Effects of diethylstilbestrol on human natural killer cells in vitro

Exposure of human peripheral blood lymphocytes to diethylstilbestrol (DES) in vitro resulted in inhibition of Natural Killer (NK) cell activity. DES inhibited NK activity in a dose and time-dependent manner with maximal effect after an 18 h exposure time. Significant reduction in cytotoxicity was obtained at concentrations of DES equal to or above 1 microM. The DES-induced inhibition of NK activity was reversible and totally abrogated within 18 h of culture in the absence of DES. Studies at the single cell level revealed that DES impaired the lytic activity of NK cells without interfering with recognition of target cells. The presence of indomethacin or aspirin during exposure to DES completely reversed the DES-induced inhibition of NK activity, indicating that a product of the cyclooxygenase system mediated the suppression.     

Effects of cadmium on cytotoxic functions of human natural killer cells

The effect of cadmium (Cd²⁺) was studied on natural killer (NK) cell-mediated cytotoxicity as well as on antibody-dependent cellular cytotoxicity (ADCC) of human peripheral blood lymphocytes. The results show that cadmium chloride inhibits human NK and ADCC activities against K562 and Ab-coated P815 target cells in a dose- and time-dependent manner. Maximal inhibition (80–90%) was observed in the presence of 100 μ -cadmium chloride, and it does not appear to be due to toxic effects on effector cells. Purification of large granular lymphocytes by Percoll density gradient centrifugation suggests that Cd²⁺ acts directly on this cell population. No effects of Cd²⁺ could be found after pre-exposure of either effector or target cells separately. The inhibitory effect of Cd²⁺ was manifested only when effector and target cells were present simultaneously. The greatest inhibition of NK and ADCC activities occurred when cadmium chloride was added to the assay within the first 60 min, suggesting that an early event was affected by Cd²⁺. However, Cd²⁺ did not block effector-target conjugate formation or affect leucocyte function associated Ag-1 expression on effector cells. This indicates that an initial triggering of effector cells by target cells was required before Cd²⁺ could exert its effect. Cd²⁺-induced inhibition of cytotoxic functions of NK cells could be only partially prevented by increasing the external Ca²⁺ concentration or by adding Zn²⁺ to the culture medium.     

Effects of sodium nitrite on natural killer cells isolated from human peripheral blood

The effect of different concentrations (0, 0.1, 0.2, 0.4, and 0.8 mg/ml) of sodium nitrite on the anti-tumor activity of natural killer (NK) cells isolated from human peripheral blood was examined. Sodium nitrite induced significant inhibition (25.3-66.6%) of NK cell activity against WEHI-164 cells. This reduction in NK cell cytotoxicity was found to be partially due to inhibition of NK cell production of interferon-gamma (25.7-92.8%) and tumor necrosis factor-alpha (26.6 76.6%). In addition, exposure to sodium nitrite resulted in a significant decrease (17.5-81.1%) in proliferation of control and interleukin-2-stimulated NK cells. Furthermore, the release of granzyme A and N-acetyl-beta-D-glucosaminidase by NK cells was also decreased by 21.7-72.2% and 33.5-81.2%, respectively. Therefore, sodium nitrite is of environmental concern in view of its inhibitory effects on NK cell activity that might contribute to tumor promotion in vivo.     

Immunomodulative effects of aflatoxins and selenium on human natural killer cells

The possible immunomodulative effects of aflatoxin B1 and selenium (as sodium selenite) at concentrations lower than 5.10(-11) M or 0.05ppb and 10(-5) M, respectively on natural killer (NK) cells from healthy volunteers were evaluated by a 51Cr release natural killer assay. Aflatoxin B1 and selenium separately had an immunosuppressive effect on NK cell activity. When they were studied in combination, they caused a statistically significant increase of the cytotoxic activity of NK cells in the presence of the lowest concentrations of aflatoxin B1 (0.005ppb) and of sodium selenite (10(-8)M).     

