Magnesium Sulfate Normalizes Placental Interleukin-6 Secretion in Preeclampsia

Abstract

Interleukin-6 (IL-6) is one of the main proinflammatory mediators of hypertension and endothelial dysfunction in preeclampsia. In this study, we investigated the capacity of the preeclamptic placenta to secrete IL-6 and the effect of magnesium sulfate (MgSO₄) on it. Placentas from normotensive (37–40 weeks) and preeclamptic (36–40 weeks) pregnancies were dually perfused for 6 h in the absence [normotensive (n = 3); preeclamptic (n = 4)] and presence [normotensive (n = 3); preeclamptic (n = 4)] of MgSO₄. Perfusate samples from the maternal and the fetal circulations were collected at each 30 min throughout the perfusion period and examined for IL-6 by enzyme-linked immunoassay. Statistical analysis was performed using the 2-way analysis of variance. In the absence of MgSO₄, IL-6 levels in the maternal and the fetal circulations of preeclamptic placentas (4.2 ± 1.3 and 0.9 ± 0.5 pg/mL/g cotyledon; respectively) were significantly higher, when compared with normotensive placentas (1.9 ± 0.5 and 0.2 ± 0.2 pg/mL/g cotyledon; respectively) (P < 0.05). Addition of MgSO₄ to the perfusate of normotensive placentas did not affect IL-6 secretion. However, exposure of preeclamptic placentas to MgSO₄ resulted in decreased IL-6 levels in the maternal circulations (1.7 ± 0.3 pg/mL/g cotyledon), when compared with the control group (P < 0.05). In the fetal circulation, the addition of MgSO₄ resulted only in a nonstatistical significant tendency toward decreased IL-6 levels, when compared with the control group. Our findings indicate that the perfused preeclamptic placenta secretes increased levels of IL-6 into the fetal and the maternal circulations and that MgSO₄ may normalize these increased secreted IL-6 levels.

Introduction

P reeclampsia is a syndrome unique to human pregnancy, characterized by multiple maternal symptoms including hypertension, proteinuria, and general edema (Redman and Sargent 2005; Sibai and others 2005). Although 5%–7% of pregnancies worldwide are complicated by preeclampsia, its etiology remains undefined (Sibai and others 2003; Zhang and others 2003). Fetal complications of this disorder include low birth weight, prematurity, and death. On the maternal side, they may include renal dysfunction, HELLP syndrome (hemolysis, elevated liver enzymes, and thrombocytopenia), liver failure, cerebral edema with seizures, and rarely death (Mutter and Karumanchi 2008).

The placenta is known to have a key role in the pathogenesis of preeclampsia. The common theory suggests that defective placentation during the first stages of pregnancy triggers placental hypoxia/ischemia and increased released of circulating factors into the maternal circulation, leading to maternal endothelial dysfunction and the onset of the maternal symptoms of preeclampsia (Soleymanlou and others 2005; Mutter and Karumanchi 2008). One of the circulating factors that are believed to be released by the placenta in preeclampsia is proinflammatory cytokines.

Interleukin-6 (IL-6) is one of the main proinflammatory cytokines that are produced by a wide range of immune and nonimmune cells, including monocytes, macrophages, lymphocytes, endothelial cells, and different placental cells (Akira and others 1990; Bowen and others 2002; Holcberg and others 2007). IL-6 expression is upregulated by other proinflammatory cytokines, such as IL-1 and tumor necrosis factor-α (TNF-α), and lipopolysaccharide. IL-6 is active mainly in an endocrinic manner, and its circulating levels are rapidly increased in response to inflammatory conditions. Plasma IL-6 levels reflect the severity as well as the prognosis of the disease (Dinarello and Moldawer 2000; Gosain and Gamelli 2005). IL-6 is one of the proinflammatory cytokines suggested to be involved in the pathogenesis of preeclampsia (Rusterholz and others 2007). The maternal circulating levels of IL-6, which are already more elevated in healthy pregnant women compared with nonpregnant controls, are further raised in patients with preeclampsia (Greer and others 1994; Vince and others 1995; Conrad and others 1998). Recently, we have shown that IL-6 is secreted by the human placenta into the fetal and the maternal circulations during normal pregnancy (Holcberg and others 2007), suggesting a role for placental IL-6 in regulating the maternal immune response during pregnancy. Moreover, IL-6 as well as TNF-α and IL-1 were suggested as potential specific markers for preeclampsia, and they were reported as inducers of endothelial free oxygen radicals, such as H₂O₂ and O₂ ⁻ (Tolando and others 2000). However, the data regarding placental IL-6 expression in preeclampsia remain conflicted. One study showed the placental IL-6 levels to be unchanged in preeclampsia (Benyo and others 2001), whereas another detected decreased placental IL-6 levels in preeclampsia (Kauma and others 1995). Increased IL-6 levels in amniotic fluids of second-trimester pregnancies were detected in women who developed preeclampsia later (Nakabayashi and others 1998). However, others reported no differences in biologically active IL-6 levels in amniotic fluids from preeclamptic pregnancies at delivery (Opsjon and others 1995).

