The effect of post-treatment with caffeine on survival and UV-induced mutation frequencies in Chinese hamster and mouse lymphoma cells in vitro

The effect of post-treatment with caffeine on the survival of a number of cell lines after UV-irradiation has been studied. The mouse lymphoma cell lines P388 and L5178YS were sensitized by caffeine but only after UV doses of 50 erg/mm² and above. V79 cells also showed sensitization by caffeine but CHO cells and two cell lines YS and YR derived from Yoshida sarcoma of rats, sensitive and resistant to UV radiation, respectively, showed no effect.P388 and V79 cells were both mutable by UV, and caffeine, when studied at a single expression time (42–48 h) and at a single dose level (0.5 M and 0.75 M, respectively) suppressed the UV-induced mutation frequency in both cell lines. L51788YS cells although sensitized by caffeine showed no increase in frequency of thymidine-resistant (TdR^r) colonies when irradiated with UV.On more detaled examination, caffeine was found to delay the expression of UV-induced mutations inV79 cells, and the delay was dependent on the dose of caffine used. The effect on expression time was less when caffeine was present 0–48 h than when it was present throughout the post-irradiation incubation period. Similar results were obtained in P388 cells.The data are discussed in relation to those of other workers and to the concept that caffeine inhibits an error prone post-replication repair process in mammalian cells     

Trifluoperazine stimulates ionizing radiation induced cell killing through inhibition of DNA repair

The effect of trifluoperazine (TFP), a phenothiazine derivative antipsychotic drug, on ionizing radiation (IR) induced cell killing through inhibition of DNA repair was investigated in human cell lines. In clonogenic survival assay, TFP augmented IR induced cell killing. Also, TFP enhanced micronucleus formation in irradiated human lymphocytes. The effect of TFP and other known DNA repair inhibitors like wortmannin and caffeine, on irradiated cells, was compared by MTT assay. On the other hand, TFP failed to increase the toxicity induced by H2O2. Repair of DNA double strand breaks induced by IR was markedly inhibited by TFP, as determined by field inversion gel electrophoresis (FIGE). Further, TFP increased radiation induced apoptosis, which was accompanied by enhanced G2/M arrest. Thus, our results strongly suggest that TFP inhibits repair of DNA damage induced by IR, which significantly implicates the possibility of using TFP as an adjuvant to radiotherapy.     

Frequency of sister chromatid exchanges in human peripheral blood lymphocyte cultures after exposure to the combined action of gamma-irradiation in phase Go and caffeine

Keeping of human peripheral blood lymphocytes, irradiated in vitro with 60Co-gamma-quanta at a dose of 3 Gy at G0 phase, with caffeine of 16 and 160 micrograms/ml during cultivation with PHA had no appreciable influence on the frequency of sister chromatid exchanges. A minor increase in the number of sister chromatid exchanges was only noted when non-irradiated and irradiated lymphocytes were cultured with 160 micrograms/ml caffeine.     

The influence of caffeine on the mitomycin C-induced chromosome aberration frequency in normal human and xeroderma pigmentosum cells

The clastogenic effect of mitomycin C (MC) was determined in two normal fibroblast cell lines and two xeroderma pigmentosum (XP) cell lines, a variant and a group A excision-deficient line. The group A xeroderma cell line was substantially more sensitive to MC than either the XP variant or the normal human cells. On caffeine post-treatment potentiation of the MC-induced aberration frequency occurred in all the cell lines. The XP varian cell line exhibited a distinctly higher sensitivity to caffeine than the classical XP or the normal human cell lines.     

Caffeine eliminates gamma-ray-induced G2-phase delay in human tumor cells but not in normal cells.

