Plasma platelet-derived growth factor levels in coronary circulation in unstable angina pectoris

Nicorandil effects on platelet function, Hs-CRP, MMP-9 and myocardial antioxidation in patients with unstable angina

Nicorandil effects on platelet activation and myocardial antioxidant function in patients with unstable angina were studied. A total of 157 patients with unstable angina in the First People's Hospital of Foshan were selected and divided into experimental and control group. Patients in experimental group were treated with conventional drugs and nicorandil (15 min/day), t.i.d., for 21 days as one course of treatment, while those in control group were treated with conventional drugs. After treatment, serum indexes were detected and compared between the two groups of patients. Compared with that in control group, the platelet function of patients in the experimental group was significantly improved, and there was a statistically significant difference (P<0.05). Serum anti-oxidation factors in both groups were increased after treatment, and they were increased more significantly in experimental group (P<0.05). Serum inflammatory factors, high-sensitivity C-reactive protein and matrix metalloproteinase-9, also declined significantly in the experimental group. Nicorandil reduces inflammatory response and promotes stability of myocardial function in the treatment of unstable angina.

Platelet-derived growth factor improves cardiac function in a rodent myocardial infarction model

OBJECTIVES

The translation of cardioprotective therapies for myocardial infarction requires a preclinical demonstration of improved cardiovascular function following acute coronary occlusion. We previously showed that pretreatment of rodent hearts with platelet-derived growth factor (PDGF) promotes angiogenesis and decreases the extent of myocardial injury measured by histology. The present study aimed to determine the correlation of these histological findings with noninvasive measures of improvement in cardiac function.

METHODS

Rats were treated with intramyocardial injections of PDGF (100 ng) or phosphate buffer solution (PBS) (n = 6 per group) 24 h prior to acute, permanent ligation of the left anterior descending artery and the extent of myocardial injury was assessed by Masson's trichrome staining 14 days later. To assess the physiological effects of PDGF pretreatment after coronary occlusion, cardiac function was assessed noninvasively by electrocardiography, exercise testing and echocardiography and correlated with direct histological measures.

RESULTS

Physiological studies demonstrated that PDGF resulted in lower ST-segment elevation at the time of coronary occlusion (0.12 +/- 0.02 mV above baseline) than in PBS control rats (0.35 +/- 0.05 mV; P < 0.05). Exercise testing 14 days after coronary occlusion revealed that PDGF pretreatment resulted in faster maximal exercise speeds (28.54 +/- 3.98 m/min) than in control rats (24.98 +/- 3.13 m/min; P < 0.05). Echocardiography also revealed that the left ventricular factional shortening in the PDGF-pretreated rats was significantly greater (18.47 +/- 12.21%) than in control animals (4.91 +/- 7.21%; P<0.05).

CONCLUSIONS

These studies demonstrate that PDGF pretreatment improves cardiac function following acute coronary occlusion. Strategies based on the cardioprotective actions of PDGF may provide a significant advance in the treatment of myocardial infarction.

Elevated levels of serum vascular endothelial growth factor in patients with polycythaemia vera

Angiogenesis seems to be a prominent event of myeloproliferative diseases. There are few reported data on angiogenesis and the significance of its stimulator, the vascular endothelial growth factor (VEGF), in polycythaemia vera (PV). We report our observation of elevated serum VEGF levels in patients suffering from PV. Twenty patients with PV and 20 age-matched healthy subjects were enrolled. VEGF levels were measured by a quantitative sandwich enzyme immunoassay. Serum VEGF levels in PV were found to be very significantly higher than in healthy individuals (569.7 +/- 101.2 vs. 164.7 +/- 32.8 pg/ml, p = 0.001). We found no correlation between VEGF and haemoglobin, platelet or leucocyte counts in the patient group. Different therapeutic regimens had no influence on VEGF levels. However, in the control group, we observed a positive correlation between VEGF levels and platelet counts (r = 0.52, p = 0.02). Platelet counts did not differ between patients and healthy subjects. We also evaluated platelet-poor plasma VEGF levels in 10 patients and in all healthy individuals. We found very low levels of VEGF, approximately zero in most cases, in both groups and there was obviously no difference between the two groups. Our results indicate that VEGF is overproduced in PV. However, follow-up studies are needed to verify the role of this factor.

