GENETIC PREDISPOSITION TO PRE-ECLAMPSIA: POLYMORPHISM OF GENES INVOLVED IN REGULATION OF ENDOTHELIAL FUNCTIONS
Mozgovaia EV, Malysheva OV, Ivashchenko TE, Baranov VS*
*Corresponding Author: Professor Dr. Vladislav S. Baranov, Laboratory of Prenatal Diagnosis of Inherited Disorders, D.O. Ott Research Institute of Obstetrics and Gynecology, Russian Academy of Medical Sciences, Mendeleevskaya line 3, St. Petersburg 199034, Russia; Tel/Fax: +07-812-328-0487; E-mail: baranov@vb2475. spb.edu
page: 19

RESULTS AND DISCUSSION

Because of obvious clinical variations of our PE pa­tients they were subdivided into two main groups (pure and combined PE) with several clinical subgroups within each, as indicated in Table 1.

Polymorphism of the PLAT Gene. Endothelial dam­age is usually accompanied by retardation of fibrinolysis, determined by imbalance between tissue type plasminogen activator (t-PA) and by its main inhibitor (PAI-1). Protein products of these genes (PLAT and PAI-1, respectively) are valuable markers of endothelial dysfunction. There are few data concerning the association of the PLAT gene polymorphism (deletion/insertion of Alu-repeats in intron 8) with risk of myocardial infarction and with other car­diovascular diseases. Marked elevation of t-PA level cor­relates with an increase of PLAT gene I-allele frequency, and is considered as a risk factor for myocardium infarc­tion [2,3]. Thus far, nothing is known about the possible association of PLAT polymorphism with PE.

Frequencies of the PLAT genotypes in pure (p) and combined (c) PE patients are presented in Table 1. The frequency of I/I homozygotes in pPE patients does not differ from that in the control group, while in the group of cPE patients the frequency of these genotype is 1.5-2 times more than in the control group.

In severe cPE with arterial hypertension (nephropathia II-III and real PE) the genotype I/I frequency (twice ex­ceeded) that in cPE as a whole and was three times more than that of the control. However the small number of patients in this group does not reveal a statistical signifi­cance of these differences (c2 = 2.95; p<0.5). The highest frequency of I/I genotype (33.3%) was found in cPE pa­tients with gestational diabetes  (c2 = 4.22; p<0.25).

Thus, deletion/insertion Alu polymorphism of the PLAT gene may contribute to the pathogenesis of cPE. It may also promote the advancement of background dis­eases associated with endothelial dysfunction and throm­bophilia. Most likely, the I/I genotype predisposes to cPE with arterial hypertension and gestational diabetes as its background. The absence of D/D homozygotes in the pa­tients with severe forms of pPE and with diabetes mellitus type 1 or 2 background remains the subject for further studies.

Polymorphism of the PAI-1 Gene. Gene PAI-1 has an insertion/deletion G-base polymorphism (4G/5G) in its promotor region [4]. It has been shown that inherited fibrinolysis impairment in pregnant women with some common obstetrical complications (heavy PE, abruptio placentae, fetal growth retardation and stillbirth) was asso­ciated with polymorphism of the gene PAI-1 in such a way that the 4G/4G genotype was linked to an increased risk of PE and thrombosis [5].

Genotype frequencies of the 4G/5G PAI-1 polymor­phism in pPE and cPE are given in Table 1. The frequen­cies of the 4G/4G genotype in all groups of pPE appeared significantly above control level at the expense of substan­tial reduction in the number of relevant heterozygote (4G/5G) and homozygote (5G/5G) specimens. These re­sults demonstrate that the 4G/4G genotype is associated with pPE.


Its frequency in cPE is higher than the control values, but somewhat lower than in PE patients as a whole. The 4G/4G genotype was found exclusively in severe cPE patients with kidney disease. Only in some cPE subgroups with mild and severe arterial hypertension did frequencies of 4G homozygotes reach a statistically significant level (c2 = 3.6 and even 4.77). Some trends in reduction of 4G homozygotes were detected in the cPE patients who had the added complication of diabetes mellitus (c2 = 2.55).

Thus, it seems plausible that the PAI-1 polymorphism is involved in the development of PE. The association of the 4G/4G genotype is especially evident for pPE and for cPE, complicated by arterial hypertension and by concom­itant kidney disease.

Polymorphism of the ACE Gene. The angiotensin-converting enzyme (ACE) is a major component of the renin-angiotensin system, responsible for the conversion of angiotensin I to angiotensin II and for bradykinin inacti­vation. Its participation in augmentation of endothelial dysfunction and vasoconstriction is unequivocal. Data concerning the association of its polymorphism [deletion (D)/insertion (I)] of ALU-repeats in intron 16 with PE are scanty and inconsistent. According to one observation, the I/I genotype should be considered as a marker of reduced PE risk, while homozygosity for Alu deletion (D/D geno­type) is the marker of its increased PE risk [6]. These findings are not supported by the other studies [7].

