Adjuncts and Pain Flashcards
Transient Receptor Potential Channels (TRPs) : how many families? They are the molecular sensors of what?
6 families
Molecular sensors of taste, touch, temperature and pain
What are the 6 families of TRPs?
TRPVs (Vanilloids) TRPA (Ankyrin) TRPPs (Polycistin) TRPCs (Canonical) TRPMs (Melastatin) TRPMLs (Mucolipin)
Which TRP is sensitive to garlic, horseradish and cinnamon?
TRPA1
Which TRP is sensitive to Mint?
TRPM8
Which TRP is sensitive to BAA?
TRPV4
Which TRP is sensitive to Camphor?
TRPV3 and TRPV1
Which TRP is sensitive to Chili and garlic on top of camphor?
TRPV1
Put these TRPs in order of who is sensitive to the coolest to the hottest temperature :
TRPM8, TRPV4, TRPV3, TRPV2, TRPA1, TRPV1
Coolest TRPA1 TRPM8 TRPV4 TRPV3 TRPV1 TRPV2 Hottest
What is the hot component of chilli peppers? Where do they act?
Capsaicin
They act of sensory nerves
What is the MOA of Capsaicin?
Initial sensitization of the nerve, then a prolonged desensitization
What type of receptor is the capsaicin receptor? Where are they expressed?
TRPV1
Expressed on C-fibres and A-delta fibres
6 activators of TRPV1?
Capsaicin Endogenous agonists Acidosis Heat Na Ca
Is TRPV1 a selective or non-selective cation channel?
non-selective
Endogenous ligands of TRPV1? (2)
Exogenous ligands? (2)
Anandamine
Endovanilloids
Capsaicin
Resiniferatoxin
What happens when acute low concentrations activate TRPV1s?
Ca-dependent phosphorylation of ion channels, depolarization and action potential into the sensory neuron and pain, eventual desensitization
What happens when prolonged exposure or high concentrations act on TRPV1s?
Ca overload, mitochondrial dysfunction, destruction of nerves (C and A-delta fibres)
Two therapeutic potentials of TRPV1?
What are the adverse effects?
Topical capsaicin creams
8% capsaicin patch
Effects: skin irritation, burning, oedema
Example of a TRPV1 antagonist? What does is treat?
Low potency or high potency?
Selective or non-selective?
Why did it get withdrawn from clinical trials?
AMG517, treats inflammatory pain
Highly potent
Selective
Withdrawn because is caused concentration-dependent hyperthermia that lasted days and blocked the thermoregulatory centres in the CNS
TRPM8:
Selective or non-selective?
Where is it expressed?
Expression increases in models of _________ _____
Non-selective
Expressed in 15% of small diameter sensory neurones
Expression increases in models of neuropathic pain
What are 3 exogenous ligands for TRPM8?
Menthol
Icilin
Spearmint
Which cannabinoids are derived from the Cannabis plant? Which are man-made? Which are present naturally in the body?
Plant: Phytocannabinoids
Man-made: Synthetocannabinoids
Naturally in the body: Endocannabinoids
What are the two cannabinoid receptors? Where are they located?
CB1 : On central and peripheral nerves
CB2 : Associated with immunocytes
How do CB1 agonists given in the peripheral nerve affect Joint Mechanosensitivity?
It decreases firing frequency in neurons, essentially diminishing action potential
Dorsal horn of the spinal cord : How do cannabinoids act in this location?
- CB1 receptors are activated
- Opening of K ion channels, increase in potassium conductance to the primary afferent neuron, causing it to hyperpolarize
- Closes Ca channels
- Decreases excitatory NT release
What are the three sites of action of cannabinoids?
Peripheral nerve
Dorsal horn of the spinal cord
Suprapinal Regions
What do cannabinoids target in the suprapinal regions? (4)
Cortex
Amygdala
Periaqueductal gray
Rostral ventromedial medulla
what are the periaqueductal gray and the rostral ventromedial medulla involved in?
Descending inhibition
When cannabinoids act of the cortex, what does this cause?
Alters cognitive perception of pain
When cannabinoids act on the amygdala, what does this cause?
Alters emotional perception of pain
Which endocannabinoids are synthesized from phospholipids and Arachidonic acid? (5)
- Anandamide
- Noladin
- Virodhamine
- 2-AG: 2-Arachidonoylglycerol
- NADA: N-Arachidonyl Dopamine
what is the process of anandamide degradation?
