共查询到20条相似文献,搜索用时 15 毫秒
1.
Alexandru Vasincu Christiana M. Neophytou Simon Vlad Luca Krystyna Skalicka‐Wo
niak Anca Miron Andreas I. Constantinou 《Journal of biochemical and molecular toxicology》2020,34(3)
The aim of this study was to evaluate the impact that 6‐O‐(3″, 4″‐di‐O‐trans‐cinnamoyl)‐α‐ l ‐rhamnopyranosylcatalpol (Dicinn) and verbascoside (Verb), two compounds simultaneously reported in Verbascum ovalifolium, have on tumor cell viability, apoptosis, cell cycle kinetics, and intracellular reactive oxygen species (ROS) level. At 100 µg/mL and 48 hours incubation time, Dicinn and Verb produced good cytotoxic effects in A549, HT‐29, and MCF‐7 cells. Dicinn induced cell‐cycle arrest at the G0/G1 phase and apoptosis, whereas Verb increased the population of subG1 cells and cell apoptosis rates. Furthermore, the two compounds exhibited time‐dependent ROS generating effects in tumor cells (1‐24 hours). Importantly, no cytotoxic effects were induced in nontumor MCF‐10A cells by the two compounds up to 100 µg/mL. Overall, the effects exhibited by Verb in tumor cells were more potent, which can be correlated with its structural features, such as the presence of phenolic hydroxyl groups. 相似文献
2.
《Cell cycle (Georgetown, Tex.)》2013,12(4):621-629
Essentially every population of cancer cells within a tumor is heterogeneous, especially with regard to chemosensitivity and resistance. In the present study, we utilized the fluorescence ubiquitination-based cell cycle indicator (FUCCI) imaging system to investigate the correlation between cell-cycle behavior and apoptosis after treatment of cancer cells with chemotherapeutic drugs. HeLa cells expressing FUCCI were treated with doxorubicin (DOX) (5 μM) or cisplatinum (CDDP) (5 μM) for 3 h. Cell-cycle progression and apoptosis were monitored by time-lapse FUCCI imaging for 72 h. Time-lapse FUCCI imaging demonstrated that both DOX and CDDP could induce cell cycle arrest in S/G2/M in almost all the cells, but a subpopulation of the cells could escape the block and undergo mitosis. The subpopulation which went through mitosis subsequently underwent apoptosis, while the cells arrested in S/G2/M survived. The present results demonstrate that chemoresistant cells can be readily identified in a heterogeneous population of cancer cells by S/G2/M arrest, which can serve in future studies as a visible target for novel agents that kill cell-cycle-arrested cells. 相似文献
3.
Dedov VN Dedova IV Nicholson GA 《Apoptosis : an international journal on programmed cell death》2003,8(4):399-406
Epstein-Barr virus (EBV) is associated with a number of human malignancies. In vitro EBV infection transforms human lymphocytes into proliferating cell lines (EBV-lymphocytes). Etoposide, topoisomerase II inhibitor, induced apoptosis in EBV-lymphocytes as shown by expression of phosphatidylserine, loss of DNA and mitochondrial membrane potential, and cell shrinkage. In contrast, those cells, which had yet to display signs of apoptosis, grew to exceed their normal size. These EBV-lymphocytes had unusual cellular and nuclear morphology, higher mitochondrial membrane potential, increased expression of proteins and an amount of DNA that exceeded the maximum DNA content in normal EBV-lymphocytes by more than two-fold. Application of the caspase inhibitor Z-VAD-FMK in the presence of etoposide increased the numbers of such large cells. This data suggests that inhibition of topoisomerase II by etoposide does not inhibit DNA synthesis but rather overrides the G2/M check points of the cell cycle, resulting in cells growth over their genetically determined size. This may trigger apoptosis to eliminate cells, which failed to complete mitosis. 相似文献
4.
