Smooth muscle-specific SM22 protein is expressed in the adventitial cells of balloon-injured rabbit carotid artery

During the "response-to-injury" process after a mechanical insult to the porcine coronary arteries, the adventitial cells acquire the structural characteristics of myofibroblasts before being incorporated into smooth muscle (SM) layer. We assessed whether the SM-specific SM22 protein can be used as a tracer of adventitial cell-myofibroblast differentiation in the mild balloon injury of rabbit carotid artery. To achieve this goal, we used 2 monoclonal anti-SM22 antibodies (E-11 and 1-B8) and a molecular probe for the SM22alpha mRNA isoform in immunocytochemical and in situ hybridization experiments. The differentiation profile and the migratory and proliferative ability of activated adventitial cells were evaluated by a panel of antibodies to some SM and nonmuscle antigens and pulse- and end-labeling with bromo-deoxyuridine, respectively. In adventitial cells, SM22 antigenicity and SM22alpha mRNA were detectable at days 2 and 4 and, to a lesser extent, at days 7 and 21 after injury, particularly near the adventitia-media interface and mostly colocalizing with bromo-deoxyuridine-positive cells. The pulse-labeling experiments showed that the large majority of these cells penetrated the outermost layer of the tunica media without migrating to the subendothelial region. The phenotypic features of activated migrating and nonmigrating adventitial cells resembled those of vimentin-actin myofibroblast subtype and fetal-type SM cells. These findings indicate that a direct exposure of adventitia to the lumen is not required for phenotypic changes and proliferation/migration of these cells. After comparison of the SM22 expression in arterial vessels during early stages of development, we hypothesize that in the injured carotid artery the mural incorporation of adventitial cells and the spatiotemporal activation of SM22 expression are reminiscent of the vascular morphogenetic process and suggest the existence of a stem cell-like reservoir in adventitia. The early adventitial upregulation of SM22 expression in the injured vessel might be related to a multistep transition process in which nonmuscle cells are converted to myofibroblasts and, possibly, to SM cells.

Factors underlying the increase in carotid intima-media thickness in borderline hypertensives

To define the role played by various risk and behavioral factors in the increase of carotid intima-media thickness (IMT) observed in borderline hypertensives. Using B-mode ultrasonography, we compared 97 borderline hypertensives enrolled in the HARVEST study to 27 normotensive controls. Intima-media thickness was measured in the right and left common carotid artery, bulb, and internal carotid artery. Mean IMT (m-IMT), maximum IMT (M-IMT), the mean of M-IMT (M-MAX), and the prevalence of raised lesions (IMT>1 mm) were established. Compared to the controls, higher systolic BP, diastolic BP, mean arterial blood pressure levels and body mass index (BMI) were present in the borderline hypertensives, whereas age, smoking, physical activity, serum cholesterol, and triglycerides were similar. After adjusting for age, sex, heart rate, BMI, smoking, serum cholesterol, triglycerides, and physical activity, higher values of m-IMT and M-IMT were present in most carotid segments of borderline hypertensives compared with controls. After further adjustment for systolic BP and diastolic BP, differences were no longer significant. The adjusted M-MAX was 0.59+/-0.12 in borderline hypertensives compared with 0.50+/-0.10 in controls (P<0.001). After adjustment for systolic BP and diastolic BP it was 0.58+/-0.11 in borderline hypertensives compared with 0.50+/-0.12 in controls (P<0.005). In the various carotid segments, the prevalence of raised lesions was 1. 2% in borderline hypertensives compared with 0.3% in controls (P<0. 001). In the multivariate analysis m-IMT, M-IMT, and M-MAX were related to ambulatory mean arterial pressure, systolic BP and diastolic BP, serum cholesterol and triglycerides, BMI, age, and physical activity. Higher IMT values were found in subjects who were physically active than in those who were sedentary. In borderline hypertensives, an increase in IMT takes place not only in the common carotid artery but also in the bulb and the internal carotid segment. Blood pressure levels are a main determinant of m-IMT while the interaction of BP with other risk factors such as age and plasma lipids is more relevant for advanced intima-media thickening such as M-MAX.

