Detection of proliferating cell nuclear antigen

Lufenuron induces reproductive toxicity and genotoxic effects in pregnant albino rats and their fetuses

Insecticides and other agrochemicals have become indispensable components of the agricultural system to ensure a notable increase in crop yield and food production. As a natural consequence, chemical residues result in significantly increased contamination of both terrestrial and aquatic ecosystems. The present study evaluated the teratogenic, genotoxic, and oxidative stress effects of residual-level lufenuron exposure on pregnant rats during the organogenesis gestational period of both mother and fetus. The tested dams were divided into three groups; control (untreated), low-dose group (orally administered with 0.4 mg/kg lufenuron) and high-dose group (orally administered with 0.8 mg/kg lufenuron). The dams of the two treatment groups showed teratogenic abnormalities represented by the asymmetrical distribution of fetuses in both uterine horns, accompanied by observed resorption sites and intensive bleeding in the uterine horns, whereas their fetuses suffered from growth retardation, morphologic malformations, and skeletal deformations. Histologic examination of the liver and kidney tissues obtained from mothers and fetuses after lufenuron exposure revealed multiple histopathologic changes. DNA fragmentation and cell cycle perturbation were also detected in the liver cells of lufenuron-treated pregnant dams and their fetuses through comet assay and flow cytometry, respectively. Moreover, lufenuron-induced oxidative stress in the liver of mothers and fetuses was confirmed by the increased malondialdehyde levels and decreased levels of enzymatic antioxidants (glutathione peroxidase and superoxide dismutase). Taken together, it can be concluded that lufenuron has a great potential in exerting teratogenic, genotoxic, and oxidative stresses on pregnant rats and their fetuses upon chronic exposure to residual levels during the organogenesis gestational period. The obtained results in the present study imply that women and their fetuses may have the same risk.

Multiplex Cell Fate Tracking by Flow Cytometry

Measuring differences in cell cycle progression is often essential to understand cell behavior under different conditions, treatments and environmental changes. Cell synchronization is widely used for this purpose, but unfortunately, there are many cases where synchronization is not an option. Many cell lines, patient samples or primary cells cannot be synchronized, and most synchronization methods involve exposing the cells to stress, which makes the method incompatible with the study of stress responses such as DNA damage. The use of dual-pulse labelling using EdU and BrdU can potentially overcome these problems, but the need for individual sample processing may introduce a great variability in the results and their interpretation. Here, we describe a method to analyze cell proliferation and cell cycle progression by double staining with thymidine analogues in combination with fluorescent cell barcoding, which allows one to multiplex the study and reduces the variability due to individual sample staining, reducing also the cost of the experiment.

Evaluation of the Cytotoxicity and Apoptotic Induction in Human Liver Cell Lines Exposed to Three Food Additives

BACKGROUND

Rapid lifestyle, especially among people living in urban areas, has led to increasing reliance on the processed food market. Unfortunately, harmful effects caused by the excessive use of food additives in such type of industry are often neglected.

OBJECTIVE

This proposal investigates in vitro cytotoxic and apoptotic effects of three food preservatives commonly consumed in daily meals; sodium sulphite, boric acid, and benzoic acid.

METHODS

The effect of the three preservatives on cell viability was tested on two different cell lines; normal liver cell line THLE2 and human hepatocellular carcinoma cancer cell line HepG2 using MTT assay. Cell cycle arrest was measured using flow cytometry by propidium iodide. Measurement of expression levels of two central genes, p53 and bcl-2 that play key roles in cell cycle and apoptosis was carried out in HepG2 cells using real time-PCR.

RESULTS

Although the effect was more significantly realized in the HepG2 cell line, the viability of both cell lines was decreased by all of the three tested compounds. Flow cytometric analysis of HepG2 cells treated with sodium sulphite, boric acid, and benzoic acid has revealed an increase in G2/M phase cell cycle arrest. In Sodium sulphite and boric acid-treated cells, expression levels of p53 were up-regulated, while that of the Bcl2 was significantly down-regulated. On the other hand, Benzoic acid has shown an anti-apoptotic feature based on the increased expression levels of Bcl-2 in treated cells.

CONCLUSION

In conclusion, all of the tested compounds have decreased the cell line viability and induced both cell cycle arrest and apoptotic events indicating their high potential of being cytotoxic and genotoxic materials.

