The role of ecotype-environment interactions in intraspecific trophic niche partitioning subsequent to stocking

Worldwide, stocking of fish represents a valuable tool for conservation and maintenance of species exploited by recreational fishing. Releases of hatchery-reared fish are more and more recognized to have numerous demographic, ecological, and genetic impacts on wild populations. However, consequences on intraspecific trophic relationships have rarely been investigated. In this study, we assessed the impacts of supplementation stocking and resulting introgressive hybridization on the trophic niches occupied by stocked, local, and hybrid lake trout (Salvelinus namaycush) within populations of piscivorous and planktivorous ecotypes stocked from a wild piscivorous source population. We compared trophic niches using stable isotope analysis (δ¹³ C and δ¹⁵ N) and trophic position among the three genetic origins. Putative genetic effects were tested with phenotype-genotype association of "life history" ecological traits (body size, growth rate, condition index, and trophic niche) and genotypes (RADseq SNP markers) using redundant discriminant analysis (RDA). Results showed that sympatry resulting from the stocking of contrasting ecotypes is a risk factor for niche partitioning. Planktivorous populations are more susceptible to niche partitioning, by competitive exclusion of the local fish from a littoral niche to an alternative pelagic/profundal niche. Observed niche partitioning is probably a manifestation of competitive interactions between ecotypes. Our results emphasize that ecotypic variation should be considered for more efficient management and conservation practices and in order to mitigate negative impact of supplementation stocking.

Mental Health Diagnoses, Symptoms, and Service Utilization in US Youth with Perinatal HIV Infection or HIV Exposure

Youth perinatally HIV infected (PHIV) or HIV exposed, but uninfected (PHEU), are aging into adolescence and adulthood with multiple complex risk factors for mental health (MH) problems and poor MH treatment utilization. Our aims were to estimate prevalence of MH diagnoses, clinically significant symptoms, and MH treatment utilization among youth with PHIV and among PHEU youth, 10-22 years old. We also aimed to identify correlates of diagnoses and treatment utilization. Analyses of data from standardized interviews, behavioral assessments, and chart review of 551 youth revealed that 36% had a previous or current MH diagnosis, with no significant HIV status group differences. Prevalence of clinically significant symptoms was 15% for both groups, of whom a third had no diagnosis, and half were not receiving treatment. Among youth with a current MH diagnosis, those with PHIV had greater utilization of services than PHEU youth (67% vs. 51%; p = 0.04). Factors associated with MH diagnoses and/or treatment utilization included caregiver characteristics, age and sex of child, HIV status, and stressful life events. Prevalence of MH diagnoses was higher than in the general population, but lower than in similar perinatally HIV-exposed cohorts, with some unmet service needs, particularly in PHEU youth. Family characteristics warrant careful consideration in early diagnosis and treatment of MH problems among youth affected by HIV.

Antiretroviral Drug Resistance Among Children and Youth in the United States With Perinatal HIV

Among 234 US youths with perinatal human immunodeficiency virus, 75% had antiretroviral resistance, substantially higher than that of the reference laboratory overall (36%-44%). Resistance to newer antiretrovirals and to all antiretrovirals in a class was uncommon. The only factor independently associated with future resistance was a higher peak viral load.

Prevalence and Persistence of Varicella Antibodies in Previously Immunized Children and Youth With Perinatal HIV-1 Infection

BACKGROUND

Two doses of live-attenuated varicella-zoster vaccine are recommended for human immunodeficiency virus 1 (HIV-1)-infected children with CD4% ≥ 15%. We determined the prevalence and persistence of antibody in immunized children with perinatal HIV (PHIV) and their association with number of vaccinations, combination antiretroviral therapy (cART), and HIV status.

METHODS

The Adolescent Master Protocol is an observational study of children with PHIV and perinatally HIV-exposed but uninfected (PHEU) children conducted at 15 US sites. In a cross-sectional analysis, we tested participants' most recent stored sera for varicella antibody using whole-cell and glycoprotein enzyme-linked immunosorbent assay. Seropositivity predictors were identified using multivariable logistic regression models and C statistics.

RESULTS

Samples were available for 432 children with PHIV and 221 PHEU children; 82% of children with PHIV and 97% of PHEU children were seropositive (P < .001). Seropositivity after 1 vaccine dose among children with PHIV and PHEU children was 100% at <3 years (both), 73% and 100% at 3-<7 years (P < .05), and 77% and 97% at ≥ 7 years (P < .01), respectively. Seropositivity among recipients of 2 vaccine doses was >94% at all intervals. Independent predictors of seropositivity among children with PHIV were receipt of 2 vaccine doses, receipt of 1 dose while on ≥ 3 months of cART, compared with none (adjusted odds ratio [aOR]: 14.0 and 2.8, respectively; P < .001 for overall dose effect), and in those vaccinated ≥ 3 years previously, duration of cART (aOR: 1.29 per year increase, P = .02).

CONCLUSIONS

Humoral immune responses to varicella vaccine are best achieved when children with PHIV receive their first dose ≥ 3 months after cART initiation and maintained by completion of the 2-dose series and long-term cART use.

Iron homeostasis in osteoporosis and its clinical implications

Osteoporosis has until now been considered to be a disease associated with abnormal calcium metabolism. However, an increasing number of clinical observations strongly suggest the association of iron overload with bone diseases, particularly in osteoporosis in menopausal women. The recent identification of hepcidin sheds new light into the crucial role of iron homeostasis in bone metabolism. Decreasing iron overload in cell studies as well as in animal experiments has been shown to improve bone cell metabolism and growth in vitro and in vivo. In view of the significant iron overload found in the aging population, especially in females, the therapeutic potential of lowering iron overload for the treatment of osteoporosis is suggested.

Metabolic abnormalities and viral replication are associated with biomarkers of vascular dysfunction in HIV-infected children

OBJECTIVES

HIV-infected children may be at risk for premature cardiovascular disease. We compared levels of biomarkers of vascular dysfunction in HIV-infected children (with and without hyperlipidaemia) with those in HIV-exposed, uninfected (HEU) children enrolled in the Pediatric HIV/AIDS Cohort Study (PHACS), and determined factors associated with these biomarkers.

METHODS

A prospective cohort study was carried out. Biomarkers of inflammation [C-reactive protein (CRP), interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP1)], coagulant dysfunction (fibrinogen and P-selectin), endothelial dysfunction [soluble intracellular cell adhesion molecule-1 (sICAM), soluble vascular cell adhesion molecule-1 (sVCAM) and E-selectin], and metabolic dysfunction (adiponectin) were measured in 226 HIV-infected and 140 HEU children. Anthropometry, body composition, lipids, glucose, insulin, HIV disease severity, and antiretroviral therapy were recorded.

RESULTS

The median ages of the children were 12.3 years in the HIV-infected group and 10.1 years in the HEU group. Body mass index (BMI) z-scores, waist and hip circumferences, and percentage body fat were lower in the HIV-infected children. Total and non-high-density lipoprotein (HDL) cholesterol and triglycerides were higher in HIV-infected children. HIV-infected children also had higher MCP-1, fibrinogen, sICAM and sVCAM levels. In multivariable analyses in the HIV-infected children alone, BMI z-score was associated with higher CRP and fibrinogen, but lower MCP-1 and sVCAM. Unfavourable lipid profiles were positively associated with IL-6, MCP-1, fibrinogen, and P- and E-selectin, whereas increased HIV viral load was associated with markers of inflammation (MCP-1 and CRP) and endothelial dysfunction (sICAM and sVCAM).

