The pulmonary pharmacology of [4-methoxy-N1-(4-trans-nitrooxycyclohexyl)-N3-(3-pyridinylmethyl)-1,3-benzenedicarboxamide] (2NTX-99), an anti-atherotrombotic compound with therapeutic potential in pathological conditions that target lung vasculature.

The pharmacological activity of 2NTX-99 ([4-methoxy-N1-(4-trans-nitrooxycyclohexyl)-N3-(3-pyridinylmethyl)-1,3-benzenedicarboxamide]) was investigated in vitro in the intact, rat pulmonary vasculature and in guinea pig airways. Rat lungs were perfused at constant flow and changes in vascular tone recorded. Challenge with the TXA2 analogue 9,11-dideoxy-9α11α-methanoepoxy ProstaglandinF2 (U46619, 0.5 µM) increased vessel tone (32.48±1.5 vs 13.13±0.56 mmHg; n=12). 2NTX-99 (0.1-100 µM; n=5), caused a concentration-dependent relaxation, prevented by 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, 10 µM, n=4), an inhibitor of soluble guanylate cyclase. Acetylcholine (0.1-10 µM; n=3) and a reference NO-donor, isosorbide-5-mononitrate (5-100 µM; n=4), were ineffective. Intraluminal perfusion of washed human platelets (2 × 108 cells/ml) increased intravascular pressure after challenge with arachidonic acid (AA, 2 µM; n=5), an increase abolished by acetylsalicylic acid and significantly reduced by 2NTX-99 (40 µM; n=5). TXB2 in the lung perfusate was detected after platelet activation, 2NTX-99 inhibited TXA2 synthesis (6.45±0.6 and 1.10±0.2 ng/ml, respectively). 2NTX-99 did not alter central or peripheral airway responsiveness to Histamine (0.001-300 µM; n=6), U46619 (0.001-3 µM, n=3) or LTD4 (1 pM-1 µM; n=6). 2NTX-99 vasodilates the pulmonary vasculature via the release of nitric oxide (NO) and reduces intraluminal, AA-induced, TXA2 formation. The combined activity of 2NTX-99 as an NO-donor and a TXA2-synthesis inhibitor provides strong support for its potential therapeutic use in pathologies of the pulmonary vascular bed (e.g. pulmonary hypertension).

Hemodynamic improvement as an additional parameter to evaluate the safety and tolerability of the molecular adsorbent recirculating system in liver failure patients.

BACKGROUND: The molecular adsorbent recirculating system (MARS) is an extracorporeal acute liver failure (ALF) support system method using albumin-enriched dialysate to remove albumin-bound toxins. PATIENTS AND METHODS: Since 1999 we performed 2027 MARS treatments in 191 patients: 39 fulminant hepatic failure (FHF), 16 primary nonfunction (PNF), 21 delayed function (DF), 94 acute-on-chronic liver failure (AoCHF), 7 post-hepatic resection, and 14 intractable pruritus. RESULTS: We divided the complications by the AoCHF versus the ALF populations. Among 83 ALF patients, we observed worsening of hemodynamic parameters in 16 patients: 3 with PNF, 2 with DF without retransplantation, 9 with FHF, and 2 after hepatic resection. Among 94 AoCHF patients, 42 showed hemodynamic instability requiring intensive care unit support. Our study did not note significant adverse effects (1.8%), except for infections and hemorrhage from the central venous catheter not due to MARS treatment. The thrombocytopenia was controlled through administration of platelets before the start of treatment when a patient showed a level under 30,000 mm(3). CONCLUSION: Our results confirmed that nonbiological hepatic support by MARS was safe and tolerable.

Antagonism of thromboxane receptors by diclofenac and lumiracoxib.

