Differential activation of placental unfolded protein response pathways implies heterogeneity in causation of early- and late-onset pre-eclampsia
Based on gestational age at diagnosis and/or delivery, pre‐eclampsia (PE) is commonly divided into early‐onset (<34 weeks) and late‐onset (≥34 weeks) forms. Recently, the distinction between ‘placental’ and ‘maternal’ causation has been proposed, with ‘placental’ cases being more frequently assoc...
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| Published in | The Journal of pathology Vol. 234; no. 2; pp. 262 - 276 |
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| Main Authors | , , , , , |
| Format | Journal Article |
| Language | English |
| Published |
Chichester, UK
John Wiley & Sons, Ltd
01.10.2014
Wiley Subscription Services, Inc |
| Subjects | |
| Online Access | Get full text |
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| Summary: | Based on gestational age at diagnosis and/or delivery, pre‐eclampsia (PE) is commonly divided into early‐onset (<34 weeks) and late‐onset (≥34 weeks) forms. Recently, the distinction between ‘placental’ and ‘maternal’ causation has been proposed, with ‘placental’ cases being more frequently associated with early‐onset and intrauterine growth restriction. To test whether molecular placental pathology varies according to clinical presentation, we investigated stress‐signalling pathways, including unfolded protein response (UPR) pathways, MAPK stress pathways, heat‐shock proteins and AMPKα in placentae delivered by caesarean section for clinical indications at different gestational ages. Controls included second‐trimester, pre‐term and normal‐term placentae. BeWo cells were used to investigate how these pathways react to different severities of hypoxia–reoxygenation (H/R) and pro‐inflammatory cytokines. Activation of placental UPR and stress‐response pathways, including P‐IRE1α, ATF6, XBP‐1, GRP78 and GRP94, P‐p38/p38 and HSP70, was higher in early‐onset PE than in both late‐onset PE and normotensive controls (NTCs), with a clear inflection around 34 weeks. Placentae from ≥ 34 weeks PE and NTC were indistinguishable. Levels of UPR signalling were similar between second‐trimester and term controls, but were significantly higher in pre‐term ‘controls’ delivered vaginally for chorioamnionitis and other conditions. Severe H/R (1/20% O2) induced equivalent activation of UPR pathways, including P‐eIF2α, ATF6, P‐IRE1α, GRP78 and GRP94, in BeWo cells. By contrast, the pro‐inflammatory cytokines TNFα and IL‐1β induced only mild activation of P‐eIF2α and GRP78. AKT, a central regulator of cell proliferation, was reduced in the < 34 weeks PE placentae and severe H/R‐treated cells, but not in other conditions. These findings provide the first molecular evidence that placental stress may contribute to the pathophysiology of early‐onset pre‐eclampsia, whereas that is unlikely to be the case in the late‐onset form of the syndrome. © 2014 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland. |
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| Bibliography: | Wellcome Trust - No. 084804/2/08/Z istex:8D3DFC70CBD26D9CC7DE8B2A91F0A39D1B4FB951 ArticleID:PATH4394 ark:/67375/WNG-W33SZXWT-S Appendix S1. Supplementary information on materialsFigure S1 (A) Western blot images of all ER stress markers, p38 kinase, JNK and HSPs studied in the early-PEs, late-PEs and NTCs. Due to the limited number of samples that could be loaded on a single gel, western blotting analysis on 32 samples was performed on two groups of samples: the first contained 19 PE placentae, of which 15 were early-PEs and four were late-PEs; the second contained 16 samples, of which eight were late-PEs and eight were NTCs; three late-PE samples were duplicated in both groups in order to allow inter-gel comparison. (B) Removal of an outsider in the late-PE samples revealed a significant negative correlation between the ratio of PeIF2α:eIF2α with gestational age of delivery, and is also higher in the early-PE compared to the late-PE placentae. We have previously shown that phosphorylation of eIF2α is very sensitive to the delivery-collection interval, which could be an explanation for the outsiderFigure S2 JNK MAPK kinase and heat shock protein family members and gestational age at delivery of PE placentae. No significant correlation existed, and there was no significant difference between the groups. Pearson's correlation was used to test for significance and a power regression line was added to show the relationship; a paired non-parametric Kruskal-Wallis test with Dunn's multiple comparison test was used to show differences among the three groups. (A) JNK; (B) HSP90 and HSP27. In the correlation graphs, diamonds indicate PE samples, while squares indicate NTC samplesFigure S3 A subtle increase of ER stress in the preterm 'control' placentae compared to second-trimester and normotensive term placentae. (A) Tissue lysates from seven second-trimester (ST), seven NTC and seven PTC placentae were resolved by SDS-PAGE before probing with antibodies against the same ER stress markers as in Figure B. Densitometry of bands was expressed relative to normal controls (100%); phosphorylation status is presented as the ratio between phosphorylated and total protein, both normalized to β-actin: data are median for seven placentae/group; a, b, significance p ≤ 0.05 compared to ST and NTC, respectivelyFigure S4 Higher ER stress in cultured primary trophoblast cells than in BeWo cells. Primary trophoblast cells were isolated from the first-trimester placentae as described by Trundley et al . Both BeWo cells and freshly isolated primary trophoblast cells were cultured under either 10% (control) or 1% (hypoxia) O2 for 24 h prior for western blotting analysis with ER stress markers; β-actin was used as loading controlFigure S5 TNFα, but not IL-1β, activates phosphorylation of p38 kinase. BeWo cells were treated with TNFα (50 ng/ml) and/or IL-1β (50 ng/ml) for 24 h. (A) Images of a representative blot of P-p38, p38 and β-actin. (B) Densitometry of bands expressed relative to normal controls as 100%; phosphorylation status is presented as the ratio between phosphorylated and total protein: data are mean ± SEM for five independent experiments; a, significance at p ≤ 0.05 compared to controlTable S1.. Detail clinical characteristics of pre-eclamptic, term- and preterm- control placentas ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 These authors contributed equally to this study. No conflicts of interest were declared. |
| ISSN: | 0022-3417 1096-9896 1096-9896 |
| DOI: | 10.1002/path.4394 |