The Mechanism Of Negative Regulation Inflammation Of NIK Gene In Macrophage

NF-κB-inducing kinase(NIK) is a key regulator of the innate immunity and the proinflammatory signaling pathway. In addition, NIK plays a central role in adaptive immunity, in which it mediates signaling from T- and B-cell receptors. In response to interleukin-1, tumor necrosis factor-a, and toll-like receptor agonists, it mediates the activation of the nuclear factor κB(NF-κB), c-Jun N-terminal kinase(JNK), and p38 pathways.When J774 a.1 cells incubated with LPS, NIK expression was increasingly activated during 10-40 minutes; however, NIK activation was not changed significantly among different LPS concentrations of 10ng/ml, 100ng/ml, 1000ng/ml, so.10ng/ml was chosen to activate different macrophages in our test.The NIK protein expression was significantly reduced after NIK siRNA interference in J774 a.1 cell line,. The MEKK3 activation was increased while p-NIK expression was reduced. These result showed the opposite trend of NIK and MEKK3 activation, indicating the inhibition of NIK on MEKK3.After NIK siRNA interference on pMac, the cytokines IL-1β levels secreted was increased significantly, while IL-6, TNFα was not changed significantly; The TNFα level was also increased in BMDM cell after NIK siRNA interference. These result showed that NIK siRNA interference can enhance inflammatory response after LPS stimulation.Above all, the inflammatory response had actually strengthened after NIK siRNA interference in macrophage which is opposite from in T and B lymphocyte. The mechanism of NIK in macrophage was studied by means of investigating macrophage signal transduction. The results showed that more p-MEKK3 was expressed after NIK inhibited by siRNA in LPS-stimulating J774 A.1 cell lines, leading to the activation of downstream signaling molecules and NF-κB, and the proinflammatory cytokines of IL-1β, TNFα secreted by macrophages was elevated significantly, indicating that the NIK is a negative regulator of MEKK3.