Direct assessment of nitrative stress in lipid environments: Applications of a designer lipid-based biosensor for...

Lipid membranes and lipid-rich organelles are targets of peroxynitrite (ONOO^-), a highly reactive species generated under nitrative stress. We report a membrane-localized phospholipid (DPPC-TC-ONOO) that allows the detection of ONOO^- in diverse lipid environments: biomimetic vesicles, mammalian cell compartments, and within the lung lining. DPPC-TC-ONOO and POPC self-assemble to membrane vesicles that fluorogenically and selectively respond to ONOO^-. DPPC-TC-ONOO, delivered through lipid nanoparticles, allowed for ONOO^- detection in the endoplasmic reticulum upon cytokine-induced nitrative stress in live mammalian cells. It also responded to ONOO^- within lung tissue murine models upon acute lung injury. We observed nitrative stress around bronchioles in precision cut lung slices exposed to nitrogen mustard and in pulmonary macrophages following intratracheal bleomycin challenge. Results showed that DPPC-TC-ONOO functions specifically toward iNOS, a key enzyme modulating nitrative stress, and offers significant advantages over its hydrophilic analog in terms of localization and signal generation.