BACKGROUND AND PURPOSE: Non-steroidal anti-inflammatory drugs (NSAIDs) are analgesic and anti-inflammatory by virtue of inhibition of the cyclooxygenase (COX) reaction that initiates biosynthesis of prostaglandins. Findings in a pulmonary pharmacology project gave rise to the hypothesis that certain members of the NSAID class might also be antagonists of the thromboxane (TP) receptor. EXPERIMENTAL APPROACH: Functional responses due to activation of the TP receptor were studied in isolated airway and vascular smooth muscle preparations from guinea pigs and rats as well as in human platelets. Receptor binding and activation of the TP receptor was studied in HEK293 cells. KEY RESULTS: Diclofenac concentration-dependently and selectively inhibited the contraction responses to TP receptor agonists such as prostaglandin D2 and U-46619 in the tested smooth muscle preparations and the aggregation of human platelets. The competitive antagonism of the TP receptor was confirmed by binding studies and at the level of signal transduction. The selective COX-2 inhibitor lumiracoxib shared this activity profile, whereas a number of standard NSAIDs and other selective COX-2 inhibitors did not. CONCLUSIONS AND IMPLICATIONS: Diclofenac and lumiracoxib, in addition to being COX unselective and highly COX-2 selective inhibitors, respectively, displayed a previously unknown pharmacological activity, namely TP receptor antagonism. Development of COX-2 selective inhibitors with dual activity as potent TP antagonists may lead to coxibs with improved cardiovascular safety, as the TP receptor mediates cardiovascular effects of thromboxane A2 and isoprostanes.

A new class of nitric oxide-releasing derivatives of cetirizine; pharmacological profile in vascular and airway smooth muscle preparations.

BACKGROUND AND PURPOSE: The pharmacological properties of compounds NCX 1512 and NCX 1514, synthesized by linking the histamine H1-receptor antagonist cetirizine to NO-releasing spacer groups, are reported. The aim was to establish if the compounds retained the antihistamine action of the parent compound, to assess their efficacy as NO donors and to test if they had broader antiallergic activity than cetirizine in the lung. EXPERIMENTAL APPROACH: Antihistamine activity of NCX 1512 and NCX 1514 was investigated in vitro in the guinea pig ileum, in tracheal rings (GPTR) and lung parenchymal strips (GPLP) of the guinea-pig. The NO-releasing capacity was investigated in vascular preparations; the isolated rabbit and guinea-pig aorta and guinea-pig pulmonary artery. Kinetics of NO release were assessed in a rat whole blood assay. KEY RESULTS: Both NCX 1512 and NCX 1514 retained activity as H1-receptor antagonists in the guinea pig ileum and airway preparations. The NO-releasing NCX compounds relaxed the rabbit aorta, an action prevented by the guanylyl cyclase inhibitor ODQ (10 microM). NCX 1512 and NCX 1514 did not relax the antigen (ovalbumin) pre-contracted GPTR, whereas the NO donors NCX 2057 and DEA-NONOate relaxed guinea-pig pre-contracted vascular and tracheal preparations. Cetirizine (1-100 microM) and NCX 1512 (1-100 microM) reduced the cumulative (0.01-100 microg ml(-1)) ovalbumin-induced constriction in GPTR, but had no significant effect in GPLP. CONCLUSIONS AND IMPLICATIONS: NCX 1512 and NCX 1514 act as antihistamines and NO donors. However, there was no improved effect compared to cetirizine on antigen-induced constriction of the central and peripheral lung.

Activation of cerebral endothelium is required for mononuclear cell recruitment in a novel in vitro model of brain inflammation.

Brain inflammation is a common event in the pathogenesis of several neurological diseases. It is unknown whether leukocyte/endothelium interactions are sufficient to promote homing of blood-borne cells into the brain compartment. The role of mononuclear cells and endothelium was analyzed in a new experimental model, the isolated guinea-pig brain maintained in vitro by arterial perfusion. This preparation allows one to investigate early steps of brain inflammation that are impracticable in vivo. We demonstrate by confocal microscopy analysis that in vitro co-perfusion of pro-inflammatory agents and pre-activated fluorescent mononuclear cells induced endothelial expression of selectins and intracellular adhesion molecule-1 in correspondence of arrested mononuclear cells, and correlates with a moderate increase in blood-brain barrier permeability. Separate perfusion of pro-inflammatory agents and mononuclear cells induced neither mononuclear cell adhesion nor adhesion molecule expression. We demonstrate that co-activation of mononuclear cells and cerebral endothelium is an essential requirement for cell arrest and adhesion in the early stages of experimental cerebral inflammation.

