Spatiotemporal modeling of first and second wave outbreak dynamics of COVID-19 in Germany.

The COVID-19 pandemic has kept the world in suspense for the past year. In most federal countries such as Germany, locally varying conditions demand for state- or county-level decisions to adapt to the disease dynamics. However, this requires a deep understanding of the mesoscale outbreak dynamics between microscale agent models and macroscale global models. Here, we use a reparameterized SIQRD network model that accounts for local political decisions to predict the spatiotemporal evolution of the pandemic in Germany at county resolution. Our optimized model reproduces state-wise cumulative infections and deaths as reported by the Robert Koch Institute and predicts the development for individual counties at convincing accuracy during both waves in spring and fall of 2020. We demonstrate the dominating effect of local infection seeds and identify effective measures to attenuate the rapid spread. Our model has great potential to support decision makers on a state and community politics level to individually strategize their best way forward during the months to come.

Tomoelastography for Longitudinal Monitoring of Viscoelasticity Changes in the Liver and in Renal Allografts after Direct-Acting Antiviral Treatment in 15 Kidney Transplant Recipients with Chronic HCV Infection.

Besides the liver, hepatitis C virus (HCV) infection also affects kidney allografts. The aim of this study was to longitudinally evaluate viscoelasticity changes in the liver and in kidney allografts in kidney transplant recipients (KTRs) with HCV infection after treatment with direct-acting antiviral agents (DAAs). Fifteen KTRs with HCV infection were treated with DAAs (daclatasvir and sofosbuvir) for 3 months and monitored at baseline, end of treatment (EOT), and 3 (FU1) and 12 (FU2) months after EOT. Shear-wave speed (SWS) and loss angle of the complex shear modulus (φ), reflecting stiffness and fluidity, respectively, were reconstructed from multifrequency magnetic resonance elastography data with tomoelastography post-processing. After virus elimination by DAAs, hepatic stiffness and fluidity decreased, while kidney allograft stiffness and fluidity increased compared with baseline (hepatic stiffness change at FU1: -0.14 m/s, p < 0.01, and at FU2: -0.11 m/s, p < 0.05; fluidity at FU1: -0.05 rad, p = 0.04 and unchanged at FU2: p = 0.20; kidney allograft stiffness change at FU1: +0.27 m/s, p = 0.01, and at FU2: +0.30 m/s, p < 0.01; fluidity at FU1 and FU2: +0.06 rad, p = 0.02). These results suggest the restoration of mechanically sensitive structures and functions in both organs. Tomoelastography can be used to monitor the therapeutic results of HCV treatment non-invasively on the basis of hepatic and renal viscoelastic parameters.

Tomoelastography for Measurement of Tumor Volume Related to Tissue Stiffness in Pancreatic Ductal Adenocarcinomas.

OBJECTIVES: Estimations of tumor volume and boundary in pancreatic ductal adenocarcinoma (PDAC) are crucial for surgery planning. The aim of the study is to evaluate tomoelastography for detection of PDAC and quantification of PDAC volume based on tissue stiffness. MATERIALS AND METHODS: From March 2018 to December 2019, a total of 102 participants (30 healthy participants and 72 patients with histologically proven PDAC) were prospectively enrolled in a multicenter study. Multifrequency magnetic resonance elastography was combined with tomoelastography postprocessing to generate maps of shear wave speed (SWS) depicting highly resolved anatomical details of tissue stiffness. Subregional analysis of pancreatic head, body, and tail and reproducibility tests were performed in healthy participants, whereas tumorous (PDAC-T) and nontumorous (PDAC-NT) pancreatic tissue analysis was conducted in patients. In all patients, tumor volumes measured by computed tomography (CT) were compared with SWS-derived volumes. In addition, in 32 patients, tumor sizes were evaluated by macroscopy after resection. RESULTS: Tumor volumes were quantified in 99% and 87% of all cases with tomoelastography and CT, respectively. Pancreatic SWS was highly reproducible (repeatability coefficient = 0.12) and did not vary regionally or with patient age, sex, or body mass index (all P > 0.08). Shear wave speed was higher in PDAC-T (2.08 ± 0.38 m/s) than in healthy (1.25 ± 0.09 m/s; P < 0.001) and PDAC-NT (1.28 ± 0.14 m/s; P < 0.001) participants. A threshold of 1.47 m/s separated PDAC-T from healthy volunteers (area under the curve = 1.0, sensitivity = 100%, specificity = 100%), while 1.49 m/s separated PDAC-T from PDAC-NT with high accuracy (area under the curve = 0.99, sensitivity = 90%, specificity = 100%). Tomoelastography-derived tumor volume correlated with CT volume (r = 0.91, P < 0.001) and ex vivo tumor volume (r = 0.66, P < 0.001). CONCLUSIONS: Tomoelastography provides a quantitative imaging marker for tissue stiffness depicting PDAC boundaries and separates PDAC from unaffected pancreatic tissue.

