Exosomal miR-125b-5p derived from adipose-derived mesenchymal stem cells enhance diabetic hindlimb ischemia repair via targeting alkaline ceramidase 2.

INTRODUCTION: Ischemic diseases caused by diabetes continue to pose a major health challenge and effective treatments are in high demand. Mesenchymal stem cells (MSCs) derived exosomes have aroused broad attention as a cell-free treatment for ischemic diseases. However, the efficacy of exosomes from adipose-derived mesenchymal stem cells (ADSC-Exos) in treating diabetic lower limb ischemic injury remains unclear. METHODS: Exosomes were isolated from ADSCs culture supernatants by differential ultracentrifugation and their effect on C2C12 cells and HUVECs was assessed by EdU, Transwell, and in vitro tube formation assays separately. The recovery of limb function after ADSC-Exos treatment was evaluated by Laser-Doppler perfusion imaging, limb function score, and histological analysis. Subsequently, miRNA sequencing and rescue experiments were performed to figure out the responsible miRNA for the protective role of ADSC-Exos on diabetic hindlimb ischemic injury. Finally, the direct target of miRNA in C2C12 cells was confirmed by bioinformatic analysis and dual-luciferase report gene assay. RESULTS: ADSC-Exos have the potential to promote proliferation and migration of C2C12 cells and to promote HUVECs angiogenesis. In vivo experiments have shown that ADSC-Exos can protect ischemic skeletal muscle, promote the repair of muscle injury, and accelerate vascular regeneration. Combined with bioinformatics analysis, miR-125b-5p may be a key molecule in this process. Transfer of miR-125b-5p into C2C12 cells was able to promote cell proliferation and migration by suppressing ACER2 overexpression. CONCLUSION: The findings revealed that miR-125b-5p derived from ADSC-Exos may play a critical role in ischemic muscle reparation by targeting ACER2. In conclusion, our study may provide new insights into the potential of ADSC-Exos as a treatment option for diabetic lower limb ischemia.

LINC01087 indicates a poor prognosis of glioma patients with preoperative MRI.

Long intergenic non-coding RNA 01,087 (LINC01087) has been concerned as an oncogene in breast cancer, while its mechanism in glioma has been little surveyed. Thus, we searched the prognostic value and functional action of LINC01087 in glioma. Glioma patients after preoperative MRI diagnosis were enrolled, and LINC01087, microRNA (miR)-1277-5p, and alkaline ceramidase 3 (ACER3) levels were tested in glioma cancer tissue. The correlation between LINC01087 expression and the survival of patients were analyzed. LINC01087, miR-1277-5p, and ACER3 levels in U251 cells were altered via transfection, and cell malignant phenotypes were monitored. The relationship between miR-1277-5p and LINC01087 or ACER3 was detected. The LINC01087 and ACER3 expression was in up-regulation and the miR-1277-5p expression was in down-regulation in clinical glioma samples. High expression of LINC01087 was associated with poor prognosis of glioma patients with preoperative MRI. LINC01087 silencing restrained tumor malignancy in glioma cells. Mechanistically, LINC01087 directly interacted with miR-1277-5p. ACER3 was a known target of miR-1277-5p. Moreover, rescue assays reveal that miR-1277-5p overexpression (or ACER3 overexpression) reversed the effects of LINC01087 upregulation (or miR-1277-5p upregulation) on glioma cells. LINC01087 has prognostic significance in glioma and silencing LINC01087 deters glioma development through elevating miR-1277-5p to reduce ACER3 expression.

Arabidopsis alkaline ceramidase ACER functions in defense against insect herbivory.

