A breakthrough in paraquat-induced pulmonary fibrosis

首先，我们研究了一氧化氮（NO）和谷胱甘肽（GSH）水平对PQ毒性的影响，在A549细胞和大鼠器官暴露于PQ。我们的体外模型表明，NO显示有益和有害的行动，这取决于产生的浓度和模型系统使用。在体内模型中，我们检测到肝组织中iNOS mRNA水平和硝基酪氨酸存款显著增加，而肺组织中细胞因子基因表达增加，表明PQ中毒的器官机制不同。结果表明，PQ可引起肺组织γ-谷氨酰半胱氨酸合成酶（γ-GCS）和γ-谷氨酰转肽酶（γ-GT）的升高，并使A549细胞GSH水平略有升高。其次，通过分析胆固醇衍生的过氧化氢，我们发现低剂量PQ可引起大鼠肝脏和肾脏中7 α-OOH和7 β-OOH的积累，特别是反映了肾脏病理中更大的氧化应激。最后，为了鉴定PQ引起的氧化应激反应中差异表达的基因，我们使用20 mg/kg PQ处理3 h的大鼠肺cDNA进行了基于RT-PCR的差异显示实验。鉴定了大量上调和下调的cDNA条带;少数克隆与已知基因同源，编码者未知。分离未知的六个不同的cDNA克隆并测序。RT-PCR方法证实了这些克隆的mRNA差异表达。这些结果可能有助于阐明PQ摄入引起的肺纤维化过程中的分子变化。

First, we studied the effect of nitric oxide (NO) and glutathione (GSH) levels on PQ toxicity in A549 cells and rat organs exposed to PQ.Our in vitro models demonstrated that NO showed both beneficial and deleterious actions, depending on the concentrations produced and model system used. We detected, in vivo models, a remarkable increase in iNOS mRNA level and deposit of nitrotyrosine in liver tissues, whereas gene expressions for cytokines increased in lung tissues, suggesting that the mechanisms of PQ poisoning are different among organs exposed to PQ.We found a specific increase in GSH levels, the activities and the expression levels of the rate-limiting enzymes in GSH synthesis ; γ-glutamylcysteine synthetase (γ-GCS) and γ-glutamyl transpeptidase (γ-GT) in lungs exposed to PQ.Also, the GSH levels in A549 cells slightly increased by incubation with PQ.Next, by analyzing cholesterol-derived hydroperoxide, we found 7 α-OOH and 7 β-OOH accumulations in rat liver and kidney exposed to low dose of PQ, especially they reflected greater oxidative stress in the pathology of kidney. Finally, to identify genes that are differentially expressed in response to oxidative stress due to PQ, we carried out RT-PCR based differential display experiments using cDNAs from rat lungs that were treated for 3 hrs with 20 mg/kg PQ.Numerous cDNA bands were identified that were up-regulated and down-regulated ; a few clone were homologous to known genes and the remainders were unknown. Unknown six different cDNA clones were isolated and sequenced. The differential mRNA expression of these clones could be verified using RT-PCR method. These results may prove useful in elucidating the molecular changes during pulmonary fibrosis evoked by PQ intake.