The model is based on the assumption that the cell cycle contains a Go-phase which cells leave randomly with a constant probability per unit time, γ. After leaving the Go-phase, the cells enter the C-phase which ends with cell division. The C-phase and its constituent phases, the‘true’G1-phase, the S-phase, the G2-phase and mitosis are assumed to have constant durations of T, T1Ts, T2 and Tm, respectively. For renewal tissue it is assumed that the probability per unit time of being lost from the population is a constant for all cells irrespective of their position in the cycle. The labelled mitosis curve and labelling index for continuous labelling are derived in terms of γ, T, and Ts. The model generates labelled mitosis curves which damp quickly and reach a constant value of twice the initial labelling index, if the mean duration of the Go-phase is sufficiently long. It is shown that the predicted labelled mitosis and continuous labelling curves agree reasonably well with the experimental curves for the hamster cheek pouch if T has a value of about 60 hr. Data are presented for the rat dorsal epidermis which support the assumption that there is a constant probability per unit time of a cell being released from the Go-phase. 相似文献
5.
Shinji Miwa Shuya Yano Hiroaki Kimura Mako Yamamoto Makoto Toneri Yasunori Matsumoto Fuminari Uehara Yukihiko Hiroshima Takashi Murakami Katsuhiro Hayashi Norio Yamamoto Michael Bouvet Toshiyoshi Fujiwara Hiroyuki Tsuchiya Robert M Hoffman 《Cell cycle (Georgetown, Tex.)》2015,14(4):621-629
Essentially every population of cancer cells within a tumor is heterogeneous, especially with regard to chemosensitivity and resistance. In the present study, we utilized the fluorescence ubiquitination-based cell cycle indicator (FUCCI) imaging system to investigate the correlation between cell-cycle behavior and apoptosis after treatment of cancer cells with chemotherapeutic drugs. HeLa cells expressing FUCCI were treated with doxorubicin (DOX) (5 μM) or cisplatinum (CDDP) (5 μM) for 3 h. Cell-cycle progression and apoptosis were monitored by time-lapse FUCCI imaging for 72 h. Time-lapse FUCCI imaging demonstrated that both DOX and CDDP could induce cell cycle arrest in S/G2/M in almost all the cells, but a subpopulation of the cells could escape the block and undergo mitosis. The subpopulation which went through mitosis subsequently underwent apoptosis, while the cells arrested in S/G2/M survived. The present results demonstrate that chemoresistant cells can be readily identified in a heterogeneous population of cancer cells by S/G2/M arrest, which can serve in future studies as a visible target for novel agents that kill cell-cycle-arrested cells. 相似文献
6.
Upregulation of survivin by HIV-1 Vpr 总被引:5,自引:0,他引:5
Zhu Y Roshal M Li F Blackett J Planelles V 《Apoptosis : an international journal on programmed cell death》2003,8(1):71-79
The human survivin gene belongs to the family of inhibitor of apoptosis proteins (IAP) and is involved in apoptosis inhibition and regulation of cell division. The survivin gene is the only member of the IAP family whose expression is known to be regulated through the cell cycle. Survivin expression reaches the highest levels during the G2/M transition and then is rapidly degraded during the G1 phase. Here we report that the human immunodeficiency virus type 1 (HIV-1) upregulates Survivin expression via survivin promoter transactivation. Vpr, an HIV-1 accessory protein that induces cell cycle arrest in G2/M, is necessary and sufficient for this effect. Blocking Vpr-induced G2/M arrest leads to elimination of the survivin promoter transactivation by Vpr. Our results suggest that Survivin may be actively involved in regulating cell viability during HIV-1 infection. 相似文献
7.