Plant sphingolipids are important membrane components and bioactive molecules in development and defense responses. However, the function of sphingolipids in plant defense, especially against herbivores, is not fully understood. Here, we report that Spodoptera exigua feeding affects sphingolipid metabolism in Arabidopsis, resulting in increased levels of sphingoid long-chain bases, ceramides, and hydroxyceramides. Insect-induced ceramide and hydroxyceramide accumulation is dependent on the jasmonate signaling pathway. Loss of the Arabidopsis alkaline ceramidase ACER increases ceramides and decreases long-chain base levels in plants; in this work, we found that loss of ACER enhances plant resistance to S. exigua and improves response to mechanical wounding. Moreover, acer-1 mutants exhibited more severe root-growth inhibition and higher anthocyanin accumulation than wild-type plants in response to methyl jasmonate treatment, indicating that loss of ACER increases sensitivity to jasmonate and that ACER functions in jasmonate-mediated root growth and secondary metabolism. Transcript levels of ACER were also negatively regulated by jasmonates, and this process involves the transcription factor MYC2. Thus, our findings reveal that ACER is involved in mediating jasmonate-related plant growth and defense and that jasmonates function in regulating the expression of ACER.

ACER3-related leukoencephalopathy: expanding the clinical and imaging findings spectrum due to novel variants.

BACKGROUND: Leukodystrophies are the main subgroup of inherited CNS white matter disorders which cause significant mortality and morbidity in early years of life. Diagnosis is mostly based on clinical context and neuroimaging findings; however, genetic tools, particularly whole-exome sequencing (WES), have led to comprehending the causative gene and molecular events contributing to these disorders. Mutation in Alkaline Ceramidase 3 (ACER3) gene which encodes alkaline ceramidase enzyme that plays a crucial role in cellular growth and viability has been stated as an uncommon reason for inherited leukoencephalopathies. Merely only two ACER3 mutations in cases of progressive leukodystrophies have been reported thus far. RESULTS: In the current study, we have identified three novel variants in ACER3 gene in cases with new neurological manifestations including developmental regression, dystonia, and spasticity. The detected variants were segregated into family members. CONCLUSION: Our study expands the clinical, neuroimaging, electroencephalographic, and genetic spectrum of ACER3 mutations. Furthermore, we reviewed and compared the findings of all the previously reported cases and the cases identified here in order to facilitate their diagnosis and management.

Sphingolipid Catabolism and Glycerophospholipid Levels Are Altered in Erythrocytes and Plasma from Multiple Sclerosis Patients.

Multiple sclerosis (MS) is an autoimmune, inflammatory, degenerative disease of the central nervous system. Changes in lipid metabolism have been suggested to play important roles in MS pathophysiology and progression. In this work we analyzed the lipid composition and sphingolipid-catabolizing enzymes in erythrocytes and plasma from MS patients and healthy controls. We observed reduction of sphingomyelin (SM) and elevation of its products-ceramide (CER) and shingosine (SPH). These changes were supported by the detected up-regulation of the activity of acid sphingomyelinase (ASM) in MS plasma and alkaline ceramidase (ALCER) in erythrocytes from MS patients. In addition, Western blot analysis showed elevated expression of ASM, but not of ALCER. We also compared the ratios between saturated (SAT), unsaturated (UNSAT) and polyunsaturated fatty acids and suggest, based on the significant differences observed for this ratio, that the UNSAT/SAT values could serve as a marker distinguishing erythrocytes and plasma of MS from controls. In conclusion, the application of lipid analysis in the medical practice would contribute to definition of more precise diagnosis, analysis of disease progression, and evaluation of therapeutic strategies. Based on the molecular changes of blood lipids in neurodegenerative pathologies, including MS, clinical lipidomic analytical approaches could become a promising contemporary tool for personalized medicine.

Resveratrol Affects Sphingolipid Metabolism in A549 Lung Adenocarcinoma Cells.

