Investigation of dosimetric characteristics of radiochromic film in response to alpha particles emitted from Americium-241.

BACKGROUND: In radiotherapy, it is essential to deliver prescribed doses to tumors while minimizing damage to surrounding healthy tissue. Accurate measurements of absorbed dose are required for this purpose. Gafchromic® external beam therapy (EBT) radiochromic films have been widely used in radiotherapy. While the dosimetric characteristics of the EBT3 model film have been extensively studied for photon and charged particle beams (protons, electrons, and carbon ions), little research has been done on α $\alpha$ -particle dosimetry. α $\alpha$ -emitting radionuclides have gained popularity in cancer treatment due to their high linear energy transfer, short range in tissue, and ability to spare surrounding organs at risk, thereby delivering a more localized dose distribution to the tumor. Therefore, a dose-calibration film protocol for α $\alpha$ -particles is required. PURPOSE: This study aimed to develop a dose-calibration protocol for the α $\alpha$ -particle emitting radionuclide 241Am, using Monte Carlo (MC) simulations and measurements with unlaminated EBT3 films. METHODS: In this study, a MC-based user code was developed using the Geant4 simulation toolkit to model and simulate an 241Am source and an unlaminated EBT3 film. Two simulations were performed: one with voxelized geometries of the EBT3 active volume composition and the other using water. The dose rate was calculated within a region of interest in the voxelized geometries. Unlaminated EBT3 film pieces were irradiated with the 241Am source at various exposure times inside a black box. Film irradiations were compared to a 6-MV photon beam from a Varian TrueBeam machine. The simulated dose rate was used to convert the exposure times into absorbed doses to water, describing a radiochromic-film-based reference dosimetry protocol for α $\alpha$ -particles. The irradiated films were scanned and through an in-house Python script, the normalized pixel values from the green-color channel of scanned film images were analyzed. RESULTS: The 241Am energy spectra obtained from the simulations were in good agreement with IAEA and NIST databases, having differences < $<$ 0.516% for the emitted γ $\gamma$ -rays and produced characteristic x-rays and < $<$ 0.006% for the α $\alpha$ -particles. Due to the short range of α $\alpha$ -particles, there was no energy deposition in the voxels outside the active 241Am source region projected onto the film surface. Thus, the total dose rate within the voxels covering the source was 0.847 ± $\pm$ 0.003 Gy/min within the sensitive layer of the film (LiPCDA) and 0.847 ± $\pm$ 0.004 Gy/min in water, indicating that the active volume can be considered water equivalent for the 241Am beam quality. A novel approach was employed in α $\alpha$ -film dosimetry using an exponential fit for the green channel, which showed promising results by reducing the uncertainty in dose estimation within 5%. Although the statistical analysis did not reveal significant differences between the 6-MV photon beam and the α $\alpha$ calibration curves, the dose-response curves exhibited the expected behavior. CONCLUSIONS: The developed MC user code simulated the experimental setup for α $\alpha$ -dosimetry using radiochromic film with acceptable uncertainty. Unlaminated EBT3 film is suitable for the dosimetry of α $\alpha$ -radiation at low doses and can be used in conjunction with other unlaminated GafChromic® films for quality assurance and research purposes.

Evidence of kidney injury in preeclampsia: Increased maternal and urinary levels of NGAL and KIM-1 and their enhanced expression in proximal tubule epithelial cells.

