Insight into redox-regulated gene networks in vascular cells

Emerging Roles of Lysyl Oxidases in the Cardiovascular System: New Concepts and Therapeutic Challenges

Lysyl oxidases (LOX and LOX-likes (LOXLs) isoenzymes) belong to a family of copper-dependent enzymes classically involved in the covalent cross-linking of collagen and elastin, a pivotal process that ensures extracellular matrix (ECM) stability and provides the tensile and elastic characteristics of connective tissues. Besides this structural role, in the last years, novel biological properties have been attributed to these enzymes, which can critically influence cardiovascular function. LOX and LOXLs control cell proliferation, migration, adhesion, differentiation, oxidative stress, and transcriptional regulation and, thereby, their dysregulation has been linked to a myriad of cardiovascular pathologies. Lysyl oxidase could modulate virtually all stages of the atherosclerotic process, from endothelial dysfunction and plaque progression to calcification and rupture of advanced and complicated plaques, and contributes to vascular stiffness in hypertension. The alteration of LOX/LOXLs expression underlies the development of other vascular pathologies characterized by a destructive remodeling of the ECM, such as aneurysm and artery dissections, and contributes to the adverse myocardial remodeling and dysfunction in hypertension, myocardial infarction, and obesity. This review examines the most recent advances in the study of LOX and LOXLs biology and their pathophysiological role in cardiovascular diseases with special emphasis on their potential as therapeutic targets.

The innate immune response to ischemic injury: a multiscale modeling perspective

Background

Cell death as a result of ischemic injury triggers powerful mechanisms regulated by germline-encoded Pattern Recognition Receptors (PRRs) with shared specificity that recognize invading pathogens and endogenous ligands released from dying cells, and as such are essential to human health. Alternatively, dysregulation of these mechanisms contributes to extreme inflammation, deleterious tissue damage and impaired healing in various diseases. The Toll-like receptors (TLRs) are a prototypical family of PRRs that may be powerful anti-inflammatory targets if agents can be designed that antagonize their harmful effects while preserving host defense functions. This requires an understanding of the complex interactions and consequences of targeting the TLR-mediated pathways as well as technologies to analyze and interpret these, which will then allow the simulation of perturbations targeting specific pathway components, predict potential outcomes and identify safe and effective therapeutic targets.

Results

We constructed a multiscale mathematical model that spans the tissue and intracellular scales, and captures the consequences of targeting various regulatory components of injury-induced TLR4 signal transduction on potential pro-inflammatory or pro-healing outcomes. We applied known interactions to simulate how inactivation of specific regulatory nodes affects dynamics in the context of injury and to predict phenotypes of potential therapeutic interventions. We propose rules to link model behavior to qualitative estimates of pro-inflammatory signal activation, macrophage infiltration, production of reactive oxygen species and resolution. We tested the validity of the model by assessing its ability to reproduce published data not used in its construction.

Conclusions

These studies will enable us to form a conceptual framework focusing on TLR4-mediated ischemic repair to assess potential molecular targets that can be utilized therapeutically to improve efficacy and safety in treating ischemic/inflammatory injury.

Oxidative injury is a common consequence of BMPR2 mutations

Hereditary pulmonary arterial hypertension (PAH) is usually caused by mutations in BMPR2. Mutations are found throughout the gene, and common molecular consequences of different types of mutation are not known. Knowledge of common molecular consequences would provide insight into the molecular etiology of the disease. The objective of this study was to determine the common molecular consequences across classes of BMPR2 mutation. Increased superoxide and peroxide production and alterations in genes associated with oxidative stress were a common consequence of stable transfection of the vascular smooth muscle cells, with three distinct classes of BMPR2 mutation, in the ligand binding domain, the kinase domain and the cytoplasmic tail domain. Measurement of oxidized lipids in whole lung from transgenic mice expressing a mutation in the BMPR2 cytoplasmic tail showed a 50% increase in isoprostanes and a two-fold increase in isofurans, suggesting increased reactive oxygen species (ROS) of mitochondrial origin. Immunohistochemistry on BMPR2 transgenic mouse lung showed that oxidative stress was vascular-specific. Electron microscopy showed decreased mitochondrial size and variability in the pulmonary vessels from BMPR2-mutant mice. Measurement of oxidized lipids in urine from humans with BMPR2 mutations demonstrated increased ROS, regardless of disease status. Immunohistochemistry on hereditary PAH patient lung confirmed oxidative stress specific to the vasculature. Increased oxidative stress, likely of mitochondrial origin, is a common consequence of BMPR2 mutation across mutation types in cell culture, mice and humans.

Unraveling genetic regulatory networks of mammalian retroelements

Advances in the science of toxicogenomics have opened the door to major advances in our understanding of the molecular basis of environmental pathogenesis and the role of environmental factors in human disease. This report summarizes major findings in the laboratory defining the molecular basis of L1 retroelement activation in mammalian cells and the architecture of gene regulatory networks involved in phenotypic control.

Regulation of lysyl oxidase in vascular cells: lysyl oxidase as a new player in cardiovascular diseases

Lysyl oxidase (LOX) plays a crucial role in the maintenance of extracellular matrix stability and could participate in vascular remodelling associated with cardiovascular diseases. Evidence from in vitro and in vivo studies shows that LOX downregulation is associated with the endothelial dysfunction characteristic of earlier stages of the atherosclerotic process. Conversely, upregulation of this enzyme in vascular cells could induce neointimal thickening in atherosclerosis and restenosis. In fact, LOX is chemotactic for vascular smooth muscle cells and monocytes, is modulated by proliferative stimulus in these cells, and could control other cellular processes such as gene expression and cell transformation. Furthermore, it is conceivable that LOX downregulation could underlie plaque instability and contribute to the destructive remodelling that takes place during aneurysm development. Overall, LOX could play a key role in vascular homeostasis and, hence, it emerges as a new player in cardiovascular diseases. This review addresses the experimental evidence related to the role of LOX in vascular disorders and the potential benefits of controlling its expression and function.