SMPD1 Research Articles

Differential regulation of microRNA-15a by radiation affects angiogenesis and tumor growth via modulation of acid sphingomyelinase

Activation of acid sphingomyelinase (SMPD1) and the generation of ceramide is a critical regulator of apoptosis in response to cellular stress including radiation. Endothelial SMPD1 has been shown to regulate tumor responses to radiation therapy. We show here that the SMPD1 gene is regulated by a microRNA (miR), miR-15a, in endothelial cells (ECs). Standard low dose radiation (2 Gy) upregulates miR-15a and decreases SMPD1 levels. In contrast, high dose radiation (10 Gy and above) decreases miR-15a and increases SMPD1. Ectopic expression of miR-15a decreases both mRNA and protein levels of SMPD1. Mimicking the effects of high dose radiation with a miR-15a inhibitor decreases cell proliferation and increases active Caspase-3 & 7. Mechanistically, inhibition of miR-15a increases inflammatory cytokines, activates caspase-1 inflammasome and increases Gasdermin D, an effector of pyroptosis. Importantly, both systemic and vascular-targeted delivery of miR-15a inhibitor decreases angiogenesis and tumor growth in a CT26 murine colorectal carcinoma model. Taken together, our findings highlight a novel role for miR mediated regulation of SMPD1 during radiation responses and establish proof-of-concept that this pathway can be targeted with a miR inhibitor.

Sphingomyelin phosphodiesterase 3 methylation and silencing in oral squamous cell carcinoma results in increased migration and invasion and altered stress response.

Neutral sphingomyelinase 2 (nSMase2), the product of the sphingomyelin phosphodiesterase 3 (SMPD3) gene, catalyzes the hydrolysis of sphingomyelin to ceramide. Ceramide acts on various signaling pathways to influence cell proliferation, survival, and stress response. Altered levels of sphingolipids and ceramides have been reported in various cancer types, including oral squamous cell carcinoma (OSCC). OSCC patients exhibit a poor 5-year survival rate of 50%, a figure that has remained stagnant for decades. To overcome this requires a better understanding of the molecular events driving this disease. The molecular analysis of the oral cavity reported here has identified the SMPD3 promoter region as a site of frequent hypermethylation and downregulation in pre-malignant and malignant tissues as compared with healthy control tissues. While lentivirus-induced overexpression of SMPD3 in cell models of oral dysplasia and OSCC did not significantly alter proliferation, it did decrease migration and invasion and increased resistance to the epidermal growth factor receptor (EGFR) inhibitor erlotinib. These results suggest that SMPD3 downregulation is a common event in OSCC progression and may promote the spread of tumor cells.

Mutational spectrum of SMPD1 gene in Pakistani Niemann-Pick disease patients

Objective:Genetic variation analysis of rare autosomal recessive Niemann-Pick disease (NPD) Pakistani patients.Methods:We sequenced the SMPD1 gene including its all coding and flanking regions in seven unrelated sporadic patients suffering from Niemann-Pick disease through targeted exome sequencing. Genetic variants mapping and their protein predictions were evaluated using different bioinformatics tools and clinical phenotypes were correlated. The study was conducted from January 2018 to March 2019 at The Children’s Hospital Lahore.Results:We have mapped five different mutations in SMPD1 gene of enrolled patients with a novel homozygous missense variant (c.1718G>C) (p.Trp573Ser) in one patient. A missense mutation (c.1267C>T) (p.His423Tyr) has been identified in three unrelated patients. A nonsense mutation (c.1327C>T) (p.Arg443Term) and one missense mutation (c.1493G>A) (p.Arg498His) mapped in one patient each. A compound heterozygous mutation has been mapped in one patient (c.740G>A) (p.Gly247Asp); (c.1493G>A) (p.Arg498His). Pathogenic effect of novel variant has been predicted through in-silico analysis and has not been reported in general overall population in the globe.Conclusion:This is the first report of genetic demographic assessment of Niemann-Pick disease in Pakistan. The mapped mutations would be helpful to build a disease variants algorithm of Pakistani population. This will be used for determining disease clinical magnitude along with provision of genetic screening services in affected families.

