IL4 in Drug Induced Liver Disease and Personalized Medicine

1
IL-4 in Drug Induced Liver Disease and
Personalized Medicine
Timothy Quinn, M.D., Pauline Ryan, Ph.D., Lance
Pohl, PharmD, Ph.D.
National Institutes of Health National Heart,
Lung, and Blood Institute
Georgetown University
Abstract
NRF-2 and ?-GCL Integral to Hepatocyte Survival
Drug Induced Liver Disease (DILD) is a
major cause of morbidity and mortality in
medicine and is also a concern for pharmaceutical
companies that invest money and resources into
potential therapeutic agents only to find it
causes severe side effects, albeit, usually in a
small percentage of the population. Why some
individuals have an adverse reaction to a
medication while the majority of the population
do not is an important question. The focus of our
research at the National Institutes of Health is
twofold 1. To better understand the cellular
mechanism of liver injury by studying cell
signaling and which proteins are regulated. 2.
To study how genetic variation plays a role in
why some individuals are more susceptible to Drug
Induced Liver Disease. By using
Wild Type and IL-4 KO mice, we have shown that
IL-4 is hepatoprotective to toxic levels of
acetaminophen. We have also refined a reliable
technique to isolate nuclear and cellular
proteins from whole liver tissue to study how
transcription factor NRF-2 is instrumental to
this process.
Cysteine
Glycine
ADP P i
ATP
ADP P i
ATP
g-Glu-Cys-Gly Glutathione (GSH)
g-Glu-Cys
Glutamate
g-glutamyl cysteine Ligase
Glutathione synthetase
X
Oxidative Stress
Fig. 2b.
Fig. 2a.
Rate limiting step
Fig. 2a. depicts the role of NRF-2. NRF-2 is a
transcription factor that normally resides in the
cytosol bound to Keap-1. When hepatocytes are
exposed to reactive oxygen species such as NAPQI,
the interaction between Keap-1 and NRF-2 is
disrupted allowing NRF-2 to translocate into the
nucleus and bind to the Antioxidant Response
Element (ARE) leading to increased synthesis of
?-GCL. The result is increased production of
Glutathione, detoxification of NAPQI, and,
ultimately, cell survival. This mechanism has
also been shown in retina pigment epithelium.1
Fig. 2b. illustrates the biochemical mechanism of
glutathione synthesis, a key antioxidant that
detoxifies reactive intermediates produced from
APAP metabolism and, subsequently, prevents
oxidative stress. The rate-limiting step of ?-GCL
synthesis is highlighted.
Fig. 3a. is a Western Blot showing the level of
NRF-2 in nuclei isolated from livers of Wild Type
mice is greater than in IL-4 KO mice as a
function of time after exposure to APAP.
Fig. 3b. shows that expression of ?-GCL is
increased in the Wild Type mice and is decreased
in the IL-4 KO mice which explains the increase
in drug induced injury seen in the IL-4 KO mice.
Fig. 3a.
Fig. 3b.
IL-4 is Hepatoprotective
Fig. 1a.
Fig. 1b.
Fig. 4.
Fig. 4. is a flowchart of the protocol I
developed to isolate cytosolic and
nucelar fractions from whole liver tissue used in
Fig. 3a.
In Fig. 1a., production of IL-4 in Wild Type mice
is increased after a single dose of APAP while,
predictably, the level of IL-4 remains the same
in IL-4 KO mice after exposure to APAP. Fig. 1b.
Demonstrates liver injury as measured by ALT.
Wild Type mice endure less liver injury secondary
to acetaminophen over 24 hours than IL-4 KO mice.
The conclusion is that IL-4 plays a role in
preventing
Drug Induced Liver Injury.
Personalized Medicine
The long-term application of our research is to
develop a way to predict which patients will have
an adverse reaction to a medication or how to
more precisely dose a medication based on the
genetic make-up of the individual patient. The
key is to better understand which interleukins
and transcription factors are integral to
detoxification and to develop an inexpensive
method to measure them and gauge the patients
ability to mount an appropriate response to
oxidative stress.
Reference

• Wang, L., et al. Essential Roles of the PI3
  Kinase/Akt Pathway in Regulating Nrf2-Dependent
  Antioxidant functions in the RPE. Investigative
  Ophthalmology Visual Science. April 2008, Vol.
  49, No. 4.