Department of Environmental Medicine, Lung Biology and Disease Program, University of Rochester Medical Center, Rochester, New York , USA.
Am J Physiol Lung Cell Mol Physiol. 2010 Feb;298(2):L197-209. doi: 10.1152/ajplung.00265.2009. Epub 2009 Dec 4.
NF-kappaB-mediated proinflammatory response to cigarette smoke (CS) plays a pivotal role in the pathogenesis of chronic obstructive pulmonary disease (COPD). The heterodimer of RelA/p65-p50 (subunits of NF-kappaB) is involved in transactivation of NF-kappaB-dependent genes, but interestingly p50 has no transactivation domain. The endogenous role of p50 subunit, particularly in regulation of CS-mediated inflammation in vivo, is not known. We therefore hypothesized that p50 subunit plays a regulatory role on RelA/p65, and genetic ablation of p50 (p50(-/-)) leads to increased lung inflammation and lung destruction in response to CS exposure in mouse. To test this hypothesis, p50-knockout and wild-type (WT) mice were exposed to CS for 3 days to 6 mo, and inflammatory responses as well as air space enlargement were assessed. Lungs of p50-deficient mice showed augmented proinflammatory response to acute and chronic CS exposures as evidenced by increased inflammatory cell influx and proinflammatory mediators release such as monocyte chemoattractant protein-1 (MCP-1) and interferon-inducible protein-10 (IP-10) compared with WT mice. IKK2 inhibitor (IMD-0354), which reduces the nuclear translocation of RelA/p65, attenuated CS-mediated neutrophil influx in bronchoalveolar lavage fluid and cytokine (MCP-1 and IP-10) levels in lungs of WT but not in p50-deficient mice. Importantly, p50 deficiency resulted in increased phosphorylation (Ser276 and Ser536), acetylation (Lys310), and DNA binding activity of RelA/p65 in mouse lung, associated with increased chromatin remodeling evidenced by specific phosphoacetylation of histone H3 (Ser10/Lys9) and acetylation of H4 (Lys12) in response to CS exposure. Surprisingly, p50-null mice showed spontaneous air space enlargement, which was further increased after CS exposure compared with WT mice. Thus our data showed that p50 endogenously regulates the activity of RelA/p65 by decreasing its phosphoacetylation and DNA binding activity and specific histone modifications and that genetic ablation of p50 leads to air space enlargement in mouse.
NF-κB 介导的对香烟烟雾 (CS) 的促炎反应在慢性阻塞性肺疾病 (COPD) 的发病机制中起关键作用。RelA/p65-p50（NF-κB 的亚基）异二聚体参与 NF-κB 依赖性基因的反式激活，但有趣的是 p50 没有反式激活结构域。p50 亚基的内源性作用，特别是在体内调节 CS 介导的炎症，尚不清楚。因此，我们假设 p50 亚基在 RelA/p65 上发挥调节作用，并且 p50 缺失（p50(-/-)) 会导致在 CS 暴露后小鼠的肺部炎症和肺破坏增加。为了验证这一假设，对 p50 敲除和野生型 (WT) 小鼠进行 CS 暴露 3 天至 6 个月，并评估炎症反应和气道扩张。与 WT 小鼠相比，p50 缺失小鼠的肺部表现出对急性和慢性 CS 暴露的促炎反应增强，表现为炎症细胞浸润增加和促炎介质释放增加，如单核细胞趋化蛋白-1 (MCP-1) 和干扰素诱导蛋白-10 (IP-10)。IKK2 抑制剂 (IMD-0354)，可减少 RelA/p65 的核易位，可减轻 WT 小鼠但不能减轻 p50 缺失小鼠支气管肺泡灌洗液中的 CS 介导的中性粒细胞浸润和细胞因子 (MCP-1 和 IP-10) 水平。重要的是，p50 缺失导致小鼠肺中 RelA/p65 的磷酸化 (Ser276 和 Ser536)、乙酰化 (Lys310) 和 DNA 结合活性增加，与 CS 暴露后组蛋白 H3 (Ser10/Lys9) 的特定磷酸化乙酰化和 H4 (Lys12) 的乙酰化导致染色质重塑增加有关。令人惊讶的是，p50 缺失的小鼠自发出现气道扩张，与 WT 小鼠相比，CS 暴露后气道扩张进一步增加。因此，我们的数据表明，p50 通过降低 RelA/p65 的磷酸化乙酰化和 DNA 结合活性以及特定的组蛋白修饰来内源调节 RelA/p65 的活性，并且 p50 的基因缺失会导致小鼠的气道扩张。
