Evidence for a protective role of trimetazidine during cold ischemia: targeting inflammation and nephron mass

Ischemia-reperfusion injury (IRI) is associated with an increased risk of acute rejection, delayed graft function, or chronic graft dysfunction. Mitochondria plays a central role in this process. Using an autotransplant pig kidney model, changes in renal function and morphology were determined after different periods of cold ischemia in kidneys preserved in the University of Wisconsin solution (UW), high-Na(+) version of UW (HEH) or Celsior (CEL) a newly developed high-Na(+) solution, with or without trimetazidine (TMZ). Kidney function was better preserved in HEH after 24 hr and particularly 48- and 72-hr cold storage than in CEL and UW. TMZ improved the preservation quality when added to the different solutions tested, particularly after 48- and 72-hr cold storage. Interstitial fibrosis and tubular atrophy were reduced in HEH with TMZ. CD4(+) T-cell infiltration was also modulated by the preservation conditions. Peripheral-type benzodiazepine receptor (PBR) positive cells infiltration was also modulated by preservation conditions. TMZ was efficient to reduce IRI when added in the various preservation solutions. These results suggest that protection of the mitochondrial function should be a major target to limit IRI. In addition, this study outlines the role of CD4(+) T cells and PBR expression in inflammatory responses after IRI.     

Erythropoietin regulates apoptosis, inflammation and tissue remodelling via caspase-3 and IL-1β in isolated hemoperfused kidneys

Ischemia reperfusion injury associated with apoptosis and inflammation plays crucial roles in renal transplantation. Erythropoietin provides renoprotection, but its effects and mechanisms on kidney preservation are not fully defined. Porcine kidneys, subjected to 10 min warm ischemia, underwent 16 h cold storage followed by 2 h normothermic hemoperfusion with or without 5000 units/L erythropoietin. Apoptotic cells were increased in tubular lumens and interstitial areas by normothermic perfusion alone, but decreased in tubular areas by additional erythropoietin. Myeloperoxidase+ cells, free cells and cell debris in tubular lumens were gradually increased by cold storage, normothermic perfusion and erythropoietin in normothermic perfusion. Accordingly, caspase-3 activity as well as its active proteins was increased by normothermic perfusion and furthered by erythropoietin. In contrast, macrophage L1 protein positive cells in tubulointerstitial areas, cytokine interleukin (IL)-1β activation, tubular dilation and vacuolation were raised by normothermic perfusion, but all alleviated by erythropoietin, with higher urine output. The migration of myeloperoxidase+ cells with apoptotic features and apoptotic cells with polymorphous nuclei from tubulointerstitial areas into tubular lumens was widely displayed in the kidneys, especially those preserved by erythropoietin in normothermic perfusion. HSP70 protein was enhanced by normothermic perfusion regardless of erythropoietin. In addition, erythropoietin induced a dose-dependent increase in caspase-3 precursor in porcine proximal tubular cells (LLC-PK1) and also stimulated caspase-3 cleavage in cisplatin-treated cells. In conclusion, erythropoietin promotes inflammatory cell apoptosis, drives inflammatory and apoptotic cells into tubular lumens, eventually leads to inflammation clearance, renoprotection and tissue remodelling through caspase-3 and IL-1β in isolated haemoperfused kidneys.     

Responsiveness of monkey skeletal muscle arteries to vasoconstrictor substances before and after cold storage

The stainless steel cannula inserting method was used to observe effects of alpha-adrenoceptor agonists, 5-HT and KCl before and after cold storage (3-5 days, at 4 degrees C) in skeletal muscle branches of the simian deep femoral artery. Epinephrine (EPI), norepinephrine (NE), phenylephrine (PE), methoxamine (MT) and 5-hydroxytryptamine (5-HT) induced marked monophasic vasoconstrictions in a dose-dependent manner. 5-HT induced a greater vasoconstriction in larger diameter vessels (old animals) than that in smaller ones (young animals), suggesting age-related responses. A selective alpha 2-stimulant, clonidine (CLO) or xylazine (XYL), produced only a slight vasoconstriction. Tyramine (TYR) also produced only a slight vasoconstrictor response. The order of potencies for inducing vasoconstrictions was EPI greater than or equal to 5-HT greater than or equal to NE greater than MT = PE much greater than KCl greater than CLO = XYL = TYR. The vasoconstrictor responses to all used adrenergic agonists and 5-HT were not significantly influenced by the prolonged cold storage. However, KCI-induced constrictions were significantly suppressed by the cold storage. These results suggest that the postjunctional alpha-adrenoceptor in simian skeletal muscle arteries is mainly of the alpha 1-type. Since cold storage caused a significant suppression of the KCl-induced response but not those of adrenoceptor agonists and 5-HT, it was considered that the mechanism of calcium entry to the vascular smooth muscle of skeletal muscle arteries might be significantly damaged by the cold storage.     

