Does excess endothelin-A receptor signaling cause cerebral vasoconstriction and endothelial dysfunction?

Excess endothelin-A (ETA) receptor signaling is a biologically credible contributor to impaired cerebral vascular regulation and neuronal susceptibility, particularly in aging and Alzheimer disease–relevant settings. The causal chain is strongest in experimental models; human outcome data support the importance of cerebral perfusion but do not establish ETA excess as the sole driver.

Vascular and endothelial effects

• ETA activation on cerebral vascular smooth muscle causes arterial constriction, and ETA signaling on pericytes can constrict capillaries. In aged rats, increased cerebral-artery ETA expression and myogenic tone, alongside reduced endothelin-B-mediated dilation, favor a constricted vascular state.
• ETA-mediated endothelial injury is supported by experiments in which endothelin-1 activated endothelial Rho-kinase (ROCK), altered eNOS phosphorylation, and reduced nitric-oxide production; the ETA antagonist BQ123 prevented these effects.
• ET-1 also impaired functional hyperemia—activity-related increases in local blood flow—and ETA blockade restored selected cerebral blood-flow responses. Thus, impaired perfusion reserve may be more relevant than uniformly reduced resting flow.

Perfusion and neuronal consequences

• In an amyloid-β rat model, ETA blockade preserved cerebral vascular conductance and flow while preventing pathological vasoconstriction.
• In probable Alzheimer disease, temporal-pole hypoperfusion was associated with later atrophy in the same region, although atrophy also predicted later perfusion decline, consistent with a self-reinforcing relationship.
• In the Rotterdam population study, lower baseline cerebral perfusion predicted faster cognitive decline and greater subsequent dementia risk. Mechanistically, inadequate oxygen and glucose delivery can cause mitochondrial ATP failure, ion dysregulation, oxidative stress, synaptic dysfunction, and neuronal injury.

Bottom line

• The claim is well supported mechanistically: excessive ETA signaling can promote cerebral vasoconstriction and endothelial dysfunction, impair demand-responsive perfusion, and plausibly increase neuronal vulnerability. Its clinical relevance in older humans is compelling but not yet directly established as a primary cause of hypoperfusion or neurodegeneration.