It has been known for many years that caffeine reduces or eliminates the G2-phase cell cycle delay normally seen in human HeLa cells or Chinese hamster ovary (CHO) cells after exposure to X or gamma rays. In light of our recent demonstration of a consistent difference between human normal and tumor cells in a G2-phase checkpoint response in the presence of microtubule-active drugs, we examined the effect of caffeine on the G2-phase delays after exposure to gamma rays for cells of three human normal cell lines (GM2149, GM4626, AG1522) and three human tumor cell lines (HeLa, MCF7, OVGI). The G2-phase delays after a dose of 1 Gy were similar for all six cell lines. In agreement with the above-mentioned reports for HeLa and CHO cells, we also observed that the G2-phase delays were eliminated by caffeine in the tumor cell lines. In sharp contrast, caffeine did not eliminate or even reduce the gamma-ray-induced G2-phase delays in any of the human normal cell lines. Since caffeine has several effects in cells, including the inhibition of cAMP and cGMP phosphodiesterases, as well as causing a release of Ca(++) from intracellular stores, we evaluated the effects of other drugs affecting these processes on radiation-induced G2-phase delays in the tumor cell lines. Drugs that inhibit cAMP or cGMP phosphodiesterases did not eliminate the radiation-induced G2-phase delay either separately or in combination. The ability of caffeine to eliminate radiation-induced G2-phase delay was, however, partially reduced by ryanodine and eliminated by thapsigargin, both of which can modulate intracellular calcium, but by different mechanisms. To determine if caffeine was acting through the release of calcium from intracellular stores, calcium was monitored in living cells using a fluorescent calcium indicator, furaII, before and after the addition of caffeine. No calcium release was seen after the addition of caffeine in either OVGI tumor cells or GM2149 normal cells, even though a large calcium release was measured in parallel experiments with ciliary neurons. Thus it is likely that caffeine is eliminating the radiation-induced G2-phase delay through a Ca(++)-independent mechanism, such as the inhibition of a cell cycle-regulating kinase.     

Replicative bypass repair of ultraviolet damage to DNA of mammalian cells: Caffeine sensitive and caffeine resistant mechanisms

Replicative bypass repair of UV damage to DNA was studied in wide variety of human, mouse and hamster cells in culture. Survival curve analysis revealed that in established cell lines (mouse L, Chinese hamster V79, HeLa S3 and SV40-transformed xeroderma pigmentosum (XP)), post-UV caffeine treatment potentiated cell killing by reducing the extrapolation number and mean lethal UV fluence (Do). In the Do reduction as the result of random inactivation by caffeine of sensitive repair there were marked clonal differences among such cell lines, V79 being most sensitive to caffeine potentiation. However, other diploid cell lines (normal human, excision-defective XP and Syrian hamster) exhibited no obvious reduction in Do by caffeine. In parallel, alkaline sucrose sedimentation results showed that the conversion of initially smaller segments of DNA synthetized after irradiation with 10 J/m² to high-molecular-weight DNA was inhibited by caffeine in transformed XP cells, but not in the diploid human cell lines. Exceptionall, diploid XP variants had a retarded ability of bypass repair which was drastically prevented by caffeine, so that caffeine enhanced the lethal effect of UV. Neutral CsCl study on the bypass repair mechanism by use of bromodeoxyuridine for DNA synthesis on damaged template suggests that the pyrimidine dimer acts as a block to replication and subsequently it is circumvented presumably by a new process involving replicative bypassing following strand displacement, rather than by gap-filling de novo. This mechanism worked similarly in normal and XP cells, whether or not caffeine was present, indicating that excision of dimer is not always necessary. However, replicative became defective in XP variant and transformed XP cells when caffeine was present. It appears, therefore, that the replicative bypass repair process is either caffeine resistant or sensitive, depending on the cell type used, but not necessarily on the excision repair capability.     

Effect of caffeine on gamma-ray-induced G2 delay in ataxia telangiectasia

Exposure of normal control and ataxia-telangiectasia (A-T) lymphoblastoid cell lines to ionizing radiation gives rise to an increase in the proportion of G2 phase cells. The size and extent of the G2 phase block is greater in A-T cells than in normal cells. Caffeine has a similar overall effect in control and A-T cell lines in reducing the G2 arrest observed after ionizing radiation. While the proportion of cells accumulated in G2 in A-T cells is considerably greater than in controls, addition of caffeine at the time of maximal G2 block brings about a return of G2 phase cell numbers to unirradiated values in 3 hours in both cell types. In normal control cells the caffeine-mediated decrease in G2 cells is reflected by an increase in mitotic cells. These mitotic cells have a higher frequency of chromosome aberrations compared to cells harvested in the absence of caffeine. Similarly in A-T cells addition of caffeine to irradiated cultures, delayed in G2 phase, increased the number of mitotic cells and the frequency of chromosome aberrations.     

