Change in the activity of glucosylceramide synthase in human hepatoma cell line with hepatitis B virus infection in vitro / 临床肝胆病杂志

ObjectiveTo investigate the change in the activity of glucosylceramide synthase, the key enzyme in glycosphingolipid metabolism and synthesis, in Huh7 cells infected by hepatitis B virus (HBV) in vitro. MethodsBlood samples were collected from nine previously untreated patients with acute hepatitis B who attended Department of Infectious Diseases, The First Hospital of Lanzhou University, from June to August, 2019, and the blood samples collected from seven healthy individuals who underwent physical examination were established as control. Huh7 cells were inoculated with the high-copy HBV particles (＞9.9×107 IU/ml) in the serum of patients with HBV infection (infection group), and Huh7 cells co-cultured with the serum of healthy individuals were established as control group. The expression levels of HBsAg and HBV DNA in the cytoplasm of HBV-infected Huh7 cells were measured, and the correlation between GCS activity and virus was analyzed. A one-way analysis of variance was used for comparison of continuous data between multiple groups, and the least significant difference t-test was used for further comparison between two groups, and a Pearson correlation analysis was performed. ResultsCompared with the control group, the infection group had a significant reduction in the number of cells, an increase in cell volume, and cell membrane fragmentation. The infection group had a significant increase in the expression of HBsAg in cytoplasm at 4 hours, 8 hours, 2 days, and 5 days after infection (P＜0.05); the expression level of HBV DNA tended to increase significantly from 4 hours after infection to 8 hours, 2 days, and 5 days after infection (16.67±11.55 IU/ml vs 112.01±25.94 IU/ml/328.01±10350 IU/ml/101.60±49.84 IU/ml, P＜0.001), with the highest level at 2 days after infection. During HBV infection, the activity of GCS gradually increased with the increase in viral replication from 4 hours after infection (126.21±9.59 IU/ml) and reached a peak at 2 days after infection (226.53±36.27 IU/ml), with a significant difference between the infection group and the control group at 2 days after infection (226.53±36.27 IU/ml vs 136.50±1544 IU/ml, t=3.956, P=0.016 7). The activity of GCS was positively correlated with HBV DNA level (r=0.576 8, P=0047 1). ConclusionHuh7 cells are successfully infected with the high-copy HBV particles in the serum of patients with HBV infection, which mimics the characteristics of HBV infection in vitro to a certain degree. The activity of GCS may be associated with HBV infection, suggesting that glycosphingolipid synthesis and metabolism may be closely associated with HBV.

Development of a Label-Free LC-MS/MS-Based Glucosylceramide Synthase Assay and Its Application to Inhibitors Screening for Ceramide-Related Diseases

Ceramide metabolism is known to be an essential etiology for various diseases, such as atopic dermatitis and Gaucher disease. Glucosylceramide synthase (GCS) is a key enzyme for the synthesis of glucosylceramide (GlcCer), which is a main ceramide metabolism pathway in mammalian cells. In this article, we developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine GCS activity using synthetic non-natural sphingolipid C8-ceramide as a substrate. The reaction products, C8-GlcCer for GCS, could be separated on a C18 column by reverse-phase high-performance liquid chromatography (HPLC). Quantification was conducted using the multiple reaction monitoring (MRM) mode to monitor the precursor-to-product ion transitions of m/z 588.6 → 264.4 for C8-GlcCer at positive ionization mode. The calibration curve was established over the range of 0.625–160 ng/mL, and the correlation coefficient was larger than 0.999. This method was successfully applied to detect GCS in the human hepatocellular carcinoma cell line (HepG2 cells) and mouse peripheral blood mononuclear cells. We also evaluated the inhibition degree of a known GCS inhibitor 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) on GCS enzymatic activity and proved that this method could be successfully applied to GCS inhibitor screening of preventive and therapeutic drugs for ceramide metabolism diseases, such as atopic dermatitis and Gaucher disease.

