Transcript Andrew Somogyi - Faculty of pain medicine

Genetics –Epigenetics- Who is more
vulnerable?
Andrew Somogyi
Discipline of Pharmacology, Faculty of Health Sciences, University of
Adelaide, Australia
[email protected]
FPM Refresher Course Day
1 May 2015 Adelaide
SESSION: The Faces of Pain: Acute to Chronic
Overview
• Factors influencing acute to chronic pain transition
– Non-genetic
• Genetics/Genomics (what is it) Factors
– COMT: pain perception
– GCH1, FKBP5
– Inflammation: TGFB1, IL8
– Haplotype-Epistasis
• Epigenetic Factors
– What is it? TRPA1
• Research problems
Acute to Chronic Pain Transition
• Epidemiology: Mostly postsurgical setting
–S
MacIntyre et al Acute Pain Management 2010
Shipton Trends Anaesth & Crit Care 4,
67, 2014
• Any injury can be the sensitizer: traumatic stress
Acute to Chronic Pain Transition: Factors
Psychosocial
Shipton Trends Anaesth
& Crit Care 4, 67, 2014
Phenotype: what is it?
Acute to Chronic Pain Transition: Risk Factors
MacIntyre et al Acute Pain Management 2010
Shipton Trends Anaesth & Crit Care 4, 67, 2014
Genetic/Genomics!
• Mutations in coding region
• Mutations in noncoding region
• Candidate Genes
• Haplotypes
• Epistasis
• Epigenetic
• Few studies in postsurgical transition
What is ‘Omics?
• “a coined phrase and refers to a field of study in biology that ends
in the suffix - omics, such as genomics..” (Wikipedia)
• Opposite to reductionism: understanding complex systems by
reducing to simpler /more fundamental parts
Extremeomics, facebookomics, nonsenseomics, balomics, omics-schmomics!
What is Genomics?
• Study of genes or gene products in a person or organism.
• Coined by Dr Tom Roderick (geneticist- Jackson Lab
(Maine)) in 1986 over a beer at meeting in Maryland on
the mapping of the human genome
Two types of Genetics: Somatic, Germline
Somatic: Tumour
Germline: Host
Germline
• Inherited variations
• Pharmacokinetics: CYP2D6
• Pharmacodynamic: mu receptor
Hertz & Mcleod, J Hum Gen 2013
And then there is Epigenetics!!
Gene Mutations
• Changes in base sequence of DNA
– SNPs [single nucleotide polymorphisms]
– Indels [Insertions/Deletions]
• Coding SNPs: Changes in amino acid structure of protein (drug target) ->
altered binding to drug
• Transcriptional SNPs: / protein (drug target) expression or degradation
• Loss of function alleles much more common than gain of function
• Genetic Polymorphisms: frequency of >1% population
Reading the Genetic Code
• Genes consist of EXONS and introns
iiiiiiiiTHE iiiiiiiiBAD AND iiiiiiiiiOLD HiiiiiiiiOG ATETiiiiiiiiiiHE FATiiiii iiiRAT ENDiiiii
• Normal processed “gene” message is read in blocks of 3
bases (codons)
– THE BAD AND OLD HOG ATE THE FAT RAT END
– Think of this as:
• the normal functioning enzyme/protein- system
On time
Missense Mutation:SNP
Mutation changing H to L
iiiiiiiiTHE iiiiiiBAD AND iiiiiiiiiOLD LiiiiiiiiOG ATETiiiiiiiiiiiiHE FATiiiii RAT ENDiiiiiiiii
THE BAD AND OLD LOG ATE THE FAT RAT END
Readable but Makes no Sense.
• Mutated enzyme with some (but not 100%)
function
Splice site mutation
Mutated splice site leading to exon skipping
iiiiiiiiTHE iiiiiiBAD AND iiiiiiOLD HiiiiiOG ATETiiiiiiiiiHE FATiiiii RAT ENDiiiiiiiii
THE BAD AND OLDH OGA TET HEF ATR ATE NDi iii
Loss of genetic message
• 100% loss of function enzyme
COMT: Catechol-O-Methyltransferase
• Metabolizes catecholamines in glial & postsynaptic
neurons: CNS, other tissues
– Noradrenaline, adrenaline, dopamine
• Pain, Sympathetic tone, Mood, Inflammation
• Descending inhibitory pathway
COMT: Genetics
• > 900 SNP variants of gene (COMT)
• Val158Met:widely studied
– Met/Met: 4-fold  in activity
– MetMet[26%] individuals versus ValVal[25%]
• higher sensory & affective pain ratings
• Lower morphine doses
• Increased risk of chronic pain with Met individuals (
fibromyalgia, TMD)
COMT and Postoperative Persistent Pain
J Clin Anaesth 23, 482, 2011
• Small numbers:n=42; Post Surgical Persistent Pain: 43%
• Val158Met: 27% Val/Val; 39% Val/Met
• Odd’s Ratio: 3.5 (0.6-22) P=0.17
COMT: Chronic Pain Development
BUT: Val158Met not the only variant
Haplotypes: multiple SNPs in gene
200 females: risk of TMD (temporomandibular joint disorder)
Val158Mett
• From these haplotype combinations-> pain sensitivity phenotype
Diatchenko et al Human Mol Gen 14, 135, 2005
Haplotype Analysis:
Differentiates less with
more pain sensitivity
• Pressure & thermal pain testing
• Less pain sensitive: GCGG
• High pain sensitive: ATCA/ACCG
Diatchenko et al Human Mol Gen 14, 135, 2005
Incidence of TMD was
higher in High Pain
sensitivity haplotype
group (65%) than in
Low pain sensitivity
haplotype group (28%)
Diatchenko et al Human Mol Gen 14, 135, 2005
More than 1 gene in COMT
Pathway: Epistasis