Fish intake, independent of apo(a) size, accounts for lower plasma lipoprotein(a) levels in Bantu fishermen of Tanzania: The Lugalawa Study

Plasma lipoprotein(a) [Lp(a)] levels are largely genetically determined by sequences linked to the gene encoding apolipoprotein(a) [apo(a)], the distinct protein component of Lp(a). Apo(a) is highly polymorphic in length due to variation in the numbers of a sequence encoding the apo(a) kringle 4 domain, and plasma levels of Lp(a) are inversely correlated with apo(a) size. In 2 racially homogeneous Bantu populations from Tanzania differing in their dietary habits, we found that median plasma levels of Lp(a) were 48% lower in those living on a fish diet than in those living on a vegetarian diet. Considering the relationship between apo(a) size and Lp(a) plasma concentration, we have extensively evaluated apo(a) isoform distribution in the 2 populations to determine the impact of apo(a) size in the determination of Lp(a) values. The majority of individuals (82% of the fishermen and 80% of the vegetarians) had 2 expressed apo(a) alleles. Additionally, the fishermen had a high frequency of large apo(a) isoforms, whereas a higher frequency of small isoforms was found in the vegetarians. When subjects from the 2 groups were matched for apo(a) phenotype, the median Lp(a) value was 40% lower in Bantus on the fish diet than in those on the vegetarian diet. A significant inverse relationship was also found between plasma n-3 polyunsaturated fatty acids and Lp(a) levels (r=-0.24, P=0.01). The results of this study are consistent with the concept that a diet rich in n-3 polyunsaturated fatty acids, and not genetic differences, is responsible for the lower plasma levels of Lp(a) in the fish-eating Bantus and strongly suggest that a sustained fish-based diet is able to lower plasma levels of Lp(a).

Endothelin-1 and its mRNA in the wall layers of human arteries ex vivo

BACKGROUND

The participation of endothelin-1 (ET-1) in the control of vascular tone in humans has been questioned, on the basis of the finding of subthreshold immunoreactive (ir) ET-1 plasma levels. However, because most ET-1 is secreted abluminally, it might attain a higher concentration in the tunica media than in plasma. Furthermore, evidence indicates that vascular smooth muscle cells (VSMCs) can synthesize ET-1 on stimulation in vitro. We therefore looked for irET-1 in the different layers of the wall of human arteries, including renal, gastric, and internal thoracic artery wall, obtained ex vivo from consenting patients with coronary artery disease and/or high blood pressure undergoing surgery, as well as from young organ donors.

METHODS AND RESULTS

We performed immunohistochemistry with specific anti-ET-1 and anti-vWF antibodies followed by detection with an avidin-biotin complex ultrasensitive kit. The presence of preproET-1 and human endothelin-converting enzyme-1 (hECE-1) mRNA was also investigated by reverse transcription-polymerase chain reaction in homogenates of vessel wall, including preparations deprived of both endothelium and adventitia, and in isolated VSMCs. We detected irET-1 in the endothelium of all arteries and in the tunica media of internal thoracic artery from most patients with coronary artery disease. PreproET-1 and hECE-1 mRNA was also detected in VSMCs isolated from these vessels. irET-1 and irvWF staining in endothelium and tunica media was measured by use of microscope-coupled computer-assisted technology. Significant correlations between the amount of irET-1 in the tunica media and mean blood pressure (P<0.05), total serum cholesterol (P<0.05), and number of atherosclerotic sites (P<0.001) were found. Thus, in organ donors, irET-1 was detectable almost exclusively in endothelial cells, whereas in patients with coronary artery disease and/or arterial hypertension, sizable amounts of irET-1 were detectable in the tunica media of different types of arteries. In addition, VSMCs isolated from these vessels coexpressed the preproET-1 and hECE-1 genes.

CONCLUSIONS

Collectively, these findings are consistent with the contention that endothelial damage occurs in most patients with atherosclerosis and/or hypertension and that ET-1 is synthesized in VSMCs of these patients.

Relationship of tachycardia with high blood pressure and metabolic abnormalities: a study with mixture analysis in three populations

Faster resting heart rate has been shown to be associated with a higher risk of developing hypertension and a greater incidence of cardiovascular morbidity and mortality. The aim of this study was to investigate the distribution of heart rate and its relationship with blood pressure and other cardiovascular risk factors in three populations. One European general population (Belgian study), one North American general population (Tecumseh study), and one European hypertensive population (HARVEST trial) were studied. Within each population, mixture analysis was used to investigate whether a mixture of two normal distributions explained the variance in heart rate better than a single distribution. In the men of all populations, mixture analysis identified a larger subpopulation of subjects with normal heart rate and a smaller one with fast heart rate. The subgroups with tachycardia had higher blood pressure and lipid levels than those with normal heart rate. In the populations in which they were measured, fasting insulin and postload glucose were also higher in the men with faster heart rate. A subgroup with tachycardia could also be singled out among the women from Tecumseh, but no relation between heart rate and blood pressure could be found. These findings show that in Western societies, high heart rate pertains to a distinct subgroup of subjects, who are more frequently men and exhibit the characteristic features of the insulin resistance syndrome. Sympathetic overactivity is likely to be the mechanism underlying this clinical condition.

Blood pressure, serum cholesterol and nutritional state in Tanzania and in the Amazon: comparison with an Italian population

OBJECTIVE

To confirm that westernization of dietary habits represents a stimulus for the expression of cardiovascular risk.