Background and objective: Proteinuria and glomerular endotheliosis are characteristics of glomerular injury in preeclampsia, a hypertensive disorder in human pregnancy. Neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) are biomarkers of acute/chronic renal tubule injury. To determine if tubule injury occurs in preeclampsia, we determined maternal plasma and urine NGAL and KIM-1 levels and evaluated NGAL and KIM-1 expression in kidney biopsy specimens from women with preeclampsia. Methods: Prenatal and postpartum maternal blood and urinary samples were collected from three groups of pregnant women: normal pregnancy (n = 100), preeclampsia (n = 83), and pregnancy complicated with chronic hypertension (n = 20). Plasma and urine levels of NGAL and KIM-1 were measured by ELISA. Kidney biopsy tissue sections from patients with preeclampsia (n = 5) were obtained from Pathology Archives and processed to determine NGAL and KIM-1 expression by immunostaining and high kidney solution images were assessed by electron microscopy (EM). Results: Prenatal plasma and urine levels of NGAL and KIM-1 were significantly higher in preeclamptic than in normal controls, p < 0.01. In normal pregnancy, both plasma and urine levels of NGAL and KIM-1 at 24-48 h after delivery and 6-8 weeks postpartum were relatively comparable to that of antenatal levels. In preeclampsia, urine, but not plasma, NGAL levels were reduced at 6-8 weeks postpartum compared to the antenatal levels, p < 0.05. Although maternal and urine KIM-1 levels were reduced at 6-8 weeks postpartum compared to the antenatal levels in preeclampsia, the levels were still higher than those in normal pregnancy. Positive expression of NGAL and KIM-1 was detected in proximal tubule epithelial cells in kidney tissue specimens from preeclampsia but not in non-pregnancy controls. EM examination showed glomerular and tubular injury in preeclampsia. Conclusion: Our findings of increased maternal levels and urine secretion of NGAL and KIM-1, along with the upregulation of NGAL and KIM-1 expression in tubular epithelial cells in preeclampsia, provide plausible evidence that tubular injury exists in preeclampsia. The higher postpartum NGAL and KIM-1 levels in preeclamptic pregnancies indicate that tubular injury would not resolve within 2-3 months after delivery and suggest that proper follow-up and management of kidney function in women with preeclampsia would be necessary to reduce chronic kidney diseases in those women later in life.

Downregulation of miR-126-3p expression contributes to increased inflammatory response in placental trophoblasts in preeclampsia.

MiR-126-3p is a prototype of an endothelial miRNA and has protective effects on endothelial cells. However, little is known about the effects of miR-126-3p on placental trophoblasts. In the present study, we tested the hypothesis that aberrant miR-126-3p expression is present in preeclamptic placenta which contributes to increased inflammatory response in trophoblasts. Placentas were obtained immediately after delivery from normotensive and preeclamptic pregnancies. Villous tissue was either fixed with formalin or used for trophoblast isolation. Trophoblast miR-126-3p expression was assessed by in situ hybridization of formalin-fixed tissue sections and by RT-PCR in cultured syncytiotrophoblasts. Culture medium was collected for measurement of IL-6, TNFα, and 8-Isoprostane production by ELISA and total cellular protein was collected for evaluation of HIF1α expression by Western blot. Effects of overexpression of miR-126-3p in trophoblasts on cytokine production were tested by transfection of pre-mir-126, a precursor of miR-126, into primary isolated trophoblasts. We found that downregulation of miR-126-3p expression was associated with increased IL-6 and TNFα production in trophoblasts from preeclamptic placentas vs. normal placentas. Moreover, transient overexpression of miR-126-3p significantly reduced IL-6 and TNFα production in trophoblasts from both normal and preeclamptic placentas. We further found that increase in miR-126-3p expression not only suppressed hypoxia-induced increases in IL-6 and TNFα production, but also attenuated hypoxia-induced increases in HIF1α expression and 8-Isoprostane production in trophoblasts cultured under hypoxic condition. These results provide plausible evidence that downregulation of miR-126-3p expression reduces anti-inflammatory and anti-oxidative stress activities in placental trophoblasts in preeclampsia.

Upregulation of METTL3 expression and m6A RNA methylation in placental trophoblasts in preeclampsia.

