Abstract Body: Introduction: Individuals with endothelial dysfunction exhibit a loss of NO-mediated vasodilation, achieving vasodilation instead through mitochondria-derived H₂O₂. Mitochondrial dynamics is an important autoregulatory mechanism that contributes to mitochondrial and endothelial homeostasis and plays a direct role in formation of reactive oxygen species (ROS), including H₂O₂.
Hypothesis: Dysregulation of endothelial mitochondrial dynamics contributes to the pathogenesis of endothelial dysfunction and CAD.
Methods & Results: Western blot and immunohistochemistry analysis indicates that individuals with CAD have increased DRP1 expression and decreased MFN1/2 expression compared to those without CAD (non-CAD) in microvessels (unpaired t test, p<0.05) and in left ventricular tissue (unpaired t test, p<0.05). This data correlates with increased endothelial mitochondrial fragmentation observed in microvessels taken from individuals with CAD compared to non-CAD (fragmentation count = 45.5 to 8.3, unpaired t test p<0.05) and increased fragmentation in CD31-magnetic bead isolated primary endothelial cells (fragmentation count= 5.4 to 1.8, unpaired t test p<0.05). On a functional level, promotion of fission, achieved either by AAV upregulation of DRP1 or silencing RNA of MNF2, in non-CAD vessels promotes H₂O₂-mediated vasodilation (peg-cat inhibitable, two-way ANOVA p<0.05) while promotion of mitochondrial fusion, achieved both by silencing DRP1 or upregulating MFN2, in CAD vessels restored NO-mediated dilation (L-NAME inhibitable, two-way ANOVA p<0.05). An ATP fluorescent probe also indicates that CAD vessels have decreased ATP production when vessels are exposed to flow compared to non-CAD (unpaired t test p<0.05). Our data further indicates that mitochondrial ROS production, as a byproduct of mitochondrial fission, is only partially responsible for the phenotypic switch as acute treatment of a non-CAD vessel post treatment with mitoTempo does not fully restore NO-mediated dilation (peg-cat & L-NAME inhibitable, two-way ANOVA p<0.05).
Conclusion: Proper regulation of endothelial mitochondrial dynamics may be a suitable treatment for individuals with endothelial microvascular dysfunction.