Unspliced X-box-binding protein 1 (XBP1) protects endothelial cells from oxidative stress through interaction with histone deacetylase 3.
Bottom Line: In this study, we found that disturbed flow activated anti-oxidative reactions via up-regulating heme oxygenase 1 (HO-1) in an X-box-binding protein 1 (XBP1) and histone deacetylase 3 (HDAC3)-dependent manner.Knockdown of HDAC3 ablated XBP1u-mediated effects.Thus, we demonstrate that XBP1u and HDAC3 exert a protective effect on disturbed flow-induced oxidative stress via up-regulation of mTORC2-dependent Akt1 phosphorylation and Nrf2-mediated HO-1 expression.
Affiliation: From the Cardiovascular Division, King's College London, London SE5 9NU, United Kingdom.Show MeSH
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Mentions: As described above, both XBP1u and HDAC3 up-regulate HO-1 expression, whereas flow-induced HDAC3 is XBP1-dependent. Therefore, we hypothesized that there was cross-talk between XBP1u and HDAC3 during the regulation of HO-1. To test this, co-expression of HDAC3 and XBP1u was first introduced into HUVECs by co-infection with two viruses. As shown in Fig. 5A, overexpression of either XBP1u or HDAC3 alone up-regulated Akt1 phosphorylation, Nrf2 and HO-1, whereas co-expression of XBP1u and HDAC3 had a synergistic effect. Further experiments revealed that knockdown of HDAC3 attenuated XBP1u-induced Akt1 phosphorylation and HO-1 expression (Fig. 5B). Co-immunoprecipitation assays revealed that XBP1u physically bound to HDAC3 in transfected cells (Fig. 5C). Using truncated HDAC3 mutants, the binding domain in HDAC3 molecule could be defined to the amino acid 201∼323 region (Fig. 5D). Immunoprecipitation with antibody against endogenous XBP1u revealed that XBP1u bound to HDAC3 and Akt1 under disturbed flow (Fig. 5E). Double immunofluorescence staining showed that mTOR/Akt1, Akt1/HDAC3, Akt1/XBP1u, and HDAC3/XBP1u co-localized in the cytoplasm (Fig. 5F). These results suggest XBP1u/HDAC3/Akt1/mTOR may form a complex to regulate Akt1 phosphorylation, leading to Nrf2 stabilization and HO-1 expression.
Affiliation: From the Cardiovascular Division, King's College London, London SE5 9NU, United Kingdom.