Memory-based meso-scale modeling of Covid-19: County-resolved timelines in Germany.

The COVID-19 pandemic has led to an unprecedented world-wide effort to gather data, model, and understand the viral spread. Entire societies and economies are desperate to recover and get back to normality. However, to this end accurate models are of essence that capture both the viral spread and the courses of disease in space and time at reasonable resolution. Here, we combine a spatially resolved county-level infection model for Germany with a memory-based integro-differential approach capable of directly including medical data on the course of disease, which is not possible when using traditional SIR-type models. We calibrate our model with data on cumulative detected infections and deaths from the Robert-Koch Institute and demonstrate how the model can be used to obtain county- or even city-level estimates on the number of new infections, hospitality rates and demands on intensive care units. We believe that the present work may help guide decision makers to locally fine-tune their expedient response to potential new outbreaks in the near future.

Ultrasound Time-Harmonic Elastography of the Pancreas: Reference Values and Clinical Feasibility.

OBJECTIVES: Pancreatic ductal adenocarcinoma (PDAC) is a very aggressive tumor with a very low 5-year survival rate of 8%. The aims of this study are to determine reference values and physiologic confounders in healthy pancreas and to assess the diagnostic accuracy of ultrasound time-harmonic elastography (THE) in the detection of PDAC. MATERIALS AND METHODS: From March 2017 through May 2019, a total of 54 study participants with healthy pancreas (n = 33, CTR) or PDAC (n = 21) were prospectively enrolled. Repeatability of THE was tested in a CTR subgroup (n = 5) undergoing repeat measurement on 4 different days. Interobserver variability was analyzed in 10 healthy volunteers. Age-matched and sex-matched subgroups of CTR (n = 13) and PDAC (n = 13) were compared. In participants with histopathologically proven PDAC, measurements were performed separately in tumorous (PDAC-T) and nontumorous pancreatic tissue (PDAC-NT). Diagnostic performance of pancreatic THE was assessed by receiver operating characteristic curve analysis. RESULTS: Time-harmonic elastography was highly repeatable (intraclass correlation coefficient, 0.99), and interobserver agreement was excellent (intraclass correlation coefficient, 0.97). Shear wave speed (SWS) of PDAC-T (mean [95% confidence interval] in meters per second, 1.88 ± 0.07 [1.84-1.92]) was higher than SWS of CTR (1.63 ± 0.04 [1.60-1.66], P < 0.001) and PDAC-NT (1.59 ± 0.03 [1.57-1.61], P < 0.001). The exploratory diagnostic performance of THE in separating PDAC-T was excellent (area under the receiver operating characteristic curve, 1.0). Tumorous pancreatic ductal adenocarcinoma was distinguished from CTR and PDAC-NT with cutoff values of 1.73 m/s and 1.70 m/s, respectively. CONCLUSIONS: Pancreatic ultrasound THE has high repeatability and provides excellent imaging contrast based on SWS, allowing detection of PDAC without overlap to nontumorous pancreatic tissue.

