Respiratory epithelial cell expression of human transforming growth factor-alpha induces lung fibrosis in transgenic mice.

Increased production of EGF or TGF-alpha by the respiratory epithelial cells has been associated with the pathogenesis of various forms of lung injury. Growth factors and cytokines are thought to act locally, via paracrine and autocrine mechanisms, to stimulate cell proliferation and matrix deposition by interstitial lung cells resulting in pulmonary fibrosis. To test whether TGF-alpha mediates pulmonary fibrotic responses, we have generated transgenic mice expressing human TGF-alpha under control of regulatory regions of the human surfactant protein C (SP-C) gene. Human TGF-alpha mRNA was expressed in pulmonary epithelial cells in the lungs of the transgenic mice. Adult mice bearing the SP-C-TGF-alpha transgene developed severe pulmonary fibrosis. Fibrotic lesions were observed in peribronchial, peribronchiolar, and perivascular regions, as well as subjacent to pleural surfaces. Lesions consisted of fibrous tissue that included groups of epithelial cells expressing endogenous SP-C mRNA, consistent with their identification as distal respiratory epithelial cells. Peripheral fibrotic regions consisted of thickened pleura associated with extensive collagen deposition. Alveolar architecture was disrupted in the transgenic mice with loss of alveoli in the lung parenchyma. Pulmonary epithelial cell expression of TGF-alpha in transgenic mice disrupts alveolar morphogenesis and produces fibrotic lesions mediated by paracrine signaling between respiratory epithelial and interstitial cells of the lung.     

百草枯反复小剂量腹腔给药诱导小鼠肺纤维化模型

目的 建立百草枯(PQ)诱导肺损伤及肺纤维化小鼠动物模型,并比较其与博莱霉素( BLM)的成模差异,进而建立一个更理想的动物模型.方法 采用8～10周龄雄性C57BL/6J(C57)小鼠(n=30),随机(随机数字)分为百草枯腹腔给药组(n=10),博莱霉素气管给药组(n=10)及阴性对照组(n=10),PQ组经腹腔注射PQ 10 mg/kg,每3d一次,共5次,BLM组气管内注射BLM 3 mg/kg.分别于第7,14,21天处死小鼠,监测小鼠一般情况、体质量及肺组织病理改变.数据收集后采用SPSS 13.0统计软件进行分析,两组之间的比较采用Mann-Whitney U检验.结果 PQ腹腔注射及气管注射BLM给药,都能造成肺损伤及纤维化模型.通过比较生存率、体质量变化、肺组织病理学的变化、成模率等指标,显示反复小剂量腹腔注射PQ较传统的BIM气管内注射的方法造模更方便有效,成功率更高.结论 通过小鼠肺损伤及肺纤维化动物造模方法的比较,反复小剂量腹腔注射PQ为更理想的造模方式,并且较BLM诱导的方法有更高的成功率.     

Mn‐loaded apoferritin: a highly sensitive MRI imaging probe for the detection and characterization of hepatocarcinoma lesions in a transgenic mouse model

Mn‐Apo is a highly sensitive MRI contrast agent consisting of ca. 1000 manganese atoms entrapped in the inner cavity of apoferritin. Part of the metallic payload is in the form of Mn²⁺ ions that endow the nano‐sized system with a very high relaxivity that can be exploited to detect hepatocellular carcinoma in mice. Cellular studies showed that Mn‐Apo is readily taken up by normal hepatocytes via the ferritin transporting route. Conversely, hepatoma cells (HTC) displayed a markedly reduced ability to entrap Mn‐Apo from the culture medium. The i.v. administration of Mn‐Apo into C57BL/6 J mice resulted in a marked liver tissue hyperintensity in T₁‐weighted MR image 20 min after injection. When injected into HBV‐tg transgenic mice that spontaneously develop hepatocellular carcinoma (HCC), Mn‐Apo allowed a clear delineation of healthy liver tissue and tumor lesions as hyperintense and hypointense T₁‐weighted MR images, respectively. Immunohistochemistry analysis correlated Mn‐Apo cellular uptake to SCARA5 receptor expression. When the MRI contrast induced by Mn‐Apo was compared with that induced by Gd–BOPTA (a commercial contrast agent known to enter mouse hepatocytes through organic anion transporters) it was found that only some of the lesions were detected by both agents while others could only be visualized by one of the two. These results suggest that Mn‐Apo may be useful to detect otherwise invisible lesions and that the extent of its uptake directly reports the expression/regulation of SCARA5 receptors. Mn‐Apo contrast‐enhanced MR images may therefore contribute to improving HCC lesion detection and characterization. Copyright © 2012 John Wiley & Sons, Ltd.     

