Saray Varona

Lysyl oxidase (LOX) in vascular remodelling. Insight from a new animal model.

Lysyl oxidase (LOX) is an extracellular matrix-modifying enzyme that seems to play a critical role in vascular remodelling. However, the lack of viable LOX-deficient animal models has been an obstacle to deep in LOX biology. In this study we have developed a transgenic mouse model that over-expresses LOX in vascular smooth muscle cells (VSMC) to clarify whether LOX could regulate VSMC phenotype and vascular remodelling. The SM22α proximal promoter drove the expression of a transgene containing the human LOX cDNA. Two stable transgenic lines, phenotypically indistinguishable, were generated by conventional methods (TgLOX). Transgene expression followed the expected SMC-specific pattern. In TgLOX mice, real-time PCR and immunohistochemistry evidenced a strong expression of LOX in the media from aorta and carotid arteries, coincident with a higher proportion of mature collagen. VSMC isolated from TgLOX mice expressed high levels of LOX pro-enzyme, which was properly secreted and processed into mature and bioactive LOX. Interestingly, cell proliferation was significantly reduced in cells from TgLOX mice. Transgenic VSMC also exhibited low levels of Myh10 (marker of SMC phenotypic switching), PCNA (marker of cell proliferation) and MCP-1, and a weak activation of Akt and ERK1/2 in response to mitogenic stimuli. Accordingly, neointimal thickening induced by carotid artery ligation was attenuated in TgLOX mice that also displayed a reduction in PCNA and MCP-1 immunostaining. Our results give evidence that LOX plays a critical role in vascular remodelling. We have developed a new animal model to study the role of LOX in vascular biology.

The lysyl oxidase inhibitor β-aminopropionitrile reduces body weight gain and improves the metabolic profile in diet-induced obesity in rats

ABSTRACT Extracellular matrix (ECM) remodelling of the adipose tissue plays a pivotal role in the pathophysiology of obesity. The lysyl oxidase (LOX) family of amine oxidases, including LOX and LOX-like (LOXL) isoenzymes, controls ECM maturation, and upregulation of LOX activity is essential in fibrosis; however, its involvement in adipose tissue dysfunction in obesity is unclear. In this study, we observed that LOX is the main isoenzyme expressed in human adipose tissue and that its expression is strongly upregulated in samples from obese individuals that had been referred to bariatric surgery. LOX expression was also induced in the adipose tissue from male Wistar rats fed a high-fat diet (HFD). Interestingly, treatment with β-aminopropionitrile (BAPN), a specific and irreversible inhibitor of LOX activity, attenuated the increase in body weight and fat mass that was observed in obese animals and shifted adipocyte size toward smaller adipocytes. BAPN also ameliorated the increase in collagen content that was observed in adipose tissue from obese animals and improved several metabolic parameters – it ameliorated glucose and insulin levels, decreased homeostasis model assessment (HOMA) index and reduced plasma triglyceride levels. Furthermore, in white adipose tissue from obese animals, BAPN prevented the downregulation of adiponectin and glucose transporter 4 (GLUT4), as well as the increase in suppressor of cytokine signaling 3 (SOCS3) and dipeptidyl peptidase 4 (DPP4) levels, triggered by the HFD. Likewise, in the TNFα-induced insulin-resistant 3T3-L1 adipocyte model, BAPN prevented the downregulation of adiponectin and GLUT4 and the increase in SOCS3 levels, and consequently normalised insulin-stimulated glucose uptake. Therefore, our data provide evidence that LOX plays a pathologically relevant role in the metabolic dysfunction induced by obesity and emphasise the interest of novel pharmacological interventions that target adipose tissue fibrosis and LOX activity for the clinical management of this disease. Highlighted Article: Lysyl oxidase (LOX) could play a role in the metabolic dysfunction induced by obesity, and consequently the inhibition of LOX activity could be a valuable strategy to ameliorate obesity-related metabolic disturbances.

Lysyl Oxidase Induces Vascular Oxidative Stress and Contributes to Arterial Stiffness and Abnormal Elastin Structure in Hypertension: Role of p38MAPK

