Antiplatelet activity of carnosol is mediated by the inhibition of TXA2 receptor and cytosolic calcium mobilization

Carnosol, a naturally occurring phenolic diterpene found in rosemary, has been reported to exhibit antioxidant, anticancer and hepatoprotective effects. In the present study, the antiplatelet activity of carnosol was investigated. Carnosol concentration-dependently inhibited washed rabbit platelet aggregation induced by collagen and arachidonic acid (AA), with IC(50) values of 5.5+/-0.3 and 42.5+/-0.9 microM, respectively, while failed to inhibit that induced by, ADP and thrombin. Consist with inhibition of collagen-induced platelet aggregation, carnosol revealed blocking of collagen-mediated cytosolic calcium mobilization, serotonin secretion and arachidonic acid liberation. However, contrary to the inhibition of AA-induced platelet aggregation, carnosol has no effect on AA-mediated TXA(2) and PGD(2) formation, indicating carnosol may directly inhibit TXA(2) receptor, which was supported by the finding that carnosol potently inhibited U46619 (a TXA(2) mimic)-induced platelet aggregation, with an IC(50) value of 22.0+/-2.5 microM. In addition, the U46619-induced concentration-response curve was downward shifted by the application of carnosol at concentrations of 22 and 50 microM, indicating a typical non-competitive antagonism on TXA(2) receptor. Taken together, these results suggest that antiplatelet activity of carnosol may be mediated by the inhibition of TXA(2) receptor and cytosolic calcium mobilization, and carnosol has a potential to be developed as a novel-antiplatelet agent.     

Cholestatic effect of epigallocatechin gallate in rats is mediated via decreased expression of Mrp2

Epigallocatechin gallate (EGCG) has been shown to be protective in various experimental models of liver injury, although opposite effects have also been reported. Since its effect on biliary physiology has not been thoroughly investigated, the present study evaluated effect of EGCG on bile flow and bile acid homeostasis in rats. Compared to controls, EGCG treatment decreased bile flow by 23%. Hepatic paracellular permeability and biliary bile acid excretion were not altered by EGCG administration, but biliary glutathione excretion was reduced by 70%. Accordingly, the main glutathione transporter on the hepatocyte canalicular membrane, multidrug resistance-associated protein 2 (Mrp2), was significantly decreased at the protein level. EGCG administration also doubled plasma bile acid levels compared to controls. While protein levels of the main hepatic bile acid transporters were unchanged, the rate-limiting enzyme in the bile acid synthesis, Cyp7a1, was significantly increased by EGCG. Enhanced bile acid synthesis in these animals was also confirmed by a 2-fold increase in plasma marker 7α-hydroxy-4-cholesten-3-one. In contrast, EGCG markedly downregulated major bile acid transporters (Asbt and Ostα) and regulatory molecules (Shp and Fgf15) in the ileum. When EGCG was coadministered with ethinylestradiol, a potent cholestatic agent, it did not show any additional effect on the induced cholestasis. This study shows ability of EGCG to raise plasma bile acid concentrations, mainly through Cyp7a1 upregulation, and to decrease bile production through reduction in Mrp2-mediated bile acid-independent bile flow. In conclusion, our data demonstrate that under certain conditions EGCG may induce cholestasis.     

Antiplatelet activity of green tea catechins is mediated by inhibition of cytoplasmic calcium increase.

We have previously reported that green tea catechins (GTC) display a potent antithrombotic activity, which might be due to antiplatelet rather than anticoagulation effects. In the current study, we investigated the antiplatelet mechanism of GTC. We tested the effects of GTC on the aggregation of human platelets and on the binding of fluorescein isothiocyanate-conjugated fibrinogen to human platelet glycoprotein (GP) IIb/IIIa. GTC inhibited the collagen-, thrombin-, adenosine diphosphate (ADP)-, and calcium ionophore A23187-induced aggregation of washed human platelets, with 50% inhibitory concentration values of 0.64, 0.52, 0.63, and 0.45 mg/ml, respectively. GTC significantly inhibited fibrinogen binding to human platelet surface GPIIb/IIIa complex but failed to inhibit binding to purified GPIIb/IIIa complex. These results indicate that the antiplatelet activity of GTC may be due to inhibition of an intracellular pathway preceding GPIIb/IIIa complex exposure. We also investigated the effects of GTC on intracellular calcium levels, which are critical in determining the activation status of platelets and on induction of platelet aggregation by thapsigargin, which is a selective inhibitor of the Ca(2+)-ATPase pump. Pretreatment of human platelets with GTC significantly inhibited the rise in intracellular Ca(2+) concentration induced by thrombin treatment, and GTC significantly inhibited the thapsigargin-induced platelet aggregation. We also examined the effect of GTC on the second messenger, inositol 1,4,5-triphosphate (IP(3)). GTC significantly inhibited the phosphoinositide breakdown induced by thrombin. Taken together, these observations suggest that the antiplatelet activity of GTC is be mediated by inhibition of cytoplasmic calcium increase, which leads to the inhibition of fibrinogen-GPIIb/IIIa binding via the activation of Ca(2+)-ATPase and inhibition of IP(3) formation.     

