Hormonal control of glucose production and pyruvate kinase activity in isolated rat liver cells: influence of hypothyroidism

Hormonal control of glucose production and of -pyruvate kinase activity has been measured in isolated liver cells from fed control and thyroidectomized rats. In hypothyroid rats, sensitivity to isoproterenol as measured by these parameters was increased: the apparent K_0.5 for isoproterenol-induced stimulation of glucose production decreased from 8.0 ± 3 × 10⁻⁶ M in control rats to 2.0 ± 0.2 × 10⁻⁸ M in hypothyroid rats (P < 0.001) and the apparent K_0.5 for inhibition of -pyruvate kinase was 5 ± 2 X 10⁻⁷ M vs. 7 ± 2 × 10⁻⁹ M (P < 0.001) in control and thyroidectomized rats, respectively. Utilisation of specific adrenergic antagonists confirmed increased β-adrenergic responsiveness in hypothyroid rats. This phenomenon was not reversed by 3 days of T₃ treatment (10 μg/100 g body weight). Sensitivity to the -agonist was unchanged by thyroid status. Stimulation of glucose production and inhibition of -pyruvate kinase activity by glucagon and their reversal by insulin were not affected by hypothyroidism. The dose-response curve to vasopressin and its maximal effect measured on stimulation of glucose production were unchanged in thyroidectomized rats. Thus, hypothyroidism produces a specific enhancement of liver β-adrenergic responsiveness without affecting sensitivity to glucagon, insulin and vasopressin.     

Injury produced by free fatty acids to lysosomes and mitochondria in cultured heart muscle and endothelial cells

Four-day primary coverglass cultures of rat heart muscle (M) and endothelioid (E) cells were treated for 30 min with stearic, oleic or linoleic acids in a FFA/albumin ratio of 6:1 at concentrations from 5 × 10⁻⁶ M to 5 × 10⁻⁴ M. Labilization of lysosomes and mitochondria was measured by acid phosphatase and succinic dehydrogenase staining activity respectively.

Stearate or linoleate, but not oleate, labilized M cell lysosomes at 5 × 10⁻⁶ M. Lysosomes of E cells were not significantly affected by any of the FFA at 5 × 10⁻⁴ M. The order of activity of these FFA for M cell lysosomes was LINOLEATE = stearate > oleate.

Both E and M cell mitochondria were significantly labilized by oleate or linoleate, 5 × 10⁻⁶ M, and by stearate, 5 × 10⁻⁵ M. The order of activity was linoleate > oleate > stearate.

Treatment of cultures for 24 hr with 50 μg/ml of hydrocortisone before the FFA at 5 × 10⁻⁵ M provided significant protection only against stearate-induced lysosomal labilization.     

The role of melatonin on gastric mucosal cell proliferation and telomerase activity in ageing

Abstract:  Despite antiproliferative effects of melatonin on cultured tumor cells, its effects on normal cells are less clear. The action of melatonin on telomerase activity in ageing of gastric mucosal tissues also is not known. In this study, we investigated the age-related changes in telomerase activity and cellular proliferation rate of gastric mucosa and the effect of melatonin. A total of 37 young (4 months old), and aged (20 months old) Wistar rats, kept under equal periods of light and dark, were divided into control [(PBS), i.p. for 21 days] and melatonin-treated (10 mg/kg melatonin, i.p. for 21 days) groups. Telomerase activity, cell proliferation rate, malondialdehyde (MDA) and glutathione (GSH) levels of the stomach were determined. Melatonin significantly inhibited the gastric mucosal proliferation rate of both young and aged rats. Telomerase activity was significantly reduced in aged rats compared to young animals. Melatonin significantly increased the telomerase activity of both young and aged rats. The MDA levels of gastric mucosa in the aged rats were significantly higher than those of the younger rats. On the contrary, the GSH levels of gastric mucosa of the aged group were significantly lower than that of the young rats. While melatonin had no effect on GSH levels of either young or aged rats, it significantly decreased the MDA levels in aged animals. In conclusion, melatonin may delay the ageing of gastric mucosa by inhibiting the replicative cellular senescence via its stimulatory effect on telomerase activity and suppressive effect on cellular proliferation and lipid peroxidation.     

