Development of synthetic surfactant and its protective effect on alveolar type II cell

(1)合成表面活性剂蛋白的研制。利用pET80载体和合成DNA在大肠杆菌中表达了一种模拟表面活性剂蛋白c （Sp-C）的合成肽。然而，合成肽的产率极低。接下来，我们尝试用pQE40载体将合成的肽与DHPP蛋白融合表达，用pET32a载体将合成的肽与氟还氧蛋白融合表达。然而，这两种情况的收益率都很低。低产量被认为是由于合成肽对大肠杆菌的高毒性。因此，我们无法成功地表达合成肽。(2)高碳酸血症的保护作用。高浓度二氧化碳抑制IL-1刺激肺泡II型细胞释放TNF的增加。炎症细胞因子mRNA水平未升高。因此，高浓度的二氧化碳在转录后水平抑制TNF的释放。(3)尼古丁酰胺对肺缺血再灌注损伤的影响。成年大鼠左肺缺血90 min后再灌注。烟酰胺给药大鼠动脉氧压为290±80 (SD) mmHg，明显高于对照组（约100 mmHg）。尼古丁酰胺明显减轻肺缺血再灌注损伤。(4)表面活性剂损伤后肺扩张情况分析。未成熟新生兔经表面活性剂与血清混合处理机械通气后，小肺泡塌陷，大肺泡过度扩张。然而，这种表面活性剂对潮气量的增加程度与普通表面活性剂相同。正常的潮气量剂量不一定意味着表面活性剂功能正常，并可能导致表面活性剂功能受损的忽视。

(1)Development of a synthetic surfactant protein. A synthetic peptide mimicking surfactant protein-C (Sp-C) was expressed in E.coli, by using pET80 vector and synthetic DNA. However, the yield of synthetic peptide was extremely low. Next, we tried to express the synthetic peptide as fusion proteins fused with DHPP protein using pQE40 vector and with tluoredoxin using pET32a. However, the yields were low in both cases. The low yield is thought to be because of high toxicity of the synthetic peptide to E.coli. So, we could not succeed in expressing synthetic peptide.(2)Protective of effect of hypercapnia. High concentration of carbon dioxide (suppressed the increase of TNF released from alveolar type II cell stimulated by IL-1 under cell culture. The levels of mRNA for inflammatory cytokine were not elevated. So, high concentration of carbon dioxide inhibits TNF release at the post-transcription level.(3)Effect of nicotine amide of lung ischemia rperfuusion injury. The left lung of adult rats was reperfirsed after 90 min of ischemia. The arterial oxygen pressure of rats given nicotinamide was 290±80 (SD) mmHg and was significantly higher than that of the control rat (about 100 mmHg). Nicotine amide significantly reduced the lung ischemia reperfusion injury.(4)Analysis of the lung expansion after surfactant impairment. Mechanical ventilation of immature newborn rabbits treated with surfactant mixed with serum causes the collapse of small alveoli and the overexpansion of large alveoli. However, this surfactant increased the tidal volume to the same extent as normal surfactant. Normal tidal volume dose not necessarily mean normal surfactant function and may lead to overlooking impaired surfactant function.