The Influence And Mechanism Of Suppressive Oligodeoxynucleotides On Silica Induced Early Pulmonary Inflammation In Mice

Silicosis, an occupational disease with the characteristics of externalcell matrix（ECM）deposition in lung interstitial, is due to the long-timeinhalation of free SiO2dust. The Ministry of Public Health announced a totalof27,240cases of occupational diseases in2010, of which23,812caseswere new cases of pneumoconiosis. The proportion which newpneumoconiosis accounted is up to87.42%. Therefore, pneumoconiosis isstill the most serious occupational diseases and the incidence is still grim.Experts found that only10%-20%of the pneumoconiosis patients have donethe diagnosis of occupational diseases and registered in CDC, so the actualcases is much higher than the report number, the experts estimated thepneumoconiosis actual number of cases is not less than100million people.Therefore, to further investigate the pathogenesis of silicosis and looking fornew drugs on silicosis prevention, treatment and even the eventualelimination of silicosis has important significance. The present studysuggests that T lymphocytes activated by silica which was modified bydendritic cells and macrophages and other antigen presenting cells. Although the Th1/Th2polarization in the pathogenesis of silicosis is still notcompletely clear, but studies show that Th1-type cytokines play a major rolein the inflammation stage of the silicosis, Th2-type cytokines play a majorrole in the fibrosis stage of the silicosis. IFN-γis a typical Th1cytokines,which can activate macrophages and NK cells, promote differentiationfrom the initial T cells to Th1cells. The Th1cells differentiation andmature need IFN-γ-dependent STAT1and STAT4phosphorylationsignaling cascade. The experiments confirmed that the rich repeat“TTAGGG” motif ODN has the role of a lowered Th1-type cytokines andproinflammatory mediators. So we can use such ODN for silicosis study,observe its effect on early inflammation of silicosis, and the influence ofinflammatory cytokines.ObjectiveTo observe the influence of Sup ODN on early inflammation ofsilica-treated mice, explore the mechanism of Sup ODN on this disease andevaluate its application value.MethodsSixty female Balb/c mice were randomly divided into4groups, normalcontrol group, silicious group, suppressive oligodeoxynucleotide (Sup ODN)group, control oligodeoxynucleotide (Con ODN) group. Except the normalcontrol group injected normal saline, the rest groups were induced by theintratracheal instillation of0.1ml (5g/L) of streilized silica suspension. Sup ODN group and Con ODN group were treated by i.p. injection of0.3mL(1mg/mL) of suppressive or control ODN3h before silicaadministration. After7days, the animals were killed and use Wright’sstaining to count serum leukocyte. The levels of IFN-γ and TNF-α weredetected by ELISA. The pathologic changes in lung tissues of mice wereobserved with HE staining. Sirius red staining detected I and III typecollagens. Expressions of IFN-γ and pSTAT4in lung tissue were detectedwith immunohistochemistry and quantified by Image-Pro Plus7.0Results1. HE staining proved that the mice model of silicosis was successfullyestablished by intratracheal instillation of silica suspension.2.Compared with the normal control group and Con ODN group,IFN-γ in the serum of Sup ODN group decreased significangtly(P<0.01).The lung tissue of silicious group were damaged seriously thanSup ODN group. Compared with the normal control group, IFN-γ in lungtissue increased (P <0.05), but decreased after treated with Sup ODN.Compared with the normal control group, pSTAT4in lung tissue increasedsignificantly (P<0.01), but decreased significantly after treated with SupODN (P<0.01).Conclusions1.Silica dust can incresed expression of IFN-γ and TNF-α in the serumof silica-treated mice,Sup ODN can reduces IFN-γ production, while no effect on TNF-α.2.Sup ODN may inhibit the expression of IFN-γ and pSTAT4,thenreduce the Th1-type immune response and ultimately achieve its protectiveeffect exposed to silica dust and lung inflammation in mice. In summary, thisstudy results show that Sup ODN has a certain protective effect onsilica-induced pulmonary inflammation in mice. It has opened up newavenues for the silicosis prevention and inflammation adjuvant therapy.