Effect of inhibitors and stimulators on isolated liver cell mitochondrial protein synthesis from young and old rats

Mitochondria isolated from the livers of old rats (26–30 months) were found to incorporate 41% less leucine into mitochondrial proteins as compared to those from young rats (2–3 months). The initial rates of incorporation of label were 145 cpm/mg/min for the “old” animals, and 320 cpm/mg/min for the young animal. No difference in either amino acid pool size or leakage of label through the mitochondrial membrane was detected in the two age groups. Young rats were treated in vivo with cycloheximide (10 mg/kg) followed by isolation and incubation of their mitochondria in vitro two hours later. There was a two-fold increase in incorporation of leucine into mitochondrial proteins. In contrast, mitochondria isolated from old rats showed a markedly blunted response to cycloheximide pre-treatment. When mitochondria isolated from young and old rats were exposed to inhibitors of mitochondrial protein synthesis, --dipyridyl (2 × 10⁻⁴M) and ethanol (0.15M), the old mitochondria showed greater susceptibility to inhibition. These results suggest that the control of the biosynthesis of mitochondrial proteins is altered in the old animals.     

The pulmonary effects of buthionine sulfoximine treatment and glutathione depletion in rats

Buthionine sulfoximine (BSO), an inhibitor of de novo synthesis of glutathione (GSH), was used to deplete rats of GSH and determine the effect of treatment on antioxidant enzyme responses, lung injury, and the susceptibility to concurrent sublethal or lethal hyperoxia. In a preliminary experiment, total lung nonprotein sulfhydryl (NPSH) and GSH levels were measured at various times after single doses of BSO. The lowest concentrations were observed at 12 to 18 h. These experiments were used to establish a repeated dosing protocol for more prolonged GSH depletion. The lungs of rats treated with BSO for 4 days demonstrated markedly decreased GSH and NPSH levels (10 to 40% of control values) and glutathione peroxidase activity (45 to 60% of control values). Superoxide dismutase activities were elevated, glutathione reductase activity was slightly elevated, and catalase activity was unchanged. These changes were dose-responsive. The lungs of treated rats were grossly and microscopically normal. BSO treatment of additional rats did not increase susceptibility to lethal hyperoxia (greater than 98% oxygen). Combined treatment of rats with both BSO and sublethal hyperoxia (80% oxygen) for 4 days did not alter the biochemical responses demonstrated by rats treated solely with BSO. The marked increase in catalase activity obtained after hyperoxia alone was not observed in rats treated with both hyperoxia and BSO. The lungs of saline- and BSO-treated rats exposed to sublethal hyperoxia demonstrated a patchy distribution of slight perivascular and peribronchiolar edema.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glutathione deficiency potentiates manganese-induced increases in compounds associated with high-energy phosphate degradation in discrete brain areas of young and aged rats

Aging is a factor known to increase neuronal vulnerability to oxidative stress, which is widely accepted as a mechanism of manganese-induced neuronal damage. We previously showed that subchronic exposure to manganese induced greater energy impairment (as revealed by increases in hypoxanthine, xanthine and uric acid levels) in the striatum and brainstem of aged rats vs young rats. This study shows that inhibition of glutathione (GSH) synthesis, by means of buthionine (SR) sulfoximine, decreased GSH levels and increased the ascorbic acid oxidation status in the striatum and limbic forebrain of both young and aged rats. In addition, inhibition of GSH synthesis greatly potentiated the manganese-induced increase in inosine, hypoxanthine, xanthine and uric acid levels in both regions of aged rats; moreover, inhibition of GSH synthesis significantly increased inosine, hypoxanthine, xanthine and uric acid levels in both regions of young rats, compared with the manganese-treated group. These results suggest that an impairment in the neuronal antioxidant system renders young rats susceptible to manganese-induced energetic impairment, and further support the hypothesis that an impairment in this system plays a permissive role in the increase of neuronal vulnerability that occurs with aging.     

Glutathione regulates activation-dependent DNA synthesis in highly purified normal human T lymphocytes stimulated via the CD2 and CD3 antigens.

