科研之友
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摘要
Aim: Daidzein (4 ',7-dihydroxyisoflavone) is an isoflavone exiting in many herbs that has shown anti-inflammation activity. The aim of this study was to investigate the mechanism underlying its anti-inflammatory action in murine lung epithelial cells. Methods: C57BL/6 mice were intranasally exposed to TNF-alpha to induce lung inflammation. The mice were injected with daidzein (400 mg/kg, ip) before TNF-alpha challenge, and sacrificed 12 h after TNF-alpha challenge, and lung tissues were collected for analyisis. In in vitro studies, murine MLE-12 epithelial cells were treated with TNF-alpha (20 ng/mL). The expression of pro-inflammatory chemokine Cxcl2 mRNA and NF-kappa B transcriptional activity were examined using real-time PCR and a dual reporter assay. Protein poly-adenosine diphosphate-ribosylation (PARylation) was detecyed using Western blotting and immunoprecipitation assays. Results: Pretreatment of the mice with daidzein markedly attenuated TNF-alpha-induced lung inflammation, and inhibited Cxcl2 expression in lung tissues. Furthermore, daidzein (10 mu mol/L) prevented TNF-alpha-induced increases in Cxcl2 expression and activity and NF-kappa B transcriptional activity, and markedly inhibited TNF-alpha-induced protein PARylation in MLE-12 cells in vitro. In MLE-12 cells co-transfected with the PARP-1 expression plasmid and NF-kappa B-luc (or Cxcl2-luc) reporter plasmid, TNF-a markedly increased NF-kappa B (or Cxcl2) activation, which were significantly attenuated in the presence of daidzein (or the protein PARylation inhibitor PJ 34). PARP-1 activity assay showed that daidzein (10 mu mol/L) reduced the activity of PARP-1 by similar to 75%. Conclusion: The anti-inflammatory action of daidzein in murine lung epithelial cells seems to be mediated via a direct interaction with PARP-1, which inhibits RelA/p65 protein PARylation required for the transcriptional modulation of pro-inflammatory chemokines such as Cxcl2.