Effect of dibutyltin on ATP levels in human natural killer cells

This study investigates the role that decreased ATP levels may play in dibutyltin (DBT)-induced decreases in the tumor-cell-lysing (lytic) function of natural killer (NK) cells. NK cells are a subset of lymphocytes capable of killing tumor cells, virally infected cells, and antibody coated cells. DBT is used as stabilizer in PVC plastics and has also been used as a deworming product in poultry. NK cells were exposed to various concentrations of DBT for 1 h, 24 h, 48 h, and 6 days before determining ATP levels and lytic function. ATP levels and lytic function were also determined in NK cells that were exposed to DBT for 1 h followed by 24 h, 48 h, and 6 days in DBT-free media. The results indicated that exposure of NK cells to 10 muM DBT for 1 h did not cause any significant decrease in NK cell ATP levels but did cause a very significant loss in lytic function. NK cells exposed to 500 nM DBT for 24 h showed significant loss of lytic function but showed no decrease in ATP levels. However, 48 h and 6 days exposures to those concentrations of DBT that caused decreases in tumor lysing function also caused significant decreases in ATP levels. Exposures of NK cells to varying DBT concentrations for 1 h followed by 24 h, 48 h, and 6 days in DBT free media produced effects on lytic function and ATP levels that were similar to those seen with continuous DBT exposures. The results indicate that DBT exposures decrease ATP levels in NK cells but that tumor lysing function can be reduced independent of any decreases in ATP levels. Additionally the results show that the effects of a range of DBT concentrations on ATP levels and tumor lysing function are irreversible.     

Pentachlorophenol decreases ATP levels in human natural killer cells

Pentachlorophenol (PCP) is used as a wood preservative and is found in human blood and urine. PCP causes significant decreases in the tumor-killing (lytic) function of human natural killer (NK) cells, a critical immune defense. The current study examined the association between decreased lytic function and decreased ATP levels, as well as the ability of antioxidants (vitamin E and reduced glutathione) to prevent PCP-induced decreases in either ATP levels or lytic function. Exposure of NK cells to 10 microm PCP decreased ATP levels by 15% at 24 h, and exposure to 5 microm PCP decreased ATP levels by 32% at 48 h. No effects were seen with 0.5 microm at 48 h or with 5 microm at 24 h. However, 10 microm PCP decreased lytic function by 69% at 24 h and 5 microm decreased it by 90% at 48 h. Even 0.5 microm PCP decreased lytic function by 46% at 48 h. None of these effects were prevented by pretreatment with 1 mm vitamin E or reduced glutathione.     

Effects of methimazole on human lymphocyte proliferation and natural killer cell activity

Methimazole (MM), an antithyroid drug, was examined for its ability to modulate immune functions. The increase in [3H]thymidine incorporation in plant mitogen-stimulated lymphocytes and augmentation of NK cell activity by MM were used as a measure of the immunomodulatory activity of MM. The results demonstrated that lymphocytes from 5 different donors had a mean increase of 632% of [3H]thymidine incorporation in the presence of MM at a concentration of 114.2 micrograms/ml (P less than 0.005). Lymphocyte response to PHA, Con A or PWM was potentiated by 27 to 482% in the presence of MM. The MM mediated increase in lymphocyte proliferation was more obvious in cases where the mitogenic stimulation was low. Lymphocyte cytotoxicity to both K562 cells and malignant B cells was also augmented when lymphocytes were cultured in the presence of MM. A maximal effect was observed when lymphocytes were treated with a concentration of 20 micrograms/ml of MM for 12-16 hr. Maximum augmentation was usually exerted when the NK cell activity of cultured lymphocytes was low. This was particularly seen with lymphocyte from cultured B cell leukemia (3163).     

自然杀伤细胞与人类免疫缺陷病毒的相互作用及影响

自然杀伤细胞是固有免疫体系中具有抗病毒效应的重要成分,可发挥免疫清除和调节作用.其表面具有的一系列活化性受体和抑制性受体,共同决定着NK细胞的免疫功能.在HIV感染中,NK细胞能够通过细胞毒作用裂解靶细胞和免疫调节作用抑制HIV复制.但随着感染时间的延长,HIV患者之NK细胞亚群分布出现变化,低能/失能NK细胞频数增多,进而弱化了NK细胞对HIV的控制作用.予以抗病毒治疗后,感染者体内的NK细胞功能通常会有所恢复.     

Tributyltin and dibutyltin alter secretion of tumor necrosis factor alpha from human natural killer cells and a mixture of T cells and natural killer cells

