Downregulation of Mitofusin 2 in Placenta Is Related to Preeclampsia

A mitochondrial regulator protein, MNRR1, is elevated in the maternal blood of women with preeclampsia

OBJECTIVE

Preeclampsia, one of the most serious obstetric complications, is a heterogenous disorder resulting from different pathologic processes. However, placental oxidative stress and an anti-angiogenic state play a crucial role. Mitochondria are a major source of cellular reactive oxygen species. Abnormalities in mitochondrial structures, proteins, and functions have been observed in the placentae of patients with preeclampsia, thus mitochondrial dysfunction has been implicated in the mechanism of the disease. Mitochondrial nuclear retrograde regulator 1 (MNRR1) is a newly characterized bi-organellar protein with pleiotropic functions. In the mitochondria, this protein regulates cytochrome c oxidase activity and reactive oxygen species production, whereas in the nucleus, it regulates the transcription of a number of genes including response to tissue hypoxia and inflammatory signals. Since MNRR1 expression changes in response to hypoxia and to an inflammatory signal, MNRR1 could be a part of mitochondrial dysfunction and involved in the pathologic process of preeclampsia. This study aimed to determine whether the plasma MNRR1 concentration of women with preeclampsia differed from that of normal pregnant women.

METHODS

This retrospective case-control study included 97 women with preeclampsia, stratified by gestational age at delivery into early (<34 weeks, n = 40) and late (≥34 weeks, n = 57) preeclampsia and by the presence or absence of placental lesions consistent with maternal vascular malperfusion (MVM), the histologic counterpart of an anti-angiogenic state. Women with an uncomplicated pregnancy at various gestational ages who delivered at term served as controls (n = 80) and were further stratified into early (n = 25) and late (n = 55) controls according to gestational age at venipuncture. Maternal plasma MNRR1 concentrations were determined by an enzyme-linked immunosorbent assay.

RESULTS

1) Women with preeclampsia at the time of diagnosis (either early or late disease) had a significantly higher median (interquartile range, IQR) plasma MNRR1 concentration than the controls [early preeclampsia: 1632 (924-2926) pg/mL vs. 630 (448-4002) pg/mL, p = .026, and late preeclampsia: 1833 (1441-5534) pg/mL vs. 910 (526-6178) pg/mL, p = .021]. Among women with early preeclampsia, those with MVM lesions in the placenta had the highest median (IQR) plasma MNRR1 concentration among the three groups [with MVM: 2066 (1070-3188) pg/mL vs. without MVM: 888 (812-1781) pg/mL, p = .03; and with MVM vs. control: 630 (448-4002) pg/mL, p = .04]. There was no significant difference in the median plasma MNRR1 concentration between women with early preeclampsia without MVM lesions and those with an uncomplicated pregnancy (p = .3). By contrast, women with late preeclampsia, regardless of MVM lesions, had a significantly higher median (IQR) plasma MNRR1 concentration than women in the control group [with MVM: 1609 (1392-3135) pg/mL vs. control: 910 (526-6178), p = .045; and without MVM: 2023 (1578-8936) pg/mL vs. control, p = .01].

CONCLUSIONS

MNRR1, a mitochondrial regulator protein, is elevated in the maternal plasma of women with preeclampsia (both early and late) at the time of diagnosis. These findings may reflect some degree of mitochondrial dysfunction, intravascular inflammation, or other unknown pathologic processes that characterize this obstetrical syndrome.