Antiplatelet activity of geranylgeraniol isolated from Pterodon pubescens fruit oil is mediated by inhibition of cyclooxygenase-1

Geranylgeraniol is a natural isoprenoid with anti-inflammatory properties extracted from the Pterodon pubescens Benth. fruit oil (PpO). In this work, the antiplatelet effect of both PpO and geranylgeraniol is investigated. ADP-, thrombin- and arachidonic acid (AA)-induced aggregation in human and rabbit platelets showed a prime involvement of PpO and geranylgeraniol in the arachidonic acid cascade. The lack of any significant inhibition of platelet aggregation induced by U-46 619 and thrombin, associated with PpO and geranylgeraniol suppression of prostaglandin E(2) and thromboxane A(2) formation demonstrate, for the first time, the involvement of geranylgeraniol in the AA metabolisation by inhibiting the cyclooxygenase enzyme.     

表没食子儿茶素没食子酸酯促进2型糖尿病伤口愈合的实验研究

目的系统评价表没食子儿茶素没食子酸酯( EGCG)对于 2型糖尿病 db/db小鼠伤口愈合的治疗效果。方法 3月龄雄性无特定病原体( SPF)级 db/db小鼠共 32只以及同背景的野生型雄性小鼠共 16只用于本实验,共等分为野生小鼠组( Control)、 db/db小鼠组( db/db)和 db/db小鼠 EGCG治疗组( db/db+EGCG),每组 16只。所有小鼠均构建背部圆形创口(直径 1 cm),db/ db+EGCG组小鼠在伤口模型构建后立即施以每日的 EGCG(10 mg/kg)灌胃处理。术后第 5、12、19天处死每组 4只小鼠,分析伤口愈合速率、抗张强度、局部皮肤血流速率、细胞因子表达情况。结果 db/db+EGCG组小鼠在伤口模型建立的第 5、12、19天伤口愈合率分别为( 19.4±3.2)%、(55.2±4.8)%和( 79.7±5.2)%,db/db组小鼠各时间点伤口愈合率分别为( 10.1±2.0)%、(39.1±5.2)%和( 59.2±6.2)%,db/db+EGCG组均显著高于 db/db组( P＜0.05)同时 EGCG也显著降低了 db/db小鼠伤口愈合时间( P＜0.05);并且 EGCG在术后第 5、12、19天均显著增加了 db/db小鼠伤织的生物力学抗张强度( P＜0.05)改善了伤口位置局部血流速率( P＜0.05)并显著抑制了炎性因子白细胞介素 1β(IL-1β)、白细胞介素 6(IL-6)和肿瘤坏死α(TNF-α)表达(P＜0.05),促进了血皮生长因子( VEGF)表达( P＜0.05)。结论 EGCG能够显著改善 2型糖尿病 db/db小鼠的伤口愈合口组,因子,管内,能力,具有可观的临床应用前景。     

Morphine inhibition of lymphocyte activity is mediated by an opioid dependent mechanism