AIMS Vascular stiffness, structural elastin abnormalities, and increased oxidative stress are hallmarks of hypertension. Lysyl oxidase (LOX) is an elastin crosslinking enzyme that produces H2O2 as a by-product. We addressed the interplay between LOX, oxidative stress, vessel stiffness, and elastin. RESULTS Angiotensin II (Ang II)-infused hypertensive mice and spontaneously hypertensive rats (SHR) showed increased vascular LOX expression and stiffness and an abnormal elastin structure. Mice over-expressing LOX in vascular smooth muscle cells (TgLOX) exhibited similar mechanical and elastin alterations to those of hypertensive models. LOX inhibition with β-aminopropionitrile (BAPN) attenuated mechanical and elastin alterations in TgLOX mice, Ang II-infused mice, and SHR. Arteries from TgLOX mice, Ang II-infused mice, and/or SHR exhibited increased vascular H2O2 and O2.- levels, NADPH oxidase activity, and/or mitochondrial dysfunction. BAPN prevented the higher oxidative stress in hypertensive models. Treatment of TgLOX and Ang II-infused mice and SHR with the mitochondrial-targeted superoxide dismutase mimetic mito-TEMPO, the antioxidant apocynin, or the H2O2 scavenger polyethylene glycol-conjugated catalase (PEG-catalase) reduced oxidative stress, vascular stiffness, and elastin alterations. Vascular p38 mitogen-activated protein kinase (p38MAPK) activation was increased in Ang II-infused and TgLOX mice and this effect was prevented by BAPN, mito-TEMPO, or PEG-catalase. SB203580, the p38MAPK inhibitor, normalized vessel stiffness and elastin structure in TgLOX mice. INNOVATION We identify LOX as a novel source of vascular reactive oxygen species and a new pathway involved in vascular stiffness and elastin remodeling in hypertension. CONCLUSION LOX up-regulation is associated with enhanced oxidative stress that promotes p38MAPK activation, elastin structural alterations, and vascular stiffness. This pathway contributes to vascular abnormalities in hypertension. Antioxid. Redox Signal. 27, 379-397.

Down-regulation of Fibulin-5 is associated with aortic dilation: role of inflammation and epigenetics

AIMS Destructive remodelling of extracellular matrix (ECM) and inflammation lead to dilation and ultimately abdominal aortic aneurysm (AAA). Fibulin-5 (FBLN5) mediates cell-ECM interactions and elastic fibre assembly and is critical for ECM remodelling. We aimed to characterize FBLN5 regulation in human AAA and analyse the underlying mechanisms. METHODS AND RESULTS FBLN5 expression was significantly decreased in human aneurysmatic aortas compared with healthy vessels. Local FBLN5 knockdown promoted aortic dilation and enhanced vascular expression of inflammatory markers in Ang II-infused C57BL/6J mice. Inflammatory stimuli down-regulated FBLN5 expression and transcriptional activity in human aortic vascular smooth muscle cells (VSMC). Further, aortic FBLN5 expression was reduced in LPS-challenged mice. A SOX response element was critical for FBLN5 promoter activity. The SOX9 expression pattern in human AAA parallels that of FBLN5, and like FBLN5, it was reduced in TNFα-stimulated VSMC. Interestingly, SOX9 over-expression prevented the cytokine-mediated reduction of FBLN5 expression and transcription. The inhibition of Class I histone deacetylases (HDACs) by MS-275 or gene silencing attenuated the inflammation-mediated decrease of FBLN5 expression in VSMC and in the vascular wall. Consistently, HDAC inhibition counteracted the reduction of SOX9 expression induced by inflammatory stimuli and prevented the TNFα-mediated decrease in the binding of SOX9 to FBLN5 promoter normalizing FBLN5 expression. CONCLUSION We evidence the deregulation of FBLN5 in human AAA and identify a SOX9/HDAC-dependent mechanism involved in the down-regulation of FBLN5 by inflammation. HDAC inhibitors or pharmacological approaches that aimed to preserve FBLN5 could be useful to prevent the disorganization of ECM induced by inflammation in AAA.

Induction of histone deacetylases (HDACs) in human abdominal aortic aneurysm: therapeutic potential of HDAC inhibitors

ABSTRACT Clinical management of abdominal aortic aneurysm (AAA) is currently limited to elective surgical repair because an effective pharmacotherapy is still awaited. Inhibition of histone deacetylase (HDAC) activity could be a promising therapeutic option in cardiovascular diseases. We aimed to characterise HDAC expression in human AAA and to evaluate the therapeutic potential of class I and IIa HDAC inhibitors in the AAA model of angiotensin II (Ang II)-infused apolipoprotein-E-deficient (ApoE−/−) mice. Real-time PCR, western blot and immunohistochemistry evidenced an increased expression of HDACs 1, 2 (both class I), 4 and 7 (both class IIa) in abdominal aorta samples from patients undergoing AAA open repair (n=22) compared with those from donors (n=14). Aortic aneurysms from Ang-II-infused ApoE−/− mice exhibited a similar HDAC expression profile. In these animals, treatment with a class I HDAC inhibitor (MS-275) or a class IIa inhibitor (MC-1568) improved survival, reduced the incidence and severity of AAA and limited aneurysmal expansion evaluated by Doppler ultrasonography. These beneficial effects were more potent in MC-1568-treated mice. The disorganisation of elastin and collagen fibres and lymphocyte and macrophage infiltration were effectively reduced by both inhibitors. Additionally, HDAC inhibition attenuated the exacerbated expression of pro-inflammatory markers and the increase in metalloproteinase-2 and -9 activity induced by Ang II in this model. Therefore, our data evidence that HDAC expression is deregulated in human AAA and that class-selective HDAC inhibitors limit aneurysm expansion in an AAA mouse model. New-generation HDAC inhibitors represent a promising therapeutic approach to overcome human aneurysm progression. Summary: This study reports the upregulation of HDACs in human AAA, evidences that HDAC inhibitors limit aneurysm progression in a preclinical model and suggests the therapeutic interest of HDAC inhibition in AAA.

