Circulating Nucleic Acids in Blood Cause DNA Damage?

Researchers here propose a novel method by which stochastic nuclear DNA damage can occur over the course of aging. The paper is open access, but only available in PDF format at the moment:

Whether nucleic acids that circulate in blood have any patho-physiological functions in the host have not been explored. We report here that far from being inert molecules, circulating nucleic acids have significant biological activities of their own that are deleterious to healthy cells of the body. Fragmented DNA and chromatin (DNAfs and Cfs) isolated from blood of cancer patients and healthy volunteers are readily taken up by a variety of cells in culture to be localized in their nuclei within a few minutes. The intra-nuclear DNAfs and Cfs associate themselves with host cell chromosomes to evoke a cellular DNA-damage-repair-response (DDR) followed by their incorporation into the host cell genomes. Whole genome sequencing detected the presence of tens of thousands of human sequence reads in the recipient mouse cells. Genomic incorporation of DNAfs and Cfs leads to dsDNA breaks and activation of apoptotic pathways in the treated cells.

When injected intravenously into Balb/C mice, DNAfs and Cfs undergo genomic integration into cells of their vital organs resulting in activation of DDR and apoptotic proteins in the recipient cells. Cfs have significantly greater activity than DNAfs with respect to all parameters examined, while both DNAfs and Cfs isolated from cancer patients are more active than those from normal volunteers. All the above pathological actions of DNAfs and Cfs described above can be abrogated by concurrent treatment with DNase I and/or anti-histone antibody complexed nanoparticles both in vitro and in vivo. Taken together, our results suggest that circulating DNAfs and Cfs are physiological, continuously arising, endogenous DNA damaging agents with implications to ageing and a multitude of human pathologies including initiation of cancer.

Link: http://www.ncbi.nlm.nih.gov/pubmed/25740145

Comments

How does this phenomenon fit into one of the 7 deadly SENS? Is this a new 8th category of damage which is a bad thing because it would require a new approach?

Posted by: Morpheus at September 7th, 2015 8:05 PM

@Morpheus: It would fall under OncoSENS like all sources of stochastic nuclear DNA damage:

http://sens.org/research/introduction-to-sens-research/cancerous-cells

The SENS view has it that nuclear DNA damage is really only significant for cancer over the present human life span. The consensus elsewhere in the research community is that stochastic nuclear DNA damage, however it arises, is important in aging for other reasons as well, representing a form of cellular dysregulation that should be significant enough to care about. No-one has that one set of data to robustly back up their position, since it would require some way to adjust nuclear DNA damage levels present at a given age without adjusting anything else in metabolism, though there is a lot of fair evidence on either side.

Posted by: Reason at September 7th, 2015 8:09 PM

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