Leukotrienes
Main Entry: leuˇkoˇtriˇene
Pronunciation: lü-k - tr - n
Function: noun
: Any of a group of eicosanoids that are generated in basophiles, mast cells, macrophages, and human lung tissue by lipoxygenase-catalyzed oxygenation especially of arachidonic acid and that participate in allergic responses (as bronchoconstriction in asthma)
A family of biologically active compounds derived from arachidonic acid by oxidative metabolism through the 5-lipoxygenase pathway. They participate in host defense reactions and patho-physiological conditions such as immediate hypersensitivity and inflammation. They have potent actions on many essential organs and systems, including the cardiovascular, pulmonary, and central nervous system as well as the gastrointestinal tract and the immune system.
Leukotrienes are inflammatory lipid mediators whose formation from arachidonic acid is initiated by 5-lipoxygenase (5-LO). 5-LO is also expressed in neurons and can be activated by brain injuries, whereas 5-LO inhibitors can provide neuro-protection. The expression of the 5-LO gene appears to be inhibited by the pineal hormone, melatonin, which also is a potent neuro-protective agent. Melatonin deficiency normally develops with aging. We found that old or pinealectomized, i.e., melatonin-deficient, rats are more susceptible to kainite-triggered excitotoxic limbic brain injury than the corresponding young or sham-pinealectomized controls, and that pinealectomy or aging result in an enhanced expression of 5-LO in limbic structures.
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