DESIGN

Three representative age- and sex-matched samples of general populations of three continents were compared cross-sectionally by analysis of variance.

PARTICIPANTS

In total 1110 subjects aged 22-89 years, divided into three groups (370 from Tanzania and Uganda, 370 from the Amazonian region of Brazil, and 370 from northern Italy; 111 men and 259 women in each group).

RESULTS

The blood pressure of Africans eating a low-salt fish and vegetable' diet was lower than those of Brazilians, whose diet was based on cereals and meat, and highly urbanized Italians. The systolic blood pressure was correlated to the body mass index for all three populations, but with age only for the Brazilians and Italians. The total cholesterol level and body mass index, both of which are low among Africans, increased progressively with increasing economic level.

CONCLUSIONS

Transition from a rural to an urbanized lifestyle is accompanied by a rise in the main cardiovascular risk factors; the present data also show that environmental rather than racial factors have a crucial impact on the risk pattern of populations.

Myosin gene expression and cell phenotypes in vascular smooth muscle during development, in experimental models, and in vascular disease

In the aortic wall of mammalian species, the maturation phase of smooth muscle cell (SMC) lineage is characterized by two temporally correlated but opposite regulatory processes of gene expression: upregulation of SM type SM2 myosin isoform and downregulation of brain (myosin heavy chain B)- and platelet (myosin heavy chain A(pla))-type nonmuscle myosins. Using the myosin isoform approach to study vascular SMC biology, we have shown (1) a marked SMC heterogeneity in adult arterial vessels, ie, coexistence of an "immature" and a fully differentiated SMC population; and (2) the propensity of the immature type SMC population to be activated in experimental models and human vascular diseases that are characterized by proliferation and migration of medial SMCs into the subendothelial space.

Impaired glucose tolerance and its co-variates among 2079 non-diabetic elderly subjects. Ten-year mortality and morbidity in the CASTEL study. CArdiovascular STudy in the ELderly

This study evaluated the role of impaired glucose tolerance (IGT) as a risk factor in a general population of 2079 non-diabetic elderly subjects. The 10-year cardiovascular morbidity was similar in normal and IGT subjects. Mortality was greater in IGT, but the Cox equations of the hazard rate were different in younger and older subjects: age, sex, lung function (forced expiratory volume in 1 s, FEV1), serum uric acid, IGT and proteinuria were predictors of overall mortality in the age class 65-79 years, while only the first 4 were associated with cardiovascular mortality. The same four items also predicted overall survival in subjects over 79 years old, while only age and uric acid were predictors of cardiovascular mortality. In older subjects, total cholesterol showed an inverse predictive value. Hyperuricaemia (> 6.4 mg/dl) and proteinuria did predict mortality in normal but not in IGT subjects, while reduced FEV1 (< 60% theoretical) was predictive in all. In 65-79-year old subjects IGT predicted mortality provided that FEV1 was normal, while in those 380 years old IGT was not a predictor. These interrelationships should be taken into account to better understand the factors underlying mortality.

Atherosclerosis resistance in rats correlates with lack of expansion of an immature smooth muscle cell population

In this study we asked whether the well-known atherosclerosis resistance of rats might be reduced with aging. Two groups of young, adult and aged Wistar rats, one of which was kept on a standard, low-cholesterol (CT) diet, and the other one was fed a 2% CT diet for 2 months were enrolled. Potential modifications in the phenotypic profile of aortic smooth muscle (SM) were assessed by SDS-gel electrophoresis, Western blotting and immunofluorescence procedures using a panel of monoclonal antibodies to myosin isoforms, cytoskeletal and extracellular matrix proteins. With development and aging, the expression of 196-kD non-muscle-type myosin heavy-chain isoform (MyHC), the EIIIA fibronectin variant and keratins was downregulated, whereas that of the 204- and 200-kD SM-type MyHC isoforms, SM-type alpha-actin and desmin did not change. The levels of hypercholesterolemia achieved in this model did not substantially modify the distribution of the downregulated markers, except for the subendothelial grouping of immature SM cells in aged rats. Morphometric measurements indicated a slight increase of medial cross-sectional area accompanied by a decrease in total SM cell number, both with aging and with hypercholesterolemia. In no circumstance was the presence of atherosclerotic lesions histologically detectable. Bromo-deoxyuridine (BrdU) incorporation analysis revealed a marked age-dependent decline in DNA synthesis and the formation of binucleated cells in aged aortas. This pattern was not influenced by hypercholesterolemia, except in aged rats where BrdU-positive SM cells are almost doubled. Our data indicate that aging and hypercholesterolemia cannot affect the phenotypic stability of rat SM cells and confirm that the change from a fully differentiated to an immature state is a general prerequisite to allow the development of atherosclerotic lesions in mammalian species.

