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Background: Low sFlt-1 (soluble Fms-like tyrosine kinase-1) and ET-1 (endothelin-1) levels have been reported in preeclamptic women using proton pump inhibitors., Methods: Here, we examined whether the proton pump inhibitor omeprazole could acutely reduce sFlt-1 and ET-1 (measured as CT-proET-1 [C-terminal pro-endothelin-1]), or increase free PlGF (placental growth factor) in 20 women with confirmed preeclampsia. Primary outcome was specified as the difference in sFlt-1, PlGF, or CT-proET-1 after 4 days of omeprazole versus 20 preeclamptic women not receiving omeprazole., Results: Mean maternal age was 30 years, and median gestational age was 30 +3 weeks. Baseline sFlt-1 levels were identical in both groups, and the same was true for PlGF or CT-proET-1. After 4 days, sFlt-1 levels remained similar in women not receiving omeprazole compared with women receiving omeprazole, while the levels of PlGF and CT-proET-1 also did not differ between groups. Women receiving omeprazole had a similar prolongation of pregnancy after inclusion compared with those in the nonomeprazole group (median 15 versus 14 days). Except for a higher neonatal intubation rate in the nonomeprazole group (31% versus 4%, P =0.02), there were no differences in maternal/perinatal complications. Finally, making use of the placenta perfusion model, we established that both omeprazole and its S-isomer, esomeprazole, when maternally applied, reached the fetal compartment (fetal-to-maternal ratio's 0.43-0.59), while only esomeprazole inhibited placental sFlt-1 release., Conclusions: Administration of omeprazole to women with confirmed preeclampsia does not alter their circulating levels of sFlt-1, PlGF, or ET-1, arguing against a role of this drug as a treatment for this syndrome.

Background: Due to increased travel from endemic countries, malaria occurs more frequently in non-endemic regions. It is a challenge for diagnostic laboratories in non-endemic countries to provide reliable results, as experience of staff is often limited to only a few cases per year. This study evaluated the diagnostic accuracy of the fully automated Sysmex XN-31 malaria analyzer in a routine diagnostic setting in a non-endemic region was evaluated., Methods: Samples from 112 patients suspected for malaria were examined by the Sysmex XN-31 analyzer to determine the absolute count of malaria-infected red blood cells count (MI-RBC/µL). Microscopic examination of both Quantitative Buffy Coat capillary tubes and thick and thin blood films were used as reference methods. Limits of blank (LoB), detection (LoD) and quantification (LoQ) were investigated using an in vitro Plasmodium falciparum culture. Nine hundred twenty samples of patients with RBC abnormalities were included to determine which RBC abnormalities trigger indeterminate or false positive results., Results: No false positive nor false negative results were obtained for the examined patient samples suspected for malaria. For 3% of samples an indeterminate result by the XN-31 was obtained. The Passing-Bablok regression line for diagnostic accuracy of the parasitaemia was y = 39.75 + 0.7892 × showing a positive bias of about 21% when comparing the MI-RBC results to microscopy. The LoB, LoD and LoQ were calculated to be 4.7, 5.9, and 19.0 infected RBC/μL, respectively. From the 920 abnormal RBC samples collected, 4.6% resulted in a false positive MI-RBC result and almost half of the samples produced indeterminate results. These results were related to increases in nucleated red blood cells, reticulocytes and other abnormal RBC morphologies such as sickle cells., Conclusions: Based on the results, the XN-31 is a fast and reliable screening method in the detection and quantification of Plasmodium species in patients However, if an abnormal red blood cell morphology is present, the results of the XN-31 should be interpreted with caution as false positive results can be caused by interfering abnormal erythrocytes., (© 2022. The Author(s).)

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Competing Interests: The authors declare that there is no conflict of interest.

