Postoperative circadian patterns in wearable sensor measured heart rate: a prospective observational study.

PURPOSE: This study aimed to describe the 24-hour cycle of wearable sensor-obtained heart rate in patients with deterioration-free recovery and to compare it with patients experiencing postoperative deterioration. METHODS: A prospective observational trial was performed in patients following bariatric or major abdominal cancer surgery. A wireless accelerometer patch (Healthdot) continuously measured postoperative heart rate, both in the hospital and after discharge, for a period of 14 days. The circadian pattern, or diurnal rhythm, in the wearable sensor-obtained heart rate was described using peak, nadir and peak-nadir excursions. RESULTS: The study population consisted of 137 bariatric and 100 major abdominal cancer surgery patients. In the latter group, 39 experienced postoperative deterioration. Both surgery types showed disrupted diurnal rhythm on the first postoperative days. Thereafter, the bariatric group had significantly lower peak heart rates (days 4, 7-12, 14), lower nadir heart rates (days 3-14) and larger peak-nadir excursions (days 2, 4-14). In cancer surgery patients, significantly higher nadir (days 2-5) and peak heart rates (days 2-3) were observed prior to deterioration. CONCLUSIONS: The postoperative diurnal rhythm of heart rate is disturbed by different types of surgery. Both groups showed recovery of diurnal rhythm but in patients following cancer surgery, both peak and nadir heart rates were higher than in the bariatric surgery group. Especially nadir heart rate was identified as a potential prognostic marker for deterioration after cancer surgery.

The Accuracy of Wrist-Worn Photoplethysmogram-Measured Heart and Respiratory Rates in Abdominal Surgery Patients: Observational Prospective Clinical Validation Study.

BACKGROUND: Postoperative deterioration is often preceded by abnormal vital parameters. Therefore, vital parameters of postoperative patients are routinely measured by nursing staff. Wrist-worn sensors could potentially provide an alternative tool for the measurement of vital parameters in low-acuity settings. These devices would allow more frequent or even continuous measurements of vital parameters without relying on time-consuming manual measurements, provided their accuracy in this clinical population is established. OBJECTIVE: This study aimed to assess the accuracy of heart rate (HR) and respiratory rate (RR) measures obtained via a wearable photoplethysmography (PPG) wristband in a cohort of postoperative patients. METHODS: The accuracy of the wrist-worn PPG sensor was assessed in 62 post-abdominal surgery patients (mean age 55, SD 15 years; median BMI 34, IQR 25-40 kg/m2). The wearable obtained HR and RR measurements were compared to those of the reference monitor in the postanesthesia or intensive care unit. Bland-Altman and Clarke error grid analyses were performed to determine agreement and clinical accuracy. RESULTS: Data were collected for a median of 1.2 hours per patient. With a coverage of 94% for HR and 34% for RR, the device was able to provide accurate measurements for the large majority of the measurements as 98% and 93% of the measurements were within 5 bpm or 3 rpm of the reference signal. Additionally, 100% of the HR and 98% of the RR measurements were clinically acceptable on Clarke error grid analysis. CONCLUSIONS: The wrist-worn PPG device is able to provide measurements of HR and RR that can be seen as sufficiently accurate for clinical applications. Considering the coverage, the device was able to continuously monitor HR and report RR when measurements of sufficient quality were obtained. TRIAL REGISTRATION: ClinicalTrials.gov NCT03923127; https://www.clinicaltrials.gov/ct2/show/NCT03923127.

The Metabolic Health Index Identifies Patients That Will Benefit From Metabolic Surgery.

