Cerebral atherosclerosis in Japanese. 1. Lipids and glycosaminoglycans in cerebral arteries

Cholesterol-dependent changes of glycosaminoglycan pattern in human aorta

Glycosaminoglycans are regular constituents of the arterial wall and essential for its structure and function. The arteriosclerosis-dependent changes of glycosaminoglycans were investigated, the degree of arteriosclerosis was monitored by the cholesterol content of the tissue. Histological characterization was achieved by electron microscopy. Total glycosaminoglycans were isolated from 33 delipidated segments of human aorta thoracica after exhaustive proteolytic digestion, and fractionated into the individual glycosaminoglycans by a multistep purification procedure. Chondroitin sulfate (CS), dermatan sulfate (DS), heparan sulfate (HS), and hyaluronate (HA) were identified and quantified by chemical and enzymatic analysis. The concentration of total and individual glycosaminoglycans, expressed as mg/g delipidated dry weight of tissue, decreased significantly with increasing cholesterol content of tissue (p = 0.0005-0.005). The extent of decrease differed between the individual glycosaminoglycans as indicated by a shift in the CS/DS:HA:HS ratio from 47:32:21 in low cholesterol aortic segments to 59:29:12 in cholesterol-rich specimens. Determination of the relative molecular masses (Mr) revealed 58 kDa for CS/DS and 92 kDa for HS with a (statistically not significant) increase of the molecular mass of CS/DS and a decrease of HS with increasing cholesterol content. The copolymeric CS/DS glycosaminoglycans were disintegrated enzymatically into CS and DS containing fragments. A significantly higher relative DS content (p = 0.01) was found in cholesterol-rich arterial tissue (32.5%) as compared with low cholesterol tissue samples (28.8%). Cell culture experiments revealed that human arterial HS is able to inhibit the proliferation of cultured human arterial smooth muscle cells. The HS concentration required for a 30% inhibition of smooth muscle cell proliferation was in the same order as the tissue concentration of HS. This confirms the function of HS as an endogenous inhibitor of cell division and its impact for the development of atherosclerosis.

Acidic glycosaminoglycans in human atherosclerotic cerebral arterial tissues

The glycosaminoglycan (GAG) content of normal and atherosclerotic areas of cerebral arterial tissue isolated from human males was measured. The main trunk and distal branches of the arteries were obtained at autopsy on 12-89-year-old Japanese subjects. The GAG components were analysed by high-performance liquid chromatography (HPLC) after enzymatic digestion, using specific GAG lyases. Both total GAGs and water content were lower in the diseased arteries than those in the normal state. In contrast, the reverse was noted for the lipid content. The main GAG component of the normal cerebral arteries was heparan sulfates (HS), comprising half the total GAGs, followed by dermatan sulfate (DS) and chondroitin 6-sulfate (Ch-6S) constituting 1/5 to 1/9 the total GAGs. Chondroitin 4-sulfate (Ch-4S) comprised approx. 1/10 the total GAGs. Oversulfated chondroitin sulfate isomers were detected as novel peaks of the chondroitin sulfate types G, B, E and H on HPLC analysis. Small amounts of hyaluronic acid (HA) and chondroitin were also detected. The total GAG content decreased with severity of atherosclerosis. The content and proportions of HS to the total GAGs decreased remarkably, and those of Ch-4S, HA and chondroitin showed a moderate decrease. The reverse was the case for those of DS, Ch-6S and oversulfated DS and/or Ch-S. The lipid components, in particular cholesterol ester, in the diseased tissue were significantly greater than in the visibly normal parts while the opposite was the case for the water content. Thus, the GAG species and their contents in human cerebral arteries showed a characteristic distribution. As oversulfated DS and Ch-S isomers have anticoagulant and anti-atherosclerotic activities, they may play a pertinent role in the disease process.

Distribution of acidic glycosaminoglycans, lipids and water in normal human cerebral arteries at various ages

Functional alterations in arterial acidic glycosaminoglycans (AGAG) may be related to the pathogenesis of some forms of cerebrovascular disease. We measured the AGAG, lipid and water content of human cerebral artery of 275 normal males at various ages. These measures were separately carried out in the main trunk and distal branches. The AGAG components were analyzed by an enzymatic assay method employing specific enzymes which digest AGAG to assess topographic change and aging variations. The total AGAG content was higher in the main cerebral artery than in the distal branches. The main AGAG component of the normal main cerebral artery was heparan sulfates (HS), constituting half the total AGAG, followed by moderate amounts of dermatan sulfate (DS), chondroitin-6-sulfate (C-6S) and chondroitin-4-sulfate (C-4S). Hyaluronic acid (HA) was a minor component and it was more prominent in young arteries. Heparin could be occasionally detected. With advancing age, the relative amounts of HS, HA, chondroitin and C-4S both in the main trunk and distal branches decreased but those of DS and C-6S increased. The total lipid, cholesterol ester and triglyceride content was greater in the main trunk than in the distal branches; the total lipid content increased with age. A possible function of the cerebral arterial AGAG is discussed with respect to change in lipid and water content according to topographic sites and aging.

Cerebral atherosclerosis in Japanese. Part 4: relationship between lipid content and macroscopic severity of atherosclerosis

In order to evaluate chemically the macroscopic scoring methods for severity of arteriosclerosis in the cerebral arteries, concentrations of total lipids, esterified and free cholesterol and lipid phosphorus were compared to the macroscopic severity of lesions in the cerebral arteries obtained from 376 Japanese persons after unexpected death. An increase of cholesterol content was correlated significantly with an increase of Baker's score and/or Gore's atherosclerotic index. The correlation coefficient between Baker's score and total or esterified cholesterol was the highest among the tested correlations (r = 0.82, n = 376).

Cerebral atherosclerosis in Japanese. Part 5: relationship between cholesterol deposition and glycosaminoglycans

Concentrations of various lipids and glycosaminoglycans (GAG) in the intima of the grossly normal and atherosclerotic cerebral arteries were compared with those of the aorta and coronary arteries. The lowest percentage of esterified cholesterol (EC) in total cholesterol, and of chondroitin sulfate-4/6 (CS-4/6) in total glycosaminoglycans and the highest percentage of heparin sulfate (HS) in total GAG are the characteristic features of the normal intima of normal cerebral arteries when compared with those in the aorta and coronary artery. In the cerebral arterial intimas, but not in the aorta or coronary arteries, there was a significant positive correlation between contents of EC and percentage and total content of CS-4/6. Atherogenesis in cerebral arteries is discussed in comparison to that of the aorta and coronary vessels.

Composition of acidic glycosaminoglycans in human cerebral arteries

(1) The composition of acidic glycosaminoglycans (AGAG) in the pooled human cerebral arteries was investigated by electrophoretic characterization before and after digestion with chondroitinases. Constitution of the chondroitin sulfate (CS) family was determined qualitatively on the basis of the disaccharide subunits of the CS chains after depolymerization with the enzymes. (2) The data obtained indicated that the AGAG in cerebral arteries consisted of, in order of amount, heparan sulfates, chondroitin-6-sulfate, dermatan sulfate, chondroitin-4-sulfate and hyaluronic acid. (3) The existence of oversulfated CS and undersulfated CS in the cerebral AGAG was supported by the detection of unsaturated di-sulfated and non-sulfated disaccharides on paper chromatography. In addition, the presence of hyaluronic acid was indicated by electrophoretic and enzymatic separation. (4) The distribution of the individual AGAG in cerebral arteries was also examined on the basis of molecular weight by gel filtration on a Sephadex G-100 column.