Integrated imaging and circulating biomarkers for the assessment of drug-induced hepatotoxicity
Date
06/07/2019Embargo end date
06/07/2020Author
De Bois Brillant Andreu, Nathalie
Metadata
Abstract
Drug-induced liver injury (DILI) is a major burden for health care systems and a
principal reason for attrition during drug development. Prediction of clinical DILI
remains difficult and diagnosis is usually based on exclusion using blood-based
biomarkers for cell injury. Currently used chemistry parameters lack sensitivity,
specificity and prognostic capability. More importantly, they provide little insight
into the underlying mechanistic basis of DILI hindering stratification and
appropriate therapeutic intervention. A panel of circulating biomarkers that can
identify liver injury in patients with DILI with enhanced sensitivity and specificity
over currently used tests and translational to animal models has been previously
described. Serum microRNA-122 (miR-122) has shown liver specificity and
higher sensitivity than alanine aminotransferase (ALT) and High mobility group
box 1 (HMGB1) is an informative and early serum indicator of cell death and
inflammatory processes in Paracetamol (APAP)-induced liver injury (APAP-ILI).
The mechanistic nature of these biomarkers allows for a deeper understanding
of the basis to the toxicological events in DILI scenarios. However, this
biomarkers panel is made up of analytes that reflect cell death mode or
inflammation processes and lacks novel mechanisms for determining liver
function.
Multispectral Optoacoustic Tomography (MSOT) is an imaging modality that
facilitates the whole-body imaging of toxicological processes in organs that can
be observed in vivo, real-time and with high resolution. MSOT imaging operates
in the near-infrared (NIR) spectral window and high detection specificity is
achieved by multispectral reconstruction which allows accurate monitoring of
biodistribution of relevant molecules. It has been used preclinically to assess
kidney function in Adriamycin-induced nephropathy mouse model where
clearance of the near infrared dye IRDye 800CW carboxylate was assessed.
Indocyanine green (ICG) is a fluorescent dye that can also be detected in the
system by MSOT imaging. It is removed from circulation exclusively by the liver
parenchyma and is clinically used in medical diagnostics as a marker for liver
function. Here for the first time, we demonstrate that ICG clearance from blood
can be monitored using real-time and non-invasive MSOT imaging. Established
(ALT and total bilirubin; TBIL) and novel (miR-122 and HMGB1) serum
biomarkers were analysed and histopathological examination for liver injury was
assessed in APAP-ILI mouse model. Data showed a significant increase of ICG
half-life at 3 hours (h) post-APAP followed by a gradual decrease at 24 h time-point
and a second peak of ICG clearance delay at 48 h with full recovery at 96 h post-
APAP. The strong correlation between parameters demonstrated the utility of
MSOT imaging for the assessment and monitoring of liver function in DILI mouse
model. Furthermore, a cohort of mice received APAP antidote, N-Acetyl-Cysteine
(NAC), for the evaluation of MSOT imaging utility in reporting the efficacy of
therapeutic intervention. We were able to monitor recovery after NAC treatment
using non-invasive imaging. This work was then extrapolated to a chronic DILI
model where mice received carbon tetrachloride (CCl4) twice per week for up to
12 weeks (w) and had the same parameters than above measured at different
timepoints throughout the timecourse. MSOT imaging delivered interesting and
novel data regarding liver function in this model. Finally, a cohort of mice received
a potential cell therapy and MSOT imaging was used to monitor efficacy of this
novel therapy as well as tracking the fate of these cells in the animal. This time
MSOT proved the multimodal utility in drug development. Furthermore, the lack
of understanding of the mechanisms of release in blood of biomarkers and its
relationship with tissue injury was addressed. We showed for the first time the
tissue-periphery distribution of miR-122 and HMGB1 in APAP-ILI. Thorough
histopathological examination and quantification of miR-122 in situ hybridisation
(ISH) and HMGB1 immunohistochemistry (IH) and liver injury severity
assessment was performed. This data was then correlated with serum
biomarkers levels. Serum miR-122 and HMGB1 elevation directly correlated to
high expression of miR-122 and HMGB1 translocation in hepatocytes undergoing
cell stress.
In summary, the data in this thesis provides a novel approach for the diagnosis
of DILI using a novel photoacoustic imaging technology which allows the non-invasive
and real-time monitoring of liver function in combination with novel panel
of circulating biomarkers for liver injury. Altogether proved to be more sensitive,
specific and importantly more informative of the underlying mechanistic basis of
DILI.