Magnesium sulfate (MgSO₄) is considered as the ideal agent for treatment and prevention of seizures in women with preeclampsia, and it is also used in prophylaxis for preterm delivery (National High blood Pressure Education Program Working Group on High Blood Pressure in Pregnancy 2000; Sibai 2005). In preeclampsia, MgSO₄ provides a number of beneficial effects including blocking of glutamate receptors, vasodilatation of brain small blood vessels (Belfort and Moise 1992), relaxation of vascular smooth muscle and reduction in blood pressure (D'Angelo and others 1992), and maternal systemic vascular resistance (Scardo and others 1995). Recently, we have shown that placental perfusion with MgSO₄ may selectively attenuate angiotensin II (Ang-II) and endothelin-1-induced placental vasoconstriction (Holcberg and others 2004), although the mechanism for this effect remains incompletely defined.

Neonatal neuroprotective effects of MgSO₄ have been suggested by a number of epidemiological studies (Doyle and others 2007). Collective data suggest that exposure to MgSO₄ during pregnancy may reduce neurological morbidities, such as intraventricular hemorrhage and cerebral palsy (CP) in neonates weighing under 1,500 g (Kuban and others 1992; Nelson and Grether 1995). The specific mechanism of action by which MgSO₄ might be neuroprotective remains unclear. However, inflammatory cytokines, including IL-6, have been linked to an increased risk for neuronal morbidities such as CP (Dammann and Leviton 1997; Yoon and others 1997; Nelson and others 1998). Previously we have shown that MgSO₄ may affect IL-6 secretion into the maternal and the fetal circulations of normotensive human placenta, in the presence of Ang-II (Holcberg and others 2006). Together with these data, it is possible to suggest that MgSO₄ may act as a therapeutic agent, or a neuroprotective agent, by affecting placental secretion of proinflammatory cytokines, such as IL-6, into the maternal and the fetal circulations.

Therefore, the aim of this study was to evaluate the secretion levels of IL-6 into the maternal and the fetal circulations of preeclamptic placentas, when compared with normal placentas, and to examine the potential effect of MgSO₄ on the capacity of these placentas to secrete IL-6.

Materials and Methods

Placenta collection

Placentas from term (37–40 weeks) normotensive pregnancies (n = 6) and from preeclamptic (36–40 weeks) pregnancies (n = 8) were collected immediately after vaginal or caesarean deliveries. Preeclampsia was defined as a new onset of hypertension (systolic blood pressure >140 mmHg or diastolic blood pressure >90 mmHg on 2 occasions at least 4 h apart) and proteinuria (2+ or greater on urine dipstick) after 20 weeks of gestation. All preeclamptic placentas were collected at 24–48 h after the onset of preeclampsia. Exclusions include women with preexisting complications such as chronic hypertension, diabetes mellitus, autoimmune, and renal diseases. Women with intrauterine fetal death or women with preterm (<37 weeks of gestation) delivery also were excluded.

Placental perfusion

Three normotensive placentas and 4 preeclamptic placentas were perfused for 6 h with medium alone (control medium); and another 3 normotensive placentas and 4 preeclamptic placentas were perfused for 6 h with medium containing 6–7 mg% of MgSO₄ in the maternal reservoir (equal to the plasma levels of magnesium after maternal administration of standard doses of MgSO₄ for preeclampsia). The perfusion experiments were performed using the method previously described by Holcberg and others (2008), with minor modifications.

