Search

Lysyl oxidase (LOX) is an extracellular matrix (ECM)-modifying enzyme that has been involved in cardiovascular remodeling. We explore the impact of LOX inhibition in ECM alterations induced by obesity in the cardiovascular system. LOX is overexpressed in the heart and aorta from rats fed a high-fat diet (HFD). beta-Aminopropionitrile (BAPN), an inhibitor of LOX activity, significantly attenuated the increase in body weight and cardiac hypertrophy observed in HFD rats. No significant differences were found in cardiac function or blood pressure among any group. However, HFD rats showed cardiac and vascular fibrosis and enhanced levels of superoxide anion (O-2(center dot-)), collagen I and transforming growth factor beta (TGF-beta) in heart and aorta and connective tissue growth factor (CTGF) in aorta, effects that were attenuated by LOX inhibition. Interestingly, BAPN also prevented the increase in circulating leptin levels detected in HFD fed animals. Leptin increased protein levels of collagen I, TGF-beta and CTGF, Akt phosphorylation and O-2(center dot-) production in both cardiac myofibroblasts and vascular smooth muscle cells in culture, while LOX inhibition ameliorated these alterations. LOX knockdown also attenuated leptin-induced collagen I production in cardiovascular cells. Our findings indicate that LOX inhibition attenuates the fibrosis and the oxidative stress induced by a HFD on the cardiovascular system. The reduction of leptin levels by BAPN in vivo and the ability of this compound to inhibit leptin-induced profibrotic mediators and ROS production in cardiac and vascular cells suggest that interactions between leptin and LOX regulate downstream events responsible for myocardial and vascular fibrosis in obesity. (C) 2016 Elsevier Ltd. All rights reserved.

This is the peer-reviewed version of the following article: "Toll-like receptor 4 contributes to vascular remodelling and endothelial dysfunction in angiotensin II-induced hypertension", British Journal of Pharmacology 172.12 (2015): 3159-76 which has been published in final form at http://dx.doi.org/10.1111/bph.13117 This article may be used for non-commercial purposes in accordance with Wiley-VCH Terms and Conditions for Self-Archiving, Background and Purpose Toll-like receptor 4 (TLR4) signalling contributes to inflammatory cardiovascular diseases, but its role in hypertension and the associated vascular damage is not known. We investigated whether TLR4 activation contributed to angiotensin II (AngII)-induced hypertension and the associated vascular structural, mechanical and functional alterations. Experimental Approach AngII was infused (1.44 mg·kg−1·day−1, s.c.) for 2 weeks in C57BL6 mice, treated with a neutralizing anti-TLR4 antibody or IgG (1 μg·day−1); systolic BP (SBP) and aortic cytokine levels were measured. Structural, mechanical and contractile properties of aortic and mesenteric arterial segments were measured with myography and histology. RT-PCR and Western blotting were used to analyse these tissues and cultured vascular smooth muscle cells (VSMC) from hypertensive rats (SHR). Key Results Aortic TLR4 mRNA levels were raised by AngII infusion. Anti-TLR4 antibody treatment of AngII-treated mice normalised: (i) increased SBP and TNF-α, IL-6 and CCL2 levels; (ii) vascular structural and mechanical changes; (iii) altered aortic phenylephrine- and ACh-induced responses; (iv) increased NOX-1 mRNA levels, superoxide anion production and NAD(P)H oxidase activity and effects of catalase, apocynin, ML-171 and Mito-TEMPO on vascular responses; and (v) reduced NO release and effects of L-NAME on phenylephrine-induced contraction. In VSMC, the MyD88 inhibitor ST-2825 reduced AngII-induced NAD(P)H oxidase activity. The TLR4 inhibitor CLI-095 reduced AngII-induced increased phospho-JNK1/2 and p65 NF-κB subunit nuclear protein expression. Conclusions and Implications TLR4 up-regulation by AngII contributed to the inflammation, endothelial dysfunction, vascular remodelling and stiffness associated with hypertension by mechanisms involving oxidative stress. MyD88-dependent activation and JNK/NF-κB signalling pathways participated in these alterations, This work was supported by Ministerio de Economía y Competitividad (SAF2012-36400), Instituto de Salud Carlos III (Red de Investigación Cardiovascular RD12/0042/0024 and RD12/0042/0033) and URJC (PRIN13_CS12). AMB was supported by the Ramón y Cajal Program (RYC-2010-06473).

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 beta-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 TNF alpha-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.

Aldosterone not only contributes to salt and water homeostasis, but also exerts direct cardiovascular and renal effects. Numerous experimental and clinical studies indicate that aldosterone participate in cardiac alterations associated with hypertension, heart failure, diabetes and other pathological entities. It is important to mention that dietary salt is a key factor in aldosterone-mediated cardiovascular damage, since damage was moreevident in animals on a high-salt diet than animals on a low salt diet. A pathophysiological action of aldosterone involves development of extracellular matrix and fibrosis, inflammation, stimulation of reactive oxygen species production, endothelial dysfunction, cell growth and proliferation. Many studies showed local extra-adrenal production of aldosterone in brain blood vessel, and the heart, which contribute in an important manner to the pathological actions of this mineralocorticoid.Several studies such as RALES, EPHESUS, 4E and others, recently showed that mineralocorticoid-receptor (MR) antagonists, alone or in combination with ACE inhibitors or ARBs, reduced the risk of progressive target organ damage and hospitalization in patients with hypertension and heart failure. These clinical benefits support the therapeutic usefulness of MR antagonists.

