Evidence of fetal C-reactive protein urinary excretion in early gestation

Biomarkers used in studying air pollution exposure during pregnancy and perinatal outcomes: a review

PURPOSE

This review focuses on studies among pregnant women that used biomarkers to assess air pollution exposure, or to understand the mechanisms by which it affects perinatal outcomes.

METHODS

We searched PubMed and Google scholar databases to find articles.

RESULTS AND CONCLUSIONS

We found 29 articles, mostly consisting of cohort studies. Interpolation models were most frequently used to assess exposure. The most consistent positive association was between polycyclic aromatic hydrocarbon (PAH) exposure during entire pregnancy and cord blood PAH DNA adducts. Exposure to particulate matter (PM) and nitrogen dioxide (NO₂) showed consistent inverse associations with mitochondrial DNA (mtDNA) content, particularly in the third trimester of pregnancy. No single pollutant showed strong associations with all the biomarkers included in this review. C-reactive proteins (CRPs) and oxidative stress markers increased, whereas telomere length decreased with increasing air pollution exposure. Placental global DNA methylation and mtDNA methylation showed contrasting results with air pollution exposure, the mechanism behind which is unclear. Most studies except those on PAH DNA adducts and mtDNA content provided insufficient evidence for characterizing a critical exposure window. Further research using biomarkers is warranted to understand the relationship between air pollution and perinatal outcomes.

Aldosterone Receptor Antagonism Reduces Urinary C-Reactive Protein Excretion in Angiotensin II-Infused, Hypertensive Rats

BACKGROUND

Elevated C-reactive protein (CRP) may contribute to elevated arterial pressure in Ang II-dependent hypertension. However, the in vivo effects of Ang II and of mineralocorticoid receptor (MR) antagonism on CRP during Ang II-dependent hypertension have not been examined. In addition, urinary CRP excretion as a method to monitor the progression of Ang II-induced inflammation has not been evaluated.

METHODS

Urine samples were collected from three groups (n = 10/group) of rats: 1) normotensive control, 2) angiotensin II infused (Ang II; 60 ng/min), and 3) Ang II + eplerenone (epl; 25 mg/d). A diet containing epl (0.1 %) was provided after 1 week of Ang II infusion.

RESULTS

After 28 d, Ang II increased SBP from 136 +/- 5 to 207 +/- 8 mmHg; this response in SBP was not altered following MR antagonism (215 +/- 6 mmHg). Ang II-infusion increased plasma CRP from 14 +/- 2 to 26 +/- 3 mug/mL and increased urinary CRP excretion nearly 8-fold (143 +/- 26 vs 1102 +/- 115 ng/d). Treatment with eplerenone reduced plasma CRP by 25 % and urinary immunoreactive CRP (irCRP) by 34 % in Ang II-infused rats suggesting that aldosterone contributes to the CRP-associated inflammatory response in Ang II-dependent hypertension.

CONCLUSIONS

The increase in SBP preceded the increase in irCRP excretion by at least 4 days suggesting that CRP does not significantly contribute to increased arterial blood pressure in Ang II-dependent hypertension. The blockade of MR reduced plasma CRP and urinary irCRP excretion demonstrating the contribution of aldosterone to the Ang II-induced generation of CRP. Furthermore, urinary CRP may serve as a non-invasive index for monitoring cardiovascular inflammation during hypertension.

Maternal and fetal C-reactive protein genotype and first trimester CRP concentrations in maternal plasma

Maternal plasma CRP concentrations in pregnancy are increased over pre-pregnancy values and high concentrations have been associated with adverse obstetrical outcomes. The objective of this study was to explore the relationship between maternal and fetal variation in C-reactive protein (CRP) genotype and maternal plasma CRP concentrations in the first trimester in low risk patients. DNA was extracted from maternal and cord blood of subjects in a prospective observational cohort. Single-nucleotide polymorphism (SNP) selection was made using a linkage disequilibrium bin approach. CRP concentrations were measured in first trimester maternal plasma using an enzyme-linked immunosorbent assay (ELISA) kit. Kruskal-Wallis rank testing was used to analyze genetic and clinical determinants of CRP concentrations. Genotype results were available in 190 mother-baby pairs. There was no significant difference in CRP concentration among maternal or fetal CRP genotypes. Thus, first trimester concentrations of maternal plasma CRP in low risk subjects do not appear to be significantly associated with CRP genotype. Instead, differences in clinical factors probably have more influence on baseline maternal CRP concentrations.

C-Reactive Protein Production in Term Human Placental Tissue

OBJECTIVE

C-reactive protein (CRP) is a marker of systemic inflammation. Recently, it has been shown that CRP is present in amniotic fluid and fetal urine, and that elevated levels are associated with adverse pregnancy outcome. However, the precise source of amniotic fluid CRP, its regulation, and function during pregnancy is still a matter of debate. The present in vivo and in vitro studies were designed to investigate the production of CRP in human placental tissues.

MATERIAL AND METHODS

Ten paired blood samples from peripheral maternal vein (MV), umbilical cord artery (UA) and umbilical vein (UV) were collected from women with elective caesarean sections at term. The placental protein accumulation capacity of hCG, hPL, leptin and CRP was compared with the dual in vitro perfusion method of an isolated cotyledon of human term placentae and quantified by ELISA. Values for accumulation (release) were calculated as total accumulation of maternal and fetal circuits normalized for tissue weight and duration of perfusion. For gene expression, RNA was extracted from placental tissue and reverse transcribed. RT-PCR and real-time PCR were performed using specific primers.

RESULTS

The median (range) CRP level was significantly different between UA and UV [50.1 ng/ml (12.1-684.6) vs. 61 ng/ml (16.9-708.1)]. The median (range) difference between UV and UA was 9.3 ng/ml (2.2-31.6). A significant correlation was found between MV CRP and both UA and UV CRP levels. Median (range) MV CRP levels [2649 ng/ml (260.1-8299)] were 61.2 (6.5-96.8) fold higher than in the fetus. In vitro, the total accumulation rates (mean+/-SD) were 31+/-13 (mU/g/min, hCG), 1.16+/-0.19 (microg/g/min, hPL), 4.71+/-1.91 (ng/g/min, CRP), and 259+/-118 (pg/g/min, leptin). mRNA for hCG, hPL and leptin was detectable using conventional RT-PCR, while CRP mRNA could only be demonstrated by applying real-time RT-PCR. In the perfused tissue the transcript levels for the four proteins were comparable to those detected in the native control tissue.

CONCLUSIONS

Our results demonstrate that the human placenta produces and releases CRP mainly into the maternal circulation similarly to other analyzed placental proteins under in vitro conditions. Further studies are needed to explore the exact role of placental CRP during pregnancy.