Eicosanoids and COX Enzymes Overview

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Questions and Answers

What is the major starting material for the synthesis of eicosanoids?

Leukotriene A4

Prostaglandin E1

Cyclooxygenase

Arachidonic Acid (correct)

Which enzyme is responsible for producing leukotrienes from Arachidonic Acid?

Cyclooxygenase

Lipoxygenase (correct)

Phospholipase A2

Cytochrome P450

Which of the following statements best describes COX-1's role in the body?

It produces prostanoids that promote inflammation.

It is primarily found in white blood cells.

It generates prostanoids that are beneficial for protecting gastric integrity. (correct)

It is expressed only during stress responses.

What type of compound is misoprostol classified as?

A PGE1 derivative Signup and view all the answers

Which of the following eicosanoids is primarily involved in mediating inflammation in asthma?

Leukotrienes Signup and view all the answers

Which prostanoid is primarily synthesized from COX-2 in response to stress?

Prostaglandin E2 Signup and view all the answers

What is the role of phospholipase A2 in eicosanoid synthesis?

It releases Arachidonic Acid from cell membranes. Signup and view all the answers

Which product is NOT formed from the action of Cyclooxygenase enzymes on Arachidonic Acid?

Leukotrienes Signup and view all the answers

What is the role of prostaglandins (PG) in platelet function?

They induce aggregation at low doses, affected by aspirin. Signup and view all the answers

What major biological role does thromboxane (TXA) play in the vascular system?

It serves as a potent vasoconstrictor. Signup and view all the answers

Which prostaglandins are primarily associated with inflammation?

PGE<del>2</del> and PGI<del>2</del> Signup and view all the answers

What is the mechanism by which corticosteroids inhibit eicosanoid synthesis?

By inhibiting the phospholipase enzyme that releases arachidonic acid. Signup and view all the answers

How do leukotrienes affect immune response?

They activate white cells and promote inflammation. Signup and view all the answers

Which eicosanoid is used to prevent NSAID-induced peptic ulcers?

Misoprostol Signup and view all the answers

What effect does chronic inhibition of the kidney COX enzyme have on the kidneys?

Results in kidney damage due to loss of beneficial prostaglandins. Signup and view all the answers

Which fatty acid sources provide biologically inactive eicosanoids?

Linoleic acid from sunflower and corn oils. Signup and view all the answers

Which of the following is described below:

-polyunsaturated long-chain fatty acids

produced in a wide range of tissues, highly bioactive

mediators of inflammation, redness etc.

Eicosanoids Signup and view all the answers

Which of the following is described below:

-prostaglandins, thromboxane, prostacyclin are in this group?

Prostanoids Signup and view all the answers

Match each arachidonic acid enzyme to its products

= Cytochrome P450 = epoxyeicostrienoic acids (EETs) Lipoxygenase (LOX) = leukotrienes, lipoxins Cyclooxygenase (COX) = prostaglandins, prostacyclin, thromboxane Signup and view all the answers

What is the role of COX-2?

Makes prostanoids that cause inflammation Signup and view all the answers

COX-2 is inducible and its expression requires a stimulus.

True Signup and view all the answers

What do the letters A, B, G, H, etc. for prostaglandins define?

substituents in the pentane ring Signup and view all the answers

What do the subscripts for prostaglandins such as PGE1 count?

Number of double bonds in the side chain Signup and view all the answers

Which of the following is a PGE1 derivative used to relax smooth muscle and to treat impotence?

alprostadil Signup and view all the answers

Which of the following is a PGE1 derivative, cytoprotective prostaglandin used to prevent peptic ulcer?

Misoprostol Signup and view all the answers

Where is LOX mostly found in the body?

White blood cells Signup and view all the answers

Match each body system to the effect PGs and TXs have on it

Vascular Smooth Muscle = TXA potent vasoconstrictor; PG promote vasodilation GI Smooth Muscle = mixed effects of contraction and relaxation Airways Smooth Muscle = PG relax and some PGs and TXs constrict Platelets = dose related but PG induce aggregation Signup and view all the answers

Study Notes

Eicosanoids, Prostaglandins, Thromboxanes, Leukotrienes

Eicosanoids are polyunsaturated fatty acids produced in tissues. They are highly bioactive and mediate inflammation and redness.
Prostanoids are a type of eicosanoid including prostaglandins, thromboxane, and prostacyclin.
Arachidonic Acid (AA) is the main starting material for eicosanoid synthesis. It's found in cell membranes.
Phospholipase A2 removes AA from cell membranes.
AA is then enzymatically converted into various products. These include epoxyeicosatrienoic acids (EETs), leukotrienes, lipoxins, prostaglandins, prostacyclin, and thromboxane.
These products are produced by enzymes like Lipoxygenase (LOX) and Cyclooxygenase (COX).

COX Enzymes

COX-1 is found in most cells and produces prostanoids vital for bodily functions, including protecting the stomach lining and kidneys.
COX-2 is an inducible enzyme, meaning its production is triggered by stimuli (stress, cytokines, tissue injury) and results in the production of prostanoids that cause inflammation.
Non-steroidal anti-inflammatory drugs (NSAIDs), like aspirin and ibuprofen, inhibit COX enzymes, thus reducing inflammation.

Products of COX Enzymes

Prostaglandins are involved in various functions, including uterine contractions during childbirth, blood flow regulation, and influencing blood clotting.
Thromboxanes promote platelet aggregation (blood clotting).
Prostacyclin prevents platelet aggregation.

Prostaglandins as Drugs

Alprostadil is a PGE1 used for smooth muscle relaxation and treatment of impotence.
Misoprostol is a PGE1 derivative used to prevent peptic ulcers. Dinoprostone is another PGE analog used for uterine contractions.

Lipoxygenase (LOX) Products

Leukotrienes are LOX products mainly found in white blood cells.
Leukotrienes are important mediators of inflammation (e.g., in asthma).

Biological Effects of Prostaglandins and Thromboxanes

Prostaglandins and thromboxanes (TXs) affect various tissues. They can cause vasoconstriction (narrowing of blood vessels) and vasodilation (widening of blood vessels).
Prostaglandins and TXs are involved in smooth muscle contraction and relaxation in the gastrointestinal tract and airways.
TXA is a potent vasoconstrictor.
PGs promote vasodilation.

Inhibition of Eicosanoid Synthesis

Corticosteroids are the gold standard for inhibiting eicosanoid synthesis, largely by inhibiting phospholipase enzymes.
NSAIDs like ibuprofen and indomethacin inhibit COX enzymes, preventing prostaglandin production.

Dietary Manipulation of Arachidonic Acid (AA)

Linoleic acid, found in sunflower and corn oils, can act as a substitute for AA. However, the eicosanoids produced aren't identical.
Cold-water fish oils contain omega-3 fatty acids which can also affect eicosanoid production.

Other Notes

Aspirin inhibits platelet aggregation by inhibiting PG synthesis.
Kidney function relies on prostaglandins for various processes, and decreased PG production can negatively affect kidney health.
Prostaglandins play critical roles in the central nervous system (CNS), including fever responses and neurotransmitter release.
Eicosanoids are linked with inflammation, bone remodeling, and various other physiological responses.

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Description

This quiz covers the roles and functions of eicosanoids, including prostaglandins, thromboxanes, and leukotrienes. It will also delve into the significance of COX enzymes and their contributions to various bodily processes. Test your knowledge of these crucial inflammatory mediators and their enzymatic pathways.