Department of Otorhinolaryngology-Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
Cells. 2024 May 24;13(11):902. doi: 10.3390/cells13110902.
Akt is an important kinase in metabolism. Akt also phosphorylates and activates endothelial and neuronal nitric oxide (NO) synthases (eNOS and nNOS, respectively) expressed in M0 (unpolarized) macrophages. We showed that e/nNOS NO production downstream of bitter taste receptors enhances macrophage phagocytosis. In airway epithelial cells, we also showed that the activation of Akt by a small molecule (SC79) enhances NO production and increases levels of nuclear Nrf2, which reduces IL-8 transcription during concomitant stimulation with Toll-like receptor (TLR) 5 agonist flagellin. We hypothesized that SC79's production of NO in macrophages might likewise enhance phagocytosis and reduce the transcription of some pro-inflammatory cytokines. Using live cell imaging of fluorescent biosensors and indicator dyes, we found that SC79 induces Akt activation, NO production, and downstream cGMP production in primary human M0 macrophages. This was accompanied by a reduction in IL-6, IL-8, and IL-12 production during concomitant stimulation with bacterial lipopolysaccharide, an agonist of pattern recognition receptors including TLR4. Pharmacological inhibitors suggested that this effect was dependent on Akt and Nrf2. Together, these data suggest that several macrophage immune pathways are regulated by SC79 via Akt. A small-molecule Akt activator may be useful in some infection settings, warranting future in vivo studies.
Akt 是代谢过程中的一种重要激酶。Akt 还可使表达于 M0（未极化）巨噬细胞中的内皮型和神经元型一氧化氮合酶（分别为 eNOS 和 nNOS）磷酸化并激活。我们表明，苦味受体下游的 e/nNOS-NO 产生可增强巨噬细胞的吞噬作用。在气道上皮细胞中，我们还表明，小分子（SC79）激活 Akt 可增强 NO 产生并增加核 Nrf2 水平，从而在与 Toll 样受体（TLR）5 激动剂鞭毛蛋白同时刺激时减少 IL-8 转录。我们假设，SC79 在巨噬细胞中产生的 NO 可能同样增强吞噬作用并减少某些促炎细胞因子的转录。通过使用荧光生物传感器和指示剂染料的活细胞成像，我们发现 SC79 可诱导原代人 M0 巨噬细胞中的 Akt 激活、NO 产生和下游 cGMP 产生。这伴随着在与细菌脂多糖（包括 TLR4 在内的模式识别受体的激动剂）同时刺激时，IL-6、IL-8 和 IL-12 的产生减少。药理抑制剂表明，这种作用依赖于 Akt 和 Nrf2。总之，这些数据表明，SC79 通过 Akt 调节几种巨噬细胞免疫途径。小分子 Akt 激活剂在某些感染情况下可能有用，值得进一步进行体内研究。