Creatine kinase system in failing and nonfailing human myocardium

BACKGROUND

The creatine kinase (CK) reaction is important for rapid resynthesis of ATP when the heart increases its work. Studies defining the CK system in human failing and nonfailing myocardium are limited and in conflict. To resolve this conflict, we measured the activities of CK and its isoenzymes and the contents of creatine and CK-B in homogenates of human myocardium.

METHODS AND RESULTS

Myocardium was sampled from 23 subjects who underwent heart transplant, 36 subjects maintained in an intensive care unit before heart harvesting, 13 accident victims, and 2 patients undergoing heart surgery. Since the characteristics of myocardium of potential organ donors differed from those of myocardium of accident victims, data are presented for three groups: failing, donor, and control. CK activity was 7.7 +/- 1.9 and 6.0 +/- 1.4 IU/mg protein in left (LV) and right (RV) ventricles of failing, 9.4 +/- 2.5 and 10.7 +/- 2 IU/mg protein in LV and RV of donor, and 11.6 +/- 2.4 IU/mg protein in LV of control hearts. CK-MM and the mitochondrial isoenzyme activities were lower in failing and donor LV, and CK-MB activity and CK-B content were higher in failing and donor hearts. Creatine contents were 64 +/- 25 and 56 +/- 18.6 nmol/mg protein in LV and RV of failing, 96 +/- 30 and 110 +/- 24 nmol/mg protein in LV and RV of donor, and 131 +/- 28 nmol/mg protein in LV of control hearts.

CONCLUSIONS

In failing and nonfailing donor human myocardium, there is a combined decrease of CK activity and creatine that may impair the ability to deliver ATP to energy-consuming systems.

Blood pressure and atherogenic lipoprotein profiles of fish-diet and vegetarian villagers in Tanzania: the Lugalawa study

BACKGROUND

There is evidence that populations with a high intake of fish, and specifically fish oils, are at reduced risk of cardiovascular disease. To explore the effect of fish intake, we compared two groups of Bantu villagers in Tanzania; one group live on the shores of Lake Nyasa and their diet includes large amounts of freshwater fish; the other group live in the nearby hills and have a vegetarian diet.

METHODS

We carried out a cross-sectional study of 622 fish-consuming villagers and 686 vegetarian villagers. 618 (99.4%) and 645 (94.0%), respectively, agreed to take part. Anthropometric and self-reported medical history data were collected by one local physician and a medical assistant, who also measured blood pressure and took blood samples for measurement of plasma lipids. A dietary questionnaire was administered to 25 families (about 15% of the study population) in each village.

FINDINGS

After adjustment for age, sex, and alcohol intake the fish-consuming group had lower mean blood pressure than the vegetarian group (123/72 vs 133/76 mm Hg, p < 0.001). The frequencies of definite and borderline hypertension (by WHO criteria) were lower in the fish-consuming than in the vegetarian group (2.8 vs 16.4%; 9.7 vs 22.3%, respectively). Plasma concentrations of total cholesterol (mean 3.53 [SD 1.04] vs 4.10 [1.04] mmol/L), triglycerides (0.92 [0.64] vs 1.31 [0.64] mmol/L), and lipoprotein(a) (201 [213] vs 321 [212] mg/L), were all lower (p < 0.0001) in the fish-consuming group than in the vegetarian group. The proportions of n-3 polyunsaturated fatty acids in plasma lipids were higher (p < 0.0001) in the fish-consuming group than in the vegetarian group (eicosapentaenoic acid 2.3 [1.3] vs 0.7 [0.2]%; docosapentaenoic acid 1.1 [0.4] vs 0.6 [0.3]%; docosahexaenoic acid 5.7 [1.6] vs 1.5 [1.1]%).

INTERPRETATION

In these villagers, consumption of freshwater fish (300-600 g daily) was associated with raised plasma concentrations of n-3 polyunsaturated fatty acids, lower blood pressure, and lower plasma lipid concentrations.

Human cytomegalovirus and restenosis of the internal carotid artery

BACKGROUND

Although human cytomegalovirus (HCMV) has been implicated in coronary restenosis, data on the presence of HCMV in the restenosis lesion of the internal carotid artery (ICA) are lacking.

SUMMARY OF REPORT

We studied endarterectomy tissue from 5 ICA restenosis and 5 primary atherosclerotic lesions and tissue from 5 normal ICAs. The extracted DNA was tested for HCMV sequences with polymerase chain reaction by use of three primer pairs that amplify different genomic regions. The AD 169 strain of HCMV served as the positive control. No trace of the HCMV genome was found in the intima or in the underlying media of endarterectomy specimens from restenosis and primary lesions. The media from control arteries was also HCMV negative.

