Anti-inflammatory and Immunosuppressant Drugs Flashcards
What are NSAIDs?
Non-steroidal anti-inflammatory drugs
What was the first non-steroidal anti-inflammatory drug synthesized in a lab?
Aspirin ( acetal salicylic acid)
How many non-steroidal anti-inflammatory drugs (NSAIDs) are there?
Over 50.
How do Aspirin, Paracetamol, and Ibuprofen work and what is their outcome?
> All of these drugs inhibit production of inflammatory mediators, especially target inflammatory mediators called prostaglandins and thromboxane, by inhibiting cyclooxygenases (COX enzymes).
> Reduces pain and swelling.
What is the function of inflammatory mediators, like prostaglandins and thromboxane, and how is this possible?
> They cause a localised inflammatory response
> They are lipid soluble (fat soluble) so can diffuse out of cells to do paracrine signalling.
What are the 3 steps of production for prostaglandins and thromboxane inflammatory mediators?
- Phospholipase A2 generates pre-curser called arachidonate from phospholipids in cell membrane.
- COX enzymes (cyclooxygenases) acts on arachidonate.
- The inflammatory mediator is converted into prostaglandins or thromboxane.
What do a)Prostaglandin F2 b)Prostaglandin D2 c)Prostaglandin E2 control?
a) Prostaglandin F2 controls myometrial contraction (initiation of labour)
b) Prostaglandin D2, inhibits platelet aggregation, and is a vasodilator
c) Prostaglandin E2, is a vasodilator, and a hyperalgesia (increases pain perception by acting directly on nociceptors)
>It increases signalling by bradykinin and 5-HT (serotonin) to nociceptors.
> They all attract immune cells to damaged areas.
What do Thromboxanes control?
They all act as Vasoconstrictors
What are the 3 therapeutic functions of NSAIDs?
1) Anti-inflammatory
2) Analgesic (reduce certain sorts of pain
3) Antipyretic (lower raised temperature)
How do NSAIDs have anti-inflammatory effects, and when is this ineffective?
> They decrease vasodilation and in turn oedema (swelling).
> Ineffective against mediators causing tissue damage, usually associated with chronic inflammatory conditions.
What symptom does NSAIDs inhibit by increasing vasodilation of vessels to the head?
This stops headaches as these are caused by vasoconstriction of blood vessels to the head.
How do NSAIDs have Antipyretic effects?
> Thermostat in hypothalamus activated by the chemical mediator called IL-1 (raises temperature of body), this signalling involves COX2 production of Prostaglandin.
> So NSAIDs inhibiting COX2, returns body temperature back to normal.
How do NSAIDs have analgesic effects?
> Decrease production of Prostaglandins E2 in damaged and inflamed tissue which sensitizes nociceptors.
> So, nociceptors send out less pain signals to the brain.
How do NSAIDs have antipyretic effects?
Thermostat in hypothalamus activated via IL-1 induced COX2 production of PGE, NSAIDs inhibit this.
How many isoforms of COX (cyclooxygenases) enzymes are there?
3
Where are the 3 isoforms of COX (cyclooxygenases) enzymes found and what is their function?
1) COX-1
>Produced in platelets, Stomach, Kidney, Colon, and most tissues
>For homeostatic effects.
2) COX-2
>An inducible enzyme, made in response to injury and inflammation (only present in injured cells)
>For inflammatory repones
3) COX-3
>Found in brain and kidneys
>Not much known about this enzyme.
How many subunits and catalytic sites do COX enzymes have?
2 subunits and 2 catalytic sites.
What intracellular organelle are COX enzymes embedded in?
endoplasmic reticulum
How do COX enzymes interact with the endoplasmic reticulum membrane to produce prostaglandins or thromboxane in 3 steps?
1) Arachidonic acid floats to ER membrane (produced at plasma membrane) from cytosol of cell
2) Arachidonic acid moves through the ER membrane and into the cyclooxygenase site of an embedded COX enzyme and binds.
3) COX enzyme activates ad produces prostaglandins or thromboxane.
What are the 2 catalytic sites of a COX enzyme called?
