Induction of Placental Heme Oxygenase-1 Is Protective Against TNFα-induced Cytotoxicity and Promotes Vessel Relaxation

Involvement of the Heme Oxygenase System in the Development of Preeclampsia and as a Possible Therapeutic Target

The enzyme heme oxygenase (HO) is an important regulatory molecule present in most nucleated mammalian cells which functions to break down the pro-oxidant molecule heme into three products, carbon monoxide (CO), biliverdin and free iron. The HO system has been associated with many physiologic functions, including vascular tone, regulation of inflammation and apoptosis, angiogenesis and antioxidant capabilities. Deficiencies in HO are associated with several pregnancy disorders, including preeclampsia. With no present cure, this disorder continues to affect 5–7% of all pregnancies worldwide, leading to maternal and fetal morbidity and mortality. Researchers continue to strive for therapeutic potentials and this review will outline the possible use of the HO/CO system as a target treatment/prevention of preeclampsia in the future.

Tetrabromobisphenol A activates inflammatory pathways in human first trimester extravillous trophoblasts in vitro

Tetrabromobisphenol A (TBBPA) is a widely used flame retardant. Despite the presence of TBBPA in gestational tissues and the importance of proper regulation of inflammatory networks for successful pregnancy, there is no prior study on the effects of TBBPA on inflammatory responses in gestational tissues. The present study aimed to investigate TBBPA activation of inflammatory pathways, specifically cytokine and prostaglandin production, in the human first trimester placental cell line HTR-8/SVneo. TBBPA enhanced release of interleukin (IL)-6, IL-8, and prostaglandin E2 (PGE2), and suppressed TGF-β release in HTR-8/SVneo cells. The lowest effective concentration was 10 μM TBBPA. A commercial immune response PCR array revealed increased expression of genes involved in inflammatory pathways stimulated by TBBPA in HTR-8/SVneo cells. Because proper regulation of inflammatory mediators in the gestational compartment is necessary for normal placental development and successful pregnancy, further investigation on the impact of TBBPA-stimulated responses on trophoblast function is warranted.

Expression of placenta growth factor, soluble fms-like tyrosine kinase-1, metal-responsive transcription factor-1, heme oxygenase 1 and hypoxia inducible factor-1α mRNAs in pre-eclampsia placenta and the effect of pre-eclampsia sera on their expression of choriocarcinoma cells

AIM

We studied the effect of pre-eclampsia sera on the expression of placenta growth factor (PlGF), soluble fms-like tyrosine kinase-1 (sFlt-1), metal-responsive transcription factor-1 (MTF-1), heme oxygenase 1 (HO-1) and hypoxia inducible factor-1α (HIF-1α) mRNAs in JEG-3 cells (trophoblast-derived cells) and placenta from pre-eclampsia patients to investigate pre-eclampsia pathophysiology.

MATERIAL AND METHODS

Placenta and serum samples were taken from pre-eclampsia and normal pregnancy patients. JEG-3 cells were cultured with pre-eclampsia and normal pregnant sera in 24-well tissue culture plates. RNA was purified from placental trophoblast cells and JEG-3 cells 24 h after incubation. The expression of mRNA was measured using real-time polymerase chain reaction.

RESULTS

The expression of sFlt-1 mRNA increased, and that of PlGF and HO-1 mRNA decreased in JEG-3 cells after incubation with pre-eclampsia sera. The expression of PlGF mRNA decreased, and that of sFlt-1mRNA increased in pre-eclampsia placenta. The expression of MTF-1 and HO-1 mRNA decreased. A correlation was found between PlGF mRNA expression and the expression of MTF-1 and HIF-1α mRNA. A correlation between sFlt-1 and HIF-1α mRNA expression was also found.

CONCLUSION

Changes in PlGF mRNA expression in pre-eclampsia placenta may relate to serum factors and the expression of MTF-1 and HIF-α mRNA. Changes in sFlt-1mRNA expression may relate to serum factors and the expression of HIF-α mRNA. We suggest that serum factors play a role in PlGF and sFlt-1 expression in pre-eclampsia placenta.

Increased serum heme oxygenase-1 levels as a diagnostic marker of oxidative stress in preeclampsia

OBJECTIVE

To evaluate the utility of serum biomarkers in the diagnosis of preeclampsia (PE) and also investigate possible correlation with pathogenesis of PE.

METHODS

Maternal serum concentrations of heme oxygenase-1 (HO1) and N-myc downstream-regulated gene 1 (NDRG1) were measured at 27-34 weeks of gestation in a case-control study of 33 pregnant women diagnosed with PE and in 43 normotensive pregnant women without proteinuria. The Mann-Whitney U test and Spearman's correlation were used for statistical analysis.

RESULTS

The median serum HO1 level was found to be significantly higher in the PE group [76.7 ng/ml (23.4-445.7)] than control group [55.9 ng/ml (3.7-354.3)] (p = 0.006). Positive correlation was found between HO1 levels with presence of PE (r = 0.316, p = 0.005). There was no significant difference in NDRG1 values between the two groups (p = 0.226).

CONCLUSIONS

Serum HO1 levels were found to be increased in patients with PE compared with normotensive pregnant women.

The heme oxygenases: important regulators of pregnancy and preeclampsia

The heme oxygenase system has long been believed to act largely as a housekeeping unit, converting prooxidant free heme from heme protein degradation into the benign bilirubin for conjugation and safe excretion. In recent decades, however, heme oxygenases have emerged as important regulators of cardiovascular function, largely through the production of their biologically active metabolites: carbon monoxide, bilirubin, and elemental iron. Even more recently, a number of separate lines of evidence have demonstrated an important role for the heme oxygenases in the establishment and maintenance of pregnancy. Early preclinical and clinical studies have associated defects in the heme oxygenase with the obstetrical complication preeclampsia, as well as failure to establish adequate placental blood flow, an underlying mechanism of the disorder. Several recent preclinical studies have suggested, however, that the heme oxygenase system could serve as a valuable therapeutic tool for the management of preeclampsia, which currently has few pharmacological options. This review will summarize the role of heme oxygenases in pregnancy and highlight their potential in advancing the management of patients with preeclampsia.

Microsatellite polymorphism in the heme oxygenase-1 promoter is associated with nonsevere and late-onset preeclampsia

Preeclampsia is a serious and phenotypically heterogeneous vascular pregnancy disorder. Heme oxygenase-1 (HO-1) is a stress response enzyme that may protect the maternal endothelium and facilitate adequate metabolic adaptation to pregnancy by its antioxidant and anti-inflammatory functions. HO-1 stress response is modulated by HO-1 gene (HMOX1) polymorphisms. Individuals with the long allele of a guanine-thymine (GTn) microsatellite repeat located in the promoter region of HMOX1 have a higher risk of cardiometabolic diseases compared with those with the short allele. We investigated whether the long GTn allele of HMOX1 is associated with subtypes of preeclampsia. The GTn repeat was genotyped in 759 patients and in 779 controls from the Finnish Genetics of Preeclampsia Consortium (FINNPEC) cohort using DNA fragment analysis. In subtype analyses, the long-long (LL) genotype was associated with nonsevere (additive model: odds ratio [OR], 1.94; 95% confidence interval [CI], 1.13-3.31; recessive model: OR, 1.39; 95% CI, 1.02-1.89) and late-onset (additive model: OR, 1.44; 95% CI, 1.02-2.05; recessive model: OR, 1.28; 95% CI, 1.02-1.59) preeclampsia and with preeclampsia without a small-for-gestational-age infant (recessive model: OR, 1.27; 95% CI, 1.02-1.58). The long allele was associated with nonsevere (OR, 1.35; 95% CI, 1.07-1.70) and late-onset (OR, 1.21; 95% CI, 1.03-1.42) preeclampsia and with preeclampsia without a small-for-gestational-age infant (OR, 1.19; 95% CI, 1.02-1.40). Moreover, both the LL genotype and the long allele were associated with preeclampsia in women who had smoked during pregnancy. In conclusion, the GTn long allele seems to predispose to late-onset, less severe form of preeclampsia. This finding supports the role of HO-1 in the pathogenesis of preeclampsia and suggests that the HO-1 pathway may provide a potential target for the treatment of preeclampsia.

