Fernandes Alexandre F, Zhou Jilin, Zhang Xinyu, Bian Qingning, Sparrow Janet, Taylor Allen, Pereira Paulo, Shang Fu
Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA.
J Biol Chem. 2008 Jul 25;283(30):20745-53. doi: 10.1074/jbc.M800268200. Epub 2008 May 23.
Oxidative stress and inflammation are implicated in the pathogenesis of many age-related diseases. Stress-induced overproduction of inflammatory cytokines, such as interleukin-8 (IL-8), is one of the early events of inflammation. The objective of this study was to elucidate mechanistic links between oxidative stress and overproduction of IL-8 in retinal pigment epithelial (RPE) cells. We found that exposure of RPE cells to H(2)O(2), paraquat, or A2E-mediated photooxidation resulted in increased expression and secretion of IL-8. All of these oxidative stressors also inactivated the proteasome in RPE cells. In contrast, tert-butylhydroperoxide (TBH), a lipophilic oxidant that did not stimulate IL-8 production, also did not inactivate the proteasome. Moreover, prolonged treatment of RPE cells with proteasome-specific inhibitors recapitulated the stimulation of IL-8 production. These data suggest that oxidative inactivation of the proteasome is a potential mechanistic link between oxidative stress and up-regulation of the proinflammatory IL-8. The downstream signaling pathways that govern the production of IL-8 include NF-kappaB and p38 MAPK. Proteasome inhibition both attenuated the activation and delayed the turnoff of NF-kappaB, resulting in biphasic effects on the production of IL-8. Prolonged proteasome inhibition (>2 h) resulted in activation of p38 MAPK via activation of MKK3/6 and increased the production of IL-8. Chemically inhibiting the p38 MAPK blocked the proteasome inhibition-induced up-regulation of IL-8. Together, these data indicate that oxidative inactivation of the proteasome and the related activation of the p38 MAPK pathway provide a potential link between oxidative stress and overproduction of proinflammatory cytokines, such as IL-8.
氧化应激和炎症与许多年龄相关疾病的发病机制有关。应激诱导的炎性细胞因子如白细胞介素-8（IL-8）的过度产生是炎症的早期事件之一。本研究的目的是阐明视网膜色素上皮（RPE）细胞中氧化应激与IL-8过度产生之间的机制联系。我们发现，将RPE细胞暴露于过氧化氢（H₂O₂）、百草枯或A2E介导的光氧化作用下会导致IL-8的表达和分泌增加。所有这些氧化应激源还会使RPE细胞中的蛋白酶体失活。相比之下，叔丁基过氧化氢（TBH）是一种不刺激IL-8产生的亲脂性氧化剂，它也不会使蛋白酶体失活。此外，用蛋白酶体特异性抑制剂对RPE细胞进行长时间处理可重现对IL-8产生的刺激作用。这些数据表明，蛋白酶体的氧化失活是氧化应激与促炎细胞因子IL-8上调之间的潜在机制联系。控制IL-8产生的下游信号通路包括核因子κB（NF-κB）和p38丝裂原活化蛋白激酶（p38 MAPK）。蛋白酶体抑制既减弱了NF-κB的激活，又延迟了其关闭，从而对IL-8的产生产生双相影响。长时间的蛋白酶体抑制（>2小时）通过激活MKK3/6导致p38 MAPK激活，并增加了IL-8的产生。化学抑制p38 MAPK可阻断蛋白酶体抑制诱导的IL-8上调。总之，这些数据表明，蛋白酶体的氧化失活和p38 MAPK途径的相关激活为氧化应激与促炎细胞因子如IL-8的过度产生之间提供了潜在联系。