Increased blood vascular endothelial growth factor levels in patients with acute myocardial infarction

Vascular endothelial growth factor (VEGF) is a growth factor for vascular endothelial cells in vitro. The present study was designed to determine whether serum VEGF levels increase in patients with acute myocardial infarction (AMI) compared with patients with stable exertional angina and control subjects, and to examine the serial changes of serum VEGF levels in patients with AMI. We examined serum VEGF levels by using antibody prepared from serum immunized with human VEGF(121). The serum VEGF level (pg/ml) was higher (p < 0. 0001) on admission in the patients with AMI (177 +/- 19) than in those with stable exertional angina (61 +/- 7) and control subjects (62 +/- 6). The serum VEGF level (pg/ml) of the patients with AMI was 177 +/- 19 on admission, 125 +/- 9 on day 3, 137 +/- 11 on day 5, 242 +/- 18 at 1 week, and 258 +/- 22 at 2 weeks after admission. The value was higher on admission than on day 3 after admission (p = 0.014), the values were higher at 1 week and 2 weeks than on admission, on day 3, and 5 (p < 0.01). Furthermore, there were correlations between peak VEGF levels at 1 week or 2 weeks after admission and peak creatine kinase levels. The increase of VEGF on admission in the patients with AMI may be due to the hypoxia of acute myocardial ischemia. The elevation at 1 week and 2 weeks from the onset may cause the development of collateral circulation in relation to the healing of the infarction site.

A vascular bed-specific pathway

The endothelial nitric oxide synthase (eNOS) gene is induced by a variety of extracellular signals under both in vitro and in vivo conditions. To gain insight into the mechanisms underlying environmental regulation of eNos expression, transgenic mice were generated with the 1,600-bp 5' flanking region of the human eNos promoter coupled to the coding region of the LacZ gene. In multiple independent lines of mice, transgene expression was detected within the endothelium of the brain, heart, skeletal muscle, and aorta. beta-galactosidase activity was consistently absent in the vascular beds of the liver, kidney, and spleen. In stable transfection assays of murine endothelial progenitor cells, the 1,600-bp promoter region was selectively induced by conditioned media from cardiac myocytes, skeletal myocytes, and brain astrocytes. Cardiac myocyte-mediated induction was partly abrogated by neutralizing anti-platelet-derived growth factor (PDGF) antibodies. In addition, promoter activity was upregulated by PDGF-AB. Analysis of promoter deletions revealed that a PDGF response element lies between -744 and -1,600 relative to the start site of transcription, whereas a PDGF-independent cardiac myocyte response element is present within the first 166 bp of the 5' flanking region. Taken together, these results suggest that the eNos gene is regulated in the cardiac endothelium by both a PDGF-dependent and PDGF-independent microvascular bed-specific signaling pathway.

Platelet-derived growth factor-induced vasodilatation in mesenteric resistance arteries by nitric oxide: blunted response in spontaneous hypertension

Platelet-derived growth factor (PDGF) is a potent mitogen for vascular smooth-muscle cells, but its effects on vasomotion remain controversial. Both vasoconstriction and vasodilatation of isolated rat aortic rings have been reported. The effects of PDGF on responses of perfused mesenteric resistance arteries from normotensive Wistar-Kyoto and spontaneously hypertensive rats were studied by using a video dimension analyzer. PDGF receptor messenger RNA (mRNA) expression in endothelial cells isolated from mesenteric arteries of both normotensive and hypertensive rats was studied by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. In both normotensive and hypertensive rats, PDGF-BB concentration-dependently induced vasodilatation (maximal response, 25 +/- 4% and 13 +/- 4% at 10(-8) M, respectively; p < 0.05, normotensive vs. hypertensive rats). Endothelium removal or preincubation with N(omega)-nitro-L-arginine methyl ester, but not indomethacin, inhibited these relaxations, indicating that these vasodilatations are endothelium dependent and mediated by nitric oxide. RT-PCR analysis showed that both PDGF-alpha and -beta receptor mRNAs were present in endothelial cells of the mesenteric arteries of normotensive as well as hypertensive rats. In addition, relaxations induced by both PDGF-AA and -AB were significantly less than those induced by PDGF-BB in both strains, suggesting that vasodilatation is mediated mainly by the PDGF-beta receptor subtype. No vasoconstriction was observed after application of PDGF-BB to both normotensive and hypertensive mesenteric arteries with or without endothelium. In rat mesenteric resistance arteries, PDGF induces endothelium-dependent vasodilatation mediated by nitric oxide. At sites where PDGF is released or locally produced, therefore, the growth factor may participate in regulating vascular tone, and this endothelium-dependent regulation is attenuated in spontaneous hypertension.

