Inhibition of CXCL10 release by monomeric C3bi and C4b.

Cellulose acetate (CA) beads are often used for leucocyte apheresis therapy against inflammatory bowel disease. In order to clarify the mechanism of the anti-inflammatory effects of CA, global analysis of the molecules generated in blood by the interaction with CA beads was performed in this study. An activated medium was collected from whole blood that had been preincubated with CA beads, and the effects of the CA-activated medium on leucocyte function were investigated. Fresh blood was stimulated with lipopolysaccharide (LPS) or interferon (IFN)-ß in the presence of the activated medium, and levels of chemokines and cytokines, including CXCL10 (IFN-inducible protein-10), and phosphorylated STAT1 (signal transducer and activator of transcription 1), which is known to be essential for CXCL10 production in leucocytes, were measured. IFN-ß- or LPS-induced CXCL10 production, expression of CXCL10 mRNA and phosphorylation of STAT1 were significantly reduced in the presence of the medium pretreated with CA beads compared with the control without the CA bead treatment. The factors inhibiting CXCL10 production were identified as the C3 and C4 fragments by mass spectrometry. The monomeric C3bi and C4b proteins were abundant in the medium pretreated with CA beads. Furthermore, purified C3bi and C4b were found to inhibit IFN-ß-induced CXCL10 production and STAT1 phosphorylation. Thus, STAT1-mediated CXCL10 production induced by stimulation with LPS or IFN was potently inhibited by monomeric C3bi and C4b generated by the interaction of blood with CA beads. These mechanisms mediated by monomeric C3bi and C4b may be involved in the anti-inflammatory effects of CA.

The mode of actions of the Adacolumn therapeutic leucocytapheresis in patients with inflammatory bowel disease: a concise review.

Patients with active inflammatory bowel disease (IBD) have elevated and activated myeloid leucocytes which infiltrate the colonic mucosa in vast numbers. Myeloid leucocytes such as the CD14(+) CD16(+) monocytes are major sources of tumour necrosis factor (TNF)-α, and therefore selective granulocyte/monocyte (GM) adsorption (GMA) should promote remission or enhance efficacy of pharmacological therapy. However, studies in IBD have reported both impressive as well as disappointing efficacy outcomes, indicating that patients' demographic factors might determine responders or non-responders to GMA. Nonetheless, this non-drug intervention has an excellent safety profile, and therapeutic GMA is expected to expand. In this review, attempts have been made to compile an update on the mode of actions (MoA) of the Adacolumn GMA. The MoA of GMA appears to be more than adsorption of excess neutrophils and TNF-producing CD14(+) CD16(+) monocytes per se. Adsorbed GMs release interleukin (IL)-1 receptor antagonist, hepatocyte growth factor and soluble TNF receptors, which are anti-inflammatory. Additionally, a sustained increase in lymphocytes including the regulatory CD4(+) CD25(+) T cells (lymphocyte sparing) is seen post-GMA. The impact of GMA on the immune system is potentially very interesting in the context of treating immune-related diseases. Future studies are expected to add intriguing insights to the MoA of GMA.

Review article: diet and inflammatory bowel disease--epidemiology and treatment.

BACKGROUND: Diet is thought to have an important role in the immunopathogenesis and treatment of inflammatory bowel disease (IBD). AIM: To identify dietary constituents as risk factors for development of IBD and the therapeutic efficacy of dietary modifications or enteral nutrition in IBD. METHODS: The Medline and the Cochrane Library were searched for clinical trials and meta-analyses in the scope of diet and nutrition in IBD. RESULTS: There are many studies in small cohorts of patients that claim that intake of certain diet constituents like fat, refined sugar, fruits, vegetables and fibre affect the expression of IBD. These are often compromised by insufficient data or methodological limitations and do not provide unequivocal evidence to incriminate any particular dietary factor. Among various dietary interventions, none has shown striking efficacy with the possible exception of complete enteral nutrition. Enteral nutrition appears effective in both active and quiescent Crohn's disease (CD), but independent meta-analyses have shown enteral nutrition to be inferior to corticosteroids in the management of active CD, when assessed on an intention-to-treat basis. CONCLUSIONS: The current levels of knowledge concerning dietary risk factors for IBD, and the therapeutic efficacy of dietary and nutritional interventions need to be supported by well-designed trials in large cohorts of patients.