An integral role of mitochondrial function in the pathophysiology of preeclampsia

Preeclampsia (PE) is associated with high maternal and perinatal morbidity and mortality. The development of effective treatment strategies remains a major challenge due to the limited understanding of the pathogenesis. In this review, we summarize the current understanding of PE research, focusing on the molecular basis of mitochondrial function in normal and PE placentas, and discuss perspectives on future research directions. Mitochondria integrate numerous physiological processes such as energy production, cellular redox homeostasis, mitochondrial dynamics, and mitophagy, a selective autophagic clearance of damaged or dysfunctional mitochondria. Normal placental mitochondria have evolved innovative survival strategies to cope with uncertain environments (e.g., hypoxia and nutrient starvation). Cytotrophoblasts, extravillous trophoblast cells, and syncytiotrophoblasts all have distinct mitochondrial morphology and function. Recent advances in molecular studies on the spatial and temporal changes in normal mitochondrial function are providing valuable insight into PE pathogenesis. In PE placentas, hypoxia-mediated mitochondrial fission may induce activation of mitophagy machinery, leading to increased mitochondrial fragmentation and placental tissue damage over time. Repair mechanisms in mitochondrial function restore placental function, but disruption of compensatory mechanisms can induce apoptotic death of trophoblast cells. Additionally, molecular markers associated with repair or compensatory mechanisms that may influence the development and progression of PE are beginning to be identified. However, contradictory results have been obtained regarding some of the molecules that control mitochondrial biogenesis, dynamics, and mitophagy in PE placentas. In conclusion, understanding how the mitochondrial morphology and function influence cell fate decisions of trophoblast cells is an important issue in normal as well as pathological placentation biology. Research focusing on mitochondrial function will become increasingly important for elucidating the pathogenesis and effective treatment strategies of PE.

Mitochondrial quality control alterations and placenta-related disorders

Mitochondria are ubiquitous in eukaryotic cells. Normal maintenance of function is the premise and basis for various physiological activities. Mitochondrial dysfunction is commonly observed in a wide range of pathological conditions, such as neurodegenerative, metabolic, cardiovascular, and various diseases related to foetal growth and development. The placenta is a highly energy-dependent organ that acts as an intermediary between the mother and foetus and functions to maintain foetal growth and development. Recent studies have demonstrated that mitochondrial dysfunction is associated with placental disorders. Defects in mitochondrial quality control mechanisms may lead to preeclampsia and foetal growth restriction. In this review, we address the quality control mechanisms of mitochondria and the relevant pathologies of mitochondrial dysfunction in placenta-related diseases, such as preeclampsia and foetal growth restriction. This review also investigates the relation between mitochondrial dysfunction and placental disorders.

Quercetin stimulates trophoblast fusion via the mitochondrial function

The fusion of mononuclear trophoblasts into multinucleate syncytiotrophoblasts is the critical event in the process of syncytialization, and its dysregulation can lead to pregnancy complications, notably hypertensive disorders of pregnancy (HDP). Oxidative stress may disrupt trophoblast syncytialization in HDP. Specifically, placentas with HDP exhibit impaired mitochondria, giving rise to the generation of reactive oxygen species (ROS) and subsequent oxidative stress. Quercetin, a bioflavonoid known for its antioxidant and anti-aging properties, has the potential to mitigate oxidative stress during trophoblast syncytialization. However, the precise mechanism underlying the action of quercetin in these processes remains to be elucidated. To explore the impact of quercetin on syncytialization, mitochondrial function, and ROS generation, cyclic AMP-stimulated BeWo cells were treated with quercetin. The expression of markers associated with cell fusion, mitochondrial function, and oxidative stress was determined using qPCR and western blotting. Additionally, morphological syncytialization and mitophagy (mitochondrial degradation) were assessed by immunofluorescence analysis. Our results revealed that quercetin increased the expression of syncytialization markers and promoted cell fusion. Furthermore, this compound also upregulated markers associated with mitophagy and mitochondrial fusion, which are corroborated by visual evidence of mitophagy through the fluorescence microscope. Cell fusion naturally stimulated ROS generation, which was attenuated by quercetin. Quercetin downregulated the expression of NRF2 and HO-1 during syncytialization, while increasing the expression of sirtuin1/3/6, which are known to play essential roles in antioxidant responses. In conclusion, quercetin effectively regulates mitochondrial function through its antioxidant properties and the suppression of ROS generation, ultimately promoting trophoblast fusion, suggesting that the flavonoid has the potential to ameliorate pregnancy-related disorder stemming from placental dysplasia.

