Inflammation and GI Diseases Flashcards
What is a tolerogen?
Antigens that induce tolerance rather than immune reactivity
What is an immunogen?
A substance capable of eliciting an immune response
What is autoimmunity?
An immune response against self antigens.
What is central tolerance?
The limitation of the development of autoreactive B and T cells, essentially stopping new B and T cells from attacking our own cells.
What is peripheral tolerance?
The regulation of autoreactive cells already in circulation. This stops mature cells from attacking own cells.
Where do T-cells undergo development/maturation?
In the Thymus
Where do B-cells undergo development/maturation?
In the Bone Marrow
What are the different reactions of T-cell to a self antigen, and the consequent actions?
Strong reaction - Negative selection/Apoptosis
Intermediate reaction - Becomes T-regulatory cell
Weak reaction - Positive selection
No reaction - Apoptosis
What are the different reactions of B-cell to a self antigen, and the consequent actions?
High avidity - receptor editing to make new light chain of antibodies that are no longer reactive to self antigen. If editing fails, apoptosis occurs.
Low avidity - antigen receptor expression is reduced and cells become anergic (functionally unresponsive).
What occurs to a mature T-cell that responds to a self-antigen?
Anergy - functional unresponsiveness, without necessary co-stimulatory signals
Suppression - block in activation by T regulatory cells
Deletion - apoptosis
What occurs to a mature B-cell that responds to a self antigen?
If a B-cell responds to a self antigen without T-cell help, it can either become functionally unresponsive (anergic), undergo apoptosis, or can become regulated by inhibitory receptors.
What do T-cells do?
They recognise all different kinds of antigens.
What do B-cells do?
They create antibodies to antigens that are recognised by T-cells.
Where will peripheral anergy occur?
In the Secondary Lymphoid Tissue
What are the secondary lymphoid tissues?
Lymph nodes, Spleen, Tonsils, and other mucous membranes in the body i.e. the bowels
List types of self tolerance in different locations around the body
Central tolerance, antigen segregation, peripheral anergy, regulatory cells, cytokine deviation, clonal deletion
How do autoimmune diseases arise in the body?
Develops when multiple layers of self tolerance are dysfunctional and fail. A response to endogenous self antigens lead to tissue damage and since the antigen cannot be eliminated, the response is sustained. Results from a combination of genetic susceptibility, breakdown of natural tolerance mechanisms and environmental triggers.
List some common Autoimmune Diseases
Rheumatoid Arthritis, Myasthenia Gravis, Grave’s Disease, Autoimmune Diabetes
Describe how a fever occurs in the body
- A macrophage will ingest a bacterium (gram negative)
- The bacterium is degraded, which releases endotoxins which induce IL-1 production inside the macrophage.
- IL-1 will travel through the bloodstream to the hypothalamus.
- IL-1 causes the hypothalamus to produce prostaglandins which ‘reset’ the body to a higher temperature causing a fever.
Describe the sequence of the inflammatory response.
- Insult by trauma or pathogen causes acute phase reaction.
- Platelets adhere and due to histamine release there is a rapid, short term vasoconstriction of nearby vessels.
- Then, there is a cytokine-induced vasodilation of nearby vessels (increased heat & blood flow)
- Activation of complement, coagulation, fibrinolytic and kinin systems.
- Phagocytes marginate, and perform diapedesis, forcing their way into the tissue through gaps in the endothelium
- Increased vascular permeability and extravasation of serum proteins (exudate) with resultant tissue swelling
- Phagocytosis of foreign material with pus formation
- Wound healing and tissue remodelling
What are some pro-inflammatory mediators?
Acute phase proteins, complement system (C3a, C5a), kinins, cytokines (TNF, IL-6, IL-1),
chemokines (CXCL8, CCL2, CCL5), growth factors (M-CSF, GM-CSF), adhesion molecules (VCAM-1, ICAM-1), MMPs (3&9), clotting factors, prostaglandins
What are some acute phase proteins?
C-reactive protein, fibrinogen, serum amyloid A, complement factors, haptoglobin and ferritin
What do the acute phase proteins do?