Assessment of the reliability of the motor unit size index (MUSIX) in single subject "round-robin" and multi-centre settings.

OBJECTIVE: The motor unit size index (MUSIX) is incorporated into the motor unit number index (MUNIX). Our objective was to assess the intra-/inter-rater reliability of MUSIX in healthy volunteers across single subject "round robin" and multi-centre settings. METHODS: Data were obtained from (i) a round-robin assessment in which 12 raters (6 with prior experience and 6 without) assessed six muscles (abductor pollicis brevis, abductor digiti minimi, biceps brachii, tibialis anterior, extensor digitorum brevis and abductor hallucis) and (ii) a multi-centre study with 6 centres studying the same muscles in 66 healthy volunteers. Intra/inter-rater data were provided by 5 centres, 1 centre provided only intra-rater data. Intra/inter-rater variability was assessed using the coefficient of variation (COV), Bland-Altman plots, bias and 95% limits of agreement. RESULTS: In the round-robin assessment intra-rater COVs for MUSIX ranged from 7.8% to 28.4%. Inter-rater variability was between 7.8% and 16.2%. Prior experience did not impact on MUSIX values. In the multi-centre study MUSIX was more consistent than the MUNIX. Abductor hallucis was the least reliable muscle. CONCLUSIONS: The MUSIX is a reliable neurophysiological biomarker of reinnervation. SIGNIFICANCE: MUSIX could provide insights into the pathophysiology of a range of neuromuscular disorders, providing a quantitative biomarker of reinnervation.

Is survival improved by the use of NIV and PEG in amyotrophic lateral sclerosis (ALS)? A post-mortem study of 80 ALS patients.

BACKGROUND: Non-invasive ventilation (NIV) and percutaneous gastrostomy (PEG) are guideline-recommended interventions for symptom management in amyotrophic lateral sclerosis (ALS). Their effect on survival is controversial and the impact on causes of death is unknown. OBJECTIVE: To investigate the effect of NIV and PEG on survival and causes of death in ALS patients. METHODS: Eighty deceased ALS patients underwent a complete post mortem analysis for causes of death between 2003 and 2015. Forty-two of these patients consented for genetic testing. Effects of NIV and PEG on survival and causes of death were analyzed in a multivariable Cox proportional hazard regression. RESULTS: Six patients, who requested assisted suicide causing drug-induced hypoxia, were excluded from final analysis. Respiratory failure was the main cause of death in 72 out of 74 patients. Fifteen out of 74 died of aspiration pneumonia 23/74 of bronchopneumonia and 8/74 of a combination of aspiration pneumonia and bronchopneumonia. Twenty died of hypoxia without concomitant infection, and six patients had pulmonary embolism alone or in combination with pneumonia. NIV (p = 0.01) and PEG (p<0.01) had a significant impact on survival. In patients using NIV bronchopneumonia was significantly more frequent (p <0.04) compared to non-NIV patients. This effect was even more pronounced in limb onset patients (p<0.002). Patients with C9orf72 hexanucleotide repeat expansions showed faster disease progression and shorter survival (p = 0.01). CONCLUSION: The use of NIV and PEG prolongs survival in ALS. This study supports current AAN and EFNS guidelines which recommend NIV and PEG as a treatment option in ALS. The risk of bronchopneumonia as cause of death may be increased by NIV.

Longitudinal assessment of the Edinburgh Cognitive and Behavioural Amyotrophic Lateral Sclerosis Screen (ECAS): lack of practice effect in ALS patients?

