HIF activation and VEGF overexpression are coupled with ZO-1 up-phosphorylation in the brain of dystrophic MDX mouse

In Duchenne muscular dystrophy (DMD) metabolic and structural alterations of the central nervous system are described. Here, we investigated in the brain of 10 mdx mice and in five control ones, the expression of hypoxia inducible factor-1 alpha (HIF-1 alpha) and we correlated it with the expression of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 (VEGFR-2) and of the endothelial tight junction proteins zonula occludens-1 (ZO-1) and claudin-1. Results showed an activation of mRNA HIF-1 alpha by reverse transcription polymerase chain reaction (RT-PCR) and a strong HIF1-alpha labeling of perivascular glial cells and cortical neurons by immunohistochemistry, in mdx mouse. Moreover, overexpression of VEGF and VEGFR-2, respectively, in neurons and in endothelial cells coupled with changes to endothelial ZO-1 and claudin-1 expression in the latter were detected by immunoblotting and immunohistochemistry, in the mdx brain. Furthermore, by immunoprecipitation, an up-phosphorylation of ZO-1 was demonstrated in mdx endothelial cells in parallel with the reduction in ZO-1 protein content. These data suggest that the activation of HIF-1 alpha in the brain of dystrophic mice coupled with VEGF and VEGFR-2 up-regulation and ZO-1 and claudin-1 rearrangement might contribute to both blood-brain barrier opening and increased angiogenesis.