Design, Synthesis, In Vitro and In Vivo Characterization of Selective NKCC1 Inhibitors for the Treatment of Core Symptoms in Down Syndrome

Abstract

Intracellular chloride concentration [Cl – ] i is defective in several neurological disorders. In neurons, [Cl – ] i is mainly regulated by the action of the Na + –K + –Cl – importer NKCC1 and the K + –Cl – exporter KCC2. Recently, we have reported the discovery of ARN23746 as the lead candidate of a novel class of selective inhibitors of NKCC1. Importantly, ARN23746 is able to rescue core symptoms of Down syndrome (DS) and autism in mouse models. Here, we describe the discovery and extensive characterization of this chemical class of selective NKCC1 inhibitors, with focus on ARN23746 and other promising derivatives. In particular, we present compound 40 ( ARN24092 ) as a backup/follow-up lead with in vivo efficacy in a mouse model of DS. These results further strengthen the potential of this new class of compounds for the treatment of core symptoms of brain disorders characterized by the defective NKCC1/KCC2 expression ratio.

Structural basis for inhibition of the Cation-chloride cotransporter NKCC1 by the diuretic drug bumetanide

“…Inhibition of NKCC1 by bumetanide and other loop diuretics is a double-edged sword in clinical medicine. On the one hand, antagonizing neuronal NKCC1 represents an emerging attractive strategy for the treatment of a wide range of brain disorders such as seizure and autism 14 , 53 , 54 . On the other hand, inhibition of NKCC1 also causes side effect of ototoxicity in the treatment of edema/hypertension 8 , 9 .…”

Overproduction of hydrogen sulfide, generated by cystathionine β-synthase, disrupts brain wave patterns and contributes to neurobehavioral dysfunction in a rat model of down syndrome

“…DYRK1) have been recently identified, and certain pharmacological agents (e.g. a pharmacological inhibitor of the Na + -K + -Cl-importer) appears to show efficacy both in autism and DS models [ [59] , [60] , [61] , [62] ]. Further work is required to explore the potential connection of DS and autism and the potential involvement of various H 2 S-associated pathways.…”

How Staying Negative Is Good for the (Adult) Brain: Maintaining Chloride Homeostasis and the GABA-Shift in Neurological Disorders

“…In addition to the above study that demonstrated the beneficial effects of NKCC1-specific inhibitor bumetanide, commonly used clinically as a diuretic, it has been shown to be a useful treatment in mouse models of SZ , Down Syndrome (DS) (Deidda et al, 2015), Rett Syndrome (Banerjee et al, 2016), 22q11.2 deletion (DiGeorge) syndrome (Amin et al, 2017), neonatal epilepsy (Dzhala et al, 2005), and ID (Maset et al, 2021). More recent studies have further identified a novel therapeutic molecule known as ARN23746 (Savardi et al, 2020;Borgogno et al, 2021) and a series of KCC2 expression-enhancing compounds (KEECs) to be effective against the core symptoms exhibited by DS and ASD mouse models (Tang et al, 2019). Whereas ARN23746 targets NKCC1 selectively (thus limiting off-target diuretic side effects exhibited by bumetanide), the KEECs act via distinct cell signaling pathways [activation of the sirtuin 1 (SIRT1) or transient receptor potential cation channel subfamily V member 1 (TRPV1) pathways, or inhibition of fms-like tyrosine kinase 3 (FLT3) or glycogen synthase kinase 3β (GSK3β) pathways] to upregulate KCC2 expression at both mRNA and protein levels.…”