Edaravone inhibits hypoxia-induced trophoblast-soluble Fms-like tyrosine kinase 1 expression: a possible therapeutic approach to preeclampsia

OBJECTIVE

To investigate the effects of edaravone, a potent free radical scavenger used clinically, on hypoxia-induced trophoblast-soluble Fms-like tyrosine kinase 1 (sFlt-1) expression.

METHODS

A trophoblast cell line (HRT-8/SVneo) impaired by cobalt chloride (CoCl2) was used as the cell model under hypoxic conditions. 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolium bromide (MTT) was used to measure the viability of cells exposed to CoCl2 and edaravone. The levels of intracellular reactive oxygen species (ROS) were analyzed by flow cytometry. mRNA expression of sFlt-1, vascular endothelial growth factor (VEGF), and placental growth factor (PlGF) in trophoblasts was measured by real-time polymerase chain reaction, and the secretion of sFlt-1, VEGF, and PlGF proteins was analyzed by enzyme-linked immunosorbent assays (ELISAs). A human umbilical vein endothelial cell (HUVEC) tube-formation assay was performed to identify the effects of CoCl2 and edaravone on vascular development.

RESULTS

CoCl2 treatment caused the loss of trophoblast viability, the formation of ROS, and sFlt-1 mRNA and protein expression in a dose-dependent manner. Pretreatment with edaravone significantly inhibited hypoxia-induced oxidative stress formation and sFlt-1 expression in trophoblasts. Neither PlGF nor VEGF mRNA or protein expression was increased by CoCl2. In the in vitro tube formation assay, edaravone showed a protective role in vascular development under hypoxic conditions.

CONCLUSION

This study demonstrated that hypoxia leading to increased sFlt-1 release in trophoblasts may contribute to the placental vascular formation abnormalities observed in preeclampsia and suggested that the free radical scavenger edaravone could be a candidate for the effective treatment of preeclampsia.

Effect of selenium on markers of risk of pre-eclampsia in UK pregnant women: a randomised, controlled pilot trial

Pre-eclampsia is a serious hypertensive condition of pregnancy associated with high maternal and fetal morbidity and mortality. Se intake or status has been linked to the occurrence of pre-eclampsia by our own work and that of others. We hypothesised that a small increase in the Se intake of UK pregnant women of inadequate Se status would protect against the risk of pre-eclampsia, as assessed by biomarkers of pre-eclampsia. In a double-blind, placebo-controlled, pilot trial, we randomised 230 primiparous pregnant women to Se (60 μg/d, as Se-enriched yeast) or placebo treatment from 12 to 14 weeks of gestation until delivery. Whole-blood Se concentration was measured at baseline and 35 weeks, and plasma selenoprotein P (SEPP1) concentration at 35 weeks. The primary outcome measure of the present study was serum soluble vascular endothelial growth factor receptor-1 (sFlt-1), an anti-angiogenic factor linked with the risk of pre-eclampsia. Other serum/plasma components related to the risk of pre-eclampsia were also measured. Between 12 and 35 weeks, whole-blood Se concentration increased significantly in the Se-treated group but decreased significantly in the placebo group. At 35 weeks, significantly higher concentrations of whole-blood Se and plasma SEPP1 were observed in the Se-treated group than in the placebo group. In line with our hypothesis, the concentration of sFlt-1 was significantly lower at 35 weeks in the Se-treated group than in the placebo group in participants in the lowest quartile of Se status at baseline (P= 0·039). None of the secondary outcome measures was significantly affected by treatment. The present finding that Se supplementation has the potential to reduce the risk of pre-eclampsia in pregnant women of low Se status needs to be validated in an adequately powered trial.

Heme oxygenase-1 promotes migration and β-epithelial Na+ channel expression in cytotrophoblasts and ischemic placentas

Preeclampsia is thought to arise from inadequate cytotrophoblast migration and invasion of the maternal spiral arteries, resulting in placental ischemia and hypertension. Evidence suggests that altered expression of epithelial Na(+) channel (ENaC) proteins may be a contributing mechanism for impaired cytotrophoblast migration. ENaC activity is required for normal cytotrophoblast migration. Moreover, β-ENaC, the most robustly expressed placental ENaC message, is reduced in placentas from preeclamptic women. We recently demonstrated that heme oxygenase-1 (HO-1) protects against hypertension in a rat model of placental ischemia; however, whether HO-1 regulation of β-ENaC contributes to the beneficial effects of HO-1 is unknown. The purpose of this study was to determine whether β-ENaC mediates cytotrophoblast migration and whether HO-1 enhances ENaC-mediated migration. We showed that placental ischemia, induced by reducing uterine perfusion suppressed, and HO-1 induction restored, β-ENaC expression in ischemic placentas. Using an in vitro model, we found that HO-1 induction, using cobalt protoporphyrin, stimulates cytotrophoblast β-ENaC expression by 1.5- and 1.8-fold (10 and 50 μM). We then showed that silencing of β-ENaC in cultured cytotrophoblasts (BeWo cells), by expression of dominant-negative constructs, reduced migration to 56 ± 13% (P < 0.05) of control. Importantly, HO-1 induction enhanced migration (43 ± 5% of control, P < 0.05), but the enhanced migratory response was entirely blocked by ENaC inhibition with amiloride (10 μM). Taken together, our results suggest that β-ENaC mediates cytotrophoblast migration and increasing β-ENaC expression by HO-1 induction enhances migration. HO-1 regulation of cytotrophoblast β-ENaC expression and migration may be a potential therapeutic target in preeclamptic patients.

Therapeutic potential of statins and the induction of heme oxygenase-1 in preeclampsia

Heme oxygenase (Hmox) is an endogenous system that offers protection against placental cytotoxic damage associated with preeclampsia. The Hmox1/carbon monoxide (CO) pathway inhibits soluble Flt-1 (sFlt-1) and soluble Endoglin (sEng). More importantly, statins induce Hmox1 and suppress the release of sFlt-1 and sEng; thus, statins and Hmox1 activators are potential novel therapeutic agents for treating preeclampsia. The contribution of the Hmox system to the pathogenesis of preeclampsia has been further indicated by the incidence of preeclampsia being reduced by a third in smokers, who had reduced levels of circulating sFlt-1. Interestingly, preeclamptic women exhale less CO compared with women with healthy pregnancies. Hmox1 is reduced prior to the increase in sFlt-1 as Hmox1 mRNA expression in the trophoblast is decreased in the first trimester in women who go on to develop preeclampsia. Induction of Hmox1 or exposure to CO or bilirubin has been shown to inhibit the release of sFlt-1 and sEng in animal models of preeclampsia. The functional benefit of statins and Hmox1 induction in women with preeclampsia is valid not only because they inhibit sFlt-1 release, but also because statins and Hmox1 are associated with anti-apoptotic, anti-inflammatory, and anti-oxidant properties. The StAmP trial is the first randomized control trial (RCT) evaluating the use of pravastatin to ameliorate severe preeclampsia. This proof-of-concept study will pave the way for future global RCT, the success of which will greatly contribute to achieving the United Nations Millennium Development Goals (MDG4 and MDG5) and offering an affordable and easily accessible therapy for preeclampsia.

