**1. Introduction**

Autophagy is an intracellular degradation system conserved among eukaryotes [1] characterized as a natural defense mechanism capable to reduce damages related to inflammatory responses and infectious, neoplasia and degenerative diseases. Defects in this process are directly linked to several diseases [2, 3]. The main role of autophagy is to maintain cellular homeostasis by recycling intracellular materials. Cells under starvation or with organelle damage trigger the autophagy mechanism in order to clean their cytoplasm and restore a source of energy [4–6].There are three types of autophagy: microautopahgy, chaperone-mediated autophagy, and macroautophagy [7]. The most characteristic process of autophagy is the macroautophagy. This process is characterized by the creation of a double membrane compartment in the cytoplasm called phagophore. This structure develops into an autophagosome, a double lipid bilayer membrane-bound structure. The autophagosome merges with lysosomes leading to the autolysosome formation. Continuing the process of autophagy, the autolysosome is finally degenerated, releasing in the cytosol a number of monomers that can be reused by the cell as important sources of energy (**Figure 1**) [8, 9].

The beginning of the autophagy process is dependent on the inhibition of the mammalian target of rapamycin (mTOR) and then autophagy proteins become crucial to the completion of the cascade generated [5, 10]. In this manner, cells under sufficient nutrition or without structural damages maintain a state of activation of mTOR, keeping blocked the mechanism of autophagy. After being triggered, mTOR provides a catalytic subunit by two distinct multiprotein complexes,

#### **Figure 1.**

*Autolysosome formation. The process starts with a development of a double membrane named phagophore. This structure develops into an autophagosome, merging with lysosomes to form the autolysosome. During the process of autophagy, the autolysosome is degraded, releasing monomers into the cytosol, which can be reused by the cell as a source of energy. Source: own authorship.*

mTORC1 (mechanistic target of rapamycin complex 1), and mTORC2 (mechanistic target of rapamycin complex 2). Some proteins are common for both complexes (GβL and Deptor), but others reflect specific functions for each of them, as raptor for mTORC1 and rictor for mTORC2 [11]. Regarding functions, mTORC1 coordinates the synthesis of lipids and proteins to promote cell growth, while mTORC2 acts in the cytoskeletal actin control [12]. Therefore, mTORC1 complex finally establishes the autophagy process via ULK1 (mammalian ortholog of yeast autophagy-related gene 1) kinase activity. The process of autophagosome formation involves about 38 Atgs (autophagy-related genes), and the initial process of autophagy in mammals is controlled by Atg1/ULK complex, which consists in ULK1/2 (UNC-51-like kinase 1), mAtg13, FIP200 (interaction protein of 200KD, homolog of the yeast Atg17), and Atg101. During nutrient rich conditions or in the presence of cell integrity, mTORC1 phosphorylates and inhibits ULK1/2 and mAtg13, deregulating the contact between ULK and AMPK (AMP-activated protein kinase), a kinase with activation effect on ULK1. But under altered conditions, mTORC1 is inhibited, and the activation of ULK1/2 leads to phosphorylation and activation of mAtg13 and FIP200 [13].

Atg plays crucial roles as ubiquitin-like protein conjugation system that mediates protein lipidation and participation in autophagy-specific protein kinase complexes [14, 15] for accomplishment of autophagy. Atg1 and Atg12-Atg5 complexes are essential for the autophagic machinery. Another important gene is Atg8 (a yeast autophagy-related gene ortholog of LC3), a membrane marker during the formation of autophagosome. Atg9 transmembrane protein and regulators of its trafficking (Atg2 and Atg18) participate in the expansion of phagophore after the formation of the Atg1 complex. There are two systems, Atg12 (Atg5, Atg7, Atg10, Atg12, and Atg16) and Atg8 (Atg3, Atg4, Atg7, and Atg8), which are responsible for expansion of the vesicle [1, 16].

The establishment of the autophagy is also dependent of two proteins: beclin-1 protein and LC3 (light chain protein 3) [17, 18]. Beclin-1 (homolog of yeast Apg6/ Vps30) promotes the recruitment of membranes to form the autophagosome, nucleation of the autophagic vesicle, and recruitment of proteins from the cytosol [19]. Three isoforms of LC3 have been described: LC3A, LC3B, and LC3C. After synthesis and activation (LC3-I to LC3-II), LC3-II for incorporating cytosolic denatured proteins and damaged organelles into the autophagosome [20, 21]. The relative amounts of LC3-II reflect autophagic activity [22]. Considering the autophagy pathway, LC3-II has been proposed to be used to measure autophagy activity.

