Clinical applications of the altered iron kinetics of toxemia of pregnancy

A Dormant Microbial Component in the Development of Preeclampsia

Preeclampsia (PE) is a complex, multisystem disorder that remains a leading cause of morbidity and mortality in pregnancy. Four main classes of dysregulation accompany PE and are widely considered to contribute to its severity. These are abnormal trophoblast invasion of the placenta, anti-angiogenic responses, oxidative stress, and inflammation. What is lacking, however, is an explanation of how these themselves are caused. We here develop the unifying idea, and the considerable evidence for it, that the originating cause of PE (and of the four classes of dysregulation) is, in fact, microbial infection, that most such microbes are dormant and hence resist detection by conventional (replication-dependent) microbiology, and that by occasional resuscitation and growth it is they that are responsible for all the observable sequelae, including the continuing, chronic inflammation. In particular, bacterial products such as lipopolysaccharide (LPS), also known as endotoxin, are well known as highly inflammagenic and stimulate an innate (and possibly trained) immune response that exacerbates the inflammation further. The known need of microbes for free iron can explain the iron dysregulation that accompanies PE. We describe the main routes of infection (gut, oral, and urinary tract infection) and the regularly observed presence of microbes in placental and other tissues in PE. Every known proteomic biomarker of "preeclampsia" that we assessed has, in fact, also been shown to be raised in response to infection. An infectious component to PE fulfills the Bradford Hill criteria for ascribing a disease to an environmental cause and suggests a number of treatments, some of which have, in fact, been shown to be successful. PE was classically referred to as endotoxemia or toxemia of pregnancy, and it is ironic that it seems that LPS and other microbial endotoxins really are involved. Overall, the recognition of an infectious component in the etiology of PE mirrors that for ulcers and other diseases that were previously considered to lack one.

Is the level of maternal serum prohepcidin associated with preeclampsia?

OBJECTIVE

The objective of the study was to compare pro-hepcidin, hemoglobin (Hb) concentration, hematocrit (Hct), C-reactive protein (CRP), IL-6 and iron status parameters in preeclamptic (PE) and healthy pregnant women, and to examine the relationship between serum pro-hepcidin levels and iron parameters of preeclampsia (PE).

METHODS

In a prospective controlled study, we collected serum from women with normal pregnancy (n = 37) and from women with PE (n = 30) at the Department of Obstetrics and Gynecology at Turgut Ozal University between February 2010 and January 2013. Pro-hepcidin, hemoglobin (Hb) concentration, hematocrit (Hct), CRP, IL-6 and iron status parameters were measured in all patients and compared between groups.

RESULTS

Levels of serum prohepcidin in PE and control groups were similar and amount 69.4 ± 19.7 and 71.9 ± 22.1 ng/ml, respectively. The difference was not statistically significant (p: 0.694). On the other hand, the study group had a statistically lower iron binding capacity (IBC), total iron binding capacity, transferin, total protein, albumin levels (p < 0.05). No significant differences were found among prohepcidin, Hb concentration, Hct, iron, ferritin, IL-6, urea and creatine in both the groups.

CONCLUSION

In pregnancies complicated by PE with normal values of hemoglobin and hematocrit, serum prohepcidin concentrations are similar to those observed in healthy pregnant women. The analysis revealed no significant correlations between prohepcidin level and serum iron, serum ferritin or transferrin in the PE.

Evaluation of the changes in serum iron levels in pre-eclampsia

Serum iron levels were studied in 50 patients with pre-eclampsia and the results were compared with 50 control cases. Their serum iron levels were found to be higher than the controls. Increase in serum iron was directly proportional to the increased levels of uric acid, urea and creatinine. Mean reticulocyte counts, plasma free haemoglobin and unconjugated bilirubin levels were also higher in these patients. It is suggested that haemolysis may be a major contributory factor for the increased levels of serum iron in pre-eclampsia.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Abnormal iron parameters in the pregnancy syndrome preeclampsia

OBJECTIVE

Our purpose was to investigate iron status parameters in preeclampsia with a view to exploring their possible contribution to the etiology.

STUDY DESIGN

In prepared serum samples from 40 preeclamptic women and matched pregnant control subjects at the John Radcliffe Hospital, Oxford, a number of iron status parameters were measured. Statistical analysis was by the Wilcoxon signed rank test and linear regression.

RESULTS

Serum iron concentration, ferritin, and percent saturation of transferrin were significantly higher in the preeclamptic patients than in control subjects, whereas unsaturated iron-binding capacity and apotransferrin levels were significantly lower. No difference was found in hemopexin concentrations in the two groups. Gestational age at the time of sampling was correlated (positively) with only two parameters, total and unsaturated iron-binding capacity, but only in the preeclampsia group. Eighteen percent of preeclamptic subjects had percent transferrin saturation levels in the region associated with iron overload.