Resveratrol is a naturally occurring polyphenol which has various beneficial effects, such as anti-inflammatory, anti-tumor, anti-aging, antioxidant, and neuroprotective effects, among others. The anti-cancer activity of resveratrol has been related to alterations in sphingolipid metabolism. We analyzed the effect of resveratrol on the enzymes responsible for accumulation of the two sphingolipids with highest functional activity-apoptosis promoting ceramide (CER) and proliferation-stimulating sphingosine-1-phosphate (S1P)-in human lung adenocarcinoma A549 cells. Resveratrol treatment induced an increase in CER and sphingosine (SPH) and a decrease in sphingomyelin (SM) and S1P. Our results showed that the most common mode of CER accumulation, through sphingomyelinase-induced hydrolysis of SM, was not responsible for a CER increase despite the reduction in SM in A549 plasma membranes. However, both the activity and the expression of CER synthase 6 were upregulated in resveratrol-treated cells, implying that CER was accumulated as a result of stimulated de novo synthesis. Furthermore, the enzyme responsible for CER hydrolysis, alkaline ceramidase, was not altered, suggesting that it was not related to changes in the CER level. The enzyme maintaining the balance between apoptosis and proliferation, sphingosine kinase 1 (SK1), was downregulated, and its expression was reduced, resulting in a decrease in S1P levels in resveratrol-treated lung adenocarcinoma cells. In addition, incubation of resveratrol-treated A549 cells with the SK1 inhibitors DMS and fingolimod additionally downregulated SK1 without affecting its expression. The present studies provide information concerning the biochemical processes underlying the influence of resveratrol on sphingolipid metabolism in A549 lung cancer cells and reveal possibilities for combined use of polyphenols with specific anti-proliferative agents that could serve as the basis for the development of complex therapeutic strategies.

Maternal and fetal alkaline ceramidase 2 is required for placental vascular integrity in mice.

Sphingolipids have been implicated in mammalian placental development and function, but their regulation in the placenta remains unclear. Herein we report that alkaline ceramidase 2 (ACER2) plays a key role in sustaining the integrity of the placental vasculature by regulating the homeostasis of sphingolipids in mice. The mouse alkaline ceramidase 2 gene (Acer2) is highly expressed in the placenta between embryonic day (E) 9.5 and E12.5. Acer2 deficiency in both the mother and fetus decreases the placental levels of sphingolipids, including sphingoid bases (sphingosine and dihydrosphingosine) and sphingoid base-1-phosphates (sphingosine-1-phosphate and dihydrosphingosine-1-phosphate) and results in the in utero death of ≈50% of embryos at E12.5 whereas Acer2 deficiency in either the mother or fetus has no such effects. Acer2 deficiency causes hemorrhages from the maternal vasculature in the junctional and/or labyrinthine zones in E12.5 placentas. Moreover, hemorrhagic but not non-hemorrhagic Acer2-deficient placentas exhibit an expansion of parietal trophoblast giant cells with a concomitant decrease in the area of the fetal blood vessel network in the labyrinthine zone, suggesting that Acer2 deficiency results in embryonic lethality due to the atrophy of the fetal blood vessel network in the placenta. Taken together, these results suggest that ACER2 sustains the integrity of the placental vasculature by controlling the homeostasis of sphingolipids in mice.

Transcriptional changes revealed genes and pathways involved in the deficient testis caused by the inhibition of alkaline ceramidase (Dacer) in Drosophila melanogaster.

Sphingolipids are ubiquitous structural components of eukaryotic cell membranes which are vital for maintaining the integrity of cells. Alkaline ceramidase is a key enzyme in sphingolipid biosynthesis pathway; however, little is known about the role of the enzyme in the male reproductive system of Drosophila melanogaster. To investigate the impact of alkaline ceramidase (Dacer) on male Drosophila, we got Dacer deficiency mutants (MUs) and found they displayed apparent defects in the testis's phenotype. To profile the molecular changes associated with this abnormal phenotype, we performed de novo transcriptome analyses of the MU and wildtype (WT) testes; and revealed 1239 upregulated genes and 1102 downregulated genes. Then, six upregulated DEGs (papilin [Ppn], croquemort [Crq], terribly reduced optic lobes [Trol], Laminin, Wunen-2, collagen type IV alpha 1 [Cg25C]) and three downregulated DEGs (mucin related 18B [Mur18B], rhomboid-7 [Rho-7], CG3168) were confirmed through quantitative real-time polymerase chain reaction in WT and MU samples. The differentially expressed genes were mainly associated with catalytic activity, oxidoreductase activity and transmembrane transporter activity, which significantly contributed to extracellular matrix-receptor interaction, fatty acids biosynthesis as well as glycine, serine, and threonine metabolism. The results highlight the importance of Dacer in the reproductive system of D. melanogaster and provide valuable resources to dig out the specific biological functions of Dacer in insect reproduction.

