The Inhibition of Protein Kinase C β Contributes to the Pathogenesis of Preeclampsia by Activating Autophagy

Abstract

Background: Preeclampsia is a devastating hypertensive disorder of pregnancy with unknown mechanism. Recent studies have considered abnormal autophagy as a new cellular mechanism for this disorder, while little is known about how autophagy is specifically involved and what factors are implicated. Here, we report a previously unrecognized preeclampsia-associated autophagic regulator, PKCb, that is involved in placental angiogenesis. Methods: PKCb levels were evaluated by quantitative real-time PCR, western blotting, immunofluorescence and by the analysis of public data. The autophagy-regulating role of PKCb inhibition in preeclampsia pathogenesis was studied in a mouse model, and in human umbilical vein endothelial cells (HUVECs) and human choriocarcinoma cells (JEG-3). Findings: PKCb was significantly downregulated in human preeclamptic placentas. In a mouse model, the selective inhibition of PKCb by Ruboxistaurin was sufficient to induce preeclampsia-like symptoms, accompanied by excessive autophagic flux and a disruption in the balance of pro-and anti-angiogenic factors in mouse placentas. In contrast, autophagic inhibition by 3-methyladenine partially normalized hypertension, proteinuria and placental angiogenic imbalance in PKCb-inhibited mice. Our in vitro experiments demonstrated that PKCb inhibition activated autophagy, thus blocking VEGFA-induced HUVEC tube formation and resulting in the significant upregulation of sFLT1 and downregulation of VEGFA in JEG-3 cells. Interpretation: These data support a novel model in which autophagic activation due to PKCb inhibition leads to the impairment of angiogenesis and eventually results in preeclampsia.

Ceramide-Induced Lysosomal Biogenesis and Exocytosis in Early-Onset Preeclampsia Promotes Exosomal Release of SMPD1 Causing Endothelial Dysfunction

“…This pool of lysosomes is central to the degradation and recycling of macromolecules delivered by endocytosis and autophagy. This increase in lysosomes in E-PE agrees with numerous reports of elevated autophagy in preeclamptic placentae ( Oh et al, 2008 ; Kalkat et al, 2013 ; Akaishi et al, 2014 ; Gao et al, 2015 ; Melland-Smith et al, 2015 ; Akcora Yildiz et al, 2017 ; Hutabarat et al, 2017 ; Ausman et al, 2018 ; Zhao et al, 2020 ). Lysosome biogenesis is regulated by a lysosome-to-nucleus signaling mechanism that involves TFEB.…”

“…In contrast, Nakashima et al (2020) reported that autophagolysosomal degradation is defective in preeclamptic placentae due to reduced TFEB and LAMP1 expression. Although their finding may explain the build up of protein aggregates in preeclamptic placentae, it clashes with the generally accepted view of elevated autophagy flux in preeclamptic placentae ( Oh et al, 2008 ; Kalkat et al, 2013 ; Akaishi et al, 2014 ; Gao et al, 2015 ; Melland-Smith et al, 2015 ; Akcora Yildiz et al, 2017 ; Hutabarat et al, 2017 ; Ausman et al, 2018 ; Zhao et al, 2020 ). Unfortunately, the authors did not verify their findings at the ultrastructural level (TEM is the gold standard for surveillance of organelles and autophagy) and mainly focused on extravillous trophoblasts while we surveyed the villous trophoblast layers.…”

Autophagy in preeclampsia: A new target?

“…Studies of autophagy in preeclampsia provide conflicting roles of this homeostatic mechanism on preeclampsia development and progression [ 7 ]. In this issue of EBioMedicine , Zhao and colleagues report the results of a hybrid study using clinical placental samples and a mouse model of preeclampsia to identify a novel preeclampsia-associated regulator of autophagy [ 8 ]. The regulation of autophagy in preeclampsia is an area of research that has been increasing in interest over the past several years and the results reported in this featured article sought to identify a new target with therapeutic potential.…”

“…The regulation of autophagy in preeclampsia is an area of research that has been increasing in interest over the past several years and the results reported in this featured article sought to identify a new target with therapeutic potential. Analysis of mRNA levels and protein expression of protein kinase C isoform β (PKCβ) in control and preeclamptic patient placentas demonstrated significantly lower expression of PKCβ in preeclampsia [ 8 ]. Furthermore, analysis of PKCβ mRNA expression using the Gene Expression Omnibus (GEO) dataset confirmed suppression of PKCβ in preeclampsia.…”

“…The findings from the study by Zhao et al have provided additional insight into the potentially complex network between the PKC pathway and now autophagy [ 8 ]. Importantly, activation of autophagy is thought to be associated with immune activation, which is increased in the setting of preeclampsia, with a role in facilitating antigen presentation on MHCII [ 5 , 7 ].…”