Abstract: Here we investigated the mechanisms by which cardiovascular CB1 cannabinoid receptors may modulate the cardiac dysfunction, oxidative stress, and interrelated cell death pathways associated with acute/chronic cardiomyopathy induced by the widely used anti-tumour compound doxorubicin (DOX).
Abstract: Tissue factor (TF), a major initiator of blood coagulation, contributes to inflammation, atherosclerosis, angiogenesis, and vascular remodeling. Pharmacological agonists of soluble guanylate cyclase (sGC) attenuate systemic and pulmonary hypertension, vascular remodeling, and platelet aggregation. However, the influence of these novel pharmacophores on TF is unknown.
Abstract: Chronic pseudomonal bronchopulmonary infections in cystic fibrosis patients are frequently controlled with inhaled antibiotics. Dry-powder inhalable antibiotics are an attractive alternative to nebulized medications. We produced and evaluated microparticles composed of dipalmitoylphosphatidylcholine, albumin, and lactose as a model system for intrapulmonary delivery of ceftazidime, ciprofloxacin, and several combinations of the two, none of which is presently available for inhalation. Microparticles containing one or both antibiotics were prepared by spray-drying. Their Anderson cascade impactor deposition profiles showed 10-30% fine particle fractions of the nominal dose. Microparticles containing varying amounts of each antibiotic showed statistically different deposition profiles. Aerodynamics and deposition of microparticles co-encapsulating both antibiotics were similar to those of single-drug microparticles with the same proportion of ciprofloxacin alone. The antipseudomonal activities of microparticles co-encapsulating half of the 50% effective concentration (EC(50)) of both ceftazidime and ciprofloxacin (5 mg of particles containing 5% ceftazidime and 10% ciprofloxacin) were at least additive compared to particles containing the EC(50) of each antibiotic separately (5 mg of particles containing 10% ceftazidime or 5 mg of particles containing 20% ciprofloxacin). Co-encapsulation of the antibiotics in microparticles ensures co-deposition at desired ratios, improves the particles' aerodynamics and fine particle fraction, as compared to microparticles with equivalent amounts of ceftazidime alone, and achieves additive antipseudomonal activity.
Abstract: Hypoxic pulmonary vasoconstriction (HPV) preserves systemic arterial oxygenation during lung injury by diverting blood flow away from poorly ventilated lung regions. Ventilator-induced lung injury (VILI) is characterized by pulmonary inflammation, lung edema, and impaired HPV leading to systemic hypoxemia. Studying mice congenitally deficient in inducible nitric oxide synthase (NOS2) and wild-type mice treated with a selective NOS2 inhibitor, L-N(6)-(1-iminoethyl)lysine (L-NIL), we investigated the contribution of NOS2 to the impairment of HPV in anesthetized mice subjected to 6 h of either high tidal volume (HV(T)) or low tidal volume (LV(T)) ventilation. HPV was estimated by measuring the changes of left lung pulmonary vascular resistance (LPVR) in response to left mainstem bronchus occlusion (LMBO). LMBO increased the LPVR similarly in wild-type, NOS2(-/-), and wild-type mice treated with L-NIL 30 min before commencing 6 h of LV(T) ventilation (96% +/- 30%, 103% +/- 33%, and 80% +/- 16%, respectively, means +/- SD). HPV was impaired in wild-type mice subjected to 6 h of HV(T) ventilation (23% +/- 16%). In contrast, HPV was preserved after 6 h of HV(T) ventilation in NOS2(-/-) and wild-type mice treated with L-NIL either 30 min before or 6 h after commencing HV(T) ventilation (66% +/- 22%, 82% +/- 29%, and 85% +/- 16%, respectively). After 6 h of HV(T) ventilation and LMBO, systemic arterial oxygen tension was higher in NOS2(-/-) than in wild-type mice (192 +/- 11 vs. 171 +/- 17 mmHg; P < 0.05). We conclude that either congenital NOS2 deficiency or selective inhibition of NOS2 protects mice from the impairment of HPV occurring after 6 h of HV(T) ventilation.