Regulation of proliferation of normal human T lymphocytes (T cells) by glutathione (GSH) was explored with T-cell activation models that do not require accessory cell signals. L-Buthionine-(S,R)-sulfoximine (BSO), which inactivates gamma-glutamylcysteine synthetase and therefore inhibits GSH synthesis, inhibited proliferation elicited by monoclonal antibodies directed at cluster designation 2 (CD2) and CD3 antigens, or by sn-1,2-dioctanoylglycerol and ionomycin. L-Buthionine-(R)-sulfoximine, which does not inactivate gamma-glutamylcysteine synthetase, did not affect proliferation. BSO-induced inhibition of accessory cell-independent T-cell proliferation was not reversed by recombinant human interleukin 2, despite activation-dependent expression of interleukin 2 receptor alpha by T cells treated with BSO. However, BSO-associated inhibition of T-cell proliferation was reversed by GSH or GSH ester. These studies, which show that GSH can directly modulate proliferation of highly purified T cells, suggest that GSH is essential for steps close to or at DNA synthesis. The availability of methods for decreasing and for increasing GSH levels suggest therapies to produce (i) immunosuppression (of value in organ transplantation), and (ii) immunopotentiation (of potential value in treatment of immunodeficiency states such as AIDS).     

Vasomotor responses of coronary stenoses to acetylcholine and their relation to serum lipid levels in stable angina pectoris

The effects of acetylcholine administration on coronary stenoses in relation to serum lipids level were evaluated in 18 patients (15 men, 3 women) with coronary artery disease and stable angina. Intracoronary acetylcholine was infused in concentrations 10⁻⁷, 10^−6, 10⁻⁵ M, followed by intracoronary bolus administration of isosorbide dinitrate. Computerized angiography was used to assess the changes in the diameter of stenoses and of proximal and distal segments. During acetylcholine infusion, at concentrations between 10⁻⁷ to 10 ⁻⁵M, there was a significant (p <0.01) dose-dependent constriction of proximal and distal segments and of stenoses reversed by isosorbide dinitrate. There was no correlation between the serum total cholesterol level and the responses of proximal and distal segments to acetylcholine or nitrate. A correlation (p <0.05) was found between the serum total cholesterol level and the response of stenoses to acetylcholine, but there was no correlation with the response to isosorbide dinitrate. In conclusion, in patients with stable angina current serum total cholesterol level correlates with the vasomotor response of coronary stenoses to intracoronary acetylcholine. These findings are consistent with a direct effect of cholesterol, increasing basal coronary vasomotor tone and increasing the stimulated vasoconstrictor response of stenoses.     

Effects of insulin, dexamethasone and glucagon on the production of apolipoprotein A-I in cultured rat hepatocytes

Cultured rat hepatocytes were used to study the effects of hormones on the production of apo A-I. In addition, we compared these effects with the production of albumin. Hepatocytes were isolated from normal adult rat livers and cultured in MEM, as nearly confluent monolayers. In the absence of hormones, apo A-I and albumin accumulated in the culture medium almost linearly for periods up to 24 h. The rates of accumulation of apo A-1 and albumin in the medium were 22 ng/mg cell protein per h and 1.2 μg/mg cell protein per h, respectively. During the incubations the cellular contents of apo A-1 remained constant.

Insulin stimulated the production of albumin at concentrations over 10⁻¹⁰ M, but inhibited the production of apo A-I at concentrations over 10⁻⁸ M. Dexamethasone showed no significant effects on albumin production but stimulated apo A-1 production at concentrations over 10⁻⁶ M. Glucagon inhibited the production of albumin and apo A-I dose-dependently at concentrations over 10⁻¹⁰ M. Thus, the production of albumin and apo A-1 are presumably controlled by different regulatory mechanisms.     

The role of calcium in diuretic hormone action on locust Malpighian tubules

Fluid secretion by the Malpighian tubules (MTs) of Locusta is drastically reduced in the absence of extracellular calcium. Verapamil (10⁻⁴ M) inhibits basal secretion, whereas the ionophore A23187 (10⁻⁵ M) elevates the secretory rate. Cyclic guanosine monophosphate (cGMP) stimulates fluid secretion at a concentration of 10⁻³ M. A factor extractable in methanol from the storage lobes of the corpora cardiaca stimulates increased guanylate cyclase activity in MTs, resulting in a 10-fold elevation in intracellular cGMP levels. Attempts to separate the factor stimulating guanylate cyclase by high-performance size-exclusion chromatography proved unsuccessful. Neither 5-hydroxytryptamine (5-HT) (10⁻⁴ M) nor A23187 (10⁻⁵ M) are able to elevate intracellular cGMP levels. Elevations of both intracellular cAMP and cGMP levels in response to diuretic hormone (DH) are potentiated in the absence of extracellular calcium. Consistent with these elevations are increases in the rates of fluid secretion by tubules deprived of extracellular calcium. It is concluded that, although calcium has an important role in the regulation of fluid secretion, its role in the mechanism of hormone-stimulated secretion may be modulatory rather than regulatory.     

