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Adipose tissue as an endocrine organ: role of leptin and adiponectin in the pathogenesis of cardiovascular diseases.

Obesity, the most common nutritional disorder in industrial countries, is associated with increased cardiovascular mortality and morbidity. Nevertheless, the molecular basis linking obesity with cardiovascular disturbances have not yet been fully clarified. Recent advances in the biology of adipose tissue indicate that it is not simply an energy storage organ, but also a secretory organ, producing a variety of bioactive substances, including leptin and adiponectin, that may influence the function as well as the structural integrity of the cardiovascular system. Leptin, besides being a satiety signal for the central nervous system and to be related to insulin and glucose metabolism, may also play an important role in regulating vascular tone because of the widespread distribution of functional receptors in the vascular cells. On the other hand, the more recently discovered protein, adiponectin, seems to play a protective role in experimental models of vascular injury, in probable relation to its ability to suppress the attachment of monocytes to endothelial cells, which is an early event in the atherosclerotic process. There is already considerable evidence linking altered production of some adipocyte hormones with the cardiovascular complications of obesity. Therefore, the knowledge of alterations in the endocrine function of adipose tissue may help to further understand the high cardiovascular risk associated with obesity.

Parameters related to oxygen free radicals in erythrocytes, plasma and epidermis of the hairless rat.

The following parameters related to oxygen free radicals (OFR) were determined in erythrocytes and the epidermis of hairless rats: catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), reduced (GSH) and oxidized (GSSG) glutathione, glutathione S-transferase (GST), superoxide dismutase (SOD) and thiobarbituric acid reactive substances (TBARS). GSH, GSSG and TBARS were also analyzed in plasma. In erythrocytes, the Pearson correlation coefficients (r) were significant (p < 0.001) between glutathione and other parameters as follows: GSH correlated negatively with GSSG (r = -0.665) and TBARS (r = -0.669); GSSG correlated positively with SOD (r = 0.709) and TBARS (r = 0.752). Plasma GSSG correlated negatively with erythrocytic thermostable GST activity (r = -0.608; p=0.001) and with erythrocytic total GST activity (r = -0.677; p < 0.001). In epidermis (p < 0.001 in all cases), GSH content correlated with GSSG (r = 0.682) and with GPx (r = 0.663); GSSG correlated with GPx (r = 0.731) and with GR (r = 0.794). By multiple linear regression analysis some predictor variables (R(2)) were found: in erythrocytes, thermostable GST was predicted by total GST activity and GSSG, GSSG content was predicted by GSH and by the GSH/GSSG ratio and GPx activity was predicted by GST, CAT and SOD activities; in epidermis, GSSG was predicted by GR and SOD activities and GR was predicted by GSSG, TBARS and GPx. It is concluded that the hairless rat is a good model for studying OFR-related parameters simultaneously in blood and skin, and that it may provide valuable information about other animals under oxidative stress.

Oxidative stress in arterial hypertension: role of NAD(P)H oxidase.

Increased vascular reactive oxygen species production, especially superoxide anion, contributes significantly in the functional and structural alterations present in hypertension. An enhanced superoxide production causes a diminished NO bioavailability by an oxidative reaction that inactivates NO. Exaggerated superoxide levels and a low NO bioavailability lead to endothelial dysfunction and hypertrophy of vascular cells. It has been shown that the enzyme NAD(P)H oxidase plays a major role as the most important source of superoxide anion in vascular cells. Several experimental observations have shown an enhanced superoxide generation as a result of the activation of vascular NAD(P)H oxidase in hypertension. Although this enzyme responds to stimuli such as vasoactive factors, growth factors, and cytokines, some recent data suggest the existence of a genetic background modulating the expression of its different components. New polymorphisms have been identified in the promoter of the p22(phox) gene, an essential subunit of NAD(P)H oxidase, influencing the activity of this enzyme. Genetic investigations of these polymorphisms will provide novel markers for determination of genetic susceptibility to oxidative stress in hypertension.

Cardiomyocyte apoptotic cell death in arterial hypertension: mechanisms and potential management.