Abstract: Phosphodiesterase 1 (PDE1) modulates vascular tone and the development of tolerance to nitric oxide (NO)-releasing drugs in the systemic circulation. Any role of PDE1 in the pulmonary circulation remains largely uncertain. We measured the expression of genes encoding PDE1 isozymes in the pulmonary vasculature and examined whether or not selective inhibition of PDE1 by vinpocetine attenuates pulmonary hypertension and augments the pulmonary vasodilator response to inhaled NO in lambs. Using RT-PCR, we detected PDE1A, PDE1B, and PDE1C mRNAs in pulmonary arteries and veins isolated from healthy lambs. In 13 lambs, the thromboxane A(2) analog U-46619 was infused intravenously to increase mean pulmonary arterial pressure to 35 mmHg. Four animals received an intravenous infusion of vinpocetine at incremental doses of 0.3, 1, and 3 mg.kg(-1).h(-1). In nine lambs, inhaled NO was administered in a random order at 2, 5, 10, and 20 ppm before and after an intravenous infusion of 1 mg.kg(-1).h(-1) vinpocetine. Administration of vinpocetine did not alter pulmonary and systemic hemodynamics or transpulmonary cGMP or cAMP release. Inhaled NO selectively reduced mean pulmonary arterial pressure, pulmonary capillary pressure, and pulmonary vascular resistance index, while increasing transpulmonary cGMP release. The addition of vinpocetine enhanced pulmonary vasodilation and transpulmonary cGMP release induced by NO breathing without causing systemic vasodilation but did not prolong the duration of pulmonary vasodilation after NO inhalation was discontinued. Our findings demonstrate that selective inhibition of PDE1 augments the therapeutic efficacy of inhaled NO in an ovine model of acute chemically induced pulmonary hypertension.
Abstract: Soluble guanylate cyclase (sGC) is a key signal-transduction enzyme activated by nitric oxide (NO). Impaired bioavailability and/or responsiveness to endogenous NO has been implicated in the pathogenesis of cardiovascular and other diseases. Current therapies that involve the use of organic nitrates and other NO donors have limitations, including non-specific interactions of NO with various biomolecules, lack of response and the development of tolerance following prolonged administration. Compounds that activate sGC in an NO-independent manner might therefore provide considerable therapeutic advantages. Here we review the discovery, biochemistry, pharmacology and clinical potential of haem-dependent sGC stimulators (including YC-1, BAY 41-2272, BAY 41-8543, CFM-1571 and A-350619) and haem-independent sGC activators (including BAY 58-2667 and HMR-1766).
Abstract: Reactive oxygen and nitrogen species, particularly peroxynitrite, are potent inducers of tissue damage during systemic inflammatory response and circulatory shock. Recent evidence indicates that the toxicity of these species largely depends on their ability to trigger activation of the nuclear enzyme poly(adenosine 5'-diphosphate ribose) polymerase-1 (PARP-1). Following excessive activation, PARP-1 depletes the intracellular stores of its substrate, nicotinamide adenine dinucleotide, thus slowing glycolysis, generation of high energy phosphates, and mitochondrial electron transport. Consequently, the severe metabolic crisis induced by PARP-1 activation results in acute cell dysfunction and necrotic cell death. In addition, activation of PARP-1 plays an important role in the upregulation of inflammatory cascades via a functional association with mitogen-activated protein kinases and several transcription factors, such as nuclear factor kappa B, resulting in augmented expression of pro-inflammatory cytokines, chemokines, adhesion molecules, and enzymes. In severe sepsis and hemorrhage, PARP-1 activation has emerged as one of the central mechanisms of systemic inflammation, endothelial dysfunction, peripheral vascular failure, and reduction of cardiac contractility. Innovative therapeutic strategies based on the pharmacological inhibition of PARP-1 catalytic activity might provide benefits by preventing tissue injury, organ dysfunction, and lethality associated with these conditions.