COVID-19 induces haemocytometric changes. Complete blood count changes, including new cell activation parameters, from 982 confirmed COVID-19 adult patients from 11 European hospitals were retrospectively analysed for distinctive patterns based on age, gender, clinical severity, symptom duration, and hospital days. The observed haemocytometric patterns formed the basis to develop a multi-haemocytometric-parameter prognostic score to predict, during the first three days after presentation, which patients will recover without ventilation or deteriorate within a two-week timeframe, needing intensive care or with fatal outcome. The prognostic score, with ROC curve AUC at baseline of 0.753 (95% CI 0.723-0.781) increasing to 0.875 (95% CI 0.806-0.926) on day 3, was superior to any individual parameter at distinguishing between clinical severity. Findings were confirmed in a validation cohort. Aim is that the score and haemocytometry results are simultaneously provided by analyser software, enabling wide applicability of the score as haemocytometry is commonly requested in COVID-19 patients., Competing Interests: JL, JS, MM is a permanent employee of Sysmex Europe GMBH who provided free of charge study reagents to the study centres. AE, MB, MS, GP, Sv, HR, AV, JG, JR, Ed, IM, AD, VS, HA, KD, SB, LV, YK, ML No competing interests declared, Av has an ad hoc consultancy agreement with Sysmex Europe GMBH who provided free of charge study reagents to the study centres., (© 2020, Linssen et al.)

To assess the incremental value of a single determination of the serum levels of sFlt-1 (soluble Fms-like tyrosine kinase 1) and PlGF (placental growth factor) or their ratio, without using cutoff values, for the prediction of maternal and fetal/neonatal complications and pregnancy prolongation, 620 women with suspected/confirmed preeclampsia, aged 18 to 48 years, were included in a prospective, multicenter, observational cohort study. Women had singleton pregnancies and a median pregnancy duration of 34 (range, 20-41) weeks. Complications occurred in 118 women and 248 fetuses. The median duration between admission and delivery was 12 days. To predict prolongation, PlGF showed the highest incremental value ( R 2 =0.72) on top of traditional predictors (gestational age at inclusion, diastolic blood pressure, proteinuria, creatinine, uric acid, alanine transaminase, lactate dehydrogenase, and platelets) compared with R 2 =0.53 for the traditional predictors only. sFlt-1 showed the highest value to discriminate women with and without maternal complications (C-index=0.83 versus 0.72 for the traditional predictors only), and the sFlt-1/PlGF ratio showed the highest value to discriminate fetal/neonatal complications (C-index=0.86 versus 0.78 for the traditional predictors only). Applying previously suggested cutoff values for the sFlt-1/PlGF ratio yielded lower incremental values than applying continuous values. In conclusion, sFlt-1 and PlGF are strong and independent predictors for days until delivery along with maternal and fetal/neonatal complications on top of the traditional criteria. Their use as continuous variables (instead of applying cutoff values for different gestational ages) should now be tested in a prospective manner, making use of an algorithm calculating the risk of an individual woman with suspected/confirmed preeclampsia to develop complications., (© 2017 American Heart Association, Inc.)

Women with preeclampsia display low renin-angiotensin-aldosterone system activity and a high antiangiogenic state, the latter characterized by high levels of soluble Fms-like tyrosine kinase (sFlt)-1 and reduced placental growth factor levels. To investigate whether renin-angiotensin-aldosterone system suppression in preeclampsia is because of this disturbed angiogenic balance, we measured mean arterial pressure, creatinine, endothelin-1 (ET-1), and renin-angiotensin-aldosterone system components in pregnant women with a high (≥85; n=38) or low (<85; n=65) soluble Fms-like tyrosine kinase-1/placental growth factor ratio. Plasma ET-1 levels were increased in women with a high ratio, whereas their plasma renin activity and plasma concentrations of renin, angiotensinogen, and aldosterone were decreased. Plasma renin activity-aldosterone relationships were identical in both the groups. Multiple regression analysis revealed that plasma renin concentration correlated independently with mean arterial pressure and plasma ET-1. Plasma ET-1 correlated positively with soluble Fms-like tyrosine kinase-1 and negatively with plasma renin concentration, and urinary protein correlated with plasma ET-1 and mean arterial pressure. Despite the lower plasma levels of renin and angiotensinogen in the high-ratio group, their urinary levels of these components were elevated. Correction for albumin revealed that this was because of increased glomerular filtration. Subcutaneous arteries obtained from patients with preeclampsia displayed an enhanced, AT2 receptor-mediated response to angiotensin II. In conclusion, a high antiangiogenic state associates with ET-1 activation, which together with the increased mean arterial pressure may underlie the parallel reductions in renin and aldosterone in preeclampsia. Because ET-1 also was a major determinant of urinary protein, our data reveal a key role for ET-1 in the pathogenesis of preeclampsia. Finally, the enhanced angiotensin responsiveness in preeclampsia involves constrictor AT2 receptors., (© 2015 American Heart Association, Inc.)

