RESUMO
BACKGROUND: Sphingomyelin (SM) and cholesterol are 2 key lipid partners on cell membranes and on lipoproteins. Many studies have indicated the influence of cholesterol on SM metabolism. This study examined the influence of SM biosynthesis on cholesterol metabolism. METHODS: Inducible global Sms1 KO (knockout)/global Sms2 KO mice were prepared to evaluate the effect of whole-body SM biosynthesis deficiency on lipoprotein metabolism. Tissue cholesterol, SM, ceramide, and glucosylceramide levels were measured. Triglyceride production rate and LDL (low-density lipoprotein) catabolism were measured. Lipid rafts were isolated and LDL receptor mass and function were evaluated. Also, the effects of exogenous sphingolipids on hepatocytes were investigated. RESULTS: We found that total SMS (SM synthase) depletion significantly reduced plasma SM levels. Also, the total deficiency significantly induced plasma cholesterol, apoB (apolipoprotein B), and apoE (apolipoprotein E) levels. Importantly, total SMS deficiency, but not SMS2 deficiency, dramatically decreased LDL receptors in the liver and attenuated LDL uptake through the receptor. Further, we found that total SMS deficiency greatly reduced LDL receptors in the lipid rafts, which contained significantly lower SM and significantly higher glucosylceramide, as well as cholesterol. Furthermore, we treated primary hepatocytes and Huh7 cells (a human hepatoma cell line) with SM, ceramide, or glucosylceramide, and we found that only SM could upregulate LDL receptor levels in a dose-dependent fashion. CONCLUSIONS: Whole-body SM biosynthesis plays an important role in LDL cholesterol catabolism. The total SMS deficiency, but not SMS2 deficiency, reduces LDL uptake and causes LDL cholesterol accumulation in the circulation. Given the fact that serum SM level is a risk factor for cardiovascular diseases, inhibiting SMS2 but not SMS1 should be the desirable approach.
Assuntos
Glucosilceramidas , Esfingomielinas , Camundongos , Humanos , Animais , LDL-Colesterol , Ceramidas/metabolismo , Colesterol/metabolismo , Receptores de LDL , Apolipoproteínas , Transferases (Outros Grupos de Fosfato Substituídos)/metabolismoRESUMO
The 17q21 asthma susceptibility locus includes asthma risk alleles associated with decreased sphingolipid synthesis, likely resulting from increased expression of ORMDL3. ORMDL3 inhibits serine-palmitoyl transferase (SPT), the rate-limiting enzyme of de novo sphingolipid synthesis. There is evidence that decreased sphingolipid synthesis is critical to asthma pathogenesis. Children with asthma and 17q21 asthma risk alleles display decreased sphingolipid synthesis in blood cells. Reduced SPT activity results in airway hyperreactivity, a hallmark feature of asthma. 17q21 asthma risk alleles are also linked to childhood infections with human rhinovirus (RV). This study evaluates the interaction of RV with the de novo sphingolipid synthesis pathway, and the alterative effects of concurrent SPT inhibition in SPT-deficient mice and human airway epithelial cells. In mice, RV infection shifted lung sphingolipid synthesis gene expression to a pattern that resembles genetic SPT deficiency, including decreased expression of Sptssa, a small SPT subunit. This pattern was pronounced in lung epithelial cellular adhesion molecule (EpCAM+) cells and reproduced in human bronchial epithelial cells. RV did not affect Sptssa expression in lung CD45+ immune cells. RV increased sphingolipids unique to the de novo synthesis pathway in mouse lung and human airway epithelial cells. Interestingly, these de novo sphingolipid species were reduced in the blood of RV-infected wild-type mice. RV exacerbated SPT deficiency-associated airway hyperreactivity. Airway inflammation was similar in RV-infected wild-type and SPT-deficient mice. This study reveals the effects of RV infection on the de novo sphingolipid synthesis pathway, elucidating a potential mechanistic link between 17q21 asthma risk alleles and rhinoviral infection.