Abstract: Nitric oxide (NO), synthesized by NO synthases (NOS), plays a pivotal role in regulation of pulmonary vascular tone. To examine the role of endothelial NOS (NOS3) in hypoxic pulmonary vasoconstriction (HPV), we measured left lung pulmonary vascular resistance (LPVR), intrapulmonary shunting, and arterial PO2 (PaO2) before and during left mainstem bronchus occlusion (LMBO) in mice with and without a deletion of the gene encoding NOS3. The increase of LPVR induced by LMBO was greater in NOS3-deficient mice than in wild-type mice (151 +/- 39% vs. 109 +/- 36%, mean +/- SD; P < 0.05). NOS3-deficient mice had a lower intrapulmonary shunt fraction than wild-type mice (17.1 +/- 3.6% vs. 21.7 +/- 2.4%, P < 0.05) during LMBO. Both real-time PaO2 monitoring with an intra-arterial probe and arterial blood-gas analysis during LMBO showed higher PaO2 in NOS3-deficient mice than in wild-type mice (P < 0.05). Inhibition of all three NOS isoforms with Nomega-nitro-L-arginine methyl ester (L-NAME) augmented the increase of LPVR induced by LMBO in wild-type mice (183 +/- 67% in L-NAME treated vs. 109 +/- 36% in saline treated, P < 0.01) but not in NOS3-deficient mice. Similarly, systemic oxygenation during one-lung ventilation was augmented by L-NAME in wild-type mice but not in NOS3-deficient mice. These findings indicate that NO derived from NOS3 modulates HPV in vivo and that inhibition of NOS3 improves systemic oxygenation during acute unilateral lung hypoxia.
Abstract: To evaluate the cardiopulmonary effects of the novel endothelin receptor antagonist tezosentan in endotoxin-induced lung injury in sheep and to assess the dose response to tezosentan and endothelin-1 in healthy sheep.
Abstract: Aging is associated with profound changes in the structure and function of the heart. A fundamental understanding of these processes, using relevant animal models, is required for effective prevention and treatment of cardiovascular disease in the elderly. Here, we studied cardiac performance in 4- to 5-mo-old (young) and 24- to 26-mo-old (old) Fischer 344 male rats using the Millar pressure-volume (P-V) conductance catheter system. We evaluated systolic and diastolic function in vivo at different preloads, including preload recruitable stroke work (PRSW), maximal slope of the systolic pressure increment (+dP/dt), and its relation to end-diastolic volume (+dP/dt-EDV) as well as the time constant of left ventricular pressure decay, as an index of relaxation. The slope of the end-diastolic P-V relation (EDPVR), an index of left ventricular stiffness, was also calculated. Aging was associated with decrease in left ventricular systolic pressure, +dP/dt, maximal slope of the diastolic pressure decrement, +dP/dt-EDV, PRSW, ejection fraction, stroke volume, cardiac and stroke work indexes, and efficiency. In contrast, total peripheral resistance, left ventricular end-diastolic volume, left ventricular end-diastolic pressure, and EDPVR were greater in aging than in young animals. Taken together, these data suggest that advanced aging is characterized by decreased systolic performance accompanied by delayed relaxation and increased diastolic stiffness of the heart in male Fischer 344 rats. P-V analysis is a sensitive method to determine cardiac function in rats.
Abstract: Inhaled nitric oxide (NO) is a potent and selective pulmonary vasodilator, which induces cGMP synthesis by activating soluble guanylate cyclase (sGC) in ventilated lung regions. Carbon monoxide (CO) has also been proposed to influence smooth muscle tone via activation of sGC. We examined whether direct stimulation of sGC by BAY 41-2272 would produce pulmonary vasodilation and augment the pulmonary responses to inhaled NO or CO.
