ELSEVIER Brief Communication ASCORBYL RADICAL EFFECT Free Radical Biology & Medicine.Vol. 20, No. I. pp. 139-143, 1996 Copyright © 1995 ElsevierScience Inc. Printed in the USA. All rights reserved 0891-5849/96 $15.00 + .00 0891-5849(95)02022-3 FORMATION IN PATIENTS WITH SEPSIS: OF ASCORBATE LOADING HELEN F. GALLEY, *$ MICHAEL J. DAVIES,* and NIGEL R. WEBSTER* *Academic Unit of Anaesthesia & Intensive Care, University of Aberdeen, UK; and *Department of Chemistry, University of York, UK (Received 21 March 1995; Revised 27 June 1995; Accepted 10 July 1995) Abstract--Patients with sepsis have low concentrations of antioxidants, including ascorbic acid, and also have increased concentrations of markers of free radical damage. Although ascorbic acid is a potent antioxidant, it can act as a prooxidant by promoting iron-catalysed reactions. We measured baseline total vitamin C and bleomycin-detectable "free" iron levels and ascorbyl radical concentrations before and after intravenous infusion of l g ascorbic acid in patients with sepsis and healthy control subjects. Vitamin C concentrations were decreased in patients compared to healthy subjects (p < 0.0001), and "free" iron was increased (p < 0.002). Preinfusion ascorbyl radical concentrations were not different in patients and controls. Postinfusion ascorbyl radical levels increased in both controls and patients, with larger increases in healthy subjects (p < 0.0001), suggesting suboptimal basal vitamin C levels and increased scavenging of a constant oxidant pool by ascorbate in the controls. In the patients, who were all vitamin C deficient, infused ascorbate was rapidly consumed, either via the promotion of redox cycling of iron or as a result of radical scavenging. This study demonstrates markedly different handling of infused ascorbate in patients with sepsis and healthy subjects, and further studies are needed to elucidate the relative anti- and pro-antioxidant mechanisms of ascorbate in patients with raised "free" iron levels. Keywords--Ascorbic acid, Free radicals, Iron, Electron paramagnetic resonance spectroscopy, Septicemia, Spin traps, Vitamin C INTRODUCTION Intensive care patients with sepsis have been shown to have abnormally low concentrations of protective antioxidants j 3 and high levels of the products of free radical attack L2 associated with clinical disease sever- ity.1 These observations suggest that these patients are exposed to increased levels of oxidative stress and en- dogenous free radical production, which may be aris- ing from activated phagocytic cells, thought to be in- volved in the pathophysiology of the disease process. 4 Activated phagocytes generate a wide range of reactive oxygen species including superoxide radicals, hydro- gen peroxide, singlet oxygen, hypochlorous acid, and nitric oxide. Though some of these species are inher- ently reactive and damaging, others such as hydrogen peroxide require the presence of other cofactors to ex- ert maximum damage. The toxicity of hydrogen perox- ide is known to be exacerbated by the presence of Formerly Goode. Address correspondence to: Helen F. Galley, Academic Unit of Anaesthesia & Intensive Care, Department of Medicine & Therapeu- tics, Polwarth Building, Foresterhill, Aberdeen AB9 2ZD, UK. certain low-valency transition metal ions such as cop- per and iron, which can catalyse the generation of the highly damaging hydroxyl radical through metal-ion catalysed Haber-Weiss and Fenton reactions. 5 The po- tentially toxic nature of such transition metal ions dic- tates that in normal circumstances they are found in the circulation in a bound form, rendering them unable to participate in such reactions. The amount of un- bound "catalytic" metal ions present in the circulation may therefore play a key role in determining the levels of free radicals produced and, hence, the degree of oxidant stress. 6 Elevated levels of catalytic metal ions have been demonstrated in a number of diseases in- cluding sepsis. 7 In addition, activation of the comple- ment system as part of the inflammatory response me- diates the endotoxin-induced inhibition of ascorbic acid transport, suggesting that inadequate tissue con- centrations of vitamin C may result even when circulat- ing levels appear normal, s To combat such increased oxidant stress resulting from radical generation, antioxidant therapy, including ascorbic acid administration, has been advocated. However, although ascorbic acid is a potent antioxi- 139