Recent insights into the pathophysiology of preeclampsia

Preeclampsia, characterized by new-onset gestational hypertension and proteinuria, is a common and serious complication of pregnancy. Evidence from both animal and human studies has implicated placental ischemia and hypoxia as a central causative factor in the etiology of the disorder. The ischemic placenta in turn initiates a cascade of secondary effector mechanisms, including altered proangiogenic and antiangiogenic factor balance, increase in maternal oxidative stress and endothelial and immunological dysfunction. The full elucidation of these mechanisms will hopefully lead to a more complete understanding of the etiology of preeclampsia and lead to successful therapeutic intervention through the targeted disruption of new and novel pathways.

Carbon monoxide promotes proliferation of uterine natural killer cells and remodeling of spiral arteries in pregnant hypertensive heme oxygenase-1 mutant mice

Heme Oxygenase-1 (HO-1) and its metabolite carbon monoxide (CO) promote implantation and placentation. Pregnancy disorders such as preeclampsia and intrauterine growth restriction are linked to both HO-1 diminution and impaired remodeling of maternal spiral arteries (SAs). Here, we investigated whether CO is able to prevent preeclampsia and intrauterine growth restriction through the modulation of uterine natural killer (uNK) cells that are necessary for initiation of SA remodeling. Hmox1(+/-) or Hmox1(-/-) implantations presented fewer uNK cell numbers and lower expression of uNK-related angiogeneic factors compared with Hmox1(+/+) sites. Quantitative histology revealed that Hmox1(+/-) and Hmox1(-/-) implantations had shallow SA development that was accompanied by intrauterine growth restriction and gestational hypertension. Application of CO at low dose during early to midgestation prevented intrauterine growth restriction in Hmox1(+/-) mothers, this being associated with enhanced in situ proliferation of uNK cells and normalization of angiogenic parameters. Most importantly, CO improved SA remodeling and normalized blood pressure, ensuring a proper fetal growth. Thus, CO emerges as a key molecular player in pregnancy success by modulating uNK cells, which results in promotion of SA remodeling, adequate fetal support/growth, and prevention of hypertension.

VEGFR-1, Bcl-2, and HO-1 Ratios in Pregnant Women With Hypertension

BACKGOUND/AIM

Preeclampsia (PE) is a multisystem disease resulting in high maternal-fetal morbidity and mortality. The aim of the study was to investigate antiangiogenesis-associated alterations in antiapoptotic and antioxidative proteins in PE.

METHOD

Of the 46 patients with PE, 25 (54.3%) were with gestational hypertension (GH), 12 (26%) were with mild, and 9 (19.5%) were with severe PE. The serum levels of vascular endothelial growth factor receptor 1 (VEGFR-1), heme oxygenase 1 (HO-1), and B-cell lymphoma/leukemia (Bcl-2) levels were measured by enzyme-linked immunosorbent assay.

RESULTS

In the severe PE group, the VEGFR-1 serum levels (27.3 ± 16.8 vs 13.3 ± 10.7 ng/mL, P = .023) were higher, but the Bcl-2 levels (1.5 ± 0.2 vs 2.1 ± 1.7 ng/mL, P = .047) were lower than the levels in the GH-mild PE group (P = .047). Also, VEGFR-1/Bcl-2 ratio in the severe PE group was significantly higher (P = .003) than the ratio in the GH-mild PE group.

CONCLUSION

The Bcl-2 and HO-1 proteins seem to have important roles in the antiangiogenic environment of preeclampsia.

Heme oxygenase in pregnancy and preeclampsia

PURPOSE OF REVIEW

Emerging evidence supports an important role for the heme oxygenase system in the maintenance of a healthy pregnancy. This review attempts to collect these wide-ranging data and summarize the recent progress in the field.

RECENT FINDINGS

New studies looking at heme oxygenase depletion in a variety of animal models have demonstrated that the heme oxygenase system is an important regulator of placental development, particularly in vascular structure. Furthermore, emerging studies demonstrate a role for heme oxygenase in the maintenance of pregnancy, especially during pathological challenge. Intriguingly, it now appears that the heme oxygenase system can be dramatically altered by pathological disorders of pregnancy, in particular preeclampsia, perhaps functionally in the symptomatic phase of the disorder. Promisingly, however, recent data suggest that induction of the heme oxygenase system, or administration of its bioactive metabolites, could provide a promising novel therapeutic approach to the management of this currently untreatable disease.

SUMMARY

Long considered a molecular housekeeping system, the heme oxygenase system is now known to be an important stress response pathway. New evidence suggests that it is also an important player in pregnancy and preeclampsia. However, the evidence now also suggests that it may provide a therapeutic approach for this common disease with few management options.

Pathophysiology of hypertension in pre-eclampsia: a lesson in integrative physiology

Despite being one of the leading causes of maternal death and a major contributor of maternal and perinatal morbidity, the mechanisms responsible for the pathogenesis of pre-eclampsia have yet to be fully elucidated. However, it is evident that this is a complex disorder involving multiple organ systems, and by using integrative approaches, enormous progress has been made towards understanding the pathophysiology of pre-eclampsia. Growing evidence supports the concept that the placenta plays a central role in the pathogenesis of pre-eclampsia and that reduced uteroplacental perfusion, which develops as a result of abnormal cytotrophoblast invasion of spiral arterioles, triggers the cascade of events leading to the maternal disorder. Placental ischaemia leads to release of soluble placental factors, many of which are classified as anti-angiogenic or pro-inflammatory. Once these ischaemic placental factors reach the maternal circulation, they cause widespread activation and dysfunction of the maternal vascular endothelium that results in enhanced formation of endothelin-1 and superoxide, increased vascular sensitivity to angiotensin II and decreased formation of vasodilators such as nitric oxide. This review highlights these links between placental ischaemia, maternal endothelial activation and renal dysfunction in the pathogenesis of hypertension in pre-eclampsia.

Heme oxygenase inhibition increases blood pressure in pregnant rats

BACKGROUND

During normal gestation, the placenta is a relatively hypoxic organ and, as such, is subject to significant oxidative stress. In the preeclamptic patient, inadequate remodeling of the maternal vasculature severely exacerbates placental oxidative stress, which has been shown to be an important component of maternal hypertension. There is emerging evidence that Heme Oxygenase-1 (HO-1) acts as an important regulator of placental and cardiovascular function during normal pregnancy. Here, we have examined the effect of Heme Oxygenase (HO) inhibition in late gestation on maternal blood pressure, angiogenic balance, and placental oxidative stress in pregnant rats.

METHODS

HO activity was inhibited with tin mesoporphyrin (SnMP), which was administered on gestational day 14, and blood pressure was measured on gestational day 19. Placental angiogenic balance and plasma Vascular Endothelial Growth Factor (VEGF) were determined by sandwich enzyme-linked immunosorbent assay. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity was measured by lucigenin chemilluminescence.

RESULTS

In response to SnMP treatment, maternal mean arterial pressure (MAP) was significantly increased (99±1 vs. 113±2mm Hg; P < 0.05; n = 15 per group). Placental soluble fms-like tyrosine kinase-1 (sFlt-1) (631±47 vs. 648±26 pg/mg; P = 0.76) levels in the placenta were not affected by HO inhibition. Additionally, there was no significant difference in free VEGF in the maternal circulation (287±22 vs. 329±14 pg/ml; P = 0.11). There was, however, a significant decrease in placental VEGF (23±2 vs. 16±1 pg/mg; P < 0.05) and a significant increase in placental NADPH oxidase activity in SnMP-treated rats (2021±238 vs. 3005±301 RLU/min/mg; P < 0.05).