Abstract C20: Smpd3 augments chemotherapy and thwarts PDA progression

Abstract Deregulated sphingolipid metabolism alters pancreatic cancer progression; for that reason, bioactive lipid signaling molecules such as ceramide show promise as both biomarkers for disease progression and novel therapeutic targets. Intracellular ceramide levels are critical for regulating cellular senescence, apoptosis, and cell cycle arrest in response to stress stimuli such as chemotherapeutics. Our data show Sphingomyelin Phosphodiesterase 3 (Smpd3), a regulator of ceramide synthesis and exosome biogenesis, has a protumorigenic function in pancreatic ductal adenocarcinoma (PDA). Immunodeficient mice orthotopically implanted with Smpd3-deficient PDA cell lines demonstrate significantly reduced tumor burden and longer survival when compared with controls. This observation was mirrored by our KPC; Smpd3f/f mouse model, in which loss of Smpd3 expression significantly correlated with longer survival and decreased metastasis when compared to KPC; Smpd3wt/wt controls. Analysis of SMPD3 in PDA patients revealed that low SMPD3 RNA and protein expression is significantly associated with worse survival. Because chemotherapeutics have been shown to affect expression and function of SMPD3, we stratified patient cohorts into individuals who received adjuvant chemotherapy, more than 95% of which was gemcitabine, and those who did not receive adjuvant chemotherapy. We found that high SMPD3 expression in surgically resected PDA significantly correlated with longer patient survival only in patients receiving adjuvant chemotherapy, and not in the no-adjuvant-chemotherapy group. These data suggest an interaction between adjuvant chemotherapy with gemcitabine and SMPD3 expression. Furthermore, we found that gemcitabine stimulates both the enzymatic activity and expression of SMPD3 in vitro in a panel of human PDA cell lines. Our results suggest a crucial role for SMPD3 in facilitating a protumorigenic environment during PDA progression and implicate SMPD3 as a potential novel biomarker for guiding individualized chemotherapeutic regimens for PDA patients. Citation Format: Audrey M. Hendley, Atsushi Urano, Natanya R. Kerper, Phat Duong, Peter Bailey, David K. Chang, Andrew V. Biankin, David W. Dawson, Grace Kim, Robert L. Raffai, Matthias Hebrok. Smpd3 augments chemotherapy and thwarts PDA progression [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr C20.

Characterization of Niemann-Pick diseases genes mutation spectrum in Iran and identification of a novel mutation in SMPD1 gene.

Background: Niemann-Pick diseases are rare inherited lipid storage disorders caused by mutations in the SMPD1, NPC1, and NPC2 genes. The aim of this study was to assess the mutation spectrum of a cohort of Iranian Niemann-Pick patients. Methods: A consanguineous couple with a child suspected of having Niemann-Pick disease type A (died at age 2) was screened for gene mutations in the SMPD1 gene. Sanger sequencing was performed for all exons and exon-intron boundary regions. A literature review on SMPD1, NPC1, and NPC2 genes mutations in Iran was conducted using published original papers on this subject. Results: A novel frameshift c.762delG (p.Leu256fs*) at a heterozygous state was identified in the parents. According to the review study, identified mutations in 39 Iranian patients were concentrated in exon 2 of the SMPD1 gene and exons 8 and 9 of the NPC1 gene. Conclusion: Niemann-Pick diseases genes mutation analysis (SMPD1, NPC1, and NPC2) in Iran shows the genetic heterogeneity of these diseases in this country. More studies with larger sample sizes should be conducted to further examine genetic changes associated with Niemann-Pick diseases in Iran.

Medial calcification in the arterial wall of smooth muscle cell-specific Smpd1 transgenic mice: A ceramide-mediated vasculopathy.

