A Novel Aldosterone Antagonist Limits Renal Injury in 5/6 Nephrectomy

Aldosterone antagonists slow the progression of chronic kidney disease (CKD), but their use is limited by hyperkalemia, especially when associated with RAS inhibitors. We examined the renoprotective effects of Ly, a novel non-steroidal mineralocorticoid receptor (MR) blocker, through two experimental protocols: In Protocol 1, male Munich-Wistar rats underwent 5/6 renal ablation (Nx), being divided into: Nx+V, receiving vehicle, Nx+Eple, given eplerenone, 150 mg/kg/day, and Nx+Ly, given Ly, 20 mg/kg/day. A group of untreated sham-operated rats was also studied. Ly markedly raised plasma renin activity (PRA) and aldosterone, and exerted more effective anti-albuminuric and renoprotective action than eplerenone. In Protocol 2, Nx rats remained untreated until Day 60, when they were divided into: Nx+V receiving vehicle; Nx+L treated with losartan, 50 mg/kg/day; Nx+L+Eple, given losartan and eplerenone, and Nx+L+Ly, given losartan and Ly. Treatments lasted for 90 days. As an add-on to losartan, Ly normalized blood pressure and albuminuria, and prevented CKD progression more effectively than eplerenone. This effect was associated with strong stimulation of PRA and aldosterone. Despite exhibiting higher affinity for the MR than either eplerenone or spironolactone, Ly caused no hyperkalemia. Ly may become a novel asset in the effort to detain the progression of CKD.

Characterization of atherosclerosis in LDL receptor knockout mice: macrophage accumulation correlates with rapid and sustained expression of aortic MCP-1/JE

Atherosclerosis and the expression of monocyte chemoattractant protein-1 (MCP-1) were quantified in low density lipoprotein receptor knockout (LDLR KO) mice fed 1.25% cholesterol (study #1) or 0.2% cholesterol (study #2). In study #1 plasma total cholesterols leveled-off at 1800 mg/dl whereas plasma triglycerides remained low. In en face specimens of the aortic root and arch, intimal foam cells plus extracellular lipid particles accumulated and by 8 weeks the fatty streak surface area had rapidly expanded at both sites. In study #2, total cholesterols averaged 400 mg/dl and fatty streaks were 2-3-fold smaller compared to those in study #1. In study #3, LDLR KO mice were fed chow or 1.25% cholesterol, and immunostaining demonstrated a few Mac-2-positive intimal macrophages in mice fed chow, and during the first 10 weeks of hypercholesterolemia the number of intimal macrophages increased continuously. In chow-fed mice (0 weeks) there was little MCP-1 in the aorta. After 2 days of hypercholesterolemia intimal macrophages stained for MCP-1, and during the next 10 weeks recently recruited arterial macrophages also expressed MCP-1. Macrophage accumulation was highly correlated with MCP-1 expression. In study #4, feeding LDLR KO mice 1.25% cholesterol for 6 months produced atherosclerotic plaques at both sites and they contained a fibrous cap of smooth muscle cells, macrophage-foam cells, connective tissue and cholesterol crystals. In summary, LDLR KO mice fed cholesterol develop fatty streaks that transform into fibrous plaques. Hypercholesterolemia rapidly triggers MCP-1 expression in resident intimal macrophages, which is followed by the accumulation of more macrophages that also express MCP-1, suggesting that this chemokine may both initiate and amplify monocyte recruitment to the artery wall during early atherogenesis.

Increased severity of glomerulonephritis in C-C chemokine receptor 2 knockout mice

Increased severity of glomerulonephritis in C-C chemokine receptor 2 knockout mice.

BACKGROUND

The C-C chemokine receptor 2 (CCR2) is expressed on monocytes and facilitates monocyte migration. CCR2 is a prominent receptor for monocyte chemoattractant protein-1 (MCP-1). This chemokine recruits monocytes to sites of inflammation. It has been suggested that CCR2 and its ligand, MCP-1, play a role in the pathogenesis of glomerulonephritis. The goal of this study was to determine the contribution of CCR2 in a murine model of accelerated nephrotoxic nephritis. We measured the extent of development of renal disease in CCR2 wild-type and knockout mice after the administration of antiglomerular basement membrane antibody.

