W3: Pharmacology of Inflammation Flashcards
What pain killer is normally associated with arthiritis?
Steroids
What painkiller is normally associated with injury?
NSAIDs
What is the chemical origin of aspirin?
Salicylic acid (willow bark)
Is acetylated to form acetylsalicylic acid - this is the aspirin compound.
What are the clinical used of aspirin?
Like all NSAIDs it is:
- analgesic
- anti-pyretic
- anti-inflammatory
Unique to aspirin: is an anti-thrombotic
What are the pathological localised responses in inflammation that can be targeted by drugs?
Vasodilation - increased blood flow
Increased blood vessel permeability - leakiness
Increased neuronal sensitisation - causes pain
What are the different types of mediators of inflammation?
(aware not memorise)
Peptides: bradykinins, neuropeptides (substance P), C3a C5a, thrombin
Cytokines: IFN-alpha, IFNy, TNFalpha
Small molcules: Histamine, seratonon, ATP, adenosine
Free radicals: NO, ROS
Lipids: Eicosanoid, platelet activating factor
What is an eicosanoid?
A lipid that mediates inflammation.
Lipid based signalling molecules derived from arachidonic acid that have a role in the innate immune response.
Describe the structure of a lipid membrane bilayer
Hydrophobic tails (two fatty acid chains)
Hydrophilic heads (phosphate group potentially with an additional group bound)
Arranged in two layers with tails facing inwards towards each other.
Two groups are joined by binding to glycerol.
What is the structure of arachidonic acid?
Consists of 20 carbons and 4 unsaturated bonds (polyunsaturated fatty acid)
C20:49(ω:6)
As when starting from terminal omega carbon first double bond is on carbon six.
How does arachidonic acid link to the structure of the lipid membrane?
Can be found on C2 on the phospholipid
Makes up some of the hydrophobic tails.
What is the structure of eicosapentaenoic acid?
What is its useful function clinically?
Fatty acid -COOH group
20 carbons
5 unsaturaded bonds
ω3
Reduce cardiovascular deaths**
What enzymes are involved in the degradation of phospholipids?
Phospholipase A2 is the one to memorise
Phospholipase A1 - hydrolyse ester bond at sn1 position
IMPORTANT ONE ONLY - Phospholipase A2 - hydrlyse ester bond at sn2 position
Phosphlolipase C -hydrolyse glycerophosphate bond
Phospholipase D - released head group of phospholipid molecule
Describe how active prostaglandins are made via the COX pathway?
Arachidonic acid is released from membrane phospholipids by phospholipase A2.
Arachidonic acid is then converted to Prostaglandin G2 by COX enzyme (dioxygenase reaction)
Then converted to prostaglandin H2 by COX enzyme (peroxidation) (commitment step in prostaglandin production)
Why is COX considered a bifunctional enzyme?
Catalyses two reactions
1. Dioxygenation of arachidonic acid
2. Peroxidation of PGE2 (this COX action can also be referred to as PGE2 synthase)
What is the pharmacology of aspirin?
Targets cyclo-oxygenase enzyme
Acts as an irreversible inhibitor
Acetylates the Ser530 residue in the COX enzyme, this residue is found within the active site of the cox enzyme.
Aspirin is converted to salicylic acid in the process.
Therefore preventing the binding of arachidonic acid to the COX enzyme.
Why does the production of prostaglandins vary between different tissues?
Different tissues will produce different enzymes
Different enzymes will be responsible for converting PGH2 to different terminal prostaglandins.
What are the five different types of prostaglandins produces at the end of PG synthesis?
PGD2
PGF2alpha
PGE2
TxA2
PGI2
Note the number refers to the number of double bonds
How is PGD2 produced?
What receptor does it act on?
PGH2 converted by PGD2 synthase
Binds to DP1 and DP2 receptors
Can be converted to PGF2 by PGF synthase
How is PGF2alpha produced?
What receptor does it act on?
PGD2 converted by PGF2alpha synthase
PGE2 convereted by PGE2 9-ketoreductase
Also can be produced from PGH2
Acts of FP receptors
How is PGE2 produced?
What receptor does it act on?
PGH2 converted to PGE2 synthase
Acts on EP1,2,3,4 receptors
How is thromboxane produced?
What receptor does it act on?
PGH2 converted by thromboxona synthase
Acts of TP receptors
How is PGI2 produced?
What receptor does it act on?
PGH2 converted by PGI synthase
Acts on IP receptors
What are the common features of prostanoid receptors?
GPCRs
Expressed in different levels in different tissues
How does the naming of drugs relate to their effect on prostaglandins?
prost - agonists
piprant - antagonist
What is the role of treprostinil?
is a PGI2 analogue
IP receptor agonist
Causes vasodilation
Used to treat hypertension in pulmonary arteries
What is the physiological role of PGD2?
Produced by mast cells, CNS, heart and male reproductive organs.
Role in allergic inflammatory response, vasodilatory and a chemoattractant
What is the physiological role of PGF2alpha?
Is wideley expressed including by the female reporductive system
Responsible for uterine contractions and luteolysis
What is the physiological role of PGE2?
Is widely expressed
Causes inflammation, fever, nerve sensitisation (pain) and vasodilation
What is the physiological role of TxA2?
Thromboxane
Produced by platelets, lungs etc
Role in platelet activation and vasoconstriction
What is the physiological effects of PGI2?
Is widely expressed, including by the endothelium.
Role in platelet inhibition and vasodilation (feature of inflammation)
Why are prostaglandins only suited to be para/autocrine?
Very short half life.
What are the mechanisms underpinning the anti-inflammatory effects of NSAIDs?
PGE2/D2 reduced as production inhibited
Do not function - inhibits vasodilation (increased blood supply and fluid extravasation)
How do NSAIDs act as anti-pyretics?
Inhibit PGE2 production
Inhibit PGE2 from acting as an endogenous pyrogene on the hypothalamus.
How do NSAIDs act as analgesics?
Inhibit PGE2 prodcution
Inhibit action of sensitising free nerve endings
How can the decrease in thromboxane caused by NSAIDs have varying effects in different patients?
Less Thromboxane produced by platelets
Some patients is beneficial as an anti-thrombotic to reduce risk of MI
Some patients have side effects as also anti-haemostatic - so increased risk of bleeding.