To investigate the role and underlying mechanism of spermidine (SPD) in intracerebral hemorrhage (ICH).

Male C57BL/6 mice were subjected to establish a collagenase-induced ICH model. The 108 mice were randomly divided into Sham group, ICH group and ICH+SPD group (intraperitoneal injection of 15 mg/kg SPD for 3 consecutive days after modeling), with 36 mice in each group. On the 3rd day after ICH, neurological deficits were evaluated using modified Garcia scoring and forelimb placing test; brain pathological damage was assessed with HE staining; activation of microglia/macrophages (Iba-1) and astrocytes (GFAP) was detected by immunofluorescence assay; expression of autophagy markers (Beclin-1, P62) and inflammatory factors (MMP-9, NLRP3, COX-2) was measured with Western blotting. In in vitro experiments, hemin was used to stimulate HT-22 cells to mimic ICH. The HT-22 cells were randomly divided into Control group, Hemin group, Hemin+SPD group, and Hemin+SPD+3-methyladenine (3-MA, an autophagy inhibitor) group (n=7). After 24 h of hemin treatment, cell viability was detected with CCK-8 assay, the expression of autophagy-related proteins (LC3-II and P62) were detected with Western blotting, and oxidative stress was determined by measuring superoxide dismutase (SOD) activity and malondialdehyde (MDA) content.

On day 3 post-ICH, SPD significantly reduced the area of brain damage (P<0.05), improved neurological recovery (P<0.05), activated autophagy with up-regulation of Beclin-1 while down-regulation of P62 (P<0.05), suppressed the activation of microglia/macrophage and astrocytes (P<0.01), reduced the expression of MMP-9, NLRP3 and COX-2, and enhanced SOD activity and decreased MDA content (P<0.05) when compared with the ICH group. SPD increased the viability of HT-22 cells (P<0.05), improved SOD activity and reduced MDA content (P<0.01). Autophagy inhibitor 3-MA effectively blocked the down-regulation of LC3-II and up-regulation of P62, and completely reversed above protective effects caused by SPD (P<0.05).

SPD activates autophagy after ICH and improves post-ICH brain injury by suppressing neuroinflammation and oxidative stress.