CONCLUSIONS

Our results demonstrate that HO is an important regulator of blood pressure and an important antioxidant in the developing placenta.

HO-1 as modulator of the innate immune response in pregnancy

PROBLEM

The immune modulatory effect of heme oxygenase-1 (HO-1) is well documented in studies about sepsis and transplantation. This work evaluates the influence of HO-1 on the innate immune response during pregnancy.

METHOD OF STUDY

Human first-trimester trophoblasts derived from normal pregnancies or spontaneous abortions were analyzed for their basal HO-1, BCL-associated athanogene-1 (Bag-1), and cytokine production before and after LPS treatment. In vivo, pregnant Hmox1+/+ and Hmox1+/- female mice were treated with LPS, and the production of Bag-1 was evaluated.

RESULTS

Human trophoblasts up-regulated the expression of both HO-1 and pro-inflammatory cytokines after LPS treatment, whereas the basal level of HO-1 was higher in normal pregnancies. In vivo, HO-1 deficiency provoked diminished Bag-1 level upon LPS treatment.

CONCLUSION

HO-1 deficiency causes an inflammatory immune reaction and diminished expression of protective molecules in trophoblasts. Thus, HO-1 emerges as one important modulator of innate immune responses in pregnancy.

Carbon monoxide: present and future indications for a medical gas

Gaseous molecules continue to hold new promise in molecular medicine as experimental and clinical therapeutics. The low molecular weight gas carbon monoxide (CO), and similar gaseous molecules (e.g., H2S, nitric oxide) have been implicated as potential inhalation therapies in inflammatory diseases. At high concentration, CO represents a toxic inhalation hazard, and is a common component of air pollution. CO is also produced endogenously as a product of heme degradation catalyzed by heme oxygenase enzymes. CO binds avidly to hemoglobin, causing hypoxemia and decreased oxygen delivery to tissues at high concentrations. At physiological concentrations, CO may have endogenous roles as a signal transduction molecule in the regulation of neural and vascular function and cellular homeostasis. CO has been demonstrated to act as an effective anti-inflammatory agent in preclinical animal models of inflammation, acute lung injury, sepsis, ischemia/reperfusion injury, and organ transplantation. Additional experimental indications for this gas include pulmonary fibrosis, pulmonary hypertension, metabolic diseases, and preeclampsia. The development of chemical CO releasing compounds constitutes a novel pharmaceutical approach to CO delivery with demonstrated effectiveness in sepsis models. Current and pending clinical evaluation will determine the usefulness of this gas as a therapeutic in human disease.

Nitric oxide and carbon monoxide production and metabolism in preeclampsia

OBJECTIVE

To elucidate the regulation of the nitric oxide (NO) and carbon monoxide (CO) pathways in preeclampsia and to evaluate the ratio of asymmetric dimethylarginine (ADMA) to symmetric dimethylarginine (SDMA) as a marker for preeclampsia.

METHODS

Maternal plasma and placental samples were obtained from 20 participants with preeclampsia and 23 controls. Enzyme-linked immunosorbent assay was used to measure plasma NO, ADMA, and SDMA as well as placental NO and hemeoxygnase 1 (HO-1). Western blot was used to measure placental dimethylarginine dimethylaminotransferases (DDAH-I and DDAH-II).

RESULTS

Placental DDAH-I, placental DDAH-II, placental NO, and placental HO-1 were significantly decreased in participants with preeclampsia. While ADMA and SDMA levels were decreased in preeclampsia, the ADMA-SDMA ratio was not significantly different.

CONCLUSIONS

Decreased DDAH and HO with preeclampsia suggest that they are important points in the regulatory pathways of NO and CO production that are altered in preeclampsia. The ADMA-SDMA ratio is not a useful test for preeclampsia.

A deficiency in haem oxygenase-1 induces foetal growth restriction by placental vasculature defects

Haem oxygenase-1 (HO-1), the rate-limiting enzyme in haem degradation, plays a role in angiogenesis and vasculogenesis and is highly expressed in the placenta. Deficiencies in HO-1 are associated with several pregnancy disorders, such as recurrent miscarriages and pre-eclampsia. The unique combination of tissue protective, smooth muscle relaxing and angiogenesis regulatory properties makes HO-1 a key player in the maintenance of a healthy pregnancy through a direct effect on placental structural and vascular development, thus affecting foetal development.

CONCLUSION

  Therefore, we conclude that HO-1 plays an important role in placental vasculature development and a deficiency in HO-1 may contribute to pregnancy complications, such as pre-eclampsia, spontaneous abortions and premature births.

Is inflammation the cause of pre-eclampsia?

It has been proposed that either excessive inflammation or an imbalance in angiogenic factors cause pre-eclampsia. In the present review, the arguments for and against the role of inflammation and/or angiogenic imbalance as the cause of pre-eclampsia are discussed on the basis of the Bradford–Hill criteria for disease causation. Although both angiogenic imbalance and systemic inflammation are implicated in pre-eclampsia, the absence of temporality of inflammatory markers with pre-eclampsia challenges the concept that excessive inflammation is the cause of pre-eclampsia. In contrast, the elevation of anti-angiogenic factors that precede the clinical signs of pre-eclampsia fulfils the criterion of temporality. The second most important criterion is the dose–response relationship. Although such a relationship has not been proven between pro-inflammatory cytokines and pre-eclampsia, high levels of anti-angiogenic factors have been shown to correlate with increased incidence and disease severity, hence satisfying this condition. Finally, as the removal of circulating sFlt-1 (soluble Fms-like tyrosine kinase receptor-1) from pre-eclamptic patients significantly improves the clinical outcome, it fulfils the Hill's experiment principle, which states that removal of the cause by an appropriate experimental regimen should ameliorate the condition. In contrast, treatment with high doses of corticosteroid fails to improve maternal outcome in pre-eclampsia, despite suppressing inflammation. Inflammation may enhance the pathology induced by the imbalance in the angiogenic factors, but does not by itself cause pre-eclampsia. Development of therapies based on the angiogenic and cytoprotective mechanisms seems more promising.

Resveratrol inhibits the release of soluble fms-like tyrosine kinase (sFlt-1) from human placenta

OBJECTIVE

Soluble vascular endothelial growth factor receptor-1 (also know as soluble fms-like tyrosine kinase [sFlt]-1) is a key causative factor of preeclampsia. Resveratrol, a plant phytoalexin, has antiinflammatory and cardioprotective properties. We sought to determine the effect of resveratrol on sFlt-1 release.

STUDY DESIGN

Human umbilical vein endothelial cells, transformed human trophoblast-8 (HTR/SVneo)-8/SVneo trophoblast cells, or placental explants were incubated with cytokines and/or resveratrol. Conditioned media were assayed for sFlt-1 by enzyme-linked immunosorbent assay and cell proteins used for Western blotting.

RESULTS

Resveratrol inhibited cytokine-induced release of sFlt-1 from normal placental explants and from preeclamptic placental explants. Preincubation of human umbilical vein endothelial cells or HTR-8/SVneo cells with resveratrol abrogated sFlt-1 release. Resveratrol prevented the up-regulation of early growth response protein-1 (Egr-1), a transcription factor necessary for induction of the vascular endothelial growth factor receptor-1 gene and caused up-regulation of heme oxygenase-1, a cytoprotective enzyme found to be dysfunctional in preeclampsia.

CONCLUSION

In summary, resveratrol can inhibit sFlt-1 release and up-regulate heme oxygenase-1; thus, may offer therapeutic potential in preeclampsia.