CONCLUSIONS

HIV-infected children have higher levels of biomarkers of vascular dysfunction than do HEU children. Risk factors associated with higher biomarkers include unfavourable lipid levels and active HIV replication.

Activation of peritoneal macrophages during the evolution of type 1 diabetes (insulitis) in streptozotocin-treated mice

The effects of lipopolysaccharide (LPS) and desArg9Bradykinin (DBK) on the release of nitric oxide (NO) from macrophages of mice 8, 12 and 18 days after having been treated with low doses of streptozotocin (STZ; 5 × 45 mg/kg) were studied. The results showed that LPS stimulated the release of NO from macrophages of untreated animals by 50% whereas the bradykinin B(1) agonist desArg9Bradykinin (DBK) increased the level of NO by 20%. This increased NO production was totally abolished by incubating the cells with R-954, a selective bradykinin B(1) antagonist. The release of NO from macrophages of STZ-treated mice incubated in the presence of LPS was more marked and reached approximately 220, 300 and 270% respectively from cells collected 8, 12 and 18 days after the STZ treatment. These significant increases were completely blocked by R-954 and were even below control values. Similarly the results showed that DBK stimulated by 50-75% the release of NO from macrophages of STZ-treated mice. The most marked stimulation was noted when the cells were collected 18 days after the treatment of the animals with STZ. Again in this set of experiments the B(1) antagonist completely blocked the release of NO which went even below control values. The results clearly suggest the upregulation of bradykinin B(1) receptors in mouse macrophages in the early phase of STZ-induced diabetes, an event that could even precede the onset of the diabetic hyperglycemia.

Therapeutic potential of RNA interference against cellular targets of HIV infection

RNA interference is not only very promising in identifying new targets for drug development, siRNA/shRNA themselves may be directly used as therapeutic agents. In inhibiting viral infections by RNA interference, both viral targets and cellular proteins have been evaluated. Most of the early studies in this field had chosen viral targets for RNA interference. However, recent efforts are mainly focusing on cellular proteins for RNA silencing due to the realization that a variety of viral responses substantially minimize siRNA effects. With the application of siRNA approaching, many new cellular targets relevant to HIV infection have been identified. The value of siRNA/shRNA in the treatment of AIDS is largely dependent on better understanding of the biology of HIV replication. Efforts in the identification of cellular processes with the employment of siRNA/shRNA have shed some new lights on our understanding of how HIV infection occurs. Furthermore, the relative specific effects and simplicity of design makes siRNA/shRNA themselves to be favorable drug leads.

The first preclinical pharmacotoxicological safety assessment of CGS 35601, a triple vasopeptidase inhibitor, in chronically instrumented, conscious, and unrestrained spontaneously hypertensive rats

CGS 35601 is a triple vasopeptidase inhibitor (VPI) of angiotensin-converting enzyme, neutral endopeptidase, and endothelin-converting enzyme-1 with respective IC50 values of 22, 2, and 55 nM. We characterized the safety profile and toxicity of escalating doses of CGS 35601 over a 20-day period in chronically instrumented, unrestrained, conscious, male, spontaneously hypertensive rats (SHR). Once instrumented with an arterial catheter, the SHR were placed in metabolic cages allowing daily assessment of hemodynamics and blood sampling for biochemical and hematological measurements. After a 7-day stabilization period, the SHR were divided into 2 groups: Gr. 1, (n = 13 to 18) receiving CGS 35601 at 0.01, 0.1, 1 and 5 mg kg(-1) day(-1) (continuous i.a. infusion) for 5 consecutive days/dose, followed by a 5-day washout; and Gr. 2, (n = 10) receiving vehicle (saline). The highest dose of CGS 35601 dose-dependently reduced MABP from 156 +/- 4 up to 94 +/- 5 mm Hg, whereas heart rate, metabolic, electrolytic, and hematological profiles, growth, diuresis, and renal activity were unaffected, and no hepatic or liver toxicities were observed. These results suggest that this novel triple VPI presents no safety concerns at this stage and may become of interest for the treatment of hypertension and other cardiovascular disorders. Long-term chronic experiments are needed to assess possible angioedema and increases in vascular permeability.

Triple VPI CGS 35601 reduces high blood pressure in low-renin, high-salt Dahl salt-sensitive rats

We previously reported that CGS 35601, a potent triple inhibitor of angiotensin-converting enzyme, neutral endopeptidase, and endothelin-converting enzyme 1, completely normalized mean arterial blood pressure (MABP) in 36-week-old spontaneously hypertensive rats, a normal renin model. The aim of the present study was to determine the effects of this triple vasopeptidase inhibitor (VPI) on the hemodynamic profile of instrumented, conscious, and unrestrained Dahl salt-sensitive (DSS) rats, a gene-prone, high-salt diet-induced low-renin hypertension model. Male DSS rats (mean weight [+/-SEM], 385 +/- 10 g) were fed a normal diet (Group 1) or a high-salt diet (Groups 2 and 3; 8% NaCl in food) for 6 weeks and then instrumented with a carotid catheter and placed individually in metabolic cages for 30 days. The hemodynamic, hematological, and biochemical profiles were assessed daily. Dose-dependent treatment started after a 7-day stabilization period in Groups 1 and 2 (vehicle dosage, 250 microl/hr) and Group 3 (CGS 35601 dosages of 0.1, 1, and 5 mg/kg/day for 6 days per dose by means of constant intra-arterial infusion), followed by a 5-day washout period. Two additional groups included normotensive Wistar rats (Group 4) and DSS rats that received a double high-salt solid (8% NaCl) and liquid (1% NaCl) diet (Group 5). The MABP in rats receiving CGS 35601 decreased in a dose-dependent fashion toward the baseline level observed in DSS rats receiving a normal diet. The heart rate was unaffected. The hemodynamic profile returned to normal during the washout period. This novel triple VPI is a potent and effective antihypertensive agent with a safe short-term profile that may be of interest for treating hypertension and other cardiovascular diseases. Other hypertensive rat models are being tested.

The hemodynamic and metabolic profiles of Zucker diabetic fatty rats treated with a single molecule triple vasopeptidase inhibitor, CGS 35601

CGS 35601 is a triple vasopeptidase inhibitor (VPI) of angiotensin converting enzyme (ACE), neutral endopeptidase (NEP), and endothelin (ET) converting enzyme-1 (ECE-1), with respective IC(50) values of 22, 2, and 55 nM. The aim of the present study was to establish the hemodynamic profile of Zucker diabetic fatty (Zdf)-Fatty rats, a high-fat diet gene-prone model developing spontaneous Type 2 diabetes (T2D) and the effects of CGS 35601. Male Zdf-Fatty (14 weeks, n = 17-23), Zdf-Lean (14 weeks, n = 8-10), and Wistar (14 weeks, n = 9-10) rats on distinct diets were implanted with a catheter in the left carotid and placed individually in a metabolic cage for 30 days. The hemodynamic profile and some metabolic biomarkers were assessed daily. After a 7-day stabilization period, the Zdf-Fatty rats were divided into two groups: Group 1, controls (n = 7-10) receiving vehicle-saline (250 microl/hr) and Group 2, (n = 10-13) receiving increasing doses of CGS 35601 (0.1, 1, and 5 mg/kg/day x 6 days each, intra-arterially) followed by a 5-day washout period. Mean arterial blood pressure (MABP) of young Zdf-Fatty rats was compared with age-matched Zdf-Lean and Wistar rats, which were found similar. MABP decreased by 5.9% (from baseline at 102 +/- 5 to 96 +/- 4 mmHg), 12.7% (to 89 +/- 6 mmHg) and 21.6% (to 80 +/- 4 mmHg), at 0.1, 1, and 5 mg/kg/day, respectively, in CGS 35601-treated Zdf-Fatty rats. Systolic and diastolic blood pressures were similarly reduced. The heart rate was not affected. Hyperglycemic status and insulin-resistance were not modulated by short-term treatment. CGS 35601 presented an excellent short-term safety profile. This novel molecule and class of VPI may be of interest for lowering vascular tone. Further long-term studies, once cardiovascular and renal complications have developed in this T2D rat model are warranted to define the efficacy of this class of VPI.