Assuntos
Proteínas de Membrana , Rhinovirus , Animais , Criança , Humanos , Pulmão/metabolismo , Proteínas de Membrana/metabolismo , Camundongos , Serina C-Palmitoiltransferase/genética , Serina C-Palmitoiltransferase/metabolismo , Esfingolipídeos/metabolismoRESUMO
Multiple myeloma (MM) is a bone marrow cancer of resident plasma cells that affects 125,000 patients in the U.S. with about 30,000 new cases per year. Its signature is the clonal proliferation of a single plasma cell that secretes a patient specific monoclonal immunoglobulin (M-Ig). Targeting the M-Ig in patient serum could allow sensitive and noninvasive identification of minimal residual disease in multiple myeloma. Aptamers, which are single-stranded oligonucleotides with affinity and specificity to a target molecule, have recently been introduced as affinity reagents for recognition of MM M-Igs. Here we exploit microfluidic SELEX technology to enable rapid and efficient generation of aptamers against M-Ig proteins from MM patients. We first characterize the technology by isolating aptamers with affinity towards the monoclonal antibody rituximab as a model M-Ig and then apply the technology to isolating aptamers specifically targeting M-Igs obtained from serum samples of MM patients. We demonstrate that high-affinity DNA aptamers (KD < 50 nM) for M-Ig proteins from a patient sample could be isolated via microfluidic SELEX within approximately 12 h and using less than 100 micrograms of patient M-Ig. Such aptamers can potentially be used in personalized monitoring of minimal residual disease in MM patients.
Assuntos
Mieloma Múltiplo , Humanos , Neoplasia Residual , Microfluídica , Anticorpos MonoclonaisRESUMO
Asthma is the most prevalent chronic respiratory disease worldwide and the leading serious chronic illness in children. Clinical characteristics are wheezing, reversible airway obstruction, airway inflammation, and airway hyperreactivity. Asthma susceptibility is influenced by genes and environment. 17q12-21 is the most significant genetic asthma susceptibility locus and single nucleotide polymorphisms (SNPs) within that high-risk locus are linked to increased expression of the Ormdl sphingolipid biosynthesis regulator (ORMDL) 3. ORMDL3 is an endoplasmic reticulum protein that stabilizes the serine palmitoyl transferase (SPT) complex that regulates sphingolipid de novo synthesis. Sphingolipids essential for formation and integrity of cellular membranes and bioactive molecules that regulate key cellular processes can be synthesized de novo and through recycling pathways. Their metabolism is tightly regulated through feedback regulation. ORMDL3 inhibits de novo synthesis when it engages subunit 1 of the SPT complex. This chapter focuses on the effect of decreased sphingolipid synthesis on asthma features and summarizes studies in mouse models and in children with and without asthma.
Assuntos
Asma , Esfingolipídeos , Animais , Asma/genética , Asma/metabolismo , Suscetibilidade a Doenças , Proteínas de Membrana/metabolismo , Camundongos , Polimorfismo de Nucleotídeo Único , Serina C-Palmitoiltransferase/genética , Serina C-Palmitoiltransferase/metabolismo , Esfingolipídeos/metabolismoRESUMO
Impaired sphingolipid synthesis is linked genetically to childhood asthma and functionally to airway hyperreactivity (AHR). The objective was to investigate whether sphingolipid synthesis could be a target for asthma therapeutics. The effects of GlyH-101 and fenretinide via modulation of de novo sphingolipid synthesis on AHR was evaluated in mice deficient in SPT (serine palmitoyl-CoA transferase), the rate-limiting enzyme of sphingolipid synthesis. The drugs were also used directly in human airway smooth-muscle and epithelial cells to evaluate changes in de novo sphingolipid metabolites and calcium release. GlyH-101 and fenretinide increased sphinganine and dihydroceramides (de novo sphingolipid metabolites) in lung epithelial and airway smooth-muscle cells, decreased the intracellular calcium concentration in airway smooth-muscle cells, and decreased agonist-induced contraction in proximal and peripheral airways. GlyH-101 also decreased AHR in SPT-deficient mice in vivo. This study identifies the manipulation of sphingolipid synthesis as a novel metabolic therapeutic strategy to alleviate AHR.
Assuntos
Hiper-Reatividade Brônquica/metabolismo , Esfingolipídeos/biossíntese , Células Epiteliais Alveolares/efeitos dos fármacos , Células Epiteliais Alveolares/metabolismo , Bradicinina/farmacologia , Cálcio/metabolismo , Sinalização do Cálcio/efeitos dos fármacos , Fenretinida/farmacologia , Glicina/análogos & derivados , Glicina/farmacologia , Humanos , Hidrazinas/farmacologia , Metaboloma/efeitos dos fármacos , Cloreto de Metacolina/farmacologia , Contração Muscular/efeitos dos fármacos , Serina C-Palmitoiltransferase/metabolismoRESUMO
Serine palmitoyltransferase is the key enzyme in sphingolipid biosynthesis. Mice lacking serine palmitoyltransferase are embryonic lethal. We prepared liver-specific mice deficient in the serine palmitoyltransferase long chain base subunit 2 gene using an albumin-cyclization recombination approach and found that the deficient mice have severe jaundice. Moreover, the deficiency impairs hepatocyte polarity, attenuates liver regeneration after hepatectomy, and promotes tumorigenesis. Importantly, we show that the deficiency significantly reduces sphingomyelin but not other sphingolipids in hepatocyte plasma membrane; greatly reduces cadherin, the major protein in adherens junctions, on the membrane; and greatly induces cadherin phosphorylation, an indication of its degradation. The deficiency affects cellular distribution of ß-catenin, the central component of the canonical Wnt pathway. Furthermore, such a defect can be partially corrected by sphingomyelin supplementation in vivo and in vitro. CONCLUSION: The plasma membrane sphingomyelin level is one of the key factors in regulating hepatocyte polarity and tumorigenesis. (Hepatology 2016;64:2089-2102).
