(±)12(13)-DiHOME is the diol form of (±)12(13)-EpOME , a cytochrome P450-derived epoxide of linoleic acid also known as isoleukotoxin. [1] It is formed from 12(13)-EpOME by soluble epoxide hydrolase (sEH) in neutrophils. [2] 12(13)-DiHOME is toxic to Sf21 cells expressing sEH and to lacZ-expressing control cells, unlike isoleukotoxin, which is only toxic to cells containing sEH.[1] [2] Levels of 12(13)-DiHOME are increased in rat spinal cord following burn injury, and it enhances cold tolerance, increases fatty acid uptake into brown adipocytes, and decreases serum triglyceride levels in mice. Levels are also elevated in bronchoalveolar lavage fluid (BALF) in humans following exposure to biodiesel exhaust and in exhaled breath condensate in patients with allergic asthma following allergen exposure.[5] [6] Plasma levels of 12(13)-DiHOME are increased immediately following moderate-intensity exercise in mice and humans, an effect that can be prevented by brown adipose tissue removal in the mouse.[7]
Cytochrome P450 metabolites of arachidonic acid, such as 11(12)-EpETrE and 14(15)-EpETrE have been identified as endothelium derived hyperpolarizing factors with vasodilator activity. Soluble epoxide hydrolase (sEH) catalyzes the conversion of EpETrEs to the corresponding DiHETrEs thereby diminishing their activity. Inhibitors of sEH may therefore have clinical utility for treating hypertension and systemic inflammation. S-NEPC is a colorimetric substrate used to measure sEH activity. It also is a substrate for Glutathione S-transferase, microsomal epoxide hydrolase and porcine liver carboxylesterase. Hydrolysis of S-NEPC by sEH yields 4-nitrophenol which can be quantified spectrophotometrically at 405 nm. S-NEPC is adaptable for use in 96-well microwell plate readers.
(±)9(10)-DiHOME, the diol derivative of (±)9(10)-EpOME—a cytochrome P450-derived epoxide of linoleic acid also known as leukotoxin—is formed through the action of soluble epoxide hydrolase (sEH) in neutrophils. It exhibits toxicity towards Sf21 cells expressing sEH as well as tolacZ-expressing control cells, differing from leukotoxin which only harms sEH-containing cells. Furthermore, combined exposure to 9(10)- and 12(13)-DiHOME leads to cell death in rabbit renal proximal tubule cells by disrupting mitochondrial respiration, and causes lung injury, respiratory distress, and mortality in mice, highlighting its role as a toxic lipid mediator. Specifically, 9(10)-DiHOME has been associated with acute respiratory distress syndrome (ARDS), a severe and often deadly complication in patients with major burns. Elevated levels of this compound have been detected in the bronchoalveolar lavage fluid (BALF) of women, but not men, with chronic obstructive pulmonary disease (COPD), and its levels are also increased in patients with allergic asthma, indicating its significance in respiratory conditions.