The effects of acutely-administered morphine on mitogen stimulated lymphocyte proliferation and natural killer cell cytolytic activity were investigated. Two hours after a subcutaneous injection of morphine (25 mg/kg), blood lymphocyte proliferation was found to be 70% depressed, compared to saline-injected controls. This effect was partially antagonized in animals pretreated with naltrexone (10 mg/kg) and was present only in blood lymphocytes, since proliferative responses of splenic lymphocytes were not significantly altered. The administration of morphine, however, did result in a 30-40% inhibition of cytolytic activity of natural killer cells, which was completely antagonized in naltrexone-pretreated animals. Naltrexone alone was found to have no effect on either proliferation of blood and splenic lymphocytes or the cytolytic activity of splenic lymphocytes. Although naltrexone had no effect on the activity of lymphocytes, animals treated with either naltrexone or morphine alone, or their combination, had 4- to 8-fold increases in corticosterone in plasma. These results demonstrate that the effect of morphine on immune cells was dependent on the tissue source of lymphocytes. Furthermore, the suppression of blood lymphocyte proliferation and splenic cytolytic activity of natural killer cells by morphine was opiate receptor-mediated, as indicated by the reversibility by naltrexone of the observed effects of morphine. Finally, the accompanying increase in circulating levels of corticosterone most likely did not contribute to these effects.     

The antiplatelet activity of Geiji-Bokryung-Hwan,Korean traditional formulation,is mediated through inhibition of phospholipase C and inhibition of TxB(2) synthetase activity

Geiji-Bokryung-Hwan (GBH), consisting of herbes of Cinnamomi ramulus (Geiji), Poria cocos (Bokryun), Mountan cortex radicis (Mokdanpi), Paeoniae radix (Jakyak), and Persicae semen (Doin), on antiplatelet activity in human platelet suspensions was studied. The mechanism involved in the antiplatelet activity of GBH in human platelet suspensions was investigated. GBH did not significantly affect the thromboxane synthetase activity of aspirin-treated platelet microsomes and GBH (15 and 30 microg/ml) significantly inhibited [3H]arachidonic acid released in collagen-activated platelets but not in unactivated-platelets. Nitric oxide (NO) production in human platelets was measured by a chemiluminesence detection method in this study. GBH did not significantly affect nitrate production in collagen (10 microg/ml)-induced human platelet aggregation. Various concentrations of GBH (0, 5, 10, 15, and 30 microg/ml) dose-dependently inhibited [3H]inositol monophosphate formation stimulated by collagen (10 microg/ml) in [3H]myoinositol-loaded platelets at different incubation times (1, 2, 3, and 5 min). These results indicated that the antiplatelet activity of GBH may possibly be due to the inhibition of phospholipase C (PLC) activity, leading to reduce phosphoinositide breakdown, followed by the inhibition of thromboxane A(2) formation, and then inhibition of [Ca(2+)](i) mobilization of platelet aggregation stimulated by agonists. In conclusion, GBH suppressed PLC in a dose-dependent manner, and may have pharmaceutical applications. These data suggest that GBH extracts merit investigation as a potential anti-atherosclerogenic agent in humans.     

Tanshinones inhibit mast cell degranulation by interfering with IgE receptor-mediated tyrosine phosphorylation of PLCgamma2 and MAPK

Recently we have isolated four active components from Tanshen (the root of Salvia miltiorrhiza Bunge, Labiatae) responsible for the anti-allergic activities. In this study, the molecular mechanism of action of tanshinones for the inhibition of mast cell degranulation was investigated by testing their effects on the signaling components of the high affinity IgE receptor FcepsilonRI. Activation of FcepsilonRI produced immediate tyrosine phosphorylation of Syk, mitogen-activated protein kinase extracellular signal-regulated kinase, ERK1/ERK2 (p44, p42), and phospholipase Cgamma2 (PLCgamma2). 5,16-Dihydrotanshinone-I possessed the strongest inhibitory effects on mast cell degranulation and markedly reduced FcepsilonRI-mediated tyrosine phosphorylation of ERK and PLCgamma2. This suggests that tanshinones possibly exert their anti-allergic activities by affecting FcepsilonRI-mediated tyrosine phosphorylation of ERK and PLCgamma2. Abbreviations. FcepsilonRI:high affinity IgE receptor ERK:extracellular signal regulated kinase PLC: phospholipase C     

Antiplatelet effect of phloroglucinol is related to inhibition of cyclooxygenase, reactive oxygen species, ERK/p38 signaling and thromboxane A(2) production

