Abstract Tu0020: Potential Role of Circulating Mitochondrial DNA Fragments in the Manifestation of Anti-Cancer Therapy-Induced Microvascular Endothelial Dysfunction

Cancer survivors are at an increased risk for CVD mortality compared to the general population. Recent data suggest CTx-induced damage to the microvascular endothelium may contribute. Our preliminary studies suggest a roll for toll-like receptor 9 (TLR9) mediated inflammation in the onset of this pathology. TLR9 is activated by mitochondrial DNA ( mt DNA) fragments released from damaged tissue. Given CTx-induced tumor damage results in release of debris into the circulation, we tested the hypothesis that plasma samples obtained after CTx would contain higher levels of mt DNA fragments than those obtained pre-CTx, and that this rise in plasma mt DNA would correspond to impairments in microvascular endothelial function. To test this, we used qPCR to quantify mt DNA fragments (D-Loop, ATPase 6-8) in plasma from hepatocellular carcinoma patients obtained prior to and 1-month post-CTx (ind. samples t-test, mean±SD). Videomicroscopy was used to assess microvascular function using healthy human adipose arterioles from surgical discard tissue. Arterioles were incubated for 15-20 hours with pre- or post-CTx plasma (10% dilution, intraluminal). Endothelium-dependent dilation (flow mediated dilation, FMD) was assessed at pressure gradients between 5 and 100 cmH2O (2-Way RM ANOVA, %max diameter±SD) whereas endothelium-independent dilation was assessed with 100µm papaverine (ind. samples t-test, %max diameter±SD). Plasma D-Loop was significantly elevated post-CTx compared to pre-CTx (post-CTx: n=12, 1.17±0.17 au; pre-CTx: n=8, 1.01±.15 au; p=0.04) whereas levels of ATPase 6-8 were not significantly different between conditions (post-CTx: n=12, 3.15±2.70 au; pre-CTx: n=8, 1.34±1.25 au; p=0.09). In arterioles treated with pre- and post-CTx plasma, a significant pressure gradient x group interaction was present (p=0.0003), with post-CTx (n=8) plasma samples impairing FMD to a greater degree than pre-CTx (n=5) samples. However, there were no differences between groups at individual pressure gradients (all P>0.05). Dilatory responses to papaverine were not different between groups (pre-CTx: n=5, 92±5%; post-CTx: n=8, 87±13%; p=0.43). In conclusion, these preliminary findings suggest a potential rise in plasma mt DNA from pre-to post CTx which may contribute to the onset of CTx-induced microvascular endothelial dysfunction. Future work aims to determine the source of the mt DNA (i.e., tumor vs healthy tissue) as well as the specificity of the mt DNA-TLR9 axis in this pathology.