Lysyl oxidase overexpression accelerates cardiac remodeling and aggravates angiotensin II–induced hypertrophy

Lysyl oxidase (LOX) controls matrix remodeling, a key process that underlies cardiovascular diseases and heart failure; however, a lack of suitable animal models has limited our knowledge with regard to the contribution of LOX to cardiac dysfunction. Here, we assessed the impact of LOX overexpression on ventricular function and cardiac hypertrophy in a transgenic LOX (TgLOX) mouse model with a strong cardiac expression of human LOX. TgLOX mice exhibited high expression of the transgene in cardiomyocytes and cardiofibroblasts, which are associated with enhanced LOX activity and H2O2 production and with cardiofibroblast reprogramming. LOX overexpression promoted an age‐associated concentric remodeling of the left ventricle and impaired diastolic function. Furthermore, LOX transgenesis aggravated angiotensin II (Ang II)–induced cardiac hypertrophy and dysfunction, which triggered a greater fibrotic response that was characterized by stronger collagen deposition and cross‐linking and high expression of fibrotic markers. In addition, LOX transgenesis increased the Ang II–induced myocardial inflammatory infiltrate, exacerbated expression of proinflammatory markers, and decreased that of cardioprotective factors. Mechanistically, LOX overexpression enhanced oxidative stress and potentiated the Ang II–mediated cardiac activation of p38 MAPK while reducing AMPK activation. Our findings suggest that LOX induces an age‐dependent disturbance of diastolic function and aggravates Ang II–induced hypertrophy, which provides novel insights into the role of LOX in cardiac performance.—Galán, M., Varona, S., Guadall, A., Orriols, M., Navas, M., Aguiló, S., deDiego, A., Navarro, M. A., García‐Dorado, D., Rodríguez‐Sinovas, A., Martínez‐González, J., Rodriguez, C. Lysyl oxidase overexpression accelerates cardiac remodeling and aggravates angiotensin II–induced hypertrophy. FASEB J. 31, 3787–3799 (2017). www.fasebj.org—Galán, María, Varona, Saray, Guadall, Anna, Orriols, Mar, Navas, Miquel, Aguiló, Silvia, de Diego, Alicia, Navarro, María A., García‐Dorado, David, Rodríguez‐Sinovas, Antonio, Martínez‐González, José, Rodriguez, Cristina Lysyl oxidase overexpression accelerates cardiac remodeling and aggravates angiotensin II–induced hypertrophy. FASEB J. 31, 3787–3799 (2017)

La inflamación inhibe la expresión vascular de la fibulina-5: implicación del factor de transcripción SOX9 ☆

INTRODUCTION Fibulin-5 (FBLN5) is an elastogenic protein critically involved in extracellular matrix (ECM) remodelling, a key process in abdominal aortic aneurysm (AAA). However, the possible contribution of FBLN5 to AAA development has not been addressed. METHODS Expression levels were determined by real-time PCR and Western blot in human abdominal aorta from patients with AAA or healthy donors, as well as in human aortic vascular smooth muscle cells (VSMC). Lentiviral transduction, transient transfections, and chromatin immunoprecipitation (ChIP) assays were also performed. RESULTS The expression of FBLN5 in human AAA was significantly lower than in healthy donors. FBLN5 mRNA and protein levels and their secretion to the extracellular environment were down-regulated in VSMC exposed to inflammatory stimuli. Interestingly, FBLN5 transcriptional activity was inhibited by TNFα and lipopolysaccharide (LPS), and depends on a SOX response element. In fact, SOX9 expression was reduced in VMSC induced by inflammatory mediators and in human AAA, and correlated with that of FBLN5. Furthermore, SOX9 over-expression limited the reduction of FBLN5 expression induced by cytokines in VSMC. Finally, it was observed that SOX9 interacts with FBLN5 promoter, and that this binding was reduced upon TNFα exposure. CONCLUSIONS FBLN5 downregulation in human AAA could contribute to extracellular matrix remodelling induced by the inflammatory component of the disease.