PKCδ and Pharmacomechanical Coupling in the Cerebral Circulation: Mechanisms to In Vivo Application

Introduction: Constrictor stimuli set cerebral arterial blood flow through coupling mechanisms dependent on (electromechanical) and independent of (pharmacomechanical) membrane potential. Each elicit unique “vasomotor signatures”, the latter (via protein kinase C, PKC) allowing small arterial segments to work independently of the broader network. What PKC isoforms drive pharmacomechanical coupling and if focal vasomotor behavior is observable in vivo are questions to be addressed herein. Methods: A multiscale approach from cell-to-live brain, mice-to-humans and which includes western blotting, immunofluorescence, vessel myography, two photon fluorescence microscopy and computational modeling will be employed. Results: A classic GPCR agonist, U46619, was first shown to drive a concentration dependent constriction, with electromechanical coupling preceding pharmacomechanical, the latter coupled to PKC. PKCδ, rather than PKCα mediated the pharmacomechanical response, irrespective of whether the agonist was superfused or applied by pipette to elicit focal constriction. This functional work aligned with cell analysis showing that PKCδ translocates to the membrane upon U46619 stimulation (indicative of activation) and western blot analysis noting that PKCδ blockade attenuated the phosphorylation of key pharmacomechanical regulators (CPI-17, HSP27). Pharmacomechanical coupling was observed in vivo (two photon microscopy) by monitoring the variance in diameter along a penetrating arteriole; this key measure of focal constriction attenuated diminished by PKCδ blockade. Realistic modeling of hemodynamic control revealed that focal constriction will markedly impact blood flow distribution among arteriolar branches. Conclusion: PKCδ was identified as the key isoform mediating pharmacomechanical coupling and focal tone control in cerebral arteries. Discrete phamacomechanical control, as observed in live brain tissue, optimizes blood flow distribution among brain cortical layers. We theorize that augmented pharmacomechanical control underlies brain vascular pathobiology, including arterial vasospasm and transient ischemic attack. Heart and Stroke Foundation of Canada, Natural Science and Engineering Council of Canada, Rorabeck Chair in Neuroscience and Vascular Biology This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.