Human alkaline ceramidase 2 promotes the growth, invasion, and migration of hepatocellular carcinoma cells via sphingomyelin phosphodiesterase acid-like 3B.

Hepatocellular carcinoma (HCC) is the most common type of liver cancer. It has a poor prognosis because it is often diagnosed at the advanced stage when treatments are limited. In addition, HCC pathogenesis is not fully understood, and this has affected early diagnosis and treatment of this disease. Human alkaline ceramidase 2 (ACER2), a key enzyme that regulates hydrolysis of cellular ceramides, affects cancer cell survival, however its role in HCC has not been well characterized. Our results showed that ACER2 is overexpressed in HCC tissues and cell lines. In addition, high ACER2 protein expression was associated with tumor growth; ACER2 knockdown resulted in decreased cell growth and migration. Sphingomyelin phosphodiesterase acid-like 3B (SMPDL3B) promoted HCC cell growth, invasion, and migration; SMPDL3B knockdown had a significant inhibitory effect on HCC tumor growth in vivo. Moreover, ACER2 positively regulated the protein level of SMPDL3B. Of note, ACER2/SMPDL3B promoted ceramide hydrolysis and S1P production. This axis induced HCC survival and could be blocked by inhibition of S1P formation. In conclusion, ACER2 promoted HCC cell survival and migration, possibly via SMPDL3B. Thus, inhibition of ACER2/SMPDL3B may be a novel therapeutic target for HCC treatment.

Identification of Acer2 as a First Susceptibility Gene for Lithium-Induced Nephrogenic Diabetes Insipidus in Mice.

BACKGROUND: Lithium, mainstay treatment for bipolar disorder, causes nephrogenic diabetes insipidus and hypercalcemia in about 20% and 10% of patients, respectively, and may lead to acidosis. These adverse effects develop in only a subset of patients treated with lithium, suggesting genetic factors play a role. METHODS: To identify susceptibility genes for lithium-induced adverse effects, we performed a genome-wide association study in mice, which develop such effects faster than humans. On day 8 and 10 after assigning female mice from 29 different inbred strains to normal chow or lithium diet (40 mmol/kg), we housed the animals for 48 hours in metabolic cages for urine collection. We also collected blood samples. RESULTS: In 17 strains, lithium treatment significantly elevated urine production, whereas the other 12 strains were not affected. Increased urine production strongly correlated with lower urine osmolality and elevated water intake. Lithium caused acidosis only in one mouse strain, whereas hypercalcemia was found in four strains. Lithium effects on blood pH or ionized calcium did not correlate with effects on urine production. Using genome-wide association analyses, we identified eight gene-containing loci, including a locus containing Acer2, which encodes a ceramidase and is specifically expressed in the collecting duct. Knockout of Acer2 led to increased susceptibility for lithium-induced diabetes insipidus development. CONCLUSIONS: We demonstrate that genome-wide association studies in mice can be used successfully to identify susceptibility genes for development of lithium-induced adverse effects. We identified Acer2 as a first susceptibility gene for lithium-induced diabetes insipidus in mice.

New fluorogenic probes for neutral and alkaline ceramidases.

