Multimodal Imaging Probe Development for Pancreatic ß Cells: From Fluorescence to PET.

Pancreatic ß cells are responsible for insulin secretion and are important for glucose regulation in a healthy body and diabetic disease patient without prelabeling of islets. While the conventional biomarkers for diabetes have been glucose and insulin concentrations in the blood, the direct determination of the pancreatic ß cell mass would provide critical information for the disease status and progression. By combining fluorination and diversity-oriented fluorescence library strategy, we have developed a multimodal pancreatic ß cell probe PiF for both fluorescence and for PET (positron emission tomography). By simple tail vein injection, PiF stains pancreatic ß cells specifically and allows intraoperative fluorescent imaging of pancreatic islets. PiF-injected pancreatic tissue even facilitated an antibody-free islet analysis within 2 h, dramatically accelerating the day-long histological procedure without any fixing and dehydration step. Not only islets in the pancreas but also the low background of PiF in the liver allowed us to monitor the intraportal transplanted islets, which is the first in vivo visualization of transplanted human islets without a prelabeling of the islets. Finally, we could replace the built-in fluorine atom in PiF with radioactive 18F and successfully demonstrate in situ PET imaging for pancreatic islets.

Novel Inhibitor of Mixed-Lineage Kinase Domain-Like Protein: The Antifibrotic Effects of a Necroptosis Antagonist.

The pseudokinase mixed-lineage kinase domain-like protein plays a crucial role in programmed cell death via necroptosis. We developed a novel mixed-lineage kinase domain-like inhibitor, P28, which demonstrated potent necroptosis inhibition and antifibrotic effects. P28 treatment directly inhibited mixed-lineage kinase domain-like phosphorylation and oligomerization after necroptosis induction, inhibited immune cell death after necroptosis, and reduced the expression of adhesion molecules. Additionally, P28 treatment reduced the level of activation of hepatic stellate cells and the expression of hepatic fibrosis markers induced by necroptosis stimulation. Unlike the necrosulfonamide treatment, the P28 treatment did not induce cytotoxicity. Finally, the cysteine covalent bonding of P28 was confirmed by liquid chromatography-tandem mass spectrometry.