OBJECTIVE: The study objective was to assess whether controls and ALS patients show a practice effect in the Edinburgh Cognitive and Behavioural ALS Screen (ECAS) on repeated longitudinal testing and if the ECAS detects progression of cognitive or behavioural changes over time. METHODS: The ECAS was administered serially to ALS patients (n = 24 after six months, n = 10 after 12-18 months) and controls (n = 21 after six months). The ECAS was fully performed by all participants. For comparison purposes the Frontal Assessment Battery (FAB) was administered to a subgroup of 14 patients and 14 controls. RESULTS: After six months controls showed a significantly higher overall score (p < 0.001) and significantly higher scores in all subdomains of the ECAS, except for visuospatial function and fluency. ALS patients showed no significant difference in any score of the ECAS after six months and up to18 months. Behavioural changes were increasingly, but not statistically, significant, noted by patient carers. The FAB was no longer applicable due to progressive motor deficits in 20% of ALS patients. CONCLUSIONS: In conclusion, in contrast to healthy controls, ALS patients show no practice effects. This could reflect 'pre-symptomatic' cognitive decline and progressive behavioural symptoms.

Motor Unit Number Index (MUNIX) detects motor neuron loss in pre-symptomatic muscles in Amyotrophic Lateral Sclerosis.

OBJECTIVE: Motor Unit Number Index (MUNIX) is a quantitative neurophysiological measure that provides an index of the number of lower motor neurons supplying a muscle. It reflects the loss of motor neurons in patients with Amyotrophic Lateral Sclerosis (ALS). However, it is unclear whether MUNIX also detects motor unit loss in strong, non-wasted muscles. METHODS: Three centres measured MUNIX in 49 ALS patients every three months in six different muscles (abductor pollicis brevis, abductor digiti minimi, biceps brachii, tibialis anterior, extensor digitorum brevis, abductor hallucis) on the less affected side. The decline of MUNIX in initially non-wasted, clinically strong muscles (manual muscle testing, MMT grade 5) was analysed before and after onset of weakness. RESULTS: In 49 subjects, 151 clinically strong muscles developed weakness and were included for analysis. The average monthly relative loss of MUNIX was 5.0% before and 5.6% after onset of weakness. This rate of change was significantly higher compared to ALS functional rating scale (ALSFRS-R) and compound muscle action potential (CMAP) change over 12months prior to the onset of muscle weakness (p=0.024). CONCLUSION: MUNIX is an electrophysiological marker that detects lower motor neuron loss in ALS, before clinical weakness becomes apparent by manual muscle testing. SIGNIFICANCE: This makes MUNIX a good biomarker candidate for disease progression and possibly pharmacodynamics responds.

Sequence variations in C9orf72 downstream of the hexanucleotide repeat region and its effect on repeat-primed PCR interpretation: a large multinational screening study.

A large GGGGCC-repeat expansion mutation (HREM) in C9orf72 is the most common known cause of ALS and FTD in European populations. Sequence variations immediately downstream of the HREM region have previously been observed and have been suggested to be one reason for difficulties in interpreting RP-PCR data. Our objective was to determine the properties of these sequence variations with regard to prevalence, the range of variation, and effect on disease prognosis. We screened a multi-national cohort (n = 6981) for the HREM and samples with deviant RP-PCR curves were identified. The deviant samples were subsequently sequenced to determine sequence alteration. Our results show that in the USA and European cohorts (n = 6508) 10.7% carried the HREM and 3% had a sequence variant, while no HREM or sequence variants were observed in the Japanese cohort (n = 473). Sequence variations were more common on HREM alleles; however, certain population specific variants were associated with a non-expanded allele.In conclusion, we identified 38 different sequence variants, most located within the first 50 bp downstream of the HREM region. Furthermore, the presence of an HREM was found to be coupled to a lower age of onset and a shorter disease survival, while sequence variation did not have any correlation with these parameters.

Quality Control of Motor Unit Number Index (MUNIX) Measurements in 6 Muscles in a Single-Subject "Round-Robin" Setup.

