RvD1binding with FPR2 attenuates inflammation via Rac1/NOX2 pathway after neonatal hypoxic-ischemic injury in rats.

Neuroinflammation plays a crucial role in the pathological development after neonatal hypoxia-ischemia (HI). Resolvin D1 (RvD1), an agonist of formyl peptide receptor 2 (FPR2), has been shown to exert anti-inflammatory effects in many diseases. The objective of this study was to explore the protective role of RvD1 through reducing inflammation after HI and to study the contribution of Ras-related C3 botulinum toxin substrate 1 (Rac1)/nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2) pathways in RvD1-mediated protection. Rat pups (10-day old) were subjected to HI or sham surgery. RvD1 was administrated by intraperitoneal injection 1 h after HI. FPR2 small interfering ribonucleic acid (siRNA) and Rac1 activation CRISPR were administered prior to RvD1 treatment to elucidate the possible mechanisms. Time course expression of FPR2 by Western blot and RvD1 by ELISA were conducted at 6 h, 12 h, 24 h, 48 h and 72 h post HI. Infarction area, short-term neurological deficits, immunofluorescent staining and Western blot were conducted at 24 h post HI. Long-term neurological behaviors were evaluated at 4 weeks post HI. Endogenous expression levels of RvD1 decreased in time dependent manner while the expression of FPR2 increased after HI, peaking at 24 h post HI. Activation of FPR2, with RvD1, reduced percent infarction area, and alleviated short- and long-term neurological deficits. Administration of RvD1 attenuated inflammation after HI, while, either inhibition of FPR2 with siRNA or activation of Rac1 with CRISPR reversed those effects. Our results showed that RvD1 attenuated neuroinflammation through FPR2, which then interacted with Rac1/NOX2 signaling pathway, thereby reducing infarction area and alleviating neurological deficits after HI in neonatal rat pups. RvD1 may be a potential therapeutic approach to reduce inflammation after HI.