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*Autophagy in Preeclampsia*

*DOI: http://dx.doi.org/10.5772/intechopen.85592*

Defective autophagy caused by mutations or genetic alterations can lead to various clinical syndromes [23], such as static encephalopathy of childhood with neurodegeneration in adulthood (SENDA), Vici syndrome, hereditary spastic paraparesis, Parkinson's disease, lysosomal storage disorders, cancer, and Crohn's disease.

As a lysosomal degradation pathway, removing protein aggregates and organelles damaged, maintaining cell integrity, autophagy may be impaired in pregnant women with preeclampsia (PE) due to the presence of placental lesions caused by hypoxia/ischemia [24]. In preeclampsia, there is deficient myometrial penetration by extravillous cytotrophoblast during the first trimester of pregnancy, leading to placental insufficiency [25]. On the other hand, it has been reported that proteins related to autophagy, LC3-II, and beclin-1 are present in trophoblastic villi during normal pregnancy, and high levels of LC3-II are present in the placenta of pregnant women with severe preeclampsia [26]. The induction of hypoxia on choriocarcinoma cell line JEG-3 with the purpose of exploring the mechanism of regulatory proteins involved in autophagy showed a slight increase in the expression of LC3-II, with a reduction in beclin-1. Treatment of these cells with TNF-α induced a significant increase in the expression of LC3-II without modifying the expression of beclin-1. The results suggest that the increased autophagic activity mediated by

LC3-II may be involved in the pathophysiology of preeclampsia [26].

induced by nutrient deprivation and oxygen [27].

development of preeclampsia [39].

**2. Autophagy and placenta**

Studies with autophagy in the placenta are scarce, and most of the work done employs cell lines or cultures of trophoblast cells in vitro to evaluate autophagy

The systemic inflammatory response exacerbated in preeclampsia seems to be related to the release of substances capable of inducing inflammation as membrane fragments of syncytiotrophoblast, fetal DNA, soluble microparticles derived from leukocytes, and inflammatory cytokines in plasma of pregnant women, causing activation of cells of innate immunity [28–30]. Other cellular components present in plasma, such as protein derivatives, polysaccharides, and lipids, as well as extracellular matrix products are named "damage-associated molecular patterns" (DAMPS) and are considered important modulators of the inflammatory response. DAMPs are represented by molecules like uric acid, reactive oxygen intermediates, heat shock proteins (Hsp) [31], proteins released from dead cells, as the high mobility group box 1—HMGB1 [32], and products released from the extracellular matrix, such as fibronectin and hyaluronan [33, 34]. Both protein hsp70 [35, 36] and hyaluronan [37, 38] are elevated in plasma of pregnant women with preeclampsia and may be associated with systemic inflammation and oxidative stress. However, the role of these factors in the pathophysiology of preeclampsia is not well understood. A major cause of preeclampsia is the accumulation of reactive oxygen species (ROS), resulting in impaired antioxidant protection and activation of autophagy. According to research in trophoblasts, expression of LC3 and beclin-1 and the formation of autophagosomes are higher than in normal placentas, suggesting that autophagy is regulated during placentation and appears to be a possible factor in the

The placental development requires multiples roles of autophagy. Experimental studies suggest that autophagy plays important functions in survival of neonates during nutritional deficiency at the early stage of birth [40]. Moreover, it was seen that the growth and remodeling of cervical fascia progress by autophagy regulation. Meanwhile, it has not been reported that autophagy affects differentiation

#### *Autophagy in Preeclampsia DOI: http://dx.doi.org/10.5772/intechopen.85592*

*Prediction of Maternal and Fetal Syndrome of Preeclampsia*

*the cell as a source of energy. Source: own authorship.*

mTORC1 (mechanistic target of rapamycin complex 1), and mTORC2 (mechanistic target of rapamycin complex 2). Some proteins are common for both complexes (GβL and Deptor), but others reflect specific functions for each of them, as raptor for mTORC1 and rictor for mTORC2 [11]. Regarding functions, mTORC1 coordinates the synthesis of lipids and proteins to promote cell growth, while mTORC2 acts in the cytoskeletal actin control [12]. Therefore, mTORC1 complex finally establishes the autophagy process via ULK1 (mammalian ortholog of yeast autophagy-related gene 1) kinase activity. The process of autophagosome formation involves about 38 Atgs (autophagy-related genes), and the initial process of autophagy in mammals is controlled by Atg1/ULK complex, which consists in ULK1/2 (UNC-51-like kinase 1), mAtg13, FIP200 (interaction protein of 200KD, homolog of the yeast Atg17), and Atg101. During nutrient rich conditions or in the presence of cell integrity, mTORC1 phosphorylates and inhibits ULK1/2 and mAtg13, deregulating the contact between ULK and AMPK (AMP-activated protein kinase), a kinase with activation effect on ULK1. But under altered conditions, mTORC1 is inhibited, and the activation of ULK1/2 leads to phosphorylation and activation of

