FISH-OIL PRECONDITIONING UP-REGULATES EXPRESSION OF SPLENIC ARG1 POSITIVE M2 TYPE MACROPHAGES AND THE ARG1/INOS2 RATIO AFTER EXPERIMENTAL INDUCED TRANSIENT CEREBRAL ISCHEMIA

During a stroke, the contraction of the spleen can mobilize inflammatory cells that infiltrate the damaged brain tissue. We analysed the effects of transient cerebral ischemia and fish oil preconditioning on the spleen volume, architecture, and macrophage polarization. Wistar rats were subjected to middle cerebral artery occlusion (ischemic and treatment groups, each n = 10), and were sacrificed after 24 hrs, along with a sham group (n = 10). The spleen volume suffered only mild variations, while the marginal zone showed size reduction in the ischemic group, compared to treated and control groups. Granulopoiesis and myeloperoxidase positivity were significantly increased in spleens of ischemic animals (p < 0.001 vs. the treatment and sham groups). Arginase 1 was up-regulated and the Arg1/iNOS2 expression ratio showed a significant shift on macrophages of marginal zone/red pulp interface in the treatment group compared to ischemic rats (p < 0.001). Argl positive M2 type monocytes/macrophages participate in resolution and tissue repair thus may feature as potential therapeutical targets in cerebral ischemia.