Musculoskeletal conditions and inflammation Flashcards
describe the control in endocrine hormone systems
see corticosteroid lecture slide 4
describe the Hypothalamic-Pituitary-Adrenal (HPA) Axis
see corticosteroid lecture slide 5
Contrast Gluco versus Mineralocorticoid actions
-both produced from the adrenal cortex (zones??)
- both bind to specific receptors in the body
- Glucocorticoid receptor: widely expressed
- Mineralocorticoid receptor: mainly expressed in epithelial cells in kidney, colon, bladder
- glucocorticoids widely used in as anti-inflammatory drugs in medicine (see rest of lecture)
- mineralocorticoids such as aldosterone regulate electrolyte balance in the kidney (e.g. fludrocortisone used in Addison’s disease)
- Glucocorticoids have low activity in the kidney due to the action of the enzyme 11-b-hydroxysteroid dehydrogenase which inactivates GCs
give some examples of steroids both glucocorticoids and mineralcorticoids say their mode of action
Glucocorticoids: - hydrocortisone
- prednisolone, deflazacort Betamethasone, dexamethasone (potent) Beclomethasone (asthma)
- Bind to the Glucocorticoid Receptor in the cytoplasm (widely expressed)
- Anti-insulin
Mineralocorticoids:
- aldosterone, fludrocortisone
-Bind to the mineralocorticoid receptor expressed mainly in kidney,
epithelial cells of colon and bladder, regulate electrolyte balance
what is the precursor for mineralocorticoids and glucocorticoids
cholesterol
describe the properties of the glucocorticoid receptor
see corticosteroid lecture slide 11
How does the activated Glucocorticoid Receptor identify its target genes in the nucleus?
-GC receptor dimers bind to specific hormone response elements (HREs) on target genes
what are the actions of glucocorticoids
- Metabolic
- Anti-inflammatory
- Immunosuppressive
what happens when there’s too much corticosteroids and what happens when there’s too much corticosteroids
see corticosteroid lecture slide 16
describe the metabolic effects of glucocorticoids
“protecting glucose-dependent tissues (brain and heart) from starvation”
- effect carbohydrate and protein metabolism
- Liver: decrease glucose uptake and utilization increase gluconeogenesis
- tendency towards hyperglycemia
- Decreased protein synthesis andIncreased protein breakdown - cushings disease
- provides amino acids and glycerol for gluconeogenesis
- Long-term use can lead to fat redistribution (Cushing’s Syndrome)
describe the clinical use of glucocorticoids
- Replacement therapy for Addison’s disease (adrenal failure)
hydrocortisone (GC), fludrocortisone (MC) - anti-inflammatory/immunosupressive therapy
prednisolone, dexamethasone - asthma: beclometasone (inhalation) ICBA2
- eczema }
- allergic conjunctivitis
- rhinitis
- autoimmune disease-rheumatoid arthritis, inflammatory bowel disease
- transplant patients to prevent graft v host reactions
used in cancer:
- combination with cytotoxic drugs e.g. Hodkins, leukemia
- reduce cerebral oedema in patients with brain tumor (dex)
- anti-emetic therapy in conjunction with chemotherapy - weight gain to stimulate appetite (cachexia)
Give details of the uses of steroids to treat rheumatoid arthritis and other muscle/bone inflammation
- Rheumatoid Arthritis
- Systemic Lupus Erythematosus (SLE) -Juvenile Idiopathic arthritis
- all autoimmune diseases of joints, connective tissue etc.
- treatment with supraphysiological doses of steroids reduces inflammation
How do corticosteroids reduce inflammation in SLE/RA?
- steroids suppress all phases of early inflammation
- decrease in numbers of activated macrophages, T-cells especially T-helper (CD4+) cells
- decreased IL-1, IL-2 production (lymphocyte activators)
- decreased transcription of COX-2, PLA2, IL-2R (mediators of inflammation) via inhibition of AP-1, NFkB signalling
- suppression of chronic inflammation
a) increased annexin-1 (lipocortin) levels in leukocytes, inhibition of phospholipase A2 - reduced arachadonic acid levels
- reduced prostaglandin, leukotriene levels
List the common side-effects of steroids, and the features of Cushing’s syndrome
Side-Effects/Adverse Drug Reactions of Glucocorticoids:
- mainly due to large doses and prolonged administration
- exogenous GC suppress normal H-P-A response to illness
- withdrawal from GC needs to be phased
- patients need to carry a steroid card alerting doctors to the fact that they are on steroid therapy
Main side-effect of glucocorticoids is suppression of the HPA axis
side effects see slide 32 corticosteroid lecture
Adverse effects:
Physiological:
- Adrenal and/or pituitary suppression
- Pathological
Cardiovascular;
Increased blood pressure Gastrointestinal
Peptic ulceration exacerbation (possibly)
Pancreatitis Renal
Polyuria
Nocturia Central nervous
Depression Euphoria Psychosis Insomnia
Endocrine
Weight gain Glycosuria/hyperglycaemia/diabetes Impaired growth in children
Bone and muscle
Osteoporosis
Proximal myopathy and wasting Aseptic necrosis of the hip Pathological fractures
Skin
Thinning
Easy bruising Eyes
Cataracts (including inhaled drug) Increased susceptibility to infection
(signs and fever are frequently masked) Septicaemia
Reactivation of TB
Skin (e.g. fungi-oral thrush)
Why do glucocorticoids cause osteoporosis?