METHODS

Eight groups of animals were treated (N = 10 per group). Four days after IgG immunization, CCR2 wild-type and knockout mice received control serum or nephrotoxic serum. The urinary protein/creatinine ratio was measured on days 1 and 3; plasma and kidneys were collected on days 4 and 7. Kidneys were evaluated by light microscopy, immunohistochemistry, and immunofluorescence. The genotype of mice was confirmed by tissue analysis.

RESULTS

Protective effects of CCR2 knockout on the urinary protein/creatinine ratio were observed on day 1, as values for this parameter were significantly lower (35 +/- 3.6) than in nephritic wild-type mice (50 +/- 6.8). There was a marked increase in proteinuria in nephritic wild-type mice on day 1 compared with vehicle-treated, wild-type animals (5 +/- 1.0). On day 3, the ameliorative effects of CCR2 knockout were not observed; the increase in the urinary protein/creatinine ratio was similar in nephritic CCR2 wild-type (92 +/- 11.2) and knockout mice (102 +/- 9. 2). Plasma markers of disease were evaluated on days 4 and 7. At these time points, there were no beneficial effects of CCR2 receptor knockout on plasma levels of urea nitrogen, creatinine, albumin, or cholesterol. On day 7, blood urea nitrogen (248 +/- 19.9 mg/dL) and plasma cholesterol were higher in nephritic CCR2 knockout mice than in wild-type mice (142 +/- 41.7 mg/dL) that received nephrotoxic serum. Histopathologic injury was more severe in nephritic CCR2 knockout mice than nephritic wild-type mice on day 4 (3.1 +/- 0.3 vs. 2.0 +/- 0.3) and day 7 (3.6 +/- 0.2 vs. 2.9 +/- 0.3). By immunohistochemical analysis at day 4, there were significantly fewer mac-2-positive cells, representative of macrophages in the glomeruli of nephritic CCR2 knockout (2.1 +/- 0.6) mice than nephritic wild-type (3.9 +/- 0.5) animals. By indirect immunofluorescence, there was a moderate, diffuse linear IgG deposition of equivalent severity present in glomeruli of both wild-type and CCR2 knockout nephritic mice.

CONCLUSION

These results suggest that our strategy was successful in reducing macrophage infiltration, but this model of glomerulonephritis is not solely dependent on the presence of CCR2 for progression of disease. After a transient ameliorative effect on proteinuria, CCR2 knockout led to more severe injury in nephritic mice. This raises the intriguing possibility that a CCR2 gene product ameliorates glomerulonephritis in this murine model. Although effects that occur in chemokine knockout mice are not equivalent to those expected with prolonged use of a chemokine antagonist, this study may nevertheless have implications for consideration of long-term use of chemokine antagonists in renal disease.

Prospective identification of biologically active structures by topomer shape similarity searching

The principle of bioisosterism-similarly shaped molecules are more likely to share biological properties than are other molecules-has long helped to guide drug discovery. An algorithmic implementation of this principle, based on shape comparisons of a single rule-generated "topomer" conformation per molecule, had been found to be the descriptor most consistently predictive of similar biological properties, in retrospective studies, and also to be well-suited for searching large (>10(12)) "virtual libraries" of potential reaction products. Therefore a prospective trial of this shape similarity searching method was carried out, with synthesis of 425 compounds and testing of them for inhibition of binding of angiotensin II (A-II). The 63 compounds that were identified by shape searching as most similar to any of four query structures included all of the seven compounds found to be highly active, with none of the other 362 structures being highly active (p < 0.001). Additional consistent relations (p < 0.05) were found, among all 425 compounds, between the degree of shape similarity to the nearest query structure and the frequency of various levels of observed activity. Known "SAR" (rules specifying structural features required for A-II antagonism) were also regenerated within the biological data for the 63 shape similar structures.

Enhanced reduction of atherosclerosis in hamsters treated with pravastatin and captopril: ACE in atheromas provides cellular targets for captopril

