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Products of the lipoxygenase pathway in human natural killer cell cytotoxicity
Abstract:
As earlier data suggested the importance of lipoxygenase activation for expression of human NK cell cytotoxicity, four different lipoxygenase inhibitors were tested for suppression of natural killer (NK) cell lysis. All inhibitors were found active at nontoxic concentrations with 50% inhibition at approximately 15 microM for nordihydroguaiaretic acid (NDGA). NK cell lysis could be reconstituted to NDGA-suppressed cells with leukotriene B4 (LTB4), the all-trans isomers 6-trans-LTB4 and 12-epi-6-trans-LTB4, and 20-COOH-LTB4. LTB4 reconstitution was best in the concentration range 1-100 pM and near control levels at both higher and lower concentrations. Herpesvirus Ateles-transformed killer T cells could also be inhibited by NDGA. These data indicate that lipoxygenase activity is required for human NK cell lysis and that several different LTB4-related products can restore NK activity in inhibited cells; they also suggest that the lipoxygenase pathway is present in the killer cell population.
Insights
Lipoxygenase activity is crucial for natural killer (NK) cell cytotoxicity. Inhibitors block NK cell lysis, but this can be restored with specific leukotriene B4 (LTB4) products, confirming the pathway
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Earlier studies indicated lipoxygenase activation is vital for human NK cell cytotoxicity.
- Natural killer (NK) cells are critical for innate immunity and tumor surveillance.
Purpose of the Study:
- To investigate the role of lipoxygenase activity in human NK cell-mediated cytotoxicity.
- To identify specific lipoxygenase pathway products capable of restoring NK cell function.
Main Methods:
- Tested four lipoxygenase inhibitors for their ability to suppress NK cell lysis.
- Assessed the reconstitution of NK cell activity using various leukotriene B4 (LTB4) products in inhibited cells.
- Investigated the effect of nordihydroguaiaretic acid (NDGA) on Herpesvirus Ateles-transformed killer T cells.
Main Results:
- All tested lipoxygenase inhibitors suppressed NK cell lysis at non-toxic concentrations, with 50% inhibition around 15 microM for NDGA.
- NK cell lysis was restored by LTB4 and its isomers (6-trans-LTB4, 12-epi-6-trans-LTB4) and 20-COOH-LTB4, particularly in the 1-100 pM range.
- NDGA also inhibited Herpesvirus Ateles-transformed killer T cells, suggesting the lipoxygenase pathway is present in killer cells.
Conclusions:
- Lipoxygenase activity is essential for human NK cell-mediated cytotoxicity.
- Specific LTB4-related molecules can restore NK cell activity when the pathway is inhibited.
- The findings suggest the lipoxygenase pathway is active within the NK cell population.