Vascular endothelial cells synthesize and release vasodilator (nitric oxide, prostacyclin, endothelium-derived hyperpolarizing factor) and vasoconstrictor factors (thromboxane A2, prostaglandin H2, endothelin 1), which play a key role in the local regulation of vascular tone and participate in a crucial manner in the regulation of blood pressure. Hypertension has been shown to be associated with functional changes in the endothelium. In fact, decreased endothelium-dependent relaxations and increased endothelium-dependent contractions have been reported in both conduit arteries and resistance arteries obtained from various animal models of hypertension. During hypertension, the vessel wall experiences changes in the balance of the oxidative and the antioxidative enzyme system, resulting in increases in O2- release. This contributes to endothelial dysfunction by nitric oxide oxidation and the subsequent formation of peroxynitrite (ONOO-), a potent oxidant and potential mediator of vascular tissue injury. Finally, hypertension also allows the action or the production of vasoconstrictor factors such as endothelin 1 and thromboxane A2. As a consequence of these mechanisms, basal and/or stimulated nitric oxide availability is reduced, allowing vasoconstrictor systems, such as angiotensin II, sympathetic nervous system and others to over-express their actions. The mechanisms responsible for the alterations leading to endothelial dysfunction not only affect vasomotor tone, but also platelet aggregation and coagulation mechanisms.

A defect in the endothelium-dependent vasorelaxation could contribute to the development of arterial hypertension through the facilitation of renal vasoconstriction and sodium retention. In this study, we tested the hypothesis that aging impairs kidney function in essential hypertension through a derangement of nitric oxide-dependent renal mechanisms. To this end, we compared the renal response to an intravenous infusion of the precursor of nitric oxide synthesis, L-arginine, in young and aged essential hypertensives. In young hypertensives, L-arginine induced a significant increase in renal plasma flow, glomerular filtration rate, natriuresis and kaliuresis, without changes in filtration fraction. These effects were not observed in aged hypertensives. Neither PRA nor PA were affected by L-arginine infusion in any group. These results indicate that aging produces a derangement of endothelial function in essential hypertension.

A radioimmunoassay for the determination of 6-keto-PGF1 alpha (stable metabolite of Prostacyclin) in urine using a specific antiserum, is described. The antibody used, showed no significant cross-reactivity with other PGS. (3H)-6-keto-PGF1 alpha has been used as tracer and a 30% Hydroxyapatite suspension was utilized for the separation of bound and free fractions. Standard curve ranges between 2 and 1000 pg thus allowing measurements in urine. Aliquots of 0.2 to 1 ml of 24 hours urinary samples were submitted to a preextraction step with Hexane in order to eliminate neutral fats. After acidifying with 0.1 N HCl to pH = 3.5-4, an Ethyl Ether extraction step was performed showing a recovery of 66%. Repeated analysis of a rat urine pool, showed 7.7 intraassay and 9.8 interassay variation coefficients. Values obtained amounted to 38.3 +/- 4.6 ng/24 h in normal rats and 133 +/- 32 ng/24 h in 5% NaCl loaded rats (p less than 0.001). The values obtained in healthy men were 508 +/- 94 ng/24 h and in women 375 +/- 136 (p less than 0.05).

Several factors, including mineralocorticoids, have been implicated in the renal damage associated with hypertension. Peroxisome proliferator activated receptor gamma (PPAR-γ) agonists improve renal damage associated with different pathologies. Therefore, our hypothesis was that mineralocorticoid receptor blockade ameliorates renal damage associated with hypertension and that this improvement may be mediated by PPAR-γ. Spontaneously hypertensive rats (SHR) were treated with either vehicle or eplerenone, a mineralocorticoid receptor antagonist, at two different doses: 30 and 100 mg/kg/day for 10 weeks. Age-matched Wistar Kyoto rats (WKY) were used as a normotensive reference group. SHR showed tubulointersticial fibrosis and mild tubular atrophy. These alterations were accompanied by increases in renal cortex gene expression of transforming growth factor beta (TGF-β) connective tissue growth factor (CTGF) and phosphorylated Smad2 protein levels, factors involved in the fibrotic response. Interleukin 1-beta (IL-1β) and tumor necrosis factor alpha (TNF-α) gene expression were also increased. By contrast, lysyl oxidase (LOX) expression and PPAR-γ protein levels were decreased in SHR as compared with normotensive animals. Only the high dose of eplerenone was able to reduce blood pressure and partially prevent LOX down-regulation in SHR. Both eplerenone doses significantly ameliorated interstitial fibrosis and tubular atrophy, reduced TGF-β, CTGF and cytokine gene expression, and decreased Smad2 activation, while normalizing PPAR-γ protein levels.Mineralocorticoid receptor activation participates in hypertension-associated renal damage. This effect seems to involve stimulation of both fibrotic and inflammatory processes mediated (at least in part) by a down-regulation of PPAR-γ that can favour an up-regulation of the TGF-β/Smad signalling pathway.

