| Acute lung injury (ALI) is a kind of inflammatory syndrome clinically characterized as the increase in blood vessel permeability. It's induced by various dangerous factors outside pulmonary system with complicated pathogenesis. Until now there is still no effective therapeutic principles and the mortality reaches as high as 50-70%. Nuclear factor kappa B (NF-B) is a kind of eukaryon cell transcription factor which is transported to the cell nucleus by extracellular stimulus such as LPS, shock and so on through signal transmission pathway. It promotes and regulates the gene transcription of some inflammatory mediators(TNF-a,etc) and it closely relates to ALI. It is now believed that NF-B plays an important role in both inflammation andimmune reaction. IKK-beta, a kind of sub form of IKK, play the critical role in the activated process of NF-B. Polymyxin B (PMB) is a kind of antibiotics with obvious anti-endotoxin. It restricts the activation of IKK-beta. Recently, great achievements were gone on endotoxin antagonist activity pyrogenicity as well as the acute period reaction of PMB. But it's not seen whether PMB influent the NF-icB activation channel. This study observes the influence of PMB on the activation of NF-B caused by LPS anti-inflammation mechanism on the cell level. At the same time, we discuss the activation pathway of NF-icB and the possible anti-inflammation mechanism of PMB in ALLMethods: Rat PAMs were isolated and cultured. The PAMs were divided into 3 groups, namely, normal control group (PAMs+normal solution), LPS stimulation group (PAMs+10mg/L LPS) and PMB interference group(after PMB treatment for o.5h ,using LPS stimulation). The PAMs were fixed respectively at 0,1/4, 1/2, 1, 2 and 4 hours after stimulation. Nucleoprotein was extracted from cultured PAMs and culture supernatant of the PAMs was collected. The expression of IKK-b mRNA in the PAMs, NF-icB activity in PMB nucleoprotein extractive, TNF-a content in culture supernatant of the PAMs were detected by in situ hybridisation (ISH), electrophoretic mobility shift assay (EMSA) and ELISA, respectively.Results: IKK- P mRNA level in LPS group at 1/4 hour, reached the peak at 1/2 hour, while 1KB-a level turned out contrary to IKK-b mRNA level. The peak of NF-icB activity appeared at 1-2 hours after stimulation was significantly higher than those of pre-stimulation and normal control group (p<0.01). In PMA interference group, NF-icB activity and TNF- a level weremarkedly lower than those in LPS stimulation group (p<0.01). The lowest level of IB-a was notably higher than that in LPS stimulation group, while the peak of IKK- b mRNA was obviously lower than that in LPS stimulation group (p<0.01).Conclusion: After the stimulation of LPS on PAM, IKK-b activation, IB-a degradation and TNF-a release occur. Among them the NF-B rapid activation is probably the key step that PAM release a large amount of inflammatory factors such as TNF-a . There is a continuous signal transmission pathway of IKK-b-IB-a-NF-B-TNF-a which is important to ALL PMB restricts this effect of LPS and functions in the ALI cell model as inflammatory inhibitor. The possible mechanism of its anti-inflammation may be its direct antagonist on LPS besides its antibotic effect. At the same time, PMB, as the IKK-b inhibitor, inhibits the activation of NF-KB on gene transcription level through its influence on the downstream activation IKK-b activation. Therefore, the final results are the block of the out-of-control release of the cytokines and inflammation mediator ( such as TNF-a, and so on). |
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