Enhancement of cytokine-mediated NF-[kappa]B activation by phosphatidylinositol 3-kinase inhibitors in monocytic cells

• Published in: International immunopharmacology 2006-01, Vol.6 (6), p.908-915
• Main Authors: Choi, Eun-Kyoung, Jang, Ho-Cheol, Kim, Jae-Hyung, Kim, Hyun-Jin, Kang, Ho-Cheol, Paek, Yun-Woong, Lee, Hyun-Chul, Lee, Seung-Hoon, Oh, Won-Mann, Kang, In-Chol
• Format: Article
• Language: English
• ISSN: 1567-5769
• DOI: 10.1016/j.intimp.2006.01.007

Nuclear factor-[kappa]B (NF-[kappa]B) is a transcription factor that plays crucial roles in inflammation and immunity. Understanding the positive and negative regulation of NF-[kappa]B activity is therefore of fundamental importance. A few previous studies reported that inhibition of the phosphatidylinositol 3-kinase (PI3K)-Akt pathway enhances lipopolysaccharide (LPS)-induced activation of NF-[kappa]B. However, many aspects of the PI3K negative regulation of NF-[kappa]B activation remain to be clarified. The present study was conducted to shed light on cell-type specificity, stimulus specificity, and upstream mechanisms of the enhanced NF-[kappa]B activation by PI3K inhibitors. Gel shift assays showed that LY294002 (LY29) potently increased interleukin (IL)-1-induced NF-[kappa]B DNA binding in human monocytic THP-1 cells. Moreover, another PI3K inhibitor 3-methyladenine also strongly enhanced IL-1-induced NF-[kappa]B DNA binding, while LY303511, an inactive analogue of LY29, did not increase the NF-[kappa]B DNA binding. Compared with LY29, wortmannin (WM) effected only a marginal enhancement of NF-[kappa]B DNA binding. LY29 treatment also augmented tumor necrosis factor (TNF)-mediated NF-[kappa]B DNA binding. Furthermore, LY29, but not WM, increased cyclooxygenase (COX)-2 mRNA expression by IL-1 or TNF in THP-1 cells. Likewise, prostaglandin E sub(2) production by IL-1 was increased by LY29, but not by WM. Western blot analysis demonstrated that I[kappa]B kinase (IKK) activation as well as I[kappa]B- alpha degradation and NF-[kappa]B nuclear translocation was elevated by LY29 and WM. Among the tested cell lines (HL-60, ECV304, Hep-2, and Molt-4), only HL-60, a promyelocytic cell line, showed enhanced NF-[kappa]B DNA binding by LY29. These results suggest that pharmacological inhibition of PI3K enhances the NF- [kappa]B-activating pathways by IL-1 through augmentation of IKK activation in myeloid/monocytic cells and the NF-[kappa]B enhancement is more robustly achieved by LY29 than by WM.