Oxidative stress in critically ill neonatal foals

Abstract

Background: Oxidative injury occurs in septic people, but the role of oxidative stress and antioxidants has rarely been evaluated in foals.

Objectives/hypothesis: To measure reactive oxygen species (ROS), biomarkers of oxidative injury, and antioxidants in neonatal foals. We hypothesized that ill foals would have higher blood concentrations of ROS and biomarkers of oxidative injury and lower concentrations of antioxidants compared to healthy foals.

Animals: Seventy-two hospitalized and 21 healthy neonatal foals.

Methods: Prospective cohort study. Reactive oxygen species (hydrogen peroxide [H₂O₂]), biomarkers of oxidative injury (malondialdehyde [MDA], protein carbonyl), and antioxidants (superoxide dismutase [SOD], catalase [CAT], glutathione, and glutathione reductase [GR] and peroxidase [GPx]) were measured from foals at admission. Measured variables were compared between healthy and ill foals using a 1-way ANOVA by Tukey's multiple comparisons test.

Results: Ill foals (n = 51) had significantly higher mean concentrations of H₂O₂ (healthy 2.6 ± 1.4 nmol/mL, ill 6.8 ± 4.6 L nmol/mL; 95% CI), MDA (healthy 31.2 ± 14.4 nmol/mL, ill 114.3 ± 94.0 nmol/mL; 95% CI), and protein carbonyl (healthy 0.07 ± 0.01 nmol/mg protein, ill 0.12 ± 0.02 nmol/mg protein, 95% CI). Significant lower CAT (healthy 0.4 ± 0.3 mU/mg protein, ill 0.02 ± 0.02 mU/mg protein, 95% CI), glutathione (healthy 238.5 ± 101.9 μg/mL, ill 110.7 ± 37.8 μg/mL, 95% CI; P < .0001), GR (healthy 1.6 ± 1.8 mU/mg protein, ill 0.4 ± 0.5 mU/mg protein, 95% CI), and GPx (healthy 0.01 ± 0.003 mU/mg protein, ill 0.007 ± 0.002 mU/mg protein, 95% CI) were also noted.

Conclusions and clinical importance: Oxidative stress and lower antioxidant concentrations occur in ill and bacteremic neonatal foals. These variables should be considered during the treatment of ill foals.

Keywords: antioxidant; ascorbic acid; oxidative injury; reactive oxygen species; sepsis.

FIGURE 1

(A‐K) Comparison of various measured variables between control groups and mild, moderate, and severe illness groups. *Indicates a statistically significant difference between groups; please see the results section for specific P values. CAT, catalase; GPX, glutathione peroxidase; GR, glutathione reductase; GSH : GSSG, reduced to oxidized glutathione ratio; H₂O₂, hydrogen peroxide; MDA, malondialdehyde; ns, not significant; SOD, superoxide dismutase.

FIGURE 2

Heat map displaying Pearson correlation coefficients between different oxidative stress and antioxidant defense variables, culture status, sepsis score, and case fatality rate. Minimal statistical significance was accepted at P < .05. Positive correlations are in blue, and negative correlations are in red. CAT, catalase; culture (+/−), blood culture positive or negative; GR, glutathione reductase; GSH + GSSG, total glutathione; GSH, reduced glutathione; GSH : GSSG, reduced to oxidized glutathione ratio; GSSG, oxidized glutathione; H₂O₂, hydrogen peroxide; MDA, malondialdehyde; PC, protein carbonyl; SOD, superoxide dismutase.