- osteoporosis and increased fractures seen with steroid therapy
- important to consider when using e.g. prednisolone
- GCs regulate Ca2+/PO4– metabolism
- GCs regulate collagen synthesis by osteoblasts
- GCs inhibit Vit D3 induction of genes in osteoblasts
- GCs inhibit osteoblasts (bone formation) and activate osteoclasts (digestion of bone matrix)
what causes cushings syndrome
- arises from excess circulating glucocorticoids
- mainly caused by increased circulating levels of GC or ACTH
- ACTH from pituitary (65 % of cases-Cushing’s Disease)
- ACTH from non-pituitary tumor (10 % of cases)
- excess secretion of GC from adrenal tumor (25 % of cases)
- suppression of ACTH secretion
name some Important NSAIDs commonly in use in medicine
- aspirin
- ibuprofen
- Naproxen (Alleve)
- Indomethacin-powerful NSAID with wide ranging use/side-effects -Diclofenac
- Paracetamol
describe the mechanism of action of NSAIDs
reduce inflammatory response and pain
-NSAIDs work by inhibition the action of cyclooxygenase (COX) enzymes -2 main isoforms: COX-1 and COX-2
- NSAIDs work by inhibiting COX enzymes, lowering levels of prostaglandins e.g. PGE2, PGI2
- Prostaglandins cause:
- vasodilation
- oedema
- pain (increasing Bradykinin-mediated nociception)
General Rule of Thumb:
- Majority of anti-inflammatory effects of NSAIDs occur via COX-2 inhibition
- Most side-effects of NSAIDs occur via COX-1 inhibition
Appreciate the different roles of COX-1 versus COX-2 inhibition
-2 main isoforms: COX-1 (constitutively active) COX-2 (inducible)
COX-1:
- expressed in most tissues including platelets general “housekeeping” COX enzyme
- Prostaglandins produced by COX-1 involved in
a) protection of gastric mucosa
b) platelet aggregation
c) renal blood flow autoregulation
COX-2:
- inducible form of enzyme
expressed in activated inflammatory cells e.g. basophils, eosinophils
Other points to consider:
- COX-1 and COX-2 have approximately 60 % sequence identity
- both have similar ability to induce arachidonic acid oxidation
- differences in COX tissue expression define their different roles/side-effects
- most NSAIDS are non-selective between COX-1 versus COX-2
List the main medical uses of NSAIDs
- anti-inflammatory
- analgesic
- anti-pyretic
also:
Anti-platelet: Aspirin (COX-1 inhibition)
- Stroke prevention
- MI prevention
- Unstable angina
- Deep venous thrombosis (DVT) prevention
Colon cancer prevention:
- low dose, long-term (5 years) aspirin may reduce the risk of colon and other GI cancers - not sure how this works
what are the main side effects of NSAIDs
- gastric irritation
- compromised renal blood flow
- increased bleeding
- increase risk of MI (COX-2)
describe the mode of action of NSAIDs as anti-inflammatory drugs
Anti-inflammatory-NSAID inhibition of COX-2 predominantly
NSAIDs: decreased PGE2, PGI2 levels which:
- decreases blood flow
- decreases pain
- decrease swelling
Clinically useful in:
- Inflammatory arthritis
- Dental pain
- Oro-facial pain
- Post operative pain
- Bone metastases in cancer
NB-NSAIDs have no effect on the disease causing the inflammation e.g. RA
describe the mode of action of NSAIDs as analgesic drugs
Analgesic-mild/moderate pain due to inflammation or tissue damage
Mechanism:
i) decreased Prostaglandins, reduced sensitization of Bradykinin nociception (reduced pain reception)
- Effective in arthritis, muscle pain, toothache, dysmenorrhea postpartum pain, cancer metastasis in bone pain
- Headache: NSAIDs reduce PG-induced vasodilation in brain
- reduce postoperative pain, reduce the amount of opioids needed by up to 30 %
describe the mode of action of NSAIDs as anti-pyretic drugs
Anti-pyretic: decreased PG production in the hypothalamus
“NSAIDs reset the bodies thermostat” (paracetamol primarily used)
How?
- not sure - could be -vasodilation, sweating (COX-3) - NB-no effect on normal body temperature
list some side effects of NSAIDs
- high burden of side-effects with NSAIDs
- due to the inhibition of COX activity and PG production in non-inflammatory tissues
- common side-effects include:
- GI disturbances*
- Adverse Renal Effects*
- Rashes
- CNS effects
- Bone Marrow effects
- Aspirin sensitive asthma
- Liver toxicity (paracetamol)
describe GI disturbances with NSAIDs
Gastrointestinal Disturbances-perforations, ulcers, bleeds
- diarrohea, constipation, nausea, vomitting also common
-occurs in approximately 1/3 of patients taking NSAIDs
- approx 100,000 people in the USA hospitalised as a result of GI effects of NSAIDs
- 15 % of these people die-tend to be older patients taking NSAIDs for arthritis
- Cause: NSAIDs inhibit gastric COX-1 which generates PGE2 that stimulates mucus production and inhibits acid secretion from the parietal cells in the stomach:
> limit this effect by giving Misoprostol which is a PGE1 analogue (avoid in pregnancy!!)
> other types of ulcer protection also used (PPIs, antacids)
ICBA 2
describe adverse renal effects with NSAIDs
- in healthy patients, no risk to kidney function
- patients with compromised renal function-NSAIDs can cause acute renal failure
- neonates, elderly, heart, liver, kidney disease patients at risk of this side-effect
Cause:
- COX inhibition, reduced PGE2, PGI2 production, altered renal blood flow
- Na+ retention, leading to hypertension