Hypertensive heart disease is a progressive condition in which the compensatory left ventricular hypertrophy that maintains cardiac output leads to myocardial remodeling, characterized by fibrosis, insufficient vascularization, and alterations in cardiomyocytes, including contractile disturbances, changes in gene expression, and decrease in the number of cells. Structural abnormalities in the myocardial wall accelerate the development of diastolic and systolic dysfunction, resulting in heart failure. Many observations point to the apoptotic cell death of cardiomyocytes as a relevant factor in the transition from compensatory hypertrophy to pump failure in experimental and human hypertension. Potential inducers of cardiomyocyte apoptosis in overloaded hearts include extrinsic factors, such as mechanical forces, neurohormonal activation, oxidative stress, hypoxia, and cytokines. Some lines of evidence indicate that angiotensin II and the overstretching of cardiomyocytes are originally involved in the triggering of apoptosis in hypertension, whereas other factors are being investigated. Furthermore, intracellular changes, such as downregulation of survival proteins or activation of death proteins, seem to play an important role. The assumption that the apoptosis of cardiomyocytes worsens hypertensive heart disease prognosis brings forth new approaches to avoid or slow the transition to pump failure. In this respect, experimental data indicate that currently used antihypertensive drugs interfere with cardiomyocyte apoptosis. Moreover, the knowledge of intracellular apoptotic processes in cardiomyocytes provides novel therapeutic strategies to be added to the multimodal approach in the prevention of heart failure.

Is the balance between nitric oxide and superoxide altered in spontaneously hypertensive rats with endothelial dysfunction?

BACKGROUND: Increases in oxidant stress, i.e. excessive production of superoxide anion (O2(.-)), have been reported in different models of hypertension. This study was designed to test the hypothesis that increased O2(.-) production, more than diminished nitric oxide (NO) generation, plays a critical role in endothelial dysfunction present in spontaneously hypertensive rats (SHR). METHODS: The study was performed in 30-week-old normotensive Wistar-Kyoto rats (WKY) and SHR. In addition, 16-week-old SHR were treated with oral irbesartan (average dose 20 mg/kg per day) for 14 weeks (SHR-I). Aortic nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NADH/NADPH) oxidase activity was determined by use of chemiluminescence with lucigenin. Aortic constitutive nitric oxide synthase (cNOS) activity was determined by measuring the conversion of L-arginine to L-citrulline. Vascular responses to acetylcholine were determined by isometric tension studies. RESULTS: Whereas systolic blood pressure (SBP) was significantly increased in SHR compared with WKY, no differences were observed in SBP between SHR-I and WKY. In SHR compared with WKY, we found significantly greater NADH/NADPH-driven O2(.-) production, similar cNOS-mediated NO production and an impaired vasodilation in response to acetylcholine. Treated SHR had similar NADH/NADPH oxidase activity and significantly lower cNOS activity than the WKY group. Vasodilation in response to acetylcholine was improved in SHR-I. CONCLUSIONS: These findings suggest that a diminished availability of NO secondary to an enhanced NADH/NADPH oxidase-dependent O2(.-) production may play a critical role in endothelial dysfunction of adult SHR.

Effects of loop diuretics on angiotensin II-stimulated vascular smooth muscle cell growth.

BACKGROUND: Torasemide and furosemide are diuretics that inhibit the Na(+), K(+), 2Cl(-) co-transporter localized in cells from the ascending limb of the loop of Henle. The effects of torasemide and furosemide on cell growth induced by angiotensin II (Ang II) were investigated in cultured vascular smooth muscle cells (VSMCs) obtained from the aorta of adult spontaneously hypertensive rats (SHR). METHODS: Cell growth was determined by DNA and protein synthesis as measured by [3H]thymidine and [3H]leucine incorporation, respectively. Proliferation of VSMCs was measured using a non-radioactive colorimetric cell proliferation assay. RESULTS: Ang II (10(-7) M) signficantly increased DNA and protein synthesis and cell proliferation in VSMCS: These effects were completely abolished by the Ang II type 1 receptor antagonist irbesartan (10(-6) M). Ang II-induced [3H]leucine incorporation was reduced in a dose-dependent way by torasemide (IC(50) value: 7.7+/-0.8x10(-7) M) but not by furosemide. Neither torasemide nor furosemide modified Ang II-stimulated [3H]thymidine incorporation or proliferation in VSMCs. CONCLUSIONS: These results indicate that torasemide, but not furosemide, inhibits Ang II-induced protein synthesis in VSMCs from SHR. Thus, it is suggested that the capacity of torasemide to block this trophic action of Ang II in rat VSMCs is not mediated by inhibition of the Na(+), K(+), 2Cl(-) co-transport mechanism.

The loop diuretic torasemide interferes with endothelin-1 actions in the aorta of hypertensive rats.