Butyltins (BTs) have been in widespread use. Tributyltin (TBT) has been used as a biocide in a variety of applications and is found in human blood samples. Dibutyltin (DBT) has been used as a stabilizer in polyvinyl chloride plastics and as a de‐worming agent in poultry. DBT, like TBT, is found in human blood. Human natural killer (NK) cells are the earliest defense against tumors and viral infections and secrete the cytokine tumor necrosis factor‐alpha (TNF‐α). TNF‐α is an important regulator of adaptive and innate immune responses. TNF‐α promotes inflammation and an association between malignant transformation and inflammation has been established. Previously, we have shown that TBT and DBT were able to interfere with the ability of NK cells to lyse tumor target cells. Here we show that BTs alter cytokine secretion by NK cells as well as a mixture of T and NK lymphocytes (T/NK cells). We examined 24‐, 48‐h and 6‐day exposures to TBT (200–2.5 nM) and DBT (5–0.05 μM) on TNF‐α secretion by highly enriched human NK cells and T/NK cells. The results indicate that TBT (200–2.5 nM) decreased TNF‐α secretion from NK cells. In the T/NK cells, 200 nM TBT decreased secretion whereas 100–5 nM TBT increased secretion of TNF‐α. NK cells or T/NK cells exposed to higher concentrations of DBT showed decreased TNF‐α secretion whereas lower concentrations showed increased secretion. The effects of BTs on TNF‐α secretion are seen at concentrations present in human blood. Copyright © 2012 John Wiley & Sons, Ltd.     

Requirement of expression of P-glycoprotein on human natural killer leukemia cells for cell-mediated cytotoxicity

The requirement of P-glycoprotein, a product of the multidrug resistance (MDR)1 gene, for natural killer (NK) cell-mediated cytotoxicity was examined by using a human NK-like cell line, YTN, which is cytotoxic toward JY cells. YTN cells express P-glycoprotein, a judged by flow cytometry and polymerase chain reaction of reverse-transcribed mRNA. YTN cell-mediated cytotoxicity was inhibited by MDR-reversing reagents as well as the F(ab')2 fragment of a monoclonal antibody against P-glycoprotein. Furthermore, antisense oligonucleotides for MDR1 mRNA inhibited expression of P-glycoprotein as well as YTN cell-mediated cytotoxicity. Thus, this study provides firm evidence that P-glycoprotein plays an essential role in cell-mediated cytotoxicity.     

Effect of a series of triorganotins on the immune function of human natural killer cells

Natural killer (NK) cells are our initial immune defense against viral infections and cancer development. They are able to destroy tumor and virally infected cells. Thus, agents that are able to interfere with their function increase the risk of cancer and/or infection. Organotins (OTs) have been shown to interfere with the tumor-destroying function of human NK cells. The purpose of the current study was to explore the relationship of a series of triorganotins, that differ in structure by only a single organic group, for their capacity to block NK tumor-cell destroying (lytic) function. Here we examine the series: trimethyltin (TMT), dimethylphenyltin (DMPT), methyldiphenyltin (MDPT), and triphenyltin (TPT). NK cells were exposed to TMT, DMPT, MDPT or TPT for 1, 24, 48h, or 6d. A 1h exposure to TMT, at concentrations as high as 20μM, had no effect on lytic function. However, concentrations as low as 2.5μM were able to decrease NK tumor-destroying function after 6d. A 1h exposure to DMPT had no effect on lytic function, however, after 6d there was an 80-90% decrease in lytic function at 1μM. Exposure to MDPT (as low as 2.5μM) decreased NK function at 1h, after 6d there was as much as a 90% decrease at concentrations as low as 100nM MDPT. TPT decreased lytic function in a manner similar to MDPT, however, it was more effective at 1h than MDPT. The effect of the triorganotins on the ability of NK cells to bind to targets was studied, to determine if this contributed to the loss of lytic function. The relative immunotoxic potential of this series of compounds is TPT≈MDPT>DMPT>TMT.     

Hexabromocyclododecane decreases the lytic function and ATP levels of human natural killer cells

This study investigates the effect of hexabromocyclododecane (HBCD) on the lytic function of human natural killer (NK) cells and on ATP levels in NK cells. NK cells are capable of lysing tumor cells, virally infected cells, and antibody‐coated cells. HBCD is a brominated cyclic alkane used primarily as an additive flame retardant. If HBCD interferes with NK cell function, this could increase risk of tumor development and/or viral infection. NK cells were exposed to various concentrations of HBCD for 24 and 48 h and 6 days before determining lytic function and ATP levels. ATP levels and lytic function were also determined in NK cells that were exposed to HBCD for 1 h followed by 24 and 48 h, and 6 days in HBCD‐free media. The results indicated that exposure of NK cells to 10 µm HBCD for 24 h causes a very significant decrease in both NK cell lytic function and ATP levels (93.5 and 90.5%, respectively). Exposure of NK cells to 10 µm HBCD for 1 h followed by 24 h in HBCD‐free media showed a progressive and persistent loss of lytic function (89.3%) as well as a decrease in ATP levels (46.1%). The results indicate that HBCD exposures decreased lytic function as well as ATP levels. However, a decrease in lytic function was not necessarily accompanied by a similar decrease in ATP. Importantly, these results also indicate that a brief (1 h) exposure to HBCD causes a progressive loss of lytic function over a 6 day period. Copyright © 2009 John Wiley & Sons, Ltd.     

