A fluorogenic near-infrared imaging agent for quantifying plasma and local tissue renin activity in vivo and ex vivo

• Published in: American journal of physiology. Renal physiology Vol. 303; no. 4; pp. F593 - F603
• Main Authors: Zhang, Jun, Preda, Dorin V, Vasquez, Kristine O, Morin, Jeff, Delaney, Jeannine, Bao, Bagna, Percival, M David, Xu, Daigen, McKay, Dan, Klimas, Michael, Bednar, Bohumil, Sur, Cyrille, Gao, David Z, Madden, Karen, Yared, Wael, Rajopadhye, Milind, Peterson, Jeffrey D
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 15.08.2012
• Subjects: Animal Feed - analysis; Animals; Cathepsin D; Cathepsin G; Female; Fluorescence; Fluorescent Dyes - pharmacology; Humans; Innovative Methodology; Kidneys; Mice; Mice, Inbred C57BL; Peptides - pharmacology; Peptidyl-Dipeptidase A - metabolism; Plasma; Rats; Renin - blood; Renin - metabolism; Renin-Angiotensin System - physiology; Rodents; Sensitivity and Specificity; Sodium; Sodium, Dietary; Tissues
• DOI: 10.1152/ajprenal.00361.2011
• ISSN: 1931-857X

The renin-angiotensin system (RAS) is well studied for its regulation of blood pressure and fluid homeostasis, as well as for increased activity associated with a variety of diseases and conditions, including cardiovascular disease, diabetes, and kidney disease. The enzyme renin cleaves angiotensinogen to form angiotensin I (ANG I), which is further cleaved by angiotensin-converting enzyme to produce ANG II. Although ANG II is the main effector molecule of the RAS, renin is the rate-limiting enzyme, thus playing a pivotal role in regulating RAS activity in hypertension and organ injury processes. Our objective was to develop a near-infrared fluorescent (NIRF) renin-imaging agent for noninvasive in vivo detection of renin activity as a measure of tissue RAS and in vitro plasma renin activity. We synthesized a renin-activatable agent, ReninSense 680 FAST (ReninSense), using a NIRF-quenched substrate derived from angiotensinogen that is cleaved specifically by purified mouse and rat renin enzymes to generate a fluorescent signal. This agent was assessed in vitro, in vivo, and ex vivo to detect and quantify increases in plasma and kidney renin activity in sodium-sensitive inbred C57BL/6 mice maintained on a low dietary sodium and diuretic regimen. Noninvasive in vivo fluorescence molecular tomographic imaging of the ReninSense signal in the kidney detected increased renin activity in the kidneys of hyperreninemic C57BL/6 mice. The agent also effectively detected renin activity in ex vivo kidneys, kidney tissue sections, and plasma samples. This approach could provide a new tool for assessing disorders linked to altered tissue and plasma renin activity and to monitor the efficacy of therapeutic treatments.