Anti-GM1 ganglioside antibodies modulate membrane-associated sphingomyelin metabolism by altering neutral sphingomyelinase activity.

Previous studies have shown that patients with Guillain-Barré syndrome express autoantibodies against ganglioside GM1 (GM1), although its pathogenic significance for the development of the disease remains to be elucidated. nSMase2 is the best characterized neutral sphingomyelinase (nSMase) found in neuronal cells. Activation of this enzyme leads to ceramide production, which is a known second messenger of the cell-death program in neuronal cells. We have explored the effects of anti-GM1 antibodies on sphingomyelin metabolism of PC12 cells stably transfected with human trk cDNA (PCtrk cells) by determining their effects on nSMase2 activity. The data we present here strongly suggest that anti-GM1 caused a significant change in sphingomyelin content of the membrane fraction in PCtrk cells. Both nSMase2 activity and the level of nSMase2 protein were significantly decreased by anti-GM1 treatment of PCtrk cells, while acidic SMase activities remained unchanged. Our results indicate, for the first time, that anti-GM1 may produce profound impacts on lipid metabolism in neuronal cell membranes.

The Usefulness and Limitations of Point-of-care Cardiac Troponin Measurement in the Emergency Department.

Objective This study was carried out to examine the usefulness of point-of-care (POC) cardiac troponin in diagnosing acute coronary syndrome (ACS) and to understand the limitations of a POC cardiac troponin I/T-based diagnoses. Methods Patients whose cardiac troponin levels were measured in the emergency department using a POC system (AQT System; Radiometer, Tokyo, Japan) between January and December 2016 were retrospectively examined (N=1,449). Patients who were < 20 years of age or who were admitted with cardiopulmonary arrest were excluded. The sensitivity and specificity of the POC cardiac troponin levels for the diagnosis of ACS were determined. Result One hundred and twenty of 1,449 total patients had ACS (acute myocardial infarction, n=88; unstable angina n=32). On comparing the receiver operating characteristic (ROC) curves, the area under the curve (AUC) values for POC cardiac troponin I and cardiac troponin T were 0.833 and 0.786, respectively. The sensitivity and specificity of POC cardiac troponin I when using the 99th percentile (0.023 ng/mL) as the diagnostic cut-off value were 69.0% and 88.1%, respectively. The sensitivity of POC cardiac troponin I (99th percentile) was higher in the patients sampled > 3 hours after symptom onset (83.3%) than in those sampled ≤ 3 hours after symptom onset (58.8%, p < 0.01). Conclusion When sampled > 3 hours after the onset of symptoms, the POC cardiac troponin I level is considered to be suitable for use in diagnosing ACS. However, when sampled ≤ 3 hours after the onset of symptoms, careful interpretation of POC cardiac troponins is therefore required to rule out ACS.

Olive oil phenolic extract regulates interleukin-8 expression by transcriptional and posttranscriptional mechanisms in Caco-2 cells.

In this study, we investigated the ability of a phenolic extract from extra virgin olive oil (OPE) to modulate the inflammatory response in intestinal epithelial cells. Undifferentiated and differentiated Caco-2 cells were challenged with LPS (50 µg/mL) or IL-1ß (5 ng/mL) to mimic the early and intermediate phase of intestinal inflammation, respectively. The effects of OPE on nuclear factor-κB-driven transcription and IL-8 promoter activity were evaluated in transfection assays, coupled to p65 nuclear translocation. Modulation of IL-8 mRNA levels by OPE was measured by quantitative RT-PCR while effects on protein levels by ELISA. Specific mitogen activated protein kinases inhibitors were used to investigate mRNA stability and the involvement of related signaling pathways. OPE prevented IL-8 expression and secretion in LPS-treated Caco-2 cells. In the presence of IL-1ß OPE exhibited opposing effects on IL-8 gene transcription and mRNA/protein levels. While in IL-1ß-treated cells IL-8 promoter activity was inhibited by treatment with OPE, IL-8 mRNA stability was strongly enhanced, leading to increased protein expression. Inhibitors of p38 and extracellular signal-regulated kinases partly prevented OPE effect on IL-8 mRNA levels. Intestinal epithelial cells represent a direct target of the action of olive oil phenols where they regulate IL-8 expression by transcriptional and posttranscriptional mechanisms.

Abnormal cross-talk between mutant presenilin 1 (I143T, G384A) and glycosphingolipid biosynthesis.

Mutations in the presenilin 1 (PS1) gene are associated with early onset familial Alzheimer's disease (FAD). In this study, we found that the expression of mutant-PS1 in stable transfectants of SH-SY5Y neuroblastoma cells results in a reduction of the biosynthesis and steady-state levels of glucosylceramide. As an in vivo corroboration of these data, there was a significant reduction of brain glucosylceramide and gangliosides in an animal model of FAD. In mutant-PS1-transfectants (I143T, G384A), immunocytochemistry disclosed a remarkable reduction of glucosylceramide synthase (GlcT-1)-like immunoreactivity in the cells when compared with those of mock- and wild-PS1 transfectants. Immunoprecipitation of GlcT-1 protein from mutant-PS1 transfectants demonstrated a marked reduction in GlcT-1 protein, but there was no reduction in the levels of GlcT-1 mRNA. Both coprecipitation and γ-secretase inhibition experiments suggest that mutant-PS1 seems to form a complex with GlcT-1 protein and to be involved in GlcT-1 degradation, which was never found in other cell types. Thus, mutations in the PS1 gene result in profound glycosphingolipids abnormalities by abnormal molecular interaction with GlcT-1.