Arterial medial calcification (AMC) is associated with crystallization of hydroxyapatite in the extracellular matrix and arterial smooth muscle cells (SMCs) leading to reduced arterial compliance. The study was performed to test whether lysosomal acid sphingomyelinase (murine gene code: Smpd1)‐derived ceramide contributes to the small extracellular vesicle (sEV) secretion from SMCs and consequently leads to AMC. In Smpd1 trg/SMcre mice with SMC‐specific overexpression of Smpd1 gene, a high dose of Vit D (500 000 IU/kg/d) resulted in increased aortic and coronary AMC, associated with augmented expression of RUNX2 and osteopontin in the coronary and aortic media compared with their littermates (Smpd1 trg/SMwt and WT/WT mice), indicating phenotypic switch. However, amitriptyline, an acid sphingomyelinase (ASM) inhibitor, reduced calcification and reversed phenotypic switch. Smpd1 trg/SMcre mice showed increased CD63, AnX2 and ALP levels in the arterial wall, accompanied by reduced co‐localization of lysosome marker (Lamp‐1) with multivesicular body (MVB) marker (VPS16), a parameter for lysosome‐MVB interaction. All these changes related to lysosome fusion and sEV release were substantially attenuated by amitriptyline. Increased arterial stiffness and elastin disorganization were found in Smpd1 trg /SMcre mice as compared to their littermates. In cultured coronary arterial SMCs (CASMCs) from Smpd1 trg/SMcre mice, increased Pi concentrations led to markedly increased calcium deposition, phenotypic change and sEV secretion compared with WT CASMCs, accompanied by reduced lysosome‐MVB interaction. However, amitriptyline prevented these changes in Pi‐treated CASMCs. These data indicate that lysosomal ceramide plays a critical role in phenotype change and sEV release in SMCs, which may contribute to the arterial stiffness during the development of AMC.

Characterization of Niemann-Pick diseases genes mutation spectrum in Iran and identification of a novel mutation in SMPD1 gene

Characterization of Niemann-Pick diseases genes mutation spectrum in Iran and identification of a novel mutation in SMPD1 gene

The Neuroprotective Effect of Amitriptyline on Radiation-Induced Impairment of Hippocampal Neurogenesis.

The radioprotective effect of amitriptyline, an inhibitor of acid sphingomyelinase (ASMase), on radiation-induced impairment of hippocampal neurogenesis, loss of interneuron, and animal weight changes was investigated in BALB/c mice by immunostaining of biomarkers for cell division (Ki67), immature neurons (doublecortin or DCX), and interneurons (parvalbumin or PV) in the dentate gyrus (DG) of hippocampus. The results indicated that preirradiation (with 10 mg/kg, 2 times per day, for 7 consecutive days) or postirradiation (with 10 mg/kg, 2 times per day, for 14 consecutive days) treatment (pretreatment or posttreatment) with intraperitoneal injection of amitriptyline prevented the loss of newly generated neurons, proliferating cells, and interneurons in the subgranular zone of the DG. At the molecular level, pretreatment or posttreatment inhibited the expression of sphingomyelin phosphodiesterase 1 (SMPD1) gene which codes for ASMase. The pretreatment for 7 days also prevented radiation-induced weight loss from 2 to 3 weeks, but not within 1 week after irradiation. On the other hand, the posttreatment with amitriptyline for 14 days could improve animal weight gain from 4 to 6 weeks after irradiation. The present study suggests that amitriptyline may be a promising candidate radio-neuroprotective drug to improve radiation-induced impairment of hippocampal neurogenesis and relevant neurological and neuropsychological disorders.

Serum proteome of dogs at subclinical and clinical onset of canine leishmaniosis.

The objective of this study was to identify changes in serum proteome in dogs that may occur after an experimental infection at subclinical and clinical stages of canine leishmaniosis (CanL). For this purpose, canine pre- and post-infection with Leishmania infantum serum proteomes in the same dogs were analysed by a high-throughput label-based quantitative LC-MS/MS proteomic approach. A total of 169 proteins were identified, and 74 of them including complement C8 alpha chain, adiponectin, transferrin, sphingomyelin phosphodiesterase acid-like 3A and immunoglobulins showed different modulation between the different stages of CanL. These proteins could be considered as potential serumbiomarkers of early diagnostic or disease progression in CanL. Additionally, biological pathways modulated during CanL such as blood coagulation or gonadotropin-releasing hormone receptor were revealed, which could help to understand the pathological mechanisms of the disease.

