Role of TGF-β/Smad signaling pathway in pulmonary fibrosis after rheumatoid arthritis in mice / 中国药理学通报

Aim To investigate the role of TGF-β/Smad signaling pathway in rheumatoid arthritis (RA) - associated postinterstitial pulmonary fibrosis in mice. Methods The mouse model of RA was constructed by subcutaneous administration of complete Freund's adjuvant (CFA) and chicken II collagen (Col-II) to the tail root of mice. The blank group was given the same amount of distilled water, and the control group was given the same amount of glacial acetic acid (solvent). The degree of toe swelling (joint swelling degree and arthritis index) was monitored to evaluate the mouse modeling. The pathological changes of mouse lung tissues were observed by HE and Masson staining. The expression of TGF-β in lung tissues were observed by immunohistochemical staining. The level of hydroxyproline in lung tissues was measured by chemiluminescence method. The expressions of Smad2, Smad3 and phosphorylated p-Smad2 and phosphorylated p-Smad3 in lung tissues were detected by Western blot. Results Compared with blank group and solvent group, the joint swelling and arthritis index of model group significantly increased. Twenty-one days after administration, HE staining showed inflammatory changes in lung interstitium of the model group, Masson staining showed collagen fiber deposition and obvious fibrosis in lung interstitium of the model group, and immunohistochemical staining showed that the expression of TGF-β in cytoplasm of lung interstitial cells of the model group increased, which was brown and yellow. Meanwhile, hydroxyproline was significantly raised in lung tissue homogenate of the model group. Further WB analysis showed that compared with blank group and solvent group, the expression of p-Smad2 and pSmad3 in lung tissues of the model group was significantly up-regulated (P < 0. 05, P < 0. 01). Conclusions RA can give rise to pulmonary fibrosis, and the expressions of p-Smad2 and p-Smad3 are up-regulated, which is be pivotal in pulmonary fibrosis and RA-related post-interstitial pulmonary fibrosis.

A Tetrahydrofolate-Dependent Methyltransferase Catalyzing the Demethylation of Dicamba in Sphingomonas sp. Strain Ndbn-20.

UNLABELLED: Sphingomonas sp. strain Ndbn-20 degrades and utilizes the herbicide dicamba as its sole carbon and energy source. In the present study, a tetrahydrofolate (THF)-dependent dicamba methyltransferase gene, dmt, was cloned from the strain, and three other genes, metF, dhc, and purU, which are involved in THF metabolism, were found to be located downstream of dmt A transcriptional study revealed that the four genes constituted one transcriptional unit that was constitutively transcribed. Lysates of cells grown with glucose or dicamba exhibited almost the same activities, which further suggested that the dmt gene is constitutively expressed in the strain. Dmt shared 46% and 45% identities with the methyltransferases DesA and LigM from Sphingomonas paucimobilis SYK-6, respectively. The purified Dmt catalyzed the transfer of methyl from dicamba to THF to form the herbicidally inactive metabolite 3,6-dichlorosalicylic acid (DCSA) and 5-methyl-THF. The activity of Dmt was inhibited by 5-methyl-THF but not by DCSA. The introduction of a codon-optimized dmt gene into Arabidopsis thaliana enhanced resistance against dicamba. In conclusion, this study identified a THF-dependent dicamba methyltransferase, Dmt, with potential applications for the genetic engineering of dicamba-resistant crops. IMPORTANCE: Dicamba is a very important herbicide that is widely used to control more than 200 types of broadleaf weeds and is a suitable target herbicide for the engineering of herbicide-resistant transgenic crops. A study of the mechanism of dicamba metabolism by soil microorganisms will benefit studies of its dissipation, transformation, and migration in the environment. This study identified a THF-dependent methyltransferase, Dmt, capable of catalyzing dicamba demethylation in Sphingomonas sp. Ndbn-20, and a preliminary study of its enzymatic characteristics was performed. Introduction of a codon-optimized dmt gene into Arabidopsis thaliana enhanced resistance against dicamba, suggesting that the dmt gene has potential applications for the genetic engineering of herbicide-resistant crops.

Rhizorhabdus dicambivorans sp. nov., a dicamba-degrading bacterium isolated from compost.

Strain Ndbn-20T, a Gram-staining-negative, non-spore-forming bacterium, was isolated from compost of plant litter. The strain was able to degrade dicamba. Phylogenetic analysis based on 16S rRNA gene sequences indicated that Ndbn-20Trepresented a member of the family Sphingomonadaceae of the Alphaproteobacteria and showed high sequence similarities to Rhizorhabdusargentea SP1T (98.8 %), Sphingomonaswittichii RW1T (97.9 %), Sphingomonasstarnbergensis 382T (97.7 %) and Sphingomonashistidinilytica UM2T (97.7 %). However, the strain showed low DNA sequence relatedness with R. argentea SP1T (45.6±1.9 %), S. wittichii RW1T (33.5±2.3 %), S.histidinilytica UM2T (39.4±3.6 %) and S. starnbergensis382T (42.1±4.1 %). Ndbn-20T possessed Q-10 as the predominant ubiquinone, spermidine as the major polyamine, and summed feature 8 (comprising C18 : 1ω7c/C18 : 1ω6c), summed feature 3 (comprising C16 : 1ω7c/C16 : 1ω6c), C17 : 1ω6c, C16 : 0 and C14 : 02-OH as the major fatty acids (>5 % of the total). The profile of polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, glycolipid, sphingoglycolipid, phosphatidyldimethylethanolamine and phosphatidylglycerol. The DNA G+C content was 65.4 mol%. Based on a polyphasic taxonomic analysis, strain Ndbn-20T is proposed to represent a novel species of the genus Rhizorhabdus, with the proposed name of Rhizorhabdus dicambivorans sp. nov. The type strain is Ndbn-20T (=CCTCC AB 2016143=KACC 18661).