PDGF mediates cardiac microvascular communication

The diversity of cellular and tissue functions within organs requires that local communication circuits control distinct populations of cells. Recently, we reported that cardiac myocytes regulate the expression of both von Willebrand factor (vWF) and a transgene with elements of the vWF promoter in a subpopulation of cardiac microvascular endothelial cells (J. Cell Biol. 138:1117). The present study explores this communication. Histological examination of the cardiac microvasculature revealed colocalization of the vWF transgene with the PDGF alpha-receptor. Transcript analysis demonstrated that in vitro cardiac microvascular endothelial cells constitutively express PDGF-A, but not B. Cardiac myocytes induced endothelial expression of PDGF-B, resulting in PDGF-AB. Protein measurement and transcript analysis revealed that PDGF-AB, but not PDGF-AA, induced endothelial expression of vWF and its transgene. Antibody neutralization of PDGF-AB blocked the myocyte-mediated induction. Immunostaining demonstrated that vWF induction is confined to PDGF alpha-receptor-positive endothelial cells. Similar experiments revealed that the PDGF-AB/alpha-receptor communication also induces expression of vascular endothelial growth factor and Flk-1, critical components of angiogenesis. The existence of this communication pathway was confirmed in vivo. Injection of PDGF-AB neutralizing antibody into the amniotic fluid surrounding murine embryos extinguished expression of the transgene. In summary, these studies suggest that environmental induction of PDGF-AB/alpha-receptor interaction is central to the regulation of cardiac microvascular endothelial cell hemostatic and angiogenic activity.

The assessment of platelet derived growth factor concentration in post myocardial infarction and stable angina patients

Platelet derived growth factor (PDGF) has been implicated in the pathogenesis of atherosclerosis. PDGF is released by aggregating platelets and monocytes which gather around sites of arterial injury. In the study reported here the concentration of plasma PDGF was measured in post myocardial infarction (MI) patients (n = 28), angina patients (n = 25), and control subjects (n = 27). Venous blood samples were taken and the concentration of PDGF determined by an enzyme linked immunosorbent assay (ELISA). Plasma PDGF concentrations were significantly higher in the post MI group compared to both the control and angina groups (P < or = 0.05). The increase in PDGF concentration may be due to increased activation of platelets or monocytes since these two cells are major sources of plasma PDGF. High concentrations of PDGF in the circulation could further accelerate the progression of the disease.

The omnipotent platelet. Part II: Further observations

Observation of platelet responses during acute injury or pathology can provide important information. The initial response is thrombocytopenia followed by thrombocytosis. In the case of injury with negative X-ray and appropriate thrombocytosis, a bone scan is indicated. The platelet responds like a sedimentation rate, which indicates the course of the injury or pathology.

Increased expression of genes for platelet-derived growth factor in circulating mononuclear cells of hypercholesterolemic patients

Platelet-derived growth factor (PDGF) is implicated in the accumulation of smooth muscle cells in atherosclerotic lesions following monocyte migration through the vascular endothelium. We show here a 15- to 20-fold increase in expression of PDGF-A and -B genes (as measured by a quantitative reverse transcription-polymerase chain reaction assay of mRNA concentration) in circulating monocytes of hypercholesterolemic and hyperlipidemic patients compared with normocholesterolemic individuals. Strong positive correlations between PDGF-A and -B mRNA concentrations indicate that the two genes are coordinately regulated in mononuclear cells in both normal and hypercholesterolemic individuals. PDGF gene expression in patients correlates with concentrations of plasma total cholesterol and low-density lipoprotein cholesterol, a proven risk factor for atherosclerosis. Activation of monocyte PDGF expression may be an important component of the atherosclerotic risk associated with raised cholesterol levels and may represent an essential step in the early stages of atherogenesis. However, the marked increases in PDGF mRNA levels in patients with modest hypercholesterolemia compared with normal subjects suggest that other factors are involved. The relationship of monocyte PDGF expression to other atherosclerotic risk factors and to the different stages of atherosclerosis needs to be carefully evaluated.

The omnipotent platelet

This information was derived from the increase in platelets of patients following fractures and/or bone surgery and in conjunction with a vast amount of published literature. The increase in numbers of platelets reflects the extent of bone involvement, especially noted in the hip, knee, post-coronary artery bypass graft, and multiple fractures. The role of the platelet in any and all tissues, i.e. soft tissue or bone, whether beneficial or detrimental, is multifunctional. The platelet responds to all physiologic and pathologic states and, if tissue involved is sufficient, the role of the platelet becomes obvious.

