Effects of M-1, a Major Metabolite of Sarpogrelate, on 5-HT-Induced Constriction of Isolated Human Internal Thoracic Artery.

Sarpogrelate, a selective 5-hydroxytryptamine (5-HT)2A receptor antagonist, inhibits 5-HT-induced platelet aggregation and vasoconstriction. It improves ischemic symptoms in patients with arteriosclerosis obliterans. M-1 is a major metabolite of sarpogrelate, and has been reported to show a higher affinity for the 5-HT2A receptor on platelets than sarpogrelate. However, the effects of M-1 on 5-HT-induced constrictive response in human blood vessels have not been investigated. The internal thoracic artery (ITA) is the key conduit for coronary artery bypass grafting (CABG). 5-HT has been implicated as playing an important role in the pathogenesis of vasospasm. Thus, in the present study, the effects of M-1 on 5-HT-induced vasoconstriction were examined in isolated human endothelium denuded ITA. M-1 inhibited 5-HT-induced vasoconstriction in a concentration-dependent manner. At the highest concentration, M-1 almost completely inhibited the 5-HT-induced vasoconstriction. Expression of 5-HT2A and 5-HT1B receptor proteins in the membrane fraction of ITA smooth muscle cells was confirmed by Western blot analysis. Individually, supramaximal concentrations of sarpogrelate and SB224289, a selective 5-HT1B receptor antagonist, only partially inhibited the 5-HT-induced vasoconstriction. However, simultaneous pretreatment with both these antagonists almost completely inhibited the 5-HT-induced vasoconstriction. The inhibitory effect of M-1 pretreatment mimicked the inhibitory effect of simultaneous pretreatment with sarpogrelate and SB224289. These results suggest that M-1 has antagonistic effects not only on the 5-HT2A receptor but also on the 5-HT1B receptor in human ITA smooth muscle cells. M-1 may be useful as a lead compound for the development of drugs for the treatment of 5-HT-induced vasospasms in CABG.

Diabetes Mellitus Induces Hyperreactivity of 5-Hydroxytryptamine (5-HT)-Induced Constriction in Human Internal Thoracic Artery and Is Associated with Increase in the Membrane Protein Level of 5-HT2A Receptor.

Studies indicate that 5-hydroxytryptamine (5-HT) released from activated platelets in coronary artery bypass grafting (CABG) induces 5-HT2A receptor-mediated graft spasm. We previously reported that 5-HT-induced constriction of human endothelium-denuded saphenous vein (SV) was significantly augmented in patients with diabetes mellitus (DM) than in patients without DM (non-DM), without changes in the levels of the membrane-bound 5-HT2A receptor of their smooth muscle cells. Although the internal thoracic artery (ITA) is the key graft conduit for CABG, the effect of DM on the ITA graft spasm is still unclear. Therefore, in this study, we investigated the effect of DM on 5-HT-induced vasoconstriction and the level of membrane-bound 5-HT2A receptor in ITA grafts. 5-HT-induced constriction of the isolated human endothelial-denuded ITA was significantly higher in patients with DM than in patients without DM. In addition, the level of the 5-HT2A receptor in the membrane fraction of human ITA smooth muscle cells was significantly higher in patients with DM than in those without DM. These results demonstrate that DM is a risk factor for CABG in both venous and arterial conduits, and that it differentially affects the level of the membrane-bound 5-HT2A receptor in the venous and arterial smooth muscle cells.

Angiotensin II, as well as 5-hydroxytriptamine, is a potent vasospasm inducer of saphenous vein graft for coronary artery bypass grafting in patients with diabetes mellitus.

Diabetes mellitus (DM) is an important risk factor for adverse outcomes of coronary artery bypass grafting. The bypass grafts harvested from patients with DM tend to go into spasm after their implantation into the coronary circulation. To clarify the contribution of 5-hydroxytriptamine (5-HT) and angiotensin II (AngII) in the bypass graft spasm, we examined the contractile reactivity to 5-HT or AngII of isolated human endothelium-denuded saphenous vein (SV) harvested from DM and non-DM patients. The 5-HT-induced constriction of the SV was significantly augmented in the DM group than in the non-DM group, which is similar to our previous report. AngII-induced constriction of the SV was also significantly augmented in the DM group than the non-DM group. Especially in the non-DM group, the AngII-induced maximal vasoconstriction was markedly lower than the 5-HT-induced one. Meanwhile, the increasing rates of AngII-induced vasoconstriction in the DM group to the non-DM group were significantly greater than those of 5-HT-induced vasoconstriction. These results indicate that 5-HT is a potent inducer of SV graft spasm in both DM and non-DM patients, while AngII is a potent inducer of SV graft spasm only in patients with DM. Furthermore, the protein level of AngII AT1 receptor (AT1R), but not the protein level of 5-HT2A receptor, in the membrane fraction of the SV smooth muscle cells of DM patients was significantly increased as compared with that of the non-DM patients. These results suggest that the mechanism for hyperreactivity to AngII in the SV from DM patients is due to, at least in part, the increase in the amount of AT1R on membrane of the SV smooth muscle cells.