The expression profile of functional regulatory T cells, CD4+CD25high+/forkhead box protein P3+, in patients with ulcerative colitis during active and quiescent disease.

Regulatory T cells (T(reg)) have an essential role in maintaining immune tolerance in the gut. The functional CD4(+) T(reg) express the transcription factor forkhead box protein 3 (FoxP3) or a CD25(high) in humans. Further, depletion of elevated granulocytes/monocytes by extracorporeal adsorption (GMA) induces immunomodulation in patients with ulcerative colitis (UC). We investigated the impact of GMA on T(reg). Thirty-one UC patients, clinical activity index (CAI) 12.1 +/- 2.97, refractory to conventional medications including intravenous corticosteroid and 13 healthy controls (HC), were included. Patients received five GMA sessions over 5 weeks. Biopsies from the rectal mucosa and blood samples at baseline and post-GMA were immunostained with anti-CD4/FoxP3 and anti-CD4/CD25 antibodies for immunohistochemistry and flow cytometry. Following GMA, 22 of 31 patients achieved remission (CAI

Treating ulcerative colitis by Adacolumn therapeutic leucocytapheresis: clinical efficacy and safety based on surveillance of 656 patients in 53 centres in Japan.

BACKGROUND/AIM: The Adacolumn selectively depletes granulocytes and monocytes/macrophages, which are thought to be part of the immunopathogenesis of ulcerative colitis. This work aims at evaluating the safety and clinical efficacy of the Adacolumn in patients with ulcerative colitis in large population-based data sets. METHODS: The Adacolumn post marketing surveillance in Japan was undertaken on 697 patients in 53 medical institutions over 7 years from 29 October 1999 to 28 October 2006. Clinical efficacy and safety data were provided by patients' physicians in the participating institutes. RESULTS: Safety was evaluated in all the 697 patients and efficacy in 656 patients. At entry, 92% of the patients were on salicylates, 74% on prednisolone and only 9% on immunomodulators. Approximately 40% of patients had severe ulcerative colitis and over 70% had ulcerative colitis that was refractory to conventional medications. There was no serious adverse events; mild to moderate adverse events were seen in 7.7% of the patients. The overall response (remission or significantly improved) was 77.3%; the remission rate based on clinical activity index was 71.1%, while 17.1% remained unchanged and 5.6% worsened. Patients were subgrouped into severe, moderate and mild ulcerative colitis based on clinical activity index (n=578), the response rates were 63.2%, 65.7% and 80.4%, respectively (P<0.001). Endoscopic assessment of efficacy showed very significant mucosal healing, Matts' endoscopic index improved from 3.2+/-0.04 to 2.1+/-0.7 (n=219, P<0.001); reduction in prednisolone dose (P<0.0001); leucocyte count (n=358, P<0.0001) and C-reactive protein (n=314, P<0.0001). Patients who received > or =6 Adacolumn sessions (n=319) did better than patients who received < or =5 sessions (n=188, P=0.004) and multivariate logistic regression analysis revealed that baseline granulocyte count was the strongest predictor of clinical response to Adacolumn (P=0.0191, odds ratio 1.151). CONCLUSION: This post marketing surveillance provides the largest ever efficacy and safety data on the Adacolumn therapeutic leucocytapheresis in patients with ulcerative colitis. As a non-pharmacologic treatment for patients with active ulcerative colitis most of whom were refractory to conventional drug therapy, the observed efficacy was very significant. Baseline granulocyte count was convincingly an independent predictor of clinical response.

Factors affecting clinical and endoscopic efficacies of selective leucocytapheresis for ulcerative colitis.