INTRODUCTION: N6-methyladenosine (m6A) has been recognized as one of the most abundant and functionally relevant modifications of RNAs and plays critical roles in biological and pathological processes. Placental trophoblast dysfunction significantly contributes to the pathogenesis of preeclampsia. The present study aimed to determine if altered m6A expression occurs in placental trophoblasts in preeclampsia. Expression of m6A methyltransferase (methyltransferase like 3 (METTL3)), m6A demethylases (fat mass and obesity-associated protein (FTO) and AlkB homolog 5 (ALKBH5)), and m6A reader protein, heterogeneous nuclear ribonucleoprotein C1/C2 (hnRNPC1/C2), were also examined. METHODS: A total of 43 placentas (20 normal term, 5 normotensive preterm, and 18 preeclamptic) were used in the study. Expression of m6A, METTL3, FTO, ALKBH5, and hnRNPC1/C2 were examined by immunostaining in villous tissue sections and/or by Western blot of total cellular protein in trophoblasts isolated from normotensive and preeclamptic placentas. Total RNA extracted from trophoblasts was used to measure m6A RNA methylation. Effects of METTL3 on m6A RNA methylation and hnRNPC1/C2 expression were assessed by transfection of METTL3 siRNA in trophoblasts from preeclamptic placentas. RESULTS: Expression of m6A and m6A RNA methylation were significantly increased in trophoblasts from preeclamptic vs. normotensive placentas, p < 0.05. Expression of METTL3 and hnRNPC1/C2, but not FTO and ALKBH5, was significantly upregulated in trophoblasts from preeclamptic vs. normotensive placentas, p < 0.01. Transfection of METTL3 siRNA significantly reduced the level of m6A RNA methylation and hnRNPC1/C2 expression in trophoblasts from preeclamptic placentas, p < 0.05. CONCLUSION: The finding of increased METTL3 expression and m6A RNA methylation associated with increased hnRNPC1/C2 expression provides a new posttranscriptional mechanism that aberrant m6A modification may contribute to trophoblast dysfunction in preeclampsia.

Report of AAPM Task Group 235 Radiochromic Film Dosimetry: An Update to TG-55.

The use of radiochromic film (RCF) dosimetry in radiation therapy is extensive due to its high level of achievable accuracy for a wide range of dose values and its suitability under a variety of measurement conditions. However, since the publication of the 1998 AAPM Task Group 55, Report No. 63 on RCF dosimetry, the chemistry, composition, and readout systems for RCFs have evolved steadily. There are several challenges in using the new RCFs, readout systems and validation of the results depending on their applications. Accurate RCF dosimetry requires understanding of RCF selection, handling and calibration methods, calibration curves, dose conversion methods, correction methodologies as well as selection, operation and quality assurance (QA) programs of the readout systems. Acquiring this level of knowledge is not straight forward, even for some experienced users. This Task Group report addresses these issues and provides a basic understanding of available RCF models, dosimetric characteristics and properties, advantages and limitations, configurations, and overall elemental compositions of the RCFs that have changed over the past 20 yr. In addition, this report provides specific guidelines for data processing and analysis schemes and correction methodologies for clinical applications in radiation therapy.

Prevention of preterm birth with vaginal progesterone or 17-alpha-hydroxyprogesterone caproate: a critical examination of efficacy and safety.

Progestogens are the first drugs to demonstrate reproducibly a reduction in the rate of early preterm birth. The efficacy and safety of progestogens are related to individual pharmacologic properties of each drug within this class of medication and characteristics of the population that is treated. The synthetic 17-hydroxyprogesterone caproate and natural progesterone have been studied with the use of a prophylactic strategy in women with a history of preterm birth and in women with a multiple gestation. Evidence from a single large comparative efficacy trial suggests that vaginal natural progesterone is superior to 17-hydroxyprogesterone caproate as a prophylactic treatment in women with a history of mid-trimester preterm birth. Progestogen therapy is indicated for women with this highest risk profile based on evidence from 2 trials. A therapeutic approach based on the identification of a sonographic short cervix has been studied in several phase III trials. Independent phase III trials and an individual patient metaanalysis suggest that vaginal progesterone is efficacious and safe in women with a singleton and a short cervix. Two trials that tested 17-hydroxyprogesterone caproate in women with a short cervix showed no benefit. No consistent benefit for the prophylactic or therapeutic use of progestogens has been demonstrated in larger trials of women whose pregnancies were complicated by a multiple gestation (twins or triplets), preterm labor, or preterm rupture of membranes. Unfortunately, several large randomized trials in multiple gestations have identified harm related to 17-hydroxyprogesterone caproate exposure, and the synthetic drug is contraindicated in this population. The current body of evidence is evaluated by the Grading of Recommendations Assessment, Development, and Evaluation guidelines to derive the strength of recommendation in each of these populations. A large confirmatory trial that is testing 17-hydroxyprogesterone caproate exposure in women with a singleton pregnancy and a history of preterm birth is near completion. Additional study of the efficacy and safety of progestogens is suggested in well-selected populations based on the presence of biomarkers.

