Biochem exam - Module 4

• deals with all drugs in the society - legal and illegal

• explains how drugs interact with the body

• clinical pharmacology - how drugs interact with humans - with minimal adverse effects but have therapeutic outcome

pharmacology

• drug - chemical which can affect a living proccess

• therapeutics - use of drugs to diagnose, prevent or treat a disease

basic drug terms

• from micro-organsims,

• plants - e.g. atropine

• animals - insulin, thryoxine

• minerals - ferrous sulphate

• synthetic

• biopharmaceuticals - proteins, antibodies uses as drugs

• gene therapy - addition of gene to prevent or cure disease

drug sources

• right drug - selective for the condition, thinking about what the drug is used for, how it works, why it is chosen

• drug dose - depending on the patient and the condition

• right client - who the patient is - child, preg

• right RoA - topical, oral

• right time - when it should be taken, with food

5 Rights of good drug managment

• chemical mediators - histamine

• acting on organ system - salbutamol

• acting on nervous system - antidepressants

• treatment of infection and cancer - antibacterials or chemotherapy

classification of drugs

• chemical name

• generic name

• brand name

• ending of drugs - e.g. olol - beta blockers, tidine - histamine antagonist

names of drugs

• s2 - cold, cough

• s3 - required professional advice

• s4 - prescription - bronchodilators

• s8 - morphine

schedule of drugs

• prescribed dose - influenced by the medication and patient’s compliance

• administered dose and is concentration at the site of action - influenced by how the body interacts with the drug - pharmacokinetics

• intensity of the response depends on - what the drug does to the body (pharmcodynamics) - how it effects body at cellular or molecular level resulting in a therapeutic or toxic effect

• this is impacted by how the drug is distributed, absorbed (affecting bioavaliability) metabolised (if it is at toxic or therapeutic levels) and excreted

what influences drug action

• interacts with receptors - salbutamol interacts with B2 adrengeric receptors to allow for bronchiole dilation in asthma.

• interacts physically - osmotic diuretics - can promote urination

• chemically - antacids - neutralise stomach acids

• interact with endogenous proteins, antibodies for monoclonal antibody therapy

• interact with genetic material for gene therapy

• interact with enzymes for inhibition (NSAIDs) ion channels inhibiton (local pain relief), transporter inhibitor - (antidepressents)

targets of the drug sites

• binds to the receptor and activates or inhibits it - resulting in transduction - causing enzyme activation, ion channel modulation, transcription

• can be a molecule or drug

• usually reverisible binding

• binding is due to intermolecular forces between agonist and receptor

• stronger forces of attraction - higher affinity receptor has for agonist

• agonist binds and can change the receptor structure and stimulates transducers

• high degree of receptor activation - high efficacy

• effiacy is whether the agonist-receptor complex induces a response

• mimic actions of endogenous molecules - e.g. pheylephedrine - vasoconstriction

agonist

• it binds to the receptor and blocks it to prevent an effect.

• blocks the affects of endogenous ligands

• e.g., prazosin

antagonist

• agonist binds to the receptor, causing the channel to open and causes ions to move

• cause hyperpolarisation or depolarisation

• cellular response within milliseconds

• e.g. acetylcholine binds to nicotinic receptors causing skeletal muscle contraction

Ligand-gated ion channel receptor

• the agonist binds to receptor, the receptor then activates the G protein

• the G protein activates another enzyme which caused a secondary messenger response

• a transducer relays signs from the extracellular signal to intracellular then creating a secondary messenger response

• cellular response within seconds

• salbutamol binds to b2 adrenergic receptors activating adenylyl cylase enzyme, activating secondary messengers like cAMP causing bronchodilation

G-protein coupled receptors

• agonist binds to the receptor activating enzyme which produces, the receptor activates the enzyme, MAPK (mitogen-activated protein kinase) causing a secondary messenger response

• may take minutes for a response

• insulin binds to the receptor, causing MAPK activation, causing a metabolic effect or growth and cell survival

Enzyme-linked receptors

• the agonist move into the cell, attaching to the receptor in the cytosol or nucleus, which can cause transcription changes

• may take hours for a response

Nuclear receptors

• blockers - permeant and prevent it from working

• modulators - increase or decrease the probability of opening

• Lignocaine - sodium channel blocker - prevent sodium from entering the cell thus blocking nerve conduction, to inhibit pain sensation

Blockers and modulators

• inhibitors - binds to receptors and inhibits a normal reaction - antidepressents work to inhibit serotonin or 5HT reuptake

• false substrate - active molecule metabolized by the body into an abnormal, often disruptive product.

