Small Molecule Antagonists of NAADP-Induced Ca2+ Release in T-Lymphocytes Suggest Potential Therapeutic Agents for Autoimmune Disease

摘要

Nicotinic acid adenine dinucleotide phosphate (NAADP) is the most potent Ca²⁺-releasing second messenger known to date, but the precise NAADP/Ca²⁺ signalling mechanisms are still controversial. We report the synthesis of small-molecule inhibitors of NAADP-induced Ca²⁺ release based upon the nicotinic acid motif. Alkylation of nicotinic acid with a series of bromoacetamides generated a diverse compound library. However, many members were only weakly active or had poor physicochemical properties. Structural optimisation produced the best inhibitors that interact specifically with the NAADP/Ca²⁺ release mechanism, having no effect on Ca²⁺ mobilized by the other well-known second messengers d-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] or cyclic adenosine 5′-diphospho-ribose (cADPR). Lead compound >(2) was an efficient antagonist of NAADP-evoked Ca²⁺ release in vitro in intact T lymphocytes and ameliorated clinical disease in vivo in a rat experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis. Compound >(3) (also known as BZ194) was synthesized as its bromide salt, confirmed by crystallography, and was more membrane permeant than >2. The corresponding zwitterion (>3a), was also prepared and studied by crystallography, but >3 had more desirable physicochemical properties. >3 Is potent in vitro and in vivo and has found widespread use as a tool to modulate NAADP effects in autoimmunity and cardiovascular applications. Taken together, data suggest that the NAADP/Ca²⁺ signalling mechanism may serve as a potential target for T cell- or cardiomyocyte-related diseases such as multiple sclerosis or arrhythmia. Further modification of these lead compounds may potentially result in drug candidates of clinical use.