Fetal and Placental DNA Stimulation of TLR9: A Mechanism Possibly Contributing to the Pro-inflammatory Events During Parturition.
INTRODUCTION
While there is evidence for a relationship between cell-free fetal DNA (cffDNA) and parturition, questions remain regarding whether cffDNA could trigger a pro-inflammatory response on the pathway to parturition. We hypothesized that placental and/or fetal DNA stimulates toll-like receptor 9 (TLR9) leading to secretion of pro-inflammatory cytokines by macrophage cells.


METHODS
Four in vitro DNA stimulation studies were performed using RAW 264.7 mouse peritoneal macrophage cells incubated in media containing the following DNA particles: an oligodeoxynucleotide (ODN2395), intact genomic DNA (from mouse placentas, fetuses and adult liver), mouse DNA complexed with DOTAP (a cationic liposome forming compound), and telomere-depleted mouse DNA. Interleukin 6 (IL6) secretion was measured in the media by enzyme-linked immunosorbent assay; and the cell pellet was homogenized for protein content (picograms IL6/mg protein).


RESULTS
Robust IL6 secretion was observed in response to ODN2395 (a CpG-rich TLR9 agonist), mouse DNA-DOTAP complexes, and telomere-depleted mouse DNA in concentrations of 5 to 15 μg/mL. In contrast, ODN A151 (containing telomere sequence motifs), intact genomic mouse DNA, and restriction enzyme-digested DNA had no effect on IL6 secretion. The IL6 response was significantly inhibited by chloroquine (10 μg/mL), thereby confirming the important role for TLR9 in the response by macrophage cells.


CONCLUSIONS
DNA derived from mouse placentas and fetuses, and depleted of telomeric sequences, stimulates a robust pro-inflammatory response by macrophage cells, thereby supporting the hypothesis that cffDNA is able to stimulate an innate immune response that could trigger the onset of parturition. These findings are of clinical importance, as we search for effective treatment/prevention of preterm parturition.
['Goldfarb|Ilona Telefus|IT|', 'Adeli|Sharareh|S|', 'Berk|Tucker|T|', 'Phillippe|Mark|M|']
D000818:Animals D004247:DNA D005260:Female D005333:Fetus D007249:Inflammation D015850:Interleukin-6 D008264:Macrophages D051379:Mice D036801:Parturition D010920:Placenta D011247:Pregnancy D000067996:RAW 264.7 Cells D016615:Telomere D051217:Toll-Like Receptor 9
placental DNA toll-like receptor 9 telomeres fetal cell-free DNA mouse macrophage cells