Helen F. Goode

Decreased antioxidant status and increased lipid peroxidation in patients with septic shock and secondary organ dysfunction

OBJECTIVE To determine antioxidant vitamin concentrations, lipid peroxidation, and an index of nitric oxide production in patients in the intensive care unit (ICU) with septic shock and relate the findings to the presence of secondary organ failure. DESIGN A prospective, observational study. SETTING A nine-bed ICU in a University teaching hospital. PATIENTS Sixteen consecutive patients with septic shock, defined as: a) clinical evidence of acute infection; b) hypo- or hyperthermia (< 35.6 degrees C or > 38.3 degrees C); c) tachypnea (> 20 breaths/min or being mechanically ventilated); d) tachycardia (> 90 beats/min); e) shock (systolic pressure < 90 mm Hg) or receiving inotropes. Fourteen patients also had secondary organ dysfunction. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS Antioxidant vitamin concentrations were significantly lower in the patients than the reference range obtained from a comparable group of healthy controls. The mean plasma retinol (vitamin A) concentration was 26.5 +/- 19.3 micrograms/dL compared with 73.5 +/- 18.3 micrograms/dL in healthy subjects (p < .01). Additionally, 13 (81%) patients had retinol values below the lower limit of our reference range (< 37.0 micrograms/dL). Tocopherol (vitamin E) plasma concentrations were below the reference range in all patients (< 9.0 mg/L), with a mean value of 3.6 +/- 2.0 mg/L compared with 11.5 +/- 1.3 mg/L in healthy subjects (p < .001). Plasma beta carotene and lycopene concentrations were undetectable (< 15 micrograms/L) in eight (50%) patients, and below our reference range (< 101 micrograms/L and < 154 micrograms/L, respectively) in the remaining patients. In the five patients with three or more dysfunctional secondary organs, plasma thiobarbituric acid-reactive substances were significantly increased (p < .05), suggesting increased lipid peroxidation. Concentrations of thiobarbituric acid-reactive substances correlated negatively with both plasma retinol and plasma tocopherol (r2 = .42, p < .01 and r2 = .48, p < .005, respectively). In the five patients from whom we were able to collect urine, nitrite excretion was increased approximately 400-fold (p < .001). CONCLUSIONS These data indicate decreased antioxidant status in the face of enhanced free radical activity, and suggest potential therapeutic strategies involving antioxidant repletion.

Free radicals and antioxidants in sepsis

Objectives:The clinical condition of sepsis is caused by the release of numerous mediators from many cells. The purpose of this review is to describe the results of studies in which the role of free radicals and/or the potential therapeutic value of antioxidants are assessed. Data Sources:The studies described in this review come from a variety of sources, including Med-Line CD-ROM computerized database, Index Medicus, and references identified from the bibliographies of pertinent articles and books. Reports were confined to English language articles from 1966 to 1992. Study Selection:All retrieved references in which free-radical activity was assessed or antioxidants were measured or administered in sepsis or endotoxemia were included. This selection process encompassed clinical, animal and in vitro cell culture work. Data Extraction:Cited literature was found in reputable peer-reviewed clinical or basic science journals. Data Synthesis:Any contradictions in the results of studies are discussed. Conclusions:There is evidence that free radicals play an important role in the pathogenesis of sepsis. Antioxidant therapy has the potential to protect against such injury. It is suggested that combination therapy, which augments the endogenous antioxidant defenses, is likely to be the best approach. (Crit Care Med 1993; 21:1770–1776)

Zinc concentrations in pure populations of peripheral blood neutrophils, lymphocytes and monocytes

It is doubtful if the measurement of plasma or serum zinc is of value in assessing zinc status. Leucocyte zinc has been suggested as an alternative since it may be representative of tissue zinc stores; but in many studies poorly defined cell populations make interpretation difficult. This paper describes detailed techniques for the isolation and analysis of pure populations of neutrophils, lymphocytes and monocytes. Zinc concentrations (± 1SD) in normal subjects were 1·;26 ± 0·;27 nmol/mg protein, 1·;85 ± 0·;32 nmol/mg protein and 2·;58 ±0·;65 nmol/mg protein in neutrophils, lymphocytes and monocytes respectively. Fasting caused a significant decrease in neutrophil and lymphocyte zinc, and an increase in monocyte zinc. Supplementation of zinc-replete subjects with 135 mg zinc/day for 3 weeks had no significant effect on cellular zinc concentrations.

