Abstract:
The present invention relates to a method of screening placental proteins responsible for pathophysiology of preeclampsia, and a marker for early diagnosis and prediction of preeclampsia. In accordance with one aspect of the present invention, there is provided a method of screening placental proteins responsible for pathophysiology of preeclampsia by 2D E-proteomics analysis, comprising: isolating placental proteins from a placental tissue; separating the isolated proteins two-dimensionally through 2D electrophoresis; and comparing and analyzing the separated proteins based on scanned gel images and differences in the images between normal placental proteins and preeclamptic placental proteins, wherein the comparison and analysis of the placental proteins based on the scanned gel images and differences in the images are accomplished by selecting proteins with differences of 140% or more between two placentas.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method of screening placental proteins responsible for pathophysiology of preeclampsia, and a marker for early diagnosis and prediction of preeclampsia. 
       BACKGROUND OF THE INVENTION 
       [0002]    Preeclampsia in pregnancy can be a very serious health problem. It can cause fetal growth restriction, fetal death and morbidity, premature deliveries, and death of the mother. The exact cause of preeclampsia is not known, and treatments for efficiently curing or preventing preeclampsia are not also available yet. Preeclampsia is known to cause several problems at the same time, such as high blood pressure (hypertension), pathological edema and leakage of protein into the urine (proteinuria). Further, preeclampsia is one of the pregnancy complications that bring hypertension, proteinuria and traumatism to the mother. It is known that preeclampsia occurs to only about 3-5% of pregnant women, but it can seriously affect both the mother and her unborn (or newborn) baby, and thus, acts as a major cause of increasing perinatal mortality and morbidity rates. 
         [0003]    Globally, at least 200,000 pregnant women die from preeclampsia every year. Its symptoms typically become evident after the 20 th  week of pregnancy. Preeclampsia is usually diagnosed by detecting high blood pressure of a pregnant woman or by checking her urine for protein. Early diagnosis and timely treatment of preeclampsia can remarkably reduce risks to the mother and her unborn baby, but such a monitoring method by using those symptoms as criteria is not effective for an early diagnosis of preeclampsia. Further, no treatments are currently available to cure preeclampsia. Preeclampsia can be mild, but potentially life-threatening depending on the severity of the disease. Despite such clinical risks, however, it is difficult to find the cause or the pathogenesis of preeclampsia at an early stage, or to make an early diagnosis and prognosis. 
         [0004]    Therefore, if it becomes possible to suggest the pathogenesis of preeclampsia and make an early diagnosis and prognosis based on the same, the mother having preeclampsia and her unborn baby can be protected, and the death rate would be reduced. Even if many researches have been conducted to monitor and predict the occurrence of preeclampsia, they are limited to using a specific protein or substance, which is not sufficient to explain the whole phenomenon about the occurrence of preeclampsia and the pathogenesis thereof. 
         [0005]    While the inventors of the present invention have been trying to discover the pathogenesis of preeclampsia, they checked entire protein expressions in a placenta that plays a key role in the onset of preeclampsia and analyzed any change in the protein expressions in a preeclamptic placenta. Based on this, they devised a method of screening placental proteins responsible for pathophysiology of preeclampsia and a marker for early diagnosis and prediction of preeclampsia and also suggested a comprehensive theory of the pathogenesis of preeclampsia to complete the present invention. 
       SUMMARY OF THE INVENTION 
       [0006]    It is, therefore, a primary object of the present invention to provide a method of screening placental proteins responsible for pathophysiology of preeclampsia. 
         [0007]    It is another object of the present invention to provide a marker protein for early diagnosis and prediction of preeclampsia. 
         [0008]    In accordance with one aspect of the present invention, there is provided a method of screening placental proteins responsible for pathophysiology of preeclampsia by 2D E-proteomics analysis, comprising: isolating placental proteins from a placental tissue; separating the isolated proteins two-dimensionally through 2D electrophoresis; and comparing and analyzing the separated proteins based on scanned gel images and differences in the images between normal placental proteins and preeclamptic placental proteins, wherein the comparison and analysis of the placental proteins based on the scanned gel images and differences in the images are accomplished by selecting proteins with differences of 140% or more between two placentas. 
