Apoptosis Of THP-1 Macrophages Research Articles

Apoptosis of THP-1 macrophages induced by protoporphyrin IX-mediated sonodynamic therapy

BackgroundSonodynamic therapy (SDT) was developed as a localized ultrasound-activated cytotoxic therapy for cancer. The ability of SDT to destroy target tissues selectively is especially appealing for atherosclerotic plaque, in which selective accumulation of the sonosensitizer, protoporphyrin IX (PpIX), had been demonstrated. Here we investigate the effects of PpIX-mediated SDT on macrophages, which are the main culprit in progression of atherosclerosis.Methods and resultsCultured THP-1 derived macrophages were incubated with PpIX. Fluorescence microscopy showed that the intracellular PpIX concentration increased with the concentration of PpIX in the incubation medium. MTT assay demonstrated that SDT with PpIX significantly decreased cell viability, and this effect increased with duration of ultrasound exposure and PpIX concentration. PpIX-mediated SDT induced both apoptosis and necrosis, and the maximum apoptosis to necrosis ratio was obtained after SDT with 20 μg/mL PpIX and five minutes of sonication. Production of intracellular singlet oxygen and secondary disruption of the cytoskeleton were also observed after SDT with PpIX.ConclusionPpIX-mediated SDT had apoptotic effects on THP-1 macrophages via generation of intracellular singlet oxygen and disruption of the cytoskeleton. PpIX-mediated SDT may be a potential treatment to attenuate progression of atherosclerotic plaque.

Abstract 343: Induction of Apoptosis in Human Macrophages by 7-ketocholesterol and Iron Ascorbate

Inflammation is the new paradigm for the development and progression of atherosclerotic lesions in coronary artery disease. Factors that increase oxidative stress and apoptosis of cells within the lesion contribute to sustaining the inflammatory response. It was hypothesized that redox-active iron and oxysterols, which have both been found in association with atherosclerotic plaques, contribute to oxidative stress and apoptosis by distinct, but overlapping signaling pathways. The human acute monocytic leukemia cell line THP-1 was used as a model system to study the roles of redox-active iron and 7-ketocholesterol in macrophage apoptosis. The ability of both reagents to induce apoptosis in THP-1 macrophages was demonstrated using flow cytometry. The kinetics of poly(ADP-ribose) polymerase (PARP) cleavage as measured by ELISA were also similar. qRT-PCR was used to measure mRNA levels of several pro- and anti-apoptotic genes. While 7-ketocholesterol increased the level of CHOP mRNA (a transcription factor in endoplasmic reticulum (ER)-initiated apoptosis), there was no similar increase in response to iron ascorbate treatment. Expression of other markers of ER stress, like the transcription factors ATF3 and CEBPbeta, was increased by both compounds, but the timing of changes in gene expression was different. TNFalpha regulates both apoptosis and inflammatory cytokine production. Macrophages are major producers of TNFalpha as well as being highly responsive to the cytokine. A comparison of the changes in TNFalpha mRNA and protein levels in response to iron ascorbate and 7-ketocholesterol suggested that while ERK1/2 and NFkB signaling are important in TNFalpha expression, differentially regulated post-transcriptional processes determine the release of TNFalpha by macrophages. These preliminary results suggest that the apoptotic pathways activated by oxysterols and redox-active iron may be different and that these compounds may have additive or synergistic effects on lesion progression.

Beryllium uptake and related biological effects studied in THP-1 differentiated macrophages

