Adenosine A2 Receptors and Imaging of Inflammation in Lung Reperfusion Injury

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Project Summary Ischemia-reperfusion injury (IRI), which leads to primary graft dysfunction (PGD), is a major source of early mortality after lung transplantation. Current clinical methods to diagnose PGD are limited to chest x-ray, CT, and functional tests, none of which specifically address acute inflammation or immune cell activation; key components of lung IRI. FDG-PET imaging is often used clinically as an indication of inflammation and neutrophil activity; however, FDG-PET is non-specific by imaging general metabolic activity. The primary objective of this proposal is to develop novel, cell-specific SPECT imaging methods to provide sensitive and early diagnosis of IRI after lung transplantation. Using a murine model of lung IRI, Aim 1 will validate three novel molecular probes for SPECT imaging of lung IRI: 99mTc-cFLFLF that targets formyl peptide receptor on activated neutrophils, 99mTc-EC20 that targets activated, pro- inflammatory M1 macrophages, and 99mTc-labeled anti-mannose receptor Nanobodies that target alternatively activated, anti-inflammatory M2 macrophages. We hypothesize that targeting of M1 macrophages will provide the earliest diagnosis of IRI prior to manifestation of PGD while targeting of M2 macrophages will allow informative assessment of the resolution of IRI via immunosuppressive actions. SPECT imaging with these probes will be compared to FDG-PET imaging. Aim 2 will use SPECT imaging in mice to monitor the response to adenosine receptor-targeted therapies aimed at attenuating IRI. Attenuation of IRI by adenosine A2A receptor (A2AR) agonism and/or A2BR antagonism will be focused on, and alveolar epithelial mechanisms for A2BR antagonist-mediated protection from IRI will be determined. Aim 3 will translate our results to a clinically relevant, large animal lung transplant model by determining if SPECT imaging will provide early diagnosis of lung IRI after transplantation of porcine lungs. The successful completion of our proposal could result in translation of these novel imaging methods to the clinical setting with the goal of providing an effective, non- invasive means for early diagnosis of IRI in order to permit rapid, targeted therapeutic interventions to prevent PGD and thus improve short- and long-term outcomes in lung transplant recipients.