Effects of phenytoin and carbamazepine on human natural killer cell activity and genotoxicity in vitro

Human peripheral blood mononuclear cells (PBMC) were isolated from healthy volunteers and exposed in vitro to phenytoin or carbamazepine, two widely used antiepileptic drugs (AED). This study investigated the effects of these drugs on natural killer (NK) cell activity and antibody-dependent cell-mediated cytotoxicity (ADCC), which are both thought to protect against developing neoplasms. Also, the genotoxicity of phenytoin on human PBMC was investigated by gravity-flow alkaline elution. Concentrations of phenytoin considered therapeutic (10 and 20 micrograms/ml) and a dose considered acutely toxic (40 micrograms/ml) were used while carbamazepine levels of 8 micrograms/ml (therapeutic) and 10 and 16 micrograms/ml (acutely toxic) were tested. Phenytoin at all three concentrations significantly suppressed NK cell activity in a dose-dependent manner. Carbamazepine had no significant effect on NK cell activity at the dose levels studied. Incubation in propylene glycol, the diluent for carbamazepine, significantly decreased NK cell activity compared to saline. Phenytoin also significantly depressed interferon augmentation of NK cell cytotoxicity in a dose dependent manner. ADCC activity was significantly depressed with 20 and 40 micrograms/ml phenytoin. Alkaline elution showed a slight but significant increase in DNA single-strand breaks of PBMC exposed to 40 micrograms/ml phenytoin for 18 or 72 hr. These results show phenytoin may induce pronounced immunosuppression of NK cell and ADCC activity in patients receiving antiepileptic therapy and that this agent has a potential for genotoxic side effects. Phenytoin may also increase the potential for neoplasm development by a direct interaction with cellular DNA and/or an indirect mechanism by immunosuppression.     

The effects of beta-adrenoceptor stimulation on adhesion of human natural killer cells to cultured endothelium.

1. The circulation of natural killer (NK) cells in vivo is influenced by physical exercise, mental stress, and infusion of beta-adrenoceptor agonists. We have previously presented in vitro data, showing that beta 2-adrenoceptor agonists induce detachment of NK cells from endothelial cells (EC), supporting the hypothesis that NK cells can be recruited from the marginating pool in blood vessels. 2. Because NK cells as well as EC express beta 2-adrenoceptors, the present study was conducted to investigate whether stimulation of the beta-adrenoceptors on NK cells, EC or both cell types is required to induce detachment from EC. 3. Cells were pretreated (15 min) with a selective beta 2-adrenoceptor antagonist, GR81706, at various concentrations. The duration of beta-adrenoceptor blockade was tested by determining the adenosine 3',5'-cyclic monophosphate (cyclic AMP) production induced by terbutaline (a beta 2-adrenoceptor specific agonist). This receptor-mediated response was effectively inhibited for at least 4 h, whereas the cyclic AMP production in response to forskolin (a direct activator of adenylate-cyclase) was not affected. 4. Functional adhesion assays were then performed to determine the role of beta-adrenoceptors on the different cell types involved (NK and EC) in catecholamine-induced detachment. Peripheral blood mononuclear cells were allowed to adhere for 1 h to monolayers of unstimulated EC in the presence or absence of cyclic AMP inducing agents, and the percentage of NK cells in the adhering lymphocyte fraction was determined by flow cytometry. 5. Both adrenaline (10(-5) M) and forskolin (10(-5) M) caused detachment of NK cells from EC.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glutathione diminishes tributyltin- and dibutyltin-induced loss of lytic function in human natural killer cells

This study investigated whether reduced glutathione (GSH) was able to alter the negative effects of tributyltin (TBT) or dibutyltin (DBT) on the lytic function of human natural killer (NK) cells. NK cells are an initial immune defense against the development of tumors or viral infections. TBT and DBT are widespread environmental contaminants, due to their various industrial applications. Both TBT and DBT have been shown to decrease the ability of NK cells to lyse tumor cells (lytic function). The results indicated that the presence of GSH during the exposure of NK cells to TBT or DBT diminished the negative effect of the butyltin on the lytic function of NK cells. This suggests that the interaction of TBT and DBT with functionally relevant sulfhydryl groups in NK cells may be part of the mechanism by which they decrease NK lytic function.