elastin and carbamylhydrazine

To investigate a putative role for semicarbazide-sensitive amine oxidase (SSAO) in arterial extracellular matrix (ECM) organization, we compared arteries of growing Brown Norway (BN) rats after chronic administration of semicarbazide (SCZ) and beta-aminopropionitrile (BAPN), two inhibitors with different properties and relative specificities for SSAO and lysyl oxidase (LOX). The BN model is particularly well adapted to evaluating effects of toxic compounds on the arterial elastic network. We measured aortic LOX and SSAO activities and quantified several ECM parameters. After a pilot study comparing doses previously studied and testing for additivity, we studied low and high equimolar doses of SCZ and BAPN. Both compounds similarly inhibited LOX, whereas SCZ inhibited SSAO far more effectively than BAPN. Both decreased carotid wall rupture pressure, increased tail tendon collagen solubility, decreased aortic insoluble elastin (% dry weight) and dose-dependently increased defects in the internal elastic lamina of abdominal aorta, iliac and renal arteries. Our results suggest that either these effects are mediated by LOX inhibition, SCZ being slightly more effective than BAPN in our conditions, or SSAO acts similarly to and in synergy with LOX on ECM, the greater SCZ effect reflecting the simultaneous inhibition of both enzymes. However, the high SCZ dose increased aortic collagen and ECM proteins other than insoluble elastin markedly more than did equimolar BAPN, possibly revealing a specific effect of SSAO inhibition. To discriminate between the two above possibilities, and to demonstrate unequivocally a specific effect of SSAO inhibition on ECM formation or organization, we must await availability of more specific inhibitors.

Topics: Amine Oxidase (Copper-Containing); Aminopropionitrile; Animals; Aorta, Thoracic; Body Weight; Carotid Arteries; Collagen; Drug Synergism; Elastin; Extracellular Matrix; Male; Pilot Projects; Protein-Lysine 6-Oxidase; Rats; Rats, Inbred BN; Semicarbazides

Semicarbazide-sensitive amine oxidase (SSAO)-deficient mice present no alteration in elastin cross-linking processes and carotid mechanical properties. In contrast, previous studies have shown that SSAO inhibitors induced marked anomalies in arterial structure and function. The aim of the present study was to examine the effect of semicarbazide (SCZ), an efficient SSAO inhibitor, on the arterial phenotype of the carotid artery in relation to modulation of SSAO and lysyl oxidase activities in growing rats. We first show that after 6 weeks of SCZ treatment (100 mg/kg per day), SSAO activity was reduced by 90%, whereas lysyl oxidase activity was only partially inhibited (<60%) in carotid artery, compared with controls. There was significant growth inhibition and no difference in mean arterial pressure but an increase in pulse pressure with a smaller arterial diameter in SCZ-treated rats. SCZ decreased aortic insoluble elastin without a change in total collagen. In addition, extracellular proteins other than insoluble elastin and collagen were increased in SCZ-treated rats. All of the elastic lamellae presented globular masses along their periphery, and focal disorganization was observed in the ascending aorta. Carotid artery mechanical strength was lower in SCZ-treated rats, and the elastic modulus-wall stress curve was shifted leftward compared with controls, indicating increased stiffness. Thus, SCZ modifies arterial geometry and mechanical properties, alters elastic fiber structure, and reduces the content of cross-linked elastin. Because these abnormalities are essentially absent in SSAO-deficient mice, our results suggest that lysyl oxidase inhibition is responsible for the major part of the vascular phenotype of SCZ-treated rats.

