RvD1/FPR2 attenuates cerebral ischemic injury through inhibiting inflammation and oxidative stress

Oxidative stress and inflammation are two closely related pathogenesis processes during ischemic injury. The current study investigated the neuroprotective effects of resolvin D1 (RvD1, a pro-resolving mediator) and its corresponding receptor formyl peptide receptor 2 (FPR2) in a rat model of middle cerebral artery occlusion (MCAO). Dynamic expressions of endogenous RvD1 and FPR2 in ischemic hemisphere were firstly examined by ELISA and western blot respectively. To explore the therapeutic effects of RvD1/FPR2 on ischemic injury, exogenous RvD1 were given at 0.4 µg/kg after MCAO (i.p.). Boc-2 (specific FPR2 antagonist to inhibit effects of RvD1/FPR2) were administered at 0.4 mg/kg (i.p.) 30 min before MCAO to inhibit the binding of RvD1 to FPR2. For evaluating ischemic injury, neurological performances were determined by deficit score and grip strength, and infarction volume were assayed by TTC. Neuronal damage was further observed by stainings of H&E, Fluoro-Jade C (FJC), and TUNEL. Inflammation markers were assayed by MPO immunostaining and mRNA dectection. Oxidative stress was determined by related kits (MDA, NO, GSH and SOD) and MitoSOX staining. Our results showed that endogenous cerebral levels of RvD1 were decreased after focal ischemia, but expression of FPR2 was increased. Exogenous RvD1 treatment alleviated neurological deficits, reduced infarct volume and attenuated neuronal apoptosis, however, inhibition of FPR2 by Boc-2 inhibited these effects. Furthermore, RvD1 reduced MPO positive cells and mRNA levels of pro-inflammatory mediators (TNF-α, IL-1β, and iNOS), but increased mRNA levels of anti-inflammatory mediators (TGF-β1 and IL-10). Concurrently, RvD1 inhibited oxidative stress, evidenced by down-regulated pro-oxidative mediators (such as MDA and NO) and up-regulated anti-oxidative mediators (SOD and GSH). Boc-2 alleviated the anti-inflammatory and anti-oxidant effects of RvD1. Mechanistically, RvD1 decreased expression of NOX2 in microglia and astrocytes, while co-administration of Boc-2 reversed these effects. These finding demonstrate that RvD1/FPR2 alleviated cerebral ischemic injury by attenuating inflammation and oxidative stress, which is beneficial to break the vicious cycle between inflammation and oxidative stress, thus highlighting its potential role in treatment for ischemic stroke.