Hinojosa Cecilia A, Akula Suresh Babu Ramya, Rahman Md M, Fernandes Gabriel, Boyd Angela R, Orihuela Carlos J
Center for Airway Inflammation, Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
Department of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
Exp Gerontol. 2014 Jun;54:58-66. doi: 10.1016/j.exger.2014.01.007. Epub 2014 Jan 17.
Advanced age is associated with chronic low-grade inflammation (i.e. inflamm-aging) and poor macrophage function that includes a weak pro-inflammatory cytokine response to bacteria and diminished phagocytosis (i.e. age-dependent macrophage dysfunction [ADMD]). One reason for this is that ADMD is associated with poor NFκB and MAPK activation following Toll-like receptor stimulation. Herein, we tested the hypothesis that inflamm-aging induces production of A20, a cytosolic and homeostatic suppressor of the NFκB and MAPK signaling cascades that deubiquitinates (i.e. inactivates) the common upstream signaling molecule TRAF6, and this is responsible for ADMD. Western blots and immunohistochemistry comparing tissues from young, mature, and aged C57BL/6 mice indicated that A20 was strongly elevated in the lungs of aged mice but not in other tissues. Elevated A20 was also detected in alveolar macrophages (AM) from aged mice. In contrast CYLD, a second deubiquitinase that also negatively regulates the NFκB pathway was decreased with aging. Following co-incubation of AM with the bacteria Streptococcus pneumoniae, TRAF6 polyubiquitination was diminished in AM isolated from aged versus young mice. A20 production was inducible in the J774A.1 macrophage cell line and C57BL/6AM by overnight incubation with TNFα but not IL-6. Retrovirus-induced expression of A20 in J774A.1 cells resulted in their diminished production of IL-6 following exposure to S. pneumoniae but had no effect on levels of phagocytosis. Overnight incubation of AM from young mice with TNFα also resulted in a dampened IL-6 response to S. pneumoniae. Finally, dietary supplementation of aged mice with anti-inflammatory n-3 polyunsaturated fatty acids in the form of fish oil lowered lung A20 levels and enhanced resistance, including a 100-fold reduction in bacterial titers in the lungs, to experimental challenge with S. pneumoniae. We conclude that elevated A20 due to TNFα partially explains the ADMD phenotype and that ADMD is potentially reversible.
高龄与慢性低度炎症（即炎症衰老）及巨噬细胞功能不佳相关，后者包括对细菌的促炎细胞因子反应较弱以及吞噬作用减弱（即年龄依赖性巨噬细胞功能障碍[ADMD]）。其原因之一是，ADMD与Toll样受体刺激后NFκB和MAPK激活不佳有关。在此，我们检验了以下假设：炎症衰老诱导A20生成，A20是NFκB和MAPK信号级联反应的胞质内稳态抑制因子，可使常见上游信号分子TRAF6去泛素化（即使其失活），这导致了ADMD。比较年轻、成熟和老龄C57BL/6小鼠组织的蛋白质免疫印迹和免疫组化表明，老龄小鼠肺中A20强烈升高，但其他组织中未升高。在老龄小鼠的肺泡巨噬细胞（AM）中也检测到A20升高。相比之下，同样对NFκB途径起负调节作用的另一种去泛素酶CYLD随衰老而减少。将AM与肺炎链球菌共同孵育后，从老龄小鼠分离的AM中TRAF6多聚泛素化比从年轻小鼠分离的AM中减少。通过与TNFα过夜孵育，可在J774A.1巨噬细胞系和C57BL/6AM中诱导A20生成，但IL-6不能。逆转录病毒诱导J774A.1细胞表达A20，导致其在暴露于肺炎链球菌后IL-6生成减少，但对吞噬作用水平无影响。用TNFα对年轻小鼠的AM进行过夜孵育，也导致对肺炎链球菌的IL-6反应减弱。最后，用鱼油形式的抗炎n-3多不饱和脂肪酸对老龄小鼠进行饮食补充，可降低肺中A20水平并增强抵抗力，包括使肺部细菌滴度降低100倍，以应对肺炎链球菌的实验性攻击。我们得出结论，TNFα导致的A20升高部分解释了ADMD表型，且ADMD可能是可逆的。