Abstract: Flagellin is a recently identified bacterial product that elicits immune response via toll-like receptor 5. Here, we demonstrate that flagellin is an extraordinarily potent proinflammatory stimulus in the lung during sepsis. In vitro, flagellin triggers the production of interleukin (IL)-8 by human lung epithelial (A549) cells, with 50% of the maximal response obtained at a concentration of 2 x 10(-14) M. Flagellin also induces the expression of ICAM-1 in vitro. Intravenous administration of flagellin to mice elicited a severe acute lung inflammation that was significantly more pronounced than following lipopolysaccharide (LPS) administration. Flagellin induced a local release of proinflammatory cytokines, the accumulation of inflammatory cells, and the development of pulmonary hyperpermeability. These effects were associated with the nuclear translocation of the transcription NF-kappaB in the lung. Flagellin remained active in inducing pulmonary inflammation at doses as low as 10 ng/mouse. In the plasma of patients with sepsis, flagellin levels amounted to 7.1 +/- 0.1 ng/mL. Plasma flagellin levels showed a significant positive correlation with the lung injury score, with the alveolar-arterial oxygen difference as well as with the duration of the sepsis. Flagellin emerges as a potent trigger of acute respiratory complications in gram-negative bacterial sepsis.
Abstract: To evaluate the effects of a combination of methylene blue, an inhibitor of the nitric oxide pathway, and inhaled nitric oxide on endotoxin-induced acute lung injury in awake sheep.
Abstract: The aim of the present study was to test the effects of a topical administration of a novel nitric oxide donor, linear polyethylenimine-nitric oxide/nucleophile adduct (DS1), on vaginal blood flow and hemodynamics in rats. Laser Doppler flowmetry was used to measure blood flow changes following topical application of DS1 (0.3 or 1.5 mg in 0.15 ml saline) into the vagina of anesthetized Wistar rats. In vivo hemodynamic parameters were measured with Millar-tip-catheter placed in the left ventricle. DS1 (1.5 mg) increased vaginal blood flow by 191+/-24, 226+/-22 and 166+/-23% of the baseline value (at 5, 15 and 30 min, respectively, after application) without affecting systemic blood pressure, heart rate and cardiac function. The increased vaginal blood flow following DS1 application returned to baseline between 45 and 60 min. Thus, topical application of nitric oxide donors such as DS1 may be useful for the treatment of female sexual dysfunction that develops due to an impairment of local blood flow supply to the vaginal tissue.
Abstract: Recent experimental evidence suggests that activation of adenosine triphosphate (ATP)-sensitive potassium channels contributes to vascular failure and early mortality after hemorrhagic shock. The present investigation evaluated the effects of the water-soluble sodium salt of glipizide, an inhibitor of ATP-sensitive potassium channels, in anesthetized and awake rats subjected to severe controlled hemorrhage.
Abstract: The authors recently demonstrated that methylene blue (MB), an inhibitor of the nitric oxide (NO) pathway, reduces the increments in pulmonary capillary pressure, lung lymph flow and protein clearance in endotoxaemic sheep. In the present study, the authors examined whether MB influences pulmonary haemodynamics and accumulation of extravascular lung water (EVLW) by mechanisms other than the NO pathway. Sixteen awake, chronically-instrumented sheep randomly received either an intravenous injection of MB 10 mg x kg(-1) or isotonic saline. Thirty minutes later, all sheep received an intravenous infusion of Escherichia coli endotoxin 1 microg x kg(-1) for 20 min and either an intravenous infusion of MB 2.5 mg x kg(-1) x h(-1) or isotonic saline for 6 h. MB markedly attenuated the endotoxin-induced pulmonary hypertension and right ventricular failure, and reduced the accumulation of EVLW. Moreover, MB reduced the increments in plasma thromboxane B2 and 6-keto-prostaglandin F1alpha, and abolished the febrile response. However, MB had no effect on the changes in circulating neutrophils, serum hyaluronan, and total haemolytic activity of the alternative complement pathway. The authors conclude that in sheep, methylene blue attenuates the endotoxin-induced pulmonary hypertension and oedema, at least in part, by inhibiting the cyclo-oxygenase products of arachidonic acid. This is a novel effect of methylene blue in vivo.