BACKGROUND: Granulocyte, monocyte/macrophage adsorptive apheresis is a novel treatment for active ulcerative colitis. However, as yet no study has reported on a subset of patients who might respond well to granulocyte, monocyte/macrophage adsorptive apheresis therapy. AIM: To identify factors affecting clinical and endoscopic efficacies of granulocyte, monocyte/macrophage in patients with ulcerative colitis. METHODS: Fifty consecutive patients with active ulcerative colitis initially received five granulocyte, monocyte/macrophage adsorptive apheresis sessions with the Adacolumn over five consecutive weeks. Patients who improved without achieving remission received five additional granulocyte, monocyte/macrophage adsorptive apheresis sessions. RESULTS: One week after the last granulocyte, monocyte/macrophage adsorptive apheresis session, 26 (52%) and 17 patients (34%) achieved clinical and endoscopic remission, respectively. In the multivariate analysis, the dose of prednisolone administered at entry and the cumulative dose of prednisolone administered before entry were independent significant factors for both clinical and endoscopic remission, negatively impacted the efficacy of granulocyte, monocyte/macrophage adsorptive apheresis. Age, gender, duration of ulcerative colitis, number of prior relapses, duration of current exacerbation, extent and severity of ulcerative colitis, extra-intestinal manifestations, entry haematology values and C-reactive protein did not affect the outcome. CONCLUSIONS: Based on the outcomes of this study, it appears that steroid-naïve patients and patients on low dose steroid and short duration of exposure respond to granulocyte, monocyte/macrophage adsorptive apheresis. Further studies in larger cohorts of patients should strengthen our findings.

Adhesion dependent release of hepatocyte growth factor and interleukin-1 receptor antagonist from human blood granulocytes and monocytes: evidence for the involvement of plasma IgG, complement C3 and beta2 integrin.

OBJECTIVE: Evolving evidence of anti-inflammatory effects is observed in patients with rheumatoid arthritis or ulcerative colitis following periodic adsorptive granulocyte and monocyte (GM) apheresis with a column containing cellulose acetate (CA) beads as apheresis carriers. This study was undertaken to obtain insights into mechanisms of anti-inflammatory actions of adsorptive GM apheresis with CA beads. METHODS: In a series of in-vitro experiments, we investigated the effects of plasma proteins and the leucocytes beta2 integrin (CD18) on granulocyte adsorption to CA beads. RESULTS: Granulocyte adsorption to CA beads required plasma IgG, the complement C3 and was inhibited by an antibody to leucocytes CD18. Further, hepatocyte growth factor (HGF) and interleukin-1 receptor antagonist (IL-1ra) which have strong anti-inflammatory actions were released by granulocytes that adhered to CA beads. CONCLUSIONS: Plasma IgG, C3 derived complement activation fragments and leucocytes CD18 are involved in granulocyte adhesion to CA beads and hence the release of HGF and IL-1ra.

Remnant-like lipoprotein particles as risk factors for coronary artery disease in elderly patients.

Although remnant-like lipoprotein particles (RLPs) are known to be atherogenic, the relationship between serum RLP-cholesterol (RLP-C) level and coronary artery disease (CAD) has not as yet been evaluated. This clinical study was aimed at investigating the pathological significance of serum RLP-C among several coronary risk factors with a clear focus on elderly patients. We took fasting venous blood samples to determine lipid profiles including RLP-C from 188 patients with angiographically identified CAD and 68 control patients. Overall analysis showed that the RLP-C/HDL-C ratio was higher in both single-vessel CAD group (n = 67; p < 0.01) and multi-vessel CAD group (n = 121; p < 0.001) compared to controls. Further, multiple logistic regression analysis indicated that the diabetes, HDL-C and the RLP-C/HDL-C ratio could discriminate CAD patients from controls. In patients younger than 65 years, diabetes, HDL-C, LDL-C and the LDL-C/HDL-C ratio as well as the RLP-C/HDL-C ratio could discriminate CAD. In patients 65 aged years or older, however, diabetes, triglyceride and RLP-C as well as the RLP-C/HDL-C ratio could discriminate CAD, whereas LDL-C and the LDL-C/HDL-C ratio could not. These results led us to believe that the contribution of a given risk factor to the development of CAD in elderly patients may be different from that in younger patients. In elderly patients, RLP-C rather than LDL-C was strongly associated with the development of CAD. Accordingly, serum RLP-C levels may serve as a convenient and reliable index for assessing CAD.