Profiling biochemical and hemodynamic markers using chronically instrumented, conscious and unrestrained rats undergoing severe, acute controlled hemorrhagic hypovolemic shock as an integrated in-vivo model system to assess new blood substitutes

The aim of the present study was to assess several biochemical and physiological endpoint parameters alongside controlled hemorrhagic and recovery phases of chronically instrumented, conscious and unrestrained healthy rats. Male Sprague-Dawley rats (12-14 weeks; 430+/-20 g; n=22-18) were instrumented with a saline-perfused femoral arterial catheter and placed individually in a metabolic cage for up to 20 days, allowing instant assessments of the hemodynamic profile and blood and urine sampling for hematological profile and biochemical measurements to assess hepatic, renal and metabolic functions. In addition, body weight, food and water intake, and diuresis were monitored daily. After a 7-day stabilization period, the rats underwent severe and acute hemorrhagic shock (HS) (removal of 50% of total circulating blood volume), kept in hypovolemic shock for an ischemic period of 50 min and then resuscitated over 10 min. Gr. 1 was re-infused with autologous shed blood (AB; n=10) whereas Gr. 2 was infused 1:1 with a solution of sterile saline-albumin (SA; 7% w/v) (n=8-12). Ischemic rats recovered much more rapidly following AB re-infusion than those receiving SA. Normal hemodynamic and biochemical profiles were re-established after 24 h. Depressed blood pressure lasted 4-5 days in SA rats. The hematological profile in the SA resuscitated rats was even more drastically affected. Circulating plasma concentrations of hemoglobin (-40%), hematocrit (-50%), RBC (-40%) and platelets (-41%) counts were still severely decreased 24 h after the acute ischemic event whereas WBC counts increased 2.2-fold by day 4. It took 5-9 days for these profiles to normalize after ischemia-reperfusion with SA. Diuresis increased in both groups (by 45+/-7% on day 1) but presented distinct electrolytic profiles. Hepatic and renal functions were normal in AB rats whereas altered in SA rats. The present set of experiments enabled us to validate a model of HS in conscious rats and the use of an integrated in vivo platform as a valuable tool to characterize HS-induced stress and to test new classes of blood substitutes in real time, post-event, over days.

Pathways for the bradykinin B1 receptor-mediated diabetic hyperalgesia in mice

OBJECTIVE

Experimental evidence has shown that the bradykinin B1 receptor (BKB1-R) is involved in the development of hyperalgesia associated with diabetes since specific BKB1-R antagonists significantly inhibited the hyperalgesic activity observed in streptozotocin (STZ)-mice in thermal nociceptive tests.

MATERIALS AND METHODS

The involvement of the nitric oxide (NO), the substance P (SP) and the calcitonin gene-related peptide (CGRP) pathways in mediating BKB1-R-induced hyperalgesia was evaluated. Diabetes was induced in male CD-1 mice by injecting STZ (200 mg/kg; i.p.). Nociception was assessed using the hot plate and tail immersion tests, one week following the injection of STZ.

RESULTS

The nitric oxide synthase (NOS) inhibitors (L-NNA, 20 mg/kg; L-NMMA, 30 mg/kg and AGUA, 50 mg/kg; i.p.), the SP antagonists (sendide and L-732,138, 100 microg/kg; i.v.) and the CGRP antagonist (hCGRP8-37, 100 microg/kg; i.v.) significantly attenuated the hyperalgesic activity and also reversed the potentiating effect of the BKB1- R agonist, DBK on diabetic hyperalgesia in STZ-mice.

CONCLUSIONS

These results support the involvement of BKB1-R in the development of diabetic hyperalgesia in STZ-mice through activation of the NO, SP and CGRP pathways.

Association of Endothelin with Lung Hemorrhage Induced by Immune Complexes in Rats

The participation of endothelins (ETs) in a model of neutrophil-dependent lung injury induced by intrabronchial instillation of rabbit antibodies to ovalbumin followed by i.v. injection of the antigens (Arthus reaction) was investigated. Hemorrhagic lesions were evaluated by measuring the extravasations of hemoglobin in lung parenchyma. From 5 min to 24 h after the Arthus reaction (AR), endothelin (ir-ET) levels in bronchoalveolar lavage fluid (BALF) and in plasma were measured by radioimmunoassay. BALF levels of ir-ET were not different between control and AR animals for the first 90 min after the antigen challenge but increased from 2 to 24 h after induction of AR. ET levels in the plasma did not change from the respective controls over the same 24 h period. Increased ir-ET in BALF was not affected by pretreatment with L-NAME (30 mg/kg, i.v.). A PAF antagonist (BN52021; 5 and 10 mg/kg, i.v.) increased ET content in BALF and decreased the intensity of the AR. Thiorphan (2 mg/kg, i.v.) inhibited the AR-induced hemorrhagic lesions in lungs. An ET(A) receptor antagonist, BQ-123 (1 mg/kg, i.v.) potentiated, whereas the ET(B) antagonist, BQ-788 (1 mg/kg, i.v.) inhibited the lung hemorrhage. It is concluded that ETs are released during and play a role in the lung AR.

Modulation of allergic and immune complex-induced lung inflammation by bradykinin receptor antagonists

OBJECTIVE

The effect of bradykinin (B(1) or B(2)) receptor antagonists was studied in allergic and immune-complex-induced lung inflammation.

METHODS

Lungs of BALB/c mice were examined 24 h after induction of lung inflammation, either allergic (ovalbumin-sensitized submitted to two aerosol of antigen, one week apart) or immune-complex induced (intratracheal instillation of IgG antibodies followed by intravenous antigen). The bradykinin B(2) receptor antagonist, HOE-140 or bradykinin B(1) receptor antagonist, R-954 were given intraperitoneally (100 microg/kg), 30 min before induction.

RESULTS

In allergic inflammation, pre-treatment with R-954 reduced eosinophil infiltration into the lungs, mucus secretion and the airway hyperreactivity to methacholine. Pre-treatment with HOE-140 increased eosinophil infiltration but did not affect the other parameters. In immune-complex inflammation, HOE-140 increased neutrophil infiltration but not their activation nor the hemorrhagic lesions. R-594 pre-treatment did not change the parameters examined.

CONCLUSION

These results show important modulatory effects of bradykinin B(1) and B(2) receptor antagonists in both models of lung inflammation.

[Oxygen and the superoxide anion. Modulation of NADPH oxidase?]

Oxidative stress which results from an imbalance between oxidant production and antioxidant defense mechanisms can promote modifications of lipids, proteins and nucleic acids. This review focuses on the different pathways leading to Reactive Oxygen Species (ROS) production in particular on NADPH oxidase activation. This enzyme is localized in numerous cells including phagocytes and vascular cells and composed of membrane and cytosolic sub-units. The activation of the NADPH oxidase is largely involved in inflammation associated diseases such as asthma, Systemic Inflammatory Response Syndrome and aging associated diseases such as atherosclerosis and neurodeneratives diseases. The modulation of NADPH oxidase could be a way to limit or prevent the development of these diseases.