Epithelial cell α3β1 integrin links β-catenin and Smad signaling to promote myofibroblast formation and pulmonary fibrosis

Pulmonary fibrosis, in particular idiopathic pulmonary fibrosis (IPF), results from aberrant wound healing and scarification. One population of fibroblasts involved in the fibrotic process is thought to originate from lung epithelial cells via epithelial-mesenchymal transition (EMT). Indeed, alveolar epithelial cells (AECs) undergo EMT in vivo during experimental fibrosis and ex vivo in response to TGF-β1. As the ECM critically regulates AEC responses to TGF-β1, we explored the role of the prominent epithelial integrin α3β1 in experimental fibrosis by generating mice with lung epithelial cell–specific loss of α3 integrin expression. These mice had a normal acute response to bleomycin injury, but they exhibited markedly decreased accumulation of lung myofibroblasts and type I collagen and did not progress to fibrosis. Signaling through β-catenin has been implicated in EMT; we found that in primary AECs, α3 integrin was required for β-catenin phosphorylation at tyrosine residue 654 (Y654), formation of the pY654–β-catenin/pSmad2 complex, and initiation of EMT, both in vitro and in vivo during the fibrotic phase following bleomycin injury. Finally, analysis of lung tissue from IPF patients revealed the presence of pY654–β-catenin/pSmad2 complexes and showed accumulation of pY654–β-catenin in myofibroblasts. These findings demonstrate epithelial integrin–dependent profibrotic crosstalk between β-catenin and Smad signaling and support the hypothesis that EMT is an important contributor to pathologic fibrosis.     

Angiotensin II type 1 receptor blocker inhibits pulmonary injury

PURPOSE: Pulmonary damage and fibrosis may be the result of diverse forms of injury and there is an association between pulmonary diseases and cardiovascular events. The purpose of this study was to evaluate the effects of an angiotensin II type 1 receptor blocker, valsartan, on systemic, cellular, and fibrotic consequences of pulmonary injury induced by the anti-neoplastic antibiotic, bleomycin. METHODS: Sprague Dawly rats were used in the classical bleomycin model of pulmonary fibrosis. Bleomycin (1 unit, n = 7) was administered intra-tracheally to induce lung injury. Valsartan (0.66 mg) was given either concomitantly (n = 9) or for two days prior to bleomycin (n = 8). A control group (n = 6) was given normal saline. RESULTS: Valsartan-treated animals showed abrogation of weight loss, suppression of release of total and active transforming growth factor beta-1 (TGF-beta1), and diminished connective tissue synthesis. In an explant, lung tissue culture model devoid of alveolar macrophages (saline control, n = 3; bleomycin, n = 6; bleomycin plus valsartan, n = 12), both total and active TGF-beta1 were suppressed in the valsartan-treated cohort. CONCLUSIONS: Valsartan, known to have cardio-protective properties, was shown to be protective of bleomycin-induced pulmonary injury. Thus, ARBs may be beneficial in both cardiac and pulmonary diseases.     

Plasma and pulmonary pharmacokinetics of bleomycin in murine strains that are sensitive and resistant to bleomycin-induced pulmonary fibrosis