Context: Adequate thyroid hormone availability during fetal and early life is crucial for normal child growth and development. Fetal growth heavily depends on angiogenesis. Placental growth factor (PlGF) is a proangiogenic factor sharing high homology with vascular endothelial growth factor, whereas soluble FMS-like tyrosine kinase-1 (sFlt1) is a potent antagonist of vascular endothelial growth factor and PlGF signaling. Because the thyroid is a highly vascularized organ, we hypothesized that fetal angiogenic factors influence in utero thyrogenesis and impair newborn thyroid function. Therefore, we investigated the association between sFlt1 and PlGF on newborn thyroid function., Design, Setting, and Participants: sFlt1, PlGF, TSH, and free T4 (FT4) were determined in cord serum of 3525 newborns from a large prospective cohort study. Analyses were adjusted for relevant maternal and child covariates., Results: sFlt1 levels were positively associated with TSH (β 0.07 ± 0.02 mU/L; P < .001) and inversely with FT4 (β -0.58 ± 0.11; P < .001). PlGF showed a positive association with FT4 (β 0.19 ± 0.02; P < .001). Elevated levels of sFlt1 were associated with a 2.8-fold increased risk of hypothyroxinemia (P = .04). Decreased levels of PlGF were associated with a 6.7-fold increased risk of hypothyroxinemia (P < .001). Within the normal range, a dose-dependent effect of sFlt1 on thyroid dysfunction was observed: high-normal sFlt1 levels were associated with a 17.7-fold increased risk of hypothyroxinemia (P < .001) and a 2.7-fold increased risk of hyperthyrotropinemia (P = .01)., Conclusion: Fetal angiogenic factors sFlt1 and PlGF are associated with newborn thyroid function. Possible effects are most likely mediated through effects on in utero thyrogenesis. Abnormal as well as normal-range fetal sFlt1 and PlGF levels influence the risk of impaired newborn thyroid function, which has been associated with adverse neurodevelopmental effects. These data provide important novel insights into the physiology of thyrogenesis and into the etiology of newborn thyroid (dys)function.

Background: Air pollution exposure during pregnancy might affect placental growth and function, perhaps leading to pregnancy complications., Objective: We prospectively evaluated the associations of maternal air pollution exposure with markers of placental growth and function among 7,801 pregnant women in the Netherlands., Methods: We estimated levels of particulate matter ≤ 10 µm in aerodynamic diameter (PM10) and nitrogen dioxide (NO2) at the home address for different periods during pregnancy using dispersion modeling techniques. Pro- and anti-angiogenic factors [placental growth factor (PlGF) and soluble fms-like tyrosine kinase 1 (sFlt-1), respectively] were measured in first- and second-trimester maternal blood and in fetal cord blood samples at delivery. Pulsatility index of the uterine and umbilical arteries was measured by Doppler ultrasound in second and third trimester, and notching was assessed in third trimester. Placenta weight and birth weight were obtained from medical records., Results: Higher PM10 and NO2 exposure levels were associated with lower second-trimester maternal sFlt-1 and PlGF levels. PM10 and NO2 exposures averaged over total pregnancy were associated with higher sFlt-1 and lower PlGF levels in fetal cord blood, consistent with an anti-angiogenic state. PM10 and NO2 exposures were not consistently associated with second- or third-trimester placental resistance indices. NO2 exposure was associated with third-trimester notching (odds ratio 1.33; 95% CI: 0.99, 1.78 per 10-µg/m3 increase in the prior 2 months). PM10 and NO2 exposures were associated with lower placenta weight (-11.8 g; 95% CI: -20.9, -2.7, and -10.7 g; 95% CI: -19.0, -2.4, respectively, per 10-µg/m3 increase in the prior 2 months), but not with placenta to birth weight ratio., Conclusions: Our results suggest that maternal air pollution exposure may influence markers of placental growth and function. Future studies are needed to confirm these findings and explore the maternal and fetal consequences.

