Potassium channelopathy-like defect underlies early-stage cerebrovascular dysfunction in a genetic model of small vessel disease

Abstract

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), caused by dominant mutations in the NOTCH3 receptor in vascular smooth muscle, is a genetic paradigm of small vessel disease (SVD) of the brain. Recent studies using transgenic (Tg)Notch3 R169C mice, a genetic model of CADASIL, revealed functional defects in cerebral (pial) arteries on the surface of the brain at an early stage of disease progression. Here, using parenchymal arterioles (PAs) from within the brain, we determined the molecular mechanism underlying the early functional deficits associated with this Notch3 mutation. At physiological pressure (40 mmHg), smooth muscle membrane potential depolarization and constriction to pressure (myogenic tone) were blunted in PAs from TgNotch3 R169C mice. This effect was associated with an ∼60% increase in the number of voltage-gated potassium (K V ) channels, which oppose pressure-induced depolarization. Inhibition of K V 1 channels with 4-aminopyridine (4-AP) or treatment with the epidermal growth factor receptor agonist heparin-binding EGF (HB-EGF), which promotes K V 1 channel endocytosis, reduced K V current density and restored myogenic responses in PAs from TgNotch3 R169C mice, whereas pharmacological inhibition of other major vasodilatory influences had no effect. K V 1 currents and myogenic responses were similarly altered in pial arteries from TgNotch3 R169C mice, but not in mesenteric arteries. Interestingly, HB-EGF had no effect on mesenteric arteries, suggesting a possible mechanistic basis for the exclusive cerebrovascular manifestation of CADASIL. Collectively, our results indicate that increasing the number of K V 1 channels in cerebral smooth muscle produces a mutant vascular phenotype akin to a channelopathy in a genetic model of SVD.

Ion channel networks in the control of cerebral blood flow

“…The balance of these signaling elements controls Ca 2þ entry into the myocyte and thus the contractile state of the cell. Adapted from Dabertrand et al 83 resting V m lies within this range, closely matching that of the electrically connected overlying SM.…”

Mechanistic insights into a TIMP3-sensitive pathway constitutively engaged in the regulation of cerebral hemodynamics

“…Importantly, application of sHB-EGF was found to normalize K V current density and restore myogenic responses in cerebral arteries from TgNotch3 R169C mice (Dabertrand et al, 2015). In light of this and the above, we investigated the involvement of TIMP3 and ADAM17 in this upregulation of K V current density.…”

“…Notably, an influence of the endothelium in myogenic tone deficit was ruled out (Dabertrand et al, 2015). K V channels play an important and dynamic role in opposing pressure-induced depolarization and vasoconstriction (Longden et al, 2015).…”

Isolation and Cannulation of Cerebral Parenchymal Arterioles

“…In mice, we utilized this technique to assess Ca 2+ signals in pressurized PA smooth muscle cells under physiological conditions and acidosis by coupling PA cannulation to laser scanning confocal microscopy to assess Ca 2+ waves and sparks in smooth muscle cells 13 . We also tested several neurovascular coupling agents 3 and demonstrated, using pharmacological tools in conjunction with membrane potential recordings, that cerebrospecific up-regulation of voltage-gated potassium channels K V 1 causes a channelopathy-like defect in small vessel disease genetic model 7 . These examples illustrate the viability of this preparation to answer different research questions.…”

“…As a result, dysfunction of parenchymal arterioles contributes to the development of cerebrovascular diseases such as vascular cognitive impairment and small ischemic strokes (also known as silent or lacunar strokes). Studies indicate that parenchymal arterioles dysfunction can be induced by essential hypertension 5 , chronic stress 6 , and is an early event in small vessel disease genetic mouse model 7 . Further, experimentally-induced occlusion of single penetrating arterioles in rats is sufficient to cause small ischemic strokes that are cylindrical in shape, similar those observed in older humans 8 .…”