Assuntos
Junções Aderentes/fisiologia , Carcinogênese , Fígado/enzimologia , Serina C-Palmitoiltransferase/deficiência , Fatores Etários , Animais , CamundongosRESUMO
PURPOSE OF REVIEW: Genome-wide association studies identified ORMDL3, a protein of the endoplasmic reticulum, as a significant asthma risk factor. ORMDL3 is one of three ORMDL proteins that integrate multiple signals to maintain sphingolipid homeostasis. Studies that investigated potential mechanisms for how increased ORMDL3 might affect asthma are summarized. RECENT FINDINGS: Investigations focused on decreased sphingolipid synthesis and on the unfolded protein response because ORMDL3 had been implicated in both.Airway reactivity is increased in a genetic model with decreased de-novo sphingolipid synthesis and in wild-type mice treated with myriocin, a sphingolipid synthesis inhibitor. Inflammation, mucus production and airway smooth muscle hypertrophy are absent. ORMDL3 was not evaluated directly but results suggest that decreased sphingolipid synthesis is sufficient to induce airway hyperreactivity (AHR).Direct effects of ORMDL3 were investigated in allergic asthma models. Sensitization with ovalbumin, house dust mites and Alternaria alternata increase ORMDL3 mRNA. Universal overexpression of ORMDL3 decreases serum sphingolipids, increases inflammatory markers, airway remodeling and AHR in response to allergic stimuli. Addition of myriocin during sensitization drastically exacerbates house dust mites-induced AHR.ORMDL3 knockout mice are protected from developing A. alternata-induced AHR. The effect is specific to Alternaria and limited to smooth muscle contraction, as inflammation persists. ORMDL3 might have a critical role for smooth muscle contraction.Little is known about how the different ORMDL3 single nucleotide polymorphisms affect human blood and tissue sphingolipid profiles. One group measured total sphingoid levels and found no association with ORMDL3 single nucleotide polymorphisms in a general population. Others evaluated sphingolipid profiles in 7-8-year old children with mild asthma and found significantly higher C18 and C20 ceramides in those with persistence of asthma symptoms 3 years later, suggesting that sphingolipid profiles might predict asthma persistence. SUMMARY: Possible mechanisms how ORMDL3 affects asthma include inhibition of sphingolipid synthesis, synergistic effects with known allergens and a combination of both.
Assuntos
Asma/metabolismo , Proteínas de Membrana/fisiologia , Esfingolipídeos/biossíntese , Alérgenos/metabolismo , Animais , Humanos , CamundongosRESUMO
BACKGROUND: Airway instrumentation can evoke upper airway reflexes including bronchoconstriction and cough which can cause serious complications including airway trauma, laryngospasm or bronchospasm which may in turn lead to difficulty with ventilation and hypoxemia. These airway events are mediated in part by irritant-induced neuronal modulation of airway tone and cough responses. We investigated whether the commonly used anesthetic agents dexmedetomidine, lidocaine or remifentanil attenuated neuronal and airway smooth muscle responses in the upper airways of guinea pigs. METHODS: The ability of dexmedetomidine, lidocaine or remifentanil to attenuate direct cholinergic nerve stimulation, C-fiber stimulation or direct smooth muscle contraction were studied using isolated tracheal rings from male guinea pigs under four paradigms; (1) the magnitude of contractile force elicited by cholinergic electrical field stimulation (EFS); (2) the amount of acetylcholine released during cholinergic EFS; (3) the direct airway smooth muscle relaxation of a sustained acetylcholine-induced contraction and (4) the magnitude of C-fiber mediated contraction. RESULTS: Dexmedetomidine (1-100 µM) and lidocaine (1 mM) attenuated cholinergic 30Hz EFS-induced tracheal ring contraction while remifentanil (10 µM) had no effect. Dexmedetomidine at 10 µM (p = 0.0047) and 100 µM (p = 0.01) reduced cholinergic EFS-induced acetylcholine release while lidocaine (10 µM-1 mM) and remifentanil (0.1-10 µM) did not. Tracheal ring muscle force induced by the exogenous addition of the contractile agonist acetylcholine or by a prototypical C-fiber analogue of capsaicin were also attenuated by 100 µM dexmedetomidine (p = 0.0061 and p = 0.01, respectively). The actual tracheal tissue concentrations of dexmedetomidine achieved (0.54-26 nM) following buffer application of 1-100 µM of dexmedetomidine were within the range of clinically achieved plasma concentrations (12 nM). CONCLUSIONS: The α2 adrenoceptor agonist dexmedetomidine reduced cholinergic EFS-induced contractions and acetylcholine release consistent with the presence of inhibitory α2 adrenoceptors on the prejunctional side of the postganglionic cholinergic nerve-smooth muscle junction. Dexmedetomidine also attenuated both exogenous acetylcholine-induced contraction and C-fiber mediated contraction, suggesting a direct airway smooth muscle effect and an underlying mechanism for cough suppression, respectively.
