Analysis of polyunsaturated fatty acids and omega-6 inflammatory pathway in hepatic ischemia–reperfusion

Hepatic vascular insufficiency accopained by periodic restoration of blood flow, places ischemic tissues at risk of additional injury a proinflammatory state. Polyunsaturated fatty acids (PUFAs) regulate inflammatory responses through the production of eicosanoids including prostaglandins (PGs), thromboxanes (TXs) and leukotrienes (LTs). The aim of this study was to assess omega-3 (n-3) and omega-6 (n-6) PUFA in liver tissue and evaluate changes in n-6 inflammatory pathway following liver ischemia-reperfusion (IR) injury. Male Wistar rats which were allowed free access to standard rat chow were included in the study. Blood vessels supplying the median and left lateral hepatic lobes were occluded with an arterial clamp for 60 min, followed by 60 min reperfusion. At the end of the experimental period, blood samples were obtained from the right ventricule to determine serum alanine aminotransferase (ALT) activity and animals were sacrificed to obtain samples of nonischemic and postischemic liver tissue. Levels of arachidonic acid (AA, C20:4n-6), dihomo-gamma-linolenic acid (DGLA, C20:3n-6), eicosapentaenoic acid (EPA, C20:5n-3) and docosahexaenoic acid (DHA, C22:6n-3) in liver tissue were determined by an optimized multiple reaction monitoring (MRM) method using ultra fast-liquid chromatography (UFLC) coupled with tandem mass spectrometry (MS/MS). Phospholipase A2 (PLA2), cyclooxygenase (COX) and prostaglandin E2 (PGE2) were measured in tissue samples to evaluate changes in n-6 inflammatory pathways. Total histopathological score of cellular damage was significantly increased following hepatic IR injury. Omega-3 and n-6 PUFA levels were significantly increased in postischemic liver tissue compared to nonischemic controls. No significant difference was observed in AA/DHA and AA/EPA ratio in postischemic liver tissue compared to control. Tissue activity of PLA2, COX and PGE2 levels were significantly increased in postischemic liver tissue compared to nonischemic controls. Current results suggest that increased hydrolysis of fatty acids via PLA2 triggers activity of COX and leads to increased PGE2 levels. Future studies evaluating agenta which block formation of eicosanoids derived from n-6 PUFAs can facilitate the development and application of treatment strategies in liver I/R injury. Keywords: Liver, ischemia–reperfusion, polyunsaturated fatty acids