Glucosylceramide synthase upregulates apoptosis-related gene bcl-2 ex-pression via MEK/ERK signaling pathway in leukemia multidrug-resis-tant cell line / 中国病理生理杂志

AIM: To investigate whether glucosylceramide synthase (GCS) regulates apoptosis-related gene bcl-2 expression via MEK/ERK signaling pathway , thus enhancing drug resistance of K 562/A02 human leukemia multidrug resistant cell line.METHODS:siRNA targeting GCS was transfected into K562/A02 cells.Bcl-2, p-ERK and total ERK expression at mRNA and protein levels after GCS knockdown were detected by real-time PCR and Western blotting .After exposed to MEK-ERK pathway inhibitor U0126, the expression of Bcl-2 at mRNA and protein levels also was analyzed by real-time PCR and Western blotting , respectively.The viability of the cells was evaluated by CCK-8 assay.RESULTS:The expression of GCS and Bcl-2, as well as MEK/ERK signaling were significantly inhibited in K 562/A02 cells by GCS siRNA transfection compared with negative control group .Inactivation of MEK/ERK signaling due to U0126 treatment de-creased Bcl-2 mRNA and protein levels in a concentration-dependent manner , and sensitized K562/A02 cells to adriamy-cin.CONCLUSION:GCS may affect the expression of apoptosis-related gene bcl-2 by MEK/ERK signaling pathway , thus regulating multidrug resistance of human leukemia K 562/A02 cells.

Quantification of glucosylceramide in plasma of Gaucher disease patients

Gaucher disease is a sphingolipidosis that leads to an accumulation of glucosylceramide. The objective of this study was to develop a methodology, based on the extraction, purification and quantification of glucosylceramide from blood plasma, for use in clinical research laboratories. Comparison of the glucosylceramide content in plasma from Gaucher disease patients, submitted to enzyme replacement therapy or otherwise, against that from normal individuals was also carried out. The glucosylceramide, separated from other glycosphingolipids by high performance thin layer chromatography (HPTLC) was chemically developed (CuSO4 / H3PO4) and the respective band confirmed by immunostaining (human anti-glucosylceramide antibody / peroxidase-conjugated secondary antibody). Chromatogram quantification by densitometry demonstrated that the glucosylceramide content in Gaucher disease patients was seventeen times higher than that in normal individuals, and seven times higher than that in patients on enzyme replacement therapy. The results obtained indicate that the methodology established can be used in complementary diagnosis and for treatment monitoring of Gaucher disease patients.

A doença de Gaucher é uma esfingolipidose caracterizada pelo acúmulo de glicosilceramida. O objetivo deste estudo foi desenvolver metodologia baseada na extração, purificação e quantificação da glicosilceramida plasmática a qual possa ser usada em laboratórios de pesquisa clínica. Após o desenvolvimento desta metodologia, foi proposto, também, comparar o conteúdo de glicosilceramida presente no plasma de pacientes com doença de Gaucher, submetidos ou não a tratamento, com aquele de indivíduos normais. A glicosilceramida, separada de outros glicoesfingolipídios por cromatografia de camada delgada de alto desempenho (HPTLC), foi revelada quimicamente (CuSO4/H3PO4) e a respectiva banda foi confirmada por imunorrevelação (anticorpo anti-glicosilceramida humana/anticorpo secundário conjudado à peroxidase). A quantificação do cromatograma por densitometria demonstrou que o conteúdo de glicosilceramida nos pacientes com doença de Gaucher era 17 vezes maior que aquele de indivíduos normais e 7 vezes maior que aquele dos pacientes com doença de Gaucher submetidos a tratamento com terapia de reposição enzimática. Os resultados obtidos demonstram que a metodologia estabelecida pode ser usada como diagnóstico complementar e como monitoração do tratamento de pacientes com doença de Gaucher.

Avaliação de dois anos de tratamento da doença de Gaucher tipo 1 com terapia de reposição enzimática em pacientes do estado de São Paulo, Brasil / Evaluation of two years of treatment with enzyme replacement therapy in type 1 Gaucher disease patients of São Paulo State, Brazil

