Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A BMS346 Epithelial Physiology > ASL, influenza and ion channels > Flashcards

ASL, influenza and ion channels Flashcards

1
Q

What impacts on the ASL?

A

1) Normally physiology - lungs are dynamic in how they deal with ASL
2) Pathogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the problem with the movement of the ASL?

What is needed to overcome this problem?

A

As the fluid moves up the respiratory tract - small airways converge in the bronchial region and the surface area decreases
–> get a volume load

If lungs don’t do anything, as the fluid moves up the respiratory tract:

  • The height of the ASL gets bigger because the surface area is smaller
  • Height is no longer optimum

To overcome this problem:
- Have active and passive mechanism under normal physiological conditions to regulate the height of the liquid layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the height of the ASL in the distal airways?

A

Same height

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the proximal airways?

A

Closer to the external environment (bronchi)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the distal airways?

A

Further away from the external environment (in the alveoli)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the PASSIVE control of the ASL

A

Mucous layer acts as a RESERVOIR:
- Height of the layer too heigh - excess fluid into mucus layer –> height drop

  • Height of the layer too low - liquid from the mucus layer
  • -> height increases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe the ACTIVE control of the ASL

A

Active ion transport (and following water) controls the salt level in the PCL:
- Via complimentary ENaC and CFTR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do CFTR and ENaC interact in the upper airway?

A

They are COMPLIMENTARY:

- When one is active the other is inactive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the optimum of the ASL in VITRO?

A

7-7.5 microns

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What happens in VITRO when increase the height of the ASL to 30 microns?

When does this occur?

A

The layer of the cells in culture actively DECREASE the height of the layer down the optimum layer

Happens in the first 24hrs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens when the height of the ASL is HIGH?

A

ENaC (Na absorption) PREDOMINATES/upregulated:

  • Na out of the PCL
  • Water follows (PARACELLUARLY)
  • Heigh goes down
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens when the height of the ASL is LOW/STEADY STATE?

A

CFTR (Cl secretion) PREDOMINATES/is upregulated:
- Balance between Cl secretion and a little bit of Na absorption maintains the height of the ASL

  • No net water movement paracellularly across the epithelium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens to the Vte when experimentally increase the height of the ASL too high?

A
  • Increases with the increase of the height of the ASL

- Decreases as the height of the ASL decreases (due to the active mechanisms)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What happens to the Vte of cells when add Amiloride 0h after experimentally increasing the height of the ASL?

48hrs?

A

At 0hr - 65% decrease in Vte (65% inhibition of Vte)

At 48hr - 30% decrease in Vte (30% inhibition of Vte)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens to the Vte of cells when add Bumetanide 0h after experimentally increasing the height of the ASL?

48hrs?

A

At 0hr - 18% decrease in Vte (18% inhibition of the Vte)

At 48hr - 52% decrease in Vte (52% inhibition of Vte)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the function of Amiloride?

A

Blocks ENaC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the function of Bumetanide?

A

Blocks NKCC1 (on the basolateral membrane of the upper airway epithelial cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

When add a blocker the the cell and there is a X% decrease/inhibition of Vte what does this show?

A

That the ion channel that is blocked contributes to X% of the Vte

The bigger the shift in the Vte with the potential - the bigger the function of the blocked protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What disrupts the balance between ENaC and CFTR function?

A

Inherited conditions and acquired conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the inherited conditions that disrupt the balance between ENaC and CFTR function?

A
  • Cystic fibrosis
  • Atypical CF
  • PHA type 1
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the acquired conditions that disrupt the balance between ENaC and CFTR function?

A
  • Infections (influenza)
  • Smoking
  • Vaping?
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the effects of influenza?

A

Kills ~ 12K to 61K individuals / year USA
~ 600 to 13K individuals / year UK

10% hospital admissions during flu season are due to:

1) Influenza linked bronchopneumonia & oedema
2) Acquired respiratory distress syndrome

Lung function is compromised so much you need to be hospitalised to enable to get treatment to get oxygen in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How does influenza cause damage to the body?

A

Alters ENaC and CFTR function –> impacts on ASL level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the contradictory data regarding influenza and ASL height?