• prodrug - inactive form of the drug which is converted to active drug form in the body

Inhibitors, false substrate, prodrug

• drugs that target inhibit the breakdown of cholinesterase - an enzyme which breaks down acetylcholine

• atropine also binds to muscarinic receptors and competes with acetylcholine to prevent the action of excess acetylcholine

• by inhibiting destruction of acetylcholine resulting in accumulation of acetylcholine at the synapse to further bind to M3 receptors in the neuromuscular junction to produce a stronger more sustained muscle contraction

• indirect agonist - doesnt binds directly to acetycholine receptors, but allows for acetycholine to bind to its receptors

• neostigimine overdose - reversible competitive acetylcholine receptor

• an example is neostigmine

• indirect cholingeric agonist and enzyme inhibitor for anticholinesterase

anti cholinesterase

• attraction of a drug to a particular receptor - based on the chemical properties of the drug and receptor

affinity

• how well a drug and receptor will fit or bind - the number of targets the drug has with the receptor

• may be group with specificity

• ideal drug would only interact with one target and have one effect - not possible

selectivity

• number of effects the drug produces

• may be grouped with selectivity

specificity

• how well a drug produced a therapeutic effect

efficacy

• how much drug is need to have a proper effect

• maximal response on dose response curve - is when all the receptors are occupied - when drugs have maximal response they are full agonist

• for agonists potency may be expressed as 50% of the agonists maximal response (EC50)

• lower the EC50, the more potent the drug - two agonists can be compared

• depends on affinity and efficacy and tissue dependent factors like number of receptors

potency of agonists

• different cells have different types and number of receptors depending on hormones and neurotransmitters

• receptors have specificity to ligands

• the receptor depends on chemical structure and stereoselectivity

• more selectivity of drug to receptor reduces the side effects of drugs

• one drug can act on multiple receptors

• e.g increase of salbutamol - binds to b1 adrengic receptors in the heart - causing increase heart rate and contraction - cause cause tachycardia

receptors

• submaximal response - not full maximal response

• have a low efficacy - low level of activation when bound to receptors

• depending on characteristics of the tissue like number of receptors, it may even act as a partial agonist, full agonist or a competitive antagonist

partial agonists

• binds at a site away from the active site and increase the response of the agonist or it can decrease the response (antagonist)

allosteric modulator

• competes with agonist for the receptor - decrease response

• reversible binding to agonist

• it increases the EC50 of the agonist to create a response, reducing its potency

reversible competitive antagonist

• binds irreversibly to the agonist, reducing the number of receptors the agonist can occupy - causing no response to occur with those receptors

• reduces the slope and maximum response

• higher antagonist dose, cause a larger effect

irreversible competitive antagonists

• binds independently, blocking the response to the agonist at some point within the receptor - cascade

• reduces the space for agonist to bind to receptor - decrease response

• binds with the agonist

noncompetitive antagonist

• auto-immune condition due to the body creating antibodies to the acetylcholine receptors - which are nicotinic receptors - ligand-gated ion channels

• double vision, drooping eyelids

• antibodies cause destriction of nicotinic receptors at neuromuscular junction

• antibodies decrease the sensitivity and density of the nicotinic receptors for acetylcholine.

• antibody can impair acetylcholine binding to the receptor

• decreasing depolarisation and muscle contraction

• pupil contraction - neostigmine increase acetylcholine at receptors, despite being few receptors it is able to have a higher chance to bind to nicotinic receptors - relieving muscle weakness

myasthenia gravis

• 4-5 membrane-spanning subunits

• swelling regions at the intracellular and extracellular ends

• membrane spanning region - passes through lipid bilayer

• When closed, no ions can cross membrane

• protein subunits - alpha, beta, gamma, delta The

• composition of subunits determines the physiological and pharmacological properties of the receptor

ligand-gated ion channel structure

• pentameric ligand-gated ion channel

• 5 subunits

• 2 alpha, 1 beta, one gamma and delta

• activated by acetylcholine and increases permeability of sodium and calcium depolarisation and exicitation