Short cervix and vaginal progesterone: a model on how to tackle the problem of idiopathic preterm labor.

Preterm deliveries continue to be a major problem in obstetrics and pediatrics. Short cervical length has been identified as the most accurate way to predict preterm delivery. Recently, vaginally administered progesterone has been shown in separate studies to dramatically decrease the prematurity rate in patients with a short cervix. The research that came to this conclusion is a good model to be used to approach other etiologies of preterm labor and delivery.

Elevated maternal soluble Gp130 and IL-6 levels and reduced Gp130 and SOCS-3 expressions in women complicated with preeclampsia.

Increased inflammatory response plays a significant role in the vascular pathophysiology in preeclampsia. However, the mechanism for increased inflammatory response in preeclampsia is largely unknown. Interleukin (IL)-6 levels are elevated in women with preeclampsia. IL-6 and its receptors, IL-6R and glycoprotein (gp)130, play a critical role in mediating antiinflammatory response via induction of SOCS-3 (suppressor of cytokine signaling-3). However, IL-6 receptor levels and expressions have not been studied in preeclampsia. In this study, we measured IL-6 and its 2 soluble receptors, soluble IL-6R and soluble gp130, in maternal plasma from normal and preeclamptic pregnant women and found that not only IL-6 but also soluble gp130 levels were significantly higher in preeclamptic women than in normotensive pregnant controls. We further examined IL-6R, gp130, and SOCS-3 expressions in maternal vessels and leukocytes and found that gp130 and SOCS-3 expressions were downregulated in both vessel endothelium and leukocytes from preeclampsia. Different patterns for IL-6R and gp130 expressions were found. IL-6R expression was also downregulated in leukocytes from preeclampsia. Our results suggest that increased plasma soluble gp130/soluble IL-6R/IL-6 ratio and reduced membrane transsignaling gp130 expression could contribute to decreased SOCS-3 expression and subsequent reduction in SOCS-3 antiinflammatory activity in women with preeclampsia. Thus, reduced gp130 and SOCS-3 expressions may offer, at least in part, a plausible explanation of reduced antiinflammatory protection in the maternal vascular system in preeclampsia.

Digoxin immune fab treatment for severe preeclampsia.

We evaluated the efficacy, safety, and biological mechanisms of digoxin immune Fab (DIF) treatment of severe preeclampsia. Fifty-one severe preeclamptic patients were randomized in double-blind fashion to DIF ( N = 24) or placebo ( N = 27) for 48 hours. Primary outcomes were change in creatinine clearance (CrCl) at 24 to 48 hours and antihypertensive drug use. Serum sodium pump inhibition, a sequela of endogenous digitalis-like factors (EDLF), was also assessed. CrCl in DIF subjects was essentially unchanged from baseline versus a decrease with placebo (-3 +/- 10 and -34 +/- 10 mL/min, respectively, P = 0.02). Antihypertensive use was similar between treatments (46 and 52%, respectively, P = 0.7). Serum sodium pump inhibition was decreased with DIF compared with placebo at 24 hours after treatment initiation (least squares mean difference, 19 percentage points, P = 0.03). DIF appeared to be well tolerated. These results suggest DIF prevents a decline in renal function in severe preeclampsia by neutralizing EDLF. Sodium pump inhibition was significantly improved. Further research is warranted.