Cassy Spiller Dagmar Wilhelm Peter Koopman 《Biology of the cell / under the auspices of the European Cell Biology Organization》2009,101(10):587-598
Background information. Primordial germ cells in developing male and female gonads are responsive to somatic cell cues that direct their sex‐specific differentiation into functional gametes. The first divergence of the male and female pathways is a change in cell cycle state observed from 12.5 dpc (days post coitum) in mice. At this time XY and XX germ cells cease mitotic division and enter G1/G0 arrest and meiosis prophase I respectively. Aberrant cell cycle regulation at this time can lead to disrupted ovarian development, germ cell apoptosis, reduced fertility and/or the formation of germ cell tumours. Results. In order to unravel the mechanisms utilized by germ cells to achieve and maintain the correct cell cycle states, we analysed the expression of a large number of cell cycle genes in purified germ cells across the crucial time of sex differentiation. Our results revealed common signalling for both XX and XY germ cell survival involving calcium signalling. A robust mechanism for apoptosis and checkpoint control was observed in XY germ cells, characterized by p53 and Atm (ataxia telangiectasia mutated) expression. Additionally, a member of the retinoblastoma family and p21 were identified, linking these factors to XY germ cell G1/G0 arrest. Lastly, in XX germ cells we observed a down‐regulation of genes involved in both G1‐ and G2‐phases of the cell cycle consistent with their entry into meiosis. Conclusion. The present study has provided a detailed analysis of cell cycle gene expression during fetal germ cell development and identified candidate factors warranting further investigation in order to understand cases of aberrant cell cycle control in these specialized cells. 相似文献
8.
To date two inhibitors of epidermal cell proliferation have been characterized: (1) a factor which depresses DNA synthesis, and (2) a factor which depresses mitotic rate. In the absence of experimental proof it has been assumed that the respective targets for these purified inhibitory factors are in G1 and G2 phases of the cell cycle. In the experiments reported here both these fractions were subjected to cell cycle phase specificity tests in order to verify these assumptions. In addition, an epidermally derived “cell line” (the sebaceous gland) and two nonectodermal tissues were examined for a response. The results suggest that the response induced by the inhibitor of DNA synthesis is cell cycle phase-specific, that the target cells are at the G1-S phase boundary, and that only epidermal cells respond. Similarly the factor which depresses the flow of cells from G2 into mitosis had no measurable effect on DNA synthesis by any of the tissues tested. The G2 inhibitor lacks an inhibitory effect on mitosis in the sebaceous gland.The physiological roles which epidermal chalones may play are briefly discussed. It is suggested that a G1–G2 chalone system may have been effective in isolating kinetically cell populations with modified function during the evolutionary development in the vertebrates. 相似文献
9.
Tehranian N Sepehri H Mehdipour P Biramijamal F Hossein-Nezhad A Sarrafnejad A Hajizadeh E 《Cell biology international》2012,36(7):601-610
The effect of PectaSol on Dox (Doxorubicin) cytotoxicity in terms of apoptosis and cell cycle changes in PCa (prostate cancer) cell lines (DU‐145 and LNCaP) has been investigated. Combination of PectaSol and Dox resulted in a viability of 29.4 and 32.6% (P<0.001) in DU‐145 and LNCaP cells. The IC50 values decreased 1.5‐fold and 1.3‐fold in the DU‐145 and LNCaP cells respectively. In the DU‐145 cells, combination of PectaSol and Dox resulted in a reduction in p27 gene and protein expression (P<0.001). In LNCaP cells, this combination increased p53, p27 and Bcl‐2 expression. Treatment with both drugs in DU‐145 cells led to an increase in sub‐G1 arrest (54.6% compared with 12.2% in Dox). In LNCaP cells, combination of the drugs led to an increased in G2/M arrest (61.7% compared with 53.6% in Dox). Based on these findings, progressive cytotoxicity effect of Dox and PectaSol together rapidly induce cell death in DU‐145 through apoptosis and in LNCaP cells through cell cycle arrest (G2/M arrest). 相似文献
10.
