11,12-Epoxyeicosatrienoic Acid Attenuates Synthesis of Prostaglandin E₂in Rat Monocytes Stimulated with Lipopolysaccharide

Abstract

Cytochrome P-450 monooxygenase (epoxygenase)-derived arachidonic acid (AA) metabolites, including 11,12-epoxyeicosatrienoic acid (11,12-EET), possess anti-inflammatory and antipyretic properties. Prostaglandin E2 (PGE2), a cyclooxygenase (COX)-derived metabolite of AA, is a well-defined mediator of fever and inflammation. We have tested the hypothesis that 11,12-EET attenuates synthesis of PGE2 in monocytes, which are the cells that are indispensable for induction of fever and initiation of inflammation. Monocytes isolated from freshly collected rat blood were stimulated with lipopolysaccharide (LPS; 100 ng/2 x 10(5) cells) to induce COX-2 and stimulate generation of PGE2. SKF-525A, an inhibitor of epoxygenases, significantly augmented the lipopolysaccharide-provoked synthesis of PGE2 in cell culture in a concentration-dependent manner. It did not affect, however, elevation of the expression of COX-2 protein in monocytes stimulated with LPS. 11,12-EET also did not affect the induction of COX-2 in monocytes incubated with lipopolysaccharide. However, 11,12-EET suppressed, in a concentration-dependent fashion, the generation of PGE2 in incubates. Preincubation of a murine COX-2 preparation for 0-5 min with three concentrations of 11,12-EET (1, 5, and 10 microM) inhibited the oxygenation of [14C]-labeled AA by the enzyme. The inhibitory effect of 11,12-EET on COX-2 was time-and-concentration-dependent, suggesting a mechanism-based inhibition. Based on these data, we conclude that 11,12-EET suppresses generation of PGE2 in monocytes via modulating the activity of COX-2. These data support the hypothesis that epoxygenase-derived AA metabolites constitute a negative feedback on the enhanced synthesis of prostaglandins upon inflammation.

Epoxyeicosatrienoic Acids Function as Selective, Endogenous Antagonists of Native Thromboxane Receptors: Identification of a Novel Mechanism of Vasodilation

“…Statistical comparisons of EC 50 and E max responses were made using a paired, two-tailed t test or ANOVA (Dunnett's post test analysis). phenylephrine under identical conditions [any reversal of phenylephrine but not U-46619 tone was abolished by pretreatment with indomethacin, consistent with the observations that these EET and DHET analogs can serve as substrates for COX (Carroll et al, 1993) or modulate its function (Kozak et al, 2003)]. …”

“…Although there are a few examples of EETinduced reversal of a non-TP receptor spasmogen (e.g., endothelin-1 or phenylephrine) (Zou et al, 1996;Oltman et al, 1998;Larsen et al, 2006), such examples might be a result of downstream effects on COX rather than a direct receptor/ion channel interaction. For example, 5,6-EET and 8,9-EET are substrates for COX (forming vasoactive prostaglandin analogs) (Carroll et al, 1993;Homma et al, 1993), and 11,12-EET has been shown to inhibit COX-2 in a time-and concentration-dependent manner (Kozak et al, 2003).…”

Inhibition of lipoxygenases and cyclooxygenase-2 enzymes by extracts isolated from Bacopa monniera (L.) Wettst

“…COX and 5-LOX are two important enzymes which catalyze the formation of mediators involved in the inflammatory process. Inhibitors of COXs are the main strays of current therapy aimed to modulate pain, inflammation and to control fever (Kozak et al, 2003). Many COX-2 or 5-LOX inhibitors have been developed as drugs to treat inflammation; however, some have been withdrawn from the market, indicating a need for inhibitors free of side effects (Chen et al, 2005).…”

Inhibition of soluble epoxide hydrolase reduces LPS-induced thermal hyperalgesia and mechanical allodynia in a rat model of inflammatory pain

“…Effects of EETs on other membrane ion channels have also been reported, including inhibition of voltage-activated Na + channels (Lee et al, 1999), and either potentiation or inhibition of Ltype voltage-activated Ca ++ channels (Chen et al, 1999;Fang et al, 1999). The antiinflammatory mechanisms of EETs that may play a role in alleviating inflammatory pain are their ability to inhibit PGE 2 production (Fang et al, 1998;Kozak et al, 2003) as well as NF-κB-mediated gene transcription and cell adhesion molecule 1 expression induced by TNFα, IL-1α, or LPS (Node et al, 1999). Thus, the ability of sEHIs and EETs to modulate ion channel function and block many aspects of the inflammatory process suggest potential mechanisms by which these compounds might suppress peripheral and perhaps central sensitization of pain pathways.…”