Characterization of the enhancing effect of caffeine on sister-chromatid exchanges induced by ultraviolet radiation in excision-proficient xeroderma pigmentosum lymphoblastoid cells

Cells of some excision-proficient xeroderma pigmentosum (XP) cell lines are highly sensitive to post-UV caffeine treatment in terms of sister-chromatid exchange (SCE) induction as well as cell lethality. In the present study, we conducted a detailed investigation of the enhancing effect of caffeine on SCE frequency induced by UV in excision-proficient XP cells, and obtained the following results. (1) Continuous post-UV treatment with 1 mM caffeine markedly enhances UV-induced SCEs and such enhanced SCEs occur with similar frequency during either the 1st or the 2nd cell cycle in the presence of caffeine and 5-bromodeoxyuridine (BrdUrd). (2) The high sensitivity of the cells to post-UV caffeine treatment persists for at least 2 days after UV when irradiated cells are held in either the proliferating or the nonproliferating state prior to the addition of BrdUrd. (3) Caffeine exerts its effect on cells in S phase. (4) Neither BrdUrd in the medium nor the incorporated 5-bromodeoxyuridine monophosphate (BrdUMP) in DNA plays an appreciable role in the expression of the enhancing effect of caffeine. The most likely explanation for our findings is as follows. In excision-proficient XP cells, the cause of SCE formation such as UV-induced lesions or resulting perturbations of DNA replication persists until the 2nd round or more of post-UV DNA replication. If caffeine is given as post-UV treatment, such abnormalities may be amplified, resulting in a synergistic increase in SCE frequency.     

Angiogenesis-inducing ability of human bladder epithelium cell lines and "spontaneously" transformed murine fibroblasts

Ten human bladder epithelium cell lines were tested for their ability to induce blood vessel formation after intradermal injection into irradiated ST/a mice. Cell lines that were shown to be tumorigenic in nude mice, were able to evoke angiogenesis of a higher intensity than nontumorigenic cell lines. No difference was observed between the angiogeneic ability of tumorigenic cells originating from tumors and from in vitro transformed urothelium of nontumor origin. Similarly the origin of nontumorigenic urothelial cell lines did not show any influence on their angiogeneic abilities, but nontumorigenic cell lines which had undergone "infinite growth transformation" exhibited a higher angiogeneic activity than nontumorigenic cell lines with a finite life. The angiogeneic reaction evoked by human bladder epithelium cell lines showed cell dose- and time-dependence; but it was unrelated to the growth potential of the cultured cells. Two "spontaneously" altered sarcoma-producing murine cell lines showed a higher angiogeneic activity than tumorigenic human bladder epithelial cells. The angiogeneic response to these two murine cell lines was unrelated to morphological signs of transformation and to differences in growth rate, serum requirement, saturation density, anchorage dependence, and isoimmunizing properties.     

咖啡因抑制辐照区和旁区细胞的γ-H2AX foci的形成

辐射诱导的旁效应不仅在体外实验存在,也在动物体内存在,这对辐射剂量的计算和辐射风险的评估有重要影响。咖啡因是一个模式辐射敏感剂,显著增强辐射的细胞毒性。咖啡因也显著增强辐射诱导的旁效应,咖啡因处理使未受辐照的旁细胞对损伤信号更加敏感,但其机理并不清楚。在正常人原代细胞AG1522中,分析了咖啡因处理对组蛋白H2AX磷酸化的影响,咖啡因显著减少α粒子辐射区和旁区γ-H2AX foci阳性细胞的比率和每个细胞γ-H2AX foci点数,表明咖啡因处理抑制了H2AX磷酸化,后者启动细胞对DNA双链断裂的修复,从而提示咖啡因增强辐射旁效应可能的机理,对辐射治疗具有重要意义。     

The effect of caffeine posttreatment of X-ray-induced chromosomal aberrations in human blood lymphocytes in vitro

Summary The potentiating effect of caffeine on X-ray-induced chromosomal aberrations in human blood lymphocytes has been investigated, with special reference to cell cycle stages (G0 and G2). Both quantitative and qualitative differences in the yield of chromosomal aberrations were detected in caffeine-posttreated cells, depending on the cell stage irradiated. The studies on caffeine potentiating effects on X-irradiated G0 lymphocytes from normal adults, newborns, Down syndrome patients, and an ataxia telangiectasia patient pointed to interindividual variations in the response to caffeine potentiation among normal probands and a very profound effect in ataxia cells.     

