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Reversible inhibition of lymphokine-activated killer cell activity by lipoxygenase-pathway inhibitors
Abstract:
Natural killer (NK) cells and lymphokine-activated killer (LAK) cells are anomalous cytotoxic cells which are potentially important in host defense against cancer. Several studies have demonstrated that natural killer (NK) cell activity can be suppressed by chemical inhibitors of the lipoxygenase pathway through inhibition of the production of leukotriene B4 (LTB4). The present study investigated the effects of the lipoxygenase inhibitors BW755C and nordihydroguaiaretic acid (NDGA) on NK and LAK cell activity. NK cell function of fresh peripheral blood mononuclear cells (PBMC) was determined via a standard chromium release assay employing K562 as the tumor target. The LAK cell activity of PBMC which had been stimulated with 10 IU of interleukin-2 for 72 hr was determined against the NK-resistant cell line Daudi. Both BW755C and NDGA inhibited NK and LAK cell function at a variety of concentrations. Indomethacin, a prostaglandin synthesis inhibitor, did not bring about an appreciable diminution in NK or LAK cell activity. Inhibition of NK and LAK cell activities by BW755C and NDGA could be reversed by washing the effector cell suspensions prior to the cytotoxic assay or by adding LTB4 (10(-11)-10(-8) M) directly to the effector:target suspensions. These data indicate that certain arachidonic acid oxidation products of the lipoxygenase pathway are essential for the function of LAK cells.
Insights
Lipoxygenase inhibitors BW755C and NDGA suppress natural killer (NK) and lymphokine-activated killer (LAK) cell activity. This inhibition, linked to leukotriene B4 (LTB4) production, can be reversed, highlighting LTB4
Area of Science:
- Immunology
- Cell Biology
- Cancer Research
Background:
- Natural killer (NK) and lymphokine-activated killer (LAK) cells are crucial cytotoxic lymphocytes for anti-cancer immune responses.
- Previous research suggests lipoxygenase pathway products, specifically leukotriene B4 (LTB4), modulate NK cell activity.
- Understanding the role of arachidonic acid metabolites in NK and LAK cell function is vital for immunotherapy development.
Purpose of the Study:
- To investigate the impact of lipoxygenase inhibitors BW755C and nordihydroguaiaretic acid (NDGA) on NK and LAK cell cytotoxic functions.
- To determine if inhibition of NK and LAK cell activity by these agents is reversible and mediated by LTB4.
Main Methods:
- NK cell activity assessed using chromium release assays with K562 tumor targets and peripheral blood mononuclear cells (PBMC).
- LAK cell activity evaluated against the NK-resistant Daudi cell line after PBMC stimulation with interleukin-2.
- Effects of BW755C, NDGA, and indomethacin on cytotoxic assays were measured; reversibility was tested by washing cells or adding LTB4.
Main Results:
- Both BW755C and NDGA significantly inhibited NK and LAK cell cytotoxic activity across various concentrations.
- Indomethacin, a prostaglandin synthesis inhibitor, showed no significant effect on NK or LAK cell activity.
- The inhibitory effects of BW755C and NDGA were reversible upon washing or by the addition of exogenous LTB4.
Conclusions:
- Specific arachidonic acid oxidation products generated via the lipoxygenase pathway are essential for optimal NK and LAK cell function.
- Leukotriene B4 (LTB4) plays a critical role in mediating the cytotoxic activity of these immune cells.
- Targeting the lipoxygenase pathway could represent a novel strategy in modulating cellular immunotherapy against cancer.