Glutathione responsive and mitochondria targeting enhanced photodynamic therapy and cascade triggered carbon monoxide release for all in one tumor therapy ScienceDirect What is Mast Cell Activation Syndrome? Longevity Health Mast cells are hypersensitive immune cells that release histamine and other inflammatory mediatorsoften in response to oxidative stress, environmental toxins, and immune imbalance. Many patients with MCAS have low levels of glutathione. Mast cells are hypersensitive immune cells that release histamine and other inflammatory mediatorsoften in response to oxidative stress, environmental toxins, and immune imbalance. Many patients with MCAS have low levels of glutathione.