Study Set Content:
Lipid mediators that are produced from arachidonic acid (AA) present in membrane
phospholipids and stimulate vascular and cellular reactions in acute inflammation.
prostaglandins & leukotrienes
is a 20-carbon polyunsaturated fatty acid that is derived from dietary sources or by synthesis from a precursor molecule, the essential fatty acid linoleic acid.
AA
AA-derived mediators, they are derived from 20-carbon fatty acids; Greek eicosa \= 20
Eicosanoids
What synthesizes eicosanoids?
Cyclooxygenases & Lipoxygenases
generate prostaglandins
Cyclooxygenases
produce leukotrienes and lipoxins
Lipoxygenases
mast cells, macrophages, endothelial cells, and many other cell types, and
are involved in the vascular and systemic reactions of inflammation
Prostaglandins
They are generated by the actions of two cyclooxygenases, called
COX - 1 & COX - 2
constitutively expressed in most tissues, where it may serve various homeostatic functions and is also induced by inflammatory stimuli.
COX - 1
mainly confined to cells that are participating in inflammatory reactions.
COX - 2
Prostaglandins are named based on common structural features coded by a letter which are:
PGD, PGE, PGF, PGG, & PGH
The most important ones in inflammation are
PGE2, PGD2, PGF2a, PGI2 (prostacyclin) & thromboxane A2 (TxA2)
a potent platelet-aggregating agent and vasoconstrictor, is itself unstable and rapidly converted to its inactive form
TxA2
is responsible for the formation of prostacyclin (PGI2) and its stable end product PGF1a.
prostacyclin synthase
a vasodilator and a potent inhibitor of platelet aggregation
Prostacyclin
is the major prostaglandin made by mast cells; is also a chemoattractant for neutrophils.
PGD2
is hyperalgesic, making the skin hypersensitive to painful stimuli such as intradermal injection of suboptimal concentrations of histamine and bradykinin
PGE2
produced in leukocytes and mast cells by the action of lipoxygenase and are involved in vascular and smooth muscle reactions and leukocyte recruitment.
Leukotrienes
the predominant one in neutrophils; converts AA to 5-hydroxyeicosatetraenoic acid
5-lipoxygenase
chemotactic for neutrophils and is the precursor of the leukotrienes
5-hydroxyeicosatetraenoic acid,