Changes in vasoconstrictive hormones, natriuretic peptides, and left ventricular remodeling soon after anterior myocardial infarction

OBJECTIVE

Our purpose was to study the changes in vasoconstrictive neurohormones, N-terminal proatrial natriuretic peptide (Nt-proANP), and brain natriuretic peptide (BNP) and their relationship with left ventricular (LV) remodeling soon after anterior myocardial infarction (MI).

BACKGROUND

The Healing and Afterload Reducing Therapy (HEART) trial has shown that early use of ramipril improves left ventricular ejection fraction (LVEF) and attenuates LV remodeling when initiated soon after MI. This neurohumoral substudy of HEART investigates the changes in vasoconstrictive and natriuretic peptides and their relationship with LV remodeling.

METHODS

One hundred twenty-two patients had blood drawn for the measurement of catecholamines, endothelin-I, angiotensin II, Nt-proANP and BNP, and prostacyclins within 24 hours of an MI, and at 3, 14, and 90 days after the MI. Quantitative echocardiograms were performed at baseline and at 14 days.

RESULTS

All neurohormones except angiotensin II (P =.12) and prostaglandins were significantly elevated at baseline. Vasoconstrictive neurohormones decreased significantly over time but remained elevated at 14 days. Both Nt-proANP and BNP were elevated within the first 14 days. BNP decreased significantly by 90 days, whereas Nt-proANP exhibited no change between 14 and 90 days. Ramipril decreased plasma levels of angiotensin II at 3 days but had no effect on the other neurohormones.

CONCLUSIONS

Neurohumoral activation occurs and persists in patients with anterior MI and overall preserved LV function. Ramipril had only a modest impact on neurohormones despite its significant benefits on LV remodeling soon after MI.

Permeability of endothelial monolayers to albumin is increased by bradykinin and inhibited by prostaglandins

Using monolayers of bovine aortic endothelial cells (BAEC) in modified Boyden chambers, we examined the role of prostaglandins (PGs) in the bradykinin (BK)-induced increase of albumin permeability. BK induced a concentration-dependent increase of the permeability of BAEC, which reached 49.9 +/- 1% at the concentration of 10(-8) M. Two inhibitors of the prostaglandin G/H synthase, indomethacin (2.88 microM) and ibuprofen (10 microM), potentiated BK-induced permeability 1.8- and 3.9-fold, respectively. Exogenously administered PGE2 and iloprost, a stable analog of prostacyclin, attenuated the effect of BK in a concentration-dependent manner. Butaprost equally reduced the effect of BK, suggesting the participation of the EP2 receptor in this phenomenon. However, the EP4-selective antagonist AH-23848 did not significantly inhibit the protective effect of PGE2. The inhibitory effect of PGE2 was reversed by the adenylate cyclase inhibitor MDL-12330A (10 microM). These results suggest that BK-induced increase of permeability of BAEC monolayer to (125)I-labeled albumin is negatively regulated by PGs. This postulated autocrine activity of PGs may involve an increase in the intracellular level of cAMP.

Antigen-induced bronchial hyperreactivity and bronchopulmonary inflammation in rats: effect of TNF receptor binding protein

The effect of a receptor binding protein for tumor necrosis factor (TNFrbp) on cell infiltration, bronchial hyperreactivity, and release of inflammatory mediators were studied following antigen challenge in sensitized rats. A 3-fold increase in total cell number, mainly neutrophils and eosinophils, was noted in bronchoalveolar lavage (BAL) fluid 8 hours after antigen challenge. Antigen challenge also induced a significant hyperreactivity of the lower bronchus to carbachol and serotonin, but did not affect the reactivity of the trachea and upper bronchus. This increased responsiveness of the lower bronchus was transient, being detected 8 hours but not 24 hours after antigen challenge. Thromboxane B2 (TxB2), prostaglandin E2 (PGF2), and nitric oxide (NO) levels increased in the BAL fluid of sensitized rats 8 hours after antigen challenge by 197%, 172%, and 173%, respectively. TNFrbp treatment reduced by 83% the antigen-induced cell infiltration, with neutrophils being the cells most affected. The bronchial hyperreactivity induced by antigen challenge was also significantly inhibited by TNFrbp, whereas TxB2, PGE2, and NO levels in the BAL fluid were not affected. In our animal model, the cell infiltration and bronchial hyperreactivity appear to be mediated to some extent by TNF, but not by prostanoids nor NO.

Effects of a selective neutral endopeptidase and a nonselective neutral endopeptidase/endothelin-converting enzyme inhibitor on lipopolysaccharide-induced endotoxaemia in anaesthetized Sprague-Dawley rats

The gene expression and levels of endothelins (ETs) are increased in various animal models of lipopolysaccharide-(LPS) induced septic shock as well as in patients with endotoxaemia (ENDO). A positive correlation was reported between the expression and production of ETs, and the severity of haemodynamic and haematological disturbances, organ injury and circulatory failure in ENDO. Previous studies using ET(A)- and/or ET(B)-receptor antagonists exacerbated the effects of LPS in anaesthetized and conscious rats. We investigated the effect of a selective neutral endopeptidase (NEP) (CGS 24592) or a mixed NEP/endothelin-converting enzyme (ECE) (CGS 26303) inhibitor in LPS-induced ENDO in anaesthetized Sprague-Dawley rats. Four hours post-LPS injection, blood pressure was 39% lower in the presence of CGS 26303, compared to control-saline or LPS-injected rats. In rats treated with CGS 26303, white blood cells and platelet counts decreased, whereas lymphocytes increased. In addition, progressive liver dysfunction, characterized by increases in plasma bilirubin and alanine transferase, became even more apparent (higher than in those injected with LPS). Plasma creatinine and blood urea were similar to those of the LPS-injected group. Similar results were observed with CGS 24592. Thus, these inhibitors enhanced some, but not all, of the LPS-induced deleterious effects.

Effects of tranexamic acid and aprotinin, two antifibrinolytic drugs, on PAF-induced plasma extravasation in unanesthetized rats

Two antifibrinolytic drugs, tranexamic acid (TXA), and aprotinin (APR), are currently used to improve the recovery of patients following major surgery while reducing blood loss. Their mechanisms of action have yet to be fully understood. Here, we examined (1) the effects of TXA or APR on basal vascular permeability (VP) and (2) the effects of TXA or APR on platelet-activating factor (PAF)-induced increase of VP in normal unanesthetized rats. Evans blue dye (EB) bound to albumin was used as the marker of extravasation in selected tissues. In normal rats, PAF (1 microg/kg i.v.) increased VP in most selected tissues including bronchi, aorta, duodenum and pancreas without affecting blood pressure. TXA (up to 300 mg/kg i.v.) had no significant effect on basal VP in any tissues, while APR (30000 KIU/kg i.v.) decreased basal VP in 5 out of 8 tissues. Pre-treatment with TXA decreased PAF-induced increases of VP in the microcirculation of the thoracic and abdominal aorta, the duodenum and the pancreas, from 35% to 41%. TXA was mostly effective at an i.v. dose of 100 mg/kg with a 2 h of pre-treatment period. Pre-treatment with APR also reduced PAF-induced increases of VP in selected tissues by 35 to 61%. The i.v. dose of 30000 KIU/mg was optimal when injected at least 30 min before the administration of PAF + Evans blue. These results suggest that the beneficial effect of APR and TXA, following cardiopulmonary bypass (CPB) and other type of surgeries, may be attributed to the inhibition of plasma exudation mediated, at least in part, by PAF. Thus, TXA and APR may improve patients recovery by reducing the capillary leakage of albumin, associated with interstitial edema formation, and maintaining intravascular fluid volume.