Contribution of alpha4beta1 integrin to the antiallergic effect of levocabastine

Levocabastine is an antiallergic drug acting as a histamine H1-receptor antagonist. In allergic conjunctivitis (AC), it may also antagonize up-regulation of the intercellular adhesion molecule-1 (ICAM-1) expressed on epithelial conjunctival cells. However, little is known about its effects on eosinophils, important effector cells in AC. The adhesion molecule integrin alpha(4)beta(1) is expressed in eosinophils; it interacts with the vascular cell adhesion molecule-1 (VCAM-1) and fibronectin (FN) in vascular endothelial cells and contributes to eosinophil activation and infiltration in AC. This study provides evidence that in a scintillation proximity assay levocabastine (IC(50) 406 microM), but not the first-generation antihistamine chlorpheniramine, displaced (125)I-FN binding to human integrin alpha(4)beta(1) and, in flow cytometry analysis, levocabastine antagonized the binding of a primary antibody to integrin alpha(4) expressed on the Jurkat cell surface. Levocabastine, but not chlorpheniramine, binds the alpha(4)beta(1) integrin and prevents eosinophil adhesion to VCAM-1, FN or human umbilical vascular endothelial cells (HUVEC) in vitro. Similarly, levocabastine affects alpha(L)beta(2)/ICAM-1-mediated adhesion of Jurkat cells. In a model of AC levocabastine eye drops reduced the clinical aspects of the late-phase reaction and the conjunctival expression of alpha(4)beta(1) integrin by reducing infiltrated eosinophils. We propose that blockade of integrin-mediated cell adhesion might be a target of the antiallergic action of levocabastine and may play a role in preventing eosinophil adhesion and infiltration in AC.     

Augmented potentiation of renal vasoconstrictor responses by thromboxane A2 receptor stimulation in the alloxan-diabetic rat

Dose-response curves were obtained to bolus injections of noradrenaline (NA) and 5-hydroxytryptamine (5-HT) in blood and Krebs-perfused kidneys of male Wistar rats. Vasoconstrictor responses to both NA and 5-HT were significantly attenuated in blood-perfused kidneys of alloxan-treated 14 day diabetic rats compared with non-diabetic animals. Responses to low doses of NA were also significantly attenuated in Krebs-perfused kidneys from diabetic rats but responses to 5-HT were augmented. Dose-dependent potentiation of vasoconstrictor responses to NA and 5-HT in Krebs-perfused kidneys of both non-diabetic and diabetic rats occurred during infusion of the thromboxane A2 (TxA2)-mimetic U46619 [15S)-hydroxy-11 alpha, 9 alpha-(epoxymethano) prosta-5Z, 13E-dienoic acid). The potentiation by U46619 (11 ng mL-1) was inhibited in both groups during infusion of the thromboxane receptor antagonist AH23848 [( 1 alpha(Z), 2 beta, 5 alpha]-(+/-)-7-[5[[(1,1'-biphenyl)-4-yl]methoxyl]-2-(4- morpholinyl)-3-oxocyclopentyl]-4-heptenoic acid). Infusion of 5-HT in Krebs-perfused kidneys of non-diabetic rats, causing a rise in perfusion pressure of similar magnitude to that produced by infusion of 111ng mL-1 U46619, did not significantly affect responses to bolus injections of NA. Potentiation of vasoconstrictor responses to low concentrations of 5-HT by U46619 was significantly greater in Krebs-perfused kidneys of diabetic rats than kidneys from non-diabetic animals. Activation of vascular TxA2 receptors augments the vasoconstrictor effects of 5-HT in Krebs-perfused diabetic rat kidneys to a greater extent than in non-diabetic kidneys.     