Topics: Amine Oxidase (Copper-Containing); Animals; Aorta, Thoracic; Blood Pressure; Carotid Arteries; Collagen; Elasticity; Elastin; Male; Phenotype; Protein-Lysine 6-Oxidase; Rats; Rats, Sprague-Dawley; Semicarbazides

A chemical-induced, nonlethal, dissecting aortic aneurysm (DAA) is described following in utero exposure to semicarbazide, an inhibitor of the vascular enzyme semicarbazide sensitive amine oxidase (SSAO).. Sprague-Dawley rat dams were given semicarbazide (0.096-49.000 mg/kg/day) by IP injection on gestation days (GDs) 14-20, a period of rapid aortic development. Newborn rats (day 1) were killed and their thoracic organs were removed en bloc for near-serial cross sections and routine histopathology, Movat stain for elastin, and immunohistochemistry to differentiate cells involved in the evolution of the DAA. In subsequent experiments, pups from treated dams (0.096-6.125 mg/kg/day) were allowed to survive for 7 or 28 days.. DAA occurred in nearly 100% of the rats at all doses except the lowest tested (1.530, 0.096 mg/kg/day). Dissections frequently extended to the carotids and, less frequently, to the abdominal aorta. Remodeling of vascular lesions proceeded by organization of collections of blood in vascular media (the "false lumen"), proliferation of vascular smooth muscle cells, fibrosis, and formation of irregular frayed elastic lamellae in healed vascular media. Biochemical quantitation and Western blot analysis of main extracellular matrix proteins on GD 20 showed no overt difference in expression of collagen type I, fibrillin-1, or elastin.. This developmental model provides investigators an opportunity to explore the pathologic mechanisms of DAA and to examine the potential long-term effects of vascular remodeling of DAA.

Topics: Amine Oxidase (Copper-Containing); Analysis of Variance; Animals; Animals, Newborn; Aorta, Thoracic; Aortic Aneurysm, Thoracic; Aortic Dissection; Collagen; Dose-Response Relationship, Drug; Elastin; Female; Gestational Age; Immunohistochemistry; Injections, Intraperitoneal; Models, Biological; Pregnancy; Rats; Rats, Sprague-Dawley; Semicarbazides

The endogenous substrate(s) and physiological function(s) of semicarbazide-sensitive amine oxidase (SSAO), a group of enzymes exhibiting highest activity in vascular smooth muscle cells of the mammalian aortic wall, remain undetermined. This study examines the pathophysiological effects in the thoracic aortic wall resulting from specific in vivo SSAO inhibition. Weanling Sprague-Dawley rats were treated acutely or chronically with either semicarbazide hydrochloride or the allylamine derivatives MDL-72274 or MDL-72145 (Marion Merrell Dow Research Institute, Cincinnati, OH). Treatment with these compounds produced acute (6 and 24 h) and chronic (21 day) lowering of SSAO activity in aorta and lung with little effect on the activity of the vital matrix-forming enzyme, lysyl oxidase, in aortas of chronically treated animals. Chronic SSAO inhibition produced lesions consisting of striking disorganization of elastin architecture within the aortic media accompanied by degenerative medial changes and metaplastic changes in vascular smooth muscle cells. No significant difference in the total weight of dry, lipid-extracted aortic elastin and collagen components were observed between chronically SSAO inhibited and control animals. However, the amount of mature elastin was lowered and mature collagen was raised in the aortas of animals treated chronically with semicarbazide. Descending thoracic aortic rings isolated from chronically SSAO-inhibited animals had larger cross-sectional diameters (i.e., exhibited dilation) when compared to corresponding rings from control animals. This study demonstrates that developmental toxicity, characterized by striking vascular lesions and dilated thoracic aortas, can result from specific in vivo SSAO inhibition, suggesting a role for SSAO in connective tissue matrix development and maintenance, and specifically in the development of normal elastin.

Topics: Allyl Compounds; Allylamine; Amine Oxidase (Copper-Containing); Animals; Aorta, Thoracic; Blood Vessels; Collagen; Elastin; Enzyme Inhibitors; Lung; Male; Monoamine Oxidase Inhibitors; Propylamines; Protein-Lysine 6-Oxidase; Rats; Rats, Sprague-Dawley; Semicarbazides