The effect of agonists and antagonists on the morphology of non-transformed human smooth muscle cell in vitro.

In the present study we used scanning electron microscopy (SEM) to investigate morphological changes of non-transformed line of human bronchial smooth muscle cells (bSMC) induced by different agonists. Explants of normal bronchi were dissected and subcultured between 2 and 6 passage. In addition, smooth muscle actin content was assessed by SDS-PAGE electrophoresis, and its isoelectric point by IPG followed by immunoblotting. SMC were fixed by 2.0% paraformaldehyde and 2% glutaraldehyde and then were post-fixed by OSO4 and followed by dehydration and gold coating. Cytosolic free calcium was measured using adherent cells incubated with 500 microM Fura-2 acetoxymethylester and monitored by single excitation fluorimetry. Cultured cells possess predominantly charged actin isoforms with pI at 4.95; they respond to acetylcholine (100 microM), bradykinin (5 microM) and sulfidopeptide leukotriens (0.3-1.0 microM) with contraction, marked morphological lesions, such as widespread monolayer disorganization, extension of cell contacts. The number of microvilli on the cell surfaces was correlated with the degree of the alterations of the cellular morphology. Receptor antagonists antagonized these changes: atropine (0.3 microM), HOE 140 (1 microM) and MK 571 (1 microM). Acetylcholine and bradykinin induced a biphasic elevation of cytosolic calcium, which was antagonized by their receptor antagonists. Calcium changes in response to agonists were maintained over repetitive passages. Therefore, morphological changes seen in human bronchial SMC in culture with physiological response to various, structurally unrelated agonists can be future concern for the study the possible testing of the different pharmacological substances.

Neutrophils, endothelial cells, and cysteinyl leukotrienes: a new approach to neutrophil-dependent inflammation?

Cysteinyl leukotrienes (cys-LT) have been historically involved with the pathogenesis of asthma, and cys-LT receptor antagonists and synthesis inhibitors are currently in use for the therapy of this disease. Nevertheless cys-LT possess very potent proinflammatory activities and may play a significant role in inflammatory processes other than asthma. Recent evidences obtained in our laboratory, as well as in others, show that unexpected, biologically significant amounts of cys-LT are formed upon cell-cell cooperation between neutrophils and endothelial cells, resulting from transfer of the synthesis intermediate leukotriene A4 from neutrophils to endothelial cells. Cys-LT formed upon neutrophil adhesion to endothelial cells may contribute to the alterations of microvasculature associated with the inflammatory response. In particular, nonsteroidal anti-inflammatory drug (NSAIDs)-induced neutrophil adhesion to gastric wall microvessels may contribute to the gastric damage associated to the use of NSAIDs. In agreement with this hypothesis, dual 5-LOX/COX inhibitors are characterized by reduced gastric damage when compared to nonspecific COX-inhibitors. Evidence provide support for the involvement of cys-LT in neutrophil-dependent inflammatory responses and suggest new potential application of 5-LO inhibition in anti-inflammatory pharmacological treatment.

The Cycloxygenase-2 inhibitor SC58236 is neuroprotective in an in vivo model of focal ischemia in the rat.

