The Effect Of Pentoxifylline On Immunopathology In Mice Chronically Exposed To Cigarette Smoke And Possible Mechanisms

Background Two of the cardinal points in smoke-induced emphysema (SIE), isexcessive activation of inflammatory cells and chemotaxis of immunoreactant Cellsinto the lung, while chemoreactants and certain signaling pathways are playing anessential role in the process of SIE.In previous research, we have discovered thatadministration of pentoxifylline (PTX) may prevent Guinea pigs from SIE, and that insome animals PTX even leads to a fibrotic phenotype.Wnt/β-catenin signalingpathway is a key regulatory pathway which determines growth, differentiation,proliferation and apoptosis in cells, activation of which has been identified to beassociated with human idiopathic pulmonary fibrosis-usual interstitial pneumonia(IPF/UIP) and epithelial-mesenchymal transition, the key events of pulmonaryfibrosis.However, it's not clear whether PTX could prevent SIE or lead to pulmonaryfibrosis in BALB/c mice, yet it's not clear whether and how PTX regulates theimmune mechanisms and Wnt/β-catenin signaling.Objective To investigate the effect of PTX on pulmonary pathology inBALB/c mice and its correlations with expression of interferon-g (IFN-γ) and interleukin-4 (IL-4), on interferon-γ-inducible protein-10 (IP-10)-mediatedchemotaxis of CXCR3+Th1 and Tc1 cells, and on Wnt/β-catenin signaling。Methods Using Hematoxylin and eosin staining to observe the pathologicalchanges in BALB/c mice chronically exposed to cigarette smoke and oral PTX.Usingenzyme-linked immunnoabsorbant assay (ELISA) to determine the level of IFN-γ,IL-4 and IP-10 in BALF and lung TGF-β1 in vivo, and the level of IP-10 in culturemedium of cigarette smoke extract-stimulated RAW264.7 macrophage cell line invitro.Using immunohistochemical methods to detect the number of CXCR3 orβ-catenin positive cells.Using Western blot assay to detect the expression ofβ-cateninand cyclinD1 in in vivo animal models.Using reverse-transcriptase polymereasechain reaction (RT-PCR) to detect the expression of TCF-1 and LEF-1 mRNA in micelungs.Results Administration of PTX prevented BALB/c mice chronically exposedto cigarette smoke (exposure duration: 4 months) from SIE and lead to pulmonaryfibrosis, accompanied by reversal of the proportion of IFN-γto IL-4 in BALF.PTXinhibited IP-10 release both in BALF in smoking mice (exposure duration: 1 week)and in cigarette smoke extract-stimulated RAW264.7 cells in vitro, and decreasedCXCR3~+ Th1 and Tc1 cell number in smoking mice lungs.Administration of PTXincreasedβ-catenin level in lung tissue and facilitated its transportation to the nucleus,boosted the expression of TCF-1 and TGF-β1, but has shown no significant impacton expression level of cyclinD1 and LEF-1.Conclusions Administration of PTX prevent BALB/c mice chronically exposedto cigarette smoke (exposure duration: 4 months) from SIE and lead to puhnonaryfibrosis, which may be associated with its regulatory effect on Th1/Th2 cytokineprofile balance, inhibitory effect on IP-10-mediated chemotaxis of CXCR3+Th1 andTc1 cells to the lung, as well as activation of certain genes downstreamingWnt/β-catenin signaling pathway.