Within 15–20 min of delivery, a fetal artery and corresponding vein from an intact cotyledon (lateral cotyledons containing part of the membranes) were cannulated. Following successful establishment of the fetal circulation, the placenta was mounted in a perfusion chamber and the maternal circulation was simulated by placing 4 catheters into the intervillous space of the lobe, corresponding to the isolated perfused cotyledon. Maternal perfusate that returned from the intervillous space was continuously drained by a maternal venous catheter, placed at the lowest level on the maternal decidual surface to avoid significant pooling of perfusate.

Perfusion medium consisted of 2 L of M-199 cell culture medium (M-199 media; Sigma Chemicals), enriched with bovine serum albumin (1 g/L), glucose (1 g/L; Sigma Chemicals), heparin (10 IU/mL; Beit Kama), and gentamycin (40 μg/mL; Teva). The pH of the medium was adjusted to 7.4 with bicarbonate (Sigma Chemicals).

The 2 reservoirs, containing the perfusion medium for the maternal and the fetal circuit, were placed into heated water baths at 37°C and were equilibrated with a prehumidified gas mixture of 95% oxygen and 5% CO₂ in the maternal reservoir and 95% N₂ and 5% CO₂ in the fetal reservoir. Perfusion pressure of 20–40 mmHg, giving a flow rate of 6–8 mL/min in the fetal circulation and 10–12 mL/min in the maternal circulation, was established. The venous return could be recycled into the respective reservoir, giving a closed circuit perfusion.

Perfusate samples from the fetal and the maternal circulations were collected in each experiment every 30 min until the end of the perfusion and stored at −70°C until examined for IL-6 levels by enzyme-linked immunoassay (ELISA). Perfused cotyledon in each placenta was weighed at the end of the perfusion. ELISA results were normalized for gram of perfused cotyledon to minimize the error that may result from variations in perfused cotyledon weights from different placentas.

To minimize the possible effect of labor and/or in vivo exposure to MgSO₄ on placental release of cytokines, each normotensive or preeclamptic placental cotyledon, either after vaginal or caesarean delivery, was perfused for 30 min with lactated ringer's (Hartman solution; Teva Medical), followed by 30 min of perfusion with medium enriched with albumin (1 g/L), glucose (1 g/L), and heparin (10 IU/mL). Subsequently, the perfusion medium in the fetal and the maternal compartments was exchanged with fresh enriched medium.

Validation of placental integrity of each experiment was established throughout the experimental period by ensuring that the rate of perfusate input in both the maternal and the fetal circuits equaled the rate of output, and that histological examination of the cotyledon at the end of each experiment revealed no significant morphological changes.

Examination of collected samples by ELISA

IL-6 levels in the perfusate samples were measured by ELISA, using mouse monoclonal anti-human IL-6 antibodies (first antibodies; Biosource) and mouse monoclonal anti-human IL-6 biotin conjugate antibodies (second antibodies; Biosource). Sensitivity of the kit was <16 pg/mL, and standard curve range was 4–2,000 pg/mL of recombinant human IL-6 (Genzyme Diagnostics).

First antibodies were incubated overnight in 96-well ELISA plates in 4°C, followed by washing and addition of blocking buffer, consisted of 10% fetal calf serum (Beit HaEmek) in phosphate-buffered saline (Beit HaEmek), for 2 h at 37°C. Thereafter, blocking buffer was removed and the samples or recombinant IL-6 were added for 1 h incubation at 37°C. After washing, second antibodies were added and the plates were incubated for additional 1 h at 37°C. Following incubation, the plates were washed and streptavidin horseradish peroxidase was added for 30 min at 37°C. After removal and washing, tetramethyl benzidine (DakoCytomation) was added for 15 min and color development reaction was stopped by addition of 2 N H₂SO₄. Optical absorbance was read using ELISA reader (model 550; Biorad) at 450 nm.

Statistical analysis

Statistical analysis was performed with the SPSS package (SPSS). Continuous parameters were summarized as mean ± standard deviation and examined using the Student's t-test. Categorical parameters were summarized using frequency measures, and statistical analysis was made using the Fisher's exact test. Comparisons of IL-6 levels in normotensive versus preeclamptic and in control groups versus MgSO₄ groups were performed using the 2-way analysis of variance. P < 0.05 was considered statistically significant.

Results

Table 1 summarizes the clinical data of participants. There were no significant statistical differences in maternal age, gravidity and parity, body mass index, and mode of delivery between the normotensive and the preeclamptic groups.

Table 1.