SMPDL3b modulates insulin receptor signaling in diabetic kidney disease

Sphingomyelin phosphodiesterase acid-like 3b (SMPDL3b) is a lipid raft enzyme that regulates plasma membrane (PM) fluidity. Here we report that SMPDL3b excess, as observed in podocytes in diabetic kidney disease (DKD), impairs insulin receptor isoform B-dependent pro-survival insulin signaling by interfering with insulin receptor isoforms binding to caveolin-1 in the PM. SMPDL3b excess affects the production of active sphingolipids resulting in decreased ceramide-1-phosphate (C1P) content as observed in human podocytes in vitro and in kidney cortexes of diabetic db/db mice in vivo. Podocyte-specific Smpdl3b deficiency in db/db mice is sufficient to restore kidney cortex C1P content and to protect from DKD. Exogenous administration of C1P restores IR signaling in vitro and prevents established DKD progression in vivo. Taken together, we identify SMPDL3b as a modulator of insulin signaling and demonstrate that supplementation with exogenous C1P may represent a lipid therapeutic strategy to treat diabetic complications such as DKD.

An induced pluripotent stem cell line (TRNDi009-C) from a Niemann-Pick disease type A patient carrying a heterozygous p.L302P (c.905 T>C) mutation in the SMPD1 gene

Niemann-Pick disease type A (NPA) is a rare autosomal recessive lysosomal storage disease caused by mutations in the SMPD1 gene, which encodes for the protein acid sphingomyelinase. A human induced pluripotent stem cell (iPSC) line was generated from dermal fibroblasts of a 21-fetal-week-old female patient with NPA that has a heterozygous mutation of a p.L302P variant (c.905 T > C) using non-integrating Sendai virus technique. This iPSC line offers a useful resource to study the disease pathophysiology and as a cell-based model for drug development to treat NPA.

Niemann-Pick disease A or B in four pediatric patients and SMPD1 mutation carrier frequency in the Mexican population

Introduction and ObjectivesNiemann-Pick disease type A (NPD-A) and B (NPD-B) are lysosomal storage diseases with a birth prevalence of 0.4–0.6/100,000. They are caused by a deficiency in acid sphingomyelinase, an enzyme encoded by SMPD1. We analyzed the phenotype and genotype of four unrelated Mexican patients, one with NPD-A and three with NPD-B. Patients and methodsFour female patients between 1 and 7 years of age were diagnosed with NPD-A or NPD-B by hepatosplenomegaly, among other clinical characteristics, and by determining the level of acid sphingomyelinase enzymatic activity and sequencing of the SMPD1 gene. Additionally, a 775bp amplicon of SMPD1 (from 11:6393835_6394609, including exons 5 and 6) was analyzed by capillary sequencing in a control group of 50 unrelated healthy Mexican Mestizos. ResultsAn infrequent variant (c.1343A>G p.Tyr448Cys) was observed in two patients. One is the first NPD-A homozygous patient reported with this variant and the other a compound heterozygous NPD-B patient with the c.1829_1831delGCC p.Arg610del variant. Another compound heterozygous patient had the c.1547A>G p.His516Arg variant (not previously described in affected individuals) along with the c.1805G>A p.Arg602His variant. A new c.1263+8C>T pathogenic variant was encountered in a homozygous state in a NPD-B patient. Among the healthy control individuals there was a heterozygous carrier for the c.1550A>T (rs142787001) pathogenic variant, but none with the known pathogenic variants in the 11:6393835_6394609 region of SMPD1. ConclusionsThe present study provides further NPD-A or B phenotype-genotype correlations. We detected a heterozygous carrier with a pathogenic variant in 1/50 healthy Mexican mestizos.