Involvement of LTD(4)in allergic pulmonary inflammation in mice: modulation by cysLT(1)antagonist MK-571

Cysteinyl leukotrienes are potent inflammatory molecules playing a major role in asthma. The involvement of these mediators in hypersensitivity in mice is not well known. This study aimed at elucidating their implication by using MK-571, a cysLT(1)receptor antagonist. Mice were sensitized with a suspension of ovalbumin (8 microg) adsorbed to alum (2 mg) and were challenged with an aerosolized ovalbumin solution (0.5%). Inflammatory cell infiltration in the bronchoalveolar lavage (mostly eosinophils) following antigen challenge was inhibited by dexamethasone (0.1, 1 and 5 mg kg(-1)s.c.) and MK-571 (1, 10, 100 mg kg(-1)i.v.) in a dose-dependent manner. Maximal inhibition was 95% with 5 mg kg(-1)dexamethasone and 90% with 100 mg kg(-1)MK-571. When injected together they showed an additive inhibitory effect on eosinophil infiltration. Bronchial hyperreactivity, measured by the increased pulmonary insufflation pressure to carbachol injections, was also inhibited dose-dependently by MK-571. The EC(50)values for carbachol were of 22.39+/-1.12 microg kg(-1)in sensitized and challenged animals that did not receive MK-571 and increased to 43.65+/-1.10, 50.12+/-1.15 and 83.18+/-1.16 microg kg(-1)in animals treated with 1, 10 and 100 mg kg(-1)MK-571 respectively. Lung microvascular leakage (as measured by Evans blue extravasation) induced by antigen bronchoprovocation was reduced by 22% after treatment with 10 mg kg(-1)MK-571. All these inhibitory effects of MK-571 suggest a role for leukotriene D(4)in this animal model of allergic asthma.

Neurohormonal activation in severe heart failure: relations to patient death and the effect of treatment with flosequinan

BACKGROUND

Flosequinan is a direct-acting vasodilator that exerts beneficial hemodynamic effects and improves the exercise tolerance of patients with heart failure. However, a multicenter trial has demonstrated that long-term administration of flosequinan is associated with increased mortality rate. To explore a possible role of neurohormonal activation on this adverse outcome, we conducted a substudy to examine the plasma levels of 3 neurohormonal systems known to have prognostic implications in heart failure.

METHODS

At 20 participating Canadian centers, paired plasma samples at baseline and 1 month after randomization for the measurement of N-terminal atrial natriuretic peptide (N-ANP), angiotensin II, and norepinephrine were obtained in 234 patients (114 receiving flosequinan and 120 receiving placebo).

RESULTS

Treatment with flosequinan was associated with a decline in median plasma N-ANP levels (2139 pmol/L at baseline to 1625 pmol/L at 1 month [P =. 0001]), unchanged plasma angiotensin II levels (40 to 50 pmol/L [P =. 2700]), and a modest increase in plasma norepinephrine levels (391 to 439 pg/mL [P =.002]). These changes were not observed in the placebo group. Multivariate analysis of baseline variables revealed that plasma norepinephrine level predicted patients' death whereas analysis incorporating both baseline and 1-month variables indicated that plasma N-ANP level predicted patients' death. Furthermore, in the flosequinan group, a significant decline in plasma N-ANP level was observed in the survivors only. On multivariate analysis of baseline and 1-month data, the increase in plasma norepinephrine level did not predict the increase in heart rate associated with the use of flosequinan, suggesting that the 2 effects might be mediated by separate mechanisms.

CONCLUSIONS

Results of our study demonstrate that in patients with severe heart failure, baseline norepinephrine level predicts death. Flosequinan increases plasma norepinephrine level and heart rate in these patients through mechanisms that override its beneficial hemodynamic effects. Our study reinforces the concept that the direct actions of a pharmacologic agent may have a more profound impact on the prognosis of these patients than the hemodynamic effects.

Contribution of B(2) receptors for bradykinin in arthus reaction-induced plasma extravasation in wild-type or B(2) transgenic knockout mice

The aim of the present study was to investigate the contribution of bradykinin (BK) B(1) and B(2) receptors in a model of type III hypersensitivity, the reverse passive Arthus reaction (RPA), in wild-type mice and transgenic B(2) knockout littermates. BK (10 microg mouse(-1)) or bovine serum albumin (0.5 mg mouse(-1)) induced a sustained Evans blue extravasation for more than 80 min in naive or rabbit anti-bovine serum albumin-treated mice (RPA model), respectively. The response to the two stimuli was prevented by the B(2) receptor antagonist, HOE-140, but not by [Leu(8)]desArg(9)-BK (B(1) receptor antagonist). In contrast to the wild-type littermates, RPA and bradykinin were unable to trigger an increase in plasma extravasation in B(2) knockout mice. Furthermore, endothelin-1 (5 microg mouse(-1)) and a selective NK-1 receptor agonist [Sar(9),Met (O(2))(11)]-SP (20 microg mouse(-1)), triggered a significant increase in peritoneal plasma extravasation in both wild-type and B(2) knockout animals. A pretreatment with indomethacin (200 microg mouse(-1)) significantly reduced the RPA-induced but not the BK-induced increase in Evans blue extravasation. Furthermore, RPA, but not BK, triggered a significant indomethacin-sensitive increase in peritoneal prostaglandin E(2) content. Our results suggest a pivotal role for B(2) receptors in the mechanism of plasma extravasation which occurs during the reverse passive Arthus reaction in the mouse. Moreover, our results suggest an important contribution of prostanoids in the plasma leakage mechanisms triggered by RPA but not by bradykinin.

Effects of eicosanoids, neuromediators and bioactive peptides on murine airways

The effects of several mediators including prostanoids, neuromediators, bioactive peptides and leukotrienes were investigated on the trachea, upper bronchi, lower bronchi and lung parenchyma of selected strains of mice mounted in a cascade superfusion system. The upper airways (trachea, upper bronchi) responded with greater maxima than lower airways (lower bronchi, lung parenchyma). Acetylcholine, carbachol, serotonin and 9, 11-dideoxy-9alpha,11alpha-epoxymethano-prostaglandin F(2alpha)serotonin>/=acetylcholine. Prostaglandins E(2), F(2alpha) and D(2)90% relaxation in some cases. The rank order of potency for the prostaglandins was E(2)>/=F(2alpha)D(2) with the exception of the lower bronchi on which prostaglandins had the following order of potency: F(2alpha)>/=E(2)D(2). The effects of prostaglandins were similar in four commonly used strains of mice (CD-1, BALB/c, C57BL/c6 and C3H) with some variations in efficacy. Iloprost was a weak mouse airway relaxant. It had the greatest effect on the trachea and bronchi of BALB/c and C57BL/c6 mice, whereas it had little or no effect on the airways of the CD-1 and C3H mouse strains. Vasoactive intestinal peptide potently relaxed the carbachol and precontracted the mouse trachea and bronchi. However, vasopressin, another bioactive peptide, potently and efficaciously contracted the mouse trachea and upper bronchi but had little effect on the lower bronchi. Vasopressin was the most potent and efficacious contractile agonist tested in this study. Contractions were observed with endothelins-1, -2 and -3 on mouse trachea and bronchi, but marked tachyphylaxis was present. Sarafotoxin s6c followed the same pattern suggesting the presence of endothelin ET(B) receptors on the mouse airways. Of all leukotrienes assayed (B(4), C(4), D(4) and E(4)) only leukotriene C(4) weakly contracted the mouse trachea and upper bronchi, but tachyphylaxis was most evident.

