Eicosanoids Flashcards
Eicosanoids are derivatives of … C fatty acids
20
What is meant by polyunsaturated fatty acids?
More than one double bond
Docosanoids are derivatives of … C fatty acids
22
What is a healthy ratio of linoleic acid to a-linoleic acid (Omega 6/3)?
4:1
Eicosanoids act as what?
Local signaling molecules
What are the 4 major categories of Eicosanoids?
Prostaglandins (PG), Prostacyclins, Leukotrienes (LT), Thromboxanes (TX)
Where are PGs formed?
Many tissues
Where are Prostacyclins produced?
Endothelium
Where are Leukotrienes produced?
Immune system cells
Where are Thromboxanes produced?
Platelets
What structure is the basis for all PGs?
Prostanoic acid
Which bonds projecting from the rings are in a trans position?
8-12
All PGs have a hydroxyl at which carbon?
C-15
What is the order of double bonds for PGs designation?
13-14, 5-6, 17-18
Leukotrienes are …. structures containing … bonds
Open-chain; 3-5 double bonds
What are all leukotrienes derivative of?
HPETEs
What does the numerical subscript indicate in the naming of leukotrienes?
The number of double bonds
Is arachidonic acid an omega 3?
No, it is an omega 6
How many double bonds in arachidonic acid? Where are they?
20:4 delta 5, 8, 11, 14
Arachidonic acid is central to the synthesis of which lipids?
Prostaglandins, thromboxanes, and leukotrienes
Where are aa and other precursors for eicosanoids stored in the cells?
C2 position of membrane pospholipids
What enzyme releases aa from storage?
Phospholipase a2
Linoleic acid is the parent of which fatty acid family?
Omega 6
a-linolenic acid is the parent of which fatty acid family?
Omega 3
What is the delta designation of linoleic acid?
18:2^9,12
What is the delta designation of a-linolenic acid?
18:3^9,12,15
The physiological effects of the various eicosanoids may be manipulated by changing what?
Fatty acid composition of the diet.
Thromboxanes are similar to PG except that…
The ring is 6-membered, oxy-heterocyclic
What is the definition of a leukotrienes?
Open-chain structures containing 3-5 double bonds
What class of enzymes initiate conversion of arachidonate and other precursors into PG’s and TX’s?
Cyclooxygenases (COX)
What do cyclooxygenases initiate?
Conversion of arachidonate and other precursors into PGs, TXs
What class of enzymes convert arachidonate into HPETEs (precursor for LTs) or into lipoxins?
Lipoxygenases (LOX)
Lipoxygenases (LOX) convert what?
Arachidonate into HPETEs, (precursor for LT), or into lipoxins
Which pathway is referred to as the cyclic pathway?
COX
Which pathway is referred to as the linear pathway?
LOX
When are eicosanoids inactivated?
When the hydroxyl at C15 is oxidized to a ketone.
How to steroids act as an anti-inflammatory?
Induce synthesis of lipocortin, which inhibits phospholipase A2
How do NSAIDs work?
Inhibit COX
Is aspirin reversible or irreversible?
Irreversible
Is ibuprofen reversible or irreversible?
Reversible
What do steroids and NSAIDs modulate?
Modifying aa release
The capacity for arachidonic acid synthesis is greater with which diet addition?
G-linolenic acid (GLA)
