Pharmacology Flashcards
In the parasympathetic division, which nerve carries preganglionic fibres?
Vagus nerve
In the parasympathetic division, where are the ganglia embedded?
In the walls of bronchi and bronchioles
What do post-ganglionic fibres of the parasympathetic division do?
Innervate bronchial smooth muscle and submucosal glands
What 3 things does stimulation of the parasymapthetic division cause?
- Bronchial smooth muscle contraction mediated by ACh acting upon M3 muscarinic ACh receptors
- Increased mucus secretion mediated by ACh acting upon M3-muscarinic ACh receptors
- Collectively, increased airway resistance
A distinct subpopulation of postganglionic parasympathetic fibres employ vasoactive intestinal peptide (VIP) and nitric oxide (NO) as transmitters - when stimulated what do these do?
Relax bronchial smooth muscle
What division has no, or sparse innervation of bronchial smooth muscle in humans?
Sympathetic division
What do postganglionic fibres of the sympathetic division supply?
Sub-mucosal glands and smooth muscle of blood vessels
What does stimulation of the sympathetic division do to bronchial smooth muscle?
Relaxation (via beta-2-adrenoceptors activated by adrenaline released from the adrenal gland)
In the sympathetic division: pre-ganglionic fibres release ACh - what does this activate?
Nicotinic ACh receptors on adrenal chromaffin cells
Sympathetic division: once ACh from pre-ganglionic fibres have been received at nicotinic ACh receptors what is released?
Adrenaline (and noradrenaline) into circulation
Sympathetic division: once noradrenaline has been released into the circulation what receptors are activated and what occurs?
Activation of beta-2-adrenoceptors on bronchial smooth muscle cells by adrenaline causes relaxation.
What does stimulation of the sympathetic division do to mucus secretion?
Decreases mucus secretion mediated by beta-2-adrenoceptors
What does stimulation of the sympathetic division do to mucociliary clearance?
Increases it mediated by beta-2-adrenoceptors
What is the name for a recurrent and reversible obstruction to teh airways in response to substances which are not necessarily noxious?
Asthma
Give 4 common causes of asthma attacks
- Allergens (in atopic individuals)
- Exercise (cold,dry air)
- Respiratory infections (e.g. viral)
- Smoke, dust, environmental pollutants
In asthma what 3 things are caused by intermittent attacks of bronchoconstriction?
- Cough
- Wheezing
- Difficulty in breathing
What involves pathalogical changes to the bronchioles that result from long standing inflammation?
Chronic asthma
Give 4 pathological changes caused by chronic asthma
- Increased mass of smooth muscle (hyperplasia and hypertrophy)
- Accumulation of intersitial fluid (oedema)
- Increased secretion of mucus
- Epithelial damage (exposing sensory nerve endings)
Airway narrowing by inflammation and bronchoconstriction increase airway resistance, what do they decrease?
FEV1 and PEFR
Name 2 sensory nerve endings exposed by epithlial damage
- C-fibres
2. Irritant receptors
What contributes to increased sensitivity of the airways to bronchoconstriction influences (and may cause neurogenic inflammation) by the release of various peptides?
Epithelial damage
What is another term for inhaled bronchoconstrictors?
Spasmogens (e.g. histamine or methacholine [muscarinic ACh receptor agonist])
What two phases comprise an asthma attack?
Immediate - bronchospasm
Delayed - inflammatory reaction
When an individual is exposed to an allergen what first step occurs?
Phagocytosis by antigen presenting dendritic cell
In a non-atopic individual, after phagocytosis by the dendritic cell what type of response occurs?
Low-level TH1 response
What type of response is a cell-mediated immune response involving IgG and macrophages?
Low-level TH1 response
In an atopic individual, ocne a dendritic cell has phagocytosed the antigen what response occurs?
Strong TH2 response
What is a strong TH2 response?
Antibody-mediated immune response involving IgE
What are the two phases in the development of allergic asthma?
Induction phase
Effector phase
In the induction phase of teh development of allergic asthma - what does the antigen presenting cell present the processed antigen to?
CD4 T cell
During the induction phase in the development of asthma - what does the CD4 T cell do to TH0 cells?
Causes them to preferentially mature to TH2 cells that produce a cytokine environment
During the induction phase in the development of allergic asthma - what do the T helper 2 cells activate and how?
Activate B cells by binding to them and by IL-4 production
During the induction phase of the development of allergic asthma - what happens to the B cells?