Ramipril prevents impaired endothelium-dependent relaxation in arteries from rabbits fed an atherogenic diet

Endothelium-dependent relaxation in arteries is attenuated in clinical and experimental atherosclerosis. This study investigates the endothelial preservation properties of the angiotensin converting enzyme inhibitor, ramipril, by assessing its ability to restore endothelium-dependent responsiveness in blood vessels from rabbits fed an atherogenic diet (0.25% cholesterol; 3% coconut oil; 12 weeks). Seven rabbits fed the atherogenic diet received ramipril (3 mg/kg mixed into their food daily) and 6 rabbits were maintained on the atherogenic diet alone. Control rabbits (n = 6) were fed a standard diet and did not receive ramipril. At the end of the dietary intervention, the rabbits were killed and blood was collected for measurement of the lipid profile. The thoracic aorta was isolated and half was frozen for pathologic review while the other half was cut into rings and placed in a muscle bath for measurement of isometric force development. Dose response curves to phenylephrine (10⁻⁹ to 10⁻⁵ M) and angiotensin II (10⁻¹⁰ to 3 × 10⁻⁷ M) were completed. There was a minimal decrease in responsiveness to phenylephrine in vessels from rabbits eating the atherogenic diet compared with controls and no significant differences in the response to angiotensin II for any of the vessels. Following contraction by phenylephrine, acetylcholine (10⁻⁹ to 10⁻⁵ M) and nitroglycerin (10⁻¹⁰ to 10⁻⁵ M) dose response curves were completed. Relaxation to acetylcholine in aortic rings from control rabbits was observed, although in arteries from atherogenic rabbits relaxation was attenuated. This effect was prevented in the atherogenic rabbits fed ramipril. Responsiveness to the endothelium-independent vasodilator, nitroglycerin, was similar in arteries from the three rabbit groups. Total cholesterol levels were elevated in the rabbits fed the atherogenic diet and in the rabbits fed the atherogenic diet containing ramipril. High density lipoprotein (HDL) cholesterol levels were not affected by the atherogenic diet alone, but when ramipril was added, there was a significant increase in HDL cholesterol levels. The percentage of aortic surface covered with lipid streaks was not significantly different in the three rabbit groups. We conclude that ramipril prevents endothelial dysfunction in arteries from rabbits fed an atherogenic diet. Mechanistically, this effect of ramipril on the endothelium must occur prior to the release of nitric oxide as no alteration in the dose response curve to nitroglycerine could be identified. Additionally, this improvement in endothelial function in rabbits supplemented with ramipril appears to be independent of morphologic changes in response to the atherogenic diet.     

The modulation of intracellular glutathione level modulates the mitochondrial response in proliferating rat splenocytes

We have investigated the effect of intracellular reduced glutathione (GSH) levels on the mitochondrial parameters of proliferating rat splenocytes. The intracellular GSH content of the cells was altered by continuous culture with buthionine-S, R-sulfoximine (BSO), a specific inhibitor of GSH synthesis. BSO decreased the GSH levels, inhibited DNA synthesis and caused depolarization of mitochondria in 52% of cells stimulated to proliferate for 72 h. These data support the proposition that GSH influences the lymphocyte proliferation at more than one site, one of which is the energy producing machinery.     

Role of steroid hormones and prostaglandins in the regulation of DNA synthesis by decidual cells in culture

The effect of oestrogen and progesterone on prostaglandin synthesis and on DNA synthesis by rat decidual cells was studied in a culture system. The cells were explanted from deciduoma either during the proliferation phase (namely on the 5th day of leukocytic smear, Day L₅: “L₅ cells”) or during the maintenance phase (“L₈ cells”) and examined on the second day of culture.

Oestradiol-17β (7 × 10⁻¹¹ M) and progesterone (6 × 10⁻⁸ M) significantly inhibited accumulation of PGE by cells explanted on Day L₅: L₈-cell cultures showed no significant response to oestradiol and the progesterone effect was markedly reduced.

Progesterone stimulated [³H]thymidine incorporation into cells explanted on Day L₅, but had no effect on L₈-cell cultures. Other inhibitors of PG synthesis, namely cortisol, flufenamic acid and indomethacin, also had a stimulatory effect on DNA synthesis by L₅ cells.

