The role of the paraoxonases in pre-eclampsia and labour

Human parturition involves interaction of hormonal, neurological, mechanical stretch and inflammatory pathways and the placenta plays a crucial role. The paraoxonases (PONs 1-3) protect against oxidative damage and lipid peroxidation, modulation of endoplasmic reticulum stress and regulation of apoptosis. Nothing is known about the role of PON2 in the placenta and labour. Since PON2 plays a role in oxidative stress and inflammation, both features of labour, the hypothesis was that placental PON2 expression would alter during labour. PON2 was examined in placentas obtained from women who delivered by caesarean section and were not in labour and compared to the equivalent zone of placentas obtained from women who delivered vaginally following an uncomplicated labour. Samples were obtained from 12 sites within each placenta: 4 equally spaced apart pieces were sampled from the inner, middle and outer placental regions. PON2 expression was investigated by Western blotting and real time PCR. Two PON2 forms, one at 62 kDa and one at 43 kDa were found in all samples. No difference in protein expression of either isoform was found between the three sites in either the labour or non-labour group. At the middle site there was a highly significant decrease in PON2 expression in the labour group when compared to the non-labour group for both the 62 kDa form (p = 0.02) and the 43 kDa form (p = 0.006). No spatial differences were found within placentas at the mRNA level in either labour or non-labour. There was, paradoxically, an increase in PON2 mRNA in the labour group at the middle site only. This is the first report to describe changes in PON2 in the placenta in labour. The physiological and pathological significance of these remains to be elucidated but since PON2 is anti-inflammatory further studies are warranted to understand its role. Pre-eclampsia (PE) is associated with maternal and placental oxidative stress. The second aim was to determine the expression of PON2 in the placenta in pre-eclampsia. PON2 was examined in placentas obtained from non-labouring women who delivered by caesarean section (normal pregnancy and pre-eclampsia) and compared to women who delivered vaginally (normal pregnancy and pre-eclampsia). Samples were obtained from 8 sites within each placenta: Four equally spaced apart pieces were sampled from the inner and 4 from the middle regions. PON2 expression was investigated by Western blotting and qRT-PCR. Two PON2 bands (62 kDa and 43 kDa were found in all samples. When PON2 expression in the non-labour control group was compared to the non-labour PE group at the inner placental site no differences were found. At the middle placental site a reduction in both PON2 isoforms was observed in the non-labour PE group compared to the non-labour control group (p=0.02 for both isoforms). No difference was found between labour control and labour PE at the inner site. A reduction in PON2 was observed in the labour PE group compared to the labour control group (PON2 62 kDa p=0.008, PON2 43kDa p=0.001). No differences in mRNA were found. Conclusion: This is the first study to investigate the expression of PON2 in PE. Given the protective roles of paraoxonases future studies including measurement of PONs in maternal blood, PONs gene polymorphism and paraoxanase induction experiment on this family of proteins may reveal new insights into understanding PE. The third aim was to perform the same experiments as above but for PON3. There was no difference in expression of PON3 between the three sites (inner, middle, outer) within individual placentas for both labour and non-labour. PON3 was significantly decreased in the labour group when compared to the non-labour group at the inner site. No other differences were found. There was a significant decrease in PON3 expression in the PE non-labour group compared to the control non-labour group in the middle site only. There was a significant decrease in the PE labour group compared to the control labour at the middle site only. Finally preliminary experiments were performed to determine if different zones of the placenta were more susceptible to ischemic-reperfusion injury in vitro. The number of experiments was not sufficient to make definitive conclusions but the pilot data suggest this should be explored more in future studies include more placenta tissue exposed to ischemic-reperfusion injury to understand how placental stress might affect placental function

Paraoxonase 2 protein is spatially expressed in the human placenta and selectively reduced in labour

Humans parturition involves interaction of hormonal, neurological, mechanical stretch and inflammatory pathways and the placenta plays a crucial role. The paraoxonases (PONs 1–3) protect against oxidative damage and lipid peroxidation, modulation of endoplasmic reticulum stress and regulation of apoptosis. Nothing is known about the role of PON2 in the placenta and labour. Since PON2 plays a role in oxidative stress and inflammation, both features of labour, we hypothesised that placental PON2 expression would alter during labour. PON2 was examined in placentas obtained from women who delivered by cesarean section and were not in labour and compared to the equivalent zone of placentas obtained from women who delivered vaginally following an uncomplicated labour. Samples were obtained from 12 sites within each placenta: 4 equally spaced apart pieces were sampled from the inner, middle and outer placental regions. PON2 expression was investigated by Western blotting and real time PCR. Two PON2 forms, one at 62 kDa and one at 43 kDa were found in all samples. No difference in protein expression of either isoform was found between the three sites in either the labour or non-labour group. At the middle site there was a highly significant decrease in PON2 expression in the labour group when compared to the non-labour group for both the 62 kDa form (p = 0.02) and the 43 kDa form (p = 0.006). No spatial differences were found within placentas at the mRNA level in either labour or non-labour. There was, paradoxically, an increase in PON2 mRNA in the labour group at the middle site only. This is the first report to describe changes in PON2 in the placenta in labour. The physiological and pathological significance of these remains to be elucidated but since PON2 is anti-inflammatory further studies are warranted to understand its role

Le rêve impérial

<p>The graphs show the box and whiskers analysis of the blots. Comparison between zones was performed using Friedman analysis. Graph A, 62; Graph B, 43 kDa isoform 2. NLG non-labour group, LG labour group.</p

Western blots showing PON2 expression in inner, middle and outer zones of three individual placentas (labour group).

<p>Four quadrants were sampled in each zone. A, B and C show the 62 kDa isoform 1. D, E and F show the 43 kDa isoform 2.</p

RQ values for mRNA measurements in inner, middle and outer placental sites within individual placentas.

<p>A non-labour and B labour. Comparison between zones was performed using Friedman analysis.</p

Graphs show median and interquartile range for PON2 isoforms 1 and 2 for the combined 4 quadrants sampled in the inner, middle and outer zones of three different placentas (A, B, C non-labour group) shown in Figure 1.

<p>Comparison between zones was performed using Friedman analysis.</p

Western blots showing PON2 expression in inner, middle and outer zones of three individual placentas (non-labour group).

<p>Four quadrants were sampled in each zone. A, B and C show the 62<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096754#pone-0096754-g001" target="_blank">Figure 1</a>. D, E and F show the 43 kDa isoform 2 for the 3 placentas also shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096754#pone-0096754-g001" target="_blank">Figure 1</a>.</p

Graphs show median and interquartile range for the 4 quadrants sampled in the inner, middle and outer zones of each of the three placentas (labour group) shown in Figure 3.

<p>Comparison between zones was performed using Friedman analysis.</p