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase and angiotensin-converting enzyme (ACE) reduce experimental atherosclerosis by different mechanisms. To determine whether dual-drug therapy additively retards the progression of early lesions, control hyperlipidemic hamsters were compared with those treated with pravastatin, captopril, and pravastatin plus captopril. After 8 weeks of treatment, pravastatin (34 mg/kg/day) reduced plasma total cholesterol and triglycerides by 41 and 84%, respectively, whereas captopril (100 mg/kg/day) reduced normal blood pressure by 21%. The combination of pravastatin and captopril (33 and 100 mg/kg/day) decreased plasma total cholesterol and triglycerides by 44 and 84%, and blood pressure was decreased by 14%. In the aortic arch, pravastatin reduced macrophage-foam cell size and fatty streak area by 21 and 31%, respectively, whereas captopril decreased macrophage-foam cell number and fatty streak area by 34 and 35%. Pravastatin plus captopril decreased macrophage-foam cell number, foam cell size, and fatty streak area by 38, 24, and 67%. ACE inhibitors were previously reported to retard atherosclerosis without affecting blood pressure, suggesting that these agents acted on the artery wall. Therefore the expression of arterial ACE was determined in normal and atherosclerotic hamster aortas. ACE messenger RNA (mRNA) and protein were detected in endothelial cells, intimal macrophage-foam cells and medial smooth-muscle cells of atherosclerotic arteries indicating an upregulation of ACE expression with hyperlipidemia and atherosclerosis. In conclusion, dual-therapy with pravastatin and captopril produced an additive reduction in fatty streak area compared with either drug alone and suggested that atherogenesis can be retarded beyond the level achieved with monotherapy. The presence of ACE in endothelial cells and intimal macrophage-foam cells provides cellular targets for captopril to directly modify the formation of early atherosclerotic lesions.

Fibrinogen deficiency is compatible with the development of atherosclerosis in mice

A critical role of the coagulation system in the development of atherosclerosis has been frequently postulated based on a variety of indirect observations, including the expression of procoagulants and fibrinolytic factors within atherosclerotic vessels, the presence of substantial amounts of fibrin(ogen) and fibrin degradation products within intimal lesions, the cellular infiltration and assimilation of mural thrombi into developing plaques, and the identification of high plasma fibrinogen (Fib) levels as an independent risk factor for the development of ischemic heart disease. To directly examine the role of fibrin(ogen) in atherogenesis, Fib-deficient mice were crossed to atherosclerosis-prone apolipoprotein E (apo E)-deficient mice. Both apo E-/- and apo E-/-/Fib-/- mice developed lesions throughout the entire aortic tree, ranging in appearance from simple fatty streaks to complex fibrous plaques. Furthermore, remarkably little difference in lesion size and complexity was observed within the aortae of age- and gender-matched apo E-/- and apo E-/-/Fib-/- mice. These results indicate that the contribution of fibrin(ogen) to intimal mass and local cell adhesion, migration, and proliferation is not strictly required for the development of advanced atherosclerotic disease in mice with a severe defect in lipid metabolism.

Plasminogen deficiency accelerates vessel wall disease in mice predisposed to atherosclerosis

A critical link between hemostatic factors and atherosclerosis has been inferred from a variety of indirect observations, including the expression of procoagulant and fibrinolytic factors within atherosclerotic vessels, the presence of fibrin in intimal lesions, and the cellular infiltration of mural thrombi leading to their incorporation into developing plaques. To directly examine the role of the key fibrinolytic factor, plasminogen, in atherogenesis, plasminogen-deficient mice were crossed to hypercholesterolemic, apolipoprotein E-deficient mice predisposed to atherosclerosis. We report that the loss of plasminogen greatly accelerates the formation of intimal lesions in apolipoprotein E-deficient animals, whereas plasminogen deficiency alone does not cause appreciable atherosclerosis. These studies provide direct evidence that circulating hemostatic factors strongly influence vessel wall disease in the context of a disorder in lipid metabolism.

Stimulation of activin A expression in rat aortic smooth muscle cells by thrombin and angiotensin II correlates with neointimal formation in vivo