Focal ischemia was induced in the fronto-parietal region of rat brain, by injection of Rose Bengal, followed by light activation. Focal ischemia was accompanied by formation of PGD(2) peaking 60-90 min post irradiation and declining thereafter. Increased Cycloxygenase-2 (COX-2) expression was also observed. Control ischemic rats showed distinct morphological alterations with necrosis of neurons, glial cells and blood vessels, surrounded by a halo with pyknotic cells with cytoplasm swelling and vacuolization. Compound SC58236, a selective COX-2 inhibitor, dose-dependently prevented, ischemia-induced eicosanoid formation (area under the curve (AUC) of controls: 3.11 +/- 0.87; AUC of 20 mg/kg SC58236: 0.39 +/- 0.24), and caused significant reduction of damaged area (30.7 and 18.9% at SC58236 20 and 6.6 mg/kg), suggesting that selective inhibitors of COX-2 are neuroprotective.

Leukotriene D4-induced activation of smooth-muscle cells from human bronchi is partly Ca2+-independent.

Cysteine-containing leukotrienes (cysteinyl-LTs) are potent bronchoconstrictors and play a key role in asthma. We found that histamine and LTD4 markedly constrict strips of human bronchi (HB) with similar efficacy. However, in human airway smooth-muscle (HASM) cells, LTD4, at variance with histamine, elicited only a small, transient change in intracellular calcium ion concentration. HASM cells express both Ca2+-dependent and -independent isoforms of protein kinase C (PKC) (i.e., PKC-alpha and PKC-alpha ). Western blot analysis showed that PKC-alpha is activated by histamine and, to a lesser extent, by LTD4, whereas only LTD4 translocates PKC-alpha. This translocation was specifically inhibited by the LTD4 antagonist pobilukast. Phorbol-dibutyrate ester (PDBu) (a PKC activator) contracted HB strips to the same extent in the presence as in the absence of extra- and intracellular Ca2+. In the absence of Ca2+, LTD4 contracted HB strips to the same extent as did PDBu, suggesting the involvement of a Ca2+-independent PKC in LTD4-mediated signal transduction. PDBu-induced desensitization and the PKC inhibitor H7 abolished the slow and sustained LTD4-triggered contraction of HB strips in the absence of Ca2+, although H7 did not greatly affect the response in the presence of the ion. Thus, in human airways, we identified a novel LTD4 transduction mechanism linked to bronchial smooth-muscle contraction, which is partly independent of Ca2+ and involves the activation of PKC-alpha.

Effect of endogenous and exogenous prostaglandin E(2) on interleukin-1 beta-induced cyclooxygenase-2 expression in human airway smooth-muscle cells.

We studied the effect of endogenous and exogenous prostaglandin E(2) (PGE(2)), a metabolite of arachidonic acid through the cyclooxygenase (COX) pathway, on interleukin (IL)-1 beta-induced COX-2 expression, using primary cultures of human bronchial smooth-muscle cells (HBSMC). Treatment with exogenous PGE(2) resulted in enhanced expression of IL-1 beta-induced COX-2 protein and messenger RNA (mRNA) as compared with the effect of the cytokine per se. Inhibition of PGE(2) production with a nonselective COX inhibitor (flurbiprofen, 10 microM) resulted in a significant reduction in IL-1 beta- induced COX-2 expression, supporting a role of endogenous COX metabolites in the modulation of COX-2 expression. None of the experimental conditions used in the study affected the expression of constitutive cyclooxygenase (COX-1). Treatment with cycloheximide to inhibit translation, and with dexamethasone or actinomycin D to inhibit transcription, linked the effect of PGE(2) to the transcriptional level of COX-2 mRNA rather than to a potential effect on protein and/or mRNA stabilization. PGE(2) increased adenylate cyclase activity in a concentration dependent manner, and forskolin, a direct activator of adenylate cyclase, caused a marked increase in IL-1 beta-dependent COX-2, suggesting the existence of a causal relationship between the two events. The same results were observed with salbutamol, a bronchodilator that acts by increasing cyclic adenosine monophosphate. The effect of PGE(2) on COX-2 expression may contribute to the hypothesized antiinflammatory role of PGE(2) in human airways, providing a self-amplifying loop leading to increased biosynthesis of PGE(2) during an inflammatory event.