Water-soluble jack-knife prawn extract inhibits 5-hydroxytryptamine-induced vasoconstriction and platelet aggregation in humans.

Coronary artery spasm plays an important role in the pathogenesis of various ischemic heart diseases or serious arrhythmia. The aim of this study is to look for functional foods which have physiologically active substances preventing 5-hydroxytryptamine (5-HT)-related vasospastic diseases including peri- and postoperative ischemic complications of coronary artery bypass grafting (CABG) from ocean resources in Japanese coastal waters. First, we evaluated the effect of water-soluble ocean resource extracts on the response to 5-HT in HEK293 cells which have forcibly expressed cyan fluorescent protein-fused 5-HT2A receptors (5-HT2A-CFP). Among 5 different water-soluble extracts of ocean resources, the crude water-soluble jack-knife prawn extract (WJPE) significantly reduced maximal Ca(2+) influx induced by 0.1 µM 5-HT in a concentration-dependent manner. The Crude WJPE significantly inhibited, in a concentration-dependent manner, 5-HT-induced constriction of human saphenous vein. 5-HT released from activated platelets plays a crucial roles in the constriction of coronary artery. Next the WJPE was purified for applying the experiment of 5-HT-induced human platelet aggregation. The purified WJPE significantly inhibited 5-HT-induced human platelet aggregation also in a concentration-dependent manner. Based on our findings, jack-knife prawn could be one of a functional food with health-promoting benefits for most people with vasospastic diseases including patients who have gone CABG.

Association of cognitive dysfunction with cardiovascular disease events in elderly hypertensive patients.

OBJECTIVES: This study assesses whether presence of cognitive dysfunction can be a marker associated with the development of cardiovascular disease (CVD) events independent of ambulatory blood pressure (BP) or other indices of target organ damage (TOD) in elderly hypertensive patients. METHODS: We recruited 585 hypertensive patients (mean age, 73 years; 41% men) who were ambulatory, lived independently, and were without clinically overt dementia. Cognitive function was assessed by Mini-Mental State Examination (MMSE) at baseline, and CVD events (coronary artery disease, stroke, congestive heart failure, and sudden death) were prospectively ascertained. Cognitive dysfunction was defined as the lowest quartile of MMSE scores (n = 183, median 24 points). RESULTS: CVD events occurred in 42 people over an average of 2.8 years (1644 person-years). The prevalence of cognitive dysfunction was higher in patients with CVD events than those without (57 vs. 29%; both P <0.001) at baseline. Cognitive dysfunction was associated with CVD events, after adjustment for nocturnal SBP and evidence of TOD [i.e. albuminuria, cardiac hypertrophy, and carotid-artery intima-media thickness (IMT)], hazard ratio 2.5-2.9 (all P <0.01). Incorporation of MMSE in the risk model (including age, estimated glomerular filtration rate, and preexisting CVD) improved the C-statistics (from 0.691 to 0.741) and resulted in a net reclassification improvement of 17.6% (P = 0.02). In contrast, incorporation of albuminuria, cardiac hypertrophy, and high carotid-artery IMT added little further improvement in the risk prediction. CONCLUSION: Cognitive dysfunction is an independent marker associated with increased risk of CVD events in elderly hypertensive patients.

Insulin induces internalization of the plasma membrane 5-hydroxytryptamine2A (5-HT2A) receptor in the isolated human endothelium-denuded saphenous vein via the phosphatidylinositol 3-kinase pathway.

The aim of this study was to investigate the relaxant effect of insulin on the 5-hydroxytryptamine (5-HT)-induced constriction of the human endothelium-denuded saphenous vein (SV) and its signal transduction pathway. During the 5-HT-induced sustained constriction of vessels, insulin induced vasorelaxation in a concentration-dependent manner. This insulin-induced vasorelaxation was partially attenuated by L-NAME, a nitric oxide synthase (NOS) inhibitor, and was abolished by wortmannin, a phosphatidylinositol 3-kinase (PI3-K) inhibitor. Insulin increased the Ser(473) phosphorylation of Akt. Endothelial NOS and inducible NOS protein expressions were observed in SV smooth muscle when insulin induced relaxation of SV vessels preconstricted with 5-HT. Although insulin did not affect the total protein level of 5-HT(2A) receptors, it decreased the particulate protein level and reciprocally increased the soluble protein level of 5-HT(2A) receptors in a concentration-dependent manner. These results demonstrate that insulin can induce the internalization of 5-HT(2A) receptors from the plasma membrane to the cytoplasm. The insulin-induced internalization of 5-HT(2A) receptors was abolished by wortmannin but was not affected by L-NAME. These results suggest that the relaxant effect of insulin on 5-HT-induced vasoconstriction is mediated in part by the internalization of plasma membrane 5-HT(2A) receptors and the production of nitric oxide via the PI3-K/Akt pathway.