CONCLUSION

Released iron species in preeclampsia may contribute to the etiology and will exacerbate lipid peroxidation and endothelial cell injury. Given the high prevalence of heterozygosity for hemochromatosis with the associated reduced ability to exclude ingested iron, it would seem inadvisable, in the absence of evidence of iron deficiency, to give iron supplements to pregnant women at high risk for preeclampsia.

Defective antioxidant mechanisms via changes in serum ceruloplasmin and total iron binding capacity of serum in women with pre-eclampsia

OBJECTIVES

The aim of this study was to investigate the role of serum ceruloplasmin, its ferroxidase activity and total iron binding capacity in women with pre-eclampsia.

METHODS

Thirty primigravidas between 32 and 36 weeks of gestation were studied. The subjects were divided into two groups: group A consisted of 15 normal pregnancies with a mean gestational age of 33.9 weeks, and group B consisted of 15 pre-eclamptics with a mean gestational age of 32.8 weeks.

RESULTS

The pre-eclamptics presented significantly higher serum ceruloplasmin levels compared to those with normal pregnancies (P<0.01), while the mean ferroxidase activity levels of ceruloplasmin did not differ significantly between the two groups (450.13+/-110.88 and 467.26+/-135.35 micromol/l/min in groups A and B, respectively). The mean+/-S.D. serum iron level (104.48+/-39.81 microg/dl) was greater whereas the total iron binding capacity (55.59+/-8.47 micromol/l) was lower in women with preeclampsia when compared to normal pregnancies (P<0.01 and P<0.0001 respectively).

CONCLUSIONS

Our results indicate that the plasma of pre-eclamptic women shows a loss of ferroxidase activity of ceruloplasmin as well as a reduction of total iron binding capacity. Thus, it seems that the plasma of pre-eclamptic women lacks the protective anti-oxidative action of these substances.

Decreased transferrin and increased transferrin saturation in sera of women with preeclampsia: implications for oxidative stress

OBJECTIVE

The concerted iron-binding antioxidant activity of transferrin and ceruloplasmin decreases with increasing transferrin saturation by iron. We examined interactions between serum iron and iron-binding capacity and concentrations of the lipid peroxidation metabolite malondialdehyde in normal and preeclamptic pregnancies. We also asked if the release of iron from free hemoglobin by lipid hydroperoxides is a potential mechanism to increase transferrin saturation in preeclampsia.

STUDY DESIGN

Predelivery and 24 to 48 hour postpartum venous blood was collected from 19 women with uncomplicated pregnancies and 17 with preeclampsia. Serum iron, iron binding capacity, and malondialdehyde were measured. In a subset of predelivery samples electron paramagnetic resonance spectroscopy was used to determine diferric transferrin, total transferrin, and ceruloplasmin concentrations and to examine interactions of an organic hydroperoxide with hemoglobin and transferrin.

RESULTS

Antepartum serum iron concentrations were 46% greater, percent saturation of iron binding capacity was 98% greater, and malondialdehyde 50% greater, whereas total iron-binding capacity was 14% lower, in women with preeclampsia. By 48 hours post partum group differences between these variables other than total iron-binding capacity were not observed. Electron paramagnetic resonance spectroscopy confirmed antepartum differences and that total iron-binding capacity and percent saturation were equivalent to total transferrin and the ratio diferric transferrin/total transferrin, respectively. Antepartum concentrations of ceruloplasmin were not different. Antepartum malondialdehyde concentrations correlated positively with percent transferrin saturation and negatively with unsaturated iron-binding capacity (apotransferrin). Electron paramagnetic resonance spectroscopy demonstrated that the release of iron from free hemoglobin by lipid hydroperoxides in serum is a potential mechanism to increase transferrin saturation.

CONCLUSION

Increased transferrin saturation and decreased unsaturated iron-binding capacity in preeclampsia may occur consequent to oxidative stress and then further promote oxidative stress by decreasing serum antioxidant buffering against redox-active iron.

Hemostasis and diagnosis of preeclampsia

The diagnosis of preeclampsia, with all of its consequences, is at times difficult to establish, especially when the patient has underlying chronic hypertension and is not known from prior prenatal care visits. Many screening tests have been proposed. These should be sensitive, relatively specific, easy to perform, of low cost, and have a reasonable interval from prediction to disease onset. Laboratory assays would obviously be useful. We evaluated hemostasis tests for the diagnosis of preeclampsia, and compared fibronectin, antithrombin III and alpha 2-antiplasmin in 48 preeclamptics and 86 control nulliparas. Receive operator characteristic (ROC) curve analysis suggested that fibronectin is the most effective of these tests. A similar analysis comparing the results of previous studies using serum iron, angiotensin infusion, urinary calcium/creatinine ratio, the rollover test and uric acid suggested a possible role for fibronectin in the diagnosis of preeclampsia. While not ideal, there seems to be, at present, no other, easy to perform laboratory test that outperforms fibronectin in predicting preeclampsia.

