Kidney CLC-K chloride channels inhibitors: structure-based studies and efficacy in hypertension and associated CLC-K polymorphisms

Objective: Alterations in the handling of renal salt reabsorption may contribute to interindividual differences in blood pressure regulation and susceptibility to hypertension. CLC-K chloride channels and their accessory subunit barttin play a pivotal role in kidney by controlling chloride and water absorption. Compounds selective for CLC-Ks, such as the benzofuran derivative MT-189, may have a significant therapeutic potential. Here, we assessed the feasibility of using CLC-K blockers in hypertension and aimed at enhancing drug inhibitory affinity. Methods and results: We demonstrated that acute in-vivo administration of MT-189 to spontaneously hypertensive rats (SHR) caused a reduction of blood pressure and defined the CLC-K/barttin gene expression pattern in kidney of SHR in comparison with normotensive Wistar–Kyoto rats. Based on MT-189, we designed and tested a new series of benzofuran derivatives on CLC-K chloride channels heterologously expressed in HEK293 cells. These studies enabled us to elucidate the causative molecular relationship for obtaining the most potent and selective inhibitor (SRA-36) described so far, with an IC50 of 6.6 ± 1 &mgr;mol/l. The biophysical and pharmacological characterization of A447T CLC-Ka and Y315F CLC-Ka, both polymorphisms associated with hypertension, showed that SRA-36 is an efficacious inhibitor of the chloride currents sustained by these polymorphisms. Molecular docking studies allowed hypothesizing an inhibition mechanism for the considered ligands, laying the foundations for the rational design of new and more effective CLC-K inhibitors. Conclusion: The SRA-36 molecule represents a new potential therapeutic option for hypertension.