GCH1: guanosine-5-triphosphate cyclohydrolase 1; ESR1: oestrogen receptor 1
GCH1: cofactor for catecholamine synthesis; ESR1: regulates COMT gene expression
Met individuals :  musculoskeletal pain
Met individuals + GCH1 variant: increased pain threshold ( pain)
Val individuals + ESR1 Variant:  pain
TMD cases vs
Controls
Tegeder et al Nat Med 12, 1269, 2006
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•
•
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GTP cyclohydrolase – tetrahydrobiopterin (BH4) formation
BH4: modulates peripheral neuropathic and inflammatory pain
BH4: cofactor in serotonin, catecholamine & NO production
BH4 inhibition -> neuropathic pain /inflammatory pain in rats
168 patients- surgical diskectomy
Assessed at 1 year post surgery
Genetics: 15 SNPs tested: Haplotype analysis
1 haplotype: 15% patients associated with low pain
scores (0.44 vs 0.84 Z-score)
2 copies of low pain haplotype = minimal pain at leg rest
0,1 copy = pain at leg rest common
0= 0 copy
X = 1 copy
X=- 2 copies
Bortsov et al Pain 154, 1419, 2013
• Traumatic events: potent stressors activate neurobiological stress
response systems
• HPA contributes to developing persistent posttraumatic pain
• FK506 protein 1: interacts with HSP90 which binds to glucocorticoid
receptor and regulates its sensitivity; receptor co-chaperone
• Discovery cohort: n= 949 Experienced MVA
• Replication: women experiencing sexual assault (n=54)
• Exclusion: oral morphine (< 30 mg/day); beta antagonists
• 6 weeks: overall pain & neck pain (MVA)
• Genotyping: 33 FKBP5 SNPS
Bortsov et al
Pain 154,
1419, 2013
MVA: 6 SNPS associated with overall pain (OR ~4) & neck pain (OR~3)
Sexual Assault: 4 assoc with overall pain & 3 neck pain
MVA: Haplotype: h2 & h3 associated: low overall and neck pain but no
statistics!
Problems: no haplotype analysis but mechanistic basis is sound
Same Study: Different Gene- OPRM1 (A118G)
Linnstaedt et al J Pain 2015
Inflammation Biomarkers
• Cytokines contribute to pathophysiol TMD & widespread pain
• Acute Setting: MCP-1 & IL-8 confer survival
– immune response; limit tissue damage; initiate remodeling
• Persistent  MCP-1 & IL8: tissue pathology & nociceptor
function changes
• Proinflammatory cytokines concs correlate with  pain
sensitivity
• Case Control: 355 females
• TMP-WPT: without widespread palpation tenderness
• TMT+ WPT: with widespread palpation tenderness
• 22 cytokine gene SNPS: MCP-1, IL-1Ra, IL-8, TGFB1
Inflammation Biomarkers
No SNP (22) associated with Odd’s of TMP-WPT or TMT+ WPT cf
control
BUT
Significant gene-gene interaction (epistasis):
IL-8 SNP (proinflammatory chemokine) and TGFB1 SNP (regulates
gene expression (incl IL8)
Inflammation Biomarkers:
Epistasis1 copy T variant (minor) TGFB1
+ 0 copy IL-8 variant = OR 2.6
+ 1 copy IL-8 variant = OR 0.56
+ 2 copy IL-8 variant = OR 0.11
TMD + WPT (wide spread pain
palpation)
Slade et al 2011 Pain 152, 2802
Problems
• Replication studies- numbers
• Phenotype of persistent pain
– Post surgical: acute to chronic: not been adequately studied
– Trauma: stress only
– TMD
• Statistics: many other factors often not considered
• Candidate Gene approach
– Acts as a pointer only
– Magnitude of effect: unlikely to be major
• GWAS or NGS: who will fund? Big numbers
• Epigenetics
On Epigenetics
• Tissue specific:
• CNS a problem
• Environmentalstress
Epigenetic Phenomena:
Phenotypic changes not involving DNA sequence
alterations
Ageing
Ingelman-Sundberg 2009
Twins same epigenome at birth- Environmental factors through
development alter epigenome -> phenotype differences (No pain/ pain)
Acute to Chronic Pain Transition: Epigenetics
• Inflammatory cytokine expression
• Glucocorticoid receptor expression
• Glutamic acid decarboxylase (pain regulatory enzyme)
• Mu opioid receptor expression
• ALL GENES
2014
• 50 monozygotic twins- 50 controls
• Heat pain: low vs high sensitivity
• Methylation rate TRPA1 related to pain sensitivity
TRPA1: ligand gated cation channel- sensor for pain, cold, stretch; chemicals:
mustard, wasabi, horse radish
Genetic and
environment
interactions
contribute to pain
development and
response to
treatment
• Germline mutations
• Epigenetics
Diatchenko et al; Nat Rev Rheumatol 9, 340, 2013
Take Home Message
• Transiting from acute to chronic pain
– Highly complex biochemical & biosocial process
– Many factors:
• Genetics: germline and epigenetics
• We need postsurgery studies
• We need replication studies
What am I doing?
• Predictors of persistent post surgical pain following total
knee joint arthroplasty
– Michal Kluger (Auckland)
• 973 patients undergoing scheduled total hysterectomy
under general anesthesia.
– Alex Sia (Singapore)
– ~ 25% persistent postsurgical pain