Placental Mitochondrial Function and Dysfunction in Preeclampsia

The placenta is a vital organ of pregnancy, regulating adaptation to pregnancy, gestational parent/fetal exchange, and ultimately, fetal development and growth. Not surprisingly, in cases of placental dysfunction-where aspects of placental development or function become compromised-adverse pregnancy outcomes can result. One common placenta-mediated disorder of pregnancy is preeclampsia (PE), a hypertensive disorder of pregnancy with a highly heterogeneous clinical presentation. The wide array of clinical characteristics observed in pregnant individuals and neonates of a PE pregnancy are likely the result of distinct forms of placental pathology underlying the PE diagnosis, explaining why no one common intervention has proven effective in the prevention or treatment of PE. The historical paradigm of placental pathology in PE highlights an important role for utero-placental malperfusion, placental hypoxia and oxidative stress, and a critical role for placental mitochondrial dysfunction in the pathogenesis and progression of the disease. In the current review, the evidence of placental mitochondrial dysfunction in the context of PE will be summarized, highlighting how altered mitochondrial function may be a common feature across distinct PE subtypes. Further, advances in this field of study and therapeutic targeting of mitochondria as a promising intervention for PE will be discussed.

Mitofusin 1 and 2 differentially regulate mitochondrial function underlying Ca2+ signaling and proliferation in rat aortic smooth muscle cells

Mitochondria play a substantial role in cytosolic Ca²⁺ buffering and energy metabolism. We recently demonstrated that mitofusin 2 (Mfn2) regulated Ca²⁺ signaling by tethering mitochondria and sarcoplasmic reticulum (SR), and thus, facilitated mitochondrial function and the proliferation of vascular smooth muscle cells (VSMCs). However, the physiological role of mitofusin 1 (Mfn1) on Ca²⁺ signaling and mitochondrial function remains unclear. Herein, the roles of Mfn1 and Mfn2 in mitochondrial function underlying Ca²⁺ signaling, ATP production, and cell proliferation were examined in rat aortic smooth muscle A10 cells. Following an arginine vasopressin-induced increase in cytosolic Ca²⁺ concentration ([Ca²⁺]_cyt), Mfn2 siRNA (siMfn2) reduced cytosolic Ca²⁺ removal and mitochondrial Ca²⁺ uptake. However, Mfn1 siRNA (siMfn1) attenuated mitochondrial Ca²⁺ uptake, facilitated Ca²⁺ removal from mitochondria, and resulted in increased [Ca²⁺]_cyt, which was mediated by the downregulation of mitochondrial Ca²⁺ uniporter (MCU) expression and the upregulation of mitochondrial Na⁺/Ca²⁺ exchanger (NCLX) expression. Furthermore, siMfn1 increased the mitochondrial membrane potential, ATP production by adenine nucleotide translocase (ANT), and cell proliferation, whereas siMfn2 exhibited the opposite responses. In conclusion, Mfn1 modulates the expressions of MCU, NCLX, and ANT, and Mfn2 tethers mitochondria to SR, which demonstrates their different mitochondrial functions for Ca²⁺ signaling, ATP production, and the proliferation of VSMCs.

Mitochondrial Dysfunction, Mitophagy and Their Correlation with Perinatal Complications: Preeclampsia and Low Birth Weight