Platelet dysfunction is a major risk factor of cardiovascular diseases such as atherosclerosis, stroke and myocardial infarction. Many antiplatelet agents are used for prevention and treatment of these diseases. In this study, phloroglucinol (2.5-25 μM) suppressed AA-induced platelet aggregation and thromboxane B₂ (TXB₂) production, but not U46619-induced platelet aggregation. Phloroglucinol (100-250 μM) showed little cytotoxicity to platelets. Phloroglucinol inhibited the COX-1 and COX-2 activities by 45-74% and 49-72% respectively at concentrations of 10-50 μM. At concentrations of 1 and 5 μM, phloroglucinol attenuated the AA-induced ROS production in platelets by 30% and 53%, with an IC₅₀ of 13.8 μM. Phloroglucinol also inhibited the PMA-stimulated ROS production in PMN. Preincubation of platelets by phloroglucinol (10-25 μM) markedly attenuated the AA-induced ERK and p38 phosphorylation. Intravenous administration of phloroglucinol (2.5 and 5 μmol/mouse) suppressed the ex vivo AA-induced platelet aggregation by 57-71%. Phloroglucinol administration also elevated the mice tail bleeding time. Moreover, phloroglucinol inhibited the IL-1β-induced PGE₂ production in pulp fibroblasts. These results indicate that antiplatelet and anti-inflammatory effects of phloroglucinol are related to inhibition of COX, ROS and TXA2 production as well as ERK/p38 phosphorylation in platelets. Phloroglucinol further suppress PMA-induced ROS production in PMN. The antiplatelet effect of phloroglucinol was confirmed by ex vivo study. Clinically, the consumption of phloroglucinol-containing food/natural products as nutritional supplement may be helpful to cardiovascular health. Phloroglucinol has potential pharmacological use.     

Inhibition of epigallocatechin gallate on orthotopic colon cancer by upregulating the Nrf2-UGT1A signal pathway in nude mice

Epigallocatechin gallate (EGCG), a key active ingredient in green tea, has many anti-carcinogenic activities. The aim of the present study was to investigate whether EGCG could prevent the occurrence or metastases of orthotopic colon cancer and probe the underlined mechanisms. We observed the inhibition of EGCG on growth and metastases of colon tumor implanted orthotopically in the cecum of nude mice. Immunohistochemistry and Western-blotting analysis were used to detect NF-E2-related factor 2 (Nrf2) protein expressions. RT-PCR was also applied to detect the mRNA levels of Nrf2, uridine 5'-diphosphate-glucuronosyltransferase (UGT) 1A, UGT1A8 and UGT1A10 in colon tumors. As a result, the inhibition rates on tumor growth in the 3 EGCG groups were significantly different (all p < 0.001) compared with the control group. In addition, different doses of EGCG were able to inhibit liver and pulmonary metastases to varying degrees. The protein level of Nrf2 and the mRNA levels of Nrf2, UGT1A, UGT1A8 and UGT1A10 significantly increased in EGCG-treated mice in comparison with the control group (all p < 0.01). The results demonstrated that EGCG has a preventive effect on the growth and liver and pulmonary metastases of orthotopic colon cancer in nude mice, and this anticancer effect could be partly caused by activating the Nrf2-UGT1A signal pathway.     

TASK1 (K(2P)3.1) K(+) channel inhibition by endothelin-1 is mediated through Rho kinase-dependent phosphorylation

BACKGROUND AND PURPOSE

TASK1 (K_2P3.1) two-pore-domain K⁺ channels contribute substantially to the resting membrane potential in human pulmonary artery smooth muscle cells (hPASMC), modulating vascular tone and diameter. The endothelin-1 (ET-1) pathway mediates vasoconstriction and is an established target of pulmonary arterial hypertension (PAH) therapy. ET-1-mediated inhibition of TASK1 currents in hPASMC is implicated in the pathophysiology of PAH. This study was designed to elucidate molecular mechanisms underlying inhibition of TASK1 channels by ET-1.

EXPERIMENTAL APPROACH

Two-electrode voltage clamp and whole-cell patch clamp electrophysiology was used to record TASK1 currents from hPASMC and Xenopus oocytes.

KEY RESULTS

ET-1 inhibited TASK1-mediated I_KN currents in hPASMC, an effect attenuated by Rho kinase inhibition with Y-27632. In Xenopus oocytes, TASK1 current reduction by ET-1 was mediated by endothelin receptors ET_A (IC₅₀= 0.08 nM) and ET_B (IC₅₀= 0.23 nM) via Rho kinase signalling. TASK1 channels contain two putative Rho kinase phosphorylation sites, Ser³³⁶ and Ser³⁹³. Mutation of Ser³⁹³ rendered TASK1 channels insensitive to ET_A- or ET_B-mediated current inhibition. In contrast, removal of Ser³³⁶ selectively attenuated ET_A-dependent TASK1 regulation without affecting the ET_B pathway.