Nitric oxide synthase inhibitors unmask acetylcholine-mediated constriction of cerebral vessels in the in vitro isolated guinea-pig brain.

The control of arterial vascular tone by acetylcholine contributes to the regulation of cerebral blood flow. We analysed the effects of intraluminal application of acetylcholine (1microM) on the cerebral vascular tone by measuring changes in resistance to perfusion pressure in an isolated guinea-pig brain preparation maintained in vitro by arterial perfusion under constant flow. Acetylcholine induced a reproducible, fast-onset dilation that was prevented by the nitric oxide scavenger Methylene Blue (10microM) and by the muscarinic receptor antagonist atropine (0.1microM). Prolonged arterial perfusion with the nitric oxide synthase inhibitors N-nitro-L-arginine (1mM) and N-nitro-L-arginine methyl ester (30-100microM) induced a slowly developing increase of 25.9+/-13. 44mmHg in vascular tone and blocked the acetylcholine-induced vasodilation. In these experimental conditions, the dilation determined by the nitric oxide donor nitroprusside (0.1microM) was unaffected. In five experiments, the blockade of dilation unmasked a slow acetylcholine-mediated vasoconstriction (14.40+/-3.85mmHg) that was antagonized by atropine.The results demonstrate that acetylcholine exerts two simultaneous and opposite effects on guinea-pig cerebral vessels, characterized by a slow direct constriction concealed in physiological conditions by a fast vasodilation mediated through the release of nitric oxide by endothelial cells. Acetylcholine-mediated increase in vascular tone may play a role in aggravating cerebral perfusion when endothelial cell damage occurs during brain ischemia.

Monoclonal anti-CD18 antibody prevents transcellular biosynthesis of cysteinyl leukotrienes in vitro and in vivo and protects against leukotriene-dependent increase in coronary vascular resistance and myocardial stiffness.

BACKGROUND: Cysteinyl leukotrienes (cys-LT) can constrict small and large vessels and increase vascular permeability. Formation of cys-LT arising from polymorphonuclear leukocytes (PMNL) and endothelial cell cooperation (transcellular synthesis) led to the hypothesis that PMNL-endothelial cell adhesion may represent a key step toward the formation of vasoactive cys-LT. METHODS AND RESULTS: We studied the effect of pretreatment with a monoclonal antibody directed against the CD18 subunit of PMNL beta(2)-integrin on the synthesis of cys-LT in a PMNL-perfused isolated rabbit heart in vitro and in a model of permanent ligature of the left descending coronary artery in the rabbit in vivo. Challenge of PMNL-perfused rabbit hearts with formyl-met-leu-phe (0.3 micromol/L) caused synthesis of cys-LT and increase in coronary perfusion pressure that were prevented by the anti-CD18 antibody. Similar results were obtained with the use of A-23187 (0.5 micromol/L) as a challenge. Persistence of PMNL-associated myeloperoxidase activity in the perfusion buffer was observed in the presence of the anti-CD18 antibody, indicating decreased PMNL infiltration. Coronary artery ligature in vivo increased urinary excretion of leukotriene E(4), supporting the activation of the 5-lipoxygenase pathway during experimental acute myocardial infarction. Pretreatment with the anti-CD18 antibody (1 mg/kg) prevented the increase in leukotriene E(4) excretion. CONCLUSIONS: These data support the importance of adhesion in promoting cys-LT formation, originating from PMNL-endothelial cell cooperation, and contributing to myocardial stiffness and increased coronary resistance.

Differential metabolism of exogenous and endogenous arachidonic acid in human neutrophils.