On the identity of the damage expressed by treatment of X-irradiated HeLa cells with different agents

To determine whether different agents that enhance the expression of potentially lethal X-ray damage (PLD) interact with the same or different lesions (or spectrum of lesions), cell killing was measured in three kinds of experiments: (1) When cells were irradiated in G1 phase and treated with caffeine or hydroxyurea at concentrations that yield maximal response, the same survival plateaus were reached. (2) Treatment of cells irradiated in G1 phase either with caffeine or with hydroxyurea so as to yield survival levels that differed twofold after 4 h incubation, followed by treatment with caffeine to allow expression of PLD in G2 phase, resulted eventually in the same level of survival. (3) When cells were irradiated and treated with caffeine, hydroxyurea, or 9-beta-D-arabinofuranosyladenine (araA) after progressively longer delays, to trace the time course of recovery from the PLD, the responses obtained with caffeine and araA were similar; sensitivity to hydroxyurea was lost more rapidly. The results are consistent with the possibility that these three agents interact with the same lesions, but that different steps in the repair process are inhibited by caffeine or araA than by hydroxyurea.     

Cell cycle age dependence for radiation-induced G2 arrest: evidence for time-dependent repair

Exponentially growing eucaryotic cells, irradiated in interphase, are delayed in progression to mitosis chiefly by arrest in G2. The sensitivity of Chinese hamster ovary cells to G2-arrest induction by X rays increases through the cell cycle, up to the X-ray transition point (TP) in G2. This age response can be explained by cell cycle age-dependent changes in susceptibility of the target(s) for G2 arrest and/or by changes in capability for postirradiation recovery from G2-arrest damage. Discrimination between sensitivity changes and repair phenomena is possible only if the level of G2-arrest-causing damage sustained by a cell at the time of irradiation and the level ultimately expressed as arrest can be determined. The ability of caffeine to ameliorate radiation-induced G2 arrest, while inhibiting repair of G2-arrest-causing damage makes such an analysis possible. CHO cell monolayers were irradiated (1.5 Gy), then exposed to 5 mM caffeine for periods of 0-10 hr. Cell progression was monitored by the mitotic cell selection procedure. In the presence of caffeine, progression of irradiated cells was relatively unperturbed, but on caffeine removal, G2 arrest was expressed. The duration of G2 arrest was independent of the length of the prior caffeine exposure and, since cells of all ages were ultimately examined, the duration of arrest was also independent of cell cycle age at the time of irradiation. This finding indicates that the target for G2-arrest induction is present throughout the cell cycle and that the level of G2-arrest damage incurred is initially constant for all cell cycle phases. The data are consistent with the existence of a time-dependent recovery mechanism to explain the age dependence for radiation induction of G2 arrest.     

The action of caffeine on X-irradiated HeLa cells. VII. Evidence that caffeine enhances expression of potentially lethal radiation damage

HeLa cells irradiated with 2 Gy of 220-kV X rays suffer a 60-70% loss of colony-forming ability which is increased to 90% by postirradiation treatment with 10 mM caffeine for 6 hr. The detailed postirradiation patterns of cell death and sister-cell fusion in such cultures and in cultures in which the colony-forming ability was brought to about the same level by treatment with a larger (4 Gy) X-ray dose alone or by longer (48 hr) treatment with 10 mM caffeine alone were recorded by time-lapse cinemicrography. Because the patterns of cell death and fusion differ radically in irradiated and in caffeine-treated cultures, the response of the additional cells killed by the combined treatment can be identified as X-ray induced rather than caffeine induced. The appearance of cultures after several days of incubation confirms the similarity of the post-treatment patterns of proliferation in cultures suffering enhanced killing to those occurring in cultures treated with larger doses of X rays alone. It is concluded that X rays do not sensitize cells to caffeine, but rather that caffeine enhances the expression of potentially lethal radiation-induced damage.     

The stability and maturation of the H2A histone mRNAs from Trypanosoma cruzi are implicated in their post-transcriptional regulation

The toxicity of the five methylxanthine derivatives, caffeine, pentoxifylline, A802710, propentofylline and A802715, was determined against the two human melanoma lines, Be11 and MeWo, and against the two human squamous cell carcinoma lines, 4197 and 4451, by vital dye staining assay. Pentoxifylline and A802710 emerge as the least toxic showing TD(50) (toxic dose of 50%) levels of 3.0-4.0 mM. Propentofylline and caffeine take an intermediate position. A802715 has a TD(50) of 0.9-1.1 mM and is the most toxic. Subtoxic concentrations (相似文献   

UV survival of human mycoplasmas: evidence of dark reactivation in Mycoplasma buccale.