INTRODUCTION: Metabolic syndrome is a modern world's major health hazard related to comorbidities like type 2 diabetes and cardiovascular disease. Bariatric surgery is well known to lower this health risk in patients with obesity. There is a need for an objective measure to assess the intended reduction in health hazard and indirectly the eligibility for bariatric surgery. The Metabolic Health Index (MHI) quantitatively summarizes the cumulative impact of the metabolic syndrome on health status on a scale from 1 to 6. This study describes the use of the MHI as a supportive tool in the decision for and outcome assessment of bariatric surgery. METHODS: The general usability of the MHI was tested by extending its application to patient data of five other bariatric centers in the Netherlands. Retrospective laboratory and national bariatric quality registry data of 11,501 patients were collected. RESULTS: The quantification of (improvement in) metabolic health burden as measured by the MHI was independent of the dataset that was used to derive the MHI model. Patients with MHI > 2.8 prior to surgery improved significantly more in MHI 12 mo after surgery compared to patients with MHI ≤ 2.8 (1.1 compared to 0.4 MHI points, respectively; P < 0.001). CONCLUSIONS: The MHI is robust between centers and is suitable for general use in clinical decision-making. As changes in MHI over time reflect metabolic health alterations, it is suitable as an outcome measure of surgery. An MHI cut-off value of 2.8 helps to predict the likelihood of significant improvement after surgery, independent of body mass index and known metabolic comorbidities.

A wearable patch based remote early warning score (REWS) in major abdominal cancer surgery patients.

INTRODUCTION: The shift toward remote patient monitoring methods to detect clinical deterioration requires testing of wearable devices in real-life clinical settings. This study aimed to develop a remote early warning scoring (REWS) system based on continuous measurements using a wearable device, and compare its diagnostic performance for the detection of deterioration to the diagnostic performance of the conventional modified early warning score (MEWS). MATERIALS AND METHODS: The study population of this prospective, single center trial consisted of patients who underwent major abdominal cancer surgery and were monitored using routine in-hospital spotcheck measurements of the vital parameters. Heart and respiratory rates were measured continuously using a wireless accelerometer patch (HealthDot). The prediction by MEWS of deterioration toward a complication graded Clavien-Dindo of 2 or higher was compared to the REWS derived from continuous measurements by the wearable patch. MAIN RESULTS: A total of 103 patients and 1909 spot-check measurements were included in the analysis. Postoperative deterioration was observed in 29 patients. For both EWS systems, the sensitivity (MEWS: 0.20 95% CI: [0.13-0.29], REWS: 0.20 95% CI: [0.13-0.29]) and specificity (MEWS: 0.96 95% CI: [0.95-0.97], REWS: 0.96 95% CI: [0.95-0.97]) were assessed. CONCLUSIONS: The diagnostic value of the REWS method, based on continuous measurements of the heart and respiratory rates, is comparable to that of the MEWS in patients following major abdominal cancer surgery. The wearable patch could detect the same amount of deteriorations, without requiring manual spot check measurements.

Prognostic Value of Combined Biomarkers in Patients With Heart Failure: The Heartmarker Score.

Background: Heart failure (HF) biomarkers have prognostic value. The aim of this study was to combine HF biomarkers into an objective classification system for risk stratification of patients with HF. Methods: HF biomarkers were analyzed in a population of HF outpatients and expressed relative to their cut-off values (N-terminal pro-B-type natriuretic peptide [NT-proBNP] >1,000 pg/mL, soluble suppression of tumorigenesis-2 [ST2] >35 ng/mL, growth differentiation factor-15 [GDF-15] >2,000 pg/mL, and fibroblast growth factor-23 [FGF-23] >95.4 pg/mL). Biomarkers that remained significant in multivariable analysis were combined to devise the Heartmarker score. The performance of the Heartmarker score was compared to the widely used New York Heart Association (NYHA) classification based on symptoms during ordinary activity. Results: HF biomarkers of 245 patients were analyzed, 45 (18%) of whom experienced the composite endpoint of HF hospitalization, appropriate implantable cardioverter-defibrillator shock, or death. HF biomarkers were elevated more often in patients that reached the composite endpoint than in patients that did not reach the endpoint. NT-proBNP, ST2, and GDF-15 were independent predictors of the composite endpoint and were thus combined as the Heartmarker score. The event-free survival and distance covered in 6 minutes of walking decreased with an increasing Heartmarker score. Compared with the NYHA classification, the Heartmarker score was better at discriminating between different risk classes and had a comparable relationship to functional capacity. Conclusions: The Heartmarker score is a reproducible and intuitive model for risk stratification of outpatients with HF, using routine biomarker measurements.

