Reduced histone deacetylase in COPD: clinical implications

COPD is characterized by progressive inflammation in the small airways and lung parenchyma, and this is mediated by the increased expression of multiple inflammatory genes. The increased expression of inflammatory genes is regulated by acetylation of core histones around which DNA is wound, and conversely these activated genes are switched off by deacetylation of these histones. Histone deacetylases (HDACs) suppress inflammatory gene expression, but their activity and expression (particularly of HDAC-2) is reduced in the peripheral lung and in alveolar macrophages of patients with COPD. This results in amplification of the inflammatory response as COPD progresses but also accounts for corticosteroid resistance in COPD, since HDAC-2 is required by corticosteroids to switch off activated inflammatory genes. The reduction in HDAC-2 appears to be secondary to the increased oxidative and nitrative stress in COPD lungs. Antioxidants and inhibitors of nitric oxide synthesis may therefore restore corticosteroid sensitivity in COPD, but this can also be achieved by low doses of theophylline, which is an HDAC activator. This mechanism is also relevant to asthmatic patients who smoke, patients with severe asthma and cystic fibrosis, in whom oxidative stress is also increased.     

The effects of cigarette smoke on airway inflammation in asthma and COPD: therapeutic implications

Asthma and COPD are two chronic inflammatory disorders of the airway characterized by airflow limitation. While many similarities exist between these two diseases, they are pathologically distinct due to the involvement of different inflammatory cells; predominantly neutrophils, CD8 lymphocytes in COPD and eosinophils and CD4 lymphocytes in asthma. Cigarette smoking is associated with accelerated decline of lung function, increased mortality, and worsening of symptoms in both asthma and COPD. Furthermore, exposure to cigarette smoke can alter the inflammatory mechanisms in asthma to become similar to that seen in COPD with increasing CD8 cells and neutrophils and may therefore alter the response to therapy. Cigarette smoke exposure has been associated with a poor response to inhaled corticosteroids which are recommended as first line anti-inflammatory medications in asthma and as an add-on therapy in patients with severe COPD with history of exacerbations. While the main proposed mechanism for this altered response is the reduction of the histone deacetylase 2 (HDAC2) enzyme system, other possible mechanisms include the overexpression of GR-β, activation of p38 MAPK pathway and increased production of inflammatory cytokines such as IL-2, 4, 8, TNF-α and NF-K?. Few clinical trials suggest that leukotriene modifiers may be an alternative to corticosteroids in smokers with asthma but there are currently no drugs which effectively reduce the progression of inflammation in smokers with COPD. However, several HDAC2 enhancers including low dose theophylline and other potential anti-inflammatory therapies including PDE4 inhibitors and p38 MAPK inhibitors are being evaluated.     

组蛋白去乙酰化酶在支气管哮喘和过敏性疾病发病机制中的作用

组蛋白乙酰化作用可以调节细胞的各种功能,如炎症基因的表达、DNA修复以及细胞增殖.组蛋白去乙酰化酶(HDAC)可以调节炎症或免疫基因的表达.HDAC抑制剂可以进一步促进炎症基因的表达;非组蛋白的乙酰化和去乙酰化状态也影响炎症基因的表达.HDAC2的表达和其活性在严重支气管哮喘患者以及吸烟支气管哮喘患者的肺巨噬细胞、肺组织以及血细胞都是降低的.因此,以参与这个过程的特殊酶为靶标可能成为新的治疗途径.     

慢性阻塞性肺疾病的抗炎治疗进展

在全世界范围内慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)是导致成人发病率及病死率的主要原因.各种炎症细胞和炎症介质参与了COPD的发生发展,因此可能成为COPD的治疗靶点.现将糖皮质激素、细胞信号抑制剂、白三烯B4对抗物、趋化因子抑制剂、细胞因子及其调节剂和黏附分子抑制剂在COPD抗炎治疗中的应用作一综述.     

组蛋白去乙酰化酶与新生血管形成的关系

真核细胞中染色质的基本单位是核小体,它是由核心组蛋白(H2A、H2B、H3和H4)、H1及DNA组成.核心蛋白的乙酰化和去乙酰化是基因表达过程中重要的调控方式,负责组蛋白乙酰化和去乙酰化的是一对功能相互拮抗的蛋白酶家族组蛋白乙酰基转移酶(HAT)和组蛋白去乙酰化酶(HDAC).HAT激活基因转录,而HDAC的功能相反,抑制基因的转录.HDAC的功能异常被证实与肿瘤的发生和发展及缺氧和病理状态下的血管增生有直接关系.本文就HDAC与新生血管形成之间的关系作一综述.     

