platelet activation was studied by cone and platelet analyzer (CPA) and rapid-platelet-function-assay (RPFA). CPA analysis showed that DMSO-treated platelets exhibit a lower adherence in response to shear stress (-15.54+/-0.9427%, n=5, P<0.0001 versus control). Additionally, aggregometry studies revealed that DMSO-treated, arachidonate-stimulated platelets had an increased lag phase (18.0%+/-4.031, n=9, P=0.0004 versus control) as well as a decreased maximal aggregation (-6.388+/-2.212%, n=6, P=0.0162 versus control). Inhibitory action of DMSO could be rescued by exogenous thromboxane A2 and was mediated, at least in part, by COX-1 inhibition.

CONCLUSIONS

Clinically relevant concentrations of DMSO impair platelet activation by a thromboxane A2-dependent, COX-1-mediated effect. This finding may be crucial for the previously reported anti-thrombotic property displayed by DMSO. Our findings support a role for DMSO as a novel drug to prevent not only proliferation, but also thrombotic complications of drug eluting stents.

PDGF-CC induces tissue factor expression: role of PDGF receptor alpha/beta

Tissue factor (TF) is the principal trigger of the coagulation cascade and involved in arterial thrombus formation. Platelet-derived growth factor CC (PDGF-CC) is a recently discovered member of the PDGF family released upon platelet activation. This study assesses the impact of PDGF-CC on TF expression in human cells. PDGF-CC concentration-dependently induced TF expression by 2.5-fold in THP-1 cells, by 2.0-fold in human peripheral blood monocytes, by 1.4-fold in vascular smooth muscle cells, and by 2.6-fold in microvascular endothelial cells, but did not affect TF expression in aortic endothelial cells. A similar pattern was observed with PDGF-BB. In contrast, PDGF-AA did not alter TF expression in THP-1 cells. TF whole cell activity was induced following stimulation with PDGF-BB and PDGF-CC in THP-1 cells. Real-time polymerase chain reaction revealed that PDGF-CC induced TF mRNA. PDGF-CC transiently activated p42/44 MAP kinase [extracellular signal-regulated kinase (ERK)], while phosphorylation of the MAP kinases c-Jun NH(2)-terminal kinase (JNK) and p38 remained unaffected. PD98059, a specific inhibitor of ERK phosphorylation, but not the p38 inhibitor SB203580 or the JNK inhibitor SP600125 prevented PDGF-CC induced TF expression in a concentration-dependent manner. The effect of PDGF-CC was antagonized by both PDGF receptor alpha and PDGF receptor beta neutralizing antibodies; in contrast, PDGF-BB was only inhibited by PDGF receptor beta blocking antibody. PDGF receptor alpha and PDGF receptor beta inhibition prevented PDGF-CC-induced ERK phosphorylation. PDGF-CC induces TF expression via activation of alpha/beta receptor heterodimers and an ERK-dependent signal transduction pathway.

Passive and active polymer coatings for intracoronary stents: novel devices to promote arterial healing

Coronary stent implantation is the second great advance in the treatment of obstructive coronary artery disease since the introduction of balloon catheter angioplasty. However, in-stent restenosis (ISR) caused by neointimal hyperplasia has been a major limitation of stents, occurring in up to 30% of cases. Advances in coronary stent technology both in terms of stent design and function and especially drug-eluting stents (DES) have significantly improved the safety and efficacy of percutaneous coronary intervention (PCI) with stenting, including marked reduction in ISR. This has led to use of DES for increasingly challenging clinical and lesional subsets, with potential for increased risk of stent-associated complications, especially late stent thrombosis (LST). Because restenosis and stent thrombosis are caused by multiple and often interrelated factors, ideal agents for stent coatings should inhibit thrombus formation, inflammatory reaction, and cellular proliferation, while supporting reendothelialization. To avoid undesirable effects of currently applied (durable) polymers, biocompatible, and bioabsorbable polymers as well as DES delivery systems that minimize polymer burden have been produced and tested. Bioabsorbable stents, both polymeric and metallic, have been developed to decrease potential late complications after stent implantation. Novel strategies to address some of these challenges are in various stages of research and development. In this article we outline developments in the field of passive and active stent coatings and evaluate the ongoing role of such coatings in the contemporary era of DES.