Elucidating the role of an immunomodulatory protein in cancer: From protein expression to functional characterization

Several fundamental discoveries made over the last two decades, in the field of cancer biology, have increased our understanding of the complex tumor micro- and macroenvironments. This has shifted the current empirical cancer therapies to more rationalized treatments targeting immunomodulatory proteins. From the point of identification, a protein target undergoes several interrogations, which are necessary to truly define its druggability. Here, we outline some basic steps that can be followed for in vitro characterization of a potential immunomodulatory protein target. We describe procedures for recombinant protein expression and purification including key annotations on protein cloning, expression systems, purification strategies and protein characterization using structural and biochemical approaches. For functional characterization, we provide detailed protocols for using flow-cytometric techniques in cell lines or primary cells to study protein expression profiles, proliferation, apoptosis and cell-cycle changes. This multilevel approach can provide valuable, in-depth understanding of any protein target with potential immunomodulatory effects.

Alterations of cell cycle control proteins SHP‑1/2, p16, CDK4 and cyclin D1 in radioresistant nasopharyngeal carcinoma cells

The primary treatment for nasopharyngeal carcinoma (NPC) is radiotherapy, with or without concurrent chemotherapy. However, resistance to radiotherapy is not uncommon. The aim of the present study was to establish a radioresistant NPC cell line to study the molecular mechanisms of radioresistance by measuring the expression of cell cycle control proteins src homology 2 domain-containing phosphatase (SHP)-1/2, p16, CDK4 and cyclin D1. Human nasopharyngeal carcinoma CNE-2 cells were cultured, divided into two groups (CNE-2S1 and CNE-2S2) and irradiated with a dose of 6 Gy x5 or 2 Gy x15, respectively. The cells were subcultured between doses of irradiation. The surviving sublines (CNE-2S1 and CNE-2S2 clones) were then passaged for three months and their radiosensitivity was determined. The cell cycle distribution and protein expression of SHP-1/2, p16, CDK4 and cyclin D1 in parental and progenitor cell lines were measured. Small interfering (si)RNA-mediated knockdown of SHP-1 and SHP-2 in the NPC cells was used to further examine their roles in radiosensitivity and cell cycle distribution. CNE-2S1, a radio-resistant cell line, had a significantly higher percentage of cells in S phase and a lower percentage of cells in G1 phase, enhanced expression levels of SHP-1, CDK4 and cyclin D1, and reduced expression of p16, respectively, as compared with the parent cells. Stable suppression of SHP-1 mRNA in CNE-2 cells resulted in increased radiosensitivity compared with the parental cells, a decrease in the number of cells in S phase and an increase in the expression of p16. The results suggested that the SHP-1/p16/cyclin D1/CDK4 pathway may have a role in regulating radiosensitivity and cell cycle distribution in nasopharyngeal cells.

Proliferation of germ cells and somatic cells in first trimester human embryonic gonads as indicated by S and S+G2+M phase fractions

OBJECTIVES

The number of germ cells and somatic cells in human embryonic and foetal gonads has previously been estimated by stereological methods, which are time- and labour-consuming with little information concerning cell proliferation. Here, we studied whether flow cytometry could be applied as an easier method, also enabling estimation of the fraction of cells in S or S+G(2)+M (SG(2) M) cell-cycle phases as indicators of cell proliferation.

METHODS

Cell suspensions from 35 human embryonic gonads at days 37 to 68 post-conception (pc) were immunomagnetically sorted into C-KIT positive (germ) cells and negative (somatic) cells. They were stained for DNA content and analysed by flow cytometry. S and SG(2) M fractions could be measured for 13 of the female and 20 of the male gonads. The number of cells was estimated using fluorescent reference beads.

RESULTS

During the period from 37 to 68 days pc, female germ and somatic cells had a stable S and SG(2) M fractions indicating steady growth of both subpopulations, whereas they decreased in both male germ and somatic cells. The number of germ and somatic cells estimated by flow cytometry was significantly lower than in stereological estimates, suggesting loss of cells during preparation.

CONCLUSIONS

Cell proliferation as indicated by S and SG(2) M fractions could be estimated specifically for primordial germ and somatic cells. Estimation of total number of germ and somatic cells was not feasible.