Bronchial hyper-responsiveness and exhaled nitric oxide in chronic obstructive pulmonary disease

Several lung diseases including asthma and chronic obstructive pulmonary disease (COPD) involve chronic inflammation of the airways. Therefore, there is great interest in non-invasive methods assessing airway inflammation. Measurement of bronchial hyper-responsiveness (BHR) and exhaled nitric oxide (NO) are such indirect markers of airway inflammation. Additional information about severity of disease, prognosis and possible response to anti-inflammatory treatment with inhaled corticosteroids can be gained by these methods. However, they are not yet established in assessing patients with COPD in clinical routine. BHR has long been recognised as a hallmark of asthma. Less is known about prevalence and clinical relevance of BHR in the general population and in COPD patients. Longitudinal studies have shown that BHR in healthy persons is a risk factor for development of respiratory symptoms, asthma and COPD. BHR has also been shown to increase the detrimental effect of cigarette smoke and is associated with a decline in lung function. Furthermore, studies indicate that the presence of BHR is a prognostic factor in COPD. Increased BHR to histamine has been shown to be a predictor for mortality in COPD patients. Based on current guidelines, treatment of patients with severe COPD (GOLD stage III and IV) and regular exacerbations includes therapy with inhaled corticosteroids. Inhaled corticosteroids have been shown to reduce frequency of exacerbations but they have not been shown to modify long-term decline in FEV1. However, one small study found that BHR to inhaled mannitol could possibly predict responsiveness to inhaled corticosteroids in patients with moderately severe COPD and identify a subgroup of patients that is likely to benefit from this treatment. Exhaled NO has been shown to correlate with other inflammatory markers and to be elevated in asthma. In COPD patients, data is inconsistent. However, measuring exhaled NO may have a role in the identification of patients with severe, unstable COPD who were shown to have higher NO levels compared to patients with stable COPD. This suggests that exhaled NO might be a method to assess and monitor disease activity in COPD. Possible explanations for the contradictory results are different measurement techniques of exhaled NO and different smoking histories of patients in various studies. Smoking has been found to be a confounding factor by reducing NO levels significantly, an effect which might counteract the potentially increased exhaled NO due to airway inflammation. In conclusion, measuring BHR and exhaled NO in patients with COPD might provide additional information about disease severity, prognosis and possible response to anti-inflammatory medical treatment. However, to establish these methods in clinical routine in COPD patients, more data is clearly needed.     

Addition of inhaled corticosteroid on combined bronchodilator therapy in patients with COPD

PURPOSE: Bronchodilator therapy is the first step treatment in patients with COPD. The beneficial effects of corticosteroids either in health status or in airway inflammation in COPD have been previously studied. The aim of this study was to evaluate whether adding inhaled corticosteroids to combined bronchodilator therapy has additive clinical and anti-inflammatory effects in COPD patients. SUBJECTS AND METHODS: Thirty patients with COPD were included in the study. All patients were receiving inhaled anticholinergic and long-acting beta-2 agonist. Inhaled corticosteroid (budesonide 800 microg daily) was added to their current medications for 12 weeks. Before and after this treatment period, spirometric values and arterial blood gas parameters were determined, blood was drawn for measurement of serum inflammatory markers and sputum was induced. RESULTS: All patients were male, mean age was 67.7+/-8.7 years and duration of disease was 9.7+/-4.3 years. The induced sputum total cell counts, eosinophil and neutrophil counts decreased with corticosteroid treatment. The induced sputum IL-8 and TNF-alpha levels decreased significantly (IL-8; 835.9+/-217 versus 378.4+/-105 pg/ml, p=0.0001, TNF-alpha; 320.7+/-129 versus 201.3+/-52 pg/ml, p=0.003). Serum inflammatory markers and sputum LTB4 levels did not change with treatment. CONCLUSION: These results suggested that the addition of inhaled corticosteroids to combined bronchodilator therapy might have anti-inflammatory effects in patients with COPD.     

慢性阻塞性肺疾病组蛋白去乙酰化酶与糖皮质激素抵抗

慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)是一种慢性气道炎症,炎症基因的表达受组蛋白去乙酰化酶(histone deacetylase,HDAC)和组蛋白乙酰化酶(histone acetyltransferase,HAT)调控,通常组蛋白乙酰化增高促进基因转录,降低则抑制基因转录.糖皮质激素(glucocorticoid,GC)的一个重要作用是募集HDAC2到基因表达位点,使基因组蛋白乙酰化程度降低,从而抑制炎症基因表达.由吸烟引起的COPD患者,香烟烟雾氧化应激使得HDAC2减少,降低了GC的抗炎作用,导致GC抵抗,而GC抵抗是COPD抗炎治疗的主要障碍.本文讨论GC抵抗的一些分子机制,为COPD患者治疗方案的制定及改善预后提供理论参考依据.