• found in CNS - selective for sodium and skeletal muscle - selective for sodium and calcium

• one acetylcholine molecule binds to each of the 2 alpha units, opening the channel causing sodium influx, causing depolarisation and skeletal muscle contraction

nicotinic receptor structure

• inhibitory neurotransmitter - causing hyperpolarisation

• it has receptors

• GABA a receptor - ligand-gated chloride channel - opens fast and decreases excitation - inhibiting neuronal conduction

• GABA b receptor - slower prolonged inhibition by secondary messengers - linked to G protein coupled receptors specifically Gi alpha

• relates to motor control, memory and consciousness

• used to treat muscle control, insomnia, anxiety

GABA

• hyperpolarisation

• mediate most of the fast inhibitory neurotransmission in CNS

• pentameric

• each subunit contains 4 domains which are spread across the cell membrane

• alpha, beta, gamma subunits

• two gaba binding sites between alpha and beta subunits

• one benzodiazepine modulatory site - between alpha and gamma - away from gaba binding - acts as allosteric modulator and increases gaba effects

GABA receptor structure

• creates change in the gaba receptor structure enhancing affinity for gaba neurotransmitter

• acts only in GABA presence

other ways that benzodiazepine works in terms of gaba

• pre and post synaptic actions

• inhibiton and excitation neurotransmitter

• sodium and potassium influx

• 5HT1 - inhibition by g protein couple receptor Gia - cortex and target for anxiety drugs

• 5HT1 - excitation by g protein couple receptor GQa - hallucinogenic effects - cortex and hippocamus of brain

• 5HT3 - excitation by ligand-gated ion channel - in brainsteam - related to vomiting

• modulate mood, emotion, sleep, appetite, vomiting

Serotonin

• n-methyl-d-aspartic acid (NMDA)

• glutamate binds to NMDA

• allows influx of sodium, calcium, out potassium

• only two antagonists are clinically useful - ketamine, memantine

NMDA receptor

• non-NMDA

• glutamate binds to receptor

• sodium influx

• depolarisation and exictation of neuron

AMPA receptor

• for glycine

• increase chloride conduction into cell

• inhibition of neuronal conduction

• ionotropic

Glycine receptor

• muscarine - activates parasympathetic system

• acetylcholine binds to muscarinic receptors

• causing vomiting, stomach pain, diarrhoea, nausea

• muscarine - direct agonist

mushroom poisoning

• seven helix transmembrane receptors - in bilayer which crosses 7 times

• serpentine receptors - zig zag structure

• metabotropic receptors - transmits a signal instead of ion influx or out

• ligand binding site

• 3 subunits - alpha, beta, gamma

• G-alpha protein classes

G protein coupled receptor structure

• Gs - activates adenylyl cyclase

• Gi - inhibits adenylyl cyclase

• Gq - activates phosphoplipase C

G-alpha protein classes

• regulatory

• binding produces a change conformation of receptor - increasing affinity of receptor to G protein

• mediators for cell-surface proteins

• links surface receptors to effector proteins - generate intracellular second messengers

• e.g. adenylate cylase- cAMP

• or phospholipae C - inositol P3

G protein

• adrenaline bind to beta adrenergic receptors

• receptore activate G protein alpha S

• activates adenylyl cyclase

• activates cAMP

• this activates protein kinase A causing glycogen breakdown

Adrenaline action

• receptor binds to heterotrimeric G protein, causing conformational change in g protein alpha

• G alpha - binds to GTP and GDP and possesses GTPase activity

• g protein alphas has GTPase synthase activity converting GDP to GTP

• g alpha dissosicates from hetertrimetric structure and binds to adenylyl cylase or phospholipase c , causing synthesis of cAMP or inotiol-phosphate 3 or diaceylglycerol , causing intracellular signalling cascade and responses

• GTP hydroylsed back to GDP - inactivating adenyl cyclase

• g-alpha dissosicated from adenylyl cyclase and binds back to heterometric structure