It interacts with CB receptor, Anandamide membrane transport rapidly transports it into the cell where FAAH degrades it into ehtanolamine and AA
How do you inhibit the degradation of endocannabinoids?
block the enzymes that cause degradation
Which drug inhibits FAAH from degrading anandamine?
URB597
What are the effects of inhibiting FAAH on OA Joint mechanosensivity?
Decrease in neuronal firing
Describe leukocyte trafficking in an inflamed joint
Leukocytes usually travel freely in vascular space.
A signal from the endothelium is made when there is inflammation
Leukocytes undergo a rolling process to cross the membrane into the extravascular space
Releases mediators once in the specific tissue
What 6 diseases use medical cannabis? %?
Arthritis 36% Spinal Cord Injury 16% AIDS/HIV 15% MS 14% Spinal Cord Disease 10% Cancer 6% Epilepsy 3%
Name 4 prescription cannabinoids
Dronabinol
Nabilone
Nabiximols
Herbal Cannabis
Which two prescription cannabinoids are oral capsules? What are they approved for? (2)
Dronabinol
Nabilone
Chemotherapy-induced nausea and vomiting
Anorexia associated with HIV/AIDS
What are nabiximols approved for? (3)
How are they injnected?
MS-associated neuropathic pain
Spasticity
Advanced cancer pain
Oralmucosal spray
Which prescription cannibinoid is not formally approved?
herbal cannabis
What are 4 advantages to smoking cannabis?
Rapid pain relief
Improved sleep
Reduced anxiety
Easy to titrate
What are 4 disadvantages to smoking cannabis?
Not appropriate or all patients
Psychotropic side-effects
Smoking isn’t the safest mode of administration
Various levels of cannabinoids and non-cannabinoid chemicals
What is the average THC and CBD levels in Cannabis Strains in 2015?
17,5% THC
0.3% CBD
What are three ways to ingest cannabis?
Oil
Butter
Brownies
What is to onset of effects inhaled vs. ingested cannabis?
Inhaled 10min
Ingested 3h
What is the duration of effects inhaled vs. ingested cannabis?
Inhaled 0-30min
Ingested 30min-2h
What is one advantage of ingesting cannabis?
Two disadvantages?
No respiratory irritation
Slower onset of effect
Difficult to titrate best dose
What are proteinases?
enzymes that hydrolyse peptide bonds in proteins
What are 5 mechanisms that proteinases are involved in?
Generate active peptides Coagluation cascade Inflammation Tissue destruction/remodelling Signal pain
5 types of proteinases?
Metalloproteinases Threonine proteinases Cysteine proteinases Aspartic proteinases Serine proteinases
How do Proteinase Activated Receptors function as opposed to regular ligand-receptor binding?
Proteinase cleaves the N-terminal part of the tethered ligand sequence of the GPCR
Once it is cleaved, it is capable of binding to the ligand binding domain
How do you bypass the need for a proteinase and the cleavage of the receptor sequence when you want to activate the PAR?
You can synthetically create a peptide that will bind to the
What are 4 different ways a PAR can be modified?
- Normal state (cleavage site intact)
- Activated Receptor (Proteinase cleaves N-terminus)
- Disarmed Receptor (Entire ligand binding domain is cleaved off by proteinase)
- Antagonist blockade (Antagonist can block ligand binding domain)
4 types of PAR? Which proteinase activates each?
PAR1 : thrombin
PAR2 : Trypsin, Tryptase, Elastase
PAR3 : Thrombin
PAR4 : Thrombin, Cathepsin G, Plasmin
What is the function of PAR1?
Vasorelaxation
Decrease pain
What is the function of PAR2?
Vasorelaxation
Increase pain
What is the function of PAR3?
Unknown
What is the function of PAR4?
Vasorelaxation
Increase or decrease pain depending on tissue
What is the most common form of arthritis?
Osteoarthritis
Osteoarthritis is a _____________ disease.
degenerative disease
Destruction in osteoarthritis is elicited by what?
serine proteinases
two types of pain behaviour tests for joint pain?
Weight bearing
von Frey Hair Algesiometer
What is the effect of neutrophil elastase (weight bearing test and the von Frey test) on joint pain?
Weight bearing : % weight on ipsilateral paw decreases, more pain
Von Frey : Need less force to withdraw paw, meaning more pain
Which receptor does Mast Cell Tryptase activate?
PAR2
What is the effect of Mast Cell Tryptase on Hind limb weight bearing?
Effect reduced in what type of mice?
Reduction in hind limb weight bearing (difference in distribution)
TPRV1 knockout mice
What is the effect of Mast Cell Tryptase on Tactile Allodynia?