Cellulose acetate beads induce release of interleukin-1 receptor antagonist, but not tumour necrosis factor-alpha or interleukin-1beta in human peripheral blood.

OBJECTIVE: Dramatic improvements in clinical symptoms of rheumatoid arthritis and ulcerative colitis were observed after patients received granulocyte and monocyte adsorptive apheresis with a column containing cellulose acetate (CA) beads as adsorptive carriers. This study was to investigate the effect of CA beads on the generation of anti-inflammatory and pro-inflammatory cytokines in human blood. MATERIALS AND METHODS: We incubated human whole blood with CA beads at 37 degrees C for up to 2 h and measured tumour necrosis factor-alpha (TNF-alpha) interleukin-1beta (IL-1beta) and IL-1 receptor antagonist (IL-1ra) produced by leucocytes. IL-1ra was also measured at the inflow and outflow of a column containing CA beads as leucocyte adsorptive carriers for the treatment of patients with ulcerative colitis. RESULTS: CA beads induced significant release of IL-1ra from leucocytes, but not TNF-alpha or IL-1beta. In contrast, all three cytokines were released when leucocytes were stimulated with lipopolysaccharide. IL-1ra was also markedly elevated in the outflow of the leucocyte apheresis column. CONCLUSIONS: These results indicate that CA beads selectively induce IL-1ra release from leucocytes which should contribute to the anti-inflammatory effect of granulocyte and monocyte adsorptive apheresis with CA beads as apheresis carriers.

Impaired blood rheology by remnant-like lipoprotein particles: studies in patients with fatty liver disease.

Fatty liver disease (FLD) characterised by a high plasma levels of lipoproteins and remnant-like lipoproteins (RLP) is a risk factor for impaired microvascular blood flow, endothelial cell dysfunction and atherosclerosis. Using an immunoseparation technique with a gel mixture containing human monoclonal antibodies to apo A-I and apo B-100, we separated and measured RLP cholesterol (RLP-C) levels which reflect RLP in patients with FLD (n=20). Whole blood transit time (TT) was determined by a microchannel method (MC-FAN) which allows blood flow to be viewed via a microscope connected to an image display unit. RLP-C levels were higher (P<0.01) in FLD, 15.6 +/- 1.0 mg/dl compared with 4.8 +/- 0.5 mg/dl for controls (n=20). Similarly, TT was longer (P<0.01) in FLD, 284.5 +/- 26.1 sec/100 microl compared with 82.8 +/- 1.0 sec/100 microl for controls. Since the liver is a major site for RLP formation and degradation, it is affected to a greater extent in patients with FLD. It is likely that high levels of RLP can impair microvascular perfusion in the liver tissue and contribute to the development and progression of FLD.

Safety and efficacy of granulocyte and monocyte adsorption apheresis in patients with active ulcerative colitis: a multicenter study.

Active ulcerative colitis (UC) is characterized by activation and infiltration of granulocytes and monocytes/macrophages into the colonic mucosa. The infiltrated leukocytes can cause mucosal damage by releasing degradative proteases, reactive oxygen derivatives, and proinflammatory cytokines. The aim of this trial (conducted in 14 specialist centers) was to assess safety and efficacy of granulocyte and monocyte adsorption apheresis in patients with active UC most of whom were refractory to conventional drug therapy. We used a new adsorptive type extracorporeal column (G-1 Adacolumn) filled with cellulose acetate beads (carriers) of 2 mm in diameter, which selectively adsorb granulocytes and monocytes/macrophages. Patients (n = 53) received five apheresis sessions, each of 60 minutes duration, flow rate 30 ml per minute for 5 consecutive weeks in combination with 24.4 +/- 3.60 mg prednisolone (mean +/- SE per patient per day, baseline dose). During 60 minutes apheresis, 26% of granulocytes, 19.5% of monocytes and 2% of lymphocytes adsorbed to the carriers. At week 7, 58.5% of patients had remission or improved, the dose of prednisolone was reduced to 14.2 +/- 2.25 mg (n = 37). The apheresis treatment was fairly safe, only eight non-severe side effects (in 5 patients) were reported. Based on our results, we believe that in patients with active severe UC, patients who are refractory to conventional drugs, granulocyte and monocyte adsorption apheresis is a useful adjunct to conventional therapy. This procedure should have the potential to allow tapering the dose of corticosteroids, shorten the time to remission and delay relapse.