C-reactive protein - acts as an opsonin
Fibrinogen - coagulation
Serum Amyloid A - cell recruitment and MMP inducer
Complement factors - act as opsonins, lysis, clumping, chemotaxis
Haptoglobin and ferritin - bind haemoglobin and Fe
Describe some of the major pro-inflammatory cytokines and their functions
IL-1 - induces inflammation, acts on hypothalamus, induces APPs from liver
TNFalpha - induces inflammation, induces APPs from liver, induces cell death, neutrophil activation
IL-12 - induces NK cells, promotes Th1
IL-6 - induces APPs, influences adaptive immunity
IFNalpha/beta - induces antiviral state, activates NK cells
Describe adhesion molecules and the different types
Transmembrane receptors that bind to other cells or to the ECM. Made up of four families: Ig superfamily (VCAM-1, ICAM-1), cadherins (E,P,N), selectins (E,P,L), integrins
Describe the metalloproteinases involved in inflammation and what they do
Matrix metalloproteinases - degrade and remodel ECM
ADAMs - cleave cytokine and adhesion molecules from cell surface
ADAMTs - cleaves the same as ADAMS and degrades proteoglycans
What is NFkB?
A family of transcription factors that regulate hundreds of pro-inflammatory mediators. It is activated by the phosphorylation of IkB and moves into the nucleus to begin transcription.
What mediators of inflammation does NFkB induce?
Cytokines (TNF, IL-6, IL-1), chemokines and their receptors, adhesion molecules, MMPs, growth factors, APPs
Name some anti-inflammatory mediators and their role
Anti-inflammatory cytokines (TGFbeta, IL-4, IL-10)
Soluble adhesion molecules - removes adhesion molecules
Tissue inhibitors of MMPs (TIMPs) - inhibit MMPs
Plasmin system - breaks down clot
Opioid peptides - counteract pain
Resolvins/protectins - anti-inflammatory lipid mediators
Describe the different types of inflammation.
Acute - necessary part of immune response, has a resolution phase
Chronic - sustained acute inflammatory response, no resolution phase, tissue destruction, can lead to disease.
Describe the process whereby prostaglandins are synthesised.
- Phospholipids are transformed by Phospholipase A2 in response to a stimulus.
- Arachidonic acid is made. This will then enter the COX enzyme and become PGG2 and then be rapidly changed into PGH2.
- PGH2 is the precursor to all other prostaglandins. These can be synthesised by other pathways from PGH2.
Describe the process whereby leukotrienes and thromboxanes can be synthesised.
- Phospholipids are transformed by Phospholipase A2 in response to a stimulus.
- Arachidonic acid is made. This will then enter a different pathway involving lipooxygenases which act on arachidonic acid.
- These lipooxygenases will turn arachidonic acid into different leukotrienes which can mediate allergy responses.
- With respect to thromboxane, arachidonic can again enter the COX enzyme, be transformed to PGG2 then PGH2.
- After this, thromboxane synthase can act on PGH2 and change it to thromboxane A2.
Describe COX-1
A constitutive enzyme present in most cells. It produces prostanoids which act as homeostatic regulators.
Describe COX-2
This enzyme is not normally present in the body (except for CNS and renal tissue), but it is induced by inflammatory stimuli.
Describe the pathophysiology of Rheumatoid Arthritis (PHASES).
- Initiator phase - beginning of autoimmunity as joint. APCs and citrullination of proteins now seen as non-self.
- Inflammation phase - self antigens presented. Increased numbers of T and B cells, uncontrolled by T-reg cells
- Self perpetuating phase - inflammatory damage in synovium causes self antigens previously not recognised by immune system become visible. Immune response against cartilage and infiltration of immune cells.
- Destruction phase - synovial fibroblasts and osteoclasts activated by cytokines (TNF, IL-6), destroy bone and cartilage.
Describe what T-cells do in Rheumatoid Arthritis.
Potentially activate monocytes, macrophages and synovial fibroblasts –> production of TNFalpha, IL-6 and IL-1, which induce the production of MMPs which degrade cartilage.
