Mitochondrial ATP production provides long-range control of endothelial inositol trisphosphate-evoked calcium...

Endothelial cells are reported to be glycolytic and to minimally rely on mitochondria for ATP generation. Rather than providing energy, mitochondria in endothelial cells may act as signaling organelles that control cytosolic Ca²⁺ signaling or modify reactive oxygen species (ROS). To control Ca²⁺ signaling, these organelles are often observed close to influx and release sites and may be tethered near Ca²⁺ transporters. In this study, we used high-resolution, wide-field fluorescence imaging to investigate the regulation of Ca²⁺ signaling by mitochondria in large numbers of endothelial cells (∼50 per field) in intact arteries from rats. We observed that mitochondria were mostly spherical or short-rod structures and were distributed widely throughout the cytoplasm. The density of these organelles did not increase near contact sites with smooth muscle cells. However, local inositol trisphosphate (IP₃)-mediated Ca²⁺ signaling predominated near these contact sites and required polarized mitochondria. Of note, mitochondrial control of Ca²⁺ signals occurred even when mitochondria were far from Ca²⁺ release sites. Indeed, the endothelial mitochondria were mobile and moved throughout the cytoplasm. Mitochondrial control of Ca²⁺ signaling was mediated by ATP production, which, when reduced by mitochondrial depolarization or ATP synthase inhibition, eliminated local IP₃-mediated Ca²⁺ release events. ROS buffering did not significantly alter local Ca²⁺ release events. These results highlight the importance of mitochondrial ATP production in providing long-range control of endothelial signaling via IP₃-evoked local Ca²⁺ release in intact endothelium.