Demographic and Clinical Characteristics and Neonatal Outcomes of Study Subjects

Characteristic	Normotensive ^a	Preeclamptic ^a	P value ^b
Number of cases	6	10
Control group	3	5
MgSO₄ group	3	5
Maternal age (years)	25 ± 4.6	25.4 ± 6	NS
Gravity (No. of pregnancies)	2.3 ± 2	1.5 ± 0.7	NS
Parity (No. of deliveries)	2.3 ± 2	1.1 ± 0.3	NS
Body mass index (kg/m²)	28.6 ± 0.7	31.3 ± 4.5	NS
Mode of delivery (PS^c:CS^d)	6:0	7:3	NS
Gestational age (weeks)	40 ± 1.8	37.3 ± 2.4	P < 0.05
Systolic BP (mmHg)	128.7 ± 8.9	158.6 ± 12.7	P < 0.001
Diastolic BP (mmHg)	75.8 ± 2.7	103.4 ± 9.9	P < 0.001
Proteinuria (urine dipstick)	0	+3	P < 0.001
Neonatal outcome
Newborn weight (g)	3,125 ± 344	2,668 ± 715	NS
Mean Apgar 1	9	8 ± 2.2	NS
Mean Apgar 5	10	9.5 ± 1.1	NS
Umbilical pH	7.30 ± 0.12	7.28 ± 0.07	NS
Placental weight (g)	563 ± 127	532 ± 127	NS
Cotyledon weight (g)	30 ± 6.5	24 ± 6.1	NS

Plus–minus values are mean ± standard deviation.

Statistical analysis between the normotensive and the preeclamptic groups was made using Student's t-test. Categorical parameters were summarized using frequency measures, and statistical analysis was made using Fisher's exact test.

Vaginal delivery.

Cesarean delivery.

Abbreviations: BP, blood pressure; MgSO₄, magnesium sulfate; NS, not significant.

Secretion of IL-6 by perfused human normotensive and preeclamptic placentas

During perfusion with control medium, IL-6 levels in the fetal circulation of preeclamptic placentas increased with time reaching significantly higher IL-6 levels at the end of perfusion (after 6 h) (0.9 ± 0.5 pg/mL/g cotyledon), when compared with IL-6 levels in the fetal circulation of normotensive placentas (0.2 ± 0.2 pg/mL/g cotyledon; P < 0.05) (Fig. 1A). Similarly, IL-6 levels in the maternal circulation of preeclamptic placentas increased with time reaching significantly higher IL-6 levels at the end of perfusion (4.2 ± 1.3 pg/mL/g cotyledon), when compared with IL-6 levels in the maternal circulation of normotensive placentas (1.9 ± 0.5 pg/mL/g cotyledon; P < 0.05) (Fig. 1B).

FIG. 1.

IL-6 levels in the fetal (A) and the maternal (B) circulations of normotensive (n = 3) and preeclamptic (n = 4) placentas after 6 h of perfusion with control medium (without the addition of magnesium sulfate). Results are displayed as mean ± standard deviation; ^* P < 0.05 (2-way analysis of variance). IL-6, interleukin-6.

Further, as shown in Fig. 1A and B, normotensive placentas as well as preeclamptic placentas perfused with control medium secreted significantly increased levels of IL-6 into the maternal circulations, when compared with IL-6 levels in the fetal circulations. In the normotensive placentas, IL-6 levels in the maternal circulation were 1.9 ± 0.5 pg/mL/g cotyledon, when compared with the fetal circulation (0.2 ± 0.2 pg/mL/g cotyledon; P < 0.01), at the end of perfusion. Moreover, IL-6 levels in the maternal circulation of preeclamptic placentas were 4.2 ± 1.3 pg/mL/g cotyledon, when compared with the fetal circulation (0.9 ± 0.5 pg/mL/g cotyledon; P < 0.01), at the end of perfusion (Fig. 1A, B).

Effect of MgSO₄ on IL-6 levels in the fetal and the maternal circulations of perfused human normotensive and preeclamptic placentas

Addition with MgSO₄ into the maternal reservoir of the perfused normotensive placentas did not affect IL-6 secretion levels into the fetal or the maternal circulations (Fig. 2A and B, respectively).

FIG. 2.

IL-6 levels in the fetal (A) and the maternal (B) circulations of normotensive placentas after 6 h of perfusion in the absence (n = 3) or presence (n = 3) of MgSO₄ (6–7 mg%) in the maternal reservoir. Results are displayed as mean ± standard deviation. IL-6, interleukin-6; MgSO₄, magnesium sulfate.