• receptor dissociates from G protein, g protein inactivated, ligand dissociated,

how G protein coupled receptor works

• beta adrenergic receptor - salbutamol, noradrenaline

• hormone receptor - corticotropin, glucagon, parathyroid

• stimulates adenylyl cylase to produce cAMP and protein kinase A

• Noradrenaline - acts on actin-myosin to cause smooth muscle contractions

G alpha s receptors and ligands

• a2-adrenergic receptors

• m2 muscarinic receptors - works in heart acetylcholine

• opiod receptors - morphine

• inhibits adenylyl cylase - opens potassium channels

• closes calcium channels

G alpha i receptors and ligands

• alpha 1 adrenergic - adrenaline

• m3 receptors - acetylcholine

• ADH receptor

• activates phospholipase C - producing IP3 - releasing calcium ions

• produces DAG and protein kinase C

• for adrenaline - causes smooth muscle contraction and glycogen breakdown

G alpha q receptors and ligands

• works on rhodopsin receptor - absorbs light

• activates cGMP phosphodiesterase

• break down of cGMP and protein kinase G

G alpha t

• odorant receptors

• activates adenylyl cyclase and protein kinase A

G alpha olf

• M1(cns) M3 coupled to G q protein

• activation of G q protein results in activation of phospholipase c - producting IP3 and DAG and calcium ion release ang glycogen breakdown

• smooth muscle contraction and secretion

• M2 coupled to Gi protein

• inhibits adenyl cyclase and decreases cAMP - opens potassium and closes calcium channels - decrease cardiac conduction and cns effects

Muscarine receptors

• a1 coupled to G q proteins

• phospholipase C activation -producing ip3 and DAG - increase calcium ions - smooth muscle vasoconstriction

• a2 coupled to G i proteins - inhibits adenyl cylase and camp, close calcium channels and potassium opens - hyperpolarisation

adrenergic receptors

• b1 - heart

• b2 - lungs

• coupled to G alpha s

• activation of adenyl cylase - activates cAMP, and protein kinases A

• PKA causes bronchiole dilation of bronchioles and phosphorylates calcium channels, increase calcium and rate and force of heart contractions

beta receptors

• vasopressin receptor - diabetes insipidus - kidneys dont reabsorb water

• adrenocortric hormones - glucocorticoid def - failure to make glucocorticoids

• cone cell opsin - colour blindness

• rhodopsin - retinal degerneration

defective GPCR

• gs - cholera, thyroid tumours

• gi - whooping cough, ovarian tumours, adrenocortical issues

defective g alpha subunits

• has a tyrosine kinase component in intracellular component

• auto-phosphorylates tyrosine kinase residues

• receptor for growth factors - like epidermal growth, nerve growth factor

• enzyme linked receptor

Receptor tyrosine kinase

• receptors for transforming growth factor

• cytokine receptors - for cytokines such as interferons

receptor serine/ threonine kinases

• receptors for insulin and insulin-like growth factor

• dimer

• two disulphide bridges

• extracellular regions - two alpha subunits and cysteine rich domains

• intracellular regions - beta subunits with tyrosine kinase residues

RTK type 1 insulin receptor

• immediate - within minutes, no protein synthesis or nuclear signaling, increase carbohydrate, fat and protein metabolism

• long term - hours or days - increased expression of certain enzymes, protein synthesis

• overall - uptake, utilising, storing of glucose, amino acids, and fats after a meal

effects of insulin

• immediate

• activation of protein kinase b - increase in number of cell surface glucose transporters

• glucose transporters - glut 1 and 4

• depends on insulin receptor substrate

• Glut 1 - low levels on cell surface even in insulin abscence

• Glut 4 - in the membrane of intracellular vesicles

• in fat and muscle tissue

RAS independent pathway

• long term effects

• involves activation of MAP kinase - interacts with transcription factors in nucleus - causing growth and cell survival

• depends on Insulin receptor substrate

• kinases - have a role in signal transduction - controling growth and gene transcription

• protein kinase phosphorylation - crucial in signal transduction for enzyme activity - for cell growth

RAS dependent pathway

• binding of insulin to alpha subunits causing movement of beta subunits to move closer together

• auto- phosphorylation of tyrosine kinase residues results in activation of receptor, which catalyses the insulin receptor substrate, activating RAS