Evidence Implicating Peroxisome Proliferator-Activated Receptor-γ in the Pathogenesis of Preeclampsia

Preeclampsia, a major cause of maternal and perinatal mortality and morbidity, is thought to be attributed, in part, to impaired trophoblast invasion. Peroxisome proliferator-activated receptors are ligand-activated transcription factors expressed in trophoblasts, which regulate the expression of a number of genes involved in cell differentiation and proliferation. We investigated the effect of the administration of a peroxisome proliferator-activated receptor-γ antagonist during uncomplicated pregnancy in rats. Using an intraperitoneal miniosmotic pump, healthy pregnant rats were administered either vehicle or the peroxisome proliferator-activated receptor-γ–specific antagonist, T0070907 (1 mg/kg per day from gestational days 11–15). Rats treated with T0070907 developed key features of preeclampsia, including elevated mean arterial blood pressure, proteinuria, endothelial dysfunction, reduced pup weight, and increased platelet aggregation. T0070907-treated rats had reduced plasma vascular endothelial growth factor and increased plasma soluble fms-like tyrosine kinase 1. Furthermore, increases in total placental soluble fms-like tyrosine kinase 1 mRNA and fms-like tyrosine kinase 1 protein were also demonstrated, suggesting the placenta as the main contributor to the increased circulating levels of soluble fms-like tyrosine kinase 1. The labyrinthine trophoblast in the placentas of T0070907-treated rats were less differentiated, had increased cellular proliferation, and were strongly immunopositive for CD-31 staining, indicating adaptive angiogenesis. The present study suggests that peroxisome proliferator-activated receptor-γ may play a pivotal role in the progression of a healthy pregnancy and may critically regulate the risk of preeclampsia. These findings have important implications regarding the underlying etiology of preeclampsia and potential therapeutic targets.

Haem oxygenase-1 dictates intrauterine fetal survival in mice via carbon monoxide

Pregnancy establishment implies the existence of a highly vascularized and transient organ, the placenta, which ensures oxygen supply to the fetus via haemoproteins. Haem metabolism, including its catabolism by haem oxygenase-1 (HO-1), should be of importance in maintaining the homeostasis of haemoproteins and controlling the deleterious effects associated with haem release from maternal or fetal haemoglobins, thus ensuring placental function and fetal development. We demonstrate that HO-1 expression is essential to promote placental function and fetal development, thus determining the success of pregnancy. Hmox1 deletion in mice has pathological consequences for pregnancy, namely suboptimal placentation followed by intrauterine fetal growth restriction (IUGR) and fetal lethality. These pathological effects can be mimicked by administration of exogenous haem in wild-type mice. Fetal and maternal HO-1 is required to prevent post-implantation fetal loss through a mechanism that acts independently of maternal adaptive immunity and hormones. The protective HO-1 effects on placentation and fetal growth can be mimicked by the exogenous administration of carbon monoxide (CO), a product of haem catabolism by HO-1 that restores placentation and fetal growth. In a clinical relevant model of IUGR, CO reduces the levels of free haem in circulation and prevents fetal death. We unravel a novel physiological role for HO-1/CO in sustaining pregnancy which aids in understanding the biology of pregnancy and reveals a promising therapeutic application in the treatment of pregnancy pathologies.

Loss of Akt activity increases circulating soluble endoglin release in preeclampsia: identification of inter-dependency between Akt-1 and heme oxygenase-1

AIMS

Endothelial dysfunction is a hallmark of preeclampsia. Desensitization of the phosphoinositide 3-kinase (PI3K)/Akt pathway underlies endothelial dysfunction and haeme oxygenase-1 (HO-1) is decreased in preeclampsia. To identify therapeutic targets, we sought to assess whether these two regulators act to suppress soluble endoglin (sEng), an antagonist of transforming growth factor-β (TGF-β) signalling, which is known to be elevated in preeclampsia.

METHODS AND RESULTS

Vascular endothelial growth factor-A (VEGF-A), fibroblast growth factor (FGF-2), angiopoietin-1 (Ang-1), and insulin, which all activate the PI3K/Akt pathway, inhibited the release of sEng from endothelial cells. Inhibition of the PI3K/Akt pathway, by overexpression of phosphatase and tensin homolog (PTEN) or a dominant-negative isoform of Akt (Akt(dn)) induced sEng release from endothelial cells and prevented the inhibitory effect of VEGF-A. Conversely, overexpression of a constitutively active Akt (Akt(myr)) inhibited PTEN and cytokine-induced sEng release. Systemic delivery of Akt(myr) to mice significantly reduced circulating sEng, whereas Akt(dn) promoted sEng release. Phosphorylation of Akt was reduced in preeclamptic placenta and this correlated with the elevated level of circulating sEng. Knock-down of Akt using siRNA prevented HO-1-mediated inhibition of sEng release and reduced HO-1 expression. Furthermore, HO-1 null mice have reduced phosphorylated Akt in their organs and overexpression of Akt(myr) failed to suppress the elevated levels of sEng detected in HO-1 null mice, indicating that HO-1 is required for the Akt-mediated inhibition of sEng.

CONCLUSION

The loss of PI3K/Akt and/or HO-1 activity promotes sEng release and positive manipulation of these pathways offers a strategy to circumvent endothelial dysfunction.

Induction of heme oxygenase 1 attenuates placental ischemia-induced hypertension

Recent in vitro studies have reported that heme oxygenase 1 (HO-1) downregulates the angiostatic protein soluble fms-like tyrosine kinase 1 from placental villous explants and that the HO-1 metabolites CO and bilirubin negatively regulate endothelin 1 and reactive oxygen species. Although soluble fms-like tyrosine kinase 1, endothelin 1, and reactive oxygen species have been implicated in the pathophysiology of hypertension during preeclampsia and in response to placental ischemia in pregnant rats, it is unknown whether chronic induction of HO-1 alters the hypertensive response to placental ischemia. The present study examined the hypothesis that HO-1 induction in a rat model of placental ischemia would beneficially affect blood pressure, angiogenic balance, superoxide, and endothelin 1 production in the ischemic placenta. To achieve this goal we examined the effects of cobalt protoporphyrin, an HO-1 inducer, in the reduced uterine perfusion pressure (RUPP) placental ischemia model and in normal pregnant rats. In response to RUPP treatment, mean arterial pressure increases 29 mm Hg (136±7 versus 106±5 mm Hg), which is significantly attenuated by cobalt protoporphyrin (118±5 mm Hg). Although RUPP treatment causes placental soluble fms-like tyrosine kinase 1/vascular endothelial growth factor ratios to alter significantly to an angiostatic balance (1.00±0.10 versus 1.27±0.20), treatment with cobalt protoporphyrin causes a significant shift in the ratio to an angiogenic balance (0.68±0.10). Placental superoxide increased in RUPP (952.5±278.8 versus 243.9±70.5 relative light units/min per milligram) but was significantly attenuated by HO-1 induction (482.7±117.4 relative light units/min per milligram). Also, the preproendothelin message was significantly increased in RUPP, which was prevented by cobalt protoporphyrin. These data indicate that HO-1, or its metabolites, is a potential therapeutic for the treatment of preeclampsia.

A transcriptional profile of the decidua in preeclampsia

OBJECTIVE

We sought to obtain insight into possible mechanisms underlying preeclampsia using genomewide transcriptional profiling in decidua basalis.

STUDY DESIGN

Genomewide transcriptional profiling was performed on decidua basalis tissue from preeclamptic (n = 37) and normal (n = 58) pregnancies. Differentially expressed genes were identified and merged into canonical pathways and networks.