Mitochondria are essential organelles and crucial for cellular survival. Mitochondrial biogenesis and mitophagy are dynamic features that are essential for both maintaining the health of the mitochondrial network and cellular demands. The accumulation of damaged mitochondria has been shown to be related to a wide range of pathologies ranging from neurological to musculoskeletal. Mitophagy is the selective autophagy of mitochondria, eliminating dysfunctional mitochondria in cells by engulfment within double-membraned vesicles. Preeclampsia and low birth weight constitute prenatal complications during pregnancy and are leading causes of maternal and fetal mortality and morbidity. Both placental implantation and fetal growth require a large amount of energy, and a defect in the mitochondrial quality control mechanism may be responsible for the pathophysiology of these diseases. In this review, we compiled current studies investigating the role of BNIP3, DRAM1, and FUNDC1, mediators of receptor-mediated mitophagy, in the progression of preeclampsia and the role of mitophagy pathways in the pathophysiology of low birth weight. Recent studies have indicated that mitochondrial dysfunction and accumulation of reactive oxygen species are related to preeclampsia and low birth weight. However, due to the lack of studies in this field, the results are controversial. Therefore, mitophagy-related pathways associated with these pathologies still need to be elucidated. Mitophagy-related pathways are among the promising study targets that can reveal the pathophysiology behind preeclampsia and low birth weight.

Mitochondrial Dysfunction in the Pathogenesis of Preeclampsia

PURPOSE OF REVIEW

Preeclampsia complicates 5-10% of all pregnancies and is a leading cause of maternal and perinatal mortality and morbidity. The placenta plays a pivotal role in determining pregnancy outcome by supplying the fetus with oxygen and nutrients and by synthesizing hormones. Placental function is highly dependent on energy supplied by mitochondria. It is well-known that preeclampsia is originated from placental dysfunction, although the etiology of it remains elusive.

RECENT FINDINGS

During the last three decades, substantial evidence suggests that mitochondrial abnormality is a major contributor to placental dysfunction. In addition, mitochondrial damage caused by circulating bioactive factors released from the placenta may cause endothelial dysfunction and subsequent elevation in maternal blood pressure. In this review, we summarize the current knowledge of mitochondrial abnormality in the pathogenesis of preeclampsia and discuss therapeutic approaches targeting mitochondria for treatment of preeclampsia.

Current Studies of Mitochondrial Quality Control in the Preeclampsia

Mitochondria are cellular energy powerhouses that play important roles in regulating cellular processes. Mitochondrial quality control (mQC), including mitochondrial biogenesis, mitophagy, mitochondrial fusion and fission, maintains physiological demand and adapts to changed conditions. mQC has been widely investigated in neurodegeneration, cardiovascular disease and cancer because of the high demand for ATP in these diseases. Although placental implantation and fetal growth similarly require a large amount of energy, the investigation of mQC in placental-originated preeclampsia (PE) is limited. We elucidate mitochondrial morphology and function in different pregnancy stages, outline the role of mQC in cellular homeostasis and PE and summarize the current findings of mQC-related PE studies. This review also provides suggestions on the future investigation of mQC in PE, which will lead to the development of new prevention and therapy strategies for PE.

The effect of gestational diabetes on the expression of mitochondrial fusion proteins in placental tissue

INTRODUCTION

Gestational diabetes mellitus (GDM) poses a risk factor for fetal mortality and morbidity by directly affecting the placenta and fetus. Mitochondria are dynamic organelles that play a key role in energy production and conversion in placental tissue. Mitochondrial fusion and fission proteins are important in terms of providing mitochondrial dynamics, the adaptation of the cell to different conditions, and maintaining the metabolic stability of the cells. Although GDM shares many features with Type 2 diabetes mellitus (T2DM), different effects of these conditions on the mother and the child suggest that GDM may have specific pathological effects on placental cells. The aim of this study is to investigate the expression of mitochondrial dynamics, and mitochondrial protein folding markers in placentas from GDM patients and women with pre-existing diabetes mellitus.

METHODS

Placentas were properly collected from women, who had pre-existing diabetes (Pre-DM), from women with gestational diabetes mellitus (GDM) and from healthy (non-diabetic) pregnant women. Levels of mitochondrial fusion markers were determined in these placentas by real time quantitative PCR and Western blot experiments.

