Feeding long-chain polyunsaturated fats beneficially modulates the splenocyte lipid composition and oxylipin production after an ovalbumin challenge

Oral tolerance (OT) is an immunosuppression process towards innocuous food antigens. Failure to develop OT can lead to food allergy. Our lab found that the provision of arachidonic acid (ARA) and docosahexaenoic acid (DHA) in early life promotes OT development. However, the mechanisms involved remain unknown. One of the hypotheses is that ARA and DHA can be incorporated into cell membranes and metabolized into oxylipins to regulate tolerogenic responses after antigen exposure. To verify this, allergy-prone BALB/c pups consumed milk from dams fed either a control (0% ARA, 0% DHA) or an ARA+DHA (1% ARA+1% DHA) diet during suckling (0-3wks) and continued on the same diet at weaning (3-6wks). On Day 42, pups were terminated and splenocyte phospholipid fatty acid composition was measured by gas-liquid chromatography. Isolated splenocytes were incubated with ovalbumin for 48 hours and the supernatant was collected to measure oxylipin production by liquid chromatography-mass spectrometry. Data were compared using an unpaired Student t-test or Mann-Whitney test. Compared to the control group, pups fed ARA+DHA had a higher percentage of linoleic acid, ARA, eicosapentaenoic acid and DHA in splenocyte phospholipids (all P< 0.02). Feeding ARA+DHA resulted in higher splenocyte production of PGD2, 5-HETE, 15-HETE (ARA-derived oxylipins, all P≤ 0.03) and 20-HDHA (DHA-derived oxylipin, P=0.01) after ovalbumin stimulation. ARA+DHA supplementation also led to lower production of TXB2 and 12-HETE (ARA-derived oxylipins, both P< 0.01). The higher production of pro-resolving oxylipins (15-HETE and 20-HDHA) and lower production of inflammatory oxylipins (TXB2 and 12-HETE) suggests that ARA+DHA supplementation beneficially modulated the oxylipins production to support a more tolerogenic immune response which is consistent with OT development. Our research shows that oxylipins likely play a role in the regulatory effects of dietary long-chain polyunsaturated fats on food allergy, enhancing the understanding of their immunoregulatory effects in food allergy prevention.