Diagnosing Drug-Induced Liver Injury by Multispectral Optoacoustic Tomography and Fluorescence Imaging Using a Leucine-Aminopeptidase-Activated Probe

Abstract

Drug-induced liver injury (DILI) is a frequent cause of hepatic dysfunction as well as the single most frequent reason for removing approved medications from the market, and multispectral optoacoustic tomography (MSOT) is an emerging and noninvasive imaging modality for diagnosing and monitoring diseases. Herein, we report an activatable optoacoustic probe for imaging DILI through detecting the activity of leucine aminopeptidase (LAP). In this probe, an N-terminal leucyl moiety serving as the LAP recognition element is linked with a chromene-benzoindolium chromophore via 4-aminobenzylalcohol group. The elevated expression of hepatic LAP as a result of DILI cleaves the leucyl moiety and causes the red-shift of the probe’s absorption band, thereby generating prominent optoacoustic signals for MSOT imaging. During this process, the probe also exhibits prominent NIR fluorescence, which can be utilized for fluorescent imaging. More importantly, by rendering stacks of cross-sectional images as maximal intensity projection (MIP) images, we could precisely locate the focus of drug-induced liver injury in mice. This probe is expected to serve a powerful tool for studying physiological and pathological processes related to LAP.

Most recent advances on enzyme‐activatable optical probes for bioimaging

“…Most recently, by taking advantage of an LAP‐activatable probe, drug‐induced liver injury (DILI) was diagnosed. [ 102 ] DILI caused by therapeutic drugs or other chemicals poses a severe threat to human health, as LAP is a cytosolic enzyme existing in liver tissue. In general, liver diseases, for example, liver cirrhosis, liver necrosis/injury, and hepatitis, usually cause an elevation in the activity of LAP in serum.…”

“…Recently, activatable probes for the evaluation of the activity of APs, including leucine AP and aminopeptidase N (APN), have been reported. [ 101–104 ]…”

“…Wu's group smartly designed a molecular LAP‐activatable probe DLP for DILI diagnosis by assessing the raised LAP level in liver tissue of mice with both PA and FL imaging. [ 102 ] In DLP, the chromene‐benzoindolium chromophore acts as the signal reporter, the N ‐terminal leucyl unit functions as the recognizing element, and the 4‐aminobenzylalcohol serves as the connecter, respectively. The N ‐terminal leucyl moiety is cleaved by the hepatic LAP and a cascade of reactions are induced, the probe is thus activated and the sensitive probing of LAP is realized.…”

Design Strategies of Photoacoustic Molecular Probes

“…Then enolic intermediate had a tautomerization which would greatly shift emission and absorption so that ratiometric imaging for HS ‐ by fluorescent and PA dual modes. Wu's group designed several cyanine‐like PA probes for detecting H 2 S, [35] hypoxia, [36] leucine aminopeptidase (LAP), [37] alkaline phosphatase (ALP) and β‐galactosidase [38] . Through capping the dinitrophenyl ether, azo linker, N‐terminal leucyl, and specific disease biomarkers on NIR chromophore, the probes can accurately detecting and imaging of biological models of interest (Figure 2d–f).…”

“…f) LAP, reproduced with permission from ref. [37]. g) Peroxynitrite, reproduced with permission from ref.…”