RESULTS

Of the 26,504 expressed transcripts detected, 455 were differentially expressed (P < .05; false discovery rate, P < .1). Both novel (ARL5B, SLITRK4) and previously reported preeclampsia-associated (PLA2G7, HMOX1) genes were identified. Pathway analysis revealed that tryptophan metabolism, endoplasmic reticulum stress, linoleic acid metabolism, notch signaling, fatty acid metabolism, arachidonic acid metabolism, and NRF2-mediated oxidative stress response were overrepresented canonical pathways.

CONCLUSION

In the present study single genes, canonical pathways, and gene-gene networks that are likely to play an important role in the pathogenesis of preeclampsia have been identified. Future functional studies are needed to accomplish a greater understanding of the mechanisms involved.

Maternal serum levels of TNF-alpha and IL-6 long after delivery in preeclamptic and normotensive pregnant women

AIM

To evaluate maternal TNF-alpha and IL-6 plasma levels in normotensive pregnant women, women with preeclampsia, and to examine the temporal changes in their levels from the antepartum to the postpartum period correlated with the regression of preeclampsia.

METHOD

A prospective study was performed in the 2nd Department of Obstetrics and Gynecology, University of Athens. Blood samples were obtained: (1) antepartum at the time of clinical diagnosis of the syndrome, 2. 12-14 weeks postpartum.

RESULTS

No statistically significant differences were found in IL-6 levels, whereas a difference was found in TNF-alpha levels between preeclamptic and controls in antepartum period (0.80 pg/ml versus 0.60 pg/ml, P : .04). Long after delivery, TNF-alpha levels were significantly higher in preeclamptic compared to normotensive controls (0.86 pg/ml versus 0.60 pg/ml, P : .004). No difference was observed in TNF-alpha before and after delivery in both groups. No difference was noticed in IL-6 levels in women of normotensive group long after delivery compared to that before delivery. Long after delivery IL-6 levels were statistically significant higher in preeclamptic women compared to normal controls (3.53 ± 0.52 pg/ml versus 1.69 ± 0.48 pg/ml, P : .02).

CONCLUSION

Preeclamptic women remain under a status of increased inflammatory stress up to 12-14 weeks postpartum despite the fact that all the other signs of preeclampsia are resolved.

The origin of pre-eclampsia: from decidual "hyperoxia" to late hypoxia

Normal gestation implants on a relatively hypoxic deciduas so that trophoblast deeply invades endometrium and angiogenesis seeks for oxygen supply. If implantation occurs before those hypoxic conditions occur, trophoblast invasion is defective, due to the relatively high oxygen tension in the decidual environment, laying the foundations for subsequent pre-eclampsia.

Angiotensin receptor agonistic autoantibody-mediated tumor necrosis factor-alpha induction contributes to increased soluble endoglin production in preeclampsia

BACKGROUND

Preeclampsia is a prevalent life-threatening hypertensive disorder of pregnancy. The circulating antiangiogenic factor, soluble endoglin (sEng), is elevated in the blood circulation of women with preeclampsia and contributes to disease pathology; however, the underlying mechanisms responsible for its induction in preeclampsia are unknown.

METHODS AND RESULTS

Here, we discovered that a circulating autoantibody, the angiotensin receptor agonistic autoantibody (AT(1)-AA), stimulates sEng production via AT(1) angiotensin receptor activation in pregnant mice but not in nonpregnant mice. We subsequently demonstrated that the placenta is a major source contributing to sEng induction in vivo and that AT(1)-AA-injected pregnant mice display impaired placental angiogenesis. Using drug screening, we identified tumor necrosis factor-alpha as a circulating factor increased in the serum of autoantibody-injected pregnant mice contributing to AT(1)-AA-mediated sEng induction in human umbilical vascular endothelial cells. Subsequently, among all the drugs screened, we found that hemin, an inducer of heme oxygenase, functions as a break to control AT(1)-AA-mediated sEng induction by suppressing tumor necrosis factor-alpha signaling in human umbilical vascular endothelial cells. Finally, we demonstrated that the AT(1)-AA-mediated decreased angiogenesis seen in human placenta villous explants was attenuated by tumor necrosis factor-alpha-neutralizing antibodies, soluble tumor necrosis factor-alpha receptors, and hemin by abolishing both sEng and soluble fms-like tyrosine kinase-1 induction.

CONCLUSIONS

Our findings demonstrate that AT(1)-AA-mediated tumor necrosis factor-alpha induction, by overcoming its negative regulator, heme oxygenase-1, is a key underlying mechanism responsible for impaired placental angiogenesis by inducing both sEng and soluble fms-like tyrosine kinase-1 secretion from human villous explants. Our results provide important new targets for diagnosis and therapeutic intervention in the management of preeclampsia.

Interleukin-10 reduces inflammation, endothelial dysfunction, and blood pressure in hypertensive pregnant rats

Hypertensive disorders of pregnancy are characterized by systemic and placental inflammation; however, treatment for these conditions has remained elusive. We tested whether administration of the anti-inflammatory cytokine interleukin-10 (IL-10) during pregnancy would attenuate the hypertension, endothelial dysfunction, proteinuria, and inflammation seen in pregnant DOCA/saline-treated (PDS) rats. Normal pregnant (NP) rats and PDS were given daily intraperitoneal injections of recombinant IL-10 from gestational day 13 until death on day 20. Systolic blood pressure, aortic endothelium-dependent relaxation responses, and urinary protein excretion were measured on days 13 and 20 of gestation. Fetal number and development, plasma endothelin-1 levels, serum and placental levels of IFNgamma and IL-10, and aortic and placental levels of platelet endothelial cell adhesion molecule (PECAM) were assessed on gestational day 20. Systolic blood pressure, aortic endothelial dysfunction, and urinary protein excretion were significantly increased at gestational day 13 in PDS rats. However, all of these were restored to NP levels following IL-10 treatment in PDS rats. IL-10 treatment also significantly increased the number of pups per litter in PDS rats and did not further affect fetal development. The beneficial effects of IL-10 in PDS rats were likely mediated by the decreased plasma levels of endothelin-1, decreased levels of circulating and placental IFNgamma, as well as decreased aortic and placental expression of PECAM. These data demonstrate that exogenous IL-10 can normalize blood pressure and endothelial function in pregnancy-induced hypertensive rats and may be beneficial in women with hypertensive disorders of pregnancy.

Can the biology of VEGF and haem oxygenases help solve pre-eclampsia?

Pre-eclampsia, a pregnancy-specific multi-organ syndrome characterized by widespread endothelial damage, is a new risk factor for cardiovascular disease. No therapies exist to prevent or treat this condition, even to achieve a modest improvement in pregnancy length or birth weight. Co-administration of soluble VEGFR-1 [VEGF (vascular endothelial growth factor) receptor-1; more commonly known as sFlt-1 (soluble Fms-like tyrosine kinase-1)] and sEng (soluble endoglin) to pregnant rats elicits severe pre-eclampsia-like symptoms. These two anti-angiogenic factors are increased dramatically prior to the clinical onset of pre-eclampsia and are quite possibly the ‘final common pathway’ responsible for the accompanying signs of hypertension and proteinuria as they can be reversed by VEGF administration in animal models. HO-1 (haem oxygenase-1), an anti-inflammatory enzyme, and its metabolite, CO (carbon monoxide), exert protective effects in several organs against oxidative stimuli. In a landmark publication, we showed that the HO-1 pathway inhibits sFlt-1 and sEng in cultured cells and human placental tissue explants. Both CO and NO (nitric oxide) promote vascular homoeostasis and vasodilatation, and activation of VEGFR-1 or VEGFR-2 induced eNOS (endothelial nitric oxide synthase) phosphorylation, NO release and HO-1 expression. Our studies established the HO-1/CO pathway as a negative regulator of cytokine-induced sFlt-1 and sEng release and eNOS as a positive regulator of VEGF-mediated vascular morphogenesis. These findings provide compelling evidence for a protective role of HO-1 in pregnancy and identify it as a target for the treatment of pre-eclampsia. Any agent that is known to up-regulate HO-1, such as statins, may have potential as a therapy. Any intervention achieving even a modest prolongation of pregnancy or amelioration of the condition could have a significant beneficial health impact worldwide.