Previous studies have shown that C57Bl/6N mice are sensitive and BALB/c mice are resistant to the pulmonary fibrotic effects of bleomycin (BLM). We assessed the plasma elimination and pulmonary content of BLM in C57Bl/6N and BALB/c mice treated with a single dose of [3H]BLM (80 mg/kg i.v.) to determine whether these murine strains show corresponding differences in BLM pharmacokinetics and pulmonary disposition after systemic administration of the drug. Serial blood samples were obtained from each animal and lungs were collected after pulmonary lavage or vascular perfusion with saline. Administration of BLM (80 mg/kg i.v.) produced significant elevations in lung hydroxyproline (35%) in C57Bl/6N but not in BALB/c mice. In contrast, BALB/c mice were more sensitive to pulmonary fibrosis induced with cyclophosphamide (200 mg/kg i.p.) compared to C57Bl/6N mice, indicating that strain sensitivity to pulmonary fibrosis is drug specific in these mice. BLM showed first order plasma elimination kinetics over 30 min in both strains with a shorter half-life in the sensitive strain (9.6 +/- 0.3 min in C57Bl/6N vs. 12.7 +/- 1.9 min in BALB/c). Plasma elimination deviated from first order kinetics after 30 min in both strains and plasma levels of BLM were up to 2-fold higher in the resistant strain over a 3-hr time course. Radioactivity in saline-perfused lungs was also significantly higher (1.5-2-fold) in BALB/c mice for least 1 hr after BLM injection. A similar fraction of the total lung radioactivity (approximately 80%) was recovered from both strains by pulmonary lavage, suggesting that BLM enters the alveolar spaces relatively freely in each strain.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevention of bleomycin-induced pulmonary fibrosis after adenovirus-mediated transfer of the bacterial bleomycin resistance gene.

A serious limitation in the use of the DNA-cleaving, antitumoral-antibiotic, bleomycin during chemotherapy is pulmonary toxicity. Lung injury induced by bleomycin is characterized by an increased deposition of interstitial extracellular matrix proteins in the alveolar wall that compromises respiratory function. Several drugs have been tested in animal models to prevent the pulmonary toxicity of bleomycin, but have not led to a useful clinical treatment because of their adverse effects on other tissues. We have shown that transgenic mice expressing Streptoalloteichus hindustanus (Sh) ble bleomycin resistance protein in pulmonary epithelial cells in the lungs are protected against bleomycin-induced toxicity in lungs. In the present study, we used intranasal administration by adenovirus-mediated gene transfer of the bleomycin resistance Sh ble gene to mouse lung for prevention of bleomycin-induced pulmonary fibrosis. We constructed recombinant adenoviruses Ad.CMVble and Ad.RSVble harboring the bleomycin resistance Sh ble gene under the control of the cytomegalovirus early promoter and the Rous sarcoma virus early promoter, respectively. Transgene expression was detected in epithelia of conducting airways and alveolar septa by immunostaining with a rabbit polyclonal antibody directed against the bleomycin resistance protein and persisted for the duration of drug treatment; i.e., up to 17 d. No toxic effect was seen in adenovirus-treated mice. Pretreatment of mice with Ad.CMVble or Ad.RSVble completely prevented collagen deposition 42-133 d after bleomycin treatment, as measured by lung OH-proline content. Histologic studies indicated that there was little or no lung injury in the adenovirus/bleomycin-treated mice compared with the bleomycin-treated mice. These observations may lead to new approaches for the prevention of bleomycin-induced pulmonary fibrosis.     

Inhibition of pulmonary fibrosis in mice by CXCL10 requires glycosaminoglycan binding and syndecan-4

Pulmonary fibrosis is a progressive, dysregulated response to injury culminating in compromised lung function due to excess extracellular matrix production. The heparan sulfate proteoglycan syndecan-4 is important in mediating fibroblast-matrix interactions, but its role in pulmonary fibrosis has not been explored. To investigate this issue, we used intratracheal instillation of bleomycin as a model of acute lung injury and fibrosis. We found that bleomycin treatment increased syndecan-4 expression. Moreover, we observed a marked decrease in neutrophil recruitment and an increase in both myofibroblast recruitment and interstitial fibrosis in bleomycin-treated syndecan-4–null (Sdc4^–/–) mice. Subsequently, we identified a direct interaction between CXCL10, an antifibrotic chemokine, and syndecan-4 that inhibited primary lung fibroblast migration during fibrosis; mutation of the heparin-binding domain, but not the CXCR3 domain, of CXCL10 diminished this effect. Similarly, migration of fibroblasts from patients with pulmonary fibrosis was inhibited in the presence of CXCL10 protein defective in CXCR3 binding. Furthermore, administration of recombinant CXCL10 protein inhibited fibrosis in WT mice, but not in Sdc4^–/– mice. Collectively, these data suggest that the direct interaction of syndecan-4 and CXCL10 in the lung interstitial compartment serves to inhibit fibroblast recruitment and subsequent fibrosis. Thus, administration of CXCL10 protein defective in CXCR3 binding may represent a novel therapy for pulmonary fibrosis.     