The defective protein level of myosin light chain phosphatase (MLCP) in the isolated saphenous vein, as a vascular conduit in coronary artery bypass grafting (CABG), harvested from patients with diabetes mellitus (DM).

We examined the contractile reactivity to 5-hydroxytryptamine (5-HT) in isolated human saphenous vein (SV), as a vascular conduit in coronary artery bypass grafting (CABG), harvested from patients with diabetes mellitus (DM) and non-DM (NDM). Vascular rings of endothelium-denuded SV were used for functional and biochemical experiments. The vasoconstrictions caused by 5-HT were significantly greater (hyperreactivity) in the DM group than in the NDM group. RhoA/ROCK pathway is activated by various G-protein-coupled receptor agonists and consequently induces phosphorylation of myosin phosphatase target subunit 1 (MYPT1), a subunit of myosin light chain phosphatase (MLCP), which inhibits MLCP activity. In the resting state of the vessels, total tissue protein levels of 5-HT(2A) receptor, 5-HT(1B) receptor, RhoA, ROCK1, and ROCK2 did not differ between NDM and DM groups. However, the total protein level of MYPT1 was significantly lower in the DM group than in the NDM group. Furthermore, the ratio of P(Thr(696))-MYPT1 to total MYPT1 was significantly higher in the DM group than in the NDM group. These results suggest that the hyperreactivity to 5-HT in the SV smooth muscle of patients with DM is due to not only enhanced phosphorylation of MLCP but also defective protein level of MLCP. Thus, we reveal for the first time that the defective protein level of MLCP in the DM group can partially explain the poor patency of SV graft harvested from patients with DM.

Regional differences in hypertensive cardiovascular remodeling between fishing and farming communities in Japan.

BACKGROUND: Effects of dietary n-3 polyunsaturated fatty acids (n-3 PUFA) intake on the cardiovascular system have been reported, and thus we hypothesized that the prevalence of hypertensive cardiovascular remodeling would be lower in a fishing than a farming community. METHODS: We recruited 263 essential hypertensives from a fishing and 333 from a farming village; all subjects were ≥40 years (mean 73 years; 42% men). They were cross-sectionally examined for serum eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), asymmetric dimethylarginine (ADMA) levels, left ventricular mass index (LVMI), and common-carotid artery (CCA) and internal-carotid artery (ICA) intima-media thickness (IMT). RESULTS: Compared to the patients in the farming village, those in the fishing village had higher serum EPA and DHA levels (63.3 vs.70.9 µg/ml, 137.2 vs.157.8 µg/ml) and lower ADMA levels (0.49 vs.0.47 nmol/ml; all P < 0.05). LVMI and both CCA-IMT and ICA-IMT levels were lower in the fishing than the farming village (113.2 vs.121.6 g/m(2), 0.88 vs.0.94 mm, 1.10 vs.1.17 mm: all P < 0.01) even after adjustment for age, sex, body mass index (BMI), duration of hypertensive medication, number of antihypertensive medications, and 24-h systolic blood pressure (SBP) level. The differences in LVMI and IMT levels between these communities also remained unchanged (all P < 0.01) after additional adjustment for the regional differences in EPA, DHA, and ADMA levels. A multivariable linear regression analysis showed that the difference in place of residence was independently associated with LVMI as well as with both CCA-IMT and ICA-IMT levels (all P < 0.01). CONCLUSION: The prevalence of cardiovascular remodeling was significantly lower in patients in the fishing community than in those in the farming community. Further investigations are required to explain the mechanisms underlying this association.

Relative contributions of 5-hydroxytryptamine (5-HT) receptor subtypes in 5-HT-induced vasoconstriction of the distended human saphenous vein as a coronary artery bypass graft.