RESULTS

mRNA expressions and protein levels of mitochondrial fusion markers, mitofusin 1, mitofusin 2 (MFN1 and MFN2) and optical atrophy 1 (OPA1) proteins were found to be significantly lower in both Pre-DM placentas and those with GDM compared to healthy (non-diabetic) control group. Likewise, proteins involved in mitochondrial protein folding were also found to be significantly reduced compared to control group.

DISCUSSION

Diabetes during pregnancy leads to processes that correlate with mitochondria dysfunction in placenta. Our results showed that mitochondrial fusion markers significantly decrease in placental tissue of women with GDM, compared to the healthy non-diabetic women. The decrease in mitochondrial fusion markers was more severe during GDM compared to the Pre-DM. Our results suggest that there may be differences in the pathophysiology of these conditions.

Bioenergetics adaptations and redox homeostasis in pregnancy and related disorders

Pregnancy is a challenging physiological process that involves maternal adaptations to the increasing energetics demands imposed by the growing conceptus. Failure to adapt to these requirements may result in serious health complications for the mother and the baby. The mitochondria are biosynthetic and energy-producing organelles supporting the augmented energetic demands of pregnancy. Evidence suggests that placental mitochondria display a dynamic phenotype through gestation. At early stages of pregnancy placental mitochondria are mainly responsible for the generation of metabolic intermediates and reactive oxygen species (ROS), while at later stages of gestation, the placental mitochondria exhibit high rates of oxygen consumption. This review describes the metabolic fingerprint of the placental mitochondria at different stages of pregnancy and summarises key signs of mitochondrial dysfunction in pathological pregnancy conditions, including preeclampsia, gestational diabetes and intrauterine growth restriction (IUGR). So far, the effects of placental-driven metabolic changes governing the metabolic adaptations occurring in different maternal tissues in both, healthy and pathological pregnancies, remain to be uncovered. Understanding the function and molecular aspects of the adaptations occurring in placental and maternal tissue's mitochondria will unveil potential targets for further therapeutic exploration that could address pregnancy-related disorders. Targeting mitochondrial metabolism is an emerging approach for regulating mitochondrial bioenergetics. This review will also describe the potential therapeutic use of compounds with a recognised effect on mitochondria, for the management of preeclampsia.

Placental Mitochondrial Abnormalities in Preeclampsia

Preeclampsia complicates 5–8% of all pregnancies worldwide, and although its pathophysiology remains obscure, placental oxidative stress and mitochondrial abnormalities are considered to play a key role. Mitochondrial abnormalities in preeclamptic placentae have been described, but the extent to which mitochondrial content and the molecular pathways controlling this (mitochondrial biogenesis and mitophagy) are affected in preeclamptic placentae is unknown. Therefore, in preeclamptic (n = 12) and control (n = 11) placentae, we comprehensively assessed multiple indices of placental antioxidant status, mitochondrial content, mitochondrial biogenesis, mitophagy, and mitochondrial fusion and fission. In addition, we also explored gene expression profiles related to inflammation and apoptosis. Preeclamptic placentae were characterized by higher levels of oxidized glutathione, a higher total antioxidant capacity, and higher mRNA levels of the mitochondrial-located antioxidant enzyme manganese-dependent superoxide dismutase 2 compared to controls. Furthermore, mitochondrial content was significantly lower in preeclamptic placentae, which was accompanied by an increased abundance of key constituents of glycolysis. Moreover, mRNA and protein levels of key molecules involved in the regulation of mitochondrial biogenesis were lower in preeclamptic placentae, while the abundance of constituents of the mitophagy, autophagy, and mitochondrial fission machinery was higher compared to controls. In addition, we found evidence for activation of apoptosis and inflammation in preeclamptic placentae. This study is the first to comprehensively demonstrate abnormalities at the level of the mitochondrion and the molecular pathways controlling mitochondrial content/function in preeclamptic placentae. These aberrations may well contribute to the pathophysiology of preeclampsia by upregulating placental inflammation, oxidative stress, and apoptosis.

