In detail, the rank of affinity toward [CysLT.sub.1]R is LTD4 > LTC4 > LTE4 whereas for [CysT.sub.2]R is LTC4 = LTD4 >> LTE4 [9, 10].
Nevertheless, the administration in rat and dog of LY203647, described as a potent and selective antagonist of responses to both LTD4 and LTE4, did not alter the magnitude of myocardial ischemia .
Leukotrienes LTA4, LTB4, LTC4, LTD4 and LTE4 are metabolized at different levels via the 5-1ipoxygenase pathway in response to certain antigens causing bronchoconstriction, increased mucous production, and inflammation (Bisgaard, 2001; Coffey & Peters-Golden, 2003; Krawiec & Wenzel, 1999; Lasley, 2003).
It inhibits the binding of three leukotrienes (LTC4, LTD4 and LTE4) that are responsible for smooth muscle constriction and hyperresponsiveness after contact with an allergen challenge including exercise (Krawiec & Wenzel, 1999).
These endogenous mediators show different affinity toward their receptors : LTD4 indeed is the most potent ligand for CysLTR-1 followed by LTC4 and LTE4
, whereas LTC4 and LTD4 equally bound CysLTR-2, while LTE4
shows only low affinity to this receptor .
They exert these effects by inhibiting pro-inflammatory arachidonic acid (AA) metabolites, release of platelet-activating factor (PAF), increasing formation of anti-inflammatory eicosapentaenoic acid (EPA) derivatives.6,7 In most studies, omega-3 fatty acid addition to diets reduced production of prostaglandin E2 (PGE2), thromboxane B2 (TXB2), LTE4
and LTB4 from inflammatory cells.
Sisteinil lokotrienler (LTC4, LTD4, LTE4
) ve LTB4 RSV enfeksiyonlu cocuklarda ve fare orneklerinde defalarca nazofaringeal ve trakeobronsiyal salgi larda saptanmislardir (48).
The exposure of eosinophils to LTE4
also induces cAMP production .
The most reproducible and informative biomarker to distinguish NERD from ATA is a high-level urinary LTE4
5-LO generates a wide variety of mediators, through the action of specialized terminal enzymes variously expressed in different cell types, which act on the initial 5-LO products and their immediate derivatives, like leukotriene (LT) A4, to yield leukotriene B4 and the cysteinyl-leukotrienes (CysLT), LTC4, LTD4, and LTE4
Urinary leukotriene E4 (LTE4
, a validated marker of proinflammatory cysteinyl leukotriene production) and 11-dehydro-thromboxane B2 (11-DHTXB2) were quantified using liquid chromatography-tandem mass spectrometry .
The 5-LO pathway leads to the formation of two biologically relevant classes of leukotrienes (LTs): non-cysteinyl LTs such as [LTB.sub.4];and cysteinyl-LTs (cys-LTs) such as [LTC.sub.4],LTD4, and LTE4
; and the activity of 5-LO seems to be a common step in LXA4 synthesis .