Abstract: Pulmonary hypertension and edema are mainstays of acute lung injury (ALI). We synthesized linear polyethylenimine-nitric oxide/nucleophile adduct (DS-1), a water-soluble nitric oxide donor, and demonstrated that it is a potent relaxant of precontracted rat aortic rings without inducing desensitization. Moreover, DS-1 does not suppress the viability of human pulmonary epithelial cells in vitro. We also tested whether DS-1 counteracts ALI in endotoxemic sheep. Animals were instrumented for a chronic study. In 16 awake, spontaneously breathing sheep, Escherichia coli endotoxin (10 ng/kg/minute) was infused for 8 hours. From 2 hours of endotoxemia, sheep received either nebulized DS-1 (1 mg/kg/hour) or isotonic saline. DS-1 reduced endotoxin-induced rises in pulmonary arterial and microwedge pressures and vascular resistance index by 40-70%. In parallel, DS-1 decreased the accumulation of extravascular lung water by 60-70% and reduced the increment in right ventricle stroke work index and the falls in right ventricle ejection fraction, stroke volume, and left ventricle stroke work indices. Furthermore, DS-1 reduced venous admixture and improved arterial oxygen saturation. In four healthy animals, DS-1 alone slightly increased arterial oxygenation but had no other effects. Thus, aerosolized DS-1 attenuates endotoxin-induced ALI in sheep by reducing pulmonary hypertension and edema and improving myocardial function and gas exchange.
Abstract: To determine whether methylene blue (MB), an inhibitor of soluble guanylate cyclase and nitric oxide synthase, alters lung hemodynamics and fluid filtration after endotoxin in sheep.
Abstract: To evaluate the effects of continuous infusion of methylene blue (MB), an inhibitor of the nitric oxide pathway, on hemodynamics and organ functions in human septic shock.
Abstract: In endotoxemia and septic shock, enhanced generation of endogenous nitric oxide (NO) contributes to myocardial depression, hypotension, and derangement of gas exchange. We hypothesized that continuous infusion of methylene blue (MB), an inhibitor of the NO pathway, would counteract these effects in endotoxemic sheep.
Abstract: It has been suggested that enhanced generation of nitric oxide by inducible nitric oxide synthase (iNOS) may contribute to acute lung injury. We hypothesized that aminoguanidine (AG), a proposed selective inhibitor of iNOS, would alter pulmonary hemodynamics, fluid filtration, and gas exchange after endotoxin in chronically instrumented awake sheep. Eighteen sheep were randomly assigned to receive either AG (10 mg/kg + 1 mg/kg/h), or NaCl 0.9% intravenously for 4 h, beginning 2 h after injection of Escherichia coli endotoxin (1 microgram/kg). After endotoxin, pulmonary artery pressure (Ppa), capillary pressure (Pc), and vascular resistance index (PVRI) rose concomitantly with six-fold increments in lung lymph flow (Q L) and protein clearance (CL). Extravascular lung water (EVLW) doubled, as assessed with the thermal dye dilution technique; Pa(O(2)) decreased, AaPO(2) and venous admixture (Q S/Q T) increased. After AG, Q L and CL increased further by approximately 30%, whereas EVLW remained unchanged, despite an additional increase in Pc. Ppa, PVRI, and systemic vascular resistance index rose, whereas cardiac index and pulmonary blood volume index declined. In addition, Pa(O(2)) rose, and AaPO(2) and Q S/Q T decreased. We conclude that in endotoxemic sheep, AG improves gas exchange and increases Q L and CL, whereas EVLW remains unchanged in spite of enhanced Pc. Apparently, increased lymphatic drainage prevents EVLW from rising after AG.