Steps leading up to RAS pathway activation

• binding of insulin activates insulin receptor substrate

• promotes protein kinase B activation causing exocytosis of GLUT 4 - increasing number of cell surface transporters and increase glucose uptake

Regulation

• once insulin signal is removed, GLUT 4 endocytosis back to membrane, reducing of plasma membrane glut 4

• lower uptake of glucose

Steps for RAS independent pathway

• by RAS dependent pathway

• multiplication and differentiation of cells in normal tissue is regulated

• mutiplication in the absence of growth factors and resistant to apoptosis signals

• mutations in proteins

cancer control

• Her 2 receptor - valine to glutamine mutation

• epidermal growth factor receptor - deletion of the extracellular ligan-binding domain

• mutations results dimerisation of receptors in absence of ligand, active tyrosine kinase, uncontrolled growth, cancer

oncogenic mutations for RTK

• not embedded in membrane

• located in cytoplasm and translocated to nucleus after binding of ligand to receptor in cytoplasm

• regulate/modify gene transcription

• can interact with DNA directly

• control gene expression of many genes and proteins - regulating metabolic, developmental and other processes

• important targets for drugs - target nuclear receptors

• steriod hormone receptors - estrogen and glucocorticoids

nuclear receptors

• class 1 - endocrine sterioid hormone receptors - estrogen, progesterone cytoplasm, mainly in negative feedback - minercorticosteriods - aldosterone - target for spironolactone, hormone regulation

• class 2 - lipid receptors, peroxisome proliferator activated receptor - lipids as ligands and target for thiazolidinediones

• class 3,4

Classes of nuclear receptors

• muscarinic competitive antagonist

• blocks the binding of acetylcholine to M3 receptors or competes with acetylcholine

• no effect - decreasing acetylcholine in experiment

Atropine

• mimics the effect of the neurotransmitter of parasympathetic nervous system

• gastrointestinal motility, salvation, secretion,

• mushroom poisoning causes this overactivation of the parasympathetic nervous system

• m3 receptors are g protein coupled receptor, acted upon by g protein q which causes phospholipase c activation, causing activation of IP3 and DAG and calcium ions and phosphokinase C which cause smooth muscle contraction and the assosicated symptoms of vomiting and abdominal pain

• can be helped with a reversible competitive antagonist to block muscarine effects

muscarine action

• inhibit cholinesterase - an enzyme which breaks down acetylcholine

• anti cholinesterase poisoning - build up of acetycholine at the synapse

Anticholinesterase

• iontropic

• G protein alpha s and q

acetylcholine

• PRISH

• capillary dilation

• leukocytes infiltration, swelling

• acute or chronic

• acute - vascular then cellular phase

• pain - increased sensitsation

• immobility - due to edema

Inflammation

• momentary vasoconstriction of arterioles then prolonged vasodilation

• permeability increases, protein and fluid migrate

• odema from exudate, release of sensory mediators

• stagnation of blood flow followed by clotting

vascular phase of acute inflammation

• monocytes, macrophages and mast cells release to attractant mediators

• migration of neurophils, macrophages and leukocytes by diapedsis

• chemotaxis - recruiting more white blood cells

• activation of neutrophils and macrophages - phagocytosis

• monocytes mature into macrophages which can be in the tissue

cellular phase of inflammation

• due to infection, injury, allergic reactions, toxins, foreign particles

• immediate

• days

• PRISH

• neutrophils, mast cells, monocytes, macrophages, eosinophils, platelets

• histamine, prostaglandins, thromboxane A2, bradykinin, complement interleukins, chemokines

• increase permeability

• collection of pus and may progress to chronic inflammation

acute inflammation

• persistent infection

• incomplete removal of foreign particles

• prolonged exposure to toxins

• autoimmune

• delayed - months to years

• macrophages, lymphocytes T and B, fibroblasts

• prostagladins, complement, cytokines, growth factors, proteases (removal and tissue remodelling) nitric oxide

• vessel remodelling

• ongoing cycles of damage and repair - fibrosis and scarring

chronic inflammation

• synthesised in the liver

• secreted into the circulation

• preformed, stored or synthesised on demand

• vasodilation or constriction, plasma proteases, chemotatic factors, cytokines

• cytokines - produce effect on cells, chemokines promotes migration of substances

inflammatory mediators

• vasoactive amine

• decarboxylation of histidine and stored in mast cells and basophils

• high concentrations in the GIT, skin, lungs

• binding of C3a, C5a, IgE to receptors causing its activation

• H1 - antihistamines

• H2 - treatment of gastroesophageal disease

histamine

• increase chemotaxis and production of prostaglandins, thromboxane, nitric acid and platelet activating factor. Initiation of smooth muscle contraction and vasocon

H1

• increase cardiac rate and output, secretion of stomach acid.