BACKGROUND: Motor Unit Number Index (MUNIX) is a neurophysiological measure that provides an index of the number of lower motor neurons in a muscle. Its performance across centres in healthy subjects and patients with Amyotrophic Lateral Sclerosis (ALS) has been established, but inter-rater variability between multiple raters in one single subject has not been investigated. OBJECTIVE: To assess reliability in a set of 6 muscles in a single subject among 12 examiners (6 experienced with MUNIX, 6 less experienced) and to determine variables associated with variability of measurements. METHODS: Twelve raters applied MUNIX in six different muscles (abductor pollicis brevis (APB), abductor digiti minimi (ADM), biceps brachii (BB), tibialis anterior (TA), extensor dig. brevis (EDB), abductor hallucis (AH)) twice in one single volunteer on consecutive days. All raters visited at least one training course prior to measurements. Intra- and inter-rater variability as determined by the coefficient of variation (COV) between different raters and their levels of experience with MUNIX were compared. RESULTS: Mean intra-rater COV of MUNIX was 14.0% (±6.4) ranging from 5.8 (APB) to 30.3% (EDB). Mean inter-rater COV was 18.1 (±5.4) ranging from 8.0 (BB) to 31.7 (AH). No significant differences of variability between experienced and less experienced raters were detected. CONCLUSION: We provide evidence that quality control for neurophysiological methods can be performed with similar standards as in laboratory medicine. Intra- and inter-rater variability of MUNIX is muscle-dependent and mainly below 20%. Experienced neurophysiologists can easily adopt MUNIX and adequate teaching ensures reliable utilization of this method.

Age and education-matched cut-off scores for the revised German/Swiss-German version of ECAS.

The Edinburgh Cognitive and Behavioural ALS Screen (ECAS) has been developed to assess cognition and behaviour in patients with amyotrophic lateral sclerosis (ALS). Cognitive impairments of ALS-specific and ALS-non-specific functions can be determined using cut-off scores based on performance of healthy subjects. However, detailed analyses show that older healthy subjects perform worse than younger ones, whereas highly-educated individuals perform better than those with lower education levels. As a consequence, this study presents new age and education matched cut-off scores for the revised German/Swiss-German version of the ECAS based on the performance of 86 healthy subjects.

Motor unit number index in the nasalis muscle in healthy subjects and patients with amyotrophic lateral sclerosis.

INTRODUCTION: Motor unit number index (MUNIX) is a quick and feasible electrophysiological technique that estimates the number of motor neurons in limb muscles in healthy and amyotrophic lateral sclerosis (ALS) subjects. In this study we explored the feasibility, reliability, and differences of MUNIX in nasalis muscles in healthy subjects and ALS patients. METHODS: MUNIX of the nasalis muscle of 50 healthy and 20 ALS subjects with bulbar involvement was compared. Functional impairment was evaluated by the ALS Functional Rating Scale-Revised and its bulbar subscore. RESULTS: MUNIX was well tolerated and quickly performed. Bulbar ALS patients showed non-significant lower nasalis MUNIX values and a lower functional bulbar subscore. Intra- and interrater reliability showed high intraclass correlation coefficients (ICCs) in healthy subjects (0.87) and ALS patients (0.92). CONCLUSION: MUNIX of the nasalis muscle is a reproducible method, but it showed no significant difference between healthy and bulbar ALS subjects and seems not to be a useful marker of disease progression in ALS. Muscle Nerve 54: 733-737, 2016.

Tracking motor neuron loss in a set of six muscles in amyotrophic lateral sclerosis using the Motor Unit Number Index (MUNIX): a 15-month longitudinal multicentre trial.

