CD4+CD25+ Tregs as dependent factor in the course of bleomycin-induced pulmonary fibrosis in mice.

The immune system is felt to play an essential role in pulmonary fibrosis (PF). CD4+CD25+ regulatory T cells (Tregs) are crucial in maintaining immune tolerance and immune homeostasis, but their role in the pathogenesis of PF is controversial and still unclear. We here explored the relationship between peripheral blood CD4+CD25+ Tregs and the course of bleomycin-induced PF in mice. Mouse PF models were established by intratracheal instillation of bleomycin. Lung histology, hydroxyproline, Th1/Th2 balanc, CD4+CD25+ Tregse were analyzed at the 3rd，7th，14th，21st and 28th days after instillation. CD4+CD25+ Tregs were also transferred into mice with or without PF by tail vein injection. The trend of CD4+CD25+ Tregs changes was increased firstly, decreased, increased again from 7th to 28th days after bleomycin instillation, which had great relevance with alveolitis and fibrosis scores. There also were high Th1 polarization index from 3rd to 14th days and high Th2 polarization index at 21st and 28th days after bleomycin treatment. CD4+CD25+ Tregs could promote the secretion of Th2 cytokines and inhibit the secretion of Th1 cytokines, allow the Th1/Th2 balance to Th2 direction in PF. Moreover, preventive adoptive transfer of CD4+CD25+ Tregs may ameliorate the process of PF, while acute adoptive transfer of CD4+CD25+ Tregs may aggravate the process of PF. These findings suggested that the dynamic changes of CD4+CD25+ Tregs as dependent factor might designate a different course of PF induced by bleomycin in mice, and might be a selected drug use indicator for therapy of PF.

Ambient fine particles (PM2.5 ) attenuate collagen-induced platelet activation through interference of the PLCγ2/Akt/GSK3ß signaling pathway.

AIMS: It has been proven that carbon nanoparticles or diesel exhaust particles stimulate platelet activation. However, the effect of fine particle matter (PM2.5 ) on platelet activation remains unknown, which motivates this study. METHODS: PM2.5 samples were collected in an urban area of Zhengzhou, China. To study the morphological characteristics and the mass concentrations of trace elements of PM2.5 samples, a filed-emission scanning electron microscope, the Image-J software, and an inductively coupled plasma mass spectrometry were used. Washed human platelets or platelet-rich-plasma were used to study the effect of PM2.5 on platelet aggregation, P-selectin expression, or platelet signaling pathways. The cytotoxicity in platelets exposed to PM2.5 was evaluated by a lactate dehydrogenase assay kit. In addition, platelet adhesion and spreading were studied on collagen-coated surfaces in stable conditions. RESULTS: The filed-emission scanning electron microscope scanning showed that PM2.5 samples varied in shape and size distributions. The mean equivalent spherical diameter of these particles was 1.97 ± 0.04 µm, of which 82.40% were particles with equivalent spherical diameters of less than 2.5 µm. The mass concentration of Ca was higher than that of other elements. The other elements followed the trend of Al>Fe>Zn>Mg>Pb>K>Mn>Cu>Ti>Ba>As>Sr>Sn>Sb>Cd>B>Se>Mo>Ag>Ni>TI>V>Co. Furthermore, pretreatment of PM2.5 significantly inhibited rather than potentiated collagen-induced platelet aggregation and P-selectin expression, whereas it had no significant effect on ADP-induced platelet aggregation and P-selectin expression. The lactate dehydrogenase analysis showed trivial cytotoxic effect of PM2.5 exposure on platelets. Pretreatment of PM2.5 inhibited platelet adhesion on immobilized collagen-coated surfaces; however, it almost did not impact the platelet spreading. Immunoblotting analysis indicated that PM2.5 reduced collagen-induced phosphorylation of phospholipase C gamma-2 (PLCγ2) at Tyr759, Akt at Ser473, and glycogen synthase kinase 3ß (GSK3ß) at Ser9. CONCLUSIONS: PM2.5 attenuated collagen-induced platelet aggregation, α-granule secretion and adhesion, with the potential mechanism of impairing PLCγ2, Akt, and GSK3ß signaling. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 530-540, 2017.