BACKGROUND: The direct effects of torasemide and furosemide on vasoconstriction and increases in intracellular free calcium concentration ([Ca(2+)]i) induced by endothelin-1 (ET-1) were investigated in the aorta of spontaneously hypertensive rats (SHR). METHODS: Vascular responses were assessed in endothelium-denuded aortic rings using an organ bath system. Changes of [Ca(2+)]i in cultured vascular smooth muscle cells (VSMCs) were assessed using fura-2 methodology. RESULTS: ET-1-induced vasoconstriction was reduced in a dose-dependent way by torasemide and furosemide (IC(50) values: 4.3+/-1.4x10(-5) and 9.8+/-5.6 x10(-5) M, respectively). The ET-1-induced biphasic [Ca(2+)]i increase was blocked by torasemide (IC(50)=2.0+/-0.2x10(-8) and 2.7+/-0.6x10(-6) M, respectively). Furosemide inhibited the initial rise in [Ca(2+)]i induced by ET-1, with no effect on the second rise. The specific chloride (Cl(-)) channel blocker diphenylamine-2-carboxylate inhibits both ET-1-induced responses in VSMCs (IC(50)=8.0+/-0.3x10(-9) and 2.5+/-0.7x10(-7) M, respectively). CONCLUSIONS: These results suggest that the ability of loop diuretics to interfere with the vascular actions of ET-1 may involve different molecular mechanisms. The ability of torasemide to block the vasoconstrictive action of ET-1 could include an inhibitory action on Cl(-) channels.

Polymorphisms and promoter overactivity of the p22(phox) gene in vascular smooth muscle cells from spontaneously hypertensive rats.

In a previous study, we found that the p22(phox) subunit of the NADH/NADPH oxidase is overexpressed in vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHRs) with enhanced vascular production of superoxide anion ((.)O(2)(-)). Thus, we have investigated whether changes in the sequence or activity of the promoter region of p22(phox) gene are present in SHRs. To carry out this analysis, first of all, we characterized the rat gene structure and promoter region for the p22(phox) subunit. The p22(phox) gene spans approximately 10 kb and contains 6 exons and 5 introns. Primer extension analysis indicated the transcriptional start site 100 bp upstream from the translational start site. The immediate promoter region of the p22(phox) gene does not contain a TATA box, but there are a CCAC box and putative recognition sites for nuclear factors, such as SP1, gamma-interferon, and nuclear factor-kappaB. Using reporter-gene transfection analysis, we found that this promoter was functional in VSMCs. Furthermore, we observed that p22(phox) promoter activity was significantly higher in VSMCs from SHRs than from normotensive Wistar-Kyoto rats. In addition, we found that there were 5 polymorphisms in the sequence of p22(phox) promoter between Wistar-Kyoto rats and SHRs and that they were functional. The results obtained in this study provide a tool to explore the mechanisms that regulate the expression of p22(phox) gene in rat VSMCs. Furthermore, our findings show that changes in the sequence of p22(phox) gene promoter and in the degree of activation of VSMCs are responsible for upregulated expression of p22(phox) in SHRs.

Valor pronóstico de los receptores hormonales, índice de proliferación celular (Ki-67) y factores clinicopatológicos en el carcinoma ductal infiltrante de mama. estudio inmunohistoquímico de 192 pacientes / Prognostic value of hormonal receptors, cell proliferation index (Ki-67) and clinicopathologic factors of invasive ductal carcinoma of the breast. An immunohistochemical study of 192 patients

Objetivo. Valorar la relación entre los factores pronósticos clínicos, histológicos e inmunohistoquímicos en el carcinoma ductal infiltrante de mama. Material y métodos. Se estudiaron variables clínicas e histológicas, receptores hormonales e índice de proliferación celular (Ki-67) en 192 pacientes con carcinoma ductal infiltrante. Los receptores de estrógenos y progesterona fueron medidos de acuerdo con la intensidad de la tinción (I), con valores comprendidos entre 0 y 3, y el porcentaje de células positivas (P). Se calculó un histoscore para la fórmula (I + 1) × P (rango: 0-400). Los casos con un valor de histoscore por encima de 100 fueron considerados positivos. El índice de proliferación celular (Ki-67) fue medido contando 500 células, expresando el número de células positivas en porcentaje. Resultados.En 64,24 por ciento de los tumores se encontró tinción positiva para los receptores de estrógenos, mientras que el 49,12 por ciento fueron receptores de progesterona positivos. En 21,87 por ciento de los pacientes se encontró un índice de proliferación celular alto (> 25 por ciento). El tamaño tumoral, el número de mitosis, la presencia de necrosis y el estado ganglionar fueron factores pronósticos independientes en nuestro estudio estadístico. Conclusiones. Los receptores hormonales y el Ki-67 no son factores pronósticos independientes para la recidiva y la supervivencia global en nuestro estudio. Sólo los factores histológicos clásicos se han mostrado como factores pronósticos independientes. (AU)

Vascular oxidant stress: molecular mechanisms and pathophysiological implications.

