Development of Mitochondria-Targeted Small-Molecule Dyes for Myocardial PET and Fluorescence Bimodal Imaging

Construction and Preliminary Evaluation of Two 18F-Labeled Radiopharmaceuticals for Myocardial Perfusion Imaging

AIMS

PET myocardial perfusion imaging (MPI) is the gold standard for the noninvasive diagnosis of ischemic myocardial. Construction of 18F-labeled PET MPI probe showed benefits to reduce the imaging cost, and enhance the image quality and patient-friendliness.

METHODS

Two 18F-labeled MPI probes (18F-BoMPI) were developed. Detailed in vitro/vivo evaluation including photophysical properties, in vitro stability, myocardial cell uptake kinetics and mechanisms, cytotoxicity and IC50, biodistribution and plasma clearance curve were investigated. Resting and stressing myocardial perfusion PET imaging were performed in healthy and myocardial ischemic mice.

RESULTS

18F-BoMPI could be quickly labeled and easily postprocessed, and demonstrated excellent in vitro stability. Cell assays indicated that 18F-BoMPI exhibited mitochondria-targeting but potential-independent myocardial uptake. In vivo evaluation revealed the effective myocardial uptake and rapid background clearance. PET MPI confirmed effective probe accumulation in the healthy heart, but rapidly clearance in the background, making heart clearly delineated in the images. Ischemic myocardial could be clearly distinguished as the region of radioactivity sparsity in PET MPI.

CONCLUSION

The 18F-labeled probes showed great potentials to reduce the practicability threshold of PET MPI.

Mitochondrial targeting derivatives of honokiol enhanced selective antitumor activity in NCI-H446 cells and decreased in vivo toxicity in Caenorhabditis elegans

Mitochondria, responsible for ATP production and apoptosis regulation, play a key role in cancer cells. Honokiol regulates apoptosis through the endogenous mitochondrial pathway but does not specifically target tumor cells. We designed 28 novel derivatives of honokiol using triple-function delocalized lipophilic cations such as berberine and F16 as mitochondrion-targeting carriers. While all derivatives exhibited enhanced cytotoxicity toward tumor cells compared to honokiol, the derivative 2E-3-F16 exhibited a substantial tumor cell selectivity between NCI-H446 cancer cells and HBE cells by one order of magnitude and enhanced the sensitivity of A549 cells to cisplatin. Mechanistically, it targeted mitochondria and induced apoptosis by preventing tumor cells from entering the G0/G1 phases as well as inducing an abnormal elevation of reactive oxygen species, thereby decreasing the mitochondrial membrane potential level. It also showed lower toxicity toward Caenorhabditis elegans than honokiol. This study provides a possible method for developing mitochondrion-targeting antitumor drugs with high efficiency and low toxicity based on natural products.

The in vivo drug delivery pattern of the organelle-targeting small molecules

Eukaryotic cell organelles sustain the life of cells. Their structural changes and dysfunctions can cause abnormal physiological activities and lead to various diseases. Molecular imaging technology enables the visualization of subcellular structures, cells, organs, and the whole living body's structure and metabolism dynamic changes. This could help to reveal the pharmacology mechanisms and drug delivery pathway in vivo. This article discusses the relationship between organelles and human disease, reviews recent probes targeting organelles and their behavior in vivo. We found that mitochondria-targeting probes prefer accumulation in the intestine, heart, and tumor. The lysosome-targeting probe accumulates in the intestine and tumor. Few studies on endoplasmic reticulum- or Golgi apparatus-targeting probes have been reported for in vivo imaging. We hope this review could provide new insights for developing and applying organelle-targeting probes.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Highlight selection of radiochemistry and radiopharmacy developments by editorial board

Background

The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biyearly highlight commentary to update the readership on trends in the field of radiopharmaceutical development.

Results

This commentary of highlights has resulted in 23 different topics selected by each member of the Editorial Board addressing a variety of aspects ranging from novel radiochemistry to first in man application of novel radiopharmaceuticals and also a contribution in relation to MRI-agents is included.

Conclusion

Trends in (radio)chemistry and radiopharmacy are highlighted demonstrating the progress in the research field being the scope of EJNMMI Radiopharmacy and Chemistry.