Describe what B cells do in Rheumatoid Arthritis.
Produce autoantibodies which can activate complement system and also bind to macrophages in synovium which can perpetuate inflammation.
Describe what autoantibodies do in Rheumatoid Arthritis
Rheumatoid factor (RF) and anti-citrullinated peptides (anti-CCP) are directed against self antigens on cells outside of joint.
Describe the mechanism of action of Methotrexate.
It is a competitive, reversible inhibitor of dihydrofolate reductase. It reduces the formation of dihydrofolate, tetrahydrofolate and N5,N10-methylenetetrahydrofolate. In turn, this will affect the synthesis of purines used for DNA synthesis.
Describe the mechanism of action of Azathioprine.
It is a pro-drug of 6-mercaptopurine. In the body, it is activated by glutathione to mercaptopurine. It then enters the purine salvage pathway where it undergoes metabolism in the body by hypoxanthine-guaninephosphoribosyltransferase which changes the molecule to a nucleoside derivative (TIMP) which can then undergo more enzymatic transformations into TGMP and TdGTP which act as substrates for DNA polymerase and becomes incorporated into DNA/RNA, inhibiting DNA synthesis.
Describe the mechanism of action of Allopurinol
Allopurinol works to inhibit xanthine oxidase which is responsible for the synthesis of uric acid. It does this by inhibiting xanthine synthesis and uric acid synthesis. In the body, some of the Allopurinol is metabolised into Oxypurinol in the liver.
Describe the mechanism of action of Febuxostat.
It blocks the active site of xanthine oxidase, stopping entry of substrate.
Describe the mechanism of action of Leflunomide.
It inhibits dihydroorotate dehydrogenase which is responsible for the synthesis of de novo pyrimidines. This affect the synthesis of new DNA/RNA.
Describe the differences and similarities of COX-1 and COX-2.
- Both enzymes have: a hydrophobic binding channel, a catalytic binding site, an acylation site (Serine 529), an arginine residue for ionic interactions.
- However, COX-1 has an Isoleucine residue at 523, where as COX-2 has a smaller Valine residue which allows for an extra hydrophilic binding pocket - this means there is more selectivity available for COX-2.
Describe the mechanism of action of Aspirin.
Aspirin is unique. It is the only non-selective NSAID that can irreversibly inhibit the COX enzyme. Aspirin forms a covalent bond with Serine 523 residue in both isoforms of COX, which blocks arachidonic acid access to binding site.
Describe the mechansim of action of non-selective NSAIDs.
The bulky molecule will block the COX channel, restricting the access of arachidonic acid to the active site. As well as this, the acid group in most non-selective NSAIDs mimics the acid group in arachidonic acid, allowing the drug to anchor itself in place at Arginine 120.
Describe the mechanism of action of COX-2 selective NSAIDs.
The sulfur containing group in COX-2 selective drugs (Sulfonamide, Sulfone) allows for a specific interaction in the hydrophilic binding pocket that is unique to COX-2 (Valine). This group must be able to hydrogen bond too. This allows for a stronger blockage of the enzyme’s active site from arachidonic acid, and prevents arachidonic acid from ionically binding with Arginine 120.
What is Infliximab?
Chimeric (mouse/human) anti-TNF mAb
What is Adalimumab?
Anti-TNF, fully human recombinant mAb
What is Etanercept?
Recombinant soluble human TNF p75 fusion protein (two p75 receptors) linked to Fc portion of human IgG
What are the signs and symptoms of Myasthenia Gravis?
- Patients USUALLY present with ocular symptoms (diplopia, drooping eyelids, restricted eye movement.
- Dysphagia, slurred speech, weakness in arms, legs, neck, chewing difficulties, lack of facial expression, shortness of breath (Myasthenic crisis)
Describe how Acetylcholine helps induce a muscle contraction.
- Action potential travels down motor neuron.
- Action potential opens voltage-gated Ca2+ channel.
- Calcium enters synaptic terminal.
- This causes Acetylcholine to be exocytosed, and diffuses across synaptic cleft.
