Polyphyllin D induces apoptosis in human erythrocytes through Ca²âº rise and membrane permeabilization.

Polyphyllin D (PD) is a potent anticancer agent isolated from a traditional medicinal herb Paris polyphylla that has been used in China for many years to treat cancer. PD is not a substrate of p-glycoprotein, and it can bypass the multi-drug resistance in cancer cell line R-HepG2. However, the effect of PD on the induction of cell death in human erythrocytes remains unknown. Given that PD is a small molecule that can depolarize the mitochondrial membrane potential and release apoptosis-inducing factor (AIF) in isolated mitochondria, we hypothesized that the apoptogenic effect of PD in human erythrocytes devoid of mitochondria would be minimal. This study therefore tried to evaluate the in vitro effect of PD on hemolysis and apoptosis in human erythrocytes. Apoptosis in human red blood cells (RBCs), also known as eryptosis or erythroptosis, after PD treatment was determined by flow cytometry and confocal microscopy for the phosphatidyl-serine externalization and other apoptosis feature events. False to our prediction, PD caused hemolysis and eryptosis/erythroptosis in human RBCs. Mechanistically, elevation in the cytosolic Ca²âº ion level seems to be a key but not the only mediator in the PD-mediated eryptosis/erythroptosis because depletion of the external Ca²âº could not eliminate the PD effect. Also, PD was able to permeabilize the membrane of RBC ghosts in a way similar to digitonin. Taken together, we report here for the first time the toxicity of PD in human RBCs as well as its underlying mechanism for the hemolysis and eryptosis/erythroptosis.

In vitro effect of CTAB- and PEG-coated gold nanorods on the induction of eryptosis/erythroptosis in human erythrocytes.

Gold nanorods (Au-NRs) have attracted enormous interest due to their size and unique optical properties. Many studies have demonstrated their use in biomedical systems. However, their potential toxicity is not fully understood. This study evaluated the effects of the Au-NRs (15 nM × 64 nM) coated with CTAB (cetyltrimethylammonium bromide) or PEG (polyethylene glycol) in human erythrocytes on the induction of haemolysis and erythroptosis. In our study, erythroptosis (also known as eryptosis) was determined systematically through the measurement of feature events of apoptosis by flow cytometry. We found that the CTAB- and PEG-coated Au-NRs up to 0.5 nM did not cause severe haemolysis. However, the CTAB-Au-NRs were more toxic than the PEG-Au-NRs. The toxicity of the CTAB-Au-NRs was largely due to the CTAB residues from desorption or incomplete purification. Mechanistically, cytosolic Ca(2+) ions seem to be the key mediator in the eryptosis/erythroptosis mediated by the CTAB or CTAB-Au-NRs while caspase-3 and reactive oxygen species did not contribute much to the process.

Aptamer-based bio-barcode assay for the detection of cytochrome-c released from apoptotic cells.

The recently developed bio-barcode (BBC) assay using polymerase chain reaction (PCR) to generate signals has been shown to be an extraordinarily sensitive method to detect protein targets. The BBC assay involves a magnetic microparticle (with antibody to capture the target of interest) and gold nanoparticle (with recognition antibody and thiolated single-stranded barcode DNAs) to form a sandwich around the target. The concentration of target is determined by the amount of barcode DNA released from the nanoparticles. Here we describe a modification using aptamers to substitute the gold nanoparticles for the BBC assay. In this study, we isolated a 76-mer monoclonal aptamer against cytochrome-c (cyto-c) and this single-stranded DNA in defined 3D structure for cyto-c was used in the BBC assay for both recognition and readout reporting. After magnetic separation, the aptamer was amplified by PCR and this aptamer-based barcode (ABC) assay was sensitive enough to detect the cyto-c in culture medium released from the apoptotic cells after drug treatment at the picomolar level. When compared to the conventional cyto-c detection by Western blot analysis, our ABC assay is sensitive, and time for the detection and quantification with ready-made probes was only 3 h.