Data on the frequencies of the ACE genotypes are presented in Table 2. There is a marked increase in both types of homozygotes (I/I and D/D) in the pPE group, especially in the patients with pPE corresponding to neph­ropathia I and II (c2 = 9.1). In cPE the increase in the num­ber of D/D homozygotes was also quite obvious, especially among patients with mild cPE augmented by heavy AH (c2 = 3.36). On the other hand, in severe pPE and in the subgroup of severe cPE with mild AH, the frequency of the D/D genotype was more than twice below that of the control value (c2 = 10.4). The distribution of the ACE genotypes was within normal ranges in cPE patients with accompanying kidney disease.

Thus, the greatest difference from the control group in the frequencies of ACE polymorphism is seen in pPE group corresponding to nephropathia I and II. The associa­tion of this polymorphism with cPE is less evident. At present, it can mainly be attributed to cPE complicated by AH. The insufficient number of patients in separate sub­groups does not permit a final conclusion on the associa­tion of the D/D ACE gene genotype with various forms of cPE.

Polymorphism of the eNOS Gene. Endothelial nitric oxide synthetase (eNOS) participates in NO synthesis in the endothelium and, hence, in regulation of a vascular tone, circulation and blood arterial pressure [8]. The 4a/4b polymorphism in intron 4 of the eNOS gene (Table 1) was found to be associated with increased risk of PE [9]. Pre-eclampsia patients with even only one 4a allele demon­strated elevated arterial blood pressure. Earlier manifesta­tion and heavier progression of PE was found in 4a/4a homozygotes [10]. The detrimental effects of this allele were especially pronounced in early pregnancy and ap­peared to decrease with gestational age [11].

Distribution of eNOS genotypes in our PE patients and in the control group is shown in Table 2. Not a single 4a/4a genotype was identified in pPE patients, and it was rather rare in both control and cPE groups. The genotype 4a/4b was detected in patients with mild pPE, whereas all pregnant women with severe pPE had genotype 4b/4b (c2 = 8.2). The association of a 4a/4b polymorphism with mild forms of cPE in combination with AH was observed. The increase of 4a homozygotes and decrease in 4b allele frequencies were statistically significant in patients in this category (c2 = 4.87). The 4a/4a genotype was also encoun­tered in cPE patients with diabetes mellitus type 1. No other subgroups of cPE patients carried this genotype. Thus, the 4b/4b genotype of the eNOS gene correlates with heavy pPE, while genotype 4a/4a dominates in some forms of cPE.

Polymorphism of the TNF-a Gene. TNF-a is one of the most aggressive inflammatory cytokines. Its increased activity is known to stimulate generation of free radicals, induces apoptosis and accompanies endothelial dysfunc­tion [10]. The data on association of the TNF-a gene poly­morphism with endothelial dysfunction are conflicting [12,13].

As may be inferred from Table 2, only two genotypes (238)G/G and (238)A/G, were found in both PE and in the control groups. In the subgroup with heavy pPE only G/G homozygotes were noted. In cPE complicated with arterial hypertension, a marked increase of heterozygote frequency was found. It was especially significant in cPE patients with mild arterial hypertension (c2 = 8.53) and with kidney disorders (c2 = 9.97).


Polymorphism of the GSTP1 Gene. GSTP1 belongs to the detoxification enzyme superfamily, playing a cru­cial role in the metabolic reaction of various xenobiotics and in the function of the antioxidant system, providing resistance of the cells to lipid peroxidation and free radi­cal damage in the endothelium. Genetic polymorphism of GSTP1 is represented by three functionally different forms of enzyme: GSTP1*a (isoleucine in position 105 and ala­nine in position 114); GSTP1*b (valine in position 105 and alanine in position 114); GSTP1*c (valine in position 105 and valine in position 114). Both mutant forms (GSTP1*b and GSTP1*c) are functionally less active than GSTP1*a [14]. Some preliminary data concerning the association of gene GSTP1 polymorphism with PE are available [15].

Frequencies of the GSTP1 genotypes are presented in Table 3. A marked increase of the 1a/1b genotype fre­quency was found in pPE patients, especially in the mild PE subgroup (c2 = 5.12). The genotypes 1b/1b; 1b/1c; 1c/1c were not detected in patients with severe forms of pPE. Genotypes 1a/1c, and especially 1c/1c, were quite common for cPE patients. Substantial increase in hetero­zygous 1a/1c frequency was registered in all groups of cPE, especially with mild AH (c2 = 4.45-6.6), and with gestational diabetes (c2 = 6.4). At the same time, the fre­quencies of the functionally most favorable genotypes (1a/1a and 1a/1b), which prevailed in the control group, were significantly decreased in all PE patients.

Thus, an association of GSTP1 polymorphism with PE is quite obvious in patients with cPE, especially when combined with AH or with diabetes mellitus. Substantial increase in functionally defective 1c allele frequency was typical for the group of mild pPE.

