Discovery of Quinazoline-Based Fluorescent Probes to α1-Adrenergic Receptors

Abstract

α1-Adrenergic receptors (α1-ARs), as the essential members of G protein-coupled receptors (GPCRs), can mediate numerous physiological responses in the sympathetic nervous system. In the current research, a series of quinazoline-based small-molecule fluorescent probes to α1-ARs (1a-1e), including two parts, a pharmacophore for α1-AR recognition and a fluorophore for visualization, were well designed and synthesized. The biological evaluation results displayed that these probes held reasonable fluorescent properties, high affinity, accepted cell toxicity, and excellent subcellular localization imaging potential for α1-ARs.

Keywords: cell imaging; fluorescent probes; quinazoline; subcellular localization; α1-Adrenergic receptors.

Scheme 1. Structures of Quinazoline Derivatives as α₁-AR Antagonists

Scheme 2. Designed Quinazoline-Based Fluorescent Probes for α₁-ARs

Figure 1

Proposed docking conformation of prazosin (red sticks) and 1a (white sticks) in the human α_1A-AR binding site.

Scheme 3. Synthetic Routes of Designed Fluorescent Probes

Figure 2

Confocal fluorescence image of HEK293 cell using compound 1a. All cells are incubated with 1a at 37 °C for 5 min and washed immediately, and the exposure time is the same. The background was adjusted by ImageJ software. (A) Image of HEK293A-α_1A-AR cells incubated with 1a (15 nM) and DiD; (B) image of HEK293A-α_1D-AR cells incubated with 1a (15 nM) and DiD; (C) image of HEK293A cells incubated with 1a (15 nM) and DID; (D) image of HEK293A-α_1A-AR cells incubated with 1a (15 nM), DID, and tamsulosin (300 nM); (E) image of HEK293A-α_1D-AR cells incubated with 1a (15 nM), DID, and tamsulosin (300 nM). Scale bar (yellow) = 20 μm.

Figure 3

Fluorescence image of cancer cells using compound 1d. The background was adjusted by ImageJ software. (A) PC-3 cells were with incubated with 1d (1 μM) at 37 °C for 30 min, then washed immediately; (B) PC-3 cells were with incubated with 1d (1 μM) and doxazosin (10 μM) at 37 °C for 30 min, then washed immediately; (C) HepG2 cells were incubated with 1d (1 μM) at 37 °C for 30 min, then washed immediately. Scale bar (yellow) = 20 μm.