1) Cyclooxygenase site
2) Peroxidase site
What is different between COX1 and COX2 and what advantage does this have?
> COX1 has smaller cyclooxygenase pore as isoleucine is a larger amino acid blocking it
> COX2 cyclooxygenase pore is wider due to smaller amino acid Valine blocking it; so larger drugs can enter
> Allows us to make selective drugs for both (useful as both enzymes have different function).
Why do we want to have NSAIDs which are selective in inhibiting COX2 enzymes and not COX1?
As COX1 prostaglandins have important homeostatic effects so we want to be able to inhibit COX2 without the side-effects of inhibiting COX1.
What are 3 homeostatic mechanisms for COX1 enzymes?
The Prostaglandins produced by COX1 play key role in maintaining mucus layer surrounding stomach and GI (protecting lining from acid), Controlling blood loss (through platelet aggregation), maintaining blood flow to kidneys
What are 3 unwanted side effect of NSAIDs that are selective to just COX1 enzymes (like aspirin) and why?
1)Ulcers in stomach
>Because COX1 prostaglandins produce mucus layer surrounding stomach and GI tract.
2)Prolonged bleeding
>As platelet aggregation is mediated by COX1.
3) Kidneys don’t receive sufficient blood flow
>As COX1 maintains blood flow to kidneys.
What is a suicide inhibitor and an example?
> Suicide inhibitor= drug that covalently binds to target to cause permanent inactivation of target
> E.g. Aspirin
How does aspirin work?
> Aspirin is a suicide inhibitor binding covalently to an Acetyl group in the cyclooxygenase pore of a COX enzyme.
> Arachidonic acid can’t enter cyclooxygenase pore so Prostaglandins and Thromboxane cannot be synthesized.
How long does Aspirin last and why?
> Lasts 3 hours
> As Aspirin needs to be excreted and new COX1 enzymes have to be synthesized (as aspirin is a suicide inhibitor it binds strongly with covalent bonds) till normal levels have been reached.
What COX enzyme are a)Aspirin b)Ibuprofen c)Coxibs d) Paracetamol selective to?
a) COX1 selective
b)COX1 selective
c)COX2 selective
d) COX1 and COX3 selective
What are 5 side effects of NSAIDs and why are they caused?
1) In the Gut
>Ulcers, Diarrhoea, vomiting, gastric bleeding
>Prostaglandins produce mucous layer protecting stomach and GI tract from acid.
2) Renal Function failure
>Prostaglandins maintain renal blood flow.
3) Liver damage
>Paracetamol overdose, first phase metabolism generates very reactive chemical that kills cells.
4) Bronchospasm asthma attacks
>due to allergies from aspirin
5) Skin Rashes
What risk varies with different NSAIDs?
Risk of GI complications.
How high a risk of GI complications does aspirin have?
Aspirin in moderate doses is safe/ low risk of GI complications (can be taken daily)
Why do people at risk of stroke take COX1 inhibitors (anti-thrombosis) but what is an unwanted side-effect?
> COX1 controls blood clot formation, people at risk with strokes take daily low levels of COX1 inhibitor to decrease blood clots.
> Causes Undesirable gastrotoxicity
What is advantageous about taking COX2 selective inhibitors and what is disadvantageous?
> Are good anti inflamatory, good analgesics, and don’t effect gut
> Issue is as COX2 plays an important role in kidneys, inhibition in COX2 increases blood pressure and increased Na+ conc in body.
What is an issue with Rofecoxib being taken?
> It is a Coxib so is very COX2 selective.
> Taking it lead to an increase in Na+ and blood pressure leading to heart attacks.
What are 3 positive effects of taking Aspirin?
1) Anti-platelet action (stops blood clots)
2) Reduced risk of colonic and rectal cancer
3) Reduced risk of Alzheimer’s / speed of progression
Why is Aspirin efficiently absorbed into the ileum?
As it’s a weak acid.
What 2 symptoms does Paracetamol treat and why?
> Headache or high temperature
> Paracetamol is a Analgesic-antipyretic so gives pain relief and reduces body temperature back to normal.