However, exposure of perfused preeclamptic placentas to MgSO₄ differently affected IL-6 secretion levels into the fetal and the maternal circulations (Fig. 3A and B, respectively). In the fetal circulation, a tendency toward decreased secretion levels of IL-6, in the presence of MgSO₄, was detected throughout the perfusion period, although this tendency did not reach statistical significance (Fig. 3A). On the other hand, IL-6 levels in the maternal circulation of preeclamptic placentas were significantly lower in the presence of MgSO₄ (1.7 ± 0.3 pg/mL/g cotyledon), when compared with IL-6 levels in the maternal circulation of the preeclamptic control group (4.2 ± 1.3 pg/mL/g cotyledon; P < 0.05), at the end of perfusion (Fig. 3B).

FIG. 3.

IL-6 levels in the fetal (A) and the maternal (B) circulations of preeclamptic placentas after 6 h of perfusion in the absence (n = 4) or presence (n = 4) of MgSO₄ (6–7 mg%) in the maternal reservoir. Results are displayed as mean ± standard deviation; *P < 0.05 (2-way analysis of variance). IL-6, interleukin-6; MgSO₄, magnesium sulfate.

Further, IL-6 levels detected at the end of perfusion, in the fetal and the maternal circulations of preeclamptic placentas exposed to MgSO₄ (0.5 ± 0.1 and 1.7 ± 0.3 pg/mL/g cotyledon, respectively), were statistically equal to IL-6 levels in the fetal and the maternal circulations of normotensive placentas perfused with control medium (0.2 ± 0.2 and 1.9 ± 0.5 pg/mL/g cotyledon, respectively).

Discussion

In this study, we used the ex vivo placental perfusion model to evaluate the capacity of the human preeclamptic placenta to secrete IL-6, when compared with placentas from normotensive pregnancies. Our results show an increased secretion of IL-6 by the preeclamptic placenta into the maternal and the fetal circulations, compared with that in normotensive placentas. These results indicate that the placenta may contribute, at least partially, to the elevation of circulating IL-6 levels in preeclampsia. Further, these data may confirm the theory about the role of ischemic placenta in maternal endothelial dysfunction and in the onset of clinical manifestations in preeclampsia. Recently, it has been shown that chronic IL-6 infusion into pregnant rats resulted in hypertension and reduced renal function (Gadonski and others 2006).

Nevertheless, our results are in disagreement with other reports regarding decreased/unchanged placental IL-6 production in preeclampsia (Kauma and others 1995; Opsjon and others 1995; Nakabayashi and others 1998; Benyo and others 2001). This contradiction may be a result of differences between methods of cytokine evaluation used in each work, severity of preeclampsia in women included, gestational age, and ethnic and genetic variances. Benyo and others (2001) reported about unchanged placental IL-6 levels in preeclamptic women with gestational age of 28–38 weeks, ignoring possible gestational age-related changes in placental cytokine expression. In contrast, all placentas included in the present study were of 36–40 weeks gestational age and severe preeclamptic pregnancies, compared with other studies that do not take into consideration these data. The difference between the results reported by using biological assays and by using ELISA (such as in the present study) may suggest a possible change in the expression levels of various regulatory factors, such as cytokine-binding proteins, in preeclampsia.

In our previous study (Holcberg and others 2006), we examined the effect of MgSO₄ on IL-6 secretion by Ang-II-induced normotensive placenta. The designed study aimed to examine the effect of Ang-II on the secretion of IL-6 by MgSO₄-perfused placentas. We suggested that Ang-II decreased IL-6 secretion by MgSO₄-perfused placentas. In the present study, we examined the effect of MgSO₄ on the capacity of normotensive and preeclamptic perfused placentas to secrete IL-6. In addition, the 2 studies were conducted under different perfusion conditions and with different protocols, with notable differences such as duration of perfusion, total volume of perfusion media, and total exposure time to MgSO₄. These changes, in the present study, were adapted to preeclamptic placentas, which are more sensitive than normotensive placentas in the perfusion system.

The increased placental secretion of IL-6 into the fetal circulation in preeclampsia, as demonstrated here, may have a special clinical importance as IL-6 is one of the main proinflammatory cytokines that have been linked to neuronal damage in newborns (Dammann and Leviton 1997; Yoon and others 1997; Nelson and others 1998). Therefore, it is possible that the placenta may contribute to the increased risk for neonatal morbidities in preeclampsia, by oversecretion of proinflammatory cytokines, such as IL-6, into the fetal circulation.