Maternal circulating TNF-alpha levels are highly correlated with IL-10 levels, but not IL-6 and IL-8 levels, in women with pre-eclampsia.

PROBLEM: Several lines of evidence have shown that maternal cytokine levels of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, IL-8, and IL-10 were altered in women with pre-eclampsia (PE) compared to those from normal pregnancies. In this study, we determined whether these cytokine levels are correlated before and after delivery in patients with PE. METHOD OF STUDY: Venous blood was obtained from 50 women diagnosed with severe PE at the time of admission and 24 hr after delivery. Plasma concentrations for TNF-alpha, IL-6, IL-8, and IL-10 were measured by ELISA. RESULTS: There were no statistical differences for maternal levels of TNF-alpha, IL-6, IL-8, and IL-10 before and 24 hr postpartum. TNF-alpha and IL-10, but not IL-6 and IL-8, levels were significantly correlated before and 24 hr after delivery: TNF-alpha: y = 19.963 + 0.953*x; r(2) = 0.924; IL-10: y = 10.521 + 1.113*x; r(2) = 0.984, P < 0.001, respectively. Furthermore, TNF-alpha levels were correlated with IL-10 levels, but not with IL-6 and IL-8 levels. CONCLUSION: The correlation patterns of TNF-alpha with IL-10 and TNF-alpha with IL-6 and IL-8 suggest disparity in functional regulations between these cytokines in maternal circulation in PE.

Spontaneous left main coronary artery dissection complicated by pseudoaneurysm formation in pregnancy: role of CT coronary angiography.

We report a case of a 26-year-old female, who presented at 34 weeks of an uncomplicated pregnancy with an acute ST elevation anterior wall myocardial infarction. Cardiac catheterization suggested a left main coronary artery dissection with pseudoaneurysm formation. The patient's course was complicated by congestive heart failure. She was initially managed conservatively by a multidisciplinary team including heart failure specialists, obstetricians, and cardiovascular surgeons. 4 days after admission, her LMC was imaged by dual-source 64 slice Cardiac computed tomography, coronary dissection was identified extending to the lumen, and the presence of pseudoaneurysm was confirmed. She underwent subsequently a staged procedure, which included placement of an intra-aortic balloon pump, cesarean section, and coronary artery bypass grafting. This case illustrates the utility of coronary artery CT imaging to assess the complexity and stability of coronary artery dissections, thereby helping to determine the need for, and timing of revascularization procedures.

Progestins for the prevention of spontaneous preterm birth: review and implications of recent studies.

Progesterone plays a central role in the mechanisms of parturition in many species. Despite remarkable advances in our understanding of this hormone's mechanism of action, its roles in human pregnancy maintenance and parturition are not fully appreciated. Proper scientific hypothesis testing of progestins to prevent preterm birth has been limited because of the issues that can plague interventional trials in obstetrics, including patient selection, choice of outcome and power. The largest studies enrolling patients with a history of prior preterm birth alone to prevent recurrence appear contradictory. In contrast, consistent evidence from one multinational trial and a secondary analysis of another suggests cervical length may serve to identify potential responders to this therapy. Finally, the safety of progestin administration is a legitimate concern and a meta-analysis justifies the need for further investigation of safety issues. This review presents recent findings regarding progestin therapy from both clinical and laboratory data and considers unresolved issues for use of these agents.

Temperature and hydration effects on absorbance spectra and radiation sensitivity of a radiochromic medium.

The effects of temperature on real time changes in optical density (DeltaOD) of GAFCHROMIC EBT film were investigated. The spectral peak of maximum change in absorbance (lambdamax) was shown to downshift linearly when the temperature of the film was increased from 22 to 38 degrees C. The DeltaOD values were also shown to decrease linearly with temperature, and this decrease could not be attributed to the shift in lambdamax. A compensation scheme using lambdamax and a temperature-dependent correction factor was investigated, but provided limited improvement. Part of the reason may be the fluctuations in hydration of the active component, which were found to affect both position of absorbance peaks and the sensitivity of the film. To test the effect of hydration, laminated and unlaminated films were desiccated. This shifted both the major and minor absorbance peaks in the opposite direction to the change observed with temperature. The desiccated film also exhibited reduced sensitivity to ionizing radiation. Rehydration of the desiccated films did not reverse the effects, but rather gave rise to another form of the polymer with absorbance maxima upshifted further 20 nm. Hence, the spectral characteristics and sensitivity of the film can be dependent on its history, potentially complicating both real-time and conventional radiation dosimetry.