It is established that the segment of saphenous vein (SV) that is widely used as a conduit vessel in coronary artery bypass graft (CABG) surgery is distended with high pressure to check for leaks and to increase the patency before implantation into coronary arterial circulation. The aim of the present study was to elucidate the relative contributions of 5-hydroxytryptamine (5-HT) receptor subtypes responsible for 5-HT-induced vasoconstriction of the distended human SV. Whereas about half of the 5-HT-induced vasoconstriction still remained in the presence of supramaximum concentration of sarpogrelate or of SB224289 (5-HT(2A) and 5-HT(1B) receptor antagonists, respectively), simultaneous treatment with sarpogrelate and SB224289 almost completely inhibited the 5-HT-induced vasoconstriction. Immunopositive staining for 5-HT(2A) and 5-HT(1B) receptors was detected in smooth muscle cells of the distended human SV and there was no significant difference between the immunopositive areas of 5-HT(2A) and 5-HT(1B) receptors. These results demonstrate that 5-HT(2A) and 5-HT(1B) receptors similarly contribute to 5-HT-induced vasoconstriction in human distended SV. Thus, when the SV is used as a CABG conduit, a combination of 5-HT(2A) and 5-HT(1B) receptor antagonists would appear to be most useful to prevent 5-HT-induced spasm.

Both 5-hydroxytryptamine 5-HT2A and 5-HT1B receptors are involved in the vasoconstrictor response to 5-HT in the human isolated internal thoracic artery.

1. The 5-hydroxytryptamine (5-HT, serotonin) receptor subtypes that mediate vasoconstriction in the human internal thoracic artery (ITA), which is frequently used as an arterial graft, remain unclear. The aim of the present study was to elucidate the 5-HT receptor subtypes responsible for 5-HT-induced contraction of the human ITA. 2. The contractile responses to 5-HT of endothelium-denuded human ITA obtained from patients undergoing coronary bypass surgery were examined. In addition, we investigated the effects of sarpogrelate and SB224289, antagonists of 5-HT(2A) and 5-HT(1B) receptors, respectively, on the 5-HT-induced vasoconstriction. Finally, 5-HT(2A) and 5-HT(1B) receptors in the human ITA were immunolabelled. 3. 5-Hydroxytryptamine (1 nmol/L-10 micromol/L) caused vasoconstriction in a concentration-dependent manner. Both sarpogrelate (1 micromol/L) and SB224289 (1 micromol/L) significantly, but not completely, inhibited 5-HT-induced vasoconstriction. 4. Conversely, simultaneous pretreatment with supramaximum concentrations (1 micromol/L for both) of sarpogrelate and SB224289 almost completely inhibited the 5-HT-induced vasoconstriction. 5. Immunopositive staining for 5-HT(2A) and 5-HT(1B) receptors was detected in smooth muscle cells of the human ITA. 6. These results demonstrate that, in human ITA, 5-HT-induced vasoconstriction is mediated by activation of both 5-HT(2A) and 5-HT(1B) receptors. Thus, when the human ITA is used as an arterial graft, a combination of 5-HT(2A) and 5-HT(1B) receptor antagonists would appear to be most useful to prevent 5-HT-induced vasospasm.

Mycotic pseudoaneurysm of the brachiocephalic artery.

A 73-year-old woman with a history of hypertension and hyperlipidemia presented with a sharp pain ranging from the right shoulder to the upper limb. She had suffered a sharp pain at rest accompanied by general fatigue and nausea for about ten months prior to admission. Her white blood cell count was 12,800/microl, and her serum C-reactive protein was 17.5 mg/dl. A chest computed tomography scan revealed an aneurysmal change of the origin of the brachiocephalic artery. Pseudoaneurysm due to infection and aortic dissection was considered as a preoperative diagnosis. A total arch replacement was performed under cardiopulmonary bypass, deep hypothermia, and selective cerebral perfusion. Postoperatively, a bacteriologic culture of the contents of the aneurysm revealed Staphylococcus aureus. Perioperative administration of antibiotics was effective and the postoperative course was uneventful.

Protruding thrombus in the left atrium found 7 years after percutaneous transvenous mitral commissurotomy: report of a case.

A 50-year-old man was transferred to our hospital for investigation of cerebellar infarction, thought to have been caused by cardiac thromboembolism. We assumed that the cardiac thromboembolism had occurred as a late complication of a percutaneous transvenous mitral commissurotomy (PTMC) performed 7 years earlier. An echocardiogram and thoracic computed tomography revealed a protruding thrombus in the left atrium and an emergency operation was performed. The protruding thrombus was found to originate from the scar that penetrated into the intra-atrial muscular septum caused by the PTMC. After removing the thrombus, the scar was covered with normal endothelium and the mitral valve was replaced with a 27-mm St. Jude Medical prosthetic valve. We think that the thromboembolism was caused by mitral valve restenosis, atrial fibrillation, and endothelial injury in the interatrial septum during PTMC. Therefore, long-term follow-up and appropriate medication is recommended after PTMC, since restenosis and thrombosis are likely to occur.