5-hydroxymethyl-furfural and structurally related compounds block the ion conductance in human aquaporin-1 channels, and slow cancer cell migration and invasion

Abstract

Aquaporin-1 (AQP1) dual water and ion channels enhance migration and invasion when upregulated in leading edges of certain classes of cancer cells. Work here identifies structurally-related furan compounds as novel inhibitors of AQP1 ion channels. 5-Hydroxymethyl-2-furfural (5HMF), a component of natural medicinal honeys, and three structurally-related compounds nitrofuroic acid (5NFA), acetoxymethylfuraldehyde (5AMF), and methylnitrofuroate (M5NF), were analyzed for effects on water and ion channel activities of human AQP1 channels expressed in Xenopus oocytes. Two-electrode voltage clamp showed dose-dependent block of the AQP1 ion current by 5HMF (IC50 0.43 mM ), 5NFA (IC50 1.2 mM), 5AMF (IC50 ~3 mM), but no inhibition by M5NF. In silico docking predicted the active ligands interacted with glycine 165, located in loop D gating domains surrounding the intracellular vestibule of the tetrameric central pore. Water fluxes through separate intrasubunit pores were unaltered by the furan compounds (at concentrations up to 5mM). Effects on cell migration, invasion and cytoskeletal organization in vitro were tested in high AQP1-expressing cancer lines, HT29 and MDA, and low AQP1-expressing SW480. 5HMF, 5NFA and 5AMF selectively impaired cell motility in the AQP1-enriched cell lines. In contrast M5NF immobilized all the cancer lines by disrupting actin cytoskeleton. No reduction in cell viability was observed at doses that were effective in blocking motility. These results define furans as a new class of AQP1 ion channel inhibitors for basic research, and potential lead compounds for development of therapeutic agents targeting aquaporin channel activity. SIGNIFICANCE STATEMENT: 5-hydroxymethyl furfural (5HMT), a component of natural medicinal honeys, blocks the ion conductance but not the water flux through human Aquaporin-1 (AQP1) channels, and impairs AQP1-dependent cell migration and invasiveness in cancer cell lines. Analyses of 5HMT and structural analogs demonstrate a structure-activity relationship for furan compounds, supported by in silico docking modeling. This work identifies new low-cost pharmacological antagonists for AQP1 available to researchers internationally. Furans merit consideration as a new class of therapeutic agents for controlling cancer metastasis.