A

Different studies show that the height of the ASL in influenza to go up or down

Dependant on many different factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What was the mice study that displayed the evidence that the influenza viruses impact on ENaC and CFTR

A

Measurement of murine nasal potential differences in response to the PR8 virus:

  • Measure the Vte across the nasal epithelium with a references and recording electrode up the nose of the mouse

Then, add different drugs to see the shift in the Vte:
1) Amiloride

2) Forskkolin
3) GLyH-101

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the PR8 virus?

A

An influenza virus that expresses a GFP-NS1 protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the affect on the nasal Vte in mice when Amiloride is added (not in the presence of the PR8 virus) What does this show?

A

Shift in Vte - indication that the ENaC channel is important in the membrane potential

28
Q

What does the shift in the Vte when block a channel show?

What does a big shift in this value show?

A

Shows the function of that channel

  • The bigger the shift the bigger the function the channel that is blocked
29
Q

What is the Na+ dependant Amiloride inhibited NPD?

Describe this value and how it changes over time with infection with PR8

What does this show about the virus?

A

The shift in Vte when amiloride is added (showing the function of the Na channel)

30
Q

What is the Na+ dependant Amiloride inhibited NPD at no infection?

Day 5 infection?

Day 10/15 of infection?

What does this show?

A 
No infection (control):
- Around -12mV

Day 5 infection:
- Very close to 0mV

  • Shows hardly any change in ENaC inhibition when Amiloride is added
  • ENaC already inhibited (by the virus)

Day 10/15 of infection:
- Amiloride sensitive NPD increases

  • Shows more of the channels to be inhibited by Amiloride (ENaC no longer inhibited by the virus - recovery of function)

–> TRANSIENT inhibition of ENaC with the virus

31
Q

If add Amiloride to a channel and the Amiloride sensitive NPD is 0, what information does this show about the channel prior to addition of Amiloride?

A

Shows that the channel is inhibited prior to the addition of Amiloride

32
Q

What is the affect in the nasal Vte in mice when Forskolin is added (following Amiloride addition)

What does this show?

A

Opposite shift in the Vte

Shows the activation of CFTR

33
Q

What is the affect in the nasal Vte in mice when GlyH-101 (CFTR inhibitor) is added (following Forskolin and Amiloride addition)

What does this show?

A

Shift in Vte

Shows inactivation of CFTR - contributes the the Vm?

34
Q

What is the Cl dependant GlyH-101 inhibited NPD at no infection?

Day 5 infection?

Day 10/15 of infection?

What does this show?

A 
No infection (control):
- About -17mV

Day 5 infection:

  • Closer to 0mV
  • Shows hardly any change in CFTR inhibition when GlyH-101 is added
  • CFTR already inhibited (by the virus)

Day 10/15 of infection:
- Sustained inhibition

35
Q

What is the effect of of PR8 (influenza virus) on ENaC and CFTR?

A

By day 5 BOTH ENaC and CFTR channels are inhibited in the upper airway

36
Q

What other cell is the nasal epithelium a model for?

A

Bronchial epithelial cells

37
Q

What is H1N1?

A

Another influenza virus

38
Q

What happens to the SCC in HBE cells when Amiloride is added?

A

SCC falls

39
Q

What does a decrease in SCC when a channel blocker is added determine?

A

Determines the function of the ion channel in the cell:

The bigger the drop in SCC - the bigger the function in the cell

40
Q

What is the function of Forskolin?

What impact does this have on the SCC in the cell?

A

Stimulates Cl secretion

Increases the SCC with a transient effect - increases to a peak and then reaches a lower steady state

41
Q

How does Vte relate to SCC?

A

If the resistance stays the same:
- If Vte increases SCC increases??

  • If Vte decreases SCC decreases??
42
Q

What happens to SCC when CFTR inhibitor is added?

A

SCC reduces

43
Q

What is the effect on the SCC mediated by ENaC in infected cells compared to in uninfected cells?

How is this seen?

A

SCC mediated by ENaC is less than half than what is seen in uninfected cells

Smaller amiloride sensitive SCC
–> shows a reduced function of ENaC

44
Q

What is Forskolin a measure of?

A

Cl ion secretion through the CFTR channel

45
Q

What happens to Forskolin function in the presence of H1N1?

What does this show?