Developmental adaptations due to early nutritional exposures may have permanent health consequences. Studies of diet and fetal size have mainly focused on individual nutrients despite evidence that the pattern of food consumption may be of significance. Hence, we evaluated the associations of dietary habits in early pregnancy (gestational age < 18 weeks) with fetal size, uteroplacental vascular resistance, placental weight and birth weight in a prospective observational study of 3207 Caucasian pregnant mothers in Rotterdam, the Netherlands. Participants completed a semiquantitative FFQ during early pregnancy. Logistic regression analysis was used to predict the occurrence of intra-uterine growth retardation at birth as a function of food intake. The derived solution was considered as the dietary pattern. As it was characterised by higher intakes of fruit, vegetables, vegetable oil, fish, pasta and rice, and lower intakes of meat, potatoes and fatty sauces, it was labelled the 'Mediterranean' diet. The degree of adherence to the diet was positively associated with plasma folate and serum vitamin B12 concentrations and showed an inverse relationship with homocysteine and high-sensitivity C-reactive protein plasma concentrations (P <0·05). Important fetal size and placental parameters were associated with the degree of adherence to the diet, revealing a 72 g lower birth weight (95% CI -110·8, -33·3) and a 15 g lower placental weight (95% CI -29·8, -0·2) for women with low adherence to the diet. To conclude, low adherence to a Mediterranean diet in early pregnancy seems associated with decreased intra-uterine size with a lower placental and a lower birth weight.

Background: Exposure to air pollution has been associated with higher C-reactive protein (CRP) levels, suggesting an inflammatory response. Not much is known about this association in pregnancy., Objectives: We investigated the associations of air pollution exposure during pregnancy with maternal and fetal CRP levels in a population-based cohort study in the Netherlands., Methods: Particulate matter (PM) with an aerodynamic diameter ≤ 10 μm (PM10) and nitrogen dioxide (NO2) levels were estimated at the home address using dispersion modeling for different averaging periods preceding the blood sampling (1 week, 2 weeks, 4 weeks, and total pregnancy). High-sensitivity CRP levels were measured in maternal blood samples in early pregnancy (n = 5,067) and in fetal cord blood samples at birth (n = 4,450)., Results: Compared with the lowest quartile, higher PM10 exposure levels for the prior 1 and 2 weeks were associated with elevated maternal CRP levels (> 8 mg/L) in the first trimester [fourth PM10 quartile for the prior week: odds ratio (OR), 1.32; 95% confidence interval (CI): 1.08, 1.61; third PM10 quartile for the prior 2 weeks: OR, 1.28; 95% CI: 1.06, 1.56]; however, no clear dose-response relationships were observed. PM10 and NO2 exposure levels for 1, 2, and 4 weeks preceding delivery were not consistently associated with fetal CRP levels at delivery. Higher long-term PM10 and NO2 exposure levels (total pregnancy) were associated with elevated fetal CRP levels (> 1 mg/L) at delivery (fourth quartile PM10: OR, 2.18; 95% CI: 1.08, 4.38; fourth quartile NO2: OR, 3.42; 95% CI: 1.36, 8.58; p-values for trend < 0.05)., Conclusions: Our results suggest that exposure to air pollution during pregnancy may lead to maternal and fetal inflammatory responses.