Adenosine induces cyclic-AMP formation and inhibits endothelin-1 production/secretion in guinea-pig tracheal epithelial cells through A(2B) adenosine receptors

1. The adenosine receptor subtype mediating adenosine 3' : 5'-cyclic monophosphate (cyclic AMP) formation and the effect of its activation on endothelin-1 (ET-1) secretion were studied in primary cultures of tracheal epithelial cells. 2. Adenosine analogues showed the following rank order of potency (pD(2) value) and intrinsic activity on the generation of cyclic AMP by tracheal epithelial cells: 5'-N-ethylcarboxyamidoadenosine (NECA, A(1)/A(2A)/A(2B), pD(2): 5.44+/-0.16)>adenosine (ADO, non selective, pD(2): 4.99+/-0. 09; 71+/-9% of NECA response) >/=2-Cl-adenosine (2CADO, non selective, pD(2): 4.72+/-0.14; 65+/-9% of NECA response)>>>CGS21680 (A(2A); inactive at up to 100 microM). 3. Cyclic AMP formation stimulated by NECA in guinea-pig tracheal epithelial cells was inhibited by adenosine receptor antagonist with the following order of apparent affinity (pA(2) value): Xanthine amine congeners (XAC, A(2A)/A(2B), 7.89+/-0.22)>CGS15943 (A(2A)/A(2B), 7.24+/-0. 26)>ZM241385 (A(2A), 6.69+/-0.14)>DPCPX (A(1), 6.51+/-0. 14)>3n-propylxanthine (weak A(2B), 4.30+/-0.10). This rank order of potency is typical for A(2B)-adenosine receptor. 4. Adenosine decreased basal and LPS-stimulated irET production in a concentration-dependent manner. Moreover, NECA but not CGS21680 inhibited LPS-induced irET production. 5. The inhibitory effect of NECA on LPS-induced irET production was reversed by XAC (pA(2)=8.84+/-0. 12) and DPCPX (pA(2)=8.10+/-0.22). 6. These results suggested that adenosine increased cyclic AMP formation and inhibited irET production/secretion by guinea-pig tracheal epithelial cells through the activation of a functional adenosine receptor that is most likely the A(2B) subtype. This adenosine receptor may be involved in the regulation of the level of ET-1 production/secretion by guinea-pig tracheal epithelial cells in physiological as well as in pathophysiological conditions.

Early bronchial hyperresponsiveness following injection of sephadex beads in the guinea pig: involvement of platelet activating factor and thromboxane A2

The effects of an intravenous injection (i.v.) of Sephadex beads (20 mg kg(-1)) were examined on bronchial responsiveness to ACh (1-200 microg kg(-1) i.v.) as well as on cell accumulation in guinea-pig lung. Bronchial hyperreactivity to ACh, measured as increase in pulmonary insufflation pressure (PIP), was observed 3 h following the i.v. injection of Sephadex beads. However, no significant increase in bronchial reactivity to ACh was measured at 6 and 12 h following Sephadex injection. A second later increase in bronchial hyperresponsiveness was observed at 24 h. Bronchoalveolar lavage performed at 3 h following Sephadex treatment showed that there was no significant increase in total or differential cell number. At 6 h and 12 h, a significant increase in total cell counts was observed. At 24 h, a greater than 5-fold increase in cell number was observed and was related to a marked eosinophil, neutrophil and macrophage infiltration. A platelet-activating factor (PAF) antagonist, CV-3988 (10 mg kg(-1) i.v.), and a thromboxane A2 (TxA2) antagonist, L655,240 (10 mg kg(-1) i.v.), significantly attenuated the Sephadex-induced bronchial hyperresponsiveness to ACh observed at 3 h. The results show that an i.v. injection of Sephadex beads in guinea pigs can induce an early bronchial hyperresponsiveness to ACh that is mediated by the release of both PAF and TxA2 and is independent of airway cell infiltration.

Involvement of bradykinin B1 and B2 receptors in pulmonary leukocyte accumulation induced by Sephadex beads in guinea pigs

The effects of selected bradykinin receptor antagonists on leukocyte infiltration into the lungs were studied in a model of guinea pig lung inflammation induced by the intravenous injection of Sephadex beads. The bradykinin B1 receptor antagonist, [Leu8]desArg9-BK (40 mg kg(-1) 24 h(-1)) and the bradykinin B2 receptor antagonist, DArg[Hyp3,Thi5,DTic7,Oic8]BK (code name HOE 140; 4 mg kg(-1) 24 h(-1)), administered intravenously by osmotic pumps, significantly reduced eosinophil counts by 33% and 42% in bronchoalveolar fluid, respectively. HOE 140 decreased neutrophil counts by 35%. LysLys[Hyp3,Igl5,D-Igl7,Oic8]desArg9BK+ ++ (code name B 9858), a newly described bradykinin B1 receptor antagonist, administered intraperitoneally (1 mg kg(-1)), decreased eosinophil and neutrophil counts by 45% in bronchoalveolar fluid. D-Arg[Hyp3,Igl5,D-Igl7,Oic8]BK (code name B 9430), a non-selective bradykinin B1/B2 receptor antagonist, also administered intraperitoneally (1 mg kg(-1)), decreased eosinophil and macrophage counts by 62% and 80% in bronchoalveolar fluid. These results suggest that bradykinin B1 and B2 receptors are involved in leukocyte recruitment in our model of lung inflammation.

Evidence for the activation of blood complement in Sephadex beads-induced lung inflammation in guinea pigs

OBJECTIVE AND DESIGN

This study evaluated the complement activation in guinea pigs that were given an intravenous injection of Sephadex and its correlation with markers of the development of inflammation.

MATERIALS AND METHODS

Dunkin Hartley guinea pigs (250-300 g) were used. Whole blood was collected by heart puncture in a sodium citrate solution (0.315 g/ml) for complement measurements. Complement activation was measured using a colorimetric haemolytic assay. Bronchoalveolar lavages (BAL) were performed to monitor cell infiltration and inflammation was monitored by measurements of eosinophil peroxidase (EPO), histamine, beta-glucuronidase, albumin and total proteins in the BAL fluid.

TREATMENT

Guinea pigs were pre-treated with aprotinin (40000 IKU/kg) 30 min before they were given an intravenous injection of Sephadex beads (24 mg/kg). Carboxymethyl (CM)-Sephadex (24 mg/kg) was administered alone.

RESULTS

Sephadex beads activated the complement system in vitro (14.12+/-2.29 U/ml) and in vivo (9.95+/-0.08 U/ml) reaching a peak 6 h after the injection. This activation was accompanied by other characteristic features of inflammation such as leukocyte infiltration and activation. Both CM-Sephadex and aprotinin reduced the blood complement activation and eosinophil infiltration/activation observed.

CONCLUSIONS

Our results strongly suggest that complement is involved in the cascade of events leading to the inflammatory state observed in guinea pig following the intravenous injection of Sephadex beads.

