China-Japan Research Institute of Medical and Pharmaceutical Sciences, Shenyang Pharmaceutical University , 103 Wenhua Road, Shenyang , People's Republic of China.
Free Radic Res. 2012 Oct;46(10):1207-19. doi: 10.3109/10715762.2012.700515. Epub 2012 Jul 4.
We previously demonstrated that oridonin-induced autophagy enhanced efferocytosis (phagocytosis of apoptotic cells) by macrophage-like U937 cells through activation of the inflammatory pathways. In this study, exposure of U937 cells to 2.5 μM oridonin caused up-regulation of inducible nitric oxide synthase (iNOS) expression and continuous endogenous generation of nitric oxide (NO), which was reversed by pre-treatment with the inhibitors of nitric oxide synthase 1400 W (dihydrochloride) or L-NAME (hydrochloride). NO donor sodium nitroprusside (SNP) and efferocytosis irritant lipopolysaccharide (LPS) could also exert NO generation and iNOS expression. Moreover, oridonin-induced stimulation of efferocytosis was significantly suppressed by 1400 W or L-NAME. In addition, 1400 W or L-NAME impaired oridonin-induced autophagy. Inhibition of autophagy with 3-methyladenine (3MA) or Beclin-1 siRNA attenuated the uptake of apoptotic cells with a slight increase in the production of NO. The pro-inflammatory cytokine interleukin-1β (IL-1β) has been reported to be involved in oridonin-induced efferocytosis in U937 cells and interact with NO to contribute to inflammatory responses. 1400 W or L-NAME blocked the secretion of IL-1β and the activation of NF-κB and COX-2. Provision of SNP or LPS in place of oridonin resulted in the similar enhancement of efferocytosis, autophagy, the release of IL-1β and the expression of signal protein. NO augmented the oridonin-induced efferocytosis by mediating autophagy and activating the NF-κB-COX-2-IL-1β pathway. Inhibition of NF-κB or COX-2 in turn decreased the production of NO and the expression of iNOS. There exists a positive feedback loop between NO generation and NF-κB-COX-2-IL-1β pathway.
我们之前的研究表明，冬凌草甲素通过激活炎症通路增强了巨噬细胞样 U937 细胞的自噬作用（吞噬凋亡细胞）。在这项研究中，U937 细胞暴露于 2.5 μM 冬凌草甲素导致诱导型一氧化氮合酶（iNOS）表达上调和内源性一氧化氮（NO）的持续产生，而一氧化氮合酶抑制剂 1400W（二盐酸盐）或 L-NAME（盐酸盐）预处理可逆转这一过程。NO 供体硝普钠（SNP）和吞噬作用刺激物脂多糖（LPS）也可以发挥生成 NO 和诱导 iNOS 表达的作用。此外，1400W 或 L-NAME 显著抑制了冬凌草甲素诱导的吞噬作用。此外，1400W 或 L-NAME 抑制了冬凌草甲素诱导的自噬作用。用 3-甲基腺嘌呤（3MA）或 Beclin-1 siRNA 抑制自噬作用，会轻微增加 NO 的产生，同时减少凋亡细胞的摄取。据报道，促炎细胞因子白细胞介素-1β（IL-1β）参与了 U937 细胞中冬凌草甲素诱导的吞噬作用，并与 NO 相互作用，有助于炎症反应。1400W 或 L-NAME 阻断了 IL-1β 的分泌和 NF-κB 和 COX-2 的激活。用 SNP 或 LPS 代替冬凌草甲素会导致吞噬作用、自噬作用、IL-1β 的释放和信号蛋白的表达得到类似的增强。NO 通过介导自噬作用并激活 NF-κB-COX-2-IL-1β 通路增强了冬凌草甲素诱导的吞噬作用。抑制 NF-κB 或 COX-2 会降低 NO 的产生和 iNOS 的表达。NO 的产生和 NF-κB-COX-2-IL-1β 通路之间存在正反馈回路。