Vasoactive GTP-binding protein-coupled receptor agonists (e.g., angiotensin II [AII] and alpha-thrombin) stimulate the production of mitogenic factors from vascular smooth muscle cells. In experiments to identify mitogens secreted from AII- or alpha-thrombin-stimulated rat aortic smooth muscle (RASM) cells, neutralizing antibodies directed against several growth factors (e.g., PDGF and basic fibroblast growth factor [basic FGF]) failed to inhibit the mitogenic activity of conditioned media samples derived from the cells. In this report, we found that polyclonal neutralizing antibodies directed against purified human placental basic FGF reduced the mitogenic activity of AII-stimulated RASM cell-conditioned media and in immunoblot experiments identified a 26-kD protein (14 kD under reducing conditions) that was distinct from basic FGF. After purification from RASM cell-conditioned medium, amino acid sequence analysis identified the protein as activin A, a member of the TGF-beta superfamily. Increased activin A expression was observed after treatment of the RASM cells with AII, alpha-thrombin, and the protein kinase C agonist PMA. In contrast, PDGF-BB or serum caused only a minor induction of this protein. Although activin A alone only weakly stimulated RASM cell DNA synthesis, it demonstrated a potent comitogenic effect in combination with either EGF or heparin-binding EGF-like growth factor in the RASM cells, increasing DNA synthesis by up to fourfold. Furthermore, in a rat carotid injury model, activin A mRNA was upregulated within 6 h after injury followed by increases in immunoreactive protein detected in the expanding neointima 7 and 14 d later. Taken together, these results indicate that activin A is a vascular smooth muscle cell-derived factor induced by vasoactive agonists that may, either alone or in combination with other vascular derived growth factors, have a role in neointimal formation after arterial injury.

Selective blockade of the endothelin subtype A receptor decreases early atherosclerosis in hamsters fed cholesterol

Recent studies suggest that endothelin and its receptors may be involved in atherogenesis. To test this hypothesis, cholesterol-fed hamsters were treated with a selective endothelin subtype A (ETA) receptor antagonist BMS-182874. Characterization of hamster atherosclerotic plaques indicated that they contained a fibrous cap of smooth muscle cells, large macrophage-foam cells, and epitopes of oxidized low density lipoprotein. Messenger RNA for both ETA and ETB receptors was detected in aortic endothelial cells, in medial smooth muscle cells, and in macrophage-foam cells and smooth muscle cells of the fibro-fatty plaques. BMS-182874 inhibited the endothelin-1-induced pressor response whereas the depressor effect was unaltered, suggesting that vascular ETA receptors were selectively blocked in vivo. In hyperlipidemic hamsters, BMS-182874 decreased the area of the fatty streak by reducing the number and size of macrophage-foam cells. The results indicated that ETA receptors and thus endothelin promoted the early inflammatory phase of atherosclerosis.

Regression of early atherosclerosis in hyperlipidemic hamsters induced by fosinopril and captopril

We determined whether inhibiting angiotensin-converting enzyme (ACE) with fosinopril or captopril induced the regression of atherosclerosis in hamsters. A pressor experiment demonstrated that 100 mg/kg fosinopril or captopril almost completely inhibited ACE activity in vivo. Another study established that feeding hamsters 0.05% cholesterol and 10% coconut oil resulted in rapid and progressive accumulation of oil red O-stained macrophage-foam cells in the aortic arch. In the regression study, three groups of hamsters were fed the same atherogenic diet for 4 weeks to induce fatty lesions in the arch. After 4 weeks, plasma lipids, blood pressure (BP), and atherosclerosis were quantified in control hamsters. Beginning at 4 weeks, the two remaining groups of hamsters were treated with 100 mg/kg/day fosinopril or 100 mg/kg/day captopril for 6 more weeks while receiving the atherogenic diet. After 6-week treatment, plasma lipids, BP, and atherosclerosis were quantified in the two treated groups (i.e., study week 10), and they were compared with the 4-week controls. As compared with that in controls, fosinopril decreased plasma low density lipoprotein (LDL) and very low density lipoprotein (VLDL) cholesterols by approximately 69%. High density lipoprotein (HDL) cholesterol decreased by 16% and total triglycerides decreased by 56% as compared with that of controls. Captopril did not alter LDL plus VLDL cholesterols or total triglycerides, but HDL cholesterol decreased by 24% as compared with that of the control group. As compared with that of control hamsters, mean arterial BP (MAP) decreased by 9% with captopril treatment, and heart rate (HR) was decreased by both fosinopril and captopril.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitors of angiotensin converting enzyme decrease early atherosclerosis in hyperlipidemic hamsters. Fosinopril reduces plasma cholesterol and captopril inhibits macrophage-foam cell accumulation independently of blood pressure and plasma lipids

