11C-methionine PET identifies astroglia involvement in heart-Brain inflammation networking after acute myocardial infarction

Abstract

Acute myocardial infarction (MI) triggers a local and systemic inflammatory response. We recently showed microglia involvement using translocator protein imaging. Here, we evaluated whether 11C-methionine provides further insight into heart-brain inflammation networking. Methods: Male C57BL/6 mice underwent permanent coronary artery ligation followed by 11C-methionine PET at 3 and 7 d (n 5 3). In subgroups, leukocyte homing was blocked by integrin antibodies (n 5 5). The cellular substrate for PET signal was identified using brain section immunostaining. Results: 11C-methionine uptake (percentage injected dose/cm3) peaked in the MI region on day 3 (5.9 ± 0.9 vs. 2.4 ± 0.5), decreasing to the control level by day 7 (4.3 ± 0.6). Brain uptake was proportional to cardiac uptake (r 5 0.47, P, 0.05), peaking also on day 3 (2.9 ± 0.4 vs. 2.4 ± 0.3) and returning to baseline on day 7 (2.3 ± 0.4). Integrin blockade reduced uptake at every time point. Immunostaining on day 3 revealed colocalization of the L-type amino acid transporter, with glial fibrillary acidic protein-positive astrocytes but not CD68-positive microglia. Conclusion: PET imaging with 11C-methionine specifically identifies an astrocyte component, enabling further dissection of the heart-brain axis in post-MI inflammation.