The arachidonic acid (AA) cascade plays a central role in the biosynthesis of lipid mediators (LMs) with anti-inflammatory properties cascade plays an important role in the biosynthesis of lipid mediators (LMs). Additionally, in mammalian cells, phospholipids release AA by cytosolic phospholipase A2 (cPLA2) upon stimulation.
There are 3 different pathways for arachidonic acid converting to bioactive lipid mediators (LMs).  The cyclooxygenases (Cox) catalyze the initial step in the formation of inflammation-initiating prostaglandins (PGs) and thromboxane (TX). Additionally, lipoxygenases (LOXs) form hydroperoxyeicosatetra enoic acids (HPETEs), leukotrienes (LTs), and lipoxins (LXs). Furthermore, AA is transformed to monohydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs) by cytochrome P450 enzymes. EETs have anti-inflammatory properties. And It will lose its beneficial effects by soluble epoxide hydrolase (sEH) degradation.

Diflapolin is a highly active dual 5-lipoxygenase-activating protein (FLAP)/sEH inhibitor with anti-inflammatory efficacy.

Diflapolin inhibits 5-LOX product formation in intact human monocytes with an IC₅₀ of 30 nM. It also inhibits the formation of 5-LOX products in neutrophils (IC₅₀=170 nM). sEH is a bifunctional enzyme with a C-terminal epoxide hydrolase (EH) and an N-terminal phosphatase activity. Additionally, in a cell-free assay, Diflapolin suppresses the activity of isolated sEH with an IC₅₀ of 20 nM.

The human liver cancer cell line HepG2 highly expresses sEH and it is a suitable cell-based test system for evaluation of Diflapolin for sEH inhibition. AUDA is a well-recognized reference inhibitor of sEH. both Diflapolin and AUDA inhibit cellular sEH activity to ~50% at 1 µM. However, in a cell-free assay against the phosphatase activity, Diflapolin failed to inhibit the phosphatase activity even at high concentrations (10 µM).
In zymosan-induced peritonitis male CD-1 model. Diflapolin exhibits potent anti-inflammatory properties in in-vivo experiments. It Induces a significant reduction of LTC4 and LTB4 peritoneal levels before zymosan injection. Whatmore, this effect is starting from the dose of 1 mg/kg and comparable to the effect of MK886.

In conclusion, Diflapolin is a valuable chemical tool for studying the biology of FLAP and sEH. Besides, it may have the therapeutic potential of dual FLAP and sEH inhibition in inflammatory and cardiovascular disorders.

Reference:

Garscha U, et al. Sci Rep. 2017;7(1):9398. Published 2017 Aug 24.