Corrigendum to: “Characterization of Sphingomyelin Phosphodiesterase Expression in Bumblebee (Bombus lantschouensis)”

Corrigendum to: “Characterization of Sphingomyelin Phosphodiesterase Expression in Bumblebee (Bombus lantschouensis)”

ITRAQ-based quantitative proteomic analysis of mycelium in different predation periods in nematode trapping fungus Duddingtonia flagrans

Duddingtonia flagrans, as a representative species of nematode-trapping fungi, has a strong environmental tolerance and nematode-trapping ability and is thought of as the most promising candidate for use as a biological agent. To clarify the proteomic differences during different predation periods and to explore the molecular background of the nematode-trapping mechanism, we carried out an iTRAQ (isobaric tags for relative and absolute quantitation)-based quantitative proteomic analysis for Duddingtonia flagrans during three predatory stages (0 h, 12 h, and 48 h). A total of 4244 proteins were detected; 474 of these showed differential protein abundance from 0 h to 12 h, while 119 showed differential protein abundance from 12 h to 48 h. The 474 proteins from 0 h to 12 h were primarily associated with catalytic activity, molecular binding function, transport activity, biological regulation, stress response, biolocation and carbon utilization, while the 119 proteins from 12 h to 48 h were involved in substance and energy metabolism. Further bioinformatics analysis showed that these proteins could be mapped to various pathways, eight of which were significantly enriched after mapping to KEGG pathways from 0 h to 12 h, and substance and energy metabolism were enriched from 12 h to 48 h. Interestingly, many of these differentially expressed proteins were involved in the significantly enriched pathways of ubiquitin-mediated proteolysis, endoplasmic reticulum protein processing, sphingolipid metabolism, adhesion processes, MAPK signaling pathway, AMPK signaling pathway, energy and carbon metabolism, peroxidase, and oxidative phosphorylation, including acid phosphatase, neutral ceramidase, sphingomyelin phosphodiesterase, tyrosinase, and serine protease. These findings not only deepen our understanding of the proteome during different predation periods in Duddingtonia flagrans but also provide a basis for screening and identification of predation-related proteins to reveal the biological processes of the fungus and its action on nematodes, thereby helping to elucidate the nematode-trapping mechanism of D. flagrans.

Generation of an induced pluripotent stem cell line (TRNDi004-I) from a Niemann-Pick disease type B patient carrying a heterozygous mutation of p.L43_A44delLA in the SMPD1 gene

Niemann-Pick disease type B (NPB) is a rare autosomal recessive lysosomal storage disease caused by mutations in the SMPD1 gene, which encodes for acid sphingomyelinase. A human induced pluripotent stem cell (iPSC) line was generated from dermal fibroblasts of a 1-year old male patient with NPB that has a heterozygous mutation of a p.L43_A44delLA of SMPD1 using non-integrating Sendai virus technique. This iPSC line offers a useful resource to study the disease pathophysiology and as a cell-based model for drug development to treat NPB.

Ceramide‐Mediated Enhancement of Inflammatory Exosome Secretion from Podocytes during Hyperhomocysteinemia

Exosome secretion has been shown increased during podocyte injury and associated glomerular diseases, and this increased exosome secretion may be important in mediating release of inflammasome products to activate glomerular inflammatory response leading to chronic glomerular disease. Given the crucial role of ceramide in the control of exosome biogenesis and release, the present study used a podocyte‐specific sphingomyelin phosphodiesterase 1 (Smpd1) transgenic mouse strain (Smpd1trg/Podocre mice) to test whether ceramide production enhanced by Smpd1 gene overexpression promotes inflammatory exosome release from podocyte leading to glomerular inflammation during Hcys. We demonstrated that in Smpd1trg/Podocre mice, hHcy (induced by the FF diet) produced significant podocyte inflammasome activation accompanied by large increases in urinary podocyte‐derived exosomes. By immunohistochemical detection, we found that the glomerular inflammatory responses was more remarkably activated by hHcy in Smpd1trg/Podocre mice than their littermates, as shown by increased staining of lymphocyte and T‐cell markers such as CD45 and CD43. Under electronic microscopy, we observed that hHcy induced more severe podocyte injury and exosome release around these podocytes in Smpd1trg/Podocre mice than their littermates. Using confocal microscopy, about 2.8 folds increase colocalization of multivesicle body marker (MVB) Vps16 and NLRP3 inflammasome product IL‐1β, but about 0.4 folds decrease interaction of Vps16 with lysosome (Lamp‐1) (a process determining MVB fate and exosome release) were found in the glomeruli of Smpd1trg/Podocre mice with hHcy compared to their littermates. In cultured podocytes, the nanoparticle tracking analysis confirmed that L‐Hcy treatment significantly increased microparticle release into supernatants especially from 50nm to 150nm and they were characterized as podocytes‐derived IL‐1β‐containing exosomes as shown by detection of synaptopodin, CD63 and IL‐1β via Western blot analysis. This L‐Hcy‐induced podocyte release of IL‐1β exosomes was mimicked by AC inhibitor carmofur, but attenuated by AC inducer, genistein. It was also found that L‐Hcy‐induced decreases in Vps16 and Lamp‐1 interaction could be simulated by carmofur and inhibited by genistein. All these results together suggest that increased ceramide in podocytes enhances release of inflammatory exosomes during hHcy by reduction of lysosome‐MVBs interaction and prolongation of MVBs to facilitate exosome secretion.Support or Funding Informationsupported by NIH grant DK54927, DK120491 and HL057244This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Lysosome Dysfunction and Medial Calcification in the Arterial Wall of Smooth Muscle Cell‐Specific Smpd1 Transgenic Mice: A Ceramide‐Mediated Vasculopathy