Up-regulation of CYP1A/B in rat lung and liver, and human liver precision-cut slices by a series of polycyclic aromatic hydrocarbons; association with the Ah locus and importance of molecular size.

Exposure of precision-cut rat liver slices to six structurally diverse polycyclic aromatic hydrocarbons, namely benzo[a]pyrene, benzo[b]fluoranthene, dibenzo[a,h]anthracene, dibenzo[a,l]pyrene, fluoranthene and 1-methylphenanthrene, led to induction of ethoxyresorufin O-deethylase, CYP1A apoprotein and CYP1A1 mRNA levels, but to a markedly different extent. In liver slices, constitutive CYP1A1 mRNA levels were higher, as well as being markedly more inducible by PAHs, compared with CYP1B1, a similar profile to that observed in human liver slices following exposure to the PAHs. Increase in ethoxyresorufin O-deethylase and in CYP1A1 apoprotein levels was also observed when precision-cut rat lung slices were incubated with the same PAHs, the order of induction potency being similar to that observed in liver slices. Under the same conditions of exposure, CYP1B1 apoprotein levels were elevated in the lung. Up-regulation of CYP1A1 by the six PAHs correlated with their affinity for the Ah receptor, determined using the chemical-activated luciferase expression (CALUX) assay. It may be concluded that (a) precision-cut liver and lung slices may be used to assess the CYP1 induction potential of chemicals at the activity, apoprotein and mRNA levels; (b) rat is a promising surrogate animal for human in studies to evaluate CYP1 induction potential; (c) CYP1A1 is far more inducible than CYP1B1 in both rat liver and lung; (d) CYP1 up-regulation by PAHs is related to their affinity for the Ah receptor, and finally (e) computer analysis revealed that the ratio of molecular length/width is an important determinant of CYP1 induction potency among equiplanar PAHs.

Placental productions and expressions of soluble endoglin, soluble fms-like tyrosine kinase receptor-1, and placental growth factor in normal and preeclamptic pregnancies.

CONTEXT: Increased production of antiangiogenic factors soluble endoglin (sEng) and soluble fms-like tyrosine kinase receptor-1 (sFlt-1) by the placenta contributes to the pathophysiology in preeclampsia (PE). OBJECTIVE: Our objective was to determine the differences in endoglin (Eng), fms-like tyrosine kinase receptor-1 (Flt-1), and placental growth factor (PlGF) expressions between normal and PE placentas and sEng, sFlt-1, and PlGF production by trophoblast cells (TC) cultured under lowered oxygen conditions. METHODS: TCs isolated from normal and PE placentas were cultured under regular (5% CO2/air) and lowered (2% O2/5% CO2/93% N2) oxygen conditions. sEng, sFlt-1, and PlGF productions were determined by ELISA. Protein expressions for Eng, Flt-1, and PlGF in the placental tissues were accessed by immunohistochemical staining and Western blot analysis. Deglycosylated Eng, Flt-1, and PlGF protein expressions in placental tissues were also examined. RESULTS: PE TCs produced significantly more sEng, sFlt-1, and PlGF compared with those from normal TCs (P < 0.05). Under lowered oxygen conditions, PE TCs, but not normal TCs, released more sEng and sFlt-1. In contrast, both normal and PE TCs released less PlGF (P < 0.05). Enhanced expressions of Eng and Flt-1, as well as glycosylated Eng and Flt-1, were observed in PE placentas. Immunoblot also revealed that TCs released glycosylated sFlt-1, but not sEng, in culture. CONCLUSIONS: PE TCs produce more sEng, sFlt-1, and PlGF than normal TCs. Lowered oxygen conditions promote sEng and sFlt-1, but reduce PlGF, productions by PE TCs. More glycosylated sEng and sFlt-1 are present in PE placentas. Trophoblasts release glycosylated sFlt-1, but unglycosylated sEng, in culture.

