Systems Pharmacology 3320 2017 Respiratory Pharmacology · Systems Pharmacology 3320 2017 ... - general aspects of the lab session ... The quiz will be in the MCQ/cloze test format

Systems Pharmacology 3320 2017

A/Professor Peter Henry 1

Respiratory Pharmacology

Associate Professor Peter Henry (Rm 1.34)[email protected]

Division of Pharmacology, School of Biomedical Sciences

Systems Pharmacology 3320 – 2017

1 Asthma: interactions between allergens & epithelium

2 Allergic inflammation: Th2 cells, Il-4 and mast cells

3 Allergic inflammation: Th2 cells, Il-5 and eosinophils

4 Inhibiting allergic airways inflammation

5 Key mediators of allergic airways inflammation

6 Bronchodilators and Airway Hyperresponsiveness

Lecture series : General outline



People with allergic asthma

allergen induces an inappropriately large immune response

inflammation of the airways (chemicals released from resident and inflammatory cells)

wheeze, cough, chest tightness

We are all continuously being exposed to innocuous airborne proteins.

allergen largely ignored

at worst, weak responselow levels of IgG

no symptoms

People without asthma

Why do people with allergic asthma develop these inappropriately large immune responses to allergens? It is not clear, but it seems the immune system is ‘tricked’ into reacting to these innocuous allergens in the same way as it does to signals derived from parasites such as worms and ticks.

Allergens as triggers of asthma

allergens are inhaled and the first cells they come in contact with are the epithelial cells … Ciliated epithelia:

200-300 cilia/cell which beat and move the mucus toward the mouth

Mucous-producing epithelia: produce mucus that covers the airwaysBasal cells: attach epithelial cells to basement membrane (not shown)

Many different types of epithelial cell.

allergen

The journey of an inhaled allergen …



To the asthmatic airways, allergens are foreign invaders.

most inhaled allergen is trapped by mucusand swept away by the rapidly beating cilia

If not, then the allergen meets the next line of defense, the tight junctions between the cells of the epithelium.

Interactions of allergens with epithelial cells …

Tight junctions act as ‘gate-keepers’, controlling outward flow of fluid and the inward flow of macromolecules such as allergens.

How do the inhaled allergens get past the tight-junctions ?

Interactions with epithelial cell tight junctions …



Characteristic features of allergens

Allergens are important inducers of asthma in genetically predisposed people

Many allergens are proteins, and some of these are proteases.

Important sources of allergens include: cockroaches pets, esp. cats molds pollens …

… and, in particular, house-dust mites

House Dust Mite allergens

House dust mites

are arachnids, related to spiders, scorpions etc.

live in bedding, carpets etc. feed off human skin scales produce faecal pellets (10-50 mm)

that contain large amounts of digestive enzymes (proteases)

the faecal pellets are dry and can be readily inhaled

Der P 1 is a cysteine proteaseisolated from a common house dust mite, Der P.

Dermatophagoidespteronyssinus (Der P)

… with faecal pellets containing allergens, such as Der P 1



Tight junction proteins include occludin and claudin-1

Der P 1Tight junctions

Epithelial cell Opening of epithelial barrier

and delivery of allergen

Der P 1 can penetrate epithelial tight junctions

allergens such as Der P 1 can bypass the gate-keeper …

and move through the epithelial layer …



The body’s immune response to this ‘alien’ begins when the allergen comes in contact with antigen presenting cells (APCs)at the base of the epithelium …

APC

Interactions with antigen-presenting cells

Although some other cells act as APCs, the most important APC in lung is the dendritic cell (DC).

DCs are starfish-shaped cellsthat form an extensive network throughout the epithelium.

… act as “Sentries”

e.g. Prof Joyce’smacrophages

to detect the presence of foreign invaders

Antigen presenting cells



DCs are wildly phagocytic (takeup about 4 times their volume inextracellular fluid per hour).

Allergen taken up into DCs is chopped into small peptides, which are loaded into a MHC II-peptide, and transported to the surface for display.

[ MHC = major histocompatibility complex. MHC II is like a billboard that displays what

peptides are present outside the cell ].

… mostly suck-in & spit out

… DCs present allergen fragments like a trophy

DC

Antigen presenting cells

Antigen processing by APCs

Allergen

dismembered allergen …

intactallergen …



thus, DCs take a ‘snapshot’ (piece of antigen) of what is happening on the ‘frontlines’ (within the epithelial barrier)

… stop sucking & start moving

activated DCs then leave the epithelium, and carry this snapshot (attached to the MHC II ‘billboard’) via the lymphatic system to the T cell region of the draining lymph nodes.

DC

must alert others about the foreign invaders …

Antigen processing by APCs

other potential antigen presenting cells (B cells & macrophages) don’t seem to play any role in this process since they don’t migrate to the lymph nodes.

In the lymph nodes, dendritic cells present their complex of MHC class II & antigen to naïve T cells. A minute fraction of naïve T cells express a T cell receptor that is activated by the complex & these cells are induced to proliferate (clonal expansion) & acquire the characteristics of T helper (Th2) cells.

The newly-formed ‘memory’, allergen-specific Th2 cells then travel from lymph nodes to the airways to orchestrate a military response against the foreign invaders …

Co-stimulatory proteins (e.g. Jagged and Notch) and cytokines (e.g. Il-4) are also required for clonal expansion of Th2 cells to proceed.

Antigen presentation & Th2 cell generation



Summary

So, house dust mites release Der P1, which is a protease that promotes antigen access into the airway wall.