Significance of serum iron levels as a biochemical marker in pregnancy-induced hypertension

OBJECTIVE

To determine the changes in serum iron levels, if any, as a biochemical marker of pregnancy-induced hypertension (PIH).

METHOD

Fifty-four primigravidas with PIH formed the study group and 20 normotensive primigravidas comprised the control group in a prospective study. Serum iron levels were estimated at diagnosis of PIH, at termination of pregnancy and in the postpartum period. Data was analyzed using Student's t-test, the chi 2-test and regression analysis.

RESULTS

Subjects with PIH were found to have higher serum iron levels at diagnosis of PIH (recruitment value) and at termination of pregnancy than the controls (P < 0.001). Serum iron levels in the PIH subjects decreased markedly in the postpartum period simultaneously with the clinical recovery from PIH. Serum iron values of > or = 110 micrograms/dl was found to differentiate PIH from normotensive pregnancies with a sensitivity and specificity of 89% and 90%, respectively.

CONCLUSIONS

Changes in serum iron levels correlated with the clinical course of PIH and appeared to be a uniform and specific biochemical marker of PIH although its correlation with the severity of PIH was found to be poor.

A prospective study of several potential biologic markers for early prediction of the development of preeclampsia

OBJECTIVE

The purpose of this study was to prospectively evaluate the predictive performance of several potential biologic markers of preeclampsia used alone or in combination.

STUDY DESIGN

A prospective cohort of 1366 nulliparous women was followed up longitudinally on three occasions during pregnancy. The predictive performance of the tests, used either alone or in combination (stepwise multiple logistic regression), was assessed and compared with that of the mean arterial pressure.

RESULTS

Preeclampsia occurred in 109 of the pregnant women. At a specificity of 80% the sensitivity and the positive and negative predictive values for mean arterial pressure (at a threshold of 87 mm Hg) were 46.6%, 23.5%, and 92.0%, respectively, and the corresponding values for a multiple logistic model at 15 to 24 weeks that included some biologic markers, as well as the mean arterial pressure, were 57.1%, 26.9%, and 93.7%, respectively.

CONCLUSION

Preeclampsia can be predicted by a combination of simple biologic tests with a performance similar to second-trimester mean arterial pressure. However, this procedure is insufficient in terms of clinical usefulness.

Prevention and treatment of pregnancy-associated hypertension: what have we learned in the last 10 years?

High blood pressure (BP) complicates approximately 10% of all pregnancies. Hypertension in pregnancy falls into four categories: (1) preeclampsia-eclampsia, (2) chronic hypertension of whatever cause, (3) preeclampsia-eclampsia superimposed to chronic hypertension or renal disease, and (4) transient or late hypertension (gestational hypertension). Preeclampsia, the association of hypertension, proteinuria, and edema, accounts for more than 50% of all the hypertensive disorders of pregnancy and is a major cause of fetal and maternal morbidity and mortality. Unfortunately, distinguishing between preeclampsia and other causes of hypertension on clinical grounds can be difficult because of the lack of specific tests for differential diagnosis. Increased vascular resistance has been claimed as the primary cause of preeclampsia; however, a variable hemodynamic profile with relatively high cardiac outputs, normal filling pressures, and inappropriately high systemic vascular resistances is now reported by most investigators. Imbalance between vasodilator and vasoconstrictor eicosanoids may account for platelet activation and increased responsiveness to pressor peptides. Altered prostacyclin (PGI2) to thromboxane A2 (TxA2) ratio in maternal uteroplacental vascular bed may favor local platelet activation and vasoconstriction contributing to placental insufficiency and fetal distress. Alternatively, recent evidence seems to suggest that fetal umbilical placental circulation may be the site of the primary vascular injury. Whether low-dose aspirin prevents preeclampsia because it inhibits the excessive maternal TxA2 or whether the partial inhibition of fetal TxA2 is also of therapeutic value remains to be established. Treatment of severe hypertension in pregnancy is probably important to prevent cardiac failure or cerebrovascular accidents in the mother. The need for pharmacological therapy of mild to moderate hypertension is still debated, since no formal studies are available to clarify whether pharmacological treatment in such instances effectively reduces maternal or fetal risk. For the treatment of preeclampsia, hydralazine and nifedipine may be used when delivery is not applicable. Labetalol and diazoxide are effective for hypertensive emergencies. Life-threatening hypertension that does not respond to more conventional therapy is an indication for the use of sodium nitroprusside. For chronic hypertension, alpha-methyldopa remains the treatment of choice; if ineffective, hydralazine or beta-blockers are suitable. Effectiveness and safety of other molecules remain elusive.