Selective inflammatory response induced by intratracheal and intravenous administration of poly-L-arginine in guinea pig lungs

Major basic protein (MBP) is a cationic protein found in eosinophil granules that was postulated to participate in the pathogenesis of bronchial asthma. Recently, it has been demonstrated that MBP level in serum or bronchoalveolar lavage (BAL) fluid was correlated with bronchial hyperresponsiveness (BHR) in asthmatics. A number a studies have established that MBP actions could be mimicked by synthetic polycations as poly-L-arginine. In this study, we investigated the effects of intratracheal and intravenous administration of poly-L-arginine on lung inflammatory response development. The intratracheal injection of poly-L-arginine at the doses of 1, 10, 100 nmol/animal increased the number of eosinophils (up to 3.2 fold) and neutrophils (up to 12 fold) in BAL fluid. Eosinophil and neutrophil infiltration was reversed by 88% and 67% respectively following low molecular weight heparin treatment (500 microg/animal). The intravenous injection of increasing doses of poly-L-arginine (1, 10, 100, 500 nmol/animal) increased the number of eosinophils (up to 2.7 fold) but not neutrophil infiltration in guinea pig lungs. Eosinophil infiltration was reversed by 87% following low molecular weight heparin treatment (1.5 mg/animal). Intratracheal treatment with poly-L-arginine (100 nmol/animal) produced an important increase of beta-glucuronidase, histamine, eosinophil peroxidase (EPO) and albumin levels in BAL fluid, whereas the intravenous treatment (500 nmol/animal) did not. These results show that the route of administration of poly-L-arginine greatly influences its effect on inflammatory cell recruitment since both administration routes elicited eosinophil migration but only the intratracheal route stimulated the migration of neutrophils. Moreover, poly-L-arginine appeared to induce other inflammatory responses since it increased beta-glucuronidase, histamine, EPO and albumin levels in BAL fluid following intratracheal treatment. These results also showed that low molecular weight heparin significantly blocks the inflammatory responses elicited by poly-L-arginine.

A rat model presenting eosinophilia in the airways, lung eosinophil activation, and pulmonary hyperreactivity

The aim of this study was to examine antigen-induced lung cell migration, eosinophil activation, and pulmonary reactivity of Wistar rats exposed to a new sensitization technique. The animals were sensitized with a single subcutaneous implant of a fragment of heat coagulated hen egg white and challenged 21 days later with an intratracheal injection of heat-aggregated ovalbumin (EWI). For comparison, another group of rats were sensitized by an intraperitoneal injection of ovalbumin in alum as adjuvant, with one booster on day 14 and challenge on day 21 post immunization (OVA/AL). Twenty-four hours after antigen challenge, the EWI group presented a higher number of eosinophils in the bronchoalveolar lavage (BAL) (4.85 +/- 1.43 x 10(6)) than the OVA/AL group (0.2 +/- 0.06 x 10(6)) or the control group, where the level of eosinophils were essentially undetectable. Levels of eosinophil peroxidase activity were increased in the cell-free BAL and homogenates of lung tissue in the EWI group (12.10 +/- 2.97 mg/mL and 36.14 +/- 7.21 ng/mg, respectively), but not in the OVA/AL group (4.83 +/- 1.4 ng/mL and 11.95 +/- 2.54 ng/mg, respectively), as compared with controls (5.16 +/- 1.65 ng/mL and 12.13 +/- 1.74 ng/mg, respectively). Thromboxane B2 levels were also increased in the BAL of EWI group (2.89 +/- 0.54 ng/mL) but not the OVA/AL group (1.13 +/- 0.23 ng/mL) as compared with controls (1.14 +/- 0.19 ng/mL). In contrast, the levels of prostaglandin E2 in the BAL were increased in both groups (456.4 +/- 11.8 pg/mL in the EWI group and 303.5 +/- 31.7 pg/mL in the OVA/AL group) as compared with controls (205.7 +/- 29.7 ng/mL). Moreover, only the EWI group developed increased pulmonary reactivity to serotonin (around two-fold), 24 hours after antigen challenge. The extent of lung eosinophil migration and activation and the pulmonary hyperreactivity induced by this novel sensitization procedure without adjuvants represents a significant improvement over existing experimental models of asthma.

Technology evaluation: ISIS-3521

It is well known that the PKC family of enzymes is involved in the propagation of intracellular signals and is implicated in cancers, inflammatory processes, cardiovascular and endocrinological diseases. Relatively low isozyme specificity has largely limited the clinical use of PKC antagonists. The members of the PKC family differ from each other at the mRNA level and the selectivity of antisense compounds is distinguished by this feature. According to ISIS Pharmaceuticals Inc antisense compounds are highly selective inhibitors even within a family of closely-related genes [321211]. The use of these compounds could be invaluable as tools to discover the mechanisms and roles of specific PKC isozyme in normal and diseased tissues and could provide the information for better cancer treatments [226799]. The isozyme of PKC-alpha is believed to play an important role in the proliferation of several types of cancer cells [234471-323703]. Recently, ISIS Pharmaceuticals received a patent US-05885970, covering the antisense technique targeting human PKC-alpha for cancer therapy (US-0588970). In the past few years, several effective antisense oligonucleotides (AS ONs) targeting murine and human PKC-alpha isozymes have been developed and a series of positive results have been obtained in cell culture and in nude mice cancer transplantation [327453]. Phase I clinical trials have shown that relatively high doses were well tolerated with no obvious side-effects [226799]. Whether these AS ONs are beneficial to patients suffering from cancer, either alone or in combination with other chemotherapy drugs is still under evaluation in a clinical setting.

Endothelin A receptor blockade causes adverse left ventricular remodeling but improves pulmonary artery pressure after infarction in the rat

BACKGROUND

Endothelin A (ETA) receptor antagonists have been shown to improve ventricular remodeling and survival in rats when started 10 days after infarction. Whether starting them earlier would have a more or less beneficial effect is uncertain.

METHODS AND RESULTS

Rats surviving an acute myocardial infarction (MI) for 24 hours (n=403) were assigned to saline or the ETA receptor antagonist LU 127043 or its active enantiomer LU 135252 for 4 weeks. Chronic LU treatment had no effect on survival, with 46% of LU rats and 47% of saline-treated rats with large MI surviving to the end of the study. LU treatment led to scar thinning, further left ventricular (LV) dilatation, an increase in LV end-diastolic pressure, and an increase in wet lung weight (P<0.05). Despite this detrimental effect on LV function, LU led to a significant decrease in RV systolic (50+/-2 to 44+/-2 mm Hg, P<0.05 vs saline) and right atrial pressures. LU treatment also prevented the increase in pulmonary ET-1 found in saline-treated rats with large MI but did not modify the increase in cardiac ET-1 in hearts with large MI.

CONCLUSIONS

The early use of the ETA receptor antagonists LU 127043 or its active enantiomer LU 135252 after infarction in the rat leads to impaired scar healing and LV dilatation and dysfunction. This is accompanied by a decrease in RV systolic and right atrial pressures and a decrease in pulmonary but not cardiac ET-1 levels. It would thus appear that the early use of ETA receptor antagonists after infarction may be detrimental.

Inhibition of airway hyperreactivity, edema, and lung cell infiltration by compound U-83836E in sensitized guinea pigs

Sensitized guinea pigs were used to assess the effect of treatment with the compound U-83836E ((-)-2-[[4-(2,6-di-1-pyrrolidinyl-4-pyrimidinyl)-1-piperazinyl]methyl]-3 ,4-dihydro-2,5,7,8-tetramethyl-2H--benzopyran-6-ol, dihydrochloride) on the antigen-induced late-phase (16 h) airway hyperreactivity, increase in inflammatory cell number, edema, and release of inflammatory mediators in the bronchoalveolar lavage (BAL) fluid. After antigen challenge, an increase of the in vitro reactivity of the trachea and upper bronchi to acetylcholine and histamine and an increase in the number of leukocytes in the BAL fluid, mainly eosinophils and mononuclear cells, were observed. The concentrations of proteins, histamine, and PGE2 in the BAL fluid were also significantly increased by 53, 57, and 216%, respectively, after antigen challenge. Treatment with U-83836E (10 mg/kg) given i.p. 17 and 3 h before and 6 h after antigen challenge inhibited by approximately 80% the total cell number in the airways and the BAL fluid protein content. Moreover, this treatment totally inhibited airway hyperreactivity. Histamine and PGE2 levels in the BAL fluid were not significantly affected by U-83836E treatment. These results indicate that U-83836E is effective against some of the characteristic features of asthma in ovalbumin-sensitized guinea pigs.