Ex-vivo purging of circulating monocytes results in immunovirologic improvement in partially HAART responder HIV-infected patients.

AIDS pathogenesis results from a complex array of immune alterations which include, among others, changes in the pattern of cytokine production. Some monocyte-derived cytokines, like TNFalpha play a major role in HIV pathogenesis. TNFalpha transactivates HIV NF-kB thereby inducing viral replication, potentiates HIV replication in lymphomonocytes TNFalpha is one of the main factors of HIV-induced cachexia and might be involved in HAART-associated lipodystrophy. In addition, monocytes are infectable by HIV in vitro and infected monocytes can be recovered from the blood of HIV infected patients. For these reasons, we tested whether renewal of the pool of circulating monocytes by selective monocyte apheresis may improve the immune reconstitution which follows treatment with highly active anti-retrovirals (HAART). HIV-infected HAART receiving (> 1 year) patients who were either virologically non-responders (HIV-1 RNA >50,000 copies/ml) or immunologically non-responders (CD4 counts < 200) were treated with a novel monocyte apheresis device (G-1 Adacolumn). Plasma HIV viral load, proviral DNA and phenotypic and functional immunological analyses were performed. G-1 apheresis was well tolerated, not accompanied by adverse responses, and followed by clinical improvement. TNFalpha production was suppressed and CD4 T cell counts increased. In one G-1 patient with elevated HIV-1 proviral DNA a significant reduction (from 1,500 to 40 copies/10(5) cells) was observed. Neither immunologic nor virologic parameters were modified in the control patients who received HAART alone. Thus, purging of circulating monocytes by G-1 apheresis has a dramatic suppressive effect on TNFalpha production and is followed by both clinical and immunovirological improvement. G-1 apheresis should be considered in patients in whom HAART is only partially effective.

[Aggregation of human blood platelets by remnant-like lipoprotein particles].

The action of lipoprotein lipase on chylomicrons (CM) and very low density lipoproteins (VLDL) produces remnant lipoproteins (RLP) that are rich in triglycerides, cholesterol and apolipoprotein E (apo E). Apo E serves as a ligand for the LDL receptor and mediates uptake of RLP by macrophages, vascular wall and other cells that express the LDL receptor. Uptake of RLP can profoundly alter the physiology of cells and promote atherosclerosis and thrombosis. Like RLP, blood platelets also have roles in atherosclerosis and thrombosis; hence it is likely that RLP can influence platelet activity as well. Platelet aggregation was assessed by measuring the loss of single platelets. Apo E3/3-rich RLP derived from normal human plasma VLDL and CM were prepared by an immunoseparation method. At 2.5 to 10 microliters, RLP induced platelet aggregation that increased with the dose of RLP, but decreased it at 25 to 200 microliters. Unlike apo E3/3-rich RLP, apo E4/3 (heterozygous phenotype) rich RLP caused platelet aggregation in a dose-dependent manner, without producing a bell-shape dose-response relationship. Scanning electron microscopy revealed that activated platelets had adhered to and formed aggregates on the red cell membrane. The platelet response was unaffected by aspirin, but was inhibited by apyrase (an ADP scavenger), 2-chloroadenosine (a platelet ADP-receptor antagonist) and cilostazol, a phosphodiesterase type III inhibitor. It is thought that RLP cause leakage of ADP from red cells, which then mediates platelet aggregation.

Granulocyte apheresis as a possible new approach in cancer therapy: A pilot study involving two cases.