H2

• vasodilation, regulation of histamine release, increase in immune antigen processing (proteins from pathogens are broken down into smaller molecules) itching and bronchoconstriction

H3

• increase cytokine production, chemotaxis and diapedesis, regulation of monocyte function and role in cancer cells

H4

• most stored in the enterochromaffin cells (neuroendocrine) of the intestinal mucosa.

• stored in platelets as granules

• 7 types of receptors (5HT) that are all G protein coupled except type 3 which is sodium and calcium ion channel

• Regulatory role in the function of specialised T cell subsets - for gut inflammation

• controlling macrophage function increasing phagocytosis and anti-infammatory effect

• assists in diapedesis of mast cells and its degradation to release histamine

• activation of 5HT receptors causes platelet aggregation

Serotonin

• C3 is broken into C3a and C3b

• C5 is broken into C5a and C5b

• C3a - anaphylaxtonin (inflammatory) - causes mast cell degranulation, chemotaxis

• C3b - allows molecules to be coated to promotes phagocytosis

• C5a - inflammatory and chemotaxis

• C5b - gathering of C6,7,8,9 to form membrane attack complex (MAC) to form pores in bacterial walls - lysis

complement cascade

• clotting factors can activate the complement system

• clotting factors can act as proteases to cause breakdown of C5 and C3

• these include thrombin (protease for activation of plasmin and kallikrein), plasmin, (protease) kallikrein (proteases in bradykinin production)

coagulation cross linked activation

• comes from the plasma or tissue

• product of kallikrein-kinin system

• Kallekrein is a protease in tissue and plasma which cleaves ‘heavy’ (from plasma) and ‘light’ (tissue)

• Kininogen molecules to produce Bradykinin directly in plasma or by conversion of Kallidin to Bradykinin in tissue

• In inflammation, leakage of Factor XII (Hageman factor) and prekallekrein drive the formation of heavy kininogen and subsequent bradykinin formation.

• acts on B1 receptors - induced or B2 receptors which are always open - G protein coupled

• B1 - cytokine production

• B2 - pain sensitation, mitosis, blood vessel formation

Bradykinin production and receptors

• caused immobility in inflammation

• vasodilation and increase permeability through smooth muscle relaxation

• histamine release from mast cells and basophils

• strong contractions of smooth muscle - uriterine, GI, bronchioles

• increases pain sensitivity in combination with PGI2, nitric oxide - neurotransmitters, induces release of other neurotransmitters

• overproduction - nasal congestion, smooth muscle hypertrophy, cough

• degrades by kinases and ACE

Bradykinin

• highly potent vasodilator - synthesed by nitroxide synthase from arginine synthesis

• short half life, water soluble

• endogenous - by arginine

• exogenous - dietary nitrites

• pain sensitivity, cytokine release from leukocytes - neutrophils, macrophages

• increase prostaglandin formation

• anti-inflammatory effect - t and b regulation

• antitumour and antimicrobial

• control of leukocyte chemotaxis and migration by modifying its adhesion

• inhibit platelet aggregation

• high concentration are harmful

Nitric oxide

• Control of cell death by either apoptosis or necrosis with application to oncology.

• Beta cell destruction in type 1 diabetes (pathological state), or insulin secretion (homeostatic state).

• CNS neurotransmission (↑ glutamate excitation) or RNS damage to neuronal proteins

• Male and female sex cell development

• Bone metabolism and wound healing

other effects of nitric oxide

• endothelial NOS and Neuronal NOS - always open and has calcium binding region, with electron transfered by FMN, FAD, BH4

• inducible NOS - barely detected in homestasis and huge activation in inflammation

• NOS - has two NOS molecules

nitric oxide synthase

• activation of guanylate cyclase

• guanylate cyclase is water soluble and senses nitric oxide

• nitric oxide interacts with the heme centre-group of guanyl cyclase and increases its affinity to convert guanosine triphosphate (GTP) to cyclic guanosine monophosphate cGMP.