The term oxidative stress refers to a situation in which cells are exposed to excessive levels of either molecular oxygen or chemical derivatives of oxygen (ie, reactive oxygen species). Three enzyme systems produce reactive oxygen species in the vascular wall: NADH/NADPH oxidase, xanthine oxidoreductase, and endothelial nitric oxide synthase. Among vascular reactive oxygen species superoxide anion plays a critical role in vascular biology because it is the source for many other reactive oxygen species and various vascular cell functions. It is currently thought that increases in oxidant stress, namely excessive production of superoxide anion, are involved in the pathophysiology of endothelial dysfunction that accompanies a number of cardiovascular risk factors including hypercholesterolemia, hypertension and cigarette smoking. On the other hand, vascular oxidant stress plays a pivotal role in the evolution of clinical conditions such as atherosclerosis, diabetes and heart failure.

Vascular NADH/NADPH oxidase is involved in enhanced superoxide production in spontaneously hypertensive rats.

This study was designed to test the hypothesis that stimulation of nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NADH/NADPH) oxidase is involved in increased vascular superoxide anion (*O(2)(-)) production in spontaneously hypertensive rats (SHR). The study was performed in 16-week-old and 30-week-old normotensive Wistar-Kyoto rats (WKY(16) and WKY(30), respectively) and in 16-week-old and 30-week-old SHR (SHR(16) and SHR(30), respectively). In addition, 16-week-old SHR were treated with oral irbesartan (average dose 20 mg/kg per day) for 14 weeks (SHR(30)-I). Aortic NADH/NADPH oxidase activity was determined by use of chemiluminescence with lucigenin. The expression of p22phox messenger RNA was assessed by competitive reverse transcription-polymerase chain reaction. Vascular responses to acetylcholine were determined by isometric tension studies. Aortic wall structure was studied, determining the media thickness and the cross-sectional area by morphometric analysis. Whereas systolic blood pressure was significantly increased in the 2 groups of hypertensive animals compared with their normotensive controls, no differences were observed in systolic blood pressure between SHR(30) and SHR(16). No other differences in the parameters measured were found between WKY(16) and SHR(16). In SHR(30) compared with WKY(30), we found significantly greater p22phox mRNA level, NADH/NADPH-driven *O(2)(-) production, media thickness, and cross-sectional area and an impaired vasodilation in response to acetylcholine. Treated SHR had similar NADH/NADPH oxidase activity and p22phox expression as the WKY(30) group. The vascular functional and morphological parameters were improved in SHR(30)-I. These findings suggest that an association exists between p22phox gene overexpression and NADH/NADPH overactivity in the aortas of adult SHR. Enhanced NADH/NADPH oxidase-dependent *O(2)(-) production may contribute to endothelial dysfunction and vascular hypertrophy in this genetic model of hypertension.

Mechanisms of increased susceptibility to angiotensin II-induced apoptosis in ventricular cardiomyocytes of spontaneously hypertensive rats.