CONCLUSIONS AND IMPLICATIONS

ET-1 regulated vascular TASK1 currents through ET_A and ET_B receptors mediated by downstream activation of Rho kinase and direct channel phosphorylation. The Rho kinase pathway in PASMC may provide a more specific therapeutic target in pulmonary arterial hypertension treatment.     

The antiplatelet activity of PMC, a potent alpha-tocopherol analogue, is mediated through inhibition of cyclo-oxygenase.

PMC, a potent alpha-tocopherol derivative, dose-dependently (5-25 microM) inhibited the ATP-release reaction and platelet aggregation in washed human platelets stimulated by agonists (collagen and ADP). PMC also dose-dependently inhibited the intracellular Ca2+ mobilization, whereas it did not inhibit phosphoinositide breakdown in human platelets stimulated by collagen. PMC (10 and 25 microM) significantly inhibited collagen-stimulated thromboxane A2 (TxA2) formation in human platelets. On the other hand, PMC (25 and 100 microM) did not increase the formation of cyclic AMP or cyclic GMP in platelets. Moreover, PMC (25, 100, and 200 microM) did not affect the thromboxane synthetase activity of aspirin-treated platelet microsomes. PMC (10 and 25 microM) markedly inhibited the exogenous arachidonic acid (100 microM)-induced prostaglandin E2 (PGE2) formation in the presence of imidazole (600 microM) in washed human platelets, indicating that PMC inhibits cyclo-oxygenase activity. We conclude that PMC may exert its anti-platelet aggregation activity by inhibiting cyclooxygenase activity, which leads to reduced prostaglandin formation; this, in turn, is followed by a reduction of TxA2 formation, and finally inhibition of [Ca2+]i mobilization and ATP-release.     

Cardiotoxicity of sorafenib is mediated through elevation of ROS level and CaMKII activity and dysregulation of calcium homoeostasis

Sorafenib, a multi‐kinase inhibitor, is recommended as a new standard therapy for advanced hepatocellular carcinoma (HCC); however, it also exhibits severe cardiotoxicity and the toxicity mechanisms are not completely elucidated. Recent studies suggested that sorafenib‐enhanced ROS may partially contribute to its anti‐HCC effect, which implies that redox mechanism might also be involved in sorafenib's cardiotoxicity. In this study, we aimed to investigate if sorafenib is able to induce oxidative stress and how this may impair cellular functions in cardiomyocyte, ultimately accounting for its cardiotoxicity. Our results showed that in isolated rat hearts, sorafenib caused ventricular arrhythmias and left ventricular dysfunction, which were alleviated by the antioxidant N‐(2‐mercaptopropionyl)‐glycine (MPG). In isolated ventricular myocytes, sorafenib increased diastolic intracellular Ca²⁺ levels, decreased Ca transients and the occurrence of Ca²⁺ waves. These changes were eliminated by MPG, CaMKII inhibitor KN‐93 and the mitochondrial permeability transition pore (mPTP)inhibitor cyclosporin A (CsA). Moreover, the levels of oxidized and phosphorylated CaMKII were significantly increased. Sorafenib elevated ROS levels, which was reversed by CsA and MPG; additionally, sorafenib reduced the activity of mitochondrial complex III and augmented mitochondrial ROS production. In vivo rats treated with sorafenib exhibited a reduction of antioxidant defence and abnormal histological alterations including hypertrophy, increased fibrosis, disordered myofibrils and damaged mitochondria, which were protected by MPG. We conclude that sorafenib induces the disruption of Ca²⁺ homoeostasis and cardiac injury via enhanced ROS potentially through inhibiting mitochondrial complex III, the opening of mPTP and overactivating CaMKII. These results provide a potential strategy for preventing or reducing cardiotoxicity of sorafenib.     