Assuntos
Acetilcolina/metabolismo , Neurônios Colinérgicos/efeitos dos fármacos , Neurônios Colinérgicos/metabolismo , Dexmedetomidina/farmacologia , Traqueia/inervação , Anestésicos/farmacologia , Animais , Relação Dose-Resposta a Droga , Estimulação Elétrica , Cobaias , Técnicas In Vitro , Lidocaína/farmacologia , Masculino , Contração Muscular/efeitos dos fármacos , Contração Muscular/fisiologia , Músculo Liso/efeitos dos fármacos , Músculo Liso/fisiologia , Piperidinas/farmacologia , Remifentanil , Traqueia/efeitos dos fármacosRESUMO
INTRODUCTION: γ-amino butyric acid (GABA) is not only the major inhibitory neurotransmitter in the central nervous system (CNS), but it also plays an important role in the lung, mediating airway smooth muscle relaxation and mucus production. As kinases such as protein kinase A (PKA) are known to regulate the release and reuptake of GABA in the CNS by GABA transporters, we hypothesized that ß-agonists would affect GABA release from airway epithelial cells through activation of PKA. METHODS: C57/BL6 mice received a pretreatment of a ß-agonist or vehicle (PBS), followed by methacholine or PBS. Bronchoalveolar lavage (BAL) was collected and the amount of GABA was quantified using HPLC mass spectrometry. For in vitro studies, cultured BEAS-2B human airway epithelial cells were loaded with (3)H-GABA. (3)H-GABA released was measured during activation and inhibition of PKA and tyrosine kinase signaling pathways. RESULTS: ß-agonist pretreatment prior to methacholine challenge attenuated in vivo GABA release in mouse BAL and (3)H-GABA release from depolarized BEAS-2B cells. GABA release was also decreased in BEAS-2B cells by increases in cAMP but not by Epac or tyrosine kinase activation. CONCLUSION: ß-agonists decrease GABA release from airway epithelium through the activation of cAMP and PKA. This has important therapeutic implications as ß-agonists and GABA are important mediators of both mucus production and airway smooth muscle tone.
Assuntos
Agonistas Adrenérgicos beta/farmacologia , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Células Epiteliais/metabolismo , Mucosa Respiratória/metabolismo , Terbutalina/farmacologia , Ácido gama-Aminobutírico/metabolismo , Antagonistas Adrenérgicos beta/farmacologia , Animais , Líquido da Lavagem Broncoalveolar/química , Linhagem Celular , Colforsina/farmacologia , AMP Cíclico/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/antagonistas & inibidores , Ativadores de Enzimas/farmacologia , Glutamato Descarboxilase/genética , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Humanos , Masculino , Cloreto de Metacolina/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Miócitos de Músculo Liso/metabolismo , Fator de Crescimento Derivado de Plaquetas/farmacologia , Propranolol/farmacologia , RNA Mensageiro/metabolismo , Receptores Proteína Tirosina Quinases/antagonistas & inibidores , Mucosa Respiratória/citologia , Rifabutina/análogos & derivados , Rifabutina/farmacologia , Transdução de Sinais/efeitos dos fármacos , Ácido gama-Aminobutírico/análiseRESUMO
Genetic variations in the 17q21 locus are strongly associated with childhood nonallergic asthma. Expression of the 17q21 genes, orosomucoid like 3 (ORMDL3) and gasdermin B (GSMDB), is affected by these disease-associated variants. However, until recently, no functional connection of the protein products coded by these genes with asthma was known. Lately, it has been identified that ORMDL3 function has been related to various cellular processes that could be relevant for the pathogenesis of asthma. This includes dysregulation of the unfolded protein response (UPR) associated with airway remodeling and also an effect of ORMDL3-dysregulated sphingolipid synthesis on bronchial hyperreactivity. These findings are crucial for a better understanding of the mechanism of childhood asthma and may lead to asthma therapeutics that target pathways previously not thought to be related to this common pediatric respiratory disease. Furthermore, this may validate the unbiased genome-wide association study (GWAS) approach for complex diseases such as asthma, to better define pathomechanisms and drug targets.
