Pentoxifylline attenuates cigarette smoke-induced overexpression of CXCR3 and IP-10 in mice / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Cigarette smoke-induced emphysema is associated with overexpression of the chemokine receptor CXCR3 and its ligands. Previously, we have demonstrated that pentoxifylline (PTX) alleviated cigarette smoke-induced emphysema. The aim of this study was to determine if the overexpression of CXCR3 and its ligand interferon-inducible protein-10 (IP-10) that was elicited by smoke exposure were attenuated by PTX.</p><p><b>METHODS</b>(1) The study in vitro: a given number of RAW264.7 macrophages with decreasing concentrations of PTX in the culture medium were challenged with cigarette smoke extract (CSE); (2) The study in vivo: male BALB/c mice were randomized into four groups, i.e., sham-smoke, smoke only, smoke with 2 mg/kg PTX, and smoke with 10 mg/kg PTX. The smoke exposure time was 90 minutes once a day, 6 days a week for 16 weeks. PTX was given intraperitoneally before each episode of smoke exposure. Interferon (IFN)-γ and IP-10 in broncho-alveolar lavage fluid (BALF) and in culture medium were measured by enzyme-linked immunosorbent assay (ELISA). IP-10 mRNA in lung tissue was assessed by RT-PCR. CXCR3 positive cells in lung sections were visualized by immunochemistry staining.</p><p><b>RESULTS</b>Up-regulation of IFN-γ and IP-10 in the culture medium of macrophages elicited by CSE was inhibited by PTX in a dose-dependent manner. Chronic cigarette smoke exposure led to overexpression of IFN-γ and IP-10 in BALF, upregulation of IP-10 mRNA and increased infiltration of CXCR3(+) cells into lung parenchyma. Administration of PTX decreased the level of IFN-γ from (6.26 ± 1.38) ng/ml to (4.43 ± 0.66) ng/ml by low dose PTX or to (1.74 ± 0.28) ng/ml by high dose PTX. IP-10 was reduced from (10.35 ± 1.49) ng/ml to (8.19 ± 0.79) ng/ml by low dose PTX or to (7.51 ± 0.60) ng/ml by high dose PTX. The expression of IP-10 mRNA was also down-regulated (P < 0.05). But only with a high dose of PTX was the ratio of CXCR3(+) cells decreased; 15.2 ± 7.3 vs. 10.4 ± 1.8 (P < 0.05).</p><p><b>CONCLUSION</b>PTX attenuates cigarette smoke-induced overexpression of chemokine receptor CXCR3 and its ligand IP-10, which is relevant to its inhibitory effect on pulmonary emphysema.</p>

Effects of pentoxifylline on Wnt/β-catenin signaling in mice chronically exposed to cigarette smoke / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Previous discovery that long-term administration of pentoxifylline (PTX) to mice chronically exposed to smoke led to the development of pulmonary fibrosis rather than emphysema initiated our curiosity on whether the Wnt/β-catenin pathway, a set of signaling proteins essential to organ development and lung morphogenesis in particular were activated in the pathogenesis of pulmonary fibrosis.</p><p><b>METHODS</b>Male BALB/c mice were randomized into four study groups: Group Sm, smoke exposure and taken regular forage; Group PTX, no smoke but taken PTX-rich forage; Group Sm + PTX, smoke exposure and taken PTX-rich forage; Group control: shamed smoke exposure and taken regular forage. Animals were sacrificed at day 120. Morphometry of the lung sections and the expressions of TGF-β(1), hydroxyproline, β-catenin, cyclin D1, T cell factor 1 (Tcf-1) and lymphoid enhancer factor 1 (Lef-1) mRNA, etc, in the lung homogenate or in situ were qualitatively or quantitatively analyzed.</p><p><b>RESULTS</b>As expected, smoke exposure along with PTX administration for 120 days, lungs of the mice progressed to be a fibrosis-like phenotype, with elevated fibrosis score (3.9 ± 1.1 vs. 1.7 ± 0.6 in Group Sm, P < 0.05). TGF-β(1) (pg/g) (1452.4 ± 465.7 vs. 818.9 ± 202.8 in Group Sm, P < 0.05) and hydroxyproline (mg/g) (5.6 ± 0.6, vs. 2.4 ± 0.1 in Group Sm, P < 0.05) were also consistently increased. The upregulation of β-catenin measured either by counting the cell with positive staining in microscopic field (17.4 ± 7.9 vs. 9.9 ± 2.9 in Group Sm, P < 0.05) or by estimation of the proportion of blue-stained area by Masson's trichrome (11.8 ± 5.6 vs. 4.7 ± 2.4 in Group Sm) in Group SM + PTX was much more noticeable as than those in Group Sm. The expression of β-catenin measured by positive cell counts was correlated to TGF-β(1) concentration in lung tissue (r = 0.758, P < 0.001). PTX per se caused neither fibrosis nor emphysema though expression of β-catenin and downstream gene cyclin D(1) may also be altered by this medication.</p><p><b>CONCLUSIONS</b>PTX mediated transformation of pulmonary emphysema into pulmonary fibrosis under chronic cigarette smoke exposure is associated with upregulation of β-catenin and elevation of TGF-β(1), implying that activation of Wnt/β-catenin signaling may be involved in the pathogenesis of pulmonary fibrosis.</p>