Der P1 and other components of HDM, such as bacterial LPS, also stimulate the release of substances from epithelial cells, such as TSLP, that promote the activation, migration and maturation of dendritic cells.

TSLP = Thymic stromal lymphopoietin

When Th2 cells come in contact with APCs that are presenting their specific antigen (via MHC II), then the T cells become activated and increase production and release of a series of cytokines, most notably a number of interleukins (IL), including IL-4, IL-5, Il-9 and IL-13.

Th2 cell

waves of released cytokines(Il-4, Il-5)

Th2 cells are like the Generals in this war against allergen

How do Th2 cells orchestrate allergic inflammation ?



is produced by Th2 lymphocytes (& mast cells)

expression is increased in asthmatic airways

exerts many effects that are relevant to asthma:

stimulates B cells to produce immunoglobulin E (IgE) upregulates adhesion molecule (VCAM-1)

expression on vascular endothelial cells stimulates Th2 cell production

and IL-13 have many overlapping actions because they share common elements in their receptor and intracellular signaling pathway

Interleukin-4 (IL-4)

stimulates Il-4 receptors (Il-4R) on B cells to secrete IgE

IgE secretedfrom B cell

Wave of IL-4 from Th2 cells

B cell‘antibody factory’

Il-4R

a specific antibody that recognises the allergen …

Interleukin-4 (IL-4)



binds to FceRI receptors expressed by mast cells

Mast cell

IgE

antigen

Immunoglobulin E (IgE)

Allergen binds to IgE

promoting degranulation of mast cells



constrictors of ASM such as histamine and leukotrienes, and

chemotactic factors and cytokines that promote leukocyte infiltration and exacerbate the inflammatory response

Degranulatingmast cell

mast cells are like foot soldiers in the war against allergen …

Degranulation of mast cells releases …

are found in high concentrations in the airways

are found in the airway smooth muscle bundles of people with asthma, but not without asthma

Brightling et al., 2002 Cruse & Bradding 2016

Mast cells



can be activated by the binding of allergen to specific IgE antibodies bound to cell surface IgE receptors

undergo regulated exocytosis of:

preformed granule mediators (e.g. histamine, 1-5 min)

newly formed lipid mediators (e.g. leukotrienes, 5-30 min)

range of newly formed cytokines and chemokines (e.g. IL-4, requiring protein synthesis, hours)

further promote allergic inflammation

[ Effects produced by histamine and leukotrienes will be examined later in the lecture series and in our laboratory sessions ]

Contract ASM

Mast cells

Histamine

H1 receptor

Leukotrienes

cysLT1R

Contraction of ASM

Activation of mast cellsRapid release of preformed histamine, then slower synthesis & release of LTs

on airway smooth muscle cells

Inhaled allergen

Cross-linking of IgE on mast cell surface

Narrowing of airways in people with allergic asthma

activation of …

Allergen induces the release of histamine & leukotrienes from mast cells, causing rapid-onset airway narrowing in airways of people with allergic asthma (early phase reaction), but not non-asthmatic airways.

Non-asthmatic person

Asthmatic person

Early phase reaction

Time post inhalation (hours)

Inhaled allergen

Forced expiratory volume (FEV1) (L)

Mast cells



Summary

1. Many allergens have …….……………activity which enables them to penetrate tight junctions. An example of such an allergen is ……….... from the faecal pellets of the ………………………...

2. Allergens that enter the airway wall encounter antigen presenting cells called ………….…………, which chop the allergen into small ……..…….. & present it on the cell surface via ..........……………………………………………………...

3. Activated DCs move to the ……………………………..… via the ………..……… where they present the antigen-MHCII complex to naïve ……………..…………via a specific ……….……………... If the receptor is activated (good fit to antigen-MHC complex) the T cells undergo …………………………… and move to the airways. The airways now have ……….…… of prior allergen exposure & upon subsequent exposure to allergen Th2 cells can release cytokines such as .……………..………

5 key revision points



4. Il-4 stimulates ……….. to secrete …… which binds to FceR1 on the surface of ……………… .

5. Binding of allergen to IgE causes degranulation and immediate release of preformed mediators such as …… …….……, the rapid generation of ……………………and the slower generation of cytokines and chemokines. This referred to as the ......... phase reaction.

5 key revision points

At the completion of this lecture you will be able to:

describe the interactions of proteolytic allergens, such as Der p 1, with the airway epithelium & antigen presenting cells.

describe the properties of house dust mite allergens.

discuss how antigen presenting cells process antigen and present it to naïve T cells within regional lymph nodes.

describe the mechanisms through which Th2 cell-derived cytokines such as interleukin-4 may promote allergicinflammation and hyperresponsiveness

describe the role of mast cells in allergic inflammation

Lecture 2: Outcomes



Read and understand the handout for our lab sessions on 28th, 29th and 30th August.

A pre-lab on-line quiz is to be completed prior to attending the lab session. It is now open & will close at 11:00 AM Monday 28th August.

The quiz will cover: - general aspects of the lab session- drugs used in the lab session- the process of allergic inflammationUse lab handout, lecture material and online resources.

Once you start the quiz on the LMS (PHAR3321), you will have 1 hour to complete it and you will get one attempt at it.

The quiz will be in the MCQ/cloze test format (31 questions) and will count for 10% of your lab mark.

Notices (for PHAR3321)

Documents

Systems Pharmacology 3320 2017 Respiratory Pharmacology · Systems Pharmacology 3320 2017 ... - general aspects of the lab session ... The quiz will be in the MCQ/cloze test format