When fat tissue around the heart and blood vessels was soaked in a blue dye called methylene blue for a day in the lab, it made less of a harmful enzyme and produced fewer damaging chemicals, which might help explain how the dye could protect cells.

Scientists found that adding a small amount of methylene blue to fat tissue around the heart and blood vessels lowered a harmful enzyme (MAO-A) and reduced damaging chemicals called free radicals, suggesting methylene blue can help calm oxidative stress in these tissues.