Chromatin-bound PCNA as S-phase marker in mononuclear blood cells of patients with acute lymphoblastic leukaemia or multiple myeloma

OBJECTIVES

Proliferating cell nuclear antigen (PCNA) has often been used as a marker to aid assessment of tumour growth fraction. This paper addresses the question of whether it can be used as an S-phase marker, when the non-chromatin-bound form of the protein is removed by pepsin treatment.

MATERIALS AND METHODS

Cytofluorometric measurements were carried out after immunofluorescence staining of PCNA and counterstaining of DNA. S-phase fraction was determined with the help of windows on PCNA versus DNA scattergrams, or mathematically from DNA histograms.

RESULTS

S-phase fractions obtained using the two methods correlated well, but did not always agree, exact discrepancies depending on the mathematical model used for histogram analysis.

CONCLUSIONS

Determination of S-phase fractions with the help of PCNA immunofluorescence staining is possible, and probably more reliable than calculation of S-fractions from DNA histograms. It thus offers an alternative to assays involving BrdU labelling in vivo.

Cell confluency is as efficient as serum starvation for inducing arrest in the G0/G1 phase of the cell cycle in granulosa and fibroblast cells of cattle

The cell cycle stage of donor cells is an important factor influencing developmental ability of nuclear transfer embryos. In the present experiment, cumulus and fibroblast cells of cattle were subjected to flow cytometric cell cycle analysis before being used in somatic cloning experiments. The following experimental groups were analyzed for each cell type: (1) actively dividing cells, (2) cells confluent for 4 days, (3) cells starved for 1, 2, 3 or 5 days. Using the propidium iodide flow cytometric assay, there were no significant differences (P > or = 0.05) in the percentage of cells in G0/G1 regardless of origin and type of cell, after confluency or serum starvation. Differences with the growing cells were found (P < or = 0.01). To determine what subset of cells in G0/G1 were in the G0 subphase of the cell cycle, an immunofluorescence analysis was conducted using monoclonal anti-PCNA antibodies in a FACS assay. There were not statistically significant differences in the percentage of cells that enter G0, between confluent and any starved group for either type of cells. Bovine fibroblast cells, confluent or serum starved for 3 days, were used in nuclear transfer experiments. A slight trend for a more desirable fusion rate in starved cells was detected, and embryo cleavage was greater in starved cells, however, in vitro development to blastocysts was similar between groups. Data indicate that prolonged culture of cells in the absence of serum does not imply a shift in the percentage of cells that enter G0/G1 or G0 alone, and that confluency is sufficient to induce quiescence. This finding can be beneficial in nuclear transfer programs, because there are negative effects such as apoptosis, associated with serum starvation.

Practical aspects of donor cell selection for nuclear cloning

Choosing the right nuclear donor is the most critical decision in cloning by nuclear transfer (NT), or nuclear cloning, because the cloned animal will be a genetic copy of the donor cell genome used for NT. Both donor cell type and cell cycle stage are important methodological parameters and influence nuclear cloning efficiency. Cloning, however, is a multi-step procedure and the exact contribution of the nuclear donor to overall cloning success must be determined in comparative studies. This requires strict standardization of isolation, purification, and culture protocols, and application of stringent identification criteria in order to obtain a homogenous donor cell population. In all these respects, the standards in the cloning field are currently poor. The aim of this review is to provide a brief guideline for the major practical aspects of donor cell selection, cell cycle synchronization and preparation for NT.

Flow cytometry in analysis of cell cycle and apoptosis

The capacity for multiparametric measurement of large cell populations rapidly and accurately offered by cytometry has made this methodology indispensable in studies of cell proliferation and cell death. The reviewed cell cycle applications include (1) the univariate analysis of cellular DNA content for identification of G(0/1) versus S versus G(2)/M cells; (2) discrimination between noncycling (G(0); quiescent) and proliferating cells, based on the presence of proliferation-associated proteins; (3) identification of mitotic cells by histone H3 phosphorylation; (4) bivariate analysis of expression of cyclins D, E, A, or B1 versus DNA content; and (5) detection of DNA replicating cells and analysis of cell kinetics from the bivariate distributions of 5-bromo-2'-deoxyuridine (BrdU) incorporation versus DNA content. For the identification of apoptotic cells and discrimination between apoptosis and necrosis, flow cytometry techniques are applied to evaluate for changes in cell morphology, the presence of phosphatidylserine on cell surface, collapse of mitochondrial transmembrane potential, DNA fragmentation, and evidence of caspase activation. Semin Hematol 38:179-193.