It has been reported that multivesicular body (MVB) trafficking and release of exosomes are a hallmark of vascular calcification. Since ceramide is a crucial regulator of lysosome function, the present study was performed to test whether lysosomal acid sphingomyelinase (its mouse gene code is Smpd1)‐derived ceramide contributes to the exosome secretion from smooth muscle cells (SMCs) and consequently lead to arterial calcification. In Smpd1trg/SMcre mice with SMC‐specific overexpression of Smpd1 gene, a high dose of Vit D (500,000 IU/kg/day) induced much more aortic and coronary arterial medial calcification compared to their littermates (Smpd1fl/fl/WT and WT/WT mice), as detected by Alizarin Red S and Von Kossa staining. It was also found that there was more significantly increased expression of RUNX2 and osteopontin in the coronary and aortic media of Smpd1trg/SMcre mice than their littermates, indicating a SMC phenotypic transition to osteogenic in these SMC‐specific Smpd1 transgenic mice. When these mice received treatment with amitriptyline, an Asm inhibitor, the calcification and phenotypic switch in both coronary and aortic medial SMCs were reversed. Furthermore, Smpd1trg/SMcre mice were found to have increased annexin 2 (AnX2) and alkaline phosphatase (ALP) levels (exosome markers) in the arterial wall, which was accompanied by reduced co‐localization of lysosome marker (LAMP‐1) with MVB marker (VPS16), a parameter for lysosome‐MVB interaction. All these changes related to lysosome function and exosome release from SMCs in Smpd1trg/SMcre mice were substantially attenuated by amitriptyline treatment. These data indicate that lysosomal ceramide plays a critical role in phenotype change and exosome release in SMCs, which may contribute to the control of mineral metabolism or deposition in the arterial wall.Support or Funding InformationSupported by NIH grants HL057244, HL075316 and DK120491This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Acid Sphingomyelinase Inhibition Attenuates Cell Death in Mechanically Ventilated Newborn Rat Lung.

Premature infants subjected to mechanical ventilation (MV) are prone to lung injury that may result in bronchopulmonary dysplasia. MV causes epithelial cell death and halts alveolar development. The exact mechanism of MV-induced epithelial cell death is unknown. To determine the contribution of autophagy to MV-induced epithelial cell death in newborn rat lungs. Newborn rat lungs and fetal rat lung epithelial (FRLE) cells were exposed to MV and cyclic stretch, respectively, and were then analyzed by immunoblotting and mass spectrometry for autophagy, apoptosis, and bioactive sphingolipids. Both MV and stretch first induce autophagy (ATG 5-12 [autophagy related 5-12] and LC3B-II [microtubule-associated proteins 1A/1B light chain 3B-II] formation) followed by extrinsic apoptosis (cleaved CASP8/3 [caspase-8/3] and PARP [poly(ADP-ribose) polymerase] formation). Stretch-induced apoptosis was attenuated by inhibiting autophagy. Coimmunoprecipitation revealed that stretch promoted an interaction between LC3B and the FAS (first apoptosis signal) cell death receptor in FRLE cells. Ceramide levels, in particular C16 ceramide, were rapidly elevated in response to ventilation and stretch, and C16 ceramide treatment of FRLE cells induced autophagy and apoptosis in a temporal pattern similar to that seen with MV and stretch. SMPD1 (sphingomyelin phosphodiesterase 1) was activated by ventilation and stretch, and its inhibition prevented ceramide production, LC3B-II formation, LC3B/first apoptosis signal interaction, caspase-3 activation, and, ultimately, FLRE cell death. SMPD1 inhibition also attenuated ventilation-induced autophagy and apoptosis in newborn rats. Ventilation-induced ceramides promote autophagy-mediated cell death, and identifies SMPD1 as a potential therapeutic target for the treatment of ventilation-induced lung injury in newborns.