Leukotrienes can be produced by cooperative interactions between cells in which, for example, arachidonate derived from one cell is oxidized to leukotriene A(4) (LTA(4)) by another and this can then be exported for conversion to LTB(4) or cysteinyl leukotrienes (cys-LTs) by yet another. Neutrophils do not contain LTC(4) synthase but are known to cooperate with endothelial cells or platelets (which do have this enzyme) to generate cys-LTs. Stimulation of human neutrophils perfusing isolated rabbit hearts resulted in production of cys-LTs, whereas these were not seen with perfused hearts alone or isolated neutrophils. In addition, the stimulated, neutrophil-perfused hearts generated much greater amounts of total LTA(4) products, suggesting that the hearts were supplying arachidonate to the neutrophils and, in addition, that this externally derived arachidonate was preferentially used for exported LTA(4) that could be metabolized to cys-LTs by the coronary endothelium. Stable isotope-labeled arachidonate and electrospray tandem mass spectrometry were used to differentially follow metabolism of exogenous and endogenous arachidonate. Isolated, adherent neutrophils at low concentrations (to minimize transcellular metabolism between them) were shown to generate higher proportions of nonenzymatic LTA(4) products from exogenous arachidonate (deuterium-labeled) than from endogenous (unlabeled) sources. The endogenous arachidonate, on the other hand, was preferentially used for conversion to LTB(4) by the LTA(4) hydrolase. This result was not because of saturation of the LTA(4) hydrolase, because it occurred at widely differing concentrations of exogenous arachidonate. Finally, in the presence of platelets (which contain LTC(4) synthase), the LTA(4) synthesized from exogenous deuterium-labeled arachidonate was converted to cys-LTs to a greater degree than that from endogenous sources. These experiments suggest that exogenous arachidonate is preferentially converted to LTA(4) for export (not intracellular conversion) and raises the likelihood that there are different intracellular pathways for arachidonate metabolism.

Interleukin-4 enhances 15-lipoxygenase activity and incorporation of 15(S)-HETE into cellular phospholipids in cultured pulmonary epithelial cells.

15(S)-Hydroxyeicosatetraenoic acid (15[S]-HETE) is a 15-lipoxygenase (15-LO) metabolite that may play an important role in different pulmonary diseases. 15-HETE is synthesized by different epithelial cells and may be subsequently incorporated into cellular phospholipids. We studied the role of interleukin-4 (IL-4) on 15-LO activity and on 15(S)-HETE incorporation into cellular phospholipids by WI-26 pulmonary epithelial cells. 15-LO activity was evaluated by measuring 15(S)-HETE production, through combined reverse-phase-high-pressure liquid chromatography (RP-HPLC) separation and specific radioimmunoassay (RIA), after incubation with arachidonic acid (AA). We also studied 15-LO messenger RNA (mRNA) expression, using primed in situ (PRINS) labeling. IL-4 (10 ng/ml) markedly increased the percentage of 15-LO mRNA-bearing cells as well as 15-LO activity after 24, 48, and 72 h, with a maximal response at 48 h. Uptake and incorporation into cellular phospholipid was studied with [3H]15(S)-HETE, which showed that IL-4 was able to increase significantly 15(S)-HETE incorporation into WI-26 cells, with a maximal effect observed at 72 h. Cellular-lipid-associated [3H]15(S)-HETE, evaluated with RP-HPLC after base-catalyzed hydrolysis, increased concomitantly with disappearance of the radiolabel from the supernatant. Class separation of cellular lipids with normal-phase HPLC (NP-HPLC) showed that IL-4 increased [3H]15(S)- HETE incorporation mainly in the phosphatidylinositol (PI) fraction. The ability of IL-4 to promote 15-LO activity and incorporation into cellular phospholipids of human lung epithelial cells may be important in airway inflammation and in modulation of the potential autocrine function of 15(S)-HETE.

Inhibition of prostanoid synthesis protects against neuronal damage induced by focal ischemia in rat brain.