Anti-proliferative and apoptotic effects of oleuropein and hydroxytyrosol on human breast cancer MCF-7 cells 总被引:1,自引:0,他引:1
Olive oil intake has been shown to induce significant levels of apoptosis in various cancer cells. These anti-cancer properties
are thought to be mediated by phenolic compounds present in olive. These beneficial health effects of olive have been attributed,
at least in part, to the presence of oleuropein and hydroxytyrosol. In this study, oleuropein and hydroxytyrosol, major phenolic
compound of olive oil, was studied for its effects on growth in MCF-7 human breast cancer cells using assays for proliferation
(MTT assay), cell viability (Guava ViaCount assay), cell apoptosis, cellcycle (flow cytometry). Oleuropein or hydroxytyrosol
decreased cell viability, inhibited cell proliferation, and induced cell apoptosis in MCF-7 cells. Result of MTT assay showed
that 200 μg/mL of oleuropein or 50 μg/mL of hydroxytyrosol remarkably reduced cell viability of MCF-7 cells. Oleuropein or
hydroxytyrosol decrease of the number of MCF-7 cells by inhibiting the rate of cell proliferation and inducing cell apoptosis.
Also hydroxytyrosol and oleuropein exhibited statistically significant block of G1 to S phase transition manifested by the increase of cell number in G0/G1 phase. 相似文献
11.
Ye Yuan Kiho Lee Kwang-Wook Park Lee Spate Randall S. Prather Kevin Wells 《Cell cycle (Georgetown, Tex.)》2014,13(8):1265-1276
Nuclear transfer (NT) from porcine iPSC to create cloned piglets is unusually inefficient. Here we examined whether such failure might be related to the cell cycle stage of donor nuclei. Porcine iPSC, derived here from the inner cell mass of blastocysts, have a prolonged S phase and are highly sensitive to drugs normally used for synchronization. However, a double-blocking procedure with 0.3 μM aphidicolin for 10 h followed by 20 ng/ml nocodazole for 4 h arrested 94.3% of the cells at G2/M and, after release from the block, provided 70.1% cells in the subsequent G1 phase without causing any significant loss of cell viability or pluripotent phenotype. Nuclei from different cell cycle stages were used as donors for NT to in vitro-matured metaphase II oocytes. G2/M nuclei were more efficient than either G1 and S stage nuclei in undergoing first cleavage and in producing blastocysts, but all groups had a high incidence of chromosomal/nuclear abnormalities at 2 h and 6 h compared with non-synchronized NT controls from fetal fibroblasts. Many G2 embryos extruded a pseudo-second polar body soon after NT and, at blastocyst, tended to be either polyploid or diploid. By contrast, the few G1 blastocysts that developed were usually mosaic or aneuploid. The poor developmental potential of G1 nuclei may relate to lack of a G1/S check point, as the cells become active in DNA synthesis shortly after exit from mitosis. Together, these data provide at least a partial explanation for the almost complete failure to produce cloned piglets from piPSC. 相似文献
12.
Accumulation patterns of mRNAs corresponding to histones H2A and H4, ribosomal protein genes rpL27 and rpL34, MAP kinase, cdc2 kinase and cyclin B were analyzed during growth-dormancy cycles in pea (Pisum sativum cv. Alaska) axillary buds. The level of each of these mRNAs was low in dormant buds on intact plants, increased when buds were stimulated to grow by decapitating the terminal bud, decreased when buds ceased growing and became dormant, and then increased when buds began to grow again. Flow cytometry was used to determine nuclear DNA content during these developmental transitions. Dormant buds contain G1 and G2 nuclei (about 3:1 ratio), but only low levels of S phase nuclei. It is hypothesized that cells in dormant buds are arrested at three points in the cell cycle, in mid-G1, at the G1/S boundary and near the S/G2 boundary. Based on the accumulation of histone H2A and H4 mRNAs, which are markers for S phase, cells arrested at the G1/S boundary enter S within one hour of decaptitation. The presence of a cell population arrested in mid-G1 is indicated by a second peak of histone mRNA accumulation 6 h after the first peak. Based on the accumulation of cyclin B mRNA, a marker for late G2 and mitosis, cells arrested at G1/S begin to divide between 12 and 18 h after decapitation. A small increase in the level of cyclin B mRNA at 6 h after decapitation may represent mitosis of the cells that had been arrested near the S/G2 boundary. Accumulation of MAP kinase, cdc2 kinase, rpL27 and rpL34 mRNAs are correlated with cell proliferation but not with a particular phase of the cell cycle. 相似文献
13.
