RESUMEN
Increased levels of the physiological amino acid homocysteine (Hcy) are considered a risk factor for vascular disease. Hyperhomocysteinemia causes an intense remodelling of the extracellular matrix in arterial walls, particularly an elastolysis involving metalloproteinases. We investigated the activation of the latent elastolytic metalloproteinase proMMP-2 (72 kDa) by Hcy. Hcy was proved to exert a dual effect, activating proMMP-2 at low molar ratio (MR 10:1) and inhibiting active MMP2 at high molar ratio (MR > 1000:1). Methionine and the disulphide homocystine did not activate nor inhibit MMP-2, showing that the activation as well as the inhibition requires the thiol group to be free. The activation of proMMP-2 by Hcy is in accordance with the "cysteine-switch" mechanism, but occurs without further autoproteolysis of the enzyme molecule. In contrast with Hcy, the other physiological thiol compounds cysteine and reduced glutathione did not activate proMMP-2. These results suggest that the direct activation of proMMP2 by Hcy could be one of the mechanisms involved in the extracellular matrix deterioration in hyperhomocysteinemia-associated arteriosclerosis.
Asunto(s)
Precursores Enzimáticos/efectos de los fármacos , Gelatinasas/efectos de los fármacos , Homocisteína/farmacología , Metaloendopeptidasas/efectos de los fármacos , Cisteína/farmacología , Activación Enzimática/efectos de los fármacos , Gelatina/metabolismo , Gelatinasas/antagonistas & inhibidores , Glutatión/farmacología , Homocistina/farmacología , Humanos , Hiperhomocisteinemia/etiología , Hiperhomocisteinemia/patología , Metaloproteinasa 2 de la Matriz , Metaloendopeptidasas/antagonistas & inhibidores , Metionina/farmacologíaRESUMEN
Hyperhomocysteinemia is a risk factor for arterial diseases, and the deterioration of the arterial elastic structures is one of the possible mechanisms underlying this epidemiological association. The aim of this paper is to quantitatively characterize such structural alterations and to explore their causes in a previous model of dietary induced mild hyperhomocysteinemia in minipigs. After four months, both a morphodensitometrical analysis of the elastic structure and a biochemical analysis of elastin and elastase activities were performed on the infrarenal abdominal aorta (IRAA) and the proximal left interventricular coronary artery (LIVCA) of control (C), hyperhomocysteinemic (H) and captopril-hydrochlorothiazide (Cp-Htz, 25 + 12.5 mg/d)-treated (H+/-Cp) minipigs (n = 8/group). Hyperhomocysteinemia was found to induce an increase in parietal elastolytic metalloproteinase activities. It resulted in opening and enlargement of fenestrae through the medial elastic laminae and in a decrease in medial elastin content (p < 10(-3)), expressed as well as volume density (%) as weight concentration (microg elastin/mg dry tissue). The thickness of the media and its basic lamellar organization was unchanged. The reduction in volume density was more dramatic in LIVCA (H: 4.7 +/- 0.9 vs C: 8.8 +/- 2.4), where it was evenly distributed within the media, than in IRAA (H: 6.7 +/- 1.1 vs C: 9.3 +/- 1.2), where the deep medial layers were less affected. Cp-Htz partly prevented the hyperhomocysteinemia-induced reduction of the medial elastin content in LIVCA (5.7 +/- 1.2) and IRAA (7.9 +/- 1.4). This effect, occurring in the subintimal layers of the media in both arteries but not in the deeper layers, resulted in a less beneficial effect in LIVCA than in IRAA. This result parallels the moderate beneficial therapeutic effect of ACE inhibitors against coronary atherosclerosis in humans. This paper reports for the first time a quantitative analysis of the arterial site-dependent deterioration of the elastic structure caused by mild hyperhomocysteinemia and the involvement of metalloproteinases in this process. These results confirm that the plaque-independent damage to elastic structure previously described in hyperhomocysteinemic-atherosclerotic minipigs was mainly due to homocysteine. This highlights that the metalloproteinase-related elastolysis and the subsequent structural deterioration is one of the major events underlying the epidemiological association between mild hyperhomocysteinemia and arterial diseases.