• increase cGMP produces activation of protein kinase G and phosphorylation of target proteins in cytosol and nucleus and biological effects

• nitrosylation of target proteins - adding a –NO group to a metal cation within the protein structure, a tyrosine residue –NO2 or cysteine residue --SNO - causing structural and functional protein and enzyme changes

nitric oxide receptor mechanisms

• Derived from membrane phospholipids when hydrolysed by phospholipase A2 to produce arachidonic acid.

• lyso-PAF which is then acetylated to produce active PAF.

• Vasodilation

• Increased vessel permeability: hypersensitivity reactions.

• Bronchoconstriction

• Platelet aggregation

• Chemotaxis of neutrophils, eosinophils, monocytes

• ligand for PAF receptors on endothelial cells and leucocytes.

• Regulated by PAF acetylhydrolases

• receptors are G protein coupled found on platelets, leukocytes, CNS neurons

• Gq - increase phospholipase C and calcium and Gi - reduces protein kinase A activity and cAMP

• too much can cause atherosclerosis, cancer, diabetes, AIDS and multiple sclerosis amongst others

Platelet activating factor

• messenger proteins

• Interleukins - signalling from one leukocyte to another

• Interferon - antiviral

• paracrine - neighbouring cells, endocrine - far away cells, autocrine, self cells

• inflammtory or anti-inflammatory

• mutiple cytokines can effect one cell type and can be tissue specific or widespread

• rapidly produced and released for inflammation

• can influence each others expression and work together or separately

• target for immune disorders

Cytokines

• antiviral and antitumor

• alpha - antiviral and anti tumour

• beta - antiviral

• gamma - antiviral - recruit t helper cells - includes activation of endogenous antiviral mechanisms by nearby cells

• binding to alpha, beta or gamma receptors

• phosphorylation cascade - nuclear effect and gene expression

Interferons

• includes NSAIDs which inhibits mediators

• H1 and H2 receptor inhibition

• nitrate formulations - mimic vasodilatory effect - angina relief

• monoclonal antibodies

clinical implications

• lipid based mediators derived from fatty acids - 20 carbon atoms in their chain

• arachidonic acid - starting material

• cyclooxygenase pathway - prostaglandins and thromboxanes - prostanoids

• lipooxgyenase pathway - leukotrienes

eicosanoid classification and chemistry

• part of polyunsaturated fatty acid group

• human body - cant add double bonds beyond Carbon 9

• conversion of a-linolenic acid and linolenic acid - essential fatty acids which must be derived from the diet

• alpha- linolenic acid can be elongated from an 18C chain to eicosapentanoic acid or EPA (20c) or docosahexanoic acid or DHA (22C)

• bodily conversion of a-linolenic acid to EPA is poor - dietary sources are required

• linoleic acid is elongated to arachidonic acid

• has double bonds thus non-linear structure

omega 3 and omega 6 fatty acids

• located in cell membrane bilayer or lipoprotein monolayer

• most common fatty acid is in the second chain of hydrophobic tail

• cell damage, angiotensin 2, adrenaline, complement, antibody and antigen complexation, cytokine stimulate arachidonic acid production

• formation of this causes the bi product of lysophosphatidyl choline - which is acetylated to PAF which is an inflammatory mediator

Arachidonic acid

• cell membrane phospholipids are hydrolysed to form phospholipid R2 chain using phospholipase A2 creating a bi product of free arachidonic acid and LPS which is converted to PAF

• arachnoid acid is then converted to prostagladin G2 and then to prostagladins, thromboxanes and leukotrienes

forming lipid mediators from arachidonic acid

• prostaglandins synthesised along cyclooxgyenase pathway from arachidonic acid

• PGG2 converted to PGH2

• individual prostaglandins are synthesised by prostaglandin synthase

• prostaglandin dehydrogenase - breakdown of prostaglandins

• continually prostaglandin synthesis causes vasoconstriction, vasodilation, inhibition of platelet aggregation, secretion of gastric mucus, smooth muscle contraction - uterine

Cyclooxgyenase pathway