A 29-year-old male presented at the emergency department of our hospital in a confused state. He had a history of psychoses and substance abuse. Physical examination revealed hyperventilation and abdominal tenderness. Blood gas analysis in the emergency department using an ABL 725 Radiometer analyser showed a severe metabolic acidosis with massive lactate elevation. Lactate acidosis due to mesenteric ischaemia was suspected. However, toxicology screening demonstrated ethylene glycol intoxication. Treatment with ethanol infusion and acute haemodialysis was started. Repeated laboratory measurements using a clinical chemistry analyser showed minimal plasma lactate elevation. Falsely elevated lactate measurement is a little known phenomenon that can occur in ethylene glycol intoxication and can cause serious delay in diagnosis. Therefore, elevated lactate concentrations measured on intensive care unit and emergency department blood gas analysers should be confirmed by a clinical chemistry analyser in the main laboratory in case of suspected ethylene glycol intoxication.

The glucocorticoid receptor (GR) is widely expressed in various tissues throughout the human body. At least three different 3'-splice variants of the GR have been reported: GR-alpha, which is functionally active; GR-beta, which is a dominant negative inhibitor of GR-alpha function; and GR-P, which is thought to activate the function of GR-alpha. At least seven different variants for exon 1 exist, 1A-1F and 1H, each with its own promoter. In this study, we explored if tissue-specific splicing of the 3'-end variants of the GR is influenced by alternative promoter usage. cDNAs of different tissues and cell lines were used to investigate which part of transcripts carrying each of the three major variants for exons 1, 1A, 1B, or 1C, encodes for the splice variants GR-alpha, GR-beta, and GR-P. Our data demonstrate that the expression of GR-alpha is preferentially regulated by promoter 1C and that for the expression of GR-P promoter 1B is predominantly used. This indicates that regulation of GR splice variants could partly occur through selective use of the multiple promoters, and that this is another way to sensitize cells and tissues to the different activities of the GR isoforms.

Context: Glucocorticoids (GCs) are extensively used in the treatment of inflammatory and autoimmune diseases. Their beneficial effects are thought to be mediated by GC transrepression on gene expression. However, their use is limited by serious adverse effects, presumably mediated by GC transactivation of gene expression., Objective: The objective of the study was to investigate the effect of the GC receptor haplotype, characterized by the GR-9beta polymorphism, on GC transactivation and transrepression., Design and Methods: This was a cross-sectional study in 216 persons randomly selected from participants in The Rotterdam Study, a population-based cohort study in the elderly. Clinical and biochemical parameters of GC sensitivity were measured: weight, height, waist to hip ratio, glucose, insulin, total cholesterol, high-density lipoprotein, and C-reactive protein. In a dexamethasone suppression test, the response of serum cortisol concentrations was studied. Genotyping for four GC receptor polymorphisms was performed. In addition, ex vivo experiments were performed with leukocytes of 10 healthy controls and two persons homozygous for the GR-9beta polymorphism, in which the expression of two GC-sensitive genes, GC-induced leucine zipper and IL-2, was measured., Results: Persons carrying the GR-9beta haplotype without 22/23EK (n = 53) revealed no significant differences in their body mass index, waist to hip ratio, fat spectrum, and insulin sensitivity or in their cortisol response to dexamethasone and levels of C-reactive protein, compared with noncarriers (n = 113). Ex vivo, GC-induced up-regulation of GC-induced leucine zipper mRNA via transactivation did not significantly differ in GR-9beta homozygotes, whereas the down-regulation of IL-2 expression via transrepression was decreased., Conclusion: Persons carrying the GR-9beta haplotype seem to have a decreased GC transrepression with normal transactivation.

Context: The clinical presentation of abnormalities in glucocorticoid (GC) sensitivity is diverse, and therefore it is difficult to diagnose this condition., Objective and Design: The objective of the study was to develop strategies for the characterization of GC sensitivity disorders., Setting: The study was conducted in an outpatient clinic., Patients: Nine patients with GC sensitivity disorders participated., Interventions: Sequence analysis of the GC receptor (GR), determination of GR number per cell, GR ligand-binding affinity, and GR splice regulation were performed in freshly prepared peripheral blood mononuclear lymphocytes and Epstein-Barr virus-transformed lymphoblasts. Cellular GC sensitivity was determined ex vivo by measuring the effect of dexamethasone on GC-induced leucine-zipper and IL-2 mRNA levels and on cell proliferation., Results: Differences in GR number per cell, GR affinity, GR splice variants, and effects on transactivation or transrepression of GC-sensitive genes were observed between patients and controls. Epstein-Barr virus transformation of lymphoblasts had no influence on GR affinity but increased the GR number 5-fold in healthy controls. In patients diagnosed as cortisol resistant, however, GR number after transformation was increased significantly less than 5-fold, whereas a higher GR number was observed in a patient suspected of cortisol hypersensitivity., Conclusion: This study illustrates several strategies to define abnormalities in GC sensitivity by describing nine patients with affected GC sensitivity, all with a unique clinical course and background.