To investigate the mechanism by which nitric oxide (NO) induces cell death in colon cancer cells, we compared two types of colon cancer cells with different p53 status: HCT116 (p53 wild-type) cells and SW620 (p53-deficient) cells. We found that S-nitrosoglutathione (GSNO), the NO donor, induced apoptosis in both types of colon cancer cells. However, SW620 cells were much more susceptible than HCT116 cells to apoptotic death by NO. We investigated the role of extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 kinase on NO-induced apoptosis in both types of colon cancer cells. GSNO treatment effectively stimulated activation of the ERK1/2 and p38 kinase in both types of cells. In HCT116 cells, pretreatment with PD98059, an inhibitor of ERK1/2, or SB203580, an inhibitor of p38 kinase, had no marked effect on GSNO-induced apoptosis. However, in SW620 cells, SB203580 significantly reduced the NO-induced apoptosis, whereas PD098059 increases NO-induced apoptosis. Furthermore, we found evidence of cell cycle arrest of the G0/G1 phase in SW620 cells but not in HCT116 cells. Inhibition of ERK1/2 with PD098059, or of p38 kinase with SB203580, reduced the GSNO-induced cell cycle arrest of the G0/G1 phase in SW620 cells. We therefore conclude that NO-induced apoptosis in colon cancer cells is mediated by a p53-independent mechanism and that the pathways of ERK1/2 and p38 kinase are important in NO-induced apoptosis and in the cell cycle arrest of the G0/G1 phase. 相似文献
14.
The proliferation of normal non-tumourigenic mouse fibroblasts is stringently controlled by regulatory mechanisms located in the postmitotic stage of G1 (which we have designated G1 pm). Upon exposure to growth factor depletion or a lowered de novo protein synthesis, the normal cells leave the cell cycle from G1 pm and enter G0. The G1 pm phase is characterized by a remarkably constant length (the duration of which is 3 h in Swiss 3T3 cells), whereas the intercellular variability of intermitotic time is mainly ascribable to late G1 or pre S phase (G1 ps) (Zetterberg & Larsson (1985) Proc. Natl. Acad. Sci. USA 82 , 5365). As shown in the present study two tumour-transformed derivatives of mouse fibroblasts, i.e. BPA31 and SVA31, did not respond at all, or only responded partially, respectively, to serum depletion and inhibition of protein synthesis. If the tumour cells instead were subjected to 25-hydroxycholesterol (an inhibitor of 3-hydroxy-3 methyglutaryl coenzyme A reductase activity), their growth was blocked as measured by growth curves and [3H]-thymidine uptake. Time-lapse analysis revealed that the cells were blocked specifically in early G1 (3-4h after mitosis), and DNA cytometry confirmed that the arrested cells contained a G1 amount of DNA. Closer kinetic analysis revealed that the duration of the postmitotic phase containing cells responsive to 25-hydroxycholesterol was constant. These data suggest that transformed 3T3 cells also contain a ‘G1 pm program’, which has to be completed before commitment to mitosis. By repeating the experiments on a large number of tumour-transformed cells, including human carcinoma cells and glioma cells, it was demonstrated that all of them possessed a G1 pm-like stage. Our conclusion is that G1 pm is a general phenomenon in mammalian cells, independent of whether the cells are normal or neoplastic. 相似文献
15.
Cultures of Euglena gracilis (strain Z from French CNRS collection) can be made cadmium resistant if grown in a medium with 5x10-4M cadmium chloride. This resistance is reflected by the appearance of a second exponential growth phase. The development of this resistance was studied at the cellular level by determining the relative content of DNA at different stages of the cell cycle in an asynchronously grown culture. The culture was followed until the second, cadmium resistant, growth phase had reached its stationary state. During the first exponential growth phase, cells were mostly in the late period of DNA synthesis (stage S of the cell cycle), or in the gap preceding mitosis (stage G2 of the cell cycle). In addition, some cells contained high multiples of the normal amount of DNA. In the beginning of the second exponential growth phase, a few cells were again in G1 (the post mitotic stage of the cell cycle preceding DNA synthesis). These G1 cells were predominant at the end of the second growth period. During the second stationary phase the DNA content of the cadmium treated cells was similar to the stationary phase of the control culture. Cells had stopped growing in G1 with an unreplicated genome. The implications of these data are discussed. 相似文献
16.
