Leonurine Sulfate

Medicine intervention is the major clinical treatment used to relieve the symptoms and delay the progression of rheumatoid arthritis (RA), but is limited by its poor targeted delivery and short therapeutic duration. Herein, we developed an injectable and bioadhesive gelatin-based (Gel) hydrogel as a local depot of leonurine (Leon)-loaded and folate-functionalized polydopamine (FA-PDA@Leon) nanoparticles for anti-inflammation and chondroprotection in RA. The nanoparticles could protect Leon and facilitate its entry into the M1 phenotype macrophage for intracellular delivery of Leon, while the hydrogel tightly adhered to the tissues in the joint cavity and prolonged the retention of FA-PDA@Leon nanoparticles, thus achieving higher availability and therapeutic efficiency of Leon. In vitro and in vivo experiments demonstrated that the Gel/FA-PDA@Leon hydrogel could strongly suppress the inflammatory response by down-regulating the JAK2/STAT3 signaling pathway in macrophages and protect the chondrocytes from ferritinophagy/ferroptosis. This contributed to maintaining the structural integrity of articular cartilage and accelerating the joint functional recovery. This work provides an effective and convenient strategy to achieve higher bioavailability and long-lasting therapeutic duration of medicine intervention in arthritis diseases.

Caenorhabditis elegans (C. elegans) has been recognized for being a useful model organism in small-molecule drug screens and drug efficacy investigation. However, there remain bottlenecks in evaluating such processes as drug uptake and distribution due to a lack of appropriate chemical tools.

This study aims to prepare fluorescence-labeled leonurine as an example to monitor drug uptake and distribution of small molecule in C. elegans and living cells.

FITC-conjugated leonurine (leonurine-P) was synthesized and characterized by LC/MS, NMR, UV absorption and fluorescence intensity. Leonurine-P was used to stain C. elegans and various mammalian cell lines. Different concentrations of leonurine were tested in conjunction with a competing parent molecule to determine whether leonurine-P and leonurine shared the same biological targets. Drug distribution was analyzed by imaging. Fluorometry in microplates and flow cytometry were performed for quantitative measurements of drug uptake.

The UV absorption peak of leonurine-P was 490∼495 nm and emission peak was 520 nm. Leonurine-P specifically bound to endogenous protein targets in C. elegans and mammalian cells, which was competitively blocked by leonurine. The highest enrichment levels of leonurine-P were observed around 72 h following exposure in C. elegans. Leonurine-P can be used in a variety of cells to observe drug distribution dynamics. Flow cytometry of stained cells can be facilely carried out to quantitatively detect probe signals.

The strategy of fluorescein-labeled drugs reported herein allows quantification of drug enrichment and visualization of drug distribution, thus illustrates a convenient approach to study phytodrugs in pharmacological contexts.