Increasing evidence suggests that microglial polarization plays an important role in the
pathological processes of
neuroinflammation following
subarachnoid hemorrhage (SAH). Previous studies indicated that
milk fat globule-epidermal growth factor-8 (MFG-E8) has potential anti-apoptotic and anti-inflammatory effects in
cerebral ischemia. However, the effects of MFG-E8 on microglial polarization have not been evaluated after SAH. Therefore, the aim of this study was to explore the role of MFG-E8 in anti-
inflammation, and its effects on microglial polarization following SAH. We established the SAH model via prechiasmatic cistern blood injection in mice. Double-immunofluorescence staining, western blotting and quantitative real-time polymerase chain reaction (q-PCR) were performed to investigate the expression and cellular distribution of MFG-E8. Two different dosages (1 and 5 μg) of recombinant human MFG-E8 (rhMFG-E8) were injected intracerebroventricularly (i.c.v.) at 1 h after SAH. Brain water content, neurological scores, beam-walking score,
Fluoro-Jade C (FJC), and
terminal deoxynucleotidyl transferase dUTP nick endlabeling staining (TUNEL) were measured at 24 h. Suppression of MFG-E8,
integrin β3 and phosphorylation of STAT3 were achieved by specific siRNAs (500 pmol/5 μl) and the STAT3 inhibitor
Stattic (5 μM). The potential signaling pathways and microglial polarization were measured by immunofluorescence labeling and western blotting. SAH induction increased the levels of inflammatory mediators and the proportion of M1 cells, and caused neuronal apoptosis in mice at 24 h. Treatment with rhMFG-E8 (5 μg) remarkably decreased
brain edema, improved neurological functions, reduced the levels of proinflammatory factors, and promoted the microglial to shift to M2 phenotype. However, knockdown of MFG-E8 and
integrin β3 via
siRNA abolished the effects of MFG-E8 on anti-
inflammation and M2 phenotype polarization. The STAT3 inhibitor
Stattic further clarified the role of rhMFG-E8 in microglial polarization by regulating the
protein levels of the
integrin β3/SOCS3/STAT3 pathway. rhMFG-E8 inhibits neuronal
inflammation by transformation the microglial phenotype toward M2 and its direct protective effect on neurons after SAH, which may be mediated by modulation of the
integrin β3/SOCS3/STAT3 signaling pathway, highlighting rhMFG-E8 as a potential therapeutic target for the treatment of SAH patients.