Changes in prostanoids concentration and effects of the non-specific COX inhibitor indomethacin on prostanoids levels and extension of tissue damage were studied following focal ischemia induction in the fronto-parietal region of rat brain. Ischemia was induced in animals bearing a transcerebral microdialysis probe by injection of Rose Bengal, a photosensitive dye, followed by light activation. Prostanoid levels were determined in the dialysate using immunoenzymatic techniques. PGD2 levels rose significantly up to 237+/-22 pg/ml compared to a basal level measured before ischemia induction which was below the detection limit. TXB2 changes were smaller and had a different time course. Treatment with indomethacin abolished the ischemia-induced PGD2 release and reduced the extent of injury to the area by 43+/-3.7%. These results suggest that prostanoid release may play an important role in neurodegenerative processes and that cyclooxygenase inhibitors may contribute to protect against cerebral tissue damage.

Simultaneous investigation of the neuronal and vascular compartments in the guinea pig brain isolated in vitro.

We describe a new method for studying the interactions between vascular tone changes and neuronal activity in the arterially perfused isolated brain of the adult guinea pig maintained in vitro. Electrophysiological recordings were performed in the piriform and entorhinal cortices with the entire arterial bed preserved or after vascular restriction to the territories of median and posterior cerebral arteries of one hemisphere. The changes in vascular tone were measured by means of a pressure transducer. The arterial pressure was 53.77+/-12.74 mmHg in control conditions at 30 degreesC. Intraluminal application of vasoactive drugs, such as the tromboxane A2 receptor agonist U46619 (0.1 microM) and 5-HT (3 microM), induced an increase in the resistance to perfusion pressure that was prevented by the selective antagonists. The preservation of the endothelial function was verified by inducing the release of endogenous endothelial relaxant factor after intraluminal application of 1 microM acetylcholine. The study of the reciprocal interactions between neuronal activity and vascular tone modifications demonstrated that evoked responses in the piriform and entorhinal cortices were not modulated by rapid changes of the vascular tone. A sustained and elevated plateau of vasoconstriction maintained for several minutes determined a cortical spreading depression. Epileptiform discharges induced in limbic cortices by GABAa receptor blockade were consistently associated with a vasodilation (8.26+/-2.8 mmHg). The results demonstrate that the in vitro isolated guinea pig brain preparation can be exploited for studying simultaneously neuronal activity and cerebrovascular motility.

Delapril slows the progression of atherosclerosis and maintains endothelial function in cholesterol-fed rabbits.

The renin-angiotensin system is an important modulator of arterial blood pressure and inhibitors of the angiotensin-converting enzyme (ACE-Is) and are currently used in the treatment of hypertension. The pleiotropic actions exerted by angiotensin II (AngII) on the functionality of the vessel wall may have pro-atherosclerotic outcomes; evidence for an anti-atherosclerotic effect of ACE-Is has been presented and an antioxidant effect has been attributed to thiol-containing ACE-Is, like Captopril. The present study has been undertaken to investigate the effect of Delapril, a lipophilic ACE-I, on the development of atherosclerosis in cholesterol-fed rabbits. While it did not correct hyperlipidemia, Delapril dose dependently inhibited the development of atherosclerosis, expressed as aortic area covered by lesions (23.3+/-4.1, 21.3+/-2.4 and 18.5+/-3.3% with Delapril at the daily dose of 5, 10 and 20 mg/kg, respectively, versus 38.2%+/-6.4 for control animals) and its effect was similar to that of Captopril (14.5+/-5.1% at the daily dose of 25 mg/kg). Furthermore, Delapril partially and dose dependently restored endothelium-dependent relaxation, which is impaired in vessels from hypercholesterolemic animals (51.80+/-12.18, 59.74+/-5.16, 69.13+/-8.70 maximal percent relaxation versus 48.26+/-3.05% for the untreated control and 67.67+/-6.72% for Captopril-treated animals). An antioxidant mechanism is unlikely to explain this data, since Delapril does not contain thiol groups. These observations suggest that Delapril may represent an effective pharmacological approach for the treatment of atherosclerosis during its early phases.