Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Wayne State University School of Medicine and Detroit Medical Center, Detroit, MI 48201.
Division of Critical Care, Department of Pediatrics, Wayne State University School of Medicine and Detroit Medical Center, Detroit, MI 48201.
J Immunol. 2019 Mar 15;202(6):1815-1825. doi: 10.4049/jimmunol.1801477. Epub 2019 Feb 1.
LPS-activated macrophages require metabolic reprogramming and glucose uptake mediated by hypoxia-inducible factor (HIF)-1 α and glucose transporter 1 (Glut1) expression for proinflammatory cytokine production, especially IL-1β. This process is tightly regulated through activation of MAPK kinases, including the MEK/ERK pathway as well as several transcription factors including HIF-1α. Although MAPK kinase (MEK) 2 deficiency had no significant effect on NO, TNF-α, or IL-12 production in response to LPS challenge, MEK2-deficient murine bone marrow-derived macrophages (BMDMs) exhibited lower IL-10 production. Importantly, MEK2-deficient BMDMs exhibited a preserved ERK1/2 phosphorylation, higher HIF-1α and Glut1 levels, and substantially increased IL-1β as well as IL-6 production in response to LPS stimulation. Knockdown of HIF-1α expression via short interference RNA decreased the level of HIF-1α expression in MEK2-deficient BMDMs and decreased IL-1β production in response to LPS treatment. Furthermore, we performed gain of function experiments by overexpressing MEK2 protein in RAW264.7 cells. LPS stimulation of MEK2 overexpressed in RAW264.7 cells led to a marked decreased IL-1β production. Finally, we investigated the role of and double and triple mutation on ERK phosphorylation, HIF-1α expression, and IL-1β production. We found that MEK2 is the major kinase, which inversely proportionally regulates HIF-1α and IL-1β expression independent of ERK activation. Our findings demonstrate a novel regulatory function for MEK2 in response to TLR4 activation in IL-1β production through modulating HIF-1α expression.
脂多糖（LPS）激活的巨噬细胞需要代谢重编程和葡萄糖摄取，这一过程由缺氧诱导因子（HIF）-1α和葡萄糖转运蛋白 1（Glut1）表达介导，以产生促炎细胞因子，特别是白细胞介素-1β（IL-1β）。这一过程受到 MAPK 激酶（包括 MEK/ERK 通路）和包括 HIF-1α在内的几种转录因子的激活的严格调控。尽管 MAPK 激酶（MEK）2 缺陷对 LPS 刺激下的 NO、TNF-α 或 IL-12 的产生没有显著影响，但 MEK2 缺陷型小鼠骨髓来源的巨噬细胞（BMDM）的 IL-10 产生较低。重要的是，MEK2 缺陷型 BMDM 的 ERK1/2 磷酸化水平较高，HIF-1α和 Glut1 水平较高，对 LPS 刺激的 IL-1β和 IL-6 产生明显增加。通过短发夹 RNA（siRNA）敲低 HIF-1α 的表达，降低了 MEK2 缺陷型 BMDM 中的 HIF-1α 表达水平，并降低了 LPS 处理时的 IL-1β 产生。此外，我们通过在 RAW264.7 细胞中过表达 MEK2 蛋白进行了功能获得实验。LPS 刺激 RAW264.7 细胞中过表达的 MEK2 导致 IL-1β 产生明显减少。最后，我们研究了 和 双突变和三突变对 ERK 磷酸化、HIF-1α 表达和 IL-1β 产生的作用。我们发现 MEK2 是主要的激酶，它通过调节 HIF-1α 表达，与 ERK 激活无关，呈反相关比例调节 HIF-1α 和 IL-1β 的表达。我们的研究结果表明，MEK2 在 TLR4 激活诱导的 IL-1β 产生中具有调节作用，其通过调节 HIF-1α 表达发挥作用。
