Characterisation of a novel coumarin-based fluorescent probe for monitoring nitric oxide production in macrophages.

Nitric oxide (NO) is an important effector molecule in host defence against bacterial pathogens. The development of fluorescence imaging to monitor NO production in vitro and in vivo will increase our understanding of its biological role. Recently, a novel 'trappable' fluorescent blue 'turn-on' Cu(II)-complexed coumarin-based probe (CB) has been developed to detect NO. In this study, CB was investigated to evaluate its ability to detect NO in macrophages. Using confocal microscopy, NO was successfully detected in macrophages in the presence of stimuli that induce nitric oxide synthase (iNOS), the enzyme responsible for production of NO. The time dependence and subcellular compartmentalisation of CB in macrophages were evaluated. The probe can be trapped within cells and reacts directly and specifically with NO, rendering it a promising tool for imaging NO in response to pharmacological agents that modulate its level, for example during bacterial infections.