Protective effect of anti-high mobility group box 1 on cerebral ischemia reperfusion injury in diabetic mice

Objective To investigate whether cerebral ischemia reperfusion (I/R) injury combined with diabetes mellitus (DM) could elevate concentrations of serum high mobility group box 1 (HMGB1) and its related inflammatory factors, and to explore the underlying mechanism of cerebral I/R injury combined with DM by blocking HMGB1. Methods One hundred and forty healthy male C57BL/6 mice were randomly divided into four groups: normoglycemia (NG) group (n=25), NG+I/R group (n=25), hyperglycemia (HG) group (n=25), and HG+I/R group (n=65); 40 mice in the HG+I/R group were chosen and divided into anti-HMGB1 group and IgG control group (n=20). High-fat feeding and i.p. injection of streptozotocin were used to establish HG mouse models, and then, middle cerebral artery occlusion was performed to establish the HG+I/R mouse models. Mice were treated with tail intravenous injection of 30 μg/g anti-HMGB1 polyclonal antibody or control IgG 1 h before ischemia as previously described. After accomplishment of animal models, serum HMGB1 concentrations were evaluated by ELISA, the permeability of blood brain barrier (BBB) was observed by Evans-blue fluorescence quantitative method, quantitative real-time PCR was introduced to detect the mRNA expressions of interleukin (IL)-1β, IL-6, and inducible nitric oxide synthase (iNOS). Morphology changes of damaged brains were observed by HE staining. Results The serum HMGB1 level in the HG+I/R group was significantly higher than that in the NG+I/R group (P<0.05). HG+I/R group had significantly higher BBB permeability than NG+I/R group (P<0.05), while anti-HMGB1 group had significantly lower BBB permeability than HG+I/R group (P<0.05). As compared with the NG group, the HG+I/R group had unclear cellular structures in the brain tissues with necrosis neurocytes and interstitial edema, while the cellular structures were obviously improved in the anti-HMGB1 group. Expressions of IL-1β, IL-6 and iNOS in the HG+I/R group were significantly elevated as compared with those in the NG+I/R group (P<0.05), while those in the anti-HMGB1 group had significantly decreased levels of IL-1β and iNOS as compared with those in the HG+I/R group (P<0.05), and the IL-6 level showed no significant difference between the two groups (P<0.05). Conclusion The pathogenesis of DM could increase concentration of serum HMGB1, and anti-HMGB1 mAb could alleviate brain injury by blocking HMGB1, and render a new promising therapeutic way for DM patients suffered with ischemic stroke. Key words: High mobility group box 1; Cerebral ischemia-reperfusion injury; Diabetes mellitus; Inflammation reaction