Antioxidant enzyme activities in patients with severe sepsis

Background

Severe sepsis with systemic inflammatory response caused by excessive secretion of proinflammatory mediators is associated with significant morbidity and mortality. Experimental evidence suggests that reactive oxygen species may be important mediators of cellular injury during sepsis.

Objective

To assess antioxidant enzyme activities in critically ill patients with sepsis compared with control patients without sepsis and to evaluate changes of antioxidant enzyme activities in the convalescent period after successful treatment of sepsis.

Patients and methods

It is a prospective case–control study in a medical adult intensive care unit with 13 beds. Routine venous blood samples were obtained from septic patients (n = 16, age 26–80 years) with APACHE II score > 10 without antioxidant treatment and from 16 age-matched, sex-matched hospitalised control patients without clinical and laboratory signs of sepsis. Paired convalescent samples taken 1 week after recovery were available in five patients. We measured the activity of superoxide dismutase with copper and zinc (EC 1.15.1.1, CuZn-SOD) in erytrocytes, based on superoxide generation by xanthine oxidase and tetrazolium reduction. The activity of paraoxonase (EC 3.1.8.1, PON1) in serum with paraoxon and phenylacetate, and the serum concentrations of total, high-density lipoprotein (HDL) cholesterol and C-reactive protein were also measured. We considered P < 0.05 to be statistically significant.

Results

There was higher CuZn-SOD activity (mean ± SEM, 30,332.5 ± 2369.9 U/g Hb) in septic patients in comparison with healthy controls (23,192.2 ± 1078.7 U/g Hb; P = 0.01). On the other hand, PON1 activity measured with paraoxon (5.58 ± 0.71 U/ml) resp. phenylacetate (17,642.3 ± 1501.1 U/ml) was lower in sepsis when compared with controls (9.55 ± 0.93 U/ml resp. 29,181.1 ± 2198,6 U/ml; P < 0.01 resp. P = 0.001). After recovery there was no difference in activity of both CuZn-SOD and PON1 of patients and controls. Moreover, we found positive correlation between activity of PON1 and level of total and HDL cholesterol in sepsis and after recovery. We observed no age and sex dependence in activity of both enzymes in septic patients and controls.

Conclusion

Patients admitted to the intensive care unit with severe sepsis exhibit abnormal anitoxidant enzyme activities.