New fluorogenic ceramidase substrates derived from the N-acyl modification of our previously reported probes (RBM14) are reported. While none of the new probes were superior to the known RBM14C12 as acid ceramidase substrates, the corresponding nervonic acid amide (RBM14C24:1) is an efficient and selective substrate for the recombinant human neutral ceramidase, both in cell lysates and in intact cells. A second generation of substrates, incorporating the natural 2-(N-acylamino)-1,3-diol-4-ene framework (compounds RBM15) is also reported. Among them, the corresponding fatty acyl amides with an unsaturated N-acyl chain can be used as substrates to determine alkaline ceramidase (ACER)1 and ACER2 activities. In particular, compound RBM15C18:1 has emerged as the best fluorogenic probe reported so far to measure ACER1 and ACER2 activities in a 96-well plate format.

Alkaline ceramidase 2 is essential for the homeostasis of plasma sphingoid bases and their phosphates.

Sphingosine-1-phosphate (S1P) plays important roles in cardiovascular development and immunity. S1P is abundant in plasma because erythrocytes-the major source of S1P-lack any S1P-degrading activity; however, much remains unclear about the source of the plasma S1P precursor, sphingosine (SPH), derived mainly from the hydrolysis of ceramides by the action of ceramidases that are encoded by 5 distinct genes, acid ceramidase 1 ( ASAH1)/ Asah1, ASAH2/ Asah2, alkaline ceramidase 1 ( ACER1)/ Acer1, ACER2/ Acer2, and ACER3/ Acer3, in humans/mice. Previous studies have reported that knocking out Asah1 or Asah2 failed to reduce plasma SPH and S1P levels in mice. In this study, we show that knocking out Acer1 or Acer3 also failed to reduce the blood levels of SPH or S1P in mice. In contrast, knocking out Acer2 from either whole-body or the hematopoietic lineage markedly decreased the blood levels of SPH and S1P in mice. Of interest, knocking out Acer2 from whole-body or the hematopoietic lineage also markedly decreased the levels of dihydrosphingosine (dhSPH) and dihydrosphingosine-1-phosphate (dhS1P) in blood. Taken together, these results suggest that ACER2 plays a key role in the maintenance of high plasma levels of sphingoid base-1-phosphates-S1P and dhS1P-by controlling the generation of sphingoid bases-SPH and dhSPH-in hematopoietic cells.-Li, F., Xu, R., Low, B. E., Lin, C.-L., Garcia-Barros, M., Schrandt, J., Mileva, I., Snider, A., Luo, C. K., Jiang, X.-C., Li, M.-S., Hannun, Y. A., Obeid, L. M., Wiles, M. V., Mao, C. Alkaline ceramidase 2 is essential for the homeostasis of plasma sphingoid bases and their phosphates.

Alkaline Ceramidase Mediates the Oxidative Stress Response in Drosophila melanogaster Through Sphingosine.

Alkaline ceramidase (Dacer) in Drosophila melanogaster was demonstrated to be resistant to paraquat-induced oxidative stress. However, the underlying mechanism for this resistance remained unclear. Here, we showed that sphingosine feeding triggered the accumulation of hydrogen peroxide (H2O2). Dacer-deficient D. melanogaster (Dacer mutant) has higher catalase (CAT) activity and CAT transcription level, leading to higher resistance to oxidative stress induced by paraquat. By performing a quantitative proteomic analysis, we identified 79 differentially expressed proteins in comparing Dacer mutant to wild type. Three oxidoreductases, including two cytochrome P450 (CG3050, CG9438) and an oxoglutarate/iron-dependent dioxygenase (CG17807), were most significantly upregulated in Dacer mutant. We presumed that altered antioxidative activity in Dacer mutant might be responsible for increased oxidative stress resistance. Our work provides a novel insight into the oxidative antistress response in D. melanogaster.

Colon Cancer and Perturbations of the Sphingolipid Metabolism.