Context: Interindividual variation in glucocorticoid (GC)-sensitivity can be partly explained by polymorphisms in the GC receptor (GR) gene. The ER22/23EK and N363S polymorphisms have been described to be associated with lower and higher GC sensitivity, respectively., Objective and Design: We examined the basis of this altered GC sensitivity by expressing GR(N363S) and GR(ER22/23EK) in COS-1 cells and investigating their transactivating and transrepressing capacities using a GC response element-luciferase reporter and a p65-activated nuclear factor kappaB-luciferase reporter, respectively. Furthermore, we evaluated the transactivating and transrepressing capacities of the GR in peripheral blood mononuclear lymphocytes of homozygous and heterozygous carriers of these polymorphisms by determining the maximum effect of dexamethasone on transactivation of the GC-induced leucine-zipper and transinhibition of the IL-2 gene by means of real-time RT-PCR., Results: The effects of the polymorphisms in the GR gene previously observed in population studies were also detected at the level of gene expression. The ER22/23EK polymorphism resulted in a significant reduction of transactivating capacity, in both transfection experiments (-14 +/- 5%, P < 0.05) and peripheral blood mononuclear lymphocytes of carriers of this polymorphism (homozygous: -48 +/- 6%, P < 0.01, n = 1; heterozygous: -21 +/- 4%, P = 0.08, n = 3). The N363S polymorphism, associated with increased GC sensitivity, resulted in a significantly increased transactivating capacity, both in vitro (8 +/- 3%; P < 0.02) and ex vivo (homozygous: 204 +/- 19%, P < 0.0001, n = 1; heterozygous: 124 +/- 8%, P = 0.05, n = 3). Neither the ER22/23EK nor the N363S polymorphism seemed to influence the transrepressing capacity of the GR., Conclusion: The presence of these and other GC sensitivity-modulating polymorphisms may have consequences for the use of GCs in a clinical setting.

One of the most intriguing polymorphisms in the GR [glucocorticoid (GC) receptor] gene is in codons 22 and 23 [GAGAGG(GluArg) --> GAAAAG (GluLys)]. This polymorphism is associated with a reduced GC sensitivity, a better metabolic and cardiovascular health profile, and an increased survival rate. Recently, Yudt and Cidlowski reported that two different methionine codons in the GR mRNA may be used as initiation codon: AUG-1 and AUG-27, resulting in two isoforms, the GR-A and the GR-B proteins, respectively. They also showed that the GR-B protein had a stronger transactivating effect in transient transfection experiments. In this study, we elucidated the molecular basis for the reduced GC sensitivity by investigating the influence of the ER22/23EK polymorphism on synthesis of GR-A and GR-B by expressing them independently from constructs with and without the polymorphic site. Binding studies with [(3)H]-dexamethasone and transactivation studies showed that, when the ER22/23EK polymorphism is present, approximately 15% more GR-A protein was expressed, whereas total GR levels (GR-A + GR-B) were not affected. These results show that the transcriptional activity in GR(ER22/23EK) carriers is decreased because more of the less transcriptionally active GR-A isoform is formed. This is probably caused by altered secondary mRNA structure.