Chronic visceral acid sphingomyelinase deficiency (Niemann-Pick disease type B) in 16 Polish patients: long-term follow-up

BackgroundAcid sphingomyelinase deficiency (ASMD), due to mutations in the sphingomyelin phosphodiesterase 1 (SMPD1) gene, is divided into infantile neurovisceral ASMD (Niemann-Pick type A), chronic neurovisceral ASMD (intermediate form, Niemann-Pick type A/B) and chronic visceral ASMD (Niemann-Pick type B).We conducted a long-term observational, single-center study including 16 patients with chronic visceral ASMD.Results12 patients were diagnosed in childhood and 4 others in adulthood, the oldest at the age of 50. The mean time of follow-up was approximately 10 years (range: 6 months – 36 years). Splenomegaly was noted in all patients at diagnosis. Hepatomegaly was observed in 88% of patients. Moderately elevated (several-fold above the upper limit of normal values) serum transaminases were noted in 38% of patients. Cherry-red spots were found in five Gypsy children from one family and also in one adult Polish patient, a heterozygote for p.delR610 mutation. Dyslipidemia was noted in 50% of patients. Interstitial lung disease was diagnosed in 44% of patients. Plasmatic lysosphingomyelin (SPC) was elevated in all the patients except one with p.V36A homozygosity and a very mild phenotype also presenting with elevated plasmatic SPC-509 but normal chitotriosidase activity. The most common variant of SMPD1 gene was p.G166R. We found a previously unreported variant in exon 2 (c.491G > T, p.G164 V) in one patient.ConclusionsChronic visceral ASMD could constitute a slowly progressing disease with a relatively good outcome. The combined measurement of lysosphingomyelin (SPC) and lysospingomyelin-509 (SPC-509) is an essential method for the assessment of ASMD course.

Role of SMPD3 during Bone Fracture Healing and Regulation of Its Expression.

Sphingomyelin phosphodiesterase 3 (SMPD3), a lipid-metabolizing enzyme present in bone and cartilage, has important roles in the developing skeleton. We previously showed that SMPD3 deficiency results in delayed extracellular matrix (ECM) mineralization and severe skeletal deformities in an inducible knockout mouse model, Smpd3flox/flox ; Osx-Cre mice, in which Smpd3 was ablated in Osx-expressing chondrocytes and osteoblasts during early skeletogenesis. However, as shown in the current study, ablation of Smpd3 postnatally in 3-month-old Smpd3flox/flox ; Osx-Cre mice resulted in only a mild bone mineralization defect. Interestingly, though, there was a marked increase of unmineralized osteoid in the fractured tibiae of 3-month-old Smpd3flox/flox ; Osx-Cre mice. As was the case in the embryonic bones, we also observed impaired chondrocyte apoptosis at the fracture sites of Smpd3flox/flox ; Osx-Cre mice. We further examined how Smpd3 expression is regulated in ATDC5 chondrogenic cells by two major regulators of chondrogenesis, bone morphogenetic protein 2 (BMP-2) and PTHrP. Our data show that BMP-2 positively regulates Smpd3 expression via p38 mitogen-activated protein kinase. Taken together, our findings show that SMPD3 plays a significant role in ECM mineralization and chondrocyte apoptosis during fracture healing. Furthermore, our gene expression analyses suggest that BMP-2 and PTHrP exert opposing effects on the regulation of Smpd3 expression in chondrocytes.