Asunto(s)
Antihipertensivos/farmacología , Aorta Abdominal/patología , Captopril/farmacología , Vasos Coronarios/patología , Hidroclorotiazida/farmacología , Hiperhomocisteinemia/patología , Animales , Aorta Abdominal/efectos de los fármacos , Vasos Coronarios/efectos de los fármacos , Modelos Animales de Enfermedad , Tejido Elástico/patología , Elasticidad , Elastina/metabolismo , Porcinos , Porcinos EnanosRESUMEN
Using a model of atherosclerosis in minipigs, we analyzed changes in elastic structure within the medial sections of the abdominal aorta and left interventricular coronary artery both in the vicinity of and distal to atheromatous plaques. Twenty-four animals, divided into three groups, were fed either a control diet or a hypercholesterolemic and hyperhomocysteinic atherogenic diet, alone or in association with an antihypertensor, namely isosorbide dinitrate (Risordan). The atherogenic diet, administered for a period of four months, induced in the minipig advanced noncalcified atherosclerotic lesions that were histologically similar to those found in humans. A morphodensitometric analysis of the medial elastic structures was carried out on images obtained from specifically stained transverse arterial sections examined under a light microscope. The volume density of the elastic structures was diminished in the arterial media of the atherosclerotic animals due to opening and widening of the fenestrae in the elastic laminate and increased communication between the interlamellar spaces. Whereas this elastolytic process was uniform and independent of the proximity of atheromatous plaques in the left interventricular coronary artery, it was intensified in the vicinity of the plaques in the abdominal aorta. Overall elastolytic activity was increased in the walls of atheromatous artery in both arterial sites, and metalloproteinases were implied in this increase of activity. We previously reported that treatment with isosorbide dinitrate significantly reduced the moderate systolic hypertension and the increase in transparietal stress observed in the abdominal aorta of atheromatous animals. We report here that isosorbide dinitrate prevented the atherogenic-diet-induced deterioration of the elastic structure in these arteries; complete inhibition of changes to the elastic laminae was evident in areas remote from plaque formation, but only partial inhibition in the vicinity of such plaques. It did not, however, prevent structural damage in the left interventricular coronary artery or modify the increase in parietal elastolytic activity in either of the two arteries. This suggests that damage to the elastic structure in atheromatous arteries is dependent not only on overall elastolytic activity but also on localized factors, possibly related to parietal stresses, affected by the presence of atheromatous plaques.
Asunto(s)
Arteriosclerosis/complicaciones , Tejido Elástico/patología , Aminoácidos/sangre , Aminoácidos/metabolismo , Animales , Aorta Abdominal/patología , Arterias/enzimología , Colesterol/sangre , Colesterol/metabolismo , Vasos Coronarios/patología , Densitometría , Dieta Aterogénica , Elastina/análisis , Masculino , Elastasa Pancreática/metabolismo , Porcinos , Porcinos EnanosRESUMEN
Whether the arterial elastic structures are involved in the beneficial effects of long-term treatment with organic nitrates on atherosclerosis-induced changes in hemodynamics and arterial wall viscoelastic properties, are case for angiotensin-converting enzyme (ACE) inhibitors, is not known. In the present study, atherogenic (A) diet, and isosorbide dinitrate (ISDN) (I) (60 mg Risordan LP, daily dose) were given concomitantly for 4 months to adult Pitman-Moore minipigs (A + I animals, n = 8), which were compared with A (n = 8) or control (C, n = 8) animals. Blood flow was investigated by hemodynamics in the hindlimb arterial bed; and wall rheology, histomorphometry and elastin; and desmosine (DES) and isodesmosine (IDE) contents in the abdominal aorta. Atherosclerosis prominently impaired the function of capacitance and resistance arteries, altered blood pressure contours, increased aortic stiffness and wall tension, and reduced parietal viscoelasticity through viscous component blunting. The treatment with ISDN significantly improved aortic pulsatility, arteriolar opposition to blood flow, and blood pressure (BP) contours by restoring, at least in part, the wall viscoelastic properties. However, there was no significant change in the area of the pressure-diameter curve hysteresis between the three animal groups. In contrast, ISDN reduced neither the cross-sectional area of lesions nor the losses in wall elastin content and had no influence on lipid accumulations in vessels and in the blood. The present results demonstrate that the beneficial hemodynamic and wall viscoelastic effects elicited by ISDN in atherosclerotic minipigs are not accounted for by therapeutic properties of the nitric oxide (NO) donor against alterations of elastic structures, but by the viscoelastic properties in the arterial wall.