Intracellular iron redistribution. An important determinant of reperfusion damage to rabbit kidneys

These studies were designed to examine the possible role of low molecular weight intracellular iron chelates (desferrioxamine-available (DFX-A) iron) in the damage which occurs during cold storage and subsequent reperfusion of kidneys. The level of DFX-A iron increased significantly (P less than 0.005) in the cortex of rabbit kidneys rendered cold ischaemic (CI) for 24 hr and the amount of iron available for DFX chelation increased significantly (P less than 0.05) in both the cortex and medulla of kidneys stored for 48 or 72 hr compared with fresh non-ischaemic controls. During ex vivo reperfusion of the organs with an oxygenated asanguinous perfusate, DFX-A iron returned rapidly to pre-ischaemic levels in 24 hr CI kidneys, but remained elevated following 48 and 72 hr CI (P less than 0.05 compared with 24 hr CI kidneys after 5 min reperfusion), returning to control levels only after 30 min reperfusion. There was no concurrent increase in total iron levels, indicating that a redistribution of iron to more accessible pools had occurred within the tissue. We suggest that decompartmentalization of intracellular iron during ischaemia and raised DFX-A iron levels over an extended period during subsequent reperfusion are responsible for increased catalysis of oxygen-derived free radical-mediated lipid peroxidation, and are an important factor in the deterioration of physiological function observed in rabbit kidneys following extended periods of cold storage.     

Lidocaine as a protective agent during pancreas cold ischemia

Pancreatic islet transplantation in humans is a promising alternative for substitutive insulin therapy of IDDM (Insulin Dependent Diabetes Mellitus). Storage of harvested organs is a one of the most important factors, which influence efficacy of islet isolation process. In this sense, appropriate pancreas storage is the main point the successful pancreatic islet isolation. The purpose of the present study was to find out whether lidocaine, a well known membrane stabilizer and PLA2 (phospholipase A2) inhibitor could be applied in pancreas preservation for protection of endo- and exocrine pancreatic tissue from cells damage which occurs during and after storage. For this purpose, the effects of lidocaine on 1) viability and 2) endocrine function of pancreatic islets, isolated from pancreases exposed to cold ischemia, were investigated in this study. Our study showed hat lidocaine, injected intraductally before pancreas harvesting, improves efficacy of islet isolation. We found that the yields of islets in the groups treated with lidocaine were significantly higher when compared with controls. Glucose challenge test performed on these islets indicated that after the treatment with lidocaine, islets were more sensitive to glucose stimulation when compared with control islets, although the metabolic activity estimated by MTT test was comparable in both groups. In summary, donor pretreatment with lidocaine seems to be the safe method of protection of preserved pancreases from cell damage, caused by membranes destruction during cold ischemia.     

Glycofection: The Ubiquitous Roles of Sugar Bound on Glycoplexes

Glycofection (transfection by using sugar-substituted polylysine) was assessed in order to provide an alternative to viral vectors for the transfer of genes into vascular smooth muscle cells. A rabbit vascular smooth muscle cell line (Rb-1 cells) was selectively transfected by using glycoplexes (glycosylated polylysine/pSV2LUC complexes) in the presence of 10 mu M of the fusogenic peptide GALA. A sugar-specific transfection was obtained when the glycofection was conducted for 1 h with glycoplexes containing either alpha Gal, alpha -Glc, alpha -GalNAc, beta -GlcNAc, or beta -GalNAc residues. The gene expression was high after transfection, with glycoplexes bearing alpha Gal, alpha -GalNAc, or beta -GalNAc residues that were weakly internalized, and low with glycoplexes carrying Lact or Rha residues that were well taken up by cells. These results suggest that 1) glycofection can be a good approach for a selective transfer of genes intovascular smooth muscle cells, 2) an efficient uptake of the glycoplexes is not the unique limiting step for an efficient transfection, and 3) the sugar-dependent trafficking of the glycoplexes inside the cells may account for the transfection efficiency.     

Kinetic study of the polymorphic transformations of phenylbutazone

The polymorphic transformations of phenylbutazone from metastable forms alpha and beta to stable form delta were studied quantitatively at four temperature and five humidity levels by X-ray powder diffractometry. The transformation of form alpha conformed with the Avrami-Erofe'ev kinetic model and form beta conformed with apparent first-order kinetics. In the two transformation systems, the induction periods depended on the storage conditions and were prolonged with lowering of temperature and humidity. The transformation rate of form alpha was not affected by humidity, whereas that of form beta increased according to a rise in humidity. The temperature dependency of the transformation rate constant was remarkable. The Arrhenius treatment was applicable to the beta----delta transformation at low temperatures. The overall half-life, including induction period, revealed that form alpha was more stable than form beta under any storage condition. A good linear relationship existed between the induction period and the transformation rate constant, irrespective of the storage conditions. The scanning electron photomicrographs of forms alpha and beta demonstrated that acicular crystals of form delta grew as the transformation progressed. This could be confirmed as the change in particle diameter of the samples.     