Barsukova A. S. Fedorova N. E. Medzhidova A. A. Zatsepina O. V. Kushch A. A. 《Russian Journal of Developmental Biology》2001,32(1):24-28
The effect of the cytomegalovirus on the cell cycle was studied autoradiographically in an asynchronous culture of human diploid fibroblasts. The analysis of labeled mitosis showed that some cells infected in the S phase ceased to progress through the cell cycle at one of its phases (S, G
2, or M); at the same time, at least part of the infected cells remained capable of entering mitosis. Beginning from day 2 after infection by cytomegalovirus, the accumulation of pathological mitotic cells blocked at metaphase was observed in the culture. Approximately 50% of these cells contained 3H-thymidine label above chromosomes. This suggested the possibility of pathological mitosis in cells that were infected both at the S and other phases of the cell cycle. The detailed morphological analysis of chromosomes at different stages of infection demonstrated that the degree of their morphological changes increases from slight (stronger condensation) to severe pathology (fragmentation). In the aggregate, the results of the study suggested that abnormal chromosome morphology resulted from irreversible cell division arrest under the effect of the cytomegalovirus. 相似文献
17.
Stephen C. Cosenza Gladys Yumet Dianne Robert Soprano Kenneth J. Soprano 《Journal of cellular biochemistry》1994,55(4):503-512
The proto-oncogenes c-fos and c-jun have been shown in numerous model systems to be induced within minutes of growth factor stimulation, during the G0/G1 transition. In this report we use the mitotic shake-off procedure to generate a population of highly synchronized Swiss 3T3 cells. We show that both of these immediate-early, competence genes are also induced during the M/G1 transition, immediately after completion of mitosis. While c-fos mRNA levels drop to undetectable levels within 2 hr after division, c-jun mRNA levels are maintained at a basal level which is ~ 30% maximum throughout the remainder of G1. In order to access the functional significance of these patterns of c-fos and c-jun expression, antisense oligodeoxynucleotides specific to c-fos or c-jun were added to either actively growing Swiss 3T3 cells or mitotically synchronized cells, and their ability to inhibit DNA synthesis and cell division determined. Our results show that treatment of Swiss 3T3 cells with either c-fos or c-jun antisense oligodeoxynucleotides, while actively growing, during mitosis, or in early G1, results in a reduction in ability to enter S and subsequently divide. This was also true if Swiss 3T3 cells were treated during mid-G1 with c-jun antisense oligodeoxynucleotides. These results demonstrate that the regulation of G1 progression following mitosis is dependent upon the expression and function of the immediate-early, competence proto-oncogenes c-fos and c-jun. © 1994 Wiley-Liss, Inc. 相似文献
18.
Kazuhiro Nomura Takao Hoshino Kathy Knebel Marvin Barker 《In vitro cellular & developmental biology. Plant》1978,14(2):174-179
Summary Autoradiographic and flow microfluorometry analyses have been applied to a study of perturbed cell kinetics in 9L rat brain
tumor cells treated with dibutyryl cyclic AMP and theophylline alone and in combination in vitro. At a concentration of 1
mM each, cell growth ceased shortly after the administration of these drugs. The results indicate that cells in S and G2 phase at the time of drug administration can undergo mitosis even though a considerable prolongation of G2 phase was apparent. However, cells in G1 at the time of drug administration were arrested in that phase whereas those cells in S or G2 were able to complete one mitosis before becoming arrested in the G1 phase. This blocking effect was reversible, and cells resumed proliferation at a normal rate shortly after the removal of
these drugs.
This work was supported in part by NIH Cancer Research Center Grant CA-13525 and CA-19992 from NCI, and by the Association
for Brain Tumor Research.
Presented at the 6th International Cell Cycle Conference, March, 1976, New Orleans, Louisiana.