*Autolysosome formation. The process starts with a development of a double membrane named phagophore. This structure develops into an autophagosome, merging with lysosomes to form the autolysosome. During the process of autophagy, the autolysosome is degraded, releasing monomers into the cytosol, which can be reused by* 

Atg plays crucial roles as ubiquitin-like protein conjugation system that mediates

The establishment of the autophagy is also dependent of two proteins: beclin-1 protein and LC3 (light chain protein 3) [17, 18]. Beclin-1 (homolog of yeast Apg6/ Vps30) promotes the recruitment of membranes to form the autophagosome, nucleation of the autophagic vesicle, and recruitment of proteins from the cytosol [19]. Three isoforms of LC3 have been described: LC3A, LC3B, and LC3C. After synthesis and activation (LC3-I to LC3-II), LC3-II for incorporating cytosolic denatured proteins and damaged organelles into the autophagosome [20, 21]. The relative amounts of LC3-II reflect autophagic activity [22]. Considering the autophagy pathway, LC3-II has been proposed to be used to measure autophagy activity.

protein lipidation and participation in autophagy-specific protein kinase complexes [14, 15] for accomplishment of autophagy. Atg1 and Atg12-Atg5 complexes are essential for the autophagic machinery. Another important gene is Atg8 (a yeast autophagy-related gene ortholog of LC3), a membrane marker during the formation of autophagosome. Atg9 transmembrane protein and regulators of its trafficking (Atg2 and Atg18) participate in the expansion of phagophore after the formation of the Atg1 complex. There are two systems, Atg12 (Atg5, Atg7, Atg10, Atg12, and Atg16) and Atg8 (Atg3, Atg4, Atg7, and Atg8), which are responsible for

**78**

mAtg13 and FIP200 [13].

**Figure 1.**

expansion of the vesicle [1, 16].

Defective autophagy caused by mutations or genetic alterations can lead to various clinical syndromes [23], such as static encephalopathy of childhood with neurodegeneration in adulthood (SENDA), Vici syndrome, hereditary spastic paraparesis, Parkinson's disease, lysosomal storage disorders, cancer, and Crohn's disease.

As a lysosomal degradation pathway, removing protein aggregates and organelles damaged, maintaining cell integrity, autophagy may be impaired in pregnant women with preeclampsia (PE) due to the presence of placental lesions caused by hypoxia/ischemia [24]. In preeclampsia, there is deficient myometrial penetration by extravillous cytotrophoblast during the first trimester of pregnancy, leading to placental insufficiency [25]. On the other hand, it has been reported that proteins related to autophagy, LC3-II, and beclin-1 are present in trophoblastic villi during normal pregnancy, and high levels of LC3-II are present in the placenta of pregnant women with severe preeclampsia [26]. The induction of hypoxia on choriocarcinoma cell line JEG-3 with the purpose of exploring the mechanism of regulatory proteins involved in autophagy showed a slight increase in the expression of LC3-II, with a reduction in beclin-1. Treatment of these cells with TNF-α induced a significant increase in the expression of LC3-II without modifying the expression of beclin-1. The results suggest that the increased autophagic activity mediated by LC3-II may be involved in the pathophysiology of preeclampsia [26].

Studies with autophagy in the placenta are scarce, and most of the work done employs cell lines or cultures of trophoblast cells in vitro to evaluate autophagy induced by nutrient deprivation and oxygen [27].

The systemic inflammatory response exacerbated in preeclampsia seems to be related to the release of substances capable of inducing inflammation as membrane fragments of syncytiotrophoblast, fetal DNA, soluble microparticles derived from leukocytes, and inflammatory cytokines in plasma of pregnant women, causing activation of cells of innate immunity [28–30]. Other cellular components present in plasma, such as protein derivatives, polysaccharides, and lipids, as well as extracellular matrix products are named "damage-associated molecular patterns" (DAMPS) and are considered important modulators of the inflammatory response. DAMPs are represented by molecules like uric acid, reactive oxygen intermediates, heat shock proteins (Hsp) [31], proteins released from dead cells, as the high mobility group box 1—HMGB1 [32], and products released from the extracellular matrix, such as fibronectin and hyaluronan [33, 34]. Both protein hsp70 [35, 36] and hyaluronan [37, 38] are elevated in plasma of pregnant women with preeclampsia and may be associated with systemic inflammation and oxidative stress. However, the role of these factors in the pathophysiology of preeclampsia is not well understood. A major cause of preeclampsia is the accumulation of reactive oxygen species (ROS), resulting in impaired antioxidant protection and activation of autophagy. According to research in trophoblasts, expression of LC3 and beclin-1 and the formation of autophagosomes are higher than in normal placentas, suggesting that autophagy is regulated during placentation and appears to be a possible factor in the development of preeclampsia [39].
