Transforming growth factor-beta1 inhibits thrombin activation of endothelial cells

Thrombin stimulation of proteoglycan synthesis in vascular smooth muscle is mediated by protease-activated receptor-1 transactivation of the transforming growth factor beta type I receptor

Growth factors modify the structure of the glycosaminoglycan (GAG) chains on biglycan leading to enhanced LDL binding. G-protein receptor-coupled agonists such as thrombin, signal changes the structure of proteoglycans produced by vascular smooth muscle cells (VSMCs). One component of classical G-protein-coupled receptor (GPCR) signaling invokes transactivation of protein tyrosine kinase receptors such as the epidermal growth factor receptor. Serine/threonine receptor growth factors such as transforming growth factor-(TGF)-beta are potent activators of proteoglycan synthesis. We have used the model of proteoglycan synthesis to demonstrate that the signaling paradigm of GPCR signaling can be extended to include the transactivation of serine/threonine receptor, specifically the TGF-beta type I receptor (TbetaRI) also known as activin-like kinase (ALK) V. Thrombin stimulated elongation of GAG chains and increased proteoglycan core protein expression and these responses were blocked by the TbetaRI antagonist, SB431542 and TbetaRI siRNA knockdown, as well as several protease-activated receptor (PAR)-1 antagonists. The canonical downstream response to TGF-beta is increased C-terminal phosphorylation of the transcription factor Smad2 generating phospho-Smad2C (phosphorylation of Smad2 C-terminal region). Thrombin stimulated increased phospho-Smad2C levels, and the response was blocked by SB431542 and JNJ5177094. The proteolytically inactive thrombin mimetic thrombin-receptor activating peptide also stimulated an increase in cytosolic phospho-Smad2C. Signaling pathways for growth factor regulated proteoglycan synthesis represent therapeutic targets for the prevention of atherosclerosis, but the novel finding of a GPCR-mediated transactivation of a serine/threonine growth factor receptor almost certainly has implications well beyond the synthesis of proteoglycans.

Common pathogenic features of atherosclerosis and calcific aortic stenosis: role of transforming growth factor-beta

Calcific aortic stenosis and atherosclerosis have been investigated separately in experimental in vitro and in vivo studies and in clinical studies. The similarities identified in both diseases suggest that similar pathogenic pathways are involved in both conditions. Most current therapeutic studies are focused on statins. The evidence suggests that statin effects on valves may, in large part, be independent of the lipid lowering effects of the drug. There are several molecules that play significant regulatory roles on the development and progression of valve sclerosis and calcification and on growth and complications of atherosclerotic plaques. The purpose of this review is to discuss the pathogenic features of the two conditions, highlight the important similarities, and then review the data that suggest that transforming growth factor-beta may play a key regulatory role in both diseases and that this is worthy of study as a potential therapeutic target for both conditions.

TGF-beta prevents eosinophilic lung disease but impairs pathogen clearance

Respiratory infections are the third leading cause of death worldwide. Complications arise directly as a consequence of pathogen replication or indirectly due to aberrant or excessive immune responses. In the following report, we evaluate the efficacy, in a murine model, of nasally delivered DNA encoding TGF-beta1 to suppress immunopathology in response to a variety of infectious agents. A single nasal administration suppressed lymphocyte responses to Cryptococcus neoformans, influenza virus and respiratory syncytial virus. The suppression did not depend on the phenotype of the responding T cell, since both Th1 and Th2 responses were affected. During Th2-inducing infection, pulmonary eosinophilic responses were significantly suppressed. In all cases, however, suppressed immunity correlated with increased susceptibility to infection. We conclude that nasal TGF-beta treatment could be used to prevent pulmonary, pathogen-driven eosinophilic disease, although anti-pathogen strategies will need to be administered concordantly.