The effect of two angiotensin converting enzyme (ACE) inhibitors on the development of atherosclerosis was determined in hyperlipidemic hamsters. Preliminary studies indicated that only fosinopril (50 mg/kg) temporarily decreased mean arterial pressure, while after chronic dosing fosinopril and captopril (50 mg/kg) were ineffective. The same dose of fosinopril and captopril inhibited the angiotensin I pressor response, indicating these agents suppressed ACE activity in vivo. In the 3 week atherosclerosis experiment, all hamsters were fed chow supplemented with 0.05% cholesterol and 10% coconut oil. Control hamsters were compared with those receiving either 50 mg/kg per day of fosinopril or 50 mg/kg per day of captopril. After 3 weeks, fosinopril reduced plasma total cholesterol, low density lipoprotein (LDL) plus very low density lipoprotein cholesterol and total triglycerides by 17%, 27% and 45%, respectively. Captopril only reduced high density lipoprotein cholesterol by 20%. Neither fosinopril or captopril altered blood pressure at 3 weeks. Atherosclerosis was quantified from en face preparations of the lesion-prone aortic arch that were stained with oil red O (for cholesteryl ester and triglycerides). In control hamsters, oil red O labeled numerous subendothelial macrophage-foam cells located along the inner curvature of the aortic arch. Compared with controls, fosinopril reduced the number of intimal macrophage-foam cells/mm2, foam cell size and the fatty streak area by 85%, 38% and 90%, respectively. Captopril decreased these parameters by 44%, 16% and 53%. Thus captopril decreased early atherosclerosis without affecting plasma LDL cholesterol or blood pressure, which suggested that inhibiting ACE (or kininase II) directly impeded the accumulation and formation of macrophage-foam cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostacyclin agonists reduce early atherosclerosis in hyperlipidemic hamsters. Octimibate and BMY 42393 suppress monocyte chemotaxis, macrophage cholesteryl ester accumulation, scavenger receptor activity, and tumor necrosis factor production

We determined the effects of two prostacyclin agonists (octimibate and BMY 42393) on the progression of the fatty streak in vivo and on macrophage function in vitro. Hamsters were fed chow plus 0.05% cholesterol and 10% coconut oil. Control hamsters were compared with animals receiving either octimibate (10 or 30 mg/kg per day) or BMY 42393 (30 mg/kg per day). After 10 weeks of treatment, octimibate decreased plasma total cholesterol and triglycerides by 43% and 32%, respectively. Neither agonist affected blood pressure or heart rate. Lesion-prone aortic arches were stained with hematoxylin and oil red O and examined en face. Compared with controls, octimibate and BMY 42393 on average decreased mononuclear cells attached to the luminal surface by 44% and reduced subendothelial macrophage-foam cell number by 56%, foam cell size by 38%, and fatty streak area by 63%. Since octimibate is a putative inhibitor of acyl coenzyme A cholesterol acyltransferase, we studied the effect of both agents on cholesteryl ester metabolism in murine macrophages. At 10 microM, octimibate and BMY 42393 decreased cholesteryl ester accumulation in macrophages by 90% and 41%, respectively. Octimibate inhibited cholesteryl ester synthesis by 96% and increased the rate of cholesteryl ester degradation by 52%. Both prostacyclin agonists reduced macrophage scavenger receptor-mediated uptake of acetylated low density lipoprotein by 24-66% and increased cyclic adenosine monophosphate levels. Octimibate and BMY 42393 inhibited the secretion of tumor necrosis factor by 80-88% when macrophages were activated with lipopolysaccharide. At 10 microM, both agents decreased human monocyte chemotaxis to N-formyl-methionyl-leucyl-phenylalanine by 64-79%. The in vitro results with octimibate and BMY 42393 are consistent with the low number of small foam cells quantified in vivo. We suggest that octimibate and BMY 42393 suppress monocyte-macrophage atherogenic activity and cytokine production and thus inhibit the development of early atherosclerosis.

Doxazosin and cholestyramine similarly decrease fatty streak formation in the aortic arch of hyperlipidemic hamsters