They mature into IgE secreting plasma cells
During the effector phase in the development of allergic asthma - what do the eosinophils differentiate and activate in response to?
IL-5 released from TH2 cells
During the effector phase in the development of allergic asthma - what do mast cells in airway tissue express IgE receptors in response to?
IL-4 and IL-13 released from TH2 cells
During the development of allergic asthma - what does the subsequent presentation of antigen cross link with?
IgE receptors
During the development of asthma - what does subsequent presentation of antigen stimulate?
Calcium entry into mast cells and the release of Ca2+ from intracellular stores
During the development of allergic asthma - what does the increase in intracellular calcium cause the release of?
- Secretory granules containing preformed histamine and the production and release of other agents (e.g. leukotrienes LTC4 and LTD4) that cause airway smooth muscle contraction.
- Substances (e.g. LTB4 and platelet-activating factor PAF and prostaglandins (PGD2) that attract cells causing inflammation (e..g mononuclear cells and eosinophils) into the area
What are chemotaxins and chemokines (LTB4, PAF, PGD2) and spasmogens (histamine, leukotrienes - LTC4, LTD4) released from and what are they released in response to?
Activated mast cell in response to increased intracellular calcium ion levels.
During the immediate phase of asthma - what are the first two cells to react?
Mast cells and mononuclear cells
During the immediate phase of asthma - what two substances do mast cells release?
Spasmogens (cysLTs and histamine)
Chemotaxins and chemokines
In the late phase of asthma - what do chemotaxins and chemokines released from mast cells do?
Infiltration of cytokines releasing TH2 cells and monocytes, activation of inflammatory cells, particularly eosinophils
During the late phase of asthma - what two substances do eosinophils release?
Mediators cysLTs and others
Eosinophil major basic and catonic proteins
In the late phase of asthma - what do the mediators cysLTs and others cause?
Airway inflammation, airway hypersensitivity
Bronchospasm, wheezing and cough
During the late phase of asthma - what do eisoniphil major basic and catonic proteins cause?
Epithelial damage which leads to airway hypersensitivity
What two basic classes can drugs used in the treatment of asthma be placed into?
Relievers and controllers/preventors
What do relievers act as?
Bronchodilators
What do controllers/preventors act as?
Inflamamtory agents that reduce airway inflammation
Name 3 types of drugs that act as relievers in asthma
- Short acting beta-2-adrenoceptor agonists
- Long acting beta-2-adrenoceptor agonists
- CysLT receptor antagonists
Name 3 groups of drugs that are controllers/preventors
- Glucocorticoids
- Chromoglicate
- Humanised monoclonal IgE antibodies
Which group of drugs is both a reliever and a controller/preventor?
Methylxanthines
What act as physiological antagonists of all spasmogens?
Beta-2-adrenoceptor agonists
When a beta-2-adrenoceptor agonist acts on a beta-2-adrenoceptor on airway smooth muscle, what becomes activated?
Gs which then activates denylyl cylase
Once a beta-2-adrenoceptor agonist has acted on a receptor and caused stimulation of Gs and then Adenylyl cylcase, what does adenylyl cyclase then catalyse?
The conversion of ATP to cyclic adenosine monophosphate (cAMP)
Once a beta-2-adrenoceptor agonist has acted on a receptor and caused the conversion of ATP to cAMP, what does cAMP then inhibit and stimulate?
Inhibits PDE - 5 AMP
Stimulates PKA
Once a beta-2-adrenoceptor agonist has acted on a receptor andc caused the stimulation of PKA (protein kinase A), what becomes phosphorylated and what is the end result?
Phosphorylation of MLCK (myosin light chain kinase)
Relaxation of airway smooth muscle
In common with most G protein coupled receptors (GPCR), what does persistent activation of beta-2-adrenoceptors cause?
Receptor desensitisation and endocytosis (resulting in loss of function)
During over activation of beta-2-adrenoceptors and desensitisation, what two kinases are involved?
- Protein kinase A (PKA)
2. G protein receptor kinases (GPRKs) - specifically beta-adrenoceptor kinases
During the desensitisation of beta-2-adrenoceptors, what do protein kinase A and G-protein receptor kinase do to the activated beta-2-adrenoceptor?
Phosphorylate it
What can be said about hte phosphorylation of a protein kinase A receptor?
Can be phosphorylated with no agonist bound
What can be said about a g-protein receptor kinase receptor in relation to phosphorylation?