PGE₂ (5–10 μg/ml) inhibited DNA synthesis in control, indomethacin-treated and progesterone-treated L₅-cell cultures, suggesting that the progesterone-induced stimulation of DNA synthesis may in part be due to its inhibitory effect on PGE accumulation by decidual cells. The possibility is discussed that during the proliferation phase of decidual development in vivo, the rate of DNA synthesis may be influenced by steroid-induced changes in PGE content of the tissue.     

Biochemical Changes in the Platelet Energy Transferring System during Concomitant Action of Cephalin and Serotonin

S ummary . The paper concerns the investigations of the changes in the concentrations of endogenous nicotinamide adenine nucleotides (NAD⁺, NADH, NADP⁺ and NADPH) and reduced glutathione (GSH) during the incubation of canine blood platelets with cephalin and/or serotonin. Activity of NADH-dependent glutathione reductase in this instance was also determined. These investigations have revealed the following findings: (1) platelets maintained constant levels of nicotinamide adenine nucleotides and GSH during incubation in Hanks' solution; (2) 5-HT induced a marked immediate increase in the amounts of NAD⁺, NADH and GSH and a moderate reduction in the amount of NADPH; no significant change was seen in the amount of NADP⁺ or in the activity of NADH-dependent glutathione reductase; (3) cephalin had similar effects on NAD⁺, NADH and GSH, but to a lesser extent; in addition, it induced a significant decrease in the amounts of NADP⁺ and NADPH and a marked activation of NADH-dependent glutathione reductase; (4) cephalin in addition to 5-HT amplified these modifications, except for GSH increase (despite an important cephalin-induced activation of NADH-dependent glutathione reductase) and produced a marked fall of NADP⁺ and NADPH. These findings suggest that: (a) platelet nicotinamide adenine nucleotides and GSH exhibit a high sensitivity to these different substances (a phosphatide and an amine) with implications for platelet function and aggregation; (b) cephalin and 5-HT, despite their different chemical nature, act somewhat similarly on these compounds.     

Binding sites for peptide-histidine-isoleucine (PHI) on rat insulinoma-derived RINm5F cells

Specific binding sites for ¹²⁵I-labelled rat peptide-histidine-isoleucine (PHI) were identified on rat insulinoma-derived RINm5F cells. The concentrations of peptides producing half-maximal displacement of label were rat PHI, 0.36 ± 0.14 nM, vasoactive intestinal polypeptide (VIP), 0.38 ± 0.13 nM and secretin, approximately 0.2 μM. Glucagon and glucagon-like peptide-1(7–36)amide were without effect on binding. PHI and VIP produced dose-dependent increases in cAMP production in the cells that were significantly (P < 0.05) above unstimulated rates for ligand concentrations between 10⁻⁸ and 10 ⁻⁶ M. Both PHI and VIP produced a small but significant (P < 0.05) enhancement in the rate of release of immunoreactive insulin from the cells but the effect was not dose dependent.     

Adenylate cyclase of catfish hepatocyte membranes: basal properties and sensitivity to catecholamines and glucagon

Some characteristics of adenylate cyclase of catfish (Ictalurus melas) liver membranes were studied, and the effects of catecholamines and of glucagon were tested. The enzyme has an optimum temperature of 40 °C, and a K_m for ATP of 0.16 mM at 30 °C, and requires Mg²⁺ for its activity. The enzyme activity is inhibited with a Ca²⁺ concentration higher than 5 × 10⁻⁵ M, and enhanced with F⁻ higher than 10⁻⁴ M. The response of adenylate cyclase to GTP is biphasic, with a maximum of activity at 10⁻⁵ M GTP. Catecholamines (epinephrine, norepinephrine, isoproterenol, phenylephrine) enhance cyclase activity. Propranolol inhibits the increase in enzyme activity induced by catecholamines, whereas phentolamine is ineffective. This indicates that catecholamines (phenylephrine included) activate adenylate cyclase through a β-adrenergic mechanism. Glucagon (mammalian) has a smaller effect than epinephrine in increasing the enzyme activity of catfish hepatocyte membranes. This fact is the opposite of that observed for the cyclase activity of rat liver membranes.     