CONCLUSIONS

At variance with previous studies carried out in coronary arteries, our results do not support the hypothesis that HCMV infection is implicated in restenosis of the ICA.

Anipamil prevents intimal thickening in the aorta of hypertensive rabbits through changes in smooth muscle cell phenotype

The aim of this study was to evaluate the effect of anipamil, a phenyalkylamine-derived Ca(2+)-antagonist, on aortic intimal thickening and smooth muscle cell (SMC) phenotype in 2K-1C hypertensive rabbits. Monoclonal antimyosin antibodies [SM-E7, NM-G2, and NM-F6, which respectively, recognize smooth muscle (SM), A-type-, and B-type-like nonmuscle (NM) myosin heavy chains (MyHC)] identify different aortic SMC types: adult (SM-E7-positive), postnatal (SM-E7- and NM-G2-positive), and fetal (SM-E7-, NM-G2-, and NM-F6-positive). Twenty-four hypertensive rabbits were studied 2.5 months (n = 12) and 4 months (n = 12) after clipping. Six animals from each group were given anipamil (40 mg orally, once daily) immediately after surgery. The remaining 2K-1C were given a daily oral placebo. Normotensive age-matched controls were also studied. Transverse cryosections of aorta were taken for computerized morphometry and immunocytochemical studies. Primary and secondary SMC cultures were used to define potential changes in cell phenotype after adding anipamil to the culture medium. In untreated 2K-1C, intimal thickening, mainly composed of postnatal-type SMC, was found by 2.5 months after clipping. Morphometric and immunofluorescence studies in anipamil-treated 2K-1C rabbits revealed absent or negligible intimal thickening and a decrease of postnatal-type SMC from the underlying media. In culture experiments, growth inhibition of SMC by anipamil was accompanied by the expression of SM-MyHC in all SMC, ie, the appearance of a more differentiated cell phenotype compared to control cultures. In conclusion, prevention of intimal thickening in anipamil-treated 2K-1C was achieved through selective reduction in the media of the postnatal-type SMC. This could be achieved by reducing NM-MyHC content or increasing synthesis of SM-MyHC expression. As blood pressure was not significantly lowered by anipamil treatment, a direct and specific antiproliferative action of this drug on medial SMC is likely to take place.

Blood pressure, serum lipids, and fatty acids in populations on a lake-fish diet or on a vegetarian diet in Tanzania

Major risk factors for coronary heart disease were assessed in two populations of Tanzania, one on a fish diet (FD) living along the coast of Lake Nyasa, and the other, mainly on a vegetarian diet (VD), living in a farming area. Lower blood pressure values were found in the FD subjects (n = 618) vs. VD (n = 618) (systolic blood pressure, SBP, 120 +/- 15 vs. 135 +/- 20, P < 0.01; diastolic blood pressure, DBP, 70 +/- 9 vs. 78 +/- 11, P < 0.01, respectively). In an FD subgroup (n = 61), total cholesterol (TC) (122 vs. 136 mg/dL, P < 0.01); triglycerides (TG) (82 vs. 105 mg/dL, P < 0.01); and lipoprotein (a) [Lp(a)] (19.9 +/- 18.4 vs. 32.3 +/- 22.4, P < 0.001) were lower than in a VD subgroup (n = 55). Serum fatty acids (FA) in the FD subgroup were as follows: eicosapentaenoic acid (EPA) (20:5) 2.48 vs. 0.72%, docosahexaenoic acid (DHA) (22:6) 5.93 vs. 1.49%, vs. the VD, respectively. Arachidonic acid (AA) (20:4n-6) also was higher in the FD vs. the VD group (9.85 vs. 8.30%, P < 0.05), whereas 18:2n-6 was about double (23.97 and 14.85%) in VD vs. FD. The peculiar serum FA pattern in FD reflected the FA of dietary fish. In fact, in four main species of lake fish, DHA was 8-19%, higher than EPA (1.8-4.2%), in contrast with the situation in cold-water fish, and AA was 5.8-8%, higher than in cold-water fish. The data, obtained in populations strictly on natural, unprocessed, low-fat diets, show that a diet based on freshwater fish results in lower BP, serum TC, TG, and Lp(a), and suggests that serum AA is not reduced when the major dietary n-3 is DNA rather than EPA.