Assuntos
Asma/genética , Cromossomos Humanos Par 17 , Variação Genética , Proteínas de Membrana/genética , Fatores Etários , Remodelação das Vias Aéreas , Antiasmáticos/uso terapêutico , Asma/tratamento farmacológico , Asma/metabolismo , Asma/fisiopatologia , Interação Gene-Ambiente , Predisposição Genética para Doença , Humanos , Pulmão/metabolismo , Pulmão/fisiopatologia , Proteínas de Membrana/metabolismo , Fenótipo , Prognóstico , Fatores de RiscoRESUMO
Vacuolar protein sorting 35 (VPS35), the core component of the retromer complex which regulates endosomal trafficking, is genetically linked with Parkinson's disease (PD). Impaired vision is a common non-motor manifestation of PD. Here, we show mouse retinas with VPS35-deficient rods exhibit synapse loss and visual deficit, followed by progressive degeneration concomitant with the emergence of Lewy body-like inclusions and phospho-α-synuclein (P-αSyn) aggregation. Ultrastructural analyses reveal VPS35-deficient rods accumulate aggregates in late endosomes, deposited as lipofuscins bound to P-αSyn. Mechanistically, we uncover a protein network of VPS35 and its interaction with HSC70. VPS35 deficiency promotes sequestration of HSC70 and P-αSyn aggregation in late endosomes. Microglia which engulf lipofuscins and P-αSyn aggregates are activated, displaying autofluorescence, observed as bright dots in fundus imaging of live animals, coinciding with pathology onset and progression. The Rod∆Vps35 mouse line is a valuable tool for further mechanistic investigation of αSyn lesions and retinal degenerative diseases.
Assuntos
Degeneração Retiniana , Proteínas de Transporte Vesicular , alfa-Sinucleína , Animais , alfa-Sinucleína/metabolismo , alfa-Sinucleína/genética , Proteínas de Transporte Vesicular/metabolismo , Proteínas de Transporte Vesicular/genética , Camundongos , Degeneração Retiniana/genética , Degeneração Retiniana/metabolismo , Degeneração Retiniana/patologia , Células Fotorreceptoras Retinianas Bastonetes/metabolismo , Células Fotorreceptoras Retinianas Bastonetes/patologia , Endossomos/metabolismo , Microglia/metabolismo , Microglia/patologia , Doença de Parkinson/genética , Doença de Parkinson/metabolismo , Doença de Parkinson/patologia , Retina/metabolismo , Retina/patologia , Camundongos Knockout , Modelos Animais de Doenças , Humanos , Sinapses/metabolismo , Sinapses/patologia , MasculinoRESUMO
Dysfunction of the cystic fibrosis transmembrane regulator (CFTR) leads to chronic inflammation and infection of the respiratory tract. The role of CFTR for cells of the pulmonary immune system is only partly understood. The present study analyzes the phenotype and immune stimulatory capacity of lung dendritic cells (DCs) from CFTR knockout (CF) mice. Total numbers of conventional DCs, plasmacytoid DCs, and CD103-positive DCs were lower in CF mice compared with wild-type (WT) control mice, as was the expression of major histocompatibility complex class II molecules (MHCII), CD40, and CD86. After pulmonary infection with respiratory syncytial virus, DC numbers increased in WT mice but not in CF mice, and the T cell-stimulatory capacity of CF DCs was impaired. The culture of CF lung DCs with bronchoalveolar lavage fluid (BALF) from WT mice increased the expression of MHCII, CD40, and CD86. The supplementation of CF BALF with sphingosine-1-phosphate (S1P), a mediator of immune cell migration and activation that is decreased in CF BALF, rescued the reduced expression of MHCII and CD40 in WT lung DCs and human blood DCs. These findings suggest that DCs are impaired in the CF lung, and that altered S1P affects lung DC function. These findings provide a novel link between defective CFTR and pulmonary innate immune dysfunction in CF.
