Clinical and inflammatory effects of dietary l-arginine in patients with intractable angina pectoris

N itric oxide (NO) is primarily synthesized by endothelial cells and is a potent vasodilator. Larginine, a precursor of the enzyme nitric oxide synthase (NOS)1 has been extensively studied in animal models and in human beings. L-arginine enhances NO bioavailability in the vascular endothelium,2 attenuates enhanced monocyte-vascular endothelium adhesiveness, and restores endothelium-dependent vasodilation.3 L-arginine can be given intra-arterially,4 intravenously,5 and orally.6 The advantage of the oral route is the longer half-life and longer term effect, which are both short (,1 minute) in the intra-arterial and the intravenous routes. This study assesses the effects of oral L-arginine on the clinical and inflammatory state of patients with coronary artery disease and intractable angina pectoris. • • • The inclusion criteria were coronary artery disease documented by coronary angiography, angina pectoris functional class IV, previous revascularization (coronary angioplasty or coronary artery bypass surgery), and a thallium perfusion scan that demonstrated a reversible perfusion defect in $1 segment. The exclusion criteria included significant heart failure (New York Heart Association more than or equal to class III), chronic disease, and malignancy. This study was a prospective, case-controlled, pilot study. Ten men were enrolled, all had undergone coronary angiography and angioplasty, and 9 had undergone coronary artery bypass surgery before enrollment. All suffered angina pectoris class IV and had frequent attacks of angina at rest and at night despite large doses of b blockers, calcium channel blockers, nitrates, and aspirin; no further intervention could be offered to these patients. The average age was 72 6 10 years (range 48 to 80); all were men with hypercholesterolemia (well treated), 6 were hypertensive, and 4 had diabetes mellitus (noninsulin dependent). Mean left ventricular ejection fraction was 56 6 13%. Each patient had a clinical examination before starting the study, and monthly afterwards for 3 months. Patients were requested to fill out The Seattle Angina Questionnaire7,8 before treatment and after 1 and 3 months of treatment. Blood samples were taken at enrollment and at each of the 3 monthly visits. The serum was separated by centrifugation and stored at 270° C until analyzed in 1 batch. Serum concentration of soluble intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), E-selectin, P-selectin, and L-selectin were measured by monoclonal antibody based enzyme-linked immunosorbent assay kits (British Biotechnology Products Ltd., Abdington, Oxfordshire, United Kingdom and Takara Biomedicals, Kurume, Japan). Briefly, known concentrations (for a standard curve) of adhesion molecules and serum samples (100 ml) were added to 96-well plates precoated with the first monoclonal antibody and incubated for 1 to 2 hours at 37°C. After washing, a second antibody labeled with horseradish peroxidase was added for additional inclusion (1 hour at 37°C) and the plates were vigorously washed again. Substrate solutions were then added for a short incubation period (30 minutes) followed by the addition of 1 N H2SO4, and the reaction stopped. Absorbance was read at 492 nm. Serum concentrations of cellular adhesion molecules were calculated based on the standard curve. Circulating tumor necrosis factor-a, interleukin 1-b, and interleukin-6 were measured by specific non–crossreactive radioimmunoassay as described. 9-11 Cytokine concentrations were read from a log plot of percent specific binding versus the log concentration of serially diluted standard cytokines from the linear portion of the curve (between 35% to 75% specific binding). The lower limit of detection of the assays were 40 pg for tumor necrosis-a, and 78 pg for interleukin 1-b and interleukin-6. Data were expressed as mean 6 SD. For data comparisons the nonparametric test for 2 matched samples and the paired Student’s t test were used. All patients took L-arginine 9 g daily for 3 months. No one reported side effects from the L-arginine (constipation, diarrhea, hypotension, abdominal cramps). Seven patients improved clinically (from angina pectoris functional class IV to functional class II); their improvement was persistent and continued as long as L-arginine was taken. Discontinuing L-arginine supplementation (after 3 months) caused a “rebound phenomena,” and they deteriorated to functional class IV. One patient improved to functional class III, and 2 patients remained in functional class IV. After 1 month of L-arginine, cell adhesion molecule and cytokine levels remained stable throughout 3 months of the study. Individual data are presented in Table I. In 7 patients who had a significant clinical improvement, P-selectin level decreased from 338 6 40 pg/ml to 304 6 31 pg/ml (p 5 0.01), ICAM level decreased from 315 6 57 pg/ml to 274 6 36 pg/ml (p 5 0.08), and E-selectin changed from 47 6 10 to 44 6 11 (p 5 0.09). VCAM and L-selectin levels From the Cardiology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland; and Cardiology Department and Internal Medicine B, Tel-Aviv Sourasky Medical Center and Tel-Aviv University, Tel-Aviv, Israel. Dr. Miller’s address is: Catheterization Laboratory, Tel-Aviv Medical Center, 6 Weizman St., Tel-Aviv, 64239, Israel. E-mail: himiller@tasmc.health.gov.il. Manuscript received November 19, 1998; revised manuscript received and accepted January 14, 1999.