Lecture - AAT (blood virtual lecture)

Question 1

1. What are some stimuli for acute inflammation?
2. What happens in AI?
3. What do the leukocyte effect mechanisms do?
4. What are the mediators of AI?

Answer 1

1. It could be infection or anything that affects like like smoking
2. There are vascular changes (vasodilation) and cellular changes (increase neutrophils)
3. The effect mechanisms like how macrophage should eliminate microbe and dead tissue but it can also damage normal tissue
4. There are cell derived and protein derived mediators of AI. The cell derived are histamine and cytokine. The protein-derived are like AAT

Question 2

Proteins of acute phase response:

What 7 proteins are involved?

Answer 2

1. Coagnulation proteins (fibrinogen etc)
2. Complement
3. Kinins
4. Lysosomal proteases (enzymes which break down proteins and peptides). This is like elastase released by neutrophils and monocytes
5. AAT from liver
6. CRP - this is a sensitive diagnostic maker of general inflammation- for chronic disease as well as infection. ESR is also another marker but CRP is more rapid and decrease faster.
7. hs-CRP, it’s a high sensitivity CRP and indicates increased risk of heart disease

Question 3

What does elastase have to do with emphysema?

Answer 3

Elastase is released by neutrophils and it helps to destroy the microbes but some of these enzymes are pleased into lungs and can potentially damage the alveoli in lungs.

Question 4

AAT:

1. Where is it produced?
2. So it diffuses into tissues and it is a serine protease inhibitor - what does that mean?. What does it inhibit in vitro and in vivo?
3. What is the mechanism of inhibition?

Answer 4

1. In the liver - hepatocytes
2. Serine proteases are enzymes that cleave peptide bonds in proteins in which serine serves as the nucleophilic aa’ at the active site. So AAT inhibits trypsin in vitro and elastase in vivo - these are are both serine proteases
3. So the AAT with bind 1 to 1 with the elastase. The elastase will cleave it (because that’s its job - to cut the proteins) but when it does that, there is a conformational change which completely disrupts the protease and the whole complex will be destroyed. This is why it’s called a suicide inhibitor.

Question 5

Genetic variation in AAT gene:

Go read that and ask about it in lab

Answer 5

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Question 6

Tell me about how you determine the AAT amounts in the blood

• confounded by?
• what can you see in IEL?
• how to see genotype?

Answer 6

The phenotype is the AAT activity and so you can do inhibition assay as well as AAT protein concentration (immunodiffusion and immunoelectrophoresis)

But that can be confounded by APR (because that increases the AAT)

You can see protein isoform variant by IEL. You’ll get two bands even if you have two identical alleles because two different glycosylation forms of the same protein.

If you wanna know genotype then do specific mutation testing.

Question 7

What is the treatment of AAT deficiency?

Answer 7

1. Reduce environmental damage like smoking etc
2. Can have genetic counselling since AR autosomal recessive
3. Exercise
4. You could do IV AAT augmentation following emphysema decline (do a weekly infusion)
5. Can do liver or lung transplant.

Question 8

What is the gene-environment interaction with SERPINA1 gene mutation and smoking?

Answer 8

Basically smoking and level of it will affect prognosis

Those with ZZ are are smokers will have severe reduction in life expectancy

Need to communicate genetic risk to those people