The effect of anticoagulant choice on apparent total antioxidant capacity using three different methods

We assessed total antioxidant capacity using three different methods, in plasma samples treated with either EDTA or heparin as anticoagulant, from 26 healthy subjects. Total antioxidant capacity was determined using an oxygen electrode (as the total peroxyl radical-trapping antioxidant parameter), by enhanced chemiluminescence, and by measurement of the antioxidant-mediated quenching of the absorbance of a radical cation. The choice of anticoagulant had a profound effect on antioxidant capacity with heparinized plasma giving consistently higher values than plasma anticoagulated with EDTA. Using the oxygen electrode the mean value was 786·5 ± 171·5 μmol/L (heparin) compared to 681·4 ± 160·4 μmol/L (EDTA, P < 0·01). The chemiluminescence technique gave a mean antioxidant capacity of 915·6 ± 214·1 μmol/L in heparin samples and 714·4 ± 195·4 μmol/L in EDTA samples (P < 0·0001). The absorbance quenching technique gave a mean value of 867·0 ± 199·2 μmol/L (heparin) and 675·5 ± 245·4 μmol/L (EDTA, P < 0·001). All methods tested showed comparable results for EDTA plasma, but the chemiluminescence technique gave higher apparent antioxidant capacity than either of the other two techniques when heparin plasma was used. We suggest that either heparin is interacting to enhance antioxidant protection perhaps through release of superoxide dismutase, or the chelation of metal ions by EDTA is limiting the activity of antioxidant metalloenzymes. Consistency in the choice of anticoagulant is clearly extremely important.

Monocyte zinc andIn vitro prostaglandin E2 and interleukin-1β production by cultured peripheral blood monocytes in patients with Crohn's disease

This study investigated the relationship between zinc status and prostaglandin E2 and interleukin-1β production by cultured monocytes in patients with Crohns disease. Monocyte zinc was significantly decreased in both 12 inpatients and 22 outpatients compared with controls (P<0.001) but lymphocyte and polymorphonuclear cell zinc were normal. When cultured monocytes from 10 outpatients with Crohns disease were stimulated with lipopolysaccharide, prostaglandin E2 production increased markedly, coupled with a fall in monocyte zinc. In matched controls, prostaglandin E2 production was significantly less and monocyte zinc remained stable. No difference in interleukin-1 release was noted between patients and controls. The addition of prednisolone to cell cultures suppressed prostaglandin E2, interleukin-1 synthesis, and monocyte zinc did not change. Zinc chloride augmented prostaglandin E2 production in patients, but not controls, and interleukin-1 remained stable. These results demonstrate a link between low monocyte zinc concentration and excessive prostaglandin production in patients with Crohns disease.

The effects of acute infection on indices of zinc status

Various indices of zinc status were assessed in 12 patients with acute urinary tract or chest infections on Day 1 and Day 7 of the infection. Leucocyte counts were raised on Day 1 but had returned to near normal by Day 7. Plasma zinc was decreased on Day 1 in conjunction with depressed plasma albumin concentrations (r = 0.71, p < 0.001) but both had returned to normal by Day 7. Mononuclear cell zinc was raised in all patients on Day 1 compared to Day 7 and control values, but polymorphonuclear cell zinc remained unchanged. However, polymorphonuclear cell alkaline phosphatase activity was grossly increased on Day 1 and correlated with leucocyte count (r = 0.61, p < 0.01). Plasma alkaline phosphatase activity was variable. These results indicate that in patients with infections measurement of plasma mononuclear cell zinc concentration and alkaline phosphatase activity are misleading indicators of zinc status. Polymorphonuclear cell zinc is unaffected by leucocytosis, inflammation and stress and may therefore provide a more reliable index of zinc status in such patients.

The effect of dietary vitamin E deficiency on plasma zinc and copper concentrations

Vitamin E and zinc have a number of functions in common, including membrane stabilisation, antioxidant function and modulation of prostaglandin metabolism. Previous studies have shown vitamin E malabsorption during zinc depletion and it appears that there is an interaction between the two nutrients. In this study we have investigated whether vitamin E deficiency affects zinc and copper concentrations in experimental animals. Male Wistar rats were maintained on a vitamin E deficient diet for either 6 or 10 months. At the end of the experimental period all animals had undetectable plasma vitamin E levels and increased red cell fragility. Plasma zinc concentrations were significantly reduced in all vitamin E deficient animals compared to control rats (p<0.002) and copper levels were reciprocally elevated (p<0.002). It appears likely that decreased zinc levels may represent redistribution of circulating zinc to tissues and cells as a secondary antioxidant, or for membrane stabilisation or prostaglandin synthesis.

Correction of cellular zinc depletion by oral zinc supplementation in elderly subjects

Immune function declines with age, and has been implicated in the increased incidence of cancer and infections in the elderly. In this hospital, many elderly patients have evidence of zinc depletion. In the present study, we supplemented those elderly patients who had depressed polymorphonuclear cell (PMNC) zinc levels with 135 mg oral zinc sulphate for 4 weeks. Plasma and PMNC zinc increased markedly but the percentage of peripheral blood T-lymphocytes expressing the surface markers CD3, CD4 and CD8 were unchanged. Plasma concentrations of vitamins A and E also remained constant. This study confirms the 25-30% incidence of cellular zinc depletion in this patient population, and demonstrates that zinc concentrations can be brought back to within normal limits by oral zinc supplements, but with no effect on T-cell phenotypes.