Individual glucocorticoid (GC) sensitivity was determined by measuring the effects of several clinically used GCs on transactivation of the GC-induced leucine zipper (GILZ) gene and on transrepression of the IL-2 gene using quantitative real-time PCR. A clear difference in relative potencies for transactivation and transrepression of the various GCs was observed, suggesting differential effects. To determine whether the in vitro outcomes could predict in vivo effects of GCs, 15 individuals underwent a 0.25-mg dexamethasone (DEX) suppression test (DST) while determining GILZ and IL-2 mRNA levels in their peripheral blood mononuclear cells incubated with hydrocortisone, DEX, budesonide, and prednisolone. No correlations were found between the DST and the two expression assays. However, significant correlations existed between hydrocortisone and DEX (r = 0.52; P = 0.046), hydrocortisone and budesonide (r = 0.48; P = 0.069), and hydrocortisone and prednisolone (r = 0.86; P = 0.007) regarding GILZ mRNA levels, and between hydrocortisone and DEX (r = 0.62; P = 0.014), hydrocortisone and budesonide (r = 0.71; P = 0.003), and hydrocortisone and prednisolone (r = 0.71; P = 0.047) regarding IL-2 mRNA levels. In conclusion, intra- and inter-individual variations in GC sensitivity were observed using two expression assays representing GC-mediated transactivation and transrepression. The two expression assays did not correlate with each other or with the results of the DST. This suggests that regulation of the hypothalamic-pituitary-adrenal axis is more complex. However, within an individual person, these two tests combined might predict what type and dosage of GC will be preferable in individual patients for its inhibitory clinical effects, together with relatively fewer transactivating effects related to adverse effects.

Recently, we recognized two genes, gbpA and gbpB, encoding putative cGMP-binding proteins with a Zn(2+)-hydrolase domain and two cyclic nucleotide binding domains. The Zn(2+)-hydrolase domains belong to the superfamily of beta-lactamases, also harboring a small family of class II phosphodiesterases from bacteria and lower eukaryotes. Gene inactivation and overexpression studies demonstrate that gbpA encodes the cGMP-stimulated cGMP-phosphodiesterase that was characterized biochemically previously and was shown to be involved in chemotaxis. cAMP neither activates nor is a substrate of GbpA. The gbpB gene is expressed mainly in the multicellular stage and seems to encode a dual specificity phosphodiesterase with preference for cAMP. The enzyme hydrolyses cAMP approximately 9-fold faster than cGMP and is activated by cAMP and cGMP with a K(A) value of approximately 0.7 and 2.3 microM, respectively. Cells with a deletion of the gbpB gene have increased basal and receptor stimulated cAMP levels and are sporogeneous. We propose that GbpA and GbpB hydrolyze the substrate in the Zn(2+)-hydrolase domain, whereas the cyclic nucleotide binding domains mediate activation. The human cGMP-stimulated cAMP/cGMP phosphodiesterase has similar biochemical properties, but a completely different topology: hydrolysis takes place by a class I catalytic domain and GAF domains mediate cGMP activation.

Chemotactic stimulation of Dictyostelium cells results in a transient increase in cGMP levels, and transient phosphorylation of myosin II heavy and regulatory light chains. In Dictyostelium, two guanylyl cyclases and four candidate cGMP-binding proteins (GbpA- GbpD) are implicated in cGMP signalling. GbpA and GbpB are homologous proteins with a Zn2+-hydrolase domain. A double gbpA/gbpB gene disruption leads to a reduction of cGMP-phosphodiesterase activity and a 10-fold increase of basal and stimulated cGMP levels. Chemotaxis in gbpA(-)B(-) cells is associated with increased myosin II phosphorylation compared with wild-type cells; formation of lateral pseudopodia is suppressed resulting in enhanced chemotaxis. GbpC is homologous to GbpD, and contains Ras, MAPKKK and Ras-GEF domains. Inactivation of the gbp genes indicates that only GbpC harbours high affinity cGMP-binding activity. Myosin phosphorylation, assembly of myosin in the cytoskeleton as well as chemotaxis are severely impaired in mutants lacking GbpC and GbpD, or mutants lacking both guanylyl cyclases. Thus, a novel cGMP signalling cascade is critical for chemotaxis in Dictyostelium, and plays a major role in myosin II regulation during this process.