Hypoxia-induced mitochondrial abnormalities in cells of the placenta

INTRODUCTION

Impaired utero-placental perfusion is a well-known feature of early preeclampsia and is associated with placental hypoxia and oxidative stress. Although aberrations at the level of the mitochondrion have been implicated in PE pathophysiology, whether or not hypoxia-induced mitochondrial abnormalities contribute to placental oxidative stress is unknown.

METHODS

We explored whether abnormalities in mitochondrial metabolism contribute to hypoxia-induced placental oxidative stress by using both healthy term placentae as well as a trophoblast cell line (BeWo cells) exposed to hypoxia. Furthermore, we explored the therapeutic potential of the antioxidants MitoQ and quercetin in preventing hypoxia-induced placental oxidative stress.

RESULTS

Both in placental explants as well as BeWo cells, hypoxia resulted in reductions in mitochondrial content, decreased abundance of key molecules involved in the electron transport chain and increased expression and activity of glycolytic enzymes. Furthermore, expression levels of key regulators of mitochondrial biogenesis were decreased while the abundance of constituents of the mitophagy, autophagy and mitochondrial fission machinery was increased in response to hypoxia. In addition, placental hypoxia was associated with increased oxidative stress, inflammation, and apoptosis. Moreover, experiments with MitoQ revealed that hypoxia-induced reactive oxygen species originated from the mitochondria in the trophoblasts.

DISCUSSION

This study is the first to demonstrate that placental hypoxia is associated with mitochondrial-generated reactive oxygen species and significant alterations in the molecular pathways controlling mitochondrial content and function. Furthermore, our data indicate that targeting mitochondrial oxidative stress may have therapeutic benefit in the management of pathologies related to placental hypoxia.

Oxidative stress and mitochondrial dysfunction in early-onset and late-onset preeclampsia

Preeclampsia is a pregnancy-specific syndrome with multisystem involvement which leads to foetal, neonatal, and maternal morbidity and mortality. This syndrome is characterized by the onset of clinical signs and symptoms and delivery before (early-onset preeclampsia, eoPE), or after (late-onset preeclampsia, loPE), the 34 weeks of gestation. Preeclampsia is a mitochondrial disorder where its differential involvement in eoPE and loPE is unclear. Mitochondria regulate cell metabolism and are a significant source of reactive oxygen species (ROS). The syncytiotrophoblast in eoPE and loPE show altered mitochondrial structure and function resulting in ROS overproduction, oxidative stress, and cell damage and death. Mitochondrial dysfunction in eoPE may result from altered expression of several molecules, including dynamin-related protein 1 and mitofusins, compared with loPE where these factors are either reduced or unaltered. Equally, mitochondrial fusion/fission dynamics seem differentially modulated in eoPE and loPE. It is unclear whether the electron transport chain and oxidative phosphorylation are differentially altered in these two subgroups of preeclampsia. However, the activity of complex IV (cytochrome c oxidase) and the expression of essential proteins involved in the electron transport chain are reduced, leading to lower oxidative phosphorylation and mitochondrial respiration in the preeclamptic placenta. Interventional studies in patients with preeclampsia using the coenzyme Q₁₀, a key molecule in the electron transport chain, suggest that agents that increase the antioxidative capacity of the placenta may be protective against preeclampsia development. In this review, the mitochondrial dysfunction in both eoPE and loPE is summarized. Therapeutic approaches are discussed in the context of contributing to the understanding of mitochondrial dysfunction in eoPE and loPE.

Stomatin-like protein 2 (SLP2) regulates the proliferation and invasion of trophoblast cells by modulating mitochondrial functions

INTRODUCTION

Stomatin-like protein 2 (SLP2) is highly expressed in human first trimester trophoblast cells, but its functions in placental morpho-physiology remain unknown. This study aimed to determine the role of SLP2 in the proliferation and invasion of human first trimester trophoblast cells.

