Glutaredoxin-1 promotes pregnancy-induced vascular complications by altering placental angiogenesis

Aims: Preeclampsia (PE) is a severe pregnancy complication characterised by increased oxidative stress and high levels of the anti-angiogenic factor sFlt-1 in the placenta and maternal circulation. Yet, antioxidant therapy has failed, in some cases worsening pregnancy outcomes. S-glutathionylation is a common oxidative post-translational modification (ox-PTM) reversed by Glutaredoxin (Glrx) and is emerging as an important redox-switch in cardiovascular diseases. Of significance, preeclamptic placenta are associated with higher levels of Glrx and S-glutathionylation removal during pregnancy promotes preeclampsia-like vascular complications and elevated sFlt-1 levels. Although S-glutathionylation is known to alter angiogenesis by modulating various targets in the VEGF pathway, its role has not been investigated in the context of PE. We aimed to identify the molecular basis for how S-glutathionylation removal may alter angiogenic signalling at the maternal-foetal interface and contribute to PE.

Methods: We combined bioinformatics proteomic analysis with in vitro studies and Affymetrix exon-level microarray analyses to investigate the role of protein ox-PTM in angiogenic signalling and development of PE phenotype.

Results: Adenoviral Glrx overexpression disrupted EC angiogenic sprouting, inhibited trophoblast migration and fusion. Glrx mediated angiogenic imbalance by rising sFlt-1:PlGF ratio in EC, while opposite effects were detected in extra-villous trophoblasts. The sFlt-1 changes detected in EC were isoform-specific as the sFlt1-e15a splice variant was elevated while sFlt1-i13 levels remained unchanged. A genome-wide exon-level profiling of overexpressing Glrx transgenic vs littermate control mice placenta revealed a global alteration of alternative splicing events. Bioinformatic analysis identified redox-sensitive targets directly relevant to splicing and PE, and ox-PTM removal was found to disrupt the spliceosome machinery consequently affecting Flt-1 splicing to promote sFlt1-e15a expression.

Conclusions: Glrx-mediated removal of ox-PTMs disrupts placental angiogenic balance in a cell type-specific manner via the modulation of redox-sensitive targets in the spliceosome machinery, which may promote sFlt-e15a release from the placenta and the PE phenotype