不同时段剂量腹腔注射百草枯致小鼠肺损伤及肺纤维化效果评价

目的 观察不同时段、剂量腹腔注射百草枯(PQ)对于小鼠肺损伤及肺纤维化诱导效果的区别,以期建立更为合适、操作简便且结果稳定的肺损伤和/或肺纤维化动物模型.方法 8～10周龄雄性C57BL/6J小鼠,分别采取腹腔注射单次给药(40 mg/kg、50 mg/kg、60 mg/kg),连续给药(10 mg/kg、12.5 mg/kg、15 mg/kg),以及间断给药(20 mg/kg、22.5 mg/kg、25 mg/kg)的方法,同组随机(随机数字法)匹配生理盐水对照组.分别于末次给药后1周、2周处死小鼠.监测小鼠一般情况,体质量状况及病死率.收获日检测肺功能指标;肺泡支气管灌洗液(BALF)细胞计数及分类;羟脯氨酸浓度;以及组织病理学分析.结果 单次或间断腹腔注射不同剂量PQ,均可诱导部分小鼠发生急性肺损伤,早期观察时间点的炎症表现随剂量增高而加重;晚期观察点少量存活小鼠可发生肺间质纤维化.病理切片见损伤部位主要集中在背后段、外周及胸膜下.但以上两组给药方式早期均有较高病死率,故晚期肺纤维化致病率较低.小剂量PQ连续给药法在各时间点诱导C57BL/6J小鼠的肺部病变缺乏显著意义.结论 单次大剂量或间断中等剂量腹腔注射作为PQ全身性给药的方法之一,可以成功诱导出早期小鼠急性肺损伤,但研究终点肺纤维化的致病率较低.PQ小剂量连续给药法致C57BL/6J鼠系肺损伤及肺纤维化的效果不明显.     

Regulation of pulmonary fibrosis by chemokine receptor CXCR3

CXC chemokine receptor 3 (CXCR3) is the receptor for the IFN-gamma-inducible C-X-C chemokines MIG/CXCL9, IP-10/CXCL10, and I-TAC/CXCL11. CXCR3 is expressed on activated immune cells and proliferating endothelial cells. The role of CXCR3 in fibroproliferation has not been investigated. We examined the role of CXCR3 in pulmonary injury and repair in vivo. CXCR3-deficient mice demonstrated increased mortality with progressive interstitial fibrosis relative to WT mice. Increased fibrosis occurred without increased inflammatory cell recruitment. CXCR3 deficiency resulted in both a reduced early burst of IFN-gamma production and decreased expression of CXCL10 after lung injury. We identified a relative deficiency in lung NK cells in the unchallenged CXCR3-deficient lung and demonstrated production of IFN-gamma by WT lung NK cells in vivo following lung injury. The fibrotic phenotype in the CXCR3-deficient mice was significantly reversed following administration of exogenous IFN-gamma or restoration of endogenous IFN-gamma production by adoptive transfer of WT lymph node and spleen cells. Finally, pretreatment of WT mice with IFN-gamma-neutralizing Ab's enhanced fibrosis following lung injury. These data demonstrate a nonredundant role for CXCR3 in limiting tissue fibroproliferation and suggest that this effect may be mediated, in part, by the innate production of IFN-gamma following lung injury.     

Attenuation effects of heparin–superoxide dismutase conjugate on bleomycin-induced lung fibrosis in vivo and radiation-induced inflammatory cytokine expression in vitro

In this study, the effects of heparin–superoxide dismutase conjugate (heparin–SOD) on bleomycin-induced pulmonary fibrosis in vivo and on inflammatory cytokine expression in vitro were evaluated. To investigate the effects of heparin–SOD on pulmonary fibrosis, heparin–SOD was administered to bleomycin (BLM)-treated mice by intraperitoneal injection once a day and the hydroxyproline content in lung was determined per 7 days. The degree of fibrosis was assessed quantitatively using histopathologic features. The results showed that heparin–SOD inhibited BLM-induced lung fibrotic lesions as reflected by the decrease of lung hydroxyproline content and lung fibrosis grade 28 days after BLM instillation. The in vitro effects on the cytokine level expressed by irradiated 3T3 fibroblasts showed that heparin–SOD significantly lowered the levels of transforming growth factor-β1 and interleukin-1β. These results strongly demonstrated that heparin–SOD might be useful in the prevention and treatment of pulmonary fibrosis.     