Patients with advanced cancer often develop immunodeficiency which may be associated with granulocytosis. The granulocytes have the potential to deplete cytotoxic T cells, resulting in accelerated tumor growth and metastasis. To study the elimination of excess granulocytes using granulocyte apheresis in patients with elevated granulocyte to lymphocyte ratios, 2 patients with recurrent metastatic tumors, were selected. Granulocyte apheresis was performed by extracorporeal vein-to-vein circulation with the G-1 granulocyte and monocyte/macrophage apheresis column filled with cellulose acetate beads, each 2 mm in diameter to adsorb granulocytes and monocytes/macrophages. The patients received 1 or 2 apheresis of 30 to 50 min duration per week, at a flow rate of 30-50 ml/min, with 15 sessions constituting one therapeutic course. Apheresis markedly reduced tumor size and prolonged patient survival time without causing any serious adverse events. The results of the present study suggest that granulocyte and monocyte/macrophage apheresis may be beneficial in patients with metastasizing tumors.

Association of plasma triglyceride-rich lipoprotein remnants with coronary atherosclerosis in cases of sudden cardiac death.

Among the risk factors for coronary atherosclerosis, elevated LDL-C level is best known. The action of lipoprotein lipase on triglyceride-rich lipoproteins produces remnant lipoprotein particles enriched in cholesterol and apolipoprotein E (apo E). Apo E serves as the ligand for uptake of remnant lipoproteins via the LDL-receptor or the remnant receptor. In this study, postmortem plasma total cholesterol, triglycerides (TG), VLDL-C, HDL-C, lipoprotein (a) [Lp(a)] and remnant-like lipoprotein particles (RLP)-cholesterol, RLP-TG, apolipoproteins B, C III and E were measured, together with LDL-C to assess their potential contribution to the severity of coronary and aortic atherosclerosis of the 197 cases of sudden death (132 cardiac death and 65 non-cardiac death). In all cases, the severity of coronary atherosclerosis was determined at postmortem pathological examination. RLP-cholesterol (RLP-C) and LDL-C concentrations were significantly higher in cases with advanced coronary atherosclerosis compared with those without coronary atherosclerosis; respective median values were 13.5 vs 8.4 mg/dl (P < 0.001) and 140 vs 115 mg/dl (P < 0.05). RLP-C levels were more strongly correlated with the severity score of coronary atherosclerosis than LDL-C.

Granulocyte and monocyte apheresis suppresses symptoms of rheumatoid arthritis: a pilot study.

To investigate if granulocyte and monocyte apheresis mitigates the symptoms of rheumatoid arthritis (RA), and influences production of panmyelocytes (CD15+ CD16- cells) at the bone marrow level, 27 RA patients who had elevated granulocyte counts were recruited. The granulocyte and monocyte apheresis column (G-1 column) is an extracorporeal type device packed with 220 g cellulose acetate beads to which granulocytes and monocytes specifically adhere. Patients received apheresis of 1 hr duration twice per week, 8 times over a period of 4 weeks. To prepare CD15+CD16- cells, iliac bone marrow aspirate was obtained at baseline and at 2 weeks after completion of the apheresis course. Ex-vivo proliferation of bone marrow low density cells and production of IgM-RF were also investigated. Following granulocyte and monocyte apheresis, there was a suppressed tendency in the number of CD15+CD16- cells in patients with high bone marrow CD15+CD16- cell counts at baseline. Clinical assessments 2 weeks after the completion of apheresis therapy showed improvements in swollen joint count (P < 0.001), tender joint count (P < 0.001) and duration of morning stiffness (P < 0.005). The results suggest that granulocytes and monocytes/macrophages have a pathological role in RA and apheresis treatment to reduce or suppress these cells should benefit patients with RA.

Adenosine 5'-diphosphate as a factor in platelet aggregation induced by human plasma remnant lipoproteins.