Assessment of Comorbidity in Bariatric Patients through a Biomarker-Based Model-A Multicenter Validation of the Metabolic Health Index.

BACKGROUND: The metabolic health index (MHI) is a biomarker-based model that objectively assesses the cumulative impact of comorbidities type 2 diabetes mellitus, hypertension and dyslipidemia on the health state of bariatric patients. The MHI was developed on a single-center cohort using a fully laboratory data-driven approach, resulting in a MHI score on a range from 1 to 6. To show universal applicability in clinical care, the MHI was validated externally and potential laboratory-related shortcomings were evaluated. METHODS: Retrospective laboratory and national bariatric quality registry data were collected from five Dutch renowned bariatric centers (n = 11 501). MHI imprecision was derived from the cumulative effect of biological and analytical variance of the individual input variables of the MHI model. The performance of the MHI (model) was assessed in terms of discrimination and calibration. RESULTS: The cumulative imprecision in MHI was 0.25 MHI points. Calibration of the MHI model diverged over the different centers but was accounted for by misregistration of comorbidity after cross-checking the data. Discriminative performance of the MHI model was consistent across the different centers. CONCLUSIONS: The MHI model can be applied in clinical practice of bariatric centers, regardless of patient mix and analytical platform. Because the MHI is based on objective parameters, it is insensitive to diverging clinical definitions of comorbidities. Therefore, the MHI can be used to objectify severity of metabolic comorbidities in bariatric patients. The MHI can support the patient-selection process for surgery and objectively assessing the effect of surgery on the metabolic health state.

Accuracy of vital parameters measured by a wearable patch following major abdominal cancer surgery.

INTRODUCTION: Recent advances in wearable technology allow for the development of wirelessly connected sensors to continuously measure vital parameters in the general ward or even at home. The present study assesses the accuracy of a wearable patch (Healthdot) for continuous monitoring of heartrate (HR) and respiration rate (RR). MATERIALS AND METHODS: The Healthdot measures HR and RR by means of chest accelerometry. The study population consisted of patients following major abdominal oncological surgery. The analysis focused on the agreement between HR and RR measured by the Healthdot and the gold standard patient monitor in the intensive and post-anesthesia care unit. RESULTS: For HR, a total of 112 h of measurements was collected in 26 patients. For RR, a total of 102 h of measurements was collected in 21 patients. On second to second analysis, 97% of the HR and 87% of the RR measurements were within 5 bpm and 3 rpm of the reference monitor. Assessment of 5-min averaged data resulted in 96% of the HR and 95% of the RR measurements within 5 bpm and 3 rpm of the reference monitor. A Clarke error grid analysis showed that 100% of the HR and 99.4% of the 5-min averaged data was clinically acceptable. CONCLUSION: The Healthdot accurately measured HR and RR in a cohort of patients recovering from major abdominal surgery, provided that good quality data was obtained. These results push the Healthdot forward as a clinically acceptable tool in low acuity settings for unobtrusive, automatic, wireless and continuous monitoring.

Visual Analysis of Biomarkers Reveals Differences in Lipid Profiles and Liver Enzymes before and after Gastric Sleeve and Bypass.