A

Smaller increase in SCC and loss of transient behaviour is lost compared to in non-infected cells

Shows a reduces function in CFTR (as Forks is a measure of Cl secretion through CFTR)

46
Q

What does the influenza data show so far?

A

Evidence that the ENaC and CFTR function are inhibited in the presence of influenza in both:

1) In VIVO - in the mouse
2) In VITRO human cell culture

47
Q

What is the SCC a measure of?

A

The sum of:

  • Number of channel
  • Open probability
  • V-Vrev (driving force)
  • g

For EACH of the channels looking at?

48
Q

What are two things that can change SCC in terms of infection?

A
  • Number of channels

- Open probability

49
Q

How can we distinguish between PR8 infected and P8 non-infected cells?

A

PR8 with GFP:
- Infected (green - GFP)

  • Non-infected (not green)
50
Q

Describe the Po of ENaC in non-infected cells prior to infection?

Following infection?

A
  • High Po (many openings and closings of the channel
  • ENaC channels are open 1/3 (Po is 0.3)
  • Following infection - Po is constant?????
51
Q

What is the conductance of the ENaC channel?

A

Has 2 different conductances depending on the subunit concentration of ENaC?

  • Small conductance (4pS channel)
  • Large conductance (18pS channel)
52
Q

Describe the Po of the infected cells

Is this a transient or permanent change?

A

Reduced number of opening events –> reduced Po

Transient reduction - increases again after peak low at 7 days

53
Q

Describe the Po of CFTR in infected and non-infected cells?

A

In infected cells - Po is REDUCED (from 0.6 –> 0.1)

54
Q

What are the different subunits of ENaC?

A

Alpha, Beta and Gamma (also Delta in the lungs)

55
Q

What is the function of the ENaC alpha subunit?

What is required for the proper function of ENaC?

A

Alph subunit can form a channel that functions BUT the size of the currents through this subunit alone are very small

So only get normal function of the channel with alpha, beta and gamma subunits to form the channel

56
Q

What do densitometry recordings of the subunits of ENaC show?

What does this mean?

A

Compared to the control, there is a REDUCED protein level of the subunits in the membrane

Shows that the number of the channels in the membrane is reduced

57
Q

What do densitometry recordings of the subunits of CFTR show?

A

Number of CFTR in the membrane are reduced

58
Q

What do densitometry recordings of the subunits of the alpha subunit of the ATPase show?

What does this cause?Why?

A

Reduced protein level in the membrane

Reduces the ability to set up the driving force to allow Na and Cl movement (affects Na and Cl handling)

59
Q

What ion channels are affected in the membrane by influenza?

A
  • ENaC (Po, number of channels, Rte, SCC)
  • CFTR (Po, number of channels, Rte, SCC)
  • NaKATPase (number of channels)
60
Q

What is the impact on ASL in HBE cells in culture when infected with H1N1?

A

48hr post-infection - height of ASL drops

61
Q

What is the impact on ASL in murine trachea when infected with H1N1?

A

4 days post-infection - height of the ASL drops

62
Q

What does the reduction in the ASL in HBE cells in culture and in the murine trachea suggest?

Why?

A

Suggest a bigger impact of influenza on CFTR over ENaC (more CFTR inhibition, less ENaC inhibition)

Why?
- As normally, there is a balance between CFTR and ENaC function

  • Inhibit CFTR more, ENaC can still function, absorption can still occur and water follows
63
Q

How do the height of the ASL impact on ciliary beat frequency in HBE at 48hrs?

At 72hrs?

Why?

A

48hrs:

  • Drop in ciliary beat frequency
  • Due to the cilia being bent over –> cannot beat

72hrs:

  • Height of the layer remains low but the CBF recovered
  • Compensation of the cells –> allow cilia to function (even though the height of the layer is down)
64
Q

What is the impact of a reduced ciliary beat frequency?

A

Problem clearing liquid and mucus from the lungs

65
Q

What type of drug is Lumacaftor?

What is the impact on the CFTR channel in H1N1 infected cells?ASL?

A

A corrector compound

Traffics CFTR to the membrane –> more channels in the membrane –> reduce the decrease of the height of the ASL layer –> increase height –> increase CBF

66
Q

What is the affect of Lumacaftor in H1N1 uninfected cells?

A

No effect

A BMS346 Epithelial Physiology (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions