Sackheim, A. | Search bioRxiv

bioRxiv2026

Spatial uncoupling of endothelial calcium signaling from phospha-tidylserine externalization in vascular injury

Ca2+ is both the signal that spreads injury information through the endothelium and the trigger for phospholipid scrambling that makes a membrane procoagulant. How a blood vessel can disseminate the first without broadcasting the second is unknown. Here, we combine single-cell laser injury in endothelial monolayers with imaging of intact mesenteric vessels in vitro and intravital Ca2+ imaging in vivo. Injury generated a coherent Ca2+ wavefront that spread rapidly before progressively slowing and terminating at a reproducible boundary 197 {+/-} 7 m from the wound, engaging 50 {+/-} 8 cells. The first ring of neighboring cells exhibited a distinct response that was prevented by carbenoxolone, whereas propagation beyond this ring required extracellular ATP, purinergic receptor activation, and IP3-dependent Ca2+ release. Wavefront kinematics were consistent with ATP diffusion. In vivo, injury elicited vasoconstriction and bidirectional Ca2+ waves propagating 205 {+/-} 28 m before terminating. Remarkably, despite widespread Ca2+ elevations, phosphatidylserine (PS) externalization remained confined to the wounded cell in monolayers and intact vessels in vitro. In contrast, ionomycin-induced Ca2+ overload exposed phosphatidylserine in nearly all endothelial cells. These findings reveal an unexpected spatial uncoupling between endothelial Ca2+ signaling and phospholipid scrambling, demonstrating that Ca2+ dependent scramblase activation is subject to additional spatial regulation. The endothelium can therefore propagate injury signals across a broad field of cells while maintaining a highly localized procoagulant membrane response.

physiology↗

bioRxiv2023

Pathogenic soluble tau peptide disrupts endothelial calcium signaling and vasodilation in the brain microvasculature

The accumulation of the microtubule-associated tau protein in and around blood vessels contributes to brain microvascular dysfunction through mechanisms that are incompletely understood. Delivery of nutrients to active neurons in the brain relies on capillary inositol 1,4,5-triphosphate receptor (IP3R)-mediated calcium (Ca2+) signals to direct blood flow. The initiation and amplification of endothelial cell IP3R-mediated Ca2+ signals requires an intact microtubule cytoskeleton. Since tau accumulation in endothelial cells disrupts native microtubule stability, we reasoned that tau-induced microtubule destabilization would impair endothelial IP3-evoked Ca2+ signaling. We tested the hypothesis that tau disrupts the regulation of local cerebral blood flow by reducing endothelial cell Ca2+ signals and endothelial-dependent vasodilation. We used a pathogenic soluble tau peptide (T-peptide) model of tau aggregation and mice with genetically encoded endothelial Ca2+ sensors to measure cerebrovascular endothelial responses to tau exposure. T-peptide significantly attenuated endothelial Ca2+ activity and cortical capillary blood flow in vivo within 120 seconds. Further, T-peptide application constricted pressurized cerebral arteries and inhibited endothelium-dependent vasodilation. This study demonstrates that pathogenic tau alters cerebrovascular function through direct attenuation of endothelial Ca2+ signaling and endothelium-dependent vasodilation.

neuroscience↗