ABSTRACT
The development of sensitive and reliable fluorescent probes for the early diagnosis of Alzheimer's disease (AD) is highly challenging and plays an important role in achieving effective treatments. Herein, we designed and synthesized an indole-based fluorophore for TTR in human plasma, an important hallmark of AD pathogenesis. This robust and simple fluorescent method allows quantification of TTR in the complex biological matrix.
Subject(s)
Alzheimer Disease/diagnosis , Fluorescent Dyes/chemistry , Prealbumin/metabolism , Alzheimer Disease/blood , Amyloid beta-Peptides/metabolism , Humans , Limit of Detection , Spectrometry, FluorescenceABSTRACT
With ultraviolet and visible light exposure, some pharmaceutical substances applied systemically or topically may cause phototoxic skin irritation. The major factor in phototoxicity is the generation of reactive oxygen species (ROS) such as singlet oxygen and superoxide anion that cause oxidative damage to DNA, lipids and proteins. Thus, measuring the generation of ROS can predict the phototoxic potential of a given substance indirectly. For this reason, a standard ROS assay (ROS assay) was developed and validated and provides an alternative method for phototoxicity evaluation. However, negative substances are over-predicted by the assay. Except for ultraviolet A (UVA), other UV ranges are not a major factor in causing phototoxicity and may lead to incorrect labeling of some non-phototoxic substances as being phototoxic in the ROS assay when using a solar simulator. A UVA stimulator is also widely used to evaluate phototoxicity in various test substances. Consequently, we identified the applicability of a UVA simulator to the ROS assay for photoreactivity. In this study, we tested 60 pharmaceutical substances including 50 phototoxins and 10 non-phototoxins to predict their phototoxic potential via the ROS assay with a UVA simulator. Following the ROS protocol, all test substances were dissolved in dimethyl sulfoxide or sodium phosphate buffer. The final concentration of the test solutions in the reaction mixture was 20 to 200 µM. The exposure was with 2.0~2.2 mW/cm2 irradiance and optimization for a relevant dose of UVA was performed. The generation of ROS was compared before and after UVA exposure and was measured by a microplate spectrophotometer. Sensitivity and specificity values were 85.7% and 100.0% respectively, and the accuracy was 88.1%. From this analysis, the ROS assay with a UVA simulator is suitable for testing the photoreactivity and estimating the phototoxic potential of various test pharmaceutical substances.
ABSTRACT
Sialylation, the attachment of sialic acid residues to a protein, can affect the biological activity and in vivo circulatory half-life of glycoproteins. Human alpha2,3- sialyltransferase (alpha2,3-ST) and beta1,4-galactosyltransferase (beta1,4-GT) are responsible for terminal sialylation and galactosylation, respectively. Enhanced sialylation of human erythropoietin (EPO) by the expression of alpha2,3-ST and beta1,4-GT was achieved using recombinant Chinese hamster ovary (CHO) cells (EC1). The sialic acid content and sialylation of N-glycans were evaluated by HPLC. When alpha2,3-ST was expressed in CHO cells (EC1-ST2), the sialic acid content (moles of sialic acid/mole of EPO) increased from 6.7 to 7.5. In addition, the amount of trisialylated glycans increased from 17.3% to 26.1%. When alpha2,3-ST and beta1,4-GT were coexpressed in CHO cells (EC1-GTST15), the degree of sialylation was greater than that in EC1-ST2 cells. In the case of EC1-GTST15 cells, the sialic acid content increased to 8.2 and the proportion of trisialylated glycans was markedly increased from 17.3% to 35.5%. Interestingly, the amount of asialoglycans decreased only in the case of GTST15 cells (21.4% to 14.2%). These results show that coexpression of alpha2,3- ST and beta1,4-GT is more effective than the expression of alpha2,3-ST alone. Coexpression of alpha2,3-ST and beta1,4-GT did not affect CHO cell growth and metabolism or EPO production. Thus, coexpression of alpha2,3-ST and beta1,4-GT may be beneficial for producing therapeutic glycoproteins with enhanced sialylation in CHO cells.