Previous findings have shown that hypotensive doses of losartan prevent the excess of apoptosis present in the hypertrophied left ventricle of adult spontaneously hypertensive rats (SHR). This study was designed to determine whether angiotensin II facilitates apoptosis in cardiomyocytes of adult SHR. Primary cultures of ventricular cardiomyocytes from 30-week-old normotensive Wistar-Kyoto rats (WKY) and SHR with left ventricular hypertrophy were exposed to 10(-)(9) mol/L angiotensin II for 24 hours. Apoptotic cells were assessed by terminal deoxynucleotidyl transferase assay and confirmed by Annexin V detection. The expression of Bax-alpha, Bcl-2, p53, and caspase-3 proteins was assessed by Western blot assays. The expression of BAX gene was assessed by Northern blot. Angiotensin II increased (P<0.01) cardiomyocyte apoptosis, and this effect was higher (P<0.001) in SHR cells than in WKY cells. Whereas losartan (10(-7) mol/L) blocked the apoptotic effect of the octapeptide in cells from the two strains of rats, PD123319 (10(-7) mol/L) inhibited angiotensin II-mediated apoptosis only in SHR cells. Angiotensin II stimulated (P<0.01) Bax-alpha protein, and this effect was higher (P<0.01) in SHR cells than in WKY cells. Angiotensin II did not modify Bcl-2, p53, and BAX mRNA in cells from the two strains of rats. Angiotensin II induced a similar increase (P<0.05) in the ratio caspase-3/procaspase-3 (an index of caspase-3 activation) in cardiomyocytes from the two strains of rats. The present in vitro results indicate that SHR cardiomyocytes exhibit enhanced susceptibility to angiotensin II-induced apoptosis. Ligand binding to angiotensin II type 1 and type 2 receptors leading to changes in posttranscriptional processing of Bax-alpha and accumulation of this proapoptotic protein may be involved in the abnormal response of SHR cardiomyocytes. These data support a role for angiotensin II in apoptosis observed in the left ventricle of these rats.

CCK-mediated response in the activation of 5-HT receptor types in the guinea-pig ileum.

The possible interaction between cholecystokinin (CCK) and 5-hydroxytryptamine (5-HT) was evaluated in vitro in the longitudinal muscle-myenteric plexus of the guinea-pig ileum. Devazepide and L-365,260 were used to block CCKA and CCK(B) receptors and ondansetron and tropisetron to block 5-HT3 and 5-HT4 receptors, respectively. The CCK receptor antagonists blocked, in a dose-dependent manner, the response to 5-HT and to the selective agonists at 5-HT3 and 5-HT4 receptors, 2-methyl-5-hydroxytryptamine (2-Me-5-HT) and 5-methoxytryptamine (5-MeOT), respectively. The blockade was almost complete on the first phase of the concentration response curve to 5-HT and for all the concentrations of 5-MeOT tested. In the 2-Me-5-HT-induced contractile response there was a component with the same sensitivity to devazepide and to the selective NK1 receptor antagonist, GR 82334, and another resistant component that was abolished by atropine. However, the blockade of the NK1 receptor did not produce a significant increase in the inhibition obtained when atropine or devazepide were separately tested on the 5-MeOT-induced response. These results suggest that CCK is involved in the 5-HT-induced contractile response, particularly in the response induced by 5-HT4 receptor stimulation.

Torasemide inhibits angiotensin II-induced vasoconstriction and intracellular calcium increase in the aorta of spontaneously hypertensive rats.

Torasemide is a loop diuretic that is effective at low once-daily doses in the treatment of arterial hypertension. Because its antihypertensive mechanism of action may not be based entirely on the elimination of salt and water from the body, a vasodilator effect of this drug can be considered. In the present study, the ability of different concentrations of torasemide to modify angiotensin II (Ang II)-induced vascular responses was examined, with the use of an organ bath system, in endothelium-denuded aortic rings from spontaneously hypertensive rats. Ang II-induced increases of intracellular free calcium concentration ([Ca(2+)](i)) were also examined by image analysis in cultured vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats. A dose-response curve to Ang II was plotted for cumulative concentrations (from 10(-9) to 10(-6) mol/L) in endothelium-denuded aortic rings (pD(2)=7.5+/-0.3). Isometric contraction induced by a submaximal concentration of Ang II (10(-7) mol/L) was reduced in a dose-dependent way by torasemide (IC(50)=0.5+/-0.04 micromol/L). Incubation of VSMCs with different concentrations of Ang II (from 10(-10) to 10(-6) mol/L) resulted in a dose-dependent rise of [Ca(2+)](i) (pD(2)=7.5+/-0.3). The stimulatory effect of [Ca(2+)](i) induced by a submaximal concentration of Ang II (10(-7) mol/L) was blocked by torasemide (IC(50)=0.5+/-0.3 nmol/L). Our findings suggest that torasemide blocks the vasoconstrictor action of Ang II in vitro. This action can be related to the ability of torasemide to block the increase of [Ca(2+)](i) induced by Ang II in VSMCs. It is proposed that these actions might be involved in the antihypertensive effect of torasemide observed in vivo.

p53-mediated upregulation of BAX gene transcription is not involved in Bax-alpha protein overexpression in the left ventricle of spontaneously hypertensive rats.