 

 

 

 

Gene Localization

 

Polymorphism

 

Structure of the Primers (5'->3')

 

PLAT (8p12)

 

del/ins of Alu-repeats in intron 8

 

F: GTG AAA AGC AAG GTC TAC CAG
R: GAC ACC GAG TTC ATC TTG AC

 

PAI-1 (7q21-22)

 

del/ins (4G/5G) in 675 bp
of promoter

 

F: CAC AGA GAG AGT CTG GCC ACT T
R: GGC CCA ACA GAG GAC TCT TG

 

TNF-a (6p21.3)

 

polymorphic site in 238 bp G(N)/A(M)

 

A1: ATC TGG AGG AAG CGG TAG TG
M2: AGA AGA CCC CCC TCG GAA CC

 

eNOS (7q33-56)

 

polymorphic site in 27 bp
4/5 in intron 4

 

F: AGG CCC TAT GGT AGT GCC TT
R: TCT CTT AGT GCT GTG GTC AC

 

ACE (17q23)

 

del/ins 287 bp in intron 16

 

F: CTG GAG ACC ACT CCC ATC CTT TCT
R: ATG TGG CCA TCA CAT TCG TCA GAT

 

GSTP1 (11q13)

 

 

Fragment of 192 bp
Ile105-192 bp
M: Val105-80 bp + 112 bp

 

1F: CTC TAT GGG AAG GAC CAG CAG GAG
2R: CAA GCC ACC TGA GGG GTA AGG

 

Fragment of 146 bp
Ala114-121 bp + 25 bp
M: Val114-146 bp

 

3F: GTT GTG GGG AGC AAG CAG AGG
4R: GCC TTC ACA TAG TCA TCC TTG CGC

Figure 1. Polymorphic loci of investigated genes and oligoprimers used for PCR amplification

 

 

 

PLAT Polymorphism

 

n

 

Genotype
D/D (%)

 

Genotype
I/D (%)

 

Genotype
I/I (%)

 

c2

 

OR

 

Control group

 

73

 

50.6

 

39.7

 

9.5

 

 

 

Pure PE

  • mild
  • severe

 

41
35
16

 

57.5
57.5
60.0

 

35.5
34.2
40.0

 

6.6
8.5
0.0

 

0.67
0.397
1.65

 

0.69
0.83

 

Combined PE

  • with AH
  • mild with mild AH
  • severe with mild AH
  • with kidney disease
  • with diabetes, types 1 and 2
  • with gestational diabetes

 

76
45
21
11
15
14
5

 

42.1
46.6
52.3
45.4
33.3
42.8
16.6

 

42.1
35.5
33.3
27.2
53.3
57.1
50.0

 

15.7
17.7
14.2
27.2
13.3
0.0
33.3

 

1.76
1.69
0.52
1.69
1.503
2.72 (p<0.5)

 

5.66

 

Table 1. Polymorphisms of the PLAT and PAI-1 genes in pregnant women with pre-eclampsia.

 



Number 22
VOL. 22(1), 2019
Number 22
VOL. 22, 2019 Accepted articles
Number 22
VOL. 22, 2019 Supplement
Number 21
VOL. 21(2), 2018
Number 21
VOL. 21 (1), 2018
Number 21
VOL. 21, 2018 Accepted articles
Number 21
VOL. 21, 2018 Supplement
Number 20
VOL. 20 (2), 2017
Number 20
VOL. 20 (1), 2017
Number 19
VOL. 19 (2), 2016
Number 19
VOL. 19 (1), 2016
Number 18
VOL. 18 (2), 2015
Number 18
VOL. 18 (1), 2015
Number 17
VOL. 17 (2), 2014
Number 17
VOL. 17 (1), 2014
Number 16
VOL. 16 (2), 2013
Number 16
VOL. 16 (1), 2013
Number 15
VOL. 15 (2), 2012
Number 15
VOL. 15, 2012 Supplement
Number 15
Vol. 15 (1), 2012
Number 14
14 - Vol. 14 (2), 2011
Number 14
The 9th Balkan Congress of Medical Genetics
Number 14
14 - Vol. 14 (1), 2011
Number 13
Vol. 13 (2), 2010
Number 13
Vol.13 (1), 2010
Number 12
Vol.12 (2), 2009
Number 12
Vol.12 (1), 2009
Number 11
Vol.11 (2),2008
Number 11
Vol.11 (1),2008
Number 10
Vol.10 (2), 2007
Number 10
10 (1),2007
Number 9
1&2, 2006
Number 9
3&4, 2006
Number 8
1&2, 2005
Number 8
3&4, 2004
Number 7
1&2, 2004
Number 6
3&4, 2003
Number 6
1&2, 2003
Number 5
3&4, 2002
Number 5
1&2, 2002
Number 4
Vol.3 (4), 2000
Number 4
Vol.2 (4), 1999
Number 4
Vol.1 (4), 1998
Number 4
3&4, 2001
Number 4
1&2, 2001
Number 3
Vol.3 (3), 2000
Number 3
Vol.2 (3), 1999
Number 3
Vol.1 (3), 1998
Number 2
Vol.3(2), 2000
Number 2
Vol.1 (2), 1998
Number 2
Vol.2 (2), 1999
Number 1
Vol.3 (1), 2000
Number 1
Vol.2 (1), 1999
Number 1
Vol.1 (1), 1998

 

 


 About the journal ::: Editorial ::: Subscription ::: Information for authors ::: Contact
 Copyright © Balkan Journal of Medical Genetics 2006