- Once diffused, Acetylcholine interacts with nicotinic acetylcholine receptor.
- Once bound, a ligand-gated ion channel opens allowing Na+ into the muscle cell.
- With Na+ inside the muscle cell, the end plate action potential contracts the muscle fibers
- Once the contraction is completed, acetylcholinesterase removes acetylcholine, and the muscle relaxes.
Describe the pathophysiology of Myasthenia Gravis.
In Myasthenia Gravis, there is a loss of nicotinic acetylcholine receptors. This results in impaired transmission of the action potential. The loss of receptors is caused by autoantibodies.
What are the effects of acetylcholinesterase inhibitors?
Acetylcholinesterase inhibitors are parasympathomimetic drugs, so they mimic the body’s parasympathetic nervous system (“rest and digest”).
Actions on:
- Cardiovascular system - bradycardia, decreased cardiac output, vasodilation (decrease blood pressure).
- Smooth muscle - contraction of smooth muscle, increased peristaltic activity, bladder contraction, constriction of bronchioles
- Eye - pupil constriction, constriction of ciliary muscle (decreased intraocular pressure)
- Glands - increased secretion (saliva, tears, bronchial secretion, digestive enzymes, sweating)
What can exacerbate Myasthenia Gravis?
Infection (flu jabs!!!), stress/trauma, thyroid dysfunction, withdrawal of acetylcholinesterase inhibitors, rapid introduction or increase of steroids, anaemia, electrolyte disturbances, some drugs
What drugs can interfere with neuromuscular transmission?
- Phenytoin, Carbamazepine
- Clindamycin, Aminoglycosides (Gentamycin, Amikacin), Fluoroquinolones, Macrolides
- Lithium, Chlorpromazine
- Hydroxychloroquine
What drugs can increase muscle weakness?
- Magnesium causing hypermagnesemia
- Benzodiazepines
- Beta-blockers
- Diuretics
- Verapamil
- Statins
Dose for Pyridostigmine
15mg QDS initially, can step up to 60mg 4-6 times a day (WITH FOOD)
What side effects can present with acetylcholinesterase inhibitor treatment?
Nicotinic effects - muscle and abdominal cramps
Muscarinic effects - gut hypermobility (cramps/diarrhoea), increased sweat/salivation/crying, hypotension, bradycardia, miosis (small pupils), urinary incontinence, increased bronchial secretions, and tachypnoea (rapid breathing).
How do you manage side effects in Myasthenia Gravis treatment with Acetylcholinesterase inhibitors?
- Take with food, will reduce GI side effects
- Co-prescribing with anti-muscarinic will help prevent unwanted muscarinic effects (Glycopyrrolate, Propantheline)
- Diarrhoea can be managed with Loperamide
What can happen with excessive acetylcholinesterase inhibitor treatment?
Patients can experience as cholinergic crisis (muscle weakness that is not worsening MG)
Describe the mechanism of action of Pyridostigmine.
Pyridostigmine is a reversible inhibitor of Acetylcholinesterase. It inactivates the enzyme by carbamylating the hydroxyl group of the Serine residue. The enzyme’s regeneration by water is very slow, hence the inhibition is reversible.
What are the special patient groups for Paracetamol?
Children, patients with body weight <50kg, patients with liver impairment
What groups of patients would you resort to Paracetamol instead of an NSAID for pain relief?
Elderly, patients with hypertension, CVD, renal impairment, GI issues and patients who take medicines interacting with NSAIDs (Warfarin).
What are the special patient groups for Aspirin?
Contraindicated in patients: <16y/o, previous/active peptic ulcer, bleeding disorders, severe cardiac failure, previous allergic reaction to Aspirin or NSAID, patients with Asthma
What interactions does Aspirin have with other drugs?
- Drugs that increase risk of GI irritation and bleeding (Steroids, NSAIDS, SSRIs, anticoagulants)
- Drugs that increase the risk of renal side effects (Bisphosphonates)
- Drugs where Aspirin can increase the toxicity of other drugs (Methotrexate)
When will analgesic effects be experienced by patients with NSAID usage?