Effect reduced in what type of mice?
Reduction in paw touch sensitivity
Effect reduced in TRPV1 knockout mice
What is the potential role of PAR2?
-Sensitization of Joint Afferents by Proteinase Signaling
Explain the mechanism of proteinase signaling via PAR2
- Neutrophil elastase or Mast Cell Tryptase cleave PAR2
- Activation of TRPV1
- Sensitizes the nerve and activates SP and NK1
- Leads to peripheral sensitization (nerve firing increases)
Explain the mechanism of proteinase signaling via PAR1
- Thrombin released to extravascular space
- Cleaves PAR1
- Peripheral release of endogenous opioids
- Act on u-opioid receptor which causes analgesia
Explain the mechanism of proteinase signaling via PAR4
Remember it depends on tissue!!
-Direct activation of PAR4 in the peripheral nerve by thrombin and cathepsin G to cause analgesia in digestive tract
-PAR4 expression on mast cells which releases bradykinin
activates B2 on nerve terminals, leads to pain in joints
What are cytokines?
Are they soluble in water?
Synthesis is activated by what?
Extracellular signaling molecules
Mostly water soluble
Synthesis activated by mitogen-activated protein kinase (MAPK)
Name 5 types of cytokines
- Interleukins
- Tumour necrosis factors
- Chemokines
- Interferons
- Transforming growth factors
IL-1
What acts on IL-1R1 ?
IL-1alpha
IL-1beta
Name an endogenous receptor antagonist of IL-1R
This antagonist blocks which disease?
IL-1Ra
LPS-induced hyperalgesia
Does IL-1 increase or decrease during inflammation and injury?
Increase
Two types of IL-1beta? What is the effect of each?
IL-1B (i.pl) : decreases mechanosensitivity threshold
IL-1B (i.p) : decreases thermosensitivity threshold
IL-6
Signaling requires what?
Does IL-6 increase or decrease pain?
IL-6R and gp130 signal transducing subunit of cytokine class I receptor superfamily Increases pain
Is IL-6R soluble or membrane bound?
BOTH
What drug can bind to IL-6R to block binding of IL-6?
Tocilizumab
What does IL-10 do?
Which intracellular pathway does it follow?
Does it increase or decrease pain?
Inhibits cytokine production from T-cells
JAK/STAT pathway
Decreases pain
Explain the JAK/STAT pathway
- IL-10 binding to IL-10R activates JAK
- JAK autophosphorylates and phosphorylates to receptor
- STATs are recruited and are phosphorylated by JAK
- STATs dimerize
- STATs translocate to nucleus to modulate target gene expression
What is TNF-alpha?
Two isoforms?
2 TNF receptors?
Cytokine producing inflammation, pain, joint erosion
Two isoforms:
Membrane bound TNF (mTNF)
Soluble TNF (sTNF)
2 Receptors:
TNF-R1
TNF-R2
soluble TNF binds to what receptor? What is the mechanism to get this receptor soluble?
Binds to TNF-R1
TACE cleaves TNF-R1 from surface of the cell
TACE (TNFalpha converting enzyme) cleaves what? (2)
TNF-R1
mTNF to make it sTNF
What are two types of TNFalpha blockers?
Soluble Receptor
Monoclonal Ab
Name a drug that is a soluble receptor TNFalpha blocker
Etanercept
Name two drugs that are monoclonal Ab TNFalpha blockers
Infliximab
Adalimumab
TNFalpha blockers are usually taken with what?
How effective is it?
What are side effects? (3)
Methotrexate
Works in 2/3 patients
Side-effects : fever, infection, cost
What is a biosimilar?
What is the nomenclature of biosimilars?
Biologic product that is very similar to an approved product and has no clinical difference in safety of effectiveness
Nomenclature is the non-proprietary name of the originator + 4 letter suffix
What is the process of manufacturing biologics? (6)
What could be a difference at each step in different companies?
- Clone Gene into DNA vector (same AA-maybe same genetic sequence)
- Transfer into Host (diff. vector)
- Cell culture of fermentation (different recombinant cell system)
- Downstream processing (Diff. in-process controls)
- Purification (diff. purification protocol)
- Formulate product for use (maybe different formulation)
4 facts about biosimilars that make it different from originator
- Immunogenicity (poor efficacy if Ab found previously on originator)
- Variable manufacture
- Can bypass phase III trial
- Can substitute from originator to improve efficacy, avoid side effects an minimize cost
