Fig. 1.

Neuroprotective effect of rPKM2 and expression levels of PKM2 in the normal and stroke brain. Adult male mice were subjected to focal cerebral ischemia targeting the right sensorimotor cortex. The effect of rPKM2 intranasal administration (1 or 24 h after stroke) on brain damage was measured using 2,3,5-triphenyltetrazolium chloride (TTC) staining in brain sections 3 days after stroke. PKM2 and the downstream molecule STAT3 were measured using Western blotting. A Brain sections of TTC staining images in stroke control, stroke with 1-h-delayed rPKM2 (160 ng/kg, intranasal delivery), and stroke with 24-h-delayed rPKM2. White color represents the ischemic infarction. The bar graph on the right summarizes the infarction ratio in the 3 groups. With 1-h delay, rPKM2 showed significant neuroprotective effect of reducing the brain infarct formation. Asterisk, p < 0.05 versus stroke control, n = 6 per group. mean ± SEM. B Western blot analysis of PKM2 levels in the normal (sham) and stroke brains. A basal and significant expression of PKM2 protein was readily identified in the normal cortex. The bar graph on the right shows that after a focal ischemic insult, the PKM2 level was upregulated at 1 day after stroke. The PKM2 level gradually decreased thereafter and declined to a level significantly lower than 1 day after stroke as well as that in sham controls. 1-way ANOVA: asterisk, p < 0.05 versus sham; number sign, p < 0.05 versus 1 day after stroke and sham, n = 5 per group. C PKM2 expression in the peri-infarct region 14 days after stroke with and without rPKM2 treatment (160 ng/kg per day, intranasal delivery). Student t test: asterisk, p < 0.05 versus sham. n = 5 in stroke group, n = 3 in stroke + PKM2 group. D The phosphorylation level of STAT3 expression in the peri-infarct region at 7 days after stroke. The pSTA3 level increased after stroke whereas the rPKM2 treatment further upregulated its expression. The STAT3 inhibitor BP-1-102 (BP) eliminated the effect of rPKM2. 2-way ANOVA: asterisk, p < 0.05 versus sham; number sign, p < 0.05 versus stroke; delta, p < 0.05 versus stroke + PKM2. n = 4 in sham group, n = 5 in stroke, stroke + PKM2, and stroke + PKM2 + BP groups