         [0009]    In accordance with another aspect of the present invention, there is provided a marker for early diagnosis and prediction of preeclampsia, comprising one or more proteins selected from the protein group consisting of chaperonin, ER-60 protease, isocitrate dehydrogenase 1, aldehyde reductase 1, fidaresta chain B bonded to human aldose reductase, voltage-dependent anion channel 1, nuclear chloride channel, cathepsin D chain H, phosphoglycerate mutase 1, endoplasmic reticulum protein, PSMA2 protein, glutathione S-transferase, Ig heavy chain v region, smooth muscle myosin alkali light chain, and fatty acid binding protein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The above and other objects and features of the present invention will become apparent from the following description of the preferred examples given in conjunction with the accompanying drawings, in which: 
           [0011]      FIG. 1  shows 2-D gel E-proteomics analysis pictures taken for the identification of changes in placental proteins of a pregnant woman with preeclampsia, in which  FIG. 1A  is a gel picture of placental proteins in normal pregnancy and  FIG. 1B  is a gel picture of placental proteins in pregnancy with preeclampsia; 
           [0012]      FIG. 2  presents comparative pictures of 21 proteins which show big differences in expression between normal placenta and preeclamptic placenta (left-hand side: normal cell; right-hand side: gastric cancer cell) in result of the E-proteomics analysis depicted in  FIG. 1 ; and 
           [0013]      FIG. 3  offers a conceptual diagram suggesting the pathogenesis of preeclampsia on the basis of the analysis of proteins exhibiting different expression in preeclamptic placenta. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0014]    In the following detailed description, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that the various embodiments of the invention, although different, are not necessarily mutually exclusive. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims that should be appropriately interpreted along with the full range of equivalents to which the claims are entitled. 
         [0015]    Then, experiments performed for better understanding the present invention will be described in detail as follows, which are set forth to illustrate, but are not to be construed to limit the present invention. 
         [0016]    Hereinafter, the present invention will be described in more detail. 
         [0017]    The present invention is directed to analyzing protein expression in preeclamptic placenta. More specifically, the present invention is directed to analyzing placental proteins that demonstrate more changes in expression in preeclamptic pregnancy than in normal pregnancy, thus identifying proteins responsible for pathophysiology of preeclampsia. 
         [0018]    In order to identify proteins associated with pathophysiology of preeclampsia, the inventors conducted 2D E-proteomics analysis on the expression of placental proteins, and compared protein expression in a normal placenta and in a preeclamptic placenta to verify the differences in protein expression between them. The “2D E-proteomics analysis” perceives cell or tissue proteins in a packet and identifies an overall change, not individual changes, in proteins reflected in electrical and physical natures proved by electrophoresis. This research method is now actively being used worldwide and is largely composed of primary separation of proteins by isoelectric point and secondary gel-based protein separation by molecular mass. Images of proteins that are broadly distributed over the gel through the two-step protein separation technique were analyzed by an image analyzer for comparison of quantitative expression of proteins. Among them, proteins showing big differences were collected, and molecular weight in unit of peptide (a small cut piece of protein) of which were measured by a molecular weight measurement technique called MALDI-TOF MS. Each of the measured peptide masses was again calculated in terms of the mass of amino acids constituting a peptide. The final masses were compared with those in the already known peptide mass database to prove nature of original proteins. 
         [0019]    The present invention suggests, based on the 2D E-proteomics analysis, 21 proteins demonstrating big differences in expression in a preeclamptic placenta. These proteins may be used for explaining abnormal metabolism in a preeclamptic placenta and its pathophysiology. Further, the proteins are expected to be effectively used for early diagnosis and prediction of preeclampsia in pregnant women. 
         [0020]    For the 2D E-proteomics analysis, the inventors obtained normal placenta tissues and preeclamptic placenta tissues and separated placental proteins according to their isoelectric point (the primary separation step) and according to their molecular weight (the secondary separation step). The gel obtained after electrophoresis was stained by silver nitrate. Then, the stained gel was scanned with a flatbed scanner and analyzed through an image analysis program. Proteins showing differences of 140% or more in two groups of placental samples were selected and finally identified. Twenty one proteins were collected and peaks of protein mass spectrometry were searched by MASCOT PMF based on the NCBI database (see Table 1). Seventeen out of those twenty one proteins were analyzed, and most of them were identified as ones associated with placental metabolism (see Table 2). These proteins may be categorized into different types on the basis of their association with antioxidant activities, recombination related to stress, apoptosis, glycolysis, immunomodulation, or remodeling of reduced NADP, such that the pathophysiology of protein-underlying preeclampsia can be presented (see  FIG. 3 ). 