Expression of non-muscle myosin isoforms in rabbit myometrium is estrogen-dependent

The putatative effects of different estrogen levels on the expression of non-muscle myosin isoforms in rabbit myometrium have been investigated using three monoclonal anti-platelet myosin heavy chain (MyHC) antibodies (NM-F6, NM-G2, and NM-A9). Western blotting analysis of proteolytic digests of human platelet actomyosin indicates that these antibodies are specific for three distinct epitopes. Comparative immunofluorescence tests on cultered human fibroblasts with polyclonal sequence-specific anti-MyHCA antibody suggest that the patterns of NM-F6, NM-.G2 and NM-A9, although similar, do not overlap with that of type-A MyHC. Distribution of NM myosin isoforms has been studied in indirect immunofluorescence assays using cryosections of tissues from rabbits at various stages of development, pregnancy, or from ovariectomized, 17beta-estradiol-treated ovariectomized, and human chorionic gonadotropin-treated animals. Non-muscle myosin antigenicity is still present in the myometrium when the female becomes sexually competent. The immunoreactivity of non-muscle myosin for NM-F6 is steroid-independent, since it does not change with pregnancy or ovariectomy, but that of NM-G2 is estrogen-dependent; the latter disappears during pregnancy and in ovariectomized animals treated with estradiol, whereas it is expressed in ovariectomized rabbits. Although non-muscle myosin immunoreactivity for NM-A9 is detectable under all the experimental conditions, it can assume different patterns of intracellular distribution in vitro (punctate vs filamentous), depending on culture conditions and the presence of estrogens.

Antiatherogenic action of nitrendipine in hypercholesterolemic rabbits: changes in aortic macrophage accumulation and smooth muscle cell phenotype

Intimal accumulation of macrophages and changes in the phenotype and growth properties of vascular smooth muscle cells (SMCs) represent key events in the development of atherosclerotic lesions. Here we report on the in vivo effect exerted by nitrendipine on aortic tissue of cholesterol-fed rabbits. We have focused especially on the myosin heavy chain (MyHC) pattern expressed by aortic SMC, taken as a marker of cell differentiation. Using monoclonal antibodies specific to the different forms of MyHC, three differentiation steps were determined: adult, postnatal, and fetal. Nitrendipine administered in conjunction with a cholesterol-enriched diet reduced the development of atherosclerotic lesions (atherosclerosis index: 0.21 vs. 0.32 in untreated animals, p< 0.005), despite persistently high serum cholesterol levels. Compared to untreated controls, nitrendipine-treated animals displayed a decreased number of postnatal-type SMCs in the media underlying the plaque (prevalence index: 0.07 vs. 0.26, p < 0.0001 and a lower aortic cholesterol content (free cholesterol: 3.3 vs. 11.5 ng/mg, p< 0.0001; esterified cholesterol: 7.2 vs. 40.5 ng/mg, p< 0.0001). Moreover, nitrendipine treatment decreased the intimal accumulation of macrophages and fetal-type SMCs. It is conceivable that calcium antagonists may exert their antiatherogenic effect, at least in part, through cellular changes unrelated to the classical risk factors.

Smooth muscle cell types at different aortic levels and in microvasculature of rabbits with renovascular hypertension

BACKGROUND

The monoclonal antimyosin antibodies smooth muscle (SM)-E7, non-muscle (NM)-G2 and NM-F6 recognize smooth muscle myosin heavy chains, and A- and B-like non-muscle myosin heavy chains, respectively. On this basis, aortic smooth muscle cell types have been identified as adult (SM-E7-positive), postnatal (SM-E7- and NM-G2-positive) and fetal (SM-E7-, NM-G2- and NM-F6-positive). We have demonstrated previously that hypertrophy of the smooth muscle cell layer of the upper aorta in two-kidney, one clip hypertensive rabbits is achieved via a selective increase in postnatal-type smooth muscle cells.

OBJECTIVE

To monitor the time-course change of postnatal-type smooth muscle cells along the entire aortic tree and to define the phenotypic characteristics of the microvasculature in the same rabbit model.

MATERIALS AND METHODS

Hypertensive rabbits were killed 0.5, 1, 2.5, 4, 6 and 8 months after clipping. Normotensive age-matched rabbits served as controls. The entire aorta was frozen during perfusion at a constant pressure for morphometric and immunocytochemical studies. Transverse cryosections were taken 1 cm from the aortic valve (level A), immediately after the anonymous trunk (level B), immediately before the diaphragm (level C), and near the bifurcation (level D). Small vessels and arterioles were studied in psoas skeletal muscle and in left ventricular myocardium.

RESULTS

On the whole, aortae from hypertensive rabbits displayed a striking increase in postnatal-type smooth muscle cells at all levels by 4 months of hypertension and a progressive decrease in the number of these cells to near the control value by 8 months of hypertension. A peculiar pattern of myosin heavy chain expression was found in the microvasculature. In control and in hypertensive rabbits, both at 4 and at 8 months, small vessels and arterioles were equally reactive with the three antimyosin heavy chain antibodies. This indicates a basic prevalence of fetal-type smooth muscle cells, which is little influenced by blood pressure.

CONCLUSIONS

The present data elucidate some of the basic changes which the entire aortic segment and microvasculature undergo in the present experimental model.

