Abstract Body: OBJECTIVE: Neuroprotection to attenuate or block the ischemic cascade and salvage neuronal damage has been explored for treating ischemic stroke. This study focuses on the neuroprotective bioactivity of docosanoid mediators Neuroprotectin D1 (NPD1) and Resolvin D1 (RvD1) in experimental stroke. These lipid mediators are biosynthesized “on-demand” in response to stroke onset to restore homeostasis and functional integrity to resolve neuroinflammation. Recently, we have shown that NPD1+RvD1 improved behavior when they were allowed to survive for 7 days after a stroke. This study established whether neuroprotection induced by NPD1+RvD1 persists with chronic survival and whether NPD1+RvD1 affects the expression of microglia and astrocyte-specific genes.
METHODS: Male Sprague-Dawley rats (270-360g) were anesthetized with isoflurane/nitrous oxide and received 2h of middle cerebral artery occlusion (MCAo). Behavior was evaluated on days 1, 2, 3, 7, 14, 21, 28. Rats were treated with NPD1 (222 µg/kg at 3h) and RvD1 (222 µg/kg at 3:15) or vehicle (n=6-8 / group) after the onset of MCAo. Thirty days after MCAo, rats were perfused with 4% paraformaldehyde, and a brain MRI was conducted. Molecular targets of NPD1 and RvD1 were defined at 24 h after MCAo.
RESULTS: Physiological variables were stable and showed no significant differences between groups. Combinatory treatment improved behavioral scores on days 1, 2, 3, 7, 14, 21, and 28 by 32, 35, 39, 40, 46, 48, and 50% compared to the vehicle group. NPD1+RvD1 significantly reduced lesions (computed from T2WI) in the cortex (0.4% vs. 5.1%), subcortex (0.2% vs. 1.5%), and total lesion (0.6% vs. 6.5%) compared to the vehicle group, respectively. Transcriptomic analysis revealed differentially regulated genes by NPD1+RvD1 at 24h after treatment. We uncovered that protection after MCAo by the lipid mediators elicits expression of microglia and astrocyte-specific genes (Tmem119, Fcrls, Osmr, Msr1, Cd68, Cd163, Amigo2, Thbs1, and Tm4sf1).
CONCLUSION: Our results indicate that NPD1+RvD1 exerts potent, long-term neuroprotective effects in the model of focal cerebral ischemia in rats. Uncovered genes will likely enhance homeostatic microglia, modulate neuroinflammation, activate NPC differentiation, maturation, and synapse integrity, and contribute to cell survival. Our findings strengthen the notion that combinatory might be of clinical usefulness for treating acute stroke.