Interleukin‐2‐Induced Nitric Oxide Synthase and Nuclear Factor‐κB Activity in Activated Natural Killer Cells and the Production of Interferon‐γ

Abstract

We have previously shown that inducible nitric oxide synthase (iNOS) was up-regulated in natural killer (NK) cells when AK-5 tumour cells were transplanted subcutaneously into syngeneic Wistar rats. This study was designed to investigate the role of interleukin (IL)-2 during the induction of iNOS and to understand the subsequent events involved in NK cell activation. There was up-regulation of iNOS expression when naïve NK cells were cultured in the presence of recombinant IL-2. These NK cells produced a higher nitrite content and possessed cytotoxic activity against YAC-1 and AK-5 tumour cells. Induction of iNOS enhanced nuclear factor (NF)-κB binding activity in IL-2 activated NK cells, which was confirmed using l-NAME, an NO synthesis inhibitor. Addition of L-NAME along with rIL-2 significantly blocked NF-κB activity and also down-regulated the production of NO and the cytotoxic activity of NK cells. Furthermore, injection of anti-IL-2 antibody in subcutaneous tumour transplanted animals abrogated significantly the expression of iNOS and NF-κB activity, leading to reduced NO production and cytotoxic activity of NK cells against YAC-1 and AK-5 cells. In addition, the expression of interferon (IFN)-γ by NK cells was also inhibited in anti-IL-2 antibody injected animals compared with the control animals. Finally, there was enhanced tumour growth and delayed regression in anti-IL-2 injected animals compared with control animals.