Cell-free chromatin particles damage genomic DNA of healthy cells via an ROS-independent mechanism

Several hundred billion cells die daily in the human body, releasing cell-free chromatin particles (cfChPs) in the process, which then enter the blood circulation and get taken up by healthy cells. We have previously reported that, these internalized cfChPs damage genomic DNA as well cause physical damage to mitochondria, resulting in increased mitochondrial ROS production. In the current study, we evaluated the potential damaging effects of the cfChP-induced increase in ROS production on genomic DNA. NIH3T3 mouse fibroblast cells were treated with cfChPs isolated from the sera of healthy individuals (H-cfChPs) or patients with cancer (C-cfChPs) in the presence or absence of the ROS scavenger Mito-TEMPO. The pre-incubation of cfChP-treated cells with Mito-TEMPO abolished ROS production, but did not prevent genomic DNA damage induced by H-cfChPs and C-cfChPs. Our results suggest that cfChP-induced genomic DNA damage occurs in an ROS-independent manner. These findings align with emerging evidence suggesting that mitochondrial ROS may not be a direct cause of genomic DNA damage and suggest that DNA damage attributed to ROS may in-fact be induced by cfChPs. This possibility opens up new therapeutic approaches involving deactivation of cfChPs to retard ageing and other degenerative conditions traditionally attributed to oxidative stress.