Assuntos
Células Dendríticas/patologia , Pulmão/patologia , Lisofosfolipídeos/metabolismo , Esfingosina/análogos & derivados , Animais , Líquido da Lavagem Broncoalveolar , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Antígenos de Histocompatibilidade Classe II/metabolismo , Ativação Linfocitária , Camundongos , Camundongos Knockout , Esfingosina/metabolismoRESUMO
OBJECTIVE: Macrophage endothelial lipase (EL) is associated with increased atherosclerosis and inflammation. Because of their anti-inflammatory properties we hypothesized that n-3 fatty acids, in contrast to saturated fatty acids, would lower macrophages and arterial EL and inflammatory markers. METHODS AND RESULTS: Murine J774 and peritoneal macrophages were incubated with eicosapentaenoic acid or palmitic acid in the presence or absence of lipopolysaccaride (LPS). LPS increased EL mRNA and protein. Palmitic acid alone or with LPS dose-dependently increased EL mRNA and protein. In contrast, eicosapentaenoic acid dose-dependently abrogated effects of LPS or palmitic acid on increasing EL expression. EL expression closely linked to peroxisome proliferator activated receptor (PPAR)γ expression. Eicosapentaenoic acid blocked rosiglitazone (a PPARγ agonist)-mediated EL activation and GW9662 (a PPARγ antagonist)-blocked palmitic acid-mediated EL stimulation. Eicosapentaenoic acid alone or with LPS blunted LPS-mediated stimulation of macrophage proinflammatory interleukin-6, interleukin-12p40, and toll-like receptor-4 mRNA and increased anti-inflammatory interleukin-10 and mannose receptor mRNA. In vivo studies in low density lipoprotein receptor knockout mice showed that high saturated fat rich diets, but not n-3 diets, increased arterial EL, PPARγ, and proinflammatory cytokine mRNA. CONCLUSIONS: n-3 fatty acids, in contrast to saturated fatty acids, decrease EL in parallel with modulating pro- and anti-inflammatory markers, and these effects on EL link to PPARγ.
Assuntos
Aorta/metabolismo , Ácidos Graxos Ômega-3/farmacologia , Ácidos Graxos/farmacologia , Interleucina-6/metabolismo , Lipase/metabolismo , Macrófagos Peritoneais/metabolismo , PPAR gama/metabolismo , Animais , Aorta/efeitos dos fármacos , Biomarcadores/metabolismo , Linhagem Celular , Relação Dose-Resposta a Droga , Ácido Eicosapentaenoico/farmacologia , Técnicas In Vitro , Subunidade p40 da Interleucina-12/metabolismo , Lipopolissacarídeos/farmacologia , Macrófagos Peritoneais/efeitos dos fármacos , Masculino , Camundongos , Camundongos Knockout , Modelos Animais , Ácido Palmítico/farmacologia , Receptores de LDL/deficiência , Receptores de LDL/genética , Receptores de LDL/metabolismo , Receptor 4 Toll-Like/metabolismoAssuntos
Asma Induzida por Exercício/sangue , Sons Respiratórios/etiologia , Esfingolipídeos/sangue , Asma Induzida por Exercício/diagnóstico , Asma Induzida por Exercício/genética , Asma Induzida por Exercício/metabolismo , Biomarcadores/sangue , Criança , Seguimentos , Humanos , Modelos Logísticos , Espectrometria de Massas , Polimorfismo de Nucleotídeo Único , Sons Respiratórios/diagnóstico , Esfingolipídeos/metabolismoRESUMO
Background: Sphingomyelin (SM) and cholesterol are two key lipid partners on cell membranes and on lipoproteins. Many studies have indicated the influence of cholesterol on SM metabolism. This study examined the influence of SM biosynthesis on cholesterol metabolism. Methods: Inducible global Sms1 KO/global Sms2 KO mice were prepared to evaluate the effect of whole-body SM biosynthesis deficiency on lipoprotein metabolism. Tissue cholesterol, SM, ceramide, and glucosylceramide levels were measured. TG production rate and LDL catabolism were measured. Lipid rafts were isolated and LDL receptor mass and function were evaluated. Also, the effects of exogenous sphingolipids on hepatocytes were investigated. Results: We found that total SMS depletion significantly reduced plasma SM levels. Also, the total deficiency significantly induced plasma cholesterol, apoB, and apoE levels. Importantly, total SMS deficiency, but not SMS2 deficiency, dramatically decreased LDL receptors in the liver and attenuated LDL uptake through the receptor. Further, we found that total SMS deficiency greatly reduced LDL receptors in the lipid rafts which contained significantly lower SM and significantly higher glucosylceramide as well as cholesterol. Furthermore, we treated primary hepatocytes and Huh7 cells (a human hepatoma cell line) with SM, ceramide, or glucosylceramide, and we found that only SM could up-regulate LDL receptor levels in a dose-dependent fashion. Conclusions: Whole-body SM biosynthesis plays an important role in LDL-cholesterol catabolism. The total SMS deficiency, but not SMS2 deficiency, reduces LDL uptake and causes LDL-cholesterol accumulation in the circulation. Given the fact that serum SM level is a risk factor for cardiovascular diseases, inhibiting SMS2 but not SMS1 should be the desirable approach.