Urolithiasis in pregnancy: Current diagnosis, treatment, and pregnancy complications.

UNLABELLED: Urolithiasis complicates up to one in every 200 pregnancies; consequently, the practicing obstetrician should be aware of the symptoms of urolithiasis, the diagnostic procedures available for its diagnosis, and their associated risks. These include ultrasound, urography, and magnetic resonance imaging. Diagnosis of urolithiasis during pregnancy can be a challenge as a result of the normal physiological changes of pregnancy. Conservative management is the first-line treatment for noncomplicated urolithiasis in pregnancy. If spontaneous passage of the stone does not occur or if complications develop, urologic consultation should be obtained. Several obstetric complications have been associated with urolithiasis, including preterm labor and preterm premature rupture of membranes, although the reported rates of these complications in association with urolithiasis vary widely and overlap normal background rates. Given that urolithiasis will be encountered by most obstetricians, and that obstetricians are often on the front line of management for this condition, an appreciation of current diagnostic modalities, treatment protocols, and associated potential obstetric complications is warranted. TARGET AUDIENCE: Obstetricians & Gynecologists, Family Physicians. LEARNING OBJECTIVES: After completion of this article, the reader should be able to recall that urolithiasis is common in pregnancy, state that there are a variety of diagnostic procedures, summarize that conservative treatment is usually successful, and explain that complications of pregnancy usually occur when there is failure of conservative treatment.

Investigating human P450s involved in drug metabolism via homology with high-resolution P450 crystal structures of the CYP2C subfamily.

The important role of high-resolution crystal structures of cytochrome P450 (CYP) enzymes for the generation of P450 models by homology is discussed. The main focus is on human P450 enzymes involved in drug metabolism, where the role of homology modelling has been emphasized in the recent literature. Report of the first human P450 crystal structure has provided an opportunity for comparison between those modelled from other crystallographic templates, and the recent substrate-bound rabbit CYP2C5 structure exemplifies the relevance of high-resolution template structures to generating 3-D models of P450s where the homology is relatively high. In particular, the homology models of human CYP1 and CYP2 family enzymes are presented, where good agreement with experiment findings are apparent.

Inhibition of human CYP1A2 oxidation of 5,6-dimethyl-xanthenone-4-acetic acid by acridines: a molecular modelling study.

1. The aim of the present study was to investigate the structural requirements for the inhibition of 6-methyl-hydroxylation of the antitumour agent 5,6-dimethyl-xanthenone-4-acetic acid (DMXAA) by acridine analogues and use a CYP1A2 homology model to provide some insight into this interaction. 2. Concentrations causing 50% inhibition (IC50) of the 6-methylhydroxylation of DMXAA were determined in human liver microsomes in the presence of various acridines. Some of the acridines were also tested for their ability to inhibit the CYP1A2-mediated 7-ethoxyresorufin O-de-ethylation. The molecular modelling studies of human CYP1A2 used the crystal structure of rabbit CYP2C5 as a template based on protein sequence homology and an interactive docking procedure using a dynamic hydrogen bond feature. 3. The in vitro IC50 studies for the inhibition of 6-methylhydroxylation of DMXAA indicated: (i) the importance of the position of the carboxamide side-chain on the acridine nucleus (and, to a lesser extent, its composition); (ii) the addition of hydroxyl groups to the 5-, 6- and 7-position of the acridine nucleus diminished the inhibitory potency; and (iii) amsacrine (acridine nucleus with methansulphonanilide side-chain at the 9-position) had no significant inhibitory effect. Similar structural trends were observed for the inhibition of O-de-ethylation of 7-ethoxyresorufin by acridines, supporting the involvement of CYP1A2 in DMXAA 6-methyl hydroxylation. 4. The molecular modelling studies indicated: (i) both DMXAA and N-[2-(dimethylamino)-ethyl]acridine-4-carboxamide (DACA) form two hydrogen bonds plus putative pi-pi stacking interactions with the CYP1A2-binding domain, typical of CYP1A2 substrates and inhibitors; (ii) the DMXAA 6-methyl group is 4.0 A from the central iron atom of the heme moiety and ideal for oxidation; (iii) the known oxidation sites for DACA are orientated away from the heme iron, supporting the non-involvement of CYP1A2; and (iv) amsacrine did not fit the putative CYP1A2 site owing to the steric hindrance of the bulky methanesulphonanilide side-chain. 5. These results suggest that docking studies with this homology model may be useful in the design of further acridine anticancer agents, in particular to identify agents that do not interact either as substrates or inhibitors with the CYP1A2-binding domain.