Bleomycin-induced pulmonary fibrosis in transgenic mice that either lack or overexpress the murine plasminogen activator inhibitor-1 gene.

Impaired fibrinolytic activity within the lung is a common manifestation of acute and chronic inflammatory lung diseases. Because the fibrinolytic system is active during repair processes that restore injured tissues to normal, reduced fibrinolytic activity may contribute to the subsequent development of pulmonary fibrosis. To examine the relationship between the fibrinolytic system and pulmonary fibrosis, lung inflammation was induced by bleomycin in transgenic mice that either overexpressed or were completely deficient in murine plasminogen activator inhibitor-1 (PAI-1). 2 wk after 0.075 U of bleomycin, the lungs of transgenic mice overexpressing PAI-1 contained significantly more hydroxyproline (118 +/- 8 micrograms) than littermate controls (70.5 +/- 8 micrograms, P < 0.005). 3 wk after administration of a higher dose of bleomycin (0.15 U), the lung hydroxyproline content of mice completely deficient in PAI-1 (49 +/- 8 micrograms) was not significantly different (P = 0.63) than that of control animals receiving saline (37 +/- 1 micrograms), while hydroxyproline content was significantly increased in heterozygote (77 +/- 12 micrograms, P = 0.06) and wild-type (124 +/- 19 micrograms, P < 0.001) littermates. These data demonstrate a direct correlation between the genetically determined level of PAI-1 expression and the extent of collagen accumulation that follows inflammatory lung injury. These results strongly support the hypothesis that alterations in fibrinolytic activity influence the extent of pulmonary fibrosis that occurs after inflammatory injury.     

Paramagnetic self‐assembled nanoparticles as supramolecular MRI contrast agents

Nanometer‐sized materials offer a wide range of applications in biomedical technologies, particularly imaging and diagnostics. Current scaffolds in the nanometer range predominantly make use of inorganic particles, organic polymers or natural peptide‐based macromolecules. In contrast we hereby report a supramolecular approach for the preparation of self‐assembled dendritic‐like nanoparticles for applications as MRI contrast agents. This strategy combines the benefits from low molecular weight imaging agents with the ones of high molecular weight. Their in vitro properties are confirmed by in vivo measurements: post injection of well‐defined and meta‐stable nanoparticles allows for high‐resolution blood‐pool imaging, even at very low Gd(III) doses. These dynamic and modular imaging agents are an important addition to the young field of supramolecular medicine using well‐defined nanometer‐sized assemblies. Copyright © 2012 John Wiley & Sons, Ltd.     

博莱霉素致小鼠肺纤维化模型的动态演变及其发生机制

目的 了解小鼠肺纤维化模型的动态演变，探讨博莱霉素致肺纤维化的作用机制。方法 36只雄性ICR小鼠，按随机数字表法分为阴性对照组（NC组）和肺纤维化模型组（FMA、FMB、FMC、FMD、FME组），每组6只。除NC组外，其余各组经鼻滴入博莱霉素建立肺纤维化模型。分别于6、14、21、28和35d处死各组小鼠，取外周血经流式细胞仪测定T细胞亚群Th1／Th2和Tc1／Tc2，计数支气管肺泡灌洗液（BALF）中总细胞数和细胞分类，右肺行苏木素-伊红（HE）及Masson染色，测定左肺组织中羟脯氨酸（HYP）的含量；并提取左肺组织总RNA，采用半定量逆转录-聚合酶链反应（RT—PCR）了解肺组织中多种细胞因子的表达。测定35d处死小鼠的潮气量（Vt）、0．1秒用力呼气容积／用力肺活量（FEV0．1／FVC）和静态肺顺应性（Cst）。结果 ①肺纤维化各组小鼠BALF中细胞总数与NC组比较均显著增高（P均〈O．01），且其肺组织中HYP含量除FMA组外均显著升高（P均〈0．01）。②FME组VT和Cst均较NC组明显降低（P均〈0．01），FEV0．1／FVC则显著升高（P〈O．05）。③在肺纤维化模型炎症期（FMA组），T细胞Th1／Th2和Tc1／Tc2之间的平衡呈Th1、Tc1优势表达为主；在纤维化形成期（FMB、FMC组），则以Th2、Tc2优势表达；在肺纤维化形成后，Th1、Tc1再度呈优势表达的状态。④肺纤维化模型组中转化生长因子-β1（TGF—β1）和金属蛋白酶组织抑制因子-1（TIMP-1）均较NC组显著升高（P均〈0．01）。结论 博莱霉素致肺纤维化小鼠肺功能为限制性通气功能障碍，Th2、Tc2及促纤维化生成因子在肺纤维化形成过程中发挥重要作用。     