Correlation between the presence of an immature smooth muscle cell population in tunica media and the development of atherosclerotic lesion. A study on different-sized rabbit arteries from cholesterol-fed and Watanabe heritable hyperlipemic rabbits

Mapping the distribution of an immature smooth muscle cell (SMC) subpopulation in large- and small-sized arterial vessels was carried out in normocholesterolemic rabbits and compared with the mapping atherosclerotic lesions in endogenously (Watanabe heritable hyperlipemic, WHHL) and exogenously derived (cholesterol-fed, CT) hypercholesterolemic rabbits. This cell subset is identified by a specific myosin isoform content and displays an intermediate degree of differentiation between fetal- and adult-type SMC. Monoclonal anti-myosin antibodies, immunofluorescence procedures, and different arterial segments of a rabbit vessel tree, i.e. from aorta to dental pulp (common carotid, external carotid, lingual, facial, maxillary, inferior alveolar arteries, and dental branches of alveolar arteries) were studied. WHHL of different ages (3 to 12 months), and two different concentrations of CT (2% and 0.2%) in the diet for 3 and 12 months, respectively, were used. The results of the present study indicate that: (1) using a diet with a higher percentage of CT (rabbits fed 2% CT-diet for 3 months) there is maximum expansion of atherosclerotic lesions from the aorta up to the maxillary artery; (2) localization of atherosclerotic lesions with a lower CT content in the diet is dependent on the duration of feeding and may involve the aorta up to the external carotid artery; (3) the development of the atherosclerotic lesion in hypercholesterolemic rabbit is strictly related to the appearance of an intermediate SMC subtype; (4) atherosclerotic lesions occur only in those arterial sites which, in corresponding normocholesterolemic rabbit, contain intermediate-type SMC; and (5) no differences can be found in the distribution of SMC subpopulations present in the lesions from WHHL, CT-fed animals, or at various arterial levels, whereas some discrepancies can be shown in aortic atherogenesis.

Enalapril treatment increases cardiac performance and energy reserve via the creatine kinase reaction in myocardium of Syrian myopathic hamsters with advanced heart failure

BACKGROUND

Converting enzyme inhibitor treatment of congestive heart failure slows progression to failure and reduces mortality rate. It is known whether these benefits are due solely to improved hemodynamics or also to improved myocyte energetics. This study examines the effect of enalapril treatment on both isovolumic contractile performance and its biochemical correlate, flux through the creatine kinase (CK) system, in an animal model of severely failing myocardium.

METHODS AND RESULTS

Seven-month-old Syrian cardiomyopathic (TO-2 strain) and normal golden Syrian (FIB strain) hamsters were each randomly assigned to one of three groups supplied daily with either no, low (25 mg/kg body wt), or high (100 mg/kg body wt) doses of enalapril for 12 to 14 weeks. At 10 months of age, all substrates and products and flux through the CK reaction were measured in isolated perfused hearts by 31P magnetization transfer and chemical assay. Compared with normal hamsters, the myopathic hamsters exhibited significantly lower body weights and higher biventricular heart weights, which were partially reversed by drug treatment. The Langendorff-perfused hearts showed decreased isovolumic contractile performance with identical load conditions. This was partially reversed by drug treatment. In the failing hearts, the following substrate and product concentrations and enzyme activities were decreased compared with nonfailing hearts but were unchanged by drug treatment: ATP (-28%), phosphocreatine (-48%), free creatine (-64%), ADP (-51%), and CK (-34%, primarily MM isoenzyme). Flux through the CK reaction for the untreated cardiomyopathic hamster hearts was decreased by 67%, and this decrease was almost completely reversed by enalapril treatment. The increased CK flux is due to an increase in the rate constant for the reaction, since substrate concentrations are unchanged, and is not predicted by the rate equation. In enalapril-treated failing hearts, phosphoryl transfer via the CK reaction increased with contractile performance. This was not observed in the nonfailing hearts, in which energy reserve is adequate to support changes in contractile performance.

CONCLUSIONS

Decreased flux through CK reaction leads to decreased capacity for ATP synthesis and may contribute to decreased contractile performance in cardiomyopathic hamster hearts. Enalapril treatment results in increased phosphoryl transfer through the CK reaction in failing myocardium, and this increase is coupled to improved cardiac performance. Decreased CK flux in failing hearts is due to a combination of decreased Vmax and lower guanidino pool; this mechanism fails to explain changes in CK flux in enalapril-treated failing hearts.