The inactivation by ultraviolet (UV) light irradiation of mycoplasma cells of five human strains was monitored by investigating the colony-forming ability. The survival curves of five strains tested indicated that the cells of Mycoplasma buccale only are single and homogenously susceptible to UV light. The effect of the repair inhibitor, caffeine, on the colony-forming ability of UV-irradiated cells was investigated with M. buccale because of its homogenous susceptibility to UV light. The colony formation of irradiated cells was markedly depressed by post-irradiation treatment with caffeine at concentrations that had little or no effect on the colony formation of unirradiated cells. The colony-forming units (CFU) of UV-irradiated cells which were kept in broth without caffeine in the dark increased without a lag as the time in the dark increased. The colony-forming ability of the irradiated cells completely recovered after 3 hr in the dark. However, when irradiated cells were kept in the presence of caffeine, no increase in their CFU was observed. The mode of action of caffeine on UV-irradiated cells closely resembles that described for other organisms which possess dark reactivation systems for UV-induced damage in deoxyribonucleic acid (DNA). Thus, the results obtained provide evidence for the existence of a dark repair function in M. buccale.     

Suppression of apoptosis and clonogenic survival in irradiated human lymphoblasts with different TP53 status

The influence of radiation-induced apoptosis on radiosensitivity was studied in a set of closely related human lymphoblastoid cell lines differing in TP53 status. The clonogenic survival of irradiated TK6 cells (expressing wild-type TP53), WTK1 cells (overexpressing mutant TP53), and TK6E6 cells (negative for TP53 owing to transfection with HPV16 E6) was assessed in relation to the induction of apoptosis and its suppression by caspase inhibition or treatment with PMA as well as after treatment with caffeine. Measurements using the alkaline comet assay and pulsed-field electrophoresis of the induction and repair of DNA strand breaks showed similar kinetics of the processing of early DNA damage in these cell lines. The cytochalasin B micronucleus assay revealed identical levels of residual damage in the first postirradiation mitosis of these cells. Abrogation of TP53-dependent apoptosis in TK6E6 cells resulted in a distinct increase in radioresistance. Further suppression of apoptosis as observed in WTK1 cells overexpressing mutant TP53 apparently was not responsible for the high radioresistance of WTK1 cells, since other means of highly efficient suppression of apoptosis (caspase inhibition or PMA treatment) increased the clonogenic survival of irradiated TK6 cells only to levels similar to those of TK6E6 cells with abrogated TP53-dependent apoptosis. Considering the similar levels of residual chromosomal damage in TK6E6 cells and WTK1 cells, a hitherto unknown mechanism of tolerance needs to be inferred for these TP53 mutant cells. This residual damage tolerance, however, appears to require an intact G2/M-phase checkpoint function since the relative radioresistance of the WTK1 cells was completely lost upon caffeine treatment, which also resulted in a failure of the TK6 and TK6E6 cells to execute apoptosis. In this situation, the cellular response seems to be dominated entirely by TP53-independent mitotic failure.     

Arthritis by autoreactive T cell lines obtained from rats after injection of intestinal bacterial cell wall fragments.

T cell lines (B13, B19) were isolated from the lymph nodes of Lewis rats 12 days after an arthritogenic injection of cell wall fragments of Eubacterium aerofaciens (ECW), a major resident of the human intestinal flora. These cell wall fragments consist of peptidoglycan polysaccharide complexes (PPC). The cell lines that bear the helper phenotype were arthritogenic in knee or ankle joints upon intravenous injection into irradiated Lewis recipients. B13 was, however, not arthritogenic in irradiated F344 recipients that are largely RT1 identical. The arthritis induced in the knee joints of the irradiated Lewis rats was clearly shown by a 99mtechnetium-pertechnetate scanning technique and was confirmed histologically. In vitro the cell lines showed a proliferative response after stimulation with syngeneic spleen cells alone. The proliferation was significantly higher when bacterial PPC, isolated in soluble form from normal feces or ileostomy fluid were added. Recognition by B13 appeared to be MHC class II restricted. These results show that autoreactive T cell lines can be isolated from rats after injection of bacterial cell wall antigens and that these cell lines can be arthritogenic. This suggests a role for autoreactive T cells in the induction of bacterial cell wall arthritis and might give a clue for the arthritogenic properties of the normal human intestinal flora.     

Embryonic stem cell lines derived from blastocysts by a simplified technique

We have isolated euploid, pluripotent stem cell lines directly from mouse blastocysts by a simple culture technique. Our method permits cell lines to be derived from individual embryos, without the use of ovariectomy, immunosurgery and conditioned medium. We cultured individual intact blastocysts in MicroTest plates on top of a feeder layer of lethally irradiated STO mouse fibroblasts in a 10-microliters volume of Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% fetal calf serum (FCS). The cell lines maintain a stable complement of 40 chromosomes, form embryoid bodies and differentiate both in culture and in solid tumors.