Hypothermic storage of isolated human hepatocytes: a comparison between University of Wisconsin solution and a hypothermosol platform

Until now little is known about the functional integrity of human hepatocytes after hypothermic storage. In order to address this limitation, we evaluated several commercially available hypothermic preservation media for their abilities to protect freshly isolated hepatocytes during prolonged cold storage. Human hepatocytes were isolated from non-transplantable/rejected donor livers and resuspended in ice-cold University of Wisconsin solution (UW), HypoThermosol-Base (HTS-Base), or HypoThermosol-FRS (HTS-FRS) with or without the addition of fetal bovine serum. Cells were stored at 4°C for 24–72 h, and evaluated for hepatocyte viability (trypan blue exclusion, or labeling with fluorochromes), cell attachment, and function. The energy status of hepatocytes was evaluated by measurement of intracellular adenosine 5′-triphosphate. To determine whether the test cells expressed metabolic functions of freshly isolated cells, the activities of major phase I (cytochromes P450, FMO) and phase II (UGT, ST) drug-metabolizing enzymes were examined. Although hepatocytes are shown to be satisfactory after 24 h storage in all of the tested solutions, the cell viability, energy status, and xenobiotic metabolism following cold preservation in HTS-FRS was consistently and, in some cases, markedly higher when compared with other systems. The same metabolites for each of the tested substrates were detected in all groups of cells. Moreover, the use of HTS-FRS eliminates the need for serum in preservation solutions. HTS-FRS represents an improved solution compared to HTS-Base and UW for extending the shipping/storage time of human hepatocytes.     

Hepatocellular uptake of cyclodextrin‐complexed curcumin during liver preservation: A feasibility study

The increasing demand for donor organs and the decreasing organ quality is prompting research toward new methods to reduce ischemia reperfusion injury (IRI). Several strategies have been proposed to protect preserved organs from this injury. Before curcumin/dextrin complex (CDC), a potent antioxidant and anti‐inflammatory agent, can be used clinically we need to better understand the intracellular uptake under hypothermic conditions on a rat model of liver donation after circulatory death (DCD) and brain death (DBD). To be able to use the fluorescence of CDC for quantification the stability of CDC in different preservation solutions at 4°C or 37°C was investigated. Livers from Wistar rats were procured after being flushed‐out through the portal vein using CDC‐enriched preservation solutions and stored at 4°C for variable periods. The CDC signal was stable in different preservation solutions over a period of 4 h and allowed the rapid and lasting uptake of curcumin into cells. After 4 h of preservation, CDC was no longer visible microscopically, and HPLC analysis showed very low to non‐detectable tissue levels of CDC, proving metabolization during preservation. However, the distribution of CDC was not affected by warm ischemia damage (p = 0.278) nor by flushing the livers before or after 4 h of cold storage and without a warm preflush. Finally, curcumin reduced oxidative stress, lowered histological injury and did not change gene expression after WI/cold storage. Therefore, the use of CDC flush solution for the initial organ flush can offer a promising approach to the enhancement of liver preservation and the maintenance of its quality.     

Identification of potent and novel alpha4beta1 antagonists using in silico screening