BACKGROUND: Motor Unit Number Index (MUNIX) is a novel neurophysiological measure that provides an index of the number of functional lower motor neurons in a given muscle. So far its performance across centres in patients with amyotrophic lateral sclerosis (ALS) has not been investigated. OBJECTIVE: To perform longitudinal MUNIX recordings in a set of muscles in a multicentre setting in order to evaluate its value as a marker of disease progression. METHODS: Three centres applied MUNIX in 51 ALS patients over 15 months. Six different muscles (abductor pollicis brevis, abductor digiti minimi, biceps brachii, tibialis anterior, extensor dig. brevis, abductor hallucis) were measured every 3 months on the less affected side. The decline between MUNIX and ALSFRS-R was compared. RESULTS: 31 participants reached month 12. For all participants, ALSFRS-R declined at a rate of 2.3%/month. Using the total score of all muscles, MUNIX declined significantly faster by 3.2%/month (p ≤ 0.02). MUNIX in individual muscles declined between 2.4% and 4.2%, which differed from ASLFRS-R decline starting from month 3 (p ≤ 0.05 to 0.002). Subgroups with bulbar, lower and upper limb onset showed different decline rates of ALSFRS-R between 1.9% and 2.8%/month, while MUNIX total scores showed similar decline rates over all subgroups. Mean intraclass correlation coefficient for MUNIX intra-rater reliability was 0.89 and for inter-rater reliability 0.80. CONCLUSION: MUNIX is a reliable electrophysiological biomarker to track lower motor neuron loss in ALS.

Percutaneous endoscopic gastrostomy in amyotrophic lateral sclerosis: a prospective observational study.

Weight loss is increasingly considered as a negative prognostic marker in amyotrophic lateral sclerosis (ALS). Despite the critical importance of nutritional issues in ALS, and the common use of percutaneous endoscopic gastrostomy (PEG), there is a general lack of knowledge on peri-interventional treatment, optimal parameters of enteral nutrition, its timing during disease progression and its potential disease-modifying effects in ALS patients. Here we report the results of a multi-center prospective study of percutaneous endoscopic gastrostomy (PEG) in ALS. In this observational clinical trial, 89 ALS patients were prospectively enrolled over a 3-year period and longitudinal data were collected over 18 months. PEG was a safe procedure even in patients with low forced vital capacity, and prophylactic single-shot antibiosis as well as slow increase of caloric nutrition via PEG was beneficial to avoid complications. No signs of refeeding syndrome were observed. High-caloric intake (>1,500 kcal/d) via PEG in patients that lived at least 12 months after PEG insertion was correlated with prolonged survival. Additional oral food intake was not associated with a worse prognosis. Our results suggest that peri-interventional PEG management should include prophylactic single-shot antibiosis, slow increase of caloric intake, and long-term high-caloric nutrition. Although our results indicate that PEG might be more beneficial when applied early, we believe that it can also be performed safely in patients with far advanced disease. Because of its explorative and observational character, most of our results have to be confirmed by a randomized interventional trial.

The Edinburgh Cognitive and Behavioural Amyotrophic Lateral Sclerosis Screen: a cross-sectional comparison of established screening tools in a German-Swiss population.

The Edinburgh Cognitive and Behavioural ALS Screen (ECAS) has recently been developed as a fast and easy cognitive screening tool specifically designed for patients with motor impairments in routine clinical use. The German/Swiss-German version of the ECAS was validated in a German-Swiss consortium. One hundred and thirty-six non-demented ALS patients and 160 healthy controls were included in the study. In addition, the Frontal Assessment Battery (FAB), Montreal Cognitive Assessment (MoCA) and Consortium to Establish a Registry for Alzheimer's Disease plus Scale (CERAD plus) were administered to subgroups of patients. Results showed that administration of ECAS was fast (mean 24 min). Similar to the population in the UK version, ALS patients performed significantly worse in the ALS-specific functions (p < 0.001), specifically in the domain of language (p < 0.001), verbal fluency (p = 0.005) and executive functions (p = 0.02), but not for the non-ALS-specific functions. Carers reported behavioural abnormalities in about 30% and psychotic symptoms in 6% of the patients. Compared to ECAS, FAB, MoCA and CERAD were more generic and performance was not adjusted to motor speed. We conclude that the German/Swiss-German version of the ECAS is a fast and easy to administer cognitive screening instrument sensitive for ALS-specific dysfunctions and behaviour change.