Hypoxia promotes interleukin-6 and -8 but reduces interleukin-10 production by placental trophoblast cells from preeclamptic pregnancies.

OBJECTIVE: Placental hypoxia and altered placental cytokine productions have been considered to play a significant role in the pathophysiology of preeclampsia. The objective of this study was to determine whether hypoxia could modify interleukin (IL)-6, IL-8, and IL-10 production by placental trophoblast cells (TCs) from normal and preeclamptic (PE) pregnancies. METHODS: Placentas were obtained from nine normal and nine PE pregnancies immediately after delivery. Placental TCs were isolated and cultured under normoxic (21% O(2)/air) and hypoxic (2% O(2)/5% CO(2)/92% N(2)) conditions for 48 hours. TC productions of IL-6, IL-8, and IL-10 were measured by enzyme-linked immunosorbent assay (ELISA). Unpaired t tests or paired t test was used for the statistical analysis and data are expressed as means +/- SE (pg/mug cellular protein). A P value less than .05 was considered statistically significant. RESULTS: PE-TCs produced significantly more IL-6, IL-8, and IL-10 than those of normal-TCs when they were cultured under normoxic condition, P < .05. Both normal-TCs and PE-TCs produced more IL-6 and IL-8 when they were cultured under hypoxic conditions. Hypoxia reduced IL-10 production by PE-TCs, but had no effect on IL-10 production by normal-TCs. CONCLUSIONS: Hypoxia promotes both IL-6 and IL-8 but reduces IL-10 production by placental TCs from PE pregnancies.

Cytochromes P450 in the bioactivation of chemicals.

The initial view that the cytochrome P450 enzyme system functions simply in the deactivation of xenobiotics is anachronistic on the face of mounting evidence that this system can also transform many innocuous chemicals to toxic products. However, not all xenobiotic-metabolising cytochrome P450 subfamilies show the same propensity in the bioactivation of chemicals. For example, the CYP2C, 2B and 2D subfamilies play virtually no role in the bioactivation of toxic and carcinogenic chemicals, whereas the CYP1A, 1B and 2E subfamilies are responsible for the bioactivation of the majority of xenobiotics. Electronic and molecular structural features of organic chemicals appear to predispose them to either bioactivation by one cytochrome P450 enzyme or deactivation by another. Consequently, the fate of a chemical in the body is largely dependent on the cytochrome P450 profile at the time of exposure. Any factor that modulates the enzymes involved in the metabolism of a certain chemical will also influence its toxicity and carcinogenicity. For example, many chemical carcinogens bioactivated by CYP1, on repeated administration, selectively induce this family, thus exacerbating their carcinogenicity. CYP1 induction potency by chemicals appears to be determined by a combination of their molecular shape and electron activation. The function of cytochromes P450 in the bioactivation of chemicals is currently being exploited to design systems that can be used clinically to facilitate the metabolic conversion of prodrugs to their biologically-active metabolites in cells that poorly express them, such as tumour cells, in the so-called gene-directed prodrug therapy.