Oxidative stress in polymorphonuclear leukocytes (PMNs) and mononuclear cells (MNCs) may be independent predictors of the risk for cardiovascular events, according to a large study conducted by Osaka City University investigators.

Kenichi Yasunari and colleagues conducted a prospective study of 529 subjects followed for a mean of 1 year to study the association between PMN and MNC oxidative stress and cardiovascular events. Cardiovascular events were defined as heart failure, need for coronary revascularization, and stroke. Intracellular oxidative stress of PMNs and MNCs was measured by gated flow cytometry using carboxyfluorescin diacetate bis-acetoxymethyl ester. In vitro studies had previously shown that oxidative stress in smooth muscle cells can be increased by chronic high glucose administration, oxidized LDL cholesterol, and high blood pressure

Traditional risk factors were also evaluated, including age, sex, body mass index, lipid levels, hemoglobin A1c, and mean blood pressure, as well as the nontraditional risk factors of insulin action, homeostatis model assessment (HOMA-IR), and C-reactive protein. The study population was divided into four groups: normotensive subjects with no diabetes; hypertensive subjects with no diabetes; normotensive subjects with diabetes; and hypertensive subjects with diabetes.

Multiple regression analysis showed a significant relationship between mean blood pressure and PMN oxidative stress (r = 0.115; p = 0.012); as mean blood pressure increased, PMN but not MNC oxidative stress increased (Figure 1). There was also a significant relationship between increasing C-reactive protein and increases in MNC but not PMN oxidative stress (r = 0.121; p = 0.625) (Figure 2). Also, as hemoglobin A1c increased, PMN and MNC oxidative stress increased. With regard to the subsets of subjects, the most significant increase in PMN and MNC oxidative stress was observed in the hypertensive/diabetes group.

In sum, an increase in PMN oxidative stress was significantly related to higher levels of blood pressure and hemoglobin A1c. An increase in MNC oxidative stress was significantly related only to C-reactive protein, suggesting a link to vascular inflammation.

During 1 year of follow-up, there were 56 cardiovascular events among the 529 subjects: 39 strokes and 17 cases of heart diseases, including 11 cases of heart failure and 6 nonfatal myocardial infarctions. A case-control study showed that both PMN and MNC oxidative stress was increased in cases versus controls, but the other traditional and nontraditional risk factors were not different.

According to a Cox proportional analysis, both PMN and MNC oxidative stress were significantly predictive of the risk of a cardiovascular event, even after an adjustment for other risk factors. In fact, among all 12 risk factors, the only significant predictive factors were PMN oxidative stress, for which the relative risk was 1.48, and MNC oxidative stress, with a relative risk of 1.28. The results suggest that hypertension leads to the activation of PMNs and that C-reactive protein is related to MNC oxidative stress. The measurement of PMN and MNC oxidative stress may help identify risk of future cardiovascular events, Dr. Yasunari predicted.

Asymmetrical dimethyl-arginine (ADMA), an endogenous inhibitor of nitric oxide synthase, is a novel marker of vascular endothelial dysfunction and atherosclerosis. Plasma levels of ADMA may also predict which patients will experience restenosis after stent implantation, according to a multicenter study presented at the meeting by Masashi Fujita of Kansai Rosai Hospital, Amagasaki.

Neointimal hyperplasia after stent implantation is partially due to endothelial activation, and reduction of nitric oxide release causes endothelial dysfunction. To check the relation between the plasma level of ADMA, nitric oxide and stent restenosis, the investigators measured the plasma level of ADMA and the end-products of nitric oxide in 37 patients (mean age 65) with coronary artery disease before stent implantation and after 6 months.

The plasma level of ADMA was measured by high-performance liquid chromatography and nitric oxide was measured by the Griess method. Intravascular ultrasound (IVUS) was also performed on all lesions before and 6 months after stent implantation. Stent volume and intimal hyperplasia volume were calculated by 3-dimensional IVUS analysis with 0.5-mm intervals throughout the stented segment, and the percent volume stenosis was calculated. Pre-stent reference diameter was 2.79 mm, minimal lumen diameter was 1.15 mm, and diameter of stenosis was 60%. Post-procedure, these numbers were 3.29 mm, 2.93 mm, and 11.78%, respectively.

Indeed, baseline ADMA levels seemed to predict the risk for stent restenosis. The plasma level of ADMA before stent implantation was much higher in patients with progressive neointimal hyperplasia than non-progressive neointimal hyperplasia. Since patients with type 2 diabetes have an increased risk for restenosis, ADMA levels were examined separately in these patients and found to be significantly higher in diabetics than in patients without type 2 diabetes.

Percent volume restenosis was also significantly correlated with the baseline plasma ADMA level. The higher the ADMA level, the more progressive the neointimal hyperplasia. Percent volume restenosis was also correlated significantly with fasting blood sugar and hemoglobin A1c (Figure 3). No association was found between percent volume stenosis and LDL or total cholesterol levels (Figure 4). The investigators concluded that the plasma level of ADMA is important in the pathophysiology of neointimal hyperplasia and may be a predictor of coronary stent restenosis.