The effect of doxazosin, an alpha-1 adrenergic inhibitor, on atherosclerosis was determined in hyperlipidemic hamsters. Control hamsters fed chow plus 0.05% cholesterol and 10% coconut oil were compared to chow baseline animals, and to those receiving either 10 mg/kg/day doxazosin, or 245 mg/kg/day cholestyramine in the atherogenic diet. During 8 weeks of treatment, plasma lipids, mean arterial pressure (MAP) and heart rate (HR) were measured, then the ascending aortic arch was examined en face. Numbers of subendothelial macrophage-foam cells/mm2 and their average size (microns 2) were determined, and Oil red O staining (micrograms ORO/mm2) was quantitated to estimate lipid accumulation. Ultracentrifugation of control plasma demonstrate that low density lipoprotein (LDL) carried most of the cholesterol, and very low density lipoprotein (VLDL) was rich in triglycerides. Compared to controls, doxazosin and cholestyramine similarly decreased plasma total and LDL plus VLDL cholesterols, and total triglycerides on average by 46%, 61% and 45% respectively. High density lipoprotein cholesterol was unchanged. Doxazosin also reduced MAP by 18% without affecting HR. In all hamsters, foam cells and lipid accumulated in a lesion-prone area characterized by elevated endothelial cell density, and a thick intima of basement membrane-like material layered over "pads" of smooth muscle cells. Compared to controls, doxazosin and cholestyramine uniformly reduced the number of foam cells/mm2, foam cell size and ORO staining on average by 66%, 29% and 56%, respectively. We conclude that doxazosin decreases plasma lipids and inhibits the development of the fatty streak to a similar level as cholestyramine treatment.

Effect of dietary fat saturation and cholesterol on LDL composition and metabolism. In vivo studies of receptor and nonreceptor-mediated catabolism of LDL in cebus monkeys

The mechanism(s) by which polyunsaturated fats reduce low density lipoprotein (LDL) cholesterol and apolipoprotein (apo) B were investigated in 20 cebus monkeys (Cebus albifrons) fed diets containing corn oil or coconut oil as fat (31% of calories) with or without dietary cholesterol (0.1% by weight) for 3 to 10 years. Coconut-oil feeding compared to corn-oil feeding resulted in significant increases in levels of plasma total cholesterol (176%), very low density lipoprotein (VLDL)-LDL cholesterol (236%), high density lipoprotein (HDL) cholesterol (148%), apo B (78%), and apo A-I (112%). The addition of dietary cholesterol to corn oil compared to corn oil alone resulted in smaller, but significant, increases in levels of total cholesterol (44%), HDL cholesterol (40%), and apo A-I (33%). Although the increases in VLDL-LDL cholesterol were of similar magnitude (52%), they barely failed to reach statistical significance (p less than 0.08), while the changes in apo B levels were negligible. The addition of dietary cholesterol to coconut oil, compared to coconut oil alone, resulted in no significant changes in lipoprotein cholesterol or apoproteins, although levels of VLDL-LDL cholesterol and apo B values increased 22% and 16%, respectively. Although hepatic free cholesterol content was not altered by diet, coconut-oil compared to corn-oil feeding resulted in significant increases in hepatic cholesteryl esters (236%) and triglycerides (325%), the latter increasing still further when dietary cholesterol was added to coconut oil (563%). To further assess the effects of these dietary changes on LDL metabolism, radioiodinated normal and glucosylated LDL kinetics were performed. The production rate of LDL apo B was not altered by diet. With corn-oil feeding, 63% of LDL catabolism was via the receptor-mediated pathway. Coconut-oil compared to corn-oil feeding resulted in a 50% decrease in receptor-mediated LDL apo B fractional catabolic rate (FCR) and a 27% reduction in nonreceptor-mediated LDL apo B FCR. The addition of dietary cholesterol to corn oil, compared to corn oil alone, resulted in no significant effect on LDL apo B catabolism. The addition of dietary cholesterol to coconut oil, compared to coconut oil alone, was associated with no significant change in nonreceptor catabolism of LDL apo B but with a 58% decrease in receptor-mediated catabolism of LDL (p less than 0.059). The diet-induced alterations of LDL catabolism were significantly correlated with hepatic lipids, which were enriched in saturated fatty acids.(ABSTRACT TRUNCATED AT 400 WORDS)

Low density lipoprotein heterogeneity in the cebus monkey

In studies of cebus monkey plasma lipoproteins, we have used an ultracentrifugally generated density gradient to isolate two distinct species of low density lipoproteins (LDL). Compositional analyses revealed that each of the ultracentrifugally isolated fractions was enriched in cholesteryl esters and contained a single apolipoprotein which in terms of its mobility on SDS gels corresponded to apolipoprotein B-100, the major apolipoprotein of human LDL. Hydrodynamic measurements carried out in the analytical ultracentrifuge showed that F1.20 values were 30.0 for LDL1 and 23.5 for LDL2. In a solution of density 1.0069 g/ml, the sedimentation rates were 5.9 and 7.2 S for LDL1 and LDL2, respectively. In addition to sedimentation velocity data, we describe a new approach for using these same data to obtain calculated values for molecular weight. The hydrated densities calculated for the two fractions were 1.033 and 1.045 g/ml and calculated molecular weights were 3.08 million for LDL1 and 2.42 million for LDL2. Hydrated density values were in excellent agreement with those calculated from compositional data. Electron microscopy data showed that LDL1 had a larger mean diameter of 26.7 nm than LDL2 which had a diameter of 19.3 nm. Native gel electrophoretic analyses of the two LDL fractions in 3.5% acrylamide showed that, consistent with its size, LDL1 had slower mobility than LDL2.