Cellular mRNA expressions of anti-oxidant factors in the blood of preeclamptic women

OBJECTIVE

To assess the alterations of mRNA expressions associated with oxidative stress in the cellular component of blood from pregnant women with pre-eclampsia.

METHODS

Peripheral blood samples were obtained from pregnant women with and without pre-eclampsia. Cellular RNA was subjected to a reverse transcription polymerase chain reaction (PCR) assay in order to examine the mRNA distribution among women with pre-eclampsia (n = 24) and control subjects (n = 24) during 35-41 weeks of gestation. The data were analyzed by non-parametric statistics.

RESULTS

Significant differences between the pre-eclampsia subjects and the controls were observed in the gene expressions associated with oxidative stress. Lower values in the pre-eclampsia group were found for heme oxygenase (HO)-1, HO-2, catalase and superoxide dismutase (SOD). The HO-1, HO-2 and the catalase levels significantly correlated with proteinuria, and the HO-2 level with systolic blood pressure.

CONCLUSION

Significantly lower concentrations of HO-1, HO-2, SOD and catalase are found in the cellular component of blood from pre-eclamptic patients. The values correlate with the severity of pre-eclampsia. These findings indicate that enhanced oxidative stress and a decrease in the number of anti-oxidant enzymes may be associated with pre-eclampsia.

Effect of heme oxygenase-1 deficiency on placental development

Heme oxygenase (HO) is the rate-limiting enzyme in the heme catabolic pathway and highly expressed in the placenta. Deficiencies in HO-1, the inducible isoform, have been associated with pregnancy disorders, such as recurrent miscarriages, intrauterine growth retardation, and pre-eclampsia. The aim of this study was to identify if a deficiency in HO-1 affects placental development using a mouse model. When HO-1 heterozygote (Het, HO-1(+/-)) mice were cross-bred, an extremely low birth rate in homozygote (Mut, HO-1(-/-)) offspring (2.4%) and small litter sizes were observed. Placentas and fetuses from Het cross-breedings were relatively smaller and weighed less than those from wild-type (WT) cross-breedings at E12.5 and E15.5. Furthermore, Het placentas had significantly less HO-1 mRNA and protein levels than WT placentas, but no significant differences in placental HO activity. Interestingly, HO-2, the constituitive HO isoform, as well as iNOS and eNOS expression were significantly upregulated in Het placentas. Histological examination showed that the junctional zone (JZ) of Het placentas were markedly thinner than those of WT placentas and appeared to be due to an increase in apoptosis. Immunohistochemistry revealed that HO-1-expressing cells were located primarily in the JZ of Het placentas, specifically in the spongiotrophoblast layer. In addition, diastolic blood pressures and plasma soluble VEGFR-1 (sFlt-1) levels were significantly elevated in pregnant Het mice. We conclude that a partial deficiency in HO-1 is associated with morphological changes in the placenta and elevations in maternal diastolic blood pressure and plasma sFlt-1 levels, despite a compensatory increase in HO-2 expression.

Acute effect of cigarette smoking on placental circulation - a study by carbon-monoxide measurement and Doppler assessment

OBJECTIVE

Carbon-monoxide (CO) decreases placental vascular impedance. We assessed the consequences of smoking-induced temporary maternal CO-increase on fetal and placental circulation.

STUDY DESIGN

In a prospective study twenty-nine smoking pregnant women and their fetuses were evaluated. We determined the changes in maternal blood CO levels after smoking, and the concomitant changes in maternal and fetal circulation. Changes in fetal heart rate, uterine artery (UTA), middle cerebral artery (MCA), and descending aorta (DA) flow were measured by Doppler velocimetry. Changes in maternal CO level and umbilical flow value were assessed by paired t-test. The correlation between CO level and placental flow was assessed by partial correlation test.

RESULTS

CO level increased (mean +/-SD 1.7 +/- 0.065% vs. 2.36 +/- 0.89, p<0.0001). Nicotine-related maternal circulatory parameters changed significantly, but uterine flow values remained unchanged. Fetal heart rate increased, while flow in MCA and DA showed no change. CO-dependent umbilical artery impedance remained unchanged (Pulsatility Index: 0.956 +/- 0.18 vs. 0.948 +/- 0.21). Partial correlation between CO level and umbilical arterial impedance showed no significance (r:-0.324).

CONCLUSION

Despite significant CO elevation, the mainly CO-regulated placental flow remained unchanged.

Specific systemic antioxidant response to preeclampsia in late pregnancy: the study of intracellular glutathione peroxidases in maternal and fetal blood

OBJECTIVE

The physiopathology of preeclampsia is still unclear, but an imbalance between reactive oxygen species (ROS) and antioxidants, also called oxidative stress, appears to be an important contributing factor. The ROS promote lipid oxidation and are known to induce stress proteins, such as hemeoxygenase 1 (HO-1) and heat-shock protein 70 (Hsp-70). We hypothesized that glutathione peroxidases (GPx), a major class of antioxidant enzymes that regulate cell homeostasis by neutralizing lipid peroxides, are altered in the blood of preeclamptic women and neonates (venous cord blood).

METHODS

Thirty-one preeclamptic and 30 normotensive pregnancies were recruited. The blood was fractionated using a discontinuous gradient to separate the different cell types. The messenger ribonucleic acid (mRNA) expression of GPx-1 and -4, HO-1, and Hsp-70 were analyzed by quantitative reverse transcriptase-polymerase chain reaction. GPx-1 and -4 protein level in blood cells was also detected by Western blot. The experiments were analyzed using the Student t test.

RESULTS

The HO-1 and Hsp-70 mRNA expression in whole blood was significantly higher in both fetal and maternal circulations (P < .05). We also discovered that GPx-4 mRNA was 1.6-fold higher in blood of women with preeclampsia than in control pregnancies (P = .04). The latter was associated with an increase of both GPx-1 and GPx-4 protein and mRNA levels in the lymphocyte/monocyte fraction of the blood. Significantly higher GPx-4 mRNA levels in the fetal circulation of the preeclamptic group than the control group were also detected (P < .001).

CONCLUSION

These data indicate that preeclampsia is associated with a specific antioxidant response in both maternal and fetal circulations, likely in response to the deleterious oxidative stress observed in this syndrome.