The development and progression of colorectal cancer (CRC), a major cause of cancer-related death in the western world, is accompanied with alterations of sphingolipid (SL) composition in colon tumors. A number of enzymes involved in the SL metabolism have been found to be deregulated in human colon tumors, in experimental rodent studies, and in human colon cancer cells in vitro. Therefore, the enzymatic pathways that modulate SL levels have received a significant attention, due to their possible contribution to CRC development, or as potential therapeutic targets. Many of these enzymes are associated with an increased sphingosine-1-phosphate/ceramide ratio, which is in turn linked with increased colon cancer cell survival, proliferation and cancer progression. Nevertheless, more attention should also be paid to the more complex SLs, including specific glycosphingolipids, such as lactosylceramides, which can be also deregulated during CRC development. In this review, we focus on the potential roles of individual SLs/SL metabolism enzymes in colon cancer, as well as on the pros and cons of employing the current in vitro models of colon cancer cells for lipidomic studies investigating the SL metabolism in CRC.

Loss of alkaline ceramidase inhibits autophagy in Arabidopsis and plays an important role during environmental stress response.

Sphingolipids, a class of bioactive lipids found in cell membranes, can modulate the biophysical properties of the membranes and play a critical role in signal transduction. Sphingolipids are involved in autophagy in humans and yeast, but their role in autophagy in plants is not well understood. In this study, we reported that the AtACER, an alkaline ceramidase that hydrolyses ceramide to long-chain base (LCB), functions in autophagy process in Arabidopsis. Our empirical data showed that the loss of AtACER inhibited autophagy, and its overexpression promoted autophagy under nutrient, salinity, and oxidative stresses. Interestingly, nitrogen deprivation significantly affected the sphingolipid's profile in Arabidopsis thaliana, especially the LCBs. Furthermore, the exogenous application of LCBs also induced autophagy. Our findings revealed a novel function of AtACER, where it was found to involve in the autophagy process, thus, playing a crucial role in the maintenance of a dynamic loop between sphingolipids and autophagy for cellular homeostasis under various environmental stresses.

Alkaline Ceramidase 3 Deficiency Results in Purkinje Cell Degeneration and Cerebellar Ataxia Due to Dyshomeostasis of Sphingolipids in the Brain.

Dyshomeostasis of both ceramides and sphingosine-1-phosphate (S1P) in the brain has been implicated in aging-associated neurodegenerative disorders in humans. However, mechanisms that maintain the homeostasis of these bioactive sphingolipids in the brain remain unclear. Mouse alkaline ceramidase 3 (Acer3), which preferentially catalyzes the hydrolysis of C18:1-ceramide, a major unsaturated long-chain ceramide species in the brain, is upregulated with age in the mouse brain. Acer3 knockout causes an age-dependent accumulation of various ceramides and C18:1-monohexosylceramide and abolishes the age-related increase in the levels of sphingosine and S1P in the brain; thereby resulting in Purkinje cell degeneration in the cerebellum and deficits in motor coordination and balance. Our results indicate that Acer3 plays critically protective roles in controlling the homeostasis of various sphingolipids, including ceramides, sphingosine, S1P, and certain complex sphingolipids in the brain and protects Purkinje cells from premature degeneration.

Alkaline ceramidase 1 is essential for mammalian skin homeostasis and regulating whole-body energy expenditure.

The epidermis is the outermost layer of skin that acts as a barrier to protect the body from the external environment and to control water and heat loss. This barrier function is established through the multistage differentiation of keratinocytes and the presence of bioactive sphingolipids such as ceramides, the levels of which are tightly regulated by a balance of ceramide synthase and ceramidase activities. Here we reveal the essential role of alkaline ceramidase 1 (Acer1) in the skin. Acer1-deficient (Acer1(-/-) ) mice showed elevated levels of ceramide in the skin, aberrant hair shaft cuticle formation and cyclic alopecia. We demonstrate that Acer1 is specifically expressed in differentiated interfollicular epidermis, infundibulum and sebaceous glands and consequently Acer1(-/-) mice have significant alterations in infundibulum and sebaceous gland architecture. Acer1(-/-) skin also shows perturbed hair follicle stem cell compartments. These alterations result in Acer1(-/-) mice showing increased transepidermal water loss and a hypermetabolism phenotype with associated reduction of fat content with age. We conclude that Acer1 is indispensable for mammalian skin homeostasis and whole-body energy homeostasis. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Gene expression of sphingolipid metabolism pathways is altered in hidradenitis suppurativa.

