Semiquantitative histochemical investigation of lysosomal enzyme activities in the aortic endothelial cells of spontaneously hypertensive rats

Biomarkers of oxidative stress and endothelial dysfunction in glucose intolerance and diabetes mellitus

OBJECTIVES

To evaluate biomarkers of endothelial dysfunction and oxidative stress in glucose intolerance (GI) compared to overt diabetes (DM2).

DESIGN AND METHODS

140 volunteers including 96 with DM2, 32 with GI and 12 controls (C) were studied. (*)NO metabolites, (*)NO synthase inhibitors, thiols and N-acetyl-beta-glucosaminidase (NAGase) activity were analyzed by chemiluminescence, capillary electrophoresis, ELISA and colorimetric assay, respectively.

RESULTS

(*)NO metabolites were higher in GI (NOx: p=0.03; S-nitrosothiols: p=0.001) and DM2 (p=0.006; p=0.0006) groups in relation to group C, while nitrotyrosine was higher only in the DM2 group in comparison to the other groups. NAGase activity was elevated in GI (p=0.003) and DM2 (p=0.0004) groups in relation to group C, as well as, ADMA (p=0.01; p=0.003) and GSSG (p=0.01; p=0.002).

CONCLUSIONS

(*)NO metabolites, (*)NO synthase inhibitors, thiols and NAGase are biomarkers suitable to indicate endothelial dysfunction and oxidative stress in the early stages of impaired response to insulin.

Analysis of secretion and expression of platelet-derived growth factor in cultured endothelial cells from stroke-prone spontaneously hypertensive rat

1. We characterized the endothelial cell-derived growth factors of SHRSP and Wistar Kyoto rats (WKY), respectively and found that platelet-derived growth factor (PDGF)-B chain related growth factor constituted a major portion of the mitogenic activity of the conditioned media of endothelial cells from both animals. There were no remarkable qualitative differences between the endothelial cell-derived growth factors of SHRSP and WKY. 2. Northern analysis revealed that the expression of PDGF-B chain was 2-4-fold enhanced in cultured aortic endothelial cells of SHRSP. This enhanced expression of PDGF-B chain, which may be induced under chronic hypertensive conditions, is suggested to contribute to the increase in endothelial cell-derived growth factors reported in this animal.

Lysosomal enzyme activities in the cerebral microvessels in spontaneously and renal hypertensive rats

In an attempt to clarify the role of lysosomal enzymes in the developmental mechanisms of the changes of cerebral microvessels under hypertensive conditions, the activities of acid phosphatase, N-acetyl-beta-glucosaminidase, and beta-glucuronidase in the isolated microvessels from the cerebral cortex of spontaneously and renal hypertensive rats were biochemically studied. The activities of all the enzymes were higher than those in normotensive control animals, although there was a variation in intensity according to the age and kind of enzymes. The enzyme activities in spontaneously hypertensive rats showed a tendency to increase with advancing age. Hypertension seems to increase activities of lysosomal enzymes in cerebral microvessels, and this activation may in turn play a role in the development of further hypertensive cerebrovascular and cerebral changes.

Role of lysosomes in mesenteric arterial lesions of renal hypertensive rats

The acid phosphatase activities of arterial cells in the mesenteric arteries of renal hypertensive rats were investigated by both light and electron microscopy. Light microscopically, strongly positive acid phosphatase reactions were confirmed in endothelial cells, intimal cells, medial cells and adventitial cells of the mesenteric arteries, together with considerable deposition of fibrinoid substance in the intima and media in contrast to the appearance in control rats. Electron microscopically, lysosomes with acid phosphatase-positive reaction products were increased in number in endothelial cells, intimal smooth muscle cells, medial smooth muscle cells and adventitial neutrophils or macrophages. The lysosomes in intimal smooth muscle cells and those which were extracellularly discharged were responsible for lysis of the fibrinoid substance. In the media, acid phosphatase-positive lysosomes of medial cells and extracellularly discharged matrix lysosomes with acid phosphatase-positive reactions were also involved in the hydrolysis of necrotic substances and extracellular matrix. These acid phosphatase-positive reactions were diminished both light and electron microscopically in endothelial cells, intimal cells, medial muscle cells and adventitial cells in the regions of healing arteries where fibrinoid substance had been degradated and the intima showed cellulofibrous thickening. The possible role of this acid phosphatase activation for the clearance of cell debris as well as exudative substances in the healing of damaged arterial tissue was discussed.

Effect of hypertension on lysosomal enzyme activities in aortic endothelial cells

In order to obtain information about the changes in lysosomal enzyme activities in arterial endothelial cells under hypertensive conditions, a biochemical study was performed on 5 lysosomal enzymes, acid phosphatase, N-acetyl-beta-glucosaminidase (NAGase), cathepsin B, cathepsin D and beta-glucuronidase, in endothelial cells isolated by an enzymatic technique from the aorta of spontaneously and renal hypertensive rats, and normotensive control rats. The aortic endothelial cells in the old spontaneously and the renal hypertensive rats showed increased activities of enzymes examined in comparison with those in the age-matched control rats. Endothelial cells in young spontaneously hypertensive rats did not show any elevated enzyme activities compared with those in the controls, and the enzyme activities tended to increase with aging. From this, it is deduced that hypertension activates lysosomal enzyme activities in aortic endothelial cells. The differences in the activities of NAGase, cathepsin B and cathepsin D between hypertensive and control animals increased markedly with advancing age. These activated lysosomal enzymes seem to be involved in the developmental mechanism of arterial endothelial cell injury in hypertension and in further development of hypertensive vascular changes.

Tunica media changes in the spontaneously hypertensive rat (SHR)

The histological, ultrastructural, morphometrical and histochemical aspects of the arterial media were studied in young and aged SHR, and compared to normotensive Wistar Kyoto rats. The diffuse thickening was the most characteristic feature of the hypertensive media. It seems due to three processes: Early generalized hypertrophy of smooth muscle cells (smc); connective matrix neogenesis and smc proliferation, more evident in peripheral vasculature. The present paper discusses the following hypertensive tunica media changes in relation to the atherosclerotic process: the decrease in lipolytic esterase and cholinesterase activities; the activation of some lysosomal enzymes; the increase in collagen, glycosaminoglycan and elastin content; the increased media thickness; the modified smc behavior (migration, secretion, proliferation). These alterations might positively influence arterial susceptibility to atherosclerosis through reduced smc lipolytic activity; slowed transmural diffusion; perturbed efflux and aggravated media hypoxia.

Semiquantitative histochemical investigation of lysosomal enzyme activities in the aortic endothelial cells of rats with renal hypertension

To obtain information about changes in lysosomal enzyme activities in the aortic endothelial cells in arterial hypertension, semi-quantitative histochemical investigations of acid phosphatase (Ac-Pase) and N-acetyl-beta-glucosaminidase (NAGase) activities in the aorta of rats with renal hypertension were performed on "Häutchen" monolayer preparations. The aortic endothelial cells in renal hypertensive animals showed increased Ac-Pase and NAGase activities compared with those in control normotensive rats and tended to increase with advancing age. These results, like our previous data from spontaneously hypertensive rats (SHR), indicated that degeneration of endothelial cells, expressed by increased lysosomal enzyme activity, was accelerated by hypertension, and the possible participation of genetic factors in the activation of these enzymes in SHR was ruled out. Increased lysosomal enzyme activity may be involved in the development of other hypertensive vascular changes.