Platelet-derived growth factor (PDGF) in patients with different degrees of chronic arterial obstructive disease

Platelet activation and platelet-derived growth factor (PDGF) play a pivotal role in the pathogenesis of atherosclerosis. Evidence has been accumulating that in the evolution of chronic arterial obstructive disease (CAOD) platelets are also crucially important. The aim of the present study was, therefore, to assess plasma levels of PDGF in patients with different degrees of CAOD according to Fontaine. Twenty patients (17 men, 3 women, mean age sixty-eight +/- seven years) with intermittent claudication (Fontaine stage II) entered the study and their PDGF levels were assessed by radioimmunoassay. Ten additional patients (7 men, 3 women, mean age seventy-three +/- seven years) with more severe CAOD (leg pain at rest/skin ulcers) were also studied. Ten healthy subjects (6 men, 4 women, mean age fifty-four +/- six years) comprised the control group. Patients in stage II were reinvestigated after sixty days of a "training" procedure. Patients with both intermittent claudication and more severe disease had higher levels of PDGF than controls (controls 165.9 +/- 119.1 pg/mL; Fontaine stage II 403.5 +/- 218.4; Fontaine stage III/IV 578.1 +/- 637.2: ANOVA P = 0.04) with no difference between the two groups of patients. After the training period, PDGF levels were significantly higher than at baseline (863.7 +/- 819.6 pg/mL vs 403.5 +/- 218.4) but without significant improvement of physical performance. The elevation of PDGF levels in blood from CAOD patients could be the result of marked platelet activation due to interaction with a widely damaged peripheral vasculature. The same was not true for coronary heart disease, in which normal values of PDGF in venous blood were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular and cellular concepts in atherosclerosis

Atherosclerosis is a complex disease of uncertain cause. Its pathobiology is believed to represent an abnormal expression of the processes of vascular healing. Etiologic models derive from a 'response to injury' paradigm and can be divided into three separate disease stages: endothelial dysfunction, smooth muscle proliferation and architectural disruption. The initiating event of endothelial dysfunction is unknown, but is believed to be related to low-density lipoproteins and/or their oxidized derivatives. Endothelial injury is signalled to the smooth muscle cells of the media by three routes: direct cell-cell interaction, secretion of soluble growth factors and monocyte-derived cytokines. Monocytes are recruited by the endothelium and invade the subintimal space by a complex interaction of a variety of adhesion proteins and receptors on both cell types. Smooth muscle cell proliferation is initiated by a change in phenotype expression from 'contractile' to 'synthetic' resulting from the binding of fibronectin to specific integrin receptors. Three functionally distinct activities may represent separate subtypes of the 'synthetic phenotype': migration from the media to the intima, increased proliferation and inappropriate extracellular matrix synthesis. The loss of normal regulatory control and anchorage independence of proliferation suggest a relationship to oncogenic transformation. Both migration and proliferation result from the binding of platelet-derived growth factor-like factors to smooth muscle cell receptors, which initiates a cascade of intracellular molecular events leading either to cytoskeletal locomotory restructuring or cell cycle activation. Both pathways also appear to be coregulated by integrin receptors and both depend upon phosphorylation of cell membrane, cytosolic and nuclear regulatory proteins. Clinical expression of atherosclerosis may follow sudden loss of architectural integrity of the intimal plaque by three different mechanisms: plaque fissuring, intraluminal plaque rupture or intramural hemorrhage related to abnormal vessel wall stress and/or biochemistry.

Increased plasma plasminogen activator inhibitor activity after coronary spasm

To examine whether ischemic attack induced by coronary spasm changes fibrinolytic activity, we examined plasma levels of tissue-plasminogen activator antigen and plasminogen activator inhibitor activity before and after hyperventilation test in patients with variant angina and in control subjects. In 12 patients with variant angina, ischemic attack associated with ST-segment elevation on the electrocardiogram was induced by hyperventilation and plasma plasminogen activator inhibitor activity levels increased significantly 15 min after the attacks (pre, 5.1 +/- 0.8; immediately after, 5.8 +/- 1.1; and 15 min after, 7.2 +/- 0.9 IU/ml, P < 0.01). In 12 control subjects, plasminogen activator inhibitor activity levels did not change. Plasma tissue-plasminogen activator antigen levels did not change in both two groups. We conclude that coronary artery spasm increases plasma plasminogen activator inhibitor activity and that it may thereby lead to the coronary thrombus formation.