Effects of prazosin on hemodynamics, hemostasis, and serum lipid and lipoprotein levels in normal and hypercholesterolemic monkeys

The effect of prazosin on hemodynamics, hemostasis, and serum lipid and lipoprotein levels was investigated in normal and hypercholesterolemic rhesus (Macaca mulatta) and cynomolgus (Macaca fascicularis) monkeys. Administration of prazosin (2 mg/kg bodyweight, orally, twice a day) for three weeks caused significant reductions in plasma cholesterol, including low- plus very low-density lipoprotein cholesterol, apolipoprotein B, and triglyceride levels. Drug therapy was associated with increased high-density lipoprotein cholesterol levels, although in one group of monkeys this rise also was associated with a reduction in apolipoprotein A1. Prazosin treatment significantly decreased mean arterial pressure in normal and hypercholesterolemic monkeys. As was expected, acute administration of phenylephrine caused mean arterial pressure to rise, with animals receiving normal- or high-cholesterol-containing diets showing similar responses. After prazosin treatment, however, a greater inhibition in the phenylephrine pressor response was observed in hypercholesterolemic monkeys compared with normal animals. Platelet aggregation in response to adenosine 5'-diphosphate, prothrombin time, and activated partial thromboplastin time were not altered by prazosin. Thus, in our nonhuman primate models of hypercholesterolemia, administration of prazosin resulted in reduction in lipid and apoprotein levels with no change in hemostasis.

Effect of doxazosin on plasma lipids and atherogenesis: a preliminary report

Chronic treatment with selective alpha 1-inhibitors has a beneficial impact on plasma lipids and arterial pressure. To study the effect of selective alpha 1-inhibition on atherogenesis, gerbils and hamsters were fed rodent chow containing 0.2% cholesterol and 10% coconut oil (by weight). One group of each species received the selective alpha 1-inhibitor doxazosin (gerbil, 17 mg/kg/day; hamster, 11 mg/kg/day) in the diet. In gerbils treated for 6 weeks with doxazosin, plasma total cholesterol fell by 39% and very-low-density lipoprotein (VLDL) plus low-density lipoprotein (LDL) cholesterol by 52% compared with control levels. Plasma triglyceride and high-density lipoprotein (HDL) cholesterol were unaffected. In hamsters treated with doxazosin for 6 weeks, plasma total cholesterol, VLDL plus LDL cholesterols, and triglyceride were reduced by approximately 40% compared with hyperlipidemic controls. HDL cholesterol, mean arterial pressure, and heart rate were not significantly altered. Using en face preparations of the hamster aortic arch, intimal macrophage-derived foam cells were quantitated. Compared with controls, doxazosin reduced the number of intimal foam cells/mm2 by 71%. We suggest that selective alpha 1-inhibition reduces foam cell accumulation by lowering plasma lipids and/or by a direct effect on the arterial wall.

Serum lipids, lipoproteins, hemodynamics, and hemostasis in doxazosin-treated monkeys

The effect of doxazosin administration on hemodynamics, hemostasis, and serum lipid and lipoprotein levels was investigated in cynomolgus monkeys (Macaca fascicularis) with diet-induced hypercholesterolemia. Acute administration of doxazosin (1 and 5 mg/kg) reduced resting mean arterial pressure by 20% without affecting heart rate, and completely inhibited the pressor response to phenylephrine. Platelet aggregation, prothrombin time, and activated partial thromboplastin time were not altered by the drug. Long-term doxazosin administration (1, 10, and 20 mg/kg/day) was associated with significant reductions in levels of total serum cholesterol (13%), very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) cholesterol (14%), and apolipoprotein B (15%) without any significant effects on high-density lipoprotein (HDL) cholesterol and apolipoprotein A-1. A 76% reduction in serum triglycerides, independent of drug level, was also seen in doxazosin-treated monkeys. In monkeys removed from drug treatment, serum cholesterol initially exceeded and then returned to pretreatment levels, whereas serum triglycerides remained low for 3 weeks. In our hypercholesterolemic monkey model, the administration of doxazosin resulted in beneficial changes in lipid and apolipoprotein profiles, hemostasis, and hemodynamics.