The antigen alpha4beta1 (very late antigen-4, VLA-4) plays an important role in the migration of white blood cells to sites of inflammation. It has been implicated in the pathology of a variety of diseases including asthma, multiple sclerosis, and rheumatoid arthritis. We describe a series of potent inhibitors of alpha4beta1 that were discovered using computational screening for replacements of the peptide region of an existing tetrapeptide-based alpha4beta1 inhibitor (1; 4-[N'-(2-methylphenyl)ureido]phenylacetyl-Leu-Asp-Val) derived from fibronectin. The search query was constructed using a model of 1 that was based upon the X-ray conformation of the related integrin-binding region of vascular cell adhesion molecule-1 (VCAM-1). The 3D search query consisted of the N-terminal cap and the carboxyl side chain of 1 because, upon the basis of existing structure-activity data on this series, these were known to be critical for high-affinity binding to alpha4beta1. The computational screen identified 12 reagents from a virtual library of 8624 molecules as satisfying the model and our synthetic filters. All of the synthesized compounds tested inhibit alpha4beta1 association with VCAM-1, with the most potent compound having an IC(50) of 1 nM, comparable to the starting compound. Using CATALYST, a 3D QSAR was generated that rationalizes the variation in activities of these alpha4beta1 antagonists. The most potent compound was evaluated in a sheep model of asthma, and a 30 mg nebulized dose was able to inhibit early and late airway responses in allergic sheep following antigen challenge and prevented the development of nonspecific airway hyperresponsiveness to carbachol. Our results demonstrate that it is possible to rapidly identify nonpeptidic replacements of integrin peptide antagonists. This approach should be useful in identification of nonpeptidic alpha4beta1 inhibitors with improved pharmacokinetic properties relative to their peptidic counterparts.     

Alpha3beta4 subunit-containing nicotinic receptors dominate function in rat medial habenula neurons.

Regional-specific differences in nicotinic acetylcholine receptors (nAChRs) were examined using the whole-cell patch clamp technique in rat medial habenula (MHb) slices. The majority of cells in the ventral two thirds of the MHb responded robustly to local pressure application of nAChR agonists. Mean agonist potency profiles in the middle and ventral thirds of the MHb were similar: cytisine was the most potent agonist and DMPP the weakest, consistent with a significant contribution of the beta4 subunit to functional nAChRs in all areas of the MHb. In acutely isolated MHb neurons, the alpha3beta4-selective toxin alpha-CTx-AuIB (1 microM) reversibly blocked approximately 75% of the nicotine-induced currents, as expected for cells solely expressing alpha3beta4 nAChRs. However, the alpha3beta2-selective toxin, alpha-CTx-MII (100 nM), blocked a variable fraction (0-90%) of the MHb nicotinic response implying that beta2 subunits may contribute to some functional receptors. We suggest that the effects of alpha-CTx-MII may arise from interaction with alpha3beta2beta4 subunit-containing nAChRs. This idea is supported by the findings (1) that alpha-CTx-MII antagonizes receptors comprised of alpha3, beta2 and beta4 subunits in Xenopus oocytes, and (2) that a mutant alpha-CTx-MII toxin[H12A], which blocks alpha3beta2beta4 receptors but not alpha3beta2 or alpha3beta4 nAChRs, also reduces nicotinic currents in some MHb neurons. Overall these data imply that most functional nAChRs on MHb cells contain at least alpha3 and beta4 subunits, and that a variable subpopulation additionally contains the beta2 subunit.     

Effect of tumor necrosis factor on granule release and LTB4 production in adherent human polymorphonuclear leukocytes

Tumor necrosis factor (rTNF) has previously been shown to induce PMN chemotaxis, stimulate PMN adhesion to vascular endothelium and stimulate hydrogen peroxide secretion from PMNs adhered to biological surfaces. We investigated the activity of both rTNF alpha and rTNF beta on adherent and suspension cultures of human PMNs. rTNF alpha selectively stimulated the release of the specific granule in a dose dependent manner. Exocytosis of the specific granule was measured with an enzyme-immunoassay for lactoferrin and a radioassay for vitamin B12-binding protein. Adherent PMNs released up to 60% of the total lactoferrin content of the cells with no increase in myeloperoxidase (MPO) secretion when stimulated with 0.1-10 nM rTNF alpha. The PMNs in suspension cultures also selectively released the specific granule, although total release was reduced suggesting that adherence of PMNs increased their ability to respond to physiological stimuli. When PMNs in suspension cultures or adherent cells were stimulated with rTNF alpha, no LTB4 production was detectable, yet the cells retained the ability to synthesize LTB4 when stimulated with calcium ionophore A23187. Neither rTNF alpha or rTNF beta stimulated the release of the azurophilic granule, measured by the secretion of MPO and neutrophil elastase activity. These results suggest that a function of rTNF alpha and rTNF beta on PMNs is the release of the contents within the specific granule.     