RESUMO
Aptameric receptors are important biosensor components, yet our ability to identify them depends on the target structures. We analyzed the contributions of individual functional groups on small molecules to binding within 27 target-aptamer pairs, identifying potential hindrances to receptor isolation-for example, negative cooperativity between sterically hindered functional groups. To increase the probability of aptamer isolation for important targets, such as leucine and voriconazole, for which multiple previous selection attempts failed, we designed tailored strategies focused on overcoming individual structural barriers to successful selections. This approach enables us to move beyond standardized protocols into functional group-guided searches, relying on sequences common to receptors for targets and their analogs to serve as anchors in regions of vast oligonucleotide spaces wherein useful reagents are likely to be found.
Assuntos
Antifúngicos , Aptâmeros de Nucleotídeos , Técnicas Biossensoriais , Leucina , Técnica de Seleção de Aptâmeros , Voriconazol , Aptâmeros de Nucleotídeos/química , Técnica de Seleção de Aptâmeros/métodos , Leucina/sangue , Voriconazol/análise , Antifúngicos/análiseRESUMO
Omega-3 polyunsaturated fatty acids (n-3 PUFAs) are essential nutrients that can affect inflammatory responses. While n-3 PUFAs are generally considered beneficial for cardiovascular disease and obesity, the effects on asthma, the most common inflammatory lung disease are unclear. While prenatal dietary n-3 PUFAs decrease the risk for childhood wheezing, postnatal dietary n-3 PUFAs can worsen allergic airway inflammation. Sphingolipid metabolism is also affected by dietary n-3 PUFAs. Decreased sphingolipid synthesis leads to airway hyperreactivity, besides inflammation, a cardinal feature of asthma, and common genetic asthma risk alleles lead to lower sphingolipid synthesis. We investigated the effect of dietary n-3 PUFAs on sphingolipid metabolism and airway reactivity. Comparing a fish-oil diet with a high n-3 PUFA content (FO) to an isocaloric coconut oil-enriched diet (CO), we found an n-3 PUFA-dependent effect on increased airway reactivity, that was not accompanied by inflammation. Lung and whole blood content of dihydroceramides, ceramides, sphingomyelins, and glucosylceramides were lower in mice fed the n-3 PUFA enriched diet consistent with lower sphingolipid synthesis. In contrast, phosphorylated long chain bases such as sphingosine 1-phosphate were increased. These findings suggest that dietary n-3 PUFAs affect pulmonary sphingolipid composition to favor innate airway hyperreactivity, independent of inflammation, and point to an important role of n-3 PUFAs in sphingolipid metabolism.
