Download Epigenetic regulators as novel treatments

Epigenetic regulators as novel treatments
for sepsis (Grant in collaboration with GSK)
S. Opal Toronto CCCF Oct. 27, 2015
Some definitions: Epigenetics-the study of heritable changes
in gene expression without changing the DNA sequence; this occurs
at 3 levels of organization:
1) methylation of cytosine nucleotides within coding
sequences and at promoter sites that alter transcription rates
2) changes in chromatin protein structure and function-usually
post - translational modifications of histone protein tails: the
acetylated histone targets by Sirt-1 or i-BET compounds
3) silencing sequences of non-coding RNA-microRNAs
Epigenetic control of heterochromatin (inactive) and
euchromatin (active) DNA and via interacting nucleosomes
Heterochromatin
(tightly wrapped)
Euchromatin
(open)
Cornell T T et al. Pediatrics 2010;125:1248-1258
1o
2o
3o
Activating transcription factor 3
CCAAT/enhancer-binding factor d
Minutes: proinflammatory Hours: anti-inflammatory
+ host defense genes
1o response genes
2o/3oresponse genes: de novo synthesis
Days: mixed response +
immunometabolic genes
Positive-transcription elongation factor b
BRM-related gene 1
Transcriptional
start site
Medzhitov&Horng
2009;9:692
The Nucleosome and
Histone modifications
Nucleosomes 147
bp DNA tightly
wrapped around
histone octamers
2
3
4
5
1
Acetylated tails activate
while de-acetylated tails
inactivate transcription
Dawson N Engl J Med 2012;367:647
O
CH3
Acetyl Lysine
O
C
NH2
NH
Free e amino
group
+
deacetylated
histone
(- regulation)
+
N
Nicotinamide
NH2
2’O-acetyl
ADP ribose
P’-P’-O
Sirtuin
N
N
N
N
O
OH O
O
plus
NAD+
Activators of Sirt1 affect multiple
metabolic pathways, one important
function of nuclear Sirt1 is deacetylation of histone tails
CH3
Sirt1: NAD-dependent deacetylation of Histones inhibits initial APP response
Epigenetic Regulators
Writers:
Enzymes that Post
translationally modify
Histone proteins
Erasers:
Enzymes that catalyse
the removal of
modified histones
Readers:
Regulatory elements
that recognize and bind
to specially modified
sites for DNA binding
and promoter sites
Dawson MA et al. N Engl J Med
2012;367:647-657
BET
Bromodomain
and extraterminaI
(BET) is a
modified
histone reader
i-BET
I-BET
(inhibitor)
occupies
acetylated
Histone binding
site blocking
BET recognition
of start signal
for transcription
Acetylated
Histone
binding site
BET
Activate
Dawson et al. N Engl J Med
2012;367:647-657
RNA polymerase
Transcriptional
start site
Nicodeme et al.
Nature
2010;468:1119
i-BET
inhibits at
nm conc.
i-BET rapidly alters
the transcription of
≈300 inflammatory
genes induced by LPS
Similar data for Sirt1
activators given early
(anti-inflammatory), or
Sirt1 inhibitors given
late to reconstitute
the inflammatory
response
(McCall et al. Exp Rev Clin
Immunol 2014;10 (9):1-10)
Nicodeme et al.
Nature
2010;468:1119
KC (IL-8)
Nicodeme et al. Nature 2010;468:1119
IBET12102013
Delayed Rx (6-24h after CLP)
with antibiotics alone vs antibiotics and i-BET
Kaplan-M eier Survival Curve
*
1. 00
I bet10Mox206hr
n=10
*
S urvi val
0. 75
Mox206hr
n=10
I bet10Mox2012hr
n=10
0. 50
Mox2012hr
n=10
I bet10Mox2024hr
n=5
0. 25
Mox2024hr
n=5
0. 00
0
24
48
72
96
120
144
168
Hours
*No antibiotic control (n=5) no survivors at 96hr; Moxi-moxifloxacin
Can iBET and other epigenetic therapies targeting histones
succeed where other immune modulators have failed in sepsis?
-they have proven to be tolerable in oncology patients
-Sirt1 and i-BET alter a wide spectrum of acute inflammatory genes
-potentially fewer off target effects than corticosteroids
-can be given after insult and can still work as salvage Rx
DNA
NFkB
nuclear
localization
sequence
5’
3’
5’
3’

Host response and antimicrobial
defense programs