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Hypoxia‐inducible factor and nuclear factor kappa‐B activation in blood–brain barrier endothelium under hypoxic/reoxygenation stress

This investigation focuses on transcription factor involvement in blood–brain barrier (BBB) endothelial cell‐induced alterations under conditions of hypoxia and post‐hypoxia/reoxygenation (H/R), using established in vivo/ex vivo and in vitro BBB models. Protein/DNA array analyses revealed a correlation in key transcription factor activation during hypoxia and H/R, including NFκB and hypoxia‐inducible factor (HIF)1. Electrophoretic mobility shift assays confirmed NFκB and HIF1 binding activity ex vivo and in vitro, under conditions of hypoxia and H/R. Hypoxia‐ and H/R‐treated BBB endothelium showed increased HIF1α protein expression in both cytoplasmic and nuclear fractions, in ex vivo and in vitro models. Co‐immunoprecipitation of HIF1α and HIF1β was shown in the nuclear fraction under conditions of hypoxia and H/R in both models. Hypoxia‐ and H/R‐treated BBB endothelium showed increased expression of NFκB‐p65 protein in both cytoplasmic and nuclear fractions. Co‐immunoprecipitation of NFκB‐p65 with NFκB‐p50 was shown in the nuclear fraction under conditions of hypoxia and H/R in the ex vivo model, and after H/R in the in vitro model. These data offer novel avenues in which to alter and/or investigate BBB activity across model systems and to further our understanding of upstream regulators during hypoxia and H/R.