Impact of Hypromellose Acetate Succinate Grade on Drug Amorphous Solubility and In Vitro Membrane Transport

Abstract Background: Choline binding proteins (CBPs) are a family of proteins that can interact with pneumococcal cell wall by choline binding domains (CBDs). In this study, we found a modified choline binding repeat (ChBp-I) with a pI of 7.66 can promote the development of biofilm in vitro. Thus, we aim to characterize the function of CBDs of LytA, LytC and CbpD in biofilm formation.Results: By transcriptome analysis, 81 genes were identified as down regulated and 138 genes were up regulated (|log2 fold change|≥1.5) under ChBp-I of 50mg/L. The up regulated genes are well clustered in membrane transport (carbohydrate, lipid, protein, cation and phosphate) and carbohydrate metabolism (fructose, mannose, galactose, starch, sucrose, amino sugar and nucleotide) related pathways. The up-regulated genes are mostly regulated the same under CBD-A, CBD-C and CBD-D. Phenotype analysis reveal high concentrations of CBD-C and CBD-D (>100μg/mL) but not CBD-A (negative charged) can promote the biofilm formation. Meanwhile, the existence of CBD-C and CBD-D promote the growth rate and both CBDs inhibit the autolysis of pneumococcal cell. By component analysis, these three CBDs were proved involved in the regulation of extracellular DNA, protein, cation and phosphate, and promote the forming of insoluble precipitates.Conclusions: The binding of CBPs can influence the membrane transport pathways and react with extracellular DNA and protein to promote biofilm formation in S. pneumoniae.

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Thrombocytopenia after meta-iodobenzylguanidine (MIBG) therapy in neuroblastoma patients may be caused by selective MIBG uptake via the serotonin transporter located on megakaryocytes

EJNMMI Research ◽

10.1186/s13550-021-00823-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Thomas Blom ◽

Rutger Meinsma ◽

Franca di Summa ◽

Emile van den Akker ◽

André B. P. van Kuilenburg ◽

...

Keyword(s):

Plasma Membrane ◽

Membrane Transport ◽

Serotonin Transporter ◽

Hek293 Cells ◽

Pharmacological Intervention ◽

Mibg Uptake ◽

Hematopoietic Stem ◽

Specific Uptake ◽

Mibg Therapy

Abstract Background The therapeutic use of [131I]meta-iodobenzylguanidine ([131I]MIBG) is often accompanied by hematological toxicity, primarily consisting of severe and persistent thrombocytopenia. We hypothesize that this is caused by selective uptake of MIBG via the serotonin transporter (SERT) located on platelets and megakaryocytes. In this study, we have investigated whether in vitro cultured human megakaryocytes are capable of selective plasma membrane transport of MIBG and whether pharmacological intervention with selective serotonin reuptake inhibitors (SSRIs) may prevent this radiotoxic MIBG uptake. Methods Peripheral blood CD34+ cells were differentiated to human megakaryocytic cells using a standardized culture protocol. Prior to [3H]serotonin and [125I]MIBG uptake experiments, the differentiation status of megakaryocyte cultures was assessed by flow cytometry. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to assess SERT and NET (norepinephrine transporter) mRNA expression. On day 10 of differentiation, [3H]serotonin and [125I]MIBG uptake assays were conducted. Part of the samples were co-incubated with the SSRI citalopram to assess SERT-specific uptake. HEK293 cells transfected with SERT, NET, and empty vector served as controls. Results In vitro cultured human megakaryocytes are capable of selective plasma membrane transport of MIBG. After 10 days of differentiation, megakaryocytic cell culture batches from three different hematopoietic stem and progenitor cell donors showed on average 9.2 ± 2.4 nmol of MIBG uptake per milligram protein per hour after incubation with 10–7 M MIBG (range: 6.6 ± 1.0 to 11.2 ± 1.0 nmol/mg/h). Co-incubation with the SSRI citalopram led to a significant reduction (30.1%—41.5%) in MIBG uptake, implying SERT-specific uptake of MIBG. A strong correlation between the number of mature megakaryocytes and SERT-specific MIBG uptake was observed. Conclusion Our study demonstrates that human megakaryocytes cultured in vitro are capable of MIBG uptake. Moreover, the SSRI citalopram selectively inhibits MIBG uptake via the serotonin transporter. The concomitant administration of citalopram to neuroblastoma patients during [131I]MIBG therapy might be a promising strategy to prevent the onset of thrombocytopenia.

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Characteristics of membrane transport losses during reticulocyte maturation

Biochemistry and Cell Biology ◽

10.1139/o87-113 ◽

1987 ◽

Vol 65 (10) ◽

pp. 869-875 ◽

Cited By ~ 15

Author(s):

Rhoda Blostein ◽

Eva Grafova

Keyword(s):

Membrane Transport ◽

Binding Sites ◽

Sodium Pump ◽

Proteolytic Processing ◽

Atp Depletion ◽

Nucleoside Transport ◽

Transport Systems ◽

Nucleoside Transporter ◽

Transport Losses

The decline in activity of distinct membrane transport systems was followed during in vitro maturation of sheep reticulocytes, namely the sodium pump (measured as specific ouabain binding sites), Na+–glycine cotransport, and the nucleoside transporter (measured as specific nitrobenzylthioinosine binding sites). Certain features of this maturation-associated decline in membrane transport are clarified. Thus, the apparent retardation of loss by metabolic (ATP) depletion, reported previously for the sodium pump and Na+–glycine cotransport, is applicable also to the decline in nucleoside transport. The absolute losses, as well as relative effects of ATP depletion, are different for the three distinct systems. Inhibitors of membrane recycling and (or) intracellular processing, such as chloroquine, as well as ATP depletion, prevent not only the loss but also cause a transient increase in nucleoside transport sites apparent at the surface. Proteolytic processing, at least in the case of the nucleoside transporter, is probably also involved since leupeptin retards the loss in binding sites. Protection against the decline in transporters can also be affected by specific ligands as evidenced in ouabain protection of sodium pump sites. The results provide evidence that membrane transporter recycling is a fundamental process underlying the energy-dependent, maturation-associated loss in membrane transport functions.

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