Effect of cold hypoxic storage and reoxygenation at 37°C of cultured precision-cut rat liver slices on paracetamol metabolism

The influence of cold storage and reoxygenation at 37 degrees C of precision-cut rat liver slices on paracetamol metabolism was studied. A depressed metabolism was observed after cold preservation, but during reoxygenation at 37 degrees C slices were capable of synthesizing proteins and maintaining both glutathione and ATP levels. Recovery was faster in slices under aerobic cold conditions than in those under cold hypoxia. Glycogen levels were dramatically decreased under both conditions and subsequent reoxygenation at 37 degrees C still increased the glycogenolysis. Xenobiotic metabolism after reoxygenation of cold-preserved slices shows that glucuronide and sulfate conjugates of paracetamol represent about 50% of those of fresh slices at zero time. The amounts of phase II apoproteins were virtually unchanged, thus suggesting that loss of enzyme activities are most probably due to lack of cofactors. Reoxygenation at 37 degrees C did not impair cell metabolism, and a potential role for nitric oxide and other cytokines released form Kupffer cells appears unlikely since nitrite was not formed after bacterial endotoxin stimulation. The maintenance of energetic stores during cold preservation appears, therefore, to be a critical issue for the survival and metabolic activity of cells.     

Interaction of dopamine, (+/-)-dobutamine and the (-)-enantiomer of dobutamine with alpha- and beta-adrenoceptors in the pulmonary circulation of the dog

The effects of dopamine, (+/-)-dobutamine (racemic mixture) and (-)-dobutamine on alpha-adrenoceptor-mediated vasoconstriction were evaluated in the pulmonary circulation of the anesthetized dog. The drugs were studied in the absence and presence of propranolol (1 mg/kg, i.v.) in order to assess beta-adrenoceptor-mediated effects in the pulmonary circulation. Intra-arterial administration of dopamine, (+/-)-dobutamine and (-)-dobutamine elicited dose-dependent increases in pulmonary perfusion pressure, reflecting increases in pulmonary vascular resistance. In control animals, dopamine elicited the largest increases in pulmonary perfusion pressure (45% above resting pulmonary pressure) followed by (-)-dobutamine (30% increase) and (+/-)-dobutamine (15% increase). The pressor effects of dopamine in the pulmonary circulation were mediated by both postjunctional vascular alpha 1- and alpha 2-adrenoceptors, since prazosin, (100 micrograms/kg, i.v.), a selective alpha 1-adrenoceptor antagonist, and rauwolscine (100 micrograms/kg, i.v.), a selective alpha 2-adrenoceptor antagonist, both inhibited the vasopressor response elicited by dopamine to roughly equivalent degrees. Pulmonary vasoconstriction produced by (+/-)-dobutamine and (-)-dobutamine was mediated primarily by postsynaptic vascular alpha 1-adrenoceptors, although alpha 2-adrenoceptor-mediated vasoconstriction was observed. In propranolol-pretreated animals, the increase in pulmonary perfusion pressure elicited by dopamine and (-)-dobutamine was qualitatively and quantitatively similar to that observed in control animals, suggesting that these agents have little activity on vascular beta 2-adrenoceptors in the pulmonary circulation. In marked contrast, the maximum pulmonary vasopressor response obtained with (+/-)-dobutamine were greater in propranolol-pretreated animals, indicating that (+/-)-dobutamine also has the capacity to stimulate pulmonary vascular beta 2-adrenoceptors which mediate pulmonary vasodilation that, in part, mask alpha-adrenoceptor-mediated pulmonary vasoconstriction. Since the (-)-enantiomer of dobutamine has little or no beta 2-adrenoceptor agonist activity, the beta 2-adrenoceptor-mediated effect of (+/-)-dobutamine must result from the (+)-enantiomer as has been previously proposed. The results of the present study indicate that dopamine has a greater propensity for increasing pulmonary vascular resistance, and therefore pulmonary arterial blood pressure, relative to (+/-)-dobutamine. This results, at least in part, from the relatively weaker activity of dopamine in stimulating pulmonary vascular beta 2-adrenoceptors which mediate vasodilation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Pharmacological analysis of integrin function: inhibition of vascular stenosis and identification of a novel antiplatelet substance

