摘要
Background 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. Methods （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）-y 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. Results 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-y 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）. Conclusion 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.
Background 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. Methods （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）-y 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. Results 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-y 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）. Conclusion 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.
基金
This study was supported by a grant from the Natural Science Foundation of Hubei Province, China （No. 2008cdb 153）. The authors have no conflict of interest to declare.Acknowledgements： We are grateful to Dr. TIAN Yuan, Surgery Laboratory of Union Hospital, Tongji Medical College for his generous donation of the macrophage cell line and guidance on cell culture. We also thank Prof. WU Ping and Ms. O1oo Stella Anne for their assistance on revision of this manuscript.