Identification of novel trophoblast invasion-related genes: heme oxygenase-1 controls motility via peroxisome proliferator-activated receptor gamma

Invasion of cytotrophoblasts (CTBs) into uterine tissues is essential for placental development. To identify molecules regulating trophoblast invasion, mRNA signatures of purified villous (CTB, poor invasiveness) and extravillous trophoblasts (EVTs) (high invasiveness) isolated from first trimester human placentae and villous explant cultures, respectively, were compared using GeneChip analyses yielding 991 invasion/migration-related transcripts. Several genes involved in physiological and pathological cell invasion, including A disintegrin and metalloprotease-12, -19, -28, as well as Spondin-2, were up-regulated in EVTs. Pathway prediction analyses identified several functional modules associated with either the invasive or noninvasive trophoblast phenotype. One of the genes that was down-regulated in the invasive mRNA pool, heme oxygenase-1 (HO-1), was selected for functional analyses. Real-time PCR analyses, Western blotting, and immunofluorescence of first trimester placentae and differentiating villous explant cultures demonstrated down-regulation of HO-1 in invasive EVTs as compared with CTBs. Modulation of HO-1 expression in loss-of as well as gain-of function cell models (BeWo and HTR8/SVneo, respectively) demonstrated an inverse relationship of HO-1 expression with trophoblast migration in transwell and wound healing assays. Importantly, HO-1 expression led to an increase in protein levels and activity of the nuclear hormone receptor peroxisome proliferator activated receptor (PPAR) gamma. Pharmacological inhibition of PPARgamma abrogated the inhibitory effects of HO-1 on trophoblast migration. Collectively, our results demonstrate that gene expression profiling of EVTs and CTBs can be used to unravel novel regulators of cell invasion. Accordingly, we identify HO-1 as a negative regulator of trophoblast motility acting via up-regulation of PPARgamma.

Gene expression in chorionic villous samples at 11 weeks' gestation from women destined to develop preeclampsia

OBJECTIVE

To evaluate the direct alterations in mRNA expression among chorionic villous samples from 11 weeks' pregnant women who would develop preeclampsia (PE) later in the pregnancy.

METHOD

Case-control study encompassing five women destined to develop PE [cases matched 1:5 for gestational age (GA) with 25 controls]. We quantified mRNA expression on tissue samples from chorionic villous sampling (CVS) of normal and PE patients. We then assessed mRNA expressions of vascular endothelial growth factor (VEGFA), VEGFA receptor 1 (Flt-1), endoglin (Eng), placental growth factor (PlGF), transforming growth factor-beta1 (TGF-beta1), heme oxygenase-1 (HO-1) and superoxide dismutase (SOD). Data were analyzed by nonparametric rank analysis.

RESULTS

For all the mRNA species considered in this study, all the mean observed ranks in the PE group were significantly altered compared to the rank expectation among controls. mRNA for Eng and TGF-beta1 were the markers with the highest degree of aberration in PE, in respect to controls. The results are consistent with those already reported for the corresponding circulating proteins. mRNA for HO-1 and SOD were instead associated with the lowest aberration.

CONCLUSION

It is assumed that the pathogenesis of PE is associated with pathophysiological alterations to trophoblasts in early gestation. Our study has directly proved that gene expressions relating to angiogenesis or oxidative stress are altered in the first trimester trophoblasts that go on to develop PE later. These results would put the basis for a possible screening method for PE by using residual CVS.

Hypertension produced by placental ischemia in pregnant rats is associated with increased soluble endoglin expression

Recent clinical studies indicate that an excess of angiostatic factors, such as soluble endoglin (sEng), is related to the occurrence of preeclampsia. Although recent clinical studies report that sEng is increased in preeclamptic women, the mechanisms underlying its overexpression remain unclear. Evidence suggests that hypoxia and induction of heme oxygenase-1 have opposing effects on sEng expression, the former stimulatory and the latter inhibitory. Hence, we hypothesized that placental ischemia because of reduced uterine perfusion pressure (RUPP) in the pregnant rat would increase sEng expression and decrease heme oxygenase-1. Mean arterial pressure was obtained via arterial catheter, and serum and placental proteins were measured by Western blot. Mean arterial pressure was increased (132+/-3 mm Hg versus 102+/-2 mm Hg; P<0.001), and fetal (2.35+/-0.05 g versus 1.76+/-0.08 g; P<0.001) and placental weight were decreased (0.47+/-0.04 g versus 0.58+/-0.03 g; P<0.01) in the RUPP compared with normal pregnant controls. Serum sEng (0.10+/-0.02 arbitrary pixel units [apu] versus 0.05+/-0.01 apu; P<0.05) and placental endoglin (4.7+/-2.3 apu versus 1.45+/-0.42 apu; P<0.05) were increased along with placental hypoxia inducible factor-1 alpha (1.42+/-0.25 apu versus 0.68+/-0.09 apu; P<0.05) expression in the RUPP versus the normal pregnant dams. Placental HO-1 (1.4+/-0.3 apu versus 2.5+/-0.1 apu; P<0.05) expression decreased in the RUPP compared with normal pregnant dams. The present findings support our hypothesis that placental ischemia because of RUPP increases the expression of sEng and shifts the balance of angiogenic factors in the maternal circulation toward an angiostatic state. The present study provides further evidence that placental ischemia is a strong in vivo stimulus of angiostatic factors during pregnancy.

Fractional excretion of tumor necrosis factor-alpha in women with severe preeclampsia

OBJECTIVE

Proinflammatory cytokines of placental or systemic origin are thought to play a central role in the pathophysiology of preeclampsia. We sought to estimate the fractional excretion of tumor necrosis factor (TNF)-alpha in relationship to proteinuria in women with severe preeclampsia.

METHODS

In a cross-sectional study, we evaluated the serum and urine levels of TNF-alpha in 45 women diagnosed with severe preeclampsia (mean+/-standard error of the mean, gestational age 29.1+/-0.5 weeks). Forty-five healthy pregnant women matched for parity, maternal age, and gestational age at recruitment (30.1+/-0.4 weeks) made up the control group. Urinary concentrations were normalized to creatinine. The fractional excretion of TNF-alpha was interpreted in relationship to that of total proteins and soluble fms-like tyrosine kinase-1 (sFlt-1).

RESULTS

We found that the women with preeclampsia had significantly higher serum TNF-alpha concentrations compared with the women in the control group (mean+/-standard error of the mean, preeclampsia: 1.39+/-0.09 versus control: 0.93+/-0.07 pg/mL, P<.001). In contrast, urinary levels of TNF-alpha were significantly decreased in the women with preeclampsia compared with the healthy women (median [interquartile range], preeclampsia: 0.26 [0.10-0.91] versus control: 0.58 [0.21-1.29] pg/mg creatinine, P=.003), even though the hypertensive women had higher levels of proteinuria. In contrast to sFlt-1, urinary TNF-alpha did not correlate with the degree of proteinuria. Additionally, in preeclampsia, the fractional excretion of TNF-alpha was significantly lower (preeclampsia: 1.92% [0.46-4.20] versus control: 7.2% [2.44-12.07], P<.001).

CONCLUSION

The fractional excretion of TNF-alpha is significantly reduced in women with severe preeclampsia despite proteinuria. The decreased clearance and altered renal excretion of this cytokine may contribute to the exaggerated inflammatory response observed in preeclampsia.

LEVEL OF EVIDENCE

II.

Heme oxygenase-1 and carbon monoxide in vascular pathobiology: focus on angiogenesis

Angiogenesis involves the formation of new blood vessels and is critical for fundamental events such as development and repair after injury. Perturbances in angiogenesis contribute to the pathogenesis of diverse clinical conditions including cancer, complications of diabetes mellitus, ischemia/reperfusion injury of the heart and other organs, and preeclampsia, as well as a number of inflammatory disorders. Recent work has identified heme oxygenase-1 and its gaseous product, carbon monoxide, to possess potent proangiogenic properties in addition to well-recognized antiinflammatory, antioxidant, and antiapoptotic effects. Angiogenic factors, such as vascular endothelial growth factor and stromal cell-derived factor-1, mediate their proangiogenic effects through induction of heme oxygenase-1, making it an attractive target for therapeutic intervention. This review will provide an overview of the role of heme oxygenase-1 and carbon monoxide in angiogenesis.