The current results indicate that the normotensive as well as the preeclamptic placenta secretes significantly higher levels of IL-6 into the maternal circulation when compared with the fetal circulation. These data demonstrate the pivotal role that the placenta may have in regulating the maternal immune response during normal or pathological pregnancy. These data are also supported by results previously reported by us (Holcberg and others 2007). Therefore, the placenta seems to be an important resource for the elevation in plasma IL-6 during pregnancy (Austgulen and others 1994). Previous studies demonstrated that IL-6 is produced by trophoblasts of the placenta, decidual cells, and epithelial cells and trophoblasts of the fetal membranes, in addition to immune cells (Bowen and others 2002).

It has been suggested that magnesium may improve endothelial function in preeclampsia. This effect of magnesium may be mediated by its direct vasodilator effect, or by its ability to induce the release of endothelial vasodilator factors, such as prostacyclin (Sontia and Touyz 2007). However, an additional manner, by which magnesium may regulate endothelial function, is by anti-inflammatory action (Weglicki and others 1992). In the present study, we demonstrated that exposure of preeclamptic placentas to MgSO₄ during perfusion normalizes placental IL-6 secretion levels into the maternal circulation of these placentas. These data indicate an anti-inflammatory effect of MgSO₄ on preeclamptic placental tissue, suggesting that MgSO₄ may improve maternal endothelial function by preventing the enhanced placental secretion of IL-6 into the maternal circulation.

These findings are supported by previously reported data showing that MgSO₄ downregulates endotoxin-induced IL-8 secretion by amnion and decidual cells (Makhlouf and Simhan 2006). Moreover, MgSO₄ was shown to prevent inflammatory response in human umbilical vein endothelial cells, via downregulation of nuclear factor-kappa B (NF-κB) activity (Rochelson and others 2007). Recently, it was suggested that decreased magnesium levels resulted in increased pro-oxidative level in endothelial cells, a process that is partially mediated by proinflammatory cytokines, such as IL-6 and IL-1 (Wolf and others 2008). Recently, we demonstrated that MgSO₄ may also reduce the capacity of the preeclamptic placenta to secrete TNF-α (Amash and others 2010). Together with our current results, these data suggest that MgSO₄ may induce anti-inflammatory effect on placental tissues by downregulation of NF-κB activity, and in this way it may reduce the secretion of key inflammatory cytokines, such as IL-6 and TNF-α.

In contrast, although the reduction in IL-6 secretion into the fetal circulation of preeclamptic placenta was only tendentious, it is possible to suggest that the anti-inflammatory effect of MgSO₄ may be noticed also in the fetal compartment of the placenta. Consequently, this may explain, at least partially, the epidemiological reports regarding the possible neuroprotective effect of MgSO₄ in newborns (Kuban and others 1992; Nelson and Grether 1995; Doyle and others 2007).

In conclusion, we showed that increased IL-6 levels are secreted by the perfused preeclamptic placenta when compared with normotensive placentas, and that exposure to MgSO₄ may normalize these levels. These data may have a clinical significance while considering the so long discussion about the efficacy and the mechanism of action of MgSO₄ in preeclampsia. Nevertheless, future studies on the effect of MgSO₄ on other cytokines in the placental–maternal interface should be conducted to better understand the mechanism of action by which MgSO₄ may act as a therapeutic agent in hypertensive disorders, such as preeclampsia.

Footnotes

Acknowledgment

This work was partially supported by a grant (no. 80557101) from the Ministry of Health, Jerusalem, Israel.

Author Disclosure Statement

No competing financial interests exist.

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Magnesium Sulfate Normalizes Placental Interleukin-6 Secretion in Preeclampsia

Abstract

Introduction

Materials and Methods

Placenta collection

Placental perfusion

Examination of collected samples by ELISA

Statistical analysis

Results

Secretion of IL-6 by perfused human normotensive and preeclamptic placentas

Effect of MgSO4 on IL-6 levels in the fetal and the maternal circulations of perfused human normotensive and preeclamptic placentas

Discussion

Footnotes

Acknowledgment

Author Disclosure Statement

References

Effect of MgSO₄ on IL-6 levels in the fetal and the maternal circulations of perfused human normotensive and preeclamptic placentas