Angiotensin II (A II), the active component of the renin-angiotensin system, plays a major role in the regulation of blood pressure and renal function. A II actions are mediated by the interaction of this peptide with specific receptors that have been classified into two major types. AT1 and AT2. AT1 receptors have been associated with all of the known cardiovascular and renal effects of A II. Losartan, the first nonpeptide A II-receptor antagonist, exerts its antihypertensive action through the inhibition of A II binding to AT1 receptors. However, additional mechanisms seem to be involved in the actions of losartan in the rat. Administration of the nitric oxide (NO)-synthase inhibitor, NG-nitro-L-arginine methyl ester (LNAME), prevented the hypotensive effect induced by losartan in spontaneously hypertensive rats (SHR). Similarly, pretreatment with LNAME reduced the increases in renal plasma flow and glomerular filtration rate produced by this AT1-receptor antagonist in SHR. Furthermore, concurrent administration of the prostaglandin (PG)-synthesis inhibitor indomethacin attenuated vasodepressor, diuretic, and natriuretic effects of losartan in SHR. Finally, it should be mentioned that losartan was able to reduce the "ex vivo" vasoconstriction induced by phenylephrine in aortic rings from SHR. This effect was not observed in endothelium-denuded rings, suggesting a mediatory role of an endothelium-derived factor in this effect of losartan. Consequently, these data suggest a contributory role of NO and PGs in the vasodepressor and renal actions of AT1-receptor antagonists in SHR.

The effects of losartan on blood pressure and on renal function have mainly been attributed to AT1 receptor blockade. Experimental evidence suggests that these effects could also be related to the actions of angiotensin II through AT2 receptors or to vasodilatory systems. The present study was therefore designed to investigate the manner in which the acute effects of losartan on renal excretory function are affected during simultaneous administration of an AT2 receptor antagonist, a kinin B2 receptor antagonist, a cyclo-oxygenase inhibitor or a nitric oxide synthesis inhibitor.The AT2 receptor antagonist PD 123319 (10 mg/kg), the bradykinin B2 receptor antagonist Hoe 140 (30 mu g/kg), the cyclo-oxygenase inhibitor meclofenamate (5 mg/kg) and the nitric oxide synthesis inhibitor NG-monomethyl-L-arginine (1 mu g/kg per min) were administered separately with acute intravenous losartan (1 mg/kg) to spontaneously hypertensive rats and the effects on mean arterial pressure and renal excretory function were assessed.Losartan reduced mean arterial pressure by 11.1 +/- 5.7 mmHg and increased the glomerular filtration rate, urine flow and sodium excretion rate. The decrease in mean arterial pressure was blocked in the presence of NG-monomethyl-L-arginine but not during concurrent administration of PD 123319, Hoe 140 or meclofenamate. The increase in glomerular filtration rate induced by losartan was blunted by Hoe 140, meclofenamate and NG-monomethyl-L-arginine. Co-administration of PD 123319, Hoe 140 or meclofenamate, but not of NG-monomethyl-L-arginine, partially blunted the diuresis and natriuresis induced by losartan.Nitric oxide participates in the antihypertensive action of losartan. Kinins, prostaglandins and nitric oxide appear to be involved in the effects of losartan on the glomerular filtration rate. The increases in urine flow and sodium excretion rate induced by losartan depend partially on AT2 receptors, kinins and prostaglandins.

The long-term interaction between nitric oxide (NO) and prostaglandins (PGs) in the pressure diuresis and natriuresis response has been studied. Experiments were performed in rats with chronic (8 weeks) inhibition of NO (NG-nitro L-arginine methyl Ester, L-NAME, 40 mg/kg/day) with or without simultaneous PGs synthesis blockade (indomethacin, 1 mg/kg/day). A time control group with no treatment was studied in parallel. At the end of this period, the animals were anesthetized and renal hemodynamics and excretion were studied at three levels of renal perfusion pressure (RPP; 100, 125 and 150 mm Hg). Renal blood flow, glomerular filtration rate, diuresis and natriuresis were lower at the three RPP levels in both L-NAME-treated groups than in the control or indomethacin-treated animals. Simultaneous administration of indomethacin plus L-NAME did not further modify the hemodynamic or excretory responses observed in the L-NAME-treated animals. These results show that chronic NO inhibition impairs the renal excretory response to changes in renal perfusion pressure, and simultaneous NO and prostaglandin synthesis inhibition does not reduce those responses further. It is concluded that, on a long-term basis, a preserved NO production, but not prostaglandin production, is critical for a normal pressure diuretic and natriuretic mechanism.