Investigation of cellular uptake of metal compounds is important in understanding metal-related toxicity and diseases. Inhalation of beryllium aerosols can cause chronic beryllium disease, a progressive, granulomatous fibrosis of the lung. Studies in laboratory animals and cultured animal cells indicate that alveolar macrophages take up beryllium compounds and participate in a hypersensitivity immune response to a beryllium-containing antigen. In the present work, human monocyte cell line THP-1 was induced with phorbol myristate acetate to differentiate into a macrophage. This cell with characteristics of human alveolar macrophages was employed to study cellular beryllium uptake and related biological effects. Morphological changes, phagocytosis of fluorescent latex beads, and cell surface CD14 expression were used to verify the successful differentiation of THP-1 monocytes into macrophages. An improved mass spectrometry method for quantitative analysis of intracellular beryllium as opposed to the traditional radioisotopic approach was developed using ICP-MS. The influence of the solubility of beryllium compounds, exposure duration, and beryllium concentration on the incorporation of beryllium was studied. Our data indicated that the uptake of particulate BeO was much more significant than that of soluble BeSO(4), suggesting the major cellular uptake pathway is phagocytosis. Nevertheless, subsequent DAPI nuclear staining and PARP cleavage study indicated that beryllium uptake had a negligible effect on the apoptosis of THP-1 macrophages compared to the unstimulated macrophage control. Meanwhile, no substantial variation of tumour necrosis factor-alpha production was observed for THP-1 macrophages upon beryllium exposure. These data imply alveolar macrophages could have some level of tolerance to beryllium and this may explain why most Be-exposed individuals remain healthy throughout life.

Pigment epithelium-derived factor induces THP-1 macrophage apoptosis and necrosis by the induction of the peroxisome proliferator-activated receptor gamma

Pigment epithelial-derived factor (PEDF) is a potent anti-angiogenic factor, partially through the induction of endothelial cell apoptosis. Here we report that PEDF can also induce the apoptosis of human THP-1 monocytic leukemia cell line-derived macrophage cells (THP-1 macrophages) and peroxisome proliferator-activated receptor gamma (PPARγ), a pleiotropic transcriptional factor is involved in the signaling. TUNEL and propidium iodide permeability assays demonstrated that PEDF dose- and time-dependently induces both apoptosis and necrosis of THP-1 macrophages while inducing the cleavages of procaspase-9, -3, the release of cytochrome c and the overexpression of p53. All these PEDF effects can be attenuated by either PPARγ inhibitor GW9662 or PPARγ small interfering RNA. The effects of PEDF can be reproduced by transient expression of PPARγ by a PPARγ-expression plasmid transfection. PEDF increased the expression and transcriptional activity of PPARγ in THP-1 macrophages. In addition, PEDF also induced apoptosis in primary human monocyte-derived macrophages (MDMs) while inducing the expression of PPARγ. Our observations indicate that PEDF induces macrophage apoptosis and necrosis through the signaling of PPARγ. This suggests a novel mechanism through which PEDF can modulate inflammation.

Anti-apoptotic Effects of Probucol are Associated with Downregulation of Daxx Expression in THP-1 Macrophage

To study the relationship between Daxx expression and the antiapoptotic effects of probucol in THP-1 macrophage. Apoptosis of THP-1 derived macrophages was induced by exposure to oxidized low density lipoprotein (oxLDL). The development of apoptosis was determined by flow cytometry analysis and nucleic acid-binding dye acridin orange. Reverse transcriptase-polymerase chain reaction (RT-PCR), Western blotting and indirect immunofluorescence were used to evaluate the expression of Daxx and caspase-3 at both mRNA and protein level. As expected, THP-1 macrophages exposed to 100 mg/l oxLDL for 48 h exhibited typical morphologic changes of apoptosis, including condensed chromatin and shrunken nucleus. oxLDL treatment markedly increased Daxx expression in a time- and dose-dependent manner, and facilitated Daxx translocation from cytoplasm to nucleus. The percentage of cells with Daxx in nuclei was significantly increased from 8 to 59%. Treatment with probucol (50 micromol/l) for 4 h prior to exposure to oxLDL significantly inhibited Daxx expression and THP-1 macrophage apoptosis by 61.3%. Furthermore, oxLDL enhanced caspase-3 expression with increased mRNA and protein levels, but without obvious change in translocation of caspase-3 (the cells with nuclear Daxx: 14 vs 8%). In contrast, probucol attenuated oxLDL-stimulated caspase-3 expression in THP-1 macrophages. OxLDL-induced apoptosis of THP-1 macrophage is associated with Daxx up-regulation; while inhibition of apoptosis by probucol is related to decreased Daxx expression and nuclear translocation.