Effect of Natural Compounds on NK Cell Activation (original) (raw)
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Activation of NK cell cytotoxicity
Molecular …, 2005
Natural killer (NK) cells are innate effector lymphocytes necessary for defence against stressed, microbe-infected, or malignant cells. NK cells kill target cells by either of two major mechanisms that require direct contact between NK cells and target cells. In the first pathway, cytoplasmic granule toxins, predominantly a membrane-disrupting protein known as perforin, and a family of structurally related serine proteases (granzymes) with various substrate specificities, are secreted by exocytosis and together induce apoptosis of the target cell. The granule-exocytosis pathway potently activates cell-death mechanisms that operate through the activation of apoptotic cysteine proteases (caspases), but can also cause cell death in the absence of activated caspases. The second pathway involves the engagement of death receptors (e.g. Fas/CD95) on target cells by their cognate ligands (e.g. FasL) on NK cells, resulting in classical caspase-dependent apoptosis. The comparative role of these pathways in the pathophysiology of many diseases is being dissected by analyses of gene-targeted mice that lack these molecules, and humans who have genetic mutations affecting these pathways. We are also now learning that the effector function of NK cells is controlled by interactions involving specific NK cell receptors and their cognate ligands, either on target cells, or other cells of the immune system. This review will discuss the functional importance of NK cell cytotoxicity and the receptor/ligand interactions that control these processes.
Studies of the Mechanism of Natural Killer (NK) Degranulation and Cytotoxicity
Journal of Leukocyte Biology, 1990
Exocytosis of cytotoxic granule contents towards bound target cells is thought to be of central importance in natural killer (NK) cell-mediated killing. Although cellular cytotoxicity involving degranulation is thought to be calcium-dependent, the biochemical mechanisms that mediate this granule mobilization are unknown. Inositol-1,4,5-tris-phosphate (IP3), which acts to elevate internal calcium levels, and 1,2-diacylglycerol (DAG), which activates protein kinase C, are potent second messengers that have been shown to synergistically mediate secretion in other cell types. Production of these products of inositol phospholipid metabolism has previously been demonstrated in a rat NK cell line RNK upon exposure to susceptible tumor targets. We therefore Investigated the role of IP3 and DAG in NK-mediated cytotoxicity, specifically at the level of degranulation. Pretreatment of RNK cells with neomycin, a drug that interferes with the hydrolysis of inositol phospholipids and thus inhibits...
Pharmaceutical Biology, 2020
Context: Natural killer (NK) cells can eliminate malignant cells and play a vital role in immunosurveillance. Administration of natural compounds represents a promising approach for antitumor immunotherapy, which may enhance the NK cell activity via multiple mechanisms. Objective: Establishing approaches to evaluate the effect of select natural products on NK cell-mediated cytotoxicity. Materials and methods: We selected a natural product library containing 2880 pure compounds, which was provided by the National Centre for Drug Screening of China. 0.1% DMSO was employed as a negative control, and 100 U/mL human recombinant IL-2 was employed as a positive control. To evaluate the % of tumour cells which were killed by NK cells, expanded NK cells were co-cultured with tumour cells and then treated with natural products at the concentration of 10 lM. After 24-h co-incubation, luminescent signal was detected and percent lysis was calculated. Results: We report on the results of a three-round high-throughput screening effort that identified 20deoxyingenol 3-angelate (DI3A) and its analogue ingenol 3-angelate (I3A) as immuno enhancers which boosts NK cell-mediated killing of non-small cell lung cancer cells (NSCLCs). Biophotonic cytotoxicity assay and calcein release assay were used as two well-established NK cell cytotoxicity detection assays to validate the immuno-enhancing effects of DI3A and I3A, which was achieved by increasing degranulation and interferon-gamma secretion of NK cells. Conclusions: Our newly established ATP-based method was a valuable and information-rich screening tool to investigate the biological effects of natural products on both NK cells and tumour cells.
Role of target and effector cell structures in natural killer-mediated cytotoxicity
La Ricerca in clinica e in laboratorio
An analysis of target and effector cell structures involved in the in vitro natural killer (NK)-mediated cytotoxicity has been performed. The degree of surface expression of transferrin receptor (TR) was only in part correlated with that of cell lysis. Moreover, the lysis could not be blocked by treating target cells with two anti-TR monoclonal antibodies. Finally, cell lines poorly affected by NK cells express TR only at the cytoplasmic level. As to the effector cells, the integrity of cytoskeleton components (especially microtubules) was found to be essential for the occurrence of cell lysis. In fact, vinblastine, an anti-microtubule agent, was able to significantly reduce the percentage cell lysis. This effect was not due to a selective depletion in NK cells induced by the drug. It is concluded that the mechanisms underlying NK activity are complex and involve both target and effector cell structures.