Receptor is phosphorylated only when agonist is bound
What does a PKA phosphorylated beta-2-adrenoceptor result in?
Reduced G-protein coupling
What does a GRK phosphorylated beta-2-adrenoceptor result in?
Formation of beta-arrestin receptor complex which leads to loss of G-protein coupling/endocytosis
What acts as a scaffold protein that links the desensitised beta-adrenoceptors to endocytic machinery that internilise the receptor?
Beta-arrestin
How are receptors internalised by beta-arrestin?
In clathrin-coated pits and vesicles and trafficked to either endosomes for recycling, or lysosomes for degradation.
When does beta-arrestin unbind from the vesicle?
Between endocytosis and the endosomal vesicle
In an endosomal vesicle the agonist is still in the receptor on the membrane, when the agonist moves in what occurs to the cell environment?
Turns more acidic (acidic vesicle)
Name two short acting beta-2-adrenoceptor agonists
- Salbutamol
2. Albuterol
What are the first line treatment for mild, intermittent asthma?
Beta-2-adrenoceptor agonists - short acting
How long does it take for a short acting beta-2-adrenoceptor agonists to reach maximal effect and how long does relaxation persist for?
30 minutes
Persists for 4-6 hours
What increases mucus clearance and decreases mediator release from mast cells and neutrophils?
Short acting Beta-2-adrenoceptor agonists
Give two adverse effects due to unwanted systemic absorption of inhaled short acting beta-2-adrenoceptor agonists
- Fine tremor
2. Occasional tachycardia
Name a long acting beta-2-adrenoceptor agonist?
Salmeterol
What type of beta-2-adrenoceptor agonists are useful for nocturnal asthma?
Long acting beta-2-adrenoceptor agonists because of their long half life
Can long acting beta-2-adrenoceptor agonists be used as monotherapy?
No
What does the use of selective beta-2-adrenoceptor agonists reduce?
Potentially harmful stimulation of cardiac beta-1-adrenoceptors
Why are non-selective beta-adrenoceptor antagonists (e.g. propranolol) contraindicated in asthma?
Because the risk of bronchospasm
Where do cysLT antagonists act competitively at?
The CysLT receptor
Name three CysLTs?
LTC4, LTD4, LTE4
Where are cysLTs derived from?
Mast cells
When cysLTs infiltrate inflammatory cells what occurs?
Smooth muscle contraction, mucus secretion and oedema
During the use of cysLT receptor antagonists, once mast cells have been activated what does phospholipase A2 release?
Intracellular arachidonic acid
During cysLT antagonist use, what does arachidonic acid stimulate?
Mast cell 5-lipoxygenase by FLAP
What is 5-lipoxygenase blocked by?
Zileuton
During cysLT antagonist use, what occurs once mast cell 5-lipoxygenase has been stimulated by FLAP?
LTA4 is produced which in turn creates LTB4 and LTC4
During cysLT antagonist drug use, what two substances are transported across the mast cell membrane?
LTB4 and LTC4
During cysLT antagonist drug use, what does LTB4 do once it has crossed the mast cell membrane?
Infiltration of inflammatory cells released cysLTs
During cysLT receptor mechanisms, once LTC4 has crossed the mast cell membrane, what occurs?
It splits into LTD4 and LTE4 which act on the cysLT receptor (which antagonists block)
Once the cysLT receptor has been activated what two responses occur?
- Bronchoconstriction (early phase)
2. Inflammation (delayed phase)
Name 2 cysLT receptor antagonists?
Montelukast and Zafirlukast
What drugs are effective as add on therapy in mild persistent asthma and in combination with other medications in more severe conditions?
CysLT receptor antagonists such as Montelukast and Zafirlukast
What two induced bronchospasms are cysLT receptor antagonists such as montelukast and zafirlukast used for?
Antigen-induced and exercise induced bronchospasm
How are cysLT receptor antagonists such as Montelukast and Zafirlukast delivered?
By the oral route
Name 2 xanthines?
Theophylline and aminophylline
What type of bronchodilators are present in coffee, tea and chocolate beverages?
Xanthines
What type of bronchodilators have an uncertain molecular mechanism of action - might involve inhibition of isoforms of phosphodieterases (i.e. PDE III and IV) that inactivate cAMP and cGMP (second messengers that relax smooth muscle and perhaps exert an anti-inflammatory effect)
Xanthines
What are second line drugs used in combination with beta-2-adrenoceptor agonists and glucocorticoids?
Xanthines such as theophylline and aminophylline