Intimal changes in the aorta of prehypertensive rats

Intimal changes were quantitated in several rat models of arterial hypertension. One kidney-one clip rats drinking water (1K-1C-water), one-kidney rats treated with deoxycorticosterone acetate and drinking 1% NaCl (1K-DOCA-salt), and two-kidney rats drinking 1% NaCl (2K-salt) were studied after 1 to 8 weeks. The thoracic aorta was examined en face and by electron microscopy. Surprisingly, all 2K-salt, most 1K-DOCA-salt (17 out of 19), and two-thirds of 1K-1C-water rats (12 out of 18) had normal arterial pressure at sacrifice. In these normotensive 2K-salt, 1K-1C-water, and 1K-DOCA-salt animals, intimal mononuclear cells (which emigrated from the blood) increased between three- and ninefold. In these same normotensive 1K-1C-water and 1K-DOCA-salt rats, endothelial cell mitoses increased three- to sixfold with a corresponding increase in endothelial cell numbers. In the latter two groups, there was no evidence of endothelial cell denudation or changes in aortic circumference, and the subendothelial space widened mainly with reticular basement membrane presumably synthesized by the endothelium. In normotensive 1K-DOCA-salt rats, most of the endothelial cells were thick and there were several intercellular gaps. Endothelial proliferation, synthesis of macromolecules, and gap formation, as well as increased mononuclear cell emigration, indicate functional changes in mononuclear cells and in endothelial cells. We suggest that the experimental procedures designed to produce hypertension also generate factor(s) which activates mononuclear cells and/or endothelial cells. This cellular activation leads to intimal changes independent of hypertension.

Cellular changes during hypertension: a quantitative study of the rat aorta

Using rats made hypertensive by aortic ligation or by the one kidney--one clip method, we searched the aorta for morphologic clues that could explain why hypertension aggravates atherosclerosis. Both atherosclerosis and hypertension are characterized by an increased migration of mononuclear cells into the aortic intima; we therefore quantitated this phenomenon and studied its time course. In the thoracic aorta of hypertensive rats intimal cells (emigrated mononuclear cells) increased up to 15 times 2 weeks after surgery and remained stationary thereafter. In both control and experimental rats, leukocyte emigration was heavier in the thoracic aorta than in the abdominal region. A two- to threefold increase in medial smooth muscle herniae into the intima (myointimal herniae) was also found at 8 weeks, indicating a smooth muscle cell dysfunction. Electron microscopic study of the intima showed that its thickening was due to blood-borne material and also to extracellular matrix synthesized by the endothelium. Heightened secretion reflects cell activation, a condition that (in the endothelium) leads also to leukocyte adhesion. These data suggest that, in renovascular hypertension, the aortic endothelium is in an activated state, possibly through a hormonal stimulus.

The popliteal lymph node of the mouse: internal architecture, vascular distribution and lymphatic supply

The architecture of the mouse popliteal lymph nodes differs from that shown in conventional diagrams. The cortical lymphoid tissue, rather than forming a continuous outer layer, is organised into one or two hemispherical aggregates which project towards the hilus. These aggregates are surrounded by medullary tissue which thus extends to large areas of the surface of the node. The vascular distribution in the lymphoid aggregates is relatively sparse and contrasts with the dense meshwork of capillaries and venules around them. It also contrasts with the high vascularity of medullary tissue. Arterial vessels, especially those of larger calibre, are predominantly seen in the hilar area of the node suggesting that there is extensive branching as the artery enters the node. Capillaries associated with the lymphoid aggregates are usually lined by continuous endothelium, while those in the medulla are generally of the fenestrated type. The microcirculation has an extensive venous capacity and many venous segments are high endothelium venules whose walls are permeated by lymphocytes. Each node receives one or two afferent lymphatic vessels and is drained by up to four or five efferent lymphatic vessels. In approximately half the nodes examined, there were extranodal communications between afferent and efferent lymphatic vessels allowing some lymph to bypass the node.