METHODS

Immunofluorescence was used to determine the expression and localization of SLP2 in normal and miscarriage human first trimester placenta. Western blot was used to determine the expression of SLP2, PCNA, Cyclin D3, N-cadherin, Vimentin, PGC1α and PPARα in HTR-8/SVneo cells. SLP2 was knocked down in the HTR-8/SVneo cells by using si-Slp2. Wound healing and migration assays were used to determine the effect of SLP2 knockdown on the migration and invasion in the HTR-8/SVneo cells. Mitochondrial membrane potential, reactive oxygen species (ROS), ATP production and biogenesis were measured to assess the effects of SLP2 knockdown on mitochondrial functions.

RESULT

SLP2 was strongly expressed in the cytotrophoblasts (CTB), syncytiotrophoblast (STB) and extravillous trophoblasts (EVT) of normal pregnancy placenta as compared to miscarriage placenta. SLP2 was highly expressed in the invasive EVT cell lines, HTR-8/SVneo and HPT-8 compared to the CTB cell line JAR. Knockdown of SLP2 significantly inhibited the migration and invasion of HTR-8/SVneo cells and placental villous explants, and repressed mitochondrial biogenesis and functions in HTR-8/SVneo cells.

DISCUSSION

Silencing of SLP2 inhibited the proliferation, migration and invasion of HTR-8/SVneo cells via the impairment of mitochondrial functions. This indicates that the downregulation of SLP2 in miscarriage placenta could be part of the pathogenesis and pathophysiology of the disease.

Placental mitochondria and reactive oxygen species in the physiology and pathophysiology of pregnancy

Mitochondria are central to cell function. The placenta forms the interface between maternal and fetal systems, and placental mitochondria have critical roles in maintaining pregnancy. The placenta is unusual in having two adjacent cell layers (cytotrophoblasts and the syncytiotrophoblast) with vastly different mitochondria that have distinct functions in health and disease. Mitochondria both produce the majority of reactive oxygen species (ROS), and are sensitive to ROS. ROS are important in allowing cells to sense their environment through mitochondrial-centred signalling, and this signalling also helps cells/tissues adapt to changing environments. However, excessive ROS are damaging, and increased ROS levels are associated with pregnancy complications, including the important disorders preeclampsia and gestational diabetes mellitus. Here we review the function of placental mitochondria in healthy pregnancy, and also in pregnancy complications. Placental mitochondria are critical to cell function, and mitochondrial damage is a feature of pregnancy complications. However, the responsiveness of mitochondria to ROS signalling may be central to placental adaptations that mitigate damage, and placental mitochondria are an attractive target for the development of therapeutics to improve pregnancy outcomes.

Maternal serum mitofusin-2 levels in patients with preeclampsia: the possible role of mitochondrial dysfunction in preeclampsia

Purpose: Hypoxia alters mitochondria function and our aim was to measure mitochondrial fusion protein mitofusin-2 (Mfn2) in patients with preeclampsia.Materials and methods: This cross-sectional study was conducted including 82 pregnant women, 27 with normal pregnancy and 55 with preeclampsia (27 with early-onset preeclampsia and 28 with late-onset preeclampsia). Maternal serum levels of Mfn2 were measured by using enzyme-linked immunosorbent assay kits.Results: The mean serum mitofusin-2 levels were higher in women with preeclampsia than in the control group (68.02 ± 8.7 pg/mL vs. 99.72 ± 37.27 pg/mL, p < .0001). The mean serum mitofusin-2 level was found to be the highest in the early-onset preeclampsia (EOPE) group (EOPE: 101.6 ± 38.5 pg/mL). Maternal serum mitofusin-2 levels correlated with both systolic and diastolic blood pressures as well as uterine artery pulsatility index. The optimal cutoff value of Mfn2 for determining preeclampsia was 75.3 pg/mL.Conclusion: Mfn2 has regulatory roles in stress response. Maternal serum Mfn2 is higher in patients with preeclampsia suggesting that Mfn2 increases in the maternal system as a stress response against hypoxia and endothelial dysfunction.What do the results of this study add? Hypoxia causes mitochondrial dysfunction that has been linked to the etiology of many diseases including preeclampsia. Mitofusin-2 is a mitochondrial fusion protein, and the levels can be altered in preeclampsia. For the first time, we showed that maternal levels of mitofusin-2 are higher in patients with preeclampsia. Further, we reported the correlation of mitofusin-2 with blood pressures and uterine artery pulsatility index. These findings will open up other avenues for researchers to investigate other mitochondrial molecules while under stress.

