0160 : Critical role of PTP1B in endoplasmic reticulum stress-induced endothelial dysfunction

Abstract

We previously showed that protein tyrosine phosphatase 1B (PTP1B) contributes to impaired NO production and endothelial dysfunction in various diseases. In non-cardiovascular tissues, PTP1B modulates endoplasmic reticulum stress (ERS), while ERS has been shown to induce endothelial dysfunction and impaired NO production. However, the link between PTP1B, ERS and endothelial dysfunction has not been studied. To assess the role of PTP1B in ERS-mediated endothelial dysfunction, isolated mesenteric arteries of WT and PTP1B -/- mice were incubated for 4h with the ERS inducer Tunicamycin (Tm 10μg/mL). In parallel, to confirm the implication of ERS in endothelial dysfunction, we used a model of Lipopolysaccharide (LPS)-induced septic shock, where the inhibition of PTP1B has been previously shown to be protective. A severe endothelial dysfunction was observed in WT mice after Tm incubation, attested by a strong alteration of endothelium-dependent, flow mediated dilatation (FMD) of isolated, perfused phenylephrine-preconstricted arteries (WT Sham: 20.5±1.3 vs WT Tm: 8.2±1.7, n=7, p<0.01), which was significantly reversed by the ERS antagonist 4PBA. PTP1B-/- mice display no Tm-induced alteration of FMD (PTP1B -/- Tm: 23.2±3.2, p=NS vs WT sham, p<0.01 vs WT Tm). Western Blot analyses on isolated arteries showed an increase in ERS markers GRP78, P-eiF2α and ATF6α after Tm treatment. Interestingly, PTP1B -/- mice displayed higher levels of P-eiF2α and ATF6α under basal conditions when compared to WT mice. Moreover, analysis of the PTP1B interaction with molecular mediators of ERS (using proximity ligation assay, PLA) showed that endothelial PTP1B/PPERK and PTP1B/P-IRE1α interactions were decreased after Tm treatment, whereas PTP1B/GRP78 interaction was increased. Finally, 4PBA treatment reversed LPS-induced endothelial and cardiac dysfunction. Thus our work demonstrates for the first time that PTP1B is a crucial regulator of ERS-induced endothelial dysfunction. The author hereby declares no conflict of interest