Comparative efficacy of umbilical arterial Doppler indices for predicting adverse perinatal outcome

A variety of descriptor indices for the umbilical arterial Doppler waveform are currently in use for predicting perinatal outcome. However, there is a paucity of data regarding the relative diagnostic merits of these indices. We addressed this issue in a prospective, blind study in which the diagnostic efficacy of the following Doppler indices was compared: resistance index, systolic/diastolic ratio, pulsatility index, and diastolic average ratio. The analytic technique consisted of the receiver operating characteristic method, which evaluates a test's ability to discriminate a diseased from a healthy population. The patient population consisted of 350 pregnant patients with gestational ages of 34 to 36 weeks. A continuous-wave Doppler device with a 4 MHz transducer was used to investigate the umbilical vessels. The test was performed only once in each patient. The abnormal outcome parameters included small for gestational age (less than 10th percentile), Apgar score less than 7 at 5 minutes, fetal distress (late and severe variable decelerations, absent variability, fetal scalp pH less than 7.20), umbilical cord arterial pH less than 7.10, presence of thick meconium, and admission to neonatal intensive care unit (greater than 48 hours). The results showed that the resistance index had the best discriminatory ability when compared with other Doppler indices: the systolic/diastolic ratio (p less than 0.05), the pulsatility index (p less than 0.001), and the diastolic/average ratio (p less than 0.05). It is concluded that of the various Doppler indices assessed in this investigation, the resistance index offers the best diagnostic efficacy in predicting perinatal compromise.

[Preeclampsia: physiopathology and prospects for early detection]

Preeclampsia is a complication of pregnancy characterized by hypertension, edema and proteinuria, beginning after 20 weeks of gestation. Six percent of the pregnant women in North America develop this disease, which is associated with increased morbidity and mortality for the mother and her baby. The physiopathology remains uncertain despite many research efforts. Actual hypotheses seek to explain the vasospasm that characterizes the disease. Among the many factors influencing vascular reactivity and possibly implicated are: the renin-angiotensin system, prostaglandins, progesterone and its metabolites, calcium, magnesium, digoxin-like immunoreactive substance(s), auricular natriuretic factor, substances secreted by platelets and leukotrienes. Prevention of the disease is limited by the absence of a biological or clinical marker with good sensitivity and appropriate specificity. Many biochemical or hematological parameters have been reported: uric acid, calcium, magnesium, proteinuria, blood iron, hematocrit, platelet count, antithrombin III, estrogen and progesterone. The combination of several tests could be superior to the use of each test individually, providing a better sensitivity and improving the positive predictive value. With early detection, new therapies for the prevention of the disease could be experimented on the higher risk women before the apparition of clinical symptoms or signs. Furthermore, those tests could be used in the study of the pathophysiology and in the choice of the best therapy.

The origin of increased serum iron in pregnancy-induced hypertension

Serum iron was measured in 30 patients with pregnancy-induced hypertension and 24 normal pregnant women. The mean iron concentration was significantly higher in the group with pregnancy-induced hypertension (111 +/- 26 micrograms/ml) than in the controls (69 +/- 17 micrograms/ml) (p less than 0.0001). Readily available laboratory variables were used to determine whether the increased serum iron was the result of (1) hemolysis, (2) hepatocellular injury, or (3) intravascular volume contraction leading to hemoconcentration. It appears that a clinically silent, ongoing hemolytic reaction is responsible for the increase in serum iron seen in patients with pregnancy-induced hypertension.

Increased levels of carboxyhemoglobin and serum iron as an indicator of increased red cell turnover in preeclampsia

Patients with severe preeclampsia are reported to have microangiopathic hemolytic anemia. This study demonstrates that increased red cell turnover with heme catabolism is also common in mild preeclampsia. Heme catabolism results in equimolar production of carboxyhemoglobin, iron, and bilirubin. A concomitant rise in these constituents of venous blood would support this hypothesis. Patients with antepartum preeclampsia had mean carboxyhemoglobin concentrations (2.72% total hemoglobin) greater than those of control patients (0.65%) (p less than 0.001) and serum iron concentrations (98.5 micrograms/dl) greater than those of control patients (66.1 micrograms/dl) (p less than 0.01). Bilirubin concentrations were not different. Post partum, carboxyhemoglobin and iron concentrations returned toward normal (1.38% and 50.2 micrograms/dl, respectively). Disparity in the magnitude of increase of heme catabolites produced in equimolar proportion is explained by differences in the kinetics of clearance. The data are most consistent with increased destruction of maternal red cells, even in mild preeclampsia. Potential implications of elevated carboxyhemoglobin on maternal and fetal oxygenation are discussed.