Fig. 3

Brain penetration effects and levels of IL-1RA and IL-1RA-PEP. a, b At 24 h after ischemia-reperfusion, the permeation effect on brain tissue was assessed by immunohistochemical staining. The rats with middle cerebral artery occlusion (MCAO) in separate groups were injected intravenously with IL-1RA or IL-1RA-PEP. c, d High magnification of double immunofluorescence images show co-localization of IL-1RA with NeuN (arrows) and IL-1RA-PEP with NeuN (arrows). Scale bar, 5.0 mm and 50 μm for the inserts. e The permeation effect was expressed as a percentage increase in staining intensity in the cerebral cortex and striatum of the contralateral hemisphere. f The concentration of IL-1RA in the ipsilateral ischemic brain hemisphere of rats subjected to MCAO, 4 h after a single intravenous injection of IL-1RA (50 mg/kg) or IL-1RA-PEP (50 mg/kg), was measured by ELISA. Panels show IL-1RA concentration in the cerebral cortex and striatum area, respectively. Data are shown as mean ± SEM; *P < 0.05 in comparison with the rat intravenously injected with IL-1RA, n = 4–6 per group, based on the Student’s t test with Welch’s correction