Does Src Kinase Mediated Vasoconstriction Impair Penumbral Reperfusion?

Despite successful recanalization, a significant number of patients with ischemic stroke experience impaired local brain tissue reperfusion with adverse clinical outcome. The cause and mechanism of this multifactorial complication are yet to be understood. At the current moment, major attention is given to dysfunction in blood-brain barrier and capillary blood flow but contribution of exaggerated constriction of cerebral arterioles has also been suggested. In the brain, arterioles significantly contribute to vascular resistance and thus control of perfusion. Accordingly, pathological changes in arteriolar wall function can, therefore, limit sufficient reperfusion in ischemic stroke, but this has not yet received sufficient attention. Although an increased vascular tone after reperfusion has been demonstrated in several studies, the mechanism behind it remains to be characterized. Importantly, the majority of conventional mechanisms controlling vascular contraction failed to explain elevated cerebrovascular tone after reperfusion. We propose here that the Na,K-ATPase-dependent Src kinase activation are the key mechanisms responsible for elevation of cerebrovascular tone after reperfusion. The Na,K-ATPase, which is essential to control intracellular ion homeostasis, also executes numerous signaling functions. Under hypoxic conditions, the Na,K-ATPase is endocytosed from the membrane of vascular smooth muscle cells. This initiates the Src kinase signaling pathway that sensitizes the contractile machinery to intracellular Ca resulting in hypercontractility of vascular smooth muscle cells and, thus, elevated cerebrovascular tone that can contribute to impaired reperfusion after stroke. This mechanism integrates with cerebral edema that was suggested to underlie impaired reperfusion and is further supported by several studies, which are discussed in this article. However, final demonstration of the molecular mechanism behind Src kinase-associated arteriolar hypercontractility in stroke remains to be done.