Histamine upregulates gene expression of endothelial nitric oxide synthase in human vascular endothelial cells.

BACKGROUND: Histamine has a short-term, transient, stimulating effect on endothelial nitric oxide synthase (eNOS) activity; however, long-term effects on eNOS have not been described yet. In addition, the vascular effect of histamine seems to depend critically on eNOS functionality. Therefore, we studied the effects of histamine on eNOS gene expression and function. METHODS AND RESULTS: In human umbilical vein endothelial cells (HUVECs) and HUVEC-derived EA.hy 926 cells, histamine upregulated eNOS mRNA (RNase protection assay) and protein (electron microscopic immunocytochemistry) expression. The upregulation of eNOS could be prevented by mepyramine, a selective antagonist at the H1 receptor, but not by H2 and H3 receptor antagonists. Incubation of EA.hy 926 cells with histamine led to the activation of calcium/calmodulin-dependent protein kinase II (CaMK II; in vitro phosphorylation assay). The histamine-induced eNOS expression was completely prevented by KN-93, an inhibitor of CaMK II. Histamine increased the activity of a 1.6-kb human eNOS promoter fragment (luciferase reporter gene assay), an effect that was also blocked by mepyramine. Under normal conditions, eNOS upregulation by histamine resulted in increased nitric oxide production (measured by nitric oxide chemiluminescence and RFL-6 reporter cell assay). Under conditions of oxidative stress, however, the eNOS upregulated by histamine produced reactive oxygen species (CM-H2DCFDA oxidation-based fluorescence assay). CONCLUSIONS: Stimulation of the H1 receptor increases eNOS transcription in endothelial cells by a signaling pathway involving CaMK II. This eNOS upregulation may be protective under normal conditions, but it may become harmful under conditions of oxidative stress when eNOS produces reactive oxygen species at the expense of nitric oxide.

Dual effect of ceramide on human endothelial cells: induction of oxidative stress and transcriptional upregulation of endothelial nitric oxide synthase.

BACKGROUND: Generation of the second-messenger molecule ceramide by stimulated sphingomyelinase activity has been implicated in the inflammatory processes contributing to the pathogenesis of atherosclerosis. However, reports of stimulatory effects of ceramide on endothelial NO production in animal models suggest antiatherosclerotic effects of the molecule. Therefore, we investigated long-term effects of ceramide on NO generation in human endothelial cells. METHODS AND RESULTS: In human umbilical vein endothelial cells (HUVECs) and in HUVEC-derived EA.hy 926 endothelial cells, C6-ceramide (N-hexanoyl-D-erythro-sphingosine) reduced the generation of bioactive NO (RFL-6 reporter-cell assay). At the same time, the signaling molecule increased endothelial NO synthase (eNOS) mRNA (RNase protection assay) and protein expression (Western blot). C6-ceramide stimulated eNOS transcription by a signaling mechanism involving protein phosphatase PP2A but did not modify the stability of the eNOS mRNA. Endothelial generation of reactive oxygen species (ROS) was increased by C6-ceramide [5-(and-6)-chloromethyl-2', 7'-dichlorodihydrofluorescein diacetate (CM-H(2)DCFDA) oxidation-based fluorescence assay], and this effect was partially reversed by the NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). On the other hand, (6R)-5,6,7,8-tetrahydro-L-biopterin (BH(4)) normalized in part the ceramide-induced reduction in bioactive NO. CONCLUSIONS: Ceramide produces oxidative stress in human endothelial cells, thereby reducing bioactive NO. The partial reversal of this reduction by BH(4) and the diminution of ROS generation by L-NAME suggest that ceramide promotes NADPH oxidase activity of eNOS, leading to ROS formation at the expense of NO synthesis. The ceramide-induced upregulation of eNOS gene transcription can be considered an ineffective compensatory mechanism. The decreased bioavailability of NO is likely to favor a proatherogenic role of ceramide.