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The last step of ex novo ceramide biosynthesis consists of the conversion of dihydroceramide into ceramide catalyzed by sphingolipid Δ4-desaturase DEGS1. DEGS1 variants were found to be responsible for heterogeneous clinical pictures belonging to the family of hypomyelinating leukodystrophies. To investigate the mechanisms making such variants pathogenic, we designed a procedure for the efficient detection of desaturase activity in vitro using LC-MS/MS and prepared a suitable cell model knocking out DEGS1 in HEK-293T cells through CRISPR-Cas9 genome editing (KO-DES-HEK). Transfecting KO-DES-HEK cells with DEGS1 variants, we found that their transcripts were all overexpressed as much as the WT transcripts, while the levels of cognate protein were 40%-80% lower. In vitro desaturase activity was lost by many variants except L175Q and N255S, which maintain a catalytic efficiency close to 12% of the WT enzyme. Metabolic labeling of KO-DES-HEK with deuterated palmitate followed by LC-MS/MS analysis of the formed sphingolipids revealed that the ceramide/dihydroceramide and sphingomyelin/dihydrosphingomyelin ratios were low and could be reverted by the overexpression of WT DEGS1 as well as of L175Q and N255S variants, but not by the overexpression of all other variants. Similar analyses performed on fibroblasts from a patient heterozygous for the N255S variant showed very low variant DEGS1 levels and a low ratio between the same unsaturated and saturated sphingolipids formed upon metabolic labeling, notwithstanding the residual activity measured at high substrate and homogenate protein concentrations. We conclude that loss of function and reduced protein levels are both relevant in disease pathogenesis., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Recent clinical trials show the efficacy of Adipose-derived Stromal Cells (ASCs) in contrasting the osteoarthritis scenario. Since it is quite accepted that ASCs act predominantly through a paracrine mechanism, their secretome may represent a valid therapeutic substitute. The aim of this study was to investigate the effects of ASC conditioned medium (ASC-CM) on TNFα-stimulated human primary articular chondrocytes (CHs). CHs were treated with 10 ng/ml TNFα and/or ASC-CM (1:5 recipient:donor cell ratio). ASC-CM treatment blunted TNFα-induced hypertrophy, reducing the levels of Osteocalcin (-37%), Collagen X (-18%) and MMP-13 activity (-61%). In addition, it decreased MMP-3 activity by 59%. We showed that the reduction of MMP activity correlates to the abundance of TIMPs (Tissue Inhibitors of MMPs) in ASC secretome (with TIMP-1 exceeding 200 ng/ml and TIMP-2/3 in the ng/ml range) rather than to a direct down-modulation of the expression and/or release of these proteases. In addition, ASC secretome contains high levels of other cartilage protecting factors, i.e. OPG and DKK-1. ASC-CM comprises cartilage-protecting factors and exerts anti-hypertrophic and anti-catabolic effects on TNFα-stimulated CHs in vitro. Our results support a future use of this cell-derived but cell-free product as a therapeutic approach in the management of osteoarthritis., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Phosphatidylethanols (PEths) are currently under investigation as highly sensitive and specific direct biomarkers of long-term alcohol abuse. PEths belong to a group of aberrant phospholipids formed in erythrocyte membranes in presence of ethanol by the catalytic action of the enzyme phospholipase D on phosphatidylcholine. Compared to other alcohol biomarkers, a higher sensitivity (94.5-100%) and specificity (100%) characterizes PEth species., Method: Prior to detection, an important practical aspect in the work-flow of PEths analysis is the sample preparation step. To date, traditional techniques such as liquid-liquid extraction (LLE) and solid phase extraction (SPE) require multiple steps to remove blood interferences. Due to the simplicity of use and the possibility of automation, sample filtration is also a widespread technique in biomedical laboratories. In this work, a reliable sample preparation method based on an automated filtration with Phree™ Phospholipid Removal Plates (Phenomenex, California, USA) was developed to extract PEths from human whole blood. Surface characteristics of Phospholipids Removal material allow phospholipids retention on the filter and a suitable PEths recovery after elution. The blood samples were added with internal standard (IS) and purified in acetonitrile (1 mL). After centrifugation, supernatants were applied to the Phospholipids Removal Plates in an automated workstation. After washing, the phospholipids retained on the filter were eluted with 1-mL 2-propanol 1% ammonia. PEth 16:0/18:1, PEth 16:0/16:0 and PEth 18:1/18:1 were extracted using the proposed method and detected by LC-MS/MS operated in electron spray ionization (ESI). The detection of all compounds was based on multiple reaction monitoring (MRM) transitions. This method was validated for the quantitative profiling of PEth molecular species in human blood collected from heavy and social drinkers., Results: The method was validated according to Food and Drug Administration (FDA) guidelines. Linearity was observed in the 25-1250 (PEth 16:0/18:1) and 5-250 (PEth 16:0/16:0 and PEth 18:1/18:1) ng/mL range with a correlation coefficient (r²) between 0.997 and 0.999 for all three compounds. Moreover, the nominal concentrations of non-zero calibrators were ±15%. Variation coefficient (%CV) was < 10% for all the analytes, while lowest limit of quantitation (LLOQ) was found to be 1.25 ng/mL for PEth 16:0/18:1, 0.50 ng/mL for PEth 16:0/16:0 and 0.50 ng/mL for PEth 18:1/18:1. Intra- and inter-day precision and accuracy were always lower than 14% and 11%, respectively. Analytical recovery was higher than 68.8% for all analytes. Sample stability at 4 °C and -20 °C showed a concentration drop lower than 20% up to 4 weeks. Extracts were stable for 7 days in the autosampler and 30 days at -20 °C and 4 °C in a closed vial. The procedure was successfully applied to blood samples collected from heavy drinkers (n = 8), social drinkers (n = 5), and teetotalers (n = 7)., Conclusions: Due to the simplicity of application and the possibility of automation, sample filtration is well suited for a clinical and forensic laboratory. To monitor alcohol consumption, an analytical method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) with novel and automated sample preparation was developed and validated for the simultaneous quantification of PEth 16:0/18:1, PEth 16:0/16:0 and PEth 18:1/18:1 in whole blood samples, characterized by a fast sample preparation and lower pre-analysis costs than other extraction procedures., (Copyright © 2018 Elsevier B.V. All rights reserved.)