Rapid inhibition of the contraction of rat tail artery by progesterone is mediated by inhibition of calcium currents

Progesterone induced rapid relaxation of KCl-contracted tail artery helical strips from rats. The effect was dose dependent, with an IC50 (inhibitory concentration which produces 50% of the maximal response) of 8.9 microM progesterone. The actions of progesterone were not blocked by bicuculline, indicating that in this tissue the non-genomic actions of progesterone were not mediated via a gamma-aminobutyric acid (GABA)-A receptor. Fura-2 was used to measure intracellular calcium levels ([Ca(2+)](i)) in isolated vascular smooth muscle cells (VSMC). Incubation of cultured VSMC for 15 min with progesterone (10 microM) resulted in an inhibition of the KCl-induced [Ca(2+)](i )increase. The whole-cell patch-clamp technique was used to examine Ca(2+)-channel currents in the membrane of isolated VSMC. Progesterone suppressed the L-type Ca(2+)-channel currents in cells held at a potential of -40 mV. The effects of progesterone were quickly reversed by washout in all three experimental protocols suggesting that these effects on vascular tissues are non-genomic. The correlation of the effects on all these preparations, their time course and reversibility suggested that the rapid relaxation of the rat tail artery induced by progesterone is mediated at least in part by inhibition of L-type calcium channels, leading to inhibition of calcium responses in the VSMC of this tissue.     

Phosphatidate and monooleylphosphatidate inhibition of fibroblast adenylate cyclase is mediated by the inhibitory coupling protein, Ni

It has previously been shown that monooleylphosphatidate (MOPA) and phosphatidate inhibit cAMP accumulation in VA13 and WI-38 fibroblasts. In this study we investigated whether this inhibition might be due to a decrease in adenylate cyclase activity. Our results showed that both MOPA and phosphatidate inhibit prostaglandin E1-stimulated adenylate cyclase in WI-38 membranes in a concentration-dependent manner with half-maximal inhibitions at 0.1 and 0.5 microM, respectively, and maximal inhibitions of 35-55%. A 5 microM concentration of structurally similar lipids caused no significant inhibition. The inhibitory effects of MOPA and phosphatidate on adenylate cyclase were GTP dependent, greater at low concentrations of Mg2+, eliminated following treatment of cells with islet-activating protein, nonadditive with carbachol, and noncompetitive with prostaglandin E1. Collectively these data suggested that MOPA and phosphatidate inhibitions of cAMP accumulation were due at least in part to an Ni-mediated inhibition of adenylate cyclase. Furthermore, the inhibitions showed the same characteristics normally associated with hormonal inhibition of this enzyme.     

Trichinella spiralis infection is mediated by MCP-1 and MIP-2, while echinococcus granulosus is strongly mediated by MCP-1, but not MIP-2

The chemokine supergene family are small proteins (8-10 KD) inducible in a number of pathophysiological processes. C-X-C family members are specific largely on neutrophils; whereas C-C chemokines act primarily on monocytes, T-cells, basophils and eosinophils. A wide variety of cell types produce chemokines in response to stimuli, including: infections, mitogens and inflammatory cytokines. Here we found that parasitic diseases, such as Trichinella spiralis and Echinococcus granulosus produce, MCP-1 (beta-chemokine) and MIP-2 (alpha-chemokine), or MCP-1, respectively. The specificity of production of these chemokines in the two parasitic diseases may help to achieve therapeutic strategies in inhibiting inflammation.     

Study on the pharmacokinetics of deoxyschizandrin and schizandrin in combination with epigallocatechin gallate,a component of green tea,in rats

1.?Green tea is commonly used worldwide due to its potential positive health benefits. We have examined the effects of epigallocatechin gallate (EGCG), the most abundant catechin in green tea, on the pharmacokinetics of deoxyschizandrin (DSD) and schizandrin (SD), which are the representative lignans in popular traditional Chinese medicines Fructus schisandrae, in rats.

2.?The effects on the transport in Caco-2 cells and metabolism in human liver microsomes (HLMs) of DSD and SD by EGCG were determined to analyze their interactions thoroughly.

3.?In pharmacokinetic studies, rats were divided into four groups. Each group was orally treated with DSD alone (Group 1), DSD combined with EGCG (Group 2), SD alone (Group 3) and SD combined with EGCG (Group 4). The pharmacokinetic parameters of DSD and SD in rats were determined by UPLC-MS/MS.

4.?The in vivo results indicated that EGCG had no significant influence on the pharmacokinetic behaviors of DSD or SD in rats, which were in accordance with the in vitro transport and metabolism studies. However, there were marked differences between male and female rats among C_max, AUC_0–t, AUC_0–∞ of DSD and SD. This disparity suggested that gender differences might exist in the pharmacokinetic processes of DSD or SD in rats.     