Within a week
When will anti-inflammatory effects be experienced by patients with NSAID usage?
Around 3 weeks
What KEY side effects can be experienced with NSAID usage?
GI mucosa, renal, cardiovascular system
What GI side effects are caused by NSAID usage?
- Suppression of homeostatic prostanoids (COX-1 inhibition) - reduced mucus protection, reduced bicarbonate production, reduced mucosal perfusion
- Topical irritation and direct damage of mucosa
What are the highest and lowest risk NSAIDS for GI side effects
Highest risk: Piroxicam, Ketoprofen, Ketorolac
Intermediate risk: Indometacin, Diclofenac, Naproxen
Lower risk: Ibuprofen (low dose, max. 1.2g/day)
Lowest risk: ‘coxib’ drugs - selective COX-2 inhibitors
Why are selective COX-2 inhibitors preferred over non-selective NSAIDs?
They are designed to inhibit the prostanoids from the COX-2 isoform, which are more heavily involved with inflammatory responses and play less of a role in GI homeostasis.
What key points are there for reducing risk of GI side effects with NSAID usage?
- Co-prescribe with PPI
- Take with food to reduce contact irritation
- Lowest effective dose for shortest time
What are the highest and lowest risk NSAIDS for cardiovascular events?
Highest thrombotic risk: COX-2 inhibitors, Diclofenac (150mg/day), Ibuprofen (2.4g or more/day)
Lower thrombotic risk: Naproxen (1g/day)
No evidence of risk: Ibuprofen (low dose, 1.2g or less/day)
What key points are there for reducing the risk of cardiovascular events with NSAID usage?
- Careful selection of NSAID
- Lowest effective dose for shortest time
- COX-2 inhibitors, Diclofenac and high dose Ibuprofen are contraindicated in ischaemic heart disease, cerebrovascular disease and some stages of heart failure
What interactions can occur with NSAID use with respect to the cardiovascular system?
- NSAIDs can block the effect of anti-hypertensives, which can increase blood pressure
- Anti-platelet dose of Aspirin
How can NSAIDs effect the renal system?
NSAIDs can:
- decrease renal blood flow and increase the risk of AKI
- increase sodium and water retention - oedema and hypertension
What risk factors are there for experiencing renal side effects with NSAID usage?
Advanced age, renal impairment, heart failure, volume depletion, liver cirrhosis
What interactions can occur with NSAIDs use with respect to the renal system?
- Co-prescribed nephrotoxic drugs (ACEi, diuretics)
- NSAIDs can block the effect of anti-hypertensives, which can increase blood pressure
- Lithium and Methotrexate - decreased renal elimination causing toxicity
How often is Methotrexate taken?
ONCE a week, on the same day each week.
What strength of Methotrexate should be used?
Increments of 2.5mg tablets, to avoid incorrect administration (NOT 10MG TABS)
What tests should be done before commencing Methotrexate therapy?
Full blood count, LFTs, U&Es, renal function (eGFR/CrCL), chest X-ray
What tests need to be done during Methotrexate therapy?
LFTs, renal function (eGFR/CrCL), full blood count - every 1/2 weeks until stabilised then every 2/3 months
What red flag symptoms should patients be made aware of with Methotrexate?
- signs of severe immunosuppression (sore throat, bruising, bleeding)
- signs of liver toxicity (nausea, vomiting, abdominal discomfort, dark urine)
- signs of respiratory effects (shortness of breath)
What are the key side effects of Methotrexate?
Bone marrow suppression, GI toxicity, liver toxicity, pulmonary toxicity, skin reactions
What should be co-prescribed alongside Methotrexate?
Folic acid 5mg once daily, taken on non-MTX day(s).
What are the contraindications of Methotrexate?
Active infection, severe renal impairment, hepatic impairment, bone marrow suppression, immunodeficiency, pregnancy/breastfeeding
What interactions can occur with Methotrexate?
- Anti-folates - Co-trimoxazole, Trimethoprim
- NSAIDs
- Live vaccines (recommend pnuemococcal and influenzae)
- Ciclosporin
What is the dose for Leflunomide in Rheumatoid Arthritis?
