Cellular and Molecular Mechanisms

Question 1

Describe the signalling for allergic eosinophilic asthma

Answer 1

Question 2

Desscribe the signalling for non-eosinophilic asthma

Answer 2

Question 3

What are some features of Th2-high asthma

Answer 3

• ↑Blood and BAL eosinophils
• ↑Serum IgE
• ↑Mucin MUC5AC
• ↑IL-5 and IL-13 in biopsies
• Bronchial hyperresponsiveness
• FEV1 increase with ICS

Question 4

Steroids are effective at suppressing immune system. What are some side effects

Answer 4

• ↓growth veolicty in children
• Bone mineral loss
• Cataracts and Glaucoma
• T2DM

Inhalation devices have decreased SE but not completely eliminated them as above. SE are because they get to the systemic circulation

Question 5

Currently, our GCs are effective but have many side effects. What other approaches have we taken to reduce SE?

Answer 5

• Soft Steroids
  
  • Tipredane
  • Ineffective - broken down by lung esterases
• Pro-drugs
  
  • Ciclesonide Taylow DA 1999
  • Device has problems?

Question 6

Describe the structure of a glucocorticosteroid receptor

Answer 6

• Ligand Binding Domain (LBD)
• DNA Binding Domain (DBD)
• Activation Domain (NT)
  
  • Recruits co-factors which stimulate transcription

Held in cytosol until ligand binds by chaperone proteins - HSP90 (Heat Shock Protein 90)

Question 7

Describe how the GC receptor gets activated

Answer 7

Ligand Binds to its LBD

Conformational change to expose DBD

Translocation to the nucleus for transcription of genes

Question 8

What are the mechanisms of action of GC receptor in the nucleus

Answer 8

1. Trans-activation
   
   1. ↑transcription of anti-inflammatory genes
2. Cis-repression
   
   1. Side effects
3. Trans-repression
   
   1. Binding and inhibition of NF-kB and AP-1

Question 9

How has visualtisation of the crystal structure improved drug design

Answer 9

• GR has a binding pocket
  
  • The more this pocket domain is filled the greater effect of NF-kB inhibition
• Allowed us to change its PK properties
  
  • Duration of action
  • Lipophilicity

Question 10

With the mechanisms of GR in mind, how can we improve the therapeutic index of GC the future?

Answer 10

• Keep the trans-activation effect to upregulate anti-inflammatory genes (SLPI, Annexin-1, IκB-α, GILZ, MKP-1)
• Keep the trans-repression of NF-kB and AP-1
• Eliminate the cis-repression of genes which would lead to side effects

Question 11

Name some mechanisms which could explain glucocorticosteroid insensitivity

Answer 11

• ↓GR expression and import in severe asthma ASM
  
  • Chang, Bhavsar AJRCCM 2015
• Loss of importin-7 = ↓ nuclear translocation
  
  • Hakim 2012
• Oxidative stress reduces GR nuclear translocatoin

Question 12

Explain the mechanism of glucocorticoid resistance/insensitivity (in COPD)

Answer 12

Question 13

What four pathways lead to NF-kB activation and which are steroid-sensitive/-insensitive

Answer 13

Steroid Sensitive

• IKK
• PI3K
• p38

Steroid Insensitive

• JAK/STAT