The tumor used in this study was provided by William H. Sweet, Paul T. Kornblith, Janette L. Messer and Beverly O. Whitman
of the Massachusetts General Hospital, Boston, Massachusetts. 相似文献
19.
Shinji Miwa Shuya Yano Hiroaki Kimura Mako Yamamoto Makoto Toneri Takashi Murakami Katsuhiro Hayashi Norio Yamamoto Toshiyoshi Fujiwara Hiroyuki Tsuchiya Robert M Hoffman 《Cell cycle (Georgetown, Tex.)》2015,14(12):1932-1937
The present study analyzed the heterogeneous cell-cycle dependence and fate of single cancer cells in a population treated with UVB using a fluorescence ubiquitination-based cell-cycle (FUCCI) imaging system. HeLa cells expressing FUCCI were irradiated by 100 or 200 J/m2 UVB. Modulation of the cell-cycle and apoptosis were observed by time-lapse confocal microscopy imaging every 30 min for 72 h. Correlation between cell survival and factors including cell-cycle phase at the time of the irradiation of UVB, mitosis and the G1/S transition were analyzed using the Kaplan–Meier method along with the log rank test. Time-lapse FUCCI imaging of HeLa cells demonstrated that UVB irradiation induced cell-cycle arrest in S/G2/M phase in the majority of the cells. The cells irradiated by 100 or 200 J/m2 UVB during G0/G1 phase had a higher survival rate than the cells irradiated during S/G2/M phase. A minority of cells could escape S/G2/M arrest and undergo mitosis which significantly correlated with decreased survival of the cells. In contrast, G1/S transition significantly correlated with increased survival of the cells after UVB irradiation. UVB at 200 J/m2 resulted in a greater number of apoptotic cells. 相似文献
20.
Intracellular degradation of collagen by phagocytosis in fibroblasts is essential for physiological remodeling of the extracellular matrix in a wide variety of connective tissues but imbalances between degradation and synthesis can lead to loss of tissue collagen. As aging is associated with loss of dermal and periodontal collagen and with increased lysomomal enzyme content in fibroblasts, we examined the regulation of collagen phagocytosis by integrin expression and the cell cycle in anin vitrofibroblast aging model. Two different fibroblast lines (CL1; CL2) at the fourth subculture were passaged up to replicative senescence to model aging processesin vitro.Cells were incubated with collagen-coated or BSA-coated green fluorescent beads for 3 h to assess α2β1-integrin-mediated or nonspecific phagocytosis, respectively. Single-cell suspensions were stained with DAPI and sulforhodamine 101 to separate cycling G1and noncycling G0cells. Staining for α2-integrin, bead internalization, and bivariate analyses of DNA/protein content were measured by three-color flow cytometry. Serum deprivation was used to induce increases in the proportion of G0cells. For G1cells, the proportion of collagen phagocytic cells was >50% for all passages and collagen beads were internalized >5-fold more frequently than BSA beads. In contrast, G0cells with diploid DNA content but low protein content exhibited greatly reduced phagocytic capacity (<10% of cells internalized collagen or BSA beads), the number of beads per cells was 4-fold less, and α2integrin expression was very low compared to G1cells. The proportion of collagen phagocytic cells and the proportion of α2-integrin-positive cells increased with transit through the cell cycle. At higher passage numbers mean cell volume and cytoplasmic granularity were reduced 30% but at replicative senescence cells with large surface area and subdiploid DNA predominated. The proportion of collagen and BSA phagocytic G1cells increased 1.5- and 5-fold, respectively, and the number of beads per cell increased <3-fold. However, surface α2-integrin staining remained unchanged. These data indicate that the collagen and nonspecific internalization pathways were greatly upregulated, independent of cell cycle phase, and that cellular agingin vitrostrongly influences the specificity and rate of phagocytic processes in fibroblasts. We suggest that age-related loss of collagen in connective tissues undergoing turnover may be a manifestation of a deregulated increase of collagen phagocytosis in which the net loss of degraded collagen exceeds new synthesis. 相似文献