INTRODUCTION: Bariatric surgery results in both intentional and unintentional metabolic changes. In a high-volume bariatric center, extensive laboratory panels are used to monitor these changes pre- and postoperatively. Consecutive measurements of relevant biochemical markers allow exploration of the health state of bariatric patients and comparison of different patient groups. OBJECTIVE: The objective of this study is to compare biomarker distributions over time between 2 common bariatric procedures, i.e., sleeve gastrectomy (SG) and gastric bypass (RYGB), using visual analytics. METHODS: Both pre- and postsurgical (6, 12, and 24 months) data of all patients who underwent primary bariatric surgery were collected retrospectively. The distribution and evolution of different biochemical markers were compared before and after surgery using asymmetric beanplots in order to evaluate the effect of primary SG and RYGB. A beanplot is an alternative to the boxplot that allows an easy and thorough visual comparison of univariate data. RESULTS: In total, 1,237 patients (659 SG and 578 RYGB) were included. The sleeve and bypass groups were comparable in terms of age and the prevalence of comorbidities. The mean presurgical BMI and the percentage of males were higher in the sleeve group. The effect of surgery on lowering of glycated hemoglobin was similar for both surgery types. After RYGB surgery, the decrease in the cholesterol concentration was larger than after SG. The enzymatic activity of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphate in sleeve patients was higher presurgically but lower postsurgically compared to bypass values. CONCLUSIONS: Beanplots allow intuitive visualization of population distributions. Analysis of this large population-based data set using beanplots suggests comparable efficacies of both types of surgery in reducing diabetes. RYGB surgery reduced dyslipidemia more effectively than SG. The trend toward a larger decrease in liver enzyme activities following SG is a subject for further investigation.

Detecting patients with PMI post-CABG based on cardiac troponin-T profiles: A latent class mixed modeling approach.

BACKGROUND: Diagnosis of perioperative myocardial infarction (PMI) after coronary artery bypass grafting (CABG) is fraught with complexity since it is primarily based on a single cut-off value for cardiac troponin (cTn) that is exceeded in over 90% of CABG patients, including non-PMI patients. In this study we applied an unsupervised statistical modeling approach to uncover clinically relevant cTn release profiles post-CABG, including PMI, and used this to improve diagnostic accuracy of PMI. METHODS: In 624 patients that underwent CABG, cTnT concentration was serially measured up to 24 h post aortic cross clamping. 2857 cTnT measurements were available to fit latent class linear mixed models (LCMMs). RESULTS: Four classes were found, described by: normal, high, low and rising cTnT release profiles. With the clinical diagnosis of PMI as golden standard, the rising profile had a diagnostic accuracy of 97%, compared to 83% for an optimally chosen cut-off and 21% for the guideline recommended cut-off value. CONCLUSION: Clinically relevant subgroups, including patients with PMI, can be uncovered using serially measured cTnT and a LCMM. The LCMM showed superior diagnostic accuracy of PMI. A rising cTnT profile is potentially a better criterion than a single cut-off value in diagnosing PMI post-CABG.

Metabolic Health Index (MHI): Assessment of Comorbidity in Bariatric Patients Based on Biomarkers.

PURPOSE: The focus of bariatric surgery is reduction of weight, reflected in body mass index (BMI). However, the resolution of comorbidity is a second important outcome indicator. The degree of comorbidity is hard to quantify objectively as comorbidities develop gradually and are interdependent. Multiple scoring systems quantifying comorbidity exist but they lack continuity and objectivity. In analogy with BMI as index for weight, the Metabolic Health Index (MHI) is developed as objective quantification of metabolic health status. Laboratory data were used as comorbidities affect biomarkers. Conversely, laboratory data can be used as objectively obtained variables to describe comorbidity. METHODS: Laboratory data were collected and crosschecked by national quality registry entries. Machine learning was applied to develop an ordinal logistic regression model, using 4 clinical and 32 laboratory input variables. The output was mathematically transformed into a continuous score for intuitive interpretation, ranging from 1 to 6 (MHI). RESULTS: In total, 4778 data records of 1595 patients were used. The degree of comorbidity is best described by age at phlebotomy, estimated Glomerular Filtration Rate (eGFR), and concentrations of glycated hemoglobin (HbA1c), triglycerides, and potassium. The model is independent of day of sampling and type of surgery. Mean MHI was significantly different between patient subgroups with increasing number of comorbidities. CONCLUSION: The MHI reflects severity of comorbidity, enabling objective assessment of a bariatric patient's metabolic health state, regardless day of sampling and surgery type. Next to weight-focused outcome measures like %TWL, the MHI can serve as outcome measure for metabolic health.

