Evaluation of Angiogenesis Using Micro-Computed Tomography in a Xenograft Mouse Model of Lung Cancer

Quantitative evaluation of lung tumor angiogenesis using immunohistochemical techniques has been limited by difficulties in generating reproducible data. To analyze intrapulmonary tumor angiogenesis, we used high-resolution micro-computed tomography (micro-CT) of lung tumors of mice inoculated with mouse Lewis lung carcinoma (LLC1) or human adenocarcinoma (A549) cell lines. The lung vasculature was filled with the radiopaque silicone rubber, Microfil, through the jugular vein (in vivo application) or pulmonary artery (ex vivo application). In addition, human adenocarcinoma lung tumor-bearing mice treated site-specifically with humanized monoclonal antibody (bevacizumab) against vascular endothelial growth factor. Quantitative analysis of lung tumor microvessels imaged with micro-CT showed that more vessels (mainly small, <0.02 mm2) were filled using the in vivo (5.4%) compared with the ex vivo (2.1%) method. Furthermore, bevacizumab-treated lung tumor-bearing mice showed significantly reduced lung tumor volume and lung tumor angiogenesis compared with untreated mice as assessed by micro-CT. Interestingly, microvascularization of mainly the smaller vessels (<0.02 mm2) was reduced after bevacizumab treatment. This observation with micro-CT was nicely correlated with immunohistochemical measurement of microvessels. Therefore, micro-CT is a novel method for investigating lung tumor angiogenesis, and this might be considered as an additional complementary tool for precise quantification of angiogenesis

Mast cell chymase: an indispensable instrument in the pathological symphony of idiopathic pulmonary fibrosis?

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and fatal lung disease with no known etiology and treatment options. The hallmarks of the histopathology, which is characteristic of usual interstitial pneumonia (UIP) pattern, include interstitial fibrosis, honeycomb changes and fibroblast foci that develop owing to fibroblast proliferation and excessive matrix deposition. Although the complete pathomechanism is not yet understood, several molecular culprits, including transforming growth factor (TGF)-ß, Angiotensin (Ang) II, endothelin (ET)-1, matrix metalloproteinases (MMPs) and cytokines have been identified. IPF is increasingly believed to be an epithelial-driven disease; however, the literature does support an implication of altered immune response and inflammatory processes in the onset or progression of the disease. Mast cells (MCs) are multifunctional tissue resident cells involved in the inflammatory and immune response. An increasing body of evidence suggests a role of MCs and their mediator chymase in the pathology of IPF. With regard to the underlying mechanisms, it is conceivable that MC chymase may function via activation or processing of factors such as proteases, cytokines and growth factors. In this review, we will discuss how MC chymase is linked to and can potentially contribute to the development of IPF. Moreover, the findings from animal model studies will be discussed to highlight the chymase inhibitors as a promising strategy for the treatment of pulmonary fibrosis

Role of the prostanoid EP4 receptor in iloprost-mediated vasodilatation in pulmonary hypertension

Rationale Iloprost is effective for the treatment of pulmonary hypertension. It acts through elevation of CAMP by binding to the prostacyclin receptor (IP receptor). However, there is evidence that patients with severe pulmonary hypertension have decreased expression of the IP receptor in the remodeled pulmonary arterial smooth muscle. Objectives: We hypothesized that prostanoid receptors other than the IP receptor are involved in signal transduction by iloprost. Methods: Immunoblotting was used to detect the IP and prostanoid EP4 receptor in lung tissue from patients with idiopathic pulmonary arterial hypertension, and immunohistochemistry was used to detect these receptors in lung sections from rats treated with monocrotaline (MCT28d). Protein and mRNA were isolated from pulmonary arterial smooth muscle cells (PASMCs) from control and MCT28d rats treated with AH6809 (an EP2 receptor antagonist) and AH23848 (an EP4 receptor antagonist) in combination with iloprost. Intracellular cAMP was also assessed in these tissues. Measurements and Main Results: IP receptor expression was reduced in idiopathic pulmonary arterial hypertension patient lung samples and MCT28d rat lungs compared with the controls. Reverse transcriptase-polymerase chain reaction and immunoblotting of MCT28d rat PASMC extracts revealed scant expression of the IP receptor but stable expression of EP4 receptor, compared with controls. Iloprost-induced elevation in intracellular CAMP in PASMCs was dose-dependently reduced by AH23848, but not by AH6809. Conclusions: Iloprost mediates vasodilatory functions via the EP4 receptor in the case of low IP receptor expression associated with pulmonary arterial hypertension. This is a previously unrecognized mechanism for iloprost, and illustrates that the EP4 receptor may be a novel therapeutic approach for the treatment of pulmonary arterial hypertension

Expression and Activity of Phosphodiesterase Isoforms during Epithelial Mesenchymal Transition: The Role of Phosphodiesterase 4

Epithelial–mesenchymal transition (EMT) has emerged as a critical event in the pathogenesis of organ fibrosis and cancer and is typically induced by the multifunctional cytokine transforming growth factor (TGF)-β1. The present study was undertaken to evaluate the potential role of phosphodiesterases (PDEs) in TGF-β1-induced EMT in the human alveolar epithelial type II cell line A549. Stimulation of A549 with TGF-β1 induced EMT by morphological alterations and by expression changes of the epithelial phenotype markers E-cadherin, cytokeratin-18, zona occludens-1, and the mesenchymal phenotype markers, collagen I, fibronectin, and α-smooth muscle actin. Interestingly, TGF-β1 stimulation caused twofold increase in total cAMP-PDE activity, contributed mostly by PDE4. Furthermore, mRNA and protein expression demonstrated up-regulation of PDE4A and PDE4D isoforms in TGF-β1-stimulated cells. Most importantly, treatment of TGF-β1 stimulated epithelial cells with the PDE4-selective inhibitor rolipram or PDE4 small interfering RNA potently inhibited EMT changes in a Smad-independent manner by decreasing reactive oxygen species, p38, and extracellular signal-regulated kinase phosphorylation. In contrast, the ectopic overexpression of PDE4A and/or PDE4D resulted in a significant loss of epithelial marker E-cadherin but did not result in changes of mesenchymal markers. In addition, Rho kinase signaling activated by TGF-β1 during EMT demonstrated to be a positive regulator of PDE4. Collectively, the findings presented herein suggest that TGF-β1 mediated up-regulation of PDE4 promotes EMT in alveolar epithelial cells. Thus, targeting PDE4 isoforms may be a novel approach to attenuate EMT-associated lung diseases such as pulmonary fibrosis and lung cancer