The action of lipoprotein lipase on chylomicrons (CM) and very low density lipoproteins (VLDL) produces remnant lipoproteins (RLP) which are rich in triglycerides, cholesterol and apolipoprotein E (apo E). Apo E serves as a ligand for uptake of RLP by macrophages, platelets, endothelial cells and other cells expressing the LDL-receptor or the remnant receptor, thus having a major role in the clearance of plasma cholesterol and triglycerides, but at the same time, uptake of apo E-bearing RLP can profoundly alter the physiology of these cells and promote atherosclerosis. Like RLP, blood platelets also have roles in atherosclerosis and thrombosis, hence it is likely that RLP influence platelet activity as well. RLP derived from normal human plasma VLDL and CM were prepared using two monoclonal antibodies, anti-apo B-100 (JI-H) and anti-apo A-I (H-12) coupled to Sepharose 4B gel to form an immunoaffinity column. Lipoproteins containing apo B-100 including VLDL and LDL adsorb to (JI-H)-gel, while CM and HDL with apo A-I adsorb to (H-12)-gel. The particles in the unbound fraction (RLP) are rich in apo B-48, apo E and apo B-100 containing particles with multiple molecules of apo E. The RLP fraction with a total triglyceride of 14+/-3.2 mg/ml; cholesterol, 0.39+/-0.1 mg/ml and protein, 0.78+/-0.24 mg/ml (n=19) was added to aliquots of blood of man, rabbits, guinea pigs, mice, and rats at protein equivalents of 0.98 to 78 microg/ml blood and agitated gently at 37 degrees C for 40 sec. Platelet aggregation was measured as a fall in single platelet count. RLP induced aggregation of platelets in man (p<0.005) rabbit (p<0.0005), guinea pig (p<0.002) and mouse (p<0.0001), but no RLP induced platelet aggregation was observed in the rat blood. Scanning electron microscopy revealed that in the presence of RLP, platelets had adhered to and formed aggregates on red cells. The platelet response to RLP was inhibited by apyrase known to scavenge ADP, by 5 microM 2-chloroadenosine, a platelet ADP receptor antagonist and by 3.4 microM cilostazol, a phosphodiesterase type III inhibitor known to raise cyclic AMP level in platelets. It is thought that RLP cause leakage of ADP from red cells which then mediates platelet aggregation.

Impaired endothelium-dependent acetylcholine-induced coronary artery relaxation in patients with high serum remnant lipoprotein particles.

Acetylcholine (Ach)-induced vascular relaxation is mediated by nitric oxide released from the endothelium. Hence, impaired Ach-induced relaxation reflects endothelial dysfunction. The action of lipoprotein lipase on chylomicrons and very low density lipoproteins produces remnant lipoproteins (RLP) rich in triglycerides (TG), cholesterol (C) and apolipoprotein E (apo E). Apo E on RLP serves as a ligand for uptake of RLP by macrophages, endothelial cells and other cells expressing the LDL receptor or the remnant receptor; uptake of RLP by vascular wall cells can promote atherosclerosis. Serum C, TG, Lp(a), apo E, apo A-I, apo B, HDL-C and RLP-C were measured in 652 patients who underwent diagnostic coronary angiography. Of these, 48 (32 males and 16 females, age 59 +/- 10 years) were suspected of having ischaemic heart disease because they had chest pain, but without angiographic evidence of atherosclerotic coronary artery disease defined as a discrete stenosis or intimal irregularity, and without any other known underlying heart disease. These were selected for acetylcholine provocation test in the left coronary artery. Nineteen of 48 patients had high RLP-C ( > or = 5 mg/dl, mean 8.7 +/- 3.1 mg/dl), 29 had normal RLP-C ( < or = 5 mg/dl, mean 2.4 +/- 0.4 mg/dl, P < 0.0001). The percent change (-, constriction, or +, dilation) in coronary artery diameter after intracoronary injection of Ach was smaller in the high RLP-C group, compared with the normal RLP-C group thus, in the left anterior descending artery, -33 +/- 23 vs -8 +/- 25 in the proximal segment (P <0.01), -30 +/- 37 vs -3 +/- 29 in the mid segment (P < 0.01), -17 +/- 47 vs 16 +/- 43 in the distal segment (P < 0.001); in the left circumflex artery, -29 +/- 46 vs -9 +/- 28 in the proximal segment (P < 0.01), -29 +/- 43 vs -5 +/- 34 in the mid segment (P < 0.01), -26 +/- 43 vs 10 +/- 31 in the distal segment (P < 0.001). There were no significant differences in other lipid levels. These results suggest that there is an association between high serum RLP-C and coronary vascular endothelial cell dysfunction and that RLP-C may be taken as a marker of early stage coronary artery atherosclerosis not detectable by angiography.