Eicosanoid inhibition

Four principal mechanisms have been cited to explain the diverse physiological mechanisms of ginger. Broadly, these are (1) eicosanoid inhibition, (2) serotonin antagonism, (3) substance P release, and (4) Ca2-i-/ATPase activity. 

Eicosanoid inhibition Umbelliferone (I) Inhibitor of prostaglandin synthesis [213]... 

Compounds 111 having structural features of the dual cyclooxygenase (COX)/5-lipooxygenase (5-LO) inhibitor tepoxalin and the 5-LO inhibitor ABT-761 were prepared. Many of these hybrid compounds are potent COX and 5-LO inhibitors two compounds (111, r =McO, R = R" = R = H, R = NH2, R = Me and r = MeO, R = R = Me, R" = R = H, R = Cl) inhibited eicosanoid biosynthesis in an ex vivo assay, but neither improved on the main deficiency of tepoxalin, duration of 5-LO inhibitory activity (99BMCL979). Compounds 111 inhibit the production of arachidonic acid products associated with 5-lipoxygenase and cyclooxygenase and are useful in the treatment of inflammatory disorders (99USP5925769). 

Prostaglandins are a group of lipid autacoids known as eicosanoids. They are produced from membrane phospholipids and found in almost every tissue and body fluid. They are involved in a number of physiological processes including inflammation, smooth muscle tone and gastrointestinal secretion. In the central nervous system they have been reported to produce both excitation and inhibition of neuronal activity. 

Patients with chronic idiopathic urticaria, who develop cutaneous reactions in response to aspirin, display certain similarities in eicosanoid profile with AIA. The mechanism of the reactions is often related to COX-1 inhibition [18]. Therefore, aspirin and all drugs that inhibit COX-1 should be avoided in patients who already have had cutaneous reactions to NSAID. Coxibs are usually well tolerated, although occasional adverse reactions have been reported [19, 20]. For treatment of the reactions, antihistamines are usually sufficient, but in more severe cases adrenaline and corticosteroids may be warranted. 

FIGURE 57-2. Eicosanoid synthesis pathway. Cyclooxygenase is inhibited by nonsteroidal anti-inflammatory drugs and aspirin. (From Widmaier EP, Raff H, Strang KT, et al, (eds.) Vander, Sherman, Luciano s Human Physiology The Mechanisms of Body Function. 9th ed. New York McGraw-Hill 2004, Figure 5-11.)... 

Hyperforin, the major constituent in Hypericum perforatum (St. John s Wort), inhibits the enzymatic activity of 5-lipoxygenase and COX-1 in platelets, acts as a dual inhibitor of 5-lipoxygenase and COX-1, and might have some potential in inflammatory and allergic diseases connected to eicosanoids (32), Several Hypericum species are of medicinal value in Asia and the Pacific. One of these is Hypericum erectum Thunb., the potential of which as a source of 5-lipoxygenase is given here. 

Pang L, de las Heras B, Hoult JR. A novel diterpenoid labdane from Sideritis javalam-brensis inhibits eicosanoid generation from stimulated macrophages but enhances arachidonate release. Biochem Pharmacol 1996 51 863-868. 

A variety of biochemical and molecular mechanisms have been described to explain how PUFAs can modulate immune cell fate and function. The primary mechanism of action of dietary n-3 PUFAs involves the replacement of AA in the lipid membrane of the cells with either EPA or DHA. This, in effect, competitively inhibits the oxygenation of AA by the COX enzymes. For example, the EPA-induced suppression in the production of AA-derived eicosanoids is followed by a subsequent increase in the production of those from EPA. Generally, the EPA-derived eicosanoids are considered to be much less potent than those from AA, thus explaining, at least partially, the anti-inflammatory effects of PUFAs. A similar mechanism of action can be demonstrated for DHA, either directly or by retroconversion to EPA. 

Sambo 1988). Nonsesquiterpene lactones in feverfew were also found to inhibit eicosanoid synthesis with high potency (Sumner et al. 1992). 

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