Natural killer cell cytotoxic activity: measurement of the apoptotic inducing mechanisms
Clinical and Experimental Medical Sciences, 2013
Natural Killer cell cytotoxic activity is vital for the clearance of viral and malignantly transformed cells. The aim of this study was to investigate the apoptotic inducing mechanisms of NK cells to propose an additional measurement for NK cell effector function. 19 healthy controls (age=31±7.2 years) participated in this study. Flow cytometric protocols assessed NK cell cytotoxic activity against tumour K562 cells, lytic proteins, degranulation and interferon gamma production. Perforin release was significantly correlated with cytotoxic activity (r=-0.46, p<0.05) and degranulation (r=-0.60, p<0.05). These results suggest that perforin may be an additional measure for NK cell cytotoxic effector function.
Relevance of target cell-induced apoptosis as mechanism of resistance against natural killer cells
Annals of Hematology, 2010
Natural killer (NK) cells contribute to the graftversus-leukemia effect after allogeneic stem cell transplantation. However, the efficacy of NK cell-mediated tumor cell lysis is limited due to target cell resistance, and target cellinduced apoptosis (TiA) was proposed to contribute to differences in susceptibility to NK cells. Here we analyzed the effects of target cells on the apoptosis of cytokineactivated NK cells in vitro. We found no association of target cell susceptibility and TiA of NK cells in an array of human and murine target-effector cell combinations. Incubation of NK cells with caspase inhibitors blocked TiA incompletely, indicating that TiA is partly based on caspase-independent mechanisms. Modulating NK cell susceptibility against TiA by caspase inhibition did not influence cytotoxic efficacy. Furthermore, we found cytotoxic potential of NK cells to be markedly decreased following first target cell contact. Exhaustion of NK cell activity by first target cell contact was, however, not mediated by TiA. In addition, we found no relevant TiA by lymphoma cell lines against activated murine NK cells. We conclude that TiA represents only a minor factor of target cell resistance against NK cell-mediated cytolysis.
Cellular redox status influences both cytotoxic and NF-kappaB activation in natural killer cells
Immunology, 1997
The role of cellular redox status in both cytotoxic activity and NF-K B activation in natural killer (NK) cells was investigated. The results indicate that stimulation of NK cells, either freshly isolated from peripheral blood lymphocytes (PBL) or long-term cultured NK clones, with specific cell targets results in an increased binding activity of NF-KB and AP-l transcription factors measured by gel retardation. Pretreatment of NK cells with the antioxidant pyrrolidine dithiocarbarmate (PDTC) leads to the inhibition of NF-KB activation but the AP-1 binding to DNA was superinduced. The inhibition of NF-KB by PDTC paralleled with an inhibition of spontaneous cytotoxicity mediated by NK cells. Moreover, the inhibitors of serine proteases, N-a-tosyl-L-lysine chloromethyl ketone and N-cX-tosyl-L-phenylalanine chloromethyl ketone, also blocked the cytolytic activity of NK cells against the sensitive target K562. In contrast, NK activity was not affected by pretreatment of the effector cells with the proteasome inhibitor N-acetyl-leu-leu-norleucinal which selectively inhibits NF-KB activation. Altogether, these results support the hypothesis that the activation of NK cells involved transcriptional and post-transcriptional events, and that reactive intermediates may play an important role in the molecular processes related with the generation of a cytotoxic response by NK cells.
Target-cell-induced anergy in natural killer cells: suppression of cytotoxic function
Cancer Immunology, Immunotherapy, 2000
Our earlier studies have demonstrated that natural killer (NK) cells are the eectors that participate during the spontaneous regression of AK-5 tumour in syngeneic hosts. We have shown that the tumour cells are killed by necrosis and apoptosis. In this study, we have examined the induction of functional anergy in NK cells following coculture with ®xed AK-5 tumour cells at high ratio. NK cells, upon coculture with ®xed AK-5 cells (1:1 ratio), showed loss of cytotoxic function against both AK-5 (antibody-dependent cell cytotoxicity) as well as YAC-1 targets. The response of these cells to the activation by recombinant interleukin-2 and recombinant interferon c was poor. Induction of tumour necrosis factor a (TNFa) secretion was observed after coculture of NK cells with ®xed AK-5 cells. The cocultured cell supernatant inhibited the cytotoxic activity of NK cells, which was partially restored with anti-TNFa antibody. In addition, NK cells, after treatment with ®xed tumour cells showed overexpression of the Fas receptor. We have also observed induction of apoptosis in cocultured NK cells. These studies suggest that the ®xed tumour cells (antigen) at high ratio are able to suppress NK cell function as well as induce death in NK cells.