Assessment of tumor angiogenesis: dynamic contrast‐enhanced MRI with paramagnetic nanoparticles compared with Gd‐DTPA in a rabbit Vx‐2 tumor model

The purpose of this study was to evaluate the suitability of a macromolecular MRI contrast agent (paramagnetic nanoparticles, PNs) for the characterization of tumor angiogenesis. Our aim was to estimate the permeability of PNs in developing tumor vasculature and compare it with that of a low molecular weight contrast agent (Gd‐DTPA) using dynamic contrast‐enhanced MRI (DCE). Male New Zealand white rabbits (n = 5) underwent DCE MRI 12–14 days after Vx‐2 tumor fragments were implanted into the left hind limb. Each contrast agent (PNs followed by Gd‐DTPA) was evaluated using a DCE protocol and transendothelial transfer coefficient (K_i) maps were calculated using a two‐compartment model. Two regions of interest (ROIs) were located within the tumor core and hindlimb muscle and five ROIs were placed within the tumor rim. Comparisons were performed using repeated measures analysis of variance (ANOVA). The K_i values estimated using PNs were significantly lower than those obtained for Gd‐DTPA (p = 0.018). When PNs and Gd‐DTPA data were analyzed separately, significant differences were identified among tumor rim ROIs for PNs (p < 0.0001), but not for Gd‐DTPA data (p = 0.34). The mean K_i for the tumor rim was significantly greater than that of either the core or the hindlimb muscle for both contrast agents (p < 0.05 for each comparison). In summary, the extravasation of Gd‐DTPA was far greater than that of PNs, suggesting that PNs can reveal regional differences in tumor vascular permeability that are not otherwise apparent with clinical contrast agents such as Gd‐DTPA. These results suggest that PNs show potential for the noninvasive delineation of tumor angiogenesis. Copyright © 2010 John Wiley & Sons, Ltd.     

Measurement of cross-linked elastin synthesis in bleomycin-induced pulmonary fibrosis using a highly sensitive assay for desmosine and isodesmosine

Cross-linked elastin synthesis was measured in the intratracheal bleomycin model of interstitial pulmonary fibrosis by incorporation of 14C-lysine into the elastin-specific crosslinks, desmosine and isodesmosine. Detection of the labeled crosslinks was facilitated by development of a highly sensitive assay utilizing thin-layer electrophoresis. The results indicate that crosslinked elastin synthesis is significantly elevated from controls (p less than 0.05) at 1 to 3 weeks after exposure to bleomycin and returns to normal by 5 weeks. The increases in labeled elastin synthesis are not directly related to changes in either total lung protein synthesis or the pool size of the 14C-lysine. In comparison with collagen and glycosaminoglycan synthesis in this model of lung injury, maximal increases in cross-linked elastin formation occur later, but overlap with the elevated synthesis of these other connective tissue components. The marked increase from normal in cross-linked elastin synthesis in this model suggests that this tissue component is an important part of the fibrotic response of the pulmonary parenchyma and may play a role in the observed alterations in lung structure and function.     

Bleomycin-induced pulmonary fibrosis in fibrinogen-null mice

Mice deleted for the plasminogen activator inhibitor-1 (PAI-1) gene are relatively protected from developing pulmonary fibrosis induced by bleomycin. We hypothesized that PAI-1 deficiency reduces fibrosis by promoting plasminogen activation and accelerating the clearance of fibrin matrices that accumulate within the damaged lung. In support of this hypothesis, we found that the lungs of PAI-1(-/-) mice accumulated less fibrin after injury than wild-type mice, due in part to enhanced fibrinolytic activity. To further substantiate the importance of fibrin removal as the mechanism by which PAI-1 deficiency limited bleomycin-induced fibrosis, bleomycin was administered to mice deficient in the gene for the Aalpha-chain of fibrinogen (fib). Contrary to our expectation, fib(-/-) mice developed pulmonary fibrosis to a degree similar to fib(+/-) littermate controls, which have a plasma fibrinogen level that is 70% of that of wild-type mice. Although elimination of fibrin from the lung was not in itself protective, the beneficial effect of PAI-1 deficiency was still associated with proteolytic activity of the plasminogen activation system. In particular, inhibition of plasmin activation and/or activity by tranexamic acid reversed both the accelerated fibrin clearance and the protective effect of PAI-1 deficiency. We conclude that protection from fibrosis by PAI-1 deficiency is dependent upon increased proteolytic activity of the plasminogen activation system; however, complete removal of fibrin is not sufficient to protect the lung.     