100mg OD (loading dose) then reduce to 10-20mg OD
What risks are associated with a loading dose of Leflunomide?
It can increase the risk of adverse effects, and can be omitted if necessary.
What tests should be done before and during Leflunomide therapy?
LFTs, full blood count, blood pressure
What key side effects are associated with Leflunomide?
Hepatic impairment, bone marrow suppression, increased blood pressure
What common side effects can occur with Leflunomide?
GI disturbances, alopecia, skin reactions, dizziness
What are the contraindications of Leflunomide?
Hepatic impairment, severe immunodeficiency, severe infection, severe hypoproteinaemia, moderate to severe renal impairment, pregnancy/breastfeeding
What is the step-down/washout procedure of Leflunomide?
- Monitoring after discontinuation
- Washout procedure - stop treatment, give Cholestyramine 8g TDS or activated charcoal 50g QDS, treat for 11 DAYS
What is the mechanism of action of Ciclosporin?
- Ciclosporin binds to the intracellular receptor, cylocphilin-1, which creates a complex.
- The complex inhibits calcineurin, in turn preventing dephosphorylation of nuclear factor of activated T-cells (NF-AT).
- The inhibition of NF-AT prevents pro-inflammatory mediators from being transcripted.
What key side effects are associated with Ciclosporin therapy?
Headaches, tremor, hypertension, hirsutism, renal impairment, increased risk of infections, increased risk of malignancies
What are the contraindications of Ciclosporin?
Abnormal baselines renal function, malignancy, uncontrolled hypertension, uncontrolled infection
What tests should be done before and during Ciclosporin therapy?
Renal function, hepatic function, blood pressure, lipids, U&Es, uric acid
What are the clinical signs and symptoms of Rheumatoid Arthritis?
- Symmetrical articular inflammation
- Stiffness (can be intermittent - morning is common)
- Area is warm and tender
- Positive metacarpophalangeal squeeze test (tenderness on palpation of joint(s)
- Weight loss, fatigue, fever
- Extra-articular manifestations - lungs, heart, eyes, skin
What result in a blood test can indicate Rheumatoid Arthritis?
Elevated inflammatory markers (ESR, CRP)
Elevated immunological parameters (RF, ANA, anti-CCP)
What is DAS28?
A score of disease activity in Rheumatoid Arthritis. It is measured using number of swollen and tender joints, ESR/CRP levels and a global assessment of health.
What does a DAS28 score of >5.1 mean?
Active disease
What does a DAS28 score of <3.2 mean?
Low disease activity
What does a DAS28 score of <2.6 mean?
Remission
What are some general pharmaceutical considerations to take with patients beginning anti-TNF agents?
- Increased risk of infection (stopping therapy around surgery)
- Potential risk of malignancies
- Potential risk to patients in Class III or IV heart failure
- Use of alcohol (keep within normal limits)
What monitoring would be done before commencing anti-TNF/biologic treatment?
- Co-morbidities
- FBC, renal function, LFTs
- Tuberculosis and Hepatitis (B&C) screen
- Chest X-ray
What is the pathophysiology of osteoarthritis?
Osteoarthritis occurs when:
- rate of damage of joint > rate of repair
- the joint fails to dissipate ‘load’ efficiently
- cycle of degeneration occurs
- more load = more damage
- loss of cartilage and build up of bony masses (osteophytes)
- joint space narrows
- synovitis and effusion
What are the risk factors for osteoarthritis?
- Age 45+ y/o
- Gender = female
- Obesity (BMI >25)
- Physically demanding occupation
What signs and symptoms can be associated with osteoarthritis?
- activity related joint pain
- morning stiffness lasting no longer than 30 mins
- muscle wasting
- hands/fingers presenting as nodes
What pharmacological approaches are there to osteoarthritis?
Pain relief:
1st line - Topical NSAIDs or topical Capsaicin
2nd line (if ineffective or unsuitable) - Oral NSAIDs (+PPI), paracetamol, weak opioids