Dysbacteriosis an Inciting Cause of Endothelial Dysfunction mediated through Mitochondrial DNA Interactions
Authors: Ait‐Aissa Karima , Hockenberry Joseph C. , Kadlec Andrew O. , Chabowski Dawid S. , Linn Jasmine M. , Gutterman David D. , Beyer Andreas M. 
Published: June 2021

Dysbacteriosis is associated with several conditions including obesity, diabetes, inflammation, and atherosclerosis. Vascular endothelial dysfunction in large and small vessels is well established to be one of the leading risk factors of Coronary Artery Disease (CAD). Although indirect evidence demonstrates that a disrupted gut microbiome is linked with endothelial dysfunction in large vessels, it is entirely unknown whether dysbacteriosis contributes to endothelial dysfunction and elevated reactive oxygen species levels (and reduced NO) in the human microcirculation, nor has a microvascular mechanism been identified. Recent reports suggest that dysbacteriosis might cause release of harmful damage‐associated molecular patterns (DAMPs) from host cells that increase cellular ROS and may thereby reduce NO bioavailability. We have previously shown that in subjects with CAD, microvascular endothelium‐dependent flow mediated dilation (FMD) switches from a nitric oxide (NO)‐mediated to a mitochondrial hydrogen peroxide (mtH2O2) mediated mechanism. Thus, we hypothesized that alteration of the gut microbiome in healthy mice will induce release of mtDNA from host endothelial cells, which in turn acts as a DAMP in the microcirculation, resulting in endothelial dysfunction.

We treated healthy C57Bl6 mice with a cocktail of antibiotics (AB; Metronidazole 1 g/L; Ampicillin 1 g/L; Neomycin 1 g/L; Vancomycin 0.5 g/L) for 12 days to disrupt the microbiome. The level of plasma mtDNA quantified by quantitative PCR (D‐Loop primers) increased 4‐fold in mice treated with AB compared to control mice. Relaxation to Acetylcholine was decreased in the mesenteric resistance artery (MA) (Max Dilation % Vehicle 83±4 vs AB 29±7*; N=4; *p<0.05, Two Way Anova) from mice treated with AB vs. control mice. The magnitude of dilation to flow was not affected by AB (Max Dilation % Vehicle 50±7 vs AB 45± 14; N=4). However, FMD was not inhibitable by L‐NAME in the AB group suggesting a different mediator of dilation (Max Dilation % Vehicle AB 45±14 vs L‐NAME AB 58±17; N=4). To evaluate the impact of mtDNA fragments (mtDAMPs; a subclass of DAMPs) on FMD in the human microvasculature, we pre‐incubated adipose micro‐vessels from subjects without CAD with mtDAMPs. mtDAMPs (1μg/mL) had no effect on the magnitude of FMD. However, as with AB treatment the dilation was not inhibited by L‐NAME; instead peg‐Catalase (H2O2 scavenger) inhibited FMD by 50%, indicating that H2O2 is a component of the mechanism of dilation after mtDAMPs treatment. Incubation with higher level of mtDAMPs (2.5 μg/mL) caused a decrease in endothelial dilator capacity (Max Dilation %: Historic Control 75±4; mtDAMPs 1 μg/mL: 76±8 vs mtDAMPs 2.5 μg/mL: 43±9; N=5).

Our data suggest a potential pathogenic role of gut microbiome changes in microvascular function via increases in circulating mtDNA, which act on endothelial cells to reduce NO bioavailability and induce endothelial dysfunction possibly predisposing to CAD.

Support or Funding Information

NIH‐R21OD018306/AHA‐POST26430075

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.