Violacein induces cell death by triggering mitochondrial membrane hyperpolarization in vitro.

BACKGROUND: Violacein is a purple pigment from Chromobacterium violaceum that possesses diverse biological and pharmacological properties. Among these, pro-oxidant and antioxidant activities have been suggested. However, the cytotoxic mechanisms induced by violacein are poorly understood and the improvement in knowledge regarding these cell death mechanisms will be useful to develop new therapeutic approaches. Considering this, in our work, we investigated the pro-oxidant effects of violacein in non-tumor (CHO-K1 and MRC-5) and tumor (HeLa) cell lines, searching for a better understanding of reactive oxygen species (ROS) production and cell death induction. RESULTS: Cytotoxicity induced by violacein was observed in the three cell lines; however, MRC-5 and HeLa cells were shown to be more sensitive to violacein treatment. Although punctual alterations in the antioxidant apparatus and increase in oxidative stress biomarkers was observed in some violacein concentrations, no association was found between increased oxidative stress and induction of cell death. However, the increase of mitochondrial membrane potential was observed. CONCLUSIONS: In fact, the increase of mitochondrial membrane potential in MRC-5 and HeLa cells suggests that mitochondrial membrane hyperpolarization might be the main cause of cell death triggered by violacein.

Surface modification by argon plasma treatment improves antioxidant defense ability of CHO-k1 cells on titanium surfaces.

Titanium is one of the most used materials in implants and changes in its surface can modify the cellular functional response to better implant fixation. An argon plasma treatment generates a surface with improved mechanical proprieties without modifying its chemical composition. Oxidative stress induced by biomaterials is considered one of the major causes of implant failure and studies in this field are fundamental to evaluate the biocompatibility of a new material. Therefore, in this work, induction of oxidative stress by titanium surfaces subjected to plasma treatment (PTTS) was evaluated. The viability of CHO-k1 cells was higher on PTTS discs. Cells grown on titanium surfaces are subjected to intracellular oxidative stress. Titanium discs subjected to the plasma treatment induced less oxidative stress than the untreated ones, which resulted in improved cellular survival. These were associated with improved cellular antioxidant response in Plasma Treated Titanium Surface (PTTS). Furthermore, a decrease in protein and DNA oxidative damage was observed on cells grown on the roughed surface when compared to the smooth one. In conclusion, our data suggest that the treatment of titanium with argon plasma may improve its biocompatible, thus improving its performance as implants or as a scaffold in tissue engineering.