         [0021]    Hereinafter, the present invention will be explained in more detail through examples. However, it will be apparent to those skilled in the art that these examples are only for the purpose of explaining the present invention in detail, but not intended to limit the scope of the invention. 
       Example 1 
     Separation of Placental Proteins 
       [0022]    Normal placenta and preeclamptic placenta were prepared for 2D E-proteomics analysis. Placental tissues were ground to fine powder in presence of liquid nitrogen, and a buffer (tissue: 0.2 g/10 ml) was added thereto. The samples were then divided into tubes, boiled for five minutes, put into the ice bath for five minutes, and centrifuged at 8,000 rpm and 4° C. for 10 minutes. Each of the upper phases was transferred to a new tube by 800 μl, treated with enzymes (DNase/RNase), and put into the ice bath for 10 minutes. Next, 200 μl of 10% TCA/acetone preparation-50% TCA/acetone was added to each tube. The tubes were placed into the ice bath for a period of 1 hour. The samples were then centrifuged at 12,000 rpm and 4° C. for 10 minutes, and the resulting pallets were washed with acetone. The remaining dry powders were kept at −20° C. 
       Example 2 
     Separation of Proteins by 2D E-Proteomics 
       [0023]    &lt;2-1&gt; Primary Separation of Proteins by Isoelectric Point 
         [0024]    Proteins are primarily separated based on isoelectric point. Dry immobilized pH gradient (IPG) strips of 13 cm were added with 250 μl isoelectric point marker containing 50 μg protein and rehydrated over 10 hours. The rehydrated IPG strips were subjected to isoelectric point separation in an IPG phore (GE Healthcare, USA). The isoelectric point separation was carried out for 1 hour at 500 V, for 1 hour at 1,000 V, and finally at 8,000 V until the final accumulated voltage becomes 60,000 V. At this time, the highest current was set to 50 μA per strip. The strips separated by isoelectric point were slowly stirred over a period of 15 minutes in presence of a primary phase equilibrium solution (50 mM Tris-HCl containing 6M urea, 30% glycerol, 2% SDS, bromophenol blue and 1% DTT, pH 8.8). These primary phase equilibrated strips were soaked in a secondary phase equilibrium solution (50 mM Tris-HCl containing 6M urea, 30% glycerol, 2% SDS, bromophenol blue and 2.5% iodoacetamide, pH 8.8) and stirred again over a period of 15 minutes. 
         [0025]    &lt;2-2&gt; Secondary Protein Electrophoresis 
         [0026]    Proteins are separated in a polyacrylamide gel depending on their molecular weight. A 12.5% sodium dodecyl sulfate polyacrylamide gel was prepared in size of 13 cm through SE 600 Ruby electrophoresis set (Amersham, USA). Phase equilibrated strips were put on the gel, and the gap between the strip and the gel was filled with a sealing Aga. A running buffer (25 mM Tris, 192 mM glycine, 2.5 mM SDS, pH 8.3) was poured into the set, and proteins of the strips were transferred to the gel within the first 20 minutes at 80V, and electrophoresis was carried out for the next 5 hours at 240V. The electrophoresed gel was stained with silver nitrate. In result, by comparing a gel picture of placental proteins in normal pregnancy by 2D electrophoresis (see  FIG. 1A ) with a gel picture of placental proteins in pregnancy with preeclampsia by 2D electrophoresis (see  FIG. 1B ), the inventors could verify changes in placental proteins in pregnancy with preeclampsia. 
       Example 3 
     Gel Scanning and Gel Image Analysis 
       [0027]    The stained gel was scanned through a flatbed scanner (UMAX PowerLook 1100, USA). During scanning, the option of a transmissive type with 300 dpi resolution was chosen. The scanned gel images were analyzed through an image analysis program (Image Master 2D Platinum, GE Healthcare, USA). Based on the image analysis result, proteins showing differences up to 140% or more in two groups of placental samples were selected and finally identified. In result, the inventors checked proteins showing big differences between normal placenta and preeclamptic placenta by electrophoresis shown in  FIG. 1  (In  FIG. 2 , left-hand side: normal cell; right-hand side: gastric cancer cell), and identified 21 proteins with differences in expression between normal placenta and preeclamptic placenta. 
       Example 4 
     Protein Identification 
       [0028]    The 21 proteins with differences in expression between normal placenta and preeclamptic placenta used were collected and sent to IN2GEN Co., Ltd. for protein mass analysis based on MALDI-TOF MS technique. Peaks of protein mass spectrometry analyzed were searched by MASCOT PMF (http://www.matrixscience.com) based on the NCBI database and listed with GeneBank IDs in Table 1 below. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Spot # 
                 NCBI acc# 
                 protein identification 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 49522865 
                 chaperonin 
               
