Involvement of endogenous hydrogen sulfide in cigarette smoke-induced changes in airway responsiveness and inflammation of rat lung.

Hydrogen sulfide (H2S), recently considered the third endogenous gaseous transmitter, may have an important role in systemic inflammation. We investigated whether endogenous H2S may be a crucial mediator in airway responsiveness and airway inflammation in a rat model of chronic exposure to cigarette smoke (CS). Rats randomly divided into control and CS-exposed groups were treated with or without sodium hydrosulfide (NaHS, donor of H2S) or propargylglycine (PPG, inhibitor of cystathionine-γ-lyase [CSE], an H2S-synthesizing enzyme) for 4-month exposure. Serum H2S level and CSE protein expression in lung tissue were higher, by 2.04- and 2.33-fold, respectively, in CS-exposed rats than in controls (P<0.05). Exogenous administration of NaHS to CS-exposed rats alleviated airway reactivity induced by acetylcholine (Ach) or potassium chloride (KCl) by 17.4% and 13.8%, respectively, decreased lung pathology score by 32.7%, inhibited IL-8 and TNF- α concentrations in lung tissue by 34.2% and 31.4%, respectively, as compared with CS-exposed rats (all P<0.05). However, blocking endogenous CSE with PPG in CS-exposed rats increased airway reactivity induced by Ach or KCl, by 24.1% and 24.5%, respectively, and aggravated lung pathology score, by 44.8%, as compared with CS-exposed rats (all P<0.01). Incubation in vitro with NaHS, 1-3 mmol/L, relaxed rat tracheal smooth muscle precontracted by Ach or KCl. However, the NaHS-induced relaxation was not blocked by glibenclamide (10⁻4 mol/L), L-NAME (10⁻4 mol/L), or ODQ (1 µmol/L) or denudation of epithelium. Endogenous H2S may have a protective role of anti-inflammation and bronchodilation in chronic CS-induced pulmonary injury.

[Isolation and characterization of a new Pseudomonas strain against Phytophthora capsici].

One Pseudomonas strain GP72, which was against Phytophthora capsici, was isolated from green pepper rhizosphere in Jiangsu province. It had distinctively inhibitive effect on several kinds of pathogenic fungi; mostly of them are soilborne pathogens. Therefore, this strain may be used for an effective biocontrol strain in the crop protection. The morphological, biochemical and physiological characteristics, Biolog GN, G + C mol% content and 16S rDNA sequence analysis of this strain were studied. In comparison and conclusion of all the experimental data, GP72 is identified as Pseudomonas chlororaphis. The strain is single-cellular and motile by means of single polar flagellum. It was not able to accumulate ploy-beta-hydroxybutyrate. Compared to P. aureofaciens 30-84, the strain was able to survive at the concentration of 5% NaCl. It could strongly utilize 45 of 95 carbon-substrates; weakly utilize 6 of the whole carbon-substrates and never utilize 43 of the whole carbon-substrates resulting from analysis of Biolog GN, bearing the similarity probability of 98% with Pseudomonas chlororaphis and with the similarity index 0.72. The G + C content of the strain DNA was 65.1 mol% using the thermal denaturation method. A phylogenetic tree was constructed by comparing with the validly published 16S rDNA sequences of the related type strains from GenBank, using the Neighbor-Joining method of Saitou and Nei and the Clustal X program to do the multiple alignments. The tree topology was tested by a bootstrap analysis of 1000 samplings. The overall similarity value between strain GP72 and typical is the closest in the phylogenetic tree. For the latest taxonomical development has put genus Pseudomonas aureofaciens to the genus Pseudomonas chlororaphis, then it is appropriate to say that GP72 belongs to the genus Pseudomonas chlororaphis. This is the first time in China to report that a strain of Pseudomonas chlororaphis was isolated from green pepper rhizosphere, having a strong inhibitive effect on Phytophthora capsici and other soilborne pathogenic fungus. The other characteristics and the biocontrol mechanism are yet to be further studied.