Correction to: Do Specialized Bariatric Multivitamins Lower Deficiencies After Sleeve Gastrectomy?

The second sentence of the Conclusion section should read as follows.

Do Specialized Bariatric Multivitamins Lower Deficiencies After Sleeve Gastrectomy?

BACKGROUND: Vitamin and mineral deficiencies are common after a sleeve gastrectomy (SG). The aim of this study is to examine the effectiveness of a specialized bariatric multivitamin (WLS Optimum) for SG patients on deficiencies compared with a regular multivitamin (MVS) for up to 5 years. METHODS: Data of all patients who underwent a SG procedure in the Catharina Hospital Eindhoven (CZE) between July 2011 and July 2016 were collected and retrospectively analyzed. All patients who completed a preoperative blood test and at least one blood withdrawal during the first operative year were included in this study. RESULTS: This study included 970 patients; 291 patients in the WLS-user group and 679 patients in the non-WLS-user group. In favor of the user group, significantly less de novo deficiencies were found of vitamin B1 (2 years) and vitamin B6 (two and three), folic acid (1 and 2 years), and vitamin B12 (at 1 year). Binomial logistic regression showed a significant influence of multivitamin supplementation mainly on ferritin; vitamins B1, B6, B12, and D; and folic acid, (all p < 0.05). The total number of de novo deficiencies was significantly reduced during the whole study for all WLS Optimum users. CONCLUSIONS: Vitamin deficiencies are common, and postoperative nutritional management after SG is underestimated. The use of a specialized multivitamin supplement resulted in higher mean serum concentrations and less deficiencies of vitamin B1, folic acid, and vitamin B12. This study shows that SG patients benefit from the specialized multivitamin supplements, but adjustments are required for iron and vitamin B6 content.

Clinical interpretation of prostate-specific antigen values: Type of applied cut-off value exceeds methods bias as the major source of variation.

BACKGROUND: Prostate-specific antigen is the biochemical gold standard for the (early) detection and monitoring of prostate cancer. Interpretation of prostate-specific antigen is both dependent on the method and cut-off. The aim of this study was to examine the effect of method-specific differences and cut-off values in a national external quality assessment scheme (EQAS). METHODS: The Dutch EQAS for prostate-specific antigen comprised an annual distribution of 12 control materials. The results of two distributions were combined with the corresponding cut-off value. Differences between methods were quantified by simple linear regression based on the all laboratory trimmed mean. To assess the clinical consequence of method-specific differences and cut-off values, a clinical data-set of 1040 patients with an initial prostate-specific antigen measurement and concomitant conclusive prostate biopsy was retrospectively collected. Sensitivity and specificity for prostate cancer were calculated for all EQAS participants individually. RESULTS: In the Netherlands, seven different prostate-specific antigen methods are used. Interestingly, 67% of these laboratories apply age-specific cut-off values. Methods showed a maximal relative difference of 26%, which were not reflected in the cut-off values. The largest differences were caused by the type of cut-off, for example in the Roche group the cut-off value differed maximal 217%. Clinically, a fixed prostate-specific antigen cut-off has a higher sensitivity than an age-specific cut-off (mean 89% range 86-93% versus 79% range 63-95%, respectively). CONCLUSIONS: This study shows that the differences in cut-off values exceed the method-specific differences. These results emphasize the need for (inter)national harmonization/standardization programmes including cut-off values to allow for laboratory-independent clinical decision-making.

Improved testing for vitamin B12 deficiency: correcting MMA for eGFR reduces the number of patients classified as vitamin B12 deficient.