Differentiation and growth of vascular smooth muscle cells in experimental hypertension

In this review we have analyzed the present knowledge about the differentiation and growth processes in vascular smooth muscle cells (SMC) in hypertension. The study of smooth muscle (SM) and nonmuscle (NM) myosin isoform expression has permitted us to identify a three-stage specific maturational pathway, namely, fetal, postnatal, and adult. In the renovascular (rabbit) and genetic (rat) models of hypertension, adaptive changes occurring in hypertensive vessels make SMC resemble those found in the early stages of development (smooth muscle plasticity). In fact, based on SM- and NM-myosin isoform distribution, postnatal-type SMC predominate in the arterial media during the early remodeling of the arterial wall that occurs in hypertension, whereas postnatal- and fetal-type SMC predominate in the intimal thickening. Locally produced or activated autocrine/paracrine factors, such as growth factors or cytokines, along with circulating hormones, seem to be involved in the growth response or changes in the differentiation pattern of SMC. Thus, these factors not only play a specific role in the regulation of blood pressure, but also are likely to be responsible for the remodeling of the arterial wall in hypertension.

Hyperplastic growth of aortic smooth muscle cells in renovascular hypertensive rabbits is characterized by the expansion of an immature cell phenotype

Smooth muscle cells (SMCs) of rabbit aorta undergo marked changes in myosin isoform content during development. Analysis of nonmuscle myosin composition at the protein level has permitted the identification of three phases in the SMC differentiation process: fetal, postnatal, and adult. Using monoclonal antibodies specific for smooth muscle and nonmuscle myosins and extra domain A of fibronectin as well as cDNA probes for platelet-derived growth factors (PDGF) and various procollagens, we have evaluated the differentiation pattern of aortic SMCs in two-kidney, one-clip hypertensive rabbits. Morphometric and bromo-deoxyuridine studies indicate that hypertrophy of aortic media along with intimal thickening occurring in hypertensive animals is due to SMC hyperplasia. Western blotting experiments performed on aortic specimens from hypertensive animals with antimyosin antibodies revealed the appearance of a myosin isoform pattern of the "immature" type. Immunofluorescence tests showed that these cells are localized in the thickened intima or distributed in the underlying media (sparsely or in groups). Similarly, the fibronectin variant showing the extra domain A, peculiar to "phenotypically modulated" SMCs, appeared in intimal thickening, and its expression followed the time course of nonmuscle myosin expression. Counting of postnatal-type SMCs in the aortic media revealed that this cell population increases markedly with hypertension (2- up to 15-fold at 4 months) and then declines to near control level in 8-month hypertensive rabbits. Diminution of postnatal-type SMCs at later stages of hypertension was temporally correlated with the slowing down of aortic wall hypertrophy. Average levels of mRNAs, as determined by densitometric analysis in aortas from 1- and 2.5-month hypertensive rabbits, showed an increased expression for PDGF beta receptor (up to twofold), procollagen type I (alpha 1, threefold), procollagen type III (alpha 1, twofold), and fibronectin (up to threefold) compared with controls. Conversely, the steady-state levels of mRNAs for PDGF (A and B chain), PDGF alpha receptor, TGF-beta 1, and procollagen type IV (alpha 1) did not increase significantly. These results provide evidence that in adult renovascular hypertensive rabbits, the hyperplastic growth of aortic SMCs is accompanied by the expansion of an "immature" cell phenotype characteristic of the early stages of development.

Hypertension prevalence and age-related changes of blood-pressure in semi-nomadic and urban Oromos of Ethiopia

We evaluated the prevalence of hypertension and the age-related behaviour of systolic blood pressure (SBP) and diastolic blood pressure (DBP) in a wide sample of male and female Ethiopian Oromos living in rural or pre-industrial urbanized settings. Blood pressure (BP) was measured in the sitting position after 5 min rest in 5277 Oromos. In the group, 4928 were semi-nomadic shepherds, while 349 came from a town of 60,000 inhabitants where they were involved in low-technology jobs. The first subgroup was composed of 2482 men and 2446 women. All subjects were divided into 3 age groups: 15-44, 45-64, and > or = 65 years. Body weight (BW) and the Quetelet index (QI) were matched to BP levels using Pearson's method. In semi-nomadic men, SBP was 121.4 +/- 8.4 mmHg versus 132.4 +/- 10.4 mmHg in urban men (p < 0.001). In women, SBP was 120.5 +/- 7.9 mmHg versus 128.1 +/- 10.1 mmHg (p < 0.001). The prevalence of hypertension was 0.40% in the semi-nomadic and 3.15% in the urban population. In the latter, significant increases in BW and QI were found, which were significantly correlated to both SBP and DBP. In semi-nomadic men, a 5.33% increase in SBP and a 5.22% in DBP was found between age groups 1 and 2 (p < 0.001 in both). In urban men the increase was 4.77% and 3.41% respectively (p < 0.001). In both male populations no difference in SBP and DBP was observed between age groups 2 and 3.(ABSTRACT TRUNCATED AT 250 WORDS)