N-乙酰半胱氨酸对脂多糖诱导的小鼠肝MAPK磷酸化的影响

目的： 探讨N-乙酰半胱氨酸（NAC）对脂多糖（LPS）诱导的肝MAPK磷酸化的影响。方法: 雄性昆明种小鼠54只随机分为对照组(n=6)：0.9 % NaCl 0.2 mL ip；LPS组（n=24）：LPS 5 mg ip；NAC+LPS组（n=24）：NAC 150 mg·kg-1·d-1ip，连续3 d；第3 d NAC灌胃后1 h时，LPS 5 mg ip。将小鼠分别在注射LPS或生理盐水后0.5 h、1 h、2 h和6 h时，在戊巴比妥钠麻醉下开腹取肝，测定肝MDA和还原型谷胱甘肽（GSH）含量；Western blotting方法测定肝脏MEK1/2、ERK1/2、p38MAPK磷酸化水平，放免法测定肝TNF-α含量。结果: NAC预处理使肝MDA含量明显下降，使肝GSH含量升高。NAC预处理显著抑制了LPS所致的肝MEK1/2、ERK1/2、p38MAPK磷酸化，同时使肝TNF-α水平显著降低。结论: 在LPS诱导的急性肝损伤过程中，活性氧（ROS）在激活MAPK信号转导中起重要作用。NAC通过其抗氧化作用部分抑制了LPS诱导的MAPK磷酸化，使TNF-α生成减少，从而发挥抗损伤作用。

Effects of N-acetylcysteine on the lipopolysaccharide-induced MAPK phosphorylation in mouse liver

AIM: To investigate the effects of antioxidant N-acetylcysteine (NAC) on the lipopolysaccharide (LPS)-induced MAPK phosphorylation in mouse liver. METHODS: 54 male mice were divided into three groups: control (n=6), 0.9% sodium chloride 0.2 mL ip; LPS group (n=24): LPS 5 mg ip; NAC+LPS group (n=24): NAC 150 mg·kg-1·d-1 ip, for 3 d; LPS 5 mg ip after 1 h of NAC administration at 3rd day. The liver was excised with carbrital anesthesia after LPS or 0.9 % sodium chloride injection at 0.5 h, 1 h, 2 h and 6 h for GSH and MDA assays. The protein extracted from liver was assayed for the phosphorylation of MEK1/2, ERK1/2, p38 MAPK by Western blotting. TNF-α in liver was assayed by radioimmunoassay. RESULTS: MDA in the liver was decreased remarkably and the GSH in the liver was increased significantly by NAC pretreatment. The phosphorylation of MEK1/2, ERK1/2 and p38 MAPK in liver were inhibited significantly by NAC pretreatment after LPS challenge. Meanwhile, TNF-α in liver was decreased markedly. CONCLUSION: Reactive oxygen species plays a critical role in MAPK signaling during the LPS induced acute liver injury. NAC partially inhibits LPS-induced MAPK signaling by antioxidant effect and decreases TNF-α production.