BACKGROUND: Hidradenitis suppurativa (HS) is a debilitating skin disease characterized by painful recurrent nodules and abscesses caused by chronic inflammation. Early events in the development of HS are believed to occur in the folliculopilosebaceous unit; however, the signaling pathways behind this mechanism are unknown. Sphingolipids, such as ceramide, are essential components of the skin and appendages and have important structural and signaling roles. OBJECTIVE: We sought to explore whether the gene expression of enzymes involved in sphingolipid metabolic pathways is altered in HS. METHODS: A microarray data set including 30 samples was used to compare the expression of sphingolipid-related enzymes in inflammatory skin lesions from HS patients (n = 17) with the expression in clinically healthy skin tissue (n = 13). Differential expression of sphingolipid metabolism-related genes was analyzed using Gene Expression Omnibus 2R. RESULTS: HS lesional skin samples have significantly decreased expression of enzymes generating ceramide and sphingomyelin, increased expression of enzymes catabolizing ceramide to sphingosine, and increased expression of enzymes converting ceramide to galactosylceramide and gangliosides. LIMITATIONS: Limitations of this study include assessing the expression of sphingolipid-related enzymes without assessing the levels of the related sphingolipids. CONCLUSION: Our study suggests that sphingolipid metabolism is altered in HS lesional skin compared with normal skin.

Deficiency of the alkaline ceramidase ACER3 manifests in early childhood by progressive leukodystrophy.

BACKGROUND/AIMS: Leukodystrophies due to abnormal production of myelin cause extensive morbidity in early life; their genetic background is still largely unknown. We aimed at reaching a molecular diagnosis in Ashkenazi-Jewish patients who suffered from developmental regression at 6-13 months, leukodystrophy and peripheral neuropathy. METHODS: Exome analysis, determination of alkaline ceramidase activity catalysing the conversion of C18:1-ceramide to sphingosine and D-ribo-C12-N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) (NBD)-phytoceramide to NBD-C12-fatty acid using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and thin layer chromatography, respectively, and sphingolipid analysis in patients' blood by LC-MS/MS. RESULTS: The patients were homozygous for p.E33G in the ACER3, which encodes a C18:1-alkaline ceramidase and C20:1-alkaline ceramidase. The mutation abolished ACER3 catalytic activity in the patients' cells and failed to restore alkaline ceramidase activity in yeast mutant strain. The levels of ACER3 substrates, C18:1-ceramides and dihydroceramides and C20:1-ceramides and dihydroceramides and other long-chain ceramides and dihydroceramides were markedly increased in the patients' plasma, along with that of complex sphingolipids, including monohexosylceramides and lactosylceramides. CONCLUSIONS: Homozygosity for the p.E33G mutation in the ACER3 gene results in inactivation of ACER3, leading to the accumulation of various sphingolipids in blood and probably in brain, likely accounting for this new form of childhood leukodystrophy.

ACER3 supports development of acute myeloid leukemia.

No new therapy for acute myeloid leukemia (AML) has been approved for more than 30 years. To effectively treat AML, new molecular targets and therapeutic approaches must be identified. In silico analysis of several databases of AML patients demonstrated that the expression of alkaline ceramidase 3 (ACER3) significantly inversely correlates with the overall survival of AML patients. To determine whether ACER3 supports AML development, we employed an shRNA-encoding lentivirus system to inhibit acer3 expression in human AML cells including NB4, U937, and THP-1 cells. The ACER3 deficiency resulted in decreased cell growth and colony formation, elevated apoptosis, and lower AKT signaling of leukemia cells. Our study indicates that ACER3 contributes to AML pathogenesis, and suggests that alkaline ceramidase inhibition is an option to treat AML.