| 摘要: | 重症病患或加護病房住院病人約有百分之五十的比例會感染敗血症病導致死亡，且約有百分之五十的比例會有急性肺傷害的產生。肺泡巨噬細胞對於肺臟的防禦及免疫調節中扮演著相當重要的角色，所以本篇研究探討急性肺傷害以及肺泡巨噬細胞的關係。在之前的研究發現晚期的敗血症肺泡巨噬細胞數量比起早期是減少的(0.73×107 ± 0.1×107 vs. 1.0×107 ± 0.05×107; p<0.05)，即假設敗血症中晚期的肺泡巨噬細胞數量減少是因為細胞凋亡，因此，以盲腸穿孔及結紮的方式引起Sprague-Dawley白鼠的敗血症，手術後三小時、九小時和二十小時分別代表敗血症的更早期、早期以及晚期。以支氣管灌流方式分離肺泡巨噬細胞，純度皆大於95%。以流式細胞儀分析肺泡巨噬細胞，以相對細胞大小及顆粒性區分出兩個細胞族群，相對細胞較大者為RB，相對細胞較小者為RS，九小時的敗血組RB和RS的細胞凋亡比例分別為33.5±4.4 % and 8.2±1.4%，p<0.05 and p<0.05，皆較對照組高(17.8± 5.2% and 5.1±1.3%)，二十小時的RB和RS的細胞凋亡比例分別為15.4±2.3% and 5.8±2.5%，亦較其對照組高(35.4±2.3% and 22.7±1.1%; p<0.01 and p<0.01)。結果顯示在敗血症的早期或是晚期RB和RS的細胞凋亡比例皆較其對照組高。結果顯示RS族群可能是在敗血症所引起的急性肺傷害中最容易受的損傷的細胞，而RB族群不論是早期或晚期敗血症中的細胞凋亡比例皆類似，推測可能與敗血症終非特異性的發炎反應較有關，而且應是作用很快速的細胞。RB和RS的吞噬功能則沒有差異。 因為RB族群在敗血症更早期時即有大量的細胞凋亡比例，推測應與引起RS族群的細胞凋亡有關，所以，降低RB族群在敗血症更早期帶來的傷害，可能可以降低急性肺傷害所帶來的損傷。; Acute lung injury (ALI), such as acute respiratory distress syndrome, frequently follows the occurrence of sepsis not only in various animal models but in human. However, the mechanism(s) of ALI are not fully established. In the lungs, alveolar macrophages (AM) play an important role in defenses and immunoregulation. In our previous studies, the number of AM was significantly decreased in late phase of cecal ligation and puncture (CLP)-induced sepsis. We hypothesized that the death of AM, probably via apoptosis, is responsible for sepsis-induced ALI. In the present study, Sprague-Dawley rats were employed to investigate the percentage of AM apoptosis. At 3h, 9 h and 20 h, i.e., very early, early and late phases of sepsis, respectively, CLP- and sham -operated (control) animalswere sacrificed and lungs were removed. Alveolar macrophages (AM) were isolated by bronchoalveolar lavage (BAL) with phosphate-buffered saline. The AM obtained were labeled with Annexin-V and the percentage of apoptosis was determined by a flow cytometer. The results showed that the number of AM in late phase of sepsis (0.73×107± 0.1×107) is less than that of early phase (1.0×107± 0.05×107), p<0.02. The purity of AM, as stained by Giemsa, from both groups was >95%. Based on cell size and granularity, two subsets of AM, a big (RB) and a small (RS) ones, were identified by using a flow cytometer. At 9 h after CLP, more percentages of apoptotic cells were detected in RB than in Rs from septic rats (33.5±4.4% vs. 11.8±2.2%), both of which were much more than those of corresponding control subsets (17.8±5.2% and 5.1±1.3%; p<0.05 vs. p<0.05). Likewise, the apoptotic percentages of RB and RS AM from 20 h control rats were, 15.4±2.3% vs. 5.8±2.5%, respectively. The cells from 20 h septic rats (35.4±2.3% and 22.7±1.1%; p<0.01 vs. p<0.01) died by apoptosis to a greater degree an those from the corresponding ones. These data revealed that more baseline apoptosis was found in RB than in RS. At early and late sepsis phases, as compared to the control groups, cells of Rs suffered from 2- and 4-fold, respectively, increases in apoptosis, while those of RB only 2-fold. The phagocytotic abilities of control and septic group had no difference in 3h, 9h and 20 h. It is likely that, not the whole populations of lung macrophages, but rather Rs subset of AM was among the most liable cells of septic lung injury. Considering that AM of small size and granularity presumably represents young in-situ lung macrophages with optimal functions, these results suggested that the defensive ability of septic lungs might be reduced and could explain, at least in part, the increased susceptibility of septic lung to superimposed infections and to the occurrence of ARDS. |