The long-lasting success of PTCA, a common treatment for patients with coronary artery disease, is hampered by acute reocclusion due to thrombus and by late restenosis due to smooth muscle cell (SMC) migration and proliferation. Recently potent antiplatelet agents such as inhibitors of platelet glycoprotein (GP) IIb/IIIa (alpha IIb/beta 3) have become available and are highly effective in humans. We investigated the inhibitory effects of these compounds on vascular stenosis. Administration of an RGD-containing peptide (non-selective alpha IIb/beta 3 antagonist) results in reduction of neointima, but selective alpha IIb/beta 3 antagonists have no effect. This effect is due both to an early event, which could be due to the inhibition of secretion of PDGF from activated platelets with blocked alpha IIb/beta 3, and to a late event, by interference with SMC alpha v/beta 3. Moreover, platelet adhesion via GPIb/V/IX is a trigger for thrombus formation. Inhibition of platelet adhesion results in the prevention of thrombus formation and the suppression of neointima. However, this effect was supported by the reduction of SMC proliferation. Therefore, these dual inhibitions markedly reduced vascular stenosis. Finally some low molecular mass heat shock proteins (HSPs) appear to act as molecular chaperones, but their physiological roles have not been fully elucidated. We have investigated the physiological role of p20, a kind of HSP, on platelet function. p20 inhibited platelet aggregation. Our findings may provide the basis for a novel defensive system against thrombus formation.     

Norethisterone is bioconverted to oestrogenic compounds that activate both the oestrogen receptor alpha and oestrogen receptor beta in vitro

In the present study, we used [3H]norethisterone to explore the bioconversion of this compound to A-ring reduced metabolites in African Green Monkey Kidney CV-1 cells and breast cancer T-47D cells. Additionally, we analyzed the capability of each norethisterone tetrahydro-reduced compound to bind the human oestrogen receptors alpha and beta and transactivate an oestrogen-sensitive reporter gene. The results showed that norethisterone is mainly metabolized to 3 alpha,5 alpha-norethisterone (>85% of total [3H]norethisterone added) by CV-1 and T-47D cells, and that both A-ring tetrahydro-reduced metabolites exhibit different capabilities to displace [3H]17beta-oestradiol from the oestrogen receptor alpha and beta, being 3 alpha,5 alpha-norethisterone the weakest competitor. We also found that 3 alpha,5 alpha-norethisterone and 3beta,5 alpha-norethisterone activate both oestrogen receptors at nanomolar concentrations and that the transactivation induced by the oestrogen receptor alpha was generally higher (1.7- to 4.0-fold) than that provoked by the beta receptor isoform. In oestrogen receptor alpha-transfected CV-1 and T-47 D cells, the oestrogenic-like potency of the 3beta,5 alpha-tetrahydro-reduced form was similar to that exhibited by 17beta-oestradiol and 2.5- to 4.0-fold higher than that shown by the 3 alpha,5 alpha-reduced compound; conversely, in the oestrogen receptor beta system the potency of the natural ligand was higher than that presented by the 3beta,5 alpha-tetrahydro-reduced metabolite. In CV-1 cells expressing the oestrogen receptor beta, the transactivation potency of 3beta,5 alpha-norethisterone was approximately 2-fold higher than that exhibited by its 3 alpha,5 alpha-tetrahydro-reduced isomer, whereas in T-47D cells the potency of the 3 alpha,5 alpha-tetrahydro-reduced compound was slightly higher than that shown by the 3beta,5 alpha A-ring reduced norethisterone metabolite. These results demonstrate that CV-1 and T-47D cells possess the enzymatic machinery to bioconvert norethisterone into the 5 alpha-reduced, 3 alpha-hydroxylated form and that neither 3 alpha,5 alpha- or 3beta,5 alpha-norethisterone exhibit preference or selectivity towards a particular oestrogen receptor isoform to induce a particular oestrogenic effect in these cell lines.     

alpha(v)beta(3) Integrin antagonists as inhibitors of bone resorption

The alpha(v)beta(3) integrin is a non-covalent, heterodimeric, cell-surface protein that is expressed with varying density on numerous cell types, including osteoclasts, vascular smooth muscle cells, endothelial cells and a variety of tumour cells. Functionally, alpha(v)beta(3) mediates a diverse range of biological events including the adhesion of osteoclasts to bone matrix, smooth muscle cell migration and angiogenesis. Specifically, there has been significant attention focused on the preparation of inhibitors of alpha(v)beta(3) for use as inhibitors of bone resorption, in recognition of the medical need for improved prevention and treatment of osteoporosis. Herein, we summarise the pertinent chemistry and biological advances in the medicinal design and biological evaluation of peptide and small molecule alpha(v)beta(3) antagonists as inhibitors of bone resorption.