Fish Oil Supplementation Decreases Oxidative Stress but Does Not Affect Platelet‐Activating Factor Bioactivity in Lungs of Asthmatic Rats

Abstract

Dietary fish oil supplementation increases the content of n-3 polyunsaturated fatty acids (PUFA) in cellular membranes. The highly unsaturated nature of n-3 PUFA could result in an enhanced lipid peroxidation in the oxidative environment characteristic of asthma. The oxidative reaction cascade culminates in an increased production of components associated to oxidative stress and of an important proinflammatory mediator platelet-activating factor (PAF)-like lipid. We evaluated the effect of fish oil supplementation in asthmatic rats upon the PAF bioactivity and parameters related to oxidative stress in the lung. Fish oil supplementation of asthmatic rats resulted in lower concentrations of nitrite (1.719 ± 0.137 vs. 2.454 ± 0.163 nmol/mL) and lipid hydroperoxide (72.190 ± 7.327 vs. 120.200 ± 11.270 nmol/mg protein). In asthmatic animals, fish oil increased the activities of superoxide dismutase (EC 1.15.1.1) (33.910 ± 2.325 vs. 24.110 ± 0.618 U/mg protein) and glutathione peroxidase (EC 1.11.1.9) (164.100 ± 31.250 vs. 12.590 ± 5.234 U/mg protein). However, fish oil did not affect PAF bioactivity in lung tissue of asthmatic rats (0.545 ± 0.098 340/380 vs. 0.669 ± 0.101 340/380 nm ratio). Considering the two-step process--oxidative stress and PAF bioactivity--fish oil exhibited a divergent action on these aspects of asthmatic inflammation, since the supplement lowered oxidative stress in the lungs of asthmatic rats, presenting an antioxidant effect, but did not affect PAF bioactivity. This suggests a dual effect of fish oil on oxidative stress and inflammation in asthma.

A systematic review of the association between fish oil supplementation and the development of asthma exacerbations

“…Fish oil supplementation significantly lowered the concentrations of both BALF nitrite (~30%, p < 0.005) and lipid hydroperoxide (~40%, p < 0.001) in asthmatic rats. 15 Furthermore, increased antioxidant levels of superoxide dismutase (~40%, p < 0.05) and glutathione peroxidase (13-fold increase, p < 0.05) were observed in the fish-oil asthma group as compared to the control group. 15 Fish oil also resulted in significantly lower catalase activity (p < 0.001) in non-asthmatic rats.…”

“…15 Furthermore, increased antioxidant levels of superoxide dismutase (~40%, p < 0.05) and glutathione peroxidase (13-fold increase, p < 0.05) were observed in the fish-oil asthma group as compared to the control group. 15 Fish oil also resulted in significantly lower catalase activity (p < 0.001) in non-asthmatic rats. 15 …”

“…15 Fish oil also resulted in significantly lower catalase activity (p < 0.001) in non-asthmatic rats. 15 …”

“…Zanatta et al’s 15 (1.25 EPA:DHA ratio) study was the only study that measured markers of oxidative stress, namely, BALF nitrite, lipid hydroperoxide, superoxide dismutase, and glutathione peroxidase. Fish oil supplementation significantly lowered the concentrations of both BALF nitrite (~30%, p < 0.005) and lipid hydroperoxide (~40%, p < 0.001) in asthmatic rats.…”

Diet and asthma

“…However, there was no effect on the bioactivity of a pro-inflammatory mediator (platelet-activating factor) in lung tissue (38). Further suggesting complex and divergent effects of the components of fish oil supplements on allergic airway inflammation, an experiment in OVA-sensitized mice showed that high dietary intake of DHA for 6 weeks leads to significantly increased eosinophils and IL-6 in BAL, and a trend for increased levels of IL-4 and IL-13 in BAL.…”