Enhanced Na+ -K+ -2Cl- cotransporter 1 underlies motor dysfunction in huntington's disease

Abstract

Background: Altered γ-aminobutyric acid signaling is believed to disrupt the excitation/inhibition balance in the striatum, which may account for the motor symptoms of Huntington's disease. Na-K-2Cl cotransporter-1 is a key molecule that controls γ-aminobutyric acid-ergic signaling. However, the role of Na-K-2Cl cotransporter-1 and efficacy of γ-aminobutyric acid-ergic transmission remain unknown in Huntington's disease.

Methods: We determined the levels of Na-K-2Cl cotransporter-1 in brain tissue from Huntington's disease mice and patients by real-time quantitative polymerase chain reaction, western blot, and immunocytochemistry. Gramicidin-perforated patch-clamp recordings were used to measure the E_{γ-aminobutyric acid} in striatal brain slices. To inhibit Na-K-2Cl cotransporter-1 activity, R6/2 mice were treated with an intraperitoneal injection of bumetanide or adeno-associated virus-mediated delivery of Na-K-2Cl cotransporter-1 short-hairpin RNA into the striatum. Motor behavior assays were employed.

Results: Expression of Na-K-2Cl cotransporter-1 was elevated in the striatum of R6/2 and Hdh^150Q/7Q mouse models. An increase in Na-K-2Cl cotransporter-1 transcripts was also found in the caudate nucleus of Huntington's disease patients. Accordingly, a depolarizing shift of E_{γ-aminobutyric acid} was detected in the striatum of R6/2 mice. Expression of the mutant huntingtin in astrocytes and neuroinflammation were necessary for enhanced expression of Na-K-2Cl cotransporter-1 in HD mice. Notably, pharmacological or genetic inhibition of Na-K-2Cl cotransporter-1 rescued the motor deficits of R6/2 mice.

Conclusions: Our findings demonstrate that aberrant γ-aminobutyric acid-ergic signaling and enhanced Na-K-2Cl cotransporter-1 contribute to the pathogenesis of Huntington's disease and identify a new therapeutic target for the potential rescue of motor dysfunction in patients with Huntington's disease. © 2019 International Parkinson and Movement Disorder Society.

Keywords: GABAergic signaling; NKCC1; bmetanide; inflammation; mutant Huntingtin.