               
                 2 
                 1208427 
                 ER-60protease 
               
               
                 3 
                 1167843 
                 alpha-enolase 
               
               
                 4 
                 28178825 
                 Isocitrate dehydrogenase 1 
               
               
                 5 
                 1633300 
                 Aldehyde reductase 
               
               
                 6 
                 493797 
                 Chain B, Fidarestat Bound to human Aldose 
               
               
                   
                   
                 reductase 
               
               
                 7 
                 14250132 
                 Voltage-depentant anion channel 1 
               
               
                 8 
                 4588526 
                 Nuclear chloride channel 
               
               
                 9 
                 5822091 
                 Chain H, Cathepsin D 
               
               
                 10 
                 56081766 
                 Phosphoglycerate mutase 1 
               
               
                 11 
                 5803013 
                 Endoplasmic reticulum protein 
               
               
                 12 
                 50881968 
                 PSMA2 protein 
               
               
                 13 
                 2204207 
                 Glutathione S-transferase 
               
               
                 14 
                 8249777 
                 Ig heavy chain v region 
               
               
                 15 
                 16924329 
                 Smooth muscle myosin alkali light chain 
               
               
                 17 
                 4557581 
                 Fatty acid binding protein 
               
               
                   
               
             
          
         
       
     
         [0029]    The above Table 1 presents the analysis result on the 21 proteins obtained by MALDI-TOF MS technique, verifying that all of the 21 proteins except one were expressed remarkably high in the preeclamptic placenta compared with the normal placenta. 
       Example 5 
     Protein Analysis and Suggestion of Pathophysiology 
       [0030]    The inventors analyzed 17 out of the 21 proteins and confirmed that most of the proteins were associated with placenta metabolism. To be more specific, the inventors analyzed not only functions of those 21 proteins, but also changes in protein expression detected in the preeclamptic placenta compared with that of the normal placenta, wherein the analysis result is listed in Table 2 below. 
         [0000]    
       
         
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                 Relative 
               
               
                   
                   
                 change 
               
               
                 Category 
                 Protein 
                 (%) 
               
               
                   
               
             
             
               
                 Structural 
                 Smooth muscle myosin alkali light chain 
                 191 
               
               
                 Antioxidant 
                 Glutathione S-transferase 
                 177 
               
               
                 and detoxicant 
                 Isocitrate dehydrogenase 
                 155 
               
               
                 Stress-related 
                 Chaperonin (heat shock protein 60) 
                 223 
               
               
                 protein 
               
               
                 remodeling 
               
               
                 Apoptosis 
                 Voltage-dependent anion channel 
                 185 
               
               
                   
                 Nuclear-chloride channel 
                 208 
               
               
                   
                 Chain H, Cathepsin D at pH 7.5 
                 245 
               
               
                 Reduced NADP + - 
                 Aldehyde reductase 
                 142 
               
               
                 regeneration 
                 Chain B, Fidarestat bound to human aldose 
                 151 
               
               
                 Glycolysis 
                 Phpsphoglycerate mutase 
                 267 
               
               
                   
                 Alpha enolase 
                 149 
               
               
                 Immuno- 
                 ER-60 protease 
                 179 
               
               
                 remodeling 
               
               
                 Other 
                 Endoplasmic reticulum protein 29 
                 242 
               
               
                   
                 PSMA2 protein 
                 156 
               
               
                   
                 Ig heavy chain v region 
                 216 
               
               
                   
                 Fatty acid binding protein 5 
                 220 
               
               
                   
               
             
          
         
       
     
         [0031]    The proteins were categorized into different types based on their association with antioxidant activities, recombination related to stress, apoptosis, glycolysis, immunomodulation, or remodeling of reduced NADP such that the pathophysiology of protein-underlying preeclampsia can be presented as shown in  FIG. 3 . 
         [0032]    As discussed above, according to the present invention, the variation in certain protein expression in a preeclamptic placenta can be identified by a 2-D E-proteomics analysis, thus making it possible to present a theory on the pathogenesis of preeclampsia. Further, the screening method and marker of the present invention can screen placental proteins of different expressions in the placenta of a pregnant woman with preeclampsia, and those proteins can be used as a marker for prevention and early treatment of preeclampsia. 
         [0033]    While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and the scope of the invention as defined in the following claims.