Background Methylmalonic acid (MMA) can detect functional vitamin B12 deficiencies as it accumulates early when intracellular deficits arise. However, impaired clearance of MMA from blood due to decreased glomerular filtration rate (eGFR) also results in elevated plasma MMA concentrations. Alternative to clinical trials, a data mining approach was chosen to quantify and compensate for the effect of decreased eGFR on MMA concentration. Methods Comprehensive data on patient's vitamin B12, eGFR and MMA concentrations were collected ( n = 2906). The relationship between vitamin B12, renal function (eGFR) and MMA was modelled using weighted multiple linear regression. The obtained model was used to estimate the influence of decreased eGFR on MMA. Clinical impact was examined by comparing the number of patients labelled vitamin B12 deficient with and without adjustment in MMA. Results Adjusting measured MMA concentrations for eGFR in the group of patients with low-normal vitamin B12 concentrations (90-300 pmol/L) showed that the use of unadjusted MMA concentrations overestimates vitamin B12 deficiency by 40%. Conclusions Through a data mining approach, the influence of eGFR on the relation between MMA and vitamin B12 can be quantified and used to correct the measured MMA concentration for decreased eGFR. Especially in the elderly, eGFR-based correction of MMA may prevent over-diagnosis of vitamin B12 deficiency and corresponding treatment.

Stem cell factor synergistically enhances thrombopoietin-induced STAT5 signaling in megakaryocyte progenitors through JAK2 and Src kinase.

Stem cell factor (SCF) has a potent synergistic effect during megakaryopoiesis when administered in combination with the major megakaryocytic cytokine, thrombopoietin (TPO). In this study we analyzed the underlying mechanisms with regard to STAT5 activity. TPO stimulation of MO7e cells resulted in STAT5 transactivation, which could be enhanced 1.6-fold by costimulation with SCF, whereas SCF alone did not induce STAT5 transcriptional activity. This costimulatory effect of SCF was reflected in an increase in TPO-induced STAT5 DNA binding and increased and prolonged STAT5 tyrosine phosphorylation in both MO7e cells and primary human megakaryocyte progenitors. In contrast, serine phosphorylation of STAT5 was constitutive and associated with an inhibitory effect on STAT5 transactivation. Signal transduction pathways that might synergize in TPO-mediated STAT5 transactivation were analyzed using specific pharmacological inhibitors and indicated an essential role for Janus-activated kinase 2 (JAK2) and a partial role for Src-family kinases. Costimulation with SCF was found to increase and prolong tyrosine phosphorylation of JAK2 and the TPO receptor c-mpl. In addition, the Src kinase inhibitor SU6656 partially downregulated the additional effect of SCF costimulation on STAT5 tyrosine phosphorylation. SCF-induced enhancement of JAK2 phosphorylation was not affected by inhibition of Src kinase, suggesting that both JAK2 and Src kinase mediate STAT5 tyrosine phosphorylation. Synergistic activation of JAK2 and Src kinase may thus contribute to the enhanced STAT5 signaling in the presence of TPO and SCF.

Stem cell factor enhances erythropoietin-mediated transactivation of signal transducer and activator of transcription 5 (STAT5) via the PKA/CREB pathway.

OBJECTIVE: To define whether the observed synergistic effects of erythropoietin (EPO) and stem cell factor (SCF) on erythroid cells can, in part, be mediated by the signal transducer and activator of transcription 5 (STAT5). METHODS: STAT5 activation was examined in erythroid cell lines by analyzing the effects of EPO and SCF on STAT5 tyrosine phosphorylation, serine phosphorylation, DNA binding, and STAT5-mediated gene transactivation. RESULTS: EPO induced a 5.0-fold+/-0.4-fold increase in STAT5 transactivation, which could be further enhanced by SCF. SCF pretreatment followed by EPO stimulation resulted in a 9.0-fold+/-0.9-fold increase in STAT5 transactivation, while SCF alone did not increase STAT5 transactivation. This costimulatory effect of SCF was not mediated by increased STAT5 tyrosine or serine phosphorylation or increased STAT5 DNA binding. In addition, enhanced STAT5 transactivation was independent of the phosphatidyl inositol 3-kinase and MAPK(p42/p44) pathways. Instead, the protein kinase A (PKA) inhibitor protein PKI and the PKA inhibitor H89 prevented the costimulatory SCF effect. Furthermore, the PKA target CREB showed a strongly increased and prolonged serine-133 phosphorylation after costimulation with SCF + EPO. The involvement of CREB in STAT5 transactivation was demonstrated by overexpression of serine-133-mutated CREB, which completely blocked the SCF effect. In addition, the CREB-binding protein CBP/p300 was shown to be essential for EPO- and SCF-mediated STAT5 transactivation. CONCLUSION: SCF enhances the EPO-mediated STAT5 transactivation by triggering a PKA/CREB-dependent pathway.

cAMP/PKA-mediated regulation of erythropoiesis.