An association of increased apoptosis with overexpression of the proapoptotic protein Bax-alpha has been reported in the left ventricle of adult spontaneously hypertensive rats (SHR). Both alterations were corrected in SHR that received long-term treatment with the AT1 antagonist losartan. To gain insight into the regulation of cardiac Bax-alpha protein in genetic hypertension, we investigated the expression of the protein p53 (a BAX gene transcription factor) and BAX mRNA in the left ventricle of 30-week-old Wistar-Kyoto rats (WKY), SHR, and SHR treated with losartan (20 mg. kg-1. d-1) during 14 weeks before death. The expression of p53 and Bax proteins was assessed by Western blot analysis. The expression of BAX mRNA was assessed by Northern blot analysis. The density of apoptotic cells was assessed by direct immunoperoxidase detection of biotin-labeled deoxyuridine nucleotides. Compared with WKY, untreated SHR exhibited increased apoptosis (P<0.05), increased Bax-alpha protein (P<0.05), and similar levels of p53 protein and BAX mRNA. Losartan given long term was associated with the normalization of apoptosis and Bax-alpha protein expression. The expression of BAX mRNA was decreased (P<0. 05) in treated SHR compared with untreated SHR. No changes in the expression of p53 protein were observed in losartan-treated SHR. These results suggest that overexpression of the Bax-alpha protein seen in the left ventricle of adult SHR with increased apoptosis is not related to a p53-mediated upregulation of BAX gene transcription. Our data also suggest that normalization of Bax-alpha protein observed in SHR after long-term blockade of angiotensin II type 1 receptors may be due to the inhibition of BAX gene transcription.

Altered regulation of smooth muscle cell proliferation and apoptosis in small arteries of spontaneously hypertensive rats.

AIM: It has been proposed that alterations of the balance between programmed cell death and cell replication might be involved in abnormalities of smooth muscle cell growth in arterial hypertension. This study was designed to analyse some regulators of apoptosis and proliferation in smooth muscle cells of small intra-myocardial arteries from the left ventricle of adult normotensive Wistar-Kyoto rats (WKY) and adult spontaneously hypertensive rats (SHR). Therefore, we assessed the expression of the cytoplasmic proteins Bax and Bcl-2, respectively a promoter and an inhibitor of apoptosis, and the expression of cyclin A, a nuclear protein that induces proliferation of smooth muscle cells. METHODS AND RESULTS: We measured the percentages of smooth muscle cells expressing these proteins using monoclonal antibodies and the avidin-biotin immunoperoxidase method. Compared with WKY, cells from SHR exhibited normal Bax expression, increased (P < 0.001) Bcl-2 expression and increased (P < 0.001) cyclin A expression. The ratio of Bax to Bcl-2, an index of cell susceptibility to apoptosis, was lower (P < 0.001) in SHR than in WKY. Systolic blood pressure was directly correlated (P < 0.01) with Bcl-2 and cyclin A in SHR. CONCLUSION: These results suggest that apoptosis and proliferation of smooth muscle cells might be inhibited and stimulated, respectively, in small arteries of adult SHR. The imbalance between these two processes may account for abnormalities of smooth muscle cell growth in the arterial wall in genetic hypertension.

Synthesis and stereochemical structure-activity relationships of 1,3-dioxoperhydropyrido[1,2-c]pyrimidine derivatives: potent and selective cholecystokinin-A receptor antagonists.

The synthesis and stereochemical structure--activity relationships of a new class of potent and selective non-peptide cholecystokinin-A (CCK-A) receptor antagonists based on the 1,3-dioxoperhydropyrido[1,2-c]pyrimidine skeleton are described. The most potent member of this series of eight diastereoisomers, (4aS,5R)-2-benzyl-5-[N-[(tert-butoxycarbonyl)-L-tryptophyl]-amino] - 1,3-dioxoperhydropyrido[1,2-c]pyrimidine, displays nanomolar CCK-A receptor affinity and higher than 8000-fold potency at the CCK-A than at the CCK-B receptor. As CCK-A antagonist, this compound inhibits the CCK-8-evoked amylase release from pancreatic acinar cells at a low concentration, similar to that of the typical antagonist Devazepide. Highly strict stereochemical requirements for CCK-A receptor binding and selectivity have been found. The L-Trp and the 4a,5-trans disposition of the bicyclic perhydropyrido[1,2-c]pyrimidine are essential for binding potency and selectivity.