Biological processing of dinuclear ruthenium complexes in eukaryotic cells

Understanding how metal-based compounds interact with eukaryotic cells is essential for drug development. Prior research has shown that certain ruthenium complexes can affect cell membranes and induce apoptosis. However, the specific mechanisms of uptake and intracellular localization remain unclear. This gap motivated the investigation of dinuclear ruthenium complexes in eukaryotic cells. No prior work had resolved the differences in uptake mechanisms between similar compounds. The effects of these complexes on mitochondrial membranes and reactive oxygen species (ROS) production are not well established. This study addresses these uncertainties by comparing two ruthenium complexes in three cell lines. The role of active transport versus passive mechanisms in uptake is a key unresolved question. The connection between membrane damage and apoptosis in these compounds is also underexplored.

This study aimed to examine how two dinuclear ruthenium complexes interact with eukaryotic cells. The researchers focused on uptake mechanisms, effects on membranes, and the induction of reactive oxygen species. The goal was to compare the biological processing of two ruthenium complexes in three cell lines. The specific problem addressed was the lack of clarity on how these compounds enter cells and affect their structures. The motivation was to determine if these complexes could selectively target bacteria over eukaryotic cells. The study sought to clarify the role of active transport and passive diffusion in uptake. The researchers also aimed to assess mitochondrial localization and apoptosis. The findings could inform the design of selective antimicrobial agents.

The study used flow cytometry to assess uptake in three eukaryotic cell lines. The compounds tested were [{Ru(phen)2}2{μ-bb12}](4+) and [Ru(phen)2(μ-bb7)Ru(tpy)Cl](3+). The cell lines included baby hamster kidney, human embryonic kidney, and liver carcinoma cells. Confocal microscopy was used to determine intracellular localization. JC-1 assays were employed to evaluate mitochondrial membrane potential. Annexin V and TO-PRO-3 double-staining was used to assess cell death mechanisms. Superoxide dismutase activity was measured to evaluate ROS production. The methods combined biochemical and imaging techniques to provide a comprehensive analysis.

Rubb12 and Rubb7-Cl entered cells primarily through active transport. Rubb12 also used carrier-assisted diffusion, while Rubb7-Cl relied on passive diffusion. Rubb12 caused significant membrane damage, particularly in HepG2 cells. Rubb7-Cl induced more apoptosis than membrane damage. Confocal microscopy showed Rubb12 did not accumulate in mitochondria. Rubb7-Cl showed significant mitochondrial accumulation. Both compounds increased ROS production, affecting superoxide dismutase activity. The results suggest Rubb12 kills cells mainly by damaging cytoplasmic membranes.

The findings suggest that Rubb12 kills eukaryotic cells via cytoplasmic membrane damage. Rubb7-Cl primarily induces apoptosis with less membrane damage. The uptake mechanisms differ between the two compounds. Rubb12 relies on active transport and carrier-assisted diffusion. Rubb7-Cl uses passive diffusion and active transport. Mitochondrial localization is a key difference between the two compounds. Both compounds induce ROS-mediated cell death. The results support the potential for selective bacterial toxicity with these complexes.