A doença de Gaucher tipo 1 é a doença de depósito lisossômico mais freqüente. De herança autossômica recessiva, é caracterizada pela deficiência da atividade da enzima glicocerebrosidase e o acúmulo patológico de seu substrato, a glicosilceramida, nas células da linhagem dos monócitos/macrófagos principalmente no baço, fígado e medula óssea. As manifestações são heterogêneas e incluem hepatoesplenomegalia, anemia, trombocitopenia, infiltração da medula óssea e lesões esqueléticas. Avaliaram-se os efeitos da terapia de reposição enzimática (TRE) sobre a anemia, trombocitopenia, hepatoesplenomegalia, estatura (crianças e adolescentes) e dor óssea em noventa pacientes com doença de Gaucher tipo 1 tratados por período de 24 meses no estado de São Paulo. Os principais sinais e sintomas antes do início do tratamento foram anemia (50 por cento), trombocitopenia (59 por cento), hepatomegalia (97 por cento), esplenomegalia (96 por cento), baixa estatura (46 por cento) e dor óssea (62 por cento). A dose média de TRE foi 35U/kg a cada duas semanas. A recuperação da anemia, da trombocitopenia e da dor óssea foi mais intensa aos seis meses de tratamento, e da hepatoesplenomegalia e da baixa estatura aos 18 meses. Após a melhora, a maioria dos pacientes manteve-se estável. Ao final de 24 meses de TRE, pelo menos 88 por cento dos pacientes atingiram os objetivos terapêuticos para anemia, 80 por cento para trombocitopenia, 34 por cento para hepatoesplenomegalia, 77 por cento para baixa estatura e 76 por cento para dor óssea. Novos estudos são necessários para avaliar a resposta terapêutica em longo prazo, principalmente em relação às alterações ósseas e de estatura, que podem apresentar resposta mais tardia e lenta.

Type 1 Gaucher's disease, the most common lysosomal storage disorder, is caused by an autosomal recessive deficiency of glucocerebrosidase that results in a pathologic accumulation of its substrate, glucocerebroside, in the cells of the monocyte/macrophage lineage mainly of the spleen, liver and bone marrow. The symptoms are heterogeneous and include hepatosplenomegaly, anemia, thrombocytopenia, bone marrow infiltration, and skeletal lesions. We evaluated the effects of enzyme replacement therapy (ERT) on anemia, thrombocytopenia, hepatosplenomegaly, growth retardation (children and adolescents) and bone pain among 90 patients with type 1 Gaucher's disease treated during 24 months in Sao Paulo State. Baseline signs and symptoms were anemia (50 percent), thrombocytopenia (59 percent), hepatomegaly (97 percent), splenomegaly (96 percent), growth retardation (46 percent) and bone pain (62 percent). The mean dose of ERT was 35 U/kg every two weeks. Reduction in anemia, thrombocytopenia and bone pain was greatest during the first six months of ERT and of hepatosplenomegaly and growth retardation within 18 months. Improvements were sustained by most of the patients during the follow-up. Within 24 months of ERT, therapeutic goals were achieved in at least 88 percent of patients with anemia, 80 percent with thrombocytopenia, 34 percent with hepatosplenomegaly, 77 percent with growth retardation and 76 percent with bone pain. Other studies are needed to evaluate the treatment efficacy over a longer period, mainly for skeletal lesions and growth retardation, which may present a slower recovery due to low penetration of imiglucerase in bones.

Inhibition of glucosylceramide synthase expression and reversal of multidrug resistance in human breast cancer cells by shRNA / 基础医学与临床

Objective To construct the plasmid containing short hairpin RNA (shRNA) of GCS in order to suppress the expression of GCS and to reverse the multidrug resistance in drug-resistant breast cancer cells. Methods Two reverse repeated motifs of sequence targeting GCS with 6 bp spacer were designed and synthesized in vitro,then they were inserted into the plasmid pSUPER. The recombinant plasmids were transfected into human breast cancer cells. GCS expression was detected by Western blot and immunocytochemistry. caspase-3 expression and its activity were assessed using Western blot and colorimetry,flow cytometry was performed to analyze the ratio of apoptosis. Results MTT method was used to evaluate the 50% inhibition concentration. Enzyme digestion analysis and DNA sequencing confirmed that the recombinant plasmids were successfully constructed. GCS protein content decreased 80%,82% respectively after transfection with recombinant plasmids. The positive rate of GCS expression reduced to 18.1%,16.7% respectively. caspase-3 expression and its activity were significantly higherand the apoptosis of cells increased dramatically. The drug resistance of breast cancer cells to antineoplastic drugs declined significantly. Conclusion shRNA can suppress GCS expression in human drug-resistant breast cancer cells effectively and restore the sensitivity to several antineoplastic drugs.