Methemoglobin exposure produces toxicological effects in macrophages due to multiple ROS spike induced apoptosis.

Macrophages are an integral part of the immune system, required to produce a robust immune response against an infectious organism. Presence of methemoglobin in body fluids such as blood, cerebrospinal fluid and urine is associated with tissue damage. We tested cytotoxic effects of MetHb and underlying molecular events in mouse macrophage cell line J774A.1. MetHb exposure dose dependently reduced macrophage viability in an MTT assay. Light microscopy and scanning electron microscopic (SEM) observation of MetHb treated macrophage indicated death (less number of cells per field), severe damage to membrane structure and accumulation of particulate matter in the cytosol. The macrophage death during MetHb exposure was due to induction of apoptosis as indicated by annexin-V/FITC staining and DNA fragmentation analysis. MetHb treatment generated a periodic ROS spikes with time in the macrophage cytosol to develop oxidative stress. Scavenging ROS spikes with NAC, mannitol or PBN dose dependently protected macrophages against MetHb induced toxicity, apoptosis and cellular membrane damage. Our work highlighted the contributions of MetHb mediated toxicity toward macrophage and its potential role in tissue damage and immune depression during malaria and other hemolytic disorders.