| 摘要: | 慢性阻塞性肺病 (Chronic Obstructive Pulmonary Disease, COPD) 是一種以持續性氣道阻塞和肺泡損傷為特徵的常見且可治療的疾病，經由長期接觸有害顆粒和氣體所引起，香煙煙霧是其中最重要的風險因子。肺部巨噬細胞通過引發炎症的調節對於肺部的防禦至關重要，而肺部巨噬細胞的亞型和功能亦受香菸煙霧所調控。香菸煙霧調節的促炎性巨噬細胞(pro-inflammatory macrophage, M1)被認為參與促進COPD的病理機轉，然而抗炎性巨噬細胞(anti-inflammatory macrophage, M2)也被報導會大量存在在吸煙者和COPD患者的肺部。由於香菸煙霧暴露下異常的M1/M2巨噬細胞表型仍不清楚，因此本篇的研究將針對香菸煙霧調節巨噬細胞重編程的潛在機制進行探究。本篇研究證實，香菸煙霧暴露可能會透過減弱類鐸受體4 (Toll-like Receptor 4, TLR4)信號傳導進而影響巨噬細胞的重編程。我們發現新鮮製備的香煙煙霧萃取物(Cigarette Smoke Extract, CSE)可以有效地刺激誘導型一氧化氮合? (Inducible Nitric Oxide Synthase, iNOS)/一氧化氮 (Nitric Oxide, NO)和環氧化?(Cyclooxygenase, COX)-2的表現，並激活介導絲裂原活化蛋白激? (Mitogen-activated protein kinases, MAPKs)，而 RAW264.7 細胞表面的TLR4表現則無顯著變化。有趣的是，CSE的預前處理顯著抑制了脂多醣(Lipopolysaccharide, LPS)所介導的iNOS/NO、COX-2和介白素(Interleukin, IL)-6在 RAW264.7 細胞中的表現。此外，利用過氧化氫 (Hydrogen peroxide, H2O2) 和尼古丁預前處理的實驗結果同樣顯示， LPS所誘發的促炎性因子表現出現類似地被抑制作用。LPS 激活的NF-κB (Nuclear factor kappa B)訊號傳遞，同樣也在CSE、H2O2和尼古丁的預前處理下顯著地被減弱。活性氧物質(Reactive oxidative stress, ROS)的抑制劑 N-乙?半胱氨酸(N-acetyl cysteine, NAC)的存在下，可以顯著地減緩CSE對於LPS/iNOS/NO的抑制作用。此外，NAC也抑制了CSE所誘導的SHP2 (Src homology 2 domain-containing phosphatase 2) 活化。根據上述的結果顯示，CSE可以通過ROS和尼古丁依賴性的調節有效減弱TLR4所介導的NF-κB活化和促炎細胞因子生成，這可能表明M2導向的免疫調節在香菸煙霧暴露中的潛在機制。
Chronic obstructive pulmonary disease (COPD) is a common and treatable disease characterized by progressive airway obstruction and alveolar destruction. COPD is caused by prolonged exposure to noxious particles and gases, mainly the cigarette smoke (CS). Lung macrophages (LMs) are essential for defense against inhaled toxic substances through initiating inflammation, where the phenotypes and functions of LMs are potentially altered by CS. CS-mediated proinflammatory M1 macrophages have been recognized to regulate COPD pathogenesis, however the anti-inflammatory M2 macrophages are shown abundantly in smokers and COPD patients as well. Since the abnormal M1/M2 macrophage phenotypes in CS exposure remains unclear, we therefore investigate the potential mechanisms of macrophage reprogramming in CS stimulation. In the present study, we demonstrated that CS exposure might affect macrophage reprogramming through attenuating Toll-Like Receptor 4 (TLR4) signaling. Freshly prepared cigarette smoke extract (CSE) could effectively induce expressions of inducible nitric oxide synthase (iNOS)/ nitric oxide (NO) and cyclooxygenase-2 (COX-2), and mediate mitogen-activated protein kinases (MAPKs) activation, whereas the surface TLR4 expression remained no significant changes in RAW264.7 cells. Interestingly, CSE pretreatment significantly inhibited lipopolysaccharide (LPS)-mediated expressions of iNOS/NO, COX-2, and IL-6 in RAW264.7 cells. Meanwhile, RAW264.7 cells pretreated with hydrogen peroxide (H2O2) and nicotine also presented similar inhibitions in LPS-regulated proinflammation. LPS-activated NF-κB was attenuated as well in CSE, H2O2, and nicotine pre-stimulation. The presence of ROS scavenger N-acetylcysteine (NAC) significantly reversed CSE-mediated suppression of iNOS/NO in LPS stimulation. Moreover, CSE-induced Src homology 2 domain-containing phosphatase 2 (SHP2) activation was also inhibited by NAC. In summary, this study demonstrated that CSE attenuated TLR4-mediated NF-κB activation and proinflammatory cytokine induction through ROS- and nicotine-dependent regulation, which might suggest the potential mechanisms of M2-skewed immunoregulation in CS exposure. |