Developmental changes in synthesis of and responsiveness to prostaglandins I2 and E2 in hypoxic lamb lungs

Previous studies have shown that the attenuated hypoxic pulmonary vasoconstriction (HPV) of young newborn lamb lungs was enhanced by cyclooxygenase inhibition. We sought to determine whether this reflected greater synthesis of and (or) responsiveness to dilator prostaglandins (PG). Protocol 1 measured responses to graded hypoxia and perfusate concentrations of 6-keto-PGF1alpha (the stable metabolite of PGI2) and PGE2 in isolated lungs from 1-day- and 1-month-old lambs. Protocol 2 compared dose responses and segmental vascular resistances during infusion of PGI2 and PGE2 in hypoxic, cyclooxygenase-inhibited, lungs from 1- to 2-day-old and 1- to 3-month-old lambs. Lungs of 1-day-old lambs with attenuated responses to 4% O2 had significantly higher perfusate concentrations of 6-keto-PGF1alpha and PGE2, but responses to both PGE2 and the more potent vasodilator, PGI2 did not differ with age. These data support the hypothesis that attenuated HPV in young newborn lamb lungs is due to increased synthesis of dilator PG, particularly PGI2.

Effects of dual endothelin-converting enzyme/neutral endopeptidase inhibitors, CGS 26303 and CGS 26393, on lipopolysaccharide or interleukin-1 beta-stimulated release of endothelin from guinea pig tracheal epithelial cells

A number of studies using endothelin (ET) receptor antagonists support the participation of ETs in a variety of cardiovascular, renal, and other disorders. It has also been established that a number of cytokines, which are released in such diseases, modulate the expression and production of ETs and thus activate the ET system. This effect may represent one pathway by which these inflammatory mediators operate. By regulating endothelin-converting enzyme (ECE) activities, and thus ET synthesis, one can potentiate or attenuate the production of ETs and the receptor affinity/density in such pathologic conditions. Here, the stimulated (lipopolysaccharide or interleukin-1 beta) production of ET-1 from guinea pig tracheal epithelial cells was abolished by CGS 26303 or CGS 26393, two ECE/neutral endopeptidase (NEP) inhibitors, but was unaffected by CGS 24592, a specific NEP inhibitor. Therefore, such dual, and eventually selective ECE inhibitors are effective agents to prevent the stimulated production of ETs.

Roles of endothelins and their receptors in immune complex-induced/polymorphonuclear-mediated lung injury (reversed passive arthus reaction) in CD-1 mice

A number of pro-inflammatory mediators (leukotrienes, platelet activating factor, cytokines) participate in the process of neutrophil-dependent lung injury induced by immune complexes. Here, we studied the role of endothelins (ET) in the reversed passive Arthus reaction (AR) as a model of pneumonitis in CD-1 mice. We examined the broncholaveolar lavage fluid (BALF) for signs of inflammation such as the accumulation of cells, myeloperoxidase (MPO) activity and hemoglobin (Hb) levels, as a measure of hemorrhagic lesions, 24 h after injection. We used a selective ETA (BQ-123) or a non-selective ETA/ETB-R (SB 209670) receptor antagonist at various concentrations (2.5, 5 or 10 mg/kg ip at -8, 0, 8 and 16 h) to assess the involvement of ET. Challenged mice revealed signs of acute inflammation and hemorrhagic lesions. Levels of Hb and MPO, total and neutrophil cell counts increased by 9-, 9-, 3.2- and 63-fold, respectively. The lower dose of SB 209670 reduced Hb levels by 21% (P<0.05), without affecting cell accumulation or MPO. The mid-dose had no effect; the highest dose caused 60, 57 and 70% increases in Hb levels, total cell and neutrophil counts, respectively. Conversely, the highest dose of BQ-123 decreased Hb, total cell and neutrophil counts and MPO levels by 36, 35, 42 and 70%, respectively. These results support a role for ET in AR lung injuries. They also suggests that blocking ETA-R may be beneficial, while blockade of ETB-R (using a high dose of SB 209670) may be detrimental. A beneficial ETB-mediated response may exist that naturally interferes with events triggered by the formation of immune complexes such as cell accumulation and their subsequent activation leading to acute lung injury.

Adenosine-induced inhibition of basal endothelin-1 production from guinea-pig tracheal epithelial cells: a mechanism involving the release of cAMP

Guinea-pig tracheal epithelial cells, like other pulmonary cells in various species, have been reported to synthesize and release endothelins (ET). Their production is inducible by many agents and inhibited by ET-converting enzyme inhibitors, corticosteroids and beta agonists. Here, we studied the effect of adenosine on (1) the formation of adenosine 3', 5'-cyclic monophosphate (cAMP) and (2) concomitant effect on the basal release of ET from primary cultured tracheal epithelial cells isolated from guinea-pigs (GPTEpC). Adenosine (10(-7)-10(-3) M), the endogenous non-selective purinergic receptor agonist, induced the production of cAMP in a concentration-dependent manner (pD2=4.99+/-0.09). Concomitantly, adenosine decreased by a maximum of 39% ET-1-production over the same concentration range (with a 96% correlation). The inhibitory effect over ET-1-production was abolished by CGS15943 (10(-4) M), a non-selective A1/A2A receptor antagonist, and a xanthine amine congener (10(-4) M), a selective A1 receptor antagonist. Thus, these results suggest that adenosine attenuates the production of ET-1 from GPTEpC by stimulating the release of cAMP via the direct activation of adenosine receptors.

ET(B) receptor and nitric oxide synthase blockade induce BQ-123-sensitive pressor effects in the rabbit

Endothelin-1 (0.25 nmol/kg, injected into the left cardiac ventricle) induces a protracted increase of mean arterial pressure that is significantly reduced by the selective ET(A) receptor antagonist BQ-123 (1 and 10 mg/kg) in the anesthetized rabbit. The sole administration of the selective ET(B) antagonist BQ-788 (0.25 mg/kg) induces a pressor response abolished by BQ-123 (1 mg/kg). Concomitant to the increase in mean arterial pressure, BQ-788 induces a significant increase in plasma levels of endothelin-1 and its precursor big endothelin-1. The nitric oxide synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME; 10 mg/kg) also increases arterial blood pressure, and the response is reduced dose-dependently by BQ-123 (1 and 10 mg/kg). In addition, the administration of BQ-788 in the presence of L-NAME induced a further increase in arterial blood pressure. The duration of the pressor response to L-NAME is also significantly reduced by an endothelin-converting enzyme inhibitor, phosphoramidon (10 mg/kg). Finally, L-NAME induces an increase in plasma levels of big endothelin-1 but not endothelin-1. Our results illustrate that blockade of either nitric oxide synthase or ET(B) receptors triggers a raise in plasma levels of endothelin-1 or its precursor. These later moieties are suggested to be significantly involved, through the activation of ET(A) receptors, in the pressor effects of L-NAME and BQ-788 in the anesthetized rabbit.