The pulmonary toxicity of nitrosoureas

Drug-induced pulmonary fibrosis in cancer chemotherapy has become a more serious problem as treatment regimens are refined, larger total doses of cytotoxic drugs are administered and patient prognosis improves. The nitrosoureas are a class of chemotherapeutic agents whose clinical use is severely limited by drug-induced toxicities. The myelosuppression caused by nitrosourea administration can be managed clinically; however, the development of irreversible pulmonary fibrosis is a more serious clinical problem. Studies are needed to identify biochemical markers for early lung injury so that the amount of pulmonary tissue damage can be assessed and monitored. Additionally, considerable research is needed to understand the mechanisms by which these agents produce lung injury, so that therapeutic regimens can be developed to minimize or prevent lung toxicity. In understanding the mechanisms of toxicity, potentially the pulmonary injury caused by nitrosourea administration can be altered without affecting the clinical antitumor activity of this class of compounds. In the future, knowledge on mechanisms of drug-induced pulmonary injury can be used in the development of antineoplastic agents which are more disease specific and less pulmonary toxic.     

黄芩苷对博来霉素诱导肺纤维化小鼠的保护作用及其机制

目的观察黄芩苷对博来霉素诱导肺纤维化小鼠的保护作用及其机制。 方法将18只小鼠分为对照组、博来霉素组和黄芩苷组,每组6只。博来霉素组和黄芩苷组小鼠给予博来霉素（5 mg/kg）气管内给药以建立小鼠肺纤维化模型,对照组小鼠给予等量等渗NaCl溶液。建模后3 d黄芩苷组小鼠给予黄芩苷（25 g/kg）隔天腹腔注射,对照组和博来霉素组小鼠分别于相同时间点腹腔注射等量等渗NaCl溶液,均持续25 d。建模28 d后处死小鼠取肺组织,采用苏木素-伊红（HE）染色及Masson染色观察小鼠肺组织炎症和纤维化情况,并比较各组小鼠间肺组织纤维化评分及羟脯氨酸含量;采用实时荧光定量PCR（qPCR）检测纤维胶原蛋白基因[Collagen 1a1信使RNA（mRNA）、Collagen 3a1 mRNA],Wnt3a/β-catenin信号通路相关基因[Wnt3a mRNA、基质金属蛋白酶3（MMP-3）mRNA、MMP-9 mRNA和Cyclin D1 mRNA]表达水平;采用Western-blotting检测上皮细胞-间充质细胞转分化（EMT）相关蛋白[Vimentin、α-平滑肌肌动蛋白（α-SMA）]和β-catenin蛋白的表达水平。 结果光镜下观察发现,对照组小鼠肺组织结构完整,未见炎症细胞浸润;博来霉素组小鼠肺组织结构破坏,炎症细胞浸润,呈弥漫性肺纤维化改变;而黄芩苷组小鼠肺组织炎症细胞浸润及肺纤维化程度较博来霉素组小鼠均明显减轻。3组小鼠间肺纤维化评分、羟脯氨酸含量、Collagen 1a1 mRNA、Collagen 3a1 mRNA、Wnt3a mRNA、MMP-3 mRNA、MMP-9 mRNA、Cyclin D1 mRNA、Vimentin、α-SMA及β-catenin蛋白的比较,差异均有统计学意义（F = 12.012、8.414、46.224、30.179、85.912、125.435、19.521、40.247、72.731、58.169、70.471,P均< 0.001）。且进一步两两比较发现,博来霉素组小鼠上述指标较对照组均明显升高,而黄芩苷组小鼠上述指标较博来霉素组小鼠均显著降低（P均< 0.05）。 结论黄芩苷对于博来霉素诱导的肺纤维化小鼠具有保护作用,该保护作用与抑制Wnt3a/β-catenin信号通路和EMT相关蛋白的活化有关。