The metabolic role of LncZBTB39-1:2 in the trophoblast mobility of preeclampsia

Preeclampsia is characterized by new onset of hypertension and proteinuria after 20 weeks' gestation and is a leading cause of maternal and neonatal morbidity and mortality. The pathogenesis of preeclampsia is often associated with aberrant trophoblast function that leads to shallow placental implantation. However, the exact underlying mechanisms remain unclear. Placental LncZBTB39-1:2 expression level was investigated in 20 healthy placentae and 20 placentae with preeclampsia using qRT-PCR, and the metabolic profile of trophoblasts overexpressing LncZBTB39-1:2 in vitro was analysed using gas chromatography-mass spectrometry (GC-MS). In this study, we found that the expression of LncZBTB39-1:2 was significantly higher in preeclamptic placentae than in healthy placentae. Our metabolomics results have shown that tricarboxylic acid cycle intermediates and metabolites related to carbohydrate metabolism were decreased with the overexpression of LncZBTB39-1:2 in HTR8/SVneo cells. These findings were validated by detecting a lower level of intracellular ATP in HTR8/Vneo cells. Furthermore, the migration of HTR8/SVneo cells was compromised when cells were transfected with a plasmid encompassing LncZBTB39-1:2 overexpression. From these results, we conclude that abnormal levels of LncZBTB39-1:2 expression might lead to aberrant conditions in HTR-8/SVneo trophoblast cells. Aberrant conditions might be associated with dysregulated trophoblast migration and subsequent failure of uterine spiral artery remodelling, a pathogenesis recognised as a contributing factor in the aetiology of preeclampsia.

Ceramide-induced BOK promotes mitochondrial fission in preeclampsia

Mitochondria are in a constant balance of fusing and dividing in response to cellular cues. Fusion creates healthy mitochondria, whereas fission results in removal of non-functional organelles. Changes in mitochondrial dynamics typify several human diseases. However, the contribution of mitochondrial dynamics to preeclampsia, a hypertensive disorder of pregnancy characterized by placental cell autophagy and death, remains unknown. Herein, we show that the mitochondrial dynamic balance in preeclamptic placentae is tilted toward fission (increased DRP1 expression/activation and decreased OPA1 expression). Increased phosphorylation of DRP1 (p-DRP1) in mitochondrial isolates from preeclamptic placentae and transmission electron microscopy corroborated augmented mitochondrial fragmentation in cytotrophoblast cells of PE placentae. Increased fission was accompanied by build-up of ceramides (CERs) in mitochondria from preeclamptic placentae relative to controls. Treatment of human choriocarcinoma JEG3 cells and primary isolated cytrophoblast cells with CER 16:0 enhanced mitochondrial fission. Loss- and gain-of-function experiments showed that Bcl-2 member BOK, whose expression is increased by CER, positively regulated p-DRP1/DRP1 and MFN2 expression, and localized mitochondrial fission events to the ER/MAM compartments. We also identified that the BH3 and transmembrane domains of BOK were vital for BOK regulation of fission. Moreover, we found that full-length PTEN-induced putative kinase 1 (PINK1) and Parkin, were elevated in mitochondria from PE placentae, implicating mitophagy as the process that degrades excess mitochondria fragments produced from CER/BOK-induced fission in preeclampsia. In summary, our study uncovered a novel CER/BOK-induced regulation of mitochondrial fission and its functional consequence for heightened trophoblast cell autophagy in preeclampsia.