The role of cyclic AMP (cAMP) as second messenger in erythropoiesis has been suggested in the early 1980s. However, careful analysis showed that cAMP is not generated in direct response to the main erythropoiesis-controlling cytokines such as erythropoietin (Epo). As a result, cAMP disappeared from the central stage in research of erythropoiesis. Instead, other signal transduction pathways, including the Ras/extracellular regulated kinase (ERK)-pathway, the phosphatidylinositol 3-kinase (P13K) and the signal transducer and activator of transcription (STAT5)-pathways, have been found and explored. In concert, these signaling pathways control the transcriptional machinery of erythroid cells. Although cAMP is not directly generated in response to Epo stimulation, it has recently been demonstrated that increased cAMP-levels and in particular the cAMP-dependent protein kinase A (PKA) can modulate erythroid signal transduction pathways. In some cases, like the ERK-signaling pathway, PKA affects signal transduction by regulating the balance between specific phosphatases and kinases. In other cases, such as the STAT5 pathway, PKA enhances Epo signaling by inducing recruitment of additional co-regulators of transcription. In addition to STAT5, PKA also activates other transcription factors that are required for erythroid gene expression. This review discusses the impact of cAMP/PKA on Epo-mediated signaling pathways and summarizes the role of cAMP in malignant erythropoiesis.

Prostaglandin-E2 enhances EPO-mediated STAT5 transcriptional activity by serine phosphorylation of CREB.

Erythroid colony formation in response to erythropoietin (EPO) stimulation is enhanced by costimulating the cells with prostaglandin-E2 (PGE2). The present study further analyzed the underlying mechanisms and demonstrated that EPO-mediated STAT5 transactivation in the erythroid AS-E2 cell line was enhanced 6-fold by PGE2 (10 microM), without affecting the STAT5 tyrosine phosphorylation or STAT5-DNA binding. Moreover, the PGE2-enhancing effect was independent of STAT5 serine phosphorylation. In AS-E2 cells STAT5 is constitutively phosphorylated on Ser780 (STAT5A) and EPO-dependently phosphorylated on Ser726/731 (STAT5A/STAT5B), but overexpression of STAT5 serine mutants did not affect STAT5 transactivation. In addition, PGE2 did not affect STAT5 serine phosphorylation. Instead, the stimulatory effect of PGE2 on STAT5 signaling could be mimicked by dibutyryl-cyclic adenosine monophosphate (cAMP) and the phosphodiesterase inhibitor IBMX, suggesting that the effect was mediated by cAMP. Activation of the cAMP pathway resulted in cAMP-response element binding protein (CREB) phosphorylation, which was sustained in the presence of EPO plus PGE2 and transient on EPO stimulation alone. The costimulatory effect of PGE2 on EPO-mediated STAT5 transactivation was inhibited by overexpression of serine-dead CREB or protein kinase A (PKA) inhibitor (PKI), in contrast to EPO-mediated transactivation, which was PKA independent. Furthermore, CREB-binding protein (CBP)/p300 was shown to be involved in EPO-mediated STAT5 transactivation, and a CBP mutant with increased affinity for CREB resulted in an additional enhancement of the PGE2 effect. Finally, we demonstrated that the STAT5 target genes Bcl-X, SOCS2, and SOCS3 were up-regulated by costimulation with PGE2. In summary, these studies demonstrate that PGE2 enhancement of EPO-induced STAT5 transactivation is mediated by the cAMP/PKA/CREB pathway.