Age-related changes in the rat brain mitochondrial antioxidative enzyme ratios: Modulation by melatonin

Oxidative stress is an important factor for aging. The antioxidative enzymes glutathione peroxidase (GPx), glutathione reductase (GRd) and superoxide dismutase (SOD) play a crucial role protecting the organism against the age-dependent oxidative stress. Glutathione (GSH) is present in nearly all living cells. GSH is one of the main antioxidants in the cell and it serves several physiological functions. Our purpose was to evaluate the age-related changes in mitochondrial GPx, GRd and SOD activities, and mitochondrial GSH pool in the brains of young (3months) and aged rats (24months). We also investigated whether melatonin administration influences these brain mitochondrial enzyme activities and GSH levels in young and aged rats. The results showed that GPx activity increased with age, whereas melatonin treatment decreased GPx activity in the aged rats at levels similar to those in young and young+melatonin groups. The activities of GRd and SOD, however, did not change with age. But, melatonin treatment increased SOD activity in the aged rats. GSH levels, which also increased with age, were not modified by melatonin treatment. The reduction in the SOD/GPx and GR/GPx ratios with age was prevented by melatonin administration. Together, our results suggest that the age-related oxidative stress in rat brain mitochondria is more apparent when the antioxidant enzyme ratios are analyzed instead of their absolute values. The antioxidative effects of melatonin were also supported by the recovery of the enzyme ratios during aging.     

Redox control of K+ channel remodeling in rat ventricle

Electrical remodeling of the diseased heart contributes to contractile dysfunction and arrhythmias, and is characterized by down-regulation of K(+) channels that control action potential morphology. We have recently shown that remodeling of K(+) channels underlying the transient outward current (I(to)) involves a shift in cell redox balance that is reflected by a depletion of the endogenous redox buffer, glutathione (GSH). This study used a pharmacological model to further examine the role of redox-mediated mechanisms in regulating cardiac K(+) currents. Inhibition of major redox pathways was elicited in normal rats by daily injections of 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of thioredoxin and glutathione reductases, and buthionine sulfoximine (BSO), a blocker of GSH synthesis. Fluorescence microscopy studies showed that [GSH] in isolated ventricular myocytes was decreased ~50% from control after 3 days of BCNU/BSO treatment (P<0.05), consistent with a shift in cell redox state. In voltage-clamp experiments, maximum I(to) density was decreased 33% from control in left ventricular myocytes from BCNU/BSO-treated rats (P<0.05), while the inward rectifier and steady state outward currents were not significantly altered. Decreased I(to) density correlated with significant decreases in Kv4.2 mRNA and proteins levels of Kv4.2 and Kv1.4. Down-regulation of I(to) in myocytes from BCNU/BSO rats was reversed in vitro by exogenous GSH or N-acetylcysteine, a GSH precursor and antioxidant. I(to) density and [GSH] were also up-regulated by receptor tyrosine kinase activation with insulin or a tyrosine phosphatase inhibitor. The effect of these activators on I(to) was blocked by inhibitors of PI 3-kinase, MEK and p38 MAP kinases. These data suggest that expression of cardiac I(to) channels is regulated by endogenous oxidoreductase systems and that receptor tyrosine kinase signaling functionally impacts K(+) channel remodeling through its control of cell redox state.     

ACAT inhibitor pactimibe sulfate (CS-505) reduces and stabilizes atherosclerotic lesions by cholesterol-lowering and direct effects in apolipoprotein E-deficient mice

The objective of the present study was to determine whether a novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, pactimibe sulfate (CS-505), could reduce atherosclerotic lesions beyond and independent of the reduction achieved by cholesterol lowering alone from two different types of lesions. (1) Early lesion model. Twelve-week-old apolipoprotein E (apoE)^−/− mice were treated with 0.03 or 0.1% (w/w) CS-505, 0.1 or 0.3% avasimibe (CI-1011), or 3% cholestyramine for 12 weeks. Each treatment significantly reduced plasma cholesterol by a similar degree (43–48%). The antiatherosclerotic activity of 0.1% CS-505, however, was more efficacious than the effects of the other treatments (90% versus 40–50%). (2) Advanced lesion model. Twenty-four-week-old apoE^−/− mice were treated with 0.03 or 0.1% CS-505 or 0.1% CI-1011 for 12 weeks. CS-505 at 0.1% revealed enhanced lesion reduction compared with 0.1% CI-1011 (77% versus 54%), whereas the plasma cholesterol-lowering effect of 0.1% CS-505 was almost the same as that of 0.1% CI-1011. Furthermore, immunohistochemical analysis demonstrated that CS-505 significantly reduced the number of macrophages and expression of matrix metalloproteinase (MMP)-2, MMP-9, and MMP-13. These data indicate that CS-505 can reduce and stabilize atherosclerotic lesions. This antiatherosclerotic activity is exerted via both cholesterol lowering and direct ACAT inhibition in plaque macrophages.