Antiatherogenic effect of quercetin is mediated by proteasome inhibition in the aorta and circulating leukocytes

Quercetin, a plant-derived flavonoid, has attracted considerable attention as promising compound for heart disease prevention and therapy. It has been linked to decreased mortality from heart disease and decreased incidence of stroke. Here, we report new data showing the angioprotective properties of quercetin mediated by its effect on proteasomal proteolysis. This study was designed to investigate the ability of quercetin to modulate proteasomal activity in a rabbit model of cholesterol-induced atherosclerosis. First, we show proteasomal trypsin-like (TL) activity increased up to 2.4-fold, chymotrypsin-like (CTL) activity increased by up to 43% and peptidyl-glutamyl peptide-hydrolyzing (PGPH) activity increased by up to 10% after 8 weeks of a cholesterol-rich diet. A single intravenous injection of the water-soluble form of quercetin (Corvitin) significantly decreased proteasomal TL activity 1.85-fold in monocytes, and decreased the CTL and PGPH activities more than 2-fold in polymorphonuclear leukocytes (PMNL) after 2 h. Prolonged administration (1 month) of Corvitin to animals following a cholesterol-rich diet significantly decreased all types of proteolytic proteasome activities both in tissues and in circulating leukocytes and was associated with the reduction of atherosclerotic lesion areas in the aorta. Additionally, the pharmacological form of quercetin (Quertin) was shown to have an antiatherogenic effect and an ability to inhibit proteasome activities.     

Torcetrapib-induced blood pressure elevation is independent of CETP inhibition and is accompanied by increased circulating levels of aldosterone

BACKGROUND AND PURPOSE: Inhibition of cholesteryl ester transfer protein (CETP) with torcetrapib in humans increases plasma high density lipoprotein (HDL) cholesterol levels but is associated with increased blood pressure. In a phase 3 clinical study, evaluating the effects of torcetrapib in atherosclerosis, there was an excess of deaths and adverse cardiovascular events in patients taking torcetrapib. The studies reported herein sought to evaluate off-target effects of torcetrapib. EXPERIMENTAL APPROACH: Cardiovascular effects of the CETP inhibitors torcetrapib and anacetrapib were evaluated in animal models. KEY RESULTS: Torcetrapib evoked an acute increase in blood pressure in all species evaluated whereas no increase was observed with anacetrapib. The pressor effect of torcetrapib was not diminished in the presence of adrenoceptor, angiotensin II or endothelin receptor antagonists. Torcetrapib did not have a contractile effect on vascular smooth muscle suggesting its effects in vivo are via the release of a secondary mediator. Treatment with torcetrapib was associated with an increase in plasma levels of aldosterone and corticosterone and, in vitro, was shown to release aldosterone from adrenocortical cells. Increased adrenal steroid levels were not observed with anacetrapib. Inhibition of adrenal steroid synthesis did not inhibit the pressor response to torcetrapib whereas adrenalectomy prevented the ability of torcetrapib to increase blood pressure in rats. CONCLUSIONS AND IMPLICATIONS: Torcetrapib evoked an acute increase in blood pressure and an acute increase in plasma adrenal steroids. The acute pressor response to torcetrapib was not mediated by adrenal steroids but was dependent on intact adrenal glands.     

Mn2+ sequestration by mitochondria and inhibition of oxidative phosphorylation.

Manganese is known to accumulate in mitochondria and in mitochondria-rich tissues in vivo. Although Ca2+ enhances mitochondrial Mn2+ uptake, ATP-bound Mn2+ is not sequestered by suspended rat brain mitochondria, and ATP binds Mn2+ even more tightly than it binds Mg2+. Physiological levels of the polyamine spermine enhanced 54 Mn2+ uptake at the low [Ca2+]s characteristic of unstimulated cells (approximately 100 nM). With succinate as substrate, Mn2+ inhibited oxygen consumption by suspensions of rat liver mitochondria after the addition of ADP but not after the addition of uncoupler. With glutamate/malate as substrate, Mn2+ inhibited ADP-stimulated respiration and also slightly inhibited uncoupler-stimulated respiration. State 4 (resting) respiration was unchanged in all cases, indicating that the inner membrane retained its impermeability to protons. These results suggest that Mn2+ was not oxidized and that it can interfere directly with oxidative phosphorylation, most likely by binding to the F1 ATPase. Mn2+ may also bind to the NADH dehydrogenase complex, but not strongly enough to affect electron transport in vivo. It is suggested that accumulation of manganese within the mitochondria of globus pallidus may help explain the distinctive pathology of manganism.