W1 5 Anti-inflammatory steroids Flashcards
Where are corticosteroids synthesised?
Middle layer of adrenal cortex
What are corticosteroids split into?
Glucocorticoids and mineralocorticoids
What is the endogenous glucocorticoid?
Cortisol
What is cortisol synthesised from?
Cholesterol. Retains 4 ring chemical structure.
What compound is made chemically to mimic cortisol?
Hydrocortisone
What chemical properties of hydrocortisone make it differ from cortisol?
Position of side-groups increase selectivity to gluco and mineralocorticoids
Fluoridation increases half-life of drugs
Double bond in ring increases potency
What actions does cortisol have?
Anti-inflammatory actions
What axis is cortisol part of?
Hypothalamus-pituitary adrenal axis - HPA axis
Describe the negative feedback loop involving cortisol - PG46
Hypothalamus releases CRH stimulating the anterior pituitary gland to release ACTH, stimulating the adrenal gland to release cortisol.
Cortisol negatively feedbacks on the HPA to decrease its own production
It acts on many tissues to have metabolic effects
Pro-inflammatory mediators flow to HPA axis to generate cortisol and limit inflammation
Chronic stimulation of cortisol might shut down the HPA system, causing atrophy
Stress, inflammation, immune system all can cause the system to release cortisol
What is the implication of being a steroid for absorption?
Steroids are lipophilic and easily absorbed in the gut
Not in plasma freely, so are bound to a carrier protein
Which proteins are steroids bound too?
Transcortin is a specific carrier protein. It has a high affinity for steroids but low capacity.
Majority are bound to albumin. It has a high capacity but low affinity.
Once in the tissues, the steroid freely diffuses into the cell cytoplasm, where the glucocorticoid receptor is located. What are the different domains of a glucocorticoid receptor?
Ligand binding domain - where steroid will bind
DNA binding domain - related to an action
HSP binding domain - anchors it to the cytoplasm
What happens as the steroid binds to the receptor?
The binding to the HSP is broken and thus free the receptor to allow it to move into the nucleus.
What happens once the steroid is inside the nucleus?
Can turn a gene on = trans activation - upregulates anti-inflammatory mediators
Can bind to genes and turn them off = transrepression - down regulates the pro-inflammatory mediators
How long does the typical steroid anti-inflammatory effect take?
6-8hrs
Do anti-inflammatory drugs need an initiating stimulus to work?
No, anti-inflammatory drugs will work independent of initiating stimulus