Assuntos
Asma , Ácidos Graxos Ômega-3 , Gravidez , Feminino , Animais , Camundongos , Ácidos Graxos Ômega-3/farmacologia , Ácidos Graxos , Dieta , Ácidos Graxos Insaturados/metabolismo , Inflamação/metabolismo , EsfingolipídeosRESUMO
This chapter focuses on the role of sphingolipids in the regulation of sterol-regulatory element binding protein (SREBP) dependent lipid synthesis and ATP-binding cassette protein ABCA1 and ABCG1 mediated lipid efflux, key regulators of cellular lipid homeostasis. Sphingolipid synthesis activates SREBPs independently of whether sphingolipid synthesis occurs through recycling or de novo pathways. SREBPs are major transcription factors of lipid metabolism that regulate more than 30 genes of cholesterol, fatty acid and phospholipid synthetic enzymes and they required NADPH cofactors. SREBPs are downstream of sphingolipid synthesis and do not regulate activity of sphingolipid synthetic enzymes. Cells that cannot synthesize sphingolipids fail to increase SREBP in response to lipid depletion. Similar mechanisms are found in D. melanogaster in which SREBP activity depends on expression of a ceramide synthase analog. SREBP is inhibited by its end products cholesterol and unsaturated fatty acids. Ceramide decreases SREBP by inhibiting sphingolipid synthesis. Molecular mechanisms of regulation are related to the effect of sphingolipids on intracellular trafficking but are overall not clear. Several groups have investigated the effect of sphingolipids in the regulation of cholesterol efflux receptors ABCA1 and ABCG1, major regulators of plasma high-density lipoprotein (HDL) concentration, an important anti-atherogenic lipoprotein. Data indicate an inverse relationship between sphingolipid de novo synthesis and cholesterol efflux. Inhibition of sphingolipid de-novo synthesis increases ABCA1 mediated cholesterol efflux independent of sphingomyelin. Potential mechanisms include the physical interaction of subunit 1 of serine-palmitoyl transferase (SPT), the rate limiting enzyme of de-novo sphingolipid synthesis, with ABCA1. ABCG1 mediated efflux, in contrast, is dependent on sphingomyelin mass. Animal studies support the findings made in cultured cells. Inhibition of sphingolipid de novo synthesis increases anti-atherogenic lipoproteins and decreases atherosclerosis in mouse models. Together, manipulation of sphingolipid synthetic pathways is a potentially promising therapeutic target for treatment of low-HDL dyslipidemia and atherosclerosis.
Assuntos
Homeostase/fisiologia , Metabolismo dos Lipídeos/fisiologia , Esfingolipídeos/biossíntese , Transportador 1 de Cassete de Ligação de ATP , Membro 1 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/metabolismo , Animais , Aterosclerose/metabolismo , Aterosclerose/prevenção & controle , Doenças Cardiovasculares/epidemiologia , Doenças Cardiovasculares/metabolismo , Colesterol/biossíntese , Colesterol/farmacologia , Modelos Animais de Doenças , Ácidos Graxos/biossíntese , Ácidos Graxos/farmacologia , Humanos , Lipoproteínas HDL/metabolismo , Camundongos , Modelos Biológicos , Fosfolipídeos/biossíntese , Risco , Serina C-Palmitoiltransferase/metabolismo , Esfingolipídeos/fisiologia , Esfingomielinas/metabolismo , Proteínas de Ligação a Elemento Regulador de Esterol/antagonistas & inibidores , Proteínas de Ligação a Elemento Regulador de Esterol/metabolismoRESUMO
Glucosylceramide (GluCer) was accumulated in sphingomyelin synthase 1 (SMS1) but not SMS2 deficient mouse tissues. In current study, we studied GluCer accumulation-mediated metabolic consequences. Livers from liver-specific Sms1/global Sms2 double-knockout (dKO) exhibited severe steatosis under a high-fat diet. Moreover, chow diet-fed ≥6-month-old dKO mice had liver impairment, inflammation, and fibrosis, compared with wild type and Sms2 KO mice. RNA sequencing showed 3- to 12-fold increases in various genes which are involved in lipogenesis, inflammation, and fibrosis. Further, we found that direct GluCer treatment (in vitro and in vivo) promoted hepatocyte to secrete more activated TGFß1, which stimulated more collagen 1α1 production in hepatic stellate cells. Additionally, GluCer promoted more ß-catenin translocation into the nucleus, thus promoting tumorigenesis. Importantly, human NASH patients had higher liver GluCer synthase and higher plasma GluCer. These findings implicated that GluCer accumulation is one of triggers promoting the development of NAFLD into NASH, then, fibrosis, and tumorigenesis.
RESUMO
Studies in mice using germfree animals as controls for microbial colonization have shown that the gut microbiome mediates diet-induced obesity. Such studies use diets rich in saturated fat, however, Western diets in the United States America are enriched in soybean oil, composed of unsaturated fatty acids, either linoleic or oleic acid. Here, we addressed whether the microbiome is a variable in fat metabolism in mice on a soybean oil diet. We used conventionally-raised, low-germ, and germfree mice fed for 10 weeks diets either high or low in high-linoleic-acid soybean oil as the sole source of fat. Conventional and germfree mice gained relative fat weight and all mice consumed more calories on the high fat vs. low fat soybean oil diet. Plasma fatty acid levels were generally dependent on diet, with microbial colonization status affecting iso-C18:0, C20:3n-6, C14:0, and C15:0 levels. Colonization status, but not diet, impacted levels of liver sphingolipids including ceramides, sphingomyelins, and sphinganine. Our results confirm that absorbed fatty acids are mainly a reflection of the diet and that microbial colonization influences liver sphingolipid pools regardless of diet.